diff --git a/README.md b/README.md
index 02affdd52..621435471 100644
--- a/README.md
+++ b/README.md
@@ -26,548 +26,548 @@ If you would like to have collaborator permissions on the repo to merge your own
 
 ### Arrays & Hashing
 
-<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
----- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
-<sub>[0217 - Contains Duplicate](https://leetcode.com/problems/contains-duplicate/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0217-contains-duplicate.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0217-contains-duplicate.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0217-contains-duplicate.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0217-contains-duplicate.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0217-contains-duplicate.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0217-contains-duplicate.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0217-contains-duplicate.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0217-contains-duplicate.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0217-contains-duplicate.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0217-contains-duplicate.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0217-contains-duplicate.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0217-contains-duplicate.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0217-contains-duplicate.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0217-contains-duplicate.ts)</div></sub>
-<sub>[0242 - Valid Anagram](https://leetcode.com/problems/valid-anagram/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0242-valid-anagram.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0242-valid-anagram.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0242-valid-anagram.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0242-valid-anagram.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0242-valid-anagram.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0242-valid-anagram.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0242-valid-anagram.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0242-valid-anagram.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0242-valid-anagram.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0242-valid-anagram.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0242-valid-anagram.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0242-valid-anagram.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0242-valid-anagram.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0242-valid-anagram.ts)</div></sub>
-<sub>[1929 - Concatenation of Array](https://leetcode.com/problems/concatenation-of-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1929-concatenation-of-array.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1929-concatenation-of-array.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1929-concatenation-of-array.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F1929-concatenation-of-array.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F1929-concatenation-of-array.go)</div></sub> | <sub><div align='center'>[✔️](java%2F1929-concatenation-of-array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1929-concatenation-of-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1929-concatenation-of-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1929-concatenation-of-array.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F1929-concatenation-of-array.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F1929-concatenation-of-array.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F1929-concatenation-of-array.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F1929-concatenation-of-array.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F1929-concatenation-of-array.ts)</div></sub>
-<sub>[1299 - Replace Elements With Greatest Element On Right Side](https://leetcode.com/problems/replace-elements-with-greatest-element-on-right-side/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1299-Replace-Elements-With-Greatest-Element-On-Right-Side.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1299-Replace-Elements-with-Greatest-Element-on-Right-Side.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1299-Replace-Elements-With-Greatest-Element-On-Right-Side.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F1299-replace-elements-with-greatest-element-on-right-side.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F1299-Replace-Elements-With-Greatest-Element-On-Right-Side.go)</div></sub> | <sub><div align='center'>[✔️](java%2F1299-Replace-Elements-With-Greatest-Element-On-Right-Side.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1299-Replace-Elements-with-Greatest-Element-on-Right-Side.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1299-replace-elements-with-greatest-element-on-right-side.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1299-replace-elements-with-greatest-element-on-right-side.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1299-Replace-Elements-With-Greatest-Element-On-Right-Side.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1299-replace-elements-with-greatest-element-on-right-side.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F1299-Replace-Elements-With-Greatest-Element-On-Right-Side.ts)</div></sub>
-<sub>[0392 - Is Subsequence](https://leetcode.com/problems/is-subsequence/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0392-is-subsequence.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0392-is-subsequence.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0392-is-subsequence.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0392-is-subsequence.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0392-is-subsequence.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0392-is-subsequence.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0392-is-subsequence.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0392-is-subsequence.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0392-is-subsequence.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0392-is-subsequence.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0392-is-subsequence.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0392-is-subsequence.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0392-is-subsequence.ts)</div></sub>
-<sub>[0058 - Length of Last Word](https://leetcode.com/problems/length-of-last-word/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0058-length-of-last-word.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0058-length-of-last-word.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0058-length-of-last-word.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0058-length-of-last-word.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0058-Length-of-Last-Word.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0058-length-of-last-word.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0058-length-of-last-word.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0058-length-of-last-word.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0058-length-of-last-word.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0058-length-of-last-word.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0058-length-of-last-word.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0058-length-of-last-word.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0058-Length-of-Last-Word.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0058-length-of-last-word.ts)</div></sub>
-<sub>[0001 - Two Sum](https://leetcode.com/problems/two-sum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0001-two-sum.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0001-two-sum.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0001-two-sum.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0001-two-sum.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0001-two-sum.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0001-two-sum.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0001-two-sum.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0001-two-sum.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0001-two-sum.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0001-two-sum.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0001-two-sum.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0001-two-sum.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0001-two-sum.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0001-two-sum.ts)</div></sub>
-<sub>[0014 - Longest Common Prefix](https://leetcode.com/problems/longest-common-prefix/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0014-Longest-Common-Prefix.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0014-longest-common-prefix.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0014-longest-common-prefix.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0014-longest-common-prefix.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0014-longest-common-prefix.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0014-longest-common-prefix.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0014-longest-common-prefix.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0014-longest-common-prefix.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0014-longest-common-prefix.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0014-longest-common-prefix.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0014-longest-common-prefix.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0014-longest-common-prefix.ts)</div></sub>
-<sub>[0049 - Group Anagrams](https://leetcode.com/problems/group-anagrams/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0049-group-anagrams.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0049-group-anagrams.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0049-group-anagrams.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0049-group-anagrams.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0049-group-anagrams.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0049-group-anagrams.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0049-group-anagrams.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0049-group-anagrams.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0049-group-anagrams.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0049-group-anagrams.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0049-group-anagrams.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0049-group-anagrams.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0049-group-anagrams.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0049-group-anagrams.ts)</div></sub>
-<sub>[0118 - Pascals Triangle](https://leetcode.com/problems/pascals-triangle/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0118-pascals-triangle.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0118-pascals-triangle.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0118-pascals-triangle.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0118-pascals-triangle.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0118-pascals-triangle.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0118-pascals-triangle.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0118-pascals-triangle.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0118-pascals-triangle.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0118-pascals-triangle.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0118-pascals-triangle.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0118-pascals-triangle.ts)</div></sub>
-<sub>[0027 - Remove Element](https://leetcode.com/problems/remove-element/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0027-remove-element.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0027-remove-element.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0027-remove-element.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0027-remove-element.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0027-remove-element.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0027-remove-element.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0027-remove-element.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0027-remove-element.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0027-remove-element.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0027-remove-element.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0027-Remove-Element.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0027-remove-element.ts)</div></sub>
-<sub>[0929 - Unique Email Addresses](https://leetcode.com/problems/unique-email-addresses/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0929-unique-email-addresses.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0929-unique-email-addresses.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0929-unique-email-addresses.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0929-unique-email-addresses.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0929-unique-email-addresses.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0929-unique-email-addresses.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0929-unique-email-addresses.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0929-unique-email-addresses.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0929-unique-email-addresses.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0929-unique-email-addresses.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0929-unique-email-addresses.ts)</div></sub>
-<sub>[0205 - Isomorphic Strings](https://leetcode.com/problems/isomorphic-strings/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0205-isomorphic-strings.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0205-Isomorphic-Strings.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0205-isomorphic-strings.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0205-isomorphic-strings.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0205-isomorphic-strings.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0205-isomorphic-strings.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0205-isomorphic-strings.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0205-isomorphic-strings.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0205-isomorphic-strings.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0205-isomorphic-strings.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0205-isomorphic-strings.ts)</div></sub>
-<sub>[0605 - Can Place Flowers](https://leetcode.com/problems/can-place-flowers/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0605-can-place-flowers.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0605-can-place-flowers.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0605-can-place-flowers.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0605-can-place-flowers.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0605-can-place-flowers.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0605-can-place-flowers.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0605-can-place-flowers.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0605-can-place-flowers.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0605-can-place-flowers.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0605-can-place-flowers.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0605-can-place-flowers.ts)</div></sub>
-<sub>[0169 - Majority Element](https://leetcode.com/problems/majority-element/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0169-majority-element.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0169-majority-element.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0169-majority-element.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0169-majority-element.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0169-majority-element.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0169-majority-element.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0169-majority-element.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0169-majority-element.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0169-majority-element.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0169-majority-element.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0169-majority-element.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0169-majority-element.ts)</div></sub>
-<sub>[0496 - Next Greater Element I](https://leetcode.com/problems/next-greater-element-i/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0496-next-greater-element-i.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0496-next-greater-element-i.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0496-next-greater-element-i.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0496-next-greater-element-i.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0496-next-greater-element-i.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0496-next-greater-element-i.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0496-next-greater-element-i.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0496-next-greater-element-i.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0496-next-greater-element-I.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0496-next-greater-element-i.ts)</div></sub>
-<sub>[0724 - Find Pivot Index](https://leetcode.com/problems/find-pivot-index/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0724-find-pivot-index.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0724-find-pivot-index.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0724-find-pivot-index.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0724-find-pivot-index.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0724-find-pivot-index.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0724-find-pivot-index.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0724-find-pivot-index.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0724-find-pivot-index.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0724-find-pivot-index.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0724-find-pivot-index.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0724-find-pivot-index.ts)</div></sub>
-<sub>[0303 - Range Sum Query - Immutable](https://leetcode.com/problems/range-sum-query-immutable/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0303-range-sum-query-immutable.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0303-range-sum-query-immutable.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0303-range-sum-query-immutable.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0303-range-sum-query.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0303-range-sum-query-immutable.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0303-range-sum-query-immutable.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0303-range-sum-query-immutable.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0303-range-sum-query-immutable.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0303-range-sum-query-immutable.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0303-range-sum-query-immutable.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0303-range-sum-query-immutable.ts)</div></sub>
-<sub>[0448 - Find All Numbers Disappeared in An Array](https://leetcode.com/problems/find-all-numbers-disappeared-in-an-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0448-Find-All-Numbers-Disappeared-in-an-Array.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0448-find-all-numbers-disappeared-in-an-array.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0448-find-all-numbers-disappeared-in-an-array.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0448-find-all-numbers-disappeared-in-an-array.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0448-find-all-numbers-disappeared-in-an-array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0448-find-all-numbers-disappeared-in-an-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0448-find-all-numbers-disappeared-in-an-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0448-find-all-numbers-disappeared-in-an-array.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0448-find-all-numbers-disappeared-in-an-array.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0448-find-all-numbers-disappeared-in-an-array.ts)</div></sub>
-<sub>[1189 - Maximum Number of Balloons](https://leetcode.com/problems/maximum-number-of-balloons/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1189-Maximum-Number-of-Balloons.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1189-maximum-number-of-balloons.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1189-maximum-number-of-balloons.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1189-maximum-number-of-balloons.go)</div></sub> | <sub><div align='center'>[✔️](java%2F1189-maximum-number-of-balloons.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1189-maximum-number-of-balloons.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1189-maximum-number-of-balloons.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1189-maximum-number-of-balloons.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1189-maximum-number-of-balloons.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F1189-maximum-number-of-balloons.ts)</div></sub>
-<sub>[0290 - Word Pattern](https://leetcode.com/problems/word-pattern/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0290-Word-Pattern.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0290-word-pattern.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0290-word-pattern.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0290-word-pattern.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0290-word-pattern.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0290-word-pattern.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0290-word-pattern.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0290-word-pattern.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0290-word-pattern.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0290-word-pattern.ts)</div></sub>
-<sub>[0705 - Design HashSet](https://leetcode.com/problems/design-hashset/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0705-design-hashset.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0705-design-hashset.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0705-design-hashset.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0705-design-hashset.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0705-design-hashset.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0705-design-hashset.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0705-design-hashset.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0705-design-hashset.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0705-design-hashset.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0706 - Design HashMap](https://leetcode.com/problems/design-hashmap/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0706-design-hashmap.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0706-design-hashmap.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0706-design-hashmap.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0706-design-hashmap.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0706-design-hashmap.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0706-design-hashmap.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0706-design-hashmap.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0706-design-hashmap.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0706-design-hashmap.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0706-design-hashmap.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0912 - Sort an Array](https://leetcode.com/problems/sort-an-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0912-sort-an-array.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0912-sort-an-array.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0912-sort-an-array.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0912-sort-an-array.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0912-sort-an-array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0912-sort-an-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0912-sort-an-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0912-sort-an-array.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0912-sort-an-array.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0912-sort-an-array.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0347 - Top K Frequent Elements](https://leetcode.com/problems/top-k-frequent-elements/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0347-top-k-frequent-elements.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0347-top-k-frequent-elements.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0347-top-k-frequent-elements.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0347-top-k-frequent-elements.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0347-top-k-frequent-elements.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0347-top-k-frequent-elements.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0347-top-k-frequent-elements.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0347-top-k-frequent-elements.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0347-top-k-frequent-elements.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0347-top-k-frequent-elements.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0347-top-k-frequent-elements.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0347-top-k-frequent-elements.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0347-top-k-frequent-elements.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0347-top-k-frequent-elements.ts)</div></sub>
-<sub>[0238 - Product of Array Except Self](https://leetcode.com/problems/product-of-array-except-self/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0238-product-of-array-except-self.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0238-product-of-array-except-self.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0238-product-of-array-except-self.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0238-product-of-array-except-self.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0238-product-of-array-except-self.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0238-product-of-array-except-self.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0238-product-of-array-except-self.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0238-product-of-array-except-self.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0238-product-of-array-except-self.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0238-product-of-array-except-self.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0238-product-of-array-except-self.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0238-product-of-array-except-self.ts)</div></sub>
-<sub>[0036 - Valid Sudoku](https://leetcode.com/problems/valid-sudoku/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0036-valid-sudoku.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0036-valid-sudoku.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0036-valid-sudoku.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0036-valid-sudoku.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0036-valid-sudoku.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0036-valid-sudoku.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0036-valid-sudoku.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0036-valid-sudoku.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0036-valid-sudoku.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0036-valid-sudoku.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0036-valid-sudoku.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0036-valid-sudoku.scala)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0036-valid-sudoku.ts)</div></sub>
-<sub>[0271 - Encode and Decode Strings](https://leetcode.com/problems/encode-and-decode-strings/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0271-encode-and-decode-strings.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0271-encode-and-decode-strings.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0271-encode-and-decode-strings.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0271-encode-and-decode-strings.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0271-encode-and-decode-strings.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0271-encode-and-decode-strings.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0271-encode-and-decode-strings.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0271-encode-and-decode-strings.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0271-encode-and-decode-strings.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0271-encode-and-decode-strings.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0271-encode-and-decode-strings.ts)</div></sub>
-<sub>[0128 - Longest Consecutive Sequence](https://leetcode.com/problems/longest-consecutive-sequence/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0128-longest-consecutive-sequence.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0128-longest-consecutive-sequence.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0128-longest-consecutive-sequence.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0128-longest-consecutive-sequence.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0128-longest-consecutive-sequence.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0128-longest-consecutive-sequence.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0128-longest-consecutive-sequence.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0128-longest-consecutive-sequence.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0128-longest-consecutive-sequence.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0128-longest-consecutive-sequence.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0128-longest-consecutive-sequence.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0128-longest-consecutive-sequence.ts)</div></sub>
-<sub>[0075 - Sort Colors](https://leetcode.com/problems/sort-colors/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0075-sort-colors.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0075-Sort-colors.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0075-sort-colors.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0075-sort-colors.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0075-sort-colors.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0075-sort-colors.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0075-sort-colors.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0075-sort-colors.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0075-sort-colors.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0075-sort-colors.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0075-sort-colors.ts)</div></sub>
-<sub>[0535 - Encode and Decode TinyURL](https://leetcode.com/problems/encode-and-decode-tinyurl/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0535-encode-and-decode-tinyurl.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0535-encode-and-decode-tinyurl.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0535-encode-and-decode-tinyurl.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0535-encode-and-decode-tinyurl.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0535-encode-and-decode-tinyurl.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0535-encode-and-decode-tinyurl.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0535-encode-and-decode-tinyurl.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0535-encode-and-decode-tinyurl.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0535-encode-and-decode-tinyURL.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0535-Encode-and-Decode-TinyURL.Swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0535-encode-and-decode-tinyurl.ts)</div></sub>
-<sub>[0554 - Brick Wall](https://leetcode.com/problems/brick-wall/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0554-Brick-Wall.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0554-brick-wall.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0554-brick-wall.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0554-brick-wall.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0554-brick-wall.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0554-brick-wall.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0554-brick-wall.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0554-brick-wall.ts)</div></sub>
-<sub>[0122 - Best Time to Buy And Sell Stock II](https://leetcode.com/problems/best-time-to-buy-and-sell-stock-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0122-best-time-to-buy-and-sell-stock-ii.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0122-best-time-to-buy-and-sell-stock-ii.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0122-best-time-to-buy-and-sell-stock-ii.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0122-best-time-to-buy-and-sell-stock-II.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0122-best-time-to-buy-and-sell-stock-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0122-best-time-to-buy-and-sell-stock-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0122-best-time-to-buy-and-sell-stock-ii.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0122-best-time-to-buy-and-sell-stock-ii.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0560 - Subarray Sum Equals K](https://leetcode.com/problems/subarray-sum-equals-k/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0560-subarray-sum-equals-k.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0560-subarray-sum-equals-k.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0560-subarray-sum-equals-k.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0560-subarray-sum-equals-k.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0560-subarray-sum-equals-k.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0560-subarray-sum-equals-k.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0560-subarray-sum-equals-k.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0560-subarray-sum-equals-k.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0560-subarray-sum-equals-k.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0560-subarray-sum-equals-k.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0560-subarray-sum-equals-k.ts)</div></sub>
-<sub>[1930 - Unique Length 3 Palindromic Subsequences](https://leetcode.com/problems/unique-length-3-palindromic-subsequences/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1930-unique-length-3-palindromic-subsequences.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1930-unique-length-3-palindromic-subsequences.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1930-unique-length-3-palindromic-subsequences.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1930-unique-length-3-palindromic-subsequences.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1930-unique-length-3-palindromic-subsequences.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1930-unique-length-3-palindromic-subsequences.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1930-unique-length-3-palindromic-subsequences.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F1930-unique-length-3-palindromic-subsequences.ts)</div></sub>
-<sub>[1963 - Minimum Number of Swaps to Make The String Balanced](https://leetcode.com/problems/minimum-number-of-swaps-to-make-the-string-balanced/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1963-minimum-number-of-swaps-to-make-the-string-balanced.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1963-minimum-number-of-swaps-to-make-the-string-balanced.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1963-minimum-number-of-swaps-to-make-the-string-balanced.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1963-minimum-number-of-swaps-to-make-the-string-balanced.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1963-minimum-number-of-swaps-to-make-the-string-balanced.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1963-minimum-number-of-swaps-to-make-the-string-balanced.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1963-minimum-number-of-swaps-to-make-the-string-balanced.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1963-minimum-number-of-swaps-to-make-the-string-balanced.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2001 - Number of Pairs of Interchangeable Rectangles](https://leetcode.com/problems/number-of-pairs-of-interchangeable-rectangles/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F2001-number-of-pairs-of-interchangeable-rectangles.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F2001-number-of-pairs-of-interchangeable-rectangles.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F2001-number-of-pairs-of-interchangeable-rectangles.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F2001-number-of-pairs-of-interchangeable-rectangles.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2001-number-of-pairs-of-interchangeable-rectangles.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F2001-number-of-pairs-of-interchangeable-rectangles.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F2001-number-of-pairs-of-interchangeable-rectangles.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2002 - Maximum Product of The Length of Two Palindromic Subsequences](https://leetcode.com/problems/maximum-product-of-the-length-of-two-palindromic-subsequences/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F2002-maximum-product-of-the-length-of-two-palindromic-subsequences.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F2002-maximum-product-of-the-length-of-two-palindromic-subsequences.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F2002-maximum-product-of-the-length-of-two-palindromic-subsequences.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F2002-maximum-product-of-the-length-of-two-palindromic-subsequences.go)</div></sub> | <sub><div align='center'>[✔️](java%2F2002-maximum-product-of-the-length-of-two-palindromic-subsequences.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F2002-maximum-product-of-the-length-of-two-palindromic-subsequences.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2002-maximum-product-of-the-length-of-two-palindromic-subsequences.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F2002-maximum-product-of-the-length-of-two-palindromic-subsequences.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F2002-maximum-product-of-the-length-of-two-palindromic-subsequences.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F2002-maximum-product-of-the-length-of-two-palindromic-subsequences.ts)</div></sub>
-<sub>[2017 - Grid Game](https://leetcode.com/problems/grid-game/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F2017-grid-game.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F2017-grid-game.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F2017-grid-game.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2017-grid-game.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F2017-grid-game.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F2017-grid-game.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0438 - Find All Anagrams in a String](https://leetcode.com/problems/find-all-anagrams-in-a-string/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0438-find-all-anagrams-in-a-string.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0438-find-all-anagrams-in-a-string.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0438-find-all-anagrams-in-a-string.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0438-find-all-anagrams-in-a-string.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0438-find-all-anagrams-in-a-string.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0438-find-all-anagrams-in-a-string.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0438-find-all-anagrams-in-a-string.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0438-find-all-anagrams-in-a-string.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0438-find-all-anagrams-in-a-string.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0438-find-all-anagrams-in-a-string.ts)</div></sub>
-<sub>[0028 - Find The Index of The First Occurrence in a String](https://leetcode.com/problems/find-the-index-of-the-first-occurrence-in-a-string/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0028-find-the-index-of-the-first-occurrence-in-a-string.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0028-find-the-index-of-the-first-occurrence-in-a-string.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0028-find-the-index-of-the-first-occurrence-in-a-string.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0028-find-the-index-of-the-first-occurrence-in-a-string.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0028-find-the-index-of-the-first-occurrence-in-a-string.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0028-find-the-index-of-the-first-occurrence-in-a-string.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0028-find-the-index-of-the-first-occurrence-in-a-string.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0028-find-the-index-of-the-first-occurrence-in-a-string.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0028-find-the-index-of-the-first-occurrence-in-a-string.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0028-find-the-index-of-the-first-occurrence-in-a-string.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0280 - Wiggle Sort](https://leetcode.com/problems/wiggle-sort/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0280-wiggle-sort.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0280-wiggle-sort.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0280-wiggle-sort.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0179 - Largest Number](https://leetcode.com/problems/largest-number/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0179-largest-number.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0179-largest-number.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0179-largest-number.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0179-largest-number.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0179-largest-number.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0179-largest-number.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0179-largest-number.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0179-largest-number.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0179-largest-number.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0179-largest-number.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0179-largest-number.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0179-largest-number.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0179-largest-number.ts)</div></sub>
-<sub>[0523 - Continuous Subarray Sum](https://leetcode.com/problems/continuous-subarray-sum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0523-continuous-subarray-sum.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0523-continuous-subarray-sum.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0523-continuous-subarray-sum.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0523-continuous-subarray-sum.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0523-continuous-subarray-sum.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0523-continuous-subarray-sum.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0523-continuous-subarray-sum.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0523-continuous-subarray-sum.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0838 - Push Dominoes](https://leetcode.com/problems/push-dominoes/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0838-push-dominoes.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0838-push-dominoes.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0838-push-dominoes.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0838-push-dominoes.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0838-push-dominoes.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0838-push-dominoes.ts)</div></sub>
-<sub>[0187 - Repeated DNA Sequences](https://leetcode.com/problems/repeated-dna-sequences/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0187-repeated-dna-sequences.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0187-repeated-dna-sequences.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0187-repeated-dna-sequences.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0187-repeated-dna-sequences.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0187-repeated-dna-sequences.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0187-repeated-dna-sequences.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0187-repeated-dna-sequences.ts)</div></sub>
-<sub>[0380 - Insert Delete Get Random O(1)](https://leetcode.com/problems/insert-delete-getrandom-o1/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0380-insert-delete-getrandom-o1.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0380-insert-delete-getrandom-o1.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0380-insert-delete-getrandom-o1.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0380-insert-delete-getrandom-o1.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0380-insert-delete-getrandom-o1.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0380-insert-delete-getrandom-o1.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0380-insert-delete-getrandom-o1.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0380-insert-delete-getrandom-o1.ts)</div></sub>
-<sub>[1461 - Check if a String Contains all Binary Codes of Size K](https://leetcode.com/problems/check-if-a-string-contains-all-binary-codes-of-size-k/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1461-check-if-a-string-contains-all-binary-codes-of-size-k.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1461-check-if-a-string-contains-all-binary-codes-of-size-k.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1461-check-if-a-string-contains-all-binary-codes-of-size-k.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1461-check-if-a-string-contains-all-binary-codes-of-size-k.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1461-check-if-a-string-contains-all-binary-codes-of-size-k.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0304 - Range Sum Query 2D Immutable](https://leetcode.com/problems/range-sum-query-2d-immutable/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0304-range-sum-query-2d-immutable.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0304-range-sum-query-2d-immutable.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0304-range-sum-query-2d-immutable.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0304-range-sum-query-2d-immutable.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0304-range-sum-query-2d-immutable.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0304-range-sum-query-2d-immutable.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0665 - Non Decreasing Array](https://leetcode.com/problems/non-decreasing-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0665-non-decreasing-array.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0665-non-decreasing-array.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0665-non-decreasing-array.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0665-non-decreasing-array.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0665-non-decreasing-array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0665-non-decreasing-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0665-non-decreasing-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0665-non-decreasing-array.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](scala%2F0665-non-decreasing-array.scala)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0665-non-decreasing-array.ts)</div></sub>
-<sub>[0041 - First Missing Positive](https://leetcode.com/problems/first-missing-positive/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0041-first-missing-positive.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0041-first-missing-positive.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0041-first-missing-positive.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0041-first-missing-positive.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0041-first-missing-positive.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0041-first-missing-positive.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0041-first-missing-positive.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0041-first-missing-positive.ts)</div></sub>
-<sub>[1822 - Sign of An Array](https://leetcode.com/problems/sign-of-the-product-of-an-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1822-sign-of-the-product-of-an-array.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1822-sign-of-the-product-of-an-array.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1822-sign-of-the-product-of-an-array.go)</div></sub> | <sub><div align='center'>[✔️](java%2F1822-sign-of-the-product-of-an-array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1822-sign-of-the-product-of-an-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1822-sign-of-the-product-of-an-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1822-sign-of-the-product-of-an-array.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1822-sign-of-the-product-of-an-array.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F1822-sign-of-the-product-of-an-array.ts)</div></sub>
-<sub>[2215 - Find the Difference of Two Arrays](https://leetcode.com/problems/find-the-difference-of-two-arrays/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F2215-find-the-difference-of-two-arrays.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F2215-find-the-difference-of-two-arrays.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F2215-find-the-difference-of-two-arrays.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F2215-find-the-difference-of-two-arrays.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F2215-find-the-difference-of-two-arrays.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2215-find-the-difference-of-two-arrays.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F2215-find-the-difference-of-two-arrays.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F2215-find-the-difference-of-two-arrays.ts)</div></sub>
-<sub>[1603 - Design Parking System](https://leetcode.com/problems/design-parking-system/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1603-design-parking-system.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1603-design-parking-system.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1603-design-parking-system.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1603-design-parking-system.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1603-design-parking-system.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1603-design-parking-system.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2348 - Number of Zero-Filled Subarrays](https://leetcode.com/problems/number-of-zero-filled-subarrays/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F2348-number-of-zero-filled-subarrays.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F2348-number-of-zero-filled-subarrays.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F2348-number-of-zero-filled-subarrays.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2348-number-of-zero-filled-subarrays.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F2348-number-of-zero-filled-subarrays.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2405 - Optimal Partition of String](https://leetcode.com/problems/optimal-partition-of-string/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F2405-optimal-partition-of-string.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2405-optimal-partition-of-string.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F2405-optimal-partition-of-string.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1396 - Design Underground System](https://leetcode.com/problems/design-underground-system/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](csharp%2F1396-design-underground-system.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1396-design-underground-system.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1396-design-underground-system.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1396-design-underground-system.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1396-design-underground-system.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2483 - Minimum Penalty for a Shop](https://leetcode.com/problems/minimum-penalty-for-a-shop/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F2483-minimum-penalty-for-a-shop.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F2483-minimum-penalty-for-a-shop.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2483-minimum-penalty-for-a-shop.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F2483-minimum-penalty-for-a-shop.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0068 - Text Justification](https://leetcode.com/problems/text-justification/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0068-text-justification.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0068-text-justification.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2306 - Naming a Company](https://leetcode.com/problems/naming-a-company/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F2306-naming-a-company.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F2306-naming-a-company.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F2306-naming-a-company.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2306-naming-a-company.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F2306-naming-a-company.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>hints</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
+---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
+<sub>[0217 - Contains Duplicate](https://leetcode.com/problems/contains-duplicate/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0217-contains-duplicate.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0217-contains-duplicate.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0217-contains-duplicate.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0217-contains-duplicate.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0217-contains-duplicate.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0217-contains-duplicate.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0217-contains-duplicate.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0217-contains-duplicate.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0217-contains-duplicate.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0217-contains-duplicate.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0217-contains-duplicate.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0217-contains-duplicate.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0217-contains-duplicate.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0217-contains-duplicate.ts)</div></sub>
+<sub>[0242 - Valid Anagram](https://leetcode.com/problems/valid-anagram/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0242-valid-anagram.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0242-valid-anagram.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0242-valid-anagram.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0242-valid-anagram.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0242-valid-anagram.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0242-valid-anagram.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0242-valid-anagram.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0242-valid-anagram.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0242-valid-anagram.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0242-valid-anagram.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0242-valid-anagram.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0242-valid-anagram.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0242-valid-anagram.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0242-valid-anagram.ts)</div></sub>
+<sub>[1929 - Concatenation of Array](https://leetcode.com/problems/concatenation-of-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1929-concatenation-of-array.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1929-concatenation-of-array.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1929-concatenation-of-array.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F1929-concatenation-of-array.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F1929-concatenation-of-array.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1929-concatenation-of-array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1929-concatenation-of-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1929-concatenation-of-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1929-concatenation-of-array.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F1929-concatenation-of-array.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F1929-concatenation-of-array.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F1929-concatenation-of-array.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F1929-concatenation-of-array.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F1929-concatenation-of-array.ts)</div></sub>
+<sub>[1299 - Replace Elements With Greatest Element On Right Side](https://leetcode.com/problems/replace-elements-with-greatest-element-on-right-side/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1299-Replace-Elements-With-Greatest-Element-On-Right-Side.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1299-Replace-Elements-with-Greatest-Element-on-Right-Side.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1299-Replace-Elements-With-Greatest-Element-On-Right-Side.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F1299-replace-elements-with-greatest-element-on-right-side.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F1299-Replace-Elements-With-Greatest-Element-On-Right-Side.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1299-Replace-Elements-With-Greatest-Element-On-Right-Side.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1299-Replace-Elements-with-Greatest-Element-on-Right-Side.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1299-replace-elements-with-greatest-element-on-right-side.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1299-replace-elements-with-greatest-element-on-right-side.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F1299-replace-elements-with-greatest-element-on-right-side.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F1299-Replace-Elements-With-Greatest-Element-On-Right-Side.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1299-replace-elements-with-greatest-element-on-right-side.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F1299-Replace-Elements-With-Greatest-Element-On-Right-Side.ts)</div></sub>
+<sub>[0392 - Is Subsequence](https://leetcode.com/problems/is-subsequence/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0392-is-subsequence.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0392-is-subsequence.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0392-is-subsequence.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0392-is-subsequence.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0392-is-subsequence.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0392-is-subsequence.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0392-is-subsequence.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0392-is-subsequence.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0392-is-subsequence.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0392-is-subsequence.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0392-is-subsequence.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0392-is-subsequence.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0392-is-subsequence.ts)</div></sub>
+<sub>[0058 - Length of Last Word](https://leetcode.com/problems/length-of-last-word/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0058-length-of-last-word.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0058-length-of-last-word.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0058-length-of-last-word.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0058-length-of-last-word.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0058-Length-of-Last-Word.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0058-length-of-last-word.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0058-length-of-last-word.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0058-length-of-last-word.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0058-length-of-last-word.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0058-length-of-last-word.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0058-length-of-last-word.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0058-length-of-last-word.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0058-Length-of-Last-Word.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0058-length-of-last-word.ts)</div></sub>
+<sub>[0001 - Two Sum](https://leetcode.com/problems/two-sum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0001-two-sum.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0001-two-sum.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0001-two-sum.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0001-two-sum.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0001-two-sum.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0001-two-sum.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0001-two-sum.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0001-two-sum.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0001-two-sum.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0001-two-sum.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0001-two-sum.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0001-two-sum.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0001-two-sum.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0001-two-sum.ts)</div></sub>
+<sub>[0014 - Longest Common Prefix](https://leetcode.com/problems/longest-common-prefix/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0014-Longest-Common-Prefix.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0014-longest-common-prefix.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0014-longest-common-prefix.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0014-longest-common-prefix.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0014-longest-common-prefix.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0014-longest-common-prefix.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0014-longest-common-prefix.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0014-longest-common-prefix.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0014-longest-common-prefix.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0014-longest-common-prefix.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0014-longest-common-prefix.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0014-longest-common-prefix.ts)</div></sub>
+<sub>[0049 - Group Anagrams](https://leetcode.com/problems/group-anagrams/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0049-group-anagrams.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0049-group-anagrams.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0049-group-anagrams.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0049-group-anagrams.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0049-group-anagrams.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0049-group-anagrams.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0049-group-anagrams.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0049-group-anagrams.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0049-group-anagrams.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0049-group-anagrams.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0049-group-anagrams.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0049-group-anagrams.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0049-group-anagrams.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0049-group-anagrams.ts)</div></sub>
+<sub>[0118 - Pascals Triangle](https://leetcode.com/problems/pascals-triangle/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0118-pascals-triangle.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0118-pascals-triangle.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0118-pascals-triangle.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0118-pascals-triangle.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0118-pascals-triangle.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0118-pascals-triangle.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0118-pascals-triangle.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0118-pascals-triangle.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0118-pascals-triangle.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0118-pascals-triangle.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0118-pascals-triangle.ts)</div></sub>
+<sub>[0027 - Remove Element](https://leetcode.com/problems/remove-element/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0027-remove-element.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0027-remove-element.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0027-remove-element.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0027-remove-element.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0027-remove-element.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0027-remove-element.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0027-remove-element.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0027-remove-element.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0027-remove-element.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0027-remove-element.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0027-Remove-Element.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0027-remove-element.ts)</div></sub>
+<sub>[0929 - Unique Email Addresses](https://leetcode.com/problems/unique-email-addresses/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0929-unique-email-addresses.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0929-unique-email-addresses.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0929-unique-email-addresses.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0929-unique-email-addresses.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0929-unique-email-addresses.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0929-unique-email-addresses.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0929-unique-email-addresses.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0929-unique-email-addresses.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0929-unique-email-addresses.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0929-unique-email-addresses.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0929-unique-email-addresses.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0929-unique-email-addresses.ts)</div></sub>
+<sub>[0205 - Isomorphic Strings](https://leetcode.com/problems/isomorphic-strings/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0205-isomorphic-strings.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0205-Isomorphic-Strings.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0205-isomorphic-strings.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0205-isomorphic-strings.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0205-isomorphic-strings.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0205-isomorphic-strings.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0205-isomorphic-strings.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0205-isomorphic-strings.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0205-isomorphic-strings.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0205-isomorphic-strings.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0205-isomorphic-strings.ts)</div></sub>
+<sub>[0605 - Can Place Flowers](https://leetcode.com/problems/can-place-flowers/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0605-can-place-flowers.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0605-can-place-flowers.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0605-can-place-flowers.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0605-can-place-flowers.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0605-can-place-flowers.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0605-can-place-flowers.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0605-can-place-flowers.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0605-can-place-flowers.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0605-can-place-flowers.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0605-can-place-flowers.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0605-can-place-flowers.ts)</div></sub>
+<sub>[0169 - Majority Element](https://leetcode.com/problems/majority-element/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0169-majority-element.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0169-majority-element.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0169-majority-element.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0169-majority-element.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0169-majority-element.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0169-majority-element.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0169-majority-element.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0169-majority-element.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0169-majority-element.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0169-majority-element.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0169-majority-element.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0169-majority-element.ts)</div></sub>
+<sub>[0496 - Next Greater Element I](https://leetcode.com/problems/next-greater-element-i/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0496-next-greater-element-i.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0496-next-greater-element-i.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0496-next-greater-element-i.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0496-next-greater-element-i.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0496-next-greater-element-i.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0496-next-greater-element-i.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0496-next-greater-element-i.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0496-next-greater-element-i.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0496-next-greater-element-I.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0496-next-greater-element-i.ts)</div></sub>
+<sub>[0724 - Find Pivot Index](https://leetcode.com/problems/find-pivot-index/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0724-find-pivot-index.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0724-find-pivot-index.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0724-find-pivot-index.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0724-find-pivot-index.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0724-find-pivot-index.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0724-find-pivot-index.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0724-find-pivot-index.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0724-find-pivot-index.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0724-find-pivot-index.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0724-find-pivot-index.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0724-find-pivot-index.ts)</div></sub>
+<sub>[0303 - Range Sum Query - Immutable](https://leetcode.com/problems/range-sum-query-immutable/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0303-range-sum-query-immutable.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0303-range-sum-query-immutable.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0303-range-sum-query-immutable.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0303-range-sum-query.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0303-range-sum-query-immutable.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0303-range-sum-query-immutable.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0303-range-sum-query-immutable.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0303-range-sum-query-immutable.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0303-range-sum-query-immutable.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0303-range-sum-query-immutable.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0303-range-sum-query-immutable.ts)</div></sub>
+<sub>[0448 - Find All Numbers Disappeared in An Array](https://leetcode.com/problems/find-all-numbers-disappeared-in-an-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0448-Find-All-Numbers-Disappeared-in-an-Array.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0448-find-all-numbers-disappeared-in-an-array.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0448-find-all-numbers-disappeared-in-an-array.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0448-find-all-numbers-disappeared-in-an-array.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0448-find-all-numbers-disappeared-in-an-array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0448-find-all-numbers-disappeared-in-an-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0448-find-all-numbers-disappeared-in-an-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0448-find-all-numbers-disappeared-in-an-array.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0448-find-all-numbers-disappeared-in-an-array.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0448-find-all-numbers-disappeared-in-an-array.ts)</div></sub>
+<sub>[1189 - Maximum Number of Balloons](https://leetcode.com/problems/maximum-number-of-balloons/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1189-Maximum-Number-of-Balloons.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1189-maximum-number-of-balloons.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1189-maximum-number-of-balloons.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1189-maximum-number-of-balloons.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1189-maximum-number-of-balloons.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1189-maximum-number-of-balloons.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1189-maximum-number-of-balloons.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1189-maximum-number-of-balloons.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1189-maximum-number-of-balloons.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F1189-maximum-number-of-balloons.ts)</div></sub>
+<sub>[0290 - Word Pattern](https://leetcode.com/problems/word-pattern/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0290-Word-Pattern.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0290-word-pattern.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0290-word-pattern.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0290-word-pattern.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0290-word-pattern.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0290-word-pattern.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0290-word-pattern.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0290-word-pattern.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0290-word-pattern.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0290-word-pattern.ts)</div></sub>
+<sub>[0705 - Design HashSet](https://leetcode.com/problems/design-hashset/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0705-design-hashset.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0705-design-hashset.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0705-design-hashset.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0705-design-hashset.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0705-design-hashset.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0705-design-hashset.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0705-design-hashset.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0705-design-hashset.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0705-design-hashset.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0705-design-hashset.ts)</div></sub>
+<sub>[0706 - Design HashMap](https://leetcode.com/problems/design-hashmap/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0706-design-hashmap.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0706-design-hashmap.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0706-design-hashmap.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0706-design-hashmap.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0706-design-hashmap.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0706-design-hashmap.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0706-design-hashmap.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0706-design-hashmap.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0706-design-hashmap.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0706-design-hashmap.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0912 - Sort an Array](https://leetcode.com/problems/sort-an-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0912-sort-an-array.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0912-sort-an-array.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0912-sort-an-array.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0912-sort-an-array.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0912-sort-an-array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0912-sort-an-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0912-sort-an-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0912-sort-an-array.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0912-sort-an-array.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0912-sort-an-array.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0347 - Top K Frequent Elements](https://leetcode.com/problems/top-k-frequent-elements/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0347-top-k-frequent-elements.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0347-top-k-frequent-elements.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0347-top-k-frequent-elements.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0347-top-k-frequent-elements.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0347-top-k-frequent-elements.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0347-top-k-frequent-elements.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0347-top-k-frequent-elements.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0347-top-k-frequent-elements.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0347-top-k-frequent-elements.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0347-top-k-frequent-elements.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0347-top-k-frequent-elements.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0347-top-k-frequent-elements.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0347-top-k-frequent-elements.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0347-top-k-frequent-elements.ts)</div></sub>
+<sub>[0238 - Product of Array Except Self](https://leetcode.com/problems/product-of-array-except-self/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0238-product-of-array-except-self.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0238-product-of-array-except-self.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0238-product-of-array-except-self.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0238-product-of-array-except-self.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0238-product-of-array-except-self.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0238-product-of-array-except-self.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0238-product-of-array-except-self.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0238-product-of-array-except-self.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0238-product-of-array-except-self.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0238-product-of-array-except-self.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0238-product-of-array-except-self.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0238-product-of-array-except-self.ts)</div></sub>
+<sub>[0036 - Valid Sudoku](https://leetcode.com/problems/valid-sudoku/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0036-valid-sudoku.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0036-valid-sudoku.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0036-valid-sudoku.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0036-valid-sudoku.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0036-valid-sudoku.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0036-valid-sudoku.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0036-valid-sudoku.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0036-valid-sudoku.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0036-valid-sudoku.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0036-valid-sudoku.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0036-valid-sudoku.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0036-valid-sudoku.scala)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0036-valid-sudoku.ts)</div></sub>
+<sub>[0271 - Encode and Decode Strings](https://leetcode.com/problems/encode-and-decode-strings/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0271-encode-and-decode-strings.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0271-encode-and-decode-strings.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0271-encode-and-decode-strings.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0271-encode-and-decode-strings.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0271-encode-and-decode-strings.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0271-encode-and-decode-strings.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0271-encode-and-decode-strings.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0271-encode-and-decode-strings.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0271-encode-and-decode-strings.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0271-encode-and-decode-strings.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0271-encode-and-decode-strings.ts)</div></sub>
+<sub>[0128 - Longest Consecutive Sequence](https://leetcode.com/problems/longest-consecutive-sequence/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0128-longest-consecutive-sequence.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0128-longest-consecutive-sequence.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0128-longest-consecutive-sequence.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0128-longest-consecutive-sequence.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0128-longest-consecutive-sequence.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0128-longest-consecutive-sequence.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0128-longest-consecutive-sequence.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0128-longest-consecutive-sequence.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0128-longest-consecutive-sequence.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0128-longest-consecutive-sequence.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0128-longest-consecutive-sequence.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0128-longest-consecutive-sequence.ts)</div></sub>
+<sub>[0075 - Sort Colors](https://leetcode.com/problems/sort-colors/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0075-sort-colors.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0075-Sort-colors.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0075-sort-colors.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0075-sort-colors.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0075-sort-colors.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0075-sort-colors.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0075-sort-colors.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0075-sort-colors.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0075-sort-colors.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0075-sort-colors.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0075-sort-colors.ts)</div></sub>
+<sub>[0535 - Encode and Decode TinyURL](https://leetcode.com/problems/encode-and-decode-tinyurl/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0535-encode-and-decode-tinyurl.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0535-encode-and-decode-tinyurl.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0535-encode-and-decode-tinyurl.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0535-encode-and-decode-tinyurl.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0535-encode-and-decode-tinyurl.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0535-encode-and-decode-tinyurl.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0535-encode-and-decode-tinyurl.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0535-encode-and-decode-tinyurl.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0535-encode-and-decode-tinyURL.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0535-Encode-and-Decode-TinyURL.Swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0535-encode-and-decode-tinyurl.ts)</div></sub>
+<sub>[0554 - Brick Wall](https://leetcode.com/problems/brick-wall/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0554-Brick-Wall.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0554-brick-wall.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0554-brick-wall.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0554-brick-wall.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0554-brick-wall.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0554-brick-wall.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0554-brick-wall.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0554-brick-wall.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0554-brick-wall.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0554-brick-wall.ts)</div></sub>
+<sub>[0122 - Best Time to Buy And Sell Stock II](https://leetcode.com/problems/best-time-to-buy-and-sell-stock-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0122-best-time-to-buy-and-sell-stock-ii.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0122-best-time-to-buy-and-sell-stock-ii.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0122-best-time-to-buy-and-sell-stock-ii.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0122-best-time-to-buy-and-sell-stock-II.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0122-best-time-to-buy-and-sell-stock-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0122-best-time-to-buy-and-sell-stock-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0122-best-time-to-buy-and-sell-stock-ii.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0122-best-time-to-buy-and-sell-stock-ii.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0560 - Subarray Sum Equals K](https://leetcode.com/problems/subarray-sum-equals-k/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0560-subarray-sum-equals-k.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0560-subarray-sum-equals-k.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0560-subarray-sum-equals-k.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0560-subarray-sum-equals-k.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0560-subarray-sum-equals-k.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0560-subarray-sum-equals-k.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0560-subarray-sum-equals-k.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0560-subarray-sum-equals-k.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0560-subarray-sum-equals-k.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0560-subarray-sum-equals-k.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0560-subarray-sum-equals-k.ts)</div></sub>
+<sub>[1930 - Unique Length 3 Palindromic Subsequences](https://leetcode.com/problems/unique-length-3-palindromic-subsequences/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1930-unique-length-3-palindromic-subsequences.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1930-unique-length-3-palindromic-subsequences.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1930-unique-length-3-palindromic-subsequences.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1930-unique-length-3-palindromic-subsequences.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1930-unique-length-3-palindromic-subsequences.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1930-unique-length-3-palindromic-subsequences.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1930-unique-length-3-palindromic-subsequences.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F1930-unique-length-3-palindromic-subsequences.ts)</div></sub>
+<sub>[1963 - Minimum Number of Swaps to Make The String Balanced](https://leetcode.com/problems/minimum-number-of-swaps-to-make-the-string-balanced/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1963-minimum-number-of-swaps-to-make-the-string-balanced.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1963-minimum-number-of-swaps-to-make-the-string-balanced.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1963-minimum-number-of-swaps-to-make-the-string-balanced.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1963-minimum-number-of-swaps-to-make-the-string-balanced.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1963-minimum-number-of-swaps-to-make-the-string-balanced.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1963-minimum-number-of-swaps-to-make-the-string-balanced.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1963-minimum-number-of-swaps-to-make-the-string-balanced.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1963-minimum-number-of-swaps-to-make-the-string-balanced.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1963-minimum-number-of-swaps-to-make-the-string-balanced.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2001 - Number of Pairs of Interchangeable Rectangles](https://leetcode.com/problems/number-of-pairs-of-interchangeable-rectangles/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F2001-number-of-pairs-of-interchangeable-rectangles.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F2001-number-of-pairs-of-interchangeable-rectangles.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F2001-number-of-pairs-of-interchangeable-rectangles.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F2001-number-of-pairs-of-interchangeable-rectangles.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2001-number-of-pairs-of-interchangeable-rectangles.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F2001-number-of-pairs-of-interchangeable-rectangles.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F2001-number-of-pairs-of-interchangeable-rectangles.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2002 - Maximum Product of The Length of Two Palindromic Subsequences](https://leetcode.com/problems/maximum-product-of-the-length-of-two-palindromic-subsequences/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F2002-maximum-product-of-the-length-of-two-palindromic-subsequences.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F2002-maximum-product-of-the-length-of-two-palindromic-subsequences.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F2002-maximum-product-of-the-length-of-two-palindromic-subsequences.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F2002-maximum-product-of-the-length-of-two-palindromic-subsequences.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F2002-maximum-product-of-the-length-of-two-palindromic-subsequences.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F2002-maximum-product-of-the-length-of-two-palindromic-subsequences.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2002-maximum-product-of-the-length-of-two-palindromic-subsequences.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F2002-maximum-product-of-the-length-of-two-palindromic-subsequences.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F2002-maximum-product-of-the-length-of-two-palindromic-subsequences.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F2002-maximum-product-of-the-length-of-two-palindromic-subsequences.ts)</div></sub>
+<sub>[2017 - Grid Game](https://leetcode.com/problems/grid-game/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F2017-grid-game.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F2017-grid-game.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F2017-grid-game.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2017-grid-game.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F2017-grid-game.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F2017-grid-game.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0438 - Find All Anagrams in a String](https://leetcode.com/problems/find-all-anagrams-in-a-string/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0438-find-all-anagrams-in-a-string.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0438-find-all-anagrams-in-a-string.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0438-find-all-anagrams-in-a-string.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0438-find-all-anagrams-in-a-string.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0438-find-all-anagrams-in-a-string.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0438-find-all-anagrams-in-a-string.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0438-find-all-anagrams-in-a-string.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0438-find-all-anagrams-in-a-string.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0438-find-all-anagrams-in-a-string.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0438-find-all-anagrams-in-a-string.ts)</div></sub>
+<sub>[0028 - Find The Index of The First Occurrence in a String](https://leetcode.com/problems/find-the-index-of-the-first-occurrence-in-a-string/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0028-find-the-index-of-the-first-occurrence-in-a-string.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0028-find-the-index-of-the-first-occurrence-in-a-string.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0028-find-the-index-of-the-first-occurrence-in-a-string.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0028-find-the-index-of-the-first-occurrence-in-a-string.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0028-find-the-index-of-the-first-occurrence-in-a-string.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0028-find-the-index-of-the-first-occurrence-in-a-string.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0028-find-the-index-of-the-first-occurrence-in-a-string.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0028-find-the-index-of-the-first-occurrence-in-a-string.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0028-find-the-index-of-the-first-occurrence-in-a-string.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0028-find-the-index-of-the-first-occurrence-in-a-string.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0280 - Wiggle Sort](https://leetcode.com/problems/wiggle-sort/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0280-wiggle-sort.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0280-wiggle-sort.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0280-wiggle-sort.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0280-wiggle-sort.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0179 - Largest Number](https://leetcode.com/problems/largest-number/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0179-largest-number.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0179-largest-number.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0179-largest-number.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0179-largest-number.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0179-largest-number.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0179-largest-number.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0179-largest-number.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0179-largest-number.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0179-largest-number.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0179-largest-number.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0179-largest-number.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0179-largest-number.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0179-largest-number.ts)</div></sub>
+<sub>[0523 - Continuous Subarray Sum](https://leetcode.com/problems/continuous-subarray-sum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0523-continuous-subarray-sum.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0523-continuous-subarray-sum.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0523-continuous-subarray-sum.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0523-continuous-subarray-sum.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0523-continuous-subarray-sum.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0523-continuous-subarray-sum.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0523-continuous-subarray-sum.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0523-continuous-subarray-sum.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0838 - Push Dominoes](https://leetcode.com/problems/push-dominoes/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0838-push-dominoes.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0838-push-dominoes.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0838-push-dominoes.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0838-push-dominoes.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0838-push-dominoes.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0838-push-dominoes.ts)</div></sub>
+<sub>[0187 - Repeated DNA Sequences](https://leetcode.com/problems/repeated-dna-sequences/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0187-repeated-dna-sequences.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0187-repeated-dna-sequences.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0187-repeated-dna-sequences.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0187-repeated-dna-sequences.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0187-repeated-dna-sequences.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0187-repeated-dna-sequences.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0187-repeated-dna-sequences.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0187-repeated-dna-sequences.ts)</div></sub>
+<sub>[0380 - Insert Delete Get Random O(1)](https://leetcode.com/problems/insert-delete-getrandom-o1/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0380-insert-delete-getrandom-o1.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0380-insert-delete-getrandom-o1.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0380-insert-delete-getrandom-o1.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0380-insert-delete-getrandom-o1.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0380-insert-delete-getrandom-o1.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0380-insert-delete-getrandom-o1.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0380-insert-delete-getrandom-o1.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0380-insert-delete-getrandom-o1.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0380-insert-delete-getrandom-o1.ts)</div></sub>
+<sub>[1461 - Check if a String Contains all Binary Codes of Size K](https://leetcode.com/problems/check-if-a-string-contains-all-binary-codes-of-size-k/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1461-check-if-a-string-contains-all-binary-codes-of-size-k.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1461-check-if-a-string-contains-all-binary-codes-of-size-k.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1461-check-if-a-string-contains-all-binary-codes-of-size-k.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1461-check-if-a-string-contains-all-binary-codes-of-size-k.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1461-check-if-a-string-contains-all-binary-codes-of-size-k.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0304 - Range Sum Query 2D Immutable](https://leetcode.com/problems/range-sum-query-2d-immutable/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0304-range-sum-query-2d-immutable.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0304-range-sum-query-2d-immutable.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0304-range-sum-query-2d-immutable.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0304-range-sum-query-2d-immutable.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0304-range-sum-query-2d-immutable.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0304-range-sum-query-2d-immutable.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0665 - Non Decreasing Array](https://leetcode.com/problems/non-decreasing-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0665-non-decreasing-array.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0665-non-decreasing-array.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0665-non-decreasing-array.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0665-non-decreasing-array.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0665-non-decreasing-array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0665-non-decreasing-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0665-non-decreasing-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0665-non-decreasing-array.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](scala%2F0665-non-decreasing-array.scala)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0665-non-decreasing-array.ts)</div></sub>
+<sub>[0041 - First Missing Positive](https://leetcode.com/problems/first-missing-positive/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0041-first-missing-positive.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0041-first-missing-positive.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0041-first-missing-positive.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0041-first-missing-positive.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0041-first-missing-positive.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0041-first-missing-positive.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0041-first-missing-positive.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0041-first-missing-positive.ts)</div></sub>
+<sub>[1822 - Sign of An Array](https://leetcode.com/problems/sign-of-the-product-of-an-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1822-sign-of-the-product-of-an-array.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1822-sign-of-the-product-of-an-array.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1822-sign-of-the-product-of-an-array.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1822-sign-of-the-product-of-an-array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1822-sign-of-the-product-of-an-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1822-sign-of-the-product-of-an-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1822-sign-of-the-product-of-an-array.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1822-sign-of-the-product-of-an-array.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F1822-sign-of-the-product-of-an-array.ts)</div></sub>
+<sub>[2215 - Find the Difference of Two Arrays](https://leetcode.com/problems/find-the-difference-of-two-arrays/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F2215-find-the-difference-of-two-arrays.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F2215-find-the-difference-of-two-arrays.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F2215-find-the-difference-of-two-arrays.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F2215-find-the-difference-of-two-arrays.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F2215-find-the-difference-of-two-arrays.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2215-find-the-difference-of-two-arrays.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F2215-find-the-difference-of-two-arrays.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F2215-find-the-difference-of-two-arrays.ts)</div></sub>
+<sub>[1603 - Design Parking System](https://leetcode.com/problems/design-parking-system/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1603-design-parking-system.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1603-design-parking-system.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1603-design-parking-system.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1603-design-parking-system.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1603-design-parking-system.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1603-design-parking-system.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2348 - Number of Zero-Filled Subarrays](https://leetcode.com/problems/number-of-zero-filled-subarrays/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F2348-number-of-zero-filled-subarrays.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F2348-number-of-zero-filled-subarrays.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F2348-number-of-zero-filled-subarrays.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2348-number-of-zero-filled-subarrays.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F2348-number-of-zero-filled-subarrays.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2405 - Optimal Partition of String](https://leetcode.com/problems/optimal-partition-of-string/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F2405-optimal-partition-of-string.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F2405-optimal-partition-of-string.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2405-optimal-partition-of-string.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F2405-optimal-partition-of-string.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1396 - Design Underground System](https://leetcode.com/problems/design-underground-system/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](csharp%2F1396-design-underground-system.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1396-design-underground-system.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1396-design-underground-system.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1396-design-underground-system.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1396-design-underground-system.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2483 - Minimum Penalty for a Shop](https://leetcode.com/problems/minimum-penalty-for-a-shop/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F2483-minimum-penalty-for-a-shop.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F2483-minimum-penalty-for-a-shop.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2483-minimum-penalty-for-a-shop.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F2483-minimum-penalty-for-a-shop.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0068 - Text Justification](https://leetcode.com/problems/text-justification/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0068-text-justification.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0068-text-justification.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0068-text-justification.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2306 - Naming a Company](https://leetcode.com/problems/naming-a-company/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F2306-naming-a-company.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F2306-naming-a-company.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F2306-naming-a-company.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2306-naming-a-company.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F2306-naming-a-company.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
 
 ### Two Pointers
 
-<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
----- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
-<sub>[0125 - Valid Palindrome](https://leetcode.com/problems/valid-palindrome/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0125-valid-palindrome.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0125-valid-palindrome.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0125-valid-palindrome.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0125-valid-palindrome.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0125-valid-palindrome.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0125-valid-palindrome.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0125-valid-palindrome.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0125-valid-palindrome.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0125-valid-palindrome.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0125-valid-palindrome.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0125-valid-palindrome.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0125-valid-palindrome.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0125-valid-palindrome.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0125-valid-palindrome.ts)</div></sub>
-<sub>[0680 - Valid Palindrome II](https://leetcode.com/problems/valid-palindrome-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0680-valid-palindrome-ii.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0680-valid-palindrome-ii.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0680-valid-palindrome-ii.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0680-valid-palindrome-ii.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0680-valid-palindrome-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0680-valid-palindrome-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0680-valid-palindrome-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0680-valid-palindrome-ii.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0680-valid-palindrome-II.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0680-valid-palindrome-ii.ts)</div></sub>
-<sub>[1984 - Minimum Difference Between Highest And Lowest of K Scores](https://leetcode.com/problems/minimum-difference-between-highest-and-lowest-of-k-scores/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1984-minimum-difference-between-highest-and-lowest-of-k-scores.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1984-minimum-difference-between-highest-and-lowest-of-k-scores.go)</div></sub> | <sub><div align='center'>[✔️](java%2F1984-minimum-difference-between-highest-and-lowest-of-k-scores.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1984-Minimum-Difference-Between-Highest-and-Lowest-of-K-Scores.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1984-minimum-difference-between-highest-and-lowest-of-k-scores.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1984-minimum-difference-between-highest-and-lowest-of-k-scores.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1984-minimum-difference-between-highest-and-lowest-of-k-scores.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F1984-minimum-difference-between-highest-and-lowest-of-k-scores.ts)</div></sub>
-<sub>[1768 - Merge Strings Alternately](https://leetcode.com/problems/merge-strings-alternately/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1768-merge-strings-alternately.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1768-merge-strings-alternately.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1768-merge-strings-alternately.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1768-merge-strings-alternately.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1768-merge-strings-alternately.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1768-merge-strings-alternately.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F1768-merge-strings-alternately.ts)</div></sub>
-<sub>[0344 - Reverse String](https://leetcode.com/problems/reverse-string/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0344-reverse-string.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0344-Reverse-String.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0344-reverse-string.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0344-reverse-string.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0344-reverse-string.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0344-reverse-string.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0344-reverse-string.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0344-reverse-string.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0344-reverse-string.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0344-reverse-string.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0344-reverse-string.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0344-reverse-string.ts)</div></sub>
-<sub>[0088 - Merge Sorted Array](https://leetcode.com/problems/merge-sorted-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0088-merge-sorted-array.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0088-Merge-sorted-array.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0088-merge-sorted-array.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0088-merge-sorted-array.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0088-merge-sorted-array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0088-merge-sorted-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0088-merge-sorted-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0088-merge-sorted-array.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0088-merge-sorted-array.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0088-merge-sorted-array.ts)</div></sub>
-<sub>[0283 - Move Zeroes](https://leetcode.com/problems/move-zeroes/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0283-move-zeroes.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0283-move-zeroes.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0283-move-zeroes.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0283-move-zeroes.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0283-move-zeroes.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0283-move-zeroes.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0283-move-zeroes.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0283-move-zeroes.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0283-move-zeroes.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0283-Move-Zeroes.Swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0283-move-zeroes.ts)</div></sub>
-<sub>[0026 - Remove Duplicates From Sorted Array](https://leetcode.com/problems/remove-duplicates-from-sorted-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0026-remove-duplicates-from-sorted-array.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0026-remove-duplicates-from-sorted-array.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0026-remove-duplicates-from-sorted-array.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0026-remove-duplicates-from-sorted-array.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0026-remove-duplicates-from-sorted-array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0026-remove-duplicates-from-sorted-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0026-remove-duplicates-from-sorted-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0026-remove-duplicates-from-sorted-array.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0026-remove-duplicates-from-sorted-array.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0026-Remove-Duplicates-from-Sorted-Array.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0026-remove-duplicates-from-sorted-array.ts)</div></sub>
-<sub>[0080 - Remove Duplicates From Sorted Array II](https://leetcode.com/problems/remove-duplicates-from-sorted-array-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0080-remove-duplicates-from-sorted-array-ii.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0080-remove-duplicates-from-sorted-array-ii.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0080-remove-duplicates-from-sorted-array-ii.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0080-remove-duplicates-from-sorted-array-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0080-remove-duplicates-from-sorted-array-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0080-remove-duplicates-from-sorted-array-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0080-remove-duplicates-from-sorted-array-ii.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0080-remove-duplicates-from-sorted-array-ii.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0080-remove-duplicates-from-sorted-array-ii.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0167 - Two Sum II Input Array Is Sorted](https://leetcode.com/problems/two-sum-ii-input-array-is-sorted/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0167-two-sum-ii-input-array-is-sorted.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0167-two-sum-ii-input-array-is-sorted.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0167-two-sum-ii-input-array-is-sorted.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0167-two-sum-ii-input-array-is-sorted.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0167-two-sum-ii-input-array-is-sorted.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0167-two-sum-ii-input-array-is-sorted.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0167-two-sum-ii-input-array-is-sorted.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0167-two-sum-ii-input-array-is-sorted.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0167-two-sum-ii-input-array-is-sorted.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0167-two-sum-ii-input-array-is-sorted.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0167-two-sum-ii-input-array-is-sorted.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0167-two-sum-ii-input-array-is-sorted.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0167-two-sum-ii-input-array-is-sorted.ts)</div></sub>
-<sub>[0015 - 3Sum](https://leetcode.com/problems/3sum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0015-3sum.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0015-3sum.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0015-3sum.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0015-3sum.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0015-3sum.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0015-3sum.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0015-3sum.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0015-3sum.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0015-3sum.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0015-3sum.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0015-3sum.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0015-3sum.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0015-3sum.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0015-3sum.ts)</div></sub>
-<sub>[0018 - 4Sum](https://leetcode.com/problems/4sum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0018-4sum.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0018-4Sum.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0018-4sum.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0018-4sum.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0018-4sum.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0018-4sum.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0018-4sum.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0018-4sum.ts)</div></sub>
-<sub>[0011 - Container With Most Water](https://leetcode.com/problems/container-with-most-water/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0011-container-with-most-water.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0011-container-with-most-water.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0011-container-with-most-water.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0011-container-with-most-water.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0011-container-with-most-water.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0011-container-with-most-water.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0011-container-with-most-water.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0011-container-with-most-water.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0011-container-with-most-water.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0011-container-with-most-water.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0011-container-with-most-water.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0011-container-with-most-water.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0011-container-with-most-water.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0011-container-with-most-water.ts)</div></sub>
-<sub>[1498 - Number of Subsequences That Satisfy The Given Sum Condition](https://leetcode.com/problems/number-of-subsequences-that-satisfy-the-given-sum-condition/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1498-number-of-subsequences-that-satisfy-the-given-sum-condition.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1498-number-of-subsequences-that-satisfy-the-given-sum-condition.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1498-number-of-subsequences-that-satisfy-the-given-sum-condition.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0189 - Rotate Array](https://leetcode.com/problems/rotate-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0189-rotate-array.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0189-rotate-array.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0189-rotate-array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0189-rotate-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0189-rotate-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0189-rotate-array.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0189-rotate-array.ts)</div></sub>
-<sub>[1968 - Array With Elements Not Equal to Average of Neighbors](https://leetcode.com/problems/array-with-elements-not-equal-to-average-of-neighbors/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1968-array-with-elements-not-equal-to-average-of-neighbors.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1968-array-with-elements-not-equal-to-average-of-neighbors.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1968-array-with-elements-not-equal-to-average-of-neighbors.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1968-array-with-elements-not-equal-to-average-of-neighbors.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1968-array-with-elements-not-equal-to-average-of-neighbors.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1968-array-with-elements-not-equal-to-average-of-neighbors.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0881 - Boats to Save People](https://leetcode.com/problems/boats-to-save-people/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0881-boats-to-save-people.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0881-boats-to-save-people.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0881-boats-to-save-people.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0881-boats-to-save-people.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0881-boats-to-save-people.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0881-boats-to-save-people.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0881-boats-to-save-people.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0881-boats-to-save-people.ts)</div></sub>
-<sub>[0042 - Trapping Rain Water](https://leetcode.com/problems/trapping-rain-water/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0042-trapping-rain-water.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0042-trapping-rain-water.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0042-trapping-rain-water.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0042-trapping-rain-water.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0042-trapping-rain-water.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0042-trapping-rain-water.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0042-trapping-rain-water.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0042-trapping-rain-water.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0042-trapping-rain-water.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0042-trapping-rain-water.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0042-trapping-rain-water.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0042-trapping-rain-water.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0042-trapping-rain-water.ts)</div></sub>
+<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>hints</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
+---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
+<sub>[0125 - Valid Palindrome](https://leetcode.com/problems/valid-palindrome/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0125-valid-palindrome.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0125-valid-palindrome.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0125-valid-palindrome.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0125-valid-palindrome.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0125-valid-palindrome.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0125-valid-palindrome.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0125-valid-palindrome.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0125-valid-palindrome.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0125-valid-palindrome.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0125-valid-palindrome.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0125-valid-palindrome.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0125-valid-palindrome.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0125-valid-palindrome.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0125-valid-palindrome.ts)</div></sub>
+<sub>[0680 - Valid Palindrome II](https://leetcode.com/problems/valid-palindrome-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0680-valid-palindrome-ii.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0680-valid-palindrome-ii.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0680-valid-palindrome-ii.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0680-valid-palindrome-ii.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0680-valid-palindrome-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0680-valid-palindrome-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0680-valid-palindrome-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0680-valid-palindrome-ii.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0680-valid-palindrome-II.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0680-valid-palindrome-ii.ts)</div></sub>
+<sub>[1984 - Minimum Difference Between Highest And Lowest of K Scores](https://leetcode.com/problems/minimum-difference-between-highest-and-lowest-of-k-scores/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1984-minimum-difference-between-highest-and-lowest-of-k-scores.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1984-minimum-difference-between-highest-and-lowest-of-k-scores.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1984-minimum-difference-between-highest-and-lowest-of-k-scores.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1984-minimum-difference-between-highest-and-lowest-of-k-scores.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1984-minimum-difference-between-highest-and-lowest-of-k-scores.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1984-Minimum-Difference-Between-Highest-and-Lowest-of-K-Scores.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1984-minimum-difference-between-highest-and-lowest-of-k-scores.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1984-minimum-difference-between-highest-and-lowest-of-k-scores.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1984-minimum-difference-between-highest-and-lowest-of-k-scores.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F1984-minimum-difference-between-highest-and-lowest-of-k-scores.ts)</div></sub>
+<sub>[1768 - Merge Strings Alternately](https://leetcode.com/problems/merge-strings-alternately/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1768-merge-strings-alternately.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1768-merge-strings-alternately.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1768-merge-strings-alternately.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1768-merge-strings-alternately.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1768-merge-strings-alternately.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1768-merge-strings-alternately.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F1768-merge-strings-alternately.ts)</div></sub>
+<sub>[0344 - Reverse String](https://leetcode.com/problems/reverse-string/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0344-reverse-string.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0344-Reverse-String.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0344-reverse-string.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0344-reverse-string.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0344-reverse-string.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0344-reverse-string.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0344-reverse-string.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0344-reverse-string.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0344-reverse-string.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0344-reverse-string.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0344-reverse-string.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0344-reverse-string.ts)</div></sub>
+<sub>[0088 - Merge Sorted Array](https://leetcode.com/problems/merge-sorted-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0088-merge-sorted-array.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0088-Merge-sorted-array.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0088-merge-sorted-array.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0088-merge-sorted-array.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0088-merge-sorted-array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0088-merge-sorted-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0088-merge-sorted-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0088-merge-sorted-array.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0088-merge-sorted-array.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0088-merge-sorted-array.ts)</div></sub>
+<sub>[0283 - Move Zeroes](https://leetcode.com/problems/move-zeroes/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0283-move-zeroes.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0283-move-zeroes.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0283-move-zeroes.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0283-move-zeroes.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0283-move-zeroes.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0283-move-zeroes.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0283-move-zeroes.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0283-move-zeroes.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0283-move-zeroes.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0283-Move-Zeroes.Swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0283-move-zeroes.ts)</div></sub>
+<sub>[0026 - Remove Duplicates From Sorted Array](https://leetcode.com/problems/remove-duplicates-from-sorted-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0026-remove-duplicates-from-sorted-array.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0026-remove-duplicates-from-sorted-array.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0026-remove-duplicates-from-sorted-array.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0026-remove-duplicates-from-sorted-array.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0026-remove-duplicates-from-sorted-array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0026-remove-duplicates-from-sorted-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0026-remove-duplicates-from-sorted-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0026-remove-duplicates-from-sorted-array.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0026-remove-duplicates-from-sorted-array.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0026-Remove-Duplicates-from-Sorted-Array.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0026-remove-duplicates-from-sorted-array.ts)</div></sub>
+<sub>[0080 - Remove Duplicates From Sorted Array II](https://leetcode.com/problems/remove-duplicates-from-sorted-array-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0080-remove-duplicates-from-sorted-array-ii.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0080-remove-duplicates-from-sorted-array-ii.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0080-remove-duplicates-from-sorted-array-ii.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0080-remove-duplicates-from-sorted-array-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0080-remove-duplicates-from-sorted-array-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0080-remove-duplicates-from-sorted-array-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0080-remove-duplicates-from-sorted-array-ii.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0080-remove-duplicates-from-sorted-array-ii.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0080-remove-duplicates-from-sorted-array-ii.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0167 - Two Sum II Input Array Is Sorted](https://leetcode.com/problems/two-sum-ii-input-array-is-sorted/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0167-two-sum-ii-input-array-is-sorted.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0167-two-sum-ii-input-array-is-sorted.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0167-two-sum-ii-input-array-is-sorted.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0167-two-sum-ii-input-array-is-sorted.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0167-two-sum-ii-input-array-is-sorted.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0167-two-sum-ii-input-array-is-sorted.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0167-two-sum-ii-input-array-is-sorted.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0167-two-sum-ii-input-array-is-sorted.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0167-two-sum-ii-input-array-is-sorted.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0167-two-sum-ii-input-array-is-sorted.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0167-two-sum-ii-input-array-is-sorted.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0167-two-sum-ii-input-array-is-sorted.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0167-two-sum-ii-input-array-is-sorted.ts)</div></sub>
+<sub>[0015 - 3Sum](https://leetcode.com/problems/3sum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0015-3sum.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0015-3sum.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0015-3sum.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0015-3sum.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0015-3sum.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0015-3sum.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0015-3sum.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0015-3sum.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0015-3sum.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0015-3sum.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0015-3sum.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0015-3sum.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0015-3sum.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0015-3sum.ts)</div></sub>
+<sub>[0018 - 4Sum](https://leetcode.com/problems/4sum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0018-4sum.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0018-4Sum.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0018-4sum.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0018-4sum.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0018-4sum.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0018-4sum.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0018-4sum.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0018-4sum.ts)</div></sub>
+<sub>[0011 - Container With Most Water](https://leetcode.com/problems/container-with-most-water/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0011-container-with-most-water.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0011-container-with-most-water.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0011-container-with-most-water.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0011-container-with-most-water.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0011-container-with-most-water.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0011-container-with-most-water.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0011-container-with-most-water.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0011-container-with-most-water.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0011-container-with-most-water.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0011-container-with-most-water.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0011-container-with-most-water.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0011-container-with-most-water.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0011-container-with-most-water.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0011-container-with-most-water.ts)</div></sub>
+<sub>[1498 - Number of Subsequences That Satisfy The Given Sum Condition](https://leetcode.com/problems/number-of-subsequences-that-satisfy-the-given-sum-condition/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1498-number-of-subsequences-that-satisfy-the-given-sum-condition.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1498-number-of-subsequences-that-satisfy-the-given-sum-condition.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1498-number-of-subsequences-that-satisfy-the-given-sum-condition.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1498-number-of-subsequences-that-satisfy-the-given-sum-condition.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0189 - Rotate Array](https://leetcode.com/problems/rotate-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0189-rotate-array.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0189-rotate-array.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0189-rotate-array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0189-rotate-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0189-rotate-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0189-rotate-array.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0189-rotate-array.ts)</div></sub>
+<sub>[1968 - Array With Elements Not Equal to Average of Neighbors](https://leetcode.com/problems/array-with-elements-not-equal-to-average-of-neighbors/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1968-array-with-elements-not-equal-to-average-of-neighbors.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1968-array-with-elements-not-equal-to-average-of-neighbors.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1968-array-with-elements-not-equal-to-average-of-neighbors.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1968-array-with-elements-not-equal-to-average-of-neighbors.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1968-array-with-elements-not-equal-to-average-of-neighbors.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1968-array-with-elements-not-equal-to-average-of-neighbors.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1968-array-with-elements-not-equal-to-average-of-neighbors.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0881 - Boats to Save People](https://leetcode.com/problems/boats-to-save-people/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0881-boats-to-save-people.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0881-boats-to-save-people.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0881-boats-to-save-people.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0881-boats-to-save-people.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0881-boats-to-save-people.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0881-boats-to-save-people.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0881-boats-to-save-people.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0881-boats-to-save-people.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0881-boats-to-save-people.ts)</div></sub>
+<sub>[0042 - Trapping Rain Water](https://leetcode.com/problems/trapping-rain-water/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0042-trapping-rain-water.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0042-trapping-rain-water.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0042-trapping-rain-water.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0042-trapping-rain-water.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0042-trapping-rain-water.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0042-trapping-rain-water.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0042-trapping-rain-water.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0042-trapping-rain-water.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0042-trapping-rain-water.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0042-trapping-rain-water.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0042-trapping-rain-water.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0042-trapping-rain-water.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0042-trapping-rain-water.ts)</div></sub>
 
 ### Sliding Window
 
-<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
----- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
-<sub>[0121 - Best Time to Buy And Sell Stock](https://leetcode.com/problems/best-time-to-buy-and-sell-stock/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0121-best-time-to-buy-and-sell-stock.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0121-best-time-to-buy-and-sell-stock.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0121-best-time-to-buy-and-sell-stock.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0121-best-time-to-buy-and-sell-stock.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0121-best-time-to-buy-and-sell-stock.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0121-best-time-to-buy-and-sell-stock.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0121-best-time-to-buy-and-sell-stock.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0121-best-time-to-buy-and-sell-stock.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0121-best-time-to-buy-and-sell-stock.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0121-best-time-to-buy-and-sell-stock.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0121-best-time-to-buy-and-sell-stock.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0121-best-time-to-buy-and-sell-stock.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0121-best-time-to-buy-and-sell-stock.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0121-best-time-to-buy-and-sell-stock.ts)</div></sub>
-<sub>[0219 - Contains Duplicate II](https://leetcode.com/problems/contains-duplicate-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0219-contains-duplicate-ii.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0219-contains-duplicate-ii.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0219-contains-duplicate-ii.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0219-contains-duplicate-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0219-contains-duplicate-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0219-contains-duplicate-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0219-contains-duplicate-ii.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0219-contains-duplicate-ii.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0219-contains-duplicate-ii.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0219-contains-duplicate-ii.ts)</div></sub>
-<sub>[1343 - Number of Sub Arrays of Size K and Avg Greater than or Equal to Threshold](https://leetcode.com/problems/number-of-sub-arrays-of-size-k-and-average-greater-than-or-equal-to-threshold/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1343-number-of-sub-arrays-of-size-k-and-average-greater-than-or-equal-to-threshold.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1343-number-of-sub-arrays-of-size-k-and-average-greater-than-or-equal-to-threshold.go)</div></sub> | <sub><div align='center'>[✔️](java%2F1343-number-of-sub-arrays-of-size-k-and-average-greater-than-or-equal-to-threshold.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1343-number-of-sub-arrays-of-size-k-and-average-greater-than-or-equal-to-threshold.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1343-number-of-sub-arrays-of-size-k-and-average-greater-than-or-equal-to-threshold.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1343-number-of-sub-arrays-of-size-k-and-average-greater-than-or-equal-to-threshold.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1343-number-of-sub-arrays-of-size-k-and-average-greater-than-or-equal-to-threshold.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0003 - Longest Substring Without Repeating Characters](https://leetcode.com/problems/longest-substring-without-repeating-characters/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0003-longest-substring-without-repeating-characters.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0003-longest-substring-without-repeating-characters.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0003-longest-substring-without-repeating-characters.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0003-longest-substring-without-repeating-characters.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0003-longest-substring-without-repeating-characters.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0003-longest-substring-without-repeating-characters.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0003-longest-substring-without-repeating-characters.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0003-longest-substring-without-repeating-characters.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0003-longest-substring-without-repeating-characters.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0003-longest-substring-without-repeating-characters.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0003-longest-substring-without-repeating-characters.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0003-longest-substring-without-repeating-characters.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0003-longest-substring-without-repeating-characters.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0003-longest-substring-without-repeating-characters.ts)</div></sub>
-<sub>[0424 - Longest Repeating Character Replacement](https://leetcode.com/problems/longest-repeating-character-replacement/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0424-longest-repeating-character-replacement.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0424-longest-repeating-character-replacement.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0424-longest-repeating-character-replacement.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0424-longest-repeating-character-replacement.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0424-longest-repeating-character-replacement.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0424-longest-repeating-character-replacement.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0424-longest-repeating-character-replacement.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0424-longest-repeating-character-replacement.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0424-longest-repeating-character-replacement.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0424-longest-repeating-character-replacement.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0424-longest-repeating-character-replacement.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0424-longest-repeating-character-replacement.ts)</div></sub>
-<sub>[0567 - Permutation In String](https://leetcode.com/problems/permutation-in-string/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0567-permutation-in-string.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0567-permutation-in-string.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0567-permutation-in-string.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0567-permutation-in-string.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0567-permutation-in-string.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0567-permutation-in-string.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0567-permutation-in-string.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0567-permutation-in-string.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0567-permutation-in-string.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0567-permutation-in-string.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0567-permutation-in-string.ts)</div></sub>
-<sub>[1838 - Frequency of The Most Frequent Element](https://leetcode.com/problems/frequency-of-the-most-frequent-element/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1838-frequency-of-the-most-frequent-element.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1838-frequency-of-the-most-frequent-element.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1838-Frequency-Of-The-Most-Frequent-Element.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1838-frequency-of-the-most-frequent-element.go)</div></sub> | <sub><div align='center'>[✔️](java%2F1838-frequency-of-the-most-frequent-element.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1838-frequency-of-the-most-frequent-element.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1838-frequency-of-the-most-frequent-element.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1838-frequency-of-the-most-frequent-element.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1838-frequency-of-the-most-frequent-element.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F1838-frequency-of-the-most-frequent-element.ts)</div></sub>
-<sub>[0904 - Fruits into Basket](https://leetcode.com/problems/fruit-into-baskets/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0904-fruit-into-baskets.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0904-fruit-into-baskets.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0904-fruit-into-baskets.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0904-fruit-into-baskets.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0904-fruit-into-baskets.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0904-fruit-into-baskets.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0904-fruit-into-baskets.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0904-fruit-into-baskets.ts)</div></sub>
-<sub>[1456 - Maximum Number of Vowels in a Substring of Given Length](https://leetcode.com/problems/maximum-number-of-vowels-in-a-substring-of-given-length/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1456-maximum-number-of-vowels-in-a-substring-of-given-length.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1456-maximum-number-of-vowels-in-a-substring-of-given-length.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1456-maximum-number-of-vowels-in-a-substring-of-given-length.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1456-maximum-number-of-vowels-in-a-substring-of-given-length.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1456-maximum-number-of-vowels-in-a-substring-of-given-length.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1888 - Minimum Number of Flips to Make The Binary String Alternating](https://leetcode.com/problems/minimum-number-of-flips-to-make-the-binary-string-alternating/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1888-minimum-number-of-flips-to-make-the-binary-string-alternating.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F1888-minimum-number-of-flips-to-make-the-binary-string-alternating.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1888-minimum-number-of-flips-to-make-the-binary-string-alternating.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1888-minimum-number-of-flips-to-make-the-binary-string-alternating.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F1888-minimum-number-of-flips-to-make-the-binary-string-alternating.ts)</div></sub>
-<sub>[0209 - Minimum Size Subarray Sum](https://leetcode.com/problems/minimum-size-subarray-sum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0209-minimum-size-subarray-sum.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0209-minimum-size-subarray-sum.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0209-minimum-size-subarray-sum.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0209-minimum-size-subarray-sum.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0209-minimum-size-subarray-sum.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0209-minimum-size-subarray-sum.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0209-minimum-size-subarray-sum.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0209-minimum-size-subarray-sum.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0658 - Find K Closest Elements](https://leetcode.com/problems/find-k-closest-elements/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0658-find-k-closest-elements.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0658-find-k-closest-elements.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0658-find-k-closest-elements.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0658-find-k-closest-elements.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0658-find-k-closest-elements.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0658-find-k-closest-elements.ts)</div></sub>
-<sub>[1658 - Minimum Operations to Reduce X to Zero](https://leetcode.com/problems/minimum-operations-to-reduce-x-to-zero/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1658-minimum-operations-to-reduce-x-to-zero.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1658-minimum-operations-to-reduce-x-to-zero.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1658-minimum-operations-to-reduce-x-to-zero.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0076 - Minimum Window Substring](https://leetcode.com/problems/minimum-window-substring/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0076-minimum-window-substring.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0076-minimum-window-substring.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0076-minimum-window-substring.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0076-minimum-window-substring.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0076-minimum-window-substring.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0076-minimum-window-substring.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0076-minimum-window-substring.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0076-minimum-window-substring.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0076-minimum-window-substring.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0076-minimum-window-substring.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0076-minimum-window-substring.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0076-minimum-window-substring.ts)</div></sub>
-<sub>[0239 - Sliding Window Maximum](https://leetcode.com/problems/sliding-window-maximum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0239-sliding-window-maximum.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0239-sliding-window-maximum.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0239-sliding-window-maximum.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0239-sliding-window-maximum.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0239-sliding-window-maximum.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0239-sliding-window-maximum.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0239-sliding-window-maximum.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0239-sliding-window-maximum.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0239-sliding-window-maximum.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0239-sliding-window-maximum.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0239-sliding-window-maximum.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0239-sliding-window-maximum.ts)</div></sub>
+<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>hints</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
+---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
+<sub>[0121 - Best Time to Buy And Sell Stock](https://leetcode.com/problems/best-time-to-buy-and-sell-stock/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0121-best-time-to-buy-and-sell-stock.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0121-best-time-to-buy-and-sell-stock.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0121-best-time-to-buy-and-sell-stock.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0121-best-time-to-buy-and-sell-stock.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0121-best-time-to-buy-and-sell-stock.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0121-best-time-to-buy-and-sell-stock.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0121-best-time-to-buy-and-sell-stock.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0121-best-time-to-buy-and-sell-stock.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0121-best-time-to-buy-and-sell-stock.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0121-best-time-to-buy-and-sell-stock.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0121-best-time-to-buy-and-sell-stock.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0121-best-time-to-buy-and-sell-stock.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0121-best-time-to-buy-and-sell-stock.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0121-best-time-to-buy-and-sell-stock.ts)</div></sub>
+<sub>[0219 - Contains Duplicate II](https://leetcode.com/problems/contains-duplicate-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0219-contains-duplicate-ii.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0219-contains-duplicate-ii.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0219-contains-duplicate-ii.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0219-contains-duplicate-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0219-contains-duplicate-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0219-contains-duplicate-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0219-contains-duplicate-ii.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0219-contains-duplicate-ii.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0219-contains-duplicate-ii.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0219-contains-duplicate-ii.ts)</div></sub>
+<sub>[1343 - Number of Sub Arrays of Size K and Avg Greater than or Equal to Threshold](https://leetcode.com/problems/number-of-sub-arrays-of-size-k-and-average-greater-than-or-equal-to-threshold/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1343-number-of-sub-arrays-of-size-k-and-average-greater-than-or-equal-to-threshold.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1343-number-of-sub-arrays-of-size-k-and-average-greater-than-or-equal-to-threshold.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1343-number-of-sub-arrays-of-size-k-and-average-greater-than-or-equal-to-threshold.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1343-number-of-sub-arrays-of-size-k-and-average-greater-than-or-equal-to-threshold.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1343-number-of-sub-arrays-of-size-k-and-average-greater-than-or-equal-to-threshold.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1343-number-of-sub-arrays-of-size-k-and-average-greater-than-or-equal-to-threshold.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1343-number-of-sub-arrays-of-size-k-and-average-greater-than-or-equal-to-threshold.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1343-number-of-sub-arrays-of-size-k-and-average-greater-than-or-equal-to-threshold.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0003 - Longest Substring Without Repeating Characters](https://leetcode.com/problems/longest-substring-without-repeating-characters/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0003-longest-substring-without-repeating-characters.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0003-longest-substring-without-repeating-characters.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0003-longest-substring-without-repeating-characters.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0003-longest-substring-without-repeating-characters.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0003-longest-substring-without-repeating-characters.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0003-longest-substring-without-repeating-characters.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0003-longest-substring-without-repeating-characters.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0003-longest-substring-without-repeating-characters.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0003-longest-substring-without-repeating-characters.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0003-longest-substring-without-repeating-characters.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0003-longest-substring-without-repeating-characters.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0003-longest-substring-without-repeating-characters.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0003-longest-substring-without-repeating-characters.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0003-longest-substring-without-repeating-characters.ts)</div></sub>
+<sub>[0424 - Longest Repeating Character Replacement](https://leetcode.com/problems/longest-repeating-character-replacement/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0424-longest-repeating-character-replacement.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0424-longest-repeating-character-replacement.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0424-longest-repeating-character-replacement.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0424-longest-repeating-character-replacement.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0424-longest-repeating-character-replacement.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0424-longest-repeating-character-replacement.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0424-longest-repeating-character-replacement.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0424-longest-repeating-character-replacement.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0424-longest-repeating-character-replacement.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0424-longest-repeating-character-replacement.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0424-longest-repeating-character-replacement.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0424-longest-repeating-character-replacement.ts)</div></sub>
+<sub>[0567 - Permutation In String](https://leetcode.com/problems/permutation-in-string/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0567-permutation-in-string.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0567-permutation-in-string.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0567-permutation-in-string.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0567-permutation-in-string.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0567-permutation-in-string.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0567-permutation-in-string.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0567-permutation-in-string.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0567-permutation-in-string.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0567-permutation-in-string.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0567-permutation-in-string.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0567-permutation-in-string.ts)</div></sub>
+<sub>[1838 - Frequency of The Most Frequent Element](https://leetcode.com/problems/frequency-of-the-most-frequent-element/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1838-frequency-of-the-most-frequent-element.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1838-frequency-of-the-most-frequent-element.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1838-Frequency-Of-The-Most-Frequent-Element.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1838-frequency-of-the-most-frequent-element.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1838-frequency-of-the-most-frequent-element.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1838-frequency-of-the-most-frequent-element.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1838-frequency-of-the-most-frequent-element.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1838-frequency-of-the-most-frequent-element.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1838-frequency-of-the-most-frequent-element.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F1838-frequency-of-the-most-frequent-element.ts)</div></sub>
+<sub>[0904 - Fruits into Basket](https://leetcode.com/problems/fruit-into-baskets/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0904-fruit-into-baskets.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0904-fruit-into-baskets.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0904-fruit-into-baskets.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0904-fruit-into-baskets.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0904-fruit-into-baskets.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0904-fruit-into-baskets.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0904-fruit-into-baskets.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0904-fruit-into-baskets.ts)</div></sub>
+<sub>[1456 - Maximum Number of Vowels in a Substring of Given Length](https://leetcode.com/problems/maximum-number-of-vowels-in-a-substring-of-given-length/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1456-maximum-number-of-vowels-in-a-substring-of-given-length.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1456-maximum-number-of-vowels-in-a-substring-of-given-length.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1456-maximum-number-of-vowels-in-a-substring-of-given-length.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1456-maximum-number-of-vowels-in-a-substring-of-given-length.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1456-maximum-number-of-vowels-in-a-substring-of-given-length.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1456-maximum-number-of-vowels-in-a-substring-of-given-length.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1888 - Minimum Number of Flips to Make The Binary String Alternating](https://leetcode.com/problems/minimum-number-of-flips-to-make-the-binary-string-alternating/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1888-minimum-number-of-flips-to-make-the-binary-string-alternating.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F1888-minimum-number-of-flips-to-make-the-binary-string-alternating.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1888-minimum-number-of-flips-to-make-the-binary-string-alternating.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1888-minimum-number-of-flips-to-make-the-binary-string-alternating.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F1888-minimum-number-of-flips-to-make-the-binary-string-alternating.ts)</div></sub>
+<sub>[0209 - Minimum Size Subarray Sum](https://leetcode.com/problems/minimum-size-subarray-sum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0209-minimum-size-subarray-sum.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0209-minimum-size-subarray-sum.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0209-minimum-size-subarray-sum.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0209-minimum-size-subarray-sum.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0209-minimum-size-subarray-sum.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0209-minimum-size-subarray-sum.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0209-minimum-size-subarray-sum.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0209-minimum-size-subarray-sum.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0658 - Find K Closest Elements](https://leetcode.com/problems/find-k-closest-elements/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0658-find-k-closest-elements.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0658-find-k-closest-elements.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0658-find-k-closest-elements.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0658-find-k-closest-elements.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0658-find-k-closest-elements.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0658-find-k-closest-elements.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0658-find-k-closest-elements.ts)</div></sub>
+<sub>[1658 - Minimum Operations to Reduce X to Zero](https://leetcode.com/problems/minimum-operations-to-reduce-x-to-zero/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1658-minimum-operations-to-reduce-x-to-zero.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1658-minimum-operations-to-reduce-x-to-zero.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1658-minimum-operations-to-reduce-x-to-zero.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1658-minimum-operations-to-reduce-x-to-zero.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0076 - Minimum Window Substring](https://leetcode.com/problems/minimum-window-substring/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0076-minimum-window-substring.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0076-minimum-window-substring.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0076-minimum-window-substring.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0076-minimum-window-substring.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0076-minimum-window-substring.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0076-minimum-window-substring.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0076-minimum-window-substring.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0076-minimum-window-substring.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0076-minimum-window-substring.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0076-minimum-window-substring.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0076-minimum-window-substring.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0076-minimum-window-substring.ts)</div></sub>
+<sub>[0239 - Sliding Window Maximum](https://leetcode.com/problems/sliding-window-maximum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0239-sliding-window-maximum.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0239-sliding-window-maximum.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0239-sliding-window-maximum.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0239-sliding-window-maximum.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0239-sliding-window-maximum.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0239-sliding-window-maximum.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0239-sliding-window-maximum.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0239-sliding-window-maximum.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0239-sliding-window-maximum.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0239-sliding-window-maximum.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0239-sliding-window-maximum.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0239-sliding-window-maximum.ts)</div></sub>
 
 ### Stack
 
-<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
----- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
-<sub>[0020 - Valid Parentheses](https://leetcode.com/problems/valid-parentheses/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0020-valid-parentheses.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0020-valid-parentheses.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0020-valid-parentheses.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0020-valid-parentheses.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0020-valid-parentheses.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0020-valid-parentheses.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0020-valid-parentheses.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0020-valid-parentheses.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0020-valid-parentheses.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0020-valid-parentheses.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0020-valid-parentheses.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0020-valid-parentheses.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0020-valid-parentheses.ts)</div></sub>
-<sub>[0682 - Baseball Game](https://leetcode.com/problems/baseball-game/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0682-baseball-game.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0682-baseball-game.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0682-baseball-game.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0682-baseball-game.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0682-baseball-game.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0682-Baseball-Game.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0682-baseball-game.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0682-baseball-game.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0682-baseball-game.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0682-baseball-game.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0682-baseball-game.ts)</div></sub>
-<sub>[0225 - Implement Stack Using Queues](https://leetcode.com/problems/implement-stack-using-queues/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0225-implement-stack-using-queues.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0225-implement-stack-using-queues.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0225-implement-stack-using-queues.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0225-implement-stack-using-queues.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0225-implement-stack-using-queues.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0225-implement-stack-using-queues.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0225-implement-stack-using-queues.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0225-implement-stack-using-queues.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0225-implement-stack-using-queues.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0225-implement-stack-using-queues.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0225-implement-stack-using-queues.ts)</div></sub>
-<sub>[0155 - Min Stack](https://leetcode.com/problems/min-stack/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0155-min-stack.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0155-min-stack.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0155-min-stack.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0155-min-stack.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0155-min-stack.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0155-min-stack.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0155-min-stack.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0155-min-stack.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0155-min-stack.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0155-min-stack.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0155-min-stack.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0155-min-stack.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0155-min-stack.ts)</div></sub>
-<sub>[0150 - Evaluate Reverse Polish Notation](https://leetcode.com/problems/evaluate-reverse-polish-notation/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0150-evaluate-reverse-polish-notation.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0150-evaluate-reverse-polish-notation.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0150-evaluate-reverse-polish-notation.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0150-evaluate-reverse-polish-notation.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0150-evaluate-reverse-polish-notation.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0150-evaluate-reverse-polish-notation.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0150-evaluate-reverse-polish-notation.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0150-evaluate-reverse-polish-notation.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0150-evaluate-reverse-polish-notation.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0150-evaluate-reverse-polish-notation.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0150-evaluate-reverse-polish-notation.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0150-evaluate-reverse-polish-notation.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0150-evaluate-reverse-polish-notation.ts)</div></sub>
-<sub>[2390 - Removing Stars From a String](https://leetcode.com/problems/removing-stars-from-a-string/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F2390-removing-stars-from-a-string.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F2390-removing-stars-from-a-string.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F2390-removing-stars-from-a-string.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F2390-removing-stars-from-a-string.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2390-removing-stars-from-a-string.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F2390-removing-stars-from-a-string.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F2390-removing-stars-from-a-string.ts)</div></sub>
-<sub>[0946 - Validate Stack Sequences](https://leetcode.com/problems/validate-stack-sequences/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0946-validate-stack-sequences.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0946-validate-stack-sequences.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0946-validate-stack-sequences.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0946-validate-stack-sequences.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0022 - Generate Parentheses](https://leetcode.com/problems/generate-parentheses/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0022-generate-parentheses.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0022-generate-parentheses.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0022-generate-parentheses.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0022-generate-parentheses.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0022-generate-parentheses.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0022-generate-parentheses.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0022-generate-parentheses.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0022-generate-parentheses.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0022-generate-parentheses.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0022-generate-parentheses.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0022-generate-parentheses.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0022-generate-parentheses.ts)</div></sub>
-<sub>[0735 - Asteroid Collision](https://leetcode.com/problems/asteroid-collision/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0735-asteroid-collision.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0735-asteroid-collision.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0735-asteroid-collision.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0735-asteroid-collision.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0735-asteroid-collision.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0735-asteroid-collision.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0735-asteroid-collision.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0735-asteroid-collision.ts)</div></sub>
-<sub>[0739 - Daily Temperatures](https://leetcode.com/problems/daily-temperatures/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0739-daily-temperatures.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0739-daily-temperatures.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0739-daily-temperatures.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0739-daily-temperatures.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0739-daily-temperatures.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0739-daily-temperatures.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0739-daily-temperatures.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0739-daily-temperatures.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0739-daily-temperatures.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0739-daily-temperatures.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0739-daily-temperatures.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0739-daily-temperatures.ts)</div></sub>
-<sub>[0901 - Online Stock Span](https://leetcode.com/problems/online-stock-span/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0901-online-stock-span.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0901-online-stock-span.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0901-online-stock-span.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0901-online-stock-span.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0901-online-stock-span.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0901-online-stock-span.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0901-online-stock-span.ts)</div></sub>
-<sub>[0853 - Car Fleet](https://leetcode.com/problems/car-fleet/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0853-car-fleet.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0853-car-fleet.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0853-car-fleet.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0853-car-fleet.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0853-car-fleet.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0853-car-fleet.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0853-car-fleet.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0853-car-fleet.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0853-car-fleet.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0853-car-fleet.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0853-car-fleet.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0853-car-fleet.ts)</div></sub>
-<sub>[0071 - Simplify Path](https://leetcode.com/problems/simplify-path/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0071-simplify-path.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0071-simplify-path.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0071-simplify-path.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0071-simplify-path.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0071-simplify-path.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0071-simplify-path.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0071-simplify-path.ts)</div></sub>
-<sub>[0394 - Decode String](https://leetcode.com/problems/decode-string/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0394-decode-string.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0394-decode-string.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0394-decode-string.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0394-decode-string.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0394-decode-string.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0394-decode-string.scala)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0394-decode-string.ts)</div></sub>
-<sub>[0402 - Remove K Digits](https://leetcode.com/problems/remove-k-digits/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0402-remove-k-digits.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0402-remove-k-digits.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0402-remove-k-digits.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0402-remove-k-digits.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0402-remove-k-digits.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0402-remove-k-digits.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0402-remove-k-digits.ts)</div></sub>
-<sub>[1209 - Remove All Adjacent Duplicates In String II](https://leetcode.com/problems/remove-all-adjacent-duplicates-in-string-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1209-Remove-All-Adjacent-Duplicates-in-String-II.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1209-remove-all-adjacent-duplicates-in-string-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1209-Remove-All-Adjacent-Duplicates-in-String-II.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1209-remove-all-adjacent-duplicates-in-string-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1209-remove-all-adjacent-duplicates-in-string-ii.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1209-remove-all-adjacent-duplicates-in-string-II.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F1209-remove-all-adjacent-duplicates-in-string-II.ts)</div></sub>
-<sub>[0456 - 132 Pattern](https://leetcode.com/problems/132-pattern/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0456-132-pattern.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0456-132-pattern.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0456-132-pattern.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0456-132-pattern.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0456-132-pattern.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0456-132-pattern.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0456-132-pattern.ts)</div></sub>
-<sub>[0895 - Maximum Frequency Stack](https://leetcode.com/problems/maximum-frequency-stack/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0895-maximum-frequency-stack.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0895-maximum-frequency-stack.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0895-maximum-frequency-stack.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0895-maximum-frequency-stack.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0895-maximum-frequency-stack.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0895-maximum-frequency-stack.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0895-maximum-frequency-stack.ts)</div></sub>
-<sub>[0084 - Largest Rectangle In Histogram](https://leetcode.com/problems/largest-rectangle-in-histogram/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0084-largest-rectangle-in-histogram.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0084-largest-rectangle-in-histogram.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0084-largest-rectangle-in-histogram.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0084-largest-rectangle-in-histogram.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0084-largest-rectangle-in-histogram.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0084-largest-rectangle-in-histogram.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0084-largest-rectangle-in-histogram.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0084-largest-rectangle-in-histogram.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0084-largest-rectangle-in-histogram.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0084-largest-rectangle-in-histogram.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0084-largest-rectangle-in-histogram.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0084-largest-rectangle-in-histogram.ts)</div></sub>
+<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>hints</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
+---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
+<sub>[0020 - Valid Parentheses](https://leetcode.com/problems/valid-parentheses/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0020-valid-parentheses.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0020-valid-parentheses.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0020-valid-parentheses.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0020-valid-parentheses.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0020-valid-parentheses.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0020-valid-parentheses.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0020-valid-parentheses.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0020-valid-parentheses.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0020-valid-parentheses.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0020-valid-parentheses.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0020-valid-parentheses.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0020-valid-parentheses.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0020-valid-parentheses.ts)</div></sub>
+<sub>[0682 - Baseball Game](https://leetcode.com/problems/baseball-game/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0682-baseball-game.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0682-baseball-game.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0682-baseball-game.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0682-baseball-game.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0682-baseball-game.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0682-Baseball-Game.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0682-baseball-game.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0682-baseball-game.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0682-baseball-game.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0682-baseball-game.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0682-baseball-game.ts)</div></sub>
+<sub>[0225 - Implement Stack Using Queues](https://leetcode.com/problems/implement-stack-using-queues/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0225-implement-stack-using-queues.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0225-implement-stack-using-queues.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0225-implement-stack-using-queues.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0225-implement-stack-using-queues.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0225-implement-stack-using-queues.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0225-implement-stack-using-queues.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0225-implement-stack-using-queues.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0225-implement-stack-using-queues.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0225-implement-stack-using-queues.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0225-implement-stack-using-queues.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0225-implement-stack-using-queues.ts)</div></sub>
+<sub>[0155 - Min Stack](https://leetcode.com/problems/min-stack/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0155-min-stack.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0155-min-stack.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0155-min-stack.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0155-min-stack.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0155-min-stack.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0155-min-stack.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0155-min-stack.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0155-min-stack.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0155-min-stack.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0155-min-stack.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0155-min-stack.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0155-min-stack.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0155-min-stack.ts)</div></sub>
+<sub>[0150 - Evaluate Reverse Polish Notation](https://leetcode.com/problems/evaluate-reverse-polish-notation/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0150-evaluate-reverse-polish-notation.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0150-evaluate-reverse-polish-notation.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0150-evaluate-reverse-polish-notation.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0150-evaluate-reverse-polish-notation.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0150-evaluate-reverse-polish-notation.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0150-evaluate-reverse-polish-notation.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0150-evaluate-reverse-polish-notation.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0150-evaluate-reverse-polish-notation.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0150-evaluate-reverse-polish-notation.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0150-evaluate-reverse-polish-notation.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0150-evaluate-reverse-polish-notation.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0150-evaluate-reverse-polish-notation.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0150-evaluate-reverse-polish-notation.ts)</div></sub>
+<sub>[2390 - Removing Stars From a String](https://leetcode.com/problems/removing-stars-from-a-string/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F2390-removing-stars-from-a-string.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F2390-removing-stars-from-a-string.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F2390-removing-stars-from-a-string.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F2390-removing-stars-from-a-string.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2390-removing-stars-from-a-string.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F2390-removing-stars-from-a-string.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F2390-removing-stars-from-a-string.ts)</div></sub>
+<sub>[0946 - Validate Stack Sequences](https://leetcode.com/problems/validate-stack-sequences/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0946-validate-stack-sequences.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0946-validate-stack-sequences.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0946-validate-stack-sequences.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0946-validate-stack-sequences.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0022 - Generate Parentheses](https://leetcode.com/problems/generate-parentheses/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0022-generate-parentheses.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0022-generate-parentheses.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0022-generate-parentheses.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0022-generate-parentheses.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0022-generate-parentheses.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0022-generate-parentheses.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0022-generate-parentheses.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0022-generate-parentheses.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0022-generate-parentheses.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0022-generate-parentheses.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0022-generate-parentheses.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0022-generate-parentheses.ts)</div></sub>
+<sub>[0735 - Asteroid Collision](https://leetcode.com/problems/asteroid-collision/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0735-asteroid-collision.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0735-asteroid-collision.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0735-asteroid-collision.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0735-asteroid-collision.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0735-asteroid-collision.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0735-asteroid-collision.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0735-asteroid-collision.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0735-asteroid-collision.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0735-asteroid-collision.ts)</div></sub>
+<sub>[0739 - Daily Temperatures](https://leetcode.com/problems/daily-temperatures/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0739-daily-temperatures.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0739-daily-temperatures.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0739-daily-temperatures.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0739-daily-temperatures.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0739-daily-temperatures.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0739-daily-temperatures.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0739-daily-temperatures.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0739-daily-temperatures.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0739-daily-temperatures.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0739-daily-temperatures.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0739-daily-temperatures.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0739-daily-temperatures.ts)</div></sub>
+<sub>[0901 - Online Stock Span](https://leetcode.com/problems/online-stock-span/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0901-online-stock-span.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0901-online-stock-span.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0901-online-stock-span.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0901-online-stock-span.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0901-online-stock-span.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0901-online-stock-span.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0901-online-stock-span.ts)</div></sub>
+<sub>[0853 - Car Fleet](https://leetcode.com/problems/car-fleet/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0853-car-fleet.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0853-car-fleet.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0853-car-fleet.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0853-car-fleet.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0853-car-fleet.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0853-car-fleet.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0853-car-fleet.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0853-car-fleet.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0853-car-fleet.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0853-car-fleet.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0853-car-fleet.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0853-car-fleet.ts)</div></sub>
+<sub>[0071 - Simplify Path](https://leetcode.com/problems/simplify-path/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0071-simplify-path.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0071-simplify-path.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0071-simplify-path.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0071-simplify-path.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0071-simplify-path.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0071-simplify-path.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0071-simplify-path.ts)</div></sub>
+<sub>[0394 - Decode String](https://leetcode.com/problems/decode-string/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0394-decode-string.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0394-decode-string.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0394-decode-string.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0394-decode-string.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0394-decode-string.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0394-decode-string.scala)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0394-decode-string.ts)</div></sub>
+<sub>[0402 - Remove K Digits](https://leetcode.com/problems/remove-k-digits/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0402-remove-k-digits.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0402-remove-k-digits.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0402-remove-k-digits.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0402-remove-k-digits.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0402-remove-k-digits.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0402-remove-k-digits.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0402-remove-k-digits.ts)</div></sub>
+<sub>[1209 - Remove All Adjacent Duplicates In String II](https://leetcode.com/problems/remove-all-adjacent-duplicates-in-string-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1209-Remove-All-Adjacent-Duplicates-in-String-II.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1209-remove-all-adjacent-duplicates-in-string-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1209-Remove-All-Adjacent-Duplicates-in-String-II.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1209-remove-all-adjacent-duplicates-in-string-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1209-remove-all-adjacent-duplicates-in-string-ii.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1209-remove-all-adjacent-duplicates-in-string-II.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F1209-remove-all-adjacent-duplicates-in-string-II.ts)</div></sub>
+<sub>[0456 - 132 Pattern](https://leetcode.com/problems/132-pattern/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0456-132-pattern.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0456-132-pattern.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0456-132-pattern.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0456-132-pattern.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0456-132-pattern.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0456-132-pattern.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0456-132-pattern.ts)</div></sub>
+<sub>[0895 - Maximum Frequency Stack](https://leetcode.com/problems/maximum-frequency-stack/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0895-maximum-frequency-stack.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0895-maximum-frequency-stack.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0895-maximum-frequency-stack.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0895-maximum-frequency-stack.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0895-maximum-frequency-stack.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0895-maximum-frequency-stack.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0895-maximum-frequency-stack.ts)</div></sub>
+<sub>[0084 - Largest Rectangle In Histogram](https://leetcode.com/problems/largest-rectangle-in-histogram/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0084-largest-rectangle-in-histogram.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0084-largest-rectangle-in-histogram.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0084-largest-rectangle-in-histogram.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0084-largest-rectangle-in-histogram.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0084-largest-rectangle-in-histogram.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0084-largest-rectangle-in-histogram.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0084-largest-rectangle-in-histogram.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0084-largest-rectangle-in-histogram.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0084-largest-rectangle-in-histogram.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0084-largest-rectangle-in-histogram.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0084-largest-rectangle-in-histogram.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0084-largest-rectangle-in-histogram.ts)</div></sub>
 
 ### Binary Search
 
-<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
----- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
-<sub>[0704 - Binary Search](https://leetcode.com/problems/binary-search/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0704-binary-search.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0704-binary-search.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0704-binary-search.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0704-binary-search.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0704-binary-search.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0704-binary-search.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0704-binary-search.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0704-binary-search.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0704-binary-search.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0704-binary-search.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0704-binary-search.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0704-binary-search.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0704-binary-search.ts)</div></sub>
-<sub>[0035 - Search Insert Position](https://leetcode.com/problems/search-insert-position/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0035-search-insert-position.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0035-search-insert-position.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0035-search-insert-position.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0035-search-insert-position.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0035-search-insert-position.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0035-search-insert-position.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0035-search-insert-position.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0035-search-insert-position.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0035-search-insert-position.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0035-search-insert-position.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0035-search-insert-position.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0035-search-insert-position.ts)</div></sub>
-<sub>[0374 - Guess Number Higher Or Lower](https://leetcode.com/problems/guess-number-higher-or-lower/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0374-guess-number-higher-or-lower.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0374-guess-number-higher-or-lower.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0374-guess-number-higher-or-lower.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0374-guess-number-higher-or-lower.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0374-guess-number-higher-or-lower.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0374-guess-number-higher-or-lower.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0374-guess-number-higher-or-lower.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0374-guess-number-higher-or-lower.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0374-guess-number-higher-or-lower.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0374-guess-number-higher-or-lower.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0441 - Arranging Coins](https://leetcode.com/problems/arranging-coins/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0441-arranging-coins.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0441-arranging-coins.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0441-arranging-coins.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0441-arranging-coins.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0441-arranging-coins.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0977 - Squares of a Sorted Array](https://leetcode.com/problems/squares-of-a-sorted-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0977-squares-of-a-sorted-array.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0977-squares-of-a-sorted-array.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0977-squares-of-a-sorted-array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0977-squares-of-a-sorted-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0977-squares-of-a-sorted-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0977-squares-of-a-sorted-array.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0977-squares-of-a-sorted-array.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0977-squares-of-a-sorted-array.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0977-squares-of-a-sorted-array.ts)</div></sub>
-<sub>[0367 - Valid Perfect Square](https://leetcode.com/problems/valid-perfect-square/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0367-valid-perfect-square.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0367-valid-perfect-square.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0367-valid-perfect-square.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0367-valid-perfect-square.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0367-valid-perfect-square.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0367-valid-perfect-square.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0367-valid-perfect-square.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0069 - Sqrt(x) ](https://leetcode.com/problems/sqrtx/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0069-sqrtx.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0069-sqrtx.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0069-sqrtx.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0069-sqrtx.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0069-sqrtx.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0069-sqrtx.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0540 - Single Element in a Sorted Array](https://leetcode.com/problems/single-element-in-a-sorted-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0540-single-element-in-a-sorted-array.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0540-single-element-in-a-sorted-array.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0540-single-element-in-a-sorted-array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0540-single-element-in-a-sorted-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0540-single-element-in-a-sorted-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0540-single-element-in-a-sorted-array.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0540-single-element-in-a-sorted-array.ts)</div></sub>
-<sub>[1011 - Capacity to Ship Packages](https://leetcode.com/problems/capacity-to-ship-packages-within-d-days/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1011-capacity-to-ship-packages-within-d-days.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1011-capacity-to-ship-packages-within-d-days.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1011-capacity-to-ship-packages-within-d-days.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1011-capacity-to-ship-packages-within-d-days.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0162 - Find Peak Element](https://leetcode.com/problems/find-peak-element/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0162-find-peak-element.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0162-find-peak-element.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0162-find-peak-element.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0162-find-peak-element.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0162-find-peak-element.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0162-find-peak-element.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2300 - Successful Pairs of Spells and Potions](https://leetcode.com/problems/successful-pairs-of-spells-and-potions/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F2300-successful-pairs-of-spells-and-potions.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F2300-successful-pairs-of-spells-and-potions.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2300-successful-pairs-of-spells-and-potions.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F2300-successful-pairs-of-spells-and-potions.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0074 - Search a 2D Matrix](https://leetcode.com/problems/search-a-2d-matrix/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0074-search-a-2d-matrix.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0074-search-a-2d-matrix.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0074-search-a-2d-matrix.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0074-search-a-2d-matrix.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0074-search-a-2d-matrix.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0074-search-a-2d-matrix.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0074-search-a-2d-matrix.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0074-search-a-2d-matrix.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0074-search-a-2d-matrix.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0074-search-a-2d-matrix.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0074-search-a-2d-matrix.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0074-search-a-2d-matrix.ts)</div></sub>
-<sub>[0875 - Koko Eating Bananas](https://leetcode.com/problems/koko-eating-bananas/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0875-koko-eating-bananas.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0875-koko-eating-bananas.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0875-koko-eating-bananas.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0875-koko-eating-bananas.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0875-koko-eating-bananas.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0875-koko-eating-bananas.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0875-koko-eating-bananas.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0875-koko-eating-bananas.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0875-koko-eating-bananas.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0875-koko-eating-bananas.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0875-koko-eating-bananas.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0875-koko-eating-bananas.ts)</div></sub>
-<sub>[2616 - Minimize the Maximum Difference of Pairs](https://leetcode.com/problems/minimize-the-maximum-difference-of-pairs/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F2616-minimize-the-maximum-difference-of-pairs.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2616-minimize-the-maximum-difference-of-pairs.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F2616-minimize-the-maximum-difference-of-pairs.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0153 - Find Minimum In Rotated Sorted Array](https://leetcode.com/problems/find-minimum-in-rotated-sorted-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0153-find-minimum-in-rotated-sorted-array.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0153-find-minimum-in-rotated-sorted-array.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0153-find-minimum-in-rotated-sorted-array.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0153-find-minimum-in-rotated-sorted-array.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0153-find-minimum-in-rotated-sorted-array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0153-find-minimum-in-rotated-sorted-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0153-find-minimum-in-rotated-sorted-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0153-find-minimum-in-rotated-sorted-array.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0153-find-minimum-in-rotated-sorted-array.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0153-find-minimum-in-rotated-sorted-array.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0153-find-minimum-in-rotated-sorted-array.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0153-find-minimum-in-rotated-sorted-array.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0153-find-minimum-in-rotated-sorted-array.ts)</div></sub>
-<sub>[0033 - Search In Rotated Sorted Array](https://leetcode.com/problems/search-in-rotated-sorted-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0033-search-in-rotated-sorted-array.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0033-search-in-rotated-sorted-array.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0033-search-in-rotated-sorted-array.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0033-search-in-rotated-sorted-array.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0033-search-in-rotated-sorted-array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0033-search-in-rotated-sorted-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0033-search-in-rotated-sorted-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0033-search-in-rotated-sorted-array.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0033-search-in-rotated-sorted-array.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0033-search-in-rotated-sorted-array.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0033-search-in-rotated-sorted-array.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0033-search-in-rotated-sorted-array.ts)</div></sub>
-<sub>[0081 - Search In Rotated Sorted Array II](https://leetcode.com/problems/search-in-rotated-sorted-array-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0081-search-in-rotated-sorted-array-ii.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0081-search-in-rotated-sorted-array-ii.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0981 - Time Based Key Value Store](https://leetcode.com/problems/time-based-key-value-store/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0981-time-based-key-value-store.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0981-time-based-key-value-store.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0981-time-based-key-value-store.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0981-time-based-key-value-store.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0981-time-based-key-value-store.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0981-time-based-key-value-store.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0981-time-based-key-value-store.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0981-time-based-key-value-store.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0981-Time-Based-Key-Value-Store.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0981-time-based-key-value-store.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0981-time-based-key-value-store.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0981-time-based-key-value-store.ts)</div></sub>
-<sub>[0034 - Find First And Last Position of Element In Sorted Array](https://leetcode.com/problems/find-first-and-last-position-of-element-in-sorted-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0034-find-first-and-last-position-of-element-in-sorted-array.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0034-find-first-and-last-position-of-element-in-sorted-array.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0034-find-first-and-last-position-of-element-in-sorted-array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0034-find-first-and-last-position-of-element-in-sorted-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0034-find-first-and-last-position-of-element-in-sorted-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0034-find-first-and-last-position-of-element-in-sorted-array.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0034-find-first-and-last-position-of-element-in-sorted-array.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1898 - Maximum Number of Removable Characters](https://leetcode.com/problems/maximum-number-of-removable-characters/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1898-maximum-number-of-removable-characters.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1898-maximum-number-of-removable-characters.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1898-maximum-number-of-removable-characters.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0116 - Populating Next Right Pointers In Each Node](https://leetcode.com/problems/populating-next-right-pointers-in-each-node/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0116-populating-next-right-pointers-in-each-node.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0116-populating-next-right-pointers-in-each-node.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0116-populating-next-right-pointers-in-each-node.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0116-populating-next-right-pointers-in-each-node.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0116-populating-next-right-pointers-in-each-node.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1268 - Search Suggestions System](https://leetcode.com/problems/search-suggestions-system/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1268-search-suggestions-system.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1268-search-suggestions-system.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1268-search-suggestions-system.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0410 - Split Array Largest Sum](https://leetcode.com/problems/split-array-largest-sum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0410-split-array-largest-sum.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0410-split-array-largest-sum.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0410-split-array-largest-sum.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0410-split-array-largest-sum.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0004 - Median of Two Sorted Arrays](https://leetcode.com/problems/median-of-two-sorted-arrays/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0004-median-of-two-sorted-arrays.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0004-median-of-two-sorted-arrays.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0004-median-of-two-sorted-arrays.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0004-median-of-two-sorted-arrays.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0004-median-of-two-sorted-arrays.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0004-median-of-two-sorted-arrays.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0004-median-of-two-sorted-arrays.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0004-median-of-two-sorted-arrays.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0004-median-of-two-sorted-arrays.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0004-median-of-two-sorted-arrays.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0004-median-of-two-sorted-arrays.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0004-median-of-two-sorted-arrays.ts)</div></sub>
+<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>hints</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
+---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
+<sub>[0704 - Binary Search](https://leetcode.com/problems/binary-search/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0704-binary-search.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0704-binary-search.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0704-binary-search.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0704-binary-search.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0704-binary-search.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0704-binary-search.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0704-binary-search.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0704-binary-search.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0704-binary-search.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0704-binary-search.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0704-binary-search.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0704-binary-search.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0704-binary-search.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0704-binary-search.ts)</div></sub>
+<sub>[0035 - Search Insert Position](https://leetcode.com/problems/search-insert-position/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0035-search-insert-position.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0035-search-insert-position.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0035-search-insert-position.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0035-search-insert-position.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0035-search-insert-position.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0035-search-insert-position.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0035-search-insert-position.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0035-search-insert-position.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0035-search-insert-position.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0035-search-insert-position.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0035-search-insert-position.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0035-search-insert-position.ts)</div></sub>
+<sub>[0374 - Guess Number Higher Or Lower](https://leetcode.com/problems/guess-number-higher-or-lower/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0374-guess-number-higher-or-lower.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0374-guess-number-higher-or-lower.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0374-guess-number-higher-or-lower.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0374-guess-number-higher-or-lower.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0374-guess-number-higher-or-lower.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0374-guess-number-higher-or-lower.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0374-guess-number-higher-or-lower.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0374-guess-number-higher-or-lower.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0374-guess-number-higher-or-lower.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0374-guess-number-higher-or-lower.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0441 - Arranging Coins](https://leetcode.com/problems/arranging-coins/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0441-arranging-coins.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0441-arranging-coins.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0441-arranging-coins.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0441-arranging-coins.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0441-arranging-coins.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0441-arranging-coins.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0977 - Squares of a Sorted Array](https://leetcode.com/problems/squares-of-a-sorted-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0977-squares-of-a-sorted-array.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0977-squares-of-a-sorted-array.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0977-squares-of-a-sorted-array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0977-squares-of-a-sorted-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0977-squares-of-a-sorted-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0977-squares-of-a-sorted-array.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0977-squares-of-a-sorted-array.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0977-squares-of-a-sorted-array.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0977-squares-of-a-sorted-array.ts)</div></sub>
+<sub>[0367 - Valid Perfect Square](https://leetcode.com/problems/valid-perfect-square/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0367-valid-perfect-square.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0367-valid-perfect-square.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0367-valid-perfect-square.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0367-valid-perfect-square.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0367-valid-perfect-square.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0367-valid-perfect-square.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0367-valid-perfect-square.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0367-valid-perfect-square.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0069 - Sqrt(x) ](https://leetcode.com/problems/sqrtx/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0069-sqrtx.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0069-sqrtx.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0069-sqrtx.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0069-sqrtx.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0069-sqrtx.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0069-sqrtx.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0069-sqrtx.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0540 - Single Element in a Sorted Array](https://leetcode.com/problems/single-element-in-a-sorted-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0540-single-element-in-a-sorted-array.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0540-single-element-in-a-sorted-array.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0540-single-element-in-a-sorted-array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0540-single-element-in-a-sorted-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0540-single-element-in-a-sorted-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0540-single-element-in-a-sorted-array.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0540-single-element-in-a-sorted-array.ts)</div></sub>
+<sub>[1011 - Capacity to Ship Packages](https://leetcode.com/problems/capacity-to-ship-packages-within-d-days/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1011-capacity-to-ship-packages-within-d-days.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1011-capacity-to-ship-packages-within-d-days.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1011-capacity-to-ship-packages-within-d-days.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1011-capacity-to-ship-packages-within-d-days.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0162 - Find Peak Element](https://leetcode.com/problems/find-peak-element/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0162-find-peak-element.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0162-find-peak-element.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0162-find-peak-element.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0162-find-peak-element.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0162-find-peak-element.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0162-find-peak-element.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2300 - Successful Pairs of Spells and Potions](https://leetcode.com/problems/successful-pairs-of-spells-and-potions/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F2300-successful-pairs-of-spells-and-potions.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F2300-successful-pairs-of-spells-and-potions.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2300-successful-pairs-of-spells-and-potions.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F2300-successful-pairs-of-spells-and-potions.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0074 - Search a 2D Matrix](https://leetcode.com/problems/search-a-2d-matrix/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0074-search-a-2d-matrix.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0074-search-a-2d-matrix.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0074-search-a-2d-matrix.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0074-search-a-2d-matrix.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0074-search-a-2d-matrix.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0074-search-a-2d-matrix.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0074-search-a-2d-matrix.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0074-search-a-2d-matrix.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0074-search-a-2d-matrix.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0074-search-a-2d-matrix.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0074-search-a-2d-matrix.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0074-search-a-2d-matrix.ts)</div></sub>
+<sub>[0875 - Koko Eating Bananas](https://leetcode.com/problems/koko-eating-bananas/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0875-koko-eating-bananas.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0875-koko-eating-bananas.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0875-koko-eating-bananas.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0875-koko-eating-bananas.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0875-koko-eating-bananas.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0875-koko-eating-bananas.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0875-koko-eating-bananas.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0875-koko-eating-bananas.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0875-koko-eating-bananas.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0875-koko-eating-bananas.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0875-koko-eating-bananas.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0875-koko-eating-bananas.ts)</div></sub>
+<sub>[2616 - Minimize the Maximum Difference of Pairs](https://leetcode.com/problems/minimize-the-maximum-difference-of-pairs/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F2616-minimize-the-maximum-difference-of-pairs.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2616-minimize-the-maximum-difference-of-pairs.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F2616-minimize-the-maximum-difference-of-pairs.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0153 - Find Minimum In Rotated Sorted Array](https://leetcode.com/problems/find-minimum-in-rotated-sorted-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0153-find-minimum-in-rotated-sorted-array.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0153-find-minimum-in-rotated-sorted-array.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0153-find-minimum-in-rotated-sorted-array.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0153-find-minimum-in-rotated-sorted-array.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0153-find-minimum-in-rotated-sorted-array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0153-find-minimum-in-rotated-sorted-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0153-find-minimum-in-rotated-sorted-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0153-find-minimum-in-rotated-sorted-array.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0153-find-minimum-in-rotated-sorted-array.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0153-find-minimum-in-rotated-sorted-array.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0153-find-minimum-in-rotated-sorted-array.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0153-find-minimum-in-rotated-sorted-array.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0153-find-minimum-in-rotated-sorted-array.ts)</div></sub>
+<sub>[0033 - Search In Rotated Sorted Array](https://leetcode.com/problems/search-in-rotated-sorted-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0033-search-in-rotated-sorted-array.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0033-search-in-rotated-sorted-array.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0033-search-in-rotated-sorted-array.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0033-search-in-rotated-sorted-array.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0033-search-in-rotated-sorted-array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0033-search-in-rotated-sorted-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0033-search-in-rotated-sorted-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0033-search-in-rotated-sorted-array.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0033-search-in-rotated-sorted-array.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0033-search-in-rotated-sorted-array.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0033-search-in-rotated-sorted-array.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0033-search-in-rotated-sorted-array.ts)</div></sub>
+<sub>[0081 - Search In Rotated Sorted Array II](https://leetcode.com/problems/search-in-rotated-sorted-array-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0081-search-in-rotated-sorted-array-ii.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0081-search-in-rotated-sorted-array-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0081-search-in-rotated-sorted-array-ii.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0981 - Time Based Key Value Store](https://leetcode.com/problems/time-based-key-value-store/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0981-time-based-key-value-store.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0981-time-based-key-value-store.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0981-time-based-key-value-store.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0981-time-based-key-value-store.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0981-time-based-key-value-store.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0981-time-based-key-value-store.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0981-time-based-key-value-store.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0981-time-based-key-value-store.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0981-Time-Based-Key-Value-Store.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0981-time-based-key-value-store.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0981-time-based-key-value-store.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0981-time-based-key-value-store.ts)</div></sub>
+<sub>[0034 - Find First And Last Position of Element In Sorted Array](https://leetcode.com/problems/find-first-and-last-position-of-element-in-sorted-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0034-find-first-and-last-position-of-element-in-sorted-array.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0034-find-first-and-last-position-of-element-in-sorted-array.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0034-find-first-and-last-position-of-element-in-sorted-array.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0034-find-first-and-last-position-of-element-in-sorted-array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0034-find-first-and-last-position-of-element-in-sorted-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0034-find-first-and-last-position-of-element-in-sorted-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0034-find-first-and-last-position-of-element-in-sorted-array.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0034-find-first-and-last-position-of-element-in-sorted-array.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1898 - Maximum Number of Removable Characters](https://leetcode.com/problems/maximum-number-of-removable-characters/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1898-maximum-number-of-removable-characters.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1898-maximum-number-of-removable-characters.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1898-maximum-number-of-removable-characters.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1898-maximum-number-of-removable-characters.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0116 - Populating Next Right Pointers In Each Node](https://leetcode.com/problems/populating-next-right-pointers-in-each-node/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0116-populating-next-right-pointers-in-each-node.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0116-populating-next-right-pointers-in-each-node.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0116-populating-next-right-pointers-in-each-node.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0116-populating-next-right-pointers-in-each-node.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0116-populating-next-right-pointers-in-each-node.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1268 - Search Suggestions System](https://leetcode.com/problems/search-suggestions-system/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1268-search-suggestions-system.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1268-search-suggestions-system.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1268-search-suggestions-system.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0410 - Split Array Largest Sum](https://leetcode.com/problems/split-array-largest-sum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0410-split-array-largest-sum.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0410-split-array-largest-sum.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0410-split-array-largest-sum.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0410-split-array-largest-sum.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0004 - Median of Two Sorted Arrays](https://leetcode.com/problems/median-of-two-sorted-arrays/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0004-median-of-two-sorted-arrays.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0004-median-of-two-sorted-arrays.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0004-median-of-two-sorted-arrays.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0004-median-of-two-sorted-arrays.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0004-median-of-two-sorted-arrays.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0004-median-of-two-sorted-arrays.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0004-median-of-two-sorted-arrays.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0004-median-of-two-sorted-arrays.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0004-median-of-two-sorted-arrays.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0004-median-of-two-sorted-arrays.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0004-median-of-two-sorted-arrays.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0004-median-of-two-sorted-arrays.ts)</div></sub>
 
 ### Linked List
 
-<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
----- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
-<sub>[0206 - Reverse Linked List](https://leetcode.com/problems/reverse-linked-list/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0206-reverse-linked-list.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0206-reverse-linked-list.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0206-reverse-linked-list.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0206-reverse-linked-list.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0206-reverse-linked-list.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0206-reverse-linked-list.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0206-reverse-linked-list.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0206-reverse-linked-list.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0206-reverse-linked-list.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0206-reverse-linked-list.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0206-reverse-linked-list.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0206-reverse-linked-list.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0206-reverse-linked-list.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0206-reverse-linked-list.ts)</div></sub>
-<sub>[0021 - Merge Two Sorted Lists](https://leetcode.com/problems/merge-two-sorted-lists/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0021-merge-two-sorted-lists.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0021-merge-two-sorted-lists.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0021-merge-two-sorted-lists.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0021-merge-two-sorted-lists.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0021-merge-two-sorted-lists.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0021-merge-two-sorted-lists.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0021-merge-two-sorted-lists.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0021-merge-two-sorted-lists.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0021-merge-two-sorted-lists.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0021-merge-two-sorted-lists.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0021-merge-two-sorted-lists.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0021-merge-two-sorted-lists.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0021-merge-two-sorted-lists.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0021-merge-two-sorted-lists.ts)</div></sub>
-<sub>[0234 - Palindrome Linked List](https://leetcode.com/problems/palindrome-linked-list/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0234-palindrome-linked-list.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0234-palindrome-linked-list.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0234-palindrome-linked-list.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0234-palindrome-linked-list.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0234-palindrome-linked-list.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0234-palindrome-linked-list.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0234-palindrome-linked-list.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0203 - Remove Linked List Elements](https://leetcode.com/problems/remove-linked-list-elements/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0203-remove-linked-list-elements.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0203-remove-linked-list-elements.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0203-remove-linked-list-elements.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0203-remove-linked-list-elements.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0203-remove-linked-list-elements.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0203-remove-linked-list-elements.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0203-remove-linked-list-elements.ts)</div></sub>
-<sub>[0083 - Remove Duplicates From Sorted List](https://leetcode.com/problems/remove-duplicates-from-sorted-list/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0083-remove-duplicates-from-sorted-list.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0083-remove-duplicates-from-sorted-list.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0083-remove-duplicates-from-sorted-list.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0083-remove-duplicates-from-sorted-list.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0083-remove-duplicates-from-sorted-list.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0083-remove-duplicates-from-sorted-list.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0083-remove-duplicates-from-sorted-list.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0083-remove-duplicates-from-sorted-list.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0876 - Middle of the Linked List](https://leetcode.com/problems/middle-of-the-linked-list/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0876-middle-of-the-linked-list.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0876-middle-of-the-linked-list.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0876-middle-of-the-linked-list.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0876-middle-of-the-linked-list.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0876-middle-of-the-linked-list.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0876-middle-of-the-linked-list.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0876-middle-of-the-linked-list.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0876-middle-of-the-linked-list.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0876-middle-of-the-linked-list.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0876-middle-of-the-linked-list.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0876-middle-of-the-linked-list.ts)</div></sub>
-<sub>[0160 - Intersection of Two Linked Lists](https://leetcode.com/problems/intersection-of-two-linked-lists/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0160-intersection-of-two-linked-lists.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0160-intersection-of-two-linked-lists.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0160-intersection-of-two-linked-lists.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0160-intersection-of-two-linked-lists.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0160-intersection-of-two-linked-lists.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0160-intersection-of-two-linked-lists.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0160-intersection-of-two-linked-lists.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0143 - Reorder List](https://leetcode.com/problems/reorder-list/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0143-reorder-list.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0143-reorder-list.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0143-reorder-list.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0143-reorder-list.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0143-reorder-list.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0143-reorder-list.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0143-reorder-list.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0143-reorder-list.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0143-reorder-list.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0143-reorder-list.ts)</div></sub>
-<sub>[2130 - Maximum Twin Sum Of A Linked List](https://leetcode.com/problems/maximum-twin-sum-of-a-linked-list/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F2130-maximum-twin-sum-of-a-linked-list.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F2130-maximum-twin-sum-of-a-linked-list.go)</div></sub> | <sub><div align='center'>[✔️](java%2F2130-maximum-twin-sum-of-a-linked-list.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F2130-maximum-twin-sum-of-a-linked-list.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2130-maximum-twin-sum-of-a-linked-list.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F2130-maximum-twin-sum-of-a-linked-list.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F2130-maximum-twin-sum-of-a-linked-list.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0019 - Remove Nth Node From End of List](https://leetcode.com/problems/remove-nth-node-from-end-of-list/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0019-remove-nth-node-from-end-of-list.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0019-remove-nth-node-from-end-of-list.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0019-remove-nth-node-from-end-of-list.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0019-remove-nth-node-from-end-of-list.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0019-remove-nth-node-from-end-of-list.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0019-remove-nth-node-from-end-of-list.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0019-remove-nth-node-from-end-of-list.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0019-remove-nth-node-from-end-of-list.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0019-remove-nth-node-from-end-of-list.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0019-remove-nth-node-from-end-of-list.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0019-remove-nth-node-from-end-of-list.ts)</div></sub>
-<sub>[1721 - Swapping Nodes in a Linked List](https://leetcode.com/problems/swapping-nodes-in-a-linked-list/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1721-swapping-nodes-in-a-linked-list.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1721-swapping-nodes-in-a-linked-list.go)</div></sub> | <sub><div align='center'>[✔️](java%2F1721-swapping-nodes-in-a-linked-list.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1721-swapping-nodes-in-a-linked-list.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1721-swapping-nodes-in-a-linked-list.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0460 - LFU Cache](https://leetcode.com/problems/lfu-cache/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F0460-lfu-cache.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0460-lfu-cache.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0138 - Copy List With Random Pointer](https://leetcode.com/problems/copy-list-with-random-pointer/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0138-copy-list-with-random-pointer.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0138-copy-list-with-random-pointer.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0138-copy-list-with-random-pointer.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0138-copy-list-with-random-pointer.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0138-copy-list-with-random-pointer.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0138-copy-list-with-random-pointer.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0138-copy-list-with-random-pointer.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0138-copy-list-with-random-pointer.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0138-copy-list-with-random-pointer.rb)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0138-copy-list-with-random-pointer.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0138-copy-list-with-random-pointer.ts)</div></sub>
-<sub>[0707 - Design Linked List](https://leetcode.com/problems/design-linked-list/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0707-design-linked-list.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0707-design-linked-list.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0707-design-linked-list.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0707-design-linked-list.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0707-design-linked-list.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0707-design-linked-list.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1472 - Design Browser History](https://leetcode.com/problems/design-browser-history/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1472-design-browser-history.go)</div></sub> | <sub><div align='center'>[✔️](java%2F1472-design-browser-history.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1472-design-browser-history.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1472-design-browser-history.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1472-design-browser-history.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1472-design-browser-history.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1472-design-browser-history.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F1472-design-browser-history.ts)</div></sub>
-<sub>[0002 - Add Two Numbers](https://leetcode.com/problems/add-two-numbers/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0002-add-two-numbers.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0002-add-two-numbers.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0002-add-two-numbers.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0002-add-two-numbers.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0002-add-two-numbers.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0002-add-two-numbers.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0002-add-two-numbers.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0002-add-two-numbers.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0002-add-two-numbers.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0002-add-two-numbers.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0002-add-two-numbers.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0002-add-two-numbers.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0002-add-two-numbers.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0002-add-two-numbers.ts)</div></sub>
-<sub>[0141 - Linked List Cycle](https://leetcode.com/problems/linked-list-cycle/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0141-linked-list-cycle.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0141-linked-list-cycle.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0141-linked-list-cycle.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0141-linked-list-cycle.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0141-linked-list-cycle.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0141-linked-list-cycle.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0141-linked-list-cycle.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0141-linked-list-cycle.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0141-linked-list-cycle.rb)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](scala%2F0141-linked-list-cycle.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0141-linked-list-cycle.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0141-linked-list-cycle.ts)</div></sub>
-<sub>[0287 - Find The Duplicate Number](https://leetcode.com/problems/find-the-duplicate-number/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0287-find-the-duplicate-number.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0287-find-the-duplicate-number.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0287-find-the-duplicate-number.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0287-find-the-duplicate-number.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0287-find-the-duplicate-number.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0287-find-the-duplicate-number.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0287-find-the-duplicate-number.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0287-find-the-duplicate-number.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0287-find-the-duplicate-number.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0287-find-the-duplicate-number.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0287-find-the-duplicate-number.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0287-find-the-duplicate-number.ts)</div></sub>
-<sub>[0024 - Swap Nodes In Pairs](https://leetcode.com/problems/swap-nodes-in-pairs/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0024-swap-nodes-in-pairs.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0024-swap-nodes-in-pairs.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0024-swap-nodes-in-pairs.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0024-swap-nodes-in-pairs.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0024-swap-nodes-in-pairs.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0024-swap-nodes-in-pairs.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0148 - Sort List](https://leetcode.com/problems/sort-list/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0148-sort-list.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0148-sort-list.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0148-sort-list.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0148-sort-list.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0148-sort-list.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0148-sort-list.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0086 - Partition List](https://leetcode.com/problems/partition-list/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0086-partition-list.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0086-partition-list.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0086-partition-list.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0061 - Rotate List](https://leetcode.com/problems/rotate-list/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0061-rotate-list.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0061-rotate-list.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0061-rotate-list.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0061-rotate-list.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0092 - Reverse Linked List II](https://leetcode.com/problems/reverse-linked-list-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0092-reverse-linked-list-ii.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0092-reverse-linked-list-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0092-reverse-linked-list-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0092-reverse-linked-list-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0092-reverse-linked-list-ii.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0622 - Design Circular Queue](https://leetcode.com/problems/design-circular-queue/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0622-design-circular-queue.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0622-design-circular-queue.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0622-design-circular-queue.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0622-design-circular-queue.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0147 - Insertion Sort List](https://leetcode.com/problems/insertion-sort-list/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0147-insertion-sort-list.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0147-insertion-sort-list.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0147-insertion-sort-list.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0147-insertion-sort-list.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0147-insertion-sort-list.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0725 - Split Linked List in Parts](https://leetcode.com/problems/split-linked-list-in-parts/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0725-split-linked-list-in-parts.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0725-split-linked-list-in-parts.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0146 - LRU Cache](https://leetcode.com/problems/lru-cache/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0146-lru-cache.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0146-lru-cache.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0146-lru-cache.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0146-lru-cache.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0146-lru-cache.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0146-lru-cache.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0146-lru-cache.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0146-lru-cache.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0146-lru-cache.rb)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0146-lru-cache.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0146-lru-cache.ts)</div></sub>
-<sub>[0023 - Merge K Sorted Lists](https://leetcode.com/problems/merge-k-sorted-lists/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0023-merge-k-sorted-lists.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0023-merge-k-sorted-lists.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0023-merge-k-sorted-lists.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0023-merge-k-sorted-lists.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0023-merge-k-sorted-lists.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0023-merge-k-sorted-lists.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0023-merge-k-sorted-lists.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0023-merge-k-sorted-lists.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0023-merge-k-sorted-lists.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0023-merge-k-sorted-lists.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0023-merge-k-sorted-lists.ts)</div></sub>
-<sub>[0025 - Reverse Nodes In K Group](https://leetcode.com/problems/reverse-nodes-in-k-group/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0025-reverse-nodes-in-k-group.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0025-reverse-nodes-in-k-group.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0025-reverse-nodes-in-k-group.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0025-reverse-nodes-in-k-group.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0025-reverse-nodes-in-k-group.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0025-reverse-nodes-in-k-group.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0025-reverse-nodes-in-k-group.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0025-reverse-nodes-in-k-group.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0025-reverse-nodes-in-k-group.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0025-reverse-nodes-in-k-group.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0025-reverse-nodes-in-k-group.ts)</div></sub>
+<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>hints</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
+---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
+<sub>[0206 - Reverse Linked List](https://leetcode.com/problems/reverse-linked-list/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0206-reverse-linked-list.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0206-reverse-linked-list.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0206-reverse-linked-list.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0206-reverse-linked-list.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0206-reverse-linked-list.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0206-reverse-linked-list.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0206-reverse-linked-list.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0206-reverse-linked-list.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0206-reverse-linked-list.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0206-reverse-linked-list.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0206-reverse-linked-list.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0206-reverse-linked-list.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0206-reverse-linked-list.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0206-reverse-linked-list.ts)</div></sub>
+<sub>[0021 - Merge Two Sorted Lists](https://leetcode.com/problems/merge-two-sorted-lists/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0021-merge-two-sorted-lists.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0021-merge-two-sorted-lists.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0021-merge-two-sorted-lists.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0021-merge-two-sorted-lists.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0021-merge-two-sorted-lists.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0021-merge-two-sorted-lists.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0021-merge-two-sorted-lists.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0021-merge-two-sorted-lists.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0021-merge-two-sorted-lists.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0021-merge-two-sorted-lists.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0021-merge-two-sorted-lists.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0021-merge-two-sorted-lists.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0021-merge-two-sorted-lists.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0021-merge-two-sorted-lists.ts)</div></sub>
+<sub>[0234 - Palindrome Linked List](https://leetcode.com/problems/palindrome-linked-list/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0234-palindrome-linked-list.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0234-palindrome-linked-list.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0234-palindrome-linked-list.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0234-palindrome-linked-list.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0234-palindrome-linked-list.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0234-palindrome-linked-list.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0234-palindrome-linked-list.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0203 - Remove Linked List Elements](https://leetcode.com/problems/remove-linked-list-elements/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0203-remove-linked-list-elements.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0203-remove-linked-list-elements.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0203-remove-linked-list-elements.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0203-remove-linked-list-elements.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0203-remove-linked-list-elements.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0203-remove-linked-list-elements.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0203-remove-linked-list-elements.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0203-remove-linked-list-elements.ts)</div></sub>
+<sub>[0083 - Remove Duplicates From Sorted List](https://leetcode.com/problems/remove-duplicates-from-sorted-list/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0083-remove-duplicates-from-sorted-list.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0083-remove-duplicates-from-sorted-list.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0083-remove-duplicates-from-sorted-list.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0083-remove-duplicates-from-sorted-list.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0083-remove-duplicates-from-sorted-list.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0083-remove-duplicates-from-sorted-list.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0083-remove-duplicates-from-sorted-list.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0083-remove-duplicates-from-sorted-list.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0876 - Middle of the Linked List](https://leetcode.com/problems/middle-of-the-linked-list/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0876-middle-of-the-linked-list.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0876-middle-of-the-linked-list.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0876-middle-of-the-linked-list.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0876-middle-of-the-linked-list.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0876-middle-of-the-linked-list.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0876-middle-of-the-linked-list.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0876-middle-of-the-linked-list.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0876-middle-of-the-linked-list.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0876-middle-of-the-linked-list.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0876-middle-of-the-linked-list.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0876-middle-of-the-linked-list.ts)</div></sub>
+<sub>[0160 - Intersection of Two Linked Lists](https://leetcode.com/problems/intersection-of-two-linked-lists/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0160-intersection-of-two-linked-lists.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0160-intersection-of-two-linked-lists.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0160-intersection-of-two-linked-lists.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0160-intersection-of-two-linked-lists.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0160-intersection-of-two-linked-lists.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0160-intersection-of-two-linked-lists.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0160-intersection-of-two-linked-lists.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0143 - Reorder List](https://leetcode.com/problems/reorder-list/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0143-reorder-list.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0143-reorder-list.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0143-reorder-list.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0143-reorder-list.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0143-reorder-list.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0143-reorder-list.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0143-reorder-list.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0143-reorder-list.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0143-reorder-list.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0143-reorder-list.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0143-reorder-list.ts)</div></sub>
+<sub>[2130 - Maximum Twin Sum Of A Linked List](https://leetcode.com/problems/maximum-twin-sum-of-a-linked-list/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F2130-maximum-twin-sum-of-a-linked-list.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F2130-maximum-twin-sum-of-a-linked-list.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F2130-maximum-twin-sum-of-a-linked-list.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F2130-maximum-twin-sum-of-a-linked-list.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2130-maximum-twin-sum-of-a-linked-list.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F2130-maximum-twin-sum-of-a-linked-list.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F2130-maximum-twin-sum-of-a-linked-list.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0019 - Remove Nth Node From End of List](https://leetcode.com/problems/remove-nth-node-from-end-of-list/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0019-remove-nth-node-from-end-of-list.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0019-remove-nth-node-from-end-of-list.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0019-remove-nth-node-from-end-of-list.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0019-remove-nth-node-from-end-of-list.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0019-remove-nth-node-from-end-of-list.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0019-remove-nth-node-from-end-of-list.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0019-remove-nth-node-from-end-of-list.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0019-remove-nth-node-from-end-of-list.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0019-remove-nth-node-from-end-of-list.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0019-remove-nth-node-from-end-of-list.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0019-remove-nth-node-from-end-of-list.ts)</div></sub>
+<sub>[1721 - Swapping Nodes in a Linked List](https://leetcode.com/problems/swapping-nodes-in-a-linked-list/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1721-swapping-nodes-in-a-linked-list.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1721-swapping-nodes-in-a-linked-list.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1721-swapping-nodes-in-a-linked-list.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1721-swapping-nodes-in-a-linked-list.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1721-swapping-nodes-in-a-linked-list.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0460 - LFU Cache](https://leetcode.com/problems/lfu-cache/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0460-lfu-cache.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0460-lfu-cache.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0460-lfu-cache.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0138 - Copy List With Random Pointer](https://leetcode.com/problems/copy-list-with-random-pointer/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0138-copy-list-with-random-pointer.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0138-copy-list-with-random-pointer.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0138-copy-list-with-random-pointer.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0138-copy-list-with-random-pointer.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0138-copy-list-with-random-pointer.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0138-copy-list-with-random-pointer.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0138-copy-list-with-random-pointer.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0138-copy-list-with-random-pointer.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0138-copy-list-with-random-pointer.rb)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0138-copy-list-with-random-pointer.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0138-copy-list-with-random-pointer.ts)</div></sub>
+<sub>[0707 - Design Linked List](https://leetcode.com/problems/design-linked-list/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0707-design-linked-list.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0707-design-linked-list.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0707-design-linked-list.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0707-design-linked-list.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0707-design-linked-list.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0707-design-linked-list.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0707-design-linked-list.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1472 - Design Browser History](https://leetcode.com/problems/design-browser-history/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1472-design-browser-history.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1472-design-browser-history.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1472-design-browser-history.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1472-design-browser-history.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1472-design-browser-history.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1472-design-browser-history.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1472-design-browser-history.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F1472-design-browser-history.ts)</div></sub>
+<sub>[0002 - Add Two Numbers](https://leetcode.com/problems/add-two-numbers/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0002-add-two-numbers.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0002-add-two-numbers.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0002-add-two-numbers.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0002-add-two-numbers.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0002-add-two-numbers.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0002-add-two-numbers.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0002-add-two-numbers.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0002-add-two-numbers.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0002-add-two-numbers.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0002-add-two-numbers.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0002-add-two-numbers.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0002-add-two-numbers.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0002-add-two-numbers.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0002-add-two-numbers.ts)</div></sub>
+<sub>[0141 - Linked List Cycle](https://leetcode.com/problems/linked-list-cycle/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0141-linked-list-cycle.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0141-linked-list-cycle.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0141-linked-list-cycle.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0141-linked-list-cycle.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0141-linked-list-cycle.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0141-linked-list-cycle.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0141-linked-list-cycle.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0141-linked-list-cycle.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0141-linked-list-cycle.rb)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](scala%2F0141-linked-list-cycle.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0141-linked-list-cycle.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0141-linked-list-cycle.ts)</div></sub>
+<sub>[0287 - Find The Duplicate Number](https://leetcode.com/problems/find-the-duplicate-number/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0287-find-the-duplicate-number.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0287-find-the-duplicate-number.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0287-find-the-duplicate-number.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0287-find-the-duplicate-number.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0287-find-the-duplicate-number.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0287-find-the-duplicate-number.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0287-find-the-duplicate-number.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0287-find-the-duplicate-number.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0287-find-the-duplicate-number.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0287-find-the-duplicate-number.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0287-find-the-duplicate-number.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0287-find-the-duplicate-number.ts)</div></sub>
+<sub>[0024 - Swap Nodes In Pairs](https://leetcode.com/problems/swap-nodes-in-pairs/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0024-swap-nodes-in-pairs.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0024-swap-nodes-in-pairs.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0024-swap-nodes-in-pairs.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0024-swap-nodes-in-pairs.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0024-swap-nodes-in-pairs.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0024-swap-nodes-in-pairs.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0148 - Sort List](https://leetcode.com/problems/sort-list/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0148-sort-list.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0148-sort-list.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0148-sort-list.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0148-sort-list.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0148-sort-list.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0148-sort-list.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0086 - Partition List](https://leetcode.com/problems/partition-list/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0086-partition-list.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0086-partition-list.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0086-partition-list.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0061 - Rotate List](https://leetcode.com/problems/rotate-list/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0061-rotate-list.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0061-rotate-list.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0061-rotate-list.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0061-rotate-list.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0092 - Reverse Linked List II](https://leetcode.com/problems/reverse-linked-list-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0092-reverse-linked-list-ii.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0092-reverse-linked-list-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0092-reverse-linked-list-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0092-reverse-linked-list-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0092-reverse-linked-list-ii.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0622 - Design Circular Queue](https://leetcode.com/problems/design-circular-queue/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0622-design-circular-queue.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0622-design-circular-queue.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0622-design-circular-queue.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0622-design-circular-queue.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0147 - Insertion Sort List](https://leetcode.com/problems/insertion-sort-list/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0147-insertion-sort-list.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0147-insertion-sort-list.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0147-insertion-sort-list.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0147-insertion-sort-list.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0147-insertion-sort-list.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0725 - Split Linked List in Parts](https://leetcode.com/problems/split-linked-list-in-parts/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0725-split-linked-list-in-parts.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0725-split-linked-list-in-parts.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0146 - LRU Cache](https://leetcode.com/problems/lru-cache/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0146-lru-cache.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0146-lru-cache.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0146-lru-cache.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0146-lru-cache.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0146-lru-cache.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0146-lru-cache.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0146-lru-cache.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0146-lru-cache.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0146-lru-cache.rb)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0146-lru-cache.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0146-lru-cache.ts)</div></sub>
+<sub>[0023 - Merge K Sorted Lists](https://leetcode.com/problems/merge-k-sorted-lists/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0023-merge-k-sorted-lists.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0023-merge-k-sorted-lists.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0023-merge-k-sorted-lists.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0023-merge-k-sorted-lists.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0023-merge-k-sorted-lists.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0023-merge-k-sorted-lists.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0023-merge-k-sorted-lists.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0023-merge-k-sorted-lists.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0023-merge-k-sorted-lists.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0023-merge-k-sorted-lists.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0023-merge-k-sorted-lists.ts)</div></sub>
+<sub>[0025 - Reverse Nodes In K Group](https://leetcode.com/problems/reverse-nodes-in-k-group/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0025-reverse-nodes-in-k-group.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0025-reverse-nodes-in-k-group.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0025-reverse-nodes-in-k-group.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0025-reverse-nodes-in-k-group.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0025-reverse-nodes-in-k-group.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0025-reverse-nodes-in-k-group.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0025-reverse-nodes-in-k-group.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0025-reverse-nodes-in-k-group.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0025-reverse-nodes-in-k-group.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0025-reverse-nodes-in-k-group.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0025-reverse-nodes-in-k-group.ts)</div></sub>
 
 ### Trees
 
-<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
----- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
-<sub>[0094 - Binary Tree Inorder Traversal](https://leetcode.com/problems/binary-tree-inorder-traversal/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0094-binary-tree-inorder-traversal.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0094-binary-tree-inorder-traversal.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0094-binary-tree-inorder-traversal.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0094-binary-tree-inorder-traversal.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0094-binary-tree-inorder-traversal.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0094-binary-tree-inorder-traversal.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0094-binary-tree-inorder-traversal.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0094-binary-tree-inorder-traversal.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0094-binary-tree-inorder-traversal.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0094-binary-tree-inorder-traversal.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0094-binary-tree-inorder-traversal.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0094-binary-tree-inorder-traversal.ts)</div></sub>
-<sub>[0144 - Binary Tree Preorder Traversal](https://leetcode.com/problems/binary-tree-preorder-traversal/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0144-binary-tree-preorder-traversal.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0144-binary-tree-preorder-traversal.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0144-binary-tree-preorder-traversal.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0144-binary-tree-preorder-traversal.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0144-binary-tree-preorder-traversal.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0144-binary-tree-preorder-traversal.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0144-binary-tree-preorder-traversal.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0144-binary-tree-preorder-traversal.ts)</div></sub>
-<sub>[0145 - Binary Tree Postorder Traversal](https://leetcode.com/problems/binary-tree-postorder-traversal/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0145-binary-tree-postorder-traversal.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0145-binary-tree-postorder-traversal.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0145-binary-tree-postorder-traversal.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0145-binary-tree-postorder-traversal.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0145-binary-tree-postorder-traversal.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0145-binary-tree-postorder-traversal.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0145-binary-tree-postorder-traversal.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0145-binary-tree-postorder-traversal.ts)</div></sub>
-<sub>[0226 - Invert Binary Tree](https://leetcode.com/problems/invert-binary-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0226-invert-binary-tree.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0226-invert-binary-tree.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0226-invert-binary-tree.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0226-invert-binary-tree.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0226-invert-binary-tree.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0226-invert-binary-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0226-invert-binary-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0226-invert-binary-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0226-invert-binary-tree.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0226-invert-binary-tree.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0226-invert-binary-tree.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0226-invert-binary-tree.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0226-invert-binary-tree.ts)</div></sub>
-<sub>[0104 - Maximum Depth of Binary Tree](https://leetcode.com/problems/maximum-depth-of-binary-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0104-maximum-depth-of-binary-tree.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0104-maximum-depth-of-binary-tree.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0104-maximum-depth-of-binary-tree.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0104-maximum-depth-of-binary-tree.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0104-maximum-depth-of-binary-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0104-maximum-depth-of-binary-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0104-maximum-depth-of-binary-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0104-maximum-depth-of-binary-tree.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0104-maximum-depth-of-binary-tree.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0104-maximum-depth-of-binary-tree.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0104-maximum-depth-of-binary-tree.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0104-maximum-depth-of-binary-tree.ts)</div></sub>
-<sub>[0543 - Diameter of Binary Tree](https://leetcode.com/problems/diameter-of-binary-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0543-diameter-of-binary-tree.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0543-diameter-of-binary-tree.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0543-diameter-of-binary-tree.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0543-diameter-of-binary-tree.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0543-diameter-of-binary-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0543-diameter-of-binary-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0543-diameter-of-binary-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0543-diameter-of-binary-tree.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0543-diameter-of-binary-tree.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0543-diameter-of-binary-tree.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0543-diameter-of-binary-tree.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0543-diameter-of-binary-tree.ts)</div></sub>
-<sub>[0110 - Balanced Binary Tree](https://leetcode.com/problems/balanced-binary-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0110-balanced-binary-tree.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0110-balanced-binary-tree.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0110-balanced-binary-tree.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0110-balanced-binary-tree.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0110-balanced-binary-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0110-balanced-binary-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0110-balanced-binary-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0110-balanced-binary-tree.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0110-balanced-binary-tree.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0110-balanced-binary-tree.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0110-balanced-binary-tree.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0110-balanced-binary-tree.ts)</div></sub>
-<sub>[0100 - Same Tree](https://leetcode.com/problems/same-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0100-same-tree.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0100-same-tree.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0100-same-tree.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0100-same-tree.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0100-same-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0100-same-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0100-same-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0100-same-tree.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0100-same-tree.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0100-same-tree.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0100-same-tree.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0100-same-tree.ts)</div></sub>
-<sub>[0572 - Subtree of Another Tree](https://leetcode.com/problems/subtree-of-another-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0572-subtree-of-another-tree.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0572-subtree-of-another-tree.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0572-subtree-of-another-tree.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0572-subtree-of-another-tree.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0572-subtree-of-another-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0572-subtree-of-another-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0572-subtree-of-another-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0572-subtree-of-another-tree.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0572-subtree-of-another-tree.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0572-subtree-of-another-tree.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0572-subtree-of-another-tree.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0572-subtree-of-another-tree.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0572-subtree-of-another-tree.ts)</div></sub>
-<sub>[0108 - Convert Sorted Array to Binary Search Tree](https://leetcode.com/problems/convert-sorted-array-to-binary-search-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0108-convert-sorted-array-to-binary-search-tree.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0108-convert-sorted-array-to-binary-search-tree.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0108-convert-sorted-array-to-binary-search-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0108-convert-sorted-array-to-binary-search-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0108-convert-sorted-array-to-binary-search-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0108-convert-sorted-array-to-binary-search-tree.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0617 - Merge Two Binary Trees](https://leetcode.com/problems/merge-two-binary-trees/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0617-merge-two-binary-trees.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0617-merge-two-binary-trees.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0617-merge-two-binary-trees.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0617-merge-two-binary-trees.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0617-merge-two-binary-trees.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0617-merge-two-binary-trees.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0617-merge-two-binary-trees.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0617-merge-two-binary-trees.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0617-merge-two-binary-trees.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0112 - Path Sum](https://leetcode.com/problems/path-sum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0112-path-sum.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0112-path-sum.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0112-path-sum.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0112-path-sum.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0112-path-sum.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0112-path-sum.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0112-path-sum.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0112-path-sum.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0112-path-sum.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0606 - Construct String From Binary Tree](https://leetcode.com/problems/construct-string-from-binary-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0606-construct-string-from-binary-tree.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0606-construct-string-from-binary-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0606-construct-string-from-binary-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0606-construct-string-from-binary-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0606-construct-string-from-binary-tree.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0235 - Lowest Common Ancestor of a Binary Search Tree](https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-search-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0235-lowest-common-ancestor-of-a-binary-search-tree.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0235-lowest-common-ancestor-of-a-binary-search-tree.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0235-lowest-common-ancestor-of-a-binary-search-tree.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0235-lowest-common-ancestor-of-a-binary-search-tree.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0235-lowest-common-ancestor-of-a-binary-search-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0235-lowest-common-ancestor-of-a-binary-search-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0235-lowest-common-ancestor-of-a-binary-search-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0235-lowest-common-ancestor-of-a-binary-search-tree.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0235-lowest-common-ancestor-of-a-binary-search-tree.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0235-lowest-common-ancestor-of-a-binary-search-tree.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0235-lowest-common-ancestor-of-a-binary-search-tree.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0235-lowest-common-ancestor-of-a-binary-search-tree.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0235-lowest-common-ancestor-of-a-binary-search-tree.ts)</div></sub>
-<sub>[0701 - Insert into a Binary Search Tree](https://leetcode.com/problems/insert-into-a-binary-search-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0701-insert-into-a-binary-search-tree.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0701-insert-into-a-binary-search-tree.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0701-insert-into-a-binary-search-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0701-insert-into-a-binary-search-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0701-insert-into-a-binary-search-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0701-insert-into-a-binary-search-tree.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0701-insert-into-a-binary-search-tree.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0701-insert-into-a-binary-search-tree.ts)</div></sub>
-<sub>[0450 - Delete Node in a BST](https://leetcode.com/problems/delete-node-in-a-bst/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0450-delete-node-in-a-bst.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0450-delete-node-in-a-bst.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0450-delete-node-in-a-bst.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0450-delete-node-in-a-bst.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0450-delete-node-in-a-bst.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0450-delete-node-in-a-bst.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0450-delete-node-in-a-bst.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0450-delete-node-in-a-bst.ts)</div></sub>
-<sub>[0102 - Binary Tree Level Order Traversal](https://leetcode.com/problems/binary-tree-level-order-traversal/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0102-binary-tree-level-order-traversal.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0102-binary-tree-level-order-traversal.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0102-binary-tree-level-order-traversal.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0102-binary-tree-level-order-traversal.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0102-binary-tree-level-order-traversal.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0102-binary-tree-level-order-traversal.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0102-binary-tree-level-order-traversal.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0102-binary-tree-level-order-traversal.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0102-binary-tree-level-order-traversal.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0102-binary-tree-level-order-traversal.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0102-binary-tree-level-order-traversal.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0102-binary-tree-level-order-traversal.ts)</div></sub>
-<sub>[0199 - Binary Tree Right Side View](https://leetcode.com/problems/binary-tree-right-side-view/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0199-binary-tree-right-side-view.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0199-binary-tree-right-side-view.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0199-binary-tree-right-side-view.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0199-binary-tree-right-side-view.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0199-binary-tree-right-side-view.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0199-binary-tree-right-side-view.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0199-binary-tree-right-side-view.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0199-binary-tree-right-side-view.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0199-binary-tree-right-side-view.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0199-binary-tree-right-side-view.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0199-binary-tree-right-side-view.ts)</div></sub>
-<sub>[0783 - Minimum Distance between BST Nodes](https://leetcode.com/problems/minimum-distance-between-bst-nodes/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0783-minimum-distance-between-bst-nodes.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0783-minimum-distance-between-bst-nodes.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0783-minimum-distance-between-bst-nodes.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0783-minimum-distance-between-bst-nodes.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0101 - Symmetric Tree ](https://leetcode.com/problems/symmetric-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0101-symmetric-tree.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0101-symmetric-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0101-symmetric-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0101-symmetric-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0101-symmetric-tree.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0101-symmetric-tree.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1443 - Minimum Time to Collect All Apples in a Tree](https://leetcode.com/problems/minimum-time-to-collect-all-apples-in-a-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F1443-minimum-time-to-collect-all-apples-in-a-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1443-minimum-time-to-collect-all-apples-in-a-tree.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1443-minimum-time-to-collect-all-apples-in-a-tree.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0103 - Binary Tree Zigzag Level Order Traversal](https://leetcode.com/problems/binary-tree-zigzag-level-order-traversal/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0103-binary-tree-zigzag-level-order-traversal.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0103-binary-tree-zigzag-level-order-traversal.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0103-binary-tree-zigzag-level-order-traversal.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0103-binary-tree-zigzag-level-order-traversal.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0103-binary-tree-zigzag-level-order-traversal.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0427 - Construct Quad Tree](https://leetcode.com/problems/construct-quad-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0427-construct-quad-tree.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0427-construct-quad-tree.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0652 - Find Duplicate Subtrees](https://leetcode.com/problems/find-duplicate-subtrees/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F0652-find-duplicate-subtrees.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0652-find-duplicate-subtrees.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0958 - Check Completeness of a Binary Tree](https://leetcode.com/problems/check-completeness-of-a-binary-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0958-check-completeness-of-a-binary-tree.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0958-check-completeness-of-a-binary-tree.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0958-check-completeness-of-a-binary-tree.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F0958-check-completeness-of-a-binary-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0958-check-completeness-of-a-binary-tree.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0106 - Construct Binary Tree from Inorder and Postorder Traversal](https://leetcode.com/problems/construct-binary-tree-from-inorder-and-postorder-traversal/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0106-construct-binary-tree-from-inorder-and-postorder-traversal.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0106-construct-binary-tree-from-inorder-and-postorder-traversal.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0106-construct-binary-tree-from-inorder-and-postorder-traversal.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0106-construct-binary-tree-from-inorder-and-postorder-traversal.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0662 - Maximum Width of Binary Tree ](https://leetcode.com/problems/maximum-width-of-binary-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0662-maximum-width-of-binary-tree.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0662-maximum-width-of-binary-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0662-maximum-width-of-binary-tree.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1376 - Time Needed to Inform All Employees ](https://leetcode.com/problems/time-needed-to-inform-all-employees/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1376-time-needed-to-inform-all-employees.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1376-time-needed-to-inform-all-employees.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1376-time-needed-to-inform-all-employees.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1448 - Count Good Nodes In Binary Tree](https://leetcode.com/problems/count-good-nodes-in-binary-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1448-Count-Good-Nodes-in-Binary-Tree.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1448-Count-Good-Nodes-In-Binary-Tree.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1448-Count-Good-Nodes-in-Binary-Tree.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1448-count-good-nodes-in-binary-tree.go)</div></sub> | <sub><div align='center'>[✔️](java%2F1448-Count-Good-Nodes-in-Binary-Tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1448-Count-Good-Nodes-in-Binary-Tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1448-Count-Good-Nodes-In-Binary-Tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1448-count-good-nodes-in-binary-tree.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1448-count-good-nodes-in-binary-tree.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1448-count-good-nodes-in-binary-tree.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F1448-Count-Good-Nodes-in-Binary-Tree.ts)</div></sub>
-<sub>[0098 - Validate Binary Search Tree](https://leetcode.com/problems/validate-binary-search-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0098-validate-binary-search-tree.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0098-validate-binary-search-tree.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0098-validate-binary-search-tree.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0098-validate-binary-search-tree.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0098-validate-binary-search-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0098-validate-binary-search-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0098-validate-binary-search-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0098-validate-binary-search-tree.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0098-validate-binary-search-tree.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0098-validate-binary-search-tree.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0098-validate-binary-search-tree.ts)</div></sub>
-<sub>[0230 - Kth Smallest Element In a Bst](https://leetcode.com/problems/kth-smallest-element-in-a-bst/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0230-kth-smallest-element-in-a-bst.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0230-kth-smallest-element-in-a-bst.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0230-kth-smallest-element-in-a-bst.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0230-kth-smallest-element-in-a-bst.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0230-kth-smallest-element-in-a-bst.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0230-kth-smallest-element-in-a-bst.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0230-kth-smallest-element-in-a-bst.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0230-kth-smallest-element-in-a-bst.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0230-kth-smallest-element-in-a-bst.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0230-kth-smallest-element-in-a-bst.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0230-kth-smallest-element-in-a-bst.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0230-kth-smallest-element-in-a-bst.ts)</div></sub>
-<sub>[0105 - Construct Binary Tree From Preorder And Inorder Traversal](https://leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0105-construct-binary-tree-from-preorder-and-inorder-traversal.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0105-construct-binary-tree-from-preorder-and-inorder-traversal.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0105-construct-binary-tree-from-preorder-and-inorder-traversal.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0105-construct-binary-tree-from-preorder-and-inorder-traversal.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0105-construct-binary-tree-from-preorder-and-inorder-traversal.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0105-construct-binary-tree-from-preorder-and-inorder-traversal.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0105-construct-binary-tree-from-preorder-and-inorder-traversal.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0105-construct-binary-tree-from-preorder-and-inorder-traversal.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0105-construct-binary-tree-from-preorder-and-inorder-traversal.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0105-construct-binary-tree-from-preorder-and-inorder-traversal.ts)</div></sub>
-<sub>[0096 - Unique Binary Search Trees](https://leetcode.com/problems/unique-binary-search-trees/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0096-unique-binary-search-trees.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0096-unique-binary-search-trees.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0096-unique-binary-search-trees.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0096-unique-binary-search-trees.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0095 - Unique Binary Search Trees II](https://leetcode.com/problems/unique-binary-search-trees-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0095-unique-binary-search-trees-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0095-unique-binary-search-trees-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0095-unique-binary-search-trees-ii.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0129 - Sum Root to Leaf Numbers](https://leetcode.com/problems/sum-root-to-leaf-numbers/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0129-sum-root-to-leaf-numbers.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0129-sum-root-to-leaf-numbers.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0129-sum-root-to-leaf-numbers.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0129-sum-root-to-leaf-numbers.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0129-sum-root-to-leaf-numbers.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0129-sum-root-to-leaf-numbers.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0337 - House Robber III](https://leetcode.com/problems/house-robber-iii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0337-house-robber-iii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0337-house-robber-iii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0337-house-robber-iii.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0951 - Flip Equivalent Binary Trees](https://leetcode.com/problems/flip-equivalent-binary-trees/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0951-flip-equivalent-binary-trees.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0951-flip-equivalent-binary-trees.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0951-flip-equivalent-binary-trees.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1993 - Operations On Tree](https://leetcode.com/problems/operations-on-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1993-operations-on-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1993-operations-on-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1993-operations-on-tree.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0894 - All Possible Full Binary Trees](https://leetcode.com/problems/all-possible-full-binary-trees/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0894-all-possible-full-binary-trees.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0894-all-possible-full-binary-trees.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0894-all-possible-full-binary-trees.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0894-all-possible-full-binary-trees.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0513 - Find Bottom Left Tree Value](https://leetcode.com/problems/find-bottom-left-tree-value/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0513-find-bottom-left-tree-value.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0513-find-bottom-left-tree-value.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0513-find-bottom-left-tree-value.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0513-find-bottom-left-tree-value.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0669 - Trim a Binary Search Tree](https://leetcode.com/problems/trim-a-binary-search-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0669-trim-a-binary-search-tree.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0669-trim-a-binary-search-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0669-trim-a-binary-search-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0669-trim-a-binary-search-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0669-trim-a-binary-search-tree.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0669-trim-a-binary-search-tree.ts)</div></sub>
-<sub>[0173 - Binary Search Tree Iterator](https://leetcode.com/problems/binary-search-tree-iterator/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0173-binary-search-tree-iterator.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0173-binary-search-tree-iterator.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0173-binary-search-tree-iterator.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0173-binary-search-tree-iterator.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0538 - Convert Bst to Greater Tree](https://leetcode.com/problems/convert-bst-to-greater-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0538-convert-bst-to-greater-tree.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0538-convert-bst-to-greater-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0538-convert-bst-to-greater-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0538-convert-bst-to-greater-tree.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0124 - Binary Tree Maximum Path Sum](https://leetcode.com/problems/binary-tree-maximum-path-sum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0124-binary-tree-maximum-path-sum.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0124-binary-tree-maximum-path-sum.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0124-binary-tree-maximum-path-sum.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0124-binary-tree-maximum-path-sum.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0124-binary-tree-maximum-path-sum.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0124-binary-tree-maximum-path-sum.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0124-binary-tree-maximum-path-sum.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0124-binary-tree-maximum-path-sum.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0124-binary-tree-maximum-path-sum.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0124-binary-tree-maximum-path-sum.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0124-binary-tree-maximum-path-sum.ts)</div></sub>
-<sub>[0297 - Serialize And Deserialize Binary Tree](https://leetcode.com/problems/serialize-and-deserialize-binary-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0297-serialize-and-deserialize-binary-tree.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0297-serialize-and-deserialize-binary-tree.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0297-serialize-and-deserialize-binary-tree.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0297-serialize-and-deserialize-binary-tree.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0297-serialize-and-deserialize-binary-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0297-serialize-and-deserialize-binary-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0297-serialize-and-deserialize-binary-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0297-serialize-and-deserialize-binary-tree.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0297-serialize-and-deserialize-binary-tree.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0297-serialize-and-deserialize-binary-tree.ts)</div></sub>
+<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>hints</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
+---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
+<sub>[0094 - Binary Tree Inorder Traversal](https://leetcode.com/problems/binary-tree-inorder-traversal/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0094-binary-tree-inorder-traversal.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0094-binary-tree-inorder-traversal.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0094-binary-tree-inorder-traversal.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0094-binary-tree-inorder-traversal.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0094-binary-tree-inorder-traversal.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0094-binary-tree-inorder-traversal.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0094-binary-tree-inorder-traversal.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0094-binary-tree-inorder-traversal.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0094-binary-tree-inorder-traversal.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0094-binary-tree-inorder-traversal.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0094-binary-tree-inorder-traversal.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0094-binary-tree-inorder-traversal.ts)</div></sub>
+<sub>[0144 - Binary Tree Preorder Traversal](https://leetcode.com/problems/binary-tree-preorder-traversal/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0144-binary-tree-preorder-traversal.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0144-binary-tree-preorder-traversal.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0144-binary-tree-preorder-traversal.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0144-binary-tree-preorder-traversal.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0144-binary-tree-preorder-traversal.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0144-binary-tree-preorder-traversal.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0144-binary-tree-preorder-traversal.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0144-binary-tree-preorder-traversal.ts)</div></sub>
+<sub>[0145 - Binary Tree Postorder Traversal](https://leetcode.com/problems/binary-tree-postorder-traversal/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0145-binary-tree-postorder-traversal.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0145-binary-tree-postorder-traversal.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0145-binary-tree-postorder-traversal.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0145-binary-tree-postorder-traversal.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0145-binary-tree-postorder-traversal.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0145-binary-tree-postorder-traversal.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0145-binary-tree-postorder-traversal.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0145-binary-tree-postorder-traversal.ts)</div></sub>
+<sub>[0226 - Invert Binary Tree](https://leetcode.com/problems/invert-binary-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0226-invert-binary-tree.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0226-invert-binary-tree.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0226-invert-binary-tree.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0226-invert-binary-tree.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0226-invert-binary-tree.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0226-invert-binary-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0226-invert-binary-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0226-invert-binary-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0226-invert-binary-tree.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0226-invert-binary-tree.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0226-invert-binary-tree.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0226-invert-binary-tree.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0226-invert-binary-tree.ts)</div></sub>
+<sub>[0104 - Maximum Depth of Binary Tree](https://leetcode.com/problems/maximum-depth-of-binary-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0104-maximum-depth-of-binary-tree.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0104-maximum-depth-of-binary-tree.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0104-maximum-depth-of-binary-tree.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0104-maximum-depth-of-binary-tree.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0104-maximum-depth-of-binary-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0104-maximum-depth-of-binary-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0104-maximum-depth-of-binary-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0104-maximum-depth-of-binary-tree.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0104-maximum-depth-of-binary-tree.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0104-maximum-depth-of-binary-tree.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0104-maximum-depth-of-binary-tree.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0104-maximum-depth-of-binary-tree.ts)</div></sub>
+<sub>[0543 - Diameter of Binary Tree](https://leetcode.com/problems/diameter-of-binary-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0543-diameter-of-binary-tree.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0543-diameter-of-binary-tree.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0543-diameter-of-binary-tree.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0543-diameter-of-binary-tree.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0543-diameter-of-binary-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0543-diameter-of-binary-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0543-diameter-of-binary-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0543-diameter-of-binary-tree.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0543-diameter-of-binary-tree.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0543-diameter-of-binary-tree.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0543-diameter-of-binary-tree.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0543-diameter-of-binary-tree.ts)</div></sub>
+<sub>[0110 - Balanced Binary Tree](https://leetcode.com/problems/balanced-binary-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0110-balanced-binary-tree.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0110-balanced-binary-tree.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0110-balanced-binary-tree.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0110-balanced-binary-tree.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0110-balanced-binary-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0110-balanced-binary-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0110-balanced-binary-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0110-balanced-binary-tree.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0110-balanced-binary-tree.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0110-balanced-binary-tree.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0110-balanced-binary-tree.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0110-balanced-binary-tree.ts)</div></sub>
+<sub>[0100 - Same Tree](https://leetcode.com/problems/same-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0100-same-tree.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0100-same-tree.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0100-same-tree.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0100-same-tree.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0100-same-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0100-same-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0100-same-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0100-same-tree.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0100-same-tree.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0100-same-tree.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0100-same-tree.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0100-same-tree.ts)</div></sub>
+<sub>[0572 - Subtree of Another Tree](https://leetcode.com/problems/subtree-of-another-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0572-subtree-of-another-tree.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0572-subtree-of-another-tree.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0572-subtree-of-another-tree.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0572-subtree-of-another-tree.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0572-subtree-of-another-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0572-subtree-of-another-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0572-subtree-of-another-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0572-subtree-of-another-tree.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0572-subtree-of-another-tree.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0572-subtree-of-another-tree.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0572-subtree-of-another-tree.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0572-subtree-of-another-tree.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0572-subtree-of-another-tree.ts)</div></sub>
+<sub>[0108 - Convert Sorted Array to Binary Search Tree](https://leetcode.com/problems/convert-sorted-array-to-binary-search-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0108-convert-sorted-array-to-binary-search-tree.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0108-convert-sorted-array-to-binary-search-tree.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0108-convert-sorted-array-to-binary-search-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0108-convert-sorted-array-to-binary-search-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0108-convert-sorted-array-to-binary-search-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0108-convert-sorted-array-to-binary-search-tree.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0617 - Merge Two Binary Trees](https://leetcode.com/problems/merge-two-binary-trees/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0617-merge-two-binary-trees.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0617-merge-two-binary-trees.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0617-merge-two-binary-trees.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0617-merge-two-binary-trees.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0617-merge-two-binary-trees.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0617-merge-two-binary-trees.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0617-merge-two-binary-trees.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0617-merge-two-binary-trees.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0617-merge-two-binary-trees.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0112 - Path Sum](https://leetcode.com/problems/path-sum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0112-path-sum.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0112-path-sum.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0112-path-sum.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0112-path-sum.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0112-path-sum.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0112-path-sum.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0112-path-sum.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0112-path-sum.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0112-path-sum.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0606 - Construct String From Binary Tree](https://leetcode.com/problems/construct-string-from-binary-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0606-construct-string-from-binary-tree.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0606-construct-string-from-binary-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0606-construct-string-from-binary-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0606-construct-string-from-binary-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0606-construct-string-from-binary-tree.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0235 - Lowest Common Ancestor of a Binary Search Tree](https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-search-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0235-lowest-common-ancestor-of-a-binary-search-tree.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0235-lowest-common-ancestor-of-a-binary-search-tree.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0235-lowest-common-ancestor-of-a-binary-search-tree.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0235-lowest-common-ancestor-of-a-binary-search-tree.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0235-lowest-common-ancestor-of-a-binary-search-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0235-lowest-common-ancestor-of-a-binary-search-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0235-lowest-common-ancestor-of-a-binary-search-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0235-lowest-common-ancestor-of-a-binary-search-tree.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0235-lowest-common-ancestor-of-a-binary-search-tree.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0235-lowest-common-ancestor-of-a-binary-search-tree.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0235-lowest-common-ancestor-of-a-binary-search-tree.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0235-lowest-common-ancestor-of-a-binary-search-tree.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0235-lowest-common-ancestor-of-a-binary-search-tree.ts)</div></sub>
+<sub>[0701 - Insert into a Binary Search Tree](https://leetcode.com/problems/insert-into-a-binary-search-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0701-insert-into-a-binary-search-tree.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0701-insert-into-a-binary-search-tree.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0701-insert-into-a-binary-search-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0701-insert-into-a-binary-search-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0701-insert-into-a-binary-search-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0701-insert-into-a-binary-search-tree.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0701-insert-into-a-binary-search-tree.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0701-insert-into-a-binary-search-tree.ts)</div></sub>
+<sub>[0450 - Delete Node in a BST](https://leetcode.com/problems/delete-node-in-a-bst/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0450-delete-node-in-a-bst.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0450-delete-node-in-a-bst.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0450-delete-node-in-a-bst.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0450-delete-node-in-a-bst.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0450-delete-node-in-a-bst.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0450-delete-node-in-a-bst.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0450-delete-node-in-a-bst.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0450-delete-node-in-a-bst.ts)</div></sub>
+<sub>[0102 - Binary Tree Level Order Traversal](https://leetcode.com/problems/binary-tree-level-order-traversal/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0102-binary-tree-level-order-traversal.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0102-binary-tree-level-order-traversal.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0102-binary-tree-level-order-traversal.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0102-binary-tree-level-order-traversal.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0102-binary-tree-level-order-traversal.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0102-binary-tree-level-order-traversal.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0102-binary-tree-level-order-traversal.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0102-binary-tree-level-order-traversal.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0102-binary-tree-level-order-traversal.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0102-binary-tree-level-order-traversal.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0102-binary-tree-level-order-traversal.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0102-binary-tree-level-order-traversal.ts)</div></sub>
+<sub>[0199 - Binary Tree Right Side View](https://leetcode.com/problems/binary-tree-right-side-view/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0199-binary-tree-right-side-view.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0199-binary-tree-right-side-view.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0199-binary-tree-right-side-view.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0199-binary-tree-right-side-view.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0199-binary-tree-right-side-view.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0199-binary-tree-right-side-view.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0199-binary-tree-right-side-view.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0199-binary-tree-right-side-view.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0199-binary-tree-right-side-view.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0199-binary-tree-right-side-view.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0199-binary-tree-right-side-view.ts)</div></sub>
+<sub>[0783 - Minimum Distance between BST Nodes](https://leetcode.com/problems/minimum-distance-between-bst-nodes/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0783-minimum-distance-between-bst-nodes.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0783-minimum-distance-between-bst-nodes.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0783-minimum-distance-between-bst-nodes.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0783-minimum-distance-between-bst-nodes.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0101 - Symmetric Tree ](https://leetcode.com/problems/symmetric-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0101-symmetric-tree.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0101-symmetric-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0101-symmetric-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0101-symmetric-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0101-symmetric-tree.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0101-symmetric-tree.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1443 - Minimum Time to Collect All Apples in a Tree](https://leetcode.com/problems/minimum-time-to-collect-all-apples-in-a-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F1443-minimum-time-to-collect-all-apples-in-a-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1443-minimum-time-to-collect-all-apples-in-a-tree.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1443-minimum-time-to-collect-all-apples-in-a-tree.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0103 - Binary Tree Zigzag Level Order Traversal](https://leetcode.com/problems/binary-tree-zigzag-level-order-traversal/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0103-binary-tree-zigzag-level-order-traversal.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0103-binary-tree-zigzag-level-order-traversal.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0103-binary-tree-zigzag-level-order-traversal.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0103-binary-tree-zigzag-level-order-traversal.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0103-binary-tree-zigzag-level-order-traversal.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0427 - Construct Quad Tree](https://leetcode.com/problems/construct-quad-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0427-construct-quad-tree.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0427-construct-quad-tree.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0652 - Find Duplicate Subtrees](https://leetcode.com/problems/find-duplicate-subtrees/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F0652-find-duplicate-subtrees.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0652-find-duplicate-subtrees.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0958 - Check Completeness of a Binary Tree](https://leetcode.com/problems/check-completeness-of-a-binary-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0958-check-completeness-of-a-binary-tree.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0958-check-completeness-of-a-binary-tree.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0958-check-completeness-of-a-binary-tree.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F0958-check-completeness-of-a-binary-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0958-check-completeness-of-a-binary-tree.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0106 - Construct Binary Tree from Inorder and Postorder Traversal](https://leetcode.com/problems/construct-binary-tree-from-inorder-and-postorder-traversal/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0106-construct-binary-tree-from-inorder-and-postorder-traversal.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0106-construct-binary-tree-from-inorder-and-postorder-traversal.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0106-construct-binary-tree-from-inorder-and-postorder-traversal.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0106-construct-binary-tree-from-inorder-and-postorder-traversal.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0662 - Maximum Width of Binary Tree ](https://leetcode.com/problems/maximum-width-of-binary-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0662-maximum-width-of-binary-tree.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0662-maximum-width-of-binary-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0662-maximum-width-of-binary-tree.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1376 - Time Needed to Inform All Employees ](https://leetcode.com/problems/time-needed-to-inform-all-employees/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1376-time-needed-to-inform-all-employees.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1376-time-needed-to-inform-all-employees.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1376-time-needed-to-inform-all-employees.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1448 - Count Good Nodes In Binary Tree](https://leetcode.com/problems/count-good-nodes-in-binary-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1448-Count-Good-Nodes-in-Binary-Tree.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1448-Count-Good-Nodes-In-Binary-Tree.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1448-Count-Good-Nodes-in-Binary-Tree.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1448-count-good-nodes-in-binary-tree.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1448-Count-Good-Nodes-in-Binary-Tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1448-Count-Good-Nodes-in-Binary-Tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1448-Count-Good-Nodes-In-Binary-Tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1448-count-good-nodes-in-binary-tree.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1448-count-good-nodes-in-binary-tree.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1448-count-good-nodes-in-binary-tree.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F1448-Count-Good-Nodes-in-Binary-Tree.ts)</div></sub>
+<sub>[0098 - Validate Binary Search Tree](https://leetcode.com/problems/validate-binary-search-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0098-validate-binary-search-tree.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0098-validate-binary-search-tree.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0098-validate-binary-search-tree.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0098-validate-binary-search-tree.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0098-validate-binary-search-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0098-validate-binary-search-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0098-validate-binary-search-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0098-validate-binary-search-tree.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0098-validate-binary-search-tree.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0098-validate-binary-search-tree.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0098-validate-binary-search-tree.ts)</div></sub>
+<sub>[0230 - Kth Smallest Element In a Bst](https://leetcode.com/problems/kth-smallest-element-in-a-bst/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0230-kth-smallest-element-in-a-bst.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0230-kth-smallest-element-in-a-bst.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0230-kth-smallest-element-in-a-bst.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0230-kth-smallest-element-in-a-bst.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0230-kth-smallest-element-in-a-bst.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0230-kth-smallest-element-in-a-bst.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0230-kth-smallest-element-in-a-bst.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0230-kth-smallest-element-in-a-bst.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0230-kth-smallest-element-in-a-bst.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0230-kth-smallest-element-in-a-bst.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0230-kth-smallest-element-in-a-bst.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0230-kth-smallest-element-in-a-bst.ts)</div></sub>
+<sub>[0105 - Construct Binary Tree From Preorder And Inorder Traversal](https://leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0105-construct-binary-tree-from-preorder-and-inorder-traversal.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0105-construct-binary-tree-from-preorder-and-inorder-traversal.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0105-construct-binary-tree-from-preorder-and-inorder-traversal.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0105-construct-binary-tree-from-preorder-and-inorder-traversal.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0105-construct-binary-tree-from-preorder-and-inorder-traversal.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0105-construct-binary-tree-from-preorder-and-inorder-traversal.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0105-construct-binary-tree-from-preorder-and-inorder-traversal.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0105-construct-binary-tree-from-preorder-and-inorder-traversal.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0105-construct-binary-tree-from-preorder-and-inorder-traversal.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0105-construct-binary-tree-from-preorder-and-inorder-traversal.ts)</div></sub>
+<sub>[0096 - Unique Binary Search Trees](https://leetcode.com/problems/unique-binary-search-trees/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0096-unique-binary-search-trees.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0096-unique-binary-search-trees.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0096-unique-binary-search-trees.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0096-unique-binary-search-trees.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0095 - Unique Binary Search Trees II](https://leetcode.com/problems/unique-binary-search-trees-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0095-unique-binary-search-trees-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0095-unique-binary-search-trees-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0095-unique-binary-search-trees-ii.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0129 - Sum Root to Leaf Numbers](https://leetcode.com/problems/sum-root-to-leaf-numbers/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0129-sum-root-to-leaf-numbers.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0129-sum-root-to-leaf-numbers.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0129-sum-root-to-leaf-numbers.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0129-sum-root-to-leaf-numbers.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0129-sum-root-to-leaf-numbers.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0129-sum-root-to-leaf-numbers.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0337 - House Robber III](https://leetcode.com/problems/house-robber-iii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0337-house-robber-iii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0337-house-robber-iii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0337-house-robber-iii.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0951 - Flip Equivalent Binary Trees](https://leetcode.com/problems/flip-equivalent-binary-trees/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0951-flip-equivalent-binary-trees.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0951-flip-equivalent-binary-trees.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0951-flip-equivalent-binary-trees.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1993 - Operations On Tree](https://leetcode.com/problems/operations-on-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1993-operations-on-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1993-operations-on-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1993-operations-on-tree.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0894 - All Possible Full Binary Trees](https://leetcode.com/problems/all-possible-full-binary-trees/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0894-all-possible-full-binary-trees.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0894-all-possible-full-binary-trees.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0894-all-possible-full-binary-trees.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0894-all-possible-full-binary-trees.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0513 - Find Bottom Left Tree Value](https://leetcode.com/problems/find-bottom-left-tree-value/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0513-find-bottom-left-tree-value.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0513-find-bottom-left-tree-value.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0513-find-bottom-left-tree-value.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0513-find-bottom-left-tree-value.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0669 - Trim a Binary Search Tree](https://leetcode.com/problems/trim-a-binary-search-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0669-trim-a-binary-search-tree.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0669-trim-a-binary-search-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0669-trim-a-binary-search-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0669-trim-a-binary-search-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0669-trim-a-binary-search-tree.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0669-trim-a-binary-search-tree.ts)</div></sub>
+<sub>[0173 - Binary Search Tree Iterator](https://leetcode.com/problems/binary-search-tree-iterator/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0173-binary-search-tree-iterator.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0173-binary-search-tree-iterator.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0173-binary-search-tree-iterator.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0173-binary-search-tree-iterator.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0538 - Convert Bst to Greater Tree](https://leetcode.com/problems/convert-bst-to-greater-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0538-convert-bst-to-greater-tree.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0538-convert-bst-to-greater-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0538-convert-bst-to-greater-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0538-convert-bst-to-greater-tree.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0124 - Binary Tree Maximum Path Sum](https://leetcode.com/problems/binary-tree-maximum-path-sum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0124-binary-tree-maximum-path-sum.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0124-binary-tree-maximum-path-sum.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0124-binary-tree-maximum-path-sum.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0124-binary-tree-maximum-path-sum.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0124-binary-tree-maximum-path-sum.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0124-binary-tree-maximum-path-sum.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0124-binary-tree-maximum-path-sum.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0124-binary-tree-maximum-path-sum.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0124-binary-tree-maximum-path-sum.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0124-binary-tree-maximum-path-sum.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0124-binary-tree-maximum-path-sum.ts)</div></sub>
+<sub>[0297 - Serialize And Deserialize Binary Tree](https://leetcode.com/problems/serialize-and-deserialize-binary-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0297-serialize-and-deserialize-binary-tree.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0297-serialize-and-deserialize-binary-tree.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0297-serialize-and-deserialize-binary-tree.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0297-serialize-and-deserialize-binary-tree.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0297-serialize-and-deserialize-binary-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0297-serialize-and-deserialize-binary-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0297-serialize-and-deserialize-binary-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0297-serialize-and-deserialize-binary-tree.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0297-serialize-and-deserialize-binary-tree.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0297-serialize-and-deserialize-binary-tree.ts)</div></sub>
 
 ### Tries
 
-<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
----- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
-<sub>[0208 - Implement Trie Prefix Tree](https://leetcode.com/problems/implement-trie-prefix-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0208-implement-trie-prefix-tree.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0208-implement-trie-prefix-tree.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0208-implement-trie-prefix-tree.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0208-implement-trie-prefix-tree.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0208-implement-trie-prefix-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0208-implement-trie-prefix-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0208-implement-trie-prefix-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0208-implement-trie-prefix-tree.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0208-implement-trie-prefix-tree.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0208-implement-trie-prefix-tree.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0208-implement-trie-prefix-tree.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0208-implement-trie-prefix-tree.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0208-implement-trie-prefix-tree.ts)</div></sub>
-<sub>[0211 - Design Add And Search Words Data Structure](https://leetcode.com/problems/design-add-and-search-words-data-structure/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0211-design-add-and-search-words-data-structure.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0211-design-add-and-search-words-data-structure.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0211-design-add-and-search-words-data-structure.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0211-design-add-and-search-words-data-structure.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0211-design-add-and-search-words-data-structure.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0211-design-add-and-search-words-data-structure.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0211-design-add-and-search-words-data-structure.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0211-design-add-and-search-words-data-structure.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0211-design-add-and-search-words-data-structure.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0211-design-add-and-search-words-data-structure.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0211-design-add-and-search-words-data-structure.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0211-design-add-and-search-words-data-structure.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0211-design-add-and-search-words-data-structure.ts)</div></sub>
-<sub>[2707 - Extra Characters in a String](https://leetcode.com/problems/extra-characters-in-a-string/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F2707-extra-characters-in-a-string.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F2707-extra-characters-in-a-string.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0212 - Word Search II](https://leetcode.com/problems/word-search-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0212-word-search-ii.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0212-word-search-ii.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0212-word-search-ii.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0212-word-search-ii.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0212-word-search-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0212-word-search-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0212-word-search-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0212-word-search-ii.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0212-word-search-ii.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0212-word-search-ii.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0212-word-search-ii.ts)</div></sub>
+<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>hints</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
+---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
+<sub>[0208 - Implement Trie Prefix Tree](https://leetcode.com/problems/implement-trie-prefix-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0208-implement-trie-prefix-tree.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0208-implement-trie-prefix-tree.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0208-implement-trie-prefix-tree.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0208-implement-trie-prefix-tree.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0208-implement-trie-prefix-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0208-implement-trie-prefix-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0208-implement-trie-prefix-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0208-implement-trie-prefix-tree.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0208-implement-trie-prefix-tree.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0208-implement-trie-prefix-tree.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0208-implement-trie-prefix-tree.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0208-implement-trie-prefix-tree.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0208-implement-trie-prefix-tree.ts)</div></sub>
+<sub>[0211 - Design Add And Search Words Data Structure](https://leetcode.com/problems/design-add-and-search-words-data-structure/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0211-design-add-and-search-words-data-structure.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0211-design-add-and-search-words-data-structure.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0211-design-add-and-search-words-data-structure.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0211-design-add-and-search-words-data-structure.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0211-design-add-and-search-words-data-structure.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0211-design-add-and-search-words-data-structure.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0211-design-add-and-search-words-data-structure.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0211-design-add-and-search-words-data-structure.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0211-design-add-and-search-words-data-structure.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0211-design-add-and-search-words-data-structure.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0211-design-add-and-search-words-data-structure.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0211-design-add-and-search-words-data-structure.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0211-design-add-and-search-words-data-structure.ts)</div></sub>
+<sub>[2707 - Extra Characters in a String](https://leetcode.com/problems/extra-characters-in-a-string/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F2707-extra-characters-in-a-string.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F2707-extra-characters-in-a-string.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0212 - Word Search II](https://leetcode.com/problems/word-search-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0212-word-search-ii.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0212-word-search-ii.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0212-word-search-ii.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0212-word-search-ii.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0212-word-search-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0212-word-search-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0212-word-search-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0212-word-search-ii.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0212-word-search-ii.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0212-word-search-ii.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0212-word-search-ii.ts)</div></sub>
 
 ### Heap / Priority Queue
 
-<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
----- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
-<sub>[0703 - Kth Largest Element In a Stream](https://leetcode.com/problems/kth-largest-element-in-a-stream/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0703-kth-largest-element-in-a-stream.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0703-kth-largest-element-in-a-stream.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0703-kth-largest-element-in-a-stream.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0703-kth-largest-element-in-a-stream.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0703-kth-largest-element-in-a-stream.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0703-kth-largest-element-in-a-stream.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0703-kth-largest-element-in-a-stream.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0703-kth-largest-element-in-a-stream.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0703-kth-largest-element-in-a-stream.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0703-kth-largest-element-in-a-stream.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0703-kth-largest-element-in-a-stream.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1046 - Last Stone Weight](https://leetcode.com/problems/last-stone-weight/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1046-last-stone-weight.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1046-Last-Stone-Weight.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1046-Last-Stone-Weight.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1046-last-stone-weight.go)</div></sub> | <sub><div align='center'>[✔️](java%2F1046-Last-Stone-Weight.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1046-Last-Stone-Weight.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1046-last-stone-weight.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1046-last-stone-weight.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F1046-Last-Stone-Weight.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F1046-last-stone-weight.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1046-last-stone-weight.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F1046-Last-Stone-Weight.ts)</div></sub>
-<sub>[0973 - K Closest Points to Origin](https://leetcode.com/problems/k-closest-points-to-origin/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0973-k-closest-points-to-origin.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0973-k-closest-points-to-origin.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0973-k-closest-points-to-origin.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0973-k-closest-points-to-origin.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0973-k-closest-points-to-origin.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0973-k-closest-points-to-origin.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0973-k-closest-points-to-origin.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0973-k-closest-points-to-origin.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0973-k-closest-points-to-origin.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0973-k-closest-points-to-origin.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0215 - Kth Largest Element In An Array](https://leetcode.com/problems/kth-largest-element-in-an-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0215-kth-largest-element-in-an-array.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0215-kth-largest-element-in-an-array.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0215-kth-largest-element-in-an-array.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0215-kth-largest-element-in-an-array.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0215-kth-largest-element-in-an-array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0215-kth-largest-element-in-an-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0215-kth-largest-element-in-an-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0215-kth-largest-element-in-an-array.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0215-kth-largest-element-in-an-array.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0215-kth-largest-element-in-an-array.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0215-kth-largest-element-in-an-array.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0215-kth-largest-element-in-an-array.ts)</div></sub>
-<sub>[0621 - Task Scheduler](https://leetcode.com/problems/task-scheduler/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0621-task-scheduler.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0621-task-scheduler.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0621-task-scheduler.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0621-task-scheduler.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0621-task-scheduler.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0621-task-scheduler.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0621-task-scheduler.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0621-task-scheduler.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0621-task-scheduler.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0621-task-scheduler.ts)</div></sub>
-<sub>[0355 - Design Twitter](https://leetcode.com/problems/design-twitter/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0355-design-twitter.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0355-design-twitter.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0355-design-twitter.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0355-design-twitter.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0355-design-twitter.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0355-design-twitter.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0355-design-twitter.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0355-design-twitter.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1675 - Minimize Deviation in Array](https://leetcode.com/problems/minimize-deviation-in-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1675-minimize-deviation-in-array.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1675-minimize-deviation-in-array.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2542 - Maximum Subsequence Score](https://leetcode.com/problems/maximum-subsequence-score/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F2542-maximum-subsequence-score.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F2542-maximum-subsequence-score.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2542-maximum-subsequence-score.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1834 - Single Threaded Cpu](https://leetcode.com/problems/single-threaded-cpu/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1834-single-threaded-cpu.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1834-single-threaded-cpu.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1834-single-threaded-cpu.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1834-single-threaded-cpu.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1834-single-threaded-cpu.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1845 - Seat Reservation Manager](https://leetcode.com/problems/seat-reservation-manager/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1845-seat-reservation-manager.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F1845-seat-reservation-manager.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1845-seat-reservation-manager.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1845-seat-reservation-manager.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1882 - Process Tasks Using Servers](https://leetcode.com/problems/process-tasks-using-servers/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1882-process-tasks-using-servers.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1882-process-tasks-using-servers.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1882-process-tasks-using-servers.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1985 - Find The Kth Largest Integer In The Array](https://leetcode.com/problems/find-the-kth-largest-integer-in-the-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1985-Find-The-Kth-Largest-Integer-In-The-Array.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1985-find-the-kth-largest-integer-in-the-array.go)</div></sub> | <sub><div align='center'>[✔️](java%2F1985-Find-The-Kth-Largest-Integer-In-The-Array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1985-find-the-kth-largest-integer-in-the-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1985-find-the-kth-largest-integer-in-the-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1985-find-the-kth-largest-integer-in-the-array.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1985-Find-The-Kth-Largest-Integer-In-The-Array.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0767 - Reorganize String](https://leetcode.com/problems/reorganize-string/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0767-reorganize-string.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0767-reorganize-string.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0767-reorganize-string.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0767-reorganize-string.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0767-reorganize-string.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1405 - Longest Happy String](https://leetcode.com/problems/longest-happy-string/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1405-longest-happy-string.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1405-longest-happy-string.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1405-longest-happy-string.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1094 - Car Pooling](https://leetcode.com/problems/car-pooling/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1094-car-pooling.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1094-Car-Pooling.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1094-car-pooling.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1094-car-pooling.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1094-car-pooling.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0295 - Find Median From Data Stream](https://leetcode.com/problems/find-median-from-data-stream/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0295-find-median-from-data-stream.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0295-find-median-from-data-stream.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0295-find-median-from-data-stream.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0295-find-median-from-data-stream.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0295-find-median-from-data-stream.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0295-find-median-from-data-stream.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0295-find-median-from-data-stream.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0295-find-median-from-data-stream.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0295-find-median-from-data-stream.ts)</div></sub>
-<sub>[1383 - Maximum Performance of a Team](https://leetcode.com/problems/maximum-performance-of-a-team/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](csharp%2F1383-Maximum-Performance-Of-A-Team.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F1383-maximum-performance-of-a-team.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1383-maximum-performance-of-a-team.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1383-maximum-performance-of-a-team.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0502 - IPO](https://leetcode.com/problems/ipo/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0502-ipo.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0502-ipo.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0502-ipo.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0502-ipo.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0502-ipo.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0502-ipo.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0502-ipo.ts)</div></sub>
+<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>hints</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
+---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
+<sub>[0703 - Kth Largest Element In a Stream](https://leetcode.com/problems/kth-largest-element-in-a-stream/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0703-kth-largest-element-in-a-stream.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0703-kth-largest-element-in-a-stream.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0703-kth-largest-element-in-a-stream.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0703-kth-largest-element-in-a-stream.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0703-kth-largest-element-in-a-stream.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0703-kth-largest-element-in-a-stream.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0703-kth-largest-element-in-a-stream.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0703-kth-largest-element-in-a-stream.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0703-kth-largest-element-in-a-stream.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0703-kth-largest-element-in-a-stream.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0703-kth-largest-element-in-a-stream.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0703-kth-largest-element-in-a-stream.ts)</div></sub>
+<sub>[1046 - Last Stone Weight](https://leetcode.com/problems/last-stone-weight/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1046-last-stone-weight.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1046-Last-Stone-Weight.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1046-Last-Stone-Weight.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1046-last-stone-weight.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1046-Last-Stone-Weight.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1046-Last-Stone-Weight.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1046-last-stone-weight.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1046-last-stone-weight.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F1046-Last-Stone-Weight.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F1046-last-stone-weight.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1046-last-stone-weight.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F1046-Last-Stone-Weight.ts)</div></sub>
+<sub>[0973 - K Closest Points to Origin](https://leetcode.com/problems/k-closest-points-to-origin/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0973-k-closest-points-to-origin.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0973-k-closest-points-to-origin.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0973-k-closest-points-to-origin.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0973-k-closest-points-to-origin.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0973-k-closest-points-to-origin.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0973-k-closest-points-to-origin.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0973-k-closest-points-to-origin.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0973-k-closest-points-to-origin.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0973-k-closest-points-to-origin.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0973-k-closest-points-to-origin.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0215 - Kth Largest Element In An Array](https://leetcode.com/problems/kth-largest-element-in-an-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0215-kth-largest-element-in-an-array.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0215-kth-largest-element-in-an-array.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0215-kth-largest-element-in-an-array.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0215-kth-largest-element-in-an-array.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0215-kth-largest-element-in-an-array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0215-kth-largest-element-in-an-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0215-kth-largest-element-in-an-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0215-kth-largest-element-in-an-array.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0215-kth-largest-element-in-an-array.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0215-kth-largest-element-in-an-array.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0215-kth-largest-element-in-an-array.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0215-kth-largest-element-in-an-array.ts)</div></sub>
+<sub>[0621 - Task Scheduler](https://leetcode.com/problems/task-scheduler/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0621-task-scheduler.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0621-task-scheduler.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0621-task-scheduler.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0621-task-scheduler.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0621-task-scheduler.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0621-task-scheduler.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0621-task-scheduler.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0621-task-scheduler.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0621-task-scheduler.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0621-task-scheduler.ts)</div></sub>
+<sub>[0355 - Design Twitter](https://leetcode.com/problems/design-twitter/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0355-design-twitter.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0355-design-twitter.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0355-design-twitter.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0355-design-twitter.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0355-design-twitter.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0355-design-twitter.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0355-design-twitter.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0355-design-twitter.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1675 - Minimize Deviation in Array](https://leetcode.com/problems/minimize-deviation-in-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1675-minimize-deviation-in-array.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1675-minimize-deviation-in-array.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2542 - Maximum Subsequence Score](https://leetcode.com/problems/maximum-subsequence-score/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F2542-maximum-subsequence-score.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F2542-maximum-subsequence-score.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2542-maximum-subsequence-score.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1834 - Single Threaded Cpu](https://leetcode.com/problems/single-threaded-cpu/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1834-single-threaded-cpu.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1834-single-threaded-cpu.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1834-single-threaded-cpu.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1834-single-threaded-cpu.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1834-single-threaded-cpu.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1845 - Seat Reservation Manager](https://leetcode.com/problems/seat-reservation-manager/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1845-seat-reservation-manager.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F1845-seat-reservation-manager.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1845-seat-reservation-manager.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1845-seat-reservation-manager.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1882 - Process Tasks Using Servers](https://leetcode.com/problems/process-tasks-using-servers/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1882-process-tasks-using-servers.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1882-process-tasks-using-servers.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1882-process-tasks-using-servers.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1985 - Find The Kth Largest Integer In The Array](https://leetcode.com/problems/find-the-kth-largest-integer-in-the-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1985-Find-The-Kth-Largest-Integer-In-The-Array.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1985-find-the-kth-largest-integer-in-the-array.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1985-Find-The-Kth-Largest-Integer-In-The-Array.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1985-find-the-kth-largest-integer-in-the-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1985-find-the-kth-largest-integer-in-the-array.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1985-find-the-kth-largest-integer-in-the-array.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1985-Find-The-Kth-Largest-Integer-In-The-Array.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0767 - Reorganize String](https://leetcode.com/problems/reorganize-string/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0767-reorganize-string.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0767-reorganize-string.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0767-reorganize-string.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0767-reorganize-string.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0767-reorganize-string.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1405 - Longest Happy String](https://leetcode.com/problems/longest-happy-string/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1405-longest-happy-string.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1405-longest-happy-string.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1405-longest-happy-string.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1094 - Car Pooling](https://leetcode.com/problems/car-pooling/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1094-car-pooling.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1094-Car-Pooling.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1094-car-pooling.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1094-car-pooling.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1094-car-pooling.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0295 - Find Median From Data Stream](https://leetcode.com/problems/find-median-from-data-stream/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0295-find-median-from-data-stream.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0295-find-median-from-data-stream.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0295-find-median-from-data-stream.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0295-find-median-from-data-stream.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0295-find-median-from-data-stream.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0295-find-median-from-data-stream.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0295-find-median-from-data-stream.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0295-find-median-from-data-stream.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0295-find-median-from-data-stream.ts)</div></sub>
+<sub>[1383 - Maximum Performance of a Team](https://leetcode.com/problems/maximum-performance-of-a-team/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](csharp%2F1383-Maximum-Performance-Of-A-Team.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F1383-maximum-performance-of-a-team.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1383-maximum-performance-of-a-team.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1383-maximum-performance-of-a-team.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0502 - IPO](https://leetcode.com/problems/ipo/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0502-ipo.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0502-ipo.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0502-ipo.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0502-ipo.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0502-ipo.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0502-ipo.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0502-ipo.ts)</div></sub>
 
 ### Backtracking
 
-<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
----- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
-<sub>[0078 - Subsets](https://leetcode.com/problems/subsets/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0078-subsets.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0078-subsets.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0078-subsets.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0078-subsets.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0078-subsets.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0078-subsets.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0078-subsets.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0078-subsets.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0078-subsets.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0078-subsets.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0078-subsets.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0078-subsets.ts)</div></sub>
-<sub>[0039 - Combination Sum](https://leetcode.com/problems/combination-sum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0039-combination-sum.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0039-combination-sum.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0039-combination-sum.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0039-combination-sum.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0039-combination-sum.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0039-combination-sum.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0039-combination-sum.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0039-combination-sum.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0039-combination-sum.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0039-combination-sum.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0039-combination-sum.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0039-combination-sum.ts)</div></sub>
-<sub>[0077 - Combinations](https://leetcode.com/problems/combinations/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0077-combinations.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0077-combinations.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0077-combinations.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0077-combinations.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0077-combinations.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0077-combinations.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0077-combinations.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0046 - Permutations](https://leetcode.com/problems/permutations/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0046-permutations.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0046-permutations.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0046-permutations.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0046-permutations.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0046-permutations.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0046-permutations.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0046-permutations.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0046-permutations.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0046-permutations.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0046-permutations.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0046-permutations.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0046-permutations.ts)</div></sub>
-<sub>[0090 - Subsets II](https://leetcode.com/problems/subsets-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0090-subsets-ii.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0090-subsets-ii.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0090-subsets-ii.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0090-subsets-ii.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0090-subsets-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0090-subsets-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0090-subsets-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0090-subsets-ii.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0090-subsets-ii.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0090-subsets-ii.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0090-subsets-ii.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0090-subsets-ii.ts)</div></sub>
-<sub>[0040 - Combination Sum II](https://leetcode.com/problems/combination-sum-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0040-combination-sum-ii.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0040-combination-sum-ii.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0040-combination-sum-ii.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0040-combination-sum-ii.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0040-combination-sum-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0040-combination-sum-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0040-combination-sum-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0040-combination-sum-ii.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0040-combination-sum-ii.rb)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0040-combination-sum-ii.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0040-combination-sum-ii.ts)</div></sub>
-<sub>[0047 - Permutations II](https://leetcode.com/problems/permutations-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](csharp%2F0047-permutations-ii.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0047-permutations-ii.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0047-permutations-ii.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0047-permutations-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0047-permutations-ii.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0047-permutations-ii.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0047-permutations-ii.ts)</div></sub>
-<sub>[0079 - Word Search](https://leetcode.com/problems/word-search/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0079-word-search.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0079-word-search.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0079-word-search.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0079-word-search.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0079-word-search.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0079-word-search.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0079-word-search.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0079-word-search.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0079-word-search.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0079-word-search.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0079-word-search.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0079-word-search.ts)</div></sub>
-<sub>[0131 - Palindrome Partitioning](https://leetcode.com/problems/palindrome-partitioning/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0131-palindrome-partitioning.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0131-palindrome-partitioning.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0131-palindrome-partitioning.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0131-palindrome-partitioning.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0131-palindrome-partitioning.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0131-palindrome-partitioning.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0131-palindrome-partitioning.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0131-palindrome-partitioning.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0131-palindrome-partitioning.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0131-palindrome-partitioning.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0131-palindrome-partitioning.ts)</div></sub>
-<sub>[0093 - Restore IP Addresses](https://leetcode.com/problems/restore-ip-addresses/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](csharp%2F0093-restore-ip-addresses.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0093-restore-ip-addresses.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F0093-restore-ip-addresses.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0093-restore-ip-addresses.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0093-restore-ip-addresses.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0093-restore-ip-addresses.ts)</div></sub>
-<sub>[0017 - Letter Combinations of a Phone Number](https://leetcode.com/problems/letter-combinations-of-a-phone-number/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0017-letter-combinations-of-a-phone-number.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0017-letter-combinations-of-a-phone-number.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0017-letter-combinations-of-a-phone-number.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0017-letter-combinations-of-a-phone-number.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0017-letter-combinations-of-a-phone-number.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0017-letter-combinations-of-a-phone-number.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0017-letter-combinations-of-a-phone-number.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0017-letter-combinations-of-a-phone-number.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0017-letter-combinations-of-a-phone-number.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0017-letter-combinations-of-a-phone-number.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0017-letter-combinations-of-a-phone-number.ts)</div></sub>
-<sub>[0473 - Matchsticks to Square](https://leetcode.com/problems/matchsticks-to-square/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0473-matchsticks-to-square.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0473-matchsticks-to-square.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0473-matchsticks-to-square.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0473-matchsticks-to-square.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0473-matchsticks-to-square.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1849 - Splitting a String Into Descending Consecutive Values](https://leetcode.com/problems/splitting-a-string-into-descending-consecutive-values/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1849-splitting-a-string-into-descending-consecutive-values.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1849-splitting-a-string-into-descending-consecutive-values.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1849-splitting-a-string-into-descending-consecutive-values.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1849-splitting-a-string-into-descending-consecutive-values.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1980 - Find Unique Binary String](https://leetcode.com/problems/find-unique-binary-string/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1980-find-unique-binary-string.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1980-find-unique-binary-string.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1980-find-unique-binary-string.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1980-find-unique-binary-string.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1239 - Maximum Length of a Concatenated String With Unique Characters](https://leetcode.com/problems/maximum-length-of-a-concatenated-string-with-unique-characters/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](csharp%2F1239-maximum-length-of-a-concatenated-string-with-unique-characters.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1239-maximum-length-of-a-concatenated-string-with-unique-characters.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1239-maximum-length-of-a-concatenated-string-with-unique-characters.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0698 - Partition to K Equal Sum Subsets](https://leetcode.com/problems/partition-to-k-equal-sum-subsets/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0698-partition-to-k-equal-sum-subsets.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0698-partition-to-k-equal-sum-subsets.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0698-partition-to-k-equal-sum-subsets.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0051 - N Queens](https://leetcode.com/problems/n-queens/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0051-n-queens.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0051-n-queens.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0051-n-queens.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0051-n-queens.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0051-n-queens.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0051-n-queens.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0051-n-queens.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0051-n-queens.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0051-n-queens.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0051-n-queens.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0051-n-queens.ts)</div></sub>
-<sub>[0052 - N Queens II](https://leetcode.com/problems/n-queens-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0052-n-queens-ii.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0052-n-queens-ii.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0052-n-queens-ii.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0052-n-queens-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0052-n-queens-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0052-n-queens-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0052-n-queens-ii.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>hints</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
+---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
+<sub>[0078 - Subsets](https://leetcode.com/problems/subsets/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0078-subsets.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0078-subsets.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0078-subsets.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0078-subsets.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0078-subsets.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0078-subsets.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0078-subsets.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0078-subsets.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0078-subsets.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0078-subsets.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0078-subsets.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0078-subsets.ts)</div></sub>
+<sub>[0039 - Combination Sum](https://leetcode.com/problems/combination-sum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0039-combination-sum.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0039-combination-sum.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0039-combination-sum.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0039-combination-sum.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0039-combination-sum.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0039-combination-sum.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0039-combination-sum.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0039-combination-sum.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0039-combination-sum.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0039-combination-sum.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0039-combination-sum.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0039-combination-sum.ts)</div></sub>
+<sub>[0077 - Combinations](https://leetcode.com/problems/combinations/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0077-combinations.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0077-combinations.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0077-combinations.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0077-combinations.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0077-combinations.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0077-combinations.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0077-combinations.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0046 - Permutations](https://leetcode.com/problems/permutations/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0046-permutations.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0046-permutations.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0046-permutations.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0046-permutations.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0046-permutations.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0046-permutations.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0046-permutations.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0046-permutations.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0046-permutations.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0046-permutations.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0046-permutations.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0046-permutations.ts)</div></sub>
+<sub>[0090 - Subsets II](https://leetcode.com/problems/subsets-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0090-subsets-ii.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0090-subsets-ii.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0090-subsets-ii.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0090-subsets-ii.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0090-subsets-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0090-subsets-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0090-subsets-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0090-subsets-ii.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0090-subsets-ii.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0090-subsets-ii.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0090-subsets-ii.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0090-subsets-ii.ts)</div></sub>
+<sub>[0040 - Combination Sum II](https://leetcode.com/problems/combination-sum-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0040-combination-sum-ii.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0040-combination-sum-ii.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0040-combination-sum-ii.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0040-combination-sum-ii.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0040-combination-sum-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0040-combination-sum-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0040-combination-sum-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0040-combination-sum-ii.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0040-combination-sum-ii.rb)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0040-combination-sum-ii.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0040-combination-sum-ii.ts)</div></sub>
+<sub>[0047 - Permutations II](https://leetcode.com/problems/permutations-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](csharp%2F0047-permutations-ii.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0047-permutations-ii.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0047-permutations-ii.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0047-permutations-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0047-permutations-ii.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0047-permutations-ii.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0047-permutations-ii.ts)</div></sub>
+<sub>[0079 - Word Search](https://leetcode.com/problems/word-search/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0079-word-search.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0079-word-search.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0079-word-search.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0079-word-search.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0079-word-search.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0079-word-search.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0079-word-search.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0079-word-search.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0079-word-search.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0079-word-search.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0079-word-search.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0079-word-search.ts)</div></sub>
+<sub>[0131 - Palindrome Partitioning](https://leetcode.com/problems/palindrome-partitioning/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0131-palindrome-partitioning.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0131-palindrome-partitioning.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0131-palindrome-partitioning.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0131-palindrome-partitioning.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0131-palindrome-partitioning.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0131-palindrome-partitioning.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0131-palindrome-partitioning.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0131-palindrome-partitioning.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0131-palindrome-partitioning.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0131-palindrome-partitioning.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0131-palindrome-partitioning.ts)</div></sub>
+<sub>[0093 - Restore IP Addresses](https://leetcode.com/problems/restore-ip-addresses/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](csharp%2F0093-restore-ip-addresses.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0093-restore-ip-addresses.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F0093-restore-ip-addresses.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0093-restore-ip-addresses.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0093-restore-ip-addresses.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0093-restore-ip-addresses.ts)</div></sub>
+<sub>[0017 - Letter Combinations of a Phone Number](https://leetcode.com/problems/letter-combinations-of-a-phone-number/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0017-letter-combinations-of-a-phone-number.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0017-letter-combinations-of-a-phone-number.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0017-letter-combinations-of-a-phone-number.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0017-letter-combinations-of-a-phone-number.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0017-letter-combinations-of-a-phone-number.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0017-letter-combinations-of-a-phone-number.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0017-letter-combinations-of-a-phone-number.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0017-letter-combinations-of-a-phone-number.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0017-letter-combinations-of-a-phone-number.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0017-letter-combinations-of-a-phone-number.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0017-letter-combinations-of-a-phone-number.ts)</div></sub>
+<sub>[0473 - Matchsticks to Square](https://leetcode.com/problems/matchsticks-to-square/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0473-matchsticks-to-square.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0473-matchsticks-to-square.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0473-matchsticks-to-square.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0473-matchsticks-to-square.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0473-matchsticks-to-square.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1849 - Splitting a String Into Descending Consecutive Values](https://leetcode.com/problems/splitting-a-string-into-descending-consecutive-values/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1849-splitting-a-string-into-descending-consecutive-values.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1849-splitting-a-string-into-descending-consecutive-values.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1849-splitting-a-string-into-descending-consecutive-values.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1849-splitting-a-string-into-descending-consecutive-values.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1980 - Find Unique Binary String](https://leetcode.com/problems/find-unique-binary-string/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1980-find-unique-binary-string.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1980-find-unique-binary-string.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1980-find-unique-binary-string.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1980-find-unique-binary-string.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1239 - Maximum Length of a Concatenated String With Unique Characters](https://leetcode.com/problems/maximum-length-of-a-concatenated-string-with-unique-characters/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](csharp%2F1239-maximum-length-of-a-concatenated-string-with-unique-characters.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1239-maximum-length-of-a-concatenated-string-with-unique-characters.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1239-maximum-length-of-a-concatenated-string-with-unique-characters.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0698 - Partition to K Equal Sum Subsets](https://leetcode.com/problems/partition-to-k-equal-sum-subsets/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0698-partition-to-k-equal-sum-subsets.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0698-partition-to-k-equal-sum-subsets.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0698-partition-to-k-equal-sum-subsets.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0051 - N Queens](https://leetcode.com/problems/n-queens/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0051-n-queens.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0051-n-queens.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0051-n-queens.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0051-n-queens.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0051-n-queens.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0051-n-queens.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0051-n-queens.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0051-n-queens.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0051-n-queens.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0051-n-queens.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0051-n-queens.ts)</div></sub>
+<sub>[0052 - N Queens II](https://leetcode.com/problems/n-queens-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0052-n-queens-ii.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0052-n-queens-ii.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0052-n-queens-ii.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0052-n-queens-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0052-n-queens-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0052-n-queens-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0052-n-queens-ii.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
 
 ### Graphs
 
-<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
----- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
-<sub>[0463 - Island Perimeter](https://leetcode.com/problems/island-perimeter/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0463-island-perimeter.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0463-island-perimeter.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0463-island-perimeter.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0463-island-perimeter.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0463-island-perimeter.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0463-island-perimeter.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0463-island-perimeter.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0463-island-perimeter.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0953 - Verifying An Alien Dictionary](https://leetcode.com/problems/verifying-an-alien-dictionary/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0953-verifying-an-alien-dictionary.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0953-verifying-an-alien-dictionary.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0953-verifying-an-alien-dictionary.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0953-verifying-an-alien-dictionary.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0953-verifying-an-alien-dictionary.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0953-verifying-an-alien-dictionary.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0953-verifying-an-alien-dictionary.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0953-verifying-an-alien-dictionary.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0200 - Number of Islands](https://leetcode.com/problems/number-of-islands/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0200-number-of-islands.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0200-number-of-islands.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0200-number-of-islands.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0200-number-of-islands.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0200-number-of-islands.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0200-number-of-islands.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0200-number-of-islands.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0200-number-of-islands.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0200-number-of-islands.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0200-number-of-islands.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0200-number-of-islands.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0200-number-of-islands.ts)</div></sub>
-<sub>[0133 - Clone Graph](https://leetcode.com/problems/clone-graph/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0133-clone-graph.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0133-clone-graph.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0133-clone-graph.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0133-clone-graph.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0133-clone-graph.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0133-clone-graph.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0133-clone-graph.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0133-clone-graph.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0133-clone-graph.rb)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0133-clone-graph.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0133-clone-graph.ts)</div></sub>
-<sub>[0695 - Max Area of Island](https://leetcode.com/problems/max-area-of-island/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0695-max-area-of-island.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0695-max-area-of-island.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0695-max-area-of-island.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0695-max-area-of-island.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0695-max-area-of-island.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0695-max-area-of-island.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0695-max-area-of-island.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0695-max-area-of-island.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0695-max-area-of-island.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0695-max-area-of-island.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0695-max-area-of-island.ts)</div></sub>
-<sub>[1905 - Count Sub Islands](https://leetcode.com/problems/count-sub-islands/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1905-Count-Sub-Islands.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1905-count-sub-islands.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1905-Count-Sub-Islands.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1905-count-sub-islands.go)</div></sub> | <sub><div align='center'>[✔️](java%2F1905-count-sub-islands.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1905-count-sub-islands.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1905-count-sub-islands.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1905-count-sub-islands.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0417 - Pacific Atlantic Water Flow](https://leetcode.com/problems/pacific-atlantic-water-flow/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0417-pacific-atlantic-water-flow.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0417-pacific-atlantic-water-flow.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0417-pacific-atlantic-water-flow.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0417-pacific-atlantic-water-flow.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0417-pacific-atlantic-water-flow.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0417-pacific-atlantic-water-flow.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0417-pacific-atlantic-water-flow.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0417-pacific-atlantic-water-flow.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0417-pacific-atlantic-water-flow.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0417-pacific-atlantic-water-flow.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0417-pacific-atlantic-water-flow.ts)</div></sub>
-<sub>[0130 - Surrounded Regions](https://leetcode.com/problems/surrounded-regions/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0130-surrounded-regions.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0130-surrounded-regions.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0130-surrounded-regions.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0130-surrounded-regions.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0130-surrounded-regions.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0130-surrounded-regions.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0130-surrounded-regions.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0130-surrounded-regions.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0130-surrounded-regions.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0130-surrounded-regions.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0130-surrounded-regions.ts)</div></sub>
-<sub>[1466 - Reorder Routes to Make All Paths Lead to The City Zero](https://leetcode.com/problems/reorder-routes-to-make-all-paths-lead-to-the-city-zero/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1466-reorder-routes-to-make-all-paths-lead-to-the-city-zero.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1466-Reorder-Routes-to-Make-All-Paths-Lead-To-The-City-Zero.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1466-reorder-routes-to-make-all-paths-lead-to-the-city-zero.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1466-reorder-routes-to-make-all-paths-lead-to-the-city-zero.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1466-reorder-routes-to-make-all-paths-lead-to-the-city-zero.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0994 - Rotting Oranges](https://leetcode.com/problems/rotting-oranges/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0994-rotting-oranges.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0994-rotting-oranges.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0994-rotting-oranges.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0994-rotting-oranges.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0994-rotting-oranges.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0994-rotting-oranges.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0994-rotting-oranges.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0994-rotting-oranges.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0994-rotting-oranges.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0994-rotting-oranges.ts)</div></sub>
-<sub>[0286 - Walls And Gates](https://leetcode.com/problems/walls-and-gates/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0286-walls-and-gates.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0286-walls-and-gates.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0286-walls-and-gates.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0286-walls-and-gates.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0286-walls-and-gates.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0286-walls-and-gates.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0286-walls-and-gates.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0909 - Snakes And Ladders](https://leetcode.com/problems/snakes-and-ladders/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](csharp%2F0909-snakes-and-ladders.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0909-snakes-and-ladders.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0909-snakes-and-ladders.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0909-snakes-and-ladders.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0752 - Open The Lock](https://leetcode.com/problems/open-the-lock/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](csharp%2F0752-open-the-lock.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0752-open-the-lock.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0752-open-the-lock.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0752-open-the-lock.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0752-open-the-lock.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0802 - Find Eventual Safe States](https://leetcode.com/problems/find-eventual-safe-states/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0802-find-eventual-safe-states.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0802-find-eventual-safe-states.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0802-find-eventual-safe-states.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0207 - Course Schedule](https://leetcode.com/problems/course-schedule/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0207-course-schedule.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0207-course-schedule.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0207-course-schedule.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0207-course-schedule.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0207-course-schedule.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0207-course-schedule.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0207-course-schedule.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0207-course-schedule.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0207-course-schedule.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0207-course-schedule.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0207-course-schedule.ts)</div></sub>
-<sub>[0210 - Course Schedule II](https://leetcode.com/problems/course-schedule-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0210-course-schedule-ii.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0210-course-schedule-ii.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0210-course-schedule-ii.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0210-course-schedule-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0210-course-schedule-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0210-course-schedule-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0210-course-schedule-ii.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0210-course-schedule-ii.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0210-course-schedule-ii.ts)</div></sub>
-<sub>[1462 - Course Schedule IV](https://leetcode.com/problems/course-schedule-iv/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1462-course-schedule-iv.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1462-course-schedule-iv.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1462-course-schedule-iv.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1462-course-schedule-iv.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F1462-course-schedule-iv.ts)</div></sub>
-<sub>[1958 - Check if Move Is Legal](https://leetcode.com/problems/check-if-move-is-legal/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1958-check-if-move-is-legal.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1958-check-if-move-is-legal.go)</div></sub> | <sub><div align='center'>[✔️](java%2F1958-check-if-move-is-legal.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1958-check-if-move-is-legal.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1958-check-if-move-is-legal.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1958-check-if-move-is-legal.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0934 - Shortest Bridge](https://leetcode.com/problems/shortest-bridge/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F0934-shortest-bridge.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0934-shortest-bridge.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1091 - Shortest Path in Binary Matrix](https://leetcode.com/problems/shortest-path-in-binary-matrix/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1091-shortest-path-in-binary-matrix.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1091-shortest-path-in-binary-matrix.go)</div></sub> | <sub><div align='center'>[✔️](java%2F1091-shortest-path-in-binary-matrix.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1091-shortest-path-in-binary-matrix.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1091-shortest-path-in-binary-matrix.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1091-shortest-path-in-binary-matrix.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0684 - Redundant Connection](https://leetcode.com/problems/redundant-connection/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0684-redundant-connection.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0684-redundant-connection.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0684-redundant-connection.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0684-redundant-connection.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0684-redundant-connection.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0684-redundant-connection.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0684-redundant-connection.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0684-redundant-connection.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0684-redundant-connection.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0684-redundant-connection.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0684-redundant-connection.ts)</div></sub>
-<sub>[0323 - Number of Connected Components In An Undirected Graph](https://leetcode.com/problems/number-of-connected-components-in-an-undirected-graph/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0323-number-of-connected-components-in-an-undirected-graph.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0323-number-of-connected-components-in-an-undirected-graph.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0323-number-of-connected-components-in-an-undirected-graph.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0323-number-of-connected-components-in-an-undirected-graph.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0323-number-of-connected-components-in-an-undirected-graph.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0323-number-of-connected-components-in-an-undirected-graph.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0323-number-of-connected-components-in-an-undirected-graph.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0323-number-of-connected-components-in-an-undirected-graph.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0261 - Graph Valid Tree](https://leetcode.com/problems/graph-valid-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0261-graph-valid-tree.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0261-graph-valid-tree.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0261-graph-valid-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0261-graph-valid-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0261-graph-valid-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0261-graph-valid-tree.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0261-graph-valid-tree.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0261-graph-valid-tree.ts)</div></sub>
-<sub>[0721 - Accounts Merge](https://leetcode.com/problems/accounts-merge/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0721-accounts-merge.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0721-accounts-merge.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0721-accounts-merge.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0721-accounts-merge.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2359 - Find Closest Node to Given Two Nodes](https://leetcode.com/problems/find-closest-node-to-given-two-nodes/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2359-find-closest-node-to-given-two-nodes.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1162 - As Far from Land as Possible](https://leetcode.com/problems/as-far-from-land-as-possible/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1162-as-far-from-land-as-possible.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1129 - Shortest Path with Alternating Colors](https://leetcode.com/problems/shortest-path-with-alternating-colors/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1129-shortest-path-with-alternating-colors.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1129-shortest-path-with-alternating-colors.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2477 - Minimum Fuel Cost to Report to the Capital](https://leetcode.com/problems/minimum-fuel-cost-to-report-to-the-capital/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F2477-minimum-fuel-cost-to-report-to-the-capital.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2477-minimum-fuel-cost-to-report-to-the-capital.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2492 - Minimum Score of a Path Between Two Cities](https://leetcode.com/problems/minimum-score-of-a-path-between-two-cities/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2492-minimum-score-of-a-path-between-two-cities.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1254 - Number of Closed Islands](https://leetcode.com/problems/number-of-closed-islands/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1254-number-of-closed-islands.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1254-number-of-closed-islands.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1020 - Number of Enclaves](https://leetcode.com/problems/number-of-enclaves/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1020-number-of-enclaves.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1020-number-of-enclaves.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1020-number-of-enclaves.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1557 - Minimum Number of Vertices to Reach all Nodes](https://leetcode.com/problems/minimum-number-of-vertices-to-reach-all-nodes/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1557-minimum-number-of-vertices-to-reach-all-nodes.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1557-minimum-number-of-vertices-to-reach-all-nodes.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0785 - Is Graph Bipartite?](https://leetcode.com/problems/is-graph-bipartite/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0785-is-graph-bipartite.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0785-is-graph-bipartite.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0785-is-graph-bipartite.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0399 - Evaluate Division](https://leetcode.com/problems/evaluate-division/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0399-evaluate-division.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0399-evaluate-division.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0399-evaluate-division.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2101 - Detonate the Maximum Bombs](https://leetcode.com/problems/detonate-the-maximum-bombs/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2101-detonate-the-maximum-bombs.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F2101-detonate-the-maximum-bombs.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1857 - Largest Color Value in a Directed Graph](https://leetcode.com/problems/largest-color-value-in-a-directed-graph/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1857-largest-color-value-in-a-directed-graph.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1857-largest-color-value-in-a-directed-graph.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1553 - Minimum Number of Days to Eat N Oranges](https://leetcode.com/problems/minimum-number-of-days-to-eat-n-oranges/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1553-minimum-number-of-days-to-eat-n-oranges.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1553-minimum-number-of-days-to-eat-n-oranges.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0127 - Word Ladder](https://leetcode.com/problems/word-ladder/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0127-word-ladder.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0127-word-ladder.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0127-word-ladder.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0127-word-ladder.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0127-word-ladder.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0127-word-ladder.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0127-word-ladder.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0127-word-ladder.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0127-word-ladder.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0127-word-ladder.ts)</div></sub>
+<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>hints</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
+---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
+<sub>[0463 - Island Perimeter](https://leetcode.com/problems/island-perimeter/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0463-island-perimeter.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0463-island-perimeter.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0463-island-perimeter.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0463-island-perimeter.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0463-island-perimeter.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0463-island-perimeter.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0463-island-perimeter.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0463-island-perimeter.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0953 - Verifying An Alien Dictionary](https://leetcode.com/problems/verifying-an-alien-dictionary/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0953-verifying-an-alien-dictionary.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0953-verifying-an-alien-dictionary.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0953-verifying-an-alien-dictionary.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0953-verifying-an-alien-dictionary.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0953-verifying-an-alien-dictionary.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0953-verifying-an-alien-dictionary.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0953-verifying-an-alien-dictionary.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0953-verifying-an-alien-dictionary.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0200 - Number of Islands](https://leetcode.com/problems/number-of-islands/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0200-number-of-islands.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0200-number-of-islands.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0200-number-of-islands.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0200-number-of-islands.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0200-number-of-islands.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0200-number-of-islands.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0200-number-of-islands.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0200-number-of-islands.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0200-number-of-islands.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0200-number-of-islands.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0200-number-of-islands.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0200-number-of-islands.ts)</div></sub>
+<sub>[0133 - Clone Graph](https://leetcode.com/problems/clone-graph/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0133-clone-graph.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0133-clone-graph.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0133-clone-graph.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0133-clone-graph.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0133-clone-graph.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0133-clone-graph.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0133-clone-graph.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0133-clone-graph.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0133-clone-graph.rb)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0133-clone-graph.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0133-clone-graph.ts)</div></sub>
+<sub>[0695 - Max Area of Island](https://leetcode.com/problems/max-area-of-island/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0695-max-area-of-island.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0695-max-area-of-island.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0695-max-area-of-island.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0695-max-area-of-island.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0695-max-area-of-island.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0695-max-area-of-island.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0695-max-area-of-island.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0695-max-area-of-island.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0695-max-area-of-island.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0695-max-area-of-island.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0695-max-area-of-island.ts)</div></sub>
+<sub>[1905 - Count Sub Islands](https://leetcode.com/problems/count-sub-islands/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1905-Count-Sub-Islands.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1905-count-sub-islands.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1905-Count-Sub-Islands.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1905-count-sub-islands.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1905-count-sub-islands.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1905-count-sub-islands.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1905-count-sub-islands.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1905-count-sub-islands.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0417 - Pacific Atlantic Water Flow](https://leetcode.com/problems/pacific-atlantic-water-flow/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0417-pacific-atlantic-water-flow.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0417-pacific-atlantic-water-flow.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0417-pacific-atlantic-water-flow.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0417-pacific-atlantic-water-flow.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0417-pacific-atlantic-water-flow.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0417-pacific-atlantic-water-flow.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0417-pacific-atlantic-water-flow.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0417-pacific-atlantic-water-flow.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0417-pacific-atlantic-water-flow.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0417-pacific-atlantic-water-flow.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0417-pacific-atlantic-water-flow.ts)</div></sub>
+<sub>[0130 - Surrounded Regions](https://leetcode.com/problems/surrounded-regions/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0130-surrounded-regions.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0130-surrounded-regions.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0130-surrounded-regions.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0130-surrounded-regions.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0130-surrounded-regions.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0130-surrounded-regions.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0130-surrounded-regions.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0130-surrounded-regions.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0130-surrounded-regions.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0130-surrounded-regions.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0130-surrounded-regions.ts)</div></sub>
+<sub>[1466 - Reorder Routes to Make All Paths Lead to The City Zero](https://leetcode.com/problems/reorder-routes-to-make-all-paths-lead-to-the-city-zero/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1466-reorder-routes-to-make-all-paths-lead-to-the-city-zero.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1466-Reorder-Routes-to-Make-All-Paths-Lead-To-The-City-Zero.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1466-reorder-routes-to-make-all-paths-lead-to-the-city-zero.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1466-reorder-routes-to-make-all-paths-lead-to-the-city-zero.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1466-reorder-routes-to-make-all-paths-lead-to-the-city-zero.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0994 - Rotting Oranges](https://leetcode.com/problems/rotting-oranges/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0994-rotting-oranges.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0994-rotting-oranges.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0994-rotting-oranges.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0994-rotting-oranges.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0994-rotting-oranges.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0994-rotting-oranges.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0994-rotting-oranges.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0994-rotting-oranges.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0994-rotting-oranges.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0994-rotting-oranges.ts)</div></sub>
+<sub>[0286 - Walls And Gates](https://leetcode.com/problems/walls-and-gates/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0286-walls-and-gates.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0286-walls-and-gates.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0286-walls-and-gates.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0286-walls-and-gates.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0286-walls-and-gates.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0286-walls-and-gates.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0286-walls-and-gates.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0909 - Snakes And Ladders](https://leetcode.com/problems/snakes-and-ladders/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](csharp%2F0909-snakes-and-ladders.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0909-snakes-and-ladders.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0909-snakes-and-ladders.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0909-snakes-and-ladders.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0909-snakes-and-ladders.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0752 - Open The Lock](https://leetcode.com/problems/open-the-lock/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](csharp%2F0752-open-the-lock.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0752-open-the-lock.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0752-open-the-lock.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0752-open-the-lock.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0752-open-the-lock.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0802 - Find Eventual Safe States](https://leetcode.com/problems/find-eventual-safe-states/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0802-find-eventual-safe-states.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0802-find-eventual-safe-states.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0802-find-eventual-safe-states.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0207 - Course Schedule](https://leetcode.com/problems/course-schedule/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0207-course-schedule.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0207-course-schedule.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0207-course-schedule.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0207-course-schedule.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0207-course-schedule.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0207-course-schedule.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0207-course-schedule.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0207-course-schedule.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0207-course-schedule.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0207-course-schedule.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0207-course-schedule.ts)</div></sub>
+<sub>[0210 - Course Schedule II](https://leetcode.com/problems/course-schedule-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0210-course-schedule-ii.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0210-course-schedule-ii.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0210-course-schedule-ii.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0210-course-schedule-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0210-course-schedule-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0210-course-schedule-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0210-course-schedule-ii.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0210-course-schedule-ii.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0210-course-schedule-ii.ts)</div></sub>
+<sub>[1462 - Course Schedule IV](https://leetcode.com/problems/course-schedule-iv/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1462-course-schedule-iv.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1462-course-schedule-iv.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1462-course-schedule-iv.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1462-course-schedule-iv.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F1462-course-schedule-iv.ts)</div></sub>
+<sub>[1958 - Check if Move Is Legal](https://leetcode.com/problems/check-if-move-is-legal/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1958-check-if-move-is-legal.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1958-check-if-move-is-legal.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1958-check-if-move-is-legal.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1958-check-if-move-is-legal.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1958-check-if-move-is-legal.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1958-check-if-move-is-legal.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0934 - Shortest Bridge](https://leetcode.com/problems/shortest-bridge/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0934-shortest-bridge.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0934-shortest-bridge.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0934-shortest-bridge.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1091 - Shortest Path in Binary Matrix](https://leetcode.com/problems/shortest-path-in-binary-matrix/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1091-shortest-path-in-binary-matrix.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1091-shortest-path-in-binary-matrix.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1091-shortest-path-in-binary-matrix.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1091-shortest-path-in-binary-matrix.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1091-shortest-path-in-binary-matrix.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1091-shortest-path-in-binary-matrix.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0684 - Redundant Connection](https://leetcode.com/problems/redundant-connection/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0684-redundant-connection.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0684-redundant-connection.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0684-redundant-connection.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0684-redundant-connection.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0684-redundant-connection.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0684-redundant-connection.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0684-redundant-connection.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0684-redundant-connection.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0684-redundant-connection.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0684-redundant-connection.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0684-redundant-connection.ts)</div></sub>
+<sub>[0323 - Number of Connected Components In An Undirected Graph](https://leetcode.com/problems/number-of-connected-components-in-an-undirected-graph/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0323-number-of-connected-components-in-an-undirected-graph.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0323-number-of-connected-components-in-an-undirected-graph.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0323-number-of-connected-components-in-an-undirected-graph.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0323-number-of-connected-components-in-an-undirected-graph.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0323-number-of-connected-components-in-an-undirected-graph.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0323-number-of-connected-components-in-an-undirected-graph.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0323-number-of-connected-components-in-an-undirected-graph.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0323-number-of-connected-components-in-an-undirected-graph.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0261 - Graph Valid Tree](https://leetcode.com/problems/graph-valid-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0261-graph-valid-tree.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0261-graph-valid-tree.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0261-graph-valid-tree.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0261-graph-valid-tree.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0261-graph-valid-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0261-graph-valid-tree.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0261-graph-valid-tree.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0261-graph-valid-tree.ts)</div></sub>
+<sub>[0721 - Accounts Merge](https://leetcode.com/problems/accounts-merge/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0721-accounts-merge.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0721-accounts-merge.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0721-accounts-merge.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0721-accounts-merge.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2359 - Find Closest Node to Given Two Nodes](https://leetcode.com/problems/find-closest-node-to-given-two-nodes/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2359-find-closest-node-to-given-two-nodes.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1162 - As Far from Land as Possible](https://leetcode.com/problems/as-far-from-land-as-possible/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1162-as-far-from-land-as-possible.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1129 - Shortest Path with Alternating Colors](https://leetcode.com/problems/shortest-path-with-alternating-colors/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1129-shortest-path-with-alternating-colors.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1129-shortest-path-with-alternating-colors.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2477 - Minimum Fuel Cost to Report to the Capital](https://leetcode.com/problems/minimum-fuel-cost-to-report-to-the-capital/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F2477-minimum-fuel-cost-to-report-to-the-capital.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2477-minimum-fuel-cost-to-report-to-the-capital.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2492 - Minimum Score of a Path Between Two Cities](https://leetcode.com/problems/minimum-score-of-a-path-between-two-cities/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2492-minimum-score-of-a-path-between-two-cities.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1254 - Number of Closed Islands](https://leetcode.com/problems/number-of-closed-islands/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1254-number-of-closed-islands.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1254-number-of-closed-islands.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1020 - Number of Enclaves](https://leetcode.com/problems/number-of-enclaves/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1020-number-of-enclaves.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1020-number-of-enclaves.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1020-number-of-enclaves.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1557 - Minimum Number of Vertices to Reach all Nodes](https://leetcode.com/problems/minimum-number-of-vertices-to-reach-all-nodes/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1557-minimum-number-of-vertices-to-reach-all-nodes.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1557-minimum-number-of-vertices-to-reach-all-nodes.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0785 - Is Graph Bipartite?](https://leetcode.com/problems/is-graph-bipartite/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0785-is-graph-bipartite.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0785-is-graph-bipartite.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0785-is-graph-bipartite.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0399 - Evaluate Division](https://leetcode.com/problems/evaluate-division/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0399-evaluate-division.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0399-evaluate-division.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0399-evaluate-division.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2101 - Detonate the Maximum Bombs](https://leetcode.com/problems/detonate-the-maximum-bombs/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2101-detonate-the-maximum-bombs.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F2101-detonate-the-maximum-bombs.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1857 - Largest Color Value in a Directed Graph](https://leetcode.com/problems/largest-color-value-in-a-directed-graph/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1857-largest-color-value-in-a-directed-graph.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1857-largest-color-value-in-a-directed-graph.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1553 - Minimum Number of Days to Eat N Oranges](https://leetcode.com/problems/minimum-number-of-days-to-eat-n-oranges/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1553-minimum-number-of-days-to-eat-n-oranges.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1553-minimum-number-of-days-to-eat-n-oranges.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0127 - Word Ladder](https://leetcode.com/problems/word-ladder/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0127-word-ladder.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0127-word-ladder.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0127-word-ladder.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0127-word-ladder.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0127-word-ladder.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0127-word-ladder.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0127-word-ladder.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0127-word-ladder.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0127-word-ladder.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0127-word-ladder.ts)</div></sub>
 
 ### Advanced Graphs
 
-<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
----- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
-<sub>[1631 - Path with Minimum Effort](https://leetcode.com/problems/path-with-minimum-effort/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1631-path-with-minimum-effort.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1631-path-with-minimum-effort.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0332 - Reconstruct Itinerary](https://leetcode.com/problems/reconstruct-itinerary/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0332-reconstruct-itinerary.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0332-reconstruct-itinerary.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0332-reconstruct-itinerary.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0332-reconstruct-itinerary.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0332-reconstruct-itinerary.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0332-reconstruct-itinerary.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0332-reconstruct-itinerary.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0332-reconstruct-itinerary.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0332-reconstruct-itinerary.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0332-reconstruct-itinerary.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1584 - Min Cost to Connect All Points](https://leetcode.com/problems/min-cost-to-connect-all-points/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1584-Min-Cost-To-Connect-All-Points.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1584-Min-Cost-to-Connect-All-Points.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1584-min-cost-to-connect-all-points.go)</div></sub> | <sub><div align='center'>[✔️](java%2F1584-Min-Cost-to-Connect-All-Points.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1584-Min-Cost-to-Connect-all-Points.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1584-min-cost-to-connect-all-points.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1584-min-cost-to-connect-all-points.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F1584-Min-Cost-to-Connect-All-Points.rb)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1584-Min-Cost-to-Connect-All-Points.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F1584-min-cost-to-connect-all-points.ts)</div></sub>
-<sub>[0743 - Network Delay Time](https://leetcode.com/problems/network-delay-time/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0743-network-delay-time.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0743-network-delay-time.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0743-network-delay-time.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0743-network-delay-time.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0743-network-delay-time.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0743-network-delay-time.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0743-network-delay-time.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0743-network-delay-time.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0743-network-delay-time.ts)</div></sub>
-<sub>[1514 - Path with Maximum Probability](https://leetcode.com/problems/path-with-maximum-probability/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1514-path-with-maximum-probability.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1514-path-with-maximum-probability.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1514-path-with-maximum-probability.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1514-path-with-maximum-probability.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1514-path-with-maximum-probability.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1514-path-with-maximum-probability.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F1514-path-with-maximum-probability.ts)</div></sub>
-<sub>[0778 - Swim In Rising Water](https://leetcode.com/problems/swim-in-rising-water/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0778-swim-in-rising-water.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0778-swim-in-rising-water.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0778-swim-in-rising-water.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0778-swim-in-rising-water.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0778-swim-in-rising-water.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0778-swim-in-rising-water.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0778-swim-in-rising-water.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0778-swim-in-rising-water.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0778-swim-in-rising-water.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0778-swim-in-rising-water.ts)</div></sub>
-<sub>[0269 - Alien Dictionary](https://leetcode.com/problems/alien-dictionary/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0269-alien-dictionary.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0269-alien-dictionary.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0269-alien-dictionary.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0269-alien-dictionary.js)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](python%2F0269-alien-dictionary.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0269-alien-dictionary.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0787 - Cheapest Flights Within K Stops](https://leetcode.com/problems/cheapest-flights-within-k-stops/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0787-cheapest-flights-within-k-stops.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0787-cheapest-flights-within-k-stops.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0787-cheapest-flights-within-k-stops.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0787-cheapest-flights-within-k-stops.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0787-cheapest-flights-within-k-stops.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0787-cheapest-flights-within-k-stops.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0787-cheapest-flights-within-k-stops.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0787-cheapest-flights-within-k-stops.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0787-cheapest-flights-within-k-stops.ts)</div></sub>
-<sub>[2421 - Number of Good Paths](https://leetcode.com/problems/number-of-good-paths/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F2421-number-of-good-paths.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F2421-number-of-good-paths.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2421-number-of-good-paths.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F2421-number-of-good-paths.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F2421-number-of-good-paths.ts)</div></sub>
-<sub>[1579 - Remove Max Number of Edges to Keep Graph Fully Traversable](https://leetcode.com/problems/remove-max-number-of-edges-to-keep-graph-fully-traversable/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1579-remove-max-number-of-edges-to-keep-graph-fully-traversable.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1489 - Find Critical and Pseudo Critical Edges in Minimum Spanning Tree](https://leetcode.com/problems/find-critical-and-pseudo-critical-edges-in-minimum-spanning-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1489-find-critical-and-pseudo-critical-edges-in-minimum-spanning-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1489-find-critical-and-pseudo-critical-edges-in-minimum-spanning-tree.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1489-find-critical-and-pseudo-critical-edges-in-minimum-spanning-tree.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F1489-find-critical-and-pseudo-critical-edges-in-minimum-spanning-tree.ts)</div></sub>
+<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>hints</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
+---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
+<sub>[1631 - Path with Minimum Effort](https://leetcode.com/problems/path-with-minimum-effort/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1631-path-with-minimum-effort.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1631-path-with-minimum-effort.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0332 - Reconstruct Itinerary](https://leetcode.com/problems/reconstruct-itinerary/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0332-reconstruct-itinerary.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0332-reconstruct-itinerary.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0332-reconstruct-itinerary.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0332-reconstruct-itinerary.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0332-reconstruct-itinerary.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0332-reconstruct-itinerary.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0332-reconstruct-itinerary.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0332-reconstruct-itinerary.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0332-reconstruct-itinerary.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0332-reconstruct-itinerary.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1584 - Min Cost to Connect All Points](https://leetcode.com/problems/min-cost-to-connect-all-points/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1584-Min-Cost-To-Connect-All-Points.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1584-Min-Cost-to-Connect-All-Points.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1584-min-cost-to-connect-all-points.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1584-Min-Cost-to-Connect-All-Points.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1584-Min-Cost-to-Connect-all-Points.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1584-min-cost-to-connect-all-points.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1584-min-cost-to-connect-all-points.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F1584-Min-Cost-to-Connect-All-Points.rb)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1584-Min-Cost-to-Connect-All-Points.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F1584-min-cost-to-connect-all-points.ts)</div></sub>
+<sub>[0743 - Network Delay Time](https://leetcode.com/problems/network-delay-time/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0743-network-delay-time.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0743-network-delay-time.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0743-network-delay-time.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0743-network-delay-time.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0743-network-delay-time.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0743-network-delay-time.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0743-network-delay-time.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0743-network-delay-time.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0743-network-delay-time.ts)</div></sub>
+<sub>[1514 - Path with Maximum Probability](https://leetcode.com/problems/path-with-maximum-probability/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1514-path-with-maximum-probability.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1514-path-with-maximum-probability.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1514-path-with-maximum-probability.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1514-path-with-maximum-probability.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1514-path-with-maximum-probability.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1514-path-with-maximum-probability.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F1514-path-with-maximum-probability.ts)</div></sub>
+<sub>[0778 - Swim In Rising Water](https://leetcode.com/problems/swim-in-rising-water/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0778-swim-in-rising-water.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0778-swim-in-rising-water.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0778-swim-in-rising-water.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0778-swim-in-rising-water.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0778-swim-in-rising-water.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0778-swim-in-rising-water.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0778-swim-in-rising-water.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0778-swim-in-rising-water.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0778-swim-in-rising-water.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0778-swim-in-rising-water.ts)</div></sub>
+<sub>[0269 - Alien Dictionary](https://leetcode.com/problems/alien-dictionary/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0269-alien-dictionary.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0269-alien-dictionary.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0269-alien-dictionary.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0269-alien-dictionary.js)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](python%2F0269-alien-dictionary.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0269-alien-dictionary.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0787 - Cheapest Flights Within K Stops](https://leetcode.com/problems/cheapest-flights-within-k-stops/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0787-cheapest-flights-within-k-stops.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0787-cheapest-flights-within-k-stops.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0787-cheapest-flights-within-k-stops.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0787-cheapest-flights-within-k-stops.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0787-cheapest-flights-within-k-stops.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0787-cheapest-flights-within-k-stops.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0787-cheapest-flights-within-k-stops.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0787-cheapest-flights-within-k-stops.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0787-cheapest-flights-within-k-stops.ts)</div></sub>
+<sub>[2421 - Number of Good Paths](https://leetcode.com/problems/number-of-good-paths/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F2421-number-of-good-paths.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F2421-number-of-good-paths.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2421-number-of-good-paths.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F2421-number-of-good-paths.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F2421-number-of-good-paths.ts)</div></sub>
+<sub>[1579 - Remove Max Number of Edges to Keep Graph Fully Traversable](https://leetcode.com/problems/remove-max-number-of-edges-to-keep-graph-fully-traversable/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1579-remove-max-number-of-edges-to-keep-graph-fully-traversable.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1489 - Find Critical and Pseudo Critical Edges in Minimum Spanning Tree](https://leetcode.com/problems/find-critical-and-pseudo-critical-edges-in-minimum-spanning-tree/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1489-find-critical-and-pseudo-critical-edges-in-minimum-spanning-tree.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1489-find-critical-and-pseudo-critical-edges-in-minimum-spanning-tree.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1489-find-critical-and-pseudo-critical-edges-in-minimum-spanning-tree.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F1489-find-critical-and-pseudo-critical-edges-in-minimum-spanning-tree.ts)</div></sub>
 
 ### 1-D Dynamic Programming
 
-<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
----- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
-<sub>[0070 - Climbing Stairs](https://leetcode.com/problems/climbing-stairs/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0070-climbing-stairs.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0070-climbing-stairs.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0070-climbing-stairs.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0070-climbing-stairs.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0070-climbing-stairs.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0070-climbing-stairs.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0070-climbing-stairs.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0070-climbing-stairs.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0070-climbing-stairs.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0070-climbing-stairs.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0070-climbing-stairs.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0070-climbing-stairs.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0070-climbing-stairs.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0070-climbing-stairs.ts)</div></sub>
-<sub>[0746 - Min Cost Climbing Stairs](https://leetcode.com/problems/min-cost-climbing-stairs/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0746-min-cost-climbing-stairs.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0746-min-cost-climbing-stairs.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0746-min-cost-climbing-stairs.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0746-min-cost-climbing-stairs.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0746-min-cost-climbing-stairs.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0746-min-cost-climbing-stairs.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0746-min-cost-climbing-stairs.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0746-min-cost-climbing-stairs.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0746-min-cost-climbing-stairs.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0746-min-cost-climbing-stairs.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0746-min-cost-climbing-stairs.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0746-min-cost-climbing-stairs.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0746-min-cost-climbing-stairs.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0746-min-cost-climbing-stairs.ts)</div></sub>
-<sub>[0198 - House Robber](https://leetcode.com/problems/house-robber/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0198-house-robber.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0198-house-robber.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0198-house-robber.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0198-house-robber.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0198-house-robber.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0198-house-robber.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0198-house-robber.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0198-house-robber.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0198-house-robber.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0198-house-robber.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0198-house-robber.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0198-house-robber.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0198-house-robber.ts)</div></sub>
-<sub>[0213 - House Robber II](https://leetcode.com/problems/house-robber-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0213-house-robber-ii.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0213-house-robber-ii.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0213-house-robber-ii.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0213-house-robber-ii.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0213-house-robber-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0213-house-robber-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0213-house-robber-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0213-house-robber-ii.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0213-house-robber-ii.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0213-house-robber-ii.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0213-house-robber-ii.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0213-house-robber-ii.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0213-house-robber-ii.ts)</div></sub>
-<sub>[0005 - Longest Palindromic Substring](https://leetcode.com/problems/longest-palindromic-substring/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0005-longest-palindromic-substring.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0005-longest-palindromic-substring.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0005-longest-palindromic-substring.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0005-Longest-Palindromic-Substring.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0005-longest-palindromic-substring.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0005-longest-palindromic-substring.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0005-longest-palindromic-substring.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0005-longest-palindromic-substring.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0005-longest-palindromic-substring.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0005-longest-palindromic-substring.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0005-longest-palindromic-substring.ts)</div></sub>
-<sub>[0647 - Palindromic Substrings](https://leetcode.com/problems/palindromic-substrings/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0647-palindromic-substrings.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0647-palindromic-substrings.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0647-palindromic-substrings.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0647-palindromic-substrings.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0647-palindromic-substrings.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0647-palindromic-substrings.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0647-palindromic-substrings.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0647-palindromic-substrings.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0647-palindromic-substrings.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0647-palindromic-substrings.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0647-palindromic-substrings.ts)</div></sub>
-<sub>[0091 - Decode Ways](https://leetcode.com/problems/decode-ways/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0091-decode-ways.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0091-decode-ways.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0091-decode-ways.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0091-decode-ways.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0091-decode-ways.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0091-decode-ways.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0091-decode-ways.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0091-decode-ways.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0091-decode-ways.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0091-decode-ways.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0091-decode-ways.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0091-decode-ways.ts)</div></sub>
-<sub>[0322 - Coin Change](https://leetcode.com/problems/coin-change/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0322-coin-change.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0322-coin-change.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0322-coin-change.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0322-coin-change.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0322-coin-change.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0322-coin-change.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0322-coin-change.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0322-coin-change.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0322-coin-change.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0322-coin-change.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0322-coin-change.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0322-coin-change.ts)</div></sub>
-<sub>[0152 - Maximum Product Subarray](https://leetcode.com/problems/maximum-product-subarray/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0152-maximum-product-subarray.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0152-maximum-product-subarray.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0152-maximum-product-subarray.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0152-maximum-product-subarray.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0152-maximum-product-subarray.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0152-maximum-product-subarray.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0152-maximum-product-subarray.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0152-maximum-product-subarray.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0152-maximum-product-subarray.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0152-maximum-product-subarray.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0152-maximum-product-subarray.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0152-maximum-product-subarray.ts)</div></sub>
-<sub>[0139 - Word Break](https://leetcode.com/problems/word-break/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0139-word-break.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0139-word-break.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0139-word-break.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0139-word-break.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0139-word-break.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0139-word-break.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0139-word-break.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0139-word-break.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0139-word-break.ts)</div></sub>
-<sub>[0300 - Longest Increasing Subsequence](https://leetcode.com/problems/longest-increasing-subsequence/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0300-longest-increasing-subsequence.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0300-longest-increasing-subsequence.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0300-longest-increasing-subsequence.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0300-longest-increasing-subsequence.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0300-longest-increasing-subsequence.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0300-longest-increasing-subsequence.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0300-longest-increasing-subsequence.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0300-longest-increasing-subsequence.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0300-longest-increasing-subsequence.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0300-longest-increasing-subsequence.ts)</div></sub>
-<sub>[0416 - Partition Equal Subset Sum](https://leetcode.com/problems/partition-equal-subset-sum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0416-partition-equal-subset-sum.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0416-partition-equal-subset-sum.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0416-partition-equal-subset-sum.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0416-partition-equal-subset-sum.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0416-partition-equal-subset-sum.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0416-partition-equal-subset-sum.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0416-partition-equal-subset-sum.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0416-partition-equal-subset-sum.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0416-partition-equal-subset-sum.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0120 - Triangle](https://leetcode.com/problems/triangle/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0120-triangle.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0120-triangle.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0120-triangle.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0120-triangle.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0120-triangle.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0740 - Delete And Earn](https://leetcode.com/problems/delete-and-earn/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0740-delete-and-earn.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0740-delete-and-earn.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0740-delete-and-earn.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0740-delete-and-earn.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0740-delete-and-earn.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0740-delete-and-earn.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0256 - Paint House](https://leetcode.com/problems/paint-house/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](csharp%2F0256-paint-house.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0256-paint-house.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0256-paint-house.ts)</div></sub>
-<sub>[0377 - Combination Sum IV](https://leetcode.com/problems/combination-sum-iv/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0377-combination-sum-iv.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0377-combination-sum-iv.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0377-combination-sum-iv.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0377-combination-sum-iv.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0377-combination-sum-iv.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0279 - Perfect Squares](https://leetcode.com/problems/perfect-squares/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0279-perfect-squares.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0279-perfect-squares.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0279-perfect-squares.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0279-perfect-squares.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0279-perfect-squares.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2369 - Check if There is a Valid Partition For The Array](https://leetcode.com/problems/check-if-there-is-a-valid-partition-for-the-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2369-check-if-there-is-a-valid-partition-for-the-array.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1856 - Maximum Subarray Min Product](https://leetcode.com/problems/maximum-subarray-min-product/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1856-maximum-subarray-min-product.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1856-maximum-subarray-min-product.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1856-maximum-subarray-min-product.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0983 - Minimum Cost For Tickets](https://leetcode.com/problems/minimum-cost-for-tickets/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0983-minimum-cost-for-tickets.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0983-minimum-cost-for-tickets.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0983-minimum-cost-for-tickets.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0983-minimum-cost-for-tickets.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0983-minimum-cost-for-tickets.ts)</div></sub>
-<sub>[0343 - Integer Break](https://leetcode.com/problems/integer-break/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0343-integer-break.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0343-integer-break.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0343-integer-break.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0343-integer-break.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0673 - Number of Longest Increasing Subsequence](https://leetcode.com/problems/number-of-longest-increasing-subsequence/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0673-number-of-longest-increasing-subsequence.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0673-number-of-longest-increasing-subsequence.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0673-number-of-longest-increasing-subsequence.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0673-number-of-longest-increasing-subsequence.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0691 - Stickers to Spell Word](https://leetcode.com/problems/stickers-to-spell-word/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0691-stickers-to-spell-word.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0691-stickers-to-spell-word.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1137 - N-th Tribonacci Number](https://leetcode.com/problems/n-th-tribonacci-number/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1137-n-th-tribonacci-number.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1137-n-th-tribonacci-number.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1137-n-th-tribonacci-number.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1137-n-th-tribonacci-number.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F1137-n-th-tribonacci-number.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1137-n-th-tribonacci-number.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1137-n-th-tribonacci-number.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1137-n-th-tribonacci-number.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F1137-n-th-tribonacci-number.ts)</div></sub>
-<sub>[1035 - Uncrossed Lines](https://leetcode.com/problems/uncrossed-lines/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1035-uncrossed-lines.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1035-uncrossed-lines.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2140 - Solving Questions With Brainpower](https://leetcode.com/problems/solving-questions-with-brainpower/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F2140-solving-questions-with-brainpower.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F2140-solving-questions-with-brainpower.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2140-solving-questions-with-brainpower.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2466 - Count Ways to Build Good Strings](https://leetcode.com/problems/count-ways-to-build-good-strings/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F2466-count-ways-to-build-good-strings.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2466-count-ways-to-build-good-strings.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0837 - New 21 Game](https://leetcode.com/problems/new-21-game/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0837-new-21-game.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0837-new-21-game.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0837-new-21-game.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0837-new-21-game.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1626 - Best Team with no Conflicts](https://leetcode.com/problems/best-team-with-no-conflicts/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1626-best-team-with-no-conflicts.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1626-best-team-with-no-conflicts.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1626-best-team-with-no-conflicts.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1406 - Stone Game III](https://leetcode.com/problems/stone-game-iii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1406-stone-game-iii.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1406-stone-game-iii.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0472 - Concatenated Words](https://leetcode.com/problems/concatenated-words/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0472-concatenated-words.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F0472-concatenated-words.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0472-concatenated-words.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0472-concatenated-words.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0472-concatenated-words.ts)</div></sub>
-<sub>[1799 - Maximize Score after N Operations](https://leetcode.com/problems/maximize-score-after-n-operations/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1799-maximize-score-after-n-operations.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1799-maximize-score-after-n-operations.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1964 - Find the Longest Valid Obstacle Course at Each Position](https://leetcode.com/problems/find-the-longest-valid-obstacle-course-at-each-position/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1964-find-the-longest-valid-obstacle-course-at-each-position.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1964-find-the-longest-valid-obstacle-course-at-each-position.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1359 - Count all Valid Pickup and Delivery Options](https://leetcode.com/problems/count-all-valid-pickup-and-delivery-options/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1359-count-all-valid-pickup-and-delivery-options.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1359-count-all-valid-pickup-and-delivery-options.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>hints</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
+---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
+<sub>[0070 - Climbing Stairs](https://leetcode.com/problems/climbing-stairs/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0070-climbing-stairs.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0070-climbing-stairs.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0070-climbing-stairs.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0070-climbing-stairs.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0070-climbing-stairs.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0070-climbing-stairs.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0070-climbing-stairs.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0070-climbing-stairs.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0070-climbing-stairs.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0070-climbing-stairs.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0070-climbing-stairs.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0070-climbing-stairs.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0070-climbing-stairs.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0070-climbing-stairs.ts)</div></sub>
+<sub>[0746 - Min Cost Climbing Stairs](https://leetcode.com/problems/min-cost-climbing-stairs/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0746-min-cost-climbing-stairs.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0746-min-cost-climbing-stairs.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0746-min-cost-climbing-stairs.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0746-min-cost-climbing-stairs.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0746-min-cost-climbing-stairs.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0746-min-cost-climbing-stairs.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0746-min-cost-climbing-stairs.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0746-min-cost-climbing-stairs.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0746-min-cost-climbing-stairs.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0746-min-cost-climbing-stairs.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0746-min-cost-climbing-stairs.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0746-min-cost-climbing-stairs.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0746-min-cost-climbing-stairs.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0746-min-cost-climbing-stairs.ts)</div></sub>
+<sub>[0198 - House Robber](https://leetcode.com/problems/house-robber/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0198-house-robber.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0198-house-robber.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0198-house-robber.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0198-house-robber.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0198-house-robber.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0198-house-robber.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0198-house-robber.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0198-house-robber.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0198-house-robber.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0198-house-robber.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0198-house-robber.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0198-house-robber.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0198-house-robber.ts)</div></sub>
+<sub>[0213 - House Robber II](https://leetcode.com/problems/house-robber-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0213-house-robber-ii.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0213-house-robber-ii.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0213-house-robber-ii.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0213-house-robber-ii.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0213-house-robber-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0213-house-robber-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0213-house-robber-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0213-house-robber-ii.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0213-house-robber-ii.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0213-house-robber-ii.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0213-house-robber-ii.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0213-house-robber-ii.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0213-house-robber-ii.ts)</div></sub>
+<sub>[0005 - Longest Palindromic Substring](https://leetcode.com/problems/longest-palindromic-substring/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0005-longest-palindromic-substring.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0005-longest-palindromic-substring.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0005-longest-palindromic-substring.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0005-Longest-Palindromic-Substring.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0005-longest-palindromic-substring.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0005-longest-palindromic-substring.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0005-longest-palindromic-substring.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0005-longest-palindromic-substring.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0005-longest-palindromic-substring.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0005-longest-palindromic-substring.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0005-longest-palindromic-substring.ts)</div></sub>
+<sub>[0647 - Palindromic Substrings](https://leetcode.com/problems/palindromic-substrings/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0647-palindromic-substrings.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0647-palindromic-substrings.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0647-palindromic-substrings.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0647-palindromic-substrings.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0647-palindromic-substrings.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0647-palindromic-substrings.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0647-palindromic-substrings.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0647-palindromic-substrings.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0647-palindromic-substrings.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0647-palindromic-substrings.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0647-palindromic-substrings.ts)</div></sub>
+<sub>[0091 - Decode Ways](https://leetcode.com/problems/decode-ways/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0091-decode-ways.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0091-decode-ways.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0091-decode-ways.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0091-decode-ways.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0091-decode-ways.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0091-decode-ways.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0091-decode-ways.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0091-decode-ways.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0091-decode-ways.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0091-decode-ways.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0091-decode-ways.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0091-decode-ways.ts)</div></sub>
+<sub>[0322 - Coin Change](https://leetcode.com/problems/coin-change/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0322-coin-change.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0322-coin-change.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0322-coin-change.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0322-coin-change.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0322-coin-change.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0322-coin-change.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0322-coin-change.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0322-coin-change.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0322-coin-change.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0322-coin-change.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0322-coin-change.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0322-coin-change.ts)</div></sub>
+<sub>[0152 - Maximum Product Subarray](https://leetcode.com/problems/maximum-product-subarray/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0152-maximum-product-subarray.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0152-maximum-product-subarray.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0152-maximum-product-subarray.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0152-maximum-product-subarray.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0152-maximum-product-subarray.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0152-maximum-product-subarray.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0152-maximum-product-subarray.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0152-maximum-product-subarray.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0152-maximum-product-subarray.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0152-maximum-product-subarray.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0152-maximum-product-subarray.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0152-maximum-product-subarray.ts)</div></sub>
+<sub>[0139 - Word Break](https://leetcode.com/problems/word-break/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0139-word-break.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0139-word-break.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0139-word-break.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0139-word-break.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0139-word-break.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0139-word-break.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0139-word-break.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0139-word-break.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0139-word-break.ts)</div></sub>
+<sub>[0300 - Longest Increasing Subsequence](https://leetcode.com/problems/longest-increasing-subsequence/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0300-longest-increasing-subsequence.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0300-longest-increasing-subsequence.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0300-longest-increasing-subsequence.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0300-longest-increasing-subsequence.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0300-longest-increasing-subsequence.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0300-longest-increasing-subsequence.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0300-longest-increasing-subsequence.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0300-longest-increasing-subsequence.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0300-longest-increasing-subsequence.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0300-longest-increasing-subsequence.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0300-longest-increasing-subsequence.ts)</div></sub>
+<sub>[0416 - Partition Equal Subset Sum](https://leetcode.com/problems/partition-equal-subset-sum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0416-partition-equal-subset-sum.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0416-partition-equal-subset-sum.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0416-partition-equal-subset-sum.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0416-partition-equal-subset-sum.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0416-partition-equal-subset-sum.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0416-partition-equal-subset-sum.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0416-partition-equal-subset-sum.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0416-partition-equal-subset-sum.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0416-partition-equal-subset-sum.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0120 - Triangle](https://leetcode.com/problems/triangle/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0120-triangle.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0120-triangle.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0120-triangle.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0120-triangle.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0120-triangle.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0740 - Delete And Earn](https://leetcode.com/problems/delete-and-earn/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0740-delete-and-earn.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0740-delete-and-earn.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0740-delete-and-earn.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0740-delete-and-earn.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0740-delete-and-earn.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0740-delete-and-earn.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0256 - Paint House](https://leetcode.com/problems/paint-house/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](csharp%2F0256-paint-house.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0256-paint-house.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0256-paint-house.ts)</div></sub>
+<sub>[0377 - Combination Sum IV](https://leetcode.com/problems/combination-sum-iv/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0377-combination-sum-iv.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0377-combination-sum-iv.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0377-combination-sum-iv.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0377-combination-sum-iv.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0377-combination-sum-iv.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0279 - Perfect Squares](https://leetcode.com/problems/perfect-squares/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0279-perfect-squares.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0279-perfect-squares.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0279-perfect-squares.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0279-perfect-squares.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0279-perfect-squares.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2369 - Check if There is a Valid Partition For The Array](https://leetcode.com/problems/check-if-there-is-a-valid-partition-for-the-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2369-check-if-there-is-a-valid-partition-for-the-array.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1856 - Maximum Subarray Min Product](https://leetcode.com/problems/maximum-subarray-min-product/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1856-maximum-subarray-min-product.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1856-maximum-subarray-min-product.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1856-maximum-subarray-min-product.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0983 - Minimum Cost For Tickets](https://leetcode.com/problems/minimum-cost-for-tickets/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0983-minimum-cost-for-tickets.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0983-minimum-cost-for-tickets.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0983-minimum-cost-for-tickets.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0983-minimum-cost-for-tickets.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0983-minimum-cost-for-tickets.ts)</div></sub>
+<sub>[0343 - Integer Break](https://leetcode.com/problems/integer-break/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0343-integer-break.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0343-integer-break.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0343-integer-break.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0343-integer-break.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0673 - Number of Longest Increasing Subsequence](https://leetcode.com/problems/number-of-longest-increasing-subsequence/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0673-number-of-longest-increasing-subsequence.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0673-number-of-longest-increasing-subsequence.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0673-number-of-longest-increasing-subsequence.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0673-number-of-longest-increasing-subsequence.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0691 - Stickers to Spell Word](https://leetcode.com/problems/stickers-to-spell-word/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0691-stickers-to-spell-word.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0691-stickers-to-spell-word.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1137 - N-th Tribonacci Number](https://leetcode.com/problems/n-th-tribonacci-number/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1137-n-th-tribonacci-number.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1137-n-th-tribonacci-number.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1137-n-th-tribonacci-number.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1137-n-th-tribonacci-number.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F1137-n-th-tribonacci-number.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1137-n-th-tribonacci-number.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1137-n-th-tribonacci-number.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1137-n-th-tribonacci-number.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F1137-n-th-tribonacci-number.ts)</div></sub>
+<sub>[1035 - Uncrossed Lines](https://leetcode.com/problems/uncrossed-lines/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1035-uncrossed-lines.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1035-uncrossed-lines.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2140 - Solving Questions With Brainpower](https://leetcode.com/problems/solving-questions-with-brainpower/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F2140-solving-questions-with-brainpower.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F2140-solving-questions-with-brainpower.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2140-solving-questions-with-brainpower.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2466 - Count Ways to Build Good Strings](https://leetcode.com/problems/count-ways-to-build-good-strings/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F2466-count-ways-to-build-good-strings.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2466-count-ways-to-build-good-strings.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0837 - New 21 Game](https://leetcode.com/problems/new-21-game/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0837-new-21-game.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0837-new-21-game.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0837-new-21-game.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0837-new-21-game.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1626 - Best Team with no Conflicts](https://leetcode.com/problems/best-team-with-no-conflicts/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1626-best-team-with-no-conflicts.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1626-best-team-with-no-conflicts.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1626-best-team-with-no-conflicts.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1406 - Stone Game III](https://leetcode.com/problems/stone-game-iii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1406-stone-game-iii.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1406-stone-game-iii.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0472 - Concatenated Words](https://leetcode.com/problems/concatenated-words/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0472-concatenated-words.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F0472-concatenated-words.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0472-concatenated-words.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0472-concatenated-words.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0472-concatenated-words.ts)</div></sub>
+<sub>[1799 - Maximize Score after N Operations](https://leetcode.com/problems/maximize-score-after-n-operations/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1799-maximize-score-after-n-operations.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1799-maximize-score-after-n-operations.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1964 - Find the Longest Valid Obstacle Course at Each Position](https://leetcode.com/problems/find-the-longest-valid-obstacle-course-at-each-position/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1964-find-the-longest-valid-obstacle-course-at-each-position.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1964-find-the-longest-valid-obstacle-course-at-each-position.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1359 - Count all Valid Pickup and Delivery Options](https://leetcode.com/problems/count-all-valid-pickup-and-delivery-options/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1359-count-all-valid-pickup-and-delivery-options.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1359-count-all-valid-pickup-and-delivery-options.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
 
 ### 2-D Dynamic Programming
 
-<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
----- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
-<sub>[0062 - Unique Paths](https://leetcode.com/problems/unique-paths/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0062-unique-paths.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0062-unique-paths.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0062-unique-paths.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0062-unique-paths.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0062-unique-paths.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0062-unique-paths.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0062-unique-paths.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0062-unique-paths.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0062-unique-paths.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0062-unique-paths.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0062-unique-paths.ts)</div></sub>
-<sub>[0063 - Unique Paths II](https://leetcode.com/problems/unique-paths-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0063-unique-paths-ii.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0063-unique-paths-ii.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0063-unique-paths-ii.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0063-unique-paths-ii.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0063-unique-paths-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0063-unique-paths-ii.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0063-unique-paths-ii.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0063-unique-paths-ii.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1143 - Longest Common Subsequence](https://leetcode.com/problems/longest-common-subsequence/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1143-longest-common-subsequence.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1143-Longest-Common-Subsequence.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1143-Longest-Common-Subsequence.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F1143-longest-common-subsequence.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F1143-Longest-Common-Subsequence.go)</div></sub> | <sub><div align='center'>[✔️](java%2F1143-longest-common-subsequence.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1143-Longest-Common-Subsequence.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1143-Longest-Common-Subsequence.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1143-longest-common-subsequence.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1143-Longest-Common-Subsequence.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1143-Longest-Common-Subsequence.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F1143-Longest-Common-Subsequence.ts)</div></sub>
-<sub>[0516 - Longest Palindromic Subsequence](https://leetcode.com/problems/longest-palindromic-subsequence/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0516-longest-palindromic-subsequence.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0516-longest-palindromic-subsequence.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0516-longest-palindromic-subsequence.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1049 - Last Stone Weight II](https://leetcode.com/problems/last-stone-weight-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1049-last-stone-weight-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1049-last-stone-weight-ii.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1049-last-stone-weight-ii.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F1049-last-stone-weight-ii.ts)</div></sub>
-<sub>[0309 - Best Time to Buy And Sell Stock With Cooldown](https://leetcode.com/problems/best-time-to-buy-and-sell-stock-with-cooldown/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0309-best-time-to-buy-and-sell-stock-with-cooldown.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0309-best-time-to-buy-and-sell-stock-with-cooldown.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0309-best-time-to-buy-and-sell-stock-with-cooldown.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0309-best-time-to-buy-and-sell-stock-with-cooldown.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0309-best-time-to-buy-and-sell-stock-with-cooldown.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0309-best-time-to-buy-and-sell-stock-with-cooldown.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0309-best-time-to-buy-and-sell-stock-with-cooldown.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0309-best-time-to-buy-and-sell-stock-with-cooldown.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0309-best-time-to-buy-and-sell-stock-with-cooldown.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0309-best-time-to-buy-and-sell-stock-with-cooldown.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0309-best-time-to-buy-and-sell-stock-with-cooldown.ts)</div></sub>
-<sub>[0518 - Coin Change II](https://leetcode.com/problems/coin-change-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0518-coin-change-ii.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0518-coin-change-ii.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0518-coin-change-ii.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0518-coin-change-ii.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0518-coin-change-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0518-coin-change-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0518-coin-change-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0518-coin-change-ii.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0518-coin-change-ii.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0518-coin-change-ii.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0518-coin-change-ii.ts)</div></sub>
-<sub>[0494 - Target Sum](https://leetcode.com/problems/target-sum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0494-target-sum.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0494-target-sum.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0494-target-sum.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0494-target-sum.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0494-target-sum.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0494-target-sum.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0494-target-sum.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0494-target-sum.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0494-target-sum.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0494-target-sum.ts)</div></sub>
-<sub>[0097 - Interleaving String](https://leetcode.com/problems/interleaving-string/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0097-interleaving-string.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0097-interleaving-string.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0097-interleaving-string.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0097-interleaving-string.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0097-interleaving-string.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0097-interleaving-string.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0097-interleaving-string.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0097-interleaving-string.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](scala%2F0097-interleaving-string.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0097-interleaving-string.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0097-interleaving-string.ts)</div></sub>
-<sub>[0877 - Stone Game](https://leetcode.com/problems/stone-game/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0877-stone-game.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0877-stone-game.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0064 - Minimum Path Sum](https://leetcode.com/problems/minimum-path-sum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0064-minimum-path-sum.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0064-minimum-path-sum.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0064-minimum-path-sum.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0064-minimum-path-sum.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0329 - Longest Increasing Path In a Matrix](https://leetcode.com/problems/longest-increasing-path-in-a-matrix/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0329-longest-increasing-path-in-a-matrix.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0329-longest-increasing-path-in-a-matrix.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0329-longest-increasing-path-in-a-matrix.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0329-longest-increasing-path-in-a-matrix.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0329-longest-increasing-path-in-a-matrix.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0329-longest-increasing-path-in-a-matrix.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0329-longest-increasing-path-in-a-matrix.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0329-longest-increasing-path-in-a-matrix.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0221 - Maximal Square](https://leetcode.com/problems/maximal-square/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0221-maximal-square.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0221-maximal-square.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0221-maximal-square.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0221-maximal-square.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0474 - Ones and Zeroes](https://leetcode.com/problems/ones-and-zeroes/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0474-ones-and-zeroes.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0474-ones-and-zeroes.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0474-ones-and-zeroes.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0474-ones-and-zeroes.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0474-ones-and-zeroes.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0474-ones-and-zeroes.ts)</div></sub>
-<sub>[5782 - Maximum Alternating Subsequence Sum](https://leetcode.com/problems/maximum-alternating-subsequence-sum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0115 - Distinct Subsequences](https://leetcode.com/problems/distinct-subsequences/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0115-distinct-subsequences.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0115-distinct-subsequences.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0115-distinct-subsequences.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0115-distinct-subsequences.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0115-distinct-subsequences.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0115-distinct-subsequences.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0115-distinct-subsequences.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0115-distinct-subsequences.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0115-distinct-subsequences.ts)</div></sub>
-<sub>[0072 - Edit Distance](https://leetcode.com/problems/edit-distance/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0072-edit-distance.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0072-edit-distance.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0072-edit-distance.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0072-edit-distance.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0072-edit-distance.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0072-edit-distance.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0072-edit-distance.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0072-edit-distance.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0072-edit-distance.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0072-edit-distance.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0072-edit-distance.ts)</div></sub>
-<sub>[1220 - Count Vowels Permutation](https://leetcode.com/problems/count-vowels-permutation/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1220-count-vowels-permutation.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1220-count-vowels-permutation.go)</div></sub> | <sub><div align='center'>[✔️](java%2F1220-count-vowels-permutation.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1220-count-vowels-permutation.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1220-count-vowels-permutation.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0312 - Burst Balloons](https://leetcode.com/problems/burst-balloons/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0312-burst-balloons.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0312-burst-balloons.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0312-burst-balloons.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0312-burst-balloons.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0312-burst-balloons.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0312-burst-balloons.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0312-burst-balloons.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0312-burst-balloons.ts)</div></sub>
-<sub>[1866 - Number of Ways to Rearrange Sticks With K Sticks Visible](https://leetcode.com/problems/number-of-ways-to-rearrange-sticks-with-k-sticks-visible/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1866-number-of-ways-to-rearrange-sticks-with-k-sticks-visible.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0010 - Regular Expression Matching](https://leetcode.com/problems/regular-expression-matching/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0010-regular-expression-matching.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0010-regular-expression-matching.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0010-regular-expression-matching.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0010-regular-expression-matching.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0010-regular-expression-matching.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0010-regular-expression-matching.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0010-regular-expression-matching.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0010-regular-expression-matching.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0010-regular-expression-matching.ts)</div></sub>
-<sub>[1140 - Stone Game II](https://leetcode.com/problems/stone-game-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1140-stone-game-ii.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1140-stone-game-ii.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0926 - Flip String to Monotone Increasing](https://leetcode.com/problems/flip-string-to-monotone-increasing/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0926-flip-string-to-monotone-increasing.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F0926-flip-string-to-monotone-increasing.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0926-flip-string-to-monotone-increasing.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0926-flip-string-to-monotone-increasing.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0926-flip-string-to-monotone-increasing.ts)</div></sub>
-<sub>[2218 - Maximum Value of K Coins from Piles](https://leetcode.com/problems/maximum-value-of-k-coins-from-piles/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2218-maximum-value-of-k-coins-from-piles.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0920 - Number of Music Playlists](https://leetcode.com/problems/number-of-music-playlists/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0920-number-of-music-playlists.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0920-number-of-music-playlists.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1639 - Number of Ways to Form a Target String Given a Dictionary](https://leetcode.com/problems/number-of-ways-to-form-a-target-string-given-a-dictionary/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1639-number-of-ways-to-form-a-target-string-given-a-dictionary.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0879 - Profitable Schemes](https://leetcode.com/problems/profitable-schemes/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0879-profitable-schemes.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1547 - Minimum Cost to Cut a Stick](https://leetcode.com/problems/minimum-cost-to-cut-a-stick/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1547-minimum-cost-to-cut-a-stick.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>hints</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
+---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
+<sub>[0062 - Unique Paths](https://leetcode.com/problems/unique-paths/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0062-unique-paths.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0062-unique-paths.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0062-unique-paths.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0062-unique-paths.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0062-unique-paths.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0062-unique-paths.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0062-unique-paths.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0062-unique-paths.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0062-unique-paths.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0062-unique-paths.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0062-unique-paths.ts)</div></sub>
+<sub>[0063 - Unique Paths II](https://leetcode.com/problems/unique-paths-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0063-unique-paths-ii.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0063-unique-paths-ii.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0063-unique-paths-ii.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0063-unique-paths-ii.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0063-unique-paths-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0063-unique-paths-ii.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0063-unique-paths-ii.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0063-unique-paths-ii.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1143 - Longest Common Subsequence](https://leetcode.com/problems/longest-common-subsequence/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1143-longest-common-subsequence.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1143-Longest-Common-Subsequence.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1143-Longest-Common-Subsequence.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F1143-longest-common-subsequence.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F1143-Longest-Common-Subsequence.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1143-longest-common-subsequence.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1143-Longest-Common-Subsequence.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1143-Longest-Common-Subsequence.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1143-longest-common-subsequence.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1143-Longest-Common-Subsequence.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1143-Longest-Common-Subsequence.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F1143-Longest-Common-Subsequence.ts)</div></sub>
+<sub>[0516 - Longest Palindromic Subsequence](https://leetcode.com/problems/longest-palindromic-subsequence/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0516-longest-palindromic-subsequence.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0516-longest-palindromic-subsequence.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0516-longest-palindromic-subsequence.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1049 - Last Stone Weight II](https://leetcode.com/problems/last-stone-weight-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1049-last-stone-weight-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1049-last-stone-weight-ii.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1049-last-stone-weight-ii.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F1049-last-stone-weight-ii.ts)</div></sub>
+<sub>[0309 - Best Time to Buy And Sell Stock With Cooldown](https://leetcode.com/problems/best-time-to-buy-and-sell-stock-with-cooldown/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0309-best-time-to-buy-and-sell-stock-with-cooldown.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0309-best-time-to-buy-and-sell-stock-with-cooldown.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0309-best-time-to-buy-and-sell-stock-with-cooldown.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0309-best-time-to-buy-and-sell-stock-with-cooldown.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0309-best-time-to-buy-and-sell-stock-with-cooldown.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0309-best-time-to-buy-and-sell-stock-with-cooldown.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0309-best-time-to-buy-and-sell-stock-with-cooldown.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0309-best-time-to-buy-and-sell-stock-with-cooldown.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0309-best-time-to-buy-and-sell-stock-with-cooldown.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0309-best-time-to-buy-and-sell-stock-with-cooldown.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0309-best-time-to-buy-and-sell-stock-with-cooldown.ts)</div></sub>
+<sub>[0518 - Coin Change II](https://leetcode.com/problems/coin-change-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0518-coin-change-ii.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0518-coin-change-ii.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0518-coin-change-ii.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0518-coin-change-ii.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0518-coin-change-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0518-coin-change-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0518-coin-change-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0518-coin-change-ii.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0518-coin-change-ii.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0518-coin-change-ii.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0518-coin-change-ii.ts)</div></sub>
+<sub>[0494 - Target Sum](https://leetcode.com/problems/target-sum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0494-target-sum.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0494-target-sum.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0494-target-sum.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0494-target-sum.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0494-target-sum.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0494-target-sum.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0494-target-sum.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0494-target-sum.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0494-target-sum.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0494-target-sum.ts)</div></sub>
+<sub>[0097 - Interleaving String](https://leetcode.com/problems/interleaving-string/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0097-interleaving-string.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0097-interleaving-string.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0097-interleaving-string.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0097-interleaving-string.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0097-interleaving-string.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0097-interleaving-string.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0097-interleaving-string.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0097-interleaving-string.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](scala%2F0097-interleaving-string.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0097-interleaving-string.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0097-interleaving-string.ts)</div></sub>
+<sub>[0877 - Stone Game](https://leetcode.com/problems/stone-game/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0877-stone-game.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0877-stone-game.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0064 - Minimum Path Sum](https://leetcode.com/problems/minimum-path-sum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0064-minimum-path-sum.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0064-minimum-path-sum.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0064-minimum-path-sum.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0064-minimum-path-sum.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0329 - Longest Increasing Path In a Matrix](https://leetcode.com/problems/longest-increasing-path-in-a-matrix/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0329-longest-increasing-path-in-a-matrix.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0329-longest-increasing-path-in-a-matrix.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0329-longest-increasing-path-in-a-matrix.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0329-longest-increasing-path-in-a-matrix.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0329-longest-increasing-path-in-a-matrix.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0329-longest-increasing-path-in-a-matrix.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0329-longest-increasing-path-in-a-matrix.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0329-longest-increasing-path-in-a-matrix.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0329-longest-increasing-path-in-a-matrix.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0221 - Maximal Square](https://leetcode.com/problems/maximal-square/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0221-maximal-square.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0221-maximal-square.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0221-maximal-square.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0221-maximal-square.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0474 - Ones and Zeroes](https://leetcode.com/problems/ones-and-zeroes/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0474-ones-and-zeroes.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0474-ones-and-zeroes.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0474-ones-and-zeroes.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0474-ones-and-zeroes.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0474-ones-and-zeroes.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0474-ones-and-zeroes.ts)</div></sub>
+<sub>[5782 - Maximum Alternating Subsequence Sum](https://leetcode.com/problems/maximum-alternating-subsequence-sum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0115 - Distinct Subsequences](https://leetcode.com/problems/distinct-subsequences/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0115-distinct-subsequences.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0115-distinct-subsequences.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0115-distinct-subsequences.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0115-distinct-subsequences.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0115-distinct-subsequences.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0115-distinct-subsequences.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0115-distinct-subsequences.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0115-distinct-subsequences.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0115-distinct-subsequences.ts)</div></sub>
+<sub>[0072 - Edit Distance](https://leetcode.com/problems/edit-distance/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0072-edit-distance.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0072-edit-distance.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0072-edit-distance.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0072-edit-distance.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0072-edit-distance.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0072-edit-distance.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0072-edit-distance.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0072-edit-distance.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0072-edit-distance.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0072-edit-distance.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0072-edit-distance.ts)</div></sub>
+<sub>[1220 - Count Vowels Permutation](https://leetcode.com/problems/count-vowels-permutation/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1220-count-vowels-permutation.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1220-count-vowels-permutation.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1220-count-vowels-permutation.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1220-count-vowels-permutation.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1220-count-vowels-permutation.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0312 - Burst Balloons](https://leetcode.com/problems/burst-balloons/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0312-burst-balloons.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0312-burst-balloons.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0312-burst-balloons.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0312-burst-balloons.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0312-burst-balloons.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0312-burst-balloons.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0312-burst-balloons.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0312-burst-balloons.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0312-burst-balloons.ts)</div></sub>
+<sub>[1866 - Number of Ways to Rearrange Sticks With K Sticks Visible](https://leetcode.com/problems/number-of-ways-to-rearrange-sticks-with-k-sticks-visible/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1866-number-of-ways-to-rearrange-sticks-with-k-sticks-visible.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0010 - Regular Expression Matching](https://leetcode.com/problems/regular-expression-matching/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0010-regular-expression-matching.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0010-regular-expression-matching.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0010-regular-expression-matching.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0010-regular-expression-matching.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0010-regular-expression-matching.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0010-regular-expression-matching.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0010-regular-expression-matching.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0010-regular-expression-matching.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0010-regular-expression-matching.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0010-regular-expression-matching.ts)</div></sub>
+<sub>[1140 - Stone Game II](https://leetcode.com/problems/stone-game-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1140-stone-game-ii.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1140-stone-game-ii.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0926 - Flip String to Monotone Increasing](https://leetcode.com/problems/flip-string-to-monotone-increasing/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0926-flip-string-to-monotone-increasing.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F0926-flip-string-to-monotone-increasing.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0926-flip-string-to-monotone-increasing.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0926-flip-string-to-monotone-increasing.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0926-flip-string-to-monotone-increasing.ts)</div></sub>
+<sub>[2218 - Maximum Value of K Coins from Piles](https://leetcode.com/problems/maximum-value-of-k-coins-from-piles/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2218-maximum-value-of-k-coins-from-piles.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0920 - Number of Music Playlists](https://leetcode.com/problems/number-of-music-playlists/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0920-number-of-music-playlists.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0920-number-of-music-playlists.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1639 - Number of Ways to Form a Target String Given a Dictionary](https://leetcode.com/problems/number-of-ways-to-form-a-target-string-given-a-dictionary/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1639-number-of-ways-to-form-a-target-string-given-a-dictionary.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0879 - Profitable Schemes](https://leetcode.com/problems/profitable-schemes/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0879-profitable-schemes.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1547 - Minimum Cost to Cut a Stick](https://leetcode.com/problems/minimum-cost-to-cut-a-stick/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1547-minimum-cost-to-cut-a-stick.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
 
 ### Greedy
 
-<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
----- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
-<sub>[0053 - Maximum Subarray](https://leetcode.com/problems/maximum-subarray/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0053-maximum-subarray.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0053-maximum-subarray.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0053-maximum-subarray.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0053-maximum-subarray.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0053-maximum-subarray.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0053-maximum-subarray.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0053-maximum-subarray.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0053-maximum-subarray.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0053-maximum-subarray.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0053-maximum-subarray.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0053-maximum-subarray.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0053-maximum-subarray.ts)</div></sub>
-<sub>[0918 - Maximum Sum Circular Subarray](https://leetcode.com/problems/maximum-sum-circular-subarray/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0918-maximum-sum-circular-subarray.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0918-maximum-sum-circular-subarray.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0918-maximum-sum-circular-subarray.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0918-maximum-sum-circular-subarray.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0918-maximum-sum-circular-subarray.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0918-maximum-sum-circular-subarray.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0918-maximum-sum-circular-subarray.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0918-maximum-sum-circular-subarray.ts)</div></sub>
-<sub>[0978 - Longest Turbulent Array](https://leetcode.com/problems/longest-turbulent-subarray/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F0978-longest-turbulent-subarray.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0978-longest-turbulent-subarray.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0978-longest-turbulent-subarray.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0978-longest-turbulent-subarray.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0055 - Jump Game](https://leetcode.com/problems/jump-game/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0055-jump-game.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0055-jump-game.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0055-jump-game.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0055-jump-game.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0055-jump-game.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0055-jump-game.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0055-jump-game.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0055-jump-game.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0055-jump-game.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0055-jump-game.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0055-jump-game.ts)</div></sub>
-<sub>[0045 - Jump Game II](https://leetcode.com/problems/jump-game-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0045-jump-game-ii.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0045-jump-game-ii.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0045-jump-game-ii.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0045-jump-game-ii.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0045-jump-game-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0045-jump-game-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0045-jump-game-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0045-jump-game-ii.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0045-jump-game-ii.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0045-jump-game-ii.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0045-jump-game-ii.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0045-jump-game-ii.ts)</div></sub>
-<sub>[1871 - Jump Game VII](https://leetcode.com/problems/jump-game-vii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1871-jump-game-vii.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0134 - Gas Station](https://leetcode.com/problems/gas-station/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0134-gas-station.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0134-gas-station.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0134-gas-station.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0134-gas-station.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0134-gas-station.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0134-gas-station.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0134-gas-station.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0134-gas-station.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0134-gas-station.rb)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0134-gas-station.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0134-gas-station.ts)</div></sub>
-<sub>[0846 - Hand of Straights](https://leetcode.com/problems/hand-of-straights/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0846-hand-of-straights.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0846-hand-of-straights.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0846-hand-of-straights.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0846-hand-of-straights.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0846-hand-of-straights.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0846-hand-of-straights.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0846-hand-of-straights.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0846-hand-of-straights.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0846-hand-of-straights.rb)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0846-hand-of-straights.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0846-hand-of-straights.ts)</div></sub>
-<sub>[2439 - Minimize Maximum of Array](https://leetcode.com/problems/minimize-maximum-of-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F2439-minimize-maximum-of-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2439-minimize-maximum-of-array.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0649 - Dota2 Senate](https://leetcode.com/problems/dota2-senate/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0649-dota2-senate.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1423 - Maximum Points You Can Obtain From Cards](https://leetcode.com/problems/maximum-points-you-can-obtain-from-cards/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](csharp%2F1423-Maximum-Points-You-Can-Obtain-from-Cards.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F1423-maximum-points-you-can-obtain-from-cards.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1423-maximum-points-you-can-obtain-from-cards.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1423-maximum-points-you-can-obtain-from-cards.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1899 - Merge Triplets to Form Target Triplet](https://leetcode.com/problems/merge-triplets-to-form-target-triplet/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1899-merge-triplets-to-form-target-triplet.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1899-merge-triplets-to-form-target-triplet.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1899-Merge-Triplets-to-Form-Target-Triplet.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1899-merge-triplets-to-form-target-triplet.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1899-merge-triplets-to-form-target-triplet.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1899-merge-triplets-to-form-target-triplet.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1899-merge-triplets-to-form-target-triplet.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F1899-merge-triplets-to-form-target-triplet.rb)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1899-Merge-Triplets-To-Form-Target-Triplet.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F1899-Merge-Triplets-to-Form-Target-Triplet.ts)</div></sub>
-<sub>[0763 - Partition Labels](https://leetcode.com/problems/partition-labels/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0763-partition-labels.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0763-partition-labels.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0763-partition-labels.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0763-partition-labels.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0763-partition-labels.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0763-partition-labels.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0763-partition-labels.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0763-partition-labels.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0763-partition-labels.rb)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0763-partition-labels.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0678 - Valid Parenthesis String](https://leetcode.com/problems/valid-parenthesis-string/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0678-valid-parenthesis-string.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0678-valid-parenthesis-string.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0678-valid-parenthesis-string.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0678-valid-parenthesis-string.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0678-valid-parenthesis-string.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0678-valid-parenthesis-string.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0678-valid-parenthesis-string.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0678-valid-parenthesis-string.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0678-valid-parenthesis-string.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0678-valid-parenthesis-string.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0678-valid-parenthesis-string.ts)</div></sub>
-<sub>[1921 - Eliminate Maximum Number of Monsters](https://leetcode.com/problems/eliminate-maximum-number-of-monsters/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1921-eliminate-maximum-number-of-monsters.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1921-eliminate-maximum-number-of-monsters.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1921-eliminate-maximum-number-of-monsters.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1921-eliminate-maximum-number-of-monsters.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1029 - Two City Scheduling](https://leetcode.com/problems/two-city-scheduling/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1029-two-city-scheduling.go)</div></sub> | <sub><div align='center'>[✔️](java%2F1029-two-city-scheduling.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1029-two-city-scheduling.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1029-two-city-scheduling.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1029-two-city-scheduling.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1029-two-city-scheduling.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F1029-two-city-scheduling.ts)</div></sub>
-<sub>[0646 - Maximum Length of Pair Chain](https://leetcode.com/problems/maximum-length-of-pair-chain/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0646-maximum-length-of-pair-chain.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1647 - Minimum Deletions to Make Character Frequencies Unique](https://leetcode.com/problems/minimum-deletions-to-make-character-frequencies-unique/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1647-minimum-deletions-to-make-character-frequencies-unique.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1647-minimum-deletions-to-make-character-frequencies-unique.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1647-minimum-deletions-to-make-character-frequencies-unique.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[135- - Candy](https://leetcode.com/problems/candy/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>hints</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
+---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
+<sub>[0053 - Maximum Subarray](https://leetcode.com/problems/maximum-subarray/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0053-maximum-subarray.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0053-maximum-subarray.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0053-maximum-subarray.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0053-maximum-subarray.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0053-maximum-subarray.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0053-maximum-subarray.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0053-maximum-subarray.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0053-maximum-subarray.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0053-maximum-subarray.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0053-maximum-subarray.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0053-maximum-subarray.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0053-maximum-subarray.ts)</div></sub>
+<sub>[0918 - Maximum Sum Circular Subarray](https://leetcode.com/problems/maximum-sum-circular-subarray/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0918-maximum-sum-circular-subarray.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0918-maximum-sum-circular-subarray.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0918-maximum-sum-circular-subarray.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0918-maximum-sum-circular-subarray.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0918-maximum-sum-circular-subarray.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0918-maximum-sum-circular-subarray.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0918-maximum-sum-circular-subarray.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0918-maximum-sum-circular-subarray.ts)</div></sub>
+<sub>[0978 - Longest Turbulent Array](https://leetcode.com/problems/longest-turbulent-subarray/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F0978-longest-turbulent-subarray.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0978-longest-turbulent-subarray.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0978-longest-turbulent-subarray.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0978-longest-turbulent-subarray.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0055 - Jump Game](https://leetcode.com/problems/jump-game/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0055-jump-game.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0055-jump-game.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0055-jump-game.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0055-jump-game.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0055-jump-game.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0055-jump-game.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0055-jump-game.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0055-jump-game.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0055-jump-game.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0055-jump-game.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0055-jump-game.ts)</div></sub>
+<sub>[0045 - Jump Game II](https://leetcode.com/problems/jump-game-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0045-jump-game-ii.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0045-jump-game-ii.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0045-jump-game-ii.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0045-jump-game-ii.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0045-jump-game-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0045-jump-game-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0045-jump-game-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0045-jump-game-ii.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0045-jump-game-ii.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0045-jump-game-ii.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0045-jump-game-ii.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0045-jump-game-ii.ts)</div></sub>
+<sub>[1871 - Jump Game VII](https://leetcode.com/problems/jump-game-vii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1871-jump-game-vii.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0134 - Gas Station](https://leetcode.com/problems/gas-station/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0134-gas-station.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0134-gas-station.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0134-gas-station.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0134-gas-station.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0134-gas-station.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0134-gas-station.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0134-gas-station.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0134-gas-station.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0134-gas-station.rb)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0134-gas-station.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0134-gas-station.ts)</div></sub>
+<sub>[0846 - Hand of Straights](https://leetcode.com/problems/hand-of-straights/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0846-hand-of-straights.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0846-hand-of-straights.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0846-hand-of-straights.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0846-hand-of-straights.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0846-hand-of-straights.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0846-hand-of-straights.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0846-hand-of-straights.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0846-hand-of-straights.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0846-hand-of-straights.rb)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0846-hand-of-straights.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0846-hand-of-straights.ts)</div></sub>
+<sub>[2439 - Minimize Maximum of Array](https://leetcode.com/problems/minimize-maximum-of-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F2439-minimize-maximum-of-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2439-minimize-maximum-of-array.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0649 - Dota2 Senate](https://leetcode.com/problems/dota2-senate/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0649-dota2-senate.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1423 - Maximum Points You Can Obtain From Cards](https://leetcode.com/problems/maximum-points-you-can-obtain-from-cards/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](csharp%2F1423-Maximum-Points-You-Can-Obtain-from-Cards.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F1423-maximum-points-you-can-obtain-from-cards.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1423-maximum-points-you-can-obtain-from-cards.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1423-maximum-points-you-can-obtain-from-cards.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1899 - Merge Triplets to Form Target Triplet](https://leetcode.com/problems/merge-triplets-to-form-target-triplet/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1899-merge-triplets-to-form-target-triplet.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1899-merge-triplets-to-form-target-triplet.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1899-Merge-Triplets-to-Form-Target-Triplet.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1899-merge-triplets-to-form-target-triplet.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1899-merge-triplets-to-form-target-triplet.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1899-merge-triplets-to-form-target-triplet.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1899-merge-triplets-to-form-target-triplet.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F1899-merge-triplets-to-form-target-triplet.rb)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1899-Merge-Triplets-To-Form-Target-Triplet.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F1899-Merge-Triplets-to-Form-Target-Triplet.ts)</div></sub>
+<sub>[0763 - Partition Labels](https://leetcode.com/problems/partition-labels/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0763-partition-labels.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0763-partition-labels.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0763-partition-labels.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0763-partition-labels.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0763-partition-labels.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0763-partition-labels.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0763-partition-labels.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0763-partition-labels.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0763-partition-labels.rb)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0763-partition-labels.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0678 - Valid Parenthesis String](https://leetcode.com/problems/valid-parenthesis-string/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0678-valid-parenthesis-string.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0678-valid-parenthesis-string.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0678-valid-parenthesis-string.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0678-valid-parenthesis-string.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0678-valid-parenthesis-string.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0678-valid-parenthesis-string.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0678-valid-parenthesis-string.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0678-valid-parenthesis-string.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0678-valid-parenthesis-string.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0678-valid-parenthesis-string.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0678-valid-parenthesis-string.ts)</div></sub>
+<sub>[1921 - Eliminate Maximum Number of Monsters](https://leetcode.com/problems/eliminate-maximum-number-of-monsters/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1921-eliminate-maximum-number-of-monsters.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1921-eliminate-maximum-number-of-monsters.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1921-eliminate-maximum-number-of-monsters.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1921-eliminate-maximum-number-of-monsters.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1029 - Two City Scheduling](https://leetcode.com/problems/two-city-scheduling/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1029-two-city-scheduling.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1029-two-city-scheduling.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1029-two-city-scheduling.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1029-two-city-scheduling.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1029-two-city-scheduling.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1029-two-city-scheduling.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F1029-two-city-scheduling.ts)</div></sub>
+<sub>[0646 - Maximum Length of Pair Chain](https://leetcode.com/problems/maximum-length-of-pair-chain/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0646-maximum-length-of-pair-chain.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1647 - Minimum Deletions to Make Character Frequencies Unique](https://leetcode.com/problems/minimum-deletions-to-make-character-frequencies-unique/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1647-minimum-deletions-to-make-character-frequencies-unique.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1647-minimum-deletions-to-make-character-frequencies-unique.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1647-minimum-deletions-to-make-character-frequencies-unique.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[135- - Candy](https://leetcode.com/problems/candy/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
 
 ### Intervals
 
-<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
----- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
-<sub>[0057 - Insert Interval](https://leetcode.com/problems/insert-interval/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0057-insert-interval.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0057-insert-interval.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0057-insert-interval.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0057-insert-interval.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0057-insert-interval.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0057-insert-interval.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0057-insert-interval.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0057-insert-interval.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0057-insert-interval.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0057-insert-interval.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0057-insert-interval.ts)</div></sub>
-<sub>[0056 - Merge Intervals](https://leetcode.com/problems/merge-intervals/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0056-merge-intervals.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0056-merge-intervals.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0056-merge-intervals.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0056-merge-intervals.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0056-merge-intervals.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0056-merge-intervals.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0056-merge-intervals.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0056-merge-intervals.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0056-merge-intervals.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0056-merge-intervals.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0056-merge-intervals.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0056-merge-intervals.ts)</div></sub>
-<sub>[0435 - Non Overlapping Intervals](https://leetcode.com/problems/non-overlapping-intervals/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0435-non-overlapping-intervals.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0435-non-overlapping-intervals.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0435-non-overlapping-intervals.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0435-non-overlapping-intervals.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0435-non-overlapping-intervals.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0435-non-overlapping-intervals.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0435-non-overlapping-intervals.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0435-non-overlapping-intervals.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0435-non-overlapping-intervals.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0435-non-overlapping-intervals.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0435-non-overlapping-intervals.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0435-non-overlapping-intervals.ts)</div></sub>
-<sub>[0252 - Meeting Rooms](https://leetcode.com/problems/meeting-rooms/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0252-meeting-rooms.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0252-meeting-rooms.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0252-meeting-rooms.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0252-meeting-rooms.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0252-meeting-rooms.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0252-meeting-rooms.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0252-meeting-rooms.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0252-meeting-rooms.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0253 - Meeting Rooms II](https://leetcode.com/problems/meeting-rooms-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0253-meeting-rooms-ii.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0253-meeting-rooms-ii.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0253-meeting-rooms-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0253-meeting-rooms-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0253-meeting-rooms-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0253-meeting-rooms-ii.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0253-meeting-rooms-ii.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0253-meeting-rooms-ii.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1288 - Remove Covered Intervals](https://leetcode.com/problems/remove-covered-intervals/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1288-Remove-Covered-Intervals.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1288-remove-covered-intervals.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1288-remove-covered-intervals.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1851 - Minimum Interval to Include Each Query](https://leetcode.com/problems/minimum-interval-to-include-each-query/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1851-Minimum-Interval-To-Include-Each-Query.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1851-Minimum-Interval-to-Include-Each-Query.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1851-Minimum-Interval-to-Include-Each-Query.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1851-minimum-interval-to-include-each-query.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1851-minimum-interval-to-include-each-query.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1851-minimum-interval-to-include-each-query.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1851-minimum-interval-to-include-each-query.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0352 - Data Stream as Disjoint Intervals](https://leetcode.com/problems/data-stream-as-disjoint-intervals/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0352-data-stream-as-disjoint-intervals.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F0352-data-stream-as-disjoint-intervals.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0352-data-stream-as-disjoint-intervals.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0352-data-stream-as-disjoint-intervals.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0352-data-stream-as-disjoint-intervals.ts)</div></sub>
+<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>hints</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
+---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
+<sub>[0057 - Insert Interval](https://leetcode.com/problems/insert-interval/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0057-insert-interval.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0057-insert-interval.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0057-insert-interval.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0057-insert-interval.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0057-insert-interval.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0057-insert-interval.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0057-insert-interval.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0057-insert-interval.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0057-insert-interval.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0057-insert-interval.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0057-insert-interval.ts)</div></sub>
+<sub>[0056 - Merge Intervals](https://leetcode.com/problems/merge-intervals/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0056-merge-intervals.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0056-merge-intervals.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0056-merge-intervals.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0056-merge-intervals.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0056-merge-intervals.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0056-merge-intervals.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0056-merge-intervals.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0056-merge-intervals.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0056-merge-intervals.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0056-merge-intervals.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0056-merge-intervals.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0056-merge-intervals.ts)</div></sub>
+<sub>[0435 - Non Overlapping Intervals](https://leetcode.com/problems/non-overlapping-intervals/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0435-non-overlapping-intervals.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0435-non-overlapping-intervals.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0435-non-overlapping-intervals.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0435-non-overlapping-intervals.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0435-non-overlapping-intervals.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0435-non-overlapping-intervals.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0435-non-overlapping-intervals.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0435-non-overlapping-intervals.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0435-non-overlapping-intervals.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0435-non-overlapping-intervals.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0435-non-overlapping-intervals.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0435-non-overlapping-intervals.ts)</div></sub>
+<sub>[0252 - Meeting Rooms](https://leetcode.com/problems/meeting-rooms/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0252-meeting-rooms.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0252-meeting-rooms.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0252-meeting-rooms.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0252-meeting-rooms.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0252-meeting-rooms.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0252-meeting-rooms.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0252-meeting-rooms.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0252-meeting-rooms.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0253 - Meeting Rooms II](https://leetcode.com/problems/meeting-rooms-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0253-meeting-rooms-ii.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0253-meeting-rooms-ii.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0253-meeting-rooms-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0253-meeting-rooms-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0253-meeting-rooms-ii.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0253-meeting-rooms-ii.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0253-meeting-rooms-ii.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0253-meeting-rooms-ii.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1288 - Remove Covered Intervals](https://leetcode.com/problems/remove-covered-intervals/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1288-Remove-Covered-Intervals.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1288-remove-covered-intervals.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1288-remove-covered-intervals.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1851 - Minimum Interval to Include Each Query](https://leetcode.com/problems/minimum-interval-to-include-each-query/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1851-Minimum-Interval-To-Include-Each-Query.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F1851-Minimum-Interval-to-Include-Each-Query.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1851-Minimum-Interval-to-Include-Each-Query.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1851-minimum-interval-to-include-each-query.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1851-minimum-interval-to-include-each-query.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1851-minimum-interval-to-include-each-query.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F1851-minimum-interval-to-include-each-query.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0352 - Data Stream as Disjoint Intervals](https://leetcode.com/problems/data-stream-as-disjoint-intervals/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0352-data-stream-as-disjoint-intervals.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F0352-data-stream-as-disjoint-intervals.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0352-data-stream-as-disjoint-intervals.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0352-data-stream-as-disjoint-intervals.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0352-data-stream-as-disjoint-intervals.ts)</div></sub>
 
 ### Math & Geometry
 
-<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
----- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
-<sub>[0168 - Excel Sheet Column Title](https://leetcode.com/problems/excel-sheet-column-title/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](csharp%2F0168-excel-sheet-column-title.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0168-excel-sheet-column-title.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0168-excel-sheet-column-title.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0168-excel-sheet-column-title.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1071 - Greatest Common Divisor of Strings](https://leetcode.com/problems/greatest-common-divisor-of-strings/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1071-greatest-common-divisor-of-strings.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1071-greatest-common-divisor-of-strings.go)</div></sub> | <sub><div align='center'>[✔️](java%2F1071-greatest-common-divisor-of-strings.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1071-greatest-common-divisor-of-strings.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1071-greatest-common-divisor-of-strings.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1071-greatest-common-divisor-of-strings.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F1071-greatest-common-divisor-of-strings.ts)</div></sub>
-<sub>[1523 - Count Odd Numbers in an Interval Range](https://leetcode.com/problems/count-odd-numbers-in-an-interval-range/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1523-count-odd-numbers-in-an-interval-range.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1523-count-odd-numbers-in-an-interval-range.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1572 - Matrix Diagonal Sum](https://leetcode.com/problems/matrix-diagonal-sum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1572-matrix-diagonal-sum.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1572-matrix-diagonal-sum.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1572-matrix-diagonal-sum.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1572-matrix-diagonal-sum.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0149 - Maximum Points on a Line](https://leetcode.com/problems/max-points-on-a-line/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0149-max-points-on-a-line.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0149-max-points-on-a-line.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0149-max-points-on-a-line.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0149-max-points-on-a-line.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0149-max-points-on-a-line.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0149-max-points-on-a-line.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0149-max-points-on-a-line.ts)</div></sub>
-<sub>[0048 - Rotate Image](https://leetcode.com/problems/rotate-image/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0048-rotate-image.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0048-rotate-image.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0048-rotate-image.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0048-rotate-image.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0048-rotate-image.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0048-rotate-image.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0048-rotate-image.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0048-rotate-image.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0048-rotate-image.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0048-rotate-image.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0048-rotate-image.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0048-rotate-image.ts)</div></sub>
-<sub>[0054 - Spiral Matrix](https://leetcode.com/problems/spiral-matrix/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0054-spiral-matrix.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0054-spiral-matrix.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0054-spiral-matrix.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0054-spiral-matrix.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0054-spiral-matrix.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0054-spiral-matrix.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0054-spiral-matrix.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0054-spiral-matrix.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0054-spiral-matrix.rb)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0054-spiral-matrix.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0054-spiral-matrix.ts)</div></sub>
-<sub>[0059 - Spiral Matrix II ](https://leetcode.com/problems/spiral-matrix-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0059-spiral-matrix-ii.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0059-spiral-matrix-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0059-spiral-matrix-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0059-spiral-matrix-ii.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0073 - Set Matrix Zeroes](https://leetcode.com/problems/set-matrix-zeroes/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0073-set-matrix-zeroes.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0073-set-matrix-zeroes.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0073-set-matrix-zeroes.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0073-set-matrix-zeroes.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0073-set-matrix-zeroes.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0073-set-matrix-zeroes.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0073-set-matrix-zeroes.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0073-set-matrix-zeroes.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0073-set-matrix-zeroes.rb)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0073-set-matrix-zeroes.ts)</div></sub>
-<sub>[0202 - Happy Number](https://leetcode.com/problems/happy-number/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0202-happy-number.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0202-happy-number.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0202-happy-number.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0202-happy-number.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0202-happy-number.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0202-happy-number.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0202-happy-number.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0202-happy-number.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0202-happy-number.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0202-happy-number.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0202-happy-number.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0202-happy-number.ts)</div></sub>
-<sub>[0066 - Plus One](https://leetcode.com/problems/plus-one/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0066-plus-one.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0066-plus-one.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0066-plus-one.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0066-plus-one.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0066-plus-one.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0066-plus-one.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0066-plus-one.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0066-plus-one.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0066-plus-one.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0066-plus-one.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0066-plus-one.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0066-plus-one.ts)</div></sub>
-<sub>[0009 - Palindrome Number](https://leetcode.com/problems/palindrome-number/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0009-palindrome-number.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0009-palindrome-number.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0009-palindrome-number.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0009-palindrome-number.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0009-palindrome-number.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0009-palindrome-number.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0009-palindrome-number.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0009-palindrome-number.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0009-palindrome-number.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0009-palindrome-number.ts)</div></sub>
-<sub>[0263 - Ugly Number](https://leetcode.com/problems/ugly-number/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0263-ugly-number.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0263-ugly-number.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0263-ugly-number.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0263-ugly-number.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0263-ugly-number.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0263-ugly-number.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0263-ugly-number.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0263-ugly-number.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0263-ugly-number.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0263-ugly-number.ts)</div></sub>
-<sub>[1260 - Shift 2D Grid](https://leetcode.com/problems/shift-2d-grid/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1260-shift-2d-grid.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1260-shift-2d-grid.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1260-shift-2d-grid.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1260-shift-2d-grid.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1260-shift-2d-grid.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0013 - Roman to Integer](https://leetcode.com/problems/roman-to-integer/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0013-roman-to-integer.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0013-roman-to-integer.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0013-roman-to-integer.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0013-roman-to-integer.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0013-roman-to-integer.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0013-roman-to-integer.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0013-roman-to-integer.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0013-roman-to-integer.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0013-roman-to-integer.ts)</div></sub>
-<sub>[0012 - Integer to Roman](https://leetcode.com/problems/integer-to-roman/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0012-integer-to-roman.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0012-integer-to-roman.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0012-integer-to-roman.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0012-integer-to-roman.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0012-integer-to-roman.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0012-integer-to-roman.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0012-integer-to-roman.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0012-integer-to-roman.ts)</div></sub>
-<sub>[0050 - Pow(x, n)](https://leetcode.com/problems/powx-n/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0050-powx-n.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0050-powx-n.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0050-powx-n.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0050-powx-n.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0050-powx-n.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0050-powx-n.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0050-powx-n.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0050-powx-n.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0050-powx-n.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0050-powx-n.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0050-powx-n.ts)</div></sub>
-<sub>[0043 - Multiply Strings](https://leetcode.com/problems/multiply-strings/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0043-multiply-strings.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0043-multiply-strings.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0043-multiply-strings.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0043-multiply-strings.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0043-multiply-strings.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0043-multiply-strings.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0043-multiply-strings.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0043-multiply-strings.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0043-multiply-strings.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0043-multiply-strings.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0043-multiply-strings.ts)</div></sub>
-<sub>[2013 - Detect Squares](https://leetcode.com/problems/detect-squares/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F2013-Detect-Squares.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F2013-Detect-Squares.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F2013-Detect-Squares.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F2013-Detect-Squares.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2013-detect-squares.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F2013-detect-squares.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F2013-detect-squares.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F2013-detect-squares.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[1041 - Robot Bounded In Circle](https://leetcode.com/problems/robot-bounded-in-circle/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1041-robot-bounded-in-circle.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1041-robot-bounded-in-circle.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[0006 - Zigzag Conversion](https://leetcode.com/problems/zigzag-conversion/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0006-zigzag-conversion.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0006-zigzag-conversion.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0006-zigzag-conversion.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0006-zigzag-conversion.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0006-zigzag-conversion.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2028 - Find Missing Observations](https://leetcode.com/problems/find-missing-observations/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2028-find-missing-observations.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>hints</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
+---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
+<sub>[0168 - Excel Sheet Column Title](https://leetcode.com/problems/excel-sheet-column-title/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](csharp%2F0168-excel-sheet-column-title.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0168-excel-sheet-column-title.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0168-excel-sheet-column-title.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0168-excel-sheet-column-title.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1071 - Greatest Common Divisor of Strings](https://leetcode.com/problems/greatest-common-divisor-of-strings/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1071-greatest-common-divisor-of-strings.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1071-greatest-common-divisor-of-strings.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1071-greatest-common-divisor-of-strings.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1071-greatest-common-divisor-of-strings.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1071-greatest-common-divisor-of-strings.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1071-greatest-common-divisor-of-strings.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F1071-greatest-common-divisor-of-strings.ts)</div></sub>
+<sub>[1523 - Count Odd Numbers in an Interval Range](https://leetcode.com/problems/count-odd-numbers-in-an-interval-range/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1523-count-odd-numbers-in-an-interval-range.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1523-count-odd-numbers-in-an-interval-range.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1572 - Matrix Diagonal Sum](https://leetcode.com/problems/matrix-diagonal-sum/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1572-matrix-diagonal-sum.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1572-matrix-diagonal-sum.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1572-matrix-diagonal-sum.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1572-matrix-diagonal-sum.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0149 - Maximum Points on a Line](https://leetcode.com/problems/max-points-on-a-line/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0149-max-points-on-a-line.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0149-max-points-on-a-line.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0149-max-points-on-a-line.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0149-max-points-on-a-line.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0149-max-points-on-a-line.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0149-max-points-on-a-line.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0149-max-points-on-a-line.ts)</div></sub>
+<sub>[0048 - Rotate Image](https://leetcode.com/problems/rotate-image/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0048-rotate-image.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0048-rotate-image.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0048-rotate-image.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0048-rotate-image.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0048-rotate-image.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0048-rotate-image.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0048-rotate-image.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0048-rotate-image.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0048-rotate-image.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0048-rotate-image.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0048-rotate-image.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0048-rotate-image.ts)</div></sub>
+<sub>[0054 - Spiral Matrix](https://leetcode.com/problems/spiral-matrix/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0054-spiral-matrix.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0054-spiral-matrix.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0054-spiral-matrix.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0054-spiral-matrix.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0054-spiral-matrix.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0054-spiral-matrix.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0054-spiral-matrix.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0054-spiral-matrix.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0054-spiral-matrix.rb)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0054-spiral-matrix.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0054-spiral-matrix.ts)</div></sub>
+<sub>[0059 - Spiral Matrix II ](https://leetcode.com/problems/spiral-matrix-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0059-spiral-matrix-ii.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0059-spiral-matrix-ii.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0059-spiral-matrix-ii.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0059-spiral-matrix-ii.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0073 - Set Matrix Zeroes](https://leetcode.com/problems/set-matrix-zeroes/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0073-set-matrix-zeroes.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0073-set-matrix-zeroes.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0073-set-matrix-zeroes.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0073-set-matrix-zeroes.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0073-set-matrix-zeroes.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0073-set-matrix-zeroes.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0073-set-matrix-zeroes.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0073-set-matrix-zeroes.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0073-set-matrix-zeroes.rb)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0073-set-matrix-zeroes.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0073-set-matrix-zeroes.ts)</div></sub>
+<sub>[0202 - Happy Number](https://leetcode.com/problems/happy-number/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0202-happy-number.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0202-happy-number.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0202-happy-number.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0202-happy-number.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0202-happy-number.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0202-happy-number.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0202-happy-number.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0202-happy-number.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0202-happy-number.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0202-happy-number.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0202-happy-number.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0202-happy-number.ts)</div></sub>
+<sub>[0066 - Plus One](https://leetcode.com/problems/plus-one/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0066-plus-one.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0066-plus-one.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0066-plus-one.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0066-plus-one.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0066-plus-one.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0066-plus-one.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0066-plus-one.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0066-plus-one.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0066-plus-one.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0066-plus-one.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0066-plus-one.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0066-plus-one.ts)</div></sub>
+<sub>[0009 - Palindrome Number](https://leetcode.com/problems/palindrome-number/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0009-palindrome-number.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0009-palindrome-number.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0009-palindrome-number.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0009-palindrome-number.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0009-palindrome-number.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0009-palindrome-number.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0009-palindrome-number.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0009-palindrome-number.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0009-palindrome-number.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0009-palindrome-number.ts)</div></sub>
+<sub>[0263 - Ugly Number](https://leetcode.com/problems/ugly-number/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0263-ugly-number.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0263-ugly-number.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0263-ugly-number.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0263-ugly-number.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0263-ugly-number.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0263-ugly-number.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0263-ugly-number.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0263-ugly-number.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0263-ugly-number.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0263-ugly-number.ts)</div></sub>
+<sub>[1260 - Shift 2D Grid](https://leetcode.com/problems/shift-2d-grid/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F1260-shift-2d-grid.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1260-shift-2d-grid.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F1260-shift-2d-grid.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1260-shift-2d-grid.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F1260-shift-2d-grid.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0013 - Roman to Integer](https://leetcode.com/problems/roman-to-integer/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0013-roman-to-integer.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0013-roman-to-integer.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0013-roman-to-integer.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0013-roman-to-integer.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0013-roman-to-integer.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0013-roman-to-integer.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0013-roman-to-integer.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0013-roman-to-integer.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0013-roman-to-integer.ts)</div></sub>
+<sub>[0012 - Integer to Roman](https://leetcode.com/problems/integer-to-roman/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0012-integer-to-roman.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0012-integer-to-roman.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0012-integer-to-roman.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0012-integer-to-roman.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0012-integer-to-roman.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0012-integer-to-roman.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0012-integer-to-roman.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0012-integer-to-roman.ts)</div></sub>
+<sub>[0050 - Pow(x, n)](https://leetcode.com/problems/powx-n/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0050-powx-n.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0050-powx-n.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0050-powx-n.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0050-powx-n.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0050-powx-n.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0050-powx-n.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0050-powx-n.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0050-powx-n.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0050-powx-n.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0050-powx-n.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0050-powx-n.ts)</div></sub>
+<sub>[0043 - Multiply Strings](https://leetcode.com/problems/multiply-strings/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0043-multiply-strings.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0043-multiply-strings.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0043-multiply-strings.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0043-multiply-strings.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0043-multiply-strings.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0043-multiply-strings.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0043-multiply-strings.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0043-multiply-strings.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0043-multiply-strings.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0043-multiply-strings.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0043-multiply-strings.ts)</div></sub>
+<sub>[2013 - Detect Squares](https://leetcode.com/problems/detect-squares/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F2013-Detect-Squares.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F2013-Detect-Squares.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F2013-Detect-Squares.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F2013-Detect-Squares.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2013-detect-squares.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F2013-detect-squares.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F2013-detect-squares.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F2013-detect-squares.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F2013-detect-squares.swift)</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[1041 - Robot Bounded In Circle](https://leetcode.com/problems/robot-bounded-in-circle/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F1041-robot-bounded-in-circle.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1041-robot-bounded-in-circle.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[0006 - Zigzag Conversion](https://leetcode.com/problems/zigzag-conversion/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](cpp%2F0006-zigzag-conversion.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0006-zigzag-conversion.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0006-zigzag-conversion.java)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0006-zigzag-conversion.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0006-zigzag-conversion.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2028 - Find Missing Observations](https://leetcode.com/problems/find-missing-observations/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](kotlin%2F2028-find-missing-observations.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
 
 ### Bit Manipulation
 
-<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
----- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
-<sub>[0136 - Single Number](https://leetcode.com/problems/single-number/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0136-single-number.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0136-single-number.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0136-single-number.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0136-single-number.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0136-single-number.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0136-single-number.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0136-single-number.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0136-single-number.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0136-single-number.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0136-single-number.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0136-single-number.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0136-single-number.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0136-single-number.ts)</div></sub>
-<sub>[0191 - Number of 1 Bits](https://leetcode.com/problems/number-of-1-bits/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0191-number-of-1-bits.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0191-number-of-1-bits.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0191-number-of-1-bits.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0191-number-of-1-bits.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0191-number-of-1-bits.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0191-number-of-1-bits.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0191-number-of-1-bits.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0191-number-of-1-bits.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0191-number-of-1-bits.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0191-number-of-1-bits.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0191-number-of-1-bits.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0191-number-of-1-bits.ts)</div></sub>
-<sub>[0338 - Counting Bits](https://leetcode.com/problems/counting-bits/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0338-counting-bits.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0338-counting-bits.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0338-counting-bits.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0338-counting-bits.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0338-counting-bits.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0338-counting-bits.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0338-counting-bits.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0338-counting-bits.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0338-counting-bits.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0338-counting-bits.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0338-counting-bits.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0338-counting-bits.ts)</div></sub>
-<sub>[0190 - Reverse Bits](https://leetcode.com/problems/reverse-bits/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0190-reverse-bits.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0190-reverse-bits.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0190-reverse-bits.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0190-reverse-bits.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0190-reverse-bits.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0190-reverse-bits.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0190-reverse-bits.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0190-reverse-bits.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0190-reverse-bits.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0190-reverse-bits.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0190-reverse-bits.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0190-reverse-bits.ts)</div></sub>
-<sub>[0268 - Missing Number](https://leetcode.com/problems/missing-number/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0268-missing-number.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0268-missing-number.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0268-missing-number.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0268-missing-number.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0268-missing-number.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0268-missing-number.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0268-missing-number.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0268-missing-number.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0268-missing-number.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0268-missing-number.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0268-missing-number.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0268-missing-number.ts)</div></sub>
-<sub>[1470 - Shuffle the Array](https://leetcode.com/problems/shuffle-the-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1470-shuffle-the-array.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1470-shuffle-the-array.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1470-shuffle-the-array.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F1470-shuffle-the-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1470-shuffle-the-array.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1470-shuffle-the-array.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F1470-shuffle-the-array.ts)</div></sub>
-<sub>[0989 - Add to Array-Form of Integer](https://leetcode.com/problems/add-to-array-form-of-integer/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0989-add-to-array-form-of-integer.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0989-add-to-array-form-of-integer.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F0989-add-to-array-form-of-integer.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0989-add-to-array-form-of-integer.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0989-add-to-array-form-of-integer.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0989-add-to-array-form-of-integer.ts)</div></sub>
-<sub>[0371 - Sum of Two Integers](https://leetcode.com/problems/sum-of-two-integers/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0371-sum-of-two-integers.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0371-sum-of-two-integers.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0371-sum-of-two-integers.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0371-sum-of-two-integers.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0371-sum-of-two-integers.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0371-sum-of-two-integers.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0371-sum-of-two-integers.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0371-sum-of-two-integers.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0371-sum-of-two-integers.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0371-sum-of-two-integers.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0371-sum-of-two-integers.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0371-sum-of-two-integers.ts)</div></sub>
-<sub>[0007 - Reverse Integer](https://leetcode.com/problems/reverse-integer/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0007-reverse-integer.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0007-reverse-integer.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0007-reverse-integer.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0007-reverse-integer.go)</div></sub> | <sub><div align='center'>[✔️](java%2F0007-reverse-integer.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0007-reverse-integer.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0007-reverse-integer.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0007-reverse-integer.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0007-reverse-integer.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0007-reverse-integer.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0007-reverse-integer.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0007-reverse-integer.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0007-reverse-integer.ts)</div></sub>
-<sub>[0067 - Add Binary](https://leetcode.com/problems/add-binary/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0067-add-binary.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0067-Add-Binary.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0067-Add-Binary.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0067-add-binary.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0067-add-binary.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0067-add-binary.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0067-add-binary.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0067-add-binary.ts)</div></sub>
+<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>hints</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
+---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
+<sub>[0136 - Single Number](https://leetcode.com/problems/single-number/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0136-single-number.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0136-single-number.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0136-single-number.cs)</div></sub> | <sub><div align='center'>[✔️](dart%2F0136-single-number.dart)</div></sub> | <sub><div align='center'>[✔️](go%2F0136-single-number.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0136-single-number.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0136-single-number.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0136-single-number.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0136-single-number.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0136-single-number.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0136-single-number.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0136-single-number.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0136-single-number.ts)</div></sub>
+<sub>[0191 - Number of 1 Bits](https://leetcode.com/problems/number-of-1-bits/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0191-number-of-1-bits.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0191-number-of-1-bits.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0191-number-of-1-bits.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0191-number-of-1-bits.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0191-number-of-1-bits.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0191-number-of-1-bits.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0191-number-of-1-bits.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0191-number-of-1-bits.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0191-number-of-1-bits.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0191-number-of-1-bits.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0191-number-of-1-bits.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0191-number-of-1-bits.ts)</div></sub>
+<sub>[0338 - Counting Bits](https://leetcode.com/problems/counting-bits/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0338-counting-bits.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0338-counting-bits.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0338-counting-bits.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0338-counting-bits.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0338-counting-bits.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0338-counting-bits.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0338-counting-bits.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0338-counting-bits.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0338-counting-bits.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0338-counting-bits.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0338-counting-bits.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0338-counting-bits.ts)</div></sub>
+<sub>[0190 - Reverse Bits](https://leetcode.com/problems/reverse-bits/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0190-reverse-bits.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0190-reverse-bits.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0190-reverse-bits.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0190-reverse-bits.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0190-reverse-bits.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0190-reverse-bits.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0190-reverse-bits.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0190-reverse-bits.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0190-reverse-bits.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0190-reverse-bits.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0190-reverse-bits.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0190-reverse-bits.ts)</div></sub>
+<sub>[0268 - Missing Number](https://leetcode.com/problems/missing-number/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0268-missing-number.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0268-missing-number.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0268-missing-number.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0268-missing-number.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0268-missing-number.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0268-missing-number.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0268-missing-number.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0268-missing-number.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0268-missing-number.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0268-missing-number.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0268-missing-number.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0268-missing-number.ts)</div></sub>
+<sub>[1470 - Shuffle the Array](https://leetcode.com/problems/shuffle-the-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F1470-shuffle-the-array.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F1470-shuffle-the-array.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F1470-shuffle-the-array.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F1470-shuffle-the-array.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F1470-shuffle-the-array.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F1470-shuffle-the-array.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F1470-shuffle-the-array.ts)</div></sub>
+<sub>[0989 - Add to Array-Form of Integer](https://leetcode.com/problems/add-to-array-form-of-integer/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0989-add-to-array-form-of-integer.c)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0989-add-to-array-form-of-integer.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F0989-add-to-array-form-of-integer.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0989-add-to-array-form-of-integer.kt)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0989-add-to-array-form-of-integer.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0989-add-to-array-form-of-integer.ts)</div></sub>
+<sub>[0371 - Sum of Two Integers](https://leetcode.com/problems/sum-of-two-integers/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0371-sum-of-two-integers.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0371-sum-of-two-integers.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0371-sum-of-two-integers.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0371-sum-of-two-integers.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0371-sum-of-two-integers.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0371-sum-of-two-integers.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0371-sum-of-two-integers.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0371-sum-of-two-integers.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0371-sum-of-two-integers.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0371-sum-of-two-integers.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](swift%2F0371-sum-of-two-integers.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0371-sum-of-two-integers.ts)</div></sub>
+<sub>[0007 - Reverse Integer](https://leetcode.com/problems/reverse-integer/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0007-reverse-integer.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0007-reverse-integer.cpp)</div></sub> | <sub><div align='center'>[✔️](csharp%2F0007-reverse-integer.cs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](go%2F0007-reverse-integer.go)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0007-reverse-integer.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0007-reverse-integer.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0007-reverse-integer.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0007-reverse-integer.py)</div></sub> | <sub><div align='center'>[✔️](ruby%2F0007-reverse-integer.rb)</div></sub> | <sub><div align='center'>[✔️](rust%2F0007-reverse-integer.rs)</div></sub> | <sub><div align='center'>[✔️](scala%2F0007-reverse-integer.scala)</div></sub> | <sub><div align='center'>[✔️](swift%2F0007-reverse-integer.swift)</div></sub> | <sub><div align='center'>[✔️](typescript%2F0007-reverse-integer.ts)</div></sub>
+<sub>[0067 - Add Binary](https://leetcode.com/problems/add-binary/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](c%2F0067-add-binary.c)</div></sub> | <sub><div align='center'>[✔️](cpp%2F0067-Add-Binary.cpp)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](java%2F0067-Add-Binary.java)</div></sub> | <sub><div align='center'>[✔️](javascript%2F0067-add-binary.js)</div></sub> | <sub><div align='center'>[✔️](kotlin%2F0067-add-binary.kt)</div></sub> | <sub><div align='center'>[✔️](python%2F0067-add-binary.py)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](rust%2F0067-add-binary.rs)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F0067-add-binary.ts)</div></sub>
 
 ### JavaScript
 
-<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
----- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
-<sub>[2667 - Create Hello World Function](https://leetcode.com/problems/create-hello-world-function/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F2667-create-hello-world-function.js)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F2667-create-hello-world-function.ts)</div></sub>
-<sub>[2620 - Counter](https://leetcode.com/problems/counter/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F2620-counter.js)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F2620-counter.ts)</div></sub>
-<sub>[2665 - Counter II](https://leetcode.com/problems/counter-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F2665-counter-ii.js)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2635 - Apply Transform over each Element in Array](https://leetcode.com/problems/apply-transform-over-each-element-in-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2634 - Filter Elements from Array](https://leetcode.com/problems/filter-elements-from-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2626 - Array Reduce Transformation](https://leetcode.com/problems/array-reduce-transformation/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2629 - Function Composition](https://leetcode.com/problems/function-composition/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2666 - Allow One Function Call](https://leetcode.com/problems/allow-one-function-call/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2623 - Memoize](https://leetcode.com/problems/memoize/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2632 - Curry](https://leetcode.com/problems/curry/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2621 - Sleep](https://leetcode.com/problems/sleep/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2637 - Promise Time Limit](https://leetcode.com/problems/promise-time-limit/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2636 - Promise Pool](https://leetcode.com/problems/promise-pool/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2622 - Cache With Time Limit](https://leetcode.com/problems/cache-with-time-limit/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2627 - Debounce](https://leetcode.com/problems/debounce/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2676 - Throttle](https://leetcode.com/problems/throttle/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2628 - JSON Deep Equal](https://leetcode.com/problems/json-deep-equal/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F2628-json-deep-equal.js)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2633 - Convert Object to JSON String](https://leetcode.com/problems/convert-object-to-json-string/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2675 - Array of Objects to Matrix](https://leetcode.com/problems/array-of-objects-to-matrix/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2700 - Difference Between Two Objects](https://leetcode.com/problems/differences-between-two-objects/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2677 - Chunk Array](https://leetcode.com/problems/chunk-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2625 - Flatten Deeply Nested Array](https://leetcode.com/problems/flatten-deeply-nested-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2619 - Array Prototype Last](https://leetcode.com/problems/array-prototype-last/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2631 - Group By](https://leetcode.com/problems/group-by/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2618 - Check if Object Instance of Class](https://leetcode.com/problems/check-if-object-instance-of-class/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2693 - Call Function with Custom Context](https://leetcode.com/problems/call-function-with-custom-context/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2694 - Event Emitter](https://leetcode.com/problems/event-emitter/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2695 - Array Wrapper](https://leetcode.com/problems/array-wrapper/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2648 - Generate Fibonacci Sequence](https://leetcode.com/problems/generate-fibonacci-sequence/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
-<sub>[2649 - Nested Array Generator](https://leetcode.com/problems/nested-array-generator/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>Problem</sub> | <sub>articles</sub> | <sub>C</sub> | <sub>C++</sub> | <sub>C#</sub> | <sub>Dart</sub> | <sub>GO</sub> | <sub>hints</sub> | <sub>Java</sub> | <sub>JS</sub> | <sub>Kotlin</sub> | <sub>Python</sub> | <sub>Ruby</sub> | <sub>Rust</sub> | <sub>Scala</sub> | <sub>Swift</sub> | <sub>TS</sub>
+---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ----
+<sub>[2667 - Create Hello World Function](https://leetcode.com/problems/create-hello-world-function/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F2667-create-hello-world-function.js)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F2667-create-hello-world-function.ts)</div></sub>
+<sub>[2620 - Counter](https://leetcode.com/problems/counter/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F2620-counter.js)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](typescript%2F2620-counter.ts)</div></sub>
+<sub>[2665 - Counter II](https://leetcode.com/problems/counter-ii/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F2665-counter-ii.js)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2635 - Apply Transform over each Element in Array](https://leetcode.com/problems/apply-transform-over-each-element-in-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F2635-apply-transform-over-each-element-in-array.js)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2634 - Filter Elements from Array](https://leetcode.com/problems/filter-elements-from-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F2634-filter-elements-from-array.js)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2626 - Array Reduce Transformation](https://leetcode.com/problems/array-reduce-transformation/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F2626-array-reduce-transformation.js)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2629 - Function Composition](https://leetcode.com/problems/function-composition/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F2629-function-composition.js)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2666 - Allow One Function Call](https://leetcode.com/problems/allow-one-function-call/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F2666-allow-one-function-call.js)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2623 - Memoize](https://leetcode.com/problems/memoize/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F2623-memoize.js)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2632 - Curry](https://leetcode.com/problems/curry/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F2632-curry.js)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2621 - Sleep](https://leetcode.com/problems/sleep/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F2621-sleep.js)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2637 - Promise Time Limit](https://leetcode.com/problems/promise-time-limit/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2636 - Promise Pool](https://leetcode.com/problems/promise-pool/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2622 - Cache With Time Limit](https://leetcode.com/problems/cache-with-time-limit/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2627 - Debounce](https://leetcode.com/problems/debounce/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F2627-debounce.js)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2676 - Throttle](https://leetcode.com/problems/throttle/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2628 - JSON Deep Equal](https://leetcode.com/problems/json-deep-equal/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>[✔️](javascript%2F2628-json-deep-equal.js)</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2633 - Convert Object to JSON String](https://leetcode.com/problems/convert-object-to-json-string/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2675 - Array of Objects to Matrix](https://leetcode.com/problems/array-of-objects-to-matrix/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2700 - Difference Between Two Objects](https://leetcode.com/problems/differences-between-two-objects/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2677 - Chunk Array](https://leetcode.com/problems/chunk-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2625 - Flatten Deeply Nested Array](https://leetcode.com/problems/flatten-deeply-nested-array/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2619 - Array Prototype Last](https://leetcode.com/problems/array-prototype-last/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2631 - Group By](https://leetcode.com/problems/group-by/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2618 - Check if Object Instance of Class](https://leetcode.com/problems/check-if-object-instance-of-class/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2693 - Call Function with Custom Context](https://leetcode.com/problems/call-function-with-custom-context/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2694 - Event Emitter](https://leetcode.com/problems/event-emitter/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2695 - Array Wrapper](https://leetcode.com/problems/array-wrapper/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2648 - Generate Fibonacci Sequence](https://leetcode.com/problems/generate-fibonacci-sequence/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
+<sub>[2649 - Nested Array Generator](https://leetcode.com/problems/nested-array-generator/)</sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub> | <sub><div align='center'>❌</div></sub>
 
 
 
diff --git a/articles/132-pattern.md b/articles/132-pattern.md
new file mode 100644
index 000000000..b0dc31957
--- /dev/null
+++ b/articles/132-pattern.md
@@ -0,0 +1,420 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def find132pattern(self, nums: List[int]) -> bool:
+        n = len(nums)
+
+        for k in range(2, n):
+            for j in range(k - 1, 0, -1):
+                if nums[j] <= nums[k]:
+                    continue
+
+                for i in range(j - 1, -1, -1):
+                    if nums[i] < nums[k]:
+                        return True
+
+        return False
+```
+
+```java
+public class Solution {
+    public boolean find132pattern(int[] nums) {
+        int n = nums.length;
+
+        for (int k = 2; k < n; k++) {
+            for (int j = k - 1; j > 0; j--) {
+                if (nums[j] <= nums[k]) {
+                    continue;
+                }
+
+                for (int i = j - 1; i >= 0; i--) {
+                    if (nums[i] < nums[k]) {
+                        return true;
+                    }
+                }
+            }
+        }
+
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool find132pattern(vector<int>& nums) {
+        int n = nums.size();
+
+        for (int k = 2; k < n; k++) {
+            for (int j = k - 1; j > 0; j--) {
+                if (nums[j] <= nums[k]) {
+                    continue;
+                }
+
+                for (int i = j - 1; i >= 0; i--) {
+                    if (nums[i] < nums[k]) {
+                        return true;
+                    }
+                }
+            }
+        }
+
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {boolean}
+     */
+    find132pattern(nums) {
+        let n = nums.length;
+
+        for (let k = 2; k < n; k++) {
+            for (let j = k - 1; j > 0; j--) {
+                if (nums[j] <= nums[k]) {
+                    continue;
+                }
+
+                for (let i = j - 1; i >= 0; i--) {
+                    if (nums[i] < nums[k]) {
+                        return true;
+                    }
+                }
+            }
+        }
+
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Stack
+
+::tabs-start
+
+```python
+class Solution:
+    def find132pattern(self, nums: List[int]) -> bool:
+        stack = []  # pair [num, minLeft], mono decreasing
+        curMin = nums[0]
+
+        for i in range(1, len(nums)):
+            while stack and nums[i] >= stack[-1][0]:
+                stack.pop()
+            if stack and nums[i] > stack[-1][1]:
+                return True
+
+            stack.append([nums[i], curMin])
+            curMin = min(curMin, nums[i])
+
+        return False
+```
+
+```java
+public class Solution {
+    public boolean find132pattern(int[] nums) {
+        Stack<int[]> stack = new Stack<>(); // pair [num, minLeft]
+        int curMin = nums[0];
+
+        for (int i = 1; i < nums.length; i++) {
+            while (!stack.isEmpty() && nums[i] >= stack.peek()[0]) {
+                stack.pop();
+            }
+            if (!stack.isEmpty() && nums[i] > stack.peek()[1]) {
+                return true;
+            }
+
+            stack.push(new int[]{nums[i], curMin});
+            curMin = Math.min(curMin, nums[i]);
+        }
+
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool find132pattern(vector<int>& nums) {
+        stack<pair<int, int>> stack; // pair<num, minLeft>
+        int curMin = nums[0];
+
+        for (int i = 1; i < nums.size(); i++) {
+            while (!stack.empty() && nums[i] >= stack.top().first) {
+                stack.pop();
+            }
+            if (!stack.empty() && nums[i] > stack.top().second) {
+                return true;
+            }
+
+            stack.push({nums[i], curMin});
+            curMin = min(curMin, nums[i]);
+        }
+
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {boolean}
+     */
+    find132pattern(nums) {
+        const stack = []; // pair [num, minLeft]
+        let curMin = nums[0];
+
+        for (let i = 1; i < nums.length; i++) {
+            while (stack.length > 0 && nums[i] >= stack[stack.length - 1][0]) {
+                stack.pop();
+            }
+            if (stack.length > 0 && nums[i] > stack[stack.length - 1][1]) {
+                return true;
+            }
+
+            stack.push([nums[i], curMin]);
+            curMin = Math.min(curMin, nums[i]);
+        }
+
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Stack (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def find132pattern(self, nums: List[int]) -> bool:
+        stack, k = [], float('-inf')
+        
+        for i in range(len(nums) - 1, -1, -1):
+            if nums[i] < k:
+                return True
+            
+            while stack and stack[-1] < nums[i]:
+                k = stack.pop()
+            stack.append(nums[i])
+
+        return False
+```
+
+```java
+public class Solution {
+    public boolean find132pattern(int[] nums) {
+        Stack<Integer> stack = new Stack<>();
+        int k = Integer.MIN_VALUE;
+        
+        for (int i = nums.length - 1; i >= 0; i--) {
+            if (nums[i] < k) {
+                return true;
+            }
+            
+            while (!stack.isEmpty() && stack.peek() < nums[i]) {
+                k = stack.pop();
+            }
+            stack.push(nums[i]);
+        }
+        
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool find132pattern(vector<int>& nums) {
+        stack<int> stack;
+        int k = INT_MIN;
+        
+        for (int i = nums.size() - 1; i >= 0; i--) {
+            if (nums[i] < k) {
+                return true;
+            }
+            
+            while (!stack.empty() && stack.top() < nums[i]) {
+                k = stack.top();
+                stack.pop();
+            }
+            stack.push(nums[i]);
+        }
+        
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {boolean}
+     */
+    find132pattern(nums) {
+        const stack = [];
+        let k = -Infinity;
+        
+        for (let i = nums.length - 1; i >= 0; i--) {
+            if (nums[i] < k) {
+                return true;
+            }
+            
+            while (stack.length > 0 && stack[stack.length - 1] < nums[i]) {
+                k = stack.pop();
+            }
+            stack.push(nums[i]);
+        }
+        
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def find132pattern(self, nums: List[int]) -> bool:
+        n = len(nums)
+        stkTop, k = n, float('-inf')
+
+        for i in range(n - 1, -1, -1):
+            if nums[i] < k:
+                return True
+            
+            while stkTop < n and nums[i] > nums[stkTop]:
+                k = nums[stkTop]
+                stkTop += 1
+            
+            stkTop -= 1
+            nums[stkTop] = nums[i]
+        
+        return False
+```
+
+```java
+public class Solution {
+    public boolean find132pattern(int[] nums) {
+        int n = nums.length;
+        int stkTop = n;
+        int k = Integer.MIN_VALUE;
+
+        for (int i = n - 1; i >= 0; i--) {
+            if (nums[i] < k) {
+                return true;
+            }
+            
+            while (stkTop < n && nums[i] > nums[stkTop]) {
+                k = nums[stkTop++];
+            }
+            
+            nums[--stkTop] = nums[i];
+        }
+        
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool find132pattern(vector<int>& nums) {
+        int n = nums.size();
+        int stkTop = n;
+        int k = INT_MIN;
+
+        for (int i = n - 1; i >= 0; i--) {
+            if (nums[i] < k) {
+                return true;
+            }
+
+            while (stkTop < n && nums[i] > nums[stkTop]) {
+                k = nums[stkTop++];
+            }
+
+            nums[--stkTop] = nums[i];
+        }
+
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {boolean}
+     */
+    find132pattern(nums) {
+        const n = nums.length;
+        let stkTop = n;
+        let k = -Infinity;
+
+        for (let i = n - 1; i >= 0; i--) {
+            if (nums[i] < k) {
+                return true;
+            }
+            
+            while (stkTop < n && nums[i] > nums[stkTop]) {
+                k = nums[stkTop++];
+            }
+
+            nums[--stkTop] = nums[i];
+        }
+        
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/4sum.md b/articles/4sum.md
new file mode 100644
index 000000000..b590cf39e
--- /dev/null
+++ b/articles/4sum.md
@@ -0,0 +1,810 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def fourSum(self, nums: List[int], target: int) -> List[List[int]]:
+        n = len(nums)
+        nums.sort()
+        res = set()
+
+        for a in range(n):
+            for b in range(a + 1, n):
+                for c in range(b + 1, n):
+                    for d in range(c + 1, n):
+                        if nums[a] + nums[b] + nums[c] + nums[d] == target:
+                            res.add((nums[a], nums[b], nums[c], nums[d]))
+        return list(res)
+```
+
+```java
+public class Solution {
+    public List<List<Integer>> fourSum(int[] nums, int target) {
+        int n = nums.length;
+        Arrays.sort(nums);
+        Set<List<Integer>> res = new HashSet<>();
+
+        for (int a = 0; a < n; a++) {
+            for (int b = a + 1; b < n; b++) {
+                for (int c = b + 1; c < n; c++) {
+                    for (int d = c + 1; d < n; d++) {
+                        if (nums[a] + nums[b] + 0L + nums[c] + nums[d] == target) {
+                            res.add(Arrays.asList(nums[a], nums[b], nums[c], nums[d]));
+                        }
+                    }
+                }
+            }
+        }
+
+        return new ArrayList<>(res);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> fourSum(vector<int>& nums, int target) {
+        int n = nums.size();
+        sort(nums.begin(), nums.end());
+        set<vector<int>> res;
+
+        for (int a = 0; a < n; a++) {
+            for (int b = a + 1; b < n; b++) {
+                for (int c = b + 1; c < n; c++) {
+                    for (int d = c + 1; d < n; d++) {
+                        if (nums[a] + nums[b] + 0LL + nums[c] + nums[d] == target) {
+                            res.insert({nums[a], nums[b], nums[c], nums[d]});
+                        }
+                    }
+                }
+            }
+        }
+
+        return vector<vector<int>>(res.begin(), res.end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} target
+     * @return {number[][]}
+     */
+    fourSum(nums, target) {
+        let n = nums.length;
+        nums.sort((a, b) => a - b);
+        let res = new Set();
+
+        for (let a = 0; a < n; a++) {
+            for (let b = a + 1; b < n; b++) {
+                for (let c = b + 1; c < n; c++) {
+                    for (let d = c + 1; d < n; d++) {
+                        if (nums[a] + nums[b] + nums[c] + nums[d] === target) {
+                            res.add(JSON.stringify([nums[a], nums[b], nums[c], nums[d]]));
+                        }
+                    }
+                }
+            }
+        }
+
+        return Array.from(res).map(JSON.parse);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<List<int>> FourSum(int[] nums, int target) {
+        int n = nums.Length;
+        Array.Sort(nums);
+        HashSet<(int, int, int, int)> res = new HashSet<(int, int, int, int)>();
+
+        for (int a = 0; a < n; a++) {
+            for (int b = a + 1; b < n; b++) {
+                for (int c = b + 1; c < n; c++) {
+                    for (int d = c + 1; d < n; d++) {
+                        long sum = (long)nums[a] + nums[b] + nums[c] + nums[d];
+                        if (sum == target) {
+                            res.Add((nums[a], nums[b], nums[c], nums[d]));
+                        }
+                    }
+                }
+            }
+        }
+
+        var result = new List<List<int>>();
+        foreach (var quad in res) {
+            result.Add(new List<int> { quad.Item1, quad.Item2, quad.Item3, quad.Item4 });
+        }
+        return result;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 4)$
+* Space complexity: $O(m)$
+
+> Where $n$ is the size of the array $nums$ and $m$ is the number of quadruplets.
+
+---
+
+## 2. Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def fourSum(self, nums: List[int], target: int) -> List[List[int]]:
+        nums.sort()
+        count = defaultdict(int)
+        for num in nums:
+            count[num] += 1
+
+        res = []
+        for i in range(len(nums)):
+            count[nums[i]] -= 1
+            if i > 0 and nums[i] == nums[i - 1]:
+                continue
+
+            for j in range(i + 1, len(nums)):
+                count[nums[j]] -= 1
+                if j > i + 1 and nums[j] == nums[j - 1]:
+                    continue
+
+                for k in range(j + 1, len(nums)):
+                    count[nums[k]] -= 1
+                    if k > j + 1 and nums[k] == nums[k - 1]:
+                        continue
+
+                    fourth = target - (nums[i] + nums[j] + nums[k])
+                    if count[fourth] > 0:
+                        res.append([nums[i], nums[j], nums[k], fourth])
+
+                for k in range(j + 1, len(nums)):
+                    count[nums[k]] += 1
+
+            for j in range(i + 1, len(nums)):
+                count[nums[j]] += 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public List<List<Integer>> fourSum(int[] nums, int target) {
+        Arrays.sort(nums);
+        Map<Integer, Integer> count = new HashMap<>();
+        for (int num : nums) {
+            count.put(num, count.getOrDefault(num, 0) + 1);
+        }
+        List<List<Integer>> res = new ArrayList<>();
+
+        for (int i = 0; i < nums.length; i++) {
+            count.put(nums[i], count.get(nums[i]) - 1);
+            if (i > 0 && nums[i] == nums[i - 1]) continue;
+
+            for (int j = i + 1; j < nums.length; j++) {
+                count.put(nums[j], count.get(nums[j]) - 1);
+                if (j > i + 1 && nums[j] == nums[j - 1]) continue;
+
+                for (int k = j + 1; k < nums.length; k++) {
+                    count.put(nums[k], count.get(nums[k]) - 1);
+                    if (k > j + 1 && nums[k] == nums[k - 1]) continue;
+
+                    long fourth = target - (nums[i] + nums[j] + 0L + nums[k]);
+                    if (fourth > Integer.MAX_VALUE || fourth < Integer.MIN_VALUE) {
+                        continue;
+                    }
+                    if (count.getOrDefault((int) fourth, 0) > 0) {
+                        res.add(Arrays.asList(nums[i], nums[j], nums[k], (int) fourth));
+                    }
+                }
+
+                for (int k = j + 1; k < nums.length; k++) {
+                    count.put(nums[k], count.get(nums[k]) + 1);
+                }
+            }
+
+            for (int j = i + 1; j < nums.length; j++) {
+                count.put(nums[j], count.get(nums[j]) + 1);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> fourSum(vector<int>& nums, int target) {
+        sort(nums.begin(), nums.end());
+        unordered_map<int, int> count;
+        for (int num : nums) {
+            count[num]++;
+        }
+        vector<vector<int>> res;
+
+        for (int i = 0; i < nums.size(); i++) {
+            count[nums[i]]--;
+            if (i > 0 && nums[i] == nums[i - 1]) continue;
+
+            for (int j = i + 1; j < nums.size(); j++) {
+                count[nums[j]]--;
+                if (j > i + 1 && nums[j] == nums[j - 1]) continue;
+
+                for (int k = j + 1; k < nums.size(); k++) {
+                    count[nums[k]]--;
+                    if (k > j + 1 && nums[k] == nums[k - 1]) continue;
+
+                    long long fourth = target - (nums[i] + nums[j] + 0LL + nums[k]);
+                    if (fourth < INT_MIN || fourth > INT_MAX) continue;
+                    if (count[fourth] > 0) {
+                        res.push_back({nums[i], nums[j], nums[k], int(fourth)});
+                    }
+                }
+
+                for (int k = j + 1; k < nums.size(); k++) {
+                    count[nums[k]]++;
+                }
+            }
+
+            for (int j = i + 1; j < nums.size(); j++) {
+                count[nums[j]]++;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} target
+     * @return {number[][]}
+     */
+    fourSum(nums, target) {
+        nums.sort((a, b) => a - b);
+        const count = new Map();
+        for (const num of nums) {
+            count.set(num, (count.get(num) || 0) + 1);
+        }
+        const res = [];
+
+        for (let i = 0; i < nums.length; i++) {
+            count.set(nums[i], count.get(nums[i]) - 1);
+            if (i > 0 && nums[i] === nums[i - 1]) continue;
+
+            for (let j = i + 1; j < nums.length; j++) {
+                count.set(nums[j], count.get(nums[j]) - 1);
+                if (j > i + 1 && nums[j] === nums[j - 1]) continue;
+
+                for (let k = j + 1; k < nums.length; k++) {
+                    count.set(nums[k], count.get(nums[k]) - 1);
+                    if (k > j + 1 && nums[k] === nums[k - 1]) continue;
+
+                    const fourth = target - (nums[i] + nums[j] + nums[k]);
+                    if ((count.get(fourth) || 0) > 0) {
+                        res.push([nums[i], nums[j], nums[k], fourth]);
+                    }
+                }
+
+                for (let k = j + 1; k < nums.length; k++) {
+                    count.set(nums[k], count.get(nums[k]) + 1);
+                }
+            }
+
+            for (let j = i + 1; j < nums.length; j++) {
+                count.set(nums[j], count.get(nums[j]) + 1);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<List<int>> FourSum(int[] nums, int target) {
+        Array.Sort(nums);
+        Dictionary<int, int> count = new Dictionary<int, int>();
+
+        foreach (int num in nums) {
+            if (!count.ContainsKey(num)) {
+                count[num] = 0;
+            }
+            count[num]++;
+        }
+
+        List<List<int>> res = new List<List<int>>();
+
+        for (int i = 0; i < nums.Length; i++) {
+            count[nums[i]]--;
+            if (i > 0 && nums[i] == nums[i - 1]) continue;
+
+            for (int j = i + 1; j < nums.Length; j++) {
+                count[nums[j]]--;
+                if (j > i + 1 && nums[j] == nums[j - 1]) continue;
+
+                for (int k = j + 1; k < nums.Length; k++) {
+                    count[nums[k]]--;
+                    if (k > j + 1 && nums[k] == nums[k - 1]) continue;
+
+                    long fourth = (long)target - (long)nums[i] - (long)nums[j] - (long)nums[k];
+                    if (fourth > int.MaxValue || fourth < int.MinValue) {
+                        continue;
+                    }
+
+                    if (count.ContainsKey((int)fourth) && count[(int)fourth] > 0) {
+                        res.Add(new List<int> { nums[i], nums[j], nums[k], (int)fourth });
+                    }
+                }
+
+                for (int k = j + 1; k < nums.Length; k++) {
+                    count[nums[k]]++;
+                }
+            }
+
+            for (int j = i + 1; j < nums.Length; j++) {
+                count[nums[j]]++;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 3)$
+* Space complexity:
+    * $O(n)$ space for the hash map.
+    * $O(m)$ space for the output array.
+
+> Where $n$ is the size of the array $nums$ and $m$ is the number of quadruplets.
+
+---
+
+## 3. Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def fourSum(self, nums: List[int], target: int) -> List[List[int]]:
+        nums.sort()
+        n = len(nums)
+        res = []
+
+        for i in range(n):
+            if i > 0 and nums[i] == nums[i - 1]:
+                continue
+            for j in range(i + 1, n):
+                if j > i + 1 and nums[j] == nums[j - 1]:
+                    continue
+                left, right = j + 1, n - 1
+                while left < right:
+                    total = nums[i] + nums[j] + nums[left] + nums[right]
+                    if total == target:
+                        res.append([nums[i], nums[j], nums[left], nums[right]])
+                        left += 1
+                        right -= 1
+                        while left < right and nums[left] == nums[left - 1]:
+                            left += 1
+                        while left < right and nums[right] == nums[right + 1]:
+                            right -= 1
+                    elif total < target:
+                        left += 1
+                    else:
+                        right -= 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public List<List<Integer>> fourSum(int[] nums, int target) {
+        Arrays.sort(nums);
+        List<List<Integer>> res = new ArrayList<>();
+        int n = nums.length;
+
+        for (int i = 0; i < n; i++) {
+            if (i > 0 && nums[i] == nums[i - 1]) continue;
+
+            for (int j = i + 1; j < n; j++) {
+                if (j > i + 1 && nums[j] == nums[j - 1]) continue;
+
+                int left = j + 1, right = n - 1;
+                while (left < right) {
+                    long sum = (long) nums[i] + nums[j] + nums[left] + nums[right];
+                    if (sum == target) {
+                        res.add(Arrays.asList(nums[i], nums[j], nums[left], nums[right]));
+                        left++;
+                        right--;
+                        while (left < right && nums[left] == nums[left - 1]) left++;
+                        while (left < right && nums[right] == nums[right + 1]) right--;
+                    } else if (sum < target) {
+                        left++;
+                    } else {
+                        right--;
+                    }
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> fourSum(vector<int>& nums, int target) {
+        vector<vector<int>> res;
+        int n = nums.size();
+        sort(nums.begin(), nums.end());
+
+        for (int i = 0; i < n; i++) {
+            if (i > 0 && nums[i] == nums[i - 1]) continue;
+
+            for (int j = i + 1; j < n; j++) {
+                if (j > i + 1 && nums[j] == nums[j - 1]) continue;
+
+                int left = j + 1, right = n - 1;
+                while (left < right) {
+                    long long sum = (long long) nums[i] + nums[j] + nums[left] + nums[right];
+                    if (sum == target) {
+                        res.push_back({nums[i], nums[j], nums[left], nums[right]});
+                        left++;
+                        right--;
+                        while (left < right && nums[left] == nums[left - 1]) left++;
+                        while (left < right && nums[right] == nums[right + 1]) right--;
+                    } else if (sum < target) {
+                        left++;
+                    } else {
+                        right--;
+                    }
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} target
+     * @return {number[][]}
+     */
+    fourSum(nums, target) {
+        nums.sort((a, b) => a - b);
+        const res = [];
+        const n = nums.length;
+
+        for (let i = 0; i < n; i++) {
+            if (i > 0 && nums[i] === nums[i - 1]) continue;
+
+            for (let j = i + 1; j < n; j++) {
+                if (j > i + 1 && nums[j] === nums[j - 1]) continue;
+
+                let left = j + 1, right = n - 1;
+                while (left < right) {
+                    const sum = nums[i] + nums[j] + nums[left] + nums[right];
+                    if (sum === target) {
+                        res.push([nums[i], nums[j], nums[left], nums[right]]);
+                        left++;
+                        right--;
+                        while (left < right && nums[left] === nums[left - 1]) left++;
+                        while (left < right && nums[right] === nums[right + 1]) right--;
+                    } else if (sum < target) {
+                        left++;
+                    } else {
+                        right--;
+                    }
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<List<int>> FourSum(int[] nums, int target) {
+        Array.Sort(nums);
+        List<List<int>> res = new List<List<int>>();
+        int n = nums.Length;
+
+        for (int i = 0; i < n; i++) {
+            if (i > 0 && nums[i] == nums[i - 1]) continue;
+
+            for (int j = i + 1; j < n; j++) {
+                if (j > i + 1 && nums[j] == nums[j - 1]) continue;
+
+                int left = j + 1, right = n - 1;
+                while (left < right) {
+                    long sum = (long)nums[i] + nums[j] + nums[left] + nums[right];
+                    if (sum == target) {
+                        res.Add(new List<int> { nums[i], nums[j], nums[left], nums[right] });
+                        left++;
+                        right--;
+                        while (left < right && nums[left] == nums[left - 1]) left++;
+                        while (left < right && nums[right] == nums[right + 1]) right--;
+                    } else if (sum < target) {
+                        left++;
+                    } else {
+                        right--;
+                    }
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 3)$
+* Space complexity:
+    * $O(1)$ or $O(n)$ space depending on the sorting algorithm.
+    * $O(m)$ space for the output array.
+
+---
+
+## 4. K-Sum + Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def fourSum(self, nums: List[int], target: int) -> List[List[int]]:
+        nums.sort()
+        res, quad = [], []
+
+        def kSum(k, start, target):
+            if k == 2:
+                l, r = start, len(nums) - 1
+                while l < r:
+                    if nums[l] + nums[r] < target:
+                        l += 1
+                    elif nums[l] + nums[r] > target:
+                        r -= 1
+                    else:
+                        res.append(quad + [nums[l], nums[r]])
+                        l += 1
+                        r -= 1
+                        while l < r and nums[l] == nums[l - 1]:
+                            l += 1
+                        while l < r and nums[r] == nums[r + 1]:
+                            r -= 1
+                return
+
+            for i in range(start, len(nums) - k + 1):
+                if i > start and nums[i] == nums[i - 1]:
+                    continue
+                quad.append(nums[i])
+                kSum(k - 1, i + 1, target - nums[i])
+                quad.pop()
+
+        kSum(4, 0, target)
+        return res
+```
+
+```java
+public class Solution {
+    private List<List<Integer>> res;
+    private List<Integer> quad;
+
+    public List<List<Integer>> fourSum(int[] nums, int target) {
+        Arrays.sort(nums);
+        res = new ArrayList<>();
+        quad = new ArrayList<>();
+        kSum(nums, 4, 0, target);
+        return res;
+    }
+
+    private void kSum(int[] nums, int k, int start, long target) {
+        if (k == 2) {
+            int l = start, r = nums.length - 1;
+            while (l < r) {
+                long sum = nums[l] + nums[r];
+                if (sum < target) {
+                    l++;
+                } else if (sum > target) {
+                    r--;
+                } else {
+                    res.add(new ArrayList<>(quad));
+                    res.get(res.size() - 1).add(nums[l]);
+                    res.get(res.size() - 1).add(nums[r]);
+                    l++;
+                    r--;
+                    while (l < r && nums[l] == nums[l - 1]) l++;
+                    while (l < r && nums[r] == nums[r + 1]) r--;
+                }
+            }
+            return;
+        }
+
+        for (int i = start; i < nums.length - k + 1; i++) {
+            if (i > start && nums[i] == nums[i - 1]) continue;
+            quad.add(nums[i]);
+            kSum(nums, k - 1, i + 1, target - nums[i]);
+            quad.remove(quad.size() - 1);
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+    vector<vector<int>> res;
+    vector<int> quad;
+
+public:
+    vector<vector<int>> fourSum(vector<int>& nums, int target) {
+        if (nums.size() < 4) return {};
+        sort(nums.begin(), nums.end());
+        kSum(nums, 4, 0, (long long) target);
+        return res;
+    }
+
+private:
+    void kSum(vector<int>& nums, int k, int start, long long target) {
+        if (k == 2) {
+            int l = start, r = nums.size() - 1;
+            while (l < r) {
+                long long sum = (long long) nums[l] + nums[r];
+                if (sum < target) {
+                    l++;
+                } else if (sum > target) {
+                    r--;
+                } else {
+                    quad.push_back(nums[l]);
+                    quad.push_back(nums[r]);
+                    res.push_back(quad);
+                    quad.pop_back();
+                    quad.pop_back();
+                    l++;
+                    r--;
+                    while (l < r && nums[l] == nums[l - 1]) l++;
+                    while (l < r && nums[r] == nums[r + 1]) r--;
+                }
+            }
+            return;
+        }
+
+        for (int i = start; i < nums.size() - k + 1; i++) {
+            if (i > start && nums[i] == nums[i - 1]) continue;
+            quad.push_back(nums[i]);
+            kSum(nums, k - 1, i + 1, target - nums[i]);
+            quad.pop_back();
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} target
+     * @return {number[][]}
+     */
+    fourSum(nums, target) {
+        nums.sort((a, b) => a - b);
+        const res = [];
+        const quad = [];
+
+        const kSum = (k, start, target) => {
+            if (k === 2) {
+                let l = start, r = nums.length - 1;
+                while (l < r) {
+                    const sum = nums[l] + nums[r];
+                    if (sum < target) {
+                        l++;
+                    } else if (sum > target) {
+                        r--;
+                    } else {
+                        res.push([...quad, nums[l], nums[r]]);
+                        l++;
+                        r--;
+                        while (l < r && nums[l] === nums[l - 1]) l++;
+                        while (l < r && nums[r] === nums[r + 1]) r--;
+                    }
+                }
+                return;
+            }
+
+            for (let i = start; i < nums.length - k + 1; i++) {
+                if (i > start && nums[i] === nums[i - 1]) continue;
+                quad.push(nums[i]);
+                kSum(k - 1, i + 1, target - nums[i]);
+                quad.pop();
+            }
+        };
+
+        kSum(4, 0, target);
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    private List<List<int>> res;
+    private List<int> quad;
+
+    public List<List<int>> FourSum(int[] nums, int target) {
+        Array.Sort(nums);
+        res = new List<List<int>>();
+        quad = new List<int>();
+        KSum(nums, 4, 0, target);
+        return res;
+    }
+
+    private void KSum(int[] nums, int k, int start, long target) {
+        if (k == 2) {
+            int l = start, r = nums.Length - 1;
+            while (l < r) {
+                long sum = (long)nums[l] + nums[r];
+                if (sum < target) {
+                    l++;
+                } else if (sum > target) {
+                    r--;
+                } else {
+                    List<int> newQuad = new List<int>(quad);
+                    newQuad.Add(nums[l]);
+                    newQuad.Add(nums[r]);
+                    res.Add(newQuad);
+                    l++;
+                    r--;
+                    while (l < r && nums[l] == nums[l - 1]) l++;
+                    while (l < r && nums[r] == nums[r + 1]) r--;
+                }
+            }
+            return;
+        }
+
+        for (int i = start; i < nums.Length - k + 1; i++) {
+            if (i > start && nums[i] == nums[i - 1]) continue;
+            quad.Add(nums[i]);
+            KSum(nums, k - 1, i + 1, target - nums[i]);
+            quad.RemoveAt(quad.Count - 1);
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 3)$
+* Space complexity:
+    * $O(1)$ or $O(n)$ space depending on the sorting algorithm.
+    * $O(m)$ space for the output array.
\ No newline at end of file
diff --git a/articles/accounts-merge.md b/articles/accounts-merge.md
new file mode 100644
index 000000000..15b8e9881
--- /dev/null
+++ b/articles/accounts-merge.md
@@ -0,0 +1,1165 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def accountsMerge(self, accounts: List[List[str]]) -> List[List[str]]:
+        n = len(accounts)
+        emailIdx = {} # email -> id
+        emails = [] # set of emails of all accounts
+        emailToAcc = {} # email_index -> account_Id
+
+        m = 0
+        for accId, a in enumerate(accounts):
+            for i in range(1, len(a)):
+                email = a[i]
+                if email in emailIdx:
+                    continue
+                emails.append(email)
+                emailIdx[email] = m
+                emailToAcc[m] = accId
+                m += 1
+        
+        adj = [[] for _ in range(m)]
+        for a in accounts:
+            for i in range(2, len(a)):
+                id1 = emailIdx[a[i]]
+                id2 = emailIdx[a[i - 1]]
+                adj[id1].append(id2)
+                adj[id2].append(id1)
+        
+        emailGroup = defaultdict(list) # index of acc -> list of emails
+        visited = [False] * m
+        def dfs(node, accId):
+            visited[node] = True
+            emailGroup[accId].append(emails[node])
+            for nei in adj[node]:
+                if not visited[nei]:
+                    dfs(nei, accId)
+        
+        for i in range(m):
+            if not visited[i]:
+                dfs(i, emailToAcc[i])
+        
+        res = []
+        for accId in emailGroup:
+            name = accounts[accId][0]
+            res.append([name] + sorted(emailGroup[accId]))
+        
+        return res
+```
+
+```java
+public class Solution {
+    private Map<String, Integer> emailIdx = new HashMap<>(); // email -> id
+    private List<String> emails = new ArrayList<>(); // set of emails of all accounts
+    private Map<Integer, Integer> emailToAcc = new HashMap<>(); // email_index -> account_Id
+    private List<List<Integer>> adj;
+    private Map<Integer, List<String>> emailGroup = new HashMap<>(); // index of acc -> list of emails
+    private boolean[] visited;
+
+    public List<List<String>> accountsMerge(List<List<String>> accounts) {
+        int n = accounts.size();
+        int m = 0;
+
+        // Build email index and mappings
+        for (int accId = 0; accId < n; accId++) {
+            List<String> account = accounts.get(accId);
+            for (int i = 1; i < account.size(); i++) {
+                String email = account.get(i);
+                if (!emailIdx.containsKey(email)) {
+                    emails.add(email);
+                    emailIdx.put(email, m);
+                    emailToAcc.put(m, accId);
+                    m++;
+                }
+            }
+        }
+
+        // Build adjacency list
+        adj = new ArrayList<>();
+        for (int i = 0; i < m; i++) {
+            adj.add(new ArrayList<>());
+        }
+        for (List<String> account : accounts) {
+            for (int i = 2; i < account.size(); i++) {
+                int id1 = emailIdx.get(account.get(i));
+                int id2 = emailIdx.get(account.get(i - 1));
+                adj.get(id1).add(id2);
+                adj.get(id2).add(id1);
+            }
+        }
+
+        // Initialize visited array
+        visited = new boolean[m];
+
+        // DFS traversal
+        for (int i = 0; i < m; i++) {
+            if (!visited[i]) {
+                int accId = emailToAcc.get(i);
+                emailGroup.putIfAbsent(accId, new ArrayList<>());
+                dfs(i, accId);
+            }
+        }
+
+        // Build result
+        List<List<String>> res = new ArrayList<>();
+        for (int accId : emailGroup.keySet()) {
+            List<String> group = emailGroup.get(accId);
+            Collections.sort(group);
+            List<String> merged = new ArrayList<>();
+            merged.add(accounts.get(accId).get(0));
+            merged.addAll(group);
+            res.add(merged);
+        }
+
+        return res;
+    }
+
+    private void dfs(int node, int accId) {
+        visited[node] = true;
+        emailGroup.get(accId).add(emails.get(node));
+        for (int neighbor : adj.get(node)) {
+            if (!visited[neighbor]) {
+                dfs(neighbor, accId);
+            }
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+    unordered_map<string, int> emailIdx; // email -> id
+    vector<string> emails; // set of emails of all accounts
+    unordered_map<int, int> emailToAcc; // email_index -> account_Id
+    vector<vector<int>> adj;
+    unordered_map<int, vector<string>> emailGroup; // index of acc -> list of emails
+    vector<bool> visited;
+
+public:
+    vector<vector<string>> accountsMerge(vector<vector<string>>& accounts) {
+        int n = accounts.size();
+        int m = 0;
+
+        // Build email index and mappings
+        for (int accId = 0; accId < n; accId++) {
+            vector<string>& account = accounts[accId];
+            for (int i = 1; i < account.size(); i++) {
+                string& email = account[i];
+                if (emailIdx.find(email) == emailIdx.end()) {
+                    emails.push_back(email);
+                    emailIdx[email] = m;
+                    emailToAcc[m] = accId;
+                    m++;
+                }
+            }
+        }
+
+        // Build adjacency list
+        adj.resize(m);
+        for (auto& account : accounts) {
+            for (int i = 2; i < account.size(); i++) {
+                int id1 = emailIdx[account[i]];
+                int id2 = emailIdx[account[i - 1]];
+                adj[id1].push_back(id2);
+                adj[id2].push_back(id1);
+            }
+        }
+
+        visited.resize(m, false);
+        // DFS traversal
+        for (int i = 0; i < m; i++) {
+            if (!visited[i]) {
+                int accId = emailToAcc[i];
+                dfs(i, accId);
+            }
+        }
+
+        // Build result
+        vector<vector<string>> res;
+        for (auto& [accId, group] : emailGroup) {
+            sort(group.begin(), group.end());
+            vector<string> merged;
+            merged.push_back(accounts[accId][0]);
+            merged.insert(merged.end(), group.begin(), group.end());
+            res.push_back(merged);
+        }
+
+        return res;
+    }
+
+private:
+    void dfs(int node, int& accId) {
+        visited[node] = true;
+        emailGroup[accId].push_back(emails[node]);
+        for (int& neighbor : adj[node]) {
+            if (!visited[neighbor]) {
+                dfs(neighbor, accId);
+            }
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[][]} accounts
+     * @return {string[][]}
+     */
+    accountsMerge(accounts) {
+        const emailIdx = new Map(); // email -> id
+        const emails = []; // set of emails of all accounts
+        const emailToAcc = new Map(); // email_index -> account_Id
+        const adj = [];
+        const emailGroup = new Map(); // index of acc -> list of emails
+        let visited = [];
+
+        const n = accounts.length;
+        let m = 0;
+
+        // Build email index and mappings
+        for (let accId = 0; accId < n; accId++) {
+            const account = accounts[accId];
+            for (let i = 1; i < account.length; i++) {
+                const email = account[i];
+                if (!emailIdx.has(email)) {
+                    emails.push(email);
+                    emailIdx.set(email, m);
+                    emailToAcc.set(m, accId);
+                    m++;
+                }
+            }
+        }
+
+        // Build adjacency list
+        for (let i = 0; i < m; i++) {
+            adj.push([]);
+        }
+        for (const account of accounts) {
+            for (let i = 2; i < account.length; i++) {
+                const id1 = emailIdx.get(account[i]);
+                const id2 = emailIdx.get(account[i - 1]);
+                adj[id1].push(id2);
+                adj[id2].push(id1);
+            }
+        }
+
+        // Initialize visited array
+        visited = Array(m).fill(false);
+
+        // DFS traversal
+        const dfs = (node, accId) => {
+            visited[node] = true;
+            emailGroup.get(accId).push(emails[node]);
+            for (const neighbor of adj[node]) {
+                if (!visited[neighbor]) {
+                    dfs(neighbor, accId);
+                }
+            }
+        };
+
+        for (let i = 0; i < m; i++) {
+            if (!visited[i]) {
+                const accId = emailToAcc.get(i);
+                if (!emailGroup.has(accId)) {
+                    emailGroup.set(accId, []);
+                }
+                dfs(i, accId);
+            }
+        }
+
+        // Build result
+        const res = [];
+        for (const [accId, group] of emailGroup.entries()) {
+            group.sort();
+            const merged = [accounts[accId][0], ...group];
+            res.push(merged);
+        }
+
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    private Dictionary<string, int> emailIdx = new Dictionary<string, int>();
+    private List<string> emails = new List<string>();
+    private List<List<int>> adj;
+    private bool[] visited;
+    private Dictionary<int, List<string>> components = new Dictionary<int, List<string>>();
+    private Dictionary<int, string> componentName = new Dictionary<int, string>();
+
+    public List<List<string>> AccountsMerge(List<List<string>> accounts) {
+        int m = 0;
+
+        for (int accId = 0; accId < accounts.Count; accId++) {
+            var account = accounts[accId];
+            for (int i = 1; i < account.Count; i++) {
+                string email = account[i];
+                if (!emailIdx.ContainsKey(email)) {
+                    emailIdx[email] = m++;
+                    emails.Add(email);
+                }
+            }
+        }
+
+        adj = new List<List<int>>();
+        for (int i = 0; i < m; i++) adj.Add(new List<int>());
+
+        foreach (var account in accounts) {
+            for (int i = 2; i < account.Count; i++) {
+                int u = emailIdx[account[i - 1]];
+                int v = emailIdx[account[i]];
+                adj[u].Add(v);
+                adj[v].Add(u);
+            }
+        }
+
+        visited = new bool[m];
+
+        foreach (var account in accounts) {
+            string name = account[0];
+            foreach (var email in account.Skip(1)) {
+                int idx = emailIdx[email];
+                if (!visited[idx]) {
+                    components[idx] = new List<string>();
+                    componentName[idx] = name;
+                    Dfs(idx, idx);
+                }
+            }
+        }
+
+        var res = new List<List<string>>();
+        foreach (var kvp in components) {
+            var group = kvp.Value;
+            group.Sort(StringComparer.Ordinal);
+            var merged = new List<string> { componentName[kvp.Key] };
+            merged.AddRange(group);
+            res.Add(merged);
+        }
+
+        return res;
+    }
+
+    private void Dfs(int node, int root) {
+        visited[node] = true;
+        components[root].Add(emails[node]);
+        foreach (int nei in adj[node]) {
+            if (!visited[nei]) {
+                Dfs(nei, root);
+            }
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O((n * m)\log (n * m))$
+* Space complexity: $O(n * m)$
+
+> Where $n$ is the number of accounts and $m$ is the number of emails.
+
+---
+
+## 2. Breadth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def accountsMerge(self, accounts: List[List[str]]) -> List[List[str]]:
+        n = len(accounts)
+        emailIdx = {} # email -> id
+        emails = [] # set of emails of all accounts
+        emailToAcc = {} # email_index -> account_Id
+
+        m = 0
+        for accId, a in enumerate(accounts):
+            for i in range(1, len(a)):
+                email = a[i]
+                if email in emailIdx:
+                    continue
+                emails.append(email)
+                emailIdx[email] = m
+                emailToAcc[m] = accId
+                m += 1
+        
+        adj = [[] for _ in range(m)]
+        for a in accounts:
+            for i in range(2, len(a)):
+                id1 = emailIdx[a[i]]
+                id2 = emailIdx[a[i - 1]]
+                adj[id1].append(id2)
+                adj[id2].append(id1)
+        
+        emailGroup = defaultdict(list) # index of acc -> list of emails
+        visited = [False] * m
+
+        def bfs(start, accId):
+            queue = deque([start])
+            visited[start] = True
+            while queue:
+                node = queue.popleft()
+                emailGroup[accId].append(emails[node])
+                for nei in adj[node]:
+                    if not visited[nei]:
+                        visited[nei] = True
+                        queue.append(nei)
+        
+        for i in range(m):
+            if not visited[i]:
+                bfs(i, emailToAcc[i])
+        
+        res = []
+        for accId in emailGroup:
+            name = accounts[accId][0]
+            res.append([name] + sorted(emailGroup[accId]))
+        
+        return res
+```
+
+```java
+public class Solution {
+    private Map<String, Integer> emailIdx = new HashMap<>(); // email -> id
+    private List<String> emails = new ArrayList<>(); // set of emails of all accounts
+    private Map<Integer, Integer> emailToAcc = new HashMap<>(); // email_index -> account_Id
+    private List<List<Integer>> adj;
+    private Map<Integer, List<String>> emailGroup = new HashMap<>(); // index of acc -> list of emails
+    private boolean[] visited;
+
+    public List<List<String>> accountsMerge(List<List<String>> accounts) {
+        int n = accounts.size();
+        int m = 0;
+
+        // Build email index and mappings
+        for (int accId = 0; accId < n; accId++) {
+            List<String> account = accounts.get(accId);
+            for (int i = 1; i < account.size(); i++) {
+                String email = account.get(i);
+                if (!emailIdx.containsKey(email)) {
+                    emails.add(email);
+                    emailIdx.put(email, m);
+                    emailToAcc.put(m, accId);
+                    m++;
+                }
+            }
+        }
+
+        // Build adjacency list
+        adj = new ArrayList<>();
+        for (int i = 0; i < m; i++) {
+            adj.add(new ArrayList<>());
+        }
+        for (List<String> account : accounts) {
+            for (int i = 2; i < account.size(); i++) {
+                int id1 = emailIdx.get(account.get(i));
+                int id2 = emailIdx.get(account.get(i - 1));
+                adj.get(id1).add(id2);
+                adj.get(id2).add(id1);
+            }
+        }
+
+        // Initialize visited array
+        visited = new boolean[m];
+
+        // BFS traversal
+        for (int i = 0; i < m; i++) {
+            if (!visited[i]) {
+                int accId = emailToAcc.get(i);
+                emailGroup.putIfAbsent(accId, new ArrayList<>());
+                bfs(i, accId);
+            }
+        }
+
+        // Build result
+        List<List<String>> res = new ArrayList<>();
+        for (int accId : emailGroup.keySet()) {
+            List<String> group = emailGroup.get(accId);
+            Collections.sort(group);
+            List<String> merged = new ArrayList<>();
+            merged.add(accounts.get(accId).get(0));
+            merged.addAll(group);
+            res.add(merged);
+        }
+
+        return res;
+    }
+
+    private void bfs(int start, int accId) {
+        Queue<Integer> queue = new LinkedList<>();
+        queue.offer(start);
+        visited[start] = true;
+
+        while (!queue.isEmpty()) {
+            int node = queue.poll();
+            emailGroup.get(accId).add(emails.get(node));
+            for (int neighbor : adj.get(node)) {
+                if (!visited[neighbor]) {
+                    visited[neighbor] = true;
+                    queue.offer(neighbor);
+                }
+            }
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+    unordered_map<string, int> emailIdx; // email -> id
+    vector<string> emails; // set of emails of all accounts
+    unordered_map<int, int> emailToAcc; // email_index -> account_Id
+    vector<vector<int>> adj;
+    unordered_map<int, vector<string>> emailGroup; // index of acc -> list of emails
+    vector<bool> visited;
+
+public:
+    vector<vector<string>> accountsMerge(vector<vector<string>>& accounts) {
+        int n = accounts.size();
+        int m = 0;
+
+        // Build email index and mappings
+        for (int accId = 0; accId < n; accId++) {
+            vector<string>& account = accounts[accId];
+            for (int i = 1; i < account.size(); i++) {
+                string& email = account[i];
+                if (emailIdx.find(email) == emailIdx.end()) {
+                    emails.push_back(email);
+                    emailIdx[email] = m;
+                    emailToAcc[m] = accId;
+                    m++;
+                }
+            }
+        }
+
+        // Build adjacency list
+        adj.resize(m);
+        for (auto& account : accounts) {
+            for (int i = 2; i < account.size(); i++) {
+                int id1 = emailIdx[account[i]];
+                int id2 = emailIdx[account[i - 1]];
+                adj[id1].push_back(id2);
+                adj[id2].push_back(id1);
+            }
+        }
+
+        visited.resize(m, false);
+        // BFS traversal
+        for (int i = 0; i < m; i++) {
+            if (!visited[i]) {
+                int accId = emailToAcc[i];
+                bfs(i, accId);
+            }
+        }
+
+        // Build result
+        vector<vector<string>> res;
+        for (auto& [accId, group] : emailGroup) {
+            sort(group.begin(), group.end());
+            vector<string> merged;
+            merged.push_back(accounts[accId][0]);
+            merged.insert(merged.end(), group.begin(), group.end());
+            res.push_back(merged);
+        }
+
+        return res;
+    }
+
+private:
+    void bfs(int start, int accId) {
+        queue<int> q;
+        q.push(start);
+        visited[start] = true;
+
+        while (!q.empty()) {
+            int node = q.front();
+            q.pop();
+            emailGroup[accId].push_back(emails[node]);
+            for (int& neighbor : adj[node]) {
+                if (!visited[neighbor]) {
+                    visited[neighbor] = true;
+                    q.push(neighbor);
+                }
+            }
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[][]} accounts
+     * @return {string[][]}
+     */
+    accountsMerge(accounts) {
+        const emailIdx = new Map(); // email -> id
+        const emails = []; // set of emails of all accounts
+        const emailToAcc = new Map(); // email_index -> account_Id
+        const adj = [];
+        const emailGroup = new Map(); // index of acc -> list of emails
+        let visited = [];
+
+        const n = accounts.length;
+        let m = 0;
+
+        // Build email index and mappings
+        for (let accId = 0; accId < n; accId++) {
+            const account = accounts[accId];
+            for (let i = 1; i < account.length; i++) {
+                const email = account[i];
+                if (!emailIdx.has(email)) {
+                    emails.push(email);
+                    emailIdx.set(email, m);
+                    emailToAcc.set(m, accId);
+                    m++;
+                }
+            }
+        }
+
+        // Build adjacency list
+        for (let i = 0; i < m; i++) {
+            adj.push([]);
+        }
+        for (const account of accounts) {
+            for (let i = 2; i < account.length; i++) {
+                const id1 = emailIdx.get(account[i]);
+                const id2 = emailIdx.get(account[i - 1]);
+                adj[id1].push(id2);
+                adj[id2].push(id1);
+            }
+        }
+
+        // Initialize visited array
+        visited = Array(m).fill(false);
+
+        // BFS traversal
+        const bfs = (start, accId) => {
+            const queue = new Queue([start]);
+            visited[start] = true;
+
+            while (!queue.isEmpty()) {
+                const node = queue.pop();
+                emailGroup.get(accId).push(emails[node]);
+                for (const neighbor of adj[node]) {
+                    if (!visited[neighbor]) {
+                        visited[neighbor] = true;
+                        queue.push(neighbor);
+                    }
+                }
+            }
+        };
+
+        for (let i = 0; i < m; i++) {
+            if (!visited[i]) {
+                const accId = emailToAcc.get(i);
+                if (!emailGroup.has(accId)) {
+                    emailGroup.set(accId, []);
+                }
+                bfs(i, accId);
+            }
+        }
+
+        // Build result
+        const res = [];
+        for (const [accId, group] of emailGroup.entries()) {
+            group.sort();
+            const merged = [accounts[accId][0], ...group];
+            res.push(merged);
+        }
+
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<List<string>> AccountsMerge(List<List<string>> accounts) {
+        int n = accounts.Count;
+        Dictionary<string, int> emailIdx = new Dictionary<string, int>();
+        List<string> emails = new List<string>();
+        Dictionary<int, int> emailToAcc = new Dictionary<int, int>();
+
+        int m = 0;
+        for (int accId = 0; accId < n; accId++) {
+            var account = accounts[accId];
+            for (int i = 1; i < account.Count; i++) {
+                string email = account[i];
+                if (!emailIdx.ContainsKey(email)) {
+                    emailIdx[email] = m;
+                    emails.Add(email);
+                    emailToAcc[m] = accId;
+                    m++;
+                }
+            }
+        }
+
+        List<List<int>> adj = new List<List<int>>();
+        for (int i = 0; i < m; i++) adj.Add(new List<int>());
+        
+        foreach (var account in accounts) {
+            for (int i = 2; i < account.Count; i++) {
+                int id1 = emailIdx[account[i]];
+                int id2 = emailIdx[account[i - 1]];
+                adj[id1].Add(id2);
+                adj[id2].Add(id1);
+            }
+        }
+
+        Dictionary<int, List<string>> emailGroup = new Dictionary<int, List<string>>();
+        bool[] visited = new bool[m];
+
+        void Bfs(int start, int accId) {
+            Queue<int> queue = new Queue<int>();
+            queue.Enqueue(start);
+            visited[start] = true;
+
+            if (!emailGroup.ContainsKey(accId))
+                emailGroup[accId] = new List<string>();
+
+            while (queue.Count > 0) {
+                int node = queue.Dequeue();
+                emailGroup[accId].Add(emails[node]);
+
+                foreach (int nei in adj[node]) {
+                    if (!visited[nei]) {
+                        visited[nei] = true;
+                        queue.Enqueue(nei);
+                    }
+                }
+            }
+        }
+
+        for (int i = 0; i < m; i++) {
+            if (!visited[i]) {
+                Bfs(i, emailToAcc[i]);
+            }
+        }
+
+        List<List<string>> res = new List<List<string>>();
+        foreach (var kvp in emailGroup) {
+            int accId = kvp.Key;
+            string name = accounts[accId][0];
+            List<string> merged = new List<string> { name };
+            kvp.Value.Sort(StringComparer.Ordinal);
+            merged.AddRange(kvp.Value);
+            res.Add(merged);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O((n * m)\log (n * m))$
+* Space complexity: $O(n * m)$
+
+> Where $n$ is the number of accounts and $m$ is the number of emails.
+
+---
+
+## 3. Disjoint Set Union
+
+::tabs-start
+
+```python
+class UnionFind:
+    def __init__(self, n):
+        self.par = [i for i in range(n)]
+        self.rank = [1] * n
+
+    def find(self, x):
+        while x != self.par[x]:
+            self.par[x] = self.par[self.par[x]]
+            x = self.par[x]
+        return x
+
+    def union(self, x1, x2):
+        p1, p2 = self.find(x1), self.find(x2)
+        if p1 == p2:
+            return False
+        if self.rank[p1] > self.rank[p2]:
+            self.par[p2] = p1
+            self.rank[p1] += self.rank[p2]
+        else:
+            self.par[p1] = p2
+            self.rank[p2] += self.rank[p1]
+        return True
+
+class Solution:
+    def accountsMerge(self, accounts: List[List[str]]) -> List[List[str]]:
+        uf = UnionFind(len(accounts))
+        emailToAcc = {}  # email -> index of acc
+
+        for i, a in enumerate(accounts):
+            for e in a[1:]:
+                if e in emailToAcc:
+                    uf.union(i, emailToAcc[e])
+                else:
+                    emailToAcc[e] = i
+
+        emailGroup = defaultdict(list)  # index of acc -> list of emails
+        for e, i in emailToAcc.items():
+            leader = uf.find(i)
+            emailGroup[leader].append(e)
+
+        res = []
+        for i, emails in emailGroup.items():
+            name = accounts[i][0]
+            res.append([name] + sorted(emailGroup[i]))
+        return res
+```
+
+```java
+class UnionFind {
+    private int[] parent;
+    private int[] rank;
+
+    public UnionFind(int n) {
+        parent = new int[n];
+        rank = new int[n];
+        for (int i = 0; i < n; i++) {
+            parent[i] = i;
+            rank[i] = 1;
+        }
+    }
+
+    public int find(int x) {
+        if (x != parent[x]) {
+            parent[x] = find(parent[x]);
+        }
+        return parent[x];
+    }
+
+    public boolean union(int x1, int x2) {
+        int p1 = find(x1);
+        int p2 = find(x2);
+        if (p1 == p2) {
+            return false;
+        }
+        if (rank[p1] > rank[p2]) {
+            parent[p2] = p1;
+            rank[p1] += rank[p2];
+        } else {
+            parent[p1] = p2;
+            rank[p2] += rank[p1];
+        }
+        return true;
+    }
+}
+
+public class Solution {
+    public List<List<String>> accountsMerge(List<List<String>> accounts) {
+        int n = accounts.size();
+        UnionFind uf = new UnionFind(n);
+        Map<String, Integer> emailToAcc = new HashMap<>(); // email -> index of acc
+
+        // Build union-find structure
+        for (int i = 0; i < n; i++) {
+            List<String> account = accounts.get(i);
+            for (int j = 1; j < account.size(); j++) {
+                String email = account.get(j);
+                if (emailToAcc.containsKey(email)) {
+                    uf.union(i, emailToAcc.get(email));
+                } else {
+                    emailToAcc.put(email, i);
+                }
+            }
+        }
+
+        // Group emails by leader account
+        Map<Integer, List<String>> emailGroup = new HashMap<>(); // index of acc -> list of emails
+        for (Map.Entry<String, Integer> entry : emailToAcc.entrySet()) {
+            String email = entry.getKey();
+            int accId = entry.getValue();
+            int leader = uf.find(accId);
+            emailGroup.putIfAbsent(leader, new ArrayList<>());
+            emailGroup.get(leader).add(email);
+        }
+
+        // Build result
+        List<List<String>> res = new ArrayList<>();
+        for (Map.Entry<Integer, List<String>> entry : emailGroup.entrySet()) {
+            int accId = entry.getKey();
+            List<String> emails = entry.getValue();
+            Collections.sort(emails);
+            List<String> merged = new ArrayList<>();
+            merged.add(accounts.get(accId).get(0)); // Add account name
+            merged.addAll(emails);
+            res.add(merged);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class UnionFind {
+    vector<int> parent;
+    vector<int> rank;
+
+public:
+    UnionFind(int n) {
+        parent.resize(n);
+        rank.resize(n, 1);
+        for (int i = 0; i < n; i++) {
+            parent[i] = i;
+        }
+    }
+
+    int find(int x) {
+        if (x != parent[x]) {
+            parent[x] = find(parent[x]);
+        }
+        return parent[x];
+    }
+
+    bool unionSets(int x1, int x2) {
+        int p1 = find(x1);
+        int p2 = find(x2);
+        if (p1 == p2) {
+            return false;
+        }
+        if (rank[p1] > rank[p2]) {
+            parent[p2] = p1;
+            rank[p1] += rank[p2];
+        } else {
+            parent[p1] = p2;
+            rank[p2] += rank[p1];
+        }
+        return true;
+    }
+};
+
+class Solution {
+public:
+    vector<vector<string>> accountsMerge(vector<vector<string>>& accounts) {
+        int n = accounts.size();
+        UnionFind uf(n);
+        unordered_map<string, int> emailToAcc; // email -> index of acc
+
+        // Build union-find structure
+        for (int i = 0; i < n; i++) {
+            for (int j = 1; j < accounts[i].size(); j++) {
+                const string& email = accounts[i][j];
+                if (emailToAcc.count(email)) {
+                    uf.unionSets(i, emailToAcc[email]);
+                } else {
+                    emailToAcc[email] = i;
+                }
+            }
+        }
+
+        // Group emails by leader account
+        map<int, vector<string>> emailGroup; // index of acc -> list of emails
+        for (const auto& [email, accId] : emailToAcc) {
+            int leader = uf.find(accId);
+            emailGroup[leader].push_back(email);
+        }
+
+        // Build result
+        vector<vector<string>> res;
+        for (auto& [accId, emails] : emailGroup) {
+            sort(emails.begin(), emails.end());
+            vector<string> merged;
+            merged.push_back(accounts[accId][0]);
+            merged.insert(merged.end(), emails.begin(), emails.end());
+            res.push_back(merged);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class UnionFind {
+    /**
+     * @constructor
+     * @param {number} n
+     */
+    constructor(n) {
+        this.parent = Array.from({ length: n }, (_, i) => i);
+        this.rank = Array(n).fill(1);
+    }
+
+    /**
+     * @param {number} x
+     * @return {number}
+     */
+    find(x) {
+        if (x !== this.parent[x]) {
+            this.parent[x] = this.find(this.parent[x]);
+        }
+        return this.parent[x];
+    }
+
+    /**
+     * @param {number} x1
+     * @param {number} x2
+     * @return {boolean}
+     */
+    union(x1, x2) {
+        const p1 = this.find(x1);
+        const p2 = this.find(x2);
+        if (p1 === p2) {
+            return false;
+        }
+        if (this.rank[p1] > this.rank[p2]) {
+            this.parent[p2] = p1;
+            this.rank[p1] += this.rank[p2];
+        } else {
+            this.parent[p1] = p2;
+            this.rank[p2] += this.rank[p1];
+        }
+        return true;
+    }
+}
+
+class Solution {
+    /**
+     * @param {string[][]} accounts
+     * @return {string[][]}
+     */
+    accountsMerge(accounts) {
+        const n = accounts.length;
+        const uf = new UnionFind(n);
+        const emailToAcc = new Map(); // email -> index of acc
+
+        // Build union-find structure
+        for (let i = 0; i < n; i++) {
+            for (let j = 1; j < accounts[i].length; j++) {
+                const email = accounts[i][j];
+                if (emailToAcc.has(email)) {
+                    uf.union(i, emailToAcc.get(email));
+                } else {
+                    emailToAcc.set(email, i);
+                }
+            }
+        }
+
+        // Group emails by leader account
+        const emailGroup = new Map(); // index of acc -> list of emails
+        for (const [email, accId] of emailToAcc.entries()) {
+            const leader = uf.find(accId);
+            if (!emailGroup.has(leader)) {
+                emailGroup.set(leader, []);
+            }
+            emailGroup.get(leader).push(email);
+        }
+
+        // Build result
+        const res = [];
+        for (const [accId, emails] of emailGroup.entries()) {
+            emails.sort();
+            const merged = [accounts[accId][0], ...emails];
+            res.push(merged);
+        }
+
+        return res;
+    }
+}
+```
+
+```csharp
+public class UnionFind {
+    private int[] parent;
+    private int[] rank;
+
+    public UnionFind(int n) {
+        parent = new int[n];
+        rank = new int[n];
+        for (int i = 0; i < n; i++) {
+            parent[i] = i;
+            rank[i] = 1;
+        }
+    }
+
+    public int Find(int x) {
+        if (x != parent[x]) {
+            parent[x] = Find(parent[x]);
+        }
+        return parent[x];
+    }
+
+    public bool Union(int x, int y) {
+        int rootX = Find(x);
+        int rootY = Find(y);
+
+        if (rootX == rootY) return false;
+
+        if (rank[rootX] > rank[rootY]) {
+            parent[rootY] = rootX;
+            rank[rootX] += rank[rootY];
+        } else {
+            parent[rootX] = rootY;
+            rank[rootY] += rank[rootX];
+        }
+
+        return true;
+    }
+}
+
+public class Solution {
+    public List<List<string>> AccountsMerge(List<List<string>> accounts) {
+        int n = accounts.Count;
+        UnionFind uf = new UnionFind(n);
+        Dictionary<string, int> emailToAcc = new Dictionary<string, int>();
+
+        for (int i = 0; i < n; i++) {
+            for (int j = 1; j < accounts[i].Count; j++) {
+                string email = accounts[i][j];
+                if (emailToAcc.ContainsKey(email)) {
+                    uf.Union(i, emailToAcc[email]);
+                } else {
+                    emailToAcc[email] = i;
+                }
+            }
+        }
+
+        Dictionary<int, List<string>> emailGroup = new Dictionary<int, List<string>>();
+        foreach (var kvp in emailToAcc) {
+            string email = kvp.Key;
+            int leader = uf.Find(kvp.Value);
+            if (!emailGroup.ContainsKey(leader)) {
+                emailGroup[leader] = new List<string>();
+            }
+            emailGroup[leader].Add(email);
+        }
+
+        List<List<string>> res = new List<List<string>>();
+        foreach (var kvp in emailGroup) {
+            int accId = kvp.Key;
+            List<string> emails = kvp.Value;
+            emails.Sort(StringComparer.Ordinal);
+            List<string> merged = new List<string> { accounts[accId][0] };
+            merged.AddRange(emails);
+            res.Add(merged);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O((n * m)\log (n * m))$
+* Space complexity: $O(n * m)$
+
+> Where $n$ is the number of accounts and $m$ is the number of emails.
\ No newline at end of file
diff --git a/articles/add-binary.md b/articles/add-binary.md
new file mode 100644
index 000000000..424adb990
--- /dev/null
+++ b/articles/add-binary.md
@@ -0,0 +1,240 @@
+## 1. Iteration
+
+::tabs-start
+
+```python
+class Solution:
+    def addBinary(self, a: str, b: str) -> str:
+        res = ""
+        carry = 0
+
+        a, b = a[::-1], b[::-1]
+        for i in range(max(len(a), len(b))):
+            digitA = ord(a[i]) - ord("0") if i < len(a) else 0
+            digitB = ord(b[i]) - ord("0") if i < len(b) else 0
+
+            total = digitA + digitB + carry
+            char = str(total % 2)
+            res = char + res
+            carry = total // 2
+
+        if carry:
+            res = "1" + res
+
+        return res
+```
+
+```java
+public class Solution {
+    public String addBinary(String a, String b) {
+        StringBuilder res = new StringBuilder();
+        int carry = 0;
+        
+        StringBuilder sa = new StringBuilder(a).reverse();
+        StringBuilder sb = new StringBuilder(b).reverse();
+        
+        for (int i = 0; i < Math.max(sa.length(), sb.length()); i++) {
+            int digitA = i < sa.length() ? sa.charAt(i) - '0' : 0;
+            int digitB = i < sb.length() ? sb.charAt(i) - '0' : 0;
+            
+            int total = digitA + digitB + carry;
+            char c = (char)((total % 2) + '0');
+            res.append(c);
+            carry = total / 2;
+        }
+        
+        if (carry > 0) {
+            res.append('1');
+        }
+        
+        return res.reverse().toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string addBinary(string a, string b) {
+        string res = "";
+        int carry = 0;
+        
+        reverse(a.begin(), a.end());
+        reverse(b.begin(), b.end());
+        
+        for (int i = 0; i < max(a.length(), b.length()); i++) {
+            int digitA = i < a.length() ? a[i] - '0' : 0;
+            int digitB = i < b.length() ? b[i] - '0' : 0;
+            
+            int total = digitA + digitB + carry;
+            char c = (total % 2) + '0';
+            res += c;
+            carry = total / 2;
+        }
+        
+        if (carry) {
+            res += '1';
+        }
+        reverse(res.begin(), res.end());
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} a
+     * @param {string} b
+     * @return {string}
+     */
+    addBinary(a, b) {
+        let res = [];
+        let carry = 0;
+        
+        a = a.split("").reverse().join("");
+        b = b.split("").reverse().join("");
+        
+        for (let i = 0; i < Math.max(a.length, b.length); i++) {
+            const digitA = i < a.length ? a[i] - '0' : 0;
+            const digitB = i < b.length ? b[i] - '0' : 0;
+            
+            const total = digitA + digitB + carry;
+            const char = (total % 2).toString();
+            res.push(char)
+            carry = Math.floor(total / 2);
+        }
+        
+        if (carry) {
+            res.push('1');
+        }
+        res.reverse()
+        return res.join('');
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(max(m, n))$
+* Space complexity: $O(m + n)$
+
+> Where $m$ and $n$ are the lengths of the strings $a$ and $b$ respectively.
+
+---
+
+## 2. Iteration (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def addBinary(self, a: str, b: str) -> str:
+        res = []
+        carry = 0
+
+        i, j = len(a) - 1, len(b) - 1
+        while i >= 0 or j >= 0 or carry > 0:
+            digitA = int(a[i]) if i >= 0 else 0
+            digitB = int(b[j]) if j >= 0 else 0
+
+            total = digitA + digitB + carry
+            res.append(total % 2)
+            carry = total // 2
+
+            i -= 1
+            j -= 1
+
+        res.reverse()
+        return ''.join(map(str, res))
+```
+
+```java
+public class Solution {
+    public String addBinary(String a, String b) {
+        StringBuilder res = new StringBuilder();
+        int carry = 0;
+
+        int i = a.length() - 1, j = b.length() - 1;
+        while (i >= 0 || j >= 0 || carry > 0) {
+            int digitA = i >= 0 ? a.charAt(i) - '0' : 0;
+            int digitB = j >= 0 ? b.charAt(j) - '0' : 0;
+
+            int total = digitA + digitB + carry;
+            res.append(total % 2);
+            carry = total / 2;
+
+            i--;
+            j--;
+        }
+
+        return res.reverse().toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string addBinary(string a, string b) {
+        string res = "";
+        int carry = 0;
+
+        int i = a.size() - 1, j = b.size() - 1;
+        while (i >= 0 || j >= 0 || carry > 0) {
+            int digitA = i >= 0 ? a[i] - '0' : 0;
+            int digitB = j >= 0 ? b[j] - '0' : 0;
+
+            int total = digitA + digitB + carry;
+            res += (total % 2) + '0';
+            carry = total / 2;
+
+            i--;
+            j--;
+        }
+
+        reverse(res.begin(), res.end());
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} a
+     * @param {string} b
+     * @return {string}
+     */
+    addBinary(a, b) {
+        let res = [];
+        let carry = 0;
+
+        let i = a.length - 1, j = b.length - 1;
+        while (i >= 0 || j >= 0 || carry > 0) {
+            const digitA = i >= 0 ? a[i] - "0" : 0;
+            const digitB = j >= 0 ? b[j] - "0" : 0;
+
+            const total = digitA + digitB + carry;
+            res.push(total % 2);
+            carry = Math.floor(total / 2);
+
+            i--;
+            j--;
+        }
+        res.reverse()
+        return res.join('');
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(max(m, n))$
+* Space complexity: $O(max(m, n))$
+
+> Where $m$ and $n$ are the lengths of the strings $a$ and $b$ respectively.
\ No newline at end of file
diff --git a/articles/add-to-array-form-of-integer.md b/articles/add-to-array-form-of-integer.md
new file mode 100644
index 000000000..ecab6ca84
--- /dev/null
+++ b/articles/add-to-array-form-of-integer.md
@@ -0,0 +1,217 @@
+## 1. Reverse and Add
+
+::tabs-start
+
+```python
+class Solution:
+    def addToArrayForm(self, num: List[int], k: int) -> List[int]:
+        num.reverse()
+        i = 0
+        while k:
+            digit = k % 10
+            if i < len(num):
+                num[i] += digit
+            else:
+                num.append(digit)
+            carry = num[i] // 10
+            num[i] %= 10
+            k //= 10
+            k += carry
+            i += 1
+        num.reverse()
+        return num
+```
+
+```java
+public class Solution {
+    public List<Integer> addToArrayForm(int[] num, int k) {
+        List<Integer> result = new ArrayList<>();
+        for (int i = num.length - 1; i >= 0; i--) {
+            k += num[i];
+            result.add(k % 10);
+            k /= 10;
+        }
+        while (k > 0) {
+            result.add(k % 10);
+            k /= 10;
+        }
+        Collections.reverse(result);
+        return result;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> addToArrayForm(vector<int>& num, int k) {
+        reverse(num.begin(), num.end());
+        int i = 0;
+        while (k) {
+            int digit = k % 10;
+            if (i < num.size()) {
+                num[i] += digit;
+            } else {
+                num.push_back(digit);
+            }
+            int carry = num[i] / 10;
+            num[i] %= 10;
+            k /= 10;
+            k += carry;
+            i++;
+        }
+        reverse(num.begin(), num.end());
+        return num;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} num
+     * @param {number} k
+     * @return {number[]}
+     */
+    addToArrayForm(num, k) {
+        num.reverse();
+        let i = 0;
+        while (k > 0) {
+            const digit = k % 10;
+            if (i < num.length) {
+                num[i] += digit;
+            } else {
+                num.push(digit);
+            }
+            const carry = Math.floor(num[i] / 10);
+            num[i] %= 10;
+            k = Math.floor(k / 10) + carry;
+            i++;
+        }
+        num.reverse();
+        return num;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(max(n, m))$
+* Space complexity: $O(n)$.
+
+> Where $n$ is the size of the array $num$ and $m$ is the number of digits in $k$.
+
+---
+
+## 2. Without Reverse()
+
+::tabs-start
+
+```python
+class Solution:
+    def addToArrayForm(self, num: List[int], k: int) -> List[int]:
+        from collections import deque
+        result = deque()
+        i = len(num) - 1
+        carry = 0
+
+        while i >= 0 or k > 0 or carry > 0:
+            digit = k % 10
+            sum_val = carry + (num[i] if i >= 0 else 0) + digit
+
+            result.appendleft(sum_val % 10)
+            carry = sum_val // 10
+
+            k //= 10
+            i -= 1
+
+        return list(result)
+```
+
+```java
+public class Solution {
+    public List<Integer> addToArrayForm(int[] num, int k) {
+        LinkedList<Integer> result = new LinkedList<>();
+        int carry = 0, i = num.length - 1;
+
+        while (i >= 0 || k > 0 || carry > 0) {
+            int digit = k % 10;
+            int sum = carry + (i >= 0 ? num[i] : 0) + digit;
+
+            result.addFirst(sum % 10);
+            carry = sum / 10;
+
+            k /= 10;
+            i--;
+        }
+
+        return result;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> addToArrayForm(vector<int>& num, int k) {
+        list<int> result;
+        int carry = 0, i = num.size() - 1;
+
+        while (i >= 0 || k > 0 || carry > 0) {
+            int digit = k % 10;
+            int sum = carry + (i >= 0 ? num[i] : 0) + digit;
+
+            result.push_front(sum % 10);
+            carry = sum / 10;
+
+            k /= 10;
+            i--;
+        }
+
+        return vector<int>(result.begin(), result.end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} num
+     * @param {number} k
+     * @return {number[]}
+     */
+    addToArrayForm(num, k) {
+        let res = new Deque();
+        let carry = 0, i = num.length - 1;
+
+        while (i >= 0 || k > 0 || carry > 0) {
+            const digit = k % 10;
+            const sum = carry + (i >= 0 ? num[i] : 0) + digit;
+
+            res.pushFront(sum % 10);
+            carry = Math.floor(sum / 10);
+
+            k = Math.floor(k / 10);
+            i--;
+        }
+
+        const resultArray = [];
+        while (!res.isEmpty()) {
+            resultArray.push(res.popFront());
+        }
+
+        return resultArray;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(max(n, m))$
+* Space complexity: $O(n)$
+
+> Where $n$ is the size of the array $num$ and $m$ is the number of digits in $k$.
\ No newline at end of file
diff --git a/articles/add-two-numbers.md b/articles/add-two-numbers.md
index fe7827dda..118adab49 100644
--- a/articles/add-two-numbers.md
+++ b/articles/add-two-numbers.md
@@ -226,6 +226,117 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func add(l1 *ListNode, l2 *ListNode, carry int) *ListNode {
+    if l1 == nil && l2 == nil && carry == 0 {
+        return nil
+    }
+    
+    v1, v2 := 0, 0
+    if l1 != nil {
+        v1 = l1.Val
+    }
+    if l2 != nil {
+        v2 = l2.Val
+    }
+    
+    sum := v1 + v2 + carry
+    carry, val := sum/10, sum%10
+    
+    var nextNode *ListNode
+    nextL1 := l1
+    nextL2 := l2
+    if l1 != nil {
+        nextL1 = l1.Next
+    } else {
+        nextL1 = nil
+    }
+    if l2 != nil {
+        nextL2 = l2.Next
+    } else {
+        nextL2 = nil
+    }
+    nextNode = add(nextL1, nextL2, carry)
+
+    return &ListNode{Val: val, Next: nextNode}
+}
+
+func addTwoNumbers(l1 *ListNode, l2 *ListNode) *ListNode {
+    return add(l1, l2, 0)
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var li = ListNode(5)
+ * var v = li.`val`
+ * Definition for singly-linked list.
+ * class ListNode(var `val`: Int) {
+ *     var next: ListNode? = null
+ * }
+ */
+class Solution {
+    private fun add(l1: ListNode?, l2: ListNode?, carry: Int): ListNode? {
+        if (l1 == null && l2 == null && carry == 0) return null
+
+        val v1 = l1?.`val` ?: 0
+        val v2 = l2?.`val` ?: 0
+        val sum = v1 + v2 + carry
+        val newCarry = sum / 10
+        val valNode = sum % 10
+
+        val nextNode = add(l1?.next, l2?.next, newCarry)
+        return ListNode(valNode).apply { next = nextNode }
+    }
+
+    fun addTwoNumbers(l1: ListNode?, l2: ListNode?): ListNode? {
+        return add(l1, l2, 0)
+    }
+}
+```
+
+```swift
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public var val: Int
+ *     public var next: ListNode?
+ *     public init() { self.val = 0; self.next = nil; }
+ *     public init(_ val: Int) { self.val = val; self.next = nil; }
+ *     public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
+ * }
+ */
+class Solution {
+    private func add(_ l1: ListNode?, _ l2: ListNode?, _ carry: Int) -> ListNode? {
+        if l1 == nil && l2 == nil && carry == 0 {
+            return nil
+        }
+        
+        let v1 = l1?.val ?? 0
+        let v2 = l2?.val ?? 0
+        
+        let sum = v1 + v2 + carry
+        let newCarry = sum / 10
+        let val = sum % 10
+        
+        let nextNode = add(l1?.next, l2?.next, newCarry)
+        return ListNode(val, nextNode)
+    }
+
+    func addTwoNumbers(_ l1: ListNode?, _ l2: ListNode?) -> ListNode? {
+        return add(l1, l2, 0)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -233,7 +344,7 @@ public class Solution {
 * Time complexity: $O(m + n)$
 * Space complexity: $O(m + n)$
 
-> Where $m$ is the length $l1$ and $n$ is the length of $l2$.
+> Where $m$ is the length of $l1$ and $n$ is the length of $l2$.
 
 ---
 
@@ -427,11 +538,122 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func addTwoNumbers(l1 *ListNode, l2 *ListNode) *ListNode {
+    dummy := &ListNode{}
+    cur := dummy
+    carry := 0
+
+    for l1 != nil || l2 != nil || carry != 0 {
+        v1 := 0
+        if l1 != nil {
+            v1 = l1.Val
+            l1 = l1.Next
+        }
+        
+        v2 := 0
+        if l2 != nil {
+            v2 = l2.Val
+            l2 = l2.Next
+        }
+
+        val := v1 + v2 + carry
+        carry = val / 10
+        cur.Next = &ListNode{Val: val % 10}
+        cur = cur.Next
+    }
+
+    return dummy.Next
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var li = ListNode(5)
+ * var v = li.`val`
+ * Definition for singly-linked list.
+ * class ListNode(var `val`: Int) {
+ *     var next: ListNode? = null
+ * }
+ */
+class Solution {
+    fun addTwoNumbers(l1: ListNode?, l2: ListNode?): ListNode? {
+        val dummy = ListNode(0)
+        var cur = dummy
+        var carry = 0
+
+        var p1 = l1
+        var p2 = l2
+
+        while (p1 != null || p2 != null || carry != 0) {
+            val v1 = p1?.`val` ?: 0
+            val v2 = p2?.`val` ?: 0
+
+            val sum = v1 + v2 + carry
+            carry = sum / 10
+            cur.next = ListNode(sum % 10)
+
+            cur = cur.next!!
+            p1 = p1?.next
+            p2 = p2?.next
+        }
+
+        return dummy.next
+    }
+}
+```
+
+```swift
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public var val: Int
+ *     public var next: ListNode?
+ *     public init() { self.val = 0; self.next = nil; }
+ *     public init(_ val: Int) { self.val = val; self.next = nil; }
+ *     public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
+ * }
+ */
+class Solution {
+    func addTwoNumbers(_ l1: ListNode?, _ l2: ListNode?) -> ListNode? {
+        let dummy = ListNode(0)
+        var cur = dummy
+        var l1 = l1, l2 = l2
+        var carry = 0
+
+        while l1 != nil || l2 != nil || carry != 0 {
+            let v1 = l1?.val ?? 0
+            let v2 = l2?.val ?? 0
+
+            let sum = v1 + v2 + carry
+            carry = sum / 10
+            let val = sum % 10
+            cur.next = ListNode(val)
+
+            cur = cur.next!
+            l1 = l1?.next
+            l2 = l2?.next
+        }
+        return dummy.next
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(m + n)$
-* Space complexity: $O(1)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(max(m, n))$ for the output list.
 
-> Where $m$ is the length $l1$ and $n$ is the length of $l2$.
\ No newline at end of file
+> Where $m$ is the length of $l1$ and $n$ is the length of $l2$.
\ No newline at end of file
diff --git a/articles/all-possible-full-binary-trees.md b/articles/all-possible-full-binary-trees.md
new file mode 100644
index 000000000..1e75b0293
--- /dev/null
+++ b/articles/all-possible-full-binary-trees.md
@@ -0,0 +1,693 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def allPossibleFBT(self, n: int) -> List[Optional[TreeNode]]:
+        def backtrack(n):
+            if n == 0:
+                return []
+            if n == 1:
+                return [TreeNode(0)]
+
+            res = []
+            for l in range(n):
+                r = n - 1 - l
+                leftTrees, rightTrees = backtrack(l), backtrack(r)
+
+                for t1 in leftTrees:
+                    for t2 in rightTrees:
+                        res.append(TreeNode(0, t1, t2))
+            return res
+
+        return backtrack(n)
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<TreeNode> allPossibleFBT(int n) {
+        return backtrack(n);
+    }
+
+    private List<TreeNode> backtrack(int n) {
+        if (n == 0) {
+            return new ArrayList<>();
+        }
+        if (n == 1) {
+            return Arrays.asList(new TreeNode(0));
+        }
+
+        List<TreeNode> res = new ArrayList<>();
+        for (int l = 0; l < n; l++) {
+            int r = n - 1 - l;
+            List<TreeNode> leftTrees = backtrack(l);
+            List<TreeNode> rightTrees = backtrack(r);
+
+            for (TreeNode t1 : leftTrees) {
+                for (TreeNode t2 : rightTrees) {
+                    res.add(new TreeNode(0, t1, t2));
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    vector<TreeNode*> allPossibleFBT(int n) {
+        return backtrack(n);
+    }
+
+private:
+    vector<TreeNode*> backtrack(int n) {
+        if (n == 0) {
+            return {};
+        }
+        if (n == 1) {
+            return {new TreeNode(0)};
+        }
+
+        vector<TreeNode*> res;
+        for (int l = 0; l < n; l++) {
+            int r = n - 1 - l;
+            vector<TreeNode*> leftTrees = backtrack(l);
+            vector<TreeNode*> rightTrees = backtrack(r);
+
+            for (auto& t1 : leftTrees) {
+                for (auto& t2 : rightTrees) {
+                    res.push_back(new TreeNode(0, t1, t2));
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {number} n
+     * @return {TreeNode[]}
+     */
+    allPossibleFBT(n) {
+        const backtrack = (n) => {
+            if (n === 0) {
+                return [];
+            }
+            if (n === 1) {
+                return [new TreeNode(0)];
+            }
+
+            let res = [];
+            for (let l = 0; l < n; l++) {
+                let r = n - 1 - l;
+                let leftTrees = backtrack(l);
+                let rightTrees = backtrack(r);
+
+                for (let t1 of leftTrees) {
+                    for (let t2 of rightTrees) {
+                        res.push(new TreeNode(0, t1, t2));
+                    }
+                }
+            }
+            return res;
+        };
+
+        return backtrack(n);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(n * 2 ^ n)$
+
+---
+
+## 2. Recursion (Optimal)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def allPossibleFBT(self, n: int) -> List[Optional[TreeNode]]:
+        if n % 2 == 0:
+            return []
+        if n == 1:
+            return [TreeNode(0)]
+
+        res = []
+        for left in range(1, n, 2):
+            leftSubTree = self.allPossibleFBT(left)
+            rightSubTree = self.allPossibleFBT(n - 1 - left)
+            for l in leftSubTree:
+                for r in rightSubTree:
+                    root = TreeNode(0, l, r)
+                    res.append(root)
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<TreeNode> allPossibleFBT(int n) {
+        if (n % 2 == 0) {
+            return new ArrayList<>();
+        }
+        if (n == 1) {
+            return Arrays.asList(new TreeNode(0));
+        }
+
+        List<TreeNode> res = new ArrayList<>();
+        for (int left = 1; left < n; left += 2) {
+            List<TreeNode> leftSubTree = allPossibleFBT(left);
+            List<TreeNode> rightSubTree = allPossibleFBT(n - 1 - left);
+            for (TreeNode l : leftSubTree) {
+                for (TreeNode r : rightSubTree) {
+                    TreeNode root = new TreeNode(0, l, r);
+                    res.add(root);
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    vector<TreeNode*> allPossibleFBT(int n) {
+        if (n % 2 == 0) {
+            return {};
+        }
+        if (n == 1) {
+            return {new TreeNode(0)};
+        }
+
+        vector<TreeNode*> res;
+        for (int left = 1; left < n; left += 2) {
+            vector<TreeNode*> leftSubTree = allPossibleFBT(left);
+            vector<TreeNode*> rightSubTree = allPossibleFBT(n - 1 - left);
+            for (auto& l : leftSubTree) {
+                for (auto& r : rightSubTree) {
+                    TreeNode* root = new TreeNode(0, l, r);
+                    res.push_back(root);
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {number} n
+     * @return {TreeNode[]}
+     */
+    allPossibleFBT(n) {
+        if (n % 2 === 0) {
+            return [];
+        }
+        if (n === 1) {
+            return [new TreeNode(0)];
+        }
+
+        let res = [];
+        for (let left = 1; left < n; left += 2) {
+            let leftSubTree = this.allPossibleFBT(left);
+            let rightSubTree = this.allPossibleFBT(n - 1 - left);
+            for (let l of leftSubTree) {
+                for (let r of rightSubTree) {
+                    let root = new TreeNode(0, l, r);
+                    res.push(root);
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(n * 2 ^ n)$
+
+---
+
+## 3. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def allPossibleFBT(self, n: int) -> List[Optional[TreeNode]]:
+        dp = {}
+
+        def dfs(n):
+            if n % 2 == 0:
+                return []
+            if n == 1:
+                return [TreeNode(0)]
+            if n in dp:
+                return dp[n]
+
+            res = []
+            for left in range(1, n, 2):
+                leftSubTree = dfs(left)
+                rightSubTree = dfs(n - 1 - left)
+                for l in leftSubTree:
+                    for r in rightSubTree:
+                        res.append(TreeNode(0, l, r))
+
+            dp[n] = res
+            return res
+        
+        return dfs(n)
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    private List<TreeNode>[] dp;
+
+    public List<TreeNode> allPossibleFBT(int n) {
+        dp = new ArrayList[n + 1];
+        return dfs(n);
+    }
+
+    private List<TreeNode> dfs(int n) {
+        if (n % 2 == 0) {
+            return new ArrayList<>();
+        }
+        if (n == 1) {
+            return Arrays.asList(new TreeNode(0));
+        }
+        if (dp[n] != null) {
+            return dp[n];
+        }
+
+        List<TreeNode> res = new ArrayList<>();
+        for (int left = 1; left < n; left += 2) {
+            List<TreeNode> leftSubTree = dfs(left);
+            List<TreeNode> rightSubTree = dfs(n - 1 - left);
+            for (TreeNode l : leftSubTree) {
+                for (TreeNode r : rightSubTree) {
+                    res.add(new TreeNode(0, l, r));
+                }
+            }
+        }
+
+        return dp[n] = res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+private:
+    vector<vector<TreeNode*>> dp;
+
+public:
+    vector<TreeNode*> allPossibleFBT(int n) {
+        dp.resize(n + 1);
+        return dfs(n);
+    }
+
+    vector<TreeNode*> dfs(int n) {
+        if (n % 2 == 0) {
+            return {};
+        }
+        if (n == 1) {
+            return {new TreeNode(0)};
+        }
+        if (!dp[n].empty()) {
+            return dp[n];
+        }
+
+        vector<TreeNode*> res;
+        for (int left = 1; left < n; left += 2) {
+            vector<TreeNode*> leftSubTree = dfs(left);
+            vector<TreeNode*> rightSubTree = dfs(n - 1 - left);
+            for (auto& l : leftSubTree) {
+                for (auto& r : rightSubTree) {
+                    res.push_back(new TreeNode(0, l, r));
+                }
+            }
+        }
+
+        return dp[n] = res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {number} n
+     * @return {TreeNode[]}
+     */
+    allPossibleFBT(n) {
+        let dp = new Array(n + 1);
+
+        const dfs = (n) => {
+            if (n % 2 === 0) {
+                return [];
+            }
+            if (n === 1) {
+                return [new TreeNode(0)];
+            }
+            if (dp[n]) {
+                return dp[n];
+            }
+
+            let res = [];
+            for (let left = 1; left < n; left += 2) {
+                let leftSubTree = dfs(left);
+                let rightSubTree = dfs(n - 1 - left);
+                for (let t1 of leftSubTree) {
+                    for (let t2 of rightSubTree) {
+                        res.push(new TreeNode(0, t1, t2));
+                    }
+                }
+            }
+
+            return (dp[n] = res);
+        };
+
+        return dfs(n);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(n * 2 ^ n)$
+
+---
+
+## 4. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def allPossibleFBT(self, n: int) -> List[Optional[TreeNode]]:
+        if n % 2 == 0:
+            return []
+        
+        dp = [[] for _ in range(n + 1)]
+        dp[1] = [TreeNode(0)]
+
+        for nodes in range(3, n + 1, 2):
+            res = []
+            for left in range(1, nodes, 2):
+                right = nodes - 1 - left
+                for t1 in dp[left]:
+                    for t2 in dp[right]:
+                        res.append(TreeNode(0, t1, t2))
+            dp[nodes] = res
+
+        return dp[n]
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<TreeNode> allPossibleFBT(int n) {
+        if (n % 2 == 0) {
+            return new ArrayList<>();
+        }
+
+        List<TreeNode>[] dp = new ArrayList[n + 1];
+        for (int i = 0; i <= n; i++) {
+            dp[i] = new ArrayList<>();
+        }
+        dp[1].add(new TreeNode(0));
+
+        for (int nodes = 3; nodes <= n; nodes += 2) {
+            List<TreeNode> res = new ArrayList<>();
+            for (int left = 1; left < nodes; left += 2) {
+                int right = nodes - 1 - left;
+                for (TreeNode t1 : dp[left]) {
+                    for (TreeNode t2 : dp[right]) {
+                        res.add(new TreeNode(0, t1, t2));
+                    }
+                }
+            }
+            dp[nodes] = res;
+        }
+
+        return dp[n];
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    vector<TreeNode*> allPossibleFBT(int n) {
+        if (n % 2 == 0) {
+            return {};
+        }
+
+        vector<vector<TreeNode*>> dp(n + 1);
+        dp[1].push_back(new TreeNode(0));
+
+        for (int nodes = 3; nodes <= n; nodes += 2) {
+            vector<TreeNode*> res;
+            for (int left = 1; left < nodes; left += 2) {
+                int right = nodes - 1 - left;
+                for (auto& t1 : dp[left]) {
+                    for (auto& t2 : dp[right]) {
+                        res.push_back(new TreeNode(0, t1, t2));
+                    }
+                }
+            }
+            dp[nodes] = res;
+        }
+
+        return dp[n];
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {number} n
+     * @return {TreeNode[]}
+     */
+    allPossibleFBT(n) {
+        if (n % 2 === 0) {
+            return [];
+        }
+
+        let dp = Array.from({ length: n + 1 }, () => []);
+        dp[1] = [new TreeNode(0)];
+
+        for (let nodes = 3; nodes <= n; nodes += 2) {
+            let res = [];
+            for (let left = 1; left < nodes; left += 2) {
+                let right = nodes - 1 - left;
+                for (let t1 of dp[left]) {
+                    for (let t2 of dp[right]) {
+                        res.push(new TreeNode(0, t1, t2));
+                    }
+                }
+            }
+            dp[nodes] = res;
+        }
+
+        return dp[n];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(n * 2 ^ n)$
\ No newline at end of file
diff --git a/articles/anagram-groups.md b/articles/anagram-groups.md
index 251b2e043..bf41aaa79 100644
--- a/articles/anagram-groups.md
+++ b/articles/anagram-groups.md
@@ -9,7 +9,7 @@ class Solution:
         for s in strs:
             sortedS = ''.join(sorted(s))
             res[sortedS].append(s)
-        return res.values()
+        return list(res.values())
 ```
 
 ```java
@@ -85,6 +85,61 @@ public class Solution {
 }
 ```
 
+```go
+func groupAnagrams(strs []string) [][]string {
+    res := make(map[string][]string)
+
+    for _, s := range strs {
+        sortedS := sortString(s)
+        res[sortedS] = append(res[sortedS], s)
+    }
+
+    var result [][]string
+    for _, group := range res {
+        result = append(result, group)
+    }
+    return result
+}
+
+func sortString(s string) string {
+	characters := []rune(s)
+	sort.Slice(characters, func(i, j int) bool {
+		return characters[i] < characters[j]
+	})
+	return string(characters)
+}
+```
+
+```kotlin
+class Solution {
+    fun groupAnagrams(strs: Array<String>): List<List<String>> {
+        val res = mutableMapOf<String, MutableList<String>>()
+
+        for (s in strs) {
+            val sortedS = s.toCharArray().sorted().joinToString("")
+            res.getOrPut(sortedS) { mutableListOf() }.add(s)
+        }
+
+        return res.values.toList()
+    }
+}
+```
+
+```swift
+class Solution {
+    func groupAnagrams(_ strs: [String]) -> [[String]] {
+        var res = [String: [String]]()
+
+        for s in strs {
+            let sortedS = String(s.sorted())
+            res[sortedS, default: []].append(s)
+        }
+
+        return Array(res.values)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -109,7 +164,7 @@ class Solution:
             for c in s:
                 count[ord(c) - ord('a')] += 1
             res[tuple(count)].append(s)
-        return res.values()
+        return list(res.values())
 ```
 
 ```java
@@ -199,11 +254,69 @@ public class Solution {
 }
 ```
 
+```go
+func groupAnagrams(strs []string) [][]string {
+    res := make(map[[26]int][]string)
+
+    for _, s := range strs {
+        var count [26]int
+        for _, c := range s {
+            count[c-'a']++
+        }
+        res[count] = append(res[count], s)
+    }
+
+    var result [][]string
+    for _, group := range res {
+        result = append(result, group)
+    }
+    return result
+}
+```
+
+```kotlin
+class Solution {
+    fun groupAnagrams(strs: Array<String>): List<List<String>> {
+        val res = HashMap<List<Int>, MutableList<String>>()
+
+        for (s in strs) {
+            val count = MutableList(26) { 0 }
+            for (c in s) {
+                count[c - 'a']++
+            }
+            res.getOrPut(count) { mutableListOf() }.add(s)
+        }
+
+        return res.values.toList()
+    }
+}
+```
+
+```swift
+class Solution {
+    func groupAnagrams(_ strs: [String]) -> [[String]] {
+        var res = [Array<Int>: [String]]()
+
+        for s in strs {
+            var count = [Int](repeating: 0, count: 26)
+            for c in s {
+                count[Int(c.asciiValue!) - 97] += 1
+            }
+            res[count, default: []].append(s)
+        }
+
+        return Array(res.values)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(m * n)$
-* Space complexity: $O(m)$
+* Space complexity:
+    * $O(m)$ extra space.
+    * $O(m * n)$ space for the output list.
 
 > Where $m$ is the number of strings and $n$ is the length of the longest string.
\ No newline at end of file
diff --git a/articles/analyze-user-website-visit-pattern.md b/articles/analyze-user-website-visit-pattern.md
new file mode 100644
index 000000000..c43fce6ba
--- /dev/null
+++ b/articles/analyze-user-website-visit-pattern.md
@@ -0,0 +1,224 @@
+## 1. Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def mostVisitedPattern(self, username: List[str], timestamp: List[int], website: List[str]) -> List[str]:
+        arr = list(zip(timestamp, username, website))
+        arr.sort()
+
+        mp = defaultdict(list)
+        for time, user, site in arr:
+            mp[user].append(site)
+
+        count = defaultdict(int)
+        for user in mp:
+            patterns = set()
+            cur = mp[user]
+            for i in range(len(cur)):
+                for j in range(i + 1, len(cur)):
+                    for k in range(j + 1, len(cur)):
+                        patterns.add((cur[i], cur[j], cur[k]))
+            for p in patterns:
+                count[p] += 1
+
+        max_count = 0
+        res = tuple()
+        for pattern in count:
+            if count[pattern] > max_count or (count[pattern] == max_count and pattern < res):
+                max_count = count[pattern]
+                res = pattern
+
+        return list(res)
+```
+
+```java
+public class Solution {
+    public List<String> mostVisitedPattern(String[] username, int[] timestamp, String[] website) {
+        int n = timestamp.length;
+        List<int[]> arr = new ArrayList<>();
+        for (int i = 0; i < n; i++) arr.add(new int[]{timestamp[i], i});
+        arr.sort((a, b) -> Integer.compare(a[0], b[0]));
+
+        Map<String, List<String>> mp = new HashMap<>();
+        for (int[] p : arr) {
+            int idx = p[1];
+            mp.computeIfAbsent(username[idx], k -> new ArrayList<>()).add(website[idx]);
+        }
+
+        Map<String, Integer> count = new HashMap<>();
+        for (String user : mp.keySet()) {
+            List<String> cur = mp.get(user);
+            Set<String> patterns = new HashSet<>();
+            for (int i = 0; i < cur.size(); i++)
+                for (int j = i + 1; j < cur.size(); j++)
+                    for (int k = j + 1; k < cur.size(); k++)
+                        patterns.add(cur.get(i) + "#" + cur.get(j) + "#" + cur.get(k));
+            for (String p : patterns)
+                count.put(p, count.getOrDefault(p, 0) + 1);
+        }
+
+        String res = "";
+        int max_count = 0;
+        for (String p : count.keySet()) {
+            int c = count.get(p);
+            if (c > max_count || (c == max_count && p.compareTo(res) < 0)) {
+                max_count = c;
+                res = p;
+            }
+        }
+        return Arrays.asList(res.split("#"));
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<string> mostVisitedPattern(vector<string>& username, vector<int>& timestamp, vector<string>& website) {
+        int n = timestamp.size();
+        vector<pair<int,int>> arr;
+        for (int i = 0; i < n; ++i) arr.push_back({timestamp[i], i});
+        sort(arr.begin(), arr.end(),
+             [](auto& a, auto& b){ return a.first < b.first; });
+
+        unordered_map<string, vector<string>> mp;
+        for (auto& p : arr) mp[username[p.second]].push_back(website[p.second]);
+
+        unordered_map<string,int> count;
+        for (auto& kv : mp) {
+            auto& cur = kv.second;
+            unordered_set<string> patterns;
+            for (int i = 0; i < (int)cur.size(); ++i)
+                for (int j = i + 1; j < (int)cur.size(); ++j)
+                    for (int k = j + 1; k < (int)cur.size(); ++k)
+                        patterns.insert(cur[i] + "#" + cur[j] + "#" + cur[k]);
+            for (auto& p : patterns) ++count[p];
+        }
+
+        int maxCnt = 0;
+        string res;
+        for (auto& kv : count)
+            if (kv.second > maxCnt ||
+               (kv.second == maxCnt && (res.empty() || kv.first < res))) {
+                maxCnt = kv.second;
+                res = kv.first;
+            }
+
+        vector<string> ans;
+        string tmp;
+        for (char ch : res) {
+            if (ch == '#') { 
+                ans.push_back(tmp);
+                tmp.clear();
+            } else {
+                tmp += ch;
+            }
+        }
+        ans.push_back(tmp);
+        return ans;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} username
+     * @param {number[]} timestamp
+     * @param {string[]} website
+     * @return {string[]}
+     */
+    mostVisitedPattern(username, timestamp, website) {
+        const n = timestamp.length;
+        const arr = [];
+        for (let i = 0; i < n; i++) arr.push([timestamp[i], i]);
+        arr.sort((a, b) => a[0] - b[0]);
+
+        const mp = new Map();
+        for (const [, idx] of arr) {
+            const user = username[idx], site = website[idx];
+            if (!mp.has(user)) mp.set(user, []);
+            mp.get(user).push(site);
+        }
+
+        const count = new Map();
+        for (const user of mp.keys()) {
+            const cur = mp.get(user);
+            const patterns = new Set();
+            for (let i = 0; i < cur.length; i++) {
+                for (let j = i + 1; j < cur.length; j++) {
+                    for (let k = j + 1; k < cur.length; k++) {
+                        patterns.add(`${cur[i]}#${cur[j]}#${cur[k]}`);
+                    }
+                }
+            }
+            for (const p of patterns) {
+                count.set(p, (count.get(p) || 0) + 1);
+            }
+        }
+
+        let maxCnt = 0, res = "";
+        for (const [pat, c] of count.entries()) {
+            if (c > maxCnt || (c === maxCnt && (res === "" || pat < res))) {
+                maxCnt = c;
+                res = pat;
+            }
+        }
+        return res.split("#");
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<string> MostVisitedPattern(string[] username, int[] timestamp, string[] website) {
+        int n = timestamp.Length;
+        var arr = new List<(int t, int i)>();
+        for (int i = 0; i < n; i++) arr.Add((timestamp[i], i));
+        arr.Sort((a, b) => a.t.CompareTo(b.t));
+
+        var mp = new Dictionary<string, List<string>>();
+        foreach (var (t, idx) in arr) {
+            string user = username[idx], site = website[idx];
+            if (!mp.ContainsKey(user)) mp[user] = new List<string>();
+            mp[user].Add(site);
+        }
+
+        var count = new Dictionary<string,int>();
+        foreach (var kv in mp) {
+            var cur = kv.Value;
+            var patterns = new HashSet<string>();
+            for (int i = 0; i < cur.Count; i++)
+                for (int j = i + 1; j < cur.Count; j++)
+                    for (int k = j + 1; k < cur.Count; k++)
+                        patterns.Add($"{cur[i]}#{cur[j]}#{cur[k]}");
+            foreach (var p in patterns) {
+                count[p] = count.ContainsKey(p) ? count[p] + 1 : 1;
+            }
+        }
+
+        int maxCnt = 0;
+        string res = "";
+        foreach (var kv in count) {
+            if (kv.Value > maxCnt ||
+                (kv.Value == maxCnt &&
+                (res == "" || string.Compare(kv.Key, res, StringComparison.Ordinal) < 0))) {
+                maxCnt = kv.Value;
+                res = kv.Key;
+            }
+        }
+        return new List<string>(res.Split('#'));
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n + n * u +  n ^ 3 * w)$
+* Space complexity: $O(n * u + n ^ 3 * w)$
+
+> Where $n$ is the size of the array $timestamp$, $u$ is the maximum length of any string in the array $username$, and $w$ is the maximum length of any string in the array $website$.
\ No newline at end of file
diff --git a/articles/append-characters-to-string-to-make-subsequence.md b/articles/append-characters-to-string-to-make-subsequence.md
new file mode 100644
index 000000000..de5f09613
--- /dev/null
+++ b/articles/append-characters-to-string-to-make-subsequence.md
@@ -0,0 +1,210 @@
+## 1. Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def appendCharacters(self, s: str, t: str) -> int:
+        i, j = 0, 0
+
+        while i < len(s) and j < len(t):
+            if s[i] == t[j]:
+                i += 1
+                j += 1
+            else:
+                i += 1
+        return len(t) - j
+```
+
+```java
+public class Solution {
+    public int appendCharacters(String s, String t) {
+        int i = 0, j = 0;
+
+        while (i < s.length() && j < t.length()) {
+            if (s.charAt(i) == t.charAt(j)) {
+                i++;
+                j++;
+            } else {
+                i++;
+            }
+        }
+        return t.length() - j;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int appendCharacters(string s, string t) {
+        int i = 0, j = 0;
+
+        while (i < s.length() && j < t.length()) {
+            if (s[i] == t[j]) {
+                i++;
+                j++;
+            } else {
+                i++;
+            }
+        }
+        return t.length() - j;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string} t
+     * @return {number}
+     */
+    appendCharacters(s, t) {
+        let i = 0, j = 0;
+
+        while (i < s.length && j < t.length) {
+            if (s[i] === t[j]) {
+                i++;
+                j++;
+            } else {
+                i++;
+            }
+        }
+        return t.length - j;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(1)$
+
+> Where $n$ and $m$ are the lengths of the strings $s$ and $t$, respectively.
+
+---
+
+## 2. Index Jumping
+
+::tabs-start
+
+```python
+class Solution:
+    def appendCharacters(self, s: str, t: str) -> int:
+        n, m = len(s), len(t)
+        store = [[n + 1] * 26 for _ in range(n)]
+        store[n - 1][ord(s[n - 1]) - ord('a')] = n - 1
+
+        for i in range(n - 2, -1, -1):
+            store[i] = store[i + 1][:]
+            store[i][ord(s[i]) - ord('a')] = i
+
+        i, j = 0, 0
+        while i < n and j < m:
+            if store[i][ord(t[j]) - ord('a')] == n + 1:
+                break
+            
+            i = store[i][ord(t[j]) - ord('a')] + 1
+            j += 1
+
+        return m - j
+```
+
+```java
+public class Solution {
+    public int appendCharacters(String s, String t) {
+        int n = s.length(), m = t.length();
+        int[][] store = new int[n][26];
+        for (int[] row : store) {
+            Arrays.fill(row, n + 1);
+        }
+        store[n - 1][s.charAt(n - 1) - 'a'] = n - 1;
+
+        for (int i = n - 2; i >= 0; i--) {
+            store[i] = store[i + 1].clone();
+            store[i][s.charAt(i) - 'a'] = i;
+        }
+
+        int i = 0, j = 0;
+        while (i < n && j < m) {
+            if (store[i][t.charAt(j) - 'a'] == n + 1) {
+                break;
+            }
+            i = store[i][t.charAt(j) - 'a'] + 1;
+            j++;
+        }
+
+        return m - j;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int appendCharacters(string s, string t) {
+        int n = s.length(), m = t.length();
+        vector<vector<int>> store(n, vector<int>(26, n + 1));
+        store[n - 1][s[n - 1] - 'a'] = n - 1;
+
+        for (int i = n - 2; i >= 0; i--) {
+            store[i] = store[i + 1];
+            store[i][s[i] - 'a'] = i;
+        }
+
+        int i = 0, j = 0;
+        while (i < n && j < m) {
+            if (store[i][t[j] - 'a'] == n + 1) {
+                break;
+            }
+            i = store[i][t[j] - 'a'] + 1;
+            j++;
+        }
+
+        return m - j;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string} t
+     * @return {number}
+     */
+    appendCharacters(s, t) {
+        const n = s.length, m = t.length;
+        const store = Array.from({ length: n }, () => Array(26).fill(n + 1));
+        store[n - 1][s.charCodeAt(n - 1) - 97] = n - 1;
+
+        for (let i = n - 2; i >= 0; i--) {
+            store[i] = store[i + 1].slice();
+            store[i][s.charCodeAt(i) - 97] = i;
+        }
+
+        let i = 0, j = 0;
+        while (i < n && j < m) {
+            if (store[i][t.charCodeAt(j) - 97] === n + 1) {
+                break;
+            }
+            i = store[i][t.charCodeAt(j) - 97] + 1;
+            j++;
+        }
+
+        return m - j;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(n)$
+
+> Where $n$ and $m$ are the lengths of the strings $s$ and $t$, respectively.
\ No newline at end of file
diff --git a/articles/arithmetic-slices-ii-subsequence.md b/articles/arithmetic-slices-ii-subsequence.md
new file mode 100644
index 000000000..427b1557c
--- /dev/null
+++ b/articles/arithmetic-slices-ii-subsequence.md
@@ -0,0 +1,499 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def numberOfArithmeticSlices(self, nums: List[int]) -> int:
+        n = len(nums)
+        if n < 3:
+            return 0
+
+        INF = float('inf')
+        dp = {}
+
+        def dfs(i, j, diff, flag):
+            if i == n:
+                return flag
+            if (i, j, diff, flag) in dp:
+                return dp[(i, j, diff, flag)]
+
+            res = dfs(i + 1, j, diff, flag)
+            if j == -1:
+                res += dfs(i + 1, i, INF, flag)
+            else:
+                if diff == INF:
+                    res += dfs(i + 1, i, nums[i] - nums[j], flag)
+                elif diff == nums[i] - nums[j]:
+                    res += dfs(i + 1, i, diff, 1)
+
+            dp[(i, j, diff, flag)] = res
+            return res
+
+        return dfs(0, -1, INF, 0)
+```
+
+```java
+public class Solution {
+    private static final long INF = (long) 1e15;
+    private Map<String, Integer> dp = new HashMap<>();
+
+    public int numberOfArithmeticSlices(int[] nums) {
+        int n = nums.length;
+        if (n < 3) return 0;
+
+        return dfs(nums, 0, -1, INF, 0);
+    }
+
+    private int dfs(int[] nums, int i, int j, long diff, int flag) {
+        if (i == nums.length) {
+            return flag;
+        }
+        String key = i + "," + j + "," + diff + "," + flag;
+        if (dp.containsKey(key)) {
+            return dp.get(key);
+        }
+
+        int res = dfs(nums, i + 1, j, diff, flag);
+        if (j == -1) {
+            res += dfs(nums, i + 1, i, INF, flag);
+        } else {
+            if (diff == INF) {
+                res += dfs(nums, i + 1, i, nums[i] - 0L - nums[j], flag);
+            } else if (diff == nums[i] - 0L - nums[j]) {
+                res += dfs(nums, i + 1, i, diff, 1);
+            }
+        }
+
+        dp.put(key, res);
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+    static const long long INF = 1e15;
+    unordered_map<string, int> dp;
+
+    int dfs(vector<int>& nums, int i, int j, long long diff, int flag) {
+        if (i == nums.size()) {
+            return flag;
+        }
+
+        string key = to_string(i) + "," + to_string(j) + "," + to_string(diff) + "," + to_string(flag);
+        if (dp.count(key)) {
+            return dp[key];
+        }
+
+        int res = dfs(nums, i + 1, j, diff, flag);
+        if (j == -1) {
+            res += dfs(nums, i + 1, i, INF, flag);
+        } else {
+            if (diff == INF) {
+                res += dfs(nums, i + 1, i, nums[i] - 0LL - nums[j], flag);
+            } else if (diff == nums[i] - 0LL - nums[j]) {
+                res += dfs(nums, i + 1, i, diff, 1);
+            }
+        }
+
+        dp[key] = res;
+        return res;
+    }
+
+public:
+    int numberOfArithmeticSlices(vector<int>& nums) {
+        if (nums.size() < 3) return 0;
+        return dfs(nums, 0, -1, INF, 0);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    numberOfArithmeticSlices(nums) {
+        const n = nums.length;
+        if (n < 3) return 0;
+
+        const INF = Infinity;
+        const dp = new Map();
+
+        const dfs = (i, j, diff, flag) => {
+            if (i === n) {
+                return flag;
+            }
+            const key = `${i},${j},${diff},${flag}`;
+            if (dp.has(key)) {
+                return dp.get(key);
+            }
+
+            let res = dfs(i + 1, j, diff, flag);
+            if (j === -1) {
+                res += dfs(i + 1, i, INF, flag);
+            } else {
+                if (diff === INF) {
+                    res += dfs(i + 1, i, nums[i] - nums[j], flag);
+                } else if (diff === nums[i] - nums[j]) {
+                    res += dfs(i + 1, i, diff, 1);
+                }
+            }
+
+            dp.set(key, res);
+            return res;
+        };
+
+        return dfs(0, -1, INF, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 3)$
+* Space complexity: $O(n ^ 3)$
+
+---
+
+## 2. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def numberOfArithmeticSlices(self, nums: List[int]) -> int:
+        res, n = 0, len(nums)
+        dp = [defaultdict(int) for _ in range(n)]
+
+        for i in range(n):
+            for j in range(i):
+                diff = nums[i] - nums[j]
+                dp[i][diff] += 1 + dp[j][diff]
+                res += dp[j][diff]
+
+        return res
+```
+
+```java
+public class Solution {
+    public int numberOfArithmeticSlices(int[] nums) {
+        int n = nums.length;
+        int res = 0;
+        Map<Long, Integer>[] dp = new HashMap[n];
+        
+        for (int i = 0; i < n; i++) {
+            dp[i] = new HashMap<>();
+            for (int j = 0; j < i; j++) {
+                long diff = (long) nums[i] - nums[j];
+                int count = dp[j].getOrDefault(diff, 0);
+                dp[i].put(diff, dp[i].getOrDefault(diff, 0) + count + 1);
+                res += count;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numberOfArithmeticSlices(vector<int>& nums) {
+        int n = nums.size();
+        int res = 0;
+        vector<unordered_map<long long, int>> dp(n);
+        
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < i; j++) {
+                long long diff = (long long) nums[i] - nums[j];
+                int count = dp[j][diff];
+                dp[i][diff] += count + 1;
+                res += count;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    numberOfArithmeticSlices(nums) {
+        const n = nums.length;
+        let res = 0;
+        const dp = Array.from({ length: n }, () => new Map());
+
+        for (let i = 0; i < n; i++) {
+            for (let j = 0; j < i; j++) {
+                const diff = nums[i] - nums[j];
+                const count = dp[j].get(diff) || 0;
+                dp[i].set(diff, (dp[i].get(diff) || 0) + count + 1);
+                res += count;
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 3. Dynamic Programming (Optimization) - I
+
+::tabs-start
+
+```python
+class Solution:
+    def numberOfArithmeticSlices(self, nums: List[int]) -> int:
+        res, n = 0, len(nums)
+        s = set(nums)
+        dp = [defaultdict(int) for _ in range(n)]
+
+        for i in range(n):
+            for j in range(i):
+                diff = nums[i] - nums[j]
+                cnt = dp[j].get(diff, 0)
+                if nums[i] + diff in s:
+                    dp[i][diff] += cnt + 1
+                res += cnt
+
+        return res
+```
+
+```java
+public class Solution {
+    public int numberOfArithmeticSlices(int[] nums) {
+        int res = 0, n = nums.length;
+        Set<Integer> s = new HashSet<>();
+        for (int num : nums) s.add(num);
+
+        Map<Long, Integer>[] dp = new HashMap[n];
+        for (int i = 0; i < n; i++) dp[i] = new HashMap<>();
+
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < i; j++) {
+                long diff = (long) nums[i] - nums[j];
+                int cnt = dp[j].getOrDefault(diff, 0);
+                if (s.contains((int) (nums[i] + diff))) {
+                    dp[i].put(diff, dp[i].getOrDefault(diff, 0) + cnt + 1);
+                }
+                res += cnt;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numberOfArithmeticSlices(vector<int>& nums) {
+        int res = 0, n = nums.size();
+        unordered_set<int> s(nums.begin(), nums.end());
+        vector<unordered_map<long long, int>> dp(n);
+
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < i; j++) {
+                long long diff = (long long)nums[i] - nums[j];
+                int cnt = dp[j].count(diff) ? dp[j][diff] : 0;
+                if (s.count(nums[i] + diff)) {
+                    dp[i][diff] += cnt + 1;
+                }
+                res += cnt;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    numberOfArithmeticSlices(nums) {
+        let res = 0, n = nums.length;
+        const s = new Set(nums);
+        const dp = Array.from({ length: n }, () => new Map());
+
+        for (let i = 0; i < n; i++) {
+            for (let j = 0; j < i; j++) {
+                const diff = nums[i] - nums[j];
+                const cnt = dp[j].get(diff) || 0;
+                if (s.has(nums[i] + diff)) {
+                    dp[i].set(diff, (dp[i].get(diff) || 0) + cnt + 1);
+                }
+                res += cnt;
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 4. Dynamic Programming (Optimization) - II
+
+::tabs-start
+
+```python
+class Solution:
+    def numberOfArithmeticSlices(self, nums: List[int]) -> int:
+        res = 0
+        mpIdx = defaultdict(list)
+        n = len(nums)
+        dp = [[0] * n for _ in range(n)]
+
+        for i in range(n):
+            mpIdx[nums[i]].append(i)
+
+        for i in range(n):
+            for j in range(i):
+                prev = 2 * nums[j] - nums[i]
+                if prev in mpIdx:
+                    for k in mpIdx[prev]:
+                        if k >= j:
+                            break
+                        dp[i][j] += dp[j][k] + 1
+                res += dp[i][j]
+
+        return res
+```
+
+```java
+public class Solution {
+    public int numberOfArithmeticSlices(int[] nums) {
+        int res = 0;
+        Map<Integer, List<Integer>> mpIdx = new HashMap<>();
+        int n = nums.length;
+        int[][] dp = new int[n][n];
+
+        for (int i = 0; i < n; i++) {
+            mpIdx.putIfAbsent(nums[i], new ArrayList<>());
+            mpIdx.get(nums[i]).add(i);
+        }
+
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < i; j++) {
+                long prev = 2L * nums[j] - nums[i];
+                if (prev < Integer.MIN_VALUE || prev > Integer.MAX_VALUE) {
+                    continue;
+                }
+
+                if (mpIdx.containsKey((int) prev)) {
+                    for (int k : mpIdx.get((int) prev)) {
+                        if (k >= j) break;
+                        dp[i][j] += dp[j][k] + 1;
+                    }
+                }
+                res += dp[i][j];
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numberOfArithmeticSlices(vector<int>& nums) {
+        int res = 0;
+        unordered_map<int, vector<int>> mpIdx;
+        int n = nums.size();
+        vector<vector<int>> dp(n, vector<int>(n, 0));
+
+        for (int i = 0; i < n; i++) {
+            mpIdx[nums[i]].push_back(i);
+        }
+
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < i; j++) {
+                long prev = 2L * nums[j] - nums[i];
+                if (prev < INT_MIN || prev > INT_MAX) continue;
+
+                if (mpIdx.count(prev)) {
+                    for (int k : mpIdx[prev]) {
+                        if (k >= j) break;
+                        dp[i][j] += dp[j][k] + 1;
+                    }
+                }
+                res += dp[i][j];
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    numberOfArithmeticSlices(nums) {
+        let res = 0;
+        const mpIdx = new Map();
+        const n = nums.length;
+        const dp = Array.from({ length: n }, () => Array(n).fill(0));
+
+        for (let i = 0; i < n; i++) {
+            if (!mpIdx.has(nums[i])) mpIdx.set(nums[i], []);
+            mpIdx.get(nums[i]).push(i);
+        }
+
+        for (let i = 0; i < n; i++) {
+            for (let j = 0; j < i; j++) {
+                const prev = 2 * nums[j] - nums[i];
+
+                if (mpIdx.has(prev)) {
+                    for (const k of mpIdx.get(prev)) {
+                        if (k >= j) break;
+                        dp[i][j] += dp[j][k] + 1;
+                    }
+                }
+                res += dp[i][j];
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
\ No newline at end of file
diff --git a/articles/arranging-coins.md b/articles/arranging-coins.md
new file mode 100644
index 000000000..cb8920a4a
--- /dev/null
+++ b/articles/arranging-coins.md
@@ -0,0 +1,401 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def arrangeCoins(self, n: int) -> int:
+        row = 0
+        while n - row > 0:
+            row += 1
+            n -= row
+        return row
+```
+
+```java
+public class Solution {
+    public int arrangeCoins(int n) {
+        int row = 0;
+        while (n - row > 0) {
+            row++;
+            n -= row;
+        }
+        return row;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int arrangeCoins(int n) {
+        int row = 0;
+        while (n - row > 0) {
+            row++;
+            n -= row;
+        }
+        return row;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    arrangeCoins(n) {
+        let row = 0;
+        while (n - row > 0) {
+            row++;
+            n -= row;
+        }
+        return row;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\sqrt {n})$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Binary Search
+
+::tabs-start
+
+```python
+class Solution:
+    def arrangeCoins(self, n: int) -> int:
+        l, r = 1, n
+        res = 0
+
+        while l <= r:
+            mid = (l + r) // 2
+            coins = (mid * (mid + 1)) // 2
+            if coins > n:
+                r = mid - 1
+            else:
+                l = mid + 1
+                res = max(res, mid)
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int arrangeCoins(int n) {
+        int l = 1, r = n, res = 0;
+
+        while (l <= r) {
+            int mid = l + (r - l) / 2;
+            long coins = (long) mid * (mid + 1) / 2;
+            if (coins > n) {
+                r = mid - 1;
+            } else {
+                l = mid + 1;
+                res = Math.max(res, mid);
+            }
+        }
+        
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int arrangeCoins(int n) {
+        long long l = 1, r = n, res = 0;
+
+        while (l <= r) {
+            long long mid = l + (r - l) / 2;
+            long long coins = (mid * (mid + 1)) / 2;
+            if (coins > n) {
+                r = mid - 1;
+            } else {
+                l = mid + 1;
+                res = max(res, mid);
+            }
+        }
+        
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    arrangeCoins(n) {
+        let l = 1, r = n, res = 0;
+
+        while (l <= r) {
+            let mid = Math.floor((l + r) / 2);
+            let coins = (mid * (mid + 1)) / 2;
+            if (coins > n) {
+                r = mid - 1;
+            } else {
+                l = mid + 1;
+                res = Math.max(res, mid);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Binary Search (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def arrangeCoins(self, n: int) -> int:
+        if n <= 3:
+            return n if n == 1 else n - 1
+
+        l, r = 1, (n // 2) + 1
+        while l < r:
+            mid = (l + r) // 2
+            if (mid * (mid + 1)) // 2 <= n:
+                l = mid + 1
+            else:
+                r = mid
+        
+        return l - 1
+```
+
+```java
+public class Solution {
+    public int arrangeCoins(int n) {
+        if (n <= 3) {
+            return n == 1 ? 1 : n - 1;
+        }
+
+        int l = 1, r = (n / 2) + 1;
+        while (l < r) {
+            int mid = l + (r - l) / 2;
+            long coins = (long) mid * (mid + 1) / 2;
+            if (coins <= n) {
+                l = mid + 1;
+            } else {
+                r = mid;
+            }
+        }
+
+        return l - 1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int arrangeCoins(int n) {
+        if (n <= 3) {
+            return n == 1 ? 1 : n - 1;
+        }
+
+        int l = 1, r = (n / 2) + 1;
+        while (l < r) {
+            int mid = l + (r - l) / 2;
+            long long coins = (mid * (mid + 1LL)) / 2;
+            if (coins <= n) {
+                l = mid + 1;
+            } else {
+                r = mid;
+            }
+        }
+        
+        return l - 1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    arrangeCoins(n) {
+        if (n <= 3) {
+            return n == 1 ? 1 : n - 1;
+        }
+
+        let l = 1, r = (n / 2) + 1;
+        while (l < r) {
+            let mid = Math.floor((l + r) / 2);
+            let coins = (mid * (mid + 1)) / 2;
+            if (coins <= n) {
+                l = mid + 1;
+            } else {
+                r = mid;
+            }
+        }
+
+        return l - 1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
+
+---
+
+## 4. Bit Manipulation
+
+::tabs-start
+
+```python
+class Solution:
+    def arrangeCoins(self, n: int) -> int:
+        mask = 1 << 15
+        rows = 0
+        while mask > 0:
+            rows |= mask
+            coins = rows * (rows + 1) // 2
+            if coins > n:
+                rows ^= mask
+            mask >>= 1
+        return rows
+```
+
+```java
+public class Solution {
+    public int arrangeCoins(int n) {
+        int mask = 1 << 15;
+        int rows = 0;
+        while (mask > 0) {
+            rows |= mask;
+            long coins = (long) rows * (rows + 1) / 2;
+            if (coins > n) {
+                rows ^= mask;
+            }
+            mask >>= 1;
+        }
+        return rows;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int arrangeCoins(int n) {
+        int mask = 1 << 15;
+        int rows = 0;
+        while (mask > 0) {
+            rows |= mask;
+            long long coins = (long long) rows * (rows + 1) / 2;
+            if (coins > n) {
+                rows ^= mask;
+            }
+            mask >>= 1;
+        }
+        return rows;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    arrangeCoins(n) {
+        let mask = 1 << 15;
+        let rows = 0;
+        while (mask > 0) {
+            rows |= mask;
+            let coins = (rows * (rows + 1)) / 2;
+            if (coins > n) {
+                rows ^= mask;
+            }
+            mask >>= 1;
+        }
+        return rows;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$ since we iterate $15$ times.
+* Space complexity: $O(1)$
+
+---
+
+## 5. Math
+
+::tabs-start
+
+```python
+class Solution:
+    def arrangeCoins(self, n: int) -> int:
+        return int(sqrt(2 * n + 0.25) - 0.5)
+```
+
+```java
+public class Solution {
+    public int arrangeCoins(int n) {
+        return (int) (Math.sqrt(2L * n + 0.25) - 0.5);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int arrangeCoins(int n) {
+        return (int)(sqrt(2.0 * n + 0.25) - 0.5);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    arrangeCoins(n) {
+        return Math.floor(Math.sqrt(2 * n + 0.25) - 0.5);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$ or $O(\sqrt {n})$ depending on the language.
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/array-with-elements-not-equal-to-average-of-neighbors.md b/articles/array-with-elements-not-equal-to-average-of-neighbors.md
new file mode 100644
index 000000000..4e4a1daa1
--- /dev/null
+++ b/articles/array-with-elements-not-equal-to-average-of-neighbors.md
@@ -0,0 +1,338 @@
+## 1. Greedy
+
+::tabs-start
+
+```python
+class Solution:
+    def rearrangeArray(self, nums: List[int]) -> List[int]:
+        nums.sort()
+        res = []
+        l, r = 0, len(nums) - 1
+        while len(res) != len(nums):
+            res.append(nums[l])
+            l += 1
+            if l <= r:
+                res.append(nums[r])
+                r -= 1
+        return res
+```
+
+```java
+public class Solution {
+    public int[] rearrangeArray(int[] nums) {
+        Arrays.sort(nums);
+        int[] res = new int[nums.length];
+        int l = 0, r = nums.length - 1;
+        int idx = 0;
+
+        while (idx != nums.length) {
+            res[idx++] = nums[l++];
+            if (l <= r) {
+                res[idx++] = nums[r--];
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> rearrangeArray(vector<int>& nums) {
+        sort(nums.begin(), nums.end());
+        vector<int> res;
+        int l = 0, r = nums.size() - 1;
+
+        while (res.size() != nums.size()) {
+            res.push_back(nums[l++]);
+            if (l <= r) {
+                res.push_back(nums[r--]);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    rearrangeArray(nums) {
+        nums.sort((a, b) => a - b);
+        const res = [];
+        let l = 0, r = nums.length - 1;
+
+        while (res.length !== nums.length) {
+            res.push(nums[l++]);
+            if (l <= r) {
+                res.push(nums[r--]);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n\log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Greedy (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def rearrangeArray(self, nums: List[int]) -> List[int]:
+        nums.sort()
+        for i in range(1, len(nums), 2):
+            nums[i], nums[i - 1] = nums[i - 1], nums[i]
+        return nums
+```
+
+```java
+public class Solution {
+    public int[] rearrangeArray(int[] nums) {
+        Arrays.sort(nums);
+        for (int i = 1; i < nums.length; i += 2) {
+            int temp = nums[i];
+            nums[i] = nums[i - 1];
+            nums[i - 1] = temp;
+        }
+        return nums;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> rearrangeArray(vector<int>& nums) {
+        sort(nums.begin(), nums.end());
+        for (int i = 1; i < nums.size(); i += 2) {
+            swap(nums[i], nums[i - 1]);
+        }
+        return nums;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    rearrangeArray(nums) {
+        nums.sort((a, b) => a - b);
+        for (let i = 1; i < nums.length; i += 2) {
+            [nums[i], nums[i - 1]] = [nums[i - 1], nums[i]];
+        }
+        return nums;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 3. Greedy (Optimal) - I
+
+::tabs-start
+
+```python
+class Solution:
+    def rearrangeArray(self, nums: List[int]) -> List[int]:
+        n = len(nums)
+
+        for i in range(1, n - 1):
+            if 2 * nums[i] == (nums[i - 1] + nums[i + 1]):
+                nums[i], nums[i + 1] = nums[i + 1], nums[i]
+        
+        for i in range(n - 2, 0, -1):
+            if 2 * nums[i] == (nums[i - 1] + nums[i + 1]):
+                nums[i], nums[i - 1] = nums[i - 1], nums[i]
+        
+        return nums
+```
+
+```java
+public class Solution {
+    public int[] rearrangeArray(int[] nums) {
+        int n = nums.length;
+
+        for (int i = 1; i < n - 1; i++) {
+            if (2 * nums[i] == (nums[i - 1] + nums[i + 1])) {
+                int temp = nums[i];
+                nums[i] = nums[i + 1];
+                nums[i + 1] = temp;
+            }
+        }
+
+        for (int i = n - 2; i > 0; i--) {
+            if (2 * nums[i] == (nums[i - 1] + nums[i + 1])) {
+                int temp = nums[i];
+                nums[i] = nums[i - 1];
+                nums[i - 1] = temp;
+            }
+        }
+
+        return nums;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> rearrangeArray(vector<int>& nums) {
+        int n = nums.size();
+
+        for (int i = 1; i < n - 1; i++) {
+            if (2 * nums[i] == (nums[i - 1] + nums[i + 1])) {
+                swap(nums[i], nums[i + 1]);
+            }
+        }
+
+        for (int i = n - 2; i > 0; i--) {
+            if (2 * nums[i] == (nums[i - 1] + nums[i + 1])) {
+                swap(nums[i], nums[i - 1]);
+            }
+        }
+
+        return nums;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    rearrangeArray(nums) {
+        const n = nums.length;
+
+        for (let i = 1; i < n - 1; i++) {
+            if (2 * nums[i] === nums[i - 1] + nums[i + 1]) {
+                [nums[i], nums[i + 1]] = [nums[i + 1], nums[i]];
+            }
+        }
+
+        for (let i = n - 2; i > 0; i--) {
+            if (2 * nums[i] === nums[i - 1] + nums[i + 1]) {
+                [nums[i], nums[i - 1]] = [nums[i - 1], nums[i]];
+            }
+        }
+
+        return nums;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 4. Greedy Optimal - II
+
+::tabs-start
+
+```python
+class Solution:
+    def rearrangeArray(self, nums: List[int]) -> List[int]:
+        increase = nums[0] < nums[1]
+        for i in range(1, len(nums) - 1):
+            if ((increase and nums[i] < nums[i + 1]) or
+                (not increase and nums[i] > nums[i + 1])
+            ):
+                nums[i], nums[i + 1] = nums[i + 1], nums[i]
+            increase = not increase
+        return nums
+```
+
+```java
+public class Solution {
+    public int[] rearrangeArray(int[] nums) {
+        boolean increase = nums[0] < nums[1];
+        for (int i = 1; i < nums.length - 1; i++) {
+            if ((increase && nums[i] < nums[i + 1]) ||
+                (!increase && nums[i] > nums[i + 1])) {
+                int temp = nums[i];
+                nums[i] = nums[i + 1];
+                nums[i + 1] = temp;
+            }
+            increase = !increase;
+        }
+        return nums;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> rearrangeArray(vector<int>& nums) {
+        bool increase = nums[0] < nums[1];
+        for (int i = 1; i < nums.size() - 1; i++) {
+            if ((increase && nums[i] < nums[i + 1]) ||
+                (!increase && nums[i] > nums[i + 1])) {
+                swap(nums[i], nums[i + 1]);
+            }
+            increase = !increase;
+        }
+        return nums;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    rearrangeArray(nums) {
+        let increase = nums[0] < nums[1];
+        for (let i = 1; i < nums.length - 1; i++) {
+            if ((increase && nums[i] < nums[i + 1]) ||
+                (!increase && nums[i] > nums[i + 1])) {
+                [nums[i], nums[i + 1]] = [nums[i + 1], nums[i]];
+            }
+            increase = !increase;
+        }
+        return nums;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/as-far-from-land-as-possible.md b/articles/as-far-from-land-as-possible.md
new file mode 100644
index 000000000..15382ba80
--- /dev/null
+++ b/articles/as-far-from-land-as-possible.md
@@ -0,0 +1,757 @@
+## 1. Brute Force (BFS)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxDistance(self, grid: list[list[int]]) -> int:
+        N = len(grid)
+        direct = [[0, 1], [0, -1], [1, 0], [-1, 0]]
+
+        def bfs(row, col):
+            q = deque([(row, col)])
+            visit = [[False] * N for _ in range(N)]
+            dist, visit[row][col] = 0, True
+
+            while q:
+                dist += 1
+                for _ in range(len(q)):
+                    r, c = q.popleft()
+                    for dx, dy in direct:
+                        newR, newC = r + dx, c + dy
+                        if min(newR, newC) < 0 or max(newR, newC) >= N or visit[newR][newC]:
+                            continue
+                        if grid[newR][newC] == 1:
+                            return dist
+                        visit[newR][newC] = True
+                        q.append((newR, newC))
+            return -1
+
+        res = -1
+        for r in range(N):
+            for c in range(N):
+                if grid[r][c] == 0:
+                    res = max(res, bfs(r, c))
+                    if res == -1:
+                        return res
+
+        return res
+```
+
+```java
+public class Solution {
+    private static final int[][] direct = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+
+    public int maxDistance(int[][] grid) {
+        int N = grid.length;
+        int res = -1;
+
+        for (int r = 0; r < N; r++) {
+            for (int c = 0; c < N; c++) {
+                if (grid[r][c] == 0) {
+                    res = Math.max(res, bfs(grid, r, c, N));
+                    if (res == -1) return res;
+                }
+            }
+        }
+        return res;
+    }
+
+    private int bfs(int[][] grid, int row, int col, int N) {
+        Queue<int[]> q = new LinkedList<>();
+        boolean[][] visit = new boolean[N][N];
+        q.offer(new int[]{row, col});
+        visit[row][col] = true;
+        int dist = 0;
+
+        while (!q.isEmpty()) {
+            dist++;
+            for (int i = q.size(); i > 0; i--) {
+                int[] cell = q.poll();
+                int r = cell[0], c = cell[1];
+
+                for (int[] d : direct) {
+                    int newR = r + d[0], newC = c + d[1];
+                    if (newR < 0 || newC < 0 || newR >= N || newC >= N || visit[newR][newC])
+                        continue;
+                    if (grid[newR][newC] == 1)
+                        return dist;
+
+                    visit[newR][newC] = true;
+                    q.offer(new int[]{newR, newC});
+                }
+            }
+        }
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxDistance(vector<vector<int>>& grid) {
+        int N = grid.size();
+        int res = -1;
+
+        for (int r = 0; r < N; r++) {
+            for (int c = 0; c < N; c++) {
+                if (grid[r][c] == 0) {
+                    res = max(res, bfs(grid, r, c, N));
+                    if (res == -1) return res;
+                }
+            }
+        }
+        return res;
+    }
+
+private:
+    const int direct[4][2] = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+
+    int bfs(vector<vector<int>>& grid, int row, int col, int N) {
+        queue<pair<int, int>> q;
+        vector<vector<bool>> visit(N, vector<bool>(N, false));
+        q.push({row, col});
+        visit[row][col] = true;
+        int dist = 0;
+
+        while (!q.empty()) {
+            dist++;
+            for (int i = q.size(); i > 0; i--) {
+                auto [r, c] = q.front();q.pop();
+
+                for (auto& d : direct) {
+                    int newR = r + d[0], newC = c + d[1];
+                    if (newR < 0 || newC < 0 || newR >= N || newC >= N || visit[newR][newC])
+                        continue;
+                    if (grid[newR][newC] == 1)
+                        return dist;
+
+                    visit[newR][newC] = true;
+                    q.push({newR, newC});
+                }
+            }
+        }
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    maxDistance(grid) {
+        const N = grid.length;
+        const direct = [[0, 1], [0, -1], [1, 0], [-1, 0]];
+
+        const bfs = (row, col) => {
+            const q = new Queue([[row, col]]);
+            const visit = Array.from({ length: N }, () => Array(N).fill(false));
+            visit[row][col] = true;
+            let dist = 0;
+
+            while (!q.isEmpty()) {
+                dist++;
+                for (let i = q.size(); i > 0; i--) {
+                    const [r, c] = q.pop();
+                    for (let d = 0; d < 4; d++) {
+                        let newR = r + direct[d][0], newC = c + direct[d][1];
+                        if (newR < 0 || newC < 0 || newR >= N || newC >= N || visit[newR][newC]) 
+                            continue;
+                        if (grid[newR][newC] === 1) 
+                            return dist;
+
+                        visit[newR][newC] = true;
+                        q.push([newR, newC]);
+                    }
+                }
+            }
+            return -1;
+        };
+
+        let res = -1;
+        for (let r = 0; r < N; r++) {
+            for (let c = 0; c < N; c++) {
+                if (grid[r][c] === 0) {
+                    res = Math.max(res, bfs(r, c));
+                    if (res === -1) return res;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 4)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 2. Multi Source BFS (Overwriting Input)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxDistance(self, grid: List[List[int]]) -> int:
+        N = len(grid)
+        q = deque()
+        
+        for r in range(N):
+            for c in range(N):
+                if grid[r][c]:
+                    q.append([r, c])
+
+        res = -1
+        direct = [[0, 1], [1, 0], [0, -1], [-1, 0]]
+
+        while q:
+            r, c = q.popleft()
+            res = grid[r][c]
+            
+            for dr, dc in direct:
+                newR, newC = r + dr, c + dc
+                if min(newR, newC) >= 0 and max(newR, newC) < N and grid[newR][newC] == 0:
+                    q.append([newR, newC])
+                    grid[newR][newC] = grid[r][c] + 1
+
+        return res - 1 if res > 1 else -1
+```
+
+```java
+public class Solution {
+    private static final int[][] direct = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+
+    public int maxDistance(int[][] grid) {
+        int N = grid.length;
+        Queue<int[]> q = new LinkedList<>();
+        for (int r = 0; r < N; r++) {
+            for (int c = 0; c < N; c++) {
+                if (grid[r][c] == 1) {
+                    q.offer(new int[]{r, c});
+                }
+            }
+        }
+
+        int res = -1;
+        while (!q.isEmpty()) {
+            int[] cell = q.poll();
+            int r = cell[0], c = cell[1];
+            res = grid[r][c];
+            for (int d = 0; d < 4; d++) {
+                int newR = r + direct[d][0], newC = c + direct[d][1];
+                if (newR >= 0 && newC >= 0 && newR < N && newC < N && grid[newR][newC] == 0) {
+                    q.offer(new int[]{newR, newC});
+                    grid[newR][newC] = grid[r][c] + 1;
+                }
+            }
+        }
+        return res > 1 ? res - 1 : -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+    const int direct[4][2] = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+
+public:
+    int maxDistance(vector<vector<int>>& grid) {
+        int N = grid.size();
+        queue<pair<int, int>> q;
+        for (int r = 0; r < N; r++) {
+            for (int c = 0; c < N; c++) {
+                if (grid[r][c] == 1) {
+                    q.push({r, c});
+                }
+            }
+        }
+
+        int res = -1;
+        while (!q.empty()) {
+            auto [r, c] = q.front();q.pop();
+            res = grid[r][c];
+            for (int d = 0; d < 4; d++) {
+                int newR = r + direct[d][0], newC = c + direct[d][1];
+                if (newR >= 0 && newC >= 0 && newR < N && newC < N && grid[newR][newC] == 0) {
+                    q.push({newR, newC});
+                    grid[newR][newC] = grid[r][c] + 1;
+                }
+            }
+        }
+        return res > 1 ? res - 1 : -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    maxDistance(grid) {
+        const N = grid.length;
+        const q = new Queue();
+        for (let r = 0; r < N; r++) {
+            for (let c = 0; c < N; c++) {
+                if (grid[r][c] === 1) {
+                    q.push([r, c]);
+                }
+            }
+        }
+
+        let res = -1;
+        const direct = [[0, 1], [0, -1], [1, 0], [-1, 0]];
+        while (!q.isEmpty()) {
+            const [r, c] = q.pop();
+            res = grid[r][c];
+            for (let d = 0; d < 4; d++) {
+                let newR = r + direct[d][0], newC = c + direct[d][1];
+                if (newR >= 0 && newC >= 0 && newR < N && newC < N && grid[newR][newC] === 0) {
+                    q.push([newR, newC]);
+                    grid[newR][newC] = grid[r][c] + 1;
+                }
+            }
+        }
+        return res > 1 ? res - 1 : -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 3. Multi Source BFS
+
+::tabs-start
+
+```python
+class Solution:
+    def maxDistance(self, grid: List[List[int]]) -> int:
+        N = len(grid)
+        direct = [0, 1, 0, -1, 0]
+        visit = [[False] * N for _ in range(N)]
+        q = deque()
+
+        for r in range(N):
+            for c in range(N):
+                if grid[r][c] == 1:
+                    visit[r][c] = True
+                    q.append((r, c))
+
+        res = 0
+        while q:
+            res += 1
+            for _ in range(len(q)):
+                r, c = q.popleft()
+                for d in range(4):
+                    newR, newC = r + direct[d], c + direct[d + 1]
+                    if 0 <= newR < N and 0 <= newC < N and not visit[newR][newC]:
+                        q.append((newR, newC))
+                        visit[newR][newC] = True
+
+        return res - 1 if res > 1 else -1
+```
+
+```java
+public class Solution {
+    public int maxDistance(int[][] grid) {
+        int N = grid.length;
+        int[] direct = {0, 1, 0, -1, 0};
+        boolean[][] visit = new boolean[N][N];
+        Queue<int[]> q = new LinkedList<>();
+        for (int r = 0; r < N; r++) {
+            for (int c = 0; c < N; c++) {
+                if (grid[r][c] == 1) {
+                    visit[r][c] = true;
+                    q.offer(new int[]{r, c});
+                }
+            }
+        }
+
+        int res = 0;
+        while (!q.isEmpty()) {
+            res++;
+            for (int i = q.size(); i > 0; i--) {
+                int[] cur = q.poll();
+                int r = cur[0], c = cur[1];
+                for (int d = 0; d < 4; d++) {
+                    int newR = r + direct[d], newC = c + direct[d + 1];
+                    if (newR >= 0 && newC >= 0 && newR < N && newC < N && !visit[newR][newC]) {
+                        q.offer(new int[]{newR, newC});
+                        visit[newR][newC] = true;
+                    }
+                }
+            }
+        }
+        return res > 1 ? res - 1 : -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxDistance(vector<vector<int>>& grid) {
+        int N = grid.size();
+        vector<int> direct = {0, 1, 0, -1, 0};
+        vector<vector<bool>> visit(N, vector<bool>(N, false));
+        queue<pair<int, int>> q;
+        for (int r = 0; r < N; r++) {
+            for (int c = 0; c < N; c++) {
+                if (grid[r][c] == 1) {
+                    visit[r][c] = true;
+                    q.push({r, c});
+                }
+            }
+        }
+
+        int res = 0;
+        while (!q.empty()) {
+            res++;
+            for (int i = q.size(); i > 0; i--) {
+                auto [r, c] = q.front();q.pop();
+                for (int d = 0; d < 4; d++) {
+                    int newR = r + direct[d], newC = c + direct[d + 1];
+                    if (newR >= 0 && newC >= 0 && newR < N && newC < N && !visit[newR][newC]) {
+                        q.push({newR, newC});
+                        visit[newR][newC] = true;
+                    }
+                }
+            }
+        }
+        return res > 1 ? res - 1 : -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    maxDistance(grid) {
+        const N = grid.length;
+        const direct = [0, 1, 0, -1, 0];
+        const visit = Array.from({ length: N }, () => Array(N).fill(false));
+        const q = new Queue();
+        for (let r = 0; r < N; r++) {
+            for (let c = 0; c < N; c++) {
+                if (grid[r][c] === 1) {
+                    visit[r][c] = true;
+                    q.push([r, c]);
+                }
+            }
+        }
+
+        let res = 0;
+        while (!q.isEmpty()) {
+            res++;
+            for (let i = q.size(); i > 0; i--) {
+                const [r, c] = q.pop();
+                for (let d = 0; d < 4; d++) {
+                    let newR = r + direct[d], newC = c + direct[d + 1];
+                    if (newR >= 0 && newC >= 0 && newR < N && newC < N && !visit[newR][newC]) {
+                        q.push([newR, newC]);
+                        visit[newR][newC] = true;
+                    }
+                }
+            }
+        }
+        return res > 1 ? res - 1 : -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 4. Dynamic Programming (Overwrting the Input)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxDistance(self, grid: List[List[int]]) -> int:
+        N, INF = len(grid), 10**6
+
+        for r in range(N):
+            for c in range(N):
+                if grid[r][c] == 1:
+                    continue
+                grid[r][c] = INF
+                if r > 0:
+                    grid[r][c] = min(grid[r][c], grid[r - 1][c] + 1)
+                if c > 0:
+                    grid[r][c] = min(grid[r][c], grid[r][c - 1] + 1)
+
+        res = 0
+        for r in range(N - 1, -1, -1):
+            for c in range(N - 1, -1, -1):
+                if grid[r][c] == 1:
+                    continue
+                if r < N - 1:
+                    grid[r][c] = min(grid[r][c], grid[r + 1][c] + 1)
+                if c < N - 1:
+                    grid[r][c] = min(grid[r][c], grid[r][c + 1] + 1)
+                res = max(res, grid[r][c])
+
+        return res - 1 if res < INF else -1
+```
+
+```java
+public class Solution {
+    public int maxDistance(int[][] grid) {
+        int N = grid.length, INF = 1000000;
+
+        for (int r = 0; r < N; r++) {
+            for (int c = 0; c < N; c++) {
+                if (grid[r][c] == 1) continue;
+                grid[r][c] = INF;
+                if (r > 0) grid[r][c] = Math.min(grid[r][c], grid[r - 1][c] + 1);
+                if (c > 0) grid[r][c] = Math.min(grid[r][c], grid[r][c - 1] + 1);
+            }
+        }
+
+        int res = 0;
+        for (int r = N - 1; r >= 0; r--) {
+            for (int c = N - 1; c >= 0; c--) {
+                if (grid[r][c] == 1) continue;
+                if (r < N - 1) grid[r][c] = Math.min(grid[r][c], grid[r + 1][c] + 1);
+                if (c < N - 1) grid[r][c] = Math.min(grid[r][c], grid[r][c + 1] + 1);
+                res = Math.max(res, grid[r][c]);
+            }
+        }
+
+        return res < INF ? res - 1 : -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxDistance(vector<vector<int>>& grid) {
+        int N = grid.size(), INF = 1000000;
+
+        for (int r = 0; r < N; r++) {
+            for (int c = 0; c < N; c++) {
+                if (grid[r][c] == 1) continue;
+                grid[r][c] = INF;
+                if (r > 0) grid[r][c] = min(grid[r][c], grid[r - 1][c] + 1);
+                if (c > 0) grid[r][c] = min(grid[r][c], grid[r][c - 1] + 1);
+            }
+        }
+
+        int res = 0;
+        for (int r = N - 1; r >= 0; r--) {
+            for (int c = N - 1; c >= 0; c--) {
+                if (grid[r][c] == 1) continue;
+                if (r < N - 1) grid[r][c] = min(grid[r][c], grid[r + 1][c] + 1);
+                if (c < N - 1) grid[r][c] = min(grid[r][c], grid[r][c + 1] + 1);
+                res = max(res, grid[r][c]);
+            }
+        }
+
+        return res < INF ? res - 1 : -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    maxDistance(grid) {
+        const N = grid.length, INF = 1000000;
+
+        for (let r = 0; r < N; r++) {
+            for (let c = 0; c < N; c++) {
+                if (grid[r][c] === 1) continue;
+                grid[r][c] = INF;
+                if (r > 0) grid[r][c] = Math.min(grid[r][c], grid[r - 1][c] + 1);
+                if (c > 0) grid[r][c] = Math.min(grid[r][c], grid[r][c - 1] + 1);
+            }
+        }
+
+        let res = 0;
+        for (let r = N - 1; r >= 0; r--) {
+            for (let c = N - 1; c >= 0; c--) {
+                if (grid[r][c] === 1) continue;
+                if (r < N - 1) grid[r][c] = Math.min(grid[r][c], grid[r + 1][c] + 1);
+                if (c < N - 1) grid[r][c] = Math.min(grid[r][c], grid[r][c + 1] + 1);
+                res = Math.max(res, grid[r][c]);
+            }
+        }
+
+        return res < INF ? res - 1 : -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 5. Dynamic Programming
+
+::tabs-start
+
+```python
+class Solution:
+    def maxDistance(self, grid: List[List[int]]) -> int:
+        N = len(grid)
+        res, INF = -1, 10**6
+        dp = [[INF] * (N + 2) for _ in range(N + 2)]
+
+        for r in range(1, N + 1):
+            for c in range(1, N + 1):
+                if grid[r - 1][c - 1] == 1:
+                    dp[r][c] = 0
+                else:
+                    dp[r][c] = min(dp[r - 1][c], dp[r][c - 1]) + 1
+
+        for r in range(N, 0, -1):
+            for c in range(N, 0, -1):
+                if grid[r - 1][c - 1] == 0:
+                    dp[r][c] = min(dp[r][c], min(dp[r + 1][c], dp[r][c + 1]) + 1)
+                    res = max(res, dp[r][c])
+
+        return res if res < INF else -1
+```
+
+```java
+public class Solution {
+    public int maxDistance(int[][] grid) {
+        int N = grid.length;
+        int INF = 1000000;
+        int[][] dp = new int[N + 2][N + 2];
+        for (int[] row : dp) {
+            Arrays.fill(row, INF);
+        }
+
+        for (int r = 1; r <= N; r++) {
+            for (int c = 1; c <= N; c++) {
+                if (grid[r - 1][c - 1] == 1) {
+                    dp[r][c] = 0;
+                } else {
+                    dp[r][c] = Math.min(dp[r - 1][c], dp[r][c - 1]) + 1;
+                }
+            }
+        }
+
+        int res = -1;
+        for (int r = N; r > 0; r--) {
+            for (int c = N; c > 0; c--) {
+                if (grid[r - 1][c - 1] == 0) {
+                    dp[r][c] = Math.min(dp[r][c], Math.min(dp[r + 1][c], dp[r][c + 1]) + 1);
+                    res = Math.max(res, dp[r][c]);
+                }
+            }
+        }
+        return res < INF ? res : -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxDistance(vector<vector<int>>& grid) {
+        int N = grid.size();
+        int INF = 1000000, res = -1;
+        vector<vector<int>> dp(N + 2, vector<int>(N + 2, INF));
+
+        for (int r = 1; r <= N; r++) {
+            for (int c = 1; c <= N; c++) {
+                if (grid[r - 1][c - 1] == 1) {
+                    dp[r][c] = 0;
+                } else {
+                    dp[r][c] = min(dp[r - 1][c], dp[r][c - 1]) + 1;
+                }
+            }
+        }
+
+        for (int r = N; r > 0; r--) {
+            for (int c = N; c > 0; c--) {
+                if (grid[r - 1][c - 1] == 0) {
+                    dp[r][c] = min(dp[r][c], min(dp[r + 1][c], dp[r][c + 1]) + 1);
+                    res = max(res, dp[r][c]);
+                }
+            }
+        }
+        return res < INF ? res : -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    maxDistance(grid) {
+        const N = grid.length;
+        const INF = 1000000;
+        let res = -1;
+        let dp = Array.from({ length: N + 2 }, () => Array(N + 2).fill(INF));
+
+        for (let r = 1; r <= N; r++) {
+            for (let c = 1; c <= N; c++) {
+                if (grid[r - 1][c - 1] === 1) {
+                    dp[r][c] = 0;
+                } else {
+                    dp[r][c] = Math.min(dp[r - 1][c], dp[r][c - 1]) + 1;
+                }
+            }
+        }
+
+        for (let r = N; r > 0; r--) {
+            for (let c = N; c > 0; c--) {
+                if (grid[r - 1][c - 1] === 0) {
+                    dp[r][c] = Math.min(dp[r][c], Math.min(dp[r + 1][c], dp[r][c + 1]) + 1);
+                    res = Math.max(res, dp[r][c]);
+                }
+            }
+        }
+        return res < INF ? res : -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
\ No newline at end of file
diff --git a/articles/assign-cookies.md b/articles/assign-cookies.md
new file mode 100644
index 000000000..b591a8ef9
--- /dev/null
+++ b/articles/assign-cookies.md
@@ -0,0 +1,300 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def findContentChildren(self, g: List[int], s: List[int]) -> int:
+        s.sort()
+        res = 0
+
+        for i in g:
+            minIdx = -1
+            for j in range(len(s)):
+                if s[j] < i:
+                    continue
+                
+                if minIdx == -1 or s[minIdx] > s[j]:
+                    minIdx = j
+            
+            if minIdx != -1:
+                s[minIdx] = -1
+                res += 1
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int findContentChildren(int[] g, int[] s) {
+        Arrays.sort(s);
+        int res = 0;
+
+        for (int i : g) {
+            int minIdx = -1;
+            for (int j = 0; j < s.length; j++) {
+                if (s[j] < i) continue;
+
+                if (minIdx == -1 || s[minIdx] > s[j]) {
+                    minIdx = j;
+                }
+            }
+
+            if (minIdx != -1) {
+                s[minIdx] = -1;
+                res++;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findContentChildren(vector<int>& g, vector<int>& s) {
+        sort(s.begin(), s.end());
+        int res = 0;
+
+        for (int i : g) {
+            int minIdx = -1;
+            for (int j = 0; j < s.size(); j++) {
+                if (s[j] < i) continue;
+
+                if (minIdx == -1 || s[minIdx] > s[j]) {
+                    minIdx = j;
+                }
+            }
+
+            if (minIdx != -1) {
+                s[minIdx] = -1;
+                res++;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} g
+     * @param {number[]} s
+     * @return {number}
+     */
+    findContentChildren(g, s) {
+        s.sort((a, b) => a - b);
+        let res = 0;
+
+        for (let i of g) {
+            let minIdx = -1;
+            for (let j = 0; j < s.length; j++) {
+                if (s[j] < i) continue;
+
+                if (minIdx === -1 || s[minIdx] > s[j]) {
+                    minIdx = j;
+                }
+            }
+
+            if (minIdx !== -1) {
+                s[minIdx] = -1;
+                res++;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m + m \log m)$
+* Space complexity: $O(1)$ or $O(m)$ depending on the sorting algorithm.
+
+> Where $n$ is the size of the array $g$ and $m$ is the size of the array $s$.
+
+---
+
+## 2. Two Pointers - I
+
+::tabs-start
+
+```python
+class Solution:
+    def findContentChildren(self, g: List[int], s: List[int]) -> int:
+        g.sort()
+        s.sort()
+        
+        i = j = 0
+        while i < len(g):
+            while j < len(s) and g[i] > s[j]:
+                j += 1
+            if j == len(s):
+                break
+            i += 1
+            j += 1
+        return i
+```
+
+```java
+public class Solution {
+    public int findContentChildren(int[] g, int[] s) {
+        Arrays.sort(g);
+        Arrays.sort(s);
+
+        int i = 0, j = 0;
+        while (i < g.length) {
+            while (j < s.length && g[i] > s[j]) {
+                j++;
+            }
+            if (j == s.length) break;
+            i++;
+            j++;
+        }
+        return i;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findContentChildren(vector<int>& g, vector<int>& s) {
+        sort(g.begin(), g.end());
+        sort(s.begin(), s.end());
+
+        int i = 0, j = 0;
+        while (i < g.size()) {
+            while (j < s.size() && g[i] > s[j]) {
+                j++;
+            }
+            if (j == s.size()) break;
+            i++;
+            j++;
+        }
+        return i;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} g
+     * @param {number[]} s
+     * @return {number}
+     */
+    findContentChildren(g, s) {
+        g.sort((a, b) => a - b);
+        s.sort((a, b) => a - b);
+
+        let i = 0, j = 0;
+        while (i < g.length) {
+            while (j < s.length && g[i] > s[j]) {
+                j++;
+            }
+            if (j === s.length) break;
+            i++;
+            j++;
+        }
+        return i;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n + m \log m)$
+* Space complexity: $O(1)$ or $O(n + m)$ depending on the sorting algorithm.
+
+> Where $n$ is the size of the array $g$ and $m$ is the size of the array $s$.
+
+---
+
+## 3. Two Pointers - II
+
+::tabs-start
+
+```python
+class Solution:
+    def findContentChildren(self, g: List[int], s: List[int]) -> int:
+        g.sort()
+        s.sort()
+        
+        i = j = 0
+        while i < len(g) and j < len(s):
+            if g[i] <= s[j]:
+                i += 1
+            j += 1
+        
+        return i
+```
+
+```java
+public class Solution {
+    public int findContentChildren(int[] g, int[] s) {
+        Arrays.sort(g);
+        Arrays.sort(s);
+
+        int i = 0;
+        for (int j = 0; i < g.length && j < s.length; j++) {
+            if (g[i] <= s[j]) i++;
+        }
+        return i;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findContentChildren(vector<int>& g, vector<int>& s) {
+        sort(g.begin(), g.end());
+        sort(s.begin(), s.end());
+
+        int i = 0;
+        for (int j = 0; i < g.size() && j < s.size(); j++) {
+            if (g[i] <= s[j]) i++;
+        }
+        return i;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} g
+     * @param {number[]} s
+     * @return {number}
+     */
+    findContentChildren(g, s) {
+        g.sort((a, b) => a - b);
+        s.sort((a, b) => a - b);
+
+        let i = 0;
+        for (let j = 0; i < g.length && j < s.length; j++) {
+            if (g[i] <= s[j]) i++;
+        }
+        return i;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n + m \log m)$
+* Space complexity: $O(1)$ or $O(n + m)$ depending on the sorting algorithm.
+
+> Where $n$ is the size of the array $g$ and $m$ is the size of the array $s$.
\ No newline at end of file
diff --git a/articles/asteroid-collision.md b/articles/asteroid-collision.md
new file mode 100644
index 000000000..94a5993d3
--- /dev/null
+++ b/articles/asteroid-collision.md
@@ -0,0 +1,302 @@
+## 1. Stack
+
+::tabs-start
+
+```python
+class Solution:
+    def asteroidCollision(self, asteroids: List[int]) -> List[int]:
+        stack = []
+        for a in asteroids:
+            while stack and a < 0 and stack[-1] > 0:
+                diff = a + stack[-1]
+                if diff < 0:
+                    stack.pop()
+                elif diff > 0:
+                    a = 0
+                else:
+                    a = 0
+                    stack.pop()
+            if a:
+                stack.append(a)
+        return stack
+```
+
+```java
+public class Solution {
+    public int[] asteroidCollision(int[] asteroids) {
+        Stack<Integer> stack = new Stack<>();
+        for (int a : asteroids) {
+            while (!stack.isEmpty() && a < 0 && stack.peek() > 0) {
+                int diff = a + stack.peek();
+                if (diff < 0) {
+                    stack.pop();
+                } else if (diff > 0) {
+                    a = 0;
+                } else {
+                    a = 0;
+                    stack.pop();
+                }
+            }
+            if (a != 0) {
+                stack.add(a);
+            }
+        }
+        return stack.stream().mapToInt(i -> i).toArray();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> asteroidCollision(vector<int>& asteroids) {
+        vector<int> stack;
+        for (int& a : asteroids) {
+            while (!stack.empty() && a < 0 && stack.back() > 0) {
+                int diff = a + stack.back();
+                if (diff < 0) {
+                    stack.pop_back();
+                } else if (diff > 0) {
+                    a = 0;
+                } else {
+                    a = 0;
+                    stack.pop_back();
+                }
+            }
+            if (a != 0) {
+                stack.push_back(a);
+            }
+        }
+        return stack;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} asteroids
+     * @return {number[]}
+     */
+    asteroidCollision(asteroids) {
+        const stack = [];
+        for (let a of asteroids) {
+            while (stack.length && a < 0 && stack[stack.length - 1] > 0) {
+                const diff = a + stack[stack.length - 1];
+                if (diff < 0) {
+                    stack.pop();
+                } else if (diff > 0) {
+                    a = 0;
+                } else {
+                    a = 0;
+                    stack.pop();
+                }
+            }
+            if (a !== 0) {
+                stack.push(a);
+            }
+        }
+        return stack;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[] AsteroidCollision(int[] asteroids) {
+        Stack<int> stack = new Stack<int>();
+
+        foreach (int a in asteroids) {
+            int current = a;
+            while (stack.Count > 0 && current < 0 && stack.Peek() > 0) {
+                int diff = current + stack.Peek();
+                if (diff < 0) {
+                    stack.Pop();
+                } else if (diff > 0) {
+                    current = 0;
+                } else {
+                    current = 0;
+                    stack.Pop();
+                }
+            }
+            if (current != 0) {
+                stack.Push(current);
+            }
+        }
+
+        int[] result = stack.Reverse().ToArray();
+        return result;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Without Stack
+
+::tabs-start
+
+```python
+class Solution:
+    def asteroidCollision(self, asteroids: List[int]) -> List[int]:
+        n = len(asteroids)
+        j = -1
+
+        for a in asteroids:
+            while j >= 0 and asteroids[j] > 0 and a < 0:
+                if asteroids[j] > abs(a):
+                    a = 0
+                    break
+                elif asteroids[j] == abs(a):
+                    j -= 1
+                    a = 0
+                    break
+                else:
+                    j -= 1
+            if a:
+                j += 1
+                asteroids[j] = a
+
+        return asteroids[:j + 1]
+```
+
+```java
+public class Solution {
+    public int[] asteroidCollision(int[] asteroids) {
+        int n = asteroids.length;
+        int j = -1;
+
+        for (int a : asteroids) {
+            while (j >= 0 && asteroids[j] > 0 && a < 0) {
+                if (asteroids[j] > Math.abs(a)) {
+                    a = 0;
+                    break;
+                } else if (asteroids[j] == Math.abs(a)) {
+                    j--;
+                    a = 0;
+                    break;
+                } else {
+                    j--;
+                }
+            }
+            if (a != 0) {
+                asteroids[++j] = a;
+            }
+        }
+
+        return Arrays.copyOfRange(asteroids, 0, j + 1);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> asteroidCollision(vector<int>& asteroids) {
+        int n = asteroids.size();
+        int j = -1;
+
+        for (int& a : asteroids) {
+            while (j >= 0 && asteroids[j] > 0 && a < 0) {
+                if (asteroids[j] > abs(a)) {
+                    a = 0;
+                    break;
+                } else if (asteroids[j] == abs(a)) {
+                    j--;
+                    a = 0;
+                    break;
+                } else {
+                    j--;
+                }
+            }
+            if (a != 0) {
+                asteroids[++j] = a;
+            }
+        }
+
+        asteroids.resize(j + 1);
+        return asteroids;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} asteroids
+     * @return {number[]}
+     */
+    asteroidCollision(asteroids) {
+        let n = asteroids.length;
+        let j = -1;
+
+        for (let a of asteroids) {
+            while (j >= 0 && asteroids[j] > 0 && a < 0) {
+                if (asteroids[j] > Math.abs(a)) {
+                    a = 0;
+                    break;
+                } else if (asteroids[j] === Math.abs(a)) {
+                    j--;
+                    a = 0;
+                    break;
+                } else {
+                    j--;
+                }
+            }
+            if (a !== 0) {
+                asteroids[++j] = a;
+            }
+        }
+
+        return asteroids.slice(0, j + 1);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[] AsteroidCollision(int[] asteroids) {
+        int n = asteroids.Length;
+        int j = -1;
+
+        foreach (int a in asteroids) {
+            int current = a;
+
+            while (j >= 0 && asteroids[j] > 0 && current < 0) {
+                if (asteroids[j] > Math.Abs(current)) {
+                    current = 0;
+                    break;
+                } else if (asteroids[j] == Math.Abs(current)) {
+                    j--;
+                    current = 0;
+                    break;
+                } else {
+                    j--;
+                }
+            }
+
+            if (current != 0) {
+                asteroids[++j] = current;
+            }
+        }
+
+        int[] result = new int[j + 1];
+        Array.Copy(asteroids, 0, result, 0, j + 1);
+        return result;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for the output array.
\ No newline at end of file
diff --git a/articles/average-waiting-time.md b/articles/average-waiting-time.md
new file mode 100644
index 000000000..0d6c7c818
--- /dev/null
+++ b/articles/average-waiting-time.md
@@ -0,0 +1,169 @@
+## 1. Simulation - I
+
+::tabs-start
+
+```python
+class Solution:
+    def averageWaitingTime(self, customers: List[List[int]]) -> float:
+        t = 0
+        total = 0
+
+        for arrival, order in customers:
+            if t > arrival:
+                total += t - arrival
+            else:
+                t = arrival
+            total += order
+            t += order
+
+        return total / len(customers)
+```
+
+```java
+public class Solution {
+    public double averageWaitingTime(int[][] customers) {
+        long t = 0, total = 0;
+
+        for (int[] c : customers) {
+            int arrival = c[0], order = c[1];
+            if (t > arrival) {
+                total += t - arrival;
+            } else {
+                t = arrival;
+            }
+            total += order;
+            t += order;
+        }
+
+        return (double) total / customers.length;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    double averageWaitingTime(vector<vector<int>>& customers) {
+        long long t = 0, total = 0;
+
+        for (auto& c : customers) {
+            int arrival = c[0], order = c[1];
+            if (t > arrival) {
+                total += t - arrival;
+            } else {
+                t = arrival;
+            }
+            total += order;
+            t += order;
+        }
+
+        return (double) total / customers.size();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} customers
+     * @return {number}
+     */
+    averageWaitingTime(customers) {
+        let t = 0, total = 0;
+
+        for (let [arrival, order] of customers) {
+            if (t > arrival) {
+                total += t - arrival;
+            } else {
+                t = arrival;
+            }
+            total += order;
+            t += order;
+        }
+
+        return total / customers.length;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Simulation - II
+
+::tabs-start
+
+```python
+class Solution:
+    def averageWaitingTime(self, customers: List[List[int]]) -> float:
+        t = total = 0
+        for arrival, order in customers:
+            t = max(t, arrival) + order
+            total += t - arrival
+        return total / len(customers)
+```
+
+```java
+public class Solution {
+    public double averageWaitingTime(int[][] customers) {
+        long t = 0, total = 0;
+
+        for (int[] c : customers) {
+            int arrival = c[0], order = c[1];
+            t = Math.max(t, arrival) + order;
+            total += t - arrival;
+        }
+
+        return (double) total / customers.length;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    double averageWaitingTime(vector<vector<int>>& customers) {
+        long long t = 0, total = 0;
+
+        for (auto& c : customers) {
+            int arrival = c[0], order = c[1];
+            t = max(t, (long long)arrival) + order;
+            total += t - arrival;
+        }
+
+        return (double) total / customers.size();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} customers
+     * @return {number}
+     */
+    averageWaitingTime(customers) {
+        let t = 0, total = 0;
+
+        for (let [arrival, order] of customers) {
+            t = Math.max(t, arrival) + order;
+            total += t - arrival;
+        }
+
+        return total / customers.length;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/backspace-string-compare.md b/articles/backspace-string-compare.md
new file mode 100644
index 000000000..6064e5bd6
--- /dev/null
+++ b/articles/backspace-string-compare.md
@@ -0,0 +1,506 @@
+## 1. Stack
+
+::tabs-start
+
+```python
+class Solution:
+    def backspaceCompare(self, s: str, t: str) -> bool:
+        def convert(s):
+            res = []
+            for char in s:
+                if char == '#':
+                    if res:
+                        res.pop()
+                else:
+                    res.append(char)
+            return "".join(res)
+
+        return convert(s) == convert(t)
+```
+
+```java
+public class Solution {
+    public boolean backspaceCompare(String s, String t) {
+        return convert(s).equals(convert(t));
+    }
+
+    private List<Character> convert(String s) {
+        List<Character> res = new ArrayList<>();
+        for (char c : s.toCharArray()) {
+            if (c == '#') {
+                if (!res.isEmpty()) {
+                    res.remove(res.size() - 1);
+                }
+            } else {
+                res.add(c);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool backspaceCompare(string s, string t) {
+        return convert(s) == convert(t);
+    }
+
+private:
+    string convert(const string& s) {
+        string res = "";
+        for (char c : s) {
+            if (c == '#') {
+                if (!res.empty()) {
+                    res.pop_back();
+                }
+            } else {
+                res += c;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string} t
+     * @return {boolean}
+     */
+    backspaceCompare(s, t) {
+        const convert = (str) => {
+            const res = [];
+            for (const char of str) {
+                if (char === '#') {
+                    if (res.length > 0) {
+                        res.pop();
+                    }
+                } else {
+                    res.push(char);
+                }
+            }
+            return res.join('');
+        };
+        return convert(s) === convert(t);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(n + m)$
+
+> Where $n$ is the length of the string $s$ and $m$ is the length of the string $t$.
+
+---
+
+## 2. Reverse iteration
+
+::tabs-start
+
+```python
+class Solution:
+    def backspaceCompare(self, s: str, t: str) -> bool:
+        def convert(s):
+            res = []
+            backspace = 0
+            for i in range(len(s) - 1, -1, -1):
+                if s[i] == '#':
+                    backspace += 1
+                elif backspace:
+                    backspace -= 1
+                else:
+                    res.append(s[i])
+            return res
+
+        return convert(s) == convert(t)
+```
+
+```java
+public class Solution {
+    public boolean backspaceCompare(String s, String t) {
+        return convert(s).equals(convert(t));
+    }
+
+    private List<Character> convert(String s) {
+        List<Character> res = new ArrayList<>();
+        int backspace = 0;
+        for (int i = s.length() - 1; i >= 0; i--) {
+            if (s.charAt(i) == '#') {
+                backspace++;
+            } else if (backspace > 0) {
+                backspace--;
+            } else {
+                res.add(s.charAt(i));
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool backspaceCompare(string s, string t) {
+        return convert(s) == convert(t);
+    }
+
+private:
+    string convert(string s) {
+        string res;
+        int backspace = 0;
+        for (int i = s.size() - 1; i >= 0; i--) {
+            if (s[i] == '#') {
+                backspace++;
+            } else if (backspace > 0) {
+                backspace--;
+            } else {
+                res += s[i];
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string} t
+     * @return {boolean}
+     */
+    backspaceCompare(s, t) {
+        const convert = (s) => {
+           const res = [];
+            let backspace = 0;
+            for (let i = s.length - 1; i >= 0; i--) {
+                if (s[i] === '#') {
+                    backspace++;
+                } else if (backspace > 0) {
+                    backspace--;
+                } else {
+                    res.push(s[i]);
+                }
+            }
+            return res.join('');
+        };
+        return convert(s) === convert(t);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(n + m)$
+
+> Where $n$ is the length of the string $s$ and $m$ is the length of the string $t$.
+
+---
+
+## 3. Two Pointers - I
+
+::tabs-start
+
+```python
+class Solution:
+    def backspaceCompare(self, s: str, t: str) -> bool:
+        def nextValidChar(string, index):
+            backspace = 0
+            while index >= 0:
+                if string[index] == '#':
+                    backspace += 1
+                elif backspace > 0:
+                    backspace -= 1
+                else:
+                    break
+                index -= 1
+            return index
+
+        index_s, index_t = len(s) - 1, len(t) - 1
+
+        while index_s >= 0 or index_t >= 0:
+            index_s = nextValidChar(s, index_s)
+            index_t = nextValidChar(t, index_t)
+
+            char_s = s[index_s] if index_s >= 0 else ""
+            char_t = t[index_t] if index_t >= 0 else ""
+
+            if char_s != char_t:
+                return False
+
+            index_s -= 1
+            index_t -= 1
+
+        return True
+```
+
+```java
+public class Solution {
+    public boolean backspaceCompare(String s, String t) {
+        int indexS = s.length() - 1, indexT = t.length() - 1;
+
+        while (indexS >= 0 || indexT >= 0) {
+            indexS = nextValidChar(s, indexS);
+            indexT = nextValidChar(t, indexT);
+
+            char charS = indexS >= 0 ? s.charAt(indexS) : '\0';
+            char charT = indexT >= 0 ? t.charAt(indexT) : '\0';
+
+            if (charS != charT) return false;
+
+            indexS--;
+            indexT--;
+        }
+
+        return true;
+    }
+
+    private int nextValidChar(String str, int index) {
+        int backspace = 0;
+
+        while (index >= 0) {
+            if (str.charAt(index) == '#') {
+                backspace++;
+            } else if (backspace > 0) {
+                backspace--;
+            } else {
+                break;
+            }
+            index--;
+        }
+
+        return index;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool backspaceCompare(string s, string t) {
+        int indexS = s.size() - 1, indexT = t.size() - 1;
+
+        while (indexS >= 0 || indexT >= 0) {
+            indexS = nextValidChar(s, indexS);
+            indexT = nextValidChar(t, indexT);
+
+            char charS = indexS >= 0 ? s[indexS] : '\0';
+            char charT = indexT >= 0 ? t[indexT] : '\0';
+
+            if (charS != charT) return false;
+
+            indexS--;
+            indexT--;
+        }
+
+        return true;
+    }
+
+private:
+    int nextValidChar(string &str, int index) {
+        int backspace = 0;
+
+        while (index >= 0) {
+            if (str[index] == '#') {
+                backspace++;
+            } else if (backspace > 0) {
+                backspace--;
+            } else {
+                break;
+            }
+            index--;
+        }
+
+        return index;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string} t
+     * @return {boolean}
+     */
+    backspaceCompare(s, t) {
+        const nextValidChar = (str, index) => {
+            let backspace = 0;
+
+            while (index >= 0) {
+                if (str[index] === '#') {
+                    backspace++;
+                } else if (backspace > 0) {
+                    backspace--;
+                } else {
+                    break;
+                }
+                index--;
+            }
+
+            return index;
+        };
+
+        let indexS = s.length - 1, indexT = t.length - 1;
+
+        while (indexS >= 0 || indexT >= 0) {
+            indexS = nextValidChar(s, indexS);
+            indexT = nextValidChar(t, indexT);
+
+            const charS = indexS >= 0 ? s[indexS] : '';
+            const charT = indexT >= 0 ? t[indexT] : '';
+
+            if (charS !== charT) return false;
+
+            indexS--;
+            indexT--;
+        }
+
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(1)$
+
+> Where $n$ is the length of the string $s$ and $m$ is the length of the string $t$.
+
+---
+
+## 4. Two Pointers - II
+
+::tabs-start
+
+```python
+class Solution:
+    def backspaceCompare(self, s: str, t: str) -> bool:
+        index_s, index_t = len(s) - 1, len(t) - 1
+        backspace_s = backspace_t = 0
+        
+        while True:
+            while index_s >= 0 and (backspace_s or s[index_s] == '#'):
+                backspace_s += 1 if s[index_s] == '#' else -1
+                index_s -= 1
+
+            while index_t >= 0 and (backspace_t or t[index_t] == '#'):
+                backspace_t += 1 if t[index_t] == '#' else -1
+                index_t -= 1
+
+            if not (index_s >= 0 and index_t >= 0 and s[index_s] == t[index_t]):
+                return index_s == index_t == -1
+            index_s, index_t = index_s - 1, index_t - 1
+```
+
+```java
+public class Solution {
+    public boolean backspaceCompare(String s, String t) {
+        int indexS = s.length() - 1, indexT = t.length() - 1;
+        int backspaceS = 0, backspaceT = 0;
+
+        while (true) {
+            while (indexS >= 0 && (backspaceS > 0 || s.charAt(indexS) == '#')) {
+                backspaceS += s.charAt(indexS) == '#' ? 1 : -1;
+                indexS--;
+            }
+            
+            while (indexT >= 0 && (backspaceT > 0 || t.charAt(indexT) == '#')) {
+                backspaceT += t.charAt(indexT) == '#' ? 1 : -1;
+                indexT--;
+            }
+
+            if (!(indexS >= 0 && indexT >= 0 && s.charAt(indexS) == t.charAt(indexT))) {
+                return indexS == -1 && indexT == -1;
+            }
+            indexS--;
+            indexT--;
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool backspaceCompare(string s, string t) {
+        int indexS = s.size() - 1, indexT = t.size() - 1;
+        int backspaceS = 0, backspaceT = 0;
+
+        while (true) {
+            
+            while (indexS >= 0 && (backspaceS > 0 || s[indexS] == '#')) {
+                backspaceS += (s[indexS] == '#') ? 1 : -1;
+                indexS--;
+            }
+
+            while (indexT >= 0 && (backspaceT > 0 || t[indexT] == '#')) {
+                backspaceT += (t[indexT] == '#') ? 1 : -1;
+                indexT--;
+            }
+
+            if (!(indexS >= 0 && indexT >= 0 && s[indexS] == t[indexT])) {
+                return indexS == -1 && indexT == -1;
+            }
+            indexS--;
+            indexT--;
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string} t
+     * @return {boolean}
+     */
+    backspaceCompare(s, t) {
+        let indexS = s.length - 1, indexT = t.length - 1;
+        let backspaceS = 0, backspaceT = 0;
+
+        while (true) {
+            while (indexS >= 0 && (backspaceS > 0 || s[indexS] === '#')) {
+                backspaceS += s[indexS] === '#' ? 1 : -1;
+                indexS--;
+            }
+
+            while (indexT >= 0 && (backspaceT > 0 || t[indexT] === '#')) {
+                backspaceT += t[indexT] === '#' ? 1 : -1;
+                indexT--;
+            }
+
+            if (!(indexS >= 0 && indexT >= 0 && s.charAt(indexS) === t.charAt(indexT))) {
+                return indexS === -1 && indexT === -1;
+            }
+            indexS--;
+            indexT--;
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(1)$
+
+> Where $n$ is the length of the string $s$ and $m$ is the length of the string $t$.
\ No newline at end of file
diff --git a/articles/bag-of-tokens.md b/articles/bag-of-tokens.md
new file mode 100644
index 000000000..e6db737b8
--- /dev/null
+++ b/articles/bag-of-tokens.md
@@ -0,0 +1,109 @@
+## 1. Greedy + Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def bagOfTokensScore(self, tokens: List[int], power: int) -> int:
+        res = score = 0
+        tokens.sort()
+        l, r = 0, len(tokens) - 1
+        while l <= r:
+            if power >= tokens[l]:
+                power -= tokens[l]
+                l += 1
+                score += 1
+                res = max(res, score)
+            elif score > 0:
+                power += tokens[r]
+                r -= 1
+                score -= 1
+            else:
+                break
+        return res
+```
+
+```java
+public class Solution {
+    public int bagOfTokensScore(int[] tokens, int power) {
+        Arrays.sort(tokens);
+        int res = 0, score = 0, l = 0, r = tokens.length - 1;
+
+        while (l <= r) {
+            if (power >= tokens[l]) {
+                power -= tokens[l++];
+                score++;
+                res = Math.max(res, score);
+            } else if (score > 0) {
+                power += tokens[r--];
+                score--;
+            } else {
+                break;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int bagOfTokensScore(vector<int>& tokens, int power) {
+        sort(tokens.begin(), tokens.end());
+        int res = 0, score = 0, l = 0, r = tokens.size() - 1;
+
+        while (l <= r) {
+            if (power >= tokens[l]) {
+                power -= tokens[l++];
+                score++;
+                res = max(res, score);
+            } else if (score > 0) {
+                power += tokens[r--];
+                score--;
+            } else {
+                break;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} tokens
+     * @param {number} power
+     * @return {number}
+     */
+    bagOfTokensScore(tokens, power) {
+        tokens.sort((a, b) => a - b);
+        let res = 0, score = 0, l = 0, r = tokens.length - 1;
+
+        while (l <= r) {
+            if (power >= tokens[l]) {
+                power -= tokens[l++];
+                score++;
+                res = Math.max(res, score);
+            } else if (score > 0) {
+                power += tokens[r--];
+                score--;
+            } else {
+                break;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
\ No newline at end of file
diff --git a/articles/balanced-binary-tree.md b/articles/balanced-binary-tree.md
index d54120d9e..21715bc6f 100644
--- a/articles/balanced-binary-tree.md
+++ b/articles/balanced-binary-tree.md
@@ -176,6 +176,121 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func isBalanced(root *TreeNode) bool {
+    if root == nil {
+        return true
+    }
+    
+    left := height(root.Left)
+    right := height(root.Right)
+    if abs(left-right) > 1 {
+        return false
+    }
+    return isBalanced(root.Left) && isBalanced(root.Right)
+}
+
+func height(root *TreeNode) int {
+    if root == nil {
+        return 0
+    }
+    return 1 + max(height(root.Left), height(root.Right))
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+
+func abs(x int) int {
+    if x < 0 {
+        return -x
+    }
+    return x
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    fun isBalanced(root: TreeNode?): Boolean {
+        if (root == null) {
+            return true
+        }
+        
+        val left = height(root.left)
+        val right = height(root.right)
+        if (Math.abs(left - right) > 1) {
+            return false
+        }
+        return isBalanced(root.left) && isBalanced(root.right)
+    }
+    
+    private fun height(root: TreeNode?): Int {
+        if (root == null) {
+            return 0
+        }
+        return 1 + maxOf(height(root.left), height(root.right))
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func isBalanced(_ root: TreeNode?) -> Bool {
+        guard let root = root else { return true }
+
+        let left = height(root.left)
+        let right = height(root.right)
+
+        if abs(left - right) > 1 {
+            return false
+        }
+
+        return isBalanced(root.left) && isBalanced(root.right)
+    }
+
+    private func height(_ root: TreeNode?) -> Int {
+        guard let root = root else { return 0 }
+        return 1 + max(height(root.left), height(root.right))
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -369,16 +484,127 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func isBalanced(root *TreeNode) bool {
+    return dfs(root).balanced
+}
+
+type Result struct {
+    balanced bool
+    height   int
+}
+
+func dfs(root *TreeNode) Result {
+    if root == nil {
+        return Result{true, 0}
+    }
+    
+    left := dfs(root.Left)
+    right := dfs(root.Right)
+    
+    balanced := left.balanced && right.balanced && abs(left.height - right.height) <= 1
+    return Result{balanced, 1 + max(left.height, right.height)}
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+
+func abs(x int) int {
+    if x < 0 {
+        return -x
+    }
+    return x
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    fun isBalanced(root: TreeNode?): Boolean {
+        return dfs(root).first
+    }
+    
+    private fun dfs(root: TreeNode?): Pair<Boolean, Int> {
+        if (root == null) {
+            return Pair(true, 0)
+        }
+        
+        val left = dfs(root.left)
+        val right = dfs(root.right)
+        val balanced = left.first && right.first && Math.abs(left.second - right.second) <= 1
+        return Pair(balanced, 1 + maxOf(left.second, right.second))
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func isBalanced(_ root: TreeNode?) -> Bool {
+        return dfs(root).0
+    }
+
+    private func dfs(_ root: TreeNode?) -> (Bool, Int) {
+        guard let root = root else { return (true, 0) }
+
+        let left = dfs(root.left)
+        let right = dfs(root.right)
+
+        let balanced = left.0 && right.0 && abs(left.1 - right.1) <= 1
+        return (balanced, 1 + max(left.1, right.1))
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n)$
-* Space complexity: $O(n)$
+* Space complexity: $O(h)$  
+  * Best Case ([balanced tree](https://www.geeksforgeeks.org/balanced-binary-tree/)): $O(log(n))$
+  * Worst Case ([degenerate tree](https://www.geeksforgeeks.org/introduction-to-degenerate-binary-tree/)): $O(n)$
+
+> Where $n$ is the number of nodes in the tree and $h$ is the height of the tree.
 
 ---
 
-## 3. Depth First Search (Stack)
+## 3. Iterative DFS
 
 ::tabs-start
 
@@ -608,6 +834,160 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func isBalanced(root *TreeNode) bool {
+    stack := []*TreeNode{}
+    node := root
+    last := (*TreeNode)(nil)
+    depths := make(map[*TreeNode]int)
+
+    for len(stack) > 0 || node != nil {
+        if node != nil {
+            stack = append(stack, node)
+            node = node.Left
+        } else {
+            node = stack[len(stack)-1]
+            if node.Right == nil || last == node.Right {
+                stack = stack[:len(stack)-1]
+                left := depths[node.Left]
+                right := depths[node.Right]
+
+                if abs(left-right) > 1 {
+                    return false
+                }
+
+                depths[node] = 1 + max(left, right)
+                last = node
+                node = nil
+            } else {
+                node = node.Right
+            }
+        }
+    }
+    return true
+}
+
+func abs(x int) int {
+    if x < 0 {
+        return -x
+    }
+    return x
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    fun isBalanced(root: TreeNode?): Boolean {
+        val stack = mutableListOf<TreeNode?>()
+        var node = root
+        var last: TreeNode? = null
+        val depths = HashMap<TreeNode?, Int>()
+
+        while (stack.isNotEmpty() || node != null) {
+            if (node != null) {
+                stack.add(node)
+                node = node.left
+            } else {
+                node = stack.last()
+                if (node?.right == null || last == node.right) {
+                    stack.removeAt(stack.size - 1)
+                    val left = depths[node?.left] ?: 0
+                    val right = depths[node?.right] ?: 0
+
+                    if (Math.abs(left - right) > 1) {
+                        return false
+                    }
+
+                    depths[node] = 1 + Math.max(left, right)
+                    last = node
+                    node = null
+                } else {
+                    node = node.right
+                }
+            }
+        }
+        return true
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func isBalanced(_ root: TreeNode?) -> Bool {
+        var stack = [TreeNode]()
+        var node = root
+        var last: TreeNode? = nil
+        var depths = [ObjectIdentifier: Int]()
+
+        while !stack.isEmpty || node != nil {
+            if let current = node {
+                stack.append(current)
+                node = current.left
+            } else {
+                guard let current = stack.last else { break }
+                if current.right == nil || last === current.right {
+                    stack.removeLast()
+
+                    let leftDepth = current.left != nil ? depths[ObjectIdentifier(current.left!)] ?? 0 : 0
+                    let rightDepth = current.right != nil ? depths[ObjectIdentifier(current.right!)] ?? 0 : 0
+                    if abs(leftDepth - rightDepth) > 1 {
+                        return false
+                    }
+
+                    depths[ObjectIdentifier(current)] = 1 + max(leftDepth, rightDepth)
+                    last = current
+                    node = nil
+                } else {
+                    node = current.right
+                }
+            }
+        }
+
+        return true
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/baseball-game.md b/articles/baseball-game.md
new file mode 100644
index 000000000..ac8e53feb
--- /dev/null
+++ b/articles/baseball-game.md
@@ -0,0 +1,285 @@
+## 1. Stack - I
+
+::tabs-start
+
+```python
+class Solution:
+    def calPoints(self, operations: List[str]) -> int:
+        stack = []
+        for op in operations:
+            if op == "+":
+                stack.append(stack[-1] + stack[-2])
+            elif op == "D":
+                stack.append(2 * stack[-1])
+            elif op == "C":
+                stack.pop()
+            else:
+                stack.append(int(op))
+        return sum(stack)
+```
+
+```java
+public class Solution {
+    public int calPoints(String[] operations) {
+        Stack<Integer> stack = new Stack<>();
+        for (String op : operations) {
+            if (op.equals("+")) {
+                int top = stack.pop();
+                int newTop = top + stack.peek();
+                stack.push(top);
+                stack.push(newTop);
+            } else if (op.equals("D")) {
+                stack.push(2 * stack.peek());
+            } else if (op.equals("C")) {
+                stack.pop();
+            } else {
+                stack.push(Integer.parseInt(op));
+            }
+        }
+        int sum = 0;
+        for (int score : stack) {
+            sum += score;
+        }
+        return sum;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int calPoints(vector<string>& operations) {
+        vector<int> stack;
+        for (const string& op : operations) {
+            if (op == "+") {
+                int top = stack.back(); stack.pop_back();
+                int newTop = top + stack.back();
+                stack.push_back(top);
+                stack.push_back(newTop);
+            } else if (op == "D") {
+                stack.push_back(2 * stack.back());
+            } else if (op == "C") {
+                stack.pop_back();
+            } else {
+                stack.push_back(stoi(op));
+            }
+        }
+        return accumulate(stack.begin(), stack.end(), 0);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} operations
+     * @return {number}
+     */
+    calPoints(operations) {
+        const stack = [];
+        for (const op of operations) {
+            if (op === "+") {
+                const top = stack.pop();
+                const newTop = top + stack[stack.length - 1];
+                stack.push(top);
+                stack.push(newTop);
+            } else if (op === "D") {
+                stack.push(2 * stack[stack.length - 1]);
+            } else if (op === "C") {
+                stack.pop();
+            } else {
+                stack.push(parseInt(op));
+            }
+        }
+        return stack.reduce((a, b) => a + b, 0);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int CalPoints(string[] operations) {
+        Stack<int> stack = new Stack<int>();
+
+        foreach (var op in operations) {
+            if (op == "+") {
+                int top = stack.Pop();
+                int newTop = top + stack.Peek();
+                stack.Push(top);
+                stack.Push(newTop);
+            } else if (op == "D") {
+                stack.Push(2 * stack.Peek());
+            } else if (op == "C") {
+                stack.Pop();
+            } else {
+                stack.Push(int.Parse(op));
+            }
+        }
+
+        int total = 0;
+        foreach (var val in stack) {
+            total += val;
+        }
+
+        return total;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Stack - II
+
+::tabs-start
+
+```python
+class Solution:
+    def calPoints(self, operations: List[str]) -> int:
+        stack, res = [], 0
+        for op in operations:
+            if op == "+":
+                res += stack[-1] + stack[-2]
+                stack.append(stack[-1] + stack[-2])
+            elif op == "D":
+                res += (2 * stack[-1])
+                stack.append(2 * stack[-1])
+            elif op == "C":
+                res -= stack.pop()
+            else:
+                res += int(op)
+                stack.append(int(op))
+        return res
+```
+
+```java
+public class Solution {
+    public int calPoints(String[] ops) {
+        int res = 0;
+        Stack<Integer> stack = new Stack<>();
+        for (String op : ops) {
+            if (op.equals("+")) {
+                int top = stack.pop();
+                int newTop = top + stack.peek();
+                stack.push(top);
+                stack.push(newTop);
+                res += newTop;
+            } else if (op.equals("D")) {
+                stack.push(2 * stack.peek());
+                res += stack.peek();
+            } else if (op.equals("C")) {
+                res -= stack.pop();
+            } else {
+                stack.push(Integer.parseInt(op));
+                res += stack.peek();
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int calPoints(vector<string>& ops) {
+        stack<int> stack;
+        int res = 0;
+        for (const string& op : ops) {
+            if (op == "+") {
+                int top = stack.top(); stack.pop();
+                int newTop = top + stack.top();
+                stack.push(top);
+                stack.push(newTop);
+                res += newTop;
+            } else if (op == "D") {
+                stack.push(2 * stack.top());
+                res += stack.top();
+            } else if (op == "C") {
+                res -= stack.top();
+                stack.pop();
+            } else {
+                stack.push(stoi(op));
+                res += stack.top();
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} operations
+     * @return {number}
+     */
+    calPoints(operations) {
+        const stack = [];
+        let res = 0;
+        for (const op of operations) {
+            if (op === "+") {
+                const top = stack.pop();
+                const newTop = top + stack[stack.length - 1];
+                stack.push(top);
+                stack.push(newTop);
+                res += newTop;
+            } else if (op === "D") {
+                stack.push(2 * stack[stack.length - 1]);
+                res += stack[stack.length - 1];
+            } else if (op === "C") {
+                res -= stack.pop();
+            } else {
+                stack.push(parseInt(op));
+                res += stack[stack.length - 1];
+            }
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int CalPoints(string[] operations) {
+        Stack<int> stack = new Stack<int>();
+        int res = 0;
+
+        foreach (var op in operations) {
+            if (op == "+") {
+                int top = stack.Pop();
+                int second = stack.Peek();
+                int sum = top + second;
+                stack.Push(top);
+                stack.Push(sum);
+                res += sum;
+            } else if (op == "D") {
+                int doubleVal = 2 * stack.Peek();
+                stack.Push(doubleVal);
+                res += doubleVal;
+            } else if (op == "C") {
+                res -= stack.Pop();
+            } else {
+                int num = int.Parse(op);
+                stack.Push(num);
+                res += num;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/best-team-with-no-conflicts.md b/articles/best-team-with-no-conflicts.md
new file mode 100644
index 000000000..a4e77a374
--- /dev/null
+++ b/articles/best-team-with-no-conflicts.md
@@ -0,0 +1,649 @@
+## 1. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def bestTeamScore(self, scores: List[int], ages: List[int]) -> int:
+        pairs = [[scores[i], ages[i]] for i in range(len(scores))]
+        pairs.sort()
+        dp = {}
+
+        def dfs(i, j):
+            if i == len(pairs):
+                return 0
+            if (i, j) in dp:
+                return dp[(i, j)]
+
+            mScore, mAge = pairs[j] if j >= 0 else [0, 0]
+            score, age = pairs[i]
+            res = 0
+            if not (score > mScore and age < mAge):
+                res = dfs(i + 1, i) + score  # add score
+            dp[(i, j)] = max(res, dfs(i + 1, j))  # skip score
+            return dp[(i, j)]
+
+        return dfs(0, -1)
+```
+
+```java
+public class Solution {
+    private int[][] pairs;
+    private int[][] dp;
+
+    public int bestTeamScore(int[] scores, int[] ages) {
+        int n = scores.length;
+        pairs = new int[n][2];
+        for (int i = 0; i < n; i++) {
+            pairs[i][0] = scores[i];
+            pairs[i][1] = ages[i];
+        }
+        Arrays.sort(pairs, (a, b) -> a[0] == b[0] ? Integer.compare(a[1], b[1]) : Integer.compare(a[0], b[0]));
+
+        dp = new int[n][n + 1];
+        for (int[] row : dp) {
+            Arrays.fill(row, -1);
+        }
+
+        return dfs(0, -1);
+    }
+
+    private int dfs(int i, int j) {
+        if (i == pairs.length) {
+            return 0;
+        }
+        if (dp[i][j + 1] != -1) {
+            return dp[i][j + 1];
+        }
+
+        int mScore = j >= 0 ? pairs[j][0] : 0;
+        int mAge = j >= 0 ? pairs[j][1] : 0;
+        int score = pairs[i][0];
+        int age = pairs[i][1];
+
+        int res = 0;
+        if (!(score > mScore && age < mAge)) {
+            res = dfs(i + 1, i) + score;
+        }
+        dp[i][j + 1] = Math.max(res, dfs(i + 1, j));
+        return dp[i][j + 1];
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<pair<int, int>> pairs;
+    vector<vector<int>> dp;
+
+public:
+    int bestTeamScore(vector<int>& scores, vector<int>& ages) {
+        int n = scores.size();
+        pairs.resize(n);
+        for (int i = 0; i < n; i++) {
+            pairs[i] = {scores[i], ages[i]};
+        }
+        sort(pairs.begin(), pairs.end());
+
+        dp = vector<vector<int>>(n, vector<int>(n + 1, -1));
+        return dfs(0, -1);
+    }
+
+private:
+    int dfs(int i, int j) {
+        if (i == pairs.size()) {
+            return 0;
+        }
+        if (dp[i][j + 1] != -1) {
+            return dp[i][j + 1];
+        }
+
+        int mScore = j >= 0 ? pairs[j].first : 0;
+        int mAge = j >= 0 ? pairs[j].second : 0;
+        int score = pairs[i].first;
+        int age = pairs[i].second;
+
+        int res = 0;
+        if (!(score > mScore && age < mAge)) {
+            res = dfs(i + 1, i) + score;
+        }
+        dp[i][j + 1] = max(res, dfs(i + 1, j));
+        return dp[i][j + 1];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} scores
+     * @param {number[]} ages
+     * @return {number}
+     */
+    bestTeamScore(scores, ages) {
+        const n = scores.length;
+        const pairs = [];
+        for (let i = 0; i < n; i++) {
+            pairs.push([scores[i], ages[i]]);
+        }
+        pairs.sort((a, b) => (a[0] === b[0] ? a[1] - b[1] : a[0] - b[0]));
+
+        const dp = Array.from({ length: n }, () => new Array(n + 1).fill(-1));
+
+        const dfs = (i, j) => {
+            if (i === n) {
+                return 0;
+            }
+            if (dp[i][j + 1] !== -1) {
+                return dp[i][j + 1];
+            }
+
+            const [mScore, mAge] = j >= 0 ? pairs[j] : [0, 0];
+            const [score, age] = pairs[i];
+
+            let res = 0;
+            if (!(score > mScore && age < mAge)) {
+                res = dfs(i + 1, i) + score;
+            }
+            dp[i][j + 1] = Math.max(res, dfs(i + 1, j));
+            return dp[i][j + 1];
+        };
+
+        return dfs(0, -1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 2. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def bestTeamScore(self, scores: List[int], ages: List[int]) -> int:
+        pairs = [[scores[i], ages[i]] for i in range(len(scores))] 
+        pairs.sort()
+        dp = [pairs[i][0] for i in range(len(pairs))]
+
+        for i in range(len(pairs)):
+            mScore, mAge = pairs[i]
+            for j in range(i):
+                score, age = pairs[j]
+                if mAge >= age:
+                    dp[i] = max(dp[i], mScore + dp[j])
+
+        return max(dp)
+```
+
+```java
+public class Solution {
+    public int bestTeamScore(int[] scores, int[] ages) {
+        int n = scores.length;
+        int[][] pairs = new int[n][2];
+        for (int i = 0; i < n; i++) {
+            pairs[i][0] = scores[i];
+            pairs[i][1] = ages[i];
+        }
+        Arrays.sort(pairs, (a, b) -> a[0] == b[0] ? Integer.compare(a[1], b[1]) : Integer.compare(a[0], b[0]));
+
+        int[] dp = new int[n];
+        for (int i = 0; i < n; i++) {
+            dp[i] = pairs[i][0];
+        }
+
+        for (int i = 0; i < n; i++) {
+            int mScore = pairs[i][0], mAge = pairs[i][1];
+            for (int j = 0; j < i; j++) {
+                int score = pairs[j][0], age = pairs[j][1];
+                if (mAge >= age) {
+                    dp[i] = Math.max(dp[i], mScore + dp[j]);
+                }
+            }
+        }
+
+        int maxScore = 0;
+        for (int score : dp) {
+            maxScore = Math.max(maxScore, score);
+        }
+        return maxScore;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int bestTeamScore(vector<int>& scores, vector<int>& ages) {
+        int n = scores.size();
+        vector<pair<int, int>> pairs(n);
+        for (int i = 0; i < n; i++) {
+            pairs[i] = {scores[i], ages[i]};
+        }
+        sort(pairs.begin(), pairs.end());
+
+        vector<int> dp(n);
+        for (int i = 0; i < n; i++) {
+            dp[i] = pairs[i].first;
+        }
+
+        for (int i = 0; i < n; i++) {
+            int mScore = pairs[i].first, mAge = pairs[i].second;
+            for (int j = 0; j < i; j++) {
+                int score = pairs[j].first, age = pairs[j].second;
+                if (mAge >= age) {
+                    dp[i] = max(dp[i], mScore + dp[j]);
+                }
+            }
+        }
+
+        return *max_element(dp.begin(), dp.end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} scores
+     * @param {number[]} ages
+     * @return {number}
+     */
+    bestTeamScore(scores, ages) {
+        const n = scores.length;
+        const pairs = [];
+        for (let i = 0; i < n; i++) {
+            pairs.push([scores[i], ages[i]]);
+        }
+        pairs.sort((a, b) => (a[0] === b[0] ? a[1] - b[1] : a[0] - b[0]));
+
+        const dp = new Array(n).fill(0);
+        for (let i = 0; i < n; i++) {
+            dp[i] = pairs[i][0];
+        }
+
+        for (let i = 0; i < n; i++) {
+            const [mScore, mAge] = pairs[i];
+            for (let j = 0; j < i; j++) {
+                const [score, age] = pairs[j];
+                if (mAge >= age) {
+                    dp[i] = Math.max(dp[i], mScore + dp[j]);
+                }
+            }
+        }
+
+        return Math.max(...dp);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Segment Tree)
+
+::tabs-start
+
+```python
+class SegmentTree:
+    def __init__(self, N):
+        self.n = N
+        while (self.n & (self.n - 1)) != 0:
+            self.n += 1
+        self.build()
+
+    def build(self):
+        self.tree = [0] * (2 * self.n)
+
+    def update(self, i, val):
+        pos = self.n + i
+        self.tree[pos] = max(self.tree[pos], val)
+        pos >>= 1
+        while pos >= 1:
+            self.tree[pos] = max(self.tree[pos << 1], self.tree[pos << 1 | 1])
+            pos >>= 1
+
+    def query(self, l, r):
+        res = 0
+        l += self.n
+        r += self.n + 1
+        while l < r:
+            if l & 1:
+                res = max(res, self.tree[l])
+                l += 1
+            if r & 1:
+                r -= 1
+                res = max(res, self.tree[r])
+            l >>= 1
+            r >>= 1
+        return res
+
+class Solution:
+    def bestTeamScore(self, scores: list[int], ages: list[int]) -> int:
+        pairs = [[scores[i], ages[i]] for i in range(len(scores))]
+        pairs.sort()
+
+        dp = [pairs[i][0] for i in range(len(pairs))]
+        unique_ages = sorted({ age for _, age in pairs })
+        ageId = { val: idx for idx, val in enumerate(unique_ages) }
+
+        segtree = SegmentTree(len(pairs))
+
+        res = 0
+        for i in range(len(pairs)):
+            mScore, mAge = pairs[i]
+            idx = ageId[mAge]
+            j = segtree.query(0, idx)
+            dp[i] = j + mScore
+            segtree.update(idx, dp[i])
+            res = max(res, dp[i])
+
+        return res
+```
+
+```java
+class SegmentTree {
+    private int n;
+    private int[] tree;
+
+    public SegmentTree(int N) {
+        n = N;
+        while ((n & (n - 1)) != 0) {
+            n++;
+        }
+        build();
+    }
+
+    private void build() {
+        tree = new int[2 * n];
+    }
+
+    public void update(int i, int val) {
+        int pos = n + i;
+        tree[pos] = Math.max(tree[pos], val);
+        pos >>= 1;
+        while (pos >= 1) {
+            tree[pos] = Math.max(tree[pos << 1], tree[pos << 1 | 1]);
+            pos >>= 1;
+        }
+    }
+
+    public int query(int l, int r) {
+        int res = 0;
+        l += n;
+        r += n + 1;
+        while (l < r) {
+            if ((l & 1) == 1) {
+                res = Math.max(res, tree[l]);
+                l++;
+            }
+            if ((r & 1) == 1) {
+                r--;
+                res = Math.max(res, tree[r]);
+            }
+            l >>= 1;
+            r >>= 1;
+        }
+        return res;
+    }
+}
+
+public class Solution {
+    public int bestTeamScore(int[] scores, int[] ages) {
+        int n = scores.length;
+        int[][] pairs = new int[n][2];
+        for (int i = 0; i < n; i++) {
+            pairs[i][0] = scores[i];
+            pairs[i][1] = ages[i];
+        }
+        Arrays.sort(pairs, (a, b) -> a[0] == b[0] ? Integer.compare(a[1], b[1]) : Integer.compare(a[0], b[0]));
+
+        int[] dp = new int[n];
+        for (int i = 0; i < n; i++) {
+            dp[i] = pairs[i][0];
+        }
+
+        Set<Integer> uniqueAgesSet = new TreeSet<>();
+        for (int[] pair : pairs) {
+            uniqueAgesSet.add(pair[1]);
+        }
+        List<Integer> uniqueAges = new ArrayList<>(uniqueAgesSet);
+        Map<Integer, Integer> ageId = new HashMap<>();
+        for (int i = 0; i < uniqueAges.size(); i++) {
+            ageId.put(uniqueAges.get(i), i);
+        }
+
+        SegmentTree segtree = new SegmentTree(uniqueAges.size());
+
+        int res = 0;
+        for (int i = 0; i < n; i++) {
+            int mScore = pairs[i][0];
+            int mAge = pairs[i][1];
+            int idx = ageId.get(mAge);
+            int j = segtree.query(0, idx);
+            dp[i] = j + mScore;
+            segtree.update(idx, dp[i]);
+            res = Math.max(res, dp[i]);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class SegmentTree {
+private:
+    int n;
+    vector<int> tree;
+
+public:
+    SegmentTree(int N) {
+        n = N;
+        while ((n & (n - 1)) != 0) {
+            n++;
+        }
+        build();
+    }
+
+    void build() {
+        tree.resize(2 * n, 0);
+    }
+
+    void update(int i, int val) {
+        int pos = n + i;
+        tree[pos] = max(tree[pos], val);
+        pos >>= 1;
+        while (pos >= 1) {
+            tree[pos] = max(tree[pos << 1], tree[pos << 1 | 1]);
+            pos >>= 1;
+        }
+    }
+
+    int query(int l, int r) {
+        int res = 0;
+        l += n;
+        r += n + 1;
+        while (l < r) {
+            if (l & 1) {
+                res = max(res, tree[l]);
+                l++;
+            }
+            if (r & 1) {
+                r--;
+                res = max(res, tree[r]);
+            }
+            l >>= 1;
+            r >>= 1;
+        }
+        return res;
+    }
+};
+
+class Solution {
+public:
+    int bestTeamScore(vector<int>& scores, vector<int>& ages) {
+        int n = scores.size();
+        vector<pair<int, int>> pairs(n);
+        for (int i = 0; i < n; i++) {
+            pairs[i] = {scores[i], ages[i]};
+        }
+        sort(pairs.begin(), pairs.end());
+
+        vector<int> dp(n);
+        for (int i = 0; i < n; i++) {
+            dp[i] = pairs[i].first;
+        }
+
+        set<int> uniqueAgesSet;
+        for (auto& pair : pairs) {
+            uniqueAgesSet.insert(pair.second);
+        }
+        vector<int> uniqueAges(uniqueAgesSet.begin(), uniqueAgesSet.end());
+        map<int, int> ageId;
+        for (int i = 0; i < uniqueAges.size(); i++) {
+            ageId[uniqueAges[i]] = i;
+        }
+
+        SegmentTree segtree(uniqueAges.size());
+
+        int res = 0;
+        for (int i = 0; i < n; i++) {
+            int mScore = pairs[i].first;
+            int mAge = pairs[i].second;
+            int idx = ageId[mAge];
+            int j = segtree.query(0, idx);
+            dp[i] = j + mScore;
+            segtree.update(idx, dp[i]);
+            res = max(res, dp[i]);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class SegmentTree {
+    /**
+     * @constructor
+     * @param {number} N 
+     */
+    constructor(N) {
+        this.n = N;
+        while ((this.n & (this.n - 1)) !== 0) {
+            this.n++;
+        }
+        this.build();
+    }
+
+    /**
+     * @return {void}
+     */
+    build() {
+        this.tree = new Array(2 * this.n).fill(0);
+    }
+
+    /**
+     * @param {number} i
+     * @param {number} val
+     * @return {void}
+     */
+    update(i, val) {
+        let pos = this.n + i;
+        this.tree[pos] = Math.max(this.tree[pos], val);
+        pos >>= 1;
+        while (pos >= 1) {
+            this.tree[pos] = Math.max(this.tree[pos << 1], this.tree[pos << 1 | 1]);
+            pos >>= 1;
+        }
+    }
+
+    /**
+     * @param {number} l
+     * @param {number} r
+     * @return {number}
+     */
+    query(l, r) {
+        let res = 0;
+        l += this.n;
+        r += this.n + 1;
+        while (l < r) {
+            if (l & 1) {
+                res = Math.max(res, this.tree[l]);
+                l++;
+            }
+            if (r & 1) {
+                r--;
+                res = Math.max(res, this.tree[r]);
+            }
+            l >>= 1;
+            r >>= 1;
+        }
+        return res;
+    }
+}
+
+class Solution {
+    /**
+     * @param {number[]} scores
+     * @param {number[]} ages
+     * @return {number}
+     */
+    bestTeamScore(scores, ages) {
+        const n = scores.length;
+        const pairs = [];
+
+        for (let i = 0; i < n; i++) {
+            pairs.push([scores[i], ages[i]]);
+        }
+        pairs.sort((a, b) => (a[0] === b[0] ? a[1] - b[1] : a[0] - b[0]));
+
+        const dp = new Array(n).fill(0);
+        for (let i = 0; i < n; i++) {
+            dp[i] = pairs[i][0];
+        }
+
+        const uniqueAges = [...new Set(pairs.map((p) => p[1]))].sort((a, b) => a - b);
+        const ageId = new Map();
+        uniqueAges.forEach((val, idx) => ageId.set(val, idx));
+
+        const segtree = new SegmentTree(uniqueAges.length);
+
+        let res = 0;
+
+        for (let i = 0; i < n; i++) {
+            const [mScore, mAge] = pairs[i];
+            const idx = ageId.get(mAge);
+            const j = segtree.query(0, idx);
+            dp[i] = j + mScore;
+            segtree.update(idx, dp[i]);
+            res = Math.max(res, dp[i]);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/best-time-to-buy-and-sell-stock-ii.md b/articles/best-time-to-buy-and-sell-stock-ii.md
new file mode 100644
index 000000000..6562e3544
--- /dev/null
+++ b/articles/best-time-to-buy-and-sell-stock-ii.md
@@ -0,0 +1,567 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def maxProfit(self, prices: List[int]) -> int:
+        def rec(i, bought):
+            if i == len(prices):
+                return 0
+            res = rec(i + 1, bought)
+            if bought:
+                res = max(res, prices[i] + rec(i + 1, False))
+            else:
+                res = max(res, -prices[i] + rec(i + 1, True))
+            return res
+        return rec(0, False)
+```
+
+```java
+public class Solution {
+    public int maxProfit(int[] prices) {
+        return rec(prices, 0, false);
+    }
+
+    private int rec(int[] prices, int i, boolean bought) {
+        if (i == prices.length) {
+            return 0;
+        }
+        int res = rec(prices, i + 1, bought);
+        if (bought) {
+            res = Math.max(res, prices[i] + rec(prices, i + 1, false));
+        } else {
+            res = Math.max(res, -prices[i] + rec(prices, i + 1, true));
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxProfit(vector<int>& prices) {
+        return rec(prices, 0, false);
+    }
+
+private:
+    int rec(vector<int>& prices, int i, bool bought) {
+        if (i == prices.size()) {
+            return 0;
+        }
+        int res = rec(prices, i + 1, bought);
+        if (bought) {
+            res = max(res, prices[i] + rec(prices, i + 1, false));
+        } else {
+            res = max(res, -prices[i] + rec(prices, i + 1, true));
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} prices
+     * @return {number}
+     */
+    maxProfit(prices) {
+        const rec = (i, bought) => {
+            if (i === prices.length) {
+                return 0;
+            }
+            let res = rec(i + 1, bought);
+            if (bought) {
+                res = Math.max(res, prices[i] + rec(i + 1, false));
+            } else {
+                res = Math.max(res, -prices[i] + rec(i + 1, true));
+            }
+            return res;
+        };
+        return rec(0, false);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MaxProfit(int[] prices) {
+        return Rec(prices, 0, false);
+    }
+
+    private int Rec(int[] prices, int i, bool bought) {
+        if (i == prices.Length) {
+            return 0;
+        }
+
+        int res = Rec(prices, i + 1, bought);
+
+        if (bought) {
+            res = Math.Max(res, prices[i] + Rec(prices, i + 1, false));
+        } else {
+            res = Math.Max(res, -prices[i] + Rec(prices, i + 1, true));
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxProfit(self, prices: List[int]) -> int:
+        dp = {}
+
+        def rec(i, bought):
+            if i == len(prices):
+                return 0
+            if (i, bought) in dp:
+                return dp[(i, bought)]
+            res = rec(i + 1, bought)
+            if bought:
+                res = max(res, prices[i] + rec(i + 1, False))
+            else:
+                res = max(res, -prices[i] + rec(i + 1, True))
+            dp[(i, bought)] = res
+            return res
+
+        return rec(0, False)
+```
+
+```java
+public class Solution {
+    public int maxProfit(int[] prices) {
+        int n = prices.length;
+        int[][] dp = new int[n][2];
+        for (int i = 0; i < n; i++) {
+            dp[i][0] = -1;
+            dp[i][1] = -1;
+        }
+        return rec(prices, 0, 0, dp);
+    }
+
+    private int rec(int[] prices, int i, int bought, int[][] dp) {
+        if (i == prices.length) {
+            return 0;
+        }
+        if (dp[i][bought] != -1) {
+            return dp[i][bought];
+        }
+        int res = rec(prices, i + 1, bought, dp);
+        if (bought == 1) {
+            res = Math.max(res, prices[i] + rec(prices, i + 1, 0, dp));
+        } else {
+            res = Math.max(res, -prices[i] + rec(prices, i + 1, 1, dp));
+        }
+        dp[i][bought] = res;
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxProfit(vector<int>& prices) {
+        int n = prices.size();
+        vector<vector<int>> dp(n, vector<int>(2, -1));
+        return rec(prices, 0, 0, dp);
+    }
+
+private:
+    int rec(vector<int>& prices, int i, int bought, vector<vector<int>>& dp) {
+        if (i == prices.size()) {
+            return 0;
+        }
+        if (dp[i][bought] != -1) {
+            return dp[i][bought];
+        }
+        int res = rec(prices, i + 1, bought, dp);
+        if (bought == 1) {
+            res = max(res, prices[i] + rec(prices, i + 1, 0, dp));
+        } else {
+            res = max(res, -prices[i] + rec(prices, i + 1, 1, dp));
+        }
+        dp[i][bought] = res;
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} prices
+     * @return {number}
+     */
+    maxProfit(prices) {
+        const n = prices.length;
+        const dp = Array.from({ length: n }, () => Array(2).fill(-1));
+
+        const rec = (i, bought) => {
+            if (i === n) {
+                return 0;
+            }
+            if (dp[i][bought] !== -1) {
+                return dp[i][bought];
+            }
+            let res = rec(i + 1, bought);
+            if (bought) {
+                res = Math.max(res, prices[i] + rec(i + 1, 0));
+            } else {
+                res = Math.max(res, -prices[i] + rec(i + 1, 1));
+            }
+            dp[i][bought] = res;
+            return res;
+        };
+
+        return rec(0, 0);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MaxProfit(int[] prices) {
+        int n = prices.Length;
+        int[,] dp = new int[n, 2];
+
+        for (int i = 0; i < n; i++) {
+            dp[i, 0] = -1;
+            dp[i, 1] = -1;
+        }
+
+        return Rec(prices, 0, 0, dp);
+    }
+
+    private int Rec(int[] prices, int i, int bought, int[,] dp) {
+        if (i == prices.Length) {
+            return 0;
+        }
+
+        if (dp[i, bought] != -1) {
+            return dp[i, bought];
+        }
+
+        int res = Rec(prices, i + 1, bought, dp);
+
+        if (bought == 1) {
+            res = Math.Max(res, prices[i] + Rec(prices, i + 1, 0, dp));
+        } else {
+            res = Math.Max(res, -prices[i] + Rec(prices, i + 1, 1, dp));
+        }
+
+        dp[i, bought] = res;
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxProfit(self, prices: List[int]) -> int:
+        n = len(prices)
+        dp = [[0] * 2 for _ in range(n + 1)]
+        
+        for i in range(n - 1, -1, -1):
+            dp[i][0] = max(dp[i + 1][0], -prices[i] + dp[i + 1][1])
+            dp[i][1] = max(dp[i + 1][1], prices[i] + dp[i + 1][0])
+        
+        return dp[0][0]
+```
+
+```java
+public class Solution {
+    public int maxProfit(int[] prices) {
+        int n = prices.length;
+        int[][] dp = new int[n + 1][2];
+        
+        for (int i = n - 1; i >= 0; i--) {
+            dp[i][0] = Math.max(dp[i + 1][0], -prices[i] + dp[i + 1][1]);
+            dp[i][1] = Math.max(dp[i + 1][1], prices[i] + dp[i + 1][0]);
+        }
+        
+        return dp[0][0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxProfit(vector<int>& prices) {
+        int n = prices.size();
+        vector<vector<int>> dp(n + 1, vector<int>(2, 0));
+        
+        for (int i = n - 1; i >= 0; i--) {
+            dp[i][0] = max(dp[i + 1][0], -prices[i] + dp[i + 1][1]);
+            dp[i][1] = max(dp[i + 1][1], prices[i] + dp[i + 1][0]);
+        }
+        
+        return dp[0][0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} prices
+     * @return {number}
+     */
+    maxProfit(prices) {
+        const n = prices.length;
+        const dp = Array.from({ length: n + 1 }, () => Array(2).fill(0));
+        
+        for (let i = n - 1; i >= 0; i--) {
+            dp[i][0] = Math.max(dp[i + 1][0], -prices[i] + dp[i + 1][1]);
+            dp[i][1] = Math.max(dp[i + 1][1], prices[i] + dp[i + 1][0]);
+        }
+        
+        return dp[0][0];
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MaxProfit(int[] prices) {
+        int n = prices.Length;
+        int[,] dp = new int[n + 1, 2];
+
+        for (int i = n - 1; i >= 0; i--) {
+            dp[i, 0] = Math.Max(dp[i + 1, 0], -prices[i] + dp[i + 1, 1]);
+            dp[i, 1] = Math.Max(dp[i + 1, 1], prices[i] + dp[i + 1, 0]);
+        }
+
+        return dp[0, 0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxProfit(self, prices: List[int]) -> int:
+        n = len(prices)
+        next_buy = next_sell = 0
+        cur_buy = cur_sell = 0
+        
+        for i in range(n - 1, -1, -1):
+            cur_buy = max(next_buy, -prices[i] + next_sell)
+            cur_sell = max(next_sell, prices[i] + next_buy)
+            next_buy = cur_buy
+            next_sell = cur_sell
+        
+        return cur_buy
+```
+
+```java
+public class Solution {
+    public int maxProfit(int[] prices) {
+        int nextBuy = 0, nextSell = 0;
+        int curBuy = 0, curSell = 0;
+
+        for (int i = prices.length - 1; i >= 0; i--) {
+            curBuy = Math.max(nextBuy, -prices[i] + nextSell);
+            curSell = Math.max(nextSell, prices[i] + nextBuy);
+            nextBuy = curBuy;
+            nextSell = curSell;
+        }
+
+        return curBuy;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxProfit(vector<int>& prices) {
+        int nextBuy = 0, nextSell = 0;
+        int curBuy = 0, curSell = 0;
+
+        for (int i = prices.size() - 1; i >= 0; i--) {
+            curBuy = max(nextBuy, -prices[i] + nextSell);
+            curSell = max(nextSell, prices[i] + nextBuy);
+            nextBuy = curBuy;
+            nextSell = curSell;
+        }
+
+        return curBuy;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} prices
+     * @return {number}
+     */
+    maxProfit(prices) {
+        let nextBuy = 0, nextSell = 0;
+        let curBuy = 0, curSell = 0;
+
+        for (let i = prices.length - 1; i >= 0; i--) {
+            curBuy = Math.max(nextBuy, -prices[i] + nextSell);
+            curSell = Math.max(nextSell, prices[i] + nextBuy);
+            nextBuy = curBuy;
+            nextSell = curSell;
+        }
+
+        return curBuy;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MaxProfit(int[] prices) {
+        int nextBuy = 0, nextSell = 0;
+        int curBuy = 0, curSell = 0;
+
+        for (int i = prices.Length - 1; i >= 0; i--) {
+            curBuy = Math.Max(nextBuy, -prices[i] + nextSell);
+            curSell = Math.Max(nextSell, prices[i] + nextBuy);
+            nextBuy = curBuy;
+            nextSell = curSell;
+        }
+
+        return curBuy;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 5. Greedy
+
+::tabs-start
+
+```python
+class Solution:
+    def maxProfit(self, prices: List[int]) -> int:
+        profit = 0
+
+        for i in range(1, len(prices)):
+            if prices[i] > prices[i - 1]:
+                profit += (prices[i] - prices[i - 1])
+            
+        return profit
+```
+
+```java
+public class Solution {
+    public int maxProfit(int[] prices) {
+        int profit = 0;
+        for (int i = 1; i < prices.length; i++) {
+            if (prices[i] > prices[i - 1]) {
+                profit += (prices[i] - prices[i - 1]);
+            }
+        }
+        return profit;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxProfit(vector<int>& prices) {
+        int profit = 0;
+        for (int i = 1; i < prices.size(); i++) {
+            if (prices[i] > prices[i - 1]) {
+                profit += (prices[i] - prices[i - 1]);
+            }
+        }
+        return profit;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} prices
+     * @return {number}
+     */
+    maxProfit(prices) {
+        let profit = 0;
+        for (let i = 1; i < prices.length; i++) {
+            if (prices[i] > prices[i - 1]) {
+                profit += (prices[i] - prices[i - 1]);
+            }
+        }
+        return profit;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MaxProfit(int[] prices) {
+        int profit = 0;
+        for (int i = 1; i < prices.Length; i++) {
+            if (prices[i] > prices[i - 1]) {
+                profit += prices[i] - prices[i - 1];
+            }
+        }
+        return profit;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/binary-search-tree-iterator.md b/articles/binary-search-tree-iterator.md
new file mode 100644
index 000000000..873698c70
--- /dev/null
+++ b/articles/binary-search-tree-iterator.md
@@ -0,0 +1,699 @@
+## 1. Flattening the BST (DFS)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class BSTIterator:
+
+    def __init__(self, root: Optional[TreeNode]):
+        self.arr = []
+        self.itr = 0
+
+        def dfs(node):
+            if not node:
+                return
+            dfs(node.left)
+            self.arr.append(node.val)
+            dfs(node.right)
+        
+        dfs(root)
+
+    def next(self) -> int:
+        val = self.arr[self.itr]
+        self.itr += 1
+        return val
+
+    def hasNext(self) -> bool:
+        return self.itr < len(self.arr)
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class BSTIterator {
+    private List<Integer> arr;
+    private int itr;
+
+    public BSTIterator(TreeNode root) {
+        arr = new ArrayList<>();
+        itr = 0;
+        dfs(root);
+    }
+
+    private void dfs(TreeNode node) {
+        if (node == null) {
+            return;
+        }
+        dfs(node.left);
+        arr.add(node.val);
+        dfs(node.right);
+    }
+
+    public int next() {
+        return arr.get(itr++);
+    }
+
+    public boolean hasNext() {
+        return itr < arr.size();
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class BSTIterator {
+private:
+    vector<int> arr;
+    int itr;
+
+    void dfs(TreeNode* node) {
+        if (!node) {
+            return;
+        }
+        dfs(node->left);
+        arr.push_back(node->val);
+        dfs(node->right);
+    }
+
+public:
+    BSTIterator(TreeNode* root) {
+        itr = 0;
+        dfs(root);
+    }
+
+    int next() {
+        return arr[itr++];
+    }
+
+    bool hasNext() {
+        return itr < arr.size();
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class BSTIterator {
+    /**
+     * @constructor
+     * @param {TreeNode} root
+     */
+    constructor(root) {
+        this.arr = [];
+        this.itr = 0;
+
+        const dfs = (node) => {
+            if (!node) {
+                return;
+            }
+            dfs(node.left);
+            this.arr.push(node.val);
+            dfs(node.right);
+        };
+
+        dfs(root);
+    }
+
+    /**
+     * @return {number}
+     */
+    next() {
+        return this.arr[this.itr++];
+    }
+
+    /**
+     * @return {boolean}
+     */
+    hasNext() {
+        return this.itr < this.arr.length;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(n)$ time for initialization.
+    * $O(n)$ time for each $next()$ and $hasNext()$ function calls.
+* Space complexity: $O(n)$
+
+---
+
+## 2. Flatten the BST (Iterative DFS)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class BSTIterator:
+
+    def __init__(self, root: Optional[TreeNode]):
+        self.arr = []
+        self.itr = 0
+
+        stack = []
+        while root or stack:
+            while root:
+                stack.append(root)
+                root = root.left
+            root = stack.pop()
+            self.arr.append(root.val)
+            root = root.right
+
+    def next(self) -> int:
+        val = self.arr[self.itr]
+        self.itr += 1
+        return val
+
+    def hasNext(self) -> bool:
+        return self.itr < len(self.arr)
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class BSTIterator {
+    private List<Integer> arr;
+    private int itr;
+
+    public BSTIterator(TreeNode root) {
+        arr = new ArrayList<>();
+        itr = 0;
+        Stack<TreeNode> stack = new Stack<>();
+        while (root != null || !stack.isEmpty()) {
+            while (root != null) {
+                stack.push(root);
+                root = root.left;
+            }
+            root = stack.pop();
+            arr.add(root.val);
+            root = root.right;
+        }
+    }
+
+    public int next() {
+        return arr.get(itr++);
+    }
+
+    public boolean hasNext() {
+        return itr < arr.size();
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class BSTIterator {
+private:
+    vector<int> arr;
+    int itr;
+
+public:
+    BSTIterator(TreeNode* root) {
+        itr = 0;
+        stack<TreeNode*> stack;
+        while (root || !stack.empty()) {
+            while (root) {
+                stack.push(root);
+                root = root->left;
+            }
+            root = stack.top();
+            stack.pop();
+            arr.push_back(root->val);
+            root = root->right;
+        }
+    }
+
+    int next() {
+        return arr[itr++];
+    }
+
+    bool hasNext() {
+        return itr < arr.size();
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class BSTIterator {
+    /**
+     * @constructor
+     * @param {TreeNode} root
+     */
+    constructor(root) {
+        this.arr = [];
+        this.itr = 0;
+
+        let stack = [];
+        while (root || stack.length) {
+            while (root) {
+                stack.push(root);
+                root = root.left;
+            }
+            root = stack.pop();
+            this.arr.push(root.val);
+            root = root.right;
+        }
+    }
+
+    /**
+     * @return {number}
+     */
+    next() {
+        return this.arr[this.itr++];
+    }
+
+    /**
+     * @return {boolean}
+     */
+    hasNext() {
+        return this.itr < this.arr.length;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(n)$ time for initialization.
+    * $O(n)$ time for each $next()$ and $hasNext()$ function calls.
+* Space complexity: $O(n)$
+
+---
+
+## 3. Iterative DFS - I
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class BSTIterator:
+
+    def __init__(self, root: Optional[TreeNode]):
+        self.stack = []
+        while root:
+            self.stack.append(root)
+            root = root.left
+
+    def next(self) -> int:
+        res = self.stack.pop()
+        cur = res.right
+        while cur:
+            self.stack.append(cur)
+            cur = cur.left
+        return res.val
+
+    def hasNext(self) -> bool:
+        return bool(self.stack)
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class BSTIterator {
+    private Stack<TreeNode> stack;
+
+    public BSTIterator(TreeNode root) {
+        stack = new Stack<>();
+        while (root != null) {
+            stack.push(root);
+            root = root.left;
+        }
+    }
+
+    public int next() {
+        TreeNode res = stack.pop();
+        TreeNode cur = res.right;
+        while (cur != null) {
+            stack.push(cur);
+            cur = cur.left;
+        }
+        return res.val;
+    }
+
+    public boolean hasNext() {
+        return !stack.isEmpty();
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class BSTIterator {
+private:
+    stack<TreeNode*> stack;
+
+public:
+    BSTIterator(TreeNode* root) {
+        while (root) {
+            stack.push(root);
+            root = root->left;
+        }
+    }
+
+    int next() {
+        TreeNode* res = stack.top();
+        stack.pop();
+        TreeNode* cur = res->right;
+        while (cur) {
+            stack.push(cur);
+            cur = cur->left;
+        }
+        return res->val;
+    }
+
+    bool hasNext() {
+        return !stack.empty();
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class BSTIterator {
+    /**
+     * @constructor
+     * @param {TreeNode} root
+     */
+    constructor(root) {
+        this.stack = [];
+        while (root) {
+            this.stack.push(root);
+            root = root.left;
+        }
+    }
+
+    /**
+     * @return {number}
+     */
+    next() {
+        let res = this.stack.pop();
+        let cur = res.right;
+        while (cur) {
+            this.stack.push(cur);
+            cur = cur.left;
+        }
+        return res.val;
+    }
+
+    /**
+     * @return {boolean}
+     */
+    hasNext() {
+        return this.stack.length > 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$ in average for each function call.
+* Space complexity: $O(h)$
+
+> Where $n$ is the number of nodes and $h$ is the height of the given tree.
+
+---
+
+## 4. Iterative DFS - II
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class BSTIterator:
+
+    def __init__(self, root: Optional[TreeNode]):
+        self.cur = root
+        self.stack = []
+
+    def next(self) -> int:
+        while self.cur:
+            self.stack.append(self.cur)
+            self.cur = self.cur.left
+        
+        node = self.stack.pop()
+        self.cur = node.right
+        return node.val
+
+    def hasNext(self) -> bool:
+        return bool(self.cur) or bool(self.stack)
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class BSTIterator {
+    private TreeNode cur;
+    private Stack<TreeNode> stack;
+
+    public BSTIterator(TreeNode root) {
+        cur = root;
+        stack = new Stack<>();
+    }
+
+    public int next() {
+        while (cur != null) {
+            stack.push(cur);
+            cur = cur.left;
+        }
+        
+        TreeNode node = stack.pop();
+        cur = node.right;
+        return node.val;
+    }
+
+    public boolean hasNext() {
+        return cur != null || !stack.isEmpty();
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class BSTIterator {
+private:
+    TreeNode* cur;
+    stack<TreeNode*> stack;
+
+public:
+    BSTIterator(TreeNode* root) {
+        cur = root;
+    }
+
+    int next() {
+        while (cur) {
+            stack.push(cur);
+            cur = cur->left;
+        }
+        
+        TreeNode* node = stack.top();
+        stack.pop();
+        cur = node->right;
+        return node->val;
+    }
+
+    bool hasNext() {
+        return cur || !stack.empty();
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class BSTIterator {
+    /**
+     * @constructor
+     * @param {TreeNode} root
+     */
+    constructor(root) {
+        this.cur = root;
+        this.stack = [];
+    }
+
+    /**
+     * @return {number}
+     */
+    next() {
+        while (this.cur) {
+            this.stack.push(this.cur);
+            this.cur = this.cur.left;
+        }
+
+        let node = this.stack.pop();
+        this.cur = node.right;
+        return node.val;
+    }
+
+    /**
+     * @return {boolean}
+     */
+    hasNext() {
+        return this.cur !== null || this.stack.length > 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$ in average for each function call.
+* Space complexity: $O(h)$
+
+> Where $n$ is the number of nodes and $h$ is the height of the given tree.
\ No newline at end of file
diff --git a/articles/binary-search.md b/articles/binary-search.md
index 59ca1e2bc..59a970a26 100644
--- a/articles/binary-search.md
+++ b/articles/binary-search.md
@@ -97,6 +97,71 @@ public class Solution {
 }
 ```
 
+```go
+func binarySearch(l, r int, nums []int, target int) int {
+    if l > r {
+        return -1
+    }
+    m := l + (r-l)/2
+
+    if nums[m] == target {
+        return m
+    }
+    if nums[m] < target {
+        return binarySearch(m+1, r, nums, target)
+    }
+    return binarySearch(l, m-1, nums, target)
+}
+
+func search(nums []int, target int) int {
+    return binarySearch(0, len(nums)-1, nums, target)
+}
+```
+
+```kotlin
+class Solution {
+    private fun binarySearch(l: Int, r: Int, nums: IntArray, target: Int): Int {
+        if (l > r) {
+            return -1
+        }
+        val m = l + (r - l) / 2
+
+        return when {
+            nums[m] == target -> m
+            nums[m] < target -> binarySearch(m + 1, r, nums, target)
+            else -> binarySearch(l, m - 1, nums, target)
+        }
+    }
+
+    fun search(nums: IntArray, target: Int): Int {
+        return binarySearch(0, nums.size - 1, nums, target)
+    }
+}
+```
+
+```swift
+class Solution {
+    func binarySearch(_ l: Int, _ r: Int, _ nums: [Int], _ target: Int) -> Int {
+        if l > r {
+            return -1
+        }
+        let m = l + (r - l) / 2
+
+        if nums[m] == target {
+            return m
+        }
+        if nums[m] < target {
+            return binarySearch(m + 1, r, nums, target)
+        }
+        return binarySearch(l, m - 1, nums, target)
+    }
+
+    func search(_ nums: [Int], _ target: Int) -> Int {
+        return binarySearch(0, nums.count - 1, nums, target)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -215,6 +280,67 @@ public class Solution {
 }
 ```
 
+```go
+func search(nums []int, target int) int {
+    l, r := 0, len(nums)-1
+
+    for l <= r {
+        m := l + (r-l)/2
+
+        if nums[m] > target {
+            r = m - 1
+        } else if nums[m] < target {
+            l = m + 1
+        } else {
+            return m
+        }
+    }
+    return -1
+}
+```
+
+```kotlin
+class Solution {
+    fun search(nums: IntArray, target: Int): Int {
+        var l = 0
+        var r = nums.size - 1
+
+        while (l <= r) {
+            val m = l + (r - l) / 2
+
+            when {
+                nums[m] > target -> r = m - 1
+                nums[m] < target -> l = m + 1
+                else -> return m
+            }
+        }
+        return -1
+    }
+}
+```
+
+```swift
+class Solution {
+    func search(_ nums: [Int], _ target: Int) -> Int {
+        var l = 0, r = nums.count - 1
+
+        while l <= r {
+            // (l + r) // 2 can lead to overflow
+            let m = l + (r - l) / 2
+
+            if nums[m] > target {
+                r = m - 1
+            } else if nums[m] < target {
+                l = m + 1
+            } else {
+                return m
+            }
+        }
+        return -1
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -320,6 +446,62 @@ public class Solution {
 }
 ```
 
+```go
+func search(nums []int, target int) int {
+    l, r := 0, len(nums)
+
+    for l < r {
+        m := l + (r-l)/2
+        if nums[m] > target {
+            r = m
+        } else {
+            l = m + 1
+        }
+    }
+    if l > 0 && nums[l-1] == target {
+        return l - 1
+    }
+    return -1
+}
+```
+
+```kotlin
+class Solution {
+    fun search(nums: IntArray, target: Int): Int {
+        var l = 0
+        var r = nums.size
+
+        while (l < r) {
+            val m = l + (r - l) / 2
+            if (nums[m] > target) {
+                r = m
+            } else {
+                l = m + 1
+            }
+        }
+        return if (l > 0 && nums[l - 1] == target) l - 1 else -1
+    }
+}
+```
+
+```swift
+class Solution {
+    func search(_ nums: [Int], _ target: Int) -> Int {
+        var l = 0, r = nums.count
+
+        while l < r {
+            let m = l + (r - l) / 2  
+            if nums[m] > target {
+                r = m
+            } else {
+                l = m + 1
+            }
+        }
+        return (l > 0 && nums[l - 1] == target) ? l - 1 : -1
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -425,6 +607,62 @@ public class Solution {
 }
 ```
 
+```go
+func search(nums []int, target int) int {
+    l, r := 0, len(nums)
+
+    for l < r {
+        m := l + (r-l)/2
+        if nums[m] >= target {
+            r = m
+        } else {
+            l = m + 1
+        }
+    }
+    if l < len(nums) && nums[l] == target {
+        return l
+    }
+    return -1
+}
+```
+
+```kotlin
+class Solution {
+    fun search(nums: IntArray, target: Int): Int {
+        var l = 0
+        var r = nums.size
+
+        while (l < r) {
+            val m = l + (r - l) / 2
+            if (nums[m] >= target) {
+                r = m
+            } else {
+                l = m + 1
+            }
+        }
+        return if (l < nums.size && nums[l] == target) l else -1
+    }
+}
+```
+
+```swift
+class Solution {
+    func search(_ nums: [Int], _ target: Int) -> Int {
+        var l = 0, r = nums.count
+
+        while l < r {
+            let m = l + (r - l) / 2  
+            if nums[m] >= target {
+                r = m
+            } else {
+                l = m + 1
+            }
+        }
+        return (l < nums.count && nums[l] == target) ? l : -1
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -434,7 +672,7 @@ public class Solution {
 
 ---
 
-## 5. Built-In Tool
+## 5. Built-In Function
 
 ::tabs-start
 
@@ -488,6 +726,34 @@ public class Solution {
 }
 ```
 
+```go
+func search(nums []int, target int) int {
+    index := sort.Search(len(nums), func(i int) bool { return nums[i] >= target })
+    if index < len(nums) && nums[index] == target {
+        return index
+    }
+    return -1
+}
+```
+
+```kotlin
+class Solution {
+    fun search(nums: IntArray, target: Int): Int {
+        val index = nums.binarySearch(target)
+        return if (index >= 0) index else -1
+    }
+}
+```
+
+```swift
+class Solution {
+    func search(_ nums: [Int], _ target: Int) -> Int {
+        let index = nums.partitioningIndex { $0 >= target }
+        return (index < nums.count && nums[index] == target) ? index : -1
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/binary-subarrays-with-sum.md b/articles/binary-subarrays-with-sum.md
new file mode 100644
index 000000000..65a07ca78
--- /dev/null
+++ b/articles/binary-subarrays-with-sum.md
@@ -0,0 +1,381 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def numSubarraysWithSum(self, nums: List[int], goal: int) -> int:
+        n, res = len(nums), 0
+
+        for i in range(n):
+            curSum = 0
+            for j in range(i, n):
+                curSum += nums[j]
+                if curSum == goal:
+                    res += 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int numSubarraysWithSum(int[] nums, int goal) {
+        int n = nums.length, res = 0;
+
+        for (int i = 0; i < n; i++) {
+            int curSum = 0;
+            for (int j = i; j < n; j++) {
+                curSum += nums[j];
+                if (curSum == goal) {
+                    res++;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numSubarraysWithSum(vector<int>& nums, int goal) {
+        int n = nums.size(), res = 0;
+
+        for (int i = 0; i < n; i++) {
+            int curSum = 0;
+            for (int j = i; j < n; j++) {
+                curSum += nums[j];
+                if (curSum == goal) {
+                    res++;
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} goal
+     * @return {number}
+     */
+    numSubarraysWithSum(nums, goal) {
+        const n = nums.length;
+        let res = 0;
+
+        for (let i = 0; i < n; i++) {
+            let curSum = 0;
+            for (let j = i; j < n; j++) {
+                curSum += nums[j];
+                if (curSum === goal) {
+                    res++;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Prefix Sum + Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def numSubarraysWithSum(self, nums: List[int], goal: int) -> int:
+        prefixSum = 0
+        count = { 0 : 1 } # prefixSum -> count
+        res = 0
+
+        for num in nums:
+            prefixSum += num
+            res += count.get(prefixSum - goal, 0)
+            count[prefixSum] = count.get(prefixSum, 0) + 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int numSubarraysWithSum(int[] nums, int goal) {
+        int prefixSum = 0, res = 0;
+        HashMap<Integer, Integer> count = new HashMap<>();
+        count.put(0, 1);
+
+        for (int num : nums) {
+            prefixSum += num;
+            res += count.getOrDefault(prefixSum - goal, 0);
+            count.put(prefixSum, count.getOrDefault(prefixSum, 0) + 1);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numSubarraysWithSum(vector<int>& nums, int goal) {
+        int prefixSum = 0, res = 0;
+        unordered_map<int, int> count;
+        count[0] = 1;
+
+        for (int& num : nums) {
+            prefixSum += num;
+            res += count[prefixSum - goal];
+            count[prefixSum]++;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} goal
+     * @return {number}
+     */
+    numSubarraysWithSum(nums, goal) {
+        let prefixSum = 0, res = 0;
+        const count = new Map();
+        count.set(0, 1);
+
+        for (const num of nums) {
+            prefixSum += num;
+            res += count.get(prefixSum - goal) || 0;
+            count.set(prefixSum, (count.get(prefixSum) || 0) + 1);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Prefix Sum + Array
+
+::tabs-start
+
+```python
+class Solution:
+    def numSubarraysWithSum(self, nums: List[int], goal: int) -> int:
+        n = len(nums)
+        count = [0] * (n + 1)
+        count[0] = 1
+        prefixSum, res = 0, 0
+
+        for num in nums:
+            prefixSum += num
+            if prefixSum >= goal:
+                res += count[prefixSum - goal]
+            count[prefixSum] += 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int numSubarraysWithSum(int[] nums, int goal) {
+        int n = nums.length, prefixSum = 0, res = 0;
+        int[] count = new int[n + 1];
+        count[0] = 1;
+
+        for (int num : nums) {
+            prefixSum += num;
+            if (prefixSum >= goal) {
+                res += count[prefixSum - goal];
+            }
+            count[prefixSum]++;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numSubarraysWithSum(vector<int>& nums, int goal) {
+        int n = nums.size(), prefixSum = 0, res = 0;
+        vector<int> count(n + 1, 0);
+        count[0] = 1;
+
+        for (int num : nums) {
+            prefixSum += num;
+            if (prefixSum >= goal) {
+                res += count[prefixSum - goal];
+            }
+            count[prefixSum]++;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} goal
+     * @return {number}
+     */
+    numSubarraysWithSum(nums, goal) {
+        const n = nums.length;
+        const count = Array(n + 1).fill(0);
+        count[0] = 1;
+        let prefixSum = 0, res = 0;
+
+        for (const num of nums) {
+            prefixSum += num;
+            if (prefixSum >= goal) {
+                res += count[prefixSum - goal];
+            }
+            count[prefixSum]++;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Sliding Window
+
+::tabs-start
+
+```python
+class Solution:
+    def numSubarraysWithSum(self, nums: List[int], goal: int) -> int:
+        def helper(x):
+            if x < 0:
+                return 0
+            res = l = cur = 0
+            for r in range(len(nums)):
+                cur += nums[r]
+                while cur > x:
+                    cur -= nums[l]
+                    l += 1
+                res += (r - l + 1)
+            return res
+
+        return helper(goal) - helper(goal - 1)
+```
+
+```java
+public class Solution {
+    public int numSubarraysWithSum(int[] nums, int goal) {
+        return helper(nums, goal) - helper(nums, goal - 1);
+    }
+    
+    private int helper(int[] nums, int x) {
+        if (x < 0) return 0;
+        int res = 0, l = 0, cur = 0;
+        for (int r = 0; r < nums.length; r++) {
+            cur += nums[r];
+            while (cur > x) {
+                cur -= nums[l];
+                l++;
+            }
+            res += (r - l + 1);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numSubarraysWithSum(vector<int>& nums, int goal) {
+        return helper(nums, goal) - helper(nums, goal - 1);
+    }
+    
+private:
+    int helper(vector<int>& nums, int x) {
+        if (x < 0) return 0;
+        int res = 0, l = 0, cur = 0;
+        for (int r = 0; r < nums.size(); r++) {
+            cur += nums[r];
+            while (cur > x) {
+                cur -= nums[l];
+                l++;
+            }
+            res += (r - l + 1);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} goal
+     * @return {number}
+     */
+    numSubarraysWithSum(nums, goal) {
+        const helper = (x) => {
+            if (x < 0) return 0;
+            let res = 0, l = 0, cur = 0;
+            for (let r = 0; r < nums.length; r++) {
+                cur += nums[r];
+                while (cur > x) {
+                    cur -= nums[l];
+                    l++;
+                }
+                res += (r - l + 1);
+            }
+            return res;
+        };
+
+        return helper(goal) - helper(goal - 1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/binary-tree-diameter.md b/articles/binary-tree-diameter.md
index aabdfc962..b11c3e40e 100644
--- a/articles/binary-tree-diameter.md
+++ b/articles/binary-tree-diameter.md
@@ -180,6 +180,120 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func diameterOfBinaryTree(root *TreeNode) int {
+    if root == nil {
+        return 0
+    }
+    
+    leftHeight := maxHeight(root.Left)
+    rightHeight := maxHeight(root.Right)
+    diameter := leftHeight + rightHeight
+    
+    sub := max(diameterOfBinaryTree(root.Left), 
+              diameterOfBinaryTree(root.Right))
+    
+    return max(diameter, sub)
+}
+
+func maxHeight(root *TreeNode) int {
+    if root == nil {
+        return 0
+    }
+    
+    return 1 + max(maxHeight(root.Left), maxHeight(root.Right))
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    fun diameterOfBinaryTree(root: TreeNode?): Int {
+        if (root == null) {
+            return 0
+        }
+        
+        val leftHeight = maxHeight(root.left)
+        val rightHeight = maxHeight(root.right)
+        val diameter = leftHeight + rightHeight
+        
+        val sub = maxOf(
+            diameterOfBinaryTree(root.left),
+            diameterOfBinaryTree(root.right)
+        )
+        
+        return maxOf(diameter, sub)
+    }
+    
+    private fun maxHeight(root: TreeNode?): Int {
+        if (root == null) {
+            return 0
+        }
+        
+        return 1 + maxOf(maxHeight(root.left), maxHeight(root.right))
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func diameterOfBinaryTree(_ root: TreeNode?) -> Int {
+        guard let root = root else { return 0 }
+
+        let leftHeight = maxHeight(root.left)
+        let rightHeight = maxHeight(root.right)
+        let diameter = leftHeight + rightHeight
+        let sub = max(diameterOfBinaryTree(root.left), diameterOfBinaryTree(root.right))
+        
+        return max(diameter, sub)
+    }
+
+    private func maxHeight(_ root: TreeNode?) -> Int {
+        guard let root = root else { return 0 }
+        return 1 + max(maxHeight(root.left), maxHeight(root.right))
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -366,12 +480,120 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func diameterOfBinaryTree(root *TreeNode) int {
+    res := 0
+    
+    var dfs func(*TreeNode) int
+    dfs = func(root *TreeNode) int {
+        if root == nil {
+            return 0
+        }
+        
+        left := dfs(root.Left)
+        right := dfs(root.Right)
+        res = max(res, left + right)
+        
+        return 1 + max(left, right)
+    }
+    
+    dfs(root)
+    return res
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    private var res = 0
+    
+    fun diameterOfBinaryTree(root: TreeNode?): Int {
+        dfs(root)
+        return res
+    }
+    
+    private fun dfs(root: TreeNode?): Int {
+        if (root == null) {
+            return 0
+        }
+        
+        val left = dfs(root.left)
+        val right = dfs(root.right)
+        res = maxOf(res, left + right)
+        
+        return 1 + maxOf(left, right)
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func diameterOfBinaryTree(_ root: TreeNode?) -> Int {
+        var res = 0
+
+        func dfs(_ root: TreeNode?) -> Int {
+            guard let root = root else { return 0 }
+            let left = dfs(root.left)
+            let right = dfs(root.right)
+            res = max(res, left + right)
+            return 1 + max(left, right)
+        }
+
+        dfs(root)
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n)$
-* Space complexity: $O(n)$
+* Space complexity: $O(h)$  
+  * Best Case ([balanced tree](https://www.geeksforgeeks.org/balanced-binary-tree/)): $O(log(n))$
+  * Worst Case ([degenerate tree](https://www.geeksforgeeks.org/introduction-to-degenerate-binary-tree/)): $O(n)$
+
+> Where $n$ is the number of nodes in the tree and $h$ is the height of the tree.
 
 ---
 
@@ -615,6 +837,157 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func diameterOfBinaryTree(root *TreeNode) int {
+   if root == nil {
+       return 0
+   }
+   
+   stack := linkedliststack.New()
+   stack.Push(root)
+   mp := make(map[*TreeNode][]int)
+   mp[nil] = []int{0, 0}
+   
+   for !stack.Empty() {
+       val, _ := stack.Peek()
+       node := val.(*TreeNode)
+       
+       if node.Left != nil && len(mp[node.Left]) == 0 {
+           stack.Push(node.Left)
+       } else if node.Right != nil && len(mp[node.Right]) == 0 {
+           stack.Push(node.Right)
+       } else {
+           stack.Pop()
+           
+           leftHeight := mp[node.Left][0]
+           leftDiameter := mp[node.Left][1]
+           rightHeight := mp[node.Right][0]
+           rightDiameter := mp[node.Right][1]
+           
+           height := 1 + max(leftHeight, rightHeight)
+           diameter := max(leftHeight+rightHeight, 
+                         max(leftDiameter, rightDiameter))
+           
+           mp[node] = []int{height, diameter}
+       }
+   }
+   
+   return mp[root][1]
+}
+
+func max(a, b int) int {
+   if a > b {
+       return a
+   }
+   return b
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    fun diameterOfBinaryTree(root: TreeNode?): Int {
+        if (root == null) {
+            return 0
+        }
+        
+        val stack = ArrayDeque<TreeNode>()
+        stack.addLast(root)
+        
+        val mp = HashMap<TreeNode?, Pair<Int, Int>>()
+        mp[null] = Pair(0, 0)
+        
+        while (stack.isNotEmpty()) {
+            val node = stack.last()
+            
+            when {
+                node.left != null && !mp.containsKey(node.left) -> {
+                    stack.addLast(node.left)
+                }
+                node.right != null && !mp.containsKey(node.right) -> {
+                    stack.addLast(node.right)
+                }
+                else -> {
+                    stack.removeLast()
+                    
+                    val (leftHeight, leftDiameter) = mp[node.left] ?: Pair(0, 0)
+                    val (rightHeight, rightDiameter) = mp[node.right] ?: Pair(0, 0)
+                    
+                    val height = 1 + maxOf(leftHeight, rightHeight)
+                    val diameter = maxOf(leftHeight + rightHeight, 
+                                      leftDiameter, 
+                                      rightDiameter)
+                    
+                    mp[node] = Pair(height, diameter)
+                }
+            }
+        }
+        
+        return mp[root]?.second ?: 0
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func diameterOfBinaryTree(_ root: TreeNode?) -> Int {
+        guard let root = root else { return 0 }
+        var stack: [TreeNode] = [root]
+        var mp = [ObjectIdentifier: (Int, Int)]()
+
+        while !stack.isEmpty {
+            let node = stack.last!
+            if let left = node.left, mp[ObjectIdentifier(left)] == nil {
+                stack.append(left)
+            } else if let right = node.right, mp[ObjectIdentifier(right)] == nil {
+                stack.append(right)
+            } else {
+                let node = stack.removeLast()
+                let leftTuple = node.left != nil ? mp[ObjectIdentifier(node.left!)]! : (0, 0)
+                let rightTuple = node.right != nil ? mp[ObjectIdentifier(node.right!)]! : (0, 0)
+                let height = 1 + max(leftTuple.0, rightTuple.0)
+                let diameter = max(leftTuple.0 + rightTuple.0, leftTuple.1, rightTuple.1)
+                mp[ObjectIdentifier(node)] = (height, diameter)
+            }
+        }
+
+        return mp[ObjectIdentifier(root)]!.1
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/binary-tree-from-preorder-and-inorder-traversal.md b/articles/binary-tree-from-preorder-and-inorder-traversal.md
index 5886b2cdd..b21106a35 100644
--- a/articles/binary-tree-from-preorder-and-inorder-traversal.md
+++ b/articles/binary-tree-from-preorder-and-inorder-traversal.md
@@ -168,16 +168,126 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func buildTree(preorder []int, inorder []int) *TreeNode {
+    if len(preorder) == 0 || len(inorder) == 0 {
+        return nil
+    }
+    
+    root := &TreeNode{Val: preorder[0]}
+    
+    mid := 0
+    for i, val := range inorder {
+        if val == preorder[0] {
+            mid = i
+            break
+        }
+    }
+    
+    root.Left = buildTree(preorder[1:mid+1], inorder[:mid])
+    root.Right = buildTree(preorder[mid+1:], inorder[mid+1:])
+    
+    return root
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    fun buildTree(preorder: IntArray, inorder: IntArray): TreeNode? {
+        if (preorder.isEmpty() || inorder.isEmpty()) {
+            return null
+        }
+        
+        val root = TreeNode(preorder[0])
+        
+        val mid = inorder.indexOf(preorder[0])
+        
+        root.left = buildTree(
+            preorder.slice(1..mid).toIntArray(),
+            inorder.slice(0 until mid).toIntArray()
+        )
+        
+        root.right = buildTree(
+            preorder.slice(mid + 1 until preorder.size).toIntArray(),
+            inorder.slice(mid + 1 until inorder.size).toIntArray()
+        )
+        
+        return root
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func buildTree(_ preorder: [Int], _ inorder: [Int]) -> TreeNode? {
+        if preorder.isEmpty || inorder.isEmpty {
+            return nil
+        }
+
+        let rootValue = preorder[0]
+        let root = TreeNode(rootValue)
+        guard let mid = inorder.firstIndex(of: rootValue) else {
+            return root
+        }
+
+        root.left = buildTree(
+            Array(preorder[1..<(mid + 1)]), 
+            Array(inorder[0..<mid])
+        )
+
+        root.right = buildTree(
+            Array(preorder[(mid + 1)..<preorder.count]), 
+            Array(inorder[(mid + 1)..<inorder.count])
+        )
+
+        return root
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n ^ 2)$
-* Space complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
 
 ---
 
-## 2. Hash Map
+## 2. Hash Map + Depth First Search
 
 ::tabs-start
 
@@ -363,6 +473,128 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func buildTree(preorder []int, inorder []int) *TreeNode {
+    indices := make(map[int]int)
+    for i, val := range inorder {
+        indices[val] = i
+    }
+    
+    preIdx := 0
+    
+    var dfs func(int, int) *TreeNode
+    dfs = func(left, right int) *TreeNode {
+        if left > right {
+            return nil
+        }
+        
+        rootVal := preorder[preIdx]
+        preIdx++
+        
+        root := &TreeNode{Val: rootVal}
+        mid := indices[rootVal]
+        
+        root.Left = dfs(left, mid - 1)
+        root.Right = dfs(mid + 1, right)
+        
+        return root
+    }
+    
+    return dfs(0, len(inorder) - 1)
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    private var preIdx = 0
+    
+    fun buildTree(preorder: IntArray, inorder: IntArray): TreeNode? {
+        val indices = inorder.withIndex()
+            .associate { (index, value) -> value to index }
+        
+        fun dfs(left: Int, right: Int): TreeNode? {
+            if (left > right) {
+                return null
+            }
+            
+            val rootVal = preorder[preIdx++]
+            val root = TreeNode(rootVal)
+            val mid = indices[rootVal]!!
+            
+            root.left = dfs(left, mid - 1)
+            root.right = dfs(mid + 1, right)
+            
+            return root
+        }
+        
+        return dfs(0, inorder.lastIndex)
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    var preIndex = 0
+    var indexMap = [Int: Int]()
+
+    func buildTree(_ preorder: [Int], _ inorder: [Int]) -> TreeNode? {
+        for (index, value) in inorder.enumerated() {
+            indexMap[value] = index
+        }
+        return dfs(preorder, 0, inorder.count - 1)
+    }
+
+    private func dfs(_ preorder: [Int], _ left: Int, _ right: Int) -> TreeNode? {
+        if left > right {
+            return nil
+        }
+
+        let rootVal = preorder[preIndex]
+        preIndex += 1
+        let root = TreeNode(rootVal)
+        let mid = indexMap[rootVal]!
+
+        root.left = dfs(preorder, left, mid - 1)
+        root.right = dfs(preorder, mid + 1, right)
+
+        return root
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -557,9 +789,125 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func buildTree(preorder []int, inorder []int) *TreeNode {
+    preIdx, inIdx := 0, 0
+    
+    var dfs func(int) *TreeNode
+    dfs = func(limit int) *TreeNode {
+        if preIdx >= len(preorder) {
+            return nil
+        }
+        if inorder[inIdx] == limit {
+            inIdx++
+            return nil
+        }
+        
+        root := &TreeNode{Val: preorder[preIdx]}
+        preIdx++
+        
+        root.Left = dfs(root.Val)
+        root.Right = dfs(limit)
+        
+        return root
+    }
+    
+    return dfs(math.MaxInt)
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    private var preIdx = 0
+    private var inIdx = 0
+    
+    fun buildTree(preorder: IntArray, inorder: IntArray): TreeNode? {
+        fun dfs(limit: Int): TreeNode? {
+            if (preIdx >= preorder.size) {
+                return null
+            }
+            if (inorder[inIdx] == limit) {
+                inIdx++
+                return null
+            }
+            
+            val root = TreeNode(preorder[preIdx])
+            preIdx++
+            
+            root.left = dfs(root.`val`)
+            root.right = dfs(limit)
+            
+            return root
+        }
+        
+        return dfs(Int.MAX_VALUE)
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    var preIdx = 0
+    var inIdx = 0
+
+    func buildTree(_ preorder: [Int], _ inorder: [Int]) -> TreeNode? {
+        return dfs(preorder, inorder, Int.max)
+    }
+
+    private func dfs(_ preorder: [Int], _ inorder: [Int], _ limit: Int) -> TreeNode? {
+        if preIdx >= preorder.count {
+            return nil
+        }
+        if inorder[inIdx] == limit {
+            inIdx += 1
+            return nil
+        }
+
+        let root = TreeNode(preorder[preIdx])
+        preIdx += 1
+        root.left = dfs(preorder, inorder, root.val)
+        root.right = dfs(preorder, inorder, limit)
+        return root
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n)$
-* Space complexity: $O(n)$
\ No newline at end of file
+* Space complexity: $O(n)$ for recursion stack.
\ No newline at end of file
diff --git a/articles/binary-tree-inorder-traversal.md b/articles/binary-tree-inorder-traversal.md
new file mode 100644
index 000000000..84e525d71
--- /dev/null
+++ b/articles/binary-tree-inorder-traversal.md
@@ -0,0 +1,576 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def inorderTraversal(self, root: Optional[TreeNode]) -> List[int]:
+        res = []
+
+        def inorder(node):
+            if not node:
+                return
+            
+            inorder(node.left)
+            res.append(node.val)
+            inorder(node.right)
+        
+        inorder(root)
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    private List<Integer> res;
+
+    public List<Integer> inorderTraversal(TreeNode root) {
+        res = new ArrayList<>();
+        inorder(root);
+        return res;
+    }
+
+    private void inorder(TreeNode node) {
+        if (node == null) {
+            return;
+        }
+        inorder(node.left);
+        res.add(node.val);
+        inorder(node.right);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+    vector<int> res;
+
+public:
+    vector<int> inorderTraversal(TreeNode* root) {
+        inorder(root);
+        return res;
+    }
+
+private:
+    void inorder(TreeNode* node) {
+        if (!node) {
+            return;
+        }
+        inorder(node->left);
+        res.push_back(node->val);
+        inorder(node->right);
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number[]}
+     */
+    inorderTraversal(root) {
+        const res = [];
+
+        const inorder = (node) => {
+            if (!node) return;
+            inorder(node.left);
+            res.push(node.val);
+            inorder(node.right);
+        };
+
+        inorder(root);
+        return res;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<int> InorderTraversal(TreeNode root) {
+        List<int> res = new List<int>();
+        void Inorder(TreeNode node) {
+            if (node == null) return;
+            Inorder(node.left);
+            res.Add(node.val);
+            Inorder(node.right);
+        }
+        Inorder(root);
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity:
+    * $O(n)$ space for the recursion stack.
+    * $O(n)$ space for the output array.
+
+---
+
+## 2. Iterative Depth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def inorderTraversal(self, root: Optional[TreeNode]) -> List[int]:
+        res = []
+        stack = []
+        cur = root
+
+        while cur or stack:
+            while cur:
+                stack.append(cur)
+                cur = cur.left
+            cur = stack.pop()
+            res.append(cur.val)
+            cur = cur.right
+        
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<Integer> inorderTraversal(TreeNode root) {
+        List<Integer> res = new ArrayList<>();
+        Stack<TreeNode> stack = new Stack<>();
+        TreeNode cur = root;
+
+        while (cur != null || !stack.isEmpty()) {
+            while (cur != null) {
+                stack.push(cur);
+                cur = cur.left;
+            }
+            cur = stack.pop();
+            res.add(cur.val);
+            cur = cur.right;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    vector<int> inorderTraversal(TreeNode* root) {
+        vector<int> res;
+        stack<TreeNode*> stack;
+        TreeNode* cur = root;
+
+        while (cur || !stack.empty()) {
+            while (cur) {
+                stack.push(cur);
+                cur = cur->left;
+            }
+            cur = stack.top();
+            stack.pop();
+            res.push_back(cur->val);
+            cur = cur->right;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number[]}
+     */
+    inorderTraversal(root) {
+        const res = [];
+        const stack = [];
+        let cur = root;
+
+        while (cur || stack.length > 0) {
+            while (cur) {
+                stack.push(cur);
+                cur = cur.left;
+            }
+            cur = stack.pop();
+            res.push(cur.val);
+            cur = cur.right;
+        }
+
+        return res;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public IList<int> InorderTraversal(TreeNode root) {
+        List<int> res = new List<int>();
+        Stack<TreeNode> stack = new Stack<TreeNode>();
+        TreeNode cur = root;
+
+        while (cur != null || stack.Count > 0) {
+            while (cur != null) {
+                stack.Push(cur);
+                cur = cur.left;
+            }
+            cur = stack.Pop();
+            res.Add(cur.val);
+            cur = cur.right;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity:
+    * $O(n)$ space for the stack.
+    * $O(n)$ space for the output array.
+
+---
+
+## 3. Morris Traversal
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def inorderTraversal(self, root: Optional[TreeNode]) -> List[int]:
+        res = []
+        cur = root
+
+        while cur:
+            if not cur.left:
+                res.append(cur.val)
+                cur = cur.right
+            else:
+                prev = cur.left
+                while prev.right and prev.right != cur:
+                    prev = prev.right
+
+                if not prev.right:
+                    prev.right = cur
+                    cur = cur.left
+                else:
+                    prev.right = None
+                    res.append(cur.val)
+                    cur = cur.right
+
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<Integer> inorderTraversal(TreeNode root) {
+        List<Integer> res = new ArrayList<>();
+        TreeNode cur = root;
+
+        while (cur != null) {
+            if (cur.left == null) {
+                res.add(cur.val);
+                cur = cur.right;
+            } else {
+                TreeNode prev = cur.left;
+                while (prev.right != null && prev.right != cur) {
+                    prev = prev.right;
+                }
+
+                if (prev.right == null) {
+                    prev.right = cur;
+                    cur = cur.left;
+                } else {
+                    prev.right = null;
+                    res.add(cur.val);
+                    cur = cur.right;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    vector<int> inorderTraversal(TreeNode* root) {
+        vector<int> res;
+        TreeNode* cur = root;
+
+        while (cur) {
+            if (!cur->left) {
+                res.push_back(cur->val);
+                cur = cur->right;
+            } else {
+                TreeNode* prev = cur->left;
+                while (prev->right && prev->right != cur) {
+                    prev = prev->right;
+                }
+
+                if (!prev->right) {
+                    prev->right = cur;
+                    cur = cur->left;
+                } else {
+                    prev->right = nullptr;
+                    res.push_back(cur->val);
+                    cur = cur->right;
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number[]}
+     */
+    inorderTraversal(root) {
+        const res = [];
+        let cur = root;
+
+        while (cur) {
+            if (!cur.left) {
+                res.push(cur.val);
+                cur = cur.right;
+            } else {
+                let prev = cur.left;
+                while (prev.right && prev.right !== cur) {
+                    prev = prev.right;
+                }
+
+                if (!prev.right) {
+                    prev.right = cur;
+                    cur = cur.left;
+                } else {
+                    prev.right = null;
+                    res.push(cur.val);
+                    cur = cur.right;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<int> InorderTraversal(TreeNode root) {
+        List<int> res = new List<int>();
+        TreeNode cur = root;
+
+        while (cur != null) {
+            if (cur.left == null) {
+                res.Add(cur.val);
+                cur = cur.right;
+            } else {
+                TreeNode prev = cur.left;
+                while (prev.right != null && prev.right != cur) {
+                    prev = prev.right;
+                }
+
+                if (prev.right == null) {
+                    prev.right = cur;
+                    cur = cur.left;
+                } else {
+                    prev.right = null;
+                    res.Add(cur.val);
+                    cur = cur.right;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ space for the output array.
\ No newline at end of file
diff --git a/articles/binary-tree-maximum-path-sum.md b/articles/binary-tree-maximum-path-sum.md
index 20bce94b0..ebd5467bc 100644
--- a/articles/binary-tree-maximum-path-sum.md
+++ b/articles/binary-tree-maximum-path-sum.md
@@ -205,6 +205,134 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func maxPathSum(root *TreeNode) int {
+    res := -1 << 31 
+    dfs(root, &res)
+    return res
+}
+
+func dfs(root *TreeNode, res *int) {
+    if root == nil {
+        return
+    }
+    left := getMax(root.Left)
+    right := getMax(root.Right)
+    *res = max(*res, root.Val + left + right)
+    dfs(root.Left, res)
+    dfs(root.Right, res)
+}
+
+func getMax(root *TreeNode) int {
+    if root == nil {
+        return 0
+    }
+    left := getMax(root.Left)
+    right := getMax(root.Right)
+    path := root.Val + max(left, right)
+    return max(0, path)
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    private var res = Int.MIN_VALUE
+
+    fun maxPathSum(root: TreeNode?): Int {
+        dfs(root)
+        return res
+    }
+
+    private fun dfs(root: TreeNode?) {
+        if (root == null) return
+
+        val left = getMax(root.left)
+        val right = getMax(root.right)
+        res = maxOf(res, root.`val` + left + right)
+
+        dfs(root.left)
+        dfs(root.right)
+    }
+
+    private fun getMax(root: TreeNode?): Int {
+        if (root == null) return 0
+
+        val left = getMax(root.left)
+        val right = getMax(root.right)
+        val path = root.`val` + maxOf(left, right)
+        return maxOf(0, path)
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    var res = Int.min
+
+    func maxPathSum(_ root: TreeNode?) -> Int {
+        dfs(root)
+        return res
+    }
+
+    private func dfs(_ root: TreeNode?) {
+        guard let node = root else { return }
+        let left = getMax(node.left)
+        let right = getMax(node.right)
+        res = max(res, node.val + left + right)
+        dfs(node.left)
+        dfs(node.right)
+    }
+
+    private func getMax(_ root: TreeNode?) -> Int {
+        guard let node = root else { return 0 }
+        let left = getMax(node.left)
+        let right = getMax(node.right)
+        let path = node.val + max(left, right)
+        return max(0, path)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -400,6 +528,117 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func maxPathSum(root *TreeNode) int {
+    res := []int{root.Val}
+    
+    var dfs func(node *TreeNode) int
+    dfs = func(node *TreeNode) int {
+        if node == nil {
+            return 0
+        }
+        
+        leftMax := dfs(node.Left)
+        rightMax := dfs(node.Right)
+        
+        leftMax = max(leftMax, 0)
+        rightMax = max(rightMax, 0)
+        
+        res[0] = max(res[0], node.Val+leftMax+rightMax)
+        
+        return node.Val + max(leftMax, rightMax)
+    }
+    
+    dfs(root)
+    return res[0]
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    private var res = Int.MIN_VALUE
+    
+    fun maxPathSum(root: TreeNode?): Int {
+        dfs(root)
+        return res
+    }
+    
+    private fun dfs(node: TreeNode?): Int {
+        if (node == null) {
+            return 0
+        }
+        
+        val leftMax = maxOf(dfs(node.left), 0)
+        val rightMax = maxOf(dfs(node.right), 0)
+        
+        res = maxOf(res, node.`val` + leftMax + rightMax)
+        
+        return node.`val` + maxOf(leftMax, rightMax)
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func maxPathSum(_ root: TreeNode?) -> Int {
+        var res = root!.val
+
+        func dfs(_ root: TreeNode?) -> Int {
+            guard let node = root else { return 0 }
+
+            let leftMax = max(dfs(node.left), 0)
+            let rightMax = max(dfs(node.right), 0)
+
+            res = max(res, node.val + leftMax + rightMax)
+            return node.val + max(leftMax, rightMax)
+        }
+
+        dfs(root)
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/binary-tree-postorder-traversal.md b/articles/binary-tree-postorder-traversal.md
new file mode 100644
index 000000000..8853be764
--- /dev/null
+++ b/articles/binary-tree-postorder-traversal.md
@@ -0,0 +1,822 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def postorderTraversal(self, root: Optional[TreeNode]) -> List[int]:
+        res = []
+
+        def postorder(node):
+            if not node:
+                return
+            
+            postorder(node.left)
+            postorder(node.right)
+            res.append(node.val)
+        
+        postorder(root)
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    private List<Integer> res;
+
+    public List<Integer> postorderTraversal(TreeNode root) {
+        res = new ArrayList<>();
+        postorder(root);
+        return res;
+    }
+
+    private void postorder(TreeNode node) {
+        if (node == null) {
+            return;
+        }
+        postorder(node.left);
+        postorder(node.right);
+        res.add(node.val);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+    vector<int> res;
+
+public:
+    vector<int> postorderTraversal(TreeNode* root) {
+        postorder(root);
+        return res;
+    }
+
+private:
+    void postorder(TreeNode* node) {
+        if (!node) {
+            return;
+        }
+        postorder(node->left);
+        postorder(node->right);
+        res.push_back(node->val);
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number[]}
+     */
+    postorderTraversal(root) {
+        const res = [];
+
+        const postorder = (node) => {
+            if (!node) return;
+            postorder(node.left);
+            postorder(node.right);
+            res.push(node.val);
+        };
+
+        postorder(root);
+        return res;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<int> PostorderTraversal(TreeNode root) {
+        List<int> res = new List<int>();
+
+        void Postorder(TreeNode node) {
+            if (node == null) return;
+            Postorder(node.left);
+            Postorder(node.right);
+            res.Add(node.val);
+        }
+
+        Postorder(root);
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity:
+    * $O(n)$ space for the recursion stack.
+    * $O(n)$ space for the output array.
+
+---
+
+## 2. Iterative Depth First Search - I
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def postorderTraversal(self, root: Optional[TreeNode]) -> List[int]:
+        stack = [root]
+        visit = [False]
+        res = []
+
+        while stack:
+            cur, v = stack.pop(), visit.pop()
+            if cur:
+                if v:
+                    res.append(cur.val)
+                else:
+                    stack.append(cur)
+                    visit.append(True)
+                    stack.append(cur.right)
+                    visit.append(False)
+                    stack.append(cur.left)
+                    visit.append(False)
+
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<Integer> postorderTraversal(TreeNode root) {
+        Stack<TreeNode> stack = new Stack<>();
+        Stack<Boolean> visit = new Stack<>();
+        List<Integer> res = new ArrayList<>();
+
+        stack.push(root);
+        visit.push(false);
+
+        while (!stack.isEmpty()) {
+            TreeNode cur = stack.pop();
+            boolean v = visit.pop();
+
+            if (cur != null) {
+                if (v) {
+                    res.add(cur.val);
+                } else {
+                    stack.push(cur);
+                    visit.push(true);
+                    stack.push(cur.right);
+                    visit.push(false);
+                    stack.push(cur.left);
+                    visit.push(false);
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    vector<int> postorderTraversal(TreeNode* root) {
+        stack<TreeNode*> stk;
+        stack<bool> visit;
+        vector<int> res;
+
+        stk.push(root);
+        visit.push(false);
+
+        while (!stk.empty()) {
+            TreeNode* cur = stk.top();
+            bool v = visit.top();
+            stk.pop();
+            visit.pop();
+
+            if (cur) {
+                if (v) {
+                    res.push_back(cur->val);
+                } else {
+                    stk.push(cur);
+                    visit.push(true);
+                    stk.push(cur->right);
+                    visit.push(false);
+                    stk.push(cur->left);
+                    visit.push(false);
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number[]}
+     */
+    postorderTraversal(root) {
+        const stack = [root];
+        const visit = [false];
+        const res = [];
+
+        while (stack.length) {
+            const cur = stack.pop();
+            const v = visit.pop();
+
+            if (cur) {
+                if (v) {
+                    res.push(cur.val);
+                } else {
+                    stack.push(cur);
+                    visit.push(true);
+                    stack.push(cur.right);
+                    visit.push(false);
+                    stack.push(cur.left);
+                    visit.push(false);
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<int> PostorderTraversal(TreeNode root) {
+        var stack = new Stack<TreeNode>();
+        var visit = new Stack<bool>();
+        var res = new List<int>();
+
+        stack.Push(root);
+        visit.Push(false);
+
+        while (stack.Count > 0) {
+            var cur = stack.Pop();
+            var v = visit.Pop();
+
+            if (cur != null) {
+                if (v) {
+                    res.Add(cur.val);
+                } else {
+                    stack.Push(cur);
+                    visit.Push(true);
+                    stack.Push(cur.right);
+                    visit.Push(false);
+                    stack.Push(cur.left);
+                    visit.Push(false);
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity:
+    * $O(n)$ space for the stacks.
+    * $O(n)$ space for the output array.
+
+---
+
+## 3. Iterative Depth First Search - II
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def postorderTraversal(self, root: Optional[TreeNode]) -> List[int]:
+        res = []
+        stack = []
+        cur = root
+
+        while cur or stack:
+            if cur:
+                res.append(cur.val)
+                stack.append(cur)
+                cur = cur.right
+            else:
+                cur = stack.pop()
+                cur = cur.left
+
+        res.reverse()
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<Integer> postorderTraversal(TreeNode root) {
+        List<Integer> res = new ArrayList<>();
+        Stack<TreeNode> stack = new Stack<>();
+        TreeNode cur = root;
+
+        while (cur != null || !stack.isEmpty()) {
+            if (cur != null) {
+                res.add(cur.val);
+                stack.push(cur);
+                cur = cur.right;
+            } else {
+                cur = stack.pop();
+                cur = cur.left;
+            }
+        }
+
+        Collections.reverse(res);
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    vector<int> postorderTraversal(TreeNode* root) {
+        vector<int> res;
+        stack<TreeNode*> stack;
+        TreeNode* cur = root;
+
+        while (cur || !stack.empty()) {
+            if (cur) {
+                res.push_back(cur->val);
+                stack.push(cur);
+                cur = cur->right;
+            } else {
+                cur = stack.top();
+                stack.pop();
+                cur = cur->left;
+            }
+        }
+
+        reverse(res.begin(), res.end());
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number[]}
+     */
+    postorderTraversal(root) {
+        const res = [];
+        const stack = [];
+        let cur = root;
+
+        while (cur || stack.length) {
+            if (cur) {
+                res.push(cur.val);
+                stack.push(cur);
+                cur = cur.right;
+            } else {
+                cur = stack.pop();
+                cur = cur.left;
+            }
+        }
+
+        res.reverse();
+        return res;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<int> PostorderTraversal(TreeNode root) {
+        List<int> res = new List<int>();
+        Stack<TreeNode> stack = new Stack<TreeNode>();
+        TreeNode cur = root;
+
+        while (cur != null || stack.Count > 0) {
+            if (cur != null) {
+                res.Add(cur.val);
+                stack.Push(cur);
+                cur = cur.right;
+            } else {
+                cur = stack.Pop();
+                cur = cur.left;
+            }
+        }
+
+        res.Reverse();
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity:
+    * $O(n)$ space for the stack.
+    * $O(n)$ space for the output array.
+
+---
+
+## 4. Morris Traversal
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def postorderTraversal(self, root: Optional[TreeNode]) -> List[int]:
+        res = []
+        cur = root
+
+        while cur:
+            if not cur.right:
+                res.append(cur.val)
+                cur = cur.left
+            else:
+                prev = cur.right
+                while prev.left and prev.left != cur:
+                    prev = prev.left
+
+                if not prev.left:
+                    res.append(cur.val)
+                    prev.left = cur
+                    cur = cur.right
+                else:
+                    prev.left = None
+                    cur = cur.left
+                    
+        res.reverse()
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<Integer> postorderTraversal(TreeNode root) {
+        List<Integer> res = new ArrayList<>();
+        TreeNode cur = root;
+
+        while (cur != null) {
+            if (cur.right == null) {
+                res.add(cur.val);
+                cur = cur.left;
+            } else {
+                TreeNode prev = cur.right;
+                while (prev.left != null && prev.left != cur) {
+                    prev = prev.left;
+                }
+
+                if (prev.left == null) {
+                    res.add(cur.val);
+                    prev.left = cur;
+                    cur = cur.right;
+                } else {
+                    prev.left = null;
+                    cur = cur.left;
+                }
+            }
+        }
+
+        Collections.reverse(res);
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    vector<int> postorderTraversal(TreeNode* root) {
+        vector<int> res;
+        TreeNode* cur = root;
+
+        while (cur) {
+            if (!cur->right) {
+                res.push_back(cur->val);
+                cur = cur->left;
+            } else {
+                TreeNode* prev = cur->right;
+                while (prev->left && prev->left != cur) {
+                    prev = prev->left;
+                }
+
+                if (!prev->left) {
+                    res.push_back(cur->val);
+                    prev->left = cur;
+                    cur = cur->right;
+                } else {
+                    prev->left = nullptr;
+                    cur = cur->left;
+                }
+            }
+        }
+
+        reverse(res.begin(), res.end());
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number[]}
+     */
+    postorderTraversal(root) {
+        const res = [];
+        let cur = root;
+
+        while (cur) {
+            if (!cur.right) {
+                res.push(cur.val);
+                cur = cur.left;
+            } else {
+                let prev = cur.right;
+                while (prev.left && prev.left !== cur) {
+                    prev = prev.left;
+                }
+
+                if (!prev.left) {
+                    res.push(cur.val);
+                    prev.left = cur;
+                    cur = cur.right;
+                } else {
+                    prev.left = null;
+                    cur = cur.left;
+                }
+            }
+        }
+
+        res.reverse();
+        return res;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<int> PostorderTraversal(TreeNode root) {
+        List<int> res = new List<int>();
+        TreeNode cur = root;
+
+        while (cur != null) {
+            if (cur.right == null) {
+                res.Add(cur.val);
+                cur = cur.left;
+            } else {
+                TreeNode prev = cur.right;
+                while (prev.left != null && prev.left != cur) {
+                    prev = prev.left;
+                }
+
+                if (prev.left == null) {
+                    res.Add(cur.val);
+                    prev.left = cur;
+                    cur = cur.right;
+                } else {
+                    prev.left = null;
+                    cur = cur.left;
+                }
+            }
+        }
+
+        res.Reverse();
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ space for the output array.
\ No newline at end of file
diff --git a/articles/binary-tree-preorder-traversal.md b/articles/binary-tree-preorder-traversal.md
new file mode 100644
index 000000000..f7f86ffb9
--- /dev/null
+++ b/articles/binary-tree-preorder-traversal.md
@@ -0,0 +1,579 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def preorderTraversal(self, root: Optional[TreeNode]) -> List[int]:
+        res = []
+
+        def preorder(node):
+            if not node:
+                return
+            
+            res.append(node.val)
+            preorder(node.left)
+            preorder(node.right)
+        
+        preorder(root)
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    private List<Integer> res;
+
+    public List<Integer> preorderTraversal(TreeNode root) {
+        res = new ArrayList<>();
+        preorder(root);
+        return res;
+    }
+
+    private void preorder(TreeNode node) {
+        if (node == null) {
+            return;
+        }
+        res.add(node.val);
+        preorder(node.left);
+        preorder(node.right);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+    vector<int> res;
+
+public:
+    vector<int> preorderTraversal(TreeNode* root) {
+        preorder(root);
+        return res;
+    }
+
+private:
+    void preorder(TreeNode* node) {
+        if (!node) {
+            return;
+        }
+        res.push_back(node->val);
+        preorder(node->left);
+        preorder(node->right);
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number[]}
+     */
+    preorderTraversal(root) {
+        const res = [];
+
+        const preorder = (node) => {
+            if (!node) return;
+            res.push(node.val);
+            preorder(node.left);
+            preorder(node.right);
+        };
+
+        preorder(root);
+        return res;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<int> PreorderTraversal(TreeNode root) {
+        List<int> res = new List<int>();
+        Preorder(root, res);
+        return res;
+    }
+
+    private void Preorder(TreeNode node, List<int> res) {
+        if (node == null) return;
+
+        res.Add(node.val);
+        Preorder(node.left, res);
+        Preorder(node.right, res);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity:
+    * $O(n)$ space for the recursion stack.
+    * $O(n)$ space for the output array.
+
+---
+
+## 2. Iterative Depth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def preorderTraversal(self, root: Optional[TreeNode]) -> List[int]:
+        res = []
+        stack = []
+        cur = root
+
+        while cur or stack:
+            if cur:
+                res.append(cur.val)
+                stack.append(cur.right)
+                cur = cur.left
+            else:
+                cur = stack.pop()
+        
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<Integer> preorderTraversal(TreeNode root) {
+        List<Integer> res = new ArrayList<>();
+        Stack<TreeNode> stack = new Stack<>();
+        TreeNode cur = root;
+
+        while (cur != null || !stack.isEmpty()) {
+            if (cur != null) {
+                res.add(cur.val);
+                stack.push(cur.right);
+                cur = cur.left;
+            } else {
+                cur = stack.pop();
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    vector<int> preorderTraversal(TreeNode* root) {
+        vector<int> res;
+        stack<TreeNode*> stack;
+        TreeNode* cur = root;
+
+        while (cur || !stack.empty()) {
+            if (cur) {
+                res.push_back(cur->val);
+                stack.push(cur->right);
+                cur = cur->left;
+            } else {
+                cur = stack.top();
+                stack.pop();
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number[]}
+     */
+    preorderTraversal(root) {
+        const res = [];
+        const stack = [];
+        let cur = root;
+
+        while (cur || stack.length > 0) {
+            if (cur) {
+                res.push(cur.val);
+                stack.push(cur.right);
+                cur = cur.left;
+            } else {
+                cur = stack.pop();
+
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<int> PreorderTraversal(TreeNode root) {
+        List<int> res = new List<int>();
+        Stack<TreeNode> stack = new Stack<TreeNode>();
+        TreeNode cur = root;
+
+        while (cur != null || stack.Count > 0) {
+            if (cur != null) {
+                res.Add(cur.val);
+                stack.Push(cur.right);
+                cur = cur.left;
+            } else {
+                cur = stack.Pop();
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity:
+    * $O(n)$ space for the stack.
+    * $O(n)$ space for the output array.
+
+---
+
+## 3. Morris Traversal
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def preorderTraversal(self, root: Optional[TreeNode]) -> List[int]:
+        res = []
+        cur = root
+
+        while cur:
+            if not cur.left:
+                res.append(cur.val)
+                cur = cur.right
+            else:
+                prev = cur.left
+                while prev.right and prev.right != cur:
+                    prev = prev.right
+
+                if not prev.right:
+                    res.append(cur.val)
+                    prev.right = cur
+                    cur = cur.left
+                else:
+                    prev.right = None
+                    cur = cur.right
+
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<Integer> preorderTraversal(TreeNode root) {
+        List<Integer> res = new ArrayList<>();
+        TreeNode cur = root;
+
+        while (cur != null) {
+            if (cur.left == null) {
+                res.add(cur.val);
+                cur = cur.right;
+            } else {
+                TreeNode prev = cur.left;
+                while (prev.right != null && prev.right != cur) {
+                    prev = prev.right;
+                }
+
+                if (prev.right == null) {
+                    res.add(cur.val);
+                    prev.right = cur;
+                    cur = cur.left;
+                } else {
+                    prev.right = null;
+                    cur = cur.right;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    vector<int> preorderTraversal(TreeNode* root) {
+        vector<int> res;
+        TreeNode* cur = root;
+
+        while (cur) {
+            if (!cur->left) {
+                res.push_back(cur->val);
+                cur = cur->right;
+            } else {
+                TreeNode* prev = cur->left;
+                while (prev->right && prev->right != cur) {
+                    prev = prev->right;
+                }
+
+                if (!prev->right) {
+                    res.push_back(cur->val);
+                    prev->right = cur;
+                    cur = cur->left;
+                } else {
+                    prev->right = nullptr;
+                    cur = cur->right;
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number[]}
+     */
+    preorderTraversal(root) {
+        const res = [];
+        let cur = root;
+
+        while (cur) {
+            if (!cur.left) {
+                res.push(cur.val);
+                cur = cur.right;
+            } else {
+                let prev = cur.left;
+                while (prev.right && prev.right !== cur) {
+                    prev = prev.right;
+                }
+
+                if (!prev.right) {
+                    res.push(cur.val);
+                    prev.right = cur;
+                    cur = cur.left;
+                } else {
+                    prev.right = null;
+                    cur = cur.right;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<int> PreorderTraversal(TreeNode root) {
+        List<int> res = new List<int>();
+        TreeNode cur = root;
+
+        while (cur != null) {
+            if (cur.left == null) {
+                res.Add(cur.val);
+                cur = cur.right;
+            } else {
+                TreeNode prev = cur.left;
+                while (prev.right != null && prev.right != cur) {
+                    prev = prev.right;
+                }
+
+                if (prev.right == null) {
+                    res.Add(cur.val);
+                    prev.right = cur;
+                    cur = cur.left;
+                } else {
+                    prev.right = null;
+                    cur = cur.right;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ space for the output array.
\ No newline at end of file
diff --git a/articles/binary-tree-right-side-view.md b/articles/binary-tree-right-side-view.md
index 406f9295e..4d8a68b19 100644
--- a/articles/binary-tree-right-side-view.md
+++ b/articles/binary-tree-right-side-view.md
@@ -177,6 +177,101 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func rightSideView(root *TreeNode) []int {
+    var res []int
+
+    var dfs func(node *TreeNode, depth int)
+    dfs = func(node *TreeNode, depth int) {
+        if node == nil {
+            return
+        }
+        if depth == len(res) {
+            res = append(res, node.Val)
+        }
+        dfs(node.Right, depth+1)
+        dfs(node.Left, depth+1)
+    }
+    
+    dfs(root, 0)
+    return res
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    fun rightSideView(root: TreeNode?): List<Int> {
+        val res = mutableListOf<Int>()
+
+        fun dfs(node: TreeNode?, depth: Int) {
+            if (node == null) return
+            if (depth == res.size) {
+                res.add(node.`val`)
+            }
+            dfs(node.right, depth + 1)
+            dfs(node.left, depth + 1)
+        }
+
+        dfs(root, 0)
+        return res
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func rightSideView(_ root: TreeNode?) -> [Int] {
+        var res = [Int]()
+
+        func dfs(_ node: TreeNode?, _ depth: Int) {
+            guard let node = node else { return }
+            if depth == res.count {
+                res.append(node.val)
+            }
+
+            dfs(node.right, depth + 1)
+            dfs(node.left, depth + 1)
+        }
+
+        dfs(root, 0)
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -390,6 +485,129 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func rightSideView(root *TreeNode) []int {
+    if root == nil {
+        return []int{}
+    }
+    
+    res := []int{}
+    q := []*TreeNode{root}
+
+    for len(q) > 0 {
+        rightSide := 0
+        qLen := len(q)
+
+        for i := 0; i < qLen; i++ {
+            node := q[0]
+            q = q[1:]
+            
+            if node != nil {
+                rightSide = node.Val
+                if node.Left != nil {
+                    q = append(q, node.Left)
+                }
+                if node.Right != nil {
+                    q = append(q, node.Right)
+                }
+            }
+        }
+        res = append(res, rightSide)
+    }
+    
+    return res
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    fun rightSideView(root: TreeNode?): List<Int> {
+        if (root == null) return emptyList()
+
+        val res = mutableListOf<Int>()
+        val q = ArrayDeque(listOf(root))
+
+        while (q.isNotEmpty()) {
+            var rightSide: TreeNode? = null
+            var qLen = q.size
+
+            while (qLen > 0) {
+                val node = q.removeFirst()
+                if (node != null) {
+                    rightSide = node
+                    node.left?.let { q.add(it) }
+                    node.right?.let { q.add(it) }
+                }
+                qLen--
+            }
+            rightSide?.let { res.add(it.`val`) }
+        }
+        
+        return res
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func rightSideView(_ root: TreeNode?) -> [Int] {
+        var res = [Int]()
+        var q = Deque<TreeNode?>()
+        q.append(root)
+
+        while !q.isEmpty {
+            var rightSide: TreeNode?
+            let qLen = q.count
+
+            for _ in 0..<qLen {
+                if let node = q.removeFirst() {
+                    rightSide = node
+                    q.append(node.left)
+                    q.append(node.right)
+                }
+            }
+            if let rightSide = rightSide {
+                res.append(rightSide.val)
+            }
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/binary-tree-vertical-order-traversal.md b/articles/binary-tree-vertical-order-traversal.md
new file mode 100644
index 000000000..c66e08d0b
--- /dev/null
+++ b/articles/binary-tree-vertical-order-traversal.md
@@ -0,0 +1,837 @@
+## 1. Breadth First Search + Sorting
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def verticalOrder(self, root: Optional[TreeNode]) -> List[List[int]]:
+        cols = defaultdict(list)
+        que = deque([(root, 0)])
+
+        while que:
+            node, pos = que.popleft()
+            if node:
+                cols[pos].append(node.val)
+                que.append((node.left, pos - 1))
+                que.append((node.right, pos + 1))
+
+        return [cols[x] for x in sorted(cols)]
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<List<Integer>> verticalOrder(TreeNode root) {
+        if (root == null) return new ArrayList<>();
+
+        Map<Integer, List<Integer>> cols = new TreeMap<>();
+        Queue<Pair<TreeNode, Integer>> queue = new LinkedList<>();
+        queue.offer(new Pair<>(root, 0));
+
+        while (!queue.isEmpty()) {
+            Pair<TreeNode, Integer> p = queue.poll();
+            TreeNode node = p.getKey();
+            int pos = p.getValue();
+
+            cols.computeIfAbsent(pos, k -> new ArrayList<>()).add(node.val);
+
+            if (node.left != null) queue.offer(new Pair<>(node.left, pos - 1));
+            if (node.right != null) queue.offer(new Pair<>(node.right, pos + 1));
+        }
+
+        return new ArrayList<>(cols.values());
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    vector<vector<int>> verticalOrder(TreeNode* root) {
+        if (!root) return {};
+        map<int, vector<int>> cols;
+        queue<pair<TreeNode*, int>> q;
+        q.push({root, 0});
+
+        while (!q.empty()) {
+            auto [node, pos] = q.front(); q.pop();
+            cols[pos].push_back(node->val);
+            if (node->left) q.push({node->left, pos - 1});
+            if (node->right) q.push({node->right, pos + 1});
+        }
+
+        vector<vector<int>> res;
+        for (auto& [_, vec] : cols)
+            res.push_back(vec);
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number[][]}
+     */
+    verticalOrder(root) {
+        if (!root) return [];
+
+        const cols = new Map();
+        const queue = new Queue([[root, 0]]);
+
+        while (!queue.isEmpty()) {
+            const [node, pos] = queue.pop();
+            if (!cols.has(pos)) cols.set(pos, []);
+            cols.get(pos).push(node.val);
+
+            if (node.left) queue.push([node.left, pos - 1]);
+            if (node.right) queue.push([node.right, pos + 1]);
+        }
+
+        const sortedKeys = Array.from(cols.keys()).sort((a, b) => a - b);
+        return sortedKeys.map(k => cols.get(k));
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<List<int>> VerticalOrder(TreeNode root) {
+        if (root == null) return new List<List<int>>();
+
+        var cols = new SortedDictionary<int, List<int>>();
+        var queue = new Queue<(TreeNode node, int pos)>();
+        queue.Enqueue((root, 0));
+
+        while (queue.Count > 0) {
+            var (node, pos) = queue.Dequeue();
+
+            if (!cols.ContainsKey(pos))
+                cols[pos] = new List<int>();
+            cols[pos].Add(node.val);
+
+            if (node.left != null) queue.Enqueue((node.left, pos - 1));
+            if (node.right != null) queue.Enqueue((node.right, pos + 1));
+        }
+
+        return cols.Values.ToList<List<int>>();
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Depth First Search + Sorting
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def verticalOrder(self, root: Optional[TreeNode]) -> List[List[int]]:
+        cols = defaultdict(list)
+
+        def dfs(node, row, col):
+            if not node:
+                return
+            cols[col].append((row, node.val))
+            dfs(node.left, row + 1, col - 1)
+            dfs(node.right, row + 1, col + 1)
+
+        dfs(root, 0, 0)
+
+        res = []
+        for col in sorted(cols):
+            col_vals = sorted(cols[col], key=lambda x: x[0])
+            res.append([val for _, val in col_vals])
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    private Map<Integer, List<int[]>> cols = new TreeMap<>();
+
+    public List<List<Integer>> verticalOrder(TreeNode root) {
+        dfs(root, 0, 0);
+        List<List<Integer>> res = new ArrayList<>();
+
+        for (List<int[]> list : cols.values()) {
+            list.sort(Comparator.comparingInt(a -> a[0]));
+            List<Integer> colVals = new ArrayList<>();
+            for (int[] p : list) colVals.add(p[1]);
+            res.add(colVals);
+        }
+
+        return res;
+    }
+
+    private void dfs(TreeNode node, int row, int col) {
+        if (node == null) return;
+        cols.computeIfAbsent(col, k -> new ArrayList<>()).add(new int[]{row, node.val});
+        dfs(node.left, row + 1, col - 1);
+        dfs(node.right, row + 1, col + 1);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+    map<int, vector<pair<int, int>>> cols;
+
+    void dfs(TreeNode* node, int row, int col) {
+        if (!node) return;
+        cols[col].push_back({row, node->val});
+        dfs(node->left, row + 1, col - 1);
+        dfs(node->right, row + 1, col + 1);
+    }
+
+public:
+    vector<vector<int>> verticalOrder(TreeNode* root) {
+        dfs(root, 0, 0);
+        vector<vector<int>> res;
+
+        for (auto& [col, vec] : cols) {
+            stable_sort(vec.begin(), vec.end(),
+                        [](const pair<int, int>& a, const pair<int, int>& b) {
+                            return a.first < b.first;  // sort ONLY by row
+                        });
+
+            vector<int> colVals;
+            for (auto& [_, val] : vec)
+                colVals.push_back(val);
+            res.push_back(colVals);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number[][]}
+     */
+    verticalOrder(root) {
+        const cols = new Map();
+
+        const dfs = (node, row, col) => {
+            if (!node) return;
+            if (!cols.has(col)) cols.set(col, []);
+            cols.get(col).push([row, node.val]);
+            dfs(node.left, row + 1, col - 1);
+            dfs(node.right, row + 1, col + 1);
+        };
+
+        dfs(root, 0, 0);
+
+        const sortedCols = Array.from(cols.entries()).sort((a, b) => a[0] - b[0]);
+        return sortedCols.map(([_, vec]) =>
+            vec.sort((a, b) => a[0] - b[0]).map(([_, val]) => val)
+        );
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    private SortedDictionary<int, List<(int, int)>> cols = new();
+
+    public List<List<int>> VerticalOrder(TreeNode root) {
+        DFS(root, 0, 0);
+
+        List<List<int>> res = new();
+        foreach (var entry in cols) {
+            var list = entry.Value.OrderBy(x => x.Item1).Select(x => x.Item2).ToList();
+            res.Add(list);
+        }
+
+        return res;
+    }
+
+    private void DFS(TreeNode node, int row, int col) {
+        if (node == null) return;
+        if (!cols.ContainsKey(col)) cols[col] = new List<(int, int)>();
+        cols[col].Add((row, node.val));
+        DFS(node.left, row + 1, col - 1);
+        DFS(node.right, row + 1, col + 1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n \log n)$
+
+---
+
+## 3. Breadth First Search (Optimal)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def verticalOrder(self, root: Optional[TreeNode]) -> List[List[int]]:
+        if not root:
+            return []
+
+        cols = defaultdict(list)
+        queue = deque([(root, 0)])
+        minCol = maxCol = 0
+
+        while queue:
+            node, col = queue.popleft()
+            cols[col].append(node.val)
+            minCol = min(minCol, col)
+            maxCol = max(maxCol, col)
+
+            if node.left:
+                queue.append((node.left, col - 1))
+            if node.right:
+                queue.append((node.right, col + 1))
+
+        return [cols[c] for c in range(minCol, maxCol + 1)]
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<List<Integer>> verticalOrder(TreeNode root) {
+        if (root == null) return new ArrayList<>();
+
+        Map<Integer, List<Integer>> cols = new HashMap<>();
+        Queue<Pair<TreeNode, Integer>> queue = new LinkedList<>();
+        queue.offer(new Pair<>(root, 0));
+        int minCol = 0, maxCol = 0;
+
+        while (!queue.isEmpty()) {
+            Pair<TreeNode, Integer> p = queue.poll();
+            TreeNode node = p.getKey();
+            int col = p.getValue();
+
+            cols.computeIfAbsent(col, x -> new ArrayList<>()).add(node.val);
+            minCol = Math.min(minCol, col);
+            maxCol = Math.max(maxCol, col);
+
+            if (node.left != null) queue.offer(new Pair<>(node.left, col - 1));
+            if (node.right != null) queue.offer(new Pair<>(node.right, col + 1));
+        }
+
+        List<List<Integer>> res = new ArrayList<>();
+        for (int c = minCol; c <= maxCol; c++) {
+            res.add(cols.get(c));
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    vector<vector<int>> verticalOrder(TreeNode* root) {
+        if (!root) return {};
+
+        unordered_map<int, vector<int>> cols;
+        queue<pair<TreeNode*, int>> q;
+        q.push({root, 0});
+        int minCol = 0, maxCol = 0;
+
+        while (!q.empty()) {
+            auto [node, col] = q.front(); q.pop();
+            cols[col].push_back(node->val);
+            minCol = min(minCol, col);
+            maxCol = max(maxCol, col);
+
+            if (node->left) q.push({node->left, col - 1});
+            if (node->right) q.push({node->right, col + 1});
+        }
+
+        vector<vector<int>> res;
+        for (int c = minCol; c <= maxCol; ++c)
+            res.push_back(cols[c]);
+
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number[][]}
+     */
+    verticalOrder(root) {
+        if (!root) return [];
+
+        const cols = new Map();
+        const queue = new Queue([[root, 0]]);
+        let minCol = 0, maxCol = 0;
+
+        while (!queue.isEmpty()) {
+            const [node, col] = queue.pop();
+            if (!cols.has(col)) cols.set(col, []);
+            cols.get(col).push(node.val);
+            minCol = Math.min(minCol, col);
+            maxCol = Math.max(maxCol, col);
+
+            if (node.left) queue.push([node.left, col - 1]);
+            if (node.right) queue.push([node.right, col + 1]);
+        }
+
+        const res = [];
+        for (let c = minCol; c <= maxCol; c++) {
+            res.push(cols.get(c));
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<List<int>> VerticalOrder(TreeNode root) {
+        if (root == null) return new List<List<int>>();
+
+        Dictionary<int, List<int>> cols = new();
+        Queue<(TreeNode node, int col)> queue = new();
+        queue.Enqueue((root, 0));
+        int minCol = 0, maxCol = 0;
+
+        while (queue.Count > 0) {
+            var (node, col) = queue.Dequeue();
+            if (!cols.ContainsKey(col))
+                cols[col] = new List<int>();
+            cols[col].Add(node.val);
+            minCol = Math.Min(minCol, col);
+            maxCol = Math.Max(maxCol, col);
+
+            if (node.left != null) queue.Enqueue((node.left, col - 1));
+            if (node.right != null) queue.Enqueue((node.right, col + 1));
+        }
+
+        var res = new List<List<int>>();
+        for (int c = minCol; c <= maxCol; c++) {
+            res.Add(cols[c]);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Depth First Search (Optimal)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def verticalOrder(self, root: Optional[TreeNode]) -> List[List[int]]:
+        if not root:
+            return []
+
+        cols = defaultdict(list)
+        minCol = maxCol = 0
+
+        def dfs(node, row, col):
+            nonlocal minCol, maxCol
+            if not node:
+                return
+            cols[col].append((row, node.val))
+            minCol = min(minCol, col)
+            maxCol = max(maxCol, col)
+            dfs(node.left, row + 1, col - 1)
+            dfs(node.right, row + 1, col + 1)
+
+        dfs(root, 0, 0)
+
+        res = []
+        for c in range(minCol, maxCol + 1):
+            # sort by row only
+            col_vals = sorted(cols[c], key=lambda x: x[0])
+            res.append([val for _, val in col_vals])
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    private Map<Integer, List<int[]>> cols = new HashMap<>();
+    private int minCol = 0, maxCol = 0;
+
+    public List<List<Integer>> verticalOrder(TreeNode root) {
+        if (root == null) return new ArrayList<>();
+        dfs(root, 0, 0);
+
+        List<List<Integer>> res = new ArrayList<>();
+        for (int c = minCol; c <= maxCol; c++) {
+            List<int[]> list = cols.getOrDefault(c, new ArrayList<>());
+            list.sort(Comparator.comparingInt(a -> a[0])); // sort by row
+            List<Integer> colVals = new ArrayList<>();
+            for (int[] p : list) colVals.add(p[1]);
+            res.add(colVals);
+        }
+        return res;
+    }
+
+    private void dfs(TreeNode node, int row, int col) {
+        if (node == null) return;
+        cols.computeIfAbsent(col, k -> new ArrayList<>()).add(new int[]{row, node.val});
+        minCol = Math.min(minCol, col);
+        maxCol = Math.max(maxCol, col);
+        dfs(node.left, row + 1, col - 1);
+        dfs(node.right, row + 1, col + 1);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+    unordered_map<int, vector<pair<int, int>>> cols;
+    int minCol = 0, maxCol = 0;
+
+    void dfs(TreeNode* node, int row, int col) {
+        if (!node) return;
+        cols[col].emplace_back(row, node->val);
+        minCol = min(minCol, col);
+        maxCol = max(maxCol, col);
+        dfs(node->left, row + 1, col - 1);
+        dfs(node->right, row + 1, col + 1);
+    }
+
+public:
+    vector<vector<int>> verticalOrder(TreeNode* root) {
+        if (!root) return {};
+        dfs(root, 0, 0);
+        vector<vector<int>> res;
+
+        for (int c = minCol; c <= maxCol; ++c) {
+            auto& vec = cols[c];
+            stable_sort(vec.begin(), vec.end(),
+                        [](const pair<int, int>& a, const pair<int, int>& b) {
+                            return a.first < b.first; // sort by row only
+                        });
+            vector<int> colVals;
+            for (auto& [_, val] : vec)
+                colVals.push_back(val);
+            res.push_back(colVals);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number[][]}
+     */
+    verticalOrder(root) {
+        if (!root) return [];
+
+        const cols = new Map();
+        let minCol = 0, maxCol = 0;
+
+        const dfs = (node, row, col) => {
+            if (!node) return;
+            if (!cols.has(col)) cols.set(col, []);
+            cols.get(col).push([row, node.val]);
+            minCol = Math.min(minCol, col);
+            maxCol = Math.max(maxCol, col);
+            dfs(node.left, row + 1, col - 1);
+            dfs(node.right, row + 1, col + 1);
+        };
+
+        dfs(root, 0, 0);
+
+        const res = [];
+        for (let c = minCol; c <= maxCol; c++) {
+            let entries = cols.get(c) || [];
+            entries.sort((a, b) => a[0] - b[0]); // sort by row only
+            res.push(entries.map(([_, val]) => val));
+        }
+
+        return res;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    private Dictionary<int, List<(int, int)>> cols = new();
+    private int minCol = 0, maxCol = 0;
+
+    public List<List<int>> VerticalOrder(TreeNode root) {
+        if (root == null) return new List<List<int>>();
+        DFS(root, 0, 0);
+        var res = new List<List<int>>();
+
+        for (int c = minCol; c <= maxCol; c++) {
+            var list = cols.ContainsKey(c) ? cols[c] : new List<(int, int)>();
+            list.Sort((a, b) => a.Item1.CompareTo(b.Item1)); // sort by row
+            res.Add(list.Select(p => p.Item2).ToList());
+        }
+
+        return res;
+    }
+
+    private void DFS(TreeNode node, int row, int col) {
+        if (node == null) return;
+        if (!cols.ContainsKey(col)) cols[col] = new List<(int, int)>();
+        cols[col].Add((row, node.val));
+        minCol = Math.Min(minCol, col);
+        maxCol = Math.Max(maxCol, col);
+        DFS(node.left, row + 1, col - 1);
+        DFS(node.right, row + 1, col + 1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(w * h \log h)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the number of nodes, $h$ is the height of the tree (i.e. maximum number of nodes in any vertical line of the tree), and $w$ is the width of the tree (i.e. maximum number of nodes in any of the levels of the tree).
\ No newline at end of file
diff --git a/articles/binary-tree-zigzag-level-order-traversal.md b/articles/binary-tree-zigzag-level-order-traversal.md
new file mode 100644
index 000000000..d41aac9cd
--- /dev/null
+++ b/articles/binary-tree-zigzag-level-order-traversal.md
@@ -0,0 +1,647 @@
+## 1. Breadth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def zigzagLevelOrder(self, root: Optional[TreeNode]) -> List[List[int]]:
+        res = []
+        q = deque([root] if root else [])
+        while q:
+            level = []
+            for i in range(len(q)):
+                node = q.popleft()
+                level.append(node.val)
+                if node.left:
+                    q.append(node.left)
+                if node.right:
+                    q.append(node.right)
+            if len(res) % 2:
+                level.reverse()
+            res.append(level)
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<List<Integer>> zigzagLevelOrder(TreeNode root) {
+        List<List<Integer>> res = new ArrayList<>();
+        if (root == null) return res;
+
+        Queue<TreeNode> q = new LinkedList<>();
+        q.offer(root);
+
+        while (!q.isEmpty()) {
+            List<Integer> level = new ArrayList<>();
+            for (int i = q.size(); i > 0; i--) {
+                TreeNode node = q.poll();
+                level.add(node.val);
+                if (node.left != null) q.offer(node.left);
+                if (node.right != null) q.offer(node.right);
+            }
+            if (res.size() % 2 != 0) Collections.reverse(level);
+            res.add(level);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    vector<vector<int>> zigzagLevelOrder(TreeNode* root) {
+        vector<vector<int>> res;
+        if (!root) return res;
+
+        queue<TreeNode*> q;
+        q.push(root);
+
+        while (!q.empty()) {
+            vector<int> level;
+            for (int i = q.size(); i > 0; i--) {
+                TreeNode* node = q.front();
+                q.pop();
+                level.push_back(node->val);
+                if (node->left) q.push(node->left);
+                if (node->right) q.push(node->right);
+            }
+            if (res.size() % 2) reverse(level.begin(), level.end());
+            res.push_back(level);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number[][]}
+     */
+    zigzagLevelOrder(root) {
+        const res = [];
+        if (!root) return res;
+
+        const queue = new Queue([root]);
+
+        while (!queue.isEmpty()) {
+            const level = [];
+            for (let i = queue.size(); i > 0; i--) {
+                const node = queue.pop();
+                level.push(node.val);
+                if (node.left) queue.push(node.left);
+                if (node.right) queue.push(node.right);
+            }
+            if (res.length % 2 !== 0) level.reverse();
+            res.push(level);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Breadth First Search (Optimal)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def zigzagLevelOrder(self, root: Optional[TreeNode]) -> List[List[int]]:
+        res = []
+        q = deque([root] if root else [])
+        while q:
+            size = len(q)
+            level = [0] * size
+            for i in range(size):
+                node = q.popleft()
+                idx = size - i - 1 if len(res) % 2 else i
+                level[idx] = node.val
+                if node.left:
+                    q.append(node.left)
+                if node.right:
+                    q.append(node.right)
+            res.append(level)
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<List<Integer>> zigzagLevelOrder(TreeNode root) {
+        List<List<Integer>> res = new ArrayList<>();
+        if (root == null) return res;
+
+        Queue<TreeNode> q = new LinkedList<>();
+        q.offer(root);
+
+        while (!q.isEmpty()) {
+            int size = q.size();
+            Integer[] level = new Integer[size];
+            for (int i = 0; i < size; i++) {
+                TreeNode node = q.poll();
+                int idx = (res.size() % 2 == 0) ? i : size - i - 1;
+                level[idx] = node.val;
+                if (node.left != null) q.offer(node.left);
+                if (node.right != null) q.offer(node.right);
+            }
+            res.add(Arrays.asList(level));
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    vector<vector<int>> zigzagLevelOrder(TreeNode* root) {
+        vector<vector<int>> res;
+        if (!root) return res;
+
+        queue<TreeNode*> q;
+        q.push(root);
+
+        while (!q.empty()) {
+            int size = q.size();
+            vector<int> level(size);
+            for (int i = 0; i < size; ++i) {
+                TreeNode* node = q.front();
+                q.pop();
+                int idx = (res.size() % 2 == 0) ? i : size - i - 1;
+                level[idx] = node->val;
+                if (node->left) q.push(node->left);
+                if (node->right) q.push(node->right);
+            }
+            res.push_back(level);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number[][]}
+     */
+    zigzagLevelOrder(root) {
+        const res = [];
+        if (!root) return res;
+
+        const q = new Queue([root]);
+
+        while (!q.isEmpty()) {
+            const size = q.size();
+            const level = Array(size).fill(0);
+
+            for (let i = 0; i < size; i++) {
+                const node = q.pop();
+                const idx = res.length % 2 === 0 ? i : size - i - 1;
+                level[idx] = node.val;
+                if (node.left) q.push(node.left);
+                if (node.right) q.push(node.right);
+            }
+            res.push(level);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Depth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def zigzagLevelOrder(self, root: Optional[TreeNode]) -> List[List[int]]:
+        res = []
+
+        def dfs(node, depth):
+            if not node:
+                return
+            if depth == len(res):
+                res.append([])
+            res[depth].append(node.val)
+            dfs(node.left, depth + 1)
+            dfs(node.right, depth + 1)
+        
+        dfs(root, 0)
+        for i, level in enumerate(res):
+            if i & 1:
+                level.reverse()
+        
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<List<Integer>> zigzagLevelOrder(TreeNode root) {
+        List<List<Integer>> res = new ArrayList<>();
+        dfs(root, 0, res);
+        for (int i = 0; i < res.size(); i++) {
+            if ((i & 1) == 1) {
+                Collections.reverse(res.get(i));
+            }
+        }
+        return res;
+    }
+
+    private void dfs(TreeNode node, int depth, List<List<Integer>> res) {
+        if (node == null) return;
+        if (depth == res.size()) {
+            res.add(new ArrayList<>());
+        }
+        res.get(depth).add(node.val);
+        dfs(node.left, depth + 1, res);
+        dfs(node.right, depth + 1, res);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    vector<vector<int>> zigzagLevelOrder(TreeNode* root) {
+        vector<vector<int>> res;
+        dfs(root, 0, res);
+        for (int i = 0; i < res.size(); ++i) {
+            if (i & 1) {
+                reverse(res[i].begin(), res[i].end());
+            }
+        }
+        return res;
+    }
+
+private:
+    void dfs(TreeNode* node, int depth, vector<vector<int>>& res) {
+        if (!node) return;
+        if (depth == res.size()) {
+            res.push_back({});
+        }
+        res[depth].push_back(node->val);
+        dfs(node->left, depth + 1, res);
+        dfs(node->right, depth + 1, res);
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number[][]}
+     */
+    zigzagLevelOrder(root) {
+        const res = [];
+        const dfs = (node, depth) => {
+            if (!node) return;
+            if (depth === res.length) res.push([]);
+            res[depth].push(node.val);
+            dfs(node.left, depth + 1);
+            dfs(node.right, depth + 1);
+        };
+
+        dfs(root, 0);
+        for (let i = 0; i < res.length; i++) {
+            if (i % 2 === 1) res[i].reverse();
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Iterative DFS
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def zigzagLevelOrder(self, root: Optional[TreeNode]) -> List[List[int]]:
+        if not root:
+            return []
+        
+        res = []
+        stack = [(root, 0)]
+
+        while stack:
+            node, depth = stack.pop()
+            if depth == len(res):
+                res.append([])
+            
+            res[depth].append(node.val)
+
+            if node.right:
+                stack.append((node.right, depth + 1))
+            if node.left:
+                stack.append((node.left, depth + 1))
+
+        for i in range(len(res)):
+            if i % 2 == 1:
+                res[i].reverse()
+        
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<List<Integer>> zigzagLevelOrder(TreeNode root) {
+        if (root == null) return new ArrayList<>();
+
+        List<List<Integer>> res = new ArrayList<>();
+        Stack<Pair> stack = new Stack<>();
+        stack.push(new Pair(root, 0));
+
+        while (!stack.isEmpty()) {
+            Pair<TreeNode, Integer> current = stack.pop();
+            TreeNode node = current.getKey();
+            int depth = current.getValue();
+
+            if (depth == res.size()) {
+                res.add(new ArrayList<>());
+            }
+            res.get(depth).add(node.val);
+
+            if (node.right != null) stack.push(new Pair<>(node.right, depth + 1));
+            if (node.left != null) stack.push(new Pair<>(node.left, depth + 1));
+        }
+
+        for (int i = 0; i < res.size(); i++) {
+            if (i % 2 == 1) {
+                Collections.reverse(res.get(i));
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    vector<vector<int>> zigzagLevelOrder(TreeNode* root) {
+        if (!root) return {};
+
+        vector<vector<int>> res;
+        stack<pair<TreeNode*, int>> s;
+        s.push({root, 0});
+
+        while (!s.empty()) {
+            auto [node, depth] = s.top();
+            s.pop();
+
+            if (depth == res.size()) {
+                res.push_back({});
+            }
+            res[depth].push_back(node->val);
+
+            if (node->right) s.push({node->right, depth + 1});
+            if (node->left) s.push({node->left, depth + 1});
+        }
+
+        for (int i = 0; i < res.size(); i++) {
+            if (i % 2 == 1) {
+                reverse(res[i].begin(), res[i].end());
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number[][]}
+     */
+    zigzagLevelOrder(root) {
+        if (!root) return [];
+
+        const res = [];
+        const stack = [[root, 0]];
+
+        while (stack.length) {
+            const [node, depth] = stack.pop();
+
+            if (depth === res.length) res.push([]);
+            res[depth].push(node.val);
+
+            if (node.right) stack.push([node.right, depth + 1]);
+            if (node.left) stack.push([node.left, depth + 1]);
+        }
+
+        for (let i = 0; i < res.length; i++) {
+            if (i % 2 === 1) res[i].reverse();
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/bitwise-and-of-numbers-range.md b/articles/bitwise-and-of-numbers-range.md
new file mode 100644
index 000000000..6c5ab4521
--- /dev/null
+++ b/articles/bitwise-and-of-numbers-range.md
@@ -0,0 +1,292 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def rangeBitwiseAnd(self, left: int, right: int) -> int:
+        res = left
+        for i in range(left + 1, right + 1):
+            res &= i
+        return res
+```
+
+```java
+public class Solution {
+    public int rangeBitwiseAnd(int left, int right) {
+        int res = left;
+        for (int i = left + 1; i <= right; i++) {
+            res &= i;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int rangeBitwiseAnd(int left, int right) {
+        int res = left;
+        for (int i = left + 1; i <= right; i++) {
+            res &= i;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} left
+     * @param {number} right
+     * @return {number}
+     */
+    rangeBitwiseAnd(left, right) {
+        let res = left;
+        for (let i = left + 1; i <= right; i++) {
+            res &= i;
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Bit Manipulation - I
+
+::tabs-start
+
+```python
+class Solution:
+    def rangeBitwiseAnd(self, left: int, right: int) -> int:
+        res = 0
+        for i in range(32):
+            bit = (left >> i) & 1
+            if not bit:
+                continue
+
+            remain = left % (1 << (i + 1))
+            diff = (1 << (i + 1)) - remain
+            if right - left < diff:
+                res |= (1 << i)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int rangeBitwiseAnd(int left, int right) {
+        int res = 0;
+        for (int i = 0; i < 32; i++) {
+            int bit = (left >> i) & 1;
+            if (bit == 0) {
+                continue;
+            }
+
+            int remain = left % (1 << (i + 1));
+            int diff = (1 << (i + 1)) - remain;
+            if (right - left < diff) {
+                res |= (1 << i);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int rangeBitwiseAnd(int left, int right) {
+        int res = 0;
+        for (int i = 0; i < 32; i++) {
+            int bit = (left >> i) & 1;
+            if (!bit) {
+                continue;
+            }
+
+            int remain = left % (1 << (i + 1));
+            uint diff = (1ul << (i + 1)) - remain;
+            if (right - left < diff) {
+                res |= (1 << i);
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} left
+     * @param {number} right
+     * @return {number}
+     */
+    rangeBitwiseAnd(left, right) {
+        let res = 0;
+        for (let i = 0; i < 32; i++) {
+            const bit = (left >> i) & 1;
+            if (!bit) {
+                continue;
+            }
+            const next = Math.pow(2, i + 1);
+            const remain = left % next;
+            const diff = next - remain;
+            if (right - left < diff) {
+                res |= (1 << i);
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$ since we iterate $32$ times.
+* Space complexity: $O(1)$
+
+---
+
+## 3. Bit Manipulation - II
+
+::tabs-start
+
+```python
+class Solution:
+    def rangeBitwiseAnd(self, left: int, right: int) -> int:
+        i = 0
+        while left != right:
+            left >>= 1
+            right >>= 1
+            i += 1
+        return left << i
+```
+
+```java
+public class Solution {
+    public int rangeBitwiseAnd(int left, int right) {
+        int i = 0;
+        while (left != right) {
+            left >>= 1;
+            right >>= 1;
+            i++;
+        }
+        return left << i;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int rangeBitwiseAnd(int left, int right) {
+        int i = 0;
+        while (left != right) {
+            left >>= 1;
+            right >>= 1;
+            i++;
+        }
+        return left << i;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} left
+     * @param {number} right
+     * @return {number}
+     */
+    rangeBitwiseAnd(left, right) {
+        let i = 0;
+        while (left !== right) {
+            left >>= 1;
+            right >>= 1;
+            i++;
+        }
+        return left << i;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
+
+---
+
+## 4. Bit Manipulation - III
+
+::tabs-start
+
+```python
+class Solution:
+    def rangeBitwiseAnd(self, left: int, right: int) -> int:
+        while left < right:
+            right &= right - 1
+        return right
+```
+
+```java
+public class Solution {
+    public int rangeBitwiseAnd(int left, int right) {
+        while (left < right) {
+            right &= (right - 1);
+        }
+        return right;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int rangeBitwiseAnd(int left, int right) {
+        while (left < right) {
+            right &= (right - 1);
+        }
+        return right;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} left
+     * @param {number} right
+     * @return {number}
+     */
+    rangeBitwiseAnd(left, right) {
+        while (left < right) {
+            right &= (right - 1);
+        }
+        return right;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/boats-to-save-people.md b/articles/boats-to-save-people.md
new file mode 100644
index 000000000..ce0498e89
--- /dev/null
+++ b/articles/boats-to-save-people.md
@@ -0,0 +1,280 @@
+## 1. Sorting + Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def numRescueBoats(self, people: List[int], limit: int) -> int:
+        people.sort()
+        res, l, r = 0, 0, len(people) - 1
+        while l <= r:
+            remain = limit - people[r]
+            r -= 1
+            res += 1
+            if l <= r and remain >= people[l]:
+                l += 1
+        return res
+```
+
+```java
+public class Solution {
+    public int numRescueBoats(int[] people, int limit) {
+        Arrays.sort(people);
+        int res = 0, l = 0, r = people.length - 1;
+        while (l <= r) {
+            int remain = limit - people[r--];
+            res++;
+            if (l <= r && remain >= people[l]) {
+                l++;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numRescueBoats(vector<int>& people, int limit) {
+        sort(people.begin(), people.end());
+        int res = 0, l = 0, r = people.size() - 1;
+        while (l <= r) {
+            int remain = limit - people[r--];
+            res++;
+            if (l <= r && remain >= people[l]) {
+                l++;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} people
+     * @param {number} limit
+     * @return {number}
+     */
+    numRescueBoats(people, limit) {
+        people.sort((a, b) => a - b);
+        let res = 0, l = 0, r = people.length - 1;
+        while (l <= r) {
+            let remain = limit - people[r--];
+            res++;
+            if (l <= r && remain >= people[l]) {
+                l++;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int NumRescueBoats(int[] people, int limit) {
+        Array.Sort(people);
+        int res = 0, l = 0, r = people.Length - 1;
+
+        while (l <= r) {
+            int remain = limit - people[r];
+            r--;
+            res++;
+
+            if (l <= r && remain >= people[l]) {
+                l++;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 2. Counting Sort
+
+::tabs-start
+
+```python
+class Solution:
+    def numRescueBoats(self, people: List[int], limit: int) -> int:
+        m = max(people)
+        count = [0] * (m + 1)
+        for p in people:
+            count[p] += 1
+        
+        idx, i = 0, 1
+        while idx < len(people):
+            while count[i] == 0:
+                i += 1
+            people[idx] = i
+            count[i] -= 1
+            idx += 1
+
+        res, l, r = 0, 0, len(people) - 1
+        while l <= r:
+            remain = limit - people[r]
+            r -= 1
+            res += 1
+            if l <= r and remain >= people[l]:
+                l += 1
+        return res
+```
+
+```java
+public class Solution {
+    public int numRescueBoats(int[] people, int limit) {
+        int m = Arrays.stream(people).max().getAsInt();
+        int[] count = new int[m + 1];
+        for (int p : people) {
+            count[p]++;
+        }
+        
+        int idx = 0, i = 1;
+        while (idx < people.length) {
+            while (count[i] == 0) {
+                i++;
+            }
+            people[idx++] = i;
+            count[i]--;
+        }
+        
+        int res = 0, l = 0, r = people.length - 1;
+        while (l <= r) {
+            int remain = limit - people[r--];
+            res++;
+            if (l <= r && remain >= people[l]) {
+                l++;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numRescueBoats(vector<int>& people, int limit) {
+        int m = *max_element(people.begin(), people.end());
+        vector<int> count(m + 1, 0);
+        for (int p : people) {
+            count[p]++;
+        }
+        
+        int idx = 0, i = 1;
+        while (idx < people.size()) {
+            while (count[i] == 0) {
+                i++;
+            }
+            people[idx++] = i;
+            count[i]--;
+        }
+        
+        int res = 0, l = 0, r = people.size() - 1;
+        while (l <= r) {
+            int remain = limit - people[r--];
+            res++;
+            if (l <= r && remain >= people[l]) {
+                l++;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} people
+     * @param {number} limit
+     * @return {number}
+     */
+    numRescueBoats(people, limit) {
+        const m = Math.max(...people);
+        const count = new Array(m + 1).fill(0);
+        for (const p of people) {
+            count[p]++;
+        }
+        
+        let idx = 0, i = 1;
+        while (idx < people.length) {
+            while (count[i] === 0) {
+                i++;
+            }
+            people[idx++] = i;
+            count[i]--;
+        }
+        
+        let res = 0, l = 0, r = people.length - 1;
+        while (l <= r) {
+            const remain = limit - people[r--];
+            res++;
+            if (l <= r && remain >= people[l]) {
+                l++;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int NumRescueBoats(int[] people, int limit) {
+        int m = 0;
+        foreach (int p in people) {
+            m = Math.Max(m, p);
+        }
+
+        int[] count = new int[m + 1];
+        foreach (int p in people) {
+            count[p]++;
+        }
+
+        int idx = 0, iVal = 1;
+        while (idx < people.Length) {
+            while (count[iVal] == 0) {
+                iVal++;
+            }
+            people[idx] = iVal;
+            count[iVal]--;
+            idx++;
+        }
+
+        int res = 0, l = 0, r = people.Length - 1;
+        while (l <= r) {
+            int remain = limit - people[r];
+            r--;
+            res++;
+            if (l <= r && remain >= people[l]) {
+                l++;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(m)$
+
+> Where $n$ is the size of the input array and $m$ is the maximum value in the array.
\ No newline at end of file
diff --git a/articles/brick-wall.md b/articles/brick-wall.md
new file mode 100644
index 000000000..991f98ce3
--- /dev/null
+++ b/articles/brick-wall.md
@@ -0,0 +1,245 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def leastBricks(self, wall: List[List[int]]) -> int:
+        n = len(wall)
+        m = 0
+        for brick in wall[0]:
+            m += brick
+
+        gaps = [[] for _ in range(n)]
+        for i in range(n):
+            gap = 0
+            for brick in wall[i]:
+                gap += brick
+                gaps[i].append(gap)
+        
+        res = n
+        for line in range(1, m):
+            cuts = 0
+            for i in range(n):
+                if line not in gaps[i]:
+                    cuts += 1
+            
+            res = min(res, cuts)
+        return res
+```
+
+```java
+public class Solution {
+    public int leastBricks(List<List<Integer>> wall) {
+        int n = wall.size();
+        int m = 0;
+        for (int brick : wall.get(0)) {
+            m += brick;
+        }
+
+        List<List<Integer>> gaps = new ArrayList<>();
+        for (int i = 0; i < n; i++) {
+            gaps.add(new ArrayList<>());
+            int gap = 0;
+            for (int brick : wall.get(i)) {
+                gap += brick;
+                gaps.get(i).add(gap);
+            }
+        }
+
+        int res = n;
+        for (int line = 1; line < m; line++) {
+            int cuts = 0;
+            for (int i = 0; i < n; i++) {
+                if (!gaps.get(i).contains(line)) {
+                    cuts++;
+                }
+            }
+            res = Math.min(res, cuts);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int leastBricks(vector<vector<int>>& wall) {
+        int n = wall.size();
+        int m = 0;
+        for (int brick : wall[0]) {
+            m += brick;
+        }
+
+        vector<vector<int>> gaps(n);
+        for (int i = 0; i < n; i++) {
+            int gap = 0;
+            for (int brick : wall[i]) {
+                gap += brick;
+                gaps[i].push_back(gap);
+            }
+        }
+
+        int res = n;
+        for (int line = 1; line < m; line++) {
+            int cuts = 0;
+            for (int i = 0; i < n; i++) {
+                if (find(gaps[i].begin(), gaps[i].end(), line) == gaps[i].end()) {
+                    cuts++;
+                }
+            }
+            res = min(res, cuts);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} wall
+     * @return {number}
+     */
+    leastBricks(wall) {
+        const n = wall.length;
+        let m = 0;
+        for (const brick of wall[0]) {
+            m += brick;
+        }
+
+        const gaps = Array.from({ length: n }, () => []);
+        for (let i = 0; i < n; i++) {
+            let gap = 0;
+            for (const brick of wall[i]) {
+                gap += brick;
+                gaps[i].push(gap);
+            }
+        }
+
+        let res = n;
+        for (let line = 1; line < m; line++) {
+            let cuts = 0;
+            for (let i = 0; i < n; i++) {
+                if (!gaps[i].includes(line)) {
+                    cuts++;
+                }
+            }
+            res = Math.min(res, cuts);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n * g)$
+* Space complexity: $O(n * g)$
+
+> Where $m$ is the sum of widths of the bricks in the first row, $n$ is the number of rows and $g$ is the average number of gaps in each row.
+
+---
+
+## 2. Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def leastBricks(self, wall: List[List[int]]) -> int:
+        countGap = {0: 0}
+
+        for r in wall:
+            total = 0
+            for i in range(len(r) - 1):
+                total += r[i]
+                countGap[total] = 1 + countGap.get(total, 0)
+
+        return len(wall) - max(countGap.values())
+```
+
+```java
+public class Solution {
+    public int leastBricks(List<List<Integer>> wall) {
+        HashMap<Integer, Integer> countGap = new HashMap<>();
+        countGap.put(0, 0);
+
+        for (List<Integer> row : wall) {
+            int total = 0;
+            for (int i = 0; i < row.size() - 1; i++) {
+                total += row.get(i);
+                countGap.put(total, countGap.getOrDefault(total, 0) + 1);
+            }
+        }
+
+        int maxGaps = 0;
+        for (int count : countGap.values()) {
+            maxGaps = Math.max(maxGaps, count);
+        }
+
+        return wall.size() - maxGaps;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int leastBricks(vector<vector<int>>& wall) {
+        unordered_map<int, int> countGap;
+        countGap[0] = 0;
+
+        for (const auto& row : wall) {
+            int total = 0;
+            for (size_t i = 0; i < row.size() - 1; ++i) {
+                total += row[i];
+                countGap[total]++;
+            }
+        }
+
+        int maxGaps = 0;
+        for (const auto& [key, value] : countGap) {
+            maxGaps = max(maxGaps, value);
+        }
+
+        return wall.size() - maxGaps;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} wall
+     * @return {number}
+     */
+    leastBricks(wall) {
+        const countGap = new Map();
+        countGap.set(0, 0);
+        for (const row of wall) {
+            let total = 0;
+            for (let i = 0; i < row.length - 1; i++) {
+                total += row[i];
+                countGap.set(total, (countGap.get(total) || 0) + 1);
+            }
+        }
+        return wall.length - Math.max(...countGap.values());
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(N)$
+* Space complexity: $O(g)$
+
+> Where $N$ is the total number of bricks in the wall and $g$ is the total number of gaps in all the rows.
\ No newline at end of file
diff --git a/articles/build-a-matrix-with-conditions.md b/articles/build-a-matrix-with-conditions.md
new file mode 100644
index 000000000..cd7d0bfd9
--- /dev/null
+++ b/articles/build-a-matrix-with-conditions.md
@@ -0,0 +1,526 @@
+## 1. Topological Sort (DFS)
+
+::tabs-start
+
+```python
+class Solution:
+    def buildMatrix(self, k: int, rowConditions: List[List[int]], colConditions: List[List[int]]) -> List[List[int]]:
+        def dfs(src, adj, visit, path, order):
+            if src in path:
+                return False
+            if src in visit:
+                return True
+            visit.add(src)
+            path.add(src)
+            for nei in adj[src]:
+                if not dfs(nei, adj, visit, path, order):
+                    return False
+            path.remove(src)
+            order.append(src)
+            return True
+
+        def topo_sort(edges):
+            adj = defaultdict(list)
+            for src, dst in edges:
+                adj[src].append(dst)
+            
+            visit, path = set(), set()
+            order = []
+            for src in range(1, k + 1):
+                if src not in visit:
+                    if not dfs(src, adj, visit, path, order):
+                        return []
+            return order[::-1]
+
+        row_order = topo_sort(rowConditions)
+        if not row_order: return []
+        
+        col_order = topo_sort(colConditions)
+        if not col_order: return []
+        
+        val_to_row = {num: i for i, num in enumerate(row_order)}
+        val_to_col = {num: i for i, num in enumerate(col_order)}
+        res = [[0] * k for _ in range(k)]
+        for num in range(1, k + 1):
+            r, c = val_to_row[num], val_to_col[num]
+            res[r][c] = num
+        
+        return res
+```
+
+```java
+public class Solution {
+    private Set<Integer> visit;
+    private Set<Integer> path;
+    private List<Integer> order;
+
+    public int[][] buildMatrix(int k, int[][] rowConditions, int[][] colConditions) {
+        int[] rowOrder = topoSort(k, rowConditions);
+        if (rowOrder == null) return new int[0][0];
+        int[] colOrder = topoSort(k, colConditions);
+        if (colOrder == null) return new int[0][0];
+
+        Map<Integer, Integer> valToRow = new HashMap<>();
+        for (int i = 0; i < rowOrder.length; i++) {
+            valToRow.put(rowOrder[i], i);
+        }
+        Map<Integer, Integer> valToCol = new HashMap<>();
+        for (int i = 0; i < colOrder.length; i++) {
+            valToCol.put(colOrder[i], i);
+        }
+
+        int[][] res = new int[k][k];
+        for (int num = 1; num <= k; num++) {
+            int r = valToRow.get(num);
+            int c = valToCol.get(num);
+            res[r][c] = num;
+        }
+        return res;
+    }
+
+    private int[] topoSort(int k, int[][] edges) {
+        Map<Integer, List<Integer>> adj = new HashMap<>();
+        for (int i = 1; i <= k; i++) {
+            adj.put(i, new ArrayList<>());
+        }
+        for (int[] edge : edges) {
+            adj.get(edge[0]).add(edge[1]);
+        }
+
+        visit = new HashSet<>();
+        path = new HashSet<>();
+        order = new ArrayList<>();
+
+        for (int i = 1; i <= k; i++) {
+            if (!visit.contains(i)) {
+                if (!dfs(i, adj)) {
+                    return null;
+                }
+            }
+        }
+
+        Collections.reverse(order);
+        return order.stream().mapToInt(i -> i).toArray();
+    }
+
+    private boolean dfs(int src, Map<Integer, List<Integer>> adj) {
+        if (path.contains(src)) return false;
+        if (visit.contains(src)) return true;
+
+        visit.add(src);
+        path.add(src);
+        for (int nei : adj.get(src)) {
+            if (!dfs(nei, adj)) {
+                return false;
+            }
+        }
+        path.remove(src);
+        order.add(src);
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> buildMatrix(int k, vector<vector<int>>& rowConditions, vector<vector<int>>& colConditions) {
+        vector<int> rowOrder = topoSort(k, rowConditions);
+        if (rowOrder.empty()) return {};
+        vector<int> colOrder = topoSort(k, colConditions);
+        if (colOrder.empty()) return {};
+
+        unordered_map<int, int> valToRow, valToCol;
+        for (int i = 0; i < rowOrder.size(); i++) {
+            valToRow[rowOrder[i]] = i;
+        }
+        for (int i = 0; i < colOrder.size(); i++) {
+            valToCol[colOrder[i]] = i;
+        }
+
+        vector<vector<int>> res(k, vector<int>(k, 0));
+        for (int num = 1; num <= k; num++) {
+            int r = valToRow[num];
+            int c = valToCol[num];
+            res[r][c] = num;
+        }
+        return res;
+    }
+
+private:
+    unordered_set<int> visit;
+    unordered_set<int> path;
+    vector<int> order;
+
+    vector<int> topoSort(int k, vector<vector<int>>& edges) {
+        unordered_map<int, vector<int>> adj;
+        for (int i = 1; i <= k; i++) {
+            adj[i] = {};
+        }
+        for (auto& edge : edges) {
+            adj[edge[0]].push_back(edge[1]);
+        }
+
+        visit.clear();
+        path.clear();
+        order.clear();
+        for (int i = 1; i <= k; i++) {
+            if (visit.find(i) == visit.end()) {
+                if (!dfs(i, adj)) {
+                    return {};
+                }
+            }
+        }
+
+        reverse(order.begin(), order.end());
+        return order;
+    }
+
+    bool dfs(int src, unordered_map<int, vector<int>>& adj) {
+        if (path.find(src) != path.end()) return false;
+        if (visit.find(src) != visit.end()) return true;
+
+        visit.insert(src);
+        path.insert(src);
+        for (int nei : adj[src]) {
+            if (!dfs(nei, adj)) {
+                return false;
+            }
+        }
+        path.erase(src);
+        order.push_back(src);
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} k
+     * @param {number[][]} rowConditions
+     * @param {number[][]} colConditions
+     * @return {number[][]}
+     */
+    buildMatrix(k, rowConditions, colConditions) {
+        const rowOrder = this.topoSort(k, rowConditions);
+        if (!rowOrder) return [];
+        const colOrder = this.topoSort(k, colConditions);
+        if (!colOrder) return [];
+
+        const valToRow = {};
+        rowOrder.forEach((num, i) => {
+            valToRow[num] = i;
+        });
+
+        const valToCol = {};
+        colOrder.forEach((num, i) => {
+            valToCol[num] = i;
+        });
+
+        const res = Array.from({ length: k }, () => Array(k).fill(0));
+        for (let num = 1; num <= k; num++) {
+            const r = valToRow[num];
+            const c = valToCol[num];
+            res[r][c] = num;
+        }
+        return res;
+    }
+
+    /**
+     * @param {number} k
+     * @param {number[][]} edges
+     * @return {number[]}
+     */
+    topoSort(k, edges) {
+        const adj = Array.from({ length: k + 1 }, () => []);
+        edges.forEach(([src, dst]) => {
+            adj[src].push(dst);
+        });
+
+        const visit = new Set();
+        const path = new Set();
+        const order = [];
+
+        const dfs = (src) => {
+            if (path.has(src)) return false;
+            if (visit.has(src)) return true;
+
+            visit.add(src);
+            path.add(src);
+            for (const nei of adj[src]) {
+                if (!dfs(nei)) {
+                    return false;
+                }
+            }
+            path.delete(src);
+            order.push(src);
+            return true;
+        };
+
+        for (let src = 1; src <= k; src++) {
+            if (!visit.has(src)) {
+                if (!dfs(src)) {
+                    return null;
+                }
+            }
+        }
+        return order.reverse();
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(k ^ 2 + n + m)$
+* Space complexity:
+    * $O(k + n + m)$ extra space.
+    * $O(k ^ 2)$ space for the output matrix. 
+
+> Where $n$ is the size of the array $rowConditions$, $m$ is the size of the array $colConditions$, and $k$ is the size of the output matrix.
+
+---
+
+## 2. Topological Sort (Kahn's Algorithm)
+
+::tabs-start
+
+```python
+class Solution:
+    def buildMatrix(self, k: int, rowConditions: List[List[int]], colConditions: List[List[int]]) -> List[List[int]]:
+        def topo_sort(edges):
+            indegree = [0] * (k + 1)
+            adj = [[] for _ in range(k + 1)]
+            for u, v in edges:
+                adj[u].append(v)
+                indegree[v] += 1
+            
+            order = []
+            q = deque()
+            for i in range(1, k + 1):
+                if not indegree[i]:
+                    q.append(i)
+            
+            while q:
+                node = q.popleft()
+                order.append(node)
+                for nei in adj[node]:
+                    indegree[nei] -= 1
+                    if not indegree[nei]:
+                        q.append(nei)
+            
+            return order
+
+        row_order = topo_sort(rowConditions)
+        if len(row_order) != k: return []
+        
+        col_order = topo_sort(colConditions)
+        if len(col_order) != k: return []
+        
+        res = [[0] * k for _ in range(k)]
+        colIndex = [0] * (k + 1)
+        for i in range(k):
+            colIndex[col_order[i]] = i
+        
+        for i in range(k):
+            res[i][colIndex[row_order[i]]] = row_order[i]
+        return res
+```
+
+```java
+public class Solution {
+    public int[][] buildMatrix(int k, int[][] rowConditions, int[][] colConditions) {
+        int[] rowOrder = topoSort(k, rowConditions);
+        if (rowOrder.length != k) return new int[0][0];
+
+        int[] colOrder = topoSort(k, colConditions);
+        if (colOrder.length != k) return new int[0][0];
+
+        int[][] res = new int[k][k];
+        int[] colIndex = new int[k + 1];
+        for (int i = 0; i < k; i++) {
+            colIndex[colOrder[i]] = i;
+        }
+
+        for (int i = 0; i < k; i++) {
+            res[i][colIndex[rowOrder[i]]] = rowOrder[i];
+        }
+
+        return res;
+    }
+
+    private int[] topoSort(int k, int[][] edges) {
+        int[] indegree = new int[k + 1];
+        List<List<Integer>> adj = new ArrayList<>();
+        for (int i = 0; i <= k; i++) {
+            adj.add(new ArrayList<>());
+        }
+
+        for (int[] edge : edges) {
+            adj.get(edge[0]).add(edge[1]);
+            indegree[edge[1]]++;
+        }
+
+        Queue<Integer> queue = new LinkedList<>();
+        int[] order = new int[k];
+        int idx = 0;
+        for (int i = 1; i <= k; i++) {
+            if (indegree[i] == 0) {
+                queue.offer(i);
+            }
+        }
+
+        while (!queue.isEmpty()) {
+            int node = queue.poll();
+            order[idx++] = node;
+            for (int nei : adj.get(node)) {
+                indegree[nei]--;
+                if (indegree[nei] == 0) {
+                    queue.offer(nei);
+                }
+            }
+        }
+        
+        if (idx != k) return new int[0];
+        return order;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> buildMatrix(int k, vector<vector<int>>& rowConditions, vector<vector<int>>& colConditions) {
+        vector<int> rowOrder = topoSort(k, rowConditions);
+        if (rowOrder.size() != k) return {};
+
+        vector<int> colOrder = topoSort(k, colConditions);
+        if (colOrder.size() != k) return {};
+
+        vector<vector<int>> res(k, vector<int>(k, 0));
+        vector<int> colIndex(k + 1);
+        for (int i = 0; i < k; i++) {
+            colIndex[colOrder[i]] = i;
+        }
+        for (int i = 0; i < k; i++) {
+            res[i][colIndex[rowOrder[i]]] = rowOrder[i];
+        }
+        return res;
+    }
+
+private:
+    vector<int> topoSort(int k, vector<vector<int>>& edges) {
+        vector<int> indegree(k + 1, 0);
+        vector<vector<int>> adj(k + 1);
+        for (const auto& edge : edges) {
+            adj[edge[0]].push_back(edge[1]);
+            indegree[edge[1]]++;
+        }
+
+        queue<int> q;
+        vector<int> order;
+        for (int i = 1; i <= k; i++) {
+            if (indegree[i] == 0) {
+                q.push(i);
+            }
+        }
+
+        while (!q.empty()) {
+            int node = q.front();
+            q.pop();
+            order.push_back(node);
+
+            for (int nei : adj[node]) {
+                indegree[nei]--;
+                if (indegree[nei] == 0) {
+                    q.push(nei);
+                }
+            }
+        }
+
+        if (order.size() != k) return {};
+        return order;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} k
+     * @param {number[][]} rowConditions
+     * @param {number[][]} colConditions
+     * @return {number[][]}
+     */
+    buildMatrix(k, rowConditions, colConditions) {
+        const rowOrder = this.topoSort(k, rowConditions);
+        if (rowOrder.length !== k) return [];
+
+        const colOrder = this.topoSort(k, colConditions);
+        if (colOrder.length !== k) return [];
+
+        const res = Array.from({ length: k }, () => Array(k).fill(0));
+        const colIndex = Array(k + 1).fill(0);
+
+        for (let i = 0; i < k; i++) {
+            colIndex[colOrder[i]] = i;
+        }
+
+        for (let i = 0; i < k; i++) {
+            res[i][colIndex[rowOrder[i]]] = rowOrder[i];
+        }
+
+        return res;
+    }
+
+    /**
+     * @param {number} k
+     * @param {number[][]} edges
+     * @return {number[]}
+     */
+    topoSort(k, edges) {
+        const indegree = Array(k + 1).fill(0);
+        const adj = Array.from({ length: k + 1 }, () => []);
+
+        for (const [u, v] of edges) {
+            adj[u].push(v);
+            indegree[v]++;
+        }
+
+        const queue = new Queue();
+        const order = [];
+
+        for (let i = 1; i <= k; i++) {
+            if (indegree[i] === 0) {
+                queue.push(i);
+            }
+        }
+
+        while (!queue.isEmpty()) {
+            const node = queue.pop();
+            order.push(node);
+            for (const nei of adj[node]) {
+                indegree[nei]--;
+                if (indegree[nei] === 0) {
+                    queue.push(nei);
+                }
+            }
+        }
+
+        return order.length === k ? order : [];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(k ^ 2 + n + m)$
+* Space complexity:
+    * $O(k + n + m)$ extra space.
+    * $O(k ^ 2)$ space for the output matrix. 
+
+> Where $n$ is the size of the array $rowConditions$, $m$ is the size of the array $colConditions$, and $k$ is the size of the output matrix.
\ No newline at end of file
diff --git a/articles/buildings-with-an-ocean-view.md b/articles/buildings-with-an-ocean-view.md
new file mode 100644
index 000000000..9c418c11c
--- /dev/null
+++ b/articles/buildings-with-an-ocean-view.md
@@ -0,0 +1,339 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def findBuildings(self, heights: List[int]) -> List[int]:
+        n = len(heights)
+        res = []
+
+        for i in range(n):
+            flag = True
+            for j in range(i + 1, n):
+                if heights[i] <= heights[j]:
+                    flag = False
+                    break
+            if flag:
+                res.append(i)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[] findBuildings(int[] heights) {
+        int n = heights.length;
+        List<Integer> temp = new ArrayList<>();
+
+        for (int i = 0; i < n; i++) {
+            boolean flag = true;
+            for (int j = i + 1; j < n; j++) {
+                if (heights[i] <= heights[j]) {
+                    flag = false;
+                    break;
+                }
+            }
+            if (flag) temp.add(i);
+        }
+
+        int[] res = new int[temp.size()];
+        for (int i = 0; i < temp.size(); i++) {
+            res[i] = temp.get(i);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findBuildings(vector<int>& heights) {
+        int n = heights.size();
+        vector<int> res;
+
+        for (int i = 0; i < n; i++) {
+            bool flag = true;
+            for (int j = i + 1; j < n; j++) {
+                if (heights[i] <= heights[j]) {
+                    flag = false;
+                    break;
+                }
+            }
+            if (flag) res.push_back(i);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} heights
+     * @return {number[]}
+     */
+    findBuildings(heights) {
+        const n = heights.length;
+        const res = [];
+
+        for (let i = 0; i < n; i++) {
+            let flag = true;
+            for (let j = i + 1; j < n; j++) {
+                if (heights[i] <= heights[j]) {
+                    flag = false;
+                    break;
+                }
+            }
+            if (flag) res.push(i);
+        }
+
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[] FindBuildings(int[] heights) {
+        int n = heights.Length;
+        List<int> temp = new List<int>();
+
+        for (int i = 0; i < n; i++) {
+            bool flag = true;
+            for (int j = i + 1; j < n; j++) {
+                if (heights[i] <= heights[j]) {
+                    flag = false;
+                    break;
+                }
+            }
+            if (flag) temp.Add(i);
+        }
+
+        return temp.ToArray();
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$ for the output array.
+
+---
+
+## 2. Monotonic Stack
+
+::tabs-start
+
+```python
+class Solution:
+    def findBuildings(self, heights: List[int]) -> List[int]:
+        stack = []
+
+        for i, h in enumerate(heights):
+            while stack and heights[stack[-1]] <= h:
+                stack.pop()
+            stack.append(i)
+
+        return stack
+```
+
+```java
+public class Solution {
+    public int[] findBuildings(int[] heights) {
+        int n = heights.length;
+        Stack<Integer> stack = new Stack<>();
+
+        for (int i = 0; i < n; i++) {
+            while (!stack.isEmpty() && heights[stack.peek()] <= heights[i]) {
+                stack.pop();
+            }
+            stack.push(i);
+        }
+
+        int[] res = new int[stack.size()];
+        for (int i = stack.size() - 1; i >= 0; i--) {
+            res[i] = stack.get(i);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findBuildings(vector<int>& heights) {
+        vector<int> stack;
+
+        for (int i = 0; i < heights.size(); i++) {
+            while (!stack.empty() && heights[stack.back()] <= heights[i]) {
+                stack.pop_back();
+            }
+            stack.push_back(i);
+        }
+
+        return stack;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} heights
+     * @return {number[]}
+     */
+    findBuildings(heights) {
+        const stack = [];
+
+        for (let i = 0; i < heights.length; i++) {
+            while (stack.length && heights[stack[stack.length - 1]] <= heights[i]) {
+                stack.pop();
+            }
+            stack.push(i);
+        }
+
+        return stack;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[] FindBuildings(int[] heights) {
+        List<int> stack = new List<int>();
+
+        for (int i = 0; i < heights.Length; i++) {
+            while (stack.Count > 0 && heights[stack[stack.Count - 1]] <= heights[i]) {
+                stack.RemoveAt(stack.Count - 1);
+            }
+            stack.Add(i);
+        }
+
+        return stack.ToArray();
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Greedy
+
+::tabs-start
+
+```python
+class Solution:
+    def findBuildings(self, heights: List[int]) -> List[int]:
+        res = [len(heights) - 1]
+        for i in range(len(heights) - 2, -1, -1):
+            if heights[i] > heights[res[-1]]:
+                res.append(i)
+        res.reverse()
+        return res
+```
+
+```java
+public class Solution {
+    public int[] findBuildings(int[] heights) {
+        List<Integer> res = new ArrayList<>();
+        int n = heights.length;
+        res.add(n - 1);
+
+        for (int i = n - 2; i >= 0; i--) {
+            if (heights[i] > heights[res.get(res.size() - 1)]) {
+                res.add(i);
+            }
+        }
+
+        Collections.reverse(res);
+        int[] ans = new int[res.size()];
+        for (int i = 0; i < res.size(); i++) {
+            ans[i] = res.get(i);
+        }
+
+        return ans;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findBuildings(vector<int>& heights) {
+        vector<int> res;
+        int n = heights.size();
+        res.push_back(n - 1);
+
+        for (int i = n - 2; i >= 0; i--) {
+            if (heights[i] > heights[res.back()]) {
+                res.push_back(i);
+            }
+        }
+
+        reverse(res.begin(), res.end());
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} heights
+     * @return {number[]}
+     */
+    findBuildings(heights) {
+        const n = heights.length;
+        const res = [n - 1];
+
+        for (let i = n - 2; i >= 0; i--) {
+            if (heights[i] > heights[res[res.length - 1]]) {
+                res.push(i);
+            }
+        }
+
+        return res.reverse();
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[] FindBuildings(int[] heights) {
+        int n = heights.Length;
+        List<int> res = new List<int> { n - 1 };
+
+        for (int i = n - 2; i >= 0; i--) {
+            if (heights[i] > heights[res[res.Count - 1]]) {
+                res.Add(i);
+            }
+        }
+
+        res.Reverse();
+        return res.ToArray();
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ for the output array.
\ No newline at end of file
diff --git a/articles/burst-balloons.md b/articles/burst-balloons.md
index c8759cc8b..a52c66027 100644
--- a/articles/burst-balloons.md
+++ b/articles/burst-balloons.md
@@ -138,12 +138,87 @@ public class Solution {
 }
 ```
 
+```go
+func maxCoins(nums []int) int {
+    nums = append([]int{1}, nums...)
+    nums = append(nums, 1)
+
+    var dfs func(nums []int) int
+    dfs = func(nums []int) int {
+        if len(nums) == 2 {
+            return 0
+        }
+
+        maxCoins := 0
+        for i := 1; i < len(nums)-1; i++ {
+            coins := nums[i-1] * nums[i] * nums[i+1]
+            coins += dfs(append(append([]int{}, nums[:i]...), nums[i+1:]...))
+            if coins > maxCoins {
+                maxCoins = coins
+            }
+        }
+        return maxCoins
+    }
+
+    return dfs(nums)
+}
+```
+
+```kotlin
+class Solution {
+    fun maxCoins(nums: IntArray): Int {
+        val newNums = intArrayOf(1) + nums + intArrayOf(1)
+
+        fun dfs(nums: IntArray): Int {
+            if (nums.size == 2) {
+                return 0
+            }
+
+            var maxCoins = 0
+            for (i in 1 until nums.size - 1) {
+                val coins = nums[i - 1] * nums[i] * nums[i + 1]
+                val nextCoins = dfs(nums.take(i).toIntArray() + 
+                                    nums.drop(i + 1).toIntArray())
+                maxCoins = maxOf(maxCoins, coins + nextCoins)
+            }
+            return maxCoins
+        }
+
+        return dfs(newNums)
+    }
+}
+```
+
+```swift
+class Solution {
+    func maxCoins(_ nums: [Int]) -> Int {
+        var nums = [1] + nums + [1]
+
+        func dfs(_ nums: [Int]) -> Int {
+            if nums.count == 2 {
+                return 0
+            }
+
+            var maxCoins = 0
+            for i in 1..<(nums.count - 1) {
+                let coins = nums[i - 1] * nums[i] * nums[i + 1] +
+                            dfs(Array(nums[..<i]) + Array(nums[(i + 1)...]))
+                maxCoins = max(maxCoins, coins)
+            }
+            return maxCoins
+        }
+
+        return dfs(nums)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
-- Time complexity: $O(n*2^n)$
-- Space complexity: $O(n*2^n)$
+* Time complexity: $O(n*2^n)$
+* Space complexity: $O(n*2^n)$
 
 ---
 
@@ -314,12 +389,105 @@ public class Solution {
 }
 ```
 
+```go
+func maxCoins(nums []int) int {
+    nums = append([]int{1}, nums...)
+    nums = append(nums, 1)
+    n := len(nums)
+
+    dp := make([][]int, n)
+    for i := 0; i < n; i++ {
+        dp[i] = make([]int, n)
+    }
+
+    var dfs func(l, r int) int
+    dfs = func(l, r int) int {
+        if l > r {
+            return 0
+        }
+        if dp[l][r] > 0 {
+            return dp[l][r]
+        }
+
+        dp[l][r] = 0
+        for i := l; i <= r; i++ {
+            coins := nums[l-1] * nums[i] * nums[r+1]
+            coins += dfs(l, i-1) + dfs(i+1, r)
+            dp[l][r] = max(dp[l][r], coins)
+        }
+        return dp[l][r]
+    }
+
+    return dfs(1, len(nums)-2)
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun maxCoins(nums: IntArray): Int {
+        val newNums = intArrayOf(1) + nums + intArrayOf(1)
+        val n = newNums.size
+        val dp = Array(n) { IntArray(n) }
+
+        fun dfs(l: Int, r: Int): Int {
+            if (l > r) return 0
+            if (dp[l][r] > 0) return dp[l][r]
+
+            dp[l][r] = 0
+            for (i in l..r) {
+                val coins = newNums[l - 1] * newNums[i] * newNums[r + 1]
+                val totalCoins = coins + dfs(l, i - 1) + dfs(i + 1, r)
+                dp[l][r] = maxOf(dp[l][r], totalCoins)
+            }
+            return dp[l][r]
+        }
+
+        return dfs(1, newNums.size - 2)
+    }
+}
+```
+
+```swift
+class Solution {
+    func maxCoins(_ nums: [Int]) -> Int {
+        var nums = [1] + nums + [1]
+        let n = nums.count
+        var dp = Array(repeating: Array(repeating: -1, count: n), count: n)
+
+        func dfs(_ l: Int, _ r: Int) -> Int {
+            if l > r {
+                return 0
+            }
+            if dp[l][r] != -1 {
+                return dp[l][r]
+            }
+
+            dp[l][r] = 0
+            for i in l...r {
+                let coins = nums[l - 1] * nums[i] * nums[r + 1] + dfs(l, i - 1) + dfs(i + 1, r)
+                dp[l][r] = max(dp[l][r], coins)
+            }
+            return dp[l][r]
+        }
+
+        return dfs(1, n - 2)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
-- Time complexity: $O(n^3)$
-- Space complexity: $O(n^2)$
+* Time complexity: $O(n ^ 3)$
+* Space complexity: $O(n ^ 2)$
 
 ---
 
@@ -451,10 +619,86 @@ public class Solution {
 }
 ```
 
+```go
+func maxCoins(nums []int) int {
+    n := len(nums)
+    newNums := append([]int{1}, nums...)
+    newNums = append(newNums, 1)
+
+    dp := make([][]int, n+2)
+    for i := range dp {
+        dp[i] = make([]int, n+2)
+    }
+
+    for l := n; l >= 1; l-- {
+        for r := l; r <= n; r++ {
+            for i := l; i <= r; i++ {
+                coins := newNums[l-1] * newNums[i] * newNums[r+1]
+                coins += dp[l][i-1] + dp[i+1][r]
+                dp[l][r] = max(dp[l][r], coins)
+            }
+        }
+    }
+
+    return dp[1][n]
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun maxCoins(nums: IntArray): Int {
+        val n = nums.size
+        val newNums = intArrayOf(1) + nums + intArrayOf(1)
+
+        val dp = Array(n + 2) { IntArray(n + 2) }
+
+        for (l in n downTo 1) {
+            for (r in l..n) {
+                for (i in l..r) {
+                    val coins = newNums[l - 1] * newNums[i] * newNums[r + 1]
+                    dp[l][r] = maxOf(dp[l][r], coins + dp[l][i - 1] + dp[i + 1][r])
+                }
+            }
+        }
+
+        return dp[1][n]
+    }
+}
+```
+
+```swift
+class Solution {
+    func maxCoins(_ nums: [Int]) -> Int {
+        let n = nums.count
+        var newNums = [1] + nums + [1]
+
+        var dp = Array(repeating: Array(repeating: 0, count: n + 2), count: n + 2)
+
+        for l in stride(from: n, through: 1, by: -1) {
+            for r in l...n {
+                for i in l...r {
+                    let coins = (newNums[l - 1] * newNums[i] * newNums[r + 1]) +
+                                dp[l][i - 1] + dp[i + 1][r]
+                    dp[l][r] = max(dp[l][r], coins)
+                }
+            }
+        }
+
+        return dp[1][n]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
-- Time complexity: $O(n^3)$
-- Space complexity: $O(n^2)$
-  
+* Time complexity: $O(n^3)$
+* Space complexity: $O(n^2)$
\ No newline at end of file
diff --git a/articles/buy-and-sell-crypto-with-cooldown.md b/articles/buy-and-sell-crypto-with-cooldown.md
index 6b6fb8573..9c4ae550b 100644
--- a/articles/buy-and-sell-crypto-with-cooldown.md
+++ b/articles/buy-and-sell-crypto-with-cooldown.md
@@ -121,6 +121,81 @@ public class Solution {
 }
 ```
 
+```go
+func maxProfit(prices []int) int {
+    var dfs func(i int, buying bool) int
+    dfs = func(i int, buying bool) int {
+        if i >= len(prices) {
+            return 0
+        }
+        
+        cooldown := dfs(i + 1, buying)
+        if buying {
+            buy := dfs(i + 1, false) - prices[i]
+            return max(buy, cooldown)
+        } else {
+            sell := dfs(i + 2, true) + prices[i]
+            return max(sell, cooldown)
+        }
+    }
+
+    return dfs(0, true)
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun maxProfit(prices: IntArray): Int {
+        fun dfs(i: Int, buying: Boolean): Int {
+            if (i >= prices.size) return 0
+            
+            val cooldown = dfs(i + 1, buying)
+            return if (buying) {
+                val buy = dfs(i + 1, false) - prices[i]
+                maxOf(buy, cooldown)
+            } else {
+                val sell = dfs(i + 2, true) + prices[i]
+                maxOf(sell, cooldown)
+            }
+        }
+        
+        return dfs(0, true)
+    }
+}
+```
+
+```swift
+class Solution {
+    func maxProfit(_ prices: [Int]) -> Int {
+        let n = prices.count
+
+        func dfs(_ i: Int, _ buying: Bool) -> Int {
+            if i >= n {
+                return 0
+            }
+
+            let cooldown = dfs(i + 1, buying)
+            if buying {
+                let buy = dfs(i + 1, false) - prices[i]
+                return max(buy, cooldown)
+            } else {
+                let sell = dfs(i + 2, true) + prices[i]
+                return max(sell, cooldown)
+            }
+        }
+
+        return dfs(0, true)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -289,6 +364,109 @@ public class Solution {
 }
 ```
 
+```go
+func maxProfit(prices []int) int {
+    dp := make(map[[2]int]int) // key is [i, buying], value is max profit
+
+    var dfs func(i int, buying bool) int
+    dfs = func(i int, buying bool) int {
+        if i >= len(prices) {
+            return 0
+        }
+
+        key := [2]int{i, boolToInt(buying)}
+        if val, found := dp[key]; found {
+            return val
+        }
+
+        cooldown := dfs(i + 1, buying)
+        if buying {
+            buy := dfs(i + 1, false) - prices[i]
+            dp[key] = max(buy, cooldown)
+        } else {
+            sell := dfs(i + 2, true) + prices[i]
+            dp[key] = max(sell, cooldown)
+        }
+
+        return dp[key]
+    }
+
+    return dfs(0, true)
+}
+
+func boolToInt(b bool) int {
+    if b {
+        return 1
+    }
+    return 0
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun maxProfit(prices: IntArray): Int {
+        val dp = HashMap<Pair<Int, Boolean>, Int>() // key is Pair(i, buying)
+
+        fun dfs(i: Int, buying: Boolean): Int {
+            if (i >= prices.size) return 0
+
+            val key = Pair(i, buying)
+            if (key in dp) return dp[key]!!
+
+            val cooldown = dfs(i + 1, buying)
+            dp[key] = if (buying) {
+                val buy = dfs(i + 1, false) - prices[i]
+                maxOf(buy, cooldown)
+            } else {
+                val sell = dfs(i + 2, true) + prices[i]
+                maxOf(sell, cooldown)
+            }
+
+            return dp[key]!!
+        }
+
+        return dfs(0, true)
+    }
+}
+```
+
+```swift
+class Solution {
+    func maxProfit(_ prices: [Int]) -> Int {
+        let n = prices.count
+        var dp = [[Int?]](repeating: [Int?](repeating: nil, count: 2), count: n)
+
+        func dfs(_ i: Int, _ buying: Int) -> Int {
+            if i >= n {
+                return 0
+            }
+            if let cached = dp[i][buying] {
+                return cached
+            }
+
+            let cooldown = dfs(i + 1, buying)
+            if buying == 1 {
+                let buy = dfs(i + 1, 0) - prices[i]
+                dp[i][buying] = max(buy, cooldown)
+            } else {
+                let sell = dfs(i + 2, 1) + prices[i]
+                dp[i][buying] = max(sell, cooldown)
+            }
+            return dp[i][buying]!
+        }
+
+        return dfs(0, 1)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -427,6 +605,92 @@ public class Solution {
 }
 ```
 
+```go
+func maxProfit(prices []int) int {
+    n := len(prices)
+    dp := make([][]int, n+1)
+    for i := range dp {
+        dp[i] = make([]int, 2)
+    }
+
+    for i := n - 1; i >= 0; i-- {
+        for buying := 1; buying >= 0; buying-- {
+            if buying == 1 {
+                buy := dp[i+1][0] - prices[i]
+                cooldown := dp[i+1][1]
+                dp[i][1] = max(buy, cooldown)
+            } else {
+                sell := prices[i]
+                if i+2 < n {
+                    sell += dp[i+2][1]
+                }
+                cooldown := dp[i+1][0]
+                dp[i][0] = max(sell, cooldown)
+            }
+        }
+    }
+
+    return dp[0][1]
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun maxProfit(prices: IntArray): Int {
+        val n = prices.size
+        val dp = Array(n + 1) { IntArray(2) }
+
+        for (i in n - 1 downTo 0) {
+            for (buying in 1 downTo 0) {
+                dp[i][buying] = if (buying == 1) {
+                    val buy = dp[i + 1][0] - prices[i]
+                    val cooldown = dp[i + 1][1]
+                    maxOf(buy, cooldown)
+                } else {
+                    val sell = if (i + 2 < n) dp[i + 2][1] + prices[i] else prices[i]
+                    val cooldown = dp[i + 1][0]
+                    maxOf(sell, cooldown)
+                }
+            }
+        }
+
+        return dp[0][1]
+    }
+}
+```
+
+```swift
+class Solution {
+    func maxProfit(_ prices: [Int]) -> Int {
+        let n = prices.count
+        var dp = Array(repeating: [0, 0], count: n + 1)
+
+        for i in stride(from: n - 1, through: 0, by: -1) {
+            for buying in 0...1 {
+                if buying == 1 {
+                    let buy = (i + 1 < n ? dp[i + 1][0] - prices[i] : -prices[i])
+                    let cooldown = (i + 1 < n ? dp[i + 1][1] : 0)
+                    dp[i][1] = max(buy, cooldown)
+                } else {
+                    let sell = (i + 2 < n ? dp[i + 2][1] + prices[i] : prices[i])
+                    let cooldown = (i + 1 < n ? dp[i + 1][0] : 0)
+                    dp[i][0] = max(sell, cooldown)
+                }
+            }
+        }
+
+        return dp[0][1]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -450,7 +714,7 @@ class Solution:
         for i in range(n - 1, -1, -1):
             dp_buy = max(dp1_sell - prices[i], dp1_buy)
             dp_sell = max(dp2_buy + prices[i], dp1_sell)
-            dp2_buy, dp1_sell = dp1_buy, dp1_sell
+            dp2_buy = dp1_buy
             dp1_buy, dp1_sell = dp_buy, dp_sell
 
         return dp1_buy
@@ -467,7 +731,6 @@ public class Solution {
             int dp_buy = Math.max(dp1_sell - prices[i], dp1_buy);
             int dp_sell = Math.max(dp2_buy + prices[i], dp1_sell);
             dp2_buy = dp1_buy;
-            dp1_sell = dp1_sell;
             dp1_buy = dp_buy;
             dp1_sell = dp_sell;
         }
@@ -489,7 +752,6 @@ public:
             int dp_buy = max(dp1_sell - prices[i], dp1_buy);
             int dp_sell = max(dp2_buy + prices[i], dp1_sell);
             dp2_buy = dp1_buy;
-            dp1_sell = dp1_sell;
             dp1_buy = dp_buy;
             dp1_sell = dp_sell;
         }
@@ -514,7 +776,6 @@ class Solution {
             let dp_buy = Math.max(dp1_sell - prices[i], dp1_buy);
             let dp_sell = Math.max(dp2_buy + prices[i], dp1_sell);
             dp2_buy = dp1_buy;
-            dp1_sell = dp1_sell;
             dp1_buy = dp_buy;
             dp1_sell = dp_sell;
         }
@@ -535,7 +796,6 @@ public class Solution {
             int dp_buy = Math.Max(dp1_sell - prices[i], dp1_buy);
             int dp_sell = Math.Max(dp2_buy + prices[i], dp1_sell);
             dp2_buy = dp1_buy;
-            dp1_sell = dp1_sell;
             dp1_buy = dp_buy;
             dp1_sell = dp_sell;
         }
@@ -545,6 +805,70 @@ public class Solution {
 }
 ```
 
+```go
+func maxProfit(prices []int) int {
+    n := len(prices)
+    dp1_buy, dp1_sell := 0, 0
+    dp2_buy := 0
+
+    for i := n - 1; i >= 0; i-- {
+        dp_buy := max(dp1_sell - prices[i], dp1_buy)
+        dp_sell := max(dp2_buy + prices[i], dp1_sell)
+        dp2_buy, dp1_sell = dp1_buy, dp_sell
+        dp1_buy = dp_buy
+    }
+
+    return dp1_buy
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun maxProfit(prices: IntArray): Int {
+        var dp1_buy = 0
+        var dp1_sell = 0
+        var dp2_buy = 0
+
+        for (i in prices.size - 1 downTo 0) {
+            val dp_buy = maxOf(dp1_sell - prices[i], dp1_buy)
+            val dp_sell = maxOf(dp2_buy + prices[i], dp1_sell)
+            dp2_buy = dp1_buy
+            dp1_buy = dp_buy
+            dp1_sell = dp_sell
+        }
+
+        return dp1_buy
+    }
+}
+```
+
+```swift
+class Solution {
+    func maxProfit(_ prices: [Int]) -> Int {
+        let n = prices.count
+        var dp1Buy = 0, dp1Sell = 0
+        var dp2Buy = 0
+
+        for i in stride(from: n - 1, through: 0, by: -1) {
+            let dpBuy = max(dp1Sell - prices[i], dp1Buy)
+            let dpSell = max(dp2Buy + prices[i], dp1Sell)
+            dp2Buy = dp1Buy
+            dp1Buy = dpBuy
+            dp1Sell = dpSell
+        }
+
+        return dp1Buy
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/buy-and-sell-crypto.md b/articles/buy-and-sell-crypto.md
index ec7b49c24..b983fd272 100644
--- a/articles/buy-and-sell-crypto.md
+++ b/articles/buy-and-sell-crypto.md
@@ -83,6 +83,59 @@ public class Solution {
 }
 ```
 
+```go
+func maxProfit(prices []int) int {
+    res := 0
+    for i := 0; i < len(prices); i++ {
+        buy := prices[i]
+        for j := i + 1; j < len(prices); j++ {
+            sell := prices[j]
+            res = max(res, sell - buy)
+        }
+    }
+    return res
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun maxProfit(prices: IntArray): Int {
+        var res = 0
+        for (i in prices.indices) {
+            val buy = prices[i]
+            for (j in i + 1 until prices.size) {
+                val sell = prices[j]
+                res = maxOf(res, sell - buy)
+            }
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func maxProfit(_ prices: [Int]) -> Int {
+        var res = 0
+        for i in 0..<prices.count {
+            let buy = prices[i]
+            for j in (i + 1)..<prices.count {
+                let sell = prices[j]
+                res = max(res, sell - buy)
+            }
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -197,6 +250,67 @@ public class Solution {
 }
 ```
 
+```go
+func maxProfit(prices []int) int {
+    l, r := 0, 1
+    maxP := 0
+
+    for r < len(prices) {
+        if prices[l] < prices[r] {
+            profit := prices[r] - prices[l]
+            if profit > maxP {
+                maxP = profit
+            }
+        } else {
+            l = r
+        }
+        r++
+    }
+    return maxP
+}
+```
+
+```kotlin
+class Solution {
+    fun maxProfit(prices: IntArray): Int {
+        var l = 0
+        var r = 1
+        var maxP = 0
+
+        while (r < prices.size) {
+            if (prices[l] < prices[r]) {
+                val profit = prices[r] - prices[l]
+                maxP = maxOf(maxP, profit)
+            } else {
+                l = r
+            }
+            r++
+        }
+        return maxP
+    }
+}
+```
+
+```swift
+class Solution {
+    func maxProfit(_ prices: [Int]) -> Int {
+        var l = 0, r = 1
+        var maxP = 0
+
+        while r < prices.count {
+            if prices[l] < prices[r] {
+                let profit = prices[r] - prices[l]
+                maxP = max(maxP, profit)
+            } else {
+                l = r
+            }
+            r += 1
+        }
+        return maxP
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -287,6 +401,53 @@ public class Solution {
 }
 ```
 
+```go
+func maxProfit(prices []int) int {
+    maxP := 0
+    minBuy := math.MaxInt32
+
+    for _, sell := range prices {
+        if sell - minBuy > maxP {
+            maxP = sell - minBuy
+        }
+        if sell < minBuy {
+            minBuy = sell
+        }
+    }
+    return maxP
+}
+```
+
+```kotlin
+class Solution {
+    fun maxProfit(prices: IntArray): Int {
+        var maxP = 0
+        var minBuy = Int.MAX_VALUE
+
+        for (sell in prices) {
+            maxP = maxOf(maxP, sell - minBuy)
+            minBuy = minOf(minBuy, sell)
+        }
+        return maxP
+    }
+}
+```
+
+```swift
+class Solution {
+    func maxProfit(_ prices: [Int]) -> Int {
+        var maxP = 0
+        var minBuy = prices[0]
+
+        for sell in prices {
+            maxP = max(maxP, sell - minBuy)
+            minBuy = min(minBuy, sell)
+        }
+        return maxP
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/buy-two-chocolates.md b/articles/buy-two-chocolates.md
new file mode 100644
index 000000000..0b6edc79d
--- /dev/null
+++ b/articles/buy-two-chocolates.md
@@ -0,0 +1,211 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def buyChoco(self, prices: List[int], money: int) -> int:
+        res = -1
+        for i in range(len(prices)):
+            for j in range(i + 1, len(prices)):
+                if prices[i] + prices[j] <= money:
+                    res = max(res, money - prices[i] - prices[j])
+        return res if res != -1 else money
+```
+
+```java
+public class Solution {
+    public int buyChoco(int[] prices, int money) {
+        int res = -1;
+        for (int i = 0; i < prices.length; i++) {
+            for (int j = i + 1; j < prices.length; j++) {
+                if (prices[i] + prices[j] <= money) {
+                    res = Math.max(res, money - prices[i] - prices[j]);
+                }
+            }
+        }
+        return res == -1 ? money : res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int buyChoco(vector<int>& prices, int money) {
+        int res = -1;
+        for (int i = 0; i < prices.size(); i++) {
+            for (int j = i + 1; j < prices.size(); j++) {
+                if (prices[i] + prices[j] <= money) {
+                    res = max(res, money - prices[i] - prices[j]);
+                }
+            }
+        }
+        return res == -1 ? money : res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    buyChoco(prices, money) {
+        let res = -1;
+        for (let i = 0; i < prices.length; i++) {
+            for (let j = i + 1; j < prices.length; j++) {
+                if (prices[i] + prices[j] <= money) {
+                    res = Math.max(res, money - prices[i] - prices[j]);
+                }
+            }
+        }
+        return res === -1 ? money : res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 2. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def buyChoco(self, prices: List[int], money: int) -> int:
+        prices.sort()
+        buy = prices[0] + prices[1]
+        return money if buy > money else money - buy
+```
+
+```java
+public class Solution {
+    public int buyChoco(int[] prices, int money) {
+        Arrays.sort(prices);
+        int buy = prices[0] + prices[1];
+        return buy > money ? money : money - buy;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int buyChoco(vector<int>& prices, int money) {
+        sort(prices.begin(), prices.end());
+        int buy = prices[0] + prices[1];
+        return buy > money ? money : money - buy;
+    }
+};
+```
+
+```javascript
+class Solution {
+    buyChoco(prices, money) {
+        prices.sort((a, b) => a - b);
+        let buy = prices[0] + prices[1];
+        return buy > money ? money : money - buy;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 3. Greedy
+
+::tabs-start
+
+```python
+class Solution:
+    def buyChoco(self, prices: list[int], money: int) -> int:
+        min1 = min2 = float('inf')
+
+        for p in prices:
+            if p < min1:
+                min1, min2 = p, min1
+            elif p < min2:
+                min2 = p
+        
+        leftover = money - min1 - min2
+        return leftover if leftover >= 0 else money
+```
+
+```java
+public class Solution {
+    public int buyChoco(int[] prices, int money) {
+        int min1 = Integer.MAX_VALUE, min2 = Integer.MAX_VALUE;
+
+        for (int p : prices) {
+            if (p < min1) {
+                min2 = min1;
+                min1 = p;
+            } else if (p < min2) {
+                min2 = p;
+            }
+        }
+
+        int leftover = money - min1 - min2;
+        return leftover >= 0 ? leftover : money;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int buyChoco(vector<int>& prices, int money) {
+        int min1 = INT_MAX, min2 = INT_MAX;
+
+        for (int p : prices) {
+            if (p < min1) {
+                min2 = min1;
+                min1 = p;
+            } else if (p < min2) {
+                min2 = p;
+            }
+        }
+
+        int leftover = money - min1 - min2;
+        return leftover >= 0 ? leftover : money;
+    }
+};
+```
+
+```javascript
+class Solution {
+    buyChoco(prices, money) {
+        let min1 = Infinity, min2 = Infinity;
+
+        for (const p of prices) {
+            if (p < min1) {
+                min2 = min1;
+                min1 = p;
+            } else if (p < min2) {
+                min2 = p;
+            }
+        }
+
+        const leftover = money - min1 - min2;
+        return leftover >= 0 ? leftover : money;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/calculate-money-in-leetcode-bank.md b/articles/calculate-money-in-leetcode-bank.md
new file mode 100644
index 000000000..1735a4724
--- /dev/null
+++ b/articles/calculate-money-in-leetcode-bank.md
@@ -0,0 +1,248 @@
+## 1. Simulation
+
+::tabs-start
+
+```python
+class Solution:
+    def totalMoney(self, n: int) -> int:
+        day, deposit = 0, 1
+        res = 0
+
+        while day < n:
+            res += deposit
+            deposit += 1
+            day += 1
+
+            if day % 7 == 0:
+                deposit = 1 + day // 7
+
+        return res
+```
+
+```java
+public class Solution {
+    public int totalMoney(int n) {
+        int day = 0, deposit = 1, res = 0;
+
+        while (day < n) {
+            res += deposit;
+            deposit++;
+            day++;
+
+            if (day % 7 == 0) {
+                deposit = 1 + day / 7;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int totalMoney(int n) {
+        int day = 0, deposit = 1, res = 0;
+
+        while (day < n) {
+            res += deposit;
+            deposit++;
+            day++;
+
+            if (day % 7 == 0) {
+                deposit = 1 + day / 7;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    totalMoney(n) {
+        let day = 0, deposit = 1, res = 0;
+
+        while (day < n) {
+            res += deposit;
+            deposit++;
+            day++;
+
+            if (day % 7 === 0) {
+                deposit = 1 + Math.floor(day / 7);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Math
+
+::tabs-start
+
+```python
+class Solution:
+    def totalMoney(self, n: int) -> int:
+        weeks = n // 7
+        low = 28
+        high = 28 + 7 * (weeks - 1)
+        res = weeks * (low + high) // 2
+
+        monday = weeks + 1
+        for i in range(n % 7):
+            res += i + monday
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int totalMoney(int n) {
+        int weeks = n / 7;
+        int low = 28;
+        int high = 28 + 7 * (weeks - 1);
+        int res = weeks * (low + high) / 2;
+
+        int monday = weeks + 1;
+        for (int i = 0; i < n % 7; i++) {
+            res += i + monday;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int totalMoney(int n) {
+        int weeks = n / 7;
+        int low = 28;
+        int high = 28 + 7 * (weeks - 1);
+        int res = weeks * (low + high) / 2;
+
+        int monday = weeks + 1;
+        for (int i = 0; i < n % 7; i++) {
+            res += i + monday;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    totalMoney(n) {
+        const weeks = Math.floor(n / 7);
+        const low = 28;
+        const high = 28 + 7 * (weeks - 1);
+        let res = weeks * (low + high) / 2;
+
+        const monday = weeks + 1;
+        for (let i = 0; i < n % 7; i++) {
+            res += i + monday;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Math (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def totalMoney(self, n: int) -> int:
+        SUM = lambda x: (x * (x + 1)) >> 1
+        weeks = n // 7
+        res = SUM(weeks - 1) * 7 + weeks * SUM(7)
+        res += SUM(n % 7) + weeks * (n % 7)
+        return res
+```
+
+```java
+public class Solution {
+    public int totalMoney(int n) {
+        int weeks = n / 7;
+        int res = SUM(weeks - 1) * 7 + weeks * SUM(7);
+        res += SUM(n % 7) + weeks * (n % 7);
+        return res;
+    }
+
+    private int SUM(int n) {
+        return (n * (n + 1)) / 2;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int totalMoney(int n) {
+        auto SUM = [](int x) { return (x * (x + 1)) / 2; };
+
+        int weeks = n / 7;
+        int res = SUM(weeks - 1) * 7 + weeks * SUM(7);
+        res += SUM(n % 7) + weeks * (n % 7);
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    totalMoney(n) {
+        const SUM = x => (x * (x + 1)) / 2;
+
+        const weeks = Math.floor(n / 7);
+        let res = SUM(weeks - 1) * 7 + weeks * SUM(7);
+        res += SUM(n % 7) + weeks * (n % 7);
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/can-place-flowers.md b/articles/can-place-flowers.md
new file mode 100644
index 000000000..7ccaeba96
--- /dev/null
+++ b/articles/can-place-flowers.md
@@ -0,0 +1,178 @@
+## 1. Iteration - I
+
+::tabs-start
+
+```python
+class Solution:
+    def canPlaceFlowers(self, flowerbed: List[int], n: int) -> bool:
+        f = [0] + flowerbed + [0]
+        
+        for i in range(1, len(f) - 1):
+            if f[i - 1] == 0 and f[i] == 0 and f[i + 1] == 0:
+                f[i] = 1
+                n -= 1
+        
+        return n <= 0
+```
+
+```java
+public class Solution {
+    public boolean canPlaceFlowers(int[] flowerbed, int n) {
+        int[] f = new int[flowerbed.length + 2];        
+        for (int i = 0; i < flowerbed.length; i++) {
+            f[i + 1] = flowerbed[i];
+        }
+        
+        for (int i = 1; i < f.length - 1; i++) {
+            if (f[i - 1] == 0 && f[i] == 0 && f[i + 1] == 0) {
+                f[i] = 1;
+                n--;
+            }
+        }
+        return n <= 0;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool canPlaceFlowers(vector<int>& flowerbed, int n) {
+        vector<int> f(flowerbed.size() + 2, 0);
+        for (int i = 0; i < flowerbed.size(); i++) {
+            f[i + 1] = flowerbed[i];
+        }
+        
+        for (int i = 1; i < f.size() - 1; i++) {
+            if (f[i - 1] == 0 && f[i] == 0 && f[i + 1] == 0) {
+                f[i] = 1;
+                n--;
+            }
+        }
+        return n <= 0;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} flowerbed
+     * @param {number} n
+     * @return {boolean}
+     */
+    canPlaceFlowers(flowerbed, n) {
+        const f = [0, ...flowerbed, 0];
+        
+        for (let i = 1; i < f.length - 1; i++) {
+            if (f[i - 1] === 0 && f[i] === 0 && f[i + 1] === 0) {
+                f[i] = 1;
+                n--;
+            }
+        }
+        return n <= 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Iteration - II
+
+::tabs-start
+
+```python
+class Solution:
+    def canPlaceFlowers(self, flowerbed: List[int], n: int) -> bool:
+        empty = 0 if flowerbed[0] else 1
+        
+        for f in flowerbed:
+            if f:
+                n -= int((empty - 1) / 2)
+                empty = 0
+            else:
+                empty += 1
+        
+        n -= empty // 2
+        return n <= 0
+```
+
+```java
+public class Solution {
+    public boolean canPlaceFlowers(int[] flowerbed, int n) {
+        int empty = flowerbed[0] == 0 ? 1 : 0;
+        
+        for (int f : flowerbed) {
+            if (f == 1) {
+                n -= (empty - 1) / 2;
+                empty = 0;
+            } else {
+                empty++;
+            }
+        }
+        
+        n -= empty / 2;
+        return n <= 0;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool canPlaceFlowers(vector<int>& flowerbed, int n) {
+        int empty = flowerbed[0] == 0 ? 1 : 0;
+        
+        for (int f : flowerbed) {
+            if (f == 1) {
+                n -= (empty - 1) / 2;
+                empty = 0;
+            } else {
+                empty++;
+            }
+        }
+        
+        n -= empty / 2;
+        return n <= 0;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} flowerbed
+     * @param {number} n
+     * @return {boolean}
+     */
+    canPlaceFlowers(flowerbed, n) {
+        let empty = flowerbed[0] === 0 ? 1 : 0;
+        
+        for (let f of flowerbed) {
+            if (f === 1) {
+                n -= Math.floor(Math.max(0, empty - 1) / 2);
+                empty = 0;
+            } else {
+                empty++;
+            }
+        }
+        
+        n -= Math.floor(empty / 2);
+        return n <= 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/candy.md b/articles/candy.md
new file mode 100644
index 000000000..adeba0a66
--- /dev/null
+++ b/articles/candy.md
@@ -0,0 +1,399 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def candy(self, ratings: List[int]) -> int:
+        n = len(ratings)
+        arr = [1] * n
+
+        for i in range(n - 1):
+            if ratings[i] == ratings[i + 1]:
+                continue
+            if ratings[i + 1] > ratings[i]:
+                arr[i + 1] = arr[i] + 1
+            elif arr[i] == arr[i + 1]:
+                arr[i + 1] = arr[i]
+                arr[i] += 1
+                for j in range(i - 1, -1, -1):
+                    if ratings[j] > ratings[j + 1]:
+                        if arr[j + 1] < arr[j]:
+                            break
+                        arr[j] += 1
+
+        return sum(arr)
+```
+
+```java
+public class Solution {
+    public int candy(int[] ratings) {
+        int n = ratings.length;
+        int[] arr = new int[n];
+        for (int i = 0; i < n; i++) {
+            arr[i] = 1;
+        }
+
+        for (int i = 0; i < n - 1; i++) {
+            if (ratings[i] == ratings[i + 1]) {
+                continue;
+            }
+            if (ratings[i + 1] > ratings[i]) {
+                arr[i + 1] = arr[i] + 1;
+            } else if (arr[i] == arr[i + 1]) {
+                arr[i + 1] = arr[i];
+                arr[i]++;
+                for (int j = i - 1; j >= 0; j--) {
+                    if (ratings[j] > ratings[j + 1]) {
+                        if (arr[j + 1] < arr[j]) {
+                            break;
+                        }
+                        arr[j]++;
+                    }
+                }
+            }
+        }
+
+        int sum = 0;
+        for (int num : arr) {
+            sum += num;
+        }
+        return sum;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int candy(vector<int>& ratings) {
+        int n = ratings.size();
+        vector<int> arr(n, 1);
+
+        for (int i = 0; i < n - 1; i++) {
+            if (ratings[i] == ratings[i + 1]) {
+                continue;
+            }
+            if (ratings[i + 1] > ratings[i]) {
+                arr[i + 1] = arr[i] + 1;
+            } else if (arr[i] == arr[i + 1]) {
+                arr[i + 1] = arr[i];
+                arr[i]++;
+                for (int j = i - 1; j >= 0; j--) {
+                    if (ratings[j] > ratings[j + 1]) {
+                        if (arr[j + 1] < arr[j]) {
+                            break;
+                        }
+                        arr[j]++;
+                    }
+                }
+            }
+        }
+
+        return accumulate(arr.begin(), arr.end(), 0);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} ratings
+     * @return {number}
+     */
+    candy(ratings) {
+        const n = ratings.length;
+        const arr = new Array(n).fill(1);
+
+        for (let i = 0; i < n - 1; i++) {
+            if (ratings[i] === ratings[i + 1]) {
+                continue;
+            }
+            if (ratings[i + 1] > ratings[i]) {
+                arr[i + 1] = arr[i] + 1;
+            } else if (arr[i] === arr[i + 1]) {
+                arr[i + 1] = arr[i];
+                arr[i]++;
+                for (let j = i - 1; j >= 0; j--) {
+                    if (ratings[j] > ratings[j + 1]) {
+                        if (arr[j + 1] < arr[j]) {
+                            break;
+                        }
+                        arr[j]++;
+                    }
+                }
+            }
+        }
+
+        return arr.reduce((sum, num) => sum + num, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Greedy (Two Pass)
+
+::tabs-start
+
+```python
+class Solution:
+    def candy(self, ratings: List[int]) -> int:
+        n = len(ratings)
+        arr = [1] * n
+
+        for i in range(1, n):
+            if ratings[i - 1] < ratings[i]:
+                arr[i] = arr[i - 1] + 1
+        
+        for i in range(n - 2, -1, -1):
+            if ratings[i] > ratings[i + 1]:
+                arr[i] = max(arr[i], arr[i + 1] + 1)
+        
+        return sum(arr)
+```
+
+```java
+public class Solution {
+    public int candy(int[] ratings) {
+        int n = ratings.length;
+        int[] arr = new int[n];
+        Arrays.fill(arr, 1);
+
+        for (int i = 1; i < n; i++) {
+            if (ratings[i - 1] < ratings[i]) {
+                arr[i] = arr[i - 1] + 1;
+            }
+        }
+
+        for (int i = n - 2; i >= 0; i--) {
+            if (ratings[i] > ratings[i + 1]) {
+                arr[i] = Math.max(arr[i], arr[i + 1] + 1);
+            }
+        }
+
+        int sum = 0;
+        for (int num : arr) {
+            sum += num;
+        }
+        return sum;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int candy(vector<int>& ratings) {
+        int n = ratings.size();
+        vector<int> arr(n, 1);
+
+        for (int i = 1; i < n; i++) {
+            if (ratings[i - 1] < ratings[i]) {
+                arr[i] = arr[i - 1] + 1;
+            }
+        }
+
+        for (int i = n - 2; i >= 0; i--) {
+            if (ratings[i] > ratings[i + 1]) {
+                arr[i] = max(arr[i], arr[i + 1] + 1);
+            }
+        }
+
+        return accumulate(arr.begin(), arr.end(), 0);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} ratings
+     * @return {number}
+     */
+    candy(ratings) {
+        const n = ratings.length;
+        const arr = new Array(n).fill(1);
+
+        for (let i = 1; i < n; i++) {
+            if (ratings[i - 1] < ratings[i]) {
+                arr[i] = arr[i - 1] + 1;
+            }
+        }
+
+        for (let i = n - 2; i >= 0; i--) {
+            if (ratings[i] > ratings[i + 1]) {
+                arr[i] = Math.max(arr[i], arr[i + 1] + 1);
+            }
+        }
+
+        return arr.reduce((sum, num) => sum + num, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Greedy (One Pass)
+
+::tabs-start
+
+```python
+class Solution:
+    def candy(self, ratings: List[int]) -> int:
+        n = len(ratings)
+        res = n
+
+        i = 1
+        while i < n:
+            if ratings[i] == ratings[i - 1]:
+                i += 1
+                continue
+            
+            inc = 0
+            while i < n and ratings[i] > ratings[i - 1]:
+                inc += 1
+                res += inc
+                i += 1
+
+            dec = 0
+            while i < n and ratings[i] < ratings[i - 1]:
+                dec += 1
+                res += dec
+                i += 1
+            
+            res -= min(inc, dec)
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int candy(int[] ratings) {
+        int n = ratings.length;
+        int res = n;
+
+        int i = 1;
+        while (i < n) {
+            if (ratings[i] == ratings[i - 1]) {
+                i++;
+                continue;
+            }
+
+            int inc = 0;
+            while (i < n && ratings[i] > ratings[i - 1]) {
+                inc++;
+                res += inc;
+                i++;
+            }
+
+            int dec = 0;
+            while (i < n && ratings[i] < ratings[i - 1]) {
+                dec++;
+                res += dec;
+                i++;
+            }
+
+            res -= Math.min(inc, dec);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int candy(vector<int>& ratings) {
+        int n = ratings.size();
+        int res = n;
+
+        int i = 1;
+        while (i < n) {
+            if (ratings[i] == ratings[i - 1]) {
+                i++;
+                continue;
+            }
+
+            int inc = 0;
+            while (i < n && ratings[i] > ratings[i - 1]) {
+                inc++;
+                res += inc;
+                i++;
+            }
+
+            int dec = 0;
+            while (i < n && ratings[i] < ratings[i - 1]) {
+                dec++;
+                res += dec;
+                i++;
+            }
+
+            res -= min(inc, dec);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} ratings
+     * @return {number}
+     */
+    candy(ratings) {
+        const n = ratings.length;
+        let res = n;
+
+        let i = 1;
+        while (i < n) {
+            if (ratings[i] === ratings[i - 1]) {
+                i++;
+                continue;
+            }
+
+            let inc = 0;
+            while (i < n && ratings[i] > ratings[i - 1]) {
+                inc++;
+                res += inc;
+                i++;
+            }
+
+            let dec = 0;
+            while (i < n && ratings[i] < ratings[i - 1]) {
+                dec++;
+                res += dec;
+                i++;
+            }
+
+            res -= Math.min(inc, dec);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/capacity-to-ship-packages-within-d-days.md b/articles/capacity-to-ship-packages-within-d-days.md
new file mode 100644
index 000000000..dfc4f2146
--- /dev/null
+++ b/articles/capacity-to-ship-packages-within-d-days.md
@@ -0,0 +1,327 @@
+## 1. Linear Search
+
+::tabs-start
+
+```python
+class Solution:
+    def shipWithinDays(self, weights: List[int], days: int) -> int:
+        res = max(weights)
+        while True:
+            ships = 1
+            cap = res
+            for w in weights:
+                if cap - w < 0:
+                    ships += 1
+                    cap = res
+                cap -= w
+
+            if ships <= days:
+                return res
+
+            res += 1
+```
+
+```java
+public class Solution {
+    public int shipWithinDays(int[] weights, int days) {
+        int res = 0;
+        for (int weight : weights) {
+            res = Math.max(res, weight);
+        }
+        while (true) {
+            int ships = 1;
+            int cap = res;
+            for (int weight : weights) {
+                if (cap - weight < 0) {
+                    ships++;
+                    cap = res;
+                }
+                cap -= weight;
+            }
+            if (ships <= days) {
+                return res;
+            }
+            res++;
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int shipWithinDays(vector<int>& weights, int days) {
+        int res = *max_element(weights.begin(), weights.end());
+        while (true) {
+            int ships = 1, cap = res;
+            for (int w : weights) {
+                if (cap - w < 0) {
+                    ships++;
+                    cap = res;
+                }
+                cap -= w;
+            }
+            if (ships <= days) {
+                return res;
+            }
+            res++;
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} weights
+     * @param {number} days
+     * @return {number}
+     */
+    shipWithinDays(weights, days) {
+        let res = Math.max(...weights);
+        while (true) {
+            let ships = 1, cap = res;
+            for (let w of weights) {
+                if (cap - w < 0) {
+                    ships++;
+                    cap = res;
+                }
+                cap -= w;
+            }
+            if (ships <= days) {
+                return res;
+            }
+            res++;
+        }
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int ShipWithinDays(int[] weights, int days) {
+        int res = weights.Max();
+        while (true) {
+            int ships = 1;
+            int cap = res;
+            foreach (int w in weights) {
+                if (cap - w < 0) {
+                    ships++;
+                    cap = res;
+                }
+                cap -= w;
+            }
+            if (ships <= days) {
+                return res;
+            }
+            res++;
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Binary Search
+
+::tabs-start
+
+```python
+class Solution:
+    def shipWithinDays(self, weights: List[int], days: int) -> int:
+        l, r = max(weights), sum(weights)
+        res = r
+
+        def canShip(cap):
+            ships, currCap = 1, cap
+            for w in weights:
+                if currCap - w < 0:
+                    ships += 1
+                    if ships > days:
+                        return False
+                    currCap = cap
+
+                currCap -= w
+            return True
+
+        while l <= r:
+            cap = (l + r) // 2
+            if canShip(cap):
+                res = min(res, cap)
+                r = cap - 1
+            else:
+                l = cap + 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int shipWithinDays(int[] weights, int days) {
+        int l = 0, r = 0;
+        for (int w : weights) {
+            l = Math.max(l, w);
+            r += w;
+        }
+        int res = r;
+
+        while (l <= r) {
+            int cap = (l + r) / 2;
+            if (canShip(weights, days, cap)) {
+                res = Math.min(res, cap);
+                r = cap - 1;
+            } else {
+                l = cap + 1;
+            }
+        }
+        return res;
+    }
+
+    private boolean canShip(int[] weights, int days, int cap) {
+        int ships = 1, currCap = cap;
+        for (int w : weights) {
+            if (currCap - w < 0) {
+                ships++;
+                if (ships > days) {
+                    return false;
+                }
+                currCap = cap;
+            }
+            currCap -= w;
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int shipWithinDays(vector<int>& weights, int days) {
+        int l = *max_element(weights.begin(), weights.end());
+        int r = accumulate(weights.begin(), weights.end(), 0);
+        int res = r;
+
+        while (l <= r) {
+            int cap = (l + r) / 2;
+            if (canShip(weights, days, cap)) {
+                res = min(res, cap);
+                r = cap - 1;
+            } else {
+                l = cap + 1;
+            }
+        }
+        return res;
+    }
+
+private:
+    bool canShip(const vector<int>& weights, int days, int cap) {
+        int ships = 1, currCap = cap;
+        for (int w : weights) {
+            if (currCap - w < 0) {
+                ships++;
+                if (ships > days) {
+                    return false;
+                }
+                currCap = cap;
+            }
+            currCap -= w;
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} weights
+     * @param {number} days
+     * @return {number}
+     */
+    shipWithinDays(weights, days) {
+        let l = Math.max(...weights);
+        let r = weights.reduce((a, b) => a + b, 0);
+        let res = r;
+
+        const canShip = (cap) => {
+            let ships = 1, currCap = cap;
+            for (const w of weights) {
+                if (currCap - w < 0) {
+                    ships++;
+                    if (ships > days) {
+                        return false;
+                    }
+                    currCap = cap;
+                }
+                currCap -= w;
+            }
+            return true;
+        };
+
+        while (l <= r) {
+            const cap = Math.floor((l + r) / 2);
+            if (canShip(cap)) {
+                res = Math.min(res, cap);
+                r = cap - 1;
+            } else {
+                l = cap + 1;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int ShipWithinDays(int[] weights, int days) {
+        int l = weights.Max();
+        int r = weights.Sum();
+        int res = r;
+
+        bool CanShip(int cap) {
+            int ships = 1;
+            int currCap = cap;
+
+            foreach (int w in weights) {
+                if (currCap - w < 0) {
+                    ships++;
+                    if (ships > days) return false;
+                    currCap = cap;
+                }
+                currCap -= w;
+            }
+
+            return true;
+        }
+
+        while (l <= r) {
+            int cap = (l + r) / 2;
+            if (CanShip(cap)) {
+                res = Math.Min(res, cap);
+                r = cap - 1;
+            } else {
+                l = cap + 1;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/car-fleet.md b/articles/car-fleet.md
index aff2820e2..22c7a9d0f 100644
--- a/articles/car-fleet.md
+++ b/articles/car-fleet.md
@@ -106,6 +106,70 @@ public class Solution {
 }
 ```
 
+```go
+func carFleet(target int, position []int, speed []int) int {
+    n := len(position)
+    pair := make([][2]int, n)
+    for i := 0; i < n; i++ {
+        pair[i] = [2]int{position[i], speed[i]}
+    }
+    
+    sort.Slice(pair, func(i, j int) bool {
+        return pair[i][0] > pair[j][0]
+    })
+    
+    stack := []float64{}
+    for _, p := range pair {
+        time := float64(target - p[0]) / float64(p[1])
+        stack = append(stack, time)
+        if len(stack) >= 2 && stack[len(stack)-1] <= stack[len(stack)-2] {
+            stack = stack[:len(stack)-1]
+        }
+    }
+    
+    return len(stack)
+}
+```
+
+```kotlin
+class Solution {
+    fun carFleet(target: Int, position: IntArray, speed: IntArray): Int {
+        val pair = position.zip(speed).sortedByDescending { it.first }
+        val stack = mutableListOf<Double>()
+
+        for ((p, s) in pair) {
+            val time = (target - p).toDouble() / s
+            stack.add(time)
+            if (stack.size >= 2 && stack[stack.size - 1] <= stack[stack.size - 2]) {
+                stack.removeAt(stack.size - 1)
+            }
+        }
+
+        return stack.size
+    }
+}
+```
+
+```swift
+class Solution {
+    func carFleet(_ target: Int, _ position: [Int], _ speed: [Int]) -> Int {
+        var pair = zip(position, speed).map { ($0, $1) }
+        pair.sort { $0.0 > $1.0 } // Sort in descending order by position
+
+        var stack = [Double]()
+
+        for (p, s) in pair {
+            stack.append(Double(target - p) / Double(s))
+            if stack.count >= 2 && stack.last! <= stack[stack.count - 2] {
+                stack.removeLast()
+            }
+        }
+
+        return stack.count
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -115,7 +179,7 @@ public class Solution {
 
 ---
 
-## 2. Simulation
+## 2. Iteration
 
 ::tabs-start
 
@@ -236,6 +300,77 @@ public class Solution {
 }
 ```
 
+```go
+func carFleet(target int, position []int, speed []int) int {
+    n := len(position)
+    pair := make([][2]int, n)
+    for i := 0; i < n; i++ {
+        pair[i] = [2]int{position[i], speed[i]}
+    }
+    
+    sort.Slice(pair, func(i, j int) bool {
+        return pair[i][0] > pair[j][0]
+    })
+    
+    fleets := 1
+    prevTime := float64(target - pair[0][0]) / float64(pair[0][1])
+    for i := 1; i < n; i++ {
+        currTime := float64(target - pair[i][0]) / float64(pair[i][1])
+        if currTime > prevTime {
+            fleets++
+            prevTime = currTime
+        }
+    }
+    
+    return fleets
+}
+```
+
+```kotlin
+class Solution {
+    fun carFleet(target: Int, position: IntArray, speed: IntArray): Int {
+        val pair = position.zip(speed).sortedByDescending { it.first }
+        
+        var fleets = 1
+        var prevTime = (target - pair[0].first).toDouble() / pair[0].second
+        for (i in 1 until pair.size) {
+            val (p, s) = pair[i]
+            val currTime = (target - p).toDouble() / s
+            if (currTime > prevTime) {
+                fleets++
+                prevTime = currTime
+            }
+        }
+        
+        return fleets
+    }
+}
+```
+
+```swift
+class Solution {
+    func carFleet(_ target: Int, _ position: [Int], _ speed: [Int]) -> Int {
+        var pair = zip(position, speed).map { ($0, $1) }
+        pair.sort { $0.0 > $1.0 } // Sort in descending order by position
+
+        var fleets = 1
+        var prevTime = Double(target - pair[0].0) / Double(pair[0].1)
+
+        for i in 1..<pair.count {
+            let currCar = pair[i]
+            let currTime = Double(target - currCar.0) / Double(currCar.1)
+
+            if currTime > prevTime {
+                fleets += 1
+                prevTime = currTime
+            }
+        }
+
+        return fleets
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/car-pooling.md b/articles/car-pooling.md
new file mode 100644
index 000000000..df5745d6d
--- /dev/null
+++ b/articles/car-pooling.md
@@ -0,0 +1,585 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def carPooling(self, trips: List[List[int]], capacity: int) -> bool:
+        trips.sort(key=lambda x: x[1])
+
+        for i in range(len(trips)):
+            curPass = trips[i][0]
+            for j in range(i):
+                if trips[j][2] > trips[i][1]:
+                    curPass += trips[j][0]
+            if curPass > capacity:
+                return False
+
+        return True
+```
+
+```java
+public class Solution {
+    public boolean carPooling(int[][] trips, int capacity) {
+        Arrays.sort(trips, (a, b) -> Integer.compare(a[1], b[1]));
+
+        for (int i = 0; i < trips.length; i++) {
+            int curPass = trips[i][0];
+            for (int j = 0; j < i; j++) {
+                if (trips[j][2] > trips[i][1]) {
+                    curPass += trips[j][0];
+                }
+            }
+            if (curPass > capacity) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool carPooling(vector<vector<int>>& trips, int capacity) {
+        sort(trips.begin(), trips.end(), [](const vector<int>& a, const vector<int>& b) {
+            return a[1] < b[1];
+        });
+
+        for (int i = 0; i < trips.size(); i++) {
+            int curPass = trips[i][0];
+            for (int j = 0; j < i; j++) {
+                if (trips[j][2] > trips[i][1]) {
+                    curPass += trips[j][0];
+                }
+            }
+            if (curPass > capacity) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} trips
+     * @param {number} capacity
+     * @return {boolean}
+     */
+    carPooling(trips, capacity) {
+        trips.sort((a, b) => a[1] - b[1]);
+
+        for (let i = 0; i < trips.length; i++) {
+            let curPass = trips[i][0];
+            for (let j = 0; j < i; j++) {
+                if (trips[j][2] > trips[i][1]) {
+                    curPass += trips[j][0];
+                }
+            }
+            if (curPass > capacity) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool CarPooling(int[][] trips, int capacity) {
+        Array.Sort(trips, (a, b) => a[1].CompareTo(b[1]));
+
+        for (int i = 0; i < trips.Length; i++) {
+            int curPass = trips[i][0];
+            for (int j = 0; j < i; j++) {
+                if (trips[j][2] > trips[i][1]) {
+                    curPass += trips[j][0];
+                }
+            }
+            if (curPass > capacity) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 2. Min-Heap
+
+::tabs-start
+
+```python
+class Solution:
+    def carPooling(self, trips: List[List[int]], capacity: int) -> bool:
+        trips.sort(key=lambda t: t[1])
+        
+        minHeap = []  # pair of [end, numPassengers]
+        curPass = 0
+        
+        for numPass, start, end in trips:
+            while minHeap and minHeap[0][0] <= start:
+                curPass -= heapq.heappop(minHeap)[1]
+            
+            curPass += numPass
+            if curPass > capacity:
+                return False
+            
+            heapq.heappush(minHeap, [end, numPass])
+        
+        return True
+```
+
+```java
+public class Solution {
+    public boolean carPooling(int[][] trips, int capacity) {
+        Arrays.sort(trips, Comparator.comparingInt(a -> a[1]));
+        
+        PriorityQueue<int[]> minHeap = new PriorityQueue<>(Comparator.comparingInt(a -> a[0])); // [end, numPassengers]
+        int curPass = 0;
+        
+        for (int[] trip : trips) {
+            int numPass = trip[0], start = trip[1], end = trip[2];
+            
+            while (!minHeap.isEmpty() && minHeap.peek()[0] <= start) {
+                curPass -= minHeap.poll()[1];
+            }
+            
+            curPass += numPass;
+            if (curPass > capacity) {
+                return false;
+            }
+            
+            minHeap.offer(new int[]{end, numPass});
+        }
+        
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool carPooling(vector<vector<int>>& trips, int capacity) {
+        sort(trips.begin(), trips.end(), [](const vector<int>& a, const vector<int>& b) {
+            return a[1] < b[1];
+        });
+
+        priority_queue<pair<int, int>, vector<pair<int, int>>, greater<>> minHeap; // [end, numPassengers]
+        int curPass = 0;
+
+        for (const auto& trip : trips) {
+            int numPass = trip[0], start = trip[1], end = trip[2];
+
+            while (!minHeap.empty() && minHeap.top().first <= start) {
+                curPass -= minHeap.top().second;
+                minHeap.pop();
+            }
+
+            curPass += numPass;
+            if (curPass > capacity) {
+                return false;
+            }
+
+            minHeap.emplace(end, numPass);
+        }
+
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} trips
+     * @param {number} capacity
+     * @return {boolean}
+     */
+    carPooling(trips, capacity) {
+        trips.sort((a, b) => a[1] - b[1]);
+
+        const minHeap = new MinPriorityQueue(x => x[0]); // [end, numPassengers]
+        let curPass = 0;
+
+        for (const [numPass, start, end] of trips) {
+            while (!minHeap.isEmpty() && minHeap.front()[0] <= start) {
+                curPass -= minHeap.dequeue()[1];
+            }
+
+            curPass += numPass;
+            if (curPass > capacity) {
+                return false;
+            }
+
+            minHeap.enqueue([end, numPass]);
+        }
+
+        return true;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool CarPooling(int[][] trips, int capacity) {
+        Array.Sort(trips, (a, b) => a[1].CompareTo(b[1]));
+        
+        var minHeap = new PriorityQueue<int[], int>();
+        int curPass = 0;
+
+        foreach (var trip in trips) {
+            int numPass = trip[0];
+            int start = trip[1];
+            int end = trip[2];
+
+            while (minHeap.Count > 0 && minHeap.Peek()[0] <= start) {
+                curPass -= minHeap.Dequeue()[1];
+            }
+
+            curPass += numPass;
+            if (curPass > capacity) {
+                return false;
+            }
+
+            minHeap.Enqueue(new int[] { end, numPass }, end);
+        }
+
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Line Sweep - I
+
+::tabs-start
+
+```python
+class Solution:
+    def carPooling(self, trips: List[List[int]], capacity: int) -> bool:
+        points = []
+        for passengers, start, end in trips:
+            points.append([start, passengers])
+            points.append([end, -passengers])
+        
+        points.sort()
+        curPass = 0
+        for point, passengers in points:
+            curPass += passengers
+            if curPass > capacity:
+                return False
+        
+        return True
+```
+
+```java
+public class Solution {
+    public boolean carPooling(int[][] trips, int capacity) {
+        List<int[]> points = new ArrayList<>();
+        for (int[] trip : trips) {
+            int passengers = trip[0], start = trip[1], end = trip[2];
+            points.add(new int[]{start, passengers});
+            points.add(new int[]{end, -passengers});
+        }
+        
+        points.sort((a, b) -> a[0] == b[0] ? Integer.compare(a[1], b[1]) : Integer.compare(a[0], b[0]));
+        
+        int curPass = 0;
+        for (int[] point : points) {
+            curPass += point[1];
+            if (curPass > capacity) {
+                return false;
+            }
+        }
+        
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool carPooling(vector<vector<int>>& trips, int capacity) {
+        vector<pair<int, int>> points;
+        for (const auto& trip : trips) {
+            int passengers = trip[0], start = trip[1], end = trip[2];
+            points.emplace_back(start, passengers);
+            points.emplace_back(end, -passengers);
+        }
+
+        sort(points.begin(), points.end(), [](const pair<int, int>& a, const pair<int, int>& b) {
+            return a.first == b.first ? a.second < b.second : a.first < b.first;
+        });
+
+        int curPass = 0;
+        for (const auto& point : points) {
+            curPass += point.second;
+            if (curPass > capacity) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} trips
+     * @param {number} capacity
+     * @return {boolean}
+     */
+    carPooling(trips, capacity) {
+        const points = [];
+        for (const [passengers, start, end] of trips) {
+            points.push([start, passengers]);
+            points.push([end, -passengers]);
+        }
+        
+        points.sort((a, b) => a[0] === b[0] ? a[1] - b[1] : a[0] - b[0]);
+        
+        let curPass = 0;
+        for (const [point, passengers] of points) {
+            curPass += passengers;
+            if (curPass > capacity) {
+                return false;
+            }
+        }
+        
+        return true;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool CarPooling(int[][] trips, int capacity) {
+        List<int[]> points = new List<int[]>();
+        
+        foreach (var trip in trips) {
+            int passengers = trip[0];
+            int start = trip[1];
+            int end = trip[2];
+
+            points.Add(new int[] { start, passengers });
+            points.Add(new int[] { end, -passengers });
+        }
+
+        points.Sort((a, b) => {
+            if (a[0] == b[0]) return a[1] - b[1];
+            return a[0] - b[0];
+        });
+
+        int curPass = 0;
+        foreach (var point in points) {
+            curPass += point[1];
+            if (curPass > capacity) return false;
+        }
+
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Line Sweep - II
+
+::tabs-start
+
+```python
+class Solution:
+    def carPooling(self, trips: List[List[int]], capacity: int) -> bool:
+        L, R = float("inf"), float("-inf")
+        for _, start, end in trips:
+            L = min(L, start)
+            R = max(R, end)
+        
+        N = R - L + 1
+        passChange = [0] * (N + 1)
+        for passengers, start, end in trips:
+            passChange[start - L] += passengers
+            passChange[end - L] -= passengers
+        
+        curPass = 0
+        for change in passChange:
+            curPass += change
+            if curPass > capacity:
+                return False
+        
+        return True
+```
+
+```java
+public class Solution {
+    public boolean carPooling(int[][] trips, int capacity) {
+        int L = Integer.MAX_VALUE, R = Integer.MIN_VALUE;
+        for (int[] trip : trips) {
+            L = Math.min(L, trip[1]);
+            R = Math.max(R, trip[2]);
+        }
+
+        int N = R - L + 1;
+        int[] passChange = new int[N + 1];
+        for (int[] trip : trips) {
+            passChange[trip[1] - L] += trip[0];
+            passChange[trip[2] - L] -= trip[0];
+        }
+
+        int curPass = 0;
+        for (int change : passChange) {
+            curPass += change;
+            if (curPass > capacity) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool carPooling(vector<vector<int>>& trips, int capacity) {
+        int L = INT_MAX, R = INT_MIN;
+        for (const auto& trip : trips) {
+            L = min(L, trip[1]);
+            R = max(R, trip[2]);
+        }
+
+        int N = R - L + 1;
+        vector<int> passChange(N + 1, 0);
+        for (const auto& trip : trips) {
+            passChange[trip[1] - L] += trip[0];
+            passChange[trip[2] - L] -= trip[0];
+        }
+
+        int curPass = 0;
+        for (int change : passChange) {
+            curPass += change;
+            if (curPass > capacity) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} trips
+     * @param {number} capacity
+     * @return {boolean}
+     */
+    carPooling(trips, capacity) {
+        let L = Infinity, R = -Infinity;
+        for (const [passengers, start, end] of trips) {
+            L = Math.min(L, start);
+            R = Math.max(R, end);
+        }
+
+        const N = R - L + 1;
+        const passChange = Array(N + 1).fill(0);
+        for (const [passengers, start, end] of trips) {
+            passChange[start - L] += passengers;
+            passChange[end - L] -= passengers;
+        }
+
+        let curPass = 0;
+        for (const change of passChange) {
+            curPass += change;
+            if (curPass > capacity) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool CarPooling(int[][] trips, int capacity) {
+        int L = int.MaxValue, R = int.MinValue;
+
+        foreach (var trip in trips) {
+            int start = trip[1], end = trip[2];
+            L = Math.Min(L, start);
+            R = Math.Max(R, end);
+        }
+
+        int N = R - L + 1;
+        int[] passChange = new int[N + 1];
+
+        foreach (var trip in trips) {
+            int passengers = trip[0];
+            int start = trip[1];
+            int end = trip[2];
+
+            passChange[start - L] += passengers;
+            passChange[end - L] -= passengers;
+        }
+
+        int curPass = 0;
+        foreach (int change in passChange) {
+            curPass += change;
+            if (curPass > capacity) return false;
+        }
+
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + N)$
+* Space complexity: $O(N)$
+
+> Where $n$ is the size of the array $trips$ and $N$ is the difference between the rightmost location and the leftmost location.
\ No newline at end of file
diff --git a/articles/champagne-tower.md b/articles/champagne-tower.md
new file mode 100644
index 000000000..d2f36a28e
--- /dev/null
+++ b/articles/champagne-tower.md
@@ -0,0 +1,562 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def champagneTower(self, poured: int, query_row: int, query_glass: int) -> float:
+        def rec(row, glass):
+            if row < 0 or glass < 0 or glass > row:
+                return 0
+            
+            if row == 0 and glass == 0:
+                return poured
+            
+            left_parent = max(0, rec(row - 1, glass - 1) - 1)
+            right_parent = max(0, rec(row - 1, glass) - 1)
+            
+            return (left_parent + right_parent) / 2
+        
+        return min(1, rec(query_row, query_glass))
+```
+
+```java
+public class Solution {
+    public double champagneTower(int poured, int query_row, int query_glass) {
+        return Math.min(1, rec(poured, query_row, query_glass));
+    }
+
+    private double rec(int poured, int row, int glass) {
+        if (row < 0 || glass < 0 || glass > row) {
+            return 0;
+        }
+
+        if (row == 0 && glass == 0) {
+            return poured;
+        }
+
+        double leftParent = Math.max(0, rec(poured, row - 1, glass - 1) - 1);
+        double rightParent = Math.max(0, rec(poured, row - 1, glass) - 1);
+
+        return (leftParent + rightParent) / 2;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    double champagneTower(int poured, int query_row, int query_glass) {
+        return min(1.0, rec(poured, query_row, query_glass));
+    }
+
+private:
+    double rec(int poured, int row, int glass) {
+        if (row < 0 || glass < 0 || glass > row) {
+            return 0;
+        }
+
+        if (row == 0 && glass == 0) {
+            return poured;
+        }
+
+        double leftParent = max(0.0, rec(poured, row - 1, glass - 1) - 1);
+        double rightParent = max(0.0, rec(poured, row - 1, glass) - 1);
+
+        return (leftParent + rightParent) / 2;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} poured
+     * @param {number} query_row
+     * @param {number} query_glass
+     * @return {number}
+     */
+    champagneTower(poured, query_row, query_glass) {
+        const rec = (row, glass) => {
+            if (row < 0 || glass < 0 || glass > row) {
+                return 0;
+            }
+
+            if (row === 0 && glass === 0) {
+                return poured;
+            }
+
+            const leftParent = Math.max(0, rec(row - 1, glass - 1) - 1);
+            const rightParent = Math.max(0, rec(row - 1, glass) - 1);
+
+            return (leftParent + rightParent) / 2;
+        };
+
+        return Math.min(1, rec(query_row, query_glass));
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the given $queryRow$.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def champagneTower(self, poured: int, query_row: int, query_glass: int) -> float:
+        memo = { (0, 0) : poured }
+        
+        def rec(row, glass):
+            if row < 0 or glass < 0 or glass > row:
+                return 0
+            if (row, glass) in memo:
+                return memo[(row, glass)]
+            
+            left_parent = max(0, rec(row - 1, glass - 1) - 1)
+            right_parent = max(0, rec(row - 1, glass) - 1)
+            
+            memo[(row, glass)] = (left_parent + right_parent) / 2
+            return memo[(row, glass)]
+        
+        return min(1, rec(query_row, query_glass))
+```
+
+```java
+public class Solution {
+    public double champagneTower(int poured, int query_row, int query_glass) {
+        double[][] memo = new double[query_row + 5][];
+        for (int i = 0; i < query_row + 5; i++) {
+            memo[i] = new double[i + 1];
+            Arrays.fill(memo[i], -1);
+        }
+        memo[0][0] = poured;
+
+        return Math.min(1, rec(memo, query_row, query_glass));
+    }
+
+    private double rec(double[][] memo, int row, int glass) {
+        if (row < 0 || glass < 0 || glass > row) {
+            return 0;
+        }
+        
+        if (memo[row][glass] != -1) {
+            return memo[row][glass];
+        }
+
+        double leftParent = Math.max(0, rec(memo, row - 1, glass - 1) - 1);
+        double rightParent = Math.max(0, rec(memo, row - 1, glass) - 1);
+
+        memo[row][glass] = (leftParent + rightParent) / 2;
+        return memo[row][glass];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    double champagneTower(int poured, int query_row, int query_glass) {
+        vector<vector<double>> memo(query_row + 5);
+        for (int i = 0; i <= query_row + 4; i++) {
+            memo[i].resize(i + 1, -1);
+        }
+
+        memo[0][0] = poured;
+        return min(1.0, rec(memo, query_row, query_glass));
+    }
+
+private:
+    double rec(vector<vector<double>>& memo, int row, int glass) {
+        if (row < 0 || glass < 0 || glass > row) {
+            return 0;
+        }
+        
+        if (memo[row][glass] != -1) {
+            return memo[row][glass];
+        }
+
+        double leftParent = max(0.0, rec(memo, row - 1, glass - 1) - 1);
+        double rightParent = max(0.0, rec(memo, row - 1, glass) - 1);
+
+        memo[row][glass] = (leftParent + rightParent) / 2;
+        return memo[row][glass];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} poured
+     * @param {number} query_row
+     * @param {number} query_glass
+     * @return {number}
+     */
+    champagneTower(poured, query_row, query_glass) {
+        const memo = Array.from({ length: query_row + 5 }, (_, i) => Array(i + 1).fill(-1));
+        memo[0][0] = poured;
+
+        const rec = (row, glass) => {
+            if (row < 0 || glass < 0 || glass > row) {
+                return 0;
+            }
+
+            if (memo[row][glass] != -1) {
+                return memo[row][glass];
+            }
+
+            const leftParent = Math.max(0, rec(row - 1, glass - 1) - 1);
+            const rightParent = Math.max(0, rec(row - 1, glass) - 1);
+
+            memo[row][glass] = (leftParent + rightParent) / 2;
+            return memo[row][glass];
+
+            return (leftParent + rightParent) / 2;
+        };
+
+        return Math.min(1, rec(query_row, query_glass));
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n * m)$
+
+> Where $n$ is the given $queryRow$ and $m$ is the given $queryGlass$.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def champagneTower(self, poured: int, query_row: int, query_glass: int) -> float:
+        dp = [[0] * (i + 1) for i in range(query_row + 5)]
+        dp[0][0] += poured
+        
+        for row in range(min(99, query_row + 1)):
+            for glass in range(row + 1):
+                excess = (dp[row][glass] - 1.0) / 2.0
+                if excess > 0:
+                    dp[row + 1][glass] += excess
+                    dp[row + 1][glass + 1] += excess
+        
+        return min(1.0, dp[query_row][query_glass])
+```
+
+```java
+public class Solution {
+    public double champagneTower(int poured, int query_row, int query_glass) {
+        double[][] dp = new double[query_row + 5][];
+        for (int i = 0; i < query_row + 5; i++) {
+            dp[i] = new double[i + 1];
+        }
+        
+        dp[0][0] += poured;
+        
+        for (int row = 0; row < Math.min(99, query_row + 1); row++) {
+            for (int glass = 0; glass <= row; glass++) {
+                double excess = (dp[row][glass] - 1.0) / 2.0;
+                if (excess > 0) {
+                    dp[row + 1][glass] += excess;
+                    dp[row + 1][glass + 1] += excess;
+                }
+            }
+        }
+        
+        return Math.min(1.0, dp[query_row][query_glass]);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    double champagneTower(int poured, int query_row, int query_glass) {
+        vector<vector<double>> dp(query_row + 5);
+        for (int i = 0; i <= query_row + 4; i++) {
+            dp[i].resize(i + 1, 0);
+        }
+        
+        dp[0][0] += poured;
+        
+        for (int row = 0; row < min(99, query_row + 1); row++) {
+            for (int glass = 0; glass <= row; glass++) {
+                double excess = (dp[row][glass] - 1.0) / 2.0;
+                if (excess > 0) {
+                    dp[row + 1][glass] += excess;
+                    dp[row + 1][glass + 1] += excess;
+                }
+            }
+        }
+        
+        return min(1.0, dp[query_row][query_glass]);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} poured
+     * @param {number} query_row
+     * @param {number} query_glass
+     * @return {number}
+     */
+    champagneTower(poured, query_row, query_glass) {
+        const dp = Array.from({ length: query_row + 5 }, (_, i) => Array(i + 1).fill(0));
+        dp[0][0] += poured;
+
+        for (let row = 0; row < Math.min(99, query_row + 1); row++) {
+            for (let glass = 0; glass <= row; glass++) {
+                const excess = (dp[row][glass] - 1.0) / 2.0;
+                if (excess > 0) {
+                    dp[row + 1][glass] += excess;
+                    dp[row + 1][glass + 1] += excess;
+                }
+            }
+        }
+
+        return Math.min(1.0, dp[query_row][query_glass]);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n * m)$
+
+> Where $n$ is the given $queryRow$ and $m$ is the given $queryGlass$.
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def champagneTower(self, poured: int, query_row: int, query_glass: int) -> float:
+        prev_row = [poured]  # Flow
+
+        for row in range(1, query_row + 1):
+            cur_row = [0] * (row + 1)
+            for i in range(row):
+                extra = prev_row[i] - 1
+                if extra > 0:
+                    cur_row[i] += 0.5 * extra
+                    cur_row[i + 1] += 0.5 * extra
+            prev_row = cur_row
+
+        return min(1, prev_row[query_glass])
+```
+
+```java
+public class Solution {
+    public double champagneTower(int poured, int query_row, int query_glass) {
+        double[] prev_row = new double[] { poured };  // Flow
+        
+        for (int row = 1; row <= query_row; row++) {
+            double[] cur_row = new double[row + 1];
+            for (int i = 0; i < row; i++) {
+                double extra = prev_row[i] - 1;
+                if (extra > 0) {
+                    cur_row[i] += 0.5 * extra;
+                    cur_row[i + 1] += 0.5 * extra;
+                }
+            }
+            prev_row = cur_row;
+        }
+        
+        return Math.min(1.0, prev_row[query_glass]);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    double champagneTower(int poured, int query_row, int query_glass) {
+        vector<double> prev_row = {double(poured)};  // Flow
+        
+        for (int row = 1; row <= query_row; row++) {
+            vector<double> cur_row(row + 1, 0);
+            for (int i = 0; i < row; i++) {
+                double extra = prev_row[i] - 1;
+                if (extra > 0) {
+                    cur_row[i] += 0.5 * extra;
+                    cur_row[i + 1] += 0.5 * extra;
+                }
+            }
+            prev_row = cur_row;
+        }
+        
+        return min(1.0, prev_row[query_glass]);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} poured
+     * @param {number} query_row
+     * @param {number} query_glass
+     * @return {number}
+     */
+    champagneTower(poured, query_row, query_glass) {
+        let prev_row = [poured];  // Flow
+        
+        for (let row = 1; row <= query_row; row++) {
+            let cur_row = new Array(row + 1).fill(0);
+            for (let i = 0; i < row; i++) {
+                let extra = prev_row[i] - 1;
+                if (extra > 0) {
+                    cur_row[i] += 0.5 * extra;
+                    cur_row[i + 1] += 0.5 * extra;
+                }
+            }
+            prev_row = cur_row;
+        }
+        
+        return Math.min(1, prev_row[query_glass]);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the given $queryRow$ and $m$ is the given $queryGlass$.
+
+---
+
+## 5. Dynamic Programming (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def champagneTower(self, poured: int, query_row: int, query_glass: int) -> float:
+        dp = [poured] + [0] * query_row
+        
+        for row in range(1, query_row + 1):
+            for i in range(row - 1, -1, -1):
+                extra = dp[i] - 1
+                if extra > 0:
+                    dp[i] = 0.5 * extra
+                    dp[i + 1] += 0.5 * extra
+                else:
+                    dp[i] = 0
+        
+        return min(1, dp[query_glass])
+```
+
+```java
+public class Solution {
+    public double champagneTower(int poured, int query_row, int query_glass) {
+        double[] dp = new double[query_row + 1];
+        dp[0] = poured;
+
+        for (int row = 1; row <= query_row; row++) {
+            for (int i = row - 1; i >= 0; i--) {
+                double extra = dp[i] - 1;
+                if (extra > 0) {
+                    dp[i] = 0.5 * extra;
+                    dp[i + 1] += 0.5 * extra;
+                } else {
+                    dp[i] = 0;
+                }
+            }
+        }
+
+        return Math.min(1, dp[query_glass]);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    double champagneTower(int poured, int query_row, int query_glass) {
+        vector<double> dp(query_row + 1, 0);
+        dp[0] = poured;
+
+        for (int row = 1; row <= query_row; row++) {
+            for (int i = row - 1; i >= 0; i--) {
+                double extra = dp[i] - 1;
+                if (extra > 0) {
+                    dp[i] = 0.5 * extra;
+                    dp[i + 1] += 0.5 * extra;
+                } else {
+                    dp[i] = 0;
+                }
+            }
+        }
+
+        return min(1.0, dp[query_glass]);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} poured
+     * @param {number} query_row
+     * @param {number} query_glass
+     * @return {number}
+     */
+    champagneTower(poured, query_row, query_glass) {
+        let dp = new Array(query_row + 1).fill(0);
+        dp[0] = poured;
+
+        for (let row = 1; row <= query_row; row++) {
+            for (let i = row - 1; i >= 0; i--) {
+                let extra = dp[i] - 1;
+                if (extra > 0) {
+                    dp[i] = 0.5 * extra;
+                    dp[i + 1] += 0.5 * extra;
+                } else {
+                    dp[i] = 0;
+                }
+            }
+        }
+
+        return Math.min(1, dp[query_glass]);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the given $queryRow$ and $m$ is the given $queryGlass$.
\ No newline at end of file
diff --git a/articles/cheapest-flight-path.md b/articles/cheapest-flight-path.md
new file mode 100644
index 000000000..976640249
--- /dev/null
+++ b/articles/cheapest-flight-path.md
@@ -0,0 +1,844 @@
+## 1. Dijkstra's Algorithm
+
+::tabs-start
+
+```python
+class Solution:
+    def findCheapestPrice(self, n: int, flights: List[List[int]], src: int, dst: int, k: int) -> int:
+        INF = float("inf")
+        adj = [[] for _ in range(n)]
+        dist = [[INF] * (k + 5) for _ in range(n)]
+        for u, v, cst in flights:
+            adj[u].append([v, cst])
+        
+        dist[src][0] = 0
+        minHeap = [(0, src, -1)] # cost, node, stops
+        while len(minHeap):
+            cst, node, stops = heapq.heappop(minHeap)
+            if dst == node: return cst
+            if stops == k or dist[node][stops + 1] < cst:
+                continue
+            for nei, w in adj[node]:
+                nextCst = cst + w
+                nextStops = 1 + stops
+                if dist[nei][nextStops + 1] > nextCst:
+                    dist[nei][nextStops + 1] = nextCst
+                    heapq.heappush(minHeap, (nextCst, nei, nextStops))
+
+        return -1
+```
+
+```java
+public class Solution {
+    public int findCheapestPrice(int n, int[][] flights, int src, int dst, int k) {
+        int INF = Integer.MAX_VALUE;
+        List<int[]>[] adj = new ArrayList[n];
+        int[][] dist = new int[n][k + 5];
+        for (int i = 0; i < n; i++) Arrays.fill(dist[i], INF);
+        
+        for (int i = 0; i < n; i++) adj[i] = new ArrayList<>();
+        for (int[] flight : flights) {
+            adj[flight[0]].add(new int[]{flight[1], flight[2]});
+        }
+        
+        dist[src][0] = 0;
+        PriorityQueue<int[]> minHeap = new PriorityQueue<>(
+            Comparator.comparingInt(a -> a[0])
+        );
+        minHeap.offer(new int[]{0, src, -1});
+
+        while (!minHeap.isEmpty()) {
+            int[] top = minHeap.poll();
+            int cst = top[0], node = top[1], stops = top[2];
+            if (node == dst) return cst;
+            if (stops == k || dist[node][stops + 1] < cst) continue;
+            for (int[] neighbor : adj[node]) {
+                int nei = neighbor[0], w = neighbor[1];
+                int nextCst = cst + w;
+                int nextStops = stops + 1;
+                if (dist[nei][nextStops + 1] > nextCst) {
+                    dist[nei][nextStops + 1] = nextCst;
+                    minHeap.offer(new int[]{nextCst, nei, nextStops});
+                }
+            }
+        }
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findCheapestPrice(int n, vector<vector<int>>& flights, int src, int dst, int k) {
+        int INF = 1e9;
+        vector<vector<pair<int, int>>> adj(n);
+        vector<vector<int>> dist(n, vector<int>(k + 5, INF));
+        
+        for (auto& flight : flights) {
+            adj[flight[0]].emplace_back(flight[1], flight[2]);
+        }
+        
+        dist[src][0] = 0;
+        priority_queue<tuple<int, int, int>, 
+                       vector<tuple<int, int, int>>, greater<>> minHeap;
+        minHeap.emplace(0, src, -1);
+        
+        while (!minHeap.empty()) {
+            auto [cst, node, stops] = minHeap.top();
+            minHeap.pop();
+            if (node == dst) return cst;
+            if (stops == k || dist[node][stops + 1] < cst) continue;
+            for (auto& [nei, w] : adj[node]) {
+                int nextCst = cst + w;
+                int nextStops = stops + 1;
+                if (dist[nei][nextStops + 1] > nextCst) {
+                    dist[nei][nextStops + 1] = nextCst;
+                    minHeap.emplace(nextCst, nei, nextStops);
+                }
+            }
+        }
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} flights
+     * @param {number} src
+     * @param {number} dst
+     * @param {number} k
+     * @return {number}
+     */
+    findCheapestPrice(n, flights, src, dst, k) {
+        const INF = Infinity;
+        const adj = Array.from({ length: n }, () => []);
+        const dist = Array.from({ length: n }, () => 
+                     Array(k + 5).fill(INF));
+        
+        for (let [u, v, cst] of flights) {
+            adj[u].push([v, cst]);
+        }
+        
+        dist[src][0] = 0;
+        const minHeap = new MinPriorityQueue(entry => entry[0]); 
+        minHeap.push([0, src, -1]); // cost, node, stops
+        while (!minHeap.isEmpty()) {
+            const [cst, node, stops] = minHeap.pop();
+            if (node === dst) return cst;
+            if (stops === k || dist[node][stops + 1] < cst) continue;
+            for (let [nei, w] of adj[node]) {
+                const nextCst = cst + w;
+                const nextStops = stops + 1;
+                if (dist[nei][nextStops + 1] > nextCst) {
+                    dist[nei][nextStops + 1] = nextCst;
+                    minHeap.push([nextCst, nei, nextStops]);
+                }
+            }
+        }
+        return -1;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int FindCheapestPrice(int n, int[][] flights, int src, int dst, int k) {
+        int INF = int.MaxValue;
+        List<int[]>[] adj = new List<int[]>[n];
+        int[][] dist = new int[n][];
+        
+        for (int i = 0; i < n; i++) {
+            adj[i] = new List<int[]>();
+            dist[i] = new int[k + 2];
+            Array.Fill(dist[i], INF);
+        }
+        
+        foreach (var flight in flights) {
+            adj[flight[0]].Add(new int[] { flight[1], flight[2] });
+        }
+        
+        dist[src][0] = 0;
+        var minHeap = new PriorityQueue<(int cst, int node, int stops), int>();
+        minHeap.Enqueue((0, src, 0), 0);
+        
+        while (minHeap.Count > 0) {
+            var (cst, node, stops) = minHeap.Dequeue();
+            if (node == dst) return cst;
+            if (stops > k) continue;
+            
+            foreach (var neighbor in adj[node]) {
+                int nei = neighbor[0], w = neighbor[1];
+                int nextCst = cst + w;
+                int nextStops = stops + 1;
+                
+                if (dist[nei][nextStops] > nextCst) {
+                    dist[nei][nextStops] = nextCst;
+                    minHeap.Enqueue((nextCst, nei, nextStops), nextCst);
+                }
+            }
+        }
+        return -1;
+    }
+}
+```
+
+```go
+func findCheapestPrice(n int, flights [][]int, src int, dst int, k int) int {
+    INF := 1000000000
+    adj := make([][]struct{ to, cost int }, n)
+    dist := make([][]int, n)
+    for i := range dist {
+        dist[i] = make([]int, k+5)
+        for j := range dist[i] {
+            dist[i][j] = INF
+        }
+    }
+    for _, flight := range flights {
+        from, to, cost := flight[0], flight[1], flight[2]
+        adj[from] = append(adj[from], struct{ to, cost int }{to, cost})
+    }
+    dist[src][0] = 0
+    minHeap := priorityqueue.NewWith(func(a, b interface{}) int {
+        return utils.IntComparator(a.([3]int)[0], b.([3]int)[0])
+    })
+    minHeap.Enqueue([3]int{0, src, -1})
+    for !minHeap.Empty() {
+        value, _ := minHeap.Dequeue()
+        cst, node, stops := value.([3]int)[0], value.([3]int)[1], value.([3]int)[2]
+        if node == dst {
+            return cst
+        }
+        if stops == k || dist[node][stops+1] < cst {
+            continue
+        }
+        for _, nei := range adj[node] {
+            nextCst := cst + nei.cost
+            nextStops := stops + 1
+            if dist[nei.to][nextStops+1] > nextCst {
+                dist[nei.to][nextStops+1] = nextCst
+                minHeap.Enqueue([3]int{nextCst, nei.to, nextStops})
+            }
+        }
+    }
+    return -1
+}
+```
+
+```kotlin
+class Solution {
+    fun findCheapestPrice(n: Int, flights: Array<IntArray>, src: Int, dst: Int, k: Int): Int {
+        val INF = 1_000_000_000
+        val adj = Array(n) { mutableListOf<Pair<Int, Int>>() }
+        val dist = Array(n) { IntArray(k + 5) { INF } }
+        for (flight in flights) {
+            adj[flight[0]].add(Pair(flight[1], flight[2]))
+        }
+        dist[src][0] = 0
+        val minHeap = PriorityQueue(compareBy<Triple<Int, Int, Int>> { it.first })
+        minHeap.add(Triple(0, src, -1))
+        while (minHeap.isNotEmpty()) {
+            val (cst, node, stops) = minHeap.poll()
+            if (node == dst) return cst
+            if (stops == k || dist[node][stops + 1] < cst) continue
+            for ((nei, w) in adj[node]) {
+                val nextCst = cst + w
+                val nextStops = stops + 1
+                if (dist[nei][nextStops + 1] > nextCst) {
+                    dist[nei][nextStops + 1] = nextCst
+                    minHeap.add(Triple(nextCst, nei, nextStops))
+                }
+            }
+        }
+        return -1
+    }
+}
+```
+
+```swift
+struct Item: Comparable {
+    let cost: Int
+    let node: Int
+    let stops: Int
+
+    static func < (lhs: Item, rhs: Item) -> Bool {
+        return lhs.cost < rhs.cost
+    }
+}
+
+class Solution {
+    func findCheapestPrice(_ n: Int, _ flights: [[Int]], _ src: Int, _ dst: Int, _ k: Int) -> Int {
+        let INF = Int.max
+        var adj = Array(repeating: [(Int, Int)](), count: n)
+        var dist = Array(repeating: Array(repeating: INF, count: k + 5), count: n)
+
+        for flight in flights {
+            let u = flight[0], v = flight[1], cst = flight[2]
+            adj[u].append((v, cst))
+        }
+
+        var minHeap = Heap<Item>()
+        minHeap.insert(Item(cost: 0, node: src, stops: -1))
+        dist[src][0] = 0
+
+        while !minHeap.isEmpty {
+            let item = minHeap.removeMin()
+            let cst = item.cost, node = item.node, stops = item.stops
+            if node == dst { return cst }
+            if stops == k || dist[node][stops + 1] < cst { continue }
+
+            for (nei, w) in adj[node] {
+                let nextCst = cst + w
+                let nextStops = stops + 1
+                if dist[nei][nextStops + 1] > nextCst {
+                    dist[nei][nextStops + 1] = nextCst
+                    minHeap.insert(Item(cost: nextCst, node: nei, stops: nextStops))
+                }
+            }
+        }
+
+        return -1
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O((n + m) * k)$
+* Space complexity: $O(n * k)$
+
+> Where $n$ is the number of cities, $m$ is the number of flights and $k$ is the number of stops.
+
+---
+
+## 2. Bellman Ford Algorithm
+
+::tabs-start
+
+```python
+class Solution:
+    def findCheapestPrice(self, n: int, flights: List[List[int]], src: int, dst: int, k: int) -> int:
+        prices = [float("inf")] * n
+        prices[src] = 0
+
+        for i in range(k + 1):
+            tmpPrices = prices.copy()
+
+            for s, d, p in flights:  # s=source, d=dest, p=price
+                if prices[s] == float("inf"):
+                    continue
+                if prices[s] + p < tmpPrices[d]:
+                    tmpPrices[d] = prices[s] + p
+            prices = tmpPrices
+        return -1 if prices[dst] == float("inf") else prices[dst]
+```
+
+```java
+public class Solution {
+    public int findCheapestPrice(int n, int[][] flights, int src, int dst, int k) {
+        int[] prices = new int[n];
+        Arrays.fill(prices, Integer.MAX_VALUE);
+        prices[src] = 0;
+
+        for (int i = 0; i <= k; i++) {
+            int[] tmpPrices = Arrays.copyOf(prices, n);
+
+            for (int[] flight : flights) {
+                int s = flight[0];
+                int d = flight[1];
+                int p = flight[2];
+
+                if (prices[s] == Integer.MAX_VALUE) {
+                    continue;
+                }
+
+                if (prices[s] + p < tmpPrices[d]) {
+                    tmpPrices[d] = prices[s] + p;
+                }
+            }
+
+            prices = tmpPrices;
+        }
+
+        return prices[dst] == Integer.MAX_VALUE ? -1 : prices[dst];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findCheapestPrice(int n, vector<vector<int>>& flights, int src, int dst, int k) {
+        vector<int> prices(n, INT_MAX);
+        prices[src] = 0;
+
+        for (int i = 0; i <= k; i++) {
+            vector<int> tmpPrices = prices;
+
+            for (const auto& flight : flights) {
+                int s = flight[0];
+                int d = flight[1];
+                int p = flight[2];
+
+                if (prices[s] == INT_MAX)
+                    continue;
+
+                if (prices[s] + p < tmpPrices[d])
+                    tmpPrices[d] = prices[s] + p;
+            }
+
+            prices = tmpPrices;
+        }
+
+        return prices[dst] == INT_MAX ? -1 : prices[dst];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} flights
+     * @param {number} src
+     * @param {number} dst
+     * @param {number} k
+     * @return {number}
+     */
+    findCheapestPrice(n, flights, src, dst, k) {
+        let prices = new Array(n).fill(Number.MAX_SAFE_INTEGER);
+        prices[src] = 0;
+
+        for (let i = 0; i <= k; i++) {
+            const tmpPrices = [...prices];
+
+            for (const flight of flights) {
+                const s = flight[0];
+                const d = flight[1];
+                const p = flight[2];
+
+                if (prices[s] === Number.MAX_SAFE_INTEGER) continue;
+
+                if (prices[s] + p < tmpPrices[d]) tmpPrices[d] = prices[s] + p;
+            }
+
+            prices = tmpPrices;
+        }
+
+        return prices[dst] === Number.MAX_SAFE_INTEGER ? -1 : prices[dst];
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int FindCheapestPrice(int n, int[][] flights, int src, int dst, int k) {
+        int[] prices = new int[n];
+        Array.Fill(prices, int.MaxValue);
+        prices[src] = 0;
+
+        for (int i = 0; i <= k; i++) {
+            int[] tmpPrices = (int[])prices.Clone();
+
+            foreach (var flight in flights) {
+                int s = flight[0];
+                int d = flight[1];
+                int p = flight[2];
+
+                if (prices[s] == int.MaxValue)
+                    continue;
+
+                if (prices[s] + p < tmpPrices[d])
+                    tmpPrices[d] = prices[s] + p;
+            }
+
+            prices = tmpPrices;
+        }
+
+        return prices[dst] == int.MaxValue ? -1 : prices[dst];
+    }
+}
+```
+
+```go
+func findCheapestPrice(n int, flights [][]int, src int, dst int, k int) int {
+    prices := make([]int, n)
+    for i := range prices {
+        prices[i] = math.MaxInt32
+    }
+    prices[src] = 0
+
+    for i := 0; i <= k; i++ {
+        tmpPrices := make([]int, n)
+        copy(tmpPrices, prices)
+        
+        for _, flight := range flights {
+            s, d, p := flight[0], flight[1], flight[2]
+            if prices[s] == math.MaxInt32 {
+                continue
+            }
+            if prices[s] + p < tmpPrices[d] {
+                tmpPrices[d] = prices[s] + p
+            }
+        }
+        prices = tmpPrices
+    }
+    
+    if prices[dst] == math.MaxInt32 {
+        return -1
+    }
+    return prices[dst]
+}
+```
+
+```kotlin
+class Solution {
+    fun findCheapestPrice(n: Int, flights: Array<IntArray>, src: Int, dst: Int, k: Int): Int {
+        val prices = IntArray(n) { Int.MAX_VALUE }
+        prices[src] = 0
+
+        repeat(k + 1) {
+            val tmpPrices = prices.copyOf()
+            for ((s, d, p) in flights) {
+                if (prices[s] == Int.MAX_VALUE) continue
+                if (prices[s] + p < tmpPrices[d]) {
+                    tmpPrices[d] = prices[s] + p
+                }
+            }
+            tmpPrices.copyInto(prices)
+        }
+
+        return if (prices[dst] == Int.MAX_VALUE) -1 else prices[dst]
+    }
+}
+```
+
+```swift
+class Solution {
+    func findCheapestPrice(_ n: Int, _ flights: [[Int]], _ src: Int, _ dst: Int, _ k: Int) -> Int {
+        var prices = Array(repeating: Int.max, count: n)
+        prices[src] = 0
+
+        for _ in 0...k {
+            var tmpPrices = prices
+
+            for flight in flights {
+                let s = flight[0], d = flight[1], p = flight[2]
+                if prices[s] == Int.max {
+                    continue
+                }
+                if prices[s] + p < tmpPrices[d] {
+                    tmpPrices[d] = prices[s] + p
+                }
+            }
+            prices = tmpPrices
+        }
+        return prices[dst] == Int.max ? -1 : prices[dst]
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + (m * k))$
+* Space complexity: $O(n)$
+
+> Where $n$ is the number of cities, $m$ is the number of flights and $k$ is the number of stops.
+
+---
+
+## 3. Shortest Path Faster Algorithm
+
+::tabs-start
+
+```python
+class Solution:
+    def findCheapestPrice(self, n: int, flights: List[List[int]], src: int, dst: int, k: int) -> int:
+        prices = [float("inf")] * n
+        prices[src] = 0
+        adj = [[] for _ in range(n)]
+        for u, v, cst in flights:
+            adj[u].append([v, cst])
+
+        q = deque([(0, src, 0)])
+        while q:
+            cst, node, stops = q.popleft()
+            if stops > k:
+                continue
+            
+            for nei, w in adj[node]:
+                nextCost = cst + w
+                if nextCost < prices[nei]:
+                    prices[nei] = nextCost
+                    q.append((nextCost, nei, stops + 1))
+
+        return prices[dst] if prices[dst] != float("inf") else -1
+```
+
+```java
+public class Solution {
+    public int findCheapestPrice(int n, int[][] flights, int src, int dst, int k) {
+        int[] prices = new int[n];
+        Arrays.fill(prices, Integer.MAX_VALUE);
+        prices[src] = 0;
+        List<int[]>[] adj = new ArrayList[n];
+        for (int i = 0; i < n; i++) {
+            adj[i] = new ArrayList<>();
+        }
+        for (var flight : flights) {
+            adj[flight[0]].add(new int[] { flight[1], flight[2] });
+        }
+
+        Queue<int[]> q = new LinkedList<>();
+        q.offer(new int[] { 0, src, 0 });
+
+        while (!q.isEmpty()) {
+            var curr = q.poll();
+            int cst = curr[0], node = curr[1], stops = curr[2];
+            if (stops > k) continue;
+
+            for (var neighbor : adj[node]) {
+                int nei = neighbor[0], w = neighbor[1];
+                int nextCost = cst + w;
+                if (nextCost < prices[nei]) {
+                    prices[nei] = nextCost;
+                    q.offer(new int[] { nextCost, nei, stops + 1 });
+                }
+            }
+        }
+        return prices[dst] == Integer.MAX_VALUE ? -1 : prices[dst];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findCheapestPrice(int n, vector<vector<int>>& flights, int src, int dst, int k) {
+        vector<int> prices(n, INT_MAX);
+        prices[src] = 0;
+        vector<vector<pair<int, int>>> adj(n);
+        for (const auto& flight : flights) {
+            adj[flight[0]].emplace_back(flight[1], flight[2]);
+        }
+
+        queue<tuple<int, int, int>> q;
+        q.push({0, src, 0});
+
+        while (!q.empty()) {
+            auto [cst, node, stops] = q.front();
+            q.pop();
+            if (stops > k) continue;
+
+            for (const auto& neighbor : adj[node]) {
+                int nei = neighbor.first, w = neighbor.second;
+                int nextCost = cst + w;
+                if (nextCost < prices[nei]) {
+                    prices[nei] = nextCost;
+                    q.push({nextCost, nei, stops + 1});
+                }
+            }
+        }
+        return prices[dst] == INT_MAX ? -1 : prices[dst];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} flights
+     * @param {number} src
+     * @param {number} dst
+     * @param {number} k
+     * @return {number}
+     */
+    findCheapestPrice(n, flights, src, dst, k) {
+        const prices = Array(n).fill(Infinity);
+        prices[src] = 0;
+        const adj = Array.from({ length: n }, () => []);
+        
+        for (const [u, v, cst] of flights) {
+            adj[u].push([v, cst]);
+        }
+
+        const q = new Queue([[0, src, 0]]); // [cost, node, stops]
+
+        while (!q.isEmpty()) {
+            const [cst, node, stops] = q.pop();
+            if (stops > k) continue;
+
+            for (const [nei, w] of adj[node]) {
+                const nextCost = cst + w;
+                if (nextCost < prices[nei]) {
+                    prices[nei] = nextCost;
+                    q.push([nextCost, nei, stops + 1]);
+                }
+            }
+        }
+        return prices[dst] === Infinity ? -1 : prices[dst];
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int FindCheapestPrice(int n, int[][] flights, int src, int dst, int k) {
+        int[] prices = new int[n];
+        Array.Fill(prices, int.MaxValue);
+        prices[src] = 0;
+        List<int[]>[] adj = new List<int[]>[n];
+        for (int i = 0; i < n; i++) {
+            adj[i] = new List<int[]>();
+        }
+        foreach (var flight in flights) {
+            adj[flight[0]].Add(new int[] { flight[1], flight[2] });
+        }
+
+        var q = new Queue<(int cst, int node, int stops)>();
+        q.Enqueue((0, src, 0));
+
+        while (q.Count > 0) {
+            var (cst, node, stops) = q.Dequeue();
+            if (stops > k) continue;
+
+            foreach (var neighbor in adj[node]) {
+                int nei = neighbor[0], w = neighbor[1];
+                int nextCost = cst + w;
+                if (nextCost < prices[nei]) {
+                    prices[nei] = nextCost;
+                    q.Enqueue((nextCost, nei, stops + 1));
+                }
+            }
+        }
+        return prices[dst] == int.MaxValue ? -1 : prices[dst];
+    }
+}
+```
+
+```go
+func findCheapestPrice(n int, flights [][]int, src int, dst int, k int) int {
+    prices := make([]int, n)
+    for i := range prices {
+        prices[i] = math.MaxInt32
+    }
+    prices[src] = 0
+
+    adj := make([][][2]int, n)
+    for _, flight := range flights {
+        from, to, cost := flight[0], flight[1], flight[2]
+        adj[from] = append(adj[from], [2]int{to, cost})
+    }
+
+    q := [][3]int{{0, src, 0}}
+
+    for len(q) > 0 {
+        curr := q[0]
+        q = q[1:]
+        cst, node, stops := curr[0], curr[1], curr[2]
+
+        if stops > k {
+            continue
+        }
+
+        for _, neighbor := range adj[node] {
+            nei, w := neighbor[0], neighbor[1]
+            nextCost := cst + w
+            if nextCost < prices[nei] {
+                prices[nei] = nextCost
+                q = append(q, [3]int{nextCost, nei, stops + 1})
+            }
+        }
+    }
+
+    if prices[dst] == math.MaxInt32 {
+        return -1
+    }
+    return prices[dst]
+}
+```
+
+```kotlin
+class Solution {
+    fun findCheapestPrice(n: Int, flights: Array<IntArray>, src: Int, dst: Int, k: Int): Int {
+        val prices = IntArray(n) { Int.MAX_VALUE }
+        prices[src] = 0
+
+        val adj = Array(n) { mutableListOf<Pair<Int, Int>>() }
+        for (flight in flights) {
+            val (from, to, cost) = flight
+            adj[from].add(Pair(to, cost))
+        }
+
+        val q: Queue<Triple<Int, Int, Int>> = LinkedList()
+        q.offer(Triple(0, src, 0))
+
+        while (q.isNotEmpty()) {
+            val (cst, node, stops) = q.poll()
+            if (stops > k) continue
+
+            for ((nei, w) in adj[node]) {
+                val nextCost = cst + w
+                if (nextCost < prices[nei]) {
+                    prices[nei] = nextCost
+                    q.offer(Triple(nextCost, nei, stops + 1))
+                }
+            }
+        }
+
+        return if (prices[dst] == Int.MAX_VALUE) -1 else prices[dst]
+    }
+}
+```
+
+```swift
+class Solution {
+    func findCheapestPrice(_ n: Int, _ flights: [[Int]], _ src: Int, _ dst: Int, _ k: Int) -> Int {
+        var prices = Array(repeating: Int.max, count: n)
+        prices[src] = 0
+        var adj = Array(repeating: [(Int, Int)](), count: n)
+
+        for flight in flights {
+            let u = flight[0], v = flight[1], cst = flight[2]
+            adj[u].append((v, cst))
+        }
+
+        var queue = Deque<(Int, Int, Int)>()
+        queue.append((0, src, 0))
+
+        while !queue.isEmpty {
+            let (cst, node, stops) = queue.popFirst()!
+            if stops > k {
+                continue
+            }
+
+            for (nei, w) in adj[node] {
+                let nextCost = cst + w
+                if nextCost < prices[nei] {
+                    prices[nei] = nextCost
+                    queue.append((nextCost, nei, stops + 1))
+                }
+            }
+        }
+
+        return prices[dst] == Int.max ? -1 : prices[dst]
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * k)$
+* Space complexity: $O(n + m)$
+
+> Where $n$ is the number of cities, $m$ is the number of flights and $k$ is the number of stops.
\ No newline at end of file
diff --git a/articles/check-completeness-of-a-binary-tree.md b/articles/check-completeness-of-a-binary-tree.md
new file mode 100644
index 000000000..90a185822
--- /dev/null
+++ b/articles/check-completeness-of-a-binary-tree.md
@@ -0,0 +1,591 @@
+## 1. Breadth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def isCompleteTree(self, root: Optional[TreeNode]) -> bool:
+        q = deque([root])
+        while q:
+            node = q.popleft()
+            if node:
+                q.append(node.left)
+                q.append(node.right)
+            else:
+                while q:
+                    if q.popleft():
+                        return False
+        return True
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public boolean isCompleteTree(TreeNode root) {
+        Queue<TreeNode> q = new LinkedList<>();
+        q.add(root);
+
+        while (!q.isEmpty()) {
+            TreeNode node = q.poll();
+            if (node != null) {
+                q.add(node.left);
+                q.add(node.right);
+            } else {
+                while (!q.isEmpty()) {
+                    if (q.poll() != null) {
+                        return false;
+                    }
+                }
+            }
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    bool isCompleteTree(TreeNode* root) {
+        queue<TreeNode*> q;
+        q.push(root);
+
+        while (!q.empty()) {
+            TreeNode* node = q.front();
+            q.pop();
+            if (node) {
+                q.push(node->left);
+                q.push(node->right);
+            } else {
+                while (!q.empty()) {
+                    if (q.front()) {
+                        return false;
+                    }
+                    q.pop();
+                }
+            }
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {boolean}
+     */
+    isCompleteTree(root) {
+        const queue = new Queue([root]);
+
+        while (!queue.isEmpty()) {
+            const node = queue.pop();
+            if (node) {
+                queue.push(node.left);
+                queue.push(node.right);
+            } else {
+                while (!queue.isEmpty()) {
+                    if (queue.pop()) {
+                        return false;
+                    }
+                }
+            }
+        }
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Breadth First Search (Optimal)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def isCompleteTree(self, root: Optional[TreeNode]) -> bool:
+        q = deque([root])
+        nullSeen = False
+        while q:
+            node = q.popleft()
+            if node:
+                if nullSeen:
+                    return False
+                q.append(node.left)
+                q.append(node.right)
+            else:
+                nullSeen = True
+        return True
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public boolean isCompleteTree(TreeNode root) {
+        Queue<TreeNode> q = new LinkedList<>();
+        q.add(root);
+        boolean nullSeen = false;
+
+        while (!q.isEmpty()) {
+            TreeNode node = q.poll();
+            if (node != null) {
+                if (nullSeen) return false;
+                q.add(node.left);
+                q.add(node.right);
+            } else {
+                nullSeen = true;
+            }
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    bool isCompleteTree(TreeNode* root) {
+        queue<TreeNode*> q;
+        q.push(root);
+        bool nullSeen = false;
+
+        while (!q.empty()) {
+            TreeNode* node = q.front();
+            q.pop();
+            if (node) {
+                if (nullSeen) return false;
+                q.push(node->left);
+                q.push(node->right);
+            } else {
+                nullSeen = true;
+            }
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {boolean}
+     */
+    isCompleteTree(root) {
+        const queue = new Queue([root]);
+        let nullSeen = false;
+
+        while (!queue.isEmpty()) {
+            const node = queue.pop();
+            if (node) {
+                if (nullSeen) return false;
+                queue.push(node.left);
+                queue.push(node.right);
+            } else {
+                nullSeen = true;
+            }
+        }
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Depth First Search (Two Pass) 
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def isCompleteTree(self, root: Optional[TreeNode]) -> bool:
+        def dfs(node, index, n):
+            if not node:
+                return True
+            if index >= n:
+                return False
+                
+            left = dfs(node.left, 2 * index + 1, n)
+            right = dfs(node.right, 2 * index + 2, n)
+            return left and right
+        
+        def countNodes(node):
+            if not node:
+                return 0
+            return 1 + countNodes(node.left) + countNodes(node.right)
+
+        n = countNodes(root)
+        return dfs(root, 0, n)
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    private int countNodes(TreeNode root) {
+        if (root == null) return 0;
+        return 1 + countNodes(root.left) + countNodes(root.right);
+    }
+
+    private boolean dfs(TreeNode node, int index, int n) {
+        if (node == null) return true;
+        if (index >= n) return false;
+        return dfs(node.left, 2 * index + 1, n) && dfs(node.right, 2 * index + 2, n);
+    }
+
+    public boolean isCompleteTree(TreeNode root) {
+        int n = countNodes(root);
+        return dfs(root, 0, n);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int countNodes(TreeNode* root) {
+        if (!root) return 0;
+        return 1 + countNodes(root->left) + countNodes(root->right);
+    }
+
+    bool dfs(TreeNode* node, int index, int n) {
+        if (!node) return true;
+        if (index >= n) return false;
+        return dfs(node->left, 2 * index + 1, n) && dfs(node->right, 2 * index + 2, n);
+    }
+
+    bool isCompleteTree(TreeNode* root) {
+        int n = countNodes(root);
+        return dfs(root, 0, n);
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {boolean}
+     */
+    isCompleteTree(root) {
+        const countNodes = (node) => {
+            if (!node) return 0;
+            return 1 + countNodes(node.left) + countNodes(node.right);
+        };
+
+        const dfs = (node, index, n) => {
+            if (!node) return true;
+            if (index >= n) return false;
+            return dfs(node.left, 2 * index + 1, n) && dfs(node.right, 2 * index + 2, n);
+        };
+
+        const n = countNodes(root);
+        return dfs(root, 0, n);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 4. Depth First Search (Optimal)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def isCompleteTree(self, root: Optional[TreeNode]) -> bool:
+        treeHgt = 0
+        nullSeen = False
+        
+        def dfs(node, hgt):
+            nonlocal treeHgt, nullSeen
+            if not node:
+                if treeHgt == 0:
+                    treeHgt = hgt
+                elif hgt == treeHgt - 1:
+                    nullSeen = True
+                elif hgt != treeHgt:
+                    return False
+                return not (hgt == treeHgt and nullSeen)
+            
+            return dfs(node.left, hgt + 1) and dfs(node.right, hgt + 1)
+        
+        return dfs(root, 0)
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    private int treeHgt = 0;
+    private boolean nullSeen = false;
+
+    private boolean dfs(TreeNode node, int hgt) {
+        if (node == null) {
+            if (treeHgt == 0) {
+                treeHgt = hgt;
+            } else if (hgt == treeHgt - 1) {
+                nullSeen = true;
+            } else if (hgt != treeHgt) {
+                return false;
+            }
+            return !(hgt == treeHgt && nullSeen);
+        }
+
+        return dfs(node.left, hgt + 1) && dfs(node.right, hgt + 1);
+    }
+
+    public boolean isCompleteTree(TreeNode root) {
+        return dfs(root, 0);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int treeHgt = 0;
+    bool nullSeen = false;
+
+    bool dfs(TreeNode* node, int hgt) {
+        if (!node) {
+            if (treeHgt == 0) {
+                treeHgt = hgt;
+            } else if (hgt == treeHgt - 1) {
+                nullSeen = true;
+            } else if (hgt != treeHgt) {
+                return false;
+            }
+            return !(hgt == treeHgt && nullSeen);
+        }
+
+        return dfs(node->left, hgt + 1) && dfs(node->right, hgt + 1);
+    }
+
+    bool isCompleteTree(TreeNode* root) {
+        return dfs(root, 0);
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {boolean}
+     */
+    isCompleteTree(root) {
+        let treeHgt = 0;
+        let nullSeen = false;
+
+        const dfs = (node, hgt) => {
+            if (!node) {
+                if (treeHgt === 0) {
+                    treeHgt = hgt;
+                } else if (hgt === treeHgt - 1) {
+                    nullSeen = true;
+                } else if (hgt !== treeHgt) {
+                    return false;
+                }
+                return !(hgt === treeHgt && nullSeen);
+            }
+
+            return dfs(node.left, hgt + 1) && dfs(node.right, hgt + 1);
+        };
+
+        return dfs(root, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
\ No newline at end of file
diff --git a/articles/check-if-a-string-contains-all-binary-codes-of-size-k.md b/articles/check-if-a-string-contains-all-binary-codes-of-size-k.md
new file mode 100644
index 000000000..917412238
--- /dev/null
+++ b/articles/check-if-a-string-contains-all-binary-codes-of-size-k.md
@@ -0,0 +1,497 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def hasAllCodes(self, s: str, k: int) -> bool:
+        n = len(s)
+        if n < (1 << k):
+            return False
+
+        for num in range(1 << k):
+            binaryCode = format(num, f'0{k}b')
+            if binaryCode not in s:
+                return False
+
+        return True
+```
+
+```java
+public class Solution {
+    public boolean hasAllCodes(String s, int k) {
+        int n = s.length();
+        if (n < (1 << k)) {
+            return false;
+        }
+
+        for (int num = 0; num < (1 << k); num++) {
+            String binaryCode = String.format("%" + k + "s", Integer.toBinaryString(num)).replace(' ', '0');
+            if (!s.contains(binaryCode)) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool hasAllCodes(string s, int k) {
+        int n = s.size();
+        if (n < (1 << k)) {
+            return false;
+        }
+
+        for (int num = 0; num < (1 << k); num++) {
+            string binaryCode = bitset<20>(num).to_string().substr(20 - k);
+            if (s.find(binaryCode) == string::npos) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {number} k
+     * @return {boolean}
+     */
+    hasAllCodes(s, k) {
+        const n = s.length;
+        if (n < (1 << k)) {
+            return false;
+        }
+
+        for (let num = 0; num < (1 << k); num++) {
+            const binaryCode = num.toString(2).padStart(k, '0');
+            if (!s.includes(binaryCode)) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * 2 ^ k)$
+* Space complexity: $O(k)$
+
+> Where $n$ is the length of the string $s$ and $k$ is the length of the binary code.
+
+---
+
+## 2. Hash Set
+
+::tabs-start
+
+```python
+class Solution:
+    def hasAllCodes(self, s: str, k: int) -> bool:
+        if len(s) < 2 ** k:
+            return False
+        
+        codeSet = set()
+        for i in range(len(s) - k + 1):
+            codeSet.add(s[i:i + k])
+        
+        return len(codeSet) == 2 ** k
+```
+
+```java
+public class Solution {
+    public boolean hasAllCodes(String s, int k) {
+        if (s.length() < (1 << k)) {
+            return false;
+        }
+        
+        HashSet<String> codeSet = new HashSet<>();
+        for (int i = 0; i <= s.length() - k; i++) {
+            codeSet.add(s.substring(i, i + k));
+        }
+        
+        return codeSet.size() == (1 << k);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool hasAllCodes(std::string s, int k) {
+        if (s.size() < (1 << k)) {
+            return false;
+        }
+        
+        std::unordered_set<std::string> codeSet;
+        for (int i = 0; i <= s.size() - k; i++) {
+            codeSet.insert(s.substr(i, k));
+        }
+        
+        return codeSet.size() == (1 << k);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {number} k
+     * @return {boolean}
+     */
+    hasAllCodes(s, k) {
+        if (s.length < (1 << k)) {
+            return false;
+        }
+        
+        const codeSet = new Set();
+        for (let i = 0; i <= s.length - k; i++) {
+            codeSet.add(s.substring(i, i + k));
+        }
+        
+        return codeSet.size === (1 << k);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * k)$
+* Space complexity: $O(2 ^ k)$
+
+> Where $n$ is the length of the string $s$ and $k$ is the length of the binary code.
+
+---
+
+## 3. Sliding Window
+
+::tabs-start
+
+```python
+class Solution:
+    def hasAllCodes(self, s: str, k: int) -> bool:
+        n = len(s)
+        if n < (1 << k):
+            return False
+        
+        codeSet = [False] * (1 << k)
+        cur = 0
+        i = j = 0
+        bit = k - 1
+        while j < k:
+            if s[j] == '1':
+                cur |= (1 << bit)
+            bit -= 1
+            j += 1
+        
+        have = 1
+        codeSet[cur] = True
+        while j < n:
+            if s[i] == '1':
+                cur ^= (1 << (k - 1))
+            i += 1
+
+            cur <<= 1
+            if s[j] == '1':
+                cur |= 1
+            j += 1
+
+            if not codeSet[cur]:
+                have += 1
+                codeSet[cur] = True
+        
+        return have == (1 << k)
+```
+
+```java
+public class Solution {
+    public boolean hasAllCodes(String s, int k) {
+        int n = s.length();
+        if (n < (1 << k)) {
+            return false;
+        }
+
+        boolean[] codeSet = new boolean[1 << k];
+        int cur = 0;
+        int i = 0, j = 0, bit = k - 1;
+
+        while (j < k) {
+            if (s.charAt(j) == '1') {
+                cur |= (1 << bit);
+            }
+            bit--;
+            j++;
+        }
+
+        int have = 1;
+        codeSet[cur] = true;
+
+        while (j < n) {
+            if (s.charAt(i) == '1') {
+                cur ^= (1 << (k - 1));
+            }
+            i++;
+
+            cur <<= 1;
+            if (s.charAt(j) == '1') {
+                cur |= 1;
+            }
+            j++;
+
+            if (!codeSet[cur]) {
+                have++;
+                codeSet[cur] = true;
+            }
+        }
+
+        return have == (1 << k);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool hasAllCodes(string s, int k) {
+        int n = s.size();
+        if (n < (1 << k)) {
+            return false;
+        }
+
+        vector<bool> codeSet(1 << k, false);
+        int cur = 0;
+        int i = 0, j = 0, bit = k - 1;
+
+        while (j < k) {
+            if (s[j] == '1') {
+                cur |= (1 << bit);
+            }
+            bit--;
+            j++;
+        }
+
+        int have = 1;
+        codeSet[cur] = true;
+
+        while (j < n) {
+            if (s[i] == '1') {
+                cur ^= (1 << (k - 1));
+            }
+            i++;
+
+            cur <<= 1;
+            if (s[j] == '1') {
+                cur |= 1;
+            }
+            j++;
+
+            if (!codeSet[cur]) {
+                have++;
+                codeSet[cur] = true;
+            }
+        }
+
+        return have == (1 << k);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {number} k
+     * @return {boolean}
+     */
+    hasAllCodes(s, k) {
+        const n = s.length;
+        if (n < (1 << k)) {
+            return false;
+        }
+
+        const codeSet = new Array(1 << k).fill(false);
+        let cur = 0;
+        let i = 0, j = 0, bit = k - 1;
+
+        while (j < k) {
+            if (s[j] === '1') {
+                cur |= (1 << bit);
+            }
+            bit--;
+            j++;
+        }
+
+        let have = 1;
+        codeSet[cur] = true;
+
+        while (j < n) {
+            if (s[i] === '1') {
+                cur ^= (1 << (k - 1));
+            }
+            i++;
+
+            cur <<= 1;
+            if (s[j] === '1') {
+                cur |= 1;
+            }
+            j++;
+
+            if (!codeSet[cur]) {
+                have++;
+                codeSet[cur] = true;
+            }
+        }
+
+        return have === (1 << k);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(2 ^ k)$
+
+> Where $n$ is the length of the string $s$ and $k$ is the length of the binary code.
+
+---
+
+## 4. Sliding Window (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def hasAllCodes(self, s: str, k: int) -> bool:
+        n = len(s)
+        if n < (1 << k):
+            return False
+        
+        codeSet = [False] * (1 << k)
+        cur = 0
+        have = 0
+        
+        for i in range(n):
+            cur = ((cur << 1) & ((1 << k) - 1)) | (ord(s[i]) - ord('0'))
+
+            if i >= k - 1:
+                if not codeSet[cur]:
+                    codeSet[cur] = True
+                    have += 1
+        
+        return have == (1 << k)
+```
+
+```java
+public class Solution {
+    public boolean hasAllCodes(String s, int k) {
+        int n = s.length();
+        if (n < (1 << k)) {
+            return false;
+        }
+
+        boolean[] codeSet = new boolean[1 << k];
+        int cur = 0, have = 0;
+
+        for (int i = 0; i < n; i++) {
+            cur = ((cur << 1) & ((1 << k) - 1)) | (s.charAt(i) - '0');
+
+            if (i >= k - 1) {
+                if (!codeSet[cur]) {
+                    codeSet[cur] = true;
+                    have++;
+                }
+            }
+        }
+
+        return have == (1 << k);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool hasAllCodes(string s, int k) {
+        int n = s.size();
+        if (n < (1 << k)) {
+            return false;
+        }
+
+        vector<bool> codeSet(1 << k, false);
+        int cur = 0, have = 0;
+
+        for (int i = 0; i < n; i++) {
+            cur = ((cur << 1) & ((1 << k) - 1)) | (s[i] - '0');
+
+            if (i >= k - 1) {
+                if (!codeSet[cur]) {
+                    codeSet[cur] = true;
+                    have++;
+                }
+            }
+        }
+
+        return have == (1 << k);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {number} k
+     * @return {boolean}
+     */
+    hasAllCodes(s, k) {
+        const n = s.length;
+        if (n < (1 << k)) {
+            return false;
+        }
+
+        const codeSet = new Array(1 << k).fill(false);
+        let cur = 0, have = 0;
+
+        for (let i = 0; i < n; i++) {
+            cur = ((cur << 1) & ((1 << k) - 1)) | (s[i] - '0');
+
+            if (i >= k - 1) {
+                if (!codeSet[cur]) {
+                    codeSet[cur] = true;
+                    have++;
+                }
+            }
+        }
+
+        return have === (1 << k);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(2 ^ k)$
+
+> Where $n$ is the length of the string $s$ and $k$ is the length of the binary code.
\ No newline at end of file
diff --git a/articles/check-if-array-is-sorted-and-rotated.md b/articles/check-if-array-is-sorted-and-rotated.md
new file mode 100644
index 000000000..061da0d48
--- /dev/null
+++ b/articles/check-if-array-is-sorted-and-rotated.md
@@ -0,0 +1,306 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def check(self, nums: List[int]) -> bool:
+        sortedNums = sorted(nums)
+        arr = []
+
+        for i in range(len(nums)):
+            arr.insert(0, sortedNums.pop())
+            if nums == arr + sortedNums:
+                return True
+
+        return False
+```
+
+```java
+public class Solution {
+    public boolean check(int[] nums) {
+        int n = nums.length;
+        int[] sortedNums = nums.clone();
+        Arrays.sort(sortedNums);
+
+        for (int i = 0; i < n; i++) {
+            boolean match = true;
+            int idx = 0;
+            for (int j = n - i; j < n && match; j++) {
+                if (nums[idx] != sortedNums[j]) {
+                    match = false;
+                }
+                idx += 1;
+            }
+
+            for (int j = 0; j < n - i && match; j++) {
+                if (nums[idx] != sortedNums[j]) {
+                    match = false;
+                }
+                idx += 1;
+            }
+
+            if (match) return true;
+        }
+
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool check(vector<int>& nums) {
+        int n = nums.size();
+        vector<int> sortedNums = nums;
+        sort(sortedNums.begin(), sortedNums.end());
+
+        for (int i = 0; i < n; i++) {
+            bool match = true;
+            int idx = 0;
+            for (int j = n - i; j < n && match; j++) {
+                if (nums[idx] != sortedNums[j]) {
+                    match = false;
+                }
+                idx++;
+            }
+
+            for (int j = 0; j < n - i && match; j++) {
+                if (nums[idx] != sortedNums[j]) {
+                    match = false;
+                }
+                idx++;
+            }
+
+            if (match) return true;
+        }
+
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {boolean}
+     */
+    check(nums) {
+        const n = nums.length;
+        const sortedNums = [...nums].sort((a, b) => a - b);
+
+        for (let i = 0; i < n; i++) {
+            let match = true;
+            let idx = 0;
+
+            for (let j = n - i; j < n && match; j++) {
+                if (nums[idx] !== sortedNums[j]) {
+                    match = false;
+                }
+                idx++;
+            }
+
+            for (let j = 0; j < n - i && match; j++) {
+                if (nums[idx] !== sortedNums[j]) {
+                    match = false;
+                }
+                idx++;
+            }
+
+            if (match) return true;
+        }
+
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Sliding Window
+
+::tabs-start
+
+```python
+class Solution:
+    def check(self, nums: List[int]) -> bool:
+        N = len(nums)
+        count = 1
+
+        for i in range(1, 2 * N):
+            if nums[(i - 1) % N] <= nums[i % N]:
+                count += 1
+            else:
+                count = 1
+            if count == N:
+                return True
+
+        return N == 1
+```
+
+```java
+public class Solution {
+    public boolean check(int[] nums) {
+        int N = nums.length;
+        int count = 1;
+
+        for (int i = 1; i < 2 * N; i++) {
+            if (nums[(i - 1) % N] <= nums[i % N]) {
+                count++;
+            } else {
+                count = 1;
+            }
+            if (count == N) {
+                return true;
+            }
+        }
+
+        return N == 1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool check(vector<int>& nums) {
+        int N = nums.size();
+        int count = 1;
+
+        for (int i = 1; i < 2 * N; i++) {
+            if (nums[(i - 1) % N] <= nums[i % N]) {
+                count++;
+            } else {
+                count = 1;
+            }
+            if (count == N) {
+                return true;
+            }
+        }
+
+        return N == 1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {boolean}
+     */
+    check(nums) {
+        const N = nums.length;
+        let count = 1;
+
+        for (let i = 1; i < 2 * N; i++) {
+            if (nums[(i - 1) % N] <= nums[i % N]) {
+                count++;
+            } else {
+                count = 1;
+            }
+            if (count === N) {
+                return true;
+            }
+        }
+
+        return N === 1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Iteration
+
+::tabs-start
+
+```python
+class Solution:
+    def check(self, nums: List[int]) -> bool:
+        count, N = 0, len(nums)
+
+        for i in range(N):
+            if nums[i] > nums[(i + 1) % N]:
+                count += 1
+                if count > 1:
+                    return False
+
+        return True
+```
+
+```java
+public class Solution {
+    public boolean check(int[] nums) {
+        int count = 0, N = nums.length;
+
+        for (int i = 0; i < N; i++) {
+            if (nums[i] > nums[(i + 1) % N] && ++count > 1) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool check(vector<int>& nums) {
+        int count = 0, N = nums.size();
+
+        for (int i = 0; i < N; i++) {
+            if (nums[i] > nums[(i + 1) % N] && ++count > 1) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {boolean}
+     */
+    check(nums) {
+        let count = 0, N = nums.length;
+
+        for (let i = 0; i < N; i++) {
+            if (nums[i] > nums[(i + 1) % N] && ++count > 1) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/check-if-move-is-legal.md b/articles/check-if-move-is-legal.md
new file mode 100644
index 000000000..acc1d8b66
--- /dev/null
+++ b/articles/check-if-move-is-legal.md
@@ -0,0 +1,298 @@
+## 1. Iteration - I
+
+::tabs-start
+
+```python
+class Solution:
+    def checkMove(self, board: List[List[str]], rMove: int, cMove: int, color: str) -> bool:
+        ROWS, COLS = len(board), len(board[0])
+        direction = [[1, 0], [-1, 0], [0, 1], [0, -1], 
+                     [1, 1], [-1, -1], [1, -1], [-1, 1]]
+
+        board[rMove][cMove] = color
+
+        def legal(row, col, color, direc):
+            dr, dc = direc
+            row, col = row + dr, col + dc
+            length = 1
+
+            while 0 <= row < ROWS and 0 <= col < COLS:
+                length += 1
+                if board[row][col] == ".":
+                    return False
+                if board[row][col] == color:
+                    return length >= 3
+                row, col = row + dr, col + dc
+            return False
+
+        for d in direction:
+            if legal(rMove, cMove, color, d):
+                return True
+        return False
+```
+
+```java
+public class Solution {
+    public boolean checkMove(char[][] board, int rMove, int cMove, char color) {
+        int ROWS = board.length, COLS = board[0].length;
+        int[][] direction = {{1, 0}, {-1, 0}, {0, 1}, {0, -1}, 
+                             {1, 1}, {-1, -1}, {1, -1}, {-1, 1}};
+
+        board[rMove][cMove] = color;
+
+        for (int[] d : direction) {
+            if (legal(board, rMove, cMove, color, d)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    private boolean legal(char[][] board, int row, int col, char color, int[] direc) {
+        int ROWS = board.length, COLS = board[0].length;
+        int dr = direc[0], dc = direc[1];
+        row += dr;
+        col += dc;
+        int length = 1;
+
+        while (row >= 0 && row < ROWS && col >= 0 && col < COLS) {
+            length++;
+            if (board[row][col] == '.') {
+                return false;
+            }
+            if (board[row][col] == color) {
+                return length >= 3;
+            }
+            row += dr;
+            col += dc;
+        }
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool checkMove(vector<vector<char>>& board, int rMove, int cMove, char color) {
+        int ROWS = board.size(), COLS = board[0].size();
+        vector<vector<int>> direction = {{1, 0}, {-1, 0}, {0, 1}, {0, -1}, 
+                                         {1, 1}, {-1, -1}, {1, -1}, {-1, 1}};
+
+        board[rMove][cMove] = color;
+
+        for (auto& d : direction) {
+            if (legal(board, rMove, cMove, color, d)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+private:
+    bool legal(vector<vector<char>>& board, int row, int col, char color, vector<int>& direc) {
+        int ROWS = board.size(), COLS = board[0].size();
+        int dr = direc[0], dc = direc[1];
+        row += dr;
+        col += dc;
+        int length = 1;
+
+        while (row >= 0 && row < ROWS && col >= 0 && col < COLS) {
+            length++;
+            if (board[row][col] == '.') {
+                return false;
+            }
+            if (board[row][col] == color) {
+                return length >= 3;
+            }
+            row += dr;
+            col += dc;
+        }
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {character[][]} board
+     * @param {number} rMove
+     * @param {number} cMove
+     * @param {character} color
+     * @return {boolean}
+     */
+    checkMove(board, rMove, cMove, color) {
+        const ROWS = board.length, COLS = board[0].length;
+        const direction = [[1, 0], [-1, 0], [0, 1], [0, -1], 
+                           [1, 1], [-1, -1], [1, -1], [-1, 1]];
+
+        board[rMove][cMove] = color;
+
+        const legal = (row, col, color, [dr, dc]) => {
+            row += dr;
+            col += dc;
+            let length = 1;
+
+            while (row >= 0 && row < ROWS && col >= 0 && col < COLS) {
+                length++;
+                if (board[row][col] === ".") {
+                    return false;
+                }
+                if (board[row][col] === color) {
+                    return length >= 3;
+                }
+                row += dr;
+                col += dc;
+            }
+            return false;
+        };
+
+        for (let d of direction) {
+            if (legal(rMove, cMove, color, d)) {
+                return true;
+            }
+        }
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Iteration - II
+
+::tabs-start
+
+```python
+class Solution:
+    def checkMove(self, board: List[List[str]], rMove: int, cMove: int, color: str) -> bool:
+        ROWS, COLS = len(board), len(board[0])
+        direction = [0, 1, 0, -1, 0, 1, 1, -1, -1, 1]
+
+        board[rMove][cMove] = color
+
+        for d in range(9):
+            length = 1
+            row, col = rMove, cMove
+            while True:
+                row += direction[d]
+                col += direction[d + 1]
+
+                if row < 0 or col < 0 or row >= ROWS or col >= COLS or board[row][col] == ".":
+                    break
+                if board[row][col] == color:
+                    if length > 1:
+                        return True
+                    break
+                length += 1
+
+        return False
+```
+
+```java
+public class Solution {
+    public boolean checkMove(char[][] board, int rMove, int cMove, char color) {
+        int ROWS = board.length, COLS = board[0].length;
+        int[] direction = {0, 1, 0, -1, 0, 1, 1, -1, -1, 1};
+
+        board[rMove][cMove] = color;
+
+        for (int d = 0; d < 9; d++) {
+            int row = rMove, col = cMove;
+            for (int length = 1; ; ++length) {
+                row += direction[d];
+                col += direction[d + 1];
+
+                if (row < 0 || col < 0 || row >= ROWS || col >= COLS || board[row][col] == '.')
+                    break;
+                if (board[row][col] == color) {
+                    if (length > 1)
+                        return true;
+                    break;
+                }
+            }
+        }
+        return false;
+    }
+}
+
+```
+
+```cpp
+class Solution {
+public:
+    bool checkMove(vector<vector<char>>& board, int rMove, int cMove, char color) {
+        int ROWS = board.size(), COLS = board[0].size();
+        int direction[10] = {0, 1, 0, -1, 0, 1, 1, -1, -1, 1};
+
+        board[rMove][cMove] = color;
+
+        for (int d = 0; d < 9; ++d) {
+            int row = rMove, col = cMove;
+            for (int length = 1; ; ++length) {
+                row += direction[d];
+                col += direction[d + 1];
+
+                if (row < 0 || col < 0 || row >= ROWS || col >= COLS || board[row][col] == '.')
+                    break;
+                if (board[row][col] == color) {
+                    if (length > 1)
+                        return true;
+                    break;
+                }
+            }
+        }
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {character[][]} board
+     * @param {number} rMove
+     * @param {number} cMove
+     * @param {character} color
+     * @return {boolean}
+     */
+    checkMove(board, rMove, cMove, color) {
+        const ROWS = board.length, COLS = board[0].length;
+        const direction = [0, 1, 0, -1, 0, 1, 1, -1, -1, 1];
+
+        board[rMove][cMove] = color;
+
+        for (let d = 0; d < 9; d++) {
+            let row = rMove, col = cMove;
+            for (let length = 1; ; ++length) {
+                row += direction[d];
+                col += direction[d + 1];
+
+                if (row < 0 || col < 0 || row >= ROWS || col >= COLS || board[row][col] === '.')
+                    break;
+                if (board[row][col] === color) {
+                    if (length > 1)
+                        return true;
+                    break;
+                }
+            }
+        }
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/check-if-there-is-a-valid-partition-for-the-array.md b/articles/check-if-there-is-a-valid-partition-for-the-array.md
new file mode 100644
index 000000000..e855fd84d
--- /dev/null
+++ b/articles/check-if-there-is-a-valid-partition-for-the-array.md
@@ -0,0 +1,451 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def validPartition(self, nums: List[int]) -> bool:
+        def dfs(i):
+            if i == len(nums):
+                return True
+            
+            res = False
+            if i < len(nums) - 1 and nums[i] == nums[i + 1]:
+                res = dfs(i + 2)
+            if i < len(nums) - 2:
+                if ((nums[i] == nums[i + 1] == nums[i + 2]) or 
+                    (nums[i] + 1 == nums[i + 1] and nums[i + 1] + 1 == nums[i + 2])
+                ):
+                    res = res or dfs(i + 3)
+            return res
+        
+        return dfs(0)
+```
+
+```java
+public class Solution {
+    public boolean validPartition(int[] nums) {
+        return dfs(nums, 0);
+    }
+    
+    private boolean dfs(int[] nums, int i) {
+        if (i == nums.length) return true;
+        
+        boolean res = false;
+        if (i < nums.length - 1 && nums[i] == nums[i + 1]) {
+            res = dfs(nums, i + 2);
+        }
+        if (i < nums.length - 2) {
+            if ((nums[i] == nums[i + 1] && nums[i + 1] == nums[i + 2]) || 
+                (nums[i] + 1 == nums[i + 1] && nums[i + 1] + 1 == nums[i + 2])) {
+                res = res || dfs(nums, i + 3);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool validPartition(vector<int>& nums) {
+        return dfs(nums, 0);
+    }
+
+private:
+    bool dfs(vector<int>& nums, int i) {
+        if (i == nums.size()) return true;
+
+        bool res = false;
+        if (i < nums.size() - 1 && nums[i] == nums[i + 1]) {
+            res = dfs(nums, i + 2);
+        }
+        if (i < nums.size() - 2) {
+            if ((nums[i] == nums[i + 1] && nums[i + 1] == nums[i + 2]) || 
+                (nums[i] + 1 == nums[i + 1] && nums[i + 1] + 1 == nums[i + 2])) {
+                res = res || dfs(nums, i + 3);
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {boolean}
+     */
+    validPartition(nums) {
+        const dfs = (i) => {
+            if (i === nums.length) return true;
+
+            let res = false;
+            if (i < nums.length - 1 && nums[i] === nums[i + 1]) {
+                res = dfs(i + 2);
+            }
+            if (i < nums.length - 2) {
+                if ((nums[i] === nums[i + 1] && nums[i + 1] === nums[i + 2]) || 
+                    (nums[i] + 1 === nums[i + 1] && nums[i + 1] + 1 === nums[i + 2])) {
+                    res = res || dfs(i + 3);
+                }
+            }
+            return res;
+        };
+
+        return dfs(0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def validPartition(self, nums: List[int]) -> bool:
+        dp = { len(nums) : True }
+        def dfs(i):
+            if i in dp:
+                return dp[i]
+            
+            res = False
+            if i < len(nums) - 1 and nums[i] == nums[i + 1]:
+                res = dfs(i + 2)
+            if i < len(nums) - 2:
+                if ((nums[i] == nums[i + 1] == nums[i + 2]) or 
+                    (nums[i] + 1 == nums[i + 1] and nums[i + 1] + 1 == nums[i + 2])
+                ):
+                    res = res or dfs(i + 3)
+            
+            dp[i] = res
+            return res
+        
+        return dfs(0)
+```
+
+```java
+public class Solution {
+    private Map<Integer, Boolean> memo = new HashMap<>();
+
+    public boolean validPartition(int[] nums) {
+        return dfs(nums, 0);
+    }
+    
+    private boolean dfs(int[] nums, int i) {
+        if (i == nums.length) return true;
+        if (memo.containsKey(i)) return memo.get(i);
+        
+        boolean res = false;
+        if (i < nums.length - 1 && nums[i] == nums[i + 1]) {
+            res = dfs(nums, i + 2);
+        }
+        if (i < nums.length - 2) {
+            if ((nums[i] == nums[i + 1] && nums[i + 1] == nums[i + 2]) || 
+                (nums[i] + 1 == nums[i + 1] && nums[i + 1] + 1 == nums[i + 2])) {
+                res = res || dfs(nums, i + 3);
+            }
+        }
+        
+        memo.put(i, res);
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    unordered_map<int, bool> memo;
+
+    bool validPartition(vector<int>& nums) {
+        return dfs(nums, 0);
+    }
+
+private:
+    bool dfs(vector<int>& nums, int i) {
+        if (i == nums.size()) return true;
+        if (memo.count(i)) return memo[i];
+
+        bool res = false;
+        if (i < nums.size() - 1 && nums[i] == nums[i + 1]) {
+            res = dfs(nums, i + 2);
+        }
+        if (i < nums.size() - 2) {
+            if ((nums[i] == nums[i + 1] && nums[i + 1] == nums[i + 2]) || 
+                (nums[i] + 1 == nums[i + 1] && nums[i + 1] + 1 == nums[i + 2])) {
+                res = res || dfs(nums, i + 3);
+            }
+        }
+
+        return memo[i] = res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {boolean}
+     */
+    validPartition(nums) {
+        const memo = new Map();
+
+        const dfs = (i) => {
+            if (i === nums.length) return true;
+            if (memo.has(i)) return memo.get(i);
+
+            let res = false;
+            if (i < nums.length - 1 && nums[i] === nums[i + 1]) {
+                res = dfs(i + 2);
+            }
+            if (i < nums.length - 2) {
+                if ((nums[i] === nums[i + 1] && nums[i + 1] === nums[i + 2]) || 
+                    (nums[i] + 1 === nums[i + 1] && nums[i + 1] + 1 === nums[i + 2])) {
+                    res = res || dfs(i + 3);
+                }
+            }
+
+            memo.set(i, res);
+            return res;
+        };
+
+        return dfs(0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def validPartition(self, nums: List[int]) -> bool:
+        dp = [False] * (len(nums) + 1)
+        dp[0] = True
+
+        for i in range(2, len(nums) + 1):
+            if nums[i - 1] == nums[i - 2]:
+                dp[i] = dp[i] or dp[i - 2]
+            if i > 2 and ((nums[i - 1] == nums[i - 2] == nums[i - 3]) or 
+                          (nums[i - 3] + 1 == nums[i - 2] and nums[i - 2] + 1 == nums[i - 1])):
+                dp[i] = dp[i] or dp[i - 3]
+
+        return dp[len(nums)]
+```
+
+```java
+public class Solution {
+    public boolean validPartition(int[] nums) {
+        boolean[] dp = new boolean[nums.length + 1];
+        dp[0] = true;
+
+        for (int i = 2; i <= nums.length; i++) {
+            if (nums[i - 1] == nums[i - 2]) {
+                dp[i] = dp[i] || dp[i - 2];
+            }
+            if (i > 2 && ((nums[i - 1] == nums[i - 2] && nums[i - 2] == nums[i - 3]) ||
+                          (nums[i - 3] + 1 == nums[i - 2] && nums[i - 2] + 1 == nums[i - 1]))) {
+                dp[i] = dp[i] || dp[i - 3];
+            }
+        }
+
+        return dp[nums.length];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool validPartition(vector<int>& nums) {
+        vector<bool> dp(nums.size() + 1, false);
+        dp[0] = true;
+
+        for (int i = 2; i <= nums.size(); i++) {
+            if (nums[i - 1] == nums[i - 2]) {
+                dp[i] = dp[i] || dp[i - 2];
+            }
+            if (i > 2 && ((nums[i - 1] == nums[i - 2] && nums[i - 2] == nums[i - 3]) ||
+                          (nums[i - 3] + 1 == nums[i - 2] && nums[i - 2] + 1 == nums[i - 1]))) {
+                dp[i] = dp[i] || dp[i - 3];
+            }
+        }
+
+        return dp[nums.size()];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {boolean}
+     */
+    validPartition(nums) {
+        const dp = Array(nums.length + 1).fill(false);
+        dp[0] = true;
+
+        for (let i = 2; i <= nums.length; i++) {
+            if (nums[i - 1] === nums[i - 2]) {
+                dp[i] = dp[i] || dp[i - 2];
+            }
+            if (i > 2 && ((nums[i - 1] === nums[i - 2] && nums[i - 2] === nums[i - 3]) ||
+                          (nums[i - 3] + 1 === nums[i - 2] && nums[i - 2] + 1 === nums[i - 1]))) {
+                dp[i] = dp[i] || dp[i - 3];
+            }
+        }
+
+        return dp[nums.length];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def validPartition(self, nums: List[int]) -> bool:
+        dp = [False, True, True]
+
+        for i in range(len(nums) - 2, -1, -1):
+            dp1 = dp[0]
+            if nums[i] == nums[i + 1] and dp[1]:
+                dp[0] = True
+            elif i < len(nums) - 2 and dp[2] and (
+                (nums[i] == nums[i + 1] == nums[i + 2]) or 
+                (nums[i] + 1 == nums[i + 1] and nums[i + 1] == nums[i + 2] - 1)
+            ):
+                dp[0] = True
+            else:
+                dp[0] = False
+            dp[2] = dp[1]
+            dp[1] = dp1
+
+        return dp[0]
+```
+
+```java
+public class Solution {
+    public boolean validPartition(int[] nums) {
+        boolean[] dp = new boolean[3];
+        dp[2] = true;
+        dp[1] = true;
+        dp[0] = false;
+
+        for (int i = nums.length - 2; i >= 0; i--) {
+            boolean dp1 = dp[0];
+            if (nums[i] == nums[i + 1] && dp[1]) {
+                dp[0] = true;
+            } else if (i < nums.length - 2 && dp[2] && 
+                      ((nums[i] == nums[i + 1] && nums[i] == nums[i + 2]) || 
+                      (nums[i] + 1 == nums[i + 1] && nums[i + 1] == nums[i + 2] - 1))) {
+                dp[0] = true;
+            } else {
+                dp[0] = false;
+            }
+            dp[2] = dp[1];
+            dp[1] = dp1;
+        }
+        
+        return dp[0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool validPartition(vector<int>& nums) {
+        bool dp[3] = {false, true, true};
+
+        for (int i = nums.size() - 2; i >= 0; --i) {
+            bool dp1 = dp[0];
+            if (nums[i] == nums[i + 1] && dp[1]) {
+                dp[0] = true;
+            } else if (i < nums.size() - 2 && dp[2] && 
+                      ((nums[i] == nums[i + 1] && nums[i] == nums[i + 2]) || 
+                      (nums[i] + 1 == nums[i + 1] && nums[i + 1] == nums[i + 2] - 1))) {
+                dp[0] = true;
+            } else {
+                dp[0] = false;
+            }
+            dp[2] = dp[1];
+            dp[1] = dp1;
+        }
+
+        return dp[0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {boolean}
+     */
+    validPartition(nums) {
+        let dp = [false, true, true];
+
+        for (let i = nums.length - 2; i >= 0; i--) {
+            let dp1 = dp[0];
+            if (nums[i] === nums[i + 1] && dp[1]) {
+                dp[0] = true;
+            } else if (i < nums.length - 2 && dp[2] && 
+                      ((nums[i] === nums[i + 1] && nums[i] === nums[i + 2]) || 
+                      (nums[i] + 1 === nums[i + 1] && nums[i + 1] === nums[i + 2] - 1))) {
+                dp[0] = true;
+            } else {
+                dp[0] = false;
+            }
+            dp[2] = dp[1];
+            dp[1] = dp1;
+        }
+
+        return dp[0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/check-if-two-string-arrays-are-equivalent.md b/articles/check-if-two-string-arrays-are-equivalent.md
new file mode 100644
index 000000000..39805de58
--- /dev/null
+++ b/articles/check-if-two-string-arrays-are-equivalent.md
@@ -0,0 +1,270 @@
+## 1. Concatenate Strings
+
+::tabs-start
+
+```python
+class Solution:
+    def arrayStringsAreEqual(self, word1: List[str], word2: List[str]) -> bool:
+        return "".join(word1) == "".join(word2)
+```
+
+```java
+public class Solution {
+    public boolean arrayStringsAreEqual(String[] word1, String[] word2) {
+        return String.join("", word1).equals(String.join("", word2));
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool arrayStringsAreEqual(vector<string>& word1, vector<string>& word2) {
+        string str1 = accumulate(word1.begin(), word1.end(), string());
+        string str2 = accumulate(word2.begin(), word2.end(), string());
+        return str1 == str2;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} word1
+     * @param {string[]} word2
+     * @return {boolean}
+     */
+    arrayStringsAreEqual(word1, word2) {
+        return word1.join("") === word2.join("");
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(n + m)$
+
+> Where $n$ and $m$ are the total number of characters in both the arrays $word1$ and $word2$, respectively.
+
+---
+
+## 2. Concatenate Strings Of One Array
+
+::tabs-start
+
+```python
+class Solution:
+    def arrayStringsAreEqual(self, word1: List[str], word2: List[str]) -> bool:
+        s1 = "".join(word1)
+        i = 0
+        for w in word2:
+            for c in w:
+                if i == len(s1) or s1[i] != c:
+                    return False
+                i += 1
+        return i == len(s1)
+```
+
+```java
+public class Solution {
+    public boolean arrayStringsAreEqual(String[] word1, String[] word2) {
+        StringBuilder s1 = new StringBuilder();
+        for (String w : word1) {
+            s1.append(w);
+        }
+
+        int i = 0;
+        for (String w : word2) {
+            for (char c : w.toCharArray()) {
+                if (i == s1.length() || s1.charAt(i) != c) {
+                    return false;
+                }
+                i++;
+            }
+        }
+        return i == s1.length();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool arrayStringsAreEqual(vector<string>& word1, vector<string>& word2) {
+        string s1 = "";
+        for (string w : word1) s1 += w;
+
+        int i = 0;
+        for (string w : word2) {
+            for (char c : w) {
+                if (i == s1.length() || s1[i] != c) return false;
+                i++;
+            }
+        }
+        return i == s1.length();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} word1
+     * @param {string[]} word2
+     * @return {boolean}
+     */
+    arrayStringsAreEqual(word1, word2) {
+        let s1 = word1.join("");
+        let i = 0;
+
+        for (let w of word2) {
+            for (let c of w) {
+                if (i === s1.length || s1[i] !== c) {
+                    return false;
+                }
+                i++;
+            }
+        }
+        return i === s1.length;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(n)$
+
+> Where $n$ and $m$ are the total number of characters in both the arrays $word1$ and $word2$, respectively.
+
+---
+
+## 3. Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def arrayStringsAreEqual(self, word1: List[str], word2: List[str]) -> bool:
+        w1 = w2 = 0  # Index of word
+        i = j = 0    # Index of character
+
+        while w1 < len(word1) and w2 < len(word2):
+            if word1[w1][i] != word2[w2][j]:
+                return False
+
+            i, j = i + 1, j + 1
+
+            if i == len(word1[w1]):
+                w1 += 1
+                i = 0
+            if j == len(word2[w2]):
+                w2 += 1
+                j = 0
+
+        return w1 == len(word1) and w2 == len(word2)
+```
+
+```java
+public class Solution {
+    public boolean arrayStringsAreEqual(String[] word1, String[] word2) {
+        int w1 = 0, w2 = 0; // Index of word
+        int i = 0, j = 0;   // Index of character
+
+        while (w1 < word1.length && w2 < word2.length) {
+            if (word1[w1].charAt(i) != word2[w2].charAt(j)) {
+                return false;
+            }
+
+            i++;
+            j++;
+
+            if (i == word1[w1].length()) {
+                w1++;
+                i = 0;
+            }
+            if (j == word2[w2].length()) {
+                w2++;
+                j = 0;
+            }
+        }
+        return w1 == word1.length && w2 == word2.length;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool arrayStringsAreEqual(vector<string>& word1, vector<string>& word2) {
+        int w1 = 0, w2 = 0; // Index of word
+        int i = 0, j = 0;   // Index of character
+
+        while (w1 < word1.size() && w2 < word2.size()) {
+            if (word1[w1][i] != word2[w2][j]) {
+                return false;
+            }
+
+            i++;
+            j++;
+
+            if (i == word1[w1].size()) {
+                w1++;
+                i = 0;
+            }
+            if (j == word2[w2].size()) {
+                w2++;
+                j = 0;
+            }
+        }
+        return w1 == word1.size() && w2 == word2.size();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} word1
+     * @param {string[]} word2
+     * @return {boolean}
+     */
+    arrayStringsAreEqual(word1, word2) {
+        let w1 = 0, w2 = 0; // Index of word
+        let i = 0, j = 0;   // Index of character
+
+        while (w1 < word1.length && w2 < word2.length) {
+            if (word1[w1][i] !== word2[w2][j]) {
+                return false;
+            }
+
+            i++;
+            j++;
+
+            if (i === word1[w1].length) {
+                w1++;
+                i = 0;
+            }
+            if (j === word2[w2].length) {
+                w2++;
+                j = 0;
+            }
+        }
+        return w1 === word1.length && w2 === word2.length;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(1)$ extra space.
+
+> Where $n$ and $m$ are the total number of characters in both the arrays $word1$ and $word2$, respectively.
\ No newline at end of file
diff --git a/articles/cherry-pickup-ii.md b/articles/cherry-pickup-ii.md
new file mode 100644
index 000000000..cc5ccc3da
--- /dev/null
+++ b/articles/cherry-pickup-ii.md
@@ -0,0 +1,559 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def cherryPickup(self, grid: List[List[int]]) -> int:
+        ROWS, COLS = len(grid), len(grid[0])
+
+        def dfs(r, c1, c2):
+            if c1 < 0 or c2 < 0 or c1 >= COLS or c2 >= COLS or c1 > c2:
+                return 0
+            if r == ROWS - 1:
+                return grid[r][c1] + (grid[r][c2] if c1 != c2 else 0)
+            
+            res = 0
+            for c1_d in [-1, 0, 1]:
+                for c2_d in [-1, 0, 1]:
+                    res = max(res, dfs(r + 1, c1 + c1_d, c2 + c2_d))
+            
+            return res + grid[r][c1] + (grid[r][c2] if c1 != c2 else 0)
+        
+        return dfs(0, 0, COLS - 1)
+```
+
+```java
+public class Solution {
+    public int cherryPickup(int[][] grid) {
+        int ROWS = grid.length, COLS = grid[0].length;
+
+        return dfs(0, 0, COLS - 1, grid, ROWS, COLS);
+    }
+
+    private int dfs(int r, int c1, int c2, int[][] grid, int ROWS, int COLS) {
+        if (c1 < 0 || c2 < 0 || c1 >= COLS || c2 >= COLS || c1 > c2) {
+            return 0;
+        }
+        if (r == ROWS - 1) {
+            return grid[r][c1] + (c1 == c2 ? 0 : grid[r][c2]);
+        }
+
+        int res = 0;
+        for (int c1_d = -1; c1_d <= 1; c1_d++) {
+            for (int c2_d = -1; c2_d <= 1; c2_d++) {
+                res = Math.max(res, dfs(r + 1, c1 + c1_d, c2 + c2_d, grid, ROWS, COLS));
+            }
+        }
+        return res + grid[r][c1] + (c1 == c2 ? 0 : grid[r][c2]);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int cherryPickup(vector<vector<int>>& grid) {
+        int ROWS = grid.size(), COLS = grid[0].size();
+        return dfs(0, 0, COLS - 1, grid, ROWS, COLS);
+    }
+
+private:
+    int dfs(int r, int c1, int c2, vector<vector<int>>& grid, int ROWS, int COLS) {
+        if (c1 < 0 || c2 < 0 || c1 >= COLS || c2 >= COLS || c1 > c2) {
+            return 0;
+        }
+        if (r == ROWS - 1) {
+            return grid[r][c1] + (c1 == c2 ? 0 : grid[r][c2]);
+        }
+
+        int res = 0;
+        for (int c1_d = -1; c1_d <= 1; c1_d++) {
+            for (int c2_d = -1; c2_d <= 1; c2_d++) {
+                res = max(res, dfs(r + 1, c1 + c1_d, c2 + c2_d, grid, ROWS, COLS));
+            }
+        }
+        return res + grid[r][c1] + (c1 == c2 ? 0 : grid[r][c2]);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    cherryPickup(grid) {
+        const ROWS = grid.length, COLS = grid[0].length;
+
+        const dfs = (r, c1, c2) => {
+            if (c1 < 0 || c2 < 0 || c1 >= COLS || c2 >= COLS || c1 > c2) return 0;
+            if (r === ROWS - 1) {
+                return grid[r][c1] + (c1 === c2 ? 0 : grid[r][c2]);
+            }
+
+            let res = 0;
+            for (let c1_d = -1; c1_d <= 1; c1_d++) {
+                for (let c2_d = -1; c2_d <= 1; c2_d++) {
+                    res = Math.max(res, dfs(r + 1, c1 + c1_d, c2 + c2_d));
+                }
+            }
+            return res + grid[r][c1] + (c1 === c2 ? 0 : grid[r][c2]);
+        };
+
+        return dfs(0, 0, COLS - 1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * 9 ^ n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+> Where $n$ is the number of rows and $m$ is the number of columns in the grid.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def cherryPickup(self, grid: List[List[int]]) -> int:
+        ROWS, COLS = len(grid), len(grid[0])
+        cache = {}
+
+        def dfs(r, c1, c2):
+            if (r, c1, c2) in cache:
+                return cache[(r, c1, c2)]
+            if c1 == c2 or min(c1, c2) < 0 or max(c1, c2) >= COLS:
+                return 0
+            if r == ROWS - 1:
+                return grid[r][c1] + grid[r][c2]
+            
+            res = 0
+            for c1_d in [-1, 0, 1]:
+                for c2_d in [-1, 0, 1]:
+                    res = max(res, dfs(r + 1, c1 + c1_d, c2 + c2_d))
+            
+            cache[(r, c1, c2)] = res + grid[r][c1] + (grid[r][c2] if c1 != c2 else 0)
+            return cache[(r, c1, c2)]
+        
+        return dfs(0, 0, COLS - 1)
+```
+
+```java
+public class Solution {
+    private int[][][] cache;
+    public int cherryPickup(int[][] grid) {
+        int ROWS = grid.length, COLS = grid[0].length;
+        cache = new int[ROWS][COLS][COLS];
+        for (int[][] i : cache) {
+            for (int[] j : i) {
+                Arrays.fill(j, -1);
+            }
+        }
+
+        return dfs(0, 0, COLS - 1, grid);
+    }
+
+    private int dfs(int r, int c1, int c2, int[][] grid) {
+        if (Math.min(c1, c2) < 0 || Math.max(c1, c2) >= grid[0].length) {
+            return 0;
+        }
+        if (cache[r][c1][c2] != -1) {
+            return cache[r][c1][c2];
+        }
+        if (r == grid.length - 1) {
+            return cache[r][c1][c2] = grid[r][c1] + (c1 == c2 ? 0 : grid[r][c2]);
+        }
+
+        int res = 0;
+        for (int c1_d = -1; c1_d <= 1; c1_d++) {
+            for (int c2_d = -1; c2_d <= 1; c2_d++) {
+                res = Math.max(res, dfs(r + 1, c1 + c1_d, c2 + c2_d, grid));
+            }
+        }
+        return cache[r][c1][c2] = res + grid[r][c1] + (c1 == c2 ? 0 : grid[r][c2]);
+    }
+}
+```
+
+```cpp
+class Solution {
+    vector<vector<vector<int>>> cache;
+
+public:
+    int cherryPickup(vector<vector<int>>& grid) {
+        int ROWS = grid.size(), COLS = grid[0].size();
+        cache.assign(ROWS, vector<vector<int>>(COLS, vector<int>(COLS, -1)));
+        return dfs(0, 0, COLS - 1, grid);
+    }
+
+private:
+    int dfs(int r, int c1, int c2, vector<vector<int>>& grid) {
+        if (min(c1, c2) < 0 || max(c1, c2) >= grid[0].size()) {
+            return 0;
+        }
+        if (cache[r][c1][c2] != -1) {
+            return cache[r][c1][c2];
+        }
+        if (r == grid.size() - 1) {
+            return cache[r][c1][c2] = grid[r][c1] + (c1 == c2 ? 0 : grid[r][c2]);
+        }
+
+        int res = 0;
+        for (int c1_d = -1; c1_d <= 1; c1_d++) {
+            for (int c2_d = -1; c2_d <= 1; c2_d++) {
+                res = max(res, dfs(r + 1, c1 + c1_d, c2 + c2_d, grid));
+            }
+        }
+        return cache[r][c1][c2] = res + grid[r][c1] + (c1 == c2 ? 0 : grid[r][c2]);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    cherryPickup(grid) {
+        const ROWS = grid.length, COLS = grid[0].length;
+        const cache = Array.from({ length: ROWS }, () =>
+            Array.from({ length: COLS }, () =>
+                Array(COLS).fill(-1)
+            )
+        );
+
+        const dfs = (r, c1, c2) => {
+            if (Math.min(c1, c2) < 0 || Math.max(c1, c2) >= COLS) {
+                return 0;
+            }
+            if (cache[r][c1][c2] !== -1) return cache[r][c1][c2];
+            if (r === ROWS - 1) {
+                return cache[r][c1][c2] = grid[r][c1] + (c1 === c2 ? 0 : grid[r][c2]);
+            }
+
+            let res = 0;
+            for (let c1_d = -1; c1_d <= 1; c1_d++) {
+                for (let c2_d = -1; c2_d <= 1; c2_d++) {
+                    res = Math.max(res, dfs(r + 1, c1 + c1_d, c2 + c2_d));
+                }
+            }
+            return cache[r][c1][c2] = res + grid[r][c1] + (c1 === c2 ? 0 : grid[r][c2]);
+        };
+
+        return dfs(0, 0, COLS - 1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m ^ 2)$
+* Space complexity: $O(n * m ^ 2)$
+
+> Where $n$ is the number of rows and $m$ is the number of columns in the grid.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def cherryPickup(self, grid: List[List[int]]) -> int:
+        ROWS, COLS = len(grid), len(grid[0])
+        dp = [[[0] * COLS for _ in range(COLS)] for _ in range(ROWS)]
+
+        for r in range(ROWS - 1, -1, -1):
+            for c1 in range(COLS):
+                for c2 in range(COLS):
+                    res = grid[r][c1]
+                    if c1 != c2:
+                        res += grid[r][c2]
+
+                    if r != ROWS - 1:
+                        max_cherries = 0
+                        for d1 in [-1, 0, 1]:
+                            for d2 in [-1, 0, 1]:
+                                nc1, nc2 = c1 + d1, c2 + d2
+                                if 0 <= nc1 < COLS and 0 <= nc2 < COLS:
+                                    max_cherries = max(max_cherries, dp[r + 1][nc1][nc2])
+                        res += max_cherries
+
+                    dp[r][c1][c2] = res
+
+        return dp[0][0][COLS - 1]
+```
+
+```java
+public class Solution {
+    public int cherryPickup(int[][] grid) {
+        int ROWS = grid.length, COLS = grid[0].length;
+        int[][][] dp = new int[ROWS][COLS][COLS];
+
+        for (int r = ROWS - 1; r >= 0; r--) {
+            for (int c1 = 0; c1 < COLS; c1++) {
+                for (int c2 = 0; c2 < COLS; c2++) {
+                    int res = grid[r][c1];
+                    if (c1 != c2) {
+                        res += grid[r][c2];
+                    }
+
+                    if (r != ROWS - 1) {
+                        int maxCherries = 0;
+                        for (int d1 = -1; d1 <= 1; d1++) {
+                            for (int d2 = -1; d2 <= 1; d2++) {
+                                int nc1 = c1 + d1, nc2 = c2 + d2;
+                                if (nc1 >= 0 && nc1 < COLS && nc2 >= 0 && nc2 < COLS) {
+                                    maxCherries = Math.max(maxCherries, dp[r + 1][nc1][nc2]);
+                                }
+                            }
+                        }
+                        res += maxCherries;
+                    }
+
+                    dp[r][c1][c2] = res;
+                }
+            }
+        }
+
+        return dp[0][0][COLS - 1];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int cherryPickup(vector<vector<int>>& grid) {
+        int ROWS = grid.size(), COLS = grid[0].size();
+        int dp[ROWS][COLS][COLS];
+
+        for (int r = ROWS - 1; r >= 0; r--) {
+            for (int c1 = 0; c1 < COLS; c1++) {
+                for (int c2 = 0; c2 < COLS; c2++) {
+                    int res = grid[r][c1];
+                    if (c1 != c2) {
+                        res += grid[r][c2];
+                    }
+
+                    if (r != ROWS - 1) {
+                        int maxCherries = 0;
+                        for (int d1 = -1; d1 <= 1; d1++) {
+                            for (int d2 = -1; d2 <= 1; d2++) {
+                                int nc1 = c1 + d1, nc2 = c2 + d2;
+                                if (nc1 >= 0 && nc1 < COLS && nc2 >= 0 && nc2 < COLS) {
+                                    maxCherries = max(maxCherries, dp[r + 1][nc1][nc2]);
+                                }
+                            }
+                        }
+                        res += maxCherries;
+                    }
+
+                    dp[r][c1][c2] = res;
+                }
+            }
+        }
+
+        return dp[0][0][COLS - 1];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    cherryPickup(grid) {
+        const ROWS = grid.length, COLS = grid[0].length;
+        const dp = Array.from({ length: ROWS }, () =>
+            Array.from({ length: COLS }, () => Array(COLS).fill(0))
+        );
+
+        for (let r = ROWS - 1; r >= 0; r--) {
+            for (let c1 = 0; c1 < COLS; c1++) {
+                for (let c2 = 0; c2 < COLS; c2++) {
+                    let res = grid[r][c1];
+                    if (c1 !== c2) {
+                        res += grid[r][c2];
+                    }
+
+                    if (r !== ROWS - 1) {
+                        let maxCherries = 0;
+                        for (let d1 = -1; d1 <= 1; d1++) {
+                            for (let d2 = -1; d2 <= 1; d2++) {
+                                const nc1 = c1 + d1, nc2 = c2 + d2;
+                                if (nc1 >= 0 && nc1 < COLS && nc2 >= 0 && nc2 < COLS) {
+                                    maxCherries = Math.max(maxCherries, dp[r + 1][nc1][nc2]);
+                                }
+                            }
+                        }
+                        res += maxCherries;
+                    }
+
+                    dp[r][c1][c2] = res;
+                }
+            }
+        }
+
+        return dp[0][0][COLS - 1];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m ^ 2)$
+* Space complexity: $O(n * m ^ 2)$
+
+> Where $n$ is the number of rows and $m$ is the number of columns in the grid.
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def cherryPickup(self, grid: List[List[int]]) -> int:
+        ROWS, COLS = len(grid), len(grid[0])
+        dp = [[0] * COLS for _ in range(COLS)]
+
+        for r in reversed(range(ROWS)):
+            cur_dp = [[0] * COLS for _ in range(COLS)]
+            for c1 in range(COLS):
+                for c2 in range(c1, COLS):
+                    max_cherries = 0
+                    cherries = grid[r][c1] + (grid[r][c2] if c1 != c2 else 0)
+                    for d1 in [-1, 0, 1]:
+                        for d2 in [-1, 0, 1]:
+                            nc1, nc2 = c1 + d1, c2 + d2
+                            if 0 <= nc1 < COLS and 0 <= nc2 < COLS:
+                                max_cherries = max(max_cherries, cherries + dp[nc1][nc2])
+                    cur_dp[c1][c2] = max_cherries
+            dp = cur_dp
+
+        return dp[0][COLS - 1]
+```
+
+```java
+public class Solution {
+    public int cherryPickup(int[][] grid) {
+        int ROWS = grid.length, COLS = grid[0].length;
+        int[][] dp = new int[COLS][COLS];
+
+        for (int r = ROWS - 1; r >= 0; r--) {
+            int[][] cur_dp = new int[COLS][COLS];
+            for (int c1 = 0; c1 < COLS; c1++) {
+                for (int c2 = c1; c2 < COLS; c2++) {
+                    int maxCherries = 0;
+                    int cherries = grid[r][c1] + (c1 == c2 ? 0 : grid[r][c2]);
+                    for (int d1 = -1; d1 <= 1; d1++) {
+                        for (int d2 = -1; d2 <= 1; d2++) {
+                            int nc1 = c1 + d1, nc2 = c2 + d2;
+                            if (nc1 >= 0 && nc1 < COLS && nc2 >= 0 && nc2 < COLS) {
+                                maxCherries = Math.max(maxCherries, cherries + dp[nc1][nc2]);
+                            }
+                        }
+                    }
+                    cur_dp[c1][c2] = maxCherries;
+                }
+            }
+            dp = cur_dp;
+        }
+        return dp[0][COLS - 1];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int cherryPickup(vector<vector<int>>& grid) {
+        int ROWS = grid.size(), COLS = grid[0].size();
+        vector<vector<int>> dp(COLS, vector<int>(COLS, 0));
+
+        for (int r = ROWS - 1; r >= 0; r--) {
+            vector<vector<int>> cur_dp(COLS, vector<int>(COLS, 0));
+            for (int c1 = 0; c1 < COLS; c1++) {
+                for (int c2 = c1; c2 < COLS; c2++) {
+                    int maxCherries = 0;
+                    int cherries = grid[r][c1] + (c1 == c2 ? 0 : grid[r][c2]);
+                    for (int d1 = -1; d1 <= 1; d1++) {
+                        for (int d2 = -1; d2 <= 1; d2++) {
+                            int nc1 = c1 + d1, nc2 = c2 + d2;
+                            if (nc1 >= 0 && nc1 < COLS && nc2 >= 0 && nc2 < COLS) {
+                                maxCherries = max(maxCherries, cherries + dp[nc1][nc2]);
+                            }
+                        }
+                    }
+                    cur_dp[c1][c2] = maxCherries;
+                }
+            }
+            dp = cur_dp;
+        }
+        return dp[0][COLS - 1];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    cherryPickup(grid) {
+        const ROWS = grid.length, COLS = grid[0].length;
+        let dp = Array.from({ length: COLS }, () => Array(COLS).fill(0));
+
+        for (let r = ROWS - 1; r >= 0; r--) {
+            const cur_dp = Array.from({ length: COLS }, () => Array(COLS).fill(0));
+            for (let c1 = 0; c1 < COLS; c1++) {
+                for (let c2 = c1; c2 < COLS; c2++) {
+                    let maxCherries = 0;
+                    const cherries = grid[r][c1] + (c1 === c2 ? 0 : grid[r][c2]);
+                    for (let d1 = -1; d1 <= 1; d1++) {
+                        for (let d2 = -1; d2 <= 1; d2++) {
+                            const nc1 = c1 + d1, nc2 = c2 + d2;
+                            if (nc1 >= 0 && nc1 < COLS && nc2 >= 0 && nc2 < COLS) {
+                                maxCherries = Math.max(maxCherries, cherries + dp[nc1][nc2]);
+                            }
+                        }
+                    }
+                    cur_dp[c1][c2] = maxCherries;
+                }
+            }
+            dp = cur_dp;
+        }
+
+        return dp[0][COLS - 1];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m ^ 2)$
+* Space complexity: $O(m ^ 2)$
+
+> Where $n$ is the number of rows and $m$ is the number of columns in the grid.
\ No newline at end of file
diff --git a/articles/circular-sentence.md b/articles/circular-sentence.md
new file mode 100644
index 000000000..c4e969dc1
--- /dev/null
+++ b/articles/circular-sentence.md
@@ -0,0 +1,154 @@
+## 1. Splitting the String
+
+::tabs-start
+
+```python
+class Solution:
+    def isCircularSentence(self, sentence: str) -> bool:
+        w = sentence.split(" ")
+
+        for i in range(len(w)):
+            if w[i][0] != w[i - 1][-1]:
+                return False
+
+        return True
+```
+
+```java
+public class Solution {
+    public boolean isCircularSentence(String sentence) {
+        String[] w = sentence.split(" ");
+        int n = w.length;
+
+        for (int i = 0; i < n; i++) {
+            char start = w[i].charAt(0);
+            char end = w[(i - 1 + n) % n].charAt(w[(i - 1 + n) % n].length() - 1);
+            if (start != end) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isCircularSentence(string sentence) {
+        vector<string> w;
+        stringstream ss(sentence);
+        string word;
+
+        while (ss >> word) {
+            w.push_back(word);
+        }
+
+        for (int i = 0; i < w.size(); i++) {
+            char start = w[i][0];
+            char end = w[(i - 1 + w.size()) % w.size()].back();
+            if (start != end) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} sentence
+     * @return {boolean}
+     */
+    isCircularSentence(sentence) {
+        const w = sentence.split(" ");
+
+        for (let i = 0; i < w.length; i++) {
+            const start = w[i][0];
+            const prevEnd = w[(i - 1 + w.length) % w.length].slice(-1);
+            if (start !== prevEnd) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Iteration (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def isCircularSentence(self, sentence: str) -> bool:
+        for i in range(len(sentence)):
+            if sentence[i] == " " and sentence[i - 1] != sentence[i + 1]:
+                return False
+        return sentence[0] == sentence[-1]
+```
+
+```java
+public class Solution {
+    public boolean isCircularSentence(String sentence) {
+        for (int i = 0; i < sentence.length(); i++) {
+            if (sentence.charAt(i) == ' ' && sentence.charAt(i - 1) != sentence.charAt(i + 1)) {
+                return false;
+            }
+        }
+        return sentence.charAt(0) == sentence.charAt(sentence.length() - 1);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isCircularSentence(string sentence) {
+        for (int i = 0; i < sentence.size(); i++) {
+            if (sentence[i] == ' ' && sentence[i - 1] != sentence[i + 1]) {
+                return false;
+            }
+        }
+        return sentence.front() == sentence.back();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} sentence
+     * @return {boolean}
+     */
+    isCircularSentence(sentence) {
+        for (let i = 0; i < sentence.length; i++) {
+            if (sentence[i] === ' ' && sentence[i - 1] !== sentence[i + 1]) {
+                return false;
+            }
+        }
+        return sentence[0] === sentence[sentence.length - 1];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/climbing-stairs.md b/articles/climbing-stairs.md
index 72a3abc6e..126511582 100644
--- a/articles/climbing-stairs.md
+++ b/articles/climbing-stairs.md
@@ -71,6 +71,49 @@ public class Solution {
 }
 ```
 
+```go
+func climbStairs(n int) int {
+    var dfs func(i int) int
+    dfs = func(i int) int {
+        if i >= n {
+            if i == n {
+                return 1
+            }
+            return 0
+        }
+        return dfs(i + 1) + dfs(i + 2)
+    }
+    return dfs(0)
+}
+```
+
+```kotlin
+class Solution {
+    fun climbStairs(n: Int): Int {
+        fun dfs(i: Int): Int {
+            if (i >= n) return if (i == n) 1 else 0
+            return dfs(i + 1) + dfs(i + 2)
+        }
+        return dfs(0)
+    }
+}
+```
+
+```swift
+class Solution {
+    func climbStairs(_ n: Int) -> Int {
+        func dfs(_ i: Int) -> Int {
+            if i >= n {
+                return i == n ? 1 : 0
+            }
+            return dfs(i + 1) + dfs(i + 2)
+        }
+
+        return dfs(0)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -172,6 +215,67 @@ public class Solution {
 }
 ```
 
+```go
+func climbStairs(n int) int {
+    cache := make([]int, n+1)
+    for i := 0; i <= n; i++ {
+        cache[i] = -1
+    }
+
+    var dfs func(i int) int
+    dfs = func(i int) int {
+        if i >= n {
+            if i == n {
+                return 1
+            }
+            return 0
+        }
+        if cache[i] != -1 {
+            return cache[i]
+        }
+        cache[i] = dfs(i + 1) + dfs(i + 2)
+        return cache[i]
+    }
+    return dfs(0)
+}
+```
+
+```kotlin
+class Solution {
+    fun climbStairs(n: Int): Int {
+        var cache = IntArray(n+1){-1}
+        fun dfs(i: Int): Int {
+            if (i >= n) return if (i == n) 1 else 0
+            if (cache[i] != -1) return cache[i]
+            cache[i] = dfs(i + 1) + dfs(i + 2)
+            return cache[i]
+        }
+        return dfs(0)
+    }
+}
+```
+
+```swift
+class Solution {
+    func climbStairs(_ n: Int) -> Int {
+        var cache = Array(repeating: -1, count: n)
+        
+        func dfs(_ i: Int) -> Int {
+            if i >= n {
+                return i == n ? 1 : 0
+            }
+            if cache[i] != -1 {
+                return cache[i]
+            }
+            cache[i] = dfs(i + 1) + dfs(i + 2)
+            return cache[i]
+        }
+        
+        return dfs(0)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -270,6 +374,53 @@ public class Solution {
 }
 ```
 
+```go
+func climbStairs(n int) int {
+    if n <= 2 {
+        return n
+    }
+    dp := make([]int, n+1)
+    dp[1] = 1
+    dp[2] = 2
+    for i := 3; i <= n; i++ {
+        dp[i] = dp[i - 1] + dp[i - 2]
+    }
+    return dp[n]
+}
+```
+
+```kotlin
+class Solution {
+    fun climbStairs(n: Int): Int {
+        if (n <= 2) return n
+        var dp = IntArray(n + 1)
+        dp[1] = 1
+        dp[2] = 2
+        for (i in 3..n) {
+            dp[i] = dp[i - 1] + dp[i - 2];
+        }
+        return dp[n];
+    }
+}
+```
+
+```swift
+class Solution {
+    func climbStairs(_ n: Int) -> Int {
+        if n <= 2 {
+            return n
+        }
+        var dp = Array(repeating: 0, count: n + 1)
+        dp[1] = 1
+        dp[2] = 2
+        for i in 3...n {
+            dp[i] = dp[i - 1] + dp[i - 2]
+        }
+        return dp[n]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -365,6 +516,54 @@ public class Solution {
 }
 ```
 
+```go
+func climbStairs(n int) int {
+    one := 1
+    two := 1
+
+    for i := 0; i < n-1; i++ {
+        temp := one
+        one += two
+        two = temp
+    }
+
+    return one
+}
+```
+
+```kotlin
+class Solution {
+    fun climbStairs(n: Int): Int {
+        var one = 1
+        var two = 1
+
+        for (i in 0..(n - 2)) {
+            var temp = one
+            one += two
+            two = temp
+        }
+
+        return one
+    }
+}
+```
+
+```swift
+class Solution {
+    func climbStairs(_ n: Int) -> Int {
+        var one = 1, two = 1
+
+        for _ in 0..<(n - 1) {
+            let temp = one
+            one = one + two
+            two = temp
+        }
+        
+        return one
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -559,6 +758,120 @@ public class Solution {
 }
 ```
 
+```go
+func climbStairs(n int) int {
+    if n == 1 {
+        return 1
+    }
+    
+    M := [][]int{{1, 1}, {1, 0}}
+    result := matrixPow(M, n)
+    
+    return result[0][0]
+}
+
+func matrixMult(A, B [][]int) [][]int {
+    return [][]int{
+        {A[0][0]*B[0][0] + A[0][1]*B[1][0], 
+         A[0][0]*B[0][1] + A[0][1]*B[1][1]},
+        {A[1][0]*B[0][0] + A[1][1]*B[1][0], 
+         A[1][0]*B[0][1] + A[1][1]*B[1][1]},
+    }
+}
+
+func matrixPow(M [][]int, p int) [][]int {
+    result := [][]int{{1, 0}, {0, 1}}
+    base := M
+
+    for p > 0 {
+        if p%2 == 1 {
+            result = matrixMult(result, base)
+        }
+        base = matrixMult(base, base)
+        p /= 2
+    }
+
+    return result
+}
+```
+
+```kotlin
+class Solution {
+    fun climbStairs(n: Int): Int {
+        if (n == 1) return 1
+
+        val M = arrayOf(intArrayOf(1, 1), intArrayOf(1, 0))
+        val result = matrixPow(M, n)
+
+        return result[0][0]
+    }
+
+    private fun matrixMult(A: Array<IntArray>, B: Array<IntArray>): Array<IntArray> {
+        return arrayOf(
+            intArrayOf(A[0][0] * B[0][0] + A[0][1] * B[1][0], 
+                       A[0][0] * B[0][1] + A[0][1] * B[1][1]),
+            intArrayOf(A[1][0] * B[0][0] + A[1][1] * B[1][0], 
+                       A[1][0] * B[0][1] + A[1][1] * B[1][1])
+        )
+    }
+
+    private fun matrixPow(M: Array<IntArray>, p: Int): Array<IntArray> {
+        var result = arrayOf(intArrayOf(1, 0), intArrayOf(0, 1))
+        var base = M
+        var power = p
+
+        while (power > 0) {
+            if (power % 2 == 1) {
+                result = matrixMult(result, base)
+            }
+            base = matrixMult(base, base)
+            power /= 2
+        }
+
+        return result
+    }
+}
+```
+
+```swift
+class Solution {
+    func climbStairs(_ n: Int) -> Int {
+        if n == 1 {
+            return 1
+        }
+
+        func matrixMult(_ A: [[Int]], _ B: [[Int]]) -> [[Int]] {
+            return [
+                [A[0][0] * B[0][0] + A[0][1] * B[1][0], 
+                 A[0][0] * B[0][1] + A[0][1] * B[1][1]],
+                [A[1][0] * B[0][0] + A[1][1] * B[1][0], 
+                 A[1][0] * B[0][1] + A[1][1] * B[1][1]]
+            ]
+        }
+
+        func matrixPow(_ M: [[Int]], _ p: Int) -> [[Int]] {
+            var result = [[1, 0], [0, 1]]
+            var base = M
+            var power = p
+
+            while power > 0 {
+                if power % 2 == 1 {
+                    result = matrixMult(result, base)
+                }
+                base = matrixMult(base, base)
+                power /= 2
+            }
+
+            return result
+        }
+
+        let M = [[1, 1], [1, 0]]
+        let result = matrixPow(M, n)
+        return result[0][0]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -638,6 +951,40 @@ public class Solution {
 }
 ```
 
+```go
+func climbStairs(n int) int {
+    sqrt5 := math.Sqrt(5)
+    phi := (1 + sqrt5) / 2
+    psi := (1 - sqrt5) / 2
+    n++
+    return int(math.Round((math.Pow(phi, float64(n)) - 
+               math.Pow(psi, float64(n))) / sqrt5))
+}
+```
+
+```kotlin
+class Solution {
+    fun climbStairs(n: Int): Int {
+        val sqrt5 = sqrt(5.0)
+        val phi = (1 + sqrt5) / 2
+        val psi = (1 - sqrt5) / 2
+        return round((phi.pow(n + 1) - psi.pow(n + 1)) / sqrt5).toInt()
+    }
+}
+```
+
+```swift
+class Solution {
+    func climbStairs(_ n: Int) -> Int {
+        let sqrt5 = sqrt(5.0)
+        let phi = (1.0 + sqrt5) / 2.0
+        let psi = (1.0 - sqrt5) / 2.0
+        let n = n + 1
+        return Int(round((pow(phi, Double(n)) - pow(psi, Double(n))) / sqrt5))
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/clone-graph.md b/articles/clone-graph.md
index f7fee9daa..e71e55184 100644
--- a/articles/clone-graph.md
+++ b/articles/clone-graph.md
@@ -222,6 +222,115 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a Node.
+ * type Node struct {
+ *     Val int
+ *     Neighbors []*Node
+ * }
+ */
+
+func cloneGraph(node *Node) *Node {
+    oldToNew := make(map[*Node]*Node)
+
+    var dfs func(*Node) *Node
+    dfs = func(node *Node) *Node {
+        if node == nil {
+            return nil
+        }
+
+        if _, found := oldToNew[node]; found {
+            return oldToNew[node]
+        }
+
+        copy := &Node{Val: node.Val}
+        oldToNew[node] = copy
+        for _, nei := range node.Neighbors {
+            copy.Neighbors = append(copy.Neighbors, dfs(nei))
+        }
+        return copy
+    }
+
+    return dfs(node)
+}
+```
+
+```kotlin
+/**
+ * Definition for a Node.
+ * class Node(var `val`: Int) {
+ *     var neighbors: ArrayList<Node?> = ArrayList<Node?>()
+ * }
+ */
+
+class Solution {
+    fun cloneGraph(node: Node?): Node? {
+        if (node == null) return null
+        
+        val oldToNew = HashMap<Node, Node>()
+        
+        fun dfs(node: Node): Node {
+            if (node in oldToNew) {
+                return oldToNew[node]!!
+            }
+            
+            val copy = Node(node.`val`)
+            oldToNew[node] = copy
+            
+            for (nei in node.neighbors) {
+                nei?.let { copy.neighbors.add(dfs(it)) }
+            }
+            
+            return copy
+        }
+        
+        return dfs(node)
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a Node.
+ * public class Node {
+ *     public var val: Int
+ *     public var neighbors: [Node?]
+ *     public init(_ val: Int) {
+ *         self.val = val
+ *         self.neighbors = []
+ *     }
+ * }
+ */
+
+class Solution {
+    func cloneGraph(_ node: Node?) -> Node? {
+        var oldToNew = [Node: Node]()
+        
+        func dfs(_ node: Node?) -> Node? {
+            guard let node = node else { return nil }
+            
+            if let existingCopy = oldToNew[node] {
+                return existingCopy
+            }
+            
+            let copy = Node(node.val)
+            oldToNew[node] = copy
+            
+            for neighbor in node.neighbors {
+                if let clonedNeighbor = dfs(neighbor) {
+                    copy.neighbors.append(clonedNeighbor)
+                }
+            }
+            
+            return copy
+        }
+        
+        return dfs(node)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -442,6 +551,121 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a Node.
+ * type Node struct {
+ *     Val int
+ *     Neighbors []*Node
+ * }
+ */
+
+func cloneGraph(node *Node) *Node {
+    if node == nil {
+        return nil
+    }
+    
+    oldToNew := make(map[*Node]*Node)
+    oldToNew[node] = &Node{Val: node.Val, Neighbors: make([]*Node, 0)}
+    queue := make([]*Node, 0)
+    queue = append(queue, node)
+    
+    for len(queue) > 0 {
+        cur := queue[0]
+        queue = queue[1:]
+        
+        for _, nei := range cur.Neighbors {
+            if _, exists := oldToNew[nei]; !exists {
+                oldToNew[nei] = &Node{Val: nei.Val, Neighbors: make([]*Node, 0)}
+                queue = append(queue, nei)
+            }
+            oldToNew[cur].Neighbors = append(oldToNew[cur].Neighbors, oldToNew[nei])
+        }
+    }
+    
+    return oldToNew[node]
+}
+```
+
+```kotlin
+/**
+ * Definition for a Node.
+ * class Node(var `val`: Int) {
+ *     var neighbors: ArrayList<Node?> = ArrayList<Node?>()
+ * }
+ */
+
+class Solution {
+    fun cloneGraph(node: Node?): Node? {
+        if (node == null) return null
+        
+        val oldToNew = HashMap<Node, Node>()
+        oldToNew[node] = Node(node.`val`)
+        val queue = ArrayDeque<Node>()
+        queue.add(node)
+        
+        while (queue.isNotEmpty()) {
+            val cur = queue.removeFirst()
+            
+            for (nei in cur.neighbors) {
+                nei?.let { neighbor ->
+                    if (neighbor !in oldToNew) {
+                        oldToNew[neighbor] = Node(neighbor.`val`)
+                        queue.add(neighbor)
+                    }
+                    oldToNew[cur]?.neighbors?.add(oldToNew[neighbor])
+                }
+            }
+        }
+        
+        return oldToNew[node]
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a Node.
+ * public class Node {
+ *     public var val: Int
+ *     public var neighbors: [Node?]
+ *     public init(_ val: Int) {
+ *         self.val = val
+ *         self.neighbors = []
+ *     }
+ * }
+ */
+
+class Solution {
+    func cloneGraph(_ node: Node?) -> Node? {
+        if node == nil {
+            return nil
+        }
+
+        var oldToNew: [Node: Node] = [:]
+        let newNode = Node(node!.val)
+        oldToNew[node!] = newNode
+        var queue = Deque<Node>()
+        queue.append(node!)
+
+        while !queue.isEmpty {
+            let cur = queue.popFirst()!
+            for nei in cur.neighbors {
+                if let nei = nei {
+                    if oldToNew[nei] == nil {
+                        oldToNew[nei] = Node(nei.val)
+                        queue.append(nei)
+                    }
+                    oldToNew[cur]!.neighbors.append(oldToNew[nei]!)
+                }
+            }
+        }
+
+        return oldToNew[node!]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/coin-change-ii.md b/articles/coin-change-ii.md
index 3079a6843..6e4cce788 100644
--- a/articles/coin-change-ii.md
+++ b/articles/coin-change-ii.md
@@ -127,6 +127,83 @@ public class Solution {
 }
 ```
 
+```go
+func change(amount int, coins []int) int {
+    sort.Ints(coins) 
+
+    var dfs func(i, a int) int
+    dfs = func(i, a int) int {
+        if a == 0 {
+            return 1
+        }
+        if i >= len(coins) {
+            return 0
+        }
+
+        res := 0
+        if a >= coins[i] {
+            res = dfs(i+1, a)
+            res += dfs(i, a-coins[i])
+        }
+        return res
+    }
+
+    return dfs(0, amount)
+}
+```
+
+```kotlin
+class Solution {
+    fun change(amount: Int, coins: IntArray): Int {
+        coins.sort() 
+
+        fun dfs(i: Int, a: Int): Int {
+            if (a == 0) {
+                return 1
+            }
+            if (i >= coins.size) {
+                return 0
+            }
+
+            var res = 0
+            if (a >= coins[i]) {
+                res = dfs(i + 1, a)
+                res += dfs(i, a - coins[i])
+            }
+            return res
+        }
+
+        return dfs(0, amount)
+    }
+}
+```
+
+```swift
+class Solution {
+    func change(_ amount: Int, _ coins: [Int]) -> Int {
+        let coins = coins.sorted()
+
+        func dfs(_ i: Int, _ a: Int) -> Int {
+            if a == 0 {
+                return 1
+            }
+            if i >= coins.count {
+                return 0
+            }
+
+            var res = 0
+            if a >= coins[i] {
+                res = dfs(i + 1, a)
+                res += dfs(i, a - coins[i])
+            }
+            return res
+        }
+
+        return dfs(0, amount)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -283,6 +360,103 @@ public class Solution {
 }
 ```
 
+```go
+func change(amount int, coins []int) int {
+    sort.Ints(coins)
+    memo := make([][]int, len(coins) + 1)
+    for i := range memo {
+        memo[i] = make([]int, amount + 1)
+        for j := range memo[i] {
+            memo[i][j] = -1
+        }
+    }
+
+    var dfs func(i, a int) int
+    dfs = func(i, a int) int {
+        if a == 0 {
+            return 1
+        }
+        if i >= len(coins) {
+            return 0
+        }
+        if memo[i][a] != -1 {
+            return memo[i][a]
+        }
+
+        res := 0
+        if a >= coins[i] {
+            res = dfs(i+1, a)
+            res += dfs(i, a-coins[i])
+        }
+        memo[i][a] = res
+        return res
+    }
+
+    return dfs(0, amount)
+}
+```
+
+```kotlin
+class Solution {
+    fun change(amount: Int, coins: IntArray): Int {
+        coins.sort()
+        val memo = Array(coins.size + 1) { IntArray(amount + 1) { -1 } }
+
+        fun dfs(i: Int, a: Int): Int {
+            if (a == 0) {
+                return 1
+            }
+            if (i >= coins.size) {
+                return 0
+            }
+            if (memo[i][a] != -1) return memo[i][a]
+
+            var res = 0
+            if (a >= coins[i]) {
+                res = dfs(i + 1, a)
+                res += dfs(i, a - coins[i])
+            }
+            memo[i][a] = res
+            return res
+        }
+
+        return dfs(0, amount)
+    }
+}
+```
+
+```swift
+class Solution {
+    func change(_ amount: Int, _ coins: [Int]) -> Int {
+        let coins = coins.sorted()
+        var memo = Array(repeating: Array(repeating: -1, count: amount + 1), count: coins.count + 1)
+        
+        func dfs(_ i: Int, _ a: Int) -> Int {
+            if a == 0 {
+                return 1
+            }
+            if i >= coins.count {
+                return 0
+            }
+            if memo[i][a] != -1 {
+                return memo[i][a]
+            }
+            
+            var res = 0
+            if a >= coins[i] {
+                res = dfs(i + 1, a)
+                res += dfs(i, a - coins[i])
+            }
+            
+            memo[i][a] = res
+            return res
+        }
+        
+        return dfs(0, amount)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -348,8 +522,8 @@ public:
     int change(int amount, vector<int>& coins) {
         int n = coins.size();
         sort(coins.begin(), coins.end());
-        vector<vector<int>> dp(n + 1, vector<int>(amount + 1, 0));
-        
+        vector<vector<uint>> dp(n + 1, vector<uint>(amount + 1, 0));
+
         for (int i = 0; i <= n; i++) {
             dp[i][0] = 1;
         }
@@ -423,6 +597,94 @@ public class Solution {
 }
 ```
 
+```go
+func change(amount int, coins []int) int {
+    n := len(coins)
+    dp := make([][]int, n+1)
+    for i := range dp {
+        dp[i] = make([]int, amount+1)
+    }
+
+    for i := 0; i <= n; i++ {
+        dp[i][0] = 1
+    }
+
+    for i := n - 1; i >= 0; i-- {
+        for a := 0; a <= amount; a++ {
+            if a >= coins[i] {
+                dp[i][a] = dp[i+1][a] 
+                dp[i][a] += dp[i][a-coins[i]] 
+            } else {
+                dp[i][a] = dp[i+1][a]
+            }
+        }
+    }
+
+    return dp[0][amount]
+}
+```
+
+```kotlin
+class Solution {
+    fun change(amount: Int, coins: IntArray): Int {
+        val n = coins.size
+        val dp = Array(n + 1) { IntArray(amount + 1) }
+
+        for (i in 0..n) {
+            dp[i][0] = 1
+        }
+
+        for (i in n - 1 downTo 0) {
+            for (a in 0..amount) {
+                if (a >= coins[i]) {
+                    dp[i][a] = dp[i + 1][a] 
+                    dp[i][a] += dp[i][a - coins[i]] 
+                } else {
+                    dp[i][a] = dp[i + 1][a] 
+                }
+            }
+        }
+
+        return dp[0][amount]
+    }
+}
+```
+
+```swift
+class Solution {
+    func change(_ amount: Int, _ coins: [Int]) -> Int {
+        let n = coins.count
+        let sortedCoins = coins.sorted()
+        var dp = Array(
+            repeating: Array(repeating: 0, count: amount + 1),
+            count: n + 1
+        )
+        
+        for i in 0...n {
+            dp[i][0] = 1
+        }
+        
+        for i in stride(from: n - 1, through: 0, by: -1) {
+            for a in 0...amount {
+                let base = dp[i + 1][a]
+                if a >= sortedCoins[i] {
+                    let addend = dp[i][a - sortedCoins[i]]
+                    if base > Int.max - addend {
+                        dp[i][a] = 0
+                    } else {
+                        dp[i][a] = base + addend
+                    }
+                } else {
+                    dp[i][a] = base
+                }
+            }
+        }
+        
+        return dp[0][amount]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -481,10 +743,10 @@ public class Solution {
 class Solution {
 public:
     int change(int amount, vector<int>& coins) {
-        vector<int> dp(amount + 1, 0);
+        vector<uint> dp(amount + 1, 0);
         dp[0] = 1;
         for (int i = coins.size() - 1; i >= 0; i--) {
-            vector<int> nextDP(amount + 1, 0);
+            vector<uint> nextDP(amount + 1, 0);
             nextDP[0] = 1;
 
             for (int a = 1; a <= amount; a++) {
@@ -549,6 +811,82 @@ public class Solution {
 }
 ```
 
+```go
+func change(amount int, coins []int) int {
+    dp := make([]int, amount+1)
+    dp[0] = 1
+
+    for i := len(coins) - 1; i >= 0; i-- {
+        nextDP := make([]int, amount+1)
+        nextDP[0] = 1
+
+        for a := 1; a <= amount; a++ {
+            nextDP[a] = dp[a]
+            if a-coins[i] >= 0 {
+                nextDP[a] += nextDP[a-coins[i]]
+            }
+        }
+        dp = nextDP
+    }
+
+    return dp[amount]
+}
+```
+
+```kotlin
+class Solution {
+    fun change(amount: Int, coins: IntArray): Int {
+        val dp = IntArray(amount + 1)
+        dp[0] = 1
+
+        for (i in coins.size - 1 downTo 0) {
+            val nextDP = IntArray(amount + 1)
+            nextDP[0] = 1
+
+            for (a in 1..amount) {
+                nextDP[a] = dp[a]
+                if (a - coins[i] >= 0) {
+                    nextDP[a] += nextDP[a - coins[i]]
+                }
+            }
+            System.arraycopy(nextDP, 0, dp, 0, amount + 1)
+        }
+
+        return dp[amount]
+    }
+}
+```
+
+```swift
+class Solution {
+    func change(_ amount: Int, _ coins: [Int]) -> Int {
+        var dp = [Int](repeating: 0, count: amount + 1)
+        dp[0] = 1
+
+        for i in stride(from: coins.count - 1, through: 0, by: -1) {
+            var nextDP = [Int](repeating: 0, count: amount + 1)
+            nextDP[0] = 1
+
+            for a in 1..<(amount + 1) {
+                nextDP[a] = dp[a]
+                if a - coins[i] >= 0 {
+                    let addend = nextDP[a - coins[i]]
+                    if nextDP[a] > Int.max - addend {
+                        nextDP[a] = 0
+                    } else {
+                        nextDP[a] += addend
+                    }
+                }
+            }
+            
+            dp = nextDP
+        }
+
+        return dp[amount]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -592,7 +930,7 @@ public class Solution {
 class Solution {
 public:
     int change(int amount, vector<int>& coins) {
-        vector<int> dp(amount + 1, 0);
+        vector<uint> dp(amount + 1, 0);
         dp[0] = 1;
         for (int i = coins.size() - 1; i >= 0; i--) {
             for (int a = 1; a <= amount; a++) {
@@ -639,6 +977,66 @@ public class Solution {
 }
 ```
 
+```go
+func change(amount int, coins []int) int {
+    dp := make([]int, amount+1)
+    dp[0] = 1
+
+    for i := len(coins) - 1; i >= 0; i-- {
+        for a := 1; a <= amount; a++ {
+            if a-coins[i] >= 0 {
+                dp[a] += dp[a - coins[i]]
+            }
+        }
+    }
+
+    return dp[amount]
+}
+```
+
+```kotlin
+class Solution {
+    fun change(amount: Int, coins: IntArray): Int {
+        val dp = IntArray(amount + 1)
+        dp[0] = 1
+
+        for (i in coins.size - 1 downTo 0) {
+            for (a in 1..amount) {
+                if (a - coins[i] >= 0) {
+                    dp[a] += dp[a - coins[i]]
+                }
+            }
+        }
+
+        return dp[amount]
+    }
+}
+```
+
+```swift
+class Solution {
+    func change(_ amount: Int, _ coins: [Int]) -> Int {
+        var dp = [Int](repeating: 0, count: amount + 1)
+        dp[0] = 1
+
+        for i in stride(from: coins.count - 1, through: 0, by: -1) {
+            for a in 1..<(amount + 1) {
+                if coins[i] <= a {
+                    let addend = dp[a - coins[i]]
+                    if dp[a] > Int.max - addend {
+                        dp[a] = 0
+                    } else {
+                        dp[a] += addend
+                    }
+                }
+            }
+        }
+
+        return dp[amount]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/coin-change.md b/articles/coin-change.md
index 765237b04..f61f99922 100644
--- a/articles/coin-change.md
+++ b/articles/coin-change.md
@@ -115,6 +115,84 @@ public class Solution {
 }
 ```
 
+```go
+func coinChange(coins []int, amount int) int {
+    var dfs func(int) int
+    dfs = func(amt int) int {
+        if amt == 0 {
+            return 0
+        }
+        
+        res := math.MaxInt32
+        for _, coin := range coins {
+            if amt - coin >= 0 {
+                res = min(res, 1 + dfs(amt - coin))
+            }
+        }
+        
+        return res
+    }
+
+    minCoins := dfs(amount)
+    if minCoins >= math.MaxInt32 {
+        return -1
+    }
+    return minCoins
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun coinChange(coins: IntArray, amount: Int): Int {
+        val INF = 1000000000
+        fun dfs(amt: Int): Int {
+            if (amt == 0) return 0
+
+            var res = INF
+            for (coin in coins) {
+                if (amt - coin >= 0) {
+                    res = minOf(res, 1 + dfs(amt - coin))
+                }
+            }
+            return res
+        }
+
+        val minCoins = dfs(amount)
+        return if (minCoins >= INF) -1 else minCoins
+    }
+}
+```
+
+```swift
+class Solution {
+    func coinChange(_ coins: [Int], _ amount: Int) -> Int {
+        func dfs(_ amount: Int) -> Int {
+            if amount == 0 {
+                return 0
+            }
+
+            var res = Int(1e9)
+            for coin in coins {
+                if amount - coin >= 0 {
+                    res = min(res, 1 + dfs(amount - coin))
+                }
+            }
+            return res
+        }
+
+        let minCoins = dfs(amount)
+        return minCoins >= Int(1e9) ? -1 : minCoins
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -275,6 +353,99 @@ public class Solution {
 }
 ```
 
+```go
+func coinChange(coins []int, amount int) int {
+    var memo = make(map[int]int)
+    memo[0] = 0
+
+    var dfs func(int) int
+    dfs = func(amt int) int {
+        if val, ok := memo[amt]; ok {
+            return val
+        }
+        
+        res := math.MaxInt32
+        for _, coin := range coins {
+            if amt - coin >= 0 {
+                res = min(res, 1 + dfs(amt - coin))
+            }
+        }
+        memo[amt] = res
+        return res
+    }
+
+    minCoins := dfs(amount)
+    if minCoins >= math.MaxInt32 {
+        return -1
+    }
+    return minCoins
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun coinChange(coins: IntArray, amount: Int): Int {
+        val INF = 1000000000
+        var memo = hashMapOf(0 to 0)
+
+        fun dfs(amt: Int): Int {
+            if (amt in memo) {
+                return memo[amt]!!
+            }
+
+            var res = INF
+            for (coin in coins) {
+                if (amt - coin >= 0) {
+                    res = minOf(res, 1 + dfs(amt - coin))
+                }
+            }
+            memo[amt] = res
+            return res
+        }
+
+        val minCoins = dfs(amount)
+        return if (minCoins >= INF) -1 else minCoins
+    }
+}
+```
+
+```swift
+class Solution {
+    func coinChange(_ coins: [Int], _ amount: Int) -> Int {
+        var memo = [Int: Int]()
+
+        func dfs(_ amount: Int) -> Int {
+            if amount == 0 {
+                return 0
+            }
+            if let cached = memo[amount] {
+                return cached
+            }
+
+            var res = Int(1e9)
+            for coin in coins {
+                if amount - coin >= 0 {
+                    res = min(res, 1 + dfs(amount - coin))
+                }
+            }
+
+            memo[amount] = res
+            return res
+        }
+
+        let minCoins = dfs(amount)
+        return minCoins >= Int(1e9) ? -1 : minCoins
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -379,6 +550,74 @@ public class Solution {
 }
 ```
 
+```go
+func coinChange(coins []int, amount int) int {
+    dp := make([]int, amount+1)
+    for i := range dp {
+        dp[i] = amount + 1
+    }
+    dp[0] = 0
+    for a := 1; a <= amount; a++ {
+        for _, c := range coins {
+            if a-c >= 0 {
+                dp[a] = min(dp[a], 1+dp[a-c])
+            }
+        }
+    }
+    if dp[amount] > amount {
+        return -1
+    }
+    return dp[amount]
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun coinChange(coins: IntArray, amount: Int): Int {
+        val dp = IntArray(amount + 1) { amount + 1 }
+        dp[0] = 0
+        for (a in 1..amount) {
+            for (c in coins) {
+                if (a - c >= 0) {
+                    dp[a] = minOf(dp[a], 1 + dp[a - c])
+                }
+            }
+        }
+        return if (dp[amount] > amount) -1 else dp[amount]
+    }
+}
+```
+
+```swift
+class Solution {
+    func coinChange(_ coins: [Int], _ amount: Int) -> Int {
+        if amount == 0 {
+            return 0
+        }
+
+        var dp = [Int](repeating: amount + 1, count: amount + 1)
+        dp[0] = 0
+
+        for a in 1...amount {
+            for coin in coins {
+                if a - coin >= 0 {
+                    dp[a] = min(dp[a], 1 + dp[a - coin])
+                }
+            }
+        }
+
+        return dp[amount] == amount + 1 ? -1 : dp[amount]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -551,6 +790,99 @@ public class Solution {
 }
 ```
 
+```go
+func coinChange(coins []int, amount int) int {
+    if amount == 0 {
+        return 0
+    }
+    queue := []int{0}
+    seen := make([]bool, amount+1)
+    seen[0] = true
+    res := 0
+    for len(queue) > 0 {
+        res++
+        size := len(queue)
+        for i := 0; i < size; i++ {
+            cur := queue[0]
+            queue = queue[1:]
+            for _, coin := range coins {
+                next := cur + coin
+                if next == amount {
+                    return res
+                }
+                if next > amount || seen[next] {
+                    continue
+                }
+                seen[next] = true
+                queue = append(queue, next)
+            }
+        }
+    }
+    return -1
+}
+```
+
+```kotlin
+class Solution {
+    fun coinChange(coins: IntArray, amount: Int): Int {
+        if (amount == 0) return 0
+        val queue = ArrayDeque<Int>().apply { add(0) }
+        val seen = BooleanArray(amount + 1) { false }
+        seen[0] = true
+        var res = 0
+        while (queue.isNotEmpty()) {
+            res++
+            repeat(queue.size) {
+                val cur = queue.removeFirst()
+                for (coin in coins) {
+                    val next = cur + coin
+                    if (next == amount) return res
+                    if (next > amount || seen[next]) continue
+                    seen[next] = true
+                    queue.addLast(next)
+                }
+            }
+        }
+        return -1
+    }
+}
+```
+
+```swift
+class Solution {
+    func coinChange(_ coins: [Int], _ amount: Int) -> Int {
+        if amount == 0 {
+            return 0
+        }
+
+        var q = Deque([0])
+        var seen = Array(repeating: false, count: amount + 1)
+        seen[0] = true
+        var res = 0  
+
+        while !q.isEmpty {
+            res += 1
+            for _ in 0..<q.count {
+                let cur = q.popFirst()!
+                for coin in coins {
+                    let nxt = cur + coin
+                    if nxt == amount {
+                        return res
+                    }
+                    if nxt > amount || seen[nxt] {
+                        continue
+                    }
+                    seen[nxt] = true
+                    q.append(nxt)
+                }
+            }
+        }
+
+        return -1
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/combination-sum-iv.md b/articles/combination-sum-iv.md
new file mode 100644
index 000000000..b2d2c5386
--- /dev/null
+++ b/articles/combination-sum-iv.md
@@ -0,0 +1,512 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def combinationSum4(self, nums: List[int], target: int) -> int:
+        nums.sort()
+        
+        def dfs(total):
+            if total == 0:
+                return 1
+            
+            res = 0
+            for i in range(len(nums)):
+                if total < nums[i]:
+                    break
+                res += dfs(total - nums[i])
+            return res
+        
+        return dfs(target)
+```
+
+```java
+public class Solution {
+    public int combinationSum4(int[] nums, int target) {
+        Arrays.sort(nums);
+
+        return dfs(nums, target);
+    }
+    
+    private int dfs(int[] nums, int total) {
+        if (total == 0) {
+            return 1;
+        }
+        
+        int res = 0;
+        for (int num : nums) {
+            if (total < num) {
+                break;
+            }
+            res += dfs(nums, total - num);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int combinationSum4(vector<int>& nums, int target) {
+        sort(nums.begin(), nums.end());
+        return dfs(nums, target);
+    }
+    
+    int dfs(vector<int>& nums, int total) {
+        if (total == 0) {
+            return 1;
+        }
+        
+        int res = 0;
+        for (int num : nums) {
+            if (total < num) {
+                break;
+            }
+            res += dfs(nums, total - num);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} target
+     * @return {number}
+     */
+    combinationSum4(nums, target) {
+        nums.sort((a, b) => a - b);
+        
+        const dfs = (total) => {
+            if (total === 0) return 1;
+            
+            let res = 0;
+            for (let num of nums) {
+                if (total < num) break;
+                res += dfs(total - num);
+            }
+            return res;
+        };
+
+        return dfs(target);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int CombinationSum4(int[] nums, int target) {
+        Array.Sort(nums);
+        return Dfs(nums, target);
+    }
+
+    private int Dfs(int[] nums, int total) {
+        if (total == 0) {
+            return 1;
+        }
+
+        int res = 0;
+        foreach (int num in nums) {
+            if (total < num) {
+                break;
+            }
+            res += Dfs(nums, total - num);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ t)$
+* Space complexity: $O(t)$
+
+> Where $n$ is the size of the array $nums$ and $t$ is the given target.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def combinationSum4(self, nums: List[int], target: int) -> int:
+        nums.sort()
+        memo = { 0 : 1 }
+
+        def dfs(total):
+            if total in memo:
+                return memo[total]
+            
+            res = 0
+            for num in nums:
+                if total < num:
+                    break
+                res += dfs(total - num)
+            memo[total] = res
+            return res
+        
+        return dfs(target)
+```
+
+```java
+public class Solution {
+    private Map<Integer, Integer> memo;
+
+    public int combinationSum4(int[] nums, int target) {
+        Arrays.sort(nums);
+        memo = new HashMap<>();
+        memo.put(0, 1);
+        return dfs(nums, target);
+    }
+    
+    private int dfs(int[] nums, int total) {
+        if (memo.containsKey(total)) {
+            return memo.get(total);
+        }
+        
+        int res = 0;
+        for (int num : nums) {
+            if (total < num) {
+                break;
+            }
+            res += dfs(nums, total - num);
+        }
+        memo.put(total, res);
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    unordered_map<int, int> memo;
+
+public:
+    int combinationSum4(vector<int>& nums, int target) {
+        sort(nums.begin(), nums.end());
+        memo[0] = 1;
+        return dfs(nums, target);
+    }
+
+    int dfs(vector<int>& nums, int total) {
+        if (memo.count(total)) {
+            return memo[total];
+        }
+
+        int res = 0;
+        for (int num : nums) {
+            if (total < num) {
+                break;
+            }
+            res += dfs(nums, total - num);
+        }
+        memo[total] = res;
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} target
+     * @return {number}
+     */
+    combinationSum4(nums, target) {
+        nums.sort((a, b) => a - b);
+        const memo = { 0 : 1 };
+
+        const dfs = (total) => {
+            if (memo[total] !== undefined) {
+                return memo[total];
+            }
+
+            let res = 0;
+            for (let num of nums) {
+                if (total < num) break;
+                res += dfs(total - num);
+            }
+            memo[total] = res;
+            return res;
+        };
+
+        return dfs(target);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    private Dictionary<int, int> memo;
+
+    public int CombinationSum4(int[] nums, int target) {
+        Array.Sort(nums);
+        memo = new Dictionary<int, int>();
+        memo[0] = 1;
+        return Dfs(nums, target);
+    }
+
+    private int Dfs(int[] nums, int total) {
+        if (memo.ContainsKey(total)) {
+            return memo[total];
+        }
+
+        int res = 0;
+        foreach (int num in nums) {
+            if (total < num) {
+                break;
+            }
+            res += Dfs(nums, total - num);
+        }
+
+        memo[total] = res;
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * t)$
+* Space complexity: $O(t)$
+
+> Where $n$ is the size of the array $nums$ and $t$ is the given target.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up) - I
+
+::tabs-start
+
+```python
+class Solution:
+    def combinationSum4(self, nums: List[int], target: int) -> int:
+        dp = { 0 : 1 }
+
+        for total in range(1, target + 1):
+            dp[total] = 0
+            for num in nums:
+                dp[total] += dp.get(total - num, 0)
+        
+        return dp[target]
+```
+
+```java
+public class Solution {
+    public int combinationSum4(int[] nums, int target) {
+        Map<Integer, Integer> dp = new HashMap<>();
+        dp.put(0, 1);
+        
+        for (int total = 1; total <= target; total++) {
+            dp.put(total, 0);
+            for (int num : nums) {
+                dp.put(total, dp.get(total) + dp.getOrDefault(total - num, 0));
+            }
+        }
+        return dp.get(target);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int combinationSum4(vector<int>& nums, int target) {
+        unordered_map<int, long long> dp;
+        dp[0] = 1;
+        
+        for (int total = 1; total <= target; total++) {
+            dp[total] = 0;
+            for (int num : nums) {
+                if (total >= num) {
+                    dp[total] += dp[total - num];
+                }
+            }
+            if (dp[total] > INT_MAX) {
+                dp[total] = 0;
+            }
+        }
+        return dp[target];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} target
+     * @return {number}
+     */
+    combinationSum4(nums, target) {
+        let dp = {0: 1};
+        for (let total = 1; total <= target; total++) {
+            dp[total] = 0;
+            for (let num of nums) {
+                dp[total] += dp[total - num] || 0;
+            }
+        }
+        return dp[target];
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int CombinationSum4(int[] nums, int target) {
+        Dictionary<int, int> dp = new Dictionary<int, int>();
+        dp[0] = 1;
+
+        for (int total = 1; total <= target; total++) {
+            dp[total] = 0;
+            foreach (int num in nums) {
+                if (dp.ContainsKey(total - num)) {
+                    dp[total] += dp[total - num];
+                }
+            }
+        }
+
+        return dp[target];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * t)$
+* Space complexity: $O(t)$
+
+> Where $n$ is the size of the array $nums$ and $t$ is the given target.
+
+---
+
+## 4. Dynamic Programming (Bottom-Up) - II
+
+::tabs-start
+
+```python
+class Solution:
+    def combinationSum4(self, nums: List[int], target: int) -> int:
+        nums.sort()
+        dp = defaultdict(int)
+        dp[target] = 1
+        for total in range(target, 0, -1):
+            for num in nums:
+                if total < num:
+                    break
+                dp[total - num] += dp[total]
+        return dp[0]
+```
+
+```java
+public class Solution {
+    public int combinationSum4(int[] nums, int target) {
+        Arrays.sort(nums);
+        Map<Integer, Integer> dp = new HashMap<>();
+        dp.put(target, 1);
+        for (int total = target; total > 0; total--) {
+            for (int num : nums) {
+                if (total < num) break;
+                dp.put(total - num, dp.getOrDefault(total, 0) + dp.getOrDefault(total - num, 0));
+            }
+        }
+        return dp.getOrDefault(0, 0);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int combinationSum4(vector<int>& nums, int target) {
+        sort(nums.begin(), nums.end());
+        unordered_map<int, int> dp;
+        dp[target] = 1;
+
+        for (int total = target; total > 0; total--) {
+            if (dp[total] == -1) continue;
+            for (auto& num : nums) {
+                if (total < num) break;
+                if (dp[total - num] + 0LL + dp[total] > INT_MAX) {
+                    dp[total - num] = -1;
+                    break;
+                }
+                dp[total - num] += dp[total];
+            }
+        }
+        return dp[0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} target
+     * @return {number}
+     */
+    combinationSum4(nums, target) {
+        nums.sort((a, b) => a - b);
+        const dp = new Map();
+        dp.set(target, 1);
+
+        for (let total = target; total > 0; total--) {
+            for (const num of nums) {
+                if (total < num) break;
+                dp.set(total - num, (dp.get(total - num) || 0) + (dp.get(total) || 0));
+            }
+        }
+        return dp.get(0) || 0;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int CombinationSum4(int[] nums, int target) {
+        Array.Sort(nums);
+        Dictionary<int, int> dp = new Dictionary<int, int>();
+        dp[target] = 1;
+
+        for (int total = target; total > 0; total--) {
+            if (!dp.ContainsKey(total)) continue;
+            foreach (int num in nums) {
+                if (total < num) break;
+                int key = total - num;
+                if (!dp.ContainsKey(key)) {
+                    dp[key] = 0;
+                }
+                dp[key] += dp[total];
+            }
+        }
+
+        return dp.ContainsKey(0) ? dp[0] : 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * t)$
+* Space complexity: $O(t)$
+
+> Where $n$ is the size of the array $nums$ and $t$ is the given target.
\ No newline at end of file
diff --git a/articles/combination-target-sum-ii.md b/articles/combination-target-sum-ii.md
index 3994f5081..3b35aab6d 100644
--- a/articles/combination-target-sum-ii.md
+++ b/articles/combination-target-sum-ii.md
@@ -159,6 +159,92 @@ public class Solution {
 }
 ```
 
+```go
+func combinationSum2(candidates []int, target int) [][]int {
+    res := make(map[string][]int)
+    var results [][]int
+    sort.Ints(candidates)
+
+    var generateSubsets func(int, []int, int)
+    generateSubsets = func(i int, cur []int, total int) {
+        if total == target {
+            key := fmt.Sprint(cur)
+            if _, found := res[key]; !found {
+                res[key] = append([]int{}, cur...)
+                results = append(results, res[key])
+            }
+            return
+        }
+        if total > target || i == len(candidates) {
+            return
+        }
+
+        generateSubsets(i+1, append(cur, candidates[i]), total+candidates[i])
+        generateSubsets(i+1, cur, total)
+    }
+
+    generateSubsets(0, []int{}, 0)
+    return results
+}
+```
+
+```kotlin
+class Solution {
+    fun combinationSum2(candidates: IntArray, target: Int): List<List<Int>> {
+        val res = HashSet<List<Int>>()
+        candidates.sort()
+
+        fun generateSubsets(i: Int, cur: MutableList<Int>, total: Int) {
+            if (total == target) {
+                res.add(ArrayList(cur))
+                return
+            }
+            if (total > target || i == candidates.size) {
+                return
+            }
+
+            cur.add(candidates[i])
+            generateSubsets(i + 1, cur, total + candidates[i])
+            cur.removeAt(cur.size - 1)
+
+            generateSubsets(i + 1, cur, total)
+        }
+
+        generateSubsets(0, mutableListOf(), 0)
+        return res.toList()
+    }
+}
+```
+
+```swift
+class Solution {
+    func combinationSum2(_ candidates: [Int], _ target: Int) -> [[Int]] {
+        var res = Set<[Int]>()
+        let sortedCandidates = candidates.sorted()
+
+        func generateSubsets(_ i: Int, _ cur: inout [Int], _ total: Int) {
+            if total == target {
+                res.insert(cur)
+                return
+            }
+            if total > target || i == sortedCandidates.count {
+                return
+            }
+
+            cur.append(sortedCandidates[i])
+            generateSubsets(i + 1, &cur, total + sortedCandidates[i])
+            cur.removeLast()
+
+            generateSubsets(i + 1, &cur, total)
+        }
+
+        var cur: [Int] = []
+        generateSubsets(0, &cur, 0)
+        return Array(res)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -343,6 +429,103 @@ public class Solution {
 }
 ```
 
+```go
+func combinationSum2(candidates []int, target int) [][]int {
+    res := [][]int{}
+    sort.Ints(candidates)
+
+    var dfs func(int, []int, int)
+    dfs = func(i int, cur []int, total int) {
+        if total == target {
+            temp := make([]int, len(cur))
+            copy(temp, cur)
+            res = append(res, temp)
+            return
+        }
+        if total > target || i == len(candidates) {
+            return
+        }
+
+        cur = append(cur, candidates[i])
+        dfs(i+1, cur, total+candidates[i])
+        cur = cur[:len(cur)-1]
+
+        for i+1 < len(candidates) && candidates[i] == candidates[i+1] {
+            i++
+        }
+        dfs(i+1, cur, total)
+    }
+
+    dfs(0, []int{}, 0)
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun combinationSum2(candidates: IntArray, target: Int): List<List<Int>> {
+        val res = mutableListOf<List<Int>>()
+        candidates.sort()
+
+        fun dfs(i: Int, cur: MutableList<Int>, total: Int) {
+            if (total == target) {
+                res.add(ArrayList(cur))
+                return
+            }
+            if (total > target || i == candidates.size) {
+                return
+            }
+
+            cur.add(candidates[i])
+            dfs(i + 1, cur, total + candidates[i])
+            cur.removeAt(cur.size - 1)
+
+            var next = i + 1
+            while (next < candidates.size && candidates[next] == candidates[i]) {
+                next++
+            }
+            dfs(next, cur, total)
+        }
+
+        dfs(0, mutableListOf(), 0)
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func combinationSum2(_ candidates: [Int], _ target: Int) -> [[Int]] {
+        var res = [[Int]]()
+        let sortedCandidates = candidates.sorted()
+
+        func dfs(_ i: Int, _ cur: inout [Int], _ total: Int) {
+            if total == target {
+                res.append(cur)
+                return
+            }
+            if total > target || i == sortedCandidates.count {
+                return
+            }
+
+            cur.append(sortedCandidates[i])
+            dfs(i + 1, &cur, total + sortedCandidates[i])
+            cur.removeLast()
+
+            var j = i
+            while j + 1 < sortedCandidates.count && sortedCandidates[j] == sortedCandidates[j + 1] {
+                j += 1
+            }
+            dfs(j + 1, &cur, total)
+        }
+
+        var cur: [Int] = []
+        dfs(0, &cur, 0)
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -569,6 +752,129 @@ public class Solution {
 }
 ```
 
+```go
+func combinationSum2(nums []int, target int) [][]int {
+    res := [][]int{}
+    count := map[int]int{}
+    uniqueNums := []int{}
+    for _, num := range nums {
+        if count[num] == 0 {
+            uniqueNums = append(uniqueNums, num)
+        }
+        count[num]++
+    }
+    sort.Ints(uniqueNums)
+
+    var backtrack func(int, int, []int)
+    backtrack = func(target int, i int, cur []int) {
+        if target == 0 {
+            temp := make([]int, len(cur))
+            copy(temp, cur)
+            res = append(res, temp)
+            return
+        }
+        if target < 0 || i >= len(uniqueNums) {
+            return
+        }
+        
+        if count[uniqueNums[i]] > 0 {
+            cur = append(cur, uniqueNums[i])
+            count[uniqueNums[i]]--
+            backtrack(target-uniqueNums[i], i, cur)
+            count[uniqueNums[i]]++
+            cur = cur[:len(cur)-1]
+        }
+
+        backtrack(target, i+1, cur)
+    }
+
+    backtrack(target, 0, []int{})
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    private val res = mutableListOf<List<Int>>()
+    private val count = HashMap<Int, Int>()
+
+    fun combinationSum2(nums: IntArray, target: Int): List<List<Int>> {
+        val uniqueNums = mutableListOf<Int>()
+        for (num in nums) {
+            count[num] = count.getOrDefault(num, 0) + 1
+            if (count[num] == 1) {
+                uniqueNums.add(num)
+            }
+        }
+        uniqueNums.sort()
+
+        backtrack(uniqueNums, target, mutableListOf(), 0)
+        return res
+    }
+
+    fun backtrack(nums: List<Int>, target: Int, cur: MutableList<Int>, i: Int) {
+        if (target == 0) {
+            res.add(ArrayList(cur))
+            return
+        }
+        if (target < 0 || i >= nums.size) {
+            return
+        }
+        
+        if (count[nums[i]] ?: 0 > 0) {
+            cur.add(nums[i])
+            count[nums[i]] = count[nums[i]]!! - 1
+            backtrack(nums, target - nums[i], cur, i)
+            count[nums[i]] = count[nums[i]]!! + 1
+            cur.removeAt(cur.size - 1)
+        }
+
+        backtrack(nums, target, cur, i + 1)
+    }
+}
+```
+
+```swift
+class Solution {
+    func combinationSum2(_ nums: [Int], _ target: Int) -> [[Int]] {
+        var res = [[Int]]()
+        var count = [Int: Int]()
+        var uniqueNums = [Int]()
+
+        for num in nums {
+            if count[num] == nil {
+                uniqueNums.append(num)
+            }
+            count[num, default: 0] += 1
+        }
+
+        func backtrack(_ nums: [Int], _ target: Int, _ cur: inout [Int], _ i: Int) {
+            if target == 0 {
+                res.append(cur)
+                return
+            }
+            if target < 0 || i >= nums.count {
+                return
+            }
+
+            if count[nums[i], default: 0] > 0 {
+                cur.append(nums[i])
+                count[nums[i], default: 0] -= 1
+                backtrack(nums, target - nums[i], &cur, i)
+                count[nums[i], default: 0] += 1
+                cur.removeLast()
+            }
+
+            backtrack(nums, target, &cur, i + 1)
+        }
+
+        var cur: [Int] = []
+        backtrack(uniqueNums, target, &cur, 0)
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -744,6 +1050,100 @@ public class Solution {
 }
 ```
 
+```go
+func combinationSum2(candidates []int, target int) [][]int {
+    var res [][]int
+    sort.Ints(candidates)
+
+    var dfs func(int, []int, int)
+    dfs = func(idx int, path []int, cur int) {
+        if cur == target {
+            temp := make([]int, len(path))
+            copy(temp, path)
+            res = append(res, temp)
+            return
+        }
+
+        for i := idx; i < len(candidates); i++ {
+            if i > idx && candidates[i] == candidates[i-1] {
+                continue
+            }
+            if cur + candidates[i] > target {
+                break
+            }
+
+            path = append(path, candidates[i])
+            dfs(i+1, path, cur + candidates[i])
+            path = path[:len(path)-1]
+        }
+    }
+
+    dfs(0, []int{}, 0)
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun combinationSum2(candidates: IntArray, target: Int): List<List<Int>> {
+        val res = mutableListOf<List<Int>>()
+        candidates.sort()
+
+        fun dfs(idx: Int, path: MutableList<Int>, cur: Int) {
+            if (cur == target) {
+                res.add(ArrayList(path))
+                return
+            }
+
+            for (i in idx until candidates.size) {
+                if (i > idx && candidates[i] == candidates[i - 1]) continue
+                if (cur + candidates[i] > target) break
+
+                path.add(candidates[i])
+                dfs(i + 1, path, cur + candidates[i])
+                path.removeAt(path.size - 1)
+            }
+        }
+
+        dfs(0, mutableListOf(), 0)
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func combinationSum2(_ candidates: [Int], _ target: Int) -> [[Int]] {
+        var res = [[Int]]()
+        let sortedCandidates = candidates.sorted()
+
+        func dfs(_ idx: Int, _ path: inout [Int], _ cur: Int) {
+            if cur == target {
+                res.append(path)
+                return
+            }
+
+            for i in idx..<sortedCandidates.count {
+                if i > idx && sortedCandidates[i] == sortedCandidates[i - 1] {
+                    continue
+                }
+                if cur + sortedCandidates[i] > target {
+                    break
+                }
+
+                path.append(sortedCandidates[i])
+                dfs(i + 1, &path, cur + sortedCandidates[i])
+                path.removeLast()
+            }
+        }
+
+        var path: [Int] = []
+        dfs(0, &path, 0)
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/combination-target-sum.md b/articles/combination-target-sum.md
index f6082660c..46436ad64 100644
--- a/articles/combination-target-sum.md
+++ b/articles/combination-target-sum.md
@@ -141,6 +141,86 @@ public class Solution {
 }
 ```
 
+```go
+func combinationSum(nums []int, target int) [][]int {
+    res := [][]int{}
+
+    var dfs func(int, []int, int)
+    dfs = func(i int, cur []int, total int) {
+        if total == target {
+            temp := make([]int, len(cur))
+            copy(temp, cur)
+            res = append(res, temp)
+            return
+        }
+        if i >= len(nums) || total > target {
+            return
+        }
+
+        cur = append(cur, nums[i])
+        dfs(i, cur, total + nums[i])
+        cur = cur[:len(cur)-1]
+        dfs(i+1, cur, total)
+    }
+
+    dfs(0, []int{}, 0)
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun combinationSum(nums: IntArray, target: Int): List<List<Int>> {
+        val res = mutableListOf<List<Int>>()
+
+        fun dfs(i: Int, cur: MutableList<Int>, total: Int) {
+            if (total == target) {
+                res.add(ArrayList(cur))
+                return
+            }
+            if (i >= nums.size || total > target) {
+                return
+            }
+
+            cur.add(nums[i])
+            dfs(i, cur, total + nums[i])
+            cur.removeAt(cur.size - 1)
+            dfs(i + 1, cur, total)
+        }
+
+        dfs(0, mutableListOf(), 0)
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func combinationSum(_ nums: [Int], _ target: Int) -> [[Int]] {
+        var res: [[Int]] = []
+
+        func dfs(_ i: Int, _ cur: inout [Int], _ total: Int) {
+            if total == target {
+                res.append(cur)
+                return
+            }
+            if i >= nums.count || total > target {
+                return
+            }
+
+            cur.append(nums[i])
+            dfs(i, &cur, total + nums[i])
+            cur.removeLast()
+            dfs(i + 1, &cur, total)
+        }
+
+        var cur: [Int] = []
+        dfs(0, &cur, 0)
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -296,6 +376,92 @@ public class Solution {
 }
 ```
 
+```go
+func combinationSum(nums []int, target int) [][]int {
+    res := [][]int{}
+    sort.Ints(nums)
+
+    var dfs func(int, []int, int)
+    dfs = func(i int, cur []int, total int) {
+        if total == target {
+            temp := make([]int, len(cur))
+            copy(temp, cur)
+            res = append(res, temp)
+            return
+        }
+        
+        for j := i; j < len(nums); j++ {
+            if total + nums[j] > target {
+                return
+            }
+            cur = append(cur, nums[j])
+            dfs(j, cur, total + nums[j])
+            cur = cur[:len(cur)-1]
+        }
+    }
+
+    dfs(0, []int{}, 0)
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun combinationSum(nums: IntArray, target: Int): List<List<Int>> {
+        val res = mutableListOf<List<Int>>()
+        nums.sort()
+
+        fun dfs(i: Int, cur: MutableList<Int>, total: Int) {
+            if (total == target) {
+                res.add(ArrayList(cur))
+                return
+            }
+            
+            for (j in i until nums.size) {
+                if (total + nums[j] > target) {
+                    return
+                }
+                cur.add(nums[j])
+                dfs(j, cur, total + nums[j])
+                cur.removeAt(cur.size - 1)
+            }
+        }
+
+        dfs(0, mutableListOf(), 0)
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func combinationSum(_ nums: [Int], _ target: Int) -> [[Int]] {
+        var res: [[Int]] = []
+        let sortedNums = nums.sorted()
+
+        func dfs(_ i: Int, _ cur: inout [Int], _ total: Int) {
+            if total == target {
+                res.append(cur)
+                return
+            }
+
+            for j in i..<sortedNums.count {
+                if total + sortedNums[j] > target {
+                    return
+                }
+                cur.append(sortedNums[j])
+                dfs(j, &cur, total + sortedNums[j])
+                cur.removeLast()
+            }
+        }
+
+        var cur: [Int] = []
+        dfs(0, &cur, 0)
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/combinations-of-a-phone-number.md b/articles/combinations-of-a-phone-number.md
index 1b1d03d0e..51796e3f7 100644
--- a/articles/combinations-of-a-phone-number.md
+++ b/articles/combinations-of-a-phone-number.md
@@ -1,4 +1,4 @@
-## 1. Bactracking
+## 1. Backtracking
 
 ::tabs-start
 
@@ -145,12 +145,112 @@ public class Solution {
 }
 ```
 
+```go
+func letterCombinations(digits string) []string {
+    if len(digits) == 0 {
+        return []string{}
+    }
+
+    res := []string{}
+    digitToChar := map[byte]string{
+        '2': "abc",
+        '3': "def",
+        '4': "ghi",
+        '5': "jkl",
+        '6': "mno",
+        '7': "pqrs",
+        '8': "tuv",
+        '9': "wxyz",
+    }
+
+    var backtrack func(i int, curStr string)
+    backtrack = func(i int, curStr string) {
+        if len(curStr) == len(digits) {
+            res = append(res, curStr)
+            return
+        }
+        for _, c := range digitToChar[digits[i]] {
+            backtrack(i+1, curStr+string(c))
+        }
+    }
+
+    backtrack(0, "")
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun letterCombinations(digits: String): List<String> {
+        if (digits.isEmpty()) return emptyList()
+
+        val res = mutableListOf<String>()
+        val digitToChar = mapOf(
+            '2' to "abc",
+            '3' to "def",
+            '4' to "ghi",
+            '5' to "jkl",
+            '6' to "mno",
+            '7' to "pqrs",
+            '8' to "tuv",
+            '9' to "wxyz"
+        )
+
+        fun backtrack(i: Int, curStr: String) {
+            if (curStr.length == digits.length) {
+                res.add(curStr)
+                return
+            }
+            for (c in digitToChar[digits[i]]!!) {
+                backtrack(i + 1, curStr + c)
+            }
+        }
+
+        backtrack(0, "")
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func letterCombinations(_ digits: String) -> [String] {
+        guard !digits.isEmpty else { return [] }
+        
+        let digitToChar: [Character: String] = [
+            "2": "abc", "3": "def", "4": "ghi", "5": "jkl",
+            "6": "mno", "7": "pqrs", "8": "tuv", "9": "wxyz"
+        ]
+        
+        var res = [String]()
+        let digitsArray = Array(digits)
+        
+        func backtrack(_ i: Int, _ curStr: String) {
+            if curStr.count == digits.count {
+                res.append(curStr)
+                return
+            }
+            if let letters = digitToChar[digitsArray[i]] {
+                for c in letters {
+                    backtrack(i + 1, curStr + String(c))
+                }
+            }
+        }
+        
+        backtrack(0, "")
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n * 4 ^ n)$
-* Space complexity: $O(n)$
+* Space complexity:
+    * $O(n)$ extra space.
+    * $O(n * 4 ^ n)$ space for the output list.
 
 ---
 
@@ -299,9 +399,102 @@ public class Solution {
 }
 ```
 
+```go
+func letterCombinations(digits string) []string {
+    if len(digits) == 0 {
+        return []string{}
+    }
+
+    res := []string{""}
+    digitToChar := map[byte]string{
+        '2': "abc",
+        '3': "def",
+        '4': "ghi",
+        '5': "jkl",
+        '6': "mno",
+        '7': "pqrs",
+        '8': "tuv",
+        '9': "wxyz",
+    }
+
+    for i := 0; i < len(digits); i++ {
+        digit := digits[i]
+        tmp := []string{}
+        for _, curStr := range res {
+            for _, c := range digitToChar[digit] {
+                tmp = append(tmp, curStr+string(c))
+            }
+        }
+        res = tmp
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun letterCombinations(digits: String): List<String> {
+        if (digits.isEmpty()) return emptyList()
+
+        var res = listOf("")
+        val digitToChar = mapOf(
+            '2' to "abc",
+            '3' to "def",
+            '4' to "ghi",
+            '5' to "jkl",
+            '6' to "mno",
+            '7' to "pqrs",
+            '8' to "tuv",
+            '9' to "wxyz"
+        )
+
+        for (digit in digits) {
+            val tmp = mutableListOf<String>()
+            for (curStr in res) {
+                for (c in digitToChar[digit]!!) {
+                    tmp.add(curStr + c)
+                }
+            }
+            res = tmp
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func letterCombinations(_ digits: String) -> [String] {
+        guard !digits.isEmpty else { return [] }
+        
+        let digitToChar: [Character: String] = [
+            "2": "abc", "3": "def", "4": "ghi", "5": "jkl",
+            "6": "mno", "7": "pqrs", "8": "tuv", "9": "wxyz"
+        ]
+        
+        var res = [""]
+        
+        for digit in digits {
+            guard let letters = digitToChar[digit] else { continue }
+            var tmp = [String]()
+            for curStr in res {
+                for c in letters {
+                    tmp.append(curStr + String(c))
+                }
+            }
+            res = tmp
+        }
+        
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n * 4 ^ n)$
-* Space complexity: $O(n)$
\ No newline at end of file
+* Space complexity:
+    * $O(n)$ extra space.
+    * $O(n * 4 ^ n)$ space for the output list.
diff --git a/articles/combinations.md b/articles/combinations.md
new file mode 100644
index 000000000..321ffeab1
--- /dev/null
+++ b/articles/combinations.md
@@ -0,0 +1,554 @@
+## 1. Backtracking - I
+
+::tabs-start
+
+```python
+class Solution:
+    def combine(self, n: int, k: int) -> List[List[int]]:
+        res = []
+        
+        def backtrack(i, comb):
+            if i > n:
+                if len(comb) == k:
+                    res.append(comb.copy())
+                return
+            
+            comb.append(i)
+            backtrack(i + 1, comb)
+            comb.pop()
+            backtrack(i + 1, comb)
+        
+        backtrack(1, [])
+        return res
+```
+
+```java
+public class Solution {
+    private List<List<Integer>> res;
+    
+    public List<List<Integer>> combine(int n, int k) {
+        res = new ArrayList<>();
+        backtrack(1, n, k, new ArrayList<>());
+        return res;
+    }
+    
+    private void backtrack(int i, int n, int k, List<Integer> comb) {
+        if (i > n) {
+            if (comb.size() == k) {
+                res.add(new ArrayList<>(comb));
+            }
+            return;
+        }
+        
+        comb.add(i);
+        backtrack(i + 1, n, k, comb);
+        comb.remove(comb.size() - 1);
+        backtrack(i + 1, n, k, comb);
+    }
+}
+```
+
+```cpp
+class Solution {
+    vector<vector<int>> res;
+public:
+    vector<vector<int>> combine(int n, int k) {
+        vector<int> comb;
+        backtrack(1, n, k, comb);
+        return res;
+    }
+
+private:
+    void backtrack(int i, int n, int k, vector<int>& comb) {
+        if (i > n) {
+            if (comb.size() == k) {
+                res.push_back(comb);
+            }
+            return;
+        }
+
+        comb.push_back(i);
+        backtrack(i + 1, n, k, comb);
+        comb.pop_back();
+        backtrack(i + 1, n, k, comb);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} k
+     * @return {number[][]}
+     */
+    combine(n, k) {
+        const res = [];
+        
+        const backtrack = (i, comb) => {
+            if (i > n) {
+                if (comb.length === k) {
+                    res.push([...comb]);
+                }
+                return;
+            }
+            
+            comb.push(i);
+            backtrack(i + 1, comb);
+            comb.pop();
+            backtrack(i + 1, comb);
+        };
+        
+        backtrack(1, []);
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<List<int>> Combine(int n, int k) {
+        List<List<int>> res = new List<List<int>>();
+        
+        void Backtrack(int i, List<int> comb) {
+            if (i > n) {
+                if (comb.Count == k) {
+                    res.Add(new List<int>(comb));
+                }
+                return;
+            }
+
+            comb.Add(i);
+            Backtrack(i + 1, comb);
+            comb.RemoveAt(comb.Count - 1);
+            Backtrack(i + 1, comb);
+        }
+
+        Backtrack(1, new List<int>());
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(k * \frac {n!}{(n - k)! * k!})$
+* Space complexity: $O(k * \frac {n!}{(n - k)! * k!})$ for the output array.
+
+> Where $n$ is the number of elements and $k$ is the number of elements to be picked.
+
+---
+
+## 2. Backtracking - II
+
+::tabs-start
+
+```python
+class Solution:
+    def combine(self, n: int, k: int) -> List[List[int]]:
+        res = []
+
+        def backtrack(start, comb):
+            if len(comb) == k:
+                res.append(comb.copy())
+                return
+
+            for i in range(start, n + 1):
+                comb.append(i)
+                backtrack(i + 1, comb)
+                comb.pop()
+
+        backtrack(1, [])
+        return res
+```
+
+```java
+public class Solution {
+    private List<List<Integer>> res;
+
+    public List<List<Integer>> combine(int n, int k) {
+        res = new ArrayList<>();
+        backtrack(1, n, k, new ArrayList<>());
+        return res;
+    }
+
+    private void backtrack(int start, int n, int k, List<Integer> comb) {
+        if (comb.size() == k) {
+            res.add(new ArrayList<>(comb));
+            return;
+        }
+
+        for (int i = start; i <= n; i++) {
+            comb.add(i);
+            backtrack(i + 1, n, k, comb);
+            comb.remove(comb.size() - 1);
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> res;
+
+    vector<vector<int>> combine(int n, int k) {
+        res.clear();
+        vector<int> comb;
+        backtrack(1, n, k, comb);
+        return res;
+    }
+
+    void backtrack(int start, int n, int k, vector<int>& comb) {
+        if (comb.size() == k) {
+            res.push_back(comb);
+            return;
+        }
+
+        for (int i = start; i <= n; i++) {
+            comb.push_back(i);
+            backtrack(i + 1, n, k, comb);
+            comb.pop_back();
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} k
+     * @return {number[][]}
+     */
+    combine(n, k) {
+        const res = [];
+        
+        const backtrack = (start, comb) => {
+            if (comb.length === k) {
+                res.push([...comb]);
+                return;
+            }
+
+            for (let i = start; i <= n; i++) {
+                comb.push(i);
+                backtrack(i + 1, comb);
+                comb.pop();
+            }
+        };
+        
+        backtrack(1, []);
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<List<int>> Combine(int n, int k) {
+        List<List<int>> res = new List<List<int>>();
+
+        void Backtrack(int start, List<int> comb) {
+            if (comb.Count == k) {
+                res.Add(new List<int>(comb));
+                return;
+            }
+
+            for (int i = start; i <= n; i++) {
+                comb.Add(i);
+                Backtrack(i + 1, comb);
+                comb.RemoveAt(comb.Count - 1);
+            }
+        }
+
+        Backtrack(1, new List<int>());
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(k * \frac {n!}{(n - k)! * k!})$
+* Space complexity: $O(k * \frac {n!}{(n - k)! * k!})$ for the output array.
+
+> Where $n$ is the number of elements and $k$ is the number of elements to be picked.
+
+---
+
+## 3. Iteration
+
+::tabs-start
+
+```python
+class Solution:
+    def combine(self, n: int, k: int) -> List[List[int]]:
+        res = []
+        i = 0
+        comb = [0] * k
+
+        while i >= 0:
+            comb[i] += 1
+            if comb[i] > n:
+                i -= 1
+                continue
+
+            if i == k - 1:
+                res.append(comb.copy())
+            else:
+                i += 1
+                comb[i] = comb[i - 1]
+
+        return res
+```
+
+```java
+public class Solution {
+    public List<List<Integer>> combine(int n, int k) {
+        List<List<Integer>> res = new ArrayList<>();
+        int[] comb = new int[k];
+        int i = 0;
+
+        while (i >= 0) {
+            comb[i]++;
+            if (comb[i] > n) {
+                i--;
+                continue;
+            }
+
+            if (i == k - 1) {
+                List<Integer> current = new ArrayList<>();
+                for (int num : comb) {
+                    current.add(num);
+                }
+                res.add(current);
+            } else {
+                i++;
+                comb[i] = comb[i - 1];
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> combine(int n, int k) {
+        vector<vector<int>> res;
+        vector<int> comb(k, 0);
+        int i = 0;
+
+        while (i >= 0) {
+            comb[i]++;
+            if (comb[i] > n) {
+                i--;
+                continue;
+            }
+
+            if (i == k - 1) {
+                res.push_back(comb);
+            } else {
+                i++;
+                comb[i] = comb[i - 1];
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} k
+     * @return {number[][]}
+     */
+    combine(n, k) {
+        const res = [];
+        const comb = Array(k).fill(0);
+        let i = 0;
+
+        while (i >= 0) {
+            comb[i]++;
+            if (comb[i] > n) {
+                i--;
+                continue;
+            }
+
+            if (i === k - 1) {
+                res.push([...comb]);
+            } else {
+                i++;
+                comb[i] = comb[i - 1];
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<List<int>> Combine(int n, int k) {
+        List<List<int>> res = new List<List<int>>();
+        int[] comb = new int[k];
+        int i = 0;
+
+        while (i >= 0) {
+            comb[i]++;
+            if (comb[i] > n) {
+                i--;
+                continue;
+            }
+
+            if (i == k - 1) {
+                res.Add(new List<int>(comb));
+            } else {
+                i++;
+                comb[i] = comb[i - 1];
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(k * \frac {n!}{(n - k)! * k!})$
+* Space complexity: $O(k * \frac {n!}{(n - k)! * k!})$ for the output array.
+
+> Where $n$ is the number of elements and $k$ is the number of elements to be picked.
+
+---
+
+## 4. Bit Manipulation
+
+::tabs-start
+
+```python
+class Solution:
+    def combine(self, n: int, k: int) -> List[List[int]]:
+        res = []
+        for mask in range(1 << n):
+            comb = []
+            for bit in range(n):
+                if mask & (1 << bit):
+                    comb.append(bit + 1)
+            
+            if len(comb) == k:
+                res.append(comb)
+        return res
+```
+
+```java
+public class Solution {
+    public List<List<Integer>> combine(int n, int k) {
+        List<List<Integer>> res = new ArrayList<>();
+        for (int mask = 0; mask < (1 << n); mask++) {
+            List<Integer> comb = new ArrayList<>();
+            for (int bit = 0; bit < n; bit++) {
+                if ((mask & (1 << bit)) != 0) {
+                    comb.add(bit + 1);
+                }
+            }
+            if (comb.size() == k) {
+                res.add(comb);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> combine(int n, int k) {
+        vector<vector<int>> res;
+        for (int mask = 0; mask < (1 << n); ++mask) {
+            vector<int> comb;
+            for (int bit = 0; bit < n; ++bit) {
+                if (mask & (1 << bit)) {
+                    comb.push_back(bit + 1);
+                }
+            }
+            if (comb.size() == k) {
+                res.push_back(comb);
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} k
+     * @return {number[][]}
+     */
+    combine(n, k) {
+        const res = [];
+        for (let mask = 0; mask < (1 << n); mask++) {
+            if (mask.toString(2).split("1").length - 1 !== k) {
+                continue;
+            }
+
+            const comb = [];
+            for (let bit = 0; bit < n; bit++) {
+                if (mask & (1 << bit)) {
+                    comb.push(bit + 1);
+                }
+            }
+            res.push(comb);
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<List<int>> Combine(int n, int k) {
+        List<List<int>> res = new List<List<int>>();
+
+        for (int mask = 0; mask < (1 << n); mask++) {
+            List<int> comb = new List<int>();
+            for (int bit = 0; bit < n; bit++) {
+                if ((mask & (1 << bit)) != 0) {
+                    comb.Add(bit + 1);
+                }
+            }
+            if (comb.Count == k) {
+                res.Add(comb);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * 2 ^ n)$
+* Space complexity: $O(k * \frac {n!}{(n - k)! * k!})$ for the output array.
+
+> Where $n$ is the number of elements and $k$ is the number of elements to be picked.
\ No newline at end of file
diff --git a/articles/concatenated-words.md b/articles/concatenated-words.md
new file mode 100644
index 000000000..0d7eaf0d4
--- /dev/null
+++ b/articles/concatenated-words.md
@@ -0,0 +1,587 @@
+## 1. Brute Force (Backtracking)
+
+::tabs-start
+
+```python
+class Solution:
+    def findAllConcatenatedWordsInADict(self, words: List[str]) -> List[str]:
+        n = len(words)
+        res = []
+        wordSet = set(words)
+        maxLen = 0
+        for w in words:
+            maxLen = max(maxLen, len(w))
+
+        def dfs(concatWord, totLen):
+            if len(concatWord) > 1:
+                word = "".join(concatWord)
+                if word in wordSet:
+                    res.append(word)
+                    wordSet.remove(word)
+
+            for i in range(len(words)):
+                if totLen + len(words[i]) > maxLen:
+                    continue
+                concatWord.append(words[i])
+                dfs(concatWord, totLen + len(words[i]))
+                concatWord.pop()
+
+        dfs([], 0)
+        return res
+```
+
+```java
+public class Solution {
+    private Set<String> wordSet;
+    private int maxLen;
+    private List<String> res;
+    private String[] words;
+
+    public List<String> findAllConcatenatedWordsInADict(String[] words) {
+        this.words = words;
+        this.wordSet = new HashSet<>(Arrays.asList(words));
+        this.maxLen = 0;
+        this.res = new ArrayList<>();
+
+        for (String w : words) {
+            maxLen = Math.max(maxLen, w.length());
+        }
+
+        dfs(new ArrayList<>(), 0);
+        return res;
+    }
+
+    private void dfs(List<String> concatWord, int totLen) {
+        if (concatWord.size() > 1) {
+            String word = String.join("", concatWord);
+            if (wordSet.contains(word)) {
+                res.add(word);
+                wordSet.remove(word);
+            }
+        }
+
+        for (String word : words) {
+            if (totLen + word.length() > maxLen) continue;
+            concatWord.add(word);
+            dfs(concatWord, totLen + word.length());
+            concatWord.remove(concatWord.size() - 1);
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    unordered_set<string> wordSet;
+    int maxLen;
+    vector<string> res;
+    vector<string> words;
+
+public:
+    vector<string> findAllConcatenatedWordsInADict(vector<string>& words) {
+        this->words = words;
+        wordSet = unordered_set<string>(words.begin(), words.end());
+        maxLen = 0;
+        res.clear();
+
+        for (const string& w : words) {
+            maxLen = max(maxLen, (int)w.length());
+        }
+
+        vector<string> concatWord;
+        dfs(concatWord, 0);
+        return res;
+    }
+
+private:
+    void dfs(vector<string>& concatWord, int totLen) {
+        if (concatWord.size() > 1) {
+            string word = accumulate(concatWord.begin(), concatWord.end(), string(""));
+            if (wordSet.count(word)) {
+                res.push_back(word);
+                wordSet.erase(word);
+            }
+        }
+
+        for (const string& word : words) {
+            if (totLen + word.size() > maxLen) continue;
+            concatWord.push_back(word);
+            dfs(concatWord, totLen + word.length());
+            concatWord.pop_back();
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @return {string[]}
+     */
+    findAllConcatenatedWordsInADict(words) {
+        let n = words.length;
+        let res = [];
+        let wordSet = new Set(words);
+        let maxLen = 0;
+
+        for (let w of words) {
+            maxLen = Math.max(maxLen, w.length);
+        }
+
+        const dfs = (concatWord, totLen) => {
+            if (concatWord.length > 1) {
+                let word = concatWord.join("");
+                if (wordSet.has(word)) {
+                    res.push(word);
+                    wordSet.delete(word);
+                }
+            }
+
+            for (let i = 0; i < words.length; i++) {
+                if (totLen + words[i].length > maxLen) continue;
+                concatWord.push(words[i]);
+                dfs(concatWord, totLen + words[i].length);
+                concatWord.pop();
+            }
+        };
+
+        dfs([], 0);
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n ^ n)$
+* Space complexity: $O(m * n)$
+
+> Where $n$ is the size of the string array $words$ and $m$ is the length of the longest word in the array.
+
+---
+
+## 2. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def findAllConcatenatedWordsInADict(self, words: List[str]) -> List[str]:
+        wordSet = set(words)
+
+        def dfs(word):
+            for i in range(1, len(word)):
+                prefix, suffix = word[:i], word[i:]
+                if ((prefix in wordSet and suffix in wordSet) or 
+                    (prefix in wordSet and dfs(suffix))
+                ):
+                    return True
+            return False
+
+        res = []
+        for w in words:
+            if dfs(w):
+                res.append(w)
+        return res
+```
+
+```java
+public class Solution {
+    public List<String> findAllConcatenatedWordsInADict(String[] words) {
+        Set<String> wordSet = new HashSet<>(Arrays.asList(words));
+        List<String> res = new ArrayList<>();
+
+        for (String w : words) {
+            if (dfs(w, wordSet)) {
+                res.add(w);
+            }
+        }
+        return res;
+    }
+
+    private boolean dfs(String word, Set<String> wordSet) {
+        for (int i = 1; i < word.length(); i++) {
+            String prefix = word.substring(0, i);
+            String suffix = word.substring(i);
+
+            if ((wordSet.contains(prefix) && wordSet.contains(suffix)) ||
+                (wordSet.contains(prefix) && dfs(suffix, wordSet))) {
+                return true;
+            }
+        }
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<string> findAllConcatenatedWordsInADict(vector<string>& words) {
+        unordered_set<string> wordSet(words.begin(), words.end());
+        vector<string> res;
+
+        for (const string& w : words) {
+            if (dfs(w, wordSet)) {
+                res.push_back(w);
+            }
+        }
+        return res;
+    }
+
+private:
+    bool dfs(const string& word, unordered_set<string>& wordSet) {
+        for (int i = 1; i < word.size(); i++) {
+            string prefix = word.substr(0, i);
+            string suffix = word.substr(i);
+
+            if ((wordSet.count(prefix) && wordSet.count(suffix)) ||
+                (wordSet.count(prefix) && dfs(suffix, wordSet))) {
+                return true;
+            }
+        }
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @return {string[]}
+     */
+    findAllConcatenatedWordsInADict(words) {
+        const wordSet = new Set(words);
+
+        const dfs = (word) => {
+            for (let i = 1; i < word.length; i++) {
+                const prefix = word.substring(0, i);
+                const suffix = word.substring(i);
+
+                if ((wordSet.has(prefix) && wordSet.has(suffix)) || 
+                    (wordSet.has(prefix) && dfs(suffix))) {
+                    return true;
+                }
+            }
+            return false;
+        };
+
+        const res = [];
+        for (let w of words) {
+            if (dfs(w)) {
+                res.push(w);
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m ^ 4)$
+* Space complexity: $O(n * m)$
+
+> Where $n$ is the size of the string array $words$ and $m$ is the length of the longest word in the array.
+
+---
+
+## 3. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def findAllConcatenatedWordsInADict(self, words: List[str]) -> List[str]:
+        wordSet = set(words)
+        dp = {}
+
+        def dfs(word):
+            if word in dp:
+                return dp[word]
+
+            for i in range(1, len(word)):
+                prefix, suffix = word[:i], word[i:]
+                if ((prefix in wordSet and suffix in wordSet) or 
+                    (prefix in wordSet and dfs(suffix))
+                ):
+                    dp[word] = True
+                    return True
+            dp[word] = False
+            return False
+
+        res = []
+        for w in words:
+            if dfs(w):
+                res.append(w)
+        return res
+```
+
+```java
+public class Solution {
+    private Map<String, Boolean> dp;
+
+    public List<String> findAllConcatenatedWordsInADict(String[] words) {
+        Set<String> wordSet = new HashSet<>(Arrays.asList(words));
+        List<String> res = new ArrayList<>();
+        dp = new HashMap<>();
+
+        for (String w : words) {
+            if (dfs(w, wordSet)) {
+                res.add(w);
+            }
+        }
+        return res;
+    }
+
+    private boolean dfs(String word, Set<String> wordSet) {
+        if (dp.containsKey(word)) {
+            return dp.get(word);
+        }
+
+        for (int i = 1; i < word.length(); i++) {
+            String prefix = word.substring(0, i);
+            String suffix = word.substring(i);
+
+            if ((wordSet.contains(prefix) && wordSet.contains(suffix)) ||
+                (wordSet.contains(prefix) && dfs(suffix, wordSet))) {
+                dp.put(word, true);
+                return true;
+            }
+        }
+        dp.put(word, false);
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+    unordered_map<string, bool> dp;
+
+public:
+    vector<string> findAllConcatenatedWordsInADict(vector<string>& words) {
+        unordered_set<string> wordSet(words.begin(), words.end());
+        vector<string> res;
+
+        for (const string& w : words) {
+            if (dfs(w, wordSet)) {
+                res.push_back(w);
+            }
+        }
+        return res;
+    }
+
+private:
+    bool dfs(const string& word, unordered_set<string>& wordSet) {
+        if (dp.count(word)) {
+            return dp[word];
+        }
+
+        for (int i = 1; i < word.size(); i++) {
+            string prefix = word.substr(0, i);
+            string suffix = word.substr(i);
+
+            if ((wordSet.count(prefix) && wordSet.count(suffix)) ||
+                (wordSet.count(prefix) && dfs(suffix, wordSet))) {
+                dp[word] = true;
+                return true;
+            }
+        }
+        dp[word] = false;
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @return {string[]}
+     */
+    findAllConcatenatedWordsInADict(words) {
+        const wordSet = new Set(words);
+        const dp = new Map();
+
+        const dfs = (word) => {
+            if (dp.has(word)) {
+                return dp.get(word);
+            }
+
+            for (let i = 1; i < word.length; i++) {
+                const prefix = word.substring(0, i);
+                const suffix = word.substring(i);
+
+                if ((wordSet.has(prefix) && wordSet.has(suffix)) || 
+                    (wordSet.has(prefix) && dfs(suffix))) {
+                    dp.set(word, true);
+                    return true;
+                }
+            }
+            dp.set(word, false);
+            return false;
+        };
+
+        const res = [];
+        for (let w of words) {
+            if (dfs(w)) {
+                res.push(w);
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m ^ 3)$
+* Space complexity: $O(n * m)$
+
+> Where $n$ is the size of the string array $words$ and $m$ is the length of the longest word in the array.
+
+---
+
+## 4. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def findAllConcatenatedWordsInADict(self, words: List[str]) -> List[str]:
+        wordSet = set(words)
+        res = []
+
+        for word in words:
+            m = len(word)
+
+            dp = [False] * (m + 1)
+            dp[0] = True
+
+            for i in range(1, m + 1):
+                for j in range(i):
+                    if j == 0 and i == m:
+                        continue
+                    if dp[j] and word[j:i] in wordSet:
+                        dp[i] = True
+                        break
+
+            if dp[m]:
+                res.append(word)
+
+        return res
+```
+
+```java
+public class Solution {
+    public List<String> findAllConcatenatedWordsInADict(String[] words) {
+        Set<String> wordSet = new HashSet<>(Arrays.asList(words));
+        List<String> res = new ArrayList<>();
+
+        for (String word : words) {
+            int m = word.length();
+            boolean[] dp = new boolean[m + 1];
+            dp[0] = true;
+
+            for (int i = 1; i <= m; i++) {
+                for (int j = 0; j < i; j++) {
+                    if (j == 0 && i == m) continue;
+                    if (dp[j] && wordSet.contains(word.substring(j, i))) {
+                        dp[i] = true;
+                        break;
+                    }
+                }
+            }
+
+            if (dp[m]) {
+                res.add(word);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<string> findAllConcatenatedWordsInADict(vector<string>& words) {
+        unordered_set<string> wordSet(words.begin(), words.end());
+        vector<string> res;
+
+        for (string& word : words) {
+            int m = word.length();
+            vector<bool> dp(m + 1, false);
+            dp[0] = true;
+
+            for (int i = 1; i <= m; i++) {
+                for (int j = 0; j < i; j++) {
+                    if (j == 0 && i == m) continue;
+                    if (dp[j] && wordSet.count(word.substr(j, i - j))) {
+                        dp[i] = true;
+                        break;
+                    }
+                }
+            }
+
+            if (dp[m]) {
+                res.push_back(word);
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @return {string[]}
+     */
+    findAllConcatenatedWordsInADict(words) {
+        const wordSet = new Set(words);
+        const res = [];
+
+        for (const word of words) {
+            const m = word.length;
+            const dp = new Array(m + 1).fill(false);
+            dp[0] = true;
+
+            for (let i = 1; i <= m; i++) {
+                for (let j = 0; j < i; j++) {
+                    if (j === 0 && i === m) continue;
+                    if (dp[j] && wordSet.has(word.substring(j, i))) {
+                        dp[i] = true;
+                        break;
+                    }
+                }
+            }
+
+            if (dp[m]) {
+                res.push(word);
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m ^ 3)$
+* Space complexity: $O(n * m)$
+
+> Where $n$ is the size of the string array $words$ and $m$ is the length of the longest word in the array.
\ No newline at end of file
diff --git a/articles/concatenation-of-array.md b/articles/concatenation-of-array.md
new file mode 100644
index 000000000..f3740ed68
--- /dev/null
+++ b/articles/concatenation-of-array.md
@@ -0,0 +1,163 @@
+## 1. Iteration (Two Pass)
+
+::tabs-start
+
+```python
+class Solution:
+    def getConcatenation(self, nums: List[int]) -> List[int]:
+        ans = []
+        for i in range(2):
+            for num in nums:
+                ans.append(num)
+        return ans
+```
+
+```java
+public class Solution {
+    public int[] getConcatenation(int[] nums) {
+        int[] ans = new int[2 * nums.length];
+        int idx = 0;
+        for (int i = 0; i < 2; i++) {
+            for (int num : nums) {
+                ans[idx++] = num;
+            }
+        }
+        return ans;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> getConcatenation(vector<int>& nums) {
+        vector<int> ans;
+        for (int i = 0; i < 2; ++i) {
+            for (int num : nums) {
+                ans.push_back(num);
+            }
+        }
+        return ans;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    getConcatenation(nums) {
+        let ans = [];
+        for (let i = 0; i < 2; i++) {
+            for (let num of nums) {
+                ans.push(num);
+            }
+        }
+        return ans;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[] GetConcatenation(int[] nums) {
+        int[] ans = new int[2 * nums.Length];
+        int idx = 0;
+        for (int i = 0; i < 2; i++) {
+            foreach (int num in nums) {
+                ans[idx++] = num;
+            }
+        }
+        return ans;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for the output array.
+
+---
+
+## 2. Iteration (One Pass)
+
+::tabs-start
+
+```python
+class Solution:
+    def getConcatenation(self, nums: List[int]) -> List[int]:
+        n = len(nums)
+        ans = [0] * (2 * n)
+        for i, num in enumerate(nums):
+            ans[i] = ans[i + n] = num
+        return ans
+```
+
+```java
+public class Solution {
+    public int[] getConcatenation(int[] nums) {
+        int n = nums.length;
+        int[] ans = new int[2 * n];
+        for (int i = 0; i < n; i++) {
+            ans[i] = ans[i + n] = nums[i];
+        }
+        return ans;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> getConcatenation(vector<int>& nums) {
+        int n = nums.size();
+        vector<int> ans(2 * n);
+        for (int i = 0; i < n; ++i) {
+            ans[i] = ans[i + n] = nums[i];
+        }
+        return ans;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    getConcatenation(nums) {
+        let n = nums.length;
+        let ans = new Array(2 * n);
+        for (let i = 0; i < n; i++) {
+            ans[i] = ans[i + n] = nums[i];
+        }
+        return ans;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[] GetConcatenation(int[] nums) {
+        int n = nums.Length;
+        int[] ans = new int[2 * n];
+        for (int i = 0; i < n; i++) {
+            ans[i] = ans[i + n] = nums[i];
+        }
+        return ans;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for the output array.
\ No newline at end of file
diff --git a/articles/constrained-subsequence-sum.md b/articles/constrained-subsequence-sum.md
new file mode 100644
index 000000000..1c04624df
--- /dev/null
+++ b/articles/constrained-subsequence-sum.md
@@ -0,0 +1,701 @@
+## 1. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def constrainedSubsetSum(self, nums: List[int], k: int) -> int:
+        memo = [None] * len(nums)
+
+        def dfs(i):
+            if memo[i] != None:
+                return memo[i]
+
+            res = nums[i]
+            for j in range(i + 1, len(nums)):
+                if j - i > k:
+                    break
+                res = max(res, nums[i] + dfs(j))
+
+            memo[i] = res
+            return res
+
+        ans = float('-inf')
+        for i in range(len(nums)):
+            ans = max(ans, dfs(i))
+        return ans
+```
+
+```java
+public class Solution {
+    private int[] nums;
+    private Integer[] memo;
+    private int k;
+
+    public int constrainedSubsetSum(int[] nums, int k) {
+        this.nums = nums;
+        this.memo = new Integer[nums.length];
+        this.k = k;
+
+        int ans = Integer.MIN_VALUE;
+        for (int i = 0; i < nums.length; i++) {
+            ans = Math.max(ans, dfs(i));
+        }
+        return ans;
+    }
+
+    private int dfs(int i) {
+        if (memo[i] != null) {
+            return memo[i];
+        }
+
+        int res = nums[i];
+        for (int j = i + 1; j < nums.length && j - i <= k; j++) {
+            res = Math.max(res, nums[i] + dfs(j));
+        }
+
+        memo[i] = res;
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int constrainedSubsetSum(vector<int>& nums, int k) {
+        vector<int> memo(nums.size(), INT_MIN);
+        int ans = INT_MIN;
+        for (int i = 0; i < nums.size(); i++) {
+            ans = max(ans, dfs(nums, memo, k, i));
+        }
+        return ans;
+    }
+
+private:
+    int dfs(vector<int>& nums, vector<int>& memo, int k, int i) {
+        if (memo[i] != INT_MIN) {
+            return memo[i];
+        }
+
+        int res = nums[i];
+        for (int j = i + 1; j < nums.size() && j - i <= k; j++) {
+            res = max(res, nums[i] + dfs(nums, memo, k, j));
+        }
+
+        memo[i] = res;
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    constrainedSubsetSum(nums, k) {
+        const memo = new Array(nums.length).fill(null);
+
+        const dfs = (i) => {
+            if (memo[i] !== null) {
+                return memo[i];
+            }
+
+            let res = nums[i];
+            for (let j = i + 1; j < nums.length && j - i <= k; j++) {
+                res = Math.max(res, nums[i] + dfs(j));
+            }
+
+            memo[i] = res;
+            return res;
+        };
+
+        let ans = -Infinity;
+        for (let i = 0; i < nums.length; i++) {
+            ans = Math.max(ans, dfs(i));
+        }
+        return ans;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * k)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def constrainedSubsetSum(self, nums: List[int], k: int) -> int:
+        dp = [num for num in nums]
+
+        for i in range(1, len(nums)):
+            for j in range(max(0, i - k), i):
+                dp[i] = max(dp[i], nums[i] + dp[j])
+
+        return max(dp)
+```
+
+```java
+public class Solution {
+    public int constrainedSubsetSum(int[] nums, int k) {
+        int n = nums.length;
+        int[] dp = new int[n];
+        System.arraycopy(nums, 0, dp, 0, n);
+
+        for (int i = 1; i < n; i++) {
+            for (int j = Math.max(0, i - k); j < i; j++) {
+                dp[i] = Math.max(dp[i], nums[i] + dp[j]);
+            }
+        }
+
+        int res = Integer.MIN_VALUE;
+        for (int val : dp) {
+            res = Math.max(res, val);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int constrainedSubsetSum(vector<int>& nums, int k) {
+        int n = nums.size();
+        vector<int> dp(nums.begin(), nums.end());
+
+        for (int i = 1; i < n; i++) {
+            for (int j = max(0, i - k); j < i; j++) {
+                dp[i] = max(dp[i], nums[i] + dp[j]);
+            }
+        }
+
+        return *max_element(dp.begin(), dp.end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    constrainedSubsetSum(nums, k) {
+        const n = nums.length;
+        const dp = [...nums];
+
+        for (let i = 1; i < n; i++) {
+            for (let j = Math.max(0, i - k); j < i; j++) {
+                dp[i] = Math.max(dp[i], nums[i] + dp[j]);
+            }
+        }
+
+        return Math.max(...dp);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * k)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming + Segment Tree
+
+::tabs-start
+
+```python
+class SegmentTree:
+    def __init__(self, N):
+        self.n = N
+        while (self.n & (self.n - 1)) != 0:
+            self.n += 1
+        self.tree = [float('-inf')] * (2 * self.n)
+
+    def update(self, i, val):
+        i += self.n
+        self.tree[i] = val
+        while i > 1:
+            i >>= 1
+            self.tree[i] = max(self.tree[i << 1], self.tree[i << 1 | 1])
+
+    def query(self, l, r):
+        res = float('-inf')
+        l += self.n
+        r += self.n + 1
+        while l < r:
+            if l & 1:
+                res = max(res, self.tree[l])
+                l += 1
+            if r & 1:
+                r -= 1
+                res = max(res, self.tree[r])
+            l >>= 1
+            r >>= 1
+        return max(0, res)
+
+class Solution:
+    def constrainedSubsetSum(self, nums: List[int], k: int) -> int:
+        n = len(nums)
+        maxSegTree = SegmentTree(n)
+        maxSegTree.update(0, nums[0])
+        res = nums[0]
+
+        for i in range(1, n):
+            cur = nums[i] + maxSegTree.query(max(0, i - k), i - 1)
+            maxSegTree.update(i, cur)
+            res = max(res, cur)
+
+        return res
+```
+
+```java
+class SegmentTree {
+    int n;
+    int[] tree;
+    
+    public SegmentTree(int N) {
+        this.n = N;
+        while ((this.n & (this.n - 1)) != 0) {
+            this.n++;
+        }
+        tree = new int[2 * this.n];
+        for (int i = 0; i < 2 * this.n; i++) {
+            tree[i] = Integer.MIN_VALUE;
+        }
+    }
+    
+    public void update(int i, int val) {
+        i += n;
+        tree[i] = val;
+        while (i > 1) {
+            i >>= 1;
+            tree[i] = Math.max(tree[i << 1], tree[(i << 1) | 1]);
+        }
+    }
+    
+    public int query(int l, int r) {
+        int res = Integer.MIN_VALUE;
+        l += n;
+        r += n + 1;
+        while (l < r) {
+            if ((l & 1) == 1) {
+                res = Math.max(res, tree[l]);
+                l++;
+            }
+            if ((r & 1) == 1) {
+                r--;
+                res = Math.max(res, tree[r]);
+            }
+            l >>= 1;
+            r >>= 1;
+        }
+        return Math.max(0, res);
+    }
+}
+
+public class Solution {
+    public int constrainedSubsetSum(int[] nums, int k) {
+        int n = nums.length;
+        SegmentTree maxSegTree = new SegmentTree(n);
+        maxSegTree.update(0, nums[0]);
+        int res = nums[0];
+        
+        for (int i = 1; i < n; i++) {
+            int cur = nums[i] + maxSegTree.query(Math.max(0, i - k), i - 1);
+            maxSegTree.update(i, cur);
+            res = Math.max(res, cur);
+        }
+        
+        return res;
+    }
+}
+```
+
+```cpp
+class SegmentTree {
+public:
+    int n;
+    vector<int> tree;
+
+    SegmentTree(int N) {
+        n = N;
+        while ((n & (n - 1)) != 0) {
+            n++;
+        }
+        tree.assign(2 * n, INT_MIN);
+    }
+    
+    void update(int i, int val) {
+        i += n;
+        tree[i] = val;
+        while (i > 1) {
+            i >>= 1;
+            tree[i] = max(tree[i << 1], tree[i << 1 | 1]);
+        }
+    }
+    
+    int query(int l, int r) {
+        int res = INT_MIN;
+        l += n;
+        r += n + 1;
+        while (l < r) {
+            if (l & 1) {
+                res = max(res, tree[l]);
+                l++;
+            }
+            if (r & 1) {
+                r--;
+                res = max(res, tree[r]);
+            }
+            l >>= 1;
+            r >>= 1;
+        }
+        return max(0, res);
+    }
+};
+
+class Solution {
+public:
+    int constrainedSubsetSum(vector<int>& nums, int k) {
+        int n = nums.size();
+        SegmentTree maxSegTree(n);
+        maxSegTree.update(0, nums[0]);
+        int res = nums[0];
+        
+        for (int i = 1; i < n; i++) {
+            int cur = nums[i] + maxSegTree.query(max(0, i - k), i - 1);
+            maxSegTree.update(i, cur);
+            res = max(res, cur);
+        }
+        
+        return res;
+    }
+};
+```
+
+```javascript
+class SegmentTree {
+    /**
+     * @constructor
+     * @param {number} N 
+     */
+    constructor(N) {
+        this.n = N;
+        while ((this.n & (this.n - 1)) !== 0) {
+            this.n++;
+        }
+        this.tree = new Array(2 * this.n).fill(-Infinity);
+    }
+
+    /**
+     * @param {number} i
+     * @param {number} val
+     * @return {void}
+     */
+    update(i, val) {
+        i += this.n;
+        this.tree[i] = val;
+        while (i > 1) {
+            i >>= 1;
+            this.tree[i] = Math.max(this.tree[i << 1], this.tree[i << 1 | 1]);
+        }
+    }
+
+    /**
+     * @param {number} l
+     * @param {number} r
+     * @return {number}
+     */
+    query(l, r) {
+        let res = -Infinity;
+        l += this.n;
+        r += this.n + 1;
+        while (l < r) {
+            if (l & 1) {
+                res = Math.max(res, this.tree[l]);
+                l++;
+            }
+            if (r & 1) {
+                r--;
+                res = Math.max(res, this.tree[r]);
+            }
+            l >>= 1;
+            r >>= 1;
+        }
+        return Math.max(0, res);
+    }
+}
+
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    constrainedSubsetSum(nums, k) {
+        const n = nums.length;
+        const maxSegTree = new SegmentTree(n);
+        maxSegTree.update(0, nums[0]);
+        let res = nums[0];
+
+        for (let i = 1; i < n; i++) {
+            let cur = nums[i] + maxSegTree.query(Math.max(0, i - k), i - 1);
+            maxSegTree.update(i, cur);
+            res = Math.max(res, cur);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Max-Heap
+
+::tabs-start
+
+```python
+class Solution:
+    def constrainedSubsetSum(self, nums: List[int], k: int) -> int:
+        res = nums[0]
+        max_heap = [(-nums[0], 0)]  # max_sum, index
+
+        for i in range(1, len(nums)):
+            while i - max_heap[0][1] > k:
+                heapq.heappop(max_heap)
+
+            cur_max = max(nums[i], nums[i] - max_heap[0][0])
+            res = max(res, cur_max)
+            heapq.heappush(max_heap, (-cur_max, i))
+
+        return res
+```
+
+```java
+public class Solution {
+    public int constrainedSubsetSum(int[] nums, int k) {
+        int res = nums[0];
+        PriorityQueue<int[]> maxHeap = new PriorityQueue<>(
+            (a, b) -> b[0] - a[0] // max_sum, index
+        );
+        maxHeap.offer(new int[]{nums[0], 0});
+
+        for (int i = 1; i < nums.length; i++) {
+            while (i - maxHeap.peek()[1] > k) {
+                maxHeap.poll();
+            }
+
+            int curMax = Math.max(nums[i], nums[i] + maxHeap.peek()[0]);
+            res = Math.max(res, curMax);
+            maxHeap.offer(new int[]{curMax, i});
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int constrainedSubsetSum(vector<int>& nums, int k) {
+        int res = nums[0];
+        priority_queue<pair<int, int>> maxHeap; // max_sum, index
+        maxHeap.emplace(nums[0], 0);
+
+        for (int i = 1; i < nums.size(); i++) {
+            while (i - maxHeap.top().second > k) {
+                maxHeap.pop();
+            }
+
+            int curMax = max(nums[i], nums[i] + maxHeap.top().first);
+            res = max(res, curMax);
+            maxHeap.emplace(curMax, i);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    constrainedSubsetSum(nums, k) {
+        let res = nums[0];
+        const maxHeap = new PriorityQueue(
+            (a, b) => b[0] - a[0] // max_sum, index
+        );
+        maxHeap.enqueue([nums[0], 0]);
+
+        for (let i = 1; i < nums.length; i++) {
+            while (i - maxHeap.front()[1] > k) {
+                maxHeap.dequeue();
+            }
+
+            let curMax = Math.max(nums[i], nums[i] + maxHeap.front()[0]);
+            res = Math.max(res, curMax);
+            maxHeap.enqueue([curMax, i]);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 5. Monotonic Deque
+
+::tabs-start
+
+```python
+class Solution:
+    def constrainedSubsetSum(self, nums: List[int], k: int) -> int:
+        n = len(nums)
+        dq = deque([(0, nums[0])])
+        res = nums[0]
+
+        for i in range(1, n):
+            if dq and dq[0][0] < i - k:
+                dq.popleft()
+
+            cur = max(0, dq[0][1]) + nums[i]
+            while dq and cur > dq[-1][1]:
+                dq.pop()
+
+            dq.append((i, cur))
+            res = max(res, cur)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int constrainedSubsetSum(int[] nums, int k) {
+        int n = nums.length;
+        Deque<int[]> dq = new ArrayDeque<>();
+        dq.offer(new int[]{0, nums[0]});
+        int res = nums[0];
+
+        for (int i = 1; i < n; i++) {
+            if (!dq.isEmpty() && dq.peekFirst()[0] < i - k) {
+                dq.pollFirst();
+            }
+
+            int cur = Math.max(0, dq.peekFirst()[1]) + nums[i];
+            while (!dq.isEmpty() && cur > dq.peekLast()[1]) {
+                dq.pollLast();
+            }
+
+            dq.offer(new int[]{i, cur});
+            res = Math.max(res, cur);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int constrainedSubsetSum(vector<int>& nums, int k) {
+        int n = nums.size();
+        deque<pair<int, int>> dq{{0, nums[0]}};
+        int res = nums[0];
+
+        for (int i = 1; i < n; i++) {
+            if (!dq.empty() && dq.front().first < i - k) {
+                dq.pop_front();
+            }
+
+            int cur = max(0, dq.front().second) + nums[i];
+            while (!dq.empty() && cur > dq.back().second) {
+                dq.pop_back();
+            }
+
+            dq.emplace_back(i, cur);
+            res = max(res, cur);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    constrainedSubsetSum(nums, k) {
+        const n = nums.length;
+        const dq = new Deque([[0, nums[0]]]);
+        let res = nums[0];
+
+        for (let i = 1; i < n; i++) {
+            if (!dq.isEmpty() && dq.front()[0] < i - k) {
+                dq.popFront();
+            }
+
+            let cur = Math.max(0, dq.front()[1]) + nums[i];
+            while (!dq.isEmpty() && cur > dq.back()[1]) {
+                dq.popBack();
+            }
+
+            dq.pushBack([i, cur]);
+            res = Math.max(res, cur);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(k)$
\ No newline at end of file
diff --git a/articles/construct-binary-tree-from-inorder-and-postorder-traversal.md b/articles/construct-binary-tree-from-inorder-and-postorder-traversal.md
new file mode 100644
index 000000000..eb086eacd
--- /dev/null
+++ b/articles/construct-binary-tree-from-inorder-and-postorder-traversal.md
@@ -0,0 +1,470 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def buildTree(self, inorder: List[int], postorder: List[int]) -> Optional[TreeNode]:
+        if not postorder or not inorder:
+            return None
+
+        root = TreeNode(postorder[-1])
+        mid = inorder.index(postorder[-1])
+        root.left = self.buildTree(inorder[:mid], postorder[:mid])
+        root.right = self.buildTree(inorder[mid + 1:], postorder[mid:-1])
+        return root
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode buildTree(int[] inorder, int[] postorder) {
+        if (postorder.length == 0 || inorder.length == 0) {
+            return null;
+        }
+
+        TreeNode root = new TreeNode(postorder[postorder.length - 1]);
+        int mid = 0;
+        for (int i = 0; i < inorder.length; i++) {
+            if (inorder[i] == postorder[postorder.length - 1]) {
+                mid = i;
+                break;
+            }
+        }
+
+        root.left = buildTree(
+            Arrays.copyOfRange(inorder, 0, mid),
+            Arrays.copyOfRange(postorder, 0, mid)
+        );
+        root.right = buildTree(
+            Arrays.copyOfRange(inorder, mid + 1, inorder.length),
+            Arrays.copyOfRange(postorder, mid, postorder.length - 1)
+        );
+
+        return root;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    TreeNode* buildTree(vector<int>& inorder, vector<int>& postorder) {
+        if (postorder.empty() || inorder.empty()) {
+            return nullptr;
+        }
+
+        TreeNode* root = new TreeNode(postorder.back());
+        auto it = find(inorder.begin(), inorder.end(), postorder.back());
+        int mid = distance(inorder.begin(), it);
+
+        vector<int> leftInorder(inorder.begin(), inorder.begin() + mid);
+        vector<int> rightInorder(inorder.begin() + mid + 1, inorder.end());
+        vector<int> leftPostorder(postorder.begin(), postorder.begin() + mid);
+        vector<int> rightPostorder(postorder.begin() + mid, postorder.end() - 1);
+
+        root->left = buildTree(leftInorder, leftPostorder);
+        root->right = buildTree(rightInorder, rightPostorder);
+
+        return root;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {number[]} inorder
+     * @param {number[]} postorder
+     * @return {TreeNode}
+     */
+    buildTree(inorder, postorder) {
+        if (postorder.length === 0 || inorder.length === 0) {
+            return null;
+        }
+
+        const rootVal = postorder[postorder.length - 1];
+        const root = new TreeNode(rootVal);
+        const mid = inorder.indexOf(rootVal);
+
+        root.left = this.buildTree(inorder.slice(0, mid), postorder.slice(0, mid));
+        root.right = this.buildTree(inorder.slice(mid + 1), postorder.slice(mid, postorder.length - 1));
+
+        return root;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Hash Map + Depth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def buildTree(self, inorder: List[int], postorder: List[int]) -> Optional[TreeNode]:
+        inorderIdx = {v: i for i, v in enumerate(inorder)}
+
+        def dfs(l, r):
+            if l > r:
+                return None
+
+            root = TreeNode(postorder.pop())
+            idx = inorderIdx[root.val]
+            root.right = dfs(idx + 1, r)
+            root.left = dfs(l, idx - 1)
+            return root
+
+        return dfs(0, len(inorder) - 1)
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    private HashMap<Integer, Integer> inorderIdx;
+    private int postIdx;
+
+    public TreeNode buildTree(int[] inorder, int[] postorder) {
+        inorderIdx = new HashMap<>();
+        for (int i = 0; i < inorder.length; i++) {
+            inorderIdx.put(inorder[i], i);
+        }
+        postIdx = postorder.length - 1;
+
+        return dfs(0, inorder.length - 1, postorder);
+    }
+
+    private TreeNode dfs(int l, int r, int[] postorder) {
+        if (l > r) {
+            return null;
+        }
+
+        TreeNode root = new TreeNode(postorder[postIdx--]);
+        int idx = inorderIdx.get(root.val);
+        root.right = dfs(idx + 1, r, postorder);
+        root.left = dfs(l, idx - 1, postorder);
+        return root;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    unordered_map<int, int> inorderIdx;
+    int postIdx;
+
+    TreeNode* buildTree(vector<int>& inorder, vector<int>& postorder) {
+        for (int i = 0; i < inorder.size(); i++) {
+            inorderIdx[inorder[i]] = i;
+        }
+        postIdx = postorder.size() - 1;
+
+        return dfs(0, inorder.size() - 1, postorder);
+    }
+
+private:
+    TreeNode* dfs(int l, int r, vector<int>& postorder) {
+        if (l > r) {
+            return nullptr;
+        }
+
+        TreeNode* root = new TreeNode(postorder[postIdx--]);
+        int idx = inorderIdx[root->val];
+        root->right = dfs(idx + 1, r, postorder);
+        root->left = dfs(l, idx - 1, postorder);
+        return root;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {number[]} inorder
+     * @param {number[]} postorder
+     * @return {TreeNode}
+     */
+    buildTree(inorder, postorder) {
+        const inorderIdx = new Map();
+        inorder.forEach((val, idx) => inorderIdx.set(val, idx));
+        let postIdx = postorder.length - 1;
+
+        const dfs = (l, r) => {
+            if (l > r) return null;
+
+            const root = new TreeNode(postorder[postIdx--]);
+            const idx = inorderIdx.get(root.val);
+            root.right = dfs(idx + 1, r);
+            root.left = dfs(l, idx - 1);
+            return root;
+        };
+
+        return dfs(0, inorder.length - 1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Depth First Search (Optimal)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def buildTree(self, inorder: List[int], postorder: List[int]) -> Optional[TreeNode]:
+        postIdx = inIdx = len(postorder) - 1
+        def dfs(limit):
+            nonlocal postIdx, inIdx
+            if postIdx < 0:
+                return None
+            if inorder[inIdx] == limit:
+                inIdx -= 1
+                return None
+            
+            root = TreeNode(postorder[postIdx])
+            postIdx -= 1
+            root.right = dfs(root.val)
+            root.left = dfs(limit)
+            return root
+        return dfs(float('inf'))
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    private int postIdx;
+    private int inIdx;
+
+    public TreeNode buildTree(int[] inorder, int[] postorder) {
+        postIdx = postorder.length - 1;
+        inIdx = inorder.length - 1;
+
+        return dfs(postorder, inorder, Integer.MAX_VALUE);
+    }
+
+    private TreeNode dfs(int[] postorder, int[] inorder, int limit) {
+        if (postIdx < 0) {
+            return null;
+        }
+
+        if (inorder[inIdx] == limit) {
+            inIdx--;
+            return null;
+        }
+
+        TreeNode root = new TreeNode(postorder[postIdx--]);
+        root.right = dfs(postorder, inorder, root.val);
+        root.left = dfs(postorder, inorder, limit);
+        return root;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int postIdx;
+    int inIdx;
+
+    TreeNode* buildTree(vector<int>& inorder, vector<int>& postorder) {
+        postIdx = postorder.size() - 1;
+        inIdx = inorder.size() - 1;
+
+        return dfs(postorder, inorder, numeric_limits<int>::max());
+    }
+
+private:
+    TreeNode* dfs(vector<int>& postorder, vector<int>& inorder, int limit) {
+        if (postIdx < 0) {
+            return nullptr;
+        }
+
+        if (inorder[inIdx] == limit) {
+            inIdx--;
+            return nullptr;
+        }
+
+        TreeNode* root = new TreeNode(postorder[postIdx--]);
+        root->right = dfs(postorder, inorder, root->val);
+        root->left = dfs(postorder, inorder, limit);
+        return root;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {number[]} inorder
+     * @param {number[]} postorder
+     * @return {TreeNode}
+     */
+    buildTree(inorder, postorder) {
+        let postIdx = postorder.length - 1;
+        let inIdx = inorder.length - 1;
+
+        const dfs = (limit) => {
+            if (postIdx < 0) return null;
+
+            if (inorder[inIdx] === limit) {
+                inIdx--;
+                return null;
+            }
+
+            const root = new TreeNode(postorder[postIdx--]);
+            root.right = dfs(root.val);
+            root.left = dfs(limit);
+            return root;
+        };
+
+        return dfs(Infinity);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
\ No newline at end of file
diff --git a/articles/construct-quad-tree.md b/articles/construct-quad-tree.md
new file mode 100644
index 000000000..5e2b91594
--- /dev/null
+++ b/articles/construct-quad-tree.md
@@ -0,0 +1,945 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+"""
+# Definition for a QuadTree node.
+class Node:
+    def __init__(self, val, isLeaf, topLeft, topRight, bottomLeft, bottomRight):
+        self.val = val
+        self.isLeaf = isLeaf
+        self.topLeft = topLeft
+        self.topRight = topRight
+        self.bottomLeft = bottomLeft
+        self.bottomRight = bottomRight
+"""
+
+class Solution:
+    def construct(self, grid: List[List[int]]) -> 'Node':
+        def dfs(n, r, c):
+            allSame = True
+            for i in range(n):
+                for j in range(n):
+                    if grid[r][c] != grid[r + i][c + j]:
+                        allSame = False
+                        break
+            if allSame:
+                return Node(grid[r][c], True)
+            
+            n = n // 2
+            topleft = dfs(n, r, c)
+            topright = dfs(n, r, c + n)
+            bottomleft = dfs(n, r + n, c)
+            bottomright = dfs(n, r + n, c + n)
+            
+            return Node(0, False, topleft, topright, bottomleft, bottomright)
+        
+        return dfs(len(grid), 0, 0)
+```
+
+```java
+/*
+// Definition for a QuadTree node.
+class Node {
+    public boolean val;
+    public boolean isLeaf;
+    public Node topLeft;
+    public Node topRight;
+    public Node bottomLeft;
+    public Node bottomRight;
+
+    
+    public Node() {
+        this.val = false;
+        this.isLeaf = false;
+        this.topLeft = null;
+        this.topRight = null;
+        this.bottomLeft = null;
+        this.bottomRight = null;
+    }
+    
+    public Node(boolean val, boolean isLeaf) {
+        this.val = val;
+        this.isLeaf = isLeaf;
+        this.topLeft = null;
+        this.topRight = null;
+        this.bottomLeft = null;
+        this.bottomRight = null;
+    }
+    
+    public Node(boolean val, boolean isLeaf, Node topLeft, Node topRight, Node bottomLeft, Node bottomRight) {
+        this.val = val;
+        this.isLeaf = isLeaf;
+        this.topLeft = topLeft;
+        this.topRight = topRight;
+        this.bottomLeft = bottomLeft;
+        this.bottomRight = bottomRight;
+    }
+}
+*/
+
+public class Solution {
+    public Node construct(int[][] grid) {
+        return dfs(grid, grid.length, 0, 0);
+    }
+
+    private Node dfs(int[][] grid, int n, int r, int c) {
+        boolean allSame = true;
+
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < n; j++) {
+                if (grid[r][c] != grid[r + i][c + j]) {
+                    allSame = false;
+                    break;
+                }
+            }
+        }
+
+        if (allSame) {
+            return new Node(grid[r][c] == 1, true);
+        }
+
+        int mid = n / 2;
+        Node topLeft = dfs(grid, mid, r, c);
+        Node topRight = dfs(grid, mid, r, c + mid);
+        Node bottomLeft = dfs(grid, mid, r + mid, c);
+        Node bottomRight = dfs(grid, mid, r + mid, c + mid);
+
+        return new Node(false, false, topLeft, topRight, bottomLeft, bottomRight);
+    }
+}
+```
+
+```cpp
+/*
+// Definition for a QuadTree node.
+class Node {
+public:
+    bool val;
+    bool isLeaf;
+    Node* topLeft;
+    Node* topRight;
+    Node* bottomLeft;
+    Node* bottomRight;
+    
+    Node() {
+        val = false;
+        isLeaf = false;
+        topLeft = NULL;
+        topRight = NULL;
+        bottomLeft = NULL;
+        bottomRight = NULL;
+    }
+    
+    Node(bool _val, bool _isLeaf) {
+        val = _val;
+        isLeaf = _isLeaf;
+        topLeft = NULL;
+        topRight = NULL;
+        bottomLeft = NULL;
+        bottomRight = NULL;
+    }
+    
+    Node(bool _val, bool _isLeaf, Node* _topLeft, Node* _topRight, Node* _bottomLeft, Node* _bottomRight) {
+        val = _val;
+        isLeaf = _isLeaf;
+        topLeft = _topLeft;
+        topRight = _topRight;
+        bottomLeft = _bottomLeft;
+        bottomRight = _bottomRight;
+    }
+};
+*/
+
+class Solution {
+public:
+    Node* construct(vector<vector<int>>& grid) {
+        return dfs(grid, grid.size(), 0, 0);
+    }
+
+private:
+    Node* dfs(vector<vector<int>>& grid, int n, int r, int c) {
+        bool allSame = true;
+
+        for (int i = 0; i < n && allSame; ++i) {
+            for (int j = 0; j < n; ++j) {
+                if (grid[r][c] != grid[r + i][c + j]) {
+                    allSame = false;
+                    break;
+                }
+            }
+        }
+
+        if (allSame) {
+            return new Node(grid[r][c] == 1, true);
+        }
+
+        int mid = n / 2;
+        Node* topLeft = dfs(grid, mid, r, c);
+        Node* topRight = dfs(grid, mid, r, c + mid);
+        Node* bottomLeft = dfs(grid, mid, r + mid, c);
+        Node* bottomRight = dfs(grid, mid, r + mid, c + mid);
+
+        return new Node(false, false, topLeft, topRight, bottomLeft, bottomRight);
+    }
+};
+```
+
+```javascript
+/**
+ * // Definition for a QuadTree node.
+ * class Node {
+ *     constructor(val,isLeaf,topLeft,topRight,bottomLeft,bottomRight) {
+ *         this.val = val;
+ *         this.isLeaf = isLeaf;
+ *         this.topLeft = topLeft;
+ *         this.topRight = topRight;
+ *         this.bottomLeft = bottomLeft;
+ *         this.bottomRight = bottomRight;
+ *     }
+ * }
+ */
+
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {Node}
+     */
+    construct(grid) {
+        const dfs = (n, r, c) => {
+            let allSame = true;
+
+            for (let i = 0; i < n && allSame; i++) {
+                for (let j = 0; j < n; j++) {
+                    if (grid[r][c] !== grid[r + i][c + j]) {
+                        allSame = false;
+                        break;
+                    }
+                }
+            }
+
+            if (allSame) {
+                return new Node(grid[r][c] === 1, true);
+            }
+
+            const mid = Math.floor(n / 2);
+            const topLeft = dfs(mid, r, c);
+            const topRight = dfs(mid, r, c + mid);
+            const bottomLeft = dfs(mid, r + mid, c);
+            const bottomRight = dfs(mid, r + mid, c + mid);
+
+            return new Node(false, false, topLeft, topRight, bottomLeft, bottomRight);
+        };
+
+        return dfs(grid.length, 0, 0);
+    }
+}
+```
+
+```csharp
+/*
+// Definition for a QuadTree node.
+public class Node {
+    public bool val;
+    public bool isLeaf;
+    public Node topLeft;
+    public Node topRight;
+    public Node bottomLeft;
+    public Node bottomRight;
+
+    public Node() {
+        val = false;
+        isLeaf = false;
+        topLeft = null;
+        topRight = null;
+        bottomLeft = null;
+        bottomRight = null;
+    }
+    
+    public Node(bool _val, bool _isLeaf) {
+        val = _val;
+        isLeaf = _isLeaf;
+        topLeft = null;
+        topRight = null;
+        bottomLeft = null;
+        bottomRight = null;
+    }
+    
+    public Node(bool _val,bool _isLeaf,Node _topLeft,Node _topRight,Node _bottomLeft,Node _bottomRight) {
+        val = _val;
+        isLeaf = _isLeaf;
+        topLeft = _topLeft;
+        topRight = _topRight;
+        bottomLeft = _bottomLeft;
+        bottomRight = _bottomRight;
+    }
+}
+*/
+
+public class Solution {
+    public Node Construct(int[][] grid) {
+        return Dfs(grid, grid.Length, 0, 0);
+    }
+
+    private Node Dfs(int[][] grid, int n, int r, int c) {
+        bool allSame = true;
+        for (int i = 0; i < n && allSame; i++) {
+            for (int j = 0; j < n && allSame; j++) {
+                if (grid[r][c] != grid[r + i][c + j]) {
+                    allSame = false;
+                }
+            }
+        }
+
+        if (allSame) {
+            return new Node(grid[r][c] == 1, true);
+        }
+
+        int half = n / 2;
+        Node topLeft = Dfs(grid, half, r, c);
+        Node topRight = Dfs(grid, half, r, c + half);
+        Node bottomLeft = Dfs(grid, half, r + half, c);
+        Node bottomRight = Dfs(grid, half, r + half, c + half);
+
+        return new Node(false, false, topLeft, topRight, bottomLeft, bottomRight);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 \log n)$
+* Space complexity: $O(\log n)$ for recursion stack.
+
+---
+
+## 2. Recursion (Optimal)
+
+::tabs-start
+
+```python
+"""
+# Definition for a QuadTree node.
+class Node:
+    def __init__(self, val, isLeaf, topLeft, topRight, bottomLeft, bottomRight):
+        self.val = val
+        self.isLeaf = isLeaf
+        self.topLeft = topLeft
+        self.topRight = topRight
+        self.bottomLeft = bottomLeft
+        self.bottomRight = bottomRight
+"""
+
+class Solution:
+    def construct(self, grid: List[List[int]]) -> 'Node':
+        def dfs(n, r, c):
+            if n == 1:
+                return Node(grid[r][c] == 1, True)
+
+            mid = n // 2
+            topLeft = dfs(mid, r, c)
+            topRight = dfs(mid, r, c + mid)
+            bottomLeft = dfs(mid, r + mid, c)
+            bottomRight = dfs(mid, r + mid, c + mid)
+
+            if (topLeft.isLeaf and topRight.isLeaf and 
+                bottomLeft.isLeaf and bottomRight.isLeaf and
+                topLeft.val == topRight.val == bottomLeft.val == bottomRight.val):
+                return Node(topLeft.val, True)
+
+            return Node(False, False, topLeft, topRight, bottomLeft, bottomRight)
+
+        return dfs(len(grid), 0, 0)
+```
+
+```java
+/*
+// Definition for a QuadTree node.
+class Node {
+    public boolean val;
+    public boolean isLeaf;
+    public Node topLeft;
+    public Node topRight;
+    public Node bottomLeft;
+    public Node bottomRight;
+
+    
+    public Node() {
+        this.val = false;
+        this.isLeaf = false;
+        this.topLeft = null;
+        this.topRight = null;
+        this.bottomLeft = null;
+        this.bottomRight = null;
+    }
+    
+    public Node(boolean val, boolean isLeaf) {
+        this.val = val;
+        this.isLeaf = isLeaf;
+        this.topLeft = null;
+        this.topRight = null;
+        this.bottomLeft = null;
+        this.bottomRight = null;
+    }
+    
+    public Node(boolean val, boolean isLeaf, Node topLeft, Node topRight, Node bottomLeft, Node bottomRight) {
+        this.val = val;
+        this.isLeaf = isLeaf;
+        this.topLeft = topLeft;
+        this.topRight = topRight;
+        this.bottomLeft = bottomLeft;
+        this.bottomRight = bottomRight;
+    }
+}
+*/
+
+public class Solution {
+    public Node construct(int[][] grid) {
+        return dfs(grid, grid.length, 0, 0);
+    }
+
+    private Node dfs(int[][] grid, int n, int r, int c) {
+        if (n == 1) {
+            return new Node(grid[r][c] == 1, true);
+        }
+
+        int mid = n / 2;
+        Node topLeft = dfs(grid, mid, r, c);
+        Node topRight = dfs(grid, mid, r, c + mid);
+        Node bottomLeft = dfs(grid, mid, r + mid, c);
+        Node bottomRight = dfs(grid, mid, r + mid, c + mid);
+
+        if (topLeft.isLeaf && topRight.isLeaf && 
+            bottomLeft.isLeaf && bottomRight.isLeaf &&
+            topLeft.val == topRight.val && 
+            topLeft.val == bottomLeft.val && 
+            topLeft.val == bottomRight.val) {
+            return new Node(topLeft.val, true);
+        }
+
+        return new Node(false, false, topLeft, topRight, bottomLeft, bottomRight);
+    }
+}
+```
+
+```cpp
+/*
+// Definition for a QuadTree node.
+class Node {
+public:
+    bool val;
+    bool isLeaf;
+    Node* topLeft;
+    Node* topRight;
+    Node* bottomLeft;
+    Node* bottomRight;
+    
+    Node() {
+        val = false;
+        isLeaf = false;
+        topLeft = NULL;
+        topRight = NULL;
+        bottomLeft = NULL;
+        bottomRight = NULL;
+    }
+    
+    Node(bool _val, bool _isLeaf) {
+        val = _val;
+        isLeaf = _isLeaf;
+        topLeft = NULL;
+        topRight = NULL;
+        bottomLeft = NULL;
+        bottomRight = NULL;
+    }
+    
+    Node(bool _val, bool _isLeaf, Node* _topLeft, Node* _topRight, Node* _bottomLeft, Node* _bottomRight) {
+        val = _val;
+        isLeaf = _isLeaf;
+        topLeft = _topLeft;
+        topRight = _topRight;
+        bottomLeft = _bottomLeft;
+        bottomRight = _bottomRight;
+    }
+};
+*/
+
+class Solution {
+public:
+    Node* construct(vector<vector<int>>& grid) {
+        return dfs(grid, grid.size(), 0, 0);
+    }
+
+private:
+    Node* dfs(vector<vector<int>>& grid, int n, int r, int c) {
+        if (n == 1) {
+            return new Node(grid[r][c] == 1, true);
+        }
+
+        int mid = n / 2;
+        Node* topLeft = dfs(grid, mid, r, c);
+        Node* topRight = dfs(grid, mid, r, c + mid);
+        Node* bottomLeft = dfs(grid, mid, r + mid, c);
+        Node* bottomRight = dfs(grid, mid, r + mid, c + mid);
+
+        if (topLeft->isLeaf && topRight->isLeaf &&
+            bottomLeft->isLeaf && bottomRight->isLeaf &&
+            topLeft->val == topRight->val &&
+            topLeft->val == bottomLeft->val &&
+            topLeft->val == bottomRight->val) {
+            return new Node(topLeft->val, true);
+        }
+
+        return new Node(false, false, topLeft, topRight, bottomLeft, bottomRight);
+    }
+};
+```
+
+```javascript
+/**
+ * // Definition for a QuadTree node.
+ * class Node {
+ *     constructor(val,isLeaf,topLeft,topRight,bottomLeft,bottomRight) {
+ *         this.val = val;
+ *         this.isLeaf = isLeaf;
+ *         this.topLeft = topLeft;
+ *         this.topRight = topRight;
+ *         this.bottomLeft = bottomLeft;
+ *         this.bottomRight = bottomRight;
+ *     }
+ * }
+ */
+
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {Node}
+     */
+    construct(grid) {
+        const dfs = (n, r, c) => {
+            if (n === 1) {
+                return new Node(grid[r][c] === 1, true);
+            }
+
+            const mid = Math.floor(n / 2);
+            const topLeft = dfs(mid, r, c);
+            const topRight = dfs(mid, r, c + mid);
+            const bottomLeft = dfs(mid, r + mid, c);
+            const bottomRight = dfs(mid, r + mid, c + mid);
+
+            if (topLeft.isLeaf && topRight.isLeaf &&
+                bottomLeft.isLeaf && bottomRight.isLeaf &&
+                topLeft.val === topRight.val &&
+                topLeft.val === bottomLeft.val &&
+                topLeft.val === bottomRight.val) {
+                return new Node(topLeft.val, true);
+            }
+
+            return new Node(false, false, topLeft, topRight, bottomLeft, bottomRight);
+        };
+
+        return dfs(grid.length, 0, 0);
+    }
+}
+```
+
+```csharp
+/*
+// Definition for a QuadTree node.
+public class Node {
+    public bool val;
+    public bool isLeaf;
+    public Node topLeft;
+    public Node topRight;
+    public Node bottomLeft;
+    public Node bottomRight;
+
+    public Node() {
+        val = false;
+        isLeaf = false;
+        topLeft = null;
+        topRight = null;
+        bottomLeft = null;
+        bottomRight = null;
+    }
+    
+    public Node(bool _val, bool _isLeaf) {
+        val = _val;
+        isLeaf = _isLeaf;
+        topLeft = null;
+        topRight = null;
+        bottomLeft = null;
+        bottomRight = null;
+    }
+    
+    public Node(bool _val,bool _isLeaf,Node _topLeft,Node _topRight,Node _bottomLeft,Node _bottomRight) {
+        val = _val;
+        isLeaf = _isLeaf;
+        topLeft = _topLeft;
+        topRight = _topRight;
+        bottomLeft = _bottomLeft;
+        bottomRight = _bottomRight;
+    }
+}
+*/
+
+public class Solution {
+    public Node Construct(int[][] grid) {
+        return Dfs(grid, grid.Length, 0, 0);
+    }
+
+    private Node Dfs(int[][] grid, int n, int r, int c) {
+        if (n == 1) {
+            return new Node(grid[r][c] == 1, true);
+        }
+
+        int mid = n / 2;
+        Node topLeft = Dfs(grid, mid, r, c);
+        Node topRight = Dfs(grid, mid, r, c + mid);
+        Node bottomLeft = Dfs(grid, mid, r + mid, c);
+        Node bottomRight = Dfs(grid, mid, r + mid, c + mid);
+
+        if (topLeft.isLeaf && topRight.isLeaf && 
+            bottomLeft.isLeaf && bottomRight.isLeaf &&
+            topLeft.val == topRight.val &&
+            topRight.val == bottomLeft.val &&
+            bottomLeft.val == bottomRight.val) {
+            return new Node(topLeft.val, true);
+        }
+
+        return new Node(false, false, topLeft, topRight, bottomLeft, bottomRight);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(\log n)$ for recursion stack.
+
+---
+
+## 3. Recursion (Space Optimized)
+
+::tabs-start
+
+```python
+"""
+# Definition for a QuadTree node.
+class Node:
+    def __init__(self, val, isLeaf, topLeft, topRight, bottomLeft, bottomRight):
+        self.val = val
+        self.isLeaf = isLeaf
+        self.topLeft = topLeft
+        self.topRight = topRight
+        self.bottomLeft = bottomLeft
+        self.bottomRight = bottomRight
+"""
+
+class Solution:
+    def construct(self, grid: List[List[int]]) -> 'Node':
+        leafNodes = {
+            0: Node(False, True),
+            1: Node(True, True)
+        }
+
+        def dfs(n, r, c):
+            if n == 1:
+                return leafNodes[grid[r][c]]
+
+            n //= 2
+            topLeft = dfs(n, r, c)
+            topRight = dfs(n, r, c + n)
+            bottomLeft = dfs(n, r + n, c)
+            bottomRight = dfs(n, r + n, c + n)
+
+            if (topLeft.isLeaf and topRight.isLeaf and 
+                bottomLeft.isLeaf and bottomRight.isLeaf and
+                topLeft.val == topRight.val == bottomLeft.val == bottomRight.val):
+                return topLeft
+
+            return Node(False, False, topLeft, topRight, bottomLeft, bottomRight)
+
+        return dfs(len(grid), 0, 0)
+```
+
+```java
+/*
+// Definition for a QuadTree node.
+class Node {
+    public boolean val;
+    public boolean isLeaf;
+    public Node topLeft;
+    public Node topRight;
+    public Node bottomLeft;
+    public Node bottomRight;
+
+    
+    public Node() {
+        this.val = false;
+        this.isLeaf = false;
+        this.topLeft = null;
+        this.topRight = null;
+        this.bottomLeft = null;
+        this.bottomRight = null;
+    }
+    
+    public Node(boolean val, boolean isLeaf) {
+        this.val = val;
+        this.isLeaf = isLeaf;
+        this.topLeft = null;
+        this.topRight = null;
+        this.bottomLeft = null;
+        this.bottomRight = null;
+    }
+    
+    public Node(boolean val, boolean isLeaf, Node topLeft, Node topRight, Node bottomLeft, Node bottomRight) {
+        this.val = val;
+        this.isLeaf = isLeaf;
+        this.topLeft = topLeft;
+        this.topRight = topRight;
+        this.bottomLeft = bottomLeft;
+        this.bottomRight = bottomRight;
+    }
+}
+*/
+
+public class Solution {
+    private static final Node falseLeaf = new Node(false, true);
+    private static final Node trueLeaf = new Node(true, true);
+
+    public Node construct(int[][] grid) {
+        return dfs(grid, grid.length, 0, 0);
+    }
+
+    private Node dfs(int[][] grid, int n, int r, int c) {
+        if (n == 1) {
+            return grid[r][c] == 1 ? trueLeaf : falseLeaf;
+        }
+
+        n /= 2;
+        Node topLeft = dfs(grid, n, r, c);
+        Node topRight = dfs(grid, n, r, c + n);
+        Node bottomLeft = dfs(grid, n, r + n, c);
+        Node bottomRight = dfs(grid, n, r + n, c + n);
+
+        if (topLeft.isLeaf && topRight.isLeaf && 
+            bottomLeft.isLeaf && bottomRight.isLeaf &&
+            topLeft.val == topRight.val && topLeft.val == bottomLeft.val && 
+            topLeft.val == bottomRight.val) {
+            return topLeft;
+        }
+
+        return new Node(false, false, topLeft, topRight, bottomLeft, bottomRight);
+    }
+}
+```
+
+```cpp
+/*
+// Definition for a QuadTree node.
+class Node {
+public:
+    bool val;
+    bool isLeaf;
+    Node* topLeft;
+    Node* topRight;
+    Node* bottomLeft;
+    Node* bottomRight;
+    
+    Node() {
+        val = false;
+        isLeaf = false;
+        topLeft = NULL;
+        topRight = NULL;
+        bottomLeft = NULL;
+        bottomRight = NULL;
+    }
+    
+    Node(bool _val, bool _isLeaf) {
+        val = _val;
+        isLeaf = _isLeaf;
+        topLeft = NULL;
+        topRight = NULL;
+        bottomLeft = NULL;
+        bottomRight = NULL;
+    }
+    
+    Node(bool _val, bool _isLeaf, Node* _topLeft, Node* _topRight, Node* _bottomLeft, Node* _bottomRight) {
+        val = _val;
+        isLeaf = _isLeaf;
+        topLeft = _topLeft;
+        topRight = _topRight;
+        bottomLeft = _bottomLeft;
+        bottomRight = _bottomRight;
+    }
+};
+*/
+
+class Solution {
+private:
+    Node* falseLeaf = new Node(false, true);
+    Node* trueLeaf = new Node(true, true);
+
+public:
+    Node* construct(vector<vector<int>>& grid) {
+        return dfs(grid, grid.size(), 0, 0);
+    }
+
+private:
+    Node* dfs(vector<vector<int>>& grid, int n, int r, int c) {
+        if (n == 1) {
+            return grid[r][c] == 1 ? trueLeaf : falseLeaf;
+        }
+
+        n /= 2;
+        Node* topLeft = dfs(grid, n, r, c);
+        Node* topRight = dfs(grid, n, r, c + n);
+        Node* bottomLeft = dfs(grid, n, r + n, c);
+        Node* bottomRight = dfs(grid, n, r + n, c + n);
+
+        if (topLeft->isLeaf && topRight->isLeaf &&
+            bottomLeft->isLeaf && bottomRight->isLeaf &&
+            topLeft->val == topRight->val && topLeft->val == bottomLeft->val &&
+            topLeft->val == bottomRight->val) {
+            return topLeft;
+        }
+
+        return new Node(false, false, topLeft, topRight, bottomLeft, bottomRight);
+    }
+};
+```
+
+```javascript
+/**
+ * // Definition for a QuadTree node.
+ * class Node {
+ *     constructor(val,isLeaf,topLeft,topRight,bottomLeft,bottomRight) {
+ *         this.val = val;
+ *         this.isLeaf = isLeaf;
+ *         this.topLeft = topLeft;
+ *         this.topRight = topRight;
+ *         this.bottomLeft = bottomLeft;
+ *         this.bottomRight = bottomRight;
+ *     }
+ * }
+ */
+
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {Node}
+     */
+    construct(grid) {
+        const falseLeaf = new Node(false, true);
+        const trueLeaf = new Node(true, true);
+
+        const dfs = (n, r, c) => {
+            if (n === 1) {
+                return grid[r][c] === 1 ? trueLeaf : falseLeaf;
+            }
+
+            n = Math.floor(n / 2);
+            const topLeft = dfs(n, r, c);
+            const topRight = dfs(n, r, c + n);
+            const bottomLeft = dfs(n, r + n, c);
+            const bottomRight = dfs(n, r + n, c + n);
+
+            if (topLeft.isLeaf && topRight.isLeaf &&
+                bottomLeft.isLeaf && bottomRight.isLeaf &&
+                topLeft.val === topRight.val && topLeft.val === bottomLeft.val &&
+                topLeft.val === bottomRight.val) {
+                return topLeft;
+            }
+
+            return new Node(false, false, topLeft, topRight, bottomLeft, bottomRight);
+        };
+
+        return dfs(grid.length, 0, 0);
+    }
+}
+```
+
+```csharp
+/*
+// Definition for a QuadTree node.
+public class Node {
+    public bool val;
+    public bool isLeaf;
+    public Node topLeft;
+    public Node topRight;
+    public Node bottomLeft;
+    public Node bottomRight;
+
+    public Node() {
+        val = false;
+        isLeaf = false;
+        topLeft = null;
+        topRight = null;
+        bottomLeft = null;
+        bottomRight = null;
+    }
+    
+    public Node(bool _val, bool _isLeaf) {
+        val = _val;
+        isLeaf = _isLeaf;
+        topLeft = null;
+        topRight = null;
+        bottomLeft = null;
+        bottomRight = null;
+    }
+    
+    public Node(bool _val,bool _isLeaf,Node _topLeft,Node _topRight,Node _bottomLeft,Node _bottomRight) {
+        val = _val;
+        isLeaf = _isLeaf;
+        topLeft = _topLeft;
+        topRight = _topRight;
+        bottomLeft = _bottomLeft;
+        bottomRight = _bottomRight;
+    }
+}
+*/
+
+public class Solution {
+    private readonly Node falseLeaf = new Node(false, true);
+    private readonly Node trueLeaf = new Node(true, true);
+
+    public Node Construct(int[][] grid) {
+        int n = grid.Length;
+        return Dfs(grid, n, 0, 0);
+    }
+
+    private Node Dfs(int[][] grid, int n, int r, int c) {
+        if (n == 1) {
+            return grid[r][c] == 1 ? trueLeaf : falseLeaf;
+        }
+
+        int half = n / 2;
+        Node topLeft = Dfs(grid, half, r, c);
+        Node topRight = Dfs(grid, half, r, c + half);
+        Node bottomLeft = Dfs(grid, half, r + half, c);
+        Node bottomRight = Dfs(grid, half, r + half, c + half);
+
+        if (topLeft.isLeaf && topRight.isLeaf &&
+            bottomLeft.isLeaf && bottomRight.isLeaf &&
+            topLeft.val == topRight.val &&
+            topLeft.val == bottomLeft.val &&
+            topLeft.val == bottomRight.val) {
+            return topLeft;
+        }
+
+        return new Node(false, false, topLeft, topRight, bottomLeft, bottomRight);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(\log n)$ for recursion stack.
\ No newline at end of file
diff --git a/articles/construct-string-from-binary-tree.md b/articles/construct-string-from-binary-tree.md
new file mode 100644
index 000000000..98b9da146
--- /dev/null
+++ b/articles/construct-string-from-binary-tree.md
@@ -0,0 +1,518 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def tree2str(self, root: Optional[TreeNode]) -> str:
+        if not root: 
+            return ""
+        
+        cur = root.val
+        left = self.tree2str(root.left)
+        right = self.tree2str(root.right)
+        
+        if left and right:
+            return f"{cur}({left})({right})"
+        
+        if right:
+            return f"{cur}()({right})"
+        
+        if left:
+            return f"{cur}({left})"
+        
+        return str(cur)
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public String tree2str(TreeNode root) {
+        if (root == null) {
+            return "";
+        }
+
+        String cur = Integer.toString(root.val);
+        String left = tree2str(root.left);
+        String right = tree2str(root.right);
+
+        if (!left.isEmpty() && !right.isEmpty()) {
+            return cur + "(" + left + ")" + "(" + right + ")";
+        }
+
+        if (!right.isEmpty()) {
+            return cur + "()" + "(" + right + ")";
+        }
+
+        if (!left.isEmpty()) {
+            return cur + "(" + left + ")";
+        }
+
+        return cur;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    string tree2str(TreeNode* root) {
+        if (!root) {
+            return "";
+        }
+
+        string cur = to_string(root->val);
+        string left = tree2str(root->left);
+        string right = tree2str(root->right);
+
+        if (!left.empty() && !right.empty()) {
+            return cur + "(" + left + ")(" + right + ")";
+        }
+
+        if (!right.empty()) {
+            return cur + "()(" + right + ")";
+        }
+
+        if (!left.empty()) {
+            return cur + "(" + left + ")";
+        }
+
+        return cur;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {string}
+     */
+    tree2str(root) {
+        if (!root) {
+            return "";
+        }
+
+        const cur = root.val.toString();
+        const left = this.tree2str(root.left);
+        const right = this.tree2str(root.right);
+
+        if (left && right) {
+            return `${cur}(${left})(${right})`;
+        }
+
+        if (right) {
+            return `${cur}()(${right})`;
+        }
+
+        if (left) {
+            return `${cur}(${left})`;
+        }
+
+        return cur;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Depth First Search (Optimal)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def tree2str(self, root: Optional[TreeNode]) -> str:
+        res = []
+
+        def preorder(root):
+            if not root:
+                return
+            res.append("(")
+            res.append(str(root.val))
+            if not root.left and root.right:
+                res.append("()")
+            preorder(root.left)
+            preorder(root.right)
+            res.append(")")
+
+        preorder(root)
+        return "".join(res)[1:-1]
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public String tree2str(TreeNode root) {
+        StringBuilder res = new StringBuilder();
+
+        preorder(root, res);
+        return res.substring(1, res.length() - 1);
+    }
+
+    private void preorder(TreeNode root, StringBuilder res) {
+        if (root == null) return;
+
+        res.append("(").append(root.val);
+        if (root.left == null && root.right != null) {
+            res.append("()");
+        }
+        preorder(root.left, res);
+        preorder(root.right, res);
+        res.append(")");
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    string tree2str(TreeNode* root) {
+        string res;
+        preorder(root, res);
+        return res.substr(1, res.size() - 2);
+    }
+
+private:
+    void preorder(TreeNode* root, string& res) {
+        if (!root) return;
+
+        res += "(" + to_string(root->val);
+        if (!root->left && root->right) {
+            res += "()";
+        }
+        preorder(root->left, res);
+        preorder(root->right, res);
+        res += ")";
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {string}
+     */
+    tree2str(root) {
+        let res = [];
+
+        const preorder = (root) => {
+            if (!root) return;
+
+            res.push("(");
+            res.push(root.val.toString());
+            if (!root.left && root.right) {
+                res.push("()");
+            }
+            preorder(root.left);
+            preorder(root.right);
+            res.push(")");
+        };
+
+        preorder(root);
+        return res.join("").slice(1, -1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Iterative DFS
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def tree2str(self, root: Optional[TreeNode]) -> str:
+        if not root:
+            return ""
+
+        res = []
+        stack = []
+        last_visited = None
+        cur = root
+
+        while cur or stack:
+            if cur:
+                res.append(f"({cur.val}")
+                if not cur.left and cur.right:
+                    res.append("()")
+
+                stack.append(cur)
+                cur = cur.left
+            else:
+                top = stack[-1]
+                if top.right and last_visited != top.right:
+                    cur = top.right
+                else:
+                    stack.pop()
+                    res.append(")")
+                    last_visited = top
+
+        return "".join(res)[1:-1]
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public String tree2str(TreeNode root) {
+        if (root == null) {
+            return "";
+        }
+
+        StringBuilder res = new StringBuilder();
+        Stack<TreeNode> stack = new Stack<>();
+        TreeNode lastVisited = null;
+        TreeNode cur = root;
+
+        while (cur != null || !stack.isEmpty()) {
+            if (cur != null) {
+                res.append("(").append(cur.val);
+                if (cur.left == null && cur.right != null) {
+                    res.append("()");
+                }
+
+                stack.push(cur);
+                cur = cur.left;
+            } else {
+                TreeNode top = stack.peek();
+                if (top.right != null && lastVisited != top.right) {
+                    cur = top.right;
+                } else {
+                    stack.pop();
+                    res.append(")");
+                    lastVisited = top;
+                }
+            }
+        }
+
+        return res.substring(1, res.length() - 1);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    string tree2str(TreeNode* root) {
+        if (!root) {
+            return "";
+        }
+
+        string res;
+        stack<TreeNode*> stack;
+        TreeNode* lastVisited = nullptr;
+        TreeNode* cur = root;
+
+        while (cur || !stack.empty()) {
+            if (cur) {
+                res += "(" + to_string(cur->val);
+                if (!cur->left && cur->right) {
+                    res += "()";
+                }
+
+                stack.push(cur);
+                cur = cur->left;
+            } else {
+                TreeNode* top = stack.top();
+                if (top->right && lastVisited != top->right) {
+                    cur = top->right;
+                } else {
+                    stack.pop();
+                    res += ")";
+                    lastVisited = top;
+                }
+            }
+        }
+
+        return res.substr(1, res.size() - 2);
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {string}
+     */
+    tree2str(root) {
+        if (!root) {
+            return "";
+        }
+
+        let res = [];
+        let stack = [];
+        let lastVisited = null;
+        let cur = root;
+
+        while (cur || stack.length > 0) {
+            if (cur) {
+                res.push(`(${cur.val}`);
+                if (!cur.left && cur.right) {
+                    res.push("()");
+                }
+
+                stack.push(cur);
+                cur = cur.left;
+            } else {
+                let top = stack[stack.length - 1];
+                if (top.right && lastVisited !== top.right) {
+                    cur = top.right;
+                } else {
+                    stack.pop();
+                    res.push(")");
+                    lastVisited = top;
+                }
+            }
+        }
+
+        return res.join("").slice(1, -1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/contains-duplicate-ii.md b/articles/contains-duplicate-ii.md
new file mode 100644
index 000000000..cc98d9da1
--- /dev/null
+++ b/articles/contains-duplicate-ii.md
@@ -0,0 +1,313 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def containsNearbyDuplicate(self, nums: List[int], k: int) -> bool:
+        for L in range(len(nums)):
+            for R in range(L + 1, min(len(nums), L + k + 1)):
+                if nums[L] == nums[R]:
+                    return True
+        return False
+```
+
+```java
+public class Solution {
+    public boolean containsNearbyDuplicate(int[] nums, int k) {
+        for (int L = 0; L < nums.length; L++) {
+            for (int R = L + 1; R < Math.min(nums.length, L + k + 1); R++) {
+                if (nums[L] == nums[R]) {
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool containsNearbyDuplicate(vector<int>& nums, int k) {
+        for (int L = 0; L < nums.size(); L++) {
+            for (int R = L + 1; R < min((int)nums.size(), L + k + 1); R++) {
+                if (nums[L] == nums[R]) {
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {boolean}
+     */
+    containsNearbyDuplicate(nums, k) {
+        for (let L = 0; L < nums.length; L++) {
+            for (let R = L + 1; R < Math.min(nums.length, L + k + 1); R++) {
+                if (nums[L] === nums[R]) {
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool ContainsNearbyDuplicate(int[] nums, int k) {
+        for (int L = 0; L < nums.Length; L++) {
+            for (int R = L + 1; R < Math.Min(nums.Length, L + k + 1); R++) {
+                if (nums[L] == nums[R]) {
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * min(n, k))$
+* Space complexity: $O(1)$
+
+> Where $n$ is the size of the array $nums$ and $k$ is the maximum distance between two equal numbers.
+
+---
+
+## 2. Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def containsNearbyDuplicate(self, nums: List[int], k: int) -> bool:
+        mp = {}
+
+        for i in range(len(nums)):
+            if nums[i] in mp and i - mp[nums[i]] <= k:
+                return True
+            mp[nums[i]] = i
+            
+        return False 
+```
+
+```java
+public class Solution {
+    public boolean containsNearbyDuplicate(int[] nums, int k) {
+        Map<Integer, Integer> map = new HashMap<>();
+        
+        for (int i = 0; i < nums.length; i++) {
+            if (map.containsKey(nums[i]) && i - map.get(nums[i]) <= k) {
+                return true;
+            }
+            map.put(nums[i], i);
+        }
+        
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool containsNearbyDuplicate(vector<int>& nums, int k) {
+        unordered_map<int, int> mp;
+        
+        for (int i = 0; i < nums.size(); i++) {
+            if (mp.find(nums[i]) != mp.end() && i - mp[nums[i]] <= k) {
+                return true;
+            }
+            mp[nums[i]] = i;
+        }
+        
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {boolean}
+     */
+    containsNearbyDuplicate(nums, k) {
+        const map = new Map();
+
+        for (let i = 0; i < nums.length; i++) {
+            if (map.has(nums[i]) && i - map.get(nums[i]) <= k) {
+                return true;
+            }
+            map.set(nums[i], i);
+        }
+
+        return false;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool ContainsNearbyDuplicate(int[] nums, int k) {
+        Dictionary<int, int> mp = new Dictionary<int, int>();
+
+        for (int i = 0; i < nums.Length; i++) {
+            if (mp.ContainsKey(nums[i]) && i - mp[nums[i]] <= k) {
+                return true;
+            }
+            mp[nums[i]] = i;
+        }
+        
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the size of the array $nums$ and $k$ is the maximum distance between two equal numbers.
+
+---
+
+## 3. Hash Set
+
+::tabs-start
+
+```python
+class Solution:
+    def containsNearbyDuplicate(self, nums: List[int], k: int) -> bool:
+        window = set()
+        L = 0
+
+        for R in range(len(nums)):
+            if R - L > k:
+                window.remove(nums[L])
+                L += 1
+            if nums[R] in window:
+                return True
+            window.add(nums[R])
+        
+        return False
+```
+
+```java
+public class Solution {
+    public boolean containsNearbyDuplicate(int[] nums, int k) {
+        Set<Integer> window = new HashSet<>();
+        int L = 0;
+
+        for (int R = 0; R < nums.length; R++) {
+            if (R - L > k) {
+                window.remove(nums[L]);
+                L++;
+            }
+            if (window.contains(nums[R])) {
+                return true;
+            }
+            window.add(nums[R]);
+        }
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool containsNearbyDuplicate(vector<int>& nums, int k) {
+        unordered_set<int> window;
+        int L = 0;
+
+        for (int R = 0; R < nums.size(); R++) {
+            if (R - L > k) {
+                window.erase(nums[L]);
+                L++;
+            }
+            if (window.find(nums[R]) != window.end()) {
+                return true;
+            }
+            window.insert(nums[R]);
+        }
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {boolean}
+     */
+    containsNearbyDuplicate(nums, k) {
+        let window = new Set();
+        let L = 0;
+
+        for (let R = 0; R < nums.length; R++) {
+            if (R - L > k) {
+                window.delete(nums[L]);
+                L++;
+            }
+            if (window.has(nums[R])) {
+                return true;
+            }
+            window.add(nums[R]);
+        }
+        return false;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool ContainsNearbyDuplicate(int[] nums, int k) {
+        HashSet<int> window = new HashSet<int>();
+        int L = 0;
+
+        for (int R = 0; R < nums.Length; R++) {
+            if (R - L > k) {
+                window.Remove(nums[L]);
+                L++;
+            }
+            if (window.Contains(nums[R])) {
+                return true;
+            }
+            window.Add(nums[R]);
+        }
+        
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(min(n, k))$
+
+> Where $n$ is the size of the array $nums$ and $k$ is the maximum distance between two equal numbers.
\ No newline at end of file
diff --git a/articles/contiguous-array.md b/articles/contiguous-array.md
new file mode 100644
index 000000000..f13825744
--- /dev/null
+++ b/articles/contiguous-array.md
@@ -0,0 +1,341 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def findMaxLength(self, nums: List[int]) -> int:
+        n, res = len(nums), 0
+
+        for i in range(n):
+            zeros = ones = 0
+            for j in range(i, n):
+                if nums[j] == 1:
+                    ones += 1
+                else:
+                    zeros += 1
+                
+                if ones == zeros and res < (j - i + 1):
+                    res = j - i + 1
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int findMaxLength(int[] nums) {
+        int n = nums.length, res = 0;
+
+        for (int i = 0; i < n; i++) {
+            int zeros = 0, ones = 0;
+            for (int j = i; j < n; j++) {
+                if (nums[j] == 1) {
+                    ones++;
+                } else {
+                    zeros++;
+                }
+                if (ones == zeros && res < (j - i + 1)) {
+                    res = j - i + 1;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findMaxLength(vector<int>& nums) {
+        int n = nums.size(), res = 0;
+
+        for (int i = 0; i < n; i++) {
+            int zeros = 0, ones = 0;
+            for (int j = i; j < n; j++) {
+                if (nums[j] == 1) {
+                    ones++;
+                } else {
+                    zeros++;
+                }
+                if (ones == zeros && res < (j - i + 1)) {
+                    res = j - i + 1;
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    findMaxLength(nums) {
+        let n = nums.length, res = 0;
+
+        for (let i = 0; i < n; i++) {
+            let zeros = 0, ones = 0;
+            for (let j = i; j < n; j++) {
+                if (nums[j] === 1) {
+                    ones++;
+                } else {
+                    zeros++;
+                }
+                if (ones === zeros && res < (j - i + 1)) {
+                    res = j - i + 1;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Array
+
+::tabs-start
+
+```python
+class Solution:
+    def findMaxLength(self, nums: List[int]) -> int:
+        n = len(nums)
+        res = 0
+        diff_index = [None] * (2 * n + 1)
+        count = 0
+
+        for i in range(n):
+            count += 1 if nums[i] == 1 else -1
+            if count == 0:
+                res = i + 1
+            if diff_index[count + n] is not None:
+                res = max(res, i - diff_index[count + n])
+            else:
+                diff_index[count + n] = i
+
+        return res
+```
+
+```java
+public class Solution {
+    public int findMaxLength(int[] nums) {
+        int n = nums.length, res = 0, count = 0;
+        int[] diffIndex = new int[2 * n + 1];
+        Arrays.fill(diffIndex, -2);
+        diffIndex[n] = -1;
+
+        for (int i = 0; i < n; i++) {
+            count += nums[i] == 1 ? 1 : -1;
+            if (diffIndex[count + n] != -2) {
+                res = Math.max(res, i - diffIndex[count + n]);
+            } else {
+                diffIndex[count + n] = i;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findMaxLength(vector<int>& nums) {
+        int n = nums.size(), res = 0, count = 0;
+        vector<int> diffIndex(2 * n + 1, -2);
+        diffIndex[n] = -1;
+
+        for (int i = 0; i < n; i++) {
+            count += nums[i] == 1 ? 1 : -1;
+            if (diffIndex[count + n] != -2) {
+                res = max(res, i - diffIndex[count + n]);
+            } else {
+                diffIndex[count + n] = i;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    findMaxLength(nums) {
+        const n = nums.length;
+        let res = 0, count = 0;
+        const diffIndex = new Array(2 * n + 1).fill(-2);
+        diffIndex[n] = -1;
+
+        for (let i = 0; i < n; i++) {
+            count += nums[i] === 1 ? 1 : -1;
+            if (diffIndex[count + n] !== -2) {
+                res = Math.max(res, i - diffIndex[count + n]);
+            } else {
+                diffIndex[count + n] = i;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def findMaxLength(self, nums: List[int]) -> int:
+        zero = one = res = 0
+        diff_index = {}
+
+        for i, n in enumerate(nums):
+            if n == 0:
+                zero += 1
+            else:
+                one += 1
+
+            if one - zero not in diff_index:
+                diff_index[one - zero] = i
+
+            if one == zero:
+                res = one + zero
+            else:
+                idx = diff_index[one - zero]
+                res = max(res, i - idx)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int findMaxLength(int[] nums) {
+        int zero = 0, one = 0, res = 0;
+        HashMap<Integer, Integer> diffIndex = new HashMap<>();
+
+        for (int i = 0; i < nums.length; i++) {
+            if (nums[i] == 0) {
+                zero++;
+            } else {
+                one++;
+            }
+
+            int diff = one - zero;
+            if (!diffIndex.containsKey(diff)) {
+                diffIndex.put(diff, i);
+            }
+
+            if (one == zero) {
+                res = one + zero;
+            } else {
+                res = Math.max(res, i - diffIndex.get(diff));
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findMaxLength(vector<int>& nums) {
+        int zero = 0, one = 0, res = 0;
+        unordered_map<int, int> diffIndex;
+
+        for (int i = 0; i < nums.size(); i++) {
+            if (nums[i] == 0) {
+                zero++;
+            } else {
+                one++;
+            }
+
+            int diff = one - zero;
+            if (diffIndex.find(diff) == diffIndex.end()) {
+                diffIndex[diff] = i;
+            }
+
+            if (one == zero) {
+                res = one + zero;
+            } else {
+                res = max(res, i - diffIndex[diff]);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    findMaxLength(nums) {
+        let zero = 0, one = 0, res = 0;
+        const diffIndex = new Map();
+
+        for (let i = 0; i < nums.length; i++) {
+            if (nums[i] === 0) {
+                zero++;
+            } else {
+                one++;
+            }
+
+            const diff = one - zero;
+            if (!diffIndex.has(diff)) {
+                diffIndex.set(diff, i);
+            }
+
+            if (one === zero) {
+                res = one + zero;
+            } else {
+                res = Math.max(res, i - diffIndex.get(diff));
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/continuous-subarray-sum.md b/articles/continuous-subarray-sum.md
new file mode 100644
index 000000000..a6509f498
--- /dev/null
+++ b/articles/continuous-subarray-sum.md
@@ -0,0 +1,177 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def checkSubarraySum(self, nums: List[int], k: int) -> bool:
+        for i in range(len(nums) - 1):
+            sum = nums[i]
+            for j in range(i + 1, len(nums)):
+                sum += nums[j]
+                if sum % k == 0:
+                    return True
+        return False
+```
+
+```java
+public class Solution {
+    public boolean checkSubarraySum(int[] nums, int k) {
+        for (int i = 0; i < nums.length - 1; i++) {
+            int sum = nums[i];
+            for (int j = i + 1; j < nums.length; j++) {
+                sum += nums[j];
+                if (sum % k == 0) return true;
+            }
+        }
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool checkSubarraySum(vector<int>& nums, int k) {
+        for (int i = 0; i < nums.size() - 1; i++) {
+            int sum = nums[i];
+            for (int j = i + 1; j < nums.size(); j++) {
+                sum += nums[j];
+                if (sum % k == 0) return true;
+            }
+        }
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {boolean}
+     */
+    checkSubarraySum(nums, k) {
+        for (let i = 0; i < nums.length - 1; i++) {
+            let sum = nums[i];
+            for (let j = i + 1; j < nums.length; j++) {
+                sum += nums[j];
+                if (sum % k == 0) return true;
+            }
+        }
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Prefix SUm + Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def checkSubarraySum(self, nums: List[int], k: int) -> bool:
+        remainder = {0: -1}  # remainder -> end index
+        total = 0
+
+        for i, num in enumerate(nums):
+            total += num
+            r = total % k
+            if r not in remainder:
+                remainder[r] = i
+            elif i - remainder[r] > 1:
+                return True
+        
+        return False
+```
+
+```java
+public class Solution {
+    public boolean checkSubarraySum(int[] nums, int k) {
+        HashMap<Integer, Integer> remainder = new HashMap<>();
+        remainder.put(0, -1);
+        int total = 0;
+
+        for (int i = 0; i < nums.length; i++) {
+            total += nums[i];
+            int r = total % k;
+            if (!remainder.containsKey(r)) {
+                remainder.put(r, i);
+            } else if (i - remainder.get(r) > 1) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool checkSubarraySum(vector<int>& nums, int k) {
+        unordered_map<int, int> remainder;
+        remainder[0] = -1;
+        int total = 0;
+
+        for (int i = 0; i < nums.size(); i++) {
+            total += nums[i];
+            int r = total % k;
+            if (remainder.find(r) == remainder.end()) {
+                remainder[r] = i;
+            } else if (i - remainder[r] > 1) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {boolean}
+     */
+    checkSubarraySum(nums, k) {
+        const remainder = new Map();
+        remainder.set(0, -1);
+        let total = 0;
+
+        for (let i = 0; i < nums.length; i++) {
+            total += nums[i];
+            let r = total % k;
+            if (!remainder.has(r)) {
+                remainder.set(r, i);
+            } else if (i - remainder.get(r) > 1) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(k)$
+
+> Where $n$ is the size of the array $nums$ and $k$ is the number that a subarray sum needs to be multiple of.
\ No newline at end of file
diff --git a/articles/convert-an-array-into-a-2d-array-with-conditions.md b/articles/convert-an-array-into-a-2d-array-with-conditions.md
new file mode 100644
index 000000000..7f5906f0d
--- /dev/null
+++ b/articles/convert-an-array-into-a-2d-array-with-conditions.md
@@ -0,0 +1,317 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def findMatrix(self, nums: List[int]) -> List[List[int]]:
+        res = []
+
+        for num in nums:
+            r = 0
+            while r < len(res):
+                if num not in res[r]:
+                    break
+                r += 1
+            if r == len(res):
+                res.append([])
+            res[r].append(num)
+        
+        return res
+```
+
+```java
+public class Solution {
+    public List<List<Integer>> findMatrix(int[] nums) {
+        List<List<Integer>> res = new ArrayList<>();
+
+        for (int num : nums) {
+            int r = 0;
+            while (r < res.size()) {
+                if (!res.get(r).contains(num)) {
+                    break;
+                }
+                r++;
+            }
+            if (r == res.size()) {
+                res.add(new ArrayList<>());
+            }
+            res.get(r).add(num);
+        }
+        
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> findMatrix(vector<int>& nums) {
+        vector<vector<int>> res;
+
+        for (int num : nums) {
+            int r = 0;
+            while (r < res.size()) {
+                if (find(res[r].begin(), res[r].end(), num) == res[r].end()) {
+                    break;
+                }
+                r++;
+            }
+            if (r == res.size()) {
+                res.push_back({});
+            }
+            res[r].push_back(num);
+        }
+        
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[][]}
+     */
+    findMatrix(nums) {
+        const res = [];
+
+        for (const num of nums) {
+            let r = 0;
+            while (r < res.length) {
+                if (!res[r].includes(num)) {
+                    break;
+                }
+                r++;
+            }
+            if (r === res.length) {
+                res.push([]);
+            }
+            res[r].push(num);
+        }
+        
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n)$ for the output array.
+
+> Where $n$ is the size of the array $nums$ and $m$ is the frequency of the most frequent element in the given array.
+
+---
+
+## 2. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def findMatrix(self, nums: List[int]) -> List[List[int]]:
+        nums.sort()
+        res = []
+
+        i = 0
+        while i < len(nums):
+            j = i
+            r = 0
+            while j < len(nums) and nums[i] == nums[j]:
+                if r == len(res):
+                    res.append([])
+                res[r].append(nums[i])
+                r += 1
+                j += 1
+            i = j
+            
+        return res
+```
+
+```java
+public class Solution {
+    public List<List<Integer>> findMatrix(int[] nums) {
+        Arrays.sort(nums);
+        List<List<Integer>> res = new ArrayList<>();
+        
+        int i = 0;
+        while (i < nums.length) {
+            int j = i;
+            int r = 0;
+            while (j < nums.length && nums[i] == nums[j]) {
+                if (r == res.size()) {
+                    res.add(new ArrayList<>());
+                }
+                res.get(r).add(nums[i]);
+                r++;
+                j++;
+            }
+            i = j;
+        }
+        
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> findMatrix(vector<int>& nums) {
+        sort(nums.begin(), nums.end());
+        vector<vector<int>> res;
+
+        int i = 0;
+        while (i < nums.size()) {
+            int j = i, r = 0;
+            while (j < nums.size() && nums[i] == nums[j]) {
+                if (r == res.size()) {
+                    res.push_back({});
+                }
+                res[r].push_back(nums[i]);
+                r++;
+                j++;
+            }
+            i = j;
+        }
+        
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[][]}
+     */
+    findMatrix(nums) {
+        nums.sort((a, b) => a - b);
+        const res = [];
+
+        let i = 0;
+        while (i < nums.length) {
+            let j = i;
+            let r = 0;
+            while (j < nums.length && nums[i] === nums[j]) {
+                if (r === res.length) {
+                    res.push([]);
+                }
+                res[r].push(nums[i]);
+                r++;
+                j++;
+            }
+            i = j;
+        }
+        
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$ for the output array.
+
+---
+
+## 3. Frequency Count
+
+::tabs-start
+
+```python
+class Solution:
+    def findMatrix(self, nums: List[int]) -> List[List[int]]:
+        count = defaultdict(int)
+        res = []
+
+        for num in nums:
+            row = count[num]
+            if len(res) == row:
+                res.append([])
+            res[row].append(num)
+            count[num] += 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public List<List<Integer>> findMatrix(int[] nums) {
+        Map<Integer, Integer> count = new HashMap<>();
+        List<List<Integer>> res = new ArrayList<>();
+
+        for (int num : nums) {
+            int row = count.getOrDefault(num, 0);
+            if (res.size() == row) {
+                res.add(new ArrayList<>());
+            }
+            res.get(row).add(num);
+            count.put(num, row + 1);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> findMatrix(vector<int>& nums) {
+        unordered_map<int, int> count;
+        vector<vector<int>> res;
+
+        for (int num : nums) {
+            int row = count[num];
+            if (res.size() == row) {
+                res.push_back({});
+            }
+            res[row].push_back(num);
+            count[num]++;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[][]}
+     */
+    findMatrix(nums) {
+        const count = new Map();
+        const res = [];
+
+        for (const num of nums) {
+            const row = count.get(num) || 0;
+            if (res.length === row) {
+                res.push([]);
+            }
+            res[row].push(num);
+            count.set(num, row + 1);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/convert-bst-to-greater-tree.md b/articles/convert-bst-to-greater-tree.md
new file mode 100644
index 000000000..9e01d51be
--- /dev/null
+++ b/articles/convert-bst-to-greater-tree.md
@@ -0,0 +1,643 @@
+## 1. Depth First Search (Two Pass)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def convertBST(self, root: Optional[TreeNode]) -> Optional[TreeNode]:
+        def getSum(node):
+            if not node:
+                return 0
+            return node.val + getSum(node.left) + getSum(node.right)
+
+        totalSum = getSum(root)
+
+        def dfs(node):
+            nonlocal totalSum
+            if not node:
+                return
+
+            dfs(node.left)
+            tmp = node.val
+            node.val = totalSum
+            totalSum -= tmp
+            dfs(node.right)
+
+        dfs(root)
+        return root
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    private int totalSum;
+
+    public TreeNode convertBST(TreeNode root) {
+        totalSum = getSum(root);
+        dfs(root);
+        return root;
+    }
+
+    private int getSum(TreeNode node) {
+        if (node == null) return 0;
+        return node.val + getSum(node.left) + getSum(node.right);
+    }
+
+    private void dfs(TreeNode node) {
+        if (node == null) return;
+
+        dfs(node.left);
+        int tmp = node.val;
+        node.val = totalSum;
+        totalSum -= tmp;
+        dfs(node.right);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int totalSum;
+
+    TreeNode* convertBST(TreeNode* root) {
+        totalSum = getSum(root);
+        dfs(root);
+        return root;
+    }
+
+private:
+    int getSum(TreeNode* node) {
+        if (!node) return 0;
+        return node->val + getSum(node->left) + getSum(node->right);
+    }
+
+    void dfs(TreeNode* node) {
+        if (!node) return;
+
+        dfs(node->left);
+        int tmp = node->val;
+        node->val = totalSum;
+        totalSum -= tmp;
+        dfs(node->right);
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {TreeNode}
+     */
+    convertBST(root) {
+        const getSum = (node) => {
+            if (!node) return 0;
+            return node.val + getSum(node.left) + getSum(node.right);
+        };
+
+        let totalSum = getSum(root);
+
+        const dfs = (node) => {
+            if (!node) return;
+
+            dfs(node.left);
+            let tmp = node.val;
+            node.val = totalSum;
+            totalSum -= tmp;
+            dfs(node.right);
+        };
+
+        dfs(root);
+        return root;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Depth First Search (One Pass)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def convertBST(self, root: Optional[TreeNode]) -> Optional[TreeNode]:
+        curSum = 0
+
+        def dfs(node):
+            nonlocal curSum
+            if not node:
+                return
+
+            dfs(node.right)
+            tmp = node.val
+            node.val += curSum
+            curSum += tmp
+            dfs(node.left)
+
+        dfs(root)
+        return root
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    private int curSum = 0;
+
+    public TreeNode convertBST(TreeNode root) {
+        dfs(root);
+        return root;
+    }
+
+    private void dfs(TreeNode node) {
+        if (node == null) return;
+
+        dfs(node.right);
+        int tmp = node.val;
+        node.val += curSum;
+        curSum += tmp;
+        dfs(node.left);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int curSum = 0;
+
+    TreeNode* convertBST(TreeNode* root) {
+        dfs(root);
+        return root;
+    }
+
+private:
+    void dfs(TreeNode* node) {
+        if (!node) return;
+
+        dfs(node->right);
+        int tmp = node->val;
+        node->val += curSum;
+        curSum += tmp;
+        dfs(node->left);
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {TreeNode}
+     */
+    convertBST(root) {
+        let curSum = 0;
+
+        const dfs = (node) => {
+            if (!node) return;
+
+            dfs(node.right);
+            let tmp = node.val;
+            node.val += curSum;
+            curSum += tmp;
+            dfs(node.left);
+        };
+
+        dfs(root);
+        return root;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 3. Iterative DFS
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def convertBST(self, root: Optional[TreeNode]) -> Optional[TreeNode]:
+        curSum = 0
+        stack = []
+        node = root
+
+        while stack or node:
+            while node:
+                stack.append(node)
+                node = node.right
+            
+            node = stack.pop()
+            curSum += node.val
+            node.val = curSum
+            node = node.left
+
+        return root
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode convertBST(TreeNode root) {
+        int curSum = 0;
+        Stack<TreeNode> stack = new Stack<>();
+        TreeNode node = root;
+
+        while (!stack.isEmpty() || node != null) {
+            while (node != null) {
+                stack.push(node);
+                node = node.right;
+            }
+
+            node = stack.pop();
+            curSum += node.val;
+            node.val = curSum;
+            node = node.left;
+        }
+        return root;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    TreeNode* convertBST(TreeNode* root) {
+        int curSum = 0;
+        stack<TreeNode*> st;
+        TreeNode* node = root;
+
+        while (!st.empty() || node) {
+            while (node) {
+                st.push(node);
+                node = node->right;
+            }
+
+            node = st.top(); st.pop();
+            curSum += node->val;
+            node->val = curSum;
+            node = node->left;
+        }
+        return root;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {TreeNode}
+     */
+    convertBST(root) {
+        let curSum = 0;
+        const stack = [];
+        let node = root;
+
+        while (stack.length || node) {
+            while (node) {
+                stack.push(node);
+                node = node.right;
+            }
+
+            node = stack.pop();
+            curSum += node.val;
+            node.val = curSum;
+            node = node.left;
+        }
+        return root;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Morris Traversal
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def convertBST(self, root: Optional[TreeNode]) -> Optional[TreeNode]:
+        curSum = 0
+        cur = root
+
+        while cur:
+            if cur.right:
+                prev = cur.right
+                while prev.left and prev.left != cur:
+                    prev = prev.left
+
+                if not prev.left:
+                    prev.left = cur
+                    cur = cur.right
+                else:
+                    prev.left = None
+                    curSum += cur.val
+                    cur.val = curSum
+                    cur = cur.left
+            else:
+                curSum += cur.val
+                cur.val = curSum
+                cur = cur.left
+        
+        return root
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode convertBST(TreeNode root) {
+        int curSum = 0;
+        TreeNode cur = root;
+
+        while (cur != null) {
+            if (cur.right != null) {
+                TreeNode prev = cur.right;
+                while (prev.left != null && prev.left != cur) {
+                    prev = prev.left;
+                }
+
+                if (prev.left == null) {
+                    prev.left = cur;
+                    cur = cur.right;
+                } else {
+                    prev.left = null;
+                    curSum += cur.val;
+                    cur.val = curSum;
+                    cur = cur.left;
+                }
+            } else {
+                curSum += cur.val;
+                cur.val = curSum;
+                cur = cur.left;
+            }
+        }
+        return root;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    TreeNode* convertBST(TreeNode* root) {
+        int curSum = 0;
+        TreeNode* cur = root;
+
+        while (cur) {
+            if (cur->right) {
+                TreeNode* prev = cur->right;
+                while (prev->left && prev->left != cur) {
+                    prev = prev->left;
+                }
+
+                if (!prev->left) {
+                    prev->left = cur;
+                    cur = cur->right;
+                } else {
+                    prev->left = nullptr;
+                    curSum += cur->val;
+                    cur->val = curSum;
+                    cur = cur->left;
+                }
+            } else {
+                curSum += cur->val;
+                cur->val = curSum;
+                cur = cur->left;
+            }
+        }
+        return root;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {TreeNode}
+     */
+    convertBST(root) {
+        let curSum = 0;
+        let cur = root;
+
+        while (cur) {
+            if (cur.right) {
+                let prev = cur.right;
+                while (prev.left && prev.left !== cur) {
+                    prev = prev.left;
+                }
+
+                if (!prev.left) {
+                    prev.left = cur;
+                    cur = cur.right;
+                } else {
+                    prev.left = null;
+                    curSum += cur.val;
+                    cur.val = curSum;
+                    cur = cur.left;
+                }
+            } else {
+                curSum += cur.val;
+                cur.val = curSum;
+                cur = cur.left;
+            }
+        }
+        return root;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/convert-sorted-array-to-binary-search-tree.md b/articles/convert-sorted-array-to-binary-search-tree.md
new file mode 100644
index 000000000..dd933b982
--- /dev/null
+++ b/articles/convert-sorted-array-to-binary-search-tree.md
@@ -0,0 +1,437 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def sortedArrayToBST(self, nums: List[int]) -> Optional[TreeNode]:
+        if not nums:
+            return None
+        
+        mid = len(nums) // 2
+        root = TreeNode(nums[mid])
+        root.left = self.sortedArrayToBST(nums[:mid])
+        root.right = self.sortedArrayToBST(nums[mid + 1:])
+        return root
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode sortedArrayToBST(int[] nums) {
+        if (nums.length == 0) {
+            return null;
+        }
+
+        int mid = nums.length / 2;
+        TreeNode root = new TreeNode(nums[mid]);
+        root.left = sortedArrayToBST(Arrays.copyOfRange(nums, 0, mid));
+        root.right = sortedArrayToBST(Arrays.copyOfRange(nums, mid + 1, nums.length));
+        return root;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    TreeNode* sortedArrayToBST(vector<int>& nums) {
+        if (nums.empty()) {
+            return nullptr;
+        }
+
+        int mid = nums.size() / 2;
+        TreeNode* root = new TreeNode(nums[mid]);
+        vector<int> left(nums.begin(), nums.begin() + mid);
+        vector<int> right(nums.begin() + mid + 1, nums.end());
+        root->left = sortedArrayToBST(left);
+        root->right = sortedArrayToBST(right);
+        return root;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {TreeNode}
+     */
+    sortedArrayToBST(nums) {
+        if (nums.length === 0) {
+            return null;
+        }
+
+        const mid = Math.floor(nums.length / 2);
+        const root = new TreeNode(nums[mid]);
+        root.left = this.sortedArrayToBST(nums.slice(0, mid));
+        root.right = this.sortedArrayToBST(nums.slice(mid + 1));
+        return root;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Depth First Search (Optimal)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def sortedArrayToBST(self, nums: List[int]) -> TreeNode:
+        def helper(l, r):
+            if l > r:
+                return None
+            m = (l + r) // 2
+            root = TreeNode(nums[m])
+            root.left = helper(l, m - 1)
+            root.right = helper(m + 1, r)
+            return root
+
+        return helper(0, len(nums) - 1)
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode sortedArrayToBST(int[] nums) {
+        return helper(nums, 0, nums.length - 1);
+    }
+
+    private TreeNode helper(int[] nums, int l, int r) {
+        if (l > r) {
+            return null;
+        }
+        int m = (l + r) / 2;
+        TreeNode root = new TreeNode(nums[m]);
+        root.left = helper(nums, l, m - 1);
+        root.right = helper(nums, m + 1, r);
+        return root;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    TreeNode* sortedArrayToBST(vector<int>& nums) {
+        return helper(nums, 0, nums.size() - 1);
+    }
+
+private:
+    TreeNode* helper(vector<int>& nums, int l, int r) {
+        if (l > r) {
+            return nullptr;
+        }
+        int m = (l + r) / 2;
+        TreeNode* root = new TreeNode(nums[m]);
+        root->left = helper(nums, l, m - 1);
+        root->right = helper(nums, m + 1, r);
+        return root;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {TreeNode}
+     */
+    sortedArrayToBST(nums) {
+        const helper = (l, r) => {
+            if (l > r) {
+                return null;
+            }
+            const m = Math.floor((l + r) / 2);
+            const root = new TreeNode(nums[m]);
+            root.left = helper(l, m - 1);
+            root.right = helper(m + 1, r);
+            return root;
+        };
+
+        return helper(0, nums.length - 1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity:
+    * $O(\log n)$ space for recursion stack.
+    * $O(n)$ space for the output.
+
+---
+
+## 3. Iterative DFS
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def sortedArrayToBST(self, nums: List[int]) -> TreeNode:
+        if not nums:
+            return None
+        
+        root = TreeNode(0)
+        stack = [(root, 0, len(nums) - 1)]
+        
+        while stack:
+            node, l, r = stack.pop()
+            m = (l + r) // 2
+            node.val = nums[m]
+            if l <= m - 1:
+                node.left = TreeNode(0)
+                stack.append((node.left, l, m - 1))
+            if m + 1 <= r:
+                node.right = TreeNode(0)
+                stack.append((node.right, m + 1, r))
+        
+        return root
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode sortedArrayToBST(int[] nums) {
+        if (nums.length == 0) {
+            return null;
+        }
+
+        TreeNode root = new TreeNode(0);
+        Stack<int[]> stack = new Stack<>();
+        Stack<TreeNode> nodes = new Stack<>();
+        stack.push(new int[]{0, nums.length - 1});
+        nodes.push(root);
+
+        while (!stack.isEmpty()) {
+            int[] range = stack.pop();
+            TreeNode node = nodes.pop();
+            int l = range[0], r = range[1];
+            int m = (l + r) / 2;
+            node.val = nums[m];
+
+            if (l <= m - 1) {
+                node.left = new TreeNode(0);
+                stack.push(new int[]{l, m - 1});
+                nodes.push(node.left);
+            }
+            if (m + 1 <= r) {
+                node.right = new TreeNode(0);
+                stack.push(new int[]{m + 1, r});
+                nodes.push(node.right);
+            }
+        }
+
+        return root;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    TreeNode* sortedArrayToBST(vector<int>& nums) {
+        if (nums.empty()) return nullptr;
+
+        TreeNode* root = new TreeNode(0);
+        stack<tuple<TreeNode*, int, int>> stack;
+        stack.push({root, 0, (int)nums.size() - 1});
+
+        while (!stack.empty()) {
+            auto [node, l, r] = stack.top();
+            stack.pop();
+            int m = (l + r) / 2;
+            node->val = nums[m];
+
+            if (l <= m - 1) {
+                node->left = new TreeNode(0);
+                stack.push({node->left, l, m - 1});
+            }
+            if (m + 1 <= r) {
+                node->right = new TreeNode(0);
+                stack.push({node->right, m + 1, r});
+            }
+        }
+
+        return root;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {TreeNode}
+     */
+    sortedArrayToBST(nums) {
+        if (nums.length === 0) {
+            return null;
+        }
+
+        const root = new TreeNode(0);
+        const stack = [[root, 0, nums.length - 1]];
+
+        while (stack.length) {
+            const [node, l, r] = stack.pop();
+            const m = Math.floor((l + r) / 2);
+            node.val = nums[m];
+
+            if (l <= m - 1) {
+                node.left = new TreeNode(0);
+                stack.push([node.left, l, m - 1]);
+            }
+            if (m + 1 <= r) {
+                node.right = new TreeNode(0);
+                stack.push([node.right, m + 1, r]);
+            }
+        }
+
+        return root;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity:
+    * $O(\log n)$ space for the stack.
+    * $O(n)$ space for the output.
\ No newline at end of file
diff --git a/articles/copy-linked-list-with-random-pointer.md b/articles/copy-linked-list-with-random-pointer.md
index 888c0f722..0b595bf64 100644
--- a/articles/copy-linked-list-with-random-pointer.md
+++ b/articles/copy-linked-list-with-random-pointer.md
@@ -1,4 +1,4 @@
-## 1. Hash Map (Recursion)
+## 1. Recursion + Hash Map
 
 ::tabs-start
 
@@ -163,6 +163,104 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a Node.
+ * type Node struct {
+ *     Val int
+ *     Next *Node
+ *     Random *Node
+ * }
+ */
+
+var m = make(map[*Node]*Node)
+
+func copyRandomList(head *Node) *Node {
+    if head == nil {
+        return nil
+    }
+    if val, exists := m[head]; exists {
+        return val
+    }
+    
+    copy := &Node{Val: head.Val}
+    m[head] = copy
+    copy.Next = copyRandomList(head.Next)
+    copy.Random = m[head.Random]
+    return copy
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = Node(5)
+ * var v = ti.`val`
+ * Definition for a Node.
+ * class Node(var `val`: Int) {
+ *     var next: Node? = null
+ *     var random: Node? = null
+ * }
+ */
+
+class Solution {
+    private val map = HashMap<Node, Node>()
+
+    fun copyRandomList(head: Node?): Node? {
+        if (head == null) {
+            return null
+        }
+        if (map.containsKey(head)) {
+            return map[head]
+        }
+        
+        val copy = Node(head.`val`)
+        map[head] = copy
+        copy.next = copyRandomList(head.next)
+        copy.random = map[head.random]
+        return copy
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a Node.
+ * public class Node {
+ *     public var val: Int
+ *     public var next: Node?
+ *     public var random: Node?
+ *     public init(_ val: Int) {
+ *         self.val = val
+ *         self.next = nil
+ *    	   self.random = nil
+ *     }
+ * }
+ */
+
+class Solution {
+    private var map = [Node: Node]()
+    
+    func copyRandomList(_ head: Node?) -> Node? {
+        if head == nil {
+            return nil
+        }
+        
+        if let copied = map[head!] {
+            return copied
+        }
+        
+        let copy = Node(head!.val)
+        map[head!] = copy
+        
+        copy.next = copyRandomList(head!.next)
+        copy.random = copyRandomList(head!.random)
+        
+        return copy
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -366,6 +464,113 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a Node.
+ * type Node struct {
+ *     Val int
+ *     Next *Node
+ *     Random *Node
+ * }
+ */
+
+func copyRandomList(head *Node) *Node {
+    oldToCopy := map[*Node]*Node{nil: nil}
+
+    cur := head
+    for cur != nil {
+        copy := &Node{Val: cur.Val}
+        oldToCopy[cur] = copy
+        cur = cur.Next
+    }
+
+    cur = head
+    for cur != nil {
+        copy := oldToCopy[cur]
+        copy.Next = oldToCopy[cur.Next]
+        copy.Random = oldToCopy[cur.Random]
+        cur = cur.Next
+    }
+
+    return oldToCopy[head]
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = Node(5)
+ * var v = ti.`val`
+ * Definition for a Node.
+ * class Node(var `val`: Int) {
+ *     var next: Node? = null
+ *     var random: Node? = null
+ * }
+ */
+
+class Solution {
+    fun copyRandomList(head: Node?): Node? {
+        val oldToCopy = hashMapOf<Node?, Node?>(null to null)
+
+        var cur = head
+        while (cur != null) {
+            val copy = Node(cur.`val`)
+            oldToCopy[cur] = copy
+            cur = cur.next
+        }
+
+        cur = head
+        while (cur != null) {
+            val copy = oldToCopy[cur]
+            copy?.next = oldToCopy[cur.next]
+            copy?.random = oldToCopy[cur.random]
+            cur = cur.next
+        }
+
+        return oldToCopy[head]
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a Node.
+ * public class Node {
+ *     public var val: Int
+ *     public var next: Node?
+ *     public var random: Node?
+ *     public init(_ val: Int) {
+ *         self.val = val
+ *         self.next = nil
+ *    	   self.random = nil
+ *     }
+ * }
+ */
+
+class Solution {
+    func copyRandomList(_ head: Node?) -> Node? {
+        var oldToCopy: [Node?: Node?] = [nil: nil]
+
+        var cur = head
+        while cur != nil {
+            let copy = Node(cur!.val)
+            oldToCopy[cur] = copy
+            cur = cur?.next
+        }
+
+        cur = head
+        while cur != nil {
+            let copy = oldToCopy[cur]!
+            copy?.next = oldToCopy[cur?.next]!
+            copy?.random = oldToCopy[cur?.random]!
+            cur = cur?.next
+        }
+
+        return oldToCopy[head]!
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -583,6 +788,124 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a Node.
+ * type Node struct {
+ *     Val int
+ *     Next *Node
+ *     Random *Node
+ * }
+ */
+
+func copyRandomList(head *Node) *Node {
+    oldToCopy := make(map[*Node]*Node)
+    oldToCopy[nil] = nil
+
+    cur := head
+    for cur != nil {
+        if _, exists := oldToCopy[cur]; !exists {
+            oldToCopy[cur] = &Node{Val: cur.Val}
+        }
+        if cur.Next != nil {
+            if _, exists := oldToCopy[cur.Next]; !exists {
+                oldToCopy[cur.Next] = &Node{Val: cur.Next.Val}
+            }
+            oldToCopy[cur].Next = oldToCopy[cur.Next]
+        }
+        if cur.Random != nil {
+            if _, exists := oldToCopy[cur.Random]; !exists {
+                oldToCopy[cur.Random] = &Node{Val: cur.Random.Val}
+            }
+            oldToCopy[cur].Random = oldToCopy[cur.Random]
+        }
+        cur = cur.Next
+    }
+    return oldToCopy[head]
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = Node(5)
+ * var v = ti.`val`
+ * Definition for a Node.
+ * class Node(var `val`: Int) {
+ *     var next: Node? = null
+ *     var random: Node? = null
+ * }
+ */
+
+class Solution {
+    fun copyRandomList(head: Node?): Node? {
+        val oldToCopy = HashMap<Node?, Node?>()
+        oldToCopy[null] = null
+
+        var cur = head
+        while (cur != null) {
+            if (!oldToCopy.containsKey(cur)) {
+                oldToCopy[cur] = Node(cur.`val`)
+            }
+            if (cur.next != null) {
+                if (!oldToCopy.containsKey(cur.next)) {
+                    oldToCopy[cur.next] = Node(cur.next!!.`val`)
+                }
+                oldToCopy[cur]!!.next = oldToCopy[cur.next]
+            }
+            if (cur.random != null) {
+                if (!oldToCopy.containsKey(cur.random)) {
+                    oldToCopy[cur.random] = Node(cur.random!!.`val`)
+                }
+                oldToCopy[cur]!!.random = oldToCopy[cur.random]
+            }
+            cur = cur.next
+        }
+        return oldToCopy[head]
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a Node.
+ * public class Node {
+ *     public var val: Int
+ *     public var next: Node?
+ *     public var random: Node?
+ *     public init(_ val: Int) {
+ *         self.val = val
+ *         self.next = nil
+ *    	   self.random = nil
+ *     }
+ * }
+ */
+
+class Solution {
+   func copyRandomList(_ head: Node?) -> Node? {
+       var oldToCopy = [Node?: Node?]()
+
+       func getNode(_ node: Node?) -> Node? {
+           if node == nil { return nil }
+           if oldToCopy[node] == nil {
+               oldToCopy[node] = Node(0)
+           }
+           return oldToCopy[node]!
+       }
+
+       var cur = head
+       while cur != nil {
+           getNode(cur)!.val = cur!.val
+           getNode(cur)!.next = getNode(cur!.next)
+           getNode(cur)!.random = getNode(cur!.random)
+           cur = cur!.next
+       }
+
+       return getNode(head)
+   }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -856,12 +1179,166 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a Node.
+ * type Node struct {
+ *     Val int
+ *     Next *Node
+ *     Random *Node
+ * }
+ */
+
+func copyRandomList(head *Node) *Node {
+    if head == nil {
+        return nil
+    }
+
+    l1 := head
+    for l1 != nil {
+        l2 := &Node{Val: l1.Val}
+        l2.Next = l1.Next
+        l1.Next = l2
+        l1 = l2.Next
+    }
+
+    newHead := head.Next
+
+    l1 = head
+    for l1 != nil {
+        if l1.Random != nil {
+            l1.Next.Random = l1.Random.Next
+        }
+        l1 = l1.Next.Next
+    }
+
+    l1 = head
+    for l1 != nil {
+        l2 := l1.Next
+        l1.Next = l2.Next
+        if l2.Next != nil {
+            l2.Next = l2.Next.Next
+        }
+        l1 = l1.Next
+    }
+
+    return newHead
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = Node(5)
+ * var v = ti.`val`
+ * Definition for a Node.
+ * class Node(var `val`: Int) {
+ *     var next: Node? = null
+ *     var random: Node? = null
+ * }
+ */
+
+class Solution {
+    fun copyRandomList(head: Node?): Node? {
+        if (head == null) {
+            return null
+        }
+
+        var l1: Node? = head
+        while (l1 != null) {
+            val l2 = Node(l1.`val`)
+            l2.next = l1.next
+            l1.next = l2
+            l1 = l2.next
+        }
+
+        val newHead = head.next
+
+        l1 = head
+        while (l1 != null) {
+            if (l1.random != null) {
+                l1.next?.random = l1.random?.next
+            }
+            l1 = l1.next?.next
+        }
+
+        l1 = head
+        while (l1 != null) {
+            val l2 = l1.next
+            l1.next = l2?.next
+            val nextL2 = l2?.next 
+            if (nextL2 != null) {
+                l2.next = nextL2.next
+            }
+            l1 = l1.next
+        }
+
+        return newHead
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a Node.
+ * public class Node {
+ *     public var val: Int
+ *     public var next: Node?
+ *     public var random: Node?
+ *     public init(_ val: Int) {
+ *         self.val = val
+ *         self.next = nil
+ *    	   self.random = nil
+ *     }
+ * }
+ */
+
+class Solution {
+    func copyRandomList(_ head: Node?) -> Node? {
+        if head == nil {
+            return nil
+        }
+        
+        var l1 = head
+        while l1 != nil {
+            let l2 = Node(l1!.val)
+            l2.next = l1?.next
+            l1?.next = l2
+            l1 = l2.next
+        }
+        
+        let newHead = head?.next
+        l1 = head
+        while l1 != nil {
+            if let random = l1?.random {
+                l1?.next?.random = random.next
+            }
+            l1 = l1?.next?.next
+        }
+        
+        l1 = head
+        while l1 != nil {
+            let l2 = l1?.next
+            l1?.next = l2?.next
+            if l2?.next != nil {
+                l2?.next = l2?.next?.next
+            }
+            l1 = l1?.next
+        }
+        
+        return newHead
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n)$
-* Space complexity: $O(1)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ for the output.
 
 ---
 
@@ -1116,9 +1593,166 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a Node.
+ * type Node struct {
+ *     Val int
+ *     Next *Node
+ *     Random *Node
+ * }
+ */
+
+func copyRandomList(head *Node) *Node {
+    if head == nil {
+        return nil
+    }
+
+    l1 := head
+    for l1 != nil {
+        l2 := &Node{Val: l1.Val}
+        l2.Next = l1.Random
+        l1.Random = l2
+        l1 = l1.Next
+    }
+
+    newHead := head.Random
+
+    l1 = head
+    for l1 != nil {
+        l2 := l1.Random
+        if l2.Next != nil {
+            l2.Random = l2.Next.Random
+        } else {
+            l2.Random = nil
+        }
+        l1 = l1.Next
+    }
+
+    l1 = head
+    for l1 != nil {
+        l2 := l1.Random
+        l1.Random = l2.Next
+        if l1.Next != nil {
+            l2.Next = l1.Next.Random
+        } else {
+            l2.Next = nil
+        }
+        l1 = l1.Next
+    }
+
+    return newHead
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = Node(5)
+ * var v = ti.`val`
+ * Definition for a Node.
+ * class Node(var `val`: Int) {
+ *     var next: Node? = null
+ *     var random: Node? = null
+ * }
+ */
+
+class Solution {
+    fun copyRandomList(head: Node?): Node? {
+        if (head == null) {
+            return null
+        }
+
+        var l1: Node? = head
+        while (l1 != null) {
+            val l2 = Node(l1.`val`)
+            l2.next = l1.random
+            l1.random = l2
+            l1 = l1.next
+        }
+
+        val newHead = head.random
+
+        l1 = head
+        while (l1 != null) {
+            val l2 = l1.random
+            if (l2 != null) {
+                l2.random = l2.next?.random
+            }
+            l1 = l1.next
+        }
+
+        l1 = head
+        while (l1 != null) {
+            val l2 = l1.random
+            l1.random = l2?.next
+            if (l2 != null) {
+                l2.next = l1.next?.random
+            }
+            l1 = l1.next
+        }
+
+        return newHead
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a Node.
+ * public class Node {
+ *     public var val: Int
+ *     public var next: Node?
+ *     public var random: Node?
+ *     public init(_ val: Int) {
+ *         self.val = val
+ *         self.next = nil
+ *    	   self.random = nil
+ *     }
+ * }
+ */
+
+class Solution {
+    func copyRandomList(_ head: Node?) -> Node? {
+        if head == nil {
+            return nil
+        }
+
+        var l1 = head
+        while l1 != nil {
+            let l2 = Node(l1!.val)
+            l2.next = l1?.random
+            l1?.random = l2
+            l1 = l1?.next
+        }
+
+        let newHead = head?.random
+
+        l1 = head
+        while l1 != nil {
+            let l2 = l1?.random
+            l2?.random = l2?.next?.random
+            l1 = l1?.next
+        }
+
+        l1 = head
+        while l1 != nil {
+            let l2 = l1?.random
+            l1?.random = l2?.next
+            l2?.next = l1?.next?.random
+            l1 = l1?.next
+        }
+
+        return newHead
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n)$
-* Space complexity: $O(1)$
\ No newline at end of file
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ for the output.
\ No newline at end of file
diff --git a/articles/count-all-valid-pickup-and-delivery-options.md b/articles/count-all-valid-pickup-and-delivery-options.md
new file mode 100644
index 000000000..78b58d069
--- /dev/null
+++ b/articles/count-all-valid-pickup-and-delivery-options.md
@@ -0,0 +1,668 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def countOrders(self, n: int) -> int:
+        MOD = 1000000007
+
+        def dfs(picked, delivered):
+            if picked == n and delivered == n:
+                return 1
+
+            res = 0
+            if picked < n:
+                res = (res + (n - picked) * dfs(picked + 1, delivered)) % MOD
+            if delivered < picked:
+                res = (res + (picked - delivered) * dfs(picked, delivered + 1)) % MOD
+
+            return res
+
+        return dfs(0, 0)
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1_000_000_007;
+
+    public int countOrders(int n) {
+        return dfs(0, 0, n);
+    }
+
+    private int dfs(int picked, int delivered, int n) {
+        if (picked == n && delivered == n) {
+            return 1;
+        }
+
+        long res = 0;
+        if (picked < n) {
+            res = ((res + (n - picked) * 1L * dfs(picked + 1, delivered, n)) % MOD);
+        }
+        if (delivered < picked) {
+            res = ((res + (picked - delivered) * 1L * dfs(picked, delivered + 1, n)) % MOD);
+        }
+
+        return (int) res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    static const int MOD = 1'000'000'007;
+
+    int countOrders(int n) {
+        return dfs(0, 0, n);
+    }
+
+private:
+    int dfs(int picked, int delivered, int n) {
+        if (picked == n && delivered == n) {
+            return 1;
+        }
+
+        int res = 0;
+        if (picked < n) {
+            res = (res + (n - picked) * 1LL * dfs(picked + 1, delivered, n)) % MOD;
+        }
+        if (delivered < picked) {
+            res = (res + (picked - delivered) * 1LL * dfs(picked, delivered + 1, n)) % MOD;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    countOrders(n) {
+        const MOD = 1_000_000_007;
+
+        const dfs = (picked, delivered) => {
+            if (picked === n && delivered === n) {
+                return 1;
+            }
+
+            let res = 0;
+            if (picked < n) {
+                res = (res + (n - picked) * dfs(picked + 1, delivered)) % MOD;
+            }
+            if (delivered < picked) {
+                res = (res + (picked - delivered) * dfs(picked, delivered + 1)) % MOD;
+            }
+
+            return res;
+        };
+
+        return dfs(0, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def countOrders(self, n: int) -> int:
+        MOD = 1000000007
+        dp = [[-1] * (n + 1) for _ in range(n + 1)]
+        dp[n][n] = 1
+
+        def dfs(picked, delivered):
+            if dp[picked][delivered] != -1:
+                return dp[picked][delivered]
+
+            res = 0
+            if picked < n:
+                res = (res + (n - picked) * dfs(picked + 1, delivered)) % MOD
+            if delivered < picked:
+                res = (res + (picked - delivered) * dfs(picked, delivered + 1)) % MOD
+
+            dp[picked][delivered] = res
+            return res
+
+        return dfs(0, 0)
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1_000_000_007;
+    private int[][] dp;
+
+    public int countOrders(int n) {
+        dp = new int[n + 1][n + 1];
+        for (int i = 0; i <= n; i++) {
+            for (int j = 0; j <= n; j++) {
+                dp[i][j] = -1;
+            }
+        }
+        dp[n][n] = 1;
+        return dfs(0, 0, n);
+    }
+
+    private int dfs(int picked, int delivered, int n) {
+        if (dp[picked][delivered] != -1) {
+            return dp[picked][delivered];
+        }
+
+        long res = 0;
+        if (picked < n) {
+            res = ((res + (n - picked) * 1L * dfs(picked + 1, delivered, n)) % MOD);
+        }
+        if (delivered < picked) {
+            res = ((res + (picked - delivered) * 1L * dfs(picked, delivered + 1, n)) % MOD);
+        }
+
+        return dp[picked][delivered] = (int)res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    static const int MOD = 1'000'000'007;
+    vector<vector<int>> dp;
+
+    int countOrders(int n) {
+        dp.assign(n + 1, vector<int>(n + 1, -1));
+        dp[n][n] = 1;
+        return dfs(0, 0, n);
+    }
+
+private:
+    int dfs(int picked, int delivered, int n) {
+        if (dp[picked][delivered] != -1) {
+            return dp[picked][delivered];
+        }
+
+        int res = 0;
+        if (picked < n) {
+            res = (res + (n - picked) * 1LL * dfs(picked + 1, delivered, n)) % MOD;
+        }
+        if (delivered < picked) {
+            res = (res + (picked - delivered) * 1LL * dfs(picked, delivered + 1, n)) % MOD;
+        }
+
+        return dp[picked][delivered] = res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    countOrders(n) {
+        const MOD = 1_000_000_007;
+        const dp = Array.from({ length: n + 1 }, () => Array(n + 1).fill(-1));
+
+        const dfs = (picked, delivered) => {
+            if (picked === n && delivered === n) {
+                return 1;
+            }
+            if (dp[picked][delivered] !== -1) {
+                return dp[picked][delivered];
+            }
+
+            let res = 0;
+            if (picked < n) {
+                res = (res + (n - picked) * dfs(picked + 1, delivered)) % MOD;
+            }
+            if (delivered < picked) {
+                res = (res + (picked - delivered) * dfs(picked, delivered + 1)) % MOD;
+            }
+
+            dp[picked][delivered] = res;
+            return res;
+        };
+
+        return dfs(0, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def countOrders(self, n: int) -> int:
+        MOD = 1000000007
+        dp = [[0] * (n + 1) for _ in range(n + 1)]
+        dp[0][0] = 1
+
+        for picked in range(n + 1):
+            for delivered in range(n + 1):
+                if picked < n:
+                    dp[picked + 1][delivered] = (
+                        (dp[picked + 1][delivered] +
+                        (n - picked) * dp[picked][delivered]) % MOD
+                    )
+
+                if delivered < picked:
+                    dp[picked][delivered + 1] = (
+                        (dp[picked][delivered + 1] +
+                        (picked - delivered) * dp[picked][delivered]) % MOD
+                    )
+
+        return dp[n][n]
+```
+
+```java
+public class Solution {
+    public int countOrders(int n) {
+        final int MOD = 1_000_000_007;
+        int[][] dp = new int[n + 1][n + 1];
+        dp[0][0] = 1;
+
+        for (int picked = 0; picked <= n; picked++) {
+            for (int delivered = 0; delivered <= n; delivered++) {
+                if (picked < n) {
+                    dp[picked + 1][delivered] = (int) ((dp[picked + 1][delivered] + 
+                                                (n - picked) * 1L * dp[picked][delivered]) % MOD);
+                }
+                if (delivered < picked) {
+                    dp[picked][delivered + 1] = (int) ((dp[picked][delivered + 1] + 
+                                                (picked - delivered) * 1L * dp[picked][delivered]) % MOD);
+                }
+            }
+        }
+
+        return dp[n][n];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countOrders(int n) {
+        const int MOD = 1'000'000'007;
+        vector<vector<int>> dp(n + 1, vector<int>(n + 1, 0));
+        dp[0][0] = 1;
+
+        for (int picked = 0; picked <= n; picked++) {
+            for (int delivered = 0; delivered <= n; delivered++) {
+                if (picked < n) {
+                    dp[picked + 1][delivered] = (dp[picked + 1][delivered] + 
+                                                (n - picked) * 1LL * dp[picked][delivered]) % MOD;
+                }
+                if (delivered < picked) {
+                    dp[picked][delivered + 1] = (dp[picked][delivered + 1] + 
+                                                (picked - delivered) * 1LL * dp[picked][delivered]) % MOD;
+                }
+            }
+        }
+
+        return dp[n][n];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    countOrders(n) {
+        const MOD = 1_000_000_007;
+        const dp = Array.from({ length: n + 1 }, () => Array(n + 1).fill(0));
+        dp[0][0] = 1;
+
+        for (let picked = 0; picked <= n; picked++) {
+            for (let delivered = 0; delivered <= n; delivered++) {
+                if (picked < n) {
+                    dp[picked + 1][delivered] = (
+                        (dp[picked + 1][delivered] +
+                        (n - picked) * dp[picked][delivered]) % MOD
+                    );
+                }
+
+                if (delivered < picked) {
+                    dp[picked][delivered + 1] = (
+                        (dp[picked][delivered + 1] + 
+                        (picked - delivered) * dp[picked][delivered]) % MOD
+                    );
+                }
+            }
+        }
+
+        return dp[n][n];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def countOrders(self, n: int) -> int:
+        MOD = 1000000007
+        dp = [0] * (n + 1)
+        dp[0] = 1
+
+        for picked in range(n + 1):
+            for delivered in range(picked):
+                dp[delivered + 1] = (
+                    (dp[delivered + 1] +
+                    (picked - delivered) * dp[delivered]) % MOD
+                )
+
+            if picked < n:
+                next_dp = [0] * (n + 1)
+                for delivered in range(picked + 1):
+                    next_dp[delivered] = (
+                        (next_dp[delivered] +
+                        (n - picked) * dp[delivered]) % MOD
+                    )
+                dp = next_dp
+
+        return dp[n]
+```
+
+```java
+public class Solution {
+    public int countOrders(int n) {
+        int MOD = 1000000007;
+        int[] dp = new int[n + 1];
+        dp[0] = 1;
+
+        for (int picked = 0; picked <= n; picked++) {
+            for (int delivered = 0; delivered < picked; delivered++) {
+                dp[delivered + 1] = (int)((dp[delivered + 1] + 
+                                    (picked - delivered) * 1L * dp[delivered]) % MOD);
+            }
+
+            if (picked < n) {
+                int[] next_dp = new int[n + 1];
+                for (int delivered = 0; delivered <= picked; delivered++) {
+                    next_dp[delivered] = (int)((next_dp[delivered] + 
+                                         (n - picked) *  1L *dp[delivered]) % MOD);
+                }
+                dp = next_dp;
+            }
+        }
+
+        return dp[n];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countOrders(int n) {
+        const int MOD = 1000000007;
+        vector<int> dp(n + 1);
+        dp[0] = 1;
+
+        for (int picked = 0; picked <= n; picked++) {
+            for (int delivered = 0; delivered < picked; delivered++) {
+                dp[delivered + 1] = (int)((dp[delivered + 1] + 
+                                    (picked - delivered) * 1LL * dp[delivered]) % MOD);
+            }
+            if (picked < n) {
+                vector<int> next_dp(n + 1);
+                for (int delivered = 0; delivered <= picked; delivered++) {
+                    next_dp[delivered] = (int)((next_dp[delivered] + 
+                                         (n - picked) * 1LL * dp[delivered]) % MOD);
+                }
+                dp = next_dp;
+            }
+        }
+
+        return dp[n];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    countOrders(n) {
+        const MOD = 1000000007;
+        let dp = new Array(n + 1).fill(0);
+        dp[0] = 1;
+
+        for (let picked = 0; picked <= n; picked++) {
+            for (let delivered = 0; delivered < picked; delivered++) {
+                dp[delivered + 1] = (
+                    (dp[delivered + 1] +
+                    (picked - delivered) * dp[delivered]) % MOD
+                );
+            }
+    
+            if (picked < n) {
+                let next_dp = new Array(n + 1).fill(0);
+                for (let delivered = 0; delivered <= picked; delivered++) {
+                    next_dp[delivered] = (
+                        (next_dp[delivered] +
+                        (n - picked) * dp[delivered]) % MOD
+                    );
+                }
+                dp = next_dp;
+            }
+        }
+
+        return dp[n];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 5. Combinatorics
+
+::tabs-start
+
+```python
+class Solution:
+    def countOrders(self, n: int) -> int:
+        MOD = 1000000007
+        slots, res = 2 * n, 1
+        while slots > 0:
+            valid_choices = slots * (slots - 1) // 2
+            res = (res * valid_choices) % MOD
+            slots -= 2
+        return res
+```
+
+```java
+public class Solution {
+    public int countOrders(int n) {
+        int MOD = 1000000007;
+        long slots = 2 * n, res = 1;
+
+        while (slots > 0) {
+            long validChoices = slots * (slots - 1) / 2;
+            res = (res * validChoices) % MOD;
+            slots -= 2;
+        }
+        return (int) res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countOrders(int n) {
+        const int MOD = 1000000007;
+        long long slots = 2 * n, res = 1;
+
+        while (slots > 0) {
+            long long validChoices = slots * (slots - 1) / 2;
+            res = (res * validChoices) % MOD;
+            slots -= 2;
+        }
+        return (int) res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    countOrders(n) {
+        const MOD = 1000000007;
+        let slots = 2 * n, res = 1;
+
+        while (slots > 0) {
+            let validChoices = (slots * (slots - 1)) / 2;
+            res = (res * validChoices) % MOD;
+            slots -= 2;
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 6. Probability
+
+::tabs-start
+
+```python
+class Solution:
+    def countOrders(self, n: int) -> int:
+        MOD = 1000000007
+        res = 1
+
+        for slot in range(1, 2 * n + 1):
+            res  *= slot
+            if slot % 2 == 0:
+                res >>= 1
+            res %= MOD
+
+        return res
+```
+
+```java
+public class Solution {
+    public int countOrders(int n) {
+        int MOD = 1000000007;
+        long res = 1;
+
+        for (int slot = 1; slot <= 2 * n; slot++) {
+            res *= slot;
+            if (slot % 2 == 0) {
+                res >>= 1;
+            }
+            res %= MOD;
+        }
+        return (int) res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countOrders(int n) {
+        const int MOD = 1000000007;
+        long long res = 1;
+
+        for (int slot = 1; slot <= 2 * n; slot++) {
+            res *= slot;
+            if (slot % 2 == 0) {
+                res >>= 1;
+            }
+            res %= MOD;
+        }
+        return (int) res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    countOrders(n) {
+        const MOD = BigInt(1000000007);
+        let res = BigInt(1);
+
+        for (let slot = 1; slot <= 2 * n; slot++) {
+            res *= BigInt(slot);
+            if (slot % 2 === 0) {
+                res /= BigInt(2);
+            }
+            res %= MOD;
+        }
+        return Number(res);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/count-connected-components.md b/articles/count-connected-components.md
index 2b57b16dd..c31580864 100644
--- a/articles/count-connected-components.md
+++ b/articles/count-connected-components.md
@@ -165,6 +165,105 @@ public class Solution {
 }
 ```
 
+```go
+func countComponents(n int, edges [][]int) int {
+    adj := make([][]int, n)
+	visit := make([]bool, n)
+	for _, edge := range edges {
+		u, v := edge[0], edge[1]
+		adj[u] = append(adj[u], v)
+		adj[v] = append(adj[v], u)
+	}
+
+	var dfs func(int)
+	dfs = func(node int) {
+		for _, nei := range adj[node] {
+			if !visit[nei] {
+				visit[nei] = true
+				dfs(nei)
+			}
+		}
+	}
+
+	res := 0
+	for node := 0; node < n; node++ {
+		if !visit[node] {
+			visit[node] = true
+			dfs(node)
+			res++
+		}
+	}
+	return res
+}
+```
+
+```kotlin
+class Solution {
+    fun countComponents(n: Int, edges: Array<IntArray>): Int {
+        val adj = Array(n) { mutableListOf<Int>() }
+        val visit = BooleanArray(n)
+        for ((u, v) in edges) {
+            adj[u].add(v)
+            adj[v].add(u)
+        }
+
+        fun dfs(node: Int) {
+            for (nei in adj[node]) {
+                if (!visit[nei]) {
+                    visit[nei] = true
+                    dfs(nei)
+                }
+            }
+        }
+
+        var res = 0
+        for (node in 0 until n) {
+            if (!visit[node]) {
+                visit[node] = true
+                dfs(node)
+                res++
+            }
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func countComponents(_ n: Int, _ edges: [[Int]]) -> Int {
+        var adj = Array(repeating: [Int](), count: n)
+        var visit = Array(repeating: false, count: n)
+        
+        for edge in edges {
+            let u = edge[0], v = edge[1]
+            adj[u].append(v)
+            adj[v].append(u)
+        }
+        
+        func dfs(_ node: Int) {
+            for nei in adj[node] {
+                if !visit[nei] {
+                    visit[nei] = true
+                    dfs(nei)
+                }
+            }
+        }
+        
+        var res = 0
+        for node in 0..<n {
+            if !visit[node] {
+                visit[node] = true
+                dfs(node)
+                res += 1
+            }
+        }
+        
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -369,6 +468,117 @@ public class Solution {
 }
 ```
 
+```go
+func countComponents(n int, edges [][]int) int {
+    adj := make([][]int, n)
+	visit := make([]bool, n)
+	for _, edge := range edges {
+		u, v := edge[0], edge[1]
+		adj[u] = append(adj[u], v)
+		adj[v] = append(adj[v], u)
+	}
+
+	bfs := func(node int) {
+		q := []int{node}
+		visit[node] = true
+		for len(q) > 0 {
+			cur := q[0]
+			q = q[1:] 
+			for _, nei := range adj[cur] {
+				if !visit[nei] {
+					visit[nei] = true
+					q = append(q, nei) 
+				}
+			}
+		}
+	}
+
+	res := 0
+	for node := 0; node < n; node++ {
+		if !visit[node] {
+			bfs(node)
+			res++
+		}
+	}
+	return res
+}
+```
+
+```kotlin
+class Solution {
+    fun countComponents(n: Int, edges: Array<IntArray>): Int {
+        val adj = Array(n) { mutableListOf<Int>() }
+        val visit = BooleanArray(n)
+        for ((u, v) in edges) {
+            adj[u].add(v)
+            adj[v].add(u)
+        }
+
+        fun bfs(node: Int) {
+            val q: Queue<Int> = LinkedList()
+            q.offer(node)
+            visit[node] = true
+            while (q.isNotEmpty()) {
+                val cur = q.poll()
+                for (nei in adj[cur]) {
+                    if (!visit[nei]) {
+                        visit[nei] = true
+                        q.offer(nei)
+                    }
+                }
+            }
+        }
+
+        var res = 0
+        for (node in 0 until n) {
+            if (!visit[node]) {
+                bfs(node)
+                res++
+            }
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func countComponents(_ n: Int, _ edges: [[Int]]) -> Int {
+        var adj = Array(repeating: [Int](), count: n)
+        var visit = Array(repeating: false, count: n)
+        for edge in edges {
+            let u = edge[0], v = edge[1]
+            adj[u].append(v)
+            adj[v].append(u)
+        }
+        
+        func bfs(_ node: Int) {
+            var q = Deque<Int>()
+            q.append(node)
+            visit[node] = true
+            while !q.isEmpty {
+                let cur = q.removeFirst()
+                for nei in adj[cur] {
+                    if !visit[nei] {
+                        visit[nei] = true
+                        q.append(nei)
+                    }
+                }
+            }
+        }
+        
+        var res = 0
+        for node in 0..<n {
+            if !visit[node] {
+                bfs(node)
+                res += 1
+            }
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -419,7 +629,7 @@ class Solution:
 ```
 
 ```java
-public class DSU {
+class DSU {
     int[] parent;
     int[] rank;
 
@@ -641,6 +851,154 @@ public class Solution {
 }
 ```
 
+```go
+type DSU struct {
+    parent []int
+    rank   []int
+}
+
+func NewDSU(n int) *DSU {
+    dsu := &DSU{
+        parent: make([]int, n),
+        rank:   make([]int, n),
+    }
+    for i := 0; i < n; i++ {
+        dsu.parent[i] = i
+        dsu.rank[i] = 1
+    }
+    return dsu
+}
+
+func (dsu *DSU) Find(node int) int {
+    cur := node
+    for cur != dsu.parent[cur] {
+        dsu.parent[cur] = dsu.parent[dsu.parent[cur]]
+        cur = dsu.parent[cur]
+    }
+    return cur
+}
+
+func (dsu *DSU) Union(u, v int) bool {
+    pu := dsu.Find(u)
+    pv := dsu.Find(v)
+    if pu == pv {
+        return false
+    }
+    if dsu.rank[pv] > dsu.rank[pu] {
+        pu, pv = pv, pu
+    }
+    dsu.parent[pv] = pu
+    dsu.rank[pu] += dsu.rank[pv]
+    return true
+}
+
+func countComponents(n int, edges [][]int) int {
+    dsu := NewDSU(n)
+    res := n
+    for _, edge := range edges {
+        u, v := edge[0], edge[1]
+        if dsu.Union(u, v) {
+            res--
+        }
+    }
+    return res
+}
+```
+
+```kotlin
+class DSU(n: Int) {
+    val parent = IntArray(n) { it }
+    val rank = IntArray(n) { 1 }
+
+    fun find(node: Int): Int {
+        var cur = node
+        while (cur != parent[cur]) {
+            parent[cur] = parent[parent[cur]]
+            cur = parent[cur]
+        }
+        return cur
+    }
+
+    fun union(u: Int, v: Int): Boolean {
+        val pu = find(u)
+        val pv = find(v)
+        if (pu == pv) {
+            return false
+        }
+        if (rank[pv] > rank[pu]) {
+            parent[pu] = pv
+        } else {
+            parent[pv] = pu
+            rank[pu] += rank[pv]
+        }
+        return true
+    }
+}
+
+class Solution {
+    fun countComponents(n: Int, edges: Array<IntArray>): Int {
+        val dsu = DSU(n)
+        var res = n
+        for (edge in edges) {
+            val (u, v) = edge
+            if (dsu.union(u, v)) {
+                res--
+            }
+        }
+        return res
+    }
+}
+```
+
+```swift
+class DSU {
+    var parent: [Int]
+    var rank: [Int]
+    
+    init(_ n: Int) {
+        parent = Array(0..<n)
+        rank = Array(repeating: 1, count: n)
+    }
+    
+    func find(_ node: Int) -> Int {
+        var cur = node
+        while cur != parent[cur] {
+            parent[cur] = parent[parent[cur]]
+            cur = parent[cur]
+        }
+        return cur
+    }
+    
+    func union(_ u: Int, _ v: Int) -> Bool {
+        let pu = find(u)
+        let pv = find(v)
+        if pu == pv { return false }
+        var rootU = pu
+        var rootV = pv
+        if rank[rootV] > rank[rootU] {
+            swap(&rootU, &rootV)
+        }
+        parent[rootV] = rootU
+        rank[rootU] += rank[rootV]
+        return true
+    }
+}
+
+class Solution {
+    func countComponents(_ n: Int, _ edges: [[Int]]) -> Int {
+        let dsu = DSU(n)
+        var res = n
+        for edge in edges {
+            let u = edge[0], v = edge[1]
+            if dsu.union(u, v) {
+                res -= 1
+            }
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/count-good-nodes-in-binary-tree.md b/articles/count-good-nodes-in-binary-tree.md
index 9dcd4d053..d9356f32c 100644
--- a/articles/count-good-nodes-in-binary-tree.md
+++ b/articles/count-good-nodes-in-binary-tree.md
@@ -172,6 +172,117 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func goodNodes(root *TreeNode) int {
+    if root == nil {
+        return 0
+    }
+
+    var dfs func(node *TreeNode, maxVal int) int
+    dfs = func(node *TreeNode, maxVal int) int {
+        if node == nil {
+            return 0
+        }
+
+        res := 0
+        if node.Val >= maxVal {
+            res = 1
+        }
+        
+        maxVal = max(maxVal, node.Val)
+        res += dfs(node.Left, maxVal)
+        res += dfs(node.Right, maxVal)
+        
+        return res
+    }
+
+    return dfs(root, root.Val)
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    fun goodNodes(root: TreeNode?): Int {
+        if (root == null) return 0
+
+        fun dfs(node: TreeNode?, maxVal: Int): Int {
+            if (node == null) return 0
+
+            var res = 0
+            if (node.`val` >= maxVal) {
+                res = 1
+            }
+
+            val newMaxVal = maxOf(maxVal, node.`val`)
+            res += dfs(node.left, newMaxVal)
+            res += dfs(node.right, newMaxVal)
+
+            return res
+        }
+
+        return dfs(root, root.`val`)
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func goodNodes(_ root: TreeNode?) -> Int {
+        func dfs(_ node: TreeNode?, _ maxVal: Int) -> Int {
+            guard let node = node else { return 0 }
+
+            var res = node.val >= maxVal ? 1 : 0
+            let newMaxVal = max(maxVal, node.val)
+            res += dfs(node.left, newMaxVal)
+            res += dfs(node.right, newMaxVal)
+            return res
+        }
+
+        return dfs(root, root?.val ?? Int.min)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -371,6 +482,147 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func goodNodes(root *TreeNode) int {
+    if root == nil {
+        return 0
+    }
+
+    res := 0
+    q := []struct {
+        node   *TreeNode
+        maxVal int
+    }{{root, math.MinInt32}}
+
+    for len(q) > 0 {
+        front := q[0]
+        q = q[1:]
+
+        node := front.node
+        maxVal := front.maxVal
+
+        if node.Val >= maxVal {
+            res++
+        }
+
+        newMaxVal := max(maxVal, node.Val)
+
+        if node.Left != nil {
+            q = append(q, struct {
+                node   *TreeNode
+                maxVal int
+            }{node.Left, newMaxVal})
+        }
+
+        if node.Right != nil {
+            q = append(q, struct {
+                node   *TreeNode
+                maxVal int
+            }{node.Right, newMaxVal})
+        }
+    }
+
+    return res
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    fun goodNodes(root: TreeNode?): Int {
+        if (root == null) return 0
+
+        var res = 0
+        val q = ArrayDeque<Pair<TreeNode, Int>>()
+        q.add(root to Int.MIN_VALUE)
+
+        while (q.isNotEmpty()) {
+            val (node, maxVal) = q.removeFirst()
+
+            if (node.`val` >= maxVal) {
+                res++
+            }
+
+            val newMaxVal = maxOf(maxVal, node.`val`)
+
+            node.left?.let { q.add(it to newMaxVal) }
+            node.right?.let { q.add(it to newMaxVal) }
+        }
+
+        return res
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func goodNodes(_ root: TreeNode?) -> Int {
+        guard let root = root else { return 0 }
+
+        var res = 0
+        var q = Deque<(TreeNode, Int)>()
+        q.append((root, Int.min))
+
+        while !q.isEmpty {
+            let (node, maxVal) = q.popFirst()!
+            if node.val >= maxVal {
+                res += 1
+            }
+
+            let newMaxVal = max(maxVal, node.val)
+
+            if let left = node.left {
+                q.append((left, newMaxVal))
+            }
+            if let right = node.right {
+                q.append((right, newMaxVal))
+            }
+        }
+
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/count-number-of-bad-pairs.md b/articles/count-number-of-bad-pairs.md
new file mode 100644
index 000000000..936e3af7f
--- /dev/null
+++ b/articles/count-number-of-bad-pairs.md
@@ -0,0 +1,157 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def countBadPairs(self, nums: List[int]) -> int:
+        n, res = len(nums), 0
+        for i in range(n - 1):
+            for j in range(i + 1, n):
+                if j - i != nums[j] - nums[i]:
+                    res += 1
+        return res
+```
+
+```java
+public class Solution {
+    public long countBadPairs(int[] nums) {
+        int n = nums.length;
+        long res = 0;
+        for (int i = 0; i < n - 1; i++) {
+            for (int j = i + 1; j < n; j++) {
+                if (j - i != nums[j] - nums[i]) {
+                    res++;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long countBadPairs(vector<int>& nums) {
+        int n = nums.size();
+        long long res = 0;
+        for (int i = 0; i < n - 1; i++) {
+            for (int j = i + 1; j < n; j++) {
+                if (j - i != nums[j] - nums[i]) {
+                    res++;
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    countBadPairs(nums) {
+        let n = nums.length, res = 0;
+        for (let i = 0; i < n - 1; i++) {
+            for (let j = i + 1; j < n; j++) {
+                if (j - i !== nums[j] - nums[i]) {
+                    res++;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def countBadPairs(self, nums: List[int]) -> int:
+        good_pairs = 0
+        total_pairs = 0
+        count = defaultdict(int)
+
+        for i in range(len(nums)):
+            total_pairs += i
+            good_pairs += count[nums[i] - i]
+            count[nums[i] - i] += 1
+
+        return total_pairs - good_pairs
+```
+
+```java
+public class Solution {
+    public long countBadPairs(int[] nums) {
+        Map<Integer, Integer> count = new HashMap<>();
+        long total = 0, good = 0;
+        for (int i = 0; i < nums.length; i++) {
+            int key = nums[i] - i;
+            good += count.getOrDefault(key, 0);
+            count.put(key, count.getOrDefault(key, 0) + 1);
+            total += i;
+        }
+        return total - good;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long countBadPairs(vector<int>& nums) {
+        unordered_map<int, int> count;
+        long long total = 0, good = 0;
+        for (int i = 0; i < nums.size(); i++) {
+            int key = nums[i] - i;
+            good += count[key];
+            count[key]++;
+            total += i;
+        }
+        return total - good;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    countBadPairs(nums) {
+        let count = new Map();
+        let total = 0, good = 0;
+        for (let i = 0; i < nums.length; i++) {
+            let key = nums[i] - i;
+            good += count.get(key) || 0;
+            count.set(key, (count.get(key) || 0) + 1);
+            total += i;
+        }
+        return total - good;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/count-number-of-islands.md b/articles/count-number-of-islands.md
index 7972f2432..042d79082 100644
--- a/articles/count-number-of-islands.md
+++ b/articles/count-number-of-islands.md
@@ -169,6 +169,107 @@ public class Solution {
 }
 ```
 
+```go
+func numIslands(grid [][]byte) int {
+    directions := [][]int{{1, 0}, {-1, 0}, {0, 1}, {0, -1}}
+    rows, cols := len(grid), len(grid[0])
+    islands := 0
+
+    var dfs func(r, c int)
+    dfs = func(r, c int) {
+        if r < 0 || c < 0 || r >= rows || 
+           c >= cols || grid[r][c] == '0' {
+            return
+        }
+        grid[r][c] = '0'
+        for _, dir := range directions {
+            dfs(r+dir[0], c+dir[1])
+        }
+    }
+
+    for r := 0; r < rows; r++ {
+        for c := 0; c < cols; c++ {
+            if grid[r][c] == '1' {
+                dfs(r, c)
+                islands++
+            }
+        }
+    }
+
+    return islands
+}
+```
+
+```kotlin
+class Solution {
+    fun numIslands(grid: Array<CharArray>): Int {
+        val directions = arrayOf(intArrayOf(1, 0), 
+                                 intArrayOf(-1, 0), 
+                                 intArrayOf(0, 1), 
+                                 intArrayOf(0, -1))
+        val rows = grid.size
+        val cols = grid[0].size
+        var islands = 0
+
+        fun dfs(r: Int, c: Int) {
+            if (r < 0 || c < 0 || r >= rows || 
+                c >= cols || grid[r][c] == '0') {
+                return
+            }
+            grid[r][c] = '0'
+            for (dir in directions) {
+                dfs(r + dir[0], c + dir[1])
+            }
+        }
+
+        for (r in 0 until rows) {
+            for (c in 0 until cols) {
+                if (grid[r][c] == '1') {
+                    dfs(r, c)
+                    islands++
+                }
+            }
+        }
+
+        return islands
+    }
+}
+```
+
+```swift
+class Solution {
+    func numIslands(_ grid: [[Character]]) -> Int {
+        let directions = [[1, 0], [-1, 0], [0, 1], [0, -1]]
+        let ROWS = grid.count
+        let COLS = grid[0].count
+        var islands = 0
+        var grid = grid
+
+        func dfs(_ r: Int, _ c: Int) {
+            if r < 0 || c < 0 || r >= ROWS || c >= COLS || grid[r][c] == "0" {
+                return
+            }
+
+            grid[r][c] = "0"
+            for dir in directions {
+                dfs(r + dir[0], c + dir[1])
+            }
+        }
+
+        for r in 0..<ROWS {
+            for c in 0..<COLS {
+                if grid[r][c] == "1" {
+                    dfs(r, c)
+                    islands += 1
+                }
+            }
+        }
+
+        return islands
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -390,6 +491,133 @@ public class Solution {
 }
 ```
 
+```go
+func numIslands(grid [][]byte) int {
+    directions := [][]int{{1, 0}, {-1, 0}, {0, 1}, {0, -1}}
+    rows, cols := len(grid), len(grid[0])
+    islands := 0
+
+    var bfs func(r, c int)
+    bfs = func(r, c int) {
+        q := [][]int{{r, c}}
+        grid[r][c] = '0'
+
+        for len(q) > 0 {
+            front := q[0]
+            q = q[1:]
+            row, col := front[0], front[1]
+            for _, dir := range directions {
+                nr, nc := row+dir[0], col+dir[1]
+                if nr < 0 || nc < 0 || nr >= rows || 
+                   nc >= cols || grid[nr][nc] == '0' {
+                    continue
+                }
+                q = append(q, []int{nr, nc})
+                grid[nr][nc] = '0'
+            }
+        }
+    }
+
+    for r := 0; r < rows; r++ {
+        for c := 0; c < cols; c++ {
+            if grid[r][c] == '1' {
+                bfs(r, c)
+                islands++
+            }
+        }
+    }
+
+    return islands
+}
+```
+
+```kotlin
+class Solution {
+    fun numIslands(grid: Array<CharArray>): Int {
+        val directions = arrayOf(intArrayOf(1, 0), 
+                                 intArrayOf(-1, 0), 
+                                 intArrayOf(0, 1), 
+                                 intArrayOf(0, -1))
+        val rows = grid.size
+        val cols = grid[0].size
+        var islands = 0
+
+        fun bfs(r: Int, c: Int) {
+            val q: Queue<IntArray> = LinkedList()
+            grid[r][c] = '0'
+            q.add(intArrayOf(r, c))
+
+            while (q.isNotEmpty()) {
+                val (row, col) = q.poll()
+                for (dir in directions) {
+                    val nr = row + dir[0]
+                    val nc = col + dir[1]
+                    if (nr < 0 || nc < 0 || nr >= rows || 
+                        nc >= cols || grid[nr][nc] == '0') {
+                        continue
+                    }
+                    q.add(intArrayOf(nr, nc))
+                    grid[nr][nc] = '0'
+                }
+            }
+        }
+
+        for (r in 0 until rows) {
+            for (c in 0 until cols) {
+                if (grid[r][c] == '1') {
+                    bfs(r, c)
+                    islands++
+                }
+            }
+        }
+
+        return islands
+    }
+}
+```
+
+```swift
+class Solution {
+    func numIslands(_ grid: [[Character]]) -> Int {
+        let directions = [[1, 0], [-1, 0], [0, 1], [0, -1]]
+        let ROWS = grid.count
+        let COLS = grid[0].count
+        var islands = 0
+        var grid = grid
+
+        func bfs(_ r: Int, _ c: Int) {
+            var queue = Deque<(Int, Int)>()
+            grid[r][c] = "0"
+            queue.append((r, c))
+
+            while !queue.isEmpty {
+                let (row, col) = queue.popFirst()!
+                for dir in directions {
+                    let nr = row + dir[0]
+                    let nc = col + dir[1]
+                    if nr < 0 || nc < 0 || nr >= ROWS || nc >= COLS || grid[nr][nc] == "0" {
+                        continue
+                    }
+                    queue.append((nr, nc))
+                    grid[nr][nc] = "0"
+                }
+            }
+        }
+
+        for r in 0..<ROWS {
+            for c in 0..<COLS {
+                if grid[r][c] == "1" {
+                    bfs(r, c)
+                    islands += 1
+                }
+            }
+        }
+
+        return islands
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -458,7 +686,7 @@ class Solution:
 ```
 
 ```java
-public class DSU {
+class DSU {
     private int[] Parent, Size;
 
     public DSU(int n) {
@@ -744,6 +972,216 @@ public class Solution {
 }
 ```
 
+```go
+type DSU struct {
+    Parent []int
+    Size   []int
+}
+
+func NewDSU(n int) *DSU {
+    dsu := &DSU{
+        Parent: make([]int, n+1),
+        Size:   make([]int, n+1),
+    }
+    for i := 0; i <= n; i++ {
+        dsu.Parent[i] = i
+        dsu.Size[i] = 1
+    }
+    return dsu
+}
+
+func (dsu *DSU) find(node int) int {
+    if dsu.Parent[node] != node {
+        dsu.Parent[node] = dsu.find(dsu.Parent[node])
+    }
+    return dsu.Parent[node]
+}
+
+func (dsu *DSU) union(u, v int) bool {
+    pu := dsu.find(u)
+    pv := dsu.find(v)
+    if pu == pv {
+        return false
+    }
+    if dsu.Size[pu] >= dsu.Size[pv] {
+        dsu.Size[pu] += dsu.Size[pv]
+        dsu.Parent[pv] = pu
+    } else {
+        dsu.Size[pv] += dsu.Size[pu]
+        dsu.Parent[pu] = pv
+    }
+    return true
+}
+
+func numIslands(grid [][]byte) int {
+    rows, cols := len(grid), len(grid[0])
+    dsu := NewDSU(rows * cols)
+    directions := [][]int{{1, 0}, {-1, 0}, {0, 1}, {0, -1}}
+    islands := 0
+
+    index := func(r, c int) int {
+        return r*cols + c
+    }
+
+    for r := 0; r < rows; r++ {
+        for c := 0; c < cols; c++ {
+            if grid[r][c] == '1' {
+                islands++
+                for _, dir := range directions {
+                    nr, nc := r+dir[0], c+dir[1]
+                    if nr < 0 || nc < 0 || nr >= rows || 
+                       nc >= cols || grid[nr][nc] == '0' {
+                        continue
+                    }
+                    if dsu.union(index(r, c), index(nr, nc)) {
+                        islands--
+                    }
+                }
+            }
+        }
+    }
+
+    return islands
+}
+```
+
+```kotlin
+class DSU(n: Int) {
+    val Parent = IntArray(n + 1) { it }
+    val Size = IntArray(n + 1) { 1 }
+
+    fun find(node: Int): Int {
+        if (Parent[node] != node) {
+            Parent[node] = find(Parent[node])
+        }
+        return Parent[node]
+    }
+
+    fun union(u: Int, v: Int): Boolean {
+        val pu = find(u)
+        val pv = find(v)
+        if (pu == pv) return false
+        if (Size[pu] >= Size[pv]) {
+            Size[pu] += Size[pv]
+            Parent[pv] = pu
+        } else {
+            Size[pv] += Size[pu]
+            Parent[pu] = pv
+        }
+        return true
+    }
+}
+
+class Solution {
+    fun numIslands(grid: Array<CharArray>): Int {
+        val rows = grid.size
+        val cols = grid[0].size
+        val dsu = DSU(rows * cols)
+        val directions = arrayOf(intArrayOf(1, 0), 
+                                 intArrayOf(-1, 0), 
+                                 intArrayOf(0, 1), 
+                                 intArrayOf(0, -1))
+        var islands = 0
+
+        fun index(r: Int, c: Int): Int {
+            return r * cols + c
+        }
+
+        for (r in 0 until rows) {
+            for (c in 0 until cols) {
+                if (grid[r][c] == '1') {
+                    islands++
+                    for (dir in directions) {
+                        val nr = r + dir[0]
+                        val nc = c + dir[1]
+                        if (nr < 0 || nc < 0 || nr >= rows || 
+                            nc >= cols || grid[nr][nc] == '0') {
+                            continue
+                        }
+                        if (dsu.union(index(r, c), index(nr, nc))) {
+                            islands--
+                        }
+                    }
+                }
+            }
+        }
+
+        return islands
+    }
+}
+```
+
+```swift
+class DSU {
+    private var parent: [Int]
+    private var size: [Int]
+
+    init(_ n: Int) {
+        parent = Array(0...n)
+        size = Array(repeating: 1, count: n + 1)
+    }
+
+    func find(_ node: Int) -> Int {
+        if parent[node] != node {
+            parent[node] = find(parent[node])
+        }
+        return parent[node]
+    }
+
+    func union(_ u: Int, _ v: Int) -> Bool {
+        let pu = find(u)
+        let pv = find(v)
+        if pu == pv {
+            return false
+        }
+        if size[pu] >= size[pv] {
+            size[pu] += size[pv]
+            parent[pv] = pu
+        } else {
+            size[pv] += size[pu]
+            parent[pu] = pv
+        }
+        return true
+    }
+}
+
+class Solution {
+    func numIslands(_ grid: [[Character]]) -> Int {
+        let ROWS = grid.count
+        let COLS = grid[0].count
+        let dsu = DSU(ROWS * COLS)
+
+        func index(_ r: Int, _ c: Int) -> Int {
+            return r * COLS + c
+        }
+
+        let directions = [(1, 0), (-1, 0), (0, 1), (0, -1)]
+        var islands = 0
+        var grid = grid
+
+        for r in 0..<ROWS {
+            for c in 0..<COLS {
+                if grid[r][c] == "1" {
+                    islands += 1
+                    for dir in directions {
+                        let nr = r + dir.0
+                        let nc = c + dir.1
+                        if nr < 0 || nc < 0 || nr >= ROWS || nc >= COLS || grid[nr][nc] == "0" {
+                            continue
+                        }
+                        if dsu.union(index(r, c), index(nr, nc)) {
+                            islands -= 1
+                        }
+                    }
+                }
+            }
+        }
+
+        return islands
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/count-odd-numbers-in-an-interval-range.md b/articles/count-odd-numbers-in-an-interval-range.md
new file mode 100644
index 000000000..1cbaf37b8
--- /dev/null
+++ b/articles/count-odd-numbers-in-an-interval-range.md
@@ -0,0 +1,187 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def countOdds(self, low: int, high: int) -> int:
+        odd = 0
+        for num in range(low, high + 1):
+            if num & 1:
+                odd += 1
+        return odd
+```
+
+```java
+public class Solution {
+    public int countOdds(int low, int high) {
+        int odd = 0;
+        for (int num = low; num <= high; num++) {
+            if ((num & 1) == 1) {
+                odd++;
+            }
+        }
+        return odd;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countOdds(int low, int high) {
+        int odd = 0;
+        for (int num = low; num <= high; num++) {
+            if (num & 1) {
+                odd++;
+            }
+        }
+        return odd;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} low
+     * @param {number} high
+     * @return {number}
+     */
+    countOdds(low, high) {
+        let odd = 0;
+        for (let num = low; num <= high; num++) {
+            if (num & 1) {
+                odd++;
+            }
+        }
+        return odd;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+> Where $n$ is the number of integers in the given range.
+
+---
+
+## 2. Math
+
+::tabs-start
+
+```python
+class Solution:
+    def countOdds(self, low: int, high: int) -> int:
+        length = high - low + 1
+        count = length // 2
+        if length % 2 and low % 2:
+            count += 1
+        return count
+```
+
+```java
+public class Solution {
+    public int countOdds(int low, int high) {
+        int length = high - low + 1;
+        int count = length / 2;
+        if (length % 2 == 1 && low % 2 == 1) {
+            count++;
+        }
+        return count;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countOdds(int low, int high) {
+        int length = high - low + 1;
+        int count = length / 2;
+        if (length % 2 == 1 && low % 2 == 1) {
+            count++;
+        }
+        return count;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} low
+     * @param {number} high
+     * @return {number}
+     */
+    countOdds(low, high) {
+        let length = high - low + 1;
+        let count = Math.floor(length / 2);
+        if (length % 2 === 1 && low % 2 === 1) {
+            count++;
+        }
+        return count;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Math (One Liner)
+
+::tabs-start
+
+```python
+class Solution:
+    def countOdds(self, low: int, high: int) -> int:
+        return ((high + 1) >> 1) - (low >> 1)
+```
+
+```java
+public class Solution {
+    public int countOdds(int low, int high) {
+        return ((high + 1) >> 1) - (low >> 1);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countOdds(int low, int high) {
+        return ((high + 1) >> 1) - (low >> 1);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} low
+     * @param {number} high
+     * @return {number}
+     */
+    countOdds(low, high) {
+        return ((high + 1) >> 1) - (low >> 1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/count-of-matches-in-tournament.md b/articles/count-of-matches-in-tournament.md
new file mode 100644
index 000000000..2ceeeae80
--- /dev/null
+++ b/articles/count-of-matches-in-tournament.md
@@ -0,0 +1,120 @@
+## 1. Simulation
+
+::tabs-start
+
+```python
+class Solution:
+    def numberOfMatches(self, n: int) -> int:
+        res = 0
+
+        while n > 1:
+            res += n // 2
+            n = (n + 1) // 2
+
+        return res
+```
+
+```java
+public class Solution {
+    public int numberOfMatches(int n) {
+        int res = 0;
+
+        while (n > 1) {
+            res += n / 2;
+            n = (n + 1) / 2;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numberOfMatches(int n) {
+        int res = 0;
+
+        while (n > 1) {
+            res += n / 2;
+            n = (n + 1) / 2;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    numberOfMatches(n) {
+        let res = 0;
+
+        while (n > 1) {
+            res += Math.floor(n / 2);
+            n = Math.ceil(n / 2);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Math
+
+::tabs-start
+
+```python
+class Solution:
+    def numberOfMatches(self, n: int) -> int:
+        return n - 1
+```
+
+```java
+public class Solution {
+    public int numberOfMatches(int n) {
+        return n - 1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numberOfMatches(int n) {
+        return n - 1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    numberOfMatches(n) {
+        return n - 1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/count-paths.md b/articles/count-paths.md
index 8c20509f0..5db166df2 100644
--- a/articles/count-paths.md
+++ b/articles/count-paths.md
@@ -90,6 +90,55 @@ public class Solution {
 }
 ```
 
+```go
+func uniquePaths(m int, n int) int {
+    var dfs func(i, j int) int
+    dfs = func(i, j int) int {
+        if i == m-1 && j == n-1 {
+            return 1
+        }
+        if i >= m || j >= n {
+            return 0
+        }
+        return dfs(i, j+1) + dfs(i+1, j)
+    }
+    
+    return dfs(0, 0)
+}
+```
+
+```kotlin
+class Solution {
+    fun uniquePaths(m: Int, n: Int): Int {
+        fun dfs(i: Int, j: Int): Int {
+            if (i == m - 1 && j == n - 1) return 1
+            if (i >= m || j >= n) return 0
+            return dfs(i, j + 1) + dfs(i + 1, j)
+        }
+        
+        return dfs(0, 0)
+    }
+}
+```
+
+```swift
+class Solution {
+    func uniquePaths(_ m: Int, _ n: Int) -> Int {
+        func dfs(_ i: Int, _ j: Int) -> Int {
+            if i == m - 1 && j == n - 1 {
+                return 1
+            }
+            if i >= m || j >= n {
+                return 0
+            }
+            return dfs(i, j + 1) + dfs(i + 1, j)
+        }
+
+        return dfs(0, 0)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -224,6 +273,80 @@ public class Solution {
 }
 ```
 
+```go
+func uniquePaths(m int, n int) int {
+    memo := make([][]int, m)
+    for i := range memo {
+        memo[i] = make([]int, n)
+        for j := range memo[i] {
+            memo[i][j] = -1
+        }
+    }
+
+    var dfs func(i, j int) int
+    dfs = func(i, j int) int {
+        if i == m-1 && j == n-1 {
+            return 1
+        }
+        if i >= m || j >= n {
+            return 0
+        }
+        if memo[i][j] != -1 {
+            return memo[i][j]
+        }
+        
+        memo[i][j] = dfs(i, j+1) + dfs(i+1, j)
+        return memo[i][j]
+    }
+    
+    return dfs(0, 0)
+}
+```
+
+```kotlin
+class Solution {
+    fun uniquePaths(m: Int, n: Int): Int {
+        val memo = Array(m) { IntArray(n) { -1 } }
+
+        fun dfs(i: Int, j: Int): Int {
+            if (i == m - 1 && j == n - 1) return 1
+            if (i >= m || j >= n) return 0
+            if (memo[i][j] != -1) return memo[i][j]
+
+            memo[i][j] = dfs(i, j + 1) + dfs(i + 1, j)
+            return memo[i][j]
+        }
+
+        return dfs(0, 0)
+    }
+}
+```
+
+```swift
+class Solution {
+    func uniquePaths(_ m: Int, _ n: Int) -> Int {
+        var memo = Array(repeating: Array(repeating: -1, count: n), count: m)
+
+        func dfs(_ i: Int, _ j: Int) -> Int {
+            if i == m - 1 && j == n - 1 {
+                return 1
+            }
+            if i >= m || j >= n {
+                return 0
+            }
+            if memo[i][j] != -1 {
+                return memo[i][j]
+            }
+
+            memo[i][j] = dfs(i, j + 1) + dfs(i + 1, j)
+            return memo[i][j]
+        }
+
+        return dfs(0, 0)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -327,6 +450,58 @@ public class Solution {
 }
 ```
 
+```go
+func uniquePaths(m int, n int) int {
+    dp := make([][]int, m+1)
+    for i := range dp {
+        dp[i] = make([]int, n+1)
+    }
+    dp[m-1][n-1] = 1
+
+    for i := m - 1; i >= 0; i-- {
+        for j := n - 1; j >= 0; j-- {
+            dp[i][j] += dp[i+1][j] + dp[i][j+1]
+        }
+    }
+
+    return dp[0][0]
+}
+```
+
+```kotlin
+class Solution {
+    fun uniquePaths(m: Int, n: Int): Int {
+        val dp = Array(m + 1) { IntArray(n + 1) }
+        dp[m - 1][n - 1] = 1
+
+        for (i in m - 1 downTo 0) {
+            for (j in n - 1 downTo 0) {
+                dp[i][j] += dp[i + 1][j] + dp[i][j + 1]
+            }
+        }
+
+        return dp[0][0]
+    }
+}
+```
+
+```swift
+class Solution {
+    func uniquePaths(_ m: Int, _ n: Int) -> Int {
+        var dp = Array(repeating: Array(repeating: 0, count: n + 1), count: m + 1)
+        dp[m - 1][n - 1] = 1
+
+        for i in stride(from: m - 1, through: 0, by: -1) {
+            for j in stride(from: n - 1, through: 0, by: -1) {
+                dp[i][j] += dp[i + 1][j] + dp[i][j + 1]
+            }
+        }
+
+        return dp[0][0]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -432,6 +607,61 @@ public class Solution {
 }
 ```
 
+```go
+func uniquePaths(m int, n int) int {
+    row := make([]int, n)
+    for i := range row {
+        row[i] = 1
+    }
+
+    for i := 0; i < m - 1; i++ {
+        newRow := make([]int, n)
+        newRow[n-1] = 1
+        for j := n - 2; j >= 0; j-- {
+            newRow[j] = newRow[j+1] + row[j]
+        }
+        row = newRow
+    }
+
+    return row[0]
+}
+```
+
+```kotlin
+class Solution {
+    fun uniquePaths(m: Int, n: Int): Int {
+        var row = IntArray(n) { 1 }
+
+        for (i in 0 until m - 1) {
+            val newRow = IntArray(n) { 1 }
+            for (j in n - 2 downTo 0) {
+                newRow[j] = newRow[j + 1] + row[j]
+            }
+            row = newRow
+        }
+
+        return row[0]
+    }
+}
+```
+
+```swift
+class Solution {
+    func uniquePaths(_ m: Int, _ n: Int) -> Int {
+        var row = Array(repeating: 1, count: n)
+
+        for _ in 0..<(m - 1) {
+            var newRow = Array(repeating: 1, count: n)
+            for j in stride(from: n - 2, through: 0, by: -1) {
+                newRow[j] = newRow[j + 1] + row[j]
+            }
+            row = newRow
+        }
+        return row[0]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -530,6 +760,55 @@ public class Solution {
 }
 ```
 
+```go
+func uniquePaths(m int, n int) int {
+    dp := make([]int, n)
+    for i := range dp {
+        dp[i] = 1
+    }
+
+    for i := m - 2; i >= 0; i-- {
+        for j := n - 2; j >= 0; j-- {
+            dp[j] += dp[j+1]
+        }
+    }
+
+    return dp[0]
+}
+```
+
+```kotlin
+class Solution {
+    fun uniquePaths(m: Int, n: Int): Int {
+        var dp = IntArray(n) { 1 }
+
+        for (i in m - 2 downTo 0) {
+            for (j in n - 2 downTo 0) {
+                dp[j] += dp[j + 1]
+            }
+        }
+
+        return dp[0]
+    }
+}
+```
+
+```swift
+class Solution {
+    func uniquePaths(_ m: Int, _ n: Int) -> Int {
+        var dp = Array(repeating: 1, count: n)
+
+        for _ in stride(from: m - 2, through: 0, by: -1) {
+            for j in stride(from: n - 2, through: 0, by: -1) {
+                dp[j] += dp[j + 1]
+            }
+        }
+
+        return dp[0]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -663,6 +942,77 @@ public class Solution {
 }
 ```
 
+```go
+func uniquePaths(m int, n int) int {
+    if m == 1 || n == 1 {
+        return 1
+    }
+    if m < n {
+        tmp := m
+        m = n
+        n = tmp
+    }
+
+    res, j := 1, 1
+    for i := m; i < m + n - 1; i++ {
+        res *= i
+        res /= j
+        j++
+    }
+
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun uniquePaths(m: Int, n: Int): Int {
+        if (m == 1 || n == 1) return 1
+        var m = m
+        var n = n
+        if (m < n) {
+            val tmp = m
+            m = n
+            n = tmp
+        }
+
+        var res: Long = 1
+        var j = 1
+        for (i in m until m + n - 1) {
+            res *= i
+            res /= j
+            j++
+        }
+        
+        return res.toInt()
+    }
+}
+```
+
+```swift
+class Solution {
+    func uniquePaths(_ m: Int, _ n: Int) -> Int {
+        if m == 1 || n == 1 {
+            return 1
+        }
+        var m = m, n = n
+        if m < n {
+            swap(&m, &n)
+        }
+
+        var res = 1
+        var j = 1
+        for i in m..<(m + n - 1) {
+            res *= i
+            res /= j
+            j += 1
+        }
+
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/count-squares.md b/articles/count-squares.md
new file mode 100644
index 000000000..1b5defe8c
--- /dev/null
+++ b/articles/count-squares.md
@@ -0,0 +1,606 @@
+## 1. Hash Map - I
+
+::tabs-start
+
+```python
+class CountSquares:
+    def __init__(self):
+        self.ptsCount = defaultdict(int)
+        self.pts = []
+
+    def add(self, point: List[int]) -> None:
+        self.ptsCount[tuple(point)] += 1
+        self.pts.append(point)
+
+    def count(self, point: List[int]) -> int:
+        res = 0
+        px, py = point
+        for x, y in self.pts:
+            if (abs(py - y) != abs(px - x)) or x == px or y == py:
+                continue
+            res += self.ptsCount[(x, py)] * self.ptsCount[(px, y)]
+        return res
+```
+
+```java
+public class CountSquares {
+    private Map<List<Integer>, Integer> ptsCount;
+    private List<List<Integer>> pts;
+
+    public CountSquares() {
+        ptsCount = new HashMap<>();
+        pts = new ArrayList<>();
+    }
+
+    public void add(int[] point) {
+        List<Integer> p = Arrays.asList(point[0], point[1]);
+        ptsCount.put(p, ptsCount.getOrDefault(p, 0) + 1);
+        pts.add(p);
+    }
+
+    public int count(int[] point) {
+        int res = 0;
+        int px = point[0], py = point[1];
+        for (List<Integer> pt : pts) {
+            int x = pt.get(0), y = pt.get(1);
+            if (Math.abs(py - y) != Math.abs(px - x) || x == px || y == py) {
+                continue;
+            }
+            res += ptsCount.getOrDefault(Arrays.asList(x, py), 0) * 
+                   ptsCount.getOrDefault(Arrays.asList(px, y), 0);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class CountSquares {
+private:
+    unordered_map<long, int> ptsCount;
+    vector<vector<int>> pts;
+
+    long getKey(int x, int y) {
+        return (static_cast<long>(x) << 32) | static_cast<long>(y);
+    }
+
+public:
+    CountSquares() {
+    }
+
+    void add(vector<int> point) {
+        long key = getKey(point[0], point[1]);
+        ptsCount[key]++; 
+        pts.push_back(point); 
+    }
+    
+    int count(vector<int> point) {
+        int res = 0;
+        int px = point[0], py = point[1];
+
+        for (const auto& pt : pts) {
+            int x = pt[0], y = pt[1];
+            if (abs(py - y) != abs(px - x) || x == px || y == py) continue;
+            res += ptsCount[getKey(x, py)] * ptsCount[getKey(px, y)];
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class CountSquares {
+    constructor() {
+        this.ptsCount = new Map();
+        this.pts = [];
+    }
+
+    /**
+     * @param {number[]} point
+     * @return {void}
+     */
+    add(point) {
+        const p = point.join(',');
+        this.ptsCount.set(p, (this.ptsCount.get(p) || 0) + 1);
+        this.pts.push(point);
+    }
+
+    /**
+     * @param {number[]} point
+     * @return {number}
+     */
+    count(point) {
+        let res = 0;
+        const [px, py] = point;
+        for (const [x, y] of this.pts) {
+            if (Math.abs(py - y) !== Math.abs(px - x) || x === px || y === py) {
+                continue;
+            }
+            res +=
+                (this.ptsCount.get(`${x},${py}`) || 0) *
+                (this.ptsCount.get(`${px},${y}`) || 0);
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class CountSquares {
+    private Dictionary<(int, int), int> ptsCount;
+    private List<int[]> pts;
+
+    public CountSquares() {
+        ptsCount = new Dictionary<(int, int), int>();
+        pts = new List<int[]>();
+    }
+
+    public void Add(int[] point) {
+        var tuplePoint = (point[0], point[1]);
+        if (!ptsCount.ContainsKey(tuplePoint))
+            ptsCount[tuplePoint] = 0;
+        
+        ptsCount[tuplePoint]++;
+        pts.Add(point);
+    }
+
+    public int Count(int[] point) {
+        int res = 0;
+        int px = point[0];
+        int py = point[1];
+        
+        foreach (var pt in pts) {
+            int x = pt[0];
+            int y = pt[1];
+
+            if (Math.Abs(py - y) != Math.Abs(px - x) || x == px || y == py)
+                continue;
+
+            res += (ptsCount.GetValueOrDefault((x, py)) * 
+                   ptsCount.GetValueOrDefault((px, y)));
+        }
+        return res;
+    }
+}
+```
+
+```go
+type CountSquares struct {
+    ptsCount map[Point]int
+    pts      []Point
+}
+
+type Point struct {
+    x, y int
+}
+
+func Constructor() CountSquares {
+    return CountSquares{
+        ptsCount: make(map[Point]int),
+        pts:      make([]Point, 0),
+    }
+}
+
+func (this *CountSquares) Add(point []int) {
+    p := Point{point[0], point[1]}
+    this.ptsCount[p]++
+    this.pts = append(this.pts, p)
+}
+
+func (this *CountSquares) Count(point []int) int {
+    res := 0
+    px, py := point[0], point[1]
+
+    for _, pt := range this.pts {
+        if abs(py-pt.y) != abs(px-pt.x) || pt.x == px || pt.y == py {
+            continue
+        }
+        
+        p1 := Point{pt.x, py}
+        p2 := Point{px, pt.y}
+        
+        res += this.ptsCount[p1] * this.ptsCount[p2]
+    }
+    
+    return res
+}
+
+func abs(x int) int {
+    if x < 0 {
+        return -x
+    }
+    return x
+}
+```
+
+```kotlin
+class CountSquares() {
+    private val pointCounts = HashMap<Pair<Int, Int>, Int>()
+    private val points = mutableListOf<IntArray>()
+
+    fun add(point: IntArray) {
+        val pair = Pair(point[0], point[1])
+        pointCounts[pair] = pointCounts.getOrDefault(pair, 0) + 1
+        points.add(point)
+    }
+
+    fun count(point: IntArray): Int {
+        var result = 0
+        val (px, py) = point
+
+        for ((x, y) in points) {
+            if (kotlin.math.abs(py - y) != kotlin.math.abs(px - x) || 
+                x == px || y == py) {
+                continue
+            }
+            result += (pointCounts[Pair(x, py)] ?: 0) * (pointCounts[Pair(px, y)] ?: 0)
+        }
+        return result
+    }
+}
+```
+
+```swift
+class CountSquares {
+    private var ptsCount: [String: Int]
+    private var pts: [[Int]]
+
+    init() {
+        self.ptsCount = [:]
+        self.pts = []
+    }
+
+    func add(_ point: [Int]) {
+        let key = "\(point[0]),\(point[1])"
+        ptsCount[key, default: 0] += 1
+        pts.append(point)
+    }
+
+    func count(_ point: [Int]) -> Int {
+        var res = 0
+        let px = point[0], py = point[1]
+
+        for pt in pts {
+            let x = pt[0], y = pt[1]
+            if abs(py - y) != abs(px - x) || x == px || y == py {
+                continue
+            }
+            let key1 = "\(x),\(py)"
+            let key2 = "\(px),\(y)"
+            res += (ptsCount[key1] ?? 0) * (ptsCount[key2] ?? 0)
+        }
+        return res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$ for $add()$, $O(n)$ for $count()$.
+* Space complexity: $O(n)$
+
+---
+
+## 2. Hash Map - II
+
+::tabs-start
+
+```python
+class CountSquares:
+
+    def __init__(self):
+        self.ptsCount = defaultdict(lambda: defaultdict(int))
+
+    def add(self, point: List[int]) -> None:
+        self.ptsCount[point[0]][point[1]] += 1
+
+    def count(self, point: List[int]) -> int:
+        res = 0
+        x1, y1 = point
+        for y2 in self.ptsCount[x1]:
+            side = y2 - y1
+            if side == 0:
+                continue
+
+            x3, x4 = x1 + side, x1 - side
+            res += (self.ptsCount[x1][y2] * self.ptsCount[x3][y1] *
+                    self.ptsCount[x3][y2])
+
+            res += (self.ptsCount[x1][y2] * self.ptsCount[x4][y1] *
+                    self.ptsCount[x4][y2])
+        return res
+```
+
+```java
+public class CountSquares {
+    private Map<Integer, Map<Integer, Integer>> ptsCount;
+
+    public CountSquares() {
+        ptsCount = new HashMap<>();
+    }
+
+    public void add(int[] point) {
+        int x = point[0], y = point[1];
+        ptsCount.putIfAbsent(x, new HashMap<>());
+        ptsCount.get(x).put(y, ptsCount.get(x).getOrDefault(y, 0) + 1);
+    }
+
+    public int count(int[] point) {
+        int res = 0, x1 = point[0], y1 = point[1];
+
+        if (!ptsCount.containsKey(x1)) return res;
+
+        for (int y2 : ptsCount.get(x1).keySet()) {
+            int side = y2 - y1;
+            if (side == 0) continue;
+
+            int x3 = x1 + side, x4 = x1 - side;
+            res += ptsCount.get(x1).get(y2) *
+                   ptsCount.getOrDefault(x3, new HashMap<>()).getOrDefault(y1, 0) *
+                   ptsCount.getOrDefault(x3, new HashMap<>()).getOrDefault(y2, 0);
+
+            res += ptsCount.get(x1).get(y2) *
+                   ptsCount.getOrDefault(x4, new HashMap<>()).getOrDefault(y1, 0) *
+                   ptsCount.getOrDefault(x4, new HashMap<>()).getOrDefault(y2, 0);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class CountSquares {
+    unordered_map<int, unordered_map<int, int>> ptsCount;
+
+public:
+    CountSquares() {}
+    
+    void add(vector<int> point) {
+        ptsCount[point[0]][point[1]]++;
+    }
+
+    int count(vector<int> point) {
+        int res = 0;
+        int x1 = point[0], y1 = point[1];
+
+        for (auto &[y2, cnt] : ptsCount[x1]) {
+            int side = y2 - y1;
+            if (side == 0) continue;
+
+            int x3 = x1 + side, x4 = x1 - side;
+            res += cnt * ptsCount[x3][y1] * ptsCount[x3][y2];
+            res += cnt * ptsCount[x4][y1] * ptsCount[x4][y2];
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class CountSquares {
+    constructor() {
+        this.ptsCount = new Map();
+    }
+
+    /**
+     * @param {number[]} point
+     * @return {void}
+     */
+    add(point) {
+        const [x, y] = point;
+        if (!this.ptsCount.has(x)) this.ptsCount.set(x, new Map());
+        const yCount = this.ptsCount.get(x);
+        yCount.set(y, (yCount.get(y) || 0) + 1);
+    }
+
+    /**
+     * @param {number[]} point
+     * @return {number}
+     */
+    count(point) {
+        let res = 0;
+        const [x1, y1] = point;
+        if (!this.ptsCount.has(x1)) return res;
+
+        const x1Points = this.ptsCount.get(x1);
+        for (const [y2, cnt] of x1Points) {
+            const side = y2 - y1;
+            if (side === 0) continue;
+
+            const x3 = x1 + side;
+            const x4 = x1 - side;
+
+            res += cnt *
+                   (this.ptsCount.get(x3)?.get(y1) || 0) *
+                   (this.ptsCount.get(x3)?.get(y2) || 0);
+
+            res += cnt *
+                   (this.ptsCount.get(x4)?.get(y1) || 0) *
+                   (this.ptsCount.get(x4)?.get(y2) || 0);
+        }
+
+        return res;
+    }
+}
+```
+
+```csharp
+public class CountSquares {
+    private Dictionary<int, Dictionary<int, int>> ptsCount;
+
+    public CountSquares() {
+        ptsCount = new Dictionary<int, Dictionary<int, int>>();
+    }
+
+    public void Add(int[] point) {
+        int x = point[0], y = point[1];
+        if (!ptsCount.ContainsKey(x)) {
+            ptsCount[x] = new Dictionary<int, int>();
+        }
+        if (!ptsCount[x].ContainsKey(y)) ptsCount[x][y] = 0;
+        ptsCount[x][y]++;
+    }
+
+    public int Count(int[] point) {
+        int res = 0;
+        int x1 = point[0], y1 = point[1];
+
+        if (!ptsCount.ContainsKey(x1)) return res;
+
+        foreach (var kv in ptsCount[x1]) {
+            int y2 = kv.Key, cnt = kv.Value;
+            int side = y2 - y1;
+            if (side == 0) continue;
+
+            int x3 = x1 + side, x4 = x1 - side;
+
+            res += cnt *
+                   (ptsCount.ContainsKey(x3) && 
+                    ptsCount[x3].ContainsKey(y1) ? ptsCount[x3][y1] : 0) *
+                   (ptsCount.ContainsKey(x3) && 
+                    ptsCount[x3].ContainsKey(y2) ? ptsCount[x3][y2] : 0);
+
+            res += cnt *
+                   (ptsCount.ContainsKey(x4) && 
+                    ptsCount[x4].ContainsKey(y1) ? ptsCount[x4][y1] : 0) *
+                   (ptsCount.ContainsKey(x4) && 
+                    ptsCount[x4].ContainsKey(y2) ? ptsCount[x4][y2] : 0);
+        }
+
+        return res;
+    }
+}
+```
+
+```go
+type CountSquares struct {
+    ptsCount map[int]map[int]int
+}
+
+func Constructor() CountSquares {
+    return CountSquares{
+        ptsCount: make(map[int]map[int]int),
+    }
+}
+
+func (this *CountSquares) Add(point []int) {
+    x, y := point[0], point[1]
+    if this.ptsCount[x] == nil {
+        this.ptsCount[x] = make(map[int]int)
+    }
+    this.ptsCount[x][y]++
+}
+
+func (this *CountSquares) Count(point []int) int {
+    res := 0
+    x1, y1 := point[0], point[1]
+
+    for y2 := range this.ptsCount[x1] {
+        side := y2 - y1
+        if side == 0 {
+            continue
+        }
+
+        x3, x4 := x1+side, x1-side
+
+        if _, exists := this.ptsCount[x3]; exists {
+            res += this.ptsCount[x1][y2] * this.ptsCount[x3][y1] * this.ptsCount[x3][y2]
+        }
+
+        if _, exists := this.ptsCount[x4]; exists {
+            res += this.ptsCount[x1][y2] * this.ptsCount[x4][y1] * this.ptsCount[x4][y2]
+        }
+    }
+    return res
+}
+```
+
+```kotlin
+class CountSquares {
+    private val points = HashMap<Int, HashMap<Int, Int>>()
+    
+    fun add(point: IntArray) {
+        val x = point[0]
+        val y = point[1]
+        
+        if (!points.containsKey(x)) {
+            points[x] = hashMapOf()
+        }
+        
+        points[x]?.put(y, (points[x]?.get(y) ?: 0) + 1)
+    }
+
+    fun count(point: IntArray): Int {
+        var result = 0
+        val x1 = point[0]
+        val y1 = point[1]
+        
+        points[x1]?.forEach { (y2, count1) ->
+            if (y2 == y1) return@forEach
+            
+            val side = Math.abs(y2 - y1)
+            
+            val x3 = x1 + side
+            if (points.containsKey(x3)) {
+                val count2 = points[x3]?.get(y1) ?: 0
+                val count3 = points[x3]?.get(y2) ?: 0
+                result += count1 * count2 * count3
+            }
+            
+            val x4 = x1 - side
+            if (points.containsKey(x4)) {
+                val count2 = points[x4]?.get(y1) ?: 0
+                val count3 = points[x4]?.get(y2) ?: 0
+                result += count1 * count2 * count3
+            }
+        }
+        
+        return result
+    }
+}
+```
+
+```swift
+class CountSquares {
+    var ptsCount: [Int: [Int: Int]]
+    
+    init() {
+        ptsCount = [:]
+    }
+    
+    func add(_ point: [Int]) {
+        let x = point[0]
+        let y = point[1]
+        ptsCount[x, default: [:]][y, default: 0] += 1
+    }
+    
+    func count(_ point: [Int]) -> Int {
+        var res = 0
+        let x1 = point[0]
+        let y1 = point[1]
+
+        if let yMap = ptsCount[x1] {
+            for (y2, countXY2) in yMap {
+                let side = y2 - y1
+                if side == 0 { continue }
+                let x3 = x1 + side
+                let x4 = x1 - side
+                res += countXY2 * (ptsCount[x3]?[y1] ?? 0) * (ptsCount[x3]?[y2] ?? 0)
+                res += countXY2 * (ptsCount[x4]?[y1] ?? 0) * (ptsCount[x4]?[y2] ?? 0)
+            }
+        }
+        return res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$ for $add()$, $O(n)$ for $count()$.
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/count-sub-islands.md b/articles/count-sub-islands.md
new file mode 100644
index 000000000..22a7598f7
--- /dev/null
+++ b/articles/count-sub-islands.md
@@ -0,0 +1,564 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def countSubIslands(self, grid1: List[List[int]], grid2: List[List[int]]) -> int:
+        ROWS, COLS = len(grid1), len(grid1[0])
+        visit = set()
+
+        def dfs(r, c):
+            if (min(r, c) < 0 or r == ROWS or c == COLS or 
+                grid2[r][c] == 0 or (r, c) in visit):
+                return True
+            
+            visit.add((r, c))
+            res = grid1[r][c]
+            
+            res &= dfs(r - 1, c)
+            res &= dfs(r + 1, c)
+            res &= dfs(r, c - 1)
+            res &= dfs(r, c + 1)
+            return res
+        
+        count = 0
+        for r in range(ROWS):
+            for c in range(COLS):
+                if grid2[r][c] and (r, c) not in visit:
+                    count += dfs(r, c)
+        return count
+```
+
+```java
+public class Solution {
+    private boolean[][] visit;
+
+    public int countSubIslands(int[][] grid1, int[][] grid2) {
+        int ROWS = grid1.length, COLS = grid1[0].length;
+        visit = new boolean[ROWS][COLS];
+        int count = 0;
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (grid2[r][c] == 1 && !visit[r][c] && dfs(r, c, grid1, grid2)) {
+                    count++;
+                }
+            }
+        }
+        return count;
+    }
+
+    private boolean dfs(int r, int c, int[][] grid1, int[][] grid2) {
+        if (r < 0 || c < 0 || r >= grid1.length || c >= grid1[0].length || 
+            grid2[r][c] == 0 || visit[r][c]) {
+            return true;
+        }
+        visit[r][c] = true;
+        boolean res = grid1[r][c] == 1;
+        res &= dfs(r - 1, c, grid1, grid2);
+        res &= dfs(r + 1, c, grid1, grid2);
+        res &= dfs(r, c - 1, grid1, grid2);
+        res &= dfs(r, c + 1, grid1, grid2);
+        return res;
+    }
+    
+}
+```
+
+```cpp
+class Solution {
+    vector<vector<bool>> visit;
+
+public:
+    int countSubIslands(vector<vector<int>>& grid1, vector<vector<int>>& grid2) {
+        int ROWS = grid1.size(), COLS = grid1[0].size();
+        visit.assign(ROWS, vector<bool>(COLS, false));
+
+        int count = 0;
+        for (int r = 0; r < ROWS; ++r) {
+            for (int c = 0; c < COLS; ++c) {
+                if (grid2[r][c] && !visit[r][c]) {
+                    count += dfs(r, c, grid1, grid2);
+                }
+            }
+        }
+        return count;
+    }
+
+private:
+    bool dfs(int r, int c, vector<vector<int>>& grid1, vector<vector<int>>& grid2) {
+        if (r < 0 || c < 0 || r >= grid1.size() || c >= grid1[0].size() || 
+            grid2[r][c] == 0 || visit[r][c]) {
+            return true;
+        }
+
+        visit[r][c] = true;
+        bool res = grid1[r][c] == 1;
+        res &= dfs(r - 1, c, grid1, grid2);
+        res &= dfs(r + 1, c, grid1, grid2);
+        res &= dfs(r, c - 1, grid1, grid2);
+        res &= dfs(r, c + 1, grid1, grid2);
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid1
+     * @param {number[][]} grid2
+     * @return {number}
+     */
+    countSubIslands(grid1, grid2) {
+        const ROWS = grid1.length, COLS = grid1[0].length;
+        const visit = Array.from({ length: ROWS }, () => Array(COLS).fill(false));
+
+        const dfs = (r, c) => {
+            if (r < 0 || c < 0 || r >= ROWS || c >= COLS || grid2[r][c] === 0 || visit[r][c])
+                return true;
+            visit[r][c] = true;
+            let res = grid1[r][c] === 1;
+            res &= dfs(r - 1, c);
+            res &= dfs(r + 1, c);
+            res &= dfs(r, c - 1);
+            res &= dfs(r, c + 1);
+            return res;
+        };
+
+        let count = 0;
+        for (let r = 0; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                if (grid2[r][c] === 1 && !visit[r][c]) {
+                    if (dfs(r, c)) count++;
+                }
+            }
+        }
+        return count;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns.
+
+---
+
+## 2. Breadth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def countSubIslands(self, grid1: List[List[int]], grid2: List[List[int]]) -> int:
+        ROWS, COLS = len(grid1), len(grid1[0])
+        visit = [[False] * COLS for _ in range(ROWS)]
+        directions = [1, 0, -1, 0, 1]
+
+        def bfs(r, c):
+            queue = deque([(r, c)])
+            visit[r][c] = True
+            res = True
+
+            while queue:
+                r, c = queue.popleft()
+                if grid1[r][c] == 0:
+                    res = False
+
+                for i in range(4):
+                    nr, nc = r + directions[i], c + directions[i + 1]
+                    if 0 <= nr < ROWS and 0 <= nc < COLS and not visit[nr][nc] and grid2[nr][nc]:
+                        visit[nr][nc] = True
+                        queue.append((nr, nc))
+            return res
+
+        count = 0
+        for r in range(ROWS):
+            for c in range(COLS):
+                if grid2[r][c] == 1 and not visit[r][c]:
+                    if bfs(r, c):
+                        count += 1
+        return count
+```
+
+```java
+public class Solution {
+    private boolean[][] visit;
+    private int[] directions = {1, 0, -1, 0, 1};
+
+    public int countSubIslands(int[][] grid1, int[][] grid2) {
+        int ROWS = grid1.length, COLS = grid1[0].length;
+        visit = new boolean[ROWS][COLS];
+        int count = 0;
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (grid2[r][c] == 1 && !visit[r][c]) {
+                    if (bfs(r, c, grid1, grid2)) {
+                        count++;
+                    }
+                }
+            }
+        }
+        return count;
+    }
+
+    private boolean bfs(int r, int c, int[][] grid1, int[][] grid2) {
+        Queue<int[]> queue = new LinkedList<>();
+        queue.add(new int[]{r, c});
+        visit[r][c] = true;
+        boolean res = true;
+
+        while (!queue.isEmpty()) {
+            int[] cell = queue.poll();
+            int cr = cell[0], cc = cell[1];
+            if (grid1[cr][cc] == 0) {
+                res = false;
+            }
+
+            for (int i = 0; i < 4; i++) {
+                int nr = cr + directions[i], nc = cc + directions[i + 1];
+                if (nr >= 0 && nr < grid1.length && nc >= 0 && nc < grid1[0].length &&
+                    grid2[nr][nc] == 1 && !visit[nr][nc]) {
+                    visit[nr][nc] = true;
+                    queue.add(new int[]{nr, nc});
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+    vector<vector<bool>> visit;
+    vector<int> directions = {1, 0, -1, 0, 1};
+
+public:
+    int countSubIslands(vector<vector<int>>& grid1, vector<vector<int>>& grid2) {
+        int ROWS = grid1.size(), COLS = grid1[0].size();
+        visit.assign(ROWS, vector<bool>(COLS, false));
+        int count = 0;
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (grid2[r][c] == 1 && !visit[r][c]) {
+                    if (bfs(r, c, grid1, grid2)) {
+                        count++;
+                    }
+                }
+            }
+        }
+        return count;
+    }
+
+private:
+    bool bfs(int r, int c, vector<vector<int>>& grid1, vector<vector<int>>& grid2) {
+        queue<pair<int, int>> q;
+        q.push({r, c});
+        visit[r][c] = true;
+        bool res = true;
+
+        while (!q.empty()) {
+            auto [cr, cc] = q.front(); q.pop();
+
+            if (grid1[cr][cc] == 0) res = false;
+
+            for (int i = 0; i < 4; i++) {
+                int nr = cr + directions[i], nc = cc + directions[i + 1];
+                if (nr >= 0 && nr < grid1.size() && nc >= 0 && nc < grid1[0].size() &&
+                    grid2[nr][nc] == 1 && !visit[nr][nc]) {
+                    visit[nr][nc] = true;
+                    q.push({nr, nc});
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid1
+     * @param {number[][]} grid2
+     * @return {number}
+     */
+    countSubIslands(grid1, grid2) {
+        const ROWS = grid1.length, COLS = grid1[0].length;
+        const visit = Array.from({ length: ROWS }, () => Array(COLS).fill(false));
+        const directions = [1, 0, -1, 0, 1];
+        let count = 0;
+
+        const bfs = (sr, sc) => {
+            const queue = new Queue([[sr, sc]]);
+            visit[sr][sc] = true;
+            let res = true;
+
+            while (!queue.isEmpty()) {
+                const [r, c] = queue.pop();
+                if (grid1[r][c] === 0) res = false;
+
+                for (let i = 0; i < 4; i++) {
+                    const nr = r + directions[i], nc = c + directions[i + 1];
+                    if (nr >= 0 && nr < ROWS && nc >= 0 && nc < COLS &&
+                        grid2[nr][nc] === 1 && !visit[nr][nc]) {
+                        visit[nr][nc] = true;
+                        queue.push([nr, nc]);
+                    }
+                }
+            }
+            return res;
+        };
+
+        for (let r = 0; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                if (grid2[r][c] === 1 && !visit[r][c]) {
+                    if (bfs(r, c)) count++;
+                }
+            }
+        }
+        return count;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns.
+
+---
+
+## 3. Disjoint Set Union
+
+::tabs-start
+
+```python
+class DSU:
+    def __init__(self, n):
+        self.Parent = list(range(n + 1))
+        self.Size = [1] * (n + 1)
+
+    def find(self, node):
+        if self.Parent[node] != node:
+            self.Parent[node] = self.find(self.Parent[node])
+        return self.Parent[node]
+
+    def union(self, u, v):
+        pu = self.find(u)
+        pv = self.find(v)
+        if pu == pv:
+            return False
+        if self.Size[pu] < self.Size[pv]:
+            pu, pv = pv, pu
+        self.Size[pu] += self.Size[pv]
+        self.Parent[pv] = pu
+        return True
+
+class Solution:
+    def countSubIslands(self, grid1, grid2):
+        ROWS, COLS = len(grid1), len(grid1[0])
+        N = ROWS * COLS
+        dsu = DSU(N)
+
+        def getId(r, c):
+            return r * COLS + c
+        
+        land = unions = 0
+        for r in range(ROWS):
+            for c in range(COLS):
+                if not grid2[r][c]:
+                    continue
+                land += 1
+                if r + 1 < ROWS and grid2[r + 1][c]:
+                    unions += dsu.union(getId(r, c), getId(r + 1, c))
+                if c + 1 < COLS and grid2[r][c + 1]:
+                    unions += dsu.union(getId(r, c), getId(r, c + 1))
+                if not grid1[r][c]:
+                    unions += dsu.union(getId(r, c), N)
+        
+        return land - unions
+```
+
+```java
+class DSU {
+    int[] Parent, Size;
+
+    DSU(int n) {
+        Parent = new int[n + 1];
+        Size = new int[n + 1];
+        for (int i = 0; i <= n; i++) Parent[i] = i;
+    }
+
+    int find(int node) {
+        if (Parent[node] != node) Parent[node] = find(Parent[node]);
+        return Parent[node];
+    }
+
+    int union(int u, int v) {
+        int pu = find(u), pv = find(v);
+        if (pu == pv) return 0;
+        if (Size[pu] < Size[pv]) {
+            int temp = pu; pu = pv; pv = temp;
+        }
+        Size[pu] += Size[pv];
+        Parent[pv] = pu;
+        return 1;
+    }
+}
+
+public class Solution {
+    public int countSubIslands(int[][] grid1, int[][] grid2) {
+        int ROWS = grid1.length, COLS = grid1[0].length, N = ROWS * COLS;
+        DSU dsu = new DSU(N);
+
+        int land = 0, unions = 0;
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (grid2[r][c] == 0) continue;
+                land++;
+                if (r + 1 < ROWS && grid2[r + 1][c] == 1)
+                    unions += dsu.union(r * COLS + c, (r + 1) * COLS + c);
+                if (c + 1 < COLS && grid2[r][c + 1] == 1)
+                    unions += dsu.union(r * COLS + c, r * COLS + c + 1);
+                if (grid1[r][c] == 0)
+                    unions += dsu.union(r * COLS + c, N);
+            }
+        }
+        return land - unions;
+    }
+}
+```
+
+```cpp
+class DSU {
+    vector<int> Parent, Size;
+
+public:
+    DSU(int n) {
+        Parent.resize(n + 1);
+        Size.assign(n + 1, 1);
+        for (int i = 0; i <= n; i++) Parent[i] = i;
+    }
+
+    int find(int node) {
+        if (Parent[node] != node) Parent[node] = find(Parent[node]);
+        return Parent[node];
+    }
+
+    bool unionSets(int u, int v) {
+        int pu = find(u), pv = find(v);
+        if (pu == pv) return false;
+        if (Size[pu] < Size[pv]) swap(pu, pv);
+        Size[pu] += Size[pv];
+        Parent[pv] = pu;
+        return true;
+    }
+};
+
+class Solution {
+public:
+    int countSubIslands(vector<vector<int>>& grid1, vector<vector<int>>& grid2) {
+        int ROWS = grid1.size(), COLS = grid1[0].size(), N = ROWS * COLS;
+        DSU dsu(N);
+
+        int land = 0, unions = 0;
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (!grid2[r][c]) continue;
+                land++;
+                if (r + 1 < ROWS && grid2[r + 1][c])
+                    unions += dsu.unionSets(r * COLS + c, (r + 1) * COLS + c);
+                if (c + 1 < COLS && grid2[r][c + 1])
+                    unions += dsu.unionSets(r * COLS + c, r * COLS + c + 1);
+                if (!grid1[r][c])
+                    unions += dsu.unionSets(r * COLS + c, N);
+            }
+        }
+        return land - unions;
+    }
+};
+```
+
+```javascript
+class DSU {
+    constructor(n) {
+        this.Parent = Array.from({ length: n + 1 }, (_, i) => i);
+        this.Size = Array(n + 1).fill(1);
+    }
+    
+    /**
+     * @param {number} node
+     * @return {number}
+     */
+    find(node) {
+        if (this.Parent[node] !== node) {
+            this.Parent[node] = this.find(this.Parent[node]);
+        }
+        return this.Parent[node];
+    }
+
+    /**
+     * @param {number} u
+     * @param {number} v
+     * @return {boolean}
+     */
+    union(u, v) {
+        let pu = this.find(u), pv = this.find(v);
+        if (pu === pv) return false;
+        if (this.Size[pu] < this.Size[pv]) [pu, pv] = [pv, pu];
+        this.Size[pu] += this.Size[pv];
+        this.Parent[pv] = pu;
+        return true;
+    }
+}
+
+class Solution {
+    /**
+     * @param {number[][]} grid1
+     * @param {number[][]} grid2
+     * @return {number}
+     */
+    countSubIslands(grid1, grid2) {
+        const ROWS = grid1.length, COLS = grid1[0].length, N = ROWS * COLS;
+        const dsu = new DSU(N);
+
+        const getId = (r, c) => r * COLS + c;
+
+        let land = 0, unions = 0;
+        for (let r = 0; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                if (grid2[r][c] === 0) continue;
+                land++;
+                if (r + 1 < ROWS && grid2[r + 1][c] === 1)
+                    unions += dsu.union(getId(r, c), getId(r + 1, c));
+                if (c + 1 < COLS && grid2[r][c + 1] === 1)
+                    unions += dsu.union(getId(r, c), getId(r, c + 1));
+                if (grid1[r][c] === 0)
+                    unions += dsu.union(getId(r, c), N);
+            }
+        }
+        return land - unions;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns.
\ No newline at end of file
diff --git a/articles/count-subarrays-where-max-element-appears-at-least-k-times.md b/articles/count-subarrays-where-max-element-appears-at-least-k-times.md
new file mode 100644
index 000000000..c4d2a5914
--- /dev/null
+++ b/articles/count-subarrays-where-max-element-appears-at-least-k-times.md
@@ -0,0 +1,589 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def countSubarrays(self, nums: List[int], k: int) -> int:
+        n, res = len(nums), 0
+        maxi = max(nums)
+
+        for i in range(n):
+            cnt = 0
+            for j in range(i, n):
+                if nums[j] == maxi:
+                    cnt += 1
+                
+                if cnt >= k:
+                    res += 1
+        
+        return res
+```
+
+```java
+public class Solution {
+    public long countSubarrays(int[] nums, int k) {
+        int n = nums.length;
+        long res = 0;
+        int maxi = Integer.MIN_VALUE;
+
+        for (int num : nums) {
+            maxi = Math.max(maxi, num);
+        }
+
+        for (int i = 0; i < n; i++) {
+            int cnt = 0;
+            for (int j = i; j < n; j++) {
+                if (nums[j] == maxi) {
+                    cnt++;
+                }
+                
+                if (cnt >= k) {
+                    res++;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long countSubarrays(vector<int>& nums, int k) {
+        int n = nums.size();
+        long long res = 0;
+        int maxi = *max_element(nums.begin(), nums.end());
+
+        for (int i = 0; i < n; i++) {
+            int cnt = 0;
+            for (int j = i; j < n; j++) {
+                if (nums[j] == maxi) {
+                    cnt++;
+                }
+                
+                if (cnt >= k) {
+                    res++;
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    countSubarrays(nums, k) {
+        let n = nums.length, res = 0;
+        let maxi = Math.max(...nums);
+
+        for (let i = 0; i < n; i++) {
+            let cnt = 0;
+            for (let j = i; j < n; j++) {
+                if (nums[j] === maxi) {
+                    cnt++;
+                }
+                
+                if (cnt >= k) {
+                    res++;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Variable Size Sliding Window
+
+::tabs-start
+
+```python
+class Solution:
+    def countSubarrays(self, nums: List[int], k: int) -> int:
+        max_n, max_cnt = max(nums), 0
+        l = 0
+        res = 0
+
+        for r in range(len(nums)):
+            if nums[r] == max_n:
+                max_cnt += 1
+            
+            while max_cnt > k or (l <= r and max_cnt == k and nums[l] != max_n):
+                if nums[l] == max_n:
+                    max_cnt -= 1
+                l += 1
+            
+            if max_cnt == k:
+                res += l + 1
+        
+        return res
+```
+
+```java
+public class Solution {
+    public long countSubarrays(int[] nums, int k) {
+        int maxN = Integer.MIN_VALUE, maxCnt = 0, l = 0;
+        long res = 0;
+        for (int num : nums) {
+            maxN = Math.max(maxN, num);
+        }
+
+        for (int r = 0; r < nums.length; r++) {
+            if (nums[r] == maxN) {
+                maxCnt++;
+            }
+
+            while (maxCnt > k || (l <= r && maxCnt == k && nums[l] != maxN)) {
+                if (nums[l] == maxN) {
+                    maxCnt--;
+                }
+                l++;
+            }
+
+            if (maxCnt == k) {
+                res += l + 1;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long countSubarrays(vector<int>& nums, int k) {
+        int maxN = *max_element(nums.begin(), nums.end());
+        int maxCnt = 0, l = 0;
+        long long res = 0;
+
+        for (int r = 0; r < nums.size(); r++) {
+            if (nums[r] == maxN) {
+                maxCnt++;
+            }
+
+            while (maxCnt > k || (l <= r && maxCnt == k && nums[l] != maxN)) {
+                if (nums[l] == maxN) {
+                    maxCnt--;
+                }
+                l++;
+            }
+
+            if (maxCnt == k) {
+                res += l + 1;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    countSubarrays(nums, k) {
+        let maxN = Math.max(...nums);
+        let maxCnt = 0, l = 0, res = 0;
+
+        for (let r = 0; r < nums.length; r++) {
+            if (nums[r] === maxN) {
+                maxCnt++;
+            }
+
+            while (maxCnt > k || (l <= r && maxCnt === k && nums[l] !== maxN)) {
+                if (nums[l] === maxN) {
+                    maxCnt--;
+                }
+                l++;
+            }
+
+            if (maxCnt === k) {
+                res += l + 1;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Variable Size Sliding Window (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def countSubarrays(self, nums: List[int], k: int) -> int:
+        max_n, max_cnt = max(nums), 0
+        l = res = 0
+
+        for r in range(len(nums)):
+            if nums[r] == max_n:
+                max_cnt += 1
+            while max_cnt == k:
+                if nums[l] == max_n:
+                    max_cnt -= 1
+                l += 1
+            res += l
+
+        return res
+```
+
+```java
+public class Solution {
+    public long countSubarrays(int[] nums, int k) {
+        int max_n = Integer.MIN_VALUE, max_cnt = 0, l = 0;
+        long res = 0;
+        for (int num : nums) {
+            max_n = Math.max(max_n, num);
+        }
+
+        for (int r = 0; r < nums.length; r++) {
+            if (nums[r] == max_n) {
+                max_cnt++;
+            }
+            while (max_cnt == k) {
+                if (nums[l] == max_n) {
+                    max_cnt--;
+                }
+                l++;
+            }
+            res += l;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long countSubarrays(vector<int>& nums, int k) {
+        int max_n = *max_element(nums.begin(), nums.end());
+        int max_cnt = 0, l = 0;
+        long long res = 0;
+
+        for (int r = 0; r < nums.size(); r++) {
+            if (nums[r] == max_n) {
+                max_cnt++;
+            }
+            while (max_cnt == k) {
+                if (nums[l] == max_n) {
+                    max_cnt--;
+                }
+                l++;
+            }
+            res += l;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    countSubarrays(nums, k) {
+        let max_n = Math.max(...nums), max_cnt = 0, l = 0, res = 0;
+
+        for (let r = 0; r < nums.length; r++) {
+            if (nums[r] === max_n) {
+                max_cnt++;
+            }
+            while (max_cnt === k) {
+                if (nums[l] === max_n) {
+                    max_cnt--;
+                }
+                l++;
+            }
+            res += l;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 4. Fixed Size Sliding Window + Math
+
+::tabs-start
+
+```python
+class Solution:
+    def countSubarrays(self, nums: List[int], k: int) -> int:
+        n = len(nums)
+        max_n = max(nums)
+        max_indexes = [-1]
+        for i, num in enumerate(nums):
+            if num == max_n:
+                max_indexes.append(i)
+        
+        res = 0
+        for i in range(1, len(max_indexes) - k + 1):
+            cur = (max_indexes[i] - max_indexes[i - 1])
+            cur *= (n - max_indexes[i + k - 1])
+            res += cur
+        
+        return res
+```
+
+```java
+public class Solution {
+    public long countSubarrays(int[] nums, int k) {
+        int n = nums.length;
+        int max_n = Integer.MIN_VALUE;
+        for (int num : nums) {
+            max_n = Math.max(max_n, num);
+        }
+
+        List<Integer> max_indexes = new ArrayList<>();
+        max_indexes.add(-1);
+        for (int i = 0; i < n; i++) {
+            if (nums[i] == max_n) {
+                max_indexes.add(i);
+            }
+        }
+
+        long res = 0;
+        for (int i = 1; i <= max_indexes.size() - k; i++) {
+            long cur = (max_indexes.get(i) - max_indexes.get(i - 1));
+            cur *= (n - max_indexes.get(i + k - 1));
+            res += cur;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long countSubarrays(vector<int>& nums, int k) {
+        int n = nums.size();
+        int max_n = *max_element(nums.begin(), nums.end());
+        vector<int> max_indexes = {-1};
+
+        for (int i = 0; i < n; i++) {
+            if (nums[i] == max_n) {
+                max_indexes.push_back(i);
+            }
+        }
+
+        long long res = 0;
+        for (int i = 1; i <= int(max_indexes.size()) - k; i++) {
+            long long cur = (max_indexes[i] - max_indexes[i - 1]);
+            cur *= (n - max_indexes[i + k - 1]);
+            res += cur;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    countSubarrays(nums, k) {
+        const n = nums.length;
+        const max_n = Math.max(...nums);
+        const max_indexes = [-1];
+
+        for (let i = 0; i < n; i++) {
+            if (nums[i] === max_n) {
+                max_indexes.push(i);
+            }
+        }
+
+        let res = 0;
+        for (let i = 1; i <= max_indexes.length - k; i++) {
+            res += (max_indexes[i] - max_indexes[i - 1]) * (n - max_indexes[i + k - 1]);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 5. Fixed Size Sliding Window (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def countSubarrays(self, nums: List[int], k: int) -> int:
+        max_n = max(nums)
+        max_indexes = deque()
+        res = 0
+
+        for i, num in enumerate(nums):
+            if num == max_n:
+                max_indexes.append(i)
+            
+            if len(max_indexes) > k:
+                max_indexes.popleft()
+            
+            if len(max_indexes) == k:
+                res += max_indexes[0] + 1
+        
+        return res
+```
+
+```java
+public class Solution {
+    public long countSubarrays(int[] nums, int k) {
+        int maxN = Integer.MIN_VALUE;
+        for (int num : nums) {
+            maxN = Math.max(maxN, num);
+        }
+        
+        Queue<Integer> maxIndexes = new LinkedList<>();
+        long res = 0;
+
+        for (int i = 0; i < nums.length; i++) {
+            if (nums[i] == maxN) {
+                maxIndexes.add(i);
+            }
+            
+            if (maxIndexes.size() > k) {
+                maxIndexes.poll();
+            }
+            
+            if (maxIndexes.size() == k) {
+                res += maxIndexes.peek() + 1;
+            }
+        }
+        
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long countSubarrays(vector<int>& nums, int k) {
+        int maxN = *max_element(nums.begin(), nums.end());
+        queue<int> maxIndexes;
+        long long res = 0;
+
+        for (int i = 0; i < nums.size(); i++) {
+            if (nums[i] == maxN) {
+                maxIndexes.push(i);
+            }
+            
+            if (maxIndexes.size() > k) {
+                maxIndexes.pop();
+            }
+            
+            if (maxIndexes.size() == k) {
+                res += maxIndexes.front() + 1;
+            }
+        }
+        
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    countSubarrays(nums, k) {
+        const maxN = Math.max(...nums);
+        const maxIndexes = new Queue();
+        let res = 0;
+
+        for (let i = 0; i < nums.length; i++) {
+            if (nums[i] === maxN) {
+                maxIndexes.push(i);
+            }
+            
+            if (maxIndexes.size() > k) {
+                maxIndexes.pop();
+            }
+            
+            if (maxIndexes.size() === k) {
+                res += maxIndexes.front() + 1;
+            }
+        }
+        
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/count-subsequences.md b/articles/count-subsequences.md
index d281064d7..241876a84 100644
--- a/articles/count-subsequences.md
+++ b/articles/count-subsequences.md
@@ -134,6 +134,76 @@ public class Solution {
 }
 ```
 
+```go
+func numDistinct(s string, t string) int {
+    if len(t) > len(s) {
+        return 0
+    }
+
+    var dfs func(i, j int) int
+    dfs = func(i, j int) int {
+        if j == len(t) {
+            return 1
+        }
+        if i == len(s) {
+            return 0
+        }
+
+        res := dfs(i+1, j)
+        if s[i] == t[j] {
+            res += dfs(i+1, j+1)
+        }
+        return res
+    }
+
+    return dfs(0, 0)
+}
+```
+
+```kotlin
+class Solution {
+    fun numDistinct(s: String, t: String): Int {
+        if (t.length > s.length) return 0
+
+        fun dfs(i: Int, j: Int): Int {
+            if (j == t.length) return 1
+            if (i == s.length) return 0
+
+            var res = dfs(i + 1, j)
+            if (s[i] == t[j]) {
+                res += dfs(i + 1, j + 1)
+            }
+            return res
+        }
+
+        return dfs(0, 0)
+    }
+}
+```
+
+```swift
+class Solution {
+    func numDistinct(_ s: String, _ t: String) -> Int {
+        let sArray = Array(s), tArray = Array(t)
+        let sLen = sArray.count, tLen = tArray.count
+        if tLen > sLen { return 0 }
+
+        func dfs(_ i: Int, _ j: Int) -> Int {
+            if j == tLen { return 1 }
+            if i == sLen { return 0 }
+            
+            var res = dfs(i + 1, j)
+            if sArray[i] == tArray[j] {
+                res += dfs(i + 1, j + 1)
+            }
+            return res
+        }
+
+        return dfs(0, 0)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -141,6 +211,8 @@ public class Solution {
 * Time complexity: $O(2 ^ m)$
 * Space complexity: $O(m)$
 
+> Where $m$ is the length of the string $s$.
+
 ---
 
 ## 2. Dynamic Programming (Top-Down)
@@ -284,6 +356,98 @@ public class Solution {
 }
 ```
 
+```go
+func numDistinct(s string, t string) int {
+    if len(t) > len(s) {
+        return 0
+    }
+
+    dp := make([][]int, len(s)+1)
+    for i := range dp {
+        dp[i] = make([]int, len(t)+1)
+        for j := range dp[i] {
+            dp[i][j] = -1
+        }
+    }
+    
+    var dfs func(i, j int) int
+    dfs = func(i, j int) int {
+        if j == len(t) {
+            return 1
+        }
+        if i == len(s) {
+            return 0
+        }
+        if dp[i][j] != -1 {
+            return dp[i][j]
+        }
+
+        res := dfs(i+1, j)
+        if s[i] == t[j] {
+            res += dfs(i+1, j+1)
+        }
+
+        dp[i][j] = res
+        return res
+    }
+
+    return dfs(0, 0)
+}
+```
+
+```kotlin
+class Solution {
+    fun numDistinct(s: String, t: String): Int {
+        if (t.length > s.length) return 0
+
+        val dp = Array(s.length + 1) { IntArray(t.length + 1) { -1 } }
+
+        fun dfs(i: Int, j: Int): Int {
+            if (j == t.length) return 1
+            if (i == s.length) return 0
+            if (dp[i][j] != -1) return dp[i][j]
+
+            var res = dfs(i + 1, j)
+            if (s[i] == t[j]) {
+                res += dfs(i + 1, j + 1)
+            }
+
+            dp[i][j] = res
+            return res
+        }
+
+        return dfs(0, 0)
+    }
+}
+```
+
+```swift
+class Solution {
+    func numDistinct(_ s: String, _ t: String) -> Int {
+        let sArray = Array(s), tArray = Array(t)
+        let sLen = sArray.count, tLen = tArray.count
+        if tLen > sLen { return 0 }
+
+        var dp = [[Int]: Int]()
+
+        func dfs(_ i: Int, _ j: Int) -> Int {
+            if j == tLen { return 1 }
+            if i == sLen { return 0 }
+            if let val = dp[[i, j]] { return val }
+
+            var res = dfs(i + 1, j)
+            if sArray[i] == tArray[j] {
+                res += dfs(i + 1, j + 1)
+            }
+            dp[[i, j]] = res
+            return res
+        }
+
+        return dfs(0, 0)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -346,7 +510,7 @@ class Solution {
 public:
     int numDistinct(string s, string t) {
         int m = s.length(), n = t.length();
-        vector<vector<int>> dp(m + 1, vector<int>(n + 1, 0));
+        vector<vector<uint>> dp(m + 1, vector<uint>(n + 1, 0));
 
         for (int i = 0; i <= m; i++) {
             dp[i][n] = 1;
@@ -420,6 +584,92 @@ public class Solution {
 }
 ```
 
+```go
+func numDistinct(s string, t string) int {
+    m, n := len(s), len(t)
+    dp := make([][]int, m+1)
+    for i := range dp {
+        dp[i] = make([]int, n+1)
+    }
+
+    for i := 0; i <= m; i++ {
+        dp[i][n] = 1
+    }
+
+    for i := m - 1; i >= 0; i-- {
+        for j := n - 1; j >= 0; j-- {
+            dp[i][j] = dp[i+1][j]
+            if s[i] == t[j] {
+                dp[i][j] += dp[i+1][j+1]
+            }
+        }
+    }
+
+    return dp[0][0]
+}
+```
+
+```kotlin
+class Solution {
+    fun numDistinct(s: String, t: String): Int {
+        val m = s.length
+        val n = t.length
+        val dp = Array(m + 1) { IntArray(n + 1) }
+
+        for (i in 0..m) {
+            dp[i][n] = 1
+        }
+
+        for (i in m - 1 downTo 0) {
+            for (j in n - 1 downTo 0) {
+                dp[i][j] = dp[i + 1][j]
+                if (s[i] == t[j]) {
+                    dp[i][j] += dp[i + 1][j + 1]
+                }
+            }
+        }
+
+        return dp[0][0]
+    }
+}
+```
+
+```swift
+class Solution {
+    func numDistinct(_ s: String, _ t: String) -> Int {
+        let m = s.count, n = t.count
+        var dp = Array(
+            repeating: Array(repeating: 0, count: n + 1),
+            count: m + 1
+        )
+
+        let sArray = Array(s)
+        let tArray = Array(t)
+
+        for i in 0...m {
+            dp[i][n] = 1
+        }
+
+        for i in stride(from: m - 1, through: 0, by: -1) {
+            for j in stride(from: n - 1, through: 0, by: -1) {
+                let base = dp[i + 1][j]
+                dp[i][j] = base
+                if sArray[i] == tArray[j] {
+                    let addend = dp[i + 1][j + 1]
+                    if base > Int.max - addend {
+                        dp[i][j] = 0
+                    } else {
+                        dp[i][j] += addend
+                    }
+                }
+            }
+        }
+
+        return dp[0][0]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -481,8 +731,8 @@ class Solution {
 public:
     int numDistinct(string s, string t) {
         int m = s.size(), n = t.size();
-        vector<int> dp(n + 1, 0);
-        vector<int> nextDp(n + 1, 0);
+        vector<uint> dp(n + 1, 0);
+        vector<uint> nextDp(n + 1, 0);
         dp[n] = nextDp[n] = 1;
 
         for (int i = m - 1; i >= 0; i--) {
@@ -551,6 +801,87 @@ public class Solution {
 }
 ```
 
+```go
+func numDistinct(s string, t string) int {
+    m, n := len(s), len(t)
+    dp := make([]int, n+1)
+    nextDp := make([]int, n+1)
+
+    dp[n] = 1
+    nextDp[n] = 1
+
+    for i := m - 1; i >= 0; i-- {
+        for j := n - 1; j >= 0; j-- {
+            nextDp[j] = dp[j]
+            if s[i] == t[j] {
+                nextDp[j] += dp[j+1]
+            }
+        }
+        dp = append([]int(nil), nextDp...) 
+    }
+
+    return dp[0]
+}
+```
+
+```kotlin
+class Solution {
+    fun numDistinct(s: String, t: String): Int {
+        val m = s.length
+        val n = t.length
+        var dp = IntArray(n + 1)
+        var nextDp = IntArray(n + 1)
+
+        dp[n] = 1
+        nextDp[n] = 1
+
+        for (i in m - 1 downTo 0) {
+            for (j in n - 1 downTo 0) {
+                nextDp[j] = dp[j]
+                if (s[i] == t[j]) {
+                    nextDp[j] += dp[j + 1]
+                }
+            }
+            dp = nextDp.copyOf()
+        }
+
+        return dp[0]
+    }
+}
+```
+
+```swift
+class Solution {
+    func numDistinct(_ s: String, _ t: String) -> Int {
+        let m = s.count, n = t.count
+        var dp = [Int](repeating: 0, count: n + 1)
+        var nextDp = [Int](repeating: 0, count: n + 1)
+        dp[n] = 1
+        nextDp[n] = 1
+
+        let sArr = Array(s)
+        let tArr = Array(t)
+
+        for i in stride(from: m - 1, through: 0, by: -1) {
+            for j in stride(from: n - 1, through: 0, by: -1) {
+                nextDp[j] = dp[j]
+                if sArr[i] == tArr[j] {
+                    let addend = dp[j + 1]
+                    if nextDp[j] > Int.max - addend {
+                        nextDp[j] = 0
+                    } else {
+                        nextDp[j] += addend
+                    }
+                }
+            }
+            dp = nextDp
+        }
+        
+        return dp[0]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -616,13 +947,13 @@ class Solution {
 public:
     int numDistinct(string s, string t) {
         int m = s.size(), n = t.size();
-        vector<int> dp(n + 1, 0);
+        vector<uint> dp(n + 1, 0);
         dp[n] = 1;
 
         for (int i = m - 1; i >= 0; i--) {
             int prev = 1;
             for (int j = n - 1; j >= 0; j--) {
-                int res = dp[j];
+                uint res = dp[j];
                 if (s[i] == t[j]) {
                     res += prev;
                 }
@@ -692,6 +1023,84 @@ public class Solution {
 }
 ```
 
+```go
+func numDistinct(s string, t string) int {
+    m, n := len(s), len(t)
+    dp := make([]int, n+1)
+
+    dp[n] = 1
+    for i := m - 1; i >= 0; i-- {
+        prev := 1
+        for j := n - 1; j >= 0; j-- {
+            res := dp[j]
+            if s[i] == t[j] {
+                res += prev
+            }
+            prev = dp[j]
+            dp[j] = res
+        }
+    }
+
+    return dp[0]
+}
+```
+
+```kotlin
+class Solution {
+    fun numDistinct(s: String, t: String): Int {
+        val m = s.length
+        val n = t.length
+        val dp = IntArray(n + 1)
+
+        dp[n] = 1
+        for (i in m - 1 downTo 0) {
+            var prev = 1
+            for (j in n - 1 downTo 0) {
+                var res = dp[j]
+                if (s[i] == t[j]) {
+                    res += prev
+                }
+                prev = dp[j]
+                dp[j] = res
+            }
+        }
+
+        return dp[0]
+    }
+}
+```
+
+```swift
+class Solution {
+    func numDistinct(_ s: String, _ t: String) -> Int {
+        let m = s.count, n = t.count
+        var dp = [Int](repeating: 0, count: n + 1)
+        dp[n] = 1
+        let sArr = Array(s)
+        let tArr = Array(t)
+
+        for i in stride(from: m - 1, through: 0, by: -1) {
+            var prev = 1
+            for j in stride(from: n - 1, through: 0, by: -1) {
+                let base = dp[j]
+                var res = base
+                if sArr[i] == tArr[j] {
+                    if base > Int.max - prev {
+                        res = 0
+                    } else {
+                        res += prev
+                    }
+                }
+                prev = dp[j]
+                dp[j] = res
+            }
+        }
+
+        return dp[0]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/count-the-number-of-consistent-strings.md b/articles/count-the-number-of-consistent-strings.md
new file mode 100644
index 000000000..600698357
--- /dev/null
+++ b/articles/count-the-number-of-consistent-strings.md
@@ -0,0 +1,415 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def countConsistentStrings(self, allowed: str, words: List[str]) -> int:
+        res = 0
+
+        for w in words:
+            flag = 1
+            for c in w:
+                if c not in allowed:
+                    flag = 0
+                    break
+            res += flag
+
+        return res
+```
+
+```java
+public class Solution {
+    public int countConsistentStrings(String allowed, String[] words) {
+        int res = 0;
+
+        for (String w : words) {
+            boolean flag = true;
+            for (char c : w.toCharArray()) {
+                if (allowed.indexOf(c) == -1) {
+                    flag = false;
+                    break;
+                }
+            }
+            if (flag) res++;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countConsistentStrings(string allowed, vector<string>& words) {
+        int res = 0;
+
+        for (string& w : words) {
+            bool flag = true;
+            for (char c : w) {
+                if (allowed.find(c) == string::npos) {
+                    flag = false;
+                    break;
+                }
+            }
+            res += flag;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} allowed
+     * @param {string[]} words
+     * @return {number}
+     */
+    countConsistentStrings(allowed, words) {
+        let res = 0;
+
+        for (let w of words) {
+            let flag = 1;
+            for (let c of w) {
+                if (!allowed.includes(c)) {
+                    flag = 0;
+                    break;
+                }
+            }
+            res += flag;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m * l)$
+* Space complexity: $O(1)$
+
+> Where $n$ is the number of words, $m$ is the length of the string $allowed$, and $l$ is the length of the longest word.
+
+---
+
+## 2. Hash Set
+
+::tabs-start
+
+```python
+class Solution:
+    def countConsistentStrings(self, allowed: str, words: List[str]) -> int:
+        allowed = set(allowed)
+
+        res = len(words)
+        for w in words:
+            for c in w:
+                if c not in allowed:
+                    res -= 1
+                    break
+
+        return res
+```
+
+```java
+public class Solution {
+    public int countConsistentStrings(String allowed, String[] words) {
+        Set<Character> allowedSet = new HashSet<>();
+        for (char c : allowed.toCharArray()) {
+            allowedSet.add(c);
+        }
+
+        int res = words.length;
+        for (String w : words) {
+            for (char c : w.toCharArray()) {
+                if (!allowedSet.contains(c)) {
+                    res--;
+                    break;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countConsistentStrings(string allowed, vector<string>& words) {
+        unordered_set<char> allowedSet(allowed.begin(), allowed.end());
+
+        int res = words.size();
+        for (string& w : words) {
+            for (char c : w) {
+                if (allowedSet.find(c) == allowedSet.end()) {
+                    res--;
+                    break;
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} allowed
+     * @param {string[]} words
+     * @return {number}
+     */
+    countConsistentStrings(allowed, words) {
+        const allowedSet = new Set(allowed);
+        let res = words.length;
+
+        for (let w of words) {
+            for (let c of w) {
+                if (!allowedSet.has(c)) {
+                    res--;
+                    break;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * l + m)$
+* Space complexity: $O(m)$
+
+> Where $n$ is the number of words, $m$ is the length of the string $allowed$, and $l$ is the length of the longest word.
+
+---
+
+## 3. Boolean Array
+
+::tabs-start
+
+```python
+class Solution:
+    def countConsistentStrings(self, allowed: str, words: List[str]) -> int:
+        allowedArr = [False] * 26
+        for c in allowed:
+            allowedArr[ord(c) - ord('a')] = True
+
+        res = len(words)
+        for w in words:
+            for c in w:
+                if not allowedArr[ord(c) - ord('a')]:
+                    res -= 1
+                    break
+
+        return res
+```
+
+```java
+public class Solution {
+    public int countConsistentStrings(String allowed, String[] words) {
+        Set<Character> allowedSet = new HashSet<>();
+        for (char c : allowed.toCharArray()) {
+            allowedSet.add(c);
+        }
+
+        int res = words.length;
+        for (String w : words) {
+            for (char c : w.toCharArray()) {
+                if (!allowedSet.contains(c)) {
+                    res--;
+                    break;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countConsistentStrings(string allowed, vector<string>& words) {
+        bool allowedArr[26] = {};
+        for (char c : allowed) {
+            allowedArr[c - 'a'] = true;
+        }
+
+        int res = words.size();
+        for (const string& w : words) {
+            for (char c : w) {
+                if (!allowedArr[c - 'a']) {
+                    res--;
+                    break;
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} allowed
+     * @param {string[]} words
+     * @return {number}
+     */
+    countConsistentStrings(allowed, words) {
+        const allowedArr = new Array(26).fill(false);
+        for (let c of allowed) {
+            allowedArr[c.charCodeAt(0) - 97] = true;
+        }
+
+        let res = words.length;
+        for (let w of words) {
+            for (let c of w) {
+                if (!allowedArr[c.charCodeAt(0) - 97]) {
+                    res--;
+                    break;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * l + m)$
+* Space complexity: $O(m)$
+
+> Where $n$ is the number of words, $m$ is the length of the string $allowed$, and $l$ is the length of the longest word.
+
+---
+
+## 4. Bitmask
+
+::tabs-start
+
+```python
+class Solution:
+    def countConsistentStrings(self, allowed: str, words: List[str]) -> int:
+        bit_mask = 0
+        for c in allowed:
+            bit = 1 << (ord(c) - ord('a'))
+            bit_mask = bit_mask | bit
+
+        res = len(words)
+        for w in words:
+            for c in w:
+                bit = 1 << (ord(c) - ord('a'))
+                if bit & bit_mask == 0:
+                    res -= 1
+                    break
+
+        return res
+```
+
+```java
+public class Solution {
+    public int countConsistentStrings(String allowed, String[] words) {
+        int bitMask = 0;
+        for (char c : allowed.toCharArray()) {
+            bitMask |= 1 << (c - 'a');
+        }
+
+        int res = words.length;
+        for (String w : words) {
+            for (char c : w.toCharArray()) {
+                int bit = 1 << (c - 'a');
+                if ((bit & bitMask) == 0) {
+                    res--;
+                    break;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countConsistentStrings(string allowed, vector<string>& words) {
+        int bitMask = 0;
+        for (char c : allowed) {
+            bitMask |= (1 << (c - 'a'));
+        }
+
+        int res = words.size();
+        for (const string& w : words) {
+            for (char c : w) {
+                int bit = 1 << (c - 'a');
+                if ((bit & bitMask) == 0) {
+                    res--;
+                    break;
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} allowed
+     * @param {string[]} words
+     * @return {number}
+     */
+    countConsistentStrings(allowed, words) {
+        let bitMask = 0;
+        for (let c of allowed) {
+            bitMask |= 1 << (c.charCodeAt(0) - 97);
+        }
+
+        let res = words.length;
+        for (let w of words) {
+            for (let c of w) {
+                const bit = 1 << (c.charCodeAt(0) - 97);
+                if ((bit & bitMask) === 0) {
+                    res--;
+                    break;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * l + m)$
+* Space complexity: $O(1)$
+
+> Where $n$ is the number of words, $m$ is the length of the string $allowed$, and $l$ is the length of the longest word.
\ No newline at end of file
diff --git a/articles/count-triplets-that-can-form-two-arrays-of-equal-xor.md b/articles/count-triplets-that-can-form-two-arrays-of-equal-xor.md
new file mode 100644
index 000000000..129c14f82
--- /dev/null
+++ b/articles/count-triplets-that-can-form-two-arrays-of-equal-xor.md
@@ -0,0 +1,432 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def countTriplets(self, arr: List[int]) -> int:
+        N = len(arr)
+        res = 0
+
+        for i in range(N - 1):
+            for j in range(i + 1, N):
+                for k in range(j, N):
+                    a = b = 0
+                    for idx in range(i, j):
+                        a ^= arr[idx]
+                    for idx in range(j, k + 1):
+                        b ^= arr[idx]
+                    if a == b:
+                        res += 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int countTriplets(int[] arr) {
+        int N = arr.length;
+        int res = 0;
+
+        for (int i = 0; i < N - 1; i++) {
+            for (int j = i + 1; j < N; j++) {
+                for (int k = j; k < N; k++) {
+                    int a = 0, b = 0;
+                    for (int idx = i; idx < j; idx++) {
+                        a ^= arr[idx];
+                    }
+                    for (int idx = j; idx <= k; idx++) {
+                        b ^= arr[idx];
+                    }
+                    if (a == b) {
+                        res++;
+                    }
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countTriplets(vector<int>& arr) {
+        int N = arr.size();
+        int res = 0;
+
+        for (int i = 0; i < N - 1; ++i) {
+            for (int j = i + 1; j < N; ++j) {
+                for (int k = j; k < N; ++k) {
+                    int a = 0, b = 0;
+                    for (int idx = i; idx < j; ++idx) {
+                        a ^= arr[idx];
+                    }
+                    for (int idx = j; idx <= k; ++idx) {
+                        b ^= arr[idx];
+                    }
+                    if (a == b) {
+                        res++;
+                    }
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @return {number}
+     */
+    countTriplets(arr) {
+        const N = arr.length;
+        let res = 0;
+
+        for (let i = 0; i < N - 1; i++) {
+            for (let j = i + 1; j < N; j++) {
+                for (let k = j; k < N; k++) {
+                    let a = 0, b = 0;
+                    for (let idx = i; idx < j; idx++) {
+                        a ^= arr[idx];
+                    }
+                    for (let idx = j; idx <= k; idx++) {
+                        b ^= arr[idx];
+                    }
+                    if (a === b) {
+                        res++;
+                    }
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 4)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 2. Brute Force (Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def countTriplets(self, arr: List[int]) -> int:
+        N = len(arr)
+        res = 0
+
+        for i in range(N - 1):
+            a = 0
+            for j in range(i + 1, N):
+                a ^= arr[j - 1]
+                b = 0
+                for k in range(j, N):
+                    b ^= arr[k]
+                    if a == b:
+                        res += 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int countTriplets(int[] arr) {
+        int N = arr.length;
+        int res = 0;
+
+        for (int i = 0; i < N - 1; i++) {
+            int a = 0;
+            for (int j = i + 1; j < N; j++) {
+                a ^= arr[j - 1];
+                int b = 0;
+                for (int k = j; k < N; k++) {
+                    b ^= arr[k];
+                    if (a == b) {
+                        res++;
+                    }
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countTriplets(vector<int>& arr) {
+        int N = arr.size();
+        int res = 0;
+
+        for (int i = 0; i < N - 1; ++i) {
+            int a = 0;
+            for (int j = i + 1; j < N; ++j) {
+                a ^= arr[j - 1];
+                int b = 0;
+                for (int k = j; k < N; ++k) {
+                    b ^= arr[k];
+                    if (a == b) {
+                        res++;
+                    }
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @return {number}
+     */
+    countTriplets(arr) {
+        const N = arr.length;
+        let res = 0;
+
+        for (let i = 0; i < N - 1; i++) {
+            let a = 0;
+            for (let j = i + 1; j < N; j++) {
+                a ^= arr[j - 1];
+                let b = 0;
+                for (let k = j; k < N; k++) {
+                    b ^= arr[k];
+                    if (a === b) {
+                        res++;
+                    }
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 3)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 3. Math + Bitwise XOR
+
+::tabs-start
+
+```python
+class Solution:
+    def countTriplets(self, arr: List[int]) -> int:
+        N = len(arr)
+        res = 0
+
+        for i in range(N - 1):
+            cur_xor = arr[i]
+            for k in range(i + 1, N):
+                cur_xor ^= arr[k]
+                if cur_xor == 0:
+                    res += k - i
+
+        return res
+```
+
+```java
+public class Solution {
+    public int countTriplets(int[] arr) {
+        int N = arr.length;
+        int res = 0;
+
+        for (int i = 0; i < N - 1; i++) {
+            int curXor = arr[i];
+            for (int k = i + 1; k < N; k++) {
+                curXor ^= arr[k];
+                if (curXor == 0) {
+                    res += k - i;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countTriplets(vector<int>& arr) {
+        int N = arr.size();
+        int res = 0;
+
+        for (int i = 0; i < N - 1; ++i) {
+            int curXor = arr[i];
+            for (int k = i + 1; k < N; ++k) {
+                curXor ^= arr[k];
+                if (curXor == 0) {
+                    res += k - i;
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @return {number}
+     */
+    countTriplets(arr) {
+        const N = arr.length;
+        let res = 0;
+
+        for (let i = 0; i < N - 1; i++) {
+            let curXor = arr[i];
+            for (let k = i + 1; k < N; k++) {
+                curXor ^= arr[k];
+                if (curXor === 0) {
+                    res += k - i;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 4. Math + Bitwise XOR (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def countTriplets(self, arr: List[int]) -> int:
+        N = len(arr)
+        res = prefix = 0
+        count = defaultdict(int)  # number of prefixes
+        index_sum = defaultdict(int)  # sum of indices with that prefix
+        count[0] = 1
+
+        for i in range(N):
+            prefix ^= arr[i]
+            if prefix in count:
+                res += i * count[prefix] - index_sum[prefix]
+            count[prefix] += 1
+            index_sum[prefix] += i + 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int countTriplets(int[] arr) {
+        int N = arr.length, res = 0, prefix = 0;
+        Map<Integer, Integer> count = new HashMap<>(); // number of prefixes
+        Map<Integer, Integer> indexSum = new HashMap<>(); // sum of indices with that prefix
+        count.put(0, 1);
+
+        for (int i = 0; i < N; i++) {
+            prefix ^= arr[i];
+            if (count.containsKey(prefix)) {
+                res += i * count.get(prefix) - indexSum.getOrDefault(prefix, 0);
+            }
+            count.put(prefix, count.getOrDefault(prefix, 0) + 1);
+            indexSum.put(prefix, indexSum.getOrDefault(prefix, 0) + i + 1);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countTriplets(vector<int>& arr) {
+        int N = arr.size(), res = 0, prefix = 0;
+        unordered_map<int, int> count; // number of prefixes
+        unordered_map<int, int> indexSum; // sum of indices with that prefix
+        count[0] = 1;
+
+        for (int i = 0; i < N; i++) {
+            prefix ^= arr[i];
+            if (count.count(prefix)) {
+                res += i * count[prefix] - indexSum[prefix];
+            }
+            count[prefix]++;
+            indexSum[prefix] += i + 1;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @return {number}
+     */
+    countTriplets(arr) {
+        const N = arr.length;
+        let res = 0, prefix = 0;
+        const count = new Map(); // number of prefixes
+        const indexSum = new Map(); // sum of indices with that prefix
+        count.set(0, 1);
+
+        for (let i = 0; i < N; i++) {
+            prefix ^= arr[i];
+            if (count.has(prefix)) {
+                res += i * count.get(prefix) - (indexSum.get(prefix) || 0);
+            }
+            count.set(prefix, (count.get(prefix) || 0) + 1);
+            indexSum.set(prefix, (indexSum.get(prefix) || 0) + i + 1);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/count-vowel-strings-in-ranges.md b/articles/count-vowel-strings-in-ranges.md
new file mode 100644
index 000000000..22c92a839
--- /dev/null
+++ b/articles/count-vowel-strings-in-ranges.md
@@ -0,0 +1,336 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def vowelStrings(self, words: List[str], queries: List[List[int]]) -> List[int]:
+        vowels = set("aeiou")
+        res = []
+
+        for start, end in queries:
+            cnt = 0
+            for i in range(start, end + 1):
+                if words[i][0] in vowels and words[i][-1] in vowels:
+                    cnt += 1
+            res.append(cnt)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[] vowelStrings(String[] words, int[][] queries) {
+        Set<Character> vowels = Set.of('a', 'e', 'i', 'o', 'u');
+        int[] res = new int[queries.length];
+
+        for (int k = 0; k < queries.length; k++) {
+            int start = queries[k][0], end = queries[k][1], count = 0;
+
+            for (int i = start; i <= end; i++) {
+                String word = words[i];
+                if (vowels.contains(word.charAt(0)) && vowels.contains(word.charAt(word.length() - 1))) {
+                    count++;
+                }
+            }
+
+            res[k] = count;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> vowelStrings(vector<string>& words, vector<vector<int>>& queries) {
+        unordered_set<char> vowels = {'a', 'e', 'i', 'o', 'u'};
+        vector<int> res;
+
+        for (auto& q : queries) {
+            int start = q[0], end = q[1], count = 0;
+
+            for (int i = start; i <= end; i++) {
+                if (vowels.count(words[i][0]) && vowels.count(words[i].back())) {
+                    count++;
+                }
+            }
+
+            res.push_back(count);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @param {number[][]} queries
+     * @return {number[]}
+     */
+    vowelStrings(words, queries) {
+        const vowels = new Set(['a', 'e', 'i', 'o', 'u']);
+        const res = [];
+
+        for (let [start, end] of queries) {
+            let count = 0;
+            for (let i = start; i <= end; i++) {
+                const word = words[i];
+                if (vowels.has(word[0]) && vowels.has(word[word.length - 1])) {
+                    count++;
+                }
+            }
+            res.push(count);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(m)$ space for the output list.
+
+> Where $n$ is the number of words, and $m$ is the number of queries.
+
+---
+
+## 2. Prefix Sum + Hash Set
+
+::tabs-start
+
+```python
+class Solution:
+    def vowelStrings(self, words: List[str], queries: List[List[int]]) -> List[int]:
+        vowel_set = set("aeiou")
+        prefix_cnt = [0] * (len(words) + 1)
+        prev = 0
+
+        for i, w in enumerate(words):
+            if w[0] in vowel_set and w[-1] in vowel_set:
+                prev += 1
+            prefix_cnt[i + 1] = prev
+
+        res = [0] * len(queries)
+        for i, q in enumerate(queries):
+            l, r = q
+            res[i] = prefix_cnt[r + 1] - prefix_cnt[l]
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[] vowelStrings(String[] words, int[][] queries) {
+        Set<Character> vowels = Set.of('a', 'e', 'i', 'o', 'u');
+        int n = words.length;
+        int[] prefixCnt = new int[n + 1];
+
+        for (int i = 0; i < n; i++) {
+            String w = words[i];
+            prefixCnt[i + 1] = prefixCnt[i];
+            if (vowels.contains(w.charAt(0)) && vowels.contains(w.charAt(w.length() - 1))) {
+                prefixCnt[i + 1]++;
+            }
+        }
+
+        int[] res = new int[queries.length];
+        for (int i = 0; i < queries.length; i++) {
+            int l = queries[i][0], r = queries[i][1];
+            res[i] = prefixCnt[r + 1] - prefixCnt[l];
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> vowelStrings(vector<string>& words, vector<vector<int>>& queries) {
+        unordered_set<char> vowels = {'a', 'e', 'i', 'o', 'u'};
+        int n = words.size();
+        vector<int> prefixCnt(n + 1, 0);
+
+        for (int i = 0; i < n; i++) {
+            prefixCnt[i + 1] = prefixCnt[i];
+            if (vowels.count(words[i][0]) && vowels.count(words[i].back())) {
+                prefixCnt[i + 1]++;
+            }
+        }
+
+        vector<int> res;
+        for (auto& q : queries) {
+            int l = q[0], r = q[1];
+            res.push_back(prefixCnt[r + 1] - prefixCnt[l]);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @param {number[][]} queries
+     * @return {number[]}
+     */
+    vowelStrings(words, queries) {
+        const vowels = new Set(['a', 'e', 'i', 'o', 'u']);
+        const n = words.length;
+        const prefixCnt = new Array(n + 1).fill(0);
+
+        for (let i = 0; i < n; i++) {
+            prefixCnt[i + 1] = prefixCnt[i];
+            const w = words[i];
+            if (vowels.has(w[0]) && vowels.has(w[w.length - 1])) {
+                prefixCnt[i + 1]++;
+            }
+        }
+
+        const res = new Array(queries.length);
+        for (let i = 0; i < queries.length; i++) {
+            const [l, r] = queries[i];
+            res[i] = prefixCnt[r + 1] - prefixCnt[l];
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity:
+    * $O(n)$ extra space.
+    * $O(m)$ space for the output list.
+
+> Where $n$ is the number of words, and $m$ is the number of queries.
+
+---
+
+## 3. Prefix Sum + Bitmask
+
+::tabs-start
+
+```python
+class Solution:
+    def vowelStrings(self, words: List[str], queries: List[List[int]]) -> List[int]:
+        vowels = sum(1 << (ord(c) - ord('a')) for c in "aeiou")
+        prefix = [0]
+        for w in words:
+            prefix.append(prefix[-1])
+            if (1 << (ord(w[0]) - ord('a'))) & vowels and (1 << (ord(w[-1]) - ord('a'))) & vowels:
+                prefix[-1] += 1
+        return [prefix[r + 1] - prefix[l] for l, r in queries]
+```
+
+```java
+public class Solution {
+    public int[] vowelStrings(String[] words, int[][] queries) {
+        int vowels = 0;
+        for (char c : "aeiou".toCharArray()) {
+            vowels |= 1 << (c - 'a');
+        }
+
+        int[] prefix = new int[words.length + 1];
+        for (int i = 0; i < words.length; i++) {
+            int f = words[i].charAt(0) - 'a';
+            int l = words[i].charAt(words[i].length() - 1) - 'a';
+            int isVowel = ((1 << f) & vowels) != 0 && ((1 << l) & vowels) != 0 ? 1 : 0;
+            prefix[i + 1] = prefix[i] + isVowel;
+        }
+
+        int[] res = new int[queries.length];
+        for (int i = 0; i < queries.length; i++) {
+            int l = queries[i][0], r = queries[i][1];
+            res[i] = prefix[r + 1] - prefix[l];
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> vowelStrings(vector<string>& words, vector<vector<int>>& queries) {
+        int vowels = 0;
+        for (char c : string("aeiou")) {
+            vowels |= (1 << (c - 'a'));
+        }
+
+        int n = words.size();
+        vector<int> prefix(n + 1);
+        for (int i = 0; i < n; i++) {
+            int f = words[i][0] - 'a';
+            int l = words[i].back() - 'a';
+            int isVowel = ((1 << f) & vowels) && ((1 << l) & vowels);
+            prefix[i + 1] = prefix[i] + isVowel;
+        }
+
+        vector<int> res;
+        for (auto& q : queries) {
+            int l = q[0], r = q[1];
+            res.push_back(prefix[r + 1] - prefix[l]);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @param {number[][]} queries
+     * @return {number[]}
+     */
+    vowelStrings(words, queries) {
+        let vowels = 0;
+        for (let c of "aeiou") {
+            vowels |= 1 << (c.charCodeAt(0) - 97);
+        }
+
+        const prefix = [0];
+        for (let w of words) {
+            const f = w.charCodeAt(0) - 97;
+            const l = w.charCodeAt(w.length - 1) - 97;
+            const isVowel = ((1 << f) & vowels) && ((1 << l) & vowels) ? 1 : 0;
+            prefix.push(prefix[prefix.length - 1] + isVowel);
+        }
+
+        return queries.map(([l, r]) => prefix[r + 1] - prefix[l]);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity:
+    * $O(n)$ extra space.
+    * $O(m)$ space for the output list.
+
+> Where $n$ is the number of words, and $m$ is the number of queries.
\ No newline at end of file
diff --git a/articles/count-vowels-permutation.md b/articles/count-vowels-permutation.md
new file mode 100644
index 000000000..c2f561f56
--- /dev/null
+++ b/articles/count-vowels-permutation.md
@@ -0,0 +1,864 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def countVowelPermutation(self, n: int) -> int:
+        MOD = 10**9 + 7
+        follows = {
+            'a': ['e'],
+            'e': ['a', 'i'],
+            'i': ['a', 'e', 'o', 'u'],
+            'o': ['i', 'u'],
+            'u': ['a']
+        }
+
+        def dfs(i, v):
+            if i == n:
+                return 1
+            
+            total = 0
+            for nxt in follows[v]:
+                total = (total + dfs(i + 1, nxt)) % MOD
+            return total
+
+        res = 0
+        for vowel in ['a', 'e', 'i', 'o', 'u']:
+            res = (res + dfs(1, vowel)) % MOD
+        
+        return res
+```
+
+```java
+public class Solution {
+    private final int MOD = 1_000_000_007;
+    private final Map<Character, List<Character>> follows = Map.of(
+        'a', List.of('e'),
+        'e', List.of('a', 'i'),
+        'i', List.of('a', 'e', 'o', 'u'),
+        'o', List.of('i', 'u'),
+        'u', List.of('a')
+    );
+
+    public int countVowelPermutation(int n) {
+        int res = 0;
+        for (char vowel : "aeiou".toCharArray()) {
+            res = (res + dfs(1, vowel, n)) % MOD;
+        }
+        return res;
+    }
+
+    private int dfs(int i, char v, int n) {
+        if (i == n) {
+            return 1;
+        }
+        
+        int total = 0;
+        for (char next : follows.get(v)) {
+            total = (total + dfs(i + 1, next, n)) % MOD;
+        }
+        return total;
+    }
+}
+```
+
+```cpp
+class Solution {
+    const int MOD = 1e9 + 7;
+    unordered_map<char, vector<char>> follows = {
+        {'a', {'e'}},
+        {'e', {'a', 'i'}},
+        {'i', {'a', 'e', 'o', 'u'}},
+        {'o', {'i', 'u'}},
+        {'u', {'a'}}
+    };
+
+public:
+    int countVowelPermutation(int n) {
+        
+        int res = 0;
+        for (char vowel : string("aeiou")) {
+            res = (res + dfs(1, vowel, n)) % MOD;
+        }
+        return res;
+    }
+
+private:
+    int dfs(int i, char v, int n) {
+        if (i == n) {
+            return 1;
+        }
+        
+        int total = 0;
+        for (char& next : follows[v]) {
+            total = (total + dfs(i + 1, next, n)) % MOD;
+        }
+        return total;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    countVowelPermutation(n) {
+        const MOD = 1e9 + 7;
+
+        const follows = {
+            a: ['e'],
+            e: ['a', 'i'],
+            i: ['a', 'e', 'o', 'u'],
+            o: ['i', 'u'],
+            u: ['a']
+        };
+
+        const dfs = (i, v) => {
+            if (i === n) {
+                return 1;
+            }
+            
+            let total = 0;
+            for (const next of follows[v]) {
+                total = (total + dfs(i + 1, next)) % MOD;
+            }
+            return total;
+        };
+
+        let res = 0;
+        for (const vowel of ['a', 'e', 'i', 'o', 'u']) {
+            res = (res + dfs(1, vowel)) % MOD;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(4 ^ n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def countVowelPermutation(self, n: int) -> int:
+        MOD = 10**9 + 7
+        cache = {}
+        follows = {
+            'a': ['e'],
+            'e': ['a', 'i'],
+            'i': ['a', 'e', 'o', 'u'],
+            'o': ['i', 'u'],
+            'u': ['a']
+        }
+
+        def dfs(i, v):
+            if i == n:
+                return 1
+            if (i, v) in cache:
+                return cache[(i, v)]
+            
+            total = 0
+            for nxt in follows[v]:
+                total = (total + dfs(i + 1, nxt)) % MOD
+            cache[(i, v)] = total
+            return total
+
+        res = 0
+        for vowel in ['a', 'e', 'i', 'o', 'u']:
+            res = (res + dfs(1, vowel)) % MOD
+        
+        return res
+```
+
+```java
+public class Solution {
+    private final int MOD = 1_000_000_007;
+    private final Map<Integer, List<Integer>> follows = Map.of(
+        0, List.of(1),           // 'a' -> 'e'
+        1, List.of(0, 2),        // 'e' -> 'a', 'i'
+        2, List.of(0, 1, 3, 4),  // 'i' -> 'a', 'e', 'o', 'u'
+        3, List.of(2, 4),        // 'o' -> 'i', 'u'
+        4, List.of(0)            // 'u' -> 'a'
+    );
+    private int[][] dp;
+
+    public int countVowelPermutation(int n) {
+        dp = new int[n][5];
+        for (int i = 0; i < n; i++) {
+            Arrays.fill(dp[i], -1);
+        }
+
+        int res = 0;
+        for (int vowel = 0; vowel < 5; vowel++) {
+            res = (res + dfs(1, vowel, n)) % MOD;
+        }
+        return res;
+    }
+
+    private int dfs(int i, int v, int n) {
+        if (i == n) {
+            return 1;
+        }
+        if (dp[i][v] != -1) return dp[i][v];
+        
+        int total = 0;
+        for (int next : follows.get(v)) {
+            total = (total + dfs(i + 1, next, n)) % MOD;
+        }
+        return dp[i][v] = total;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    static const int MOD = 1e9 + 7;
+    vector<vector<int>> dp;
+    vector<vector<int>> follows = {
+        {1},          // 'a' -> 'e'
+        {0, 2},       // 'e' -> 'a', 'i'
+        {0, 1, 3, 4}, // 'i' -> 'a', 'e', 'o', 'u'
+        {2, 4},       // 'o' -> 'i', 'u'
+        {0}           // 'u' -> 'a'
+    };
+
+    int dfs(int i, int v, int n) {
+        if (i == n) return 1;
+        if (dp[i][v] != -1) return dp[i][v];
+
+        int total = 0;
+        for (int next : follows[v]) {
+            total = (total + dfs(i + 1, next, n)) % MOD;
+        }
+        return dp[i][v] = total;
+    }
+
+public:
+    int countVowelPermutation(int n) {
+        dp.assign(n, vector<int>(5, -1));
+
+        int res = 0;
+        for (int vowel = 0; vowel < 5; vowel++) {
+            res = (res + dfs(1, vowel, n)) % MOD;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    countVowelPermutation(n) {
+        const MOD = 1e9 + 7;
+        const dp = Array.from({ length: n }, () => Array(5).fill(-1));
+
+        const follows = {
+            0: [1],              // 'a' -> 'e'
+            1: [0, 2],           // 'e' -> 'a', 'i'
+            2: [0, 1, 3, 4],     // 'i' -> 'a', 'e', 'o', 'u'
+            3: [2, 4],           // 'o' -> 'i', 'u'
+            4: [0],              // 'u' -> 'a'
+        };
+
+        const dfs = (i, v) => {
+            if (i === n) return 1;
+            if (dp[i][v] !== -1) return dp[i][v];
+
+            let total = 0;
+            for (const next of follows[v]) {
+                total = (total + dfs(i + 1, next)) % MOD;
+            }
+            dp[i][v] = total;
+            return total;
+        };
+
+        let res = 0;
+        for (let vowel = 0; vowel < 5; vowel++) {
+            res = (res + dfs(1, vowel)) % MOD;
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def countVowelPermutation(self, n: int) -> int:
+        MOD = 10**9 + 7
+        a, e, i, o, u = 0, 1, 2, 3, 4
+        dp = [[0] * 5 for _ in range(n + 1)]
+        dp[1] = [1, 1, 1, 1, 1]
+
+        for j in range(2, n + 1):
+            dp[j][a] = (dp[j - 1][e] + dp[j - 1][i] + dp[j - 1][u]) % MOD
+            dp[j][e] = (dp[j - 1][a] + dp[j - 1][i]) % MOD
+            dp[j][i] = (dp[j - 1][e] + dp[j - 1][o]) % MOD
+            dp[j][o] = dp[j - 1][i] % MOD
+            dp[j][u] = (dp[j - 1][i] + dp[j - 1][o]) % MOD
+
+        return sum(dp[n]) % MOD
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1_000_000_007;
+
+    public int countVowelPermutation(int n) {
+        int[][] dp = new int[n + 1][5];
+        int[][] follows = {
+            {1},          // 'a' -> 'e'
+            {0, 2},       // 'e' -> 'a', 'i'
+            {0, 1, 3, 4}, // 'i' -> 'a', 'e', 'o', 'u'
+            {2, 4},       // 'o' -> 'i', 'u'
+            {0}           // 'u' -> 'a'
+        };
+
+        for (int v = 0; v < 5; v++) {
+            dp[1][v] = 1;
+        }
+
+        for (int i = 2; i <= n; i++) {
+            for (int v = 0; v < 5; v++) {
+                for (int nextV : follows[v]) {
+                    dp[i][v] = (dp[i][v] + dp[i - 1][nextV]) % MOD;
+                }
+            }
+        }
+
+        int result = 0;
+        for (int v = 0; v < 5; v++) {
+            result = (result + dp[n][v]) % MOD;
+        }
+        return result;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    static const int MOD = 1e9 + 7;
+
+public:
+    int countVowelPermutation(int n) {
+        vector<vector<int>> dp(n + 1, vector<int>(5, 0));
+        vector<vector<int>> follows = {
+            {1},          // 'a' -> 'e'
+            {0, 2},       // 'e' -> 'a', 'i'
+            {0, 1, 3, 4}, // 'i' -> 'a', 'e', 'o', 'u'
+            {2, 4},       // 'o' -> 'i', 'u'
+            {0}           // 'u' -> 'a'
+        };
+
+        for (int v = 0; v < 5; v++) {
+            dp[1][v] = 1;
+        }
+
+        for (int i = 2; i <= n; i++) {
+            for (int v = 0; v < 5; v++) {
+                for (int nextV : follows[v]) {
+                    dp[i][v] = (dp[i][v] + dp[i - 1][nextV]) % MOD;
+                }
+            }
+        }
+
+        int result = 0;
+        for (int v = 0; v < 5; v++) {
+            result = (result + dp[n][v]) % MOD;
+        }
+        return result;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    countVowelPermutation(n) {
+        const MOD = 1e9 + 7;
+        const dp = Array.from({ length: n + 1 }, () => Array(5).fill(0));
+        const follows = [
+            [1],          // 'a' -> 'e'
+            [0, 2],       // 'e' -> 'a', 'i'
+            [0, 1, 3, 4], // 'i' -> 'a', 'e', 'o', 'u'
+            [2, 4],       // 'o' -> 'i', 'u'
+            [0]           // 'u' -> 'a'
+        ];
+
+        for (let v = 0; v < 5; v++) {
+            dp[1][v] = 1;
+        }
+
+        for (let i = 2; i <= n; i++) {
+            for (let v = 0; v < 5; v++) {
+                for (const nextV of follows[v]) {
+                    dp[i][v] = (dp[i][v] + dp[i - 1][nextV]) % MOD;
+                }
+            }
+        }
+
+        return dp[n].reduce((sum, val) => (sum + val) % MOD, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def countVowelPermutation(self, n: int) -> int:
+        MOD = 10**9 + 7
+        follows = [
+            [1],           # 'a' -> 'e'
+            [0, 2],        # 'e' -> 'a', 'i'
+            [0, 1, 3, 4],  # 'i' -> 'a', 'e', 'o', 'u'
+            [2, 4],        # 'o' -> 'i', 'u'
+            [0]            # 'u' -> 'a'
+        ]
+        dp = [1] * 5
+
+        for _ in range(2, n + 1):
+            next_dp = [0] * 5
+            for v in range(5):
+                for nextV in follows[v]:
+                    next_dp[v] = (next_dp[v] + dp[nextV]) % MOD
+            dp = next_dp
+
+        return sum(dp) % MOD
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1_000_000_007;
+
+    public int countVowelPermutation(int n) {
+        int[][] follows = {
+            {1},          // 'a' -> 'e'
+            {0, 2},       // 'e' -> 'a', 'i'
+            {0, 1, 3, 4}, // 'i' -> 'a', 'e', 'o', 'u'
+            {2, 4},       // 'o' -> 'i', 'u'
+            {0}           // 'u' -> 'a'
+        };
+
+        int[] dp = {1, 1, 1, 1, 1};
+
+        for (int i = 2; i <= n; i++) {
+            int[] nextDp = new int[5];
+            for (int v = 0; v < 5; v++) {
+                for (int nextV : follows[v]) {
+                    nextDp[v] = (nextDp[v] + dp[nextV]) % MOD;
+                }
+            }
+            dp = nextDp;
+        }
+
+        int result = 0;
+        for (int count : dp) {
+            result = (result + count) % MOD;
+        }
+        return result;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    static const int MOD = 1e9 + 7;
+
+public:
+    int countVowelPermutation(int n) {
+        vector<vector<int>> follows = {
+            {1},          // 'a' -> 'e'
+            {0, 2},       // 'e' -> 'a', 'i'
+            {0, 1, 3, 4}, // 'i' -> 'a', 'e', 'o', 'u'
+            {2, 4},       // 'o' -> 'i', 'u'
+            {0}           // 'u' -> 'a'
+        };
+
+        vector<int> dp(5, 1);
+
+        for (int i = 2; i <= n; i++) {
+            vector<int> nextDp(5, 0);
+            for (int v = 0; v < 5; v++) {
+                for (int nextV : follows[v]) {
+                    nextDp[v] = (nextDp[v] + dp[nextV]) % MOD;
+                }
+            }
+            dp = nextDp;
+        }
+
+        int result = 0;
+        for (int count : dp) {
+            result = (result + count) % MOD;
+        }
+        return result;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    countVowelPermutation(n) {
+        const MOD = 1e9 + 7;
+        const follows = [
+            [1],          // 'a' -> 'e'
+            [0, 2],       // 'e' -> 'a', 'i'
+            [0, 1, 3, 4], // 'i' -> 'a', 'e', 'o', 'u'
+            [2, 4],       // 'o' -> 'i', 'u'
+            [0]           // 'u' -> 'a'
+        ];
+
+        let dp = [1, 1, 1, 1, 1];
+
+        for (let i = 2; i <= n; i++) {
+            const nextDp = [0, 0, 0, 0, 0];
+            for (let v = 0; v < 5; v++) {
+                for (const nextV of follows[v]) {
+                    nextDp[v] = (nextDp[v] + dp[nextV]) % MOD;
+                }
+            }
+            dp = nextDp;
+        }
+
+        return dp.reduce((sum, count) => (sum + count) % MOD, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ since we used array of size $5$.
+
+---
+
+## 5. Matrix Exponentiation
+
+::tabs-start
+
+```python
+class Solution:
+    MOD = 10**9 + 7
+
+    class M:
+        def __init__(self, n):
+            self.a = [[0] * n for _ in range(n)]
+
+        def __mul__(self, other):
+            n = len(self.a)
+            product = Solution.M(n)
+            for i in range(n):
+                for j in range(n):
+                    for k in range(n):
+                        product.a[i][k] = (product.a[i][k] + self.a[i][j] * other.a[j][k]) % Solution.MOD
+            return product
+
+    def matrixExpo(self, base, exp):
+        n = len(base.a)
+        result = Solution.M(n)
+        for i in range(n):
+            result.a[i][i] = 1
+        while exp > 0:
+            if exp % 2 == 1:
+                result = result * base
+            base = base * base
+            exp //= 2
+        return result
+
+    def countVowelPermutation(self, n: int) -> int:
+        follows = [
+            [0, 1, 0, 0, 0],  # 'a' -> 'e'
+            [1, 0, 1, 0, 0],  # 'e' -> 'a', 'i'
+            [1, 1, 0, 1, 1],  # 'i' -> 'a', 'e', 'o', 'u'
+            [0, 0, 1, 0, 1],  # 'o' -> 'i', 'u'
+            [1, 0, 0, 0, 0]   # 'u' -> 'a'
+        ]
+
+        base = Solution.M(5)
+        base.a = follows
+
+        result = self.matrixExpo(base, n - 1)
+
+        return sum(sum(row) for row in result.a) % self.MOD
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1_000_000_007;
+
+    static class M {
+        int[][] a;
+
+        M(int n) {
+            a = new int[n][n];
+        }
+
+        M multiply(M other) {
+            int n = a.length;
+            M product = new M(n);
+
+            for (int i = 0; i < n; i++) {
+                for (int j = 0; j < n; j++) {
+                    for (int k = 0; k < n; k++) {
+                        product.a[i][k] = (int) ((product.a[i][k] + 1L * a[i][j] * other.a[j][k]) % MOD);
+                    }
+                }
+            }
+            return product;
+        }
+    }
+
+    private M matrixExpo(M base, int exp) {
+        int n = base.a.length;
+        M result = new M(n);
+        for (int i = 0; i < n; i++) {
+            result.a[i][i] = 1;
+        }
+        while (exp > 0) {
+            if (exp % 2 == 1) {
+                result = result.multiply(base);
+            }
+            base = base.multiply(base);
+            exp /= 2;
+        }
+        return result;
+    }
+
+    public int countVowelPermutation(int n) {
+        int[][] follows = {
+            {0, 1, 0, 0, 0},  // 'a' -> 'e'
+            {1, 0, 1, 0, 0},  // 'e' -> 'a', 'i'
+            {1, 1, 0, 1, 1},  // 'i' -> 'a', 'e', 'o', 'u'
+            {0, 0, 1, 0, 1},  // 'o' -> 'i', 'u'
+            {1, 0, 0, 0, 0}   // 'u' -> 'a'
+        };
+
+        M base = new M(5);
+        base.a = follows;
+
+        M result = matrixExpo(base, n - 1);
+
+        int ans = 0;
+        for (int i = 0; i < 5; i++) {
+            for (int j = 0; j < 5; j++) {
+                ans = (ans + result.a[i][j]) % MOD;
+            }
+        }
+        return ans;
+    }
+}
+```
+
+```cpp
+class Solution {
+    static const int MOD = 1e9 + 7;
+
+    struct M {
+        vector<vector<int>> a;
+
+        M(int n) {
+            a.resize(n, vector<int>(n, 0));
+        }
+
+        M operator*(const M& other) const {
+            int n = a.size();
+            M product(n);
+
+            for (int i = 0; i < n; i++) {
+                for (int j = 0; j < n; j++) {
+                    for (int k = 0; k < n; k++) {
+                        product.a[i][k] = (product.a[i][k] + a[i][j] * 1LL * other.a[j][k]) % MOD;
+                    }
+                }
+            }
+            return product;
+        }
+    };
+
+    M matrixExpo(M base, int exp) {
+        int n = base.a.size();
+        M result(n);
+
+        for (int i = 0; i < n; i++) {
+            result.a[i][i] = 1;
+        }
+
+        while (exp > 0) {
+            if (exp % 2 == 1) {
+                result = result * base;
+            }
+            base = base * base;
+            exp /= 2;
+        }
+
+        return result;
+    }
+
+public:
+    int countVowelPermutation(int n) {
+        vector<vector<int>> follows = {
+            {0, 1, 0, 0, 0},  // 'a' -> 'e'
+            {1, 0, 1, 0, 0},  // 'e' -> 'a', 'i'
+            {1, 1, 0, 1, 1},  // 'i' -> 'a', 'e', 'o', 'u'
+            {0, 0, 1, 0, 1},  // 'o' -> 'i', 'u'
+            {1, 0, 0, 0, 0}   // 'u' -> 'a'
+        };
+
+        M base(5);
+        base.a = follows;
+
+        M result = matrixExpo(base, n - 1);
+
+        int ans = 0;
+        for (int i = 0; i < 5; i++) {
+            for (int j = 0; j < 5; j++) {
+                ans = (ans + result.a[i][j]) % MOD;
+            }
+        }
+
+        return ans;
+    }
+};
+```
+
+```javascript
+class M {
+    /**
+     * @constructor
+     * @param {number} n
+     */
+    constructor(n) {
+        this.MOD = 1e9 + 7;
+        this.a = Array.from({ length: n }, () => Array(n).fill(0));
+    }
+
+    /**
+     * @param {M}
+     * @return {M}
+     */
+    multiply(other) {
+        const n = this.a.length;
+        const product = new M(n);
+        for (let i = 0; i < n; i++) {
+            for (let j = 0; j < n; j++) {
+                let sum = 0n;
+                for (let k = 0; k < n; k++) {
+                    sum += BigInt(this.a[i][k]) * BigInt(other.a[k][j]);
+                }
+                product.a[i][j] = Number(sum % BigInt(this.MOD));
+            }
+        }
+        return product;
+    }
+}
+
+class Solution {
+    
+    /**
+     * @param {M}
+     * @param {number} exp
+     * @return {M}
+     */
+    matrixExpo(base, exp) {
+        const n = base.a.length;
+        let result = new M(n);
+        for (let i = 0; i < n; i++) {
+            result.a[i][i] = 1;
+        }
+        while (exp > 0) {
+            if (exp & 1) {
+                result = result.multiply(base);
+            }
+            base = base.multiply(base);
+            exp >>= 1;
+        }
+        return result;
+    }
+
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    countVowelPermutation(n) {
+        const MOD = 1e9 + 7;
+        const follows = [
+            [0, 1, 0, 0, 0],  // 'a' -> 'e'
+            [1, 0, 1, 0, 0],  // 'e' -> 'a', 'i'
+            [1, 1, 0, 1, 1],  // 'i' -> 'a', 'e', 'o', 'u'
+            [0, 0, 1, 0, 1],  // 'o' -> 'i', 'u'
+            [1, 0, 0, 0, 0]   // 'u' -> 'a'
+        ];
+        const base = new M(5);
+        base.a = follows;
+        const result = this.matrixExpo(base, n - 1);
+        let ans = 0;
+        for (let i = 0; i < 5; i++) {
+            for (let j = 0; j < 5; j++) {
+                ans = (ans + result.a[i][j]) % MOD;
+            }
+        }
+        return ans;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m ^ 3 \log n)$
+* Space complexity: $O(m ^ 2)$
+
+> Where $m$ is the size of the matrix used in matrix exponentiation $(5 X 5)$ and $n$ is the length of the permutation.
\ No newline at end of file
diff --git a/articles/count-ways-to-build-good-strings.md b/articles/count-ways-to-build-good-strings.md
new file mode 100644
index 000000000..a18b90526
--- /dev/null
+++ b/articles/count-ways-to-build-good-strings.md
@@ -0,0 +1,283 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def countGoodStrings(self, low: int, high: int, zero: int, one: int) -> int:
+        mod = 10**9 + 7
+
+        def dfs(length):
+            if length > high:
+                return 0
+            res = 1 if length >= low else 0
+            res += dfs(length + zero) + dfs(length + one)
+            return res % mod
+
+        return dfs(0)
+```
+
+```java
+public class Solution {
+    final int mod = 1_000_000_007;
+
+    public int countGoodStrings(int low, int high, int zero, int one) {
+        return dfs(low, high, zero, one, 0);
+    }
+
+    private int dfs(int low, int high, int zero, int one, int length) {
+        if (length > high) return 0;
+        int res = (length >= low) ? 1 : 0;
+        res = (res + dfs(low, high, zero, one, length + zero)) % mod;
+        res = (res + dfs(low, high, zero, one, length + one)) % mod;
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countGoodStrings(int low, int high, int zero, int one) {
+        const int mod = 1e9 + 7;
+
+        function<int(int)> dfs = [&](int length) {
+            if (length > high) return 0;
+            int res = (length >= low) ? 1 : 0;
+            res = (res + dfs(length + zero)) % mod;
+            res = (res + dfs(length + one)) % mod;
+            return res;
+        };
+
+        return dfs(0);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} low
+     * @param {number} high
+     * @param {number} zero
+     * @param {number} one
+     * @return {number}
+     */
+    countGoodStrings(low, high, zero, one) {
+        const mod = 1e9 + 7;
+
+        const dfs = length => {
+            if (length > high) return 0;
+            let res = length >= low ? 1 : 0;
+            res = (res + dfs(length + zero)) % mod;
+            res = (res + dfs(length + one)) % mod;
+            return res;
+        };
+
+        return dfs(0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+> Where $n$ is equal to the given $high$ value.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def countGoodStrings(self, low: int, high: int, zero: int, one: int) -> int:
+        mod = 10**9 + 7
+        dp = {}
+
+        def dfs(length):
+            if length > high:
+                return 0
+            if length in dp:
+                return dp[length]
+
+            dp[length] = 1 if length >= low else 0
+            dp[length] += dfs(length + zero) + dfs(length + one)
+            return dp[length] % mod
+
+        return dfs(0)
+```
+
+```java
+public class Solution {
+    final int mod = 1_000_000_007;
+    private int[] dp;
+
+    public int countGoodStrings(int low, int high, int zero, int one) {
+        dp = new int[high + 1];
+        Arrays.fill(dp, -1);
+        return dfs(low, high, zero, one, 0);
+    }
+
+    private int dfs(int low, int high, int zero, int one, int length) {
+        if (length > high) return 0;
+        if (dp[length] != -1) return dp[length];
+
+        dp[length] = (length >= low) ? 1 : 0;
+        dp[length] = (dp[length] + dfs(low, high, zero, one, length + zero)) % mod;
+        dp[length] = (dp[length] + dfs(low, high, zero, one, length + one)) % mod;
+        return dp[length];
+    }
+}
+```
+
+```cpp
+class Solution {
+    const int mod = 1e9 + 7;
+    vector<int> dp;
+
+public:
+    int countGoodStrings(int low, int high, int zero, int one) {
+        dp.assign(high + 1, -1);
+        return dfs(low, high, zero, one, 0);
+    }
+
+private:
+    int dfs(int low, int high, int zero, int one, int length) {
+        if (length > high) return 0;
+        if (dp[length] != -1) return dp[length];
+        dp[length] = (length >= low) ? 1 : 0;
+        dp[length] = (dp[length] + dfs(low, high, zero, one, length + zero)) % mod;
+        dp[length] = (dp[length] + dfs(low, high, zero, one, length + one)) % mod;
+        return dp[length];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} low
+     * @param {number} high
+     * @param {number} zero
+     * @param {number} one
+     * @return {number}
+     */
+    countGoodStrings(low, high, zero, one) {
+        const mod = 1e9 + 7;
+        const dp = new Array(high + 1).fill(-1);
+
+        const dfs = length => {
+            if (length > high) return 0;
+            if (dp[length] !== -1) return dp[length];
+            dp[length] = length >= low ? 1 : 0;
+            dp[length] = (dp[length] + dfs(length + zero)) % mod;
+            dp[length] = (dp[length] + dfs(length + one)) % mod;
+            return dp[length];
+        };
+
+        return dfs(0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+> Where $n$ is equal to the given $high$ value.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def countGoodStrings(self, low: int, high: int, zero: int, one: int) -> int:
+        dp = { 0 : 1 }
+        mod = 10**9 + 7
+
+        for i in range(1, high + 1):
+            dp[i] = (dp.get(i - one, 0) + dp.get(i - zero, 0)) % mod
+        
+        return sum(dp[i] for i in range(low, high + 1)) % mod
+```
+
+```java
+public class Solution {
+    public int countGoodStrings(int low, int high, int zero, int one) {
+        int[] dp = new int[high + 1];
+        int mod = 1_000_000_007, res = 0;
+        dp[0] = 1;
+
+        for (int i = 1; i <= high; i++) {
+            if (i >= zero) dp[i] = (dp[i] + dp[i - zero]) % mod;
+            if (i >= one) dp[i] = (dp[i] + dp[i - one]) % mod;
+            if (i >= low) res = (res + dp[i]) % mod;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countGoodStrings(int low, int high, int zero, int one) {
+        vector<int> dp(high + 1);
+        int mod = 1e9 + 7, res = 0;
+        dp[0] = 1;
+
+        for (int i = 1; i <= high; i++) {
+            if (i >= zero) dp[i] = (dp[i] + dp[i - zero]) % mod;
+            if (i >= one) dp[i] = (dp[i] + dp[i - one]) % mod;
+            if (i >= low) res = (res + dp[i]) % mod;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} low
+     * @param {number} high
+     * @param {number} zero
+     * @param {number} one
+     * @return {number}
+     */
+    countGoodStrings(low, high, zero, one) {
+        const mod = 1e9 + 7;
+        const dp = new Int32Array(high + 1);
+        let res = 0;
+        dp[0] = 1;
+
+        for (let i = 1; i <= high; i++) {
+            if (i >= zero) dp[i] = (dp[i] + dp[i - zero]) % mod;
+            if (i >= one) dp[i] = (dp[i] + dp[i - one]) % mod;
+            if (i >= low) res = (res + dp[i]) % mod;
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+> Where $n$ is equal to the given $high$ value.
\ No newline at end of file
diff --git a/articles/counting-bits.md b/articles/counting-bits.md
new file mode 100644
index 000000000..66b5db885
--- /dev/null
+++ b/articles/counting-bits.md
@@ -0,0 +1,655 @@
+## 1. Bit Manipulation - I
+
+::tabs-start
+
+```python
+class Solution:
+    def countBits(self, n: int) -> List[int]:
+        res = []
+        for num in range(n + 1):
+            one = 0
+            for i in range(32):
+                if num & (1 << i):
+                    one += 1
+            res.append(one)
+        return res
+```
+
+```java
+public class Solution {
+    public int[] countBits(int n) {
+        int[] res = new int[n + 1];
+        for (int num = 1; num <= n; num++) {
+            for (int i = 0; i < 32; i++) {
+                if ((num & (1 << i)) != 0) {
+                    res[num]++;
+                }
+            }
+        }       
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> countBits(int n) {
+        vector<int> res(n + 1);
+        for (int num = 1; num <= n; num++) {
+            for (int i = 0; i < 32; i++) {
+                if (num & (1 << i)) {
+                    res[num]++;
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number[]}
+     */
+    countBits(n) {
+        let res = [];
+        for (let num = 0; num <= n; num++) {
+            let one = 0;
+            for (let i = 0; i < 32; i++) {
+                if ((num & (1 << i)) != 0) {
+                    one++;
+                }
+            }
+            res.push(one);
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[] CountBits(int n) {
+        int[] res = new int[n + 1];
+        for (int num = 1; num <= n; num++) {
+            for (int i = 0; i < 32; i++) {
+                if ((num & (1 << i)) != 0) {
+                    res[num]++;
+                }
+            }
+        }       
+        return res;
+    }
+}
+```
+
+```go
+func countBits(n int) []int {
+    res := make([]int, n+1)
+    for num := 0; num <= n; num++ {
+        one := 0
+        for i := 0; i < 32; i++ {
+            if num&(1<<i) != 0 {
+                one++
+            }
+        }
+        res[num] = one
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun countBits(n: Int): IntArray {
+        val res = IntArray(n + 1)
+        for (num in 0..n) {
+            var one = 0
+            for (i in 0 until 32) {
+                if (num and (1 shl i) != 0) {
+                    one++
+                }
+            }
+            res[num] = one
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func countBits(_ n: Int) -> [Int] {
+        var res = [Int]()
+        for num in 0...n {
+            var one = 0
+            for i in 0..<32 {
+                if num & (1 << i) != 0 {
+                    one += 1
+                }
+            }
+            res.append(one)
+        }
+        return res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ space for the output array.
+
+---
+
+## 2. Bit Manipulation - II
+
+::tabs-start
+
+```python
+class Solution:
+    def countBits(self, n: int) -> List[int]:
+        res = [0] * (n + 1)
+        for i in range(1, n + 1):
+            num = i
+            while num != 0:
+                res[i] += 1
+                num &= (num - 1)
+        return res
+```
+
+```java
+public class Solution {
+    public int[] countBits(int n) {
+        int[] res = new int[n + 1];
+        for (int i = 1; i <= n; i++) {
+            int num = i;
+            while (num != 0) {
+                res[i]++;
+                num &= (num - 1);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> countBits(int n) {
+        vector<int> res(n + 1, 0);
+        for (int i = 1; i <= n; i++) {
+            int num = i;
+            while (num != 0) {
+                res[i]++;
+                num &= (num - 1);
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number[]}
+     */
+    countBits(n) {
+        let res = new Array(n + 1).fill(0);
+        for (let i = 1; i <= n; i++) {
+            let num = i;
+            while (num !== 0) {
+                res[i]++;
+                num &= (num - 1);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[] CountBits(int n) {
+        int[] res = new int[n + 1];
+        for (int i = 1; i <= n; i++) {
+            int num = i;
+            while (num != 0) {
+                res[i]++;
+                num &= (num - 1);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```go
+func countBits(n int) []int {
+    res := make([]int, n+1)
+    for i := 1; i <= n; i++ {
+        num := i
+        for num != 0 {
+            res[i]++
+            num &= (num - 1)
+        }
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun countBits(n: Int): IntArray {
+        val res = IntArray(n + 1)
+        for (i in 1..n) {
+            var num = i
+            while (num != 0) {
+                res[i]++
+                num = num and (num - 1)
+            }
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func countBits(_ n: Int) -> [Int] {
+        var res = [Int](repeating: 0, count: n + 1)
+        for i in 1..<(n + 1) {
+            var num = i
+            while num != 0 {
+                res[i] += 1
+                num &= (num - 1)
+            }
+        }
+        return res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ space for the output array.
+
+---
+
+## 3. In-Built Function
+
+::tabs-start
+
+```python
+class Solution:
+    def countBits(self, n: int) -> List[int]:
+        return [bin(i).count('1') for i in range(n + 1)]
+```
+
+```java
+public class Solution {
+    public int[] countBits(int n) {
+        int[] res = new int[n + 1];
+        for (int i = 0; i <= n; i++) {
+            res[i] = Integer.bitCount(i);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> countBits(int n) {
+        vector<int> res(n + 1, 0);
+        for (int i = 0; i <= n; i++) {
+            res[i] = __builtin_popcount(i);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number[]}
+     */
+    countBits(n) {
+        let res = [];
+        for (let i = 0; i <= n; i++) {
+            res.push(i.toString(2).split('1').length - 1);
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[] CountBits(int n) {
+        int[] res = new int[n + 1];
+        for (int i = 0; i <= n; i++) {
+            res[i] = Convert.ToString(i, 2).Count(c => c == '1');
+        }
+        return res;
+    }
+}
+```
+
+```go
+func countBits(n int) []int {
+    res := make([]int, n+1)
+    for i := 0; i <= n; i++ {
+        res[i] = bits.OnesCount(uint(i))
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun countBits(n: Int): IntArray {
+        return IntArray(n + 1) { it.countOneBits() }
+    }
+}
+```
+
+```swift
+class Solution {
+    func countBits(_ n: Int) -> [Int] {
+        var res = [Int](repeating: 0, count: n + 1)
+        for num in 1..<(n + 1) {
+            res[num] = num.nonzeroBitCount
+        }
+        return res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ space for the output array.
+
+---
+
+## 4. Bit Manipulation (DP)
+
+::tabs-start
+
+```python
+class Solution:
+    def countBits(self, n: int) -> List[int]:
+        dp = [0] * (n + 1)
+        offset = 1
+
+        for i in range(1, n + 1):
+            if offset * 2 == i:
+                offset = i
+            dp[i] = 1 + dp[i - offset]
+        return dp
+```
+
+```java
+public class Solution {
+    public int[] countBits(int n) {
+        int[] dp = new int[n + 1];
+        int offset = 1;
+
+        for (int i = 1; i <= n; i++) {
+            if (offset * 2 == i) {
+                offset = i;
+            }
+            dp[i] = 1 + dp[i - offset];
+        }
+        return dp;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> countBits(int n) {
+        vector<int> dp(n + 1);
+        int offset = 1;
+
+        for (int i = 1; i <= n; i++) {
+            if (offset * 2 == i) {
+                offset = i;
+            }
+            dp[i] = 1 + dp[i - offset];
+        }
+        return dp;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number[]}
+     */
+    countBits(n) {
+        const dp = new Array(n + 1).fill(0);
+        let offset = 1;
+
+        for (let i = 1; i <= n; i++) {
+            if (offset * 2 == i) {
+                offset = i;
+            }
+            dp[i] = 1 + dp[i - offset];
+        }
+        return dp;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[] CountBits(int n) {
+        int[] dp = new int[n + 1];
+        int offset = 1;
+
+        for (int i = 1; i <= n; i++) {
+            if (offset * 2 == i) {
+                offset = i;
+            }
+            dp[i] = 1 + dp[i - offset];
+        }
+        return dp;
+    }
+}
+```
+
+```go
+func countBits(n int) []int {
+    dp := make([]int, n+1)
+    offset := 1
+
+    for i := 1; i <= n; i++ {
+        if offset*2 == i {
+            offset = i
+        }
+        dp[i] = 1 + dp[i - offset]
+    }
+    return dp
+}
+```
+
+```kotlin
+class Solution {
+    fun countBits(n: Int): IntArray {
+        val dp = IntArray(n + 1)
+        var offset = 1
+
+        for (i in 1..n) {
+            if (offset * 2 == i) {
+                offset = i
+            }
+            dp[i] = 1 + dp[i - offset]
+        }
+        return dp
+    }
+}
+```
+
+```swift
+class Solution {
+    func countBits(_ n: Int) -> [Int] {
+        var dp = [Int](repeating: 0, count: n + 1)
+        var offset = 1
+
+        for i in 1..<(n + 1) {
+            if offset * 2 == i {
+                offset = i
+            }
+            dp[i] = 1 + dp[i - offset]
+        }
+        return dp
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ space for the output array.
+
+---
+
+## 5. Bit Manipulation (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def countBits(self, n: int) -> List[int]:
+        dp = [0] * (n + 1)
+        for i in range(n + 1):
+            dp[i] = dp[i >> 1] + (i & 1)
+        return dp
+```
+
+```java
+public class Solution {
+    public int[] countBits(int n) {
+        int[] dp = new int[n + 1];
+        for (int i = 1; i <= n; i++) {
+            dp[i] = dp[i >> 1] + (i & 1);
+        }
+        return dp;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> countBits(int n) {
+        vector<int> dp(n + 1);
+        for (int i = 1; i <= n; i++) {
+            dp[i] = dp[i >> 1] + (i & 1);
+        }
+        return dp;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number[]}
+     */
+    countBits(n) {
+        let dp = new Array(n + 1).fill(0);
+        for (let i = 1; i <= n; i++) {
+            dp[i] = dp[i >> 1] + (i & 1);
+        }
+        return dp;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[] CountBits(int n) {
+        int[] dp = new int[n + 1];
+        for (int i = 1; i <= n; i++) {
+            dp[i] = dp[i >> 1] + (i & 1);
+        }
+        return dp;
+    }
+}
+```
+
+```go
+func countBits(n int) []int {
+    dp := make([]int, n+1)
+    for i := 1; i <= n; i++ {
+        dp[i] = dp[i >> 1] + (i&1);
+    }
+    return dp
+}
+```
+
+```kotlin
+class Solution {
+    fun countBits(n: Int): IntArray {
+        val dp = IntArray(n + 1)
+        for (i in 1..n) {
+            dp[i] = dp[i shr 1] + (i and 1)
+        }
+        return dp
+    }
+}
+```
+
+```swift
+class Solution {
+    func countBits(_ n: Int) -> [Int] {
+        var dp = [Int](repeating: 0, count: n + 1)
+        for i in 0..<(n + 1) {
+            dp[i] = dp[i >> 1] + (i & 1)
+        }
+        return dp
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ space for the output array.
\ No newline at end of file
diff --git a/articles/course-schedule-ii.md b/articles/course-schedule-ii.md
index ff76fb2c2..6a3e85924 100644
--- a/articles/course-schedule-ii.md
+++ b/articles/course-schedule-ii.md
@@ -71,8 +71,7 @@ public class Solution {
         }
 
         cycle.add(course);
-        for (int pre : prereq.getOrDefault(course, 
-                                           Collections.emptyList())) {
+        for (int pre : prereq.getOrDefault(course, Collections.emptyList())) {
             if (!dfs(pre, prereq, visit, cycle, output)) {
                 return false;
             }
@@ -245,6 +244,136 @@ public class Solution {
 }
 ```
 
+```go
+func findOrder(numCourses int, prerequisites [][]int) []int {
+    prereq := make(map[int][]int)
+    for i := 0; i < numCourses; i++ {
+        prereq[i] = []int{}
+    }
+    for _, pair := range prerequisites {
+        crs, pre := pair[0], pair[1]
+        prereq[crs] = append(prereq[crs], pre)
+    }
+
+    output := []int{}
+    visit := make(map[int]bool)
+    cycle := make(map[int]bool)
+
+    var dfs func(int) bool
+    dfs = func(crs int) bool {
+        if cycle[crs] {
+            return false
+        }
+        if visit[crs] {
+            return true
+        }
+
+        cycle[crs] = true
+        for _, pre := range prereq[crs] {
+            if !dfs(pre) {
+                return false
+            }
+        }
+        cycle[crs] = false
+        visit[crs] = true
+        output = append(output, crs)
+        return true
+    }
+
+    for i := 0; i < numCourses; i++ {
+        if !dfs(i) {
+            return []int{}
+        }
+    }
+    
+    return output
+}
+```
+
+```kotlin
+class Solution {
+    fun findOrder(numCourses: Int, prerequisites: Array<IntArray>): IntArray {
+        val prereq = HashMap<Int, MutableList<Int>>()
+        for (i in 0 until numCourses) {
+            prereq[i] = mutableListOf()
+        }
+        for (pair in prerequisites) {
+            val (crs, pre) = pair
+            prereq[crs]?.add(pre)
+        }
+
+        val output = mutableListOf<Int>()
+        val visit = HashSet<Int>()
+        val cycle = HashSet<Int>()
+
+        fun dfs(crs: Int): Boolean {
+            if (crs in cycle) return false
+            if (crs in visit) return true
+
+            cycle.add(crs)
+            for (pre in prereq[crs]!!) {
+                if (!dfs(pre)) return false
+            }
+            cycle.remove(crs)
+            visit.add(crs)
+            output.add(crs)
+            return true
+        }
+
+        for (i in 0 until numCourses) {
+            if (!dfs(i)) return intArrayOf()
+        }
+
+        return output.toIntArray()
+    }
+}
+```
+
+```swift
+class Solution {
+    func findOrder(_ numCourses: Int, _ prerequisites: [[Int]]) -> [Int] {
+        var prereq = [Int: [Int]]()
+        for c in 0..<numCourses {
+            prereq[c] = []
+        }
+        for pair in prerequisites {
+            prereq[pair[0]]!.append(pair[1])
+        }
+
+        var output = [Int]()
+        var visit = Set<Int>()
+        var cycle = Set<Int>()
+
+        func dfs(_ crs: Int) -> Bool {
+            if cycle.contains(crs) {
+                return false
+            }
+            if visit.contains(crs) {
+                return true
+            }
+
+            cycle.insert(crs)
+            for pre in prereq[crs]! {
+                if !dfs(pre) {
+                    return false
+                }
+            }
+            cycle.remove(crs)
+            visit.insert(crs)
+            output.append(crs)
+            return true
+        }
+
+        for c in 0..<numCourses {
+            if !dfs(c) {
+                return []
+            }
+        }
+        return output
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -458,6 +587,127 @@ public class Solution {
 }
 ```
 
+```go
+func findOrder(numCourses int, prerequisites [][]int) []int {
+    indegree := make([]int, numCourses)
+    adj := make([][]int, numCourses)
+    for _, pair := range prerequisites {
+        src, dst := pair[0], pair[1]
+        indegree[dst]++
+        adj[src] = append(adj[src], dst)
+    }
+
+    q := []int{}
+    for i := 0; i < numCourses; i++ {
+        if indegree[i] == 0 {
+            q = append(q, i)
+        }
+    }
+
+    output := []int{}
+    finish := 0
+    for len(q) > 0 {
+        node := q[0]
+        q = q[1:]
+        output = append(output, node)
+        finish++
+        for _, nei := range adj[node] {
+            indegree[nei]--
+            if indegree[nei] == 0 {
+                q = append(q, nei)
+            }
+        }
+    }
+
+    if finish != numCourses {
+        return []int{}
+    }
+
+    for i, j := 0, len(output)-1; i < j; i, j = i+1, j-1 {
+        output[i], output[j] = output[j], output[i]
+    }
+    return output
+}
+```
+
+```kotlin
+class Solution {
+    fun findOrder(numCourses: Int, prerequisites: Array<IntArray>): IntArray {
+        val indegree = IntArray(numCourses)
+        val adj = Array(numCourses) { mutableListOf<Int>() }
+        
+        for (pair in prerequisites) {
+            val (src, dst) = pair
+            indegree[dst]++
+            adj[src].add(dst)
+        }
+
+        val q = ArrayDeque<Int>()
+        for (i in 0 until numCourses) {
+            if (indegree[i] == 0) q.add(i)
+        }
+
+        val output = mutableListOf<Int>()
+        var finish = 0
+        while (q.isNotEmpty()) {
+            val node = q.removeFirst()
+            output.add(node)
+            finish++
+            for (nei in adj[node]) {
+                indegree[nei]--
+                if (indegree[nei] == 0) {
+                    q.add(nei)
+                }
+            }
+        }
+
+        if (finish != numCourses) return intArrayOf()
+
+        output.reverse()
+        return output.toIntArray()
+    }
+}
+```
+
+```swift
+class Solution {
+    func findOrder(_ numCourses: Int, _ prerequisites: [[Int]]) -> [Int] {
+        var indegree = Array(repeating: 0, count: numCourses)
+        var adj = Array(repeating: [Int](), count: numCourses)
+
+        for pair in prerequisites {
+            let src = pair[0]
+            let dst = pair[1]
+            indegree[dst] += 1
+            adj[src].append(dst)
+        }
+
+        var queue = Deque<Int>()
+        for n in 0..<numCourses {
+            if indegree[n] == 0 {
+                queue.append(n)
+            }
+        }
+
+        var finish = 0
+        var output = [Int]()
+        while !queue.isEmpty {
+            let node = queue.popFirst()!
+            output.append(node)
+            finish += 1
+            for nei in adj[node] {
+                indegree[nei] -= 1
+                if indegree[nei] == 0 {
+                    queue.append(nei)
+                }
+            }
+        }
+
+        return finish == numCourses ? output.reversed() : []
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -661,6 +911,114 @@ public class Solution {
 }
 ```
 
+```go
+func findOrder(numCourses int, prerequisites [][]int) []int {
+    adj := make([][]int, numCourses)
+    indegree := make([]int, numCourses)
+    for _, pair := range prerequisites {
+        nxt, pre := pair[0], pair[1]
+        indegree[nxt]++
+        adj[pre] = append(adj[pre], nxt)
+    }
+
+    output := []int{}
+
+    var dfs func(int)
+    dfs = func(node int) {
+        output = append(output, node)
+        indegree[node]--
+        for _, nei := range adj[node] {
+            indegree[nei]--
+            if indegree[nei] == 0 {
+                dfs(nei)
+            }
+        }
+    }
+
+    for i := 0; i < numCourses; i++ {
+        if indegree[i] == 0 {
+            dfs(i)
+        }
+    }
+
+    if len(output) == numCourses {
+        return output
+    }
+    return []int{}
+}
+```
+
+```kotlin
+class Solution {
+    fun findOrder(numCourses: Int, prerequisites: Array<IntArray>): IntArray {
+        val adj = Array(numCourses) { mutableListOf<Int>() }
+        val indegree = IntArray(numCourses)
+        for ((nxt, pre) in prerequisites) {
+            indegree[nxt]++
+            adj[pre].add(nxt)
+        }
+
+        val output = mutableListOf<Int>()
+
+        fun dfs(node: Int) {
+            output.add(node)
+            indegree[node]--
+            for (nei in adj[node]) {
+                indegree[nei]--
+                if (indegree[nei] == 0) {
+                    dfs(nei)
+                }
+            }
+        }
+
+        for (i in 0 until numCourses) {
+            if (indegree[i] == 0) {
+                dfs(i)
+            }
+        }
+
+        return if (output.size == numCourses) output.toIntArray() else intArrayOf()
+    }
+}
+```
+
+```swift
+class Solution {
+    func findOrder(_ numCourses: Int, _ prerequisites: [[Int]]) -> [Int] {
+        var adj = Array(repeating: [Int](), count: numCourses)
+        var indegree = Array(repeating: 0, count: numCourses)
+
+        for pair in prerequisites {
+            let nxt = pair[0]
+            let pre = pair[1]
+            indegree[nxt] += 1
+            adj[pre].append(nxt)
+        }
+
+        var output = [Int]()
+
+        func dfs(_ node: Int) {
+            output.append(node)
+            indegree[node] -= 1
+            for nei in adj[node] {
+                indegree[nei] -= 1
+                if indegree[nei] == 0 {
+                    dfs(nei)
+                }
+            }
+        }
+
+        for i in 0..<numCourses {
+            if indegree[i] == 0 {
+                dfs(i)
+            }
+        }
+
+        return output.count == numCourses ? output : []
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/course-schedule-iv.md b/articles/course-schedule-iv.md
new file mode 100644
index 000000000..0738453e4
--- /dev/null
+++ b/articles/course-schedule-iv.md
@@ -0,0 +1,900 @@
+## 1. Brute Force (DFS)
+
+::tabs-start
+
+```python
+class Solution:
+    def checkIfPrerequisite(self, numCourses: int, prerequisites: List[List[int]], queries: List[List[int]]) -> List[bool]:
+        adj = [[] for _ in range(numCourses)]
+        for u, v in prerequisites:
+            adj[u].append(v)
+        
+        def dfs(node, target):
+            if node == target:
+                return True
+            for nei in adj[node]:
+                if dfs(nei, target):
+                    return True
+            return False
+
+        res = []
+        for u, v in queries:
+            res.append(dfs(u, v))
+        return res
+```
+
+```java
+public class Solution {
+    private List<Integer>[] adj;
+
+    public List<Boolean> checkIfPrerequisite(int numCourses, int[][] prerequisites, int[][] queries) {
+        adj = new ArrayList[numCourses];
+        for (int i = 0; i < numCourses; i++) adj[i] = new ArrayList<>();
+        for (int[] pre : prerequisites) adj[pre[0]].add(pre[1]);
+
+        List<Boolean> res = new ArrayList<>();
+        for (int[] query : queries) {
+            res.add(dfs(query[0], query[1]));
+        }
+        return res;
+    }
+
+    private boolean dfs(int node, int target) {
+        if (node == target) return true;
+        for (int nei : adj[node]) {
+            if (dfs(nei, target)) return true;
+        }
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+    vector<vector<int>> adj;
+    
+public:
+    vector<bool> checkIfPrerequisite(int numCourses, vector<vector<int>>& prerequisites, vector<vector<int>>& queries) {
+        adj.assign(numCourses, vector<int>());
+        for (auto& pre : prerequisites) {
+            adj[pre[0]].push_back(pre[1]);
+        }
+
+        vector<bool> res;
+        for (auto& query : queries) {
+            res.push_back(dfs(query[0], query[1]));
+        }
+        return res;
+    }
+
+private:
+    bool dfs(int node, int target) {
+        if (node == target) return true;
+        for (int nei : adj[node]) {
+            if (dfs(nei, target)) return true;
+        }
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} numCourses
+     * @param {number[][]} prerequisites
+     * @param {number[][]} queries
+     * @return {boolean[]}
+     */
+    checkIfPrerequisite(numCourses, prerequisites, queries) {
+        const adj = Array.from({ length: numCourses }, () => []);
+        for (const [u, v] of prerequisites) {
+            adj[u].push(v);
+        }
+
+        const dfs = (node, target) => {
+            if (node === target) return true;
+            for (const nei of adj[node]) {
+                if (dfs(nei, target)) return true;
+            }
+            return false;
+        };
+
+        const res = [];
+        for (const [u, v] of queries) {
+            res.push(dfs(u, v));
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<bool> CheckIfPrerequisite(int numCourses, int[][] prerequisites, int[][] queries) {
+        List<int>[] adj = new List<int>[numCourses];
+        for (int i = 0; i < numCourses; i++) {
+            adj[i] = new List<int>();
+        }
+
+        foreach (var pre in prerequisites) {
+            adj[pre[0]].Add(pre[1]);
+        }
+
+        bool Dfs(int node, int target) {
+            if (node == target) return true;
+            foreach (var nei in adj[node]) {
+                if (Dfs(nei, target)) return true;
+            }
+            return false;
+        }
+
+        var res = new List<bool>();
+        foreach (var q in queries) {
+            res.Add(Dfs(q[0], q[1]));
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O((V + E) * m)$
+* Space complexity: $O(V + E + m)$
+
+> Where $m$ is the number of queries, $V$ is the number of courses, and $E$ is the number of prerequisites.
+
+---
+
+## 2. Depth First Search (Hash Set)
+
+::tabs-start
+
+```python
+class Solution:
+    def checkIfPrerequisite(self, numCourses: int, prerequisites: List[List[int]], queries: List[List[int]]) -> List[bool]:
+        adj = defaultdict(list)
+        for prereq, crs in prerequisites:
+            adj[crs].append(prereq)
+
+        def dfs(crs):
+            if crs not in prereqMap:
+                prereqMap[crs] = set()
+                for prereq in adj[crs]:
+                    prereqMap[crs] |= dfs(prereq)
+                prereqMap[crs].add(crs)
+            return prereqMap[crs]
+
+        prereqMap = {}
+        for crs in range(numCourses):
+            dfs(crs)
+
+        res = []
+        for u, v in queries:
+            res.append(u in prereqMap[v])
+        return res
+```
+
+```java
+public class Solution {
+    private List<Integer>[] adj;
+    private Map<Integer, Set<Integer>> prereqMap;
+
+    public List<Boolean> checkIfPrerequisite(int numCourses, int[][] prerequisites, int[][] queries) {
+        adj = new ArrayList[numCourses];
+        prereqMap = new HashMap<>();
+        for (int i = 0; i < numCourses; i++) adj[i] = new ArrayList<>();
+        for (int[] pre : prerequisites) adj[pre[1]].add(pre[0]);
+
+        for (int crs = 0; crs < numCourses; crs++) dfs(crs);
+
+        List<Boolean> res = new ArrayList<>();
+        for (int[] query : queries) {
+            res.add(prereqMap.get(query[1]).contains(query[0]));
+        }
+        return res;
+    }
+
+    private Set<Integer> dfs(int crs) {
+        if (prereqMap.containsKey(crs)) return prereqMap.get(crs);
+        Set<Integer> prereqs = new HashSet<>();
+        for (int pre : adj[crs]) {
+            prereqs.addAll(dfs(pre));
+        }
+        prereqs.add(crs);
+        prereqMap.put(crs, prereqs);
+        return prereqs;
+    }
+}
+```
+
+```cpp
+
+class Solution {
+    vector<vector<int>> adj;
+    unordered_map<int, unordered_set<int>> prereqMap;
+
+public:
+    vector<bool> checkIfPrerequisite(int numCourses, vector<vector<int>>& prerequisites, vector<vector<int>>& queries) {
+        adj.assign(numCourses, vector<int>());
+        for (auto& pre : prerequisites) {
+            adj[pre[1]].push_back(pre[0]);
+        }
+        for (int crs = 0; crs < numCourses; crs++) {
+            dfs(crs);
+        }
+
+        vector<bool> res;
+        for (auto& query : queries) {
+            res.push_back(prereqMap[query[1]].count(query[0]));
+        }
+        return res;
+    }
+
+private:
+    unordered_set<int>& dfs(int crs) {
+        if (prereqMap.count(crs)) {
+            return prereqMap[crs];
+        }
+        prereqMap[crs] = unordered_set<int>();
+        for (int pre : adj[crs]) {
+            auto& cur = dfs(pre);
+            prereqMap[crs].insert(cur.begin(), cur.end());
+        }
+        prereqMap[crs].insert(crs);
+        return prereqMap[crs];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} numCourses
+     * @param {number[][]} prerequisites
+     * @param {number[][]} queries
+     * @return {boolean[]}
+     */
+    checkIfPrerequisite(numCourses, prerequisites, queries) {
+        const adj = Array.from({ length: numCourses }, () => []);
+        const prereqMap = new Map();
+
+        for (const [pre, crs] of prerequisites) {
+            adj[crs].push(pre);
+        }
+
+
+        const dfs = (crs) => {
+            if (prereqMap.has(crs)) {
+                return prereqMap.get(crs);
+            }
+            const prereqs = new Set();
+            for (const pre of adj[crs]) {
+                for (const p of dfs(pre)) prereqs.add(p);
+            }
+            prereqs.add(crs);
+            prereqMap.set(crs, prereqs);
+            return prereqs;
+        };
+
+        for (let crs = 0; crs < numCourses; crs++) {
+            dfs(crs);
+        }
+        return queries.map(([u, v]) => prereqMap.get(v).has(u));
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<bool> CheckIfPrerequisite(int numCourses, int[][] prerequisites, int[][] queries) {
+        Dictionary<int, List<int>> adj = new Dictionary<int, List<int>>();
+        for (int i = 0; i < numCourses; i++) {
+            adj[i] = new List<int>();
+        }
+
+        foreach (var pair in prerequisites) {
+            int prereq = pair[0], crs = pair[1];
+            adj[crs].Add(prereq);
+        }
+
+        Dictionary<int, HashSet<int>> prereqMap = new Dictionary<int, HashSet<int>>();
+
+        HashSet<int> Dfs(int crs) {
+            if (!prereqMap.ContainsKey(crs)) {
+                prereqMap[crs] = new HashSet<int>();
+                foreach (var prereq in adj[crs]) {
+                    prereqMap[crs].UnionWith(Dfs(prereq));
+                }
+                prereqMap[crs].Add(crs);
+            }
+            return prereqMap[crs];
+        }
+
+        for (int crs = 0; crs < numCourses; crs++) {
+            Dfs(crs);
+        }
+
+        List<bool> res = new List<bool>();
+        foreach (var q in queries) {
+            res.Add(prereqMap.ContainsKey(q[1]) && prereqMap[q[1]].Contains(q[0]));
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V * (V + E) + m)$
+* Space complexity: $O(V ^ 2 + E + m)$
+
+> Where $m$ is the number of queries, $V$ is the number of courses, and $E$ is the number of prerequisites.
+
+---
+
+## 3. Depth First Search (Memoization)
+
+::tabs-start
+
+```python
+class Solution:
+    def checkIfPrerequisite(self, numCourses: int, prerequisites: List[List[int]], queries: List[List[int]]) -> List[bool]:
+        adj = [[] for _ in range(numCourses)]
+        isPrereq = [[-1] * numCourses for _ in range(numCourses)]
+        for prereq, crs in prerequisites:
+            adj[crs].append(prereq)
+            isPrereq[crs][prereq] = True
+        
+        def dfs(crs, prereq):
+            if isPrereq[crs][prereq] != -1:
+                return isPrereq[crs][prereq] == 1
+            
+            for pre in adj[crs]:
+                if pre == prereq or dfs(pre, prereq):
+                    isPrereq[crs][prereq] = 1
+                    return True
+            
+            isPrereq[crs][prereq] = 0
+            return False
+        
+        res = []
+        for u, v in queries:
+            res.append(dfs(v, u))
+        return res
+```
+
+```java
+public class Solution {
+    private List<Integer>[] adj;
+    private int[][] isPrereq;
+
+    public List<Boolean> checkIfPrerequisite(int numCourses, int[][] prerequisites, int[][] queries) {
+        adj = new ArrayList[numCourses];
+        isPrereq = new int[numCourses][numCourses];
+        for (int i = 0; i < numCourses; i++) {
+            adj[i] = new ArrayList<>();
+            Arrays.fill(isPrereq[i], -1);
+        }
+        
+        for (int[] pre : prerequisites) {
+            adj[pre[1]].add(pre[0]);
+            isPrereq[pre[1]][pre[0]] = 1;
+        }
+
+        List<Boolean> res = new ArrayList<>();
+        for (int[] query : queries) {
+            res.add(dfs(query[1], query[0]));
+        }
+        return res;
+    }
+
+    private boolean dfs(int crs, int prereq) {
+        if (isPrereq[crs][prereq] != -1) {
+            return isPrereq[crs][prereq] == 1;
+        }
+        for (int pre : adj[crs]) {
+            if (pre == prereq || dfs(pre, prereq)) {
+                isPrereq[crs][prereq] = 1;
+                return true;
+            }
+        }
+        isPrereq[crs][prereq] = 0;
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+    vector<vector<int>> adj;
+    vector<vector<int>> isPrereq;
+
+public:
+    vector<bool> checkIfPrerequisite(int numCourses, vector<vector<int>>& prerequisites, vector<vector<int>>& queries) {
+        adj.assign(numCourses, vector<int>());
+        isPrereq.assign(numCourses, vector<int>(numCourses, -1));
+
+        for (auto& pre : prerequisites) {
+            adj[pre[1]].push_back(pre[0]);
+            isPrereq[pre[1]][pre[0]] = 1;
+        }
+
+        vector<bool> res;
+        for (auto& query : queries) {
+            res.push_back(dfs(query[1], query[0]));
+        }
+        return res;
+    }
+
+private:
+    bool dfs(int crs, int prereq) {
+        if (isPrereq[crs][prereq] != -1) {
+            return isPrereq[crs][prereq] == 1;
+        }
+        for (int pre : adj[crs]) {
+            if (pre == prereq || dfs(pre, prereq)) {
+                isPrereq[crs][prereq] = 1;
+                return true;
+            }
+        }
+        isPrereq[crs][prereq] = 0;
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} numCourses
+     * @param {number[][]} prerequisites
+     * @param {number[][]} queries
+     * @return {boolean[]}
+     */
+    checkIfPrerequisite(numCourses, prerequisites, queries) {
+        const adj = Array.from({ length: numCourses }, () => []);
+        const isPrereq = Array.from({ length: numCourses }, () => Array(numCourses).fill(-1));
+        for (const [prereq, crs] of prerequisites) {
+            adj[crs].push(prereq);
+            isPrereq[crs][prereq] = 1;
+        }
+
+        const dfs = (crs, prereq) => {
+            if (isPrereq[crs][prereq] !== -1) {
+                return isPrereq[crs][prereq] === 1;
+            }
+            for (const pre of adj[crs]) {
+                if (pre === prereq || dfs(pre, prereq)) {
+                    isPrereq[crs][prereq] = 1;
+                    return true;
+                }
+            }
+            isPrereq[crs][prereq] = 0;
+            return false;
+        };
+
+        return queries.map(([u, v]) => dfs(v, u));
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<bool> CheckIfPrerequisite(int numCourses, int[][] prerequisites, int[][] queries) {
+        List<int>[] adj = new List<int>[numCourses];
+        for (int i = 0; i < numCourses; i++) {
+            adj[i] = new List<int>();
+        }
+
+        int[,] isPrereq = new int[numCourses, numCourses];
+        for (int i = 0; i < numCourses; i++) {
+            for (int j = 0; j < numCourses; j++) {
+                isPrereq[i, j] = -1;
+            }
+        }
+
+        foreach (var pair in prerequisites) {
+            int prereq = pair[0], crs = pair[1];
+            adj[crs].Add(prereq);
+            isPrereq[crs, prereq] = 1;
+        }
+
+        bool Dfs(int crs, int prereq) {
+            if (isPrereq[crs, prereq] != -1) {
+                return isPrereq[crs, prereq] == 1;
+            }
+
+            foreach (int pre in adj[crs]) {
+                if (pre == prereq || Dfs(pre, prereq)) {
+                    isPrereq[crs, prereq] = 1;
+                    return true;
+                }
+            }
+
+            isPrereq[crs, prereq] = 0;
+            return false;
+        }
+
+        List<bool> res = new List<bool>();
+        foreach (var q in queries) {
+            res.Add(Dfs(q[1], q[0]));
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V * (V + E) + m)$
+* Space complexity: $O(V ^ 2 + E + m)$
+
+> Where $m$ is the number of queries, $V$ is the number of courses, and $E$ is the number of prerequisites.
+
+---
+
+## 4. Topological Sort (Kahn's Algorithm)
+
+::tabs-start
+
+```python
+class Solution:
+    def checkIfPrerequisite(self, numCourses: int, prerequisites: List[List[int]], queries: List[List[int]]) -> List[bool]:
+        adj = [set() for _ in range(numCourses)]
+        indegree = [0] * numCourses
+        isPrereq = [set() for _ in range(numCourses)]
+        
+        for pre, crs in prerequisites:
+            adj[pre].add(crs)
+            indegree[crs] += 1
+        
+        q = deque([i for i in range(numCourses) if indegree[i] == 0])
+        
+        while q:
+            node = q.popleft()
+            for neighbor in adj[node]:
+                isPrereq[neighbor].add(node)
+                isPrereq[neighbor].update(isPrereq[node])
+                indegree[neighbor] -= 1
+                if indegree[neighbor] == 0:
+                    q.append(neighbor)
+        
+        return [u in isPrereq[v] for u, v in queries]
+```
+
+```java
+public class Solution {
+    public List<Boolean> checkIfPrerequisite(int numCourses, int[][] prerequisites, int[][] queries) {
+        List<Set<Integer>> adj = new ArrayList<>();
+        List<Set<Integer>> isPrereq = new ArrayList<>();
+        int[] indegree = new int[numCourses];
+        for (int i = 0; i < numCourses; i++) {
+            adj.add(new HashSet<>());
+            isPrereq.add(new HashSet<>());
+        }
+
+        for (int[] pre : prerequisites) {
+            adj.get(pre[0]).add(pre[1]);
+            indegree[pre[1]]++;
+        }
+
+        Queue<Integer> q = new LinkedList<>();
+        for (int i = 0; i < numCourses; i++) {
+            if (indegree[i] == 0) q.offer(i);
+        }
+
+        while (!q.isEmpty()) {
+            int node = q.poll();
+            for (int neighbor : adj.get(node)) {
+                isPrereq.get(neighbor).add(node);
+                isPrereq.get(neighbor).addAll(isPrereq.get(node));
+                indegree[neighbor]--;
+                if (indegree[neighbor] == 0) q.offer(neighbor);
+            }
+        }
+
+        List<Boolean> res = new ArrayList<>();
+        for (int[] query : queries) {
+            res.add(isPrereq.get(query[1]).contains(query[0]));
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<bool> checkIfPrerequisite(int numCourses, vector<vector<int>>& prerequisites, vector<vector<int>>& queries) {
+        vector<unordered_set<int>> adj(numCourses), isPrereq(numCourses);
+        vector<int> indegree(numCourses, 0);
+
+        for (auto& pre : prerequisites) {
+            adj[pre[0]].insert(pre[1]);
+            indegree[pre[1]]++;
+        }
+
+        queue<int> q;
+        for (int i = 0; i < numCourses; i++) {
+            if (indegree[i] == 0) q.push(i);
+        }
+
+        while (!q.empty()) {
+            int node = q.front(); q.pop();
+            for (int neighbor : adj[node]) {
+                isPrereq[neighbor].insert(node);
+                isPrereq[neighbor].insert(isPrereq[node].begin(), isPrereq[node].end());
+                indegree[neighbor]--;
+                if (indegree[neighbor] == 0) q.push(neighbor);
+            }
+        }
+
+        vector<bool> res;
+        for (auto& query : queries) {
+            res.push_back(isPrereq[query[1]].count(query[0]));
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} numCourses
+     * @param {number[][]} prerequisites
+     * @param {number[][]} queries
+     * @return {boolean[]}
+     */
+    checkIfPrerequisite(numCourses, prerequisites, queries) {
+        const adj = Array.from({ length: numCourses }, () => new Set());
+        const isPrereq = Array.from({ length: numCourses }, () => new Set());
+        const indegree = Array(numCourses).fill(0);
+
+        for (const [pre, crs] of prerequisites) {
+            adj[pre].add(crs);
+            indegree[crs]++;
+        }
+
+        const q = new Queue();
+        for (let i = 0; i < numCourses; i++) {
+            if (indegree[i] === 0) q.push(i);
+        }
+
+        while (!q.isEmpty()) {
+            const node = q.pop();
+            for (const neighbor of adj[node]) {
+                isPrereq[neighbor].add(node);
+                for (const it of isPrereq[node]) {
+                    isPrereq[neighbor].add(it);
+                }
+                indegree[neighbor]--;
+                if (indegree[neighbor] === 0) q.push(neighbor);
+            }
+        }
+
+        return queries.map(([u, v]) => isPrereq[v].has(u));
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<bool> CheckIfPrerequisite(int numCourses, int[][] prerequisites, int[][] queries) {
+        List<HashSet<int>> adj = new List<HashSet<int>>();
+        List<HashSet<int>> isPrereq = new List<HashSet<int>>();
+        int[] indegree = new int[numCourses];
+
+        for (int i = 0; i < numCourses; i++) {
+            adj.Add(new HashSet<int>());
+            isPrereq.Add(new HashSet<int>());
+        }
+
+        foreach (var pair in prerequisites) {
+            int pre = pair[0], crs = pair[1];
+            adj[pre].Add(crs);
+            indegree[crs]++;
+        }
+
+        Queue<int> q = new Queue<int>();
+        for (int i = 0; i < numCourses; i++) {
+            if (indegree[i] == 0) {
+                q.Enqueue(i);
+            }
+        }
+
+        while (q.Count > 0) {
+            int node = q.Dequeue();
+            foreach (int neighbor in adj[node]) {
+                isPrereq[neighbor].Add(node);
+                foreach (int p in isPrereq[node]) {
+                    isPrereq[neighbor].Add(p);
+                }
+                indegree[neighbor]--;
+                if (indegree[neighbor] == 0) {
+                    q.Enqueue(neighbor);
+                }
+            }
+        }
+
+        List<bool> result = new List<bool>();
+        foreach (var query in queries) {
+            int u = query[0], v = query[1];
+            result.Add(isPrereq[v].Contains(u));
+        }
+
+        return result;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V * (V + E) + m)$
+* Space complexity: $O(V ^ 2 + E + m)$
+
+> Where $m$ is the number of queries, $V$ is the number of courses, and $E$ is the number of prerequisites.
+
+---
+
+## 5. Floyd Warshall Algorithm
+
+::tabs-start
+
+```python
+class Solution:
+    def checkIfPrerequisite(self, numCourses: int, prerequisites: List[List[int]], queries: List[List[int]]) -> List[bool]:
+        res = []
+        adj = [[False] * numCourses for _ in range(numCourses)]
+        
+        for pre, crs in prerequisites:
+            adj[pre][crs] = True
+        
+        for k in range(numCourses):
+            for i in range(numCourses):
+                for j in range(numCourses):
+                    adj[i][j] = adj[i][j] or (adj[i][k] and adj[k][j])
+        
+        for u, v in queries:
+            res.append(adj[u][v])
+        
+        return res
+```
+
+```java
+public class Solution {
+    public List<Boolean> checkIfPrerequisite(int numCourses, int[][] prerequisites, int[][] queries) {
+        boolean[][] adj = new boolean[numCourses][numCourses];
+        List<Boolean> res = new ArrayList<>();
+        
+        for (int[] pre : prerequisites) {
+            adj[pre[0]][pre[1]] = true;
+        }
+        
+        for (int k = 0; k < numCourses; k++) {
+            for (int i = 0; i < numCourses; i++) {
+                for (int j = 0; j < numCourses; j++) {
+                    adj[i][j] = adj[i][j] || (adj[i][k] && adj[k][j]);
+                }
+            }
+        }
+        
+        for (int[] q : queries) {
+            res.add(adj[q[0]][q[1]]);
+        }
+        
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<bool> checkIfPrerequisite(int numCourses, vector<vector<int>>& prerequisites, vector<vector<int>>& queries) {
+        vector<vector<bool>> adj(numCourses, vector<bool>(numCourses, false));
+        vector<bool> res;
+        
+        for (auto& pre : prerequisites) {
+            adj[pre[0]][pre[1]] = true;
+        }
+        
+        for (int k = 0; k < numCourses; k++) {
+            for (int i = 0; i < numCourses; i++) {
+                for (int j = 0; j < numCourses; j++) {
+                    adj[i][j] = adj[i][j] || (adj[i][k] && adj[k][j]);
+                }
+            }
+        }
+        
+        for (auto& q : queries) {
+            res.push_back(adj[q[0]][q[1]]);
+        }
+        
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} numCourses
+     * @param {number[][]} prerequisites
+     * @param {number[][]} queries
+     * @return {boolean[]}
+     */
+    checkIfPrerequisite(numCourses, prerequisites, queries) {
+        let adj = Array.from({ length: numCourses }, () => Array(numCourses).fill(false));
+        let res = [];
+        
+        for (let [pre, crs] of prerequisites) {
+            adj[pre][crs] = true;
+        }
+        
+        for (let k = 0; k < numCourses; k++) {
+            for (let i = 0; i < numCourses; i++) {
+                for (let j = 0; j < numCourses; j++) {
+                    adj[i][j] = adj[i][j] || (adj[i][k] && adj[k][j]);
+                }
+            }
+        }
+        
+        for (let [u, v] of queries) {
+            res.push(adj[u][v]);
+        }
+        
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<bool> CheckIfPrerequisite(int numCourses, int[][] prerequisites, int[][] queries) {
+        bool[,] adj = new bool[numCourses, numCourses];
+
+        foreach (var pair in prerequisites) {
+            int pre = pair[0], crs = pair[1];
+            adj[pre, crs] = true;
+        }
+
+        for (int k = 0; k < numCourses; k++) {
+            for (int i = 0; i < numCourses; i++) {
+                for (int j = 0; j < numCourses; j++) {
+                    adj[i, j] = adj[i, j] || (adj[i, k] && adj[k, j]);
+                }
+            }
+        }
+
+        List<bool> res = new List<bool>();
+        foreach (var query in queries) {
+            int u = query[0], v = query[1];
+            res.Add(adj[u, v]);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V ^ 3 + E + m)$
+* Space complexity: $O(V ^ 2 + E + m)$
+
+> Where $m$ is the number of queries, $V$ is the number of courses, and $E$ is the number of prerequisites.
\ No newline at end of file
diff --git a/articles/course-schedule.md b/articles/course-schedule.md
index c26936883..d57ce12c1 100644
--- a/articles/course-schedule.md
+++ b/articles/course-schedule.md
@@ -219,6 +219,142 @@ public class Solution {
 }
 ```
 
+```go
+func canFinish(numCourses int, prerequisites [][]int) bool {
+    // Map each course to its prerequisites
+    preMap := make(map[int][]int)
+    for i := 0; i < numCourses; i++ {
+        preMap[i] = []int{}
+    }
+    for _, prereq := range prerequisites {
+        crs, pre := prereq[0], prereq[1]
+        preMap[crs] = append(preMap[crs], pre)
+    }
+
+    // Store all courses along the current DFS path
+    visiting := make(map[int]bool)
+
+    var dfs func(int) bool
+    dfs = func(crs int) bool {
+        if visiting[crs] {
+            // Cycle detected
+            return false
+        }
+        if len(preMap[crs]) == 0 {
+            return true
+        }
+
+        visiting[crs] = true
+        for _, pre := range preMap[crs] {
+            if !dfs(pre) {
+                return false
+            }
+        }
+        visiting[crs] = false
+        preMap[crs] = []int{}
+        return true
+    }
+
+    for c := 0; c < numCourses; c++ {
+        if !dfs(c) {
+            return false
+        }
+    }
+    return true
+}
+```
+
+```kotlin
+class Solution {
+    fun canFinish(numCourses: Int, prerequisites: Array<IntArray>): Boolean {
+        // Map each course to its prerequisites
+        val preMap = HashMap<Int, MutableList<Int>>()
+        for (i in 0 until numCourses) {
+            preMap[i] = mutableListOf()
+        }
+        for (prereq in prerequisites) {
+            val (crs, pre) = prereq
+            preMap[crs]!!.add(pre)
+        }
+
+        // Store all courses along the current DFS path
+        val visiting = HashSet<Int>()
+
+        fun dfs(crs: Int): Boolean {
+            if (crs in visiting) {
+                // Cycle detected
+                return false
+            }
+            if (preMap[crs]!!.isEmpty()) {
+                return true
+            }
+
+            visiting.add(crs)
+            for (pre in preMap[crs]!!) {
+                if (!dfs(pre)) {
+                    return false
+                }
+            }
+            visiting.remove(crs)
+            preMap[crs] = mutableListOf()
+            return true
+        }
+
+        for (c in 0 until numCourses) {
+            if (!dfs(c)) {
+                return false
+            }
+        }
+        return true
+    }
+}
+```
+
+```swift
+class Solution {
+    func canFinish(_ numCourses: Int, _ prerequisites: [[Int]]) -> Bool {
+        // Map each course to its prerequisites
+        var preMap = [Int: [Int]]()
+        for i in 0..<numCourses {
+            preMap[i] = []
+        }
+        for pair in prerequisites {
+            preMap[pair[0]]!.append(pair[1])
+        }
+
+        // Store all courses along the current DFS path
+        var visiting = Set<Int>()
+
+        func dfs(_ crs: Int) -> Bool {
+            if visiting.contains(crs) {
+                // Cycle detected
+                return false
+            }
+            if preMap[crs]!.isEmpty {
+                return true
+            }
+
+            visiting.insert(crs)
+            for pre in preMap[crs]! {
+                if !dfs(pre) {
+                    return false
+                }
+            }
+            visiting.remove(crs)
+            preMap[crs] = []
+            return true
+        }
+
+        for c in 0..<numCourses {
+            if !dfs(c) {
+                return false
+            }
+        }
+        return true
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -410,6 +546,117 @@ public class Solution {
 }
 ```
 
+```go
+func canFinish(numCourses int, prerequisites [][]int) bool {
+    indegree := make([]int, numCourses)
+    adj := make([][]int, numCourses)
+    for i := 0; i < numCourses; i++ {
+        adj[i] = []int{}
+    }
+
+    for _, prereq := range prerequisites {
+        src, dst := prereq[0], prereq[1]
+        indegree[dst]++
+        adj[src] = append(adj[src], dst)
+    }
+
+    q := []int{}
+    for n := 0; n < numCourses; n++ {
+        if indegree[n] == 0 {
+            q = append(q, n)
+        }
+    }
+
+    finish := 0
+    for len(q) > 0 {
+        node := q[0]
+        q = q[1:]
+        finish++
+        for _, nei := range adj[node] {
+            indegree[nei]--
+            if indegree[nei] == 0 {
+                q = append(q, nei)
+            }
+        }
+    }
+
+    return finish == numCourses
+}
+```
+
+```kotlin
+class Solution {
+    fun canFinish(numCourses: Int, prerequisites: Array<IntArray>): Boolean {
+        val indegree = IntArray(numCourses) { 0 }
+        val adj = Array(numCourses) { mutableListOf<Int>() }
+        
+        for (prereq in prerequisites) {
+            val (src, dst) = prereq
+            indegree[dst]++
+            adj[src].add(dst)
+        }
+
+        val q: Queue<Int> = LinkedList()
+        for (n in 0 until numCourses) {
+            if (indegree[n] == 0) {
+                q.add(n)
+            }
+        }
+
+        var finish = 0
+        while (q.isNotEmpty()) {
+            val node = q.poll()
+            finish++
+            for (nei in adj[node]) {
+                indegree[nei]--
+                if (indegree[nei] == 0) {
+                    q.add(nei)
+                }
+            }
+        }
+
+        return finish == numCourses
+    }
+}
+```
+
+```swift
+class Solution {
+    func canFinish(_ numCourses: Int, _ prerequisites: [[Int]]) -> Bool {
+        var indegree = Array(repeating: 0, count: numCourses)
+        var adj = Array(repeating: [Int](), count: numCourses)
+
+        for pair in prerequisites {
+            let src = pair[0]
+            let dst = pair[1]
+            indegree[dst] += 1
+            adj[src].append(dst)
+        }
+
+        var queue = Deque<Int>()
+        for n in 0..<numCourses {
+            if indegree[n] == 0 {
+                queue.append(n)
+            }
+        }
+
+        var finish = 0
+        while !queue.isEmpty {
+            let node = queue.popFirst()!
+            finish += 1
+            for nei in adj[node] {
+                indegree[nei] -= 1
+                if indegree[nei] == 0 {
+                    queue.append(nei)
+                }
+            }
+        }
+
+        return finish == numCourses
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/daily-temperatures.md b/articles/daily-temperatures.md
index 8a42cdc53..f004aac40 100644
--- a/articles/daily-temperatures.md
+++ b/articles/daily-temperatures.md
@@ -122,12 +122,93 @@ public class Solution {
 }
 ```
 
+```go
+func dailyTemperatures(temperatures []int) []int {
+   n := len(temperatures)
+   res := make([]int, 0)
+   
+   for i := 0; i < n; i++ {
+       count := 1
+       j := i + 1
+       
+       for j < n {
+           if temperatures[j] > temperatures[i] {
+               break
+           }
+           j++
+           count++
+       }
+       
+       if j == n {
+           count = 0
+       }
+       
+       res = append(res, count)
+   }
+   
+   return res
+}
+```
+
+```kotlin
+class Solution {
+    fun dailyTemperatures(temperatures: IntArray): IntArray {
+        val n = temperatures.size
+        val res = mutableListOf<Int>()
+        
+        for (i in 0 until n) {
+            var count = 1
+            var j = i + 1
+            
+            while (j < n) {
+                if (temperatures[j] > temperatures[i]) {
+                    break
+                }
+                j++
+                count++
+            }
+            
+            count = if (j == n) 0 else count
+            res.add(count)
+        }
+        
+        return res.toIntArray()
+    }
+}
+```
+
+```swift
+class Solution {
+    func dailyTemperatures(_ temperatures: [Int]) -> [Int] {
+        let n = temperatures.count
+        var res = [Int]()
+
+        for i in 0..<n {
+            var count = 1
+            var j = i + 1
+            while j < n {
+                if temperatures[j] > temperatures[i] {
+                    break
+                }
+                j += 1
+                count += 1
+            }
+            count = (j == n) ? 0 : count
+            res.append(count)
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n ^ 2)$
-* Space complexity: $O(1)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ space for the output array.
 
 ---
 
@@ -231,6 +312,61 @@ public class Solution {
 }
 ```
 
+```go
+func dailyTemperatures(temperatures []int) []int {
+    res := make([]int, len(temperatures))
+    stack := []int{}
+
+    for i, t := range temperatures {
+        for len(stack) > 0 && t > temperatures[stack[len(stack)-1]] {
+            stackInd := stack[len(stack)-1]
+            stack = stack[:len(stack)-1]
+            res[stackInd] = i - stackInd
+        }
+        stack = append(stack, i)
+    }
+
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun dailyTemperatures(temperatures: IntArray): IntArray {
+        val res = IntArray(temperatures.size) { 0 }
+        val stack = mutableListOf<Int>() 
+
+        for (i in temperatures.indices) {
+            while (stack.isNotEmpty() && temperatures[i] > temperatures[stack.last()]) {
+                val stackInd = stack.removeAt(stack.size - 1)
+                res[stackInd] = i - stackInd
+            }
+            stack.add(i)
+        }
+
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func dailyTemperatures(_ temperatures: [Int]) -> [Int] {
+        var res = [Int](repeating: 0, count: temperatures.count)
+        var stack = [(Int, Int)]() // Pair: (temperature, index)
+
+        for (i, t) in temperatures.enumerated() {
+            while !stack.isEmpty && t > stack.last!.0 {
+                let (stackT, stackInd) = stack.removeLast()
+                res[stackInd] = i - stackInd
+            }
+            stack.append((t, i))
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -368,9 +504,84 @@ public class Solution {
 }
 ```
 
+```go
+func dailyTemperatures(temperatures []int) []int {
+    n := len(temperatures)
+    res := make([]int, n)
+
+    for i := n - 2; i >= 0; i-- {
+        j := i + 1
+        for j < n && temperatures[j] <= temperatures[i] {
+            if res[j] == 0 {
+                j = n
+                break
+            }
+            j += res[j]
+        }
+        
+        if j < n {
+            res[i] = j - i
+        }
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun dailyTemperatures(temperatures: IntArray): IntArray {
+        val n = temperatures.size
+        val res = IntArray(n)
+
+        for (i in n - 2 downTo 0) {
+            var j = i + 1
+            while (j < n && temperatures[j] <= temperatures[i]) {
+                if (res[j] == 0) {
+                    j = n
+                    break
+                }
+                j += res[j]
+            }
+            
+            if (j < n) {
+                res[i] = j - i
+            }
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func dailyTemperatures(_ temperatures: [Int]) -> [Int] {
+        let n = temperatures.count
+        var res = [Int](repeating: 0, count: n)
+
+        for i in stride(from: n - 2, through: 0, by: -1) {
+            var j = i + 1
+            while j < n && temperatures[j] <= temperatures[i] {
+                if res[j] == 0 {
+                    j = n
+                    break
+                }
+                j += res[j]
+            }
+
+            if j < n {
+                res[i] = j - i
+            }
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n)$
-* Space complexity: $O(1)$
\ No newline at end of file
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ space for the output array.
\ No newline at end of file
diff --git a/articles/data-stream-as-disjoint-intervals.md b/articles/data-stream-as-disjoint-intervals.md
new file mode 100644
index 000000000..a39dc70f3
--- /dev/null
+++ b/articles/data-stream-as-disjoint-intervals.md
@@ -0,0 +1,450 @@
+## 1. Brute Force (Sorting)
+
+::tabs-start
+
+```python
+class SummaryRanges:
+
+    def __init__(self):
+        self.arr = []
+
+    def addNum(self, value: int) -> None:
+        self.arr.append(value)
+
+    def getIntervals(self) -> List[List[int]]:
+        if not self.arr:
+            return []
+
+        self.arr.sort()
+        n = len(self.arr)
+        start = self.arr[0]
+        res = []
+        for i in range(1, n):
+            if self.arr[i] - self.arr[i - 1] > 1:
+                res.append([start, self.arr[i - 1]])
+                start = self.arr[i]
+
+        res.append([start, self.arr[n - 1]])
+        return res
+```
+
+```java
+public class SummaryRanges {
+    private List<Integer> arr;
+
+    public SummaryRanges() {
+        arr = new ArrayList<>();
+    }
+
+    public void addNum(int value) {
+        arr.add(value);
+    }
+
+    public List<int[]> getIntervals() {
+        List<int[]> res = new ArrayList<>();
+        if (arr.isEmpty()) return res;
+
+        Collections.sort(arr);
+        int start = arr.get(0);
+        for (int i = 1; i < arr.size(); i++) {
+            if (arr.get(i) - arr.get(i - 1) > 1) {
+                res.add(new int[]{start, arr.get(i - 1)});
+                start = arr.get(i);
+            }
+        }
+        res.add(new int[]{start, arr.get(arr.size() - 1)});
+        return res;
+    }
+}
+```
+
+```cpp
+class SummaryRanges {
+private:
+    vector<int> arr;
+
+public:
+    SummaryRanges() {}
+
+    void addNum(int value) {
+        arr.push_back(value);
+    }
+
+    vector<vector<int>> getIntervals() {
+        vector<vector<int>> res;
+        if (arr.empty()) return res;
+
+        sort(arr.begin(), arr.end());
+        int start = arr[0];
+        for (int i = 1; i < arr.size(); i++) {
+            if (arr[i] - arr[i - 1] > 1) {
+                res.push_back({start, arr[i - 1]});
+                start = arr[i];
+            }
+        }
+        res.push_back({start, arr.back()});
+        return res;
+    }
+};
+```
+
+```javascript
+class SummaryRanges {
+    constructor() {
+        this.arr = [];
+    }
+
+    /** 
+     * @param {number} value
+     * @return {void}
+     */
+    addNum(value) {
+        this.arr.push(value);
+    }
+
+    /**
+     * @return {number[][]}
+     */
+    getIntervals() {
+        if (this.arr.length === 0) return [];
+
+        this.arr.sort((a, b) => a - b);
+        let start = this.arr[0];
+        let res = [];
+
+        for (let i = 1; i < this.arr.length; i++) {
+            if (this.arr[i] - this.arr[i - 1] > 1) {
+                res.push([start, this.arr[i - 1]]);
+                start = this.arr[i];
+            }
+        }
+        res.push([start, this.arr[this.arr.length - 1]]);
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(1)$ time for initialization.
+    * $O(1)$ time for each $addNum()$ function call.
+    * $O(n \log n)$ time for each $getIntervals()$ function call.
+* Space complexity: $O(n)$
+
+---
+
+## 2. Hash Set + Sorting
+
+::tabs-start
+
+```python
+class SummaryRanges:
+
+    def __init__(self):
+        self.arr = set()
+
+    def addNum(self, value: int) -> None:
+        self.arr.add(value)
+
+    def getIntervals(self) -> List[List[int]]:
+        if not self.arr:
+            return []
+
+        lst = sorted(list(self.arr))
+        n = len(lst)
+        start = lst[0]
+        res = []
+        for i in range(1, n):
+            if lst[i] - lst[i - 1] > 1:
+                res.append([start, lst[i - 1]])
+                start = lst[i]
+
+        res.append([start, lst[n - 1]])
+        return res
+```
+
+```java
+public class SummaryRanges {
+    private Set<Integer> arr;
+
+    public SummaryRanges() {
+        arr = new TreeSet<>();
+    }
+
+    public void addNum(int value) {
+        arr.add(value);
+    }
+
+    public List<int[]> getIntervals() {
+        List<int[]> res = new ArrayList<>();
+        if (arr.isEmpty()) return res;
+
+        List<Integer> lst = new ArrayList<>(arr);
+        int start = lst.get(0);
+        for (int i = 1; i < lst.size(); i++) {
+            if (lst.get(i) - lst.get(i - 1) > 1) {
+                res.add(new int[]{start, lst.get(i - 1)});
+                start = lst.get(i);
+            }
+        }
+        res.add(new int[]{start, lst.get(lst.size() - 1)});
+        return res;
+    }
+}
+```
+
+```cpp
+class SummaryRanges {
+private:
+    set<int> arr;
+
+public:
+    SummaryRanges() {}
+
+    void addNum(int value) {
+        arr.insert(value);
+    }
+
+    vector<vector<int>> getIntervals() {
+        vector<vector<int>> res;
+        if (arr.empty()) return res;
+
+        vector<int> lst(arr.begin(), arr.end());
+        int start = lst[0];
+
+        for (int i = 1; i < lst.size(); i++) {
+            if (lst[i] - lst[i - 1] > 1) {
+                res.push_back({start, lst[i - 1]});
+                start = lst[i];
+            }
+        }
+        res.push_back({start, lst.back()});
+        return res;
+    }
+};
+```
+
+```javascript
+class SummaryRanges {
+    constructor() {
+        this.arr = new Set();
+    }
+
+    /**
+     * @param {number} value
+     * @return {number[][]}
+     */
+    addNum(value) {
+        this.arr.add(value);
+    }
+
+    /**
+     * @return {number[][]}
+     */
+    getIntervals() {
+        if (this.arr.size === 0) return [];
+
+        let lst = Array.from(this.arr).sort((a, b) => a - b);
+        let start = lst[0];
+        let res = [];
+
+        for (let i = 1; i < lst.length; i++) {
+            if (lst[i] - lst[i - 1] > 1) {
+                res.push([start, lst[i - 1]]);
+                start = lst[i];
+            }
+        }
+        res.push([start, lst[lst.length - 1]]);
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(1)$ time for initialization.
+    * $O(1)$ time for each $addNum()$ function call.
+    * $O(n \log n)$ time for each $getIntervals()$ function call.
+* Space complexity: $O(n)$
+
+---
+
+## 3. Ordered Map
+
+::tabs-start
+
+```python
+from sortedcontainers import SortedDict
+
+class SummaryRanges:
+    def __init__(self):
+        self.treeMap = SortedDict()
+
+    def addNum(self, value: int) -> None:
+        self.treeMap[value] = True
+
+    def getIntervals(self) -> List[List[int]]:
+        res = []
+        for n in self.treeMap:
+            if res and res[-1][1] + 1 == n:
+                res[-1][1] = n
+            else:
+                res.append([n, n])
+        return res
+```
+
+```java
+public class SummaryRanges {
+    private TreeMap<Integer, Boolean> treeMap;
+
+    public SummaryRanges() {
+        treeMap = new TreeMap<>();
+    }
+
+    public void addNum(int value) {
+        treeMap.put(value, true);
+    }
+
+    public List<int[]> getIntervals() {
+        List<int[]> res = new ArrayList<>();
+        for (int n : treeMap.keySet()) {
+            if (!res.isEmpty() && res.get(res.size() - 1)[1] + 1 == n) {
+                res.get(res.size() - 1)[1] = n;
+            } else {
+                res.add(new int[]{n, n});
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class SummaryRanges {
+private:
+    map<int, bool> treeMap;
+
+public:
+    SummaryRanges() {}
+
+    void addNum(int value) {
+        treeMap[value] = true;
+    }
+
+    vector<vector<int>> getIntervals() {
+        vector<vector<int>> res;
+        for (auto& [n, _] : treeMap) {
+            if (!res.empty() && res.back()[1] + 1 == n) {
+                res.back()[1] = n;
+            } else {
+                res.push_back({n, n});
+            }
+        }
+        return res;
+    }
+};
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(1)$ time for initialization.
+    * $O(\log n)$ time for each $addNum()$ function call.
+    * $O(n)$ time for each $getIntervals()$ function call.
+* Space complexity: $O(n)$
+
+---
+
+## 4. Ordered Set
+
+::tabs-start
+
+```python
+from sortedcontainers import SortedSet
+
+class SummaryRanges:
+    def __init__(self):
+        self.orderedSet = SortedSet()
+
+    def addNum(self, value: int) -> None:
+        self.orderedSet.add(value)
+
+    def getIntervals(self) -> List[List[int]]:
+        res = []
+        for n in self.orderedSet:
+            if res and res[-1][1] + 1 == n:
+                res[-1][1] = n
+            else:
+                res.append([n, n])
+        return res
+```
+
+```java
+public class SummaryRanges {
+    private TreeSet<Integer> orderedSet;
+
+    public SummaryRanges() {
+        orderedSet = new TreeSet<>();
+    }
+
+    public void addNum(int value) {
+        orderedSet.add(value);
+    }
+
+    public List<int[]> getIntervals() {
+        List<int[]> res = new ArrayList<>();
+        for (int n : orderedSet) {
+            if (!res.isEmpty() && res.get(res.size() - 1)[1] + 1 == n) {
+                res.get(res.size() - 1)[1] = n;
+            } else {
+                res.add(new int[]{n, n});
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class SummaryRanges {
+private:
+    set<int> orderedSet;
+
+public:
+    SummaryRanges() {}
+
+    void addNum(int value) {
+        orderedSet.insert(value);
+    }
+
+    vector<vector<int>> getIntervals() {
+        vector<vector<int>> res;
+        for (int n : orderedSet) {
+            if (!res.empty() && res.back()[1] + 1 == n) {
+                res.back()[1] = n;
+            } else {
+                res.push_back({n, n});
+            }
+        }
+        return res;
+    }
+};
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(1)$ time for initialization.
+    * $O(\log n)$ time for each $addNum()$ function call.
+    * $O(n)$ time for each $getIntervals()$ function call.
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/decode-string.md b/articles/decode-string.md
new file mode 100644
index 000000000..c86b9b8f1
--- /dev/null
+++ b/articles/decode-string.md
@@ -0,0 +1,554 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def decodeString(self, s: str) -> str:
+        self.i = 0
+        
+        def helper():
+            res = ""
+            k = 0
+            
+            while self.i < len(s):
+                c = s[self.i]
+                
+                if c.isdigit():
+                    k = k * 10 + int(c)
+                elif c == "[":
+                    self.i += 1
+                    res += k * helper()
+                    k = 0
+                elif c == "]":
+                    return res
+                else:
+                    res += c
+                
+                self.i += 1
+            return res
+        
+        return helper()
+```
+
+```java
+public class Solution {
+    private int i = 0;
+    
+    public String decodeString(String s) {
+        return helper(s);
+    }
+    
+    private String helper(String s) {
+        StringBuilder res = new StringBuilder();
+        int k = 0;
+        
+        while (i < s.length()) {
+            char c = s.charAt(i);
+            
+            if (Character.isDigit(c)) {
+                k = k * 10 + (c - '0');
+            } else if (c == '[') {
+                i++;
+                String subRes = helper(s);
+                while (k-- > 0) res.append(subRes);
+                k = 0;
+            } else if (c == ']') {
+                return res.toString();
+            } else {
+                res.append(c);
+            }
+            
+            i++;
+        }
+        
+        return res.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    string helper(int& i, string& s) {
+        string res;
+        int k = 0;
+
+        while (i < s.size()) {
+            char c = s[i];
+
+            if (isdigit(c)) {
+                k = k * 10 + (c - '0');
+            } else if (c == '[') {
+                i++;
+                string subRes = helper(i, s);
+                while (k-- > 0) res += subRes;
+                k = 0;
+            } else if (c == ']') {
+                return res;
+            } else {
+                res += c;
+            }
+
+            i++;
+        }
+
+        return res;
+    }
+
+public:
+    string decodeString(string s) {
+        int i = 0;
+        return helper(i, s);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string}
+     */
+    decodeString(s) {
+        let i = 0;
+
+        const helper = () => {
+            let res = "";
+            let k = 0;
+
+            while (i < s.length) {
+                const c = s[i];
+
+                if (!isNaN(c)) {
+                    k = k * 10 + parseInt(c, 10);
+                } else if (c === "[") {
+                    i++;
+                    res += helper().repeat(k);
+                    k = 0;
+                } else if (c === "]") {
+                    return res;
+                } else {
+                    res += c;
+                }
+
+                i++;
+            }
+
+            return res;
+        };
+
+        return helper();
+    }
+}
+```
+
+```csharp
+public class Solution {
+    private int i;
+
+    public string DecodeString(string s) {
+        i = 0;
+        return Helper(s);
+    }
+
+    private string Helper(string s) {
+        string res = "";
+        int k = 0;
+
+        while (i < s.Length) {
+            char c = s[i];
+
+            if (char.IsDigit(c)) {
+                k = k * 10 + (c - '0');
+            } else if (c == '[') {
+                i++;
+                string inner = Helper(s);
+                res += new string(' ', 0).PadLeft(0);
+                for (int j = 0; j < k; j++) {
+                    res += inner;
+                }
+                k = 0;
+            } else if (c == ']') {
+                return res;
+            } else {
+                res += c;
+            }
+
+            i++;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + N)$
+* Space complexity: $O(n + N)$
+
+> Where $n$ is the length of the input string and $N$ is the length of the output string.
+
+---
+
+## 2. One Stack
+
+::tabs-start
+
+```python
+class Solution:
+    def decodeString(self, s: str) -> str:
+        stack = []
+
+        for i in range(len(s)):
+            if s[i] != "]":
+                stack.append(s[i])
+            else:
+                substr = ""
+                while stack[-1] != "[":
+                    substr = stack.pop() + substr
+                stack.pop()
+
+                k = ""
+                while stack and stack[-1].isdigit():
+                    k = stack.pop() + k
+                stack.append(int(k) * substr)
+
+        return "".join(stack)
+```
+
+```java
+public class Solution {
+    public String decodeString(String s) {
+        Stack<String> stack = new Stack<>();
+
+        for (int i = 0; i < s.length(); i++) {
+            if (s.charAt(i) != ']') {
+                stack.push(String.valueOf(s.charAt(i)));
+            } else {
+                StringBuilder substr = new StringBuilder();
+                while (!stack.peek().equals("[")) {
+                    substr.insert(0, stack.pop());
+                }
+                stack.pop();
+
+                StringBuilder k = new StringBuilder();
+                while (!stack.isEmpty() && Character.isDigit(stack.peek().charAt(0))) {
+                    k.insert(0, stack.pop());
+                }
+                int count = Integer.parseInt(k.toString());
+                String repeatedStr = substr.toString().repeat(count);
+                stack.push(repeatedStr);
+            }
+        }
+
+        StringBuilder res = new StringBuilder();
+        while (!stack.isEmpty()) {
+            res.insert(0, stack.pop());
+        }
+        return res.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string decodeString(string s) {
+        vector<string> stack;
+
+        for (char& c : s) {
+            if (c != ']') {
+                stack.push_back(string(1, c));
+            } else {
+                string substr = "";
+                while (stack.back() != "[") {
+                    substr = stack.back() + substr;
+                    stack.pop_back();
+                }
+                stack.pop_back();
+
+                string k = "";
+                while (!stack.empty() && isdigit(stack.back()[0])) {
+                    k = stack.back() + k;
+                    stack.pop_back();
+                }
+                int repeatCount = stoi(k);
+
+                string repeated = "";
+                for (int i = 0; i < repeatCount; ++i) {
+                    repeated += substr;
+                }
+                stack.push_back(repeated);
+            }
+        }
+
+        string res = "";
+        for (const string& part : stack) {
+            res += part;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string}
+     */
+    decodeString(s) {
+        const stack = [];
+
+        for (let i = 0; i < s.length; i++) {
+            const char = s[i];
+
+            if (char !== "]") {
+                stack.push(char);
+            } else {
+                let substr = "";
+                while (stack[stack.length - 1] !== "[") {
+                    substr = stack.pop() + substr;
+                }
+                stack.pop();
+
+                let k = "";
+                while (stack.length > 0 && !isNaN(stack[stack.length - 1])) {
+                    k = stack.pop() + k;
+                }
+                stack.push(substr.repeat(parseInt(k, 10)));
+            }
+        }
+
+        return stack.join("");
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public string DecodeString(string s) {
+        Stack<string> stack = new Stack<string>();
+
+        for (int i = 0; i < s.Length; i++) {
+            if (s[i] != ']') {
+                stack.Push(s[i].ToString());
+            } else {
+                string substr = "";
+                while (stack.Peek() != "[") {
+                    substr = stack.Pop() + substr;
+                }
+                stack.Pop(); // remove '['
+
+                string k = "";
+                while (stack.Count > 0 && char.IsDigit(stack.Peek()[0])) {
+                    k = stack.Pop() + k;
+                }
+
+                int repeat = int.Parse(k);
+                string expanded = new StringBuilder().Insert(0, substr, repeat).ToString();
+                stack.Push(expanded);
+            }
+        }
+
+        var result = new StringBuilder();
+        foreach (string part in stack) {
+            result.Insert(0, part);
+        }
+        return result.ToString();
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + N ^ 2)$
+* Space complexity: $O(n + N)$
+
+> Where $n$ is the length of the input string and $N$ is the length of the output string.
+
+---
+
+## 3. Two Stacks
+
+::tabs-start
+
+```python
+class Solution:
+    def decodeString(self, s: str) -> str:
+        string_stack = []
+        count_stack = []
+        cur = ""
+        k = 0
+
+        for c in s:
+            if c.isdigit():
+                k = k * 10 + int(c)
+            elif c == "[":
+                string_stack.append(cur)
+                count_stack.append(k)
+                cur = ""
+                k = 0
+            elif c == "]":
+                temp = cur
+                cur = string_stack.pop()
+                count = count_stack.pop()
+                cur += temp * count
+            else:
+                cur += c
+
+        return cur
+```
+
+```java
+public class Solution {
+    public String decodeString(String s) {
+        Stack<String> stringStack = new Stack<>();
+        Stack<Integer> countStack = new Stack<>();
+        StringBuilder cur = new StringBuilder();
+        int k = 0;
+
+        for (char c : s.toCharArray()) {
+            if (Character.isDigit(c)) {
+                k = k * 10 + (c - '0');
+            } else if (c == '[') {
+                stringStack.push(cur.toString());
+                countStack.push(k);
+                cur = new StringBuilder();
+                k = 0;
+            } else if (c == ']') {
+                String temp = cur.toString();
+                cur = new StringBuilder(stringStack.pop());
+                int count = countStack.pop();
+                for (int i = 0; i < count; i++) {
+                    cur.append(temp);
+                }
+            } else {
+                cur.append(c);
+            }
+        }
+
+        return cur.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string decodeString(string s) {
+        vector<string> stringStack;
+        vector<int> countStack;
+        string cur = "";
+        int k = 0;
+
+        for (char c : s) {
+            if (isdigit(c)) {
+                k = k * 10 + (c - '0');
+            } else if (c == '[') {
+                stringStack.push_back(cur);
+                countStack.push_back(k);
+                cur = "";
+                k = 0;
+            } else if (c == ']') {
+                string temp = cur;
+                cur = stringStack.back();
+                stringStack.pop_back();
+                int count = countStack.back();
+                countStack.pop_back();
+                for (int i = 0; i < count; i++) {
+                    cur += temp;
+                }
+            } else {
+                cur += c;
+            }
+        }
+
+        return cur;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string}
+     */
+    decodeString(s) {
+        const stringStack = [];
+        const countStack = [];
+        let cur = "";
+        let k = 0;
+
+        for (const c of s) {
+            if (!isNaN(c)) {
+                k = k * 10 + parseInt(c, 10);
+            } else if (c === "[") {
+                stringStack.push(cur);
+                countStack.push(k);
+                cur = "";
+                k = 0;
+            } else if (c === "]") {
+                const temp = cur;
+                cur = stringStack.pop();
+                const count = countStack.pop();
+                cur += temp.repeat(count);
+            } else {
+                cur += c;
+            }
+        }
+
+        return cur;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public string DecodeString(string s) {
+        Stack<string> stringStack = new Stack<string>();
+        Stack<int> countStack = new Stack<int>();
+        string cur = "";
+        int k = 0;
+
+        foreach (char c in s) {
+            if (char.IsDigit(c)) {
+                k = k * 10 + (c - '0');
+            } else if (c == '[') {
+                stringStack.Push(cur);
+                countStack.Push(k);
+                cur = "";
+                k = 0;
+            } else if (c == ']') {
+                string temp = cur;
+                cur = stringStack.Pop();
+                int count = countStack.Pop();
+                for (int i = 0; i < count; i++) {
+                    cur += temp;
+                }
+            } else {
+                cur += c;
+            }
+        }
+
+        return cur;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + N)$
+* Space complexity: $O(n + N)$
+
+> Where $n$ is the length of the input string and $N$ is the length of the output string.
\ No newline at end of file
diff --git a/articles/decode-ways.md b/articles/decode-ways.md
index eaf831995..c735d1d3f 100644
--- a/articles/decode-ways.md
+++ b/articles/decode-ways.md
@@ -117,6 +117,80 @@ public class Solution {
 }
 ```
 
+```go
+func numDecodings(s string) int {
+    return dfs(s, 0)
+}
+
+func dfs(s string, i int) int {
+    if i == len(s) {
+        return 1
+    }
+    if s[i] == '0' {
+        return 0
+    }
+    res := dfs(s, i+1)
+    if i < len(s)-1 {
+        if s[i] == '1' || (s[i] == '2' && s[i+1] < '7') {
+            res += dfs(s, i+2)
+        }
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun numDecodings(s: String): Int {
+        return dfs(s, 0)
+    }
+
+    fun dfs(s: String, i: Int): Int {
+        if (i == s.length) {
+            return 1
+        }
+        if (s[i] == '0') {
+            return 0
+        }
+        var res = dfs(s, i + 1)
+        if (i < s.length - 1) {
+            if (s[i] == '1' || (s[i] == '2' && s[i + 1] < '7')) {
+                res += dfs(s, i + 2)
+            }
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func numDecodings(_ s: String) -> Int {
+        let chars = Array(s)
+        
+        func dfs(_ i: Int) -> Int {
+            if i == chars.count {
+                return 1
+            }
+            if chars[i] == "0" {
+                return 0
+            }
+
+            var res = dfs(i + 1)
+            if i < chars.count - 1 {
+                if chars[i] == "1" || (chars[i] == "2" && chars[i + 1] < "7") {
+                    res += dfs(i + 2)
+                }
+            }
+
+            return res
+        }
+
+        return dfs(0)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -277,6 +351,87 @@ public class Solution {
 }
 ```
 
+```go
+func numDecodings(s string) int {
+    return dfs(s, 0, map[int]int{len(s): 1})
+}
+
+func dfs(s string, i int, dp map[int]int) int {
+    if val, ok := dp[i]; ok {
+        return val
+    }
+    if i == len(s) {
+        return 1
+    }
+    if s[i] == '0' {
+        return 0
+    }
+    res := dfs(s, i+1, dp)
+    if i+1 < len(s) && (s[i] == '1' || 
+       (s[i] == '2' && s[i+1] <= '6')) {
+        res += dfs(s, i+2, dp)
+    }
+    dp[i] = res
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun numDecodings(s: String): Int {
+        return dfs(s, 0, hashMapOf(s.length to 1))
+    }
+
+    fun dfs(s: String, i: Int, dp: HashMap<Int, Int>): Int {
+        if (i in dp) {
+            return dp[i]!!
+        }
+        if (i == s.length) {
+            return 1
+        }
+        if (s[i] == '0') {
+            return 0
+        }
+        var res = dfs(s, i + 1, dp)
+        if (i + 1 < s.length && (s[i] == '1' || 
+           (s[i] == '2' && s[i + 1] <= '6'))) {
+            res += dfs(s, i + 2, dp)
+        }
+        dp[i] = res
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func numDecodings(_ s: String) -> Int {
+        let chars = Array(s)
+        var dp = [Int: Int]()
+        dp[chars.count] = 1
+
+        func dfs(_ i: Int) -> Int {
+            if let cached = dp[i] {
+                return cached
+            }
+            if chars[i] == "0" {
+                return 0
+            }
+
+            var res = dfs(i + 1)
+            if i + 1 < chars.count, 
+               chars[i] == "1" || (chars[i] == "2" && "0123456".contains(chars[i + 1])) {
+                res += dfs(i + 2)
+            }
+            dp[i] = res
+            return res
+        }
+
+        return dfs(0)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -396,6 +551,69 @@ public class Solution {
 }
 ```
 
+```go
+func numDecodings(s string) int {
+    dp := make(map[int]int)
+    dp[len(s)] = 1
+    for i := len(s) - 1; i >= 0; i-- {
+        if s[i] == '0' {
+            dp[i] = 0
+        } else {
+            dp[i] = dp[i+1]
+            if i+1 < len(s) && (s[i] == '1' || 
+               (s[i] == '2' && s[i+1] <= '6')) {
+                dp[i] += dp[i+2]
+            }
+        }
+    }
+    return dp[0]
+}
+```
+
+```kotlin
+class Solution {
+    fun numDecodings(s: String): Int {
+        val dp = mutableMapOf(s.length to 1)
+        for (i in s.length - 1 downTo 0) {
+            if (s[i] == '0') {
+                dp[i] = 0
+            } else {
+                dp[i] = dp[i + 1] ?: 0
+                if (i + 1 < s.length && (s[i] == '1' || 
+                   (s[i] == '2' && s[i + 1] <= '6'))) {
+                    dp[i] = dp[i]!! + (dp[i + 2] ?: 0)
+                }
+            }
+        }
+        return dp[0] ?: 0
+    }
+}
+```
+
+```swift
+class Solution {
+    func numDecodings(_ s: String) -> Int {
+        let chars = Array(s)
+        var dp = [Int: Int]()
+        dp[chars.count] = 1
+
+        for i in stride(from: chars.count - 1, through: 0, by: -1) {
+            if chars[i] == "0" {
+                dp[i] = 0
+            } else {
+                dp[i] = dp[i + 1] ?? 0
+            }
+
+            if i + 1 < chars.count, 
+               chars[i] == "1" || (chars[i] == "2" && "0123456".contains(chars[i + 1])) {
+                dp[i]! += dp[i + 2] ?? 0
+            }
+        }
+        return dp[0] ?? 0
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -528,6 +746,76 @@ public class Solution {
 }
 ```
 
+```go
+func numDecodings(s string) int {
+    dp, dp2 := 0, 0
+    dp1 := 1
+    for i := len(s) - 1; i >= 0; i-- {
+        if s[i] == '0' {
+            dp = 0
+        } else {
+            dp = dp1
+        }
+        if i+1 < len(s) && (s[i] == '1' || 
+           s[i] == '2' && s[i+1] <= '6') {
+            dp += dp2
+        }
+        dp2 = dp1
+        dp1 = dp
+        dp = 0
+    }
+    return dp1
+}
+```
+
+```kotlin
+class Solution {
+    fun numDecodings(s: String): Int {
+        var dp = 0
+        var dp2 = 0
+        var dp1 = 1
+        for (i in s.length - 1 downTo 0) {
+            if (s[i] == '0') {
+                dp = 0
+            } else {
+                dp = dp1
+            }
+            if (i + 1 < s.length && (s[i] == '1' || 
+               (s[i] == '2' && s[i + 1] <= '6'))) {
+                dp += dp2
+            }
+            dp2 = dp1
+            dp1 = dp
+        }
+        return dp1
+    }
+}
+```
+
+```swift
+class Solution {
+    func numDecodings(_ s: String) -> Int {
+        let chars = Array(s)
+        var dp = 0, dp1 = 1, dp2 = 0
+
+        for i in stride(from: chars.count - 1, through: 0, by: -1) {
+            if chars[i] == "0" {
+                dp = 0
+            } else {
+                dp = dp1
+            }
+
+            if i + 1 < chars.count, 
+               chars[i] == "1" || (chars[i] == "2" && "0123456".contains(chars[i + 1])) {
+                dp += dp2
+            }
+            (dp, dp1, dp2) = (0, dp, dp1)
+        }
+        return dp1
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/delete-and-earn.md b/articles/delete-and-earn.md
new file mode 100644
index 000000000..ae00ea5db
--- /dev/null
+++ b/articles/delete-and-earn.md
@@ -0,0 +1,586 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def deleteAndEarn(self, nums: List[int]) -> int:
+        nums.sort()
+
+        def dfs(i):
+            if i >= len(nums):
+                return 0
+            
+            cur = nums[i]
+            pick = 0
+            while i < len(nums) and nums[i] == cur:
+                pick += nums[i]
+                i += 1
+            
+            res = dfs(i)
+            while i < len(nums) and nums[i] == 1 + cur:
+                i += 1
+            
+            res = max(res, pick + dfs(i))
+            return res
+        
+        return dfs(0)
+```
+
+```java
+public class Solution {
+    public int deleteAndEarn(int[] nums) {
+        Arrays.sort(nums);
+        return dfs(nums, 0);
+    }
+
+    private int dfs(int[] nums, int i) {
+        if (i >= nums.length) return 0;
+
+        int cur = nums[i], pick = 0;
+        while (i < nums.length && nums[i] == cur) {
+            pick += nums[i];
+            i++;
+        }
+
+        int res = dfs(nums, i);
+        while (i < nums.length && nums[i] == cur + 1) {
+            i++;
+        }
+
+        res = Math.max(res, pick + dfs(nums, i));
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int deleteAndEarn(vector<int>& nums) {
+        sort(nums.begin(), nums.end());
+        return dfs(nums, 0);
+    }
+
+private:
+    int dfs(const vector<int>& nums, int i) {
+        if (i >= nums.size()) return 0;
+
+        int cur = nums[i], pick = 0;
+        while (i < nums.size() && nums[i] == cur) {
+            pick += nums[i];
+            i++;
+        }
+
+        int res = dfs(nums, i);
+        while (i < nums.size() && nums[i] == cur + 1) {
+            i++;
+        }
+
+        res = max(res, pick + dfs(nums, i));
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    deleteAndEarn(nums) {
+        nums.sort((a, b) => a - b);
+
+        const dfs = (i) => {
+            if (i >= nums.length) return 0;
+    
+            let cur = nums[i], pick = 0;
+            while (i < nums.length && nums[i] === cur) {
+                pick += nums[i];
+                i++;
+            }
+    
+            let res = dfs(i);
+            while (i < nums.length && nums[i] === cur + 1) {
+                i++;
+            }
+    
+            res = Math.max(res, pick + dfs(i));
+            return res;
+        };
+
+        return dfs(0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def deleteAndEarn(self, nums: List[int]) -> int:
+        val = defaultdict(int)
+        for num in nums:
+            val[num] += num
+        nums = sorted(list(set(nums)))
+        memo = [-1] * len(nums)
+
+        def dfs(i):
+            if i >= len(nums):
+                return 0
+            if memo[i] != -1:
+                return memo[i]
+            
+            res = val[nums[i]]
+            if i + 1 < len(nums) and nums[i] + 1 == nums[i + 1]:
+                res += dfs(i + 2)
+            else:
+                res += dfs(i + 1)
+            
+            res = max(res, dfs(i + 1))
+            memo[i] = res
+            return res
+        
+        return dfs(0)
+```
+
+```java
+public class Solution {
+    private Map<Integer, Integer> val;
+    private int[] memo;
+
+    public int deleteAndEarn(int[] nums) {
+        val = new HashMap<>();
+        for (int num : nums) {
+            val.put(num, val.getOrDefault(num, 0) + num);
+        }
+
+        List<Integer> uniqueNums = new ArrayList<>(val.keySet());
+        Collections.sort(uniqueNums);
+        memo = new int[uniqueNums.size()];
+        Arrays.fill(memo, -1);
+
+        return dfs(uniqueNums, 0);
+    }
+
+    private int dfs(List<Integer> nums, int i) {
+        if (i >= nums.size()) return 0;
+        if (memo[i] != -1) return memo[i];
+
+        int res = val.get(nums.get(i));
+        if (i + 1 < nums.size() && nums.get(i) + 1 == nums.get(i + 1)) {
+            res += dfs(nums, i + 2);
+        } else {
+            res += dfs(nums, i + 1);
+        }
+
+        res = Math.max(res, dfs(nums, i + 1));
+        memo[i] = res;
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+    unordered_map<int, int> val;
+    vector<int> memo;
+
+public:
+    int deleteAndEarn(vector<int>& nums) {
+        for (int num : nums) {
+            val[num] += num;
+        }
+
+        vector<int> uniqueNums;
+        for (auto& pair : val) {
+            uniqueNums.push_back(pair.first);
+        }
+        sort(uniqueNums.begin(), uniqueNums.end());
+        memo.resize(uniqueNums.size(), -1);
+
+        return dfs(uniqueNums, 0);
+    }
+
+private:
+    int dfs(vector<int>& nums, int i) {
+        if (i >= nums.size()) return 0;
+        if (memo[i] != -1) return memo[i];
+
+        int res = val[nums[i]];
+        if (i + 1 < nums.size() && nums[i] + 1 == nums[i + 1]) {
+            res += dfs(nums, i + 2);
+        } else {
+            res += dfs(nums, i + 1);
+        }
+
+        res = max(res, dfs(nums, i + 1));
+        memo[i] = res;
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    deleteAndEarn(nums) {
+        const val = new Map();
+        nums.forEach(num => {
+            val.set(num, (val.get(num) || 0) + num);
+        });
+        const uniqueNums = Array.from(new Set(nums)).sort((a, b) => a - b);
+        const memo = Array(uniqueNums.length).fill(-1);
+
+        const dfs = (nums, i) => {
+            if (i >= nums.length) return 0;
+            if (memo[i] !== -1) return memo[i];
+
+            let res = val.get(nums[i]);
+            if (i + 1 < nums.length && nums[i] + 1 === nums[i + 1]) {
+                res += dfs(nums, i + 2);
+            } else {
+                res += dfs(nums, i + 1);
+            }
+
+            res = Math.max(res, dfs(nums, i + 1));
+            memo[i] = res;
+            return res;
+        };
+
+        return dfs(uniqueNums, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up) - I
+
+::tabs-start
+
+```python
+class Solution:
+    def deleteAndEarn(self, nums: List[int]) -> int:
+        val = defaultdict(int)
+        for num in nums:
+            val[num] += num
+        nums = sorted(list(set(nums)))
+        
+        dp = [0] * (len(nums) + 1)
+        for i in range(len(nums) - 1, -1, -1):
+            take = val[nums[i]]
+            if i + 1 < len(nums) and nums[i + 1] == nums[i] + 1:
+                take += dp[i + 2]
+            else:
+                take += dp[i + 1]
+            dp[i] = max(dp[i + 1], take)
+        
+        return dp[0]
+```
+
+```java
+public class Solution {
+    public int deleteAndEarn(int[] nums) {
+        Map<Integer, Integer> val = new HashMap<>();
+        for (int num : nums) val.put(num, val.getOrDefault(num, 0) + num);
+        List<Integer> sortedNums = new ArrayList<>(val.keySet());
+        Collections.sort(sortedNums);
+
+        int[] dp = new int[sortedNums.size() + 1];
+        for (int i = sortedNums.size() - 1; i >= 0; i--) {
+            int take = val.get(sortedNums.get(i));
+            if (i + 1 < sortedNums.size() && sortedNums.get(i + 1) == sortedNums.get(i) + 1) {
+                take += dp[i + 2];
+            } else {
+                take += dp[i + 1];
+            }
+            dp[i] = Math.max(dp[i + 1], take);
+        }
+
+        return dp[0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int deleteAndEarn(vector<int>& nums) {
+        unordered_map<int, int> val;
+        for (int num : nums) val[num] += num;
+        vector<int> sortedNums;
+        for (auto& [key, _] : val) sortedNums.push_back(key);
+        sort(sortedNums.begin(), sortedNums.end());
+        
+        vector<int> dp(sortedNums.size() + 1);
+        for (int i = sortedNums.size() - 1; i >= 0; i--) {
+            int take = val[sortedNums[i]];
+            if (i + 1 < sortedNums.size() && sortedNums[i + 1] == sortedNums[i] + 1) {
+                take += dp[i + 2];
+            } else {
+                take += dp[i + 1];
+            }
+            dp[i] = max(dp[i + 1], take);
+        }
+        
+        return dp[0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    deleteAndEarn(nums) {
+        const val = new Map();
+        nums.forEach(num => val.set(num, (val.get(num) || 0) + num));
+        const sortedNums = Array.from(val.keys()).sort((a, b) => a - b);
+
+        const dp = Array(sortedNums.length + 1).fill(0);
+        for (let i = sortedNums.length - 1; i >= 0; i--) {
+            let take = val.get(sortedNums[i]);
+            if (i + 1 < sortedNums.length && sortedNums[i + 1] === sortedNums[i] + 1) {
+                take += dp[i + 2];
+            } else {
+                take += dp[i + 1];
+            }
+            dp[i] = Math.max(dp[i + 1], take);
+        }
+
+        return dp[0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Dynamic Programming (Bottom-Up) - II
+
+::tabs-start
+
+```python
+class Solution:
+    def deleteAndEarn(self, nums: List[int]) -> int:
+        m = max(nums)
+        dp = [0] * (m + 2)
+
+        for num in nums:
+            dp[num] += num
+        for i in range(m - 1, 0, -1):
+            dp[i] = max(dp[i + 1], dp[i + 2] + dp[i])
+        
+        return dp[1]
+```
+
+```java
+public class Solution {
+    public int deleteAndEarn(int[] nums) {
+        int m = 0;
+        for (int num : nums) m = Math.max(m, num);
+
+        int[] dp = new int[m + 2];
+        for (int num : nums) dp[num] += num;
+        for (int i = m - 1; i > 0; i--) {
+            dp[i] = Math.max(dp[i + 1], dp[i + 2] + dp[i]);
+        }
+        return dp[1];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int deleteAndEarn(vector<int>& nums) {
+        int m = *max_element(nums.begin(), nums.end());
+        vector<int> dp(m + 2);
+        for (auto& num : nums) {
+            dp[num] += num;
+        }
+        
+        for (int i = m - 1; i > 0; i--) {
+            dp[i] = max(dp[i + 1], dp[i + 2] + dp[i]);
+        }
+        return dp[1];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    deleteAndEarn(nums) {
+        const m = Math.max(...nums);
+        const dp = new Int32Array(m + 2);
+        for (let num of nums) {
+            dp[num] += num;
+        }
+
+        for (let i = m - 1; i > 0; i--) {
+            dp[i] = Math.max(dp[i + 1], dp[i + 2] + dp[i]);
+        }
+        return dp[1];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m + n)$
+* Space complexity: $O(m)$
+
+> Where $m$ is the maximum element in the array and $n$ is the size of the array.
+
+---
+
+## 5. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def deleteAndEarn(self, nums: List[int]) -> int:
+        count = Counter(nums)
+        nums = sorted(list(set(nums)))
+
+        earn1, earn2 = 0, 0
+        for i in range(len(nums)):
+            curEarn = nums[i] * count[nums[i]]
+            if i > 0 and nums[i] == nums[i - 1] + 1:
+                temp = earn2
+                earn2 = max(curEarn + earn1, earn2)
+                earn1 = temp
+            else:
+                temp = earn2
+                earn2 = curEarn + earn2
+                earn1 = temp
+        return earn2
+```
+
+```java
+public class Solution {
+    public int deleteAndEarn(int[] nums) {
+        Map<Integer, Integer> count = new HashMap<>();
+        for (int num : nums) count.put(num, count.getOrDefault(num, 0) + num);
+        List<Integer> uniqueNums = new ArrayList<>(count.keySet());
+        Collections.sort(uniqueNums);
+
+        int earn1 = 0, earn2 = 0;
+        for (int i = 0; i < uniqueNums.size(); i++) {
+            int curEarn = count.get(uniqueNums.get(i));
+            if (i > 0 && uniqueNums.get(i) == uniqueNums.get(i - 1) + 1) {
+                int temp = earn2;
+                earn2 = Math.max(curEarn + earn1, earn2);
+                earn1 = temp;
+            } else {
+                int temp = earn2;
+                earn2 = curEarn + earn2;
+                earn1 = temp;
+            }
+        }
+        return earn2;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int deleteAndEarn(vector<int>& nums) {
+        unordered_map<int, int> count;
+        for (int num : nums) count[num] += num;
+        vector<int> uniqueNums;
+        for (auto& pair : count) uniqueNums.push_back(pair.first);
+        sort(uniqueNums.begin(), uniqueNums.end());
+
+        int earn1 = 0, earn2 = 0;
+        for (int i = 0; i < uniqueNums.size(); i++) {
+            int curEarn = count[uniqueNums[i]];
+            if (i > 0 && uniqueNums[i] == uniqueNums[i - 1] + 1) {
+                int temp = earn2;
+                earn2 = max(curEarn + earn1, earn2);
+                earn1 = temp;
+            } else {
+                int temp = earn2;
+                earn2 = curEarn + earn2;
+                earn1 = temp;
+            }
+        }
+        return earn2;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    deleteAndEarn(nums) {
+        const count = new Map();
+        nums.forEach(num => count.set(num, (count.get(num) || 0) + num));
+        const uniqueNums = [...count.keys()].sort((a, b) => a - b);
+
+        let earn1 = 0, earn2 = 0;
+        for (let i = 0; i < uniqueNums.length; i++) {
+            const curEarn = count.get(uniqueNums[i]);
+            if (i > 0 && uniqueNums[i] === uniqueNums[i - 1] + 1) {
+                const temp = earn2;
+                earn2 = Math.max(curEarn + earn1, earn2);
+                earn1 = temp;
+            } else {
+                const temp = earn2;
+                earn2 = curEarn + earn2;
+                earn1 = temp;
+            }
+        }
+        return earn2;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/delete-leaves-with-a-given-value.md b/articles/delete-leaves-with-a-given-value.md
new file mode 100644
index 000000000..add3a0494
--- /dev/null
+++ b/articles/delete-leaves-with-a-given-value.md
@@ -0,0 +1,719 @@
+## 1. Recursion (Postorder Traversal)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def removeLeafNodes(self, root: Optional[TreeNode], target: int) -> Optional[TreeNode]:
+        if not root:
+            return None
+
+        root.left = self.removeLeafNodes(root.left, target)
+        root.right = self.removeLeafNodes(root.right, target)
+
+        if not root.left and not root.right and root.val == target:
+            return None
+
+        return root
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode removeLeafNodes(TreeNode root, int target) {
+        if (root == null) {
+            return null;
+        }
+
+        root.left = removeLeafNodes(root.left, target);
+        root.right = removeLeafNodes(root.right, target);
+
+        if (root.left == null && root.right == null && root.val == target) {
+            return null;
+        }
+
+        return root;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    TreeNode* removeLeafNodes(TreeNode* root, int target) {
+        if (!root) {
+            return nullptr;
+        }
+
+        root->left = removeLeafNodes(root->left, target);
+        root->right = removeLeafNodes(root->right, target);
+
+        if (!root->left && !root->right && root->val == target) {
+            return nullptr;
+        }
+
+        return root;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @param {number} target
+     * @return {TreeNode}
+     */
+    removeLeafNodes(root, target) {
+        if (!root) {
+            return null;
+        }
+
+        root.left = this.removeLeafNodes(root.left, target);
+        root.right = this.removeLeafNodes(root.right, target);
+
+        if (!root.left && !root.right && root.val === target) {
+            return null;
+        }
+
+        return root;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode RemoveLeafNodes(TreeNode root, int target) {
+        if (root == null) return null;
+
+        root.left = RemoveLeafNodes(root.left, target);
+        root.right = RemoveLeafNodes(root.right, target);
+
+        if (root.left == null && root.right == null && root.val == target) {
+            return null;
+        }
+
+        return root;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Iterative Postorder Traversal
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def removeLeafNodes(self, root: Optional[TreeNode], target: int) -> Optional[TreeNode]:
+        stack = [root]
+        visit = set()
+        parents = {root: None}
+
+        while stack:
+            node = stack.pop()
+            if not node.left and not node.right:
+                if node.val == target:
+                    p = parents[node]
+                    if not p:
+                        return None
+                    if p.left == node:
+                        p.left = None
+                    if p.right == node:
+                        p.right = None
+            elif node not in visit:
+                visit.add(node)
+                stack.append(node)
+                if node.left:
+                    stack.append(node.left)
+                    parents[node.left] = node
+                if node.right:
+                    stack.append(node.right)
+                    parents[node.right] = node
+
+        return root
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode removeLeafNodes(TreeNode root, int target) {
+        Stack<TreeNode> stack = new Stack<>();
+        Set<TreeNode> visit = new HashSet<>();
+        Map<TreeNode, TreeNode> parents = new HashMap<>();
+        parents.put(root, null);
+        stack.push(root);
+
+        while (!stack.isEmpty()) {
+            TreeNode node = stack.pop();
+            if (node.left == null && node.right == null) {
+                if (node.val == target) {
+                    TreeNode p = parents.get(node);
+                    if (p == null) {
+                        return null;
+                    }
+                    if (p.left == node) {
+                        p.left = null;
+                    }
+                    if (p.right == node) {
+                        p.right = null;
+                    }
+                }
+            } else if (!visit.contains(node)) {
+                visit.add(node);
+                stack.push(node);
+                if (node.left != null) {
+                    stack.push(node.left);
+                    parents.put(node.left, node);
+                }
+                if (node.right != null) {
+                    stack.push(node.right);
+                    parents.put(node.right, node);
+                }
+            }
+        }
+
+        return root;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    TreeNode* removeLeafNodes(TreeNode* root, int target) {
+        stack<TreeNode*> stack;
+        unordered_set<TreeNode*> visit;
+        unordered_map<TreeNode*, TreeNode*> parents;
+        parents[root] = nullptr;
+        stack.push(root);
+
+        while (!stack.empty()) {
+            TreeNode* node = stack.top();
+            stack.pop();
+            if (!node->left && !node->right) {
+                if (node->val == target) {
+                    TreeNode* p = parents[node];
+                    if (!p) {
+                        return nullptr;
+                    }
+                    if (p->left == node) {
+                        p->left = nullptr;
+                    }
+                    if (p->right == node) {
+                        p->right = nullptr;
+                    }
+                }
+            } else if (visit.find(node) == visit.end()) {
+                visit.insert(node);
+                stack.push(node);
+                if (node->left) {
+                    stack.push(node->left);
+                    parents[node->left] = node;
+                }
+                if (node->right) {
+                    stack.push(node->right);
+                    parents[node->right] = node;
+                }
+            }
+        }
+
+        return root;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @param {number} target
+     * @return {TreeNode}
+     */
+    removeLeafNodes(root, target) {
+        const stack = [root];
+        const visit = new Set();
+        const parents = new Map();
+        parents.set(root, null);
+
+        while (stack.length > 0) {
+            const node = stack.pop();
+            if (!node.left && !node.right) {
+                if (node.val === target) {
+                    const p = parents.get(node);
+                    if (!p) {
+                        return null;
+                    }
+                    if (p.left === node) {
+                        p.left = null;
+                    }
+                    if (p.right === node) {
+                        p.right = null;
+                    }
+                }
+            } else if (!visit.has(node)) {
+                visit.add(node);
+                stack.push(node);
+                if (node.left) {
+                    stack.push(node.left);
+                    parents.set(node.left, node);
+                }
+                if (node.right) {
+                    stack.push(node.right);
+                    parents.set(node.right, node);
+                }
+            }
+        }
+
+        return root;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode RemoveLeafNodes(TreeNode root, int target) {
+        if (root == null) return null;
+
+        Stack<TreeNode> stack = new Stack<TreeNode>();
+        HashSet<TreeNode> visited = new HashSet<TreeNode>();
+        Dictionary<TreeNode, TreeNode> parents = new Dictionary<TreeNode, TreeNode>();
+
+        stack.Push(root);
+        parents[root] = null;
+
+        while (stack.Count > 0) {
+            TreeNode node = stack.Pop();
+
+            if (node.left == null && node.right == null) {
+                if (node.val == target) {
+                    TreeNode parent = parents[node];
+                    if (parent == null) {
+                        return null;
+                    }
+                    if (parent.left == node) parent.left = null;
+                    if (parent.right == node) parent.right = null;
+                }
+            } else if (!visited.Contains(node)) {
+                visited.Add(node);
+                stack.Push(node);
+                if (node.left != null) {
+                    stack.Push(node.left);
+                    parents[node.left] = node;
+                }
+                if (node.right != null) {
+                    stack.Push(node.right);
+                    parents[node.right] = node;
+                }
+            }
+        }
+
+        return root;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Iterative Postorder Traversal (Optimal)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def removeLeafNodes(self, root: Optional[TreeNode], target: int) -> Optional[TreeNode]:
+        if not root:
+            return None
+
+        stack = []
+        cur = root
+        visited = None
+
+        while stack or cur:
+            while cur:
+                stack.append(cur)
+                cur = cur.left
+
+            cur = stack[-1]
+            if cur.right and cur.right != visited:
+                cur = cur.right
+                continue
+
+            stack.pop()
+            if not cur.left and not cur.right and cur.val == target:
+                if not stack:
+                    return None
+
+                parent = stack[-1]
+                if parent.left == cur:
+                    parent.left = None
+                elif parent.right == cur:
+                    parent.right = None
+            else:
+                visited = cur
+
+            cur = None
+
+        return root
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode removeLeafNodes(TreeNode root, int target) {
+        if (root == null) return null;
+
+        Stack<TreeNode> stack = new Stack<>();
+        TreeNode cur = root, visited = null;
+
+        while (!stack.isEmpty() || cur != null) {
+            while (cur != null) {
+                stack.push(cur);
+                cur = cur.left;
+            }
+
+            cur = stack.peek();
+            if (cur.right != null && cur.right != visited) {
+                cur = cur.right;
+                continue;
+            }
+
+            stack.pop();
+            if (cur.left == null && cur.right == null && cur.val == target) {
+                if (stack.isEmpty()) return null;
+
+                TreeNode parent = stack.peek();
+                if (parent.left == cur) {
+                    parent.left = null;
+                } else if (parent.right == cur) {
+                    parent.right = null;
+                }
+            } else {
+                visited = cur;
+            }
+
+            cur = null;
+        }
+
+        return root;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    TreeNode* removeLeafNodes(TreeNode* root, int target) {
+        if (!root) return nullptr;
+
+        stack<TreeNode*> stack;
+        TreeNode* cur = root;
+        TreeNode* visited = nullptr;
+
+        while (!stack.empty() || cur) {
+            while (cur) {
+                stack.push(cur);
+                cur = cur->left;
+            }
+
+            cur = stack.top();
+            if (cur->right && cur->right != visited) {
+                cur = cur->right;
+                continue;
+            }
+
+            stack.pop();
+            if (!cur->left && !cur->right && cur->val == target) {
+                if (stack.empty()) return nullptr;
+
+                TreeNode* parent = stack.top();
+                if (parent->left == cur) {
+                    parent->left = nullptr;
+                } else if (parent->right == cur) {
+                    parent->right = nullptr;
+                }
+            } else {
+                visited = cur;
+            }
+
+            cur = nullptr;
+        }
+
+        return root;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @param {number} target
+     * @return {TreeNode}
+     */
+    removeLeafNodes(root, target) {
+        if (!root) return null;
+
+        const stack = [];
+        let cur = root, visited = null;
+
+        while (stack.length > 0 || cur !== null) {
+            while (cur !== null) {
+                stack.push(cur);
+                cur = cur.left;
+            }
+
+            cur = stack[stack.length - 1];
+            if (cur.right && cur.right !== visited) {
+                cur = cur.right;
+                continue;
+            }
+
+            stack.pop();
+            if (!cur.left && !cur.right && cur.val === target) {
+                if (stack.length === 0) return null;
+
+                const parent = stack[stack.length - 1];
+                if (parent.left === cur) {
+                    parent.left = null;
+                } else if (parent.right === cur) {
+                    parent.right = null;
+                }
+            } else {
+                visited = cur;
+            }
+
+            cur = null;
+        }
+
+        return root;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode RemoveLeafNodes(TreeNode root, int target) {
+        if (root == null) return null;
+
+        Stack<TreeNode> stack = new Stack<TreeNode>();
+        TreeNode cur = root;
+        TreeNode visited = null;
+
+        while (stack.Count > 0 || cur != null) {
+            while (cur != null) {
+                stack.Push(cur);
+                cur = cur.left;
+            }
+
+            cur = stack.Peek();
+            if (cur.right != null && cur.right != visited) {
+                cur = cur.right;
+                continue;
+            }
+
+            stack.Pop();
+            if (cur.left == null && cur.right == null && cur.val == target) {
+                if (stack.Count == 0) return null;
+
+                TreeNode parent = stack.Peek();
+                if (parent.left == cur) {
+                    parent.left = null;
+                } else if (parent.right == cur) {
+                    parent.right = null;
+                }
+            } else {
+                visited = cur;
+            }
+
+            cur = null;
+        }
+
+        return root;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/delete-node-in-a-bst.md b/articles/delete-node-in-a-bst.md
new file mode 100644
index 000000000..0a9617193
--- /dev/null
+++ b/articles/delete-node-in-a-bst.md
@@ -0,0 +1,790 @@
+## 1. Recursion - I
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def deleteNode(self, root: Optional[TreeNode], key: int) -> Optional[TreeNode]:
+        if not root:
+            return root
+
+        if key > root.val:
+            root.right = self.deleteNode(root.right, key)
+        elif key < root.val:
+            root.left = self.deleteNode(root.left, key)
+        else:
+            if not root.left:
+                return root.right
+            elif not root.right:
+                return root.left
+
+            cur = root.right
+            while cur.left:
+                cur = cur.left
+            root.val = cur.val
+            root.right = self.deleteNode(root.right, root.val)
+
+        return root
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode deleteNode(TreeNode root, int key) {
+        if (root == null) return root;
+
+        if (key > root.val) {
+            root.right = deleteNode(root.right, key);
+        } else if (key < root.val) {
+            root.left = deleteNode(root.left, key);
+        } else {
+            if (root.left == null) return root.right;
+            if (root.right == null) return root.left;
+
+            TreeNode cur = root.right;
+            while (cur.left != null) {
+                cur = cur.left;
+            }
+            root.val = cur.val;
+            root.right = deleteNode(root.right, root.val);
+        }
+
+        return root;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    TreeNode* deleteNode(TreeNode* root, int key) {
+        if (!root) return root;
+
+        if (key > root->val) {
+            root->right = deleteNode(root->right, key);
+        } else if (key < root->val) {
+            root->left = deleteNode(root->left, key);
+        } else {
+            if (!root->left) return root->right;
+            if (!root->right) return root->left;
+
+            TreeNode* cur = root->right;
+            while (cur->left) {
+                cur = cur->left;
+            }
+            root->val = cur->val;
+            root->right = deleteNode(root->right, root->val);
+        }
+
+        return root;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @param {number} key
+     * @return {TreeNode}
+     */
+    deleteNode(root, key) {
+        if (!root) return root;
+
+        if (key > root.val) {
+            root.right = this.deleteNode(root.right, key);
+        } else if (key < root.val) {
+            root.left = this.deleteNode(root.left, key);
+        } else {
+            if (!root.left) return root.right;
+            if (!root.right) return root.left;
+
+            let cur = root.right;
+            while (cur.left) {
+                cur = cur.left;
+            }
+            root.val = cur.val;
+            root.right = this.deleteNode(root.right, root.val);
+        }
+
+        return root;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode DeleteNode(TreeNode root, int key) {
+        if (root == null) return null;
+
+        if (key > root.val) {
+            root.right = DeleteNode(root.right, key);
+        } else if (key < root.val) {
+            root.left = DeleteNode(root.left, key);
+        } else {
+            if (root.left == null) return root.right;
+            if (root.right == null) return root.left;
+
+            TreeNode cur = root.right;
+            while (cur.left != null) {
+                cur = cur.left;
+            }
+            root.val = cur.val;
+            root.right = DeleteNode(root.right, root.val);
+        }
+
+        return root;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(h)$
+* Space complexity: $O(h)$ for the recursion stack.
+
+> Where $h$ is the height of the given binary search tree.
+
+---
+
+## 2. Recursion - II
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def deleteNode(self, root: Optional[TreeNode], key: int) -> Optional[TreeNode]:
+        if not root:
+            return root
+
+        if key > root.val:
+            root.right = self.deleteNode(root.right, key)
+        elif key < root.val:
+            root.left = self.deleteNode(root.left, key)
+        else:
+            if not root.left:
+                return root.right
+            elif not root.right:
+                return root.left
+
+            cur = root.right
+            while cur.left:
+                cur = cur.left
+            cur.left = root.left
+            res = root.right
+            del root
+            return res
+
+        return root
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode deleteNode(TreeNode root, int key) {
+        if (root == null) return root;
+
+        if (key > root.val) {
+            root.right = deleteNode(root.right, key);
+        } else if (key < root.val) {
+            root.left = deleteNode(root.left, key);
+        } else {
+            if (root.left == null) return root.right;
+            if (root.right == null) return root.left;
+
+            TreeNode cur = root.right;
+            while (cur.left != null) {
+                cur = cur.left;
+            }
+            cur.left = root.left;
+            TreeNode res = root.right;
+            root = null;
+            return res;
+        }
+
+        return root;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    TreeNode* deleteNode(TreeNode* root, int key) {
+        if (!root) return root;
+
+        if (key > root->val) {
+            root->right = deleteNode(root->right, key);
+        } else if (key < root->val) {
+            root->left = deleteNode(root->left, key);
+        } else {
+            if (!root->left) return root->right;
+            if (!root->right) return root->left;
+
+            TreeNode* cur = root->right;
+            while (cur->left) {
+                cur = cur->left;
+            }
+            cur->left = root->left;
+            TreeNode* res = root->right;
+            delete root;
+            return res;
+        }
+
+        return root;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @param {number} key
+     * @return {TreeNode}
+     */
+    deleteNode(root, key) {
+        if (!root) return root;
+
+        if (key > root.val) {
+            root.right = this.deleteNode(root.right, key);
+        } else if (key < root.val) {
+            root.left = this.deleteNode(root.left, key);
+        } else {
+            if (!root.left) return root.right;
+            if (!root.right) return root.left;
+
+            let cur = root.right;
+            while (cur.left) {
+                cur = cur.left;
+            }
+            cur.left = root.left;
+            let res = root.right;
+            root = null;
+            return res;
+        }
+
+        return root;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode DeleteNode(TreeNode root, int key) {
+        if (root == null) return null;
+
+        if (key > root.val) {
+            root.right = DeleteNode(root.right, key);
+        } else if (key < root.val) {
+            root.left = DeleteNode(root.left, key);
+        } else {
+            if (root.left == null) return root.right;
+            if (root.right == null) return root.left;
+
+            TreeNode cur = root.right;
+            while (cur.left != null) {
+                cur = cur.left;
+            }
+            cur.left = root.left;
+            TreeNode res = root.right;
+            return res;
+        }
+
+        return root;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(h)$
+* Space complexity: $O(h)$ for the recursion stack.
+
+> Where $h$ is the height of the given binary search tree.
+
+---
+
+## 3. Iteration
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def deleteNode(self, root: Optional[TreeNode], key: int) -> Optional[TreeNode]:
+        if not root:
+            return root
+        
+        parent = None
+        cur = root
+        
+        # Find the node to delete
+        while cur and cur.val != key:
+            parent = cur
+            if key > cur.val:
+                cur = cur.right
+            else:
+                cur = cur.left
+        
+        if not cur:
+            return root
+        
+        # Node with only one child or no child
+        if not cur.left or not cur.right:
+            child = cur.left if cur.left else cur.right
+            if not parent:
+                return child
+            if parent.left == cur:
+                parent.left = child
+            else:
+                parent.right = child
+        else:
+            # Node with two children
+            par = None  # parent of right subTree min node
+            delNode = cur
+            cur = cur.right
+            while cur.left:
+                par = cur
+                cur = cur.left
+            
+            if par:  # if there was a left traversal
+                par.left = cur.right
+                cur.right = delNode.right
+            
+            cur.left = delNode.left
+            
+            if not parent:  # if we're deleting root
+                return cur
+                
+            if parent.left == delNode:
+                parent.left = cur
+            else:
+                parent.right = cur
+        
+        return root
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode deleteNode(TreeNode root, int key) {
+        if (root == null) return root;
+        
+        TreeNode parent = null;
+        TreeNode cur = root;
+        
+        // Find the node to delete
+        while (cur != null && cur.val != key) {
+            parent = cur;
+            if (key > cur.val) {
+                cur = cur.right;
+            } else {
+                cur = cur.left;
+            }
+        }
+        
+        if (cur == null) return root;
+        
+        // Node with only one child or no child
+        if (cur.left == null || cur.right == null) {
+            TreeNode child = (cur.left != null) ? cur.left : cur.right;
+            if (parent == null) return child;
+            if (parent.left == cur) {
+                parent.left = child;
+            } else {
+                parent.right = child;
+            }
+        } else {
+            // Node with two children
+            TreeNode par = null; // parent of right subtree's min node
+            TreeNode delNode = cur;
+            cur = cur.right;
+            while (cur.left != null) {
+                par = cur;
+                cur = cur.left;
+            }
+            
+            if (par != null) { // if there was a left traversal
+                par.left = cur.right;
+                cur.right = delNode.right;
+            }
+            cur.left = delNode.left;
+            
+            if (parent == null) return cur; // if deleting root
+            
+            if (parent.left == delNode) {
+                parent.left = cur;
+            } else {
+                parent.right = cur;
+            }
+        }
+        
+        return root;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    TreeNode* deleteNode(TreeNode* root, int key) {
+        if (!root) return root;
+        
+        TreeNode* parent = nullptr;
+        TreeNode* cur = root;
+        
+        // Find the node to delete
+        while (cur && cur->val != key) {
+            parent = cur;
+            if (key > cur->val) {
+                cur = cur->right;
+            } else {
+                cur = cur->left;
+            }
+        }
+        
+        if (!cur) return root;
+        
+        // Node with only one child or no child
+        if (!cur->left || !cur->right) {
+            TreeNode* child = cur->left ? cur->left : cur->right;
+            if (!parent) return child;
+            if (parent->left == cur) {
+                parent->left = child;
+            } else {
+                parent->right = child;
+            }
+        } else {
+            // Node with two children
+            TreeNode* par = nullptr; // parent of right subtree's min node
+            TreeNode* delNode = cur;
+            cur = cur->right;
+            while (cur->left) {
+                par = cur;
+                cur = cur->left;
+            }
+            
+            if (par) { // if there was a left traversal
+                par->left = cur->right;
+                cur->right = delNode->right;
+            }
+            cur->left = delNode->left;
+            
+            if (!parent) return cur; // if deleting root
+            
+            if (parent->left == delNode) {
+                parent->left = cur;
+            } else {
+                parent->right = cur;
+            }
+        }
+        
+        return root;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @param {number} key
+     * @return {TreeNode}
+     */
+    deleteNode(root, key) {
+        if (!root) return root;
+        
+        let parent = null;
+        let cur = root;
+        
+        // Find the node to delete
+        while (cur && cur.val !== key) {
+            parent = cur;
+            if (key > cur.val) {
+                cur = cur.right;
+            } else {
+                cur = cur.left;
+            }
+        }
+        
+        if (!cur) return root;
+        
+        // Node with only one child or no child
+        if (!cur.left || !cur.right) {
+            const child = cur.left || cur.right;
+            if (!parent) return child;
+            if (parent.left === cur) {
+                parent.left = child;
+            } else {
+                parent.right = child;
+            }
+        } else {
+            // Node with two children
+            let par = null; // parent of right subtree's min node
+            const delNode = cur;
+            cur = cur.right;
+            while (cur.left) {
+                par = cur;
+                cur = cur.left;
+            }
+            
+            if (par) { // if there was a left traversal
+                par.left = cur.right;
+                cur.right = delNode.right;
+            }
+            cur.left = delNode.left;
+            
+            if (!parent) return cur; // if deleting root
+            
+            if (parent.left === delNode) {
+                parent.left = cur;
+            } else {
+                parent.right = cur;
+            }
+        }
+        
+        return root;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode DeleteNode(TreeNode root, int key) {
+        if (root == null) return null;
+
+        TreeNode parent = null;
+        TreeNode cur = root;
+
+        // Find the node to delete
+        while (cur != null && cur.val != key) {
+            parent = cur;
+            if (key > cur.val) {
+                cur = cur.right;
+            } else {
+                cur = cur.left;
+            }
+        }
+
+        if (cur == null) return root;
+
+        // Node with one or no child
+        if (cur.left == null || cur.right == null) {
+            TreeNode child = cur.left != null ? cur.left : cur.right;
+
+            if (parent == null) {
+                return child;
+            }
+
+            if (parent.left == cur) {
+                parent.left = child;
+            } else {
+                parent.right = child;
+            }
+        } else {
+            // Node with two children
+            TreeNode par = null;
+            TreeNode delNode = cur;
+            cur = cur.right;
+            while (cur.left != null) {
+                par = cur;
+                cur = cur.left;
+            }
+
+            if (par != null) {
+                par.left = cur.right;
+                cur.right = delNode.right;
+            }
+
+            cur.left = delNode.left;
+
+            if (parent == null) {
+                return cur;
+            }
+
+            if (parent.left == delNode) {
+                parent.left = cur;
+            } else {
+                parent.right = cur;
+            }
+        }
+
+        return root;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(h)$
+* Space complexity: $O(1)$ extra space.
+
+> Where $h$ is the height of the given binary search tree.
\ No newline at end of file
diff --git a/articles/depth-of-binary-tree.md b/articles/depth-of-binary-tree.md
index 1813a739c..88a35751d 100644
--- a/articles/depth-of-binary-tree.md
+++ b/articles/depth-of-binary-tree.md
@@ -126,12 +126,85 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func maxDepth(root *TreeNode) int {
+    if root == nil {
+        return 0
+    }
+    return 1 + max(maxDepth(root.Left), maxDepth(root.Right))
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    fun maxDepth(root: TreeNode?): Int {
+        if (root == null) {
+            return 0
+        }
+        return 1 + maxOf(maxDepth(root.left), maxDepth(root.right))
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func maxDepth(_ root: TreeNode?) -> Int {
+        guard let root = root else { return 0 }
+        return 1 + max(maxDepth(root.left), maxDepth(root.right))
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n)$
-* Space complexity: $O(n)$
+* Space complexity: $O(h)$  
+  * Best Case ([balanced tree](https://www.geeksforgeeks.org/balanced-binary-tree/)): $O(log(n))$
+  * Worst Case ([degenerate tree](https://www.geeksforgeeks.org/introduction-to-degenerate-binary-tree/)): $O(n)$
+
+> Where $n$ is the number of nodes in the tree and $h$ is the height of the tree.
 
 ---
 
@@ -312,6 +385,120 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func maxDepth(root *TreeNode) int {
+    if root == nil {
+        return 0
+    }
+    
+    stack := list.New()
+    stack.PushBack([]interface{}{root, 1})
+    res := 0
+    
+    for stack.Len() > 0 {
+        back := stack.Back()
+        stack.Remove(back)
+        pair := back.Value.([]interface{})
+        node := pair[0].(*TreeNode)
+        depth := pair[1].(int)
+        
+        if node != nil {
+            res = max(res, depth)
+            stack.PushBack([]interface{}{node.Left, depth + 1})
+            stack.PushBack([]interface{}{node.Right, depth + 1})
+        }
+    }
+    
+    return res
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    fun maxDepth(root: TreeNode?): Int {
+        if (root == null) {
+            return 0
+        }
+        
+        val stack = ArrayDeque<Pair<TreeNode?, Int>>()
+        stack.addLast(Pair(root, 1))
+        var res = 0
+        
+        while (stack.isNotEmpty()) {
+            val (node, depth) = stack.removeLast()
+            
+            if (node != null) {
+                res = maxOf(res, depth)
+                stack.addLast(Pair(node.left, depth + 1))
+                stack.addLast(Pair(node.right, depth + 1))
+            }
+        }
+        
+        return res
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func maxDepth(_ root: TreeNode?) -> Int {
+        var stack: [(TreeNode?, Int)] = [(root, 1)]
+        var res = 0
+
+        while !stack.isEmpty {
+            let (node, depth) = stack.removeLast()
+
+            if let node = node {
+                res = max(res, depth)
+                stack.append((node.left, depth + 1))
+                stack.append((node.right, depth + 1))
+            }
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -518,6 +705,124 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func maxDepth(root *TreeNode) int {
+   if root == nil {
+       return 0
+   }
+   
+   q := linkedlistqueue.New()
+   q.Enqueue(root)
+   level := 0
+   
+   for !q.Empty() {
+       size := q.Size()
+       
+       for i := 0; i < size; i++ {
+           val, _ := q.Dequeue()
+           node := val.(*TreeNode)
+           
+           if node.Left != nil {
+               q.Enqueue(node.Left)
+           }
+           if node.Right != nil {
+               q.Enqueue(node.Right)
+           }
+       }
+       level++
+   }
+   
+   return level
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    fun maxDepth(root: TreeNode?): Int {
+        if (root == null) {
+            return 0
+        }
+        
+        val q = ArrayDeque<TreeNode>()
+        q.addLast(root)
+        var level = 0
+        
+        while (q.isNotEmpty()) {
+            val size = q.size
+            
+            repeat(size) {
+                val node = q.removeFirst()
+                
+                node.left?.let { q.addLast(it) }
+                node.right?.let { q.addLast(it) }
+            }
+            level++
+        }
+        
+        return level
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func maxDepth(_ root: TreeNode?) -> Int {
+        var queue = Deque<TreeNode>()
+        if let root = root {
+            queue.append(root)
+        }
+
+        var level = 0
+        while !queue.isEmpty {
+            for _ in 0..<queue.count {
+                let node = queue.removeFirst()
+                if let left = node.left {
+                    queue.append(left)
+                }
+                if let right = node.right {
+                    queue.append(right)
+                }
+            }
+            level += 1
+        }
+        return level
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/design-a-food-rating-system.md b/articles/design-a-food-rating-system.md
new file mode 100644
index 000000000..7be2642c1
--- /dev/null
+++ b/articles/design-a-food-rating-system.md
@@ -0,0 +1,457 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class FoodRatings:
+
+    def __init__(self, foods: List[str], cuisines: List[str], ratings: List[int]):
+        self.foodToRating = {} # food -> rating
+        self.cuisineToFood = defaultdict(list) # cuisine -> [food]
+        for i in range(len(foods)):
+            self.foodToRating[foods[i]] = ratings[i]
+            self.cuisineToFood[cuisines[i]].append(foods[i])
+
+    def changeRating(self, food: str, newRating: int) -> None:
+        self.foodToRating[food] = newRating
+
+    def highestRated(self, cuisine: str) -> str:
+        maxR, res = 0, ""
+        for food in self.cuisineToFood[cuisine]:
+            r = self.foodToRating[food]
+            if r > maxR or (r == maxR and food < res):
+                res = food
+                maxR = r
+        return res
+```
+
+```java
+public class FoodRatings {
+    private Map<String, Integer> foodToRating;
+    private Map<String, List<String>> cuisineToFood;
+
+    public FoodRatings(String[] foods, String[] cuisines, int[] ratings) {
+        foodToRating = new HashMap<>();
+        cuisineToFood = new HashMap<>();
+        for (int i = 0; i < foods.length; i++) {
+            foodToRating.put(foods[i], ratings[i]);
+            cuisineToFood.computeIfAbsent(cuisines[i], k -> new ArrayList<>()).add(foods[i]);
+        }
+    }
+
+    public void changeRating(String food, int newRating) {
+        foodToRating.put(food, newRating);
+    }
+
+    public String highestRated(String cuisine) {
+        int maxR = 0;
+        String res = "";
+        for (String food : cuisineToFood.get(cuisine)) {
+            int r = foodToRating.get(food);
+            if (r > maxR || (r == maxR && food.compareTo(res) < 0)) {
+                res = food;
+                maxR = r;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class FoodRatings {
+private:
+    unordered_map<string, int> foodToRating;
+    unordered_map<string, vector<string>> cuisineToFood;
+
+public:
+    FoodRatings(vector<string>& foods, vector<string>& cuisines, vector<int>& ratings) {
+        for (size_t i = 0; i < foods.size(); i++) {
+            foodToRating[foods[i]] = ratings[i];
+            cuisineToFood[cuisines[i]].push_back(foods[i]);
+        }
+    }
+
+    void changeRating(string food, int newRating) {
+        foodToRating[food] = newRating;
+    }
+
+    string highestRated(string cuisine) {
+        int maxR = 0;
+        string res = "";
+        for (const string& food : cuisineToFood[cuisine]) {
+            int r = foodToRating[food];
+            if (r > maxR || (r == maxR && food < res)) {
+                res = food;
+                maxR = r;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class FoodRatings {
+    /**
+     * @param {string[]} foods
+     * @param {string[]} cuisines
+     * @param {number[]} ratings
+     */
+    constructor(foods, cuisines, ratings) {
+        this.foodToRating = new Map();
+        this.cuisineToFood = new Map();
+
+        for (let i = 0; i < foods.length; i++) {
+            this.foodToRating.set(foods[i], ratings[i]);
+            if (!this.cuisineToFood.has(cuisines[i])) {
+                this.cuisineToFood.set(cuisines[i], []);
+            }
+            this.cuisineToFood.get(cuisines[i]).push(foods[i]);
+        }
+    }
+
+    /**
+     * @param {string} food
+     * @param {number} newRating
+     * @return {void}
+     */
+    changeRating(food, newRating) {
+        this.foodToRating.set(food, newRating);
+    }
+
+    /**
+     * @param {string} cuisine
+     * @return {string}
+     */
+    highestRated(cuisine) {
+        let maxR = 0, res = "";
+        for (let food of this.cuisineToFood.get(cuisine)) {
+            let r = this.foodToRating.get(food);
+            if (r > maxR || (r === maxR && food < res)) {
+                res = food;
+                maxR = r;
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(n)$ time for initialization.
+    * $O(1)$ time for each $changeRating()$ function call.
+    * $O(n)$ time for each $highestRated()$ function call.
+* Space complexity: $O(n)$
+
+---
+
+## 2. Heap
+
+::tabs-start
+
+```python
+class FoodRatings:
+
+    def __init__(self, foods: List[str], cuisines: List[str], ratings: List[int]):
+        self.foodToRating = {}  # food -> rating
+        self.foodToCuisine = {}  # food -> cuisine
+        self.cuisineToHeap = defaultdict(list)  # cuisine -> max_heap
+
+        for i in range(len(foods)):
+            self.foodToRating[foods[i]] = ratings[i]
+            self.foodToCuisine[foods[i]] = cuisines[i]
+            heappush(self.cuisineToHeap[cuisines[i]], (-ratings[i], foods[i]))
+
+    def changeRating(self, food: str, newRating: int) -> None:
+        cuisine = self.foodToCuisine[food]
+        self.foodToRating[food] = newRating
+        heappush(self.cuisineToHeap[cuisine], (-newRating, food))
+
+    def highestRated(self, cuisine: str) -> str:
+        heap = self.cuisineToHeap[cuisine]
+        while heap:
+            rating, food = heap[0]
+            if -rating == self.foodToRating[food]:
+                return food
+            heappop(heap)
+```
+
+```java
+public class FoodRatings {
+    private Map<String, Integer> foodToRating;
+    private Map<String, String> foodToCuisine;
+    private Map<String, PriorityQueue<Food>> cuisineToHeap;
+
+    private static class Food {
+        int rating;
+        String name;
+
+        Food(int rating, String name) {
+            this.rating = rating;
+            this.name = name;
+        }
+    }
+
+    public FoodRatings(String[] foods, String[] cuisines, int[] ratings) {
+        foodToRating = new HashMap<>();
+        foodToCuisine = new HashMap<>();
+        cuisineToHeap = new HashMap<>();
+
+        for (int i = 0; i < foods.length; i++) {
+            foodToRating.put(foods[i], ratings[i]);
+            foodToCuisine.put(foods[i], cuisines[i]);
+            cuisineToHeap
+                .computeIfAbsent(cuisines[i], k -> new PriorityQueue<>(
+                    (a, b) -> a.rating == b.rating ? a.name.compareTo(b.name) : b.rating - a.rating))
+                .offer(new Food(ratings[i], foods[i]));
+        }
+    }
+
+    public void changeRating(String food, int newRating) {
+        String cuisine = foodToCuisine.get(food);
+        foodToRating.put(food, newRating);
+        cuisineToHeap.get(cuisine).offer(new Food(newRating, food));
+    }
+
+    public String highestRated(String cuisine) {
+        PriorityQueue<Food> heap = cuisineToHeap.get(cuisine);
+        while (!heap.isEmpty()) {
+            Food top = heap.peek();
+            if (foodToRating.get(top.name) == top.rating) {
+                return top.name;
+            }
+            heap.poll();
+        }
+        return "";
+    }
+}
+```
+
+```cpp
+class FoodRatings {
+    unordered_map<string, int> foodToRating;
+    unordered_map<string, string> foodToCuisine;
+    struct cmp {
+        bool operator()(const pair<int, string>& a, const pair<int, string>& b) {
+            if (a.first == b.first) return a.second > b.second;
+            return a.first < b.first;
+        }
+    };
+    unordered_map<string, priority_queue<pair<int, string>,
+                    vector<pair<int, string>>, cmp>> cuisineToHeap;
+
+public:
+    FoodRatings(vector<string>& foods, vector<string>& cuisines, vector<int>& ratings) {
+        for (int i = 0; i < foods.size(); i++) {
+            foodToRating[foods[i]] = ratings[i];
+            foodToCuisine[foods[i]] = cuisines[i];
+            cuisineToHeap[cuisines[i]].push({ratings[i], foods[i]});
+        }
+    }
+
+    void changeRating(string food, int newRating) {
+        string cuisine = foodToCuisine[food];
+        foodToRating[food] = newRating;
+        cuisineToHeap[cuisine].push({newRating, food});
+    }
+
+    string highestRated(string cuisine) {
+        auto &heap = cuisineToHeap[cuisine];
+        while (!heap.empty()) {
+            auto [rating, food] = heap.top();
+            if (foodToRating[food] == rating) return food;
+            heap.pop();
+        }
+        return "";
+    }
+};
+```
+
+```javascript
+class FoodRatings {
+    /**
+     * @param {string[]} foods
+     * @param {string[]} cuisines
+     * @param {number[]} ratings
+     */
+    constructor(foods, cuisines, ratings) {
+        this.foodToRating = new Map();
+        this.foodToCuisine = new Map();
+        this.cuisineToHeap = new Map();
+
+        for (let i = 0; i < foods.length; i++) {
+            this.foodToRating.set(foods[i], ratings[i]);
+            this.foodToCuisine.set(foods[i], cuisines[i]);
+            if (!this.cuisineToHeap.has(cuisines[i])) {
+                this.cuisineToHeap.set(cuisines[i], new PriorityQueue(
+                    (a, b) => b.rating - a.rating || a.name.localeCompare(b.name)
+                ));
+            }
+            this.cuisineToHeap.get(cuisines[i]).enqueue(
+                { rating: ratings[i], name: foods[i] }
+            );
+        }
+    }
+
+    /**
+     * @param {string} food
+     * @param {number} newRating
+     * @return {void}
+     */
+    changeRating(food, newRating) {
+        let cuisine = this.foodToCuisine.get(food);
+        this.foodToRating.set(food, newRating);
+        this.cuisineToHeap.get(cuisine).enqueue(
+            { rating: newRating, name: food }
+        );
+    }
+
+    /**
+     * @param {string} cuisine
+     * @return {string}
+     */
+    highestRated(cuisine) {
+        let heap = this.cuisineToHeap.get(cuisine);
+        while (!heap.isEmpty()) {
+            let top = heap.front();
+            if (this.foodToRating.get(top.name) === top.rating) {
+                return top.name;
+            }
+            heap.dequeue();
+        }
+        return "";
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(n \log n)$ time for initialization.
+    * $O(\log n)$ time for each $changeRating()$ function call.
+    * $O(\log n)$ time for each $highestRated()$ function call.
+* Space complexity: $O(n)$
+
+---
+
+## 3. Sorted Set
+
+::tabs-start
+
+```python
+class FoodRatings:
+
+    def __init__(self, foods: List[str], cuisines: List[str], ratings: List[int]):
+        self.foodToRating = {} # food -> rating
+        self.foodToCuisine = {} # food -> cuisine
+        self.cuisineToSortedSet = defaultdict(SortedSet) # cuisine -> SortedSet[(rating, food)]
+
+        for i in range(len(foods)):
+            self.foodToRating[foods[i]] = ratings[i]
+            self.foodToCuisine[foods[i]] = cuisines[i]
+            self.cuisineToSortedSet[cuisines[i]].add((-ratings[i], foods[i]))
+
+    def changeRating(self, food: str, newRating: int) -> None:
+        cuisine = self.foodToCuisine[food]
+        oldRating = self.foodToRating[food]
+
+        self.cuisineToSortedSet[cuisine].remove((-oldRating, food))
+        self.foodToRating[food] = newRating
+        self.cuisineToSortedSet[cuisine].add((-newRating, food))
+
+    def highestRated(self, cuisine: str) -> str:
+        return self.cuisineToSortedSet[cuisine][0][1]
+```
+
+```java
+public class FoodRatings {
+    private Map<String, Integer> foodToRating;
+    private Map<String, String> foodToCuisine;
+    private Map<String, TreeSet<FoodPair>> cuisineToSortedSet;
+
+    private static class FoodPair {
+        int rating;
+        String food;
+
+        FoodPair(int rating, String food) {
+            this.rating = rating;
+            this.food = food;
+        }
+    }
+
+    public FoodRatings(String[] foods, String[] cuisines, int[] ratings) {
+        foodToRating = new HashMap<>();
+        foodToCuisine = new HashMap<>();
+        cuisineToSortedSet = new HashMap<>();
+
+        for (int i = 0; i < foods.length; i++) {
+            foodToRating.put(foods[i], ratings[i]);
+            foodToCuisine.put(foods[i], cuisines[i]);
+            cuisineToSortedSet.computeIfAbsent(cuisines[i], k -> new TreeSet<>((a, b) -> {
+                if (a.rating != b.rating) return b.rating - a.rating;
+                return a.food.compareTo(b.food);
+            })).add(new FoodPair(ratings[i], foods[i]));
+        }
+    }
+
+    public void changeRating(String food, int newRating) {
+        String cuisine = foodToCuisine.get(food);
+        int oldRating = foodToRating.get(food);
+        TreeSet<FoodPair> set = cuisineToSortedSet.get(cuisine);
+        set.remove(new FoodPair(oldRating, food));
+        foodToRating.put(food, newRating);
+        set.add(new FoodPair(newRating, food));
+    }
+
+    public String highestRated(String cuisine) {
+        return cuisineToSortedSet.get(cuisine).first().food;
+    }
+}
+```
+
+```cpp
+class FoodRatings {
+    unordered_map<string, int> foodToRating;
+    unordered_map<string, string> foodToCuisine;
+    unordered_map<string, set<pair<int, string>>> cuisineToSet;
+
+public:
+    FoodRatings(vector<string>& foods, vector<string>& cuisines, vector<int>& ratings) {
+        for (int i = 0; i < foods.size(); i++) {
+            foodToRating[foods[i]] = ratings[i];
+            foodToCuisine[foods[i]] = cuisines[i];
+            cuisineToSet[cuisines[i]].insert({-ratings[i], foods[i]});
+        }
+    }
+
+    void changeRating(string food, int newRating) {
+        string cuisine = foodToCuisine[food];
+        auto& s = cuisineToSet[cuisine];
+
+        s.erase({-foodToRating[food], food});
+        foodToRating[food] = newRating;
+        s.insert({-newRating, food});
+    }
+
+    string highestRated(string cuisine) {
+        return begin(cuisineToSet[cuisine])->second;
+    }
+};
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(n \log n)$ time for initialization.
+    * $O(\log n)$ time for each $changeRating()$ function call.
+    * $O(1)$ in Python and $O(\log n)$ in other languages for each $highestRated()$ function call.
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/design-browser-history.md b/articles/design-browser-history.md
new file mode 100644
index 000000000..a557f9151
--- /dev/null
+++ b/articles/design-browser-history.md
@@ -0,0 +1,640 @@
+## 1. Two Stacks
+
+::tabs-start
+
+```python
+class BrowserHistory:
+
+    def __init__(self, homepage: str):
+        self.back_history = [homepage]
+        self.front_history = []
+
+    def visit(self, url: str) -> None:
+        self.back_history.append(url)
+        self.front_history = []
+
+    def back(self, steps: int) -> str:
+        while steps and len(self.back_history) > 1:
+            self.front_history.append(self.back_history.pop())
+            steps -= 1
+        return self.back_history[-1]
+
+    def forward(self, steps: int) -> str:
+        while steps and self.front_history:
+            self.back_history.append(self.front_history.pop())
+            steps -= 1
+        return self.back_history[-1]
+```
+
+```java
+public class BrowserHistory {
+    private Stack<String> backHistory;
+    private Stack<String> frontHistory;
+
+    public BrowserHistory(String homepage) {
+        backHistory = new Stack<>();
+        frontHistory = new Stack<>();
+        backHistory.push(homepage);
+    }
+
+    public void visit(String url) {
+        backHistory.push(url);
+        frontHistory = new Stack<>();
+    }
+
+    public String back(int steps) {
+        while (steps > 0 && backHistory.size() > 1) {
+            frontHistory.push(backHistory.pop());
+            steps--;
+        }
+        return backHistory.peek();
+    }
+
+    public String forward(int steps) {
+        while (steps > 0 && !frontHistory.isEmpty()) {
+            backHistory.push(frontHistory.pop());
+            steps--;
+        }
+        return backHistory.peek();
+    }
+}
+```
+
+```cpp
+class BrowserHistory {
+private:
+    stack<string> backHistory, frontHistory;
+
+public:
+    BrowserHistory(string homepage) {
+        backHistory.push(homepage);
+    }
+
+    void visit(string url) {
+        backHistory.push(url);
+        frontHistory = stack<string>();
+    }
+
+    string back(int steps) {
+        while (steps-- && backHistory.size() > 1) {
+            frontHistory.push(backHistory.top());
+            backHistory.pop();
+        }
+        return backHistory.top();
+    }
+
+    string forward(int steps) {
+        while (steps-- && !frontHistory.empty()) {
+            backHistory.push(frontHistory.top());
+            frontHistory.pop();
+        }
+        return backHistory.top();
+    }
+};
+```
+
+```javascript
+class BrowserHistory {
+    /**
+     * @constructor
+     * @param {string} homepage
+     */
+    constructor(homepage) {
+        this.backHistory = [homepage];
+        this.frontHistory = [];
+    }
+
+    /** 
+     * @param {string} url
+     * @return {void}
+     */
+    visit(url) {
+        this.backHistory.push(url);
+        this.frontHistory = [];
+    }
+
+    /** 
+     * @param {number} steps
+     * @return {string}
+     */
+    back(steps) {
+        while (steps-- > 0 && this.backHistory.length > 1) {
+            this.frontHistory.push(this.backHistory.pop());
+        }
+        return this.backHistory[this.backHistory.length - 1];
+    }
+
+    /** 
+     * @param {number} steps
+     * @return {string}
+     */
+    forward(steps) {
+        while (steps-- > 0 && this.frontHistory.length > 0) {
+            this.backHistory.push(this.frontHistory.pop());
+        }
+        return this.backHistory[this.backHistory.length - 1];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(1)$ time for initialization.
+    * $O(1)$ time for each $visit()$ function call.
+    * $O(min(n, steps))$ time for each $back()$ and $forward()$ function calls.
+* Space complexity: $O(m * n)$
+
+> Where $n$ is the number of visited urls, $m$ is the average length of each url, and $steps$ is the number of steps we go forward or back.
+
+---
+
+## 2. Dynamic Array
+
+::tabs-start
+
+```python
+class BrowserHistory:
+
+    def __init__(self, homepage: str):
+        self.history = [homepage]
+        self.cur = 0
+
+    def visit(self, url: str) -> None:
+        self.cur += 1
+        self.history = self.history[:self.cur]
+        self.history.append(url)
+
+    def back(self, steps: int) -> str:
+        self.cur = max(0, self.cur - steps)
+        return self.history[self.cur]
+
+    def forward(self, steps: int) -> str:
+        self.cur = min(len(self.history) - 1, self.cur + steps)
+        return self.history[self.cur]
+```
+
+```java
+public class BrowserHistory {
+    private List<String> history;
+    private int cur;
+
+    public BrowserHistory(String homepage) {
+        history = new ArrayList<>();
+        history.add(homepage);
+        cur = 0;
+    }
+
+    public void visit(String url) {
+        cur++;
+        history = history.subList(0, cur);
+        history.add(url);
+    }
+
+    public String back(int steps) {
+        cur = Math.max(0, cur - steps);
+        return history.get(cur);
+    }
+
+    public String forward(int steps) {
+        cur = Math.min(history.size() - 1, cur + steps);
+        return history.get(cur);
+    }
+}
+```
+
+```cpp
+class BrowserHistory {
+private:
+    vector<string> history;
+    int cur;
+
+public:
+    BrowserHistory(string homepage) {
+        history.push_back(homepage);
+        cur = 0;
+    }
+
+    void visit(string url) {
+        cur++;
+        history.resize(cur);
+        history.push_back(url);
+    }
+
+    string back(int steps) {
+        cur = max(0, cur - steps);
+        return history[cur];
+    }
+
+    string forward(int steps) {
+        cur = min((int)history.size() - 1, cur + steps);
+        return history[cur];
+    }
+};
+```
+
+```javascript
+class BrowserHistory {
+    /**
+     * @constructor
+     * @param {string} homepage
+     */
+    constructor(homepage) {
+        this.history = [homepage];
+        this.cur = 0;
+    }
+
+    /** 
+     * @param {string} url
+     * @return {void}
+     */
+    visit(url) {
+        this.cur++;
+        this.history = this.history.slice(0, this.cur);
+        this.history.push(url);
+    }
+
+    /** 
+     * @param {number} steps
+     * @return {string}
+     */
+    back(steps) {
+        this.cur = Math.max(0, this.cur - steps);
+        return this.history[this.cur];
+    }
+
+    /** 
+     * @param {number} steps
+     * @return {string}
+     */
+    forward(steps) {
+        this.cur = Math.min(this.history.length - 1, this.cur + steps);
+        return this.history[this.cur];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(1)$ time for initialization.
+    * $O(n)$ time for each $visit()$ function call.
+    * $O(1)$ time for each $back()$ and $forward()$ function calls.
+* Space complexity: $O(m * n)$
+
+> Where $n$ is the number of visited urls and $m$ is the average length of each url.
+
+---
+
+## 3. Dynamic Array (Optimal)
+
+::tabs-start
+
+```python
+class BrowserHistory:
+
+    def __init__(self, homepage: str):
+        self.history = [homepage]
+        self.cur = 0
+        self.n = 1
+
+    def visit(self, url: str) -> None:
+        self.cur += 1
+        if self.cur == len(self.history):
+            self.history.append(url)
+            self.n += 1
+        else:
+            self.history[self.cur] = url
+            self.n = self.cur + 1
+
+    def back(self, steps: int) -> str:
+        self.cur = max(0, self.cur - steps)
+        return self.history[self.cur]
+
+    def forward(self, steps: int) -> str:
+        self.cur = min(self.n - 1, self.cur + steps)
+        return self.history[self.cur]
+```
+
+```java
+public class BrowserHistory {
+    private List<String> history;
+    private int cur;
+    private int n;
+
+    public BrowserHistory(String homepage) {
+        history = new ArrayList<>();
+        history.add(homepage);
+        cur = 0;
+        n = 1;
+    }
+
+    public void visit(String url) {
+        cur++;
+        if (cur == history.size()) {
+            history.add(url);
+            n++;
+        } else {
+            history.set(cur, url);
+            n = cur + 1;
+        }
+    }
+
+    public String back(int steps) {
+        cur = Math.max(0, cur - steps);
+        return history.get(cur);
+    }
+
+    public String forward(int steps) {
+        cur = Math.min(n - 1, cur + steps);
+        return history.get(cur);
+    }
+}
+```
+
+```cpp
+class BrowserHistory {
+private:
+    vector<string> history;
+    int cur, n;
+
+public:
+    BrowserHistory(string homepage) {
+        history.push_back(homepage);
+        cur = 0;
+        n = 1;
+    }
+
+    void visit(string url) {
+        cur++;
+        if (cur == history.size()) {
+            history.push_back(url);
+            n++;
+        } else {
+            history[cur] = url;
+            n = cur + 1;
+        }
+    }
+
+    string back(int steps) {
+        cur = max(0, cur - steps);
+        return history[cur];
+    }
+
+    string forward(int steps) {
+        cur = min(n - 1, cur + steps);
+        return history[cur];
+    }
+};
+```
+
+```javascript
+class BrowserHistory {
+    /**
+     * @constructor
+     * @param {string} homepage
+     */
+    constructor(homepage) {
+        this.history = [homepage];
+        this.cur = 0;
+        this.n = 1;
+    }
+
+    /** 
+     * @param {string} url
+     * @return {void}
+     */
+    visit(url) {
+        this.cur++;
+        if (this.cur === this.history.length) {
+            this.history.push(url);
+            this.n++;
+        } else {
+            this.history[this.cur] = url;
+            this.n = this.cur + 1;
+        }
+    }
+
+    /** 
+     * @param {number} steps
+     * @return {string}
+     */
+    back(steps) {
+        this.cur = Math.max(0, this.cur - steps);
+        return this.history[this.cur];
+    }
+
+    /** 
+     * @param {number} steps
+     * @return {string}
+     */
+    forward(steps) {
+        this.cur = Math.min(this.n - 1, this.cur + steps);
+        return this.history[this.cur];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(1)$ time for initialization.
+    * $O(1)$ time for each $visit()$ function call.
+    * $O(1)$ time for each $back()$ and $forward()$ function calls.
+* Space complexity: $O(m * n)$
+
+> Where $n$ is the number of visited urls and $m$ is the average length of each url.
+
+---
+
+## 4. Doubly Linked List
+
+::tabs-start
+
+```python
+class ListNode:
+    def __init__(self, val, prev=None, next=None):
+        self.val = val
+        self.prev = prev
+        self.next = next
+
+class BrowserHistory:
+
+    def __init__(self, homepage: str):
+        self.cur = ListNode(homepage)
+
+    def visit(self, url: str) -> None:
+        self.cur.next = ListNode(url, self.cur)
+        self.cur = self.cur.next
+
+    def back(self, steps: int) -> str:
+        while self.cur.prev and steps > 0:
+            self.cur = self.cur.prev
+            steps -= 1
+        return self.cur.val
+
+    def forward(self, steps: int) -> str:
+        while self.cur.next and steps > 0:
+            self.cur = self.cur.next
+            steps -= 1
+        return self.cur.val
+```
+
+```java
+class ListNode {
+    String val;
+    ListNode prev, next;
+
+    public ListNode(String val, ListNode prev, ListNode next) {
+        this.val = val;
+        this.prev = prev;
+        this.next = next;
+    }
+
+    public ListNode(String val) {
+        this(val, null, null);
+    }
+}
+
+public class BrowserHistory {
+    private ListNode cur;
+
+    public BrowserHistory(String homepage) {
+        cur = new ListNode(homepage);
+    }
+
+    public void visit(String url) {
+        cur.next = new ListNode(url, cur, null);
+        cur = cur.next;
+    }
+
+    public String back(int steps) {
+        while (cur.prev != null && steps > 0) {
+            cur = cur.prev;
+            steps--;
+        }
+        return cur.val;
+    }
+
+    public String forward(int steps) {
+        while (cur.next != null && steps > 0) {
+            cur = cur.next;
+            steps--;
+        }
+        return cur.val;
+    }
+}
+```
+
+```cpp
+class BrowserHistory {
+    struct ListNode {
+    public:
+        string val;
+        ListNode* prev;
+        ListNode* next;
+
+        ListNode(string val, ListNode* prev = nullptr, ListNode* next = nullptr) 
+            : val(val), prev(prev), next(next) {}
+    };
+
+    ListNode* cur;
+
+public:
+    BrowserHistory(string homepage) {
+        cur = new ListNode(homepage);
+    }
+
+    void visit(string url) {
+        cur->next = new ListNode(url, cur, nullptr);
+        cur = cur->next;
+    }
+
+    string back(int steps) {
+        while (cur->prev != nullptr && steps > 0) {
+            cur = cur->prev;
+            steps--;
+        }
+        return cur->val;
+    }
+
+    string forward(int steps) {
+        while (cur->next != nullptr && steps > 0) {
+            cur = cur->next;
+            steps--;
+        }
+        return cur->val;
+    }
+};
+```
+
+```javascript
+class ListNode {
+    constructor(val, prev = null, next = null) {
+        this.val = val;
+        this.prev = prev;
+        this.next = next;
+    }
+}
+
+class BrowserHistory {
+    /**
+     * @constructor
+     * @param {string} homepage
+     */
+    constructor(homepage) {
+        this.cur = new ListNode(homepage);
+    }
+
+    /** 
+     * @param {string} url
+     * @return {void}
+     */
+    visit(url) {
+        this.cur.next = new ListNode(url, this.cur, null);
+        this.cur = this.cur.next;
+    }
+
+    /** 
+     * @param {number} steps
+     * @return {string}
+     */
+    back(steps) {
+        while (this.cur.prev !== null && steps > 0) {
+            this.cur = this.cur.prev;
+            steps--;
+        }
+        return this.cur.val;
+    }
+
+    /** 
+     * @param {number} steps
+     * @return {string}
+     */
+    forward(steps) {
+        while (this.cur.next !== null && steps > 0) {
+            this.cur = this.cur.next;
+            steps--;
+        }
+        return this.cur.val;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(1)$ time for initialization.
+    * $O(1)$ time for each $visit()$ function call.
+    * $O(min(n, steps))$ time for each $back()$ and $forward()$ function calls.
+* Space complexity: $O(m * n)$
+
+> Where $n$ is the number of visited urls, $m$ is the average length of each url, and $steps$ is the number of steps we go forward or back.
\ No newline at end of file
diff --git a/articles/design-circular-queue.md b/articles/design-circular-queue.md
new file mode 100644
index 000000000..033e2cfd6
--- /dev/null
+++ b/articles/design-circular-queue.md
@@ -0,0 +1,990 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class MyCircularQueue:
+
+    def __init__(self, k: int):
+        self.q = []
+        self.k = k
+
+    def enQueue(self, value: int) -> bool:
+        if len(self.q) == self.k:
+            return False
+        self.q.append(value)
+        return True
+
+    def deQueue(self) -> bool:
+        if not self.q:
+            return False
+        self.q.pop(0)
+        return True
+
+    def Front(self) -> int:
+        if self.q:
+            return self.q[0]
+        return -1
+
+    def Rear(self) -> int:
+        if self.q:
+            return self.q[-1]
+        return -1
+
+    def isEmpty(self) -> bool:
+        return len(self.q) == 0
+
+    def isFull(self) -> bool:
+        return len(self.q) == self.k
+```
+
+```java
+public class MyCircularQueue {
+    private List<Integer> queue;
+    private int capacity;
+
+    public MyCircularQueue(int k) {
+        queue = new ArrayList<>();
+        capacity = k;
+    }
+
+    public boolean enQueue(int value) {
+        if (queue.size() == capacity) {
+            return false;
+        }
+        queue.add(value);
+        return true;
+    }
+
+    public boolean deQueue() {
+        if (queue.isEmpty()) {
+            return false;
+        }
+        queue.remove(0);
+        return true;
+    }
+
+    public int Front() {
+        return queue.isEmpty() ? -1 : queue.get(0);
+    }
+
+    public int Rear() {
+        return queue.isEmpty() ? -1 : queue.get(queue.size() - 1);
+    }
+
+    public boolean isEmpty() {
+        return queue.isEmpty();
+    }
+
+    public boolean isFull() {
+        return queue.size() == capacity;
+    }
+}
+```
+
+```cpp
+class MyCircularQueue {
+private:
+    vector<int> queue;
+    int capacity;
+
+public:
+    MyCircularQueue(int k) {
+        capacity = k;
+    }
+
+    bool enQueue(int value) {
+        if (queue.size() == capacity) {
+            return false;
+        }
+        queue.push_back(value);
+        return true;
+    }
+
+    bool deQueue() {
+        if (queue.empty()) {
+            return false;
+        }
+        queue.erase(queue.begin());
+        return true;
+    }
+
+    int Front() {
+        return queue.empty() ? -1 : queue.front();
+    }
+
+    int Rear() {
+        return queue.empty() ? -1 : queue.back();
+    }
+
+    bool isEmpty() {
+        return queue.empty();
+    }
+
+    bool isFull() {
+        return queue.size() == capacity;
+    }
+};
+```
+
+```javascript
+class MyCircularQueue {
+    /**
+     * @param {number} k
+     */
+    constructor(k) {
+        this.queue = [];
+        this.capacity = k;
+    }
+
+    /**
+     * @param {number} value
+     * @return {boolean}
+     */
+    enQueue(value) {
+        if (this.queue.length === this.capacity) {
+            return false;
+        }
+        this.queue.push(value);
+        return true;
+    }
+
+    /**
+     * @return {boolean}
+     */
+    deQueue() {
+        if (this.queue.length === 0) {
+            return false;
+        }
+        this.queue.shift();
+        return true;
+    }
+
+    /**
+     * @return {number}
+     */
+    Front() {
+        return this.queue.length === 0 ? -1 : this.queue[0];
+    }
+
+    /**
+     * @return {number}
+     */
+    Rear() {
+        return this.queue.length === 0 ? -1 : this.queue[this.queue.length - 1];
+    }
+
+    /**
+     * @return {boolean}
+     */
+    isEmpty() {
+        return this.queue.length === 0;
+    }
+
+    /**
+     * @return {boolean}
+     */
+    isFull() {
+        return this.queue.length === this.capacity;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(1)$ time for initialization.
+    * $O(1)$ time for each $enQueue()$, $Front()$, $Rear()$, $isEmpty()$ and $isFull()$ function calls.
+    * $O(n)$ time for each $deQueue()$ function call. 
+* Space complexity: $O(n)$
+
+> Where $n$ is the size of the queue.
+
+---
+
+## 2. Array
+
+::tabs-start
+
+```python
+class MyCircularQueue:
+    
+    def __init__(self, k: int):
+        self.q = [0] * k
+        self.k = k
+        self.front = 0
+        self.rear = -1
+        self.size = 0
+        
+    def enQueue(self, value: int) -> bool:
+        if self.isFull():
+            return False
+        self.rear = (self.rear + 1) % self.k
+        self.q[self.rear] = value
+        self.size += 1
+        return True
+        
+    def deQueue(self) -> bool:
+        if self.isEmpty():
+            return False
+        self.front = (self.front + 1) % self.k
+        self.size -= 1
+        return True
+        
+    def Front(self) -> int:
+        if self.isEmpty():
+            return -1
+        return self.q[self.front]
+        
+    def Rear(self) -> int:
+        if self.isEmpty():
+            return -1
+        return self.q[self.rear]
+        
+    def isEmpty(self) -> bool:
+        return self.size == 0
+        
+    def isFull(self) -> bool:
+        return self.size == self.k
+```
+
+```java
+public class MyCircularQueue {
+    private int[] queue;
+    private int size;
+    private int front;
+    private int rear;
+
+    public MyCircularQueue(int k) {
+        queue = new int[k];
+        size = 0;
+        front = 0;
+        rear = -1;
+    }
+
+    public boolean enQueue(int value) {
+        if (isFull()) {
+            return false;
+        }
+        rear = (rear + 1) % queue.length;
+        queue[rear] = value;
+        size++;
+        return true;
+    }
+
+    public boolean deQueue() {
+        if (isEmpty()) {
+            return false;
+        }
+        front = (front + 1) % queue.length;
+        size--;
+        return true;
+    }
+
+    public int Front() {
+        return isEmpty() ? -1 : queue[front];
+    }
+
+    public int Rear() {
+        return isEmpty() ? -1 : queue[rear];
+    }
+
+    public boolean isEmpty() {
+        return size == 0;
+    }
+
+    public boolean isFull() {
+        return size == queue.length;
+    }
+}
+```
+
+```cpp
+class MyCircularQueue {
+private:
+    vector<int> queue;
+    int size;
+    int front;
+    int rear;
+    int capacity;
+
+public:
+    MyCircularQueue(int k) {
+        queue = vector<int>(k);
+        size = 0;
+        front = 0;
+        rear = -1;
+        capacity = k;
+    }
+
+    bool enQueue(int value) {
+        if (isFull()) {
+            return false;
+        }
+        rear = (rear + 1) % capacity;
+        queue[rear] = value;
+        size++;
+        return true;
+    }
+
+    bool deQueue() {
+        if (isEmpty()) {
+            return false;
+        }
+        front = (front + 1) % capacity;
+        size--;
+        return true;
+    }
+
+    int Front() {
+        return isEmpty() ? -1 : queue[front];
+    }
+
+    int Rear() {
+        return isEmpty() ? -1 : queue[rear];
+    }
+
+    bool isEmpty() {
+        return size == 0;
+    }
+
+    bool isFull() {
+        return size == capacity;
+    }
+};
+```
+
+```javascript
+class MyCircularQueue {
+    /**
+     * @param {number} k
+     */
+    constructor(k) {
+        this.queue = new Array(k);
+        this.size = 0;
+        this.front = 0;
+        this.rear = -1;
+        this.capacity = k;
+    }
+
+    /**
+     * @param {number} value
+     * @return {boolean}
+     */
+    enQueue(value) {
+        if (this.isFull()) {
+            return false;
+        }
+        this.rear = (this.rear + 1) % this.capacity;
+        this.queue[this.rear] = value;
+        this.size++;
+        return true;
+    }
+
+    /**
+     * @return {boolean}
+     */
+    deQueue() {
+        if (this.isEmpty()) {
+            return false;
+        }
+        this.front = (this.front + 1) % this.capacity;
+        this.size--;
+        return true;
+    }
+
+    /**
+     * @return {number}
+     */
+    Front() {
+        return this.isEmpty() ? -1 : this.queue[this.front];
+    }
+
+    /**
+     * @return {number}
+     */
+    Rear() {
+        return this.isEmpty() ? -1 : this.queue[this.rear];
+    }
+
+    /**
+     * @return {boolean}
+     */
+    isEmpty() {
+        return this.size === 0;
+    }
+
+    /**
+     * @return {boolean}
+     */
+    isFull() {
+        return this.size === this.capacity;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(n)$ time for initialization.
+    * $O(1)$ time for each $enQueue()$, $deQueue()$, $Front()$, $Rear()$, $isEmpty()$ and $isFull()$ function calls. 
+* Space complexity: $O(n)$
+
+> Where $n$ is the size of the queue.
+
+---
+
+## 3. Doubly Linked List
+
+::tabs-start
+
+```python
+class ListNode:
+
+    def __init__(self, val, nxt, prev):
+        self.val, self.next, self.prev = val, nxt, prev
+
+class MyCircularQueue:
+
+    def __init__(self, k: int):
+        self.space = k
+        self.left = ListNode(0, None, None)
+        self.right = ListNode(0, None, self.left)
+        self.left.next = self.right
+
+    def enQueue(self, value: int) -> bool:
+        if self.isFull(): return False
+        cur = ListNode(value, self.right, self.right.prev)
+        self.right.prev.next = cur
+        self.right.prev = cur
+        self.space -= 1
+        return True
+
+    def deQueue(self) -> bool:
+        if self.isEmpty(): return False
+        self.left.next = self.left.next.next
+        self.left.next.prev = self.left
+        self.space += 1
+        return True
+
+    def Front(self) -> int:
+        if self.isEmpty(): return -1
+        return self.left.next.val
+
+    def Rear(self) -> int:
+        if self.isEmpty(): return -1
+        return self.right.prev.val
+
+    def isEmpty(self) -> bool:
+        return self.left.next == self.right
+
+    def isFull(self) -> bool:
+        return self.space == 0
+```
+
+```java
+class ListNode {
+    int val;
+    ListNode next, prev;
+
+    ListNode(int val, ListNode next, ListNode prev) {
+        this.val = val;
+        this.next = next;
+        this.prev = prev;
+    }
+}
+
+public class MyCircularQueue {
+    private int space;
+    private ListNode left, right;
+
+    public MyCircularQueue(int k) {
+        space = k;
+        left = new ListNode(0, null, null);
+        right = new ListNode(0, null, left);
+        left.next = right;
+    }
+
+    public boolean enQueue(int value) {
+        if (isFull()) {
+            return false;
+        }
+        ListNode cur = new ListNode(value, right, right.prev);
+        right.prev.next = cur;
+        right.prev = cur;
+        space--;
+        return true;
+    }
+
+    public boolean deQueue() {
+        if (isEmpty()) {
+            return false;
+        }
+        left.next = left.next.next;
+        left.next.prev = left;
+        space++;
+        return true;
+    }
+
+    public int Front() {
+        return isEmpty() ? -1 : left.next.val;
+    }
+
+    public int Rear() {
+        return isEmpty() ? -1 : right.prev.val;
+    }
+
+    public boolean isEmpty() {
+        return left.next == right;
+    }
+
+    public boolean isFull() {
+        return space == 0;
+    }
+}
+```
+
+```cpp
+class MyCircularQueue {
+private:
+    struct ListNode {
+        int val;
+        ListNode* next;
+        ListNode* prev;
+        ListNode(int v, ListNode* n = nullptr, ListNode* p = nullptr)
+            : val(v), next(n), prev(p) {}
+    };
+
+    int space;
+    ListNode* left;
+    ListNode* right;
+
+public:
+    MyCircularQueue(int k) {
+        space = k;
+        left = new ListNode(0);
+        right = new ListNode(0, nullptr, left);
+        left->next = right;
+    }
+
+    bool enQueue(int value) {
+        if (isFull()) return false;
+        ListNode* cur = new ListNode(value, right, right->prev);
+        right->prev->next = cur;
+        right->prev = cur;
+        space--;
+        return true;
+    }
+
+    bool deQueue() {
+        if (isEmpty()) return false;
+        ListNode* tmp = left->next;
+        left->next = left->next->next;
+        left->next->prev = left;
+        delete tmp;
+        space++;
+        return true;
+    }
+
+    int Front() {
+        return isEmpty() ? -1 : left->next->val;
+    }
+
+    int Rear() {
+        return isEmpty() ? -1 : right->prev->val;
+    }
+
+    bool isEmpty() {
+        return left->next == right;
+    }
+
+    bool isFull() {
+        return space == 0;
+    }
+};
+```
+
+```javascript
+class ListNode {
+    /**
+     * @param {number} val 
+     * @param {ListNode} next 
+     * @param {ListNode} prev 
+     */
+    constructor(val, next = null, prev = null) {
+        this.val = val;
+        this.next = next;
+        this.prev = prev;
+    }
+}
+
+class MyCircularQueue {
+    /**
+     * @param {number} k
+     */
+    constructor(k) {
+        this.space = k;
+        this.left = new ListNode(0);
+        this.right = new ListNode(0, null, this.left);
+        this.left.next = this.right;
+    }
+
+    /**
+     * @param {number} value
+     * @return {boolean}
+     */
+    enQueue(value) {
+        if (this.isFull()) return false;
+        const cur = new ListNode(value, this.right, this.right.prev);
+        this.right.prev.next = cur;
+        this.right.prev = cur;
+        this.space--;
+        return true;
+    }
+
+    /**
+     * @return {boolean}
+     */
+    deQueue() {
+        if (this.isEmpty()) return false;
+        this.left.next = this.left.next.next;
+        this.left.next.prev = this.left;
+        this.space++;
+        return true;
+    }
+
+    /**
+     * @return {number}
+     */
+    Front() {
+        return this.isEmpty() ? -1 : this.left.next.val;
+    }
+
+    /**
+     * @return {number}
+     */
+    Rear() {
+        return this.isEmpty() ? -1 : this.right.prev.val;
+    }
+
+    /**
+     * @return {boolean}
+     */
+    isEmpty() {
+        return this.left.next === this.right;
+    }
+
+    /**
+     * @return {boolean}
+     */
+    isFull() {
+        return this.space === 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(n)$ time for initialization.
+    * $O(1)$ time for each $enQueue()$, $deQueue()$, $Front()$, $Rear()$, $isEmpty()$ and $isFull()$ function calls. 
+* Space complexity: $O(n)$
+
+> Where $n$ is the size of the queue.
+
+---
+
+## 4. Singly Linked List
+
+::tabs-start
+
+```python
+class ListNode:
+    def __init__(self, val, nxt=None):
+        self.val = val
+        self.next = nxt
+
+class MyCircularQueue:
+    def __init__(self, k: int):
+        self.space = k
+        self.left = ListNode(0)
+        self.right = self.left
+        
+    def enQueue(self, value: int) -> bool:
+        if self.isFull(): return False
+            
+        cur = ListNode(value)
+        if self.isEmpty():
+            self.left.next = cur
+            self.right = cur
+        else:
+            self.right.next = cur
+            self.right = cur
+            
+        self.space -= 1
+        return True
+        
+    def deQueue(self) -> bool:
+        if self.isEmpty(): return False
+            
+        self.left.next = self.left.next.next
+        if self.left.next is None:
+            self.right = self.left
+            
+        self.space += 1
+        return True
+        
+    def Front(self) -> int:
+        if self.isEmpty(): return -1
+        return self.left.next.val
+        
+    def Rear(self) -> int:
+        if self.isEmpty(): return -1
+        return self.right.val
+        
+    def isEmpty(self) -> bool:
+        return self.left.next is None
+        
+    def isFull(self) -> bool:
+        return self.space == 0
+```
+
+```java
+class ListNode {
+    int val;
+    ListNode next;
+
+    ListNode(int val) {
+        this.val = val;
+        this.next = null;
+    }
+}
+
+public class MyCircularQueue {
+    private int space;
+    private ListNode left;
+    private ListNode right;
+
+    public MyCircularQueue(int k) {
+        this.space = k;
+        this.left = new ListNode(0);
+        this.right = this.left;
+    }
+
+    public boolean enQueue(int value) {
+        if (isFull()) return false;
+
+        ListNode cur = new ListNode(value);
+        if (isEmpty()) {
+            this.left.next = cur;
+            this.right = cur;
+        } else {
+            this.right.next = cur;
+            this.right = cur;
+        }
+
+        this.space--;
+        return true;
+    }
+
+    public boolean deQueue() {
+        if (isEmpty()) return false;
+
+        this.left.next = this.left.next.next;
+        if (this.left.next == null) {
+            this.right = this.left;
+        }
+
+        this.space++;
+        return true;
+    }
+
+    public int Front() {
+        return isEmpty() ? -1 : this.left.next.val;
+    }
+
+    public int Rear() {
+        return isEmpty() ? -1 : this.right.val;
+    }
+
+    public boolean isEmpty() {
+        return this.left.next == null;
+    }
+
+    public boolean isFull() {
+        return this.space == 0;
+    }
+}
+```
+
+```cpp
+class MyCircularQueue {
+private:
+    struct ListNode {
+        int val;
+        ListNode* next;
+        ListNode(int v) : val(v), next(nullptr) {}
+    };
+
+    int space;
+    ListNode* left;
+    ListNode* right;
+
+public:
+    MyCircularQueue(int k) {
+        space = k;
+        left = new ListNode(0);
+        right = left;
+    }
+
+    bool enQueue(int value) {
+        if (isFull()) return false;
+
+        ListNode* cur = new ListNode(value);
+        if (isEmpty()) {
+            left->next = cur;
+            right = cur;
+        } else {
+            right->next = cur;
+            right = cur;
+        }
+
+        space--;
+        return true;
+    }
+
+    bool deQueue() {
+        if (isEmpty()) return false;
+
+        ListNode* tmp = left->next;
+        left->next = left->next->next;
+        delete tmp;
+        if (!left->next) {
+            right = left;
+        }
+
+        space++;
+        return true;
+    }
+
+    int Front() {
+        return isEmpty() ? -1 : left->next->val;
+    }
+
+    int Rear() {
+        return isEmpty() ? -1 : right->val;
+    }
+
+    bool isEmpty() {
+        return left->next == nullptr;
+    }
+
+    bool isFull() {
+        return space == 0;
+    }
+};
+```
+
+```javascript
+class ListNode {
+    /**
+     * @param {number} val
+     * @param {ListNode} next
+     */
+    constructor(val, next = null) {
+        this.val = val;
+        this.next = next;
+    }
+}
+
+class MyCircularQueue {
+    /**
+     * @param {number} k
+     */
+    constructor(k) {
+        this.space = k;
+        this.left = new ListNode(0);
+        this.right = this.left;
+    }
+
+    /**
+     * @param {number} value
+     * @return {boolean}
+     */
+    enQueue(value) {
+        if (this.isFull()) return false;
+
+        const cur = new ListNode(value);
+        if (this.isEmpty()) {
+            this.left.next = cur;
+            this.right = cur;
+        } else {
+            this.right.next = cur;
+            this.right = cur;
+        }
+
+        this.space--;
+        return true;
+    }
+
+    /**
+     * @return {boolean}
+     */
+    deQueue() {
+        if (this.isEmpty()) return false;
+
+        this.left.next = this.left.next.next;
+        if (!this.left.next) {
+            this.right = this.left;
+        }
+
+        this.space++;
+        return true;
+    }
+
+    /**
+     * @return {number}
+     */
+    Front() {
+        return this.isEmpty() ? -1 : this.left.next.val;
+    }
+
+    /**
+     * @return {number}
+     */
+    Rear() {
+        return this.isEmpty() ? -1 : this.right.val;
+    }
+
+    /**
+     * @return {boolean}
+     */
+    isEmpty() {
+        return this.left.next === null;
+    }
+
+    /**
+     * @return {boolean}
+     */
+    isFull() {
+        return this.space === 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(n)$ time for initialization.
+    * $O(1)$ time for each $enQueue()$, $deQueue()$, $Front()$, $Rear()$, $isEmpty()$ and $isFull()$ function calls. 
+* Space complexity: $O(n)$
+
+> Where $n$ is the size of the queue.
\ No newline at end of file
diff --git a/articles/design-hashmap.md b/articles/design-hashmap.md
new file mode 100644
index 000000000..4a64bdee1
--- /dev/null
+++ b/articles/design-hashmap.md
@@ -0,0 +1,365 @@
+## 1. Array
+
+::tabs-start
+
+```python
+class MyHashMap:
+
+    def __init__(self):
+        self.map = [-1] * 1000001
+
+    def put(self, key: int, value: int) -> None:
+        self.map[key] = value
+
+    def get(self, key: int) -> int:
+        return self.map[key]
+
+    def remove(self, key: int) -> None:
+        self.map[key] = -1
+```
+
+```java
+public class MyHashMap {
+    private int[] map;
+
+    public MyHashMap() {
+        map = new int[1000001];
+        Arrays.fill(map, -1);
+    }
+
+    public void put(int key, int value) {
+        map[key] = value;
+    }
+
+    public int get(int key) {
+        return map[key];
+    }
+
+    public void remove(int key) {
+        map[key] = -1;
+    }
+}
+```
+
+```cpp
+class MyHashMap {
+private:
+    vector<int> map;
+
+public:
+    MyHashMap() : map(1000001, -1) {}
+
+    void put(int key, int value) {
+        map[key] = value;
+    }
+
+    int get(int key) {
+        return map[key];
+    }
+
+    void remove(int key) {
+        map[key] = -1;
+    }
+};
+```
+
+```javascript
+class MyHashMap {
+    constructor() {
+        this.map = new Array(1000001).fill(-1);
+    }
+
+    /** 
+     * @param {number} key 
+     * @param {number} value
+     * @return {void}
+     */
+    put(key, value) {
+        this.map[key] = value;
+    }
+
+    /** 
+     * @param {number} key
+     * @return {number}
+     */
+    get(key) {
+        return this.map[key];
+    }
+
+    /** 
+     * @param {number} key
+     * @return {void}
+     */
+    remove(key) {
+        this.map[key] = -1;
+    }
+}
+
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$ for each function call.
+* Space complexity: $O(1000000)$ since the key is in the range $[0, 1000000]$.
+
+---
+
+## 2. Linked List
+
+::tabs-start
+
+```python
+class ListNode:
+    def __init__(self, key = -1, val = -1, next = None):
+        self.key = key
+        self.val = val
+        self.next = next
+
+class MyHashMap:
+
+    def __init__(self):
+        self.map = [ListNode() for _ in range(1000)]
+    
+    def hash(self, key: int) -> int:
+        return key % len(self.map)
+
+    def put(self, key: int, value: int) -> None:
+        cur = self.map[self.hash(key)]
+        while cur.next:
+            if cur.next.key == key:
+                cur.next.val = value
+                return
+            cur = cur.next
+        cur.next = ListNode(key, value)
+
+    def get(self, key: int) -> int:
+        cur = self.map[self.hash(key)].next
+        while cur:
+            if cur.key == key:
+                return cur.val
+            cur = cur.next
+        return -1
+
+    def remove(self, key: int) -> None:
+        cur = self.map[self.hash(key)]
+        while cur.next:
+            if cur.next.key == key:
+                cur.next = cur.next.next
+                return
+            cur = cur.next
+```
+
+```java
+class ListNode {
+    int key, val;
+    ListNode next;
+
+    public ListNode(int key, int val, ListNode next) {
+        this.key = key;
+        this.val = val;
+        this.next = next;
+    }
+
+    public ListNode() {
+        this(-1, -1, null);
+    }
+}
+
+public class MyHashMap {
+    private ListNode[] map;
+
+    public MyHashMap() {
+        map = new ListNode[1000];
+        for (int i = 0; i < 1000; i++) {
+            map[i] = new ListNode();
+        }
+    }
+
+    private int hash(int key) {
+        return key % map.length;
+    }
+
+    public void put(int key, int value) {
+        ListNode cur = map[hash(key)];
+        while (cur.next != null) {
+            if (cur.next.key == key) {
+                cur.next.val = value;
+                return;
+            }
+            cur = cur.next;
+        }
+        cur.next = new ListNode(key, value, null);
+    }
+
+    public int get(int key) {
+        ListNode cur = map[hash(key)].next;
+        while (cur != null) {
+            if (cur.key == key) {
+                return cur.val;
+            }
+            cur = cur.next;
+        }
+        return -1;
+    }
+
+    public void remove(int key) {
+        ListNode cur = map[hash(key)];
+        while (cur.next != null) {
+            if (cur.next.key == key) {
+                cur.next = cur.next.next;
+                return;
+            }
+            cur = cur.next;
+        }
+    }
+}
+```
+
+```cpp
+class MyHashMap {
+private:
+    struct ListNode {
+        int key, val;
+        ListNode* next;
+
+        ListNode(int key = -1, int val = -1, ListNode* next = nullptr)
+            : key(key), val(val), next(next) {}
+    };
+
+    vector<ListNode*> map;
+    int hash(int key) {
+        return key % map.size();
+    }
+
+public:
+    MyHashMap() {
+        map.resize(1000);
+        for (auto& bucket : map) {
+            bucket = new ListNode(0);
+        }
+    }
+
+    void put(int key, int value) {
+        ListNode* cur = map[hash(key)];
+        while (cur->next) {
+            if (cur->next->key == key) {
+                cur->next->val = value;
+                return;
+            }
+            cur = cur->next;
+        }
+        cur->next = new ListNode(key, value);
+    }
+
+    int get(int key) {
+        ListNode* cur = map[hash(key)]->next;
+        while (cur) {
+            if (cur->key == key) {
+                return cur->val;
+            }
+            cur = cur->next;
+        }
+        return -1;
+    }
+
+    void remove(int key) {
+        ListNode* cur = map[hash(key)];
+        while (cur->next) {
+            if (cur->next->key == key) {
+                ListNode* tmp = cur->next;
+                cur->next = cur->next->next;
+                delete tmp;
+                return;
+            }
+            cur = cur->next;
+        }
+    }
+};
+```
+
+```javascript
+class ListNode {
+    /** 
+     * @param {number} key 
+     * @param {number} val
+     * @param {ListNode} next
+     */
+    constructor(key = -1, val = -1, next = null) {
+        this.key = key;
+        this.val = val;
+        this.next = next;
+    }
+}
+
+class MyHashMap {
+    constructor() {
+        this.map = Array.from({ length: 1000 }, () => new ListNode());
+    }
+
+    /** 
+     * @param {number} key 
+     * @return {number}
+     */
+    hash(key) {
+        return key % this.map.length;
+    }
+
+    /** 
+     * @param {number} key 
+     * @param {number} value
+     * @return {void}
+     */
+    put(key, value) {
+        let cur = this.map[this.hash(key)];
+        while (cur.next) {
+            if (cur.next.key === key) {
+                cur.next.val = value;
+                return;
+            }
+            cur = cur.next;
+        }
+        cur.next = new ListNode(key, value);
+    }
+
+    /** 
+     * @param {number} key 
+     * @return {number}
+     */
+    get(key) {
+        let cur = this.map[this.hash(key)].next;
+        while (cur) {
+            if (cur.key === key) {
+                return cur.val;
+            }
+            cur = cur.next;
+        }
+        return -1;
+    }
+
+    /** 
+     * @param {number} key 
+     * @return {void}
+     */
+    remove(key) {
+        let cur = this.map[this.hash(key)];
+        while (cur.next) {
+            if (cur.next.key === key) {
+                cur.next = cur.next.next;
+                return;
+            }
+            cur = cur.next;
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\frac{n}{k})$ for each function call.
+* Space complexity: $O(k + m)$
+
+> Where $n$ is the number of keys, $k$ is the size of the map ($1000$) and $m$ is the number of unique keys.
\ No newline at end of file
diff --git a/articles/design-hashset.md b/articles/design-hashset.md
new file mode 100644
index 000000000..9ee3f0884
--- /dev/null
+++ b/articles/design-hashset.md
@@ -0,0 +1,1028 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class MyHashSet:
+
+    def __init__(self):
+        self.data = []
+
+    def add(self, key: int) -> None:
+        if key not in self.data:
+            self.data.append(key)
+
+    def remove(self, key: int) -> None:
+        if key in self.data:
+            self.data.remove(key)
+
+    def contains(self, key: int) -> bool:
+        return key in self.data
+```
+
+```java
+public class MyHashSet {
+    private List<Integer> data;
+
+    public MyHashSet() {
+        data = new ArrayList<>();
+    }
+
+    public void add(int key) {
+        if (!data.contains(key)) {
+            data.add(key);
+        }
+    }
+
+    public void remove(int key) {
+        data.remove(Integer.valueOf(key));
+    }
+
+    public boolean contains(int key) {
+        return data.contains(key);
+    }
+}
+```
+
+```cpp
+class MyHashSet {
+private:
+    vector<int> data;
+public:
+    MyHashSet() {}
+
+    void add(int key) {
+        if (find(data.begin(), data.end(), key) == data.end()) {
+            data.push_back(key);
+        }
+    }
+
+    void remove(int key) {
+        auto it = find(data.begin(), data.end(), key);
+        if (it != data.end()) {
+            data.erase(it);
+        }
+    }
+
+    bool contains(int key) {
+        return find(data.begin(), data.end(), key) != data.end();
+    }
+};
+```
+
+```javascript
+class MyHashSet {
+    constructor() {
+        this.data = [];
+    }
+
+    /** 
+     * @param {number} key
+     * @return {void}
+     */
+    add(key) {
+        if (!this.data.includes(key)) {
+            this.data.push(key);
+        }
+    }
+
+    /** 
+     * @param {number} key
+     * @return {void}
+     */
+    remove(key) {
+        const index = this.data.indexOf(key);
+        if (index !== -1) {
+            this.data.splice(index, 1);
+        }
+    }
+
+    /** 
+     * @param {number} key
+     * @return {boolean}
+     */
+    contains(key) {
+        return this.data.includes(key);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$ for each function call.
+* Space complexity: $O(n)$
+
+---
+
+## 2. Boolean Array
+
+::tabs-start
+
+```python
+class MyHashSet:
+
+    def __init__(self):
+        self.data = [False] * 1000001
+
+    def add(self, key: int) -> None:
+        self.data[key] = True
+
+    def remove(self, key: int) -> None:
+        self.data[key] = False
+
+    def contains(self, key: int) -> bool:
+        return self.data[key]
+```
+
+```java
+public class MyHashSet {
+    private boolean[] data;
+
+    public MyHashSet() {
+        data = new boolean[1000001];
+    }
+
+    public void add(int key) {
+        data[key] = true;
+    }
+
+    public void remove(int key) {
+        data[key] = false;
+    }
+
+    public boolean contains(int key) {
+        return data[key];
+    }
+}
+```
+
+```cpp
+class MyHashSet {
+private:
+    vector<bool> data;
+public:
+    MyHashSet() : data(1000001, false) {}
+
+    void add(int key) {
+        data[key] = true;
+    }
+
+    void remove(int key) {
+        data[key] = false;
+    }
+
+    bool contains(int key) {
+        return data[key];
+    }
+};
+```
+
+```javascript
+class MyHashSet {
+    constructor() {
+        this.data = new Array(1000001).fill(false);
+    }
+
+    /** 
+     * @param {number} key
+     * @return {void}
+     */
+    add(key) {
+        this.data[key] = true;
+    }
+
+    /** 
+     * @param {number} key
+     * @return {void}
+     */
+    remove(key) {
+        this.data[key] = false;
+    }
+
+    /** 
+     * @param {number} key
+     * @return {boolean}
+     */
+    contains(key) {
+        return this.data[key];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$ for each function call.
+* Space complexity: $O(1000000)$ since the key is in the range $[0, 1000000]$.
+
+---
+
+## 3. Linked List
+
+::tabs-start
+
+```python
+class ListNode:
+    def __init__(self, key: int):
+        self.key = key
+        self.next = None
+
+class MyHashSet:
+
+    def __init__(self):
+        self.set = [ListNode(0) for _ in range(10**4)]
+
+    def add(self, key: int) -> None:
+        cur = self.set[key % len(self.set)]
+        while cur.next:
+            if cur.next.key == key:
+                return
+            cur = cur.next
+        cur.next = ListNode(key)
+
+    def remove(self, key: int) -> None:
+        cur = self.set[key % len(self.set)]
+        while cur.next:
+            if cur.next.key == key:
+                cur.next = cur.next.next
+                return
+            cur = cur.next
+
+    def contains(self, key: int) -> bool:
+        cur = self.set[key % len(self.set)]
+        while cur.next:
+            if cur.next.key == key:
+                return True
+            cur = cur.next
+        return False
+```
+
+```java
+public class MyHashSet {
+
+    private static class ListNode {
+        int key;
+        ListNode next;
+
+        ListNode(int key) {
+            this.key = key;
+        }
+    }
+
+    private final ListNode[] set;
+
+    public MyHashSet() {
+        set = new ListNode[10000];
+        for (int i = 0; i < set.length; i++) {
+            set[i] = new ListNode(0);
+        }
+    }
+
+    public void add(int key) {
+        ListNode cur = set[key % set.length];
+        while (cur.next != null) {
+            if (cur.next.key == key) {
+                return;
+            }
+            cur = cur.next;
+        }
+        cur.next = new ListNode(key);
+    }
+
+    public void remove(int key) {
+        ListNode cur = set[key % set.length];
+        while (cur.next != null) {
+            if (cur.next.key == key) {
+                cur.next = cur.next.next;
+                return;
+            }
+            cur = cur.next;
+        }
+    }
+
+    public boolean contains(int key) {
+        ListNode cur = set[key % set.length];
+        while (cur.next != null) {
+            if (cur.next.key == key) {
+                return true;
+            }
+            cur = cur.next;
+        }
+        return false;
+    }
+}
+```
+
+```cpp
+class MyHashSet {
+private:
+    struct ListNode {
+        int key;
+        ListNode* next;
+        ListNode(int k) : key(k), next(nullptr) {}
+    };
+
+    vector<ListNode*> set;
+
+    int hash(int key) {
+        return key % set.size();
+    }
+
+public:
+    MyHashSet() {
+        set.resize(10000);
+        for (auto& bucket : set) {
+            bucket = new ListNode(0);
+        }
+    }
+
+    void add(int key) {
+        ListNode* cur = set[hash(key)];
+        while (cur->next) {
+            if (cur->next->key == key) {
+                return;
+            }
+            cur = cur->next;
+        }
+        cur->next = new ListNode(key);
+    }
+
+    void remove(int key) {
+        ListNode* cur = set[hash(key)];
+        while (cur->next) {
+            if (cur->next->key == key) {
+                ListNode* temp = cur->next;
+                cur->next = temp->next;
+                delete temp;
+                return;
+            }
+            cur = cur->next;
+        }
+    }
+
+    bool contains(int key) {
+        ListNode* cur = set[hash(key)];
+        while (cur->next) {
+            if (cur->next->key == key) {
+                return true;
+            }
+            cur = cur->next;
+        }
+        return false;
+    }
+};
+```
+
+```javascript
+class ListNode {
+    /**
+     * @param {number} key
+     */
+    constructor(key) {
+        this.key = key;
+        this.next = null;
+    }
+}
+
+class MyHashSet {
+    constructor() {
+        this.set = Array.from({ length: 10000 }, () => new ListNode(0));
+    }
+
+    /**
+     * @param {number} key
+     * @return {number}
+     */
+    hash(key) {
+        return key % this.set.length;
+    }
+
+    /**
+     * @param {number} key
+     * @return {void}
+     */
+    add(key) {
+        let cur = this.set[this.hash(key)];
+        while (cur.next) {
+            if (cur.next.key === key) {
+                return;
+            }
+            cur = cur.next;
+        }
+        cur.next = new ListNode(key);
+    }
+
+    /**
+     * @param {number} key
+     * @return {void}
+     */
+    remove(key) {
+        let cur = this.set[this.hash(key)];
+        while (cur.next) {
+            if (cur.next.key === key) {
+                cur.next = cur.next.next;
+                return;
+            }
+            cur = cur.next;
+        }
+    }
+
+    /**
+     * @param {number} key
+     * @return {boolean}
+     */
+    contains(key) {
+        let cur = this.set[this.hash(key)];
+        while (cur.next) {
+            if (cur.next.key === key) {
+                return true;
+            }
+            cur = cur.next;
+        }
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\frac{n}{k})$ for each function call.
+* Space complexity: $O(k + m)$
+
+> Where $n$ is the number of keys, $k$ is the size of the set ($10000$) and $m$ is the number of unique keys.
+
+---
+
+## 4. Binary Search Tree
+
+::tabs-start
+
+```python
+class TreeNode:
+    def __init__(self, key):
+        self.key = key
+        self.left = None
+        self.right = None
+
+class BST:
+    def __init__(self):
+        self.root = None
+
+    def insert(self, root, key):
+        if not root:
+            return TreeNode(key)
+        if key < root.key:
+            root.left = self.insert(root.left, key)
+        elif key > root.key:
+            root.right = self.insert(root.right, key)
+        return root
+
+    def delete(self, root, key):
+        if not root:
+            return None
+        if key < root.key:
+            root.left = self.delete(root.left, key)
+        elif key > root.key:
+            root.right = self.delete(root.right, key)
+        else:
+            if not root.left:
+                return root.right
+            if not root.right:
+                return root.left
+            temp = self.minValueNode(root.right)
+            root.key = temp.key
+            root.right = self.delete(root.right, temp.key)
+        return root
+
+    def minValueNode(self, root):
+        while root.left:
+            root = root.left
+        return root
+
+    def search(self, root, key):
+        if not root:
+            return False
+        if key == root.key:
+            return True
+        elif key < root.key:
+            return self.search(root.left, key)
+        else:
+            return self.search(root.right, key)
+
+    def add(self, key):
+        self.root = self.insert(self.root, key)
+
+    def remove(self, key):
+        self.root = self.delete(self.root, key)
+
+    def contains(self, key):
+        return self.search(self.root, key)
+
+class MyHashSet:
+    def __init__(self):
+        self.size = 10000
+        self.buckets = [BST() for _ in range(self.size)]
+
+    def _hash(self, key):
+        return key % self.size
+
+    def add(self, key: int) -> None:
+        idx = self._hash(key)
+        if not self.contains(key):
+            self.buckets[idx].add(key)
+
+    def remove(self, key: int) -> None:
+        idx = self._hash(key)
+        self.buckets[idx].remove(key)
+
+    def contains(self, key: int) -> bool:
+        idx = self._hash(key)
+        return self.buckets[idx].contains(key)
+```
+
+```java
+class TreeNode {
+    int key;
+    TreeNode left, right;
+
+    TreeNode(int key) {
+        this.key = key;
+    }
+}
+
+class BST {
+    private TreeNode root;
+
+    private TreeNode insert(TreeNode node, int key) {
+        if (node == null) return new TreeNode(key);
+        if (key < node.key) node.left = insert(node.left, key);
+        else if (key > node.key) node.right = insert(node.right, key);
+        return node;
+    }
+
+    private TreeNode delete(TreeNode node, int key) {
+        if (node == null) return null;
+        if (key < node.key) node.left = delete(node.left, key);
+        else if (key > node.key) node.right = delete(node.right, key);
+        else {
+            if (node.left == null) return node.right;
+            if (node.right == null) return node.left;
+            TreeNode temp = minValueNode(node.right);
+            node.key = temp.key;
+            node.right = delete(node.right, temp.key);
+        }
+        return node;
+    }
+
+    private TreeNode minValueNode(TreeNode node) {
+        while (node.left != null) node = node.left;
+        return node;
+    }
+
+    private boolean search(TreeNode node, int key) {
+        if (node == null) return false;
+        if (key == node.key) return true;
+        return key < node.key ? search(node.left, key) : search(node.right, key);
+    }
+
+    public void add(int key) {
+        root = insert(root, key);
+    }
+
+    public void remove(int key) {
+        root = delete(root, key);
+    }
+
+    public boolean contains(int key) {
+        return search(root, key);
+    }
+}
+
+public class MyHashSet {
+    private final int size = 10000;
+    private BST[] buckets;
+
+    public MyHashSet() {
+        buckets = new BST[size];
+        for (int i = 0; i < size; i++) {
+            buckets[i] = new BST();
+        }
+    }
+
+    private int hash(int key) {
+        return key % size;
+    }
+
+    public void add(int key) {
+        int idx = hash(key);
+        if (!buckets[idx].contains(key)) {
+            buckets[idx].add(key);
+        }
+    }
+
+    public void remove(int key) {
+        int idx = hash(key);
+        buckets[idx].remove(key);
+    }
+
+    public boolean contains(int key) {
+        int idx = hash(key);
+        return buckets[idx].contains(key);
+    }
+}
+```
+
+```cpp
+class BST {
+private:
+    struct TreeNode {
+        int key;
+        TreeNode* left;
+        TreeNode* right;
+        TreeNode(int k) : key(k), left(nullptr), right(nullptr) {}
+    };
+
+    TreeNode* insert(TreeNode* root, int key) {
+        if (!root) return new TreeNode(key);
+        if (key < root->key)
+            root->left = insert(root->left, key);
+        else if (key > root->key)
+            root->right = insert(root->right, key);
+        return root;
+    }
+
+    TreeNode* deleteNode(TreeNode* root, int key) {
+        if (!root) return nullptr;
+        if (key < root->key)
+            root->left = deleteNode(root->left, key);
+        else if (key > root->key)
+            root->right = deleteNode(root->right, key);
+        else {
+            if (!root->left) {
+                TreeNode* temp = root->right;
+                delete root;
+                return temp;
+            }
+            if (!root->right) {
+                TreeNode* temp = root->left;
+                delete root;
+                return temp;
+            }
+            TreeNode* temp = minValueNode(root->right);
+            root->key = temp->key;
+            root->right = deleteNode(root->right, temp->key);
+        }
+        return root;
+    }
+
+    TreeNode* minValueNode(TreeNode* root) {
+        while (root->left) root = root->left;
+        return root;
+    }
+
+    bool search(TreeNode* root, int key) {
+        if (!root) return false;
+        if (key == root->key) return true;
+        return key < root->key ? search(root->left, key) : search(root->right, key);
+    }
+
+    TreeNode* root;
+
+public:
+    BST() : root(nullptr) {}
+
+    void add(int key) {
+        root = insert(root, key);
+    }
+
+    void remove(int key) {
+        root = deleteNode(root, key);
+    }
+
+    bool contains(int key) {
+        return search(root, key);
+    }
+};
+
+class MyHashSet {
+private:
+    const int size = 10000;
+    vector<BST> buckets;
+
+    int hash(int key) {
+        return key % size;
+    }
+
+public:
+    MyHashSet() : buckets(size) {}
+
+    void add(int key) {
+        int idx = hash(key);
+        if (!contains(key)) {
+            buckets[idx].add(key);
+        }
+    }
+
+    void remove(int key) {
+        int idx = hash(key);
+        buckets[idx].remove(key);
+    }
+
+    bool contains(int key) {
+        int idx = hash(key);
+        return buckets[idx].contains(key);
+    }
+};
+```
+
+```javascript
+class TreeNode {
+    /**
+     * @param {number} key
+     */
+    constructor(key) {
+        this.key = key;
+        this.left = null;
+        this.right = null;
+    }
+}
+
+class BST {
+    constructor() {
+        this.root = null;
+    }
+
+    /**
+     * @param {number} key
+     * @return {void}
+     */
+    add(key) {
+        this.root = this._insert(this.root, key);
+    }
+
+    /**
+     * @param {TreeNode} node
+     * @param {number} key
+     * @return {TreeNode}
+     */
+    _insert(node, key) {
+        if (!node) return new TreeNode(key);
+        if (key < node.key) node.left = this._insert(node.left, key);
+        else if (key > node.key) node.right = this._insert(node.right, key);
+        return node;
+    }
+
+    /**
+     * @param {number} key
+     * @return {void}
+     */
+    remove(key) {
+        this.root = this._deleteNode(this.root, key);
+    }
+
+    /**
+     * @param {TreeNode} node
+     * @param {number} key
+     * @return {TreeNode}
+     */
+    _deleteNode(node, key) {
+        if (!node) return null;
+        if (key < node.key) node.left = this._deleteNode(node.left, key);
+        else if (key > node.key) node.right = this._deleteNode(node.right, key);
+        else {
+            if (!node.left) return node.right;
+            if (!node.right) return node.left;
+            let minNode = this._minValueNode(node.right);
+            node.key = minNode.key;
+            node.right = this._deleteNode(node.right, minNode.key);
+        }
+        return node;
+    }
+
+    /**
+     * @param {TreeNode} node
+     * @return {TreeNode}
+     */
+    _minValueNode(node) {
+        while (node.left) node = node.left;
+        return node;
+    }
+
+    /** 
+     * @param {number} key
+     * @return {boolean}
+     */
+    contains(key) {
+        return this._search(this.root, key);
+    }
+
+    /** 
+     * @param {TreeNode} node
+     * @param {number} key
+     * @return {boolean}
+     */
+    _search(node, key) {
+        if (!node) return false;
+        if (key === node.key) return true;
+        if (key < node.key) return this._search(node.left, key);
+        return this._search(node.right, key);
+    }
+}
+
+class MyHashSet {
+    constructor() {
+        this.size = 10000;
+        this.buckets = Array.from({ length: this.size }, () => new BST());
+    }
+
+    _hash(key) {
+        return key % this.size;
+    }
+
+    /** 
+     * @param {number} key
+     * @return {void}
+     */
+    add(key) {
+        const idx = this._hash(key);
+        if (!this.buckets[idx].contains(key)) {
+            this.buckets[idx].add(key);
+        }
+    }
+
+    /** 
+     * @param {number} key
+     * @return {void}
+     */
+    remove(key) {
+        const idx = this._hash(key);
+        this.buckets[idx].remove(key);
+    }
+
+    /** 
+     * @param {number} key
+     * @return {boolean}
+     */
+    contains(key) {
+        const idx = this._hash(key);
+        return this.buckets[idx].contains(key);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log (\frac{n}{k}))$ in average case, $O(\frac{n}{k})$ in worst case for each function call.
+* Space complexity: $O(k + m)$
+
+> Where $n$ is the number of keys, $k$ is the size of the set ($10000$) and $m$ is the number of unique keys.
+
+---
+
+## 5. Bit Manipulation
+
+::tabs-start
+
+```python
+class MyHashSet:
+
+    def __init__(self):
+        # key is in the range [1, 1000000]
+        # 31251 * 32 = 1000032
+        self.set = [0] * 31251
+
+    def add(self, key: int) -> None:
+        self.set[key // 32] |= self.getMask(key)
+
+    def remove(self, key: int) -> None:
+        if self.contains(key):
+            self.set[key // 32] ^= self.getMask(key)
+
+    def contains(self, key: int) -> bool:
+        return self.set[key // 32] & self.getMask(key) != 0
+
+    def getMask(self, key: int) -> int:
+        return 1 << (key % 32)
+```
+
+```java
+public class MyHashSet {
+    private int[] set;
+
+    public MyHashSet() {
+        // key is in the range [1, 1000000]
+        // 31251 * 32 = 1000032
+        set = new int[31251];
+    }
+
+    public void add(int key) {
+        set[key / 32] |= getMask(key);
+    }
+
+    public void remove(int key) {
+        if (contains(key)) {
+            set[key / 32] ^= getMask(key);
+        }
+    }
+
+    public boolean contains(int key) {
+        return (set[key / 32] & getMask(key)) != 0;
+    }
+
+    private int getMask(int key) {
+        return 1 << (key % 32);
+    }
+}
+```
+
+```cpp
+class MyHashSet {
+private:
+    int set[31251];
+
+    int getMask(int key) {
+        return 1 << (key % 32);
+    }
+
+public:
+    MyHashSet() {
+        // key is in the range [1, 1000000]
+        // 31251 * 32 = 1000032
+        memset(set, 0, sizeof(set));
+    }
+
+    void add(int key) {
+        set[key / 32] |= getMask(key);
+    }
+
+    void remove(int key) {
+        if (contains(key)) {
+            set[key / 32] ^= getMask(key);
+        }
+    }
+
+    bool contains(int key) {
+        return (set[key / 32] & getMask(key)) != 0;
+    }
+};
+```
+
+```javascript
+class MyHashSet {
+    constructor() {
+        // key is in the range [1, 1000000]
+        // 31251 * 32 = 1000032
+        this.set = new Array(31251).fill(0);
+    }
+
+    /** 
+     * @param {number} key
+     * @return {void}
+     */
+    add(key) {
+        this.set[Math.floor(key / 32)] |= this.getMask(key);
+    }
+
+    /** 
+     * @param {number} key
+     * @return {void}
+     */
+    remove(key) {
+        if (this.contains(key)) {
+            this.set[Math.floor(key / 32)] ^= this.getMask(key);
+        }
+    }
+
+    /** 
+     * @param {number} key
+     * @return {boolean}
+     */
+    contains(key) {
+        return (this.set[Math.floor(key / 32)] & this.getMask(key)) !== 0;
+    }
+
+    /** 
+     * @param {number} key
+     * @return {number}
+     */
+    getMask(key) {
+        return 1 << (key % 32);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$ for each function call.
+* Space complexity: $O(k)$
+
+> Where $k$ is the size of the set $(31251)$.
\ No newline at end of file
diff --git a/articles/design-linked-list.md b/articles/design-linked-list.md
new file mode 100644
index 000000000..618c2335c
--- /dev/null
+++ b/articles/design-linked-list.md
@@ -0,0 +1,1262 @@
+## 1. Singly Linked List
+
+::tabs-start
+
+```python
+class ListNode:
+    def __init__(self, val: int):
+        self.val = val
+        self.next = None
+
+class MyLinkedList:
+    def __init__(self):
+        self.head = ListNode(0)
+        self.size = 0
+
+    def get(self, index: int) -> int:
+        if index >= self.size:
+            return -1
+        cur = self.head.next
+        for _ in range(index):
+            cur = cur.next
+        return cur.val
+
+    def addAtHead(self, val: int) -> None:
+        node = ListNode(val)
+        node.next = self.head.next
+        self.head.next = node
+        self.size += 1
+
+    def addAtTail(self, val: int) -> None:
+        node = ListNode(val)
+        cur = self.head
+        while cur.next:
+            cur = cur.next
+        cur.next = node
+        self.size += 1
+
+    def addAtIndex(self, index: int, val: int) -> None:
+        if index > self.size:
+            return
+        cur = self.head
+        for _ in range(index):
+            cur = cur.next
+        node = ListNode(val)
+        node.next = cur.next
+        cur.next = node
+        self.size += 1
+
+    def deleteAtIndex(self, index: int) -> None:
+        if index >= self.size:
+            return
+        cur = self.head
+        for _ in range(index):
+            cur = cur.next
+        cur.next = cur.next.next
+        self.size -= 1
+```
+
+```java
+class ListNode {
+    int val;
+    ListNode next;
+    ListNode(int val) {
+        this.val = val;
+        this.next = null;
+    }
+}
+
+public class MyLinkedList {
+    private ListNode head;
+    private int size;
+    MyLinkedList() {
+        head = new ListNode(0);
+        size = 0;
+    }
+    public int get(int index) {
+        if (index >= size) return -1;
+        ListNode cur = head.next;
+        for (int i = 0; i < index; i++) {
+            cur = cur.next;
+        }
+        return cur.val;
+    }
+    public void addAtHead(int val) {
+        ListNode node = new ListNode(val);
+        node.next = head.next;
+        head.next = node;
+        size++;
+    }
+    public void addAtTail(int val) {
+        ListNode node = new ListNode(val);
+        ListNode cur = head;
+        while (cur.next != null) {
+            cur = cur.next;
+        }
+        cur.next = node;
+        size++;
+    }
+    public void addAtIndex(int index, int val) {
+        if (index > size) return;
+        ListNode cur = head;
+        for (int i = 0; i < index; i++) {
+            cur = cur.next;
+        }
+        ListNode node = new ListNode(val);
+        node.next = cur.next;
+        cur.next = node;
+        size++;
+    }
+    public void deleteAtIndex(int index) {
+        if (index >= size) return;
+        ListNode cur = head;
+        for (int i = 0; i < index; i++) {
+            cur = cur.next;
+        }
+        cur.next = cur.next.next;
+        size--;
+    }
+}
+```
+
+```cpp
+class MyLinkedList {
+    struct ListNode {
+        int val;
+        ListNode* next;
+        ListNode(int val) : val(val), next(nullptr) {}
+    };
+
+public:
+    ListNode* head;
+    int size;
+    MyLinkedList() {
+        head = new ListNode(0);
+        size = 0;
+    }
+    int get(int index) {
+        if (index >= size) return -1;
+        ListNode* cur = head->next;
+        for (int i = 0; i < index; i++) {
+            cur = cur->next;
+        }
+        return cur->val;
+    }
+    void addAtHead(int val) {
+        ListNode* node = new ListNode(val);
+        node->next = head->next;
+        head->next = node;
+        size++;
+    }
+    void addAtTail(int val) {
+        ListNode* node = new ListNode(val);
+        ListNode* cur = head;
+        while (cur->next != nullptr) {
+            cur = cur->next;
+        }
+        cur->next = node;
+        size++;
+    }
+    void addAtIndex(int index, int val) {
+        if (index > size) return;
+        ListNode* cur = head;
+        for (int i = 0; i < index; i++) {
+            cur = cur->next;
+        }
+        ListNode* node = new ListNode(val);
+        node->next = cur->next;
+        cur->next = node;
+        size++;
+    }
+    void deleteAtIndex(int index) {
+        if (index >= size) return;
+        ListNode* cur = head;
+        for (int i = 0; i < index; i++) {
+            cur = cur->next;
+        }
+        ListNode* temp = cur->next;
+        cur->next = cur->next->next;
+        delete temp;
+        size--;
+    }
+};
+```
+
+```javascript
+class ListNode {
+    /**
+     * @constructor
+     * @param {number} val
+     */
+    constructor(val) {
+        this.val = val;
+        this.next = null;
+    }
+}
+
+class MyLinkedList {
+    constructor() {
+        this.head = new ListNode(0);
+        this.size = 0;
+    }
+
+    /**
+     * @param {number} index
+     * @return {number}
+     */
+    get(index) {
+        if (index >= this.size) return -1;
+        let cur = this.head.next;
+        for (let i = 0; i < index; i++) {
+            cur = cur.next;
+        }
+        return cur.val;
+    }
+
+    /**
+     * @param {number} val
+     * @return {void}
+     */
+    addAtHead(val) {
+        const node = new ListNode(val);
+        node.next = this.head.next;
+        this.head.next = node;
+        this.size++;
+    }
+
+    /**
+     * @param {number} val
+     * @return {void}
+     */
+    addAtTail(val) {
+        const node = new ListNode(val);
+        let cur = this.head;
+        while (cur.next !== null) {
+            cur = cur.next;
+        }
+        cur.next = node;
+        this.size++;
+    }
+
+    /**
+     * @param {number} index
+     * @param {number} val
+     * @return {void}
+     */
+    addAtIndex(index, val) {
+        if (index > this.size) return;
+        let cur = this.head;
+        for (let i = 0; i < index; i++) {
+            cur = cur.next;
+        }
+        const node = new ListNode(val);
+        node.next = cur.next;
+        cur.next = node;
+        this.size++;
+    }
+
+    /**
+     * @param {number} index
+     * @return {void}
+     */
+    deleteAtIndex(index) {
+        if (index >= this.size) return;
+        let cur = this.head;
+        for (let i = 0; i < index; i++) {
+            cur = cur.next;
+        }
+        cur.next = cur.next.next;
+        this.size--;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(1)$ time for initialization.
+    * $O(1)$ time for $addAtHead()$.
+    * $O(n)$ time for $get()$, $addAtTail()$, $addAtIndex()$, $deleteAtIndex()$.
+* Space complexity: $O(n)$
+
+---
+
+## 2. Singly Linked List (Optimal)
+
+::tabs-start
+
+```python
+class ListNode:
+    def __init__(self, val=0, next=None):
+        self.val = val
+        self.next = next
+
+class MyLinkedList:
+    def __init__(self):
+        self.head = ListNode(0)
+        self.size = 0
+
+    def getPrev(self, index: int) -> ListNode:
+        cur = self.head
+        for _ in range(index):
+            cur = cur.next
+        return cur
+
+    def get(self, index: int) -> int:
+        if index >= self.size:
+            return -1
+        return self.getPrev(index).next.val
+
+    def addAtHead(self, val: int) -> None:
+        self.addAtIndex(0, val)
+
+    def addAtTail(self, val: int) -> None:
+        self.addAtIndex(self.size, val)
+
+    def addAtIndex(self, index: int, val: int) -> None:
+        if index > self.size:
+            return
+        prev = self.getPrev(index)
+        node = ListNode(val, prev.next)
+        prev.next = node
+        self.size += 1
+
+    def deleteAtIndex(self, index: int) -> None:
+        if index >= self.size:
+            return
+        prev = self.getPrev(index)
+        prev.next = prev.next.next
+        self.size -= 1
+```
+
+```java
+class ListNode {
+    int val;
+    ListNode next;
+    ListNode(int val, ListNode next) {
+        this.val = val;
+        this.next = next;
+    }
+    ListNode(int val) {
+        this(val, null);
+    }
+}
+
+public class MyLinkedList {
+    ListNode head;
+    int size;
+    
+    public MyLinkedList() {
+        head = new ListNode(0, null);
+        size = 0;
+    }
+    
+    private ListNode getPrev(int index) {
+        ListNode cur = head;
+        for (int i = 0; i < index; i++) {
+            cur = cur.next;
+        }
+        return cur;
+    }
+    
+    public int get(int index) {
+        if (index >= size) {
+            return -1;
+        }
+        return getPrev(index).next.val;
+    }
+    
+    public void addAtHead(int val) {
+        addAtIndex(0, val);
+    }
+    
+    public void addAtTail(int val) {
+        addAtIndex(size, val);
+    }
+    
+    public void addAtIndex(int index, int val) {
+        if (index > size) {
+            return;
+        }
+        ListNode prev = getPrev(index);
+        ListNode node = new ListNode(val, prev.next);
+        prev.next = node;
+        size++;
+    }
+    
+    public void deleteAtIndex(int index) {
+        if (index >= size) {
+            return;
+        }
+        ListNode prev = getPrev(index);
+        prev.next = prev.next.next;
+        size--;
+    }
+}
+```
+
+```cpp
+
+class MyLinkedList {
+    struct ListNode {
+        int val;
+        ListNode* next;
+        ListNode(int val, ListNode* next) : val(val), next(next) {}
+        ListNode(int val) : val(val), next(nullptr) {}
+    };
+
+public:
+    MyLinkedList() {
+        head = new ListNode(0, nullptr);
+        size = 0;
+    }
+    
+    int get(int index) {
+        if (index >= size) return -1;
+        return getPrev(index)->next->val;
+    }
+    
+    void addAtHead(int val) {
+        addAtIndex(0, val);
+    }
+    
+    void addAtTail(int val) {
+        addAtIndex(size, val);
+    }
+    
+    void addAtIndex(int index, int val) {
+        if (index > size) return;
+        ListNode* prev = getPrev(index);
+        ListNode* node = new ListNode(val, prev->next);
+        prev->next = node;
+        size++;
+    }
+    
+    void deleteAtIndex(int index) {
+        if (index >= size) return;
+        ListNode* prev = getPrev(index);
+        ListNode* toDelete = prev->next;
+        prev->next = prev->next->next;
+        delete toDelete;
+        size--;
+    }
+    
+private:
+    ListNode* head;
+    int size;
+    
+    ListNode* getPrev(int index) {
+        ListNode* cur = head;
+        for (int i = 0; i < index; i++) {
+            cur = cur->next;
+        }
+        return cur;
+    }
+};
+```
+
+```javascript
+class ListNode {
+	/**
+     * @constructor
+	 * @param {number}
+	 * @param {ListNode|null}
+	 */
+	constructor(val = 0, next = null) {
+		this.val = val;
+		this.next = next;
+	}
+}
+
+class MyLinkedList {
+	constructor() {
+		this.head = new ListNode(0);
+		this.size = 0;
+	}
+
+	/**
+	 * @param {number} index
+	 * @return {ListNode}
+	 */
+	getPrev(index) {
+		let cur = this.head;
+		for (let i = 0; i < index; i++) {
+			cur = cur.next;
+		}
+		return cur;
+	}
+
+	/**
+	 * @param {number} index
+	 * @return {number}
+	 */
+	get(index) {
+		if (index >= this.size) {
+			return -1;
+		}
+		return this.getPrev(index).next.val;
+	}
+
+	/**
+	 * @param {number} val
+	 * @return {void}
+	 */
+	addAtHead(val) {
+		this.addAtIndex(0, val);
+	}
+
+	/**
+	 * @param {number} val
+	 * @return {void}
+	 */
+	addAtTail(val) {
+		this.addAtIndex(this.size, val);
+	}
+
+	/**
+	 * @param {number} index
+	 * @param {number} val
+	 * @return {void}
+	 */
+	addAtIndex(index, val) {
+		if (index > this.size) {
+			return;
+		}
+		let prev = this.getPrev(index);
+		let node = new ListNode(val, prev.next);
+		prev.next = node;
+		this.size++;
+	}
+
+	/**
+	 * @param {number} index
+	 * @return {void}
+	 */
+	deleteAtIndex(index) {
+		if (index >= this.size) {
+			return;
+		}
+		let prev = this.getPrev(index);
+		prev.next = prev.next.next;
+		this.size--;
+	}
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(1)$ time for initialization.
+    * $O(1)$ time for $addAtHead()$.
+    * $O(n)$ time for $get()$, $addAtTail()$, $addAtIndex()$, $deleteAtIndex()$.
+* Space complexity: $O(n)$
+
+---
+
+## 3. Doubly Linked List
+
+::tabs-start
+
+```python
+class ListNode:
+    def __init__(self, val):
+        self.val = val
+        self.prev = None
+        self.next = None
+
+class MyLinkedList:
+
+    def __init__(self):
+        self.head = ListNode(0)
+        self.tail = ListNode(0)
+        self.head.next = self.tail
+        self.tail.prev = self.head
+
+    def get(self, index: int) -> int:
+        cur = self.head.next
+        while cur and index > 0:
+            cur = cur.next
+            index -= 1
+        if cur and cur != self.tail and index == 0:
+            return cur.val
+        return -1
+
+    def addAtHead(self, val: int) -> None:
+        node, next, prev = ListNode(val), self.head.next, self.head
+        prev.next = node
+        next.prev = node
+        node.next = next
+        node.prev = prev
+
+    def addAtTail(self, val: int) -> None:
+        node, next, prev = ListNode(val), self.tail, self.tail.prev
+        prev.next = node
+        next.prev = node
+        node.next = next
+        node.prev = prev
+
+    def addAtIndex(self, index: int, val: int) -> None:
+        cur = self.head.next
+        while cur and index > 0:
+            cur = cur.next
+            index -= 1
+        if cur and index == 0:
+            node, next, prev = ListNode(val), cur, cur.prev
+            prev.next = node
+            next.prev = node
+            node.next = next
+            node.prev = prev
+
+
+    def deleteAtIndex(self, index: int) -> None:
+        cur = self.head.next
+        while cur and index > 0:
+            cur = cur.next
+            index -= 1
+        if cur and cur != self.tail and index == 0:
+            next, prev = cur.next, cur.prev
+            next.prev = prev
+            prev.next = next
+```
+
+```java
+class ListNode {
+    int val;
+    ListNode prev;
+    ListNode next;
+
+    ListNode(int val) {
+        this.val = val;
+        this.prev = null;
+        this.next = null;
+    }
+}
+
+public class MyLinkedList {
+    ListNode head;
+    ListNode tail;
+
+    MyLinkedList() {
+        head = new ListNode(0);
+        tail = new ListNode(0);
+        head.next = tail;
+        tail.prev = head;
+    }
+
+    int get(int index) {
+        ListNode cur = head.next;
+        while (cur != null && index > 0) {
+            cur = cur.next;
+            index--;
+        }
+        if (cur != null && cur != tail && index == 0) {
+            return cur.val;
+        }
+        return -1;
+    }
+
+    void addAtHead(int val) {
+        ListNode node = new ListNode(val);
+        ListNode next = head.next;
+        ListNode prev = head;
+        prev.next = node;
+        next.prev = node;
+        node.next = next;
+        node.prev = prev;
+    }
+
+    void addAtTail(int val) {
+        ListNode node = new ListNode(val);
+        ListNode next = tail;
+        ListNode prev = tail.prev;
+        prev.next = node;
+        next.prev = node;
+        node.next = next;
+        node.prev = prev;
+    }
+
+    void addAtIndex(int index, int val) {
+        ListNode cur = head.next;
+        while (cur != null && index > 0) {
+            cur = cur.next;
+            index--;
+        }
+        if (cur != null && index == 0) {
+            ListNode node = new ListNode(val);
+            ListNode next = cur;
+            ListNode prev = cur.prev;
+            prev.next = node;
+            next.prev = node;
+            node.next = next;
+            node.prev = prev;
+        }
+    }
+
+    void deleteAtIndex(int index) {
+        ListNode cur = head.next;
+        while (cur != null && index > 0) {
+            cur = cur.next;
+            index--;
+        }
+        if (cur != null && cur != tail && index == 0) {
+            ListNode next = cur.next;
+            ListNode prev = cur.prev;
+            next.prev = prev;
+            prev.next = next;
+        }
+    }
+}
+```
+
+```cpp
+class MyLinkedList {
+    struct ListNode {
+        int val;
+        ListNode* prev;
+        ListNode* next;
+        ListNode(int val) : val(val), prev(nullptr), next(nullptr) {}
+    };
+public:
+	ListNode* head;
+	ListNode* tail;
+
+	MyLinkedList() {
+		head = new ListNode(0);
+		tail = new ListNode(0);
+		head->next = tail;
+		tail->prev = head;
+	}
+
+	int get(int index) {
+		ListNode* cur = head->next;
+		while (cur && index > 0) {
+			cur = cur->next;
+			index--;
+		}
+		if (cur && cur != tail && index == 0) {
+			return cur->val;
+		}
+		return -1;
+	}
+
+	void addAtHead(int val) {
+		ListNode* node = new ListNode(val);
+		ListNode* next = head->next;
+		ListNode* prev = head;
+		prev->next = node;
+		next->prev = node;
+		node->next = next;
+		node->prev = prev;
+	}
+
+	void addAtTail(int val) {
+		ListNode* node = new ListNode(val);
+		ListNode* next = tail;
+		ListNode* prev = tail->prev;
+		prev->next = node;
+		next->prev = node;
+		node->next = next;
+		node->prev = prev;
+	}
+
+	void addAtIndex(int index, int val) {
+		ListNode* cur = head->next;
+		while (cur && index > 0) {
+			cur = cur->next;
+			index--;
+		}
+		if (cur && index == 0) {
+			ListNode* node = new ListNode(val);
+			ListNode* next = cur;
+			ListNode* prev = cur->prev;
+			prev->next = node;
+			next->prev = node;
+			node->next = next;
+			node->prev = prev;
+		}
+	}
+
+	void deleteAtIndex(int index) {
+		ListNode* cur = head->next;
+		while (cur && index > 0) {
+			cur = cur->next;
+			index--;
+		}
+		if (cur && cur != tail && index == 0) {
+			ListNode* next = cur->next;
+			ListNode* prev = cur->prev;
+			next->prev = prev;
+			prev->next = next;
+			delete cur;
+		}
+	}
+};
+```
+
+```javascript
+class ListNode {
+	/**
+     * @constructor
+	 * @param {number} val
+	 */
+	constructor(val) {
+		this.val = val;
+		this.prev = null;
+		this.next = null;
+	}
+}
+
+class MyLinkedList {
+	constructor() {
+		this.head = new ListNode(0);
+		this.tail = new ListNode(0);
+		this.head.next = this.tail;
+		this.tail.prev = this.head;
+	}
+
+	/**
+	 * @param {number} index
+	 * @return {number}
+	 */
+	get(index) {
+		let cur = this.head.next;
+		while (cur && index > 0) {
+			cur = cur.next;
+			index--;
+		}
+		if (cur && cur !== this.tail && index === 0) {
+			return cur.val;
+		}
+		return -1;
+	}
+
+	/**
+	 * @param {number} val
+	 * @return {void}
+	 */
+	addAtHead(val) {
+		const node = new ListNode(val);
+		const next = this.head.next;
+		const prev = this.head;
+		prev.next = node;
+		next.prev = node;
+		node.next = next;
+		node.prev = prev;
+	}
+
+	/**
+	 * @param {number} val
+	 * @return {void}
+	 */
+	addAtTail(val) {
+		const node = new ListNode(val);
+		const next = this.tail;
+		const prev = this.tail.prev;
+		prev.next = node;
+		next.prev = node;
+		node.next = next;
+		node.prev = prev;
+	}
+
+	/**
+	 * @param {number} index
+	 * @param {number} val
+	 * @return {void}
+	 */
+	addAtIndex(index, val) {
+		let cur = this.head.next;
+		while (cur && index > 0) {
+			cur = cur.next;
+			index--;
+		}
+		if (cur && index === 0) {
+			const node = new ListNode(val);
+			const next = cur;
+			const prev = cur.prev;
+			prev.next = node;
+			next.prev = node;
+			node.next = next;
+			node.prev = prev;
+		}
+	}
+
+	/**
+	 * @param {number} index
+	 * @return {void}
+	 */
+	deleteAtIndex(index) {
+		let cur = this.head.next;
+		while (cur && index > 0) {
+			cur = cur.next;
+			index--;
+		}
+		if (cur && cur !== this.tail && index === 0) {
+			const next = cur.next;
+			const prev = cur.prev;
+			next.prev = prev;
+			prev.next = next;
+		}
+	}
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(1)$ time for initialization.
+    * $O(1)$ time for $addAtHead()$, $addAtTail()$.
+    * $O(n)$ time for $get()$, $addAtIndex()$, $deleteAtIndex()$.
+* Space complexity: $O(n)$
+
+---
+
+## 4. Doubly Linked List (Optimal)
+
+::tabs-start
+
+```python
+class ListNode:
+    def __init__(self, val=0, next=None, prev=None):
+        self.val = val
+        self.next = next
+        self.prev = prev
+
+class MyLinkedList:
+    def __init__(self):
+        self.head = ListNode(0)
+        self.tail = ListNode(0)
+        self.head.next = self.tail
+        self.tail.prev = self.head
+        self.size = 0
+
+    def getPrev(self, index: int) -> ListNode:
+        if index <= self.size // 2:
+            cur = self.head
+            for _ in range(index):
+                cur = cur.next
+        else:
+            cur = self.tail
+            for _ in range(self.size - index + 1):
+                cur = cur.prev
+        return cur
+
+    def get(self, index: int) -> int:
+        if index >= self.size:
+            return -1
+        return self.getPrev(index).next.val
+
+    def addAtHead(self, val: int) -> None:
+        self.addAtIndex(0, val)
+
+    def addAtTail(self, val: int) -> None:
+        self.addAtIndex(self.size, val)
+
+    def addAtIndex(self, index: int, val: int) -> None:
+        if index > self.size:
+            return
+        node = ListNode(val)
+        prev = self.getPrev(index)
+        next = prev.next
+        prev.next = node
+        node.prev = prev
+        node.next = next
+        next.prev = node
+        self.size += 1
+
+    def deleteAtIndex(self, index: int) -> None:
+        if index >= self.size:
+            return
+        prev = self.getPrev(index)
+        cur = prev.next
+        next = cur.next
+        prev.next = next
+        next.prev = prev
+        self.size -= 1
+```
+
+```java
+class ListNode {
+    int val;
+    ListNode next;
+    ListNode prev;
+    
+    ListNode(int val) {
+        this(val, null, null);
+    }
+    
+    ListNode(int val, ListNode next, ListNode prev) {
+        this.val = val;
+        this.next = next;
+        this.prev = prev;
+    }
+}
+
+public class MyLinkedList {
+    ListNode head;
+    ListNode tail;
+    int size;
+    
+    public MyLinkedList() {
+        head = new ListNode(0);
+        tail = new ListNode(0);
+        head.next = tail;
+        tail.prev = head;
+        size = 0;
+    }
+
+    private ListNode getPrev(int index) {
+        if (index <= size / 2) {
+            ListNode cur = head;
+            for (int i = 0; i < index; i++) {
+                cur = cur.next;
+            }
+            return cur;
+        } else {
+            ListNode cur = tail;
+            for (int i = 0; i < size - index + 1; i++) {
+                cur = cur.prev;
+            }
+            return cur;
+        }
+    }
+    
+    public int get(int index) {
+        if (index >= size) return -1;
+        return getPrev(index).next.val;
+    }
+    
+    public void addAtHead(int val) {
+        addAtIndex(0, val);
+    }
+    
+    public void addAtTail(int val) {
+        addAtIndex(size, val);
+    }
+    
+    public void addAtIndex(int index, int val) {
+        if (index > size) return;
+        ListNode node = new ListNode(val);
+        ListNode prev = getPrev(index);
+        ListNode next = prev.next;
+        prev.next = node;
+        node.prev = prev;
+        node.next = next;
+        next.prev = node;
+        size++;
+    }
+    
+    public void deleteAtIndex(int index) {
+        if (index >= size) return;
+        ListNode prev = getPrev(index);
+        ListNode cur = prev.next;
+        ListNode next = cur.next;
+        prev.next = next;
+        next.prev = prev;
+        size--;
+    }
+}
+```
+
+```cpp
+class MyLinkedList {
+    struct ListNode {
+        int val;
+        ListNode* next;
+        ListNode* prev;
+        ListNode(int val = 0, ListNode* next = nullptr, ListNode* prev = nullptr) {
+            this->val = val;
+            this->next = next;
+            this->prev = prev;
+        }
+    };
+    
+public:
+    ListNode* head;
+    ListNode* tail;
+    int size;
+    
+    MyLinkedList() {
+        head = new ListNode(0);
+        tail = new ListNode(0);
+        head->next = tail;
+        tail->prev = head;
+        size = 0;
+    }
+    
+    ListNode* getPrev(int index) {
+        if (index <= size / 2) {
+            ListNode* cur = head;
+            for (int i = 0; i < index; i++) {
+                cur = cur->next;
+            }
+            return cur;
+        } else {
+            ListNode* cur = tail;
+            for (int i = 0; i < size - index + 1; i++) {
+                cur = cur->prev;
+            }
+            return cur;
+        }
+    }
+    
+    int get(int index) {
+        if (index >= size) return -1;
+        return getPrev(index)->next->val;
+    }
+    
+    void addAtHead(int val) {
+        addAtIndex(0, val);
+    }
+    
+    void addAtTail(int val) {
+        addAtIndex(size, val);
+    }
+    
+    void addAtIndex(int index, int val) {
+        if (index > size) return;
+        ListNode* node = new ListNode(val);
+        ListNode* prev = getPrev(index);
+        ListNode* next = prev->next;
+        prev->next = node;
+        node->prev = prev;
+        node->next = next;
+        next->prev = node;
+        size++;
+    }
+    
+    void deleteAtIndex(int index) {
+        if (index >= size) return;
+        ListNode* prev = getPrev(index);
+        ListNode* cur = prev->next;
+        ListNode* next = cur->next;
+        prev->next = next;
+        next->prev = prev;
+        delete cur;
+        size--;
+    }
+};
+```
+
+```javascript
+class ListNode {
+    /**
+     * @constructor
+     * @param {number}
+     * @param {ListNode|null}
+     * @param {ListNode|null}
+     */
+	constructor(val = 0, next = null, prev = null) {
+		this.val = val;
+		this.next = next;
+		this.prev = prev;
+	}
+}
+
+class MyLinkedList {
+	constructor() {
+		this.head = new ListNode(0);
+		this.tail = new ListNode(0);
+		this.head.next = this.tail;
+		this.tail.prev = this.head;
+		this.size = 0;
+	}
+
+	/**
+	 * @param {number} index
+	 * @return {ListNode}
+	 */
+	getPrev(index) {
+		let cur;
+		if (index <= this.size / 2) {
+			cur = this.head;
+			for (let i = 0; i < index; i++) {
+				cur = cur.next;
+			}
+		} else {
+			cur = this.tail;
+			for (let i = 0; i < this.size - index + 1; i++) {
+				cur = cur.prev;
+			}
+		}
+		return cur;
+	}
+
+	/**
+	 * @param {number} index
+	 * @return {number}
+	 */
+	get(index) {
+		if (index >= this.size) {
+			return -1;
+		}
+		return this.getPrev(index).next.val;
+	}
+
+	/**
+	 * @param {number} val
+	 * @return {void}
+	 */
+	addAtHead(val) {
+		this.addAtIndex(0, val);
+	}
+
+	/**
+	 * @param {number} val
+	 * @return {void}
+	 */
+	addAtTail(val) {
+		this.addAtIndex(this.size, val);
+	}
+
+	/**
+	 * @param {number} index
+	 * @param {number} val
+	 * @return {void}
+	 */
+	addAtIndex(index, val) {
+		if (index > this.size) {
+			return;
+		}
+		const node = new ListNode(val);
+		const prev = this.getPrev(index);
+		const next = prev.next;
+		prev.next = node;
+		node.prev = prev;
+		node.next = next;
+		next.prev = node;
+		this.size++;
+	}
+
+	/**
+	 * @param {number} index
+	 * @return {void}
+	 */
+	deleteAtIndex(index) {
+		if (index >= this.size) {
+			return;
+		}
+		const prev = this.getPrev(index);
+		const cur = prev.next;
+		const next = cur.next;
+		prev.next = next;
+		next.prev = prev;
+		this.size--;
+	}
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(1)$ time for initialization.
+    * $O(1)$ time for $addAtHead()$, $addAtTail()$.
+    * $O(n)$ time for $get()$, $addAtIndex()$, $deleteAtIndex()$.
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/design-parking-system.md b/articles/design-parking-system.md
new file mode 100644
index 000000000..4abdb9aa3
--- /dev/null
+++ b/articles/design-parking-system.md
@@ -0,0 +1,167 @@
+## 1. Array - I
+
+::tabs-start
+
+```python
+class ParkingSystem:
+
+    def __init__(self, big: int, medium: int, small: int):
+        self.spaces = [big, medium, small]
+
+    def addCar(self, carType: int) -> bool:
+        if self.spaces[carType - 1] > 0:
+            self.spaces[carType - 1] -= 1
+            return True
+        return False
+```
+
+```java
+public class ParkingSystem {
+    private int[] spaces;
+
+    public ParkingSystem(int big, int medium, int small) {
+        spaces = new int[]{big, medium, small};
+    }
+
+    public boolean addCar(int carType) {
+        if (spaces[carType - 1] > 0) {
+            spaces[carType - 1]--;
+            return true;
+        }
+        return false;
+    }
+}
+```
+
+```cpp
+class ParkingSystem {
+    int spaces[3];
+
+public:
+    ParkingSystem(int big, int medium, int small) {
+        spaces[0] = big;
+        spaces[1] = medium;
+        spaces[2] = small;
+    }
+
+    bool addCar(int carType) {
+        if (spaces[carType - 1] > 0) {
+            spaces[carType - 1]--;
+            return true;
+        }
+        return false;
+    }
+};
+```
+
+```javascript
+class ParkingSystem {
+    /**
+     * @constructor
+     * @param {number} big
+     * @param {number} medium
+     * @param {number} small
+     */
+    constructor(big, medium, small) {
+        this.spaces = [big, medium, small];
+    }
+
+    /**
+     * @param {number} carType
+     * @return {boolean}
+     */
+    addCar(carType) {
+        if (this.spaces[carType - 1] > 0) {
+            this.spaces[carType - 1]--;
+            return true;
+        }
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(1)$ time for initialization.
+    * $O(1)$ time for each $addCar()$ function call.
+* Space complexity: $O(1)$
+
+---
+
+## 2. Array - II
+
+::tabs-start
+
+```python
+class ParkingSystem:
+
+    def __init__(self, big: int, medium: int, small: int):
+        self.spaces = [big, medium, small]
+
+    def addCar(self, carType: int) -> bool:
+        self.spaces[carType - 1] -= 1
+        return self.spaces[carType - 1] >= 0
+```
+
+```java
+public class ParkingSystem {
+    int[] spaces;
+
+    public ParkingSystem(int big, int medium, int small) {
+        spaces = new int[]{big, medium, small};
+    }
+
+    public boolean addCar(int carType) {
+        return spaces[carType - 1]-- > 0;
+    }
+}
+```
+
+```cpp
+class ParkingSystem {
+    int spaces[3];
+
+public:
+    ParkingSystem(int big, int medium, int small) {
+        spaces[0] = big, spaces[1] = medium, spaces[2] = small;
+    }
+
+    bool addCar(int carType) {
+        return spaces[carType - 1]-- > 0;
+    }
+};
+```
+
+```javascript
+class ParkingSystem {
+    /**
+     * @constructor
+     * @param {number} big
+     * @param {number} medium
+     * @param {number} small
+     */
+    constructor(big, medium, small) {
+        this.spaces = [big, medium, small];
+    }
+
+    /**
+     * @param {number} carType
+     * @return {boolean}
+     */
+    addCar(carType) {
+        return this.spaces[carType - 1]-- > 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(1)$ time for initialization.
+    * $O(1)$ time for each $addCar()$ function call.
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/design-twitter-feed.md b/articles/design-twitter-feed.md
index 8b057df6e..75eade212 100644
--- a/articles/design-twitter-feed.md
+++ b/articles/design-twitter-feed.md
@@ -218,14 +218,162 @@ class Twitter {
 }
 ```
 
+```go
+type Twitter struct {
+    time      int
+    followMap map[int]map[int]bool
+    tweetMap  map[int][]Tweet
+}
+
+type Tweet struct {
+    time    int
+    tweetId int
+}
+
+func Constructor() Twitter {
+    return Twitter{
+        time:      0,
+        followMap: make(map[int]map[int]bool),
+        tweetMap:  make(map[int][]Tweet),
+    }
+}
+
+func (this *Twitter) PostTweet(userId int, tweetId int) {
+    this.tweetMap[userId] = append(this.tweetMap[userId], Tweet{this.time, tweetId})
+    this.time++
+}
+
+func (this *Twitter) GetNewsFeed(userId int) []int {
+    feed := make([]Tweet, 0)
+    feed = append(feed, this.tweetMap[userId]...)
+    
+    if follows, ok := this.followMap[userId]; ok {
+        for followeeId := range follows {
+            feed = append(feed, this.tweetMap[followeeId]...)
+        }
+    }
+    
+    sort.Slice(feed, func(i, j int) bool {
+        return feed[i].time > feed[j].time
+    })
+    
+    result := make([]int, 0)
+    for i := 0; i < len(feed) && i < 10; i++ {
+        result = append(result, feed[i].tweetId)
+    }
+    return result
+}
+
+func (this *Twitter) Follow(followerId int, followeeId int) {
+    if followerId != followeeId {
+        if this.followMap[followerId] == nil {
+            this.followMap[followerId] = make(map[int]bool)
+        }
+        this.followMap[followerId][followeeId] = true
+    }
+}
+
+func (this *Twitter) Unfollow(followerId int, followeeId int) {
+    if follows, ok := this.followMap[followerId]; ok {
+        delete(follows, followeeId)
+    }
+}
+```
+
+```kotlin
+class Twitter {
+    private var time = 0
+    private val followMap = HashMap<Int, HashSet<Int>>()
+    private val tweetMap = HashMap<Int, MutableList<Pair<Int, Int>>>()
+    
+    fun postTweet(userId: Int, tweetId: Int) {
+        if (!tweetMap.containsKey(userId)) {
+            tweetMap[userId] = mutableListOf()
+        }
+        tweetMap[userId]?.add(Pair(time, tweetId))
+        time++
+    }
+    
+    fun getNewsFeed(userId: Int): List<Int> {
+        val feed = mutableListOf<Pair<Int, Int>>()
+        tweetMap[userId]?.let { feed.addAll(it) }
+        followMap[userId]?.forEach { followeeId ->
+            tweetMap[followeeId]?.let { feed.addAll(it) }
+        }
+        
+        return feed.sortedByDescending { it.first }
+            .take(10)
+            .map { it.second }
+    }
+    
+    fun follow(followerId: Int, followeeId: Int) {
+        if (followerId != followeeId) {
+            if (!followMap.containsKey(followerId)) {
+                followMap[followerId] = HashSet()
+            }
+            followMap[followerId]?.add(followeeId)
+        }
+    }
+    
+    fun unfollow(followerId: Int, followeeId: Int) {
+        followMap[followerId]?.remove(followeeId)
+    }
+}
+```
+
+```swift
+class Twitter {
+    private var time: Int
+    private var followMap: [Int: Set<Int>]
+    private var tweetMap: [Int: [(Int, Int)]]
+
+    init() {
+        self.time = 0
+        self.followMap = [:]
+        self.tweetMap = [:]
+    }
+
+    func postTweet(_ userId: Int, _ tweetId: Int) {
+        if tweetMap[userId] == nil {
+            tweetMap[userId] = []
+        }
+        tweetMap[userId]!.append((time, tweetId))
+        time += 1
+    }
+
+    func getNewsFeed(_ userId: Int) -> [Int] {
+        var feed = tweetMap[userId] ?? []
+        if let followees = followMap[userId] {
+            for followeeId in followees {
+                if let tweets = tweetMap[followeeId] {
+                    feed.append(contentsOf: tweets)
+                }
+            }
+        }
+        feed.sort { $0.0 > $1.0 }
+        return feed.prefix(10).map { $0.1 }
+    }
+
+    func follow(_ followerId: Int, _ followeeId: Int) {
+        if followerId != followeeId {
+            followMap[followerId, default: Set()].insert(followeeId)
+        }
+    }
+
+    func unfollow(_ followerId: Int, _ followeeId: Int) {
+        followMap[followerId]?.remove(followeeId)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
-* Time complexity: $O(n \log n)$ for $getNewsFeed()$ and $O(1)$ for remaining methods.
-* Space complexity: $O(1)$
+* Time complexity: $O(n * m + t\log t)$ for each $getNewsFeed()$ call and $O(1)$ for remaining methods.
+* Space complexity: $O(N * m + N * M)$
 
-> Where $n$ is the number of tweets associated with the $useId$ and its $followeeIds$.
+> Where $n$ is the total number of $followeeIds$ associated with the $userId$, $m$ is the maximum number of tweets by any user, $t$ is the total number of tweets associated with the $userId$ and its $followeeIds$, $N$ is the total number of $userIds$ and $M$ is the maximum number of followees for any user.
 
 ---
 
@@ -383,13 +531,14 @@ public:
 
 ```javascript
 /**
- * const { MaxPriorityQueue } = require('@datastructures-js/priority-queue');
+ * const { PriorityQueue } = require('@datastructures-js/priority-queue');
  */
 
 class Twitter {
     constructor() {
-        this.users = new Map();
-        this.timestamp = 0;
+        this.count = 0; 
+        this.tweetMap = new Map(); // userId -> array of [count, tweetId]
+        this.followMap = new Map(); // userId -> set of followeeIds
     }
 
     /**
@@ -398,13 +547,11 @@ class Twitter {
      * @return {void}
      */
     postTweet(userId, tweetId) {
-        if (!this.users.has(userId)) {
-            this.users.set(userId, { tweets: [], following: new Set() });
+        if (!this.tweetMap.has(userId)) {
+            this.tweetMap.set(userId, []);
         }
-        this.users
-            .get(userId)
-            .tweets.push({ timestamp: this.timestamp, tweetId });
-        this.timestamp += 1;
+        this.tweetMap.get(userId).push([this.count, tweetId]);
+        this.count -= 1;
     }
 
     /**
@@ -412,38 +559,34 @@ class Twitter {
      * @return {number[]}
      */
     getNewsFeed(userId) {
-        if (!this.users.has(userId)) {
-            return [];
+        const res = [];
+        if (!this.followMap.has(userId)) {
+            this.followMap.set(userId, new Set());
         }
-
-        const maxPQ = new MaxPriorityQueue(tweet => tweet.timestamp);
-        const seenTweets = new Set();
-
-        const user = this.users.get(userId);
-        user.tweets.forEach(tweet => {
-            if (!seenTweets.has(tweet.tweetId)) {
-                maxPQ.enqueue(tweet);
-                seenTweets.add(tweet.tweetId);
+        this.followMap.get(userId).add(userId);
+        const minHeap = new PriorityQueue(
+            (a, b) => a[0] - b[0]
+        );
+
+        for (const followeeId of this.followMap.get(userId)) {
+            if (this.tweetMap.has(followeeId)) {
+                const tweets = this.tweetMap.get(followeeId);
+                const index = tweets.length - 1;
+                const [count, tweetId] = tweets[index];
+                minHeap.enqueue([count, tweetId, followeeId, index - 1]);
             }
-        });
+        }
 
-        user.following.forEach(followeeId => {
-            if (this.users.has(followeeId)) {
-                this.users.get(followeeId).tweets.forEach(tweet => {
-                    if (!seenTweets.has(tweet.tweetId)) {
-                        maxPQ.enqueue(tweet);
-                        seenTweets.add(tweet.tweetId);
-                    }
-                });
+        while (!minHeap.isEmpty() && res.length < 10) {
+            const [count, tweetId, followeeId, nextIndex] = minHeap.dequeue();
+            res.push(tweetId);
+            if (nextIndex >= 0) {
+                const [olderCount, olderTweetId] = this.tweetMap.get(followeeId)[nextIndex];
+                minHeap.enqueue([olderCount, olderTweetId, followeeId, nextIndex - 1]);
             }
-        });
-
-        const newsFeed = [];
-        for (let i = 0; i < 10 && !maxPQ.isEmpty(); i++) {
-            newsFeed.push(maxPQ.dequeue().tweetId);
         }
 
-        return newsFeed;
+        return res;
     }
 
     /**
@@ -452,10 +595,10 @@ class Twitter {
      * @return {void}
      */
     follow(followerId, followeeId) {
-        if (!this.users.has(followerId)) {
-            this.users.set(followerId, { tweets: [], following: new Set() });
+        if (!this.followMap.has(followerId)) {
+            this.followMap.set(followerId, new Set());
         }
-        this.users.get(followerId).following.add(followeeId);
+        this.followMap.get(followerId).add(followeeId);
     }
 
     /**
@@ -464,8 +607,8 @@ class Twitter {
      * @return {void}
      */
     unfollow(followerId, followeeId) {
-        if (this.users.has(followerId)) {
-            this.users.get(followerId).following.delete(followeeId);
+        if (this.followMap.has(followerId)) {
+            this.followMap.get(followerId).delete(followeeId);
         }
     }
 }
@@ -536,11 +679,986 @@ class Twitter {
 }
 ```
 
+```go
+type Twitter struct {
+    count     int
+    tweetMap  map[int][][]int    // userId -> list of [count, tweetId]
+    followMap map[int]map[int]bool // userId -> set of followeeId
+}
+
+func Constructor() Twitter {
+    return Twitter{
+        count:     0,
+        tweetMap:  make(map[int][][]int),
+        followMap: make(map[int]map[int]bool),
+    }
+}
+
+func (this *Twitter) PostTweet(userId int, tweetId int) {
+    if this.tweetMap[userId] == nil {
+        this.tweetMap[userId] = make([][]int, 0)
+    }
+    this.tweetMap[userId] = append(this.tweetMap[userId], []int{this.count, tweetId})
+    this.count--
+}
+
+func (this *Twitter) GetNewsFeed(userId int) []int {
+    res := make([]int, 0)
+    
+    minHeap := priorityqueue.NewWith(func(a, b interface{}) int {
+        return a.([]int)[0] - b.([]int)[0]
+    })
+    
+    if this.followMap[userId] == nil {
+        this.followMap[userId] = make(map[int]bool)
+    }
+    this.followMap[userId][userId] = true
+    
+    for followeeId := range this.followMap[userId] {
+        tweets := this.tweetMap[followeeId]
+        if len(tweets) > 0 {
+            index := len(tweets) - 1
+            count, tweetId := tweets[index][0], tweets[index][1]
+            minHeap.Enqueue([]int{count, tweetId, followeeId, index - 1})
+        }
+    }
+    
+    for minHeap.Size() > 0 && len(res) < 10 {
+        item, _ := minHeap.Dequeue()
+        curr := item.([]int)
+        count, tweetId, followeeId, index := curr[0], curr[1], curr[2], curr[3]
+        
+        res = append(res, tweetId)
+        
+        if index >= 0 {
+            tweets := this.tweetMap[followeeId]
+            count, tweetId = tweets[index][0], tweets[index][1]
+            minHeap.Enqueue([]int{count, tweetId, followeeId, index - 1})
+        }
+    }
+    
+    return res
+}
+
+func (this *Twitter) Follow(followerId int, followeeId int) {
+    if this.followMap[followerId] == nil {
+        this.followMap[followerId] = make(map[int]bool)
+    }
+    this.followMap[followerId][followeeId] = true
+}
+
+func (this *Twitter) Unfollow(followerId int, followeeId int) {
+    if this.followMap[followerId] != nil {
+        delete(this.followMap[followerId], followeeId)
+    }
+}
+```
+
+```kotlin
+class Twitter {
+    private var count = 0
+    private val tweetMap = HashMap<Int, MutableList<IntArray>>() // userId -> list of [count, tweetId]
+    private val followMap = HashMap<Int, HashSet<Int>>() // userId -> set of followeeId
+    
+    fun postTweet(userId: Int, tweetId: Int) {
+        if (!tweetMap.containsKey(userId)) {
+            tweetMap[userId] = mutableListOf()
+        }
+        tweetMap[userId]?.add(intArrayOf(count, tweetId))
+        count--
+    }
+    
+    fun getNewsFeed(userId: Int): List<Int> {
+        val res = mutableListOf<Int>()
+        val minHeap = PriorityQueue<IntArray>(compareBy { it[0] })
+        
+        if (!followMap.containsKey(userId)) {
+            followMap[userId] = HashSet()
+        }
+        followMap[userId]?.add(userId)
+        
+        followMap[userId]?.forEach { followeeId ->
+            tweetMap[followeeId]?.let { tweets ->
+                if (tweets.isNotEmpty()) {
+                    val index = tweets.size - 1
+                    val (count, tweetId) = tweets[index]
+                    minHeap.add(intArrayOf(count, tweetId, followeeId, index - 1))
+                }
+            }
+        }
+        
+        while (minHeap.isNotEmpty() && res.size < 10) {
+            val (count, tweetId, followeeId, index) = minHeap.poll()
+            res.add(tweetId)
+            
+            if (index >= 0) {
+                val tweets = tweetMap[followeeId]!!
+                val (nextCount, nextTweetId) = tweets[index]
+                minHeap.add(intArrayOf(nextCount, nextTweetId, followeeId, index - 1))
+            }
+        }
+        
+        return res
+    }
+    
+    fun follow(followerId: Int, followeeId: Int) {
+        if (!followMap.containsKey(followerId)) {
+            followMap[followerId] = HashSet()
+        }
+        followMap[followerId]?.add(followeeId)
+    }
+    
+    fun unfollow(followerId: Int, followeeId: Int) {
+        followMap[followerId]?.remove(followeeId)
+    }
+}
+```
+
+```swift
+class Twitter {
+    private var count: Int
+    private var tweetMap: [Int: [(Int, Int)]]  // userId -> list of (count, tweetId)
+    private var followMap: [Int: Set<Int>]     // userId -> set of followeeId
+    
+    init() {
+        self.count = 0
+        self.tweetMap = [:]
+        self.followMap = [:]
+    }
+    
+    func postTweet(_ userId: Int, _ tweetId: Int) {
+        tweetMap[userId, default: []].append((count, tweetId))
+        count -= 1
+    }
+    
+    func getNewsFeed(_ userId: Int) -> [Int] {
+        var res = [Int]()
+        var minHeap = Heap<Item>()
+        
+        followMap[userId, default: Set()].insert(userId)
+        if let followees = followMap[userId] {
+            for followee in followees {
+                if let tweets = tweetMap[followee], !tweets.isEmpty {
+                    let index = tweets.count - 1
+                    let (cnt, tweetId) = tweets[index]
+                    minHeap.insert(
+                        Item(
+                            count: cnt, tweetId: tweetId,
+                            followeeId: followee, index: index - 1
+                        )
+                    )
+                }
+            }
+        }
+        
+        while !minHeap.isEmpty && res.count < 10 {
+            let entry = minHeap.popMin()!
+            res.append(entry.tweetId)
+            if entry.index >= 0, let tweets = tweetMap[entry.followeeId] {
+                let (cnt, tweetId) = tweets[entry.index]
+                minHeap.insert(
+                    Item(
+                        count: cnt, tweetId: tweetId,
+                        followeeId: entry.followeeId, index: entry.index - 1
+                    )
+                )
+            }
+        }
+        return res
+    }
+    
+    func follow(_ followerId: Int, _ followeeId: Int) {
+        followMap[followerId, default: Set()].insert(followeeId)
+    }
+    
+    func unfollow(_ followerId: Int, _ followeeId: Int) {
+        followMap[followerId]?.remove(followeeId)
+    }
+}
+
+struct Item: Comparable {
+    let count: Int
+    let tweetId: Int
+    let followeeId: Int
+    let index: Int
+    
+    static func < (lhs: Item, rhs: Item) -> Bool {
+        return lhs.count < rhs.count
+    }
+    
+    static func == (lhs: Item, rhs: Item) -> Bool {
+        return lhs.count == rhs.count
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$ for each $getNewsFeed()$ call and $O(1)$ for remaining methods.
+* Space complexity: $O(N * m + N * M + n)$
+
+> Where $n$ is the total number of $followeeIds$ associated with the $userId$, $m$ is the maximum number of tweets by any user, $N$ is the total number of $userIds$ and $M$ is the maximum number of followees for any user.
+
+---
+
+## 3. Heap (Optimal)
+
+::tabs-start
+
+```python
+class Twitter:
+
+    def __init__(self):
+        self.count = 0
+        self.tweetMap = defaultdict(list)  # userId -> list of [count, tweetIds]
+        self.followMap = defaultdict(set)  # userId -> set of followeeId
+
+    def postTweet(self, userId: int, tweetId: int) -> None:
+        self.tweetMap[userId].append([self.count, tweetId])
+        if len(self.tweetMap[userId]) > 10:
+            self.tweetMap[userId].pop(0)
+        self.count -= 1
+
+    def getNewsFeed(self, userId: int) -> List[int]:
+        res = []
+        minHeap = []
+        self.followMap[userId].add(userId)
+        if len(self.followMap[userId]) >= 10:
+            maxHeap = []
+            for followeeId in self.followMap[userId]:
+                if followeeId in self.tweetMap:
+                    index = len(self.tweetMap[followeeId]) - 1
+                    count, tweetId = self.tweetMap[followeeId][index]
+                    heapq.heappush(maxHeap, [-count, tweetId, followeeId, index - 1])
+                    if len(maxHeap) > 10:
+                        heapq.heappop(maxHeap)
+            while maxHeap:
+                count, tweetId, followeeId, index = heapq.heappop(maxHeap)
+                heapq.heappush(minHeap, [-count, tweetId, followeeId, index])
+        else:
+            for followeeId in self.followMap[userId]:
+                if followeeId in self.tweetMap:
+                    index = len(self.tweetMap[followeeId]) - 1
+                    count, tweetId = self.tweetMap[followeeId][index]
+                    heapq.heappush(minHeap, [count, tweetId, followeeId, index - 1])
+
+        while minHeap and len(res) < 10:
+            count, tweetId, followeeId, index = heapq.heappop(minHeap)
+            res.append(tweetId)
+            if index >= 0:
+                count, tweetId = self.tweetMap[followeeId][index]
+                heapq.heappush(minHeap, [count, tweetId, followeeId, index - 1])
+        
+        return res
+
+    def follow(self, followerId: int, followeeId: int) -> None:
+        self.followMap[followerId].add(followeeId)
+
+    def unfollow(self, followerId: int, followeeId: int) -> None:
+        if followeeId in self.followMap[followerId]:
+            self.followMap[followerId].remove(followeeId)
+```
+
+```java
+public class Twitter {
+
+    private int count;
+    private Map<Integer, List<int[]>> tweetMap;
+    private Map<Integer, Set<Integer>> followMap;
+
+    public Twitter() {
+        this.count = 0;
+        this.tweetMap = new HashMap<>();
+        this.followMap = new HashMap<>();
+    }
+
+    public void postTweet(int userId, int tweetId) {
+        tweetMap.computeIfAbsent(userId, k -> new ArrayList<>())
+                .add(new int[]{count, tweetId});
+        if (tweetMap.get(userId).size() > 10) {
+            tweetMap.get(userId).remove(0);
+        }
+        count--;
+    }
+
+    public List<Integer> getNewsFeed(int userId) {
+        List<Integer> res = new ArrayList<>();
+        PriorityQueue<int[]> minHeap = new PriorityQueue<>(
+            (a, b) -> Integer.compare(a[0], b[0])
+        );
+        followMap.computeIfAbsent(userId, k -> new HashSet<>()).add(userId);
+        if (followMap.get(userId).size() >= 10) {
+            PriorityQueue<int[]> maxHeap = new PriorityQueue<>(
+                (a, b) -> Integer.compare(a[0], b[0])
+            );
+            for (int followeeId : followMap.get(userId)) {
+                if (!tweetMap.containsKey(followeeId)) continue;
+                List<int[]> tweets = tweetMap.get(followeeId);
+                int index = tweets.size() - 1;
+                int[] tweet = tweets.get(index);
+                maxHeap.offer(new int[]{-tweet[0], tweet[1], followeeId, index - 1});
+                if (maxHeap.size() > 10) {
+                    maxHeap.poll();
+                }
+            }
+            while (!maxHeap.isEmpty()) {
+                int[] top = maxHeap.poll();
+                minHeap.offer(new int[]{-top[0], top[1], top[2], top[3]});
+            }
+        } else {
+            for (int followeeId : followMap.get(userId)) {
+                if (!tweetMap.containsKey(followeeId)) continue;
+                List<int[]> tweets = tweetMap.get(followeeId);
+                int index = tweets.size() - 1;
+                int[] tweet = tweets.get(index);
+                minHeap.offer(new int[]{tweet[0], tweet[1], followeeId, index - 1});
+            }
+        }
+
+        while (!minHeap.isEmpty() && res.size() < 10) {
+            int[] top = minHeap.poll();
+            res.add(top[1]);
+            int nextIndex = top[3];
+            if (nextIndex >= 0) {
+                List<int[]> tweets = tweetMap.get(top[2]);
+                int[] nextTweet = tweets.get(nextIndex);
+                minHeap.offer(new int[]{nextTweet[0], nextTweet[1], top[2], nextIndex - 1});
+            }
+        }
+        return res;
+    }
+
+    public void follow(int followerId, int followeeId) {
+        followMap.computeIfAbsent(followerId, k -> new HashSet<>()).add(followeeId);
+    }
+
+    public void unfollow(int followerId, int followeeId) {
+        if (followMap.containsKey(followerId)) {
+            followMap.get(followerId).remove(followeeId);
+        }
+    }
+}
+```
+
+```cpp
+class Twitter {
+public:
+    int count;
+    unordered_map<int, vector<pair<int,int>>> tweetMap;
+    unordered_map<int, unordered_set<int>> followMap;
+
+    Twitter() {
+        count = 0;
+    }
+
+    void postTweet(int userId, int tweetId) {
+        tweetMap[userId].push_back({count, tweetId});
+        if (tweetMap[userId].size() > 10) {
+            tweetMap[userId].erase(tweetMap[userId].begin());
+        }
+        count--;
+    }
+
+    vector<int> getNewsFeed(int userId) {
+        vector<int> res;
+        followMap[userId].insert(userId);
+        priority_queue<vector<int>, vector<vector<int>>, greater<vector<int>>> minHeap;
+        if (followMap[userId].size() >= 10) {
+            priority_queue<vector<int>> maxHeap;
+            for (auto f : followMap[userId]) {
+                if (!tweetMap.count(f)) continue;
+                int idx = tweetMap[f].size() - 1;
+                auto &p = tweetMap[f][idx];
+                maxHeap.push({-p.first, p.second, f, idx - 1});
+                if (maxHeap.size() > 10) maxHeap.pop();
+            }
+            while (!maxHeap.empty()) {
+                auto t = maxHeap.top();
+                maxHeap.pop();
+                minHeap.push({-t[0], t[1], t[2], t[3]});
+            }
+        } else {
+            for (auto f : followMap[userId]) {
+                if (!tweetMap.count(f)) continue;
+                int idx = tweetMap[f].size() - 1;
+                auto &p = tweetMap[f][idx];
+                minHeap.push({p.first, p.second, f, idx - 1});
+            }
+        }
+        while (!minHeap.empty() && res.size() < 10) {
+            auto t = minHeap.top();
+            minHeap.pop();
+            res.push_back(t[1]);
+            int idx = t[3];
+            if (idx >= 0) {
+                auto &p = tweetMap[t[2]][idx];
+                minHeap.push({p.first, p.second, t[2], idx - 1});
+            }
+        }
+        return res;
+    }
+
+    void follow(int followerId, int followeeId) {
+        followMap[followerId].insert(followeeId);
+    }
+
+    void unfollow(int followerId, int followeeId) {
+        if (followMap[followerId].count(followeeId)) {
+            followMap[followerId].erase(followeeId);
+        }
+    }
+};
+```
+
+```javascript
+/**
+ * const { PriorityQueue } = require('@datastructures-js/priority-queue');
+ */
+class Twitter {
+    constructor() {
+        this.count = 0;
+        this.tweetMap = new Map();
+        this.followMap = new Map();
+    }
+
+    /**
+     * @param {number} userId
+     * @param {number} tweetId
+     * @return {void}
+     */
+    postTweet(userId, tweetId) {
+        if (!this.tweetMap.has(userId)) {
+            this.tweetMap.set(userId, []);
+        }
+        const tweets = this.tweetMap.get(userId);
+        tweets.push([this.count, tweetId]);
+        if (tweets.length > 10) {
+            tweets.shift();
+        }
+        this.count--;
+    }
+
+    /**
+     * @param {number} userId
+     * @return {number[]}
+     */
+    getNewsFeed(userId) {
+        const res = [];
+        if (!this.followMap.has(userId)) {
+            this.followMap.set(userId, new Set());
+        }
+        this.followMap.get(userId).add(userId);
+        const minHeap = new PriorityQueue((a, b) => a[0] - b[0]);
+
+        if (this.followMap.get(userId).size >= 10) {
+            const maxHeap = new PriorityQueue((a, b) => a[0] - b[0]);
+            for (const followeeId of this.followMap.get(userId)) {
+                if (!this.tweetMap.has(followeeId)) continue;
+                const tweets = this.tweetMap.get(followeeId);
+                const idx = tweets.length - 1;
+                const [cnt, tId] = tweets[idx];
+                maxHeap.enqueue([-cnt, tId, followeeId, idx - 1]);
+                if (maxHeap.size() > 10) {
+                    maxHeap.dequeue();
+                }
+            }
+            while (maxHeap.size() > 0) {
+                const [negCount, tId, fId, idx] = maxHeap.dequeue();
+                minHeap.enqueue([-negCount, tId, fId, idx]);
+            }
+
+        } else {
+            for (const followeeId of this.followMap.get(userId)) {
+                if (!this.tweetMap.has(followeeId)) continue;
+                const tweets = this.tweetMap.get(followeeId);
+                const idx = tweets.length - 1;
+                const [cnt, tId] = tweets[idx];
+                minHeap.enqueue([cnt, tId, followeeId, idx - 1]);
+            }
+        }
+
+        while (minHeap.size() > 0 && res.length < 10) {
+            const [cnt, tId, fId, idx] = minHeap.dequeue();
+            res.push(tId);
+            if (idx >= 0) {
+                const [olderCount, olderTId] = this.tweetMap.get(fId)[idx];
+                minHeap.enqueue([olderCount, olderTId, fId, idx - 1]);
+            }
+        }
+        return res;
+    }
+
+    /**
+     * @param {number} followerId
+     * @param {number} followeeId
+     * @return {void}
+     */
+    follow(followerId, followeeId) {
+        if (!this.followMap.has(followerId)) {
+            this.followMap.set(followerId, new Set());
+        }
+        this.followMap.get(followerId).add(followeeId);
+    }
+
+    /**
+     * @param {number} followerId
+     * @param {number} followeeId
+     * @return {void}
+     */
+    unfollow(followerId, followeeId) {
+        if (this.followMap.has(followerId)) {
+            this.followMap.get(followerId).delete(followeeId);
+        }
+    }
+}
+```
+
+```csharp
+public class Twitter
+{
+    private int count;
+    private Dictionary<int, List<(int, int)>> tweetMap; // userId -> list of (count, tweetId)
+    private Dictionary<int, HashSet<int>> followMap;    // userId -> set of followeeId
+
+    public Twitter()
+    {
+        count = 0;
+        tweetMap = new Dictionary<int, List<(int, int)>>();
+        followMap = new Dictionary<int, HashSet<int>>();
+    }
+
+    public void PostTweet(int userId, int tweetId)
+    {
+        if (!tweetMap.ContainsKey(userId))
+        {
+            tweetMap[userId] = new List<(int, int)>();
+        }
+        tweetMap[userId].Add((count, tweetId));
+        if (tweetMap[userId].Count > 10)
+        {
+            tweetMap[userId].RemoveAt(0);
+        }
+        count--;
+    }
+
+    public List<int> GetNewsFeed(int userId)
+    {
+        var res = new List<int>();
+        if (!followMap.ContainsKey(userId))
+        {
+            followMap[userId] = new HashSet<int>();
+        }
+        followMap[userId].Add(userId);
+        var minHeap = new PriorityQueue<(int, int, int, int), int>();
+        if (followMap[userId].Count >= 10)
+        {
+            var maxHeap = new PriorityQueue<(int, int, int, int), int>();
+            foreach (var fId in followMap[userId])
+            {
+                if (tweetMap.ContainsKey(fId))
+                {
+                    var tweets = tweetMap[fId];
+                    int idx = tweets.Count - 1;
+                    var (c, tId) = tweets[idx];
+                    maxHeap.Enqueue(
+                        ( -c, tId, fId, idx - 1 ),
+                        -c
+                    );
+                    if (maxHeap.Count > 10)
+                    {
+                        maxHeap.Dequeue();
+                    }
+                }
+            }
+
+            while (maxHeap.Count > 0)
+            {
+                var item = maxHeap.Dequeue();
+                var negCount = item.Item1;
+                var tId = item.Item2;
+                var fId = item.Item3;
+                var idx = item.Item4;
+
+                int originalCount = -negCount;
+                minHeap.Enqueue(
+                    ( originalCount, tId, fId, idx ),
+                    originalCount
+                );
+            }
+        }
+        else
+        {
+            foreach (var fId in followMap[userId])
+            {
+                if (tweetMap.ContainsKey(fId))
+                {
+                    var tweets = tweetMap[fId];
+                    int idx = tweets.Count - 1;
+                    var (c, tId) = tweets[idx];
+                    minHeap.Enqueue(
+                        ( c, tId, fId, idx - 1 ),
+                        c
+                    );
+                }
+            }
+        }
+
+        while (minHeap.Count > 0 && res.Count < 10)
+        {
+            var (c, tId, fId, idx) = minHeap.Dequeue();
+            res.Add(tId);
+            if (idx >= 0)
+            {
+                var (olderCount, olderTid) = tweetMap[fId][idx];
+                minHeap.Enqueue(
+                    ( olderCount, olderTid, fId, idx - 1 ),
+                    olderCount
+                );
+            }
+        }
+
+        return res;
+    }
+
+    public void Follow(int followerId, int followeeId)
+    {
+        if (!followMap.ContainsKey(followerId))
+        {
+            followMap[followerId] = new HashSet<int>();
+        }
+        followMap[followerId].Add(followeeId);
+    }
+
+    public void Unfollow(int followerId, int followeeId)
+    {
+        if (followMap.ContainsKey(followerId))
+        {
+            followMap[followerId].Remove(followeeId);
+        }
+    }
+}
+```
+
+```go
+type Twitter struct {
+    count     int
+    tweetMap  map[int][][2]int    // userId -> [count, tweetId]
+    followMap map[int]map[int]bool // userId -> set of followeeIds
+}
+
+func Constructor() Twitter {
+    return Twitter{
+        count:     0,
+        tweetMap:  make(map[int][][2]int),
+        followMap: make(map[int]map[int]bool),
+    }
+}
+
+func (t *Twitter) PostTweet(userId int, tweetId int) {
+    if _, exists := t.tweetMap[userId]; !exists {
+        t.tweetMap[userId] = make([][2]int, 0, 10)
+    }
+    t.tweetMap[userId] = append(t.tweetMap[userId], [2]int{t.count, tweetId})
+    if len(t.tweetMap[userId]) > 10 {
+        t.tweetMap[userId] = t.tweetMap[userId][1:]
+    }
+    t.count--
+}
+
+func maxHeapComparator(a, b interface{}) int {
+    A := a.([]int)
+    B := b.([]int)
+    switch {
+    case A[0] < B[0]:
+        return -1
+    case A[0] > B[0]:
+        return 1
+    default:
+        return 0
+    }
+}
+
+func minHeapComparator(a, b interface{}) int {
+    A := a.([]int)
+    B := b.([]int)
+    switch {
+    case A[0] < B[0]:
+        return -1
+    case A[0] > B[0]:
+        return 1
+    default:
+        return 0
+    }
+}
+
+func (t *Twitter) GetNewsFeed(userId int) []int {
+    res := []int{}
+    if _, ok := t.followMap[userId]; !ok {
+        t.followMap[userId] = make(map[int]bool)
+    }
+    t.followMap[userId][userId] = true
+    minHeap := priorityqueue.NewWith(minHeapComparator)
+
+    if len(t.followMap[userId]) >= 10 {
+        maxHeap := priorityqueue.NewWith(maxHeapComparator)
+        for fId := range t.followMap[userId] {
+            if tweets, exists := t.tweetMap[fId]; exists && len(tweets) > 0 {
+                idx := len(tweets) - 1
+                c := tweets[idx][0]
+                tId := tweets[idx][1]
+                maxHeap.Enqueue([]int{-c, tId, fId, idx - 1})
+                if maxHeap.Size() > 10 {
+                    maxHeap.Dequeue()
+                }
+            }
+        }
+
+        for !maxHeap.Empty() {
+            item, _ := maxHeap.Dequeue()
+            arr := item.([]int)
+            negCount := arr[0]
+            tId := arr[1]
+            fId := arr[2]
+            nextIdx := arr[3]
+            realCount := -negCount
+            minHeap.Enqueue([]int{realCount, tId, fId, nextIdx})
+        }
+    } else {
+        for fId := range t.followMap[userId] {
+            if tweets, exists := t.tweetMap[fId]; exists && len(tweets) > 0 {
+                idx := len(tweets) - 1
+                c := tweets[idx][0]
+                tId := tweets[idx][1]
+                minHeap.Enqueue([]int{c, tId, fId, idx - 1})
+            }
+        }
+    }
+
+    for !minHeap.Empty() && len(res) < 10 {
+        top, _ := minHeap.Dequeue()
+        arr := top.([]int)
+        tId := arr[1]
+        fId := arr[2]
+        nextIdx := arr[3]
+
+        res = append(res, tId)
+        if nextIdx >= 0 {
+            older := t.tweetMap[fId][nextIdx]
+            minHeap.Enqueue([]int{older[0], older[1], fId, nextIdx - 1})
+        }
+    }
+
+    return res
+}
+
+func (t *Twitter) Follow(followerId, followeeId int) {
+    if _, ok := t.followMap[followerId]; !ok {
+        t.followMap[followerId] = make(map[int]bool)
+    }
+    t.followMap[followerId][followeeId] = true
+}
+
+func (t *Twitter) Unfollow(followerId, followeeId int) {
+    if _, ok := t.followMap[followerId]; ok {
+        delete(t.followMap[followerId], followeeId)
+    }
+}
+```
+
+```kotlin
+class Twitter {
+    private var count = 0
+    private val tweetMap = mutableMapOf<Int, MutableList<Pair<Int, Int>>>()
+    private val followMap = mutableMapOf<Int, MutableSet<Int>>()
+
+    fun postTweet(userId: Int, tweetId: Int) {
+        if (!tweetMap.containsKey(userId)) {
+            tweetMap[userId] = mutableListOf()
+        }
+        val tweets = tweetMap[userId]!!
+        tweets.add(Pair(count, tweetId))
+        if (tweets.size > 10) {
+            tweets.removeAt(0)
+        }
+        count--
+    }
+
+    fun getNewsFeed(userId: Int): List<Int> {
+        val res = mutableListOf<Int>()
+        if (!followMap.containsKey(userId)) {
+            followMap[userId] = mutableSetOf()
+        }
+        followMap[userId]!!.add(userId)
+        val minHeap = PriorityQueue<List<Int>> { a, b -> a[0].compareTo(b[0]) }
+        if (followMap[userId]!!.size >= 10) {
+            val maxHeap = PriorityQueue<List<Int>> { a, b -> a[0].compareTo(b[0]) }
+            for (fId in followMap[userId]!!) {
+                if (!tweetMap.containsKey(fId)) continue
+                val tweets = tweetMap[fId]!!
+                if (tweets.isEmpty()) continue
+                val idx = tweets.size - 1
+                val (c, tId) = tweets[idx]
+                maxHeap.offer(listOf(-c, tId, fId, idx - 1))
+                if (maxHeap.size > 10) {
+                    maxHeap.poll()
+                }
+            }
+            while (maxHeap.isNotEmpty()) {
+                val (negCount, tId, fId, nextIdx) = maxHeap.poll()
+                val realCount = -negCount
+                minHeap.offer(listOf(realCount, tId, fId, nextIdx))
+            }
+        } else {
+            for (fId in followMap[userId]!!) {
+                if (!tweetMap.containsKey(fId)) continue
+                val tweets = tweetMap[fId]!!
+                if (tweets.isEmpty()) continue
+                val idx = tweets.size - 1
+                val (c, tId) = tweets[idx]
+                minHeap.offer(listOf(c, tId, fId, idx - 1))
+            }
+        }
+
+        while (minHeap.isNotEmpty() && res.size < 10) {
+            val (c, tId, fId, idx) = minHeap.poll()
+            res.add(tId)
+            if (idx >= 0) {
+                val (olderCount, olderTid) = tweetMap[fId]!![idx]
+                minHeap.offer(listOf(olderCount, olderTid, fId, idx - 1))
+            }
+        }
+
+        return res
+    }
+
+    fun follow(followerId: Int, followeeId: Int) {
+        if (!followMap.containsKey(followerId)) {
+            followMap[followerId] = mutableSetOf()
+        }
+        followMap[followerId]!!.add(followeeId)
+    }
+
+    fun unfollow(followerId: Int, followeeId: Int) {
+        if (followMap.containsKey(followerId)) {
+            followMap[followerId]!!.remove(followeeId)
+        }
+    }
+}
+```
+
+```swift
+struct Item: Comparable {
+    let count: Int
+    let tweetId: Int
+    let followeeId: Int
+    let index: Int
+
+    static func < (lhs: Item, rhs: Item) -> Bool {
+        return lhs.count < rhs.count
+    }
+
+    static func == (lhs: Item, rhs: Item) -> Bool {
+        return lhs.count == rhs.count &&
+               lhs.tweetId == rhs.tweetId &&
+               lhs.followeeId == rhs.followeeId &&
+               lhs.index == rhs.index
+    }
+}
+
+class Twitter {
+    private var count: Int
+    private var tweetMap: [Int: [(Int, Int)]] // userId -> list of (count, tweetId)
+    private var followMap: [Int: Set<Int>]    // userId -> set of followeeId
+
+    init() {
+        self.count = 0
+        self.tweetMap = [:]
+        self.followMap = [:]
+    }
+
+    func postTweet(_ userId: Int, _ tweetId: Int) {
+        tweetMap[userId, default: []].append((count, tweetId))
+        if tweetMap[userId]!.count > 10 {
+            tweetMap[userId]!.removeFirst()
+        }
+        count -= 1
+    }
+
+    func getNewsFeed(_ userId: Int) -> [Int] {
+        var res = [Int]()
+        var minHeap = Heap<Item>()
+        followMap[userId, default: Set()].insert(userId)
+
+        if followMap[userId]!.count >= 10 {
+            var maxHeap = Heap<Item>()
+            for followeeId in followMap[userId]! {
+                if let tweets = tweetMap[followeeId], !tweets.isEmpty {
+                    let index = tweets.count - 1
+                    let (cnt, tweetId) = tweets[index]
+                    maxHeap.insert(
+                        Item(
+                            count: cnt, tweetId: tweetId,
+                            followeeId: followeeId, index: index - 1
+                        )
+                    )
+                    if maxHeap.count > 10 {
+                        maxHeap.removeMax()
+                    }
+                }
+            }
+            while !maxHeap.isEmpty {
+                let item = maxHeap.popMax()!
+                minHeap.insert(item)
+            }
+        } else {
+            for followeeId in followMap[userId]! {
+                if let tweets = tweetMap[followeeId], !tweets.isEmpty {
+                    let index = tweets.count - 1
+                    let (cnt, tweetId) = tweets[index]
+                    minHeap.insert(
+                        Item(
+                            count: cnt, tweetId: tweetId,
+                            followeeId: followeeId, index: index - 1
+                        )
+                    )
+                }
+            }
+        }
+
+        while !minHeap.isEmpty && res.count < 10 {
+            let item = minHeap.popMin()!
+            res.append(item.tweetId)
+            if item.index >= 0, let tweets = tweetMap[item.followeeId] {
+                let (cnt, tweetId) = tweets[item.index]
+                minHeap.insert(
+                    Item(
+                        count: cnt, tweetId: tweetId,
+                        followeeId: item.followeeId, index: item.index - 1
+                    )
+                )
+            }
+        }
+
+        return res
+    }
+
+    func follow(_ followerId: Int, _ followeeId: Int) {
+        followMap[followerId, default: Set()].insert(followeeId)
+    }
+
+    func unfollow(_ followerId: Int, _ followeeId: Int) {
+        followMap[followerId]?.remove(followeeId)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
-* Time complexity: $O(n+\log n)$ for $getNewsFeed()$ and $O(1)$ for remaining methods.
-* Space complexity: $O(1)$
+* Time complexity: $O(n)$ for each $getNewsFeed()$ call and $O(1)$ for remaining methods.
+* Space complexity: $O(N * m + N * M + n)$
 
-> Where $n$ is the number of tweets associated with the $useId$ and its $followeeIds$.
\ No newline at end of file
+> Where $n$ is the total number of $followeeIds$ associated with the $userId$, $m$ is the maximum number of tweets by any user ($m$ can be at most $10$), $N$ is the total number of $userIds$ and $M$ is the maximum number of followees for any user.
\ No newline at end of file
diff --git a/articles/design-underground-system.md b/articles/design-underground-system.md
new file mode 100644
index 000000000..d03c0c9e8
--- /dev/null
+++ b/articles/design-underground-system.md
@@ -0,0 +1,357 @@
+## 1. Two HashMaps
+
+::tabs-start
+
+```python
+class UndergroundSystem:
+
+    def __init__(self):
+        self.checkInMap = {} # id -> (startStation, time)
+        self.routeMap = {} # (start, end) -> [totalTime, count]
+
+    def checkIn(self, id: int, startStation: str, t: int) -> None:
+        self.checkInMap[id] = (startStation, t)
+
+    def checkOut(self, id: int, endStation: str, t: int) -> None:
+        startStation, time = self.checkInMap[id]
+        route = (startStation, endStation)
+        if route not in self.routeMap:
+            self.routeMap[route] = [0, 0]
+        self.routeMap[route][0] += t - time
+        self.routeMap[route][1] += 1
+
+    def getAverageTime(self, startStation: str, endStation: str) -> float:
+        totalTime, count = self.routeMap[(startStation, endStation)]
+        return totalTime / count
+```
+
+```java
+public class UndergroundSystem {
+    private Map<Integer, Pair<String, Integer>> checkInMap;
+    private Map<String, int[]> routeMap;
+
+    public UndergroundSystem() {
+        checkInMap = new HashMap<>();
+        routeMap = new HashMap<>();
+    }
+
+    public void checkIn(int id, String startStation, int t) {
+        checkInMap.put(id, new Pair<>(startStation, t));
+    }
+
+    public void checkOut(int id, String endStation, int t) {
+        Pair<String, Integer> entry = checkInMap.get(id);
+        String route = entry.getKey() + "," + endStation;
+        routeMap.putIfAbsent(route, new int[]{0, 0});
+        routeMap.get(route)[0] += t - entry.getValue();
+        routeMap.get(route)[1] += 1;
+    }
+
+    public double getAverageTime(String startStation, String endStation) {
+        int[] data = routeMap.get(startStation + "," + endStation);
+        return (double) data[0] / data[1];
+    }
+}
+```
+
+```cpp
+class UndergroundSystem {
+    unordered_map<int, pair<string, int>> checkInMap;
+    unordered_map<string, pair<int, int>> routeMap;
+
+public:
+    UndergroundSystem() {}
+
+    void checkIn(int id, string startStation, int t) {
+        checkInMap[id] = {startStation, t};
+    }
+
+    void checkOut(int id, string endStation, int t) {
+        auto [startStation, time] = checkInMap[id];
+        string route = startStation + "," + endStation;
+        if (!routeMap.count(route))
+            routeMap[route] = {0, 0};
+        routeMap[route].first += t - time;
+        routeMap[route].second += 1;
+    }
+
+    double getAverageTime(string startStation, string endStation) {
+        string route = startStation + "," + endStation;
+        auto [totalTime, count] = routeMap[route];
+        return (double) totalTime / count;
+    }
+};
+```
+
+```javascript
+class UndergroundSystem {
+    /** 
+     * @constructor
+     */
+    constructor() {
+        this.checkInMap = new Map();
+        this.routeMap = new Map();
+    }
+
+    /** 
+     * @param {number} id 
+     * @param {string} startStation 
+     * @param {number} t
+     * @return {void}
+     */
+    checkIn(id, startStation, t) {
+        this.checkInMap.set(id, [startStation, t]);
+    }
+
+    /** 
+     * @param {number} id 
+     * @param {string} endStation 
+     * @param {number} t
+     * @return {void}
+     */
+    checkOut(id, endStation, t) {
+        const [startStation, time] = this.checkInMap.get(id);
+        const route = `${startStation},${endStation}`;
+        if (!this.routeMap.has(route)) this.routeMap.set(route, [0, 0]);
+        this.routeMap.get(route)[0] += t - time;
+        this.routeMap.get(route)[1] += 1;
+    }
+
+    /** 
+     * @param {string} startStation 
+     * @param {string} endStation
+     * @return {number}
+     */
+    getAverageTime(startStation, endStation) {
+        const [totalTime, count] = this.routeMap.get(`${startStation},${endStation}`);
+        return totalTime / count;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(1)$ time for initialization.
+    * $O(1)$ time for each $checkIn()$ function call.
+    * $O(m)$ time for each $checkOut()$ and $getAverageTime()$ function calls.
+* Space complexity: $O(n + N ^ 2)$
+
+> Where $n$ is the number of passengers, $N$ is the total number of stations, and $m$ is the average length of station name.
+
+---
+
+## 2. Two HashMaps + Hashing
+
+::tabs-start
+
+```python
+class UndergroundSystem:
+    MOD1, MOD2 = 768258391, 685683731
+    BASE1, BASE2 = 37, 31
+
+    def __init__(self):
+        self.checkInMap = {}  # id -> (startStation, time)
+        self.routeMap = {}  # hash(route) -> (totalTime, count)
+
+    def getHash(self, s1: str, s2: str) -> int:
+        h1, h2, p1, p2 = 0, 0, 1, 1
+        for c in s1 + ',' + s2:
+            h1 = (h1 + (ord(c) - 96) * p1) % self.MOD1
+            h2 = (h2 + (ord(c) - 96) * p2) % self.MOD2
+            p1 = (p1 * self.BASE1) % self.MOD1
+            p2 = (p2 * self.BASE2) % self.MOD2
+        return (h1 << 32) | h2
+
+    def checkIn(self, id: int, startStation: str, t: int) -> None:
+        self.checkInMap[id] = (startStation, t)
+
+    def checkOut(self, id: int, endStation: str, t: int) -> None:
+        startStation, time = self.checkInMap[id]
+        routeHash = self.getHash(startStation, endStation)
+        if routeHash not in self.routeMap:
+            self.routeMap[routeHash] = [0, 0]
+        self.routeMap[routeHash][0] += t - time
+        self.routeMap[routeHash][1] += 1
+
+    def getAverageTime(self, startStation: str, endStation: str) -> float:
+        routeHash = self.getHash(startStation, endStation)
+        totalTime, count = self.routeMap[routeHash]
+        return totalTime / count
+```
+
+```java
+public class UndergroundSystem {
+    private static final int MOD1 = 768258391, MOD2 = 685683731;
+    private static final int BASE1 = 37, BASE2 = 31;
+    private Map<Integer, Pair<String, Integer>> checkInMap;
+    private Map<Long, int[]> routeMap;
+
+    public UndergroundSystem() {
+        checkInMap = new HashMap<>();
+        routeMap = new HashMap<>();
+    }
+
+    private long getHash(String s1, String s2) {
+        long h1 = 0, h2 = 0, p1 = 1, p2 = 1;
+        String combined = s1 + "," + s2;
+
+        for (char c : combined.toCharArray()) {
+            h1 = (h1 + (c - 96) * p1) % MOD1;
+            h2 = (h2 + (c - 96) * p2) % MOD2;
+            p1 = (p1 * BASE1) % MOD1;
+            p2 = (p2 * BASE2) % MOD2;
+        }
+        return (h1 << 32) | h2;
+    }
+
+    public void checkIn(int id, String startStation, int t) {
+        checkInMap.put(id, new Pair<>(startStation, t));
+    }
+
+    public void checkOut(int id, String endStation, int t) {
+        Pair<String, Integer> checkInData = checkInMap.get(id);
+        long routeHash = getHash(checkInData.getKey(), endStation);
+        routeMap.putIfAbsent(routeHash, new int[]{0, 0});
+        int[] data = routeMap.get(routeHash);
+        data[0] += (t - checkInData.getValue());
+        data[1]++;
+    }
+
+    public double getAverageTime(String startStation, String endStation) {
+        long routeHash = getHash(startStation, endStation);
+        int[] data = routeMap.get(routeHash);
+        return (double) data[0] / data[1];
+    }
+}
+```
+
+```cpp
+class UndergroundSystem {
+private:
+    static constexpr int MOD1 = 768258391, MOD2 = 685683731;
+    static constexpr int BASE1 = 37, BASE2 = 31;
+    unordered_map<int, pair<string, int>> checkInMap;
+    unordered_map<unsigned long long, pair<int, int>> routeMap;
+
+    unsigned long long getHash(const string& s1, const string& s2) {
+        long long h1 = 0, h2 = 0, p1 = 1, p2 = 1;
+        string combined = s1 + "," + s2;
+
+        for (char c : combined) {
+            h1 = (h1 + (c - 96) * p1) % MOD1;
+            h2 = (h2 + (c - 96) * p2) % MOD2;
+            p1 = (p1 * BASE1) % MOD1;
+            p2 = (p2 * BASE2) % MOD2;
+        }
+        return (h1 << 32) | h2;
+    }
+
+public:
+    UndergroundSystem() {}
+
+    void checkIn(int id, string startStation, int t) {
+        checkInMap[id] = {startStation, t};
+    }
+
+    void checkOut(int id, string endStation, int t) {
+        auto [startStation, time] = checkInMap[id];
+        unsigned long long routeHash = getHash(startStation, endStation);
+        routeMap[routeHash].first += (t - time);
+        routeMap[routeHash].second++;
+    }
+
+    double getAverageTime(string startStation, string endStation) {
+        unsigned long long routeHash = getHash(startStation, endStation);
+        auto [totalTime, count] = routeMap[routeHash];
+        return (double) totalTime / count;
+    }
+};
+```
+
+```javascript
+class UndergroundSystem {
+    /** 
+     * @constructor
+     */
+    constructor() {
+        this.MOD1 = 768258391;
+        this.MOD2 = 685683731;
+        this.BASE1 = 37;
+        this.BASE2 = 31;
+        this.checkInMap = new Map();
+        this.routeMap = new Map();
+    }
+
+    /** 
+     * @param {string} s1 
+     * @param {string} s2
+     * @return {number}
+     */
+    getHash(s1, s2) {
+        let h1 = 0, h2 = 0, p1 = 1, p2 = 1;
+        let combined = s1 + "," + s2;
+
+        for (let i = 0; i < combined.length; i++) {
+            let c = combined.charCodeAt(i) - 96;
+            h1 = (h1 + c * p1) % this.MOD1;
+            h2 = (h2 + c * p2) % this.MOD2;
+            p1 = (p1 * this.BASE1) % this.MOD1;
+            p2 = (p2 * this.BASE2) % this.MOD2;
+        }
+        return BigInt(h1) << BigInt(32) | BigInt(h2);
+    }
+
+    /** 
+     * @param {number} id 
+     * @param {string} startStation 
+     * @param {number} t
+     * @return {void}
+     */
+    checkIn(id, startStation, t) {
+        this.checkInMap.set(id, [startStation, t]);
+    }
+
+    /** 
+     * @param {number} id 
+     * @param {string} endStation 
+     * @param {number} t
+     * @return {void}
+     */
+    checkOut(id, endStation, t) {
+        let [startStation, time] = this.checkInMap.get(id);
+        let routeHash = this.getHash(startStation, endStation);
+        if (!this.routeMap.has(routeHash)) {
+            this.routeMap.set(routeHash, [0, 0]);
+        }
+        let data = this.routeMap.get(routeHash);
+        data[0] += t - time;
+        data[1]++;
+    }
+
+    /** 
+     * @param {string} startStation 
+     * @param {string} endStation
+     * @return {number}
+     */
+    getAverageTime(startStation, endStation) {
+        let routeHash = this.getHash(startStation, endStation);
+        let [totalTime, count] = this.routeMap.get(routeHash);
+        return totalTime / count;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(1)$ time for initialization.
+    * $O(1)$ time for each $checkIn()$ function call.
+    * $O(m)$ time for each $checkOut()$ and $getAverageTime()$ function calls.
+* Space complexity: $O(n + N ^ 2)$
+
+> Where $n$ is the number of passengers, $N$ is the total number of stations, and $m$ is the average length of station name.
\ No newline at end of file
diff --git a/articles/design-word-search-data-structure.md b/articles/design-word-search-data-structure.md
index 3ac642bda..033096234 100644
--- a/articles/design-word-search-data-structure.md
+++ b/articles/design-word-search-data-structure.md
@@ -163,6 +163,101 @@ public class WordDictionary {
 }
 ```
 
+```go
+type WordDictionary struct {
+	store []string
+}
+
+func Constructor() WordDictionary {
+	return WordDictionary{store: []string{}}
+}
+
+func (this *WordDictionary) AddWord(word string) {
+	this.store = append(this.store, word)
+}
+
+func (this *WordDictionary) Search(word string) bool {
+	for _, w := range this.store {
+		if len(w) != len(word) {
+			continue
+		}
+		match := true
+		for i := 0; i < len(w); i++ {
+			if w[i] != word[i] && word[i] != '.' {
+				match = false
+				break
+			}
+		}
+		if match {
+			return true
+		}
+	}
+	return false
+}
+```
+
+```kotlin
+class WordDictionary {
+
+    private val store = mutableListOf<String>()
+
+    fun addWord(word: String) {
+        store.add(word)
+    }
+
+    fun search(word: String): Boolean {
+        for (w in store) {
+            if (w.length != word.length) continue
+            var match = true
+            for (i in w.indices) {
+                if (w[i] != word[i] && word[i] != '.') {
+                    match = false
+                    break
+                }
+            }
+            if (match) return true
+        }
+        return false
+    }
+}
+```
+
+```swift
+class WordDictionary {
+    private var store: [String]
+
+    init() {
+        self.store = []
+    }
+
+    func addWord(_ word: String) {
+        store.append(word)
+    }
+
+    func search(_ word: String) -> Bool {
+        for w in store {
+            if w.count != word.count {
+                continue
+            }
+            var i = 0
+            let wArray = Array(w)
+            let wordArray = Array(word)
+            while i < wArray.count {
+                if wArray[i] == wordArray[i] || wordArray[i] == "." {
+                    i += 1
+                } else {
+                    break
+                }
+            }
+            if i == wArray.count {
+                return true
+            }
+        }
+        return false
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -170,7 +265,7 @@ public class WordDictionary {
 * Time complexity: $O(1)$ for $addWord()$, $O(m * n)$ for $search()$.
 * Space complexity: $O(m * n)$
 
-> Where $m$ is the number of words added and $n$ is the length of the search string.
+> Where $m$ is the number of words added and $n$ is the length of the string.
 
 ---
 
@@ -461,11 +556,176 @@ public class WordDictionary {
 }
 ```
 
+```go
+type TrieNode struct {
+	children [26]*TrieNode
+	word     bool
+}
+
+func NewTrieNode() *TrieNode {
+	return &TrieNode{}
+}
+
+type WordDictionary struct {
+	root *TrieNode
+}
+
+func Constructor() WordDictionary {
+	return WordDictionary{root: NewTrieNode()}
+}
+
+func (this *WordDictionary) AddWord(word string) {
+	cur := this.root
+	for _, c := range word {
+		index := c - 'a'
+		if cur.children[index] == nil {
+			cur.children[index] = NewTrieNode()
+		}
+		cur = cur.children[index]
+	}
+	cur.word = true
+}
+
+func (this *WordDictionary) Search(word string) bool {
+	return this.dfs(word, 0, this.root)
+}
+
+func (this *WordDictionary) dfs(word string, j int, root *TrieNode) bool {
+	cur := root
+	for i := j; i < len(word); i++ {
+		c := word[i]
+		if c == '.' {
+			for _, child := range cur.children {
+				if child != nil && this.dfs(word, i+1, child) {
+					return true
+				}
+			}
+			return false
+		} else {
+			index := c - 'a'
+			if cur.children[index] == nil {
+				return false
+			}
+			cur = cur.children[index]
+		}
+	}
+	return cur.word
+}
+```
+
+```kotlin
+class TrieNode {
+    val children = Array<TrieNode?>(26) { null }
+    var word: Boolean = false
+}
+
+class WordDictionary {
+
+    private val root = TrieNode()
+
+    fun addWord(word: String) {
+        var cur = root
+        for (c in word) {
+            val index = c - 'a'
+            if (cur.children[index] == null) {
+                cur.children[index] = TrieNode()
+            }
+            cur = cur.children[index]!!
+        }
+        cur.word = true
+    }
+
+    fun search(word: String): Boolean {
+        return dfs(word, 0, root)
+    }
+
+    private fun dfs(word: String, j: Int, root: TrieNode): Boolean {
+        var cur = root
+        for (i in j until word.length) {
+            val c = word[i]
+            if (c == '.') {
+                for (child in cur.children) {
+                    if (child != null && dfs(word, i + 1, child)) {
+                        return true
+                    }
+                }
+                return false
+            } else {
+                val index = c - 'a'
+                if (cur.children[index] == null) {
+                    return false
+                }
+                cur = cur.children[index]!!
+            }
+        }
+        return cur.word
+    }
+}
+```
+
+```swift
+class TrieNode {
+    var children: [Character: TrieNode]
+    var word: Bool
+
+    init() {
+        self.children = [:]
+        self.word = false
+    }
+}
+
+class WordDictionary {
+    private let root: TrieNode
+
+    init() {
+        self.root = TrieNode()
+    }
+
+    func addWord(_ word: String) {
+        var cur = root
+        for c in word {
+            if cur.children[c] == nil {
+                cur.children[c] = TrieNode()
+            }
+            cur = cur.children[c]!
+        }
+        cur.word = true
+    }
+
+    func search(_ word: String) -> Bool {
+        func dfs(_ j: Int, _ root: TrieNode) -> Bool {
+            var cur = root
+            let wordArray = Array(word)
+
+            for i in j..<wordArray.count {
+                let c = wordArray[i]
+                if c == "." {
+                    for child in cur.children.values {
+                        if dfs(i + 1, child) {
+                            return true
+                        }
+                    }
+                    return false
+                } else {
+                    if cur.children[c] == nil {
+                        return false
+                    }
+                    cur = cur.children[c]!
+                }
+            }
+            return cur.word
+        }
+
+        return dfs(0, root)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
-* Time complexity: $O(n)$ for $addWord()$, $O(26 ^ n)$ for $search()$.
+* Time complexity: $O(n)$ for $addWord()$, $O(n)$ for $search()$.
 * Space complexity: $O(t + n)$
 
 > Where $n$ is the length of the string and $t$ is the total number of TrieNodes created in the Trie.
\ No newline at end of file
diff --git a/articles/destination-city.md b/articles/destination-city.md
new file mode 100644
index 000000000..0dc585b2b
--- /dev/null
+++ b/articles/destination-city.md
@@ -0,0 +1,253 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def destCity(self, paths: List[List[str]]) -> str:
+        for i in range(len(paths)):
+            flag = True
+            for j in range(len(paths)):
+                if paths[i][1] == paths[j][0]:
+                    flag = False
+                    break
+            if flag:
+                return paths[i][1]
+        return ""
+```
+
+```java
+public class Solution {
+    public String destCity(List<List<String>> paths) {
+        for (int i = 0; i < paths.size(); i++) {
+            boolean flag = true;
+            for (int j = 0; j < paths.size(); j++) {
+                if (paths.get(i).get(1).equals(paths.get(j).get(0))) {
+                    flag = false;
+                    break;
+                }
+            }
+            if (flag) {
+                return paths.get(i).get(1);
+            }
+        }
+        return "";
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string destCity(vector<vector<string>>& paths) {
+        for (int i = 0; i < paths.size(); i++) {
+            bool flag = true;
+            for (int j = 0; j < paths.size(); j++) {
+                if (paths[i][1] == paths[j][0]) {
+                    flag = false;
+                    break;
+                }
+            }
+            if (flag) {
+                return paths[i][1];
+            }
+        }
+        return "";
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[][]} paths
+     * @return {string}
+     */
+    destCity(paths) {
+        for (let i = 0; i < paths.length; i++) {
+            let flag = true;
+            for (let j = 0; j < paths.length; j++) {
+                if (paths[i][1] === paths[j][0]) {
+                    flag = false;
+                    break;
+                }
+            }
+            if (flag) {
+                return paths[i][1];
+            }
+        }
+        return "";
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Hash Set
+
+::tabs-start
+
+```python
+class Solution:
+    def destCity(self, paths: List[List[str]]) -> str:
+        s = set()
+        for p in paths:
+            s.add(p[0])
+
+        for p in paths:
+            if p[1] not in s:
+                return p[1]
+```
+
+```java
+public class Solution {
+    public String destCity(List<List<String>> paths) {
+        Set<String> s = new HashSet<>();
+        for (List<String> p : paths) {
+            s.add(p.get(0));
+        }
+
+        for (List<String> p : paths) {
+            if (!s.contains(p.get(1))) {
+                return p.get(1);
+            }
+        }
+        return "";
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string destCity(vector<vector<string>>& paths) {
+        unordered_set<string> s;
+        for (auto& p : paths) {
+            s.insert(p[0]);
+        }
+
+        for (auto& p : paths) {
+            if (s.find(p[1]) == s.end()) {
+                return p[1];
+            }
+        }
+        return "";
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[][]} paths
+     * @return {string}
+     */
+    destCity(paths) {
+        const s = new Set();
+        for (const p of paths) {
+            s.add(p[0]);
+        }
+
+        for (const p of paths) {
+            if (!s.has(p[1])) {
+                return p[1];
+            }
+        }
+        return "";
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def destCity(self, paths: List[List[str]]) -> str:
+        mp = {p[0]: p[1] for p in paths}
+        
+        start = paths[0][0]
+        while start in mp:
+            start = mp[start]
+        return start
+```
+
+```java
+public class Solution {
+    public String destCity(List<List<String>> paths) {
+        Map<String, String> mp = new HashMap<>();
+        for (List<String> p : paths) {
+            mp.put(p.get(0), p.get(1));
+        }
+
+        String start = paths.get(0).get(0);
+        while (mp.containsKey(start)) {
+            start = mp.get(start);
+        }
+        return start;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string destCity(vector<vector<string>>& paths) {
+        unordered_map<string, string> mp;
+        for (auto& p : paths) {
+            mp[p[0]] = p[1];
+        }
+
+        string start = paths[0][0];
+        while (mp.find(start) != mp.end()) {
+            start = mp[start];
+        }
+        return start;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[][]} paths
+     * @return {string}
+     */
+    destCity(paths) {
+        const mp = new Map();
+        for (const p of paths) {
+            mp.set(p[0], p[1]);
+        }
+
+        let start = paths[0][0];
+        while (mp.has(start)) {
+            start = mp.get(start);
+        }
+        return start;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/detonate-the-maximum-bombs.md b/articles/detonate-the-maximum-bombs.md
new file mode 100644
index 000000000..bc1a75fc9
--- /dev/null
+++ b/articles/detonate-the-maximum-bombs.md
@@ -0,0 +1,522 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def maximumDetonation(self, bombs: list[list[int]]) -> int:
+        adj = [[] for _ in range(len(bombs))]
+
+        for i in range(len(bombs)):
+            x1, y1, r1 = bombs[i]
+            for j in range(i + 1, len(bombs)):
+                x2, y2, r2 = bombs[j]
+                d = (x1 - x2) ** 2 + (y1 - y2) ** 2
+
+                if d <= r1 ** 2:
+                    adj[i].append(j)
+                if d <= r2 ** 2:
+                    adj[j].append(i)
+
+        def dfs(i, visit):
+            if i in visit:
+                return 0
+            visit.add(i)
+            for nei in adj[i]:
+                dfs(nei, visit)
+            return len(visit)
+
+        res = 0
+        for i in range(len(bombs)):
+            res = max(res, dfs(i, set()))
+        return res
+```
+
+```java
+public class Solution {
+    public int maximumDetonation(int[][] bombs) {
+        int n = bombs.length;
+        List<Integer>[] adj = new ArrayList[n];
+        for (int i = 0; i < n; i++) {
+            adj[i] = new ArrayList<>();
+        }
+
+        for (int i = 0; i < n; i++) {
+            for (int j = i + 1; j < n; j++) {
+                int x1 = bombs[i][0], y1 = bombs[i][1], r1 = bombs[i][2];
+                int x2 = bombs[j][0], y2 = bombs[j][1], r2 = bombs[j][2];
+                long d = (long) (x1 - x2) * (x1 - x2) + (long) (y1 - y2) * (y1 - y2);
+
+                if (d <= (long) r1 * r1) {
+                    adj[i].add(j);
+                }
+                if (d <= (long) r2 * r2) {
+                    adj[j].add(i);
+                }
+            }
+        }
+
+        int res = 0;
+        for (int i = 0; i < n; i++) {
+            res = Math.max(res, dfs(i, new HashSet<>(), adj));
+        }
+        return res;
+    }
+
+    private int dfs(int i, Set<Integer> visit, List<Integer>[] adj) {
+        if (!visit.add(i)) return 0;
+        for (int nei : adj[i]) {
+            dfs(nei, visit, adj);
+        }
+        return visit.size();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maximumDetonation(vector<vector<int>>& bombs) {
+        int n = bombs.size();
+        vector<vector<int>> adj(n);
+
+        for (int i = 0; i < n; i++) {
+            for (int j = i + 1; j < n; j++) {
+                long long x1 = bombs[i][0], y1 = bombs[i][1], r1 = bombs[i][2];
+                long long x2 = bombs[j][0], y2 = bombs[j][1], r2 = bombs[j][2];
+                long long d = (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
+
+                if (d <= r1 * r1) {
+                    adj[i].push_back(j);
+                }
+                if (d <= r2 * r2) {
+                    adj[j].push_back(i);
+                }
+            }
+        }
+
+        int res = 0;
+        for (int i = 0; i < n; i++) {
+            unordered_set<int> visit;
+            res = max(res, dfs(i, visit, adj));
+        }
+        return res;
+    }
+
+private:
+    int dfs(int i, unordered_set<int>& visit, vector<vector<int>>& adj) {
+        if (!visit.insert(i).second) return 0;
+        for (int nei : adj[i]) {
+            dfs(nei, visit, adj);
+        }
+        return visit.size();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} bombs
+     * @return {number}
+     */
+    maximumDetonation(bombs) {
+        let n = bombs.length;
+        let adj = Array.from({ length: n }, () => []);
+
+        for (let i = 0; i < n; i++) {
+            for (let j = i + 1; j < n; j++) {
+                let [x1, y1, r1] = bombs[i];
+                let [x2, y2, r2] = bombs[j];
+                let d = (x1 - x2) ** 2 + (y1 - y2) ** 2;
+
+                if (d <= r1 ** 2) adj[i].push(j);
+                if (d <= r2 ** 2) adj[j].push(i);
+            }
+        }
+
+        const dfs = (i, visit) => {
+            if (visit.has(i)) return 0;
+            visit.add(i);
+            for (let nei of adj[i]) {
+                dfs(nei, visit);
+            }
+            return visit.size;
+        };
+
+        let res = 0;
+        for (let i = 0; i < n; i++) {
+            res = Math.max(res, dfs(i, new Set()));
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 3)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 2. Breadth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def maximumDetonation(self, bombs: list[list[int]]) -> int:
+        n = len(bombs)
+        adj = [[] for _ in range(n)]
+
+        for i in range(n):
+            x1, y1, r1 = bombs[i]
+            for j in range(i + 1, n):
+                x2, y2, r2 = bombs[j]
+                d = (x1 - x2) ** 2 + (y1 - y2) ** 2
+
+                if d <= r1 ** 2:
+                    adj[i].append(j)
+                if d <= r2 ** 2:
+                    adj[j].append(i)
+
+        res = 0
+        for i in range(n):
+            q = deque([i])
+            visit = [False] * n
+            visit[i] = True
+            count = 1
+            while q:
+                node = q.popleft()
+                for nei in adj[node]:
+                    if not visit[nei]:
+                        visit[nei] = True
+                        count += 1
+                        q.append(nei)
+            res = max(res, count)
+        return res
+```
+
+```java
+public class Solution {
+    public int maximumDetonation(int[][] bombs) {
+        int n = bombs.length;
+        List<Integer>[] adj = new ArrayList[n];
+        for (int i = 0; i < n; i++) {
+            adj[i] = new ArrayList<>();
+        }
+
+        for (int i = 0; i < n; i++) {
+            int x1 = bombs[i][0], y1 = bombs[i][1], r1 = bombs[i][2];
+            for (int j = i + 1; j < n; j++) {
+                int x2 = bombs[j][0], y2 = bombs[j][1], r2 = bombs[j][2];
+                long d = (long) (x1 - x2) * (x1 - x2) + (long) (y1 - y2) * (y1 - y2);
+
+                if (d <= (long) r1 * r1) adj[i].add(j);
+                if (d <= (long) r2 * r2) adj[j].add(i);
+            }
+        }
+
+        int res = 0;
+        for (int i = 0; i < n; i++) {
+            Queue<Integer> q = new LinkedList<>();
+            boolean[] visit = new boolean[n];
+            q.offer(i);
+            visit[i] = true;
+            int count = 1;
+
+            while (!q.isEmpty()) {
+                int node = q.poll();
+                for (int nei : adj[node]) {
+                    if (!visit[nei]) {
+                        visit[nei] = true;
+                        count++;
+                        q.offer(nei);
+                    }
+                }
+            }
+            res = Math.max(res, count);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maximumDetonation(vector<vector<int>>& bombs) {
+        int n = bombs.size();
+        vector<vector<int>> adj(n);
+
+        for (int i = 0; i < n; i++) {
+            int x1 = bombs[i][0], y1 = bombs[i][1], r1 = bombs[i][2];
+            for (int j = i + 1; j < n; j++) {
+                int x2 = bombs[j][0], y2 = bombs[j][1], r2 = bombs[j][2];
+                long long d = (x1 - x2) * 1LL * (x1 - x2) + (y1 - y2) * 1LL * (y1 - y2);
+
+                if (d <= (long long) r1 * r1) adj[i].push_back(j);
+                if (d <= (long long) r2 * r2) adj[j].push_back(i);
+            }
+        }
+
+        int res = 0;
+        for (int i = 0; i < n; i++) {
+            queue<int> q;
+            vector<bool> visit(n, false);
+            q.push(i);
+            visit[i] = true;
+            int count = 1;
+
+            while (!q.empty()) {
+                int node = q.front();q.pop();
+                for (int& nei : adj[node]) {
+                    if (!visit[nei]) {
+                        visit[nei] = true;
+                        count++;
+                        q.push(nei);
+                    }
+                }
+            }
+            res = max(res, count);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} bombs
+     * @return {number}
+     */
+    maximumDetonation(bombs) {
+        let n = bombs.length;
+        let adj = Array.from({ length: n }, () => []);
+
+        for (let i = 0; i < n; i++) {
+            let [x1, y1, r1] = bombs[i];
+            for (let j = i + 1; j < n; j++) {
+                let [x2, y2, r2] = bombs[j];
+                let d = (x1 - x2) ** 2 + (y1 - y2) ** 2;
+
+                if (d <= r1 ** 2) adj[i].push(j);
+                if (d <= r2 ** 2) adj[j].push(i);
+            }
+        }
+
+        let res = 0;
+        for (let i = 0; i < n; i++) {
+            let q = new Queue([i]);
+            let visit = new Array(n).fill(false);
+            visit[i] = true;
+            let count = 1;
+
+            while (!q.isEmpty()) {
+                let node = q.pop();
+                for (let nei of adj[node]) {
+                    if (!visit[nei]) {
+                        visit[nei] = true;
+                        count++;
+                        q.push(nei);
+                    }
+                }
+            }
+            res = Math.max(res, count);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 3)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 3. Iterative DFS
+
+::tabs-start
+
+```python
+class Solution:
+    def maximumDetonation(self, bombs: list[list[int]]) -> int:
+        n = len(bombs)
+        adj = [[] for _ in range(n)]
+
+        for i in range(n):
+            x1, y1, r1 = bombs[i]
+            for j in range(i + 1, n):
+                x2, y2, r2 = bombs[j]
+                d = (x1 - x2) ** 2 + (y1 - y2) ** 2
+
+                if d <= r1 ** 2:
+                    adj[i].append(j)
+                if d <= r2 ** 2:
+                    adj[j].append(i)
+
+        res = 0
+        for i in range(n):
+            stack = [i]
+            visit = [False] * n
+            visit[i] = True
+            count = 1
+
+            while stack:
+                node = stack.pop()
+                for nei in adj[node]:
+                    if not visit[nei]:
+                        visit[nei] = True
+                        count += 1
+                        stack.append(nei)
+            res = max(res, count)
+        return res
+```
+
+```java
+public class Solution {
+    public int maximumDetonation(int[][] bombs) {
+        int n = bombs.length;
+        List<Integer>[] adj = new ArrayList[n];
+        for (int i = 0; i < n; i++) {
+            adj[i] = new ArrayList<>();
+        }
+
+        for (int i = 0; i < n; i++) {
+            int x1 = bombs[i][0], y1 = bombs[i][1], r1 = bombs[i][2];
+            for (int j = i + 1; j < n; j++) {
+                int x2 = bombs[j][0], y2 = bombs[j][1], r2 = bombs[j][2];
+                long d = (long) (x1 - x2) * (x1 - x2) + (long) (y1 - y2) * (y1 - y2);
+
+                if (d <= (long) r1 * r1) adj[i].add(j);
+                if (d <= (long) r2 * r2) adj[j].add(i);
+            }
+        }
+
+        int res = 0;
+        for (int i = 0; i < n; i++) {
+            Stack<Integer> stack = new Stack<>();
+            boolean[] visit = new boolean[n];
+            stack.push(i);
+            visit[i] = true;
+            int count = 1;
+
+            while (!stack.isEmpty()) {
+                int node = stack.pop();
+                for (int nei : adj[node]) {
+                    if (!visit[nei]) {
+                        visit[nei] = true;
+                        count++;
+                        stack.push(nei);
+                    }
+                }
+            }
+            res = Math.max(res, count);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maximumDetonation(vector<vector<int>>& bombs) {
+        int n = bombs.size();
+        vector<vector<int>> adj(n);
+
+        for (int i = 0; i < n; i++) {
+            int x1 = bombs[i][0], y1 = bombs[i][1], r1 = bombs[i][2];
+            for (int j = i + 1; j < n; j++) {
+                int x2 = bombs[j][0], y2 = bombs[j][1], r2 = bombs[j][2];
+                long long d = (long long)(x1 - x2) * (x1 - x2) + (long long)(y1 - y2) * (y1 - y2);
+
+                if (d <= (long long) r1 * r1) adj[i].push_back(j);
+                if (d <= (long long) r2 * r2) adj[j].push_back(i);
+            }
+        }
+
+        int res = 0;
+        for (int i = 0; i < n; i++) {
+            stack<int> stk;
+            vector<bool> visit(n, false);
+            stk.push(i);
+            visit[i] = true;
+            int count = 1;
+
+            while (!stk.empty()) {
+                int node = stk.top();stk.pop();
+                for (int& nei : adj[node]) {
+                    if (!visit[nei]) {
+                        visit[nei] = true;
+                        count++;
+                        stk.push(nei);
+                    }
+                }
+            }
+            res = max(res, count);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} bombs
+     * @return {number}
+     */
+    maximumDetonation(bombs) {
+        let n = bombs.length;
+        let adj = Array.from({ length: n }, () => []);
+
+        for (let i = 0; i < n; i++) {
+            let [x1, y1, r1] = bombs[i];
+            for (let j = i + 1; j < n; j++) {
+                let [x2, y2, r2] = bombs[j];
+                let d = (x1 - x2) ** 2 + (y1 - y2) ** 2;
+
+                if (d <= r1 ** 2) adj[i].push(j);
+                if (d <= r2 ** 2) adj[j].push(i);
+            }
+        }
+
+        let res = 0;
+        for (let i = 0; i < n; i++) {
+            let stack = [i];
+            let visit = new Array(n).fill(false);
+            visit[i] = true;
+            let count = 1;
+
+            while (stack.length) {
+                let node = stack.pop();
+                for (let nei of adj[node]) {
+                    if (!visit[nei]) {
+                        visit[nei] = true;
+                        count++;
+                        stack.push(nei);
+                    }
+                }
+            }
+            res = Math.max(res, count);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 3)$
+* Space complexity: $O(n ^ 2)$
\ No newline at end of file
diff --git a/articles/distribute-coins-in-binary-tree.md b/articles/distribute-coins-in-binary-tree.md
new file mode 100644
index 000000000..4e26d25e9
--- /dev/null
+++ b/articles/distribute-coins-in-binary-tree.md
@@ -0,0 +1,723 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def distributeCoins(self, root: Optional[TreeNode]) -> int:
+        self.res = 0
+
+        def dfs(cur):
+            if not cur:
+                return [0, 0]  # [size, coins]
+
+            l_size, l_coins = dfs(cur.left)
+            r_size, r_coins = dfs(cur.right)
+
+            size = 1 + l_size + r_size
+            coins = cur.val + l_coins + r_coins
+            self.res += abs(size - coins)
+
+            return [size, coins]
+
+        dfs(root)
+        return self.res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    private int res;
+
+    public int distributeCoins(TreeNode root) {
+        res = 0;
+        dfs(root);
+        return res;
+    }
+
+    private int[] dfs(TreeNode cur) {
+        if (cur == null) {
+            return new int[]{0, 0}; // [size, coins]
+        }
+
+        int[] left = dfs(cur.left);
+        int[] right = dfs(cur.right);
+
+        int size = 1 + left[0] + right[0];
+        int coins = cur.val + left[1] + right[1];
+        res += Math.abs(size - coins);
+
+        return new int[]{size, coins};
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+private:
+    int res;
+
+    vector<int> dfs(TreeNode* cur) {
+        if (!cur) {
+            return {0, 0}; // [size, coins]
+        }
+
+        vector<int> left = dfs(cur->left);
+        vector<int> right = dfs(cur->right);
+
+        int size = 1 + left[0] + right[0];
+        int coins = cur->val + left[1] + right[1];
+        res += abs(size - coins);
+
+        return {size, coins};
+    }
+
+public:
+    int distributeCoins(TreeNode* root) {
+        res = 0;
+        dfs(root);
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number}
+     */
+    distributeCoins(root) {
+        let res = 0;
+
+        const dfs = (cur) => {
+            if (!cur) {
+                return [0, 0]; // [size, coins]
+            }
+
+            let [lSize, lCoins] = dfs(cur.left);
+            let [rSize, rCoins] = dfs(cur.right);
+
+            let size = 1 + lSize + rSize;
+            let coins = cur.val + lCoins + rCoins;
+            res += Math.abs(size - coins);
+
+            return [size, coins];
+        };
+
+        dfs(root);
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Depth First Search (Optimal)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def distributeCoins(self, root: Optional[TreeNode]) -> int:
+        self.res = 0
+
+        def dfs(cur):
+            if not cur:
+                return 0  # extra_coins
+
+            l_extra = dfs(cur.left)
+            r_extra = dfs(cur.right)
+
+            extra_coins = cur.val - 1 + l_extra + r_extra
+            self.res += abs(extra_coins)
+            return extra_coins
+
+        dfs(root)
+        return self.res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    private int res;
+
+    public int distributeCoins(TreeNode root) {
+        res = 0;
+        dfs(root);
+        return res;
+    }
+
+    private int dfs(TreeNode cur) {
+        if (cur == null) {
+            return 0; // extra_coins
+        }
+
+        int lExtra = dfs(cur.left);
+        int rExtra = dfs(cur.right);
+
+        int extraCoins = cur.val - 1 + lExtra + rExtra;
+        res += Math.abs(extraCoins);
+        return extraCoins;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+private:
+    int res;
+
+    int dfs(TreeNode* cur) {
+        if (!cur) {
+            return 0; // extra_coins
+        }
+
+        int lExtra = dfs(cur->left);
+        int rExtra = dfs(cur->right);
+
+        int extraCoins = cur->val - 1 + lExtra + rExtra;
+        res += abs(extraCoins);
+        return extraCoins;
+    }
+
+public:
+    int distributeCoins(TreeNode* root) {
+        res = 0;
+        dfs(root);
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number}
+     */
+    distributeCoins(root) {
+        let res = 0;
+
+        const dfs = (cur) => {
+            if (!cur) {
+                return 0; // extra_coins
+            }
+
+            let lExtra = dfs(cur.left);
+            let rExtra = dfs(cur.right);
+
+            let extraCoins = cur.val - 1 + lExtra + rExtra;
+            res += Math.abs(extraCoins);
+            return extraCoins;
+        };
+
+        dfs(root);
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ fo recursion stack.
+
+---
+
+## 3. Breadth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def distributeCoins(self, root: Optional[TreeNode]) -> int:
+        res = 0
+        q = deque([root])
+        parent_map = {}
+
+        nodes = []
+        while q:
+            node = q.popleft()
+            nodes.append(node)
+            if node.left:
+                parent_map[node.left] = node
+                q.append(node.left)
+            if node.right:
+                parent_map[node.right] = node
+                q.append(node.right)
+
+        while nodes:
+            node = nodes.pop()
+            if node in parent_map:
+                parent = parent_map[node]
+                parent.val += node.val - 1
+                res += abs(node.val - 1)
+
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public int distributeCoins(TreeNode root) {
+        int res = 0;
+        Queue<TreeNode> q = new LinkedList<>();
+        Map<TreeNode, TreeNode> parentMap = new HashMap<>();
+        List<TreeNode> nodes = new ArrayList<>();
+
+        q.offer(root);
+        while (!q.isEmpty()) {
+            TreeNode node = q.poll();
+            nodes.add(node);
+            if (node.left != null) {
+                parentMap.put(node.left, node);
+                q.offer(node.left);
+            }
+            if (node.right != null) {
+                parentMap.put(node.right, node);
+                q.offer(node.right);
+            }
+        }
+
+        for (int i = nodes.size() - 1; i >= 0; i--) {
+            TreeNode node = nodes.get(i);
+            if (parentMap.containsKey(node)) {
+                TreeNode parent = parentMap.get(node);
+                parent.val += node.val - 1;
+                res += Math.abs(node.val - 1);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int distributeCoins(TreeNode* root) {
+        int res = 0;
+        queue<TreeNode*> q;
+        unordered_map<TreeNode*, TreeNode*> parentMap;
+        vector<TreeNode*> nodes;
+
+        q.push(root);
+        while (!q.empty()) {
+            TreeNode* node = q.front();
+            q.pop();
+            nodes.push_back(node);
+            if (node->left) {
+                parentMap[node->left] = node;
+                q.push(node->left);
+            }
+            if (node->right) {
+                parentMap[node->right] = node;
+                q.push(node->right);
+            }
+        }
+
+        for (int i = nodes.size() - 1; i >= 0; i--) {
+            TreeNode* node = nodes[i];
+            if (parentMap.count(node)) {
+                TreeNode* parent = parentMap[node];
+                parent->val += node->val - 1;
+                res += abs(node->val - 1);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number}
+     */
+    distributeCoins(root) {
+        let res = 0;
+        let q = new Queue();
+        let parentMap = new Map();
+        let nodes = [];
+
+        q.push(root);
+        while (!q.isEmpty()) {
+            let node = q.pop();
+            nodes.push(node);
+            if (node.left) {
+                parentMap.set(node.left, node);
+                q.push(node.left);
+            }
+            if (node.right) {
+                parentMap.set(node.right, node);
+                q.push(node.right);
+            }
+        }
+
+        for (let i = nodes.length - 1; i >= 0; i--) {
+            let node = nodes[i];
+            if (parentMap.has(node)) {
+                let parent = parentMap.get(node);
+                parent.val += node.val - 1;
+                res += Math.abs(node.val - 1);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Iterative DFS
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def distributeCoins(self, root: Optional[TreeNode]) -> int:
+        stack = [root]
+        res = 0
+        visit = set()
+
+        while stack:
+            node = stack.pop()
+
+            if node not in visit:
+                stack.append(node)
+                visit.add(node)
+
+                if node.right:
+                    stack.append(node.right)
+                if node.left:
+                    stack.append(node.left)
+            else:
+                if node.left:
+                    node.val += node.left.val
+                if node.right:
+                    node.val += node.right.val
+
+                node.val -= 1
+                res += abs(node.val)
+                visit.remove(node)
+
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public int distributeCoins(TreeNode root) {
+        Stack<TreeNode> stack = new Stack<>();
+        Set<TreeNode> visit = new HashSet<>();
+        stack.push(root);
+        int res = 0;
+
+        while (!stack.isEmpty()) {
+            TreeNode node = stack.pop();
+
+            if (!visit.contains(node)) {
+                stack.push(node);
+                visit.add(node);
+
+                if (node.right != null) {
+                    stack.push(node.right);
+                }
+                if (node.left != null) {
+                    stack.push(node.left);
+                }
+            } else {
+                if (node.left != null) {
+                    node.val += node.left.val;
+                }
+                if (node.right != null) {
+                    node.val += node.right.val;
+                }
+
+                node.val -= 1;
+                res += Math.abs(node.val);
+                visit.remove(node);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int distributeCoins(TreeNode* root) {
+        stack<TreeNode*> stack;
+        unordered_set<TreeNode*> visit;
+        stack.push(root);
+        int res = 0;
+
+        while (!stack.empty()) {
+            TreeNode* node = stack.top();
+            stack.pop();
+
+            if (visit.find(node) == visit.end()) {
+                stack.push(node);
+                visit.insert(node);
+
+                if (node->right) {
+                    stack.push(node->right);
+                }
+                if (node->left) {
+                    stack.push(node->left);
+                }
+            } else {
+                if (node->left) {
+                    node->val += node->left->val;
+                }
+                if (node->right) {
+                    node->val += node->right->val;
+                }
+
+                visit.erase(node);
+                node->val -= 1;
+                res += abs(node->val);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number}
+     */
+    distributeCoins(root) {
+        let stack = [root];
+        let visit = new Set();
+        let res = 0;
+
+        while (stack.length) {
+            let node = stack.pop();
+
+            if (!visit.has(node)) {
+                stack.push(node);
+                visit.add(node);
+
+                if (node.right) {
+                    stack.push(node.right);
+                }
+                if (node.left) {
+                    stack.push(node.left);
+                }
+            } else {
+                if (node.left) {
+                    node.val += node.left.val;
+                }
+                if (node.right) {
+                    node.val += node.right.val;
+                }
+
+                visit.delete(node);
+                node.val -= 1;
+                res += Math.abs(node.val);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/divide-array-into-arrays-with-max-difference.md b/articles/divide-array-into-arrays-with-max-difference.md
new file mode 100644
index 000000000..d969ca851
--- /dev/null
+++ b/articles/divide-array-into-arrays-with-max-difference.md
@@ -0,0 +1,238 @@
+## 1. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def divideArray(self, nums: List[int], k: int) -> List[List[int]]:
+        nums.sort()
+        res = []
+
+        for i in range(0, len(nums), 3):
+            if nums[i + 2] - nums[i] > k:
+                return []
+            res.append(nums[i: i + 3])
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int[][] divideArray(int[] nums, int k) {
+        Arrays.sort(nums);
+        int[][] res = new int[nums.length / 3][3];
+
+        for (int i = 0, idx = 0; i < nums.length; i += 3, idx++) {
+            if (nums[i + 2] - nums[i] > k) {
+                return new int[][]{};
+            }
+            res[idx][0] = nums[i];
+            res[idx][1] = nums[i + 1];
+            res[idx][2] = nums[i + 2];
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> divideArray(vector<int>& nums, int k) {
+        sort(nums.begin(), nums.end());
+        vector<vector<int>> res;
+
+        for (int i = 0; i < nums.size(); i += 3) {
+            if (nums[i + 2] - nums[i] > k) {
+                return {};
+            }
+            res.push_back({nums[i], nums[i + 1], nums[i + 2]});
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number[][]}
+     */
+    divideArray(nums, k) {
+        nums.sort((a, b) => a - b);
+        const res = [];
+
+        for (let i = 0; i < nums.length; i += 3) {
+            if (nums[i + 2] - nums[i] > k) {
+                return [];
+            }
+            res.push([nums[i], nums[i + 1], nums[i + 2]]);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$ for the output array.
+
+---
+
+## 2. Counting Sort
+
+::tabs-start
+
+```python
+class Solution:
+    def divideArray(self, nums: List[int], k: int) -> List[List[int]]:
+        max_num = max(nums)
+        count = [0] * (max_num + 1)
+        for num in nums:
+            count[num] += 1
+
+        res = []
+        group = []
+
+        for num in range(max_num + 1):
+            while count[num] > 0:
+                group.append(num)
+                count[num] -= 1
+
+                if len(group) == 3:
+                    if group[2] - group[0] > k:
+                        return []
+                    res.append(group)
+                    group = []
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[][] divideArray(int[] nums, int k) {
+        int max = 0;
+        for (int num : nums) {
+            max = Math.max(max, num);
+        }
+
+        int[] count = new int[max + 1];
+        for (int num : nums) {
+            count[num]++;
+        }
+
+        int[][] res = new int[nums.length / 3][3];
+        int[] group = new int[3];
+        int i = 0;
+
+        for (int num = 0, idx = 0; num <= max; num++) {
+            while (count[num] > 0) {
+                group[i++] = num;
+                count[num]--;
+
+                if (i == 3) {
+                    if (group[2] - group[0] > k) {
+                        return new int[][]{};
+                    }
+                    for (int j = 0; j < 3; j++) {
+                        res[idx][j] = group[j];
+                    }
+                    i = 0;
+                    idx++;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> divideArray(vector<int>& nums, int k) {
+        int maxNum = *max_element(nums.begin(), nums.end());
+        vector<int> count(maxNum + 1, 0);
+
+        for (int& num : nums) {
+            count[num]++;
+        }
+
+        vector<vector<int>> res;
+        vector<int> group;
+
+        for (int num = 0; num <= maxNum; num++) {
+            while (count[num] > 0) {
+                group.push_back(num);
+                count[num]--;
+
+                if (group.size() == 3) {
+                    if (group[2] - group[0] > k) {
+                        return {};
+                    }
+                    res.push_back(group);
+                    group.clear();
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number[][]}
+     */
+    divideArray(nums, k) {
+        const max = Math.max(...nums);
+        const count = new Array(max + 1).fill(0);
+
+        for (const num of nums) {
+            count[num]++;
+        }
+
+        const res = [];
+        let group = [];
+
+        for (let num = 0; num <= max; num++) {
+            while (count[num] > 0) {
+                group.push(num);
+                count[num]--;
+
+                if (group.length === 3) {
+                    if (group[2] - group[0] > k) {
+                        return [];
+                    }
+                    res.push(group);
+                    group = [];
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(n + m)$
+
+> Where $n$ is the size of the array $nums$ and $m$ is the maximum element in $nums$.
\ No newline at end of file
diff --git a/articles/divide-array-into-equal-pairs.md b/articles/divide-array-into-equal-pairs.md
new file mode 100644
index 000000000..bc8a01fb1
--- /dev/null
+++ b/articles/divide-array-into-equal-pairs.md
@@ -0,0 +1,290 @@
+## 1. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def divideArray(self, nums: List[int]) -> bool:
+        N = len(nums)
+        nums.sort()
+
+        i = 0
+        while i < N:
+            j = i
+            while j < N and nums[i] == nums[j]:
+                j += 1
+
+            if (j - i) % 2 != 0:
+                return False
+
+            i = j
+
+        return True
+```
+
+```java
+public class Solution {
+    public boolean divideArray(int[] nums) {
+        int N = nums.length;
+        Arrays.sort(nums);
+
+        int i = 0;
+        while (i < N) {
+            int j = i;
+            while (j < N && nums[i] == nums[j]) {
+                j++;
+            }
+
+            if ((j - i) % 2 != 0) {
+                return false;
+            }
+
+            i = j;
+        }
+
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool divideArray(vector<int>& nums) {
+        int N = nums.size();
+        sort(nums.begin(), nums.end());
+
+        int i = 0;
+        while (i < N) {
+            int j = i;
+            while (j < N && nums[i] == nums[j]) {
+                j++;
+            }
+
+            if ((j - i) % 2 != 0) {
+                return false;
+            }
+
+            i = j;
+        }
+
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {boolean}
+     */
+    divideArray(nums) {
+        const N = nums.length;
+        nums.sort((a, b) => a - b);
+
+        let i = 0;
+        while (i < N) {
+            let j = i;
+            while (j < N && nums[i] === nums[j]) {
+                j++;
+            }
+
+            if ((j - i) % 2 !== 0) {
+                return false;
+            }
+
+            i = j;
+        }
+
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 2. Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def divideArray(self, nums: List[int]) -> bool:
+        count = {}
+        for num in nums:
+            if num not in count:
+                count[num] = 0
+            count[num] += 1
+
+        for cnt in count.values():
+            if cnt % 2 == 1:
+                return False
+
+        return True
+```
+
+```java
+public class Solution {
+    public boolean divideArray(int[] nums) {
+        Map<Integer, Integer> count = new HashMap<>();
+        for (int num : nums) {
+            count.put(num, count.getOrDefault(num, 0) + 1);
+        }
+
+        for (int cnt : count.values()) {
+            if (cnt % 2 == 1) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool divideArray(vector<int>& nums) {
+        unordered_map<int, int> count;
+        for (int num : nums) {
+            count[num]++;
+        }
+
+        for (auto& [key, cnt] : count) {
+            if (cnt % 2 == 1) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {boolean}
+     */
+    divideArray(nums) {
+        const count = {};
+        for (let num of nums) {
+            if (!(num in count)) {
+                count[num] = 0;
+            }
+            count[num]++;
+        }
+
+        for (let key in count) {
+            if (count[key] % 2 === 1) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Hash Set
+
+::tabs-start
+
+```python
+class Solution:
+    def divideArray(self, nums: List[int]) -> bool:
+        odd_set = set()
+
+        for num in nums:
+            if num not in odd_set:
+                odd_set.add(num)
+            else:
+                odd_set.remove(num)
+
+        return not len(odd_set)
+```
+
+```java
+public class Solution {
+    public boolean divideArray(int[] nums) {
+        Set<Integer> oddSet = new HashSet<>();
+
+        for (int num : nums) {
+            if (!oddSet.contains(num)) {
+                oddSet.add(num);
+            } else {
+                oddSet.remove(num);
+            }
+        }
+
+        return oddSet.isEmpty();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool divideArray(vector<int>& nums) {
+        unordered_set<int> oddSet;
+
+        for (int num : nums) {
+            if (oddSet.count(num)) {
+                oddSet.erase(num);
+            } else {
+                oddSet.insert(num);
+            }
+        }
+
+        return oddSet.empty();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {boolean}
+     */
+    divideArray(nums) {
+        const oddSet = new Set();
+
+        for (let num of nums) {
+            if (oddSet.has(num)) {
+                oddSet.delete(num);
+            } else {
+                oddSet.add(num);
+            }
+        }
+
+        return oddSet.size === 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/dota2-senate.md b/articles/dota2-senate.md
new file mode 100644
index 000000000..4e30f1d55
--- /dev/null
+++ b/articles/dota2-senate.md
@@ -0,0 +1,423 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def predictPartyVictory(self, senate: str) -> str:
+        s = list(senate)
+        while True:
+            if 'R' not in s:
+                return "Dire"
+            if 'D' not in s:
+                return "Radiant"
+            
+            i = 0
+            while i < len(s):
+                if s[i] == 'R':
+                    j = (i + 1) % len(s)
+                    while s[j] == 'R':
+                        j = (j + 1) % len(s)
+                    s.pop(j)
+                    if j < i:
+                        i -= 1
+                else:
+                    j = (i + 1) % len(s)
+                    while s[j] == 'D':
+                        j = (j + 1) % len(s)
+                    s.pop(j)
+                    if j < i:
+                        i -= 1
+                i += 1
+```
+
+```java
+public class Solution {
+    public String predictPartyVictory(String senate) {
+        List<Character> s = new ArrayList<>();
+        for (char c : senate.toCharArray()) {
+            s.add(c);
+        }
+        
+        while (true) {
+            if (!s.contains('R')) {
+                return "Dire";
+            }
+            if (!s.contains('D')) {
+                return "Radiant";
+            }
+
+            int i = 0;
+            while (i < s.size()) {
+                if (s.get(i) == 'R') {
+                    int j = (i + 1) % s.size();
+                    while (s.get(j) == 'R') {
+                        j = (j + 1) % s.size();
+                    }
+                    s.remove(j);
+                    if (j < i) {
+                        i--;
+                    }
+                } else {
+                    int j = (i + 1) % s.size();
+                    while (s.get(j) == 'D') {
+                        j = (j + 1) % s.size();
+                    }
+                    s.remove(j);
+                    if (j < i) {
+                        i--;
+                    }
+                }
+                i++;
+            }
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string predictPartyVictory(string senate) {
+        vector<char> s(senate.begin(), senate.end());
+        
+        while (true) {
+            if (find(s.begin(), s.end(), 'R') == s.end()) {
+                return "Dire";
+            }
+            if (find(s.begin(), s.end(), 'D') == s.end()) {
+                return "Radiant";
+            }
+
+            int i = 0;
+            while (i < s.size()) {
+                if (s[i] == 'R') {
+                    int j = (i + 1) % s.size();
+                    while (s[j] == 'R') {
+                        j = (j + 1) % s.size();
+                    }
+                    s.erase(s.begin() + j);
+                    if (j < i) {
+                        i--;
+                    }
+                } else {
+                    int j = (i + 1) % s.size();
+                    while (s[j] == 'D') {
+                        j = (j + 1) % s.size();
+                    }
+                    s.erase(s.begin() + j);
+                    if (j < i) {
+                        i--;
+                    }
+                }
+                i++;
+            }
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} senate
+     * @return {string}
+     */
+    predictPartyVictory(senate) {
+        const s = senate.split("");
+        
+        while (true) {
+            if (!s.includes("R")) {
+                return "Dire";
+            }
+            if (!s.includes("D")) {
+                return "Radiant";
+            }
+            
+            let i = 0;
+            while (i < s.length) {
+                if (s[i] === "R") {
+                    let j = (i + 1) % s.length;
+                    while (s[j] === "R") {
+                        j = (j + 1) % s.length;
+                    }
+                    s.splice(j, 1);
+                    if (j < i) {
+                        i--;
+                    }
+                } else {
+                    let j = (i + 1) % s.length;
+                    while (s[j] === "D") {
+                        j = (j + 1) % s.length;
+                    }
+                    s.splice(j, 1);
+                    if (j < i) {
+                        i--;
+                    }
+                }
+                i++;
+            }
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Greedy (Two Queues)
+
+::tabs-start
+
+```python
+class Solution:
+    def predictPartyVictory(self, senate: str) -> str:
+        D, R = deque(), deque()
+        n = len(senate)
+
+        for i, c in enumerate(senate):
+            if c == 'R':
+                R.append(i)
+            else:
+                D.append(i)
+
+        while D and R:
+            dTurn = D.popleft()
+            rTurn = R.popleft()
+
+            if rTurn < dTurn:
+                R.append(rTurn + n)
+            else:
+                D.append(dTurn + n)
+
+        return "Radiant" if R else "Dire"
+```
+
+```java
+public class Solution {
+    public String predictPartyVictory(String senate) {
+        Queue<Integer> R = new LinkedList<>();
+        Queue<Integer> D = new LinkedList<>();
+        int n = senate.length();
+
+        for (int i = 0; i < n; i++) {
+            if (senate.charAt(i) == 'R') {
+                R.add(i);
+            } else {
+                D.add(i);
+            }
+        }
+
+        while (!R.isEmpty() && !D.isEmpty()) {
+            int rTurn = R.poll();
+            int dTurn = D.poll();
+
+            if (rTurn < dTurn) {
+                R.add(rTurn + n);
+            } else {
+                D.add(dTurn + n);
+            }
+        }
+
+        return R.isEmpty() ? "Dire" : "Radiant";
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string predictPartyVictory(string senate) {
+        queue<int> R, D;
+        int n = senate.size();
+
+        for (int i = 0; i < n; i++) {
+            if (senate[i] == 'R') {
+                R.push(i);
+            } else {
+                D.push(i);
+            }
+        }
+
+        while (!R.empty() && !D.empty()) {
+            int rTurn = R.front(); R.pop();
+            int dTurn = D.front(); D.pop();
+
+            if (rTurn < dTurn) {
+                R.push(rTurn + n);
+            } else {
+                D.push(dTurn + n);
+            }
+        }
+
+        return R.empty() ? "Dire" : "Radiant";
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} senate
+     * @return {string}
+     */
+    predictPartyVictory(senate) {
+        const R = new Queue();
+        const D = new Queue();
+        const n = senate.length;
+
+        for (let i = 0; i < n; i++) {
+            if (senate[i] === "R") {
+                R.push(i);
+            } else {
+                D.push(i);
+            }
+        }
+
+        while (!R.isEmpty() && !D.isEmpty()) {
+            const rTurn = R.pop();
+            const dTurn = D.pop();
+
+            if (rTurn < dTurn) {
+                R.push(rTurn + n);
+            } else {
+                D.push(dTurn + n);
+            }
+        }
+
+        return !R.isEmpty() ? "Radiant" : "Dire";
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Greedy
+
+::tabs-start
+
+```python
+class Solution:
+    def predictPartyVictory(self, senate: str) -> str:
+        senate = list(senate)
+        cnt = i = 0
+
+        while i < len(senate):
+            c = senate[i]
+            if c == 'R':
+                if cnt < 0:
+                    senate.append('D')
+                cnt += 1
+            else:
+                if cnt > 0:
+                    senate.append('R')
+                cnt -= 1
+            i += 1
+        
+        return "Radiant" if cnt > 0 else "Dire"
+```
+
+```java
+public class Solution {
+    public String predictPartyVictory(String senate) {
+        StringBuilder sb = new StringBuilder(senate);
+        int cnt = 0, i = 0;
+
+        while (i < sb.length()) {
+            char c = sb.charAt(i);
+            if (c == 'R') {
+                if (cnt < 0) {
+                    sb.append('D');
+                }
+                cnt++;
+            } else {
+                if (cnt > 0) {
+                    sb.append('R');
+                }
+                cnt--;
+            }
+            i++;
+        }
+
+        return cnt > 0 ? "Radiant" : "Dire";
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string predictPartyVictory(string senate) {
+        int cnt = 0, i = 0;
+
+        while (i < senate.size()) {
+            char c = senate[i];
+            if (c == 'R') {
+                if (cnt < 0) {
+                    senate.push_back('D');
+                }
+                cnt++;
+            } else {
+                if (cnt > 0) {
+                    senate.push_back('R');
+                }
+                cnt--;
+            }
+            i++;
+        }
+
+        return cnt > 0 ? "Radiant" : "Dire";
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} senate
+     * @return {string}
+     */
+    predictPartyVictory(senate) {
+        let s = senate.split('');
+        let cnt = 0, i = 0;
+
+        while (i < s.length) {
+            const c = s[i];
+            if (c === 'R') {
+                if (cnt < 0) {
+                    s.push('D');
+                }
+                cnt++;
+            } else {
+                if (cnt > 0) {
+                    s.push('R');
+                }
+                cnt--;
+            }
+            i++;
+        }
+
+        return cnt > 0 ? "Radiant" : "Dire";
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/duplicate-integer.md b/articles/duplicate-integer.md
index 25447268b..882486892 100644
--- a/articles/duplicate-integer.md
+++ b/articles/duplicate-integer.md
@@ -77,11 +77,54 @@ public class Solution {
 }
 ```
 
+```go
+func hasDuplicate(nums []int) bool {
+    for i := 0; i < len(nums); i++ {
+        for j := i + 1; j < len(nums); j++ {
+            if nums[i] == nums[j] {
+                return true
+            }
+        }
+    }
+    return false
+}
+```
+
+```kotlin
+class Solution {
+    fun hasDuplicate(nums: IntArray): Boolean {
+        for (i in nums.indices) {
+            for (j in i + 1 until nums.size) {
+                if (nums[i] == nums[j]) {
+                    return true
+                }
+            }
+        }
+        return false
+    }
+}
+```
+
+```swift
+class Solution {
+    func hasDuplicate(_ nums: [Int]) -> Bool {
+        for i in 0..<nums.count {
+            for j in (i + 1)..<nums.count {
+                if nums[i] == nums[j] {
+                    return true
+                }
+            }
+        }
+        return false
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
-* Time complexity: $O(n^2)$
+* Time complexity: $O(n ^ 2)$
 * Space complexity: $O(1)$
 
 ---
@@ -161,6 +204,46 @@ public class Solution {
 }
 ```
 
+```go
+func hasDuplicate(nums []int) bool {
+    sort.Ints(nums)
+    for i := 1; i < len(nums); i++ {
+        if nums[i] == nums[i-1] {
+            return true
+        }
+    }
+    return false
+}
+```
+
+```kotlin
+class Solution {
+    fun hasDuplicate(nums: IntArray): Boolean {
+        nums.sort()
+        for (i in 1 until nums.size) {
+            if (nums[i] == nums[i - 1]) {
+                return true
+            }
+        }
+        return false
+    }
+}
+```
+
+```swift
+class Solution {
+    func hasDuplicate(_ nums: [Int]) -> Bool {
+        var nums = nums.sorted()
+        for i in 1..<nums.count {
+            if nums[i] == nums[i - 1] {
+                return true
+            }
+        }
+        return false
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -250,6 +333,49 @@ public class Solution {
 }
 ```
 
+```go
+func hasDuplicate(nums []int) bool {
+    seen := make(map[int]bool)
+    for _, num := range nums {
+        if seen[num] {
+            return true
+        }
+        seen[num] = true
+    }
+    return false
+}
+```
+
+```kotlin
+class Solution {
+    fun hasDuplicate(nums: IntArray): Boolean {
+        val seen = HashSet<Int>()
+        for (num in nums) {
+            if (num in seen) {
+                return true
+            }
+            seen.add(num)
+        }
+        return false
+    }
+}
+```
+
+```swift
+class Solution {
+    func hasDuplicate(_ nums: [Int]) -> Bool {
+        var seen = Set<Int>()
+        for num in nums {
+            if seen.contains(num) {
+                return true
+            }
+            seen.insert(num)
+        }
+        return false
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -306,10 +432,35 @@ public class Solution {
 }
 ```
 
+```go
+func hasDuplicate(nums []int) bool {
+    seen := make(map[int]struct{})
+    for _, num := range nums {
+        seen[num] = struct{}{}
+    }
+    return len(seen) < len(nums)
+}
+```
+
+```kotlin
+class Solution {
+    fun hasDuplicate(nums: IntArray): Boolean {
+        return nums.toSet().size < nums.size
+    }
+}
+```
+
+```swift
+class Solution {
+    func hasDuplicate(_ nums: [Int]) -> Bool {
+        return Set(nums).count < nums.count
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n)$
-* Space complexity: $O(n)$
-
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/eating-bananas.md b/articles/eating-bananas.md
index 0222468b7..4acd82fb0 100644
--- a/articles/eating-bananas.md
+++ b/articles/eating-bananas.md
@@ -99,6 +99,65 @@ public class Solution {
 }
 ```
 
+```go
+func minEatingSpeed(piles []int, h int) int {
+   speed := 1
+   for {
+       totalTime := 0
+       for _, pile := range piles {
+           totalTime += int(math.Ceil(float64(pile) / float64(speed)))
+       }
+       
+       if totalTime <= h {
+           return speed
+       }
+       speed += 1
+   }
+   return speed
+}
+```
+
+```kotlin
+class Solution {
+    fun minEatingSpeed(piles: IntArray, h: Int): Int {
+        var speed = 1
+        while (true) {
+            var totalTime = 0L
+            for (pile in piles) {
+                totalTime += Math.ceil(pile.toDouble() / speed).toLong()
+            }
+            
+            if (totalTime <= h) {
+                return speed
+            }
+            speed += 1
+        }
+        return speed
+    }
+}
+```
+
+```swift
+class Solution {
+    func minEatingSpeed(_ piles: [Int], _ h: Int) -> Int {
+        var speed = 1
+        
+        while true {
+            var totalTime = 0
+            for pile in piles {
+                totalTime += Int(ceil(Double(pile) / Double(speed)))
+            }
+            
+            if totalTime <= h {
+                return speed
+            }
+            speed += 1
+        }
+        return speed
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -244,6 +303,88 @@ public class Solution {
 }
 ```
 
+```go
+func minEatingSpeed(piles []int, h int) int {
+   l, r := 1, 0
+   for _, p := range piles {
+       if p > r {
+           r = p
+       }
+   }
+   res := r
+   
+   for l <= r {
+       k := (l + r) / 2
+       totalTime := 0
+       
+       for _, p := range piles {
+           totalTime += int(math.Ceil(float64(p) / float64(k)))
+       }
+       
+       if totalTime <= h {
+           res = k
+           r = k - 1
+       } else {
+           l = k + 1
+       }
+   }
+   return res
+}
+```
+
+```kotlin
+class Solution {
+    fun minEatingSpeed(piles: IntArray, h: Int): Int {
+        var l = 1
+        var r = piles.max()!!
+        var res = r
+        
+        while (l <= r) {
+            val k = (l + r) / 2
+            var totalTime = 0L
+            
+            for (p in piles) {
+                totalTime += Math.ceil(p.toDouble() / k).toLong()
+            }
+            
+            if (totalTime <= h) {
+                res = k
+                r = k - 1
+            } else {
+                l = k + 1
+            }
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func minEatingSpeed(_ piles: [Int], _ h: Int) -> Int {
+        var l = 1, r = piles.max()!
+        var res = r
+
+        while l <= r {
+            let k = (l + r) / 2
+
+            var totalTime = 0
+            for p in piles {
+                totalTime += Int(ceil(Double(p) / Double(k)))
+            }
+
+            if totalTime <= h {
+                res = k
+                r = k - 1
+            } else {
+                l = k + 1
+            }
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/edit-distance.md b/articles/edit-distance.md
index b21f59b75..7c4b6bfeb 100644
--- a/articles/edit-distance.md
+++ b/articles/edit-distance.md
@@ -117,6 +117,79 @@ public class Solution {
 }
 ```
 
+```go
+func minDistance(word1 string, word2 string) int {
+    m, n := len(word1), len(word2)
+
+    var dfs func(i, j int) int
+    dfs = func(i, j int) int {
+        if i == m {
+            return n - j
+        }
+        if j == n {
+            return m - i
+        }
+        if word1[i] == word2[j] {
+            return dfs(i+1, j+1)
+        }
+        res := min(dfs(i+1, j), dfs(i, j+1))
+        res = min(res, dfs(i+1, j+1))
+        return res + 1
+    }
+
+    return dfs(0, 0)
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun minDistance(word1: String, word2: String): Int {
+        val m = word1.length
+        val n = word2.length
+
+        fun dfs(i: Int, j: Int): Int {
+            if (i == m) return n - j
+            if (j == n) return m - i
+            if (word1[i] == word2[j]) return dfs(i + 1, j + 1)
+
+            var res = minOf(dfs(i + 1, j), dfs(i, j + 1))
+            res = minOf(res, dfs(i + 1, j + 1))
+            return res + 1
+        }
+
+        return dfs(0, 0)
+    }
+}
+```
+
+```swift
+class Solution {
+    func minDistance(_ word1: String, _ word2: String) -> Int {
+        let m = word1.count, n = word2.count
+        let word1Array = Array(word1), word2Array = Array(word2)
+
+        func dfs(_ i: Int, _ j: Int) -> Int {
+            if i == m { return n - j }
+            if j == n { return m - i }
+            if word1Array[i] == word2Array[j] {
+                return dfs(i + 1, j + 1)
+            }
+            let res = min(dfs(i + 1, j), dfs(i, j + 1))
+            return min(res, dfs(i + 1, j + 1)) + 1
+        }
+
+        return dfs(0, 0)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -278,6 +351,105 @@ public class Solution {
 }
 ```
 
+```go
+func minDistance(word1 string, word2 string) int {
+    m, n := len(word1), len(word2)
+    dp := make([][]int, m+1)
+    for i := range dp {
+        dp[i] = make([]int, n+1)
+        for j := range dp[i] {
+            dp[i][j] = -1 
+        }
+    }
+
+    var dfs func(i, j int) int
+    dfs = func(i, j int) int {
+        if i == m {
+            return n - j
+        }
+        if j == n {
+            return m - i
+        }
+        if dp[i][j] != -1 {
+            return dp[i][j]
+        }
+
+        if word1[i] == word2[j] {
+            dp[i][j] = dfs(i+1, j+1)
+        } else {
+            insert := dfs(i, j+1)
+            delete := dfs(i+1, j)
+            replace := dfs(i+1, j+1)
+            dp[i][j] = 1 + min(insert, min(delete, replace))
+        }
+        return dp[i][j]
+    }
+
+    return dfs(0, 0)
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun minDistance(word1: String, word2: String): Int {
+        val m = word1.length
+        val n = word2.length
+        val dp = Array(m + 1) { IntArray(n + 1) { -1 } }
+
+        fun dfs(i: Int, j: Int): Int {
+            if (i == m) return n - j
+            if (j == n) return m - i
+            if (dp[i][j] != -1) return dp[i][j]
+
+            dp[i][j] = if (word1[i] == word2[j]) {
+                dfs(i + 1, j + 1)
+            } else {
+                val insert = dfs(i, j + 1)
+                val delete = dfs(i + 1, j)
+                val replace = dfs(i + 1, j + 1)
+                1 + minOf(insert, delete, replace)
+            }
+            return dp[i][j]
+        }
+
+        return dfs(0, 0)
+    }
+}
+```
+
+```swift
+class Solution {
+    func minDistance(_ word1: String, _ word2: String) -> Int {
+        let m = word1.count, n = word2.count
+        let word1Array = Array(word1), word2Array = Array(word2)
+        var dp = [[Int?]](repeating: [Int?](repeating: nil, count: n + 1), count: m + 1)
+
+        func dfs(_ i: Int, _ j: Int) -> Int {
+            if i == m { return n - j }
+            if j == n { return m - i }
+            if let val = dp[i][j] { return val }
+
+            if word1Array[i] == word2Array[j] {
+                dp[i][j] = dfs(i + 1, j + 1)
+            } else {
+                let res = min(dfs(i + 1, j), dfs(i, j + 1), dfs(i + 1, j + 1)) + 1
+                dp[i][j] = res
+            }
+            return dp[i][j]!
+        }
+
+        return dfs(0, 0)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -433,6 +605,100 @@ public class Solution {
 }
 ```
 
+```go
+func minDistance(word1, word2 string) int {
+    m, n := len(word1), len(word2)
+    dp := make([][]int, m+1)
+    for i := range dp {
+        dp[i] = make([]int, n+1)
+    }
+
+    for j := 0; j <= n; j++ {
+        dp[m][j] = n - j
+    }
+    for i := 0; i <= m; i++ {
+        dp[i][n] = m - i
+    }
+
+    for i := m - 1; i >= 0; i-- {
+        for j := n - 1; j >= 0; j-- {
+            if word1[i] == word2[j] {
+                dp[i][j] = dp[i+1][j+1]
+            } else {
+                dp[i][j] = 1 + min(dp[i+1][j], 
+                                   min(dp[i][j+1], dp[i+1][j+1]))
+            }
+        }
+    }
+
+    return dp[0][0]
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun minDistance(word1: String, word2: String): Int {
+        val m = word1.length
+        val n = word2.length
+        val dp = Array(m + 1) { IntArray(n + 1) }
+
+        for (j in 0..n) {
+            dp[m][j] = n - j
+        }
+        for (i in 0..m) {
+            dp[i][n] = m - i
+        }
+
+        for (i in m - 1 downTo 0) {
+            for (j in n - 1 downTo 0) {
+                if (word1[i] == word2[j]) {
+                    dp[i][j] = dp[i + 1][j + 1]
+                } else {
+                    dp[i][j] = 1 + minOf(dp[i + 1][j], 
+                                         minOf(dp[i][j + 1], dp[i + 1][j + 1]))
+                }
+            }
+        }
+        return dp[0][0]
+    }
+}
+```
+
+```swift
+class Solution {
+    func minDistance(_ word1: String, _ word2: String) -> Int {
+        let m = word1.count, n = word2.count
+        let word1Array = Array(word1), word2Array = Array(word2)
+        var dp = [[Int]](repeating: [Int](repeating: Int.max, count: n + 1), count: m + 1)
+
+        for j in 0...n {
+            dp[m][j] = n - j
+        }
+        for i in 0...m {
+            dp[i][n] = m - i
+        }
+
+        for i in stride(from: m - 1, through: 0, by: -1) {
+            for j in stride(from: n - 1, through: 0, by: -1) {
+                if word1Array[i] == word2Array[j] {
+                    dp[i][j] = dp[i + 1][j + 1]
+                } else {
+                    dp[i][j] = 1 + min(dp[i + 1][j], dp[i][j + 1], dp[i + 1][j + 1])
+                }
+            }
+        }
+        return dp[0][0]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -621,6 +887,119 @@ public class Solution {
 }
 ```
 
+```go
+func minDistance(word1, word2 string) int {
+    m, n := len(word1), len(word2)
+    if m < n {
+        word1, word2 = word2, word1
+        m, n = n, m
+    }
+
+    dp := make([]int, n+1)
+    nextDp := make([]int, n+1)
+
+    for j := 0; j <= n; j++ {
+        dp[j] = n - j
+    }
+
+    for i := m - 1; i >= 0; i-- {
+        nextDp[n] = m - i
+        for j := n - 1; j >= 0; j-- {
+            if word1[i] == word2[j] {
+                nextDp[j] = dp[j+1]
+            } else {
+                nextDp[j] = 1 + min(dp[j], 
+                                    min(nextDp[j+1], dp[j+1]))
+            }
+        }
+        dp, nextDp = nextDp, dp
+    }
+    
+    return dp[0]
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun minDistance(word1: String, word2: String): Int {
+        var m = word1.length
+        var n = word2.length
+        var word1Mod = word1
+        var word2Mod = word2
+
+        if (m < n) {
+            word1Mod = word2
+            word2Mod = word1
+            m = word1Mod.length
+            n = word2Mod.length
+        }
+
+        val dp = IntArray(n + 1)
+        val nextDp = IntArray(n + 1)
+
+        for (j in 0..n) {
+            dp[j] = n - j
+        }
+
+        for (i in m - 1 downTo 0) {
+            nextDp[n] = m - i
+            for (j in n - 1 downTo 0) {
+                if (word1Mod[i] == word2Mod[j]) {
+                    nextDp[j] = dp[j + 1]
+                } else {
+                    nextDp[j] = 1 + minOf(dp[j], nextDp[j + 1], dp[j + 1])
+                }
+            }
+            dp.indices.forEach { dp[it] = nextDp[it] }
+        }
+
+        return dp[0]
+    }
+}
+```
+
+```swift
+class Solution {
+    func minDistance(_ word1: String, _ word2: String) -> Int {
+        var m = word1.count, n = word2.count
+        var word1Array = Array(word1), word2Array = Array(word2)
+        
+        if m < n {
+            swap(&m, &n)
+            swap(&word1Array, &word2Array)
+        }
+
+        var dp = [Int](repeating: 0, count: n + 1)
+        var nextDp = [Int](repeating: 0, count: n + 1)
+
+        for j in 0...n {
+            dp[j] = n - j
+        }
+
+        for i in stride(from: m - 1, through: 0, by: -1) {
+            nextDp[n] = m - i
+            for j in stride(from: n - 1, through: 0, by: -1) {
+                if word1Array[i] == word2Array[j] {
+                    nextDp[j] = dp[j + 1]
+                } else {
+                    nextDp[j] = 1 + min(dp[j], nextDp[j + 1], dp[j + 1])
+                }
+            }
+            dp = nextDp
+        }
+
+        return dp[0]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -790,6 +1169,112 @@ public class Solution {
 }
 ```
 
+```go
+func minDistance(word1, word2 string) int {
+    m, n := len(word1), len(word2)
+    if m < n {
+        word1, word2 = word2, word1
+        m, n = n, m
+    }
+
+    dp := make([]int, n+1)
+    for j := 0; j <= n; j++ {
+        dp[j] = n - j
+    }
+
+    for i := m - 1; i >= 0; i-- {
+        nextDp := dp[n]
+        dp[n] = m - i
+        for j := n - 1; j >= 0; j-- {
+            temp := dp[j]
+            if word1[i] == word2[j] {
+                dp[j] = nextDp
+            } else {
+                dp[j] = 1 + min(dp[j], 
+                                min(dp[j+1], nextDp))
+            }
+            nextDp = temp
+        }
+    }
+
+    return dp[0]
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun minDistance(word1: String, word2: String): Int {
+        var m = word1.length
+        var n = word2.length
+        var word1Mod = word1
+        var word2Mod = word2
+
+        if (m < n) {
+            word1Mod = word2
+            word2Mod = word1
+            m = word1Mod.length
+            n = word2Mod.length
+        }
+
+        val dp = IntArray(n + 1) { n - it }
+
+        for (i in m - 1 downTo 0) {
+            var nextDp = dp[n]
+            dp[n] = m - i
+            for (j in n - 1 downTo 0) {
+                val temp = dp[j]
+                if (word1Mod[i] == word2Mod[j]) {
+                    dp[j] = nextDp
+                } else {
+                    dp[j] = 1 + minOf(dp[j], dp[j + 1], nextDp)
+                }
+                nextDp = temp
+            }
+        }
+
+        return dp[0]
+    }
+}
+```
+
+```swift
+class Solution {
+    func minDistance(_ word1: String, _ word2: String) -> Int {
+        var m = word1.count, n = word2.count
+        var word1Array = Array(word1), word2Array = Array(word2)
+        
+        if m < n {
+            swap(&m, &n)
+            swap(&word1Array, &word2Array)
+        }
+
+        var dp = (0...n).map { n - $0 }
+
+        for i in stride(from: m - 1, through: 0, by: -1) {
+            var nextDp = dp[n]
+            dp[n] = m - i
+            for j in stride(from: n - 1, through: 0, by: -1) {
+                let temp = dp[j]
+                if word1Array[i] == word2Array[j] {
+                    dp[j] = nextDp
+                } else {
+                    dp[j] = 1 + min(dp[j], dp[j + 1], nextDp)
+                }
+                nextDp = temp
+            }
+        }
+        return dp[0]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/eliminate-maximum-number-of-monsters.md b/articles/eliminate-maximum-number-of-monsters.md
new file mode 100644
index 000000000..551c82473
--- /dev/null
+++ b/articles/eliminate-maximum-number-of-monsters.md
@@ -0,0 +1,298 @@
+## 1. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def eliminateMaximum(self, dist: List[int], speed: List[int]) -> int:
+        minReach = [math.ceil(d / s) for d, s in zip(dist, speed)]
+        minReach.sort()
+
+        res = 0
+        for minute in range(len(minReach)):
+            if minute >= minReach[minute]:
+                return res
+            res += 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int eliminateMaximum(int[] dist, int[] speed) {
+        int n = dist.length;
+        int[] minReach = new int[n];
+
+        for (int i = 0; i < n; i++) {
+            minReach[i] = (int) Math.ceil((double) dist[i] / speed[i]);
+        }
+
+        Arrays.sort(minReach);
+
+        int res = 0;
+        for (int minute = 0; minute < n; minute++) {
+            if (minute >= minReach[minute]) {
+                return res;
+            }
+            res++;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int eliminateMaximum(vector<int>& dist, vector<int>& speed) {
+        int n = dist.size();
+        vector<int> minReach(n);
+
+        for (int i = 0; i < n; i++) {
+            minReach[i] = ceil((double)dist[i] / speed[i]);
+        }
+
+        sort(minReach.begin(), minReach.end());
+
+        int res = 0;
+        for (int minute = 0; minute < n; minute++) {
+            if (minute >= minReach[minute]) {
+                return res;
+            }
+            res++;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} dist
+     * @param {number[]} speed
+     * @return {number}
+     */
+    eliminateMaximum(dist, speed) {
+        let n = dist.length;
+        let minReach = new Array(n);
+
+        for (let i = 0; i < n; i++) {
+            minReach[i] = Math.ceil(dist[i] / speed[i]);
+        }
+
+        minReach.sort((a, b) => a - b);
+
+        let res = 0;
+        for (let minute = 0; minute < n; minute++) {
+            if (minute >= minReach[minute]) {
+                return res;
+            }
+            res++;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Sorting (Overwrting Input Array)
+
+::tabs-start
+
+```python
+class Solution:
+    def eliminateMaximum(self, dist: List[int], speed: List[int]) -> int:
+        for i in range(len(dist)):
+            dist[i] = math.ceil(dist[i] / speed[i])
+
+        dist.sort()
+        for minute in range(len(dist)):
+            if minute >= dist[minute]:
+                return minute
+
+        return len(dist)
+```
+
+```java
+public class Solution {
+    public int eliminateMaximum(int[] dist, int[] speed) {
+        int n = dist.length;
+        for (int i = 0; i < n; i++) {
+            dist[i] = (int) Math.ceil((double) dist[i] / speed[i]);
+        }
+
+        Arrays.sort(dist);
+        for (int minute = 0; minute < n; minute++) {
+            if (minute >= dist[minute]) {
+                return minute;
+            }
+        }
+
+        return n;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int eliminateMaximum(vector<int>& dist, vector<int>& speed) {
+        int n = dist.size();
+        for (int i = 0; i < n; i++) {
+            dist[i] = ceil((double)dist[i] / speed[i]);
+        }
+
+        sort(dist.begin(), dist.end());
+        for (int minute = 0; minute < n; minute++) {
+            if (minute >= dist[minute]) {
+                return minute;
+            }
+        }
+
+        return n;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} dist
+     * @param {number[]} speed
+     * @return {number}
+     */
+    eliminateMaximum(dist, speed) {
+        let n = dist.length;
+        for (let i = 0; i < n; i++) {
+            dist[i] = Math.ceil(dist[i] / speed[i]);
+        }
+
+        dist.sort((a, b) => a - b);
+        for (let minute = 0; minute < n; minute++) {
+            if (minute >= dist[minute]) {
+                return minute;
+            }
+        }
+
+        return n;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 3. Min-Heap
+
+::tabs-start
+
+```python
+class Solution:
+    def eliminateMaximum(self, dist: List[int], speed: List[int]) -> int:
+        minHeap = []
+        for i in range(len(dist)):
+            heapq.heappush(minHeap, dist[i] / speed[i])
+
+        res = 0
+        while minHeap:
+            if res >= heapq.heappop(minHeap):
+                return res
+            res += 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int eliminateMaximum(int[] dist, int[] speed) {
+        PriorityQueue<Double> minHeap = new PriorityQueue<>();
+        for (int i = 0; i < dist.length; i++) {
+            minHeap.add((double) dist[i] / speed[i]);
+        }
+
+        int res = 0;
+        while (!minHeap.isEmpty()) {
+            if (res >= minHeap.poll()) {
+                return res;
+            }
+            res++;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int eliminateMaximum(vector<int>& dist, vector<int>& speed) {
+        priority_queue<double, vector<double>, greater<double>> minHeap;
+        for (int i = 0; i < dist.size(); i++) {
+            minHeap.push((double)dist[i] / speed[i]);
+        }
+
+        int res = 0;
+        while (!minHeap.empty()) {
+            if (res >= minHeap.top()) {
+                return res;
+            }
+            minHeap.pop();
+            res++;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} dist
+     * @param {number[]} speed
+     * @return {number}
+     */
+    eliminateMaximum(dist, speed) {
+        const minHeap = new MinPriorityQueue();
+        for (let i = 0; i < dist.length; i++) {
+            minHeap.enqueue(dist[i] / speed[i]);
+        }
+
+        let res = 0;
+        while (!minHeap.isEmpty()) {
+            if (res >= minHeap.dequeue().element) {
+                return res;
+            }
+            res++;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/encode-and-decode-tinyurl.md b/articles/encode-and-decode-tinyurl.md
new file mode 100644
index 000000000..0da60014f
--- /dev/null
+++ b/articles/encode-and-decode-tinyurl.md
@@ -0,0 +1,312 @@
+## 1. List
+
+::tabs-start
+
+```python
+class Codec:
+
+    def __init__(self):
+        self.urls = []
+
+    def encode(self, longUrl: str) -> str:
+        self.urls.append(longUrl)
+        return 'http://tinyurl.com/' + str(len(self.urls) - 1)
+
+    def decode(self, shortUrl: str) -> str:
+        return self.urls[int(shortUrl.split('/')[-1])]
+```
+
+```java
+public class Codec {
+    private List<String> urls;
+
+    public Codec() {
+        urls = new ArrayList<>();
+    }
+
+    public String encode(String longUrl) {
+        urls.add(longUrl);
+        return "http://tinyurl.com/" + (urls.size() - 1);
+    }
+
+    public String decode(String shortUrl) {
+        int index = Integer.parseInt(shortUrl.substring(shortUrl.lastIndexOf('/') + 1));
+        return urls.get(index);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<string> urls;
+
+    string encode(string longUrl) {
+        urls.push_back(longUrl);
+        return "http://tinyurl.com/" + to_string(urls.size() - 1);
+    }
+
+    string decode(string shortUrl) {
+        int index = stoi(shortUrl.substr(shortUrl.find_last_of('/') + 1));
+        return urls[index];
+    }
+};
+```
+
+```javascript
+class Codec {
+    constructor() {
+        this.urls = [];
+    }
+
+    /**
+     * Encodes a URL to a shortened URL.
+     *
+     * @param {string} longUrl
+     * @return {string}
+     */
+    encode(longUrl) {
+        this.urls.push(longUrl);
+        return 'http://tinyurl.com/' + (this.urls.length - 1);
+    }
+
+    /**
+     * Decodes a shortened URL to its original URL.
+     *
+     * @param {string} shortUrl
+     * @return {string}
+     */
+    decode(shortUrl) {
+        const index = parseInt(shortUrl.split('/').pop());
+        return this.urls[index];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$ for $encode()$ and $decode()$.
+* Space complexity: $O(n * m)$
+
+> Where $n$ is the number of $longUrls$, $m$ is the average length of the URLs.
+
+---
+
+## 2. Hash Map - I
+
+::tabs-start
+
+```python
+class Codec:
+
+    def __init__(self):
+        self.url_map = {}
+        self.id = 0
+
+    def encode(self, longUrl: str) -> str:
+        self.url_map[self.id] = longUrl
+        short_url = f"http://tinyurl.com/{self.id}"
+        self.id += 1
+        return short_url
+
+    def decode(self, shortUrl: str) -> str:
+        url_id = int(shortUrl.split('/')[-1])
+        return self.url_map[url_id]
+```
+
+```java
+public class Codec {
+    private HashMap<Integer, String> urlMap;
+    private int id;
+
+    public Codec() {
+        urlMap = new HashMap<>();
+        id = 0;
+    }
+
+    public String encode(String longUrl) {
+        urlMap.put(id, longUrl);
+        return "http://tinyurl.com/" + id++;
+    }
+
+    public String decode(String shortUrl) {
+        int urlId = Integer.parseInt(shortUrl.substring(shortUrl.lastIndexOf('/') + 1));
+        return urlMap.get(urlId);
+    }
+}
+```
+
+```cpp
+class Solution {
+    unordered_map<int, string> urlMap;
+    int id;
+
+public:
+    Solution() : id(0) {}
+
+    string encode(string longUrl) {
+        urlMap[id] = longUrl;
+        return "http://tinyurl.com/" + to_string(id++);
+    }
+
+    string decode(string shortUrl) {
+        int urlId = stoi(shortUrl.substr(shortUrl.find_last_of('/') + 1));
+        return urlMap[urlId];
+    }
+};
+```
+
+```javascript
+class Codec {
+    constructor() {
+        this.urlMap = {};
+        this.id = 0;
+    }
+
+    /**
+     * Encodes a URL to a shortened URL.
+     *
+     * @param {string} longUrl
+     * @return {string}
+     */
+    encode(longUrl) {
+        this.urlMap[this.id] = longUrl;
+        return `http://tinyurl.com/${this.id++}`;
+    }
+
+    /**
+     * Decodes a shortened URL to its original URL.
+     *
+     * @param {string} shortUrl
+     * @return {string}
+     */
+    decode(shortUrl) {
+        const urlId = parseInt(shortUrl.split('/').pop(), 10);
+        return this.urlMap[urlId];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$ for $encode()$ and $decode()$.
+* Space complexity: $O(n * m)$
+
+> Where $n$ is the number of $longUrls$, $m$ is the average length of the URLs.
+
+---
+
+## 3. Hash Map - II
+
+::tabs-start
+
+```python
+class Codec:
+    
+    def __init__(self):
+        self.encodeMap = {}
+        self.decodeMap = {}
+        self.base = "http://tinyurl.com/"
+
+    def encode(self, longUrl: str) -> str:
+        if longUrl not in self.encodeMap:
+            shortUrl = self.base + str(len(self.encodeMap) + 1)
+            self.encodeMap[longUrl] = shortUrl
+            self.decodeMap[shortUrl] = longUrl
+        return self.encodeMap[longUrl]
+
+    def decode(self, shortUrl: str) -> str:
+        return self.decodeMap[shortUrl]
+```
+
+```java
+public class Codec {
+    private HashMap<String, String> encodeMap = new HashMap<>();
+    private HashMap<String, String> decodeMap = new HashMap<>();
+    private String base = "http://tinyurl.com/";
+
+    public String encode(String longUrl) {
+        if (!encodeMap.containsKey(longUrl)) {
+            String shortUrl = base + (encodeMap.size() + 1);
+            encodeMap.put(longUrl, shortUrl);
+            decodeMap.put(shortUrl, longUrl);
+        }
+        return encodeMap.get(longUrl);
+    }
+
+    public String decode(String shortUrl) {
+        return decodeMap.get(shortUrl);
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    unordered_map<string, string> encodeMap;
+    unordered_map<string, string> decodeMap;
+    string base = "http://tinyurl.com/";
+
+public:
+    string encode(string longUrl) {
+        if (encodeMap.find(longUrl) == encodeMap.end()) {
+            string shortUrl = base + to_string(encodeMap.size() + 1);
+            encodeMap[longUrl] = shortUrl;
+            decodeMap[shortUrl] = longUrl;
+        }
+        return encodeMap[longUrl];
+    }
+
+    string decode(string shortUrl) {
+        return decodeMap[shortUrl];
+    }
+};
+```
+
+```javascript
+class Codec {
+    constructor() {
+        this.encodeMap = new Map();
+        this.decodeMap = new Map();
+        this.base = "http://tinyurl.com/";
+    }
+
+    /**
+     * Encodes a URL to a shortened URL.
+     *
+     * @param {string} longUrl
+     * @return {string}
+     */
+    encode(longUrl) {
+        if (!this.encodeMap.has(longUrl)) {
+            const shortUrl = this.base + (this.encodeMap.size + 1);
+            this.encodeMap.set(longUrl, shortUrl);
+            this.decodeMap.set(shortUrl, longUrl);
+        }
+        return this.encodeMap.get(longUrl);
+    }
+
+    /**
+     * Decodes a shortened URL to its original URL.
+     *
+     * @param {string} shortUrl
+     * @return {string}
+     */
+    decode(shortUrl) {
+        return this.decodeMap.get(shortUrl);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$ for $encode()$ and $decode()$.
+* Space complexity: $O(n * m)$
+
+> Where $n$ is the number of $longUrls$, $m$ is the average length of the URLs.
\ No newline at end of file
diff --git a/articles/evaluate-boolean-binary-tree.md b/articles/evaluate-boolean-binary-tree.md
new file mode 100644
index 000000000..4b8fd67ca
--- /dev/null
+++ b/articles/evaluate-boolean-binary-tree.md
@@ -0,0 +1,309 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def evaluateTree(self, root: Optional[TreeNode]) -> bool:
+        if not root.left:
+            return root.val == 1
+
+        if root.val == 2:
+            return self.evaluateTree(root.left) or self.evaluateTree(root.right)
+
+        if root.val == 3:
+            return self.evaluateTree(root.left) and self.evaluateTree(root.right)
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public boolean evaluateTree(TreeNode root) {
+        if (root.left == null) {
+            return root.val == 1;
+        }
+
+        if (root.val == 2) {
+            return evaluateTree(root.left) || evaluateTree(root.right);
+        }
+
+        if (root.val == 3) {
+            return evaluateTree(root.left) && evaluateTree(root.right);
+        }
+
+        return false;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    bool evaluateTree(TreeNode* root) {
+        if (!root->left) {
+            return root->val == 1;
+        }
+
+        if (root->val == 2) {
+            return evaluateTree(root->left) || evaluateTree(root->right);
+        }
+
+        if (root->val == 3) {
+            return evaluateTree(root->left) && evaluateTree(root->right);
+        }
+
+        return false;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {boolean}
+     */
+    evaluateTree(root) {
+        if (!root.left) {
+            return root.val === 1;
+        }
+
+        if (root.val === 2) {
+            return this.evaluateTree(root.left) || this.evaluateTree(root.right);
+        }
+
+        if (root.val === 3) {
+            return this.evaluateTree(root.left) && this.evaluateTree(root.right);
+        }
+
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Iterative DFS
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def evaluateTree(self, root: Optional[TreeNode]) -> bool:
+        stack = [root]
+        value = {} # map (node -> value)
+
+        while stack:
+            node = stack.pop()
+
+            if not node.left:
+                value[node] = node.val == 1
+            elif node.left in value:
+                if node.val == 2:
+                    value[node] = value[node.left] or value[node.right]
+                if node.val == 3:
+                    value[node] = value[node.left] and value[node.right]
+            else:
+                stack.extend([node, node.left, node.right])
+
+        return value[root]
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public boolean evaluateTree(TreeNode root) {
+        Stack<TreeNode> stack = new Stack<>();
+        Map<TreeNode, Boolean> value = new HashMap<>();
+        stack.push(root);
+
+        while (!stack.isEmpty()) {
+            TreeNode node = stack.pop();
+
+            if (node.left == null) {
+                value.put(node, node.val == 1);
+            } else if (value.containsKey(node.left)) {
+                boolean leftValue = value.get(node.left);
+                boolean rightValue = value.get(node.right);
+
+                if (node.val == 2) {
+                    value.put(node, leftValue || rightValue);
+                } else if (node.val == 3) {
+                    value.put(node, leftValue && rightValue);
+                }
+            } else {
+                stack.push(node);
+                stack.push(node.right);
+                stack.push(node.left);
+            }
+        }
+
+        return value.get(root);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    bool evaluateTree(TreeNode* root) {
+        stack<TreeNode*> stk;
+        unordered_map<TreeNode*, bool> value;
+        stk.push(root);
+
+        while (!stk.empty()) {
+            TreeNode* node = stk.top();
+            stk.pop();
+
+            if (!node->left) {
+                value[node] = node->val == 1;
+            } else if (value.count(node->left)) {
+                bool leftValue = value[node->left];
+                bool rightValue = value[node->right];
+
+                if (node->val == 2) {
+                    value[node] = leftValue || rightValue;
+                } else if (node->val == 3) {
+                    value[node] = leftValue && rightValue;
+                }
+            } else {
+                stk.push(node);
+                stk.push(node->right);
+                stk.push(node->left);
+            }
+        }
+
+        return value[root];
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {boolean}
+     */
+    evaluateTree(root) {
+        const stack = [root];
+        const value = new Map();
+
+        while (stack.length) {
+            const node = stack.pop();
+
+            if (!node.left) {
+                value.set(node, node.val === 1);
+            } else if (value.has(node.left)) {
+                const leftValue = value.get(node.left);
+                const rightValue = value.get(node.right);
+
+                if (node.val === 2) {
+                    value.set(node, leftValue || rightValue);
+                } else if (node.val === 3) {
+                    value.set(node, leftValue && rightValue);
+                }
+            } else {
+                stack.push(node, node.right, node.left);
+            }
+        }
+
+        return value.get(root);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/evaluate-division.md b/articles/evaluate-division.md
new file mode 100644
index 000000000..9be40ad06
--- /dev/null
+++ b/articles/evaluate-division.md
@@ -0,0 +1,1037 @@
+## 1. Breadth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def calcEquation(self, equations: List[List[str]], values: List[float], queries: List[List[str]]) -> List[float]:
+        adj = collections.defaultdict(list)  # Map a -> list of [b, a/b]
+
+        for i, eq in enumerate(equations):
+            a, b = eq
+            adj[a].append((b, values[i]))
+            adj[b].append((a, 1 / values[i]))
+
+        def bfs(src, target):
+            if src not in adj or target not in adj:
+                return -1
+            q, visit = deque([(src, 1)]), set()
+            visit.add(src)
+
+            while q:
+                node, w = q.popleft()
+                if node == target:
+                    return w
+                for nei, weight in adj[node]:
+                    if nei not in visit:
+                        q.append((nei, w * weight))
+                        visit.add(nei)
+            return -1
+
+        return [bfs(q[0], q[1]) for q in queries]
+```
+
+```java
+public class Solution {
+    public double[] calcEquation(List<List<String>> equations, double[] values, List<List<String>> queries) {
+        Map<String, List<Pair>> adj = new HashMap<>(); // Map a -> list of [b, a/b]
+
+        for (int i = 0; i < equations.size(); i++) {
+            String a = equations.get(i).get(0);
+            String b = equations.get(i).get(1);
+            adj.putIfAbsent(a, new ArrayList<>());
+            adj.putIfAbsent(b, new ArrayList<>());
+            adj.get(a).add(new Pair(b, values[i]));
+            adj.get(b).add(new Pair(a, 1 / values[i]));
+        }
+
+        double[] res = new double[queries.size()];
+        for (int i = 0; i < queries.size(); i++) {
+            String src = queries.get(i).get(0);
+            String target = queries.get(i).get(1);
+            res[i] = bfs(src, target, adj);
+        }
+
+        return res;
+    }
+
+    private double bfs(String src, String target, Map<String, List<Pair>> adj) {
+        if (!adj.containsKey(src) || !adj.containsKey(target)) {
+            return -1.0;
+        }
+
+        Queue<Pair> q = new LinkedList<>();
+        Set<String> visited = new HashSet<>();
+        q.offer(new Pair(src, 1.0));
+        visited.add(src);
+
+        while (!q.isEmpty()) {
+            Pair current = q.poll();
+            String node = current.node;
+            double weight = current.weight;
+
+            if (node.equals(target)) {
+                return weight;
+            }
+
+            for (Pair neighbor : adj.get(node)) {
+                if (!visited.contains(neighbor.node)) {
+                    visited.add(neighbor.node);
+                    q.offer(new Pair(neighbor.node, weight * neighbor.weight));
+                }
+            }
+        }
+
+        return -1.0;
+    }
+
+    class Pair {
+        String node;
+        double weight;
+
+        Pair(String node, double weight) {
+            this.node = node;
+            this.weight = weight;
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<double> calcEquation(vector<vector<string>>& equations, vector<double>& values, vector<vector<string>>& queries) {
+        unordered_map<string, vector<pair<string, double>>> adj; // Map a -> list of [b, a/b]
+
+        for (int i = 0; i < equations.size(); i++) {
+            string a = equations[i][0];
+            string b = equations[i][1];
+            adj[a].emplace_back(b, values[i]);
+            adj[b].emplace_back(a, 1.0 / values[i]);
+        }
+
+        vector<double> res;
+        for (const auto& query : queries) {
+            string src = query[0];
+            string target = query[1];
+            res.push_back(bfs(src, target, adj));
+        }
+
+        return res;
+    }
+
+private:
+    double bfs(const string& src, const string& target, unordered_map<string, vector<pair<string, double>>>& adj) {
+        if (!adj.count(src) || !adj.count(target)) {
+            return -1.0;
+        }
+
+        queue<pair<string, double>> q;
+        unordered_set<string> visited;
+        q.emplace(src, 1.0);
+        visited.insert(src);
+
+        while (!q.empty()) {
+            auto [node, weight] = q.front();
+            q.pop();
+
+            if (node == target) {
+                return weight;
+            }
+
+            for (const auto& [nei, neiWeight] : adj[node]) {
+                if (!visited.count(nei)) {
+                    visited.insert(nei);
+                    q.emplace(nei, weight * neiWeight);
+                }
+            }
+        }
+
+        return -1.0;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[][]} equations
+     * @param {number[]} values
+     * @param {string[][]} queries
+     * @return {number[]}
+     */
+    calcEquation(equations, values, queries) {
+        const adj = new Map(); // Map a -> list of [b, a/b]
+
+        for (let i = 0; i < equations.length; i++) {
+            const [a, b] = equations[i];
+            if (!adj.has(a)) adj.set(a, []);
+            if (!adj.has(b)) adj.set(b, []);
+            adj.get(a).push([b, values[i]]);
+            adj.get(b).push([a, 1 / values[i]]);
+        }
+
+        const bfs = (src, target) => {
+            if (!adj.has(src) || !adj.has(target)) return -1;
+
+            const queue = new Queue([[src, 1.0]]);
+            const visited = new Set();
+            visited.add(src);
+
+            while (!queue.isEmpty()) {
+                const [node, weight] = queue.pop();
+
+                if (node === target) return weight;
+
+                for (const [nei, neiWeight] of adj.get(node)) {
+                    if (!visited.has(nei)) {
+                        visited.add(nei);
+                        queue.push([nei, weight * neiWeight]);
+                    }
+                }
+            }
+
+            return -1;
+        };
+
+        return queries.map(([src, target]) => bfs(src, target));
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public double[] CalcEquation(List<List<string>> equations, double[] values, List<List<string>> queries) {
+        var adj = new Dictionary<string, List<(string, double)>>();
+
+        for (int i = 0; i < equations.Count; i++) {
+            string a = equations[i][0];
+            string b = equations[i][1];
+            double val = values[i];
+
+            if (!adj.ContainsKey(a)) adj[a] = new List<(string, double)>();
+            if (!adj.ContainsKey(b)) adj[b] = new List<(string, double)>();
+
+            adj[a].Add((b, val));
+            adj[b].Add((a, 1.0 / val));
+        }
+
+        double Bfs(string src, string target) {
+            if (!adj.ContainsKey(src) || !adj.ContainsKey(target)) return -1.0;
+            var queue = new Queue<(string, double)>();
+            var visited = new HashSet<string>();
+
+            queue.Enqueue((src, 1.0));
+            visited.Add(src);
+
+            while (queue.Count > 0) {
+                var (node, weight) = queue.Dequeue();
+                if (node == target) return weight;
+
+                foreach (var (nei, w) in adj[node]) {
+                    if (!visited.Contains(nei)) {
+                        visited.Add(nei);
+                        queue.Enqueue((nei, weight * w));
+                    }
+                }
+            }
+
+            return -1.0;
+        }
+
+        double[] res = new double[queries.Count];
+        for (int i = 0; i < queries.Count; i++) {
+            res[i] = Bfs(queries[i][0], queries[i][1]);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(n + m)$
+
+> Where $n$ is the number of unique strings and $m$ is the number of queries.
+
+---
+
+## 2. Depth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def calcEquation(self, equations: List[List[str]], values: List[float], queries: List[List[str]]) -> List[float]:
+        adj = collections.defaultdict(list)  # Map a -> list of [b, a/b]
+
+        for i, eq in enumerate(equations):
+            a, b = eq
+            adj[a].append((b, values[i]))
+            adj[b].append((a, 1 / values[i]))
+
+        def dfs(src, target, visited):
+            if src not in adj or target not in adj:
+                return -1
+            if src == target:
+                return 1
+
+            visited.add(src)
+
+            for nei, weight in adj[src]:
+                if nei not in visited:
+                    result = dfs(nei, target, visited)
+                    if result != -1:
+                        return weight * result
+
+            return -1
+
+        return [dfs(q[0], q[1], set()) for q in queries]
+```
+
+```java
+public class Solution {
+    public double[] calcEquation(List<List<String>> equations, double[] values, List<List<String>> queries) {
+        Map<String, List<Pair>> adj = new HashMap<>(); // Map a -> list of [b, a/b]
+
+        for (int i = 0; i < equations.size(); i++) {
+            String a = equations.get(i).get(0);
+            String b = equations.get(i).get(1);
+            adj.putIfAbsent(a, new ArrayList<>());
+            adj.putIfAbsent(b, new ArrayList<>());
+            adj.get(a).add(new Pair(b, values[i]));
+            adj.get(b).add(new Pair(a, 1 / values[i]));
+        }
+
+        double[] res = new double[queries.size()];
+        for (int i = 0; i < queries.size(); i++) {
+            String src = queries.get(i).get(0);
+            String target = queries.get(i).get(1);
+            res[i] = dfs(src, target, adj, new HashSet<>());
+        }
+
+        return res;
+    }
+
+    private double dfs(String src, String target, Map<String, List<Pair>> adj, Set<String> visited) {
+        if (!adj.containsKey(src) || !adj.containsKey(target)) {
+            return -1.0;
+        }
+        if (src.equals(target)) {
+            return 1.0;
+        }
+
+        visited.add(src);
+
+        for (Pair neighbor : adj.get(src)) {
+            if (!visited.contains(neighbor.node)) {
+                double result = dfs(neighbor.node, target, adj, visited);
+                if (result != -1.0) {
+                    return neighbor.weight * result;
+                }
+            }
+        }
+
+        return -1.0;
+    }
+
+    class Pair {
+        String node;
+        double weight;
+
+        Pair(String node, double weight) {
+            this.node = node;
+            this.weight = weight;
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<double> calcEquation(vector<vector<string>>& equations, vector<double>& values, vector<vector<string>>& queries) {
+        unordered_map<string, vector<pair<string, double>>> adj; // Map a -> list of [b, a/b]
+
+        for (int i = 0; i < equations.size(); i++) {
+            string a = equations[i][0];
+            string b = equations[i][1];
+            adj[a].emplace_back(b, values[i]);
+            adj[b].emplace_back(a, 1.0 / values[i]);
+        }
+
+        vector<double> res;
+        for (const auto& query : queries) {
+            string src = query[0];
+            string target = query[1];
+            res.push_back(dfs(src, target, adj, unordered_set<string>()));
+        }
+
+        return res;
+    }
+
+private:
+    double dfs(const string& src, const string& target, unordered_map<string, vector<pair<string, double>>>& adj, unordered_set<string> visited) {
+        if (!adj.count(src) || !adj.count(target)) {
+            return -1.0;
+        }
+        if (src == target) {
+            return 1.0;
+        }
+
+        visited.insert(src);
+
+        for (const auto& [nei, weight] : adj[src]) {
+            if (!visited.count(nei)) {
+                double result = dfs(nei, target, adj, visited);
+                if (result != -1.0) {
+                    return weight * result;
+                }
+            }
+        }
+
+        return -1.0;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[][]} equations
+     * @param {number[]} values
+     * @param {string[][]} queries
+     * @return {number[]}
+     */
+    calcEquation(equations, values, queries) {
+        const adj = new Map(); // Map a -> list of [b, a/b]
+
+        for (let i = 0; i < equations.length; i++) {
+            const [a, b] = equations[i];
+            if (!adj.has(a)) adj.set(a, []);
+            if (!adj.has(b)) adj.set(b, []);
+            adj.get(a).push([b, values[i]]);
+            adj.get(b).push([a, 1 / values[i]]);
+        }
+
+        const dfs = (src, target, visited) => {
+            if (!adj.has(src) || !adj.has(target)) return -1;
+            if (src === target) return 1;
+
+            visited.add(src);
+
+            for (const [nei, weight] of adj.get(src)) {
+                if (!visited.has(nei)) {
+                    const result = dfs(nei, target, visited);
+                    if (result !== -1) {
+                        return weight * result;
+                    }
+                }
+            }
+
+            return -1;
+        };
+
+        return queries.map(([src, target]) => dfs(src, target, new Set()));
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public double[] CalcEquation(List<List<string>> equations, double[] values, List<List<string>> queries) {
+        var adj = new Dictionary<string, List<(string, double)>>();
+
+        for (int i = 0; i < equations.Count; i++) {
+            string a = equations[i][0], b = equations[i][1];
+            double val = values[i];
+
+            if (!adj.ContainsKey(a)) adj[a] = new List<(string, double)>();
+            if (!adj.ContainsKey(b)) adj[b] = new List<(string, double)>();
+
+            adj[a].Add((b, val));
+            adj[b].Add((a, 1.0 / val));
+        }
+
+        double Dfs(string src, string target, HashSet<string> visited) {
+            if (!adj.ContainsKey(src) || !adj.ContainsKey(target)) return -1.0;
+            if (src == target) return 1.0;
+
+            visited.Add(src);
+
+            foreach (var (nei, weight) in adj[src]) {
+                if (!visited.Contains(nei)) {
+                    double result = Dfs(nei, target, visited);
+                    if (result != -1.0) {
+                        return weight * result;
+                    }
+                }
+            }
+
+            return -1.0;
+        }
+
+        double[] res = new double[queries.Count];
+        for (int i = 0; i < queries.Count; i++) {
+            var visited = new HashSet<string>();
+            res[i] = Dfs(queries[i][0], queries[i][1], visited);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(n + m)$
+
+> Where $n$ is the number of unique strings and $m$ is the number of queries.
+
+---
+
+## 3. Disjoint Set Union
+
+::tabs-start
+
+```python
+class UnionFind:
+    def __init__(self):
+        self.parent = {}
+        self.weight = {}
+    
+    def add(self, x):
+        if x not in self.parent:
+            self.parent[x] = x
+            self.weight[x] = 1.0
+    
+    def find(self, x):
+        if x != self.parent[x]:
+            orig_parent = self.parent[x]
+            self.parent[x] = self.find(self.parent[x])
+            self.weight[x] *= self.weight[orig_parent]
+        return self.parent[x]
+    
+    def union(self, x, y, value):
+        self.add(x)
+        self.add(y)
+        root_x = self.find(x)
+        root_y = self.find(y)
+        
+        if root_x != root_y:
+            self.parent[root_x] = root_y
+            self.weight[root_x] = value * self.weight[y] / self.weight[x]
+    
+    def get_ratio(self, x, y):
+        if x not in self.parent or y not in self.parent or self.find(x) != self.find(y):
+            return -1.0
+        return self.weight[x] / self.weight[y]
+
+class Solution:
+    def calcEquation(self, equations: List[List[str]], values: List[float], queries: List[List[str]]) -> List[float]:
+        uf = UnionFind()
+        
+        for (a, b), value in zip(equations, values):
+            uf.union(a, b, value)
+        
+        return [uf.get_ratio(a, b) for a, b in queries]
+```
+
+```java
+class UnionFind {
+    private final Map<String, String> parent;
+    private final Map<String, Double> weight;
+
+    public UnionFind() {
+        parent = new HashMap<>();
+        weight = new HashMap<>();
+    }
+
+    public void add(String x) {
+        if (!parent.containsKey(x)) {
+            parent.put(x, x);
+            weight.put(x, 1.0);
+        }
+    }
+
+    public String find(String x) {
+        if (!x.equals(parent.get(x))) {
+            String origParent = parent.get(x);
+            parent.put(x, find(origParent));
+            weight.put(x, weight.get(x) * weight.get(origParent));
+        }
+        return parent.get(x);
+    }
+
+    public void union(String x, String y, double value) {
+        add(x);
+        add(y);
+        String rootX = find(x);
+        String rootY = find(y);
+
+        if (!rootX.equals(rootY)) {
+            parent.put(rootX, rootY);
+            weight.put(rootX, value * weight.get(y) / weight.get(x));
+        }
+    }
+
+    public double getRatio(String x, String y) {
+        if (!parent.containsKey(x) || !parent.containsKey(y) || !find(x).equals(find(y))) {
+            return -1.0;
+        }
+        return weight.get(x) / weight.get(y);
+    }
+}
+
+public class Solution {
+    public double[] calcEquation(List<List<String>> equations, double[] values, List<List<String>> queries) {
+        UnionFind uf = new UnionFind();
+
+        for (int i = 0; i < equations.size(); i++) {
+            List<String> equation = equations.get(i);
+            String a = equation.get(0);
+            String b = equation.get(1);
+            uf.union(a, b, values[i]);
+        }
+
+        double[] result = new double[queries.size()];
+        for (int i = 0; i < queries.size(); i++) {
+            List<String> query = queries.get(i);
+            String a = query.get(0);
+            String b = query.get(1);
+            result[i] = uf.getRatio(a, b);
+        }
+
+        return result;
+    }
+}
+```
+
+```cpp
+class UnionFind {
+    unordered_map<string, string> parent;
+    unordered_map<string, double> weight;
+
+public:
+    void add(const string& x) {
+        if (parent.find(x) == parent.end()) {
+            parent[x] = x;
+            weight[x] = 1.0;
+        }
+    }
+
+    string find(const string& x) {
+        if (x != parent[x]) {
+            string origParent = parent[x];
+            parent[x] = find(parent[x]);
+            weight[x] *= weight[origParent];
+        }
+        return parent[x];
+    }
+
+    void unionSets(const string& x, const string& y, double value) {
+        add(x);
+        add(y);
+        string rootX = find(x);
+        string rootY = find(y);
+
+        if (rootX != rootY) {
+            parent[rootX] = rootY;
+            weight[rootX] = value * weight[y] / weight[x];
+        }
+    }
+
+    double getRatio(const string& x, const string& y) {
+        if (parent.find(x) == parent.end() || parent.find(y) == parent.end() || find(x) != find(y)) {
+            return -1.0;
+        }
+        return weight[x] / weight[y];
+    }
+};
+
+class Solution {
+public:
+    vector<double> calcEquation(vector<vector<string>>& equations, vector<double>& values, vector<vector<string>>& queries) {
+        UnionFind uf;
+
+        for (int i = 0; i < equations.size(); i++) {
+            string a = equations[i][0];
+            string b = equations[i][1];
+            uf.unionSets(a, b, values[i]);
+        }
+
+        vector<double> result;
+        for (const auto& query : queries) {
+            string a = query[0];
+            string b = query[1];
+            result.push_back(uf.getRatio(a, b));
+        }
+
+        return result;
+    }
+};
+```
+
+```javascript
+class UnionFind {
+    constructor() {
+        this.parent = new Map();
+        this.weight = new Map();
+    }
+
+    /**
+     * @param {string} x
+     * @return {void}
+     */
+    add(x) {
+        if (!this.parent.has(x)) {
+            this.parent.set(x, x);
+            this.weight.set(x, 1.0);
+        }
+    }
+
+    /**
+     * @param {string} x
+     * @return {string}
+     */
+    find(x) {
+        if (x !== this.parent.get(x)) {
+            const origParent = this.parent.get(x);
+            this.parent.set(x, this.find(origParent));
+            this.weight.set(x, this.weight.get(x) * this.weight.get(origParent));
+        }
+        return this.parent.get(x);
+    }
+
+    /**
+     * @param {string} x
+     * @param {string} y
+     * @param {number} value
+     * @return {number}
+     */
+    union(x, y, value) {
+        this.add(x);
+        this.add(y);
+        const rootX = this.find(x);
+        const rootY = this.find(y);
+
+        if (rootX !== rootY) {
+            this.parent.set(rootX, rootY);
+            this.weight.set(rootX, (value * this.weight.get(y)) / this.weight.get(x));
+        }
+    }
+    
+    /**
+     * @param {string} x
+     * @param {string} y
+     * @return {number}
+     */
+    getRatio(x, y) {
+        if (!this.parent.has(x) || !this.parent.has(y) || this.find(x) !== this.find(y)) {
+            return -1.0;
+        }
+        return this.weight.get(x) / this.weight.get(y);
+    }
+}
+
+class Solution {
+    /**
+     * @param {string[][]} equations
+     * @param {number[]} values
+     * @param {string[][]} queries
+     * @return {number[]}
+     */
+    calcEquation(equations, values, queries) {
+        const uf = new UnionFind();
+
+        for (let i = 0; i < equations.length; i++) {
+            const [a, b] = equations[i];
+            uf.union(a, b, values[i]);
+        }
+
+        return queries.map(([a, b]) => uf.getRatio(a, b));
+    }
+}
+```
+
+```csharp
+public class UnionFind {
+    private Dictionary<string, string> parent = new Dictionary<string, string>();
+    private Dictionary<string, double> weight = new Dictionary<string, double>();
+
+    public void Add(string x) {
+        if (!parent.ContainsKey(x)) {
+            parent[x] = x;
+            weight[x] = 1.0;
+        }
+    }
+
+    public string Find(string x) {
+        if (parent[x] != x) {
+            string origParent = parent[x];
+            parent[x] = Find(origParent);
+            weight[x] *= weight[origParent];
+        }
+        return parent[x];
+    }
+
+    public void Union(string x, string y, double value) {
+        Add(x);
+        Add(y);
+        string rootX = Find(x);
+        string rootY = Find(y);
+
+        if (rootX != rootY) {
+            parent[rootX] = rootY;
+            weight[rootX] = value * weight[y] / weight[x];
+        }
+    }
+
+    public double GetRatio(string x, string y) {
+        if (!parent.ContainsKey(x) || !parent.ContainsKey(y) || Find(x) != Find(y)) {
+            return -1.0;
+        }
+        return weight[x] / weight[y];
+    }
+}
+
+public class Solution {
+    public double[] CalcEquation(List<List<string>> equations, double[] values, List<List<string>> queries) {
+        var uf = new UnionFind();
+        
+        for (int i = 0; i < equations.Count; i++) {
+            string a = equations[i][0];
+            string b = equations[i][1];
+            uf.Union(a, b, values[i]);
+        }
+
+        double[] res = new double[queries.Count];
+        for (int i = 0; i < queries.Count; i++) {
+            string a = queries[i][0];
+            string b = queries[i][1];
+            res[i] = uf.GetRatio(a, b);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O((m + n)\log n)$
+* Space complexity: $O(n + m)$
+
+> Where $n$ is the number of unique strings and $m$ is the number of queries.
+
+---
+
+## 4. Floyd Warshall
+
+::tabs-start
+
+```python
+class Solution:
+    def calcEquation(self, equations, values, queries):
+        graph = collections.defaultdict(dict)
+
+        for (a, b), value in zip(equations, values):
+            graph[a][b] = value
+            graph[b][a] = 1.0 / value
+
+        for k in graph:
+            for i in graph[k]:
+                for j in graph[k]:
+                    if j not in graph[i]:
+                        graph[i][j] = graph[i][k] * graph[k][j]
+
+        result = []
+        for a, b in queries:
+            if a in graph and b in graph[a]:
+                result.append(graph[a][b])
+            else:
+                result.append(-1.0)
+        return result
+```
+
+```java
+public class Solution {
+    public double[] calcEquation(List<List<String>> equations, double[] values, List<List<String>> queries) {
+        Map<String, Map<String, Double>> graph = new HashMap<>();
+
+        for (int i = 0; i < equations.size(); i++) {
+            String a = equations.get(i).get(0);
+            String b = equations.get(i).get(1);
+            double value = values[i];
+            graph.computeIfAbsent(a, k -> new HashMap<>()).put(b, value);
+            graph.computeIfAbsent(b, k -> new HashMap<>()).put(a, 1.0 / value);
+        }
+
+        for (String k : graph.keySet()) {
+            for (String i : graph.get(k).keySet()) {
+                for (String j : graph.get(k).keySet()) {
+                    graph.computeIfAbsent(i, x -> new HashMap<>()).putIfAbsent(j, graph.get(i).get(k) * graph.get(k).get(j));
+                }
+            }
+        }
+
+        double[] result = new double[queries.size()];
+        for (int i = 0; i < queries.size(); i++) {
+            String a = queries.get(i).get(0);
+            String b = queries.get(i).get(1);
+            if (graph.containsKey(a) && graph.get(a).containsKey(b)) {
+                result[i] = graph.get(a).get(b);
+            } else {
+                result[i] = -1.0;
+            }
+        }
+
+        return result;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<double> calcEquation(vector<vector<string>>& equations, vector<double>& values, vector<vector<string>>& queries) {
+        unordered_map<string, unordered_map<string, double>> graph;
+
+        for (int i = 0; i < equations.size(); i++) {
+            string a = equations[i][0];
+            string b = equations[i][1];
+            double value = values[i];
+            graph[a][b] = value;
+            graph[b][a] = 1.0 / value;
+        }
+
+        for (const auto& pair : graph) {
+            const string& k = pair.first;
+            for (const auto& pair1 : graph[k]) {
+                const string& i = pair1.first;
+                for (const auto& pair2 : graph[k]) {
+                    const string& j = pair2.first;
+                    if (!graph[i].count(j)) {
+                        graph[i][j] = graph[i][k] * graph[k][j];
+                    }
+                }
+            }
+        }
+
+        vector<double> result;
+        for (const auto& query : queries) {
+            const string& a = query[0];
+            const string& b = query[1];
+            if (!graph.count(a) || !graph[a].count(b)) {
+                result.push_back(-1.0);
+            } else {
+                result.push_back(graph[a][b]);
+            }
+        }
+
+        return result;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[][]} equations
+     * @param {number[]} values
+     * @param {string[][]} queries
+     * @return {number[]}
+     */
+    calcEquation(equations, values, queries) {
+        const graph = new Map();
+
+        for (let i = 0; i < equations.length; i++) {
+            const [a, b] = equations[i];
+            const value = values[i];
+            if (!graph.has(a)) graph.set(a, new Map());
+            if (!graph.has(b)) graph.set(b, new Map());
+            graph.get(a).set(b, value);
+            graph.get(b).set(a, 1 / value);
+        }
+
+        for (const k of graph.keys()) {
+            for (const i of graph.get(k).keys()) {
+                for (const j of graph.get(k).keys()) {
+                    if (!graph.get(i).has(j)) {
+                        graph.get(i).set(j, graph.get(i).get(k) * graph.get(k).get(j));
+                    }
+                }
+            }
+        }
+
+        return queries.map(([a, b]) => {
+            if (graph.has(a) && graph.get(a).has(b)) {
+                return graph.get(a).get(b);
+            } else {
+                return -1.0;
+            }
+        });
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public double[] CalcEquation(List<List<string>> equations, double[] values, List<List<string>> queries) {
+        var graph = new Dictionary<string, Dictionary<string, double>>();
+
+        for (int i = 0; i < equations.Count; i++) {
+            string a = equations[i][0];
+            string b = equations[i][1];
+            double val = values[i];
+
+            if (!graph.ContainsKey(a)) graph[a] = new Dictionary<string, double>();
+            if (!graph.ContainsKey(b)) graph[b] = new Dictionary<string, double>();
+
+            graph[a][b] = val;
+            graph[b][a] = 1.0 / val;
+        }
+
+        foreach (var k in graph.Keys.ToList()) {
+            foreach (var i in graph[k].Keys.ToList()) {
+                foreach (var j in graph[k].Keys.ToList()) {
+                    if (!graph[i].ContainsKey(j)) {
+                        graph[i][j] = graph[i][k] * graph[k][j];
+                    }
+                }
+            }
+        }
+
+        double[] result = new double[queries.Count];
+        for (int i = 0; i < queries.Count; i++) {
+            string a = queries[i][0];
+            string b = queries[i][1];
+            if (graph.ContainsKey(a) && graph[a].ContainsKey(b)) {
+                result[i] = graph[a][b];
+            } else {
+                result[i] = -1.0;
+            }
+        }
+
+        return result;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m + n ^ 3)$
+* Space complexity: $O(n ^ 2 + m)$
+
+> Where $n$ is the number of unique strings and $m$ is the number of queries.
\ No newline at end of file
diff --git a/articles/evaluate-reverse-polish-notation.md b/articles/evaluate-reverse-polish-notation.md
index 3fcc802ef..3ad96eff8 100644
--- a/articles/evaluate-reverse-polish-notation.md
+++ b/articles/evaluate-reverse-polish-notation.md
@@ -149,6 +149,106 @@ public class Solution {
 }
 ```
 
+```go
+func evalRPN(tokens []string) int {
+   for len(tokens) > 1 {
+       for i := 0; i < len(tokens); i++ {
+           if tokens[i] == "+" || tokens[i] == "-" || tokens[i] == "*" || tokens[i] == "/" {
+               a, _ := strconv.Atoi(tokens[i-2])
+               b, _ := strconv.Atoi(tokens[i-1])
+               var result int
+               
+               switch tokens[i] {
+               case "+":
+                   result = a + b
+               case "-":
+                   result = a - b 
+               case "*":
+                   result = a * b
+               case "/":
+                   result = a / b
+               }
+
+               temp := make([]string, 0)
+               temp = append(temp, tokens[:i-2]...)
+               temp = append(temp, strconv.Itoa(result))
+               temp = append(temp, tokens[i+1:]...)
+               tokens = temp
+               break
+           }
+       }
+   }
+   
+   result, _ := strconv.Atoi(tokens[0])
+   return result
+}
+```
+
+```kotlin
+class Solution {
+   fun evalRPN(tokens: Array<String>): Int {
+       val A = tokens.toMutableList()
+       
+       while (A.size > 1) {
+           for (i in A.indices) {
+               if (A[i] in setOf("+", "-", "*", "/")) {
+                   val a = A[i-2].toInt()
+                   val b = A[i-1].toInt()
+                   val result = when (A[i]) {
+                       "+" -> a + b
+                       "-" -> a - b
+                       "*" -> a * b
+                       else -> a / b
+                   }
+                   
+                   val temp = A.slice(0..i-3) + 
+                             result.toString() + 
+                             A.slice(i+1..A.lastIndex)
+                   A.clear()
+                   A.addAll(temp)
+                   break
+               }
+           }
+       }
+       
+       return A[0].toInt()
+   }
+}
+```
+
+```swift
+class Solution {
+    func evalRPN(_ tokens: [String]) -> Int {
+        var tokens = tokens
+
+        while tokens.count > 1 {
+            for i in 0..<tokens.count {
+                if "+-*/".contains(tokens[i]) {
+                    let a = Int(tokens[i-2])!
+                    let b = Int(tokens[i-1])!
+                    var result = 0
+                    
+                    if tokens[i] == "+" {
+                        result = a + b
+                    } else if tokens[i] == "-" {
+                        result = a - b
+                    } else if tokens[i] == "*" {
+                        result = a * b
+                    } else if tokens[i] == "/" {
+                        result = Int(a / b)
+                    }
+                    
+                    tokens = Array(tokens[0..<(i-2)]) + [String(result)] + Array(tokens[(i+1)...])
+                    break
+                }
+            }
+        }
+
+        return Int(tokens[0])!
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -430,6 +530,157 @@ public class Solution {
 }
 ```
 
+```go
+type DoublyLinkedList struct {
+    val  string
+    next *DoublyLinkedList
+    prev *DoublyLinkedList
+}
+
+func evalRPN(tokens []string) int {
+    head := &DoublyLinkedList{val: tokens[0]}
+    curr := head
+    
+    for i := 1; i < len(tokens); i++ {
+        newNode := &DoublyLinkedList{val: tokens[i], prev: curr}
+        curr.next = newNode
+        curr = curr.next
+    }
+    
+    for head != nil {
+        if head.val == "+" || head.val == "-" || head.val == "*" || head.val == "/" {
+            l, _ := strconv.Atoi(head.prev.prev.val)
+            r, _ := strconv.Atoi(head.prev.val)
+            
+            var res int
+            switch head.val {
+            case "+":
+                res = l + r
+            case "-":
+                res = l - r
+            case "*":
+                res = l * r
+            case "/":
+                res = l / r
+            }
+            
+            head.val = strconv.Itoa(res)
+            head.prev = head.prev.prev.prev
+            if head.prev != nil {
+                head.prev.next = head
+            }
+        }
+        
+        head = head.next
+    }
+    
+    ans, _ := strconv.Atoi(curr.val)
+    return ans
+}
+```
+
+```kotlin
+class DoublyLinkedList(
+   var value: String,
+   var next: DoublyLinkedList? = null,
+   var prev: DoublyLinkedList? = null
+)
+
+class Solution {
+   fun evalRPN(tokens: Array<String>): Int {
+       val head = DoublyLinkedList(tokens[0])
+       var curr = head
+       
+       for (i in 1 until tokens.size) {
+           val newNode = DoublyLinkedList(tokens[i], prev = curr)
+           curr.next = newNode
+           curr = newNode
+       }
+       
+       var ptr: DoublyLinkedList? = head
+       while (ptr != null) {
+           if (ptr.value in setOf("+", "-", "*", "/")) {
+               val l = ptr.prev!!.prev!!.value.toInt()
+               val r = ptr.prev!!.value.toInt()
+               
+               val res = when (ptr.value) {
+                   "+" -> l + r
+                   "-" -> l - r
+                   "*" -> l * r
+                   else -> l / r
+               }
+               
+               ptr.value = res.toString()
+               ptr.prev = ptr.prev!!.prev!!.prev
+               ptr.prev?.next = ptr
+           }
+           
+           ptr = ptr.next
+       }
+       
+       return curr.value.toInt()
+   }
+}
+```
+
+```swift
+class DoublyLinkedList {
+    var val: String
+    var next: DoublyLinkedList?
+    var prev: DoublyLinkedList?
+
+    init(val: String, next: DoublyLinkedList? = nil, prev: DoublyLinkedList? = nil) {
+        self.val = val
+        self.next = next
+        self.prev = prev
+    }
+}
+
+class Solution {
+    func evalRPN(_ tokens: [String]) -> Int {
+        var head: DoublyLinkedList? = DoublyLinkedList(val: tokens[0])
+        var curr = head
+
+        for i in 1..<tokens.count {
+            curr!.next = DoublyLinkedList(val: tokens[i], prev: curr)
+            curr = curr!.next
+        }
+
+        var ans = 0
+
+        while head != nil {
+            if "+-*/".contains(head!.val) {
+                let l = Int(head!.prev!.prev!.val)!
+                let r = Int(head!.prev!.val)!
+                var res: Int
+
+                if head!.val == "+" {
+                    res = l + r
+                } else if head!.val == "-" {
+                    res = l - r
+                } else if head!.val == "*" {
+                    res = l * r
+                } else {
+                    res = l / r
+                }
+
+                head!.val = String(res)
+                head!.prev = head!.prev!.prev!.prev
+
+                if head!.prev != nil {
+                    head!.prev!.next = head
+                }
+            }
+
+            ans = Int(head!.val)!
+            head = head!.next
+        }
+
+        return ans
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -600,6 +851,98 @@ public class Solution {
 }
 ```
 
+```go
+func evalRPN(tokens []string) int {
+    index := len(tokens) - 1
+    
+    var dfs func() int
+    dfs = func() int {
+        token := tokens[index]
+        index--
+        
+        if token != "+" && token != "-" && token != "*" && token != "/" {
+            val, _ := strconv.Atoi(token)
+            return val
+        }
+        
+        right := dfs()
+        left := dfs()
+        
+        switch token {
+        case "+":
+            return left + right
+        case "-":
+            return left - right
+        case "*":
+            return left * right
+        default:
+            return left / right
+        }
+    }
+    
+    return dfs()
+}
+```
+
+```kotlin
+class Solution {
+    private var index = 0
+    
+    fun evalRPN(tokens: Array<String>): Int {
+        index = tokens.size - 1
+        
+        fun dfs(): Int {
+            val token = tokens[index]
+            index--
+            
+            if (token !in setOf("+", "-", "*", "/")) {
+                return token.toInt()
+            }
+            
+            val right = dfs()
+            val left = dfs()
+            
+            return when (token) {
+                "+" -> left + right
+                "-" -> left - right
+                "*" -> left * right
+                else -> left / right
+            }
+        }
+        
+        return dfs()
+    }
+}
+```
+
+```swift
+class Solution {
+    func evalRPN(_ tokens: [String]) -> Int {
+        var tokens = tokens
+        
+        func dfs() -> Int {
+            let token = tokens.removeLast()
+            if let num = Int(token) {
+                return num
+            }
+
+            let right = dfs()
+            let left = dfs()
+
+            switch token {
+                case "+": return left + right
+                case "-": return left - right
+                case "*": return left * right
+                case "/": return left / right
+                default: return 0
+            }
+        }
+        
+        return dfs()
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -746,6 +1089,106 @@ public class Solution {
 }
 ```
 
+```go
+func evalRPN(tokens []string) int {
+   stack := make([]int, 0)
+   
+   for _, token := range tokens {
+       switch token {
+       case "+":
+           a := stack[len(stack)-1]
+           b := stack[len(stack)-2] 
+           stack = stack[:len(stack)-2]
+           stack = append(stack, b+a)
+       case "-":
+           a := stack[len(stack)-1]
+           b := stack[len(stack)-2]
+           stack = stack[:len(stack)-2]
+           stack = append(stack, b-a)
+       case "*":
+           a := stack[len(stack)-1]
+           b := stack[len(stack)-2]
+           stack = stack[:len(stack)-2]
+           stack = append(stack, b*a)
+       case "/":
+           a := stack[len(stack)-1]
+           b := stack[len(stack)-2]
+           stack = stack[:len(stack)-2]
+           stack = append(stack, b/a)
+       default:
+           num, _ := strconv.Atoi(token)
+           stack = append(stack, num)
+       }
+   }
+   
+   return stack[0]
+}
+```
+
+```kotlin
+class Solution {
+    fun evalRPN(tokens: Array<String>): Int {
+        val stack = ArrayDeque<Int>()
+        
+        for (token in tokens) {
+            when (token) {
+                "+" -> {
+                    val a = stack.removeLast()
+                    val b = stack.removeLast()
+                    stack.addLast(b + a)
+                }
+                "-" -> {
+                    val a = stack.removeLast()
+                    val b = stack.removeLast()
+                    stack.addLast(b - a)
+                }
+                "*" -> {
+                    val a = stack.removeLast()
+                    val b = stack.removeLast()
+                    stack.addLast(b * a)
+                }
+                "/" -> {
+                    val a = stack.removeLast()
+                    val b = stack.removeLast()
+                    stack.addLast(b / a)
+                }
+                else -> stack.addLast(token.toInt())
+            }
+        }
+        
+        return stack.last()
+    }
+}
+```
+
+```swift
+class Solution {
+    func evalRPN(_ tokens: [String]) -> Int {
+        var stack = [Int]()
+
+        for c in tokens {
+            switch c {
+                case "+":
+                    stack.append(stack.removeLast() + stack.removeLast())
+                case "-":
+                    let a = stack.removeLast()
+                    let b = stack.removeLast()
+                    stack.append(b - a)
+                case "*":
+                    stack.append(stack.removeLast() * stack.removeLast())
+                case "/":
+                    let a = stack.removeLast()
+                    let b = stack.removeLast()
+                    stack.append(b / a)
+                default:
+                    stack.append(Int(c)!)
+            }
+        }
+        return stack[0]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/even-odd-tree.md b/articles/even-odd-tree.md
new file mode 100644
index 000000000..4c5b25687
--- /dev/null
+++ b/articles/even-odd-tree.md
@@ -0,0 +1,543 @@
+## 1. Breadth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def isEvenOddTree(self, root: Optional[TreeNode]) -> bool:
+        even = True
+        q = deque([root])
+
+        while q:
+            prev = float("-inf") if even else float("inf")
+            for _ in range(len(q)):
+                node = q.popleft()
+
+                if even and (node.val % 2 == 0 or node.val <= prev):
+                    return False
+                elif not even and (node.val % 2 == 1 or node.val >= prev):
+                    return False
+
+                if node.left:
+                    q.append(node.left)
+                if node.right:
+                    q.append(node.right)
+
+                prev = node.val
+
+            even = not even
+
+        return True
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public boolean isEvenOddTree(TreeNode root) {
+        boolean even = true;
+        Queue<TreeNode> q = new LinkedList<>();
+        q.offer(root);
+
+        while (!q.isEmpty()) {
+            int prev = even ? Integer.MIN_VALUE : Integer.MAX_VALUE;
+            for (int i = q.size(); i > 0; i--) {
+                TreeNode node = q.poll();
+
+                if (even && (node.val % 2 == 0 || node.val <= prev)) return false;
+                if (!even && (node.val % 2 == 1 || node.val >= prev)) return false;
+
+                if (node.left != null) q.offer(node.left);
+                if (node.right != null) q.offer(node.right);
+
+                prev = node.val;
+            }
+            even = !even;
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    bool isEvenOddTree(TreeNode* root) {
+        bool even = true;
+        queue<TreeNode*> q;
+        q.push(root);
+
+        while (!q.empty()) {
+            int prev = even ? INT_MIN : INT_MAX;
+            for (int i = q.size(); i > 0; i--) {
+                TreeNode* node = q.front();q.pop();
+
+                if (even && (node->val % 2 == 0 || node->val <= prev)) return false;
+                if (!even && (node->val % 2 == 1 || node->val >= prev)) return false;
+
+                if (node->left) q.push(node->left);
+                if (node->right) q.push(node->right);
+
+                prev = node->val;
+            }
+            even = !even;
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {boolean}
+     */
+    isEvenOddTree(root) {
+        let even = true;
+        const q = new Queue([root]);
+
+        while (!q.isEmpty()) {
+            let prev = even ? -Infinity : Infinity;
+            for (let i = q.size(); i > 0; i--) {
+                let node = q.pop();
+
+                if (even && (node.val % 2 === 0 || node.val <= prev)) return false;
+                if (!even && (node.val % 2 === 1 || node.val >= prev)) return false;
+
+                if (node.left) q.push(node.left);
+                if (node.right) q.push(node.right);
+
+                prev = node.val;
+            }
+            even = !even;
+        }
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Depth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def isEvenOddTree(self, root: Optional[TreeNode]) -> bool:
+        levels = []
+
+        def dfs(node, level):
+            if not node:
+                return True
+
+            even = level % 2 == 0
+            if ((even and node.val % 2 == 0) or 
+                (not even and (node.val % 2 == 1))
+            ):
+                return False
+
+            if len(levels) == level:
+                levels.append(node.val)
+            else:
+                if ((even and node.val <= levels[level]) or 
+                    (not even and node.val >= levels[level])
+                ):
+                    return False
+                levels[level] = node.val
+
+            return dfs(node.left, level + 1) and dfs(node.right, level + 1)
+
+        return dfs(root, 0)
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    List<Integer> levels = new ArrayList<>();
+
+    private boolean dfs(TreeNode node, int level) {
+        if (node == null) return true;
+
+        boolean even = level % 2 == 0;
+        if ((even && node.val % 2 == 0) || 
+            (!even && node.val % 2 == 1)) {
+            return false;
+        }
+
+        if (levels.size() == level) {
+            levels.add(node.val);
+        } else {
+            if ((even && node.val <= levels.get(level)) || 
+                (!even && node.val >= levels.get(level))) {
+                return false;
+            }
+            levels.set(level, node.val);
+        }
+
+        return dfs(node.left, level + 1) && dfs(node.right, level + 1);
+    }
+
+    public boolean isEvenOddTree(TreeNode root) {
+        return dfs(root, 0);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    vector<int> levels;
+
+    bool dfs(TreeNode* node, int level) {
+        if (!node) return true;
+
+        bool even = level % 2 == 0;
+        if ((even && node->val % 2 == 0) || 
+            (!even && node->val % 2 == 1)) {
+            return false;
+        }
+
+        if (levels.size() == level) {
+            levels.push_back(node->val);
+        } else {
+            if ((even && node->val <= levels[level]) || 
+                (!even && node->val >= levels[level])) {
+                return false;
+            }
+            levels[level] = node->val;
+        }
+
+        return dfs(node->left, level + 1) && dfs(node->right, level + 1);
+    }
+
+    bool isEvenOddTree(TreeNode* root) {
+        return dfs(root, 0);
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {boolean}
+     */
+    isEvenOddTree(root) {
+        const levels = [];
+
+        const dfs = (node, level) => {
+            if (!node) return true;
+
+            const even = level % 2 === 0;
+            if ((even && node.val % 2 === 0) || 
+                (!even && node.val % 2 === 1)) {
+                return false;
+            }
+
+            if (levels.length === level) {
+                levels.push(node.val);
+            } else {
+                if ((even && node.val <= levels[level]) || 
+                    (!even && node.val >= levels[level])) {
+                    return false;
+                }
+                levels[level] = node.val;
+            }
+
+            return dfs(node.left, level + 1) && dfs(node.right, level + 1);
+        };
+
+        return dfs(root, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Iterative DFS
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def isEvenOddTree(self, root: Optional[TreeNode]) -> bool:
+        stack = [(root, 0)]
+        levels = []
+
+        while stack:
+            node, level = stack.pop()
+
+            even = level % 2 == 0
+            if ((even and node.val % 2 == 0) or 
+                (not even and node.val % 2 == 1)
+            ):
+                return False
+
+            if len(levels) == level:
+                levels.append(node.val)
+            else:
+                if ((even and node.val <= levels[level]) or 
+                    (not even and node.val >= levels[level])
+                ):
+                    return False
+                levels[level] = node.val
+
+            if node.right:
+                stack.append((node.right, level + 1))
+            if node.left:
+                stack.append((node.left, level + 1))
+
+        return True
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public boolean isEvenOddTree(TreeNode root) {
+        Stack<Pair<TreeNode, Integer>> stack = new Stack<>();
+        stack.push(new Pair<>(root, 0));
+        List<Integer> levels = new ArrayList<>();
+
+        while (!stack.isEmpty()) {
+            Pair<TreeNode, Integer> pair = stack.pop();
+            TreeNode node = pair.getKey();
+            int level = pair.getValue();
+
+            boolean even = level % 2 == 0;
+            if ((even && node.val % 2 == 0) || 
+                (!even && node.val % 2 == 1))
+                return false;
+
+            if (levels.size() == level) {
+                levels.add(node.val);
+            } else {
+                if ((even && node.val <= levels.get(level)) || 
+                    (!even && node.val >= levels.get(level)))
+                    return false;
+                levels.set(level, node.val);
+            }
+
+            if (node.right != null) stack.push(new Pair<>(node.right, level + 1));
+            if (node.left != null) stack.push(new Pair<>(node.left, level + 1));
+        }
+
+        return true;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    bool isEvenOddTree(TreeNode* root) {
+        stack<pair<TreeNode*, int>> stack;
+        stack.push({root, 0});
+        vector<int> levels;
+
+        while (!stack.empty()) {
+            auto [node, level] = stack.top();
+            stack.pop();
+
+            bool even = level % 2 == 0;
+            if ((even && node->val % 2 == 0) || 
+                (!even && node->val % 2 == 1))
+                return false;
+
+            if (levels.size() == level) {
+                levels.push_back(node->val);
+            } else {
+                if ((even && node->val <= levels[level]) || 
+                    (!even && node->val >= levels[level]))
+                    return false;
+                levels[level] = node->val;
+            }
+
+            if (node->right) stack.push({node->right, level + 1});
+            if (node->left) stack.push({node->left, level + 1});
+        }
+
+        return true;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {boolean}
+     */
+    isEvenOddTree(root) {
+        const stack = [[root, 0]];
+        const levels = [];
+
+        while (stack.length) {
+            const [node, level] = stack.pop();
+
+            const even = level % 2 === 0;
+            if ((even && node.val % 2 === 0) || 
+                (!even && node.val % 2 === 1))
+                return false;
+
+            if (levels.length === level) {
+                levels.push(node.val);
+            } else {
+                if ((even && node.val <= levels[level]) || 
+                    (!even && node.val >= levels[level]))
+                    return false;
+                levels[level] = node.val;
+            }
+
+            if (node.right) stack.push([node.right, level + 1]);
+            if (node.left) stack.push([node.left, level + 1]);
+        }
+
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/excel-sheet-column-title.md b/articles/excel-sheet-column-title.md
new file mode 100644
index 000000000..98ae4f249
--- /dev/null
+++ b/articles/excel-sheet-column-title.md
@@ -0,0 +1,142 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def convertToTitle(self, columnNumber: int) -> str:
+        if columnNumber == 0:
+            return ""
+
+        n = columnNumber - 1
+        return self.convertToTitle(n // 26) + chr(n % 26 + ord('A'))
+```
+
+```java
+public class Solution {
+    public String convertToTitle(int columnNumber) {
+        if (columnNumber == 0) {
+            return "";
+        }
+        int n = columnNumber - 1;
+        return convertToTitle(n / 26) + (char) ('A' + n % 26);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string convertToTitle(int columnNumber) {
+        if (columnNumber == 0) {
+            return "";
+        }
+        int n = columnNumber - 1;
+        return convertToTitle(n / 26) + char('A' + n % 26);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} columnNumber
+     * @return {string}
+     */
+    convertToTitle(columnNumber) {
+        if (columnNumber === 0) {
+            return "";
+        }
+        const n = columnNumber - 1;
+        return this.convertToTitle(Math.floor(n / 26)) + String.fromCharCode('A'.charCodeAt(0) + n % 26);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(\log n)$ for recursion stack.
+
+> Where $n$ is the given column number.
+
+---
+
+## 2. Iteration
+
+::tabs-start
+
+```python
+class Solution:
+    def convertToTitle(self, columnNumber: int) -> str:
+        res = []
+        while columnNumber > 0:
+            columnNumber -= 1
+            offset = columnNumber % 26
+            res += chr(ord('A') + offset)
+            columnNumber //= 26
+        
+        return ''.join(reversed(res))
+```
+
+```java
+public class Solution {
+    public String convertToTitle(int columnNumber) {
+        StringBuilder res = new StringBuilder();
+        while (columnNumber > 0) {
+            columnNumber--;
+            int offset = columnNumber % 26;
+            res.append((char) ('A' + offset));
+            columnNumber /= 26;
+        }
+        return res.reverse().toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string convertToTitle(int columnNumber) {
+        string res;
+        while (columnNumber > 0) {
+            columnNumber--;
+            int offset = columnNumber % 26;
+            res += ('A' + offset);
+            columnNumber /= 26;
+        }
+        reverse(res.begin(), res.end());
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} columnNumber
+     * @return {string}
+     */
+    convertToTitle(columnNumber) {
+        let res = [];
+        while (columnNumber > 0) {
+            columnNumber--;
+            const offset = columnNumber % 26;
+            res.push(String.fromCharCode('A'.charCodeAt(0) + offset));
+            columnNumber = Math.floor(columnNumber / 26);
+        }
+        return res.reverse().join('');
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$ extra space.
+
+> Where $n$ is the given column number.
\ No newline at end of file
diff --git a/articles/extra-characters-in-a-string.md b/articles/extra-characters-in-a-string.md
new file mode 100644
index 000000000..6b2052693
--- /dev/null
+++ b/articles/extra-characters-in-a-string.md
@@ -0,0 +1,1300 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def minExtraChar(self, s: str, dictionary: List[str]) -> int:
+        words = set(dictionary)
+
+        def dfs(i):
+            if i == len(s):
+                return 0
+
+            res = 1 + dfs(i + 1)
+            for j in range(i, len(s)):
+                if s[i:j + 1] in words:
+                    res = min(res, dfs(j + 1))
+
+            return res
+
+        return dfs(0)
+```
+
+```java
+public class Solution {
+    public int minExtraChar(String s, String[] dictionary) {
+        Set<String> words = new HashSet<>();
+        for (String word : dictionary) {
+            words.add(word);
+        }
+        return dfs(0, s, words);
+    }
+
+    private int dfs(int i, String s, Set<String> words) {
+        if (i == s.length()) {
+            return 0;
+        }
+
+        int res = 1 + dfs(i + 1, s, words);
+        for (int j = i; j < s.length(); j++) {
+            if (words.contains(s.substring(i, j + 1))) {
+                res = Math.min(res, dfs(j + 1, s, words));
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minExtraChar(string s, vector<string>& dictionary) {
+        unordered_set<string> words(dictionary.begin(), dictionary.end());
+        return dfs(0, s, words);
+    }
+
+private:
+    int dfs(int i, const string& s, unordered_set<string>& words) {
+        if (i == s.size()) {
+            return 0;
+        }
+
+        int res = 1 + dfs(i + 1, s, words);
+        for (int j = i; j < s.size(); j++) {
+            if (words.count(s.substr(i, j - i + 1))) {
+                res = min(res, dfs(j + 1, s, words));
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string[]} dictionary
+     * @return {number}
+     */
+    minExtraChar(s, dictionary) {
+        const words = new Set(dictionary);
+
+        const dfs = (i) => {
+            if (i === s.length) {
+                return 0;
+            }
+
+            let res = 1 + dfs(i + 1);
+            for (let j = i; j < s.length; j++) {
+                if (words.has(s.slice(i, j + 1))) {
+                    res = Math.min(res, dfs(j + 1));
+                }
+            }
+
+            return res;
+        };
+
+        return dfs(0);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MinExtraChar(string s, string[] dictionary) {
+        HashSet<string> words = new HashSet<string>(dictionary);
+        return Dfs(0, s, words);
+    }
+
+    private int Dfs(int i, string s, HashSet<string> words) {
+        if (i == s.Length) {
+            return 0;
+        }
+
+        int res = 1 + Dfs(i + 1, s, words);
+        for (int j = i; j < s.Length; j++) {
+            if (words.Contains(s.Substring(i, j - i + 1))) {
+                res = Math.Min(res, Dfs(j + 1, s, words));
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * 2 ^ n + m * k)$
+* Space complexity: $O(n + m * k)$
+
+> Where $n$ is the length of the string $s$, $m$ is the number of words in the dictionary, and $k$ is the average length of a word in the dictionary.
+
+---
+
+## 2. Dynamic Programming (Top-Down) Using Hash Set
+
+::tabs-start
+
+```python
+class Solution:
+    def minExtraChar(self, s: str, dictionary: List[str]) -> int:
+        words = set(dictionary)
+        dp = {len(s): 0}
+
+        def dfs(i):
+            if i in dp:
+                return dp[i]
+            res = 1 + dfs(i + 1)
+            for j in range(i, len(s)):
+                if s[i:j + 1] in words:
+                    res = min(res, dfs(j + 1))
+            dp[i] = res
+            return res
+
+        return dfs(0)
+```
+
+```java
+public class Solution {
+    public int minExtraChar(String s, String[] dictionary) {
+        Set<String> words = new HashSet<>(Arrays.asList(dictionary));
+        int n = s.length();
+        int[] dp = new int[n + 1];
+        Arrays.fill(dp, -1);
+        dp[n] = 0;
+
+        return dfs(0, s, words, dp);
+    }
+
+    private int dfs(int i, String s, Set<String> words, int[] dp) {
+        if (dp[i] != -1) return dp[i];
+        int res = 1 + dfs(i + 1, s, words, dp);
+        for (int j = i; j < s.length(); j++) {
+            if (words.contains(s.substring(i, j + 1))) {
+                res = Math.min(res, dfs(j + 1, s, words, dp));
+            }
+        }
+        dp[i] = res;
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minExtraChar(string s, vector<string>& dictionary) {
+        unordered_set<string> words(dictionary.begin(), dictionary.end());
+        int n = s.size();
+        vector<int> dp(n + 1, -1);
+        dp[n] = 0;
+        return dfs(0, s, words, dp);
+    }
+
+private:
+    int dfs(int i, string& s, unordered_set<string>& words, vector<int>& dp) {
+        if (dp[i] != -1) return dp[i];
+        int res = 1 + dfs(i + 1, s, words, dp);
+        for (int j = i; j < s.size(); j++) {
+            if (words.count(s.substr(i, j - i + 1))) {
+                res = min(res, dfs(j + 1, s, words, dp));
+            }
+        }
+        dp[i] = res;
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string[]} dictionary
+     * @return {number}
+     */
+    minExtraChar(s, dictionary) {
+        const words = new Set(dictionary);
+        const n = s.length;
+        const dp = new Array(n + 1).fill(-1);
+        dp[n] = 0;
+
+        const dfs = (i) => {
+            if (dp[i] !== -1) return dp[i];
+            let res = 1 + dfs(i + 1);
+            for (let j = i; j < n; j++) {
+                if (words.has(s.slice(i, j + 1))) {
+                    res = Math.min(res, dfs(j + 1));
+                }
+            }
+            dp[i] = res;
+            return res;
+        };
+
+        return dfs(0);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MinExtraChar(string s, string[] dictionary) {
+        HashSet<string> words = new HashSet<string>(dictionary);
+        int n = s.Length;
+        int[] dp = new int[n + 1];
+        Array.Fill(dp, -1);
+        dp[n] = 0;
+
+        return Dfs(0, s, words, dp);
+    }
+
+    private int Dfs(int i, string s, HashSet<string> words, int[] dp) {
+        if (dp[i] != -1) return dp[i];
+
+        int res = 1 + Dfs(i + 1, s, words, dp);
+        for (int j = i; j < s.Length; j++) {
+            if (words.Contains(s.Substring(i, j - i + 1))) {
+                res = Math.Min(res, Dfs(j + 1, s, words, dp));
+            }
+        }
+
+        dp[i] = res;
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 3 + m * k)$
+* Space complexity: $O(n + m * k)$
+
+> Where $n$ is the length of the string $s$, $m$ is the number of words in the dictionary, and $k$ is the average length of a word in the dictionary.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up) Using Hash Set
+
+::tabs-start
+
+```python
+class Solution:
+    def minExtraChar(self, s: str, dictionary: List[str]) -> int:
+        words = set(dictionary)
+        n = len(s)
+        dp = [0] * (n + 1)
+
+        for i in range(n - 1, -1, -1):
+            dp[i] = 1 + dp[i + 1]
+            for j in range(i, n):
+                if s[i:j + 1] in words:
+                    dp[i] = min(dp[i], dp[j + 1])
+        return dp[0]
+```
+
+```java
+public class Solution {
+    public int minExtraChar(String s, String[] dictionary) {
+        Set<String> words = new HashSet<>(Arrays.asList(dictionary));
+        int n = s.length();
+        int[] dp = new int[n + 1];
+
+        for (int i = n - 1; i >= 0; i--) {
+            dp[i] = 1 + dp[i + 1];
+            for (int j = i; j < n; j++) {
+                if (words.contains(s.substring(i, j + 1))) {
+                    dp[i] = Math.min(dp[i], dp[j + 1]);
+                }
+            }
+        }
+        return dp[0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minExtraChar(string s, vector<string>& dictionary) {
+        unordered_set<string> words(dictionary.begin(), dictionary.end());
+        int n = s.size();
+        vector<int> dp(n + 1, 0);
+
+        for (int i = n - 1; i >= 0; i--) {
+            dp[i] = 1 + dp[i + 1];
+            for (int j = i; j < n; j++) {
+                if (words.count(s.substr(i, j - i + 1))) {
+                    dp[i] = min(dp[i], dp[j + 1]);
+                }
+            }
+        }
+        return dp[0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string[]} dictionary
+     * @return {number}
+     */
+    minExtraChar(s, dictionary) {
+        const words = new Set(dictionary);
+        const n = s.length;
+        const dp = new Array(n + 1).fill(0);
+
+        for (let i = n - 1; i >= 0; i--) {
+            dp[i] = 1 + dp[i + 1];
+            for (let j = i; j < n; j++) {
+                if (words.has(s.slice(i, j + 1))) {
+                    dp[i] = Math.min(dp[i], dp[j + 1]);
+                }
+            }
+        }
+        return dp[0];
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MinExtraChar(string s, string[] dictionary) {
+        HashSet<string> words = new HashSet<string>(dictionary);
+        int n = s.Length;
+        int[] dp = new int[n + 1];
+
+        for (int i = n - 1; i >= 0; i--) {
+            dp[i] = 1 + dp[i + 1];
+            for (int j = i; j < n; j++) {
+                if (words.Contains(s.Substring(i, j - i + 1))) {
+                    dp[i] = Math.Min(dp[i], dp[j + 1]);
+                }
+            }
+        }
+
+        return dp[0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 3 + m * k)$
+* Space complexity: $O(n + m * k)$
+
+> Where $n$ is the length of the string $s$, $m$ is the number of words in the dictionary, and $k$ is the average length of a word in the dictionary.
+
+---
+
+## 4. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def minExtraChar(self, s: str, dictionary: List[str]) -> int:
+        dp = {len(s) : 0}
+
+        def dfs(i):
+            if i in dp:
+                return dp[i]
+            
+            res = 1 + dfs(i + 1)
+            for word in dictionary:
+                if i + len(word) > len(s):
+                    continue
+
+                flag = True
+                for j in range(len(word)):
+                    if s[i + j] != word[j]:
+                        flag = False
+                        break
+                if flag:
+                    res = min(res, dfs(i + len(word)))
+            
+            dp[i] = res
+            return res
+
+        return dfs(0) 
+```
+
+```java
+public class Solution {
+    public int minExtraChar(String s, String[] dictionary) {
+        Map<Integer, Integer> dp = new HashMap<>();
+        dp.put(s.length(), 0);
+        return dfs(0, s, dictionary, dp);
+    }
+
+    private int dfs(int i, String s, String[] dictionary, Map<Integer, Integer> dp) {
+        if (dp.containsKey(i)) {
+            return dp.get(i);
+        }
+
+        int res = 1 + dfs(i + 1, s, dictionary, dp);
+        for (String word : dictionary) {
+            if (i + word.length() > s.length()) continue;
+
+            boolean flag = true;
+            for (int j = 0; j < word.length(); j++) {
+                if (s.charAt(i + j) != word.charAt(j)) {
+                    flag = false;
+                    break;
+                }
+            }
+            if (flag) {
+                res = Math.min(res, dfs(i + word.length(), s, dictionary, dp));
+            }
+        }
+        dp.put(i, res);
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+    unordered_map<int, int> dp;
+
+public:
+    int minExtraChar(string s, vector<string>& dictionary) {
+        dp[s.size()] = 0;
+        return dfs(0, s, dictionary);
+    }
+
+private:
+    int dfs(int i, string& s, vector<string>& dictionary) {
+        if (dp.count(i)) {
+            return dp[i];
+        }
+
+        int res = 1 + dfs(i + 1, s, dictionary);
+        for (const string& word : dictionary) {
+            if (i + word.size() > s.size()) continue;
+
+            bool flag = true;
+            for (int j = 0; j < word.size(); j++) {
+                if (s[i + j] != word[j]) {
+                    flag = false;
+                    break;
+                }
+            }
+            if (flag) {
+                res = min(res, dfs(i + word.size(), s, dictionary));
+            }
+        }
+        return dp[i] = res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string[]} dictionary
+     * @return {number}
+     */
+    minExtraChar(s, dictionary) {
+        const dp = new Map();
+        dp.set(s.length, 0);
+
+        const dfs = (i) => {
+            if (dp.has(i)) return dp.get(i);
+
+            let res = 1 + dfs(i + 1);
+            for (const word of dictionary) {
+                if (i + word.length > s.length) continue;
+
+                let flag = true;
+                for (let j = 0; j < word.length; j++) {
+                    if (s[i + j] !== word[j]) {
+                        flag = false;
+                        break;
+                    }
+                }
+                if (flag) {
+                    res = Math.min(res, dfs(i + word.length));
+                }
+            }
+            dp.set(i, res);
+            return res;
+        };
+
+        return dfs(0);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MinExtraChar(string s, string[] dictionary) {
+        Dictionary<int, int> dp = new Dictionary<int, int>();
+        dp[s.Length] = 0;
+        return Dfs(0, s, dictionary, dp);
+    }
+
+    private int Dfs(int i, string s, string[] dictionary, Dictionary<int, int> dp) {
+        if (dp.ContainsKey(i)) {
+            return dp[i];
+        }
+
+        int res = 1 + Dfs(i + 1, s, dictionary, dp);
+
+        foreach (string word in dictionary) {
+            if (i + word.Length > s.Length) continue;
+
+            bool flag = true;
+            for (int j = 0; j < word.Length; j++) {
+                if (s[i + j] != word[j]) {
+                    flag = false;
+                    break;
+                }
+            }
+
+            if (flag) {
+                res = Math.Min(res, Dfs(i + word.Length, s, dictionary, dp));
+            }
+        }
+
+        dp[i] = res;
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m * k)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the length of the string $s$, $m$ is the number of words in the dictionary, and $k$ is the average length of a word in the dictionary.
+
+---
+
+## 5. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def minExtraChar(self, s: str, dictionary: List[str]) -> int:
+        n = len(s)
+        dp = [0] * (n + 1)
+        
+        for i in range(n - 1, -1, -1):
+            dp[i] = 1 + dp[i + 1]
+            for word in dictionary:
+                if i + len(word) <= n and s[i:i + len(word)] == word:
+                    dp[i] = min(dp[i], dp[i + len(word)])
+        
+        return dp[0]
+```
+
+```java
+public class Solution {
+    public int minExtraChar(String s, String[] dictionary) {
+        int n = s.length();
+        int[] dp = new int[n + 1];
+
+        for (int i = n - 1; i >= 0; i--) {
+            dp[i] = 1 + dp[i + 1];
+            for (String word : dictionary) {
+                if (i + word.length() <= n && s.startsWith(word, i)) {
+                    dp[i] = Math.min(dp[i], dp[i + word.length()]);
+                }
+            }
+        }
+
+        return dp[0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minExtraChar(string s, vector<string>& dictionary) {
+        int n = s.size();
+        vector<int> dp(n + 1, 0);
+
+        for (int i = n - 1; i >= 0; i--) {
+            dp[i] = 1 + dp[i + 1];
+            for (const string& word : dictionary) {
+                if (i + word.size() <= n && s.substr(i, word.size()) == word) {
+                    dp[i] = min(dp[i], dp[i + word.size()]);
+                }
+            }
+        }
+
+        return dp[0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string[]} dictionary
+     * @return {number}
+     */
+    minExtraChar(s, dictionary) {
+        const n = s.length;
+        const dp = new Array(n + 1).fill(0);
+
+        for (let i = n - 1; i >= 0; i--) {
+            dp[i] = 1 + dp[i + 1];
+            for (const word of dictionary) {
+                if (i + word.length <= n && s.slice(i, i + word.length) === word) {
+                    dp[i] = Math.min(dp[i], dp[i + word.length]);
+                }
+            }
+        }
+
+        return dp[0];
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MinExtraChar(string s, string[] dictionary) {
+        int n = s.Length;
+        int[] dp = new int[n + 1];
+
+        for (int i = n - 1; i >= 0; i--) {
+            dp[i] = 1 + dp[i + 1];
+            foreach (string word in dictionary) {
+                if (i + word.Length <= n && s.Substring(i, word.Length) == word) {
+                    dp[i] = Math.Min(dp[i], dp[i + word.Length]);
+                }
+            }
+        }
+
+        return dp[0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m * k)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the length of the string $s$, $m$ is the number of words in the dictionary, and $k$ is the average length of a word in the dictionary.
+
+---
+
+## 6. Dynamic Programming (Top-Down) Using Trie
+
+::tabs-start
+
+```python
+class TrieNode:
+    def __init__(self):
+        self.children = {}
+        self.isWord = False
+
+class Trie:
+    def __init__(self):
+        self.root = TrieNode()
+    
+    def addWord(self, word):
+        curr = self.root
+        for c in word:
+            if c not in curr.children:
+                curr.children[c] = TrieNode()
+            curr = curr.children[c]
+        curr.isWord = True
+
+class Solution:
+    def minExtraChar(self, s: str, dictionary: List[str]) -> int:
+        trie = Trie()
+        for w in dictionary:
+            trie.addWord(w)
+
+        dp = {len(s): 0}
+
+        def dfs(i):
+            if i in dp:
+                return dp[i]
+            res = 1 + dfs(i + 1)
+            curr = trie.root
+            for j in range(i, len(s)):
+                if s[j] not in curr.children:
+                    break
+                curr = curr.children[s[j]]
+                if curr.isWord:
+                    res = min(res, dfs(j + 1))
+
+            dp[i] = res
+            return res
+
+        return dfs(0)
+```
+
+```java
+class TrieNode {
+    TrieNode[] children;
+    boolean isWord;
+
+    TrieNode() {
+        children = new TrieNode[26];
+        isWord = false;
+    }
+}
+
+class Trie {
+    TrieNode root;
+
+    Trie() {
+        root = new TrieNode();
+    }
+
+    void addWord(String word) {
+        TrieNode curr = root;
+        for (char c : word.toCharArray()) {
+            if (curr.children[c - 'a'] == null) {
+                curr.children[c - 'a'] = new TrieNode();
+            }
+            curr = curr.children[c - 'a'];
+        }
+        curr.isWord = true;
+    }
+}
+
+public class Solution {
+    public int minExtraChar(String s, String[] dictionary) {
+        Trie trie = new Trie();
+        for (String word : dictionary) {
+            trie.addWord(word);
+        }
+
+        int[] dp = new int[s.length() + 1];
+        Arrays.fill(dp, -1);
+
+        return dfs(0, s, trie, dp);
+    }
+
+    private int dfs(int i, String s, Trie trie, int[] dp) {
+        if (i == s.length()) return 0;
+        if (dp[i] != -1) return dp[i];
+
+        int res = 1 + dfs(i + 1, s, trie, dp);
+        TrieNode curr = trie.root;
+
+        for (int j = i; j < s.length(); j++) {
+            if (curr.children[s.charAt(j) - 'a'] == null) break;
+            curr = curr.children[s.charAt(j) - 'a'];
+            if (curr.isWord) {
+                res = Math.min(res, dfs(j + 1, s, trie, dp));
+            }
+        }
+
+        dp[i] = res;
+        return res;
+    }
+}
+```
+
+```cpp
+class TrieNode {
+public:
+    TrieNode* children[26];
+    bool isWord;
+
+    TrieNode() {
+        for (int i = 0; i < 26; ++i) children[i] = nullptr;
+        isWord = false;
+    }
+};
+
+class Trie {
+public:
+    TrieNode* root;
+
+    Trie() {
+        root = new TrieNode();
+    }
+
+    void addWord(const string& word) {
+        TrieNode* curr = root;
+        for (char c : word) {
+            if (!curr->children[c - 'a']) {
+                curr->children[c - 'a'] = new TrieNode();
+            }
+            curr = curr->children[c - 'a'];
+        }
+        curr->isWord = true;
+    }
+};
+
+class Solution {
+public:
+    int minExtraChar(string s, vector<string>& dictionary) {
+        Trie trie;
+        for (const string& word : dictionary) {
+            trie.addWord(word);
+        }
+
+        vector<int> dp(s.size() + 1, -1);
+        return dfs(0, s, trie, dp);
+    }
+
+private:
+    int dfs(int i, const string& s, Trie& trie, vector<int>& dp) {
+        if (i == s.size()) return 0;
+        if (dp[i] != -1) return dp[i];
+
+        int res = 1 + dfs(i + 1, s, trie, dp);
+        TrieNode* curr = trie.root;
+
+        for (int j = i; j < s.size(); ++j) {
+            if (!curr->children[s[j] - 'a']) break;
+            curr = curr->children[s[j] - 'a'];
+            if (curr->isWord) {
+                res = min(res, dfs(j + 1, s, trie, dp));
+            }
+        }
+
+        dp[i] = res;
+        return res;
+    }
+};
+```
+
+```javascript
+class TrieNode {
+    constructor() {
+        this.children = {};
+        this.isWord = false;
+    }
+}
+
+class Trie {
+    constructor() {
+        this.root = new TrieNode();
+    }
+
+    /**
+     * @param {string} word
+     * @return {void}
+    */
+    addWord(word) {
+        let curr = this.root;
+        for (const c of word) {
+            if (!curr.children[c]) {
+                curr.children[c] = new TrieNode();
+            }
+            curr = curr.children[c];
+        }
+        curr.isWord = true;
+    }
+}
+
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string[]} dictionary
+     * @return {number}
+     */
+    minExtraChar(s, dictionary) {
+        const trie = new Trie();
+        for (const word of dictionary) {
+            trie.addWord(word);
+        }
+
+        const dp = Array(s.length + 1).fill(-1);
+
+        const dfs = (i) => {
+            if (i === s.length) return 0;
+            if (dp[i] !== -1) return dp[i];
+
+            let res = 1 + dfs(i + 1);
+            let curr = trie.root;
+
+            for (let j = i; j < s.length; j++) {
+                if (!curr.children[s[j]]) break;
+                curr = curr.children[s[j]];
+                if (curr.isWord) {
+                    res = Math.min(res, dfs(j + 1));
+                }
+            }
+
+            dp[i] = res;
+            return res;
+        };
+
+        return dfs(0);
+    }
+}
+```
+
+```csharp
+public class TrieNode {
+    public TrieNode[] Children = new TrieNode[26];
+    public bool IsWord = false;
+}
+
+public class Trie {
+    public TrieNode Root = new TrieNode();
+
+    public void AddWord(string word) {
+        TrieNode curr = Root;
+        foreach (char c in word) {
+            int idx = c - 'a';
+            if (curr.Children[idx] == null) {
+                curr.Children[idx] = new TrieNode();
+            }
+            curr = curr.Children[idx];
+        }
+        curr.IsWord = true;
+    }
+}
+
+public class Solution {
+    public int MinExtraChar(string s, string[] dictionary) {
+        Trie trie = new Trie();
+        foreach (string word in dictionary) {
+            trie.AddWord(word);
+        }
+
+        int[] dp = new int[s.Length + 1];
+        Array.Fill(dp, -1);
+
+        return Dfs(0, s, trie, dp);
+    }
+
+    private int Dfs(int i, string s, Trie trie, int[] dp) {
+        if (i == s.Length) return 0;
+        if (dp[i] != -1) return dp[i];
+
+        int res = 1 + Dfs(i + 1, s, trie, dp);
+        TrieNode curr = trie.Root;
+
+        for (int j = i; j < s.Length; j++) {
+            int idx = s[j] - 'a';
+            if (curr.Children[idx] == null) break;
+            curr = curr.Children[idx];
+            if (curr.IsWord) {
+                res = Math.Min(res, Dfs(j + 1, s, trie, dp));
+            }
+        }
+
+        dp[i] = res;
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 + m * k)$
+* Space complexity: $O(n + m * k)$
+
+> Where $n$ is the length of the string $s$, $m$ is the number of words in the dictionary, and $k$ is the average length of a word in the dictionary.
+
+---
+
+## 7. Dynamic Programming (Bottom-Up) Using Trie
+
+::tabs-start
+
+```python
+class TrieNode:
+    def __init__(self):
+        self.children = {}
+        self.isWord = False
+
+class Trie:
+    def __init__(self):
+        self.root = TrieNode()
+    
+    def addWord(self, word):
+        curr = self.root
+        for c in word:
+            if c not in curr.children:
+                curr.children[c] = TrieNode()
+            curr = curr.children[c]
+        curr.isWord = True
+
+class Solution:
+    def minExtraChar(self, s: str, dictionary: List[str]) -> int:
+        trie = Trie()
+        for w in dictionary:
+            trie.addWord(w)
+
+        n = len(s)
+        dp = [0] * (n + 1)
+
+        for i in range(n - 1, -1, -1):
+            dp[i] = 1 + dp[i + 1]
+            curr = trie.root
+            for j in range(i, n):
+                if s[j] not in curr.children:
+                    break
+                curr = curr.children[s[j]]
+                if curr.isWord:
+                    dp[i] = min(dp[i], dp[j + 1])
+
+        return dp[0]
+```
+
+```java
+class TrieNode {
+    TrieNode[] children;
+    boolean isWord;
+
+    TrieNode() {
+        children = new TrieNode[26];
+        isWord = false;
+    }
+}
+
+class Trie {
+    TrieNode root;
+
+    Trie() {
+        root = new TrieNode();
+    }
+
+    void addWord(String word) {
+        TrieNode curr = root;
+        for (char c : word.toCharArray()) {
+            if (curr.children[c - 'a'] == null) {
+                curr.children[c - 'a'] = new TrieNode();
+            }
+            curr = curr.children[c - 'a'];
+        }
+        curr.isWord = true;
+    }
+}
+
+public class Solution {
+    public int minExtraChar(String s, String[] dictionary) {
+        Trie trie = new Trie();
+        for (String word : dictionary) {
+            trie.addWord(word);
+        }
+
+        int n = s.length();
+        int[] dp = new int[n + 1];
+        for (int i = n - 1; i >= 0; i--) {
+            dp[i] = 1 + dp[i + 1];
+            TrieNode curr = trie.root;
+
+            for (int j = i; j < n; j++) {
+                if (curr.children[s.charAt(j) - 'a'] == null) break;
+                curr = curr.children[s.charAt(j) - 'a'];
+                if (curr.isWord) {
+                    dp[i] = Math.min(dp[i], dp[j + 1]);
+                }
+            }
+        }
+
+        return dp[0];
+    }
+}
+```
+
+```cpp
+class TrieNode {
+public:
+    TrieNode* children[26];
+    bool isWord;
+
+    TrieNode() {
+        for (int i = 0; i < 26; ++i) children[i] = nullptr;
+        isWord = false;
+    }
+};
+
+class Trie {
+public:
+    TrieNode* root;
+
+    Trie() {
+        root = new TrieNode();
+    }
+
+    void addWord(const string& word) {
+        TrieNode* curr = root;
+        for (char c : word) {
+            if (!curr->children[c - 'a']) {
+                curr->children[c - 'a'] = new TrieNode();
+            }
+            curr = curr->children[c - 'a'];
+        }
+        curr->isWord = true;
+    }
+};
+
+class Solution {
+public:
+    int minExtraChar(string s, vector<string>& dictionary) {
+        Trie trie;
+        for (const string& word : dictionary) {
+            trie.addWord(word);
+        }
+
+        int n = s.size();
+        vector<int> dp(n + 1);
+        for (int i = n - 1; i >= 0; --i) {
+            dp[i] = 1 + dp[i + 1];
+            TrieNode* curr = trie.root;
+
+            for (int j = i; j < n; ++j) {
+                if (!curr->children[s[j] - 'a']) break;
+                curr = curr->children[s[j] - 'a'];
+                if (curr->isWord) {
+                    dp[i] = min(dp[i], dp[j + 1]);
+                }
+            }
+        }
+
+        return dp[0];
+    }
+};
+```
+
+```javascript
+class TrieNode {
+    constructor() {
+        this.children = {};
+        this.isWord = false;
+    }
+}
+
+class Trie {
+    constructor() {
+        this.root = new TrieNode();
+    }
+
+    /**
+     * @param {string} word
+     * @return {void}
+    */
+    addWord(word) {
+        let curr = this.root;
+        for (const c of word) {
+            if (!curr.children[c]) {
+                curr.children[c] = new TrieNode();
+            }
+            curr = curr.children[c];
+        }
+        curr.isWord = true;
+    }
+}
+
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string[]} dictionary
+     * @return {number}
+     */
+    minExtraChar(s, dictionary) {
+        const trie = new Trie();
+        for (const word of dictionary) {
+            trie.addWord(word);
+        }
+
+        const n = s.length;
+        const dp = new Int32Array(n + 1);
+        for (let i = n - 1; i >= 0; i--) {
+            dp[i] = 1 + dp[i + 1];
+            let curr = trie.root;
+
+            for (let j = i; j < n; j++) {
+                if (!curr.children[s[j]]) break;
+                curr = curr.children[s[j]];
+                if (curr.isWord) {
+                    dp[i] = Math.min(dp[i], dp[j + 1]);
+                }
+            }
+        }
+
+        return dp[0];
+    }
+}
+```
+
+```csharp
+public class TrieNode {
+    public TrieNode[] Children = new TrieNode[26];
+    public bool IsWord = false;
+}
+
+public class Trie {
+    public TrieNode Root = new TrieNode();
+
+    public void AddWord(string word) {
+        TrieNode curr = Root;
+        foreach (char c in word) {
+            int idx = c - 'a';
+            if (curr.Children[idx] == null) {
+                curr.Children[idx] = new TrieNode();
+            }
+            curr = curr.Children[idx];
+        }
+        curr.IsWord = true;
+    }
+}
+
+public class Solution {
+    public int MinExtraChar(string s, string[] dictionary) {
+        Trie trie = new Trie();
+        foreach (string word in dictionary) {
+            trie.AddWord(word);
+        }
+
+        int n = s.Length;
+        int[] dp = new int[n + 1];
+
+        for (int i = n - 1; i >= 0; i--) {
+            dp[i] = 1 + dp[i + 1];
+            TrieNode curr = trie.Root;
+
+            for (int j = i; j < n; j++) {
+                int idx = s[j] - 'a';
+                if (curr.Children[idx] == null) break;
+                curr = curr.Children[idx];
+                if (curr.IsWord) {
+                    dp[i] = Math.Min(dp[i], dp[j + 1]);
+                }
+            }
+        }
+
+        return dp[0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 + m * k)$
+* Space complexity: $O(n + m * k)$
+
+> Where $n$ is the length of the string $s$, $m$ is the number of words in the dictionary, and $k$ is the average length of a word in the dictionary.
\ No newline at end of file
diff --git a/articles/find-all-anagrams-in-a-string.md b/articles/find-all-anagrams-in-a-string.md
new file mode 100644
index 000000000..4201b94ed
--- /dev/null
+++ b/articles/find-all-anagrams-in-a-string.md
@@ -0,0 +1,581 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def findAnagrams(self, s: str, p: str) -> List[int]:
+        n, m = len(s), len(p)
+        p = sorted(p)
+        res = []
+        for i in range(n - m + 1):
+            sub = sorted(s[i : i + m])
+            if sub == p:
+                res.append(i)
+        return res
+```
+
+```java
+public class Solution {
+    public List<Integer> findAnagrams(String s, String p) {
+        int n = s.length(), m = p.length();
+        List<Integer> res = new ArrayList<>();
+        char[] pArr = p.toCharArray();
+        Arrays.sort(pArr);
+        String sortedP = new String(pArr);
+
+        for (int i = 0; i <= n - m; i++) {
+            char[] subArr = s.substring(i, i + m).toCharArray();
+            Arrays.sort(subArr);
+            if (new String(subArr).equals(sortedP)) {
+                res.add(i);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findAnagrams(string s, string p) {
+        int n = s.size(), m = p.size();
+        vector<int> res;
+        sort(p.begin(), p.end());
+
+        for (int i = 0; i <= n - m; i++) {
+            string sub = s.substr(i, m);
+            sort(sub.begin(), sub.end());
+            if (sub == p) {
+                res.push_back(i);
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string} p
+     * @return {number[]}
+     */
+    findAnagrams(s, p) {
+        const n = s.length, m = p.length;
+        const res = [];
+        const sortedP = p.split('').sort().join('');
+
+        for (let i = 0; i <= n - m; i++) {
+            const sub = s.substring(i, i + m).split('').sort().join('');
+            if (sub === sortedP) {
+                res.push(i);
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m \log m)$
+* Space complexity: $O(m)$
+
+> Where $n$ is the length of the string $s$ and $m$ is the length of the string $p$.
+
+---
+
+## 2. Prefix Count + Sliding Window
+
+::tabs-start
+
+```python
+class Solution:
+    def findAnagrams(self, s: str, p: str) -> List[int]:
+        n, m = len(s), len(p)
+        if m > n:
+            return []
+        pCount = [0] * 26
+        for c in p:
+            pCount[ord(c) - ord('a')] += 1
+
+        prefix = [[0] * 26 for _ in range(n + 1)]
+        for i in range(1, n + 1):
+            for j in range(26):
+                prefix[i][j] = prefix[i - 1][j]
+            prefix[i][ord(s[i - 1]) - ord('a')] += 1
+
+        i, j = 0, m - 1
+        res = []
+        while j < n:
+            isValid = True
+            for c in range(26):
+                if prefix[j + 1][c] - prefix[i][c] != pCount[c]:
+                    isValid = False
+                    break
+            if isValid:
+                res.append(i)
+            i += 1
+            j += 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public List<Integer> findAnagrams(String s, String p) {
+        int n = s.length(), m = p.length();
+        if (m > n) return new ArrayList<>();
+
+        int[] pCount = new int[26];
+        for (char c : p.toCharArray()) {
+            pCount[c - 'a']++;
+        }
+
+        int[][] prefix = new int[n + 1][26];
+        for (int i = 1; i <= n; i++) {
+            System.arraycopy(prefix[i - 1], 0, prefix[i], 0, 26);
+            prefix[i][s.charAt(i - 1) - 'a']++;
+        }
+
+        List<Integer> res = new ArrayList<>();
+        int i = 0, j = m - 1;
+        while (j < n) {
+            boolean isValid = true;
+            for (int c = 0; c < 26; c++) {
+                if (prefix[j + 1][c] - prefix[i][c] != pCount[c]) {
+                    isValid = false;
+                    break;
+                }
+            }
+            if (isValid) res.add(i);
+            i++;
+            j++;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findAnagrams(string s, string p) {
+        int n = s.size(), m = p.size();
+        if (m > n) return {};
+
+        vector<int> pCount(26, 0);
+        for (char c : p) pCount[c - 'a']++;
+
+        vector<vector<int>> prefix(n + 1, vector<int>(26, 0));
+        for (int i = 1; i <= n; i++) {
+            prefix[i] = prefix[i - 1];
+            prefix[i][s[i - 1] - 'a']++;
+        }
+
+        vector<int> res;
+        int i = 0, j = m - 1;
+        while (j < n) {
+            bool isValid = true;
+            for (int c = 0; c < 26; c++) {
+                if (prefix[j + 1][c] - prefix[i][c] != pCount[c]) {
+                    isValid = false;
+                    break;
+                }
+            }
+            if (isValid) res.push_back(i);
+            i++;
+            j++;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string} p
+     * @return {number[]}
+     */
+    findAnagrams(s, p) {
+        const n = s.length, m = p.length;
+        if (m > n) return [];
+
+        const pCount = Array(26).fill(0);
+        for (const c of p) {
+            pCount[c.charCodeAt(0) - 97]++;
+        }
+
+        const prefix = Array.from({ length: n + 1 }, () => Array(26).fill(0));
+        for (let i = 1; i <= n; i++) {
+            for (let j = 0; j < 26; j++) {
+                prefix[i][j] = prefix[i - 1][j];
+            }
+            prefix[i][s.charCodeAt(i - 1) - 97]++;
+        }
+
+        const res = [];
+        let i = 0, j = m - 1;
+        while (j < n) {
+            let isValid = true;
+            for (let c = 0; c < 26; c++) {
+                if (prefix[j + 1][c] - prefix[i][c] !== pCount[c]) {
+                    isValid = false;
+                    break;
+                }
+            }
+            if (isValid) res.push(i);
+            i++;
+            j++;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the length of the string $s$ and $m$ is the length of the string $p$.
+
+---
+
+## 3. Sliding Window
+
+::tabs-start
+
+```python
+class Solution:
+    def findAnagrams(self, s: str, p: str) -> List[int]:
+        if len(p) > len(s): return []
+        pCount, sCount = {}, {}
+        for i in range(len(p)):
+            pCount[p[i]] = 1 + pCount.get(p[i], 0)
+            sCount[s[i]] = 1+ sCount.get(s[i], 0)
+
+        res = [0] if sCount == pCount else []
+        l = 0
+        for r in range(len(p), len(s)):
+            sCount[s[r]] = 1+ sCount.get(s[r], 0)
+            sCount[s[l]] -= 1
+
+            if sCount[s[l]] == 0:
+                sCount.pop(s[l])
+            l += 1
+            if sCount == pCount:
+                res.append(l)
+        return res
+```
+
+```java
+public class Solution {
+    public List<Integer> findAnagrams(String s, String p) {
+        if (p.length() > s.length()) return new ArrayList<>();
+        
+        int[] pCount = new int[26];
+        int[] sCount = new int[26];
+        
+        for (char c : p.toCharArray()) {
+            pCount[c - 'a']++;
+        }
+        for (int i = 0; i < p.length(); i++) {
+            sCount[s.charAt(i) - 'a']++;
+        }
+        
+        List<Integer> res = new ArrayList<>();
+        if (Arrays.equals(pCount, sCount)) res.add(0);
+        
+        int l = 0;
+        for (int r = p.length(); r < s.length(); r++) {
+            sCount[s.charAt(r) - 'a']++;
+            sCount[s.charAt(l) - 'a']--;
+            l++;
+            if (Arrays.equals(pCount, sCount)) {
+                res.add(l);
+            }
+        }
+        
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findAnagrams(string s, string p) {
+        if (p.size() > s.size()) return {};
+
+        vector<int> pCount(26, 0), sCount(26, 0);
+        for (char c : p) {
+            pCount[c - 'a']++;
+        }
+        for (int i = 0; i < p.size(); i++) {
+            sCount[s[i] - 'a']++;
+        }
+
+        vector<int> res;
+        if (pCount == sCount) res.push_back(0);
+
+        int l = 0;
+        for (int r = p.size(); r < s.size(); r++) {
+            sCount[s[r] - 'a']++;
+            sCount[s[l] - 'a']--;
+            l++;
+            if (pCount == sCount) {
+                res.push_back(l);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string} p
+     * @return {number[]}
+     */
+    findAnagrams(s, p) {
+        if (p.length > s.length) return [];
+
+        const pCount = new Array(26).fill(0);
+        const sCount = new Array(26).fill(0);
+        
+        for (const char of p) {
+            pCount[char.charCodeAt(0) - 97]++;
+        }
+        for (let i = 0; i < p.length; i++) {
+            sCount[s.charCodeAt(i) - 97]++;
+        }
+
+        const res = [];
+        if (pCount.toString() === sCount.toString()) res.push(0);
+
+        let l = 0;
+        for (let r = p.length; r < s.length; r++) {
+            sCount[s.charCodeAt(r) - 97]++;
+            sCount[s.charCodeAt(l) - 97]--;
+            l++;
+            if (pCount.toString() === sCount.toString()) {
+                res.push(l);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(1)$ since we have at most $26$ different characters.
+
+> Where $n$ is the length of the string $s$ and $m$ is the length of the string $p$.
+
+---
+
+## 4. Sliding Window (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def findAnagrams(self, s: str, p: str) -> List[int]:
+        n, m = len(s), len(p)
+        if m > n:
+            return []
+
+        pCount = [0] * 26
+        sCount = [0] * 26
+        for i in range(m):
+            pCount[ord(p[i]) - ord('a')] += 1
+            sCount[ord(s[i]) - ord('a')] += 1
+
+        match = sum(1 for i in range(26) if pCount[i] == sCount[i])
+        res = []
+        if match == 26:
+            res.append(0)
+
+        l = 0
+        for r in range(m, n):
+            c = ord(s[l]) - ord('a')
+            if sCount[c] == pCount[c]:
+                match -= 1
+            sCount[c] -= 1
+            l += 1
+            if sCount[c] == pCount[c]:
+                match += 1
+
+            c = ord(s[r]) - ord('a')
+            if sCount[c] == pCount[c]:
+                match -= 1
+            sCount[c] += 1
+            if sCount[c] == pCount[c]:
+                match += 1
+
+            if match == 26:
+                res.append(l)
+
+        return res
+```
+
+```java
+public class Solution {
+    public List<Integer> findAnagrams(String s, String p) {
+        int n = s.length(), m = p.length();
+        if (m > n) return new ArrayList<>();
+
+        int[] pCount = new int[26], sCount = new int[26];
+        for (int i = 0; i < m; i++) {
+            pCount[p.charAt(i) - 'a']++;
+            sCount[s.charAt(i) - 'a']++;
+        }
+
+        int match = 0;
+        for (int i = 0; i < 26; i++) {
+            if (pCount[i] == sCount[i]) match++;
+        }
+
+        List<Integer> res = new ArrayList<>();
+        if (match == 26) res.add(0);
+
+        int l = 0;
+        for (int r = m; r < n; r++) {
+            int c = s.charAt(l) - 'a';
+            if (sCount[c] == pCount[c]) match--;
+            sCount[c]--;
+            l++;
+            if (sCount[c] == pCount[c]) match++;
+
+            c = s.charAt(r) - 'a';
+            if (sCount[c] == pCount[c]) match--;
+            sCount[c]++;
+            if (sCount[c] == pCount[c]) match++;
+
+            if (match == 26) res.add(l);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findAnagrams(string s, string p) {
+        int n = s.size(), m = p.size();
+        if (m > n) return {};
+
+        vector<int> pCount(26, 0), sCount(26, 0);
+        for (int i = 0; i < m; i++) {
+            pCount[p[i] - 'a']++;
+            sCount[s[i] - 'a']++;
+        }
+
+        int match = 0;
+        for (int i = 0; i < 26; i++) {
+            if (pCount[i] == sCount[i]) match++;
+        }
+
+        vector<int> res;
+        if (match == 26) res.push_back(0);
+
+        int l = 0;
+        for (int r = m; r < n; r++) {
+            int c = s[l] - 'a';
+            if (sCount[c] == pCount[c]) match--;
+            sCount[c]--;
+            l++;
+            if (sCount[c] == pCount[c]) match++;
+
+            c = s[r] - 'a';
+            if (sCount[c] == pCount[c]) match--;
+            sCount[c]++;
+            if (sCount[c] == pCount[c]) match++;
+
+            if (match == 26) res.push_back(l);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string} p
+     * @return {number[]}
+     */
+    findAnagrams(s, p) {
+        const n = s.length, m = p.length;
+        if (m > n) return [];
+
+        const pCount = new Array(26).fill(0);
+        const sCount = new Array(26).fill(0);
+
+        for (let i = 0; i < m; i++) {
+            pCount[p.charCodeAt(i) - 97]++;
+            sCount[s.charCodeAt(i) - 97]++;
+        }
+
+        let match = 0;
+        for (let i = 0; i < 26; i++) {
+            if (pCount[i] === sCount[i]) match++;
+        }
+
+        const res = [];
+        if (match === 26) res.push(0);
+
+        let l = 0;
+        for (let r = m; r < n; r++) {
+            let c = s.charCodeAt(l) - 97;
+            if (sCount[c] === pCount[c]) match--;
+            sCount[c]--;
+            l++;
+            if (sCount[c] === pCount[c]) match++;
+
+            c = s.charCodeAt(r) - 97;
+            if (sCount[c] === pCount[c]) match--;
+            sCount[c]++;
+            if (sCount[c] === pCount[c]) match++;
+
+            if (match === 26) res.push(l);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(1)$ since we have at most $26$ different characters.
+
+> Where $n$ is the length of the string $s$ and $m$ is the length of the string $p$.
\ No newline at end of file
diff --git a/articles/find-all-duplicates-in-an-array.md b/articles/find-all-duplicates-in-an-array.md
new file mode 100644
index 000000000..3d1f99fde
--- /dev/null
+++ b/articles/find-all-duplicates-in-an-array.md
@@ -0,0 +1,440 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def findDuplicates(self, nums: List[int]) -> List[int]:
+        n = len(nums)
+        res = []
+
+        for i in range(n):
+            for j in range(i + 1, n):
+                if nums[i] == nums[j]:
+                    res.append(nums[i])
+                    break
+
+        return res
+```
+
+```java
+public class Solution {
+    public List<Integer> findDuplicates(int[] nums) {
+        int n = nums.length;
+        List<Integer> res = new ArrayList<>();
+
+        for (int i = 0; i < n; i++) {
+            for (int j = i + 1; j < n; j++) {
+                if (nums[i] == nums[j]) {
+                    res.add(nums[i]);
+                    break;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findDuplicates(vector<int>& nums) {
+        int n = nums.size();
+        vector<int> res;
+
+        for (int i = 0; i < n; i++) {
+            for (int j = i + 1; j < n; j++) {
+                if (nums[i] == nums[j]) {
+                    res.push_back(nums[i]);
+                    break;
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    findDuplicates(nums) {
+        const n = nums.length;
+        const res = [];
+
+        for (let i = 0; i < n; i++) {
+            for (let j = i + 1; j < n; j++) {
+                if (nums[i] === nums[j]) {
+                    res.push(nums[i]);
+                    break;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 2. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def findDuplicates(self, nums: List[int]) -> List[int]:
+        nums.sort()
+        res = []
+
+        for i in range(len(nums) - 1):
+            if nums[i] == nums[i + 1]:
+                res.append(nums[i])
+
+        return res
+```
+
+```java
+public class Solution {
+    public List<Integer> findDuplicates(int[] nums) {
+        Arrays.sort(nums);
+        List<Integer> res = new ArrayList<>();
+
+        for (int i = 0; i < nums.length - 1; i++) {
+            if (nums[i] == nums[i + 1]) {
+                res.add(nums[i]);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findDuplicates(vector<int>& nums) {
+        sort(nums.begin(), nums.end());
+        vector<int> res;
+
+        for (int i = 0; i < nums.size() - 1; i++) {
+            if (nums[i] == nums[i + 1]) {
+                res.push_back(nums[i]);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    findDuplicates(nums) {
+        nums.sort((a, b) => a - b);
+        const res = [];
+
+        for (let i = 0; i < nums.length - 1; i++) {
+            if (nums[i] === nums[i + 1]) {
+                res.push(nums[i]);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 3. Hash Set
+
+::tabs-start
+
+```python
+class Solution:
+    def findDuplicates(self, nums: List[int]) -> List[int]:
+        seen = set()
+        res = []
+        for num in nums:
+            if num in seen:
+                res.append(num)
+            else:
+                seen.add(num)
+        return res
+```
+
+```java
+public class Solution {
+    public List<Integer> findDuplicates(int[] nums) {
+        Set<Integer> seen = new HashSet<>();
+        List<Integer> res = new ArrayList<>();
+
+        for (int num : nums) {
+            if (seen.contains(num)) {
+                res.add(num);
+            } else {
+                seen.add(num);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findDuplicates(vector<int>& nums) {
+        unordered_set<int> seen;
+        vector<int> res;
+
+        for (int num : nums) {
+            if (seen.count(num)) {
+                res.push_back(num);
+            } else {
+                seen.insert(num);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    findDuplicates(nums) {
+        const seen = new Set();
+        const res = [];
+
+        for (const num of nums) {
+            if (seen.has(num)) {
+                res.push(num);
+            } else {
+                seen.add(num);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def findDuplicates(self, nums: List[int]) -> List[int]:
+        count = Counter(nums)
+        res = []
+
+        for num in count:
+            if count[num] == 2:
+                res.append(num)
+        
+        return res
+```
+
+```java
+public class Solution {
+    public List<Integer> findDuplicates(int[] nums) {
+        Map<Integer, Integer> count = new HashMap<>();
+        List<Integer> res = new ArrayList<>();
+
+        for (int num : nums) {
+            count.put(num, count.getOrDefault(num, 0) + 1);
+        }
+
+        for (int num : count.keySet()) {
+            if (count.get(num) == 2) {
+                res.add(num);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findDuplicates(vector<int>& nums) {
+        unordered_map<int, int> count;
+        vector<int> res;
+
+        for (int num : nums) {
+            count[num]++;
+        }
+
+        for (auto& [num, freq] : count) {
+            if (freq == 2) {
+                res.push_back(num);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    findDuplicates(nums) {
+        const count = new Map();
+        const res = [];
+
+        for (const num of nums) {
+            count.set(num, (count.get(num) || 0) + 1);
+        }
+
+        for (const [num, freq] of count.entries()) {
+            if (freq === 2) {
+                res.push(num);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 5. Negative Marking
+
+::tabs-start
+
+```python
+class Solution:
+    def findDuplicates(self, nums: List[int]) -> List[int]:
+        res = []
+
+        for num in nums:
+            idx = abs(num) - 1
+            if nums[idx] < 0:
+                res.append(abs(num))
+            nums[idx] = -nums[idx]
+        
+        return res
+```
+
+```java
+public class Solution {
+    public List<Integer> findDuplicates(int[] nums) {
+        List<Integer> res = new ArrayList<>();
+
+        for (int num : nums) {
+            int idx = Math.abs(num) - 1;
+            if (nums[idx] < 0) {
+                res.add(Math.abs(num));
+            }
+            nums[idx] = -nums[idx];
+        }
+        
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findDuplicates(vector<int>& nums) {
+        vector<int> res;
+
+        for (int num : nums) {
+            int idx = abs(num) - 1;
+            if (nums[idx] < 0) {
+                res.push_back(abs(num));
+            }
+            nums[idx] = -nums[idx];
+        }
+        
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    findDuplicates(nums) {
+        const res = [];
+
+        for (let num of nums) {
+            const idx = Math.abs(num) - 1;
+            if (nums[idx] < 0) {
+                res.push(Math.abs(num));
+            }
+            nums[idx] = -nums[idx];
+        }
+        
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/find-all-numbers-disappeared-in-an-array.md b/articles/find-all-numbers-disappeared-in-an-array.md
new file mode 100644
index 000000000..f0462dc4f
--- /dev/null
+++ b/articles/find-all-numbers-disappeared-in-an-array.md
@@ -0,0 +1,358 @@
+## 1. Hash Set
+
+::tabs-start
+
+```python
+class Solution:
+    def findDisappearedNumbers(self, nums: List[int]) -> List[int]:
+        n = len(nums)
+        store = set(range(1, n + 1))
+        
+        for num in nums:
+            store.discard(num)
+        
+        return list(store)
+```
+
+```java
+public class Solution {
+    public List<Integer> findDisappearedNumbers(int[] nums) {
+        int n = nums.length;
+        Set<Integer> store = new HashSet<>();
+        for (int i = 1; i <= n; i++) store.add(i);
+        
+        for (int num : nums) {
+            store.remove(num);
+        }
+        
+        return new ArrayList<>(store);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findDisappearedNumbers(vector<int>& nums) {
+        int n = nums.size();
+        unordered_set<int> store;
+        for (int i = 1; i <= n; i++) store.insert(i);
+        
+        for (int num : nums) {
+            store.erase(num);
+        }
+        
+        vector<int> result(store.begin(), store.end());
+        return result;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    findDisappearedNumbers(nums) {
+        const n = nums.length;
+        const store = new Set();
+        for (let i = 1; i <= n; i++) store.add(i);
+        
+        for (let num of nums) {
+            store.delete(num);
+        }
+        
+        return Array.from(store);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Boolean Array
+
+::tabs-start
+
+```python
+class Solution:
+    def findDisappearedNumbers(self, nums: List[int]) -> List[int]:
+        n = len(nums)
+        mark = [False] * n
+        
+        for num in nums:
+            mark[num - 1] = True
+        
+        res = []
+        for i in range(1, n + 1):
+            if not mark[i - 1]:
+                res.append(i)
+        return res
+```
+
+```java
+public class Solution {
+    public List<Integer> findDisappearedNumbers(int[] nums) {
+        int n = nums.length;
+        boolean[] mark = new boolean[n];
+        
+        for (int num : nums) {
+            mark[num - 1] = true;
+        }
+        
+        List<Integer> res = new ArrayList<>();
+        for (int i = 1; i <= n; i++) {
+            if (!mark[i - 1]) {
+                res.add(i);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findDisappearedNumbers(vector<int>& nums) {
+        int n = nums.size();
+        vector<bool> mark(n, false);
+        
+        for (int num : nums) {
+            mark[num - 1] = true;
+        }
+        
+        vector<int> res;
+        for (int i = 1; i <= n; i++) {
+            if (!mark[i - 1]) {
+                res.push_back(i);
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    findDisappearedNumbers(nums) {
+        const n = nums.length;
+        const mark = new Array(n).fill(false);
+        
+        for (let num of nums) {
+            mark[num - 1] = true;
+        }
+        
+        const res = [];
+        for (let i = 1; i <= n; i++) {
+            if (!mark[i - 1]) {
+                res.push(i);
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def findDisappearedNumbers(self, nums: List[int]) -> List[int]:
+        n = len(nums)
+        nums.sort()
+        
+        res = []
+        idx = 0
+        for num in range(1, n + 1):
+            while idx < n and nums[idx] < num:
+                idx += 1
+            if idx == n or nums[idx] > num:
+                res.append(num)
+        return res
+```
+
+```java
+public class Solution {
+    public List<Integer> findDisappearedNumbers(int[] nums) {
+        int n = nums.length;
+        Arrays.sort(nums);
+        
+        List<Integer> res = new ArrayList<>();
+        int idx = 0;
+        for (int num = 1; num <= n; num++) {
+            while (idx < n && nums[idx] < num) {
+                idx++;
+            }
+            if (idx == n || nums[idx] > num) {
+                res.add(num);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findDisappearedNumbers(vector<int>& nums) {
+        int n = nums.size();
+        sort(nums.begin(), nums.end());
+        
+        vector<int> res;
+        int idx = 0;
+        for (int num = 1; num <= n; num++) {
+            while (idx < n && nums[idx] < num) {
+                idx++;
+            }
+            if (idx == n || nums[idx] > num) {
+                res.push_back(num);
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    findDisappearedNumbers(nums) {
+        nums.sort((a, b) => a - b);
+        
+        const res = [];
+        let idx = 0;
+        for (let num = 1; num <= nums.length; num++) {
+            while (idx < nums.length && nums[idx] < num) {
+                idx++;
+            }
+            if (idx === nums.length || nums[idx] > num) {
+                res.push(num);
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 4. Negative Marking
+
+::tabs-start
+
+```python
+class Solution:
+    def findDisappearedNumbers(self, nums: List[int]) -> List[int]:
+        for num in nums:
+            i = abs(num) - 1
+            nums[i] = -1 * abs(nums[i]) 
+
+        res = []
+        for i, num in enumerate(nums):
+            if num > 0:
+                res.append(i + 1)
+        return res 
+```
+
+```java
+public class Solution {
+    public List<Integer> findDisappearedNumbers(int[] nums) {
+        for (int num : nums) {
+            int i = Math.abs(num) - 1;
+            nums[i] = -Math.abs(nums[i]);
+        }
+        
+        List<Integer> res = new ArrayList<>();
+        for (int i = 0; i < nums.length; i++) {
+            if (nums[i] > 0) {
+                res.add(i + 1);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findDisappearedNumbers(vector<int>& nums) {
+        for (int num : nums) {
+            int i = abs(num) - 1;
+            nums[i] = -abs(nums[i]);
+        }
+        
+        vector<int> res;
+        for (int i = 0; i < nums.size(); i++) {
+            if (nums[i] > 0) {
+                res.push_back(i + 1);
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    findDisappearedNumbers(nums) {
+        for (let num of nums) {
+            let i = Math.abs(num) - 1;
+            nums[i] = -Math.abs(nums[i]);
+        }
+        
+        const res = [];
+        for (let i = 0; i < nums.length; i++) {
+            if (nums[i] > 0) {
+                res.push(i + 1);
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ since we modified the input array without using extra space.
\ No newline at end of file
diff --git a/articles/find-all-people-with-secret.md b/articles/find-all-people-with-secret.md
new file mode 100644
index 000000000..1d1b58e20
--- /dev/null
+++ b/articles/find-all-people-with-secret.md
@@ -0,0 +1,834 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def findAllPeople(self, n: int, meetings: list[list[int]], firstPerson: int) -> list[int]:
+        secrets = set([0, firstPerson])  # People with secret
+        time_map = {}  # time -> adjacency list meetings
+
+        for src, dst, t in meetings:
+            if t not in time_map:
+                time_map[t] = defaultdict(list)
+            time_map[t][src].append(dst)
+            time_map[t][dst].append(src)
+
+        def dfs(src, adj):
+            if src in visit:
+                return
+            visit.add(src)
+            secrets.add(src)
+            for nei in adj[src]:
+                dfs(nei, adj)
+
+        for t in sorted(time_map.keys()):
+            visit = set()
+            for src in time_map[t]:
+                if src in secrets:
+                    dfs(src, time_map[t])
+
+        return list(secrets)
+```
+
+```java
+public class Solution {
+    private Set<Integer> secrets, visit;
+
+    public List<Integer> findAllPeople(int n, int[][] meetings, int firstPerson) {
+        secrets = new HashSet<>();
+        visit = new HashSet<>();
+        secrets.add(0);
+        secrets.add(firstPerson);
+        Map<Integer, Map<Integer, List<Integer>>> time_map = new HashMap<>();
+
+        for (int[] meet : meetings) {
+            int src = meet[0], dst = meet[1], t = meet[2];
+            time_map.putIfAbsent(t, new HashMap<>());
+            time_map.get(t).putIfAbsent(src, new ArrayList<>());
+            time_map.get(t).putIfAbsent(dst, new ArrayList<>());
+            time_map.get(t).get(src).add(dst);
+            time_map.get(t).get(dst).add(src);
+        }
+
+        List<Integer> timeKeys = new ArrayList<>(time_map.keySet());
+        Collections.sort(timeKeys);
+        for (int t : timeKeys) {
+            visit = new HashSet<>();
+            for (int src : time_map.get(t).keySet()) {
+                if (secrets.contains(src)) {
+                    dfs(src, time_map.get(t));
+                }
+            }
+        }
+        return new ArrayList<>(secrets);
+    }
+
+    private void dfs(int src, Map<Integer, List<Integer>> adj) {
+        if (!visit.add(src)) return;
+        secrets.add(src);
+        for (int nei : adj.getOrDefault(src, new ArrayList<>())) {
+            dfs(nei, adj);
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    unordered_set<int> secrets, visit;
+
+    vector<int> findAllPeople(int n, vector<vector<int>>& meetings, int firstPerson) {
+        secrets = {0, firstPerson};
+        unordered_map<int, unordered_map<int, vector<int>>> time_map;
+
+        for (auto& meet : meetings) {
+            int src = meet[0], dst = meet[1], t = meet[2];
+            time_map[t][src].push_back(dst);
+            time_map[t][dst].push_back(src);
+        }
+
+        vector<int> timeKeys;
+        for (auto& [t, _] : time_map) {
+            timeKeys.push_back(t);
+        }
+        sort(timeKeys.begin(), timeKeys.end());
+
+        for (int& t : timeKeys) {
+            visit.clear();
+            for (auto& [src, _] : time_map[t]) {
+                if (secrets.count(src)) {
+                    dfs(src, time_map[t]);
+                }
+            }
+        }
+
+        return vector<int>(secrets.begin(), secrets.end());
+    }
+
+private:
+    void dfs(int src, unordered_map<int, vector<int>>& adj) {
+        if (!visit.insert(src).second) return;
+        secrets.insert(src);
+        for (int& nei : adj[src]) {
+            dfs(nei, adj);
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} meetings
+     * @param {number} firstPerson
+     * @return {number[]}
+     */
+    findAllPeople(n, meetings, firstPerson) {
+        const secrets = new Set([0, firstPerson]);
+        let visit = new Set();
+        let time_map = new Map();
+
+        for (let [src, dst, t] of meetings) {
+            if (!time_map.has(t)) time_map.set(t, new Map());
+            if (!time_map.get(t).has(src)) time_map.get(t).set(src, []);
+            if (!time_map.get(t).has(dst)) time_map.get(t).set(dst, []);
+            time_map.get(t).get(src).push(dst);
+            time_map.get(t).get(dst).push(src);
+        }
+        const dfs = (src, adj) => {
+            if (visit.has(src)) return;
+            visit.add(src);
+            secrets.add(src);
+            for (let nei of (adj.get(src) || [])) {
+                dfs(nei, adj);
+            }
+        };
+
+        let timeKeys = [...time_map.keys()].sort((a, b) => a - b);
+        for (let t of timeKeys) {
+            visit.clear();
+            for (let src of time_map.get(t).keys()) {
+                if (secrets.has(src)) {
+                    dfs(src, time_map.get(t));
+                }
+            }
+        }
+
+        return [...secrets];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m \log m + n)$
+* Space complexity: $O(m + n)$
+
+> Where $m$ is the number of meetings and $n$ is the number of people.
+
+---
+
+## 2. Breadth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def findAllPeople(self, n: int, meetings: list[list[int]], firstPerson: int) -> list[int]:
+        secrets = set([0, firstPerson])  # People with secret
+        time_map = {}  # time -> adjacency list meetings
+
+        for src, dst, t in meetings:
+            if t not in time_map:
+                time_map[t] = defaultdict(list)
+            time_map[t][src].append(dst)
+            time_map[t][dst].append(src)
+
+        for t in sorted(time_map.keys()):
+            visit = set()
+            q = deque()
+
+            for src in time_map[t]:
+                if src in secrets:
+                    q.append(src)
+                    visit.add(src)
+
+            while q:
+                node = q.popleft()
+                secrets.add(node)
+                for nei in time_map[t][node]:
+                    if nei not in visit:
+                        visit.add(nei)
+                        q.append(nei)
+
+        return list(secrets)
+```
+
+```java
+public class Solution {
+    public List<Integer> findAllPeople(int n, int[][] meetings, int firstPerson) {
+        Set<Integer> secrets = new HashSet<>();
+        secrets.add(0);
+        secrets.add(firstPerson);
+        TreeMap<Integer, Map<Integer, List<Integer>>> time_map = new TreeMap<>();
+
+        for (int[] meet : meetings) {
+            int src = meet[0], dst = meet[1], t = meet[2];
+            time_map.putIfAbsent(t, new HashMap<>());
+            time_map.get(t).putIfAbsent(src, new ArrayList<>());
+            time_map.get(t).putIfAbsent(dst, new ArrayList<>());
+            time_map.get(t).get(src).add(dst);
+            time_map.get(t).get(dst).add(src);
+        }
+
+        for (int t : time_map.keySet()) {
+            Set<Integer> visit = new HashSet<>();
+            Queue<Integer> q = new LinkedList<>();
+
+            for (int src : time_map.get(t).keySet()) {
+                if (secrets.contains(src)) {
+                    q.offer(src);
+                    visit.add(src);
+                }
+            }
+
+            while (!q.isEmpty()) {
+                int node = q.poll();
+                secrets.add(node);
+                for (int nei : time_map.get(t).get(node)) {
+                    if (!visit.contains(nei)) {
+                        visit.add(nei);
+                        q.offer(nei);
+                    }
+                }
+            }
+        }
+
+        return new ArrayList<>(secrets);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findAllPeople(int n, vector<vector<int>>& meetings, int firstPerson) {
+        unordered_set<int> secrets = {0, firstPerson};
+        map<int, unordered_map<int, vector<int>>> time_map;
+
+        for (auto& meet : meetings) {
+            int src = meet[0], dst = meet[1], t = meet[2];
+            time_map[t][src].push_back(dst);
+            time_map[t][dst].push_back(src);
+        }
+
+        for (auto& [t, adj] : time_map) {
+            unordered_set<int> visit;
+            queue<int> q;
+
+            for (auto& [src, _] : adj) {
+                if (secrets.count(src)) {
+                    q.push(src);
+                    visit.insert(src);
+                }
+            }
+
+            while (!q.empty()) {
+                int node = q.front();
+                q.pop();
+                secrets.insert(node);
+                for (int nei : adj[node]) {
+                    if (!visit.count(nei)) {
+                        visit.insert(nei);
+                        q.push(nei);
+                    }
+                }
+            }
+        }
+
+        return vector<int>(secrets.begin(), secrets.end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} meetings
+     * @param {number} firstPerson
+     * @return {number[]}
+     */
+    findAllPeople(n, meetings, firstPerson) {
+        const secrets = new Set([0, firstPerson]);
+        const time_map = new Map();
+
+        for (let [src, dst, t] of meetings) {
+            if (!time_map.has(t)) time_map.set(t, new Map());
+            if (!time_map.get(t).has(src)) time_map.get(t).set(src, []);
+            if (!time_map.get(t).has(dst)) time_map.get(t).set(dst, []);
+            time_map.get(t).get(src).push(dst);
+            time_map.get(t).get(dst).push(src);
+        }
+
+        for (let t of [...time_map.keys()].sort((a, b) => a - b)) {
+            let visit = new Set();
+            const q = new Queue();
+
+            for (let src of time_map.get(t).keys()) {
+                if (secrets.has(src)) {
+                    q.push(src);
+                    visit.add(src);
+                }
+            }
+
+            while (!q.isEmpty()) {
+                let node = q.pop();
+                secrets.add(node);
+                for (let nei of time_map.get(t).get(node)) {
+                    if (!visit.has(nei)) {
+                        visit.add(nei);
+                        q.push(nei);
+                    }
+                }
+            }
+        }
+
+        return [...secrets];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m \log m + n)$
+* Space complexity: $O(m + n)$
+
+> Where $m$ is the number of meetings and $n$ is the number of people.
+
+---
+
+## 3. Iterative DFS
+
+::tabs-start
+
+```python
+class Solution:
+    def findAllPeople(self, n: int, meetings: list[list[int]], firstPerson: int) -> list[int]:
+        meetings.sort(key=lambda x: x[2])  # Sort by time
+        secrets = [False] * n
+        secrets[0] = secrets[firstPerson] = True
+
+        for _, group in groupby(meetings, key=lambda x: x[2]):
+            adj = defaultdict(list)
+            visited = set()
+
+            for u, v, _ in group:
+                adj[u].append(v)
+                adj[v].append(u)
+                if secrets[u]:
+                    visited.add(u)
+                if secrets[v]:
+                    visited.add(v)
+
+            stack = list(visited)
+            while stack:
+                node = stack.pop()
+                for nei in adj[node]:
+                    if nei not in visited:
+                        visited.add(nei)
+                        stack.append(nei)
+                        secrets[nei] = True
+
+        return [i for i in range(n) if secrets[i]]
+```
+
+```java
+public class Solution {
+    public List<Integer> findAllPeople(int n, int[][] meetings, int firstPerson) {
+        Arrays.sort(meetings, Comparator.comparingInt(a -> a[2]));
+        boolean[] secrets = new boolean[n];
+        secrets[0] = secrets[firstPerson] = true;
+
+        int i = 0, m = meetings.length;
+        while (i < m) {
+            int time = meetings[i][2];
+            Map<Integer, List<Integer>> adj = new HashMap<>();
+            Set<Integer> visited = new HashSet<>();
+
+            while (i < m && meetings[i][2] == time) {
+                int u = meetings[i][0], v = meetings[i][1];
+                adj.computeIfAbsent(u, k -> new ArrayList<>()).add(v);
+                adj.computeIfAbsent(v, k -> new ArrayList<>()).add(u);
+                if (secrets[u]) visited.add(u);
+                if (secrets[v]) visited.add(v);
+                i++;
+            }
+
+            Stack<Integer> stack = new Stack<>();
+            stack.addAll(visited);
+            while (!stack.isEmpty()) {
+                int node = stack.pop();
+                for (int nei : adj.getOrDefault(node, Collections.emptyList())) {
+                    if (!visited.contains(nei)) {
+                        visited.add(nei);
+                        stack.push(nei);
+                        secrets[nei] = true;
+                    }
+                }
+            }
+        }
+
+        List<Integer> res = new ArrayList<>();
+        for (int j = 0; j < n; j++) {
+            if (secrets[j]) res.add(j);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findAllPeople(int n, vector<vector<int>>& meetings, int firstPerson) {
+        sort(meetings.begin(), meetings.end(), [](auto& a, auto& b) {
+            return a[2] < b[2];
+        });
+
+        vector<bool> secrets(n, false);
+        secrets[0] = secrets[firstPerson] = true;
+
+        int i = 0, m = meetings.size();
+        while (i < m) {
+            int time = meetings[i][2];
+            unordered_map<int, vector<int>> adj;
+            unordered_set<int> visited;
+
+            while (i < m && meetings[i][2] == time) {
+                int u = meetings[i][0], v = meetings[i][1];
+                adj[u].push_back(v);
+                adj[v].push_back(u);
+                if (secrets[u]) visited.insert(u);
+                if (secrets[v]) visited.insert(v);
+                i++;
+            }
+
+            stack<int> stack(visited.begin(), visited.end());
+            while (!stack.empty()) {
+                int node = stack.top(); stack.pop();
+                for (int& nei : adj[node]) {
+                    if (!visited.count(nei)) {
+                        visited.insert(nei);
+                        stack.push(nei);
+                        secrets[nei] = true;
+                    }
+                }
+            }
+        }
+
+        vector<int> res;
+        for (int j = 0; j < n; j++) {
+            if (secrets[j]) res.push_back(j);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} meetings
+     * @param {number} firstPerson
+     * @return {number[]}
+     */
+    findAllPeople(n, meetings, firstPerson) {
+        meetings.sort((a, b) => a[2] - b[2]);
+        const secrets = new Array(n).fill(false);
+        secrets[0] = secrets[firstPerson] = true;
+
+        let i = 0, m = meetings.length;
+        while (i < m) {
+            const time = meetings[i][2];
+            const adj = new Map();
+            const visited = new Set();
+
+            while (i < m && meetings[i][2] === time) {
+                const [u, v] = meetings[i];
+                if (!adj.has(u)) adj.set(u, []);
+                if (!adj.has(v)) adj.set(v, []);
+                adj.get(u).push(v);
+                adj.get(v).push(u);
+                if (secrets[u]) visited.add(u);
+                if (secrets[v]) visited.add(v);
+                i++;
+            }
+
+            const stack = [...visited];
+            while (stack.length) {
+                const node = stack.pop();
+                for (const nei of (adj.get(node) || [])) {
+                    if (!visited.has(nei)) {
+                        visited.add(nei);
+                        stack.push(nei);
+                        secrets[nei] = true;
+                    }
+                }
+            }
+        }
+
+        let res = [];
+        for (let i = 0; i < n; i++) {
+            if (secrets[i]) res.push(i);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m \log m + n)$
+* Space complexity: $O(m + n)$
+
+> Where $m$ is the number of meetings and $n$ is the number of people.
+
+---
+
+## 4. Disjoint Set Union
+
+::tabs-start
+
+```python
+class DSU:
+    def __init__(self, n):
+        self.Parent = list(range(n + 1))
+        self.Size = [1] * (n + 1)
+
+    def find(self, node):
+        if self.Parent[node] != node:
+            self.Parent[node] = self.find(self.Parent[node])
+        return self.Parent[node]
+
+    def union(self, u, v):
+        pu, pv = self.find(u), self.find(v)
+        if pu == pv:
+            return False
+        if self.Size[pu] < self.Size[pv]:
+            pu, pv = pv, pu
+        self.Size[pu] += self.Size[pv]
+        self.Parent[pv] = pu
+        return True
+
+    def reset(self, node):
+        self.Parent[node] = node
+        self.Size[node] = 1
+
+class Solution:
+    def findAllPeople(self, n: int, meetings: list[list[int]], firstPerson: int) -> list[int]:
+        meetings.sort(key=lambda x: x[2])  # Sort by time
+        dsu = DSU(n)
+        dsu.union(0, firstPerson)
+
+        for _, group in groupby(meetings, key=lambda x: x[2]):
+            group_nodes = set()
+            for u, v, _ in group:
+                dsu.union(u, v)
+                group_nodes.add(u)
+                group_nodes.add(v)
+
+            for node in group_nodes:
+                if dsu.find(node) != dsu.find(0):
+                    dsu.reset(node)
+
+        return [i for i in range(n) if dsu.find(i) == dsu.find(0)]
+```
+
+```java
+class DSU {
+    int[] Parent, Size;
+
+    DSU(int n) {
+        Parent = new int[n + 1];
+        Size = new int[n + 1];
+        for (int i = 0; i <= n; i++) {
+            Parent[i] = i;
+            Size[i] = 1;
+        }
+    }
+
+    int find(int node) {
+        if (Parent[node] != node) {
+            Parent[node] = find(Parent[node]);
+        }
+        return Parent[node];
+    }
+
+    void union(int u, int v) {
+        int pu = find(u), pv = find(v);
+        if (pu == pv) return;
+        if (Size[pu] < Size[pv]) {
+            int temp = pu;
+            pu = pv;
+            pv = temp;
+        }
+        Size[pu] += Size[pv];
+        Parent[pv] = pu;
+    }
+
+    void reset(int node) {
+        Parent[node] = node;
+        Size[node] = 1;
+    }
+}
+
+public class Solution {
+    public List<Integer> findAllPeople(int n, int[][] meetings, int firstPerson) {
+        Arrays.sort(meetings, Comparator.comparingInt(a -> a[2]));
+        DSU dsu = new DSU(n);
+        dsu.union(0, firstPerson);
+
+        for (int i = 0; i < meetings.length; ) {
+            int time = meetings[i][2];
+            Set<Integer> group = new HashSet<>();
+
+            for (; i < meetings.length && meetings[i][2] == time; i++) {
+                int u = meetings[i][0], v = meetings[i][1];
+                dsu.union(u, v);
+                group.add(u);
+                group.add(v);
+            }
+
+            for (int node : group) {
+                if (dsu.find(node) != dsu.find(0)) {
+                    dsu.reset(node);
+                }
+            }
+        }
+
+        List<Integer> result = new ArrayList<>();
+        for (int i = 0; i < n; i++) {
+            if (dsu.find(i) == dsu.find(0)) result.add(i);
+        }
+        return result;
+    }
+}
+```
+
+```cpp
+class DSU {
+public:
+    vector<int> Parent, Size;
+    
+    DSU(int n) {
+        Parent.resize(n + 1);
+        Size.resize(n + 1, 1);
+        for (int i = 0; i <= n; i++) {
+            Parent[i] = i;
+        }
+    }
+
+    int find(int node) {
+        if (Parent[node] != node) {
+            Parent[node] = find(Parent[node]);
+        }
+        return Parent[node];
+    }
+
+    void unionSets(int u, int v) {
+        int pu = find(u), pv = find(v);
+        if (pu == pv) return;
+        if (Size[pu] < Size[pv]) swap(pu, pv);
+        Size[pu] += Size[pv];
+        Parent[pv] = pu;
+    }
+
+    void reset(int node) {
+        Parent[node] = node;
+        Size[node] = 1;
+    }
+};
+
+class Solution {
+public:
+    vector<int> findAllPeople(int n, vector<vector<int>>& meetings, int firstPerson) {
+        sort(meetings.begin(), meetings.end(), [](auto &a, auto &b) {
+            return a[2] < b[2];
+        });
+        DSU dsu(n);
+        dsu.unionSets(0, firstPerson);
+
+        for (int i = 0; i < meetings.size(); ) {
+            int time = meetings[i][2];
+            unordered_set<int> group;
+
+            for (; i < meetings.size() && meetings[i][2] == time; i++) {
+                int u = meetings[i][0], v = meetings[i][1];
+                dsu.unionSets(u, v);
+                group.insert(u);
+                group.insert(v);
+            }
+
+            for (int node : group) {
+                if (dsu.find(node) != dsu.find(0)) {
+                    dsu.reset(node);
+                }
+            }
+        }
+
+        vector<int> result;
+        for (int i = 0; i < n; i++) {
+            if (dsu.find(i) == dsu.find(0)) result.push_back(i);
+        }
+        return result;
+    }
+};
+```
+
+```javascript
+class DSU {
+    /**
+     * @constructor
+     * @param {number} n
+     */
+    constructor(n) {
+        this.Parent = Array.from({ length: n + 1 }, (_, i) => i);
+        this.Size = Array(n + 1).fill(1);
+    }
+
+    /**
+     * @param {number} node
+     * @return {number}
+     */
+    find(node) {
+        if (this.Parent[node] !== node) {
+            this.Parent[node] = this.find(this.Parent[node]);
+        }
+        return this.Parent[node];
+    }
+
+    /**
+     * @param {number} u
+     * @param {number} v
+     * @return {boolean}
+     */
+    union(u, v) {
+        let pu = this.find(u);
+        let pv = this.find(v);
+        if (pu === pv) return false;
+        if (this.Size[pu] >= this.Size[pv]) {
+            this.Size[pu] += this.Size[pv];
+            this.Parent[pv] = pu;
+        } else {
+            this.Size[pv] += this.Size[pu];
+            this.Parent[pu] = pv;
+        }
+        return true;
+    }
+
+    /**
+     * @param {number} node
+     * @return {void}
+     */
+    reset(node) {
+        this.Parent[node] = node;
+        this.Size[node] = 1;
+    }
+}
+
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} meetings
+     * @param {number} firstPerson
+     * @return {number[]}
+     */
+    findAllPeople(n, meetings, firstPerson) {
+        meetings.sort((a, b) => a[2] - b[2]);
+        let dsu = new DSU(n);
+        dsu.union(0, firstPerson);
+
+        for (let i = 0; i < meetings.length; ) {
+            let time = meetings[i][2];
+            let group = new Set();
+
+            for (; i < meetings.length && meetings[i][2] === time; i++) {
+                let [u, v] = meetings[i];
+                dsu.union(u, v);
+                group.add(u);
+                group.add(v);
+            }
+
+            group.forEach(node => {
+                if (dsu.find(node) !== dsu.find(0)) {
+                    dsu.reset(node);
+                }
+            });
+        }
+
+        return [...Array(n).keys()].filter(i => dsu.find(i) === dsu.find(0));
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m \log m + (m * α(n)))$
+* Space complexity:
+    * $O(n)$ extra space.
+    * $O(m)$ space depending on the sorting algorithm.
+
+> Where $m$ is the number of meetings and $n$ is the number of people.
\ No newline at end of file
diff --git a/articles/find-bottom-left-tree-value.md b/articles/find-bottom-left-tree-value.md
new file mode 100644
index 000000000..c04645674
--- /dev/null
+++ b/articles/find-bottom-left-tree-value.md
@@ -0,0 +1,633 @@
+## 1. Breadth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def findBottomLeftValue(self, root: Optional[TreeNode]) -> int:
+        q = deque([root])
+
+        while q:
+            node = q.popleft()
+            if node.right:
+                q.append(node.right)
+            if node.left:
+                q.append(node.left)
+
+        return node.val
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public int findBottomLeftValue(TreeNode root) {
+        Queue<TreeNode> q = new LinkedList<>();
+        q.offer(root);
+        TreeNode node = null;
+
+        while (!q.isEmpty()) {
+            node = q.poll();
+            if (node.right != null) q.offer(node.right);
+            if (node.left != null) q.offer(node.left);
+        }
+        return node.val;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int findBottomLeftValue(TreeNode* root) {
+        queue<TreeNode*> q;
+        q.push(root);
+        TreeNode* node = nullptr;
+
+        while (!q.empty()) {
+            node = q.front();
+            q.pop();
+            if (node->right) q.push(node->right);
+            if (node->left) q.push(node->left);
+        }
+        return node->val;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number}
+     */
+    findBottomLeftValue(root) {
+        const q = new Queue([root]);
+        let node = null;
+
+        while (!q.isEmpty()) {
+            node = q.pop();
+            if (node.right) q.push(node.right);
+            if (node.left) q.push(node.left);
+        }
+        return node.val;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Depth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def findBottomLeftValue(self, root: Optional[TreeNode]) -> int:
+        self.maxDepth, self.res = -1, root.val
+
+        def dfs(node, depth):
+            if not node:
+                return
+            if depth > self.maxDepth:
+                self.maxDepth, self.res = depth, node.val
+            
+            dfs(node.left, depth + 1)
+            dfs(node.right, depth + 1)
+
+        dfs(root, 0)
+        return self.res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    private int maxDepth = -1;
+    private int res;
+
+    public int findBottomLeftValue(TreeNode root) {
+        res = root.val;
+        dfs(root, 0);
+        return res;
+    }
+
+    private void dfs(TreeNode node, int depth) {
+        if (node == null) return;
+        if (depth > maxDepth) {
+            maxDepth = depth;
+            res = node.val;
+        }
+
+        dfs(node.left, depth + 1);
+        dfs(node.right, depth + 1);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int maxDepth = -1, res;
+
+    int findBottomLeftValue(TreeNode* root) {
+        res = root->val;
+        dfs(root, 0);
+        return res;
+    }
+
+private:
+    void dfs(TreeNode* node, int depth) {
+        if (!node) return;
+        if (depth > maxDepth) {
+            maxDepth = depth;
+            res = node->val;
+        }
+
+        dfs(node->left, depth + 1);
+        dfs(node->right, depth + 1);
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number}
+     */
+    findBottomLeftValue(root) {
+        let maxDepth = -1, res = root.val;
+
+        const dfs = (node, depth) => {
+            if (!node) return;
+            if (depth > maxDepth) {
+                maxDepth = depth;
+                res = node.val;
+            }
+
+            dfs(node.left, depth + 1);
+            dfs(node.right, depth + 1);
+        };
+
+        dfs(root, 0);
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 3. Iterative DFS
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def findBottomLeftValue(self, root: Optional[TreeNode]) -> int:
+        res, maxDepth = root.val, -1
+        stack = [(root, 0)]
+
+        while stack:
+            node, depth = stack.pop()
+            if depth > maxDepth:
+                maxDepth = depth
+                res = node.val
+
+            if node.right:
+                stack.append((node.right, depth + 1))
+            if node.left:
+                stack.append((node.left, depth + 1))
+
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public int findBottomLeftValue(TreeNode root) {
+        int res = root.val, maxDepth = -1;
+        Stack<Pair<TreeNode, Integer>> stack = new Stack<>();
+        stack.push(new Pair<>(root, 0));
+
+        while (!stack.isEmpty()) {
+            Pair<TreeNode, Integer> p = stack.pop();
+            TreeNode node = p.getKey();
+            int depth = p.getValue();
+            if (depth > maxDepth) {
+                maxDepth = depth;
+                res = node.val;
+            }
+
+            if (node.right != null) {
+                stack.push(new Pair<>(node.right, depth + 1));
+            }
+            if (node.left != null) {
+                stack.push(new Pair<>(node.left, depth + 1));
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int findBottomLeftValue(TreeNode* root) {
+        int res = root->val, maxDepth = -1;
+        stack<pair<TreeNode*, int>> stack;
+        stack.push({root, 0});
+
+        while (!stack.empty()) {
+            auto [node, depth] = stack.top();stack.pop();
+            if (depth > maxDepth) {
+                maxDepth = depth;
+                res = node->val;
+            }
+
+            if (node->right) {
+                stack.push({node->right, depth + 1});
+            }
+            if (node->left) {
+                stack.push({node->left, depth + 1});
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number}
+     */
+    findBottomLeftValue(root) {
+        let res = root.val, maxDepth = -1;
+        const stack = [[root, 0]];
+
+        while (stack.length) {
+            const [node, depth] = stack.pop();
+            if (depth > maxDepth) {
+                maxDepth = depth;
+                res = node.val;
+            }
+
+            if (node.right) stack.push([node.right, depth + 1]);
+            if (node.left) stack.push([node.left, depth + 1]);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Morris Traversal
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def findBottomLeftValue(self, root: Optional[TreeNode]) -> int:
+        res, maxDepth, curDepth = root.val, -1, 0
+        cur = root
+
+        while cur:
+            if not cur.left:
+                if curDepth > maxDepth:
+                    maxDepth, res = curDepth, cur.val
+                cur = cur.right
+                curDepth += 1
+            else:
+                prev = cur.left
+                steps = 1
+                while prev.right and prev.right != cur:
+                    prev = prev.right
+                    steps += 1
+
+                if not prev.right:
+                    prev.right = cur
+                    cur = cur.left
+                    curDepth += 1
+                else:
+                    prev.right = None
+                    curDepth -= steps
+                    cur = cur.right
+
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public int findBottomLeftValue(TreeNode root) {
+        int res = root.val, maxDepth = -1, curDepth = 0;
+        TreeNode cur = root;
+
+        while (cur != null) {
+            if (cur.left == null) {
+                if (curDepth > maxDepth) {
+                    maxDepth = curDepth;
+                    res = cur.val;
+                }
+                cur = cur.right;
+                curDepth++;
+            } else {
+                TreeNode prev = cur.left;
+                int steps = 1;
+                while (prev.right != null && prev.right != cur) {
+                    prev = prev.right;
+                    steps++;
+                }
+
+                if (prev.right == null) {
+                    prev.right = cur;
+                    cur = cur.left;
+                    curDepth++;
+                } else {
+                    prev.right = null;
+                    curDepth -= steps;
+                    cur = cur.right;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int findBottomLeftValue(TreeNode* root) {
+        int res = root->val, maxDepth = -1, curDepth = 0;
+        TreeNode* cur = root;
+
+        while (cur) {
+            if (!cur->left) {
+                if (curDepth > maxDepth) {
+                    maxDepth = curDepth;
+                    res = cur->val;
+                }
+                cur = cur->right;
+                curDepth++;
+            } else {
+                TreeNode* prev = cur->left;
+                int steps = 1;
+                while (prev->right && prev->right != cur) {
+                    prev = prev->right;
+                    steps++;
+                }
+
+                if (!prev->right) {
+                    prev->right = cur;
+                    cur = cur->left;
+                    curDepth++;
+                } else {
+                    prev->right = nullptr;
+                    curDepth -= steps;
+                    cur = cur->right;
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number}
+     */
+    findBottomLeftValue(root) {
+        let res = root.val, maxDepth = -1, curDepth = 0;
+        let cur = root;
+
+        while (cur) {
+            if (!cur.left) {
+                if (curDepth > maxDepth) {
+                    maxDepth = curDepth;
+                    res = cur.val;
+                }
+                cur = cur.right;
+                curDepth++;
+            } else {
+                let prev = cur.left, steps = 1;
+                while (prev.right && prev.right !== cur) {
+                    prev = prev.right;
+                    steps++;
+                }
+
+                if (!prev.right) {
+                    prev.right = cur;
+                    cur = cur.left;
+                    curDepth++;
+                } else {
+                    prev.right = null;
+                    curDepth -= steps;
+                    cur = cur.right;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/find-closest-node-to-given-two-nodes.md b/articles/find-closest-node-to-given-two-nodes.md
new file mode 100644
index 000000000..52cb6d365
--- /dev/null
+++ b/articles/find-closest-node-to-given-two-nodes.md
@@ -0,0 +1,669 @@
+## 1. Breadth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def closestMeetingNode(self, edges: list[int], node1: int, node2: int) -> int:
+        adj = defaultdict(list)
+        for i, nei in enumerate(edges):
+            adj[i].append(nei)
+
+        def bfs(src, distMap):
+            q = deque([(src, 0)])
+            distMap[src] = 0
+            while q:
+                node, dist = q.popleft()
+                for nei in adj[node]:
+                    if nei not in distMap:
+                        q.append((nei, dist + 1))
+                        distMap[nei] = dist + 1
+
+        node1Dist, node2Dist = {}, {}
+        bfs(node1, node1Dist)
+        bfs(node2, node2Dist)
+
+        res, resDist = -1, float("inf")
+        for i in range(len(edges)):
+            if i in node1Dist and i in node2Dist:
+                dist = max(node1Dist[i], node2Dist[i])
+                if dist < resDist:
+                    resDist, res = dist, i
+
+        return res
+```
+
+```java
+public class Solution {
+    public int closestMeetingNode(int[] edges, int node1, int node2) {
+        int n = edges.length;
+        List<Integer>[] adj = new ArrayList[n];
+        for (int i = 0; i < n; i++) adj[i] = new ArrayList<>();
+        for (int i = 0; i < n; i++) {
+            if (edges[i] != -1) adj[i].add(edges[i]);
+        }
+
+        int[] node1Dist = bfs(node1, n, adj);
+        int[] node2Dist = bfs(node2, n, adj);
+
+        int res = -1, resDist = Integer.MAX_VALUE;
+        for (int i = 0; i < n; i++) {
+            if (node1Dist[i] != -1 && node2Dist[i] != -1) {
+                int dist = Math.max(node1Dist[i], node2Dist[i]);
+                if (dist < resDist) {
+                    resDist = dist;
+                    res = i;
+                }
+            }
+        }
+        return res;
+    }
+
+    private int[] bfs(int src, int n, List<Integer>[] adj) {
+        int[] distMap = new int[n];
+        Arrays.fill(distMap, -1);
+        Queue<int[]> q = new LinkedList<>();
+        q.offer(new int[]{src, 0});
+        distMap[src] = 0;
+
+        while (!q.isEmpty()) {
+            int[] cur = q.poll();
+            int node = cur[0], dist = cur[1];
+
+            for (int nei : adj[node]) {
+                if (distMap[nei] == -1) {
+                    q.offer(new int[]{nei, dist + 1});
+                    distMap[nei] = dist + 1;
+                }
+            }
+        }
+        return distMap;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int closestMeetingNode(vector<int>& edges, int node1, int node2) {
+        int n = edges.size();
+        vector<vector<int>> adj(n);
+        for (int i = 0; i < n; i++) {
+            if (edges[i] != -1) adj[i].push_back(edges[i]);
+        }
+
+        vector<int> node1Dist = bfs(node1, n, adj);
+        vector<int> node2Dist = bfs(node2, n, adj);
+
+        int res = -1, resDist = INT_MAX;
+        for (int i = 0; i < n; i++) {
+            if (node1Dist[i] != -1 && node2Dist[i] != -1) {
+                int dist = max(node1Dist[i], node2Dist[i]);
+                if (dist < resDist) {
+                    resDist = dist;
+                    res = i;
+                }
+            }
+        }
+        return res;
+    }
+
+private:
+    vector<int> bfs(int src, int n, vector<vector<int>>& adj) {
+        vector<int> distMap(n, -1);
+        queue<pair<int, int>> q;
+        q.push({src, 0});
+        distMap[src] = 0;
+
+        while (!q.empty()) {
+            auto [node, dist] = q.front();
+            q.pop();
+
+            for (int nei : adj[node]) {
+                if (distMap[nei] == -1) {
+                    q.push({nei, dist + 1});
+                    distMap[nei] = dist + 1;
+                }
+            }
+        }
+        return distMap;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} edges
+     * @param {number} node1
+     * @param {number} node2
+     * @return {number}
+     */
+    closestMeetingNode(edges, node1, node2) {
+        const n = edges.length;
+        const adj = Array.from({ length: n }, () => []);
+        for (let i = 0; i < n; i++) {
+            if (edges[i] !== -1) adj[i].push(edges[i]);
+        }
+
+        const bfs = (src) => {
+            const distMap = Array(n).fill(-1);
+            const q = new Queue([[src, 0]]);
+            distMap[src] = 0;
+
+            while (!q.isEmpty()) {
+                const [node, dist] = q.pop();
+                for (const nei of adj[node]) {
+                    if (distMap[nei] === -1) {
+                        q.push([nei, dist + 1]);
+                        distMap[nei] = dist + 1;
+                    }
+                }
+            }
+            return distMap;
+        };
+
+        const node1Dist = bfs(node1);
+        const node2Dist = bfs(node2);
+
+        let res = -1, resDist = Infinity;
+        for (let i = 0; i < n; i++) {
+            if (node1Dist[i] !== -1 && node2Dist[i] !== -1) {
+                let dist = Math.max(node1Dist[i], node2Dist[i]);
+                if (dist < resDist) {
+                    resDist = dist;
+                    res = i;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Breadth First Search (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def closestMeetingNode(self, edges: list[int], node1: int, node2: int) -> int:
+        n = len(edges)
+
+        def bfs(src):
+            dist = [-1] * n
+            q = deque([src])
+            dist[src] = 0
+
+            while q:
+                node = q.popleft()
+                nei = edges[node]
+                if nei == -1 or dist[nei] >= 0:
+                    continue
+                q.append(nei)
+                dist[nei] = dist[node] + 1
+            return dist
+
+        node1Dist, node2Dist = bfs(node1), bfs(node2)
+
+        res, resDist = -1, float("inf")
+        for i in range(n):
+            if node1Dist[i] != -1 and node2Dist[i] != -1:
+                dist = max(node1Dist[i], node2Dist[i])
+                if dist < resDist:
+                    resDist, res = dist, i
+
+        return res
+```
+
+```java
+public class Solution {
+    public int closestMeetingNode(int[] edges, int node1, int node2) {
+        int n = edges.length;
+        int[] node1Dist = bfs(node1, edges, n);
+        int[] node2Dist = bfs(node2, edges, n);
+
+        int res = -1, resDist = Integer.MAX_VALUE;
+        for (int i = 0; i < n; i++) {
+            if (node1Dist[i] != -1 && node2Dist[i] != -1) {
+                int dist = Math.max(node1Dist[i], node2Dist[i]);
+                if (dist < resDist) {
+                    resDist = dist;
+                    res = i;
+                }
+            }
+        }
+
+        return res;
+    }
+
+    private int[] bfs(int src, int[] edges, int n) {
+        int[] dist = new int[n];
+        Arrays.fill(dist, -1);
+        Queue<Integer> q = new LinkedList<>();
+        q.offer(src);
+        dist[src] = 0;
+
+        while (!q.isEmpty()) {
+            int node = q.poll();
+            int nei = edges[node];
+            if (nei == -1 || dist[nei] != -1) {
+                continue;
+            }
+
+            q.offer(nei);
+            dist[nei] = dist[node] + 1;
+        }
+        return dist;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int closestMeetingNode(vector<int>& edges, int node1, int node2) {
+        int n = edges.size();
+        vector<int> node1Dist = bfs(node1, edges, n);
+        vector<int> node2Dist = bfs(node2, edges, n);
+
+        int res = -1, resDist = INT_MAX;
+        for (int i = 0; i < n; i++) {
+            if (node1Dist[i] != -1 && node2Dist[i] != -1) {
+                int dist = max(node1Dist[i], node2Dist[i]);
+                if (dist < resDist) {
+                    resDist = dist;
+                    res = i;
+                }
+            }
+        }
+        return res;
+    }
+
+private:
+    vector<int> bfs(int src, vector<int>& edges, int n) {
+        vector<int> dist(n, -1);
+        queue<int> q;
+        q.push(src);
+        dist[src] = 0;
+
+        while (!q.empty()) {
+            int node = q.front();
+            q.pop();
+            int nei = edges[node];
+            if (nei == -1 || dist[nei] != -1) {
+                continue;
+            }
+
+            q.push(nei);
+            dist[nei] = dist[node] + 1;
+        }
+        return dist;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} edges
+     * @param {number} node1
+     * @param {number} node2
+     * @return {number}
+     */
+    closestMeetingNode(edges, node1, node2) {
+        const n = edges.length;
+
+        const bfs = (src) => {
+            const dist = Array(n).fill(-1);
+            const q = new Queue([src]);
+            dist[src] = 0;
+
+            while (!q.isEmpty()) {
+                const node = q.pop();
+                const nei = edges[node];
+                if (nei === -1 || dist[nei] !== -1) {
+                    continue;
+                }
+
+                q.push(nei);
+                dist[nei] = dist[node] + 1;
+            }
+            return dist;
+        };
+
+        const node1Dist = bfs(node1);
+        const node2Dist = bfs(node2);
+
+        let res = -1, resDist = Infinity;
+        for (let i = 0; i < n; i++) {
+            if (node1Dist[i] !== -1 && node2Dist[i] !== -1) {
+                let dist = Math.max(node1Dist[i], node2Dist[i]);
+                if (dist < resDist) {
+                    resDist = dist;
+                    res = i;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Depth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def closestMeetingNode(self, edges: List[int], node1: int, node2: int) -> int:
+        n = len(edges)
+
+        def dfs(node, dist):
+            nei = edges[node]
+            if nei != -1 and dist[nei] == -1:
+                dist[nei] = dist[node] + 1
+                dfs(nei, dist)
+        
+        node1Dist = [-1] * n
+        node2Dist = [-1] * n
+        node1Dist[node1] = node2Dist[node2] = 0
+
+        dfs(node1, node1Dist)
+        dfs(node2, node2Dist)
+
+        res, resDist = -1, float("inf")
+        for i in range(n):
+            if min(node1Dist[i], node2Dist[i]) != -1:
+                dist = max(node1Dist[i], node2Dist[i])
+                if dist < resDist:
+                    resDist, res = dist, i
+
+        return res
+```
+
+```java
+public class Solution {
+    public int closestMeetingNode(int[] edges, int node1, int node2) {
+        int n = edges.length;
+        int[] node1Dist = new int[n];
+        int[] node2Dist = new int[n];
+        Arrays.fill(node1Dist, -1);
+        Arrays.fill(node2Dist, -1);
+        node1Dist[node1] = 0;
+        node2Dist[node2] = 0;
+
+        dfs(node1, edges, node1Dist);
+        dfs(node2, edges, node2Dist);
+
+        int res = -1, resDist = Integer.MAX_VALUE;
+        for (int i = 0; i < n; i++) {
+            if (Math.min(node1Dist[i], node2Dist[i]) != -1) {
+                int dist = Math.max(node1Dist[i], node2Dist[i]);
+                if (dist < resDist) {
+                    resDist = dist;
+                    res = i;
+                }
+            }
+        }
+        return res;
+    }
+
+    private void dfs(int node, int[] edges, int[] dist) {
+        int nei = edges[node];
+        if (nei != -1 && dist[nei] == -1) {
+            dist[nei] = dist[node] + 1;
+            dfs(nei, edges, dist);
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int closestMeetingNode(vector<int>& edges, int node1, int node2) {
+        int n = edges.size();
+        vector<int> node1Dist(n, -1), node2Dist(n, -1);
+        node1Dist[node1] = node2Dist[node2] = 0;
+
+        dfs(node1, edges, node1Dist);
+        dfs(node2, edges, node2Dist);
+
+        int res = -1, resDist = INT_MAX;
+        for (int i = 0; i < n; i++) {
+            if (min(node1Dist[i], node2Dist[i]) != -1) {
+                int dist = max(node1Dist[i], node2Dist[i]);
+                if (dist < resDist) {
+                    resDist = dist;
+                    res = i;
+                }
+            }
+        }
+        return res;
+    }
+
+private:
+    void dfs(int node, vector<int>& edges, vector<int>& dist) {
+        int nei = edges[node];
+        if (nei != -1 && dist[nei] == -1) {
+            dist[nei] = dist[node] + 1;
+            dfs(nei, edges, dist);
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} edges
+     * @param {number} node1
+     * @param {number} node2
+     * @return {number}
+     */
+    closestMeetingNode(edges, node1, node2) {
+        const n = edges.length;
+
+        const dfs = (node, dist) => {
+            const nei = edges[node];
+            if (nei !== -1 && dist[nei] === -1) {
+                dist[nei] = dist[node] + 1;
+                dfs(nei, dist);
+            }
+        };
+
+        const node1Dist = Array(n).fill(-1);
+        const node2Dist = Array(n).fill(-1);
+        node1Dist[node1] = 0;
+        node2Dist[node2] = 0;
+
+        dfs(node1, node1Dist);
+        dfs(node2, node2Dist);
+
+        let res = -1, resDist = Infinity;
+        for (let i = 0; i < n; i++) {
+            if (Math.min(node1Dist[i], node2Dist[i]) !== -1) {
+                const dist = Math.max(node1Dist[i], node2Dist[i]);
+                if (dist < resDist) {
+                    resDist = dist;
+                    res = i;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Iterative Depth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def closestMeetingNode(self, edges: list[int], node1: int, node2: int) -> int:
+        n = len(edges)
+
+        def dfs(node):
+            dist = [-1] * n
+            dist[node] = 0
+            while edges[node] != -1 and dist[edges[node]] == -1:
+                nei = edges[node]
+                dist[nei] = dist[node] + 1
+                node = nei
+            return dist
+
+
+        node1Dist, node2Dist = dfs(node1), dfs(node2)
+        res, resDist = -1, float("inf")
+        for i in range(n):
+            if min(node1Dist[i], node2Dist[i]) != -1:
+                dist = max(node1Dist[i], node2Dist[i])
+                if dist < resDist:
+                    resDist, res = dist, i
+        return res
+```
+
+```java
+public class Solution {
+    public int closestMeetingNode(int[] edges, int node1, int node2) {
+        int n = edges.length;
+        int[] node1Dist = dfs(node1, edges, n);
+        int[] node2Dist = dfs(node2, edges, n);
+
+        int res = -1, resDist = Integer.MAX_VALUE;
+        for (int i = 0; i < n; i++) {
+            if (Math.min(node1Dist[i], node2Dist[i]) != -1) {
+                int dist = Math.max(node1Dist[i], node2Dist[i]);
+                if (dist < resDist) {
+                    resDist = dist;
+                    res = i;
+                }
+            }
+        }
+        return res;
+    }
+
+    private int[] dfs(int node, int[] edges, int n) {
+        int[] dist = new int[n];
+        Arrays.fill(dist, -1);
+        dist[node] = 0;
+        while (edges[node] != -1 && dist[edges[node]] == -1) {
+            int nei = edges[node];
+            dist[nei] = dist[node] + 1;
+            node = nei;
+        }
+        return dist;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int closestMeetingNode(vector<int>& edges, int node1, int node2) {
+        int n = edges.size();
+        vector<int> node1Dist = dfs(node1, edges, n);
+        vector<int> node2Dist = dfs(node2, edges, n);
+
+        int res = -1, resDist = INT_MAX;
+        for (int i = 0; i < n; i++) {
+            if (min(node1Dist[i], node2Dist[i]) != -1) {
+                int dist = max(node1Dist[i], node2Dist[i]);
+                if (dist < resDist) {
+                    resDist = dist;
+                    res = i;
+                }
+            }
+        }
+        return res;
+    }
+
+private:
+    vector<int> dfs(int node, vector<int>& edges, int n) {
+        vector<int> dist(n, -1);
+        dist[node] = 0;
+        while (edges[node] != -1 && dist[edges[node]] == -1) {
+            int nei = edges[node];
+            dist[nei] = dist[node] + 1;
+            node = nei;
+        }
+        return dist;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} edges
+     * @param {number} node1
+     * @param {number} node2
+     * @return {number}
+     */
+    closestMeetingNode(edges, node1, node2) {
+        const n = edges.length;
+
+        const dfs = (node) => {
+            const dist = Array(n).fill(-1);
+            dist[node] = 0;
+            while (edges[node] !== -1 && dist[edges[node]] === -1) {
+                const nei = edges[node];
+                dist[nei] = dist[node] + 1;
+                node = nei;
+            }
+            return dist;
+        };
+
+        const node1Dist = dfs(node1);
+        const node2Dist = dfs(node2);
+
+        let res = -1, resDist = Infinity;
+        for (let i = 0; i < n; i++) {
+            if (Math.min(node1Dist[i], node2Dist[i]) !== -1) {
+                const dist = Math.max(node1Dist[i], node2Dist[i]);
+                if (dist < resDist) {
+                    resDist = dist;
+                    res = i;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/find-common-characters.md b/articles/find-common-characters.md
new file mode 100644
index 000000000..4a6cfe1e8
--- /dev/null
+++ b/articles/find-common-characters.md
@@ -0,0 +1,122 @@
+## 1. Frequency Count
+
+::tabs-start
+
+```python
+class Solution:
+    def commonChars(self, words: List[str]) -> List[str]:
+        cnt = Counter(words[0])
+
+        for w in words:
+            cur_cnt = Counter(w)
+            for c in cnt:
+                cnt[c] = min(cnt[c], cur_cnt[c])
+
+        res = []
+        for c in cnt:
+            for i in range(cnt[c]):
+                res.append(c)
+
+        return res
+```
+
+```java
+public class Solution {
+    public List<String> commonChars(String[] words) {
+        int[] cnt = new int[26];
+        Arrays.fill(cnt, Integer.MAX_VALUE);
+
+        for (String word : words) {
+            int[] curCnt = new int[26];
+            for (char c : word.toCharArray()) {
+                curCnt[c - 'a']++;
+            }
+
+            for (int i = 0; i < 26; i++) {
+                cnt[i] = Math.min(cnt[i], curCnt[i]);
+            }
+        }
+
+        List<String> res = new ArrayList<>();
+        for (int i = 0; i < 26; i++) {
+            for (int j = 0; j < cnt[i]; j++) {
+                res.add(String.valueOf((char) (i + 'a')));
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<string> commonChars(vector<string>& words) {
+        vector<int> cnt(26, INT_MAX);
+
+        for (string& word : words) {
+            vector<int> curCnt(26, 0);
+            for (char c : word) {
+                curCnt[c - 'a']++;
+            }
+
+            for (int i = 0; i < 26; i++) {
+                cnt[i] = min(cnt[i], curCnt[i]);
+            }
+        }
+
+        vector<string> res;
+        for (int i = 0; i < 26; i++) {
+            for (int j = 0; j < cnt[i]; j++) {
+                res.push_back(string(1, i + 'a'));
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @return {string[]}
+     */
+    commonChars(words) {
+        const cnt = new Array(26).fill(Infinity);
+
+        for (let word of words) {
+            const curCnt = new Array(26).fill(0);
+            for (let c of word) {
+                curCnt[c.charCodeAt(0) - 97]++;
+            }
+
+            for (let i = 0; i < 26; i++) {
+                cnt[i] = Math.min(cnt[i], curCnt[i]);
+            }
+        }
+
+        const res = [];
+        for (let i = 0; i < 26; i++) {
+            for (let j = 0; j < cnt[i]; j++) {
+                res.push(String.fromCharCode(i + 97));
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity:
+    * $O(1)$ extra space, since we have at most $26$ different characters.
+    * $O(n * m)$ space for the output list.
+
+> Where $n$ is the number of words and $m$ is the length of the longest word.
\ No newline at end of file
diff --git a/articles/find-critical-and-pseudo-critical-edges-in-minimum-spanning-tree.md b/articles/find-critical-and-pseudo-critical-edges-in-minimum-spanning-tree.md
new file mode 100644
index 000000000..b20fb8a09
--- /dev/null
+++ b/articles/find-critical-and-pseudo-critical-edges-in-minimum-spanning-tree.md
@@ -0,0 +1,1282 @@
+## 1. Kruskal's Algorithm - I
+
+::tabs-start
+
+```python
+class UnionFind:
+    def __init__(self, n):
+        self.par = [i for i in range(n)]
+        self.rank = [1] * n
+
+    def find(self, v1):
+        while v1 != self.par[v1]:
+            self.par[v1] = self.par[self.par[v1]]
+            v1 = self.par[v1]
+        return v1
+
+    def union(self, v1, v2):
+        p1, p2 = self.find(v1), self.find(v2)
+        if p1 == p2:
+            return False
+        if self.rank[p1] > self.rank[p2]:
+            self.par[p2] = p1
+            self.rank[p1] += self.rank[p2]
+        else:
+            self.par[p1] = p2
+            self.rank[p2] += self.rank[p1]
+        return True
+
+
+class Solution:
+    def findCriticalAndPseudoCriticalEdges(self, n: int, edges: List[List[int]]) -> List[List[int]]:
+        for i, e in enumerate(edges):
+            e.append(i)  # [v1, v2, weight, original_index]
+
+        edges.sort(key=lambda e: e[2])
+
+        mst_weight = 0
+        uf = UnionFind(n)
+        for v1, v2, w, i in edges:
+            if uf.union(v1, v2):
+                mst_weight += w
+
+        critical, pseudo = [], []
+        for n1, n2, e_weight, i in edges:
+            # Try without curr edge
+            weight = 0
+            uf = UnionFind(n)
+            for v1, v2, w, j in edges:
+                if i != j and uf.union(v1, v2):
+                    weight += w
+            if max(uf.rank) != n or weight > mst_weight:
+                critical.append(i)
+                continue
+
+            # Try with curr edge
+            uf = UnionFind(n)
+            uf.union(n1, n2)
+            weight = e_weight
+            for v1, v2, w, j in edges:
+                if uf.union(v1, v2):
+                    weight += w
+            if weight == mst_weight:
+                pseudo.append(i)
+        return [critical, pseudo]
+```
+
+```java
+class UnionFind {
+    int[] par, rank;
+
+    public UnionFind(int n) {
+        par = new int[n];
+        rank = new int[n];
+        for (int i = 0; i < n; i++) {
+            par[i] = i;
+            rank[i] = 1;
+        }
+    }
+
+    public int find(int v) {
+        if (par[v] != v) {
+            par[v] = find(par[v]);
+        }
+        return par[v];
+    }
+
+    public boolean union(int v1, int v2) {
+        int p1 = find(v1), p2 = find(v2);
+        if (p1 == p2) return false;
+        if (rank[p1] > rank[p2]) {
+            par[p2] = p1;
+            rank[p1] += rank[p2];
+        } else {
+            par[p1] = p2;
+            rank[p2] += rank[p1];
+        }
+        return true;
+    }
+}
+
+public class Solution {
+    public List<List<Integer>> findCriticalAndPseudoCriticalEdges(int n, int[][] edges) {
+        List<int[]> edgeList = new ArrayList<>();
+        for (int i = 0; i < edges.length; i++) {
+            edgeList.add(new int[] { edges[i][0], edges[i][1], edges[i][2], i });
+        }
+
+        edgeList.sort(Comparator.comparingInt(a -> a[2]));
+
+        int mstWeight = 0;
+        UnionFind uf = new UnionFind(n);
+        for (int[] edge : edgeList) {
+            if (uf.union(edge[0], edge[1])) {
+                mstWeight += edge[2];
+            }
+        }
+
+        List<Integer> critical = new ArrayList<>();
+        List<Integer> pseudo = new ArrayList<>();
+
+        for (int[] edge : edgeList) {
+            // Try without current edge
+            UnionFind ufWithout = new UnionFind(n);
+            int weight = 0;
+            for (int[] other : edgeList) {
+                if (other[3] != edge[3] && ufWithout.union(other[0], other[1])) {
+                    weight += other[2];
+                }
+            }
+            if (Arrays.stream(ufWithout.rank).max().getAsInt() != n || weight > mstWeight) {
+                critical.add(edge[3]);
+                continue;
+            }
+
+            // Try with current edge
+            UnionFind ufWith = new UnionFind(n);
+            ufWith.union(edge[0], edge[1]);
+            weight = edge[2];
+            for (int[] other : edgeList) {
+                if (ufWith.union(other[0], other[1])) {
+                    weight += other[2];
+                }
+            }
+            if (weight == mstWeight) {
+                pseudo.add(edge[3]);
+            }
+        }
+
+        return Arrays.asList(critical, pseudo);
+    }
+}
+```
+
+```cpp
+class UnionFind {
+public:
+    vector<int> par, rank;
+
+    UnionFind(int n) : par(n), rank(n, 1) {
+        iota(par.begin(), par.end(), 0);
+    }
+
+    int find(int v) {
+        if (v != par[v]) {
+            par[v] = find(par[v]);
+        }
+        return par[v];
+    }
+
+    bool unionSets(int v1, int v2) {
+        int p1 = find(v1), p2 = find(v2);
+        if (p1 == p2) return false;
+        if (rank[p1] > rank[p2]) {
+            par[p2] = p1;
+            rank[p1] += rank[p2];
+        } else {
+            par[p1] = p2;
+            rank[p2] += rank[p1];
+        }
+        return true;
+    }
+};
+
+class Solution {
+public:
+    vector<vector<int>> findCriticalAndPseudoCriticalEdges(int n, vector<vector<int>>& edges) {
+        vector<array<int, 4>> edgeList;
+        for (int i = 0; i < edges.size(); ++i) {
+            edgeList.push_back({ edges[i][0], edges[i][1], edges[i][2], i });
+        }
+
+        sort(edgeList.begin(), edgeList.end(), [](auto& a, auto& b) {
+            return a[2] < b[2];
+        });
+
+        int mstWeight = 0;
+        UnionFind uf(n);
+        for (auto& edge : edgeList) {
+            if (uf.unionSets(edge[0], edge[1])) {
+                mstWeight += edge[2];
+            }
+        }
+
+        vector<int> critical, pseudo;
+        for (auto& edge : edgeList) {
+            // Try without current edge
+            UnionFind ufWithout(n);
+            int weight = 0;
+            for (auto& other : edgeList) {
+                if (other[3] != edge[3] && ufWithout.unionSets(other[0], other[1])) {
+                    weight += other[2];
+                }
+            }
+            if (*max_element(ufWithout.rank.begin(), ufWithout.rank.end()) != n || weight > mstWeight) {
+                critical.push_back(edge[3]);
+                continue;
+            }
+
+            // Try with current edge
+            UnionFind ufWith(n);
+            ufWith.unionSets(edge[0], edge[1]);
+            weight = edge[2];
+            for (auto& other : edgeList) {
+                if (ufWith.unionSets(other[0], other[1])) {
+                    weight += other[2];
+                }
+            }
+            if (weight == mstWeight) {
+                pseudo.push_back(edge[3]);
+            }
+        }
+
+        return { critical, pseudo };
+    }
+};
+```
+
+```javascript
+class UnionFind {
+    /**
+     * @constructor
+     * @param {number} n
+     */
+    constructor(n) {
+        this.par = Array.from({ length: n }, (_, i) => i);
+        this.rank = Array(n).fill(1);
+    }
+
+    /**
+     * @param {number} v1
+     * @return {number}
+     */
+    find(v1) {
+        if (this.par[v1] !== v1) {
+            this.par[v1] = this.find(this.par[v1]);
+        }
+        return this.par[v1];
+    }
+
+    /**
+     * @param {number} v1
+     * @param {number} v2
+     * @return {boolean}
+     */
+    union(v1, v2) {
+        const p1 = this.find(v1), p2 = this.find(v2);
+        if (p1 === p2) return false;
+        if (this.rank[p1] > this.rank[p2]) {
+            this.par[p2] = p1;
+            this.rank[p1] += this.rank[p2];
+        } else {
+            this.par[p1] = p2;
+            this.rank[p2] += this.rank[p1];
+        }
+        return true;
+    }
+}
+
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} edges
+     * @return {number[][]}
+     */
+    findCriticalAndPseudoCriticalEdges(n, edges) {
+        edges = edges.map((edge, idx) => [...edge, idx]);
+        edges.sort((a, b) => a[2] - b[2]);
+
+        const uf = new UnionFind(n);
+        let mstWeight = 0;
+        for (const [v1, v2, w] of edges) {
+            if (uf.union(v1, v2)) {
+                mstWeight += w;
+            }
+        }
+
+        const critical = [];
+        const pseudo = [];
+
+        for (const [n1, n2, weight, i] of edges) {
+            // Try without current edge
+            const ufWithout = new UnionFind(n);
+            let weightWithout = 0;
+            for (const [v1, v2, w, j] of edges) {
+                if (j !== i && ufWithout.union(v1, v2)) {
+                    weightWithout += w;
+                }
+            }
+            if (Math.max(...ufWithout.rank) !== n || weightWithout > mstWeight) {
+                critical.push(i);
+                continue;
+            }
+
+            // Try with current edge
+            const ufWith = new UnionFind(n);
+            ufWith.union(n1, n2);
+            let weightWith = weight;
+            for (const [v1, v2, w, j] of edges) {
+                if (ufWith.union(v1, v2)) {
+                    weightWith += w;
+                }
+            }
+            if (weightWith === mstWeight) {
+                pseudo.push(i);
+            }
+        }
+
+        return [critical, pseudo];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(E ^ 2)$
+* Space complexity: $O(V + E)$
+
+> Where $V$ is the number of vertices and $E$ is the number of edges.
+
+---
+
+## 2. Kruskal's Algorithm - II
+
+::tabs-start
+
+```python
+class UnionFind:
+    def __init__(self, n):
+        self.n = n
+        self.Parent = list(range(n + 1))
+        self.Size = [1] * (n + 1)
+
+    def find(self, node):
+        if self.Parent[node] != node:
+            self.Parent[node] = self.find(self.Parent[node])
+        return self.Parent[node]
+
+    def union(self, u, v):
+        pu = self.find(u)
+        pv = self.find(v)
+        if pu == pv:
+            return False
+        self.n -= 1
+        if self.Size[pu] < self.Size[pv]:
+            pu, pv = pv, pu
+        self.Size[pu] += self.Size[pv]
+        self.Parent[pv] = pu
+        return True
+    
+    def isConnected(self):
+        return self.n == 1
+
+class Solution:
+    def findCriticalAndPseudoCriticalEdges(self, n: int, edges: List[List[int]]) -> List[List[int]]:
+        for i, e in enumerate(edges):
+            e.append(i)
+        edges.sort(key = lambda e : e[2])
+
+        def findMST(index, include):
+            uf = UnionFind(n)
+            wgt = 0
+            if include:
+                wgt += edges[index][2]
+                uf.union(edges[index][0], edges[index][1])
+            
+            for i, e in enumerate(edges):
+                if i == index:
+                    continue
+                if uf.union(e[0], e[1]):
+                    wgt += e[2]
+            return wgt if uf.isConnected() else float("inf")
+        
+        mst_wgt = findMST(-1, False)
+        critical, pseudo = [], []
+        for i, e in enumerate(edges):
+            if mst_wgt < findMST(i, False):
+                critical.append(e[3])
+            elif mst_wgt == findMST(i, True):
+                pseudo.append(e[3])
+        
+        return [critical, pseudo]
+```
+
+```java
+class UnionFind {
+    private int n;
+    private int[] Parent, Size;
+
+    public UnionFind(int n) {
+        this.n = n;
+        Parent = new int[n + 1];
+        Size = new int[n + 1];
+        for (int i = 0; i <= n; i++) {
+            Parent[i] = i;
+            Size[i] = 1;
+        }
+    }
+
+    public int find(int node) {
+        if (Parent[node] != node) {
+            Parent[node] = find(Parent[node]);
+        }
+        return Parent[node];
+    }
+
+    public boolean union(int u, int v) {
+        int pu = find(u), pv = find(v);
+        if (pu == pv) {
+            return false;
+        }
+        n--;
+        if (Size[pu] < Size[pv]) {
+            int temp = pu;
+            pu = pv;
+            pv = temp;
+        }
+        Size[pu] += Size[pv];
+        Parent[pv] = pu;
+        return true;
+    }
+
+    public boolean isConnected() {
+        return n == 1;
+    }
+}
+
+public class Solution {
+    public List<List<Integer>> findCriticalAndPseudoCriticalEdges(int n, int[][] edges) {
+        for (int i = 0; i < edges.length; i++) {
+            edges[i] = Arrays.copyOf(edges[i], edges[i].length + 1);
+            edges[i][3] = i;
+        }
+
+        Arrays.sort(edges, Comparator.comparingInt(a -> a[2]));
+
+
+        int mst_wgt = findMST(n, edges, -1, false);
+        List<Integer> critical = new ArrayList<>();
+        List<Integer> pseudo = new ArrayList<>();
+
+        for (int i = 0; i < edges.length; i++) {
+            if (mst_wgt < findMST(n, edges, i, false)) {
+                critical.add(edges[i][3]);
+            } else if (mst_wgt == findMST(n, edges, i, true)) {
+                pseudo.add(edges[i][3]);
+            }
+        }
+
+        return Arrays.asList(critical, pseudo);
+    }
+
+    public int findMST(int n, int[][] edges, int index, boolean include) {
+        UnionFind uf = new UnionFind(n);
+        int wgt = 0;
+        if (include) {
+            wgt += edges[index][2];
+            uf.union(edges[index][0], edges[index][1]);
+        }
+        for (int i = 0; i < edges.length; i++) {
+            if (i == index) {
+                continue;
+            }
+            if (uf.union(edges[i][0], edges[i][1])) {
+                wgt += edges[i][2];
+            }
+        }
+        return uf.isConnected() ? wgt : Integer.MAX_VALUE;
+    }
+}
+```
+
+```cpp
+class UnionFind {
+private:
+    int n;
+    vector<int> Parent, Size;
+
+public:
+    UnionFind(int n) : n(n), Parent(n + 1), Size(n + 1, 1) {
+        for (int i = 0; i <= n; ++i) {
+            Parent[i] = i;
+        }
+    }
+
+    int find(int node) {
+        if (Parent[node] != node) {
+            Parent[node] = find(Parent[node]);
+        }
+        return Parent[node];
+    }
+
+    bool unionSets(int u, int v) {
+        int pu = find(u), pv = find(v);
+        if (pu == pv) return false;
+        n--;
+        if (Size[pu] < Size[pv]) {
+            swap(pu, pv);
+        }
+        Size[pu] += Size[pv];
+        Parent[pv] = pu;
+        return true;
+    }
+
+    bool isConnected() {
+        return n == 1;
+    }
+};
+
+class Solution {
+public:
+    vector<vector<int>> findCriticalAndPseudoCriticalEdges(int n, vector<vector<int>>& edges) {
+        for (int i = 0; i < edges.size(); ++i) {
+            edges[i].push_back(i);
+        }
+
+        sort(edges.begin(), edges.end(), [](const vector<int>& a, const vector<int>& b) {
+            return a[2] < b[2];
+        });
+
+        auto findMST = [&](int index, bool include) -> int {
+            UnionFind uf(n);
+            int wgt = 0;
+            if (include) {
+                wgt += edges[index][2];
+                uf.unionSets(edges[index][0], edges[index][1]);
+            }
+            for (int i = 0; i < edges.size(); ++i) {
+                if (i == index) continue;
+                if (uf.unionSets(edges[i][0], edges[i][1])) {
+                    wgt += edges[i][2];
+                }
+            }
+            return uf.isConnected() ? wgt : INT_MAX;
+        };
+
+        int mst_wgt = findMST(-1, false);
+        vector<int> critical, pseudo;
+
+        for (int i = 0; i < edges.size(); ++i) {
+            if (mst_wgt < findMST(i, false)) {
+                critical.push_back(edges[i][3]);
+            } else if (mst_wgt == findMST(i, true)) {
+                pseudo.push_back(edges[i][3]);
+            }
+        }
+
+        return { critical, pseudo };
+    }
+};
+```
+
+```javascript
+class UnionFind {
+    /**
+     * @constructor
+     * @param {number} n
+     */
+    constructor(n) {
+        this.Parent = Array.from({ length: n + 1 }, (_, i) => i);
+        this.Size = Array(n + 1).fill(1);
+        this.n = n;
+    }
+
+    /**
+     * @param {number} node
+     * @return {number}
+     */
+    find(node) {
+        if (this.Parent[node] !== node) {
+            this.Parent[node] = this.find(this.Parent[node]);
+        }
+        return this.Parent[node];
+    }
+
+    /**
+     * @param {number} u
+     * @param {number} v
+     * @return {boolean}
+     */
+    union(u, v) {
+        let pu = this.find(u);
+        let pv = this.find(v);
+        if (pu === pv) return false;
+        this.n--;
+        if (this.Size[pu] < this.Size[pv]) {
+            [pu, pv] = [pv, pu];
+        }
+        this.Size[pu] += this.Size[pv];
+        this.Parent[pv] = pu;
+        return true;
+    }
+
+    /**
+     * @return {number}
+     */
+    isConnected() {
+        return this.n === 1;
+    }
+}
+
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} edges
+     * @return {number[][]}
+     */
+    findCriticalAndPseudoCriticalEdges(n, edges) {
+        edges.forEach((edge, i) => edge.push(i));
+        edges.sort((a, b) => a[2] - b[2]);
+
+        const findMST = (index, include) => {
+            const uf = new UnionFind(n);
+            let wgt = 0;
+            if (include) {
+                wgt += edges[index][2];
+                uf.union(edges[index][0], edges[index][1]);
+            }
+            for (let i = 0; i < edges.length; i++) {
+                if (i === index) continue;
+                if (uf.union(edges[i][0], edges[i][1])) {
+                    wgt += edges[i][2];
+                }
+            }
+            return uf.isConnected() ? wgt : Infinity;
+        };
+
+        const mst_wgt = findMST(-1, false);
+        const critical = [];
+        const pseudo = [];
+
+        edges.forEach((edge, i) => {
+            if (mst_wgt < findMST(i, false)) {
+                critical.push(edge[3]);
+            } else if (mst_wgt === findMST(i, true)) {
+                pseudo.push(edge[3]);
+            }
+        });
+
+        return [critical, pseudo];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(E ^ 2)$
+* Space complexity: $O(V + E)$
+
+> Where $V$ is the number of vertices and $E$ is the number of edges.
+
+---
+
+## 3. Dijkstra's Algorithm
+
+::tabs-start
+
+```python
+class Solution:
+    def findCriticalAndPseudoCriticalEdges(self, n: int, edges: List[List[int]]) -> List[List[int]]:
+        for i, edge in enumerate(edges):
+            edge.append(i)
+
+        adj = defaultdict(list)
+        for u, v, w, idx in edges:
+            adj[u].append((v, w, idx))
+            adj[v].append((u, w, idx))
+
+        def minimax(src, dst, exclude_idx):
+            dist = [float('inf')] * n
+            dist[src] = 0
+            pq = [(0, src)]
+
+            while pq:
+                max_w, u = heappop(pq)
+                if u == dst:
+                    return max_w
+
+                for v, weight, edge_idx in adj[u]:
+                    if edge_idx == exclude_idx:
+                        continue
+                    new_w = max(max_w, weight)
+                    if new_w < dist[v]:
+                        dist[v] = new_w
+                        heappush(pq, (new_w, v))
+
+            return float('inf')
+
+        critical, pseudo = [], []
+        for i, (u, v, w, idx) in enumerate(edges):
+            if w < minimax(u, v, idx):
+                critical.append(idx)
+            elif w == minimax(u, v, -1):
+                pseudo.append(idx)
+
+        return [critical, pseudo]
+```
+
+```java
+public class Solution {
+    private List<int[]>[] adj;
+
+    public List<List<Integer>> findCriticalAndPseudoCriticalEdges(int n, int[][] edges) {
+        for (int i = 0; i < edges.length; i++) {
+            edges[i] = Arrays.copyOf(edges[i], edges[i].length + 1);
+            edges[i][3] = i;
+        }
+
+        adj = new ArrayList[n];
+        for (int i = 0; i < n; i++) {
+            adj[i] = new ArrayList<>();
+        }
+        for (int[] edge : edges) {
+            adj[edge[0]].add(new int[]{edge[1], edge[2], edge[3]});
+            adj[edge[1]].add(new int[]{edge[0], edge[2], edge[3]});
+        }
+
+
+        List<Integer> critical = new ArrayList<>();
+        List<Integer> pseudo = new ArrayList<>();
+
+        for (int[] edge : edges) {
+            int u = edge[0], v = edge[1], w = edge[2], idx = edge[3];
+            if (w < minimax(n, u, v, idx)) {
+                critical.add(idx);
+            } else if (w == minimax(n, u, v, -1)) {
+                pseudo.add(idx);
+            }
+        }
+
+        return Arrays.asList(critical, pseudo);
+    }
+
+    public int minimax(int n, int src, int dst, int excludeIdx) {
+        int[] dist = new int[n];
+        Arrays.fill(dist, Integer.MAX_VALUE);
+        dist[src] = 0;
+
+        PriorityQueue<int[]> pq = new PriorityQueue<>(Comparator.comparingInt(a -> a[0]));
+        pq.offer(new int[]{0, src});
+
+        while (!pq.isEmpty()) {
+            int[] curr = pq.poll();
+            int maxW = curr[0], u = curr[1];
+            if (u == dst) return maxW;
+
+            for (int[] neighbor : adj[u]) {
+                int v = neighbor[0], weight = neighbor[1], edgeIdx = neighbor[2];
+                if (edgeIdx == excludeIdx) continue;
+                int newW = Math.max(maxW, weight);
+                if (newW < dist[v]) {
+                    dist[v] = newW;
+                    pq.offer(new int[]{newW, v});
+                }
+            }
+        }
+        return Integer.MAX_VALUE;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> findCriticalAndPseudoCriticalEdges(int n, vector<vector<int>>& edges) {
+        for (int i = 0; i < edges.size(); ++i) {
+            edges[i].push_back(i);
+        }
+
+        vector<vector<vector<int>>> adj(n);
+        for (const auto& edge : edges) {
+            adj[edge[0]].push_back({edge[1], edge[2], edge[3]});
+            adj[edge[1]].push_back({edge[0], edge[2], edge[3]});
+        }
+
+        auto minimax = [&](int src, int dst, int excludeIdx) -> int {
+            vector<int> dist(n, INT_MAX);
+            dist[src] = 0;
+
+            priority_queue<pair<int, int>, vector<pair<int, int>>, greater<>> pq;
+            pq.push({0, src});
+
+            while (!pq.empty()) {
+                auto [maxW, u] = pq.top();
+                pq.pop();
+                if (u == dst) return maxW;
+
+                for (const auto& neighbor : adj[u]) {
+                    int v = neighbor[0], weight = neighbor[1], edgeIdx = neighbor[2];
+                    if (edgeIdx == excludeIdx) continue;
+                    int newW = max(maxW, weight);
+                    if (newW < dist[v]) {
+                        dist[v] = newW;
+                        pq.push({newW, v});
+                    }
+                }
+            }
+            return INT_MAX;
+        };
+
+        vector<int> critical, pseudo;
+        for (const auto& edge : edges) {
+            int u = edge[0], v = edge[1], w = edge[2], idx = edge[3];
+            if (w < minimax(u, v, idx)) {
+                critical.push_back(idx);
+            } else if (w == minimax(u, v, -1)) {
+                pseudo.push_back(idx);
+            }
+        }
+
+        return {critical, pseudo};
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} edges
+     * @return {number[][]}
+     */
+    findCriticalAndPseudoCriticalEdges(n, edges) {
+        edges.forEach((edge, i) => edge.push(i));
+
+        const adj = Array.from({ length: n }, () => []);
+        for (const [u, v, w, idx] of edges) {
+            adj[u].push([v, w, idx]);
+            adj[v].push([u, w, idx]);
+        }
+
+        const minimax = (src, dst, excludeIdx) => {
+            const dist = Array(n).fill(Infinity);
+            dist[src] = 0;
+
+            const pq = new MinPriorityQueue({ compare: (a, b) => a[0] - b[0] });
+            pq.enqueue([0, src]);
+
+            while (!pq.isEmpty()) {
+                const [maxW, u] = pq.dequeue();
+                if (u === dst) return maxW;
+
+                for (const [v, weight, edgeIdx] of adj[u]) {
+                    if (edgeIdx === excludeIdx) continue;
+                    const newW = Math.max(maxW, weight);
+                    if (newW < dist[v]) {
+                        dist[v] = newW;
+                        pq.enqueue([newW, v]);
+                    }
+                }
+            }
+            return Infinity;
+        };
+
+        const critical = [];
+        const pseudo = [];
+
+        for (const [u, v, w, idx] of edges) {
+            if (w < minimax(u, v, idx)) {
+                critical.push(idx);
+            } else if (w === minimax(u, v, -1)) {
+                pseudo.push(idx);
+            }
+        }
+
+        return [critical, pseudo];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(E ^ 2 \log V)$
+* Space complexity: $O(V + E)$
+
+> Where $V$ is the number of vertices and $E$ is the number of edges.
+
+---
+
+## 4. Kruskal's Algorithm + DFS
+
+::tabs-start
+
+```python
+class UnionFind:
+    def __init__(self, n):
+        self.Parent = list(range(n + 1))
+        self.Size = [1] * (n + 1)
+        
+    def find(self, node):
+        if self.Parent[node] != node:
+            self.Parent[node] = self.find(self.Parent[node])
+        return self.Parent[node]
+    
+    def union(self, u, v):
+        pu = self.find(u)
+        pv = self.find(v)
+        if pu == pv:
+            return False
+        if self.Size[pu] < self.Size[pv]:
+            pu, pv = pv, pu
+        self.Size[pu] += self.Size[pv]
+        self.Parent[pv] = pu
+        return True
+
+class Solution:
+    def findCriticalAndPseudoCriticalEdges(self, n: int, edges: List[List[int]]) -> List[List[int]]:
+        mst = [[] for _ in range(n)]
+        mstEdge = []
+        
+        edge_list = [(w, u, v, i) for i, (u, v, w) in enumerate(edges)]
+        edge_list.sort()
+        
+        uf = UnionFind(n)
+        for w, u, v, i in edge_list:
+            if uf.union(u, v):
+                mst[u].append((v, i))
+                mst[v].append((u, i))
+                mstEdge.append(i)
+        
+        def dfs(node):
+            for next, ind in mst[node]:
+                if path and ind == path[-1]:
+                    continue
+                path.append(ind)
+                if next == dst or dfs(next):
+                    return True
+                path.pop()
+            return False
+        
+        pseudo, mstEdge = set(), set(mstEdge)
+        for ind in range(len(edges)):
+            if ind in mstEdge:
+                continue
+            path, dst = [], edges[ind][1]
+            dfs(edges[ind][0])
+            for i in path:
+                if edges[i][2] == edges[ind][2]:
+                    pseudo.add(i)
+                    pseudo.add(ind)
+        
+        return [list(mstEdge - pseudo), list(pseudo)]
+```
+
+```java
+class UnionFind {
+    private int[] parent;
+    private int[] size;
+
+    public UnionFind(int n) {
+        parent = new int[n];
+        size = new int[n];
+        for (int i = 0; i < n; i++) {
+            parent[i] = i;
+            size[i] = 1;
+        }
+    }
+
+    public int find(int node) {
+        if (parent[node] != node) {
+            parent[node] = find(parent[node]);
+        }
+        return parent[node];
+    }
+
+    public boolean union(int u, int v) {
+        int pu = find(u);
+        int pv = find(v);
+        if (pu == pv) {
+            return false;
+        }
+        if (size[pu] < size[pv]) {
+            int temp = pu;
+            pu = pv;
+            pv = temp;
+        }
+        size[pu] += size[pv];
+        parent[pv] = pu;
+        return true;
+    }
+}
+
+public class Solution {
+    private List<List<Integer>> mst;
+    private Set<Integer> mstEdges;
+    private Set<Integer> pseudoCriticalEdges;
+    private int destination;
+    private List<Integer> path;
+
+    public List<List<Integer>> findCriticalAndPseudoCriticalEdges(int n, int[][] edges) {
+        mst = new ArrayList<>();
+        mstEdges = new HashSet<>();
+        pseudoCriticalEdges = new HashSet<>();
+
+        for (int i = 0; i < n; i++) {
+            mst.add(new ArrayList<>());
+        }
+
+        List<int[]> edgeList = new ArrayList<>();
+        for (int i = 0; i < edges.length; i++) {
+            edgeList.add(new int[]{edges[i][2], edges[i][0], edges[i][1], i});
+        }
+        edgeList.sort(Comparator.comparingInt(a -> a[0]));
+
+        UnionFind uf = new UnionFind(n);
+        for (int[] edge : edgeList) {
+            int weight = edge[0], u = edge[1], v = edge[2], index = edge[3];
+            if (uf.union(u, v)) {
+                mst.get(u).add(index);
+                mst.get(v).add(index);
+                mstEdges.add(index);
+            }
+        }
+
+        for (int i = 0; i < edges.length; i++) {
+            if (mstEdges.contains(i)) {
+                continue;
+            }
+            path = new ArrayList<>();
+            destination = edges[i][1];
+            if (dfs(edges[i][0], -1, edges)) {
+                for (int p : path) {
+                    if (edges[p][2] == edges[i][2]) {
+                        pseudoCriticalEdges.add(i);
+                        pseudoCriticalEdges.add(p);
+                    }
+                }
+            }
+        }
+
+        List<Integer> critical = new ArrayList<>();
+        for (int edge : mstEdges) {
+            if (!pseudoCriticalEdges.contains(edge)) {
+                critical.add(edge);
+            }
+        }
+
+        return Arrays.asList(critical, new ArrayList<>(pseudoCriticalEdges));
+    }
+
+    private boolean dfs(int node, int parent, int[][] edges) {
+        if (node == destination) {
+            return true;
+        }
+        for (int edgeIndex : mst.get(node)) {
+            if (edgeIndex == parent) {
+                continue;
+            }
+            path.add(edgeIndex);
+            int nextNode = edges[edgeIndex][0] == node ? edges[edgeIndex][1] : edges[edgeIndex][0];
+            if (dfs(nextNode, edgeIndex, edges)) {
+                return true;
+            }
+            path.remove(path.size() - 1);
+        }
+        return false;
+    }
+}
+```
+
+```cpp
+class UnionFind {
+    vector<int> parent, size;
+
+public:
+    UnionFind(int n) {
+        parent.resize(n);
+        size.resize(n, 1);
+        for (int i = 0; i < n; ++i) {
+            parent[i] = i;
+        }
+    }
+
+    int find(int node) {
+        if (parent[node] != node) {
+            parent[node] = find(parent[node]);
+        }
+        return parent[node];
+    }
+
+    bool unionSets(int u, int v) {
+        int pu = find(u), pv = find(v);
+        if (pu == pv) return false;
+        if (size[pu] < size[pv]) swap(pu, pv);
+        size[pu] += size[pv];
+        parent[pv] = pu;
+        return true;
+    }
+};
+
+class Solution {
+    vector<vector<int>> mst;
+    set<int> mstEdges, pseudoCriticalEdges;
+    vector<int> path;
+    int destination;
+
+public:
+    vector<vector<int>> findCriticalAndPseudoCriticalEdges(int n, vector<vector<int>>& edges) {
+        mst.resize(n);
+        vector<array<int, 4>> edgeList;
+        for (int i = 0; i < edges.size(); ++i) {
+            edgeList.push_back({edges[i][2], edges[i][0], edges[i][1], i});
+        }
+        sort(edgeList.begin(), edgeList.end());
+
+        UnionFind uf(n);
+        for (auto& [w, u, v, idx] : edgeList) {
+            if (uf.unionSets(u, v)) {
+                mst[u].push_back(idx);
+                mst[v].push_back(idx);
+                mstEdges.insert(idx);
+            }
+        }
+
+        for (int i = 0; i < edges.size(); ++i) {
+            if (mstEdges.count(i)) continue;
+            path.clear();
+            destination = edges[i][1];
+            if (dfs(edges[i][0], -1, edges)) {
+                for (int p : path) {
+                    if (edges[p][2] == edges[i][2]) {
+                        pseudoCriticalEdges.insert(p);
+                        pseudoCriticalEdges.insert(i);
+                    }
+                }
+            }
+        }
+
+        vector<int> critical;
+        for (int e : mstEdges) {
+            if (!pseudoCriticalEdges.count(e)) critical.push_back(e);
+        }
+
+        return {critical, vector<int>(pseudoCriticalEdges.begin(), pseudoCriticalEdges.end())};
+    }
+
+    bool dfs(int node, int parent, vector<vector<int>>& edges) {
+        if (node == destination) return true;
+        for (int& edgeIdx : mst[node]) {
+            if (edgeIdx == parent) continue;
+            path.push_back(edgeIdx);
+            int next = edges[edgeIdx][0] == node ? edges[edgeIdx][1] : edges[edgeIdx][0];
+            if (dfs(next, edgeIdx, edges)) return true;
+            path.pop_back();
+        }
+        return false;
+    }
+};
+```
+
+```javascript
+class UnionFind {
+    /**
+     * @constructor
+     * @param {number} n
+     */
+    constructor(n) {
+        this.Parent = Array.from({ length: n + 1 }, (_, i) => i);
+        this.Size = Array(n + 1).fill(1);
+    }
+
+    /**
+     * @param {number} node
+     * @return {number}
+     */
+    find(node) {
+        if (this.Parent[node] !== node) {
+            this.Parent[node] = this.find(this.Parent[node]);
+        }
+        return this.Parent[node];
+    }
+
+    /**
+     * @param {number} u
+     * @param {number} v
+     * @return {boolean}
+     */
+    union(u, v) {
+        let pu = this.find(u);
+        let pv = this.find(v);
+        if (pu === pv) return false;
+        if (this.Size[pu] < this.Size[pv]) {
+            [pu, pv] = [pv, pu];
+        }
+        this.Size[pu] += this.Size[pv];
+        this.Parent[pv] = pu;
+        return true;
+    }
+}
+
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} edges
+     * @return {number[][]}
+     */
+    findCriticalAndPseudoCriticalEdges(n, edges) {
+        const mst = Array.from({ length: n }, () => []);
+        const mstEdges = new Set();
+        const pseudoCriticalEdges = new Set();
+        const edgeList = edges.map((e, i) => [...e, i]).sort((a, b) => a[2] - b[2]);
+
+        const uf = new UnionFind(n);
+
+        for (const [u, v, w, idx] of edgeList) {
+            if (uf.union(u, v)) {
+                mst[u].push([v, idx]);
+                mst[v].push([u, idx]);
+                mstEdges.add(idx);
+            }
+        }
+
+        let path = [];
+        let destination = null;
+
+        const dfs = (node, parent) => {
+            if (node === destination) return true;
+            for (const [next, edgeIdx] of mst[node]) {
+                if (edgeIdx === parent) continue;
+                path.push(edgeIdx);
+                if (dfs(next, edgeIdx)) return true;
+                path.pop();
+            }
+            return false;
+        };
+
+        for (let i = 0; i < edges.length; i++) {
+            if (mstEdges.has(i)) continue;
+
+            path = [];
+            destination = edges[i][1];
+            if (dfs(edges[i][0], -1)) {
+                for (const edgeIdx of path) {
+                    if (edges[edgeIdx][2] === edges[i][2]) {
+                        pseudoCriticalEdges.add(i);
+                        pseudoCriticalEdges.add(edgeIdx);
+                    }
+                }
+            }
+        }
+
+        const critical = [...mstEdges].filter(edgeIdx => !pseudoCriticalEdges.has(edgeIdx));
+        const pseudo = [...pseudoCriticalEdges];
+
+        return [critical, pseudo];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(E ^ 2)$
+* Space complexity: $O(V + E)$
+
+> Where $V$ is the number of vertices and $E$ is the number of edges.
\ No newline at end of file
diff --git a/articles/find-duplicate-integer.md b/articles/find-duplicate-integer.md
index f41762403..ef3317436 100644
--- a/articles/find-duplicate-integer.md
+++ b/articles/find-duplicate-integer.md
@@ -73,6 +73,46 @@ public class Solution {
 }
 ```
 
+```go
+func findDuplicate(nums []int) int {
+    sort.Ints(nums)
+    for i := 0; i < len(nums)-1; i++ {
+        if nums[i] == nums[i+1] {
+            return nums[i]
+        }
+    }
+    return -1
+}
+```
+
+```kotlin
+class Solution {
+    fun findDuplicate(nums: IntArray): Int {
+        nums.sort()
+        for (i in 0 until nums.size - 1) {
+            if (nums[i] == nums[i + 1]) {
+                return nums[i]
+            }
+        }
+        return -1
+    }
+}
+```
+
+```swift
+class Solution {
+    func findDuplicate(_ nums: [Int]) -> Int {
+        var nums = nums.sorted()
+        for i in 0..<nums.count - 1 {
+            if nums[i] == nums[i + 1] {
+                return nums[i]
+            }
+        }
+        return -1
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -162,6 +202,49 @@ public class Solution {
 }
 ```
 
+```go
+func findDuplicate(nums []int) int {
+    seen := make(map[int]struct{})
+    for _, num := range nums {
+        if _, exists := seen[num]; exists {
+            return num
+        }
+        seen[num] = struct{}{}
+    }
+    return -1
+}
+```
+
+```kotlin
+class Solution {
+    fun findDuplicate(nums: IntArray): Int {
+        val seen = HashSet<Int>()
+        for (num in nums) {
+            if (num in seen) {
+                return num
+            }
+            seen.add(num)
+        }
+        return -1
+    }
+}
+```
+
+```swift
+class Solution {
+    func findDuplicate(_ nums: [Int]) -> Int {
+        var seen = Set<Int>()
+        for num in nums {
+            if seen.contains(num) {
+                return num
+            }
+            seen.insert(num)
+        }
+        return -1
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -251,6 +334,49 @@ public class Solution {
 }
 ```
 
+```go
+func findDuplicate(nums []int) int {
+    seen := make([]int, len(nums))
+    for _, num := range nums {
+        if seen[num-1] == 1 {
+            return num
+        }
+        seen[num-1] = 1
+    }
+    return -1
+}
+```
+
+```kotlin
+class Solution {
+    fun findDuplicate(nums: IntArray): Int {
+        val seen = IntArray(nums.size)
+        for (num in nums) {
+            if (seen[num - 1] == 1) {
+                return num
+            }
+            seen[num - 1] = 1
+        }
+        return -1
+    }
+}
+```
+
+```swift
+class Solution {
+    func findDuplicate(_ nums: [Int]) -> Int {
+        var seen = [Int](repeating: 0, count: nums.count)
+        for num in nums {
+            if seen[num - 1] == 1 {
+                return num
+            }
+            seen[num - 1] = 1
+        }
+        return -1
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -340,6 +466,57 @@ public class Solution {
 }
 ```
 
+```go
+func findDuplicate(nums []int) int {
+    for _, num := range nums {
+        idx := abs(num) - 1
+        if nums[idx] < 0 {
+            return abs(num)
+        }
+        nums[idx] *= -1
+    }
+    return -1
+}
+
+func abs(num int) int {
+    if num < 0 {
+        return -num
+    }
+    return num
+}
+```
+
+```kotlin
+class Solution {
+    fun findDuplicate(nums: IntArray): Int {
+        for (num in nums) {
+            val idx = Math.abs(num) - 1
+            if (nums[idx] < 0) {
+                return Math.abs(num)
+            }
+            nums[idx] *= -1
+        }
+        return -1
+    }
+}
+```
+
+```swift
+class Solution {
+    func findDuplicate(_ nums: [Int]) -> Int {
+        var nums = nums
+        for num in nums {
+            let idx = abs(num) - 1
+            if nums[idx] < 0 {
+                return abs(num)
+            }
+            nums[idx] *= -1
+        }
+        return -1
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -484,6 +661,82 @@ public class Solution {
 }
 ```
 
+```go
+func findDuplicate(nums []int) int {
+    n := len(nums)
+    low, high := 1, n-1
+
+    for low < high {
+        mid := low + (high-low)/2
+        lessOrEqual := 0
+
+        for _, num := range nums {
+            if num <= mid {
+                lessOrEqual++
+            }
+        }
+
+        if lessOrEqual <= mid {
+            low = mid + 1
+        } else {
+            high = mid
+        }
+    }
+
+    return low
+}
+```
+
+```kotlin
+class Solution {
+    fun findDuplicate(nums: IntArray): Int {
+        val n = nums.size
+        var low = 1
+        var high = n - 1
+
+        while (low < high) {
+            val mid = low + (high - low) / 2
+            var lessOrEqual = 0
+
+            for (num in nums) {
+                if (num <= mid) {
+                    lessOrEqual++
+                }
+            }
+
+            if (lessOrEqual <= mid) {
+                low = mid + 1
+            } else {
+                high = mid
+            }
+        }
+
+        return low
+    }
+}
+```
+
+```swift
+class Solution {
+    func findDuplicate(_ nums: [Int]) -> Int {
+        let n = nums.count
+        var low = 1, high = n - 1
+
+        while low < high {
+            let mid = low + (high - low) / 2
+            let lessOrEqual = nums.filter { $0 <= mid }.count
+
+            if lessOrEqual <= mid {
+                low = mid + 1
+            } else {
+                high = mid
+            }
+        }
+        return low
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -631,6 +884,100 @@ public class Solution {
 }
 ```
 
+```go
+func findDuplicate(nums []int) int {
+    n := len(nums)
+    res := 0
+
+    for b := 0; b < 32; b++ {
+        x, y := 0, 0
+        mask := 1 << b
+
+        for _, num := range nums {
+            if num&mask != 0 {
+                x++
+            }
+        }
+
+        for num := 1; num < n; num++ {
+            if num&mask != 0 {
+                y++
+            }
+        }
+
+        if x > y {
+            res |= mask
+        }
+    }
+
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun findDuplicate(nums: IntArray): Int {
+        val n = nums.size
+        var res = 0
+
+        for (b in 0 until 32) {
+            var x = 0
+            var y = 0
+            val mask = 1 shl b
+
+            for (num in nums) {
+                if (num and mask != 0) {
+                    x++
+                }
+            }
+
+            for (num in 1 until n) {
+                if (num and mask != 0) {
+                    y++
+                }
+            }
+
+            if (x > y) {
+                res = res or mask
+            }
+        }
+
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func findDuplicate(_ nums: [Int]) -> Int {
+        let n = nums.count
+        var res = 0
+
+        for b in 0..<32 {
+            var x = 0, y = 0
+            let mask = 1 << b
+
+            for num in nums {
+                if num & mask != 0 {
+                    x += 1
+                }
+            }
+
+            for num in 1..<n {
+                if num & mask != 0 {
+                    y += 1
+                }
+            }
+
+            if x > y {
+                res |= mask
+            }
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -764,6 +1111,84 @@ public class Solution {
 }
 ```
 
+```go
+func findDuplicate(nums []int) int {
+    slow, fast := 0, 0
+
+    for {
+        slow = nums[slow]
+        fast = nums[nums[fast]]
+
+        if slow == fast {
+            break
+        }
+    }
+
+    slow2 := 0
+    for {
+        slow = nums[slow]
+        slow2 = nums[slow2]
+
+        if slow == slow2 {
+            return slow
+        }
+    }
+}
+```
+
+```kotlin
+class Solution {
+    fun findDuplicate(nums: IntArray): Int {
+        var slow = 0
+        var fast = 0
+
+        while (true) {
+            slow = nums[slow]
+            fast = nums[nums[fast]]
+
+            if (slow == fast) {
+                break
+            }
+        }
+
+        var slow2 = 0
+        while (true) {
+            slow = nums[slow]
+            slow2 = nums[slow2]
+
+            if (slow == slow2) {
+                return slow
+            }
+        }
+    }
+}
+```
+
+```swift
+class Solution {
+    func findDuplicate(_ nums: [Int]) -> Int {
+        var slow = 0, fast = 0
+
+        while true {
+            slow = nums[slow]
+            fast = nums[nums[fast]]
+            if slow == fast {
+                break
+            }
+        }
+
+        var slow2 = 0
+        while true {
+            slow = nums[slow]
+            slow2 = nums[slow2]
+            if slow == slow2 {
+                return slow
+            }
+        }
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/find-duplicate-subtrees.md b/articles/find-duplicate-subtrees.md
new file mode 100644
index 000000000..bf3d6d7e9
--- /dev/null
+++ b/articles/find-duplicate-subtrees.md
@@ -0,0 +1,550 @@
+## 1. Brute Force (DFS)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def findDuplicateSubtrees(self, root: Optional[TreeNode]) -> List[Optional[TreeNode]]:
+        def same(node1, node2):
+            if not node1 and not node2:
+                return True
+            if not node1 or not node2:
+                return False
+            return (node1.val == node2.val and
+                    same(node1.left, node2.left) and
+                    same(node1.right, node2.right))
+        
+        subTree = []
+        def dfs(root):
+            if not root:
+                return
+            subTree.append(root)
+            dfs(root.left)
+            dfs(root.right)
+        
+        dfs(root)
+        res = []
+        seen = set()
+        
+        for i in range(len(subTree)):
+            if subTree[i] in seen:
+                continue
+            for j in range(i + 1, len(subTree)):
+                if subTree[j] in seen:
+                    continue
+
+                if same(subTree[i], subTree[j]):
+                    if subTree[i] not in seen:
+                        res.append(subTree[i])
+                        seen.add(subTree[i])
+                    seen.add(subTree[j])
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<TreeNode> findDuplicateSubtrees(TreeNode root) {
+        List<TreeNode> res = new ArrayList<>();
+        Set<TreeNode> seen = new HashSet<>();
+        List<TreeNode> subTree = new ArrayList<>();
+        dfs(root, subTree);
+
+        for (int i = 0; i < subTree.size(); i++) {
+            if (seen.contains(subTree.get(i))) continue;
+            for (int j = i + 1; j < subTree.size(); j++) {
+                if (seen.contains(subTree.get(j))) continue;
+
+                if (same(subTree.get(i), subTree.get(j))) {
+                    if (!seen.contains(subTree.get(i))) {
+                        res.add(subTree.get(i));
+                        seen.add(subTree.get(i));
+                    }
+                    seen.add(subTree.get(j));
+                }
+            }
+        }
+        return res;
+    }
+
+    private boolean same(TreeNode node1, TreeNode node2) {
+        if (node1 == null && node2 == null) return true;
+        if (node1 == null || node2 == null) return false;
+        return node1.val == node2.val && 
+               same(node1.left, node2.left) && 
+               same(node1.right, node2.right);
+    }
+
+    private void dfs(TreeNode root, List<TreeNode> subTree) {
+        if (root == null) return;
+        subTree.add(root);
+        dfs(root.left, subTree);
+        dfs(root.right, subTree);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    vector<TreeNode*> findDuplicateSubtrees(TreeNode* root) {
+        vector<TreeNode*> res;
+        unordered_set<TreeNode*> seen;
+        vector<TreeNode*> subTree;
+        dfs(root, subTree);
+
+        for (int i = 0; i < subTree.size(); i++) {
+            if (seen.count(subTree[i])) continue;
+            for (int j = i + 1; j < subTree.size(); j++) {
+                if (seen.count(subTree[j])) continue;
+
+                if (same(subTree[i], subTree[j])) {
+                    if (!seen.count(subTree[i])) {
+                        res.push_back(subTree[i]);
+                        seen.insert(subTree[i]);
+                    }
+                    seen.insert(subTree[j]);
+                }
+            }
+        }
+        return res;
+    }
+
+private:
+    bool same(TreeNode* node1, TreeNode* node2) {
+        if (!node1 && !node2) return true;
+        if (!node1 || !node2) return false;
+        return node1->val == node2->val && 
+               same(node1->left, node2->left) && 
+               same(node1->right, node2->right);
+    }
+
+    void dfs(TreeNode* root, vector<TreeNode*>& subTree) {
+        if (!root) return;
+        subTree.push_back(root);
+        dfs(root->left, subTree);
+        dfs(root->right, subTree);
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {TreeNode[]}
+     */
+    findDuplicateSubtrees(root) {
+        const res = [];
+        const seen = new Set();
+
+        const subTree = [];
+        const dfs = (root) => {
+            if (!root) return;
+            subTree.push(root);
+            dfs(root.left);
+            dfs(root.right);
+        };
+        dfs(root);
+
+        const same = (node1, node2) => {
+            if (!node1 && !node2) return true;
+            if (!node1 || !node2) return false;
+            return node1.val === node2.val && 
+                same(node1.left, node2.left) && 
+                same(node1.right, node2.right);
+        };
+
+
+        for (let i = 0; i < subTree.length; i++) {
+            if (seen.has(subTree[i])) continue;
+            for (let j = i + 1; j < subTree.length; j++) {
+                if (seen.has(subTree[j])) continue;
+
+                if (same(subTree[i], subTree[j])) {
+                    if (!seen.has(subTree[i])) {
+                        res.push(subTree[i]);
+                        seen.add(subTree[i]);
+                    }
+                    seen.add(subTree[j]);
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 3)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. DFS + Serialization
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def findDuplicateSubtrees(self, root: Optional[TreeNode]) -> List[Optional[TreeNode]]:
+        subtrees = defaultdict(list)
+        res = []
+
+        def dfs(node):
+            if not node:
+                return "null"
+            s = ",".join([str(node.val), dfs(node.left), dfs(node.right)])
+            if len(subtrees[s]) == 1:
+                res.append(node)
+            subtrees[s].append(node)
+            return s
+
+        dfs(root)
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    private Map<String, List<TreeNode>> subtrees;
+    private List<TreeNode> res;
+
+    public List<TreeNode> findDuplicateSubtrees(TreeNode root) {
+        subtrees = new HashMap<>();
+        res = new ArrayList<>();
+        dfs(root);
+        return res;
+    }
+
+    private String dfs(TreeNode node) {
+        if (node == null) return "null";
+        String s = node.val + "," + dfs(node.left) + "," + dfs(node.right);
+        subtrees.putIfAbsent(s, new ArrayList<>());
+        if (subtrees.get(s).size() == 1) {
+            res.add(node);
+        }
+        subtrees.get(s).add(node);
+        return s;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+    unordered_map<string, vector<TreeNode*>> subtrees;
+    vector<TreeNode*> res;
+
+public:
+    vector<TreeNode*> findDuplicateSubtrees(TreeNode* root) {
+        dfs(root);
+        return res;
+    }
+
+private:
+    string dfs(TreeNode* node) {
+        if (!node) return "null";
+        string s = to_string(node->val) + "," + dfs(node->left) + "," + dfs(node->right);
+        if (subtrees[s].size() == 1) {
+            res.push_back(node);
+        }
+        subtrees[s].push_back(node);
+        return s;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {TreeNode[]}
+     */
+    findDuplicateSubtrees(root) {
+        const subtrees = new Map();
+        const res = [];
+
+        const dfs = (node) => {
+            if (!node) return "null";
+            const s = `${node.val},${dfs(node.left)},${dfs(node.right)}`;
+            if (!subtrees.has(s)) {
+                subtrees.set(s, []);
+            }
+            if (subtrees.get(s).length === 1) {
+                res.push(node);
+            }
+            subtrees.get(s).push(node);
+            return s;
+        };
+
+        dfs(root);
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 3. Depth First Search (Optimal)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def findDuplicateSubtrees(self, root: Optional[TreeNode]) -> List[Optional[TreeNode]]:
+        id_map = {}
+        count = defaultdict(int)
+        res = []
+
+        def dfs(node):
+            if not node:
+                return -1
+            cur = (dfs(node.left), node.val, dfs(node.right))
+            if cur not in id_map:
+                id_map[cur] = len(id_map) + 1
+
+            curId = id_map[cur]
+            if count[curId] == 1:
+                res.append(node)
+            count[curId] += 1
+            return curId
+
+        dfs(root)
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    private Map<String, Integer> idMap;
+    private Map<Integer, Integer> count;
+    private List<TreeNode> res;
+
+    public List<TreeNode> findDuplicateSubtrees(TreeNode root) {
+        idMap = new HashMap<>();
+        count = new HashMap<>();
+        res = new ArrayList<>();
+
+        dfs(root);
+        return res;
+    }
+
+    private int dfs(TreeNode node) {
+        if (node == null) return -1;
+        String cur = dfs(node.left) + "," + node.val + "," + dfs(node.right);
+        idMap.putIfAbsent(cur, idMap.size());
+        int curId = idMap.get(cur);
+        count.put(curId, count.getOrDefault(curId, 0) + 1);
+        if (count.get(curId) == 2) {
+            res.add(node);
+        }
+        return curId;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+    unordered_map<string, int> idMap;
+    unordered_map<int, int> count;
+    vector<TreeNode*> res;
+    
+public:
+    vector<TreeNode*> findDuplicateSubtrees(TreeNode* root) {
+        dfs(root);
+        return res;
+    }
+
+private:
+    int dfs(TreeNode* node) {
+        if (!node) return -1;
+        string cur = to_string(dfs(node->left)) + "," + 
+                     to_string(node->val) + "," + 
+                     to_string(dfs(node->right));
+        if (idMap.find(cur) == idMap.end()) {
+            idMap[cur] = idMap.size();
+        }
+        int curId = idMap[cur];
+        count[curId]++;
+        if (count[curId] == 2) {
+            res.push_back(node);
+        }
+        return curId;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {TreeNode[]}
+     */
+    findDuplicateSubtrees(root) {
+        const idMap = new Map();
+        const count = new Map();
+        const res = [];
+        
+        const dfs = (node) => {
+            if (!node) return -1;
+            
+            const cur = `${dfs(node.left)},${node.val},${dfs(node.right)}`;
+            if (!idMap.has(cur)) {
+                idMap.set(cur, idMap.size + 1);
+            }
+            
+            const curId = idMap.get(cur);
+            count.set(curId, (count.get(curId) || 0) + 1);
+            if (count.get(curId) === 2) {
+                res.push(node);
+            }
+            
+            return curId;
+        };
+        
+        dfs(root);
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/find-eventual-safe-states.md b/articles/find-eventual-safe-states.md
new file mode 100644
index 000000000..df245c8a2
--- /dev/null
+++ b/articles/find-eventual-safe-states.md
@@ -0,0 +1,308 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def eventualSafeNodes(self, graph: List[List[int]]) -> List[int]:
+        n = len(graph)
+        safe = {}
+
+        def dfs(node):
+            if node in safe:
+                return safe[node]
+            safe[node] = False
+            for nei in graph[node]:
+                if not dfs(nei):
+                    return safe[node]
+            safe[node] = True
+            return safe[node]
+
+        res = []
+        for node in range(n):
+            if dfs(node):
+                res.append(node)
+        return res
+```
+
+```java
+public class Solution {
+    private Boolean[] safe;
+    
+    public List<Integer> eventualSafeNodes(int[][] graph) {
+        int n = graph.length;
+        safe = new Boolean[n];
+        List<Integer> res = new ArrayList<>();
+        for (int node = 0; node < n; node++) {
+            if (dfs(graph, node)) {
+                res.add(node);
+            }
+        }
+        return res;
+    }
+
+    private boolean dfs(int[][] graph, int node) {
+        if (safe[node] != null) {
+            return safe[node];
+        }
+        
+        safe[node] = false;
+        for (int nei : graph[node]) {
+            if (!dfs(graph, nei)) {
+                return false;
+            }
+        }
+        safe[node] = true;
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+    vector<int> safe;
+
+public:
+    vector<int> eventualSafeNodes(vector<vector<int>>& graph) {
+        int n = graph.size();
+        vector<int> res;
+        safe.assign(n, -1);
+        for (int node = 0; node < n; node++) {
+            if (dfs(graph, node)) {
+                res.push_back(node);
+            }
+        }
+        return res;
+    }
+
+private:
+    bool dfs(vector<vector<int>>& graph, int node) {
+        if (safe[node] != -1) {
+            return safe[node];
+        }
+        safe[node] = 0;
+        for (int nei : graph[node]) {
+            if (!dfs(graph, nei)) {
+                return false;
+            }
+        }
+        safe[node] = 1;
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} graph
+     * @return {number[]}
+     */
+    eventualSafeNodes(graph) {
+        const n = graph.length;
+        const safe = Array(n).fill(undefined);
+        const res = [];
+
+        const dfs = (node) => {
+            if (safe[node] !== undefined) {
+                return safe[node];
+            }
+            safe[node] = false;
+            for (let nei of graph[node]) {
+                if (!dfs(nei)) {
+                    return false;
+                }
+            }
+            safe[node] = true;
+            return true;
+        };
+
+        for (let node = 0; node < n; node++) {
+            if (dfs(node)) {
+                res.push(node);
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + E)$
+* Space complexity: $O(V + E)$
+
+> Where $V$ is the number of vertices and $E$ is the number of edges in the given graph.
+
+---
+
+## 2. Topological Sort (Kahn's Algorithm)
+
+::tabs-start
+
+```python
+class Solution:
+    def eventualSafeNodes(self, graph: List[List[int]]) -> List[int]:
+        n = len(graph)
+        outdegree = [0] * n
+        parents = [[] for _ in range(n)]
+        queue = deque()
+
+        for node in range(n):
+            outdegree[node] = len(graph[node])
+            if outdegree[node] == 0:
+                queue.append(node)
+            for nei in graph[node]:
+                parents[nei].append(node)
+
+        while queue:
+            node = queue.popleft()
+            for parent in parents[node]:
+                outdegree[parent] -= 1
+                if outdegree[parent] == 0:
+                    queue.append(parent)
+
+        res = []
+        for node in range(n):
+            if outdegree[node] <= 0:
+                res.append(node)
+        return res
+```
+
+```java
+public class Solution {
+    public List<Integer> eventualSafeNodes(int[][] graph) {
+        int n = graph.length;
+        int[] outdegree = new int[n];
+        List<Integer>[] parents = new ArrayList[n];
+        Queue<Integer> queue = new LinkedList<>();
+        
+        for (int i = 0; i < n; i++) {
+            parents[i] = new ArrayList<>();
+        }
+        
+        for (int node = 0; node < n; node++) {
+            outdegree[node] = graph[node].length;
+            if (outdegree[node] == 0) {
+                queue.add(node);
+            }
+            for (int nei : graph[node]) {
+                parents[nei].add(node);
+            }
+        }
+        
+        while (!queue.isEmpty()) {
+            int node = queue.poll();
+            for (int parent : parents[node]) {
+                outdegree[parent]--;
+                if (outdegree[parent] == 0) {
+                    queue.add(parent);
+                }
+            }
+        }
+        
+        List<Integer> res = new ArrayList<>();
+        for (int node = 0; node < n; node++) {
+            if (outdegree[node] <= 0) {
+                res.add(node);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> eventualSafeNodes(vector<vector<int>>& graph) {
+        int n = graph.size();
+        vector<int> outdegree(n, 0);
+        vector<vector<int>> parents(n);
+        queue<int> q;
+
+        for (int node = 0; node < n; node++) {
+            outdegree[node] = graph[node].size();
+            if (outdegree[node] == 0) {
+                q.push(node);
+            }
+            for (int nei : graph[node]) {
+                parents[nei].push_back(node);
+            }
+        }
+
+        while (!q.empty()) {
+            int node = q.front();
+            q.pop();
+            for (int parent : parents[node]) {
+                outdegree[parent]--;
+                if (outdegree[parent] == 0) {
+                    q.push(parent);
+                }
+            }
+        }
+
+        vector<int> res;
+        for (int node = 0; node < n; node++) {
+            if (outdegree[node] <= 0) {
+                res.push_back(node);
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} graph
+     * @return {number[]}
+     */
+    eventualSafeNodes(graph) {
+        const n = graph.length;
+        const outdegree = Array(n).fill(0);
+        const parents = Array.from({ length: n }, () => []);
+        const queue = new Queue();
+        
+        for (let node = 0; node < n; node++) {
+            outdegree[node] = graph[node].length;
+            if (outdegree[node] === 0) {
+                queue.push(node);
+            }
+            for (let nei of graph[node]) {
+                parents[nei].push(node);
+            }
+        }
+        
+        while (!queue.isEmpty()) {
+            const node = queue.pop();
+            for (let parent of parents[node]) {
+                outdegree[parent]--;
+                if (outdegree[parent] === 0) {
+                    queue.push(parent);
+                }
+            }
+        }
+        
+        const res = [];
+        for (let node = 0; node < n; node++) {
+            if (outdegree[node] <= 0) {
+                res.push(node);
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + E)$
+* Space complexity: $O(V + E)$
+
+> Where $V$ is the number of vertices and $E$ is the number of edges in the given graph.
\ No newline at end of file
diff --git a/articles/find-first-and-last-position-of-element-in-sorted-array.md b/articles/find-first-and-last-position-of-element-in-sorted-array.md
new file mode 100644
index 000000000..e2d66f092
--- /dev/null
+++ b/articles/find-first-and-last-position-of-element-in-sorted-array.md
@@ -0,0 +1,449 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def searchRange(self, nums: List[int], target: int) -> List[int]:
+        res = [-1, -1]
+
+        for i, num in enumerate(nums):
+            if num == target:
+                if res[0] == -1:
+                    res[0] = res[1] = i
+                else:
+                    res[1] = i
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[] searchRange(int[] nums, int target) {
+        int[] res = {-1, -1};
+
+        for (int i = 0; i < nums.length; i++) {
+            if (nums[i] == target) {
+                if (res[0] == -1) {
+                    res[0] = res[1] = i;
+                } else {
+                    res[1] = i;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> searchRange(vector<int>& nums, int target) {
+        vector<int> res = {-1, -1};
+
+        for (int i = 0; i < nums.size(); i++) {
+            if (nums[i] == target) {
+                if (res[0] == -1) {
+                    res[0] = res[1] = i;
+                } else {
+                    res[1] = i;
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} target
+     * @return {number[]}
+     */
+    searchRange(nums, target) {
+        let res = [-1, -1];
+
+        for (let i = 0; i < nums.length; i++) {
+            if (nums[i] === target) {
+                if (res[0] === -1) {
+                    res[0] = res[1] = i;
+                } else {
+                    res[1] = i;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Binary Search - I
+
+::tabs-start
+
+```python
+class Solution:
+    def searchRange(self, nums: List[int], target: int) -> List[int]:
+        left = self.binarySearch(nums, target, True)
+        right = self.binarySearch(nums, target, False)
+        return [left, right]
+
+    def binarySearch(self, nums, target, leftBias):
+        l, r = 0, len(nums) - 1
+        i = -1
+        while l <= r:
+            m = (l + r) // 2
+            if target > nums[m]:
+                l = m + 1
+            elif target < nums[m]:
+                r = m - 1
+            else:
+                i = m
+                if leftBias:
+                    r = m - 1
+                else:
+                    l = m + 1
+        return i
+```
+
+```java
+public class Solution {
+    public int[] searchRange(int[] nums, int target) {
+        int left = binarySearch(nums, target, true);
+        int right = binarySearch(nums, target, false);
+        return new int[]{left, right};
+    }
+
+    private int binarySearch(int[] nums, int target, boolean leftBias) {
+        int l = 0, r = nums.length - 1, i = -1;
+        while (l <= r) {
+            int m = (l + r) / 2;
+            if (target > nums[m]) {
+                l = m + 1;
+            } else if (target < nums[m]) {
+                r = m - 1;
+            } else {
+                i = m;
+                if (leftBias) {
+                    r = m - 1;
+                } else {
+                    l = m + 1;
+                }
+            }
+        }
+        return i;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> searchRange(vector<int>& nums, int target) {
+        int left = binarySearch(nums, target, true);
+        int right = binarySearch(nums, target, false);
+        return {left, right};
+    }
+
+private:
+    int binarySearch(vector<int>& nums, int target, bool leftBias) {
+        int l = 0, r = nums.size() - 1, i = -1;
+        while (l <= r) {
+            int m = (l + r) / 2;
+            if (target > nums[m]) {
+                l = m + 1;
+            } else if (target < nums[m]) {
+                r = m - 1;
+            } else {
+                i = m;
+                if (leftBias) {
+                    r = m - 1;
+                } else {
+                    l = m + 1;
+                }
+            }
+        }
+        return i;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} target
+     * @return {number[]}
+     */
+    searchRange(nums, target) {
+        let left = this.binarySearch(nums, target, true);
+        let right = this.binarySearch(nums, target, false);
+        return [left, right];
+    }
+
+    /**
+     * @param {number[]} nums
+     * @param {number} target
+     * @param {boolean} leftBias
+     * @return {number}
+     */
+    binarySearch(nums, target, leftBias) {
+        let l = 0, r = nums.length - 1, i = -1;
+        while (l <= r) {
+            let m = Math.floor((l + r) / 2);
+            if (target > nums[m]) {
+                l = m + 1;
+            } else if (target < nums[m]) {
+                r = m - 1;
+            } else {
+                i = m;
+                if (leftBias) {
+                    r = m - 1;
+                } else {
+                    l = m + 1;
+                }
+            }
+        }
+        return i;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Binary Search - II
+
+::tabs-start
+
+```python
+class Solution:
+    def searchRange(self, nums: List[int], target: int) -> List[int]:
+        n = len(nums)
+
+        def binarySearch(target):
+            l, r = 0, n
+            while l < r:
+                m = l + (r - l) // 2
+                if nums[m] >= target:
+                    r = m
+                else:
+                    l = m + 1
+            return l
+        
+        start = binarySearch(target)
+        if start == n or nums[start] != target:
+            return [-1, -1]
+
+        return [start, binarySearch(target + 1) - 1]
+```
+
+```java
+public class Solution {
+    public int[] searchRange(int[] nums, int target) {
+        int n = nums.length;
+
+        int start = binarySearch(nums, target, n);
+        if (start == n || nums[start] != target) {
+            return new int[]{-1, -1};
+        }
+
+        return new int[]{start, binarySearch(nums, target + 1, n) - 1};
+    }
+
+    private int binarySearch(int[] nums, int target, int n) {
+        int l = 0, r = n;
+        while (l < r) {
+            int m = l + (r - l) / 2;
+            if (nums[m] >= target) {
+                r = m;
+            } else {
+                l = m + 1;
+            }
+        }
+        return l;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> searchRange(vector<int>& nums, int target) {
+        int n = nums.size();
+
+        int start = binarySearch(nums, target, n);
+        if (start == n || nums[start] != target) {
+            return {-1, -1};
+        }
+
+        return {start, binarySearch(nums, target + 1, n) - 1};
+    }
+
+private:
+    int binarySearch(vector<int>& nums, int target, int n) {
+        int l = 0, r = n;
+        while (l < r) {
+            int m = l + (r - l) / 2;
+            if (nums[m] >= target) {
+                r = m;
+            } else {
+                l = m + 1;
+            }
+        }
+        return l;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} target
+     * @return {number[]}
+     */
+    searchRange(nums, target) {
+        const n = nums.length;
+
+        const binarySearch = (target) => {
+            let l = 0, r = n;
+            while (l < r) {
+                let m = Math.floor(l + (r - l) / 2);
+                if (nums[m] >= target) {
+                    r = m;
+                } else {
+                    l = m + 1;
+                }
+            }
+            return l;
+        };
+
+        let start = binarySearch(target);
+        if (start === n || nums[start] !== target) {
+            return [-1, -1];
+        }
+
+        return [start, binarySearch(target + 1) - 1];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
+
+---
+
+## 4. In-Built Function
+
+::tabs-start
+
+```python
+class Solution:
+    def searchRange(self, nums: List[int], target: int) -> List[int]:
+        left = bisect.bisect_left(nums, target)
+        if left >= len(nums) or nums[left] != target:
+            return [-1, -1]
+
+        right = bisect.bisect_right(nums, target) - 1
+        return [left, right]
+```
+
+```java
+public class Solution {
+    public int[] searchRange(int[] nums, int target) {
+        int left = findLeft(nums, target);
+        if (left == -1) {
+            return new int[]{-1, -1};
+        }
+        
+        int right = findRight(nums, target);
+        return new int[]{left, right};
+    }
+    
+    private int findLeft(int[] nums, int target) {
+        // O(n) time in worst case
+        int index = Arrays.binarySearch(nums, target);
+        if (index < 0) return -1;
+        
+        while (index > 0 && nums[index - 1] == target) {
+            index--;
+        }
+        return index;
+    }
+    
+    private int findRight(int[] nums, int target) {
+        // O(n) time in worst case
+        int index = Arrays.binarySearch(nums, target);
+        if (index < 0) return -1;
+        
+        while (index < nums.length - 1 && nums[index + 1] == target) {
+            index++;
+        }
+        return index;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> searchRange(vector<int>& nums, int target) {
+        int left = lower_bound(nums.begin(), nums.end(), target) - nums.begin();
+        if (left == nums.size() || nums[left] != target) {
+            return {-1, -1};
+        }
+
+        int right = upper_bound(nums.begin(), nums.end(), target) - nums.begin() - 1;
+        return {left, right};
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} target
+     * @return {number[]}
+     */
+    searchRange(nums, target) {
+        let left = nums.indexOf(target);
+        let right = nums.lastIndexOf(target);
+
+        return left === -1 ? [-1, -1] : [left, right];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/find-first-palindromic-string-in-the-array.md b/articles/find-first-palindromic-string-in-the-array.md
new file mode 100644
index 000000000..03dd3683d
--- /dev/null
+++ b/articles/find-first-palindromic-string-in-the-array.md
@@ -0,0 +1,147 @@
+## 1. Reverse String
+
+::tabs-start
+
+```python
+class Solution:
+    def firstPalindrome(self, words: List[str]) -> str:
+        for w in words:
+            if w == w[::-1]:
+                return w
+        return ""
+```
+
+```java
+public class Solution {
+    public String firstPalindrome(String[] words) {
+        for (String w : words) {
+            if (w.equals(new StringBuilder(w).reverse().toString())) {
+                return w;
+            }
+        }
+        return "";
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string firstPalindrome(vector<string>& words) {
+        for (const string& w : words) {
+            string rev = w;
+            reverse(rev.begin(), rev.end());
+            if (w == rev) {
+                return w;
+            }
+        }
+        return "";
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @return {string}
+     */
+    firstPalindrome(words) {
+        for (let w of words) {
+            if (w === w.split('').reverse().join('')) {
+                return w;
+            }
+        }
+        return "";
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(m)$
+
+> Where $n$ is the size of the string array $words$ and $m$ is the average length of a word in the array.
+
+---
+
+## 2. Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def firstPalindrome(self, words: List[str]) -> str:
+        for w in words:
+            l, r = 0, len(w) - 1
+            while w[l] == w[r]:
+                if l >= r:
+                    return w
+                l, r = l + 1, r - 1
+        return ""
+```
+
+```java
+public class Solution {
+    public String firstPalindrome(String[] words) {
+        for (String w : words) {
+            int l = 0, r = w.length() - 1;
+            while (w.charAt(l) == w.charAt(r)) {
+                if (l >= r) return w;
+                l++;
+                r--;
+            }
+        }
+        return "";
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string firstPalindrome(vector<string>& words) {
+        for (const string& w : words) {
+            int l = 0, r = w.length() - 1;
+            while (w[l] == w[r]) {
+                if (l >= r) return w;
+                l++;
+                r--;
+            }
+        }
+        return "";
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @return {string}
+     */
+    firstPalindrome(words) {
+        for (let w of words) {
+            let l = 0, r = w.length - 1;
+            while (w.charAt(l) === w.charAt(r)) {
+                if (l >= r) return w;
+                l++;
+                r--;
+            }
+        }
+        return "";
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(1)$ extra space.
+
+> Where $n$ is the size of the string array $words$ and $m$ is the average length of a word in the array.
\ No newline at end of file
diff --git a/articles/find-in-mountain-array.md b/articles/find-in-mountain-array.md
new file mode 100644
index 000000000..c917a7507
--- /dev/null
+++ b/articles/find-in-mountain-array.md
@@ -0,0 +1,842 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+# """
+# This is MountainArray's API interface.
+# You should not implement it, or speculate about its implementation
+# """
+#class MountainArray:
+#    def get(self, index: int) -> int:
+#    def length(self) -> int:
+
+class Solution:
+    def findInMountainArray(self, target: int, mountainArr: 'MountainArray') -> int:
+        n = mountainArr.length()
+
+        for i in range(n):
+            if mountainArr.get(i) == target:
+                return i
+        
+        return -1
+```
+
+```java
+/**
+ * // This is MountainArray's API interface.
+ * // You should not implement it, or speculate about its implementation
+ * interface MountainArray {
+ *     public int get(int index) {}
+ *     public int length() {}
+ * }
+ */
+ 
+public class Solution {
+    public int findInMountainArray(int target, MountainArray mountainArr) {
+        int n = mountainArr.length();
+
+        for (int i = 0; i < n; i++) {
+            if (mountainArr.get(i) == target) {
+                return i;
+            }
+        }
+        
+        return -1;
+    }
+}
+```
+
+```cpp
+/**
+ * // This is the MountainArray's API interface.
+ * // You should not implement it, or speculate about its implementation
+ * class MountainArray {
+ *   public:
+ *     int get(int index);
+ *     int length();
+ * };
+ */
+
+class Solution {
+public:
+    int findInMountainArray(int target, MountainArray &mountainArr) {
+        int n = mountainArr.length();
+
+        for (int i = 0; i < n; i++) {
+            if (mountainArr.get(i) == target) {
+                return i;
+            }
+        }
+        
+        return -1;
+    }
+};
+```
+
+```javascript
+/**
+ * // This is the MountainArray's API interface.
+ * // You should not implement it, or speculate about its implementation
+ * class MountainArray {
+ *     @param {number} index
+ *     @return {number}
+ *     get(index) {
+ *         ...
+ *     }
+ *
+ *     @return {number}
+ *     length() {
+ *         ...
+ *     }
+ * }
+ */
+
+class Solution {
+    /**
+     * @param {number} target
+     * @param {MountainArray} mountainArr
+     * @return {number}
+     */
+    findInMountainArray(target, mountainArr) {
+        let n = mountainArr.length();
+
+        for (let i = 0; i < n; i++) {
+            if (mountainArr.get(i) === target) {
+                return i;
+            }
+        }
+        
+        return -1;
+    }
+}
+```
+
+```csharp
+/**
+ * // This is MountainArray's API interface.
+ * // You should not implement it, or speculate about its implementation
+ * class MountainArray {
+ *     public int Get(int index) {}
+ *     public int Length() {}
+ * }
+ */
+
+class Solution {
+    public int FindInMountainArray(int target, MountainArray mountainArr) {
+        int n = mountainArr.Length();
+
+        for (int i = 0; i < n; i++) {
+            if (mountainArr.Get(i) == target) {
+                return i;
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Binary Search
+
+::tabs-start
+
+```python
+# """
+# This is MountainArray's API interface.
+# You should not implement it, or speculate about its implementation
+# """
+#class MountainArray:
+#    def get(self, index: int) -> int:
+#    def length(self) -> int:
+
+class Solution:
+    def findInMountainArray(self, target: int, mountainArr: 'MountainArray') -> int:
+        length = mountainArr.length()
+
+        # Find Peak
+        l, r = 1, length - 2
+        while l <= r:
+            m = (l + r) // 2
+            left, mid, right = mountainArr.get(m - 1), mountainArr.get(m), mountainArr.get(m + 1)
+            if left < mid < right:
+                l = m + 1
+            elif left > mid > right:
+                r = m - 1
+            else:
+                break
+        peak = m
+
+        # Search left portion
+        l, r = 0, peak - 1
+        while l <= r:
+            m = (l + r) // 2
+            val = mountainArr.get(m)
+            if val < target:
+                l = m + 1
+            elif val > target:
+                r = m - 1
+            else:
+                return m
+
+        # Search right portion
+        l, r = peak, length - 1
+        while l <= r:
+            m = (l + r) // 2
+            val = mountainArr.get(m)
+            if val > target:
+                l = m + 1
+            elif val < target:
+                r = m - 1
+            else:
+                return m
+        
+        return -1
+```
+
+```java
+/**
+ * // This is MountainArray's API interface.
+ * // You should not implement it, or speculate about its implementation
+ * interface MountainArray {
+ *     public int get(int index) {}
+ *     public int length() {}
+ * }
+ */
+ 
+public class Solution {
+    public int findInMountainArray(int target, MountainArray mountainArr) {
+        int length = mountainArr.length();
+
+        // Find Peak
+        int l = 1, r = length - 2, peak = 0;
+        while (l <= r) {
+            int m = (l + r) / 2;
+            int left = mountainArr.get(m - 1);
+            int mid = mountainArr.get(m);
+            int right = mountainArr.get(m + 1);
+            if (left < mid && mid < right) {
+                l = m + 1;
+            } else if (left > mid && mid > right) {
+                r = m - 1;
+            } else {
+                peak = m;
+                break;
+            }
+        }
+
+        // Search left portion
+        l = 0;
+        r = peak - 1;
+        while (l <= r) {
+            int m = (l + r) / 2;
+            int val = mountainArr.get(m);
+            if (val < target) {
+                l = m + 1;
+            } else if (val > target) {
+                r = m - 1;
+            } else {
+                return m;
+            }
+        }
+
+        // Search right portion
+        l = peak;
+        r = length - 1;
+        while (l <= r) {
+            int m = (l + r) / 2;
+            int val = mountainArr.get(m);
+            if (val > target) {
+                l = m + 1;
+            } else if (val < target) {
+                r = m - 1;
+            } else {
+                return m;
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+```cpp
+/**
+ * // This is the MountainArray's API interface.
+ * // You should not implement it, or speculate about its implementation
+ * class MountainArray {
+ *   public:
+ *     int get(int index);
+ *     int length();
+ * };
+ */
+
+class Solution {
+public:
+    int findInMountainArray(int target, MountainArray &mountainArr) {
+        int length = mountainArr.length();
+
+        // Find Peak
+        int l = 1, r = length - 2, peak = 0;
+        while (l <= r) {
+            int m = (l + r) / 2;
+            int left = mountainArr.get(m - 1);
+            int mid = mountainArr.get(m);
+            int right = mountainArr.get(m + 1);
+            if (left < mid && mid < right) {
+                l = m + 1;
+            } else if (left > mid && mid > right) {
+                r = m - 1;
+            } else {
+                peak = m;
+                break;
+            }
+        }
+
+        // Search left portion
+        l = 0;
+        r = peak - 1;
+        while (l <= r) {
+            int m = (l + r) / 2;
+            int val = mountainArr.get(m);
+            if (val < target) {
+                l = m + 1;
+            } else if (val > target) {
+                r = m - 1;
+            } else {
+                return m;
+            }
+        }
+
+        // Search right portion
+        l = peak;
+        r = length - 1;
+        while (l <= r) {
+            int m = (l + r) / 2;
+            int val = mountainArr.get(m);
+            if (val > target) {
+                l = m + 1;
+            } else if (val < target) {
+                r = m - 1;
+            } else {
+                return m;
+            }
+        }
+
+        return -1;
+    }
+};
+```
+
+```javascript
+/**
+ * // This is the MountainArray's API interface.
+ * // You should not implement it, or speculate about its implementation
+ * class MountainArray {
+ *     @param {number} index
+ *     @return {number}
+ *     get(index) {
+ *         ...
+ *     }
+ *
+ *     @return {number}
+ *     length() {
+ *         ...
+ *     }
+ * }
+ */
+
+class Solution {
+    /**
+     * @param {number} target
+     * @param {MountainArray} mountainArr
+     * @return {number}
+     */
+    findInMountainArray(target, mountainArr) {
+        const length = mountainArr.length();
+
+        // Find Peak
+        let l = 1, r = length - 2, peak = 0;
+        while (l <= r) {
+            const m = Math.floor((l + r) / 2);
+            const left = mountainArr.get(m - 1);
+            const mid = mountainArr.get(m);
+            const right = mountainArr.get(m + 1);
+            if (left < mid && mid < right) {
+                l = m + 1;
+            } else if (left > mid && mid > right) {
+                r = m - 1;
+            } else {
+                peak = m;
+                break;
+            }
+        }
+
+        // Search left portion
+        l = 0;
+        r = peak - 1;
+        while (l <= r) {
+            const m = Math.floor((l + r) / 2);
+            const val = mountainArr.get(m);
+            if (val < target) {
+                l = m + 1;
+            } else if (val > target) {
+                r = m - 1;
+            } else {
+                return m;
+            }
+        }
+
+        // Search right portion
+        l = peak;
+        r = length - 1;
+        while (l <= r) {
+            const m = Math.floor((l + r) / 2);
+            const val = mountainArr.get(m);
+            if (val > target) {
+                l = m + 1;
+            } else if (val < target) {
+                r = m - 1;
+            } else {
+                return m;
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+```csharp
+/**
+ * // This is MountainArray's API interface.
+ * // You should not implement it, or speculate about its implementation
+ * class MountainArray {
+ *     public int Get(int index) {}
+ *     public int Length() {}
+ * }
+ */
+
+class Solution {
+    public int FindInMountainArray(int target, MountainArray mountainArr) {
+        int length = mountainArr.Length();
+
+        // Find Peak
+        int l = 1, r = length - 2, peak = 0;
+        while (l <= r) {
+            int m = (l + r) / 2;
+            int left = mountainArr.Get(m - 1);
+            int mid = mountainArr.Get(m);
+            int right = mountainArr.Get(m + 1);
+            if (left < mid && mid < right) {
+                l = m + 1;
+            } else if (left > mid && mid > right) {
+                r = m - 1;
+            } else {
+                peak = m;
+                break;
+            }
+        }
+
+        // Search left portion
+        l = 0;
+        r = peak - 1;
+        while (l <= r) {
+            int m = (l + r) / 2;
+            int val = mountainArr.Get(m);
+            if (val < target) {
+                l = m + 1;
+            } else if (val > target) {
+                r = m - 1;
+            } else {
+                return m;
+            }
+        }
+
+        // Search right portion
+        l = peak;
+        r = length - 1;
+        while (l <= r) {
+            int m = (l + r) / 2;
+            int val = mountainArr.Get(m);
+            if (val > target) {
+                l = m + 1;
+            } else if (val < target) {
+                r = m - 1;
+            } else {
+                return m;
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Binary Search + Caching
+
+::tabs-start
+
+```python
+# """
+# This is MountainArray's API interface.
+# You should not implement it, or speculate about its implementation
+# """
+#class MountainArray:
+#    def get(self, index: int) -> int:
+#    def length(self) -> int:
+
+class Solution:
+    def findInMountainArray(self, target: int, mountainArr: 'MountainArray') -> int:
+        length = mountainArr.length()
+        cache = {}
+
+        def get(i):
+            if i not in cache:
+                cache[i] = mountainArr.get(i)
+            return cache[i]
+
+        # Find Peak
+        l, r = 1, length - 2
+        while l <= r:
+            m = (l + r) >> 1
+            left, mid, right = get(m - 1), get(m), get(m + 1)
+            if left < mid < right:
+                l = m + 1
+            elif left > mid > right:
+                r = m - 1
+            else:
+                break
+        peak = m
+
+        def binary_search(l, r, ascending):
+            while l <= r:
+                m = (l + r) >> 1
+                val = get(m)
+                if val == target:
+                    return m
+                if ascending == (val < target):
+                    l = m + 1
+                else:
+                    r = m - 1
+            return -1
+
+        # Search left portion
+        res = binary_search(0, peak, True)
+        if res != -1:
+            return res
+
+        # Search right portion
+        return binary_search(peak, length - 1, False)
+```
+
+```java
+/**
+ * // This is MountainArray's API interface.
+ * // You should not implement it, or speculate about its implementation
+ * interface MountainArray {
+ *     public int get(int index) {}
+ *     public int length() {}
+ * }
+ */
+ 
+public class Solution {
+    private Map<Integer, Integer> cache = new HashMap<>();
+
+    private int get(int index, MountainArray mountainArr) {
+        if (!cache.containsKey(index)) {
+            cache.put(index, mountainArr.get(index));
+        }
+        return cache.get(index);
+    }
+
+    private int binarySearch(int l, int r, boolean ascending, MountainArray mountainArr, int target) {
+        while (l <= r) {
+            int m = (l + r) >> 1;
+            int val = get(m, mountainArr);
+            if (val == target) {
+                return m;
+            }
+            if (ascending == (val < target)) {
+                l = m + 1;
+            } else {
+                r = m - 1;
+            }
+        }
+        return -1;
+    }
+
+    public int findInMountainArray(int target, MountainArray mountainArr) {
+        int length = mountainArr.length();
+
+        // Find Peak
+        int l = 1, r = length - 2, peak = 0;
+        while (l <= r) {
+            int m = (l + r) >> 1;
+            int left = get(m - 1, mountainArr);
+            int mid = get(m, mountainArr);
+            int right = get(m + 1, mountainArr);
+            if (left < mid && mid < right) {
+                l = m + 1;
+            } else if (left > mid && mid > right) {
+                r = m - 1;
+            } else {
+                peak = m;
+                break;
+            }
+        }
+
+        // Search left portion
+        int res = binarySearch(0, peak, true, mountainArr, target);
+        if (res != -1) {
+            return res;
+        }
+
+        // Search right portion
+        return binarySearch(peak, length - 1, false, mountainArr, target);
+    }
+}
+```
+
+```cpp
+/**
+ * // This is the MountainArray's API interface.
+ * // You should not implement it, or speculate about its implementation
+ * class MountainArray {
+ *   public:
+ *     int get(int index);
+ *     int length();
+ * };
+ */
+
+class Solution {
+private:
+    unordered_map<int, int> cache;
+
+    int get(int index, MountainArray &mountainArr) {
+        if (cache.find(index) == cache.end()) {
+            cache[index] = mountainArr.get(index);
+        }
+        return cache[index];
+    }
+
+    int binarySearch(int l, int r, bool ascending, int target, MountainArray &mountainArr) {
+        while (l <= r) {
+            int m = (l + r) >> 1;
+            int val = get(m, mountainArr);
+            if (val == target) {
+                return m;
+            }
+            if (ascending == (val < target)) {
+                l = m + 1;
+            } else {
+                r = m - 1;
+            }
+        }
+        return -1;
+    }
+
+public:
+    int findInMountainArray(int target, MountainArray &mountainArr) {
+        int length = mountainArr.length();
+
+        // Find Peak
+        int l = 1, r = length - 2, peak = 0;
+        while (l <= r) {
+            int m = (l + r) >> 1;
+            int left = get(m - 1, mountainArr);
+            int mid = get(m, mountainArr);
+            int right = get(m + 1, mountainArr);
+            if (left < mid && mid < right) {
+                l = m + 1;
+            } else if (left > mid && mid > right) {
+                r = m - 1;
+            } else {
+                peak = m;
+                break;
+            }
+        }
+
+        // Search left portion
+        int res = binarySearch(0, peak, true, target, mountainArr);
+        if (res != -1) {
+            return res;
+        }
+
+        // Search right portion
+        return binarySearch(peak, length - 1, false, target, mountainArr);
+    }
+};
+```
+
+```javascript
+/**
+ * // This is the MountainArray's API interface.
+ * // You should not implement it, or speculate about its implementation
+ * class MountainArray {
+ *     @param {number} index
+ *     @return {number}
+ *     get(index) {
+ *         ...
+ *     }
+ *
+ *     @return {number}
+ *     length() {
+ *         ...
+ *     }
+ * }
+ */
+
+class Solution {
+    /**
+     * @param {number} target
+     * @param {MountainArray} mountainArr
+     * @return {number}
+     */
+    findInMountainArray(target, mountainArr) {
+        const cache = new Map();
+        const get = (index) => {
+            if (!cache.has(index)) {
+                cache.set(index, mountainArr.get(index));
+            }
+            return cache.get(index);
+        };
+
+        const binarySearch = (l, r, ascending) => {
+            while (l <= r) {
+                const m = Math.floor((l + r) / 2);
+                const val = get(m);
+                if (val === target) {
+                    return m;
+                }
+                if (ascending === (val < target)) {
+                    l = m + 1;
+                } else {
+                    r = m - 1;
+                }
+            }
+            return -1;
+        };
+
+        const length = mountainArr.length();
+
+        // Find Peak
+        let l = 1, r = length - 2, peak = 0;
+        while (l <= r) {
+            const m = Math.floor((l + r) / 2);
+            const left = get(m - 1);
+            const mid = get(m);
+            const right = get(m + 1);
+            if (left < mid && mid < right) {
+                l = m + 1;
+            } else if (left > mid && mid > right) {
+                r = m - 1;
+            } else {
+                peak = m;
+                break;
+            }
+        }
+
+        // Search left portion
+        let res = binarySearch(0, peak, true);
+        if (res !== -1) {
+            return res;
+        }
+
+        // Search right portion
+        return binarySearch(peak, length - 1, false);
+    }
+}
+```
+
+```csharp
+/**
+ * // This is MountainArray's API interface.
+ * // You should not implement it, or speculate about its implementation
+ * class MountainArray {
+ *     public int Get(int index) {}
+ *     public int Length() {}
+ * }
+ */
+
+class Solution {
+    private Dictionary<int, int> cache = new Dictionary<int, int>();
+
+    private int Get(int index, MountainArray mountainArr) {
+        if (!cache.ContainsKey(index)) {
+            cache[index] = mountainArr.Get(index);
+        }
+        return cache[index];
+    }
+
+    private int BinarySearch(int l, int r, bool ascending, MountainArray mountainArr, int target) {
+        while (l <= r) {
+            int m = (l + r) >> 1;
+            int val = Get(m, mountainArr);
+            if (val == target) {
+                return m;
+            }
+            if ((ascending && val < target) || (!ascending && val > target)) {
+                l = m + 1;
+            } else {
+                r = m - 1;
+            }
+        }
+        return -1;
+    }
+
+    public int FindInMountainArray(int target, MountainArray mountainArr) {
+        int length = mountainArr.Length();
+
+        // Find Peak
+        int l = 1, r = length - 2, peak = 0;
+        while (l <= r) {
+            int m = (l + r) >> 1;
+            int left = Get(m - 1, mountainArr);
+            int mid = Get(m, mountainArr);
+            int right = Get(m + 1, mountainArr);
+
+            if (left < mid && mid < right) {
+                l = m + 1;
+            } else if (left > mid && mid > right) {
+                r = m - 1;
+            } else {
+                peak = m;
+                break;
+            }
+        }
+
+        // Search left portion
+        int res = BinarySearch(0, peak, true, mountainArr, target);
+        if (res != -1) return res;
+
+        // Search right portion
+        return BinarySearch(peak, length - 1, false, mountainArr, target);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(\log n)$
\ No newline at end of file
diff --git a/articles/find-k-closest-elements.md b/articles/find-k-closest-elements.md
new file mode 100644
index 000000000..d4a177c89
--- /dev/null
+++ b/articles/find-k-closest-elements.md
@@ -0,0 +1,555 @@
+## 1. Sorting (Custom Comparator)
+
+::tabs-start
+
+```python
+class Solution:
+    def findClosestElements(self, arr: List[int], k: int, x: int) -> List[int]:
+        arr.sort(key=lambda num: (abs(num - x), num))
+        return sorted(arr[:k])
+```
+
+```java
+public class Solution {
+    public List<Integer> findClosestElements(int[] arr, int k, int x) {
+        List<Integer> list = new ArrayList<>();
+        for (int num : arr) {
+            list.add(num);
+        }
+        
+        list.sort((a, b) -> {
+            int diff = Math.abs(a - x) - Math.abs(b - x);
+            return diff == 0 ? Integer.compare(a, b) : diff;
+        });
+        
+        List<Integer> result = list.subList(0, k);
+        Collections.sort(result);
+        return result;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findClosestElements(vector<int>& arr, int k, int x) {
+        sort(arr.begin(), arr.end(), [x](int a, int b) {
+            int diff = abs(a - x) - abs(b - x);
+            return diff == 0 ? a < b : diff < 0;
+        });
+        vector<int> result(arr.begin(), arr.begin() + k);
+        sort(result.begin(), result.end());
+        return result;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @param {number} k
+     * @param {number} x
+     * @return {number[]}
+     */
+    findClosestElements(arr, k, x) {
+        arr.sort((a, b) => {
+            const diff = Math.abs(a - x) - Math.abs(b - x);
+            return diff === 0 ? a - b : diff;
+        });
+        const result = arr.slice(0, k);
+        return result.sort((a, b) => a - b);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n + k \log k)$
+* Space complexity:
+    * $O(1)$ or $O(n)$ space depending on the sorting algorithm.
+    * $O(k)$ space for the output array.
+
+> Where $n$ is the size of the input array and $k$ is the number of closest elements to find.
+
+---
+
+## 2. Linear Scan + Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def findClosestElements(self, arr: List[int], k: int, x: int) -> List[int]:
+        n = len(arr)
+        idx = 0
+        for i in range(1, n):
+            if abs(x - arr[idx]) > abs(x - arr[i]):
+                idx = i
+
+        res = [arr[idx]]
+        l, r = idx - 1, idx + 1
+
+        while len(res) < k:
+            if l >= 0 and r < n:
+                if abs(x - arr[l]) <= abs(x - arr[r]):
+                    res.append(arr[l])
+                    l -= 1
+                else:
+                    res.append(arr[r])
+                    r += 1
+            elif l >= 0:
+                res.append(arr[l])
+                l -= 1
+            elif r < n:
+                res.append(arr[r])
+                r += 1
+
+        return sorted(res)
+```
+
+```java
+public class Solution {
+    public List<Integer> findClosestElements(int[] arr, int k, int x) {
+        int n = arr.length;
+        int idx = 0;
+        for (int i = 1; i < n; i++) {
+            if (Math.abs(x - arr[idx]) > Math.abs(x - arr[i])) {
+                idx = i;
+            }
+        }
+
+        List<Integer> res = new ArrayList<>();
+        res.add(arr[idx]);
+        int l = idx - 1, r = idx + 1;
+
+        while (res.size() < k) {
+            if (l >= 0 && r < n) {
+                if (Math.abs(x - arr[l]) <= Math.abs(x - arr[r])) {
+                    res.add(arr[l--]);
+                } else {
+                    res.add(arr[r++]);
+                }
+            } else if (l >= 0) {
+                res.add(arr[l--]);
+            } else if (r < n) {
+                res.add(arr[r++]);
+            }
+        }
+
+        Collections.sort(res);
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findClosestElements(vector<int>& arr, int k, int x) {
+        int n = arr.size();
+        int idx = 0;
+        for (int i = 1; i < n; i++) {
+            if (abs(x - arr[idx]) > abs(x - arr[i])) {
+                idx = i;
+            }
+        }
+
+        vector<int> res = {arr[idx]};
+        int l = idx - 1, r = idx + 1;
+
+        while (res.size() < k) {
+            if (l >= 0 && r < n) {
+                if (abs(x - arr[l]) <= abs(x - arr[r])) {
+                    res.push_back(arr[l--]);
+                } else {
+                    res.push_back(arr[r++]);
+                }
+            } else if (l >= 0) {
+                res.push_back(arr[l--]);
+            } else if (r < n) {
+                res.push_back(arr[r++]);
+            }
+        }
+
+        sort(res.begin(), res.end());
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @param {number} k
+     * @param {number} x
+     * @return {number[]}
+     */
+    findClosestElements(arr, k, x) {
+        const n = arr.length;
+        let idx = 0;
+        for (let i = 1; i < n; i++) {
+            if (Math.abs(x - arr[idx]) > Math.abs(x - arr[i])) {
+                idx = i;
+            }
+        }
+
+        const res = [arr[idx]];
+        let l = idx - 1, r = idx + 1;
+
+        while (res.length < k) {
+            if (l >= 0 && r < n) {
+                if (Math.abs(x - arr[l]) <= Math.abs(x - arr[r])) {
+                    res.push(arr[l--]);
+                } else {
+                    res.push(arr[r++]);
+                }
+            } else if (l >= 0) {
+                res.push(arr[l--]);
+            } else if (r < n) {
+                res.push(arr[r++]);
+            }
+        }
+
+        return res.sort((a, b) => a - b);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + k \log k)$
+* Space complexity:
+    * $O(1)$ or $O(k)$ space depending on the sorting algorithm.
+    * $O(k)$ space for the output array.
+
+> Where $n$ is the size of the input array and $k$ is the number of closest elements to find.
+
+---
+
+## 3. Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def findClosestElements(self, arr: List[int], k: int, x: int) -> List[int]:
+        l, r = 0, len(arr) - 1
+        while r - l >= k:
+            if abs(x - arr[l]) <= abs(x - arr[r]):
+                r -= 1
+            else:
+                l += 1
+        
+        return arr[l: r + 1]
+```
+
+```java
+public class Solution {
+    public List<Integer> findClosestElements(int[] arr, int k, int x) {
+        int l = 0, r = arr.length - 1;
+        while (r - l >= k) {
+            if (Math.abs(x - arr[l]) <= Math.abs(x - arr[r])) {
+                r--;
+            } else {
+                l++;
+            }
+        }
+        List<Integer> result = new ArrayList<>();
+        for (int i = l; i <= r; i++) {
+            result.add(arr[i]);
+        }
+        return result;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findClosestElements(vector<int>& arr, int k, int x) {
+        int l = 0, r = arr.size() - 1;
+        while (r - l >= k) {
+            if (abs(x - arr[l]) <= abs(x - arr[r])) {
+                r--;
+            } else {
+                l++;
+            }
+        }
+        return vector<int>(arr.begin() + l, arr.begin() + r + 1);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @param {number} k
+     * @param {number} x
+     * @return {number[]}
+     */
+    findClosestElements(arr, k, x) {
+        let l = 0, r = arr.length - 1;
+        while (r - l >= k) {
+            if (Math.abs(x - arr[l]) <= Math.abs(x - arr[r])) {
+                r--;
+            } else {
+                l++;
+            }
+        }
+        return arr.slice(l, r + 1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n - k)$
+* Space complexity: $O(k)$ for the output array.
+
+> Where $n$ is the size of the input array and $k$ is the number of closest elements to find.
+
+---
+
+## 4. Binary Search + Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def findClosestElements(self, arr: List[int], k: int, x: int) -> List[int]:
+        l, r = 0, len(arr) - 1
+        while l < r:
+            mid = (l + r) // 2
+            if arr[mid] < x:
+                l = mid + 1
+            else:
+                r = mid
+
+        l, r = l - 1, l
+        while r - l - 1 < k:
+            if l < 0:
+                r += 1
+            elif r >= len(arr):
+                l -= 1
+            elif abs(arr[l] - x) <= abs(arr[r] - x):
+                l -= 1
+            else:
+                r += 1
+
+        return arr[l + 1:r]
+```
+
+```java
+public class Solution {
+    public List<Integer> findClosestElements(int[] arr, int k, int x) {
+        int l = 0, r = arr.length - 1;
+        while (l < r) {
+            int mid = (l + r) / 2;
+            if (arr[mid] < x) {
+                l = mid + 1;
+            } else {
+                r = mid;
+            }
+        }
+
+        l = l - 1;
+        r = l + 1;
+        while (r - l - 1 < k) {
+            if (l < 0) {
+                r++;
+            } else if (r >= arr.length) {
+                l--;
+            } else if (Math.abs(arr[l] - x) <= Math.abs(arr[r] - x)) {
+                l--;
+            } else {
+                r++;
+            }
+        }
+
+        List<Integer> result = new ArrayList<>();
+        for (int i = l + 1; i < r; i++) {
+            result.add(arr[i]);
+        }
+        return result;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findClosestElements(vector<int>& arr, int k, int x) {
+        int l = 0, r = arr.size() - 1;
+        while (l < r) {
+            int mid = (l + r) / 2;
+            if (arr[mid] < x) {
+                l = mid + 1;
+            } else {
+                r = mid;
+            }
+        }
+
+        l = l - 1;
+        r = l + 1;
+        while (r - l - 1 < k) {
+            if (l < 0) {
+                r++;
+            } else if (r >= arr.size()) {
+                l--;
+            } else if (abs(arr[l] - x) <= abs(arr[r] - x)) {
+                l--;
+            } else {
+                r++;
+            }
+        }
+
+        return vector<int>(arr.begin() + l + 1, arr.begin() + r);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @param {number} k
+     * @param {number} x
+     * @return {number[]}
+     */
+    findClosestElements(arr, k, x) {
+        let l = 0, r = arr.length - 1;
+        while (l < r) {
+            const mid = Math.floor((l + r) / 2);
+            if (arr[mid] < x) {
+                l = mid + 1;
+            } else {
+                r = mid;
+            }
+        }
+
+        l = l - 1;
+        r = l + 1;
+        while (r - l - 1 < k) {
+            if (l < 0) {
+                r++;
+            } else if (r >= arr.length) {
+                l--;
+            } else if (Math.abs(arr[l] - x) <= Math.abs(arr[r] - x)) {
+                l--;
+            } else {
+                r++;
+            }
+        }
+
+        return arr.slice(l + 1, r);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n + k)$
+* Space complexity: $O(k)$ for the output array.
+
+> Where $n$ is the size of the input array and $k$ is the number of closest elements to find.
+
+---
+
+## 5. Binary Search
+
+::tabs-start
+
+```python
+class Solution:
+    def findClosestElements(self, arr: List[int], k: int, x: int) -> List[int]:
+        l, r = 0, len(arr) - k
+        while l < r:
+            m = (l + r) // 2
+            if x - arr[m] > arr[m + k] - x:
+                l = m + 1
+            else:
+                r = m
+        return arr[l:l + k]
+```
+
+```java
+public class Solution {
+    public List<Integer> findClosestElements(int[] arr, int k, int x) {
+        int l = 0, r = arr.length - k;
+        while (l < r) {
+            int m = (l + r) / 2;
+            if (x - arr[m] > arr[m + k] - x) {
+                l = m + 1;
+            } else {
+                r = m;
+            }
+        }
+        List<Integer> result = new ArrayList<>();
+        for (int i = l; i < l + k; i++) {
+            result.add(arr[i]);
+        }
+        return result;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findClosestElements(vector<int>& arr, int k, int x) {
+        int l = 0, r = arr.size() - k;
+        while (l < r) {
+            int m = (l + r) / 2;
+            if (x - arr[m] > arr[m + k] - x) {
+                l = m + 1;
+            } else {
+                r = m;
+            }
+        }
+        return vector<int>(arr.begin() + l, arr.begin() + l + k);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @param {number} k
+     * @param {number} x
+     * @return {number[]}
+     */
+    findClosestElements(arr, k, x) {
+        let l = 0, r = arr.length - k;
+        while (l < r) {
+            const m = Math.floor((l + r) / 2);
+            if (x - arr[m] > arr[m + k] - x) {
+                l = m + 1;
+            } else {
+                r = m;
+            }
+        }
+        return arr.slice(l, l + k);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log (n - k) + k)$
+* Space complexity: $O(k)$ for the output array.
+
+> Where $n$ is the size of the input array and $k$ is the number of closest elements to find.
\ No newline at end of file
diff --git a/articles/find-largest-value-in-each-tree-row.md b/articles/find-largest-value-in-each-tree-row.md
new file mode 100644
index 000000000..d54ce9dfd
--- /dev/null
+++ b/articles/find-largest-value-in-each-tree-row.md
@@ -0,0 +1,462 @@
+## 1. Breadth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def largestValues(self, root: Optional[TreeNode]) -> List[int]:
+        if not root:
+            return []
+
+        res = []
+        q = deque([root])
+        while q:
+            row_max = q[0].val
+            for _ in range(len(q)):
+                node = q.popleft()
+                row_max = max(row_max, node.val)
+                if node.left:
+                    q.append(node.left)
+                if node.right:
+                    q.append(node.right)
+            res.append(row_max)
+
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<Integer> largestValues(TreeNode root) {
+        if (root == null) return new ArrayList<>();
+
+        List<Integer> res = new ArrayList<>();
+        Queue<TreeNode> q = new LinkedList<>();
+        q.offer(root);
+
+        while (!q.isEmpty()) {
+            int rowMax = q.peek().val;
+            for (int i = q.size(); i > 0; i--) {
+                TreeNode node = q.poll();
+                rowMax = Math.max(rowMax, node.val);
+                if (node.left != null) q.offer(node.left);
+                if (node.right != null) q.offer(node.right);
+            }
+            res.add(rowMax);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    vector<int> largestValues(TreeNode* root) {
+        if (!root) return {};
+
+        vector<int> res;
+        queue<TreeNode*> q;
+        q.push(root);
+
+        while (!q.empty()) {
+            int rowMax = q.front()->val;
+            for (int i = q.size(); i > 0; i--) {
+                TreeNode* node = q.front(); q.pop();
+                rowMax = max(rowMax, node->val);
+                if (node->left) q.push(node->left);
+                if (node->right) q.push(node->right);
+            }
+            res.push_back(rowMax);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number[]}
+     */
+    largestValues(root) {
+        if (!root) return [];
+
+        const res = [];
+        const q = new Queue([root]);
+
+        while (!q.isEmpty()) {
+            let rowMax = q.front().val;
+            for (let i = q.size(); i > 0; i--) {
+                const node = q.pop();
+                rowMax = Math.max(rowMax, node.val);
+                if (node.left) q.push(node.left);
+                if (node.right) q.push(node.right);
+            }
+            res.push(rowMax);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Depth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def largestValues(self, root: Optional[TreeNode]) -> List[int]:
+        if not root:
+            return []
+
+        res = []
+        def dfs(node, level):
+            if not node:
+                return
+            if level == len(res):
+                res.append(node.val)
+            else:
+                res[level] = max(res[level], node.val)
+
+            dfs(node.left, level + 1)
+            dfs(node.right, level + 1)
+
+        dfs(root, 0)
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<Integer> largestValues(TreeNode root) {
+        List<Integer> res = new ArrayList<>();
+        dfs(root, 0, res);
+        return res;
+    }
+
+    private void dfs(TreeNode node, int level, List<Integer> res) {
+        if (node == null) return;
+        if (level == res.size()) {
+            res.add(node.val);
+        } else {
+            res.set(level, Math.max(res.get(level), node.val));
+        }
+
+        dfs(node.left, level + 1, res);
+        dfs(node.right, level + 1, res);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    vector<int> largestValues(TreeNode* root) {
+        vector<int> res;
+        dfs(root, 0, res);
+        return res;
+    }
+
+private:
+    void dfs(TreeNode* node, int level, vector<int>& res) {
+        if (!node) return;
+        if (level == res.size()) {
+            res.push_back(node->val);
+        } else {
+            res[level] = max(res[level], node->val);
+        }
+
+        dfs(node->left, level + 1, res);
+        dfs(node->right, level + 1, res);
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number[]}
+     */
+    largestValues(root) {
+        if (!root) return [];
+
+        const res = [];
+        const dfs = (node, level) => {
+            if (!node) return;
+            if (level === res.length) {
+                res.push(node.val);
+            } else {
+                res[level] = Math.max(res[level], node.val);
+            }
+            dfs(node.left, level + 1);
+            dfs(node.right, level + 1);
+        };
+
+        dfs(root, 0);
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 3. Iterative DFS
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def largestValues(self, root: Optional[TreeNode]) -> List[int]:
+        if not root:
+            return []
+
+        res = []
+        stack = [(root, 0)]
+        while stack:
+            node, level = stack.pop()
+            if level == len(res):
+                res.append(node.val)
+            else:
+                res[level] = max(res[level], node.val)
+
+            if node.right:
+                stack.append((node.right, level + 1))
+            if node.left:
+                stack.append((node.left, level + 1))
+
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<Integer> largestValues(TreeNode root) {
+        if (root == null) return new ArrayList<>();
+
+        List<Integer> res = new ArrayList<>();
+        Stack<Pair<TreeNode, Integer>> stack = new Stack<>();
+        stack.push(new Pair<>(root, 0));
+        while (!stack.isEmpty()) {
+            Pair<TreeNode, Integer> p = stack.pop();
+            TreeNode node = p.getKey();
+            int level = p.getValue();
+            if (level == res.size()) {
+                res.add(node.val);
+            } else {
+                res.set(level, Math.max(res.get(level), node.val));
+            }
+
+            if (node.right != null) stack.push(new Pair<>(node.right, level + 1));
+            if (node.left != null) stack.push(new Pair<>(node.left, level + 1));
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    vector<int> largestValues(TreeNode* root) {
+        if (!root) return {};
+
+        vector<int> res;
+        stack<pair<TreeNode*, int>> stk;
+        stk.push({root, 0});
+        while (!stk.empty()) {
+            auto [node, level] = stk.top();stk.pop();
+            if (level == res.size()) {
+                res.push_back(node->val);
+            } else {
+                res[level] = max(res[level], node->val);
+            }
+
+            if (node->right) stk.push({node->right, level + 1});
+            if (node->left) stk.push({node->left, level + 1});
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number[]}
+     */
+    largestValues(root) {
+        if (!root) return [];
+
+        const res = [];
+        const stack = [[root, 0]];
+        while (stack.length) {
+            const [node, level] = stack.pop();
+            if (level === res.length) {
+                res.push(node.val);
+            } else {
+                res[level] = Math.max(res[level], node.val);
+            }
+
+            if (node.right) stack.push([node.right, level + 1]);
+            if (node.left) stack.push([node.left, level + 1]);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/find-median-in-a-data-stream.md b/articles/find-median-in-a-data-stream.md
index 6e5ec7e0e..ad27aa749 100644
--- a/articles/find-median-in-a-data-stream.md
+++ b/articles/find-median-in-a-data-stream.md
@@ -119,6 +119,73 @@ class MedianFinder {
 }
 ```
 
+```go
+type MedianFinder struct {
+    data []int
+}
+
+func Constructor() MedianFinder {
+    return MedianFinder{}
+}
+
+func (this *MedianFinder) AddNum(num int) {
+    this.data = append(this.data, num)
+}
+
+func (this *MedianFinder) FindMedian() float64 {
+    sort.Ints(this.data)
+    n := len(this.data)
+    if n%2 == 1 {
+        return float64(this.data[n/2])
+    }
+    return float64(this.data[n/2-1]+this.data[n/2]) / 2.0
+}
+```
+
+```kotlin
+class MedianFinder() {
+    private val data = mutableListOf<Int>()
+
+    fun addNum(num: Int) {
+        data.add(num)
+    }
+
+    fun findMedian(): Double {
+        data.sort()
+        val n = data.size
+        return if (n % 2 == 1) {
+            data[n / 2].toDouble()
+        } else {
+            (data[n / 2] + data[n / 2 - 1]) / 2.0
+        }
+    }
+}
+```
+
+```swift
+class MedianFinder {
+    private var data: [Int]
+
+    init() {
+        self.data = []
+    }
+
+    func addNum(_ num: Int) {
+        data.append(num)
+    }
+
+    func findMedian() -> Double {
+        data.sort()
+        let n = data.count
+        if n % 2 == 1 {
+            return Double(data[n / 2])
+        } else {
+            return (Double(data[n / 2]) + Double(data[n / 2 - 1])) / 2.0
+        }
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -318,6 +385,133 @@ public class MedianFinder {
 }
 ```
 
+```go
+type MedianFinder struct {
+    small *priorityqueue.Queue // maxHeap
+    large *priorityqueue.Queue // minHeap
+}
+
+func Constructor() MedianFinder {
+    small := priorityqueue.NewWith(func(a, b interface{}) int {
+        return b.(int) - a.(int)  // maxHeap
+    })
+    large := priorityqueue.NewWith(func(a, b interface{}) int {
+        return a.(int) - b.(int)  // minHeap
+    })
+    return MedianFinder{small: small, large: large}
+}
+
+func (this *MedianFinder) AddNum(num int) {
+    if this.large.Size() > 0 {
+        largeTop, _ := this.large.Peek()
+        if num > largeTop.(int) {
+            this.large.Enqueue(num)
+        } else {
+            this.small.Enqueue(num)
+        }
+    } else {
+        this.small.Enqueue(num)
+    }
+    
+    // Rebalance
+    if this.small.Size() > this.large.Size()+1 {
+        val, _ := this.small.Dequeue()
+        this.large.Enqueue(val)
+    }
+    if this.large.Size() > this.small.Size()+1 {
+        val, _ := this.large.Dequeue()
+        this.small.Enqueue(val)
+    }
+}
+
+func (this *MedianFinder) FindMedian() float64 {
+    if this.small.Size() > this.large.Size() {
+        val, _ := this.small.Peek()
+        return float64(val.(int))
+    }
+    if this.large.Size() > this.small.Size() {
+        val, _ := this.large.Peek()
+        return float64(val.(int))
+    }
+    smallVal, _ := this.small.Peek()
+    largeVal, _ := this.large.Peek()
+    return float64(smallVal.(int)+largeVal.(int)) / 2.0
+}
+```
+
+```kotlin
+class MedianFinder() {
+    // small is maxHeap, large is minHeap
+    private val small = PriorityQueue<Int>(compareByDescending { it })
+    private val large = PriorityQueue<Int>()
+    
+    fun addNum(num: Int) {
+        if (large.isNotEmpty() && num > large.peek()) {
+            large.add(num)
+        } else {
+            small.add(num)
+        }
+        
+        // Rebalance
+        if (small.size > large.size + 1) {
+            large.add(small.poll())
+        }
+        if (large.size > small.size + 1) {
+            small.add(large.poll())
+        }
+    }
+    
+    fun findMedian(): Double {
+        return when {
+            small.size > large.size -> small.peek().toDouble()
+            large.size > small.size -> large.peek().toDouble()
+            else -> (small.peek() + large.peek()) / 2.0
+        }
+    }
+}
+```
+
+```swift
+class MedianFinder {
+    // two heaps, large, small, minheap, maxheap
+    // heaps should be equal size
+    private var small: Heap<Int>
+    private var large: Heap<Int>
+
+    init() {
+        self.small = Heap<Int>()
+        self.large = Heap<Int>()
+    }
+
+    func addNum(_ num: Int) {
+        if let top = large.min, num > top {
+            large.insert(num)
+        } else {
+            small.insert(num)
+        }
+        if small.count > large.count + 1 {
+            if let val = small.popMax() {
+                large.insert(val)
+            }
+        }
+        if large.count > small.count + 1 {
+            if let val = large.popMin() {
+                small.insert(val)
+            }
+        }
+    }
+
+    func findMedian() -> Double {
+        if small.count > large.count {
+            return Double(small.max!)
+        } else if large.count > small.count {
+            return Double(large.min!)
+        }
+        return (Double(small.max!) + Double(large.min!)) / 2.0
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/find-minimum-in-rotated-sorted-array.md b/articles/find-minimum-in-rotated-sorted-array.md
index 2b47b3e7a..9443959d2 100644
--- a/articles/find-minimum-in-rotated-sorted-array.md
+++ b/articles/find-minimum-in-rotated-sorted-array.md
@@ -45,6 +45,34 @@ public class Solution {
 }
 ```
 
+```go
+func findMin(nums []int) int {
+    minVal := nums[0]
+    for _, num := range nums {
+        if num < minVal {
+            minVal = num
+        }
+    }
+    return minVal
+}
+```
+
+```kotlin
+class Solution {
+    fun findMin(nums: IntArray): Int {
+        return nums.min()
+    }
+}
+```
+
+```swift
+class Solution {
+    func findMin(_ nums: [Int]) -> Int {
+        return nums.min()!
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -186,6 +214,87 @@ public class Solution {
 }
 ```
 
+```go
+func findMin(nums []int) int {
+    res := nums[0]
+    l, r := 0, len(nums)-1
+
+    for l <= r {
+        if nums[l] < nums[r] {
+            if nums[l] < res {
+                res = nums[l]
+            }
+            break
+        }
+
+        m := l + (r-l)/2
+        if nums[m] < res {
+            res = nums[m]
+        }
+
+        if nums[m] >= nums[l] {
+            l = m + 1
+        } else {
+            r = m - 1
+        }
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun findMin(nums: IntArray): Int {
+        var res = nums[0]
+        var l = 0
+        var r = nums.size - 1
+
+        while (l <= r) {
+            if (nums[l] < nums[r]) {
+                res = minOf(res, nums[l])
+                break
+            }
+
+            val m = l + (r - l) / 2
+            res = minOf(res, nums[m])
+
+            if (nums[m] >= nums[l]) {
+                l = m + 1
+            } else {
+                r = m - 1
+            }
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func findMin(_ nums: [Int]) -> Int {
+        var res = nums[0]
+        var l = 0, r = nums.count - 1
+
+        while l <= r {
+            if nums[l] < nums[r] {
+                res = min(res, nums[l])
+                break
+            }
+
+            let m = (l + r) / 2
+            res = min(res, nums[m])
+
+            if nums[m] >= nums[l] {
+                l = m + 1
+            } else {
+                r = m - 1
+            }
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -288,6 +397,56 @@ public class Solution {
 }
 ```
 
+```go
+func findMin(nums []int) int {
+    l, r := 0, len(nums)-1
+    for l < r {
+        m := l + (r-l)/2
+        if nums[m] < nums[r] {
+            r = m
+        } else {
+            l = m + 1
+        }
+    }
+    return nums[l]
+}
+```
+
+```kotlin
+class Solution {
+    fun findMin(nums: IntArray): Int {
+        var l = 0
+        var r = nums.size - 1
+        while (l < r) {
+            val m = l + (r - l) / 2
+            if (nums[m] < nums[r]) {
+                r = m
+            } else {
+                l = m + 1
+            }
+        }
+        return nums[l]
+    }
+}
+```
+
+```swift
+class Solution {
+    func findMin(_ nums: [Int]) -> Int {
+        var l = 0, r = nums.count - 1
+        while l < r {
+            let m = l + (r - l) / 2
+            if nums[m] < nums[r] {
+                r = m
+            } else {
+                l = m + 1
+            }
+        }
+        return nums[l]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/find-missing-and-repeated-values.md b/articles/find-missing-and-repeated-values.md
new file mode 100644
index 000000000..58753bb0f
--- /dev/null
+++ b/articles/find-missing-and-repeated-values.md
@@ -0,0 +1,492 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def findMissingAndRepeatedValues(self, grid: List[List[int]]) -> List[int]:
+        n = len(grid)
+        double = missing = 0
+
+        for num in range(1, n * n + 1):
+            cnt = 0
+            for i in range(n):
+                for j in range(n):
+                    if num == grid[i][j]:
+                        cnt += 1
+
+            if cnt == 2:
+                double = num
+            elif cnt == 0:
+                missing = num
+
+        return [double, missing]
+```
+
+```java
+public class Solution {
+    public int[] findMissingAndRepeatedValues(int[][] grid) {
+        int n = grid.length;
+        int doubleVal = 0, missing = 0;
+
+        for (int num = 1; num <= n * n; num++) {
+            int cnt = 0;
+            for (int i = 0; i < n; i++) {
+                for (int j = 0; j < n; j++) {
+                    if (grid[i][j] == num) {
+                        cnt++;
+                    }
+                }
+            }
+
+            if (cnt == 2) {
+                doubleVal = num;
+            } else if (cnt == 0) {
+                missing = num;
+            }
+        }
+
+        return new int[]{doubleVal, missing};
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findMissingAndRepeatedValues(vector<vector<int>>& grid) {
+        int n = grid.size();
+        int doubleVal = 0, missing = 0;
+
+        for (int num = 1; num <= n * n; num++) {
+            int cnt = 0;
+            for (int i = 0; i < n; i++) {
+                for (int j = 0; j < n; j++) {
+                    if (grid[i][j] == num) {
+                        cnt++;
+                    }
+                }
+            }
+
+            if (cnt == 2) {
+                doubleVal = num;
+            } else if (cnt == 0) {
+                missing = num;
+            }
+        }
+
+        return {doubleVal, missing};
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number[]}
+     */
+    findMissingAndRepeatedValues(grid) {
+        const n = grid.length;
+        let doubleVal = 0, missing = 0;
+
+        for (let num = 1; num <= n * n; num++) {
+            let cnt = 0;
+            for (let i = 0; i < n; i++) {
+                for (let j = 0; j < n; j++) {
+                    if (grid[i][j] === num) {
+                        cnt++;
+                    }
+                }
+            }
+
+            if (cnt === 2) {
+                doubleVal = num;
+            } else if (cnt === 0) {
+                missing = num;
+            }
+        }
+
+        return [doubleVal, missing];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 4)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def findMissingAndRepeatedValues(self, grid: List[List[int]]) -> List[int]:
+        N = len(grid)
+        count = defaultdict(int)
+
+        for i in range(N):
+            for j in range(N):
+                count[grid[i][j]] += 1
+
+        double = missing = 0
+
+        for num in range(1, N * N + 1):
+            if count[num] == 0:
+                missing = num
+            if count[num] == 2:
+                double = num
+
+        return [double, missing]
+```
+
+```java
+public class Solution {
+    public int[] findMissingAndRepeatedValues(int[][] grid) {
+        int N = grid.length;
+        Map<Integer, Integer> count = new HashMap<>();
+
+        for (int i = 0; i < N; i++) {
+            for (int j = 0; j < N; j++) {
+                count.put(grid[i][j], count.getOrDefault(grid[i][j], 0) + 1);
+            }
+        }
+
+        int doubleVal = 0, missing = 0;
+
+        for (int num = 1; num <= N * N; num++) {
+            int freq = count.getOrDefault(num, 0);
+            if (freq == 0) missing = num;
+            if (freq == 2) doubleVal = num;
+        }
+
+        return new int[]{doubleVal, missing};
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findMissingAndRepeatedValues(vector<vector<int>>& grid) {
+        int N = grid.size();
+        unordered_map<int, int> count;
+
+        for (int i = 0; i < N; i++) {
+            for (int j = 0; j < N; j++) {
+                count[grid[i][j]]++;
+            }
+        }
+
+        int doubleVal = 0, missing = 0;
+
+        for (int num = 1; num <= N * N; num++) {
+            int freq = count[num];
+            if (freq == 0) missing = num;
+            if (freq == 2) doubleVal = num;
+        }
+
+        return {doubleVal, missing};
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number[]}
+     */
+    findMissingAndRepeatedValues(grid) {
+        const N = grid.length;
+        const count = {};
+
+        for (let i = 0; i < N; i++) {
+            for (let j = 0; j < N; j++) {
+                let val = grid[i][j];
+                count[val] = (count[val] || 0) + 1;
+            }
+        }
+
+        let doubleVal = 0, missing = 0;
+
+        for (let num = 1; num <= N * N; num++) {
+            let freq = count[num] || 0;
+            if (freq === 0) missing = num;
+            if (freq === 2) doubleVal = num;
+        }
+
+        return [doubleVal, missing];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 3. Hash Set
+
+::tabs-start
+
+```python
+class Solution:
+    def findMissingAndRepeatedValues(self, grid: List[List[int]]) -> List[int]:
+        N = len(grid)
+        seen = set()
+        double = missing = 0
+
+        for i in range(N):
+            for j in range(N):
+                if grid[i][j] in seen:
+                    double = grid[i][j]
+                seen.add(grid[i][j])
+
+        for num in range(1, N * N + 1):
+            if num not in seen:
+                missing = num
+                break
+
+        return [double, missing]
+```
+
+```java
+public class Solution {
+    public int[] findMissingAndRepeatedValues(int[][] grid) {
+        int N = grid.length;
+        Set<Integer> seen = new HashSet<>();
+        int doubleVal = 0, missing = 0;
+
+        for (int i = 0; i < N; i++) {
+            for (int j = 0; j < N; j++) {
+                if (seen.contains(grid[i][j])) {
+                    doubleVal = grid[i][j];
+                }
+                seen.add(grid[i][j]);
+            }
+        }
+
+        for (int num = 1; num <= N * N; num++) {
+            if (!seen.contains(num)) {
+                missing = num;
+                break;
+            }
+        }
+
+        return new int[]{doubleVal, missing};
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findMissingAndRepeatedValues(vector<vector<int>>& grid) {
+        int N = grid.size();
+        unordered_set<int> seen;
+        int doubleVal = 0, missing = 0;
+
+        for (int i = 0; i < N; i++) {
+            for (int j = 0; j < N; j++) {
+                if (seen.count(grid[i][j])) {
+                    doubleVal = grid[i][j];
+                }
+                seen.insert(grid[i][j]);
+            }
+        }
+
+        for (int num = 1; num <= N * N; num++) {
+            if (!seen.count(num)) {
+                missing = num;
+                break;
+            }
+        }
+
+        return {doubleVal, missing};
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number[]}
+     */
+    findMissingAndRepeatedValues(grid) {
+        const N = grid.length;
+        const seen = new Set();
+        let doubleVal = 0, missing = 0;
+
+        for (let i = 0; i < N; i++) {
+            for (let j = 0; j < N; j++) {
+                const val = grid[i][j];
+                if (seen.has(val)) {
+                    doubleVal = val;
+                }
+                seen.add(val);
+            }
+        }
+
+        for (let num = 1; num <= N * N; num++) {
+            if (!seen.has(num)) {
+                missing = num;
+                break;
+            }
+        }
+
+        return [doubleVal, missing];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 4. Math
+
+::tabs-start
+
+```python
+class Solution:
+    def findMissingAndRepeatedValues(self, grid: List[List[int]]) -> List[int]:
+        N = len(grid)
+        gridSum = 0
+        gridSqSum = 0
+
+        for i in range(N):
+            for j in range(N):
+                gridSum += grid[i][j]
+                gridSqSum += grid[i][j] * grid[i][j]
+
+        totSum = (N * N * (N * N + 1)) // 2
+        diff = gridSum - totSum  # a - b
+
+        totSqSum = (N * N * (N * N + 1) * (2 * N * N + 1)) // 6
+        sqDiff = gridSqSum - totSqSum  # (a^2) - (b^2)
+
+        sum = sqDiff // diff  # a + b
+
+        a = (sum + diff) // 2
+        b = sum - a
+        return [a, b]
+```
+
+```java
+public class Solution {
+    public int[] findMissingAndRepeatedValues(int[][] grid) {
+        int N = grid.length;
+        long gridSum = 0;
+        long gridSqSum = 0;
+
+        for (int i = 0; i < N; i++) {
+            for (int j = 0; j < N; j++) {
+                gridSum += grid[i][j];
+                gridSqSum += 1L * grid[i][j] * grid[i][j];
+            }
+        }
+
+        long totSum = (long) N * N * (N * N + 1) / 2;
+        long diff = gridSum - totSum; // a - b
+
+        long totSqSum = (long) N * N * (N * N + 1) * (2L * N * N + 1) / 6;
+        long sqDiff = gridSqSum - totSqSum; // (a^2) - (b^2)
+
+        long sum = sqDiff / diff; // a + b
+
+        long a = (sum + diff) / 2;
+        long b = sum - a;
+
+        return new int[]{(int) a, (int) b};
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findMissingAndRepeatedValues(vector<vector<int>>& grid) {
+        int N = grid.size();
+        long long gridSum = 0;
+        long long gridSqSum = 0;
+
+        for (int i = 0; i < N; i++) {
+            for (int j = 0; j < N; j++) {
+                gridSum += grid[i][j];
+                gridSqSum += 1LL * grid[i][j] * grid[i][j];
+            }
+        }
+
+        long long totSum = 1LL * N * N * (N * N + 1) / 2;
+        long long diff = gridSum - totSum; // a - b
+
+        long long totSqSum = 1LL * N * N * (N * N + 1) * (2 * N * N + 1) / 6;
+        long long sqDiff = gridSqSum - totSqSum; // (a^2) - (b^2)
+
+        long long sum = sqDiff / diff; // a + b
+
+        int a = (sum + diff) / 2;
+        int b = sum - a;
+
+        return {a, b};
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number[]}
+     */
+    findMissingAndRepeatedValues(grid) {
+        const N = grid.length;
+        let gridSum = 0;
+        let gridSqSum = 0;
+
+        for (let i = 0; i < N; i++) {
+            for (let j = 0; j < N; j++) {
+                gridSum += grid[i][j];
+                gridSqSum += grid[i][j] * grid[i][j];
+            }
+        }
+
+        let totSum = N * N * (N * N + 1) / 2;
+        let diff = gridSum - totSum; // a - b
+
+        let totSqSum = N * N * (N * N + 1) * (2 * N * N + 1) / 6;
+        let sqDiff = gridSqSum - totSqSum; // (a^2) - (b^2)
+
+        let sum = sqDiff / diff; // a + b
+
+        let a = (sum + diff) / 2;
+        let b = sum - a;
+
+        return [a, b];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/find-missing-observations.md b/articles/find-missing-observations.md
new file mode 100644
index 000000000..218ffed24
--- /dev/null
+++ b/articles/find-missing-observations.md
@@ -0,0 +1,210 @@
+## 1. Math - I
+
+::tabs-start
+
+```python
+class Solution:
+    def missingRolls(self, rolls: List[int], mean: int, n: int) -> List[int]:
+        m = len(rolls)
+        nTotal = (mean * (n + m)) - sum(rolls)
+
+        if nTotal < n or nTotal > n * 6:
+            return []
+
+        res = []
+        while nTotal:
+            dice = min(nTotal - n + 1, 6)
+            res.append(dice)
+            nTotal -= dice
+            n -= 1
+        return res
+```
+
+```java
+public class Solution {
+    public int[] missingRolls(int[] rolls, int mean, int n) {
+        int m = rolls.length;
+        int nTotal = (mean * (n + m)) - Arrays.stream(rolls).sum();
+
+        if (nTotal < n || nTotal > n * 6) {
+            return new int[0];
+        }
+
+        int[] res = new int[n];
+        for (int i = 0; i < n; i++) {
+            int dice = Math.min(nTotal - (n - i - 1), 6);
+            res[i] = dice;
+            nTotal -= dice;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> missingRolls(vector<int>& rolls, int mean, int n) {
+        int m = rolls.size();
+        int nTotal = (mean * (n + m)) - accumulate(rolls.begin(), rolls.end(), 0);
+
+        if (nTotal < n || nTotal > n * 6) {
+            return {};
+        }
+
+        vector<int> res;
+        for (int i = 0; i < n; ++i) {
+            int dice = min(nTotal - (n - i - 1), 6);
+            res.push_back(dice);
+            nTotal -= dice;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} rolls
+     * @param {number} mean
+     * @param {number} n
+     * @return {number[]}
+     */
+    missingRolls(rolls, mean, n) {
+        const m = rolls.length;
+        let nTotal = (mean * (n + m)) - rolls.reduce((sum, roll) => sum + roll, 0);
+
+        if (nTotal < n || nTotal > n * 6) {
+            return [];
+        }
+
+        const res = [];
+        while (nTotal > 0) {
+            const dice = Math.min(nTotal - n + 1, 6);
+            res.push(dice);
+            nTotal -= dice;
+            n--;
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m + n)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ space for the output array.
+
+> Where $m$ is the size of the array $rolls$ and $n$ is the number of missing observations.
+
+---
+
+## 2. Math - II
+
+::tabs-start
+
+```python
+class Solution:
+    def missingRolls(self, rolls: List[int], mean: int, n: int) -> List[int]:
+        m = len(rolls)
+        nTotal = (mean * (n + m)) - sum(rolls)
+
+        if nTotal < n or nTotal > n * 6:
+            return []
+
+        avg = nTotal // n
+        rem = nTotal - (avg * n)
+        return [avg] * (n - rem) + [avg + 1] * rem
+```
+
+```java
+public class Solution {
+    public int[] missingRolls(int[] rolls, int mean, int n) {
+        int m = rolls.length;
+        int nTotal = (mean * (n + m)) - Arrays.stream(rolls).sum();
+
+        if (nTotal < n || nTotal > n * 6) {
+            return new int[0];
+        }
+
+        int avg = nTotal / n;
+        int rem = nTotal - (avg * n);
+        int[] res = new int[n];
+
+        for (int i = 0; i < n - rem; i++) {
+            res[i] = avg;
+        }
+        for (int i = n - rem; i < n; i++) {
+            res[i] = avg + 1;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> missingRolls(vector<int>& rolls, int mean, int n) {
+        int m = rolls.size();
+        int nTotal = (mean * (n + m)) - accumulate(rolls.begin(), rolls.end(), 0);
+
+        if (nTotal < n || nTotal > n * 6) {
+            return {};
+        }
+
+        int avg = nTotal / n;
+        int rem = nTotal - (avg * n);
+        vector<int> res;
+
+        for (int i = 0; i < n - rem; ++i) {
+            res.push_back(avg);
+        }
+        for (int i = 0; i < rem; ++i) {
+            res.push_back(avg + 1);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} rolls
+     * @param {number} mean
+     * @param {number} n
+     * @return {number[]}
+     */
+    missingRolls(rolls, mean, n) {
+        const m = rolls.length;
+        const nTotal = (mean * (n + m)) - rolls.reduce((sum, roll) => sum + roll, 0);
+
+        if (nTotal < n || nTotal > n * 6) {
+            return [];
+        }
+
+        const avg = Math.floor(nTotal / n);
+        const rem = nTotal - (avg * n);
+        return Array(n - rem).fill(avg).concat(Array(rem).fill(avg + 1));
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m + n)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ space for the output array.
+
+> Where $m$ is the size of the array $rolls$ and $n$ is the number of missing observations.
\ No newline at end of file
diff --git a/articles/find-peak-element.md b/articles/find-peak-element.md
new file mode 100644
index 000000000..9d341f185
--- /dev/null
+++ b/articles/find-peak-element.md
@@ -0,0 +1,341 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def findPeakElement(self, nums: List[int]) -> int:
+        for i in range(len(nums) - 1):
+            if nums[i] > nums[i + 1]:
+                return i
+
+        return len(nums) - 1
+```
+
+```java
+public class Solution {
+    public int findPeakElement(int[] nums) {
+        for (int i = 0; i < nums.length - 1; i++) {
+            if (nums[i] > nums[i + 1]) {
+                return i;
+            }
+        }
+        return nums.length - 1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findPeakElement(vector<int>& nums) {
+        for (int i = 0; i < nums.size() - 1; i++) {
+            if (nums[i] > nums[i + 1]) {
+                return i;
+            }
+        }
+        return nums.size() - 1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    findPeakElement(nums) {
+        for (let i = 0; i < nums.length - 1; i++) {
+            if (nums[i] > nums[i + 1]) {
+                return i;
+            }
+        }
+        return nums.length - 1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Binary Search
+
+::tabs-start
+
+```python
+class Solution:
+    def findPeakElement(self, nums: List[int]) -> int:
+        l, r = 0, len(nums) - 1
+
+        while l <= r:
+            m = l + (r - l) // 2
+            if m > 0 and nums[m] < nums[m - 1]:
+                r = m - 1
+            elif m < len(nums) - 1 and nums[m] < nums[m + 1]:
+                l = m + 1
+            else:
+                return m
+```
+
+```java
+public class Solution {
+    public int findPeakElement(int[] nums) {
+        int l = 0, r = nums.length - 1;
+
+        while (l <= r) {
+            int m = l + (r - l) / 2;
+            if (m > 0 && nums[m] < nums[m - 1]) {
+                r = m - 1;
+            } else if (m < nums.length - 1 && nums[m] < nums[m + 1]) {
+                l = m + 1;
+            } else {
+                return m;
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findPeakElement(vector<int>& nums) {
+        int l = 0, r = nums.size() - 1;
+
+        while (l <= r) {
+            int m = l + (r - l) / 2;
+            if (m > 0 && nums[m] < nums[m - 1]) {
+                r = m - 1;
+            } else if (m < nums.size() - 1 && nums[m] < nums[m + 1]) {
+                l = m + 1;
+            } else {
+                return m;
+            }
+        }
+
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    findPeakElement(nums) {
+        let l = 0, r = nums.length - 1;
+
+        while (l <= r) {
+            let m = Math.floor(l + (r - l) / 2);
+            if (m > 0 && nums[m] < nums[m - 1]) {
+                r = m - 1;
+            } else if (m < nums.length - 1 && nums[m] < nums[m + 1]) {
+                l = m + 1;
+            } else {
+                return m;
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Recursive Binary Search
+
+::tabs-start
+
+```python
+class Solution:
+    def findPeakElement(self, nums: List[int]) -> int:
+        def binary_search(l, r):
+            if l == r:
+                return l
+            m = l + (r - l) // 2
+            if nums[m] > nums[m + 1]:
+                return binary_search(l, m)
+            return binary_search(m + 1, r)
+
+        return binary_search(0, len(nums) - 1)
+```
+
+```java
+public class Solution {
+    public int findPeakElement(int[] nums) {
+        return binarySearch(nums, 0, nums.length - 1);
+    }
+
+    private int binarySearch(int[] nums, int l, int r) {
+        if (l == r) {
+            return l;
+        }
+        int m = l + (r - l) / 2;
+        if (nums[m] > nums[m + 1]) {
+            return binarySearch(nums, l, m);
+        }
+        return binarySearch(nums, m + 1, r);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findPeakElement(vector<int>& nums) {
+        return binarySearch(nums, 0, nums.size() - 1);
+    }
+
+private:
+    int binarySearch(vector<int>& nums, int l, int r) {
+        if (l == r) {
+            return l;
+        }
+        int m = l + (r - l) / 2;
+        if (nums[m] > nums[m + 1]) {
+            return binarySearch(nums, l, m);
+        }
+        return binarySearch(nums, m + 1, r);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    findPeakElement(nums) {
+        const binarySearch = (l, r) => {
+            if (l === r) {
+                return l;
+            }
+            let m = Math.floor((l + r) / 2);
+            if (nums[m] > nums[m + 1]) {
+                return binarySearch(l, m);
+            } else {
+                return binarySearch(m + 1, r);
+            }
+        };
+
+        return binarySearch(0, nums.length - 1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(\log n)$ for recursion stack.
+
+---
+
+## 4. Binary Search (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def findPeakElement(self, nums: List[int]) -> int:
+        l, r = 0, len(nums) - 1
+
+        while l < r:
+            m = (l + r) >> 1
+            if nums[m] > nums[m + 1]:
+                r = m
+            else:
+                l = m + 1
+
+        return l
+```
+
+```java
+public class Solution {
+    public int findPeakElement(int[] nums) {
+        int l = 0, r = nums.length - 1;
+
+        while (l < r) {
+            int m = (l + r) >> 1;
+            if (nums[m] > nums[m + 1]) {
+                r = m;
+            } else {
+                l = m + 1;
+            }
+        }
+
+        return l;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findPeakElement(vector<int>& nums) {
+        int l = 0, r = nums.size() - 1;
+
+        while (l < r) {
+            int m = (l + r) >> 1;
+            if (nums[m] > nums[m + 1]) {
+                r = m;
+            } else {
+                l = m + 1;
+            }
+        }
+
+        return l;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    findPeakElement(nums) {
+        let l = 0, r = nums.length - 1;
+
+        while (l < r) {
+            let m = (l + r) >> 1;
+            if (nums[m] > nums[m + 1]) {
+                r = m;
+            } else {
+                l = m + 1;
+            }
+        }
+
+        return l;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/find-pivot-index.md b/articles/find-pivot-index.md
new file mode 100644
index 000000000..7e8568d02
--- /dev/null
+++ b/articles/find-pivot-index.md
@@ -0,0 +1,284 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def pivotIndex(self, nums: List[int]) -> int:
+        n = len(nums)
+        for i in range(n):
+            leftSum = rightSum = 0
+            for l in range(i):
+                leftSum += nums[l]
+            for r in range(i + 1, n):
+                rightSum += nums[r]
+            if leftSum == rightSum:
+                return i
+        return -1
+```
+
+```java
+public class Solution {
+    public int pivotIndex(int[] nums) {
+        int n = nums.length;
+        for (int i = 0; i < n; i++) {
+            int leftSum = 0, rightSum = 0;
+            for (int l = 0; l < i; l++) {
+                leftSum += nums[l];
+            }
+            for (int r = i + 1; r < n; r++) {
+                rightSum += nums[r];
+            }
+            if (leftSum == rightSum) {
+                return i;
+            }
+        }
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int pivotIndex(vector<int>& nums) {
+        int n = nums.size();
+        for (int i = 0; i < n; i++) {
+            int leftSum = 0, rightSum = 0;
+            for (int l = 0; l < i; l++) {
+                leftSum += nums[l];
+            }
+            for (int r = i + 1; r < n; r++) {
+                rightSum += nums[r];
+            }
+            if (leftSum == rightSum) {
+                return i;
+            }
+        }
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    pivotIndex(nums) {
+        const n = nums.length;
+        for (let i = 0; i < n; i++) {
+            let leftSum = 0, rightSum = 0;
+            for (let l = 0; l < i; l++) {
+                leftSum += nums[l];
+            }
+            for (let r = i + 1; r < n; r++) {
+                rightSum += nums[r];
+            }
+            if (leftSum === rightSum) {
+                return i;
+            }
+        }
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Prefix Sum
+
+::tabs-start
+
+```python
+class Solution:
+    def pivotIndex(self, nums: List[int]) -> int:
+        n = len(nums)
+        prefixSum = [0] * (n + 1)
+        for i in range(n):
+            prefixSum[i + 1] = prefixSum[i] + nums[i]
+        
+        for i in range(n):
+            leftSum = prefixSum[i]
+            rightSum = prefixSum[n] - prefixSum[i + 1]
+            if leftSum == rightSum:
+                return i
+        return -1
+```
+
+```java
+public class Solution {
+    public int pivotIndex(int[] nums) {
+        int n = nums.length;        
+        int[] prefixSum = new int[n + 1];
+        for (int i = 0; i < n; i++) {
+            prefixSum[i + 1] = prefixSum[i] + nums[i];
+        }
+
+        for (int i = 0; i < n; i++) {
+            int leftSum = prefixSum[i];
+            int rightSum = prefixSum[n] - prefixSum[i + 1];
+            if (leftSum == rightSum) {
+                return i;
+            }
+        }        
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int pivotIndex(vector<int>& nums) {
+        int n = nums.size();        
+        vector<int> prefixSum(n + 1, 0);
+        for (int i = 0; i < n; i++) {
+            prefixSum[i + 1] = prefixSum[i] + nums[i];
+        }
+
+        for (int i = 0; i < n; i++) {
+            int leftSum = prefixSum[i];
+            int rightSum = prefixSum[n] - prefixSum[i + 1];
+            if (leftSum == rightSum) {
+                return i;
+            }
+        }      
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    pivotIndex(nums) {
+        const n = nums.length;
+        const prefixSum = new Array(n + 1).fill(0);
+        for (let i = 0; i < n; i++) {
+            prefixSum[i + 1] = prefixSum[i] + nums[i];
+        }
+
+        for (let i = 0; i < n; i++) {
+            const leftSum = prefixSum[i];
+            const rightSum = prefixSum[n] - prefixSum[i + 1];
+            if (leftSum === rightSum) {
+                return i;
+            }
+        }
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Prefix Sum (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def pivotIndex(self, nums: List[int]) -> int:
+        total = sum(nums)
+        leftSum = 0
+        for i in range(len(nums)):
+            rightSum = total - nums[i] - leftSum
+            if leftSum == rightSum:
+                return i
+            leftSum += nums[i]
+        return -1
+```
+
+```java
+public class Solution {
+    public int pivotIndex(int[] nums) {
+        int total = 0;
+        for (int num : nums) {
+            total += num;
+        }
+
+        int leftSum = 0;
+        for (int i = 0; i < nums.length; i++) {
+            int rightSum = total - leftSum - nums[i];
+            if (leftSum == rightSum) {
+                return i;
+            }
+            leftSum += nums[i];
+        }
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int pivotIndex(vector<int>& nums) {
+        int total = 0;
+        for (int num : nums) {
+            total += num;
+        }
+
+        int leftSum = 0;
+        for (int i = 0; i < nums.size(); i++) {
+            int rightSum = total - leftSum - nums[i];
+            if (leftSum == rightSum) {
+                return i;
+            }
+            leftSum += nums[i];
+        }
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    pivotIndex(nums) {
+        let total = 0;
+        for (let num of nums) {
+            total += num;
+        }
+
+        let leftSum = 0;
+        for (let i = 0; i < nums.length; i++) {
+            let rightSum = total - leftSum - nums[i];
+            if (leftSum === rightSum) {
+                return i;
+            }
+            leftSum += nums[i];
+        }
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/find-polygon-with-the-largest-perimeter.md b/articles/find-polygon-with-the-largest-perimeter.md
new file mode 100644
index 000000000..f736cb463
--- /dev/null
+++ b/articles/find-polygon-with-the-largest-perimeter.md
@@ -0,0 +1,295 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def largestPerimeter(self, nums: List[int]) -> int:
+        n = len(nums)
+        res = -1
+
+        for i, large in enumerate(nums):
+            cur = 0
+            for j, side in enumerate(nums):
+                if i != j and side <= large:
+                    cur += side
+            if cur > large:
+                res = max(res, cur + large)
+
+        return res
+```
+
+```java
+public class Solution {
+    public long largestPerimeter(int[] nums) {
+        int n = nums.length;
+        long res = -1;
+
+        for (int i = 0; i < n; i++) {
+            int large = nums[i];
+            long cur = 0;
+
+            for (int j = 0; j < n; j++) {
+                if (i != j && nums[j] <= large) {
+                    cur += nums[j];
+                }
+            }
+
+            if (cur > large) {
+                res = Math.max(res, cur + large);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long largestPerimeter(vector<int>& nums) {
+        int n = nums.size();
+        long long res = -1;
+
+        for (int i = 0; i < n; i++) {
+            long long large = nums[i];
+            long long cur = 0;
+
+            for (int j = 0; j < n; j++) {
+                if (i != j && nums[j] <= large) {
+                    cur += nums[j];
+                }
+            }
+
+            if (cur > large) {
+                res = max(res, cur + large);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    largestPerimeter(nums) {
+        const n = nums.length;
+        let res = -1;
+
+        for (let i = 0; i < n; i++) {
+            const large = nums[i];
+            let cur = 0;
+
+            for (let j = 0; j < n; j++) {
+                if (i !== j && nums[j] <= large) {
+                    cur += nums[j];
+                }
+            }
+
+            if (cur > large) {
+                res = Math.max(res, cur + large);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 2. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def largestPerimeter(self, nums: List[int]) -> int:
+        nums.sort()
+        res = -1
+        total = 0
+        for num in nums:
+            if total > num:
+                res = total + num
+            total += num
+        return res
+```
+
+```java
+public class Solution {
+    public long largestPerimeter(int[] nums) {
+        Arrays.sort(nums);
+        long res = -1;
+        long total = 0;
+
+        for (int num : nums) {
+            if (total > num) {
+                res = total + num;
+            }
+            total += num;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long largestPerimeter(vector<int>& nums) {
+        sort(nums.begin(), nums.end());
+        long long res = -1;
+        long long total = 0;
+
+        for (int& num : nums) {
+            if (total > num) {
+                res = total + num;
+            }
+            total += num;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    largestPerimeter(nums) {
+        nums.sort((a, b) => a - b);
+        let res = -1;
+        let total = 0;
+
+        for (let num of nums) {
+            if (total > num) {
+                res = total + num;
+            }
+            total += num;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 3. Max Heap
+
+::tabs-start
+
+```python
+class Solution:
+    def largestPerimeter(self, nums: List[int]) -> int:
+        nums = [-num for num in nums]
+        heapq.heapify(nums)
+        total = -sum(nums)
+
+        while len(nums) > 2:
+            largest = -heapq.heappop(nums)
+            total -= largest
+            if largest < total:
+                return total + largest
+        return -1
+```
+
+```java
+public class Solution {
+    public long largestPerimeter(int[] nums) {
+        PriorityQueue<Integer> maxHeap = new PriorityQueue<>((a, b) -> b - a);
+        long total = 0;
+        for (int num : nums) {
+            maxHeap.add(num);
+            total += num;
+        }
+
+        while (maxHeap.size() > 2) {
+            int largest = maxHeap.poll();
+            total -= largest;
+            if (largest < total) {
+                return total + largest;
+            }
+        }
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long largestPerimeter(vector<int>& nums) {
+        priority_queue<int> maxHeap(nums.begin(), nums.end());
+        long long total = accumulate(nums.begin(), nums.end(), 0LL);
+
+        while (maxHeap.size() > 2) {
+            int largest = maxHeap.top();
+            maxHeap.pop();
+            total -= largest;
+            if (largest < total) {
+                return total + largest;
+            }
+        }
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    largestPerimeter(nums) {
+        const maxHeap = new MaxPriorityQueue();
+        let total = 0;
+
+        nums.forEach(num => {
+            total += num;
+            maxHeap.enqueue(num);
+        });
+
+        while (maxHeap.size() > 2) {
+            const largest = maxHeap.dequeue().element;
+            total -= largest;
+            if (largest < total) return total + largest;
+        }
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(n + (30\log n))$ in Python, C++, JS.
+    * $O(n \log n)$ in Java.
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/find-target-in-rotated-sorted-array.md b/articles/find-target-in-rotated-sorted-array.md
index 94e1e6b6e..b406838bb 100644
--- a/articles/find-target-in-rotated-sorted-array.md
+++ b/articles/find-target-in-rotated-sorted-array.md
@@ -69,6 +69,43 @@ public class Solution {
 }
 ```
 
+```go
+func search(nums []int, target int) int {
+    for i := 0; i < len(nums); i++ {
+        if nums[i] == target {
+            return i
+        }
+    }
+    return -1
+}
+```
+
+```kotlin
+class Solution {
+    fun search(nums: IntArray, target: Int): Int {
+        for (i in nums.indices) {
+            if (nums[i] == target) {
+                return i
+            }
+        }
+        return -1
+    }
+}
+```
+
+```swift
+class Solution {
+    func search(_ nums: [Int], _ target: Int) -> Int {
+        for i in 0..<nums.count {
+            if nums[i] == target {
+                return i
+            }
+        }
+        return -1
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -288,6 +325,127 @@ public class Solution {
 }
 ```
 
+```go
+func search(nums []int, target int) int {
+    l, r := 0, len(nums)-1
+
+    for l < r {
+        m := (l + r) / 2
+        if nums[m] > nums[r] {
+            l = m + 1
+        } else {
+            r = m
+        }
+    }
+
+    pivot := l
+
+    var binarySearch func(left, right int) int
+    binarySearch = func(left, right int) int {
+        for left <= right {
+            mid := (left + right) / 2
+            if nums[mid] == target {
+                return mid
+            } else if nums[mid] < target {
+                left = mid + 1
+            } else {
+                right = mid - 1
+            }
+        }
+        return -1
+    }
+
+    result := binarySearch(0, pivot-1)
+    if result != -1 {
+        return result
+    }
+
+    return binarySearch(pivot, len(nums)-1)
+}
+```
+
+```kotlin
+class Solution {
+    fun search(nums: IntArray, target: Int): Int {
+        var l = 0
+        var r = nums.size - 1
+
+        while (l < r) {
+            val m = (l + r) / 2
+            if (nums[m] > nums[r]) {
+                l = m + 1
+            } else {
+                r = m
+            }
+        }
+
+        val pivot = l
+
+        fun binarySearch(left: Int, right: Int): Int {
+            var left = left
+            var right = right
+            while (left <= right) {
+                val mid = (left + right) / 2
+                when {
+                    nums[mid] == target -> return mid
+                    nums[mid] < target -> left = mid + 1
+                    else -> right = mid - 1
+                }
+            }
+            return -1
+        }
+
+        var result = binarySearch(0, pivot - 1)
+        if (result != -1) {
+            return result
+        }
+
+        return binarySearch(pivot, nums.size - 1)
+    }
+}
+```
+
+```swift
+class Solution {
+    func search(_ nums: [Int], _ target: Int) -> Int {
+        var l = 0, r = nums.count - 1
+
+        while l < r {
+            let m = (l + r) / 2
+            if nums[m] > nums[r] {
+                l = m + 1
+            } else {
+                r = m
+            }
+        }
+
+        let pivot = l
+
+        func binarySearch(_ left: Int, _ right: Int) -> Int {
+            var l = left, r = right
+            while l <= r {
+                let mid = (l + r) / 2
+                if nums[mid] == target {
+                    return mid
+                } else if nums[mid] < target {
+                    l = mid + 1
+                } else {
+                    r = mid - 1
+                }
+            }
+            return -1
+        }
+
+        let result = binarySearch(0, pivot - 1)
+        if result != -1 {
+            return result
+        }
+
+        return binarySearch(pivot, nums.count - 1)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -499,6 +657,124 @@ public class Solution {
 }
 ```
 
+```go
+func search(nums []int, target int) int {
+    l, r := 0, len(nums)-1
+
+    for l < r {
+        m := (l + r) / 2
+        if nums[m] > nums[r] {
+            l = m + 1
+        } else {
+            r = m
+        }
+    }
+
+    pivot := l
+    l, r = 0, len(nums)-1
+
+    if target >= nums[pivot] && target <= nums[r] {
+        l = pivot
+    } else {
+        r = pivot - 1
+    }
+
+    for l <= r {
+        m := (l + r) / 2
+        if nums[m] == target {
+            return m
+        } else if nums[m] < target {
+            l = m + 1
+        } else {
+            r = m - 1
+        }
+    }
+
+    return -1
+}
+```
+
+```kotlin
+class Solution {
+    fun search(nums: IntArray, target: Int): Int {
+        var l = 0
+        var r = nums.size - 1
+
+        while (l < r) {
+            val m = (l + r) / 2
+            if (nums[m] > nums[r]) {
+                l = m + 1
+            } else {
+                r = m
+            }
+        }
+
+        val pivot = l
+        l = 0
+        r = nums.size - 1
+
+        if (target >= nums[pivot] && target <= nums[r]) {
+            l = pivot
+        } else {
+            r = pivot - 1
+        }
+
+        while (l <= r) {
+            val m = (l + r) / 2
+            if (nums[m] == target) {
+                return m
+            } else if (nums[m] < target) {
+                l = m + 1
+            } else {
+                r = m - 1
+            }
+        }
+
+        return -1
+    }
+}
+```
+
+```swift
+class Solution {
+    func search(_ nums: [Int], _ target: Int) -> Int {
+        var l = 0, r = nums.count - 1
+
+        while l < r {
+            let m = (l + r) / 2
+            if nums[m] > nums[r] {
+                l = m + 1
+            } else {
+                r = m
+            }
+        }
+
+        let pivot = l
+        l = 0
+        r = nums.count - 1
+
+        if target >= nums[pivot] && target <= nums[r] {
+            l = pivot
+        } else {
+            r = pivot - 1
+        }
+
+        while l <= r {
+            let m = (l + r) / 2
+            if nums[m] == target {
+                return m
+            } else if nums[m] < target {
+                l = m + 1
+            } else {
+                r = m - 1
+            }
+        }
+
+        return -1
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -667,6 +943,95 @@ public class Solution {
 }
 ```
 
+```go
+func search(nums []int, target int) int {
+    l, r := 0, len(nums)-1
+
+    for l <= r {
+        mid := (l + r) / 2
+        if target == nums[mid] {
+            return mid
+        }
+
+        if nums[l] <= nums[mid] {
+            if target > nums[mid] || target < nums[l] {
+                l = mid + 1
+            } else {
+                r = mid - 1
+            }
+        } else {
+            if target < nums[mid] || target > nums[r] {
+                r = mid - 1
+            } else {
+                l = mid + 1
+            }
+        }
+    }
+    return -1
+}
+```
+
+```kotlin
+class Solution {
+    fun search(nums: IntArray, target: Int): Int {
+        var l = 0
+        var r = nums.size - 1
+
+        while (l <= r) {
+            val mid = (l + r) / 2
+            if (target == nums[mid]) {
+                return mid
+            }
+
+            if (nums[l] <= nums[mid]) {
+                if (target > nums[mid] || target < nums[l]) {
+                    l = mid + 1
+                } else {
+                    r = mid - 1
+                }
+            } else {
+                if (target < nums[mid] || target > nums[r]) {
+                    r = mid - 1
+                } else {
+                    l = mid + 1
+                }
+            }
+        }
+        return -1
+    }
+}
+```
+
+```swift
+class Solution {
+    func search(_ nums: [Int], _ target: Int) -> Int {
+        var l = 0, r = nums.count - 1
+
+        while l <= r {
+            let mid = (l + r) / 2
+            if target == nums[mid] {
+                return mid
+            }
+
+            if nums[l] <= nums[mid] {
+                if target > nums[mid] || target < nums[l] {
+                    l = mid + 1
+                } else {
+                    r = mid - 1
+                }
+            } else {
+                if target < nums[mid] || target > nums[r] {
+                    r = mid - 1
+                } else {
+                    l = mid + 1
+                }
+            }
+        }
+        return -1
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/find-the-difference-of-two-arrays.md b/articles/find-the-difference-of-two-arrays.md
new file mode 100644
index 000000000..853638267
--- /dev/null
+++ b/articles/find-the-difference-of-two-arrays.md
@@ -0,0 +1,467 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def findDifference(self, nums1: list[int], nums2: list[int]) -> list[list[int]]:
+        res = [set(), set()]
+
+        for num1 in nums1:
+            found = False
+            for num2 in nums2:
+                if num1 == num2:
+                    found = True
+                    break
+            if not found:
+                res[0].add(num1)
+
+        for num2 in nums2:
+            found = False
+            for num1 in nums1:
+                if num1 == num2:
+                    found = True
+                    break
+            if not found:
+                res[1].add(num2)
+
+        return [list(res[0]), list(res[1])]
+```
+
+```java
+public class Solution {
+    public List<List<Integer>> findDifference(int[] nums1, int[] nums2) {
+        Set<Integer> res1 = new HashSet<>();
+        Set<Integer> res2 = new HashSet<>();
+
+        for (int num1 : nums1) {
+            boolean found = false;
+            for (int num2 : nums2) {
+                if (num1 == num2) {
+                    found = true;
+                    break;
+                }
+            }
+            if (!found) {
+                res1.add(num1);
+            }
+        }
+
+        for (int num2 : nums2) {
+            boolean found = false;
+            for (int num1 : nums1) {
+                if (num1 == num2) {
+                    found = true;
+                    break;
+                }
+            }
+            if (!found) {
+                res2.add(num2);
+            }
+        }
+
+        List<List<Integer>> result = new ArrayList<>();
+        result.add(new ArrayList<>(res1));
+        result.add(new ArrayList<>(res2));
+        return result;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> findDifference(vector<int>& nums1, vector<int>& nums2) {
+        set<int> res1, res2;
+
+        for (int num1 : nums1) {
+            bool found = false;
+            for (int num2 : nums2) {
+                if (num1 == num2) {
+                    found = true;
+                    break;
+                }
+            }
+            if (!found) {
+                res1.insert(num1);
+            }
+        }
+
+        for (int num2 : nums2) {
+            bool found = false;
+            for (int num1 : nums1) {
+                if (num1 == num2) {
+                    found = true;
+                    break;
+                }
+            }
+            if (!found) {
+                res2.insert(num2);
+            }
+        }
+
+        return {vector<int>(res1.begin(), res1.end()), 
+                vector<int>(res2.begin(), res2.end())};
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums1
+     * @param {number[]} nums2
+     * @return {number[][]}
+     */
+    findDifference(nums1, nums2) {
+        const res1 = new Set();
+        const res2 = new Set();
+
+        for (const num1 of nums1) {
+            let found = false;
+            for (const num2 of nums2) {
+                if (num1 === num2) {
+                    found = true;
+                    break;
+                }
+            }
+            if (!found) {
+                res1.add(num1);
+            }
+        }
+
+        for (const num2 of nums2) {
+            let found = false;
+            for (const num1 of nums1) {
+                if (num1 === num2) {
+                    found = true;
+                    break;
+                }
+            }
+            if (!found) {
+                res2.add(num2);
+            }
+        }
+
+        return [Array.from(res1), Array.from(res2)];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n + m)$
+
+> Where $n$ is the size of the array $nums1$ and $m$ is the size of the array $nums2$.
+
+---
+
+## 2. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def findDifference(self, nums1: list[int], nums2: list[int]) -> list[list[int]]:
+        nums1.sort()
+        nums2.sort()
+
+        def helper(A, B):
+            n, m = len(A), len(B)
+            res = []
+
+            j = 0
+            prev = float('-inf')
+            for num in A:
+                if prev == num:
+                    continue
+                while j < m and B[j] < num:
+                    j += 1
+                if j == m or B[j] != num:
+                    res.append(num)
+                prev = num
+            return res
+
+        return [helper(nums1, nums2), helper(nums2, nums1)]
+```
+
+```java
+public class Solution {
+    public List<List<Integer>> findDifference(int[] nums1, int[] nums2) {
+        Arrays.sort(nums1);
+        Arrays.sort(nums2);
+
+        List<Integer> diff1 = helper(nums1, nums2);
+        List<Integer> diff2 = helper(nums2, nums1);
+
+        List<List<Integer>> result = new ArrayList<>();
+        result.add(diff1);
+        result.add(diff2);
+
+        return result;
+    }
+
+    private List<Integer> helper(int[] A, int[] B) {
+        int n = A.length, m = B.length, j = 0;
+        List<Integer> res = new ArrayList<>();
+        int prev = Integer.MIN_VALUE;
+
+        for (int num : A) {
+            if (num == prev) continue;
+            while (j < m && B[j] < num) j++;
+            if (j == m || B[j] != num) res.add(num);
+            prev = num;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> findDifference(vector<int>& nums1, vector<int>& nums2) {
+        sort(nums1.begin(), nums1.end());
+        sort(nums2.begin(), nums2.end());
+
+        return {helper(nums1, nums2), helper(nums2, nums1)};
+    }
+
+private:
+    vector<int> helper(vector<int>& A, vector<int>& B) {
+        vector<int> res;
+        int n = A.size(), m = B.size(), j = 0, prev = INT_MIN;
+
+        for (int num : A) {
+            if (num == prev) continue;
+            while (j < m && B[j] < num) j++;
+            if (j == m || B[j] != num) res.push_back(num);
+            prev = num;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums1
+     * @param {number[]} nums2
+     * @return {number[][]}
+     */
+    findDifference(nums1, nums2) {
+        nums1.sort((a, b) => a - b);
+        nums2.sort((a, b) => a - b);
+
+        const helper = (A, B) => {
+            const res = [];
+            let j = 0;
+            let prev = -Infinity;
+
+            for (const num of A) {
+                if (num === prev) continue;
+                while (j < B.length && B[j] < num) j++;
+                if (j === B.length || B[j] !== num) res.push(num);
+                prev = num;
+            }
+
+            return res;
+        };
+
+        return [helper(nums1, nums2), helper(nums2, nums1)];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n + m \log m)$
+* Space complexity: $O(1)$ or $O(n + m)$ depending on the sorting algorithm.
+
+> Where $n$ is the size of the array $nums1$ and $m$ is the size of the array $nums2$.
+
+---
+
+## 3. Hash Set
+
+::tabs-start
+
+```python
+class Solution:
+    def findDifference(self, nums1: List[int], nums2: List[int]) -> List[List[int]]:
+        num1Set, num2Set = set(nums1), set(nums2)
+        res1, res2 = [], []
+
+        for num in num1Set:
+            if num not in num2Set:
+                res1.append(num)
+
+        for num in num2Set:
+            if num not in num1Set:
+                res2.append(num)
+
+        return [res1, res2]
+```
+
+```java
+public class Solution {
+    public List<List<Integer>> findDifference(int[] nums1, int[] nums2) {
+        Set<Integer> num1Set = new HashSet<>();
+        Set<Integer> num2Set = new HashSet<>();
+        for (int num : nums1) num1Set.add(num);
+        for (int num : nums2) num2Set.add(num);
+
+        List<Integer> res1 = new ArrayList<>();
+        List<Integer> res2 = new ArrayList<>();
+
+        for (int num : num1Set) {
+            if (!num2Set.contains(num)) res1.add(num);
+        }
+
+        for (int num : num2Set) {
+            if (!num1Set.contains(num)) res2.add(num);
+        }
+
+        return Arrays.asList(res1, res2);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> findDifference(vector<int>& nums1, vector<int>& nums2) {
+        unordered_set<int> num1Set(nums1.begin(), nums1.end());
+        unordered_set<int> num2Set(nums2.begin(), nums2.end());
+        vector<int> res1, res2;
+
+        for (int num : num1Set) {
+            if (num2Set.find(num) == num2Set.end()) res1.push_back(num);
+        }
+
+        for (int num : num2Set) {
+            if (num1Set.find(num) == num1Set.end()) res2.push_back(num);
+        }
+
+        return {res1, res2};
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums1
+     * @param {number[]} nums2
+     * @return {number[][]}
+     */
+    findDifference(nums1, nums2) {
+        const num1Set = new Set(nums1);
+        const num2Set = new Set(nums2);
+        const res1 = [];
+        const res2 = [];
+
+        for (const num of num1Set) {
+            if (!num2Set.has(num)) res1.push(num);
+        }
+
+        for (const num of num2Set) {
+            if (!num1Set.has(num)) res2.push(num);
+        }
+
+        return [res1, res2];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(n + m)$
+
+> Where $n$ is the size of the array $nums1$ and $m$ is the size of the array $nums2$.
+
+---
+
+## 4. Hash Set Difference
+
+::tabs-start
+
+```python
+class Solution:
+    def findDifference(self, nums1: List[int], nums2: List[int]) -> List[List[int]]:
+        numSet1, numSet2 = set(nums1), set(nums2)
+        return [list(numSet1 - numSet2), list(numSet2 - numSet1)]
+```
+
+```java
+public class Solution {
+    public List<List<Integer>> findDifference(int[] nums1, int[] nums2) {
+        Set<Integer> numSet1 = new HashSet<>();
+        Set<Integer> numSet2 = new HashSet<>();
+        for (int num : nums1) numSet1.add(num);
+        for (int num : nums2) numSet2.add(num);
+
+        List<Integer> res1 = new ArrayList<>(numSet1);
+        res1.removeAll(numSet2);
+
+        List<Integer> res2 = new ArrayList<>(numSet2);
+        res2.removeAll(numSet1);
+
+        return Arrays.asList(res1, res2);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> findDifference(vector<int>& nums1, vector<int>& nums2) {
+        vector<int> res1, res2;
+        set<int> numSet1(begin(nums1), end(nums1)), numSet2(begin(nums2), end(nums2));
+        
+        set_difference(begin(numSet1), end(numSet1), begin(numSet2), end(numSet2), back_inserter(res1));
+        set_difference(begin(numSet2), end(numSet2), begin(numSet1), end(numSet1), back_inserter(res2));
+        
+        return {res1, res2};
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums1
+     * @param {number[]} nums2
+     * @return {number[][]}
+     */
+    findDifference(nums1, nums2) {
+        const numSet1 = new Set(nums1);
+        const numSet2 = new Set(nums2);
+
+        const res1 = Array.from(numSet1).filter(num => !numSet2.has(num));
+        const res2 = Array.from(numSet2).filter(num => !numSet1.has(num));
+
+        return [res1, res2];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(n + m)$
+
+> Where $n$ is the size of the array $nums1$ and $m$ is the size of the array $nums2$.
\ No newline at end of file
diff --git a/articles/find-the-difference.md b/articles/find-the-difference.md
new file mode 100644
index 000000000..b06b2803f
--- /dev/null
+++ b/articles/find-the-difference.md
@@ -0,0 +1,466 @@
+## 1. Two Hash Maps
+
+::tabs-start
+
+```python
+class Solution:
+    def findTheDifference(self, s: str, t: str) -> str:
+        count_s, count_t = Counter(s), Counter(t)
+        for c in count_t:
+            if c not in count_s or count_s[c] < count_t[c]:
+                return c
+```
+
+```java
+public class Solution {
+    public char findTheDifference(String s, String t) {
+        int[] countS = new int[26];
+        int[] countT = new int[26];
+
+        for (char c : s.toCharArray()) countS[c - 'a']++;
+        for (char c : t.toCharArray()) countT[c - 'a']++;
+
+        for (int i = 0; i < 26; i++) {
+            if (countT[i] > countS[i]) {
+                return (char) (i + 'a');
+            }
+        }
+        return ' ';
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    char findTheDifference(string s, string t) {
+        vector<int> countS(26, 0), countT(26, 0);
+
+        for (char c : s) countS[c - 'a']++;
+        for (char c : t) countT[c - 'a']++;
+
+        for (int i = 0; i < 26; i++) {
+            if (countT[i] > countS[i]) {
+                return i + 'a';
+            }
+        }
+        return ' ';
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string} t
+     * @return {character}
+     */
+    findTheDifference(s, t) {
+        let countS = Array(26).fill(0);
+        let countT = Array(26).fill(0);
+
+        for (let char of s) countS[char.charCodeAt(0) - 'a'.charCodeAt(0)]++;
+        for (let char of t) countT[char.charCodeAt(0) - 'a'.charCodeAt(0)]++;
+
+        for (let i = 0; i < 26; i++) {
+            if (countT[i] > countS[i]) {
+                return String.fromCharCode(i + 'a'.charCodeAt(0));
+            }
+        }
+        return '';
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ since we have at most $26$ different characters.
+
+---
+
+## 2. One Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def findTheDifference(self, s: str, t: str) -> str:
+        count = Counter(t)
+        for c in s:
+            count[c] -= 1
+        for c in count:
+            if count[c] == 1:
+                return c
+```
+
+```java
+public class Solution {
+    public char findTheDifference(String s, String t) {
+        int[] count = new int[26];
+
+        for (char c : t.toCharArray()) count[c - 'a']++;
+        for (char c : s.toCharArray()) count[c - 'a']--;
+
+        for (int i = 0; i < 26; i++) {
+            if (count[i] == 1) {
+                return (char) (i + 'a');
+            }
+        }
+        return ' ';
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    char findTheDifference(string s, string t) {
+        vector<int> count(26);
+
+        for (char c : t) count[c - 'a']++;
+        for (char c : s) count[c - 'a']--;
+
+        for (int i = 0; i < 26; i++) {
+            if (count[i] == 1) {
+                return i + 'a';
+            }
+        }
+        return ' ';
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string} t
+     * @return {character}
+     */
+    findTheDifference(s, t) {
+        let count = Array(26).fill(0);
+
+        for (let char of t) count[char.charCodeAt(0) - 'a'.charCodeAt(0)]++;
+        for (let char of s) count[char.charCodeAt(0) - 'a'.charCodeAt(0)]--;
+
+        for (let i = 0; i < 26; i++) {
+            if (count[i] === 1) {
+                return String.fromCharCode(i + 'a'.charCodeAt(0));
+            }
+        }
+        return '';
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ since we have at most $26$ different characters.
+
+---
+
+## 3. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def findTheDifference(self, s: str, t: str) -> str:
+        s, t = sorted(s), sorted(t)
+        for c1, c2 in zip(s, t):
+            if c1 != c2:
+                return c2
+        return t[-1]
+```
+
+```java
+public class Solution {
+    public char findTheDifference(String s, String t) {
+        char[] sArr = s.toCharArray();
+        char[] tArr = t.toCharArray();
+        Arrays.sort(sArr);
+        Arrays.sort(tArr);
+        for (int i = 0; i < sArr.length; i++) {
+            if (sArr[i] != tArr[i]) {
+                return tArr[i];
+            }
+        }
+        return tArr[tArr.length - 1];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    char findTheDifference(string s, string t) {
+        sort(s.begin(), s.end());
+        sort(t.begin(), t.end());
+        for (int i = 0; i < s.size(); i++) {
+            if (s[i] != t[i]) {
+                return t[i];
+            }
+        }
+        return t[t.size() - 1];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string} t
+     * @return {character}
+     */
+    findTheDifference(s, t) {
+        s = s.split('').sort();
+        t = t.split('').sort();
+        for (let i = 0; i < s.length; i++) {
+            if (s[i] !== t[i]) {
+                return t[i];
+            }
+        }
+        return t[t.length - 1];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 4. Difference Between ASCII Values
+
+::tabs-start
+
+```python
+class Solution:
+    def findTheDifference(self, s: str, t: str) -> str:
+        sum_s, sum_t = 0, 0
+        for c in s:
+            sum_s += ord(c)
+        for c in t:
+            sum_t += ord(c)
+        return chr(sum_t - sum_s)
+```
+
+```java
+public class Solution {
+    public char findTheDifference(String s, String t) {
+        int sumS = 0, sumT = 0;
+        for (int i = 0; i < s.length(); i++) {
+            sumS += s.charAt(i);
+        }
+        for (int i = 0; i < t.length(); i++) {
+            sumT += t.charAt(i);
+        }
+        return (char) (sumT - sumS);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    char findTheDifference(string s, string t) {
+        int sumS = 0, sumT = 0;
+        for (char c : s) {
+            sumS += c;
+        }
+        for (char c : t) {
+            sumT += c;
+        }
+        return (char) (sumT - sumS);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string} t
+     * @return {character}
+     */
+    findTheDifference(s, t) {
+        let sumS = 0, sumT = 0;
+        for (let char of s) {
+            sumS += char.charCodeAt(0);
+        }
+        for (let char of t) {
+            sumT += char.charCodeAt(0);
+        }
+        return String.fromCharCode(sumT - sumS);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 5. Difference Between ASCII Values (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def findTheDifference(self, s: str, t: str) -> str:
+        res = 0
+        for c in s:
+            res -= ord(c)
+        for c in t:
+            res += ord(c)
+        return chr(res)
+```
+
+```java
+public class Solution {
+    public char findTheDifference(String s, String t) {
+        int res = 0;
+        for (int i = 0; i < s.length(); i++) {
+            res -= s.charAt(i);
+        }
+        for (int i = 0; i < t.length(); i++) {
+            res += t.charAt(i);
+        }
+        return (char) (res);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    char findTheDifference(string s, string t) {
+        int res = 0;
+        for (char c : s) {
+            res -= c;
+        }
+        for (char c : t) {
+            res += c;
+        }
+        return (char) (res);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string} t
+     * @return {character}
+     */
+    findTheDifference(s, t) {
+        let res = 0;
+        for (let char of s) {
+            res -= char.charCodeAt(0);
+        }
+        for (let char of t) {
+            res += char.charCodeAt(0);
+        }
+        return String.fromCharCode(res);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 6. Bitwise XOR
+
+::tabs-start
+
+```python
+class Solution:
+    def findTheDifference(self, s: str, t: str) -> str:
+        res = 0
+        for c in s:
+            res ^= ord(c)
+        for c in t:
+            res ^= ord(c)
+        return chr(res)
+```
+
+```java
+public class Solution {
+    public char findTheDifference(String s, String t) {
+        int res = 0;
+        for (int i = 0; i < s.length(); i++) {
+            res ^= s.charAt(i);
+        }
+        for (int i = 0; i < t.length(); i++) {
+            res ^= t.charAt(i);
+        }
+        return (char) (res);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    char findTheDifference(string s, string t) {
+        int res = 0;
+        for (char c : s) {
+            res ^= c;
+        }
+        for (char c : t) {
+            res ^= c;
+        }
+        return (char) (res);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string} t
+     * @return {character}
+     */
+    findTheDifference(s, t) {
+        let res = 0;
+        for (let char of s) {
+            res ^= char.charCodeAt(0);
+        }
+        for (let char of t) {
+            res ^= char.charCodeAt(0);
+        }
+        return String.fromCharCode(res);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/find-the-index-of-the-first-occurrence-in-a-string.md b/articles/find-the-index-of-the-first-occurrence-in-a-string.md
new file mode 100644
index 000000000..beb5b5893
--- /dev/null
+++ b/articles/find-the-index-of-the-first-occurrence-in-a-string.md
@@ -0,0 +1,633 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def strStr(self, haystack: str, needle: str) -> int:
+        n, m = len(haystack), len(needle)
+        for i in range(n - m + 1):
+            j = 0
+            while j < m:
+                if haystack[i + j] != needle[j]:
+                    break
+                j += 1
+            if j == m:
+                return i
+        return -1
+```
+
+```java
+public class Solution {
+    public int strStr(String haystack, String needle) {
+        int n = haystack.length(), m = needle.length();
+        for (int i = 0; i < n - m + 1; i++) {
+            int j = 0;
+            while (j < m) {
+                if (haystack.charAt(i + j) != needle.charAt(j)) {
+                    break;
+                }
+                j++;
+            }
+            if (j == m) return i;
+        }
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int strStr(string haystack, string needle) {
+        int n = haystack.length(), m = needle.length();
+        for (int i = 0; i < n - m + 1; i++) {
+            int j = 0;
+            while (j < m) {
+                if (haystack[i + j] != needle[j]) {
+                    break;
+                }
+                j++;
+            }
+            if (j == m) return i;
+        }
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} haystack
+     * @param {string} needle
+     * @return {number}
+     */
+    strStr(haystack, needle) {
+        let n = haystack.length, m = needle.length;
+        for (let i = 0; i < n - m + 1; i++) {
+            let j = 0;
+            while (j < m) {
+                if (haystack[i + j] !== needle[j]) {
+                    break;
+                }
+                j++;
+            }
+            if (j === m) return i;
+        }
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(1)$
+
+> Where $n$ is the length of the string $heystack$ and $m$ is the length of the string $needle$.
+
+---
+
+## 2. Knuth-Morris-Pratt (KMP) Algorithm
+
+::tabs-start
+
+```python
+class Solution:
+    def strStr(self, haystack: str, needle: str) -> int:
+        if needle == "": return 0
+        lps = [0] * len(needle)
+
+        prevLPS, i = 0, 1
+        while i < len(needle):
+            if needle[i] == needle[prevLPS]:
+                lps[i] = prevLPS + 1
+                prevLPS += 1
+                i += 1
+            elif prevLPS == 0:
+                lps[i] = 0
+                i += 1
+            else:
+                prevLPS = lps[prevLPS - 1]
+        
+        i = 0  # ptr for haystack
+        j = 0  # ptr for needle
+        while i < len(haystack):
+            if haystack[i] == needle[j]:
+                i, j = i + 1, j + 1
+            else:
+                if j == 0:
+                    i += 1
+                else:
+                    j = lps[j - 1]
+            
+            if j == len(needle):
+                return i - len(needle)
+        
+        return -1
+```
+
+```java
+public class Solution {
+    public int strStr(String haystack, String needle) {
+        if (needle.isEmpty()) return 0;
+
+        int m = needle.length();
+        int[] lps = new int[m];
+        int prevLPS = 0, i = 1;
+
+        while (i < m) {
+            if (needle.charAt(i) == needle.charAt(prevLPS)) {
+                lps[i] = prevLPS + 1;
+                prevLPS++;
+                i++;
+            } else if (prevLPS == 0) {
+                lps[i] = 0;
+                i++;
+            } else {
+                prevLPS = lps[prevLPS - 1];
+            }
+        }
+
+        i = 0;  // ptr for haystack
+        int j = 0;  // ptr for needle
+        while (i < haystack.length()) {
+            if (haystack.charAt(i) == needle.charAt(j)) {
+                i++;
+                j++;
+            } else {
+                if (j == 0) {
+                    i++;
+                } else {
+                    j = lps[j - 1];
+                }
+            }
+
+            if (j == m) {
+                return i - m;
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int strStr(string haystack, string needle) {
+        if (needle.empty()) return 0;
+
+        int m = needle.size();
+        vector<int> lps(m, 0);
+        int prevLPS = 0, i = 1;
+
+        while (i < m) {
+            if (needle[i] == needle[prevLPS]) {
+                lps[i] = prevLPS + 1;
+                prevLPS++;
+                i++;
+            } else if (prevLPS == 0) {
+                lps[i] = 0;
+                i++;
+            } else {
+                prevLPS = lps[prevLPS - 1];
+            }
+        }
+
+        i = 0;  // ptr for haystack
+        int j = 0;  // ptr for needle
+        while (i < haystack.size()) {
+            if (haystack[i] == needle[j]) {
+                i++;
+                j++;
+            } else {
+                if (j == 0) {
+                    i++;
+                } else {
+                    j = lps[j - 1];
+                }
+            }
+
+            if (j == m) {
+                return i - m;
+            }
+        }
+
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} haystack
+     * @param {string} needle
+     * @return {number}
+     */
+    strStr(haystack, needle) {
+        if (needle === "") return 0;
+
+        const m = needle.length;
+        const lps = new Array(m).fill(0);
+
+        let prevLPS = 0, i = 1;
+        while (i < m) {
+            if (needle[i] === needle[prevLPS]) {
+                lps[i] = prevLPS + 1;
+                prevLPS++;
+                i++;
+            } else if (prevLPS === 0) {
+                lps[i] = 0;
+                i++;
+            } else {
+                prevLPS = lps[prevLPS - 1];
+            }
+        }
+
+        i = 0;  // ptr for haystack
+        let j = 0;  // ptr for needle
+        while (i < haystack.length) {
+            if (haystack[i] === needle[j]) {
+                i++;
+                j++;
+            } else {
+                if (j === 0) {
+                    i++;
+                } else {
+                    j = lps[j - 1];
+                }
+            }
+
+            if (j === m) {
+                return i - m;
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(m)$
+
+> Where $n$ is the length of the string $heystack$ and $m$ is the length of the string $needle$.
+
+---
+
+## 3. Z-Algorithm
+
+::tabs-start
+
+```python
+class Solution:
+    def strStr(self, haystack: str, needle: str) -> int:
+        if not needle:
+            return 0
+        
+        s = needle + "$" + haystack
+        n = len(s)
+        z = [0] * n
+        l, r = 0, 0
+        
+        for i in range(1, n):
+            if i <= r:
+                z[i] = min(r - i + 1, z[i - l])
+            while i + z[i] < n and s[z[i]] == s[i + z[i]]:
+                z[i] += 1
+            if i + z[i] - 1 > r:
+                l, r = i, i + z[i] - 1
+        
+        for i in range(len(needle) + 1, n):
+            if z[i] == len(needle):
+                return i - len(needle) - 1
+        
+        return -1
+```
+
+```java
+public class Solution {
+    public int strStr(String haystack, String needle) {
+        if (needle.isEmpty()) return 0;
+
+        String s = needle + "$" + haystack;
+        int n = s.length();
+        int[] z = new int[n];
+        int l = 0, r = 0;
+
+        for (int i = 1; i < n; i++) {
+            if (i <= r) {
+                z[i] = Math.min(r - i + 1, z[i - l]);
+            }
+            while (i + z[i] < n && s.charAt(z[i]) == s.charAt(i + z[i])) {
+                z[i]++;
+            }
+            if (i + z[i] - 1 > r) {
+                l = i;
+                r = i + z[i] - 1;
+            }
+        }
+
+        for (int i = needle.length() + 1; i < n; i++) {
+            if (z[i] == needle.length()) {
+                return i - needle.length() - 1;
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int strStr(string haystack, string needle) {
+        if (needle.empty()) return 0;
+
+        string s = needle + "$" + haystack;
+        int n = s.size();
+        vector<int> z(n, 0);
+        int l = 0, r = 0;
+
+        for (int i = 1; i < n; i++) {
+            if (i <= r) {
+                z[i] = min(r - i + 1, z[i - l]);
+            }
+            while (i + z[i] < n && s[z[i]] == s[i + z[i]]) {
+                z[i]++;
+            }
+            if (i + z[i] - 1 > r) {
+                l = i;
+                r = i + z[i] - 1;
+            }
+        }
+
+        for (int i = needle.size() + 1; i < n; i++) {
+            if (z[i] == needle.size()) {
+                return i - needle.size() - 1;
+            }
+        }
+
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} haystack
+     * @param {string} needle
+     * @return {number}
+     */
+    strStr(haystack, needle) {
+        if (needle === "") return 0;
+
+        const s = needle + "$" + haystack;
+        const n = s.length;
+        const z = new Array(n).fill(0);
+        let l = 0, r = 0;
+
+        for (let i = 1; i < n; i++) {
+            if (i <= r) {
+                z[i] = Math.min(r - i + 1, z[i - l]);
+            }
+            while (i + z[i] < n && s[z[i]] === s[i + z[i]]) {
+                z[i]++;
+            }
+            if (i + z[i] - 1 > r) {
+                l = i;
+                r = i + z[i] - 1;
+            }
+        }
+
+        for (let i = needle.length + 1; i < n; i++) {
+            if (z[i] === needle.length) {
+                return i - needle.length - 1;
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(n + m)$
+
+> Where $n$ is the length of the string $heystack$ and $m$ is the length of the string $needle$.
+
+---
+
+## 4. Rabin-Karp Algorithm (Rolling Hash)
+
+::tabs-start
+
+```python
+class Solution:
+    def strStr(self, haystack: str, needle: str) -> int:
+        if not needle:
+            return 0
+        
+        base1, mod1 = 31, 768258391
+        base2, mod2 = 37, 685683731
+        
+        n, m = len(haystack), len(needle)
+        if m > n:
+            return -1
+
+        power1, power2 = 1, 1
+        for _ in range(m):
+            power1 = (power1 * base1) % mod1
+            power2 = (power2 * base2) % mod2
+
+        needle_hash1, needle_hash2 = 0, 0
+        haystack_hash1, haystack_hash2 = 0, 0
+
+        for i in range(m):
+            needle_hash1 = (needle_hash1 * base1 + ord(needle[i])) % mod1
+            needle_hash2 = (needle_hash2 * base2 + ord(needle[i])) % mod2
+            haystack_hash1 = (haystack_hash1 * base1 + ord(haystack[i])) % mod1
+            haystack_hash2 = (haystack_hash2 * base2 + ord(haystack[i])) % mod2
+
+        for i in range(n - m + 1):
+            if haystack_hash1 == needle_hash1 and haystack_hash2 == needle_hash2:
+                return i
+            
+            if i + m < n:
+                haystack_hash1 = (haystack_hash1 * base1 - ord(haystack[i]) * power1 + ord(haystack[i + m])) % mod1
+                haystack_hash2 = (haystack_hash2 * base2 - ord(haystack[i]) * power2 + ord(haystack[i + m])) % mod2
+
+                haystack_hash1 = (haystack_hash1 + mod1) % mod1
+                haystack_hash2 = (haystack_hash2 + mod2) % mod2
+
+        return -1
+```
+
+```java
+public class Solution {
+    public int strStr(String haystack, String needle) {
+        if (needle.isEmpty()) return 0;
+
+        int base1 = 31, mod1 = 768258391;
+        int base2 = 37, mod2 = 685683731;
+
+        int n = haystack.length(), m = needle.length();
+        if (m > n) return -1;
+
+        long power1 = 1, power2 = 1;
+        for (int i = 0; i < m; i++) {
+            power1 = (power1 * base1) % mod1;
+            power2 = (power2 * base2) % mod2;
+        }
+
+        long needleHash1 = 0, needleHash2 = 0;
+        long haystackHash1 = 0, haystackHash2 = 0;
+
+        for (int i = 0; i < m; i++) {
+            needleHash1 = (needleHash1 * base1 + needle.charAt(i)) % mod1;
+            needleHash2 = (needleHash2 * base2 + needle.charAt(i)) % mod2;
+            haystackHash1 = (haystackHash1 * base1 + haystack.charAt(i)) % mod1;
+            haystackHash2 = (haystackHash2 * base2 + haystack.charAt(i)) % mod2;
+        }
+
+        for (int i = 0; i <= n - m; i++) {
+            if (haystackHash1 == needleHash1 && haystackHash2 == needleHash2) {
+                return i;
+            }
+
+            if (i + m < n) {
+                haystackHash1 = (haystackHash1 * base1 - haystack.charAt(i) * power1 + haystack.charAt(i + m)) % mod1;
+                haystackHash2 = (haystackHash2 * base2 - haystack.charAt(i) * power2 + haystack.charAt(i + m)) % mod2;
+
+                if (haystackHash1 < 0) haystackHash1 += mod1;
+                if (haystackHash2 < 0) haystackHash2 += mod2;
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int strStr(string haystack, string needle) {
+        if (needle.empty()) return 0;
+
+        long long base1 = 31, mod1 = 768258391;
+        long long base2 = 37, mod2 = 685683731;
+
+        int n = haystack.size(), m = needle.size();
+        if (m > n) return -1;
+
+        long long power1 = 1, power2 = 1;
+        for (int i = 0; i < m; i++) {
+            power1 = (power1 * base1) % mod1;
+            power2 = (power2 * base2) % mod2;
+        }
+
+        long long needleHash1 = 0, needleHash2 = 0;
+        long long haystackHash1 = 0, haystackHash2 = 0;
+
+        for (int i = 0; i < m; i++) {
+            needleHash1 = (needleHash1 * base1 + needle[i]) % mod1;
+            needleHash2 = (needleHash2 * base2 + needle[i]) % mod2;
+            haystackHash1 = (haystackHash1 * base1 + haystack[i]) % mod1;
+            haystackHash2 = (haystackHash2 * base2 + haystack[i]) % mod2;
+        }
+
+        for (int i = 0; i <= n - m; i++) {
+            if (haystackHash1 == needleHash1 && haystackHash2 == needleHash2) {
+                return i;
+            }
+
+            if (i + m < n) {
+                haystackHash1 = (haystackHash1 * base1 - haystack[i] * power1 + haystack[i + m]) % mod1;
+                haystackHash2 = (haystackHash2 * base2 - haystack[i] * power2 + haystack[i + m]) % mod2;
+
+                if (haystackHash1 < 0) haystackHash1 += mod1;
+                if (haystackHash2 < 0) haystackHash2 += mod2;
+            }
+        }
+
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} haystack
+     * @param {string} needle
+     * @return {number}
+     */
+    strStr(haystack, needle) {
+        if (needle === "") return 0;
+
+        const base1 = 31, mod1 = 768258391;
+        const base2 = 37, mod2 = 685683731;
+
+        const n = haystack.length, m = needle.length;
+        if (m > n) return -1;
+
+        let power1 = 1, power2 = 1;
+        for (let i = 0; i < m; i++) {
+            power1 = (power1 * base1) % mod1;
+            power2 = (power2 * base2) % mod2;
+        }
+
+        let needleHash1 = 0, needleHash2 = 0;
+        let haystackHash1 = 0, haystackHash2 = 0;
+
+        for (let i = 0; i < m; i++) {
+            needleHash1 = (needleHash1 * base1 + needle.charCodeAt(i)) % mod1;
+            needleHash2 = (needleHash2 * base2 + needle.charCodeAt(i)) % mod2;
+            haystackHash1 = (haystackHash1 * base1 + haystack.charCodeAt(i)) % mod1;
+            haystackHash2 = (haystackHash2 * base2 + haystack.charCodeAt(i)) % mod2;
+        }
+
+        for (let i = 0; i <= n - m; i++) {
+            if (haystackHash1 === needleHash1 && haystackHash2 === needleHash2) {
+                return i;
+            }
+
+            if (i + m < n) {
+                haystackHash1 = (haystackHash1 * base1 - haystack.charCodeAt(i) * power1 + haystack.charCodeAt(i + m)) % mod1;
+                haystackHash2 = (haystackHash2 * base2 - haystack.charCodeAt(i) * power2 + haystack.charCodeAt(i + m)) % mod2;
+
+                if (haystackHash1 < 0) haystackHash1 += mod1;
+                if (haystackHash2 < 0) haystackHash2 += mod2;
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(1)$
+
+> Where $n$ is the length of the string $heystack$ and $m$ is the length of the string $needle$.
\ No newline at end of file
diff --git a/articles/find-the-kth-largest-integer-in-the-array.md b/articles/find-the-kth-largest-integer-in-the-array.md
new file mode 100644
index 000000000..ba70f2ed8
--- /dev/null
+++ b/articles/find-the-kth-largest-integer-in-the-array.md
@@ -0,0 +1,543 @@
+## 1. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def kthLargestNumber(self, nums: List[str], k: int) -> str:
+        return sorted(nums, key=lambda x: (len(x), x), reverse=True)[k - 1]
+```
+
+```java
+public class Solution {
+    public String kthLargestNumber(String[] nums, int k) {
+        Arrays.sort(nums,
+            (a, b) -> a.length() == b.length() ? b.compareTo(a) : b.length() - a.length()
+        );
+        return nums[k - 1];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string kthLargestNumber(vector<string>& nums, int k) {
+        sort(nums.begin(), nums.end(), [](const string& a, const string& b) {
+            return a.size() == b.size() ? a > b : a.size() > b.size();
+        });
+        return nums[k - 1];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} nums
+     * @param {number} k
+     * @return {string}
+     */
+    kthLargestNumber(nums, k) {
+        nums.sort(
+            (a, b) => a.length === b.length ? b.localeCompare(a) : b.length - a.length
+        );
+        return nums[k - 1];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+> Where $n$ is the number of strings and $m$ is the average length of a string.
+
+---
+
+## 2. Max-Heap
+
+::tabs-start
+
+```python
+class Num:
+    def __init__(self, s: str):
+        self.s = s
+
+    def __lt__(self, other: "Num") -> bool:
+        if len(self.s) != len(other.s):
+            return len(self.s) > len(other.s)
+        return self.s > other.s
+
+class Solution:
+    def kthLargestNumber(self, nums: List[str], k: int) -> str:
+        maxHeap = [Num(s) for s in nums]
+        heapq.heapify(maxHeap)
+
+        for _ in range(k - 1):
+            heapq.heappop(maxHeap)
+
+        return heapq.heappop(maxHeap).s
+```
+
+```java
+public class Solution {
+    public String kthLargestNumber(String[] nums, int k) {
+        PriorityQueue<String> maxHeap = new PriorityQueue<>((a, b) -> 
+            a.length() == b.length() ? b.compareTo(a) : Integer.compare(b.length(), a.length())
+        );
+
+        for (String num : nums) {
+            maxHeap.offer(num);
+        }
+
+        while (--k > 0) {
+            maxHeap.poll();
+        }
+
+        return maxHeap.poll();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string kthLargestNumber(vector<string>& nums, int k) {
+        auto cmp = [](const string& a, const string& b) {
+            return a.size() == b.size() ? a < b : a.size() < b.size();
+        };
+
+        priority_queue<string, vector<string>, decltype(cmp)> maxHeap(cmp);
+
+        for (const string& num : nums) {
+            maxHeap.push(num);
+        }
+
+        while (--k > 0) {
+            maxHeap.pop();
+        }
+
+        return maxHeap.top();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} nums
+     * @param {number} k
+     * @return {string}
+     */
+    kthLargestNumber(nums, k) {
+        const maxHeap = new PriorityQueue(
+            (a, b) => a.length === b.length ? b.localeCompare(a) : b.length - a.length
+        );
+
+        for (const num of nums) {
+            maxHeap.enqueue(num);
+        }
+
+        while (--k > 0) {
+            maxHeap.dequeue();
+        }
+
+        return maxHeap.dequeue();
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * (n + k) * \log n)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the number of strings and $m$ is the average length of a string.
+
+---
+
+## 3. Min-Heap
+
+::tabs-start
+
+```python
+class Num:
+    def __init__(self, s: str):
+        self.s = s
+        
+    def __lt__(self, other: "Num") -> bool:
+        if len(self.s) != len(other.s):
+            return len(self.s) < len(other.s)
+        return self.s < other.s
+
+class Solution:
+    def kthLargestNumber(self, nums: List[str], k: int) -> str:
+        minHeap = []
+        for num in nums:
+            heapq.heappush(minHeap, Num(num))
+            if len(minHeap) > k:
+                heapq.heappop(minHeap)
+        return minHeap[0].s
+```
+
+```java
+public class Solution {
+    public String kthLargestNumber(String[] nums, int k) {
+        PriorityQueue<String> minHeap = new PriorityQueue<>((a, b) -> 
+            a.length() == b.length() ? a.compareTo(b) : Integer.compare(a.length(), b.length())
+        );
+
+        for (String num : nums) {
+            minHeap.offer(num);
+            if (minHeap.size() > k) {
+                minHeap.poll();
+            }
+        }
+
+        return minHeap.peek();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string kthLargestNumber(vector<string>& nums, int k) {
+        auto cmp = [](const string& a, const string& b) {
+            return a.size() == b.size() ? a > b : a.size() > b.size();
+        };
+
+        priority_queue<string, vector<string>, decltype(cmp)> minHeap(cmp);
+
+        for (const string& num : nums) {
+            minHeap.push(num);
+            if (minHeap.size() > k) {
+                minHeap.pop();
+            }
+        }
+
+        return minHeap.top();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} nums
+     * @param {number} k
+     * @return {string}
+     */
+    kthLargestNumber(nums, k) {
+        const minHeap = new PriorityQueue(
+            (a, b) => a.length === b.length ? a.localeCompare(b) : a.length - b.length
+        );
+
+        for (const num of nums) {
+            minHeap.enqueue(num);
+            if (minHeap.size() > k) {
+                minHeap.dequeue();
+            }
+        }
+
+        return minHeap.front();
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n * \log k)$
+* Space complexity: $O(k)$
+
+> Where $n$ is the number of strings and $m$ is the average length of a string.
+
+---
+
+## 4. Quick Select
+
+::tabs-start
+
+```python
+class Solution:
+    def greater(self, x: str, y: str) -> bool:
+        if len(x) != len(y):
+            return len(x) > len(y)
+        return x > y
+
+    def less(self, x: str, y: str) -> bool:
+        if len(x) != len(y):
+            return len(x) < len(y)
+        return x < y
+
+    def partition(self, nums: List[str], left: int, right: int) -> int:
+        mid = (left + right) >> 1
+        nums[mid], nums[left + 1] = nums[left + 1], nums[mid]
+
+        if self.less(nums[left], nums[right]):
+            nums[left], nums[right] = nums[right], nums[left]
+        if self.less(nums[left + 1], nums[right]):
+            nums[left + 1], nums[right] = nums[right], nums[left + 1]
+        if self.less(nums[left], nums[left + 1]):
+            nums[left], nums[left + 1] = nums[left + 1], nums[left]
+
+        pivot = nums[left + 1]
+        i = left + 1
+        j = right
+
+        while True:
+            while True:
+                i += 1
+                if not self.greater(nums[i], pivot):
+                    break
+            while True:
+                j -= 1
+                if not self.less(nums[j], pivot):
+                    break
+            if i > j:
+                break
+            nums[i], nums[j] = nums[j], nums[i]
+        
+        nums[left + 1], nums[j] = nums[j], nums[left + 1]
+        return j
+
+    def quickSelect(self, nums: List[str], k: int) -> str:
+        left = 0
+        right = len(nums) - 1
+
+        while True:
+            if right <= left + 1:
+                if right == left + 1 and self.greater(nums[right], nums[left]):
+                    nums[left], nums[right] = nums[right], nums[left]
+                return nums[k]
+
+            j = self.partition(nums, left, right)
+            if j >= k:
+                right = j - 1
+            if j <= k:
+                left = j + 1
+
+    def kthLargestNumber(self, nums: List[str], k: int) -> str:
+        return self.quickSelect(nums, k - 1)
+```
+
+```java
+public class Solution {
+    public String kthLargestNumber(String[] nums, int k) {
+        return quickSelect(nums, k - 1);
+    }
+
+    private boolean greater(String x, String y) {
+        if (x.length() != y.length()) {
+            return x.length() > y.length();
+        }
+        return x.compareTo(y) > 0;
+    }
+
+    private boolean less(String x, String y) {
+        if (x.length() != y.length()) {
+            return x.length() < y.length();
+        }
+        return x.compareTo(y) < 0;
+    }
+
+    private int partition(String[] nums, int left, int right) {
+        int mid = (left + right) >> 1;
+        swap(nums, mid, left + 1);
+
+        if (less(nums[left], nums[right])) {
+            swap(nums, left, right);
+        }
+        if (less(nums[left + 1], nums[right])) {
+            swap(nums, left + 1, right);
+        }
+        if (less(nums[left], nums[left + 1])) {
+            swap(nums, left, left + 1);
+        }
+
+        String pivot = nums[left + 1];
+        int i = left + 1, j = right;
+
+        while (true) {
+            while (greater(nums[++i], pivot));
+            while (less(nums[--j], pivot));
+            if (i > j) break;
+            swap(nums, i, j);
+        }
+
+        swap(nums, left + 1, j);
+        return j;
+    }
+
+    private String quickSelect(String[] nums, int k) {
+        int left = 0, right = nums.length - 1;
+
+        while (true) {
+            if (right <= left + 1) {
+                if (right == left + 1 && greater(nums[right], nums[left])) {
+                    swap(nums, left, right);
+                }
+                return nums[k];
+            }
+
+            int j = partition(nums, left, right);
+            if (j >= k) {
+                right = j - 1;
+            }
+            if (j <= k) {
+                left = j + 1;
+            }
+        }
+    }
+
+    private void swap(String[] nums, int i, int j) {
+        String temp = nums[i];
+        nums[i] = nums[j];
+        nums[j] = temp;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string kthLargestNumber(vector<string>& nums, int k) {
+        return quickSelect(nums, k - 1);
+    }
+
+private:
+    bool greater(const string& x, const string& y) {
+        if (x.size() != y.size()) {
+            return x.size() > y.size();
+        }
+        return x > y;
+    }
+
+    bool less(const string& x, const string& y) {
+        if (x.size() != y.size()) {
+            return x.size() < y.size();
+        }
+        return x < y;
+    }
+
+    int partition(vector<string>& nums, int left, int right) {
+        int mid = (left + right) >> 1;
+        swap(nums[mid], nums[left + 1]);
+
+        if (less(nums[left], nums[right])) {
+            swap(nums[left], nums[right]);
+        }
+        if (less(nums[left + 1], nums[right])) {
+            swap(nums[left + 1], nums[right]);
+        }
+        if (less(nums[left], nums[left + 1])) {
+            swap(nums[left], nums[left + 1]);
+        }
+
+        string pivot = nums[left + 1];
+        int i = left + 1, j = right;
+
+        while (true) {
+            while (greater(nums[++i], pivot));
+            while (less(nums[--j], pivot));
+            if (i > j) break;
+            swap(nums[i], nums[j]);
+        }
+
+        swap(nums[left + 1], nums[j]);
+        return j;
+    }
+
+    string quickSelect(vector<string>& nums, int k) {
+        int left = 0, right = nums.size() - 1;
+
+        while (true) {
+            if (right <= left + 1) {
+                if (right == left + 1 && greater(nums[right], nums[left])) {
+                    swap(nums[left], nums[right]);
+                }
+                return nums[k];
+            }
+
+            int j = partition(nums, left, right);
+            if (j >= k) {
+                right = j - 1;
+            }
+            if (j <= k) {
+                left = j + 1;
+            }
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} nums
+     * @param {number} k
+     * @return {string}
+     */
+    kthLargestNumber(nums, k) {
+        const greater = (x, y) => x.length !== y.length ? x.length > y.length : x > y;
+        const less = (x, y) => x.length !== y.length ? x.length < y.length : x < y;
+        const swap = (arr, i, j) => [arr[i], arr[j]] = [arr[j], arr[i]];
+
+        const partition = (nums, left, right) => {
+            const mid = Math.floor((left + right) / 2);
+            swap(nums, mid, left + 1);
+
+            if (less(nums[left], nums[right])) swap(nums, left, right);
+            if (less(nums[left + 1], nums[right])) swap(nums, left + 1, right);
+            if (less(nums[left], nums[left + 1])) swap(nums, left, left + 1);
+
+            const pivot = nums[left + 1];
+            let i = left + 1, j = right;
+
+            while (true) {
+                while (greater(nums[++i], pivot));
+                while (less(nums[--j], pivot));
+                if (i > j) break;
+                swap(nums, i, j);
+            }
+
+            swap(nums, left + 1, j);
+            return j;
+        };
+
+        const quickSelect = (nums, k) => {
+            let left = 0, right = nums.length - 1;
+
+            while (true) {
+                if (right <= left + 1) {
+                    if (right === left + 1 && greater(nums[right], nums[left])) {
+                        swap(nums, left, right);
+                    }
+                    return nums[k];
+                }
+
+                const j = partition(nums, left, right);
+                if (j >= k) right = j - 1;
+                if (j <= k) left = j + 1;
+            }
+        };
+
+        return quickSelect(nums, k - 1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$ in average case, $O(m * n ^ 2)$ in worst case.
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/find-the-longest-valid-obstacle-course-at-each-position.md b/articles/find-the-longest-valid-obstacle-course-at-each-position.md
new file mode 100644
index 000000000..ff2346555
--- /dev/null
+++ b/articles/find-the-longest-valid-obstacle-course-at-each-position.md
@@ -0,0 +1,387 @@
+## 1. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def longestObstacleCourseAtEachPosition(self, obstacles: List[int]) -> List[int]:
+        n = len(obstacles)
+        dp = [[-1] * (n + 1) for _ in range(n)]
+
+        def dfs(i, prev):
+            if i < 0:
+                return 0
+            if dp[i][prev] != -1:
+                return dp[i][prev]
+
+            res = dfs(i - 1, prev)
+            if prev == n or obstacles[prev] >= obstacles[i]:
+                res = max(res, 1 + dfs(i - 1, i))
+            dp[i][prev] = res
+            return res
+
+        dfs(n - 1, n)
+        return [1] + [1 + dp[i - 1][i] for i in range(1, n)]
+```
+
+```java
+public class Solution {
+    private int[][] dp;
+
+    public int[] longestObstacleCourseAtEachPosition(int[] obstacles) {
+        int n = obstacles.length;
+        this.dp = new int[n][n + 1];
+        for (int[] row : dp) {
+            Arrays.fill(row, -1);
+        }
+
+        dfs(n - 1, n, obstacles);
+
+        int[] res = new int[n];
+        res[0] = 1;
+        for (int i = 1; i < n; i++) {
+            res[i] = 1 + dp[i - 1][i];
+        }
+        return res;
+    }
+
+    private int dfs(int i, int prev, int[] obstacles) {
+        if (i < 0) {
+            return 0;
+        }
+        if (dp[i][prev] != -1) {
+            return dp[i][prev];
+        }
+
+        int res = dfs(i - 1, prev, obstacles);
+        if (prev == obstacles.length || obstacles[prev] >= obstacles[i]) {
+            res = Math.max(res, 1 + dfs(i - 1, i, obstacles));
+        }
+        return dp[i][prev] = res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> dp;
+
+    vector<int> longestObstacleCourseAtEachPosition(vector<int>& obstacles) {
+        int n = obstacles.size();
+        this->dp = vector<vector<int>>(n, vector<int>(n + 1, -1));
+
+        dfs(n - 1, n, obstacles);
+
+        vector<int> res(n, 1);
+        for (int i = 1; i < n; i++) {
+            res[i] = 1 + dp[i - 1][i];
+        }
+        return res;
+    }
+
+private:
+    int dfs(int i, int prev, vector<int>& obstacles) {
+        if (i < 0) {
+            return 0;
+        }
+        if (dp[i][prev] != -1) {
+            return dp[i][prev];
+        }
+
+        int res = dfs(i - 1, prev, obstacles);
+        if (prev == obstacles.size() || obstacles[prev] >= obstacles[i]) {
+            res = max(res, 1 + dfs(i - 1, i, obstacles));
+        }
+        return dp[i][prev] = res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} obstacles
+     * @return {number[]}
+     */
+    longestObstacleCourseAtEachPosition(obstacles) {
+        const n = obstacles.length;
+        const dp = Array.from({ length: n }, () => new Array(n + 1).fill(-1));
+
+        const dfs = (i, prev) => {
+            if (i < 0) {
+                return 0;
+            }
+            if (dp[i][prev] !== -1) {
+                return dp[i][prev];
+            }
+
+            let res = dfs(i - 1, prev);
+            if (prev === n || obstacles[prev] >= obstacles[i]) {
+                res = Math.max(res, 1 + dfs(i - 1, i));
+            }
+            dp[i][prev] = res;
+            return res;
+        };
+
+        dfs(n - 1, n);
+
+        const res = new Array(n).fill(1);
+        for (let i = 1; i < n; i++) {
+            res[i] = 1 + dp[i - 1][i];
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 2. Dynamic Programming (Binary Search) - I
+
+::tabs-start
+
+```python
+class Solution:
+    def longestObstacleCourseAtEachPosition(self, obstacles: List[int]) -> List[int]:
+        res = []
+        dp = [10**8] * (len(obstacles) + 1)
+
+        for num in obstacles:
+            index = bisect.bisect(dp, num)
+            res.append(index + 1)
+            dp[index] = num
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[] longestObstacleCourseAtEachPosition(int[] obstacles) {
+        int n = obstacles.length;
+        int[] res = new int[n];
+        int[] dp = new int[n + 1];
+        Arrays.fill(dp, (int) 1e8);
+
+        for (int i = 0; i < n; i++) {
+            int index = upperBound(dp, obstacles[i]);
+            res[i] = index + 1;
+            dp[index] = obstacles[i];
+        }
+
+        return res;
+    }
+
+    private int upperBound(int[] dp, int target) {
+        int left = 0, right = dp.length;
+        while (left < right) {
+            int mid = left + (right - left) / 2;
+            if (dp[mid] > target) {
+                right = mid;
+            } else {
+                left = mid + 1;
+            }
+        }
+        return left;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> longestObstacleCourseAtEachPosition(vector<int>& obstacles) {
+        int n = obstacles.size();
+        vector<int> res(n);
+        vector<int> dp(n + 1, 1e8);
+
+        for (int i = 0; i < n; i++) {
+            int index = upper_bound(dp.begin(), dp.end(), obstacles[i]) - dp.begin();
+            res[i] = index + 1;
+            dp[index] = obstacles[i];
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} obstacles
+     * @return {number[]}
+     */
+    longestObstacleCourseAtEachPosition(obstacles) {
+        let n = obstacles.length;
+        let res = new Array(n).fill(0);
+        let dp = new Array(n + 1).fill(1e8);
+
+        const upperBound = (dp, target) => {
+            let left = 0, right = dp.length;
+            while (left < right) {
+                let mid = Math.floor((left + right) / 2);
+                if (dp[mid] > target) {
+                    right = mid;
+                } else {
+                    left = mid + 1;
+                }
+            }
+            return left;
+        };
+
+        for (let i = 0; i < n; i++) {
+            let index = upperBound(dp, obstacles[i]);
+            res[i] = index + 1;
+            dp[index] = obstacles[i];
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Binary Search) - II
+
+::tabs-start
+
+```python
+class Solution:
+    def longestObstacleCourseAtEachPosition(self, obstacles: List[int]) -> List[int]:
+        res = []
+        dp = []
+
+        for num in obstacles:
+            index = bisect.bisect_right(dp, num)
+            res.append(index + 1)
+
+            if index == len(dp):
+                dp.append(num)
+            else:
+                dp[index] = num
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[] longestObstacleCourseAtEachPosition(int[] obstacles) {
+        int n = obstacles.length;
+        int[] res = new int[n];
+        List<Integer> dp = new ArrayList<>();
+
+        for (int i = 0; i < n; i++) {
+            int index = upperBound(dp, obstacles[i]);
+            res[i] = index + 1;
+
+            if (index == dp.size()) {
+                dp.add(obstacles[i]);
+            } else {
+                dp.set(index, obstacles[i]);
+            }
+        }
+
+        return res;
+    }
+
+    private int upperBound(List<Integer> dp, int target) {
+        int left = 0, right = dp.size();
+        while (left < right) {
+            int mid = left + (right - left) / 2;
+            if (dp.get(mid) > target) {
+                right = mid;
+            } else {
+                left = mid + 1;
+            }
+        }
+        return left;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> longestObstacleCourseAtEachPosition(vector<int>& obstacles) {
+        int n = obstacles.size();
+        vector<int> res(n);
+        vector<int> dp;
+
+        for (int i = 0; i < n; i++) {
+            int index = upper_bound(dp.begin(), dp.end(), obstacles[i]) - dp.begin();
+            res[i] = index + 1;
+
+            if (index == dp.size()) {
+                dp.push_back(obstacles[i]);
+            } else {
+                dp[index] = obstacles[i];
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} obstacles
+     * @return {number[]}
+     */
+    longestObstacleCourseAtEachPosition(obstacles) {
+        let n = obstacles.length;
+        let res = new Array(n).fill(0);
+        let dp = [];
+
+        const upperBound = (dp, target) => {
+            let left = 0, right = dp.length;
+            while (left < right) {
+                let mid = Math.floor((left + right) / 2);
+                if (dp[mid] > target) {
+                    right = mid;
+                } else {
+                    left = mid + 1;
+                }
+            }
+            return left;
+        };
+
+        for (let i = 0; i < n; i++) {
+            let index = upperBound(dp, obstacles[i]);
+            res[i] = index + 1;
+
+            if (index === dp.length) {
+                dp.push(obstacles[i]);
+            } else {
+                dp[index] = obstacles[i];
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/find-the-maximum-sum-of-node-values.md b/articles/find-the-maximum-sum-of-node-values.md
new file mode 100644
index 000000000..d48258892
--- /dev/null
+++ b/articles/find-the-maximum-sum-of-node-values.md
@@ -0,0 +1,637 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def maximumValueSum(self, nums: List[int], k: int, edges: List[List[int]]) -> int:
+        adj = [[] for _ in range(len(nums))]
+        for u, v in edges:
+            adj[u].append(v)
+            adj[v].append(u)
+
+        def dfs(node, par):
+            res = [nums[node], nums[node] ^ k]
+            for child in adj[node]:
+                if child == par:
+                    continue
+
+                cur = dfs(child, node)
+                tmp = []
+                tmp.append(max(res[0] + cur[0], res[1] + cur[1]))
+                tmp.append(max(res[1] + cur[0], res[0] + cur[1]))
+                res = tmp
+
+            return res
+
+        return dfs(0, -1)[0]
+```
+
+```java
+public class Solution {
+    public long maximumValueSum(int[] nums, int k, int[][] edges) {
+        int n = nums.length;
+        List<Integer>[] adj = new ArrayList[n];
+        for (int i = 0; i < n; i++) adj[i] = new ArrayList<>();
+        for (int[] edge : edges) {
+            adj[edge[0]].add(edge[1]);
+            adj[edge[1]].add(edge[0]);
+        }
+
+        return dfs(0, -1, nums, k, adj)[0];
+    }
+
+    private long[] dfs(int node, int parent, int[] nums, int k, List<Integer>[] adj) {
+        long[] res = { nums[node], nums[node] ^ k };
+        for (int child : adj[node]) {
+            if (child == parent) continue;
+            
+            long[] cur = dfs(child, node, nums, k, adj);
+            long[] tmp = new long[2];
+            tmp[0] = Math.max(res[0] + cur[0], res[1] + cur[1]);
+            tmp[1] = Math.max(res[1] + cur[0], res[0] + cur[1]);
+            res = tmp;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+    vector<vector<int>> adj;
+
+public:
+    long long maximumValueSum(vector<int>& nums, int k, vector<vector<int>>& edges) {
+        int n = nums.size();
+        adj.resize(n);
+        for (const auto& edge : edges) {
+            adj[edge[0]].push_back(edge[1]);
+            adj[edge[1]].push_back(edge[0]);
+        }
+
+        return dfs(0, -1, nums, k)[0];
+    }
+
+private:
+    vector<long long> dfs(int node, int parent, vector<int>& nums, int k) {
+        vector<long long> res = { nums[node], nums[node] ^ k };
+        for (int child : adj[node]) {
+            if (child == parent) continue;
+
+            vector<long long> cur = dfs(child, node, nums, k);
+            vector<long long> tmp(2);
+            tmp[0] = max(res[0] + cur[0], res[1] + cur[1]);
+            tmp[1] = max(res[1] + cur[0], res[0] + cur[1]);
+            res = tmp;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @param {number[][]} edges
+     * @return {number}
+     */
+    maximumValueSum(nums, k, edges) {
+        const n = nums.length;
+        const adj = Array.from({ length: n }, () => []);
+
+        for (const [u, v] of edges) {
+            adj[u].push(v);
+            adj[v].push(u);
+        }
+
+        const dfs = (node, parent) => {
+            let res = [nums[node], nums[node] ^ k];
+
+            for (const child of adj[node]) {
+                if (child === parent) continue;
+
+                const cur = dfs(child, node);
+                const tmp = [];
+                tmp[0] = Math.max(res[0] + cur[0], res[1] + cur[1]);
+                tmp[1] = Math.max(res[1] + cur[0], res[0] + cur[1]);
+                res = tmp;
+            }
+
+            return res;
+        };
+
+        return dfs(0, -1)[0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def maximumValueSum(self, nums: List[int], k: int, edges: List[List[int]]) -> int:
+        dp = [[None] * 2 for _ in range(len(nums))] + [[0, float("-inf")]]
+
+        def dfs(i, xorCnt):
+            if dp[i][xorCnt] is not None:
+                return dp[i][xorCnt]
+
+            res = nums[i] + dfs(i + 1, xorCnt)
+            res = max(res, (nums[i] ^ k) + dfs(i + 1, xorCnt ^ 1))
+            dp[i][xorCnt] = res
+            return res
+
+        return dfs(0, 0)
+```
+
+```java
+public class Solution {
+    private long[][] dp;
+
+    public long maximumValueSum(int[] nums, int k, int[][] edges) {
+        int n = nums.length;
+        dp = new long[n + 1][2];
+        for (long[] row : dp) Arrays.fill(row, Long.MIN_VALUE);
+        dp[n][0] = 0;
+        dp[n][1] = Integer.MIN_VALUE;
+
+        return dfs(0, 0, nums, k);
+    }
+
+    private long dfs(int i, int xorCnt, int[] nums, int k) {
+        if (dp[i][xorCnt] != Long.MIN_VALUE) {
+            return dp[i][xorCnt];
+        }
+
+        long res = nums[i] + dfs(i + 1, xorCnt, nums, k);
+        res = Math.max(res, (nums[i] ^ k) + dfs(i + 1, xorCnt ^ 1, nums, k));
+
+        return dp[i][xorCnt] = res;
+    }
+}
+```
+
+```cpp
+class Solution {
+    vector<vector<long long>> dp;
+
+public:
+    long long maximumValueSum(vector<int>& nums, int k, vector<vector<int>>& edges) {
+        int n = nums.size();
+        dp.assign(n + 1, vector<long long>(2, LLONG_MIN));
+        dp[n][0] = 0;
+        dp[n][1] = INT_MIN;
+
+        return dfs(0, 0, nums, k);
+    }
+
+private:
+    long long dfs(int i, int xorCnt, vector<int>& nums, int k) {
+        if (dp[i][xorCnt] != LLONG_MIN) {
+            return dp[i][xorCnt];
+        }
+
+        long long res = nums[i] + dfs(i + 1, xorCnt, nums, k);
+        res = max(res, (nums[i] ^ k) + dfs(i + 1, xorCnt ^ 1, nums, k));
+        return dp[i][xorCnt] = res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @param {number[][]} edges
+     * @return {number}
+     */
+    maximumValueSum(nums, k, edges) {
+        const n = nums.length;
+        const dp = Array.from({ length: n + 1 }, () => [null, null]);
+        dp[n][0] = 0;
+        dp[n][1] = -Infinity;
+
+        const dfs = (i, xorCnt) => {
+            if (dp[i][xorCnt] !== null) return dp[i][xorCnt];
+
+            let res = nums[i] + dfs(i + 1, xorCnt);
+            res = Math.max(res, (nums[i] ^ k) + dfs(i + 1, xorCnt ^ 1));
+            return dp[i][xorCnt] = res;
+        };
+
+        return dfs(0, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def maximumValueSum(self, nums: List[int], k: int, edges: List[List[int]]) -> int:
+        n = len(nums)
+        dp = [[0, 0] for _ in range(n + 1)]
+        dp[n][1] = float("-inf")
+
+        for i in range(n - 1, -1, -1):
+            dp[i][0] = max(nums[i] + dp[i + 1][0], (nums[i] ^ k) + dp[i + 1][1])
+            dp[i][1] = max(nums[i] + dp[i + 1][1], (nums[i] ^ k) + dp[i + 1][0])
+
+        return dp[0][0]
+```
+
+```java
+public class Solution {
+    public long maximumValueSum(int[] nums, int k, int[][] edges) {
+        int n = nums.length;
+        long[][] dp = new long[n + 1][2];
+        dp[n][1] = Integer.MIN_VALUE;
+
+        for (int i = n - 1; i >= 0; i--) {
+            dp[i][0] = Math.max(nums[i] + dp[i + 1][0], (nums[i] ^ k) + dp[i + 1][1]);
+            dp[i][1] = Math.max(nums[i] + dp[i + 1][1], (nums[i] ^ k) + dp[i + 1][0]);
+        }
+
+        return dp[0][0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long maximumValueSum(vector<int>& nums, int k, vector<vector<int>>& edges) {
+        int n = nums.size();
+        vector<vector<long long>> dp(n + 1, vector<long long>(2));
+        dp[n][1] = INT_MIN;
+
+        for (int i = n - 1; i >= 0; i--) {
+            dp[i][0] = max(nums[i] + dp[i + 1][0], (nums[i] ^ k) + dp[i + 1][1]);
+            dp[i][1] = max(nums[i] + dp[i + 1][1], (nums[i] ^ k) + dp[i + 1][0]);
+        }
+
+        return dp[0][0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @param {number[][]} edges
+     * @return {number}
+     */
+    maximumValueSum(nums, k, edges) {
+        const n = nums.length;
+        const dp = Array.from({ length: n + 1 }, () => [0, 0]);
+        dp[n][1] = -Infinity;
+
+        for (let i = n - 1; i >= 0; i--) {
+            dp[i][0] = Math.max(nums[i] + dp[i + 1][0], (nums[i] ^ k) + dp[i + 1][1]);
+            dp[i][1] = Math.max(nums[i] + dp[i + 1][1], (nums[i] ^ k) + dp[i + 1][0]);
+        }
+
+        return dp[0][0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def maximumValueSum(self, nums: List[int], k: int, edges: List[List[int]]) -> int:
+        dp = [0, float("-inf")]
+
+        for i in range(len(nums) - 1, -1, -1):
+            next_dp = [0, 0]
+            next_dp[0] = max(nums[i] + dp[0], (nums[i] ^ k) + dp[1])
+            next_dp[1] = max(nums[i] + dp[1], (nums[i] ^ k) + dp[0])
+            dp = next_dp
+
+        return dp[0]
+```
+
+```java
+public class Solution {
+    public long maximumValueSum(int[] nums, int k, int[][] edges) {
+        int n = nums.length;
+        long[] dp = {0, Long.MIN_VALUE};
+
+        for (int i = n - 1; i >= 0; i--) {
+            long[] nextDp = new long[2];
+            nextDp[0] = Math.max(nums[i] + dp[0], (nums[i] ^ k) + dp[1]);
+            nextDp[1] = Math.max(nums[i] + dp[1], (nums[i] ^ k) + dp[0]);
+            dp = nextDp;
+        }
+
+        return dp[0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long maximumValueSum(vector<int>& nums, int k, vector<vector<int>>& edges) {
+        int n = nums.size();
+        vector<long long> dp = {0, LLONG_MIN};
+
+        for (int i = n - 1; i >= 0; i--) {
+            vector<long long> nextDp(2);
+            nextDp[0] = max(nums[i] + dp[0], (nums[i] ^ k) + dp[1]);
+            nextDp[1] = max(nums[i] + dp[1], (nums[i] ^ k) + dp[0]);
+            dp = nextDp;
+        }
+
+        return dp[0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @param {number[][]} edges
+     * @return {number}
+     */
+    maximumValueSum(nums, k, edges) {
+        const n = nums.length;
+        let dp = [0, -Infinity];
+
+        for (let i = n - 1; i >= 0; i--) {
+            let nextDp = [0, 0];
+            nextDp[0] = Math.max(nums[i] + dp[0], (nums[i] ^ k) + dp[1]);
+            nextDp[1] = Math.max(nums[i] + dp[1], (nums[i] ^ k) + dp[0]);
+            dp = nextDp;
+        }
+
+        return dp[0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 5. Greedy
+
+::tabs-start
+
+```python
+class Solution:
+    def maximumValueSum(self, nums: List[int], k: int, edges: List[List[int]]) -> int:
+        delta = [(num ^ k) - num for num in nums]
+        delta.sort(reverse=True)
+        res = sum(nums)
+
+        for i in range(0, len(nums), 2):
+            if i == len(nums) - 1:
+                break
+            path_delta = delta[i] + delta[i + 1]
+            if path_delta <= 0:
+                break
+            res += path_delta
+
+        return res
+```
+
+```java
+public class Solution {
+    public long maximumValueSum(int[] nums, int k, int[][] edges) {
+        int n = nums.length;
+        int[] delta = new int[n];
+        long res = 0;
+        for (int i = 0; i < n; i++) {
+            res += nums[i];
+            delta[i] = (nums[i] ^ k) - nums[i];
+        }
+
+        Arrays.sort(delta);
+        for (int i = n - 1; i > 0; i -= 2) {
+            int pathDelta = delta[i] + delta[i - 1];
+            if (pathDelta <= 0) {
+                break;
+            }
+            res += pathDelta;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long maximumValueSum(vector<int>& nums, int k, vector<vector<int>>& edges) {
+        int n = nums.size();
+        vector<int> delta(n);
+        long long res = 0;
+        for (int i = 0; i < n; i++) {
+            res += nums[i];
+            delta[i] = (nums[i] ^ k) - nums[i];
+        }
+
+        sort(delta.rbegin(), delta.rend());
+
+        for (int i = 0; i + 1 < n; i += 2) {
+            int pathDelta = delta[i] + delta[i + 1];
+            if (pathDelta <= 0) {
+                break;
+            }
+            res += pathDelta;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @param {number[][]} edges
+     * @return {number}
+     */
+    maximumValueSum(nums, k, edges) {
+        const n = nums.length;
+        let res = 0;
+        let delta = [];
+        for (let i = 0; i < n; i++) {
+            res += nums[i];
+            delta.push((nums[i] ^ k) - nums[i]);
+        }
+
+        delta.sort((a, b) => b - a);
+        for (let i = 0; i + 1 < n; i += 2) {
+            let pathDelta = delta[i] + delta[i + 1];
+            if (pathDelta <= 0) {
+                break;
+            }
+            res += pathDelta;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 6. Greedy (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def maximumValueSum(self, nums: List[int], k: int, edges: List[List[int]]) -> int:
+        xorCnt = res = 0
+        minDiff = 1 << 30
+
+        for num in nums:
+            xorNum = num ^ k
+            if xorNum > num:
+                res += xorNum
+                xorCnt ^= 1
+            else:
+                res += num
+            minDiff = min(minDiff, abs(xorNum - num))
+
+        return res - xorCnt * minDiff
+```
+
+```java
+public class Solution {
+    public long maximumValueSum(int[] nums, int k, int[][] edges) {
+        int xorCnt = 0, minDiff = 1 << 30;
+        long res = 0;
+
+        for (int num : nums) {
+            int xorNum = num ^ k;
+            if (xorNum > num) {
+                res += xorNum;
+                xorCnt ^= 1;
+            } else {
+                res += num;
+            }
+            minDiff = Math.min(minDiff, Math.abs(xorNum - num));
+        }
+
+        return res - xorCnt * minDiff;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long maximumValueSum(vector<int>& nums, int k, vector<vector<int>>& edges) {
+        int xorCnt = 0, minDiff = 1 << 30;
+        long long res = 0;
+
+        for (int& num : nums) {
+            int xorNum = num ^ k;
+            if (xorNum > num) {
+                res += xorNum;
+                xorCnt ^= 1;
+            } else {
+                res += num;
+            }
+            minDiff = min(minDiff, abs(xorNum - num));
+        }
+
+        return res - (xorCnt * minDiff);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @param {number[][]} edges
+     * @return {number}
+     */
+    maximumValueSum(nums, k, edges) {
+        let xorCnt = 0, res = 0, minDiff = 1 << 30;
+
+        for (let num of nums) {
+            let xorNum = num ^ k;
+            if (xorNum > num) {
+                res += xorNum;
+                xorCnt ^= 1;
+            } else {
+                res += num;
+            }
+            minDiff = Math.min(minDiff, Math.abs(xorNum - num));
+        }
+
+        return res - (xorCnt * minDiff);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/find-the-safest-path-in-a-grid.md b/articles/find-the-safest-path-in-a-grid.md
new file mode 100644
index 000000000..f547fa423
--- /dev/null
+++ b/articles/find-the-safest-path-in-a-grid.md
@@ -0,0 +1,1054 @@
+## 1. Multi Source BFS + Dijkstra's Algorithm
+
+::tabs-start
+
+```python
+class Solution:
+    def maximumSafenessFactor(self, grid: List[List[int]]) -> int:
+        N = len(grid)
+
+        def in_bounds(r, c):
+            return min(r, c) >= 0 and max(r, c) < N
+
+        def precompute():
+            q = deque()
+            min_dist = {}
+            for r in range(N):
+                for c in range(N):
+                    if grid[r][c]:
+                        q.append([r, c, 0])
+                        min_dist[(r, c)] = 0
+            while q:
+                r, c, dist = q.popleft()
+                nei = [[r+1, c], [r-1, c], [r, c+1], [r, c-1]]
+                for r2, c2 in nei:
+                    if in_bounds(r2, c2) and (r2, c2) not in min_dist:
+                        min_dist[(r2, c2)] = dist + 1
+                        q.append([r2, c2, dist + 1])
+            return min_dist
+
+        min_dist = precompute()
+        maxHeap = [(-min_dist[(0, 0)], 0, 0)]  # (dist, r, c)
+        visit = set()
+        visit.add((0, 0))
+
+        while maxHeap:
+            dist, r, c = heapq.heappop(maxHeap)
+            dist = -dist
+            if (r, c) == (N-1, N-1):
+                return dist
+            nei = [[r+1, c], [r-1, c], [r, c+1], [r, c-1]]
+            for r2, c2 in nei:
+                if in_bounds(r2, c2) and (r2, c2) not in visit:
+                    visit.add((r2, c2))
+                    dist2 = min(dist, min_dist[(r2, c2)])
+                    heapq.heappush(maxHeap, (-dist2, r2, c2))
+```
+
+```java
+public class Solution {
+    public int maximumSafenessFactor(List<List<Integer>> grid) {
+        int N = grid.size();
+        int[][] minDist = precompute(grid, N);
+        PriorityQueue<int[]> maxHeap = new PriorityQueue<>((a, b) -> b[0] - a[0]);
+        boolean[][] visit = new boolean[N][N];
+
+        maxHeap.offer(new int[]{minDist[0][0], 0, 0});
+        visit[0][0] = true;
+
+        while (!maxHeap.isEmpty()) {
+            int[] curr = maxHeap.poll();
+            int dist = curr[0], r = curr[1], c = curr[2];
+
+            if (r == N - 1 && c == N - 1) {
+                return dist;
+            }
+
+            for (int[] dir : new int[][]{{1, 0}, {-1, 0}, {0, 1}, {0, -1}}) {
+                int r2 = r + dir[0], c2 = c + dir[1];
+                if (inBounds(r2, c2, N) && !visit[r2][c2]) {
+                    visit[r2][c2] = true;
+                    int dist2 = Math.min(dist, minDist[r2][c2]);
+                    maxHeap.offer(new int[]{dist2, r2, c2});
+                }
+            }
+        }
+        return 0;
+    }
+
+    private int[][] precompute(List<List<Integer>> grid, int N) {
+        int[][] minDist = new int[N][N];
+        for (int[] row : minDist) Arrays.fill(row, -1);
+        Queue<int[]> q = new LinkedList<>();
+
+        for (int r = 0; r < N; r++) {
+            for (int c = 0; c < N; c++) {
+                if (grid.get(r).get(c) == 1) {
+                    q.offer(new int[]{r, c, 0});
+                    minDist[r][c] = 0;
+                }
+            }
+        }
+
+        while (!q.isEmpty()) {
+            int[] curr = q.poll();
+            int r = curr[0], c = curr[1], dist = curr[2];
+
+            for (int[] dir : new int[][]{{1, 0}, {-1, 0}, {0, 1}, {0, -1}}) {
+                int r2 = r + dir[0], c2 = c + dir[1];
+                if (inBounds(r2, c2, N) && minDist[r2][c2] == -1) {
+                    minDist[r2][c2] = dist + 1;
+                    q.offer(new int[]{r2, c2, dist + 1});
+                }
+            }
+        }
+        return minDist;
+    }
+
+    private boolean inBounds(int r, int c, int N) {
+        return r >= 0 && c >= 0 && r < N && c < N;
+    }
+}
+```
+
+```cpp
+class Solution {
+    static constexpr int directions[4][2] = {{1, 0}, {-1, 0}, {0, 1}, {0, -1}};
+
+public:
+    int maximumSafenessFactor(vector<vector<int>>& grid) {
+        int N = grid.size();
+        vector<vector<int>> minDist = precompute(grid, N);
+        priority_queue<vector<int>> maxHeap;
+        vector<vector<bool>> visit(N, vector<bool>(N, false));
+
+        maxHeap.push({minDist[0][0], 0, 0});
+        visit[0][0] = true;
+
+        while (!maxHeap.empty()) {
+            vector<int> cur = maxHeap.top(); maxHeap.pop();
+            int dist = cur[0], r = cur[1], c = cur[2];
+
+            if (r == N - 1 && c == N - 1) {
+                return dist;
+            }
+
+            for (const auto& dir : directions) {
+                int r2 = r + dir[0], c2 = c + dir[1];
+                if (inBounds(r2, c2, N) && !visit[r2][c2]) {
+                    visit[r2][c2] = true;
+                    int dist2 = min(dist, minDist[r2][c2]);
+                    maxHeap.push({dist2, r2, c2});
+                }
+            }
+        }
+        return 0;
+    }
+
+private:
+    vector<vector<int>> precompute(vector<vector<int>>& grid, int N) {
+        vector<vector<int>> minDist(N, vector<int>(N, -1));
+        queue<vector<int>> q;
+
+        for (int r = 0; r < N; r++) {
+            for (int c = 0; c < N; c++) {
+                if (grid[r][c] == 1) {
+                    q.push({r, c, 0});
+                    minDist[r][c] = 0;
+                }
+            }
+        }
+
+        while (!q.empty()) {
+            vector<int> cur = q.front();
+            q.pop();
+            int r = cur[0], c = cur[1], dist = cur[2];
+
+            for (const auto& dir : directions) {
+                int r2 = r + dir[0], c2 = c + dir[1];
+                if (inBounds(r2, c2, N) && minDist[r2][c2] == -1) {
+                    minDist[r2][c2] = dist + 1;
+                    q.push({r2, c2, dist + 1});
+                }
+            }
+        }
+        return minDist;
+    }
+
+    bool inBounds(int r, int c, int N) {
+        return r >= 0 && c >= 0 && r < N && c < N;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    maximumSafenessFactor(grid) {
+        const N = grid.length;
+        const directions = [[1, 0], [-1, 0], [0, 1], [0, -1]];
+
+        const inBounds = (r, c) => {
+            return r >= 0 && c >= 0 && r < N && c < N;
+        };
+
+        const precompute = () => {
+            const q = new Queue();
+            const minDist = Array.from({ length: N }, () => Array(N).fill(-1));
+
+            for (let r = 0; r < N; r++) {
+                for (let c = 0; c < N; c++) {
+                    if (grid[r][c] === 1) {
+                        q.push([r, c, 0]);
+                        minDist[r][c] = 0;
+                    }
+                }
+            }
+
+            while (!q.isEmpty()) {
+                let [r, c, dist] = q.pop();
+
+                for (let [dr, dc] of directions) {
+                    let r2 = r + dr, c2 = c + dc;
+                    if (inBounds(r2, c2) && minDist[r2][c2] === -1) {
+                        minDist[r2][c2] = dist + 1;
+                        q.push([r2, c2, dist + 1]);
+                    }
+                }
+            }
+            return minDist;
+        };
+
+        const minDist = precompute();
+        const maxHeap = new MaxPriorityQueue({ priority: x => x[0] });
+        const visit = Array.from({ length: N }, () => Array(N).fill(false));
+
+        maxHeap.enqueue([minDist[0][0], 0, 0]);
+        visit[0][0] = true;
+
+        while (!maxHeap.isEmpty()) {
+            let [dist, r, c] = maxHeap.dequeue().element;
+
+            if (r === N - 1 && c === N - 1) {
+                return dist;
+            }
+
+            for (let [dr, dc] of directions) {
+                let r2 = r + dr, c2 = c + dc;
+                if (inBounds(r2, c2) && !visit[r2][c2]) {
+                    visit[r2][c2] = true;
+                    let dist2 = Math.min(dist, minDist[r2][c2]);
+                    maxHeap.enqueue([dist2, r2, c2]);
+                }
+            }
+        }
+        return 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 \log n)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 2. Multi Source BFS + Dijkstra's Algorithm (Overwriting the Input)
+
+::tabs-start
+
+```python
+class Solution:
+    def maximumSafenessFactor(self, grid):
+        N = len(grid)
+        minDist = grid
+        directions = [0, 1, 0, -1, 0]
+
+        q = deque()
+        for r in range(N):
+            for c in range(N):
+                if grid[r][c] == 1:
+                    q.append(r * N + c)
+                    minDist[r][c] = 0
+                else:
+                    minDist[r][c] = -1
+
+        while q:
+            node = q.popleft()
+            r, c = divmod(node, N)
+            for i in range(4):
+                r2, c2 = r + directions[i], c + directions[i + 1]
+                if 0 <= r2 < N and 0 <= c2 < N and minDist[r2][c2] == -1:
+                    minDist[r2][c2] = minDist[r][c] + 1
+                    q.append(r2 * N + c2)
+
+        maxHeap = [(-minDist[0][0], 0)]
+        safeFactor = [0] * (N * N)
+        safeFactor[0] = minDist[0][0]
+
+        while maxHeap:
+            dist, node = heapq.heappop(maxHeap)
+            dist = -dist
+            r, c = divmod(node, N)
+            if r == N - 1 and c == N - 1:
+                return dist
+            if safeFactor[node] > dist:
+                continue
+
+            for i in range(4):
+                r2, c2 = r + directions[i], c + directions[i + 1]
+                node2 = r2 * N + c2
+                if 0 <= r2 < N and 0 <= c2 < N:
+                    dist2 = min(dist, minDist[r2][c2])
+                    if dist2 > safeFactor[node2]:
+                        safeFactor[node2] = dist2
+                        heapq.heappush(maxHeap, (-dist2, node2))
+
+        return 0
+```
+
+```java
+public class Solution {
+    public int maximumSafenessFactor(List<List<Integer>> grid) {
+        int N = grid.size();
+        int[][] minDist = new int[N][N];
+        int[] directions = {0, 1, 0, -1, 0};
+
+        Queue<Integer> q = new LinkedList<>();
+        for (int r = 0; r < N; r++) {
+            for (int c = 0; c < N; c++) {
+                if (grid.get(r).get(c) == 1) {
+                    q.offer(r * N + c);
+                    minDist[r][c] = 0;
+                } else {
+                    minDist[r][c] = -1;
+                }
+            }
+        }
+
+        while (!q.isEmpty()) {
+            int node = q.poll();
+            int r = node / N, c = node % N;
+            for (int i = 0; i < 4; i++) {
+                int r2 = r + directions[i], c2 = c + directions[i + 1];
+                if (r2 >= 0 && c2 >= 0 && r2 < N && c2 < N && minDist[r2][c2] == -1) {
+                    minDist[r2][c2] = minDist[r][c] + 1;
+                    q.offer(r2 * N + c2);
+                }
+            }
+        }
+
+        PriorityQueue<int[]> maxHeap = new PriorityQueue<>((a, b) -> Integer.compare(b[0], a[0]));
+        int[] safeFactor = new int[N * N];
+        Arrays.fill(safeFactor, -1);
+        safeFactor[0] = minDist[0][0];
+        maxHeap.offer(new int[]{safeFactor[0], 0});
+
+        while (!maxHeap.isEmpty()) {
+            int[] top = maxHeap.poll();
+            int dist = top[0], node = top[1];
+            int r = node / N, c = node % N;
+            if (r == N - 1 && c == N - 1) {
+                return dist;
+            }
+            if (safeFactor[node] > dist) {
+                continue;
+            }
+
+            for (int i = 0; i < 4; i++) {
+                int r2 = r + directions[i], c2 = c + directions[i + 1];
+                int node2 = r2 * N + c2;
+                if (r2 >= 0 && c2 >= 0 && r2 < N && c2 < N) {
+                    int dist2 = Math.min(dist, minDist[r2][c2]);
+                    if (dist2 > safeFactor[node2]) {
+                        safeFactor[node2] = dist2;
+                        maxHeap.offer(new int[]{dist2, node2});
+                    }
+                }
+            }
+        }
+        return 0;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maximumSafenessFactor(vector<vector<int>>& grid) {
+        int N = grid.size();
+        vector<int> directions = {0, 1, 0, -1, 0};
+        vector<vector<int>>& minDist = grid;
+
+        queue<int> q;
+        for (int r = 0; r < N; r++) {
+            for (int c = 0; c < N; c++) {
+                if (grid[r][c] == 1) {
+                    q.push(r * N + c);
+                    minDist[r][c] = 0;
+                } else {
+                    minDist[r][c] = -1;
+                }
+            }
+        }
+
+        while (!q.empty()) {
+            int node = q.front(); q.pop();
+            int r = node / N, c = node % N;
+            for (int i = 0; i < 4; i++) {
+                int r2 = r + directions[i], c2 = c + directions[i + 1];
+                if (r2 >= 0 && c2 >= 0 && r2 < N && c2 < N && minDist[r2][c2] == -1) {
+                    minDist[r2][c2] = minDist[r][c] + 1;
+                    q.push(r2 * N + c2);
+                }
+            }
+        }
+
+        priority_queue<pair<int, int>> maxHeap;
+        vector<int> safeFactor(N * N, 0);
+        safeFactor[0] = minDist[0][0];
+        maxHeap.push({safeFactor[0], 0});
+
+        while (!maxHeap.empty()) {
+            auto [dist, node] = maxHeap.top(); maxHeap.pop();
+            int r = node / N, c = node % N;
+            if (r == N - 1 && c == N - 1) {
+                return dist;
+            }
+            if (safeFactor[node] > dist) {
+                continue;
+            }
+
+            for (int i = 0; i < 4; i++) {
+                int r2 = r + directions[i], c2 = c + directions[i + 1], node2 = r2 * N + c2;
+                if (r2 >= 0 && c2 >= 0 && r2 < N && c2 < N) {
+                    int dist2 = min(dist, minDist[r2][c2]);
+                    if (dist2 > safeFactor[node2]) {
+                        safeFactor[node2] = dist2;
+                        maxHeap.push({dist2, node2});
+                    }
+                }
+            }
+        }
+        return 0;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    maximumSafenessFactor(grid) {
+        const N = grid.length;
+        const directions = [0, 1, 0, -1, 0];
+        const minDist = grid;
+
+        const q = new Queue();
+        for (let r = 0; r < N; r++) {
+            for (let c = 0; c < N; c++) {
+                if (grid[r][c] === 1) {
+                    q.push(r * N + c);
+                    minDist[r][c] = 0;
+                } else {
+                    minDist[r][c] = -1;
+                }
+            }
+        }
+
+        while (!q.isEmpty()) {
+            let node = q.pop();
+            let r = Math.floor(node / N), c = node % N;
+            for (let i = 0; i < 4; i++) {
+                let r2 = r + directions[i], c2 = c + directions[i + 1];
+                if (r2 >= 0 && c2 >= 0 && r2 < N && c2 < N && minDist[r2][c2] === -1) {
+                    minDist[r2][c2] = minDist[r][c] + 1;
+                    q.push(r2 * N + c2);
+                }
+            }
+        }
+
+        let maxHeap = new MaxPriorityQueue({ priority: x => x[0] });
+        let safeFactor = new Array(N * N).fill(0);
+        safeFactor[0] = minDist[0][0];
+        maxHeap.enqueue([safeFactor[0], 0]);
+
+        while (!maxHeap.isEmpty()) {
+            let [dist, node] = maxHeap.dequeue().element;
+            let r = Math.floor(node / N), c = node % N;
+            if (r === N - 1 && c === N - 1) {
+                return dist;
+            }
+            if (safeFactor[node] > dist) {
+                continue;
+            }
+
+            for (let i = 0; i < 4; i++) {
+                let r2 = r + directions[i], c2 = c + directions[i + 1], node2 = r2 * N + c2;
+                if (r2 >= 0 && c2 >= 0 && r2 < N && c2 < N) {
+                    let dist2 = Math.min(dist, minDist[r2][c2]);
+                    if (dist2 > safeFactor[node2]) {
+                        safeFactor[node2] = dist2;
+                        maxHeap.enqueue([dist2, node2]);
+                    }
+                }
+            }
+        }
+        return 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 \log n)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 3. Multi Source BFS + Binary Search
+
+::tabs-start
+
+```python
+class Solution:
+    def maximumSafenessFactor(self, grid):
+        N = len(grid)
+        minDist = grid
+        directions = [0, 1, 0, -1, 0]
+
+        q = deque()
+        for r in range(N):
+            for c in range(N):
+                if grid[r][c] == 1:
+                    q.append(r * N + c)
+                    minDist[r][c] = 0
+                else:
+                    minDist[r][c] = -1
+
+        while q:
+            node = q.popleft()
+            r, c = divmod(node, N)
+            for i in range(4):
+                r2, c2 = r + directions[i], c + directions[i + 1]
+                if 0 <= r2 < N and 0 <= c2 < N and minDist[r2][c2] == -1:
+                    minDist[r2][c2] = minDist[r][c] + 1
+                    q.append(r2 * N + c2)
+
+        def canReach(threshold):
+            q = deque([0])
+            visited = [False] * (N * N)
+            visited[0] = True
+
+            while q:
+                node = q.popleft()
+                r, c = divmod(node, N)
+                if r == N - 1 and c == N - 1:
+                    return True
+
+                for i in range(4):
+                    r2, c2 = r + directions[i], c + directions[i + 1]
+                    node2 = r2 * N + c2
+                    if (0 <= r2 < N and 0 <= c2 < N and not visited[node2] and 
+                        minDist[r2][c2] >= threshold
+                    ):
+                        visited[node2] = True
+                        q.append(node2)
+
+            return False
+
+        l, r = 0, min(minDist[0][0], minDist[N - 1][N - 1])
+        while l <= r:
+            mid = (l + r) // 2
+            if canReach(mid):
+                l = mid + 1
+            else:
+                r = mid - 1
+
+        return l - 1
+```
+
+```java
+public class Solution {
+    private static int[] directions = {0, 1, 0, -1, 0};
+
+    public int maximumSafenessFactor(List<List<Integer>> grid) {
+        int N = grid.size();
+        int[][] minDist = new int[N][N];
+
+        Queue<Integer> q = new LinkedList<>();
+        for (int r = 0; r < N; r++) {
+            for (int c = 0; c < N; c++) {
+                if (grid.get(r).get(c) == 1) {
+                    q.offer(r * N + c);
+                    minDist[r][c] = 0;
+                } else {
+                    minDist[r][c] = -1;
+                }
+            }
+        }
+
+        while (!q.isEmpty()) {
+            int node = q.poll();
+            int r = node / N, c = node % N;
+            for (int i = 0; i < 4; i++) {
+                int r2 = r + directions[i], c2 = c + directions[i + 1];
+                if (r2 >= 0 && c2 >= 0 && r2 < N && c2 < N && minDist[r2][c2] == -1) {
+                    minDist[r2][c2] = minDist[r][c] + 1;
+                    q.offer(r2 * N + c2);
+                }
+            }
+        }
+
+        int l = 0, r = Math.min(minDist[0][0], minDist[N - 1][N - 1]);
+        while (l <= r) {
+            int mid = (l + r) / 2;
+            if (canReach(minDist, N, mid)) {
+                l = mid + 1;
+            } else {
+                r = mid - 1;
+            }
+        }
+        return l - 1;
+    }
+
+    private boolean canReach(int[][] minDist, int N, int threshold) {
+        Queue<Integer> q = new LinkedList<>();
+        boolean[] visited = new boolean[N * N];
+        q.offer(0);
+        visited[0] = true;
+
+        while (!q.isEmpty()) {
+            int node = q.poll();
+            int r = node / N, c = node % N;
+            if (r == N - 1 && c == N - 1) {
+                return true;
+            }
+
+            for (int i = 0; i < 4; i++) {
+                int r2 = r + directions[i], c2 = c + directions[i + 1];
+                int node2 = r2 * N + c2;
+                if (r2 >= 0 && c2 >= 0 && r2 < N && c2 < N && !visited[node2] && 
+                    minDist[r2][c2] >= threshold) {
+                    visited[node2] = true;
+                    q.offer(node2);
+                }
+            }
+        }
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+    static constexpr int directions[5] = {0, 1, 0, -1, 0};
+
+public:
+    int maximumSafenessFactor(vector<vector<int>>& grid) {
+        int N = grid.size();
+        vector<vector<int>>& minDist = grid;
+
+        queue<int> q;
+        for (int r = 0; r < N; r++) {
+            for (int c = 0; c < N; c++) {
+                if (grid[r][c] == 1) {
+                    q.push(r * N + c);
+                    minDist[r][c] = 0;
+                } else {
+                    minDist[r][c] = -1;
+                }
+            }
+        }
+
+        while (!q.empty()) {
+            int node = q.front(); q.pop();
+            int r = node / N, c = node % N;
+            for (int i = 0; i < 4; i++) {
+                int r2 = r + directions[i], c2 = c + directions[i + 1];
+                if (r2 >= 0 && c2 >= 0 && r2 < N && c2 < N && minDist[r2][c2] == -1) {
+                    minDist[r2][c2] = minDist[r][c] + 1;
+                    q.push(r2 * N + c2);
+                }
+            }
+        }
+
+        int l = 0, r = min(minDist[0][0], minDist[N - 1][N - 1]);
+        while (l <= r) {
+            int mid = (l + r) / 2;
+            if (canReach(minDist, N, mid)) {
+                l = mid + 1;
+            } else {
+                r = mid - 1;
+            }
+        }
+        return l - 1;
+    }
+
+private:
+    bool canReach(vector<vector<int>>& minDist, int N, int threshold) {
+        queue<int> q;
+        vector<bool> visited(N * N, false);
+        q.push(0);
+        visited[0] = true;
+
+        while (!q.empty()) {
+            int node = q.front(); q.pop();
+            int r = node / N, c = node % N;
+            if (r == N - 1 && c == N - 1) {
+                return true;
+            }
+
+            for (int i = 0; i < 4; i++) {
+                int r2 = r + directions[i], c2 = c + directions[i + 1], node2 = r2 * N + c2;
+                if (r2 >= 0 && c2 >= 0 && r2 < N && c2 < N && !visited[node2] && 
+                    minDist[r2][c2] >= threshold) {
+                    visited[node2] = true;
+                    q.push(node2);
+                }
+            }
+        }
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    maximumSafenessFactor(grid) {
+        const N = grid.length;
+        const minDist = grid;
+        const directions = [0, 1, 0, -1, 0];
+
+        let q = new Queue();
+        for (let r = 0; r < N; r++) {
+            for (let c = 0; c < N; c++) {
+                if (grid[r][c] === 1) {
+                    q.push(r * N + c);
+                    minDist[r][c] = 0;
+                } else {
+                    minDist[r][c] = -1;
+                }
+            }
+        }
+
+        while (!q.isEmpty()) {
+            let node = q.pop();
+            let r = Math.floor(node / N), c = node % N;
+            for (let i = 0; i < 4; i++) {
+                let r2 = r + directions[i], c2 = c + directions[i + 1];
+                if (r2 >= 0 && c2 >= 0 && r2 < N && c2 < N && minDist[r2][c2] === -1) {
+                    minDist[r2][c2] = minDist[r][c] + 1;
+                    q.push(r2 * N + c2);
+                }
+            }
+        }
+
+        const canReach = (threshold) => {
+            q = new Queue([0]);
+            let visited = new Array(N * N).fill(false);
+            visited[0] = true;
+
+            while (!q.isEmpty()) {
+                let node = q.pop();
+                let r = Math.floor(node / N), c = node % N;
+                if (r === N - 1 && c === N - 1) return true;
+
+                for (let i = 0; i < 4; i++) {
+                    let r2 = r + directions[i], c2 = c + directions[i + 1], node2 = r2 * N + c2;
+                    if (r2 >= 0 && c2 >= 0 && r2 < N && c2 < N && !visited[node2] && 
+                        minDist[r2][c2] >= threshold) {
+                        visited[node2] = true;
+                        q.push(node2);
+                    }
+                }
+            }
+            return false;
+        };
+
+        let l = 0, r = Math.min(minDist[0][0], minDist[N - 1][N - 1]);
+        while (l <= r) {
+            let mid = Math.floor((l + r) / 2);
+            if (canReach(mid)) {
+                l = mid + 1;
+            } else {
+                r = mid - 1;
+            }
+        }
+        return l - 1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 \log n)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 4. Breadth First Search (0-1 BFS)
+
+::tabs-start
+
+```python
+class Solution:
+    def maximumSafenessFactor(self, grid):
+        N = len(grid)
+        minDist = grid
+        directions = [0, 1, 0, -1, 0]
+
+        q = deque()
+        for r in range(N):
+            for c in range(N):
+                if grid[r][c] == 1:
+                    q.append(r * N + c)
+                    minDist[r][c] = 0
+                else:
+                    minDist[r][c] = -1
+
+        while q:
+            node = q.popleft()
+            r, c = divmod(node, N)
+            for i in range(4):
+                r2, c2 = r + directions[i], c + directions[i + 1]
+                if 0 <= r2 < N and 0 <= c2 < N and minDist[r2][c2] == -1:
+                    minDist[r2][c2] = minDist[r][c] + 1
+                    q.append(r2 * N + c2)
+
+        safeFactor = [-1] * (N * N)
+        res = safeFactor[0] = min(minDist[N - 1][N - 1], minDist[0][0])
+        q.append(0)
+
+        while q:
+            node = q.popleft()
+            r, c = divmod(node, N)
+            res = min(res, safeFactor[node])
+            if r == N - 1 and c == N - 1:
+                break
+
+            for i in range(4):
+                r2, c2 = r + directions[i], c + directions[i + 1]
+                node2 = r2 * N + c2
+                if 0 <= r2 < N and 0 <= c2 < N and safeFactor[node2] == -1:
+                    safeFactor[node2] = min(safeFactor[node], minDist[r2][c2])
+                    if safeFactor[node2] < res:
+                        q.append(node2)
+                    else:
+                        q.appendleft(node2)
+
+        return res
+```
+
+```java
+public class Solution {
+    private static final int[] directions = {0, 1, 0, -1, 0};
+
+    public int maximumSafenessFactor(List<List<Integer>> grid) {
+        int N = grid.size();
+        int[][] minDist = new int[N][N];
+
+        Deque<Integer> q = new ArrayDeque<>();
+        for (int r = 0; r < N; r++) {
+            for (int c = 0; c < N; c++) {
+                if (grid.get(r).get(c) == 1) {
+                    q.offerLast(r * N + c);
+                    minDist[r][c] = 0;
+                } else {
+                    minDist[r][c] = -1;
+                }
+            }
+        }
+
+        while (!q.isEmpty()) {
+            int node = q.pollFirst();
+            int r = node / N, c = node % N;
+            for (int i = 0; i < 4; i++) {
+                int r2 = r + directions[i], c2 = c + directions[i + 1];
+                if (r2 >= 0 && c2 >= 0 && r2 < N && c2 < N && minDist[r2][c2] == -1) {
+                    minDist[r2][c2] = minDist[r][c] + 1;
+                    q.offerLast(r2 * N + c2);
+                }
+            }
+        }
+
+        int[] safeFactor = new int[N * N];
+        Arrays.fill(safeFactor, -1);
+        int res = safeFactor[0] = Math.min(minDist[N - 1][N - 1], minDist[0][0]);
+        q.offerLast(0);
+
+        while (!q.isEmpty()) {
+            int node = q.pollFirst();
+            int r = node / N, c = node % N;
+            res = Math.min(res, safeFactor[node]);
+            if (r == N - 1 && c == N - 1) {
+                break;
+            }
+
+            for (int i = 0; i < 4; i++) {
+                int r2 = r + directions[i], c2 = c + directions[i + 1], node2 = r2 * N + c2;
+                if (r2 >= 0 && c2 >= 0 && r2 < N && c2 < N && safeFactor[node2] == -1) {
+                    safeFactor[node2] = Math.min(safeFactor[node], minDist[r2][c2]);
+                    if (safeFactor[node2] < res) {
+                        q.offerLast(node2);
+                    } else {
+                        q.offerFirst(node2);
+                    }
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maximumSafenessFactor(vector<vector<int>>& grid) {
+        int N = grid.size();
+        vector<vector<int>>& minDist = grid;
+        constexpr int directions[5] = {0, 1, 0, -1, 0};
+
+        deque<int> q;
+        for (int r = 0; r < N; r++) {
+            for (int c = 0; c < N; c++) {
+                if (grid[r][c] == 1) {
+                    q.push_back(r * N + c);
+                    minDist[r][c] = 0;
+                } else {
+                    minDist[r][c] = -1;
+                }
+            }
+        }
+
+        while (!q.empty()) {
+            int node = q.front(); q.pop_front();
+            int r = node / N, c = node % N;
+            for (int i = 0; i < 4; i++) {
+                int r2 = r + directions[i], c2 = c + directions[i + 1];
+                if (r2 >= 0 && c2 >= 0 && r2 < N && c2 < N && minDist[r2][c2] == -1) {
+                    minDist[r2][c2] = minDist[r][c] + 1;
+                    q.push_back(r2 * N + c2);
+                }
+            }
+        }
+
+        vector<int> safeFactor(N * N, -1);
+        int res = safeFactor[0] = min(minDist[N - 1][N - 1], minDist[0][0]);
+        q.push_back(0);
+
+        while (!q.empty()) {
+            int node = q.front(); q.pop_front();
+            int r = node / N, c = node % N;
+            res = min(res, safeFactor[node]);
+            if (r == N - 1 && c == N - 1) {
+                break;
+            }
+
+            for (int i = 0; i < 4; i++) {
+                int r2 = r + directions[i], c2 = c + directions[i + 1], node2 = r2 * N + c2;
+                if (r2 >= 0 && c2 >= 0 && r2 < N && c2 < N && safeFactor[node2] == -1) {
+                    safeFactor[node2] = min(safeFactor[node], minDist[r2][c2]);
+                    if (safeFactor[node2] < res) {
+                        q.push_back(node2);
+                    } else {
+                        q.push_front(node2);
+                    }
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    maximumSafenessFactor(grid) {
+        const N = grid.length;
+        const minDist = grid;
+        const directions = [0, 1, 0, -1, 0];
+
+        const q = new Deque();
+        for (let r = 0; r < N; r++) {
+            for (let c = 0; c < N; c++) {
+                if (grid[r][c] === 1) {
+                    q.pushBack(r * N + c);
+                    minDist[r][c] = 0;
+                } else {
+                    minDist[r][c] = -1;
+                }
+            }
+        }
+
+        while (!q.isEmpty()) {
+            let node = q.popFront();
+            let r = Math.floor(node / N), c = node % N;
+            for (let i = 0; i < 4; i++) {
+                let r2 = r + directions[i], c2 = c + directions[i + 1];
+                if (r2 >= 0 && c2 >= 0 && r2 < N && c2 < N && minDist[r2][c2] === -1) {
+                    minDist[r2][c2] = minDist[r][c] + 1;
+                    q.pushBack(r2 * N + c2);
+                }
+            }
+        }
+
+        let safeFactor = new Array(N * N).fill(-1);
+        let res = safeFactor[0] = Math.min(minDist[N - 1][N - 1], minDist[0][0]);
+        q.pushBack(0);
+
+        while (!q.isEmpty()) {
+            let node = q.popFront();
+            let r = Math.floor(node / N), c = node % N;
+            res = Math.min(res, safeFactor[node]);
+            if (r === N - 1 && c === N - 1) {
+                break;
+            }
+
+            for (let i = 0; i < 4; i++) {
+                let r2 = r + directions[i], c2 = c + directions[i + 1], node2 = r2 * N + c2;
+                if (r2 >= 0 && c2 >= 0 && r2 < N && c2 < N && safeFactor[node2] === -1) {
+                    safeFactor[node2] = Math.min(safeFactor[node], minDist[r2][c2]);
+                    if (safeFactor[node2] < res) {
+                        q.pushBack(node2);
+                    } else {
+                        q.pushFront(node2);
+                    }
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
\ No newline at end of file
diff --git a/articles/find-the-town-judge.md b/articles/find-the-town-judge.md
new file mode 100644
index 000000000..a1343bd35
--- /dev/null
+++ b/articles/find-the-town-judge.md
@@ -0,0 +1,245 @@
+## 1. Indegree & Outdegree
+
+::tabs-start
+
+```python
+class Solution:
+    def findJudge(self, n: int, trust: List[List[int]]) -> int:
+        incoming = defaultdict(int)
+        outgoing = defaultdict(int)
+
+        for src, dst in trust:
+            outgoing[src] += 1
+            incoming[dst] += 1
+        
+        for i in range(1, n + 1):
+            if outgoing[i] == 0 and incoming[i] == n - 1:
+                return i
+        
+        return -1
+```
+
+```java
+public class Solution {
+    public int findJudge(int n, int[][] trust) {
+        int[] incoming = new int[n + 1];
+        int[] outgoing = new int[n + 1];
+        
+        for (int[] t : trust) {
+            outgoing[t[0]]++;
+            incoming[t[1]]++;
+        }
+        
+        for (int i = 1; i <= n; i++) {
+            if (outgoing[i] == 0 && incoming[i] == n - 1) {
+                return i;
+            }
+        }
+        
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findJudge(int n, vector<vector<int>>& trust) {
+        vector<int> incoming(n + 1, 0), outgoing(n + 1, 0);
+        
+        for (auto& t : trust) {
+            outgoing[t[0]]++;
+            incoming[t[1]]++;
+        }
+        
+        for (int i = 1; i <= n; i++) {
+            if (outgoing[i] == 0 && incoming[i] == n - 1)
+                return i;
+        }
+        
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} trust
+     * @return {number}
+     */
+    findJudge(n, trust) {
+        let incoming = new Array(n + 1).fill(0);
+        let outgoing = new Array(n + 1).fill(0);
+        
+        for (let [src, dst] of trust) {
+            outgoing[src]++;
+            incoming[dst]++;
+        }
+        
+        for (let i = 1; i <= n; i++) {
+            if (outgoing[i] === 0 && incoming[i] === n - 1) {
+                return i;
+            }
+        }
+        
+        return -1;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int FindJudge(int n, int[][] trust) {
+        int[] incoming = new int[n + 1];
+        int[] outgoing = new int[n + 1];
+
+        foreach (int[] t in trust) {
+            int a = t[0];
+            int b = t[1];
+            outgoing[a]++;
+            incoming[b]++;
+        }
+
+        for (int i = 1; i <= n; i++) {
+            if (outgoing[i] == 0 && incoming[i] == n - 1) {
+                return i;
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + E)$
+* Space complexity: $O(V)$
+
+> Where $V$ is the number of vertices and $E$ is the number of edges.
+
+---
+
+## 2. Indegree & Outdegree (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def findJudge(self, n: int, trust: List[List[int]]) -> int:
+        delta = defaultdict(int)
+
+        for src, dst in trust:
+            delta[src] -= 1
+            delta[dst] += 1
+        
+        for i in range(1, n + 1):
+            if delta[i] == n - 1:
+                return i
+        
+        return -1
+```
+
+```java
+public class Solution {
+    public int findJudge(int n, int[][] trust) {
+        int[] delta = new int[n + 1];
+
+        for (int[] t : trust) {
+            delta[t[0]] -= 1;
+            delta[t[1]] += 1;
+        }
+        
+        for (int i = 1; i <= n; i++) {
+            if (delta[i] == n - 1) {
+                return i;
+            }
+        }
+        
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findJudge(int n, vector<vector<int>>& trust) {
+        vector<int> delta(n + 1, 0);
+        
+        for (auto& t : trust) {
+            delta[t[0]]--;
+            delta[t[1]]++;
+        }
+        
+        for (int i = 1; i <= n; i++) {
+            if (delta[i] == n - 1) {
+                return i;
+            }
+        }
+        
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} trust
+     * @return {number}
+     */
+    findJudge(n, trust) {
+        let delta = new Array(n + 1).fill(0);
+    
+        for (let [src, dst] of trust) {
+            delta[src]--;
+            delta[dst]++;
+        }
+        
+        for (let i = 1; i <= n; i++) {
+            if (delta[i] === n - 1) {
+                return i;
+            }
+        }
+        
+        return -1;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int FindJudge(int n, int[][] trust) {
+        int[] delta = new int[n + 1];
+
+        foreach (int[] t in trust) {
+            int a = t[0];
+            int b = t[1];
+            delta[a]--;
+            delta[b]++;
+        }
+
+        for (int i = 1; i <= n; i++) {
+            if (delta[i] == n - 1) {
+                return i;
+            }
+        }
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + E)$
+* Space complexity: $O(V)$
+
+> Where $V$ is the number of vertices and $E$ is the number of edges.
\ No newline at end of file
diff --git a/articles/find-unique-binary-string.md b/articles/find-unique-binary-string.md
new file mode 100644
index 000000000..ea24db9f9
--- /dev/null
+++ b/articles/find-unique-binary-string.md
@@ -0,0 +1,685 @@
+## 1. Backtracking (Recursion)
+
+::tabs-start
+
+```python
+class Solution:
+    def findDifferentBinaryString(self, nums: List[str]) -> str:
+        strSet = {s for s in nums}
+
+        def backtrack(i, cur):
+            if i == len(nums):
+                res = "".join(cur)
+                return None if res in strSet else res
+
+            res = backtrack(i + 1, cur)
+            if res: return res
+
+            cur[i] = "1"
+            return backtrack(i + 1, cur)
+
+        return backtrack(0, ["0" for _ in nums])
+```
+
+```java
+public class Solution {
+    public String findDifferentBinaryString(String[] nums) {
+        Set<String> strSet = new HashSet<>();
+        for (String s : nums) {
+            strSet.add(s);
+        }
+        return backtrack(0, new char[nums.length], strSet, nums.length);
+    }
+
+    private String backtrack(int i, char[] cur, Set<String> strSet, int n) {
+        if (i == n) {
+            String res = new String(cur);
+            return strSet.contains(res) ? null : res;
+        }
+
+        cur[i] = '0';
+        String res = backtrack(i + 1, cur, strSet, n);
+        if (res != null) return res;
+
+        cur[i] = '1';
+        return backtrack(i + 1, cur, strSet, n);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string findDifferentBinaryString(vector<string>& nums) {
+        unordered_set<string> strSet(nums.begin(), nums.end());
+        string cur(nums.size(), '0');
+        return backtrack(0, cur, strSet, nums.size());
+    }
+
+private:
+    string backtrack(int i, string& cur, unordered_set<string>& strSet, int n) {
+        if (i == n) {
+            return strSet.count(cur) ? "" : cur;
+        }
+
+        string res = backtrack(i + 1, cur, strSet, n);
+        if (!res.empty()) return res;
+
+        cur[i] = '1';
+        return backtrack(i + 1, cur, strSet, n);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} nums
+     * @return {string}
+     */
+    findDifferentBinaryString(nums) {
+        const strSet = new Set(nums);
+        const n = nums.length;
+
+        const backtrack = (i, cur) => {
+            if (i === n) {
+                const res = cur.join("");
+                return strSet.has(res) ? null : res;
+            }
+
+            let res = backtrack(i + 1, cur);
+            if (res) return res;
+
+            cur[i] = "1";
+            return backtrack(i + 1, cur);
+        };
+
+        return backtrack(0, Array(n).fill("0"));
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Backtracking (Iteration)
+
+::tabs-start
+
+```python
+class Solution:
+    def findDifferentBinaryString(self, nums: List[str]) -> str:
+        strSet = set(nums)
+        n = len(nums)
+
+        for num in range(1 << n):  
+            res = bin(num)[2:].zfill(n)  
+            if res not in strSet:
+                return res
+
+        return ""
+```
+
+```java
+public class Solution {
+    public String findDifferentBinaryString(String[] nums) {
+        Set<String> strSet = new HashSet<>();
+        for (String s : nums) {
+            strSet.add(s);
+        }
+        int n = nums.length;
+
+        for (int num = 0; num < (n + 1); num++) {
+            String res = String.format("%" + n + "s", 
+                         Integer.toBinaryString(num)).replace(' ', '0');
+            if (!strSet.contains(res)) {
+                return res;
+            }
+        }
+
+        return "";
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string findDifferentBinaryString(vector<string>& nums) {
+        unordered_set<string> strSet(nums.begin(), nums.end());
+        int n = nums.size();
+
+        for (int num = 0; num < (n + 1); num++) {
+            string res = toBinaryString(num, n);
+            if (strSet.find(res) == strSet.end()) {
+                return res;
+            }
+        }
+
+        return "";
+    }
+
+private:
+    string toBinaryString(int num, int length) {
+        string res = "";
+        for (int i = length - 1; i >= 0; i--) {
+            res += (num & (1 << i)) ? '1' : '0';
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} nums
+     * @return {string}
+     */
+    findDifferentBinaryString(nums) {
+        const strSet = new Set(nums);
+        const n = nums.length;
+
+        for (let num = 0; num < (n + 1); num++) {
+            let res = num.toString(2).padStart(n, '0');
+            if (!strSet.has(res)) {
+                return res;
+            }
+        }
+
+        return "";
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Cantor's Diagonal Argument
+
+::tabs-start
+
+```python
+class Solution:
+    def findDifferentBinaryString(self, nums: List[str]) -> str:
+        res = []
+        for i in range(len(nums)):
+            if nums[i][i] == '0':
+                res.append('1')
+            else:
+                res.append('0')
+        return "".join(res)
+```
+
+```java
+public class Solution {
+    public String findDifferentBinaryString(String[] nums) {
+        StringBuilder res = new StringBuilder();
+        for (int i = 0; i < nums.length; i++) {
+            res.append(nums[i].charAt(i) == '0' ? '1' : '0');
+        }
+        return res.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string findDifferentBinaryString(vector<string>& nums) {
+        string res;
+        for (int i = 0; i < nums.size(); i++) {
+            res += (nums[i][i] == '0') ? '1' : '0';
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} nums
+     * @return {string}
+     */
+    findDifferentBinaryString(nums) {
+        let res = [];
+        for (let i = 0; i < nums.length; i++) {
+            res.push(nums[i][i] === '0' ? '1' : '0');
+        }
+        return res.join("");
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ space for the output string.
+
+---
+
+## 4. Randomization
+
+::tabs-start
+
+```python
+class Solution:
+    def findDifferentBinaryString(self, nums: List[str]) -> str:
+        strSet = set(nums)
+        n = len(nums)
+
+        while True:
+            res = "".join(random.choice("01") for _ in range(n))
+            if res not in strSet:
+                return res
+```
+
+```java
+public class Solution {
+    public String findDifferentBinaryString(String[] nums) {
+        Set<String> strSet = new HashSet<>();
+        for (String s : nums) {
+            strSet.add(s);
+        }
+        int n = nums.length;
+        Random random = new Random();
+
+        while (true) {
+            StringBuilder res = new StringBuilder();
+            for (int i = 0; i < n; i++) {
+                res.append(random.nextBoolean() ? '1' : '0');
+            }
+            String result = res.toString();
+            if (!strSet.contains(result)) {
+                return result;
+            }
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string findDifferentBinaryString(vector<string>& nums) {
+        unordered_set<string> strSet(nums.begin(), nums.end());
+        int n = nums.size();
+
+        while (true) {
+            string res = "";
+            for (int i = 0; i < n; i++) {
+                res += (rand() % 2) ? '1' : '0';
+            }
+            if (strSet.find(res) == strSet.end()) {
+                return res;
+            }
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} nums
+     * @return {string}
+     */
+    findDifferentBinaryString(nums) {
+        const strSet = new Set(nums);
+        const n = nums.length;
+
+        while (true) {
+            let res = Array.from({ length: n }, () => 
+                      Math.random() < 0.5 ? '0' : '1').join("");
+            if (!strSet.has(res)) {
+                return res;
+            }
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(∞)$ in worst case.
+* Space complexity: $O(n)$
+
+---
+
+## 5. Trie
+
+::tabs-start
+
+```python
+class Node:
+    def __init__(self):
+        self.children = [None, None]
+
+    def contains_bit(self, bit: int) -> bool:
+        return self.children[bit] is not None
+
+    def put(self, bit: int):
+        self.children[bit] = Node()
+
+    def get(self, bit: int):
+        return self.children[bit]
+
+class Trie:
+    def __init__(self):
+        self.root = Node()
+
+    def insert(self, s: str):
+        curr = self.root
+        for c in s:
+            bit = int(c)
+            if not curr.contains_bit(bit):
+                curr.put(bit)
+            curr = curr.get(bit)
+
+    def search(self, res: str, curr) -> bool:
+        while curr.contains_bit(0) or curr.contains_bit(1):
+            if not curr.contains_bit(0):
+                res.append('0')
+                return True
+            if not curr.contains_bit(1):
+                res.append('1')
+                return True
+
+            res.append('1')
+            curr = curr.get(1)
+
+        return False
+
+class Solution:
+    def findDifferentBinaryString(self, nums: List[str]) -> str:
+        trie = Trie()
+        for s in nums:
+            trie.insert(s)
+
+        res = []
+        trie.search(res, trie.root)
+
+        while len(res) < len(nums):
+            res.append('1')
+
+        return ''.join(res)
+```
+
+```java
+class Node {
+    Node[] children;
+
+    Node() {
+        this.children = new Node[2];
+    }
+
+    boolean containsBit(int bit) {
+        return this.children[bit] != null;
+    }
+
+    void put(int bit) {
+        this.children[bit] = new Node();
+    }
+
+    Node get(int bit) {
+        return this.children[bit];
+    }
+}
+
+class Trie {
+    Node root;
+
+    Trie() {
+        this.root = new Node();
+    }
+
+    void insert(String s) {
+        Node curr = root;
+        for (char c : s.toCharArray()) {
+            int bit = c - '0';
+            if (!curr.containsBit(bit)) {
+                curr.put(bit);
+            }
+            curr = curr.get(bit);
+        }
+    }
+
+    boolean search(StringBuilder res, Node curr) {
+        while (curr.containsBit(0) || curr.containsBit(1)) {
+            if (!curr.containsBit(0)) {
+                res.append('0');
+                return true;
+            }
+            if (!curr.containsBit(1)) {
+                res.append('1');
+                return true;
+            }
+
+            res.append('1');
+            curr = curr.get(1);
+        }
+
+        return false;
+    }
+}
+
+public class Solution {
+    public String findDifferentBinaryString(String[] nums) {
+        Trie trie = new Trie();
+        for (String s : nums) {
+            trie.insert(s);
+        }
+
+        StringBuilder res = new StringBuilder();
+        trie.search(res, trie.root);
+
+        while (res.length() < nums.length) {
+            res.append('1');
+        }
+
+        return res.toString();
+    }
+}
+```
+
+```cpp
+class Node {
+public:
+    Node *children[2];
+
+    Node() {
+        this->children[0] = nullptr;
+        this->children[1] = nullptr;
+    }
+
+    bool containsBit(int bit) {
+        return this->children[bit] != nullptr;
+    }
+
+    void put(int bit) {
+        this->children[bit] = new Node();
+    }
+
+    Node* get(int bit) {
+        return this->children[bit];
+    }
+};
+
+class Trie {
+public:
+    Node* root;
+
+    Trie() {
+        this->root = new Node();
+    }
+
+    void insert(const string& s) {
+        Node* curr = root;
+        for (char c : s) {
+            int bit = c - '0';
+            if (!curr->containsBit(bit)) {
+                curr->put(bit);
+            }
+            curr = curr->get(bit);
+        }
+    }
+
+    bool search(string& res, Node* curr) {
+        while (curr->containsBit(0) || curr->containsBit(1)) {
+            if (!curr->containsBit(0)) {
+                res += '0';
+                return true;
+            }
+            if (!curr->containsBit(1)) {
+                res += '1';
+                return true;
+            }
+
+            res += '1';
+            curr = curr->get(1);
+        }
+
+        return false;
+    }
+};
+
+class Solution {
+public:
+    string findDifferentBinaryString(vector<string>& nums) {
+        Trie trie;
+        for (const string& s : nums) {
+            trie.insert(s);
+        }
+
+        string res;
+        trie.search(res, trie.root);
+
+        while (res.length() < nums.size()) {
+            res += '1';
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Node {
+    constructor() {
+        this.children = [null, null];
+    }
+
+    /**
+     * @param {number} bit
+     * @return {boolean}
+     */
+    containsBit(bit) {
+        return this.children[bit] !== null;
+    }
+
+    /**
+     * @param {number} bit
+     */
+    put(bit) {
+        this.children[bit] = new Node();
+    }
+
+    /**
+     * @param {number} bit
+     * @return {Node}
+     */
+    get(bit) {
+        return this.children[bit];
+    }
+}
+
+class Trie {
+    constructor() {
+        this.root = new Node();
+    }
+
+    /**
+     * @param {string} s
+     */
+    insert(s) {
+        let curr = this.root;
+        for (const c of s) {
+            let bit = c === '1' ? 1 : 0;
+            if (!curr.containsBit(bit)) {
+                curr.put(bit);
+            }
+            curr = curr.get(bit);
+        }
+    }
+
+    /**
+     * @param {string[]} res
+     * @param {Node} curr
+     * @return {boolean}
+     */
+    search(res, curr) {
+        while (curr.containsBit(0) || curr.containsBit(1)) {
+            if (!curr.containsBit(0)) {
+                res.push('0');
+                return true;
+            }
+            if (!curr.containsBit(1)) {
+                res.push('1');
+                return true;
+            }
+
+            res.push('1');
+            curr = curr.get(1);
+        }
+        return false;
+    }
+}
+
+class Solution {
+    /**
+     * @param {string[]} nums
+     * @return {string}
+     */
+    findDifferentBinaryString(nums) {
+        let trie = new Trie();
+        for (const s of nums) {
+            trie.insert(s);
+        }
+
+        let res = [];
+        trie.search(res, trie.root);
+
+        while (res.length < nums.length) {
+            res.push('1');
+        }
+
+        return res.join("");
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
\ No newline at end of file
diff --git a/articles/find-words-that-can-be-formed-by-characters.md b/articles/find-words-that-can-be-formed-by-characters.md
new file mode 100644
index 000000000..4dfdf7b44
--- /dev/null
+++ b/articles/find-words-that-can-be-formed-by-characters.md
@@ -0,0 +1,391 @@
+## 1. Hash Map (Two Pass)
+
+::tabs-start
+
+```python
+class Solution:
+    def countCharacters(self, words: List[str], chars: str) -> int:
+        count = Counter(chars)
+        res = 0
+        
+        for w in words:
+            cur_word = Counter(w)
+            good = True
+            for c in cur_word:
+                if cur_word[c] > count[c]:
+                    good = False
+                    break
+            if good:
+                res += len(w)
+        return res
+```
+
+```java
+public class Solution {
+    public int countCharacters(String[] words, String chars) {
+        Map<Character, Integer> count = new HashMap<>();
+        for (char c : chars.toCharArray()) {
+            count.put(c, count.getOrDefault(c, 0) + 1);
+        }
+        int res = 0;
+        for (String w : words) {
+            Map<Character, Integer> curWord = new HashMap<>();
+            for (char c : w.toCharArray()) {
+                curWord.put(c, curWord.getOrDefault(c, 0) + 1);
+            }
+            boolean good = true;
+            for (char c : curWord.keySet()) {
+                if (curWord.get(c) > count.getOrDefault(c, 0)) {
+                    good = false;
+                    break;
+                }
+            }
+            if (good) {
+                res += w.length();
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countCharacters(vector<string>& words, string chars) {
+        unordered_map<char, int> count;
+        for (char c : chars) {
+            count[c]++;
+        }
+        int res = 0;
+        for (const string& w : words) {
+            unordered_map<char, int> curWord;
+            for (char c : w) {
+                curWord[c]++;
+            }
+            bool good = true;
+            for (const auto& p : curWord) {
+                if (p.second > count[p.first]) {
+                    good = false;
+                    break;
+                }
+            }
+            if (good) {
+                res += w.size();
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @param {string} chars
+     * @return {number}
+     */
+    countCharacters(words, chars) {
+        const count = {};
+        for (const c of chars) {
+            count[c] = (count[c] || 0) + 1;
+        }
+        let res = 0;
+        for (const w of words) {
+            const curWord = {};
+            for (const c of w) {
+                curWord[c] = (curWord[c] || 0) + 1;
+            }
+            let good = true;
+            for (const c in curWord) {
+                if (curWord[c] > (count[c] || 0)) {
+                    good = false;
+                    break;
+                }
+            }
+            if (good) {
+                res += w.length;
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + (m * k))$
+* Space complexity: $O(1)$ since we have at most $26$ different characters.
+
+> Where $n$ is the length of $chars$, $m$ is the number of words and $k$ is the average length of each word.
+
+---
+
+## 2. Hash Map (One Pass)
+
+::tabs-start
+
+```python
+class Solution:
+    def countCharacters(self, words: List[str], chars: str) -> int:
+        count = Counter(chars)
+        res = 0
+        
+        for w in words:
+            cur_word = defaultdict(int)
+            good = True
+            for c in w:
+                cur_word[c] += 1
+                if cur_word[c] > count[c]:
+                    good = False
+                    break
+            if good:
+                res += len(w)
+        return res
+```
+
+```java
+public class Solution {
+    public int countCharacters(String[] words, String chars) {
+        Map<Character, Integer> count = new HashMap<>();
+        for (char c : chars.toCharArray()) {
+            count.put(c, count.getOrDefault(c, 0) + 1);
+        }
+        int res = 0;
+        for (String w : words) {
+            Map<Character, Integer> curWord = new HashMap<>();
+            boolean good = true;
+            for (char c : w.toCharArray()) {
+                curWord.put(c, curWord.getOrDefault(c, 0) + 1);
+                if (curWord.get(c) > count.getOrDefault(c, 0)) {
+                    good = false;
+                    break;
+                }
+            }
+            if (good) {
+                res += w.length();
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countCharacters(vector<string>& words, string chars) {
+        unordered_map<char, int> count;
+        for (char c : chars) {
+            count[c]++;
+        }
+        int res = 0;
+        for (const string& w : words) {
+            unordered_map<char, int> curWord;
+            bool good = true;
+            for (char c : w) {
+                curWord[c]++;
+                if (curWord[c] > count[c]) {
+                    good = false;
+                    break;
+                }
+            }
+            if (good) {
+                res += w.size();
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @param {string} chars
+     * @return {number}
+     */
+    countCharacters(words, chars) {
+        const count = {};
+        for (const c of chars) {
+            count[c] = (count[c] || 0) + 1;
+        }
+        let res = 0;
+        for (const w of words) {
+            const curWord = {};
+            let good = true;
+            for (const c of w) {
+                curWord[c] = (curWord[c] || 0) + 1;
+                if (curWord[c] > (count[c] || 0)) {
+                    good = false;
+                    break;
+                }
+            }
+            if (good) {
+                res += w.length;
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + (m * k))$
+* Space complexity: $O(1)$ since we have at most $26$ different characters.
+
+> Where $n$ is the length of $chars$, $m$ is the number of words and $k$ is the average length of each word.
+
+---
+
+## 3. Hash Table
+
+::tabs-start
+
+```python
+class Solution:
+    def countCharacters(self, words: List[str], chars: str) -> int:
+        count = [0] * 26
+        for c in chars:
+            count[ord(c) - ord('a')] += 1
+        
+        org = count[:]
+        res = 0
+        
+        for w in words:
+            good = True
+            for c in w:
+                i = ord(c) - ord('a')
+                count[i] -= 1
+                if count[i] < 0:
+                    good = False
+                    break
+            if good:
+                res += len(w)
+
+            for i in range(26):
+                count[i] = org[i]
+        return res
+```
+
+```java
+public class Solution {
+    public int countCharacters(String[] words, String chars) {
+        int[] count = new int[26];
+        for (char c : chars.toCharArray()) {
+            count[c - 'a']++;
+        }
+        
+        int[] org = count.clone();
+        int res = 0;
+        
+        for (String w : words) {
+            boolean good = true;
+            for (int i = 0; i < w.length(); i++) {
+                int j = w.charAt(i) - 'a';
+                count[j]--;
+                if (count[j] < 0) {
+                    good = false;
+                    break;
+                }
+            }
+            if (good) {
+                res += w.length();
+            }
+            for (int i = 0; i < 26; i++) {
+                count[i] = org[i];
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countCharacters(vector<string>& words, string chars) {
+        vector<int> count(26, 0);
+        for (char c : chars) {
+            count[c - 'a']++;
+        }
+        
+        vector<int> org = count;
+        int res = 0;
+        
+        for (string& w : words) {
+            bool good = true;
+            for (char& c : w) {
+                int i = c - 'a';
+                count[i]--;
+                if (count[i] < 0) {
+                    good = false;
+                    break;
+                }
+            }
+            if (good) {
+                res += w.length();
+            }
+            for (int i = 0; i < 26; i++) {
+                count[i] = org[i];
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @param {string} chars
+     * @return {number}
+     */
+    countCharacters(words, chars) {
+        const count = new Array(26).fill(0);
+        for (let c of chars) {
+            count[c.charCodeAt(0) - 'a'.charCodeAt(0)]++;
+        }
+        
+        const org = [...count];
+        let res = 0;
+        
+        for (let w of words) {
+            let good = true;
+            for (let c of w) {
+                const i = c.charCodeAt(0) - 'a'.charCodeAt(0);
+                count[i]--;
+                if (count[i] < 0) {
+                    good = false;
+                    break;
+                }
+            }
+            
+            if (good) {
+                res += w.length;
+            }
+            for (let i = 0; i < 26; i++) {
+                count[i] = org[i];
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + (m * k))$
+* Space complexity: $O(1)$ since we have at most $26$ different characters.
+
+> Where $n$ is the length of $chars$, $m$ is the number of words and $k$ is the average length of each word.
\ No newline at end of file
diff --git a/articles/first-bad-version.md b/articles/first-bad-version.md
new file mode 100644
index 000000000..12305c833
--- /dev/null
+++ b/articles/first-bad-version.md
@@ -0,0 +1,373 @@
+## 1. Brute Force (Linear Search)
+
+::tabs-start
+
+```python
+# The isBadVersion API is already defined for you.
+# def isBadVersion(version: int) -> bool:
+
+class Solution:
+    def firstBadVersion(self, n: int) -> int:
+        for i in range(1, n):
+            if isBadVersion(i):
+                return i
+        return n
+```
+
+```java
+/* The isBadVersion API is defined in the parent class VersionControl.
+      boolean isBadVersion(int version); */
+
+public class Solution extends VersionControl {
+    public int firstBadVersion(int n) {
+        for (int i = 1; i < n; i++) {
+            if (isBadVersion(i)) {
+                return i;
+            }
+        }
+        return n;
+    }
+}
+```
+
+```cpp
+// The API isBadVersion is defined for you.
+// bool isBadVersion(int version);
+
+class Solution {
+public:
+    int firstBadVersion(int n) {
+        for (int i = 1; i < n; i++) {
+            if (isBadVersion(i)) {
+                return i;
+            }
+        }
+        return n;
+    }
+};
+```
+
+```javascript
+// The isBadVersion API is already defined in the VersionControl class.
+// isBadVersion(version: number): boolean
+
+class Solution extends VersionControl {
+    /**
+     * @param {number} n Total versions
+     * @return {number} The first bad version
+     */
+    firstBadVersion(n) {
+        for (let i = 1; i < n; i++) {
+            if (this.isBadVersion(i)) {
+                return i;
+            }
+        }
+        return n;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 2. Recursive Binary Search
+
+::tabs-start
+
+```python
+# The isBadVersion API is already defined for you.
+# def isBadVersion(version: int) -> bool:
+
+class Solution:
+    def firstBadVersion(self, n: int) -> int:
+        def helper(l, r):
+            if l > r:
+                return l
+            m = l + (r - l) // 2
+            if isBadVersion(m):
+                return helper(l, m - 1)
+            else:
+                return helper(m + 1, r)
+        
+        return helper(1, n)
+```
+
+```java
+/* The isBadVersion API is defined in the parent class VersionControl.
+      boolean isBadVersion(int version); */
+
+public class Solution extends VersionControl {
+    public int firstBadVersion(int n) {
+        return helper(1, n);
+    }
+
+    private int helper(int l, int r) {
+        if (l > r) {
+            return l;
+        }
+        int m = l + (r - l) / 2;
+        if (isBadVersion(m)) {
+            return helper(l, m - 1);
+        } else {
+            return helper(m + 1, r);
+        }
+    }
+}
+```
+
+```cpp
+// The API isBadVersion is defined for you.
+// bool isBadVersion(int version);
+
+class Solution {
+public:
+    int firstBadVersion(int n) {
+        return helper(1, n);
+    }
+
+private:
+    int helper(int l, int r) {
+        if (l > r) {
+            return l;
+        }
+        int m = l + (r - l) / 2;
+        if (isBadVersion(m)) {
+            return helper(l, m - 1);
+        } else {
+            return helper(m + 1, r);
+        }
+    }
+};
+```
+
+```javascript
+// The isBadVersion API is already defined in the VersionControl class.
+// isBadVersion(version: number): boolean
+
+class Solution extends VersionControl {
+    /**
+     * @param {number} n Total versions
+     * @return {number} The first bad version
+     */
+    firstBadVersion(n) {
+        const helper = (l, r) => {
+            if (l > r) {
+                return l;
+            }
+            const m = Math.floor(l + (r - l) / 2);
+            if (this.isBadVersion(m)) {
+                return helper(l, m - 1);
+            } else {
+                return helper(m + 1, r);
+            }
+        };
+        return helper(1, n);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(\log n)$ for recursion stack.
+
+---
+
+## 3. Iterative Binary Search
+
+::tabs-start
+
+```python
+# The isBadVersion API is already defined for you.
+# def isBadVersion(version: int) -> bool:
+
+class Solution:
+    def firstBadVersion(self, n: int) -> int:
+        l, r = 1, n
+        res = -1
+        while l <= r:
+            m = l + (r - l) // 2
+            if isBadVersion(m):
+                res = m
+                r = m - 1
+            else:
+                l = m + 1
+        return res
+```
+
+```java
+/* The isBadVersion API is defined in the parent class VersionControl.
+      boolean isBadVersion(int version); */
+
+public class Solution extends VersionControl {
+    public int firstBadVersion(int n) {
+        int l = 1, r = n, res = -1;
+        while (l <= r) {
+            int m = l + (r - l) / 2;
+            if (isBadVersion(m)) {
+                res = m;
+                r = m - 1;
+            } else {
+                l = m + 1;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+// The API isBadVersion is defined for you.
+// bool isBadVersion(int version);
+
+class Solution {
+public:
+    int firstBadVersion(int n) {
+        int l = 1, r = n, res = -1;
+        while (l <= r) {
+            int m = l + (r - l) / 2;
+            if (isBadVersion(m)) {
+                res = m;
+                r = m - 1;
+            } else {
+                l = m + 1;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+// The isBadVersion API is already defined in the VersionControl class.
+// isBadVersion(version: number): boolean
+
+class Solution extends VersionControl {
+    /**
+     * @param {number} n Total versions
+     * @return {number} The first bad version
+     */
+    firstBadVersion(n) {
+        let l = 1, r = n, res = -1;
+        while (l <= r) {
+            const m = Math.floor(l + (r - l) / 2);
+            if (this.isBadVersion(m)) {
+                res = m;
+                r = m - 1;
+            } else {
+                l = m + 1;
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
+
+---
+
+## 4. Iterative Binary Search (Lower Bound)
+
+::tabs-start
+
+```python
+# The isBadVersion API is already defined for you.
+# def isBadVersion(version: int) -> bool:
+
+class Solution:
+    def firstBadVersion(self, n: int) -> int:
+        l, r = 1, n
+        while l < r:
+            m = l + (r - l) // 2
+            if isBadVersion(m):
+                r = m
+            else:
+                l = m + 1
+        return l
+```
+
+```java
+/* The isBadVersion API is defined in the parent class VersionControl.
+      boolean isBadVersion(int version); */
+
+public class Solution extends VersionControl {
+    public int firstBadVersion(int n) {
+        int l = 1, r = n;
+        while (l < r) {
+            int m = l + (r - l) / 2;
+            if (isBadVersion(m)) {
+                r = m;
+            } else {
+                l = m + 1;
+            }
+        }
+        return r;
+    }
+}
+```
+
+```cpp
+// The API isBadVersion is defined for you.
+// bool isBadVersion(int version);
+
+class Solution {
+public:
+    int firstBadVersion(int n) {
+        int l = 1, r = n;
+        while (l < r) {
+            int m = l + (r - l) / 2;
+            if (isBadVersion(m)) {
+                r = m;
+            } else {
+                l = m + 1;
+            }
+        }
+        return r;
+    }
+};
+```
+
+```javascript
+// The isBadVersion API is already defined in the VersionControl class.
+// isBadVersion(version: number): boolean
+
+class Solution extends VersionControl {
+    /**
+     * @param {number} n Total versions
+     * @return {number} The first bad version
+     */
+    firstBadVersion(n) {
+        let l = 1, r = n;
+        while (l < r) {
+            const m = Math.floor(l + (r - l) / 2);
+            if (this.isBadVersion(m)) {
+                r = m;
+            } else {
+                l = m + 1;
+            }
+        }
+        return r;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/first-missing-positive.md b/articles/first-missing-positive.md
new file mode 100644
index 000000000..09f5f9678
--- /dev/null
+++ b/articles/first-missing-positive.md
@@ -0,0 +1,667 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def firstMissingPositive(self, nums: List[int]) -> int:
+        missing = 1
+        while True:
+            flag = True
+            for num in nums:
+                if missing == num:
+                    flag = False
+                    break
+
+            if flag:
+                return missing
+            missing += 1 
+```
+
+```java
+public class Solution {
+    public int firstMissingPositive(int[] nums) {
+        int missing = 1;
+        while (true) {
+            boolean flag = true;
+            for (int num : nums) {
+                if (missing == num) {
+                    flag = false;
+                    break;
+                }
+            }
+            if (flag) return missing;
+            missing++;
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int firstMissingPositive(vector<int>& nums) {
+        int missing = 1;
+        while (true) {
+            bool flag = true;
+            for (int& num : nums) {
+                if (missing == num) {
+                    flag = false;
+                    break;
+                }
+            }
+            if (flag) return missing;
+            missing++;
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    firstMissingPositive(nums) {
+        let missing = 1;
+        while (true) {
+            let flag = true;
+            for (let num of nums) {
+                if (missing === num) {
+                    flag = false;
+                    break;
+                }
+            }
+            if (flag) return missing;
+            missing++;
+        }
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int FirstMissingPositive(int[] nums) {
+        int missing = 1;
+        
+        while (true) {
+            bool found = false;
+            
+            foreach (int num in nums) {
+                if (num == missing) {
+                    found = true;
+                    break;
+                }
+            }
+
+            if (!found) {
+                return missing;
+            }
+
+            missing++;
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Boolean Array
+
+::tabs-start
+
+```python
+class Solution:
+    def firstMissingPositive(self, nums: list[int]) -> int:
+        n = len(nums)
+        seen = [False] * n
+        for num in nums:
+            if num > 0 and num <= n:
+                seen[num - 1] = True
+        
+        for num in range(1, n + 1):
+            if not seen[num - 1]:
+                return num
+        
+        return n + 1
+```
+
+```java
+public class Solution {
+    public int firstMissingPositive(int[] nums) {
+        int n = nums.length;
+        boolean[] seen = new boolean[n];
+        
+        for (int num : nums) {
+            if (num > 0 && num <= n) {
+                seen[num - 1] = true;
+            }
+        }
+        
+        for (int i = 0; i < n; i++) {
+            if (!seen[i]) {
+                return i + 1;
+            }
+        }
+        
+        return n + 1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int firstMissingPositive(vector<int>& nums) {
+        int n = nums.size();
+        vector<bool> seen(n, false);
+        
+        for (int num : nums) {
+            if (num > 0 && num <= n) {
+                seen[num - 1] = true;
+            }
+        }
+        
+        for (int i = 0; i < n; i++) {
+            if (!seen[i]) {
+                return i + 1;
+            }
+        }
+        
+        return n + 1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    firstMissingPositive(nums) {
+        const n = nums.length;
+        const seen = new Array(n).fill(false);
+        
+        for (const num of nums) {
+            if (num > 0 && num <= n) {
+                seen[num - 1] = true;
+            }
+        }
+        
+        for (let i = 0; i < n; i++) {
+            if (!seen[i]) {
+                return i + 1;
+            }
+        }
+        
+        return n + 1;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int FirstMissingPositive(int[] nums) {
+        int n = nums.Length;
+        bool[] seen = new bool[n];
+
+        foreach (int num in nums) {
+            if (num > 0 && num <= n) {
+                seen[num - 1] = true;
+            }
+        }
+
+        for (int num = 1; num <= n; num++) {
+            if (!seen[num - 1]) {
+                return num;
+            }
+        }
+
+        return n + 1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def firstMissingPositive(self, nums: list[int]) -> int:
+        nums.sort()
+        missing = 1
+        for num in nums:
+            if num > 0 and missing == num:
+                missing += 1
+        return missing
+```
+
+```java
+public class Solution {
+    public int firstMissingPositive(int[] nums) {
+        Arrays.sort(nums);
+        int missing = 1;
+        for (int num : nums) {
+            if (num > 0 && missing == num) {
+                missing++;
+            }
+        }
+        return missing;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int firstMissingPositive(vector<int>& nums) {
+        sort(nums.begin(), nums.end());
+        int missing = 1;
+        for (int num : nums) {
+            if (num > 0 && missing == num) {
+                missing++;
+            }
+        }
+        return missing;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    firstMissingPositive(nums) {
+        nums.sort((a, b) => a - b);
+        let missing = 1;
+        for (const num of nums) {
+            if (num > 0 && missing === num) {
+                missing++;
+            }
+        }
+        return missing;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int FirstMissingPositive(int[] nums) {
+        Array.Sort(nums);
+        int missing = 1;
+
+        foreach (int num in nums) {
+            if (num > 0 && num == missing) {
+                missing++;
+            }
+        }
+
+        return missing;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 4. Negative Marking
+
+::tabs-start
+
+```python
+class Solution:
+    def firstMissingPositive(self, nums: list[int]) -> int:
+        for i in range(len(nums)):
+            if nums[i] < 0:
+                nums[i] = 0
+
+        for i in range(len(nums)):
+            val = abs(nums[i])
+            if 1 <= val <= len(nums):
+                if nums[val - 1] > 0:
+                    nums[val - 1] *= -1
+                elif nums[val - 1] == 0:
+                    nums[val - 1] = -1 * (len(nums) + 1)
+
+        for i in range(1, len(nums) + 1):
+            if nums[i - 1] >= 0:
+                return i
+
+        return len(nums) + 1
+```
+
+```java
+public class Solution {
+    public int firstMissingPositive(int[] nums) {
+        int n = nums.length;
+
+        for (int i = 0; i < n; i++) {
+            if (nums[i] < 0) {
+                nums[i] = 0;
+            }
+        }
+
+        for (int i = 0; i < n; i++) {
+            int val = Math.abs(nums[i]);
+            if (val >= 1 && val <= n) {
+                if (nums[val - 1] > 0) {
+                    nums[val - 1] *= -1;
+                } else if (nums[val - 1] == 0) {
+                    nums[val - 1] = -1 * (n + 1);
+                }
+            }
+        }
+
+        for (int i = 1; i <= n; i++) {
+            if (nums[i - 1] >= 0) {
+                return i;
+            }
+        }
+
+        return n + 1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int firstMissingPositive(vector<int>& nums) {
+        int n = nums.size();
+
+        for (int i = 0; i < n; i++) {
+            if (nums[i] < 0) {
+                nums[i] = 0;
+            }
+        }
+
+        for (int i = 0; i < n; i++) {
+            int val = abs(nums[i]);
+            if (val >= 1 && val <= n) {
+                if (nums[val - 1] > 0) {
+                    nums[val - 1] *= -1;
+                } else if (nums[val - 1] == 0) {
+                    nums[val - 1] = -1 * (n + 1);
+                }
+            }
+        }
+
+        for (int i = 1; i <= n; i++) {
+            if (nums[i - 1] >= 0) {
+                return i;
+            }
+        }
+
+        return n + 1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    firstMissingPositive(nums) {
+        const n = nums.length;
+
+        for (let i = 0; i < n; i++) {
+            if (nums[i] < 0) {
+                nums[i] = 0;
+            }
+        }
+
+        for (let i = 0; i < n; i++) {
+            const val = Math.abs(nums[i]);
+            if (val >= 1 && val <= n) {
+                if (nums[val - 1] > 0) {
+                    nums[val - 1] *= -1;
+                } else if (nums[val - 1] === 0) {
+                    nums[val - 1] = -1 * (n + 1);
+                }
+            }
+        }
+
+        for (let i = 1; i <= n; i++) {
+            if (nums[i - 1] >= 0) {
+                return i;
+            }
+        }
+
+        return n + 1;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int FirstMissingPositive(int[] nums) {
+        int n = nums.Length;
+
+        for (int i = 0; i < n; i++) {
+            if (nums[i] < 0) {
+                nums[i] = 0;
+            }
+        }
+
+        for (int i = 0; i < n; i++) {
+            int val = Math.Abs(nums[i]);
+            if (val >= 1 && val <= n) {
+                if (nums[val - 1] > 0) {
+                    nums[val - 1] *= -1;
+                } else if (nums[val - 1] == 0) {
+                    nums[val - 1] = -(n + 1);
+                }
+            }
+        }
+
+        for (int i = 0; i < n; i++) {
+            if (nums[i] >= 0) {
+                return i + 1;
+            }
+        }
+
+        return n + 1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 5. Cycle Sort
+
+::tabs-start
+
+```python
+class Solution:
+    def firstMissingPositive(self, nums: list[int]) -> int:
+        n = len(nums)
+        i = 0
+        while i < n:
+            if nums[i] <= 0 or nums[i] > n:
+                i += 1
+                continue
+                
+            index = nums[i] - 1
+            if nums[i] != nums[index]:
+                nums[i], nums[index] = nums[index], nums[i]
+            else:
+                i += 1
+
+        for i in range(n):
+            if nums[i] != i + 1:
+                return i + 1
+
+        return n + 1
+```
+
+```java
+public class Solution {
+    public int firstMissingPositive(int[] nums) {
+        int n = nums.length;
+        int i = 0;
+
+        while (i < n) {
+            if (nums[i] <= 0 || nums[i] > n) {
+                i++;
+                continue;
+            }
+            int index = nums[i] - 1;
+            if (nums[i] != nums[index]) {
+                int temp = nums[i];
+                nums[i] = nums[index];
+                nums[index] = temp;
+            } else {
+                i++;
+            }
+        }
+
+        for (i = 0; i < n; i++) {
+            if (nums[i] != i + 1) {
+                return i + 1;
+            }
+        }
+
+        return n + 1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int firstMissingPositive(vector<int>& nums) {
+        int n = nums.size();
+        int i = 0;
+
+        while (i < n) {
+            if (nums[i] <= 0 || nums[i] > n) {
+                i++;
+                continue;
+            }
+            int index = nums[i] - 1;
+            if (nums[i] != nums[index]) {
+                swap(nums[i], nums[index]);
+            } else {
+                i++;
+            }
+        }
+
+        for (i = 0; i < n; i++) {
+            if (nums[i] != i + 1) {
+                return i + 1;
+            }
+        }
+
+        return n + 1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    firstMissingPositive(nums) {
+        let n = nums.length;
+        let i = 0;
+        while (i < n) {
+            if (nums[i] <= 0 || nums[i] > n) {
+                i++;
+                continue;
+            }
+            let index = nums[i] - 1;
+            if (nums[i] != nums[index]) {
+                [nums[i], nums[index]] = [nums[index], nums[i]];
+            } else {
+                i++;
+            }
+        }
+
+        for (let i = 0; i < n; i++) {
+            if (nums[i] != i + 1) {
+                return i + 1;
+            }
+        }
+
+        return n + 1;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int FirstMissingPositive(int[] nums) {
+        int n = nums.Length;
+        int i = 0;
+
+        while (i < n) {
+            if (nums[i] <= 0 || nums[i] > n) {
+                i++;
+                continue;
+            }
+
+            int index = nums[i] - 1;
+            if (nums[i] != nums[index]) {
+                int temp = nums[i];
+                nums[i] = nums[index];
+                nums[index] = temp;
+            } else {
+                i++;
+            }
+        }
+
+        for (i = 0; i < n; i++) {
+            if (nums[i] != i + 1) {
+                return i + 1;
+            }
+        }
+
+        return n + 1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/first-unique-character-in-a-string.md b/articles/first-unique-character-in-a-string.md
new file mode 100644
index 000000000..b60c2e4f6
--- /dev/null
+++ b/articles/first-unique-character-in-a-string.md
@@ -0,0 +1,365 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def firstUniqChar(self, s: str) -> int:
+        for i in range(len(s)):
+            flag = True
+            for j in range(len(s)):
+                if i == j:
+                    continue
+                if s[i] == s[j]:
+                    flag = False
+                    break
+            if flag:
+                return i
+        return -1
+```
+
+```java
+public class Solution {
+    public int firstUniqChar(String s) {
+        for (int i = 0; i < s.length(); i++) {
+            boolean flag = true;
+            for (int j = 0; j < s.length(); j++) {
+                if (i == j) continue;
+                if (s.charAt(i) == s.charAt(j)) {
+                    flag = false;
+                    break;
+                }
+            }
+            if (flag) return i;
+        }
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int firstUniqChar(string s) {
+        for (int i = 0; i < s.size(); i++) {
+            bool flag = true;
+            for (int j = 0; j < s.size(); j++) {
+                if (i == j) continue;
+                if (s[i] == s[j]) {
+                    flag = false;
+                    break;
+                }
+            }
+            if (flag) return i;
+        }
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    firstUniqChar(s) {
+        for (let i = 0; i < s.length; i++) {
+            let flag = true;
+            for (let j = 0; j < s.length; j++) {
+                if (i === j) continue;
+                if (s[i] === s[j]) {
+                    flag = false;
+                    break;
+                }
+            }
+            if (flag) return i;
+        }
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def firstUniqChar(self, s: str) -> int:
+        count = defaultdict(int)
+        for c in s:
+            count[c] += 1
+        
+        for i, c in enumerate(s):
+            if count[c] == 1:
+                return i
+        return -1
+```
+
+```java
+public class Solution {
+    public int firstUniqChar(String s) {
+        Map<Character, Integer> count = new HashMap<>();
+        for (char c : s.toCharArray()) {
+            count.put(c, count.getOrDefault(c, 0) + 1);
+        }
+
+        for (int i = 0; i < s.length(); i++) {
+            if (count.get(s.charAt(i)) == 1) {
+                return i;
+            }
+        }
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int firstUniqChar(string s) {
+        unordered_map<char, int> count;
+        for (char c : s) {
+            count[c]++;
+        }
+        
+        for (int i = 0; i < s.size(); i++) {
+            if (count[s[i]] == 1) {
+                return i;
+            }
+        }
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    firstUniqChar(s) {
+        const count = new Map();
+        for (const c of s) {
+            count.set(c, (count.get(c) || 0) + 1);
+        }
+
+        for (let i = 0; i < s.length; i++) {
+            if (count.get(s[i]) === 1) {
+                return i;
+            }
+        }
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ since we have at most $26$ different characters.
+
+---
+
+## 3. Hash Map (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def firstUniqChar(self, s: str) -> int:
+        n = len(s)
+        count = defaultdict(int)
+        for i, c in enumerate(s):
+            if c not in count:
+                count[c] = i
+            else:
+                count[c] = n
+        
+        res = n
+        for c in count:
+            res = min(res, count[c])
+
+        return -1 if res == n else res
+```
+
+```java
+public class Solution {
+    public int firstUniqChar(String s) {
+        int n = s.length();
+        Map<Character, Integer> count = new HashMap<>();
+        
+        for (int i = 0; i < n; i++) {
+            char c = s.charAt(i);
+            if (!count.containsKey(c)) {
+                count.put(c, i);
+            } else {
+                count.put(c, n);
+            }
+        }
+        
+        int res = n;
+        for (int index : count.values()) {
+            res = Math.min(res, index);
+        }
+        
+        return res == n ? -1 : res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int firstUniqChar(string s) {
+        int n = s.size();
+        unordered_map<char, int> count;
+
+        for (int i = 0; i < n; i++) {
+            if (count.find(s[i]) == count.end()) {
+                count[s[i]] = i;
+            } else {
+                count[s[i]] = n;
+            }
+        }
+        
+        int res = n;
+        for (auto& [key, index] : count) {
+            res = min(res, index);
+        }
+        
+        return res == n ? -1 : res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    firstUniqChar(s) {
+        const n = s.length;
+        const count = new Map();
+
+        for (let i = 0; i < n; i++) {
+            const c = s[i];
+            if (!count.has(c)) {
+                count.set(c, i);
+            } else {
+                count.set(c, n);
+            }
+        }
+
+        let res = n;
+        for (const index of count.values()) {
+            res = Math.min(res, index);
+        }
+
+        return res === n ? -1 : res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ since we have at most $26$ different characters.
+
+---
+
+## 4. Iteration
+
+::tabs-start
+
+```python
+class Solution:
+    def firstUniqChar(self, s: str) -> int:
+        res = n = len(s)
+        for ch in range(ord('a'), ord('z') + 1):
+            index = s.find(chr(ch))
+            if index != -1 and s.rfind(chr(ch)) == index:
+                res = min(res, index)
+
+        return -1 if res == n else res
+```
+
+```java
+public class Solution {
+    public int firstUniqChar(String s) {
+        int res = s.length();
+
+        for (char ch = 'a'; ch <= 'z'; ch++) {
+            int firstIndex = s.indexOf(ch);
+            if (firstIndex != -1 && s.lastIndexOf(ch) == firstIndex) {
+                res = Math.min(res, firstIndex);
+            }
+        }
+
+        return res == s.length() ? -1 : res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int firstUniqChar(string s) {
+        int res = s.size();
+
+        for (char ch = 'a'; ch <= 'z'; ch++) {
+            int firstIndex = s.find(ch);
+            if (firstIndex != string::npos && s.rfind(ch) == firstIndex) {
+                res = min(res, firstIndex);
+            }
+        }
+
+        return res == s.size() ? -1 : res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    firstUniqChar(s) {
+        let res = s.length;
+
+        for (let ch = 'a'.charCodeAt(0); ch <= 'z'.charCodeAt(0); ch++) {
+            const char = String.fromCharCode(ch);
+            const firstIndex = s.indexOf(char);
+            if (firstIndex !== -1 && s.lastIndexOf(char) === firstIndex) {
+                res = Math.min(res, firstIndex);
+            }
+        }
+
+        return res === s.length ? -1 : res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(26 * n)$ since we have at most $26$ different characters.
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/flatten-nested-list-iterator.md b/articles/flatten-nested-list-iterator.md
new file mode 100644
index 000000000..6ac2342a2
--- /dev/null
+++ b/articles/flatten-nested-list-iterator.md
@@ -0,0 +1,579 @@
+## 1. Recursion (Flatten And Store Into Global List )
+
+::tabs-start
+
+```python
+class NestedIterator:
+    def __init__(self, nestedList):
+        self.arr = []
+        self.ptr = 0
+        self.dfs(nestedList)
+
+    def next(self):
+        val = self.arr[self.ptr]
+        self.ptr += 1
+        return val
+
+    def hasNext(self):
+        return self.ptr < len(self.arr)
+
+    def dfs(self, nestedArr):
+        for num in nestedArr:
+            if num.isInteger():
+                self.arr.append(num.getInteger())
+            else:
+                self.dfs(num.getList())
+```
+
+```java
+public class NestedIterator implements Iterator<Integer> {
+
+    private List<Integer> arr;
+    private int ptr;
+
+    public NestedIterator(List<NestedInteger> nestedList) {
+        arr = new ArrayList<>();
+        ptr = 0;
+        dfs(nestedList);
+    }
+
+    @Override
+    public Integer next() {
+        return arr.get(ptr++);
+    }
+
+    @Override
+    public boolean hasNext() {
+        return ptr < arr.size();
+    }
+
+    private void dfs(List<NestedInteger> nestedArr) {
+        for (NestedInteger num : nestedArr) {
+            if (num.isInteger()) {
+                arr.add(num.getInteger());
+            } else {
+                dfs(num.getList());
+            }
+        }
+    }
+}
+```
+
+```cpp
+class NestedIterator {
+private:
+    vector<int> arr;
+    int ptr;
+
+    void dfs(const vector<NestedInteger> &nestedArr) {
+        for (const auto &num : nestedArr) {
+            if (num.isInteger()) {
+                arr.push_back(num.getInteger());
+            } else {
+                dfs(num.getList());
+            }
+        }
+    }
+
+public:
+    NestedIterator(vector<NestedInteger> &nestedList) {
+        ptr = 0;
+        dfs(nestedList);
+    }
+
+    int next() {
+        return arr[ptr++];
+    }
+
+    bool hasNext() {
+        return ptr < arr.size();
+    }
+};
+```
+
+```javascript
+class NestedIterator {
+    /**
+     * @constructor
+     * @param {NestedInteger[]} nestedList
+     */
+    constructor(nestedList) {
+        this.arr = [];
+        this.ptr = 0;
+        this.dfs(nestedList);
+    }
+
+    /**
+     * @param {NestedInteger[]} nestedArr 
+     */
+    dfs(nestedArr) {
+        for (let num of nestedArr) {
+            if (num.isInteger()) {
+                this.arr.push(num.getInteger());
+            } else {
+                this.dfs(num.getList());
+            }
+        }
+    }
+
+    /**
+     * @this NestedIterator
+     * @returns {integer}
+     */
+    next() {
+        return this.arr[this.ptr++];
+    }
+
+    /**
+     * @this NestedIterator
+     * @returns {boolean}
+     */
+    hasNext() {
+        return this.ptr < this.arr.length;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + d)$
+* Space complexity: $O(n + d)$
+
+> Where $n$ is the number of integers and $d$ is the nesting depth.
+
+---
+
+## 2. Recursion (Flatten And Return)
+
+::tabs-start
+
+```python
+class NestedIterator:
+    def __init__(self, nestedList):
+        self.arr = self.dfs(nestedList)
+        self.ptr = 0
+
+    def dfs(self, nestedArr):
+        res = []
+        for num in nestedArr:
+            if num.isInteger():
+                res.append(num.getInteger())
+            else:
+                res.extend(self.dfs(num.getList()))
+        return res
+
+    def next(self):
+        val = self.arr[self.ptr]
+        self.ptr += 1
+        return val
+
+    def hasNext(self):
+        return self.ptr < len(self.arr)
+```
+
+```java
+public class NestedIterator implements Iterator<Integer> {
+    private List<Integer> arr;
+    private int ptr;
+
+    public NestedIterator(List<NestedInteger> nestedList) {
+        arr = dfs(nestedList);
+        ptr = 0;
+    }
+
+    private List<Integer> dfs(List<NestedInteger> nestedArr) {
+        List<Integer> res = new ArrayList<>();
+        for (NestedInteger num : nestedArr) {
+            if (num.isInteger()) {
+                res.add(num.getInteger());
+            } else {
+                res.addAll(dfs(num.getList()));
+            }
+        }
+        return res;
+    }
+
+    @Override
+    public Integer next() {
+        return arr.get(ptr++);
+    }
+
+    @Override
+    public boolean hasNext() {
+        return ptr < arr.size();
+    }
+}
+```
+
+```cpp
+class NestedIterator {
+private:
+    vector<int> arr;
+    int ptr;
+
+    vector<int> dfs(const vector<NestedInteger> &nestedArr) {
+        vector<int> res;
+        for (const auto &num : nestedArr) {
+            if (num.isInteger()) {
+                res.push_back(num.getInteger());
+            } else {
+                vector<int> temp = dfs(num.getList());
+                res.insert(res.end(), temp.begin(), temp.end());
+            }
+        }
+        return res;
+    }
+
+public:
+    NestedIterator(vector<NestedInteger> &nestedList) {
+        arr = dfs(nestedList);
+        ptr = 0;
+    }
+
+    int next() {
+        return arr[ptr++];
+    }
+
+    bool hasNext() {
+        return ptr < arr.size();
+    }
+};
+```
+
+```javascript
+class NestedIterator {
+    /**
+     * @constructor
+     * @param {NestedInteger[]} nestedList
+     */
+    constructor(nestedList) {
+        this.arr = this.dfs(nestedList);
+        this.ptr = 0;
+    }
+
+    /**
+     * @param {NestedInteger[]} nestedArr 
+     */
+    dfs(nestedArr) {
+        let res = [];
+        for (let num of nestedArr) {
+            if (num.isInteger()) {
+                res.push(num.getInteger());
+            } else {
+                res.push(...this.dfs(num.getList()));
+            }
+        }
+        return res;
+    }
+
+    /**
+     * @this NestedIterator
+     * @returns {integer}
+     */
+    next() {
+        return this.arr[this.ptr++];
+    }
+
+    /**
+     * @this NestedIterator
+     * @returns {boolean}
+     */
+    hasNext() {
+        return this.ptr < this.arr.length;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + d)$
+* Space complexity: $O(n + d)$
+
+> Where $n$ is the number of integers and $d$ is the nesting depth.
+
+---
+
+## 3. Recursion + Stack
+
+::tabs-start
+
+```python
+class NestedIterator:
+    def __init__(self, nestedList: [NestedInteger]):
+        self.stack = []
+        self.dfs(nestedList)
+        self.stack.reverse()
+
+    def next(self) -> int:
+        return self.stack.pop()
+
+    def hasNext(self) -> bool:
+        return len(self.stack) > 0
+
+    def dfs(self, nested):
+        for num in nested:
+            if num.isInteger():
+                self.stack.append(num.getInteger())
+            else:
+                self.dfs(num.getList())
+```
+
+```java
+public class NestedIterator implements Iterator<Integer> {
+    private Stack<Integer> stack;
+
+    public NestedIterator(List<NestedInteger> nestedList) {
+        stack = new Stack<>();
+        dfs(nestedList);
+        Collections.reverse(stack);
+    }
+
+    private void dfs(List<NestedInteger> nested) {
+        for (NestedInteger num : nested) {
+            if (num.isInteger()) {
+                stack.push(num.getInteger());
+            } else {
+                dfs(num.getList());
+            }
+        }
+    }
+
+    @Override
+    public Integer next() {
+        return stack.pop();
+    }
+
+    @Override
+    public boolean hasNext() {
+        return !stack.isEmpty();
+    }
+}
+```
+
+```cpp
+class NestedIterator {
+private:
+    vector<int> stack;
+
+    void dfs(const vector<NestedInteger> &nested) {
+        for (const auto &num : nested) {
+            if (num.isInteger()) {
+                stack.push_back(num.getInteger());
+            } else {
+                dfs(num.getList());
+            }
+        }
+    }
+
+public:
+    NestedIterator(vector<NestedInteger> &nestedList) {
+        dfs(nestedList);
+        reverse(stack.begin(), stack.end());
+    }
+
+    int next() {
+        int val = stack.back();
+        stack.pop_back();
+        return val;
+    }
+
+    bool hasNext() {
+        return !stack.empty();
+    }
+};
+```
+
+```javascript
+class NestedIterator {
+    /**
+     * @constructor
+     * @param {NestedInteger[]} nestedList
+     */
+    constructor(nestedList) {
+        this.stack = [];
+        this.dfs(nestedList);
+        this.stack.reverse();
+    }
+
+    /** 
+     * @param {NestedInteger[]} nested
+     */
+    dfs(nested) {
+        for (let num of nested) {
+            if (num.isInteger()) {
+                this.stack.push(num.getInteger());
+            } else {
+                this.dfs(num.getList());
+            }
+        }
+    }
+
+    /**
+     * @this NestedIterator
+     * @returns {number}
+     */
+    next() {
+        return this.stack.pop();
+    }
+
+    /**
+     * @this NestedIterator
+     * @returns {boolean}
+     */
+    hasNext() {
+        return this.stack.length > 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + d)$
+* Space complexity: $O(n + d)$
+
+> Where $n$ is the number of integers and $d$ is the nesting depth.
+
+---
+
+## 4. Stack
+
+::tabs-start
+
+```python
+class NestedIterator:
+    def __init__(self, nestedList: [NestedInteger]):
+        self.stack = nestedList
+        self.stack.reverse()
+
+    def next(self) -> int:
+        return self.stack.pop().getInteger()
+
+    def hasNext(self) -> bool:
+        while self.stack:
+            top = self.stack[-1]
+            if top.isInteger():
+                return True
+                
+            self.stack.pop()
+            self.stack.extend(reversed(top.getList()))
+        return False
+```
+
+```java
+public class NestedIterator implements Iterator<Integer> {
+    private List<NestedInteger> stack;
+
+    public NestedIterator(List<NestedInteger> nestedList) {
+        stack = new ArrayList<>(nestedList);
+        Collections.reverse(stack);
+    }
+
+    @Override
+    public Integer next() {
+        return stack.remove(stack.size() - 1).getInteger();
+    }
+
+    @Override
+    public boolean hasNext() {
+        while (!stack.isEmpty()) {
+            NestedInteger top = stack.get(stack.size() - 1);
+            if (top.isInteger()) {
+                return true;
+            }
+            stack.remove(stack.size() - 1);
+            List<NestedInteger> nestedList = top.getList();
+            Collections.reverse(nestedList);
+            stack.addAll(nestedList);
+        }
+        return false;
+    }
+}
+```
+
+```cpp
+class NestedIterator {
+private:
+    vector<NestedInteger> stack;
+
+public:
+    NestedIterator(vector<NestedInteger> &nestedList) {
+        stack = nestedList;
+        reverse(stack.begin(), stack.end());
+    }
+
+    int next() {
+        int val = stack.back().getInteger();
+        stack.pop_back();
+        return val;
+    }
+
+    bool hasNext() {
+        while (!stack.empty()) {
+            NestedInteger top = stack.back();
+            if (top.isInteger()) {
+                return true;
+            }
+            stack.pop_back();
+            vector<NestedInteger> nestedList = top.getList();
+            for (auto it = nestedList.rbegin(); it != nestedList.rend(); ++it) {
+                stack.push_back(*it);
+            }
+        }
+        return false;
+    }
+};
+```
+
+```javascript
+class NestedIterator {
+    /**
+     * @constructor
+     * @param {NestedInteger[]} nestedList
+     */
+    constructor(nestedList) {
+        this.stack = nestedList;
+        this.stack.reverse();
+    }
+
+    /**
+     * @this NestedIterator
+     * @returns {number}
+     */
+    next() {
+        return this.stack.pop().getInteger();
+    }
+
+    /**
+     * @this NestedIterator
+     * @returns {boolean}
+     */
+    hasNext() {
+        while (this.stack.length > 0) {
+            const top = this.stack[this.stack.length - 1];
+            if (top.isInteger()) {
+                return true;
+            }
+            this.stack.pop();
+            const nestedList = top.getList();
+            nestedList.reverse();
+            this.stack.push(...nestedList);
+        }
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + d)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the number of integers and $d$ is the nesting depth.
\ No newline at end of file
diff --git a/articles/flip-equivalent-binary-trees.md b/articles/flip-equivalent-binary-trees.md
new file mode 100644
index 000000000..2a2549798
--- /dev/null
+++ b/articles/flip-equivalent-binary-trees.md
@@ -0,0 +1,492 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def flipEquiv(self, root1: Optional[TreeNode], root2: Optional[TreeNode]) -> bool:
+        if not root1 or not root2:
+            return not root1 and not root2
+        if root1.val != root2.val:
+            return False
+
+        return (
+                self.flipEquiv(root1.left, root2.left) and 
+                self.flipEquiv(root1.right, root2.right) or
+                self.flipEquiv(root1.left, root2.right) and 
+                self.flipEquiv(root1.right, root2.left)
+            )
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public boolean flipEquiv(TreeNode root1, TreeNode root2) {
+        if (root1 == null || root2 == null) 
+            return root1 == null && root2 == null;
+        if (root1.val != root2.val) 
+            return false;
+        
+        return (flipEquiv(root1.left, root2.left) && 
+                flipEquiv(root1.right, root2.right) ||
+                flipEquiv(root1.left, root2.right) && 
+                flipEquiv(root1.right, root2.left));
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    bool flipEquiv(TreeNode* root1, TreeNode* root2) {
+        if (!root1 || !root2) 
+            return !root1 && !root2;
+        if (root1->val != root2->val) 
+            return false;
+        
+        return (flipEquiv(root1->left, root2->left) && 
+                flipEquiv(root1->right, root2->right) ||
+                flipEquiv(root1->left, root2->right) && 
+                flipEquiv(root1->right, root2->left));
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root1
+     * @param {TreeNode} root2
+     * @return {boolean}
+     */
+    flipEquiv(root1, root2) {
+        if (!root1 || !root2) 
+            return !root1 && !root2;
+        if (root1.val !== root2.val) 
+            return false;
+        
+        return (this.flipEquiv(root1.left, root2.left) && 
+                this.flipEquiv(root1.right, root2.right) ||
+                this.flipEquiv(root1.left, root2.right) && 
+                this.flipEquiv(root1.right, root2.left));
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Breadth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def flipEquiv(self, root1: Optional[TreeNode], root2: Optional[TreeNode]) -> bool:
+        q = deque([(root1, root2)])
+
+        while q:
+            node1, node2 = q.popleft()
+            if not node1 or not node2:
+                if node1 != node2:
+                    return False
+                continue
+            
+            if node1.val != node2.val:
+                return False
+
+            if ((node1.right and node2.right and 
+                 node1.right.val == node2.right.val) or 
+                (not node1.right and not node2.right)
+            ):
+                q.append((node1.left, node2.left))
+                q.append((node1.right, node2.right))
+            else:
+                q.append((node1.left, node2.right))
+                q.append((node1.right, node2.left))
+
+        return True
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public boolean flipEquiv(TreeNode root1, TreeNode root2) {
+        Queue<TreeNode[]> q = new LinkedList<>();
+        q.offer(new TreeNode[]{root1, root2});
+
+        while (!q.isEmpty()) {
+            TreeNode[] pair = q.poll();
+            TreeNode node1 = pair[0], node2 = pair[1];
+
+            if (node1 == null || node2 == null) {
+                if (node1 != node2) return false;
+                continue;
+            }
+
+            if (node1.val != node2.val) return false;
+
+            if ((node1.left != null && node2.left != null && 
+                 node1.left.val == node2.left.val) || 
+                (node1.left == null && node2.left == null)) {
+                q.offer(new TreeNode[]{node1.left, node2.left});
+                q.offer(new TreeNode[]{node1.right, node2.right});
+            } else {
+                q.offer(new TreeNode[]{node1.left, node2.right});
+                q.offer(new TreeNode[]{node1.right, node2.left});
+            }
+        }
+
+        return true;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    bool flipEquiv(TreeNode* root1, TreeNode* root2) {
+        queue<pair<TreeNode*, TreeNode*>> q;
+        q.push({root1, root2});
+
+        while (!q.empty()) {
+            auto [node1, node2] = q.front();
+            q.pop();
+
+            if (!node1 || !node2) {
+                if (node1 != node2) return false;
+                continue;
+            }
+
+            if (node1->val != node2->val) return false;
+
+            if ((node1->left && node2->left && node1->left->val == node2->left->val) || 
+                (!node1->left && !node2->left)) {
+                q.push({node1->left, node2->left});
+                q.push({node1->right, node2->right});
+            } else {
+                q.push({node1->left, node2->right});
+                q.push({node1->right, node2->left});
+            }
+        }
+
+        return true;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root1
+     * @param {TreeNode} root2
+     * @return {boolean}
+     */
+    flipEquiv(root1, root2) {
+        let q = new Queue([[root1, root2]]);
+
+        while (!q.isEmpty()) {
+            let [node1, node2] = q.pop();
+
+            if (!node1 || !node2) {
+                if (node1 !== node2) return false;
+                continue;
+            }
+
+            if (node1.val !== node2.val) return false;
+
+            if ((node1.left && node2.left && 
+                node1.left.val === node2.left.val) || 
+                (!node1.left && !node2.left)) {
+                q.push([node1.left, node2.left]);
+                q.push([node1.right, node2.right]);
+            } else {
+                q.push([node1.left, node2.right]);
+                q.push([node1.right, node2.left]);
+            }
+        }
+
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Iterative DFS
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def flipEquiv(self, root1: Optional[TreeNode], root2: Optional[TreeNode]) -> bool:
+        stack = [(root1, root2)]
+
+        while stack:
+            node1, node2 = stack.pop()
+
+            if not node1 or not node2:
+                if node1 != node2:
+                    return False
+                continue
+
+            if node1.val != node2.val:
+                return False
+
+            if ((node1.left and node2.left and 
+                 node1.left.val == node2.left.val) or 
+                (not node1.left and not node2.left)
+            ):
+                stack.append((node1.left, node2.left))
+                stack.append((node1.right, node2.right))
+            else:
+                stack.append((node1.left, node2.right))
+                stack.append((node1.right, node2.left))
+
+        return True
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public boolean flipEquiv(TreeNode root1, TreeNode root2) {
+        Stack<TreeNode[]> stack = new Stack<>();
+        stack.push(new TreeNode[]{root1, root2});
+
+        while (!stack.isEmpty()) {
+            TreeNode[] pair = stack.pop();
+            TreeNode node1 = pair[0], node2 = pair[1];
+
+            if (node1 == null || node2 == null) {
+                if (node1 != node2) return false;
+                continue;
+            }
+
+            if (node1.val != node2.val) return false;
+
+            if ((node1.left != null && node2.left != null && 
+                 node1.left.val == node2.left.val) || 
+                (node1.left == null && node2.left == null)) {
+                stack.push(new TreeNode[]{node1.left, node2.left});
+                stack.push(new TreeNode[]{node1.right, node2.right});
+            } else {
+                stack.push(new TreeNode[]{node1.left, node2.right});
+                stack.push(new TreeNode[]{node1.right, node2.left});
+            }
+        }
+
+        return true;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    bool flipEquiv(TreeNode* root1, TreeNode* root2) {
+        stack<pair<TreeNode*, TreeNode*>> stk;
+        stk.push({root1, root2});
+
+        while (!stk.empty()) {
+            auto [node1, node2] = stk.top();stk.pop();
+
+            if (!node1 || !node2) {
+                if (node1 != node2) return false;
+                continue;
+            }
+
+            if (node1->val != node2->val) return false;
+
+            if ((node1->left && node2->left && node1->left->val == node2->left->val) || 
+                (!node1->left && !node2->left)) {
+                stk.push({node1->left, node2->left});
+                stk.push({node1->right, node2->right});
+            } else {
+                stk.push({node1->left, node2->right});
+                stk.push({node1->right, node2->left});
+            }
+        }
+
+        return true;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root1
+     * @param {TreeNode} root2
+     * @return {boolean}
+     */
+    flipEquiv(root1, root2) {
+        let stack = [[root1, root2]];
+
+        while (stack.length > 0) {
+            let [node1, node2] = stack.pop();
+
+            if (!node1 || !node2) {
+                if (node1 !== node2) return false;
+                continue;
+            }
+
+            if (node1.val !== node2.val) return false;
+
+            if ((node1.left && node2.left && 
+                node1.left.val === node2.left.val) || 
+                (!node1.left && !node2.left)) {
+                stack.push([node1.left, node2.left]);
+                stack.push([node1.right, node2.right]);
+            } else {
+                stack.push([node1.left, node2.right]);
+                stack.push([node1.right, node2.left]);
+            }
+        }
+
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/flip-string-to-monotone-increasing.md b/articles/flip-string-to-monotone-increasing.md
new file mode 100644
index 000000000..74c357f57
--- /dev/null
+++ b/articles/flip-string-to-monotone-increasing.md
@@ -0,0 +1,523 @@
+## 1. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def minFlipsMonoIncr(self, s: str) -> int:
+        dp = {}
+
+        def dfs(i, mono):
+            if (i, mono) in dp:
+                return dp[(i, mono)]
+            if i == len(s):
+                return 0
+            
+            if mono and s[i] == "0":
+                dp[(i, mono)] = min(1 + dfs(i + 1, False), dfs(i + 1, mono))
+            elif mono and s[i] == "1":
+                dp[(i, mono)] = min(1 + dfs(i + 1, mono), dfs(i + 1, False))
+            elif not mono and s[i] == "1":
+                dp[(i, mono)] = dfs(i + 1, mono)
+            else:
+                dp[(i, mono)] = 1 + dfs(i + 1, mono)
+            
+            return dp[(i, mono)]
+
+        return dfs(0, True)
+```
+
+```java
+public class Solution {
+    private int[][] dp;
+
+    public int minFlipsMonoIncr(String s) {
+        int n = s.length();
+        dp = new int[n][2];
+        for (int i = 0; i < n; i++) {
+            dp[i][0] = dp[i][1] = -1;
+        }
+        return dfs(0, 1, s);
+    }
+
+    private int dfs(int i, int mono, String s) {
+        if (i == s.length()) return 0;
+        if (dp[i][mono] != -1) return dp[i][mono];
+
+        if (mono == 1 && s.charAt(i) == '0') {
+            dp[i][mono] = Math.min(1 + dfs(i + 1, 0, s), dfs(i + 1, mono, s));
+        } else if (mono == 1 && s.charAt(i) == '1') {
+            dp[i][mono] = Math.min(1 + dfs(i + 1, mono, s), dfs(i + 1, 0, s));
+        } else if (mono == 0 && s.charAt(i) == '1') {
+            dp[i][mono] = dfs(i + 1, mono, s);
+        } else {
+            dp[i][mono] = 1 + dfs(i + 1, mono, s);
+        }
+        return dp[i][mono];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minFlipsMonoIncr(string s) {
+        int n = s.length();
+        vector<vector<int>> dp(n, vector<int>(2, -1));
+        return dfs(0, 1, s, dp);
+    }
+
+private:
+    int dfs(int i, int mono, const string& s, vector<vector<int>>& dp) {
+        if (i == s.length()) return 0;
+        if (dp[i][mono] != -1) return dp[i][mono];
+
+        if (mono == 1 && s[i] == '0') {
+            dp[i][mono] = min(1 + dfs(i + 1, 0, s, dp), dfs(i + 1, mono, s, dp));
+        } else if (mono == 1 && s[i] == '1') {
+            dp[i][mono] = min(1 + dfs(i + 1, mono, s, dp), dfs(i + 1, 0, s, dp));
+        } else if (mono == 0 && s[i] == '1') {
+            dp[i][mono] = dfs(i + 1, mono, s, dp);
+        } else {
+            dp[i][mono] = 1 + dfs(i + 1, mono, s, dp);
+        }
+        return dp[i][mono];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    minFlipsMonoIncr(s) {
+        const n = s.length;
+        const dp = Array.from({ length: n }, () => Array(2).fill(-1));
+
+        const dfs = (i, mono) => {
+            if (i === n) return 0;
+            if (dp[i][mono] !== -1) return dp[i][mono];
+
+            if (mono === 1 && s[i] === '0') {
+                dp[i][mono] = Math.min(1 + dfs(i + 1, 0), dfs(i + 1, mono));
+            } else if (mono === 1 && s[i] === '1') {
+                dp[i][mono] = Math.min(1 + dfs(i + 1, mono), dfs(i + 1, 0));
+            } else if (mono === 0 && s[i] === '1') {
+                dp[i][mono] = dfs(i + 1, mono);
+            } else {
+                dp[i][mono] = 1 + dfs(i + 1, mono);
+            }
+            return dp[i][mono];
+        };
+
+        return dfs(0, 1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def minFlipsMonoIncr(self, s: str) -> int:
+        n = len(s)
+        dp = [[0] * 2 for _ in range(n + 1)]
+
+        for i in range(n - 1, -1, -1):
+            if s[i] == '0':
+                dp[i][1] = min(1 + dp[i + 1][0], dp[i + 1][1])
+                dp[i][0] = 1 + dp[i + 1][0]
+            else:  # s[i] == '1'
+                dp[i][1] = min(1 + dp[i + 1][1], dp[i + 1][0])
+                dp[i][0] = dp[i + 1][0]
+
+        return dp[0][1]
+```
+
+```java
+public class Solution {
+    public int minFlipsMonoIncr(String s) {
+        int n = s.length();
+        int[][] dp = new int[n + 1][2];
+
+        for (int i = n - 1; i >= 0; i--) {
+            if (s.charAt(i) == '0') {
+                dp[i][1] = Math.min(1 + dp[i + 1][0], dp[i + 1][1]);
+                dp[i][0] = 1 + dp[i + 1][0];
+            } else { // s.charAt(i) == '1'
+                dp[i][1] = Math.min(1 + dp[i + 1][1], dp[i + 1][0]);
+                dp[i][0] = dp[i + 1][0];
+            }
+        }
+
+        return dp[0][1];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minFlipsMonoIncr(string s) {
+        int n = s.size();
+        vector<vector<int>> dp(n + 1, vector<int>(2, 0));
+
+        for (int i = n - 1; i >= 0; i--) {
+            if (s[i] == '0') {
+                dp[i][1] = min(1 + dp[i + 1][0], dp[i + 1][1]);
+                dp[i][0] = 1 + dp[i + 1][0];
+            } else { // s[i] == '1'
+                dp[i][1] = min(1 + dp[i + 1][1], dp[i + 1][0]);
+                dp[i][0] = dp[i + 1][0];
+            }
+        }
+
+        return dp[0][1];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    minFlipsMonoIncr(s) {
+        const n = s.length;
+        const dp = Array.from({ length: n + 1 }, () => [0, 0]);
+
+        for (let i = n - 1; i >= 0; i--) {
+            if (s[i] === '0') {
+                dp[i][1] = Math.min(1 + dp[i + 1][0], dp[i + 1][1]);
+                dp[i][0] = 1 + dp[i + 1][0];
+            } else { // s[i] === '1'
+                dp[i][1] = Math.min(1 + dp[i + 1][1], dp[i + 1][0]);
+                dp[i][0] = dp[i + 1][0];
+            }
+        }
+
+        return dp[0][1];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def minFlipsMonoIncr(self, s: str) -> int:
+        n = len(s)
+        dp = [0, 0]
+
+        for i in range(n - 1, -1, -1):
+            if s[i] == '0':
+                new_dp_1 = min(1 + dp[0], dp[1])
+                new_dp_0 = dp[0] + 1
+            else:  # s[i] == '1'
+                new_dp_1 = min(dp[1] + 1, dp[0])
+                new_dp_0 = dp[0]
+            
+            dp[1] = new_dp_1
+            dp[0] = new_dp_0
+
+        return dp[1]
+```
+
+```java
+public class Solution {
+    public int minFlipsMonoIncr(String s) {
+        int[] dp = new int[2];
+
+        for (int i = s.length() - 1; i >= 0; i--) {
+            int newDp1, newDp0;
+            if (s.charAt(i) == '0') {
+                newDp1 = Math.min(1 + dp[0], dp[1]);
+                newDp0 = 1 + dp[0];
+            } else { // s[i] == '1'
+                newDp1 = Math.min(1 + dp[1], dp[0]);
+                newDp0 = dp[0];
+            }
+
+            dp[1] = newDp1;
+            dp[0] = newDp0;
+        }
+
+        return dp[1];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minFlipsMonoIncr(string s) {
+        vector<int> dp(2, 0);
+
+        for (int i = s.length() - 1; i >= 0; i--) {
+            int newDp1, newDp0;
+            if (s[i] == '0') {
+                newDp1 = min(1 + dp[0], dp[1]);
+                newDp0 = dp[0] + 1;
+            } else { // s[i] == '1'
+                newDp1 = min(1 + dp[1], dp[0]);
+                newDp0 = dp[0];
+            }
+
+            dp[1] = newDp1;
+            dp[0] = newDp0;
+        }
+
+        return dp[1];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    minFlipsMonoIncr(s) {
+        let dp = [0, 0];
+
+        for (let i = s.length - 1; i >= 0; i--) {
+            let newDp1, newDp0;
+            if (s[i] === '0') {
+                newDp1 = Math.min(1 + dp[0], dp[1]);
+                newDp0 = dp[0] + 1;
+            } else { // s[i] === '1'
+                newDp1 = Math.min(1 + dp[1], dp[0]);
+                newDp0 = dp[0];
+            }
+
+            dp[1] = newDp1;
+            dp[0] = newDp0;
+        }
+
+        return dp[1];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 4. Prefix & Suffix Arrays
+
+::tabs-start
+
+```python
+class Solution:
+    def minFlipsMonoIncr(self, s: str) -> int:
+        n = len(s)
+        left_ones = [0] * (n + 1)
+        right_zeros = [0] * (n + 1)
+
+        for i in range(n):
+            left_ones[i + 1] = left_ones[i] + (1 if s[i] == '1' else 0)
+        
+        for i in range(n - 1, -1, -1):
+            right_zeros[i] = right_zeros[i + 1] + (1 if s[i] == '0' else 0)
+        
+        res = float('inf')
+        for i in range(n + 1):
+            res = min(res, left_ones[i] + right_zeros[i])
+
+        return res
+```
+
+```java
+public class Solution {
+    public int minFlipsMonoIncr(String s) {
+        int n = s.length();
+        int[] leftOnes = new int[n + 1];
+        int[] rightZeros = new int[n + 1];
+
+        for (int i = 0; i < n; i++) {
+            leftOnes[i + 1] = leftOnes[i] + (s.charAt(i) == '1' ? 1 : 0);
+        }
+
+        for (int i = n - 1; i >= 0; i--) {
+            rightZeros[i] = rightZeros[i + 1] + (s.charAt(i) == '0' ? 1 : 0);
+        }
+
+        int res = Integer.MAX_VALUE;
+        for (int i = 0; i <= n; i++) {
+            res = Math.min(res, leftOnes[i] + rightZeros[i]);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minFlipsMonoIncr(string s) {
+        int n = s.size();
+        vector<int> leftOnes(n + 1, 0), rightZeros(n + 1, 0);
+
+        for (int i = 0; i < n; i++) {
+            leftOnes[i + 1] = leftOnes[i] + (s[i] == '1' ? 1 : 0);
+        }
+
+        for (int i = n - 1; i >= 0; i--) {
+            rightZeros[i] = rightZeros[i + 1] + (s[i] == '0' ? 1 : 0);
+        }
+
+        int res = INT_MAX;
+        for (int i = 0; i <= n; i++) {
+            res = min(res, leftOnes[i] + rightZeros[i]);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    minFlipsMonoIncr(s) {
+        const n = s.length;
+        const leftOnes = Array(n + 1).fill(0);
+        const rightZeros = Array(n + 1).fill(0);
+
+        for (let i = 0; i < n; i++) {
+            leftOnes[i + 1] = leftOnes[i] + (s[i] === '1' ? 1 : 0);
+        }
+
+        for (let i = n - 1; i >= 0; i--) {
+            rightZeros[i] = rightZeros[i + 1] + (s[i] === '0' ? 1 : 0);
+        }
+
+        let res = Infinity;
+        for (let i = 0; i <= n; i++) {
+            res = Math.min(res, leftOnes[i] + rightZeros[i]);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 5. Dynamic Programming (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def minFlipsMonoIncr(self, s: str) -> int:
+        res  = cntOne = 0
+        for c in s:
+            if c == '1':
+                cntOne += 1
+            else:
+                res = min(res + 1, cntOne)
+        return res
+```
+
+```java
+public class Solution {
+    public int minFlipsMonoIncr(String s) {
+        int res = 0, cntOne = 0;
+        for (int i = 0; i < s.length(); i++) {
+            if (s.charAt(i) == '1') {
+                cntOne++;
+            } else {
+                res = Math.min(res + 1, cntOne);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minFlipsMonoIncr(string s) {
+        int res = 0, cntOne = 0;
+        for (char& c : s) {
+            if (c == '1') {
+                cntOne++;
+            } else {
+                res = min(res + 1, cntOne);
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    minFlipsMonoIncr(s) {
+        let res = 0, cntOne = 0;
+        for (let c of s) {
+            if (c === '1') {
+                cntOne++;
+            } else {
+                res = Math.min(res + 1, cntOne);
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/foreign-dictionary.md b/articles/foreign-dictionary.md
new file mode 100644
index 000000000..1bb32e486
--- /dev/null
+++ b/articles/foreign-dictionary.md
@@ -0,0 +1,955 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def foreignDictionary(self, words: List[str]) -> str:
+        adj = {c: set() for w in words for c in w}
+
+        for i in range(len(words) - 1):
+            w1, w2 = words[i], words[i + 1]
+            minLen = min(len(w1), len(w2))
+            if len(w1) > len(w2) and w1[:minLen] == w2[:minLen]:
+                return ""
+            for j in range(minLen):
+                if w1[j] != w2[j]:
+                    adj[w1[j]].add(w2[j])
+                    break
+
+        visited = {}
+        res = []
+
+        def dfs(char):
+            if char in visited:
+                return visited[char]
+
+            visited[char] = True
+
+            for neighChar in adj[char]:
+                if dfs(neighChar):
+                    return True
+
+            visited[char] = False
+            res.append(char)
+
+        for char in adj:
+            if dfs(char):
+                return ""
+
+        res.reverse()
+        return "".join(res)
+```
+
+```java
+public class Solution {
+    private Map<Character, Set<Character>> adj;
+    private Map<Character, Boolean> visited;
+    private List<Character> result;
+
+    public String foreignDictionary(String[] words) {
+        adj = new HashMap<>();
+        for (String word : words) {
+            for (char c : word.toCharArray()) {
+                adj.putIfAbsent(c, new HashSet<>());
+            }
+        }
+
+        for (int i = 0; i < words.length - 1; i++) {
+            String w1 = words[i], w2 = words[i + 1];
+            int minLen = Math.min(w1.length(), w2.length());
+            if (w1.length() > w2.length() && 
+                w1.substring(0, minLen).equals(w2.substring(0, minLen))) {
+                return "";
+            }
+            for (int j = 0; j < minLen; j++) {
+                if (w1.charAt(j) != w2.charAt(j)) {
+                    adj.get(w1.charAt(j)).add(w2.charAt(j));
+                    break;
+                }
+            }
+        }
+
+        visited = new HashMap<>();
+        result = new ArrayList<>();
+        for (char c : adj.keySet()) {
+            if (dfs(c)) {
+                return "";
+            }
+        }
+
+        Collections.reverse(result);
+        StringBuilder sb = new StringBuilder();
+        for (char c : result) {
+            sb.append(c);
+        }
+        return sb.toString();
+    }
+
+    private boolean dfs(char ch) {
+        if (visited.containsKey(ch)) {
+            return visited.get(ch);
+        }
+
+        visited.put(ch, true);
+        for (char next : adj.get(ch)) {
+            if (dfs(next)) {
+                return true;
+            }
+        }
+        visited.put(ch, false);
+        result.add(ch);
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    unordered_map<char, unordered_set<char>> adj;
+    unordered_map<char, bool> visited;
+    string result;
+
+    string foreignDictionary(vector<string>& words) {
+        for (const auto& word : words) {
+            for (char ch : word) {
+                adj[ch];
+            }
+        }
+
+        for (size_t i = 0; i < words.size() - 1; ++i) {
+            const string& w1 = words[i], & w2 = words[i + 1];
+            size_t minLen = min(w1.length(), w2.length());
+            if (w1.length() > w2.length() && 
+                w1.substr(0, minLen) == w2.substr(0, minLen)) {
+                return "";
+            }
+            for (size_t j = 0; j < minLen; ++j) {
+                if (w1[j] != w2[j]) {
+                    adj[w1[j]].insert(w2[j]);
+                    break;
+                }
+            }
+        }
+
+        for (const auto& pair : adj) {
+            if (dfs(pair.first)) {
+                return "";
+            }
+        }
+
+        reverse(result.begin(), result.end());
+        return result;
+    }
+
+    bool dfs(char ch) {
+        if (visited.find(ch) != visited.end()) {
+            return visited[ch];
+        }
+
+        visited[ch] = true;
+        for (char next : adj[ch]) {
+            if (dfs(next)) {
+                return true;
+            }
+        }
+        visited[ch] = false;
+        result.push_back(ch);
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @returns {string}
+     */
+    foreignDictionary(words) {
+        const adj = {};
+        for (const word of words) {
+            for (const char of word) {
+                adj[char] = new Set();
+            }
+        }
+
+        for (let i = 0; i < words.length - 1; i++) {
+            const w1 = words[i];
+            const w2 = words[i + 1];
+            const minLen = Math.min(w1.length, w2.length);
+            if (w1.length > w2.length && 
+                w1.slice(0, minLen) === w2.slice(0, minLen)) {
+                return "";
+            }
+            for (let j = 0; j < minLen; j++) {
+                if (w1[j] !== w2[j]) {
+                    adj[w1[j]].add(w2[j]);
+                    break;
+                }
+            }
+        }
+
+        const visited = {};
+        const res = [];
+
+        const dfs = (char) => {
+            if (char in visited) return visited[char];
+            visited[char] = true;
+
+            for (const neighChar of adj[char]) {
+                if (dfs(neighChar)) return true;
+            }
+
+            visited[char] = false;
+            res.push(char);
+            return false;
+        };
+
+        for (const char in adj) {
+            if (dfs(char)) return "";
+        }
+
+        res.reverse();
+        return res.join("");
+    }
+}
+```
+
+```csharp
+public class Solution {
+    private Dictionary<char, HashSet<char>> adj;
+    private Dictionary<char, bool> visited;
+    private List<char> result;
+
+    public string foreignDictionary(string[] words) {
+        adj = new Dictionary<char, HashSet<char>>();
+        foreach (var word in words) {
+            foreach (var c in word) {
+                if (!adj.ContainsKey(c)) {
+                    adj[c] = new HashSet<char>();
+                }
+            }
+        }
+
+        for (int i = 0; i < words.Length - 1; i++) {
+            var w1 = words[i];
+            var w2 = words[i + 1];
+            int minLen = Math.Min(w1.Length, w2.Length);
+            if (w1.Length > w2.Length && w1.Substring(0, minLen) == w2.Substring(0, minLen)) {
+                return "";
+            }
+            for (int j = 0; j < minLen; j++) {
+                if (w1[j] != w2[j]) {
+                    adj[w1[j]].Add(w2[j]);
+                    break;
+                }
+            }
+        }
+
+        visited = new Dictionary<char, bool>();
+        result = new List<char>();
+        foreach (var c in adj.Keys) {
+            if (dfs(c)) {
+                return "";
+            }
+        }
+
+        result.Reverse();
+        var sb = new StringBuilder();
+        foreach (var c in result) {
+            sb.Append(c);
+        }
+        return sb.ToString();
+    }
+
+    private bool dfs(char ch) {
+        if (visited.ContainsKey(ch)) {
+            return visited[ch];
+        }
+
+        visited[ch] = true;
+        foreach (var next in adj[ch]) {
+            if (dfs(next)) {
+                return true;
+            }
+        }
+        visited[ch] = false;
+        result.Add(ch);
+        return false;
+    }
+}
+```
+
+```go
+func foreignDictionary(words []string) string {
+    adj := make(map[rune]map[rune]struct{})
+    for _, w := range words {
+        for _, c := range w {
+            if _, exists := adj[c]; !exists {
+                adj[c] = make(map[rune]struct{})
+            }
+        }
+    }
+
+    for i := 0; i < len(words)-1; i++ {
+        w1, w2 := words[i], words[i+1]
+        minLen := len(w1)
+        if len(w2) < minLen {
+            minLen = len(w2)
+        }
+        if len(w1) > len(w2) && w1[:minLen] == w2[:minLen] {
+            return ""
+        }
+        for j := 0; j < minLen; j++ {
+            if w1[j] != w2[j] {
+                adj[rune(w1[j])][rune(w2[j])] = struct{}{}
+                break
+            }
+        }
+    }
+
+    visited := make(map[rune]int)
+    var res []rune
+
+    var dfs func(char rune) bool
+    dfs = func(char rune) bool {
+        if status, exists := visited[char]; exists {
+            return status == 1
+        }
+
+        visited[char] = 1
+
+        for neighChar := range adj[char] {
+            if dfs(neighChar) {
+                return true
+            }
+        }
+
+        visited[char] = -1
+        res = append(res, char)
+        return false
+    }
+
+    for char := range adj {
+        if dfs(char) {
+            return ""
+        }
+    }
+
+    var result []byte
+    for i := len(res) - 1; i >= 0; i-- {
+        result = append(result, byte(res[i]))
+    }
+
+    return string(result)
+}
+```
+
+```kotlin
+class Solution {
+    fun foreignDictionary(words: Array<String>): String {
+        val adj = HashMap<Char, HashSet<Char>>()
+        for (w in words) {
+            for (c in w) {
+                adj.putIfAbsent(c, hashSetOf())
+            }
+        }
+
+        for (i in 0 until words.size - 1) {
+            val w1 = words[i]
+            val w2 = words[i + 1]
+            val minLen = minOf(w1.length, w2.length)
+            if (w1.length > w2.length && 
+                w1.substring(0, minLen) == w2.substring(0, minLen)) {
+                return ""
+            }
+            for (j in 0 until minLen) {
+                if (w1[j] != w2[j]) {
+                    adj[w1[j]]?.add(w2[j])
+                    break
+                }
+            }
+        }
+
+        val visited = HashMap<Char, Int>()
+        val res = mutableListOf<Char>()
+
+        fun dfs(char: Char): Boolean {
+            if (char in visited) {
+                return visited[char] == 1
+            }
+
+            visited[char] = 1
+
+            for (neighChar in adj[char] ?: emptySet()) {
+                if (dfs(neighChar)) {
+                    return true
+                }
+            }
+
+            visited[char] = -1
+            res.add(char)
+            return false
+        }
+
+        for (char in adj.keys) {
+            if (dfs(char)) {
+                return ""
+            }
+        }
+
+        return res.reversed().joinToString("")
+    }
+}
+```
+
+```swift
+class Solution {
+    func foreignDictionary(_ words: [String]) -> String {
+        var adj = [Character: Set<Character>]()
+        for word in words {
+            for char in word {
+                if adj[char] == nil {
+                    adj[char] = Set<Character>()
+                }
+            }
+        }
+        
+        for i in 0..<words.count - 1 {
+            let w1 = words[i]
+            let w2 = words[i + 1]
+            let minLen = min(w1.count, w2.count)
+            if w1.count > w2.count && String(w1.prefix(minLen)) == String(w2.prefix(minLen)) {
+                return ""
+            }
+            for j in 0..<minLen {
+                let index1 = w1.index(w1.startIndex, offsetBy: j)
+                let index2 = w2.index(w2.startIndex, offsetBy: j)
+                if w1[index1] != w2[index2] {
+                    adj[w1[index1]]?.insert(w2[index2])
+                    break
+                }
+            }
+        }
+        
+        var visited = [Character: Bool]()
+        var res = [Character]()
+        
+        func dfs(_ char: Character) -> Bool {
+            if let flag = visited[char] {
+                return flag
+            }
+            visited[char] = true
+            for neigh in adj[char]! {
+                if dfs(neigh) {
+                    return true
+                }
+            }
+            visited[char] = false
+            res.append(char)
+            return false
+        }
+        
+        for char in adj.keys {
+            if dfs(char) {
+                return ""
+            }
+        }
+        
+        res.reverse()
+        return String(res)
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(N + V + E)$
+* Space complexity: $O(V + E)$
+
+> Where $V$ is the number of unique characters, $E$ is the number of edges and $N$ is the sum of lengths of all the strings.
+
+---
+
+## 2. Topological Sort (Kahn's Algorithm)
+
+::tabs-start
+
+```python
+class Solution:
+    def foreignDictionary(self, words):
+        adj = {c: set() for w in words for c in w}
+        indegree = {c: 0 for c in adj}
+        
+        for i in range(len(words) - 1):
+            w1, w2 = words[i], words[i + 1]
+            minLen = min(len(w1), len(w2))
+            if len(w1) > len(w2) and w1[:minLen] == w2[:minLen]:
+                return ""
+            for j in range(minLen):
+                if w1[j] != w2[j]:
+                    if w2[j] not in adj[w1[j]]:
+                        adj[w1[j]].add(w2[j])
+                        indegree[w2[j]] += 1
+                    break
+        
+        q = deque([c for c in indegree if indegree[c] == 0])
+        res = []
+        
+        while q:
+            char = q.popleft()
+            res.append(char)
+            for neighbor in adj[char]:
+                indegree[neighbor] -= 1
+                if indegree[neighbor] == 0:
+                    q.append(neighbor)
+        
+        if len(res) != len(indegree):
+            return ""
+        
+        return "".join(res)
+```
+
+```java
+public class Solution {
+    public String foreignDictionary(String[] words) {
+        Map<Character, Set<Character>> adj = new HashMap<>();
+        Map<Character, Integer> indegree = new HashMap<>();
+        
+        for (String word : words) {
+            for (char c : word.toCharArray()) {
+                adj.putIfAbsent(c, new HashSet<>());
+                indegree.putIfAbsent(c, 0);
+            }
+        }
+
+        for (int i = 0; i < words.length - 1; i++) {
+            String w1 = words[i];
+            String w2 = words[i + 1];
+            int minLen = Math.min(w1.length(), w2.length());
+            if (w1.length() > w2.length() && 
+                w1.substring(0, minLen).equals(w2.substring(0, minLen))) {
+                return "";
+            }
+            for (int j = 0; j < minLen; j++) {
+                if (w1.charAt(j) != w2.charAt(j)) {
+                    if (!adj.get(w1.charAt(j)).contains(w2.charAt(j))) {
+                        adj.get(w1.charAt(j)).add(w2.charAt(j));
+                        indegree.put(w2.charAt(j), 
+                                     indegree.get(w2.charAt(j)) + 1);
+                    }
+                    break;
+                }
+            }
+        }
+
+        Queue<Character> q = new LinkedList<>();
+        for (char c : indegree.keySet()) {
+            if (indegree.get(c) == 0) {
+                q.offer(c);
+            }
+        }
+
+        StringBuilder res = new StringBuilder();
+        while (!q.isEmpty()) {
+            char char_ = q.poll();
+            res.append(char_);
+            for (char neighbor : adj.get(char_)) {
+                indegree.put(neighbor, indegree.get(neighbor) - 1);
+                if (indegree.get(neighbor) == 0) {
+                    q.offer(neighbor);
+                }
+            }
+        }
+
+        if (res.length() != indegree.size()) {
+            return "";
+        }
+
+        return res.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string foreignDictionary(vector<string>& words) {
+        unordered_map<char, unordered_set<char>> adj;
+        unordered_map<char, int> indegree;
+        for (string w : words) {
+            for (char c : w) {
+                adj[c] = unordered_set<char>();
+                indegree[c] = 0;
+            }
+        }
+        
+        for (int i = 0; i < words.size() - 1; i++) {
+            string w1 = words[i], w2 = words[i + 1];
+            int minLen = min(w1.size(), w2.size());
+            if (w1.size() > w2.size() && 
+                w1.substr(0, minLen) == w2.substr(0, minLen)) {
+                return "";
+            }
+            for (int j = 0; j < minLen; j++) {
+                if (w1[j] != w2[j]) {
+                    if (!adj[w1[j]].count(w2[j])) {
+                        adj[w1[j]].insert(w2[j]);
+                        indegree[w2[j]]++;
+                    }
+                    break;
+                }
+            }
+        }
+        
+        queue<char> q;
+        for (auto &[c, deg] : indegree) {
+            if (deg == 0) {
+                q.push(c);
+            }
+        }
+        
+        string res;
+        while (!q.empty()) {
+            char char_ = q.front();
+            q.pop();
+            res += char_;
+            for (char neighbor : adj[char_]) {
+                indegree[neighbor]--;
+                if (indegree[neighbor] == 0) {
+                    q.push(neighbor);
+                }
+            }
+        }
+        
+        return res.size() == indegree.size() ? res : "";
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @returns {string}
+     */
+    foreignDictionary(words) {
+        let adj = {};
+        let indegree = {};
+        for (let w of words) {
+            for (let c of w) {
+                adj[c] = new Set();
+                indegree[c] = 0;
+            }
+        }
+        
+        for (let i = 0; i < words.length - 1; i++) {
+            let w1 = words[i], w2 = words[i + 1];
+            let minLen = Math.min(w1.length, w2.length);
+            if (w1.length > w2.length && 
+                w1.slice(0, minLen) === w2.slice(0, minLen)) {
+                return "";
+            }
+            for (let j = 0; j < minLen; j++) {
+                if (w1[j] !== w2[j]) {
+                    if (!adj[w1[j]].has(w2[j])) {
+                        adj[w1[j]].add(w2[j]);
+                        indegree[w2[j]] += 1;
+                    }
+                    break;
+                }
+            }
+        }
+        
+        let q = new Queue();
+        for (let c in indegree) {
+            if (indegree[c] === 0) {
+                q.push(c);
+            }
+        }
+        
+        let res = [];
+        while (!q.isEmpty()) {
+            let char = q.pop();
+            res.push(char);
+            for (let neighbor of adj[char]) {
+                indegree[neighbor] -= 1;
+                if (indegree[neighbor] === 0) {
+                    q.push(neighbor);
+                }
+            }
+        }
+        
+        if (res.length !== Object.keys(indegree).length) {
+            return "";
+        }
+        
+        return res.join("");
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public string foreignDictionary(string[] words) {
+        var adj = new Dictionary<char, HashSet<char>>();
+        var indegree = new Dictionary<char, int>();
+
+        foreach (var word in words) {
+            foreach (var c in word) {
+                if (!adj.ContainsKey(c)) {
+                    adj[c] = new HashSet<char>();
+                }
+                if (!indegree.ContainsKey(c)) {
+                    indegree[c] = 0;
+                }
+            }
+        }
+
+        for (int i = 0; i < words.Length - 1; i++) {
+            var w1 = words[i];
+            var w2 = words[i + 1];
+            int minLen = Math.Min(w1.Length, w2.Length);
+            if (w1.Length > w2.Length && 
+                w1.Substring(0, minLen) == w2.Substring(0, minLen)) {
+                return "";
+            }
+            for (int j = 0; j < minLen; j++) {
+                if (w1[j] != w2[j]) {
+                    if (!adj[w1[j]].Contains(w2[j])) {
+                        adj[w1[j]].Add(w2[j]);
+                        indegree[w2[j]]++;
+                    }
+                    break;
+                }
+            }
+        }
+
+        var q = new Queue<char>();
+        foreach (var c in indegree.Keys) {
+            if (indegree[c] == 0) {
+                q.Enqueue(c);
+            }
+        }
+
+        var res = new StringBuilder();
+        while (q.Count > 0) {
+            var char_ = q.Dequeue();
+            res.Append(char_);
+            foreach (var neighbor in adj[char_]) {
+                indegree[neighbor]--;
+                if (indegree[neighbor] == 0) {
+                    q.Enqueue(neighbor);
+                }
+            }
+        }
+
+        if (res.Length != indegree.Count) {
+            return "";
+        }
+
+        return res.ToString();
+    }
+}
+```
+
+```go
+func foreignDictionary(words []string) string {
+    adj := make(map[byte]map[byte]struct{})
+    indegree := make(map[byte]int)
+    
+    for _, word := range words {
+        for i := 0; i < len(word); i++ {
+            char := word[i]
+            if _, exists := adj[char]; !exists {
+                adj[char] = make(map[byte]struct{})
+            }
+            indegree[char] = 0
+        }
+    }
+    
+    for i := 0; i < len(words)-1; i++ {
+        w1, w2 := words[i], words[i+1]
+        minLen := len(w1)
+        if len(w2) < minLen {
+            minLen = len(w2)
+        }
+        
+        if len(w1) > len(w2) && w1[:minLen] == w2[:minLen] {
+            return ""
+        }
+        
+        for j := 0; j < minLen; j++ {
+            if w1[j] != w2[j] {
+                if _, exists := adj[w1[j]][w2[j]]; !exists {
+                    adj[w1[j]][w2[j]] = struct{}{}
+                    indegree[w2[j]]++
+                }
+                break
+            }
+        }
+    }
+    
+    q := []byte{}
+    for char := range indegree {
+        if indegree[char] == 0 {
+            q = append(q, char)
+        }
+    }
+    
+    res := []byte{}
+    for len(q) > 0 {
+        char := q[0]
+        q = q[1:]
+        res = append(res, char)
+        
+        for neighbor := range adj[char] {
+            indegree[neighbor]--
+            if indegree[neighbor] == 0 {
+                q = append(q, neighbor)
+            }
+        }
+    }
+    
+    if len(res) != len(indegree) {
+        return ""
+    }
+    
+    return string(res)
+}
+```
+
+```kotlin
+class Solution {
+    fun foreignDictionary(words: Array<String>): String {
+        val adj = HashMap<Char, HashSet<Char>>()
+        val indegree = HashMap<Char, Int>()
+        
+        for (word in words) {
+            for (c in word) {
+                adj.computeIfAbsent(c) { hashSetOf() }
+                indegree[c] = 0
+            }
+        }
+        
+        for (i in 0 until words.size - 1) {
+            val w1 = words[i]
+            val w2 = words[i + 1]
+            val minLen = minOf(w1.length, w2.length)
+            
+            if (w1.length > w2.length && 
+                w1.substring(0, minLen) == w2.substring(0, minLen)) {
+                return ""
+            }
+            
+            for (j in 0 until minLen) {
+                if (w1[j] != w2[j]) {
+                    if (w2[j] !in adj[w1[j]]!!) {
+                        adj[w1[j]]!!.add(w2[j])
+                        indegree[w2[j]] = indegree[w2[j]]!! + 1
+                    }
+                    break
+                }
+            }
+        }
+        
+        val q: Queue<Char> = LinkedList()
+        for ((char, degree) in indegree) {
+            if (degree == 0) {
+                q.add(char)
+            }
+        }
+        
+        val res = StringBuilder()
+        while (q.isNotEmpty()) {
+            val char = q.poll()
+            res.append(char)
+            
+            for (neighbor in adj[char]!!) {
+                indegree[neighbor] = indegree[neighbor]!! - 1
+                if (indegree[neighbor] == 0) {
+                    q.add(neighbor)
+                }
+            }
+        }
+        
+        return if (res.length != indegree.size) "" else res.toString()
+    }
+}
+```
+
+```swift
+class Solution {
+    func foreignDictionary(_ words: [String]) -> String {
+        var adj = [Character: Set<Character>]()
+        for word in words {
+            for char in word {
+                adj[char] = Set<Character>()
+            }
+        }
+        
+        var indegree = [Character: Int]()
+        for key in adj.keys {
+            indegree[key] = 0
+        }
+        
+        for i in 0..<words.count - 1 {
+            let w1 = words[i]
+            let w2 = words[i + 1]
+            let minLen = min(w1.count, w2.count)
+            if w1.count > w2.count && String(w1.prefix(minLen)) == String(w2.prefix(minLen)) {
+                return ""
+            }
+            let w1Arr = Array(w1)
+            let w2Arr = Array(w2)
+            for j in 0..<minLen {
+                if w1Arr[j] != w2Arr[j] {
+                    if !adj[w1Arr[j]]!.contains(w2Arr[j]) {
+                        adj[w1Arr[j]]!.insert(w2Arr[j])
+                        indegree[w2Arr[j]]! += 1
+                    }
+                    break
+                }
+            }
+        }
+        
+        var q = Deque<Character>()
+        for (c, deg) in indegree {
+            if deg == 0 {
+                q.append(c)
+            }
+        }
+        
+        var res = [Character]()
+        while !q.isEmpty {
+            let char = q.removeFirst()
+            res.append(char)
+            for neighbor in adj[char]! {
+                indegree[neighbor]! -= 1
+                if indegree[neighbor]! == 0 {
+                    q.append(neighbor)
+                }
+            }
+        }
+        
+        if res.count != indegree.count {
+            return ""
+        }
+        
+        return String(res)
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(N + V + E)$
+* Space complexity: $O(V + E)$
+
+> Where $V$ is the number of unique characters, $E$ is the number of edges and $N$ is the sum of lengths of all the strings.
\ No newline at end of file
diff --git a/articles/freedom-trail.md b/articles/freedom-trail.md
new file mode 100644
index 000000000..9c7ef1c89
--- /dev/null
+++ b/articles/freedom-trail.md
@@ -0,0 +1,845 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def findRotateSteps(self, ring: str, key: str) -> int:
+        def dfs(r, k):
+            if k == len(key):
+                return 0
+
+            res = float("inf")
+            for i, c in enumerate(ring):
+                if c == key[k]:
+                    min_dist = min(abs(r - i), len(ring) - abs(r - i))
+                    res = min(res, min_dist + 1 + dfs(i, k + 1))
+            return res
+
+        return dfs(0, 0)
+```
+
+```java
+public class Solution {
+    public int findRotateSteps(String ring, String key) {
+        return dfs(0, 0, ring, key);
+    }
+
+    private int dfs(int r, int k, String ring, String key) {
+        if (k == key.length()) return 0;
+
+        int res = Integer.MAX_VALUE;
+        for (int i = 0; i < ring.length(); i++) {
+            if (ring.charAt(i) == key.charAt(k)) {
+                int minDist = Math.min(Math.abs(r - i), ring.length() - Math.abs(r - i));
+                res = Math.min(res, minDist + 1 + dfs(i, k + 1, ring, key));
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findRotateSteps(string ring, string key) {
+        return dfs(0, 0, ring, key);
+    }
+
+private:
+    int dfs(int r, int k, const string& ring, const string& key) {
+        if (k == key.size()) return 0;
+
+        int res = INT_MAX;
+        for (int i = 0; i < ring.size(); i++) {
+            if (ring[i] == key[k]) {
+                int minDist = min(abs(r - i), int(ring.size()) - abs(r - i));
+                res = min(res, minDist + 1 + dfs(i, k + 1, ring, key));
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} ring
+     * @param {string} key
+     * @return {number}
+     */
+    findRotateSteps(ring, key) {
+        const dfs = (r, k) => {
+            if (k === key.length) return 0;
+
+            let res = Infinity;
+            for (let i = 0; i < ring.length; i++) {
+                if (ring[i] === key[k]) {
+                    const minDist = Math.min(
+                        Math.abs(r - i),
+                        ring.length - Math.abs(r - i)
+                    );
+                    res = Math.min(res, minDist + 1 + dfs(i, k + 1));
+                }
+            }
+            return res;
+        };
+
+        return dfs(0, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ m)$
+* Space complexity: $O(m)$ for recursion stack.
+
+> Where $n$ is the length of the $ring$ and $m$ is the length of the $key$.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def findRotateSteps(self, ring: str, key: str) -> int:
+        n = len(ring)
+        m = len(key)
+        dp = {}
+
+        def dfs(r, k):
+            if k == m:
+                return 0
+            if (r, k) in dp:
+                return dp[(r, k)]
+
+            res = float("inf")
+            for i, c in enumerate(ring):
+                if c == key[k]:
+                    min_dist = min(abs(r - i), n - abs(r - i))
+                    res = min(res, min_dist + 1 + dfs(i, k + 1))
+            dp[(r, k)] = res
+            return res
+
+        return dfs(0, 0)
+```
+
+```java
+public class Solution {
+    private int[][] dp;
+
+    public int findRotateSteps(String ring, String key) {
+        int n = ring.length();
+        int m = key.length();
+        dp = new int[n][m];
+        for (int[] row : dp) {
+            Arrays.fill(row, -1);
+        }
+        return dfs(0, 0, ring, key);
+    }
+
+    private int dfs(int r, int k, String ring, String key) {
+        if (k == key.length()) return 0;
+        if (dp[r][k] != -1) return dp[r][k];
+
+        int res = Integer.MAX_VALUE;
+        for (int i = 0; i < ring.length(); i++) {
+            if (ring.charAt(i) == key.charAt(k)) {
+                int minDist = Math.min(Math.abs(r - i), ring.length() - Math.abs(r - i));
+                res = Math.min(res, minDist + 1 + dfs(i, k + 1, ring, key));
+            }
+        }
+
+        dp[r][k] = res;
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+    vector<vector<int>> dp;
+
+public:
+    int findRotateSteps(string ring, string key) {
+        int n = ring.size();
+        int m = key.size();
+        dp.assign(n, vector<int>(m, -1));
+        return dfs(0, 0, ring, key);
+    }
+
+private:
+    int dfs(int r, int k, string& ring, string& key) {
+        if (k == key.size()) return 0;
+        if (dp[r][k] != -1) return dp[r][k];
+
+        int res = INT_MAX;
+        for (int i = 0; i < ring.size(); i++) {
+            if (ring[i] == key[k]) {
+                int minDist = min(abs(r - i), int(ring.size()) - abs(r - i));
+                res = min(res, minDist + 1 + dfs(i, k + 1, ring, key));
+            }
+        }
+
+        dp[r][k] = res;
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} ring
+     * @param {string} key
+     * @return {number}
+     */
+    findRotateSteps(ring, key) {
+        const n = ring.length;
+        const m = key.length;
+        const dp = Array.from({ length: n }, () => Array(m).fill(-1));
+
+        const dfs = (r, k) => {
+            if (k === key.length) return 0;
+            if (dp[r][k] !== -1) return dp[r][k];
+
+            let res = Infinity;
+            for (let i = 0; i < ring.length; i++) {
+                if (ring[i] === key[k]) {
+                    const minDist = Math.min(
+                        Math.abs(r - i),
+                        ring.length - Math.abs(r - i)
+                    );
+                    res = Math.min(res, minDist + 1 + dfs(i, k + 1));
+                }
+            }
+
+            dp[r][k] = res;
+            return res;
+        };
+
+        return dfs(0, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 * m)$
+* Space complexity: $O(n * m)$
+
+> Where $n$ is the length of the $ring$ and $m$ is the length of the $key$.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def findRotateSteps(self, ring: str, key: str) -> int:
+        n = len(ring)
+        m = len(key)
+        dp = [[float("inf")] * n for _ in range(m + 1)]
+
+        for i in range(n):
+            dp[m][i] = 0
+
+        for k in range(m - 1, -1, -1):
+            for r in range(n):
+                for i in range(n):
+                    if ring[i] == key[k]:
+                        min_dist = min(abs(r - i), n - abs(r - i))
+                        dp[k][r] = min(dp[k][r], min_dist + 1 + dp[k + 1][i])
+
+        return dp[0][0]
+```
+
+```java
+public class Solution {
+    public int findRotateSteps(String ring, String key) {
+        int n = ring.length();
+        int m = key.length();
+        int[][] dp = new int[m + 1][n];
+        for (int i = 0; i <= m; i++) {
+            for (int j = 0; j < n; j++) {
+                dp[i][j] = Integer.MAX_VALUE;
+            }
+        }
+
+        for (int i = 0; i < n; i++) {
+            dp[m][i] = 0;
+        }
+
+        for (int k = m - 1; k >= 0; k--) {
+            for (int r = 0; r < n; r++) {
+                for (int i = 0; i < n; i++) {
+                    if (ring.charAt(i) == key.charAt(k)) {
+                        int minDist = Math.min(Math.abs(r - i), n - Math.abs(r - i));
+                        dp[k][r] = Math.min(dp[k][r], minDist + 1 + dp[k + 1][i]);
+                    }
+                }
+            }
+        }
+        return dp[0][0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findRotateSteps(string ring, string key) {
+        int n = ring.size();
+        int m = key.size();
+        vector<vector<int>> dp(m + 1, vector<int>(n, INT_MAX));
+
+        for (int i = 0; i < n; ++i) {
+            dp[m][i] = 0;
+        }
+
+        for (int k = m - 1; k >= 0; --k) {
+            for (int r = 0; r < n; ++r) {
+                for (int i = 0; i < n; ++i) {
+                    if (ring[i] == key[k]) {
+                        int minDist = min(abs(r - i), n - abs(r - i));
+                        dp[k][r] = min(dp[k][r], minDist + 1 + dp[k + 1][i]);
+                    }
+                }
+            }
+        }
+        return dp[0][0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} ring
+     * @param {string} key
+     * @return {number}
+     */
+    findRotateSteps(ring, key) {
+        const n = ring.length;
+        const m = key.length;
+        const dp = Array.from({ length: m + 1 }, () =>
+            Array(n).fill(Infinity)
+        );
+
+        for (let i = 0; i < n; i++) {
+            dp[m][i] = 0;
+        }
+
+        for (let k = m - 1; k >= 0; k--) {
+            for (let r = 0; r < n; r++) {
+                for (let i = 0; i < n; i++) {
+                    if (ring[i] === key[k]) {
+                        const minDist = Math.min(Math.abs(r - i), n - Math.abs(r - i));
+                        dp[k][r] = Math.min(dp[k][r], minDist + 1 + dp[k + 1][i]);
+                    }
+                }
+            }
+        }
+        return dp[0][0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 * m)$
+* Space complexity: $O(n * m)$
+
+> Where $n$ is the length of the $ring$ and $m$ is the length of the $key$.
+
+---
+
+## 4. Dynamic Programming (Space Optimized) - I
+
+::tabs-start
+
+```python
+class Solution:
+    def findRotateSteps(self, ring: str, key: str) -> int:
+        n = len(ring)
+        m = len(key)
+        dp = [0] * n
+
+        adj = [[] for _ in range(26)]
+        for i in range(n):
+            adj[ord(ring[i]) - ord('a')].append(i)
+
+        for k in range(m - 1, -1, -1):
+            next_dp = [float("inf")] * n
+            for r in range(n):
+                for i in adj[ord(key[k]) - ord('a')]:
+                    min_dist = min(abs(r - i), n - abs(r - i))
+                    next_dp[r] = min(next_dp[r], min_dist + 1 + dp[i])
+            dp = next_dp
+
+        return dp[0]
+```
+
+```java
+public class Solution {
+    public int findRotateSteps(String ring, String key) {
+        int n = ring.length();
+        int m = key.length();
+        int[] dp = new int[n];
+
+        List<Integer>[] adj = new ArrayList[26];
+        for (int i = 0; i < 26; i++) {
+            adj[i] = new ArrayList<>();
+        }
+        for (int i = 0; i < n; i++) {
+            adj[ring.charAt(i) - 'a'].add(i);
+        }
+
+        for (int k = m - 1; k >= 0; k--) {
+            int[] nextDp = new int[n];
+            Arrays.fill(nextDp, Integer.MAX_VALUE);
+            for (int r = 0; r < n; r++) {
+                for (int i : adj[key.charAt(k) - 'a']) {
+                    int minDist = Math.min(Math.abs(r - i), n - Math.abs(r - i));
+                    nextDp[r] = Math.min(nextDp[r], minDist + 1 + dp[i]);
+                }
+            }
+            dp = nextDp;
+        }
+
+        return dp[0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findRotateSteps(string ring, string key) {
+        int n = ring.size();
+        int m = key.size();
+        vector<int> dp(n, 0);
+
+        vector<vector<int>> adj(26);
+        for (int i = 0; i < n; ++i) {
+            adj[ring[i] - 'a'].push_back(i);
+        }
+
+        for (int k = m - 1; k >= 0; --k) {
+            vector<int> nextDp(n, INT_MAX);
+            for (int r = 0; r < n; ++r) {
+                for (int& i : adj[key[k] - 'a']) {
+                    int minDist = min(abs(r - i), n - abs(r - i));
+                    nextDp[r] = min(nextDp[r], minDist + 1 + dp[i]);
+                }
+            }
+            dp = nextDp;
+        }
+
+        return dp[0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} ring
+     * @param {string} key
+     * @return {number}
+     */
+    findRotateSteps(ring, key) {
+        const n = ring.length;
+        const m = key.length;
+        let dp = new Array(n).fill(0);
+
+        const adj = Array.from({ length: 26 }, () => []);
+        for (let i = 0; i < n; i++) {
+            adj[ring.charCodeAt(i) - 97].push(i);
+        }
+
+        for (let k = m - 1; k >= 0; k--) {
+            const nextDp = new Array(n).fill(Infinity);
+            for (let r = 0; r < n; r++) {
+                for (const i of adj[key.charCodeAt(k) - 97]) {
+                    const minDist = Math.min(Math.abs(r - i), n - Math.abs(r - i));
+                    nextDp[r] = Math.min(nextDp[r], minDist + 1 + dp[i]);
+                }
+            }
+            dp = nextDp;
+        }
+
+        return dp[0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 * m)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the length of the $ring$ and $m$ is the length of the $key$.
+
+---
+
+## 5. Dynamic Programming (Space optimized) - II
+
+::tabs-start
+
+```python
+class Solution:
+    def findRotateSteps(self, ring: str, key: str) -> int:
+        n = len(ring)
+        m = len(key)
+        dp = [min(i, n - i) for i in range(n)]
+
+        adj = [[] for _ in range(26)]
+        for i in range(n):
+            adj[ord(ring[i]) - ord('a')].append(i)
+
+        for k in range(1, m):
+            for r in adj[ord(key[k]) - ord('a')]:
+                min_dist = float("inf")
+                for i in adj[ord(key[k - 1]) - ord('a')]:
+                    min_dist = min(
+                        min_dist,
+                        min(abs(r - i), n - abs(r - i)) + dp[i]
+                    )
+                dp[r] = min_dist
+
+        return min(dp[i] for i in adj[ord(key[-1]) - ord('a')]) + m
+```
+
+```java
+public class Solution {
+    public int findRotateSteps(String ring, String key) {
+        int n = ring.length();
+        int m = key.length();
+        int[] dp = new int[n];
+
+        for (int i = 0; i < n; i++) {
+            dp[i] = Math.min(i, n - i);
+        }
+
+        List<Integer>[] adj = new ArrayList[26];
+        for (int i = 0; i < 26; i++) {
+            adj[i] = new ArrayList<>();
+        }
+
+        for (int i = 0; i < n; i++) {
+            adj[ring.charAt(i) - 'a'].add(i);
+        }
+
+        for (int k = 1; k < m; k++) {
+            for (int r : adj[key.charAt(k) - 'a']) {
+                int minDist = Integer.MAX_VALUE;
+                for (int i : adj[key.charAt(k - 1) - 'a']) {
+                    minDist = Math.min(minDist, 
+                                Math.min(Math.abs(r - i), n - Math.abs(r - i)) + dp[i]
+                    );
+                }
+                dp[r] = minDist;
+            }
+        }
+
+        int result = Integer.MAX_VALUE;
+        for (int i : adj[key.charAt(m - 1) - 'a']) {
+            result = Math.min(result, dp[i]);
+        }
+
+        return result + m;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findRotateSteps(string ring, string key) {
+        int n = ring.size(), m = key.size();
+        vector<int> dp(n);
+
+        for (int i = 0; i < n; i++) {
+            dp[i] = min(i, n - i);
+        }
+
+        vector<vector<int>> adj(26);
+        for (int i = 0; i < n; i++) {
+            adj[ring[i] - 'a'].push_back(i);
+        }
+
+        for (int k = 1; k < m; k++) {
+            for (int r : adj[key[k] - 'a']) {
+                int minDist = INT_MAX;
+                for (int i : adj[key[k - 1] - 'a']) {
+                    minDist = min(minDist, min(abs(r - i), n - abs(r - i)) + dp[i]);
+                }
+                dp[r] = minDist;
+            }
+        }
+
+        int result = INT_MAX;
+        for (int& i : adj[key[m - 1] - 'a']) {
+            result = min(result, dp[i]);
+        }
+
+        return result + m;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} ring
+     * @param {string} key
+     * @return {number}
+     */
+    findRotateSteps(ring, key) {
+        const n = ring.length;
+        const m = key.length;
+        const dp = Array(n).fill(0).map((_, i) => Math.min(i, n - i));
+
+        const adj = Array.from({ length: 26 }, () => []);
+        for (let i = 0; i < n; i++) {
+            adj[ring.charCodeAt(i) - 97].push(i);
+        }
+
+        for (let k = 1; k < m; k++) {
+            for (let r of adj[key.charCodeAt(k) - 97]) {
+                let minDist = Infinity;
+                for (let i of adj[key.charCodeAt(k - 1) - 97]) {
+                    minDist = Math.min(minDist, 
+                                Math.min(Math.abs(r - i), n - Math.abs(r - i)) + dp[i]
+                    );
+                }
+                dp[r] = minDist;
+            }
+        }
+
+        return Math.min(...adj[key.charCodeAt(m - 1) - 97].map(i => dp[i])) + m;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 * m)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the length of the $ring$ and $m$ is the length of the $key$.
+
+---
+
+## 6. Dynamic Programming (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def findRotateSteps(self, ring: str, key: str) -> int:
+        n = len(ring)
+        m = len(key)
+        
+        dp = [0] * n
+        next_dp = [0] * n
+        
+        adj = [[] for _ in range(26)]
+        for i, c in enumerate(ring):
+            adj[ord(c) - ord('a')].append(i)
+        
+        for k in range(m - 1, -1, -1):
+            c = ord(key[k]) - ord('a')
+            it, N = 0, len(adj[c])
+
+            for r in range(n):
+                if ord(ring[r]) - ord('a') != c:
+                    next_dp[r] = float('inf')
+                    while it < N and adj[c][it] < r:
+                        it += 1
+                    
+                    nextIdx = adj[c][it] if it < N else adj[c][0]
+                    prevIdx = adj[c][it - 1] if it > 0 else adj[c][-1]
+                    
+                    next_dp[r] = min(
+                        (r - prevIdx if r > prevIdx else n - (prevIdx - r)) + dp[prevIdx],
+                        (nextIdx - r if nextIdx > r else n - (r - nextIdx)) + dp[nextIdx]
+                    )
+                else:
+                    next_dp[r] = dp[r]
+            
+            dp, next_dp = next_dp, dp
+        
+        return dp[0] + m
+```
+
+```java
+public class Solution {
+    public int findRotateSteps(String ring, String key) {
+        int n = ring.length();
+        int m = key.length();
+        
+        int[] dp = new int[n];
+        int[] nextDp = new int[n];
+        List<Integer>[] adj = new ArrayList[26];
+        
+        for (int i = 0; i < 26; i++) {
+            adj[i] = new ArrayList<>();
+        }
+        for (int i = 0; i < n; i++) {
+            adj[ring.charAt(i) - 'a'].add(i);
+        }
+        
+        for (int k = m - 1; k >= 0; k--) {
+            int c = key.charAt(k) - 'a';
+            int it = 0, N = adj[c].size();
+            
+            for (int r = 0; r < n; r++) {
+                if (ring.charAt(r) - 'a' != c) {
+                    nextDp[r] = Integer.MAX_VALUE;
+                    while (it < N && adj[c].get(it) < r) {
+                        it++;
+                    }
+                    
+                    int nextIdx = it < N ? adj[c].get(it) : adj[c].get(0);
+                    int prevIdx = it > 0 ? adj[c].get(it - 1) : adj[c].get(N - 1);
+                    
+                    nextDp[r] = Math.min(
+                        (r > prevIdx ? r - prevIdx : n - (prevIdx - r)) + dp[prevIdx],
+                        (nextIdx > r ? nextIdx - r : n - (r - nextIdx)) + dp[nextIdx]
+                    );
+                } else {
+                    nextDp[r] = dp[r];
+                }
+            }
+            
+            int[] temp = dp;
+            dp = nextDp;
+            nextDp = temp;
+        }
+        
+        return dp[0] + m;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findRotateSteps(string ring, string key) {
+        int n = ring.size(), m = key.size();
+        
+        vector<int> dp(n, 0);
+        vector<int> nextDp(n, 0);
+        vector<vector<int>> adj(26);
+        
+        for (int i = 0; i < n; i++) {
+            adj[ring[i] - 'a'].push_back(i);
+        }
+        
+        for (int k = m - 1; k >= 0; k--) {
+            int c = key[k] - 'a';
+            int it = 0, N = adj[c].size();
+            
+            for (int r = 0; r < n; r++) {
+                if (ring[r] - 'a' != c) {
+                    nextDp[r] = INT_MAX;
+                    while (it < N && adj[c][it] < r) {
+                        it++;
+                    }
+                    
+                    int nextIdx = it < N ? adj[c][it] : adj[c][0];
+                    int prevIdx = it > 0 ? adj[c][it - 1] : adj[c][N - 1];
+                    
+                    nextDp[r] = min(
+                        (r > prevIdx ? r - prevIdx : n - (prevIdx - r)) + dp[prevIdx],
+                        (nextIdx > r ? nextIdx - r : n - (r - nextIdx)) + dp[nextIdx]
+                    );
+                } else {
+                    nextDp[r] = dp[r];
+                }
+            }
+            
+            dp.swap(nextDp);
+        }
+        
+        return dp[0] + m;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} ring
+     * @param {string} key
+     * @return {number}
+     */
+    findRotateSteps(ring, key) {
+        const n = ring.length, m = key.length;
+        
+        let dp = Array(n).fill(0);
+        let nextDp = Array(n).fill(0);
+        const adj = Array.from({ length: 26 }, () => []);
+        
+        for (let i = 0; i < n; i++) {
+            adj[ring.charCodeAt(i) - 97].push(i);
+        }
+        
+        for (let k = m - 1; k >= 0; k--) {
+            const c = key.charCodeAt(k) - 97;
+            let it = 0, N = adj[c].length;
+            
+            for (let r = 0; r < n; r++) {
+                if (ring.charCodeAt(r) - 97 !== c) {
+                    nextDp[r] = Infinity;
+                    while (it < N && adj[c][it] < r) {
+                        it++;
+                    }
+                    
+                    const nextIdx = it < N ? adj[c][it] : adj[c][0];
+                    const prevIdx = it > 0 ? adj[c][it - 1] : adj[c][N - 1];
+                    
+                    nextDp[r] = Math.min(
+                        (r > prevIdx ? r - prevIdx : n - (prevIdx - r)) + dp[prevIdx],
+                        (nextIdx > r ? nextIdx - r : n - (r - nextIdx)) + dp[nextIdx]
+                    );
+                } else {
+                    nextDp[r] = dp[r];
+                }
+            }
+            
+            [dp, nextDp] = [nextDp, dp];
+        }
+        
+        return dp[0] + m;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the length of the $ring$ and $m$ is the length of the $key$.
\ No newline at end of file
diff --git a/articles/frequency-of-the-most-frequent-element.md b/articles/frequency-of-the-most-frequent-element.md
new file mode 100644
index 000000000..51c727d97
--- /dev/null
+++ b/articles/frequency-of-the-most-frequent-element.md
@@ -0,0 +1,420 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def maxFrequency(self, nums: List[int], k: int) -> int:
+        nums.sort()
+        res = 1
+        for i in range(len(nums)):
+            j = i - 1
+            tmpK = k
+            while j >= 0 and (tmpK - (nums[i] - nums[j])) >= 0:
+                tmpK -= (nums[i] - nums[j])
+                j -= 1
+            res = max(res, i - j)
+        return res
+```
+
+```java
+public class Solution {
+    public int maxFrequency(int[] nums, int k) {
+        Arrays.sort(nums);
+        int res = 1;
+
+        for (int i = 0; i < nums.length; i++) {
+            int j = i - 1;
+            long tmpK = k;
+
+            while (j >= 0 && (tmpK - (nums[i] - nums[j])) >= 0) {
+                tmpK -= (nums[i] - nums[j]);
+                j--;
+            }
+            res = Math.max(res, i - j);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxFrequency(vector<int>& nums, int k) {
+        sort(nums.begin(), nums.end());
+        int res = 1;
+
+        for (int i = 0; i < nums.size(); i++) {
+            int j = i - 1;
+            long long tmpK = k;
+
+            while (j >= 0 && (tmpK - (nums[i] - nums[j])) >= 0) {
+                tmpK -= (nums[i] - nums[j]);
+                j--;
+            }
+            res = max(res, i - j);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    maxFrequency(nums, k) {
+        nums.sort((a, b) => a - b);
+        let res = 1;
+
+        for (let i = 0; i < nums.length; i++) {
+            let j = i - 1;
+            let tmpK = k;
+
+            while (j >= 0 && (tmpK - (nums[i] - nums[j])) >= 0) {
+                tmpK -= (nums[i] - nums[j]);
+                j--;
+            }
+            res = Math.max(res, i - j);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 + n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 2. Prefix Sum + Binary Search
+
+::tabs-start
+
+```python
+class Solution:
+    def maxFrequency(self, nums: List[int], k: int) -> int:
+        nums.sort()
+        n = len(nums)
+        prefix_sum = [0] * (n + 1)
+        for i in range(n):
+            prefix_sum[i + 1] = prefix_sum[i] + nums[i]
+
+        res = 1
+        for i in range(n):
+            l, r = 0, i
+            while l <= r:
+                m = (l + r) // 2
+                curSum = prefix_sum[i + 1] - prefix_sum[m]
+                need = (i - m + 1) * nums[i] - curSum
+                if need <= k:
+                    r = m - 1
+                    res = max(res, i - m + 1)
+                else:
+                    l = m + 1
+        return res
+```
+
+```java
+public class Solution {
+    public int maxFrequency(int[] nums, int k) {
+        Arrays.sort(nums);
+        int n = nums.length;
+        long[] prefixSum = new long[n + 1];
+        for (int i = 0; i < n; i++) {
+            prefixSum[i + 1] = prefixSum[i] + nums[i];
+        }
+
+        int res = 1;
+        for (int i = 0; i < n; i++) {
+            int left = 0, right = i;
+            while (left <= right) {
+                int mid = (left + right) / 2;
+                long curSum = prefixSum[i + 1] - prefixSum[mid];
+                long need = (i - mid + 1) * 1L * nums[i] - curSum;
+                if (need <= k) {
+                    right = mid - 1;
+                    res = Math.max(res, i - mid + 1);
+                } else {
+                    left = mid + 1;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxFrequency(vector<int>& nums, int k) {
+        sort(nums.begin(), nums.end());
+        int n = nums.size();
+        vector<long long> prefixSum(n + 1, 0);
+        for (int i = 0; i < n; ++i) {
+            prefixSum[i + 1] = prefixSum[i] + nums[i];
+        }
+
+        int res = 1;
+        for (int i = 0; i < n; ++i) {
+            int l = 0, r = i;
+            while (l <= r) {
+                int m = (l + r) / 2;
+                long long curSum = prefixSum[i + 1] - prefixSum[m];
+                long long need = (i - m + 1) * 1LL * nums[i] - curSum;
+                if (need <= k) {
+                    r = m - 1;
+                    res = max(res, i - m + 1);
+                } else {
+                    l = m + 1;
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    maxFrequency(nums, k) {
+        nums.sort((a, b) => a - b);
+        const prefixSum = new Array(nums.length + 1).fill(0);
+        for (let i = 0; i < nums.length; i++) {
+            prefixSum[i + 1] = prefixSum[i] + nums[i];
+        }
+
+        let res = 1;
+        for (let i = 0; i < nums.length; i++) {
+            let left = 0, right = i;
+            while (left <= right) {
+                const mid = Math.floor((left + right) / 2);
+                const curSum = prefixSum[i + 1] - prefixSum[mid];
+                const need = (i - mid + 1) * nums[i] - curSum;
+                if (need <= k) {
+                    right = mid - 1;
+                    res = Math.max(res, i - mid + 1);
+                } else {
+                    left = mid + 1;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Sliding Window
+
+::tabs-start
+
+```python
+class Solution:
+    def maxFrequency(self, nums: List[int], k: int) -> int:
+        nums.sort()
+        total = res = 0
+        l = 0
+
+        for r in range(len(nums)):
+            total += nums[r]
+            while nums[r] * (r - l + 1) > total + k:
+                total -= nums[l]
+                l += 1
+            res = max(res, r - l + 1)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int maxFrequency(int[] nums, int k) {
+        Arrays.sort(nums);
+        long total = 0;
+        int res = 0;
+        int l = 0;
+
+        for (int r = 0; r < nums.length; r++) {
+            total += nums[r];
+            while ((long) nums[r] * (r - l + 1) > total + k) {
+                total -= nums[l];
+                l++;
+            }
+            res = Math.max(res, r - l + 1);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxFrequency(vector<int>& nums, int k) {
+        sort(nums.begin(), nums.end());
+        long long total = 0;
+        int res = 0, l = 0;
+
+        for (int r = 0; r < nums.size(); ++r) {
+            total += nums[r];
+            while ((long long)nums[r] * (r - l + 1) > total + k) {
+                total -= nums[l];
+                l++;
+            }
+            res = max(res, r - l + 1);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    maxFrequency(nums, k) {
+        nums.sort((a, b) => a - b);
+        let total = 0, res = 0, l = 0;
+
+        for (let r = 0; r < nums.length; r++) {
+            total += nums[r];
+            while (nums[r] * (r - l + 1) > total + k) {
+                total -= nums[l];
+                l++;
+            }
+            res = Math.max(res, r - l + 1);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 4. Advanced Sliding Window
+
+::tabs-start
+
+```python
+class Solution:
+    def maxFrequency(self, nums: List[int], k: int) -> int:
+        nums.sort()
+        l = 0
+        total = 0
+        
+        for r in range(len(nums)):
+            total += nums[r]
+            
+            if (r - l + 1) * nums[r] > total + k:
+                total -= nums[l]
+                l += 1
+
+        return len(nums) - l
+```
+
+```java
+public class Solution {
+    public int maxFrequency(int[] nums, int k) {
+        Arrays.sort(nums);
+        long total = 0;
+        int l = 0;
+
+        for (int r = 0; r < nums.length; r++) {
+            total += nums[r];
+            if ((r - l + 1) * 1L * nums[r] > total + k) {
+                total -= nums[l];
+                l++;
+            }
+        }
+
+        return nums.length - l;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxFrequency(vector<int>& nums, int k) {
+        sort(nums.begin(), nums.end());
+        long long total = 0;
+        int l = 0;
+
+        for (int r = 0; r < nums.size(); ++r) {
+            total += nums[r];
+            if ((r - l + 1) * 1L * nums[r] > total + k) {
+                total -= nums[l];
+                l++;
+            }
+        }
+
+        return nums.size() - l;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    maxFrequency(nums, k) {
+        nums.sort((a, b) => a - b);
+        let total = 0, l = 0;
+
+        for (let r = 0; r < nums.length; r++) {
+            total += nums[r];
+            if (nums[r] * (r - l + 1) > total + k) {
+                total -= nums[l];
+                l++;
+            }
+        }
+
+        return nums.length - l;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
\ No newline at end of file
diff --git a/articles/fruit-into-baskets.md b/articles/fruit-into-baskets.md
new file mode 100644
index 000000000..7aa1b5bbe
--- /dev/null
+++ b/articles/fruit-into-baskets.md
@@ -0,0 +1,468 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def totalFruit(self, fruits: List[int]) -> int:
+        n = len(fruits)
+        res = 0
+        for i in range(n):
+            types = set()
+            j = i
+            while j < n and (len(types) < 2 or fruits[j] in types):
+                types.add(fruits[j])
+                j += 1
+            res = max(res, j - i)
+        return res
+```
+
+```java
+public class Solution {
+    public int totalFruit(int[] fruits) {
+        int n = fruits.length, res = 0;
+
+        for (int i = 0; i < n; i++) {
+            Set<Integer> types = new HashSet<>();
+            int j = i;
+
+            while (j < n && (types.size() < 2 || types.contains(fruits[j]))) {
+                types.add(fruits[j]);
+                j++;
+            }
+            res = Math.max(res, j - i);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int totalFruit(vector<int>& fruits) {
+        int n = fruits.size(), res = 0;
+
+        for (int i = 0; i < n; i++) {
+            unordered_set<int> types;
+            int j = i;
+
+            while (j < n && (types.size() < 2 || types.count(fruits[j]))) {
+                types.insert(fruits[j]);
+                j++;
+            }
+            res = max(res, j - i);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} fruits
+     * @return {number}
+     */
+    totalFruit(fruits) {
+        let n = fruits.length, res = 0;
+
+        for (let i = 0; i < n; i++) {
+            let types = new Set();
+            let j = i;
+
+            while (j < n && (types.size < 2 || types.has(fruits[j]))) {
+                types.add(fruits[j]);
+                j++;
+            }
+            res = Math.max(res, j - i);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Sliding Window - I
+
+::tabs-start
+
+```python
+class Solution:
+    def totalFruit(self, fruits: List[int]) -> int:
+        count = defaultdict(int)
+        l, total, res = 0, 0, 0
+        
+        for r in range(len(fruits)):
+            count[fruits[r]] += 1
+            total += 1
+
+            while len(count) > 2:
+                f = fruits[l]
+                count[f] -= 1
+                total -= 1
+                l += 1
+                if not count[f]:
+                    count.pop(f)
+            
+            res = max(res, total)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int totalFruit(int[] fruits) {
+        HashMap<Integer, Integer> count = new HashMap<>();
+        int l = 0, total = 0, res = 0;
+
+        for (int r = 0; r < fruits.length; r++) {
+            count.put(fruits[r], count.getOrDefault(fruits[r], 0) + 1);
+            total++;
+
+            while (count.size() > 2) {
+                int f = fruits[l];
+                count.put(f, count.get(f) - 1);
+                total--;
+                if (count.get(f) == 0) {
+                    count.remove(f);
+                }
+                l++;
+            }
+            res = Math.max(res, total);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int totalFruit(vector<int>& fruits) {
+        unordered_map<int, int> count;
+        int l = 0, total = 0, res = 0;
+
+        for (int r = 0; r < fruits.size(); r++) {
+            count[fruits[r]]++;
+            total++;
+
+            while (count.size() > 2) {
+                int f = fruits[l];
+                count[f]--;
+                total--;
+                if (count[f] == 0) {
+                    count.erase(f);
+                }
+                l++;
+            }
+            res = max(res, total);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} fruits
+     * @return {number}
+     */
+    totalFruit(fruits) {
+        let count = new Map();
+        let l = 0, total = 0, res = 0;
+
+        for (let r = 0; r < fruits.length; r++) {
+            count.set(fruits[r], (count.get(fruits[r]) || 0) + 1);
+            total++;
+
+            while (count.size > 2) {
+                let f = fruits[l];
+                count.set(f, count.get(f) - 1);
+                total--;
+                if (count.get(f) === 0) {
+                    count.delete(f);
+                }
+                l++;
+            }
+            res = Math.max(res, total);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 3. Sliding Window - II
+
+::tabs-start
+
+```python
+class Solution:
+    def totalFruit(self, fruits: List[int]) -> int:
+        count = defaultdict(int)
+        l = 0
+
+        for r in range(len(fruits)):
+            count[fruits[r]] += 1
+
+            if len(count) > 2:
+                count[fruits[l]] -= 1
+                if count[fruits[l]] == 0:
+                    count.pop(fruits[l])
+                l += 1
+        
+        return len(fruits) - l
+```
+
+```java
+public class Solution {
+    public int totalFruit(int[] fruits) {
+        HashMap<Integer, Integer> count = new HashMap<>();
+        int l = 0;
+
+        for (int r = 0; r < fruits.length; r++) {
+            count.put(fruits[r], count.getOrDefault(fruits[r], 0) + 1);
+
+            if (count.size() > 2) {
+                count.put(fruits[l], count.get(fruits[l]) - 1);
+                if (count.get(fruits[l]) == 0) {
+                    count.remove(fruits[l]);
+                }
+                l++;
+            }
+        }
+
+        return fruits.length - l;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int totalFruit(vector<int>& fruits) {
+        unordered_map<int, int> count;
+        int l = 0;
+
+        for (int r = 0; r < fruits.size(); r++) {
+            count[fruits[r]]++;
+
+            if (count.size() > 2) {
+                count[fruits[l]]--;
+                if (count[fruits[l]] == 0) {
+                    count.erase(fruits[l]);
+                }
+                l++;
+            }
+        }
+
+        return fruits.size() - l;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} fruits
+     * @return {number}
+     */
+    totalFruit(fruits) {
+        let count = new Map();
+        let l = 0;
+
+        for (let r = 0; r < fruits.length; r++) {
+            count.set(fruits[r], (count.get(fruits[r]) || 0) + 1);
+
+            if (count.size > 2) {
+                count.set(fruits[l], count.get(fruits[l]) - 1);
+                if (count.get(fruits[l]) === 0) {
+                    count.delete(fruits[l]);
+                }
+                l++;
+            }
+        }
+
+        return fruits.length - l;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 4. Sliding Window - III
+
+::tabs-start
+
+```python
+class Solution:
+    def totalFruit(self, fruits: list[int]) -> int:
+        l = 0
+        fruit1_lastIdx = 0
+        fruit2_lastIdx = -1
+        fruit1 = fruits[0]
+        fruit2 = -1
+        total = res = 1
+
+        for r in range(len(fruits)):
+            f = fruits[r]
+            if f == fruit1:
+                total += 1
+                fruit1_lastIdx = r
+            elif f == fruit2 or fruit2 == -1:
+                total += 1
+                fruit2_lastIdx = r
+                fruit2 = f
+            else:
+                if fruit2_lastIdx == min(fruit1_lastIdx, fruit2_lastIdx):
+                    fruit1_lastIdx, fruit2_lastIdx = fruit2_lastIdx, fruit1_lastIdx
+                    fruit1, fruit2 = fruit2, fruit1
+
+                total -= (fruit1_lastIdx - l + 1)
+                l = fruit1_lastIdx + 1
+                fruit1 = f
+                fruit1_lastIdx = r
+            res = max(res, r - l + 1)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int totalFruit(int[] fruits) {
+        int l = 0, fruit1_lastIdx = 0, fruit2_lastIdx = -1;
+        int fruit1 = fruits[0], fruit2 = -1, total = 1, res = 1;
+
+        for (int r = 0; r < fruits.length; r++) {
+            int f = fruits[r];
+            if (f == fruit1) {
+                total++;
+                fruit1_lastIdx = r;
+            } else if (f == fruit2 || fruit2 == -1) {
+                total++;
+                fruit2_lastIdx = r;
+                fruit2 = f;
+            } else {
+                if (fruit2_lastIdx == Math.min(fruit1_lastIdx, fruit2_lastIdx)) {
+                    int tempIdx = fruit1_lastIdx;
+                    fruit1_lastIdx = fruit2_lastIdx;
+                    fruit2_lastIdx = tempIdx;
+                    int tempFruit = fruit1;
+                    fruit1 = fruit2;
+                    fruit2 = tempFruit;
+                }
+                total -= (fruit1_lastIdx - l + 1);
+                l = fruit1_lastIdx + 1;
+                fruit1 = f;
+                fruit1_lastIdx = r;
+            }
+            res = Math.max(res, r - l + 1);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int totalFruit(vector<int>& fruits) {
+        int l = 0, fruit1_lastIdx = 0, fruit2_lastIdx = -1;
+        int fruit1 = fruits[0], fruit2 = -1, total = 1, res = 1;
+
+        for (int r = 0; r < fruits.size(); r++) {
+            int f = fruits[r];
+            if (f == fruit1) {
+                total++;
+                fruit1_lastIdx = r;
+            } else if (f == fruit2 || fruit2 == -1) {
+                total++;
+                fruit2_lastIdx = r;
+                fruit2 = f;
+            } else {
+                if (fruit2_lastIdx == min(fruit1_lastIdx, fruit2_lastIdx)) {
+                    swap(fruit1_lastIdx, fruit2_lastIdx);
+                    swap(fruit1, fruit2);
+                }
+                total -= (fruit1_lastIdx - l + 1);
+                l = fruit1_lastIdx + 1;
+                fruit1 = f;
+                fruit1_lastIdx = r;
+            }
+            res = max(res, r - l + 1);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} fruits
+     * @return {number}
+     */
+    totalFruit(fruits) {
+        let l = 0, fruit1_lastIdx = 0, fruit2_lastIdx = -1;
+        let fruit1 = fruits[0], fruit2 = -1, total = 1, res = 1;
+
+        for (let r = 0; r < fruits.length; r++) {
+            let f = fruits[r];
+            if (f === fruit1) {
+                total++;
+                fruit1_lastIdx = r;
+            } else if (f === fruit2 || fruit2 === -1) {
+                total++;
+                fruit2_lastIdx = r;
+                fruit2 = f;
+            } else {
+                if (fruit2_lastIdx === Math.min(fruit1_lastIdx, fruit2_lastIdx)) {
+                    [fruit1_lastIdx, fruit2_lastIdx] = [fruit2_lastIdx, fruit1_lastIdx];
+                    [fruit1, fruit2] = [fruit2, fruit1];
+                }
+                total -= (fruit1_lastIdx - l + 1);
+                l = fruit1_lastIdx + 1;
+                fruit1 = f;
+                fruit1_lastIdx = r;
+            }
+            res = Math.max(res, r - l + 1);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/furthest-building-you-can-reach.md b/articles/furthest-building-you-can-reach.md
new file mode 100644
index 000000000..24ca0ef3b
--- /dev/null
+++ b/articles/furthest-building-you-can-reach.md
@@ -0,0 +1,723 @@
+## 1. Brute Force (Greedy)
+
+::tabs-start
+
+```python
+class Solution:
+    def furthestBuilding(self, heights: List[int], bricks: int, ladders: int) -> int:
+        n = len(heights)
+
+        for i in range(1, n):
+            if ladders >= i:
+                continue
+
+            diffs = []
+            for j in range(i):
+                if heights[j + 1] > heights[j]:
+                    diffs.append(heights[j + 1] - heights[j])
+
+            diffs.sort()
+            brickSum = 0
+            for j in range(len(diffs) - ladders):
+                brickSum += diffs[j]
+
+            if brickSum > bricks:
+                return i - 1
+
+        return n - 1
+```
+
+```java
+public class Solution {
+    public int furthestBuilding(int[] heights, int bricks, int ladders) {
+        int n = heights.length;
+
+        for (int i = 1; i < n; i++) {
+            if (ladders >= i) {
+                continue;
+            }
+
+            List<Integer> diffs = new ArrayList<>();
+            for (int j = 0; j < i; j++) {
+                if (heights[j + 1] > heights[j]) {
+                    diffs.add(heights[j + 1] - heights[j]);
+                }
+            }
+
+            Collections.sort(diffs);
+            long brickSum = 0;
+            for (int j = 0; j < diffs.size() - ladders; j++) {
+                brickSum += diffs.get(j);
+            }
+
+            if (brickSum > bricks) {
+                return i - 1;
+            }
+        }
+
+        return n - 1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int furthestBuilding(vector<int>& heights, int bricks, int ladders) {
+        int n = heights.size();
+
+        for (int i = 1; i < n; i++) {
+            if (ladders >= i) {
+                continue;
+            }
+
+            vector<int> diffs;
+            for (int j = 0; j < i; j++) {
+                if (heights[j + 1] > heights[j]) {
+                    diffs.push_back(heights[j + 1] - heights[j]);
+                }
+            }
+
+            sort(diffs.begin(), diffs.end());
+            long long brickSum = 0;
+            for (int j = 0; j < int(diffs.size()) - ladders; j++) {
+                brickSum += diffs[j];
+            }
+
+            if (brickSum > bricks) {
+                return i - 1;
+            }
+        }
+
+        return n - 1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} heights
+     * @param {number} bricks
+     * @param {number} ladders
+     * @return {number}
+     */
+    furthestBuilding(heights, bricks, ladders) {
+        let n = heights.length;
+
+        for (let i = 1; i < n; i++) {
+            if (ladders >= i) {
+                continue;
+            }
+
+            let diffs = [];
+            for (let j = 0; j < i; j++) {
+                if (heights[j + 1] > heights[j]) {
+                    diffs.push(heights[j + 1] - heights[j]);
+                }
+            }
+
+            diffs.sort((a, b) => a - b);
+            let brickSum = 0;
+            for (let j = 0; j < diffs.length - ladders; j++) {
+                brickSum += diffs[j];
+            }
+
+            if (brickSum > bricks) {
+                return i - 1;
+            }
+        }
+
+        return n - 1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Binary Search On Buildings
+
+::tabs-start
+
+```python
+class Solution:
+    def furthestBuilding(self, heights: List[int], bricks: int, ladders: int) -> int:
+        def canReach(mid):
+            diffs = []
+            for i in range(mid):
+                if heights[i + 1] > heights[i]:
+                    diffs.append(heights[i + 1] - heights[i])
+
+            diffs.sort()
+            brickSum = 0
+            for j in range(len(diffs) - ladders):
+                brickSum += diffs[j]
+                if brickSum > bricks:
+                    return False
+
+            return True
+
+        l, r = ladders - 1, len(heights) - 1
+        while l <= r:
+            mid = (l + r) // 2
+            if canReach(mid):
+                l = mid + 1
+            else:
+                r = mid - 1
+
+        return l - 1
+```
+
+```java
+public class Solution {
+    public int furthestBuilding(int[] heights, int bricks, int ladders) {
+        int l = ladders - 1, r = heights.length - 1;
+
+        while (l <= r) {
+            int mid = (l + r) / 2;
+            if (canReach(heights, mid, bricks, ladders)) {
+                l = mid + 1;
+            } else {
+                r = mid - 1;
+            }
+        }
+
+        return l - 1;
+    }
+
+    private boolean canReach(int[] heights, int mid, int bricks, int ladders) {
+        List<Integer> diffs = new ArrayList<>();
+
+        for (int i = 0; i < mid; i++) {
+            if (heights[i + 1] > heights[i]) {
+                diffs.add(heights[i + 1] - heights[i]);
+            }
+        }
+
+        Collections.sort(diffs);
+        int brickSum = 0;
+
+        for (int j = 0; j < diffs.size() - ladders; j++) {
+            brickSum += diffs.get(j);
+            if (brickSum > bricks) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int furthestBuilding(vector<int>& heights, int bricks, int ladders) {
+        int l = ladders - 1, r = heights.size() - 1;
+
+        while (l <= r) {
+            int mid = (l + r) / 2;
+            if (canReach(heights, mid, bricks, ladders)) {
+                l = mid + 1;
+            } else {
+                r = mid - 1;
+            }
+        }
+
+        return l - 1;
+    }
+
+private:
+    bool canReach(vector<int>& heights, int mid, int bricks, int ladders) {
+        vector<int> diffs;
+
+        for (int i = 0; i < mid; i++) {
+            if (heights[i + 1] > heights[i]) {
+                diffs.push_back(heights[i + 1] - heights[i]);
+            }
+        }
+
+        sort(diffs.begin(), diffs.end());
+        long long brickSum = 0;
+
+        for (int j = 0; j < int(diffs.size()) - ladders; j++) {
+            brickSum += diffs[j];
+            if (brickSum > bricks) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} heights
+     * @param {number} bricks
+     * @param {number} ladders
+     * @return {number}
+     */
+    furthestBuilding(heights, bricks, ladders) {
+        let l = ladders - 1, r = heights.length - 1;
+
+        const canReach = (mid) => {
+            let diffs = [];
+            for (let i = 0; i < mid; i++) {
+                if (heights[i + 1] > heights[i]) {
+                    diffs.push(heights[i + 1] - heights[i]);
+                }
+            }
+
+            diffs.sort((a, b) => a - b);
+            let brickSum = 0;
+
+            for (let j = 0; j < diffs.length - ladders; j++) {
+                brickSum += diffs[j];
+                if (brickSum > bricks) {
+                    return false;
+                }
+            }
+
+            return true;
+        };
+
+        while (l <= r) {
+            let mid = Math.floor((l + r) / 2);
+            if (canReach(mid)) {
+                l = mid + 1;
+            } else {
+                r = mid - 1;
+            }
+        }
+
+        return l - 1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log ^ 2 n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Binary Search On Buildings (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def furthestBuilding(self, heights: List[int], bricks: int, ladders: int) -> int:
+        diffs = []
+        for i in range(1, len(heights)):
+            if heights[i] > heights[i - 1]:
+                diffs.append((heights[i] - heights[i - 1], i))
+
+        diffs.sort(reverse=True)
+
+        def canReach(index):
+            useLadders = useBricks = 0
+            for diff, i in diffs:
+                if i > index:
+                    continue
+
+                if useLadders < ladders:
+                    useLadders += 1
+                else:
+                    useBricks += diff
+                    if useBricks > bricks:
+                        return False
+            return True
+
+        l, r = 1, len(heights) - 1
+        while l <= r:
+            mid = (l + r) >> 1
+            if canReach(mid):
+                l = mid + 1
+            else:
+                r = mid - 1
+        return l - 1
+```
+
+```java
+public class Solution {
+    public int furthestBuilding(int[] heights, int bricks, int ladders) {
+        List<int[]> diffs = new ArrayList<>();
+        for (int i = 1; i < heights.length; i++) {
+            if (heights[i] > heights[i - 1]) {
+                diffs.add(new int[]{heights[i] - heights[i - 1], i});
+            }
+        }
+
+        diffs.sort((a, b) -> Integer.compare(b[0], a[0]));
+
+        int l = 1, r = heights.length - 1;
+        while (l <= r) {
+            int mid = (l + r) >> 1;
+            if (canReach(diffs, mid, bricks, ladders)) {
+                l = mid + 1;
+            } else {
+                r = mid - 1;
+            }
+        }
+
+        return l - 1;
+    }
+
+    private boolean canReach(List<int[]> diffs, int index, int bricks, int ladders) {
+        int useLadders = 0;
+        long useBricks = 0;
+        for (int[] diff : diffs) {
+            int jump = diff[0], i = diff[1];
+
+            if (i > index) continue;
+
+            if (useLadders < ladders) {
+                useLadders++;
+            } else {
+                useBricks += jump;
+                if (useBricks > bricks) {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int furthestBuilding(vector<int>& heights, int bricks, int ladders) {
+        vector<pair<int, int>> diffs;
+        for (int i = 1; i < heights.size(); i++) {
+            if (heights[i] > heights[i - 1]) {
+                diffs.emplace_back(heights[i] - heights[i - 1], i);
+            }
+        }
+
+        sort(diffs.rbegin(), diffs.rend()); // Sort in descending order
+
+        int l = 1, r = heights.size() - 1;
+        while (l <= r) {
+            int mid = (l + r) >> 1;
+            if (canReach(diffs, mid, bricks, ladders)) {
+                l = mid + 1;
+            } else {
+                r = mid - 1;
+            }
+        }
+
+        return l - 1;
+    }
+
+private:
+    bool canReach(vector<pair<int, int>>& diffs, int index, int bricks, int ladders) {
+        int useLadders = 0;
+        long long useBricks = 0;
+        for (auto& diff : diffs) {
+            int jump = diff.first, i = diff.second;
+
+            if (i > index) continue;
+
+            if (useLadders < ladders) {
+                useLadders++;
+            } else {
+                useBricks += jump;
+                if (useBricks > bricks) {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} heights
+     * @param {number} bricks
+     * @param {number} ladders
+     * @return {number}
+     */
+    furthestBuilding(heights, bricks, ladders) {
+        let diffs = [];
+        for (let i = 1; i < heights.length; i++) {
+            if (heights[i] > heights[i - 1]) {
+                diffs.push([heights[i] - heights[i - 1], i]);
+            }
+        }
+
+        diffs.sort((a, b) => b[0] - a[0]);
+
+        const canReach = (index) => {
+            let useLadders = 0, useBricks = 0;
+            for (let [diff, i] of diffs) {
+                if (i > index) continue;
+
+                if (useLadders < ladders) {
+                    useLadders++;
+                } else {
+                    useBricks += diff;
+                    if (useBricks > bricks) {
+                        return false;
+                    }
+                }
+            }
+            return true;
+        };
+
+        let l = 1, r = heights.length - 1;
+        while (l <= r) {
+            let mid = (l + r) >> 1;
+            if (canReach(mid)) {
+                l = mid + 1;
+            } else {
+                r = mid - 1;
+            }
+        }
+
+        return l - 1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Max-Heap
+
+::tabs-start
+
+```python
+class Solution:
+    def furthestBuilding(self, heights: List[int], bricks: int, ladders: int) -> int:
+        heap = []  # Max heap of bricks used
+
+        for i in range(len(heights) - 1):
+            diff = heights[i + 1] - heights[i]
+            if diff <= 0:
+                continue
+
+            bricks -= diff
+            heapq.heappush(heap, -diff)
+
+            if bricks < 0:
+                if ladders == 0:
+                    return i
+                ladders -= 1
+                bricks += -heapq.heappop(heap)
+
+        return len(heights) - 1
+```
+
+```java
+public class Solution {
+    public int furthestBuilding(int[] heights, int bricks, int ladders) {
+        PriorityQueue<Integer> maxHeap = new PriorityQueue<>((a, b) -> b - a);
+
+        for (int i = 0; i < heights.length - 1; i++) {
+            int diff = heights[i + 1] - heights[i];
+            if (diff <= 0) continue;
+
+            bricks -= diff;
+            maxHeap.offer(diff);
+
+            if (bricks < 0) {
+                if (ladders == 0) return i;
+                ladders--;
+                bricks += maxHeap.poll();
+            }
+        }
+
+        return heights.length - 1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int furthestBuilding(vector<int>& heights, int bricks, int ladders) {
+        priority_queue<int> maxHeap;
+
+        for (int i = 0; i < heights.size() - 1; i++) {
+            int diff = heights[i + 1] - heights[i];
+            if (diff <= 0) continue;
+
+            bricks -= diff;
+            maxHeap.push(diff);
+
+            if (bricks < 0) {
+                if (ladders == 0) return i;
+                ladders--;
+                bricks += maxHeap.top();
+                maxHeap.pop();
+            }
+        }
+
+        return heights.size() - 1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} heights
+     * @param {number} bricks
+     * @param {number} ladders
+     * @return {number}
+     */
+    furthestBuilding(heights, bricks, ladders) {
+        const maxHeap = new MaxPriorityQueue();
+
+        for (let i = 0; i < heights.length - 1; i++) {
+            let diff = heights[i + 1] - heights[i];
+            if (diff <= 0) continue;
+
+            bricks -= diff;
+            maxHeap.enqueue(diff);
+
+            if (bricks < 0) {
+                if (ladders === 0) return i;
+                ladders--;
+                bricks += maxHeap.dequeue().element;
+            }
+        }
+
+        return heights.length - 1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 5. Min-Heap
+
+::tabs-start
+
+```python
+class Solution:
+    def furthestBuilding(self, heights: List[int], bricks: int, ladders: int) -> int:
+        minHeap = []
+
+        for i in range(len(heights) - 1):
+            diff = heights[i + 1] - heights[i]
+            if diff <= 0:
+                continue
+
+            heapq.heappush(minHeap, diff)
+            if len(minHeap) > ladders:
+                bricks -= heapq.heappop(minHeap)
+                if bricks < 0:
+                    return i
+
+        return len(heights) - 1
+```
+
+```java
+public class Solution {
+    public int furthestBuilding(int[] heights, int bricks, int ladders) {
+        PriorityQueue<Integer> minHeap = new PriorityQueue<>();
+
+        for (int i = 0; i < heights.length - 1; i++) {
+            int diff = heights[i + 1] - heights[i];
+            if (diff <= 0) continue;
+
+            minHeap.offer(diff);
+            if (minHeap.size() > ladders) {
+                bricks -= minHeap.poll();
+                if (bricks < 0) return i;
+            }
+        }
+
+        return heights.length - 1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int furthestBuilding(vector<int>& heights, int bricks, int ladders) {
+        priority_queue<int, vector<int>, greater<int>> minHeap;
+
+        for (int i = 0; i < int(heights.size()) - 1; i++) {
+            int diff = heights[i + 1] - heights[i];
+            if (diff <= 0) continue;
+
+            minHeap.push(diff);
+            if (minHeap.size() > ladders) {
+                bricks -= minHeap.top(); minHeap.pop();
+                if (bricks < 0) return i;
+            }
+        }
+
+        return int(heights.size()) - 1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} heights
+     * @param {number} bricks
+     * @param {number} ladders
+     * @return {number}
+     */
+    furthestBuilding(heights, bricks, ladders) {
+        const minHeap = new MinPriorityQueue();
+
+        for (let i = 0; i < heights.length - 1; i++) {
+            let diff = heights[i + 1] - heights[i];
+            if (diff <= 0) continue;
+
+            minHeap.enqueue(diff);
+            if (minHeap.size() > ladders) {
+                bricks -= minHeap.dequeue().element;
+                if (bricks < 0) return i;
+            }
+        }
+
+        return heights.length - 1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/gas-station.md b/articles/gas-station.md
new file mode 100644
index 000000000..9e779b1d8
--- /dev/null
+++ b/articles/gas-station.md
@@ -0,0 +1,611 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def canCompleteCircuit(self, gas: List[int], cost: List[int]) -> int:
+        n = len(gas)
+
+        for i in range(n):
+            tank = gas[i] - cost[i]
+            if tank < 0:
+                continue
+
+            j = (i + 1) % n
+            while j != i:
+                tank += gas[j]
+                tank -= cost[j]
+                if tank < 0:
+                    break
+                j += 1
+                j %= n
+
+            if j == i:
+                return i
+        return -1
+```
+
+```java
+public class Solution {
+    public int canCompleteCircuit(int[] gas, int[] cost) {
+        int n = gas.length;
+
+        for (int i = 0; i < n; i++) {
+            int tank = gas[i] - cost[i];
+            if (tank < 0) continue;
+
+            int j = (i + 1) % n;
+            while (j != i) {
+                tank += gas[j] - cost[j];
+                if (tank < 0) break;
+                j = (j + 1) % n;
+            }
+
+            if (j == i) return i;
+        }
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int canCompleteCircuit(vector<int>& gas, vector<int>& cost) {
+        int n = gas.size();
+
+        for (int i = 0; i < n; i++) {
+            int tank = gas[i] - cost[i];
+            if (tank < 0) continue;
+
+            int j = (i + 1) % n;
+            while (j != i) {
+                tank += gas[j] - cost[j];
+                if (tank < 0) break;
+                j = (j + 1) % n;
+            }
+
+            if (j == i) return i;
+        }
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} gas
+     * @param {number[]} cost
+     * @return {number}
+     */
+    canCompleteCircuit(gas, cost) {
+        const n = gas.length;
+
+        for (let i = 0; i < n; i++) {
+            let tank = gas[i] - cost[i];
+            if (tank < 0) continue;
+
+            let j = (i + 1) % n;
+            while (j !== i) {
+                tank += gas[j] - cost[j];
+                if (tank < 0) break;
+                j = (j + 1) % n;
+            }
+
+            if (j === i) return i;
+        }
+        return -1;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int CanCompleteCircuit(int[] gas, int[] cost) {
+        int n = gas.Length;
+
+        for (int i = 0; i < n; i++) {
+            int tank = gas[i] - cost[i];
+            if (tank < 0) continue;
+
+            int j = (i + 1) % n;
+            while (j != i) {
+                tank += gas[j] - cost[j];
+                if (tank < 0) break;
+                j = (j + 1) % n;
+            }
+
+            if (j == i) return i;
+        }
+
+        return -1;
+    }
+}
+```
+
+```go
+func canCompleteCircuit(gas []int, cost []int) int {
+    n := len(gas)
+
+    for i := 0; i < n; i++ {
+        tank := gas[i] - cost[i]
+        if tank < 0 {
+            continue
+        }
+
+        j := (i + 1) % n
+        for j != i {
+            tank += gas[j]
+            tank -= cost[j]
+            if tank < 0 {
+                break
+            }
+            j = (j + 1) % n
+        }
+
+        if j == i {
+            return i
+        }
+    }
+
+    return -1
+}
+```
+
+```kotlin
+class Solution {
+    fun canCompleteCircuit(gas: IntArray, cost: IntArray): Int {
+        val n = gas.size
+        for (i in 0 until n) {
+            var tank = gas[i] - cost[i]
+            if (tank < 0) {
+                continue
+            }
+            var j = (i + 1) % n
+            while (j != i) {
+                tank += gas[j]
+                tank -= cost[j]
+                if (tank < 0) {
+                    break
+                }
+                j = (j + 1) % n
+            }
+            if (j == i) {
+                return i
+            }
+        }
+        return -1
+    }
+}
+```
+
+```swift
+class Solution {
+    func canCompleteCircuit(_ gas: [Int], _ cost: [Int]) -> Int {
+        let n = gas.count
+
+        for i in 0..<n {
+            var tank = gas[i] - cost[i]
+            if tank < 0 {
+                continue
+            }
+
+            var j = (i + 1) % n
+            while j != i {
+                tank += gas[j]
+                tank -= cost[j]
+                if tank < 0 {
+                    break
+                }
+                j += 1
+                j %= n
+            }
+
+            if j == i {
+                return i
+            }
+        }
+
+        return -1
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def canCompleteCircuit(self, gas: List[int], cost: List[int]) -> int:
+        n = len(gas)
+        start, end = n - 1, 0
+        tank = gas[start] - cost[start]
+        while start > end:
+            if tank < 0:
+                start -= 1
+                tank += gas[start] - cost[start]
+            else:
+                tank += gas[end] - cost[end]
+                end += 1
+        return start if tank >= 0 else -1
+```
+
+```java
+public class Solution {
+    public int canCompleteCircuit(int[] gas, int[] cost) {
+        int n = gas.length;
+        int start = n - 1, end = 0;
+        int tank = gas[start] - cost[start];
+        while (start > end) {
+            if (tank < 0) {
+                start--;
+                tank += gas[start] - cost[start];
+            } else {
+                tank += gas[end] - cost[end];
+                end++;
+            }
+        }
+        return tank >= 0 ? start : -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int canCompleteCircuit(vector<int>& gas, vector<int>& cost) {
+        int n = gas.size();
+        int start = n - 1, end = 0;
+        int tank = gas[start] - cost[start];
+        while (start > end) {
+            if (tank < 0) {
+                start--;
+                tank += gas[start] - cost[start];
+            } else {
+                tank += gas[end] - cost[end];
+                end++;
+            }
+        }
+        return tank >= 0 ? start : -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} gas
+     * @param {number[]} cost
+     * @return {number}
+     */
+    canCompleteCircuit(gas, cost) {
+        const n = gas.length;
+        let start = n - 1, end = 0;
+        let tank = gas[start] - cost[start];
+        while (start > end) {
+            if (tank < 0) {
+                start--;
+                tank += gas[start] - cost[start];
+            } else {
+                tank += gas[end] - cost[end];
+                end++;
+            }
+        }
+        return tank >= 0 ? start : -1;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int CanCompleteCircuit(int[] gas, int[] cost) {
+        int n = gas.Length;
+        int start = n - 1, end = 0;
+        int tank = gas[start] - cost[start];
+        while (start > end) {
+            if (tank < 0) {
+                start--;
+                tank += gas[start] - cost[start];
+            } else {
+                tank += gas[end] - cost[end];
+                end++;
+            }
+        }
+        return tank >= 0 ? start : -1;
+    }
+}
+```
+
+```go
+func canCompleteCircuit(gas []int, cost []int) int {
+    n := len(gas)
+    start, end := n-1, 0
+    tank := gas[start] - cost[start]
+
+    for start > end {
+        if tank < 0 {
+            start--
+            tank += gas[start] - cost[start]
+        } else {
+            tank += gas[end] - cost[end]
+            end++
+        }
+    }
+
+    if tank >= 0 {
+        return start
+    }
+    return -1
+}
+```
+
+```kotlin
+class Solution {
+    fun canCompleteCircuit(gas: IntArray, cost: IntArray): Int {
+        val n = gas.size
+        var start = n - 1
+        var end = 0
+        var tank = gas[start] - cost[start]
+
+        while (start > end) {
+            if (tank < 0) {
+                start--
+                tank += gas[start] - cost[start]
+            } else {
+                tank += gas[end] - cost[end]
+                end++
+            }
+        }
+
+        return if (tank >= 0) start else -1
+    }
+}
+```
+
+```swift
+class Solution {
+    func canCompleteCircuit(_ gas: [Int], _ cost: [Int]) -> Int {
+        let n = gas.count
+        var start = n - 1
+        var end = 0
+        var tank = gas[start] - cost[start]
+
+        while start > end {
+            if tank < 0 {
+                start -= 1
+                tank += gas[start] - cost[start]
+            } else {
+                tank += gas[end] - cost[end]
+                end += 1
+            }
+        }
+
+        return tank >= 0 ? start : -1
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Greedy
+
+::tabs-start
+
+```python
+class Solution:
+    def canCompleteCircuit(self, gas: List[int], cost: List[int]) -> int:
+        if sum(gas) < sum(cost):
+            return -1
+
+        total = 0
+        res = 0
+        for i in range(len(gas)):
+            total += (gas[i] - cost[i])
+
+            if total < 0:
+                total = 0
+                res = i + 1
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int canCompleteCircuit(int[] gas, int[] cost) {
+        if (Arrays.stream(gas).sum() < Arrays.stream(cost).sum()) {
+            return -1;
+        }
+
+        int total = 0;
+        int res = 0;
+        for (int i = 0; i < gas.length; i++) {
+            total += (gas[i] - cost[i]);
+
+            if (total < 0) {
+                total = 0;
+                res = i + 1;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int canCompleteCircuit(vector<int>& gas, vector<int>& cost) {
+        if (accumulate(gas.begin(), gas.end(), 0) < 
+            accumulate(cost.begin(), cost.end(), 0)) {
+            return -1;
+        }
+
+        int total = 0;
+        int res = 0;
+        for (int i = 0; i < gas.size(); i++) {
+            total += (gas[i] - cost[i]);
+
+            if (total < 0) {
+                total = 0;
+                res = i + 1;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} gas
+     * @param {number[]} cost
+     * @return {number}
+     */
+    canCompleteCircuit(gas, cost) {
+        if (gas.reduce((acc, val) => acc + val, 0) <
+            cost.reduce((acc, val) => acc + val, 0)) {
+            return -1;
+        }
+
+        let total = 0;
+        let res = 0;
+        for (let i = 0; i < gas.length; i++) {
+            total += gas[i] - cost[i];
+
+            if (total < 0) {
+                total = 0;
+                res = i + 1;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int CanCompleteCircuit(int[] gas, int[] cost) {
+        if (gas.Sum() < cost.Sum()) {
+            return -1;
+        }
+
+        int total = 0;
+        int res = 0;
+        for (int i = 0; i < gas.Length; i++) {
+            total += (gas[i] - cost[i]);
+
+            if (total < 0) {
+                total = 0;
+                res = i + 1;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```go
+func canCompleteCircuit(gas []int, cost []int) int {
+    if sum(gas) < sum(cost) {
+        return -1
+    }
+
+    total := 0
+    res := 0
+
+    for i := range gas {
+        total += gas[i] - cost[i]
+        if total < 0 {
+            total = 0
+            res = i + 1
+        }
+    }
+
+    return res
+}
+
+func sum(nums []int) int {
+    var total int
+    for _, num := range nums {
+        total += num
+    }
+    return total
+}
+```
+
+```kotlin
+class Solution {
+    fun canCompleteCircuit(gas: IntArray, cost: IntArray): Int {
+        if (gas.sum() < cost.sum()) {
+            return -1
+        }
+
+        var total = 0
+        var res = 0
+
+        for (i in gas.indices) {
+            total += gas[i] - cost[i]
+            if (total < 0) {
+                total = 0
+                res = i + 1
+            }
+        }
+
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func canCompleteCircuit(_ gas: [Int], _ cost: [Int]) -> Int {
+        if gas.reduce(0, +) < cost.reduce(0, +) {
+            return -1
+        }
+
+        var total = 0
+        var res = 0
+        for i in 0..<gas.count {
+            total += (gas[i] - cost[i])
+
+            if total < 0 {
+                total = 0
+                res = i + 1
+            }
+        }
+
+        return res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/generate-parentheses.md b/articles/generate-parentheses.md
index 09165620e..635ef1af4 100644
--- a/articles/generate-parentheses.md
+++ b/articles/generate-parentheses.md
@@ -154,6 +154,109 @@ public class Solution {
 }
 ```
 
+```go
+func generateParenthesis(n int) []string {
+   res := make([]string, 0)
+   
+   var valid func(string) bool
+   valid = func(s string) bool {
+       open := 0
+       for _, c := range s {
+           if c == '(' {
+               open++
+           } else {
+               open--
+           }
+           if open < 0 {
+               return false
+           }
+       }
+       return open == 0
+   }
+   
+   var dfs func(string)
+   dfs = func(s string) {
+       if len(s) == n*2 {
+           if valid(s) {
+               res = append(res, s)
+           }
+           return
+       }
+       
+       dfs(s + "(")
+       dfs(s + ")")
+   }
+   
+   dfs("")
+   return res
+}
+```
+
+```kotlin
+class Solution {
+    fun generateParenthesis(n: Int): List<String> {
+        val res = mutableListOf<String>()
+        
+        fun valid(s: String): Boolean {
+            var open = 0
+            for (c in s) {
+                if (c == '(') open++ else open--
+                if (open < 0) return false
+            }
+            return open == 0
+        }
+        
+        fun dfs(s: String) {
+            if (s.length == n * 2) {
+                if (valid(s)) {
+                    res.add(s)
+                }
+                return
+            }
+            
+            dfs(s + "(")
+            dfs(s + ")")
+        }
+        
+        dfs("")
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func generateParenthesis(_ n: Int) -> [String] {
+        var res = [String]()
+
+        func isValid(_ s: String) -> Bool {
+            var open = 0
+            for c in s {
+                open += (c == "(") ? 1 : -1
+                if open < 0 {
+                    return false
+                }
+            }
+            return open == 0
+        }
+
+        func dfs(_ s: String) {
+            if s.count == n * 2 {
+                if isValid(s) {
+                    res.append(s)
+                }
+                return
+            }
+            dfs(s + "(")
+            dfs(s + ")")
+        }
+
+        dfs("")
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -311,6 +414,98 @@ public class Solution {
 }
 ```
 
+```go
+func generateParenthesis(n int) []string {
+   stack := make([]string, 0)
+   res := make([]string, 0)
+   
+   var backtrack func(int, int)
+   backtrack = func(openN, closedN int) {
+       if openN == n && closedN == n {
+           res = append(res, strings.Join(stack, ""))
+           return
+       }
+       
+       if openN < n {
+           stack = append(stack, "(")
+           backtrack(openN+1, closedN)
+           stack = stack[:len(stack)-1]
+       }
+       
+       if closedN < openN {
+           stack = append(stack, ")")
+           backtrack(openN, closedN+1)
+           stack = stack[:len(stack)-1]
+       }
+   }
+   
+   backtrack(0, 0)
+   return res
+}
+```
+
+```kotlin
+class Solution {
+    fun generateParenthesis(n: Int): List<String> {
+        val stack = mutableListOf<String>()
+        val res = mutableListOf<String>()
+        
+        fun backtrack(openN: Int, closedN: Int) {
+            if (openN == n && closedN == n) {
+                res.add(stack.joinToString(""))
+                return
+            }
+            
+            if (openN < n) {
+                stack.add("(")
+                backtrack(openN + 1, closedN)
+                stack.removeAt(stack.lastIndex)
+            }
+            
+            if (closedN < openN) {
+                stack.add(")")
+                backtrack(openN, closedN + 1)
+                stack.removeAt(stack.lastIndex)
+            }
+        }
+        
+        backtrack(0, 0)
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func generateParenthesis(_ n: Int) -> [String] {
+        var stack = [Character]()
+        var res = [String]()
+
+        func backtrack(_ openN: Int, _ closedN: Int) {
+            if openN == n && closedN == n {
+                res.append(String(stack))
+                return
+            }
+
+            if openN < n {
+                stack.append("(")
+                backtrack(openN + 1, closedN)
+                stack.removeLast()
+            }
+
+            if closedN < openN {
+                stack.append(")")
+                backtrack(openN, closedN + 1)
+                stack.removeLast()
+            }
+        }
+
+        backtrack(0, 0)
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -434,6 +629,68 @@ public class Solution {
 }
 ```
 
+```go
+func generateParenthesis(n int) []string {
+   res := make([][]string, n+1)
+   res[0] = []string{""}
+   
+   for k := 1; k <= n; k++ {
+       res[k] = make([]string, 0)
+       for i := 0; i < k; i++ {
+           for _, left := range res[i] {
+               for _, right := range res[k-i-1] {
+                   res[k] = append(res[k], "(" + left + ")" + right)
+               }
+           }
+       }
+   }
+   
+   return res[n]
+}
+```
+
+```kotlin
+class Solution {
+    fun generateParenthesis(n: Int): List<String> {
+        val res = Array(n + 1) { mutableListOf<String>() }
+        res[0] = mutableListOf("")
+        
+        for (k in 1..n) {
+            for (i in 0 until k) {
+                for (left in res[i]) {
+                    for (right in res[k-i-1]) {
+                        res[k].add("(" + left + ")" + right)
+                    }
+                }
+            }
+        }
+        
+        return res[n]
+    }
+}
+```
+
+```swift
+class Solution {
+    func generateParenthesis(_ n: Int) -> [String] {
+        var res = [[String]](repeating: [], count: n + 1)
+        res[0] = [""]
+
+        for k in 0...n {
+            for i in 0..<k {
+                for left in res[i] {
+                    for right in res[k - i - 1] {
+                        res[k].append("(" + left + ")" + right)
+                    }
+                }
+            }
+        }
+
+        return res[n]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/get-equal-substrings-within-budget.md b/articles/get-equal-substrings-within-budget.md
new file mode 100644
index 000000000..078230575
--- /dev/null
+++ b/articles/get-equal-substrings-within-budget.md
@@ -0,0 +1,274 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def equalSubstring(self, s: str, t: str, maxCost: int) -> int:
+        n = len(s)
+        res = 0
+
+        for i in range(n):
+            cur_cost = 0
+            for j in range(i, n):
+                cur_cost += abs(ord(t[j]) - ord(s[j]))
+                if cur_cost > maxCost:
+                    break
+                res = max(res, j - i + 1)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int equalSubstring(String s, String t, int maxCost) {
+        int n = s.length();
+        int res = 0;
+
+        for (int i = 0; i < n; i++) {
+            int curCost = 0;
+            for (int j = i; j < n; j++) {
+                curCost += Math.abs(t.charAt(j) - s.charAt(j));
+                if (curCost > maxCost) {
+                    break;
+                }
+                res = Math.max(res, j - i + 1);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int equalSubstring(string s, string t, int maxCost) {
+        int n = s.size();
+        int res = 0;
+
+        for (int i = 0; i < n; i++) {
+            int curCost = 0;
+            for (int j = i; j < n; j++) {
+                curCost += abs(t[j] - s[j]);
+                if (curCost > maxCost) {
+                    break;
+                }
+                res = max(res, j - i + 1);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string} t
+     * @param {number} maxCost
+     * @return {number}
+     */
+    equalSubstring(s, t, maxCost) {
+        const n = s.length;
+        let res = 0;
+
+        for (let i = 0; i < n; i++) {
+            let curCost = 0;
+            for (let j = i; j < n; j++) {
+                curCost += Math.abs(t.charCodeAt(j) - s.charCodeAt(j));
+                if (curCost > maxCost) {
+                    break;
+                }
+                res = Math.max(res, j - i + 1);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Sliding Window
+
+::tabs-start
+
+```python
+class Solution:
+    def equalSubstring(self, s: str, t: str, maxCost: int) -> int:
+        curCost = 0
+        l = 0
+        res = 0
+
+        for r in range(len(s)):
+            curCost += abs(ord(s[r]) - ord(t[r]))
+            while curCost > maxCost:
+                curCost -= abs(ord(s[l]) - ord(t[l]))
+                l += 1
+            res = max(res, r - l + 1)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int equalSubstring(String s, String t, int maxCost) {
+        int curCost = 0, l = 0, res = 0;
+
+        for (int r = 0; r < s.length(); r++) {
+            curCost += Math.abs(s.charAt(r) - t.charAt(r));
+            while (curCost > maxCost) {
+                curCost -= Math.abs(s.charAt(l) - t.charAt(l));
+                l++;
+            }
+            res = Math.max(res, r - l + 1);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int equalSubstring(string s, string t, int maxCost) {
+        int curCost = 0, l = 0, res = 0;
+
+        for (int r = 0; r < s.length(); r++) {
+            curCost += abs(s[r] - t[r]);
+            while (curCost > maxCost) {
+                curCost -= abs(s[l] - t[l]);
+                l++;
+            }
+            res = max(res, r - l + 1);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string} t
+     * @param {number} maxCost
+     * @return {number}
+     */
+    equalSubstring(s, t, maxCost) {
+        let curCost = 0, l = 0, res = 0;
+
+        for (let r = 0; r < s.length; r++) {
+            curCost += Math.abs(s.charCodeAt(r) - t.charCodeAt(r));
+            while (curCost > maxCost) {
+                curCost -= Math.abs(s.charCodeAt(l) - t.charCodeAt(l));
+                l++;
+            }
+            res = Math.max(res, r - l + 1);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Sliding Window (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def equalSubstring(self, s: str, t: str, maxCost: int) -> int:
+        l = 0
+        for r in range(len(s)):
+            maxCost -= abs(ord(s[r]) - ord(t[r]))
+            if maxCost < 0:
+                maxCost += abs(ord(s[l]) - ord(t[l]))
+                l += 1
+        return len(s) - l
+```
+
+```java
+public class Solution {
+    public int equalSubstring(String s, String t, int maxCost) {
+        int l = 0;
+        for (int r = 0; r < s.length(); r++) {
+            maxCost -= Math.abs(s.charAt(r) - t.charAt(r));
+            if (maxCost < 0) {
+                maxCost += Math.abs(s.charAt(l) - t.charAt(l));
+                l++;
+            }
+        }
+        return s.length() - l;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int equalSubstring(string s, string t, int maxCost) {
+        int l = 0;
+        for (int r = 0; r < s.length(); r++) {
+            maxCost -= abs(s[r] - t[r]);
+            if (maxCost < 0) {
+                maxCost += abs(s[l] - t[l]);
+                l++;
+            }
+        }
+        return s.length() - l;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string} t
+     * @param {number} maxCost
+     * @return {number}
+     */
+    equalSubstring(s, t, maxCost) {
+        let l = 0;
+        for (let r = 0; r < s.length; r++) {
+            maxCost -= Math.abs(s.charCodeAt(r) - t.charCodeAt(r));
+            if (maxCost < 0) {
+                maxCost += Math.abs(s.charCodeAt(l) - t.charCodeAt(l));
+                l++;
+            }
+        }
+        return s.length - l;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/greatest-common-divisor-of-strings.md b/articles/greatest-common-divisor-of-strings.md
new file mode 100644
index 000000000..ae138e7d6
--- /dev/null
+++ b/articles/greatest-common-divisor-of-strings.md
@@ -0,0 +1,459 @@
+## 1. Iteration
+
+::tabs-start
+
+```python
+class Solution:
+    def gcdOfStrings(self, str1: str, str2: str) -> str:
+        len1, len2 = len(str1), len(str2)
+
+        def isDivisor(l):
+            if len1 % l != 0 or len2 % l != 0:
+                return False
+            f1, f2 = len1 // l, len2 // l
+            return str1[:l] * f1 == str1 and str1[:l] * f2 == str2
+
+        for l in range(min(len1, len2), 0, -1):
+            if isDivisor(l):
+                return str1[:l]
+
+        return ""
+```
+
+```java
+public class Solution {
+    public String gcdOfStrings(String str1, String str2) {
+        int len1 = str1.length(), len2 = str2.length();
+
+        for (int l = Math.min(len1, len2); l > 0; l--) {
+            if (isDivisor(l, len1, len2, str1, str2)) {
+                return str1.substring(0, l);
+            }
+        }
+
+        return "";
+    }
+
+    public boolean isDivisor(int l, int len1, int len2, String str1, String str2) {
+        if (len1 % l != 0 || len2 % l != 0) {
+            return false;
+        }
+        String sub = str1.substring(0, l);
+        int f1 = len1 / l, f2 = len2 / l;
+        return sub.repeat(f1).equals(str1) && sub.repeat(f2).equals(str2);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string gcdOfStrings(string str1, string str2) {
+        int len1 = str1.size(), len2 = str2.size();
+
+        auto isDivisor = [&](int l) {
+            if (len1 % l != 0 || len2 % l != 0) {
+                return false;
+            }
+            string sub = str1.substr(0, l);
+            int f1 = len1 / l, f2 = len2 / l;
+            string repeated1 = "", repeated2 = "";
+            for (int i = 0; i < f1; ++i) repeated1 += sub;
+            for (int i = 0; i < f2; ++i) repeated2 += sub;
+            return repeated1 == str1 && repeated2 == str2;
+        };
+
+        for (int l = min(len1, len2); l > 0; l--) {
+            if (isDivisor(l)) {
+                return str1.substr(0, l);
+            }
+        }
+
+        return "";
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} str1
+     * @param {string} str2
+     * @return {string}
+     */
+    gcdOfStrings(str1, str2) {
+        const len1 = str1.length, len2 = str2.length;
+
+        const isDivisor = (l) => {
+            if (len1 % l !== 0 || len2 % l !== 0) {
+                return false;
+            }
+            const sub = str1.slice(0, l);
+            const f1 = len1 / l, f2 = len2 / l;
+            return sub.repeat(f1) === str1 && sub.repeat(f2) === str2;
+        };
+
+        for (let l = Math.min(len1, len2); l > 0; l--) {
+            if (isDivisor(l)) {
+                return str1.slice(0, l);
+            }
+        }
+
+        return "";
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(min(m, n) * (m + n))$
+* Space complexity: $O(m + n)$
+
+> Where $m$ and $n$ are the lengths of the strings $str1$ and $str2$ respectively.
+
+---
+
+## 2. Iteration (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def gcdOfStrings(self, str1: str, str2: str) -> str:
+        m, n = len(str1), len(str2)
+        if m < n:
+            m, n = n, m
+            str1, str2 = str2, str1
+        
+        for l in range(n, 0, -1):
+            if m % l != 0 or n % l != 0:
+                continue
+            
+            valid = True
+            for i in range(m):
+                if str1[i] != str2[i % l]:
+                    valid = False
+                    break
+            if not valid: continue
+
+            for i in range(l, n):
+                if str2[i] != str2[i % l]:
+                    valid = False
+                    break
+            if valid: return str2[:l]
+
+        return ""
+```
+
+```java
+public class Solution {
+    public String gcdOfStrings(String str1, String str2) {
+        int m = str1.length(), n = str2.length();
+        if (m < n) {
+            String temp = str1;
+            str1 = str2;
+            str2 = temp;
+            int tempLen = m;
+            m = n;
+            n = tempLen;
+        }
+
+        for (int l = n; l > 0; l--) {
+            if (m % l != 0 || n % l != 0) {
+                continue;
+            }
+
+            boolean valid = true;
+            for (int i = 0; i < m; i++) {
+                if (str1.charAt(i) != str2.charAt(i % l)) {
+                    valid = false;
+                    break;
+                }
+            }
+            if (!valid) continue;
+
+            for (int i = l; i < n; i++) {
+                if (str2.charAt(i) != str2.charAt(i % l)) {
+                    valid = false;
+                    break;
+                }
+            }
+            if (valid) {
+                return str2.substring(0, l);
+            }
+        }
+
+        return "";
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string gcdOfStrings(string str1, string str2) {
+        int m = str1.size(), n = str2.size();
+        if (m < n) {
+            swap(m, n);
+            swap(str1, str2);
+        }
+
+        for (int l = n; l > 0; l--) {
+            if (m % l != 0 || n % l != 0) {
+                continue;
+            }
+
+            bool valid = true;
+            for (int i = 0; i < m; i++) {
+                if (str1[i] != str2[i % l]) {
+                    valid = false;
+                    break;
+                }
+            }
+            if (!valid) continue;
+
+            for (int i = l; i < n; i++) {
+                if (str2[i] != str2[i % l]) {
+                    valid = false;
+                    break;
+                }
+            }
+            if (valid) {
+                return str2.substr(0, l);
+            }
+        }
+
+        return "";
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} str1
+     * @param {string} str2
+     * @return {string}
+     */
+    gcdOfStrings(str1, str2) {
+        let m = str1.length, n = str2.length;
+        if (m < n) {
+            [m, n] = [n, m];
+            [str1, str2] = [str2, str1];
+        }
+
+        for (let l = n; l > 0; l--) {
+            if (m % l !== 0 || n % l !== 0) {
+                continue;
+            }
+
+            let valid = true;
+            for (let i = 0; i < m; i++) {
+                if (str1[i] !== str2[i % l]) {
+                    valid = false;
+                    break;
+                }
+            }
+            if (!valid) continue;
+
+            for (let i = l; i < n; i++) {
+                if (str2[i] !== str2[i % l]) {
+                    valid = false;
+                    break;
+                }
+            }
+            if (valid) {
+                return str2.slice(0, l);
+            }
+        }
+
+        return "";
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(min(m, n) * (m + n))$
+* Space complexity: $O(g)$ for the output string.
+
+> Where $m$ is the length of the string $str1$, $n$ is the length of the string $str2$, and $g$ is the length of the output string.
+
+---
+
+## 3. Greatest Common Divisor
+
+::tabs-start
+
+```python
+class Solution:
+    def gcdOfStrings(self, str1: str, str2: str) -> str:
+        if str1 + str2 != str2 + str1:
+            return ""
+
+        g = gcd(len(str1), len(str2))
+        return str1[:g]
+```
+
+```java
+public class Solution {
+    public String gcdOfStrings(String str1, String str2) {
+        if (!(str1 + str2).equals(str2 + str1)) {
+            return "";
+        }
+        int g = gcd(str1.length(), str2.length());
+        return str1.substring(0, g);
+    }
+
+    private int gcd(int a, int b) {
+        return b == 0 ? a : gcd(b, a % b);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string gcdOfStrings(string str1, string str2) {
+        if (str1 + str2 != str2 + str1) {
+            return "";
+        }
+        int g = __gcd((int)str1.size(), (int)str2.size());
+        return str1.substr(0, g);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} str1
+     * @param {string} str2
+     * @return {string}
+     */
+    gcdOfStrings(str1, str2) {
+        if (str1 + str2 !== str2 + str1) {
+            return "";
+        }
+        const gcd = (a, b) => (b === 0 ? a : gcd(b, a % b));
+        const g = gcd(str1.length, str2.length);
+        return str1.slice(0, g);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m + n)$
+* Space complexity: $O(m + n)$.
+
+> Where $m$ and $n$ are the lengths of the strings $str1$ and $str2$ respectively.
+
+---
+
+## 4. Greatest Common Divisor (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def gcdOfStrings(self, str1: str, str2: str) -> str:
+        g = gcd(len(str1), len(str2))
+        
+        if all(str1[i] == str1[i % g] for i in range(len(str1))) and \
+           all(str2[i] == str1[i % g] for i in range(len(str2))):
+            return str1[:g]
+        return ""
+```
+
+```java
+public class Solution {
+    public String gcdOfStrings(String str1, String str2) {
+        int g = gcd(str1.length(), str2.length());
+
+        for (int i = 0; i < str1.length(); i++) {
+            if (str1.charAt(i) != str1.charAt(i % g)) {
+                return "";
+            }
+        }
+
+        for (int i = 0; i < str2.length(); i++) {
+            if (str2.charAt(i) != str1.charAt(i % g)) {
+                return "";
+            }
+        }
+
+        return str1.substring(0, g);
+    }
+
+    private int gcd(int a, int b) {
+        return b == 0 ? a : gcd(b, a % b);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string gcdOfStrings(string str1, string str2) {
+        int g = __gcd((int)str1.size(), (int)str2.size());
+
+        for (int i = 0; i < str1.size(); i++) {
+            if (str1[i] != str1[i % g]) {
+                return "";
+            }
+        }
+
+        for (int i = 0; i < str2.size(); i++) {
+            if (str2[i] != str1[i % g]) {
+                return "";
+            }
+        }
+
+        return str1.substr(0, g);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} str1
+     * @param {string} str2
+     * @return {string}
+     */
+    gcdOfStrings(str1, str2) {
+        const gcd = (a, b) => (b === 0 ? a : gcd(b, a % b));
+        const g = gcd(str1.length, str2.length);
+
+        for (let i = 0; i < str1.length; i++) {
+            if (str1[i] !== str1[i % g]) {
+                return "";
+            }
+        }
+
+        for (let i = 0; i < str2.length; i++) {
+            if (str2[i] !== str1[i % g]) {
+                return "";
+            }
+        }
+
+        return str1.slice(0, g);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m + n)$
+* Space complexity: $O(g)$ for the output string.
+
+> Where $m$ is the length of the string $str1$, $n$ is the length of the string $str2$, and $g$ is the GCD of $m$ and $n$.
\ No newline at end of file
diff --git a/articles/greatest-common-divisor-traversal.md b/articles/greatest-common-divisor-traversal.md
new file mode 100644
index 000000000..57628c98a
--- /dev/null
+++ b/articles/greatest-common-divisor-traversal.md
@@ -0,0 +1,1645 @@
+## 1. Brute Force (DFS)
+
+::tabs-start
+
+```python
+class Solution:
+    def canTraverseAllPairs(self, nums: List[int]) -> bool:
+        n = len(nums)
+        visit = [False] * n
+        adj = [[] for _ in range(n)]
+        for i in range(n):
+            for j in range(i + 1, n):
+                if gcd(nums[i], nums[j]) > 1:
+                    adj[i].append(j)
+                    adj[j].append(i)
+        
+        def dfs(node):
+            visit[node] = True
+            for nei in adj[node]:
+                if not visit[nei]:
+                    dfs(nei)
+        
+        dfs(0)
+        for node in visit:
+            if not node:
+                return False
+        return True
+```
+
+```java
+public class Solution {
+    public boolean canTraverseAllPairs(int[] nums) {
+        int n = nums.length;
+        boolean[] visit = new boolean[n];
+        List<List<Integer>> adj = new ArrayList<>();
+        for (int i = 0; i < n; i++) {
+            adj.add(new ArrayList<>());
+        }
+
+        for (int i = 0; i < n; i++) {
+            for (int j = i + 1; j < n; j++) {
+                if (gcd(nums[i], nums[j]) > 1) {
+                    adj.get(i).add(j);
+                    adj.get(j).add(i);
+                }
+            }
+        }
+
+        dfs(0, adj, visit);
+        for (boolean node : visit) {
+            if (!node) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    private void dfs(int node, List<List<Integer>> adj, boolean[] visit) {
+        visit[node] = true;
+        for (int nei : adj.get(node)) {
+            if (!visit[nei]) {
+                dfs(nei, adj, visit);
+            }
+        }
+    }
+
+    private int gcd(int a, int b) {
+        return b == 0 ? a : gcd(b, a % b);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool canTraverseAllPairs(vector<int>& nums) {
+        int n = nums.size();
+        vector<bool> visit(n, false);
+        vector<vector<int>> adj(n);
+        for (int i = 0; i < n; i++) {
+            for (int j = i + 1; j < n; j++) {
+                if (__gcd(nums[i], nums[j]) > 1) {
+                    adj[i].push_back(j);
+                    adj[j].push_back(i);
+                }
+            }
+        }
+
+        dfs(0, adj, visit);
+        for (bool node : visit) {
+            if (!node) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+private:
+    void dfs(int node, vector<vector<int>>& adj, vector<bool>& visit) {
+        visit[node] = true;
+        for (int& nei : adj[node]) {
+            if (!visit[nei]) {
+                dfs(nei, adj, visit);
+            }
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {boolean}
+     */
+    canTraverseAllPairs(nums) {
+        const n = nums.length;
+        const visit = new Array(n).fill(false);
+        const adj = Array.from({ length: n }, () => []);
+
+        const gcd = (a, b) => (b === 0 ? a : gcd(b, a % b));
+
+        for (let i = 0; i < n; i++) {
+            for (let j = i + 1; j < n; j++) {
+                if (gcd(nums[i], nums[j]) > 1) {
+                    adj[i].push(j);
+                    adj[j].push(i);
+                }
+            }
+        }
+
+        const dfs = (node) => {
+            visit[node] = true;
+            for (const nei of adj[node]) {
+                if (!visit[nei]) {
+                    dfs(nei);
+                }
+            }
+        };
+
+        dfs(0);
+        return visit.every((node) => node);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool CanTraverseAllPairs(int[] nums) {
+        int n = nums.Length;
+        bool[] visited = new bool[n];
+        List<int>[] adj = new List<int>[n];
+        for (int i = 0; i < n; i++) {
+            adj[i] = new List<int>();
+        }
+
+        for (int i = 0; i < n; i++) {
+            for (int j = i + 1; j < n; j++) {
+                if (GCD(nums[i], nums[j]) > 1) {
+                    adj[i].Add(j);
+                    adj[j].Add(i);
+                }
+            }
+        }
+
+        void DFS(int node) {
+            visited[node] = true;
+            foreach (int neighbor in adj[node]) {
+                if (!visited[neighbor]) {
+                    DFS(neighbor);
+                }
+            }
+        }
+
+        DFS(0);
+        foreach (bool v in visited) {
+            if (!v) return false;
+        }
+
+        return true;
+    }
+
+    private int GCD(int a, int b) {
+        while (b != 0) {
+            int temp = b;
+            b = a % b;
+            a = temp;
+        }
+        return a;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 \log n)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 2. Disjoint Set Union
+
+::tabs-start
+
+```python
+class UnionFind:
+    def __init__(self, n):
+        self.n = n
+        self.Parent = list(range(n + 1))
+        self.Size = [1] * (n + 1)
+
+    def find(self, node):
+        if self.Parent[node] != node:
+            self.Parent[node] = self.find(self.Parent[node])
+        return self.Parent[node]
+
+    def union(self, u, v):
+        pu = self.find(u)
+        pv = self.find(v)
+        if pu == pv:
+            return False
+        self.n -= 1
+        if self.Size[pu] < self.Size[pv]:
+            pu, pv = pv, pu
+        self.Size[pu] += self.Size[pv]
+        self.Parent[pv] = pu
+        return True
+    
+    def isConnected(self):
+        return self.n == 1
+
+class Solution:
+    def canTraverseAllPairs(self, nums: List[int]) -> bool:
+        uf = UnionFind(len(nums))
+
+        factor_index = {}  # f -> index of value with factor f
+        for i, n in enumerate(nums):
+            f = 2
+            while f * f <= n:
+                if n % f == 0:
+                    if f in factor_index:
+                        uf.union(i, factor_index[f])
+                    else:
+                        factor_index[f] = i
+                    while n % f == 0:
+                        n = n // f
+                f += 1
+            if n > 1:
+                if n in factor_index:
+                    uf.union(i, factor_index[n])
+                else:
+                    factor_index[n] = i
+        
+        return uf.isConnected()
+```
+
+```java
+class UnionFind {
+    private int n;
+    private int[] Parent;
+    private int[] Size;
+
+    public UnionFind(int n) {
+        this.n = n;
+        this.Parent = new int[n + 1];
+        this.Size = new int[n + 1];
+        for (int i = 0; i <= n; i++) {
+            this.Parent[i] = i;
+            this.Size[i] = 1;
+        }
+    }
+
+    public int find(int node) {
+        if (Parent[node] != node) {
+            Parent[node] = find(Parent[node]);
+        }
+        return Parent[node];
+    }
+
+    public boolean union(int u, int v) {
+        int pu = find(u);
+        int pv = find(v);
+        if (pu == pv) return false;
+        n--;
+        if (Size[pu] < Size[pv]) {
+            int temp = pu;
+            pu = pv;
+            pv = temp;
+        }
+        Size[pu] += Size[pv];
+        Parent[pv] = pu;
+        return true;
+    }
+
+    public boolean isConnected() {
+        return n == 1;
+    }
+}
+
+public class Solution {
+    public boolean canTraverseAllPairs(int[] nums) {
+        int n = nums.length;
+        UnionFind uf = new UnionFind(n);
+        Map<Integer, Integer> factorIndex = new HashMap<>();
+
+        for (int i = 0; i < n; i++) {
+            int num = nums[i];
+            int f = 2;
+            while (f * f <= num) {
+                if (num % f == 0) {
+                    if (factorIndex.containsKey(f)) {
+                        uf.union(i, factorIndex.get(f));
+                    } else {
+                        factorIndex.put(f, i);
+                    }
+                    while (num % f == 0) {
+                        num /= f;
+                    }
+                }
+                f++;
+            }
+            if (num > 1) {
+                if (factorIndex.containsKey(num)) {
+                    uf.union(i, factorIndex.get(num));
+                } else {
+                    factorIndex.put(num, i);
+                }
+            }
+        }
+
+        return uf.isConnected();
+    }
+}
+```
+
+```cpp
+class UnionFind {
+private:
+    int n;
+    vector<int> Parent;
+    vector<int> Size;
+
+public:
+    UnionFind(int n) : n(n), Parent(n + 1), Size(n + 1, 1) {
+        for (int i = 0; i <= n; i++) {
+            Parent[i] = i;
+        }
+    }
+
+    int find(int node) {
+        if (Parent[node] != node) {
+            Parent[node] = find(Parent[node]);
+        }
+        return Parent[node];
+    }
+
+    bool unionNodes(int u, int v) {
+        int pu = find(u);
+        int pv = find(v);
+        if (pu == pv) return false;
+        n--;
+        if (Size[pu] < Size[pv]) swap(pu, pv);
+        Size[pu] += Size[pv];
+        Parent[pv] = pu;
+        return true;
+    }
+
+    bool isConnected() {
+        return n == 1;
+    }
+};
+
+class Solution {
+public:
+    bool canTraverseAllPairs(vector<int>& nums) {
+        int n = nums.size();
+        UnionFind uf(n);
+
+        unordered_map<int, int> factor_index;
+
+        for (int i = 0; i < n; i++) {
+            int num = nums[i];
+            int f = 2;
+            while (f * f <= num) {
+                if (num % f == 0) {
+                    if (factor_index.count(f)) {
+                        uf.unionNodes(i, factor_index[f]);
+                    } else {
+                        factor_index[f] = i;
+                    }
+                    while (num % f == 0) {
+                        num /= f;
+                    }
+                }
+                f++;
+            }
+            if (num > 1) {
+                if (factor_index.count(num)) {
+                    uf.unionNodes(i, factor_index[num]);
+                } else {
+                    factor_index[num] = i;
+                }
+            }
+        }
+
+        return uf.isConnected();
+    }
+};
+```
+
+```javascript
+class UnionFind {
+    /**
+     * @constructor
+     * @param {number} n
+     */
+    constructor(n) {
+        this.Parent = Array.from({ length: n + 1 }, (_, i) => i);
+        this.Size = Array(n + 1).fill(1);
+        this.n = n;
+    }
+
+    /**
+     * @param {number} node
+     * @return {number}
+     */
+    find(node) {
+        if (this.Parent[node] !== node) {
+            this.Parent[node] = this.find(this.Parent[node]);
+        }
+        return this.Parent[node];
+    }
+
+    /**
+     * @param {number} u
+     * @param {number} v
+     * @return {boolean}
+     */
+    union(u, v) {
+        let pu = this.find(u);
+        let pv = this.find(v);
+        if (pu === pv) return false;
+        this.n--;
+        if (this.Size[pu] < this.Size[pv]) {
+            [pu, pv] = [pv, pu];
+        }
+        this.Size[pu] += this.Size[pv];
+        this.Parent[pv] = pu;
+        return true;
+    }
+
+    /**
+     * @return {number}
+     */
+    isConnected() {
+        return this.n === 1;
+    }
+}
+
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {boolean}
+     */
+    canTraverseAllPairs(nums) {
+        const n = nums.length;
+        const uf = new UnionFind(n);
+        const factor_index = new Map();
+
+        for (let i = 0; i < n; i++) {
+            let num = nums[i];
+            let f = 2;
+            while (f * f <= num) {
+                if (num % f === 0) {
+                    if (factor_index.has(f)) {
+                        uf.union(i, factor_index.get(f));
+                    } else {
+                        factor_index.set(f, i);
+                    }
+                    while (num % f === 0) {
+                        num = Math.floor(num / f);
+                    }
+                }
+                f++;
+            }
+            if (num > 1) {
+                if (factor_index.has(num)) {
+                    uf.union(i, factor_index.get(num));
+                } else {
+                    factor_index.set(num, i);
+                }
+            }
+        }
+
+        return uf.isConnected();
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public class UnionFind {
+        public int Count;
+        private int[] Parent;
+        private int[] Size;
+
+        public UnionFind(int n) {
+            Count = n;
+            Parent = new int[n];
+            Size = new int[n];
+            for (int i = 0; i < n; i++) {
+                Parent[i] = i;
+                Size[i] = 1;
+            }
+        }
+
+        public int Find(int x) {
+            if (Parent[x] != x) {
+                Parent[x] = Find(Parent[x]);
+            }
+            return Parent[x];
+        }
+
+        public bool Union(int x, int y) {
+            int px = Find(x);
+            int py = Find(y);
+            if (px == py) return false;
+            Count--;
+            if (Size[px] < Size[py]) {
+                int temp = px;
+                px = py;
+                py = temp;
+            }
+            Size[px] += Size[py];
+            Parent[py] = px;
+            return true;
+        }
+
+        public bool IsConnected() {
+            return Count == 1;
+        }
+    }
+
+    public bool CanTraverseAllPairs(int[] nums) {
+        int n = nums.Length;
+        if (n == 1) return true;
+        if (Array.Exists(nums, x => x == 1)) return false;
+
+        UnionFind uf = new UnionFind(n);
+        Dictionary<int, int> factorIndex = new Dictionary<int, int>();
+
+        for (int i = 0; i < n; i++) {
+            int num = nums[i];
+            int original = num;
+            for (int f = 2; f * f <= num; f++) {
+                if (num % f == 0) {
+                    if (factorIndex.ContainsKey(f)) {
+                        uf.Union(i, factorIndex[f]);
+                    } else {
+                        factorIndex[f] = i;
+                    }
+                    while (num % f == 0) {
+                        num /= f;
+                    }
+                }
+            }
+            if (num > 1) {
+                if (factorIndex.ContainsKey(num)) {
+                    uf.Union(i, factorIndex[num]);
+                } else {
+                    factorIndex[num] = i;
+                }
+            }
+        }
+
+        return uf.IsConnected();
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m + n\sqrt {m})$
+* Space complexity: $O(n \log m)$
+
+> Where $n$ is the size of the array $nums$ and $m$ is the maximum value in the array.
+
+---
+
+## 3. Sieve of Eratosthenes + DSU
+
+::tabs-start
+
+```python
+class UnionFind:
+    def __init__(self, n):
+        self.Parent = list(range(n + 1))
+        self.Size = [1] * (n + 1)
+
+    def find(self, node):
+        if self.Parent[node] != node:
+            self.Parent[node] = self.find(self.Parent[node])
+        return self.Parent[node]
+
+    def union(self, u, v):
+        pu = self.find(u)
+        pv = self.find(v)
+        if pu == pv:
+            return False
+        if self.Size[pu] < self.Size[pv]:
+            pu, pv = pv, pu
+        self.Size[pu] += self.Size[pv]
+        self.Parent[pv] = pu
+        return True
+
+class Solution:
+    def canTraverseAllPairs(self, nums: List[int]) -> bool:
+        N = len(nums)
+        if N == 1:
+            return True
+        if any(num == 1 for num in nums):
+            return False
+
+        MAX = max(nums)
+        sieve = [0] * (MAX + 1)
+        p = 2
+        while p * p <= MAX:
+            if sieve[p] == 0:
+                for composite in range(p * p, MAX + 1, p):
+                    sieve[composite] = p
+            p += 1
+
+        uf = UnionFind(N + MAX + 1)
+        for i in range(N):
+            num = nums[i]
+            if sieve[num] == 0:  # num is prime
+                uf.union(i, N + num)
+                continue
+
+            while num > 1:
+                prime = sieve[num] if sieve[num] != 0 else num
+                uf.union(i, N + prime)
+                while num % prime == 0:
+                    num //= prime
+
+        root = uf.find(0)
+        for i in range(1, N):
+            if uf.find(i) != root:
+                return False
+        return True
+```
+
+```java
+class UnionFind {
+    private int[] Parent;
+    private int[] Size;
+
+    public UnionFind(int n) {
+        Parent = new int[n + 1];
+        Size = new int[n + 1];
+        for (int i = 0; i <= n; i++) {
+            Parent[i] = i;
+            Size[i] = 1;
+        }
+    }
+
+    public int find(int node) {
+        if (Parent[node] != node) {
+            Parent[node] = find(Parent[node]);
+        }
+        return Parent[node];
+    }
+
+    public boolean union(int u, int v) {
+        int pu = find(u);
+        int pv = find(v);
+        if (pu == pv) {
+            return false;
+        }
+        if (Size[pu] < Size[pv]) {
+            int temp = pu;
+            pu = pv;
+            pv = temp;
+        }
+        Size[pu] += Size[pv];
+        Parent[pv] = pu;
+        return true;
+    }
+}
+
+public class Solution {
+    public boolean canTraverseAllPairs(int[] nums) {
+        int N = nums.length;
+        if (N == 1) {
+            return true;
+        }
+        int MAX = 0;
+        for (int num : nums) {
+            MAX = Math.max(MAX, num);
+            if (num == 1) {
+                return false;
+            }
+        }
+
+        int[] sieve = new int[MAX + 1];
+        for (int p = 2; p * p <= MAX; p++) {
+            if (sieve[p] == 0) {
+                for (int composite = p * p; composite <= MAX; composite += p) {
+                    sieve[composite] = p;
+                }
+            }
+        }
+
+        UnionFind uf = new UnionFind(N + MAX + 1);
+        for (int i = 0; i < N; i++) {
+            int num = nums[i];
+            if (sieve[num] == 0) { // num is prime
+                uf.union(i, N + num);
+                continue;
+            }
+
+            while (num > 1) {
+                int prime = sieve[num] != 0 ? sieve[num] : num;
+                uf.union(i, N + prime);
+                while (num % prime == 0) {
+                    num /= prime;
+                }
+            }
+        }
+
+        int root = uf.find(0);
+        for (int i = 1; i < N; i++) {
+            if (uf.find(i) != root) {
+                return false;
+            }
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class UnionFind {
+private:
+    vector<int> Parent, Size;
+
+public:
+    UnionFind(int n) {
+        Parent.resize(n + 1);
+        Size.resize(n + 1, 1);
+        for (int i = 0; i <= n; i++) {
+            Parent[i] = i;
+        }
+    }
+
+    int find(int node) {
+        if (Parent[node] != node) {
+            Parent[node] = find(Parent[node]);
+        }
+        return Parent[node];
+    }
+
+    bool unionSet(int u, int v) {
+        int pu = find(u);
+        int pv = find(v);
+        if (pu == pv) {
+            return false;
+        }
+        if (Size[pu] < Size[pv]) {
+            swap(pu, pv);
+        }
+        Size[pu] += Size[pv];
+        Parent[pv] = pu;
+        return true;
+    }
+};
+
+class Solution {
+public:
+    bool canTraverseAllPairs(vector<int>& nums) {
+        int N = nums.size();
+        if (N == 1) {
+            return true;
+        }
+        for (int num : nums) {
+            if (num == 1) {
+                return false;
+            }
+        }
+
+        int MAX = *max_element(nums.begin(), nums.end());
+        vector<int> sieve(MAX + 1, 0);
+        for (int p = 2; p * p <= MAX; p++) {
+            if (sieve[p] == 0) {
+                for (int composite = p * p; composite <= MAX; composite += p) {
+                    sieve[composite] = p;
+                }
+            }
+        }
+
+        UnionFind uf(N + MAX + 1);
+        for (int i = 0; i < N; i++) {
+            int num = nums[i];
+            if (sieve[num] == 0) { // num is prime
+                uf.unionSet(i, N + num);
+                continue;
+            }
+
+            while (num > 1) {
+                int prime = sieve[num] != 0 ? sieve[num] : num;
+                uf.unionSet(i, N + prime);
+                while (num % prime == 0) {
+                    num /= prime;
+                }
+            }
+        }
+
+        int root = uf.find(0);
+        for (int i = 1; i < N; i++) {
+            if (uf.find(i) != root) {
+                return false;
+            }
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+class UnionFind {
+    /**
+     * @constructor
+     * @param {number} n
+     */
+    constructor(n) {
+        this.Parent = Array.from({ length: n + 1 }, (_, i) => i);
+        this.Size = Array(n + 1).fill(1);
+    }
+
+    /**
+     * @param {number} node
+     * @return {number}
+     */
+    find(node) {
+        if (this.Parent[node] !== node) {
+            this.Parent[node] = this.find(this.Parent[node]);
+        }
+        return this.Parent[node];
+    }
+
+    /**
+     * @param {number} u
+     * @param {number} v
+     * @return {boolean}
+     */
+    union(u, v) {
+        let pu = this.find(u);
+        let pv = this.find(v);
+        if (pu === pv) return false;
+        if (this.Size[pu] < this.Size[pv]) {
+            [pu, pv] = [pv, pu];
+        }
+        this.Size[pu] += this.Size[pv];
+        this.Parent[pv] = pu;
+        return true;
+    }
+}
+
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {boolean}
+     */
+    canTraverseAllPairs(nums) {
+        const N = nums.length;
+        if (N === 1) return true;
+        if (nums.includes(1)) return false;
+
+        const MAX = Math.max(...nums);
+        const sieve = Array(MAX + 1).fill(0);
+        for (let p = 2; p * p <= MAX; p++) {
+            if (sieve[p] === 0) {
+                for (let composite = p * p; composite <= MAX; composite += p) {
+                    sieve[composite] = p;
+                }
+            }
+        }
+
+        const uf = new UnionFind(N + MAX + 1);
+        for (let i = 0; i < N; i++) {
+            let num = nums[i];
+            if (sieve[num] === 0) { // num is prime
+                uf.union(i, N + num);
+                continue;
+            }
+
+            while (num > 1) {
+                const prime = sieve[num] !== 0 ? sieve[num] : num;
+                uf.union(i, N + prime);
+                while (num % prime === 0) {
+                    num = Math.floor(num / prime);
+                }
+            }
+        }
+
+        const root = uf.find(0);
+        for (let i = 1; i < N; i++) {
+            if (uf.find(i) !== root) {
+                return false;
+            }
+        }
+        return true;
+    }
+}
+```
+
+```csharp
+public class UnionFind {
+    public int[] Parent;
+    public int[] Size;
+
+    public UnionFind(int n) {
+        Parent = new int[n];
+        Size = new int[n];
+        for (int i = 0; i < n; i++) {
+            Parent[i] = i;
+            Size[i] = 1;
+        }
+    }
+
+    public int Find(int x) {
+        if (Parent[x] != x) {
+            Parent[x] = Find(Parent[x]);
+        }
+        return Parent[x];
+    }
+
+    public bool Union(int x, int y) {
+        int px = Find(x);
+        int py = Find(y);
+        if (px == py) return false;
+        if (Size[px] < Size[py]) {
+            int temp = px;
+            px = py;
+            py = temp;
+        }
+        Parent[py] = px;
+        Size[px] += Size[py];
+        return true;
+    }
+}
+
+public class Solution {
+    public bool CanTraverseAllPairs(int[] nums) {
+        int n = nums.Length;
+        if (n == 1) return true;
+        if (Array.Exists(nums, x => x == 1)) return false;
+
+        int maxVal = nums.Max();
+        int[] sieve = new int[maxVal + 1];
+        for (int i = 2; i * i <= maxVal; i++) {
+            if (sieve[i] == 0) {
+                for (int j = i * i; j <= maxVal; j += i) {
+                    if (sieve[j] == 0) sieve[j] = i;
+                }
+            }
+        }
+
+        UnionFind uf = new UnionFind(n + maxVal + 1);
+
+        for (int i = 0; i < n; i++) {
+            int num = nums[i];
+            if (sieve[num] == 0) {
+                uf.Union(i, n + num);
+                continue;
+            }
+
+            while (num > 1) {
+                int prime = sieve[num] != 0 ? sieve[num] : num;
+                uf.Union(i, n + prime);
+                while (num % prime == 0) {
+                    num /= prime;
+                }
+            }
+        }
+
+        int root = uf.Find(0);
+        for (int i = 1; i < n; i++) {
+            if (uf.Find(i) != root) return false;
+        }
+
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m + n \log m)$
+* Space complexity: $O(n + m)$
+
+> Where $n$ is the size of the array $nums$ and $m$ is the maximum value in the array.
+
+---
+
+## 4. Sieve of Eratosthenes + DFS
+
+::tabs-start
+
+```python
+class Solution:
+    def canTraverseAllPairs(self, nums: List[int]) -> bool:
+        N = len(nums)
+        if N == 1:
+            return True
+        if any(num == 1 for num in nums):
+            return False
+
+        MAX = max(nums)
+        sieve = [0] * (MAX + 1)
+        p = 2
+        while p * p <= MAX:
+            if sieve[p] == 0:
+                for composite in range(p * p, MAX + 1, p):
+                    sieve[composite] = p
+            p += 1
+        
+        adj = defaultdict(list)
+        for i in range(N):
+            num = nums[i]
+            if sieve[num] == 0:  # num is prime
+                adj[i].append(N + num)
+                adj[N + num].append(i)
+                continue
+
+            while num > 1:
+                prime = sieve[num] if sieve[num] != 0 else num
+                adj[i].append(N + prime)
+                adj[N + prime].append(i)
+                while num % prime == 0:
+                    num //= prime
+
+        visited = set()
+        def dfs(node):
+            visited.add(node)
+            for nei in adj[node]:
+                if nei not in visited:
+                    dfs(nei)
+
+        dfs(0)
+        for i in range(N):
+            if i not in visited:
+                return False
+        return True
+```
+
+```java
+public class Solution {
+    public boolean canTraverseAllPairs(int[] nums) {
+        int N = nums.length;
+        if (N == 1) return true;
+        for (int num : nums) {
+            if (num == 1) return false;
+        }
+
+        int MAX = Arrays.stream(nums).max().getAsInt();
+        int[] sieve = new int[MAX + 1];
+        for (int p = 2; p * p <= MAX; p++) {
+            if (sieve[p] == 0) {
+                for (int composite = p * p; composite <= MAX; composite += p) {
+                    sieve[composite] = p;
+                }
+            }
+        }
+
+        Map<Integer, List<Integer>> adj = new HashMap<>();
+        for (int i = 0; i < N; i++) {
+            int num = nums[i];
+            adj.putIfAbsent(i, new ArrayList<>());
+
+            if (sieve[num] == 0) {
+                adj.putIfAbsent(N + num, new ArrayList<>());
+                adj.get(i).add(N + num);
+                adj.get(N + num).add(i);
+                continue;
+            }
+
+            while (num > 1) {
+                int prime = (sieve[num] == 0) ? num : sieve[num];
+                adj.putIfAbsent(N + prime, new ArrayList<>());
+                adj.get(i).add(N + prime);
+                adj.get(N + prime).add(i);
+                while (num % prime == 0) num /= prime;
+            }
+        }
+
+        Set<Integer> visited = new HashSet<>();
+        dfs(0, adj, visited);
+        for (int i = 0; i < N; i++) {
+            if (!visited.contains(i)) return false;
+        }
+        return true;
+    }
+
+    private void dfs(int node, Map<Integer, List<Integer>> adj, Set<Integer> visited) {
+        visited.add(node);
+        for (int neighbor : adj.get(node)) {
+            if (!visited.contains(neighbor)) {
+                dfs(neighbor, adj, visited);
+            }
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool canTraverseAllPairs(vector<int>& nums) {
+        int N = nums.size();
+        if (N == 1) return true;
+        if (find(nums.begin(), nums.end(), 1) != nums.end()) return false;
+
+        int MAX = *max_element(nums.begin(), nums.end());
+        vector<int> sieve(MAX + 1, 0);
+        for (int p = 2; p * p <= MAX; p++) {
+            if (sieve[p] == 0) {
+                for (int composite = p * p; composite <= MAX; composite += p) {
+                    sieve[composite] = p;
+                }
+            }
+        }
+
+        unordered_map<int, vector<int>> adj;
+        for (int i = 0; i < N; i++) {
+            int num = nums[i];
+            if (!adj.count(i)) adj[i] = {};
+
+            if (sieve[num] == 0) {
+                adj[N + num].push_back(i);
+                adj[i].push_back(N + num);
+                continue;
+            }
+
+            while (num > 1) {
+                int prime = (sieve[num] == 0) ? num : sieve[num];
+                adj[N + prime].push_back(i);
+                adj[i].push_back(N + prime);
+                while (num % prime == 0) num /= prime;
+            }
+        }
+
+        unordered_set<int> visited;
+        dfs(0, adj, visited);
+        for (int i = 0; i < N; i++) {
+            if (visited.find(i) == visited.end()) return false;
+        }
+        return true;
+    }
+
+private:
+    void dfs(int node, unordered_map<int, vector<int>>& adj, unordered_set<int>& visited) {
+        visited.insert(node);
+        for (int& neighbor : adj[node]) {
+            if (visited.find(neighbor) == visited.end()) {
+                dfs(neighbor, adj, visited);
+            }
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {boolean}
+     */
+    canTraverseAllPairs(nums) {
+        const N = nums.length;
+        if (N === 1) return true;
+        if (nums.includes(1)) return false;
+
+        const MAX = Math.max(...nums);
+        const sieve = new Array(MAX + 1).fill(0);
+        for (let p = 2; p * p <= MAX; p++) {
+            if (sieve[p] === 0) {
+                for (let composite = p * p; composite <= MAX; composite += p) {
+                    sieve[composite] = p;
+                }
+            }
+        }
+
+        const adj = new Map();
+        for (let i = 0; i < N; i++) {
+            if (!adj.has(i)) adj.set(i, []);
+            let num = nums[i];
+
+            if (sieve[num] === 0) {
+                if (!adj.has(N + num)) adj.set(N + num, []);
+                adj.get(i).push(N + num);
+                adj.get(N + num).push(i);
+                continue;
+            }
+
+            while (num > 1) {
+                const prime = sieve[num] === 0 ? num : sieve[num];
+                if (!adj.has(N + prime)) adj.set(N + prime, []);
+                adj.get(i).push(N + prime);
+                adj.get(N + prime).push(i);
+                while (num % prime === 0) num = Math.floor(num / prime);
+            }
+        }
+
+        const visited = new Set();
+        const dfs = (node) => {
+            visited.add(node);
+            for (const neighbor of adj.get(node) || []) {
+                if (!visited.has(neighbor)) {
+                    dfs(neighbor);
+                }
+            }
+        };
+
+        dfs(0);
+        for (let i = 0; i < N; i++) {
+            if (!visited.has(i)) return false;
+        }
+        return true;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool CanTraverseAllPairs(int[] nums) {
+        int N = nums.Length;
+        if (N == 1) return true;
+        if (Array.Exists(nums, num => num == 1)) return false;
+
+        int MAX = nums.Max();
+        int[] sieve = new int[MAX + 1];
+        for (int p = 2; p * p <= MAX; p++) {
+            if (sieve[p] == 0) {
+                for (int mult = p * p; mult <= MAX; mult += p) {
+                    if (sieve[mult] == 0) {
+                        sieve[mult] = p;
+                    }
+                }
+            }
+        }
+
+        Dictionary<int, List<int>> adj = new Dictionary<int, List<int>>();
+        for (int i = 0; i < N; i++) {
+            int num = nums[i];
+            if (sieve[num] == 0) {
+                AddEdge(adj, i, N + num);
+                continue;
+            }
+            while (num > 1) {
+                int prime = sieve[num] != 0 ? sieve[num] : num;
+                AddEdge(adj, i, N + prime);
+                while (num % prime == 0) {
+                    num /= prime;
+                }
+            }
+        }
+
+        HashSet<int> visited = new HashSet<int>();
+        DFS(0, adj, visited);
+
+        for (int i = 0; i < N; i++) {
+            if (!visited.Contains(i)) return false;
+        }
+
+        return true;
+    }
+
+    private void AddEdge(Dictionary<int, List<int>> adj, int u, int v) {
+        if (!adj.ContainsKey(u)) adj[u] = new List<int>();
+        if (!adj.ContainsKey(v)) adj[v] = new List<int>();
+        adj[u].Add(v);
+        adj[v].Add(u);
+    }
+
+    private void DFS(int node, Dictionary<int, List<int>> adj, HashSet<int> visited) {
+        visited.Add(node);
+        if (!adj.ContainsKey(node)) return;
+        foreach (int nei in adj[node]) {
+            if (!visited.Contains(nei)) {
+                DFS(nei, adj, visited);
+            }
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m + n \log m)$
+* Space complexity: $O(n + m)$
+
+> Where $n$ is the size of the array $nums$ and $m$ is the maximum value in the array.
+
+---
+
+## 5. Sieve of Eratosthenes + BFS
+
+::tabs-start
+
+```python
+class Solution:
+    def canTraverseAllPairs(self, nums: List[int]) -> bool:
+        N = len(nums)
+        if N == 1:
+            return True
+        if any(num == 1 for num in nums):
+            return False
+
+        MAX = max(nums)
+        sieve = [0] * (MAX + 1)
+        p = 2
+        while p * p <= MAX:
+            if sieve[p] == 0:
+                for composite in range(p * p, MAX + 1, p):
+                    sieve[composite] = p
+            p += 1
+
+        adj = defaultdict(list)
+        for i in range(N):
+            num = nums[i]
+            if sieve[num] == 0:  # num is prime
+                adj[i].append(N + num)
+                adj[N + num].append(i)
+                continue
+
+            while num > 1:
+                prime = sieve[num] if sieve[num] != 0 else num
+                adj[i].append(N + prime)
+                adj[N + prime].append(i)
+                while num % prime == 0:
+                    num //= prime
+
+        visited = set()
+        queue = deque([0])
+        visited.add(0)
+        while queue:
+            node = queue.popleft()
+            for nei in adj[node]:
+                if nei not in visited:
+                    visited.add(nei)
+                    queue.append(nei)
+
+        for i in range(N):
+            if i not in visited:
+                return False
+        return True
+```
+
+```java
+public class Solution {
+    public boolean canTraverseAllPairs(int[] nums) {
+        int N = nums.length;
+        if (N == 1) return true;
+        for (int num : nums) {
+            if (num == 1) return false;
+        }
+
+        int MAX = Arrays.stream(nums).max().getAsInt();
+        int[] sieve = new int[MAX + 1];
+        int p = 2;
+        while (p * p <= MAX) {
+            if (sieve[p] == 0) {
+                for (int composite = p * p; composite <= MAX; composite += p) {
+                    sieve[composite] = p;
+                }
+            }
+            p++;
+        }
+
+        Map<Integer, List<Integer>> adj = new HashMap<>();
+        for (int i = 0; i < N; i++) {
+            int num = nums[i];
+            if (sieve[num] == 0) { // num is prime
+                adj.computeIfAbsent(i, k -> new ArrayList<>()).add(N + num);
+                adj.computeIfAbsent(N + num, k -> new ArrayList<>()).add(i);
+                continue;
+            }
+
+            while (num > 1) {
+                int prime = (sieve[num] != 0) ? sieve[num] : num;
+                adj.computeIfAbsent(i, k -> new ArrayList<>()).add(N + prime);
+                adj.computeIfAbsent(N + prime, k -> new ArrayList<>()).add(i);
+                while (num % prime == 0) {
+                    num /= prime;
+                }
+            }
+        }
+
+        Set<Integer> visited = new HashSet<>();
+        Queue<Integer> queue = new LinkedList<>();
+        queue.add(0);
+        visited.add(0);
+
+        while (!queue.isEmpty()) {
+            int node = queue.poll();
+            for (int nei : adj.getOrDefault(node, new ArrayList<>())) {
+                if (!visited.contains(nei)) {
+                    visited.add(nei);
+                    queue.add(nei);
+                }
+            }
+        }
+
+        for (int i = 0; i < N; i++) {
+            if (!visited.contains(i)) {
+                return false;
+            }
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool canTraverseAllPairs(vector<int>& nums) {
+        int N = nums.size();
+        if (N == 1) return true;
+        if (find(nums.begin(), nums.end(), 1) != nums.end()) return false;
+
+        int MAX = *max_element(nums.begin(), nums.end());
+        vector<int> sieve(MAX + 1, 0);
+        int p = 2;
+        while (p * p <= MAX) {
+            if (sieve[p] == 0) {
+                for (int composite = p * p; composite <= MAX; composite += p) {
+                    sieve[composite] = p;
+                }
+            }
+            p++;
+        }
+
+        unordered_map<int, vector<int>> adj;
+        for (int i = 0; i < N; i++) {
+            int num = nums[i];
+            if (sieve[num] == 0) { // num is prime
+                adj[i].push_back(N + num);
+                adj[N + num].push_back(i);
+                continue;
+            }
+
+            while (num > 1) {
+                int prime = (sieve[num] != 0) ? sieve[num] : num;
+                adj[i].push_back(N + prime);
+                adj[N + prime].push_back(i);
+                while (num % prime == 0) {
+                    num /= prime;
+                }
+            }
+        }
+
+        unordered_set<int> visited;
+        queue<int> q;
+        q.push(0);
+        visited.insert(0);
+
+        while (!q.empty()) {
+            int node = q.front();
+            q.pop();
+            for (int& nei : adj[node]) {
+                if (visited.find(nei) == visited.end()) {
+                    visited.insert(nei);
+                    q.push(nei);
+                }
+            }
+        }
+
+        for (int i = 0; i < N; i++) {
+            if (visited.find(i) == visited.end()) {
+                return false;
+            }
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {boolean}
+     */
+    canTraverseAllPairs(nums) {
+        const N = nums.length;
+        if (N === 1) return true;
+        if (nums.includes(1)) return false;
+
+        const MAX = Math.max(...nums);
+        const sieve = Array(MAX + 1).fill(0);
+        let p = 2;
+        while (p * p <= MAX) {
+            if (sieve[p] === 0) {
+                for (let composite = p * p; composite <= MAX; composite += p) {
+                    sieve[composite] = p;
+                }
+            }
+            p++;
+        }
+
+        const adj = new Map();
+        for (let i = 0; i < N; i++) {
+            let num = nums[i];
+            if (sieve[num] === 0) { // num is prime
+                if (!adj.has(i)) adj.set(i, []);
+                if (!adj.has(N + num)) adj.set(N + num, []);
+                adj.get(i).push(N + num);
+                adj.get(N + num).push(i);
+                continue;
+            }
+
+            while (num > 1) {
+                const prime = sieve[num] !== 0 ? sieve[num] : num;
+                if (!adj.has(i)) adj.set(i, []);
+                if (!adj.has(N + prime)) adj.set(N + prime, []);
+                adj.get(i).push(N + prime);
+                adj.get(N + prime).push(i);
+                while (num % prime === 0) {
+                    num = Math.floor(num / prime);
+                }
+            }
+        }
+
+        const visited = new Set();
+        const queue = new Queue([0]);
+        visited.add(0);
+
+        while (!queue.isEmpty()) {
+            const node = queue.pop();
+            if (adj.has(node)) {
+                for (const nei of adj.get(node)) {
+                    if (!visited.has(nei)) {
+                        visited.add(nei);
+                        queue.push(nei);
+                    }
+                }
+            }
+        }
+
+        for (let i = 0; i < N; i++) {
+            if (!visited.has(i)) {
+                return false;
+            }
+        }
+        return true;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool CanTraverseAllPairs(int[] nums) {
+        int N = nums.Length;
+        if (N == 1) return true;
+        if (nums.Contains(1)) return false;
+
+        int MAX = nums.Max();
+        int[] sieve = new int[MAX + 1];
+        for (int p = 2; p * p <= MAX; p++) {
+            if (sieve[p] == 0) {
+                for (int composite = p * p; composite <= MAX; composite += p) {
+                    if (sieve[composite] == 0) {
+                        sieve[composite] = p;
+                    }
+                }
+            }
+        }
+
+        Dictionary<int, List<int>> adj = new Dictionary<int, List<int>>();
+        for (int i = 0; i < N; i++) {
+            int num = nums[i];
+            if (sieve[num] == 0) {
+                AddEdge(adj, i, N + num);
+                continue;
+            }
+
+            while (num > 1) {
+                int prime = sieve[num] != 0 ? sieve[num] : num;
+                AddEdge(adj, i, N + prime);
+                while (num % prime == 0) {
+                    num /= prime;
+                }
+            }
+        }
+
+        HashSet<int> visited = new HashSet<int>();
+        Queue<int> queue = new Queue<int>();
+        queue.Enqueue(0);
+        visited.Add(0);
+
+        while (queue.Count > 0) {
+            int node = queue.Dequeue();
+            if (!adj.ContainsKey(node)) continue;
+            foreach (int nei in adj[node]) {
+                if (!visited.Contains(nei)) {
+                    visited.Add(nei);
+                    queue.Enqueue(nei);
+                }
+            }
+        }
+
+        for (int i = 0; i < N; i++) {
+            if (!visited.Contains(i)) return false;
+        }
+
+        return true;
+    }
+
+    private void AddEdge(Dictionary<int, List<int>> adj, int u, int v) {
+        if (!adj.ContainsKey(u)) adj[u] = new List<int>();
+        if (!adj.ContainsKey(v)) adj[v] = new List<int>();
+        adj[u].Add(v);
+        adj[v].Add(u);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m + n \log m)$
+* Space complexity: $O(n + m)$
+
+> Where $n$ is the size of the array $nums$ and $m$ is the maximum value in the array.
\ No newline at end of file
diff --git a/articles/grid-game.md b/articles/grid-game.md
new file mode 100644
index 000000000..236f53012
--- /dev/null
+++ b/articles/grid-game.md
@@ -0,0 +1,354 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def gridGame(self, grid: List[List[int]]) -> int:
+        cols = len(grid[0])
+        res = float('inf')
+
+        top1 = 0
+        for i in range(cols):
+            top1 += grid[0][i]
+            bottom1 = 0
+            for j in range(i, cols):
+                bottom1 += grid[1][j]
+            
+            top2 = robot2 = 0
+            for j in range(cols):
+                if j > i:
+                    top2 += grid[0][j]
+
+                bottom2 = 0
+                for k in range(j, i):
+                    bottom2 += grid[1][k]
+                robot2 = max(robot2, top2 + bottom2)
+            
+            res = min(res, robot2)
+        
+        return res
+```
+
+```java
+public class Solution {
+    public long gridGame(int[][] grid) {
+        int cols = grid[0].length;
+        long res = Long.MAX_VALUE;
+
+        long top1 = 0;
+        for (int i = 0; i < cols; i++) {
+            top1 += grid[0][i];
+            long bottom1 = 0;
+            for (int j = i; j < cols; j++) {
+                bottom1 += grid[1][j];
+            }
+            
+            long top2 = 0, robot2 = 0;
+            for (int j = 0; j < cols; j++) {
+                if (j > i) {
+                    top2 += grid[0][j];
+                }
+                
+                long bottom2 = 0;
+                for (int k = j; k < i; k++) {
+                    bottom2 += grid[1][k];
+                }
+                robot2 = Math.max(robot2, top2 + bottom2);
+            }
+            
+            res = Math.min(res, robot2);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long gridGame(vector<vector<int>>& grid) {
+        int cols = grid[0].size();
+        long long res = LLONG_MAX;
+
+        long long top1 = 0;
+        for (int i = 0; i < cols; i++) {
+            top1 += grid[0][i];
+            long long bottom1 = 0;
+            for (int j = i; j < cols; j++) {
+                bottom1 += grid[1][j];
+            }
+
+            long long top2 = 0, robot2 = 0;
+            for (int j = 0; j < cols; j++) {
+                if (j > i) {
+                    top2 += grid[0][j];
+                }
+
+                long long bottom2 = 0;
+                for (int k = j; k < i; k++) {
+                    bottom2 += grid[1][k];
+                }
+                robot2 = max(robot2, top2 + bottom2);
+            }
+
+            res = min(res, robot2);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    gridGame(grid) {
+        let cols = grid[0].length;
+        let res = Infinity;
+
+        let top1 = 0;
+        for (let i = 0; i < cols; i++) {
+            top1 += grid[0][i];
+            let bottom1 = 0;
+            for (let j = i; j < cols; j++) {
+                bottom1 += grid[1][j];
+            }
+
+            let top2 = 0, robot2 = 0;
+            for (let j = 0; j < cols; j++) {
+                if (j > i) {
+                    top2 += grid[0][j];
+                }
+
+                let bottom2 = 0;
+                for (let k = j; k < i; k++) {
+                    bottom2 += grid[1][k];
+                }
+                robot2 = Math.max(robot2, top2 + bottom2);
+            }
+
+            res = Math.min(res, robot2);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 3)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Prefix Sum
+
+::tabs-start
+
+```python
+class Solution:
+    def gridGame(self, grid: List[List[int]]) -> int:
+        N = len(grid[0])
+        preRow1, preRow2 = grid[0].copy(), grid[1].copy()
+
+        for i in range(1, N):
+            preRow1[i] += preRow1[i - 1]
+            preRow2[i] += preRow2[i - 1]
+
+        res = float("inf")
+        for i in range(N):
+            top = preRow1[-1] - preRow1[i]
+            bottom = preRow2[i - 1] if i > 0 else 0
+            secondRobot = max(top, bottom)
+            res = min(res, secondRobot)
+        return res
+```
+
+```java
+class Solution {
+    public long gridGame(int[][] grid) {
+        int N = grid[0].length;
+        long[] preRow1 = new long[N];
+        long[] preRow2 = new long[N];
+        for (int i = 0; i < N; i++) {
+            preRow1[i] = (long)grid[0][i];
+            preRow2[i] = (long)grid[1][i];
+        }
+
+        for (int i = 1; i < N; i++) {
+            preRow1[i] += preRow1[i - 1];
+            preRow2[i] += preRow2[i - 1];
+        }
+
+        long res = Long.MAX_VALUE;
+        for (int i = 0; i < N; i++) {
+            long top = preRow1[N - 1] - preRow1[i];
+            long bottom = i > 0 ? preRow2[i - 1] : 0;
+            long secondRobot = Math.max(top, bottom);
+            res = Math.min(res, secondRobot);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long gridGame(vector<vector<int>>& grid) {
+        int N = grid[0].size();
+        vector<long long> preRow1, preRow2;
+        for (int i = 0; i < N; i++) {
+            preRow1.push_back((long)grid[0][i]);
+            preRow2.push_back((long)grid[1][i]);
+        }
+
+        for (int i = 1; i < N; i++) {
+            preRow1[i] += preRow1[i - 1];
+            preRow2[i] += preRow2[i - 1];
+        }
+
+        long long res = LLONG_MAX;
+        for (int i = 0; i < N; i++) {
+            long long top = preRow1[N - 1] - preRow1[i];
+            long long bottom = i > 0 ? preRow2[i - 1] : 0;
+            long long secondRobot = max(top, bottom);
+            res = min(res, secondRobot);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    gridGame(grid) {
+        const N = grid[0].length;
+        const preRow1 = [...grid[0]];
+        const preRow2 = [...grid[1]];
+
+        for (let i = 1; i < N; i++) {
+            preRow1[i] += preRow1[i - 1];
+            preRow2[i] += preRow2[i - 1];
+        }
+
+        let res = Infinity;
+        for (let i = 0; i < N; i++) {
+            const top = preRow1[N - 1] - preRow1[i];
+            const bottom = i > 0 ? preRow2[i - 1] : 0;
+            const secondRobot = Math.max(top, bottom);
+            res = Math.min(res, secondRobot);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Prefix Sum (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def gridGame(self, grid: List[List[int]]) -> int:
+        res = float("inf")
+        topSum = sum(grid[0])
+        bottomSum = 0
+
+        for i in range(len(grid[0])):
+            topSum -= grid[0][i]
+            res = min(res, max(topSum, bottomSum))
+            bottomSum += grid[1][i]
+
+        return res
+```
+
+```java
+public class Solution {
+    public long gridGame(int[][] grid) {
+        long res = Long.MAX_VALUE;
+        long topSum = 0, bottomSum = 0;
+
+        for (int i = 0; i < grid[0].length; i++) {
+            topSum += grid[0][i];
+        }
+
+        for (int i = 0; i < grid[0].length; i++) {
+            topSum -= grid[0][i];
+            res = Math.min(res, Math.max(topSum, bottomSum));
+            bottomSum += grid[1][i];
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long gridGame(vector<vector<int>>& grid) {
+        long long res = LLONG_MAX;
+        long long topSum = accumulate(grid[0].begin(), grid[0].end(), 0LL);
+        long long bottomSum = 0;
+
+        for (int i = 0; i < grid[0].size(); i++) {
+            topSum -= grid[0][i];
+            res = min(res, max(topSum, bottomSum));
+            bottomSum += grid[1][i];
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    gridGame(grid) {
+        let res = Infinity;
+        let topSum = grid[0].reduce((a, b) => a + b, 0);
+        let bottomSum = 0;
+
+        for (let i = 0; i < grid[0].length; i++) {
+            topSum -= grid[0][i];
+            res = Math.min(res, Math.max(topSum, bottomSum));
+            bottomSum += grid[1][i];
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/guess-number-higher-or-lower.md b/articles/guess-number-higher-or-lower.md
new file mode 100644
index 000000000..4946e4968
--- /dev/null
+++ b/articles/guess-number-higher-or-lower.md
@@ -0,0 +1,427 @@
+## 1. Linear Search
+
+::tabs-start
+
+```python
+# The guess API is already defined for you.
+# @param num, your guess
+# @return -1 if num is higher than the picked number
+#          1 if num is lower than the picked number
+#          otherwise return 0
+# def guess(num: int) -> int:
+
+class Solution:
+    def guessNumber(self, n: int) -> int:
+        for num in range(1, n + 1):
+            if guess(num) == 0:
+                return num
+```
+
+```java
+/** 
+ * Forward declaration of guess API.
+ * @param  num   your guess
+ * @return 	     -1 if num is higher than the picked number
+ *			      1 if num is lower than the picked number
+ *               otherwise return 0
+ * int guess(int num);
+ */
+
+public class Solution extends GuessGame {
+    public int guessNumber(int n) {
+        for (int num = 1; num <= n; num++) {
+            if (guess(num) == 0) return num;
+        }
+        return n;
+    }
+}
+```
+
+```cpp
+/** 
+ * Forward declaration of guess API.
+ * @param  num   your guess
+ * @return 	     -1 if num is higher than the picked number
+ *			      1 if num is lower than the picked number
+ *               otherwise return 0
+ * int guess(int num);
+ */
+
+class Solution {
+public:
+    int guessNumber(int n) {
+        for (int num = 1; num <= n; num++) {
+            if (guess(num) == 0) return num;
+        }
+        return n;
+    }
+};
+```
+
+```javascript
+/** 
+ * Forward declaration of guess API.
+ * @param {number} num   your guess
+ * @return 	     -1 if num is higher than the picked number
+ *			      1 if num is lower than the picked number
+ *               otherwise return 0
+ * function guess(num) {}
+ */
+
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    guessNumber(n) {
+        for (let num = 1; num <= n; num++) {
+            if (guess(num) === 0) return num;
+        }
+        return n;
+    }
+}
+```
+
+```csharp
+/** 
+ * Forward declaration of guess API.
+ * @param  num   your guess
+ * @return 	     -1 if num is higher than the picked number
+ *			      1 if num is lower than the picked number
+ *               otherwise return 0
+ * int guess(int num);
+ */
+
+public class Solution : GuessGame {
+    public int GuessNumber(int n) {
+        for (int num = 1; num <= n; num++) {
+            if (guess(num) == 0) return num;
+        }
+        return n;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Binary Search
+
+::tabs-start
+
+```python
+# The guess API is already defined for you.
+# @param num, your guess
+# @return -1 if num is higher than the picked number
+#          1 if num is lower than the picked number
+#          otherwise return 0
+# def guess(num: int) -> int:
+
+class Solution:
+    def guessNumber(self, n: int) -> int:
+        l, r = 1, n
+        while True:
+            m = (l + r) // 2
+            res = guess(m)
+            if res > 0:
+                l = m + 1
+            elif res < 0:
+                r = m - 1
+            else:
+                return m
+```
+
+```java
+/** 
+ * Forward declaration of guess API.
+ * @param  num   your guess
+ * @return 	     -1 if num is higher than the picked number
+ *			      1 if num is lower than the picked number
+ *               otherwise return 0
+ * int guess(int num);
+ */
+
+public class Solution extends GuessGame {
+    public int guessNumber(int n) {
+        int l = 1, r = n;
+        while (true) {
+            int m = l + (r - l) / 2;
+            int res = guess(m);
+            if (res > 0) {
+                l = m + 1;
+            } else if (res < 0) {
+                r = m - 1;
+            } else {
+                return m;
+            }
+        }
+    }
+}
+```
+
+```cpp
+/** 
+ * Forward declaration of guess API.
+ * @param  num   your guess
+ * @return 	     -1 if num is higher than the picked number
+ *			      1 if num is lower than the picked number
+ *               otherwise return 0
+ * int guess(int num);
+ */
+
+class Solution {
+public:
+    int guessNumber(int n) {
+        int l = 1, r = n;
+        while (true) {
+            int m = l + (r - l) / 2;
+            int res = guess(m);
+            if (res > 0) {
+                l = m + 1;
+            } else if (res < 0) {
+                r = m - 1;
+            } else {
+                return m;
+            }
+        }
+    }
+};
+```
+
+```javascript
+/** 
+ * Forward declaration of guess API.
+ * @param {number} num   your guess
+ * @return 	     -1 if num is higher than the picked number
+ *			      1 if num is lower than the picked number
+ *               otherwise return 0
+ * function guess(num) {}
+ */
+
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    guessNumber(n) {
+        let l = 1, r = n;
+        while (true) {
+            let m = Math.floor((l + r) / 2);
+            let res = guess(m);
+            if (res > 0) {
+                l = m + 1;
+            } else if (res < 0) {
+                r = m - 1;
+            } else {
+                return m;
+            }
+        }
+    }
+}
+```
+
+```csharp
+/** 
+ * Forward declaration of guess API.
+ * @param  num   your guess
+ * @return 	     -1 if num is higher than the picked number
+ *			      1 if num is lower than the picked number
+ *               otherwise return 0
+ * int guess(int num);
+ */
+
+public class Solution : GuessGame {
+    public int GuessNumber(int n) {
+        for (int num = 1; num <= n; num++) {
+            if (guess(num) == 0) return num;
+        }
+        return n;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Ternary Search
+
+::tabs-start
+
+```python
+# The guess API is already defined for you.
+# @param num, your guess
+# @return -1 if num is higher than the picked number
+#          1 if num is lower than the picked number
+#          otherwise return 0
+# def guess(num: int) -> int:
+
+class Solution:
+    def guessNumber(self, n: int) -> int:
+        l, r = 1, n
+        while True:
+            m1 = l + (r - l) // 3
+            m2 = r - (r - l) // 3
+            if guess(m1) == 0:
+                return m1
+            if guess(m2) == 0:
+                return m2
+            if guess(m1) + guess(m2) == 0:
+                l = m1 + 1
+                r = m2 - 1
+            elif guess(m1) == -1:
+                r = m1 - 1
+            else:
+                l = m2 + 1
+```
+
+```java
+/** 
+ * Forward declaration of guess API.
+ * @param  num   your guess
+ * @return 	     -1 if num is higher than the picked number
+ *			      1 if num is lower than the picked number
+ *               otherwise return 0
+ * int guess(int num);
+ */
+
+public class Solution extends GuessGame {
+    public int guessNumber(int n) {
+        int l = 1, r = n;
+        while (true) {
+            int m1 = l + (r - l) / 3;
+            int m2 = r - (r - l) / 3;
+            if (guess(m1) == 0) return m1;
+            if (guess(m2) == 0) return m2;
+            if (guess(m1) + guess(m2) == 0) {
+                l = m1 + 1;
+                r = m2 - 1;
+            } else if (guess(m1) == -1) {
+                r = m1 - 1;
+            } else {
+                l = m2 + 1;
+            }
+        }
+    }
+}
+```
+
+```cpp
+/** 
+ * Forward declaration of guess API.
+ * @param  num   your guess
+ * @return 	     -1 if num is higher than the picked number
+ *			      1 if num is lower than the picked number
+ *               otherwise return 0
+ * int guess(int num);
+ */
+
+class Solution {
+public:
+    int guessNumber(int n) {
+        int l = 1, r = n;
+        while (true) {
+            int m1 = l + (r - l) / 3;
+            int m2 = r - (r - l) / 3;
+            if (guess(m1) == 0) return m1;
+            if (guess(m2) == 0) return m2;
+            if (guess(m1) + guess(m2) == 0) {
+                l = m1 + 1;
+                r = m2 - 1;
+            } else if (guess(m1) == -1) {
+                r = m1 - 1;
+            } else {
+                l = m2 + 1;
+            }
+        }
+    }
+};
+```
+
+```javascript
+/** 
+ * Forward declaration of guess API.
+ * @param {number} num   your guess
+ * @return 	     -1 if num is higher than the picked number
+ *			      1 if num is lower than the picked number
+ *               otherwise return 0
+ * function guess(num) {}
+ */
+
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    guessNumber(n) {
+        let l = 1, r = n;
+        while (true) {
+            let m1 = l + Math.floor((r - l) / 3);
+            let m2 = r - Math.floor((r - l) / 3);
+            if (guess(m1) === 0) return m1;
+            if (guess(m2) === 0) return m2;
+            if (guess(m1) + guess(m2) === 0) {
+                l = m1 + 1;
+                r = m2 - 1;
+            } else if (guess(m1) === -1) {
+                r = m1 - 1;
+            } else {
+                l = m2 + 1;
+            }
+        }
+    }
+}
+```
+
+```csharp
+/** 
+ * Forward declaration of guess API.
+ * @param  num   your guess
+ * @return 	     -1 if num is higher than the picked number
+ *			      1 if num is lower than the picked number
+ *               otherwise return 0
+ * int guess(int num);
+ */
+
+public class Solution : GuessGame {
+    public int GuessNumber(int n) {
+        int l = 1, r = n;
+        while (true) {
+            int m1 = l + (r - l) / 3;
+            int m2 = r - (r - l) / 3;
+
+            if (guess(m1) == 0) return m1;
+            if (guess(m2) == 0) return m2;
+
+            if (guess(m1) + guess(m2) == 0) {
+                l = m1 + 1;
+                r = m2 - 1;
+            }
+            else if (guess(m1) == -1) {
+                r = m1 - 1;
+            }
+            else {
+                l = m2 + 1;
+            }
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log_3 n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/hand-of-straights.md b/articles/hand-of-straights.md
new file mode 100644
index 000000000..773278b86
--- /dev/null
+++ b/articles/hand-of-straights.md
@@ -0,0 +1,1022 @@
+## 1. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def isNStraightHand(self, hand, groupSize):
+        if len(hand) % groupSize:
+            return False
+
+        count = Counter(hand)
+        hand.sort()
+        for num in hand:
+            if count[num]:
+                for i in range(num, num + groupSize):
+                    if not count[i]:
+                        return False
+                    count[i] -= 1
+        return True
+```
+
+```java
+public class Solution {
+    public boolean isNStraightHand(int[] hand, int groupSize) {
+        if (hand.length % groupSize != 0) return false;
+
+        Map<Integer, Integer> count = new HashMap<>();
+        for (int num : hand) {
+            count.put(num, count.getOrDefault(num, 0) + 1);
+        }
+
+        Arrays.sort(hand);
+        for (int num : hand) {
+            if (count.get(num) > 0) {
+                for (int i = num; i < num + groupSize; i++) {
+                    if (count.getOrDefault(i, 0) == 0) return false;
+                    count.put(i, count.get(i) - 1);
+                }
+            }
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isNStraightHand(vector<int>& hand, int groupSize) {
+        if (hand.size() % groupSize != 0) return false;
+
+        unordered_map<int, int> count;
+        for (int num : hand) count[num]++;
+
+        sort(hand.begin(), hand.end());
+        for (int num : hand) {
+            if (count[num] > 0) {
+                for (int i = num; i < num + groupSize; i++) {
+                    if (count[i] == 0) return false;
+                    count[i]--;
+                }
+            }
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} hand
+     * @param {number} groupSize
+     * @return {boolean}
+     */
+    isNStraightHand(hand, groupSize) {
+        if (hand.length % groupSize !== 0) {
+            return false;
+        }
+
+        const count = {};
+        for (const num of hand) {
+            count[num] = (count[num] || 0) + 1;
+        }
+
+        hand.sort((a, b) => a - b);
+        for (const num of hand) {
+            if (count[num] > 0) {
+                for (let i = num; i < num + groupSize; i++) {
+                    if (!count[i]) return false;
+                    count[i] -= 1;
+                }
+            }
+        }
+        return true;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool IsNStraightHand(int[] hand, int groupSize) {
+        if (hand.Length % groupSize != 0) return false;
+
+        var count = new Dictionary<int, int>();
+        foreach (var num in hand) {
+            count[num] = count.GetValueOrDefault(num, 0) + 1;
+        }
+
+        Array.Sort(hand);
+        foreach (var num in hand) {
+            if (count[num] > 0) {
+                for (int i = num; i < num + groupSize; i++) {
+                    if (!count.ContainsKey(i) || count[i] == 0) {
+                        return false;
+                    }
+                    count[i]--;
+                }
+            }
+        }
+        return true;
+    }
+}
+```
+
+```go
+func isNStraightHand(hand []int, groupSize int) bool {
+    if len(hand)%groupSize != 0 {
+        return false
+    }
+
+    count := map[int]int{}
+    for _, num := range hand {
+        count[num]++
+    }
+
+    sort.Ints(hand)
+    for _, num := range hand {
+        if count[num] > 0 {
+            for i := num; i < num+groupSize; i++ {
+                if count[i] == 0 {
+                    return false
+                }
+                count[i]--
+            }
+        }
+    }
+    return true
+}
+```
+
+```kotlin
+class Solution {
+    fun isNStraightHand(hand: IntArray, groupSize: Int): Boolean {
+        if (hand.size % groupSize != 0) return false
+
+        val count = HashMap<Int, Int>()
+        hand.forEach { count[it] = count.getOrDefault(it, 0) + 1 }
+        hand.sort()
+        
+        for (num in hand) {
+            if (count[num]!! > 0) {
+                for (i in num until num + groupSize) {
+                    if (count.getOrDefault(i, 0) == 0) {
+                        return false
+                    }
+                    count[i] = count[i]!! - 1
+                }
+            }
+        }
+        return true
+    }
+}
+```
+
+```swift
+class Solution {
+    func isNStraightHand(_ hand: [Int], _ groupSize: Int) -> Bool {
+        if hand.count % groupSize != 0 {
+            return false
+        }
+
+        var count = [Int: Int]()
+        for num in hand {
+            count[num, default: 0] += 1
+        }
+
+        let sortedHand = hand.sorted()
+        for num in sortedHand {
+            if let freq = count[num], freq > 0 {
+                for i in num..<(num + groupSize) {
+                    if let f = count[i], f > 0 {
+                        count[i] = f - 1
+                    } else {
+                        return false
+                    }
+                }
+            }
+        }
+
+        return true
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Heap
+
+::tabs-start
+
+```python
+class Solution:
+    def isNStraightHand(self, hand: List[int], groupSize: int) -> bool:
+        if len(hand) % groupSize:
+            return False
+
+        count = {}
+        for n in hand:
+            count[n] = 1 + count.get(n, 0)
+
+        minH = list(count.keys())
+        heapq.heapify(minH)
+        while minH:
+            first = minH[0]
+            for i in range(first, first + groupSize):
+                if i not in count:
+                    return False
+                count[i] -= 1
+                if count[i] == 0:
+                    if i != minH[0]:
+                        return False
+                    heapq.heappop(minH)
+        return True
+```
+
+```java
+public class Solution {
+    public boolean isNStraightHand(int[] hand, int groupSize) {
+        if (hand.length % groupSize != 0)
+            return false;
+
+        Map<Integer, Integer> count = new HashMap<>();
+        for (int n : hand)
+            count.put(n, 1 + count.getOrDefault(n, 0));
+
+        PriorityQueue<Integer> minH = new PriorityQueue<>(count.keySet());
+        while (!minH.isEmpty()) {
+            int first = minH.peek();
+            for (int i = first; i < first + groupSize; i++) {
+                if (!count.containsKey(i))
+                    return false;
+                count.put(i, count.get(i) - 1);
+                if (count.get(i) == 0) {
+                    if (i != minH.peek())
+                        return false;
+                    minH.poll();
+                }
+            }
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isNStraightHand(vector<int>& hand, int groupSize) {
+        if (hand.size() % groupSize != 0)
+            return false;
+
+        unordered_map<int, int> count;
+        for (int n : hand)
+            count[n] = 1 + count[n];
+
+        priority_queue<int, vector<int>, greater<int>> minH;
+        for (auto& pair : count)
+            minH.push(pair.first);
+
+        while (!minH.empty()) {
+            int first = minH.top();
+            for (int i = first; i < first + groupSize; i++) {
+                if (count.find(i) == count.end())
+                    return false;
+                count[i] -= 1;
+                if (count[i] == 0) {
+                    if (i != minH.top())
+                        return false;
+                    minH.pop();
+                }
+            }
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+/**
+ * const { MinPriorityQueue } = require('@datastructures-js/priority-queue');
+ */
+
+class Solution {
+    /**
+     * @param {number[]} hand
+     * @param {number} groupSize
+     * @return {boolean}
+     */
+    isNStraightHand(hand, groupSize) {
+        if (hand.length % groupSize !== 0) {
+            return false;
+        }
+
+        const count = {};
+        for (const n of hand) {
+            count[n] = (count[n] || 0) + 1;
+        }
+
+        const minPQ = new MinPriorityQueue();
+        for (const key in count) {
+            minPQ.push(Number(key));
+        }
+
+        while (!minPQ.isEmpty()) {
+            const first = minPQ.front();
+            for (let i = first; i < first + groupSize; i++) {
+                if (!(i in count) || count[i] === 0) {
+                    return false;
+                }
+                count[i] -= 1;
+                if (count[i] === 0) {
+                    if (i !== minPQ.front()) {
+                        return false;
+                    }
+                    minPQ.pop();
+                }
+            }
+        }
+        return true;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool IsNStraightHand(int[] hand, int groupSize) {
+        if (hand.Length % groupSize != 0)
+            return false;
+
+        var count = new Dictionary<int, int>();
+        foreach (int num in hand) {
+            if (count.ContainsKey(num))
+                count[num]++;
+            else
+                count[num] = 1;
+        }
+
+        var minH = new PriorityQueue<int, int>();
+        foreach (var num in count.Keys)
+            minH.Enqueue(num, num);
+
+        while (minH.Count > 0) {
+            int first = minH.Peek();
+            for (int i = first; i < first + groupSize; i++) {
+                if (!count.ContainsKey(i) || count[i] == 0)
+                    return false;
+                
+                count[i]--;
+                if (count[i] == 0) {
+                    if (i != minH.Peek())
+                        return false;
+                    minH.Dequeue();
+                }
+            }
+        }
+        return true;
+    }
+}
+```
+
+```go
+func isNStraightHand(hand []int, groupSize int) bool {
+    if len(hand)%groupSize != 0 {
+        return false
+    }
+
+    count := map[int]int{}
+    for _, n := range hand {
+        count[n]++
+    }
+
+    minH := priorityqueue.NewWith(utils.IntComparator)
+    for k := range count {
+        minH.Enqueue(k)
+    }
+
+    for !minH.Empty() {
+        first, _ := minH.Peek()
+        firstKey := first.(int)
+        for i := firstKey; i < firstKey+groupSize; i++ {
+            if count[i] == 0 {
+                return false
+            }
+            count[i]--
+            if count[i] == 0 {
+                if val, _ := minH.Peek(); val.(int) != i {
+                    return false
+                }
+                minH.Dequeue()
+            }
+        }
+    }
+    return true
+}
+```
+
+```kotlin
+class Solution {
+    fun isNStraightHand(hand: IntArray, groupSize: Int): Boolean {
+        if (hand.size % groupSize != 0) return false
+
+        val count = mutableMapOf<Int, Int>()
+        for (n in hand) {
+            count[n] = count.getOrDefault(n, 0) + 1
+        }
+
+        val minH = PriorityQueue(count.keys)
+        while (minH.isNotEmpty()) {
+            val first = minH.peek()
+            for (i in first until first + groupSize) {
+                if (count.getOrDefault(i, 0) == 0) return false
+                count[i] = count[i]!! - 1
+                if (count[i] == 0) {
+                    if (i != minH.peek()) return false
+                    minH.poll()
+                }
+            }
+        }
+        return true
+    }
+}
+```
+
+```swift
+class Solution {
+    func isNStraightHand(_ hand: [Int], _ groupSize: Int) -> Bool {
+        if hand.count % groupSize != 0 {
+            return false
+        }
+
+        var count = [Int: Int]()
+        for n in hand {
+            count[n, default: 0] += 1
+        }
+
+        var minH = Heap<Int>(Array(count.keys))
+
+        while !minH.isEmpty {
+            guard let first = minH.min else { return false }
+
+            for i in first..<(first + groupSize) {
+                guard let freq = count[i] else { return false }
+                count[i] = freq - 1
+                if count[i] == 0 {
+                    if i != minH.min {
+                        return false
+                    }
+                    minH.removeMin()
+                }
+            }
+        }
+
+        return true
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Ordered Map
+
+::tabs-start
+
+```python
+class Solution:
+    def isNStraightHand(self, hand, groupSize):
+        if len(hand) % groupSize != 0:
+            return False
+
+        count = Counter(hand)
+        q = deque()
+        last_num, open_groups = -1, 0
+
+        for num in sorted(count):
+            if ((open_groups > 0 and num > last_num + 1) or 
+                open_groups > count[num]
+            ):
+                return False
+
+            q.append(count[num] - open_groups)
+            last_num = num
+            open_groups = count[num]
+
+            if len(q) == groupSize:
+                open_groups -= q.popleft()
+
+        return open_groups == 0
+```
+
+```java
+public class Solution {
+    public boolean isNStraightHand(int[] hand, int groupSize) {
+        if (hand.length % groupSize != 0) return false;
+
+        Map<Integer, Integer> count = new TreeMap<>();
+        for (int num : hand) {
+            count.put(num, count.getOrDefault(num, 0) + 1);
+        }
+
+        Queue<Integer> q = new LinkedList<>();
+        int lastNum = -1, openGroups = 0;
+
+        for (int num : count.keySet()) {
+            if ((openGroups > 0 && num > lastNum + 1) || 
+                 openGroups > count.get(num)) {
+                return false;
+            }
+
+            q.add(count.get(num) - openGroups);
+            lastNum = num;
+            openGroups = count.get(num);
+
+            if (q.size() == groupSize) {
+                openGroups -= q.poll();
+            }
+        }
+        return openGroups == 0;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isNStraightHand(vector<int>& hand, int groupSize) {
+        if (hand.size() % groupSize != 0) return false;
+
+        map<int, int> count;
+        for (int num : hand) count[num]++;
+        
+        queue<int> q;
+        int lastNum = -1, openGroups = 0;
+
+        for (auto& entry : count) {
+            int num = entry.first;
+            if ((openGroups > 0 && num > lastNum + 1) || 
+                 openGroups > count[num]) {
+                return false;
+            }
+
+            q.push(count[num] - openGroups);
+            lastNum = num;
+            openGroups = count[num];
+
+            if (q.size() == groupSize) {
+                openGroups -= q.front();
+                q.pop();
+            }
+        }
+        return openGroups == 0;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} hand
+     * @param {number} groupSize
+     * @return {boolean}
+     */
+    isNStraightHand(hand, groupSize) {
+        if (hand.length % groupSize !== 0) return false;
+
+        let count = new Map();
+        hand.forEach(num => count.set(num, (count.get(num) || 0) + 1));
+
+        let q = new Queue();
+        let lastNum = -1, openGroups = 0;
+
+        Array.from(count.keys()).sort((a, b) => a - b).forEach(num => {
+            if ((openGroups > 0 && num > lastNum + 1) || 
+                 openGroups > count.get(num)) {
+                return false;
+            }
+
+            q.push(count.get(num) - openGroups);
+            lastNum = num;
+            openGroups = count.get(num);
+
+            if (q.size() === groupSize) {
+                openGroups -= q.pop();
+            }
+        });
+
+        return openGroups === 0;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool IsNStraightHand(int[] hand, int groupSize) {
+        if (hand.Length % groupSize != 0) return false;
+
+        var count = new SortedDictionary<int, int>();
+        foreach (int num in hand) {
+            if (!count.ContainsKey(num)) count[num] = 0;
+            count[num]++;
+        }
+
+        var q = new Queue<int>();
+        int lastNum = -1, openGroups = 0;
+
+        foreach (int num in count.Keys) {
+            if ((openGroups > 0 && num > lastNum + 1) || 
+                 openGroups > count[num]) {
+                return false;
+            }
+
+            q.Enqueue(count[num] - openGroups);
+            lastNum = num;
+            openGroups = count[num];
+
+            if (q.Count == groupSize) {
+                openGroups -= q.Dequeue();
+            }
+        }
+        return openGroups == 0;
+    }
+}
+```
+
+```go
+func isNStraightHand(hand []int, groupSize int) bool {
+    if len(hand)%groupSize != 0 {
+        return false
+    }
+
+    count := make(map[int]int)
+    for _, num := range hand {
+        count[num]++
+    }
+
+    keys := make([]int, 0, len(count))
+    for k := range count {
+        keys = append(keys, k)
+    }
+    sort.Ints(keys)
+
+    q := []int{}
+    lastNum, openGroups := -1, 0
+
+    for _, num := range keys {
+        if (openGroups > 0 && num > lastNum+1) || 
+            openGroups > count[num] {
+            return false
+        }
+
+        q = append(q, count[num]-openGroups)
+        lastNum = num
+        openGroups = count[num]
+
+        if len(q) == groupSize {
+            openGroups -= q[0]
+            q = q[1:]
+        }
+    }
+    return openGroups == 0
+}
+```
+
+```kotlin
+class Solution {
+    fun isNStraightHand(hand: IntArray, groupSize: Int): Boolean {
+        if (hand.size % groupSize != 0) return false
+
+        val count = TreeMap<Int, Int>()
+        for (num in hand) {
+            count[num] = count.getOrDefault(num, 0) + 1
+        }
+
+        val q: Queue<Int> = LinkedList()
+        var lastNum = -1
+        var openGroups = 0
+
+        for (num in count.keys) {
+            if ((openGroups > 0 && num > lastNum + 1) || 
+                 openGroups > count[num]!!) {
+                return false
+            }
+
+            q.add(count[num]!! - openGroups)
+            lastNum = num
+            openGroups = count[num]!!
+
+            if (q.size == groupSize) {
+                openGroups -= q.poll()
+            }
+        }
+        return openGroups == 0
+    }
+}
+```
+
+```swift
+class Solution {
+    func isNStraightHand(_ hand: [Int], _ groupSize: Int) -> Bool {
+        if hand.count % groupSize != 0 {
+            return false
+        }
+
+        var count = [Int: Int]()
+        for num in hand {
+            count[num, default: 0] += 1
+        }
+
+        var queue = Deque<Int>()
+        var lastNum = -1
+        var openGroups = 0
+
+        for (num, numCount) in count.sorted(by: { $0.key < $1.key }) {
+            if (openGroups > 0 && num > lastNum + 1) || openGroups > numCount {
+                return false
+            }
+
+            queue.append(numCount - openGroups)
+            lastNum = num
+            openGroups = numCount
+
+            if queue.count == groupSize {
+                openGroups -= queue.removeFirst()
+            }
+        }
+        return openGroups == 0
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def isNStraightHand(self, hand: List[int], groupSize: int) -> bool:
+        if len(hand) % groupSize != 0:
+            return False
+
+        count = Counter(hand)
+        for num in hand:
+            start = num
+            while count[start - 1]:
+                start -= 1
+            while start <= num:
+                while count[start]:
+                    for i in range(start, start + groupSize):
+                        if not count[i]:
+                            return False
+                        count[i] -= 1
+                start += 1
+        return True
+```
+
+```java
+public class Solution {
+    public boolean isNStraightHand(int[] hand, int groupSize) {
+        if (hand.length % groupSize != 0) return false;
+
+        Map<Integer, Integer> count = new HashMap<>();
+        for (int num : hand) {
+            count.put(num, count.getOrDefault(num, 0) + 1);
+        }
+        
+        for (int num : hand) {
+            int start = num;
+            while (count.getOrDefault(start - 1, 0) > 0) start--;
+            while (start <= num) {
+                while (count.getOrDefault(start, 0) > 0) {
+                    for (int i = start; i < start + groupSize; i++) {
+                        if (count.getOrDefault(i, 0) == 0) return false;
+                        count.put(i, count.get(i) - 1);
+                    }
+                }
+                start++;
+            }
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isNStraightHand(vector<int>& hand, int groupSize) {
+        if (hand.size() % groupSize != 0) return false;
+
+        unordered_map<int, int> count;
+        for (int num : hand) count[num]++;
+        
+        for (int num : hand) {
+            int start = num;
+            while (count[start - 1] > 0) start--;
+            while (start <= num) {
+                while (count[start] > 0) {
+                    for (int i = start; i < start + groupSize; i++) {
+                        if (count[i] == 0) return false;
+                        count[i]--;
+                    }
+                }
+                start++;
+            }
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} hand
+     * @param {number} groupSize
+     * @return {boolean}
+     */
+    isNStraightHand(hand, groupSize) {
+        if (hand.length % groupSize !== 0) return false;
+
+        const count = new Map();
+        hand.forEach(num => count.set(num, (count.get(num) || 0) + 1));
+        
+        for (const num of hand) {
+            let start = num;
+            while (count.get(start - 1) > 0) start--;
+            while (start <= num) {
+                while (count.get(start) > 0) {
+                    for (let i = start; i < start + groupSize; i++) {
+                        if (!count.get(i)) return false;
+                        count.set(i, count.get(i) - 1);
+                    }
+                }
+                start++;
+            }
+        }
+        return true;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool IsNStraightHand(int[] hand, int groupSize) {
+        if (hand.Length % groupSize != 0) return false;
+
+        Dictionary<int, int> count = new Dictionary<int, int>();
+        foreach (int num in hand) {
+            if (!count.ContainsKey(num)) count[num] = 0;
+            count[num]++;
+        }
+
+        foreach (int num in hand) {
+            int start = num;
+            while (count.ContainsKey(start - 1) && count[start - 1] > 0) {
+                start--;
+            }
+            while (start <= num) {
+                while (count.ContainsKey(start) && count[start] > 0) {
+                    for (int i = start; i < start + groupSize; i++) {
+                        if (!count.ContainsKey(i) || count[i] == 0) {
+                            return false;
+                        }
+                        count[i]--;
+                    }
+                }
+                start++;
+            }
+        }
+        return true;
+    }
+}
+```
+
+```go
+func isNStraightHand(hand []int, groupSize int) bool {
+    if len(hand)%groupSize != 0 {
+        return false
+    }
+
+    count := map[int]int{}
+    for _, num := range hand {
+        count[num]++
+    }
+
+    for _, num := range hand {
+        start := num
+        for count[start-1] > 0 {
+            start--
+        }
+        
+        for start <= num {
+            for count[start] > 0 {
+                for i := start; i < start+groupSize; i++ {
+                    if count[i] == 0 {
+                        return false
+                    }
+                    count[i]--
+                }
+            }
+            start++
+        }
+    }
+    return true
+}
+```
+
+```kotlin
+class Solution {
+    fun isNStraightHand(hand: IntArray, groupSize: Int): Boolean {
+        if (hand.size % groupSize != 0) return false
+
+        val count = HashMap<Int, Int>()
+        hand.forEach { count[it] = count.getOrDefault(it, 0) + 1 }
+
+        for (num in hand) {
+            var start = num
+            while (count.getOrDefault(start - 1, 0) > 0) {
+                start--
+            }
+
+            while (start <= num) {
+                while (count.getOrDefault(start, 0) > 0) {
+                    for (i in start until start + groupSize) {
+                        if (count.getOrDefault(i, 0) == 0) {
+                            return false
+                        }
+                        count[i] = count[i]!! - 1
+                    }
+                }
+                start++
+            }
+        }
+        return true
+    }
+}
+```
+
+```swift
+class Solution {
+    func isNStraightHand(_ hand: [Int], _ groupSize: Int) -> Bool {
+        if hand.count % groupSize != 0 {
+            return false
+        }
+
+        var count = [Int: Int]()
+        for num in hand {
+            count[num, default: 0] += 1
+        }
+
+        for num in hand {
+            var start = num
+            while (count[start - 1] ?? 0) > 0 {
+                start -= 1
+            }
+            while start <= num {
+                while (count[start] ?? 0) > 0 {
+                    for i in start..<(start + groupSize) {
+                        if (count[i] ?? 0) == 0 {
+                            return false
+                        }
+                        count[i]! -= 1
+                    }
+                }
+                start += 1
+            }
+        }
+
+        return true
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/height-checker.md b/articles/height-checker.md
new file mode 100644
index 000000000..1e0919676
--- /dev/null
+++ b/articles/height-checker.md
@@ -0,0 +1,206 @@
+## 1. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def heightChecker(self, heights: List[int]) -> int:
+        expected = sorted(heights)
+
+        res = 0
+        for i in range(len(heights)):
+            if heights[i] != expected[i]:
+                res += 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int heightChecker(int[] heights) {
+        int[] expected = Arrays.copyOf(heights, heights.length);
+        Arrays.sort(expected);
+
+        int res = 0;
+        for (int i = 0; i < heights.length; i++) {
+            if (heights[i] != expected[i]) {
+                res++;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int heightChecker(vector<int>& heights) {
+        vector<int> expected = heights;
+        sort(expected.begin(), expected.end());
+
+        int res = 0;
+        for (int i = 0; i < heights.size(); i++) {
+            if (heights[i] != expected[i]) {
+                res++;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} heights
+     * @return {number}
+     */
+    heightChecker(heights) {
+        const expected = [...heights].sort((a, b) => a - b);
+
+        let res = 0;
+        for (let i = 0; i < heights.length; i++) {
+            if (heights[i] !== expected[i]) {
+                res++;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Counting Sort
+
+::tabs-start
+
+```python
+class Solution:
+    def heightChecker(self, heights: List[int]) -> int:
+        count = [0] * 101
+        for h in heights:
+            count[h] += 1
+
+        expected = []
+        for h in range(1, 101):
+            c = count[h]
+            for _ in range(c):
+                expected.append(h)
+
+        res = 0
+        for i in range(len(heights)):
+            if heights[i] != expected[i]:
+                res += 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int heightChecker(int[] heights) {
+        int[] count = new int[101];
+        for (int h : heights) {
+            count[h]++;
+        }
+
+        List<Integer> expected = new ArrayList<>();
+        for (int h = 1; h <= 100; h++) {
+            int c = count[h];
+            for (int i = 0; i < c; i++) {
+                expected.add(h);
+            }
+        }
+
+        int res = 0;
+        for (int i = 0; i < heights.length; i++) {
+            if (heights[i] != expected.get(i)) {
+                res++;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int heightChecker(vector<int>& heights) {
+        int count[101] = {};
+        for (int h : heights) {
+            count[h]++;
+        }
+
+        vector<int> expected;
+        for (int h = 1; h <= 100; h++) {
+            int c = count[h];
+            for (int i = 0; i < c; i++) {
+                expected.push_back(h);
+            }
+        }
+
+        int res = 0;
+        for (int i = 0; i < heights.size(); i++) {
+            if (heights[i] != expected[i]) {
+                res++;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} heights
+     * @return {number}
+     */
+    heightChecker(heights) {
+        const count = new Array(101).fill(0);
+        for (let h of heights) {
+            count[h]++;
+        }
+
+        const expected = [];
+        for (let h = 1; h <= 100; h++) {
+            let c = count[h];
+            for (let i = 0; i < c; i++) {
+                expected.push(h);
+            }
+        }
+
+        let res = 0;
+        for (let i = 0; i < heights.length; i++) {
+            if (heights[i] !== expected[i]) {
+                res++;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + k)$
+* Space complexity: $O(n + k)$
+
+> Where $n$ is the size of the input array, and $k$ is the range of numbers.
\ No newline at end of file
diff --git a/articles/house-robber-ii.md b/articles/house-robber-ii.md
index d0dc9709d..0469d73df 100644
--- a/articles/house-robber-ii.md
+++ b/articles/house-robber-ii.md
@@ -91,6 +91,65 @@ public class Solution {
 }
 ```
 
+```go
+func rob(nums []int) int {
+    if len(nums) == 1 {
+        return nums[0]
+    }
+    var dfs func(i int, flag bool) int
+    dfs = func(i int, flag bool) int {
+        if i >= len(nums) || (flag && i == len(nums)-1) {
+            return 0
+        }
+        return max(dfs(i+1, flag), nums[i] + dfs(i+2, flag || i == 0))
+    }
+    return max(dfs(0, true), dfs(1, false))
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun rob(nums: IntArray): Int {
+        val n = nums.size
+        if (n == 1) return nums[0]
+        fun dfs(i: Int, flag: Boolean): Int {
+            if (i >= nums.size || (flag && i == nums.size - 1)) {
+                return 0
+            }
+            return maxOf(dfs(i + 1, flag), 
+                         nums[i] + dfs(i + 2, flag || i == 0))
+        }
+        return maxOf(dfs(0, true), dfs(1, false))
+    }
+}
+```
+
+```swift
+class Solution {
+    func rob(_ nums: [Int]) -> Int {
+        if nums.count == 1 {
+            return nums[0]
+        }
+
+        func dfs(_ i: Int, _ flag: Bool) -> Int {
+            if i >= nums.count || (flag && i == nums.count - 1) {
+                return 0
+            }
+            return max(dfs(i + 1, flag), nums[i] + dfs(i + 2, flag || i == 0))
+        }
+
+        return max(dfs(0, true), dfs(1, false))
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -234,6 +293,97 @@ public class Solution {
 }
 ```
 
+```go
+func rob(nums []int) int {
+    if len(nums) == 1 {
+        return nums[0]
+    }
+    memo := make([][2]int, len(nums))
+    for i := range memo {
+        memo[i][0] = -1
+        memo[i][1] = -1
+    }
+
+    var dfs func(i, flag int) int
+    dfs = func(i, flag int) int {
+        if i >= len(nums) || (flag == 1 && i == len(nums)-1) {
+            return 0
+        }
+        if memo[i][flag] != -1 {
+            return memo[i][flag]
+        }
+
+        tmp := flag
+        if i == 0 {
+            tmp = 1
+        }
+        memo[i][flag] = max(dfs(i+1, flag), nums[i] + dfs(i+2, tmp))
+        return memo[i][flag]
+    }
+
+    return max(dfs(0, 1), dfs(1, 0))
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun rob(nums: IntArray): Int {
+        if (nums.size == 1) return nums[0]
+        val memo = Array(nums.size) { IntArray(2) { -1 } }
+
+        fun dfs(i: Int, flag: Int): Int {
+            if (i >= nums.size || (flag == 1 && i == nums.size - 1)) {
+                return 0
+            }
+            if (memo[i][flag] != -1) {
+                return memo[i][flag]
+            }
+            memo[i][flag] = maxOf(dfs(i + 1, flag), 
+                                  nums[i] + dfs(i + 2, flag or if (i == 0) 1 else 0))
+            return memo[i][flag]
+        }
+
+        return maxOf(dfs(0, 1), dfs(1, 0))
+    }
+}
+```
+
+```swift
+class Solution {
+    func rob(_ nums: [Int]) -> Int {
+        if nums.count == 1 {
+            return nums[0]
+        }
+
+        var memo = Array(repeating: Array(repeating: -1, count: 2), count: nums.count)
+
+        func dfs(_ i: Int, _ flag: Bool) -> Int {
+            if i >= nums.count || (flag && i == nums.count - 1) {
+                return 0
+            }
+            if memo[i][flag ? 1 : 0] != -1 {
+                return memo[i][flag ? 1 : 0]
+            }
+
+            memo[i][flag ? 1 : 0] = max(
+                dfs(i + 1, flag), nums[i] + dfs(i + 2, flag || i == 0)
+            )
+
+            return memo[i][flag ? 1 : 0]
+        }
+
+        return max(dfs(0, true), dfs(1, false))
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -385,6 +535,102 @@ public class Solution {
 }
 ```
 
+```go
+func rob(nums []int) int {
+    if len(nums) == 1 {
+        return nums[0]
+    }
+    return max(helper(nums[1:]), helper(nums[:len(nums)-1]))
+}
+
+func helper(nums []int) int {
+    if len(nums) == 0 {
+        return 0
+    }
+    if len(nums) == 1 {
+        return nums[0]
+    }
+
+    dp := make([]int, len(nums))
+    dp[0] = nums[0]
+    dp[1] = max(nums[0], nums[1])
+
+    for i := 2; i < len(nums); i++ {
+        dp[i] = max(dp[i-1], nums[i] + dp[i-2])
+    }
+
+    return dp[len(nums)-1]
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun rob(nums: IntArray): Int {
+        if (nums.size == 1) {
+            return nums[0]
+        }
+        return max(helper(nums.copyOfRange(1, nums.size)), 
+                   helper(nums.copyOfRange(0, nums.size - 1)))
+    }
+
+    fun helper(nums: IntArray): Int {
+        if (nums.isEmpty()) {
+            return 0
+        }
+        if (nums.size == 1) {
+            return nums[0]
+        }
+
+        val dp = IntArray(nums.size)
+        dp[0] = nums[0]
+        dp[1] = maxOf(nums[0], nums[1])
+
+        for (i in 2 until nums.size) {
+            dp[i] = maxOf(dp[i - 1], nums[i] + dp[i - 2])
+        }
+
+        return dp[nums.size - 1]
+    }
+}
+```
+
+```swift
+class Solution {
+    func rob(_ nums: [Int]) -> Int {
+        if nums.count == 1 {
+            return nums[0]
+        }
+        return max(helper(Array(nums[1...])), helper(Array(nums[..<(nums.count - 1)])))
+    }
+    
+    func helper(_ nums: [Int]) -> Int {
+        if nums.isEmpty {
+            return 0
+        }
+        if nums.count == 1 {
+            return nums[0]
+        }
+        
+        var dp = [Int](repeating: 0, count: nums.count)
+        dp[0] = nums[0]
+        dp[1] = max(nums[0], nums[1])
+        
+        for i in 2..<nums.count {
+            dp[i] = max(dp[i - 1], nums[i] + dp[i - 2])
+        }
+        
+        return dp.last!
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -516,6 +762,88 @@ public class Solution {
 }
 ```
 
+```go
+func rob(nums []int) int {
+    if len(nums) == 0 {
+        return 0
+    }
+    return max(nums[0], max(helper(nums[1:]), 
+                            helper(nums[:len(nums)-1])))
+}
+
+func helper(nums []int) int {
+    rob1, rob2 := 0, 0
+
+    for _, num := range nums {
+        newRob := max(rob1+num, rob2)
+        rob1 = rob2
+        rob2 = newRob
+    }
+    return rob2
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun rob(nums: IntArray): Int {
+        return maxOf(nums[0], 
+            maxOf(helper(nums.copyOfRange(1, nums.size)), 
+            helper(nums.copyOfRange(0, nums.size - 1))))
+    }
+
+    private fun helper(nums: IntArray): Int {
+        var rob1 = 0
+        var rob2 = 0
+
+        for (num in nums) {
+            val newRob = maxOf(rob1 + num, rob2)
+            rob1 = rob2
+            rob2 = newRob
+        }
+        return rob2
+    }
+}
+```
+
+```swift
+class Solution {
+    func rob(_ nums: [Int]) -> Int {
+        if nums.isEmpty {
+            return 0
+        }
+        if nums.count == 1 {
+            return nums[0]
+        }
+        
+        let candidate1 = nums[0]
+        let candidate2 = helper(Array(nums[1..<nums.count]))
+        let candidate3 = helper(Array(nums[0..<(nums.count - 1)]))
+        
+        return max(max(candidate1, candidate2), candidate3)
+    }
+
+    func helper(_ nums: [Int]) -> Int {
+        var rob1 = 0
+        var rob2 = 0
+        
+        for num in nums {
+            let newRob = max(rob1 + num, rob2)
+            rob1 = rob2
+            rob2 = newRob
+        }
+        
+        return rob2
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/house-robber-iii.md b/articles/house-robber-iii.md
new file mode 100644
index 000000000..a09238c6b
--- /dev/null
+++ b/articles/house-robber-iii.md
@@ -0,0 +1,563 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def rob(self, root: Optional[TreeNode]) -> int:
+        if not root:
+            return 0
+        
+        res = root.val
+        if root.left:
+            res += self.rob(root.left.left) + self.rob(root.left.right)
+        if root.right:
+            res += self.rob(root.right.left) + self.rob(root.right.right)
+        
+        res = max(res, self.rob(root.left) + self.rob(root.right))
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public int rob(TreeNode root) {
+        if (root == null) {
+            return 0;
+        }
+
+        int res = root.val;
+        if (root.left != null) {
+            res += rob(root.left.left) + rob(root.left.right);
+        }
+        if (root.right != null) {
+            res += rob(root.right.left) + rob(root.right.right);
+        }
+
+        res = Math.max(res, rob(root.left) + rob(root.right));
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int rob(TreeNode* root) {
+        if (!root) {
+            return 0;
+        }
+
+        int res = root->val;
+        if (root->left) {
+            res += rob(root->left->left) + rob(root->left->right);
+        }
+        if (root->right) {
+            res += rob(root->right->left) + rob(root->right->right);
+        }
+
+        res = max(res, rob(root->left) + rob(root->right));
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number}
+     */
+    rob(root) {
+        if (!root) {
+            return 0;
+        }
+
+        let res = root.val;
+        if (root.left) {
+            res += this.rob(root.left.left) + this.rob(root.left.right);
+        }
+        if (root.right) {
+            res += this.rob(root.right.left) + this.rob(root.right.right);
+        }
+
+        res = Math.max(res, this.rob(root.left) + this.rob(root.right));
+        return res;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public int Rob(TreeNode root) {
+        if (root == null) return 0;
+
+        int res = root.val;
+        if (root.left != null) {
+            res += Rob(root.left.left) + Rob(root.left.right);
+        }
+        if (root.right != null) {
+            res += Rob(root.right.left) + Rob(root.right.right);
+        }
+
+        res = Math.Max(res, Rob(root.left) + Rob(root.right));
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Dynamic Programming (Memoization)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def rob(self, root: Optional[TreeNode]) -> int:
+        cache = { None : 0 }
+
+        def dfs(root):
+            if root in cache:
+                return cache[root]
+            
+            cache[root] = root.val
+            if root.left:
+                cache[root] += dfs(root.left.left) + dfs(root.left.right)
+            if root.right:
+                cache[root] += dfs(root.right.left) + dfs(root.right.right)
+            
+            cache[root] = max(cache[root], dfs(root.left) + dfs(root.right))
+            return cache[root]
+        
+        return dfs(root)
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    private Map<TreeNode, Integer> cache;
+
+    public int rob(TreeNode root) {
+        cache = new HashMap<>();
+        cache.put(null, 0);
+        return dfs(root);
+    }
+
+    private int dfs(TreeNode root) {
+        if (cache.containsKey(root)) {
+            return cache.get(root);
+        }
+
+        int res = root.val;
+        if (root.left != null) {
+            res += dfs(root.left.left) + dfs(root.left.right);
+        }
+        if (root.right != null) {
+            res += dfs(root.right.left) + dfs(root.right.right);
+        }
+
+        res = Math.max(res, dfs(root.left) + dfs(root.right));
+        cache.put(root, res);
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+    unordered_map<TreeNode*, int> cache;
+
+public:
+    int rob(TreeNode* root) {
+        cache[nullptr] = 0;
+        return dfs(root);
+    }
+
+private:
+    int dfs(TreeNode* root) {
+        if (cache.find(root) != cache.end()) {
+            return cache[root];
+        }
+
+        int res = root->val;
+        if (root->left) {
+            res += rob(root->left->left) + rob(root->left->right);
+        }
+        if (root->right) {
+            res += rob(root->right->left) + rob(root->right->right);
+        }
+
+        res = max(res, rob(root->left) + rob(root->right));
+        cache[root] = res;
+        return res;
+
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number}
+     */
+    rob(root) {
+        const cache = new Map();
+        cache.set(null, 0);
+
+        const dfs = (root) => {
+            if (cache.has(root)) {
+                return cache.get(root);
+            }
+
+            let res = root.val;
+            if (root.left) {
+                res += dfs(root.left.left) + dfs(root.left.right);
+            }
+            if (root.right) {
+                res += dfs(root.right.left) + dfs(root.right.right);
+            }
+
+            res = Math.max(res, dfs(root.left) + dfs(root.right));
+            cache.set(root, res);
+            return res;
+        };
+
+        return dfs(root);
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    private Dictionary<TreeNode, int> cache = new();
+
+    public int Rob(TreeNode root) {
+        return Dfs(root);
+    }
+
+    private int Dfs(TreeNode root) {
+        if (root == null) return 0;
+        if (cache.ContainsKey(root)) return cache[root];
+
+        int res = root.val;
+        if (root.left != null) {
+            res += Dfs(root.left.left) + Dfs(root.left.right);
+        }
+        if (root.right != null) {
+            res += Dfs(root.right.left) + Dfs(root.right.right);
+        }
+
+        res = Math.Max(res, Dfs(root.left) + Dfs(root.right));
+        cache[root] = res;
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Optimal)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def rob(self, root: TreeNode) -> int:
+        def dfs(root):
+            if not root:
+                return [0, 0]
+
+            leftPair = dfs(root.left)
+            rightPair = dfs(root.right)
+
+            withRoot = root.val + leftPair[1] + rightPair[1]
+            withoutRoot = max(leftPair) + max(rightPair)
+
+            return [withRoot, withoutRoot]
+
+        return max(dfs(root))
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public int rob(TreeNode root) {
+        int[] result = dfs(root);
+        return Math.max(result[0], result[1]);
+    }
+
+    private int[] dfs(TreeNode root) {
+        if (root == null) {
+            return new int[]{0, 0};
+        }
+
+        int[] leftPair = dfs(root.left);
+        int[] rightPair = dfs(root.right);
+
+        int withRoot = root.val + leftPair[1] + rightPair[1];
+        int withoutRoot = Math.max(leftPair[0], leftPair[1]) + 
+                          Math.max(rightPair[0], rightPair[1]);
+
+        return new int[]{withRoot, withoutRoot};
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int rob(TreeNode* root) {
+        auto result = dfs(root);
+        return max(result.first, result.second);
+    }
+
+private:
+    pair<int, int> dfs(TreeNode* root) {
+        if (!root) {
+            return {0, 0};
+        }
+
+        auto leftPair = dfs(root->left);
+        auto rightPair = dfs(root->right);
+
+        int withRoot = root->val + leftPair.second + rightPair.second;
+        int withoutRoot = max(leftPair.first, leftPair.second) + 
+                          max(rightPair.first, rightPair.second);
+
+        return {withRoot, withoutRoot};
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number}
+     */
+    rob(root) {
+        const dfs = (node) => {
+            if (!node) {
+                return [0, 0];
+            }
+
+            const leftPair = dfs(node.left);
+            const rightPair = dfs(node.right);
+
+            const withRoot = node.val + leftPair[1] + rightPair[1];
+            const withoutRoot = Math.max(...leftPair) + Math.max(...rightPair);
+
+            return [withRoot, withoutRoot];
+        };
+
+        const result = dfs(root);
+        return Math.max(...result);
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public int Rob(TreeNode root) {
+        var result = Dfs(root);
+        return Math.Max(result.withRoot, result.withoutRoot);
+    }
+
+    private (int withRoot, int withoutRoot) Dfs(TreeNode root) {
+        if (root == null) return (0, 0);
+
+        var left = Dfs(root.left);
+        var right = Dfs(root.right);
+
+        int withRoot = root.val + left.withoutRoot + right.withoutRoot;
+        int withoutRoot = Math.Max(left.withRoot, left.withoutRoot) + Math.Max(right.withRoot, right.withoutRoot);
+
+        return (withRoot, withoutRoot);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
\ No newline at end of file
diff --git a/articles/house-robber.md b/articles/house-robber.md
index 7b3a0343b..22be9ba02 100644
--- a/articles/house-robber.md
+++ b/articles/house-robber.md
@@ -84,6 +84,55 @@ public class Solution {
 }
 ```
 
+```go
+func rob(nums []int) int {
+    var dfs func(i int) int
+    dfs = func(i int) int {
+        if i >= len(nums) {
+            return 0
+        }
+        return max(dfs(i+1), nums[i] + dfs(i+2))
+    }
+
+    return dfs(0)
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun rob(nums: IntArray): Int {
+        val n = nums.size
+        fun dfs(i: Int): Int {
+            if (i >= n) return 0
+            return maxOf(dfs(i + 1), nums[i] + dfs(i + 2))
+        }
+        return dfs(0)
+    }
+}
+```
+
+```swift
+class Solution {
+    func rob(_ nums: [Int]) -> Int {
+        func dfs(_ i: Int) -> Int {
+            if i >= nums.count {
+                return 0
+            }
+            return max(dfs(i + 1), nums[i] + dfs(i + 2))
+        }
+
+        return dfs(0)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -210,6 +259,74 @@ public class Solution {
 }
 ```
 
+```go
+func rob(nums []int) int {
+    n := len(nums)
+    memo := make([]int, n+1)
+    for i := 0; i <= n; i++ {
+        memo[i] = -1
+    }
+
+    var dfs func(i int) int
+    dfs = func(i int) int {
+        if i >= len(nums) {
+            return 0
+        }
+        if memo[i] != -1 {
+            return memo[i]
+        }
+        memo[i] = max(dfs(i+1), nums[i] + dfs(i+2))
+        return memo[i]
+    }
+
+    return dfs(0)
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun rob(nums: IntArray): Int {
+        val n = nums.size
+        var memo = IntArray(n+1){-1}
+        fun dfs(i: Int): Int {
+            if (i >= n) return 0
+            if (memo[i] != -1) return memo[i]
+            memo[i] = maxOf(dfs(i + 1), nums[i] + dfs(i + 2))
+            return memo[i]
+        }
+        return dfs(0)
+    }
+}
+```
+
+```swift
+class Solution {
+    func rob(_ nums: [Int]) -> Int {
+        var memo = Array(repeating: -1, count: nums.count)
+
+        func dfs(_ i: Int) -> Int {
+            if i >= nums.count {
+                return 0
+            }
+            if memo[i] != -1 {
+                return memo[i]
+            }
+            memo[i] = max(dfs(i + 1), nums[i] + dfs(i + 2))
+            return memo[i]
+        }
+
+        return dfs(0)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -322,6 +439,81 @@ public class Solution {
 }
 ```
 
+```go
+func rob(nums []int) int {
+    n := len(nums)
+    if n == 0 {
+        return 0
+    }
+    if n == 1 {
+        return nums[0]
+    }
+
+    dp := make([]int, n)
+    dp[0] = nums[0]
+    dp[1] = max(nums[0], nums[1])
+
+    for i := 2; i < n; i++ {
+        dp[i] = max(dp[i-1], nums[i] + dp[i-2])
+    }
+
+    return dp[n-1]
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun rob(nums: IntArray): Int {
+        if (nums.isEmpty()) {
+            return 0
+        }
+        if (nums.size == 1) {
+            return nums[0]
+        }
+
+        val dp = IntArray(nums.size)
+        dp[0] = nums[0]
+        dp[1] = maxOf(nums[0], nums[1])
+
+        for (i in 2 until nums.size) {
+            dp[i] = maxOf(dp[i - 1], nums[i] + dp[i - 2])
+        }
+
+        return dp[nums.size - 1]
+    }
+}
+```
+
+```swift
+class Solution {
+    func rob(_ nums: [Int]) -> Int {
+        if nums.isEmpty {
+            return 0
+        }
+        if nums.count == 1 {
+            return nums[0]
+        }
+
+        var dp = Array(repeating: 0, count: nums.count)
+        dp[0] = nums[0]
+        dp[1] = max(nums[0], nums[1])
+
+        for i in 2..<nums.count {
+            dp[i] = max(dp[i - 1], nums[i] + dp[i - 2])
+        }
+
+        return dp[nums.count - 1]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -413,6 +605,56 @@ public class Solution {
 }
 ```
 
+```go
+func rob(nums []int) int {
+    rob1, rob2 := 0, 0
+    for _, num := range nums {
+        temp := max(num+rob1, rob2)
+        rob1 = rob2
+        rob2 = temp
+    }
+    return rob2
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun rob(nums: IntArray): Int {
+        var rob1 = 0
+        var rob2 = 0
+        for (num in nums) {
+            val temp = maxOf(num + rob1, rob2)
+            rob1 = rob2
+            rob2 = temp
+        }
+        return rob2
+    }
+}
+```
+
+```swift
+class Solution {
+    func rob(_ nums: [Int]) -> Int {
+        var rob1 = 0, rob2 = 0
+
+        for num in nums {
+            let temp = max(num + rob1, rob2)
+            rob1 = rob2
+            rob2 = temp
+        }
+
+        return rob2
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/image-smoother.md b/articles/image-smoother.md
new file mode 100644
index 000000000..767d82e16
--- /dev/null
+++ b/articles/image-smoother.md
@@ -0,0 +1,530 @@
+## 1. Iteration (Using Extra Matrix)
+
+::tabs-start
+
+```python
+class Solution:
+    def imageSmoother(self, img: List[List[int]]) -> List[List[int]]:
+        ROWS, COLS = len(img), len(img[0])
+        res = [[0] * COLS for _ in range(ROWS)]
+
+        for r in range(ROWS):
+            for c in range(COLS):
+                total, cnt = 0, 0
+                for i in range(r - 1, r + 2):
+                    for j in range(c - 1, c + 2):
+                        if 0 <= i < ROWS and 0 <= j < COLS:
+                            total += img[i][j]
+                            cnt += 1
+                res[r][c] = total // cnt
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[][] imageSmoother(int[][] img) {
+        int ROWS = img.length, COLS = img[0].length;
+        int[][] res = new int[ROWS][COLS];
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                int total = 0, count = 0;
+                for (int i = r - 1; i <= r + 1; i++) {
+                    for (int j = c - 1; j <= c + 1; j++) {
+                        if (i >= 0 && i < ROWS && j >= 0 && j < COLS) {
+                            total += img[i][j];
+                            count++;
+                        }
+                    }
+                }
+                res[r][c] = total / count;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> imageSmoother(vector<vector<int>>& img) {
+        int ROWS = img.size(), COLS = img[0].size();
+        vector<vector<int>> res(ROWS, vector<int>(COLS, 0));
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                int total = 0, count = 0;
+                for (int i = r - 1; i <= r + 1; i++) {
+                    for (int j = c - 1; j <= c + 1; j++) {
+                        if (i >= 0 && i < ROWS && j >= 0 && j < COLS) {
+                            total += img[i][j];
+                            count++;
+                        }
+                    }
+                }
+                res[r][c] = total / count;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} img
+     * @return {number[][]}
+     */
+    imageSmoother(img) {
+        const ROWS = img.length, COLS = img[0].length;
+        const res = Array.from({ length: ROWS }, () => Array(COLS).fill(0));
+
+        for (let r = 0; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                let total = 0, count = 0;
+                for (let i = r - 1; i <= r + 1; i++) {
+                    for (let j = c - 1; j <= c + 1; j++) {
+                        if (i >= 0 && i < ROWS && j >= 0 && j < COLS) {
+                            total += img[i][j];
+                            count++;
+                        }
+                    }
+                }
+                res[r][c] = Math.floor(total / count);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n * m)$
+
+> Where $n$ is the number of rows and $m$ is the number of columns of the matrix.
+
+---
+
+## 2. Iteration (Using Extra Row)
+
+::tabs-start
+
+```python
+class Solution:
+    def imageSmoother(self, img: List[List[int]]) -> List[List[int]]:
+        ROWS, COLS = len(img), len(img[0])
+        prev_row = img[0][:]
+
+        for r in range(ROWS):
+            curr_row = img[r][:]
+
+            for c in range(COLS):
+                total, cnt = 0, 0
+                for i in range(max(0, r - 1), min(ROWS, r + 2)):
+                    for j in range(max(0, c - 1), min(COLS, c + 2)):
+                        if i == r:
+                            total += curr_row[j]
+                        elif i == r - 1:
+                            total += prev_row[j]
+                        else:
+                            total += img[i][j]
+                        cnt += 1
+                img[r][c] = total // cnt
+
+            prev_row = curr_row
+
+        return img
+```
+
+```java
+public class Solution {
+    public int[][] imageSmoother(int[][] img) {
+        int ROWS = img.length, COLS = img[0].length;
+        int[] prevRow = img[0].clone();
+
+        for (int r = 0; r < ROWS; r++) {
+            int[] currRow = img[r].clone();
+
+            for (int c = 0; c < COLS; c++) {
+                int total = 0, count = 0;
+                for (int i = Math.max(0, r - 1); i < Math.min(ROWS, r + 2); i++) {
+                    for (int j = Math.max(0, c - 1); j < Math.min(COLS, c + 2); j++) {
+                        if (i == r) {
+                            total += currRow[j];
+                        } else if (i == r - 1) {
+                            total += prevRow[j];
+                        } else {
+                            total += img[i][j];
+                        }
+                        count++;
+                    }
+                }
+                img[r][c] = total / count;
+            }
+
+            prevRow = currRow;
+        }
+
+        return img;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> imageSmoother(vector<vector<int>>& img) {
+        int ROWS = img.size(), COLS = img[0].size();
+        vector<int> prevRow = img[0];
+
+        for (int r = 0; r < ROWS; r++) {
+            vector<int> currRow = img[r];
+
+            for (int c = 0; c < COLS; c++) {
+                int total = 0, count = 0;
+                for (int i = max(0, r - 1); i < min(ROWS, r + 2); i++) {
+                    for (int j = max(0, c - 1); j < min(COLS, c + 2); j++) {
+                        if (i == r) {
+                            total += currRow[j];
+                        } else if (i == r - 1) {
+                            total += prevRow[j];
+                        } else {
+                            total += img[i][j];
+                        }
+                        count++;
+                    }
+                }
+                img[r][c] = total / count;
+            }
+
+            prevRow = currRow;
+        }
+
+        return img;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} img
+     * @return {number[][]}
+     */
+    imageSmoother(img) {
+        const ROWS = img.length, COLS = img[0].length;
+        let prevRow = [...img[0]];
+
+        for (let r = 0; r < ROWS; r++) {
+            let currRow = [...img[r]];
+
+            for (let c = 0; c < COLS; c++) {
+                let total = 0, count = 0;
+                for (let i = Math.max(0, r - 1); i < Math.min(ROWS, r + 2); i++) {
+                    for (let j = Math.max(0, c - 1); j < Math.min(COLS, c + 2); j++) {
+                        if (i === r) {
+                            total += currRow[j];
+                        } else if (i === r - 1) {
+                            total += prevRow[j];
+                        } else {
+                            total += img[i][j];
+                        }
+                        count++;
+                    }
+                }
+                img[r][c] = Math.floor(total / count);
+            }
+
+            prevRow = currRow;
+        }
+
+        return img;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n)$ extra space.
+
+> Where $n$ is the number of rows and $m$ is the number of columns of the matrix.
+
+---
+
+## 3. Iteration (Without Extra Space)
+
+::tabs-start
+
+```python
+class Solution:
+    def imageSmoother(self, img: List[List[int]]) -> List[List[int]]:
+        ROWS, COLS = len(img), len(img[0])
+        LIMIT = 256
+
+        for r in range(ROWS):
+            for c in range(COLS):
+                total, cnt = 0, 0
+                for i in range(max(0, r - 1), min(ROWS, r + 2)):
+                    for j in range(max(0, c - 1), min(COLS, c + 2)):
+                        total += img[i][j] % LIMIT
+                        cnt += 1
+                img[r][c] += (total // cnt) * LIMIT
+
+        for r in range(ROWS):
+            for c in range(COLS):
+                img[r][c] //= LIMIT
+
+        return img
+```
+
+```java
+public class Solution {
+    public int[][] imageSmoother(int[][] img) {
+        int ROWS = img.length, COLS = img[0].length;
+        int LIMIT = 256;
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                int total = 0, count = 0;
+                for (int i = Math.max(0, r - 1); i < Math.min(ROWS, r + 2); i++) {
+                    for (int j = Math.max(0, c - 1); j < Math.min(COLS, c + 2); j++) {
+                        total += img[i][j] % LIMIT;
+                        count++;
+                    }
+                }
+                img[r][c] += (total / count) * LIMIT;
+            }
+        }
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                img[r][c] /= LIMIT;
+            }
+        }
+
+        return img;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> imageSmoother(vector<vector<int>>& img) {
+        int ROWS = img.size(), COLS = img[0].size();
+        int LIMIT = 256;
+
+        for (int r = 0; r < ROWS; ++r) {
+            for (int c = 0; c < COLS; ++c) {
+                int total = 0, count = 0;
+                for (int i = max(0, r - 1); i < min(ROWS, r + 2); ++i) {
+                    for (int j = max(0, c - 1); j < min(COLS, c + 2); ++j) {
+                        total += img[i][j] % LIMIT;
+                        count++;
+                    }
+                }
+                img[r][c] += (total / count) * LIMIT;
+            }
+        }
+
+        for (int r = 0; r < ROWS; ++r) {
+            for (int c = 0; c < COLS; ++c) {
+                img[r][c] /= LIMIT;
+            }
+        }
+
+        return img;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} img
+     * @return {number[][]}
+     */
+    imageSmoother(img) {
+        const ROWS = img.length, COLS = img[0].length;
+        const LIMIT = 256;
+
+        for (let r = 0; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                let total = 0, count = 0;
+                for (let i = Math.max(0, r - 1); i < Math.min(ROWS, r + 2); i++) {
+                    for (let j = Math.max(0, c - 1); j < Math.min(COLS, c + 2); j++) {
+                        total += img[i][j] % LIMIT;
+                        count++;
+                    }
+                }
+                img[r][c] += Math.floor(total / count) * LIMIT;
+            }
+        }
+
+        for (let r = 0; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                img[r][c] = Math.floor(img[r][c] / LIMIT);
+            }
+        }
+
+        return img;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(1)$ extra space.
+
+> Where $n$ is the number of rows and $m$ is the number of columns of the matrix.
+
+---
+
+## 4. Bit Mask
+
+::tabs-start
+
+```python
+class Solution:
+    def imageSmoother(self, img: List[List[int]]) -> List[List[int]]:
+        ROWS, COLS = len(img), len(img[0])
+
+        for r in range(ROWS):
+            for c in range(COLS):
+                total, cnt = 0, 0
+                for i in range(r - 1, r + 2):
+                    for j in range(c - 1, c + 2):
+                        if i < 0 or i == ROWS or j < 0 or j == COLS:
+                            continue
+                        total += img[i][j] % 256
+                        cnt += 1
+                img[r][c] ^= ((total // cnt) << 8)
+
+        for r in range(ROWS):
+            for c in range(COLS):
+                img[r][c] >>= 8
+        return img
+```
+
+```java
+public class Solution {
+    public int[][] imageSmoother(int[][] img) {
+        int ROWS = img.length, COLS = img[0].length;
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                int total = 0, cnt = 0;
+                for (int i = r - 1; i <= r + 1; i++) {
+                    for (int j = c - 1; j <= c + 1; j++) {
+                        if (i < 0 || i >= ROWS || j < 0 || j >= COLS) {
+                            continue;
+                        }
+                        total += img[i][j] % 256;
+                        cnt++;
+                    }
+                }
+                img[r][c] ^= ((total / cnt) << 8);
+            }
+        }
+        
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                img[r][c] >>= 8;
+            }
+        }
+        return img;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> imageSmoother(vector<vector<int>>& img) {
+        int ROWS = img.size(), COLS = img[0].size();
+        
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                int total = 0, cnt = 0;
+                for (int i = r - 1; i <= r + 1; i++) {
+                    for (int j = c - 1; j <= c + 1; j++) {
+                        if (i < 0 || i >= ROWS || j < 0 || j >= COLS) {
+                            continue;
+                        }
+                        total += img[i][j] % 256;
+                        cnt++;
+                    }
+                }
+                img[r][c] ^= ((total / cnt) << 8);
+            }
+        }
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                img[r][c] >>= 8;
+            }
+        }
+        return img;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} img
+     * @return {number[][]}
+     */
+    imageSmoother(img) {
+        const ROWS = img.length, COLS = img[0].length;
+
+        for (let r = 0; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                let total = 0, cnt = 0;
+                for (let i = r - 1; i <= r + 1; i++) {
+                    for (let j = c - 1; j <= c + 1; j++) {
+                        if (i < 0 || i >= ROWS || j < 0 || j >= COLS) {
+                            continue;
+                        }
+                        total += img[i][j] % 256;
+                        cnt++;
+                    }
+                }
+                img[r][c] ^= ((total / cnt) << 8);
+            }
+        }
+
+        for (let r = 0; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                img[r][c] >>= 8;
+            }
+        }
+        return img;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(1)$ extra space.
+
+> Where $n$ is the number of rows and $m$ is the number of columns of the matrix.
\ No newline at end of file
diff --git a/articles/implement-prefix-tree.md b/articles/implement-prefix-tree.md
index e37ce6228..3e4a303f2 100644
--- a/articles/implement-prefix-tree.md
+++ b/articles/implement-prefix-tree.md
@@ -265,6 +265,160 @@ public class PrefixTree {
 }
 ```
 
+```go
+type TrieNode struct {
+	children [26]*TrieNode
+	endOfWord bool
+}
+
+type PrefixTree struct {
+	root *TrieNode
+}
+
+func Constructor() PrefixTree {
+	return PrefixTree{root: &TrieNode{}}
+}
+
+func (this *PrefixTree) Insert(word string) {
+	cur := this.root
+	for _, c := range word {
+		i := c - 'a'
+		if cur.children[i] == nil {
+			cur.children[i] = &TrieNode{}
+		}
+		cur = cur.children[i]
+	}
+	cur.endOfWord = true
+}
+
+func (this *PrefixTree) Search(word string) bool {
+	cur := this.root
+	for _, c := range word {
+		i := c - 'a'
+		if cur.children[i] == nil {
+			return false
+		}
+		cur = cur.children[i]
+	}
+	return cur.endOfWord
+}
+
+func (this *PrefixTree) StartsWith(prefix string) bool {
+	cur := this.root
+	for _, c := range prefix {
+		i := c - 'a'
+		if cur.children[i] == nil {
+			return false
+		}
+		cur = cur.children[i]
+	}
+	return true
+}
+```
+
+```kotlin
+class TrieNode {
+    val children = arrayOfNulls<TrieNode>(26)
+    var endOfWord = false
+}
+
+class PrefixTree {
+    private val root = TrieNode()
+
+    fun insert(word: String) {
+        var cur = root
+        for (c in word) {
+            val i = c - 'a'
+            if (cur.children[i] == null) {
+                cur.children[i] = TrieNode()
+            }
+            cur = cur.children[i]!!
+        }
+        cur.endOfWord = true
+    }
+
+    fun search(word: String): Boolean {
+        var cur = root
+        for (c in word) {
+            val i = c - 'a'
+            if (cur.children[i] == null) {
+                return false
+            }
+            cur = cur.children[i]!!
+        }
+        return cur.endOfWord
+    }
+
+    fun startsWith(prefix: String): Boolean {
+        var cur = root
+        for (c in prefix) {
+            val i = c - 'a'
+            if (cur.children[i] == null) {
+                return false
+            }
+            cur = cur.children[i]!!
+        }
+        return true
+    }
+}
+```
+
+```swift
+class TrieNode {
+    var children: [TrieNode?]
+    var endOfWord: Bool
+
+    init() {
+        self.children = Array(repeating: nil, count: 26)
+        self.endOfWord = false
+    }
+}
+
+class PrefixTree {
+    private let root: TrieNode
+
+    init() {
+        self.root = TrieNode()
+    }
+
+    func insert(_ word: String) {
+        var cur = root
+        for c in word {
+            let i = Int(c.asciiValue! - Character("a").asciiValue!)
+            if cur.children[i] == nil {
+                cur.children[i] = TrieNode()
+            }
+            cur = cur.children[i]!
+        }
+        cur.endOfWord = true
+    }
+
+    func search(_ word: String) -> Bool {
+        var cur = root
+        for c in word {
+            let i = Int(c.asciiValue! - Character("a").asciiValue!)
+            if cur.children[i] == nil {
+                return false
+            }
+            cur = cur.children[i]!
+        }
+        return cur.endOfWord
+    }
+
+    func startsWith(_ prefix: String) -> Bool {
+        var cur = root
+        for c in prefix {
+            let i = Int(c.asciiValue! - Character("a").asciiValue!)
+            if cur.children[i] == nil {
+                return false
+            }
+            cur = cur.children[i]!
+        }
+        return true
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -520,6 +674,149 @@ public class PrefixTree {
 }
 ```
 
+```go
+type TrieNode struct {
+	children map[rune]*TrieNode
+	endOfWord bool
+}
+
+type PrefixTree struct {
+	root *TrieNode
+}
+
+func Constructor() PrefixTree {
+	return PrefixTree{root: &TrieNode{children: make(map[rune]*TrieNode)}}
+}
+
+func (this *PrefixTree) Insert(word string) {
+	cur := this.root
+	for _, c := range word {
+		if cur.children[c] == nil {
+			cur.children[c] = &TrieNode{children: make(map[rune]*TrieNode)}
+		}
+		cur = cur.children[c]
+	}
+	cur.endOfWord = true
+}
+
+func (this *PrefixTree) Search(word string) bool {
+	cur := this.root
+	for _, c := range word {
+		if cur.children[c] == nil {
+			return false
+		}
+		cur = cur.children[c]
+	}
+	return cur.endOfWord
+}
+
+func (this *PrefixTree) StartsWith(prefix string) bool {
+	cur := this.root
+	for _, c := range prefix {
+		if cur.children[c] == nil {
+			return false
+		}
+		cur = cur.children[c]
+	}
+	return true
+}
+```
+
+```kotlin
+class TrieNode {
+    val children = mutableMapOf<Char, TrieNode>()
+    var endOfWord = false
+}
+
+class PrefixTree {
+    private val root = TrieNode()
+
+    fun insert(word: String) {
+        var cur = root
+        for (c in word) {
+            cur.children.putIfAbsent(c, TrieNode())
+            cur = cur.children[c]!!
+        }
+        cur.endOfWord = true
+    }
+
+    fun search(word: String): Boolean {
+        var cur = root
+        for (c in word) {
+            if (c !in cur.children) {
+                return false
+            }
+            cur = cur.children[c]!!
+        }
+        return cur.endOfWord
+    }
+
+    fun startsWith(prefix: String): Boolean {
+        var cur = root
+        for (c in prefix) {
+            if (c !in cur.children) {
+                return false
+            }
+            cur = cur.children[c]!!
+        }
+        return true
+    }
+}
+```
+
+```swift
+class TrieNode {
+    var children: [Character: TrieNode]
+    var endOfWord: Bool
+
+    init() {
+        self.children = [:]
+        self.endOfWord = false
+    }
+}
+
+class PrefixTree {
+    private let root: TrieNode
+
+    init() {
+        self.root = TrieNode()
+    }
+
+    func insert(_ word: String) {
+        var cur = root
+        for c in word {
+            if cur.children[c] == nil {
+                cur.children[c] = TrieNode()
+            }
+            cur = cur.children[c]!
+        }
+        cur.endOfWord = true
+    }
+
+    func search(_ word: String) -> Bool {
+        var cur = root
+        for c in word {
+            if cur.children[c] == nil {
+                return false
+            }
+            cur = cur.children[c]!
+        }
+        return cur.endOfWord
+    }
+
+    func startsWith(_ prefix: String) -> Bool {
+        var cur = root
+        for c in prefix {
+            if cur.children[c] == nil {
+                return false
+            }
+            cur = cur.children[c]!
+        }
+        return true
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/implement-queue-using-stacks.md b/articles/implement-queue-using-stacks.md
new file mode 100644
index 000000000..9d51b2ad4
--- /dev/null
+++ b/articles/implement-queue-using-stacks.md
@@ -0,0 +1,351 @@
+## 1. Using Two Stacks (Brute Force)
+
+::tabs-start
+
+```python
+class MyQueue:
+
+    def __init__(self):
+        self.stack1 = []
+        self.stack2 = []
+
+    def push(self, x: int) -> None:
+        self.stack1.append(x)
+
+    def pop(self) -> int:
+        while len(self.stack1) > 1:
+            self.stack2.append(self.stack1.pop())
+        res = self.stack1.pop()
+        while self.stack2:
+            self.stack1.append(self.stack2.pop())
+        return res
+
+    def peek(self) -> int:
+        while len(self.stack1) > 1:
+            self.stack2.append(self.stack1.pop())
+        res = self.stack1[-1]
+        while self.stack2:
+            self.stack1.append(self.stack2.pop())
+        return res
+
+    def empty(self) -> bool:
+        return not self.stack1
+```
+
+```java
+public class MyQueue {
+    private Stack<Integer> stack1;
+    private Stack<Integer> stack2;
+
+    public MyQueue() {
+        stack1 = new Stack<>();
+        stack2 = new Stack<>();
+    }
+
+    public void push(int x) {
+        stack1.push(x);
+    }
+
+    public int pop() {
+        while (stack1.size() > 1) {
+            stack2.push(stack1.pop());
+        }
+        int res = stack1.pop();
+        while (!stack2.isEmpty()) {
+            stack1.push(stack2.pop());
+        }
+        return res;
+    }
+
+    public int peek() {
+        while (stack1.size() > 1) {
+            stack2.push(stack1.pop());
+        }
+        int res = stack1.peek();
+        while (!stack2.isEmpty()) {
+            stack1.push(stack2.pop());
+        }
+        return res;
+    }
+
+    public boolean empty() {
+        return stack1.isEmpty();
+    }
+}
+```
+
+```cpp
+class MyQueue {
+private:
+    stack<int> stack1;
+    stack<int> stack2;
+
+public:
+    MyQueue() {}
+
+    void push(int x) {
+        stack1.push(x);
+    }
+
+    int pop() {
+        while (stack1.size() > 1) {
+            stack2.push(stack1.top());
+            stack1.pop();
+        }
+        int res = stack1.top();
+        stack1.pop();
+        while (!stack2.empty()) {
+            stack1.push(stack2.top());
+            stack2.pop();
+        }
+        return res;
+    }
+
+    int peek() {
+        while (stack1.size() > 1) {
+            stack2.push(stack1.top());
+            stack1.pop();
+        }
+        int res = stack1.top();
+        while (!stack2.empty()) {
+            stack1.push(stack2.top());
+            stack2.pop();
+        }
+        return res;
+    }
+
+    bool empty() {
+        return stack1.empty();
+    }
+};
+```
+
+```javascript
+class MyQueue {
+    constructor() {
+        this.stack1 = [];
+        this.stack2 = [];
+    }
+
+    /** 
+     * @param {number} x
+     * @return {void}
+     */
+    push(x) {
+        this.stack1.push(x);
+    }
+
+    /**
+     * @return {number}
+     */
+    pop() {
+        while (this.stack1.length > 1) {
+            this.stack2.push(this.stack1.pop());
+        }
+        const res = this.stack1.pop();
+        while (this.stack2.length) {
+            this.stack1.push(this.stack2.pop());
+        }
+        return res;
+    }
+
+    /**
+     * @return {number}
+     */
+    peek() {
+        while (this.stack1.length > 1) {
+            this.stack2.push(this.stack1.pop());
+        }
+        const res = this.stack1[this.stack1.length - 1];
+        while (this.stack2.length) {
+            this.stack1.push(this.stack2.pop());
+        }
+        return res;
+    }
+
+    /**
+     * @return {boolean}
+     */
+    empty() {
+        return this.stack1.length === 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(1)$ time for initialization.
+    * $O(1)$ time for each $push()$ and $empty()$ function calls.
+    * $O(n)$ time for each $pop()$ and $peek()$ function calls.
+* Space complexity: $O(n)$
+
+---
+
+## 2. Using Two Stacks (Amortized Complexity)
+
+::tabs-start
+
+```python
+class MyQueue:
+    
+    def __init__(self):
+        self.s1 = []
+        self.s2 = []
+
+    def push(self, x: int) -> None:
+        self.s1.append(x)
+
+    def pop(self) -> int:
+        if not self.s2:
+            while self.s1:
+                self.s2.append(self.s1.pop())
+        return self.s2.pop()
+
+    def peek(self) -> int:
+        if not self.s2:
+            while self.s1:
+                self.s2.append(self.s1.pop())
+        return self.s2[-1]
+
+    def empty(self) -> bool:
+        return max(len(self.s1), len(self.s2)) == 0
+```
+
+```java
+public class MyQueue {
+    private Stack<Integer> s1;
+    private Stack<Integer> s2;
+
+    public MyQueue() {
+        s1 = new Stack<>();
+        s2 = new Stack<>();
+    }
+
+    public void push(int x) {
+        s1.push(x);
+    }
+
+    public int pop() {
+        if (s2.isEmpty()) {
+            while (!s1.isEmpty()) {
+                s2.push(s1.pop());
+            }
+        }
+        return s2.pop();
+    }
+
+    public int peek() {
+        if (s2.isEmpty()) {
+            while (!s1.isEmpty()) {
+                s2.push(s1.pop());
+            }
+        }
+        return s2.peek();
+    }
+
+    public boolean empty() {
+        return s1.isEmpty() && s2.isEmpty();
+    }
+}
+```
+
+```cpp
+class MyQueue {
+private:
+    stack<int> s1, s2;
+
+public:
+    MyQueue() {}
+
+    void push(int x) {
+        s1.push(x);
+    }
+
+    int pop() {
+        if (s2.empty()) {
+            while (!s1.empty()) {
+                s2.push(s1.top());
+                s1.pop();
+            }
+        }
+        int res = s2.top();
+        s2.pop();
+        return res;
+    }
+
+    int peek() {
+        if (s2.empty()) {
+            while (!s1.empty()) {
+                s2.push(s1.top());
+                s1.pop();
+            }
+        }
+        return s2.top();
+    }
+
+    bool empty() {
+        return s1.empty() && s2.empty();
+    }
+};
+```
+
+```javascript
+class MyQueue {
+    constructor() {
+        this.s1 = [];
+        this.s2 = [];
+    }
+
+    /** 
+     * @param {number} x
+     * @return {void}
+     */
+    push(x) {
+        this.s1.push(x);
+    }
+
+    /**
+     * @return {number}
+     */
+    pop() {
+        if (this.s2.length === 0) {
+            while (this.s1.length > 0) {
+                this.s2.push(this.s1.pop());
+            }
+        }
+        return this.s2.pop();
+    }
+
+    /**
+     * @return {number}
+     */
+    peek() {
+        if (this.s2.length === 0) {
+            while (this.s1.length > 0) {
+                this.s2.push(this.s1.pop());
+            }
+        }
+        return this.s2[this.s2.length - 1];
+    }
+
+    /**
+     * @return {boolean}
+     */
+    empty() {
+        return this.s1.length === 0 && this.s2.length === 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(1)$ time for initialization.
+    * $O(1)$ time for each $push()$ and $empty()$ function calls.
+    * $O(1)$ amortized time for each $pop()$ and $peek()$ function calls.
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/implement-stack-using-queues.md b/articles/implement-stack-using-queues.md
new file mode 100644
index 000000000..ee6199220
--- /dev/null
+++ b/articles/implement-stack-using-queues.md
@@ -0,0 +1,438 @@
+## 1. Using Two Queues
+
+::tabs-start
+
+```python
+class MyStack:
+
+    def __init__(self):
+        self.q1 = deque()
+        self.q2 = deque()
+
+    def push(self, x: int) -> None:
+        self.q2.append(x)
+        while self.q1:
+            self.q2.append(self.q1.popleft())
+        
+        self.q1, self.q2 = self.q2, self.q1
+
+    def pop(self) -> int:
+        return self.q1.popleft()
+
+    def top(self) -> int:
+        return self.q1[0]
+
+    def empty(self) -> bool:
+        return len(self.q1) == 0
+```
+
+```java
+public class MyStack {
+    private Queue<Integer> q1;
+    private Queue<Integer> q2;
+
+    public MyStack() {
+        q1 = new LinkedList<>();
+        q2 = new LinkedList<>();
+    }
+
+    public void push(int x) {
+        q2.offer(x);
+        while (!q1.isEmpty()) {
+            q2.offer(q1.poll());
+        }
+        Queue<Integer> temp = q1;
+        q1 = q2;
+        q2 = temp;
+    }
+
+    public int pop() {
+        return q1.poll();
+    }
+
+    public int top() {
+        return q1.peek();
+    }
+
+    public boolean empty() {
+        return q1.isEmpty();
+    }
+}
+```
+
+```cpp
+class MyStack {
+private:
+    queue<int> q1;
+    queue<int> q2;
+
+public:
+    MyStack() {}
+
+    void push(int x) {
+        q2.push(x);
+        while (!q1.empty()) {
+            q2.push(q1.front());
+            q1.pop();
+        }
+        swap(q1, q2);
+    }
+
+    int pop() {
+        int top = q1.front();
+        q1.pop();
+        return top;
+    }
+
+    int top() {
+        return q1.front();
+    }
+
+    bool empty() {
+        return q1.empty();
+    }
+};
+```
+
+```javascript
+class MyStack {
+    constructor() {
+        this.q1 = new Queue();
+        this.q2 = new Queue();
+    }
+
+    /**
+     * @param {number} x
+     * @return {void}
+     */
+    push(x) {
+        this.q2.push(x);
+   
+        while (!this.q1.isEmpty()) {
+            this.q2.push(this.q1.pop());
+        }
+        
+        [this.q1, this.q2] = [this.q2, this.q1];
+    }
+
+    /**
+     * @return {number}
+     */
+    pop() {
+        return this.q1.pop();
+    }
+
+    /**
+     * @return {number}
+     */
+    top() {
+        return this.q1.front();
+    }
+
+    /**
+     * @return {boolean}
+     */
+    empty() {
+        return this.q1.isEmpty();
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(1)$ time for initialization.
+    * $O(n)$ time for each $push()$ function call.
+    * $O(1)$ time for each $pop()$ function call.
+* Space complexity: $O(n)$
+
+---
+
+## 2. Using One Queue
+
+::tabs-start
+
+```python
+class MyStack:
+
+    def __init__(self):
+        self.q = deque()
+
+    def push(self, x: int) -> None:
+        self.q.append(x)
+        for _ in range(len(self.q) - 1):
+            self.q.append(self.q.popleft())
+
+    def pop(self) -> int:
+        return self.q.popleft()
+
+    def top(self) -> int:
+        return self.q[0]
+
+    def empty(self) -> bool:
+        return len(self.q) == 0
+```
+
+```java
+public class MyStack {
+    private Queue<Integer> q;
+
+    public MyStack() {
+        q = new LinkedList<>();
+    }
+
+    public void push(int x) {
+        q.offer(x);
+        for (int i = q.size() - 1; i > 0; i--) {
+            q.offer(q.poll());
+        }
+    }
+
+    public int pop() {
+        return q.poll();
+    }
+
+    public int top() {
+        return q.peek();
+    }
+
+    public boolean empty() {
+        return q.isEmpty();
+    }
+}
+```
+
+```cpp
+class MyStack {
+    queue<int> q;
+
+public:
+    MyStack() {}
+
+    void push(int x) {
+        q.push(x);
+        for (int i = q.size() - 1; i > 0; i--) {
+            q.push(q.front());
+            q.pop();
+        }
+    }
+
+    int pop() {
+        int top = q.front();
+        q.pop();
+        return top;
+    }
+
+    int top() {
+        return q.front();
+    }
+
+    bool empty() {
+        return q.empty();
+    }
+};
+```
+
+```javascript
+class MyStack {
+    constructor() {
+        this.q = new Queue();
+    }
+
+    /**
+     * @param {number} x
+     * @return {void}
+     */
+    push(x) {
+        this.q.push(x);
+   
+        for (let i = this.q.size() - 1; i > 0; i--) {
+            this.q.push(this.q.pop());
+        }
+    }
+
+    /**
+     * @return {number}
+     */
+    pop() {
+        return this.q.pop();
+    }
+
+    /**
+     * @return {number}
+     */
+    top() {
+        return this.q.front();
+    }
+
+    /**
+     * @return {boolean}
+     */
+    empty() {
+        return this.q.isEmpty();
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(1)$ time for initialization.
+    * $O(n)$ time for each $push()$ function call.
+    * $O(1)$ time for each $pop()$ function call.
+* Space complexity: $O(n)$
+
+---
+
+## 3. Queue Of Queues
+
+::tabs-start
+
+```python
+class MyStack:
+
+    def __init__(self):
+        self.q = None
+
+    def push(self, x: int) -> None:
+        self.q = deque([x, self.q])
+
+    def pop(self) -> int:
+        top = self.q.popleft()
+        self.q = self.q.popleft()
+        return top
+
+    def top(self) -> int:
+        return self.q[0]
+
+    def empty(self) -> bool:
+        return not self.q
+```
+
+```java
+public class MyStack {
+    private Queue<Object> q;
+
+    public MyStack() {
+        q = null;
+    }
+
+    public void push(int x) {
+        Queue<Object> newQueue = new LinkedList<>();
+        newQueue.add(x);
+        newQueue.add(q);
+        q = newQueue;
+    }
+
+    public int pop() {
+        if (q == null) return -1;
+
+        int top = (int) q.poll();
+        q = (Queue<Object>) q.poll();
+        return top;
+    }
+
+    public int top() {
+        if (q == null) return -1;
+        return (int) q.peek();
+    }
+
+    public boolean empty() {
+        return q == null;
+    }
+}
+```
+
+```cpp
+class MyStack {
+private:
+    struct Node {
+        int val;
+        shared_ptr<Node> next;
+        Node(int v, shared_ptr<Node> n) : val(v), next(n) {}
+    };
+    shared_ptr<Node> q;
+
+public:
+    MyStack() : q(nullptr) {}
+
+    void push(int x) {
+        q = make_shared<Node>(x, q);
+    }
+
+    int pop() {
+        if (!q) return -1;
+        int top = q->val;
+        q = q->next;
+        return top;
+    }
+
+    int top() {
+        if (!q) return -1;
+        return q->val;
+    }
+
+    bool empty() {
+        return q == nullptr;
+    }
+};
+```
+
+```javascript
+class MyStack {
+    constructor() {
+        this.q = null;
+    }
+
+    /**
+     * @param {number} x
+     * @return {void}
+     */
+    push(x) {
+        const newQueue = new Queue();
+        newQueue.enqueue(x);
+        newQueue.enqueue(this.q);
+        this.q = newQueue;
+    }
+
+    /**
+     * @return {number}
+     */
+    pop() {
+        if (this.q === null) return -1;
+
+        const top = this.q.dequeue();
+        this.q = this.q.dequeue();
+        return top;
+    }
+
+    /**
+     * @return {number}
+     */
+    top() {
+        if (this.q === null) return -1;
+        return this.q.front();
+    }
+
+    /**
+     * @return {boolean}
+     */
+    empty() {
+        return this.q === null;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(1)$ time for initialization.
+    * $O(1)$ time for each $push()$ function call.
+    * $O(1)$ time for each $pop()$ function call.
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/insert-delete-getrandom-o1.md b/articles/insert-delete-getrandom-o1.md
new file mode 100644
index 000000000..000979641
--- /dev/null
+++ b/articles/insert-delete-getrandom-o1.md
@@ -0,0 +1,300 @@
+## 1. Hash Map
+
+::tabs-start
+
+```python
+class RandomizedSet:
+    
+    def __init__(self):
+        self.numMap = {}
+        self.size = 0
+
+    def insert(self, val: int) -> bool:
+        if val in self.numMap:
+            return False
+        self.numMap[val] = 1
+        self.size += 1
+        return True
+
+    def remove(self, val: int) -> bool:
+        if val not in self.numMap:
+            return False
+        del self.numMap[val]
+        self.size -= 1
+        return True
+
+    def getRandom(self) -> int:
+        idx = random.randint(0, self.size - 1)
+        return list(self.numMap.keys())[idx]
+```
+
+```java
+public class RandomizedSet {
+    private HashMap<Integer, Integer> numMap;
+    private int size;
+
+    public RandomizedSet() {
+        numMap = new HashMap<>();
+        size = 0;
+    }
+
+    public boolean insert(int val) {
+        if (numMap.containsKey(val)) {
+            return false;
+        }
+        numMap.put(val, 1);
+        size++;
+        return true;
+    }
+
+    public boolean remove(int val) {
+        if (!numMap.containsKey(val)) {
+            return false;
+        }
+        numMap.remove(val);
+        size--;
+        return true;
+    }
+
+    public int getRandom() {
+        int idx = new Random().nextInt(size);
+        Iterator<Integer> it = numMap.keySet().iterator();
+        while (idx-- > 0) {
+            it.next();
+        }
+        return it.next();
+    }
+}
+```
+
+```cpp
+class RandomizedSet {
+private:
+    unordered_map<int, int> numMap;
+    int size;
+
+public:
+    RandomizedSet() : size(0) {}
+
+    bool insert(int val) {
+        if (numMap.count(val)) return false;
+        numMap[val] = 1;
+        size++;
+        return true;
+    }
+
+    bool remove(int val) {
+        if (!numMap.count(val)) return false;
+        numMap.erase(val);
+        size--;
+        return true;
+    }
+
+    int getRandom() {
+        int idx = rand() % size;
+        auto it = numMap.begin();
+        advance(it, idx);
+        return it->first;
+    }
+};
+```
+
+```javascript
+class RandomizedSet {
+    constructor() {
+        this.numMap = new Map();
+        this.size = 0;
+    }
+
+    /** 
+     * @param {number} val
+     * @return {boolean}
+     */
+    insert(val) {
+        if (this.numMap.has(val)) return false;
+        this.numMap.set(val, 1);
+        this.size++;
+        return true;
+    }
+
+    /** 
+     * @param {number} val
+     * @return {boolean}
+     */
+    remove(val) {
+        if (!this.numMap.has(val)) return false;
+        this.numMap.delete(val);
+        this.size--;
+        return true;
+    }
+
+    /**
+     * @return {number}
+     */
+    getRandom() {
+        const keys = Array.from(this.numMap.keys());
+        const idx = Math.floor(Math.random() * this.size);
+        return keys[idx];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$ for $getRandom()$, $O(1)$ for other function calls.
+* Space complexity: $O(n)$
+
+---
+
+## 2. Hash Map + List
+
+::tabs-start
+
+```python
+class RandomizedSet:
+    
+    def __init__(self):
+        self.numMap = {}
+        self.nums = []
+
+    def insert(self, val: int) -> bool:
+        if val in self.numMap:
+            return False
+        self.numMap[val] = len(self.nums)
+        self.nums.append(val)
+        return True
+
+    def remove(self, val: int) -> bool:
+        if val not in self.numMap:
+            return False
+        idx = self.numMap[val]
+        last = self.nums[-1]
+        self.nums[idx] = last
+        self.numMap[last] = idx
+        self.nums.pop()
+        del self.numMap[val]
+        return True
+
+    def getRandom(self) -> int:
+        return random.choice(self.nums)
+```
+
+```java
+public class RandomizedSet {
+    private Map<Integer, Integer> numMap;
+    private List<Integer> nums;
+    private Random rand;
+
+    public RandomizedSet() {
+        numMap = new HashMap<>();
+        nums = new ArrayList<>();
+        rand = new Random();
+    }
+
+    public boolean insert(int val) {
+        if (numMap.containsKey(val)) return false;
+        numMap.put(val, nums.size());
+        nums.add(val);
+        return true;
+    }
+
+    public boolean remove(int val) {
+        if (!numMap.containsKey(val)) return false;
+        int idx = numMap.get(val);
+        int last = nums.get(nums.size() - 1);
+        nums.set(idx, last);
+        numMap.put(last, idx);
+        nums.remove(nums.size() - 1);
+        numMap.remove(val);
+        return true;
+    }
+
+    public int getRandom() {
+        return nums.get(rand.nextInt(nums.size()));
+    }
+}
+```
+
+```cpp
+class RandomizedSet {
+private:
+    unordered_map<int, int> numMap;
+    vector<int> nums;
+
+public:
+    RandomizedSet() {}
+
+    bool insert(int val) {
+        if (numMap.count(val)) return false;
+        numMap[val] = nums.size();
+        nums.push_back(val);
+        return true;
+    }
+
+    bool remove(int val) {
+        if (!numMap.count(val)) return false;
+        int idx = numMap[val];
+        int last = nums.back();
+        nums[idx] = last;
+        numMap[last] = idx;
+        nums.pop_back();
+        numMap.erase(val);
+        return true;
+    }
+
+    int getRandom() {
+        return nums[rand() % nums.size()];
+    }
+};
+```
+
+```javascript
+class RandomizedSet {
+    constructor() {
+        this.numMap = new Map();
+        this.nums = [];
+    }
+
+    /** 
+     * @param {number} val
+     * @return {boolean}
+     */
+    insert(val) {
+        if (this.numMap.has(val)) return false;
+        this.numMap.set(val, this.nums.length);
+        this.nums.push(val);
+        return true;
+    }
+
+    /** 
+     * @param {number} val
+     * @return {boolean}
+     */
+    remove(val) {
+        if (!this.numMap.has(val)) return false;
+        const idx = this.numMap.get(val);
+        const last = this.nums[this.nums.length - 1];
+        this.nums[idx] = last;
+        this.numMap.set(last, idx);
+        this.nums.pop();
+        this.numMap.delete(val);
+        return true;
+    }
+
+    /**
+     * @return {number}
+     */
+    getRandom() {
+        return this.nums[Math.floor(Math.random() * this.nums.length)];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$ for each function call.
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/insert-greatest-common-divisors-in-linked-list.md b/articles/insert-greatest-common-divisors-in-linked-list.md
new file mode 100644
index 000000000..ffa61c7ce
--- /dev/null
+++ b/articles/insert-greatest-common-divisors-in-linked-list.md
@@ -0,0 +1,155 @@
+## 1. Simulation
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def insertGreatestCommonDivisors(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        def gcd(a, b):
+            while b > 0:
+                a, b = b, a % b
+            return a
+
+        cur = head
+        while cur.next:
+            n1, n2 = cur.val, cur.next.val
+            cur.next = ListNode(gcd(n1, n2), cur.next)
+            cur = cur.next.next
+
+        return head
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode insertGreatestCommonDivisors(ListNode head) {
+        if (head == null) return null;
+
+        ListNode cur = head;
+
+        while (cur.next != null) {
+            int n1 = cur.val, n2 = cur.next.val;
+            int gcdValue = gcd(n1, n2);
+            ListNode newNode = new ListNode(gcdValue, cur.next);
+            cur.next = newNode;
+            cur = newNode.next;
+        }
+
+        return head;
+    }
+
+    private int gcd(int a, int b) {
+        while (b > 0) {
+            int temp = b;
+            b = a % b;
+            a = temp;
+        }
+        return a;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* insertGreatestCommonDivisors(ListNode* head) {
+        if (!head) return nullptr;
+
+        ListNode* cur = head;
+
+        while (cur->next) {
+            int n1 = cur->val, n2 = cur->next->val;
+            int gcdValue = gcd(n1, n2);
+            ListNode* newNode = new ListNode(gcdValue, cur->next);
+            cur->next = newNode;
+            cur = newNode->next;
+        }
+
+        return head;
+    }
+
+private:
+    int gcd(int a, int b) {
+        while (b > 0) {
+            int temp = b;
+            b = a % b;
+            a = temp;
+        }
+        return a;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @return {ListNode}
+     */
+    insertGreatestCommonDivisors(head) {
+        if (!head) return null;
+        const gcd = (a, b) => {
+            while (b > 0) {
+                [a, b] = [b, a % b];
+            }
+            return a;
+        };
+
+        let cur = head;
+
+        while (cur.next) {
+            const n1 = cur.val, n2 = cur.next.val;
+            const gcdValue = gcd(n1, n2);
+            const newNode = new ListNode(gcdValue, cur.next);
+            cur.next = newNode;
+            cur = newNode.next;
+        }
+
+        return head;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * \log (min(a, b)))$
+* Space complexity:
+    * $O(n)$ space for the gcd ListNodes.
+    * $O(1)$ extra space.
+
+> Where $n$ is the length of the given list, and $a$ and $b$ are two numbers passed to the $gcd()$ function.
\ No newline at end of file
diff --git a/articles/insert-into-a-binary-search-tree.md b/articles/insert-into-a-binary-search-tree.md
new file mode 100644
index 000000000..fe0604c3a
--- /dev/null
+++ b/articles/insert-into-a-binary-search-tree.md
@@ -0,0 +1,363 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def insertIntoBST(self, root: Optional[TreeNode], val: int) -> Optional[TreeNode]:
+        if not root:
+            return TreeNode(val)
+
+        if val > root.val:
+            root.right = self.insertIntoBST(root.right, val)
+        else:
+            root.left = self.insertIntoBST(root.left, val)
+
+        return root
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode insertIntoBST(TreeNode root, int val) {
+        if (root == null) {
+            return new TreeNode(val);
+        }
+
+        if (val > root.val) {
+            root.right = insertIntoBST(root.right, val);
+        } else {
+            root.left = insertIntoBST(root.left, val);
+        }
+
+        return root;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    TreeNode* insertIntoBST(TreeNode* root, int val) {
+        if (!root) {
+            return new TreeNode(val);
+        }
+
+        if (val > root->val) {
+            root->right = insertIntoBST(root->right, val);
+        } else {
+            root->left = insertIntoBST(root->left, val);
+        }
+
+        return root;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @param {number} val
+     * @return {TreeNode}
+     */
+    insertIntoBST(root, val) {
+        if (!root) {
+            return new TreeNode(val);
+        }
+
+        if (val > root.val) {
+            root.right = this.insertIntoBST(root.right, val);
+        } else {
+            root.left = this.insertIntoBST(root.left, val);
+        }
+
+        return root;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode InsertIntoBST(TreeNode root, int val) {
+        if (root == null) {
+            return new TreeNode(val);
+        }
+
+        if (val > root.val) {
+            root.right = InsertIntoBST(root.right, val);
+        } else {
+            root.left = InsertIntoBST(root.left, val);
+        }
+
+        return root;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(h)$
+* Space complexity: $O(h)$ for the recursion stack.
+
+> Where $h$ is the height of the given binary search tree.
+
+---
+
+## 2. Iteration
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def insertIntoBST(self, root: Optional[TreeNode], val: int) -> Optional[TreeNode]:
+        if not root:
+            return TreeNode(val)
+
+        cur = root
+        while True:
+            if val > cur.val:
+                if not cur.right:
+                    cur.right = TreeNode(val)
+                    return root
+                cur = cur.right
+            else:
+                if not cur.left:
+                    cur.left = TreeNode(val)
+                    return root
+                cur = cur.left
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode insertIntoBST(TreeNode root, int val) {
+        if (root == null) {
+            return new TreeNode(val);
+        }
+
+        TreeNode cur = root;
+        while (true) {
+            if (val > cur.val) {
+                if (cur.right == null) {
+                    cur.right = new TreeNode(val);
+                    return root;
+                }
+                cur = cur.right;
+            } else {
+                if (cur.left == null) {
+                    cur.left = new TreeNode(val);
+                    return root;
+                }
+                cur = cur.left;
+            }
+        }
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    TreeNode* insertIntoBST(TreeNode* root, int val) {
+        if (!root) {
+            return new TreeNode(val);
+        }
+
+        TreeNode* cur = root;
+        while (true) {
+            if (val > cur->val) {
+                if (!cur->right) {
+                    cur->right = new TreeNode(val);
+                    return root;
+                }
+                cur = cur->right;
+            } else {
+                if (!cur->left) {
+                    cur->left = new TreeNode(val);
+                    return root;
+                }
+                cur = cur->left;
+            }
+        }
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @param {number} val
+     * @return {TreeNode}
+     */
+    insertIntoBST(root, val) {
+        if (!root) {
+            return new TreeNode(val);
+        }
+
+        let cur = root;
+        while (true) {
+            if (val > cur.val) {
+                if (!cur.right) {
+                    cur.right = new TreeNode(val);
+                    return root;
+                }
+                cur = cur.right;
+            } else {
+                if (!cur.left) {
+                    cur.left = new TreeNode(val);
+                    return root;
+                }
+                cur = cur.left;
+            }
+        }
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode InsertIntoBST(TreeNode root, int val) {
+        if (root == null) {
+            return new TreeNode(val);
+        }
+
+        TreeNode cur = root;
+        while (true) {
+            if (val > cur.val) {
+                if (cur.right == null) {
+                    cur.right = new TreeNode(val);
+                    return root;
+                }
+                cur = cur.right;
+            } else {
+                if (cur.left == null) {
+                    cur.left = new TreeNode(val);
+                    return root;
+                }
+                cur = cur.left;
+            }
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(h)$
+* Space complexity: $O(1)$ extra space.
+
+> Where $h$ is the height of the given binary search tree.
\ No newline at end of file
diff --git a/articles/insert-new-interval.md b/articles/insert-new-interval.md
new file mode 100644
index 000000000..13f29a037
--- /dev/null
+++ b/articles/insert-new-interval.md
@@ -0,0 +1,808 @@
+## 1. Linear Search
+
+::tabs-start
+
+```python
+class Solution:
+    def insert(self, intervals: List[List[int]], newInterval: List[int]) -> List[List[int]]:
+        n = len(intervals)
+        i = 0
+        res = []
+
+        while i < n and intervals[i][1] < newInterval[0]:
+            res.append(intervals[i])
+            i += 1
+
+        while i < n and newInterval[1] >= intervals[i][0]:
+            newInterval[0] = min(newInterval[0], intervals[i][0])
+            newInterval[1] = max(newInterval[1], intervals[i][1])
+            i += 1
+        res.append(newInterval)
+
+        while i < n:
+            res.append(intervals[i])
+            i += 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[][] insert(int[][] intervals, int[] newInterval) {
+        int n = intervals.length, i = 0;
+        List<int[]> res = new ArrayList<>();
+
+        while (i < n && intervals[i][1] < newInterval[0]) {
+            res.add(intervals[i]);
+            i++;
+        }
+
+        while (i < n && newInterval[1] >= intervals[i][0]) {
+            newInterval[0] = Math.min(newInterval[0], intervals[i][0]);
+            newInterval[1] = Math.max(newInterval[1], intervals[i][1]);
+            i++;
+        }
+        res.add(newInterval);
+
+        while (i < n) {
+            res.add(intervals[i]);
+            i++;
+        }
+
+        return res.toArray(new int[res.size()][]);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> insert(vector<vector<int>>& intervals, vector<int>& newInterval) {
+        int n = intervals.size(), i = 0;
+        vector<vector<int>> res;
+
+        while (i < n && intervals[i][1] < newInterval[0]) {
+            res.push_back(intervals[i]);
+            i++;
+        }
+
+        while (i < n && newInterval[1] >= intervals[i][0]) {
+            newInterval[0] = min(newInterval[0], intervals[i][0]);
+            newInterval[1] = max(newInterval[1], intervals[i][1]);
+            i++;
+        }
+        res.push_back(newInterval);
+
+        while (i < n) {
+            res.push_back(intervals[i]);
+            i++;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} intervals
+     * @param {number[]} newInterval
+     * @return {number[][]}
+     */
+    insert(intervals, newInterval) {
+        let n = intervals.length,
+        i = 0,
+        res = [];
+
+        while (i < n && intervals[i][1] < newInterval[0]) {
+            res.push(intervals[i]);
+            i++;
+        }
+
+        while (i < n && newInterval[1] >= intervals[i][0]) {
+            newInterval[0] = Math.min(newInterval[0], intervals[i][0]);
+            newInterval[1] = Math.max(newInterval[1], intervals[i][1]);
+            i++;
+        }
+        res.push(newInterval);
+
+        while (i < n) {
+            res.push(intervals[i]);
+            i++;
+        }
+
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[][] Insert(int[][] intervals, int[] newInterval) {
+        var result = new List<int[]>();
+        
+        for(var i = 0; i < intervals.Length; i++) {
+            if(newInterval[1] < intervals[i][0]) {
+                result.Add(newInterval);
+                result.AddRange(
+                    intervals.AsEnumerable().Skip(i).ToArray());
+                
+                return result.ToArray();
+            }
+            else if(newInterval[0] > intervals[i][1]) {
+                result.Add(intervals[i]);
+            } else {
+                newInterval[0] = Math.Min(intervals[i][0], newInterval[0]);
+                newInterval[1] = Math.Max(intervals[i][1], newInterval[1]);
+            }
+        }
+        
+        result.Add(newInterval);
+        
+        return result.ToArray();
+    }
+}
+```
+
+```go
+func insert(intervals [][]int, newInterval []int) [][]int {
+    n := len(intervals)
+    i := 0
+    var res [][]int
+
+    for i < n && intervals[i][1] < newInterval[0] {
+        res = append(res, intervals[i])
+        i++
+    }
+
+    for i < n && newInterval[1] >= intervals[i][0] {
+        newInterval[0] = min(newInterval[0], intervals[i][0])
+        newInterval[1] = max(newInterval[1], intervals[i][1])
+        i++
+    }
+    res = append(res, newInterval)
+
+    for i < n {
+        res = append(res, intervals[i])
+        i++
+    }
+
+    return res
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun insert(intervals: Array<IntArray>, newInterval: IntArray): Array<IntArray> {
+        val res = mutableListOf<IntArray>()
+        var i = 0
+        val n = intervals.size
+
+        while (i < n && intervals[i][1] < newInterval[0]) {
+            res.add(intervals[i])
+            i++
+        }
+
+        var newStart = newInterval[0]
+        var newEnd = newInterval[1]
+        while (i < n && newEnd >= intervals[i][0]) {
+            newStart = minOf(newStart, intervals[i][0])
+            newEnd = maxOf(newEnd, intervals[i][1])
+            i++
+        }
+        res.add(intArrayOf(newStart, newEnd))
+
+        while (i < n) {
+            res.add(intervals[i])
+            i++
+        }
+
+        return res.toTypedArray()
+    }
+}
+```
+
+```swift
+class Solution {
+    func insert(_ intervals: [[Int]], _ newInterval: [Int]) -> [[Int]] {
+        var intervals = intervals
+        var newInterval = newInterval
+        var res: [[Int]] = []
+        var i = 0
+        let n = intervals.count
+
+        while i < n && intervals[i][1] < newInterval[0] {
+            res.append(intervals[i])
+            i += 1
+        }
+
+        while i < n && newInterval[1] >= intervals[i][0] {
+            newInterval[0] = min(newInterval[0], intervals[i][0])
+            newInterval[1] = max(newInterval[1], intervals[i][1])
+            i += 1
+        }
+        res.append(newInterval)
+
+        while i < n {
+            res.append(intervals[i])
+            i += 1
+        }
+
+        return res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ space for the output list.
+
+---
+
+## 2. Binary Search
+
+::tabs-start
+
+```python
+class Solution:
+    def insert(self, intervals: List[List[int]], newInterval: List[int]) -> List[List[int]]:
+        if not intervals:
+            return [newInterval]
+
+        n = len(intervals)
+        target = newInterval[0]
+        left, right = 0, n - 1
+
+        while left <= right:
+            mid = (left + right) // 2
+            if intervals[mid][0] < target:
+                left = mid + 1
+            else:
+                right = mid - 1
+
+        intervals.insert(left, newInterval)
+
+        res = []
+        for interval in intervals:
+            if not res or res[-1][1] < interval[0]:
+                res.append(interval)
+            else:
+                res[-1][1] = max(res[-1][1], interval[1])
+        return res
+```
+
+```java
+public class Solution {
+    public int[][] insert(int[][] intervals, int[] newInterval) {
+        if (intervals.length == 0) {
+            return new int[][] { newInterval };
+        }
+
+        int n = intervals.length;
+        int target = newInterval[0];
+        int left = 0, right = n - 1;
+
+        while (left <= right) {
+            int mid = (left + right) / 2;
+            if (intervals[mid][0] < target) {
+                left = mid + 1;
+            } else {
+                right = mid - 1;
+            }
+        }
+
+        List<int[]> result = new ArrayList<>();
+        for (int i = 0; i < left; i++) {
+            result.add(intervals[i]);
+        }
+        result.add(newInterval);
+        for (int i = left; i < n; i++) {
+            result.add(intervals[i]);
+        }
+
+        List<int[]> merged = new ArrayList<>();
+        for (int[] interval : result) {
+            if (merged.isEmpty() ||
+                merged.get(merged.size() - 1)[1] < interval[0]) {
+                merged.add(interval);
+            } else {
+                merged.get(merged.size() - 1)[1] = Math.max(
+                    merged.get(merged.size() - 1)[1],
+                    interval[1]
+                );
+            }
+        }
+
+        return merged.toArray(new int[0][]);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> insert(vector<vector<int>>& intervals, vector<int>& newInterval) {
+        if (intervals.empty()) {
+            return {newInterval};
+        }
+
+        int n = intervals.size();
+        int target = newInterval[0];
+        int left = 0, right = n - 1;
+
+        while (left <= right) {
+            int mid = (left + right) / 2;
+            if (intervals[mid][0] < target) {
+                left = mid + 1;
+            } else {
+                right = mid - 1;
+            }
+        }
+
+        intervals.insert(intervals.begin() + left, newInterval);
+
+        vector<vector<int>> res;
+        for (const auto& interval : intervals) {
+            if (res.empty() || res.back()[1] < interval[0]) {
+                res.push_back(interval);
+            } else {
+                res.back()[1] = max(res.back()[1], interval[1]);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} intervals
+     * @param {number[]} newInterval
+     * @return {number[][]}
+     */
+    insert(intervals, newInterval) {
+        if (intervals.length === 0) {
+            return [newInterval];
+        }
+
+        let n = intervals.length;
+        let target = newInterval[0];
+        let left = 0,
+            right = n - 1;
+
+        while (left <= right) {
+            let mid = Math.floor((left + right) / 2);
+            if (intervals[mid][0] < target) {
+                left = mid + 1;
+            } else {
+                right = mid - 1;
+            }
+        }
+
+        intervals.splice(left, 0, newInterval);
+
+        let res = [];
+        for (let interval of intervals) {
+            if (res.length === 0 || 
+                res[res.length - 1][1] < interval[0]) {
+                res.push(interval);
+            } else {
+                res[res.length - 1][1] = Math.max(
+                    res[res.length - 1][1],
+                    interval[1],
+                );
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[][] Insert(int[][] intervals, int[] newInterval) {
+        if (intervals.Length == 0) {
+            return new int[][] { newInterval };
+        }
+
+        int n = intervals.Length;
+        int target = newInterval[0];
+        int left = 0, right = n - 1;
+
+        while (left <= right) {
+            int mid = (left + right) / 2;
+            if (intervals[mid][0] < target) {
+                left = mid + 1;
+            } else {
+                right = mid - 1;
+            }
+        }
+
+        List<int[]> result = new List<int[]>();
+        for (int i = 0; i < left; i++) {
+            result.Add(intervals[i]);
+        }
+
+        result.Add(newInterval);
+        for (int i = left; i < n; i++) {
+            result.Add(intervals[i]);
+        }
+
+        List<int[]> merged = new List<int[]>();
+        foreach (int[] interval in result) {
+            if (merged.Count == 0 ||
+                merged[merged.Count - 1][1] < interval[0]) {
+                merged.Add(interval);
+            } else {
+                merged[merged.Count - 1][1] =
+                    Math.Max(merged[merged.Count - 1][1], interval[1]);
+            }
+        }
+
+        return merged.ToArray();
+    }
+}
+```
+
+```go
+func insert(intervals [][]int, newInterval []int) [][]int {
+    if len(intervals) == 0 {
+        return [][]int{newInterval}
+    }
+
+    n := len(intervals)
+    target := newInterval[0]
+    left, right := 0, n-1
+
+    for left <= right {
+        mid := (left + right) / 2
+        if intervals[mid][0] < target {
+            left = mid + 1
+        } else {
+            right = mid - 1
+        }
+    }
+
+    intervals = append(intervals[:left], append(
+                [][]int{newInterval}, intervals[left:]...)...)
+
+    var res [][]int
+    for _, interval := range intervals {
+        if len(res) == 0 || res[len(res)-1][1] < interval[0] {
+            res = append(res, interval)
+        } else {
+            res[len(res)-1][1] = max(res[len(res)-1][1], interval[1])
+        }
+    }
+    return res
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun insert(intervals: Array<IntArray>, newInterval: IntArray): Array<IntArray> {
+        if (intervals.isEmpty()) {
+            return arrayOf(newInterval)
+        }
+
+        var left = 0
+        var right = intervals.size - 1
+        val target = newInterval[0]
+
+        while (left <= right) {
+            val mid = (left + right) / 2
+            if (intervals[mid][0] < target) {
+                left = mid + 1
+            } else {
+                right = mid - 1
+            }
+        }
+
+        val result = intervals.toMutableList()
+        result.add(left, newInterval)
+
+        val res = mutableListOf<IntArray>()
+        for (interval in result) {
+            if (res.isEmpty() || res.last()[1] < interval[0]) {
+                res.add(interval)
+            } else {
+                res[res.size - 1][1] = maxOf(res.last()[1], interval[1])
+            }
+        }
+        return res.toTypedArray()
+    }
+}
+```
+
+```swift
+class Solution {
+    func insert(_ intervals: [[Int]], _ newInterval: [Int]) -> [[Int]] {
+        if intervals.isEmpty {
+            return [newInterval]
+        }
+
+        var intervals = intervals
+        let target = newInterval[0]
+        var left = 0, right = intervals.count - 1
+
+        while left <= right {
+            let mid = (left + right) / 2
+            if intervals[mid][0] < target {
+                left = mid + 1
+            } else {
+                right = mid - 1
+            }
+        }
+
+        intervals.insert(newInterval, at: left)
+
+        var res: [[Int]] = []
+        for interval in intervals {
+            if res.isEmpty || res.last![1] < interval[0] {
+                res.append(interval)
+            } else {
+                res[res.count - 1][1] = max(res.last![1], interval[1])
+            }
+        }
+        return res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ space for the output list.
+
+---
+
+## 3. Greedy
+
+::tabs-start
+
+```python
+class Solution:
+    def insert(self, intervals: List[List[int]], newInterval: List[int]) -> List[List[int]]:
+        res = []
+
+        for i in range(len(intervals)):
+            if newInterval[1] < intervals[i][0]:
+                res.append(newInterval)
+                return res + intervals[i:]
+            elif newInterval[0] > intervals[i][1]:
+                res.append(intervals[i])
+            else:
+                newInterval = [
+                    min(newInterval[0], intervals[i][0]),
+                    max(newInterval[1], intervals[i][1]),
+                ]
+        res.append(newInterval)
+        return res
+```
+
+```java
+public class Solution {
+    public int[][] insert(int[][] intervals, int[] newInterval) {
+        List<int[]> res = new ArrayList<>();
+        for (int[] interval : intervals) {
+            if (newInterval == null || interval[1] < newInterval[0]) {
+                res.add(interval);
+            } else if (interval[0] > newInterval[1]) {
+                res.add(newInterval);
+                res.add(interval);
+                newInterval = null;
+            } else {
+                newInterval[0] = Math.min(interval[0], newInterval[0]);
+                newInterval[1] = Math.max(interval[1], newInterval[1]);
+            }
+        }
+        if (newInterval != null) res.add(newInterval);
+        return res.toArray(new int[res.size()][]);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> insert(vector<vector<int>>& intervals, vector<int>& newInterval) {
+        vector<vector<int>> res;
+        int newStart = newInterval[0];
+        int newEnd = newInterval[1];
+        int n = intervals.size();
+        for (int i = 0; i < n; i++) {
+            if (intervals[i][0] > newEnd) {
+                res.push_back(newInterval);
+                copy(intervals.begin() + i, intervals.end(), back_inserter(ans));
+                return ans;
+            } else if (intervals[i][1] < newStart) {
+                res.push_back(intervals[i]);
+            } else {
+                newInterval[0] = min(newInterval[0], intervals[i][0]);
+                newInterval[1] = max(newInterval[1], intervals[i][1]);
+            }
+        }
+        res.push_back(newInterval);
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} intervals
+     * @param {number[]} newInterval
+     * @return {number[][]}
+     */
+    insert(intervals, newInterval) {
+        const res = [];
+        for (const interval of intervals) {
+            if (newInterval === null || interval[1] < newInterval[0]) {
+                res.push(interval);
+            } else if (interval[0] > newInterval[1]) {
+                res.push(newInterval);
+                res.push(interval);
+                newInterval = null;
+            } else {
+                newInterval[0] = Math.min(interval[0], newInterval[0]);
+                newInterval[1] = Math.max(interval[1], newInterval[1]);
+            }
+        }
+        if (newInterval !== null) res.push(newInterval);
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[][] Insert(int[][] intervals, int[] newInterval) {
+        var result = new List<int[]>();
+        
+        for(var i = 0; i < intervals.Length; i++) {
+            if(newInterval[1] < intervals[i][0]) {
+                result.Add(newInterval);
+                result.AddRange(intervals.AsEnumerable().Skip(i).ToArray());
+                return result.ToArray();
+            } else if(newInterval[0] > intervals[i][1]) {
+                result.Add(intervals[i]);
+            } else {
+                newInterval[0] = Math.Min(intervals[i][0], newInterval[0]);
+                newInterval[1] = Math.Max(intervals[i][1], newInterval[1]);
+            }
+        }
+        
+        result.Add(newInterval);
+        return result.ToArray();
+    }
+}
+```
+
+```go
+func insert(intervals [][]int, newInterval []int) [][]int {
+    var res [][]int
+
+    for i := 0; i < len(intervals); i++ {
+        if newInterval[1] < intervals[i][0] {
+            res = append(res, newInterval)
+            return append(res, intervals[i:]...)
+        } else if newInterval[0] > intervals[i][1] {
+            res = append(res, intervals[i])
+        } else {
+            newInterval = []int{
+                min(newInterval[0], intervals[i][0]),
+                max(newInterval[1], intervals[i][1]),
+            }
+        }
+    }
+    res = append(res, newInterval)
+    return res
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun insert(intervals: Array<IntArray>, newInterval: IntArray): Array<IntArray> {
+        val res = mutableListOf<IntArray>()
+
+        for (interval in intervals) {
+            if (newInterval[1] < interval[0]) {
+                res.add(newInterval)
+                return (res + 
+                        intervals.sliceArray(
+                            intervals.indexOf(interval) until intervals.size
+                        )).toTypedArray()
+            } else if (newInterval[0] > interval[1]) {
+                res.add(interval)
+            } else {
+                newInterval[0] = minOf(newInterval[0], interval[0])
+                newInterval[1] = maxOf(newInterval[1], interval[1])
+            }
+        }
+        res.add(newInterval)
+        return res.toTypedArray()
+    }
+}
+```
+
+```swift
+class Solution {
+    func insert(_ intervals: [[Int]], _ newInterval: [Int]) -> [[Int]] {
+        var res = [[Int]]()
+        var newInterval = newInterval
+
+        for i in 0..<intervals.count {
+            if newInterval[1] < intervals[i][0] {
+                res.append(newInterval)
+                res.append(contentsOf: intervals[i...])
+                return res
+            } else if newInterval[0] > intervals[i][1] {
+                res.append(intervals[i])
+            } else {
+                newInterval[0] = min(newInterval[0], intervals[i][0])
+                newInterval[1] = max(newInterval[1], intervals[i][1])
+            }
+        }
+
+        res.append(newInterval)
+        return res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ space for the output list.
\ No newline at end of file
diff --git a/articles/insertion-sort-list.md b/articles/insertion-sort-list.md
new file mode 100644
index 000000000..a567be9b0
--- /dev/null
+++ b/articles/insertion-sort-list.md
@@ -0,0 +1,411 @@
+## 1. Convert To Array
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def insertionSortList(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        arr = []
+        cur = head
+        while cur:
+            arr.append(cur.val)
+            cur = cur.next
+
+        arr.sort()
+        cur = head
+        for val in arr:
+            cur.val = val
+            cur = cur.next
+        return head
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode insertionSortList(ListNode head) {
+        List<Integer> arr = new ArrayList<>();
+        ListNode cur = head;
+
+        while (cur != null) {
+            arr.add(cur.val);
+            cur = cur.next;
+        }
+
+        Collections.sort(arr);
+        cur = head;
+
+        for (int val : arr) {
+            cur.val = val;
+            cur = cur.next;
+        }
+        return head;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* insertionSortList(ListNode* head) {
+        vector<int> arr;
+        ListNode* cur = head;
+
+        while (cur) {
+            arr.push_back(cur->val);
+            cur = cur->next;
+        }
+
+        sort(arr.begin(), arr.end());
+        cur = head;
+
+        for (int val : arr) {
+            cur->val = val;
+            cur = cur->next;
+        }
+        return head;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @return {ListNode}
+     */
+    insertionSortList(head) {
+        let arr = [];
+        let cur = head;
+
+        while (cur) {
+            arr.push(cur.val);
+            cur = cur.next;
+        }
+
+        arr.sort((a, b) => a - b);
+        cur = head;
+
+        for (let val of arr) {
+            cur.val = val;
+            cur = cur.next;
+        }
+        return head;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Swapping Values
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def insertionSortList(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        cur = head.next
+        while cur:
+            tmp = head
+            while tmp != cur:
+                if tmp.val > cur.val:
+                    tmp.val, cur.val = cur.val, tmp.val
+                tmp = tmp.next
+            cur = cur.next
+        return head
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode insertionSortList(ListNode head) {
+        for (ListNode cur = head.next; cur != null; cur = cur.next) {
+            for (ListNode tmp = head; tmp != cur; tmp = tmp.next) {
+                if (tmp.val > cur.val) {
+                    int swap = tmp.val;
+                    tmp.val = cur.val;
+                    cur.val = swap;
+                }
+            }
+        }
+        return head;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* insertionSortList(ListNode* head) {
+        for (ListNode* cur = head->next; cur; cur = cur->next) {
+            for (ListNode* tmp = head; tmp != cur; tmp = tmp->next) {
+                if (tmp->val > cur->val) {
+                    swap(tmp->val, cur->val);
+                }
+            }
+        }
+        return head;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @return {ListNode}
+     */
+    insertionSortList(head) {
+        for (let cur = head.next; cur; cur = cur.next) {
+            for (let tmp = head; tmp !== cur; tmp = tmp.next) {
+                if (tmp.val > cur.val) {
+                    [tmp.val, cur.val] = [cur.val, tmp.val];
+                }
+            }
+        }
+        return head;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 3. Swapping Nodes
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def insertionSortList(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        dummy = ListNode(0, head)
+        prev, cur = head, head.next
+
+        while cur:
+            if cur.val >= prev.val:
+                prev, cur = cur, cur.next
+                continue
+            
+            tmp = dummy
+            while cur.val > tmp.next.val:
+                tmp = tmp.next
+            
+            prev.next = cur.next
+            cur.next = tmp.next
+            tmp.next = cur
+            cur = prev.next
+
+        return dummy.next
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode insertionSortList(ListNode head) {
+        ListNode dummy = new ListNode(0, head);
+        ListNode prev = head, cur = head.next;
+
+        while (cur != null) {
+            if (cur.val >= prev.val) {
+                prev = cur;
+                cur = cur.next;
+                continue;
+            }
+
+            ListNode tmp = dummy;
+            while (tmp.next.val < cur.val) {
+                tmp = tmp.next;
+            }
+
+            prev.next = cur.next;
+            cur.next = tmp.next;
+            tmp.next = cur;
+            cur = prev.next;
+        }
+
+        return dummy.next;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* insertionSortList(ListNode* head) {
+        ListNode* dummy = new ListNode(0, head);
+        ListNode* prev = head;
+        ListNode* cur = head->next;
+
+        while (cur) {
+            if (cur->val >= prev->val) {
+                prev = cur;
+                cur = cur->next;
+                continue;
+            }
+
+            ListNode* tmp = dummy;
+            while (tmp->next->val < cur->val) {
+                tmp = tmp->next;
+            }
+
+            prev->next = cur->next;
+            cur->next = tmp->next;
+            tmp->next = cur;
+            cur = prev->next;
+        }
+
+        return dummy->next;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @return {ListNode}
+     */
+    insertionSortList(head) {
+        let dummy = new ListNode(0, head);
+        let prev = head, cur = head.next;
+
+        while (cur) {
+            if (cur.val >= prev.val) {
+                prev = cur;
+                cur = cur.next;
+                continue;
+            }
+
+            let tmp = dummy;
+            while (tmp.next.val < cur.val) {
+                tmp = tmp.next;
+            }
+
+            prev.next = cur.next;
+            cur.next = tmp.next;
+            tmp.next = cur;
+            cur = prev.next;
+        }
+
+        return dummy.next;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/integer-break.md b/articles/integer-break.md
new file mode 100644
index 000000000..2330d8828
--- /dev/null
+++ b/articles/integer-break.md
@@ -0,0 +1,806 @@
+## 1. Recursion (Brute Force)
+
+::tabs-start
+
+```python
+class Solution:
+    def integerBreak(self, n: int) -> int:
+        def dfs(num):
+            if num == 1:
+                return 1
+            res = 0 if num == n else num
+            for i in range(1, num):
+                val = dfs(i) * dfs(num - i)
+                res = max(res, val)
+            return res
+        return dfs(n)
+```
+
+```java
+public class Solution {
+    public int integerBreak(int n) {
+        return dfs(n, n);
+    }
+
+    private int dfs(int num, int original) {
+        if (num == 1) return 1;
+
+        int res = (num == original) ? 0 : num;
+        for (int i = 1; i < num; i++) {
+            int val = dfs(i, original) * dfs(num - i, original);
+            res = Math.max(res, val);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int integerBreak(int n) {
+        return dfs(n, n);
+    }
+
+private:
+    int dfs(int num, int original) {
+        if (num == 1) return 1;
+
+        int res = (num == original) ? 0 : num;
+        for (int i = 1; i < num; i++) {
+            int val = dfs(i, original) * dfs(num - i, original);
+            res = max(res, val);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    integerBreak(n) {
+        const dfs = (num) => {
+            if (num === 1) return 1;
+
+            let res = (num === n) ? 0 : num;
+            for (let i = 1; i < num; i++) {
+                const val = dfs(i) * dfs(num - i);
+                res = Math.max(res, val);
+            }
+            return res;
+        };
+
+        return dfs(n, n);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    private int n;
+
+    public int IntegerBreak(int n) {
+        this.n = n;
+
+        int Dfs(int num) {
+            if (num == 1) return 1;
+            int res = num == n ? 0 : num;
+            for (int i = 1; i < num; i++) {
+                int val = Dfs(i) * Dfs(num - i);
+                res = Math.Max(res, val);
+            }
+            return res;
+        }
+
+        return Dfs(n);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def integerBreak(self, n: int) -> int:
+        def dfs(num, i):
+            if min(num, i) == 0:
+                return 1
+            
+            if i > num:
+                return dfs(num, num)
+            
+            return max(i * dfs(num - i, i), dfs(num, i - 1))
+        
+        return dfs(n, n - 1)
+```
+
+```java
+public class Solution {
+    public int integerBreak(int n) {
+        return dfs(n, n - 1);
+    }
+
+    private int dfs(int num, int i) {
+        if (Math.min(num, i) == 0) {
+            return 1;
+        }
+        
+        if (i > num) {
+            return dfs(num, num);
+        }
+        
+        return Math.max(i * dfs(num - i, i), dfs(num, i - 1));
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int integerBreak(int n) {
+        return dfs(n, n - 1);
+    }
+
+private:
+    int dfs(int num, int i) {
+        if (min(num, i) == 0) {
+            return 1;
+        }
+        
+        if (i > num) {
+            return dfs(num, num);
+        }
+        
+        return max(i * dfs(num - i, i), dfs(num, i - 1));
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    integerBreak(n) {
+        const dfs = (num, i) => {
+            if (Math.min(num, i) === 0) {
+                return 1;
+            }
+            
+            if (i > num) {
+                return dfs(num, num);
+            }
+            
+            return Math.max(i * dfs(num - i, i), dfs(num, i - 1));
+        };
+
+        return dfs(n, n - 1);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int IntegerBreak(int n) {
+        int Dfs(int num, int i) {
+            if (Math.Min(num, i) == 0) {
+                return 1;
+            }
+
+            if (i > num) {
+                return Dfs(num, num);
+            }
+
+            return Math.Max(i * Dfs(num - i, i), Dfs(num, i - 1));
+        }
+
+        return Dfs(n, n - 1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 3. Dynamic Programming (Top-Down) - I
+
+::tabs-start
+
+```python
+class Solution:
+    def integerBreak(self, n: int) -> int:
+        dp = {1: 1}
+
+        def dfs(num):
+            if num in dp:
+                return dp[num]
+
+            dp[num] = 0 if num == n else num
+            for i in range(1, num):
+                val = dfs(i) * dfs(num - i)
+                dp[num] = max(dp[num], val)
+            return dp[num]
+        
+        return dfs(n)
+```
+
+```java
+public class Solution {
+    private Map<Integer, Integer> dp;
+
+    public int integerBreak(int n) {
+        dp = new HashMap<>();
+        dp.put(1, 1);
+        return dfs(n, n);
+    }
+
+    private int dfs(int num, int n) {
+        if (dp.containsKey(num)) {
+            return dp.get(num);
+        }
+
+        int res = (num == n) ? 0 : num;
+        for (int i = 1; i < num; i++) {
+            int val = dfs(i, n) * dfs(num - i, n);
+            res = Math.max(res, val);
+        }
+
+        dp.put(num, res);
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+    unordered_map<int, int> dp;
+
+public:
+    int integerBreak(int n) {
+        dp[1] = 1;
+        return dfs(n, n);
+    }
+
+private:
+    int dfs(int num, int n) {
+        if (dp.find(num) != dp.end()) {
+            return dp[num];
+        }
+
+        int res = (num == n) ? 0 : num;
+        for (int i = 1; i < num; i++) {
+            int val = dfs(i, n) * dfs(num - i, n);
+            res = max(res, val);
+        }
+
+        dp[num] = res;
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    integerBreak(n) {
+        const dp = new Map();
+        dp.set(1, 1);
+
+        const dfs = (num) => {
+            if (dp.has(num)) {
+                return dp.get(num);
+            }
+
+            let res = (num === n) ? 0 : num;
+            for (let i = 1; i < num; i++) {
+                const val = dfs(i) * dfs(num - i);
+                res = Math.max(res, val);
+            }
+
+            dp.set(num, res);
+            return res;
+        };
+
+        return dfs(n);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int IntegerBreak(int n) {
+        Dictionary<int, int> dp = new Dictionary<int, int>();
+        dp[1] = 1;
+
+        int Dfs(int num) {
+            if (dp.ContainsKey(num)) {
+                return dp[num];
+            }
+
+            dp[num] = (num == n) ? 0 : num;
+            for (int i = 1; i < num; i++) {
+                int val = Dfs(i) * Dfs(num - i);
+                dp[num] = Math.Max(dp[num], val);
+            }
+
+            return dp[num];
+        }
+
+        return Dfs(n);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Dynamic Programming (Top-Down) - II
+
+::tabs-start
+
+```python
+class Solution:
+    def integerBreak(self, n: int) -> int:
+        dp = {}
+        def dfs(num, i):
+            if min(num, i) == 0:
+                return 1
+            if (num, i) in dp:
+                return dp[(num, i)]
+            if i > num:
+                dp[(num, i)] = dfs(num, num)
+                return dp[(num, i)]
+            
+            dp[(num, i)] = max(i * dfs(num - i, i), dfs(num, i - 1))
+            return dp[(num, i)]
+        
+        return dfs(n, n - 1)
+```
+
+```java
+public class Solution {
+    private int[][] dp;
+
+    public int integerBreak(int n) {
+        dp = new int[n + 1][n];
+        for (int i = 0; i <= n; i++) {
+            for (int j = 0; j < n; j++) {
+                dp[i][j] = -1;
+            }
+        }
+        return dfs(n, n - 1);
+    }
+
+    private int dfs(int num, int i) {
+        if (Math.min(num, i) == 0) {
+            return 1;
+        }
+        if (dp[num][i] != -1) {
+            return dp[num][i];
+        }
+        if (i > num) {
+            dp[num][i] = dfs(num, num);
+            return dp[num][i];
+        }
+        dp[num][i] = Math.max(i * dfs(num - i, i), dfs(num, i - 1));
+        return dp[num][i];
+    }
+}
+```
+
+```cpp
+class Solution {
+    vector<vector<int>> dp;
+
+public:
+    int integerBreak(int n) {
+        dp.assign(n + 1, vector<int>(n, -1));
+        return dfs(n, n - 1);
+    }
+
+private:
+    int dfs(int num, int i) {
+        if (min(num, i) == 0) {
+            return 1;
+        }
+        if (dp[num][i] != -1) {
+            return dp[num][i];
+        }
+        if (i > num) {
+            dp[num][i] = dfs(num, num);
+            return dp[num][i];
+        }
+        dp[num][i] = max(i * dfs(num - i, i), dfs(num, i - 1));
+        return dp[num][i];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    integerBreak(n) {
+        const dp = Array.from({ length: n + 1 }, () => Array(n).fill(-1));
+
+        const dfs = (num, i) => {
+            if (Math.min(num, i) === 0) {
+                return 1;
+            }
+            if (dp[num][i] !== -1) {
+                return dp[num][i];
+            }
+            if (i > num) {
+                dp[num][i] = dfs(num, num);
+                return dp[num][i];
+            }
+            dp[num][i] = Math.max(i * dfs(num - i, i), dfs(num, i - 1));
+            return dp[num][i];
+        };
+
+        return dfs(n, n - 1);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int IntegerBreak(int n) {
+        Dictionary<(int, int), int> dp = new Dictionary<(int, int), int>();
+
+        int Dfs(int num, int i) {
+            if (Math.Min(num, i) == 0) return 1;
+
+            if (dp.ContainsKey((num, i))) return dp[(num, i)];
+
+            if (i > num) {
+                dp[(num, i)] = Dfs(num, num);
+                return dp[(num, i)];
+            }
+
+            dp[(num, i)] = Math.Max(i * Dfs(num - i, i), Dfs(num, i - 1));
+            return dp[(num, i)];
+        }
+
+        return Dfs(n, n - 1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 5. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def integerBreak(self, n: int) -> int:
+        dp = [0] * (n + 1)
+        dp[1] = 1
+
+        for num in range(2, n + 1):
+            dp[num] = 0 if num == n else num
+            for i in range(1, num):
+                dp[num] = max(dp[num], dp[i] * dp[num - i])
+
+        return dp[n]
+```
+
+```java
+public class Solution {
+    public int integerBreak(int n) {
+        int[] dp = new int[n + 1];
+        dp[1] = 1;
+
+        for (int num = 2; num <= n; num++) {
+            dp[num] = (num == n) ? 0 : num;
+            for (int i = 1; i < num; i++) {
+                dp[num] = Math.max(dp[num], dp[i] * dp[num - i]);
+            }
+        }
+
+        return dp[n];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int integerBreak(int n) {
+        vector<int> dp(n + 1, 0);
+        dp[1] = 1;
+
+        for (int num = 2; num <= n; num++) {
+            dp[num] = (num == n) ? 0 : num;
+            for (int i = 1; i < num; i++) {
+                dp[num] = max(dp[num], dp[i] * dp[num - i]);
+            }
+        }
+
+        return dp[n];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    integerBreak(n) {
+        const dp = new Array(n + 1).fill(0);
+        dp[1] = 1;
+
+        for (let num = 2; num <= n; num++) {
+            dp[num] = (num === n) ? 0 : num;
+            for (let i = 1; i < num; i++) {
+                dp[num] = Math.max(dp[num], dp[i] * dp[num - i]);
+            }
+        }
+
+        return dp[n];
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int IntegerBreak(int n) {
+        int[] dp = new int[n + 1];
+        dp[1] = 1;
+
+        for (int num = 2; num <= n; num++) {
+            dp[num] = num == n ? 0 : num;
+            for (int i = 1; i < num; i++) {
+                dp[num] = Math.Max(dp[num], dp[i] * dp[num - i]);
+            }
+        }
+
+        return dp[n];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 6. Math
+
+::tabs-start
+
+```python
+class Solution:
+    def integerBreak(self, n: int) -> int:
+        if n <= 3:
+            return n - 1
+        
+        res = 1
+        while n > 4:
+            res *= 3
+            n -= 3
+        return res * n
+```
+
+```java
+public class Solution {
+    public int integerBreak(int n) {
+        if (n <= 3) return n - 1;
+
+        int res = 1;
+        while (n > 4) {
+            res *= 3;
+            n -= 3;
+        }
+        return res * n;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int integerBreak(int n) {
+        if (n <= 3) return n - 1;
+
+        int res = 1;
+        while (n > 4) {
+            res *= 3;
+            n -= 3;
+        }
+        return res * n;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    integerBreak(n) {
+        if (n <= 3) return n - 1;
+
+        let res = 1;
+        while (n > 4) {
+            res *= 3;
+            n -= 3;
+        }
+        return res * n;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int IntegerBreak(int n) {
+        if (n <= 3) {
+            return n - 1;
+        }
+
+        int res = 1;
+        while (n > 4) {
+            res *= 3;
+            n -= 3;
+        }
+
+        return res * n;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 7. Math (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def integerBreak(self, n: int) -> int:
+        if n <= 3:
+            return n - 1
+
+        res = 3 ** (n // 3)
+        if n % 3 == 1:
+            return (res // 3) * 4
+
+        return res * max(1, (n % 3))
+```
+
+```java
+public class Solution {
+    public int integerBreak(int n) {
+        if (n <= 3) {
+            return n - 1;
+        }
+
+        int res = (int) Math.pow(3, n / 3);
+        if (n % 3 == 1) {
+            return (res / 3) * 4;
+        }
+
+        return res * Math.max(1, n % 3);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int integerBreak(int n) {
+        if (n <= 3) {
+            return n - 1;
+        }
+
+        int res = pow(3, n / 3);
+        if (n % 3 == 1) {
+            return (res / 3) * 4;
+        }
+
+        return res * max(1, n % 3);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    integerBreak(n) {
+        if (n <= 3) {
+            return n - 1;
+        }
+
+        let res = Math.pow(3, Math.floor(n / 3));
+        if (n % 3 === 1) {
+            return Math.floor(res / 3) * 4;
+        }
+
+        return res * Math.max(1, n % 3);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int IntegerBreak(int n) {
+        if (n <= 3) {
+            return n - 1;
+        }
+
+        int res = (int)Math.Pow(3, n / 3);
+
+        if (n % 3 == 1) {
+            return (res / 3) * 4;
+        }
+
+        return res * Math.Max(1, n % 3);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/integer-to-roman.md b/articles/integer-to-roman.md
new file mode 100644
index 000000000..6bb15bb30
--- /dev/null
+++ b/articles/integer-to-roman.md
@@ -0,0 +1,195 @@
+## 1. Math - I
+
+::tabs-start
+
+```python
+class Solution:
+    def intToRoman(self, num: int) -> str:
+        symList = [
+            ["I", 1], ["IV", 4], ["V", 5], ["IX", 9],
+            ["X", 10], ["XL", 40], ["L", 50], ["XC", 90],
+            ["C", 100], ["CD", 400], ["D", 500], ["CM", 900],
+            ["M", 1000]
+        ]
+
+        res = ""
+        for sym, val in reversed(symList):
+            count = num // val
+            if count:
+                res += sym * count
+                num %= val
+
+        return res
+```
+
+```java
+public class Solution {
+    public String intToRoman(int num) {
+        String[][] symList = {
+            {"I", "1"}, {"IV", "4"}, {"V", "5"}, {"IX", "9"},
+            {"X", "10"}, {"XL", "40"}, {"L", "50"}, {"XC", "90"},
+            {"C", "100"}, {"CD", "400"}, {"D", "500"}, {"CM", "900"},
+            {"M", "1000"}
+        };
+
+        StringBuilder res = new StringBuilder();
+        for (int i = symList.length - 1; i >= 0; i--) {
+            String sym = symList[i][0];
+            int val = Integer.parseInt(symList[i][1]);
+            int count = num / val;
+            if (count > 0) {
+                res.append(sym.repeat(count));
+                num %= val;
+            }
+        }
+
+        return res.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string intToRoman(int num) {
+        vector<pair<string, int>> symList = {
+            {"I", 1}, {"IV", 4}, {"V", 5}, {"IX", 9},
+            {"X", 10}, {"XL", 40}, {"L", 50}, {"XC", 90},
+            {"C", 100}, {"CD", 400}, {"D", 500}, {"CM", 900},
+            {"M", 1000}
+        };
+
+        string res = "";
+        for (int i = symList.size() - 1; i >= 0; i--) {
+            string sym = symList[i].first;
+            int val = symList[i].second;
+            int count = num / val;
+            if (count > 0) {
+                res.append(count, sym[0]);
+                if (sym.size() == 2) res.append(1, sym[1]);
+                num %= val;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} num
+     * @return {string}
+     */
+    intToRoman(num) {
+        const symList = [
+            ["I", 1], ["IV", 4], ["V", 5], ["IX", 9],
+            ["X", 10], ["XL", 40], ["L", 50], ["XC", 90],
+            ["C", 100], ["CD", 400], ["D", 500], ["CM", 900],
+            ["M", 1000]
+        ];
+
+        let res = "";
+        for (let i = symList.length - 1; i >= 0; i--) {
+            const [sym, val] = symList[i];
+            let count = Math.floor(num / val);
+            if (count > 0) {
+                res += sym.repeat(count);
+                num %= val;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Math - II
+
+::tabs-start
+
+```python
+class Solution:
+    def intToRoman(self, num: int) -> str:
+        thousands = ["", "M", "MM", "MMM"]
+        hundreds = ["", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"]
+        tens = ["", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"]
+        ones = ["", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"]
+
+        return (
+            thousands[num // 1000] +
+            hundreds[(num % 1000) // 100] +
+            tens[(num % 100) // 10] +
+            ones[num % 10]
+        )
+```
+
+```java
+public class Solution {
+    public String intToRoman(int num) {
+        String[] thousands = {"", "M", "MM", "MMM"};
+        String[] hundreds = {"", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"};
+        String[] tens = {"", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"};
+        String[] ones = {"", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"};
+
+        return thousands[num / 1000] +
+               hundreds[(num % 1000) / 100] +
+               tens[(num % 100) / 10] +
+               ones[num % 10];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string intToRoman(int num) {
+        string thousands[] = {"", "M", "MM", "MMM"};
+        string hundreds[] = {"", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"};
+        string tens[] = {"", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"};
+        string ones[] = {"", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"};
+
+        return thousands[num / 1000] + 
+               hundreds[(num % 1000) / 100] + 
+               tens[(num % 100) / 10] + 
+               ones[num % 10];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} num
+     * @return {string}
+     */
+    intToRoman(num) {
+        const thousands = ["", "M", "MM", "MMM"];
+        const hundreds = ["", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"];
+        const tens = ["", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"];
+        const ones = ["", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"];
+
+        return thousands[Math.floor(num / 1000)] +
+               hundreds[Math.floor((num % 1000) / 100)] +
+               tens[Math.floor((num % 100) / 10)] +
+               ones[num % 10];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/interleaving-string.md b/articles/interleaving-string.md
index 38fef5f5a..3d124cd01 100644
--- a/articles/interleaving-string.md
+++ b/articles/interleaving-string.md
@@ -144,6 +144,94 @@ public class Solution {
 }
 ```
 
+```go
+func isInterleave(s1, s2, s3 string) bool {
+    var dfs func(i, j, k int) bool
+    dfs = func(i, j, k int) bool {
+        if k == len(s3) {
+            return i == len(s1) && j == len(s2)
+        }
+
+        if i < len(s1) && s1[i] == s3[k] {
+            if dfs(i+1, j, k+1) {
+                return true
+            }
+        }
+
+        if j < len(s2) && s2[j] == s3[k] {
+            if dfs(i, j+1, k+1) {
+                return true
+            }
+        }
+
+        return false
+    }
+
+    return dfs(0, 0, 0)
+}
+```
+
+```kotlin
+class Solution {
+    fun isInterleave(s1: String, s2: String, s3: String): Boolean {
+        fun dfs(i: Int, j: Int, k: Int): Boolean {
+            if (k == s3.length) {
+                return i == s1.length && j == s2.length
+            }
+
+            if (i < s1.length && s1[i] == s3[k]) {
+                if (dfs(i + 1, j, k + 1)) {
+                    return true
+                }
+            }
+
+            if (j < s2.length && s2[j] == s3[k]) {
+                if (dfs(i, j + 1, k + 1)) {
+                    return true
+                }
+            }
+
+            return false
+        }
+
+        return dfs(0, 0, 0)
+    }
+}
+```
+
+```swift
+class Solution {
+    func isInterleave(_ s1: String, _ s2: String, _ s3: String) -> Bool {
+        let n1 = s1.count, n2 = s2.count, n3 = s3.count
+        if n1 + n2 != n3 { return false }
+        
+        let s1 = Array(s1), s2 = Array(s2), s3 = Array(s3)
+        
+        func dfs(_ i: Int, _ j: Int, _ k: Int) -> Bool {
+            if k == n3 {
+                return i == n1 && j == n2
+            }
+            
+            if i < n1 && s1[i] == s3[k] {
+                if dfs(i + 1, j, k + 1) {
+                    return true
+                }
+            }
+            
+            if j < n2 && s2[j] == s3[k] {
+                if dfs(i, j + 1, k + 1) {
+                    return true
+                }
+            }
+            
+            return false
+        }
+        
+        return dfs(0, 0, 0)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -323,6 +411,124 @@ public class Solution {
 }
 ```
 
+```go
+func isInterleave(s1, s2, s3 string) bool {
+    if len(s1)+len(s2) != len(s3) {
+        return false
+    }
+
+    m, n := len(s1), len(s2)
+    dp := make([][]int, m+1)
+    for i := range dp {
+        dp[i] = make([]int, n+1)
+        for j := range dp[i] {
+            dp[i][j] = -1
+        }
+    }
+
+    var dfs func(i, j, k int) bool
+    dfs = func(i, j, k int) bool {
+        if k == len(s3) {
+            return i == len(s1) && j == len(s2)
+        }
+
+        if dp[i][j] != -1 {
+            return dp[i][j] == 1
+        }
+
+        res := false
+        if i < len(s1) && s1[i] == s3[k] {
+            res = dfs(i+1, j, k+1)
+        }
+        if !res && j < len(s2) && s2[j] == s3[k] {
+            res = dfs(i, j+1, k+1)
+        }
+
+        if res {
+            dp[i][j] = 1 
+        } else {
+            dp[i][j] = 0 
+        }
+
+        return res
+    }
+
+    return dfs(0, 0, 0)
+}
+```
+
+```kotlin
+class Solution {
+    fun isInterleave(s1: String, s2: String, s3: String): Boolean {
+        if (s1.length + s2.length != s3.length) {
+            return false
+        }
+
+        val m = s1.length
+        val n = s2.length
+        val dp = Array(m + 1) { IntArray(n + 1) { -1 } }
+
+        fun dfs(i: Int, j: Int, k: Int): Boolean {
+            if (k == s3.length) {
+                return i == m && j == n
+            }
+
+            if (dp[i][j] != -1) {
+                return dp[i][j] == 1
+            }
+
+            var res = false
+            if (i < s1.length && s1[i] == s3[k]) {
+                res = dfs(i + 1, j, k + 1)
+            }
+            if (!res && j < s2.length && s2[j] == s3[k]) {
+                res = dfs(i, j + 1, k + 1)
+            }
+
+            dp[i][j] = if (res) 1 else 0 
+
+            return res
+        }
+
+        return dfs(0, 0, 0)
+    }
+}
+```
+
+```swift
+class Solution {
+    func isInterleave(_ s1: String, _ s2: String, _ s3: String) -> Bool {
+        let m = s1.count, n = s2.count, l = s3.count
+        if m + n != l { return false }
+        
+        let s1 = Array(s1), s2 = Array(s2), s3 = Array(s3)
+        var dp = Array(repeating: Array(repeating: nil as Bool?, count: n + 1), count: m + 1)
+
+        func dfs(_ i: Int, _ j: Int, _ k: Int) -> Bool {
+            if k == l {
+                return i == m && j == n
+            }
+            if let cached = dp[i][j] {
+                return cached
+            }
+
+            var res = false
+            if i < m && s1[i] == s3[k] {
+                res = dfs(i + 1, j, k + 1)
+            }
+            if !res && j < n && s2[j] == s3[k] {
+                res = dfs(i, j + 1, k + 1)
+            }
+
+            dp[i][j] = res
+            return res
+        }
+
+        return dfs(0, 0, 0)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -468,6 +674,84 @@ public class Solution {
 }
 ```
 
+```go
+func isInterleave(s1 string, s2 string, s3 string) bool {
+    if len(s1) + len(s2) != len(s3) {
+        return false
+    }
+
+    dp := make([][]bool, len(s1)+1)
+    for i := range dp {
+        dp[i] = make([]bool, len(s2)+1)
+    }
+    dp[len(s1)][len(s2)] = true
+
+    for i := len(s1); i >= 0; i-- {
+        for j := len(s2); j >= 0; j-- {
+            if i < len(s1) && s1[i] == s3[i+j] && dp[i+1][j] {
+                dp[i][j] = true
+            }
+            if j < len(s2) && s2[j] == s3[i+j] && dp[i][j+1] {
+                dp[i][j] = true
+            }
+        }
+    }
+
+    return dp[0][0]
+}
+```
+
+```kotlin
+class Solution {
+    fun isInterleave(s1: String, s2: String, s3: String): Boolean {
+        if (s1.length + s2.length != s3.length) {
+            return false
+        }
+
+        val dp = Array(s1.length + 1) { BooleanArray(s2.length + 1) }
+        dp[s1.length][s2.length] = true
+
+        for (i in s1.length downTo 0) {
+            for (j in s2.length downTo 0) {
+                if (i < s1.length && s1[i] == s3[i + j] && dp[i + 1][j]) {
+                    dp[i][j] = true
+                }
+                if (j < s2.length && s2[j] == s3[i + j] && dp[i][j + 1]) {
+                    dp[i][j] = true
+                }
+            }
+        }
+
+        return dp[0][0]
+    }
+}
+```
+
+```swift
+class Solution {
+    func isInterleave(_ s1: String, _ s2: String, _ s3: String) -> Bool {
+        let m = s1.count, n = s2.count, l = s3.count
+        if m + n != l { return false }
+
+        let s1 = Array(s1), s2 = Array(s2), s3 = Array(s3)
+        var dp = Array(repeating: Array(repeating: false, count: n + 1), count: m + 1)
+        dp[m][n] = true
+
+        for i in stride(from: m, through: 0, by: -1) {
+            for j in stride(from: n, through: 0, by: -1) {
+                if i < m && s1[i] == s3[i + j] && dp[i + 1][j] {
+                    dp[i][j] = true
+                }
+                if j < n && s2[j] == s3[i + j] && dp[i][j + 1] {
+                    dp[i][j] = true
+                }
+            }
+        }
+        return dp[0][0]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -489,7 +773,7 @@ class Solution:
         m, n = len(s1), len(s2)
         if m + n != len(s3):
             return False
-        if m < n:
+        if n < m:
             s1, s2 = s2, s1
             m, n = n, m
         
@@ -512,7 +796,7 @@ public class Solution {
     public boolean isInterleave(String s1, String s2, String s3) {
         int m = s1.length(), n = s2.length();
         if (m + n != s3.length()) return false;
-        if (m < n) {
+        if (n < m) {
             String temp = s1;
             s1 = s2;
             s2 = temp;
@@ -547,7 +831,7 @@ public:
     bool isInterleave(string s1, string s2, string s3) {
         int m = s1.size(), n = s2.size();
         if (m + n != s3.size()) return false;
-        if (m < n) {
+        if (n < m) {
             swap(s1, s2);
             swap(m, n);
         }
@@ -583,7 +867,7 @@ class Solution {
     isInterleave(s1, s2, s3) {
         let m = s1.length, n = s2.length;
         if (m + n !== s3.length) return false;
-        if (m < n) {
+        if (n < m) {
             [s1, s2] = [s2, s1];
             [m, n] = [n, m];
         }
@@ -613,7 +897,7 @@ public class Solution {
     public bool IsInterleave(string s1, string s2, string s3) {
         int m = s1.Length, n = s2.Length;
         if (m + n != s3.Length) return false;
-        if (m < n) {
+        if (n < m) {
             var temp = s1;
             s1 = s2;
             s2 = temp;
@@ -642,6 +926,108 @@ public class Solution {
 }
 ```
 
+```go
+func isInterleave(s1 string, s2 string, s3 string) bool {
+    m, n := len(s1), len(s2)
+    if m + n != len(s3) {
+        return false
+    }
+    if n < m {
+        s1, s2 = s2, s1
+        m, n = n, m
+    }
+
+    dp := make([]bool, n+1)
+    dp[n] = true
+    for i := m; i >= 0; i-- {
+        nextDp := make([]bool, n+1)
+        nextDp[n] = true
+        for j := n; j >= 0; j-- {
+            if i < m && s1[i] == s3[i+j] && dp[j] {
+                nextDp[j] = true
+            }
+            if j < n && s2[j] == s3[i+j] && nextDp[j+1] {
+                nextDp[j] = true
+            }
+        }
+        dp = nextDp
+    }
+    return dp[0]
+}
+```
+
+```kotlin
+class Solution {
+    fun isInterleave(s1: String, s2: String, s3: String): Boolean {
+        var s1 = s1
+        var s2 = s2
+        var m = s1.length
+        var n = s2.length
+        if (m + n != s3.length) {
+            return false
+        }
+        if (n < m) {
+            val temp = s1
+            s1 = s2
+            s2 = temp
+
+            val temp1 = m
+            m = n
+            n = temp1
+        }
+
+        val dp = BooleanArray(n + 1)
+        dp[n] = true
+        for (i in m downTo 0) {
+            val nextDp = BooleanArray(n + 1)
+            nextDp[n] = true
+            for (j in n downTo 0) {
+                if (i < m && s1[i] == s3[i + j] && dp[j]) {
+                    nextDp[j] = true
+                }
+                if (j < n && s2[j] == s3[i + j] && nextDp[j + 1]) {
+                    nextDp[j] = true
+                }
+            }
+            System.arraycopy(nextDp, 0, dp, 0, n + 1)
+        }
+        return dp[0]
+    }
+}
+```
+
+```swift
+class Solution {
+    func isInterleave(_ s1: String, _ s2: String, _ s3: String) -> Bool {
+        var s1 = Array(s1), s2 = Array(s2), s3 = Array(s3)
+        var m = s1.count, n = s2.count
+        if m + n != s3.count { return false }
+        if n < m {
+            swap(&s1, &s2)
+            swap(&m, &n)
+        }
+
+        var dp = Array(repeating: false, count: n + 1)
+        dp[n] = true
+
+        for i in stride(from: m, through: 0, by: -1) {
+            var nextDp = Array(repeating: false, count: n + 1)
+            nextDp[n] = true
+            for j in stride(from: n, through: 0, by: -1) {
+                if i < m && s1[i] == s3[i + j] && dp[j] {
+                    nextDp[j] = true
+                }
+                if j < n && s2[j] == s3[i + j] && nextDp[j + 1] {
+                    nextDp[j] = true
+                }
+            }
+            dp = nextDp
+        }
+        return dp[0]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -663,7 +1049,7 @@ class Solution:
         m, n = len(s1), len(s2)
         if m + n != len(s3):
             return False
-        if m < n:
+        if n < m:
             s1, s2 = s2, s1
             m, n = n, m
         
@@ -687,7 +1073,7 @@ public class Solution {
     public boolean isInterleave(String s1, String s2, String s3) {
         int m = s1.length(), n = s2.length();
         if (m + n != s3.length()) return false;
-        if (m < n) {
+        if (n < m) {
             String temp = s1;
             s1 = s2;
             s2 = temp;
@@ -723,7 +1109,7 @@ public:
     bool isInterleave(string s1, string s2, string s3) {
         int m = s1.size(), n = s2.size();
         if (m + n != s3.size()) return false;
-        if (m < n) {
+        if (n < m) {
             swap(s1, s2);
             swap(m, n);
         }
@@ -760,7 +1146,7 @@ class Solution {
     isInterleave(s1, s2, s3) {
         let m = s1.length, n = s2.length;
         if (m + n !== s3.length) return false;
-        if (m < n) {
+        if (n < m) {
             [s1, s2] = [s2, s1];
             [m, n] = [n, m];
         }
@@ -791,7 +1177,7 @@ public class Solution {
     public bool IsInterleave(string s1, string s2, string s3) {
         int m = s1.Length, n = s2.Length;
         if (m + n != s3.Length) return false;
-        if (m < n) {
+        if (n < m) {
             var temp = s1;
             s1 = s2;
             s2 = temp;
@@ -821,6 +1207,111 @@ public class Solution {
 }
 ```
 
+```go
+func isInterleave(s1, s2, s3 string) bool {
+    m, n := len(s1), len(s2)
+    if m+n != len(s3) {
+        return false
+    }
+    if n < m {
+        s1, s2 = s2, s1
+        m, n = n, m
+    }
+
+    dp := make([]bool, n+1)
+    dp[n] = true
+    for i := m; i >= 0; i-- {
+        nextDp := true
+        for j := n - 1; j >= 0; j-- {
+            res := false
+            if i < m && s1[i] == s3[i+j] && dp[j] {
+                res = true
+            }
+            if j < n && s2[j] == s3[i+j] && nextDp {
+                res = true
+            }
+            dp[j] = res
+            nextDp = dp[j]
+        }
+    }
+    return dp[0]
+}
+```
+
+```kotlin
+class Solution {
+    fun isInterleave(s1: String, s2: String, s3: String): Boolean {
+        var s1 = s1
+        var s2 = s2
+        var m = s1.length
+        var n = s2.length
+        if (m + n != s3.length) {
+            return false
+        }
+        if (n < m) {
+            val temp = s1
+            s1 = s2
+            s2 = temp
+
+            val temp1 = m
+            m = n
+            n = temp1
+        }
+
+        val dp = BooleanArray(n + 1)
+        dp[n] = true
+        for (i in m downTo 0) {
+            var nextDp = true
+            for (j in n - 1 downTo 0) {
+                var res = false
+                if (i < m && s1[i] == s3[i + j] && dp[j]) {
+                    res = true
+                }
+                if (j < n && s2[j] == s3[i + j] && nextDp) {
+                    res = true
+                }
+                dp[j] = res
+                nextDp = dp[j]
+            }
+        }
+        return dp[0]
+    }
+}
+```
+
+```swift
+class Solution {
+    func isInterleave(_ s1: String, _ s2: String, _ s3: String) -> Bool {
+        var s1 = Array(s1), s2 = Array(s2), s3 = Array(s3)
+        var m = s1.count, n = s2.count
+        if m + n != s3.count { return false }
+        if n < m {
+            swap(&s1, &s2)
+            swap(&m, &n)
+        }
+
+        var dp = Array(repeating: false, count: n + 1)
+        dp[n] = true
+
+        for i in stride(from: m, through: 0, by: -1) {
+            var nextDp = true
+            for j in stride(from: n - 1, through: 0, by: -1) {
+                var res = false
+                if i < m && s1[i] == s3[i + j] && dp[j] {
+                    res = true
+                }
+                if j < n && s2[j] == s3[i + j] && nextDp {
+                    res = true
+                }
+                dp[j] = res
+                nextDp = dp[j]
+            }
+        }
+        return dp[0]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/intersection-of-two-arrays.md b/articles/intersection-of-two-arrays.md
new file mode 100644
index 000000000..5892704ec
--- /dev/null
+++ b/articles/intersection-of-two-arrays.md
@@ -0,0 +1,566 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def intersection(self, nums1: List[int], nums2: List[int]) -> List[int]:
+        res = set()
+        for i in nums1:
+            for j in nums2:
+                if i == j:
+                    res.add(i)
+                    break
+        return list(res)
+```
+
+```java
+public class Solution {
+    public int[] intersection(int[] nums1, int[] nums2) {
+        Set<Integer> res = new HashSet<>();
+        for (int i : nums1) {
+            for (int j : nums2) {
+                if (i == j) {
+                    res.add(i);
+                    break;
+                }
+            }
+        }
+        int[] result = new int[res.size()];
+        int idx = 0;
+        for (int num : res) {
+            result[idx++] = num;
+        }
+        return result;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> intersection(vector<int>& nums1, vector<int>& nums2) {
+        unordered_set<int> res;
+        for (int i : nums1) {
+            for (int j : nums2) {
+                if (i == j) {
+                    res.insert(i);
+                    break;
+                }
+            }
+        }
+        return vector<int>(res.begin(), res.end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums1
+     * @param {number[]} nums2
+     * @return {number[]}
+     */
+    intersection(nums1, nums2) {
+        const res = new Set();
+        for (const i of nums1) {
+            for (const j of nums2) {
+                if (i === j) {
+                    res.add(i);
+                    break;
+                }
+            }
+        }
+        return Array.from(res);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the size of the array $nums1$ and $m$ is the size of the array $nums2$.
+
+---
+
+## 2. Sorting + Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def intersection(self, nums1: List[int], nums2: List[int]) -> List[int]:
+        nums1.sort()
+        nums2.sort()
+
+        n, m = len(nums1), len(nums2)
+        res, i, j = [], 0, 0
+
+        while i < n and j < m:
+            while j < m and nums2[j] < nums1[i]:
+                j += 1
+            if j < m:
+                if nums1[i] == nums2[j]:
+                    res.append(nums1[i])
+                i += 1
+                while i < n and nums1[i] == nums1[i - 1]:
+                    i += 1
+            
+        return res
+```
+
+```java
+public class Solution {
+    public int[] intersection(int[] nums1, int[] nums2) {
+        Arrays.sort(nums1);
+        Arrays.sort(nums2);
+
+        List<Integer> res = new ArrayList<>();
+        int i = 0, j = 0;
+
+        while (i < nums1.length && j < nums2.length) {
+            while (j < nums2.length && nums2[j] < nums1[i]) {
+                j++;
+            }
+            if (j < nums2.length) {
+                if (nums1[i] == nums2[j]) {
+                    res.add(nums1[i]);
+                }
+                i++;
+                while (i < nums1.length && nums1[i] == nums1[i - 1]) {
+                    i++;
+                }
+            }
+        }
+
+        return res.stream().mapToInt(Integer::intValue).toArray();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> intersection(vector<int>& nums1, vector<int>& nums2) {
+        sort(nums1.begin(), nums1.end());
+        sort(nums2.begin(), nums2.end());
+
+        int n = nums1.size(), m = nums2.size();
+        vector<int> res;
+        int i = 0, j = 0;
+
+        while (i < n && j < m) {
+            while (j < m && nums2[j] < nums1[i]) {
+                ++j;
+            }
+            if (j < m) {
+                if (nums1[i] == nums2[j]) {
+                    res.push_back(nums1[i]);
+                }
+                ++i;
+                while (i < n && nums1[i] == nums1[i - 1]) {
+                    ++i;
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums1
+     * @param {number[]} nums2
+     * @return {number[]}
+     */
+    intersection(nums1, nums2) {
+        nums1.sort((a, b) => a - b);
+        nums2.sort((a, b) => a - b);
+
+        const res = [];
+        let i = 0, j = 0;
+
+        while (i < nums1.length && j < nums2.length) {
+            while (j < nums2.length && nums2[j] < nums1[i]) {
+                j++;
+            }
+            if (j < nums2.length) {
+                if (nums1[i] === nums2[j]) {
+                    res.push(nums1[i]);
+                }
+                i++;
+                while (i < nums1.length && nums1[i] === nums1[i - 1]) {
+                    i++;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n + m \log m)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the size of the array $nums1$ and $m$ is the size of the array $nums2$.
+
+---
+
+## 3. Hash Set
+
+::tabs-start
+
+```python
+class Solution:
+    def intersection(self, nums1: List[int], nums2: List[int]) -> List[int]:
+        set1 = set(nums1)
+        set2 = set(nums2)
+
+        res = []
+        for num in set1:
+            if num in set2:
+                res.append(num)
+        return res
+```
+
+```java
+public class Solution {
+    public int[] intersection(int[] nums1, int[] nums2) {
+        Set<Integer> set1 = new HashSet<>();
+        for (int num : nums1) {
+            set1.add(num);
+        }
+
+        Set<Integer> set2 = new HashSet<>();
+        for (int num : nums2) {
+            set2.add(num);
+        }
+
+        List<Integer> res = new ArrayList<>();
+        for (int num : set1) {
+            if (set2.contains(num)) {
+                res.add(num);
+            }
+        }
+
+        return res.stream().mapToInt(Integer::intValue).toArray();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> intersection(vector<int>& nums1, vector<int>& nums2) {
+        unordered_set<int> set1(nums1.begin(), nums1.end());
+        unordered_set<int> set2(nums2.begin(), nums2.end());
+
+        vector<int> res;
+        for (int num : set1) {
+            if (set2.find(num) != set2.end()) {
+                res.push_back(num);
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums1
+     * @param {number[]} nums2
+     * @return {number[]}
+     */
+    intersection(nums1, nums2) {
+        const set1 = new Set(nums1);
+        const set2 = new Set(nums2);
+
+        const res = [];
+        for (const num of set1) {
+            if (set2.has(num)) {
+                res.push(num);
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(n + m)$
+
+> Where $n$ is the size of the array $nums1$ and $m$ is the size of the array $nums2$.
+
+---
+
+## 4. Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def intersection(self, nums1: List[int], nums2: List[int]) -> List[int]:
+        seen = defaultdict(int)
+        for num in nums1:
+            seen[num] = 1
+        
+        res = []
+        for num in nums2:
+            if seen[num] == 1:
+                seen[num] = 0
+                res.append(num)
+        return res
+```
+
+```java
+public class Solution {
+    public int[] intersection(int[] nums1, int[] nums2) {
+        Map<Integer, Integer> seen = new HashMap<>();
+        for (int num : nums1) {
+            seen.put(num, 1);
+        }
+
+        List<Integer> res = new ArrayList<>();
+        for (int num : nums2) {
+            if (seen.getOrDefault(num, 0) == 1) {
+                seen.put(num, 0);
+                res.add(num);
+            }
+        }
+
+        return res.stream().mapToInt(Integer::intValue).toArray();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> intersection(vector<int>& nums1, vector<int>& nums2) {
+        unordered_map<int, int> seen;
+        for (int num : nums1) {
+            seen[num] = 1;
+        }
+
+        vector<int> res;
+        for (int num : nums2) {
+            if (seen[num] == 1) {
+                seen[num] = 0;
+                res.push_back(num);
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums1
+     * @param {number[]} nums2
+     * @return {number[]}
+     */
+    intersection(nums1, nums2) {
+        const seen = {};
+        for (const num of nums1) {
+            seen[num] = 1;
+        }
+
+        const res = [];
+        for (const num of nums2) {
+            if (seen[num] === 1) {
+                seen[num] = 0;
+                res.push(num);
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the size of the array $nums1$ and $m$ is the size of the array $nums2$.
+
+---
+
+## 5. Hash Set (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def intersection(self, nums1: List[int], nums2: List[int]) -> List[int]:
+        seen = set(nums1)
+
+        res = []
+        for num in nums2:
+            if num in seen:
+                res.append(num)
+                seen.remove(num)
+        return res
+```
+
+```java
+public class Solution {
+    public int[] intersection(int[] nums1, int[] nums2) {
+        Set<Integer> seen = new HashSet<>();
+        for (int num : nums1) {
+            seen.add(num);
+        }
+
+        List<Integer> res = new ArrayList<>();
+        for (int num : nums2) {
+            if (seen.contains(num)) {
+                res.add(num);
+                seen.remove(num);
+            }
+        }
+
+        return res.stream().mapToInt(Integer::intValue).toArray();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> intersection(vector<int>& nums1, vector<int>& nums2) {
+        unordered_set<int> seen(nums1.begin(), nums1.end());
+        vector<int> res;
+
+        for (int num : nums2) {
+            if (seen.count(num)) {
+                res.push_back(num);
+                seen.erase(num);
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums1
+     * @param {number[]} nums2
+     * @return {number[]}
+     */
+    intersection(nums1, nums2) {
+        const seen = new Set(nums1);
+        const res = [];
+
+        for (const num of nums2) {
+            if (seen.has(num)) {
+                res.push(num);
+                seen.delete(num);
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the size of the array $nums1$ and $m$ is the size of the array $nums2$.
+
+---
+
+## 6. Built-In Functions
+
+::tabs-start
+
+```python
+class Solution:
+    def intersection(self, nums1: List[int], nums2: List[int]) -> List[int]:
+            return list(set(nums1) & set(nums2))
+```
+
+```java
+public class Solution {
+    public int[] intersection(int[] nums1, int[] nums2) {
+        Set<Integer> set1 = new HashSet<>();
+        for (Integer n : nums1) {
+            set1.add(n);
+        }
+
+        Set<Integer> set2 = new HashSet<>();
+        for (Integer n : nums2) {
+            set2.add(n);
+        }
+        
+        set1.retainAll(set2);
+        int[] res= new int[set1.size()];
+        int idx = 0;
+        for (int s : set1) {
+            res[idx++] = s;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> intersection(vector<int>& nums1, vector<int>& nums2) {
+        set<int> set1(nums1.begin(), nums1.end()), set2(nums2.begin(), nums2.end());
+        vector<int> res;
+        set_intersection(set1.begin(), set1.end(), set2.begin(), set2.end(), back_inserter(res));
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums1
+     * @param {number[]} nums2
+     * @return {number[]}
+     */
+    intersection(nums1, nums2) {
+        const set2 = new Set(nums2);
+        return [...new Set(nums1)].filter(num => set2.has(num));
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$ in average case, $O(n * m)$ in worst case.
+* Space complexity: $O(n + m)$
+
+> Where $n$ is the size of the array $nums1$ and $m$ is the size of the array $nums2$.
\ No newline at end of file
diff --git a/articles/intersection-of-two-linked-lists.md b/articles/intersection-of-two-linked-lists.md
new file mode 100644
index 000000000..855f2a43f
--- /dev/null
+++ b/articles/intersection-of-two-linked-lists.md
@@ -0,0 +1,554 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+class Solution:
+    def getIntersectionNode(self, headA: ListNode, headB: ListNode) -> Optional[ListNode]:
+        while headA:
+            cur = headB
+            while cur:
+                if headA == cur:
+                    return headA
+                cur = cur.next
+            headA = headA.next
+        return None
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode(int x) {
+ *         val = x;
+ *         next = null;
+ *     }
+ * }
+ */
+public class Solution {
+    public ListNode getIntersectionNode(ListNode headA, ListNode headB) {
+        while (headA != null) {
+            ListNode cur = headB;
+            while (cur != null) {
+                if (headA == cur) {
+                    return headA;
+                }
+                cur = cur.next;
+            }
+            headA = headA.next;
+        }
+        return null;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode(int x) : val(x), next(NULL) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* getIntersectionNode(ListNode* headA, ListNode* headB) {
+        while (headA) {
+            ListNode* cur = headB;
+            while (cur) {
+                if (headA == cur) {
+                    return headA;
+                }
+                cur = cur->next;
+            }
+            headA = headA->next;
+        }
+        return nullptr;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} headA
+     * @param {ListNode} headB
+     * @return {ListNode}
+     */
+    getIntersectionNode(headA, headB) {
+        while (headA) {
+            let cur = headB;
+            while (cur) {
+                if (headA === cur) {
+                    return headA;
+                }
+                cur = cur.next;
+            }
+            headA = headA.next;
+        }
+        return null;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(1)$ extra space.
+
+> Where $m$ is the length of the first list and $n$ is the length of the second list.
+
+---
+
+## 2. Hash Set
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+class Solution:
+    def getIntersectionNode(self, headA: ListNode, headB: ListNode) -> Optional[ListNode]:
+        nodeSet = set()
+        cur = headA
+        while cur:
+            nodeSet.add(cur)
+            cur = cur.next
+        
+        cur = headB
+        while cur:
+            if cur in nodeSet:
+                return cur
+            cur = cur.next
+            
+        return None
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode(int x) {
+ *         val = x;
+ *         next = null;
+ *     }
+ * }
+ */
+public class Solution {
+    public ListNode getIntersectionNode(ListNode headA, ListNode headB) {
+        HashSet<ListNode> nodeSet = new HashSet<>();
+        
+        ListNode cur = headA;
+        while (cur != null) {
+            nodeSet.add(cur);
+            cur = cur.next;
+        }
+        
+        cur = headB;
+        while (cur != null) {
+            if (nodeSet.contains(cur)) {
+                return cur;
+            }
+            cur = cur.next;
+        }
+        
+        return null;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode(int x) : val(x), next(NULL) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* getIntersectionNode(ListNode* headA, ListNode* headB) {
+        unordered_set<ListNode*> nodeSet;
+        
+        ListNode* cur = headA;
+        while (cur) {
+            nodeSet.insert(cur);
+            cur = cur->next;
+        }
+        
+        cur = headB;
+        while (cur) {
+            if (nodeSet.find(cur) != nodeSet.end()) {
+                return cur;
+            }
+            cur = cur->next;
+        }
+        
+        return nullptr;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} headA
+     * @param {ListNode} headB
+     * @return {ListNode}
+     */
+    getIntersectionNode(headA, headB) {
+        const nodeSet = new Set();
+        
+        let cur = headA;
+        while (cur) {
+            nodeSet.add(cur);
+            cur = cur.next;
+        }
+        
+        cur = headB;
+        while (cur) {
+            if (nodeSet.has(cur)) {
+                return cur;
+            }
+            cur = cur.next;
+        }
+        
+        return null;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m + n)$
+* Space complexity: $O(m)$
+
+> Where $m$ is the length of the first list and $n$ is the length of the second list.
+
+---
+
+## 3. Two Pointers - I
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+class Solution:
+    def getIntersectionNode(self, headA: ListNode, headB: ListNode) -> Optional[ListNode]:
+        def getLength(head):
+            length, cur = 0, head
+            while cur:
+                length += 1
+                cur = cur.next
+            return length
+        
+        m = getLength(headA)
+        n = getLength(headB)
+        l1, l2 = headA, headB
+
+        if m < n:
+            m, n = n, m
+            l1, l2 = headB, headA
+        
+        while m - n:
+            m -= 1
+            l1 = l1.next
+        
+        while l1 != l2:
+            l1 = l1.next
+            l2 = l2.next
+        
+        return l1
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode(int x) {
+ *         val = x;
+ *         next = null;
+ *     }
+ * }
+ */
+public class Solution {
+    private int getLength(ListNode head) {
+        int length = 0;
+        while (head != null) {
+            length++;
+            head = head.next;
+        }
+        return length;
+    }
+    
+    public ListNode getIntersectionNode(ListNode headA, ListNode headB) {
+        int m = getLength(headA);
+        int n = getLength(headB);
+        ListNode l1 = headA, l2 = headB;
+
+        if (m < n) {
+            int temp = m; m = n; n = temp;
+            ListNode tempNode = l1; l1 = l2; l2 = tempNode;
+        }
+
+        while (m > n) {
+            l1 = l1.next;
+            m--;
+        }
+
+        while (l1 != null && l1 != l2) {
+            l1 = l1.next;
+            l2 = l2.next;
+        }
+
+        return l1;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode(int x) : val(x), next(NULL) {}
+ * };
+ */
+class Solution {
+    int getLength(ListNode* head) {
+        int length = 0;
+        while (head) {
+            length++;
+            head = head->next;
+        }
+        return length;
+    }
+    
+public:
+    ListNode* getIntersectionNode(ListNode* headA, ListNode* headB) {
+        int m = getLength(headA), n = getLength(headB);
+        ListNode* l1 = headA, *l2 = headB;
+        
+        if (m < n) {
+            swap(m, n);
+            swap(l1, l2);
+        }
+        
+        while (m-- > n) {
+            l1 = l1->next;
+        }
+        
+        while (l1 && l1 != l2) {
+            l1 = l1->next;
+            l2 = l2->next;
+        }
+        
+        return l1;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} headA
+     * @param {ListNode} headB
+     * @return {ListNode}
+     */
+    getIntersectionNode(headA, headB) {
+        const getLength = (head) => {
+            let length = 0, cur = head;
+            while (cur) {
+                length++;
+                cur = cur.next;
+            }
+            return length;
+        };
+
+        let m = getLength(headA);
+        let n = getLength(headB);
+        let l1 = headA, l2 = headB;
+
+        if (m < n) {
+            [m, n] = [n, m];
+            [l1, l2] = [l2, l1];
+        }
+
+        while (m-- > n) {
+            l1 = l1.next;
+        }
+
+        while (l1 && l1 !== l2) {
+            l1 = l1.next;
+            l2 = l2.next;
+        }
+
+        return l1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m + n)$
+* Space complexity: $O(1)$ extra space.
+
+> Where $m$ is the length of the first list and $n$ is the length of the second list.
+
+---
+
+## 4. Two Pointers - II
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+class Solution:
+    def getIntersectionNode(self, headA: ListNode, headB: ListNode) -> Optional[ListNode]:
+        l1, l2 = headA, headB
+        while l1 != l2:
+            l1 = l1.next if l1 else headB
+            l2 = l2.next if l2 else headA
+        return l1
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode(int x) {
+ *         val = x;
+ *         next = null;
+ *     }
+ * }
+ */
+public class Solution {
+    public ListNode getIntersectionNode(ListNode headA, ListNode headB) {
+        ListNode l1 = headA, l2 = headB;
+        while (l1 != l2) {
+            l1 = (l1 != null) ? l1.next : headB;
+            l2 = (l2 != null) ? l2.next : headA;
+        }
+        return l1;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode(int x) : val(x), next(NULL) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* getIntersectionNode(ListNode* headA, ListNode* headB) {
+        ListNode* l1 = headA;
+        ListNode* l2 = headB;
+        while (l1 != l2) {
+            l1 = l1 ? l1->next : headB;
+            l2 = l2 ? l2->next : headA;
+        }
+        return l1;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} headA
+     * @param {ListNode} headB
+     * @return {ListNode}
+     */
+    getIntersectionNode(headA, headB) {
+        let l1 = headA, l2 = headB;
+        while (l1 !== l2) {
+            l1 = l1 ? l1.next : headB;
+            l2 = l2 ? l2.next : headA;
+        }
+        return l1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m + n)$
+* Space complexity: $O(1)$ extra space.
+
+> Where $m$ is the length of the first list and $n$ is the length of the second list.
\ No newline at end of file
diff --git a/articles/invert-a-binary-tree.md b/articles/invert-a-binary-tree.md
index 24c2aa047..33ee15f84 100644
--- a/articles/invert-a-binary-tree.md
+++ b/articles/invert-a-binary-tree.md
@@ -161,6 +161,110 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func invertTree(root *TreeNode) *TreeNode {
+    if root == nil {
+        return nil
+    }
+    queue := arrayqueue.New()
+    queue.Enqueue(root)
+
+    for queue.Size() > 0 {
+        node, _ := queue.Dequeue()
+        current := node.(*TreeNode)
+        current.Left, current.Right = current.Right, current.Left
+
+        if current.Left != nil {
+            queue.Enqueue(current.Left)
+        }
+        if current.Right != nil {
+            queue.Enqueue(current.Right)
+        }
+    }
+    return root
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    fun invertTree(root: TreeNode?): TreeNode? {
+        if (root == null) {
+            return null
+        }
+        val queue: ArrayDeque<TreeNode?> = ArrayDeque()
+        queue.add(root)
+
+        while (queue.isNotEmpty()) {
+            val node = queue.removeFirst()
+            node?.let {
+                val temp = it.left
+                it.left = it.right
+                it.right = temp
+                queue.add(it.left)
+                queue.add(it.right)
+            }
+        }
+        return root
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func invertTree(_ root: TreeNode?) -> TreeNode? {
+        guard let root = root else { return nil }
+        var queue = Deque<TreeNode>()
+        queue.append(root)
+
+        while !queue.isEmpty {
+            let node = queue.removeFirst()
+            (node.left, node.right) = (node.right, node.left)
+            
+            if let left = node.left {
+                queue.append(left)
+            }
+            if let right = node.right {
+                queue.append(right)
+            }
+        }
+        return root
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -187,10 +291,10 @@ class Solution:
         if not root: return None
 
         root.left, root.right = root.right, root.left
-        
+
         self.invertTree(root.left)
         self.invertTree(root.right)
-        
+
         return root
 ```
 
@@ -211,16 +315,18 @@ class Solution:
  * }
  */
 
-class Solution {
+public class Solution {
     public TreeNode invertTree(TreeNode root) {
         if (root == null) return null;
-        
-        TreeNode node = new TreeNode(root.val);
 
-        node.right = invertTree(root.left);
-        node.left = invertTree(root.right);
-        
-        return node;
+        TreeNode temp = root.left;
+        root.left = root.right;
+        root.right = temp;
+
+        invertTree(root.left);
+        invertTree(root.right);
+
+        return root;
     }
 }
 ```
@@ -241,14 +347,13 @@ class Solution {
 class Solution {
 public:
     TreeNode* invertTree(TreeNode* root) {
-        if (root == nullptr) return nullptr;
+        if (!root) return nullptr;
 
-        TreeNode* node = new TreeNode(root->val);
-        
-        node->right = invertTree(root->left);
-        node->left = invertTree(root->right);
+        swap(root->left, root->right);
+        invertTree(root->left);
+        invertTree(root->right);
 
-        return node;
+        return root;
     }
 };
 ```
@@ -271,14 +376,13 @@ class Solution {
      * @return {TreeNode}
      */
     invertTree(root) {
-        if (root === null) return null;
-
-        const node = new TreeNode(root.val);
+        if (!root) return null;
 
-        node.right = this.invertTree(root.left);
-        node.left = this.invertTree(root.right);
+        [root.left, root.right] = [root.right, root.left];
+        this.invertTree(root.left);
+        this.invertTree(root.right);
 
-        return node;
+        return root;
     }
 }
 ```
@@ -302,12 +406,95 @@ public class Solution {
     public TreeNode InvertTree(TreeNode root) {
         if (root == null) return null;
 
-        TreeNode node = new TreeNode(root.val);
-        
-        node.right = InvertTree(root.left);
-        node.left = InvertTree(root.right);
+        TreeNode temp = root.left;
+        root.left = root.right;
+        root.right = temp;
 
-        return node;
+        InvertTree(root.left);
+        InvertTree(root.right);
+
+        return root;
+    }
+}
+```
+
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+
+func invertTree(root *TreeNode) *TreeNode {
+    if root == nil {
+        return nil
+    }
+
+    root.Left, root.Right = root.Right, root.Left
+    invertTree(root.Left)
+    invertTree(root.Right)
+
+    return root
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+ 
+class Solution {
+    fun invertTree(root: TreeNode?): TreeNode? {
+        if (root == null) return null
+
+        val temp = root.left
+        root.left = root.right
+        root.right = temp
+
+        invertTree(root.left)
+        invertTree(root.right)
+
+        return root
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func invertTree(_ root: TreeNode?) -> TreeNode? {
+        guard let root = root else { return nil }
+
+        (root.left, root.right) = (root.right, root.left)
+
+        invertTree(root.left)
+        invertTree(root.right)
+
+        return root
     }
 }
 ```
@@ -317,11 +504,11 @@ public class Solution {
 ### Time & Space Complexity
 
 * Time complexity: $O(n)$
-* Space complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
 
 ---
 
-## 3. Depth First Search (Stack)
+## 3. Iterative DFS
 
 ::tabs-start
 
@@ -478,6 +665,91 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func invertTree(root *TreeNode) *TreeNode {
+    if root == nil {
+        return nil
+    }
+
+    root.Left, root.Right = root.Right, root.Left
+
+    invertTree(root.Left)
+    invertTree(root.Right)
+
+    return root
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    fun invertTree(root: TreeNode?): TreeNode? {
+        if (root == null) return null
+
+        root.left = root.right.also { root.right = root.left }
+
+        invertTree(root.left)
+        invertTree(root.right)
+
+        return root
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func invertTree(_ root: TreeNode?) -> TreeNode? {
+        guard let root = root else { return nil }
+        var stack: [TreeNode] = [root]
+
+        while !stack.isEmpty {
+            let node = stack.removeLast()
+            (node.left, node.right) = (node.right, node.left)
+            
+            if let left = node.left {
+                stack.append(left)
+            }
+            if let right = node.right {
+                stack.append(right)
+            }
+        }
+        return root
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/ipo.md b/articles/ipo.md
new file mode 100644
index 000000000..87670000f
--- /dev/null
+++ b/articles/ipo.md
@@ -0,0 +1,467 @@
+## 1. Two Heaps
+
+::tabs-start
+
+```python
+class Solution:
+    def findMaximizedCapital(self, k: int, w: int, profits: List[int], capital: List[int]) -> int:
+        maxProfit = []  # Max heap
+        minCapital = [(c, p) for c, p in zip(capital, profits)]  # Min heap
+        heapq.heapify(minCapital)
+
+        for _ in range(k):
+            while minCapital and minCapital[0][0] <= w:
+                c, p = heapq.heappop(minCapital)
+                heapq.heappush(maxProfit, -p)
+            
+            if not maxProfit:
+                break
+            
+            w += -heapq.heappop(maxProfit)
+
+        return w
+```
+
+```java
+public class Solution {
+    public int findMaximizedCapital(int k, int w, int[] profits, int[] capital) {
+        PriorityQueue<int[]> minCapital = new PriorityQueue<>((a, b) -> a[0] - b[0]); // Min heap
+        PriorityQueue<Integer> maxProfit = new PriorityQueue<>((a, b) -> b - a);      // Max heap
+        
+        for (int i = 0; i < capital.length; i++) {
+            minCapital.offer(new int[]{capital[i], profits[i]});
+        }
+        
+        for (int i = 0; i < k; i++) {
+            while (!minCapital.isEmpty() && minCapital.peek()[0] <= w) {
+                maxProfit.offer(minCapital.poll()[1]);
+            }
+            if (maxProfit.isEmpty()) {
+                break;
+            }            
+            w += maxProfit.poll();
+        }
+        
+        return w;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findMaximizedCapital(int k, int w, vector<int>& profits, vector<int>& capital) {
+        priority_queue<int> maxProfit; // Max heap
+        priority_queue<pair<int, int>, vector<pair<int, int>>, greater<>> minCapital; // Min heap
+        
+        for (int i = 0; i < capital.size(); i++) {
+            minCapital.emplace(capital[i], profits[i]);
+        }
+        
+        for (int i = 0; i < k; i++) {
+            while (!minCapital.empty() && minCapital.top().first <= w) {
+                maxProfit.push(minCapital.top().second);
+                minCapital.pop();
+            }
+            if (maxProfit.empty()) {
+                break;
+            }
+            w += maxProfit.top();
+            maxProfit.pop();
+        }
+        
+        return w;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} k
+     * @param {number} w
+     * @param {number[]} profits
+     * @param {number[]} capital
+     * @return {number}
+     */
+    findMaximizedCapital(k, w, profits, capital) {
+        const minCapital = new PriorityQueue((a, b) => a[0] - b[0]); // Min heap
+        const maxProfit = new PriorityQueue((a, b) => b - a);        // Max heap
+        
+        for (let i = 0; i < capital.length; i++) {
+            minCapital.enqueue([capital[i], profits[i]]);
+        }
+        
+        for (let i = 0; i < k; i++) {
+            while (!minCapital.isEmpty() && minCapital.front()[0] <= w) {
+                maxProfit.enqueue(minCapital.dequeue()[1]);
+            }
+            if (maxProfit.isEmpty()) {
+                break;
+            }
+            w += maxProfit.dequeue();
+        }
+        
+        return w;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int FindMaximizedCapital(int k, int w, int[] profits, int[] capital) {
+        var minCapital = new List<(int c, int p)>();
+        for (int i = 0; i < capital.Length; i++) {
+            minCapital.Add((capital[i], profits[i]));
+        }
+
+        // Min-heap by capital
+        minCapital.Sort((a, b) => a.c.CompareTo(b.c));
+
+        // Max-heap by profit
+        var maxProfit = new PriorityQueue<int, int>(Comparer<int>.Create((a, b) => b.CompareTo(a)));
+        int iPtr = 0;
+
+        for (int i = 0; i < k; i++) {
+            while (iPtr < minCapital.Count && minCapital[iPtr].c <= w) {
+                maxProfit.Enqueue(minCapital[iPtr].p, minCapital[iPtr].p);
+                iPtr++;
+            }
+
+            if (maxProfit.Count == 0) {
+                break;
+            }
+
+            w += maxProfit.Dequeue();
+        }
+
+        return w;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Two Heaps (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def findMaximizedCapital(self, k: int, w: int, profits: List[int], capital: List[int]) -> int:
+        class Node:
+            def __init__(self, idx):
+                self.idx = idx
+                
+            def __lt__(self, other):
+                if capital[self.idx] != capital[other.idx]:
+                    return capital[self.idx] < capital[other.idx]
+                return self.idx < other.idx
+
+        minCapital = []
+        maxProfit = []
+        for i in range(len(capital)):
+            heapq.heappush(minCapital, Node(i))
+
+        for _ in range(k):
+            while minCapital and capital[minCapital[0].idx] <= w:
+                idx = heapq.heappop(minCapital).idx
+                heapq.heappush(maxProfit, -profits[idx])
+            
+            if not maxProfit:
+                break
+            w += -heapq.heappop(maxProfit)
+
+        return w
+```
+
+```java
+public class Solution {
+    public int findMaximizedCapital(int k, int w, int[] profits, int[] capital) {
+        PriorityQueue<Integer> minCapital = new PriorityQueue<>((a, b) -> capital[a] - capital[b]);
+        PriorityQueue<Integer> maxProfit = new PriorityQueue<>((a, b) -> profits[b] - profits[a]);
+
+        for (int i = 0; i < capital.length; i++) {
+            minCapital.offer(i);
+        }
+
+        for (int i = 0; i < k; i++) {
+            while (!minCapital.isEmpty() && capital[minCapital.peek()] <= w) {
+                maxProfit.offer(minCapital.poll());
+            }
+            if (maxProfit.isEmpty()) {
+                break;
+            }
+            w += profits[maxProfit.poll()];
+        }
+
+        return w;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findMaximizedCapital(int k, int w, vector<int>& profits, vector<int>& capital) {
+        auto cmpCapital = [&](int a, int b) { return capital[a] > capital[b]; };
+        auto cmpProfit = [&](int a, int b) { return profits[a] < profits[b]; };
+
+        priority_queue<int, vector<int>, decltype(cmpCapital)> minCapital(cmpCapital);
+        priority_queue<int, vector<int>, decltype(cmpProfit)> maxProfit(cmpProfit);
+
+        for (int i = 0; i < capital.size(); i++) {
+            minCapital.push(i);
+        }
+
+        for (int i = 0; i < k; i++) {
+            while (!minCapital.empty() && capital[minCapital.top()] <= w) {
+                maxProfit.push(minCapital.top());
+                minCapital.pop();
+            }
+            if (maxProfit.empty()) {
+                break;
+            }
+            w += profits[maxProfit.top()];
+            maxProfit.pop();
+        }
+
+        return w;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} k
+     * @param {number} w
+     * @param {number[]} profits
+     * @param {number[]} capital
+     * @return {number}
+     */
+    findMaximizedCapital(k, w, profits, capital) {
+        const minCapital = new PriorityQueue(
+            (a, b) => capital[a] - capital[b],
+        );
+        const maxProfit = new PriorityQueue(
+            (a, b) => profits[b] - profits[a],
+        );
+
+        for (let i = 0; i < capital.length; i++) {
+            minCapital.enqueue(i);
+        }
+
+        for (let i = 0; i < k; i++) {
+            while (!minCapital.isEmpty() && capital[minCapital.front()] <= w) {
+                maxProfit.enqueue(minCapital.dequeue());
+            }
+            if (maxProfit.isEmpty()) {
+                break;
+            }
+            w += profits[maxProfit.dequeue()];
+        }
+
+        return w;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int FindMaximizedCapital(int k, int w, int[] profits, int[] capital) {
+        var minCapital = new PriorityQueue<int, int>(); // index with capital as priority
+        var maxProfit = new PriorityQueue<int, int>(Comparer<int>.Create((a, b) => b.CompareTo(a))); // max heap by profit
+
+        for (int i = 0; i < capital.Length; i++) {
+            minCapital.Enqueue(i, capital[i]);
+        }
+
+        for (int i = 0; i < k; i++) {
+            while (minCapital.Count > 0 && capital[minCapital.Peek()] <= w) {
+                int idx = minCapital.Dequeue();
+                maxProfit.Enqueue(profits[idx], profits[idx]);
+            }
+
+            if (maxProfit.Count == 0) {
+                break;
+            }
+
+            w += maxProfit.Dequeue();
+        }
+
+        return w;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Sorting + Max-Heap
+
+::tabs-start
+
+```python
+class Solution:
+    def findMaximizedCapital(self, k: int, w: int, profits: List[int], capital: List[int]) -> int:
+        n = len(profits)
+        indices = list(range(n))
+        indices.sort(key=lambda i: capital[i])
+        
+        maxProfit, idx = [], 0
+        for _ in range(k):
+            while idx < n and capital[indices[idx]] <= w:
+                heapq.heappush(maxProfit, -profits[indices[idx]])
+                idx += 1
+            
+            if not maxProfit:
+                break
+            w += -heapq.heappop(maxProfit)
+        
+        return w
+```
+
+```java
+public class Solution {
+    public int findMaximizedCapital(int k, int w, int[] profits, int[] capital) {
+        int n = profits.length;
+        Integer[] indices = new Integer[n];
+        for (int i = 0; i < n; i++) {
+            indices[i] = i;
+        }
+        Arrays.sort(indices, (a, b) -> Integer.compare(capital[a], capital[b]));
+        
+        PriorityQueue<Integer> maxProfit = new PriorityQueue<>(Collections.reverseOrder());
+        int idx = 0;
+        for (int i = 0; i < k; i++) {
+            while (idx < n && capital[indices[idx]] <= w) {
+                maxProfit.add(profits[indices[idx]]);
+                idx++;
+            }   
+            if (maxProfit.isEmpty()) {
+                break;
+            }
+            w += maxProfit.poll();
+        }
+        
+        return w;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findMaximizedCapital(int k, int w, vector<int>& profits, vector<int>& capital) {
+        int n = profits.size();
+        vector<int> indices(n);
+        for (int i = 0; i < n; i++) {
+            indices[i] = i;
+        }
+        sort(indices.begin(), indices.end(), [&](int a, int b) {
+            return capital[a] < capital[b];
+        });
+        
+        priority_queue<int> maxProfit;
+        int idx = 0;
+        for (int i = 0; i < k; i++) {
+            while (idx < n && capital[indices[idx]] <= w) {
+                maxProfit.push(profits[indices[idx]]);
+                idx++;
+            }
+            if (maxProfit.empty()) {
+                break;
+            }            
+            w += maxProfit.top();
+            maxProfit.pop();
+        }
+
+        return w;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} k
+     * @param {number} w
+     * @param {number[]} profits
+     * @param {number[]} capital
+     * @return {number}
+     */
+    findMaximizedCapital(k, w, profits, capital) {
+        const n = profits.length;
+        const indices = Array.from({ length: n }, (_, i) => i);
+        indices.sort((a, b) => capital[a] - capital[b]);
+        
+        const maxProfit = new MaxPriorityQueue();
+        let idx = 0;
+        for (let i = 0; i < k; i++) {
+            while (idx < n && capital[indices[idx]] <= w) {
+                maxProfit.enqueue(profits[indices[idx]]);
+                idx++;
+            }
+            if (maxProfit.isEmpty()) {
+                break;
+            }
+            w += maxProfit.dequeue();
+        }
+        
+        return w;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int FindMaximizedCapital(int k, int w, int[] profits, int[] capital) {
+        int n = profits.Length;
+        int[] indices = new int[n];
+        for (int i = 0; i < n; i++) {
+            indices[i] = i;
+        }
+
+        Array.Sort(indices, (a, b) => capital[a].CompareTo(capital[b]));
+
+        var maxProfit = new PriorityQueue<int, int>(Comparer<int>.Create((a, b) => b.CompareTo(a)));
+        int idx = 0;
+
+        for (int i = 0; i < k; i++) {
+            while (idx < n && capital[indices[idx]] <= w) {
+                maxProfit.Enqueue(profits[indices[idx]], profits[indices[idx]]);
+                idx++;
+            }
+
+            if (maxProfit.Count == 0) {
+                break;
+            }
+
+            w += maxProfit.Dequeue();
+        }
+
+        return w;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/is-anagram.md b/articles/is-anagram.md
index 3e879f614..eb996634a 100644
--- a/articles/is-anagram.md
+++ b/articles/is-anagram.md
@@ -77,16 +77,61 @@ public class Solution {
 }
 ```
 
+```go
+func isAnagram(s string, t string) bool {
+    if len(s) != len(t) {
+        return false
+    }
+    
+    sRunes, tRunes := []rune(s), []rune(t)
+    sort.Slice(sRunes, func(i, j int) bool { 
+        return sRunes[i] < sRunes[j] 
+    })
+    sort.Slice(tRunes, func(i, j int) bool { 
+        return tRunes[i] < tRunes[j] 
+    })
+    
+    for i := range sRunes {
+        if sRunes[i] != tRunes[i] {
+            return false
+        }
+    }
+    return true
+}
+```
+
+```kotlin
+class Solution {
+    fun isAnagram(s: String, t: String): Boolean {
+        if (s.length != t.length) {
+            return false
+        }
+        
+        return s.toCharArray().sorted() == t.toCharArray().sorted()
+    }
+}
+```
+
+```swift
+class Solution {
+    func isAnagram(_ s: String, _ t: String) -> Bool {
+        return s.count == t.count && s.sorted() == t.sorted()
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
-* Time complexity: $O(n \log n)$
-* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+* Time complexity: $O(n \log n + m \log m)$
+* Space complexity: $O(1)$ or $O(n + m)$ depending on the sorting algorithm.
+
+> Where $n$ is the length of string $s$ and $m$ is the length of string $t$. 
 
 ---
 
-## 2. Hash Table
+## 2. Hash Map
 
 ::tabs-start
 
@@ -188,16 +233,82 @@ public class Solution {
 }
 ```
 
+```go
+func isAnagram(s string, t string) bool {
+    if len(s) != len(t) {
+        return false
+    }
+
+    countS, countT := make(map[rune]int), make(map[rune]int)
+    for i, ch := range s {
+        countS[ch]++
+        countT[rune(t[i])]++
+    }
+
+    for k, v := range countS {
+        if countT[k] != v {
+            return false
+        }
+    }
+    return true
+}
+```
+
+```kotlin
+class Solution {
+    fun isAnagram(s: String, t: String): Boolean {
+        if (s.length != t.length) {
+            return false
+        }
+
+        val countS = mutableMapOf<Char, Int>()
+        val countT = mutableMapOf<Char, Int>()
+
+        for (i in s.indices) {
+            countS[s[i]] = countS.getOrDefault(s[i], 0) + 1
+            countT[t[i]] = countT.getOrDefault(t[i], 0) + 1
+        }
+
+        return countS == countT
+    }
+}
+```
+
+```swift
+class Solution {
+    func isAnagram(_ s: String, _ t: String) -> Bool {
+        if s.count != t.count {
+            return false
+        }
+
+        var countS = [Character: Int]()
+        var countT = [Character: Int]()
+
+        let sArray = Array(s)
+        let tArray = Array(t)
+
+        for i in 0..<s.count {
+            countS[sArray[i], default: 0] += 1
+            countT[tArray[i], default: 0] += 1
+        }
+
+        return countS == countT
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
-* Time complexity: $O(n)$
-* Space complexity: $O(1)$
+* Time complexity: $O(n + m)$
+* Space complexity: $O(1)$ since we have at most $26$ different characters.
+
+> Where $n$ is the length of string $s$ and $m$ is the length of string $t$. 
 
 ---
 
-## 3. Hash Table (Optimal)
+## 3. Hash Table (Using Array)
 
 ::tabs-start
 
@@ -310,9 +421,81 @@ public class Solution {
 }
 ```
 
+```go
+func isAnagram(s string, t string) bool {
+    if len(s) != len(t) {
+        return false
+    }
+
+    count := [26]int{}
+    for i := 0; i < len(s); i++ {
+        count[s[i]-'a']++
+        count[t[i]-'a']--
+    }
+
+    for _, val := range count {
+        if val != 0 {
+            return false
+        }
+    }
+    return true
+}
+```
+
+```kotlin
+class Solution {
+    fun isAnagram(s: String, t: String): Boolean {
+        if (s.length != t.length) {
+            return false
+        }
+
+        val count = IntArray(26)
+        for (i in s.indices) {
+            count[s[i] - 'a']++
+            count[t[i] - 'a']--
+        }
+
+        for (value in count) {
+            if (value != 0) {
+                return false
+            }
+        }
+        return true
+    }
+}
+```
+
+```swift
+class Solution {
+    func isAnagram(_ s: String, _ t: String) -> Bool {
+        if s.count != t.count {
+            return false
+        }
+
+        var count = [Int](repeating: 0, count: 26)
+        let sArray = Array(s)
+        let tArray = Array(t)
+
+        for i in 0..<s.count {
+            count[Int(sArray[i].asciiValue!) - 97] += 1
+            count[Int(tArray[i].asciiValue!) - 97] -= 1
+        }
+
+        for val in count {
+            if val != 0 {
+                return false
+            }
+        }
+        return true
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
-* Time complexity: $O(n)$
-* Space complexity: $O(1)$
\ No newline at end of file
+* Time complexity: $O(n + m)$
+* Space complexity: $O(1)$ since we have at most $26$ different characters.
+
+> Where $n$ is the length of string $s$ and $m$ is the length of string $t$.
\ No newline at end of file
diff --git a/articles/is-graph-bipartite.md b/articles/is-graph-bipartite.md
new file mode 100644
index 000000000..2db1c9d94
--- /dev/null
+++ b/articles/is-graph-bipartite.md
@@ -0,0 +1,611 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def isBipartite(self, graph: List[List[int]]) -> bool:
+        color = [0] * len(graph)  # Map node i -> odd=1, even=-1
+
+        def dfs(i, c):
+            color[i] = c
+            for nei in graph[i]:
+                if color[nei] == c:
+                    return False
+                if color[nei] == 0 and not dfs(nei, -c):
+                    return False
+            return True
+
+        for i in range(len(graph)):
+            if color[i] == 0 and not dfs(i, 1):
+                return False
+        return True
+```
+
+```java
+public class Solution {
+    private int[] color;
+
+    public boolean isBipartite(int[][] graph) {
+        int n = graph.length;
+        color = new int[n]; // Map node i -> odd=1, even=-1
+
+        for (int i = 0; i < n; i++) {
+            if (color[i] == 0 && !dfs(graph, i, 1)) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    private boolean dfs(int[][] graph, int i, int c) {
+        color[i] = c;
+        for (int nei : graph[i]) {
+            if (color[nei] == c) {
+                return false;
+            }
+            if (color[nei] == 0 && !dfs(graph, nei, -c)) {
+                return false;
+            }
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<int> color;
+
+    bool dfs(vector<vector<int>>& graph, int i, int c) {
+        color[i] = c;
+        for (int nei : graph[i]) {
+            if (color[nei] == c) {
+                return false;
+            }
+            if (color[nei] == 0 && !dfs(graph, nei, -c)) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+public:
+    bool isBipartite(vector<vector<int>>& graph) {
+        int n = graph.size();
+        color.assign(n, 0); // Map node i -> odd=1, even=-1
+
+        for (int i = 0; i < n; i++) {
+            if (color[i] == 0 && !dfs(graph, i, 1)) {
+                return false;
+            }
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} graph
+     * @return {boolean}
+     */
+    isBipartite(graph) {
+        let n = graph.length;
+        let color = new Array(n).fill(0); // Map node i -> odd=1, even=-1
+
+        const dfs = (i, c) => {
+            color[i] = c;
+            for (let nei of graph[i]) {
+                if (color[nei] === c) {
+                    return false;
+                }
+                if (color[nei] === 0 && !dfs(nei, -c)) {
+                    return false;
+                }
+            }
+            return true;
+        };
+
+        for (let i = 0; i < n; i++) {
+            if (color[i] === 0 && !dfs(i, 1)) {
+                return false;
+            }
+        }
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + E)$
+* Space complexity: $O(V)$
+
+> Where $V$ is the number of vertices and $E$ is the number of edges.
+
+---
+
+## 2. Breadth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def isBipartite(self, graph: List[List[int]]) -> bool:
+        color = [0] * len(graph)  # Map node i -> odd=1, even=-1
+
+        def bfs(i):
+            if color[i]:
+                return True
+            q = deque([i])
+            color[i] = -1
+            while q:
+                i = q.popleft()
+                for nei in graph[i]:
+                    if color[i] == color[nei]:
+                        return False
+                    elif not color[nei]:
+                        q.append(nei)
+                        color[nei] = -1 * color[i]
+            return True
+
+        for i in range(len(graph)):
+            if not bfs(i):
+                return False
+        return True
+```
+
+```java
+public class Solution {
+    public boolean isBipartite(int[][] graph) {
+        int n = graph.length;
+        int[] color = new int[n]; // Map node i -> odd=1, even=-1
+
+        for (int i = 0; i < n; i++) {
+            if (color[i] != 0) continue;
+            Queue<Integer> q = new LinkedList<>();
+            q.offer(i);
+            color[i] = -1;
+
+            while (!q.isEmpty()) {
+                int node = q.poll();
+                for (int nei : graph[node]) {
+                    if (color[nei] == color[node]) {
+                        return false;
+                    } else if (color[nei] == 0) {
+                        q.offer(nei);
+                        color[nei] = -color[node];
+                    }
+                }
+            }
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isBipartite(vector<vector<int>>& graph) {
+        int n = graph.size();
+        vector<int> color(n, 0); // Map node i -> odd=1, even=-1
+
+        for (int i = 0; i < n; i++) {
+            if (color[i] != 0) continue;
+            queue<int> q;
+            q.push(i);
+            color[i] = -1;
+
+            while (!q.empty()) {
+                int node = q.front();
+                q.pop();
+                for (int nei : graph[node]) {
+                    if (color[nei] == color[node]) {
+                        return false;
+                    } else if (color[nei] == 0) {
+                        q.push(nei);
+                        color[nei] = -color[node];
+                    }
+                }
+            }
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} graph
+     * @return {boolean}
+     */
+    isBipartite(graph) {
+        let n = graph.length;
+        let color = new Array(n).fill(0); // Map node i -> odd=1, even=-1
+
+        for (let i = 0; i < n; i++) {
+            if (color[i] !== 0) continue;
+            let q = new Queue([i]);
+            color[i] = -1;
+
+            while (!q.isEmpty()) {
+                let node = q.pop();
+                for (let nei of graph[node]) {
+                    if (color[nei] === color[node]) {
+                        return false;
+                    } else if (color[nei] === 0) {
+                        q.push(nei);
+                        color[nei] = -color[node];
+                    }
+                }
+            }
+        }
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + E)$
+* Space complexity: $O(V)$
+
+> Where $V$ is the number of vertices and $E$ is the number of edges.
+
+---
+
+## 3. Iterative DFS
+
+::tabs-start
+
+```python
+class Solution:
+    def isBipartite(self, graph: List[List[int]]) -> bool:
+        color = [0] * len(graph)  # Map node i -> odd=1, even=-1
+        stack = []
+
+        for i in range(len(graph)):
+            if color[i] != 0:
+                continue
+            color[i] = -1
+            stack.append(i)
+            while stack:
+                node = stack.pop()
+                for nei in graph[node]:
+                    if color[node] == color[nei]:
+                        return False
+                    elif not color[nei]:
+                        stack.append(nei)
+                        color[nei] = -1 * color[node]
+
+        return True
+```
+
+```java
+public class Solution {
+    public boolean isBipartite(int[][] graph) {
+        int n = graph.length;
+        int[] color = new int[n]; // Map node i -> odd=1, even=-1
+        Stack<Integer> stack = new Stack<>();
+
+        for (int i = 0; i < n; i++) {
+            if (color[i] != 0) continue;
+            color[i] = -1;
+            stack.push(i);
+            while (!stack.isEmpty()) {
+                int node = stack.pop();
+                for (int nei : graph[node]) {
+                    if (color[node] == color[nei]) return false;
+                    if (color[nei] == 0) {
+                        stack.push(nei);
+                        color[nei] = -color[node];
+                    }
+                }
+            }
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isBipartite(vector<vector<int>>& graph) {
+        int n = graph.size();
+        vector<int> color(n); // Map node i -> odd=1, even=-1
+        stack<int> stack;
+
+        for (int i = 0; i < n; i++) {
+            if (color[i] != 0) continue;
+            color[i] = -1;
+            stack.push(i);
+            while (!stack.empty()) {
+                int node = stack.top();
+                stack.pop();
+                for (int nei : graph[node]) {
+                    if (color[node] == color[nei]) return false;
+                    if (color[nei] == 0) {
+                        stack.push(nei);
+                        color[nei] = -color[node];
+                    }
+                }
+            }
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} graph
+     * @return {boolean}
+     */
+    isBipartite(graph) {
+        let n = graph.length;
+        let color = new Array(n).fill(0); // Map node i -> odd=1, even=-1
+        let stack = [];
+
+        for (let i = 0; i < n; i++) {
+            if (color[i] !== 0) continue;
+            color[i] = -1;
+            stack.push(i);
+            while (stack.length > 0) {
+                let node = stack.pop();
+                for (let nei of graph[node]) {
+                    if (color[node] === color[nei]) return false;
+                    if (color[nei] === 0) {
+                        stack.push(nei);
+                        color[nei] = -color[node];
+                    }
+                }
+            }
+        }
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + E)$
+* Space complexity: $O(V)$
+
+> Where $V$ is the number of vertices and $E$ is the number of edges.
+
+---
+
+## 4. Disjoint Set Union
+
+::tabs-start
+
+```python
+class DSU:
+    def __init__(self, n):
+        self.Parent = list(range(n))
+        self.Size = [0] * n
+
+    def find(self, node):
+        if self.Parent[node] != node:
+            self.Parent[node] = self.find(self.Parent[node])
+        return self.Parent[node]
+
+    def union(self, u, v):
+        pu, pv = self.find(u), self.find(v)
+        if pu == pv:
+            return False
+        if self.Size[pu] > self.Size[pv]:
+            self.Parent[pv] = pu
+        elif self.Size[pu] < self.Size[pv]:
+            self.Parent[pu] = pv
+        else:
+            self.Parent[pv] = pu
+            self.Size[pu] += 1
+        return True
+
+class Solution:
+    def isBipartite(self, graph: List[List[int]]) -> bool:
+        n = len(graph)
+        dsu = DSU(n)
+
+        for node in range(n):
+            for nei in graph[node]:
+                if dsu.find(node) == dsu.find(nei):
+                    return False
+                dsu.union(graph[node][0], nei)
+
+        return True
+```
+
+```java
+public class DSU {
+    private int[] Parent, Size;
+
+    public DSU(int n) {
+        Parent = new int[n];
+        Size = new int[n];
+        for (int i = 0; i < n; i++) {
+            Parent[i] = i;
+            Size[i] = 0;
+        }
+    }
+
+    public int find(int node) {
+        if (Parent[node] != node) {
+            Parent[node] = find(Parent[node]);
+        }
+        return Parent[node];
+    }
+
+    public boolean union(int u, int v) {
+        int pu = find(u), pv = find(v);
+        if (pu == pv) return false;
+        if (Size[pu] > Size[pv]) {
+            Parent[pv] = pu;
+        } else if (Size[pu] < Size[pv]) {
+            Parent[pu] = pv;
+        } else {
+            Parent[pv] = pu;
+            Size[pu]++;
+        }
+        return true;
+    }
+}
+
+class Solution {
+    public boolean isBipartite(int[][] graph) {
+        int n = graph.length;
+        DSU dsu = new DSU(n);
+
+        for (int node = 0; node < n; node++) {
+            for (int nei : graph[node]) {
+                if (dsu.find(node) == dsu.find(nei)) {
+                    return false;
+                }
+                dsu.union(graph[node][0], nei);
+            }
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class DSU {
+private:
+    vector<int> Parent, Size;
+    
+public:
+    DSU(int n) {
+        Parent.resize(n);
+        Size.resize(n, 0);
+        for (int i = 0; i < n; i++) {
+            Parent[i] = i;
+        }
+    }
+
+    int find(int node) {
+        if (Parent[node] != node) {
+            Parent[node] = find(Parent[node]);
+        }
+        return Parent[node];
+    }
+
+    bool unionSet(int u, int v) {
+        int pu = find(u), pv = find(v);
+        if (pu == pv) return false;
+        if (Size[pu] > Size[pv]) {
+            Parent[pv] = pu;
+        } else if (Size[pu] < Size[pv]) {
+            Parent[pu] = pv;
+        } else {
+            Parent[pv] = pu;
+            Size[pu]++;
+        }
+        return true;
+    }
+};
+
+class Solution {
+public:
+    bool isBipartite(vector<vector<int>>& graph) {
+        int n = graph.size();
+        DSU dsu(n);
+
+        for (int node = 0; node < n; node++) {
+            for (int& nei : graph[node]) {
+                if (dsu.find(node) == dsu.find(nei)) {
+                    return false;
+                }
+                dsu.unionSet(graph[node][0], nei);
+            }
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+class DSU {
+    /**
+     * @constructor
+     * @param {number} n
+     */
+    constructor(n) {
+        this.parent = Array.from({ length: n + 1 }, (_, i) => i);
+        this.size = new Array(n + 1).fill(1);
+    }
+
+    /**
+     * @param {number} node
+     * @return {number}
+     */
+    find(node) {
+        if (this.parent[node] !== node) {
+            this.parent[node] = this.find(this.parent[node]);
+        }
+        return this.parent[node];
+    }
+
+    /**
+     * @param {number} u
+     * @param {number} u=v
+     * @return {boolean}
+     */
+    union(u, v) {
+        let pu = this.find(u), pv = this.find(v);
+        if (pu === pv) return false;
+        if (this.size[pu] >= this.size[pv]) {
+            this.size[pu] += this.size[pv];
+            this.parent[pv] = pu;
+        } else {
+            this.size[pv] += this.size[pu];
+            this.parent[pu] = pv;
+        }
+        return true;
+    }
+}
+
+class Solution {
+    /**
+     * @param {number[][]} graph
+     * @return {boolean}
+     */
+    isBipartite(graph) {
+        let n = graph.length;
+        let dsu = new DSU(n);
+
+        for (let node = 0; node < n; node++) {
+            for (let nei of graph[node]) {
+                if (dsu.find(node) === dsu.find(nei)) {
+                    return false;
+                }
+                dsu.union(graph[node][0], nei);
+            }
+        }
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + (E * α(V)))$
+* Space complexity: $O(V)$
+
+> Where $V$ is the number of vertices and $E$ is the number of edges. $α()$ is used for amortized complexity.
\ No newline at end of file
diff --git a/articles/is-palindrome.md b/articles/is-palindrome.md
index 35c036875..9aea0c833 100644
--- a/articles/is-palindrome.md
+++ b/articles/is-palindrome.md
@@ -84,6 +84,61 @@ public class Solution {
 }
 ```
 
+```go
+func isPalindrome(s string) bool {
+    newStr := ""
+    for _, c := range s {
+        if ('a' <= c && c <= 'z') || ('0' <= c && c <= '9') {
+            newStr += string(c)
+        } else if 'A' <= c && c <= 'Z' {
+            newStr += string(c + 'a' - 'A')
+        }
+    }
+
+    reversedStr := reverse(newStr)
+    return newStr == reversedStr
+}
+
+func reverse(s string) string {
+    runes := []rune(s)
+    n := len(runes)
+    for i := 0; i < n/2; i++ {
+        runes[i], runes[n-1-i] = runes[n-1-i], runes[i]
+    }
+    return string(runes)
+}
+```
+
+```kotlin
+class Solution {
+    fun isPalindrome(s: String): Boolean {
+        var newStr = ""
+        for (c in s) {
+            if (c.isLetterOrDigit()) {
+                newStr += c.lowercaseChar()
+            }
+        }
+        return newStr == newStr.reversed()
+    }
+}
+```
+
+```swift
+class Solution {
+    func isPalindrome(_ s: String) -> Bool {
+        var newStr = ""
+
+        for c in s {
+            if c.isLetter || c.isNumber {
+                newStr.append(c.lowercased())
+            }
+        }
+
+        return newStr == String(newStr.reversed())
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -239,6 +294,83 @@ public class Solution {
 }
 ```
 
+```go
+func isPalindrome(s string) bool {
+    l, r := 0, len(s)-1
+
+    for l < r {
+        for l < r && !isAlphaNum(rune(s[l])) {
+            l++
+        }
+        for r > l && !isAlphaNum(rune(s[r])) {
+            r--
+        }
+        if unicode.ToLower(rune(s[l])) != unicode.ToLower(rune(s[r])) {
+            return false
+        }
+        l++
+        r--
+    }
+    return true
+}
+
+func isAlphaNum(c rune) bool {
+    return unicode.IsLetter(c) || unicode.IsDigit(c)
+}
+```
+
+```kotlin
+class Solution {
+    fun isPalindrome(s: String): Boolean {
+        var l = 0
+        var r = s.length - 1
+
+        while (l < r) {
+            while (l < r && !s[l].isLetterOrDigit()) {
+                l++
+            }
+            while (r > l && !s[r].isLetterOrDigit()) {
+                r--
+            }
+            if (s[l].lowercase() != s[r].lowercase()) {
+                return false
+            }
+            l++
+            r--
+        }
+        return true
+    }
+}
+```
+
+```swift
+class Solution {
+    func isPalindrome(_ s: String) -> Bool {
+        let chars = Array(s)
+        var l = 0, r = chars.count - 1
+
+        while l < r {
+            while l < r && !isAlphaNum(chars[l]) {
+                l += 1
+            }
+            while r > l && !isAlphaNum(chars[r]) {
+                r -= 1
+            }
+            if chars[l].lowercased() != chars[r].lowercased() {
+                return false
+            }
+            l += 1
+            r -= 1
+        }
+        return true
+    }
+
+    private func isAlphaNum(_ c: Character) -> Bool {
+        return c.isLetter || c.isNumber
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/is-subsequence.md b/articles/is-subsequence.md
new file mode 100644
index 000000000..fde7628a6
--- /dev/null
+++ b/articles/is-subsequence.md
@@ -0,0 +1,513 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def isSubsequence(self, s: str, t: str) -> bool:
+        def rec(i, j):
+            if i == len(s):
+                return True
+            if j == len(t):
+                return False
+            
+            if s[i] == t[j]:
+                return rec(i + 1, j + 1)
+            return rec(i, j + 1)
+        return rec(0, 0)
+```
+
+```java
+public class Solution {
+    public boolean isSubsequence(String s, String t) {
+        return rec(s, t, 0, 0);
+    }
+
+    private boolean rec(String s, String t, int i, int j) {
+        if (i == s.length()) return true;
+        if (j == t.length()) return false;
+        if (s.charAt(i) == t.charAt(j)) {
+            return rec(s, t, i + 1, j + 1);
+        }
+        return rec(s, t, i, j + 1);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isSubsequence(string s, string t) {
+        return rec(s, t, 0, 0);
+    }
+
+private:
+    bool rec(string& s, string& t, int i, int j) {
+        if (i == s.size()) return true;
+        if (j == t.size()) return false;
+        if (s[i] == t[j]) {
+            return rec(s, t, i + 1, j + 1);
+        }
+        return rec(s, t, i, j + 1);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string} t
+     * @return {boolean}
+     */
+    isSubsequence(s, t) {
+        const rec = (i, j) => {
+            if (i === s.length) return true;
+            if (j === t.length) return false;
+            if (s[i] === t[j]) return rec(i + 1, j + 1);
+            return rec(i, j + 1);
+        };
+        return rec(0, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the length of the string $s$ and $m$ is the length of the string $t$.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def isSubsequence(self, s: str, t: str) -> bool:
+        n, m = len(s), len(t)
+        memo = [[-1] * m for _ in range(n)]
+
+        def rec(i, j):
+            if i == n:
+                return True
+            if j == m:
+                return False
+            if memo[i][j] != -1:
+                return memo[i][j] == 1
+            if s[i] == t[j]:
+                memo[i][j] = 1 if rec(i + 1, j + 1) else 0
+            else:
+                memo[i][j] = 1 if rec(i, j + 1) else 0
+            return memo[i][j] == 1
+
+        return rec(0, 0)
+```
+
+```java
+public class Solution {
+    public boolean isSubsequence(String s, String t) {
+        int n = s.length(), m = t.length();
+        int[][] memo = new int[n][m];
+        for (int[] row : memo) {
+            Arrays.fill(row, -1);
+        }
+        return rec(s, t, 0, 0, memo);
+    }
+
+    private boolean rec(String s, String t, int i, int j, int[][] memo) {
+        if (i == s.length()) return true;
+        if (j == t.length()) return false;
+        if (memo[i][j] != -1) return memo[i][j] == 1;
+        if (s.charAt(i) == t.charAt(j)) {
+            memo[i][j] = rec(s, t, i + 1, j + 1, memo) ? 1 : 0;
+        } else {
+            memo[i][j] = rec(s, t, i, j + 1, memo) ? 1 : 0;
+        }
+        return memo[i][j] == 1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isSubsequence(string s, string t) {
+        int n = s.size(), m = t.size();
+        vector<vector<int>> memo(n, vector<int>(m, -1));
+        return rec(s, t, 0, 0, memo);
+    }
+
+private:
+    bool rec(string& s, string& t, int i, int j, vector<vector<int>>& memo) {
+        if (i == s.size()) return true;
+        if (j == t.size()) return false;
+        if (memo[i][j] != -1) return memo[i][j] == 1;
+        if (s[i] == t[j]) {
+            memo[i][j] = rec(s, t, i + 1, j + 1, memo) ? 1 : 0;
+        } else {
+            memo[i][j] = rec(s, t, i, j + 1, memo) ? 1 : 0;
+        }
+        return memo[i][j] == 1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string} t
+     * @return {boolean}
+     */
+    isSubsequence(s, t) {
+        const n = s.length, m = t.length;
+        const memo = Array.from({ length: n }, () => Array(m).fill(-1));
+
+        const rec = (i, j) => {
+            if (i === n) return true;
+            if (j === m) return false;
+            if (memo[i][j] !== -1) return memo[i][j] === 1;
+            if (s[i] === t[j]) {
+                memo[i][j] = rec(i + 1, j + 1) ? 1 : 0;
+            } else {
+                memo[i][j] = rec(i, j + 1) ? 1 : 0;
+            }
+            return memo[i][j] === 1;
+        };
+
+        return rec(0, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n * m)$
+
+> Where $n$ is the length of the string $s$ and $m$ is the length of the string $t$.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def isSubsequence(self, s: str, t: str) -> bool:
+        n, m = len(s), len(t)
+        dp = [[False] * (m + 1) for _ in range(n + 1)]
+        
+        for j in range(m + 1):
+            dp[n][j] = True
+        
+        for i in range(n - 1, -1, -1):
+            for j in range(m - 1, -1, -1):
+                if s[i] == t[j]:
+                    dp[i][j] = dp[i + 1][j + 1]
+                else:
+                    dp[i][j] = dp[i][j + 1]
+        
+        return dp[0][0]
+```
+
+```java
+public class Solution {
+    public boolean isSubsequence(String s, String t) {
+        int n = s.length(), m = t.length();
+        boolean[][] dp = new boolean[n + 1][m + 1];
+        
+        for (int j = 0; j <= m; j++) {
+            dp[n][j] = true;
+        }
+        
+        for (int i = n - 1; i >= 0; i--) {
+            for (int j = m - 1; j >= 0; j--) {
+                if (s.charAt(i) == t.charAt(j)) {
+                    dp[i][j] = dp[i + 1][j + 1];
+                } else {
+                    dp[i][j] = dp[i][j + 1];
+                }
+            }
+        }
+        
+        return dp[0][0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isSubsequence(string s, string t) {
+        int n = s.size(), m = t.size();
+        vector<vector<bool>> dp(n + 1, vector<bool>(m + 1, false));
+        
+        for (int j = 0; j <= m; ++j) {
+            dp[n][j] = true;
+        }
+        
+        for (int i = n - 1; i >= 0; --i) {
+            for (int j = m - 1; j >= 0; --j) {
+                if (s[i] == t[j]) {
+                    dp[i][j] = dp[i + 1][j + 1];
+                } else {
+                    dp[i][j] = dp[i][j + 1];
+                }
+            }
+        }
+        
+        return dp[0][0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string} t
+     * @return {boolean}
+     */
+    isSubsequence(s, t) {
+        const n = s.length, m = t.length;
+        const dp = Array.from({ length: n + 1 }, () => Array(m + 1).fill(false));
+        
+        for (let j = 0; j <= m; j++) {
+            dp[n][j] = true;
+        }
+        
+        for (let i = n - 1; i >= 0; i--) {
+            for (let j = m - 1; j >= 0; j--) {
+                if (s[i] === t[j]) {
+                    dp[i][j] = dp[i + 1][j + 1];
+                } else {
+                    dp[i][j] = dp[i][j + 1];
+                }
+            }
+        }
+        
+        return dp[0][0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n * m)$
+
+> Where $n$ is the length of the string $s$ and $m$ is the length of the string $t$.
+
+---
+
+## 4. Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def isSubsequence(self, s: str, t: str) -> bool:
+        i = j = 0
+        while i < len(s) and j < len(t):
+            if s[i] == t[j]:
+                i += 1
+            j += 1
+        return i == len(s)
+```
+
+```java
+public class Solution {
+    public boolean isSubsequence(String s, String t) {
+        int i = 0, j = 0;
+        while (i < s.length() && j < t.length()) {
+            if (s.charAt(i) == t.charAt(j)) {
+                i++;
+            }
+            j++;
+        }
+        return i == s.length();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isSubsequence(string s, string t) {
+        int i = 0, j = 0;
+        while (i < s.length() && j < t.length()) {
+            if (s[i] == t[j]) {
+                i++;
+            }
+            j++;
+        }
+        return i == s.length();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string} t
+     * @return {boolean}
+     */
+    isSubsequence(s, t) {
+        let i = 0, j = 0;
+        while (i < s.length && j < t.length) {
+            if (s.charAt(i) == t.charAt(j)) {
+                i++;
+            }
+            j++;
+        }
+        return i == s.length;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(1)$
+
+> Where $n$ is the length of the string $s$ and $m$ is the length of the string $t$.
+
+## 5. Follow-Up Solution (Index Jumping)
+
+::tabs-start
+
+```python
+class Solution:
+    def isSubsequence(self, s: str, t: str) -> bool:
+        n, m = len(s), len(t)
+        if m == 0:
+            return n == 0
+        
+        store = [[m + 1] * 26 for _ in range(m)]
+        store[m - 1][ord(t[m - 1]) - ord('a')] = m - 1
+        
+        for i in range(m - 2, -1, -1):
+            store[i] = store[i + 1][:]
+            store[i][ord(t[i]) - ord('a')] = i
+        
+        i, j = 0, 0
+        while i < n and j < m:
+            j = store[j][ord(s[i]) - ord('a')] + 1
+            if j > m:
+                return False
+            i += 1
+        
+        return i == n
+```
+
+```java
+public class Solution {
+    public boolean isSubsequence(String s, String t) {
+        int n = s.length(), m = t.length();
+        if (m == 0) return n == 0;
+
+        int[][] store = new int[m][26];
+        for (int i = 0; i < m; i++) {
+            Arrays.fill(store[i], m + 1);
+        }
+
+        store[m - 1][t.charAt(m - 1) - 'a'] = m - 1;
+
+        for (int i = m - 2; i >= 0; i--) {
+            store[i] = store[i + 1].clone();
+            store[i][t.charAt(i) - 'a'] = i;
+        }
+
+        int i = 0, j = 0;
+        while (i < n && j < m) {
+            j = store[j][s.charAt(i) - 'a'] + 1;
+            if (j > m) return false;
+            i++;
+        }
+        
+        return i == n;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isSubsequence(string s, string t) {
+        int n = s.length(), m = t.length();
+        if (m == 0) return n == 0;
+
+        vector<vector<int>> store(m, vector<int>(26, m + 1));
+        store[m - 1][t[m - 1] - 'a'] = m - 1;
+        
+        for (int i = m - 2; i >= 0; i--) {
+            store[i] = store[i + 1];
+            store[i][t[i] - 'a'] = i;
+        }
+
+        int i = 0, j = 0;
+        while (i < n && j < m) {
+            j = store[j][s[i] - 'a'] + 1;
+            if (j > m) return false;
+            i++;
+        }
+
+        return i == n;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string} t
+     * @return {boolean}
+     */
+    isSubsequence(s, t) {
+        const n = s.length, m = t.length;
+        if (m === 0) return n === 0;
+
+        const store = Array.from({ length: m }, () => Array(26).fill(m + 1));
+        store[m - 1][t.charCodeAt(m - 1) - 'a'.charCodeAt(0)] = m - 1;
+
+        for (let i = m - 2; i >= 0; i--) {
+            store[i] = [...store[i + 1]];
+            store[i][t.charCodeAt(i) - 'a'.charCodeAt(0)] = i;
+        }
+
+        let i = 0, j = 0;
+        while (i < n && j < m) {
+            j = store[j][s.charCodeAt(i) - 'a'.charCodeAt(0)] + 1;
+            if (j > m) return false;
+            i++;
+        }
+
+        return i === n;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(m)$
+
+> Where $n$ is the length of the string $s$ and $m$ is the length of the string $t$.
\ No newline at end of file
diff --git a/articles/island-perimeter.md b/articles/island-perimeter.md
new file mode 100644
index 000000000..bb87939fe
--- /dev/null
+++ b/articles/island-perimeter.md
@@ -0,0 +1,651 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def islandPerimeter(self, grid: List[List[int]]) -> int:
+        rows, cols = len(grid), len(grid[0])
+        visit = set()
+
+        def dfs(i, j):
+            if i < 0 or j < 0 or i >= rows or j >= cols or grid[i][j] == 0:
+                return 1
+            if (i, j) in visit:
+                return 0
+            
+            visit.add((i, j))
+            perim = dfs(i, j + 1) + dfs(i + 1, j) + dfs(i, j - 1) + dfs(i - 1, j)
+            return perim
+        
+        for i in range(rows):
+            for j in range(cols):
+                if grid[i][j]:
+                    return dfs(i, j)
+        return 0
+```
+
+```java
+public class Solution {
+    private int[][] grid;
+    private boolean[][] visited;
+    private int rows, cols;
+
+    public int islandPerimeter(int[][] grid) {
+        this.grid = grid;
+        this.rows = grid.length;
+        this.cols = grid[0].length;
+        this.visited = new boolean[rows][cols];
+
+        for (int i = 0; i < rows; i++) {
+            for (int j = 0; j < cols; j++) {
+                if (grid[i][j] == 1) {
+                    return dfs(i, j);
+                }
+            }
+        }
+        return 0;
+    }
+
+    private int dfs(int i, int j) {
+        if (i < 0 || j < 0 || i >= rows || 
+            j >= cols || grid[i][j] == 0) {
+            return 1;
+        }
+        if (visited[i][j]) {
+            return 0;
+        }
+
+        visited[i][j] = true;
+        return dfs(i, j + 1) + dfs(i + 1, j) + 
+               dfs(i, j - 1) + dfs(i - 1, j);
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<vector<int>> grid;
+    vector<vector<bool>> visited;
+    int rows, cols;
+
+    int dfs(int i, int j) {
+        if (i < 0 || j < 0 || i >= rows || 
+            j >= cols || grid[i][j] == 0) {
+            return 1;
+        }
+        if (visited[i][j]) {
+            return 0;
+        }
+
+        visited[i][j] = true;
+        return dfs(i, j + 1) + dfs(i + 1, j) + 
+               dfs(i, j - 1) + dfs(i - 1, j);
+    }
+
+public:
+    int islandPerimeter(vector<vector<int>>& grid) {
+        this->grid = grid;
+        rows = grid.size();
+        cols = grid[0].size();
+        visited = vector<vector<bool>>(rows, vector<bool>(cols, false));
+
+        for (int i = 0; i < rows; ++i) {
+            for (int j = 0; j < cols; ++j) {
+                if (grid[i][j] == 1) {
+                    return dfs(i, j);
+                }
+            }
+        }
+        return 0;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    islandPerimeter(grid) {
+        const rows = grid.length, cols = grid[0].length;
+        const visited = Array.from({ length: rows }, () => Array(cols).fill(false));
+
+        const dfs = (i, j) => {
+            if (i < 0 || j < 0 || i >= rows || j >= cols || grid[i][j] === 0) {
+                return 1;
+            }
+            if (visited[i][j]) {
+                return 0;
+            }
+
+            visited[i][j] = true;
+            return dfs(i, j + 1) + dfs(i + 1, j) + 
+                   dfs(i, j - 1) + dfs(i - 1, j);
+        };
+
+        for (let i = 0; i < rows; i++) {
+            for (let j = 0; j < cols; j++) {
+                if (grid[i][j] === 1) {
+                    return dfs(i, j);
+                }
+            }
+        }
+        return 0;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    private int rows, cols;
+    private HashSet<(int, int)> visit;
+
+    public int IslandPerimeter(int[][] grid) {
+        rows = grid.Length;
+        cols = grid[0].Length;
+        visit = new HashSet<(int, int)>();
+
+        int Dfs(int i, int j) {
+            if (i < 0 || j < 0 || i >= rows || j >= cols || grid[i][j] == 0) {
+                return 1;
+            }
+            if (visit.Contains((i, j))) {
+                return 0;
+            }
+
+            visit.Add((i, j));
+            int perim = Dfs(i, j + 1) + Dfs(i + 1, j) + Dfs(i, j - 1) + Dfs(i - 1, j);
+            return perim;
+        }
+
+        for (int i = 0; i < rows; i++) {
+            for (int j = 0; j < cols; j++) {
+                if (grid[i][j] == 1) {
+                    return Dfs(i, j);
+                }
+            }
+        }
+
+        return 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns in the grid.
+
+---
+
+## 2. Breadth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def islandPerimeter(self, grid: List[List[int]]) -> int:
+        rows, cols = len(grid), len(grid[0])
+        visited = set()
+        directions = [(0, 1), (1, 0), (0, -1), (-1, 0)]
+        
+        def bfs(r, c):
+            queue = deque([(r, c)])
+            visited.add((r, c))
+            perimeter = 0
+            
+            while queue:
+                x, y = queue.popleft()
+                for dx, dy in directions:
+                    nx, ny = x + dx, y + dy
+                    if (nx < 0 or ny < 0 or nx >= rows or 
+                        ny >= cols or grid[nx][ny] == 0
+                    ):
+                        perimeter += 1
+                    elif (nx, ny) not in visited:
+                        visited.add((nx, ny))
+                        queue.append((nx, ny))
+            return perimeter
+        
+        for i in range(rows):
+            for j in range(cols):
+                if grid[i][j] == 1:
+                    return bfs(i, j)
+        return 0
+```
+
+```java
+public class Solution {
+    public int islandPerimeter(int[][] grid) {
+        int rows = grid.length, cols = grid[0].length;
+        boolean[][] visited = new boolean[rows][cols];
+        int[][] directions = {{0, 1}, {1, 0}, {0, -1}, {-1, 0}};
+        
+        for (int i = 0; i < rows; i++) {
+            for (int j = 0; j < cols; j++) {
+                if (grid[i][j] == 1) {
+                    Queue<int[]> queue = new LinkedList<>();
+                    queue.offer(new int[]{i, j});
+                    visited[i][j] = true;
+                    int perimeter = 0;
+                    
+                    while (!queue.isEmpty()) {
+                        int[] cell = queue.poll();
+                        int x = cell[0], y = cell[1];
+                        
+                        for (int[] dir : directions) {
+                            int nx = x + dir[0], ny = y + dir[1];
+                            if (nx < 0 || ny < 0 || nx >= rows || 
+                                ny >= cols || grid[nx][ny] == 0) {
+                                perimeter++;
+                            } else if (!visited[nx][ny]) {
+                                visited[nx][ny] = true;
+                                queue.offer(new int[]{nx, ny});
+                            }
+                        }
+                    }
+                    return perimeter;
+                }
+            }
+        }
+        return 0;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int islandPerimeter(vector<vector<int>>& grid) {
+        int rows = grid.size(), cols = grid[0].size();
+        vector<vector<bool>> visited(rows, vector<bool>(cols, false));
+        int directions[4][2] = {{0, 1}, {1, 0}, {0, -1}, {-1, 0}};
+
+        for (int i = 0; i < rows; ++i) {
+            for (int j = 0; j < cols; ++j) {
+                if (grid[i][j] == 1) {
+                    queue<pair<int, int>> q;
+                    q.push({i, j});
+                    visited[i][j] = true;
+                    int perimeter = 0;
+
+                    while (!q.empty()) {
+                        auto [x, y] = q.front();
+                        q.pop();
+
+                        for (auto& dir : directions) {
+                            int nx = x + dir[0], ny = y + dir[1];
+                            if (nx < 0 || ny < 0 || nx >= rows || 
+                                ny >= cols || grid[nx][ny] == 0) {
+                                perimeter++;
+                            } else if (!visited[nx][ny]) {
+                                visited[nx][ny] = true;
+                                q.push({nx, ny});
+                            }
+                        }
+                    }
+                    return perimeter;
+                }
+            }
+        }
+        return 0;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    islandPerimeter(grid) {
+        const rows = grid.length, cols = grid[0].length;
+        const visited = Array.from({ length: rows }, () => Array(cols).fill(false));
+        const directions = [[0, 1], [1, 0], [0, -1], [-1, 0]];
+        
+        const bfs = (r, c) => {
+            const queue = new Queue([[r, c]]);
+            visited[r][c] = true;
+            let perimeter = 0;
+            while (!queue.isEmpty()) {
+                const [x, y] = queue.pop();
+
+                for (const [dx, dy] of directions) {
+                    const nx = x + dx, ny = y + dy;
+
+                    if (nx < 0 || ny < 0 || nx >= rows || 
+                        ny >= cols || grid[nx][ny] === 0) {
+                        perimeter++;
+                    } else if (!visited[nx][ny]) {
+                        visited[nx][ny] = true;
+                        queue.push([nx, ny]);
+                    }
+                }
+            }
+            return perimeter;
+        };
+
+        for (let i = 0; i < rows; i++) {
+            for (let j = 0; j < cols; j++) {
+                if (grid[i][j] === 1) {
+                    return bfs(i, j);
+                }
+            }
+        }
+        return 0;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int IslandPerimeter(int[][] grid) {
+        int rows = grid.Length;
+        int cols = grid[0].Length;
+        var visited = new HashSet<(int, int)>();
+        int[][] directions = new int[][] {
+            new int[] { 0, 1 },
+            new int[] { 1, 0 },
+            new int[] { 0, -1 },
+            new int[] { -1, 0 }
+        };
+
+        int Bfs(int r, int c) {
+            var queue = new Queue<(int, int)>();
+            queue.Enqueue((r, c));
+            visited.Add((r, c));
+            int perimeter = 0;
+
+            while (queue.Count > 0) {
+                var (x, y) = queue.Dequeue();
+                foreach (var dir in directions) {
+                    int nx = x + dir[0];
+                    int ny = y + dir[1];
+
+                    if (nx < 0 || ny < 0 || nx >= rows || ny >= cols || grid[nx][ny] == 0) {
+                        perimeter++;
+                    } else if (!visited.Contains((nx, ny))) {
+                        visited.Add((nx, ny));
+                        queue.Enqueue((nx, ny));
+                    }
+                }
+            }
+
+            return perimeter;
+        }
+
+        for (int i = 0; i < rows; i++) {
+            for (int j = 0; j < cols; j++) {
+                if (grid[i][j] == 1) {
+                    return Bfs(i, j);
+                }
+            }
+        }
+
+        return 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns in the grid.
+
+---
+
+## 3. Iteration - I
+
+::tabs-start
+
+```python
+class Solution:
+    def islandPerimeter(self, grid: List[List[int]]) -> int:
+        m, n, res = len(grid), len(grid[0]), 0
+        for i in range(m):
+            for j in range(n):
+                if grid[i][j] == 1:
+                    res += (i + 1 >= m or grid[i + 1][j] == 0)
+                    res += (j + 1 >= n or grid[i][j + 1] == 0)
+                    res += (i - 1 < 0 or grid[i - 1][j] == 0)
+                    res += (j - 1 < 0 or grid[i][j - 1] == 0)
+        return res
+```
+
+```java
+public class Solution {
+    public int islandPerimeter(int[][] grid) {
+        int m = grid.length, n = grid[0].length, res = 0;
+        for (int i = 0; i < m; i++) {
+            for (int j = 0; j < n; j++) {
+                if (grid[i][j] == 1) {
+                    res += (i + 1 >= m || grid[i + 1][j] == 0) ? 1 : 0;
+                    res += (j + 1 >= n || grid[i][j + 1] == 0) ? 1 : 0;
+                    res += (i - 1 < 0 || grid[i - 1][j] == 0) ? 1 : 0;
+                    res += (j - 1 < 0 || grid[i][j - 1] == 0) ? 1 : 0;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int islandPerimeter(vector<vector<int>>& grid) {
+        int m = grid.size(), n = grid[0].size(), res = 0;
+        for (int i = 0; i < m; i++) {
+            for (int j = 0; j < n; j++) {
+                if (grid[i][j] == 1) {
+                    res += (i + 1 >= m || grid[i + 1][j] == 0) ? 1 : 0;
+                    res += (j + 1 >= n || grid[i][j + 1] == 0) ? 1 : 0;
+                    res += (i - 1 < 0 || grid[i - 1][j] == 0) ? 1 : 0;
+                    res += (j - 1 < 0 || grid[i][j - 1] == 0) ? 1 : 0;
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    islandPerimeter(grid) {
+        const m = grid.length, n = grid[0].length;
+        let res = 0;
+        for (let i = 0; i < m; i++) {
+            for (let j = 0; j < n; j++) {
+                if (grid[i][j] === 1) {
+                    res += (i + 1 >= m || grid[i + 1][j] === 0) ? 1 : 0;
+                    res += (j + 1 >= n || grid[i][j + 1] === 0) ? 1 : 0;
+                    res += (i - 1 < 0 || grid[i - 1][j] === 0) ? 1 : 0;
+                    res += (j - 1 < 0 || grid[i][j - 1] === 0) ? 1 : 0;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int IslandPerimeter(int[][] grid) {
+        int m = grid.Length;
+        int n = grid[0].Length;
+        int res = 0;
+
+        for (int i = 0; i < m; i++) {
+            for (int j = 0; j < n; j++) {
+                if (grid[i][j] == 1) {
+                    if (i + 1 >= m || grid[i + 1][j] == 0) res++;
+                    if (j + 1 >= n || grid[i][j + 1] == 0) res++;
+                    if (i - 1 < 0 || grid[i - 1][j] == 0) res++;
+                    if (j - 1 < 0 || grid[i][j - 1] == 0) res++;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(1)$ extra space.
+
+> Where $m$ is the number of rows and $n$ is the number of columns in the grid.
+
+---
+
+## 4. Iteration - II
+
+::tabs-start
+
+```python
+class Solution:
+    def islandPerimeter(self, grid: List[List[int]]) -> int:
+        m, n = len(grid), len(grid[0])
+        res = 0
+        for r in range(m):
+            for c in range(n):
+                if grid[r][c] == 1:
+                    res += 4
+                    if r and grid[r - 1][c]:
+                        res -= 2
+                    if c and grid[r][c - 1] == 1:
+                        res -= 2
+        return res
+```
+
+```java
+public class Solution {
+    public int islandPerimeter(int[][] grid) {
+        int m = grid.length, n = grid[0].length;
+        int res = 0;;
+        for (int r = 0; r < m; r++) {
+            for (int c = 0; c < n; c++) {
+                if (grid[r][c] == 1) {
+                    res += 4;
+                    if (r > 0 && grid[r - 1][c] == 1) {
+                        res -= 2;
+                    }
+                    if (c > 0 && grid[r][c - 1] == 1) {
+                        res -= 2;
+                    }
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int islandPerimeter(vector<vector<int>>& grid) {
+        int m = grid.size(), n = grid[0].size();
+        int res = 0;
+        for (int r = 0; r < m; r++) {
+            for (int c = 0; c < n; c++) {
+                if (grid[r][c]) {
+                    res += 4;
+                    if (r && grid[r - 1][c]) {
+                        res -= 2;
+                    }
+                    if (c && grid[r][c - 1]) {
+                        res -= 2;
+                    }
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    islandPerimeter(grid) {
+        const m = grid.length, n = grid[0].length;
+        let res = 0;
+        for (let r = 0; r < m; r++) {
+            for (let c = 0; c < n; c++) {
+                if (grid[r][c] == 1) {
+                    res += 4;
+                    if (r > 0 && grid[r - 1][c] == 1) {
+                        res -= 2;
+                    }
+                    if (c > 0 && grid[r][c - 1] == 1) {
+                        res -= 2;
+                    }
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int IslandPerimeter(int[][] grid) {
+        int m = grid.Length;
+        int n = grid[0].Length;
+        int res = 0;
+
+        for (int r = 0; r < m; r++) {
+            for (int c = 0; c < n; c++) {
+                if (grid[r][c] == 1) {
+                    res += 4;
+                    if (r > 0 && grid[r - 1][c] == 1) {
+                        res -= 2;
+                    }
+                    if (c > 0 && grid[r][c - 1] == 1) {
+                        res -= 2;
+                    }
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(1)$ extra space.
+
+> Where $m$ is the number of rows and $n$ is the number of columns in the grid.
\ No newline at end of file
diff --git a/articles/islands-and-treasure.md b/articles/islands-and-treasure.md
index 69eae6e57..86e92192f 100644
--- a/articles/islands-and-treasure.md
+++ b/articles/islands-and-treasure.md
@@ -208,6 +208,137 @@ public class Solution {
 }
 ```
 
+```go
+func islandsAndTreasure(grid [][]int) {
+    rows, cols := len(grid), len(grid[0])
+    directions := [][]int{{1, 0}, {-1, 0}, {0, 1}, {0, -1}}
+    INF := 2147483647
+    visit := make([][]bool, rows)
+    for i := range visit {
+        visit[i] = make([]bool, cols)
+    }
+
+    var dfs func(r, c int) int
+    dfs = func(r, c int) int {
+        if r < 0 || c < 0 || r >= rows || c >= cols || 
+           grid[r][c] == -1 || visit[r][c] {
+            return INF
+        }
+        if grid[r][c] == 0 {
+            return 0
+        }
+
+        visit[r][c] = true
+        res := INF
+        for _, d := range directions {
+            dx, dy := d[0], d[1]
+            res = min(res, 1+dfs(r+dx, c+dy))
+        }
+        visit[r][c] = false
+        return res
+    }
+
+    for r := 0; r < rows; r++ {
+        for c := 0; c < cols; c++ {
+            if grid[r][c] == INF {
+                grid[r][c] = dfs(r, c)
+            }
+        }
+    }
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    private val directions = arrayOf(
+        intArrayOf(1, 0), intArrayOf(-1, 0),
+        intArrayOf(0, 1), intArrayOf(0, -1)
+    )
+    private val INF = 2147483647
+    private lateinit var visit: Array<BooleanArray>
+    private var rows = 0
+    private var cols = 0
+
+    private fun dfs(grid: Array<IntArray>, r: Int, c: Int): Int {
+        if (r < 0 || c < 0 || r >= rows || c >= cols || 
+            grid[r][c] == -1 || visit[r][c]) {
+            return INF
+        }
+        if (grid[r][c] == 0) {
+            return 0
+        }
+        visit[r][c] = true
+        var res = INF
+        for (dir in directions) {
+            val cur = dfs(grid, r + dir[0], c + dir[1])
+            if (cur != INF) {
+                res = minOf(res, 1 + cur)
+            }
+        }
+        visit[r][c] = false
+        return res
+    }
+
+    fun islandsAndTreasure(grid: Array<IntArray>): Unit {
+        rows = grid.size
+        cols = grid[0].size
+        visit = Array(rows) { BooleanArray(cols) }
+
+        for (r in 0 until rows) {
+            for (c in 0 until cols) {
+                if (grid[r][c] == INF) {
+                    grid[r][c] = dfs(grid, r, c)
+                }
+            }
+        }
+    }
+}
+```
+
+```swift
+class Solution {
+    func islandsAndTreasure(_ grid: inout [[Int]]) {
+        let ROWS = grid.count
+        let COLS = grid[0].count
+        let INF = 2147483647
+        let directions = [(1, 0), (-1, 0), (0, 1), (0, -1)]
+        var visit = Array(repeating: Array(repeating: false, count: COLS), count: ROWS)
+        
+        func dfs(_ r: Int, _ c: Int) -> Int {
+            if r < 0 || c < 0 || r >= ROWS || c >= COLS || grid[r][c] == -1 || visit[r][c] {
+                return INF
+            }
+            if grid[r][c] == 0 {
+                return 0
+            }
+            
+            visit[r][c] = true
+            var res = INF
+            for (dx, dy) in directions {
+                res = min(res, 1 + dfs(r + dx, c + dy))
+            }
+            visit[r][c] = false
+            return res
+        }
+        
+        for r in 0..<ROWS {
+            for c in 0..<COLS {
+                if grid[r][c] == INF {
+                    grid[r][c] = dfs(r, c)
+                }
+            }
+        }
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -458,6 +589,151 @@ public class Solution {
 }
 ```
 
+```go
+func islandsAndTreasure(grid [][]int) {
+    rows, cols := len(grid), len(grid[0])
+    directions := [][]int{{1, 0}, {-1, 0}, {0, 1}, {0, -1}}
+    INF := 2147483647
+
+    bfs := func(r, c int) int {
+        q := [][2]int{{r, c}}
+        visit := make([][]bool, rows)
+        for i := range visit {
+            visit[i] = make([]bool, cols)
+        }
+        visit[r][c] = true
+        steps := 0
+
+        for len(q) > 0 {
+            size := len(q)
+            for i := 0; i < size; i++ {
+                current := q[0]
+                q = q[1:]
+                row, col := current[0], current[1]
+                if grid[row][col] == 0 {
+                    return steps
+                }
+                for _, dir := range directions {
+                    nr, nc := row+dir[0], col+dir[1]
+                    if nr >= 0 && nc >= 0 && nr < rows && nc < cols && 
+                       !visit[nr][nc] && grid[nr][nc] != -1 {
+                        visit[nr][nc] = true
+                        q = append(q, [2]int{nr, nc})
+                    }
+                }
+            }
+            steps++
+        }
+        return INF
+    }
+
+    for r := 0; r < rows; r++ {
+        for c := 0; c < cols; c++ {
+            if grid[r][c] == INF {
+                grid[r][c] = bfs(r, c)
+            }
+        }
+    }
+}
+```
+
+```kotlin
+class Solution {
+    private val directions = arrayOf(
+        intArrayOf(1, 0), intArrayOf(-1, 0), 
+        intArrayOf(0, 1), intArrayOf(0, -1)
+    )
+    private val INF = 2147483647
+
+    fun islandsAndTreasure(grid: Array<IntArray>): Unit {
+        val rows = grid.size
+        val cols = grid[0].size
+
+        fun bfs(r: Int, c: Int): Int {
+            val q = ArrayDeque<Pair<Int, Int>>()
+            q.add(Pair(r, c))
+            val visit = Array(rows) { BooleanArray(cols) }
+            visit[r][c] = true
+            var steps = 0
+
+            while (q.isNotEmpty()) {
+                repeat(q.size) {
+                    val (row, col) = q.removeFirst()
+                    if (grid[row][col] == 0) {
+                        return steps
+                    }
+                    for (dir in directions) {
+                        val nr = row + dir[0]
+                        val nc = col + dir[1]
+                        if (nr in 0 until rows && nc in 0 until cols && 
+                            !visit[nr][nc] && grid[nr][nc] != -1) {
+                            visit[nr][nc] = true
+                            q.add(Pair(nr, nc))
+                        }
+                    }
+                }
+                steps++
+            }
+            return INF
+        }
+
+        for (r in 0 until rows) {
+            for (c in 0 until cols) {
+                if (grid[r][c] == INF) {
+                    grid[r][c] = bfs(r, c)
+                }
+            }
+        }
+    }
+}
+```
+
+```swift
+class Solution {
+    func islandsAndTreasure(_ grid: inout [[Int]]) {
+        let ROWS = grid.count
+        let COLS = grid[0].count
+        let directions = [(1, 0), (-1, 0), (0, 1), (0, -1)]
+        let INF = 2147483647
+        
+        func bfs(_ r: Int, _ c: Int) -> Int {
+            var q = Deque<(Int, Int)>()
+            q.append((r, c))
+            var visit = Array(repeating: Array(repeating: false, count: COLS), count: ROWS)
+            visit[r][c] = true
+            var steps = 0
+            while !q.isEmpty {
+                let levelCount = q.count
+                for _ in 0..<levelCount {
+                    let (row, col) = q.removeFirst()
+                    if grid[row][col] == 0 {
+                        return steps
+                    }
+                    for (dr, dc) in directions {
+                        let nr = row + dr, nc = col + dc
+                        if (nr >= 0 && nr < ROWS && nc >= 0 && nc < COLS &&
+                            !visit[nr][nc] && grid[nr][nc] != -1) {
+                            visit[nr][nc] = true
+                            q.append((nr, nc))
+                        }
+                    }
+                }
+                steps += 1
+            }
+            return INF
+        }
+        
+        for r in 0..<ROWS {
+            for c in 0..<COLS {
+                if grid[r][c] == INF {
+                    grid[r][c] = bfs(r, c)
+                }
+            }
+        }
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -671,6 +947,129 @@ public class Solution {
 }
 ```
 
+```go
+func islandsAndTreasure(grid [][]int) {
+    m, n := len(grid), len(grid[0])
+    q := [][2]int{}
+
+    for i := 0; i < m; i++ {
+        for j := 0; j < n; j++ {
+            if grid[i][j] == 0 {
+                q = append(q, [2]int{i, j})
+            }
+        }
+    }
+    if len(q) == 0 {
+        return
+    }
+
+    dirs := [][]int{{-1, 0}, {0, -1}, {1, 0}, {0, 1}}
+
+    for len(q) > 0 {
+        node := q[0]
+        q = q[1:]
+        row, col := node[0], node[1]
+
+        for _, dir := range dirs {
+            r, c := row+dir[0], col+dir[1]
+            if r >= m || c >= n || r < 0 || c < 0 || 
+               grid[r][c] != 2147483647 {
+                continue
+            }
+            q = append(q, [2]int{r, c})
+            grid[r][c] = grid[row][col] + 1
+        }
+    }
+}
+```
+
+```kotlin
+class Solution {
+    fun islandsAndTreasure(grid: Array<IntArray>): Unit {
+        val m = grid.size
+        val n = grid[0].size
+        val q: Queue<Pair<Int, Int>> = LinkedList()
+
+        for (i in 0 until m) {
+            for (j in 0 until n) {
+                if (grid[i][j] == 0) {
+                    q.add(Pair(i, j))
+                }
+            }
+        }
+        if (q.isEmpty()) return
+
+        val dirs = arrayOf(
+            intArrayOf(-1, 0), intArrayOf(0, -1), 
+            intArrayOf(1, 0), intArrayOf(0, 1)
+        )
+
+        while (q.isNotEmpty()) {
+            val (row, col) = q.poll()
+            for (dir in dirs) {
+                val r = row + dir[0]
+                val c = col + dir[1]
+                if (r !in 0 until m || c !in 0 until n || 
+                    grid[r][c] != Int.MAX_VALUE) {
+                    continue
+                }
+                q.add(Pair(r, c))
+                grid[r][c] = grid[row][col] + 1
+            }
+        }
+    }
+}
+```
+
+```swift
+struct Item: Hashable {
+    let r: Int
+    let c: Int
+}
+
+class Solution {
+    func islandsAndTreasure(_ grid: inout [[Int]]) {
+        let ROWS = grid.count
+        let COLS = grid[0].count
+        var visit = Set<Item>()
+        var q = Deque<Item>()
+        
+        func addCell(_ r: Int, _ c: Int) {
+            if r < 0 || c < 0 || r >= ROWS || c >= COLS { return }
+            let item = Item(r: r, c: c)
+            if visit.contains(item) || grid[r][c] == -1 { return }
+            visit.insert(item)
+            q.append(item)
+        }
+        
+        for r in 0..<ROWS {
+            for c in 0..<COLS {
+                if grid[r][c] == 0 {
+                    let item = Item(r: r, c: c)
+                    q.append(item)
+                    visit.insert(item)
+                }
+            }
+        }
+        
+        var dist = 0
+        while !q.isEmpty {
+            let count = q.count
+            for _ in 0..<count {
+                let item = q.removeFirst()
+                let r = item.r, c = item.c
+                grid[r][c] = dist
+                addCell(r + 1, c)
+                addCell(r - 1, c)
+                addCell(r, c + 1)
+                addCell(r, c - 1)
+            }
+            dist += 1
+        }
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/isomorphic-strings.md b/articles/isomorphic-strings.md
new file mode 100644
index 000000000..afbaa6c10
--- /dev/null
+++ b/articles/isomorphic-strings.md
@@ -0,0 +1,201 @@
+## 1. Hash Map (Two Pass)
+
+::tabs-start
+
+```python
+class Solution:
+    def helper(self, s: str, t: str) -> bool:
+        mp = {}
+        for i in range(len(s)):
+            if (s[i] in mp) and (mp[s[i]] != t[i]):
+                return False
+            mp[s[i]] = t[i]
+        return True
+
+    def isIsomorphic(self, s: str, t: str) -> bool:
+        return self.helper(s, t) and self.helper(t, s)
+```
+
+```java
+public class Solution {
+    private boolean helper(String s, String t) {
+        HashMap<Character, Character> map = new HashMap<>();
+        for (int i = 0; i < s.length(); i++) {
+            char sc = s.charAt(i);
+            char tc = t.charAt(i);
+            if (map.containsKey(sc) && map.get(sc) != tc) {
+                return false;
+            }
+            map.put(sc, tc);
+        }
+        return true;
+    }
+
+    public boolean isIsomorphic(String s, String t) {
+        return helper(s, t) && helper(t, s);
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    bool helper(const string& s, const string& t) {
+        unordered_map<char, char> map;
+        for (int i = 0; i < s.length(); i++) {
+            if (map.count(s[i]) && map[s[i]] != t[i]) {
+                return false;
+            }
+            map[s[i]] = t[i];
+        }
+        return true;
+    }
+
+public:
+    bool isIsomorphic(string s, string t) {
+        return helper(s, t) && helper(t, s);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string} t
+     * @return {boolean}
+     */
+    helper(s, t) {
+        const map = new Map();
+        for (let i = 0; i < s.length; i++) {
+            if (map.has(s[i]) && map.get(s[i]) !== t[i]) {
+                return false;
+            }
+            map.set(s[i], t[i]);
+        }
+        return true;
+    }
+
+    /**
+     * @param {string} s
+     * @param {string} t
+     * @return {boolean}
+     */
+    isIsomorphic(s, t) {
+        return this.helper(s, t) && this.helper(t, s);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(m)$
+
+> Where $n$ is the length of the input string and $m$ is the number of unique characters in the strings.
+
+---
+
+## 2. Hash Map (One Pass)
+
+::tabs-start
+
+```python
+class Solution:
+    def isIsomorphic(self, s: str, t: str) -> bool:
+        mapST, mapTS = {}, {}
+
+        for i in range(len(s)):
+            c1, c2 = s[i], t[i]
+            if ((c1 in mapST and mapST[c1] != c2) or
+                (c2 in mapTS and mapTS[c2] != c1)):
+                return False
+            mapST[c1] = c2
+            mapTS[c2] = c1
+            
+        return True
+```
+
+```java
+public class Solution {
+    public boolean isIsomorphic(String s, String t) {
+        HashMap<Character, Character> mapST = new HashMap<>();
+        HashMap<Character, Character> mapTS = new HashMap<>();
+
+        for (int i = 0; i < s.length(); i++) {
+            char c1 = s.charAt(i), c2 = t.charAt(i);
+
+            if ((mapST.containsKey(c1) && mapST.get(c1) != c2) ||
+                (mapTS.containsKey(c2) && mapTS.get(c2) != c1)) {
+                return false;
+            }
+
+            mapST.put(c1, c2);
+            mapTS.put(c2, c1);
+        }
+        
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isIsomorphic(string s, string t) {
+        unordered_map<char, char> mapST, mapTS;
+
+        for (int i = 0; i < s.size(); i++) {
+            char c1 = s[i], c2 = t[i];
+
+            if ((mapST.count(c1) && mapST[c1] != c2) ||
+                (mapTS.count(c2) && mapTS[c2] != c1)) {
+                return false;
+            }
+
+            mapST[c1] = c2;
+            mapTS[c2] = c1;
+        }
+        
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string} t
+     * @return {boolean}
+     */
+    isIsomorphic(s, t) {
+        const mapTS = new Map();
+
+        for (let i = 0; i < s.length; i++) {
+            const c1 = s[i], c2 = t[i];
+
+            if ((mapST.has(c1) && mapST.get(c1) !== c2) ||
+                (mapTS.has(c2) && mapTS.get(c2) !== c1)) {
+                return false;
+            }
+
+            mapST.set(c1, c2);
+            mapTS.set(c2, c1);
+        }
+
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(m)$
+
+> Where $n$ is the length of the input string and $m$ is the number of unique characters in the strings.
\ No newline at end of file
diff --git a/articles/jump-game-ii.md b/articles/jump-game-ii.md
new file mode 100644
index 000000000..db4a1b445
--- /dev/null
+++ b/articles/jump-game-ii.md
@@ -0,0 +1,799 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def jump(self, nums: List[int]) -> int:
+        def dfs(i):
+            if i == len(nums) - 1:
+                return 0
+            if nums[i] == 0:
+                return float('inf')
+
+            end = min(len(nums) - 1, i + nums[i])
+            res = float('inf')
+            for j in range(i + 1, end + 1):
+                res = min(res, 1 + dfs(j))
+            return res
+
+        return dfs(0)
+```
+
+```java
+public class Solution {
+    public int jump(int[] nums) {
+        return dfs(nums, 0);
+    }
+
+    private int dfs(int[] nums, int i) {
+        if (i == nums.length - 1) {
+            return 0;
+        }
+        if (nums[i] == 0) {
+            return 1000000;
+        }
+        int res = 1000000;
+        int end = Math.min(nums.length - 1, i + nums[i]);
+        for (int j = i + 1; j <= end; j++) {
+            res = Math.min(res, 1 + dfs(nums, j));
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int jump(vector<int>& nums) {
+        return dfs(nums, 0);
+    }
+
+private:
+    int dfs(vector<int>& nums, int i) {
+        if (i == nums.size() - 1) {
+            return 0;
+        }
+        if (nums[i] == 0) {
+            return 1000000;
+        }
+
+        int res = 1000000;
+        int end = min((int)nums.size() - 1, i + nums[i]);
+        for (int j = i + 1; j <= end; ++j) {
+            res = min(res, 1 + dfs(nums, j));
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    jump(nums) {
+        const dfs = (i) => {
+            if (i === nums.length - 1) {
+                return 0;
+            }
+            if (nums[i] === 0) return 1000000;
+            let res = 1000000;
+            const end = Math.min(nums.length - 1, i + nums[i]);
+            for (let j = i + 1; j <= end; j++) {
+                res = Math.min(res, 1 + dfs(j));
+            }
+            return res;
+        }
+
+        return dfs(0);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int Jump(int[] nums) {
+        return Dfs(nums, 0);
+    }
+
+    private int Dfs(int[] nums, int i) {
+        if (i == nums.Length - 1) {
+            return 0;
+        }
+        if (nums[i] == 0) return 1000000;
+        int res = 1000000;
+        int end = Math.Min(nums.Length - 1, i + nums[i]);
+        for (int j = i + 1; j <= end; j++) {
+            res = Math.Min(res, 1 + Dfs(nums, j));
+        }
+        return res;
+    }
+}
+```
+
+```go
+func jump(nums []int) int {
+    var dfs func(int) int
+    dfs = func(i int) int {
+        if i == len(nums)-1 {
+            return 0
+        }
+        if nums[i] == 0 {
+            return math.MaxInt32
+        }
+        end := min(len(nums)-1, i+nums[i])
+        res := math.MaxInt32
+        for j := i + 1; j <= end; j++ {
+            res = min(res, 1+dfs(j))
+        }
+        return res
+    }
+    return dfs(0)
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun jump(nums: IntArray): Int {
+        fun dfs(i: Int): Int {
+            if (i == nums.size - 1) {
+                return 0
+            }
+            if (nums[i] == 0) {
+                return 1000000
+            }
+            val end = minOf(nums.size - 1, i + nums[i])
+            var minJumps = 1000000
+            for (j in i + 1..end) {
+                minJumps = minOf(minJumps, 1 + dfs(j))
+            }
+            return minJumps
+        }
+        return dfs(0)
+    }
+}
+```
+
+```swift
+class Solution {
+    func jump(_ nums: [Int]) -> Int {
+        func dfs(_ i: Int) -> Int {
+            if i == nums.count - 1 {
+                return 0
+            }
+            if nums[i] == 0 {
+                return 1000000
+            }
+
+            let end = min(nums.count - 1, i + nums[i])
+            var res = 1000000
+            for j in i + 1..<(end + 1) {
+                res = min(res, 1 + dfs(j))
+            }
+
+            return res
+        }
+        
+        return dfs(0)
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n!)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def jump(self, nums: List[int]) -> int:
+        memo = {}
+
+        def dfs(i):
+            if i in memo:
+                return memo[i]
+            if i == len(nums) - 1:
+                return 0
+            if nums[i] == 0:
+                return 1000000
+            
+            res = 1000000
+            end = min(len(nums), i + nums[i] + 1)
+            for j in range(i + 1, end):
+                res = min(res, 1 + dfs(j))
+            memo[i] = res
+            return res
+
+        return dfs(0)
+```
+
+```java
+public class Solution {
+    public int jump(int[] nums) {
+        Map<Integer, Integer> memo = new HashMap<>();
+        return dfs(nums, 0, memo);
+    }
+
+    private int dfs(int[] nums, int i, Map<Integer, Integer> memo) {
+        if (memo.containsKey(i)) {
+            return memo.get(i);
+        }
+        if (i == nums.length - 1) {
+            return 0;
+        }
+        if (nums[i] == 0) {
+            return 1000000;
+        }
+        
+        int res = 1000000;
+        int end = Math.min(nums.length, i + nums[i] + 1);
+        for (int j = i + 1; j < end; j++) {
+            res = Math.min(res, 1 + dfs(nums, j, memo));
+        }
+        memo.put(i, res);
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int jump(vector<int>& nums) {
+        unordered_map<int, int> memo;
+        return dfs(nums, 0, memo);
+    }
+
+private:
+    int dfs(vector<int>& nums, int i, unordered_map<int, int>& memo) {
+        if (memo.count(i)) {
+            return memo[i];
+        }
+        if (i == nums.size() - 1) {
+            return 0;
+        }
+        if (nums[i] == 0) {
+            return 1000000;
+        }
+        
+        int res = 1000000;
+        int end = min((int)nums.size(), i + nums[i] + 1);
+        for (int j = i + 1; j < end; j++) {
+            res = min(res, 1 + dfs(nums, j, memo));
+        }
+        memo[i] = res;
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    jump(nums) {
+        const memo = new Map();
+        const dfs = (i) => {
+            if (memo.has(i)) {
+                return memo.get(i);
+            }
+            if (i == nums.length - 1) {
+                return 0;
+            }
+            if (nums[i] === 0) {
+                return 1000000;
+            }
+            let res = 1000000;
+            const end = Math.min(nums.length - 1, i + nums[i]);
+            for (let j = i + 1; j <= end; j++) {
+                res = Math.min(res, 1 + dfs(j));
+            }
+            memo.set(i, res);
+            return res;
+        }
+
+        return dfs(0);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int Jump(int[] nums) {
+        var memo = new Dictionary<int, int>();
+        return Dfs(nums, 0, memo);
+    }
+
+    private int Dfs(int[] nums, int i, Dictionary<int, int> memo) {
+        if (memo.ContainsKey(i)) {
+            return memo[i];
+        }
+        if (i == nums.Length - 1) {
+            return 0;
+        }
+        if (nums[i] == 0) {
+            return 1000000;
+        }
+        
+        int res = 1000000;
+        int end = Math.Min(nums.Length, i + nums[i] + 1);
+        for (int j = i + 1; j < end; j++) {
+            res = Math.Min(res, 1 + Dfs(nums, j, memo));
+        }
+        memo[i] = res;
+        return res;
+    }
+}
+```
+
+```go
+func jump(nums []int) int {
+    memo := make(map[int]int)
+
+    var dfs func(int) int
+    dfs = func(i int) int {
+        if val, ok := memo[i]; ok {
+            return val
+        }
+        if i == len(nums)-1 {
+            return 0
+        }
+        if nums[i] == 0 {
+            return 1000000
+        }
+        res := 1000000
+        end := min(len(nums), i+nums[i]+1)
+        for j := i + 1; j < end; j++ {
+            res = min(res, 1+dfs(j))
+        }
+        memo[i] = res
+        return res
+    }
+    return dfs(0)
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun jump(nums: IntArray): Int {
+        val memo = HashMap<Int, Int>()
+
+        fun dfs(i: Int): Int {
+            if (i in memo) {
+                return memo[i]!!
+            }
+            if (i == nums.size - 1) {
+                return 0
+            }
+            if (nums[i] == 0) {
+                return 1000000
+            }
+            var res = 1000000
+            val end = minOf(nums.size, i + nums[i] + 1)
+            for (j in i + 1 until end) {
+                res = minOf(res, 1 + dfs(j))
+            }
+            memo[i] = res
+            return res
+        }
+
+        return dfs(0)
+    }
+}
+```
+
+```swift
+class Solution {
+    var memo: [Int: Int] = [:]
+
+    func jump(_ nums: [Int]) -> Int {
+        return dfs(nums, 0)
+    }
+
+    private func dfs(_ nums: [Int], _ i: Int) -> Int {
+        if let cachedResult = memo[i] {
+            return cachedResult
+        }
+        if i == nums.count - 1 {
+            return 0
+        }
+        if nums[i] == 0 {
+            return 1000000
+        }
+
+        var res = 1000000
+        let end = min(nums.count, i + nums[i] + 1)
+        for j in i + 1..<end {
+            res = min(res, 1 + dfs(nums, j))
+        }
+
+        memo[i] = res
+        return res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def jump(self, nums: List[int]) -> int:
+        n = len(nums)
+        dp = [1000000] * n
+        dp[-1] = 0
+
+        for i in range(n - 2, -1, -1):
+            end = min(n, i + nums[i] + 1)
+            for j in range(i + 1, end):
+                dp[i] = min(dp[i], 1 + dp[j])
+        return dp[0]
+```
+
+```java
+public class Solution {
+    public int jump(int[] nums) {
+        int n = nums.length;
+        int[] dp = new int[n];
+        Arrays.fill(dp, 1000000);
+        dp[n - 1] = 0;
+
+        for (int i = n - 2; i >= 0; i--) {
+            int end = Math.min(nums.length, i + nums[i] + 1);
+            for (int j = i + 1; j < end; j++) {
+                dp[i] = Math.min(dp[i], 1 + dp[j]);
+            }
+        }
+        return dp[0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int jump(vector<int>& nums) {
+        int n = nums.size();
+        vector<int> dp(n, 1000000);
+        dp[n - 1] = 0;
+
+        for (int i = n - 2; i >= 0; i--) {
+            int end = min((int)nums.size(), i + nums[i] + 1);
+            for (int j = i + 1; j < end; j++) {
+                dp[i] = min(dp[i], 1 + dp[j]);
+            }
+        }
+        return dp[0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    jump(nums) {
+        const n = nums.length;
+        const dp = new Array(n).fill(1000000);
+        dp[n - 1] = 0;
+
+        for (let i = n - 2; i >= 0; i--) {
+            const end = Math.min(nums.length, i + nums[i] + 1);
+            for (let j = i + 1; j < end; j++) {
+                dp[i] = Math.min(dp[i], 1 + dp[j]);
+            }
+        }
+        return dp[0];
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int Jump(int[] nums) {
+        int n = nums.Length;
+        int[] dp = new int[n];
+        Array.Fill(dp, 1000000);
+        dp[n - 1] = 0;
+
+        for (int i = n - 2; i >= 0; i--) {
+            int end = Math.Min(nums.Length, i + nums[i] + 1);
+            for (int j = i + 1; j < end; j++) {
+                dp[i] = Math.Min(dp[i], 1 + dp[j]);
+            }
+        }
+        return dp[0];
+    }
+}
+```
+
+```go
+func jump(nums []int) int {
+    n := len(nums)
+    dp := make([]int, n)
+    for i := range dp {
+        dp[i] = 1000000
+    }
+    dp[n-1] = 0
+
+    for i := n - 2; i >= 0; i-- {
+        end := min(n, i+nums[i]+1)
+        for j := i + 1; j < end; j++ {
+            dp[i] = min(dp[i], 1+dp[j])
+        }
+    }
+    return dp[0]
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun jump(nums: IntArray): Int {
+        val n = nums.size
+        val dp = IntArray(n) { 1000000 }
+        dp[n - 1] = 0
+
+        for (i in n - 2 downTo 0) {
+            val end = minOf(n, i + nums[i] + 1)
+            for (j in i + 1 until end) {
+                dp[i] = minOf(dp[i], 1 + dp[j])
+            }
+        }
+        return dp[0]
+    }
+}
+```
+
+```swift
+class Solution {
+    func jump(_ nums: [Int]) -> Int {
+        let n = nums.count
+        var dp = Array(repeating: 1000000, count: n)
+        dp[n - 1] = 0
+
+        for i in stride(from: n - 2, through: 0, by: -1) {
+            let end = min(n, i + nums[i] + 1)
+            for j in i + 1..<end {
+                dp[i] = min(dp[i], 1 + dp[j])
+            }
+        }
+
+        return dp[0]
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Breadth First Search (Greedy)
+
+::tabs-start
+
+```python
+class Solution:
+    def jump(self, nums: List[int]) -> int:
+        res = 0
+        l = r = 0
+
+        while r < len(nums) - 1:
+            farthest = 0
+            for i in range(l, r + 1):
+                farthest = max(farthest, i + nums[i])
+            l = r + 1
+            r = farthest
+            res += 1
+        return res
+```
+
+```java
+public class Solution {
+    public int jump(int[] nums) {
+        int res = 0, l = 0, r = 0;
+
+        while (r < nums.length - 1) {
+            int farthest = 0;
+            for (int i = l; i <= r; i++) {
+                farthest = Math.max(farthest, i + nums[i]);
+            }
+            l = r + 1;
+            r = farthest;
+            res++;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int jump(vector<int>& nums) {
+        int res = 0, l = 0, r = 0;
+
+        while (r < nums.size() - 1) {
+            int farthest = 0;
+            for (int i = l; i <= r; i++) {
+                farthest = max(farthest, i + nums[i]);
+            }
+            l = r + 1;
+            r = farthest;
+            res++;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    jump(nums) {
+        let res = 0, l = 0, r = 0;
+
+        while (r < nums.length - 1) {
+            let farthest = 0;
+            for (let i = l; i <= r; i++) {
+                farthest = Math.max(farthest, i + nums[i]);
+            }
+            l = r + 1;
+            r = farthest;
+            res++;
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int Jump(int[] nums) {
+        int res = 0, l = 0, r = 0;
+
+        while (r < nums.Length - 1) {
+            int farthest = 0;
+            for (int i = l; i <= r; i++) {
+                farthest = Math.Max(farthest, i + nums[i]);
+            }
+            l = r + 1;
+            r = farthest;
+            res++;
+        }
+        return res;
+    }
+}
+```
+
+```go
+func jump(nums []int) int {
+    res := 0
+    l, r := 0, 0
+
+    for r < len(nums)-1 {
+        farthest := 0
+        for i := l; i <= r; i++ {
+            farthest = max(farthest, i+nums[i])
+        }
+        l = r + 1
+        r = farthest
+        res++
+    }
+
+    return res
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun jump(nums: IntArray): Int {
+        var res = 0
+        var l = 0
+        var r = 0
+
+        while (r < nums.size - 1) {
+            var farthest = 0
+            for (i in l..r) {
+                farthest = maxOf(farthest, i + nums[i])
+            }
+            l = r + 1
+            r = farthest
+            res++
+        }
+
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func jump(_ nums: [Int]) -> Int {
+        var res = 0
+        var l = 0
+        var r = 0
+
+        while r < nums.count - 1 {
+            var farthest = 0
+            for i in l...r {
+                farthest = max(farthest, i + nums[i])
+            }
+            l = r + 1
+            r = farthest
+            res += 1
+        }
+
+        return res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/jump-game-vii.md b/articles/jump-game-vii.md
new file mode 100644
index 000000000..d2be241f9
--- /dev/null
+++ b/articles/jump-game-vii.md
@@ -0,0 +1,526 @@
+## 1. Brute Force (Memoization)
+
+::tabs-start
+
+```python
+class Solution:
+    def canReach(self, s: str, minJump: int, maxJump: int) -> bool:
+        n = len(s)
+        dp = [None] * n
+        dp[n - 1] = True
+
+        def dfs(i):
+            if dp[i] is not None:
+                return dp[i]
+
+            dp[i] = False
+            for j in range(i + minJump, min(n, i + maxJump + 1)):
+                if s[j] == '0' and dfs(j):
+                    dp[i] = True
+                    break
+
+            return dp[i]
+
+        if s[-1] == '1':
+            return False
+        return dfs(0)
+```
+
+```java
+public class Solution {
+    private Boolean[] dp;
+    private int n;
+
+    public boolean canReach(String s, int minJump, int maxJump) {
+        this.n = s.length();
+        this.dp = new Boolean[n];
+        dp[n - 1] = true;
+
+        if (s.charAt(n - 1) == '1') {
+            return false;
+        }
+
+        return dfs(0, s, minJump, maxJump);
+    }
+
+    private boolean dfs(int i, String s, int minJump, int maxJump) {
+        if (dp[i] != null) {
+            return dp[i];
+        }
+
+        dp[i] = false;
+        for (int j = i + minJump; j <= Math.min(n - 1, i + maxJump); j++) {
+            if (s.charAt(j) == '0' && dfs(j, s, minJump, maxJump)) {
+                dp[i] = true;
+                break;
+            }
+        }
+        return dp[i];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int n;
+    vector<optional<bool>> dp;
+
+    bool canReach(string s, int minJump, int maxJump) {
+        this->n = s.size();
+        dp.resize(n, nullopt);
+        dp[n - 1] = true;
+
+        if (s[n - 1] == '1') {
+            return false;
+        }
+
+        return dfs(0, s, minJump, maxJump);
+    }
+
+private:
+    bool dfs(int i, string& s, int& minJump, int& maxJump) {
+        if (dp[i].has_value()) {
+            return dp[i].value();
+        }
+
+        dp[i] = false;
+        for (int j = i + minJump; j <= min(n - 1, i + maxJump); ++j) {
+            if (s[j] == '0' && dfs(j, s, minJump, maxJump)) {
+                dp[i] = true;
+                break;
+            }
+        }
+        return dp[i].value();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {number} minJump
+     * @param {number} maxJump
+     * @return {boolean}
+     */
+    canReach(s, minJump, maxJump) {
+        const n = s.length;
+        const dp = new Array(n).fill(null);
+        dp[n - 1] = true;
+
+        const dfs = (i) => {
+            if (dp[i] !== null) {
+                return dp[i];
+            }
+
+            dp[i] = false;
+            for (let j = i + minJump; j <= Math.min(n - 1, i + maxJump); j++) {
+                if (s[j] === '0' && dfs(j)) {
+                    dp[i] = true;
+                    break;
+                }
+            }
+            return dp[i];
+        };
+
+        if (s[n - 1] === '1') {
+            return false;
+        }
+        return dfs(0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the length of the string $s$ and $m$ is the given range of the jump $(maxJump - minJump + 1)$.
+
+---
+
+## 2. Breadth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def canReach(self, s: str, minJump: int, maxJump: int) -> bool:
+        q = deque([0])
+        farthest = 0
+        
+        while q:
+            i = q.popleft()
+            start = max(i + minJump, farthest + 1)
+            for j in range(start, min(i + maxJump + 1, len(s))):
+                if s[j] == "0":
+                    q.append(j)
+                    if j == len(s) - 1:
+                        return True
+            farthest = i + maxJump
+        
+        return False
+```
+
+```java
+public class Solution {
+    public boolean canReach(String s, int minJump, int maxJump) {
+        Queue<Integer> q = new LinkedList<>();
+        q.add(0);
+        int farthest = 0;
+        int n = s.length();
+
+        while (!q.isEmpty()) {
+            int i = q.poll();
+            int start = Math.max(i + minJump, farthest + 1);
+
+            for (int j = start; j < Math.min(i + maxJump + 1, n); j++) {
+                if (s.charAt(j) == '0') {
+                    q.add(j);
+                    if (j == n - 1) {
+                        return true;
+                    }
+                }
+            }
+            farthest = i + maxJump;
+        }
+        
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool canReach(string s, int minJump, int maxJump) {
+        queue<int> q;
+        q.push(0);
+        int farthest = 0;
+        int n = s.size();
+
+        while (!q.empty()) {
+            int i = q.front();
+            q.pop();
+            int start = max(i + minJump, farthest + 1);
+
+            for (int j = start; j < min(i + maxJump + 1, n); ++j) {
+                if (s[j] == '0') {
+                    q.push(j);
+                    if (j == n - 1) {
+                        return true;
+                    }
+                }
+            }
+            farthest = i + maxJump;
+        }
+        
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {number} minJump
+     * @param {number} maxJump
+     * @return {boolean}
+     */
+    canReach(s, minJump, maxJump) {
+        const q = new Queue();
+        q.push(0);
+        let farthest = 0;
+
+        while (!q.isEmpty()) {
+            const i = q.pop();
+            const start = Math.max(i + minJump, farthest + 1);
+
+            for (let j = start; j < Math.min(i + maxJump + 1, s.length); j++) {
+                if (s[j] === '0') {
+                    q.push(j);
+                    if (j === s.length - 1) {
+                        return true;
+                    }
+                }
+            }
+            farthest = i + maxJump;
+        }
+
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Sliding Window)
+
+::tabs-start
+
+```python
+class Solution:
+    def canReach(self, s: str, minJump: int, maxJump: int) -> bool:
+        n = len(s)
+        if s[n - 1] == '1':
+            return False
+        
+        dp = [False] * n
+        dp[0] = True
+        cnt = 0
+        for i in range(1, n):
+            if i >= minJump and dp[i - minJump]:
+                cnt += 1
+            if i > maxJump and dp[i - maxJump - 1]:
+                cnt -= 1
+            if cnt > 0 and s[i] == '0':
+                dp[i] = True
+        
+        return dp[n - 1]
+```
+
+```java
+public class Solution {
+    public boolean canReach(String s, int minJump, int maxJump) {
+        int n = s.length();
+        if (s.charAt(n - 1) == '1') {
+            return false;
+        }
+
+        boolean[] dp = new boolean[n];
+        dp[0] = true;
+        int cnt = 0;
+
+        for (int i = 1; i < n; i++) {
+            if (i >= minJump && dp[i - minJump]) {
+                cnt++;
+            }
+            if (i > maxJump && dp[i - maxJump - 1]) {
+                cnt--;
+            }
+            if (cnt > 0 && s.charAt(i) == '0') {
+                dp[i] = true;
+            }
+        }
+
+        return dp[n - 1];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool canReach(string s, int minJump, int maxJump) {
+        int n = s.size();
+        if (s[n - 1] == '1') {
+            return false;
+        }
+
+        vector<bool> dp(n, false);
+        dp[0] = true;
+        int cnt = 0;
+
+        for (int i = 1; i < n; i++) {
+            if (i >= minJump && dp[i - minJump]) {
+                cnt++;
+            }
+            if (i > maxJump && dp[i - maxJump - 1]) {
+                cnt--;
+            }
+            if (cnt > 0 && s[i] == '0') {
+                dp[i] = true;
+            }
+        }
+
+        return dp[n - 1];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {number} minJump
+     * @param {number} maxJump
+     * @return {boolean}
+     */
+    canReach(s, minJump, maxJump) {
+        const n = s.length;
+        if (s[n - 1] === '1') {
+            return false;
+        }
+
+        const dp = new Array(n).fill(false);
+        dp[0] = true;
+        let cnt = 0;
+
+        for (let i = 1; i < n; i++) {
+            if (i >= minJump && dp[i - minJump]) {
+                cnt++;
+            }
+            if (i > maxJump && dp[i - maxJump - 1]) {
+                cnt--;
+            }
+            if (cnt > 0 && s[i] === '0') {
+                dp[i] = true;
+            }
+        }
+
+        return dp[n - 1];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Dynamic Programming (Two Pointers)
+
+::tabs-start
+
+```python
+class Solution:
+    def canReach(self, s: str, minJump: int, maxJump: int) -> bool:
+        n = len(s)
+        if s[n - 1] == '1':
+            return False
+        
+        dp = [False] * n
+        dp[0] = True
+        j = 0
+        for i in range(n):
+            if dp[i] == False:
+                continue
+
+            j = max(j, i + minJump)
+            while j < min(i + maxJump + 1, n):
+                if s[j] == '0':
+                    dp[j] = True
+                j += 1
+        
+        return dp[n - 1]
+```
+
+```java
+public class Solution {
+    public boolean canReach(String s, int minJump, int maxJump) {
+        int n = s.length();
+        if (s.charAt(n - 1) == '1') {
+            return false;
+        }
+
+        boolean[] dp = new boolean[n];
+        dp[0] = true;
+        int j = 0;
+
+        for (int i = 0; i < n; i++) {
+            if (!dp[i]) {
+                continue;
+            }
+            j = Math.max(j, i + minJump);
+            while (j < Math.min(i + maxJump + 1, n)) {
+                if (s.charAt(j) == '0') {
+                    dp[j] = true;
+                }
+                j++;
+            }
+        }
+
+        return dp[n - 1];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool canReach(string s, int minJump, int maxJump) {
+        int n = s.size();
+        if (s[n - 1] == '1') {
+            return false;
+        }
+
+        vector<bool> dp(n, false);
+        dp[0] = true;
+        int j = 0;
+
+        for (int i = 0; i < n; i++) {
+            if (!dp[i]) {
+                continue;
+            }
+            j = max(j, i + minJump);
+            while (j < min(i + maxJump + 1, n)) {
+                if (s[j] == '0') {
+                    dp[j] = true;
+                }
+                j++;
+            }
+        }
+
+        return dp[n - 1];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {number} minJump
+     * @param {number} maxJump
+     * @return {boolean}
+     */
+    canReach(s, minJump, maxJump) {
+        const n = s.length;
+        if (s[n - 1] === '1') {
+            return false;
+        }
+
+        const dp = new Array(n).fill(false);
+        dp[0] = true;
+        let j = 0;
+
+        for (let i = 0; i < n; i++) {
+            if (!dp[i]) {
+                continue;
+            }
+            j = Math.max(j, i + minJump);
+            while (j < Math.min(i + maxJump + 1, n)) {
+                if (s[j] === '0') {
+                    dp[j] = true;
+                }
+                j++;
+            }
+        }
+
+        return dp[n - 1];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/jump-game.md b/articles/jump-game.md
new file mode 100644
index 000000000..c5048055e
--- /dev/null
+++ b/articles/jump-game.md
@@ -0,0 +1,784 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def canJump(self, nums: List[int]) -> bool:
+        def dfs(i):
+            if i == len(nums) - 1:
+                return True
+            end = min(len(nums) - 1, i + nums[i])
+            for j in range(i + 1, end + 1):
+                if dfs(j):
+                    return True
+            return False
+
+        return dfs(0)
+```
+
+```java
+public class Solution {
+    public boolean canJump(int[] nums) {
+        return dfs(nums, 0);
+    }
+    
+    private boolean dfs(int[] nums, int i) {
+        if (i == nums.length - 1) {
+            return true;
+        }
+        int end = Math.min(nums.length - 1, i + nums[i]);
+        for (int j = i + 1; j <= end; j++) {
+            if (dfs(nums, j)) {
+                return true;
+            }
+        }
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool canJump(vector<int>& nums) {
+        return dfs(nums, 0);
+    }
+
+private:
+    bool dfs(vector<int>& nums, int i) {
+        if (i == nums.size() - 1) {
+            return true;
+        }
+        int end = min((int)nums.size() - 1, i + nums[i]);
+        for (int j = i + 1; j <= end; ++j) {
+            if (dfs(nums, j)) {
+                return true;
+            }
+        }
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {boolean}
+     */
+    canJump(nums) {
+        const dfs = (i) => {
+            if (i === nums.length - 1) {
+                return true;
+            }
+            const end = Math.min(nums.length - 1, i + nums[i]);
+            for (let j = i + 1; j <= end; j++) {
+                if (dfs(j)) {
+                    return true;
+                }
+            }
+            return false;
+        }
+
+        return dfs(0);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool CanJump(int[] nums) {
+        return Dfs(nums, 0);
+    }
+
+    private bool Dfs(int[] nums, int i) {
+        if (i == nums.Length - 1) {
+            return true;
+        }
+        int end = Math.Min(nums.Length - 1, i + nums[i]);
+        for (int j = i + 1; j <= end; j++) {
+            if (Dfs(nums, j)) {
+                return true;
+            }
+        }
+        return false;
+    }
+}
+```
+
+```go
+func canJump(nums []int) bool {
+    var dfs func(i int) bool
+    dfs = func(i int) bool {
+        if i == len(nums)-1 {
+            return true
+        }
+        
+        end := min(len(nums)-1, i+nums[i])
+        for j := i + 1; j <= end; j++ {
+            if dfs(j) {
+                return true
+            }
+        }
+        return false
+    }
+    
+    return dfs(0)
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun canJump(nums: IntArray): Boolean {
+        fun dfs(i: Int): Boolean {
+            if (i == nums.size - 1) {
+                return true
+            }
+            
+            val end = minOf(nums.size - 1, i + nums[i])
+            for (j in (i + 1)..end) {
+                if (dfs(j)) {
+                    return true
+                }
+            }
+            return false
+        }
+        
+        return dfs(0)
+    }
+}
+```
+
+```swift
+class Solution {
+    func canJump(_ nums: [Int]) -> Bool {
+
+        func dfs(_ i: Int) -> Bool {
+            if i == nums.count - 1 {
+                return true
+            }
+
+            let end = min(nums.count - 1, i + nums[i])
+            for j in i + 1..<(end + 1) {
+                if dfs(j) {
+                    return true
+                }
+            }
+            return false
+        }
+
+        return dfs(0)
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n!)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def canJump(self, nums: List[int]) -> bool:
+        memo = {}
+
+        def dfs(i):
+            if i in memo:
+                return memo[i]
+            if i == len(nums) - 1:
+                return True
+            if nums[i] == 0:
+                return False
+            
+            end = min(len(nums), i + nums[i] + 1)
+            for j in range(i + 1, end):
+                if dfs(j):
+                    memo[i] = True
+                    return True
+            memo[i] = False
+            return False
+
+        return dfs(0)
+```
+
+```java
+public class Solution {
+    public boolean canJump(int[] nums) {
+        Map<Integer, Boolean> memo = new HashMap<>();
+        return dfs(nums, 0, memo);
+    }
+
+    private boolean dfs(int[] nums, int i, Map<Integer, Boolean> memo) {
+        if (memo.containsKey(i)) {
+            return memo.get(i);
+        }
+        if (i == nums.length - 1) {
+            return true;
+        }
+        if (nums[i] == 0) {
+            return false;
+        }
+        
+        int end = Math.min(nums.length, i + nums[i] + 1);
+        for (int j = i + 1; j < end; j++) {
+            if (dfs(nums, j, memo)) {
+                memo.put(i, true);
+                return true;
+            }
+        }
+        memo.put(i, false);
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool canJump(vector<int>& nums) {
+        unordered_map<int, bool> memo;
+        return dfs(nums, 0, memo);
+    }
+
+private:
+    bool dfs(vector<int>& nums, int i, unordered_map<int, bool>& memo) {
+        if (memo.count(i)) {
+            return memo[i];
+        }
+        if (i == nums.size() - 1) {
+            return true;
+        }
+        if (nums[i] == 0) {
+            return false;
+        }
+        
+        int end = min((int)nums.size(), i + nums[i] + 1);
+        for (int j = i + 1; j < end; j++) {
+            if (dfs(nums, j, memo)) {
+                memo[i] = true;
+                return true;
+            }
+        }
+        memo[i] = false;
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {boolean}
+     */
+    canJump(nums) {
+        const memo = new Map();
+        const dfs = (i) => {
+            if (memo.has(i)) {
+                return memo.get(i);
+            }
+            if (i == nums.length - 1) {
+                return true;
+            }
+            if (nums[i] === 0) {
+                return false;
+            }
+            const end = Math.min(nums.length - 1, i + nums[i]);
+            for (let j = i + 1; j <= end; j++) {
+                if (dfs(j)) {
+                    memo.set(i, true);
+                    return true;
+                }
+            }
+            memo.set(i, false);
+            return false;
+        }
+
+        return dfs(0);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool CanJump(int[] nums) {
+        var memo = new Dictionary<int, bool>();
+        return Dfs(nums, 0, memo);
+    }
+
+    private bool Dfs(int[] nums, int i, Dictionary<int, bool> memo) {
+        if (memo.ContainsKey(i)) {
+            return memo[i];
+        }
+        if (i >= nums.Length - 1) {
+            return true;
+        }
+        if (nums[i] == 0) {
+            return false;
+        }
+        
+        int end = Math.Min(nums.Length, i + nums[i] + 1);
+        for (int j = i + 1; j < end; j++) {
+            if (Dfs(nums, j, memo)) {
+                memo[i] = true;
+                return true;
+            }
+        }
+        memo[i] = false;
+        return false;
+    }
+}
+```
+
+```go
+func canJump(nums []int) bool {
+    memo := make(map[int]bool)
+    
+    var dfs func(i int) bool
+    dfs = func(i int) bool {
+        if result, exists := memo[i]; exists {
+            return result
+        }
+        
+        if i == len(nums)-1 {
+            return true
+        }
+        if nums[i] == 0 {
+            memo[i] = false
+            return false
+        }
+        
+        end := min(len(nums), i+nums[i]+1)
+        for j := i + 1; j < end; j++ {
+            if dfs(j) {
+                memo[i] = true
+                return true
+            }
+        }
+        
+        memo[i] = false
+        return false
+    }
+    
+    return dfs(0)
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun canJump(nums: IntArray): Boolean {
+        val memo = HashMap<Int, Boolean>()
+        
+        fun dfs(i: Int): Boolean {
+            memo[i]?.let { return it }
+            
+            if (i == nums.size - 1) {
+                return true
+            }
+            if (nums[i] == 0) {
+                memo[i] = false
+                return false
+            }
+            
+            val end = minOf(nums.size, i + nums[i] + 1)
+            for (j in (i + 1) until end) {
+                if (dfs(j)) {
+                    memo[i] = true
+                    return true
+                }
+            }
+            
+            memo[i] = false
+            return false
+        }
+        
+        return dfs(0)
+    }
+}
+```
+
+```swift
+class Solution {
+    func canJump(_ nums: [Int]) -> Bool {
+        var memo: [Int: Bool] = [:]
+
+        func dfs(_ i: Int) -> Bool {
+            if let cachedResult = memo[i] {
+                return cachedResult
+            }
+            if i == nums.count - 1 {
+                return true
+            }
+            if nums[i] == 0 {
+                return false
+            }
+
+            let end = min(nums.count, i + nums[i] + 1)
+            for j in i + 1..<end {
+                if dfs(j) {
+                    memo[i] = true
+                    return true
+                }
+            }
+
+            memo[i] = false
+            return false
+        }
+
+        return dfs(0)
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def canJump(self, nums: List[int]) -> bool:
+        n = len(nums)
+        dp = [False] * n
+        dp[-1] = True
+
+        for i in range(n - 2, -1, -1):
+            end = min(n, i + nums[i] + 1)
+            for j in range(i + 1, end):
+                if dp[j]:
+                    dp[i] = True
+                    break
+        return dp[0]
+```
+
+```java
+public class Solution {
+    public boolean canJump(int[] nums) {
+        int n = nums.length;
+        boolean[] dp = new boolean[n];
+        dp[n - 1] = true;
+
+        for (int i = n - 2; i >= 0; i--) {
+            int end = Math.min(nums.length, i + nums[i] + 1);
+            for (int j = i + 1; j < end; j++) {
+                if (dp[j]) {
+                    dp[i] = true;
+                    break;
+                }
+            }
+        }
+        return dp[0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool canJump(vector<int>& nums) {
+        int n = nums.size();
+        vector<bool> dp(n, false);
+        dp[n - 1] = true;
+
+        for (int i = n - 2; i >= 0; i--) {
+            int end = min((int)nums.size(), i + nums[i] + 1);
+            for (int j = i + 1; j < end; j++) {
+                if (dp[j]) {
+                    dp[i] = true;
+                    break;
+                }
+            }
+        }
+        return dp[0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {boolean}
+     */
+    canJump(nums) {
+        const n = nums.length;
+        const dp = new Array(n).fill(false);
+        dp[n - 1] = true;
+
+        for (let i = n - 2; i >= 0; i--) {
+            const end = Math.min(nums.length, i + nums[i] + 1);
+            for (let j = i + 1; j < end; j++) {
+                if (dp[j]) {
+                    dp[i] = true;
+                    break;
+                }
+            }
+        }
+        return dp[0];
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool CanJump(int[] nums) {
+        int n = nums.Length;
+        bool[] dp = new bool[n];
+        dp[n - 1] = true;
+
+        for (int i = n - 2; i >= 0; i--) {
+            int end = Math.Min(nums.Length, i + nums[i] + 1);
+            for (int j = i + 1; j < end; j++) {
+                if (dp[j]) {
+                    dp[i] = true;
+                    break;
+                }
+            }
+        }
+        return dp[0];
+    }
+}
+```
+
+```go
+func canJump(nums []int) bool {
+    n := len(nums)
+    dp := make([]bool, n)
+    dp[n-1] = true
+    
+    for i := n - 2; i >= 0; i-- {
+        end := min(n, i + nums[i] + 1)
+        for j := i + 1; j < end; j++ {
+            if dp[j] {
+                dp[i] = true
+                break
+            }
+        }
+    }
+    return dp[0]
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun canJump(nums: IntArray): Boolean {
+        val n = nums.size
+        val dp = BooleanArray(n)
+        dp[n - 1] = true
+        
+        for (i in n - 2 downTo 0) {
+            val end = minOf(n, i + nums[i] + 1)
+            for (j in i + 1 until end) {
+                if (dp[j]) {
+                    dp[i] = true
+                    break
+                }
+            }
+        }
+        return dp[0]
+    }
+}
+```
+
+```swift
+class Solution {
+    func canJump(_ nums: [Int]) -> Bool {
+        let n = nums.count
+        var dp = [Bool](repeating: false, count: n)
+        dp[n - 1] = true
+
+        for i in (0..<n - 1).reversed() {
+            let end = min(n, i + nums[i] + 1)
+            for j in (i + 1..<end) {
+                if dp[j] {
+                    dp[i] = true
+                    break
+                }
+            }
+        }
+        return dp[0]
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Greedy
+
+::tabs-start
+
+```python
+class Solution:
+    def canJump(self, nums: List[int]) -> bool:
+        goal = len(nums) - 1
+
+        for i in range(len(nums) - 2, -1, -1):
+            if i + nums[i] >= goal:
+                goal = i
+        return goal == 0
+```
+
+```java
+public class Solution {
+    public boolean canJump(int[] nums) {
+        int goal = nums.length - 1;
+
+        for (int i = nums.length - 2; i >= 0; i--) {
+            if (i + nums[i] >= goal) {
+                goal = i;
+            }
+        }
+
+        return goal == 0;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool canJump(vector<int>& nums) {
+        int goal = nums.size() - 1;
+
+        for (int i = nums.size() - 2; i >= 0; i--) {
+            if (i + nums[i] >= goal) {
+                goal = i;
+            }
+        }
+
+        return goal == 0;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {boolean}
+     */
+    canJump(nums) {
+        let goal = nums.length - 1;
+
+        for (let i = nums.length - 2; i >= 0; i--) {
+            if (i + nums[i] >= goal) {
+                goal = i;
+            }
+        }
+
+        return goal === 0;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool CanJump(int[] nums) {
+        int goal = nums.Length - 1;
+
+        for (int i = nums.Length - 2; i >= 0; i--) {
+            if (i + nums[i] >= goal) {
+                goal = i;
+            }
+        }
+
+        return goal == 0;
+    }
+}
+```
+
+```go
+func canJump(nums []int) bool {
+    goal := len(nums) - 1
+    
+    for i := len(nums) - 2; i >= 0; i-- {
+        if i + nums[i] >= goal {
+            goal = i
+        }
+    }
+    return goal == 0
+}
+```
+
+```kotlin
+class Solution {
+    fun canJump(nums: IntArray): Boolean {
+        var goal = nums.size - 1
+        
+        for (i in nums.size - 2 downTo 0) {
+            if (i + nums[i] >= goal) {
+                goal = i
+            }
+        }
+        return goal == 0
+    }
+}
+```
+
+```swift
+class Solution {
+    func canJump(_ nums: [Int]) -> Bool {
+        var goal = nums.count - 1
+
+        for i in stride(from: nums.count - 2, through: 0, by: -1) {
+            if i + nums[i] >= goal {
+                goal = i
+            }
+        }
+
+        return goal == 0
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/k-closest-points-to-origin.md b/articles/k-closest-points-to-origin.md
index 7cb67b086..7882e7c18 100644
--- a/articles/k-closest-points-to-origin.md
+++ b/articles/k-closest-points-to-origin.md
@@ -56,6 +56,35 @@ public class Solution {
 }
 ```
 
+```go
+func kClosest(points [][]int, k int) [][]int {
+    sort.Slice(points, func(i, j int) bool {
+        return points[i][0]*points[i][0] + points[i][1]*points[i][1] < 
+               points[j][0]*points[j][0] + points[j][1]*points[j][1]
+    })
+    return points[:k]
+}
+```
+
+```kotlin
+class Solution {
+    fun kClosest(points: Array<IntArray>, k: Int): Array<IntArray> {
+        points.sortBy { it[0] * it[0] + it[1] * it[1] }
+        return points.take(k).toTypedArray()
+    }
+}
+```
+
+```swift
+class Solution {
+    func kClosest(_ points: [[Int]], _ k: Int) -> [[Int]] {
+        return points.sorted { ($0[0] * $0[0] + $0[1] * $0[1]) < ($1[0] * $1[0] + $1[1] * $1[1]) }
+                      .prefix(k)
+                      .map { $0 }
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -65,7 +94,7 @@ public class Solution {
 
 ---
 
-## 2. Min Heap
+## 2. Min-Heap
 
 ::tabs-start
 
@@ -179,6 +208,83 @@ public class Solution {
 }
 ```
 
+```go
+func kClosest(points [][]int, k int) [][]int {
+    minHeap := priorityqueue.NewWith(func(a, b interface{}) int {
+        distA := a.([]int)[0]
+        distB := b.([]int)[0]
+        return distA - distB
+    })
+
+    for _, point := range points {
+        x, y := point[0], point[1]
+        dist := x*x + y*y
+        minHeap.Enqueue([]int{dist, x, y})
+    }
+
+    res := [][]int{}
+    for i := 0; i < k; i++ {
+        item, _ := minHeap.Dequeue()
+        point := item.([]int)
+        res = append(res, []int{point[1], point[2]})
+    }
+
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun kClosest(points: Array<IntArray>, k: Int): List<IntArray> {
+        val minHeap = PriorityQueue(compareBy<IntArray> { it[0] * it[0] + it[1] * it[1] })
+
+        for (point in points) {
+            minHeap.add(point)
+        }
+
+        val res = mutableListOf<IntArray>()
+        repeat(k) {
+            res.add(minHeap.poll())
+        }
+
+        return res
+    }
+}
+```
+
+```swift
+struct Item: Comparable {
+    let dist: Int
+    let x: Int
+    let y: Int
+
+    static func < (lhs: Item, rhs: Item) -> Bool {
+        return lhs.dist < rhs.dist
+    }
+}
+
+class Solution {
+    func kClosest(_ points: [[Int]], _ k: Int) -> [[Int]] {
+        var minHeap = Heap<Item>()
+
+        for point in points {
+            let x = point[0], y = point[1]
+            let dist = x * x + y * y
+            minHeap.insert(Item(dist: dist, x: x, y: y))
+        }
+
+        var res = [[Int]]()
+        for _ in 0..<k {
+            if let item = minHeap.popMin() {
+                res.append([item.x, item.y])
+            }
+        }
+
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -315,6 +421,94 @@ public class Solution {
 }
 ```
 
+```go
+func kClosest(points [][]int, k int) [][]int {
+    maxHeap := priorityqueue.NewWith(func(a, b interface{}) int {
+        distA := a.([]int)[2]
+        distB := b.([]int)[2]
+        if distA > distB {
+            return -1
+        } else if distA < distB {
+            return 1
+        }
+        return 0
+    })
+    
+    for _, point := range points {
+        x, y := point[0], point[1]
+        dist := x*x + y*y
+        maxHeap.Enqueue([]int{x, y, dist})
+        if maxHeap.Size() > k {
+            maxHeap.Dequeue()
+        }
+    }
+    
+    result := make([][]int, k)
+    for i := k - 1; i >= 0; i-- {
+        val, _ := maxHeap.Dequeue()
+        point := val.([]int)
+        result[i] = []int{point[0], point[1]}
+    }
+    
+    return result
+}
+```
+
+```kotlin
+class Solution {
+    fun kClosest(points: Array<IntArray>, k: Int): Array<IntArray> {
+        val maxHeap = PriorityQueue<IntArray> { a, b ->
+            (b[0] * b[0] + b[1] * b[1]) - (a[0] * a[0] + a[1] * a[1])
+        }
+
+        for (point in points) {
+            maxHeap.offer(point)
+            if (maxHeap.size > k) {
+                maxHeap.poll()
+            }
+        }
+
+        return Array(k) { maxHeap.poll() }
+    }
+}
+```
+
+```swift
+struct Item: Comparable {
+    let dist: Int
+    let x: Int
+    let y: Int
+
+    static func < (lhs: Item, rhs: Item) -> Bool {
+        return lhs.dist > rhs.dist
+    }
+}
+
+class Solution {
+    func kClosest(_ points: [[Int]], _ k: Int) -> [[Int]] {
+        var maxHeap = Heap<Item>()
+
+        for point in points {
+            let x = point[0], y = point[1]
+            let dist = x * x + y * y
+            maxHeap.insert(Item(dist: dist, x: x, y: y))
+            if maxHeap.count > k {
+                _ = maxHeap.popMin()
+            }
+        }
+
+        var res = [[Int]]()
+        while !maxHeap.isEmpty {
+            if let item = maxHeap.popMin() {
+                res.append([item.x, item.y])
+            }
+        }
+
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -535,6 +729,117 @@ class Solution {
 }
 ```
 
+```go
+func kClosest(points [][]int, k int) [][]int {
+    euclidean := func(x []int) int {
+        return x[0]*x[0] + x[1]*x[1]
+    }
+
+    partition := func(points [][]int, l, r int) int {
+        pivotIdx := r
+        pivotDist := euclidean(points[pivotIdx])
+        i := l
+        for j := l; j < r; j++ {
+            if euclidean(points[j]) <= pivotDist {
+                points[i], points[j] = points[j], points[i]
+                i++
+            }
+        }
+        points[i], points[r] = points[r], points[i]
+        return i
+    }
+
+    L, R := 0, len(points)-1
+    pivot := len(points)
+
+    for pivot != k {
+        pivot = partition(points, L, R)
+        if pivot < k {
+            L = pivot + 1
+        } else {
+            R = pivot - 1
+        }
+    }
+    return points[:k]
+}
+```
+
+```kotlin
+class Solution {
+    fun kClosest(points: Array<IntArray>, k: Int): Array<IntArray> {
+        val euclidean = { x: IntArray -> x[0] * x[0] + x[1] * x[1] }
+
+        fun partition(points: Array<IntArray>, l: Int, r: Int): Int {
+            val pivotIdx = r
+            val pivotDist = euclidean(points[pivotIdx])
+            var i = l
+            for (j in l until r) {
+                if (euclidean(points[j]) <= pivotDist) {
+                    points[i] = points[j].also { points[j] = points[i] }
+                    i++
+                }
+            }
+            points[i] = points[r].also { points[r] = points[i] }
+            return i
+        }
+
+        var L = 0
+        var R = points.size - 1
+        var pivot = points.size
+
+        while (pivot != k) {
+            pivot = partition(points, L, R)
+            if (pivot < k) {
+                L = pivot + 1
+            } else {
+                R = pivot - 1
+            }
+        }
+        return points.copyOfRange(0, k)
+    }
+}
+```
+
+```swift
+class Solution {
+    func kClosest(_ points: [[Int]], _ k: Int) -> [[Int]] {
+        var points = points
+
+        func euclidean(_ point: [Int]) -> Int {
+            return point[0] * point[0] + point[1] * point[1]
+        }
+        
+        func partition(_ l: Int, _ r: Int) -> Int {
+            let pivotIdx = r
+            let pivotDist = euclidean(points[pivotIdx])
+            var i = l
+            for j in l..<r {
+                if euclidean(points[j]) <= pivotDist {
+                    points.swapAt(i, j)
+                    i += 1
+                }
+            }
+            points.swapAt(i, r)
+            return i
+        }
+        
+        var l = 0, r = points.count - 1
+        var pivot = points.count
+        
+        while pivot != k {
+            pivot = partition(l, r)
+            if pivot < k {
+                l = pivot + 1
+            } else {
+                r = pivot - 1
+            }
+        }
+        
+        return Array(points[..<k])
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/k-inverse-pairs-array.md b/articles/k-inverse-pairs-array.md
new file mode 100644
index 000000000..926e484d8
--- /dev/null
+++ b/articles/k-inverse-pairs-array.md
@@ -0,0 +1,599 @@
+## 1. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def kInversePairs(self, n: int, k: int) -> int:
+        MOD = 10**9 + 7
+        cache = {}
+
+        def count(n, k):
+            if n == 0:
+                return 1 if k == 0 else 0
+            if k < 0:
+                return 0
+            if (n, k) in cache:
+                return cache[(n, k)]
+
+            cache[(n, k)] = 0
+            for i in range(n):
+                cache[(n, k)] = (cache[(n, k)] + count(n - 1, k - i)) % MOD
+
+            return cache[(n, k)]
+
+        return count(n, k)
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1_000_000_007;
+    private int[][] dp;
+
+    public int kInversePairs(int n, int k) {
+        dp = new int[n + 1][k + 1];
+        for (int i = 0; i <= n; i++) {
+            for (int j = 0; j <= k; j++) {
+                dp[i][j] = -1;
+            }
+        }
+        return count(n, k);
+    }
+
+    private int count(int n, int k) {
+        if (n == 0) return k == 0 ? 1 : 0;
+        if (k < 0) return 0;
+        if (dp[n][k] != -1) return dp[n][k];
+
+        int res = 0;
+        for (int i = 0; i < n; i++) {
+            res = (res + count(n - 1, k - i)) % MOD;
+        }
+
+        dp[n][k] = res;
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    static const int MOD = 1e9 + 7;
+    vector<vector<int>> dp;
+
+    int count(int n, int k) {
+        if (n == 0) {
+            return k == 0 ? 1 : 0;
+        }
+        if (k < 0) {
+            return 0;
+        }
+        if (dp[n][k] != -1) {
+            return dp[n][k];
+        }
+
+        int res = 0;
+        for (int i = 0; i < n; ++i) {
+            res = (res + count(n - 1, k - i)) % MOD;
+        }
+        dp[n][k] = res;
+        return res;
+    }
+
+public:
+    int kInversePairs(int n, int k) {
+        dp.assign(n + 1, vector<int>(k + 1, -1));
+        return count(n, k);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} k
+     * @return {number}
+     */
+    kInversePairs(n, k) {
+        const MOD = 1e9 + 7;
+        const dp = Array.from({ length: n + 1 }, () => Array(k + 1).fill(-1));
+
+        const count = (n, k) => {
+            if (n === 0) return k === 0 ? 1 : 0;
+            if (k < 0) return 0;
+            if (dp[n][k] !== -1) return dp[n][k];
+
+            let res = 0;
+            for (let i = 0; i < n; i++) {
+                res = (res + count(n - 1, k - i)) % MOD;
+            }
+
+            dp[n][k] = res;
+            return res;
+        };
+
+        return count(n, k);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 * k)$
+* Space complexity: $O(n * k)$
+
+> Where $n$ is the size of the permutation and $k$ is the number of inverse pairs in the permutation.
+
+---
+
+## 2. Dynamic Programming (Top-Down Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def kInversePairs(self, n: int, k: int) -> int:
+        MOD = 10**9 + 7
+        dp = [[-1] * (k + 1) for _ in range(n + 1)]
+
+        def count(n, k):
+            if k == 0:
+                return 1
+            if n == 1:
+                return 0
+            if n * (n - 1) // 2 < k:
+                return 0
+            if n * (n - 1) // 2 == k:
+                return 1
+            if dp[n][k] != -1:
+                return dp[n][k]
+
+            res = count(n, k - 1)
+            if k >= n:
+                res -= count(n - 1, k - n)
+            res = (res + count(n - 1, k)) % MOD
+
+            dp[n][k] = res
+            return res
+
+        return count(n, k)
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1_000_000_007;
+    private int[][] dp;
+
+    public int kInversePairs(int n, int k) {
+        dp = new int[n + 1][k + 1];
+        for (int[] row : dp) {
+            Arrays.fill(row, -1);
+        }
+        return count(n, k);
+    }
+
+    private int count(int n, int k) {
+        if (k == 0) return 1;
+        if (n == 1) return 0;
+        if (n * (n - 1) / 2 < k) return 0;
+        if (n * (n - 1) / 2 == k) return 1;
+        if (dp[n][k] != -1) return dp[n][k];
+
+        long res = count(n, k - 1);
+        if (k >= n) {
+            res -= count(n - 1, k - n);
+        }
+        res = (res + count(n - 1, k)) % MOD;
+
+        dp[n][k] = (int) (res + MOD) % MOD;
+        return dp[n][k];
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    static const int MOD = 1e9 + 7;
+    vector<vector<int>> dp;
+
+    int count(int n, int k) {
+        if (k == 0) return 1;
+        if (n == 1) return 0;
+        if (n * (n - 1) / 2 < k) return 0;
+        if (n * (n - 1) / 2 == k) return 1;
+        if (dp[n][k] != -1) return dp[n][k];
+
+        long long res = count(n, k - 1);
+        if (k >= n) {
+            res -= count(n - 1, k - n);
+        }
+        res = (res + count(n - 1, k) + MOD) % MOD;
+
+        dp[n][k] = int(res);
+        return dp[n][k];
+    }
+
+public:
+    int kInversePairs(int n, int k) {
+        dp.assign(n + 1, vector<int>(k + 1, -1));
+        return count(n, k);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} k
+     * @return {number}
+     */
+    kInversePairs(n, k) {
+        const MOD = 1e9 + 7;
+        const dp = Array.from({ length: n + 1 }, () => Array(k + 1).fill(-1));
+
+        const count = (n, k) => {
+            if (k === 0) return 1;
+            if (n === 1) return 0;
+            if ((n * (n - 1)) / 2 < k) return 0;
+            if ((n * (n - 1)) / 2 === k) return 1;
+            if (dp[n][k] !== -1) return dp[n][k];
+
+            let res = count(n, k - 1);
+            if (k >= n) {
+                res -= count(n - 1, k - n);
+            }
+            res = (res + count(n - 1, k) + MOD) % MOD;
+
+            dp[n][k] = res;
+            return res;
+        };
+
+        return count(n, k);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * k)$
+* Space complexity: $O(n * k)$
+
+> Where $n$ is the size of the permutation and $k$ is the number of inverse pairs in the permutation.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def kInversePairs(self, n: int, k: int) -> int:
+        MOD = 10**9 + 7
+        dp = [[0] * (k + 1) for _ in range(n + 1)]
+        dp[0][0] = 1
+
+        for N in range(1, n + 1):
+            for K in range(k + 1):
+                for pairs in range(N):
+                    if K - pairs >= 0:
+                        dp[N][K] = (dp[N][K] + dp[N - 1][K - pairs]) % MOD
+
+        return dp[n][k]
+```
+
+```java
+public class Solution {
+    public int kInversePairs(int n, int k) {
+        final int MOD = 1000000007;
+        int[][] dp = new int[n + 1][k + 1];
+        dp[0][0] = 1;
+
+        for (int N = 1; N <= n; N++) {
+            for (int K = 0; K <= k; K++) {
+                for (int pairs = 0; pairs < N; pairs++) {
+                    if (K - pairs >= 0) {
+                        dp[N][K] = (dp[N][K] + dp[N - 1][K - pairs]) % MOD;
+                    }
+                }
+            }
+        }
+
+        return dp[n][k];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int kInversePairs(int n, int k) {
+        const int MOD = 1e9 + 7;
+        vector<vector<int>> dp(n + 1, vector<int>(k + 1, 0));
+        dp[0][0] = 1;
+
+        for (int N = 1; N <= n; N++) {
+            for (int K = 0; K <= k; K++) {
+                for (int pairs = 0; pairs < N; pairs++) {
+                    if (K - pairs >= 0) {
+                        dp[N][K] = (dp[N][K] + dp[N - 1][K - pairs]) % MOD;
+                    }
+                }
+            }
+        }
+
+        return dp[n][k];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} k
+     * @return {number}
+     */
+    kInversePairs(n, k) {
+        const MOD = 1e9 + 7;
+        const dp = Array.from({ length: n + 1 }, () => Array(k + 1).fill(0));
+        dp[0][0] = 1;
+
+        for (let N = 1; N <= n; N++) {
+            for (let K = 0; K <= k; K++) {
+                for (let pairs = 0; pairs < N; pairs++) {
+                    if (K - pairs >= 0) {
+                        dp[N][K] = (dp[N][K] + dp[N - 1][K - pairs]) % MOD;
+                    }
+                }
+            }
+        }
+
+        return dp[n][k];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 * k)$
+* Space complexity: $O(n * k)$
+
+> Where $n$ is the size of the permutation and $k$ is the number of inverse pairs in the permutation.
+
+---
+
+## 4. Dynamic Programming (Bottom-Up Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def kInversePairs(self, n: int, k: int) -> int:
+        MOD = 10**9 + 7
+        dp = [[0] * (k + 1) for _ in range(n + 1)]
+        dp[0][0] = 1
+
+        for N in range(1, n + 1):
+            for K in range(k + 1):
+                dp[N][K] = dp[N - 1][K]
+                if K > 0:
+                    dp[N][K] = (dp[N][K] + dp[N][K - 1]) % MOD
+                if K >= N:
+                    dp[N][K] = (dp[N][K] - dp[N - 1][K - N] + MOD) % MOD
+
+        return dp[n][k]
+```
+
+```java
+public class Solution {
+    public int kInversePairs(int n, int k) {
+        final int MOD = 1000000007;
+        int[][] dp = new int[n + 1][k + 1];
+        dp[0][0] = 1;
+
+        for (int N = 1; N <= n; N++) {
+            for (int K = 0; K <= k; K++) {
+                dp[N][K] = dp[N - 1][K];
+                if (K > 0) {
+                    dp[N][K] = (dp[N][K] + dp[N][K - 1]) % MOD;
+                }
+                if (K >= N) {
+                    dp[N][K] = (dp[N][K] - dp[N - 1][K - N] + MOD) % MOD;
+                }
+            }
+        }
+
+        return dp[n][k];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int kInversePairs(int n, int k) {
+        const int MOD = 1e9 + 7;
+        vector<vector<int>> dp(n + 1, vector<int>(k + 1, 0));
+        dp[0][0] = 1;
+
+        for (int N = 1; N <= n; N++) {
+            for (int K = 0; K <= k; K++) {
+                dp[N][K] = dp[N - 1][K];
+                if (K > 0) {
+                    dp[N][K] = (dp[N][K] + dp[N][K - 1]) % MOD;
+                }
+                if (K >= N) {
+                    dp[N][K] = (dp[N][K] - dp[N - 1][K - N] + MOD) % MOD;
+                }
+            }
+        }
+
+        return dp[n][k];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} k
+     * @return {number}
+     */
+    kInversePairs(n, k) {
+        const MOD = 1e9 + 7;
+        const dp = Array.from({ length: n + 1 }, () => Array(k + 1).fill(0));
+        dp[0][0] = 1;
+
+        for (let N = 1; N <= n; N++) {
+            for (let K = 0; K <= k; K++) {
+                dp[N][K] = dp[N - 1][K];
+                if (K > 0) {
+                    dp[N][K] = (dp[N][K] + dp[N][K - 1]) % MOD;
+                }
+                if (K >= N) {
+                    dp[N][K] = (dp[N][K] - dp[N - 1][K - N] + MOD) % MOD;
+                }
+            }
+        }
+
+        return dp[n][k];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * k)$
+* Space complexity: $O(n * k)$
+
+> Where $n$ is the size of the permutation and $k$ is the number of inverse pairs in the permutation.
+
+---
+
+## 5. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def kInversePairs(self, n: int, k: int) -> int:
+        MOD = 10**9 + 7
+        prev = [0] * (k + 1)
+        prev[0] = 1
+
+        for N in range(1, n + 1):
+            cur = [0] * (k + 1)
+            total = 0
+            for K in range(0, k + 1):
+                total = (total + prev[K]) % MOD
+                if K >= N:
+                    total = (total - prev[K - N] + MOD) % MOD
+                cur[K] = total
+            prev = cur
+
+        return prev[k]
+```
+
+```java
+public class Solution {
+    public int kInversePairs(int n, int k) {
+        final int MOD = 1000000007;
+        int[] prev = new int[k + 1];
+        prev[0] = 1;
+
+        for (int N = 1; N <= n; N++) {
+            int[] cur = new int[k + 1];
+            int total = 0;
+            for (int K = 0; K <= k; K++) {
+                total = (total + prev[K]) % MOD;
+                if (K >= N) {
+                    total = (total - prev[K - N] + MOD) % MOD;
+                }
+                cur[K] = total;
+            }
+            prev = cur;
+        }
+
+        return prev[k];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int kInversePairs(int n, int k) {
+        const int MOD = 1e9 + 7;
+        vector<int> prev(k + 1, 0);
+        prev[0] = 1;
+
+        for (int N = 1; N <= n; N++) {
+            vector<int> cur(k + 1, 0);
+            int total = 0;
+            for (int K = 0; K <= k; K++) {
+                total = (total + prev[K]) % MOD;
+                if (K >= N) {
+                    total = (total - prev[K - N] + MOD) % MOD;
+                }
+                cur[K] = total;
+            }
+            prev = cur;
+        }
+
+        return prev[k];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} k
+     * @return {number}
+     */
+    kInversePairs(n, k) {
+        const MOD = 1e9 + 7;
+        let prev = new Array(k + 1).fill(0);
+        prev[0] = 1;
+
+        for (let N = 1; N <= n; N++) {
+            const cur = new Array(k + 1).fill(0);
+            let total = 0;
+            for (let K = 0; K <= k; K++) {
+                total = (total + prev[K]) % MOD;
+                if (K >= N) {
+                    total = (total - prev[K - N] + MOD) % MOD;
+                }
+                cur[K] = total;
+            }
+            prev = cur;
+        }
+
+        return prev[k];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * k)$
+* Space complexity: $O(k)$
+
+> Where $n$ is the size of the permutation and $k$ is the number of inverse pairs in the permutation.
\ No newline at end of file
diff --git a/articles/k-th-symbol-in-grammar.md b/articles/k-th-symbol-in-grammar.md
new file mode 100644
index 000000000..d3f782b4c
--- /dev/null
+++ b/articles/k-th-symbol-in-grammar.md
@@ -0,0 +1,413 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def kthGrammar(self, n: int, k: int) -> int:
+        prev = ['0']
+        for i in range(2, n + 1):
+            cur = []
+            for c in prev:
+                if c == '0':
+                    cur.append('0')
+                    cur.append('1')
+                else:
+                    cur.append('1')
+                    cur.append('0')
+            prev = cur
+        return int(prev[k - 1])
+```
+
+```java
+public class Solution {
+    public int kthGrammar(int n, int k) {
+        List<Character> prev = new ArrayList<>();
+        prev.add('0');
+        for (int i = 2; i <= n; i++) {
+            List<Character> cur = new ArrayList<>();
+            for (char c : prev) {
+                if (c == '0') {
+                    cur.add('0');
+                    cur.add('1');
+                } else {
+                    cur.add('1');
+                    cur.add('0');
+                }
+            }
+            prev = cur;
+        }
+        return prev.get(k - 1) - '0';
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int kthGrammar(int n, int k) {
+        vector<char> prev = {'0'};
+        for (int i = 2; i <= n; i++) {
+            vector<char> cur;
+            for (char c : prev) {
+                if (c == '0') {
+                    cur.push_back('0');
+                    cur.push_back('1');
+                } else {
+                    cur.push_back('1');
+                    cur.push_back('0');
+                }
+            }
+            prev = cur;
+        }
+        return prev[k - 1] - '0';
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} k
+     * @return {number}
+     */
+    kthGrammar(n, k) {
+        let prev = ['0'];
+        for (let i = 2; i <= n; i++) {
+            let cur = [];
+            for (let c of prev) {
+                if (c === '0') {
+                    cur.push('0');
+                    cur.push('1');
+                } else {
+                    cur.push('1');
+                    cur.push('0');
+                }
+            }
+            prev = cur;
+        }
+        return parseInt(prev[k - 1]);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(2 ^ n)$
+
+---
+
+## 2. Binary Tree Traversal (Recursion)
+
+::tabs-start
+
+```python
+class Solution:
+    def kthGrammar(self, n: int, k: int) -> int:
+        def dfs(n, k, root):
+            if n == 1:
+                return root
+            
+            total = 1 << (n - 1)
+            if k > (total // 2):
+                return dfs(n - 1, k - (total // 2), root ^ 1)
+            else:
+                return dfs(n - 1, k, root)
+        
+        return dfs(n, k, 0)
+```
+
+```java
+public class Solution {
+    public int kthGrammar(int n, int k) {
+        return dfs(n, k, 0);
+    }
+    
+    private int dfs(int n, int k, int root) {
+        if (n == 1) {
+            return root;
+        }
+        
+        int total = 1 << (n - 1);
+        if (k > total / 2) {
+            return dfs(n - 1, k - total / 2, root ^ 1);
+        } else {
+            return dfs(n - 1, k, root);
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int kthGrammar(int n, int k) {
+        return dfs(n, k, 0);
+    }
+
+    int dfs(int n, int k, int root){
+        if (n == 1) return root;
+
+        int total = 1 << (n - 1);
+        if (k > total / 2) {
+            return dfs(n - 1, k - total / 2, root ^ 1);
+        } else {
+            return dfs(n - 1, k, root);
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} k
+     * @return {number}
+     */
+    kthGrammar(n, k) {
+        const dfs = (n, k, root) => {
+            if (n === 1) return root;
+
+            const total = 1 << (n - 1);
+            if (k > total / 2) {
+                return dfs(n - 1, k - total / 2, root ^ 1);
+            } else {
+                return dfs(n - 1, k, root);
+            }
+        };
+
+        return dfs(n, k, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 3. Binary Tree Traversal (Iteration)
+
+::tabs-start
+
+```python
+class Solution:
+    def kthGrammar(self, n: int, k: int) -> int:
+        cur = 0
+        left, right = 1, 2 ** (n - 1)
+        
+        for _ in range(n - 1):
+            mid = (left + right) // 2
+            if k <= mid:
+                right = mid
+            else:
+                left = mid + 1
+                cur = 0 if cur else 1
+        
+        return cur
+```
+
+```java
+public class Solution {
+    public int kthGrammar(int n, int k) {
+        int cur = 0;
+        int left = 1, right = 1 << (n - 1);
+        
+        for (int i = 0; i < n - 1; i++) {
+            int mid = (left + right) / 2;
+            if (k <= mid) {
+                right = mid;
+            } else {
+                left = mid + 1;
+                cur = (cur == 0) ? 1 : 0;
+            }
+        }
+        
+        return cur;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int kthGrammar(int n, int k) {
+        int cur = 0;
+        int left = 1, right = 1 << (n - 1);
+        
+        for (int i = 0; i < n - 1; i++) {
+            int mid = (left + right) / 2;
+            if (k <= mid) {
+                right = mid;
+            } else {
+                left = mid + 1;
+                cur = (cur == 0) ? 1 : 0;
+            }
+        }
+        
+        return cur;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} k
+     * @return {number}
+     */
+    kthGrammar(n, k) {
+        let cur = 0;
+        let left = 1, right = 1 << (n - 1);
+        
+        for (let i = 0; i < n - 1; i++) {
+            let mid = Math.floor((left + right) / 2);
+            if (k <= mid) {
+                right = mid;
+            } else {
+                left = mid + 1;
+                cur = cur === 0 ? 1 : 0;
+            }
+        }
+        
+        return cur;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 4. Recursion (Traverse Towards Root)
+
+::tabs-start
+
+```python
+class Solution:
+    def kthGrammar(self, n: int, k: int) -> int:
+        if n == 1:
+            return 0
+        if k & 1:
+            return self.kthGrammar(n - 1, (k + 1) // 2)
+        return self.kthGrammar(n - 1, k // 2) ^ 1
+```
+
+```java
+public class Solution {
+    public int kthGrammar(int n, int k) {
+        if (n == 1) {
+            return 0;
+        }
+        if ((k & 1) == 1) {
+            return kthGrammar(n - 1, (k + 1) / 2);
+        }
+        return kthGrammar(n - 1, k / 2) ^ 1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int kthGrammar(int n, int k) {
+        if (n == 1) {
+            return 0;
+        }
+        if (k & 1) {
+            return kthGrammar(n - 1, (k + 1) / 2);
+        }
+        return kthGrammar(n - 1, k / 2) ^ 1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} k
+     * @return {number}
+     */
+    kthGrammar(n, k) {
+        if (n === 1) {
+            return 0;
+        }
+        if (k % 2 === 1) {
+            return this.kthGrammar(n - 1, Math.floor((k + 1) / 2));
+        }
+        return this.kthGrammar(n - 1, Math.floor(k / 2)) ^ 1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 5. Math
+
+::tabs-start
+
+```python
+class Solution:
+    def kthGrammar(self, n: int, k: int) -> int:
+        return bin(k - 1).count('1') & 1
+```
+
+```java
+public class Solution {
+    public int kthGrammar(int n, int k) {
+        return Integer.bitCount(k - 1) & 1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int kthGrammar(int n, int k) {
+        return __builtin_popcount(k - 1) & 1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} k
+     * @return {number}
+     */
+    kthGrammar(n, k) {
+        return (k - 1).toString(2).split('1').length - 1 & 1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$ or $O(\log n)$ depending on the language.
\ No newline at end of file
diff --git a/articles/knight-dialer.md b/articles/knight-dialer.md
new file mode 100644
index 000000000..9c87f4c13
--- /dev/null
+++ b/articles/knight-dialer.md
@@ -0,0 +1,946 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def knightDialer(self, n: int) -> int:
+        if n == 1:
+            return 10
+
+        mod = 1000000007
+        jumps = [
+            [4, 6], [6, 8], [7, 9], [4, 8], [0, 3, 9],
+            [], [0, 1, 7], [2, 6], [1, 3], [2, 4]
+        ]
+
+        def dfs(n, d):
+            if n == 0:
+                return 1
+
+            res = 0
+            for j in jumps[d]:
+                res = (res + dfs(n - 1, j)) % mod
+            return res
+
+        res = 0
+        for d in range(10):
+            res = (res + dfs(n - 1, d)) % mod
+        return res
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1000000007;
+    private static final int[][] jumps = {
+        {4, 6}, {6, 8}, {7, 9}, {4, 8}, {0, 3, 9},
+        {}, {0, 1, 7}, {2, 6}, {1, 3}, {2, 4}
+    };
+
+    public int knightDialer(int n) {
+        if (n == 1) return 10;
+        int res = 0;
+
+        for (int d = 0; d < 10; d++) {
+            res = (res + dfs(n - 1, d)) % MOD;
+        }
+        return res;
+    }
+
+    private int dfs(int n, int d) {
+        if (n == 0) return 1;
+
+        int res = 0;
+        for (int next : jumps[d]) {
+            res = (res + dfs(n - 1, next)) % MOD;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    static constexpr int MOD = 1000000007;
+    const vector<vector<int>> jumps = {
+        {4, 6}, {6, 8}, {7, 9}, {4, 8}, {0, 3, 9},
+        {}, {0, 1, 7}, {2, 6}, {1, 3}, {2, 4}
+    };
+
+public:
+    int knightDialer(int n) {
+        if (n == 1) return 10;
+        int res = 0;
+
+        for (int d = 0; d < 10; d++) {
+            res = (res + dfs(n - 1, d)) % MOD;
+        }
+        return res;
+    }
+
+private:
+    int dfs(int n, int d) {
+        if (n == 0) return 1;
+
+        int res = 0;
+        for (int next : jumps[d]) {
+            res = (res + dfs(n - 1, next)) % MOD;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    knightDialer(n) {
+        if (n === 1) return 10;
+        const MOD = 1000000007;
+        const jumps = [
+            [4, 6], [6, 8], [7, 9], [4, 8], [0, 3, 9],
+            [], [0, 1, 7], [2, 6], [1, 3], [2, 4]
+        ];
+
+        const dfs = (n, d) => {
+            if (n === 0) return 1;
+
+            let res = 0;
+            for (const next of jumps[d]) {
+                res = (res + dfs(n - 1, next)) % MOD;
+            }
+            return res;
+        };
+
+        let res = 0;
+        for (let d = 0; d < 10; d++) {
+            res = (res + dfs(n - 1, d)) % MOD;
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(3 ^ n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def knightDialer(self, n: int) -> int:
+        if n == 1:
+            return 10
+
+        mod = 1000000007
+        jumps = [
+            [4, 6], [6, 8], [7, 9], [4, 8], [0, 3, 9],
+            [], [0, 1, 7], [2, 6], [1, 3], [2, 4]
+        ]
+
+        dp = [[-1] * (n + 1) for _ in range(10)]
+
+        def dfs(n, d):
+            if n == 0:
+                return 1
+            if dp[d][n] != -1:
+                return dp[d][n]
+            
+            dp[d][n] = 0
+            for j in jumps[d]:
+                dp[d][n] = (dp[d][n] + dfs(n - 1, j)) % mod
+            return dp[d][n]
+
+        res = 0
+        for d in range(10):
+            res = (res + dfs(n - 1, d)) % mod
+        return res
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1000000007;
+    private static final int[][] jumps = {
+        {4, 6}, {6, 8}, {7, 9}, {4, 8}, {0, 3, 9},
+        {}, {0, 1, 7}, {2, 6}, {1, 3}, {2, 4}
+    };
+    private int[][] dp;
+
+    public int knightDialer(int n) {
+        if (n == 1) return 10;
+        dp = new int[10][n + 1];
+        for (int[] row : dp) Arrays.fill(row, -1);
+
+        int res = 0;
+        for (int d = 0; d < 10; d++) {
+            res = (res + dfs(n - 1, d)) % MOD;
+        }
+        return res;
+    }
+
+    private int dfs(int n, int d) {
+        if (n == 0) return 1;
+        if (dp[d][n] != -1) return dp[d][n];
+
+        dp[d][n] = 0;
+        for (int next : jumps[d]) {
+            dp[d][n] = (dp[d][n] + dfs(n - 1, next)) % MOD;
+        }
+        return dp[d][n];
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    static constexpr int MOD = 1000000007;
+    vector<vector<int>> jumps = {
+        {4, 6}, {6, 8}, {7, 9}, {4, 8}, {0, 3, 9},
+        {}, {0, 1, 7}, {2, 6}, {1, 3}, {2, 4}
+    };
+    vector<vector<int>> dp;
+
+public:
+    int knightDialer(int n) {
+        if (n == 1) return 10;
+        dp.assign(10, vector<int>(n + 1, -1));
+
+        int res = 0;
+        for (int d = 0; d < 10; d++) {
+            res = (res + dfs(n - 1, d)) % MOD;
+        }
+        return res;
+    }
+
+private:
+    int dfs(int n, int d) {
+        if (n == 0) return 1;
+        if (dp[d][n] != -1) return dp[d][n];
+
+        dp[d][n] = 0;
+        for (int next : jumps[d]) {
+            dp[d][n] = (dp[d][n] + dfs(n - 1, next)) % MOD;
+        }
+        return dp[d][n];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    knightDialer(n) {
+        if (n === 1) return 10;
+        const MOD = 1000000007;
+        const jumps = [
+            [4, 6], [6, 8], [7, 9], [4, 8], [0, 3, 9],
+            [], [0, 1, 7], [2, 6], [1, 3], [2, 4]
+        ];
+
+        const dp = Array.from({ length: 10 }, () => Array(n + 1).fill(-1));
+
+        const dfs = (n, d) => {
+            if (n === 0) return 1;
+            if (dp[d][n] !== -1) return dp[d][n];
+
+            dp[d][n] = 0;
+            for (const next of jumps[d]) {
+                dp[d][n] = (dp[d][n] + dfs(n - 1, next)) % MOD;
+            }
+            return dp[d][n];
+        };
+
+        let res = 0;
+        for (let d = 0; d < 10; d++) {
+            res = (res + dfs(n - 1, d)) % MOD;
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def knightDialer(self, n: int) -> int:
+        if n == 1:
+            return 10
+
+        mod = 1000000007
+        jumps = [
+            [4, 6], [6, 8], [7, 9], [4, 8], [0, 3, 9],
+            [], [0, 1, 7], [2, 6], [1, 3], [2, 4]
+        ]
+
+        dp = [[0] * (n + 1) for _ in range(10)]
+
+        for d in range(10):
+            dp[d][0] = 1
+
+        for step in range(1, n):
+            for d in range(10):
+                dp[d][step] = sum(dp[j][step - 1] for j in jumps[d]) % mod
+
+        return sum(dp[d][n - 1] for d in range(10)) % mod
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1000000007;
+    private static final int[][] jumps = {
+        {4, 6}, {6, 8}, {7, 9}, {4, 8}, {0, 3, 9},
+        {}, {0, 1, 7}, {2, 6}, {1, 3}, {2, 4}
+    };
+
+    public int knightDialer(int n) {
+        if (n == 1) return 10;
+        
+        int[][] dp = new int[10][n + 1];
+        for (int d = 0; d < 10; d++) {
+            dp[d][0] = 1;
+        }
+
+        for (int step = 1; step < n; step++) {
+            for (int d = 0; d < 10; d++) {
+                for (int j : jumps[d]) {
+                    dp[d][step] = (dp[d][step] + dp[j][step - 1]) % MOD;
+                }
+            }
+        }
+
+        int res = 0;
+        for (int d = 0; d < 10; d++) {
+            res = (res + dp[d][n - 1]) % MOD;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    static constexpr int MOD = 1000000007;
+    vector<vector<int>> jumps = {
+        {4, 6}, {6, 8}, {7, 9}, {4, 8}, {0, 3, 9},
+        {}, {0, 1, 7}, {2, 6}, {1, 3}, {2, 4}
+    };
+
+public:
+    int knightDialer(int n) {
+        if (n == 1) return 10;
+        
+        vector<vector<int>> dp(10, vector<int>(n + 1, 0));
+        for (int d = 0; d < 10; d++) {
+            dp[d][0] = 1;
+        }
+
+        for (int step = 1; step < n; step++) {
+            for (int d = 0; d < 10; d++) {
+                for (int j : jumps[d]) {
+                    dp[d][step] = (dp[d][step] + dp[j][step - 1]) % MOD;
+                }
+            }
+        }
+
+        int res = 0;
+        for (int d = 0; d < 10; d++) {
+            res = (res + dp[d][n - 1]) % MOD;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    knightDialer(n) {
+        if (n === 1) return 10;
+        const MOD = 1000000007;
+        const jumps = [
+            [4, 6], [6, 8], [7, 9], [4, 8], [0, 3, 9],
+            [], [0, 1, 7], [2, 6], [1, 3], [2, 4]
+        ];
+
+        const dp = Array.from({ length: 10 }, () => Array(n + 1).fill(0));
+        for (let d = 0; d < 10; d++) {
+            dp[d][0] = 1;
+        }
+
+        for (let step = 1; step < n; step++) {
+            for (let d = 0; d < 10; d++) {
+                for (const j of jumps[d]) {
+                    dp[d][step] = (dp[d][step] + dp[j][step - 1]) % MOD;
+                }
+            }
+        }
+
+        let res = 0;
+        for (let d = 0; d < 10; d++) {
+            res = (res + dp[d][n - 1]) % MOD;
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def knightDialer(self, n: int) -> int:
+        if n == 1:
+            return 10
+
+        mod = 1000000007
+        jumps = [
+            [4, 6], [6, 8], [7, 9], [4, 8], [0, 3, 9],
+            [], [0, 1, 7], [2, 6], [1, 3], [2, 4]
+        ]
+
+        dp = [1] * 10
+        for step in range(n - 1):
+            next_dp = [0] * 10
+            for d in range(10):
+                for j in jumps[d]:
+                    next_dp[j] = (next_dp[j] + dp[d]) % mod
+            dp = next_dp
+
+        res = 0
+        for d in dp:
+            res = (res + d) % mod
+        return res
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1000000007;
+    private static final int[][] jumps = {
+        {4, 6}, {6, 8}, {7, 9}, {4, 8}, {0, 3, 9},
+        {}, {0, 1, 7}, {2, 6}, {1, 3}, {2, 4}
+    };
+
+    public int knightDialer(int n) {
+        if (n == 1) return 10;
+
+        int[] dp = new int[10];
+        Arrays.fill(dp, 1);
+
+        for (int step = 0; step < n - 1; step++) {
+            int[] nextDp = new int[10];
+            for (int d = 0; d < 10; d++) {
+                for (int j : jumps[d]) {
+                    nextDp[j] = (nextDp[j] + dp[d]) % MOD;
+                }
+            }
+            dp = nextDp;
+        }
+
+        int res = 0;
+        for (int d : dp) {
+            res = (res + d) % MOD;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    static constexpr int MOD = 1000000007;
+    vector<vector<int>> jumps = {
+        {4, 6}, {6, 8}, {7, 9}, {4, 8}, {0, 3, 9},
+        {}, {0, 1, 7}, {2, 6}, {1, 3}, {2, 4}
+    };
+
+public:
+    int knightDialer(int n) {
+        if (n == 1) return 10;
+        
+        vector<int> dp(10, 1);
+
+        for (int step = 0; step < n - 1; step++) {
+            vector<int> nextDp(10, 0);
+            for (int d = 0; d < 10; d++) {
+                for (int j : jumps[d]) {
+                    nextDp[j] = (nextDp[j] + dp[d]) % MOD;
+                }
+            }
+            dp = nextDp;
+        }
+
+        int res = 0;
+        for (int d : dp) {
+            res = (res + d) % MOD;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    knightDialer(n) {
+        if (n === 1) return 10;
+        const MOD = 1000000007;
+        const jumps = [
+            [4, 6], [6, 8], [7, 9], [4, 8], [0, 3, 9],
+            [], [0, 1, 7], [2, 6], [1, 3], [2, 4]
+        ];
+
+        let dp = new Array(10).fill(1);
+
+        for (let step = 0; step < n - 1; step++) {
+            let nextDp = new Array(10).fill(0);
+            for (let d = 0; d < 10; d++) {
+                for (const j of jumps[d]) {
+                    nextDp[j] = (nextDp[j] + dp[d]) % MOD;
+                }
+            }
+            dp = nextDp;
+        }
+
+        return dp.reduce((res, d) => (res + d) % MOD, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 5. Dynamic Programming (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def knightDialer(self, n: int) -> int:
+        if n == 1:
+            return 10
+
+        mod = 10**9 + 7
+        jumps = [1, 4, 2, 2]  # [D, A, B, C]
+
+        for _ in range(n - 1):
+            tmp = [0] * 4
+            tmp[0] = jumps[3]
+            tmp[1] = 2 * jumps[2] + 2 * jumps[3]
+            tmp[2] = jumps[1]
+            tmp[3] = 2 * jumps[0] + jumps[1]
+            jumps = tmp
+
+        return sum(jumps) % mod
+```
+
+```java
+public class Solution {
+    public int knightDialer(int n) {
+        if (n == 1) return 10;
+
+        int MOD = 1000000007;
+        long[] jumps = {1, 4, 2, 2}; // [D, A, B, C]
+
+        for (int i = 0; i < n - 1; i++) {
+            long[] tmp = new long[4];
+            tmp[0] = jumps[3];
+            tmp[1] = (2 * jumps[2] + 2 * jumps[3]) % MOD;
+            tmp[2] = jumps[1];
+            tmp[3] = (2 * jumps[0] + jumps[1]) % MOD;
+            jumps = tmp;
+        }
+
+        long res = 0;
+        for (long num : jumps) {
+            res = (res + num) % MOD;
+        }
+        return (int) res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int knightDialer(int n) {
+        if (n == 1) return 10;
+
+        const int MOD = 1000000007;
+        vector<long long> jumps = {1, 4, 2, 2}; // [D, A, B, C]
+
+        for (int i = 0; i < n - 1; i++) {
+            vector<long long> tmp(4);
+            tmp[0] = jumps[3];
+            tmp[1] = (2 * jumps[2] + 2 * jumps[3]) % MOD;
+            tmp[2] = jumps[1];
+            tmp[3] = (2 * jumps[0] + jumps[1]) % MOD;
+            jumps = tmp;
+        }
+
+        return (jumps[0] + jumps[1] + jumps[2] + jumps[3]) % MOD;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    knightDialer(n) {
+        if (n === 1) return 10;
+
+        const MOD = 1000000007;
+        let jumps = [1, 4, 2, 2]; // [D, A, B, C]
+
+        for (let i = 0; i < n - 1; i++) {
+            let tmp = new Array(4).fill(0);
+            tmp[0] = jumps[3];
+            tmp[1] = (2 * jumps[2] + 2 * jumps[3]) % MOD;
+            tmp[2] = jumps[1];
+            tmp[3] = (2 * jumps[0] + jumps[1]) % MOD;
+            jumps = tmp;
+        }
+
+        return jumps.reduce((sum, num) => (sum + num) % MOD, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 6. Matrix Exponentiation
+
+::tabs-start
+
+```python
+class Matrix:
+    def __init__(self, size):
+        self.n = size
+        self.a = [[0] * size for _ in range(size)]
+
+    def __mul__(self, other):
+        n = self.n
+        MOD = 10**9 + 7
+        product = Matrix(n)
+        for i in range(n):
+            for j in range(n):
+                for k in range(n):
+                    product.a[i][k] = (product.a[i][k] + self.a[i][j] * other.a[j][k]) % MOD
+        return product
+
+
+def matpow(mat, n, size):
+    res = Matrix(size)
+    for i in range(size):
+        res.a[i][i] = 1  # Identity matrix
+
+    while n:
+        if n & 1:
+            res = res * mat
+        mat = mat * mat
+        n >>= 1
+
+    return res
+
+
+class Solution:
+    def knightDialer(self, n: int) -> int:
+        if n == 1:
+            return 10
+
+        MOD = 10**9 + 7
+        jumps = [
+            [4, 6], [6, 8], [7, 9], [4, 8], [0, 3, 9],
+            [], [0, 1, 7], [2, 6], [1, 3], [2, 4]
+        ]
+
+        mat = Matrix(10)
+        for i in range(10):
+            for j in jumps[i]:
+                mat.a[i][j] = 1
+
+        res = matpow(mat, n - 1, 10)
+
+        ans = sum(sum(res.a[i]) for i in range(10)) % MOD
+        return ans
+```
+
+```java
+class Matrix {
+    int[][] a;
+    int size;
+    static final int MOD = 1_000_000_007;
+
+    public Matrix(int size) {
+        this.size = size;
+        a = new int[size][size];
+    }
+
+    public Matrix multiply(Matrix other) {
+        Matrix product = new Matrix(size);
+        for (int i = 0; i < size; i++) {
+            for (int j = 0; j < size; j++) {
+                for (int k = 0; k < size; k++) {
+                    product.a[i][k] = (int)((product.a[i][k] + (long) a[i][j] * other.a[j][k]) % MOD);
+                }
+            }
+        }
+        return product;
+    }
+}
+
+public class Solution {
+    private Matrix matpow(Matrix mat, int n, int size) {
+        Matrix res = new Matrix(size);
+        for (int i = 0; i < size; i++) {
+            res.a[i][i] = 1;  // Identity matrix
+        }
+
+        while (n > 0) {
+            if ((n & 1) == 1) {
+                res = res.multiply(mat);
+            }
+            mat = mat.multiply(mat);
+            n >>= 1;
+        }
+        return res;
+    }
+
+    public int knightDialer(int n) {
+        if (n == 1) return 10;
+
+        int[][] jumps = {
+            {4, 6}, {6, 8}, {7, 9}, {4, 8}, {0, 3, 9},
+            {}, {0, 1, 7}, {2, 6}, {1, 3}, {2, 4}
+        };
+
+        Matrix mat = new Matrix(10);
+        for (int i = 0; i < 10; i++) {
+            for (int j : jumps[i]) {
+                mat.a[i][j] = 1;
+            }
+        }
+
+        Matrix res = matpow(mat, n - 1, 10);
+
+        int ans = 0;
+        for (int i = 0; i < 10; i++) {
+            for (int j = 0; j < 10; j++) {
+                ans = (ans + res.a[i][j]) % Matrix.MOD;
+            }
+        }
+        return ans;
+    }
+}
+```
+
+```cpp
+class Matrix {
+public:
+    vector<vector<int>> a;
+    int size;
+    static const int MOD = 1'000'000'007;
+
+    Matrix(int n) : size(n) {
+        a.assign(n, vector<int>(n, 0));
+    }
+
+    Matrix operator*(const Matrix &other) const {
+        Matrix product(size);
+        for (int i = 0; i < size; i++) {
+            for (int j = 0; j < size; j++) {
+                for (int k = 0; k < size; k++) {
+                    product.a[i][k] = (product.a[i][k] + 1LL * a[i][j] * other.a[j][k]) % MOD;
+                }
+            }
+        }
+        return product;
+    }
+};
+
+Matrix matpow(Matrix mat, int n, int size) {
+    Matrix res(size);
+    for (int i = 0; i < size; i++) {
+        res.a[i][i] = 1; // Identity matrix
+    }
+
+    while (n > 0) {
+        if (n & 1) res = res * mat;
+        mat = mat * mat;
+        n >>= 1;
+    }
+    return res;
+}
+
+class Solution {
+public:
+    int knightDialer(int n) {
+        if (n == 1) return 10;
+
+        vector<vector<int>> jumps = {
+            {4, 6}, {6, 8}, {7, 9}, {4, 8}, {0, 3, 9},
+            {}, {0, 1, 7}, {2, 6}, {1, 3}, {2, 4}
+        };
+
+        Matrix mat(10);
+        for (int i = 0; i < 10; i++) {
+            for (int j : jumps[i]) {
+                mat.a[i][j] = 1;
+            }
+        }
+
+        Matrix res = matpow(mat, n - 1, 10);
+
+        int ans = 0;
+        for (int i = 0; i < 10; i++) {
+            for (int j = 0; j < 10; j++) {
+                ans = (ans + res.a[i][j]) % Matrix::MOD;
+            }
+        }
+        return ans;
+    }
+};
+```
+
+```javascript
+class Matrix {
+    constructor(size) {
+        this.size = size;
+        this.a = Array.from({ length: size }, () => Array(size).fill(0));
+        this.MOD = BigInt(1e9 + 7);
+    }
+
+    multiply(other) {
+        const product = new Matrix(this.size);
+        for (let i = 0; i < this.size; i++) {
+            for (let j = 0; j < this.size; j++) {
+                let sum = BigInt(0);
+                for (let k = 0; k < this.size; k++) {
+                    sum = (sum + BigInt(this.a[i][k]) * BigInt(other.a[k][j])) % this.MOD;
+                }
+                product.a[i][j] = Number(sum);
+            }
+        }
+        return product;
+    }
+}
+
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    knightDialer(n) {
+        if (n === 1) return 10;
+
+        const matpow = (mat, exp, size) => {
+            let res = new Matrix(size);
+            for (let i = 0; i < size; i++) {
+                res.a[i][i] = 1; // Identity matrix
+            }
+
+            while (exp > 0) {
+                if (exp & 1) {
+                    res = res.multiply(mat);
+                }
+                mat = mat.multiply(mat);
+                exp >>= 1;
+            }
+            return res;
+        };
+
+        const jumps = [
+            [4, 6], [6, 8], [7, 9], [4, 8], [0, 3, 9],
+            [], [0, 1, 7], [2, 6], [1, 3], [2, 4]
+        ];
+
+        const mat = new Matrix(10);
+        for (let i = 0; i < 10; i++) {
+            for (let j of jumps[i]) {
+                mat.a[i][j] = 1;
+            }
+        }
+
+        const res = matpow(mat, n - 1, 10);
+        const mod = 1e9 + 7
+        let ans = 0;
+        
+        for (let i = 0; i < 10; i++) {
+            for (let j = 0; j < 10; j++) {
+                ans = (ans + res.a[i][j]) % mod;
+            }
+        }
+        
+        return ans;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/kth-distinct-string-in-an-array.md b/articles/kth-distinct-string-in-an-array.md
new file mode 100644
index 000000000..244281490
--- /dev/null
+++ b/articles/kth-distinct-string-in-an-array.md
@@ -0,0 +1,350 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def kthDistinct(self, arr: List[str], k: int) -> str:
+        for i in range(len(arr)):
+            flag = True
+            for j in range(len(arr)):
+                if i == j:
+                    continue
+
+                if arr[i] == arr[j]:
+                    flag = False
+                    break
+
+            if flag:
+                k -= 1
+                if k == 0:
+                    return arr[i]
+        return ""
+```
+
+```java
+public class Solution {
+    public String kthDistinct(String[] arr, int k) {
+        for (int i = 0; i < arr.length; i++) {
+            boolean flag = true;
+            for (int j = 0; j < arr.length; j++) {
+                if (i == j) continue;
+
+                if (arr[i].equals(arr[j])) {
+                    flag = false;
+                    break;
+                }
+            }
+
+            if (flag) {
+                k--;
+                if (k == 0) {
+                    return arr[i];
+                }
+            }
+        }
+        return "";
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string kthDistinct(vector<string>& arr, int k) {
+        for (int i = 0; i < arr.size(); i++) {
+            bool flag = true;
+            for (int j = 0; j < arr.size(); j++) {
+                if (i == j) continue;
+
+                if (arr[i] == arr[j]) {
+                    flag = false;
+                    break;
+                }
+            }
+
+            if (flag) {
+                k--;
+                if (k == 0) {
+                    return arr[i];
+                }
+            }
+        }
+        return "";
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} arr
+     * @param {number} k
+     * @return {string}
+     */
+    kthDistinct(arr, k) {
+        for (let i = 0; i < arr.length; i++) {
+            let flag = true;
+            for (let j = 0; j < arr.length; j++) {
+                if (i === j) continue;
+
+                if (arr[i] === arr[j]) {
+                    flag = false;
+                    break;
+                }
+            }
+
+            if (flag) {
+                k--;
+                if (k === 0) {
+                    return arr[i];
+                }
+            }
+        }
+        return "";
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def kthDistinct(self, arr: List[str], k: int) -> str:
+        count = {}
+
+        for s in arr:
+            if s not in count:
+                count[s] = 0
+            count[s] += 1
+
+        for s in arr:
+            if count[s] == 1:
+                k -= 1
+                if k == 0:
+                    return s
+
+        return ""
+```
+
+```java
+public class Solution {
+    public String kthDistinct(String[] arr, int k) {
+        Map<String, Integer> count = new HashMap<>();
+
+        for (String s : arr) {
+            count.put(s, count.getOrDefault(s, 0) + 1);
+        }
+
+        for (String s : arr) {
+            if (count.get(s) == 1) {
+                k--;
+                if (k == 0) {
+                    return s;
+                }
+            }
+        }
+
+        return "";
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string kthDistinct(vector<string>& arr, int k) {
+        unordered_map<string, int> count;
+
+        for (const string& s : arr) {
+            count[s]++;
+        }
+
+        for (const string& s : arr) {
+            if (count[s] == 1) {
+                k--;
+                if (k == 0) {
+                    return s;
+                }
+            }
+        }
+
+        return "";
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} arr
+     * @param {number} k
+     * @return {string}
+     */
+    kthDistinct(arr, k) {
+        const count = {};
+
+        for (let s of arr) {
+            if (!(s in count)) {
+                count[s] = 0;
+            }
+            count[s]++;
+        }
+
+        for (let s of arr) {
+            if (count[s] === 1) {
+                k--;
+                if (k === 0) {
+                    return s;
+                }
+            }
+        }
+
+        return "";
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Hash Set
+
+::tabs-start
+
+```python
+class Solution:
+    def kthDistinct(self, arr: List[str], k: int) -> str:
+        distinct, seen = set(), set()
+
+        for s in arr:
+            if s in distinct:
+                distinct.remove(s)
+                seen.add(s)
+            elif s not in seen:
+                distinct.add(s)
+
+        for s in arr:
+            if s in distinct:
+                k -= 1
+                if k == 0:
+                    return s
+
+        return ""
+```
+
+```java
+public class Solution {
+    public String kthDistinct(String[] arr, int k) {
+        Set<String> distinct = new HashSet<>();
+        Set<String> seen = new HashSet<>();
+
+        for (String s : arr) {
+            if (distinct.contains(s)) {
+                distinct.remove(s);
+                seen.add(s);
+            } else if (!seen.contains(s)) {
+                distinct.add(s);
+            }
+        }
+
+        for (String s : arr) {
+            if (distinct.contains(s)) {
+                k--;
+                if (k == 0) {
+                    return s;
+                }
+            }
+        }
+
+        return "";
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string kthDistinct(vector<string>& arr, int k) {
+        unordered_set<string> distinct, seen;
+
+        for (const string& s : arr) {
+            if (distinct.count(s)) {
+                distinct.erase(s);
+                seen.insert(s);
+            } else if (!seen.count(s)) {
+                distinct.insert(s);
+            }
+        }
+
+        for (const string& s : arr) {
+            if (distinct.count(s)) {
+                k--;
+                if (k == 0) {
+                    return s;
+                }
+            }
+        }
+
+        return "";
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} arr
+     * @param {number} k
+     * @return {string}
+     */
+    kthDistinct(arr, k) {
+        const distinct = new Set();
+        const seen = new Set();
+
+        for (let s of arr) {
+            if (distinct.has(s)) {
+                distinct.delete(s);
+                seen.add(s);
+            } else if (!seen.has(s)) {
+                distinct.add(s);
+            }
+        }
+
+        for (let s of arr) {
+            if (distinct.has(s)) {
+                k--;
+                if (k === 0) {
+                    return s;
+                }
+            }
+        }
+
+        return "";
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/kth-largest-element-in-an-array.md b/articles/kth-largest-element-in-an-array.md
index d8875ec75..28fa1c69b 100644
--- a/articles/kth-largest-element-in-an-array.md
+++ b/articles/kth-largest-element-in-an-array.md
@@ -51,6 +51,31 @@ public class Solution {
 }
 ```
 
+```go
+func findKthLargest(nums []int, k int) int {
+    sort.Ints(nums)
+    return nums[len(nums) - k]
+}
+```
+
+```kotlin
+class Solution {
+    fun findKthLargest(nums: IntArray, k: Int): Int {
+        nums.sort()
+        return nums[nums.size - k]
+    }
+}
+```
+
+```swift
+class Solution {
+    func findKthLargest(_ nums: [Int], _ k: Int) -> Int {
+        let sortedNums = nums.sorted()
+        return sortedNums[sortedNums.count - k]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -60,7 +85,7 @@ public class Solution {
 
 ---
 
-## 2. Heap
+## 2. Min-Heap
 
 ::tabs-start
 
@@ -136,6 +161,55 @@ public class Solution {
 }
 ```
 
+```go
+func findKthLargest(nums []int, k int) int {
+    minHeap := priorityqueue.NewWith(utils.IntComparator)
+    
+    for _, num := range nums {
+        minHeap.Enqueue(num)
+        if minHeap.Size() > k {
+            minHeap.Dequeue()
+        }
+    }
+    
+    val, _ := minHeap.Peek()
+    return val.(int)
+}
+```
+
+```kotlin
+class Solution {
+    fun findKthLargest(nums: IntArray, k: Int): Int {
+        val minHeap = PriorityQueue<Int>()
+        
+        for (num in nums) {
+            minHeap.offer(num)
+            if (minHeap.size > k) {
+                minHeap.poll()
+            }
+        }
+        return minHeap.peek()
+    }
+}
+```
+
+```swift
+class Solution {
+    func findKthLargest(_ nums: [Int], _ k: Int) -> Int {
+        var minHeap = Heap<Int>()
+
+        for num in nums {
+            minHeap.insert(num)
+            if minHeap.count > k {
+                _ = minHeap.removeMin()
+            }
+        }
+
+        return minHeap.popMin()!
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -147,7 +221,7 @@ public class Solution {
 
 ---
 
-## 3. Recursive Quick Select
+## 3. Quick Select
 
 ::tabs-start
 
@@ -313,6 +387,94 @@ public class Solution {
 }
 ```
 
+```go
+func findKthLargest(nums []int, k int) int {
+    k = len(nums) - k
+    
+    var quickSelect func(l, r int) int
+    quickSelect = func(l, r int) int {
+        pivot, p := nums[r], l
+        for i := l; i < r; i++ {
+            if nums[i] <= pivot {
+                nums[p], nums[i] = nums[i], nums[p]
+                p++
+            }
+        }
+        nums[p], nums[r] = nums[r], nums[p]
+
+        if p > k {
+            return quickSelect(l, p-1)
+        } else if p < k {
+            return quickSelect(p+1, r)
+        } else {
+            return nums[p]
+        }
+    }
+
+    return quickSelect(0, len(nums)-1)
+}
+```
+
+```kotlin
+class Solution {
+    fun findKthLargest(nums: IntArray, k: Int): Int {
+        val target = nums.size - k
+
+        fun quickSelect(l: Int, r: Int): Int {
+            val pivot = nums[r]
+            var p = l
+            for (i in l until r) {
+                if (nums[i] <= pivot) {
+                    nums[p] = nums[i].also { nums[i] = nums[p] }
+                    p++
+                }
+            }
+            nums[p] = nums[r].also { nums[r] = nums[p] }
+
+            return when {
+                p > target -> quickSelect(l, p - 1)
+                p < target -> quickSelect(p + 1, r)
+                else -> nums[p]
+            }
+        }
+
+        return quickSelect(0, nums.size - 1)
+    }
+}
+```
+
+```swift
+class Solution {
+    func findKthLargest(_ nums: [Int], _ k: Int) -> Int {
+        var nums = nums
+        let k = nums.count - k
+
+        func quickSelect(_ l: Int, _ r: Int) -> Int {
+            let pivot = nums[r]
+            var p = l
+
+            for i in l..<r {
+                if nums[i] <= pivot {
+                    nums.swapAt(i, p)
+                    p += 1
+                }
+            }
+            nums.swapAt(p, r)
+
+            if p > k {
+                return quickSelect(l, p - 1)
+            } else if p < k {
+                return quickSelect(p + 1, r)
+            } else {
+                return nums[p]
+            }
+        }
+
+        return quickSelect(0, nums.count - 1)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -322,71 +484,119 @@ public class Solution {
 
 ---
 
-## 4. Iterative Quick Select
+## 4. Quick Select (Optimal)
 
 ::tabs-start
 
 ```python
 class Solution:
-
-    def findKthLargest(self, nums: List[int], k: int) -> int:
-        k = len(nums) - k
-        left, right = 0, len(nums) - 1
-
-        while left < right:
-            pivot = self.partition(nums, left, right)
-
-            if pivot < k:
-                left = pivot + 1
-            elif pivot > k:
-                right = pivot - 1
-            else:
-                break
-
-        return nums[k]
-
     def partition(self, nums: List[int], left: int, right: int) -> int:
-        pivot, fill = nums[right], left
-
-        for i in range(left, right):
-            if nums[i] <= pivot:
-                nums[fill], nums[i] = nums[i], nums[fill]
-                fill += 1
-
-        nums[fill], nums[right] = nums[right], nums[fill]
-
-        return fill
+        mid = (left + right) >> 1
+        nums[mid], nums[left + 1] = nums[left + 1], nums[mid]
+        
+        if nums[left] < nums[right]:
+            nums[left], nums[right] = nums[right], nums[left]
+        if nums[left + 1] < nums[right]:
+            nums[left + 1], nums[right] = nums[right], nums[left + 1]
+        if nums[left] < nums[left + 1]:
+            nums[left], nums[left + 1] = nums[left + 1], nums[left]
+        
+        pivot = nums[left + 1]
+        i = left + 1
+        j = right
+        
+        while True:
+            while True:
+                i += 1
+                if not nums[i] > pivot:
+                    break
+            while True:
+                j -= 1
+                if not nums[j] < pivot:
+                    break
+            if i > j:
+                break
+            nums[i], nums[j] = nums[j], nums[i]
+        
+        nums[left + 1], nums[j] = nums[j], nums[left + 1]
+        return j
+    
+    def quickSelect(self, nums: List[int], k: int) -> int:
+        left = 0
+        right = len(nums) - 1
+        
+        while True:
+            if right <= left + 1:
+                if right == left + 1 and nums[right] > nums[left]:
+                    nums[left], nums[right] = nums[right], nums[left]
+                return nums[k]
+            
+            j = self.partition(nums, left, right)
+            
+            if j >= k:
+                right = j - 1
+            if j <= k:
+                left = j + 1
+    
+    def findKthLargest(self, nums: List[int], k: int) -> int:
+        return self.quickSelect(nums, k - 1)
 ```
 
 ```java
-public class Solution {  
-    public int findKthLargest(int[] nums, int k) {
-        k = nums.length - k;
-        int left = 0, right = nums.length - 1;
-        while (left < right) {
-            int pivot = partition(nums, left, right);
-            if (pivot < k)
-                left = pivot + 1;
-            else if (pivot > k)
-                right = pivot - 1;
-            else
-                break;
+public class Solution {
+    private int partition(int[] nums, int left, int right) {
+        int mid = (left + right) >> 1;
+        swap(nums, mid, left + 1);
+        
+        if (nums[left] < nums[right]) 
+            swap(nums, left, right);
+        if (nums[left + 1] < nums[right]) 
+            swap(nums, left + 1, right);
+        if (nums[left] < nums[left + 1]) 
+            swap(nums, left, left + 1);
+        
+        int pivot = nums[left + 1];
+        int i = left + 1;
+        int j = right;
+        
+        while (true) {
+            while (nums[++i] > pivot);
+            while (nums[--j] < pivot);
+            if (i > j) break;
+            swap(nums, i, j);
         }
-        return nums[k];
+        
+        nums[left + 1] = nums[j];
+        nums[j] = pivot;
+        return j;
     }
-
-    private int partition(int[] nums, int left, int right) {
-        int pivot = nums[right], fill = left;
-        for (int i = left; i < right; i++) {
-            if (nums[i] <= pivot) {
-                int temp = nums[fill];
-                nums[fill++] = nums[i];
-                nums[i] = temp;
+    
+    private void swap(int[] nums, int i, int j) {
+        int temp = nums[i];
+        nums[i] = nums[j];
+        nums[j] = temp;
+    }
+    
+    private int quickSelect(int[] nums, int k) {
+        int left = 0;
+        int right = nums.length - 1;
+        
+        while (true) {
+            if (right <= left + 1) {
+                if (right == left + 1 && nums[right] > nums[left])
+                    swap(nums, left, right);
+                return nums[k];
             }
+            
+            int j = partition(nums, left, right);
+            
+            if (j >= k) right = j - 1;
+            if (j <= k) left = j + 1;
         }
-        nums[right] = nums[fill];
-        nums[fill] = pivot;
-        return fill;
+    }
+    
+    public int findKthLargest(int[] nums, int k) {
+        return quickSelect(nums, k - 1);
     }
 }
 ```
@@ -394,31 +604,53 @@ public class Solution {
 ```cpp
 class Solution {
 public:
-    int findKthLargest(vector<int>& nums, int k) {
-        k = nums.size() - k;
-        int left = 0, right = nums.size() - 1;
-        while (left < right) {
-            int pivot = partition(nums, left, right);
-            if (pivot < k)
-                left = pivot + 1;
-            else if (pivot > k)
-                right = pivot - 1;
-            else
-                break;
+    int partition(vector<int>& nums, int left, int right) {
+        int mid = (left + right) >> 1;
+        swap(nums[mid], nums[left + 1]);
+        
+        if (nums[left] < nums[right]) 
+            swap(nums[left], nums[right]);
+        if (nums[left + 1] < nums[right]) 
+            swap(nums[left + 1], nums[right]);
+        if (nums[left] < nums[left + 1]) 
+            swap(nums[left], nums[left + 1]);
+        
+        int pivot = nums[left + 1];
+        int i = left + 1;
+        int j = right;
+        
+        while (true) {
+            while (nums[++i] > pivot);
+            while (nums[--j] < pivot);
+            if (i > j) break;
+            swap(nums[i], nums[j]);
         }
-        return nums[k];
+        
+        nums[left + 1] = nums[j];
+        nums[j] = pivot;
+        return j;
     }
-
-private:
-    int partition(vector<int>& nums, int left, int right) {
-        int pivot = nums[right], fill = left;
-        for (int i = left; i < right; i++) {
-            if (nums[i] <= pivot) {
-                swap(nums[fill++], nums[i]);
+    
+    int quickSelect(vector<int>& nums, int k) {
+        int left = 0;
+        int right = nums.size() - 1;
+        
+        while (true) {
+            if (right <= left + 1) {
+                if (right == left + 1 && nums[right] > nums[left])
+                    swap(nums[left], nums[right]);
+                return nums[k];
             }
+            
+            int j = partition(nums, left, right);
+            
+            if (j >= k) right = j - 1;
+            if (j <= k) left = j + 1;
         }
-        swap(nums[right], nums[fill]);
-        return fill;
+    }
+    
+    int findKthLargest(vector<int>& nums, int k) {
+        return quickSelect(nums, k - 1);
     }
 };
 ```
@@ -431,69 +663,283 @@ class Solution {
      * @return {number}
      */
     findKthLargest(nums, k) {
-        k = nums.length - k;
-        let left = 0;
-        let right = nums.length - 1;
-        while (left < right) {
-            const pivot = this.partition(nums, left, right);
-            if (pivot < k) left = pivot + 1;
-            else if (pivot > k) right = pivot - 1;
-            else break;
+        function partition(left, right) {
+            const mid = (left + right) >> 1;
+            [nums[mid], nums[left + 1]] = [nums[left + 1], nums[mid]];
+            
+            if (nums[left] < nums[right])
+                [nums[left], nums[right]] = [nums[right], nums[left]];
+            if (nums[left + 1] < nums[right])
+                [nums[left + 1], nums[right]] = [nums[right], nums[left + 1]];
+            if (nums[left] < nums[left + 1])
+                [nums[left], nums[left + 1]] = [nums[left + 1], nums[left]];
+            
+            const pivot = nums[left + 1];
+            let i = left + 1;
+            let j = right;
+            
+            while (true) {
+                while (nums[++i] > pivot);
+                while (nums[--j] < pivot);
+                if (i > j) break;
+                [nums[i], nums[j]] = [nums[j], nums[i]];
+            }
+            
+            nums[left + 1] = nums[j];
+            nums[j] = pivot;
+            return j;
         }
-        return nums[k];
-    }
-
-    /**
-     * @param {number[]} nums
-     * @param {number} left
-     * @param {number} right
-     * @return {number}
-     */
-    partition(nums, left, right) {
-        const pivot = nums[right];
-        let fill = left;
-        for (let i = left; i < right; i++) {
-            if (nums[i] <= pivot) {
-                [nums[fill], nums[i]] = [nums[i], nums[fill]];
-                fill++;
+        
+        function quickSelect(k) {
+            let left = 0;
+            let right = nums.length - 1;
+            
+            while (true) {
+                if (right <= left + 1) {
+                    if (right == left + 1 && nums[right] > nums[left])
+                        [nums[left], nums[right]] = [nums[right], nums[left]];
+                    return nums[k];
+                }
+                
+                const j = partition(left, right);
+                
+                if (j >= k) right = j - 1;
+                if (j <= k) left = j + 1;
             }
         }
-        [nums[right], nums[fill]] = [nums[fill], nums[right]];
-        return fill;
+        
+        return quickSelect(k - 1);
     }
 }
 ```
 
 ```csharp
 public class Solution {
+    private int Partition(int[] nums, int left, int right) {
+        int mid = (left + right) >> 1;
+        (nums[mid], nums[left + 1]) = (nums[left + 1], nums[mid]);
+        
+        if (nums[left] < nums[right])
+            (nums[left], nums[right]) = (nums[right], nums[left]);
+        if (nums[left + 1] < nums[right])
+            (nums[left + 1], nums[right]) = (nums[right], nums[left + 1]);
+        if (nums[left] < nums[left + 1])
+            (nums[left], nums[left + 1]) = (nums[left + 1], nums[left]);
+        
+        int pivot = nums[left + 1];
+        int i = left + 1;
+        int j = right;
+        
+        while (true) {
+            while (nums[++i] > pivot);
+            while (nums[--j] < pivot);
+            if (i > j) break;
+            (nums[i], nums[j]) = (nums[j], nums[i]);
+        }
+        
+        nums[left + 1] = nums[j];
+        nums[j] = pivot;
+        return j;
+    }
+    
+    private int QuickSelect(int[] nums, int k) {
+        int left = 0;
+        int right = nums.Length - 1;
+        
+        while (true) {
+            if (right <= left + 1) {
+                if (right == left + 1 && nums[right] > nums[left])
+                    (nums[left], nums[right]) = (nums[right], nums[left]);
+                return nums[k];
+            }
+            
+            int j = Partition(nums, left, right);
+            
+            if (j >= k) right = j - 1;
+            if (j <= k) left = j + 1;
+        }
+    }
     
     public int FindKthLargest(int[] nums, int k) {
-        k = nums.Length - k;
-        int left = 0, right = nums.Length - 1;
-        while (left < right) {
-            int pivot = Partition(nums, left, right);
-            if (pivot < k)
-                left = pivot + 1;
-            else if (pivot > k)
-                right = pivot - 1;
-            else
-                break;
+        return QuickSelect(nums, k - 1);
+    }
+}
+```
+
+```go
+func findKthLargest(nums []int, k int) int {
+    var partition func(left, right int) int
+    partition = func(left, right int) int {
+        mid := (left + right) >> 1
+        nums[mid], nums[left+1] = nums[left+1], nums[mid]
+        
+        if nums[left] < nums[right] {
+            nums[left], nums[right] = nums[right], nums[left]
+        }
+        if nums[left+1] < nums[right] {
+            nums[left+1], nums[right] = nums[right], nums[left+1]
+        }
+        if nums[left] < nums[left+1] {
+            nums[left], nums[left+1] = nums[left+1], nums[left]
+        }
+        
+        pivot := nums[left+1]
+        i := left + 1
+        j := right
+        
+        for {
+            for i++; nums[i] > pivot; i++ {}
+            for j--; nums[j] < pivot; j-- {}
+            if i > j {
+                break
+            }
+            nums[i], nums[j] = nums[j], nums[i]
         }
-        return nums[k];
+        
+        nums[left+1], nums[j] = nums[j], nums[left+1]
+        return j
     }
+    
+    quickSelect := func(k int) int {
+        left := 0
+        right := len(nums) - 1
+        
+        for {
+            if right <= left+1 {
+                if right == left+1 && nums[right] > nums[left] {
+                    nums[left], nums[right] = nums[right], nums[left]
+                }
+                return nums[k]
+            }
+            
+            j := partition(left, right)
+            
+            if j >= k {
+                right = j - 1
+            }
+            if j <= k {
+                left = j + 1
+            }
+        }
+    }
+    
+    return quickSelect(k - 1)
+}
+```
 
-    private int Partition(int[] nums, int left, int right) {
-        int pivot = nums[right], fill = left;
-        for (int i = left; i < right; i++) {
-            if (nums[i] <= pivot) {
-                int temp = nums[fill];
-                nums[fill++] = nums[i];
-                nums[i] = temp;
+```kotlin
+class Solution {
+    private fun partition(nums: IntArray, left: Int, right: Int): Int {
+        val mid = (left + right) shr 1
+        nums[mid] = nums[left + 1].also { nums[left + 1] = nums[mid] }
+        
+        if (nums[left] < nums[right])
+            nums[left] = nums[right].also { nums[right] = nums[left] }
+        if (nums[left + 1] < nums[right])
+            nums[left + 1] = nums[right].also { nums[right] = nums[left + 1] }
+        if (nums[left] < nums[left + 1])
+            nums[left] = nums[left + 1].also { nums[left + 1] = nums[left] }
+        
+        val pivot = nums[left + 1]
+        var i = left + 1
+        var j = right
+        
+        while (true) {
+            while (nums[++i] > pivot);
+            while (nums[--j] < pivot);
+            if (i > j) break
+            nums[i] = nums[j].also { nums[j] = nums[i] }
+        }
+        
+        nums[left + 1] = nums[j]
+        nums[j] = pivot
+        return j
+    }
+    
+    private fun quickSelect(nums: IntArray, k: Int): Int {
+        var left = 0
+        var right = nums.size - 1
+        
+        while (true) {
+            if (right <= left + 1) {
+                if (right == left + 1 && nums[right] > nums[left])
+                    nums[left] = nums[right].also { nums[right] = nums[left] }
+                return nums[k]
             }
+            
+            val j = partition(nums, left, right)
+            
+            if (j >= k) right = j - 1
+            if (j <= k) left = j + 1
         }
-        nums[right] = nums[fill];
-        nums[fill] = pivot;
-        return fill;
+    }
+    
+    fun findKthLargest(nums: IntArray, k: Int): Int {
+        return quickSelect(nums, k - 1)
+    }
+}
+```
+
+```swift
+class Solution {
+    func partition(_ nums: inout [Int], _ left: Int, _ right: Int) -> Int {
+        let mid = (left + right) >> 1
+        nums.swapAt(mid, left + 1)
+
+        if nums[left] < nums[right] {
+            nums.swapAt(left, right)
+        }
+        if nums[left + 1] < nums[right] {
+            nums.swapAt(left + 1, right)
+        }
+        if nums[left] < nums[left + 1] {
+            nums.swapAt(left, left + 1)
+        }
+
+        let pivot = nums[left + 1]
+        var i = left + 1
+        var j = right
+
+        while true {
+            repeat { i += 1 } while nums[i] > pivot
+            repeat { j -= 1 } while nums[j] < pivot
+
+            if i > j {
+                break
+            }
+            nums.swapAt(i, j)
+        }
+
+        nums.swapAt(left + 1, j)
+        return j
+    }
+
+    func quickSelect(_ nums: inout [Int], _ k: Int) -> Int {
+        var left = 0
+        var right = nums.count - 1
+
+        while true {
+            if right <= left + 1 {
+                if right == left + 1 && nums[right] > nums[left] {
+                    nums.swapAt(left, right)
+                }
+                return nums[k]
+            }
+
+            let j = partition(&nums, left, right)
+
+            if j >= k {
+                right = j - 1
+            }
+            if j <= k {
+                left = j + 1
+            }
+        }
+    }
+
+    func findKthLargest(_ nums: [Int], _ k: Int) -> Int {
+        var nums = nums
+        return quickSelect(&nums, k - 1)
     }
 }
 ```
diff --git a/articles/kth-largest-integer-in-a-stream.md b/articles/kth-largest-integer-in-a-stream.md
index eda4c1da1..42a4f617a 100644
--- a/articles/kth-largest-integer-in-a-stream.md
+++ b/articles/kth-largest-integer-in-a-stream.md
@@ -94,18 +94,68 @@ public class KthLargest {
 }
 ```
 
+```go
+type KthLargest struct {
+    k   int
+    arr []int
+}
+
+func Constructor(k int, nums []int) KthLargest {
+    return KthLargest{k: k, arr: nums}
+}
+
+func (this *KthLargest) Add(val int) int {
+    this.arr = append(this.arr, val)
+    sort.Ints(this.arr)
+    return this.arr[len(this.arr)-this.k]
+}
+```
+
+```kotlin
+class KthLargest(k: Int, nums: IntArray) {
+    private val k = k
+    private val arr = nums.toMutableList()
+
+    fun add(`val`: Int): Int {
+        arr.add(`val`)
+        arr.sort()
+        return arr[arr.size - k]
+    }
+}
+```
+
+```swift
+class KthLargest {
+    private var k: Int
+    private var arr: [Int]
+
+    init(_ k: Int, _ nums: [Int]) {
+        self.k = k
+        self.arr = nums
+    }
+
+    func add(_ val: Int) -> Int {
+        arr.append(val)
+        arr.sort()
+        return arr[arr.count - k]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(m * n\log n)$
-* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+* Space complexity:
+    * $O(m)$ extra space.
+    * $O(1)$ or $O(n)$ space depending on the sorting algorithm.
 
 > Where $m$ is the number of calls made to $add()$ and $n$ is the current size of the array.
 
 ---
 
-## 2. Heap
+## 2. Min-Heap
 
 ::tabs-start
 
@@ -243,6 +293,83 @@ public class KthLargest {
 }
 ```
 
+```go
+type KthLargest struct {
+    minHeap *priorityqueue.Queue
+    k       int
+}
+
+func Constructor(k int, nums []int) KthLargest {
+    minHeap := priorityqueue.NewWith(utils.IntComparator)
+    for _, num := range nums {
+        minHeap.Enqueue(num)
+    }
+    for minHeap.Size() > k {
+        minHeap.Dequeue()
+    }
+    return KthLargest{minHeap: minHeap, k: k}
+}
+
+func (this *KthLargest) Add(val int) int {
+    this.minHeap.Enqueue(val)
+    if this.minHeap.Size() > this.k {
+        this.minHeap.Dequeue()
+    }
+    top, _ := this.minHeap.Peek()
+    return top.(int)
+}
+```
+
+```kotlin
+class KthLargest(k: Int, nums: IntArray) {
+    private val k = k
+    private val minHeap = PriorityQueue<Int>()
+
+    init {
+        for (num in nums) {
+            minHeap.offer(num)
+        }
+        while (minHeap.size > k) {
+            minHeap.poll()
+        }
+    }
+
+    fun add(`val`: Int): Int {
+        minHeap.offer(`val`)
+        if (minHeap.size > k) {
+            minHeap.poll()
+        }
+        return minHeap.peek()
+    }
+}
+```
+
+```swift
+class KthLargest {
+    private var minHeap: Heap<Int>
+    private let k: Int
+
+    init(_ k: Int, _ nums: [Int]) {
+        self.k = k
+        self.minHeap = Heap<Int>()
+        for num in nums {
+            minHeap.insert(num)
+            if minHeap.count > k {
+                minHeap.popMin()
+            }
+        }
+    }
+
+    func add(_ val: Int) -> Int {
+        minHeap.insert(val)
+        if minHeap.count > k {
+            minHeap.popMin()
+        }
+        return minHeap.min!
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/kth-smallest-integer-in-bst.md b/articles/kth-smallest-integer-in-bst.md
index 08ab8e7fc..ec5dfe795 100644
--- a/articles/kth-smallest-integer-in-bst.md
+++ b/articles/kth-smallest-integer-in-bst.md
@@ -166,6 +166,99 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func kthSmallest(root *TreeNode, k int) int {
+    var arr []int
+    
+    var dfs func(node *TreeNode)
+    dfs = func(node *TreeNode) {
+        if node == nil {
+            return
+        }
+        
+        dfs(node.Left)
+        arr = append(arr, node.Val)
+        dfs(node.Right)
+    }
+    
+    dfs(root)
+    return arr[k-1]
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    private val arr = mutableListOf<Int>()
+    
+    fun kthSmallest(root: TreeNode?, k: Int): Int {
+        dfs(root)
+        return arr[k - 1]
+    }
+    
+    private fun dfs(node: TreeNode?) {
+        if (node == null) {
+            return
+        }
+        
+        dfs(node.left)
+        arr.add(node.`val`)
+        dfs(node.right)
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func kthSmallest(_ root: TreeNode?, _ k: Int) -> Int {
+        var arr = [Int]()
+
+        func dfs(_ node: TreeNode?) {
+            guard let node = node else { return }
+            arr.append(node.val)
+            dfs(node.left)
+            dfs(node.right)
+        }
+
+        dfs(root)
+        arr.sort()
+        return arr[k - 1]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -338,6 +431,98 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func kthSmallest(root *TreeNode, k int) int {
+    var arr []int
+    
+    var dfs func(node *TreeNode)
+    dfs = func(node *TreeNode) {
+        if node == nil {
+            return
+        }
+        
+        dfs(node.Left)
+        arr = append(arr, node.Val)
+        dfs(node.Right)
+    }
+    
+    dfs(root)
+    return arr[k-1]
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    private val arr = mutableListOf<Int>()
+    
+    fun kthSmallest(root: TreeNode?, k: Int): Int {
+        dfs(root)
+        return arr[k - 1]
+    }
+    
+    private fun dfs(node: TreeNode?) {
+        if (node == null) {
+            return
+        }
+        
+        dfs(node.left)
+        arr.add(node.`val`)
+        dfs(node.right)
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func kthSmallest(_ root: TreeNode?, _ k: Int) -> Int {
+        var arr = [Int]()
+
+        func dfs(_ node: TreeNode?) {
+            guard let node = node else { return }
+            dfs(node.left)
+            arr.append(node.val)
+            dfs(node.right)
+        }
+
+        dfs(root)
+        return arr[k - 1]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -534,6 +719,114 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func kthSmallest(root *TreeNode, k int) int {
+    cnt, res := k, 0
+    
+    var dfs func(node *TreeNode)
+    dfs = func(node *TreeNode) {
+        if node == nil {
+            return
+        }
+        
+        dfs(node.Left)
+        cnt--
+        if cnt == 0 {
+            res = node.Val
+            return
+        }
+        dfs(node.Right)
+    }
+    
+    dfs(root)
+    return res
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    private var cnt = 0
+    private var res = 0
+    
+    fun kthSmallest(root: TreeNode?, k: Int): Int {
+        cnt = k
+        dfs(root)
+        return res
+    }
+    
+    private fun dfs(node: TreeNode?) {
+        if (node == null) {
+            return
+        }
+        
+        dfs(node.left)
+        cnt--
+        if (cnt == 0) {
+            res = node.`val`
+            return
+        }
+        dfs(node.right)
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func kthSmallest(_ root: TreeNode?, _ k: Int) -> Int {
+        var cnt = k
+        var res = root!.val
+
+        func dfs(_ node: TreeNode?) {
+            guard let node = node else { return }
+
+            dfs(node.left)
+            cnt -= 1
+            if cnt == 0 {
+                res = node.val
+                return
+            }
+            dfs(node.right)
+        }
+
+        dfs(root)
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -725,6 +1018,116 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func kthSmallest(root *TreeNode, k int) int {
+    stack := []*TreeNode{}
+    curr := root
+    
+    for len(stack) > 0 || curr != nil {
+        for curr != nil {
+            stack = append(stack, curr)
+            curr = curr.Left
+        }
+        
+        curr = stack[len(stack)-1]
+        stack = stack[:len(stack)-1]
+        
+        k--
+        if k == 0 {
+            return curr.Val
+        }
+        
+        curr = curr.Right
+    }
+    
+    return 0 
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    fun kthSmallest(root: TreeNode?, k: Int): Int {
+        val stack = mutableListOf<TreeNode>()
+        var curr: TreeNode? = root
+        var k = k
+        
+        while (stack.isNotEmpty() || curr != null) {
+            while (curr != null) {
+                stack.add(curr)
+                curr = curr.left
+            }
+            
+            curr = stack.removeLast()
+            k--
+            if (k == 0) {
+                return curr.`val`
+            }
+            
+            curr = curr.right
+        }
+        
+        return 0 
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func kthSmallest(_ root: TreeNode?, _ k: Int) -> Int {
+        var stack = [TreeNode]()
+        var curr = root
+        var k = k
+
+        while !stack.isEmpty || curr != nil {
+            while curr != nil {
+                stack.append(curr!)
+                curr = curr?.left
+            }
+            curr = stack.removeLast()
+            k -= 1
+            if k == 0 {
+                return curr!.val
+            }
+            curr = curr?.right
+        }
+        return -1
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -957,6 +1360,141 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func kthSmallest(root *TreeNode, k int) int {
+    curr := root
+    for {
+        if curr.Left == nil {
+            k--
+            if k == 0 {
+                return curr.Val
+            }
+            curr = curr.Right
+        } else {
+            pred := curr.Left
+            for pred.Right != nil && pred.Right != curr {
+                pred = pred.Right
+            }
+            if pred.Right == nil {
+                pred.Right = curr
+                curr = curr.Left
+            } else {
+                pred.Right = nil
+                k--
+                if k == 0 {
+                    return curr.Val
+                }
+                curr = curr.Right
+            }
+        }
+    }
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    fun kthSmallest(root: TreeNode?, k: Int): Int {
+        var curr: TreeNode? = root
+        var k = k
+        while (true) {
+            if (curr?.left == null) {
+                k--
+                if (k == 0) {
+                    return curr!!.`val`
+                }
+                curr = curr?.right
+            } else {
+                var pred = curr.left
+                while (pred?.right != null && pred.right != curr) {
+                    pred = pred.right
+                }
+                if (pred?.right == null) {
+                    pred.right = curr
+                    curr = curr.left
+                } else {
+                    pred.right = null
+                    k--
+                    if (k == 0) {
+                        return curr!!.`val`
+                    }
+                    curr = curr.right
+                }
+            }
+        }
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func kthSmallest(_ root: TreeNode?, _ k: Int) -> Int {
+        var curr = root
+        var k = k
+
+        while curr != nil {
+            if curr?.left == nil {
+                k -= 1
+                if k == 0 {
+                    return curr!.val
+                }
+                curr = curr?.right
+            } else {
+                var pred = curr?.left
+                while pred?.right != nil && pred?.right !== curr {
+                    pred = pred?.right
+                }
+                
+                if pred?.right == nil {
+                    pred?.right = curr
+                    curr = curr?.left
+                } else {
+                    pred?.right = nil
+                    k -= 1
+                    if k == 0 {
+                        return curr!.val
+                    }
+                    curr = curr?.right
+                }
+            }
+        }
+        return -1
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/largest-3-same-digit-number-in-string.md b/articles/largest-3-same-digit-number-in-string.md
new file mode 100644
index 000000000..f96e85ee3
--- /dev/null
+++ b/articles/largest-3-same-digit-number-in-string.md
@@ -0,0 +1,255 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def largestGoodInteger(self, num: str) -> str:
+        res = ""
+        val = 0
+        
+        for i in range(len(num) - 2):
+            if num[i] == num[i + 1] == num[i + 2]:
+                tmp = num[i : i + 3]
+                if val <= int(tmp):
+                    val = int(tmp)
+                    res = tmp
+        
+        return res
+```
+
+```java
+public class Solution {
+    public String largestGoodInteger(String num) {
+        String res = "";
+        int val = 0;
+        
+        for (int i = 0; i < num.length() - 2; i++) {
+            if (num.charAt(i) == num.charAt(i + 1) && 
+                num.charAt(i) == num.charAt(i + 2)) {
+                String tmp = num.substring(i, i + 3);
+                if (val <= Integer.parseInt(tmp)) {
+                    val = Integer.parseInt(tmp);
+                    res = tmp;
+                }
+            }
+        }
+        
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string largestGoodInteger(string num) {
+        string res = "";
+        int val = 0;
+        
+        for (int i = 0; i < num.length() - 2; i++) {
+            if (num[i] == num[i + 1] && num[i] == num[i + 2]) {
+                string tmp = num.substr(i, 3);
+                if (val <= stoi(tmp)) {
+                    val = stoi(tmp);
+                    res = tmp;
+                }
+            }
+        }
+        
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} num
+     * @return {string}
+     */
+    largestGoodInteger(num) {
+        let res = "";
+        let val = 0;
+        
+        for (let i = 0; i < num.length - 2; i++) {
+            if (num[i] === num[i + 1] && num[i] === num[i + 2]) {
+                const tmp = num.slice(i, i + 3);
+                if (val <= parseInt(tmp)) {
+                    val = parseInt(tmp);
+                    res = tmp;
+                }
+            }
+        }
+        
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Iteration
+
+::tabs-start
+
+```python
+class Solution:
+    def largestGoodInteger(self, num: str) -> str:
+        res = "0"
+        
+        for i in range(len(num) - 2):
+            if num[i] == num[i + 1] == num[i + 2]:
+                res = max(res, num[i : i + 3])
+        
+        return "" if res == "0" else res
+```
+
+```java
+public class Solution {
+    public String largestGoodInteger(String num) {
+        String res = "";
+        
+        for (int i = 0; i < num.length() - 2; i++) {
+            if (num.charAt(i) == num.charAt(i + 1) && 
+                num.charAt(i) == num.charAt(i + 2)) {
+                String curr = num.substring(i, i + 3);
+                if (curr.compareTo(res) > 0) {
+                    res = curr;
+                }
+            }
+        }
+        
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string largestGoodInteger(string num) {
+        string res = "0";
+        
+        for (int i = 0; i < num.length() - 2; i++) {
+            if (num[i] == num[i + 1] && num[i] == num[i + 2]) {
+                res = max(res, num.substr(i, 3));
+            }
+        }
+        
+        return res == "0" ? "" : res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} num
+     * @return {string}
+     */
+    largestGoodInteger(num) {
+        let res = "0";
+        
+        for (let i = 0; i < num.length - 2; i++) {
+            if (num[i] === num[i + 1] && num[i] === num[i + 2]) {
+                res = res > num.slice(i, i + 3) ? res : num.slice(i, i + 3);
+            }
+        }
+        
+        return res === "0" ? "" : res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Iteration (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def largestGoodInteger(self, num: str) -> str:
+        res = -1
+        
+        for i in range(len(num) - 2):
+            if num[i] == num[i + 1] == num[i + 2]:
+                res = max(res, int(num[i]))
+        return str(res) * 3 if res != -1 else ""
+```
+
+```java
+public class Solution {
+    public String largestGoodInteger(String num) {
+        int res = -1;
+
+        for (int i = 0; i < num.length() - 2; i++) {
+            if (num.charAt(i) == num.charAt(i + 1) && 
+                num.charAt(i) == num.charAt(i + 2)) {
+                res = Math.max(res, num.charAt(i) - '0');
+            }
+        }
+
+        return res != -1 ? String.valueOf(res).repeat(3) : "";
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string largestGoodInteger(string num) {
+        int res = -1;
+
+        for (int i = 0; i < num.length() - 2; i++) {
+            if (num[i] == num[i + 1] && num[i] == num[i + 2]) {
+                res = max(res, num[i] - '0');
+            }
+        }
+
+        return res != -1 ? string(3, res + '0') : "";
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} num
+     * @return {string}
+     */
+    largestGoodInteger(num) {
+        let res = -1;
+
+        for (let i = 0; i < num.length - 2; i++) {
+            if (num[i] === num[i + 1] && num[i] === num[i + 2]) {
+                res = Math.max(res, Number(num[i]));
+            }
+        }
+
+        return res !== -1 ? String(res).repeat(3) : "";
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/largest-color-value-in-a-directed-graph.md b/articles/largest-color-value-in-a-directed-graph.md
new file mode 100644
index 000000000..dcbf467a4
--- /dev/null
+++ b/articles/largest-color-value-in-a-directed-graph.md
@@ -0,0 +1,589 @@
+## 1. Brute Force (DFS)
+
+::tabs-start
+
+```python
+class Solution:
+    def largestPathValue(self, colors: str, edges: list[list[int]]) -> int:
+        n = len(colors)
+        adj = [[] for _ in range(n)]
+        for u, v in edges:
+            adj[u].append(v)
+
+        visit = [False] * n
+        def dfs(node, c):
+            if visit[node]:
+                return float("inf")
+
+            visit[node] = True
+            clrCnt = 0
+            for nei in adj[node]:
+                cur = dfs(nei, c)
+                if cur == float("inf"):
+                    return cur
+                clrCnt = max(clrCnt, cur)
+            visit[node] = False
+            return clrCnt + (c == (ord(colors[node]) - ord('a')))
+
+        res = -1
+        for i in range(n):
+            for c in range(26):
+                cnt = dfs(i, c)
+                if cnt == float("inf"):
+                    return -1
+                res = max(res, cnt)
+        return res
+```
+
+```java
+public class Solution {
+    private int n;
+    private List<Integer>[] adj;
+    private boolean[] visit;
+
+    public int largestPathValue(String colors, int[][] edges) {
+        this.n = colors.length();
+        this.adj = new ArrayList[n];
+        this.visit = new boolean[n];
+
+        for (int i = 0; i < n; i++) {
+            adj[i] = new ArrayList<>();
+        }
+        for (int[] edge : edges) {
+            adj[edge[0]].add(edge[1]);
+        }
+
+        int res = -1;
+        for (int i = 0; i < n; i++) {
+            for (int c = 0; c < 26; c++) {
+                int cnt = dfs(i, c, colors);
+                if (cnt == Integer.MAX_VALUE) return -1;
+                res = Math.max(res, cnt);
+            }
+        }
+        return res;
+    }
+
+    private int dfs(int node, int c, String colors) {
+        if (visit[node]) return Integer.MAX_VALUE;
+
+        visit[node] = true;
+        int clrCnt = 0;
+        for (int nei : adj[node]) {
+            int cur = dfs(nei, c, colors);
+            if (cur == Integer.MAX_VALUE) return cur;
+            clrCnt = Math.max(clrCnt, cur);
+        }
+        visit[node] = false;
+        return clrCnt + ((colors.charAt(node) - 'a') == c ? 1 : 0);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int n;
+    vector<vector<int>> adj;
+    vector<bool> visit;
+
+    int largestPathValue(string colors, vector<vector<int>>& edges) {
+        n = colors.size();
+        adj.assign(n, vector<int>());
+        visit.assign(n, false);
+
+        for (auto& edge : edges) {
+            adj[edge[0]].push_back(edge[1]);
+        }
+
+        int res = -1;
+        for (int i = 0; i < n; i++) {
+            for (int c = 0; c < 26; c++) {
+                int cnt = dfs(i, c, colors);
+                if (cnt == 1e9) return -1;
+                res = max(res, cnt);
+            }
+        }
+        return res;
+    }
+
+private:
+    int dfs(int node, int c, string& colors) {
+        if (visit[node]) return 1e9;
+
+        visit[node] = true;
+        int clrCnt = 0;
+        for (int nei : adj[node]) {
+            int cur = dfs(nei, c, colors);
+            if (cur == 1e9) return cur;
+            clrCnt = max(clrCnt, cur);
+        }
+        visit[node] = false;
+        return clrCnt + ((colors[node] - 'a') == c ? 1 : 0);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} colors
+     * @param {number[][]} edges
+     * @return {number}
+     */
+    largestPathValue(colors, edges) {
+        const n = colors.length;
+        const adj = Array.from({ length: n }, () => []);
+        for (const [u, v] of edges) {
+            adj[u].push(v);
+        }
+
+        const visit = new Array(n).fill(false);
+        const dfs = (node, c) => {
+            if (visit[node]) return Infinity;
+
+            visit[node] = true;
+            let clrCnt = 0;
+            for (const nei of adj[node]) {
+                const cur = dfs(nei, c);
+                if (cur === Infinity) return cur;
+                clrCnt = Math.max(clrCnt, cur);
+            }
+            visit[node] = false;
+            return clrCnt + (c === colors.charCodeAt(node) - 97 ? 1 : 0);
+        };
+
+        let res = -1;
+        for (let i = 0; i < n; i++) {
+            for (let c = 0; c < 26; c++) {
+                const cnt = dfs(i, c);
+                if (cnt === Infinity) return -1;
+                res = Math.max(res, cnt);
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V * (V + E))$
+* Space complexity: $O(V + E)$
+
+> Where $V$ is the number of verticies and $E$ is the number of edges.
+
+---
+
+## 2. Depth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def largestPathValue(self, colors: str, edges: list[list[int]]) -> int:
+        adj = defaultdict(list)
+        for src, dst in edges:
+            adj[src].append(dst)
+
+        def dfs(node):
+            if node in path:
+                return float("inf")
+            if node in visit:
+                return 0
+
+            visit.add(node)
+            path.add(node)
+            colorIndex = ord(colors[node]) - ord('a')
+            count[node][colorIndex] = 1
+
+            for nei in adj[node]:
+                if dfs(nei) == float("inf"):
+                    return float("inf")
+                for c in range(26):
+                    count[node][c] = max(
+                        count[node][c], 
+                        (1 if c == colorIndex else 0) + count[nei][c]
+                    )
+
+            path.remove(node)
+            return 0
+
+        n, res = len(colors), 0
+        visit, path = set(), set()
+        count = [[0] * 26 for _ in range(n)]
+
+        for i in range(n):
+            if dfs(i) == float("inf"):
+                return -1
+            res = max(res, max(count[i]))
+
+        return res
+```
+
+```java
+public class Solution {
+    private int n;
+    private List<Integer>[] adj;
+    private boolean[] visit, path;
+    private int[][] count;
+
+    public int largestPathValue(String colors, int[][] edges) {
+        this.n = colors.length();
+        this.adj = new ArrayList[n];
+        this.visit = new boolean[n];
+        this.path = new boolean[n];
+        this.count = new int[n][26];
+
+        for (int i = 0; i < n; i++) {
+            adj[i] = new ArrayList<>();
+        }
+        for (int[] edge : edges) {
+            adj[edge[0]].add(edge[1]);
+        }
+
+        int res = 0;
+        for (int i = 0; i < n; i++) {
+            if (dfs(i, colors) == Integer.MAX_VALUE) return -1;
+            for (int c = 0; c < 26; c++) {
+                res = Math.max(res, count[i][c]);
+            }
+        }
+        return res;
+    }
+
+    private int dfs(int node, String colors) {
+        if (path[node]) return Integer.MAX_VALUE;
+        if (visit[node]) return 0;
+
+        visit[node] = true;
+        path[node] = true;
+        int colorIndex = colors.charAt(node) - 'a';
+        count[node][colorIndex] = 1;
+
+        for (int nei : adj[node]) {
+            if (dfs(nei, colors) == Integer.MAX_VALUE) {
+                return Integer.MAX_VALUE;
+            }
+            for (int c = 0; c < 26; c++) {
+                count[node][c] = Math.max(
+                    count[node][c], 
+                    (c == colorIndex ? 1 : 0) + count[nei][c]
+                );
+            }
+        }
+
+        path[node] = false;
+        return 0;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int n, INF = 1e9;
+    vector<vector<int>> adj;
+    vector<bool> visit, path;
+    vector<vector<int>> count;
+
+    int largestPathValue(string colors, vector<vector<int>>& edges) {
+        this->n = colors.size();
+        adj.resize(n);
+        visit.assign(n, false);
+        path.assign(n, false);
+        count.assign(n, vector<int>(26));
+
+        for (auto& edge : edges) {
+            adj[edge[0]].push_back(edge[1]);
+        }
+
+        int res = 0;
+        for (int i = 0; i < n; i++) {
+            if (dfs(i, colors) == INF) return -1;
+            for (int c = 0; c < 26; c++) {
+                res = max(res, count[i][c]);
+            }
+        }
+        return res;
+    }
+
+private:
+    int dfs(int node, string& colors) {
+        if (path[node]) return INF;
+        if (visit[node]) return 0;
+
+        visit[node] = true;
+        path[node] = true;
+        int colorIndex = colors[node] - 'a';
+        count[node][colorIndex] = 1;
+
+        for (int& nei : adj[node]) {
+            if (dfs(nei, colors) == INF) return INF;
+            for (int c = 0; c < 26; c++) {
+                count[node][c] = max(
+                    count[node][c], 
+                    (c == colorIndex ? 1 : 0) + count[nei][c]
+                );
+            }
+        }
+
+        path[node] = false;
+        return 0;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} colors
+     * @param {number[][]} edges
+     * @return {number}
+     */
+    largestPathValue(colors, edges) {
+        const n = colors.length;
+        const adj = Array.from({ length: n }, () => []);
+        for (const [src, dst] of edges) {
+            adj[src].push(dst);
+        }
+
+        const visit = new Array(n).fill(false);
+        const path = new Array(n).fill(false);
+        const count = Array.from({ length: n }, () => new Array(26).fill(0));
+
+        const dfs = (node) => {
+            if (path[node]) return Infinity;
+            if (visit[node]) return 0;
+
+            visit[node] = true;
+            path[node] = true;
+            const colorIndex = colors.charCodeAt(node) - 'a'.charCodeAt(0);
+            count[node][colorIndex] = 1;
+
+            for (const nei of adj[node]) {
+                if (dfs(nei) === Infinity) return Infinity;
+                for (let c = 0; c < 26; c++) {
+                    count[node][c] = Math.max(
+                        count[node][c], 
+                        (c === colorIndex ? 1 : 0) + count[nei][c]
+                    );
+                }
+            }
+
+            path[node] = false;
+            return 0;
+        };
+
+        let res = 0;
+        for (let i = 0; i < n; i++) {
+            if (dfs(i) === Infinity) return -1;
+            for (let c = 0; c < 26; c++) {
+                res = Math.max(res, count[i][c]);
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + E)$
+* Space complexity: $O(V + E)$
+
+> Where $V$ is the number of verticies and $E$ is the number of edges.
+
+---
+
+## 3. Topological Sort (Kahn's Algorithm)
+
+::tabs-start
+
+```python
+class Solution:
+    def largestPathValue(self, colors: str, edges: list[list[int]]) -> int:
+        n = len(colors)
+        adj = [[] for _ in range(n)]
+        indegree = [0] * n
+        count = [[0] * 26 for _ in range(n)]
+
+        for u, v in edges:
+            adj[u].append(v)
+            indegree[v] += 1
+
+        q = deque()
+        for i in range(n):
+            if indegree[i] == 0:
+                q.append(i)
+
+        visit = res = 0
+        while q:
+            node = q.popleft()
+            visit += 1
+            colorIndex = ord(colors[node]) - ord('a')
+            count[node][colorIndex] += 1
+            res = max(res, count[node][colorIndex])
+
+            for nei in adj[node]:
+                for c in range(26):
+                    count[nei][c] = max(count[nei][c], count[node][c])
+                
+                indegree[nei] -= 1
+                if indegree[nei] == 0:
+                    q.append(nei)
+
+        return res if visit == n else -1
+```
+
+```java
+public class Solution {
+    public int largestPathValue(String colors, int[][] edges) {
+        int n = colors.length();
+        List<Integer>[] adj = new ArrayList[n];
+        int[] indegree = new int[n];
+        int[][] count = new int[n][26];
+
+        for (int i = 0; i < n; i++) {
+            adj[i] = new ArrayList<>();
+        }
+
+        for (int[] edge : edges) {
+            adj[edge[0]].add(edge[1]);
+            indegree[edge[1]]++;
+        }
+
+        Queue<Integer> q = new LinkedList<>();
+        for (int i = 0; i < n; i++) {
+            if (indegree[i] == 0) {
+                q.add(i);
+            }
+        }
+
+        int visit = 0, res = 0;
+        while (!q.isEmpty()) {
+            int node = q.poll();
+            visit++;
+            int colorIndex = colors.charAt(node) - 'a';
+            count[node][colorIndex]++;
+            res = Math.max(res, count[node][colorIndex]);
+
+            for (int nei : adj[node]) {
+                for (int c = 0; c < 26; c++) {
+                    count[nei][c] = Math.max(count[nei][c], count[node][c]);
+                }
+                if (--indegree[nei] == 0) {
+                    q.add(nei);
+                }
+            }
+        }
+
+        return visit == n ? res : -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int largestPathValue(string colors, vector<vector<int>>& edges) {
+        int n = colors.size();
+        vector<vector<int>> adj(n);
+        vector<int> indegree(n);
+        vector<vector<int>> count(n, vector<int>(26));
+
+        for (auto& edge : edges) {
+            adj[edge[0]].push_back(edge[1]);
+            indegree[edge[1]]++;
+        }
+
+        queue<int> q;
+        for (int i = 0; i < n; i++) {
+            if (indegree[i] == 0) {
+                q.push(i);
+            }
+        }
+
+        int visit = 0, res = 0;
+        while (!q.empty()) {
+            int node = q.front();q.pop();
+            visit++;
+            int colorIndex = colors[node] - 'a';
+            count[node][colorIndex]++;
+            res = max(res, count[node][colorIndex]);
+
+            for (int& nei : adj[node]) {
+                for (int c = 0; c < 26; c++) {
+                    count[nei][c] = max(count[nei][c], count[node][c]);
+                }
+                if (--indegree[nei] == 0) {
+                    q.push(nei);
+                }
+            }
+        }
+
+        return visit == n ? res : -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} colors
+     * @param {number[][]} edges
+     * @return {number}
+     */
+    largestPathValue(colors, edges) {
+        const n = colors.length;
+        const adj = Array.from({ length: n }, () => []);
+        const indegree = new Array(n).fill(0);
+        const count = Array.from({ length: n }, () => new Array(26).fill(0));
+
+        for (const [u, v] of edges) {
+            adj[u].push(v);
+            indegree[v]++;
+        }
+
+        const q = new Queue();
+        for (let i = 0; i < n; i++) {
+            if (indegree[i] === 0) {
+                q.push(i);
+            }
+        }
+
+        let visit = 0, res = 0;
+        while (!q.isEmpty()) {
+            const node = q.pop();
+            visit++;
+            const colorIndex = colors.charCodeAt(node) - 'a'.charCodeAt(0);
+            count[node][colorIndex]++;
+            res = Math.max(res, count[node][colorIndex]);
+
+            for (const nei of adj[node]) {
+                for (let c = 0; c < 26; c++) {
+                    count[nei][c] = Math.max(count[nei][c], count[node][c]);
+                }
+                if (--indegree[nei] === 0) {
+                    q.push(nei);
+                }
+            }
+        }
+
+        return visit === n ? res : -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + E)$
+* Space complexity: $O(V + E)$
+
+> Where $V$ is the number of verticies and $E$ is the number of edges.
\ No newline at end of file
diff --git a/articles/largest-divisible-subset.md b/articles/largest-divisible-subset.md
new file mode 100644
index 000000000..c5d8fa381
--- /dev/null
+++ b/articles/largest-divisible-subset.md
@@ -0,0 +1,738 @@
+## 1. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def largestDivisibleSubset(self, nums: List[int]) -> List[int]:
+        nums.sort()
+        cache = {}  # (i, prevIndex) -> List
+
+        def dfs(i, prevIndex):
+            if i == len(nums):
+                return []
+            if (i, prevIndex) in cache:
+                return cache[(i, prevIndex)]
+
+            res = dfs(i + 1, prevIndex)  # Skip nums[i]
+            if prevIndex == -1 or nums[i] % nums[prevIndex] == 0:
+                tmp = [nums[i]] + dfs(i + 1, i)  # Include nums[i]
+                res = tmp if len(tmp) > len(res) else res
+
+            cache[(i, prevIndex)] = res
+            return res
+
+        return dfs(0, -1)
+```
+
+```java
+public class Solution {
+    private List<Integer>[][] cache;
+
+    public List<Integer> largestDivisibleSubset(int[] nums) {
+        Arrays.sort(nums);
+        int n = nums.length;
+        cache = new ArrayList[n][n + 1];
+        return dfs(0, -1, nums);
+    }
+
+    private List<Integer> dfs(int i, int prevIndex, int[] nums) {
+        if (i == nums.length) return new ArrayList<>();
+        if (cache[i][prevIndex + 1] != null) return cache[i][prevIndex + 1];
+
+        List<Integer> res = dfs(i + 1, prevIndex, nums);
+
+        if (prevIndex == -1 || nums[i] % nums[prevIndex] == 0) {
+            List<Integer> tmp = new ArrayList<>();
+            tmp.add(nums[i]);
+            tmp.addAll(dfs(i + 1, i, nums));
+            if (tmp.size() > res.size()) res = tmp;
+        }
+
+        cache[i][prevIndex + 1] = res;
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<vector<vector<int>>> cache;
+
+public:
+    vector<int> largestDivisibleSubset(vector<int>& nums) {
+        sort(nums.begin(), nums.end());
+        int n = nums.size();
+        cache = vector<vector<vector<int>>>(n, vector<vector<int>>(n + 1));
+        return dfs(0, -1, nums);
+    }
+
+    vector<int> dfs(int i, int prevIndex, vector<int>& nums) {
+        if (i == nums.size()) return {};
+        if (!cache[i][prevIndex + 1].empty()) return cache[i][prevIndex + 1];
+
+        vector<int> res = dfs(i + 1, prevIndex, nums);
+
+        if (prevIndex == -1 || nums[i] % nums[prevIndex] == 0) {
+            vector<int> tmp = {nums[i]};
+            vector<int> next = dfs(i + 1, i, nums);
+            tmp.insert(tmp.end(), next.begin(), next.end());
+            if (tmp.size() > res.size()) res = tmp;
+        }
+
+        return cache[i][prevIndex + 1] = res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    largestDivisibleSubset(nums) {
+        nums.sort((a, b) => a - b);
+        const cache = new Map();
+
+        const dfs = (i, prevIndex) => {
+            if (i === nums.length) return [];
+
+            let key = `${i},${prevIndex}`;
+            if (cache.has(key)) return cache.get(key);
+
+            let res = dfs(i + 1, prevIndex);
+            if (prevIndex === -1 || nums[i] % nums[prevIndex] === 0) {
+                let tmp = [nums[i], ...dfs(i + 1, i)];
+                if (tmp.length > res.length) res = tmp;
+            }
+
+            cache.set(key, res);
+            return res;
+        };
+
+        return dfs(0, -1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 2. Dynamic Programming (Top-Down) Space Optimized
+
+::tabs-start
+
+```python
+class Solution:
+    def largestDivisibleSubset(self, nums: List[int]) -> List[int]:
+        nums.sort()
+        cache = {}
+
+        def dfs(i):
+            if i in cache:
+                return cache[i]
+
+            res = [nums[i]]
+            for j in range(i + 1, len(nums)):
+                if nums[j] % nums[i] == 0:
+                    tmp = [nums[i]] + dfs(j)
+                    if len(tmp) > len(res):
+                        res = tmp
+
+            cache[i] = res
+            return res
+
+        res = []
+        for i in range(len(nums)):
+            tmp = dfs(i)
+            if len(tmp) > len(res):
+                res = tmp
+        return res
+```
+
+```java
+public class Solution {
+    private List<Integer>[] cache;
+
+    public List<Integer> largestDivisibleSubset(int[] nums) {
+        Arrays.sort(nums);
+        int n = nums.length;
+        cache = new ArrayList[n];
+
+        List<Integer> res = new ArrayList<>();
+        for (int i = 0; i < n; i++) {
+            List<Integer> tmp = dfs(i, nums);
+            if (tmp.size() > res.size()) {
+                res = tmp;
+            }
+        }
+        return res;
+    }
+
+    private List<Integer> dfs(int i, int[] nums) {
+        if (cache[i] != null) return cache[i];
+
+        List<Integer> res = new ArrayList<>();
+        res.add(nums[i]);
+        for (int j = i + 1; j < nums.length; j++) {
+            if (nums[j] % nums[i] == 0) {
+                List<Integer> tmp = new ArrayList<>();
+                tmp.add(nums[i]);
+                tmp.addAll(dfs(j, nums));
+
+                if (tmp.size() > res.size()) {
+                    res = tmp;
+                }
+            }
+        }
+        return cache[i] = res;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<vector<int>> cache;
+
+public:
+    vector<int> largestDivisibleSubset(vector<int>& nums) {
+        sort(nums.begin(), nums.end());
+        int n = nums.size();
+        cache.resize(n, vector<int>());
+
+        vector<int> res;
+        for (int i = 0; i < n; i++) {
+            vector<int> tmp = dfs(i, nums);
+            if (tmp.size() > res.size()) {
+                res = tmp;
+            }
+        }
+        return res;
+    }
+
+    vector<int> dfs(int i, vector<int>& nums) {
+        if (!cache[i].empty()) return cache[i];
+
+        vector<int> res = {nums[i]};
+        for (int j = i + 1; j < nums.size(); j++) {
+            if (nums[j] % nums[i] == 0) {
+                vector<int> tmp = {nums[i]};
+                vector<int> next = dfs(j, nums);
+                tmp.insert(tmp.end(), next.begin(), next.end());
+
+                if (tmp.size() > res.size()) {
+                    res = tmp;
+                }
+            }
+        }
+        return cache[i] = res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    largestDivisibleSubset(nums) {
+        nums.sort((a, b) => a - b);
+        const n = nums.length;
+        const cache = new Array(n).fill(null);
+
+        const dfs = (i) => {
+            if (cache[i] !== null) return cache[i];
+
+            let res = [nums[i]];
+            for (let j = i + 1; j < n; j++) {
+                if (nums[j] % nums[i] === 0) {
+                    let tmp = [nums[i], ...dfs(j)];
+                    if (tmp.length > res.length) {
+                        res = tmp;
+                    }
+                }
+            }
+            return (cache[i] = res);
+        };
+
+        let res = [];
+        for (let i = 0; i < n; i++) {
+            let tmp = dfs(i);
+            if (tmp.length > res.length) {
+                res = tmp;
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def largestDivisibleSubset(self, nums: List[int]) -> List[int]:
+        nums.sort()
+        dp = [[num] for num in nums]  # dp[i] = longest start at i
+        res = []
+        for i in range(len(nums) - 1, -1, -1):
+            for j in range(i + 1, len(nums)):
+                if nums[j] % nums[i] == 0:
+                    tmp = [nums[i]] + dp[j]
+                    dp[i] = tmp if len(tmp) > len(dp[i]) else dp[i]
+            res = dp[i] if len(dp[i]) > len(res) else res
+        return res
+```
+
+```java
+public class Solution {
+    public List<Integer> largestDivisibleSubset(int[] nums) {
+        Arrays.sort(nums);
+        int n = nums.length;
+        List<Integer>[] dp = new ArrayList[n];
+        List<Integer> res = new ArrayList<>();
+
+        for (int i = n - 1; i >= 0; i--) {
+            dp[i] = new ArrayList<>();
+            dp[i].add(nums[i]);
+
+            for (int j = i + 1; j < n; j++) {
+                if (nums[j] % nums[i] == 0) {
+                    List<Integer> tmp = new ArrayList<>();
+                    tmp.add(nums[i]);
+                    tmp.addAll(dp[j]);
+
+                    if (tmp.size() > dp[i].size()) {
+                        dp[i] = tmp;
+                    }
+                }
+            }
+            if (dp[i].size() > res.size()) {
+                res = dp[i];
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> largestDivisibleSubset(vector<int>& nums) {
+        sort(nums.begin(), nums.end());
+        int n = nums.size();
+        vector<vector<int>> dp(n);
+        vector<int> res;
+
+        for (int i = n - 1; i >= 0; i--) {
+            dp[i].push_back(nums[i]);
+
+            for (int j = i + 1; j < n; j++) {
+                if (nums[j] % nums[i] == 0) {
+                    vector<int> tmp = dp[j];
+                    tmp.insert(tmp.begin(), nums[i]);
+
+                    if (tmp.size() > dp[i].size()) {
+                        dp[i] = tmp;
+                    }
+                }
+            }
+            if (dp[i].size() > res.size()) {
+                res = dp[i];
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    largestDivisibleSubset(nums) {
+        nums.sort((a, b) => a - b);
+        const n = nums.length;
+        const dp = new Array(n).fill(0).map(() => []);
+        let res = [];
+
+        for (let i = n - 1; i >= 0; i--) {
+            dp[i] = [nums[i]];
+
+            for (let j = i + 1; j < n; j++) {
+                if (nums[j] % nums[i] === 0) {
+                    let tmp = [nums[i], ...dp[j]];
+
+                    if (tmp.length > dp[i].length) {
+                        dp[i] = tmp;
+                    }
+                }
+            }
+            if (dp[i].length > res.length) {
+                res = dp[i];
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Dynamic Programming (Top-Down) + Tracing
+
+::tabs-start
+
+```python
+class Solution:
+    def largestDivisibleSubset(self, nums: List[int]) -> List[int]:
+        nums.sort()
+        n = len(nums)
+        dp = [[-1, -1] for _ in range(n)]  # dp[i] = [maxLen, prevIdx]
+
+        def dfs(i):
+            if dp[i][0] != -1:
+                return dp[i][0]
+
+            dp[i][0] = 1
+            for j in range(i + 1, n):
+                if nums[j] % nums[i] == 0:
+                    length = dfs(j) + 1
+                    if length > dp[i][0]:
+                        dp[i][0] = length
+                        dp[i][1] = j
+
+            return dp[i][0]
+
+        max_len, start_index = 1, 0
+        for i in range(n):
+            if dfs(i) > max_len:
+                max_len = dfs(i)
+                start_index = i
+
+        subset = []
+        while start_index != -1:
+            subset.append(nums[start_index])
+            start_index = dp[start_index][1]
+
+        return subset
+```
+
+```java
+public class Solution {
+    private int[][] dp;
+
+    public List<Integer> largestDivisibleSubset(int[] nums) {
+        Arrays.sort(nums);
+        int n = nums.length;
+        dp = new int[n][2];
+        for (int i = 0; i < n; i++) {
+            dp[i][0] = -1;
+            dp[i][1] = -1;
+        }
+
+        int maxLen = 1, startIndex = 0;
+        for (int i = 0; i < n; i++) {
+            if (dfs(i, nums) > maxLen) {
+                maxLen = dp[i][0];
+                startIndex = i;
+            }
+        }
+
+        List<Integer> subset = new ArrayList<>();
+        while (startIndex != -1) {
+            subset.add(nums[startIndex]);
+            startIndex = dp[startIndex][1];
+        }
+        return subset;
+    }
+
+    private int dfs(int i, int[] nums) {
+        if (dp[i][0] != -1) return dp[i][0];
+
+        dp[i][0] = 1;
+        for (int j = i + 1; j < nums.length; j++) {
+            if (nums[j] % nums[i] == 0) {
+                int length = dfs(j, nums) + 1;
+                if (length > dp[i][0]) {
+                    dp[i][0] = length;
+                    dp[i][1] = j;
+                }
+            }
+        }
+        return dp[i][0];
+    }
+}
+```
+
+```cpp
+class Solution {
+    vector<vector<int>> dp;
+
+public:
+    vector<int> largestDivisibleSubset(vector<int>& nums) {
+        sort(nums.begin(), nums.end());
+        int n = nums.size();
+        dp.assign(n, vector<int>(2, -1));
+
+        int maxLen = 1, startIndex = 0;
+        for (int i = 0; i < n; i++) {
+            if (dfs(i, nums) > maxLen) {
+                maxLen = dp[i][0];
+                startIndex = i;
+            }
+        }
+
+        vector<int> subset;
+        while (startIndex != -1) {
+            subset.push_back(nums[startIndex]);
+            startIndex = dp[startIndex][1];
+        }
+        return subset;
+    }
+
+private:
+    int dfs(int i, vector<int>& nums) {
+        if (dp[i][0] != -1) return dp[i][0];
+
+        dp[i][0] = 1;
+        for (int j = i + 1; j < nums.size(); j++) {
+            if (nums[j] % nums[i] == 0) {
+                int length = dfs(j, nums) + 1;
+                if (length > dp[i][0]) {
+                    dp[i][0] = length;
+                    dp[i][1] = j;
+                }
+            }
+        }
+        return dp[i][0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    largestDivisibleSubset(nums) {
+        nums.sort((a, b) => a - b);
+        let n = nums.length;
+        let dp = Array.from({ length: n }, () => [-1, -1]); // dp[i] = [maxLen, prevIdx]
+
+        const dfs = (i) => {
+            if (dp[i][0] !== -1) return dp[i][0];
+
+            dp[i][0] = 1;
+            for (let j = i + 1; j < n; j++) {
+                if (nums[j] % nums[i] === 0) {
+                    let length = dfs(j) + 1;
+                    if (length > dp[i][0]) {
+                        dp[i][0] = length;
+                        dp[i][1] = j;
+                    }
+                }
+            }
+            return dp[i][0];
+        };
+
+        let maxLen = 1, startIndex = 0;
+        for (let i = 0; i < n; i++) {
+            if (dfs(i) > maxLen) {
+                maxLen = dfs(i);
+                startIndex = i;
+            }
+        }
+
+        let subset = [];
+        while (startIndex !== -1) {
+            subset.push(nums[startIndex]);
+            startIndex = dp[startIndex][1];
+        }
+        return subset;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 5. Dynamic Programming (Bottom-Up) + Tracing
+
+::tabs-start
+
+```python
+class Solution:
+    def largestDivisibleSubset(self, nums: List[int]) -> List[int]:
+        nums.sort()
+        n = len(nums)
+        dp = [[1, -1] for _ in range(n)]  # dp[i] = [maxLen, prevIdx]
+
+        max_len, start_index = 1, 0
+
+        for i in range(n):
+            for j in range(i):
+                if nums[i] % nums[j] == 0 and dp[j][0] + 1 > dp[i][0]:
+                    dp[i][0] = dp[j][0] + 1
+                    dp[i][1] = j
+
+            if dp[i][0] > max_len:
+                max_len = dp[i][0]
+                start_index = i
+
+        subset = []
+        while start_index != -1:
+            subset.append(nums[start_index])
+            start_index = dp[start_index][1]
+        return subset
+```
+
+```java
+public class Solution {
+    public List<Integer> largestDivisibleSubset(int[] nums) {
+        Arrays.sort(nums);
+        int n = nums.length;
+        int[][] dp = new int[n][2]; // dp[i] = {maxLen, prevIdx}
+
+        int maxLen = 1, startIndex = 0;
+        for (int i = 0; i < n; i++) {
+            dp[i][0] = 1;
+            dp[i][1] = -1;
+            for (int j = 0; j < i; j++) {
+                if (nums[i] % nums[j] == 0 && dp[j][0] + 1 > dp[i][0]) {
+                    dp[i][0] = dp[j][0] + 1;
+                    dp[i][1] = j;
+                }
+            }
+
+            if (dp[i][0] > maxLen) {
+                maxLen = dp[i][0];
+                startIndex = i;
+            }
+        }
+
+        List<Integer> subset = new ArrayList<>();
+        while (startIndex != -1) {
+            subset.add(nums[startIndex]);
+            startIndex = dp[startIndex][1];
+        }
+        return subset;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> largestDivisibleSubset(vector<int>& nums) {
+        sort(nums.begin(), nums.end());
+        int n = nums.size();
+        vector<vector<int>> dp(n, vector<int>(2, -1)); // dp[i] = {maxLen, prevIdx}
+
+        int maxLen = 1, startIndex = 0;
+        for (int i = 0; i < n; i++) {
+            dp[i][0] = 1;
+            dp[i][1] = -1;
+            for (int j = 0; j < i; j++) {
+                if (nums[i] % nums[j] == 0 && dp[j][0] + 1 > dp[i][0]) {
+                    dp[i][0] = dp[j][0] + 1;
+                    dp[i][1] = j;
+                }
+            }
+
+            if (dp[i][0] > maxLen) {
+                maxLen = dp[i][0];
+                startIndex = i;
+            }
+        }
+
+        vector<int> subset;
+        while (startIndex != -1) {
+            subset.push_back(nums[startIndex]);
+            startIndex = dp[startIndex][1];
+        }
+        return subset;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    largestDivisibleSubset(nums) {
+        nums.sort((a, b) => a - b);
+        let n = nums.length;
+        let dp = Array.from({ length: n }, () => [1, -1]); // dp[i] = [maxLen, prevIdx]
+
+        let maxLen = 1, startIndex = 0;
+        for (let i = 0; i < n; i++) {
+            for (let j = 0; j < i; j++) {
+                if (nums[i] % nums[j] === 0 && dp[j][0] + 1 > dp[i][0]) {
+                    dp[i][0] = dp[j][0] + 1;
+                    dp[i][1] = j;
+                }
+            }
+
+            if (dp[i][0] > maxLen) {
+                maxLen = dp[i][0];
+                startIndex = i;
+            }
+        }
+
+        let subset = [];
+        while (startIndex !== -1) {
+            subset.push(nums[startIndex]);
+            startIndex = dp[startIndex][1];
+        }
+        return subset;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/largest-local-values-in-a-matrix.md b/articles/largest-local-values-in-a-matrix.md
new file mode 100644
index 000000000..169c4d992
--- /dev/null
+++ b/articles/largest-local-values-in-a-matrix.md
@@ -0,0 +1,439 @@
+## 1. Iteration
+
+::tabs-start
+
+```python
+class Solution:
+    def largestLocal(self, grid: List[List[int]]) -> List[List[int]]:
+        N = len(grid)
+        res = [[0] * (N - 2) for _ in range(N - 2)]
+
+        for i in range(N - 2):
+            for j in range(N - 2):
+                for r in range(i, i + 3):
+                    for c in range(j, j + 3):
+                        res[i][j] = max(res[i][j], grid[r][c])
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[][] largestLocal(int[][] grid) {
+        int N = grid.length;
+        int[][] res = new int[N - 2][N - 2];
+
+        for (int i = 0; i < N - 2; i++) {
+            for (int j = 0; j < N - 2; j++) {
+                for (int r = i; r < i + 3; r++) {
+                    for (int c = j; c < j + 3; c++) {
+                        res[i][j] = Math.max(res[i][j], grid[r][c]);
+                    }
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> largestLocal(vector<vector<int>>& grid) {
+        int N = grid.size();
+        vector<vector<int>> res(N - 2, vector<int>(N - 2, 0));
+
+        for (int i = 0; i < N - 2; i++) {
+            for (int j = 0; j < N - 2; j++) {
+                for (int r = i; r < i + 3; r++) {
+                    for (int c = j; c < j + 3; c++) {
+                        res[i][j] = max(res[i][j], grid[r][c]);
+                    }
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number[][]}
+     */
+    largestLocal(grid) {
+        const N = grid.length;
+        const res = Array.from({ length: N - 2 }, () => Array(N - 2).fill(0));
+
+        for (let i = 0; i < N - 2; i++) {
+            for (let j = 0; j < N - 2; j++) {
+                for (let r = i; r < i + 3; r++) {
+                    for (let c = j; c < j + 3; c++) {
+                        res[i][j] = Math.max(res[i][j], grid[r][c]);
+                    }
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n ^ 2)$ for the output array.
+
+---
+
+## 2. Generalized Approach (Sparse Table)
+
+::tabs-start
+
+```python
+class SparseTable:
+    def __init__(self, grid: List[List[int]]):
+        self.n = len(grid)
+        self.LOG = [0] * (self.n + 1)
+        for i in range(2, self.n + 1):
+            self.LOG[i] = self.LOG[i // 2] + 1
+
+        self.sparse_table = [[[[0] * (self.LOG[self.n] + 1) for _ in range(self.LOG[self.n] + 1)] for _ in range(self.n)] for _ in range(self.n)]
+
+        for r in range(self.n):
+            for c in range(self.n):
+                self.sparse_table[r][c][0][0] = grid[r][c]
+
+        for i in range(self.LOG[self.n] + 1):
+            for j in range(self.LOG[self.n] + 1):
+                for r in range(self.n - (1 << i) + 1):
+                    for c in range(self.n - (1 << j) + 1):
+                        if i == 0 and j == 0:
+                            self.sparse_table[r][c][i][j] = grid[r][c]
+                        elif i == 0:
+                            self.sparse_table[r][c][i][j] = max(
+                                self.sparse_table[r][c][i][j - 1],
+                                self.sparse_table[r][c + (1 << (j - 1))][i][j - 1],
+                            )
+                        elif j == 0:
+                            self.sparse_table[r][c][i][j] = max(
+                                self.sparse_table[r][c][i - 1][j],
+                                self.sparse_table[r + (1 << (i - 1))][c][i - 1][j],
+                            )
+                        else:
+                            self.sparse_table[r][c][i][j] = max(
+                                self.sparse_table[r][c][i - 1][j - 1],
+                                self.sparse_table[r + (1 << (i - 1))][c][i - 1][j - 1],
+                                self.sparse_table[r][c + (1 << (j - 1))][i - 1][j - 1],
+                                self.sparse_table[r + (1 << (i - 1))][c + (1 << (j - 1))][i - 1][j - 1],
+                            )
+
+    def query(self, x1: int, y1: int, x2: int, y2: int) -> int:
+        lx, ly = self.LOG[x2 - x1 + 1], self.LOG[y2 - y1 + 1]
+        return max(
+            self.sparse_table[x1][y1][lx][ly],
+            self.sparse_table[x2 - (1 << lx) + 1][y1][lx][ly],
+            self.sparse_table[x1][y2 - (1 << ly) + 1][lx][ly],
+            self.sparse_table[x2 - (1 << lx) + 1][y2 - (1 << ly) + 1][lx][ly],
+        )
+
+
+class Solution:
+    def largestLocal(self, grid: List[List[int]]) -> List[List[int]]:
+        N, k = len(grid), 3
+        sparse_table = SparseTable(grid)
+        res = [[0] * (N - k + 1) for _ in range(N - k + 1)]
+
+        for i in range(N - k + 1):
+            for j in range(N - k + 1):
+                res[i][j] = sparse_table.query(i, j, i + k - 1, j + k - 1)
+
+        return res
+```
+
+```java
+class SparseTable {
+    private int[][][][] sparseTable;
+    private int[] log;
+    private int n;
+
+    public SparseTable(int[][] grid) {
+        n = grid.length;
+        log = new int[n + 1];
+        for (int i = 2; i <= n; i++) {
+            log[i] = log[i >> 1] + 1;
+        }
+
+        int maxLog = log[n];
+        sparseTable = new int[n][n][maxLog + 1][maxLog + 1];
+
+        for (int r = 0; r < n; r++) {
+            for (int c = 0; c < n; c++) {
+                sparseTable[r][c][0][0] = grid[r][c];
+            }
+        }
+
+        for (int i = 0; i <= maxLog; i++) {
+            for (int j = 0; j <= maxLog; j++) {
+                for (int r = 0; r + (1 << i) <= n; r++) {
+                    for (int c = 0; c + (1 << j) <= n; c++) {
+                        if (i == 0 && j == 0) continue;
+                        if (i == 0) {
+                            sparseTable[r][c][i][j] = Math.max(
+                                sparseTable[r][c][i][j - 1],
+                                sparseTable[r][c + (1 << (j - 1))][i][j - 1]
+                            );
+                        } else if (j == 0) {
+                            sparseTable[r][c][i][j] = Math.max(
+                                sparseTable[r][c][i - 1][j],
+                                sparseTable[r + (1 << (i - 1))][c][i - 1][j]
+                            );
+                        } else {
+                            sparseTable[r][c][i][j] = Math.max(
+                                Math.max(sparseTable[r][c][i - 1][j - 1], sparseTable[r + (1 << (i - 1))][c][i - 1][j - 1]),
+                                Math.max(sparseTable[r][c + (1 << (j - 1))][i - 1][j - 1],
+                                         sparseTable[r + (1 << (i - 1))][c + (1 << (j - 1))][i - 1][j - 1])
+                            );
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    public int query(int x1, int y1, int x2, int y2) {
+        int lx = log[x2 - x1 + 1];
+        int ly = log[y2 - y1 + 1];
+        return Math.max(
+            Math.max(sparseTable[x1][y1][lx][ly], sparseTable[x2 - (1 << lx) + 1][y1][lx][ly]),
+            Math.max(sparseTable[x1][y2 - (1 << ly) + 1][lx][ly],
+                     sparseTable[x2 - (1 << lx) + 1][y2 - (1 << ly) + 1][lx][ly])
+        );
+    }
+}
+
+public class Solution {
+    public int[][] largestLocal(int[][] grid) {
+        int n = grid.length;
+        int k = 3;
+        SparseTable st = new SparseTable(grid);
+        int[][] res = new int[n - k + 1][n - k + 1];
+
+        for (int i = 0; i <= n - k; i++) {
+            for (int j = 0; j <= n - k; j++) {
+                res[i][j] = st.query(i, j, i + k - 1, j + k - 1);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class SparseTable {
+public:
+    vector<vector<vector<vector<int>>>> sparseTable;
+    vector<int> log;
+    int n;
+
+    SparseTable(vector<vector<int>>& grid) {
+        n = grid.size();
+        log.resize(n + 1, 0);
+        for (int i = 2; i <= n; i++) {
+            log[i] = log[i / 2] + 1;
+        }
+
+        int maxLog = log[n];
+        sparseTable.resize(n, vector<vector<vector<int>>>(n, vector<vector<int>>(maxLog + 1, vector<int>(maxLog + 1))));
+
+        for (int r = 0; r < n; r++) {
+            for (int c = 0; c < n; c++) {
+                sparseTable[r][c][0][0] = grid[r][c];
+            }
+        }
+
+        for (int i = 0; i <= maxLog; i++) {
+            for (int j = 0; j <= maxLog; j++) {
+                for (int r = 0; r + (1 << i) <= n; r++) {
+                    for (int c = 0; c + (1 << j) <= n; c++) {
+                        if (i == 0 && j == 0) continue;
+                        if (i == 0) {
+                            sparseTable[r][c][i][j] = max(
+                                sparseTable[r][c][i][j - 1],
+                                sparseTable[r][c + (1 << (j - 1))][i][j - 1]
+                            );
+                        } else if (j == 0) {
+                            sparseTable[r][c][i][j] = max(
+                                sparseTable[r][c][i - 1][j],
+                                sparseTable[r + (1 << (i - 1))][c][i - 1][j]
+                            );
+                        } else {
+                            sparseTable[r][c][i][j] = max(
+                                max(sparseTable[r][c][i - 1][j - 1], sparseTable[r + (1 << (i - 1))][c][i - 1][j - 1]),
+                                max(sparseTable[r][c + (1 << (j - 1))][i - 1][j - 1],
+                                    sparseTable[r + (1 << (i - 1))][c + (1 << (j - 1))][i - 1][j - 1])
+                            );
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    int query(int x1, int y1, int x2, int y2) {
+        int lx = log[x2 - x1 + 1];
+        int ly = log[y2 - y1 + 1];
+        return max(
+            max(sparseTable[x1][y1][lx][ly], sparseTable[x2 - (1 << lx) + 1][y1][lx][ly]),
+            max(sparseTable[x1][y2 - (1 << ly) + 1][lx][ly],
+                sparseTable[x2 - (1 << lx) + 1][y2 - (1 << ly) + 1][lx][ly])
+        );
+    }
+};
+
+class Solution {
+public:
+    vector<vector<int>> largestLocal(vector<vector<int>>& grid) {
+        int n = grid.size(), k = 3;
+        SparseTable st(grid);
+        vector<vector<int>> res(n - k + 1, vector<int>(n - k + 1));
+
+        for (int i = 0; i <= n - k; i++) {
+            for (int j = 0; j <= n - k; j++) {
+                res[i][j] = st.query(i, j, i + k - 1, j + k - 1);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class SparseTable {
+    /**
+     * @constructor
+     * @param {number[][]} grid
+     */
+    constructor(grid) {
+        this.n = grid.length;
+        this.log = Array(this.n + 1).fill(0);
+        for (let i = 2; i <= this.n; i++) {
+            this.log[i] = this.log[Math.floor(i / 2)] + 1;
+        }
+
+        const maxLog = this.log[this.n];
+        this.sparseTable = Array.from({ length: this.n }, () =>
+            Array.from({ length: this.n }, () =>
+                Array.from({ length: maxLog + 1 }, () =>
+                    Array(maxLog + 1).fill(0)
+                )
+            )
+        );
+
+        for (let r = 0; r < this.n; r++) {
+            for (let c = 0; c < this.n; c++) {
+                this.sparseTable[r][c][0][0] = grid[r][c];
+            }
+        }
+
+        for (let i = 0; i <= maxLog; i++) {
+            for (let j = 0; j <= maxLog; j++) {
+                for (let r = 0; r + (1 << i) <= this.n; r++) {
+                    for (let c = 0; c + (1 << j) <= this.n; c++) {
+                        if (i === 0 && j === 0) continue;
+                        if (i === 0) {
+                            this.sparseTable[r][c][i][j] = Math.max(
+                                this.sparseTable[r][c][i][j - 1],
+                                this.sparseTable[r][c + (1 << (j - 1))][i][j - 1]
+                            );
+                        } else if (j === 0) {
+                            this.sparseTable[r][c][i][j] = Math.max(
+                                this.sparseTable[r][c][i - 1][j],
+                                this.sparseTable[r + (1 << (i - 1))][c][i - 1][j]
+                            );
+                        } else {
+                            this.sparseTable[r][c][i][j] = Math.max(
+                                Math.max(
+                                    this.sparseTable[r][c][i - 1][j - 1],
+                                    this.sparseTable[r + (1 << (i - 1))][c][i - 1][j - 1]
+                                ),
+                                Math.max(
+                                    this.sparseTable[r][c + (1 << (j - 1))][i - 1][j - 1],
+                                    this.sparseTable[r + (1 << (i - 1))][c + (1 << (j - 1))][i - 1][j - 1]
+                                )
+                            );
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    /**
+     * @param {number} x1
+     * @param {number} y1
+     * @param {number} x2
+     * @param {number} y2
+     * @return {number}
+     */
+    query(x1, y1, x2, y2) {
+        const lx = this.log[x2 - x1 + 1];
+        const ly = this.log[y2 - y1 + 1];
+        return Math.max(
+            Math.max(
+                this.sparseTable[x1][y1][lx][ly],
+                this.sparseTable[x2 - (1 << lx) + 1][y1][lx][ly]
+            ),
+            Math.max(
+                this.sparseTable[x1][y2 - (1 << ly) + 1][lx][ly],
+                this.sparseTable[x2 - (1 << lx) + 1][y2 - (1 << ly) + 1][lx][ly]
+            )
+        );
+    }
+}
+
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number[][]}
+     */
+    largestLocal(grid) {
+        const n = grid.length, k = 3;
+        const st = new SparseTable(grid);
+        const res = Array.from({ length: n - k + 1 }, () =>
+            Array(n - k + 1).fill(0)
+        );
+
+        for (let i = 0; i <= n - k; i++) {
+            for (let j = 0; j <= n - k; j++) {
+                res[i][j] = st.query(i, j, i + k - 1, j + k - 1);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 \log ^ 2 n)$
+* Space complexity:
+    * $O(n ^ 2 \log ^ 2 n)$ extra space.
+    * $O((n - k) ^ 2)$ for the output matrix.
+
+> Where $n$ is the size of the given square grid and $k$ is the fixed size of the submatrix window.
\ No newline at end of file
diff --git a/articles/largest-number.md b/articles/largest-number.md
new file mode 100644
index 000000000..5b1822fb5
--- /dev/null
+++ b/articles/largest-number.md
@@ -0,0 +1,188 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def largestNumber(self, nums: List[int]) -> str:
+        arr = [str(num) for num in nums]
+        
+        res = []
+        while arr:
+            maxi = 0
+            for i in range(1, len(arr)):
+                if arr[i] + arr[maxi] > arr[maxi] + arr[i]:
+                    maxi = i
+            res.append(arr[maxi])
+            arr.pop(maxi)
+        
+        result = "".join(res)
+        return result if result[0] != '0' else '0'
+```
+
+```java
+public class Solution {
+    public String largestNumber(int[] nums) {
+        List<String> arr = new ArrayList<>();
+        for (int num : nums) {
+            arr.add(String.valueOf(num));
+        }
+
+        StringBuilder res = new StringBuilder();
+        while (!arr.isEmpty()) {
+            int maxi = 0;
+            for (int i = 1; i < arr.size(); i++) {
+                if ((arr.get(i) + arr.get(maxi)).compareTo(arr.get(maxi) + arr.get(i)) > 0) {
+                    maxi = i;
+                }
+            }
+            res.append(arr.get(maxi));
+            arr.remove(maxi);
+        }
+
+        String result = res.toString();
+        return result.charAt(0) == '0' ? "0" : result;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string largestNumber(vector<int>& nums) {
+        vector<string> arr;
+        for (int num : nums) {
+            arr.push_back(to_string(num));
+        }
+
+        string res;
+        while (!arr.empty()) {
+            int maxi = 0;
+            for (int i = 1; i < arr.size(); i++) {
+                if (arr[i] + arr[maxi] > arr[maxi] + arr[i]) {
+                    maxi = i;
+                }
+            }
+            res += arr[maxi];
+            arr.erase(arr.begin() + maxi);
+        }
+
+        return res[0] == '0' ? "0" : res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {string}
+     */
+    largestNumber(nums) {
+        let arr = nums.map(String);
+    
+        let res = [];
+        while (arr.length > 0) {
+            let maxi = 0;
+            for (let i = 1; i < arr.length; i++) {
+                if (arr[i] + arr[maxi] > arr[maxi] + arr[i]) {
+                    maxi = i;
+                }
+            }
+            res.push(arr[maxi]);
+            arr.splice(maxi, 1);
+        }
+
+        let result = res.join("");
+        return result[0] === "0" ? "0" : result;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * N)$
+* Space complexity: $O(N)$
+
+> Where $n$ is the size of the array $nums$ and $N$ is the total number of digits in the array $nums$.
+
+---
+
+## 2. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def largestNumber(self, nums: List[int]) -> str:
+        for i, num in enumerate(nums):
+            nums[i] = str(num)
+
+        def compare(n1, n2):
+            if n1 + n2 > n2 + n1:
+                return -1
+            else:
+                return 1
+        nums = sorted(nums, key=cmp_to_key(compare))
+        return str(int("".join(nums)))
+```
+
+```java
+public class Solution {
+    public String largestNumber(int[] nums) {
+        String[] arr = Arrays.stream(nums).mapToObj(String::valueOf).toArray(String[]::new);
+        Arrays.sort(arr, (a, b) -> (b + a).compareTo(a + b));
+        String res = String.join("", arr);
+        return res.charAt(0) == '0' ? "0" : res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string largestNumber(vector<int>& nums) {
+        vector<string> arr;
+        for (int num : nums) {
+            arr.push_back(to_string(num));
+        }
+
+        sort(arr.begin(), arr.end(), [](string& a, string& b) {
+            return a + b > b + a;
+        });
+
+        string res;
+        for (string& num : arr) {
+            res += num;
+        }
+
+        return res[0] == '0' ? "0" : res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {string}
+     */
+    largestNumber(nums) {
+        let arr = nums.map(String);
+        arr.sort((a, b) => ((b + a) - (a + b)));
+        let res = arr.join("");
+        return res[0] === "0" ? "0" : res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(N \log N)$
+* Space complexity: $O(N)$
+
+> Where $N$ is the total number of digits in the array $nums$.
\ No newline at end of file
diff --git a/articles/largest-odd-number-in-string.md b/articles/largest-odd-number-in-string.md
new file mode 100644
index 000000000..566fb7c11
--- /dev/null
+++ b/articles/largest-odd-number-in-string.md
@@ -0,0 +1,166 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def largestOddNumber(self, num: str) -> str:
+        res = ""
+        for i in range(len(num)):
+            for j in range(i, len(num)):
+                ones_digit = ord(num[j]) - ord('0')
+                if ones_digit & 1:
+                    cur = num[i:j + 1]
+                    if len(res) < len(cur) or (len(cur) == len(res) and res < cur):
+                        res = cur
+        return res
+```
+
+```java
+public class Solution {
+    public String largestOddNumber(String num) {
+        String res = "";
+        int n = num.length();
+        
+        for (int i = 0; i < n; i++) {
+            for (int j = i; j < n; j++) {
+                int onesDigit = num.charAt(j) - '0';
+                if ((onesDigit & 1) == 1) {
+                    String cur = num.substring(i, j + 1);
+                    if (res.length() < cur.length() || 
+                       (res.length() == cur.length() && res.compareTo(cur) < 0)) {
+                        res = cur;
+                    }
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string largestOddNumber(string num) {
+        string res = "";
+        int n = num.size();
+
+        for (int i = 0; i < n; i++) {
+            for (int j = i; j < n; j++) {
+                int onesDigit = num[j] - '0';
+                if (onesDigit & 1) {
+                    string cur = num.substr(i, j - i + 1);
+                    if (res.size() < cur.size() || 
+                       (res.size() == cur.size() && res < cur)) {
+                        res = cur;
+                    }
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} num
+     * @return {string}
+     */
+    largestOddNumber(num) {
+        let res = "";
+        const n = num.length;
+
+        for (let i = 0; i < n; i++) {
+            for (let j = i; j < n; j++) {
+                const onesDigit = num[j].charCodeAt(0) - '0'.charCodeAt(0);
+                if (onesDigit & 1) {
+                    const cur = num.slice(i, j + 1);
+                    if (res.length < cur.length || 
+                    (res.length === cur.length && res < cur)) {
+                        res = cur;
+                    }
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 3)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Find The Rightmost Odd Digit
+
+::tabs-start
+
+```python
+class Solution:
+    def largestOddNumber(self, num: str) -> str:
+        for i in range(len(num) - 1, -1, -1):
+            if int(num[i]) % 2:
+                return num[:i + 1]
+        return ""
+```
+
+```java
+public class Solution {
+    public String largestOddNumber(String num) {
+        for (int i = num.length() - 1; i >= 0; i--) {
+            if ((num.charAt(i) - '0') % 2 == 1) {
+                return num.substring(0, i + 1);
+            }
+        }
+        return "";
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string largestOddNumber(string num) {
+        for (int i = num.size() - 1; i >= 0; i--) {
+            if ((num[i] - '0') % 2 == 1) {
+                return num.substr(0, i + 1);
+            }
+        }
+        return "";
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} num
+     * @return {string}
+     */
+    largestOddNumber(num) {
+        for (let i = num.length - 1; i >= 0; i--) {
+            if (parseInt(num[i]) % 2 === 1) {
+                return num.slice(0, i + 1);
+            }
+        }
+        return "";
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ for the output string.
\ No newline at end of file
diff --git a/articles/largest-rectangle-in-histogram.md b/articles/largest-rectangle-in-histogram.md
index 916fb2827..75df88ffe 100644
--- a/articles/largest-rectangle-in-histogram.md
+++ b/articles/largest-rectangle-in-histogram.md
@@ -142,6 +142,96 @@ public class Solution {
 }
 ```
 
+```go
+func largestRectangleArea(heights []int) int {
+    n := len(heights)
+    maxArea := 0
+    
+    for i := 0; i < n; i++ {
+        height := heights[i]
+        
+        rightMost := i + 1
+        for rightMost < n && heights[rightMost] >= height {
+            rightMost++
+        }
+        
+        leftMost := i
+        for leftMost >= 0 && heights[leftMost] >= height {
+            leftMost--
+        }
+        
+        rightMost--
+        leftMost++
+        
+        area := height * (rightMost - leftMost + 1)
+        if area > maxArea {
+            maxArea = area
+        }
+    }
+    
+    return maxArea
+}
+```
+
+```kotlin
+class Solution {
+    fun largestRectangleArea(heights: IntArray): Int {
+        val n = heights.size
+        var maxArea = 0
+        
+        for (i in 0 until n) {
+            val height = heights[i]
+            
+            var rightMost = i + 1
+            while (rightMost < n && heights[rightMost] >= height) {
+                rightMost++
+            }
+            
+            var leftMost = i
+            while (leftMost >= 0 && heights[leftMost] >= height) {
+                leftMost--
+            }
+            
+            rightMost--
+            leftMost++
+            
+            maxArea = maxOf(maxArea, height * (rightMost - leftMost + 1))
+        }
+        
+        return maxArea
+    }
+}
+```
+
+```swift
+class Solution {
+    func largestRectangleArea(_ heights: [Int]) -> Int {
+        let n = heights.count
+        var maxArea = 0
+
+        for i in 0..<n {
+            let height = heights[i]
+
+            var rightMost = i + 1
+            while rightMost < n && heights[rightMost] >= height {
+                rightMost += 1
+            }
+
+            var leftMost = i
+            while leftMost >= 0 && heights[leftMost] >= height {
+                leftMost -= 1
+            }
+
+            rightMost -= 1
+            leftMost += 1
+            maxArea = max(maxArea, height * (rightMost - leftMost + 1))
+        }
+
+        return maxArea
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -536,6 +626,256 @@ public class Solution {
 }
 ```
 
+```go
+type MinIdxSegtree struct {
+    n   int
+    INF int
+    A   []int
+    tree []int
+}
+
+func NewMinIdxSegtree(N int, A []int) *MinIdxSegtree {
+    st := &MinIdxSegtree{
+        n:   N,
+        INF: 1000000000,
+        A:   make([]int, N),
+    }
+    copy(st.A, A)
+    
+    for (st.n & (st.n - 1)) != 0 {
+        st.A = append(st.A, st.INF)
+        st.n++
+    }
+    
+    st.tree = make([]int, 2*st.n)
+    st.build()
+    return st
+}
+
+func (st *MinIdxSegtree) build() {
+    for i := 0; i < st.n; i++ {
+        st.tree[st.n+i] = i
+    }
+    
+    for j := st.n - 1; j > 0; j-- {
+        a := st.tree[j<<1]
+        b := st.tree[(j<<1)+1]
+        if st.A[a] <= st.A[b] {
+            st.tree[j] = a
+        } else {
+            st.tree[j] = b
+        }
+    }
+}
+
+func (st *MinIdxSegtree) update(i, val int) {
+    st.A[i] = val
+    j := (st.n + i) >> 1
+    for j >= 1 {
+        a := st.tree[j<<1]
+        b := st.tree[(j<<1)+1]
+        if st.A[a] <= st.A[b] {
+            st.tree[j] = a
+        } else {
+            st.tree[j] = b
+        }
+        j >>= 1
+    }
+}
+
+func (st *MinIdxSegtree) query(ql, qh int) int {
+    return st.queryHelper(1, 0, st.n-1, ql, qh)
+}
+
+func (st *MinIdxSegtree) queryHelper(node, l, h, ql, qh int) int {
+    if ql > h || qh < l {
+        return st.INF
+    }
+    if l >= ql && h <= qh {
+        return st.tree[node]
+    }
+    a := st.queryHelper(node<<1, l, (l+h)>>1, ql, qh)
+    b := st.queryHelper((node<<1)+1, ((l+h)>>1)+1, h, ql, qh)
+    if a == st.INF {
+        return b
+    }
+    if b == st.INF {
+        return a
+    }
+    if st.A[a] <= st.A[b] {
+        return a
+    }
+    return b
+}
+
+func getMaxArea(heights []int, l, r int, st *MinIdxSegtree) int {
+    if l > r {
+        return 0
+    }
+    if l == r {
+        return heights[l]
+    }
+    minIdx := st.query(l, r)
+    area1 := getMaxArea(heights, l, minIdx-1, st)
+    area2 := getMaxArea(heights, minIdx+1, r, st)
+    area3 := (r - l + 1) * heights[minIdx]
+    
+    maxArea := area1
+    if area2 > maxArea {
+        maxArea = area2
+    }
+    if area3 > maxArea {
+        maxArea = area3
+    }
+    return maxArea
+}
+
+func largestRectangleArea(heights []int) int {
+    n := len(heights)
+    st := NewMinIdxSegtree(n, heights)
+    return getMaxArea(heights, 0, n-1, st)
+}
+```
+
+```kotlin
+class MinIdxSegtree(private var n: Int, input: IntArray) {
+    private val INF = 1000000000
+    private val A: IntArray
+    private val tree: IntArray
+    
+    init {
+        var size = n
+        while (size and (size - 1) != 0) size++
+        A = IntArray(size) { if (it < n) input[it] else INF }
+        n = size
+        tree = IntArray(2 * n)
+        for (i in 0 until n) tree[n + i] = i
+        for (j in n - 1 downTo 1) {
+            val left = tree[j shl 1]
+            val right = tree[j shl 1 or 1]
+            tree[j] = if (A[left] <= A[right]) left else right
+        }
+    }
+    
+    fun query(ql: Int, qh: Int): Int = queryHelper(1, 0, n - 1, ql, qh)
+    
+    private fun queryHelper(node: Int, l: Int, h: Int, ql: Int, qh: Int): Int {
+        if (ql > h || qh < l) return INF
+        if (l >= ql && h <= qh) return tree[node]
+        
+        val mid = (l + h) shr 1
+        val a = queryHelper(node shl 1, l, mid, ql, qh)
+        val b = queryHelper((node shl 1) + 1, mid + 1, h, ql, qh)
+        
+        return when {
+            a == INF -> b
+            b == INF -> a
+            A[a] <= A[b] -> a
+            else -> b
+        }
+    }
+}
+
+class Solution {
+    fun largestRectangleArea(heights: IntArray): Int {
+        val n = heights.size
+        val st = MinIdxSegtree(n, heights)
+        
+        fun getMaxArea(l: Int, r: Int): Int {
+            if (l > r) return 0
+            if (l == r) return heights[l]
+            val minIdx = st.query(l, r)
+            val area = (r - l + 1) * heights[minIdx]
+            val leftArea = getMaxArea(l, minIdx - 1)
+            val rightArea = getMaxArea(minIdx + 1, r)
+            return maxOf(area, leftArea, rightArea)
+        }
+        
+        return getMaxArea(0, n - 1)
+    }
+}
+```
+
+```swift
+class MinIdxSegmentTree {
+    private var n: Int
+    private var INF = Int(1e9)
+    private var A: [Int]
+    private var tree: [Int]
+
+    init(_ N: Int, _ A: [Int]) {
+        self.n = N
+        self.A = A
+        while (self.n & (self.n - 1)) != 0 {
+            self.A.append(self.INF)
+            self.n += 1
+        }
+        self.tree = [Int](repeating: 0, count: 2 * self.n)
+        build()
+    }
+
+    private func build() {
+        for i in 0..<n {
+            tree[n + i] = i
+        }
+        for j in stride(from: n - 1, through: 1, by: -1) {
+            let a = tree[j << 1]
+            let b = tree[(j << 1) + 1]
+            tree[j] = (A[a] <= A[b]) ? a : b
+        }
+    }
+
+    func update(_ i: Int, _ val: Int) {
+        A[i] = val
+        var j = (n + i) >> 1
+        while j >= 1 {
+            let a = tree[j << 1]
+            let b = tree[(j << 1) + 1]
+            tree[j] = (A[a] <= A[b]) ? a : b
+            j >>= 1
+        }
+    }
+
+    func query(_ ql: Int, _ qh: Int) -> Int {
+        return _query(1, 0, n - 1, ql, qh)
+    }
+
+    private func _query(_ node: Int, _ l: Int, _ h: Int, _ ql: Int, _ qh: Int) -> Int {
+        if ql > h || qh < l {
+            return INF
+        }
+        if l >= ql && h <= qh {
+            return tree[node]
+        }
+        let a = _query(node << 1, l, (l + h) >> 1, ql, qh)
+        let b = _query((node << 1) + 1, ((l + h) >> 1) + 1, h, ql, qh)
+        if a == INF { return b }
+        if b == INF { return a }
+        return (A[a] <= A[b]) ? a : b
+    }
+}
+
+class Solution {
+    func getMaxArea(_ heights: [Int], _ l: Int, _ r: Int, _ st: MinIdxSegmentTree) -> Int {
+        if l > r { return 0 }
+        if l == r { return heights[l] }
+
+        let minIdx = st.query(l, r)
+        return max(
+            max(getMaxArea(heights, l, minIdx - 1, st),
+                getMaxArea(heights, minIdx + 1, r, st)),
+            (r - l + 1) * heights[minIdx]
+        )
+    }
+
+    func largestRectangleArea(_ heights: [Int]) -> Int {
+        let n = heights.count
+        let st = MinIdxSegmentTree(n, heights)
+        return getMaxArea(heights, 0, n - 1, st)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -753,6 +1093,137 @@ public class Solution {
 }
 ```
 
+```go
+func largestRectangleArea(heights []int) int {
+    n := len(heights)
+    stack := make([]int, 0)
+    
+    leftMost := make([]int, n)
+    for i := range leftMost {
+        leftMost[i] = -1
+    }
+    
+    for i := 0; i < n; i++ {
+        for len(stack) > 0 && heights[stack[len(stack)-1]] >= heights[i] {
+            stack = stack[:len(stack)-1]
+        }
+        if len(stack) > 0 {
+            leftMost[i] = stack[len(stack)-1]
+        }
+        stack = append(stack, i)
+    }
+    
+    stack = stack[:0]
+    rightMost := make([]int, n)
+    for i := range rightMost {
+        rightMost[i] = n
+    }
+    
+    for i := n - 1; i >= 0; i-- {
+        for len(stack) > 0 && heights[stack[len(stack)-1]] >= heights[i] {
+            stack = stack[:len(stack)-1]
+        }
+        if len(stack) > 0 {
+            rightMost[i] = stack[len(stack)-1]
+        }
+        stack = append(stack, i)
+    }
+    
+    maxArea := 0
+    for i := 0; i < n; i++ {
+        leftMost[i]++
+        rightMost[i]--
+        area := heights[i] * (rightMost[i] - leftMost[i] + 1)
+        if area > maxArea {
+            maxArea = area
+        }
+    }
+    
+    return maxArea
+}
+```
+
+```kotlin
+class Solution {
+    fun largestRectangleArea(heights: IntArray): Int {
+        val n = heights.size
+        val stack = ArrayDeque<Int>()
+        
+        val leftMost = IntArray(n) { -1 }
+        for (i in 0 until n) {
+            while (stack.isNotEmpty() && heights[stack.last()] >= heights[i]) {
+                stack.removeLast()
+            }
+            if (stack.isNotEmpty()) {
+                leftMost[i] = stack.last()
+            }
+            stack.addLast(i)
+        }
+        
+        stack.clear()
+        val rightMost = IntArray(n) { n }
+        for (i in n - 1 downTo 0) {
+            while (stack.isNotEmpty() && heights[stack.last()] >= heights[i]) {
+                stack.removeLast()
+            }
+            if (stack.isNotEmpty()) {
+                rightMost[i] = stack.last()
+            }
+            stack.addLast(i)
+        }
+        
+        var maxArea = 0
+        for (i in 0 until n) {
+            leftMost[i]++
+            rightMost[i]--
+            maxArea = maxOf(maxArea, heights[i] * (rightMost[i] - leftMost[i] + 1))
+        }
+        
+        return maxArea
+    }
+}
+```
+
+```swift
+class Solution {
+    func largestRectangleArea(_ heights: [Int]) -> Int {
+        let n = heights.count
+        var stack = [Int]()
+
+        var leftMost = [Int](repeating: -1, count: n)
+        for i in 0..<n {
+            while !stack.isEmpty && heights[stack.last!] >= heights[i] {
+                stack.removeLast()
+            }
+            if !stack.isEmpty {
+                leftMost[i] = stack.last!
+            }
+            stack.append(i)
+        }
+
+        stack.removeAll()
+        var rightMost = [Int](repeating: n, count: n)
+        for i in stride(from: n - 1, through: 0, by: -1) {
+            while !stack.isEmpty && heights[stack.last!] >= heights[i] {
+                stack.removeLast()
+            }
+            if !stack.isEmpty {
+                rightMost[i] = stack.last!
+            }
+            stack.append(i)
+        }
+
+        var maxArea = 0
+        for i in 0..<n {
+            leftMost[i] += 1
+            rightMost[i] -= 1
+            maxArea = max(maxArea, heights[i] * (rightMost[i] - leftMost[i] + 1))
+        }
+        return maxArea
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -762,7 +1233,7 @@ public class Solution {
 
 ---
 
-## 4. Stack (Optimal)
+## 4. Stack (One Pass)
 
 ::tabs-start
 
@@ -903,6 +1374,89 @@ public class Solution {
 }
 ```
 
+```go
+func largestRectangleArea(heights []int) int {
+    maxArea := 0
+    stack := make([][2]int, 0)
+    
+    for i, h := range heights {
+        start := i
+        for len(stack) > 0 && stack[len(stack)-1][1] > h {
+            index := stack[len(stack)-1][0]
+            height := stack[len(stack)-1][1]
+            stack = stack[:len(stack)-1]
+            area := height * (i - index)
+            if area > maxArea {
+                maxArea = area
+            }
+            start = index
+        }
+        stack = append(stack, [2]int{start, h})
+    }
+    
+    n := len(heights)
+    for _, pair := range stack {
+        area := pair[1] * (n - pair[0])
+        if area > maxArea {
+            maxArea = area
+        }
+    }
+    
+    return maxArea
+}
+```
+
+```kotlin
+class Solution {
+    fun largestRectangleArea(heights: IntArray): Int {
+        var maxArea = 0
+        val stack = ArrayDeque<Pair<Int, Int>>()
+        
+        heights.forEachIndexed { i, h ->
+            var start = i
+            while (stack.isNotEmpty() && stack.last().second > h) {
+                val (index, height) = stack.removeLast()
+                maxArea = maxOf(maxArea, height * (i - index))
+                start = index
+            }
+            stack.addLast(start to h)
+        }
+        
+        val n = heights.size
+        for ((i, h) in stack) {
+            maxArea = maxOf(maxArea, h * (n - i))
+        }
+        
+        return maxArea
+    }
+}
+```
+
+```swift
+class Solution {
+    func largestRectangleArea(_ heights: [Int]) -> Int {
+        var maxArea = 0
+        var stack = [(Int, Int)]() // Pair: (index, height)
+
+        for (i, h) in heights.enumerated() {
+            var start = i
+            while !stack.isEmpty && stack.last!.1 > h {
+                let (index, height) = stack.removeLast()
+                maxArea = max(maxArea, height * (i - index))
+                start = index
+            }
+            stack.append((start, h))
+        }
+
+        for (i, h) in stack {
+            maxArea = max(maxArea, h * (heights.count - i))
+        }
+
+        return maxArea
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -912,7 +1466,7 @@ public class Solution {
 
 ---
 
-## 5. Stack (One Pass)
+## 5. Stack (Optimal)
 
 ::tabs-start
 
@@ -1022,6 +1576,77 @@ public class Solution {
 }
 ```
 
+```go
+func largestRectangleArea(heights []int) int {
+    n := len(heights)
+    maxArea := 0
+    stack := make([]int, 0)
+    
+    for i := 0; i <= n; i++ {
+        for len(stack) > 0 && (i == n || heights[stack[len(stack)-1]] >= heights[i]) {
+            height := heights[stack[len(stack)-1]]
+            stack = stack[:len(stack)-1]
+            
+            width := i
+            if len(stack) > 0 {
+                width = i - stack[len(stack)-1] - 1
+            }
+            
+            area := height * width
+            if area > maxArea {
+                maxArea = area
+            }
+        }
+        if i < n {
+            stack = append(stack, i)
+        }
+    }
+    
+    return maxArea
+}
+```
+
+```kotlin
+class Solution {
+    fun largestRectangleArea(heights: IntArray): Int {
+        val n = heights.size
+        var maxArea = 0
+        val stack = ArrayDeque<Int>()
+        
+        for (i in 0..n) {
+            while (stack.isNotEmpty() && (i == n || heights[stack.last()] >= heights[i])) {
+                val height = heights[stack.removeLast()]
+                val width = if (stack.isEmpty()) i else i - stack.last() - 1
+                maxArea = maxOf(maxArea, height * width)
+            }
+            if (i < n) stack.addLast(i)
+        }
+        
+        return maxArea
+    }
+}
+```
+
+```swift
+class Solution {
+    func largestRectangleArea(_ heights: [Int]) -> Int {
+        let n = heights.count
+        var maxArea = 0
+        var stack = [Int]()
+
+        for i in 0...n {
+            while !stack.isEmpty && (i == n || heights[stack.last!] >= heights[i]) {
+                let height = heights[stack.removeLast()]
+                let width = stack.isEmpty ? i : i - stack.last! - 1
+                maxArea = max(maxArea, height * width)
+            }
+            stack.append(i)
+        }
+        return maxArea
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/largest-submatrix-with-rearrangements.md b/articles/largest-submatrix-with-rearrangements.md
new file mode 100644
index 000000000..bebc4c94e
--- /dev/null
+++ b/articles/largest-submatrix-with-rearrangements.md
@@ -0,0 +1,522 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def largestSubmatrix(self, matrix: List[List[int]]) -> int:
+        ROWS, COLS = len(matrix), len(matrix[0])
+        res = 0
+
+        for start_row in range(ROWS):
+            ones = deque(list(range(COLS)))
+
+            for r in range(start_row, ROWS):
+                if not ones:
+                    break
+                for _ in range(len(ones)):
+                    c = ones.popleft()
+                    if matrix[r][c] == 1:
+                        ones.append(c)
+
+                res = max(res, len(ones) * (r - start_row + 1))
+
+        return res
+```
+
+```java
+public class Solution {
+    public int largestSubmatrix(int[][] matrix) {
+        int ROWS = matrix.length, COLS = matrix[0].length;
+        int res = 0;
+
+        for (int startRow = 0; startRow < ROWS; startRow++) {
+            Queue<Integer> ones = new LinkedList<>();
+            for (int c = 0; c < COLS; c++) {
+                ones.add(c);
+            }
+
+            for (int r = startRow; r < ROWS; r++) {
+                if (ones.isEmpty()) break;
+
+                for (int i = ones.size(); i > 0; i--) {
+                    int c = ones.poll();
+                    if (matrix[r][c] == 1) {
+                        ones.add(c);
+                    }
+                }
+
+                res = Math.max(res, ones.size() * (r - startRow + 1));
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int largestSubmatrix(vector<vector<int>>& matrix) {
+        int ROWS = matrix.size(), COLS = matrix[0].size();
+        int res = 0;
+
+        for (int startRow = 0; startRow < ROWS; startRow++) {
+            queue<int> ones;
+            for (int c = 0; c < COLS; c++) {
+                ones.push(c);
+            }
+
+            for (int r = startRow; r < ROWS; r++) {
+                if (ones.empty()) break;
+
+                for (int i = ones.size(); i > 0; i--) {
+                    int c = ones.front(); ones.pop();
+                    if (matrix[r][c] == 1) {
+                        ones.push(c);
+                    }
+                }
+
+                res = max(res, (int)ones.size() * (r - startRow + 1));
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} matrix
+     * @return {number}
+     */
+    largestSubmatrix(matrix) {
+        const ROWS = matrix.length, COLS = matrix[0].length;
+        let res = 0;
+
+        for (let startRow = 0; startRow < ROWS; startRow++) {
+            const ones = new Queue();
+            for (let c = 0; c < COLS; c++) {
+                ones.push(c);
+            }
+
+            for (let r = startRow; r < ROWS; r++) {
+                if (ones.isEmpty()) break;
+
+                for (let i = ones.size(); i > 0; i--) {
+                    let c = ones.pop();
+                    if (matrix[r][c] === 1) {
+                        ones.push(c);
+                    }
+                }
+
+                res = Math.max(res, ones.size() * (r - startRow + 1));
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n ^ 2)$
+* Space complexity: $O(n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns.
+
+---
+
+## 2. Greedy + Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def largestSubmatrix(self, matrix: List[List[int]]) -> int:
+        ROWS, COLS = len(matrix), len(matrix[0])
+        res = 0
+        prev_heights = [0] * COLS
+
+        for r in range(ROWS):
+            heights = matrix[r][:]
+            for c in range(COLS):
+                if heights[c] > 0:
+                    heights[c] += prev_heights[c]
+
+            sorted_heights = sorted(heights, reverse=True)
+            for i in range(COLS):
+                res = max(res, (i + 1) * sorted_heights[i])
+
+            prev_heights = heights
+
+        return res
+```
+
+```java
+public class Solution {
+    public int largestSubmatrix(int[][] matrix) {
+        int ROWS = matrix.length, COLS = matrix[0].length;
+        int res = 0;
+        int[] prevHeights = new int[COLS];
+
+        for (int r = 0; r < ROWS; r++) {
+            int[] heights = Arrays.copyOf(matrix[r], COLS);
+            int[] sortedHgts = Arrays.copyOf(matrix[r], COLS);
+
+            for (int c = 0; c < COLS; c++) {
+                if (heights[c] > 0) {
+                    heights[c] += prevHeights[c];
+                    sortedHgts[c] = heights[c];
+                }
+            }
+
+            Arrays.sort(sortedHgts);
+            for (int i = COLS - 1; i >= 0; i--) {
+                res = Math.max(res, (COLS - i) * sortedHgts[i]);
+            }
+
+            prevHeights = heights;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int largestSubmatrix(vector<vector<int>>& matrix) {
+        int ROWS = matrix.size(), COLS = matrix[0].size();
+        int res = 0;
+        vector<int> prevHeights(COLS);
+
+        for (int r = 0; r < ROWS; r++) {
+            vector<int> heights = matrix[r];
+            vector<int> sortedHgts = matrix[r];
+
+            for (int c = 0; c < COLS; c++) {
+                if (heights[c] > 0) {
+                    heights[c] += prevHeights[c];
+                    sortedHgts[c] = heights[c];
+                }
+            }
+
+            sort(sortedHgts.begin(), sortedHgts.end(), greater<int>());
+            for (int i = 0; i < COLS; i++) {
+                res = max(res, (i + 1) * sortedHgts[i]);
+            }
+
+            prevHeights = heights;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} matrix
+     * @return {number}
+     */
+    largestSubmatrix(matrix) {
+        const ROWS = matrix.length, COLS = matrix[0].length;
+        let res = 0;
+        let prevHeights = new Array(COLS).fill(0);
+
+        for (let r = 0; r < ROWS; r++) {
+            let heights = [...matrix[r]];
+            let sortedHgts = [...matrix[r]];
+
+            for (let c = 0; c < COLS; c++) {
+                if (heights[c] > 0) {
+                    heights[c] += prevHeights[c];
+                    sortedHgts[c] = heights[c];
+                }
+            }
+
+            sortedHgts.sort((a, b) => b - a);
+            for (let i = 0; i < COLS; i++) {
+                res = Math.max(res, (i + 1) * sortedHgts[i]);
+            }
+
+            prevHeights = heights;
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n \log n)$
+* Space complexity: $O(n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns.
+
+---
+
+## 3. Greedy + Sorting (Overwriting the Input)
+
+::tabs-start
+
+```python
+class Solution:
+    def largestSubmatrix(self, matrix: List[List[int]]) -> int:
+        ROWS, COLS = len(matrix), len(matrix[0])
+        res = 0
+
+        for r in range(1, ROWS):
+            for c in range(COLS):
+                if matrix[r][c]:
+                    matrix[r][c] += matrix[r - 1][c]
+
+        for r in range(ROWS):
+            matrix[r].sort(reverse=True)
+            for i in range(COLS):
+                res = max(res, (i + 1) * matrix[r][i])
+
+        return res
+```
+
+```java
+public class Solution {
+    public int largestSubmatrix(int[][] matrix) {
+        int ROWS = matrix.length, COLS = matrix[0].length;
+        int res = 0;
+
+        for (int r = 1; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (matrix[r][c] > 0) {
+                    matrix[r][c] += matrix[r - 1][c];
+                }
+            }
+        }
+
+        for (int r = 0; r < ROWS; r++) {
+            Arrays.sort(matrix[r]);
+            for (int i = 0; i < COLS; i++) {
+                res = Math.max(res, (COLS - i) * matrix[r][i]);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int largestSubmatrix(vector<vector<int>>& matrix) {
+        int ROWS = matrix.size(), COLS = matrix[0].size();
+        int res = 0;
+
+        for (int r = 1; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (matrix[r][c] > 0) {
+                    matrix[r][c] += matrix[r - 1][c];
+                }
+            }
+        }
+
+        for (int r = 0; r < ROWS; r++) {
+            sort(matrix[r].begin(), matrix[r].end(), greater<int>());
+            for (int i = 0; i < COLS; i++) {
+                res = max(res, (i + 1) * matrix[r][i]);
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} matrix
+     * @return {number}
+     */
+    largestSubmatrix(matrix) {
+        const ROWS = matrix.length, COLS = matrix[0].length;
+        let res = 0;
+
+        for (let r = 1; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                if (matrix[r][c] > 0) {
+                    matrix[r][c] += matrix[r - 1][c];
+                }
+            }
+        }
+
+        for (let r = 0; r < ROWS; r++) {
+            matrix[r].sort((a, b) => b - a);
+            for (let i = 0; i < COLS; i++) {
+                res = Math.max(res, (i + 1) * matrix[r][i]);
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algoirhtm.
+
+> Where $m$ is the number of rows and $n$ is the number of columns.
+
+---
+
+## 4. Greedy
+
+::tabs-start
+
+```python
+class Solution:
+    def largestSubmatrix(self, matrix: List[List[int]]) -> int:
+        ROWS, COLS = len(matrix), len(matrix[0])
+        res = 0
+        prevHeights = []
+
+        for r in range(ROWS):
+            heights = []
+            for c in prevHeights:
+                if matrix[r][c]:
+                    matrix[r][c] += matrix[r - 1][c]
+                    heights.append(c)
+
+            for c in range(COLS):
+                if matrix[r][c] == 1:
+                    heights.append(c)
+
+            for i, c in enumerate(heights):
+                res = max(res, (i + 1) * matrix[r][c])
+
+            prevHeights = heights
+
+        return res
+```
+
+```java
+public class Solution {
+    public int largestSubmatrix(int[][] matrix) {
+        int ROWS = matrix.length, COLS = matrix[0].length;
+        int res = 0;
+        List<Integer> prevHeights = new ArrayList<>();
+
+        for (int r = 0; r < ROWS; r++) {
+            List<Integer> heights = new ArrayList<>();
+
+            for (int c : prevHeights) {
+                if (matrix[r][c] == 1) {
+                    matrix[r][c] += matrix[r - 1][c];
+                    heights.add(c);
+                }
+            }
+
+            for (int c = 0; c < COLS; c++) {
+                if (matrix[r][c] == 1) {
+                    heights.add(c);
+                }
+            }
+
+            for (int i = 0; i < heights.size(); i++) {
+                res = Math.max(res, (i + 1) * matrix[r][heights.get(i)]);
+            }
+
+            prevHeights = heights;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int largestSubmatrix(vector<vector<int>>& matrix) {
+        int ROWS = matrix.size(), COLS = matrix[0].size(), res = 0;
+        vector<int> prevHeights;
+
+        for (int r = 0; r < ROWS; r++) {
+            vector<int> heights;
+
+            for (int c : prevHeights) {
+                if (matrix[r][c] == 1) {
+                    matrix[r][c] += matrix[r - 1][c];
+                    heights.push_back(c);
+                }
+            }
+
+            for (int c = 0; c < COLS; c++) {
+                if (matrix[r][c] == 1) {
+                    heights.push_back(c);
+                }
+            }
+
+            for (int i = 0; i < heights.size(); i++) {
+                res = max(res, (i + 1) * matrix[r][heights[i]]);
+            }
+
+            prevHeights = heights;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} matrix
+     * @return {number}
+     */
+    largestSubmatrix(matrix) {
+        const ROWS = matrix.length, COLS = matrix[0].length;
+        let res = 0, prevHeights = [];
+
+        for (let r = 0; r < ROWS; r++) {
+            let heights = [];
+
+            for (let c of prevHeights) {
+                if (matrix[r][c] === 1) {
+                    matrix[r][c] += matrix[r - 1][c];
+                    heights.push(c);
+                }
+            }
+
+            for (let c = 0; c < COLS; c++) {
+                if (matrix[r][c] === 1) {
+                    heights.push(c);
+                }
+            }
+
+            for (let i = 0; i < heights.length; i++) {
+                res = Math.max(res, (i + 1) * matrix[r][heights[i]]);
+            }
+
+            prevHeights = heights;
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns.
\ No newline at end of file
diff --git a/articles/largest-substring-between-two-equal-characters.md b/articles/largest-substring-between-two-equal-characters.md
new file mode 100644
index 000000000..dc4108a60
--- /dev/null
+++ b/articles/largest-substring-between-two-equal-characters.md
@@ -0,0 +1,380 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def maxLengthBetweenEqualCharacters(self, s: str) -> int:
+        n = len(s)
+        res = -1
+
+        for i in range(n):
+            for j in range(i + 1, n):
+                if s[i] == s[j]:
+                    res = max(res, j - i - 1)
+        return res
+```
+
+```java
+public class Solution {
+    public int maxLengthBetweenEqualCharacters(String s) {
+        int n = s.length();
+        int res = -1;
+
+        for (int i = 0; i < n; i++) {
+            for (int j = i + 1; j < n; j++) {
+                if (s.charAt(i) == s.charAt(j)) {
+                    res = Math.max(res, j - i - 1);
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxLengthBetweenEqualCharacters(string s) {
+        int n = s.size();
+        int res = -1;
+
+        for (int i = 0; i < n; i++) {
+            for (int j = i + 1; j < n; j++) {
+                if (s[i] == s[j]) {
+                    res = max(res, j - i - 1);
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    maxLengthBetweenEqualCharacters(s) {
+        const n = s.length;
+        let res = -1;
+
+        for (let i = 0; i < n; i++) {
+            for (let j = i + 1; j < n; j++) {
+                if (s[i] === s[j]) {
+                    res = Math.max(res, j - i - 1);
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. First And Last Index
+
+::tabs-start
+
+```python
+class Solution:
+    def maxLengthBetweenEqualCharacters(self, s: str) -> int:
+        res = -1
+        firstIdx = {}
+        lastIdx = {}
+        
+        for i, c in enumerate(s):
+            if c not in firstIdx:
+                firstIdx[c] = i
+            else:
+                lastIdx[c] = i
+        
+        for c in lastIdx:
+            res = max(res, lastIdx[c] - firstIdx[c] - 1)
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int maxLengthBetweenEqualCharacters(String s) {
+        Map<Character, Integer> firstIdx = new HashMap<>();
+        Map<Character, Integer> lastIdx = new HashMap<>();
+        int res = -1;
+
+        for (int i = 0; i < s.length(); i++) {
+            char c = s.charAt(i);
+            if (!firstIdx.containsKey(c)) {
+                firstIdx.put(c, i);
+            } else {
+                lastIdx.put(c, i);
+            }
+        }
+
+        for (char c : lastIdx.keySet()) {
+            res = Math.max(res, lastIdx.get(c) - firstIdx.get(c) - 1);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxLengthBetweenEqualCharacters(string s) {
+        unordered_map<char, int> firstIdx, lastIdx;
+        int res = -1;
+
+        for (int i = 0; i < s.size(); i++) {
+            if (firstIdx.find(s[i]) == firstIdx.end()) {
+                firstIdx[s[i]] = i;
+            } else {
+                lastIdx[s[i]] = i;
+            }
+        }
+
+        for (auto& [c, idx] : lastIdx) {
+            res = max(res, lastIdx[c] - firstIdx[c] - 1);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    maxLengthBetweenEqualCharacters(s) {
+        const firstIdx = new Map();
+        const lastIdx = new Map();
+        let res = -1;
+
+        for (let i = 0; i < s.length; i++) {
+            if (!firstIdx.has(s[i])) {
+                firstIdx.set(s[i], i);
+            } else {
+                lastIdx.set(s[i], i);
+            }
+        }
+
+        for (const [char, idx] of lastIdx) {
+            res = Math.max(res, lastIdx.get(char) - firstIdx.get(char) - 1);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ since we have at most $26$ different characters.
+
+---
+
+## 3. First Index (Hash Map)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxLengthBetweenEqualCharacters(self, s: str) -> int:
+        char_index = {}  # char -> first index
+        res = -1
+
+        for i, c in enumerate(s):
+            if c in char_index:
+                res = max(res, i - char_index[c] - 1)
+            else:
+                char_index[c] = i
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int maxLengthBetweenEqualCharacters(String s) {
+        Map<Character, Integer> charIndex = new HashMap<>();
+        int res = -1;
+
+        for (int i = 0; i < s.length(); i++) {
+            char c = s.charAt(i);
+            if (charIndex.containsKey(c)) {
+                res = Math.max(res, i - charIndex.get(c) - 1);
+            } else {
+                charIndex.put(c, i);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxLengthBetweenEqualCharacters(string s) {
+        unordered_map<char, int> charIndex;
+        int res = -1;
+
+        for (int i = 0; i < s.size(); i++) {
+            if (charIndex.find(s[i]) != charIndex.end()) {
+                res = max(res, i - charIndex[s[i]] - 1);
+            } else {
+                charIndex[s[i]] = i;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    maxLengthBetweenEqualCharacters(s) {
+        const charIndex = new Map();
+        let res = -1;
+
+        for (let i = 0; i < s.length; i++) {
+            if (charIndex.has(s[i])) {
+                res = Math.max(res, i - charIndex.get(s[i]) - 1);
+            } else {
+                charIndex.set(s[i], i);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ since we have at most $26$ different characters.
+
+---
+
+## 4. First Index (Array)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxLengthBetweenEqualCharacters(self, s: str) -> int:
+        firstIdx = [-1] * 26
+        res = -1
+
+        for i, c in enumerate(s):
+            j = ord(c) - ord('a')
+            if firstIdx[j] != -1:
+                res = max(res, i - firstIdx[j] - 1)
+            else:
+                firstIdx[j] = i
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int maxLengthBetweenEqualCharacters(String s) {
+        int[] firstIdx = new int[26];
+        for (int i = 0; i < 26; i++) {
+            firstIdx[i] = -1;
+        }
+        int res = -1;
+
+        for (int i = 0; i < s.length(); i++) {
+            int j = s.charAt(i) - 'a';
+            if (firstIdx[j] != -1) {
+                res = Math.max(res, i - firstIdx[j] - 1);
+            } else {
+                firstIdx[j] = i;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxLengthBetweenEqualCharacters(string s) {
+        int firstIdx[26];
+        fill(begin(firstIdx), end(firstIdx), -1);
+        int res = -1;
+
+        for (int i = 0; i < s.size(); i++) {
+            int j = s[i] - 'a';
+            if (firstIdx[j] != -1) {
+                res = max(res, i - firstIdx[j] - 1);
+            } else {
+                firstIdx[j] = i;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    maxLengthBetweenEqualCharacters(s) {
+        const firstIdx = Array(26).fill(-1);
+        let res = -1;
+
+        for (let i = 0; i < s.length; i++) {
+            const j = s.charCodeAt(i) - 'a'.charCodeAt(0);
+            if (firstIdx[j] !== -1) {
+                res = Math.max(res, i - firstIdx[j] - 1);
+            } else {
+                firstIdx[j] = i;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ since we have at most $26$ different characters.
\ No newline at end of file
diff --git a/articles/last-stone-weight-ii.md b/articles/last-stone-weight-ii.md
new file mode 100644
index 000000000..f902d45d2
--- /dev/null
+++ b/articles/last-stone-weight-ii.md
@@ -0,0 +1,619 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def lastStoneWeightII(self, stones: List[int]) -> int:
+        stoneSum = sum(stones)
+        target = (stoneSum + 1) // 2
+
+        def dfs(i, total):
+            if total >= target or i == len(stones):
+                return abs(total - (stoneSum - total))
+            return min(dfs(i + 1, total), dfs(i + 1, total + stones[i]))
+
+        return dfs(0, 0)
+```
+
+```java
+public class Solution {
+    public int lastStoneWeightII(int[] stones) {
+        int stoneSum = 0;
+        for (int stone : stones) {
+            stoneSum += stone;
+        }
+        int target = (stoneSum + 1) / 2;
+
+        return dfs(0, 0, stones, stoneSum, target);
+    }
+
+    private int dfs(int i, int total, int[] stones, int stoneSum, int target) {
+        if (total >= target || i == stones.length) {
+            return Math.abs(total - (stoneSum - total));
+        }
+        return Math.min(
+            dfs(i + 1, total, stones, stoneSum, target),
+            dfs(i + 1, total + stones[i], stones, stoneSum, target)
+        );
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int lastStoneWeightII(vector<int>& stones) {
+        int stoneSum = accumulate(stones.begin(), stones.end(), 0);
+        int target = (stoneSum + 1) / 2;
+        return dfs(0, 0, stones, stoneSum, target);
+    }
+
+private:
+    int dfs(int i, int total, const vector<int>& stones, int stoneSum, int target) {
+        if (total >= target || i == stones.size()) {
+            return abs(total - (stoneSum - total));
+        }
+        return min(
+            dfs(i + 1, total, stones, stoneSum, target),
+            dfs(i + 1, total + stones[i], stones, stoneSum, target)
+        );
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} stones
+     * @return {number}
+     */
+    lastStoneWeightII(stones) {
+        const stoneSum = stones.reduce((a, b) => a + b, 0);
+        const target = Math.ceil(stoneSum / 2);
+
+        const dfs = (i, total) => {
+            if (total >= target || i === stones.length) {
+                return Math.abs(total - (stoneSum - total));
+            }
+            return Math.min(
+                dfs(i + 1, total),
+                dfs(i + 1, total + stones[i])
+            );
+        };
+
+        return dfs(0, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(min(n, m))$ for recursion stack.
+
+> Where $n$ is the number of stones and $m$ is the sum of the weights of the stones.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def lastStoneWeightII(self, stones: List[int]) -> int:
+        stoneSum = sum(stones)
+        target = (stoneSum + 1) // 2
+        dp = {}
+
+        def dfs(i, total):
+            if total >= target or i == len(stones):
+                return abs(total - (stoneSum - total))
+            if (i, total) in dp:
+                return dp[(i, total)]
+
+            dp[(i, total)] = min(dfs(i + 1, total), dfs(i + 1, total + stones[i]))
+            return dp[(i, total)]
+
+        return dfs(0, 0)
+```
+
+```java
+public class Solution {
+    private int[][] dp;
+
+    public int lastStoneWeightII(int[] stones) {
+        int stoneSum = 0;
+        for (int stone : stones) {
+            stoneSum += stone;
+        }
+        int target = (stoneSum + 1) / 2;
+        dp = new int[stones.length][target + 1];
+        for (int i = 0; i < stones.length; i++) {
+            for (int j = 0; j <= target; j++) {
+                dp[i][j] = -1;
+            }
+        }
+
+        return dfs(0, 0, stones, stoneSum, target);
+    }
+
+    private int dfs(int i, int total, int[] stones, int stoneSum, int target) {
+        if (total >= target || i == stones.length) {
+            return Math.abs(total - (stoneSum - total));
+        }
+        if (dp[i][total] != -1) {
+            return dp[i][total];
+        }
+
+        dp[i][total] = Math.min(
+            dfs(i + 1, total, stones, stoneSum, target),
+            dfs(i + 1, total + stones[i], stones, stoneSum, target)
+        );
+        return dp[i][total];
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<vector<int>> dp;
+
+public:
+    int lastStoneWeightII(vector<int>& stones) {
+        int stoneSum = accumulate(stones.begin(), stones.end(), 0);
+        int target = (stoneSum + 1) / 2;
+        dp = vector<vector<int>>(stones.size(), vector<int>(target + 1, -1));
+        return dfs(0, 0, stones, stoneSum, target);
+    }
+
+private:
+    int dfs(int i, int total, const vector<int>& stones, int stoneSum, int target) {
+        if (total >= target || i == stones.size()) {
+            return abs(total - (stoneSum - total));
+        }
+        if (dp[i][total] != -1) {
+            return dp[i][total];
+        }
+
+        dp[i][total] = min(
+            dfs(i + 1, total, stones, stoneSum, target),
+            dfs(i + 1, total + stones[i], stones, stoneSum, target)
+        );
+        return dp[i][total];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} stones
+     * @return {number}
+     */
+    lastStoneWeightII(stones) {
+        const stoneSum = stones.reduce((a, b) => a + b, 0);
+        const target = Math.ceil(stoneSum / 2);
+        const dp = Array.from({ length: stones.length }, () => Array(target + 1).fill(-1));
+
+        const dfs = (i, total) => {
+            if (total >= target || i === stones.length) {
+                return Math.abs(total - (stoneSum - total));
+            }
+            if (dp[i][total] !== -1) {
+                return dp[i][total];
+            }
+
+            dp[i][total] = Math.min(
+                dfs(i + 1, total),
+                dfs(i + 1, total + stones[i])
+            );
+            return dp[i][total];
+        };
+
+        return dfs(0, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n * m)$
+
+> Where $n$ is the number of stones and $m$ is the sum of the weights of the stones.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def lastStoneWeightII(self, stones: List[int]) -> int:
+        stoneSum = sum(stones)
+        target = stoneSum // 2
+        n = len(stones)
+
+        dp = [[0] * (target + 1) for _ in range(n + 1)]
+
+        for i in range(1, n + 1):
+            for t in range(target + 1):
+                if t >= stones[i - 1]:
+                    dp[i][t] = max(dp[i - 1][t], dp[i - 1][t - stones[i - 1]] + stones[i - 1])
+                else:
+                    dp[i][t] = dp[i - 1][t]
+
+        return stoneSum - 2 * dp[n][target]
+```
+
+```java
+public class Solution {
+    public int lastStoneWeightII(int[] stones) {
+        int stoneSum = 0;
+        for (int stone : stones) {
+            stoneSum += stone;
+        }
+        int target = stoneSum / 2;
+        int n = stones.length;
+
+        int[][] dp = new int[n + 1][target + 1];
+
+        for (int i = 1; i <= n; i++) {
+            for (int t = 0; t <= target; t++) {
+                if (t >= stones[i - 1]) {
+                    dp[i][t] = Math.max(dp[i - 1][t], dp[i - 1][t - stones[i - 1]] + stones[i - 1]);
+                } else {
+                    dp[i][t] = dp[i - 1][t];
+                }
+            }
+        }
+
+        return stoneSum - 2 * dp[n][target];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int lastStoneWeightII(vector<int>& stones) {
+        int stoneSum = accumulate(stones.begin(), stones.end(), 0);
+        int target = stoneSum / 2;
+        int n = stones.size();
+
+        vector<vector<int>> dp(n + 1, vector<int>(target + 1, 0));
+
+        for (int i = 1; i <= n; i++) {
+            for (int t = 0; t <= target; t++) {
+                if (t >= stones[i - 1]) {
+                    dp[i][t] = max(dp[i - 1][t], dp[i - 1][t - stones[i - 1]] + stones[i - 1]);
+                } else {
+                    dp[i][t] = dp[i - 1][t];
+                }
+            }
+        }
+
+        return stoneSum - 2 * dp[n][target];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} stones
+     * @return {number}
+     */
+    lastStoneWeightII(stones) {
+        const stoneSum = stones.reduce((a, b) => a + b, 0);
+        const target = Math.floor(stoneSum / 2);
+        const n = stones.length;
+
+        const dp = Array.from({ length: n + 1 }, () => Array(target + 1).fill(0));
+
+        for (let i = 1; i <= n; i++) {
+            for (let t = 0; t <= target; t++) {
+                if (t >= stones[i - 1]) {
+                    dp[i][t] = Math.max(dp[i - 1][t], dp[i - 1][t - stones[i - 1]] + stones[i - 1]);
+                } else {
+                    dp[i][t] = dp[i - 1][t];
+                }
+            }
+        }
+
+        return stoneSum - 2 * dp[n][target];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n * m)$
+
+> Where $n$ is the number of stones and $m$ is the sum of the weights of the stones.
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def lastStoneWeightII(self, stones: List[int]) -> int:
+        stoneSum = sum(stones)
+        target = stoneSum // 2
+        dp = [0] * (target + 1)
+
+        for stone in stones:
+            for t in range(target, stone - 1, -1):
+                dp[t] = max(dp[t], dp[t - stone] + stone)
+
+        return stoneSum - 2 * dp[target]
+```
+
+```java
+public class Solution {
+    public int lastStoneWeightII(int[] stones) {
+        int stoneSum = 0;
+        for (int stone : stones) {
+            stoneSum += stone;
+        }
+        int target = stoneSum / 2;
+        int[] dp = new int[target + 1];
+
+        for (int stone : stones) {
+            for (int t = target; t >= stone; t--) {
+                dp[t] = Math.max(dp[t], dp[t - stone] + stone);
+            }
+        }
+
+        return stoneSum - 2 * dp[target];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int lastStoneWeightII(vector<int>& stones) {
+        int stoneSum = accumulate(stones.begin(), stones.end(), 0);
+        int target = stoneSum / 2;
+        vector<int> dp(target + 1, 0);
+
+        for (int stone : stones) {
+            for (int t = target; t >= stone; t--) {
+                dp[t] = max(dp[t], dp[t - stone] + stone);
+            }
+        }
+
+        return stoneSum - 2 * dp[target];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} stones
+     * @return {number}
+     */
+    lastStoneWeightII(stones) {
+        const stoneSum = stones.reduce((a, b) => a + b, 0);
+        const target = Math.floor(stoneSum / 2);
+        const dp = new Array(target + 1).fill(0);
+
+        for (const stone of stones) {
+            for (let t = target; t >= stone; t--) {
+                dp[t] = Math.max(dp[t], dp[t - stone] + stone);
+            }
+        }
+
+        return stoneSum - 2 * dp[target];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(m)$
+
+> Where $n$ is the number of stones and $m$ is the sum of the weights of the stones.
+
+---
+
+## 5. Dynamic Programming (Hash Set)
+
+::tabs-start
+
+```python
+class Solution:
+    def lastStoneWeightII(self, stones: List[int]) -> int:
+        stoneSum = sum(stones)
+        target = stoneSum // 2
+        dp = {0}
+
+        for stone in stones:
+            new_dp = set(dp)
+            for val in dp:
+                if val + stone == target:
+                    return stoneSum - 2 * target
+                if val + stone < target:
+                    new_dp.add(val + stone)
+            dp = new_dp
+
+        return stoneSum - 2 * max(dp)
+```
+
+```java
+public class Solution {
+    public int lastStoneWeightII(int[] stones) {
+        int stoneSum = 0;
+        for (int stone : stones) {
+            stoneSum += stone;
+        }
+        int target = stoneSum / 2;
+
+        Set<Integer> dp = new HashSet<>();
+        dp.add(0);
+
+        for (int stone : stones) {
+            Set<Integer> newDp = new HashSet<>(dp);
+            for (int val : dp) {
+                if (val + stone == target) {
+                    return stoneSum - 2 * target;
+                }
+                if (val + stone < target) {
+                    newDp.add(val + stone);
+                }
+            }
+            dp = newDp;
+        }
+
+        int maxVal = 0;
+        for (int val : dp) {
+            maxVal = Math.max(maxVal, val);
+        }
+
+        return stoneSum - 2 * maxVal;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int lastStoneWeightII(vector<int>& stones) {
+        int stoneSum = accumulate(stones.begin(), stones.end(), 0);
+        int target = stoneSum / 2;
+
+        unordered_set<int> dp = {0};
+
+        for (int& stone : stones) {
+            unordered_set<int> newDp(dp);
+            for (int val : dp) {
+                if (val + stone == target) {
+                    return stoneSum - 2 * target;
+                }
+                if (val + stone < target) {
+                    newDp.insert(val + stone);
+                }
+            }
+            dp = newDp;
+        }
+
+        int maxVal = 0;
+        for (int val : dp) {
+            maxVal = max(maxVal, val);
+        }
+
+        return stoneSum - 2 * maxVal;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} stones
+     * @return {number}
+     */
+    lastStoneWeightII(stones) {
+        const stoneSum = stones.reduce((a, b) => a + b, 0);
+        const target = Math.floor(stoneSum / 2);
+
+        let dp = new Set([0]);
+
+        for (const stone of stones) {
+            const newDp = new Set(dp);
+            for (const val of dp) {
+                if (val + stone === target) {
+                    return stoneSum - 2 * target;
+                }
+                if (val + stone < target) {
+                    newDp.add(val + stone);
+                }
+            }
+            dp = newDp;
+        }
+
+        return stoneSum - 2 * Math.max(...dp);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(m)$
+
+> Where $n$ is the number of stones and $m$ is the sum of the weights of the stones.
+
+---
+
+## 6. Dynamic Programming (Bitset)
+
+::tabs-start
+
+```python
+class Solution:
+    def lastStoneWeightII(self, stones: List[int]) -> int:
+        stoneSum = sum(stones)
+        target = stoneSum // 2
+        dp = 1  
+
+        for stone in stones:
+            dp |= dp << stone
+
+        for t in range(target, -1, -1):
+            if dp & (1 << t):
+                return stoneSum - 2 * t
+```
+
+```cpp
+class Solution {
+public:
+    int lastStoneWeightII(vector<int>& stones) {
+        int stoneSum = accumulate(stones.begin(), stones.end(), 0);
+        int target = stoneSum / 2;        
+        bitset<3001> dp;
+        dp[0] = true;
+        
+        for (int stone : stones) {
+            dp |= (dp << stone);
+        }
+        
+        for (int t = target; t >= 0; --t) {
+            if (dp[t]) {
+                return stoneSum - 2 * t;
+            }
+        }
+        return 0;
+    }
+};
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(m)$
+
+> Where $n$ is the number of stones and $m$ is the sum of the weights of the stones.
\ No newline at end of file
diff --git a/articles/last-stone-weight.md b/articles/last-stone-weight.md
index e66544028..69ab3403a 100644
--- a/articles/last-stone-weight.md
+++ b/articles/last-stone-weight.md
@@ -93,6 +93,58 @@ public class Solution {
 }
 ```
 
+```go
+func lastStoneWeight(stones []int) int {
+    for len(stones) > 1 {
+		sort.Ints(stones)
+		cur := stones[len(stones)-1] - stones[len(stones)-2]
+		stones = stones[:len(stones)-2]
+		if cur > 0 {
+			stones = append(stones, cur)
+		}
+	}
+	if len(stones) == 0 {
+		return 0
+	}
+	return stones[0]   
+}
+```
+
+```kotlin
+class Solution {
+    fun lastStoneWeight(stones: IntArray): Int {
+        var stonesList = stones.toMutableList()
+        
+        while (stonesList.size > 1) {
+            stonesList.sort()
+            val cur = stonesList.removeAt(stonesList.size - 1) - stonesList.removeAt(stonesList.size - 1)
+            if (cur > 0) {
+                stonesList.add(cur)
+            }
+        }
+        return if (stonesList.isEmpty()) 0 else stonesList[0]
+    }
+}
+```
+
+```swift
+class Solution {
+    func lastStoneWeight(_ stones: [Int]) -> Int {
+        var stones = stones
+        
+        while stones.count > 1 {
+            stones.sort()
+            let cur = stones.removeLast() - stones.removeLast()
+            if cur > 0 {
+                stones.append(cur)
+            }
+        }
+        
+        return stones.isEmpty ? 0 : stones[0]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -270,6 +322,104 @@ public class Solution {
 }
 ```
 
+```go
+func lastStoneWeight(stones []int) int {
+    sort.Ints(stones)
+    n := len(stones)
+    
+    for n > 1 {
+        cur := stones[n-1] - stones[n-2]
+        n -= 2
+        
+        if cur > 0 {
+            pos := sort.Search(n, func(i int) bool {
+                return stones[i] >= cur
+            })
+            
+            for i := n; i > pos; i-- {
+                stones[i] = stones[i-1]
+            }
+            stones[pos] = cur
+            n++
+        }
+    }
+    
+    if n > 0 {
+        return stones[0]
+    }
+    return 0
+}
+```
+
+```kotlin
+class Solution {
+    fun lastStoneWeight(stones: IntArray): Int {
+        stones.sort()
+        var n = stones.size
+        
+        while (n > 1) {
+            val cur = stones[n-1] - stones[n-2]
+            n -= 2
+            
+            if (cur > 0) {
+                var l = 0
+                var r = n
+                while (l < r) {
+                    val mid = (l + r) / 2
+                    if (stones[mid] < cur) {
+                        l = mid + 1
+                    } else {
+                        r = mid
+                    }
+                }
+                
+                for (i in n downTo l+1) {
+                    stones[i] = stones[i-1]
+                }
+                stones[l] = cur
+                n++
+            }
+        }
+        
+        return if (n > 0) stones[0] else 0
+    }
+}
+```
+
+```swift
+class Solution {
+    func lastStoneWeight(_ stones: [Int]) -> Int {
+        var stones = stones.sorted()
+        var n = stones.count
+
+        while n > 1 {
+            let cur = stones.removeLast() - stones.removeLast()
+            n -= 2
+            if cur > 0 {
+                var l = 0, r = n
+                while l < r {
+                    let mid = (l + r) / 2
+                    if stones[mid] < cur {
+                        l = mid + 1
+                    } else {
+                        r = mid
+                    }
+                }
+                let pos = l
+                stones.append(0)
+                n += 1
+                for i in stride(from: n - 1, to: pos, by: -1) {
+                    stones[i] = stones[i - 1]
+                }
+                stones[pos] = cur
+            }
+        }
+
+        return n > 0 ? stones[0] : 0
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -399,6 +549,68 @@ public class Solution {
 }
 ```
 
+```go
+func lastStoneWeight(stones []int) int {
+    pq := priorityqueue.NewWith(func(a, b interface{}) int {
+        return a.(int) - b.(int)  
+    })
+    
+    for _, s := range stones {
+        pq.Enqueue(-s)
+    }
+    
+    for pq.Size() > 1 {
+        first, _ := pq.Dequeue()
+        second, _ := pq.Dequeue()
+        if second.(int) > first.(int) {
+            pq.Enqueue(first.(int) - second.(int))
+        }
+    }
+    
+    pq.Enqueue(0)
+    result, _ := pq.Dequeue()
+    return -result.(int)
+}
+```
+
+```kotlin
+class Solution {
+    fun lastStoneWeight(stones: IntArray): Int {
+        val minHeap = PriorityQueue<Int>()
+        for (s in stones) {
+            minHeap.offer(-s)
+        }
+        
+        while (minHeap.size > 1) {
+            val first = minHeap.poll()
+            val second = minHeap.poll()
+            if (second > first) {
+                minHeap.offer(first - second)
+            }
+        }
+        
+        minHeap.offer(0)
+        return Math.abs(minHeap.peek())
+    }
+}
+```
+
+```swift
+class Solution {
+    func lastStoneWeight(_ stones: [Int]) -> Int {
+        var heap = Heap(stones)
+        while heap.count > 1 {
+            let first = heap.popMax()!
+            let second = heap.popMax()!
+            if first > second {
+                heap.insert(first - second)
+            }
+        }
+        return heap.isEmpty ? 0 : heap.popMax()!
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -610,6 +822,135 @@ public class Solution {
 }
 ```
 
+```go
+func lastStoneWeight(stones []int) int {
+    maxStone := 0
+    for _, stone := range stones {
+        if stone > maxStone {
+            maxStone = stone
+        }
+    }
+    
+    bucket := make([]int, maxStone+1)
+    for _, stone := range stones {
+        bucket[stone]++
+    }
+    
+    first, second := maxStone, maxStone
+    for first > 0 {
+        if bucket[first]%2 == 0 {
+            first--
+            continue
+        }
+        
+        j := min(first-1, second)
+        for j > 0 && bucket[j] == 0 {
+            j--
+        }
+        
+        if j == 0 {
+            return first
+        }
+        second = j
+        bucket[first]--
+        bucket[second]--
+        bucket[first-second]++
+        first = max(first-second, second)
+    }
+    return first
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun lastStoneWeight(stones: IntArray): Int {
+        val maxStone = stones.max()!!
+        val bucket = IntArray(maxStone + 1)
+        for (stone in stones) {
+            bucket[stone]++
+        }
+        
+        var first = maxStone
+        var second = maxStone
+        while (first > 0) {
+            if (bucket[first] % 2 == 0) {
+                first--
+                continue
+            }
+            
+            var j = minOf(first - 1, second)
+            while (j > 0 && bucket[j] == 0) {
+                j--
+            }
+            
+            if (j == 0) {
+                return first
+            }
+            second = j
+            bucket[first]--
+            bucket[second]--
+            bucket[first - second]++
+            first = maxOf(first - second, second)
+        }
+        return first
+    }
+}
+```
+
+```swift
+class Solution {
+    func lastStoneWeight(_ stones: [Int]) -> Int {
+        guard let maxStone = stones.max() else { return 0 }
+
+        var bucket = [Int](repeating: 0, count: maxStone + 1)
+        for stone in stones {
+            bucket[stone] += 1
+        }
+
+        var first = maxStone
+        var second = maxStone
+
+        while first > 0 {
+            if bucket[first] % 2 == 0 {
+                first -= 1
+                continue
+            }
+            
+            var j = min(first - 1, second)
+            while j > 0 && bucket[j] == 0 {
+                j -= 1
+            }
+            
+            if j == 0 {
+                return first
+            }
+            
+            second = j
+            bucket[first] -= 1
+            bucket[second] -= 1
+            bucket[first - second] += 1
+            first = max(first - second, second)
+        }
+        
+        return first
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/leaf-similar-trees.md b/articles/leaf-similar-trees.md
new file mode 100644
index 000000000..5e92ef739
--- /dev/null
+++ b/articles/leaf-similar-trees.md
@@ -0,0 +1,504 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def leafSimilar(self, root1: Optional[TreeNode], root2: Optional[TreeNode]) -> bool:
+        def dfs(root, leaf):
+            if not root:
+                return
+            if not root.left and not root.right:
+                leaf.append(root.val)
+                return
+            dfs(root.left, leaf)
+            dfs(root.right, leaf)
+
+        leaf1, leaf2 = [], []
+        dfs(root1, leaf1)
+        dfs(root2, leaf2)
+        return leaf1 == leaf2  
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public boolean leafSimilar(TreeNode root1, TreeNode root2) {
+        List<Integer> leaf1 = new ArrayList<>();
+        List<Integer> leaf2 = new ArrayList<>();
+        
+        dfs(root1, leaf1);
+        dfs(root2, leaf2);
+        
+        return leaf1.equals(leaf2);
+    }
+
+    private void dfs(TreeNode root, List<Integer> leaf) {
+        if (root == null) return;
+        if (root.left == null && root.right == null) {
+            leaf.add(root.val);
+            return;
+        }
+        dfs(root.left, leaf);
+        dfs(root.right, leaf);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    bool leafSimilar(TreeNode* root1, TreeNode* root2) {
+        vector<int> leaf1, leaf2;
+        dfs(root1, leaf1);
+        dfs(root2, leaf2);
+        return leaf1 == leaf2;
+    }
+
+private:
+    void dfs(TreeNode* root, vector<int>& leaf) {
+        if (!root) return;
+        if (!root->left && !root->right) {
+            leaf.push_back(root->val);
+            return;
+        }
+        dfs(root->left, leaf);
+        dfs(root->right, leaf);
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root1
+     * @param {TreeNode} root2
+     * @return {boolean}
+     */
+    leafSimilar(root1, root2) {
+        const dfs = (root, leaf) => {
+            if (!root) return;
+            if (!root.left && !root.right) {
+                leaf.push(root.val);
+                return;
+            }
+            dfs(root.left, leaf);
+            dfs(root.right, leaf);
+        };
+
+        const leaf1 = [];
+        const leaf2 = [];
+        dfs(root1, leaf1);
+        dfs(root2, leaf2);
+
+        return JSON.stringify(leaf1) === JSON.stringify(leaf2);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(n + m)$
+
+> Where $n$ and $m$ are the number of nodes in the given trees.
+
+---
+
+## 2. Depth First Search (Space Optimized)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def leafSimilar(self, root1: Optional[TreeNode], root2: Optional[TreeNode]) -> bool:
+        def dfs(root, leaf):
+            if not root:
+                return
+            if not root.left and not root.right:
+                leaf.append(root.val)
+                return
+            dfs(root.left, leaf)
+            dfs(root.right, leaf)
+        
+        leaf1 = []
+        dfs(root1, leaf1)
+
+        def dfs1(root, leaf):
+            if not root:
+                return True
+            if not root.left and not root.right:
+                if not leaf:
+                    return False
+                return leaf.pop() == root.val            
+            return dfs1(root.right, leaf) and dfs1(root.left, leaf)
+        
+        return dfs1(root2, leaf1) and not leaf1
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public boolean leafSimilar(TreeNode root1, TreeNode root2) {
+        Stack<Integer> leaf1 = new Stack<>();
+        dfs(root1, leaf1);
+        return dfs1(root2, leaf1) && leaf1.isEmpty();
+    }
+
+    private void dfs(TreeNode root, Stack<Integer> leaf) {
+        if (root == null) return;
+        if (root.left == null && root.right == null) {
+            leaf.push(root.val);
+            return;
+        }
+        dfs(root.left, leaf);
+        dfs(root.right, leaf);
+    }
+
+    private boolean dfs1(TreeNode root, Stack<Integer> leaf) {
+        if (root == null) return true;
+        if (root.left == null && root.right == null) {
+            if (leaf.isEmpty()) return false;
+            return leaf.pop() == root.val;
+        }
+        return dfs1(root.right, leaf) && dfs1(root.left, leaf);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    bool leafSimilar(TreeNode* root1, TreeNode* root2) {
+        vector<int> leaf1;
+        dfs(root1, leaf1);
+        return dfs1(root2, leaf1) && leaf1.empty();
+    }
+
+private:
+    void dfs(TreeNode* root, vector<int>& leaf) {
+        if (!root) return;
+        if (!root->left && !root->right) {
+            leaf.push_back(root->val);
+            return;
+        }
+        dfs(root->left, leaf);
+        dfs(root->right, leaf);
+    }
+
+    bool dfs1(TreeNode* root, vector<int>& leaf) {
+        if (!root) return true;
+        if (!root->left && !root->right) {
+            if (leaf.empty() || leaf.back() != root->val) {
+                return false;
+            }
+            leaf.pop_back();
+            return true;
+        }
+        return dfs1(root->right, leaf) && dfs1(root->left, leaf);
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root1
+     * @param {TreeNode} root2
+     * @return {boolean}
+     */
+    leafSimilar(root1, root2) {
+        const dfs = (root, leaf) => {
+            if (!root) return;
+            if (!root.left && !root.right) {
+                leaf.push(root.val);
+                return;
+            }
+            dfs(root.left, leaf);
+            dfs(root.right, leaf);
+        };
+
+        const dfs1 = (root, leaf) => {
+            if (!root) return true;
+            if (!root.left && !root.right) {
+                if (!leaf.length) return false;
+                return leaf.pop() === root.val;
+            }
+            return dfs1(root.right, leaf) && dfs1(root.left, leaf);
+        };
+
+        const leaf1 = [];
+        dfs(root1, leaf1);
+        return dfs1(root2, leaf1) && leaf1.length === 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(n + m)$
+
+> Where $n$ and $m$ are the number of nodes in the given trees.
+
+---
+
+## 3. Iterative DFS
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def leafSimilar(self, root1: Optional[TreeNode], root2: Optional[TreeNode]) -> bool:
+        def getPathLeaf(stack):
+            while stack:
+                node = stack.pop()
+                if node.right:
+                    stack.append(node.right)
+                if node.left:
+                    stack.append(node.left)
+                if not node.left and not node.right:
+                    return node.val
+
+        stack1, stack2 = [root1], [root2]
+        while stack1 and stack2:
+            if getPathLeaf(stack1) != getPathLeaf(stack2):
+                return False
+        
+        return not stack1 and not stack2
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public boolean leafSimilar(TreeNode root1, TreeNode root2) {
+        Stack<TreeNode> stack1 = new Stack<>();
+        Stack<TreeNode> stack2 = new Stack<>();
+        stack1.push(root1);
+        stack2.push(root2);
+
+        while (!stack1.isEmpty() && !stack2.isEmpty()) {
+            if (getPathLeaf(stack1) != getPathLeaf(stack2)) {
+                return false;
+            }
+        }
+        return stack1.isEmpty() && stack2.isEmpty();
+    }
+
+    private int getPathLeaf(Stack<TreeNode> stack) {
+        while (!stack.isEmpty()) {
+            TreeNode node = stack.pop();
+            if (node.right != null) {
+                stack.push(node.right);
+            }
+            if (node.left != null) {
+                stack.push(node.left);
+            }
+            if (node.left == null && node.right == null) {
+                return node.val;
+            }
+        }
+        return -1;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    bool leafSimilar(TreeNode* root1, TreeNode* root2) {
+        stack<TreeNode*> stack1, stack2;
+        stack1.push(root1);
+        stack2.push(root2);
+
+        while (!stack1.empty() && !stack2.empty()) {
+            if (getPathLeaf(stack1) != getPathLeaf(stack2)) {
+                return false;
+            }
+        }
+        return stack1.empty() && stack2.empty();
+    }
+
+private:
+    int getPathLeaf(stack<TreeNode*>& stack) {
+        while (!stack.empty()) {
+            TreeNode* node = stack.top();
+            stack.pop();
+            if (node->right) {
+                stack.push(node->right);
+            }
+            if (node->left) {
+                stack.push(node->left);
+            }
+            if (!node->left && !node->right) {
+                return node->val;
+            }
+        }
+        return -1;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root1
+     * @param {TreeNode} root2
+     * @return {boolean}
+     */
+    leafSimilar(root1, root2) {
+        const getPathLeaf = (stack) => {
+            while (stack.length) {
+                const node = stack.pop();
+                if (node.right) stack.push(node.right);
+                if (node.left) stack.push(node.left);
+                if (!node.left && !node.right) return node.val;
+            }
+        };
+
+        const stack1 = [root1], stack2 = [root2];
+        while (stack1.length && stack2.length) {
+            if (getPathLeaf(stack1) !== getPathLeaf(stack2)) {
+                return false;
+            }
+        }
+        return stack1.length === 0 && stack2.length === 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(n + m)$
+
+> Where $n$ and $m$ are the number of nodes in the given trees.
\ No newline at end of file
diff --git a/articles/least-number-of-unique-integers-after-k-removals.md b/articles/least-number-of-unique-integers-after-k-removals.md
new file mode 100644
index 000000000..ddffbfb03
--- /dev/null
+++ b/articles/least-number-of-unique-integers-after-k-removals.md
@@ -0,0 +1,343 @@
+## 1. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def findLeastNumOfUniqueInts(self, arr: List[int], k: int) -> int:
+        freq = sorted(Counter(arr).values())
+        n = len(freq)
+        for i in range(n):
+            if k >= freq[i]:
+                k -= freq[i]
+            else:
+                return n - i
+        return 0
+```
+
+```java
+public class Solution {
+    public int findLeastNumOfUniqueInts(int[] arr, int k) {
+        Map<Integer, Integer> freqMap = new HashMap<>();
+        for (int num : arr) {
+            freqMap.put(num, freqMap.getOrDefault(num, 0) + 1);
+        }
+
+        List<Integer> freq = new ArrayList<>(freqMap.values());
+        Collections.sort(freq);
+
+        int n = freq.size();
+        for (int i = 0; i < n; i++) {
+            if (k >= freq.get(i)) {
+                k -= freq.get(i);
+            } else {
+                return n - i;
+            }
+        }
+        return 0;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findLeastNumOfUniqueInts(vector<int>& arr, int k) {
+        unordered_map<int, int> freqMap;
+        for (int num : arr) {
+            freqMap[num]++;
+        }
+
+        vector<int> freq;
+        for (auto& [_, count] : freqMap) {
+            freq.push_back(count);
+        }
+
+        sort(freq.begin(), freq.end());
+
+        int n = freq.size();
+        for (int i = 0; i < n; i++) {
+            if (k >= freq[i]) {
+                k -= freq[i];
+            } else {
+                return n - i;
+            }
+        }
+        return 0;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @param {number} k
+     * @return {number}
+     */
+    findLeastNumOfUniqueInts(arr, k) {
+        let freqMap = new Map();
+        for (let num of arr) {
+            freqMap.set(num, (freqMap.get(num) || 0) + 1);
+        }
+
+        let freq = Array.from(freqMap.values()).sort((a, b) => a - b);
+
+        let n = freq.length;
+        for (let i = 0; i < n; i++) {
+            if (k >= freq[i]) {
+                k -= freq[i];
+            } else {
+                return n - i;
+            }
+        }
+        return 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Min-Heap
+
+::tabs-start
+
+```python
+class Solution:
+    def findLeastNumOfUniqueInts(self, arr: List[int], k: int) -> int:
+        freq = Counter(arr)
+        heap = list(freq.values())
+        heapq.heapify(heap)
+
+        res = len(heap)
+        while k > 0 and heap:
+            f = heapq.heappop(heap)
+            if k >= f:
+                k -= f
+                res -= 1
+        return res
+```
+
+```java
+public class Solution {
+    public int findLeastNumOfUniqueInts(int[] arr, int k) {
+        Map<Integer, Integer> freqMap = new HashMap<>();
+        for (int num : arr) {
+            freqMap.put(num, freqMap.getOrDefault(num, 0) + 1);
+        }
+
+        PriorityQueue<Integer> minHeap = new PriorityQueue<>(freqMap.values());
+
+        int res = minHeap.size();
+        while (k > 0 && !minHeap.isEmpty()) {
+            int f = minHeap.poll();
+            if (k >= f) {
+                k -= f;
+                res--;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findLeastNumOfUniqueInts(vector<int>& arr, int k) {
+        unordered_map<int, int> freqMap;
+        for (int num : arr) {
+            freqMap[num]++;
+        }
+
+        priority_queue<int, vector<int>, greater<int>> minHeap;
+        for (auto& [_, count] : freqMap) {
+            minHeap.push(count);
+        }
+
+        int res = minHeap.size();
+        while (k > 0 && !minHeap.empty()) {
+            int f = minHeap.top();
+            minHeap.pop();
+            if (k >= f) {
+                k -= f;
+                res--;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @param {number} k
+     * @return {number}
+     */
+    findLeastNumOfUniqueInts(arr, k) {
+        let freqMap = new Map();
+        for (let num of arr) {
+            freqMap.set(num, (freqMap.get(num) || 0) + 1);
+        }
+
+        const minHeap = MinPriorityQueue.fromArray([...freqMap.values()]);
+
+        let res = minHeap.size();
+        while (k > 0 && !minHeap.isEmpty()) {
+            let f = minHeap.pop();
+            if (k >= f) {
+                k -= f;
+                res--;
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Bucket Sort
+
+::tabs-start
+
+```python
+class Solution:
+    def findLeastNumOfUniqueInts(self, arr: List[int], k: int) -> int:
+        freq = Counter(arr)
+        freq_list = [0] * (len(arr) + 1)
+
+        for n, f in freq.items():
+            freq_list[f] += 1
+
+        res = len(freq)
+        for f in range(1, len(freq_list)):
+            remove = freq_list[f]
+            if k >= f * remove:
+                k -= f * remove
+                res -= remove
+            else:
+                remove = k // f
+                res -= remove
+                break
+        return res
+```
+
+```java
+public class Solution {
+    public int findLeastNumOfUniqueInts(int[] arr, int k) {
+        Map<Integer, Integer> freqMap = new HashMap<>();
+        for (int num : arr) {
+            freqMap.put(num, freqMap.getOrDefault(num, 0) + 1);
+        }
+
+        int[] freqList = new int[arr.length + 1];
+        for (int f : freqMap.values()) {
+            freqList[f]++;
+        }
+
+        int res = freqMap.size();
+        for (int f = 1; f < freqList.length; f++) {
+            int remove = freqList[f];
+            if (k >= f * remove) {
+                k -= f * remove;
+                res -= remove;
+            } else {
+                remove = k / f;
+                res -= remove;
+                break;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findLeastNumOfUniqueInts(vector<int>& arr, int k) {
+        unordered_map<int, int> freqMap;
+        for (int num : arr) {
+            freqMap[num]++;
+        }
+
+        vector<int> freqList(arr.size() + 1, 0);
+        for (auto& [_, f] : freqMap) {
+            freqList[f]++;
+        }
+
+        int res = freqMap.size();
+        for (int f = 1; f < freqList.size(); f++) {
+            int remove = freqList[f];
+            if (k >= f * remove) {
+                k -= f * remove;
+                res -= remove;
+            } else {
+                remove = k / f;
+                res -= remove;
+                break;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @param {number} k
+     * @return {number}
+     */
+    findLeastNumOfUniqueInts(arr, k) {
+        let freqMap = new Map();
+        for (let num of arr) {
+            freqMap.set(num, (freqMap.get(num) || 0) + 1);
+        }
+
+        let freqList = new Array(arr.length + 1).fill(0);
+        for (let f of freqMap.values()) {
+            freqList[f]++;
+        }
+
+        let res = freqMap.size;
+        for (let f = 1; f < freqList.length; f++) {
+            let remove = freqList[f];
+            if (k >= f * remove) {
+                k -= f * remove;
+                res -= remove;
+            } else {
+                remove = Math.floor(k / f);
+                res -= remove;
+                break;
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/lemonade-change.md b/articles/lemonade-change.md
new file mode 100644
index 000000000..662b4dc91
--- /dev/null
+++ b/articles/lemonade-change.md
@@ -0,0 +1,241 @@
+## 1. Iteration - I
+
+::tabs-start
+
+```python
+class Solution:
+    def lemonadeChange(self, bills: List[int]) -> bool:
+        five, ten = 0, 0
+        for b in bills:
+            if b == 5:
+                five += 1
+            elif b == 10:
+                ten += 1
+                if five > 0:
+                    five -= 1
+                else:
+                    return False
+            else:
+                change = b - 5
+                if change == 15 and five > 0 and ten > 0:
+                    five -= 1
+                    ten -= 1
+                elif change == 15 and five >= 3:
+                    five -= 3
+                else:
+                    return False
+        return True
+```
+
+```java
+public class Solution {
+    public boolean lemonadeChange(int[] bills) {
+        int five = 0, ten = 0;
+        for (int b : bills) {
+            if (b == 5) {
+                five++;
+            } else if (b == 10) {
+                ten++;
+                if (five > 0) {
+                    five--;
+                } else {
+                    return false;
+                }
+            } else {
+                if (five > 0 && ten > 0) {
+                    five--;
+                    ten--;
+                } else if (five >= 3) {
+                    five -= 3;
+                } else {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool lemonadeChange(vector<int>& bills) {
+        int five = 0, ten = 0;
+        for (int b : bills) {
+            if (b == 5) {
+                five++;
+            } else if (b == 10) {
+                ten++;
+                if (five > 0) {
+                    five--;
+                } else {
+                    return false;
+                }
+            } else {
+                if (five > 0 && ten > 0) {
+                    five--;
+                    ten--;
+                } else if (five >= 3) {
+                    five -= 3;
+                } else {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} bills
+     * @return {boolean}
+     */
+    lemonadeChange(bills) {
+        let five = 0, ten = 0;
+        for (let b of bills) {
+            if (b === 5) {
+                five++;
+            } else if (b === 10) {
+                ten++;
+                if (five > 0) {
+                    five--;
+                } else {
+                    return false;
+                }
+            } else {
+                if (five > 0 && ten > 0) {
+                    five--;
+                    ten--;
+                } else if (five >= 3) {
+                    five -= 3;
+                } else {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 2. Iteration - II
+
+::tabs-start
+
+```python
+class Solution:
+    def lemonadeChange(self, bills: List[int]) -> bool:
+        five, ten = 0, 0
+        for b in bills:
+            if b == 5:
+                five += 1
+            elif b == 10:
+                five, ten = five - 1, ten + 1
+            elif ten > 0:
+                five, ten = five - 1, ten - 1
+            else:
+                five -= 3
+            if five < 0:
+                return False
+        return True
+```
+
+```java
+public class Solution {
+    public boolean lemonadeChange(int[] bills) {
+        int five = 0, ten = 0;
+        for (int b : bills) {
+            if (b == 5) {
+                five++;
+            } else if (b == 10) {
+                five--;
+                ten++;
+            } else if (ten > 0) {
+                five--;
+                ten--;
+            } else {
+                five -= 3;
+            }
+            if (five < 0) {
+                return false;
+            }
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool lemonadeChange(vector<int>& bills) {
+        int five = 0, ten = 0;
+        for (int b : bills) {
+            if (b == 5) {
+                five++;
+            } else if (b == 10) {
+                five--;
+                ten++;
+            } else if (ten > 0) {
+                five--;
+                ten--;
+            } else {
+                five -= 3;
+            }
+            if (five < 0) {
+                return false;
+            }
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} bills
+     * @return {boolean}
+     */
+    lemonadeChange(bills) {
+        let five = 0, ten = 0;
+        for (let b of bills) {
+            if (b === 5) {
+                five++;
+            } else if (b === 10) {
+                five--;
+                ten++;
+            } else if (ten > 0) {
+                five--;
+                ten--;
+            } else {
+                five -= 3;
+            }
+            if (five < 0) {
+                return false;
+            }
+        }
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/length-of-last-word.md b/articles/length-of-last-word.md
new file mode 100644
index 000000000..baa94e557
--- /dev/null
+++ b/articles/length-of-last-word.md
@@ -0,0 +1,230 @@
+## 1. Iteration - I
+
+::tabs-start
+
+```python
+class Solution:
+    def lengthOfLastWord(self, s: str) -> int:
+        length = i = 0
+        while i < len(s):
+            if s[i] == ' ':
+                while i < len(s) and s[i] == ' ':
+                    i += 1
+                if i == len(s):
+                    return length
+                length = 0
+            else:
+                length += 1
+                i += 1
+        return length
+```
+
+```java
+public class Solution {
+    public int lengthOfLastWord(String s) {
+        int length = 0, i = 0;
+        while (i < s.length()) {
+            if (s.charAt(i) == ' ') {
+                while (i < s.length() && s.charAt(i) == ' ') {
+                    i++;
+                }
+                if (i == s.length()) {
+                    return length;
+                }
+                length = 0;
+            } else {
+                length++;
+                i++;
+            }
+        }
+        return length;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int lengthOfLastWord(string s) {
+        int length = 0, i = 0;
+        while (i < s.length()) {
+            if (s[i] == ' ') {
+                while (i < s.length() && s[i] == ' ') {
+                    i++;
+                }
+                if (i == s.length()) {
+                    return length;
+                }
+                length = 0;
+            } else {
+                length++;
+                i++;
+            }
+        }
+        return length;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    lengthOfLastWord(s) {
+        let length = 0, i = 0;
+        while (i < s.length) {
+            if (s[i] === ' ') {
+                while (i < s.length && s[i] === ' ') {
+                    i++;
+                }
+                if (i === s.length) {
+                    return length;
+                }
+                length = 0;
+            } else {
+                length++;
+                i++;
+            }
+        }
+        return length;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Iteration - II
+
+::tabs-start
+
+```python
+class Solution:
+    def lengthOfLastWord(self, s: str) -> int:
+        i, length = len(s) - 1, 0
+        while s[i] == ' ':
+            i -= 1
+        while i >= 0 and s[i] != ' ':
+            i -= 1
+            length += 1
+        return length
+```
+
+```java
+public class Solution {
+    public int lengthOfLastWord(String s) {
+        int n = s.length();
+        int i = n - 1, length = 0;
+        while (s.charAt(i) == ' ') {
+            i--;
+        }
+        while (i >= 0 && s.charAt(i) != ' ') {
+            i--;
+            length++;
+        }
+        return length;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int lengthOfLastWord(string s) {
+        int n = s.length();
+        int i = n - 1, length = 0;
+        while (s[i] == ' ') i--;
+        while (i >= 0 && s[i] != ' ') {
+            i--;
+            length++;
+        }
+        return length;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    lengthOfLastWord(s) {
+        let n = s.length;
+        let i = n - 1, length = 0;
+        while (s.charAt(i) === ' ') {
+            i--;
+        }
+        while (i >= 0 && s.charAt(i) !== ' ') {
+            i--;
+            length++;
+        }
+        return length;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Built-In Function
+
+::tabs-start
+
+```python
+class Solution:
+    def lengthOfLastWord(self, s: str) -> int:
+        return len(s.split().pop())
+```
+
+```java
+public class Solution {
+    public int lengthOfLastWord(String s) {
+        s = s.trim(); 
+        return s.length() - s.lastIndexOf(" ") - 1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int lengthOfLastWord(string s) {
+        s.erase(s.find_last_not_of(' ') + 1); 
+        return s.substr(s.find_last_of(' ') + 1).length();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    lengthOfLastWord(s) {
+        return s.trim().split(' ').pop().length
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/length-of-longest-subarray-with-at-most-k-frequency.md b/articles/length-of-longest-subarray-with-at-most-k-frequency.md
new file mode 100644
index 000000000..5726525c2
--- /dev/null
+++ b/articles/length-of-longest-subarray-with-at-most-k-frequency.md
@@ -0,0 +1,278 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def maxSubarrayLength(self, nums: List[int], k: int) -> int:
+        n, res = len(nums), 0
+
+        for i in range(n):
+            count = defaultdict(int)
+            for j in range(i, n):
+                count[nums[j]] += 1
+                if count[nums[j]] > k:
+                    break
+                res = max(res, j - i + 1)
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int maxSubarrayLength(int[] nums, int k) {
+        int n = nums.length, res = 0;
+
+        for (int i = 0; i < n; i++) {
+            Map<Integer, Integer> count = new HashMap<>();
+            for (int j = i; j < n; j++) {
+                count.put(nums[j], count.getOrDefault(nums[j], 0) + 1);
+                if (count.get(nums[j]) > k) {
+                    break;
+                }
+                res = Math.max(res, j - i + 1);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxSubarrayLength(vector<int>& nums, int k) {
+        int n = nums.size(), res = 0;
+
+        for (int i = 0; i < n; i++) {
+            unordered_map<int, int> count;
+            for (int j = i; j < n; j++) {
+                count[nums[j]]++;
+                if (count[nums[j]] > k) {
+                    break;
+                }
+                res = max(res, j - i + 1);
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    maxSubarrayLength(nums, k) {
+        let n = nums.length, res = 0;
+
+        for (let i = 0; i < n; i++) {
+            let count = new Map();
+            for (let j = i; j < n; j++) {
+                count.set(nums[j], (count.get(nums[j]) || 0) + 1);
+                if (count.get(nums[j]) > k) {
+                    break;
+                }
+                res = Math.max(res, j - i + 1);
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Sliding Window
+
+::tabs-start
+
+```python
+class Solution:
+    def maxSubarrayLength(self, nums: List[int], k: int) -> int:
+        res = 0
+        count = defaultdict(int)
+        l = 0
+        for r in range(len(nums)):
+            count[nums[r]] += 1
+            while count[nums[r]] > k:
+                count[nums[l]] -= 1
+                l += 1
+            res = max(res, r - l + 1)
+        return res
+```
+
+```java
+public class Solution {
+    public int maxSubarrayLength(int[] nums, int k) {
+        int res = 0;
+        Map<Integer, Integer> count = new HashMap<>();
+        int l = 0;
+
+        for (int r = 0; r < nums.length; r++) {
+            count.put(nums[r], count.getOrDefault(nums[r], 0) + 1);
+            while (count.get(nums[r]) > k) {
+                count.put(nums[l], count.get(nums[l]) - 1);
+                l++;
+            }
+            res = Math.max(res, r - l + 1);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxSubarrayLength(vector<int>& nums, int k) {
+        int res = 0;
+        unordered_map<int, int> count;
+        int l = 0;
+
+        for (int r = 0; r < nums.size(); r++) {
+            count[nums[r]]++;
+            while (count[nums[r]] > k) {
+                count[nums[l]]--;
+                l++;
+            }
+            res = max(res, r - l + 1);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    maxSubarrayLength(nums, k) {
+        let res = 0;
+        let count = new Map();
+        let l = 0;
+
+        for (let r = 0; r < nums.length; r++) {
+            count.set(nums[r], (count.get(nums[r]) || 0) + 1);
+            while (count.get(nums[r]) > k) {
+                count.set(nums[l], count.get(nums[l]) - 1);
+                l++;
+            }
+            res = Math.max(res, r - l + 1);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Sliding Window (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxSubarrayLength(self, nums: List[int], k: int) -> int:
+        count = defaultdict(int)
+        l = res = 0
+        cnt = 0  # count of numbers with freq > k
+        for r in range(len(nums)):
+            count[nums[r]] += 1
+            cnt += count[nums[r]] > k
+            if cnt > 0:
+                cnt -= count[nums[l]] > k
+                count[nums[l]] -= 1
+                l += 1
+        return len(nums) - l
+```
+
+```java
+public class Solution {
+    public int maxSubarrayLength(int[] nums, int k) {
+        HashMap<Integer, Integer> count = new HashMap<>();
+        int l = 0, cnt = 0; // count of numbers with freq > k
+        for (int r = 0; r < nums.length; r++) {
+            count.put(nums[r], count.getOrDefault(nums[r], 0) + 1);
+            if (count.get(nums[r]) > k) cnt++;
+            if (cnt > 0) {
+                if (count.get(nums[l]) > k) cnt--;
+                count.put(nums[l], count.get(nums[l]) - 1);
+                l++;
+            }
+        }
+        return nums.length - l;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxSubarrayLength(vector<int>& nums, int k) {
+        unordered_map<int, int> count;
+        int l = 0, cnt = 0; // count of numbers with freq > k
+        for (int r = 0; r < nums.size(); r++) {
+            count[nums[r]]++;
+            cnt += count[nums[r]] > k;
+            if (cnt > 0) {
+                cnt -= count[nums[l]] > k;
+                count[nums[l]]--;
+                l++;
+            }
+        }
+        return nums.size() - l;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    maxSubarrayLength(nums, k) {
+        let count = new Map();
+        let l = 0, cnt = 0; // count of numbers with freq > k
+        for (let r = 0; r < nums.length; r++) {
+            count.set(nums[r], (count.get(nums[r]) || 0) + 1);
+            if (count.get(nums[r]) > k) cnt++;
+            if (cnt > 0) {
+                if (count.get(nums[l]) > k) cnt--;
+                count.set(nums[l], count.get(nums[l]) - 1);
+                l++;
+            }
+        }
+        return nums.length - l;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/level-order-traversal-of-binary-tree.md b/articles/level-order-traversal-of-binary-tree.md
index ccb2cb491..28df7fc5f 100644
--- a/articles/level-order-traversal-of-binary-tree.md
+++ b/articles/level-order-traversal-of-binary-tree.md
@@ -19,11 +19,11 @@ class Solution:
                 return None
             if len(res) == depth:
                 res.append([])
-            
+
             res[depth].append(node.val)
             dfs(node.left, depth + 1)
             dfs(node.right, depth + 1)
-        
+
         dfs(root, 0)
         return res
 ```
@@ -186,6 +186,109 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func levelOrder(root *TreeNode) [][]int {
+    res := [][]int{}
+    
+    var dfs func(node *TreeNode, depth int)
+    dfs = func(node *TreeNode, depth int) {
+        if node == nil {
+            return
+        }
+        
+        if len(res) == depth {
+            res = append(res, []int{})
+        }
+        
+        res[depth] = append(res[depth], node.Val)
+        dfs(node.Left, depth+1)
+        dfs(node.Right, depth+1)
+    }
+    
+    dfs(root, 0)
+    return res
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    fun levelOrder(root: TreeNode?): List<List<Int>> {
+        val res = mutableListOf<MutableList<Int>>()
+        
+        fun dfs(node: TreeNode?, depth: Int) {
+            if (node == null) return
+            
+            if (res.size == depth) {
+                res.add(mutableListOf())
+            }
+            
+            res[depth].add(node.`val`)
+            dfs(node.left, depth + 1)
+            dfs(node.right, depth + 1)
+        }
+        
+        dfs(root, 0)
+        return res
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func levelOrder(_ root: TreeNode?) -> [[Int]] {
+        var res = [[Int]]()
+
+        func dfs(_ node: TreeNode?, _ depth: Int) {
+            guard let node = node else { return }
+
+            if res.count == depth {
+                res.append([])
+            }
+
+            res[depth].append(node.val)
+            dfs(node.left, depth + 1)
+            dfs(node.right, depth + 1)
+        }
+
+        dfs(root, 0)
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -404,6 +507,128 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func levelOrder(root *TreeNode) [][]int {
+    res := [][]int{}
+    if root == nil {
+        return res
+    }
+
+    q := []*TreeNode{root}
+
+    for len(q) > 0 {
+        qLen := len(q)
+        level := []int{}
+
+        for i := 0; i < qLen; i++ {
+            node := q[0]
+            q = q[1:] 
+            level = append(level, node.Val)
+
+            if node.Left != nil {
+                q = append(q, node.Left)
+            }
+            if node.Right != nil {
+                q = append(q, node.Right)
+            }
+        }
+        
+        res = append(res, level)
+    }
+
+    return res
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    fun levelOrder(root: TreeNode?): List<List<Int>> {
+        val res = mutableListOf<List<Int>>()
+        if (root == null) return res
+
+        val q = ArrayDeque<TreeNode>()
+        q.add(root)
+
+        while (q.isNotEmpty()) {
+            val level = mutableListOf<Int>()
+            val qLen = q.size
+            
+            for (i in 0 until qLen) {
+                val node = q.removeFirst()
+                level.add(node.`val`)
+
+                node.left?.let { q.add(it) }
+                node.right?.let { q.add(it) }
+            }
+            
+            res.add(level)
+        }
+        
+        return res
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func levelOrder(_ root: TreeNode?) -> [[Int]] {
+        var res = [[Int]]()
+        var q = Deque<TreeNode?>()
+        q.append(root)
+
+        while !q.isEmpty {
+            let qLen = q.count
+            var level = [Int]()
+
+            for _ in 0..<qLen {
+                if let node = q.removeFirst() {
+                    level.append(node.val)
+                    q.append(node.left)
+                    q.append(node.right)
+                }
+            }
+            if !level.isEmpty {
+                res.append(level)
+            }
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/lfu-cache.md b/articles/lfu-cache.md
new file mode 100644
index 000000000..ec31ef4fb
--- /dev/null
+++ b/articles/lfu-cache.md
@@ -0,0 +1,715 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class LFUCache:
+    
+    def __init__(self, capacity: int):
+        self.capacity = capacity
+        self.cache = {}  # key -> [value, frequency, timestamp]
+        self.timestamp = 0
+        
+    def get(self, key: int) -> int:
+        if key not in self.cache:
+            return -1
+            
+        self.cache[key][1] += 1
+        self.timestamp += 1
+        self.cache[key][2] = self.timestamp
+        return self.cache[key][0]
+        
+    def put(self, key: int, value: int) -> None:
+        if self.capacity <= 0:
+            return
+            
+        self.timestamp += 1
+        if key in self.cache:
+            self.cache[key][0] = value
+            self.cache[key][1] += 1
+            self.cache[key][2] = self.timestamp
+            return
+            
+        if len(self.cache) >= self.capacity:
+            min_freq = float('inf')
+            min_timestamp = float('inf')
+            lfu_key = None
+            
+            for k, (_, freq, ts) in self.cache.items():
+                if freq < min_freq or (freq == min_freq and ts < min_timestamp):
+                    min_freq = freq
+                    min_timestamp = ts
+                    lfu_key = k
+            if lfu_key is not None:
+                del self.cache[lfu_key]
+                
+        self.cache[key] = [value, 1, self.timestamp]
+```
+
+```java
+class Node {
+    int value, freq, timestamp;
+
+    Node(int value, int freq, int timestamp) {
+        this.value = value;
+        this.freq = freq;
+        this.timestamp = timestamp;
+    }
+}
+
+public class LFUCache {
+
+    private int capacity, timestamp;
+    private Map<Integer, Node> cache;
+
+    public LFUCache(int capacity) {
+        this.capacity = capacity;
+        this.timestamp = 0;
+        this.cache = new HashMap<>();
+    }
+
+    public int get(int key) {
+        if (!cache.containsKey(key)) return -1;
+
+        Node node = cache.get(key);
+        node.freq++;
+        node.timestamp = ++timestamp;
+        return node.value;
+    }
+
+    public void put(int key, int value) {
+        if (capacity <= 0) return;
+
+        timestamp++;
+        if (cache.containsKey(key)) {
+            Node node = cache.get(key);
+            node.value = value;
+            node.freq++;
+            node.timestamp = timestamp;
+            return;
+        }
+
+        if (cache.size() >= capacity) {
+            int minFreq = Integer.MAX_VALUE, minTimestamp = Integer.MAX_VALUE, lfuKey = -1;
+
+            for (Map.Entry<Integer, Node> entry : cache.entrySet()) {
+                Node node = entry.getValue();
+                if (node.freq < minFreq || (node.freq == minFreq && node.timestamp < minTimestamp)) {
+                    minFreq = node.freq;
+                    minTimestamp = node.timestamp;
+                    lfuKey = entry.getKey();
+                }
+            }
+
+            cache.remove(lfuKey);
+        }
+
+        cache.put(key, new Node(value, 1, timestamp));
+    }
+}
+```
+
+```cpp
+class LFUCache {
+    struct Node {
+        int value, freq, timestamp;
+        Node(int v, int f, int t) : value(v), freq(f), timestamp(t) {}
+    };
+
+    int capacity, timestamp;
+    unordered_map<int, Node*> cache;
+
+public:
+    LFUCache(int capacity) : capacity(capacity), timestamp(0) {}
+
+    int get(int key) {
+        if (cache.find(key) == cache.end()) return -1;
+
+        cache[key]->freq++;
+        cache[key]->timestamp = ++timestamp;
+        return cache[key]->value;
+    }
+
+    void put(int key, int value) {
+        if (capacity <= 0) return;
+
+        timestamp++;
+        if (cache.find(key) != cache.end()) {
+            cache[key]->value = value;
+            cache[key]->freq++;
+            cache[key]->timestamp = timestamp;
+            return;
+        }
+
+        if (cache.size() >= capacity) {
+            int minFreq = INT_MAX, minTimestamp = INT_MAX, lfuKey = -1;
+
+            for (const auto& [k, node] : cache) {
+                if (node->freq < minFreq || (node->freq == minFreq && node->timestamp < minTimestamp)) {
+                    minFreq = node->freq;
+                    minTimestamp = node->timestamp;
+                    lfuKey = k;
+                }
+            }
+            delete cache[lfuKey];
+            cache.erase(lfuKey);
+        }
+
+        cache[key] = new Node(value, 1, timestamp);
+    }
+};
+```
+
+```javascript
+class LFUCache {
+    /**
+     * @param {number} capacity
+     */
+    constructor(capacity) {
+        this.capacity = capacity;
+        this.timestamp = 0;
+        this.cache = new Map();
+    }
+
+    /** 
+     * @param {number} key
+     * @return {number}
+     */
+    get(key) {
+        if (!this.cache.has(key)) return -1;
+
+        const node = this.cache.get(key);
+        node.freq++;
+        node.timestamp = ++this.timestamp;
+        return node.value;
+    }
+
+    /** 
+     * @param {number} key 
+     * @param {number} value
+     * @return {void}
+     */
+    put(key, value) {
+        if (this.capacity <= 0) return;
+
+        this.timestamp++;
+        if (this.cache.has(key)) {
+            const node = this.cache.get(key);
+            node.value = value;
+            node.freq++;
+            node.timestamp = this.timestamp;
+            return;
+        }
+
+        if (this.cache.size >= this.capacity) {
+            let minFreq = Infinity, minTimestamp = Infinity, lfuKey = null;
+
+            for (const [k, node] of this.cache.entries()) {
+                if (node.freq < minFreq || (node.freq === minFreq && node.timestamp < minTimestamp)) {
+                    minFreq = node.freq;
+                    minTimestamp = node.timestamp;
+                    lfuKey = k;
+                }
+            }
+
+            if (lfuKey !== null) this.cache.delete(lfuKey);
+        }
+
+        this.cache.set(key, { value, freq: 1, timestamp: this.timestamp });
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(1)$ time for initialization.
+    * $O(1)$ time for each $get()$ function call.
+    * $O(n)$ time for each $put()$ function call.
+* Space complexity: $O(n)$
+
+---
+
+## 2. Doubly Linked List
+
+::tabs-start
+
+```python
+class ListNode:
+
+    def __init__(self, val, prev=None, next=None):
+        self.val = val
+        self.prev = prev
+        self.next = next
+
+class LinkedList:
+
+    def __init__(self):
+        self.left = ListNode(0)
+        self.right = ListNode(0, self.left)
+        self.left.next = self.right
+        self.map = {}
+
+    def length(self):
+        return len(self.map)
+
+    def pushRight(self, val):
+        node = ListNode(val, self.right.prev, self.right)
+        self.map[val] = node
+        self.right.prev = node
+        node.prev.next = node
+
+    def pop(self, val):
+        if val in self.map:
+            node = self.map[val]
+            next, prev = node.next, node.prev
+            next.prev = prev
+            prev.next = next
+            self.map.pop(val, None)
+    
+    def popLeft(self):
+        res = self.left.next.val
+        self.pop(self.left.next.val)
+        return res
+    
+    def update(self, val):
+        self.pop(val)
+        self.pushRight(val)
+
+class LFUCache:
+
+    def __init__(self, capacity: int):
+        self.cap = capacity
+        self.lfuCnt = 0
+        self.valMap = {} # Map key -> val
+        self.countMap = defaultdict(int) # Map key -> count
+        # Map count of key -> linkedlist
+        self.listMap = defaultdict(LinkedList)
+
+    def counter(self, key):
+        cnt = self.countMap[key]
+        self.countMap[key] += 1
+        self.listMap[cnt].pop(key)
+        self.listMap[cnt + 1].pushRight(key)
+
+        if cnt == self.lfuCnt and self.listMap[cnt].length() == 0:
+            self.lfuCnt += 1
+        
+
+    def get(self, key: int) -> int:
+        if key not in self.valMap:
+            return -1
+        self.counter(key)
+        return self.valMap[key]
+
+    def put(self, key: int, value: int) -> None:
+        if self.cap == 0:
+            return
+        
+        if key not in self.valMap and len(self.valMap) == self.cap:
+            res = self.listMap[self.lfuCnt].popLeft()
+            self.valMap.pop(res)
+            self.countMap.pop(res)
+        
+        self.valMap[key] = value
+        self.counter(key)
+        self.lfuCnt = min(self.lfuCnt, self.countMap[key])
+```
+
+```java
+class ListNode {
+    int val;
+    ListNode prev, next;
+
+    ListNode(int val) {
+        this.val = val;
+    }
+
+    ListNode(int val, ListNode prev, ListNode next) {
+        this.val = val;
+        this.prev = prev;
+        this.next = next;
+    }
+}
+
+class DoublyLinkedList {
+    private ListNode left, right;
+    private Map<Integer, ListNode> map;
+
+    DoublyLinkedList() {
+        this.left = new ListNode(0);
+        this.right = new ListNode(0, this.left, null);
+        this.left.next = this.right;
+        this.map = new HashMap<>();
+    }
+
+    public int length() {
+        return map.size();
+    }
+
+    public void pushRight(int val) {
+        ListNode node = new ListNode(val, this.right.prev, this.right);
+        this.map.put(val, node);
+        this.right.prev.next = node;
+        this.right.prev = node;
+    }
+
+    public void pop(int val) {
+        if (this.map.containsKey(val)) {
+            ListNode node = this.map.get(val);
+            ListNode prev = node.prev, next = node.next;
+            prev.next = next;
+            next.prev = prev;
+            this.map.remove(val);
+        }
+    }
+
+    public int popLeft() {
+        int res = this.left.next.val;
+        pop(res);
+        return res;
+    }
+
+    public void update(int val) {
+        pop(val);
+        pushRight(val);
+    }
+}
+
+public class LFUCache {
+    private int capacity;
+    private int lfuCount;
+    private Map<Integer, Integer> valMap;
+    private Map<Integer, Integer> countMap;
+    private Map<Integer, DoublyLinkedList> listMap;
+
+    public LFUCache(int capacity) {
+        this.capacity = capacity;
+        this.lfuCount = 0;
+        this.valMap = new HashMap<>();
+        this.countMap = new HashMap<>();
+        this.listMap = new HashMap<>();
+    }
+
+    private void counter(int key) {
+        int count = countMap.get(key);
+        countMap.put(key, count + 1);
+        listMap.putIfAbsent(count, new DoublyLinkedList());
+        listMap.get(count).pop(key);
+        
+        listMap.putIfAbsent(count + 1, new DoublyLinkedList());
+        listMap.get(count + 1).pushRight(key);
+
+        if (count == lfuCount && listMap.get(count).length() == 0) {
+            lfuCount++;
+        }
+    }
+
+    public int get(int key) {
+        if (!valMap.containsKey(key)) {
+            return -1;
+        }
+        counter(key);
+        return valMap.get(key);
+    }
+
+    public void put(int key, int value) {
+        if (capacity == 0) {
+            return;
+        }
+
+        if (!valMap.containsKey(key) && valMap.size() == capacity) {
+            int toRemove = listMap.get(lfuCount).popLeft();
+            valMap.remove(toRemove);
+            countMap.remove(toRemove);
+        }
+
+        valMap.put(key, value);
+        countMap.putIfAbsent(key, 0);
+        counter(key);
+        lfuCount = Math.min(lfuCount, countMap.get(key));
+    }
+}
+```
+
+```cpp
+class LFUCache {
+    struct ListNode {
+        int val;
+        ListNode* prev;
+        ListNode* next;
+
+        ListNode(int val) : val(val), prev(nullptr), next(nullptr) {}
+        ListNode(int val, ListNode* prev, ListNode* next) : val(val), prev(prev), next(next) {}
+    };
+
+    struct LinkedList {
+        ListNode* left;
+        ListNode* right;
+        unordered_map<int, ListNode*> map;
+        
+        LinkedList() {
+            left = new ListNode(0);
+            right = new ListNode(0);
+            left->next = right;
+            right->prev = left;
+        }
+        
+        ~LinkedList() {
+            while (left->next != right) {
+                ListNode* temp = left->next;
+                left->next = temp->next;
+                delete temp;
+            }
+            delete left;
+            delete right;
+        }
+
+        int length() {
+            return map.size();
+        }
+
+        void pushRight(int val) {
+            ListNode* node = new ListNode(val, right->prev, right);
+            map[val] = node;
+            right->prev->next = node;
+            right->prev = node;
+        }
+
+        void pop(int val) {
+            if (map.find(val) != map.end()) {
+                ListNode* node = map[val];
+                ListNode* prev = node->prev;
+                ListNode* next = node->next;
+                prev->next = next;
+                next->prev = prev;
+                map.erase(val);
+                delete node;
+            }
+        }
+
+        int popLeft() {
+            int res = left->next->val;
+            pop(res);
+            return res;
+        }
+
+        void update(int val) {
+            pop(val);
+            pushRight(val);
+        }
+    };
+
+    int capacity;
+    int lfuCount;
+    unordered_map<int, int> valMap; // Map key -> value
+    unordered_map<int, int> countMap; // Map key -> count
+    unordered_map<int, LinkedList*> listMap; // Map count -> linked list
+
+    void counter(int key) {
+        int count = countMap[key];
+        countMap[key] = count + 1;
+
+        listMap[count]->pop(key);
+        
+        if (!listMap.count(count + 1)) {
+            listMap[count + 1] = new LinkedList();
+        }
+        listMap[count + 1]->pushRight(key);
+
+        if (count == lfuCount && listMap[count]->length() == 0) {
+            lfuCount++;
+        }
+    }
+
+public:
+    LFUCache(int capacity) : capacity(capacity), lfuCount(0) {
+        listMap[0] = new LinkedList();
+    }
+    
+    ~LFUCache() {
+        for (auto& pair : listMap) {
+            delete pair.second;
+        }
+    }
+
+    int get(int key) {
+        if (valMap.find(key) == valMap.end()) {
+            return -1;
+        }
+        counter(key);
+        return valMap[key];
+    }
+
+    void put(int key, int value) {
+        if (capacity == 0) {
+            return;
+        }
+
+        if (valMap.find(key) == valMap.end() && valMap.size() == capacity) {
+            int toRemove = listMap[lfuCount]->popLeft();
+            valMap.erase(toRemove);
+            countMap.erase(toRemove);
+        }
+
+        valMap[key] = value;
+        if (countMap.find(key) == countMap.end()) {
+            countMap[key] = 0;
+            listMap[0]->pushRight(key);
+            lfuCount = 0;
+        }
+        counter(key);
+    }
+};
+```
+
+```javascript
+class ListNode {
+    /**
+     * @param {number} val
+     * @param {ListNode} prev
+     * @param {ListNode} next
+     */
+    constructor(val, prev = null, next = null) {
+        this.val = val;
+        this.prev = prev;
+        this.next = next;
+    }
+}
+
+class LinkedList {
+    constructor() {
+        this.left = new ListNode(0);
+        this.right = new ListNode(0);
+        this.left.next = this.right;
+        this.right.prev = this.left;
+        this.map = new Map();
+    }
+
+    /**
+     * @return {number}
+     */
+    length() {
+        return this.map.size;
+    }
+
+    /**
+     * @param {number} val
+     */
+    pushRight(val) {
+        const node = new ListNode(val, this.right.prev, this.right);
+        this.map.set(val, node);
+        this.right.prev.next = node;
+        this.right.prev = node;
+    }
+
+    /**
+     * @param {number} val
+     */
+    pop(val) {
+        if (this.map.has(val)) {
+            const node = this.map.get(val);
+            const prev = node.prev;
+            const next = node.next;
+            prev.next = next;
+            next.prev = prev;
+            this.map.delete(val);
+        }
+    }
+
+    /**
+     * @return {number}
+     */
+    popLeft() {
+        const res = this.left.next.val;
+        this.pop(res);
+        return res;
+    }
+
+    /**
+     * @param {number} val
+     */
+    update(val) {
+        this.pop(val);
+        this.pushRight(val);
+    }
+}
+
+class LFUCache {
+    /**
+     * @param {number} capacity
+     */
+    constructor(capacity) {
+        this.capacity = capacity;
+        this.lfuCount = 0;
+        this.valMap = new Map();
+        this.countMap = new Map();
+        this.listMap = new Map();
+        this.listMap.set(0, new LinkedList());
+    }
+
+    /**
+     * @param {number} key
+     */
+    counter(key) {
+        const count = this.countMap.get(key);
+        this.countMap.set(key, count + 1);
+
+        this.listMap.get(count).pop(key);
+
+        if (!this.listMap.has(count + 1)) {
+            this.listMap.set(count + 1, new LinkedList());
+        }
+        this.listMap.get(count + 1).pushRight(key);
+
+        if (count === this.lfuCount && this.listMap.get(count).length() === 0) {
+            this.lfuCount++;
+        }
+    }
+
+    /**
+     * @param {number} key
+     * @return {number}
+     */
+    get(key) {
+        if (!this.valMap.has(key)) {
+            return -1;
+        }
+        this.counter(key);
+        return this.valMap.get(key);
+    }
+
+    /**
+     * @param {number} key
+     * @param {number} value
+     */
+    put(key, value) {
+        if (this.capacity === 0) return;
+
+        if (!this.valMap.has(key) && this.valMap.size === this.capacity) {
+            const toRemove = this.listMap.get(this.lfuCount).popLeft();
+            this.valMap.delete(toRemove);
+            this.countMap.delete(toRemove);
+        }
+
+        this.valMap.set(key, value);
+        if (!this.countMap.has(key)) {
+            this.countMap.set(key, 0);
+            this.listMap.get(0).pushRight(key);
+            this.lfuCount = 0;
+        }
+        this.counter(key);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(1)$ time for initialization.
+    * $O(1)$ time for each $get()$ and $put()$ function calls.
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/linked-list-cycle-detection.md b/articles/linked-list-cycle-detection.md
index b7eff8aab..f8d574c77 100644
--- a/articles/linked-list-cycle-detection.md
+++ b/articles/linked-list-cycle-detection.md
@@ -138,6 +138,85 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func hasCycle(head *ListNode) bool {
+    seen := make(map[*ListNode]bool)
+    cur := head
+    for cur != nil {
+        if seen[cur] {
+            return true
+        }
+        seen[cur] = true
+        cur = cur.Next
+    }
+    return false
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var li = ListNode(5)
+ * var v = li.`val`
+ * Definition for singly-linked list.
+ * class ListNode(var `val`: Int) {
+ *     var next: ListNode? = null
+ * }
+ */
+
+class Solution {
+    fun hasCycle(head: ListNode?): Boolean {
+        val seen = HashSet<ListNode>()
+        var cur = head
+        while (cur != null) {
+            if (!seen.add(cur)) {
+                return true
+            }
+            cur = cur.next
+        }
+        return false
+    }
+}
+```
+
+```swift
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public var val: Int
+ *     public var next: ListNode?
+ *     public init(_ val: Int) {
+ *         self.val = val
+ *         self.next = nil
+ *     }
+ * }
+ */
+
+class Solution {
+    func hasCycle(_ head: ListNode?) -> Bool {
+        var seen = Set<ObjectIdentifier>()
+        var cur = head
+
+        while cur != nil {
+            let nodeId = ObjectIdentifier(cur!)
+            if seen.contains(nodeId) {
+                return true
+            }
+            seen.insert(nodeId)
+            cur = cur?.next
+        }
+        return false
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -290,6 +369,85 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func hasCycle(head *ListNode) bool {
+    slow := head
+    fast := head
+    for fast != nil && fast.Next != nil {
+        slow = slow.Next
+        fast = fast.Next.Next
+        if slow == fast {
+            return true
+        }
+    }
+    return false
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var li = ListNode(5)
+ * var v = li.`val`
+ * Definition for singly-linked list.
+ * class ListNode(var `val`: Int) {
+ *     var next: ListNode? = null
+ * }
+ */
+
+class Solution {
+    fun hasCycle(head: ListNode?): Boolean {
+        var slow = head
+        var fast = head
+        while (fast != null && fast?.next != null) {
+            slow = slow?.next
+            fast = fast?.next?.next
+            if (slow == fast) {
+                return true
+            }
+        }
+        return false
+    }
+}
+```
+
+```swift
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public var val: Int
+ *     public var next: ListNode?
+ *     public init(_ val: Int) {
+ *         self.val = val
+ *         self.next = nil
+ *     }
+ * }
+ */
+
+class Solution {
+    func hasCycle(_ head: ListNode?) -> Bool {
+        var slow = head
+        var fast = head
+
+        while fast != nil && fast?.next != nil {
+            slow = slow?.next
+            fast = fast?.next?.next
+            if slow === fast {
+                return true
+            }
+        }
+        return false
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/linked-list-cycle-ii.md b/articles/linked-list-cycle-ii.md
new file mode 100644
index 000000000..2964377b8
--- /dev/null
+++ b/articles/linked-list-cycle-ii.md
@@ -0,0 +1,264 @@
+## 1. Hash Set
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+
+class Solution:
+    def detectCycle(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        seen = set()
+        cur = head
+        while cur:
+            if cur in seen:
+                return cur
+            seen.add(cur)
+            cur = cur.next
+        return None
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode(int x) {
+ *         val = x;
+ *         next = null;
+ *     }
+ * }
+ */
+public class Solution {
+    public ListNode detectCycle(ListNode head) {
+        Set<ListNode> seen = new HashSet<>();
+        ListNode cur = head;
+        while (cur != null) {
+            if (seen.contains(cur)) {
+                return cur;
+            }
+            seen.add(cur);
+            cur = cur.next;
+        }
+        return null;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode(int x) : val(x), next(NULL) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* detectCycle(ListNode* head) {
+        unordered_set<ListNode*> seen;
+        ListNode* cur = head;
+        while (cur) {
+            if (seen.find(cur) != seen.end()) {
+                return cur;
+            }
+            seen.insert(cur);
+            cur = cur->next;
+        }
+        return nullptr;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @return {ListNode}
+     */
+    detectCycle(head) {
+        const seen = new Set();
+        let cur = head;
+        while (cur) {
+            if (seen.has(cur)) {
+                return cur;
+            }
+            seen.add(cur);
+            cur = cur.next;
+        }
+        return null;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Fast & Slow Pointers
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+
+class Solution:
+    def detectCycle(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        if not head or not head.next:
+            return None
+        
+        slow, fast = head, head
+        while fast and fast.next:
+            slow = slow.next
+            fast = fast.next.next
+            if slow == fast:
+                slow = head
+                while slow != fast:
+                    slow = slow.next
+                    fast = fast.next
+                return slow
+        return None
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode(int x) {
+ *         val = x;
+ *         next = null;
+ *     }
+ * }
+ */
+public class Solution {
+    public ListNode detectCycle(ListNode head) {
+        if (head == null || head.next == null) {
+            return null;
+        }
+
+        ListNode slow = head, fast = head;
+        while (fast != null && fast.next != null) {
+            slow = slow.next;
+            fast = fast.next.next;
+            if (slow == fast) {
+                slow = head;
+                while (slow != fast) {
+                    slow = slow.next;
+                    fast = fast.next;
+                }
+                return slow;
+            }
+        }
+        return null;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode(int x) : val(x), next(NULL) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* detectCycle(ListNode* head) {
+        if (!head || !head->next) {
+            return nullptr;
+        }
+
+        ListNode* slow = head;
+        ListNode* fast = head;
+
+        while (fast && fast->next) {
+            slow = slow->next;
+            fast = fast->next->next;
+
+            if (slow == fast) {
+                slow = head;
+                while (slow != fast) {
+                    slow = slow->next;
+                    fast = fast->next;
+                }
+                return slow;
+            }
+        }
+        return nullptr;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @return {ListNode}
+     */
+    detectCycle(head) {
+        if (!head || !head.next) {
+            return null;
+        }
+
+        let slow = head, fast = head;
+
+        while (fast && fast.next) {
+            slow = slow.next;
+            fast = fast.next.next;
+
+            if (slow === fast) {
+                slow = head;
+                while (slow !== fast) {
+                    slow = slow.next;
+                    fast = fast.next;
+                }
+                return slow;
+            }
+        }
+        return null;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/longest-common-prefix.md b/articles/longest-common-prefix.md
new file mode 100644
index 000000000..936377d1c
--- /dev/null
+++ b/articles/longest-common-prefix.md
@@ -0,0 +1,621 @@
+## 1. Horizontal Scanning
+
+::tabs-start
+
+```python
+class Solution:
+    def longestCommonPrefix(self, strs: List[str]) -> str:
+        prefix = strs[0]
+        for i in range(1, len(strs)):
+            j = 0
+            while j < min(len(prefix), len(strs[i])):
+                if prefix[j] != strs[i][j]:
+                    break
+                j += 1
+            prefix = prefix[:j]
+        return prefix
+```
+
+```java
+public class Solution {
+    public String longestCommonPrefix(String[] strs) {
+        String prefix = strs[0];
+        for (int i = 1; i < strs.length; i++) {
+            int j = 0;
+            while (j < Math.min(prefix.length(), strs[i].length())) {
+                if (prefix.charAt(j) != strs[i].charAt(j)) {
+                    break;
+                }
+                j++;
+            }
+            prefix = prefix.substring(0, j);
+        }
+        return prefix;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string longestCommonPrefix(vector<string>& strs) {
+        string prefix = strs[0];
+        for (int i = 1; i < strs.size(); i++) {
+            int j = 0;
+            while (j < min(prefix.length(), strs[i].length())) {
+                if (prefix[j] != strs[i][j]) {
+                    break;
+                }
+                j++;
+            }
+            prefix = prefix.substr(0, j);
+        }
+        return prefix;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} strs
+     * @return {string}
+     */
+    longestCommonPrefix(strs) {
+        let prefix = strs[0];
+        for (let i = 1; i < strs.length; i++) {
+            let j = 0;
+            while (j < Math.min(prefix.length, strs[i].length)) {
+                if (prefix[j] !== strs[i][j]) {
+                    break;
+                }
+                j++;
+            }
+            prefix = prefix.slice(0, j);
+        }
+        return prefix;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public string LongestCommonPrefix(string[] strs) {
+        string prefix = strs[0];
+
+        for (int i = 1; i < strs.Length; i++) {
+            int j = 0;
+            while (j < Math.Min(prefix.Length, strs[i].Length)) {
+                if (prefix[j] != strs[i][j]) {
+                    break;
+                }
+                j++;
+            }
+            prefix = prefix.Substring(0, j);
+        }
+
+        return prefix;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(1)$
+
+> Where $n$ is the length of the shortest string and $m$ is the number of strings.
+
+---
+
+## 2. Vertical Scanning
+
+::tabs-start
+
+```python
+class Solution:
+    def longestCommonPrefix(self, strs: List[str]) -> str:
+        for i in range(len(strs[0])):
+            for s in strs:
+                if i == len(s) or s[i] != strs[0][i]:
+                    return s[:i]
+        return strs[0]
+```
+
+```java
+public class Solution {
+    public String longestCommonPrefix(String[] strs) {
+        for (int i = 0; i < strs[0].length(); i++) {
+            for (String s : strs) {
+                if (i == s.length() || s.charAt(i) != strs[0].charAt(i)) {
+                    return s.substring(0, i);
+                }
+            }
+        }
+        return strs[0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string longestCommonPrefix(vector<string>& strs) {
+        for (int i = 0; i < strs[0].length(); i++) {
+            for (const string& s : strs) {
+                if (i == s.length() || s[i] != strs[0][i]) {
+                    return s.substr(0, i);
+                }
+            }
+        }
+        return strs[0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} strs
+     * @return {string}
+     */
+    longestCommonPrefix(strs) {
+        for (let i = 0; i < strs[0].length; i++) {
+            for (let s of strs) {
+                if (i === s.length || s[i] !== strs[0][i]) {
+                    return s.slice(0, i);
+                }
+            }
+        }
+        return strs[0];
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public string LongestCommonPrefix(string[] strs) {
+        for (int i = 0; i < strs[0].Length; i++) {
+            foreach (string s in strs) {
+                if (i == s.Length || s[i] != strs[0][i]) {
+                    return s.Substring(0, i);
+                }
+            }
+        }
+        return strs[0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(1)$ since we did not use extra space.
+
+> Where $n$ is the length of the shortest string and $m$ is the number of strings.
+
+---
+
+## 3. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def longestCommonPrefix(self, strs: List[str]) -> str:
+        if len(strs) == 1:
+            return strs[0]
+        
+        strs = sorted(strs)
+        for i in range(min(len(strs[0]), len(strs[-1]))):
+            if strs[0][i] != strs[-1][i]:
+                return strs[0][:i]
+        return strs[0]
+```
+
+```java
+public class Solution {
+    public String longestCommonPrefix(String[] strs) {
+        if (strs.length == 1) {
+            return strs[0];
+        }
+        
+        Arrays.sort(strs);
+        int N = Math.min(strs[0].length(), strs[strs.length - 1].length());
+        for (int i = 0; i < N; i++) {
+            if (strs[0].charAt(i) != strs[strs.length - 1].charAt(i)) {
+                return strs[0].substring(0, i);
+            }
+        }
+        return strs[0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string longestCommonPrefix(vector<string>& strs) {
+        if (strs.size() == 1) {
+            return strs[0];
+        }
+        
+        sort(strs.begin(), strs.end());
+        for (int i = 0; i < min(strs[0].length(), strs.back().length()); i++) {
+            if (strs[0][i] != strs.back()[i]) {
+                return strs[0].substr(0, i);
+            }
+        }
+        return strs[0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} strs
+     * @return {string}
+     */
+    longestCommonPrefix(strs) {
+        if (strs.length === 1) {
+            return strs[0];
+        }
+        
+        strs.sort();
+        let N = Math.min(strs[0].length, strs[strs.length - 1].length);
+        for (let i = 0; i < N; i++) {
+            if (strs[0][i] !== strs[strs.length - 1][i]) {
+                return strs[0].slice(0, i);
+            }
+        }
+        return strs[0];
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public string LongestCommonPrefix(string[] strs) {
+        if (strs.Length == 1) {
+            return strs[0];
+        }
+
+        Array.Sort(strs);
+        string first = strs[0];
+        string last = strs[strs.Length - 1];
+
+        int i = 0;
+        while (i < Math.Min(first.Length, last.Length)) {
+            if (first[i] != last[i]) {
+                return first.Substring(0, i);
+            }
+            i++;
+        }
+
+        return first;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m \log m)$
+* Space complexity: $O(1)$ or $O(m)$ depending on the sorting algorithm.
+
+> Where $n$ is the length of the longest string and $m$ is the number of strings.
+
+---
+
+## 4. Trie
+
+::tabs-start
+
+```python
+class TrieNode:
+    def __init__(self):
+        self.children = {}
+
+class Trie:
+    def __init__(self):
+        self.root = TrieNode()
+
+    def insert(self, word: str) -> None:
+        node = self.root
+        for char in word:
+            if char not in node.children:
+                node.children[char] = TrieNode()
+            node = node.children[char]
+    
+    def lcp(self, word: str, prefixLen: int) -> int:
+        node = self.root
+        for i in range(min(len(word), prefixLen)):
+            if word[i] not in node.children:
+                return i
+            node = node.children[word[i]]
+        return min(len(word), prefixLen)
+
+class Solution:
+    def longestCommonPrefix(self, strs: list[str]) -> str:
+        if len(strs) == 1:
+            return strs[0]
+
+        mini = 0
+        for i in range(1, len(strs)):
+            if len(strs[mini]) > len(strs[i]):
+                mini = i
+
+        trie = Trie()
+        trie.insert(strs[mini])
+        prefixLen = len(strs[mini])
+        for i in range(len(strs)):
+            prefixLen = trie.lcp(strs[i], prefixLen)
+        return strs[0][:prefixLen]
+```
+
+```java
+class TrieNode {
+    Map<Character, TrieNode> children = new HashMap<>();
+}
+
+class Trie {
+    TrieNode root = new TrieNode();
+
+    void insert(String word) {
+        TrieNode node = root;
+        for (char c : word.toCharArray()) {
+            node.children.putIfAbsent(c, new TrieNode());
+            node = node.children.get(c);
+        }
+    }
+
+    int lcp(String word, int prefixLen) {
+        TrieNode node = root;
+        int i = 0;
+        while (i < Math.min(word.length(), prefixLen)) {
+            if (!node.children.containsKey(word.charAt(i))) {
+                return i;
+            }
+            node = node.children.get(word.charAt(i));
+            i++;
+        }
+        return Math.min(word.length(), prefixLen);
+    }
+}
+
+public class Solution {
+    public String longestCommonPrefix(String[] strs) {
+        if (strs.length == 1) {
+            return strs[0];
+        }
+
+        int mini = 0;
+        for (int i = 1; i < strs.length; i++) {
+            if (strs[mini].length() > strs[i].length()) {
+                mini = i;
+            }
+        }
+
+        Trie trie = new Trie();
+        trie.insert(strs[mini]);
+        int prefixLen = strs[mini].length();
+
+        for (int i = 0; i < strs.length; i++) {
+            prefixLen = trie.lcp(strs[i], prefixLen);
+        }
+
+        return strs[0].substring(0, prefixLen);
+    }
+}
+```
+
+```cpp
+class TrieNode {
+public:
+    unordered_map<char, TrieNode*> children;
+};
+
+class Trie {
+public:
+    TrieNode* root;
+    Trie() {
+        root = new TrieNode();
+    }
+
+    void insert(const string& word) {
+        TrieNode* node = root;
+        for (char c : word) {
+            if (node->children.find(c) == node->children.end()) {
+                node->children[c] = new TrieNode();
+            }
+            node = node->children[c];
+        }
+    }
+
+    int lcp(const string& word, int prefixLen) {
+        TrieNode* node = root;
+        int i = 0;
+        while (i < min((int)word.length(), prefixLen)) {
+            if (node->children.find(word[i]) == node->children.end()) {
+                return i;
+            }
+            node = node->children[word[i]];
+            i++;
+        }
+        return min((int)word.length(), prefixLen);
+    }
+};
+
+class Solution {
+public:
+    string longestCommonPrefix(vector<string>& strs) {
+        if (strs.size() == 1) {
+            return strs[0];
+        }
+        int mini = 0;
+        for (int i = 1; i < strs.size(); i++) {
+            if (strs[mini].size() > strs[i].size()) {
+                mini = i;
+            }
+        }
+
+        Trie trie;
+        trie.insert(strs[mini]);
+        int prefixLen = strs[mini].length();
+
+        for (int i = 0; i < strs.size(); i++) {
+            prefixLen = trie.lcp(strs[i], prefixLen);
+        }
+
+        return strs[0].substr(0, prefixLen);
+    }
+};
+```
+
+```javascript
+class TrieNode {
+    constructor() {
+        this.children = {};
+    }
+}
+
+class Trie {
+    constructor() {
+        this.root = new TrieNode();
+    }
+
+    /**
+     * @param {string} word
+     * @return {void}
+     */
+    insert(word) {
+        let node = this.root;
+        for (let char of word) {
+            if (!node.children[char]) {
+                node.children[char] = new TrieNode();
+            }
+            node = node.children[char];
+        }
+    }
+
+    /**
+     * @param {string} word
+     * @param {number} prefixLen
+     * @return {number}
+     */
+    lcp(word, prefixLen) {
+        let node = this.root;
+        let i = 0;
+        while (i < Math.min(word.length, prefixLen)) {
+            if (!node.children[word[i]]) {
+                return i;
+            }
+            node = node.children[word[i]];
+            i++;
+        }
+        return Math.min(word.length, prefixLen);
+    }
+}
+
+class Solution {
+    /**
+     * @param {string[]} strs
+     * @return {string}
+     */
+    longestCommonPrefix(strs) {
+        if (strs.length === 1) {
+            return strs[0];
+        }
+        
+        let mini = 0;
+        for (let i = 1; i < strs.length; i++) {
+            if (strs[mini].length > strs[i].length) {
+                mini = i;
+            }
+        }
+
+        const trie = new Trie();
+        trie.insert(strs[mini]);
+        let prefixLen = strs[mini].length;
+
+        for (let i = 0; i < strs.length; i++) {
+            prefixLen = trie.lcp(strs[i], prefixLen);
+        }
+
+        return strs[0].substring(0, prefixLen);
+    }
+}
+```
+
+```csharp
+public class TrieNode {
+    public Dictionary<char, TrieNode> Children = new Dictionary<char, TrieNode>();
+}
+
+public class Trie {
+    public TrieNode Root;
+
+    public Trie() {
+        Root = new TrieNode();
+    }
+
+    public void Insert(string word) {
+        TrieNode node = Root;
+        foreach (char c in word) {
+            if (!node.Children.ContainsKey(c)) {
+                node.Children[c] = new TrieNode();
+            }
+            node = node.Children[c];
+        }
+    }
+
+    public int Lcp(string word, int prefixLen) {
+        TrieNode node = Root;
+        for (int i = 0; i < Math.Min(word.Length, prefixLen); i++) {
+            if (!node.Children.ContainsKey(word[i])) {
+                return i;
+            }
+            node = node.Children[word[i]];
+        }
+        return Math.Min(word.Length, prefixLen);
+    }
+}
+
+public class Solution {
+    public string LongestCommonPrefix(string[] strs) {
+        if (strs.Length == 1) return strs[0];
+
+        int mini = 0;
+        for (int i = 1; i < strs.Length; i++) {
+            if (strs[i].Length < strs[mini].Length) {
+                mini = i;
+            }
+        }
+
+        Trie trie = new Trie();
+        trie.Insert(strs[mini]);
+
+        int prefixLen = strs[mini].Length;
+        for (int i = 0; i < strs.Length; i++) {
+            prefixLen = trie.Lcp(strs[i], prefixLen);
+        }
+
+        return strs[0].Substring(0, prefixLen);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the length of the shortest string and $m$ is the number of strings.
\ No newline at end of file
diff --git a/articles/longest-common-subsequence.md b/articles/longest-common-subsequence.md
index 14228a9f3..95c23cd86 100644
--- a/articles/longest-common-subsequence.md
+++ b/articles/longest-common-subsequence.md
@@ -99,6 +99,64 @@ public class Solution {
 }
 ```
 
+```go
+func longestCommonSubsequence(text1 string, text2 string) int {
+    var dfs func(i, j int) int
+    dfs = func(i, j int) int {
+        if i == len(text1) || j == len(text2) {
+            return 0
+        }
+        if text1[i] == text2[j] {
+            return 1 + dfs(i+1, j+1)
+        }
+        return max(dfs(i+1, j), dfs(i, j+1))
+    }
+    return dfs(0, 0)
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun longestCommonSubsequence(text1: String, text2: String): Int {
+        fun dfs(i: Int, j: Int): Int {
+            if (i == text1.length || j == text2.length) return 0
+            if (text1[i] == text2[j]) return 1 + dfs(i + 1, j + 1)
+            return maxOf(dfs(i + 1, j), dfs(i, j + 1))
+        }
+
+        return dfs(0, 0)
+    }
+}
+```
+
+```swift
+class Solution {
+    func longestCommonSubsequence(_ text1: String, _ text2: String) -> Int {
+        let arr1 = Array(text1)
+        let arr2 = Array(text2)
+
+        func dfs(_ i: Int, _ j: Int) -> Int {
+            if i == arr1.count || j == arr2.count {
+                return 0
+            }
+            if arr1[i] == arr2[j] {
+                return 1 + dfs(i + 1, j + 1)
+            }
+            return max(dfs(i + 1, j), dfs(i, j + 1))
+        }
+
+        return dfs(0, 0)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -261,6 +319,100 @@ public class Solution {
 }
 ```
 
+```go
+func longestCommonSubsequence(text1 string, text2 string) int {
+    m, n := len(text1), len(text2)
+    memo := make([][]int, m+1)
+    for i := range memo {
+        memo[i] = make([]int, n+1)
+        for j := range memo[i] {
+            memo[i][j] = -1
+        }
+    }
+
+    var dfs func(i, j int) int
+    dfs = func(i, j int) int {
+        if i == m || j == n {
+            return 0
+        }
+        if memo[i][j] != -1 {
+            return memo[i][j]
+        }
+        
+        if text1[i] == text2[j] {
+            memo[i][j] = 1 + dfs(i+1, j+1)
+        } else {
+            memo[i][j] = max(dfs(i+1, j), dfs(i, j+1))
+        }
+        
+        return memo[i][j]
+    }
+
+    return dfs(0, 0)
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun longestCommonSubsequence(text1: String, text2: String): Int {
+        val m = text1.length
+        val n = text2.length
+        val memo = Array(m + 1) { IntArray(n + 1) { -1 } }
+
+        fun dfs(i: Int, j: Int): Int {
+            if (i == m || j == n) return 0
+            if (memo[i][j] != -1) return memo[i][j]
+
+            memo[i][j] = if (text1[i] == text2[j]) {
+                1 + dfs(i + 1, j + 1)
+            } else {
+                maxOf(dfs(i + 1, j), dfs(i, j + 1))
+            }
+            
+            return memo[i][j]
+        }
+
+        return dfs(0, 0)
+    }
+}
+```
+
+```swift
+class Solution {
+    func longestCommonSubsequence(_ text1: String, _ text2: String) -> Int {
+        let arr1 = Array(text1)
+        let arr2 = Array(text2)
+        var memo = [String: Int]()
+
+        func dfs(_ i: Int, _ j: Int) -> Int {
+            if i == arr1.count || j == arr2.count {
+                return 0
+            }
+            let key = "\(i),\(j)"
+            if let val = memo[key] {
+                return val
+            }
+
+            if arr1[i] == arr2[j] {
+                memo[key] = 1 + dfs(i + 1, j + 1)
+            } else {
+                memo[key] = max(dfs(i + 1, j), dfs(i, j + 1))
+            }
+            return memo[key]!
+        }
+
+        return dfs(0, 0)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -381,6 +533,82 @@ public class Solution {
 }
 ```
 
+```go
+func longestCommonSubsequence(text1 string, text2 string) int {
+    m, n := len(text1), len(text2)
+    dp := make([][]int, m+1)
+    for i := range dp {
+        dp[i] = make([]int, n+1)
+    }
+
+    for i := m - 1; i >= 0; i-- {
+        for j := n - 1; j >= 0; j-- {
+            if text1[i] == text2[j] {
+                dp[i][j] = 1 + dp[i+1][j+1]
+            } else {
+                dp[i][j] = max(dp[i+1][j], dp[i][j+1])
+            }
+        }
+    }
+
+    return dp[0][0]
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun longestCommonSubsequence(text1: String, text2: String): Int {
+        val m = text1.length
+        val n = text2.length
+        val dp = Array(m + 1) { IntArray(n + 1) }
+
+        for (i in m - 1 downTo 0) {
+            for (j in n - 1 downTo 0) {
+                dp[i][j] = if (text1[i] == text2[j]) {
+                    1 + dp[i + 1][j + 1]
+                } else {
+                    maxOf(dp[i + 1][j], dp[i][j + 1])
+                }
+            }
+        }
+
+        return dp[0][0]
+    }
+}
+```
+
+```swift
+class Solution {
+    func longestCommonSubsequence(_ text1: String, _ text2: String) -> Int {
+        let m = text1.count
+        let n = text2.count
+        let arr1 = Array(text1)
+        let arr2 = Array(text2)
+
+        var dp = Array(repeating: Array(repeating: 0, count: n + 1), count: m + 1)
+
+        for i in stride(from: m - 1, through: 0, by: -1) {
+            for j in stride(from: n - 1, through: 0, by: -1) {
+                if arr1[i] == arr2[j] {
+                    dp[i][j] = 1 + dp[i + 1][j + 1]
+                } else {
+                    dp[i][j] = max(dp[i][j + 1], dp[i + 1][j])
+                }
+            }
+        }
+
+        return dp[0][0]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -532,6 +760,99 @@ public class Solution {
 }
 ```
 
+```go
+func longestCommonSubsequence(text1 string, text2 string) int {
+    if len(text1) < len(text2) {
+        text1, text2 = text2, text1
+    }
+    
+    prev := make([]int, len(text2)+1)
+    curr := make([]int, len(text2)+1)
+
+    for i := len(text1) - 1; i >= 0; i-- {
+        for j := len(text2) - 1; j >= 0; j-- {
+            if text1[i] == text2[j] {
+                curr[j] = 1 + prev[j+1]
+            } else {
+                curr[j] = max(curr[j+1], prev[j])
+            }
+        }
+        prev, curr = curr, prev
+    }
+
+    return prev[0]
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun longestCommonSubsequence(text1: String, text2: String): Int {
+        var t1 = text1
+        var t2 = text2
+
+        if (t1.length < t2.length) {
+            t1 = text2
+            t2 = text1
+        }
+
+        val prev = IntArray(t2.length + 1)
+        val curr = IntArray(t2.length + 1)
+
+        for (i in t1.length - 1 downTo 0) {
+            for (j in t2.length - 1 downTo 0) {
+                curr[j] = if (t1[i] == t2[j]) {
+                    1 + prev[j + 1]
+                } else {
+                    maxOf(curr[j + 1], prev[j])
+                }
+            }
+            val temp = prev
+            prev.fill(0) 
+            prev.indices.forEach { prev[it] = curr[it] }
+            curr.fill(0) 
+        }
+
+        return prev[0]
+    }
+}
+```
+
+```swift
+class Solution {
+    func longestCommonSubsequence(_ text1: String, _ text2: String) -> Int {
+        var t1 = Array(text1)
+        var t2 = Array(text2)
+
+        if t1.count < t2.count {
+            swap(&t1, &t2)
+        }
+
+        var prev = Array(repeating: 0, count: t2.count + 1)
+        var curr = Array(repeating: 0, count: t2.count + 1)
+
+        for i in stride(from: t1.count - 1, through: 0, by: -1) {
+            for j in stride(from: t2.count - 1, through: 0, by: -1) {
+                if t1[i] == t2[j] {
+                    curr[j] = 1 + prev[j + 1]
+                } else {
+                    curr[j] = max(curr[j + 1], prev[j])
+                }
+            }
+            swap(&prev, &curr)
+        }
+
+        return prev[0]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -686,6 +1007,99 @@ public class Solution {
 }
 ```
 
+```go
+func longestCommonSubsequence(text1 string, text2 string) int {
+    if len(text1) < len(text2) {
+        text1, text2 = text2, text1
+    }
+
+    dp := make([]int, len(text2)+1)
+
+    for i := len(text1) - 1; i >= 0; i-- {
+        prev := 0
+        for j := len(text2) - 1; j >= 0; j-- {
+            temp := dp[j]
+            if text1[i] == text2[j] {
+                dp[j] = 1 + prev
+            } else {
+                dp[j] = max(dp[j], dp[j+1])
+            }
+            prev = temp
+        }
+    }
+
+    return dp[0]
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun longestCommonSubsequence(text1: String, text2: String): Int {
+        var t1 = text1
+        var t2 = text2
+
+        if (t1.length < t2.length) {
+            t1 = text2
+            t2 = text1
+        }
+
+        val dp = IntArray(t2.length + 1)
+
+        for (i in t1.length - 1 downTo 0) {
+            var prev = 0
+            for (j in t2.length - 1 downTo 0) {
+                val temp = dp[j]
+                dp[j] = if (t1[i] == t2[j]) {
+                    1 + prev
+                } else {
+                    maxOf(dp[j], dp[j + 1])
+                }
+                prev = temp
+            }
+        }
+
+        return dp[0]
+    }
+}
+```
+
+```swift
+class Solution {
+    func longestCommonSubsequence(_ text1: String, _ text2: String) -> Int {
+        var t1 = Array(text1)
+        var t2 = Array(text2)
+
+        if t1.count < t2.count {
+            swap(&t1, &t2)
+        }
+
+        var dp = Array(repeating: 0, count: t2.count + 1)
+
+        for i in stride(from: t1.count - 1, through: 0, by: -1) {
+            var prev = 0
+            for j in stride(from: t2.count - 1, through: 0, by: -1) {
+                let temp = dp[j]
+                if t1[i] == t2[j] {
+                    dp[j] = 1 + prev
+                } else {
+                    dp[j] = max(dp[j], dp[j + 1])
+                }
+                prev = temp
+            }
+        }
+
+        return dp[0]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/longest-consecutive-sequence.md b/articles/longest-consecutive-sequence.md
index 0c62e3d72..22cd5db3f 100644
--- a/articles/longest-consecutive-sequence.md
+++ b/articles/longest-consecutive-sequence.md
@@ -101,6 +101,71 @@ public class Solution {
 }
 ```
 
+```go
+func longestConsecutive(nums []int) int {
+    res := 0
+    store := make(map[int]struct{})
+    for _, num := range nums {
+        store[num] = struct{}{}
+    }
+
+    for _, num := range nums {
+        streak, curr := 0, num
+        for _, ok := store[curr]; ok; _, ok = store[curr] {
+            streak++
+            curr++
+        }
+        if streak > res {
+            res = streak
+        }
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun longestConsecutive(nums: IntArray): Int {
+        var res = 0
+        val store = nums.toSet()
+
+        for (num in nums) {
+            var streak = 0
+            var curr = num
+            while (curr in store) {
+                streak++
+                curr++
+            }
+            res = maxOf(res, streak)
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func longestConsecutive(_ nums: [Int]) -> Int {
+        var res = 0
+        let store = Set(nums)
+
+        for num in nums {
+            var streak = 0
+            var curr = num
+
+            while store.contains(curr) {
+                streak += 1
+                curr += 1
+            }
+
+            res = max(res, streak)
+        }
+
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -246,12 +311,99 @@ public class Solution {
 }
 ```
 
+```go
+func longestConsecutive(nums []int) int {
+    if len(nums) == 0 {
+        return 0
+    }
+    sort.Ints(nums)
+    
+    res := 0
+    curr, streak := nums[0], 0
+    i := 0
+    for i < len(nums) {
+        if curr != nums[i] {
+            curr = nums[i]
+            streak = 0
+        }
+        for i < len(nums) && nums[i] == curr {
+            i++
+        }
+        streak++
+        curr++
+        if streak > res {
+            res = streak
+        }
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun longestConsecutive(nums: IntArray): Int {
+        if (nums.isEmpty()) return 0
+        nums.sort()
+
+        var res = 0
+        var curr = nums[0]
+        var streak = 0
+        var i = 0
+        while (i < nums.size) {
+            if (curr != nums[i]) {
+                curr = nums[i]
+                streak = 0
+            }
+            while (i < nums.size && nums[i] == curr) {
+                i++
+            }
+            streak++
+            curr++
+            res = maxOf(res, streak)
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func longestConsecutive(_ nums: [Int]) -> Int {
+        if nums.isEmpty {
+            return 0
+        }
+        
+        var res = 0
+        var nums = nums.sorted()
+        
+        var curr = nums[0]
+        var streak = 0
+        var i = 0
+        
+        while i < nums.count {
+            if curr != nums[i] {
+                curr = nums[i]
+                streak = 0
+            }
+            while i < nums.count && nums[i] == curr {
+                i += 1
+            }
+            streak += 1
+            curr += 1
+            res = max(res, streak)
+        }
+        
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n \log n)$
-* Space complexity: $O(1)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
 
 ---
 
@@ -362,6 +514,74 @@ public class Solution {
 }
 ```
 
+```go
+func longestConsecutive(nums []int) int {
+    numSet := make(map[int]struct{})
+    for _, num := range nums {
+        numSet[num] = struct{}{}
+    }
+
+    longest := 0
+    for num := range numSet {
+        if _, found := numSet[num-1]; !found {
+            length := 1
+            for {
+                if _, exists := numSet[num+length]; exists {
+                    length++
+                } else {
+                    break
+                }
+            }
+            if length > longest {
+                longest = length
+            }
+        }
+    }
+    return longest
+}
+```
+
+```kotlin
+class Solution {
+    fun longestConsecutive(nums: IntArray): Int {
+        val numSet = nums.toSet()
+        var longest = 0
+
+        for (num in numSet) {
+            if ((num - 1) !in numSet) {
+                var length = 1
+                while ((num + length) in numSet) {
+                    length++
+                }
+                longest = maxOf(longest, length)
+            }
+        }
+        return longest
+    }
+}
+```
+
+```swift
+class Solution {
+    func longestConsecutive(_ nums: [Int]) -> Int {
+        let numSet = Set(nums)
+        var longest = 0
+
+        for num in numSet {
+            if !numSet.contains(num - 1) {
+                var length = 1
+                while numSet.contains(num + length) {
+                    length += 1
+                }
+                longest = max(length, longest)
+            }
+        }
+
+        return longest
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -474,6 +694,75 @@ public class Solution {
 }
 ```
 
+```go
+func longestConsecutive(nums []int) int {
+    mp := make(map[int]int)
+    res := 0
+
+    for _, num := range nums {
+        if mp[num] == 0 {
+            left := mp[num - 1]
+            right := mp[num + 1]
+            sum := left + right + 1
+            mp[num] = sum
+            mp[num - left] = sum
+            mp[num + right] = sum
+            if sum > res {
+                res = sum
+            }
+        }
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun longestConsecutive(nums: IntArray): Int {
+        val mp = HashMap<Int, Int>()
+        var res = 0
+
+        for (num in nums) {
+            if (mp[num] == null) {
+                val left = mp[num - 1] ?: 0
+                val right = mp[num + 1] ?: 0
+                val sum = left + right + 1
+                mp[num] = sum
+                mp[num - left] = sum
+                mp[num + right] = sum
+                res = maxOf(res, sum)
+            }
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func longestConsecutive(_ nums: [Int]) -> Int {
+        var mp = [Int: Int]()
+        var res = 0
+
+        for num in nums {
+            if mp[num] == nil {
+                let left = mp[num - 1] ?? 0
+                let right = mp[num + 1] ?? 0
+                let length = left + right + 1
+
+                mp[num] = length
+                mp[num - left] = length
+                mp[num + right] = length
+
+                res = max(res, length)
+            }
+        }
+        
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/longest-happy-string.md b/articles/longest-happy-string.md
new file mode 100644
index 000000000..3b669e0e4
--- /dev/null
+++ b/articles/longest-happy-string.md
@@ -0,0 +1,567 @@
+## 1. Greedy
+
+::tabs-start
+
+```python
+class Solution:
+    def longestDiverseString(self, a: int, b: int, c: int) -> str:
+        count = [a, b, c]
+        res = []
+
+        def getMax(repeated):
+            idx = -1
+            maxCnt = 0
+            for i in range(3):
+                if i == repeated or count[i] == 0:
+                    continue
+                if maxCnt < count[i]:
+                    maxCnt = count[i]
+                    idx = i
+            return idx
+
+        repeated = -1
+        while True:
+            maxChar = getMax(repeated)
+            if maxChar == -1:
+                break
+            res.append(chr(maxChar + ord('a')))
+            count[maxChar] -= 1
+            if len(res) > 1 and res[-1] == res[-2]:
+                repeated = maxChar
+            else:
+                repeated = -1
+
+        return ''.join(res)
+```
+
+```java
+public class Solution {
+    public String longestDiverseString(int a, int b, int c) {
+        int[] count = {a, b, c};
+        StringBuilder res = new StringBuilder();
+
+        int repeated = -1;
+        while (true) {
+            int maxChar = getMax(count, repeated);
+            if (maxChar == -1) {
+                break;
+            }
+            res.append((char) (maxChar + 'a'));
+            count[maxChar]--;
+
+            if (res.length() > 1 && res.charAt(res.length() - 1) == res.charAt(res.length() - 2)) {
+                repeated = maxChar;
+            } else {
+                repeated = -1;
+            }
+        }
+
+        return res.toString();
+    }
+
+    private int getMax(int[] count, int repeated) {
+        int idx = -1, maxCnt = 0;
+        for (int i = 0; i < 3; i++) {
+            if (i == repeated || count[i] == 0) {
+                continue;
+            }
+            if (maxCnt < count[i]) {
+                maxCnt = count[i];
+                idx = i;
+            }
+        }
+        return idx;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string longestDiverseString(int a, int b, int c) {
+        vector<int> count = {a, b, c};
+        string res;
+
+        int repeated = -1;
+        while (true) {
+            int maxChar = getMax(count, repeated);
+            if (maxChar == -1) {
+                break;
+            }
+            res += (char)(maxChar + 'a');
+            count[maxChar]--;
+
+            if (res.size() > 1 && res.back() == res[res.size() - 2]) {
+                repeated = maxChar;
+            } else {
+                repeated = -1;
+            }
+        }
+
+        return res;
+    }
+
+private:
+    int getMax(const vector<int>& count, int repeated) {
+        int idx = -1, maxCnt = 0;
+        for (int i = 0; i < 3; i++) {
+            if (i == repeated || count[i] == 0) {
+                continue;
+            }
+            if (maxCnt < count[i]) {
+                maxCnt = count[i];
+                idx = i;
+            }
+        }
+        return idx;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} a
+     * @param {number} b
+     * @param {number} c
+     * @return {string}
+     */
+    longestDiverseString(a, b, c) {
+        const count = [a, b, c];
+        const res = [];
+
+        const getMax = (repeated) => {
+            let idx = -1;
+            let maxCnt = 0;
+            for (let i = 0; i < 3; i++) {
+                if (i === repeated || count[i] === 0) {
+                    continue;
+                }
+                if (maxCnt < count[i]) {
+                    maxCnt = count[i];
+                    idx = i;
+                }
+            }
+            return idx;
+        };
+
+        let repeated = -1;
+        while (true) {
+            const maxChar = getMax(repeated);
+            if (maxChar === -1) {
+                break;
+            }
+            res.push(String.fromCharCode(maxChar + 97));
+            count[maxChar]--;
+
+            if (res.length > 1 && res[res.length - 1] === res[res.length - 2]) {
+                repeated = maxChar;
+            } else {
+                repeated = -1;
+            }
+        }
+
+        return res.join('');
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public string LongestDiverseString(int a, int b, int c) {
+        int[] count = new int[] { a, b, c };
+        List<char> res = new List<char>();
+
+        int GetMax(int repeated) {
+            int idx = -1;
+            int maxCnt = 0;
+            for (int i = 0; i < 3; i++) {
+                if (i == repeated || count[i] == 0) continue;
+                if (maxCnt < count[i]) {
+                    maxCnt = count[i];
+                    idx = i;
+                }
+            }
+            return idx;
+        }
+
+        int repeated = -1;
+        while (true) {
+            int maxChar = GetMax(repeated);
+            if (maxChar == -1) break;
+
+            res.Add((char)(maxChar + 'a'));
+            count[maxChar]--;
+
+            if (res.Count > 1 && res[res.Count - 1] == res[res.Count - 2]) {
+                repeated = maxChar;
+            } else {
+                repeated = -1;
+            }
+        }
+
+        return new string(res.ToArray());
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ space for the output string.
+
+---
+
+## 2. Greedy (Max-Heap)
+
+::tabs-start
+
+```python
+class Solution:
+    def longestDiverseString(self, a: int, b: int, c: int) -> str:
+        res = ""
+        maxHeap = []
+        for count, char in [(-a, "a"), (-b, "b"), (-c, "c")]:
+            if count != 0:
+                heapq.heappush(maxHeap, (count, char))
+        
+        while maxHeap:
+            count, char = heapq.heappop(maxHeap)
+            if len(res) > 1 and res[-1] == res[-2] == char:
+                if not maxHeap:
+                    break
+                count2, char2 = heapq.heappop(maxHeap)
+                res += char2
+                count2 += 1
+                if count2:
+                    heapq.heappush(maxHeap, (count2, char2))
+                heapq.heappush(maxHeap, (count, char))
+            else:
+                res += char
+                count += 1
+                if count:
+                    heapq.heappush(maxHeap, (count, char))
+
+        return res
+```
+
+```java
+public class Solution {
+    public String longestDiverseString(int a, int b, int c) {
+        StringBuilder res = new StringBuilder();
+        PriorityQueue<int[]> maxHeap = new PriorityQueue<>((x, y) -> y[0] - x[0]);
+
+        if (a > 0) maxHeap.offer(new int[]{a, 'a'});
+        if (b > 0) maxHeap.offer(new int[]{b, 'b'});
+        if (c > 0) maxHeap.offer(new int[]{c, 'c'});
+
+        while (!maxHeap.isEmpty()) {
+            int[] first = maxHeap.poll();
+            if (res.length() > 1 && res.charAt(res.length() - 1) == first[1] && res.charAt(res.length() - 2) == first[1]) {
+                if (maxHeap.isEmpty()) break;
+                int[] second = maxHeap.poll();
+                res.append((char) second[1]);
+                second[0]--;
+                if (second[0] > 0) maxHeap.offer(second);
+                maxHeap.offer(first);
+            } else {
+                res.append((char) first[1]);
+                first[0]--;
+                if (first[0] > 0) maxHeap.offer(first);
+            }
+        }
+
+        return res.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string longestDiverseString(int a, int b, int c) {
+        string res;
+        priority_queue<pair<int, char>> maxHeap;
+        if (a > 0) maxHeap.push({a, 'a'});
+        if (b > 0) maxHeap.push({b, 'b'});
+        if (c > 0) maxHeap.push({c, 'c'});
+
+        while (!maxHeap.empty()) {
+            auto [count, ch] = maxHeap.top();
+            maxHeap.pop();
+
+            if (res.size() > 1 && res[res.size() - 1] == ch && res[res.size() - 2] == ch) {
+                if (maxHeap.empty()) break;
+                auto [count2, ch2] = maxHeap.top();
+                maxHeap.pop();
+                res += ch2;
+                if (--count2 > 0) maxHeap.push({count2, ch2});
+                maxHeap.push({count, ch});
+            } else {
+                res += ch;
+                if (--count > 0) maxHeap.push({count, ch});
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} a
+     * @param {number} b
+     * @param {number} c
+     * @return {string}
+     */
+    longestDiverseString(a, b, c) {
+        const res = [];
+        const maxHeap = new MaxPriorityQueue(x => x[0]);
+
+        if (a > 0) maxHeap.enqueue([a, 'a']);
+        if (b > 0) maxHeap.enqueue([b, 'b']);
+        if (c > 0) maxHeap.enqueue([c, 'c']);
+
+        while (!maxHeap.isEmpty()) {
+            const [count, char] = maxHeap.dequeue();
+
+            if (res.length > 1 && res[res.length - 1] === char && res[res.length - 2] === char) {
+                if (maxHeap.isEmpty()) break;
+                const [count2, char2] = maxHeap.dequeue();
+                res.push(char2);
+                if (count2 - 1 > 0) maxHeap.enqueue([count2 - 1, char2]);
+                maxHeap.enqueue([count, char]);
+            } else {
+                res.push(char);
+                if (count - 1 > 0) maxHeap.enqueue([count - 1, char]);
+            }
+        }
+
+        return res.join('');
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public string LongestDiverseString(int a, int b, int c) {
+        string res = "";
+        PriorityQueue<(int count, char ch), int> maxHeap = new PriorityQueue<(int, char), int>();
+
+        void AddToHeap(int count, char ch) {
+            if (count > 0) {
+                maxHeap.Enqueue((count, ch), -count);
+            }
+        }
+
+        AddToHeap(a, 'a');
+        AddToHeap(b, 'b');
+        AddToHeap(c, 'c');
+
+        while (maxHeap.Count > 0) {
+            var (count1, ch1) = maxHeap.Dequeue();
+            if (res.Length >= 2 && res[^1] == ch1 && res[^2] == ch1) {
+                if (maxHeap.Count == 0) break;
+                var (count2, ch2) = maxHeap.Dequeue();
+                res += ch2;
+                count2--;
+                if (count2 > 0) {
+                    maxHeap.Enqueue((count2, ch2), -count2);
+                }
+                maxHeap.Enqueue((count1, ch1), -count1);
+            } else {
+                res += ch1;
+                count1--;
+                if (count1 > 0) {
+                    maxHeap.Enqueue((count1, ch1), -count1);
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ space for the output string.
+
+---
+
+## 3. Greedy (Recursion)
+
+::tabs-start
+
+```python
+class Solution:
+    def longestDiverseString(self, a: int, b: int, c: int) -> str:
+        def rec(max1, max2, max3, char1, char2, char3):
+            if max1 < max2:
+                return rec(max2, max1, max3, char2, char1, char3)
+            if max2 < max3:
+                return rec(max1, max3, max2, char1, char3, char2)
+            if max2 == 0:
+                return [char1] * min(2, max1)
+            
+            use1 = min(2, max1)
+            use2 = 1 if max1 - use1 >= max2 else 0
+            res = [char1] * use1 + [char2] * use2
+            return res + rec(max1 - use1, max2 - use2, max3, char1, char2, char3)
+        
+        return ''.join(rec(a, b, c, 'a', 'b', 'c'))
+```
+
+```java
+public class Solution {
+    public String longestDiverseString(int a, int b, int c) {
+        return String.join("", rec(a, b, c, 'a', 'b', 'c'));
+    }
+
+    private List<String> rec(int max1, int max2, int max3, char char1, char char2, char char3) {
+        if (max1 < max2) {
+            return rec(max2, max1, max3, char2, char1, char3);
+        }
+        if (max2 < max3) {
+            return rec(max1, max3, max2, char1, char3, char2);
+        }
+        if (max2 == 0) {
+            List<String> result = new ArrayList<>();
+            for (int i = 0; i < Math.min(2, max1); i++) {
+                result.add(String.valueOf(char1));
+            }
+            return result;
+        }
+
+        int use1 = Math.min(2, max1);
+        int use2 = (max1 - use1 >= max2) ? 1 : 0;
+
+        List<String> res = new ArrayList<>();
+        for (int i = 0; i < use1; i++) {
+            res.add(String.valueOf(char1));
+        }
+        for (int i = 0; i < use2; i++) {
+            res.add(String.valueOf(char2));
+        }
+
+        res.addAll(rec(max1 - use1, max2 - use2, max3, char1, char2, char3));
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string longestDiverseString(int a, int b, int c) {
+        vector<char> res = rec(a, b, c, 'a', 'b', 'c');
+        return string(res.begin(), res.end());
+    }
+
+private:
+    vector<char> rec(int max1, int max2, int max3, char char1, char char2, char char3) {
+        if (max1 < max2) {
+            return rec(max2, max1, max3, char2, char1, char3);
+        }
+        if (max2 < max3) {
+            return rec(max1, max3, max2, char1, char3, char2);
+        }
+        if (max2 == 0) {
+            vector<char> result(min(2, max1), char1);
+            return result;
+        }
+
+        int use1 = min(2, max1);
+        int use2 = (max1 - use1 >= max2) ? 1 : 0;
+
+        vector<char> res(use1, char1);
+        res.insert(res.end(), use2, char2);
+
+        vector<char> rest = rec(max1 - use1, max2 - use2, max3, char1, char2, char3);
+        res.insert(res.end(), rest.begin(), rest.end());
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} a
+     * @param {number} b
+     * @param {number} c
+     * @return {string}
+     */
+    longestDiverseString(a, b, c) {
+        const rec = (max1, max2, max3, char1, char2, char3) => {
+            if (max1 < max2) {
+                return rec(max2, max1, max3, char2, char1, char3);
+            }
+            if (max2 < max3) {
+                return rec(max1, max3, max2, char1, char3, char2);
+            }
+            if (max2 === 0) {
+                return Array(Math.min(2, max1)).fill(char1);
+            }
+
+            const use1 = Math.min(2, max1);
+            const use2 = max1 - use1 >= max2 ? 1 : 0;
+
+            const res = Array(use1).fill(char1).concat(Array(use2).fill(char2));
+            return res.concat(rec(max1 - use1, max2 - use2, max3, char1, char2, char3));
+        };
+
+        return rec(a, b, c, 'a', 'b', 'c').join('');
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public string LongestDiverseString(int a, int b, int c) {
+        return string.Join("", Rec(a, b, c, 'a', 'b', 'c'));
+    }
+
+    private List<char> Rec(int max1, int max2, int max3, char char1, char char2, char char3) {
+        if (max1 < max2) return Rec(max2, max1, max3, char2, char1, char3);
+        if (max2 < max3) return Rec(max1, max3, max2, char1, char3, char2);
+        if (max2 == 0) {
+            int use = Math.Min(2, max1);
+            var res = new List<char>();
+            for (int i = 0; i < use; i++) res.Add(char1);
+            return res;
+        }
+
+        int use1 = Math.Min(2, max1);
+        int use2 = (max1 - use1 >= max2) ? 1 : 0;
+
+        var result = new List<char>();
+        for (int i = 0; i < use1; i++) result.Add(char1);
+        for (int i = 0; i < use2; i++) result.Add(char2);
+
+        result.AddRange(Rec(max1 - use1, max2 - use2, max3, char1, char2, char3));
+        return result;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity:
+    * $O(n)$ for recursion stack.
+    * $O(n)$ space for the output string.
\ No newline at end of file
diff --git a/articles/longest-ideal-subsequence.md b/articles/longest-ideal-subsequence.md
new file mode 100644
index 000000000..2162b48ec
--- /dev/null
+++ b/articles/longest-ideal-subsequence.md
@@ -0,0 +1,422 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def longestIdealString(self, s: str, k: int) -> int:
+        def dfs(i, prev):
+            if i == len(s):
+                return 0
+            skip = dfs(i + 1, prev)
+            include = 0
+            if prev == "" or abs(ord(s[i]) - ord(prev)) <= k:
+                include = 1 + dfs(i + 1, s[i])
+            return max(skip, include)
+
+        return dfs(0, "")
+```
+
+```java
+public class Solution {
+    public int longestIdealString(String s, int k) {
+        return dfs(0, -1, s, k);
+    }
+
+    private int dfs(int i, int prev, String s, int k) {
+        if (i == s.length()) {
+            return 0;
+        }
+        int skip = dfs(i + 1, prev, s, k);
+        int include = 0;
+        if (prev == -1 || Math.abs(s.charAt(i) - prev) <= k) {
+            include = 1 + dfs(i + 1, s.charAt(i), s, k);
+        }
+        return Math.max(skip, include);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int longestIdealString(string s, int k) {
+        return dfs(0, -1, s, k);
+    }
+
+private:
+    int dfs(int i, int prev, const string &s, int k) {
+        if (i == s.size()) {
+            return 0;
+        }
+        int skip = dfs(i + 1, prev, s, k);
+        int include = 0;
+        if (prev == -1 || abs(s[i] - prev) <= k) {
+            include = 1 + dfs(i + 1, s[i], s, k);
+        }
+        return max(skip, include);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {number} k
+     * @return {number}
+     */
+    longestIdealString(s, k) {
+        const dfs = (i, prev) => {
+            if (i === s.length) {
+                return 0;
+            }
+            const skip = dfs(i + 1, prev);
+            let include = 0;
+            if (prev === -1 || Math.abs(s.charCodeAt(i) - prev) <= k) {
+                include = 1 + dfs(i + 1, s.charCodeAt(i));
+            }
+            return Math.max(skip, include);
+        };
+
+        return dfs(0, -1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def longestIdealString(self, s: str, k: int) -> int:
+        cache = [[-1] * 27 for _ in range(len(s))]
+
+        def dfs(i, prev):
+            if i == len(s):
+                return 0
+            if cache[i][prev + 1] != -1:
+                return cache[i][prev + 1]
+
+            skip = dfs(i + 1, prev)
+            include = 0
+            c = ord(s[i]) - ord('a')
+            if prev == -1 or abs(c - prev) <= k:
+                include = 1 + dfs(i + 1, c)
+            cache[i][prev + 1] = max(skip, include)
+            return cache[i][prev + 1]
+
+        return dfs(0, -1)
+```
+
+```java
+public class Solution {
+    private int[][] dp;
+
+    public int longestIdealString(String s, int k) {
+        dp = new int[s.length()][27];
+        for (int i = 0; i < s.length(); i++) {
+            for (int j = 0; j < 27; j++) {
+                dp[i][j] = -1;
+            }
+        }
+        return dfs(0, -1, s, k);
+    }
+
+    private int dfs(int i, int prev, String s, int k) {
+        if (i == s.length()) {
+            return 0;
+        }
+        if (dp[i][prev + 1] != -1) {
+            return dp[i][prev + 1];
+        }
+        int skip = dfs(i + 1, prev, s, k);
+        int include = 0;
+        if (prev == -1 || Math.abs(s.charAt(i) - ('a' + prev)) <= k) {
+            include = 1 + dfs(i + 1, s.charAt(i) - 'a', s, k);
+        }
+        dp[i][prev + 1] = Math.max(skip, include);
+        return Math.max(skip, include);
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<vector<int>> dp;
+
+public:
+    int longestIdealString(string s, int k) {
+        dp = vector<vector<int>>(s.size(), vector<int>(27, -1));
+        return dfs(0, -1, s, k);
+    }
+
+private:
+    int dfs(int i, int prev, const string &s, int k) {
+        if (i == s.size()) {
+            return 0;
+        }
+        if (dp[i][prev + 1] != -1) {
+            return dp[i][prev + 1];
+        }
+        int skip = dfs(i + 1, prev, s, k);
+        int include = 0;
+        if (prev == -1 || abs(s[i] - ('a' + prev)) <= k) {
+            include = 1 + dfs(i + 1, s[i] - 'a', s, k);
+        }
+        dp[i][prev + 1] = max(skip, include);
+        return max(skip, include);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {number} k
+     * @return {number}
+     */
+    longestIdealString(s, k) {
+        const dp = Array.from({ length: s.length }, () => Array(27).fill(-1));
+
+        const dfs = (i, prev) => {
+            if (i === s.length) {
+                return 0;
+            }
+            if (dp[i][prev + 1] !== -1) {
+                return dp[i][prev + 1];
+            }
+            const skip = dfs(i + 1, prev);
+            let include = 0;
+            if (prev === -1 || Math.abs(s.charCodeAt(i) - ('a'.charCodeAt(0) + prev)) <= k) {
+                include = 1 + dfs(i + 1, s.charCodeAt(i) - 'a'.charCodeAt(0));
+            }
+            dp[i][prev + 1] = Math.max(skip, include);
+            return Math.max(skip, include);
+        };
+
+        return dfs(0, -1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def longestIdealString(self, s: str, k: int) -> int:
+        dp = [[0] * 26 for _ in range(len(s) + 1)]
+
+        for i in range(1, len(s) + 1):
+            curr = ord(s[i - 1]) - ord('a')
+            for prev in range(26):
+                dp[i][prev] = max(dp[i][prev], dp[i - 1][prev])
+                if abs(curr - prev) <= k:
+                    dp[i][curr] = max(dp[i][curr], 1 + dp[i - 1][prev])
+        
+        return max(dp[len(s)])
+```
+
+```java
+public class Solution {
+    public int longestIdealString(String s, int k) {
+        int n = s.length();
+        int[][] dp = new int[n + 1][26];
+
+        for (int i = 1; i <= n; i++) {
+            int curr = s.charAt(i - 1) - 'a';
+            for (int prev = 0; prev < 26; prev++) {
+                dp[i][prev] = Math.max(dp[i][prev], dp[i - 1][prev]);
+                if (Math.abs(curr - prev) <= k) {
+                    dp[i][curr] = Math.max(dp[i][curr], 1 + dp[i - 1][prev]);
+                }
+            }
+        }
+
+        int max = 0;
+        for (int val : dp[n]) {
+            max = Math.max(max, val);
+        }
+        return max;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int longestIdealString(string s, int k) {
+        int n = s.size();
+        vector<vector<int>> dp(n + 1, vector<int>(26, 0));
+
+        for (int i = 1; i <= n; i++) {
+            int curr = s[i - 1] - 'a';
+            for (int prev = 0; prev < 26; prev++) {
+                dp[i][prev] = max(dp[i][prev], dp[i - 1][prev]);
+                if (abs(curr - prev) <= k) {
+                    dp[i][curr] = max(dp[i][curr], 1 + dp[i - 1][prev]);
+                }
+            }
+        }
+
+        return *max_element(dp[n].begin(), dp[n].end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {number} k
+     * @return {number}
+     */
+    longestIdealString(s, k) {
+        const n = s.length;
+        const dp = Array.from({ length: n + 1 }, () => Array(26).fill(0));
+
+        for (let i = 1; i <= n; i++) {
+            const curr = s.charCodeAt(i - 1) - 'a'.charCodeAt(0);
+            for (let prev = 0; prev < 26; prev++) {
+                dp[i][prev] = Math.max(dp[i][prev], dp[i - 1][prev]);
+                if (Math.abs(curr - prev) <= k) {
+                    dp[i][curr] = Math.max(dp[i][curr], 1 + dp[i - 1][prev]);
+                }
+            }
+        }
+        return Math.max(...dp[n]);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def longestIdealString(self, s: str, k: int) -> int:
+        dp = [0] * 26
+
+        for c in s:
+            curr = ord(c) - ord('a')
+            longest = 1
+            for prev in range(26):
+                if abs(curr - prev) <= k:
+                    longest = max(longest, 1 + dp[prev])
+            dp[curr] = max(dp[curr], longest)
+        
+        return max(dp)
+```
+
+```java
+public class Solution {
+    public int longestIdealString(String s, int k) {
+        int[] dp = new int[26];
+
+        for (char c : s.toCharArray()) {
+            int curr = c - 'a'; // 0-25
+            int longest = 1;
+            for (int prev = 0; prev < 26; prev++) {
+                if (Math.abs(curr - prev) <= k) {
+                    longest = Math.max(longest, 1 + dp[prev]);
+                }
+            }
+            dp[curr] = Math.max(dp[curr], longest);
+        }
+
+        int max = 0;
+        for (int val : dp) {
+            max = Math.max(max, val);
+        }
+        return max;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int longestIdealString(string s, int k) {
+        vector<int> dp(26, 0);
+
+        for (char c : s) {
+            int curr = c - 'a';
+            int longest = 1;
+            for (int prev = 0; prev < 26; prev++) {
+                if (abs(curr - prev) <= k) {
+                    longest = max(longest, 1 + dp[prev]);
+                }
+            }
+            dp[curr] = max(dp[curr], longest);
+        }
+
+        return *max_element(dp.begin(), dp.end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {number} k
+     * @return {number}
+     */
+    longestIdealString(s, k) {
+        const dp = Array(26).fill(0);
+
+        for (const c of s) {
+            const curr = c.charCodeAt(0) - 'a'.charCodeAt(0);
+            let longest = 1;
+            for (let prev = 0; prev < 26; prev++) {
+                if (Math.abs(curr - prev) <= k) {
+                    longest = Math.max(longest, 1 + dp[prev]);
+                }
+            }
+            dp[curr] = Math.max(dp[curr], longest);
+        }
+
+        return Math.max(...dp);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ since we have at most 26 different characters.
\ No newline at end of file
diff --git a/articles/longest-increasing-path-in-matrix.md b/articles/longest-increasing-path-in-matrix.md
index 153a80027..e529b1ded 100644
--- a/articles/longest-increasing-path-in-matrix.md
+++ b/articles/longest-increasing-path-in-matrix.md
@@ -159,6 +159,106 @@ public class Solution {
 }
 ```
 
+```go
+func longestIncreasingPath(matrix [][]int) int {
+    rows, cols := len(matrix), len(matrix[0])
+    directions := [][]int{{-1, 0}, {1, 0}, {0, -1}, {0, 1}}
+
+    var dfs func(r, c, prevVal int) int
+    dfs = func(r, c, prevVal int) int {
+        if r < 0 || r >= rows || c < 0 || c >= cols || 
+           matrix[r][c] <= prevVal {
+            return 0
+        }
+
+        res := 1
+        for _, d := range directions {
+            res = max(res, 1 + dfs(r + d[0], c + d[1], matrix[r][c]))
+        }
+        return res
+    }
+
+    LIP := 0
+    for r := 0; r < rows; r++ {
+        for c := 0; c < cols; c++ {
+            LIP = max(LIP, dfs(r, c, -1<<31))
+        }
+    }
+    return LIP
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    private val directions = arrayOf(
+        intArrayOf(-1, 0), intArrayOf(1, 0), 
+        intArrayOf(0, -1), intArrayOf(0, 1)
+    )
+
+    fun longestIncreasingPath(matrix: Array<IntArray>): Int {
+        val rows = matrix.size
+        val cols = matrix[0].size
+
+        fun dfs(r: Int, c: Int, prevVal: Int): Int {
+            if (r < 0 || r >= rows || c < 0 || c >= cols || 
+                matrix[r][c] <= prevVal) {
+                return 0
+            }
+
+            var res = 1
+            for (d in directions) {
+                res = maxOf(res, 1 + dfs(r + d[0], c + d[1], matrix[r][c]))
+            }
+            return res
+        }
+
+        var LIP = 0
+        for (r in 0 until rows) {
+            for (c in 0 until cols) {
+                LIP = maxOf(LIP, dfs(r, c, Int.MIN_VALUE))
+            }
+        }
+        return LIP
+    }
+}
+```
+
+```swift
+class Solution {
+    func longestIncreasingPath(_ matrix: [[Int]]) -> Int {
+        let rows = matrix.count, cols = matrix[0].count
+        let directions = [(-1, 0), (1, 0), (0, -1), (0, 1)]
+
+        func dfs(_ r: Int, _ c: Int, _ prevVal: Int) -> Int {
+            if r < 0 || c < 0 || r >= rows || c >= cols || matrix[r][c] <= prevVal {
+                return 0
+            }
+            
+            var res = 1
+            for (dr, dc) in directions {
+                res = max(res, 1 + dfs(r + dr, c + dc, matrix[r][c]))
+            }
+            return res
+        }
+
+        var lip = 0
+        for r in 0..<rows {
+            for c in 0..<cols {
+                lip = max(lip, dfs(r, c, Int.min))
+            }
+        }
+        return lip
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -367,6 +467,121 @@ public class Solution {
 }
 ```
 
+```go
+func longestIncreasingPath(matrix [][]int) int {
+    rows, cols := len(matrix), len(matrix[0])
+    dp := make([][]int, rows)
+    for i := range dp {
+        dp[i] = make([]int, cols)
+    }
+
+    var dfs func(r, c, prevVal int) int
+    dfs = func(r, c, prevVal int) int {
+        if r < 0 || r >= rows || c < 0 || c >= cols || 
+           matrix[r][c] <= prevVal {
+            return 0
+        }
+        if dp[r][c] != 0 {
+            return dp[r][c]
+        }
+
+        res := 1
+        res = max(res, 1 + dfs(r+1, c, matrix[r][c]))
+        res = max(res, 1 + dfs(r-1, c, matrix[r][c]))
+        res = max(res, 1 + dfs(r, c+1, matrix[r][c]))
+        res = max(res, 1 + dfs(r, c-1, matrix[r][c]))
+        dp[r][c] = res
+        return res
+    }
+
+    maxPath := 0
+    for r := 0; r < rows; r++ {
+        for c := 0; c < cols; c++ {
+            maxPath = max(maxPath, dfs(r, c, -1))
+        }
+    }
+    return maxPath
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun longestIncreasingPath(matrix: Array<IntArray>): Int {
+        val rows = matrix.size
+        val cols = matrix[0].size
+        val dp = Array(rows) { IntArray(cols) }
+
+        fun dfs(r: Int, c: Int, prevVal: Int): Int {
+            if (r < 0 || r >= rows || c < 0 || c >= cols || 
+                matrix[r][c] <= prevVal) {
+                return 0
+            }
+            if (dp[r][c] != 0) {
+                return dp[r][c]
+            }
+
+            var res = 1
+            res = maxOf(res, 1 + dfs(r + 1, c, matrix[r][c]))
+            res = maxOf(res, 1 + dfs(r - 1, c, matrix[r][c]))
+            res = maxOf(res, 1 + dfs(r, c + 1, matrix[r][c]))
+            res = maxOf(res, 1 + dfs(r, c - 1, matrix[r][c]))
+            dp[r][c] = res
+            return res
+        }
+
+        var maxPath = 0
+        for (r in 0 until rows) {
+            for (c in 0 until cols) {
+                maxPath = maxOf(maxPath, dfs(r, c, -1))
+            }
+        }
+        return maxPath
+    }
+}
+```
+
+```swift
+class Solution {
+    func longestIncreasingPath(_ matrix: [[Int]]) -> Int {
+        let rows = matrix.count, cols = matrix[0].count
+        var dp = Array(repeating: Array(repeating: -1, count: cols), count: rows)
+
+        func dfs(_ r: Int, _ c: Int, _ prevVal: Int) -> Int {
+            if r < 0 || r >= rows || c < 0 || c >= cols || matrix[r][c] <= prevVal {
+                return 0
+            }
+            if dp[r][c] != -1 {
+                return dp[r][c]
+            }
+
+            var res = 1
+            res = max(res, 1 + dfs(r + 1, c, matrix[r][c]))
+            res = max(res, 1 + dfs(r - 1, c, matrix[r][c]))
+            res = max(res, 1 + dfs(r, c + 1, matrix[r][c]))
+            res = max(res, 1 + dfs(r, c - 1, matrix[r][c]))
+
+            dp[r][c] = res
+            return res
+        }
+
+        var maxPath = 0
+        for r in 0..<rows {
+            for c in 0..<cols {
+                maxPath = max(maxPath, dfs(r, c, -1))
+            }
+        }
+        return maxPath
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -383,8 +598,6 @@ public class Solution {
 ::tabs-start
 
 ```python
-from collections import deque
-
 class Solution:
     def longestIncreasingPath(self, matrix: List[List[int]]) -> int:
         ROWS, COLS = len(matrix), len(matrix[0])
@@ -639,6 +852,166 @@ public class Solution {
 }
 ```
 
+```go
+func longestIncreasingPath(matrix [][]int) int {
+    rows, cols := len(matrix), len(matrix[0])
+    indegree := make([][]int, rows)
+    for i := range indegree {
+        indegree[i] = make([]int, cols)
+    }
+    
+    directions := [][]int{{-1, 0}, {1, 0}, {0, -1}, {0, 1}}
+
+    for r := 0; r < rows; r++ {
+        for c := 0; c < cols; c++ {
+            for _, d := range directions {
+                nr, nc := r + d[0], c + d[1]
+                if nr >= 0 && nr < rows && nc >= 0 && nc < cols && 
+                   matrix[nr][nc] < matrix[r][c] {
+                    indegree[r][c]++
+                }
+            }
+        }
+    }
+
+    queue := [][]int{}
+    for r := 0; r < rows; r++ {
+        for c := 0; c < cols; c++ {
+            if indegree[r][c] == 0 {
+                queue = append(queue, []int{r, c})
+            }
+        }
+    }
+
+    lis := 0
+    for len(queue) > 0 {
+        size := len(queue)
+        for i := 0; i < size; i++ {
+            node := queue[0]
+            queue = queue[1:]
+            r, c := node[0], node[1]
+            for _, d := range directions {
+                nr, nc := r + d[0], c + d[1]
+                if nr >= 0 && nr < rows && nc >= 0 && nc < cols && 
+                   matrix[nr][nc] > matrix[r][c] {
+                    indegree[nr][nc]--
+                    if indegree[nr][nc] == 0 {
+                        queue = append(queue, []int{nr, nc})
+                    }
+                }
+            }
+        }
+        lis++
+    }
+
+    return lis
+}
+```
+
+```kotlin
+class Solution {
+    fun longestIncreasingPath(matrix: Array<IntArray>): Int {
+        val rows = matrix.size
+        val cols = matrix[0].size
+        val indegree = Array(rows) { IntArray(cols) }
+        val directions = arrayOf(intArrayOf(-1, 0), intArrayOf(1, 0), 
+                                 intArrayOf(0, -1), intArrayOf(0, 1))
+
+        for (r in 0 until rows) {
+            for (c in 0 until cols) {
+                for (d in directions) {
+                    val nr = r + d[0]
+                    val nc = c + d[1]
+                    if (nr in 0 until rows && nc in 0 until cols && 
+                        matrix[nr][nc] < matrix[r][c]) {
+                        indegree[r][c]++
+                    }
+                }
+            }
+        }
+
+        val queue: Queue<IntArray> = LinkedList()
+        for (r in 0 until rows) {
+            for (c in 0 until cols) {
+                if (indegree[r][c] == 0) {
+                    queue.offer(intArrayOf(r, c))
+                }
+            }
+        }
+
+        var lis = 0
+        while (queue.isNotEmpty()) {
+            repeat(queue.size) {
+                val (r, c) = queue.poll()
+                for (d in directions) {
+                    val nr = r + d[0]
+                    val nc = c + d[1]
+                    if (nr in 0 until rows && nc in 0 until cols && 
+                        matrix[nr][nc] > matrix[r][c]) {
+                        if (--indegree[nr][nc] == 0) {
+                            queue.offer(intArrayOf(nr, nc))
+                        }
+                    }
+                }
+            }
+            lis++
+        }
+
+        return lis
+    }
+}
+```
+
+```swift
+class Solution {
+    func longestIncreasingPath(_ matrix: [[Int]]) -> Int {
+        let rows = matrix.count, cols = matrix[0].count
+        let directions = [(-1, 0), (1, 0), (0, -1), (0, 1)]
+        var indegree = Array(repeating: Array(repeating: 0, count: cols), count: rows)
+
+        for r in 0..<rows {
+            for c in 0..<cols {
+                for (dr, dc) in directions {
+                    let nr = r + dr, nc = c + dc
+                    if (nr >= 0 && nr < rows && nc >= 0 && nc < cols &&
+                        matrix[nr][nc] < matrix[r][c]) {
+                        indegree[r][c] += 1
+                    }
+                }
+            }
+        }
+
+        var q = Deque<(Int, Int)>()
+        for r in 0..<rows {
+            for c in 0..<cols {
+                if indegree[r][c] == 0 {
+                    q.append((r, c))
+                }
+            }
+        }
+
+        var LIS = 0
+        while !q.isEmpty {
+            for _ in 0..<q.count {
+                let (r, c) = q.popFirst()!
+                for (dr, dc) in directions {
+                    let nr = r + dr, nc = c + dc
+                    if (nr >= 0 && nr < rows && nc >= 0 && nc < cols &&
+                        matrix[nr][nc] > matrix[r][c]) {
+                        indegree[nr][nc] -= 1
+                        if indegree[nr][nc] == 0 {
+                            q.append((nr, nc))
+                        }
+                    }
+                }
+            }
+            LIS += 1
+        }
+        return LIS
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/longest-increasing-subsequence-ii.md b/articles/longest-increasing-subsequence-ii.md
new file mode 100644
index 000000000..1d7a0030e
--- /dev/null
+++ b/articles/longest-increasing-subsequence-ii.md
@@ -0,0 +1,746 @@
+## 1. Brute Force (Recursion)
+
+::tabs-start
+
+```python
+class Solution:
+    def lengthOfLIS(self, nums: List[int], k: int) -> int:
+        def dfs(i):
+            res = 1
+            for j in range(i + 1, len(nums)):
+                if nums[j] <= nums[i]:
+                    continue
+                if nums[j] - nums[i] <= k:
+                    res = max(res, 1 + dfs(j))
+            return res
+        
+        res = 0
+        for i in range(len(nums)):
+            res = max(res, dfs(i))
+        return res
+```
+
+```java
+public class Solution {
+    public int lengthOfLIS(int[] nums, int k) {
+        int n = nums.length;
+        int res = 0;
+
+        for (int i = 0; i < n; i++) {
+            res = Math.max(res, dfs(nums, k, i));
+        }
+
+        return res;
+    }
+
+    private int dfs(int[] nums, int k, int i) {
+        int res = 1;
+
+        for (int j = i + 1; j < nums.length; j++) {
+            if (nums[j] <= nums[i]) continue;
+            if (nums[j] - nums[i] <= k) {
+                res = Math.max(res, 1 + dfs(nums, k, j));
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int lengthOfLIS(vector<int>& nums, int k) {
+        int n = nums.size();
+        int res = 0;
+
+        for (int i = 0; i < n; i++) {
+            res = max(res, dfs(nums, k, i));
+        }
+
+        return res;
+    }
+
+private:
+    int dfs(vector<int>& nums, int k, int i) {
+        int res = 1;
+
+        for (int j = i + 1; j < nums.size(); j++) {
+            if (nums[j] <= nums[i]) continue;
+            if (nums[j] - nums[i] <= k) {
+                res = max(res, 1 + dfs(nums, k, j));
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    lengthOfLIS(nums, k) {
+        const dfs = (i) => {
+            let res = 1;
+
+            for (let j = i + 1; j < nums.length; j++) {
+                if (nums[j] <= nums[i]) continue;
+                if (nums[j] - nums[i] <= k) {
+                    res = Math.max(res, 1 + dfs(j));
+                }
+            }
+
+            return res;
+        };
+
+        let res = 0;
+        for (let i = 0; i < nums.length; i++) {
+            res = Math.max(res, dfs(i));
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * 2 ^ n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def lengthOfLIS(self, nums: List[int], k: int) -> int:
+        n, res = len(nums), 0
+        dp = [1] * n
+        for i in range(n):
+            for j in range(i):
+                if nums[j] >= nums[i]:
+                    continue
+                if nums[i] - nums[j] <= k:
+                    dp[i] = max(dp[i], 1 + dp[j])
+            res = max(res, dp[i])
+        return res
+```
+
+```java
+public class Solution {
+    public int lengthOfLIS(int[] nums, int k) {
+        int n = nums.length, res = 0;
+        int[] dp = new int[n];
+        Arrays.fill(dp, 1);
+
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < i; j++) {
+                if (nums[j] >= nums[i]) continue;
+                if (nums[i] - nums[j] <= k) {
+                    dp[i] = Math.max(dp[i], 1 + dp[j]);
+                }
+            }
+            res = Math.max(res, dp[i]);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int lengthOfLIS(vector<int>& nums, int k) {
+        int n = nums.size(), res = 0;
+        vector<int> dp(n, 1);
+
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < i; j++) {
+                if (nums[j] >= nums[i]) continue;
+                if (nums[i] - nums[j] <= k) {
+                    dp[i] = max(dp[i], 1 + dp[j]);
+                }
+            }
+            res = max(res, dp[i]);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    lengthOfLIS(nums, k) {
+        const n = nums.length;
+        let res = 0;
+        const dp = new Array(n).fill(1);
+
+        for (let i = 0; i < n; i++) {
+            for (let j = 0; j < i; j++) {
+                if (nums[j] >= nums[i]) continue;
+                if (nums[i] - nums[j] <= k) {
+                    dp[i] = Math.max(dp[i], 1 + dp[j]);
+                }
+            }
+            res = Math.max(res, dp[i]);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming + Segment Tree (Coordinate Compression)
+
+::tabs-start
+
+```python
+class SegmentTree:
+    def __init__(self, N):
+        self.n = N
+        while (self.n & (self.n - 1)) != 0:
+            self.n += 1
+        self.tree = [0] * (2 * self.n)
+
+    def update(self, i, val):
+        if val <= self.tree[self.n + i]:
+            return
+        self.tree[self.n + i] = val
+        j = (self.n + i) >> 1
+        while j >= 1:
+            self.tree[j] = max(self.tree[j << 1], self.tree[j << 1 | 1])
+            j >>= 1
+
+    def query(self, ql, qh):
+        l = ql + self.n
+        r = qh + self.n + 1
+        res = 0
+        while l < r:
+            if l & 1:
+                res = max(res, self.tree[l])
+                l += 1
+            if r & 1:
+                r -= 1
+                res = max(res, self.tree[r])
+            l >>= 1
+            r >>= 1
+        return res
+
+
+class Solution:
+    def lengthOfLIS(self, nums: List[int], k: int) -> int:
+        n = len(nums)
+        mp = {}
+        tmp = set([0])
+        for num in nums:
+            if num - k > 0:
+                tmp.add(num - k)
+            if num - 1 > 0:
+                tmp.add(num - 1)
+            tmp.add(num)
+
+        index = 0
+        for value in sorted(tmp):
+            mp[value] = index
+            index += 1
+
+        ST = SegmentTree(index)
+        res = 0
+        for num in nums:
+            l = mp.get(num - k, 0)
+            r = mp.get(num - 1, 0)
+            curr = ST.query(l, r) + 1
+            res = max(res, curr)
+            ST.update(mp[num], curr)
+
+        return res
+```
+
+```java
+class SegmentTree {
+    private int n;
+    private int[] tree;
+
+    public SegmentTree(int N) {
+        this.n = N;
+        while (Integer.bitCount(n) != 1) {
+            n++;
+        }
+        tree = new int[2 * n];
+    }
+
+    public void update(int i, int val) {
+        if (val <= tree[n + i]) return;
+        tree[n + i] = val;
+        for (int j = (n + i) >> 1; j >= 1; j >>= 1) {
+            tree[j] = Math.max(tree[j << 1], tree[(j << 1) + 1]);
+        }
+    }
+
+    public int query(int ql, int qh) {
+        int l = ql + n, r = qh + n + 1, res = 0;
+        while (l < r) {
+            if ((l & 1) == 1) res = Math.max(res, tree[l++]);
+            if ((r & 1) == 1) res = Math.max(res, tree[--r]);
+            l >>= 1;
+            r >>= 1;
+        }
+        return res;
+    }
+}
+
+public class Solution {
+    public int lengthOfLIS(int[] nums, int k) {
+        int n = nums.length;
+        TreeSet<Integer> tmp = new TreeSet<>();
+        tmp.add(0);
+        for (int num : nums) {
+            if (num - k > 0) tmp.add(num - k);
+            if (num - 1 > 0) tmp.add(num - 1);
+            tmp.add(num);
+        }
+
+        Map<Integer, Integer> mp = new HashMap<>();
+        int index = 0;
+        for (int val : tmp) {
+            mp.put(val, index++);
+        }
+
+        SegmentTree ST = new SegmentTree(index);
+        int res = 0;
+        for (int num : nums) {
+            int l = mp.getOrDefault(num - k, 0);
+            int r = mp.getOrDefault(num - 1, 0);
+            int curr = ST.query(l, r) + 1;
+            res = Math.max(res, curr);
+            ST.update(mp.get(num), curr);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class SegmentTree {
+public:
+    int n;
+    vector<int> tree;
+
+    SegmentTree(int N) {
+        this->n = N;
+        while (__builtin_popcount(n) != 1) {
+            n++;
+        }
+        tree.resize(2 * n, 0);
+    }
+
+    void update(int i, int val) {
+        if (val <= tree[n + i]) return;
+        tree[n + i] = val;
+        for (int j = (n + i) >> 1; j >= 1; j >>= 1) {
+            tree[j] = max(tree[j << 1], tree[(j << 1) + 1]);
+        }
+    }
+
+    int query(int ql, int qh) {
+        int l = ql + n, r = qh + n + 1, res = 0;
+        while (l < r) {
+            if (l & 1) res = max(res, tree[l++]);
+            if (r & 1) res = max(res, tree[--r]);
+            l >>= 1;
+            r >>= 1;
+        }
+        return res;
+    }
+};
+
+class Solution {
+public:
+    int lengthOfLIS(vector<int>& nums, int k) {
+        int n = nums.size();
+        unordered_map<int, int> mp;
+        set<int> tmp = {0};
+        
+        for (int num : nums) {
+            if (num - k > 0) tmp.insert(num - k);
+            if (num - 1 > 0) tmp.insert(num - 1);
+            tmp.insert(num);
+        }
+
+        int index = 0;
+        for (const int& val : tmp) {
+            mp[val] = index++;
+        }
+
+        SegmentTree ST(index);
+        int ans = 0;
+        for (int& num : nums) {
+            int l = mp[num - k];
+            int r = mp[num - 1];
+            int curr = ST.query(l, r) + 1;
+            ans = max(ans, curr);
+            ST.update(mp[num], curr);
+        }
+
+        return ans;
+    }
+};
+```
+
+```javascript
+class SegmentTree {
+    /**
+     * @constructor
+     * @param {number} N
+     */
+    constructor(N) {
+        this.n = N;
+        while ((this.n & (this.n - 1)) !== 0) {
+            this.n++;
+        }
+        this.tree = Array(2 * this.n).fill(0);
+    }
+
+    /**
+     * @param {number} i
+     * @param {number} val
+     * @return {void}
+     */
+    update(i, val) {
+        if (val <= this.tree[this.n + i]) return;
+        this.tree[this.n + i] = val;
+        for (let j = (this.n + i) >> 1; j >= 1; j >>= 1) {
+            this.tree[j] = Math.max(this.tree[j << 1], this.tree[(j << 1) + 1]);
+        }
+    }
+
+    /**
+     * @param {number} ql
+     * @param {number} qh
+     * @return {number}
+     */
+    query(ql, qh) {
+        let l = ql + this.n, r = qh + this.n + 1, res = 0;
+        while (l < r) {
+            if (l & 1) res = Math.max(res, this.tree[l++]);
+            if (r & 1) res = Math.max(res, this.tree[--r]);
+            l >>= 1;
+            r >>= 1;
+        }
+        return res;
+    }
+}
+
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    lengthOfLIS(nums, k) {
+        const n = nums.length;
+        const tmp = new Set([0]);
+        for (const num of nums) {
+            if (num - k > 0) tmp.add(num - k);
+            if (num - 1 > 0) tmp.add(num - 1);
+            tmp.add(num);
+        }
+
+        const mp = new Map();
+        let index = 0;
+        Array.from(tmp).sort((a, b) => a - b).forEach(val => mp.set(val, index++));
+
+        const ST = new SegmentTree(index);
+        let ans = 0;
+        for (const num of nums) {
+            const l = mp.has(num - k) ? mp.get(num - k) : 0;
+            const r = mp.has(num - 1) ? mp.get(num - 1) : 0;
+            const curr = ST.query(l, r) + 1;
+            ans = Math.max(ans, curr);
+            ST.update(mp.get(num), curr);
+        }
+        return ans;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Dynamic Programming + Segment Tree
+
+::tabs-start
+
+```python
+class SegmentTree:
+    def __init__(self, N):
+        self.n = N
+        while (self.n & (self.n - 1)) != 0:
+            self.n += 1
+        self.tree = [0] * (2 * self.n)
+
+    def update(self, i, val):
+        if val <= self.tree[self.n + i]:
+            return
+        self.tree[self.n + i] = val
+        j = (self.n + i) >> 1
+        while j >= 1:
+            self.tree[j] = max(self.tree[j << 1], self.tree[j << 1 | 1])
+            j >>= 1
+
+    def query(self, ql, qh):
+        l = ql + self.n
+        r = qh + self.n + 1
+        res = 0
+        while l < r:
+            if l & 1:
+                res = max(res, self.tree[l])
+                l += 1
+            if r & 1:
+                r -= 1
+                res = max(res, self.tree[r])
+            l >>= 1
+            r >>= 1
+        return res
+
+
+class Solution:
+    def lengthOfLIS(self, nums: List[int], k: int) -> int:
+        max_val = max(nums)
+        ST = SegmentTree(max_val + 1)
+        res = 0
+        for num in nums:
+            l = max(0, num - k)
+            r = max(0, num - 1)
+            curr = ST.query(l, r) + 1
+            res = max(res, curr)
+            ST.update(num, curr)
+
+        return res
+```
+
+```java
+class SegmentTree {
+    private int[] tree;
+    private int n;
+
+    public SegmentTree(int N) {
+        this.n = N;
+        while ((this.n & (this.n - 1)) != 0) {
+            this.n++;
+        }
+        this.tree = new int[2 * this.n];
+    }
+
+    public void update(int i, int val) {
+        if (val <= tree[n + i]) return;
+        tree[n + i] = val;
+        for (int j = (n + i) >> 1; j >= 1; j >>= 1) {
+            tree[j] = Math.max(tree[j << 1], tree[(j << 1) + 1]);
+        }
+    }
+
+    public int query(int l, int r) {
+        l += n;
+        r += n + 1;
+        int res = 0;
+        while (l < r) {
+            if ((l & 1) == 1) {
+                res = Math.max(res, tree[l++]);
+            }
+            if ((r & 1) == 1) {
+                res = Math.max(res, tree[--r]);
+            }
+            l >>= 1;
+            r >>= 1;
+        }
+        return res;
+    }
+}
+
+public class Solution {
+    public int lengthOfLIS(int[] nums, int k) {
+        int maxVal = 0;
+        for (int num : nums) {
+            maxVal = Math.max(maxVal, num);
+        }
+
+        SegmentTree ST = new SegmentTree(maxVal + 1);
+        int res = 0;
+        for (int num : nums) {
+            int l = Math.max(0, num - k);
+            int r = Math.max(0, num - 1);
+            int curr = ST.query(l, r) + 1;
+            res = Math.max(res, curr);
+            ST.update(num, curr);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class SegmentTree {
+public:
+    int n;
+    vector<int> tree;
+
+    SegmentTree(int N) {
+        n = N;
+        while ((n & (n - 1)) != 0) {
+            n++;
+        }
+        tree.resize(2 * n, 0);
+    }
+
+    void update(int i, int val) {
+        if (val <= tree[n + i]) return;
+        tree[n + i] = val;
+        for (int j = (n + i) >> 1; j >= 1; j >>= 1) {
+            tree[j] = max(tree[j << 1], tree[(j << 1) + 1]);
+        }
+    }
+
+    int query(int l, int r) {
+        l += n;
+        r += n + 1;
+        int res = 0;
+        while (l < r) {
+            if (l & 1) {
+                res = max(res, tree[l++]);
+            }
+            if (r & 1) {
+                res = max(res, tree[--r]);
+            }
+            l >>= 1;
+            r >>= 1;
+        }
+        return res;
+    }
+};
+
+class Solution {
+public:
+    int lengthOfLIS(vector<int>& nums, int k) {
+        int maxVal = *max_element(nums.begin(), nums.end());
+        SegmentTree ST(maxVal + 1);
+        int res = 0;
+        for (int& num : nums) {
+            int l = max(0, num - k);
+            int r = max(0, num - 1);
+            int curr = ST.query(l, r) + 1;
+            res = max(res, curr);
+            ST.update(num, curr);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class SegmentTree {
+    /**
+     * @constructor
+     * @param {number} N
+     */
+    constructor(N) {
+        this.n = N;
+        while ((this.n & (this.n - 1)) !== 0) {
+            this.n++;
+        }
+        this.tree = Array(2 * this.n).fill(0);
+    }
+
+    /**
+     * @param {number} i
+     * @param {number} val
+     * @return {void}
+     */
+    update(i, val) {
+        if (val <= this.tree[this.n + i]) return;
+        this.tree[this.n + i] = val;
+        for (let j = (this.n + i) >> 1; j >= 1; j >>= 1) {
+            this.tree[j] = Math.max(this.tree[j << 1], this.tree[(j << 1) + 1]);
+        }
+    }
+
+    /**
+     * @param {number} ql
+     * @param {number} qh
+     * @return {number}
+     */
+    query(ql, qh) {
+        let l = ql + this.n, r = qh + this.n + 1, res = 0;
+        while (l < r) {
+            if (l & 1) res = Math.max(res, this.tree[l++]);
+            if (r & 1) res = Math.max(res, this.tree[--r]);
+            l >>= 1;
+            r >>= 1;
+        }
+        return res;
+    }
+}
+
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    lengthOfLIS(nums, k) {
+        const maxVal = Math.max(...nums);
+        const ST = new SegmentTree(maxVal + 1);
+        let res = 0;
+        for (const num of nums) {
+            const l = Math.max(0, num - k);
+            const r = Math.max(0, num - 1);
+            const curr = ST.query(l, r) + 1;
+            res = Math.max(res, curr);
+            ST.update(num, curr);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n\log m)$
+* Space complexity: $O(m)$
+
+> Where $n$ is the size of the array $nums$ and $m$ is the maximum element in the array.
\ No newline at end of file
diff --git a/articles/longest-increasing-subsequence.md b/articles/longest-increasing-subsequence.md
index 823956254..79391921a 100644
--- a/articles/longest-increasing-subsequence.md
+++ b/articles/longest-increasing-subsequence.md
@@ -120,6 +120,78 @@ public class Solution {
 }
 ```
 
+```go
+func lengthOfLIS(nums []int) int {
+    var dfs func(i, j int) int
+    dfs = func(i, j int) int {
+        if i == len(nums) {
+            return 0
+        }
+
+        LIS := dfs(i + 1, j) // not include
+
+        if j == -1 || nums[j] < nums[i] {
+            LIS = max(LIS, 1 + dfs(i + 1, i)) // include
+        }
+
+        return LIS
+    }
+
+    return dfs(0, -1)
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun lengthOfLIS(nums: IntArray): Int {
+        fun dfs(i: Int, j: Int): Int {
+            if (i == nums.size) {
+                return 0
+            }
+
+            var LIS = dfs(i + 1, j) // not include
+
+            if (j == -1 || nums[j] < nums[i]) {
+                LIS = maxOf(LIS, 1 + dfs(i + 1, i)) // include
+            }
+
+            return LIS
+        }
+
+        return dfs(0, -1)
+    }
+}
+```
+
+```swift
+class Solution {
+    func lengthOfLIS(_ nums: [Int]) -> Int {
+        func dfs(_ i: Int, _ j: Int) -> Int {
+            if i == nums.count {
+                return 0
+            }
+
+            var LIS = dfs(i + 1, j) // not include
+
+            if j == -1 || nums[j] < nums[i] {
+                LIS = max(LIS, 1 + dfs(i + 1, i)) // include
+            }
+
+            return LIS
+        }
+
+        return dfs(0, -1)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -129,29 +201,30 @@ public class Solution {
 
 ---
 
-## 2. Dynamic Programming (Top-Down)
+## 2. Dynamic Programming (Top-Down) - I
 
 ::tabs-start
 
 ```python
 class Solution:
-    def lengthOfLIS(self, nums: List[int]) -> int:
-        memo = {}
-        
+    def lengthOfLIS(self, nums):
+        n = len(nums)
+        memo = [[-1] * (n + 1) for _ in range(n)]  
+
         def dfs(i, j):
-            if i == len(nums):
+            if i == n:
                 return 0
-            if (i, j) in memo:
-                return memo[(i, j)]
+            if memo[i][j + 1] != -1:
+                return memo[i][j + 1]
 
             LIS = dfs(i + 1, j)
 
             if j == -1 or nums[j] < nums[i]:
                 LIS = max(LIS, 1 + dfs(i + 1, i))
 
-            memo[(i, j)] = LIS
+            memo[i][j + 1] = LIS
             return LIS
-        
+
         return dfs(0, -1)
 ```
 
@@ -173,17 +246,539 @@ public class Solution {
             LIS = Math.max(LIS, 1 + dfs(i + 1, i, nums));
         }
 
-        memo[i][j + 1] = LIS;
-        return LIS;
-    }
+        memo[i][j + 1] = LIS;
+        return LIS;
+    }
+
+    public int lengthOfLIS(int[] nums) {
+        int n = nums.length;
+        memo = new int[n][n + 1];  
+        for (int[] row : memo) {
+            Arrays.fill(row, -1);  
+        }
+        return dfs(0, -1, nums);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> memo;
+    
+    int dfs(int i, int j, vector<int>& nums) {
+        if (i == nums.size()) {
+            return 0;
+        }
+        if (memo[i][j + 1] != -1) {  
+            return memo[i][j + 1];
+        }
+
+        int LIS = dfs(i + 1, j, nums);
+
+        if (j == -1 || nums[j] < nums[i]) {
+            LIS = max(LIS, 1 + dfs(i + 1, i, nums));
+        }
+
+        memo[i][j + 1] = LIS;
+        return LIS;
+    }
+    
+    int lengthOfLIS(vector<int>& nums) {
+        int n = nums.size();
+        memo = vector<vector<int>>(n, vector<int>(n + 1, -1)); 
+        return dfs(0, -1, nums);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    lengthOfLIS(nums) {
+        const n = nums.length;
+        const memo = Array.from({ length: n }, () => 
+                     Array(n + 2).fill(-1));
+        
+        return this.dfs(nums, 0, -1, memo);
+    }
+
+    /**
+     * @param {number[]} nums
+     * @param {number} i
+     * @param {number} j
+     * @param {number[][]} memo
+     * @return {number}
+     */
+    dfs(nums, i, j, memo) {
+        if (i === nums.length) return 0; 
+        if (memo[i][j + 1] !== -1) 
+            return memo[i][j + 1];
+
+        let LIS = this.dfs(nums, i + 1, j, memo);
+
+        if (j === -1 || nums[j] < nums[i]) {
+            LIS = Math.max(LIS, 1 + this.dfs(nums, i + 1, i, memo));
+        }
+
+        memo[i][j + 1] = LIS;
+        return LIS;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int LengthOfLIS(int[] nums) {
+        int n = nums.Length;
+        int[,] memo = new int[n, n + 1];
+
+        for (int i = 0; i < n; i++)
+            for (int j = 0; j <= n; j++)
+                memo[i, j] = -1;
+
+        return DFS(nums, 0, -1, memo);
+    }
+
+    private int DFS(int[] nums, int i, int j, int[,] memo) {
+        if (i == nums.Length) return 0; 
+        if (memo[i, j + 1] != -1) {
+            return memo[i, j + 1];
+        }
+
+        int LIS = DFS(nums, i + 1, j, memo);
+
+        if (j == -1 || nums[j] < nums[i]) {
+            LIS = Math.Max(LIS, 1 + DFS(nums, i + 1, i, memo));
+        }
+
+        memo[i, j + 1] = LIS;
+        return LIS;
+    }
+}
+```
+
+```go
+func lengthOfLIS(nums []int) int {
+    n := len(nums)
+    memo := make([][]int, n)
+    for i := range memo {
+        memo[i] = make([]int, n+1)  
+        for j := range memo[i] {
+            memo[i][j] = -1  
+        }
+    }
+
+    var dfs func(i, j int) int
+    dfs = func(i, j int) int {
+        if i == n {
+            return 0
+        }
+        if memo[i][j+1] != -1 {
+            return memo[i][j+1]
+        }
+
+        LIS := dfs(i + 1, j)  
+
+        if j == -1 || nums[j] < nums[i] {
+            LIS = max(LIS, 1 + dfs(i + 1, i))  
+        }
+
+        memo[i][j+1] = LIS
+        return LIS
+    }
+
+    return dfs(0, -1)
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    private lateinit var memo: Array<IntArray>
+
+    private fun dfs(i: Int, j: Int, nums: IntArray): Int {
+        if (i == nums.size) {
+            return 0
+        }
+        if (memo[i][j + 1] != -1) {
+            return memo[i][j + 1]
+        }
+
+        var LIS = dfs(i + 1, j, nums)  
+
+        if (j == -1 || nums[j] < nums[i]) {
+            LIS = maxOf(LIS, 1 + dfs(i + 1, i, nums))  
+        }
+
+        memo[i][j + 1] = LIS
+        return LIS
+    }
+
+    fun lengthOfLIS(nums: IntArray): Int {
+        val n = nums.size
+        memo = Array(n) { IntArray(n + 1) { -1 } }  
+        return dfs(0, -1, nums)
+    }
+}
+```
+
+```swift
+class Solution {
+    func lengthOfLIS(_ nums: [Int]) -> Int {
+        let n = nums.count
+        var memo = Array(repeating: Array(repeating: -1, count: n + 1), count: n)
+
+        func dfs(_ i: Int, _ j: Int) -> Int {
+            if i == n {
+                return 0
+            }
+            if memo[i][j + 1] != -1 {
+                return memo[i][j + 1]
+            }
+
+            var LIS = dfs(i + 1, j) // not include
+
+            if j == -1 || nums[j] < nums[i] {
+                LIS = max(LIS, 1 + dfs(i + 1, i)) // include
+            }
+
+            memo[i][j + 1] = LIS
+            return LIS
+        }
+
+        return dfs(0, -1)
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 3. Dynamic Programming (Top-Down) - II
+
+::tabs-start
+
+```python
+class Solution:
+    def lengthOfLIS(self, nums: List[int]) -> int:
+        n = len(nums)
+        memo = [-1] * n
+
+        def dfs(i):
+            if memo[i] != -1:
+                return memo[i]
+
+            LIS = 1
+            for j in range(i + 1, n):
+                if nums[i] < nums[j]:
+                    LIS = max(LIS, 1 + dfs(j))
+
+            memo[i] = LIS
+            return LIS
+
+        return max(dfs(i) for i in range(n))
+```
+
+```java
+public class Solution {
+    private int[] memo;
+
+    public int lengthOfLIS(int[] nums) {
+        int n = nums.length;
+        memo = new int[n];
+        Arrays.fill(memo, -1);
+
+        int maxLIS = 1;
+        for (int i = 0; i < n; i++) {
+            maxLIS = Math.max(maxLIS, dfs(nums, i));
+        }
+        return maxLIS;
+    }
+
+    private int dfs(int[] nums, int i) {
+        if (memo[i] != -1) {
+            return memo[i];
+        }
+
+        int LIS = 1;
+        for (int j = i + 1; j < nums.length; j++) {
+            if (nums[i] < nums[j]) {
+                LIS = Math.max(LIS, 1 + dfs(nums, j));
+            }
+        }
+
+        memo[i] = LIS;
+        return LIS;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<int> memo;
+    
+    int dfs(vector<int>& nums, int i) {
+        if (memo[i] != -1) {
+            return memo[i];
+        }
+
+        int LIS = 1;
+        for (int j = i + 1; j < nums.size(); j++) {
+            if (nums[i] < nums[j]) {
+                LIS = max(LIS, 1 + dfs(nums, j));
+            }
+        }
+
+        return memo[i] = LIS;
+    }
+
+public:
+    int lengthOfLIS(vector<int>& nums) {
+        int n = nums.size();
+        memo.assign(n, -1);
+
+        int maxLIS = 1;
+        for (int i = 0; i < n; i++) {
+            maxLIS = max(maxLIS, dfs(nums, i));
+        }
+        return maxLIS;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    lengthOfLIS(nums) {
+        const n = nums.length;
+        const memo = new Array(n).fill(-1);
+
+        const dfs = (i) => {
+            if (memo[i] !== -1) {
+                return memo[i];
+            }
+
+            let LIS = 1;
+            for (let j = i + 1; j < n; j++) {
+                if (nums[i] < nums[j]) {
+                    LIS = Math.max(LIS, 1 + dfs(j));
+                }
+            }
+
+            memo[i] = LIS;
+            return LIS;
+        };
+
+        return Math.max(...nums.map((_, i) => dfs(i)));
+    }
+}
+```
+
+```csharp
+public class Solution {
+    private int[] memo;
+
+    public int LengthOfLIS(int[] nums) {
+        int n = nums.Length;
+        memo = new int[n];
+        Array.Fill(memo, -1);
+
+        int maxLIS = 1;
+        for (int i = 0; i < n; i++) {
+            maxLIS = Math.Max(maxLIS, Dfs(nums, i));
+        }
+        return maxLIS;
+    }
+
+    private int Dfs(int[] nums, int i) {
+        if (memo[i] != -1) {
+            return memo[i];
+        }
+
+        int LIS = 1;
+        for (int j = i + 1; j < nums.Length; j++) {
+            if (nums[i] < nums[j]) {
+                LIS = Math.Max(LIS, 1 + Dfs(nums, j));
+            }
+        }
+
+        memo[i] = LIS;
+        return LIS;
+    }
+}
+```
+
+```go
+func lengthOfLIS(nums []int) int {
+    n := len(nums)
+    memo := make([]int, n)
+    for i := range memo {
+        memo[i] = -1
+    }
+
+    var dfs func(int) int
+    dfs = func(i int) int {
+        if memo[i] != -1 {
+            return memo[i]
+        }
+
+        LIS := 1
+        for j := i + 1; j < n; j++ {
+            if nums[i] < nums[j] {
+                LIS = max(LIS, 1+dfs(j))
+            }
+        }
+
+        memo[i] = LIS
+        return LIS
+    }
+
+    maxLIS := 1
+    for i := 0; i < n; i++ {
+        maxLIS = max(maxLIS, dfs(i))
+    }
+
+    return maxLIS
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    private lateinit var memo: IntArray
+
+    fun lengthOfLIS(nums: IntArray): Int {
+        val n = nums.size
+        memo = IntArray(n) { -1 }
+
+        var maxLIS = 1
+        for (i in nums.indices) {
+            maxLIS = maxOf(maxLIS, dfs(nums, i))
+        }
+        return maxLIS
+    }
+
+    private fun dfs(nums: IntArray, i: Int): Int {
+        if (memo[i] != -1) {
+            return memo[i]
+        }
+
+        var LIS = 1
+        for (j in i + 1 until nums.size) {
+            if (nums[i] < nums[j]) {
+                LIS = maxOf(LIS, 1 + dfs(nums, j))
+            }
+        }
+
+        memo[i] = LIS
+        return LIS
+    }
+}
+```
+
+```swift
+class Solution {
+    func lengthOfLIS(_ nums: [Int]) -> Int {
+        let n = nums.count
+        var memo = Array(repeating: -1, count: n)
+
+        func dfs(_ i: Int) -> Int {
+            if memo[i] != -1 {
+                return memo[i]
+            }
+
+            var LIS = 1
+            for j in (i + 1)..<n {
+                if nums[i] < nums[j] {
+                    LIS = max(LIS, 1 + dfs(j))
+                }
+            }
+
+            memo[i] = LIS
+            return LIS
+        }
+
+        return (0..<n).map { dfs($0) }.max()!
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Dynamic Programming (Bottom-Up) - I
+
+::tabs-start
+
+```python
+class Solution:
+    def lengthOfLIS(self, nums):
+        n = len(nums)
+        dp = [[0] * (n + 1) for _ in range(n + 1)]  
+
+        for i in range(n - 1, -1, -1):
+            for j in range(i - 1, -2, -1):
+                LIS = dp[i + 1][j + 1]  # Not including nums[i]
+
+                if j == -1 or nums[j] < nums[i]:
+                    LIS = max(LIS, 1 + dp[i + 1][i + 1])  # Including nums[i]
+
+                dp[i][j + 1] = LIS
+
+        return dp[0][0]
+```
 
+```java
+public class Solution {
     public int lengthOfLIS(int[] nums) {
         int n = nums.length;
-        memo = new int[n][n + 1];  
-        for (int[] row : memo) {
-            Arrays.fill(row, -1);  
+        int[][] dp = new int[n + 1][n + 1];
+
+        for (int i = n - 1; i >= 0; i--) {
+            for (int j = i - 1; j >= -1; j--) {
+                int LIS = dp[i + 1][j + 1]; // Not including nums[i]
+
+                if (j == -1 || nums[j] < nums[i]) {
+                    LIS = Math.max(LIS, 1 + dp[i + 1][i + 1]); // Including nums[i]
+                }
+
+                dp[i][j + 1] = LIS;
+            }
         }
-        return dfs(0, -1, nums);
+
+        return dp[0][0];
     }
 }
 ```
@@ -191,30 +786,23 @@ public class Solution {
 ```cpp
 class Solution {
 public:
-    vector<vector<int>> memo;
-    
-    int dfs(int i, int j, vector<int>& nums) {
-        if (i == nums.size()) {
-            return 0;
-        }
-        if (memo[i][j + 1] != -1) {  
-            return memo[i][j + 1];
-        }
+    int lengthOfLIS(vector<int>& nums) {
+        int n = nums.size();
+        vector<vector<int>> dp(n + 1, vector<int>(n + 1, 0));
 
-        int LIS = dfs(i + 1, j, nums);
+        for (int i = n - 1; i >= 0; --i) {
+            for (int j = i - 1; j >= -1; --j) {
+                int LIS = dp[i + 1][j + 1]; // Not including nums[i]
 
-        if (j == -1 || nums[j] < nums[i]) {
-            LIS = max(LIS, 1 + dfs(i + 1, i, nums));
+                if (j == -1 || nums[j] < nums[i]) {
+                    LIS = max(LIS, 1 + dp[i + 1][i + 1]); // Including nums[i]
+                }
+
+                dp[i][j + 1] = LIS;
+            }
         }
 
-        memo[i][j + 1] = LIS;
-        return LIS;
-    }
-    
-    int lengthOfLIS(vector<int>& nums) {
-        int n = nums.size();
-        memo = vector<vector<int>>(n, vector<int>(n + 1, -1)); 
-        return dfs(0, -1, nums);
+        return dp[0][0];
     }
 };
 ```
@@ -227,32 +815,21 @@ class Solution {
      */
     lengthOfLIS(nums) {
         const n = nums.length;
-        const memo = Array.from({ length: n }, () => 
-                     Array(n + 2).fill(-1));
-        
-        return this.dfs(nums, 0, -1, memo);
-    }
+        const dp = Array.from({ length: n + 1 }, () => new Array(n + 1).fill(0));
 
-    /**
-     * @param {number[]} nums
-     * @param {number} i
-     * @param {number} j
-     * @param {number[][]} memo
-     * @return {number}
-     */
-    dfs(nums, i, j, memo) {
-        if (i === nums.length) return 0; 
-        if (memo[i][j + 1] !== -1) 
-            return memo[i][j + 1];
+        for (let i = n - 1; i >= 0; i--) {
+            for (let j = i - 1; j >= -1; j--) {
+                let LIS = dp[i + 1][j + 1]; // Not including nums[i]
 
-        let LIS = this.dfs(nums, i + 1, j, memo);
+                if (j === -1 || nums[j] < nums[i]) {
+                    LIS = Math.max(LIS, 1 + dp[i + 1][i + 1]); // Including nums[i]
+                }
 
-        if (j === -1 || nums[j] < nums[i]) {
-            LIS = Math.max(LIS, 1 + this.dfs(nums, i + 1, i, memo));
+                dp[i][j + 1] = LIS;
+            }
         }
 
-        memo[i][j + 1] = LIS;
-        return LIS;
+        return dp[0][0];
     }
 }
 ```
@@ -261,29 +838,98 @@ class Solution {
 public class Solution {
     public int LengthOfLIS(int[] nums) {
         int n = nums.Length;
-        int[,] memo = new int[n, n + 1];
+        int[,] dp = new int[n + 1, n + 1];
 
-        for (int i = 0; i < n; i++)
-            for (int j = 0; j <= n; j++)
-                memo[i, j] = -1;
+        for (int i = n - 1; i >= 0; i--) {
+            for (int j = i - 1; j >= -1; j--) {
+                int LIS = dp[i + 1, j + 1]; // Not including nums[i]
 
-        return DFS(nums, 0, -1, memo);
+                if (j == -1 || nums[j] < nums[i]) {
+                    LIS = Math.Max(LIS, 1 + dp[i + 1, i + 1]); // Including nums[i]
+                }
+
+                dp[i, j + 1] = LIS;
+            }
+        }
+
+        return dp[0, 0];
     }
+}
+```
 
-    private int DFS(int[] nums, int i, int j, int[,] memo) {
-        if (i == nums.Length) return 0; 
-        if (memo[i, j + 1] != -1) {
-            return memo[i, j + 1];
+```go
+func lengthOfLIS(nums []int) int {
+    n := len(nums)
+    dp := make([][]int, n+1)
+    for i := range dp {
+        dp[i] = make([]int, n+1)
+    }
+
+    for i := n - 1; i >= 0; i-- {
+        for j := i - 1; j >= -1; j-- {
+            LIS := dp[i+1][j+1] // Not including nums[i]
+
+            if j == -1 || nums[j] < nums[i] {
+                LIS = max(LIS, 1+dp[i+1][i+1]) // Including nums[i]
+            }
+
+            dp[i][j+1] = LIS
         }
+    }
 
-        int LIS = DFS(nums, i + 1, j, memo);
+    return dp[0][0]
+}
 
-        if (j == -1 || nums[j] < nums[i]) {
-            LIS = Math.Max(LIS, 1 + DFS(nums, i + 1, i, memo));
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun lengthOfLIS(nums: IntArray): Int {
+        val n = nums.size
+        val dp = Array(n + 1) { IntArray(n + 1) }
+
+        for (i in n - 1 downTo 0) {
+            for (j in i - 1 downTo -1) {
+                var LIS = dp[i + 1][j + 1] // Not including nums[i]
+
+                if (j == -1 || nums[j] < nums[i]) {
+                    LIS = maxOf(LIS, 1 + dp[i + 1][i + 1]) // Including nums[i]
+                }
+
+                dp[i][j + 1] = LIS
+            }
         }
 
-        memo[i, j + 1] = LIS;
-        return LIS;
+        return dp[0][0]
+    }
+}
+```
+
+```swift
+class Solution {
+    func lengthOfLIS(_ nums: [Int]) -> Int {
+        let n = nums.count
+        var dp = Array(repeating: Array(repeating: 0, count: n + 1), count: n + 1)
+
+        for i in stride(from: n - 1, through: 0, by: -1) {
+            for j in stride(from: i - 1, through: -1, by: -1) {
+                var LIS = dp[i + 1][j + 1] // Not including nums[i]
+
+                if j == -1 || nums[j] < nums[i] {
+                    LIS = max(LIS, 1 + dp[i + 1][i + 1]) // Including nums[i]
+                }
+
+                dp[i][j + 1] = LIS
+            }
+        }
+
+        return dp[0][0]
     }
 }
 ```
@@ -297,7 +943,7 @@ public class Solution {
 
 ---
 
-## 3. Dynamic Programming (Bottom-Up)
+## 5. Dynamic Programming (Bottom-Up) - II
 
 ::tabs-start
 
@@ -388,6 +1034,69 @@ public class Solution {
 }
 ```
 
+```go
+func lengthOfLIS(nums []int) int {
+    LIS := make([]int, len(nums))
+    for i := range LIS {
+        LIS[i] = 1
+    }
+    
+    for i := len(nums) - 1; i >= 0; i-- {
+        for j := i + 1; j < len(nums); j++ {
+            if nums[i] < nums[j] {
+                if 1 + LIS[j] > LIS[i] {
+                    LIS[i] = 1 + LIS[j]
+                }
+            }
+        }
+    }
+    
+    maxLen := 1
+    for _, length := range LIS {
+        if length > maxLen {
+            maxLen = length
+        }
+    }
+    
+    return maxLen
+}
+```
+
+```kotlin
+class Solution {
+    fun lengthOfLIS(nums: IntArray): Int {
+        val LIS = IntArray(nums.size) { 1 }
+        
+        for (i in nums.size - 1 downTo 0) {
+            for (j in (i + 1) until nums.size) {
+                if (nums[i] < nums[j]) {
+                    LIS[i] = maxOf(LIS[i], 1 + LIS[j])
+                }
+            }
+        }
+        
+        return LIS.maxOrNull() ?: 1
+    }
+}
+```
+
+```swift
+class Solution {
+    func lengthOfLIS(_ nums: [Int]) -> Int {
+        var LIS = Array(repeating: 1, count: nums.count)
+
+        for i in stride(from: nums.count - 1, through: 0, by: -1) {
+            for j in (i + 1)..<nums.count {
+                if nums[i] < nums[j] {
+                    LIS[i] = max(LIS[i], 1 + LIS[j])
+                }
+            }
+        }
+        return LIS.max()!
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -397,7 +1106,7 @@ public class Solution {
 
 ---
 
-## 4. Segment Tree
+## 6. Segment Tree
 
 ::tabs-start
 
@@ -456,7 +1165,7 @@ class Solution:
 ```
 
 ```java
-public class SegmentTree {
+class SegmentTree {
     int n;
     int[] tree;
 
@@ -741,6 +1450,214 @@ public class Solution {
 }
 ```
 
+```go
+type SegmentTree struct {
+	n    int
+	tree []int
+}
+
+func NewSegmentTree(N int) *SegmentTree {
+	n := N
+	for (n & (n - 1)) != 0 {
+		n++
+	}
+	tree := make([]int, 2*n)
+	return &SegmentTree{n: n, tree: tree}
+}
+
+func (seg *SegmentTree) Update(i, val int) {
+	seg.tree[seg.n+i] = val
+	j := (seg.n + i) >> 1
+	for j >= 1 {
+		seg.tree[j] = max(seg.tree[j<<1], seg.tree[j<<1|1])
+		j >>= 1
+	}
+}
+
+func (seg *SegmentTree) Query(l, r int) int {
+	if l > r {
+		return 0
+	}
+	res := -1 << 63
+	l += seg.n
+	r += seg.n + 1
+	for l < r {
+		if l&1 != 0 {
+			res = max(res, seg.tree[l])
+			l++
+		}
+		if r&1 != 0 {
+			r--
+			res = max(res, seg.tree[r])
+		}
+		l >>= 1
+		r >>= 1
+	}
+	return res
+}
+
+func compress(arr []int) []int {
+	sortedArr := make([]int, len(arr))
+	copy(sortedArr, arr)
+	sort.Ints(sortedArr)
+	order := make([]int, len(arr))
+	for i, num := range arr {
+		order[i] = sort.SearchInts(sortedArr, num)
+	}
+	return order
+}
+
+func lengthOfLIS(nums []int) int {
+	nums = compress(nums)
+	n := len(nums)
+	segTree := NewSegmentTree(n)
+	LIS := 0
+	for _, num := range nums {
+		curLIS := segTree.Query(0, num-1) + 1
+		segTree.Update(num, curLIS)
+		LIS = max(LIS, curLIS)
+	}
+	return LIS
+}
+
+func max(a, b int) int {
+	if a > b {
+		return a
+	}
+	return b
+}
+```
+
+```kotlin
+class SegmentTree(N: Int) {
+    var n: Int = N
+    var tree: IntArray
+
+    init {
+        while ((n and (n - 1)) != 0) {
+            n++
+        }
+        tree = IntArray(2 * n)
+    }
+
+    fun update(i: Int, value: Int) {
+        tree[n + i] = value
+        var j = (n + i) / 2
+        while (j >= 1) {
+            tree[j] = max(tree[j * 2], tree[j * 2 + 1])
+            j /= 2
+        }
+    }
+
+    fun query(l: Int, r: Int): Int {
+        if (l > r) return 0
+        var res = Int.MIN_VALUE
+        var left = l + n
+        var right = r + n + 1
+        while (left < right) {
+            if (left and 1 != 0) {
+                res = max(res, tree[left])
+                left++
+            }
+            if (right and 1 != 0) {
+                right--
+                res = max(res, tree[right])
+            }
+            left /= 2
+            right /= 2
+        }
+        return res
+    }
+}
+
+class Solution {
+    fun compress(arr: IntArray): IntArray {
+        val sortedArr = arr.toSortedSet().toIntArray()
+        return arr.map { sortedArr.binarySearch(it) }.toIntArray()
+    }
+
+    fun lengthOfLIS(nums: IntArray): Int {
+        val compressedNums = compress(nums)
+        val n = compressedNums.size
+        val segTree = SegmentTree(n)
+        var LIS = 0
+        for (num in compressedNums) {
+            val curLIS = segTree.query(0, num - 1) + 1
+            segTree.update(num, curLIS)
+            LIS = max(LIS, curLIS)
+        }
+        return LIS
+    }
+}
+```
+
+```swift
+class SegmentTree {
+    private var n: Int
+    private var tree: [Int]
+
+    init(_ N: Int) {
+        self.n = N
+        while (self.n & (self.n - 1)) != 0 {
+            self.n += 1
+        }
+        self.tree = Array(repeating: 0, count: 2 * self.n)
+    }
+
+    func update(_ i: Int, _ val: Int) {
+        tree[n + i] = val
+        var j = (n + i) >> 1
+        while j >= 1 {
+            tree[j] = max(tree[j << 1], tree[j << 1 | 1])
+            j >>= 1
+        }
+    }
+
+    func query(_ l: Int, _ r: Int) -> Int {
+        if l > r {
+            return 0
+        }
+        var res = Int.min
+        var l = l + n
+        var r = r + n + 1
+        while l < r {
+            if l & 1 == 1 {
+                res = max(res, tree[l])
+                l += 1
+            }
+            if r & 1 == 1 {
+                r -= 1
+                res = max(res, tree[r])
+            }
+            l >>= 1
+            r >>= 1
+        }
+        return res
+    }
+}
+
+class Solution {
+    func lengthOfLIS(_ nums: [Int]) -> Int {
+        func compress(_ arr: [Int]) -> [Int] {
+            let sortedArr = Array(Set(arr)).sorted()
+            return arr.map { sortedArr.firstIndex(of: $0)! }
+        }
+
+        let nums = compress(nums)
+        let n = nums.count
+        let segTree = SegmentTree(n)
+
+        var LIS = 0
+        for num in nums {
+            let curLIS = segTree.query(0, num - 1) + 1
+            segTree.update(num, curLIS)
+            LIS = max(LIS, curLIS)
+        }
+        return LIS
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -750,7 +1667,7 @@ public class Solution {
 
 ---
 
-## 5. Binary Search
+## 7. Dynamic Programming + Binary Search
 
 ::tabs-start
 
@@ -882,6 +1799,85 @@ public class Solution {
 }
 ```
 
+```go
+func lengthOfLIS(nums []int) int {
+	dp := []int{}
+	dp = append(dp, nums[0])
+
+	LIS := 1
+	for i := 1; i < len(nums); i++ {
+		if dp[len(dp)-1] < nums[i] {
+			dp = append(dp, nums[i])
+			LIS++
+			continue
+		}
+
+		idx := sort.Search(len(dp), func(j int) bool {
+			return dp[j] >= nums[i]
+		})
+		dp[idx] = nums[i]
+	}
+
+	return LIS
+}
+```
+
+```kotlin
+class Solution {
+    fun lengthOfLIS(nums: IntArray): Int {
+        val dp = mutableListOf<Int>()
+        dp.add(nums[0])
+
+        var LIS = 1
+        for (i in 1 until nums.size) {
+            if (dp[dp.size - 1] < nums[i]) {
+                dp.add(nums[i])
+                LIS++
+                continue
+            }
+
+            val idx = dp.binarySearch(nums[i]).let { if (it < 0) -it - 1 else it }
+            dp[idx] = nums[i]
+        }
+
+        return LIS
+    }
+}
+```
+
+```swift
+class Solution {
+    func lengthOfLIS(_ nums: [Int]) -> Int {
+        var dp = [nums[0]]
+        var LIS = 1
+
+        for i in 1..<nums.count {
+            if let last = dp.last, last < nums[i] {
+                dp.append(nums[i])
+                LIS += 1
+            } else {
+                let idx = binarySearch(dp, nums[i])
+                dp[idx] = nums[i]
+            }
+        }
+        return LIS
+    }
+
+    private func binarySearch(_ dp: [Int], _ target: Int) -> Int {
+        var left = 0, right = dp.count - 1
+        while left < right {
+            let mid = (left + right) / 2
+            if dp[mid] < target {
+                left = mid + 1
+            } else {
+                right = mid
+            }
+        }
+        return left
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/longest-palindrome.md b/articles/longest-palindrome.md
new file mode 100644
index 000000000..635b7a163
--- /dev/null
+++ b/articles/longest-palindrome.md
@@ -0,0 +1,419 @@
+## 1. Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def longestPalindrome(self, s: str) -> int:
+        count = defaultdict(int)
+        res = 0
+
+        for c in s:
+            count[c] += 1
+            if count[c] % 2 == 0:
+                res += 2
+
+        for cnt in count.values():
+            if cnt % 2:
+                res += 1
+                break
+
+        return res
+```
+
+```java
+public class Solution {
+    public int longestPalindrome(String s) {
+        Map<Character, Integer> count = new HashMap<>();
+        int res = 0;
+
+        for (char c : s.toCharArray()) {
+            count.put(c, count.getOrDefault(c, 0) + 1);
+            if (count.get(c) % 2 == 0) {
+                res += 2;
+            }
+        }
+
+        for (int cnt : count.values()) {
+            if (cnt % 2 == 1) {
+                res += 1;
+                break;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int longestPalindrome(string s) {
+        unordered_map<char, int> count;
+        int res = 0;
+
+        for (char c : s) {
+            count[c]++;
+            if (count[c] % 2 == 0) {
+                res += 2;
+            }
+        }
+
+        for (auto& [ch, cnt] : count) {
+            if (cnt % 2 == 1) {
+                res += 1;
+                break;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    longestPalindrome(s) {
+        const count = {};
+        let res = 0;
+
+        for (let c of s) {
+            count[c] = (count[c] || 0) + 1;
+            if (count[c] % 2 === 0) {
+                res += 2;
+            }
+        }
+
+        for (let key in count) {
+            if (count[key] % 2 === 1) {
+                res += 1;
+                break;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(m)$
+
+> Where $n$ is the length of the given string, and $m$ is the number of distinct characters in the string.
+
+---
+
+## 2. Hash Map (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def longestPalindrome(self, s: str) -> int:
+        count = defaultdict(int)
+        res = 0
+
+        for c in s:
+            count[c] += 1
+            if count[c] % 2 == 0:
+                res += 2
+
+        return res + (res < len(s))
+```
+
+```java
+public class Solution {
+    public int longestPalindrome(String s) {
+        Map<Character, Integer> count = new HashMap<>();
+        int res = 0;
+
+        for (char c : s.toCharArray()) {
+            count.put(c, count.getOrDefault(c, 0) + 1);
+            if (count.get(c) % 2 == 0) {
+                res += 2;
+            }
+        }
+
+        return res + (res < s.length() ? 1 : 0);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int longestPalindrome(string s) {
+        unordered_map<char, int> count;
+        int res = 0;
+
+        for (char c : s) {
+            count[c]++;
+            if (count[c] % 2 == 0) {
+                res += 2;
+            }
+        }
+
+        return res + (res < s.size());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    longestPalindrome(s) {
+        const count = {};
+        let res = 0;
+
+        for (let c of s) {
+            count[c] = (count[c] || 0) + 1;
+            if (count[c] % 2 === 0) {
+                res += 2;
+            }
+        }
+
+        return res + (res < s.length ? 1 : 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(m)$
+
+> Where $n$ is the length of the given string, and $m$ is the number of distinct characters in the string.
+
+---
+
+## 3. Hash Set
+
+::tabs-start
+
+```python
+class Solution:
+    def longestPalindrome(self, s: str) -> int:
+        seen = set()
+        res = 0
+
+        for c in s:
+            if c in seen:
+                seen.remove(c)
+                res += 2
+            else:
+                seen.add(c)
+
+        return res + 1 if seen else res
+```
+
+```java
+public class Solution {
+    public int longestPalindrome(String s) {
+        Set<Character> seen = new HashSet<>();
+        int res = 0;
+
+        for (char c : s.toCharArray()) {
+            if (seen.contains(c)) {
+                seen.remove(c);
+                res += 2;
+            } else {
+                seen.add(c);
+            }
+        }
+
+        return seen.isEmpty() ? res : res + 1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int longestPalindrome(string s) {
+        unordered_set<char> seen;
+        int res = 0;
+
+        for (char c : s) {
+            if (seen.count(c)) {
+                seen.erase(c);
+                res += 2;
+            } else {
+                seen.insert(c);
+            }
+        }
+
+        return seen.empty() ? res : res + 1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    longestPalindrome(s) {
+        const seen = new Set();
+        let res = 0;
+
+        for (let c of s) {
+            if (seen.has(c)) {
+                seen.delete(c);
+                res += 2;
+            } else {
+                seen.add(c);
+            }
+        }
+
+        return seen.size === 0 ? res : res + 1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(m)$
+
+> Where $n$ is the length of the given string, and $m$ is the number of distinct characters in the string.
+
+---
+
+## 4. Bitmask
+
+::tabs-start
+
+```python
+class Solution:
+    def longestPalindrome(self, s: str) -> int:
+        mask1 = 0  # [a - z]
+        mask2 = 0  # [A - Z]
+        res = 0
+
+        for c in s:
+            if 'a' <= c <= 'z':
+                bit = 1 << (ord(c) - ord('a'))
+                if mask1 & bit:
+                    res += 2
+                mask1 ^= bit
+            else:
+                bit = 1 << (ord(c) - ord('A'))
+                if mask2 & bit:
+                    res += 2
+                mask2 ^= bit
+
+        return res + 1 if mask1 or mask2 else res
+```
+
+```java
+public class Solution {
+    public int longestPalindrome(String s) {
+        int mask1 = 0; // [a - z]
+        int mask2 = 0; // [A - Z]
+        int res = 0;
+
+        for (char c : s.toCharArray()) {
+            if (c >= 'a' && c <= 'z') {
+                int bit = 1 << (c - 'a');
+                if ((mask1 & bit) != 0) {
+                    res += 2;
+                }
+                mask1 ^= bit;
+            } else {
+                int bit = 1 << (c - 'A');
+                if ((mask2 & bit) != 0) {
+                    res += 2;
+                }
+                mask2 ^= bit;
+            }
+        }
+
+        return (mask1 != 0 || mask2 != 0) ? res + 1 : res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int longestPalindrome(string s) {
+        int mask1 = 0; // [a - z]
+        int mask2 = 0; // [A - Z]
+        int res = 0;
+
+        for (char c : s) {
+            if ('a' <= c && c <= 'z') {
+                int bit = 1 << (c - 'a');
+                if (mask1 & bit) {
+                    res += 2;
+                }
+                mask1 ^= bit;
+            } else {
+                int bit = 1 << (c - 'A');
+                if (mask2 & bit) {
+                    res += 2;
+                }
+                mask2 ^= bit;
+            }
+        }
+
+        return (mask1 || mask2) ? res + 1 : res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    longestPalindrome(s) {
+        let mask1 = 0; // [a - z]
+        let mask2 = 0; // [A - Z]
+        let res = 0;
+
+        for (let c of s) {
+            if (c >= 'a' && c <= 'z') {
+                let bit = 1 << (c.charCodeAt(0) - 97);
+                if (mask1 & bit) {
+                    res += 2;
+                }
+                mask1 ^= bit;
+            } else {
+                let bit = 1 << (c.charCodeAt(0) - 65);
+                if (mask2 & bit) {
+                    res += 2;
+                }
+                mask2 ^= bit;
+            }
+        }
+
+        return (mask1 || mask2) ? res + 1 : res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/longest-palindromic-subsequence.md b/articles/longest-palindromic-subsequence.md
new file mode 100644
index 000000000..c216ab542
--- /dev/null
+++ b/articles/longest-palindromic-subsequence.md
@@ -0,0 +1,557 @@
+## 1. Dynamic Programming (Top Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def longestPalindromeSubseq(self, s: str) -> int:
+        n = len(s)
+        dp = [[-1] * n for _ in range(n)]
+
+        def dfs(i, j):
+            if i < 0 or j == n:
+                return 0
+            if dp[i][j] != -1:
+                return dp[i][j]
+            
+            if s[i] == s[j]:
+                length = 1 if i == j else 2
+                dp[i][j] = length + dfs(i - 1, j + 1)
+            else:
+                dp[i][j] = max(dfs(i - 1, j), dfs(i, j + 1))
+            
+            return dp[i][j]
+
+        for i in range(n):
+            dfs(i, i)  # odd length
+            dfs(i, i + 1)  # even length
+        
+        return max(max(row) for row in dp if row != -1)
+```
+
+```java
+public class Solution {
+    private int[][] dp;
+
+    public int longestPalindromeSubseq(String s) {
+        int n = s.length();
+        dp = new int[n][n];
+
+        for (int[] row : dp) {
+            Arrays.fill(row, -1);
+        }
+
+        for (int i = 0; i < n; i++) {
+            dfs(i, i, s);       // Odd length
+            dfs(i, i + 1, s);   // Even length
+        }
+
+        int maxLength = 0;
+        for (int[] row : dp) {
+            for (int val : row) {
+                maxLength = Math.max(maxLength, val);
+            }
+        }
+
+        return maxLength;
+    }
+
+    private int dfs(int i, int j, String s) {
+        if (i < 0 || j == s.length()) {
+            return 0;
+        }
+        if (dp[i][j] != -1) {
+            return dp[i][j];
+        }
+
+        if (s.charAt(i) == s.charAt(j)) {
+            int length = (i == j) ? 1 : 2;
+            dp[i][j] = length + dfs(i - 1, j + 1, s);
+        } else {
+            dp[i][j] = Math.max(dfs(i - 1, j, s), dfs(i, j + 1, s));
+        }
+
+        return dp[i][j];
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<vector<int>> dp;
+
+public:
+    int longestPalindromeSubseq(string s) {
+        int n = s.size();
+        dp.resize(n, vector<int>(n, -1));
+
+        for (int i = 0; i < n; i++) {
+            dfs(i, i, s);       // Odd length
+            dfs(i, i + 1, s);   // Even length
+        }
+
+        int maxLength = 0;
+        for (const auto& row : dp) {
+            for (int val : row) {
+                maxLength = max(maxLength, val);
+            }
+        }
+
+        return maxLength;
+    }
+
+private:
+    int dfs(int i, int j, const string& s) {
+        if (i < 0 || j == s.size()) {
+            return 0;
+        }
+        if (dp[i][j] != -1) {
+            return dp[i][j];
+        }
+
+        if (s[i] == s[j]) {
+            int length = (i == j) ? 1 : 2;
+            dp[i][j] = length + dfs(i - 1, j + 1, s);
+        } else {
+            dp[i][j] = max(dfs(i - 1, j, s), dfs(i, j + 1, s));
+        }
+
+        return dp[i][j];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    longestPalindromeSubseq(s) {
+        const n = s.length;
+        const dp = Array.from({ length: n }, () => Array(n).fill(-1));
+
+        const dfs = (i, j) => {
+            if (i < 0 || j === n) {
+                return 0;
+            }
+            if (dp[i][j] !== -1) {
+                return dp[i][j];
+            }
+
+            if (s[i] === s[j]) {
+                const length = i === j ? 1 : 2;
+                dp[i][j] = length + dfs(i - 1, j + 1);
+            } else {
+                dp[i][j] = Math.max(dfs(i - 1, j), dfs(i, j + 1));
+            }
+
+            return dp[i][j];
+        };
+
+        for (let i = 0; i < n; i++) {
+            dfs(i, i);       // Odd length
+            dfs(i, i + 1);   // Even length
+        }
+
+        let maxLength = 0;
+        for (const row of dp) {
+            for (const val of row) {
+                maxLength = Math.max(maxLength, val);
+            }
+        }
+
+        return maxLength;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 2. Dynamic Programming (Top-Down Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def longestPalindromeSubseq(self, s: str) -> int:
+        cache = {}
+
+        def dfs(i, j):
+            if i > j:
+                return 0
+            if i == j:
+                return 1
+            if (i, j) in cache:
+                return cache[(i, j)]
+            
+            if s[i] == s[j]:
+                cache[(i, j)] = dfs(i + 1, j - 1) + 2
+            else:
+                cache[(i, j)] = max(dfs(i + 1, j), dfs(i, j - 1))
+            
+            return cache[(i, j)]
+
+        return dfs(0, len(s) - 1)
+```
+
+```java
+public class Solution {
+    private int[][] dp;
+
+    public int longestPalindromeSubseq(String s) {
+        int n = s.length();
+        dp = new int[n][n];
+
+        for (int[] row : dp) {
+            Arrays.fill(row, -1);
+        }
+
+        return dfs(0, n - 1, s);
+    }
+
+    private int dfs(int i, int j, String s) {
+        if (i > j) {
+            return 0;
+        }
+        if (i == j) {
+            return 1;
+        }
+        if (dp[i][j] != -1) {
+            return dp[i][j];
+        }
+
+        if (s.charAt(i) == s.charAt(j)) {
+            dp[i][j] = dfs(i + 1, j - 1, s) + 2;
+        } else {
+            dp[i][j] = Math.max(dfs(i + 1, j, s), dfs(i, j - 1, s));
+        }
+
+        return dp[i][j];
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<vector<int>> dp;
+
+public:
+    int longestPalindromeSubseq(string s) {
+        int n = s.size();
+        dp.resize(n, vector<int>(n, -1));
+        return dfs(0, n - 1, s);
+    }
+
+private:
+    int dfs(int i, int j, const string& s) {
+        if (i > j) {
+            return 0;
+        }
+        if (i == j) {
+            return 1;
+        }
+        if (dp[i][j] != -1) {
+            return dp[i][j];
+        }
+
+        if (s[i] == s[j]) {
+            dp[i][j] = dfs(i + 1, j - 1, s) + 2;
+        } else {
+            dp[i][j] = max(dfs(i + 1, j, s), dfs(i, j - 1, s));
+        }
+
+        return dp[i][j];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    longestPalindromeSubseq(s) {
+        const n = s.length;
+        const dp = Array.from({ length: n }, () => Array(n).fill(-1));
+
+        const dfs = (i, j) => {
+            if (i > j) {
+                return 0;
+            }
+            if (i === j) {
+                return 1;
+            }
+            if (dp[i][j] !== -1) {
+                return dp[i][j];
+            }
+
+            if (s[i] === s[j]) {
+                dp[i][j] = dfs(i + 1, j - 1) + 2;
+            } else {
+                dp[i][j] = Math.max(dfs(i + 1, j), dfs(i, j - 1));
+            }
+
+            return dp[i][j];
+        };
+
+        return dfs(0, n - 1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 3. Dynamic Programming (Using LCS Idea)
+
+::tabs-start
+
+```python
+class Solution:
+    def longestPalindromeSubseq(self, s: str) -> int:
+        return self.longestCommonSubsequence(s, s[::-1])
+
+    def longestCommonSubsequence(self, s1: str, s2: str) -> int:
+        N, M = len(s1), len(s2)
+        dp = [[0] * (M + 1) for _ in range(N + 1)]
+
+        for i in range(N):
+            for j in range(M):
+                if s1[i] == s2[j]:
+                    dp[i + 1][j + 1] = 1 + dp[i][j]
+                else:
+                    dp[i + 1][j + 1] = max(dp[i + 1][j], dp[i][j + 1])
+
+        return dp[N][M]
+```
+
+```java
+public class Solution {
+    public int longestPalindromeSubseq(String s) {
+        return longestCommonSubsequence(s, new StringBuilder(s).reverse().toString());
+    }
+
+    public int longestCommonSubsequence(String s1, String s2) {
+        int N = s1.length(), M = s2.length();
+        int[][] dp = new int[N + 1][M + 1];
+
+        for (int i = 0; i < N; i++) {
+            for (int j = 0; j < M; j++) {
+                if (s1.charAt(i) == s2.charAt(j)) {
+                    dp[i + 1][j + 1] = 1 + dp[i][j];
+                } else {
+                    dp[i + 1][j + 1] = Math.max(dp[i + 1][j], dp[i][j + 1]);
+                }
+            }
+        }
+
+        return dp[N][M];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int longestPalindromeSubseq(string s) {
+        string reversedS = s;
+        reverse(reversedS.begin(), reversedS.end());
+        return longestCommonSubsequence(s, reversedS);
+    }
+
+    int longestCommonSubsequence(const string& s1, const string& s2) {
+        int N = s1.size(), M = s2.size();
+        vector<vector<int>> dp(N + 1, vector<int>(M + 1, 0));
+
+        for (int i = 0; i < N; i++) {
+            for (int j = 0; j < M; j++) {
+                if (s1[i] == s2[j]) {
+                    dp[i + 1][j + 1] = 1 + dp[i][j];
+                } else {
+                    dp[i + 1][j + 1] = max(dp[i + 1][j], dp[i][j + 1]);
+                }
+            }
+        }
+
+        return dp[N][M];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    longestPalindromeSubseq(s) {
+        return this.longestCommonSubsequence(s, s.split('').reverse().join(''));
+    }
+
+    /**
+     * @param {string} s1
+     * @param {string} s2
+     * @return {number}
+     */
+    longestCommonSubsequence(s1, s2) {
+        const N = s1.length, M = s2.length;
+        const dp = Array.from({ length: N + 1 }, () => Array(M + 1).fill(0));
+
+        for (let i = 0; i < N; i++) {
+            for (let j = 0; j < M; j++) {
+                if (s1[i] === s2[j]) {
+                    dp[i + 1][j + 1] = 1 + dp[i][j];
+                } else {
+                    dp[i + 1][j + 1] = Math.max(dp[i + 1][j], dp[i][j + 1]);
+                }
+            }
+        }
+
+        return dp[N][M];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def longestPalindromeSubseq(self, s: str) -> int:
+        n = len(s)
+        dp = [0] * n
+
+        for i in range(n - 1, -1, -1):
+            dp[i] = 1
+            prev = 0
+            for j in range(i + 1, n):
+                temp = dp[j]
+
+                if s[i] == s[j]:
+                    dp[j] = prev + 2
+                else:
+                    dp[j] = max(dp[j], dp[j - 1])
+                
+                prev = temp
+
+        return dp[n - 1]
+```
+
+```java
+public class Solution {
+    public int longestPalindromeSubseq(String s) {
+        int n = s.length();
+        int[] dp = new int[n];
+        
+        for (int i = n - 1; i >= 0; i--) {
+            dp[i] = 1;
+            int prev = 0;
+            for (int j = i + 1; j < n; j++) {
+                int temp = dp[j];
+
+                if (s.charAt(i) == s.charAt(j)) {
+                    dp[j] = prev + 2;
+                } else {
+                    dp[j] = Math.max(dp[j], dp[j - 1]);
+                }
+                prev = temp;
+            }
+        }
+        
+        return dp[n - 1];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int longestPalindromeSubseq(string s) {
+        int n = s.size();
+        vector<int> dp(n, 0);
+
+        for (int i = n - 1; i >= 0; i--) {
+            dp[i] = 1;
+            int prev = 0;
+            for (int j = i + 1; j < n; j++) {
+                int temp = dp[j];
+
+                if (s[i] == s[j]) {
+                    dp[j] = prev + 2;
+                } else {
+                    dp[j] = max(dp[j], dp[j - 1]);
+                }
+
+                prev = temp;
+            }
+        }
+
+        return dp[n - 1];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    longestPalindromeSubseq(s) {
+        const n = s.length;
+        const dp = new Array(n).fill(0);
+
+        for (let i = n - 1; i >= 0; i--) {
+            dp[i] = 1;
+            let prev = 0;
+            for (let j = i + 1; j < n; j++) {
+                const temp = dp[j];
+
+                if (s[i] === s[j]) {
+                    dp[j] = prev + 2;
+                } else {
+                    dp[j] = Math.max(dp[j], dp[j - 1]);
+                }
+
+                prev = temp;
+            }
+        }
+
+        return dp[n - 1];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/longest-palindromic-substring.md b/articles/longest-palindromic-substring.md
index 73e9af55a..1d0f82c17 100644
--- a/articles/longest-palindromic-substring.md
+++ b/articles/longest-palindromic-substring.md
@@ -129,12 +129,89 @@ public class Solution {
 }
 ```
 
+```go
+func longestPalindrome(s string) string {
+    res := ""
+    resLen := 0
+
+    for i := 0; i < len(s); i++ {
+        for j := i; j < len(s); j++ {
+            l, r := i, j
+            for l < r && s[l] == s[r] {
+                l++
+                r--
+            }
+
+            if l >= r && resLen < (j-i+1) {
+                res = s[i : j+1]
+                resLen = j - i + 1
+            }
+        }
+    }
+
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun longestPalindrome(s: String): String {
+        var res = ""
+        var resLen = 0
+
+        for (i in s.indices) {
+            for (j in i until s.length) {
+                var l = i
+                var r = j
+                while (l < r && s[l] == s[r]) {
+                    l++
+                    r--
+                }
+
+                if (l >= r && resLen < (j - i + 1)) {
+                    res = s.substring(i, j + 1)
+                    resLen = j - i + 1
+                }
+            }
+        }
+
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func longestPalindrome(_ s: String) -> String {
+        let chars = Array(s)
+        var res = ""
+        var resLen = 0
+
+        for i in 0..<chars.count {
+            for j in i..<chars.count {
+                var l = i, r = j
+                while l < r && chars[l] == chars[r] {
+                    l += 1
+                    r -= 1
+                }
+                
+                if l >= r && resLen < (j - i + 1) {
+                    res = String(chars[i...j])
+                    resLen = j - i + 1
+                }
+            }
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n ^ 3)$
-* Space complexity: $O(1)$
+* Space complexity: $O(n)$
 
 ---
 
@@ -274,6 +351,83 @@ public class Solution {
 }
 ```
 
+```go
+func longestPalindrome(s string) string {
+    n := len(s)
+    resIdx, resLen := 0, 0
+
+    dp := make([][]bool, n)
+    for i := range dp {
+        dp[i] = make([]bool, n)
+    }
+
+    for i := n - 1; i >= 0; i-- {
+        for j := i; j < n; j++ {
+            if s[i] == s[j] && (j-i <= 2 || dp[i+1][j-1]) {
+                dp[i][j] = true
+                if resLen < (j-i+1) {
+                    resIdx = i
+                    resLen = j - i + 1
+                }
+            }
+        }
+    }
+
+    return s[resIdx : resIdx+resLen]
+}
+```
+
+```kotlin
+class Solution {
+    fun longestPalindrome(s: String): String {
+        val n = s.length
+        var resIdx = 0
+        var resLen = 0
+
+        val dp = Array(n) { BooleanArray(n) }
+
+        for (i in n - 1 downTo 0) {
+            for (j in i until n) {
+                if (s[i] == s[j] && (j - i <= 2 || dp[i + 1][j - 1])) {
+                    dp[i][j] = true
+                    if (resLen < (j - i + 1)) {
+                        resIdx = i
+                        resLen = j - i + 1
+                    }
+                }
+            }
+        }
+
+        return s.substring(resIdx, resIdx + resLen)
+    }
+}
+```
+
+```swift
+class Solution {
+    func longestPalindrome(_ s: String) -> String {
+        let chars = Array(s)
+        let n = chars.count
+        var resIdx = 0, resLen = 0
+        var dp = Array(repeating: Array(repeating: false, count: n), count: n)
+
+        for i in stride(from: n - 1, through: 0, by: -1) {
+            for j in i..<n {
+                if chars[i] == chars[j] && (j - i <= 2 || dp[i + 1][j - 1]) {
+                    dp[i][j] = true
+                    if resLen < (j - i + 1) {
+                        resIdx = i
+                        resLen = j - i + 1
+                    }
+                }
+            }
+        }
+
+        return String(chars[resIdx..<resIdx + resLen])
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -470,12 +624,120 @@ public class Solution {
 }
 ```
 
+```go
+func longestPalindrome(s string) string {
+    resIdx, resLen := 0, 0
+
+    for i := 0; i < len(s); i++ {
+        // odd length
+        l, r := i, i
+        for l >= 0 && r < len(s) && s[l] == s[r] {
+            if r-l+1 > resLen {
+                resIdx = l
+                resLen = r - l + 1
+            }
+            l--
+            r++
+        }
+
+        // even length
+        l, r = i, i+1
+        for l >= 0 && r < len(s) && s[l] == s[r] {
+            if r-l+1 > resLen {
+                resIdx = l
+                resLen = r - l + 1
+            }
+            l--
+            r++
+        }
+    }
+
+    return s[resIdx : resIdx+resLen]
+}
+```
+
+```kotlin
+class Solution {
+    fun longestPalindrome(s: String): String {
+        var resIdx = 0
+        var resLen = 0
+
+        for (i in s.indices) {
+            // odd length
+            var l = i
+            var r = i
+            while (l >= 0 && r < s.length && s[l] == s[r]) {
+                if (r - l + 1 > resLen) {
+                    resIdx = l
+                    resLen = r - l + 1
+                }
+                l--
+                r++
+            }
+
+            // even length
+            l = i
+            r = i + 1
+            while (l >= 0 && r < s.length && s[l] == s[r]) {
+                if (r - l + 1 > resLen) {
+                    resIdx = l
+                    resLen = r - l + 1
+                }
+                l--
+                r++
+            }
+        }
+
+        return s.substring(resIdx, resIdx + resLen)
+    }
+}
+```
+
+```swift
+class Solution {
+    func longestPalindrome(_ s: String) -> String {
+        let chars = Array(s)
+        var resIdx = 0
+        var resLen = 0
+
+        for i in 0..<chars.count {
+            // Odd length palindrome
+            var l = i, r = i
+            while l >= 0 && r < chars.count && chars[l] == chars[r] {
+                if (r - l + 1) > resLen {
+                    resIdx = l
+                    resLen = r - l + 1
+                }
+                l -= 1
+                r += 1
+            }
+
+            // Even length palindrome
+            l = i
+            r = i + 1
+            while l >= 0 && r < chars.count && chars[l] == chars[r] {
+                if (r - l + 1) > resLen {
+                    resIdx = l
+                    resLen = r - l + 1
+                }
+                l -= 1
+                r += 1
+            }
+        }
+
+        return String(chars[resIdx..<resIdx + resLen])
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n ^ 2)$
-* Space complexity: $O(1)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ space for the output string.
 
 ---
 
@@ -662,6 +924,128 @@ public class Solution {
 }
 ```
 
+```go
+func longestPalindrome(s string) string {
+    manacher := func(s string) []int {
+        t := "#"
+        for i := 0; i < len(s); i++ {
+            t += string(s[i]) + "#"
+        }
+        n := len(t)
+        p := make([]int, n)
+        l, r := 0, 0
+        for i := 0; i < n; i++ {
+            if i < r {
+                p[i] = min(r-i, p[l+(r-i)])
+            }
+            for i+p[i]+1 < n && i-p[i]-1 >= 0 && t[i+p[i]+1] == t[i-p[i]-1] {
+                p[i]++
+            }
+            if i + p[i] > r {
+                l, r = i - p[i], i + p[i]
+            }
+        }
+        return p
+    }
+    
+    p := manacher(s)
+    resLen, centerIdx := 0, 0
+    for i, v := range p {
+        if v > resLen {
+            resLen = v
+            centerIdx = i
+        }
+    }
+    
+    resIdx := (centerIdx - resLen) / 2
+    return s[resIdx : resIdx + resLen]
+}
+```
+
+```kotlin
+class Solution {
+    fun longestPalindrome(s: String): String {
+        fun manacher(s: String): IntArray {
+            val t = "#" + s.chunked(1).joinToString("#") + "#"
+            val n = t.length
+            val p = IntArray(n)
+            var l = 0
+            var r = 0
+            
+            for (i in 0 until n) {
+                p[i] = if (i < r) Math.min(r - i, p[l + (r - i)]) else 0
+                while (i + p[i] + 1 < n && i - p[i] - 1 >= 0 && 
+                       t[i + p[i] + 1] == t[i - p[i] - 1]) {
+                    p[i]++
+                }
+                if (i + p[i] > r) {
+                    l = i - p[i]
+                    r = i + p[i]
+                }
+            }
+            return p
+        }
+        
+        val p = manacher(s)
+        var resLen = 0
+        var centerIdx = 0
+        for (i in p.indices) {
+            if (p[i] > resLen) {
+                resLen = p[i]
+                centerIdx = i
+            }
+        }
+        
+        val resIdx = (centerIdx - resLen) / 2
+        return s.substring(resIdx, resIdx + resLen)
+    }
+}
+```
+
+```swift
+class Solution {
+    func longestPalindrome(_ s: String) -> String {
+        func manacher(_ s: String) -> [Int] {
+            let t = "#" + s.map { String($0) }.joined(separator: "#") + "#"
+            let tArray = Array(t)
+            let n = tArray.count
+            var p = [Int](repeating: 0, count: n)
+            var l = 0, r = 0
+
+            for i in 0..<n {
+                if i < r {
+                    p[i] = min(r - i, p[l + (r - i)])
+                } else {
+                    p[i] = 0
+                }
+                while (i + p[i] + 1 < n && i - p[i] - 1 >= 0 &&
+                       tArray[i + p[i] + 1] == tArray[i - p[i] - 1]) {
+                    p[i] += 1
+                }
+                if i + p[i] > r {
+                    l = i - p[i]
+                    r = i + p[i]
+                }
+            }
+            return p
+        }
+
+        let p = manacher(s)
+        var resLen = 0, centerIndex = 0
+        for (i, v) in p.enumerated() {
+            if v > resLen {
+                resLen = v
+                centerIndex = i
+            }
+        }
+        let resIdx = (centerIndex - resLen) / 2
+        let start = s.index(s.startIndex, offsetBy: resIdx)
+        let end = s.index(start, offsetBy: resLen)
+        return String(s[start..<end])
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/longest-repeating-substring-with-replacement.md b/articles/longest-repeating-substring-with-replacement.md
index 6c313fe85..481559d2d 100644
--- a/articles/longest-repeating-substring-with-replacement.md
+++ b/articles/longest-repeating-substring-with-replacement.md
@@ -106,6 +106,75 @@ public class Solution {
 }
 ```
 
+```go
+func characterReplacement(s string, k int) int {
+    res := 0
+    for i := 0; i < len(s); i++ {
+        count := make(map[byte]int)
+        maxf := 0
+        for j := i; j < len(s); j++ {
+            count[s[j]]++
+            maxf = max(maxf, count[s[j]])
+            if (j - i + 1) - maxf <= k {
+                res = max(res, j - i + 1)
+            }
+        }
+    }
+    return res
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun characterReplacement(s: String, k: Int): Int {
+        var res = 0
+        for (i in s.indices) {
+            val count = HashMap<Char, Int>()
+            var maxf = 0
+            for (j in i until s.length) {
+                count[s[j]] = count.getOrDefault(s[j], 0) + 1
+                maxf = maxOf(maxf, count[s[j]]!!)
+                if ((j - i + 1) - maxf <= k) {
+                    res = maxOf(res, j - i + 1)
+                }
+            }
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func characterReplacement(_ s: String, _ k: Int) -> Int {
+        var res = 0
+        let chars = Array(s)
+
+        for i in 0..<chars.count {
+            var count = [Character: Int]()
+            var maxf = 0
+
+            for j in i..<chars.count {
+                count[chars[j], default: 0] += 1
+                maxf = max(maxf, count[chars[j]]!)
+
+                if (j - i + 1) - maxf <= k {
+                    res = max(res, j - i + 1)
+                }
+            }
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -263,6 +332,104 @@ public class Solution {
 }
 ```
 
+```go
+func characterReplacement(s string, k int) int {
+    res := 0
+    charSet := make(map[byte]bool)
+    
+    for i := 0; i < len(s); i++ {
+        charSet[s[i]] = true
+    }
+
+    for c := range charSet {
+        count, l := 0, 0
+        for r := 0; r < len(s); r++ {
+            if s[r] == c {
+                count++
+            }
+
+            for (r - l + 1) - count > k {
+                if s[l] == c {
+                    count--
+                }
+                l++
+            }
+
+            res = max(res, r - l + 1)
+        }
+    }
+    
+    return res
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun characterReplacement(s: String, k: Int): Int {
+        var res = 0
+        val charSet = s.toSet()
+
+        for (c in charSet) {
+            var count = 0
+            var l = 0
+            for (r in s.indices) {
+                if (s[r] == c) {
+                    count++
+                }
+
+                while ((r - l + 1) - count > k) {
+                    if (s[l] == c) {
+                        count--
+                    }
+                    l++
+                }
+
+                res = maxOf(res, r - l + 1)
+            }
+        }
+
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func characterReplacement(_ s: String, _ k: Int) -> Int {
+        var res = 0
+        let charSet = Set(s)
+        let chars = Array(s)
+
+        for c in charSet {
+            var count = 0, l = 0
+
+            for r in 0..<chars.count {
+                if chars[r] == c {
+                    count += 1
+                }
+
+                while (r - l + 1) - count > k {
+                    if chars[l] == c {
+                        count -= 1
+                    }
+                    l += 1
+                }
+
+                res = max(res, r - l + 1)
+            }
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -400,6 +567,80 @@ public class Solution {
 }
 ```
 
+```go
+func characterReplacement(s string, k int) int {
+    count := make(map[byte]int)
+    res, l, maxf := 0, 0, 0
+
+    for r := 0; r < len(s); r++ {
+        count[s[r]]++
+        if count[s[r]] > maxf {
+            maxf = count[s[r]]
+        }
+
+        for (r - l + 1) - maxf > k {
+            count[s[l]]--
+            l++
+        }
+        
+        if r - l + 1 > res {
+            res = r - l + 1
+        }
+    }
+    
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun characterReplacement(s: String, k: Int): Int {
+        val count = mutableMapOf<Char, Int>()
+        var res = 0
+        var l = 0
+        var maxf = 0
+
+        for (r in s.indices) {
+            count[s[r]] = count.getOrDefault(s[r], 0) + 1
+            maxf = maxOf(maxf, count[s[r]]!!)
+
+            while (r - l + 1 - maxf > k) {
+                count[s[l]] = count[s[l]]!! - 1
+                l++
+            }
+            
+            res = maxOf(res, r - l + 1)
+        }
+
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func characterReplacement(_ s: String, _ k: Int) -> Int {
+        var count = [Character: Int]()
+        var res = 0
+        var l = 0, maxf = 0
+        let chars = Array(s)
+
+        for r in 0..<chars.count {
+            count[chars[r], default: 0] += 1
+            maxf = max(maxf, count[chars[r]]!)
+
+            while (r - l + 1) - maxf > k {
+                count[chars[l], default: 0] -= 1
+                l += 1
+            }
+            res = max(res, r - l + 1)
+        }
+        
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/longest-strictly-increasing-or-strictly-decreasing-subarray.md b/articles/longest-strictly-increasing-or-strictly-decreasing-subarray.md
new file mode 100644
index 000000000..4c55b7a6b
--- /dev/null
+++ b/articles/longest-strictly-increasing-or-strictly-decreasing-subarray.md
@@ -0,0 +1,454 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def longestMonotonicSubarray(self, nums: List[int]) -> int:
+        n = len(nums)
+        res = 1
+
+        for i in range(n - 1):
+            curLen = 1
+            for j in range(i + 1, n):
+                if nums[j] == nums[j - 1] or ((nums[i] < nums[i + 1]) != (nums[j - 1] < nums[j])):
+                    break
+                curLen += 1
+
+            res = max(res, curLen)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int longestMonotonicSubarray(int[] nums) {
+        int n = nums.length;
+        int res = 1;
+
+        for (int i = 0; i < n - 1; i++) {
+            int curLen = 1;
+            for (int j = i + 1; j < n; j++) {
+                if (nums[j] == nums[j - 1] || ((nums[i] < nums[i + 1]) != (nums[j - 1] < nums[j]))) {
+                    break;
+                }
+                curLen++;
+            }
+            res = Math.max(res, curLen);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int longestMonotonicSubarray(vector<int>& nums) {
+        int n = nums.size();
+        int res = 1;
+
+        for (int i = 0; i < n - 1; i++) {
+            int curLen = 1;
+            for (int j = i + 1; j < n; j++) {
+                if (nums[j] == nums[j - 1] || ((nums[i] < nums[i + 1]) != (nums[j - 1] < nums[j]))) {
+                    break;
+                }
+                curLen++;
+            }
+            res = max(res, curLen);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    longestMonotonicSubarray(nums) {
+        let n = nums.length;
+        let res = 1;
+
+        for (let i = 0; i < n - 1; i++) {
+            let curLen = 1;
+            for (let j = i + 1; j < n; j++) {
+                if (nums[j] === nums[j - 1] || ((nums[i] < nums[i + 1]) !== (nums[j - 1] < nums[j]))) {
+                    break;
+                }
+                curLen++;
+            }
+            res = Math.max(res, curLen);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Iteration - I
+
+::tabs-start
+
+```python
+class Solution:
+    def longestMonotonicSubarray(self, nums: List[int]) -> int:
+        cur = 1
+        res = 1
+        increasing = 0
+
+        for i in range(1, len(nums)):
+            if nums[i - 1] < nums[i]:
+                if increasing > 0:
+                    cur += 1
+                else:
+                    cur = 2
+                    increasing = 1
+            elif nums[i - 1] > nums[i]:
+                if increasing < 0:
+                    cur += 1
+                else:
+                    cur = 2
+                    increasing = -1
+            else:
+                cur = 1
+                increasing = 0
+            res = max(res, cur)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int longestMonotonicSubarray(int[] nums) {
+        int cur = 1;
+        int res = 1;
+        int increasing = 0;
+
+        for (int i = 1; i < nums.length; i++) {
+            if (nums[i - 1] < nums[i]) {
+                if (increasing > 0) {
+                    cur++;
+                } else {
+                    cur = 2;
+                    increasing = 1;
+                }
+            } else if (nums[i - 1] > nums[i]) {
+                if (increasing < 0) {
+                    cur++;
+                } else {
+                    cur = 2;
+                    increasing = -1;
+                }
+            } else {
+                cur = 1;
+                increasing = 0;
+            }
+            res = Math.max(res, cur);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int longestMonotonicSubarray(vector<int>& nums) {
+        int cur = 1;
+        int res = 1;
+        int increasing = 0;
+
+        for (int i = 1; i < nums.size(); i++) {
+            if (nums[i - 1] < nums[i]) {
+                if (increasing > 0) {
+                    cur++;
+                } else {
+                    cur = 2;
+                    increasing = 1;
+                }
+            } else if (nums[i - 1] > nums[i]) {
+                if (increasing < 0) {
+                    cur++;
+                } else {
+                    cur = 2;
+                    increasing = -1;
+                }
+            } else {
+                cur = 1;
+                increasing = 0;
+            }
+            res = max(res, cur);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    longestMonotonicSubarray(nums) {
+        let cur = 1;
+        let res = 1;
+        let increasing = 0;
+
+        for (let i = 1; i < nums.length; i++) {
+            if (nums[i - 1] < nums[i]) {
+                if (increasing > 0) {
+                    cur++;
+                } else {
+                    cur = 2;
+                    increasing = 1;
+                }
+            } else if (nums[i - 1] > nums[i]) {
+                if (increasing < 0) {
+                    cur++;
+                } else {
+                    cur = 2;
+                    increasing = -1;
+                }
+            } else {
+                cur = 1;
+                increasing = 0;
+            }
+            res = Math.max(res, cur);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Iteration - II
+
+::tabs-start
+
+```python
+class Solution:
+    def longestMonotonicSubarray(self, nums: List[int]) -> int:
+        inc = dec = 1
+        res = 1
+
+        for i in range(1, len(nums)):
+            if nums[i] == nums[i - 1]:
+                inc = dec = 1
+            elif nums[i] > nums[i - 1]:
+                inc, dec = inc + 1, 1
+            else:
+                inc, dec = 1, dec + 1
+
+            res = max(res, inc, dec)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int longestMonotonicSubarray(int[] nums) {
+        int inc = 1, dec = 1, res = 1;
+
+        for (int i = 1; i < nums.length; i++) {
+            if (nums[i] == nums[i - 1]) {
+                inc = dec = 1;
+            } else if (nums[i] > nums[i - 1]) {
+                inc = inc + 1;
+                dec = 1;
+            } else {
+                inc = 1;
+                dec = dec + 1;
+            }
+            res = Math.max(res, Math.max(inc, dec));
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int longestMonotonicSubarray(vector<int>& nums) {
+        int inc = 1, dec = 1, res = 1;
+
+        for (int i = 1; i < nums.size(); i++) {
+            if (nums[i] == nums[i - 1]) {
+                inc = dec = 1;
+            } else if (nums[i] > nums[i - 1]) {
+                inc = inc + 1;
+                dec = 1;
+            } else {
+                inc = 1;
+                dec = dec + 1;
+            }
+            res = max(res, max(inc, dec));
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    longestMonotonicSubarray(nums) {
+        let inc = 1, dec = 1, res = 1;
+
+        for (let i = 1; i < nums.length; i++) {
+            if (nums[i] === nums[i - 1]) {
+                inc = dec = 1;
+            } else if (nums[i] > nums[i - 1]) {
+                inc = inc + 1;
+                dec = 1;
+            } else {
+                inc = 1;
+                dec = dec + 1;
+            }
+            res = Math.max(res, inc, dec);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 4. Iteration - III
+
+::tabs-start
+
+```python
+class Solution:
+    def longestMonotonicSubarray(self, nums: List[int]) -> int:
+        curLen = res = 1
+
+        for i in range(1, len(nums)):
+            if (nums[i] == nums[i - 1] or
+                ((nums[i - curLen] < nums[i - curLen + 1]) != (nums[i - 1] < nums[i]))
+            ):
+                curLen = 1 if (nums[i] == nums[i - 1]) else 2
+                continue
+
+            curLen += 1
+            res = max(res, curLen)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int longestMonotonicSubarray(int[] nums) {
+        int curLen = 1, res = 1;
+
+        for (int i = 1; i < nums.length; i++) {
+            if (nums[i] == nums[i - 1] ||
+                ((nums[i - curLen] < nums[i - curLen + 1]) != (nums[i - 1] < nums[i]))) {
+                curLen = (nums[i] == nums[i - 1]) ? 1 : 2;
+                continue;
+            }
+
+            curLen++;
+            res = Math.max(res, curLen);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int longestMonotonicSubarray(vector<int>& nums) {
+        int curLen = 1, res = 1;
+
+        for (int i = 1; i < nums.size(); i++) {
+            if (nums[i] == nums[i - 1] ||
+                ((nums[i - curLen] < nums[i - curLen + 1]) != (nums[i - 1] < nums[i]))) {
+                curLen = (nums[i] == nums[i - 1]) ? 1 : 2;
+                continue;
+            }
+
+            curLen++;
+            res = max(res, curLen);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    longestMonotonicSubarray(nums) {
+        let curLen = 1, res = 1;
+
+        for (let i = 1; i < nums.length; i++) {
+            if (
+                nums[i] === nums[i - 1] ||
+                ((nums[i - curLen] < nums[i - curLen + 1]) !== (nums[i - 1] < nums[i]))
+            ) {
+                curLen = nums[i] === nums[i - 1] ? 1 : 2;
+                continue;
+            }
+
+            curLen++;
+            res = Math.max(res, curLen);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/longest-string-chain.md b/articles/longest-string-chain.md
new file mode 100644
index 000000000..b033bad4a
--- /dev/null
+++ b/articles/longest-string-chain.md
@@ -0,0 +1,435 @@
+## 1. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def longestStrChain(self, words: List[str]) -> int:
+        words.sort(key=lambda w: -len(w))
+        word_index = {}  # map word to index
+        for i, w in enumerate(words):
+            word_index[w] = i
+
+        dp = {}  # index of word -> length of longest chain
+        def dfs(i):
+            if i in dp:
+                return dp[i]
+            res = 1
+            for j in range(len(words[i])):
+                w = words[i]
+                pred = w[:j] + w[j+1:]
+                if pred in word_index:
+                    res = max(res, 1 + dfs(word_index[pred]))
+            dp[i] = res
+            return res
+
+        for i in range(len(words)):
+            dfs(i)
+        return max(dp.values())
+```
+
+```java
+public class Solution {
+    public int longestStrChain(String[] words) {
+        Arrays.sort(words, (a, b) -> Integer.compare(b.length(), a.length()));
+        Map<String, Integer> wordIndex = new HashMap<>();
+        for (int i = 0; i < words.length; i++) {
+            wordIndex.put(words[i], i);
+        }
+
+        int[] dp = new int[words.length];
+        Arrays.fill(dp, -1);
+
+        int maxChain = 1;
+        for (int i = 0; i < words.length; i++) {
+            maxChain = Math.max(maxChain, dfs(i, words, wordIndex, dp));
+        }
+        return maxChain;
+    }
+
+    private int dfs(int i, String[] words, Map<String, Integer> wordIndex, int[] dp) {
+        if (dp[i] != -1) {
+            return dp[i];
+        }
+
+        int res = 1;
+        String w = words[i];
+        for (int j = 0; j < w.length(); j++) {
+            String pred = w.substring(0, j) + w.substring(j + 1);
+            if (wordIndex.containsKey(pred)) {
+                res = Math.max(res, 1 + dfs(wordIndex.get(pred), words, wordIndex, dp));
+            }
+        }
+        dp[i] = res;
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int longestStrChain(vector<string>& words) {
+        sort(words.begin(), words.end(), [](const string& a, const string& b) {
+            return b.length() < a.length();
+        });
+
+        unordered_map<string, int> wordIndex;
+        for (int i = 0; i < words.size(); i++) {
+            wordIndex[words[i]] = i;
+        }
+
+        vector<int> dp(words.size(), -1);
+        int maxChain = 1;
+        for (int i = 0; i < words.size(); i++) {
+            maxChain = max(maxChain, dfs(i, words, wordIndex, dp));
+        }
+        return maxChain;
+    }
+
+private:
+    int dfs(int i, vector<string>& words, unordered_map<string, int>& wordIndex, vector<int>& dp) {
+        if (dp[i] != -1) {
+            return dp[i];
+        }
+
+        int res = 1;
+        string w = words[i];
+        for (int j = 0; j < w.length(); j++) {
+            string pred = w.substr(0, j) + w.substr(j + 1);
+            if (wordIndex.find(pred) != wordIndex.end()) {
+                res = max(res, 1 + dfs(wordIndex[pred], words, wordIndex, dp));
+            }
+        }
+        dp[i] = res;
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @return {number}
+     */
+    longestStrChain(words) {
+        words.sort((a, b) => b.length - a.length);
+        const wordIndex = new Map();
+        for (let i = 0; i < words.length; i++) {
+            wordIndex.set(words[i], i);
+        }
+
+        const dp = new Array(words.length).fill(-1);
+
+        const dfs = (i) => {
+            if (dp[i] !== -1) {
+                return dp[i];
+            }
+
+            let res = 1;
+            const w = words[i];
+            for (let j = 0; j < w.length; j++) {
+                const pred = w.slice(0, j) + w.slice(j + 1);
+                if (wordIndex.has(pred)) {
+                    res = Math.max(res, 1 + dfs(wordIndex.get(pred)));
+                }
+            }
+            dp[i] = res;
+            return res;
+        };
+
+        let maxChain = 1;
+        for (let i = 0; i < words.length; i++) {
+            maxChain = Math.max(maxChain, dfs(i));
+        }
+        return maxChain;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m ^ 2)$
+* Space complexity: $O(n * m)$
+
+> Where $n$ is the number of words and $m$ is the average length of each word.
+
+---
+
+## 2. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def longestStrChain(self, words: List[str]) -> int:
+        def isPred(w1, w2):
+            i = 0
+            for c in w2:
+                if i == len(w1):
+                    return True
+                if w1[i] == c:
+                    i += 1
+            return i == len(w1)
+
+        words.sort(key=len)
+        n = len(words)
+        dp = [1] * n
+
+        for i in range(1, n):
+            for j in range(i - 1, -1, -1):
+                if len(words[j]) + 1 < len(words[i]):
+                    break
+                if len(words[j]) + 1 > len(words[i]) or not isPred(words[j], words[i]):
+                    continue
+                dp[i] = max(dp[i], 1 + dp[j])
+
+        return max(dp)
+```
+
+```java
+public class Solution {
+    public int longestStrChain(String[] words) {
+        Arrays.sort(words, Comparator.comparingInt(String::length));
+        int n = words.length;
+        int[] dp = new int[n];
+        Arrays.fill(dp, 1);
+
+        for (int i = 1; i < n; i++) {
+            for (int j = i - 1; j >= 0; j--) {
+                if (words[j].length() + 1 < words[i].length()) {
+                    break;
+                }
+                if (words[j].length() + 1 > words[i].length() || !isPred(words[j], words[i])) {
+                    continue;
+                }
+                dp[i] = Math.max(dp[i], 1 + dp[j]);
+            }
+        }
+
+        int maxChain = 0;
+        for (int chain : dp) {
+            maxChain = Math.max(maxChain, chain);
+        }
+        return maxChain;
+    }
+
+    private boolean isPred(String w1, String w2) {
+        int i = 0;
+        for (char c : w2.toCharArray()) {
+            if (i == w1.length()) {
+                return true;
+            }
+            if (w1.charAt(i) == c) {
+                i++;
+            }
+        }
+        return i == w1.length();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int longestStrChain(vector<string>& words) {
+        sort(words.begin(), words.end(), [](const string& a, const string& b) {
+            return a.length() < b.length();
+        });
+
+        int n = words.size();
+        vector<int> dp(n, 1);
+
+        for (int i = 1; i < n; i++) {
+            for (int j = i - 1; j >= 0; j--) {
+                if (words[j].length() + 1 < words[i].length()) {
+                    break;
+                }
+                if (words[j].length() + 1 > words[i].length() || !isPred(words[j], words[i])) {
+                    continue;
+                }
+                dp[i] = max(dp[i], 1 + dp[j]);
+            }
+        }
+
+        return *max_element(dp.begin(), dp.end());
+    }
+
+private:
+    bool isPred(const string& w1, const string& w2) {
+        int i = 0;
+        for (char c : w2) {
+            if (i == w1.length()) {
+                return true;
+            }
+            if (w1[i] == c) {
+                i++;
+            }
+        }
+        return i == w1.length();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @return {number}
+     */
+    longestStrChain(words) {
+        words.sort((a, b) => a.length - b.length);
+        const n = words.length;
+        const dp = new Array(n).fill(1);
+
+        const isPred = (w1, w2) => {
+            let i = 0;
+            for (const c of w2) {
+                if (i === w1.length) {
+                    return true;
+                }
+                if (w1[i] === c) {
+                    i++;
+                }
+            }
+            return i === w1.length;
+        };
+
+        for (let i = 1; i < n; i++) {
+            for (let j = i - 1; j >= 0; j--) {
+                if (words[j].length + 1 < words[i].length) {
+                    break;
+                }
+                if (words[j].length + 1 > words[i].length || !isPred(words[j], words[i])) {
+                    continue;
+                }
+                dp[i] = Math.max(dp[i], 1 + dp[j]);
+            }
+        }
+
+        return Math.max(...dp);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 * m)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the number of words and $m$ is the average length of each word.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def longestStrChain(self, words: List[str]) -> int:
+        words.sort(key=len)
+        dp = {}
+        res = 0
+
+        for word in words:
+            dp[word] = 1
+            for i in range(len(word)):
+                pred = word[:i] + word[i+1:]
+                if pred in dp:
+                    dp[word] = max(dp[word], dp[pred] + 1)
+            res = max(res, dp[word])
+
+        return res
+```
+
+```java
+public class Solution {
+    public int longestStrChain(String[] words) {
+        Arrays.sort(words, Comparator.comparingInt(String::length));
+        Map<String, Integer> dp = new HashMap<>();
+        int res = 0;
+
+        for (String word : words) {
+            dp.put(word, 1);
+            for (int i = 0; i < word.length(); i++) {
+                String pred = word.substring(0, i) + word.substring(i + 1);
+                if (dp.containsKey(pred)) {
+                    dp.put(word, Math.max(dp.get(word), dp.get(pred) + 1));
+                }
+            }
+            res = Math.max(res, dp.get(word));
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int longestStrChain(vector<string>& words) {
+        sort(words.begin(), words.end(), [](const string& a, const string& b) {
+            return a.length() < b.length();
+        });
+
+        unordered_map<string, int> dp;
+        int res = 0;
+
+        for (const string& word : words) {
+            dp[word] = 1;
+            for (int i = 0; i < word.length(); i++) {
+                string pred = word.substr(0, i) + word.substr(i + 1);
+                if (dp.find(pred) != dp.end()) {
+                    dp[word] = max(dp[word], dp[pred] + 1);
+                }
+            }
+            res = max(res, dp[word]);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @return {number}
+     */
+    longestStrChain(words) {
+        words.sort((a, b) => a.length - b.length);
+        const dp = new Map();
+        let res = 0;
+
+        for (const word of words) {
+            dp.set(word, 1);
+            for (let i = 0; i < word.length; i++) {
+                const pred = word.slice(0, i) + word.slice(i + 1);
+                if (dp.has(pred)) {
+                    dp.set(word, Math.max(dp.get(word), dp.get(pred) + 1));
+                }
+            }
+            res = Math.max(res, dp.get(word));
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m ^ 2)$
+* Space complexity: $O(n * m)$
+
+> Where $n$ is the number of words and $m$ is the average length of each word.
\ No newline at end of file
diff --git a/articles/longest-substring-without-duplicates.md b/articles/longest-substring-without-duplicates.md
index 2f173a37e..3d197dc21 100644
--- a/articles/longest-substring-without-duplicates.md
+++ b/articles/longest-substring-without-duplicates.md
@@ -97,6 +97,67 @@ public class Solution {
 }
 ```
 
+```go
+func lengthOfLongestSubstring(s string) int {
+    res := 0
+
+    for i := 0; i < len(s); i++ {
+        charSet := make(map[byte]bool)
+        for j := i; j < len(s); j++ {
+            if charSet[s[j]] {
+                break
+            }
+            charSet[s[j]] = true
+        }
+        if len(charSet) > res {
+            res = len(charSet)
+        }
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun lengthOfLongestSubstring(s: String): Int {
+        var res = 0
+
+        for (i in s.indices) {
+            val charSet = mutableSetOf<Char>()
+            for (j in i until s.length) {
+                if (s[j] in charSet) {
+                    break
+                }
+                charSet.add(s[j])
+            }
+            res = maxOf(res, charSet.size)
+        }
+        return res
+    }
+}
+```
+
+```kotlin
+class Solution {
+    func lengthOfLongestSubstring(_ s: String) -> Int {
+        var res = 0
+        let chars = Array(s)
+
+        for i in 0..<chars.count {
+            var charSet = Set<Character>()
+            for j in i..<chars.count {
+                if charSet.contains(chars[j]) {
+                    break
+                }
+                charSet.insert(chars[j])
+            }
+            res = max(res, charSet.count)
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -213,6 +274,65 @@ public class Solution {
 }
 ```
 
+```go
+func lengthOfLongestSubstring(s string) int {
+    charSet := make(map[byte]bool)
+    l, res := 0, 0
+
+    for r := 0; r < len(s); r++ {
+        for charSet[s[r]] {
+            delete(charSet, s[l])
+            l++
+        }
+        charSet[s[r]] = true
+        if r - l + 1 > res {
+            res = r - l + 1
+        }
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun lengthOfLongestSubstring(s: String): Int {
+        val charSet = HashSet<Char>()
+        var l = 0
+        var res = 0
+
+        for (r in s.indices) {
+            while (s[r] in charSet) {
+                charSet.remove(s[l])
+                l++
+            }
+            charSet.add(s[r])
+            res = maxOf(res, r - l + 1)
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func lengthOfLongestSubstring(_ s: String) -> Int {
+        var charSet = Set<Character>()
+        var l = 0, res = 0
+        let chars = Array(s)
+
+        for r in 0..<chars.count {
+            while charSet.contains(chars[r]) {
+                charSet.remove(chars[l])
+                l += 1
+            }
+            charSet.insert(chars[r])
+            res = max(res, r - l + 1)
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -320,6 +440,62 @@ public class Solution {
 }
 ```
 
+```go
+func lengthOfLongestSubstring(s string) int {
+    mp := make(map[byte]int)
+    l, res := 0, 0
+
+    for r := 0; r < len(s); r++ {
+        if idx, found := mp[s[r]]; found {
+            l = max(idx+1, l)
+        }
+        mp[s[r]] = r
+        if r - l + 1 > res {
+            res = r - l + 1
+        }
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun lengthOfLongestSubstring(s: String): Int {
+        val mp = HashMap<Char, Int>()
+        var l = 0
+        var res = 0
+
+        for (r in s.indices) {
+            if (s[r] in mp) {
+                l = maxOf(mp[s[r]]!! + 1, l)
+            }
+            mp[s[r]] = r
+            res = maxOf(res, r - l + 1)
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func lengthOfLongestSubstring(_ s: String) -> Int {
+        var mp = [Character: Int]()
+        var l = 0, res = 0
+        let chars = Array(s)
+
+        for r in 0..<chars.count {
+            if let index = mp[chars[r]] {
+                l = max(index + 1, l)
+            }
+            mp[chars[r]] = r
+            res = max(res, r - l + 1)
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/longest-turbulent-subarray.md b/articles/longest-turbulent-subarray.md
new file mode 100644
index 000000000..a7876d5c0
--- /dev/null
+++ b/articles/longest-turbulent-subarray.md
@@ -0,0 +1,638 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def maxTurbulenceSize(self, arr: List[int]) -> int:
+        n = len(arr)
+        res = 1
+        
+        for i in range(n - 1):
+            if arr[i] == arr[i + 1]:
+                continue
+            
+            sign = 1 if arr[i] > arr[i + 1] else 0
+            j = i + 1
+            while j < n - 1:
+                if arr[j] == arr[j + 1]:
+                    break
+                curSign = 1 if arr[j] > arr[j + 1] else 0
+                if sign == curSign:
+                    break        
+                sign = curSign
+                j += 1
+            
+            res = max(res, j - i + 1)
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int maxTurbulenceSize(int[] arr) {
+        int n = arr.length;
+        int res = 1;
+
+        for (int i = 0; i < n - 1; i++) {
+            if (arr[i] == arr[i + 1]) continue;
+
+            int sign = arr[i] > arr[i + 1] ? 1 : 0;
+            int j = i + 1;
+
+            while (j < n - 1) {
+                if (arr[j] == arr[j + 1]) break;
+
+                int curSign = arr[j] > arr[j + 1] ? 1 : 0;
+                if (sign == curSign) break;
+
+                sign = curSign;
+                j++;
+            }
+
+            res = Math.max(res, j - i + 1);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxTurbulenceSize(vector<int>& arr) {
+        int n = arr.size();
+        int res = 1;
+
+        for (int i = 0; i < n - 1; i++) {
+            if (arr[i] == arr[i + 1]) continue;
+
+            int sign = arr[i] > arr[i + 1] ? 1 : 0;
+            int j = i + 1;
+
+            while (j < n - 1) {
+                if (arr[j] == arr[j + 1]) break;
+
+                int curSign = arr[j] > arr[j + 1] ? 1 : 0;
+                if (sign == curSign) break;
+
+                sign = curSign;
+                j++;
+            }
+
+            res = max(res, j - i + 1);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @return {number}
+     */
+    maxTurbulenceSize(arr) {
+        const n = arr.length;
+        let res = 1;
+
+        for (let i = 0; i < n - 1; i++) {
+            if (arr[i] === arr[i + 1]) continue;
+
+            let sign = arr[i] > arr[i + 1] ? 1 : 0;
+            let j = i + 1;
+
+            while (j < n - 1) {
+                if (arr[j] === arr[j + 1]) break;
+
+                let curSign = arr[j] > arr[j + 1] ? 1 : 0;
+                if (sign === curSign) break;
+
+                sign = curSign;
+                j++;
+            }
+
+            res = Math.max(res, j - i + 1);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxTurbulenceSize(self, arr: List[int]) -> int:
+        n = len(arr)
+        memo = {}
+
+        def dfs(i, sign):
+            if i == n - 1:
+                return 1
+            if (i, sign) in memo:
+                return memo[(i, sign)]
+
+            res = 1
+            if ((sign and arr[i] > arr[i + 1]) or 
+                (not sign and arr[i] < arr[i + 1])
+            ):
+                res = 1 + dfs(i + 1, not sign)
+
+            memo[(i, sign)] = res
+            return res
+
+        max_len = 1
+        for i in range(n):
+            max_len = max(max_len, dfs(i, True), dfs(i, False))
+
+        return max_len
+```
+
+```java
+public class Solution {
+    private int[][] memo;
+
+    public int maxTurbulenceSize(int[] arr) {
+        int n = arr.length;
+        memo = new int[n][2];
+
+        for (int i = 0; i < n; i++) {
+            memo[i][0] = -1;
+            memo[i][1] = -1;
+        }
+
+        int maxLen = 1;
+        for (int i = 0; i < n; i++) {
+            maxLen = Math.max(maxLen, dfs(i, true, arr));
+            maxLen = Math.max(maxLen, dfs(i, false, arr));
+        }
+
+        return maxLen;
+    }
+
+    private int dfs(int i, boolean sign, int[] arr) {
+        int signIndex = sign ? 1 : 0;
+        if (i == arr.length - 1) return 1;
+        if (memo[i][signIndex] != -1) {
+            return memo[i][signIndex];
+        }
+
+        int res = 1;
+        if ((sign && arr[i] > arr[i + 1]) || 
+            (!sign && arr[i] < arr[i + 1])) {
+            res = 1 + dfs(i + 1, !sign, arr);
+        }
+
+        memo[i][signIndex] = res;
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+    vector<vector<int>> memo;
+
+public:
+    int maxTurbulenceSize(vector<int>& arr) {
+        int n = arr.size();
+        memo.assign(n, vector<int>(2, -1));
+
+        int maxLen = 1;
+        for (int i = 0; i < n; i++) {
+            maxLen = max(maxLen, dfs(i, true, arr));
+            maxLen = max(maxLen, dfs(i, false, arr));
+        }
+
+        return maxLen;
+    }
+
+    int dfs(int i, bool sign, vector<int>& arr) {
+        int signIndex = sign ? 1 : 0;
+        if (i == arr.size() - 1) return 1;
+        if (memo[i][signIndex] != -1) {
+            return memo[i][signIndex];
+        }
+
+        int res = 1;
+        if ((sign && arr[i] > arr[i + 1]) || 
+            (!sign && arr[i] < arr[i + 1])) {
+            res = 1 + dfs(i + 1, !sign, arr);
+        }
+
+        memo[i][signIndex] = res;
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @return {number}
+     */
+    maxTurbulenceSize(arr) {
+        const n = arr.length;
+        const memo = Array.from({ length: n }, () => [-1, -1]);
+
+        const dfs = (i, sign) => {
+            const signIndex = sign ? 1 : 0;
+            if (i === n - 1) return 1;
+            if (memo[i][signIndex] !== -1) {
+                return memo[i][signIndex];
+            }
+
+            let res = 1;
+            if ((sign && arr[i] > arr[i + 1]) || 
+                (!sign && arr[i] < arr[i + 1])) {
+                res = 1 + dfs(i + 1, !sign);
+            }
+
+            memo[i][signIndex] = res;
+            return res;
+        };
+
+        let maxLen = 1;
+        for (let i = 0; i < n; i++) {
+            maxLen = Math.max(maxLen, dfs(i, true), dfs(i, false));
+        }
+
+        return maxLen;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxTurbulenceSize(self, arr: List[int]) -> int:
+        n = len(arr)
+        if n == 1:
+            return 1
+
+        dp = [[1] * 2 for _ in range(n)]
+
+        max_len = 1
+        for i in range(1, n):
+            if arr[i] > arr[i - 1]:
+                dp[i][1] = dp[i - 1][0] + 1
+            elif arr[i] < arr[i - 1]:
+                dp[i][0] = dp[i - 1][1] + 1
+
+            max_len = max(max_len, dp[i][0], dp[i][1])
+
+        return max_len
+```
+
+```java
+public class Solution {
+    public int maxTurbulenceSize(int[] arr) {
+        int n = arr.length;
+        if (n == 1) return 1;
+
+        int[][] dp = new int[n][2];
+        for (int i = 0; i < n; i++) {
+            dp[i][0] = dp[i][1] = 1;
+        }
+
+        int maxLen = 1;
+        for (int i = 1; i < n; i++) {
+            if (arr[i] > arr[i - 1]) {
+                dp[i][1] = dp[i - 1][0] + 1;
+            } else if (arr[i] < arr[i - 1]) {
+                dp[i][0] = dp[i - 1][1] + 1;
+            }
+            maxLen = Math.max(maxLen, dp[i][0]);
+            maxLen = Math.max(maxLen, dp[i][1]);
+        }
+
+        return maxLen;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxTurbulenceSize(vector<int>& arr) {
+        int n = arr.size();
+        if (n == 1) return 1;
+
+        vector<vector<int>> dp(n, vector<int>(2, 1));
+        int maxLen = 1;
+
+        for (int i = 1; i < n; ++i) {
+            if (arr[i] > arr[i - 1]) {
+                dp[i][1] = dp[i - 1][0] + 1;
+            } else if (arr[i] < arr[i - 1]) {
+                dp[i][0] = dp[i - 1][1] + 1;
+            }
+            maxLen = max(maxLen, max(dp[i][0], dp[i][1]));
+        }
+
+        return maxLen;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @return {number}
+     */
+    maxTurbulenceSize(arr) {
+        const n = arr.length;
+        if (n === 1) return 1;
+
+        const dp = Array.from({ length: n }, () => [1, 1]);
+
+        let maxLen = 1;
+        for (let i = 1; i < n; i++) {
+            if (arr[i] > arr[i - 1]) {
+                dp[i][1] = dp[i - 1][0] + 1;
+            } else if (arr[i] < arr[i - 1]) {
+                dp[i][0] = dp[i - 1][1] + 1;
+            }
+            maxLen = Math.max(maxLen, dp[i][0], dp[i][1]);
+        }
+
+        return maxLen;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Sliding Window
+
+::tabs-start
+
+```python
+class Solution:
+    def maxTurbulenceSize(self, arr: List[int]) -> int:
+        l, r, res, prev = 0, 1, 1, ""
+
+        while r < len(arr):
+            if arr[r - 1] > arr[r] and prev != ">":
+                res = max(res, r - l + 1)
+                r += 1
+                prev = ">"
+            elif arr[r - 1] < arr[r] and prev != "<":
+                res = max(res, r - l + 1)
+                r += 1
+                prev = "<"
+            else:
+                r = r + 1 if arr[r] == arr[r - 1] else r
+                l = r - 1
+                prev = ""
+
+        return res
+```
+
+```java
+public class Solution {
+    public int maxTurbulenceSize(int[] arr) {
+        int l = 0, r = 1, res = 1;
+        String prev = "";
+
+        while (r < arr.length) {
+            if (arr[r - 1] > arr[r] && !">".equals(prev)) {
+                res = Math.max(res, r - l + 1);
+                r++;
+                prev = ">";
+            } else if (arr[r - 1] < arr[r] && !"<".equals(prev)) {
+                res = Math.max(res, r - l + 1);
+                r++;
+                prev = "<";
+            } else {
+                r = (arr[r] == arr[r - 1]) ? r + 1 : r;
+                l = r - 1;
+                prev = "";
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxTurbulenceSize(vector<int>& arr) {
+        int l = 0, r = 1, res = 1;
+        string prev = "";
+
+        while (r < arr.size()) {
+            if (arr[r - 1] > arr[r] && prev != ">") {
+                res = max(res, r - l + 1);
+                r++;
+                prev = ">";
+            } else if (arr[r - 1] < arr[r] && prev != "<") {
+                res = max(res, r - l + 1);
+                r++;
+                prev = "<";
+            } else {
+                r = (arr[r] == arr[r - 1]) ? r + 1 : r;
+                l = r - 1;
+                prev = "";
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @return {number}
+     */
+    maxTurbulenceSize(arr) {
+        let l = 0, r = 1, res = 1, prev = "";
+
+        while (r < arr.length) {
+            if (arr[r - 1] > arr[r] && prev !== ">") {
+                res = Math.max(res, r - l + 1);
+                r++;
+                prev = ">";
+            } else if (arr[r - 1] < arr[r] && prev !== "<") {
+                res = Math.max(res, r - l + 1);
+                r++;
+                prev = "<";
+            } else {
+                r = (arr[r] === arr[r - 1]) ? r + 1 : r;
+                l = r - 1;
+                prev = "";
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 5. Iteration
+
+::tabs-start
+
+```python
+class Solution:
+    def maxTurbulenceSize(self, arr: List[int]) -> int:
+        n = len(arr)
+        res = cnt = 0
+        sign = -1
+        
+        for i in range(n - 1):
+            if arr[i] > arr[i + 1]:
+                cnt = cnt + 1 if sign == 0 else 1
+                sign = 1
+            elif arr[i] < arr[i + 1]:
+                cnt = cnt + 1 if sign == 1 else 1
+                sign = 0
+            else:
+                cnt = 0
+                sign = -1
+                
+            res = max(res, cnt)
+            
+        return res + 1
+```
+
+```java
+public class Solution {
+    public int maxTurbulenceSize(int[] arr) {
+        int n = arr.length;
+        int res = 0, cnt = 0, sign = -1;
+        
+        for (int i = 0; i < n - 1; i++) {
+            if (arr[i] > arr[i + 1]) {
+                cnt = (sign == 0) ? cnt + 1 : 1;
+                sign = 1;
+            } else if (arr[i] < arr[i + 1]) {
+                cnt = (sign == 1) ? cnt + 1 : 1;
+                sign = 0;
+            } else {
+                cnt = 0;
+                sign = -1;
+            }
+            
+            res = Math.max(res, cnt);
+        }
+        
+        return res + 1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxTurbulenceSize(vector<int>& arr) {
+        int n = arr.size();
+        int res = 0, cnt = 0, sign = -1;
+        
+        for (int i = 0; i < n - 1; i++) {
+            if (arr[i] > arr[i + 1]) {
+                cnt = (sign == 0) ? cnt + 1 : 1;
+                sign = 1;
+            } else if (arr[i] < arr[i + 1]) {
+                cnt = (sign == 1) ? cnt + 1 : 1;
+                sign = 0;
+            } else {
+                cnt = 0;
+                sign = -1;
+            }
+            
+            res = max(res, cnt);
+        }
+        
+        return res + 1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @return {number}
+     */
+    maxTurbulenceSize(arr) {
+        const n = arr.length;
+        let res = 0, cnt = 0, sign = -1;
+        
+        for (let i = 0; i < n - 1; i++) {
+            if (arr[i] > arr[i + 1]) {
+                cnt = (sign === 0) ? cnt + 1 : 1;
+                sign = 1;
+            } else if (arr[i] < arr[i + 1]) {
+                cnt = (sign === 1) ? cnt + 1 : 1;
+                sign = 0;
+            } else {
+                cnt = 0;
+                sign = -1;
+            }
+            
+            res = Math.max(res, cnt);
+        }
+        
+        return res + 1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/lowest-common-ancestor-in-binary-search-tree.md b/articles/lowest-common-ancestor-in-binary-search-tree.md
index 298aba06e..798316614 100644
--- a/articles/lowest-common-ancestor-in-binary-search-tree.md
+++ b/articles/lowest-common-ancestor-in-binary-search-tree.md
@@ -150,6 +150,99 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val   int
+ *     Left  *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+
+func lowestCommonAncestor(root, p, q *TreeNode) *TreeNode {
+    if root == nil || p == nil || q == nil {
+        return nil
+    }
+    if max(p.Val, q.Val) < root.Val {
+        return lowestCommonAncestor(root.Left, p, q)
+    } else if min(p.Val, q.Val) > root.Val {
+        return lowestCommonAncestor(root.Right, p, q)
+    } else {
+        return root
+    }
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+/**
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int = 0) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+
+class Solution {
+    fun lowestCommonAncestor(root: TreeNode?, p: TreeNode?, q: TreeNode?): TreeNode? {
+        if (root == null || p == null || q == null) {
+            return null
+        }
+        return when {
+            maxOf(p.`val`, q.`val`) < root.`val` -> lowestCommonAncestor(root.left, p, q)
+            minOf(p.`val`, q.`val`) > root.`val` -> lowestCommonAncestor(root.right, p, q)
+            else -> root
+        }
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init(_ val: Int) {
+ *         self.val = val
+ *         self.left = nil
+ *         self.right = nil
+ *     }
+ * }
+ */
+
+class Solution {
+    func lowestCommonAncestor(_ root: TreeNode?, _ p: TreeNode?, _ q: TreeNode?) -> TreeNode? {
+        guard let root = root, let p = p, let q = q else {
+            return nil
+        }
+
+        if max(p.val, q.val) < root.val {
+            return lowestCommonAncestor(root.left, p, q)
+        } else if min(p.val, q.val) > root.val {
+            return lowestCommonAncestor(root.right, p, q)
+        } else {
+            return root
+        }
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -322,6 +415,94 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val   int
+ *     Left  *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+
+func lowestCommonAncestor(root, p, q *TreeNode) *TreeNode {
+    cur := root
+
+    for cur != nil {
+        if p.Val > cur.Val && q.Val > cur.Val {
+            cur = cur.Right
+        } else if p.Val < cur.Val && q.Val < cur.Val {
+            cur = cur.Left
+        } else {
+            return cur
+        }
+    }
+    return nil
+}
+```
+
+```kotlin
+/**
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int = 0) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+
+class Solution {
+    fun lowestCommonAncestor(root: TreeNode?, p: TreeNode?, q: TreeNode?): TreeNode? {
+        var cur = root
+
+        while (cur != null) {
+            if (p!!.`val` > cur.`val` && q!!.`val` > cur.`val`) {
+                cur = cur.right
+            } else if (p!!.`val` < cur.`val` && q!!.`val` < cur.`val`) {
+                cur = cur.left
+            } else {
+                return cur
+            }
+        }
+        return null
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init(_ val: Int) {
+ *         self.val = val
+ *         self.left = nil
+ *         self.right = nil
+ *     }
+ * }
+ */
+
+class Solution {
+    func lowestCommonAncestor(_ root: TreeNode?, _ p: TreeNode?, _ q: TreeNode?) -> TreeNode? {
+        var cur = root
+
+        while let node = cur {
+            if let p = p, let q = q {
+                if p.val > node.val && q.val > node.val {
+                    cur = node.right
+                } else if p.val < node.val && q.val < node.val {
+                    cur = node.left
+                } else {
+                    return node
+                }
+            }
+        }
+        return nil
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/lru-cache.md b/articles/lru-cache.md
index f7925f929..2bd939f9c 100644
--- a/articles/lru-cache.md
+++ b/articles/lru-cache.md
@@ -201,6 +201,124 @@ public class LRUCache {
 }
 ```
 
+```go
+type LRUCache struct {
+    cache    [][2]int
+    capacity int
+}
+
+func Constructor(capacity int) LRUCache {
+    return LRUCache{
+        cache:    make([][2]int, 0),
+        capacity: capacity,
+    }
+}
+
+func (this *LRUCache) Get(key int) int {
+    for i := range this.cache {
+        if this.cache[i][0] == key {
+            tmp := this.cache[i]
+            this.cache = append(this.cache[:i], this.cache[i+1:]...)
+            this.cache = append(this.cache, tmp)
+            return tmp[1]
+        }
+    }
+    return -1
+}
+
+func (this *LRUCache) Put(key int, value int) {
+    for i := range this.cache {
+        if this.cache[i][0] == key {
+            tmp := this.cache[i]
+            this.cache = append(this.cache[:i], this.cache[i+1:]...)
+            tmp[1] = value
+            this.cache = append(this.cache, tmp)
+            return
+        }
+    }
+    
+    if len(this.cache) == this.capacity {
+        this.cache = this.cache[1:]
+    }
+    
+    this.cache = append(this.cache, [2]int{key, value})
+}
+```
+
+```kotlin
+class LRUCache(capacity: Int) {
+    private val capacity = capacity
+    private val cache = mutableListOf<Pair<Int, Int>>()
+    
+    fun get(key: Int): Int {
+        for (i in cache.indices) {
+            if (cache[i].first == key) {
+                val tmp = cache.removeAt(i)
+                cache.add(tmp)
+                return tmp.second
+            }
+        }
+        return -1
+    }
+    
+    fun put(key: Int, value: Int) {
+        for (i in cache.indices) {
+            if (cache[i].first == key) {
+                cache.removeAt(i)
+                cache.add(Pair(key, value))
+                return
+            }
+        }
+        
+        if (cache.size == capacity) {
+            cache.removeAt(0)
+        }
+        
+        cache.add(Pair(key, value))
+    }
+}
+```
+
+```swift
+class LRUCache {
+    private var cache: [(Int, Int)]
+    private let capacity: Int
+
+    init(_ capacity: Int) {
+        self.cache = []
+        self.capacity = capacity
+    }
+
+    func get(_ key: Int) -> Int {
+        for i in 0..<cache.count {
+            if cache[i].0 == key {
+                let tmp = cache.remove(at: i)
+                cache.append(tmp)
+                return tmp.1
+            }
+        }
+        return -1
+    }
+
+    func put(_ key: Int, _ value: Int) {
+        for i in 0..<cache.count {
+            if cache[i].0 == key {
+                var tmp = cache.remove(at: i)
+                tmp.1 = value
+                cache.append(tmp)
+                return
+            }
+        }
+
+        if cache.count == capacity {
+            cache.removeFirst()
+        }
+
+        cache.append((key, value))
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -557,6 +675,204 @@ public class LRUCache {
 }
 ```
 
+```go
+type Node struct {
+    key, val   int
+    prev, next *Node
+}
+
+type LRUCache struct {
+    cap        int
+    cache      map[int]*Node
+    left,right *Node
+}
+
+func Constructor(capacity int) LRUCache {
+    lru := LRUCache{
+        cap:   capacity,
+        cache: make(map[int]*Node),
+        left:  &Node{},
+        right: &Node{},
+    }
+    lru.left.next = lru.right
+    lru.right.prev = lru.left
+    return lru
+}
+
+func (this *LRUCache) remove(node *Node) {
+    prev, next := node.prev, node.next
+    prev.next = next
+    next.prev = prev
+}
+
+func (this *LRUCache) insert(node *Node) {
+    prev, next := this.right.prev, this.right
+    prev.next = node
+    next.prev = node
+    node.next = next
+    node.prev = prev
+}
+
+func (this *LRUCache) Get(key int) int {
+    if node, ok := this.cache[key]; ok {
+        this.remove(node)
+        this.insert(node)
+        return node.val
+    }
+    return -1
+}
+
+func (this *LRUCache) Put(key int, value int) {
+    if node, ok := this.cache[key]; ok {
+        this.remove(node)
+        delete(this.cache, key)
+    }
+    
+    node := &Node{key: key, val: value}
+    this.cache[key] = node
+    this.insert(node)
+    
+    if len(this.cache) > this.cap {
+        lru := this.left.next
+        this.remove(lru)
+        delete(this.cache, lru.key)
+    }
+}
+```
+
+```kotlin
+class LRUCache(capacity: Int) {
+    private val capacity = capacity
+    private class Node(
+        val key: Int,
+        var value: Int,
+        var prev: Node? = null,
+        var next: Node? = null
+    )
+    
+    private val cache = mutableMapOf<Int, Node>()
+    private val left = Node(0, 0)
+    private val right = Node(0, 0)
+    
+    init {
+        left.next = right
+        right.prev = left
+    }
+    
+    private fun remove(node: Node) {
+        val prev = node.prev
+        val next = node.next
+        prev?.next = next
+        next?.prev = prev
+    }
+    
+    private fun insert(node: Node) {
+        val prev = right.prev
+        val next = right
+        prev?.next = node
+        next.prev = node
+        node.next = next
+        node.prev = prev
+    }
+    
+    fun get(key: Int): Int {
+        return cache[key]?.let { node ->
+            remove(node)
+            insert(node)
+            node.value
+        } ?: -1
+    }
+    
+    fun put(key: Int, value: Int) {
+        cache[key]?.let { node ->
+            remove(node)
+            cache.remove(key)
+        }
+        
+        val node = Node(key, value)
+        cache[key] = node
+        insert(node)
+        
+        if (cache.size > capacity) {
+            left.next?.let { lru ->
+                remove(lru)
+                cache.remove(lru.key)
+            }
+        }
+    }
+}
+```
+
+```swift
+class Node {
+    var key: Int
+    var val: Int
+    var prev: Node?
+    var next: Node?
+
+    init(_ key: Int, _ val: Int) {
+        self.key = key
+        self.val = val
+    }
+}
+
+class LRUCache {
+    private var cap: Int
+    private var cache: [Int: Node] = [:]
+    private var left: Node
+    private var right: Node
+
+    init(_ capacity: Int) {
+        self.cap = capacity
+        self.left = Node(0, 0)
+        self.right = Node(0, 0)
+        self.left.next = self.right
+        self.right.prev = self.left
+    }
+
+    private func remove(_ node: Node?) {
+        let prev = node?.prev
+        let next = node?.next
+        prev?.next = next
+        next?.prev = prev
+    }
+
+    private func insert(_ node: Node?) {
+        let prev = right.prev
+        let next = right
+        prev?.next = node
+        next.prev = node
+        node?.prev = prev
+        node?.next = next
+    }
+
+    func get(_ key: Int) -> Int {
+        if let node = cache[key] {
+            remove(node)
+            insert(node)
+            return node.val
+        }
+        return -1
+    }
+
+    func put(_ key: Int, _ value: Int) {
+        if let node = cache[key] {
+            remove(node)
+        }
+        let newNode = Node(key, value)
+        cache[key] = newNode
+        insert(newNode)
+
+        if cache.count > cap {
+            if let lru = left.next {
+                remove(lru)
+                cache.removeValue(forKey: lru.key)
+            }
+        }
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -729,6 +1045,112 @@ public class LRUCache {
 }
 ```
 
+```go
+type LRUCache struct {
+    capacity int
+    keys     []int
+    values   map[int]int
+}
+
+func Constructor(capacity int) LRUCache {
+    return LRUCache{
+        capacity: capacity,
+        keys:     make([]int, 0, capacity),
+        values:   make(map[int]int),
+    }
+}
+
+func (this *LRUCache) Get(key int) int {
+    if val, exists := this.values[key]; exists {
+        for i := range this.keys {
+            if this.keys[i] == key {
+                this.keys = append(this.keys[:i], this.keys[i+1:]...)
+                break
+            }
+        }
+        this.keys = append(this.keys, key)
+        return val
+    }
+    return -1
+}
+
+func (this *LRUCache) Put(key int, value int) {
+    if _, exists := this.values[key]; exists {
+        for i := range this.keys {
+            if this.keys[i] == key {
+                this.keys = append(this.keys[:i], this.keys[i+1:]...)
+                break
+            }
+        }
+    } else {
+        if len(this.keys) >= this.capacity {
+            delete(this.values, this.keys[0])
+            this.keys = this.keys[1:]
+        }
+    }
+    this.values[key] = value
+    this.keys = append(this.keys, key)
+}
+```
+
+```kotlin
+class LRUCache(capacity: Int) {
+    private val capacity = capacity
+    private val cache = object : LinkedHashMap<Int, Int>(capacity, 0.75f, true) {
+        override fun removeEldestEntry(eldest: MutableMap.MutableEntry<Int, Int>): Boolean {
+            return size > capacity
+        }
+    }
+    
+    fun get(key: Int): Int {
+        return cache.getOrDefault(key, -1)
+    }
+    
+    fun put(key: Int, value: Int) {
+        cache[key] = value
+    }
+}
+```
+
+```swift
+class LRUCache {
+    private var capacity: Int
+    private var cache: [Int: Int] = [:]
+    private var keyOrder: [Int] = []
+
+    init(_ capacity: Int) {
+        self.capacity = capacity
+    }
+
+    func get(_ key: Int) -> Int {
+        if let value = cache[key] {
+            if let index = keyOrder.firstIndex(of: key) {
+                keyOrder.remove(at: index)
+            }
+            keyOrder.append(key)
+            return value
+        }
+        return -1
+    }
+
+    func put(_ key: Int, _ value: Int) {
+        if cache[key] != nil {
+            if let index = keyOrder.firstIndex(of: key) {
+                keyOrder.remove(at: index)
+            }
+        } else if cache.count >= capacity {
+            if let lruKey = keyOrder.first {
+                cache.removeValue(forKey: lruKey)
+                keyOrder.removeFirst()
+            }
+        }
+
+        cache[key] = value
+        keyOrder.append(key)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/majority-element-ii.md b/articles/majority-element-ii.md
new file mode 100644
index 000000000..aca6e49c3
--- /dev/null
+++ b/articles/majority-element-ii.md
@@ -0,0 +1,746 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def majorityElement(self, nums: List[int]) -> List[int]:
+        res = set()
+        for num in nums:
+            count = sum(1 for i in nums if i == num)
+            if count > len(nums) // 3:
+                res.add(num)
+        return list(res)
+```
+
+```java
+public class Solution {
+    public List<Integer> majorityElement(int[] nums) {
+        Set<Integer> res = new HashSet<>();
+        for (int num : nums) {
+            int count = 0;
+            for (int i : nums) {
+                if (i == num) count++;
+            }
+            if (count > nums.length / 3) {
+                res.add(num);
+            }
+        }
+        return new ArrayList<>(res);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> majorityElement(vector<int>& nums) {
+        unordered_set<int> res;
+        for (int num : nums) {
+            int count = 0;
+            for (int i : nums) {
+                if (i == num) count++;
+            }
+            if (count > nums.size() / 3) {
+                res.insert(num);
+            }
+        }
+        return vector<int>(res.begin(), res.end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    majorityElement(nums) {
+        const res = new Set();
+        for (const num of nums) {
+            let count = 0;
+            for (const i of nums) {
+                if (i === num) count++;
+            }
+            if (count > Math.floor(nums.length / 3)) {
+                res.add(num);
+            }
+        }
+        return Array.from(res);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<int> MajorityElement(int[] nums) {
+        HashSet<int> res = new HashSet<int>();
+        int n = nums.Length;
+
+        foreach (int num in nums) {
+            int count = nums.Count(x => x == num);
+            if (count > n / 3) {
+                res.Add(num);
+            }
+        }
+
+        return res.ToList();
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$ since output array size will be at most $2$.
+
+---
+
+## 2. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def majorityElement(self, nums: List[int]) -> List[int]:
+        nums.sort()
+        res, n = [], len(nums)
+        
+        i = 0
+        while i < n:
+            j = i + 1
+            while j < n and nums[i] == nums[j]:
+                j += 1
+            if (j - i) > n // 3:
+                res.append(nums[i])
+            i = j
+
+        return res
+```
+
+```java
+public class Solution {
+    public List<Integer> majorityElement(int[] nums) {
+        Arrays.sort(nums);
+        List<Integer> res = new ArrayList<>();
+        int n = nums.length;
+
+        int i = 0;
+        while (i < n) {
+            int j = i + 1;
+            while (j < n && nums[i] == nums[j]) {
+                j++;
+            }
+            if (j - i > n / 3) {
+                res.add(nums[i]);
+            }
+            i = j;
+        }
+        
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> majorityElement(vector<int>& nums) {
+        sort(nums.begin(), nums.end());
+        vector<int> res;
+        int n = nums.size();
+
+        int i = 0;
+        while (i < n) {
+            int j = i + 1;
+            while (j < n && nums[i] == nums[j]) {
+                j++;
+            }
+            if (j - i > n / 3) {
+                res.push_back(nums[i]);
+            }
+            i = j;
+        }
+        
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    majorityElement(nums) {
+        nums.sort((a, b) => a - b);
+        const res = [];
+        const n = nums.length;
+
+        let i = 0;
+        while (i < n) {
+            let j = i + 1;
+            while (j < n && nums[i] === nums[j]) {
+                j++;
+            }
+            if (j - i > Math.floor(n / 3)) {
+                res.push(nums[i]);
+            }
+            i = j;
+        }
+        
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<int> MajorityElement(int[] nums) {
+        Array.Sort(nums);
+        List<int> res = new List<int>();
+        int n = nums.Length;
+        
+        int i = 0;
+        while (i < n) {
+            int j = i + 1;
+            while (j < n && nums[j] == nums[i]) {
+                j++;
+            }
+            if (j - i > n / 3) {
+                res.Add(nums[i]);
+            }
+            i = j;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 3. Frequency Count
+
+::tabs-start
+
+```python
+class Solution:
+    def majorityElement(self, nums: List[int]) -> List[int]:
+        count = Counter(nums)
+        res = []
+
+        for key in count:
+            if count[key] > len(nums) // 3:
+                res.append(key)
+        
+        return res
+```
+
+```java
+public class Solution {
+    public List<Integer> majorityElement(int[] nums) {
+        Map<Integer, Integer> count = new HashMap<>();
+        for (int num : nums) {
+            count.put(num, count.getOrDefault(num, 0) + 1);
+        }
+
+        List<Integer> res = new ArrayList<>();
+        for (int key : count.keySet()) {
+            if (count.get(key) > nums.length / 3) {
+                res.add(key);
+            }
+        }
+        
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> majorityElement(vector<int>& nums) {
+        unordered_map<int, int> count;
+        for (int num : nums) {
+            count[num]++;
+        }
+
+        vector<int> res;
+        for (auto& pair : count) {
+            if (pair.second > nums.size() / 3) {
+                res.push_back(pair.first);
+            }
+        }
+        
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    majorityElement(nums) {
+        const count = new Map();
+        for (const num of nums) {
+            count.set(num, (count.get(num) || 0) + 1);
+        }
+
+        const res = [];
+        for (const [key, value] of count.entries()) {
+            if (value > Math.floor(nums.length / 3)) {
+                res.push(key);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<int> MajorityElement(int[] nums) {
+        Dictionary<int, int> count = new Dictionary<int, int>();
+        List<int> res = new List<int>();
+        int n = nums.Length;
+
+        foreach (int num in nums) {
+            if (!count.ContainsKey(num)) {
+                count[num] = 0;
+            }
+            count[num]++;
+        }
+
+        foreach (var kvp in count) {
+            if (kvp.Value > n / 3) {
+                res.Add(kvp.Key);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Boyer-Moore Voting Algorithm
+
+::tabs-start
+
+```python
+class Solution:
+    def majorityElement(self, nums: List[int]) -> List[int]:
+        n = len(nums)
+        num1 = num2 = -1
+        cnt1 = cnt2 = 0
+
+        for num in nums:
+            if num == num1:
+                cnt1 += 1
+            elif num == num2:
+                cnt2 += 1
+            elif cnt1 == 0:
+                cnt1 = 1
+                num1 = num
+            elif cnt2 == 0:
+                cnt2 = 1
+                num2 = num
+            else:
+                cnt1 -= 1
+                cnt2 -= 1
+        
+        cnt1 = cnt2 = 0
+        for num in nums:
+            if num == num1:
+                cnt1 += 1
+            elif num == num2:
+                cnt2 += 1
+        
+        res = []
+        if cnt1 > n // 3:
+            res.append(num1)
+        if cnt2 > n // 3:
+            res.append(num2)
+        
+        return res
+```
+
+```java
+public class Solution {
+    public List<Integer> majorityElement(int[] nums) {
+        int n = nums.length;
+        int num1 = -1, num2 = -1, cnt1 = 0, cnt2 = 0;
+
+        for (int num : nums) {
+            if (num == num1) {
+                cnt1++;
+            } else if (num == num2) {
+                cnt2++;
+            } else if (cnt1 == 0) {
+                cnt1 = 1;
+                num1 = num;
+            } else if (cnt2 == 0) {
+                cnt2 = 1;
+                num2 = num;
+            } else {
+                cnt1--;
+                cnt2--;
+            }
+        }
+
+        cnt1 = cnt2 = 0;
+        for (int num : nums) {
+            if (num == num1) {
+                cnt1++;
+            } else if (num == num2) {
+                cnt2++;
+            }
+        }
+
+        List<Integer> res = new ArrayList<>();
+        if (cnt1 > n / 3) res.add(num1);
+        if (cnt2 > n / 3) res.add(num2);
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> majorityElement(vector<int>& nums) {
+        int n = nums.size();
+        int num1 = -1, num2 = -1, cnt1 = 0, cnt2 = 0;
+
+        for (int num : nums) {
+            if (num == num1) {
+                cnt1++;
+            } else if (num == num2) {
+                cnt2++;
+            } else if (cnt1 == 0) {
+                num1 = num;
+                cnt1 = 1;
+            } else if (cnt2 == 0) {
+                num2 = num;
+                cnt2 = 1;
+            } else {
+                cnt1--;
+                cnt2--;
+            }
+        }
+
+        cnt1 = cnt2 = 0;
+        for (int num : nums) {
+            if (num == num1) cnt1++;
+            else if (num == num2) cnt2++;
+        }
+
+        vector<int> res;
+        if (cnt1 > n / 3) res.push_back(num1);
+        if (cnt2 > n / 3) res.push_back(num2);
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    majorityElement(nums) {
+        const n = nums.length;
+        let num1 = -1, num2 = -1, cnt1 = 0, cnt2 = 0;
+
+        for (const num of nums) {
+            if (num === num1) {
+                cnt1++;
+            } else if (num === num2) {
+                cnt2++;
+            } else if (cnt1 === 0) {
+                cnt1 = 1;
+                num1 = num;
+            } else if (cnt2 === 0) {
+                cnt2 = 1;
+                num2 = num;
+            } else {
+                cnt1--;
+                cnt2--;
+            }
+        }
+
+        cnt1 = cnt2 = 0;
+        for (const num of nums) {
+            if (num === num1) cnt1++;
+            else if (num === num2) cnt2++;
+        }
+
+        const res = [];
+        if (cnt1 > Math.floor(n / 3)) res.push(num1);
+        if (cnt2 > Math.floor(n / 3)) res.push(num2);
+
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<int> MajorityElement(int[] nums) {
+        int n = nums.Length;
+        int num1 = -1, num2 = -1;
+        int cnt1 = 0, cnt2 = 0;
+
+        foreach (int num in nums) {
+            if (num == num1) {
+                cnt1++;
+            } else if (num == num2) {
+                cnt2++;
+            } else if (cnt1 == 0) {
+                num1 = num;
+                cnt1 = 1;
+            } else if (cnt2 == 0) {
+                num2 = num;
+                cnt2 = 1;
+            } else {
+                cnt1--;
+                cnt2--;
+            }
+        }
+
+        cnt1 = cnt2 = 0;
+        foreach (int num in nums) {
+            if (num == num1) cnt1++;
+            else if (num == num2) cnt2++;
+        }
+
+        List<int> res = new List<int>();
+        if (cnt1 > n / 3) res.Add(num1);
+        if (cnt2 > n / 3) res.Add(num2);
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ since output array size will be at most $2$.
+
+---
+
+## 5. Boyer-Moore Voting Algorithm (Hash Map)
+
+::tabs-start
+
+```python
+class Solution:
+    def majorityElement(self, nums: List[int]) -> List[int]:
+        count = defaultdict(int)
+        
+        for num in nums:
+            count[num] += 1
+            
+            if len(count) <= 2:
+                continue
+            
+            new_count = defaultdict(int)
+            for num, c in count.items():
+                if c > 1:
+                    new_count[num] = c - 1
+            count = new_count
+        
+        res = []
+        for num in count:
+            if nums.count(num) > len(nums) // 3:
+                res.append(num)
+        
+        return res
+```
+
+```java
+public class Solution {
+    public List<Integer> majorityElement(int[] nums) {
+        Map<Integer, Integer> count = new HashMap<>();
+
+        for (int num : nums) {
+            count.put(num, count.getOrDefault(num, 0) + 1);
+
+            if (count.size() > 2) {
+                Map<Integer, Integer> newCount = new HashMap<>();
+                for (Map.Entry<Integer, Integer> entry : count.entrySet()) {
+                    if (entry.getValue() > 1) {
+                        newCount.put(entry.getKey(), entry.getValue() - 1);
+                    }
+                }
+                count = newCount;
+            }
+        }
+
+        List<Integer> res = new ArrayList<>();
+        for (int key : count.keySet()) {
+            int frequency = 0;
+            for (int num : nums) {
+                if (num == key) frequency++;
+            }
+            if (frequency > nums.length / 3) {
+                res.add(key);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> majorityElement(vector<int>& nums) {
+        unordered_map<int, int> count;
+
+        for (int num : nums) {
+            count[num]++;
+
+            if (count.size() > 2) {
+                unordered_map<int, int> newCount;
+                for (auto& entry : count) {
+                    if (entry.second > 1) {
+                        newCount[entry.first] = entry.second - 1;
+                    }
+                }
+                count = newCount;
+            }
+        }
+
+        vector<int> res;
+        for (auto& entry : count) {
+            int frequency = 0;
+            for (int num : nums) {
+                if (num == entry.first) frequency++;
+            }
+            if (frequency > nums.size() / 3) {
+                res.push_back(entry.first);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    majorityElement(nums) {
+        let count = new Map();
+
+        for (const num of nums) {
+            count.set(num, (count.get(num) || 0) + 1);
+
+            if (count.size > 2) {
+                const newCount = new Map();
+                for (const [key, value] of count.entries()) {
+                    if (value > 1) {
+                        newCount.set(key, value - 1);
+                    }
+                }
+                count = newCount;
+            }
+        }
+
+        const res = [];
+        for (const [key] of count.entries()) {
+            const frequency = nums.filter(num => num === key).length;
+            if (frequency > Math.floor(nums.length / 3)) {
+                res.push(key);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<int> MajorityElement(int[] nums) {
+        Dictionary<int, int> count = new Dictionary<int, int>();
+
+        foreach (int num in nums) {
+            if (count.ContainsKey(num)) {
+                count[num]++;
+            } else {
+                count[num] = 1;
+            }
+
+            if (count.Count <= 2) {
+                continue;
+            }
+
+            Dictionary<int, int> newCount = new Dictionary<int, int>();
+            foreach (var kvp in count) {
+                if (kvp.Value > 1) {
+                    newCount[kvp.Key] = kvp.Value - 1;
+                }
+            }
+            count = newCount;
+        }
+
+        List<int> res = new List<int>();
+        foreach (int candidate in count.Keys) {
+            int freq = 0;
+            foreach (int num in nums) {
+                if (num == candidate) {
+                    freq++;
+                }
+            }
+            if (freq > nums.Length / 3) {
+                res.Add(candidate);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ since output array size will be at most $2$.
\ No newline at end of file
diff --git a/articles/majority-element.md b/articles/majority-element.md
new file mode 100644
index 000000000..225347051
--- /dev/null
+++ b/articles/majority-element.md
@@ -0,0 +1,606 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def majorityElement(self, nums: List[int]) -> int:
+        n = len(nums)
+        for num in nums:
+            count = sum(1 for i in nums if i == num)
+            if count > n // 2:
+                return num
+```
+
+```java
+public class Solution {
+    public int majorityElement(int[] nums) {
+        int n = nums.length;
+        for (int num : nums) {
+            int count = 0;
+            for (int i : nums) {
+                if (i == num) {
+                    count++;
+                }
+            }
+            if (count > n / 2) {
+                return num;
+            }
+        }
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int majorityElement(vector<int>& nums) {
+        int n = nums.size();
+        for (int num : nums) {
+            int count = 0;
+            for (int i : nums) {
+                if (i == num) {
+                    count++;
+                }
+            }
+            if (count > n / 2) {
+                return num;
+            }
+        }
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    majorityElement(nums) {
+        let n = nums.length;
+        for (let num of nums) {
+            let count = nums.reduce((acc, val) => acc + (val === num ? 1 : 0), 0);
+            if (count > Math.floor(n / 2)) {
+                return num;
+            }
+        }
+        return -1;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MajorityElement(int[] nums) {
+        int n = nums.Length;
+        foreach (int num in nums) {
+            int count = 0;
+            foreach (int i in nums) {
+                if (i == num) {
+                    count++;
+                }
+            }
+            if (count > n / 2) {
+                return num;
+            }
+        }
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def majorityElement(self, nums: List[int]) -> int:
+        count = defaultdict(int)
+        res = maxCount = 0
+
+        for num in nums:
+            count[num] += 1
+            if maxCount < count[num]:
+                res = num
+                maxCount = count[num]
+        return res
+```
+
+```java
+public class Solution {
+    public int majorityElement(int[] nums) {
+        HashMap<Integer, Integer> count = new HashMap<>();
+        int res = 0, maxCount = 0;
+
+        for (int num : nums) {
+            count.put(num, count.getOrDefault(num, 0) + 1);
+            if (count.get(num) > maxCount) {
+                res = num;
+                maxCount = count.get(num);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int majorityElement(vector<int>& nums) {
+        unordered_map<int, int> count;
+        int res = 0, maxCount = 0;
+
+        for (int num : nums) {
+            count[num]++;
+            if (count[num] > maxCount) {
+                res = num;
+                maxCount = count[num];
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    majorityElement(nums) {
+        const count = new Map();
+        let res = 0, maxCount = 0;
+
+        for (let num of nums) {
+            count.set(num, (count.get(num) || 0) + 1);
+            if (count.get(num) > maxCount) {
+                res = num;
+                maxCount = count.get(num);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MajorityElement(int[] nums) {
+        Dictionary<int, int> count = new Dictionary<int, int>();
+        int res = 0, maxCount = 0;
+
+        foreach (int num in nums) {
+            if (!count.ContainsKey(num)) {
+                count[num] = 0;
+            }
+            count[num]++;
+
+            if (count[num] > maxCount) {
+                res = num;
+                maxCount = count[num];
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def majorityElement(self, nums: List[int]) -> int:
+        nums.sort()
+        return nums[len(nums) // 2]
+```
+
+```java
+public class Solution {
+    public int majorityElement(int[] nums) {
+        Arrays.sort(nums);
+        return nums[nums.length / 2];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int majorityElement(vector<int>& nums) {
+        sort(nums.begin(), nums.end());
+        return nums[nums.size() / 2];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    majorityElement(nums) {
+        nums.sort();
+        return nums[Math.floor(nums.length / 2)];
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MajorityElement(int[] nums) {
+        Array.Sort(nums);
+        return nums[nums.Length / 2];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 4. Bit Manipulation
+
+::tabs-start
+
+```python
+class Solution:
+    def majorityElement(self, nums: List[int]) -> int:
+        n = len(nums)
+        bit = [0] * 32
+        for num in nums:
+            for i in range(32):
+                bit[i] += ((num >> i) & 1)
+        
+        res = 0
+        for i in range(32):
+            if bit[i] > (n // 2):
+                if i == 31: 
+                    res -= (1 << i)
+                else:
+                    res |= (1 << i)
+        return res
+```
+
+```java
+public class Solution {
+    public int majorityElement(int[] nums) {
+        int n = nums.length;
+        int[] bit = new int[32];
+        for (int num : nums) {
+            for (int i = 0; i < 32; i++) {
+                bit[i] += (num >> i) & 1;
+            }
+        }
+
+        int res = 0;
+        for (int i = 0; i < 32; i++) {
+            if (bit[i] > n / 2) {
+                res |= (1 << i);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int majorityElement(vector<int>& nums) {
+        int n = nums.size();
+        vector<int> bit(32, 0);
+        for (int num : nums) {
+            for (int i = 0; i < 32; i++) {
+                bit[i] += (num >> i) & 1;
+            }
+        }
+
+        int res = 0;
+        for (int i = 0; i < 32; i++) {
+            if (bit[i] > n / 2) {
+                res |= (1 << i);
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    majorityElement(nums) {
+        const n = nums.length;
+        const bit = Array(32).fill(0);
+        for (let num of nums) {
+            for (let i = 0; i < 32; i++) {
+                bit[i] += (num >> i) & 1;
+            }
+        }
+
+        let res = 0;
+        for (let i = 0; i < 32; i++) {
+            if (bit[i] > Math.floor(n / 2)) {
+                res |= (1 << i);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MajorityElement(int[] nums) {
+        int n = nums.Length;
+        int[] bit = new int[32];
+
+        foreach (int num in nums) {
+            for (int i = 0; i < 32; i++) {
+                bit[i] += (num >> i) & 1;
+            }
+        }
+
+        int res = 0;
+        for (int i = 0; i < 32; i++) {
+            if (bit[i] > n / 2) {
+                res |= (1 << i);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * 32)$
+* Space complexity: $O(32)$
+
+> $32$ represents the number of bits as the given numbers are integers.
+
+---
+
+## 5. Boyer-Moore Voting Algorithm
+
+::tabs-start
+
+```python
+class Solution:
+    def majorityElement(self, nums):
+        res = count = 0
+
+        for num in nums:
+            if count == 0:
+                res = num
+            count += (1 if num == res else -1)
+        return res
+```
+
+```java
+public class Solution {
+    public int majorityElement(int[] nums) {
+        int res = 0, count = 0;
+
+        for (int num : nums) {
+            if (count == 0) {
+                res = num;
+            }
+            count += (num == res) ? 1 : -1;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int majorityElement(vector<int>& nums) {
+        int res = 0, count = 0;
+
+        for (int num : nums) {
+            if (count == 0) {
+                res = num;
+            }
+            count += (num == res) ? 1 : -1;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    majorityElement(nums) {
+        let res = 0, count = 0;
+
+        for (let num of nums) {
+            if (count === 0) {
+                res = num;
+            }
+            count += (num === res) ? 1 : -1;
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MajorityElement(int[] nums) {
+        int res = 0, count = 0;
+
+        foreach (int num in nums) {
+            if (count == 0) {
+                res = num;
+            }
+            count += (num == res) ? 1 : -1;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 6. Randomization
+
+::tabs-start
+
+```python
+class Solution:
+    def majorityElement(self, nums):
+        n = len(nums)
+        while True:
+            candidate = random.choice(nums)
+            if nums.count(candidate) > n // 2:
+                return candidate
+```
+
+```java
+public class Solution {
+    public int majorityElement(int[] nums) {
+        Random rand = new Random();
+        int n = nums.length;
+
+        while (true) {
+            int candidate = nums[rand.nextInt(n)];
+            int count = 0;
+            for (int num : nums) {
+                if (num == candidate) {
+                    count++;
+                }
+            }
+            if (count > n / 2) {
+                return candidate;
+            }
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int majorityElement(vector<int>& nums) {
+        int n = nums.size();
+
+        while (true) {
+            int candidate = nums[rand() % n];
+            int count = 0;
+            for (int num : nums) {
+                if (num == candidate) {
+                    count++;
+                }
+            }
+            if (count > n / 2) {
+                return candidate;
+            }
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    majorityElement(nums) {
+        const n = nums.length;
+        while (true) {
+            const candidate = nums[Math.floor(Math.random() * n)];
+            let count = 0;
+            for (const num of nums) {
+                if (num === candidate) {
+                    count++;
+                }
+            }
+            if (count > Math.floor(n / 2)) {
+                return candidate;
+            }
+        }
+    }
+}
+```
+
+```csharp
+public class Solution {
+    private static Random random = new Random();
+
+    public int MajorityElement(int[] nums) {
+        int n = nums.Length;
+
+        while (true) {
+            int candidate = nums[random.Next(n)];
+            int count = nums.Count(x => x == candidate);
+
+            if (count > n / 2) {
+                return candidate;
+            }
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+> The probability of randomly choosing the majority element is greater than $50\%$, so the expected number of iterations in the outer while loop is constant.
\ No newline at end of file
diff --git a/articles/make-sum-divisible-by-p.md b/articles/make-sum-divisible-by-p.md
new file mode 100644
index 000000000..493f5732c
--- /dev/null
+++ b/articles/make-sum-divisible-by-p.md
@@ -0,0 +1,235 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def minSubarray(self, nums: List[int], p: int) -> int:
+        n = len(nums)
+        totSum = sum(nums)
+
+        if totSum % p == 0:
+            return 0
+
+        for l in range(1, n):
+            curSum = 0
+            for i in range(n):
+                curSum += nums[i]
+                if i >= l:
+                    curSum -= nums[i - l]
+
+                remainSum = totSum - curSum
+                if remainSum % p == 0:
+                    return l
+
+        return -1
+```
+
+```java
+public class Solution {
+    public int minSubarray(int[] nums, int p) {
+        int n = nums.length;
+        long totSum = 0;
+        for (int num : nums) totSum += num;
+
+        if (totSum % p == 0) return 0;
+
+        for (int l = 1; l < n; l++) {
+            long curSum = 0;
+            for (int i = 0; i < n; i++) {
+                curSum += nums[i];
+                if (i >= l) curSum -= nums[i - l];
+
+                long remainSum = totSum - curSum;
+                if (remainSum % p == 0) return l;
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minSubarray(vector<int>& nums, int p) {
+        int n = nums.size();
+        long long totSum = 0;
+        for (int num : nums) totSum += num;
+
+        if (totSum % p == 0) return 0;
+
+        for (int l = 1; l < n; l++) {
+            long long curSum = 0;
+            for (int i = 0; i < n; i++) {
+                curSum += nums[i];
+                if (i >= l) curSum -= nums[i - l];
+
+                long long remainSum = totSum - curSum;
+                if (remainSum % p == 0) return l;
+            }
+        }
+
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} p
+     * @return {number}
+     */
+    minSubarray(nums, p) {
+        const n = nums.length;
+        let totSum = nums.reduce((a, b) => a + b, 0);
+
+        if (totSum % p === 0) return 0;
+
+        for (let l = 1; l < n; l++) {
+            let curSum = 0;
+            for (let i = 0; i < n; i++) {
+                curSum += nums[i];
+                if (i >= l) curSum -= nums[i - l];
+
+                const remainSum = totSum - curSum;
+                if (remainSum % p === 0) return l;
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Prefix Sum
+
+::tabs-start
+
+```python
+class Solution:
+    def minSubarray(self, nums: List[int], p: int) -> int:
+        total = sum(nums)
+        remain = total % p
+        if remain == 0:
+            return 0
+
+        res = len(nums)
+        cur_sum = 0
+        remain_to_idx = {0: -1}
+
+        for i, n in enumerate(nums):
+            cur_sum = (cur_sum + n) % p
+            prefix = (cur_sum - remain + p) % p
+            if prefix in remain_to_idx:
+                length = i - remain_to_idx[prefix]
+                res = min(res, length)
+            remain_to_idx[cur_sum] = i
+
+        return -1 if res == len(nums) else res
+```
+
+```java
+public class Solution {
+    public int minSubarray(int[] nums, int p) {
+        long total = 0;
+        for (int num : nums) total += num;
+        int remain = (int)(total % p);
+        if (remain == 0) return 0;
+
+        int res = nums.length;
+        long curSum = 0;
+        Map<Integer, Integer> map = new HashMap<>();
+        map.put(0, -1);
+
+        for (int i = 0; i < nums.length; i++) {
+            curSum = (curSum + nums[i]) % p;
+            int prefix = (int)((curSum - remain + p) % p);
+            if (map.containsKey(prefix)) {
+                res = Math.min(res, i - map.get(prefix));
+            }
+            map.put((int)curSum, i);
+        }
+
+        return res == nums.length ? -1 : res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minSubarray(vector<int>& nums, int p) {
+        long total = 0;
+        for (int num : nums) total += num;
+        int remain = total % p;
+        if (remain == 0) return 0;
+
+        int res = nums.size();
+        long curSum = 0;
+        unordered_map<int, int> map;
+        map[0] = -1;
+
+        for (int i = 0; i < nums.size(); i++) {
+            curSum = (curSum + nums[i]) % p;
+            int prefix = (curSum - remain + p) % p;
+            if (map.count(prefix)) {
+                res = min(res, i - map[prefix]);
+            }
+            map[curSum] = i;
+        }
+
+        return res == nums.size() ? -1 : res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} p
+     * @return {number}
+     */
+    minSubarray(nums, p) {
+        let total = nums.reduce((a, b) => a + b, 0);
+        let remain = total % p;
+        if (remain === 0) return 0;
+
+        let res = nums.length;
+        let curSum = 0;
+        const map = new Map();
+        map.set(0, -1);
+
+        for (let i = 0; i < nums.length; i++) {
+            curSum = (curSum + nums[i]) % p;
+            let prefix = (curSum - remain + p) % p;
+            if (map.has(prefix)) {
+                res = Math.min(res, i - map.get(prefix));
+            }
+            map.set(curSum, i);
+        }
+
+        return res === nums.length ? -1 : res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/make-the-string-great.md b/articles/make-the-string-great.md
new file mode 100644
index 000000000..f8ee712f7
--- /dev/null
+++ b/articles/make-the-string-great.md
@@ -0,0 +1,334 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def makeGood(self, s: str) -> str:
+        n = len(s)
+        i = 0
+        while i < n:
+            if i and s[i] != s[i - 1] and s[i].lower() == s[i - 1].lower():
+                s = s[:i - 1] + s[i + 1:]
+                n -= 2
+                i -= 2
+            i += 1
+        return s
+```
+
+```java
+public class Solution {
+    public String makeGood(String s) {
+        int n = s.length();
+        int i = 0;
+        while (i < n) {
+            if (i > 0 && s.charAt(i) != s.charAt(i - 1) && 
+                Character.toLowerCase(s.charAt(i)) == Character.toLowerCase(s.charAt(i - 1))) {
+                s = s.substring(0, i - 1) + s.substring(i + 1);
+                n -= 2;
+                i -= 2;
+            }
+            i++;
+        }
+        return s;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string makeGood(string s) {
+        int n = s.length();
+        int i = 0;
+        while (i < n) {
+            if (i > 0 && s[i] != s[i - 1] && tolower(s[i]) == tolower(s[i - 1])) {
+                s = s.substr(0, i - 1) + s.substr(i + 1);
+                n -= 2;
+                i -= 2;
+            }
+            i++;
+        }
+        return s;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string}
+     */
+    makeGood(s) {
+        let n = s.length;
+        let i = 0;
+        while (i < n) {
+            if (i > 0 && s[i] !== s[i - 1] && s[i].toLowerCase() === s[i - 1].toLowerCase()) {
+                s = s.slice(0, i - 1) + s.slice(i + 1);
+                n -= 2;
+                i -= 2;
+            }
+            i++;
+        }
+        return s;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Stack - I
+
+::tabs-start
+
+```python
+class Solution:
+    def makeGood(self, s: str) -> str:
+        def lower(c):
+            if ord(c) < ord('a'):
+                return chr(ord('a') + ord(c) - ord('A'))
+            return c
+
+        stack = []
+        i = 0
+        while i < len(s):
+            if stack and stack[-1] != s[i] and lower(stack[-1]) == lower(s[i]):
+                stack.pop()
+            else:
+                stack.append(s[i])
+            i += 1
+        return "".join(stack)
+```
+
+```java
+public class Solution {
+    public String makeGood(String s) {
+        StringBuilder stack = new StringBuilder();
+        for (char c : s.toCharArray()) {
+            if (stack.length() > 0 && stack.charAt(stack.length() - 1) != c && 
+                Character.toLowerCase(stack.charAt(stack.length() - 1)) == Character.toLowerCase(c)) {
+                stack.deleteCharAt(stack.length() - 1);
+            } else {
+                stack.append(c);
+            }
+        }
+        return stack.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string makeGood(string s) {
+        string stack;
+        for (char c : s) {
+            if (!stack.empty() && stack.back() != c && 
+                tolower(stack.back()) == tolower(c)) {
+                stack.pop_back();
+            } else {
+                stack.push_back(c);
+            }
+        }
+        return stack;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string}
+     */
+    makeGood(s) {
+        const stack = [];
+        for (const c of s) {
+            if (stack.length > 0 && stack[stack.length - 1] !== c && 
+                stack[stack.length - 1].toLowerCase() === c.toLowerCase()) {
+                stack.pop();
+            } else {
+                stack.push(c);
+            }
+        }
+        return stack.join("");
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Stack - II
+
+::tabs-start
+
+```python
+class Solution:
+    def makeGood(self, s: str) -> str:
+        stack = []
+        for i in range(len(s)):
+            if stack and abs(ord(s[i]) - ord(stack[-1])) == 32:
+                stack.pop()
+            else:
+                stack.append(s[i])
+        return "".join(stack)
+```
+
+```java
+public class Solution {
+    public String makeGood(String s) {
+        StringBuilder stack = new StringBuilder();
+        for (int i = 0; i < s.length(); i++) {
+            if (stack.length() > 0 && 
+                Math.abs(stack.charAt(stack.length() - 1) - s.charAt(i)) == 32) {
+                stack.deleteCharAt(stack.length() - 1);
+            } else {
+                stack.append(s.charAt(i));
+            }
+        }
+        return stack.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string makeGood(string s) {
+        string stack;
+        for (char& c : s) {
+            if (!stack.empty() && abs(stack.back() - c) == 32) {
+                stack.pop_back();
+            } else {
+                stack.push_back(c);
+            }
+        }
+        return stack;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string}
+     */
+    makeGood(s) {
+        const stack = [];
+        for (const c of s) {
+            if (stack.length > 0 && 
+                Math.abs(stack[stack.length - 1].charCodeAt(0) - c.charCodeAt(0)) === 32) {
+                stack.pop();
+            } else {
+                stack.push(c);
+            }
+        }
+        return stack.join("");
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def makeGood(self, s: str) -> str:
+        l = 0
+        s = list(s)
+        for r in range(len(s)):
+            if l > 0 and abs(ord(s[r]) - ord(s[l - 1])) == 32:
+                l -= 1
+            else:
+                s[l] = s[r]
+                l += 1
+        return ''.join(s[:l])
+```
+
+```java
+public class Solution {
+    public String makeGood(String s) {
+        int l = 0;
+        char[] arr = s.toCharArray();
+        for (int r = 0; r < arr.length; r++) {
+            if (l > 0 && Math.abs(arr[r] - arr[l - 1]) == 32) {
+                l--;
+            } else {
+                arr[l++] = arr[r];
+            }
+        }
+        return new String(arr, 0, l);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string makeGood(string s) {
+        int l = 0;
+        for (int r = 0; r < s.length(); r++) {
+            if (l > 0 && abs(s[r] - s[l - 1]) == 32) {
+                l--;
+            } else {
+                s[l++] = s[r];
+            }
+        }
+        return s.substr(0, l);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string}
+     */
+    makeGood(s) {
+        let l = 0;
+        let arr = s.split('');
+        for (let r = 0; r < arr.length; r++) {
+            if (l > 0 && Math.abs(arr[r].charCodeAt(0) - arr[l - 1].charCodeAt(0)) === 32) {
+                l--;
+            } else {
+                arr[l++] = arr[r];
+            }
+        }
+        return arr.slice(0, l).join('');
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the language.
\ No newline at end of file
diff --git a/articles/matchsticks-to-square.md b/articles/matchsticks-to-square.md
new file mode 100644
index 000000000..ae760c5ac
--- /dev/null
+++ b/articles/matchsticks-to-square.md
@@ -0,0 +1,586 @@
+## 1. Backtracking (Brute Force)
+
+::tabs-start
+
+```python
+class Solution:
+    def makesquare(self, matchsticks: List[int]) -> bool:
+        if sum(matchsticks) % 4 != 0:
+            return False
+        
+        sides = [0] * 4
+        
+        def dfs(i):
+            if i == len(matchsticks):
+                return sides[0] == sides[1] == sides[2] == sides[3]
+            
+            for side in range(4):
+                sides[side] += matchsticks[i]
+                if dfs(i + 1):
+                    return True
+                sides[side] -= matchsticks[i]
+            
+            return False
+        
+        return dfs(0)
+```
+
+```java
+public class Solution {
+    public boolean makesquare(int[] matchsticks) {
+        int sum = Arrays.stream(matchsticks).sum();
+        if (sum % 4 != 0) return false;
+
+        int[] sides = new int[4];
+        return dfs(matchsticks, sides, 0);
+    }
+
+    private boolean dfs(int[] matchsticks, int[] sides, int i) {
+        if (i == matchsticks.length) {
+            return sides[0] == sides[1] && sides[1] == sides[2] && sides[2] == sides[3];
+        }
+
+        for (int j = 0; j < 4; j++) {
+            sides[j] += matchsticks[i];
+            if (dfs(matchsticks, sides, i + 1)) return true;
+            sides[j] -= matchsticks[i];
+        }
+
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool makesquare(vector<int>& matchsticks) {
+        int sum = accumulate(matchsticks.begin(), matchsticks.end(), 0);
+        if (sum % 4 != 0) return false;
+
+        vector<int> sides(4, 0);
+        return dfs(matchsticks, sides, 0);
+    }
+
+private:
+    bool dfs(vector<int>& matchsticks, vector<int>& sides, int i) {
+        if (i == matchsticks.size()) {
+            return sides[0] == sides[1] && sides[1] == sides[2] && sides[2] == sides[3];
+        }
+
+        for (int j = 0; j < 4; j++) {
+            sides[j] += matchsticks[i];
+            if (dfs(matchsticks, sides, i + 1)) return true;
+            sides[j] -= matchsticks[i];
+        }
+
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} matchsticks
+     * @return {boolean}
+     */
+    makesquare(matchsticks) {
+        const sum = matchsticks.reduce((a, b) => a + b, 0);
+        if (sum % 4 !== 0) return false;
+
+        const sides = Array(4).fill(0);
+        const dfs = (i) => {
+            if (i === matchsticks.length) {
+                return sides[0] === sides[1] && sides[1] === sides[2] && sides[2] === sides[3];
+            }
+
+            for (let j = 0; j < 4; j++) {
+                sides[j] += matchsticks[i];
+                if (dfs(i + 1)) return true;
+                sides[j] -= matchsticks[i];
+            }
+
+            return false;
+        };
+
+        return dfs(0);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool Makesquare(int[] matchsticks) {
+        int total = 0;
+        foreach (int stick in matchsticks) {
+            total += stick;
+        }
+        if (total % 4 != 0) return false;
+
+        int target = total / 4;
+        int[] sides = new int[4];
+
+        bool Dfs(int i) {
+            if (i == matchsticks.Length) {
+                return sides[0] == sides[1] && sides[1] == sides[2] && sides[2] == sides[3];
+            }
+
+            for (int side = 0; side < 4; side++) {
+                sides[side] += matchsticks[i];
+                if (sides[side] <= target && Dfs(i + 1)) {
+                    return true;
+                }
+                sides[side] -= matchsticks[i];
+            }
+
+            return false;
+        }
+
+        return Dfs(0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(4 ^ n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Backtracking (Pruning)
+
+::tabs-start
+
+```python
+class Solution:
+    def makesquare(self, matchsticks: List[int]) -> bool:
+        total_length = sum(matchsticks)
+        if total_length % 4 != 0:
+            return False
+        
+        length = total_length // 4
+        sides = [0] * 4
+        matchsticks.sort(reverse=True)
+        
+        def dfs(i):
+            if i == len(matchsticks):
+                return True
+            
+            for side in range(4):
+                if sides[side] + matchsticks[i] <= length:
+                    sides[side] += matchsticks[i]
+                    if dfs(i + 1):
+                        return True
+                    sides[side] -= matchsticks[i]
+                
+                if sides[side] == 0:
+                    break
+            
+            return False
+        
+        return dfs(0)
+```
+
+```java
+public class Solution {
+    public boolean makesquare(int[] matchsticks) {
+        int totalLength = Arrays.stream(matchsticks).sum();
+        if (totalLength % 4 != 0) return false;
+        
+        int length = totalLength / 4;
+        int[] sides = new int[4];
+        Arrays.sort(matchsticks);
+        reverse(matchsticks);
+        
+        return dfs(matchsticks, sides, 0, length);
+    }
+    
+    private boolean dfs(int[] matchsticks, int[] sides, int index, int length) {
+        if (index == matchsticks.length) {
+            return true;
+        }
+        
+        for (int i = 0; i < 4; i++) {
+            if (sides[i] + matchsticks[index] <= length) {
+                sides[i] += matchsticks[index];
+                if (dfs(matchsticks, sides, index + 1, length)) return true;
+                sides[i] -= matchsticks[index];
+            }
+            
+            if (sides[i] == 0) break;
+        }
+        
+        return false;
+    }
+    
+    private void reverse(int[] matchsticks) {
+        for (int i = 0, j = matchsticks.length - 1; i < j; i++, j--) {
+            int temp = matchsticks[i];
+            matchsticks[i] = matchsticks[j];
+            matchsticks[j] = temp;
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool makesquare(vector<int>& matchsticks) {
+        int totalLength = accumulate(matchsticks.begin(), matchsticks.end(), 0);
+        if (totalLength % 4 != 0) return false;
+
+        int length = totalLength / 4;
+        vector<int> sides(4, 0);
+        sort(matchsticks.rbegin(), matchsticks.rend());
+
+        return dfs(matchsticks, sides, 0, length);
+    }
+
+private:
+    bool dfs(vector<int>& matchsticks, vector<int>& sides, int index, int length) {
+        if (index == matchsticks.size()) {
+            return true;
+        }
+
+        for (int i = 0; i < 4; i++) {
+            if (sides[i] + matchsticks[index] <= length) {
+                sides[i] += matchsticks[index];
+                if (dfs(matchsticks, sides, index + 1, length)) return true;
+                sides[i] -= matchsticks[index];
+            }
+
+            if (sides[i] == 0) break;
+        }
+
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} matchsticks
+     * @return {boolean}
+     */
+    makesquare(matchsticks) {
+        const totalLength = matchsticks.reduce((a, b) => a + b, 0);
+        if (totalLength % 4 !== 0) return false;
+
+        const length = totalLength / 4;
+        const sides = Array(4).fill(0);
+        matchsticks.sort((a, b) => b - a);
+
+        const dfs = (index) => {
+            if (index === matchsticks.length) {
+                return true;
+            }
+
+            for (let i = 0; i < 4; i++) {
+                if (sides[i] + matchsticks[index] <= length) {
+                    sides[i] += matchsticks[index];
+                    if (dfs(index + 1)) return true;
+                    sides[i] -= matchsticks[index];
+                }
+
+                if (sides[i] === 0) break;
+            }
+
+            return false;
+        };
+
+        return dfs(0);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool Makesquare(int[] matchsticks) {
+        int totalLength = 0;
+        foreach (int stick in matchsticks) {
+            totalLength += stick;
+        }
+
+        if (totalLength % 4 != 0) {
+            return false;
+        }
+
+        int length = totalLength / 4;
+        int[] sides = new int[4];
+        Array.Sort(matchsticks, (a, b) => b.CompareTo(a)); // Sort in descending order
+
+        bool Dfs(int i) {
+            if (i == matchsticks.Length) {
+                return true;
+            }
+
+            for (int side = 0; side < 4; side++) {
+                if (sides[side] + matchsticks[i] <= length) {
+                    sides[side] += matchsticks[i];
+                    if (Dfs(i + 1)) return true;
+                    sides[side] -= matchsticks[i];
+                }
+
+                if (sides[side] == 0) break;
+            }
+
+            return false;
+        }
+
+        return Dfs(0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(4 ^ n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 3. Dynamic Programming (Bit Mask)
+
+::tabs-start
+
+```python
+class Solution:
+    def makesquare(self, matchsticks: List[int]) -> bool:
+        total_length = sum(matchsticks)
+        if total_length % 4 != 0:
+            return False
+        
+        length = total_length // 4
+        if max(matchsticks) > length:
+            return False
+        
+        n = len(matchsticks)
+        dp = [float("-inf")] * (1 << n)
+        matchsticks.sort(reverse=True)
+
+        def dfs(mask):
+            if mask == 0:
+                return 0
+            if dp[mask] != float("-inf"):
+                return dp[mask]
+            
+            for i in range(n):
+                if mask & (1 << i):
+                    res = dfs(mask ^ (1 << i))
+                    if res >= 0 and res + matchsticks[i] <= length:
+                        dp[mask] = (res + matchsticks[i]) % length
+                        return dp[mask]
+                    if mask == (1 << n) - 1:
+                        dp[mask] = -1
+                        return -1
+            
+            dp[mask] = -1
+            return -1
+        
+        return not dfs((1 << n) - 1)
+```
+
+```java
+public class Solution {
+    private int[] dp;
+    private int length;
+    private int n;
+
+    public boolean makesquare(int[] matchsticks) {
+        int totalLength = Arrays.stream(matchsticks).sum();
+        if (totalLength % 4 != 0) return false;
+
+        length = totalLength / 4;
+        if (Arrays.stream(matchsticks).max().getAsInt() > length) {
+            return false;
+        }
+
+        Arrays.sort(matchsticks);
+        reverse(matchsticks);
+        this.n = matchsticks.length;
+        this.dp = new int[1 << n];
+        Arrays.fill(dp, Integer.MIN_VALUE);
+
+        return dfs((1 << n) - 1, matchsticks) == 0;
+    }
+
+    private int dfs(int mask, int[] matchsticks) {
+        if (mask == 0) return 0;
+        if (dp[mask] != Integer.MIN_VALUE) return dp[mask];
+
+        for (int i = 0; i < n; i++) {
+            if ((mask & (1 << i)) != 0) {
+                int res = dfs(mask ^ (1 << i), matchsticks);
+                if (res >= 0 && res + matchsticks[i] <= length) {
+                    dp[mask] = (res + matchsticks[i]) % length;
+                    return dp[mask];
+                }
+
+                if (mask == (1 << n) - 1) {
+                    dp[mask] = -1;
+                    return -1;
+                }
+            }
+        }
+
+        dp[mask] = -1;
+        return dp[mask];
+    }
+
+    private void reverse(int[] matchsticks) {
+        for (int i = 0, j = matchsticks.length - 1; i < j; i++, j--) {
+            int temp = matchsticks[i];
+            matchsticks[i] = matchsticks[j];
+            matchsticks[j] = temp;
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+    vector<int> dp;
+    int length, n;
+
+public:
+    bool makesquare(vector<int>& matchsticks) {
+        int totalLength = accumulate(matchsticks.begin(), matchsticks.end(), 0);
+        if (totalLength % 4 != 0) return false;
+
+        length = totalLength / 4;
+        if (*max_element(matchsticks.begin(), matchsticks.end()) > length) {
+            return false;
+        }
+        
+        sort(matchsticks.rbegin(), matchsticks.rend());
+        n = matchsticks.size();
+        dp.resize(1 << n, INT_MIN);
+
+        return dfs((1 << n) - 1, matchsticks) == 0;
+    }
+
+private:
+    int dfs(int mask, vector<int>& matchsticks) {
+        if (mask == 0) return 0;
+        if (dp[mask] != INT_MIN) return dp[mask];
+
+        for (int i = 0; i < n; i++) {
+            if (mask & (1 << i)) {
+                int res = dfs(mask ^ (1 << i), matchsticks);
+                if (res >= 0 && res + matchsticks[i] <= length) {
+                    dp[mask] = (res + matchsticks[i]) % length;
+                    return dp[mask];
+                }
+
+                if (mask == (1 << n) - 1) {
+                    dp[mask] = -1;
+                    return -1;
+                }
+            }
+        }
+
+        dp[mask] = -1;
+        return dp[mask];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} matchsticks
+     * @return {boolean}
+     */
+    makesquare(matchsticks) {
+        const totalLength = matchsticks.reduce((a, b) => a + b, 0);
+        if (totalLength % 4 !== 0) return false;
+
+        const length = totalLength / 4;
+        if (Math.max(...matchsticks) > length) return false;
+
+        matchsticks.sort((a, b) => b - a);
+        const n = matchsticks.length;
+        const dp = new Array(1 << n).fill(-Infinity);
+
+        const dfs = (mask) => {
+            if (mask === 0) return 0;
+            if (dp[mask] !== -Infinity) return dp[mask];
+
+            for (let i = 0; i < n; i++) {
+                if (mask & (1 << i)) {
+                    const res = dfs(mask ^ (1 << i));
+                    if (res >= 0 && res + matchsticks[i] <= length) {
+                        dp[mask] = (res + matchsticks[i]) % length;
+                        return dp[mask];
+                    }
+
+                    if (mask === (1 << n) - 1) {
+                        dp[mask] = -1;
+                        return -1;
+                    }
+                }
+            }
+
+            dp[mask] = -1;
+            return dp[mask];
+        };
+
+        return dfs((1 << n) - 1) === 0;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool Makesquare(int[] matchsticks) {
+        int totalLength = matchsticks.Sum();
+        if (totalLength % 4 != 0) return false;
+
+        int length = totalLength / 4;
+        if (matchsticks.Max() > length) return false;
+
+        int n = matchsticks.Length;
+        int[] dp = Enumerable.Repeat(int.MinValue, 1 << n).ToArray();
+        Array.Sort(matchsticks, (a, b) => b.CompareTo(a)); // Sort descending
+
+        int Dfs(int mask) {
+            if (mask == 0) return 0;
+            if (dp[mask] != int.MinValue) return dp[mask];
+
+            for (int i = 0; i < n; i++) {
+                if ((mask & (1 << i)) != 0) {
+                    int res = Dfs(mask ^ (1 << i));
+                    if (res >= 0 && res + matchsticks[i] <= length) {
+                        dp[mask] = (res + matchsticks[i]) % length;
+                        return dp[mask];
+                    }
+                    if (mask == (1 << n) - 1) {
+                        dp[mask] = -1;
+                        return -1;
+                    }
+                }
+            }
+
+            dp[mask] = -1;
+            return -1;
+        }
+
+        return Dfs((1 << n) - 1) != -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * 2 ^ n)$
+* Space complexity: $O(n + 2 ^ n)$
\ No newline at end of file
diff --git a/articles/matrix-diagonal-sum.md b/articles/matrix-diagonal-sum.md
new file mode 100644
index 000000000..8524ff1a7
--- /dev/null
+++ b/articles/matrix-diagonal-sum.md
@@ -0,0 +1,184 @@
+## 1. Iteration
+
+::tabs-start
+
+```python
+class Solution:
+    def diagonalSum(self, mat: List[List[int]]) -> int:
+        n = len(mat)
+
+        def helper(matrix):
+            res = 0
+            for i in range(n):
+                for j in range(n):
+                    if i == j:
+                        res += matrix[i][j]
+                matrix[i].reverse()
+            return res
+
+        return helper(mat) + helper(mat) - (mat[n // 2][n // 2] if n & 1 else 0)
+```
+
+```java
+public class Solution {
+    public int diagonalSum(int[][] mat) {
+        int n = mat.length;
+        return helper(mat) + helper(mat) - (n % 2 == 1 ? mat[n / 2][n / 2] : 0);
+    }
+
+    int helper(int[][] matrix) {
+        int res = 0, n = matrix.length;
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < n; j++) {
+                if (i == j) {
+                    res += matrix[i][j];
+                }
+            }
+            reverse(matrix[i]);
+        }
+        return res;
+    }
+
+    void reverse(int[] row) {
+        int left = 0, right = row.length - 1;
+        while (left < right) {
+            int temp = row[left];
+            row[left++] = row[right];
+            row[right--] = temp;
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int diagonalSum(vector<vector<int>>& mat) {
+        int n = mat.size();
+        return helper(mat) + helper(mat) - (n % 2 == 1 ? mat[n / 2][n / 2] : 0);
+    }
+
+private:
+    int helper(vector<vector<int>>& matrix) {
+        int res = 0, n = matrix.size();
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < n; j++) {
+                if (i == j) {
+                    res += matrix[i][j];
+                }
+            }
+            reverse(matrix[i].begin(), matrix[i].end());
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} mat
+     * @return {number}
+     */
+    diagonalSum(mat) {
+        const n = mat.length;
+
+        const helper = (matrix) => {
+            let res = 0;
+            for (let i = 0; i < n; i++) {
+                for (let j = 0; j < n; j++) {
+                    if (i === j) {
+                        res += matrix[i][j];
+                    }
+                }
+                matrix[i].reverse();
+            }
+            return res;
+        };
+
+        return helper(mat) + helper(mat) - (n % 2 === 1 ? mat[Math.floor(n / 2)][Math.floor(n / 2)] : 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 2. Iteration (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def diagonalSum(self, mat: List[List[int]]) -> int:
+        res, n = 0, len(mat)
+
+        for r in range(n):
+            res += mat[r][r]
+            res += mat[r][n - r - 1]
+
+        return res - (mat[n // 2][n // 2] if n & 1 else 0)
+```
+
+```java
+public class Solution {
+    public int diagonalSum(int[][] mat) {
+        int res = 0, n = mat.length;
+
+        for (int r = 0; r < n; r++) {
+            res += mat[r][r];
+            res += mat[r][n - r - 1];
+        }
+
+        return res - (n % 2 == 1 ? mat[n / 2][n / 2] : 0);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int diagonalSum(vector<vector<int>>& mat) {
+        int res = 0, n = mat.size();
+
+        for (int r = 0; r < n; r++) {
+            res += mat[r][r];
+            res += mat[r][n - r - 1];
+        }
+
+        return res - (n % 2 == 1 ? mat[n / 2][n / 2] : 0);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} mat
+     * @return {number}
+     */
+    diagonalSum(mat) {
+        let res = 0, n = mat.length;
+
+        for (let r = 0; r < n; r++) {
+            res += mat[r][r];
+            res += mat[r][n - r - 1];
+        }
+
+        return res - (n % 2 == 1 ? mat[Math.floor(n / 2)][Math.floor(n / 2)] : 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/max-area-of-island.md b/articles/max-area-of-island.md
index 4be58cfec..cb69ca56d 100644
--- a/articles/max-area-of-island.md
+++ b/articles/max-area-of-island.md
@@ -173,6 +173,93 @@ public class Solution {
 }
 ```
 
+```go
+func maxAreaOfIsland(grid [][]int) int {
+    rows, cols := len(grid), len(grid[0])
+    visit := make(map[[2]int]bool)
+
+    var dfs func(r, c int) int
+    dfs = func(r, c int) int {
+        if r < 0 || r >= rows || c < 0 || c >= cols || 
+           grid[r][c] == 0 || visit[[2]int{r, c}] {
+            return 0
+        }
+        visit[[2]int{r, c}] = true
+        return 1 + dfs(r+1, c) + dfs(r-1, c) + dfs(r, c+1) + dfs(r, c-1)
+    }
+
+    area := 0
+    for r := 0; r < rows; r++ {
+        for c := 0; c < cols; c++ {
+            area = max(area, dfs(r, c))
+        }
+    }
+    return area
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun maxAreaOfIsland(grid: Array<IntArray>): Int {
+        val rows = grid.size
+        val cols = grid[0].size
+        val visit = HashSet<Pair<Int, Int>>()
+
+        fun dfs(r: Int, c: Int): Int {
+            if (r < 0 || r >= rows || c < 0 || c >= cols || 
+                grid[r][c] == 0 || visit.contains(r to c)) {
+                return 0
+            }
+            visit.add(r to c)
+            return 1 + dfs(r + 1, c) + dfs(r - 1, c) + dfs(r, c + 1) + dfs(r, c - 1)
+        }
+
+        var area = 0
+        for (r in 0 until rows) {
+            for (c in 0 until cols) {
+                area = maxOf(area, dfs(r, c))
+            }
+        }
+        return area
+    }
+}
+```
+
+```swift
+class Solution {
+    func maxAreaOfIsland(_ grid: [[Int]]) -> Int {
+        let ROWS = grid.count
+        let COLS = grid[0].count
+        var visit = Set<[Int]>()
+        var grid = grid
+
+        func dfs(_ r: Int, _ c: Int) -> Int {
+            if (r < 0 || r == ROWS || c < 0 || c == COLS ||
+                grid[r][c] == 0 || visit.contains([r, c])) {
+                return 0
+            }
+            visit.insert([r, c])
+            return 1 + dfs(r + 1, c) + dfs(r - 1, c) + dfs(r, c + 1) + dfs(r, c - 1)
+        }
+
+        var area = 0
+        for r in 0..<ROWS {
+            for c in 0..<COLS {
+                area = max(area, dfs(r, c))
+            }
+        }
+        return area
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -404,6 +491,149 @@ public class Solution {
 }
 ```
 
+```go
+func maxAreaOfIsland(grid [][]int) int {
+    directions := [][]int{{1, 0}, {-1, 0}, {0, 1}, {0, -1}}
+    rows, cols := len(grid), len(grid[0])
+    area := 0
+
+    var bfs func(r, c int) int
+    bfs = func(r, c int) int {
+        q := [][]int{{r, c}}
+        grid[r][c] = 0
+        res := 1
+
+        for len(q) > 0 {
+            front := q[0]
+            q = q[1:]
+            row, col := front[0], front[1]
+            for _, dir := range directions {
+                nr, nc := row+dir[0], col+dir[1]
+                if nr < 0 || nc < 0 || nr >= rows || 
+                   nc >= cols || grid[nr][nc] == 0 {
+                    continue
+                }
+                q = append(q, []int{nr, nc})
+                grid[nr][nc] = 0
+                res++
+            }
+        }
+        return res
+    }
+
+    for r := 0; r < rows; r++ {
+        for c := 0; c < cols; c++ {
+            if grid[r][c] == 1 {
+                area = max(area, bfs(r, c))
+            }
+        }
+    }
+    return area
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun maxAreaOfIsland(grid: Array<IntArray>): Int {
+        val directions = arrayOf(intArrayOf(1, 0), 
+                                 intArrayOf(-1, 0), 
+                                 intArrayOf(0, 1), 
+                                 intArrayOf(0, -1))
+        val rows = grid.size
+        val cols = grid[0].size
+        var area = 0
+        
+        fun bfs(r: Int, c: Int): Int {
+            val queue = ArrayDeque<Pair<Int, Int>>()
+            grid[r][c] = 0
+            queue.add(Pair(r, c))
+            var res = 1
+            
+            while (queue.isNotEmpty()) {
+                val (row, col) = queue.removeFirst()
+                
+                for ((dr, dc) in directions) {
+                    val nr = dr + row
+                    val nc = dc + col
+                    
+                    if (nr < 0 || nc < 0 || nr >= rows || 
+                        nc >= cols || grid[nr][nc] == 0) {
+                        continue
+                    }
+                    
+                    queue.add(Pair(nr, nc))
+                    grid[nr][nc] = 0
+                    res++
+                }
+            }
+            
+            return res
+        }
+        
+        for (r in 0 until rows) {
+            for (c in 0 until cols) {
+                if (grid[r][c] == 1) {
+                    area = maxOf(area, bfs(r, c))
+                }
+            }
+        }
+        
+        return area
+    }
+}
+```
+
+```swift
+class Solution {
+    func maxAreaOfIsland(_ grid: [[Int]]) -> Int {
+        let directions = [[1, 0], [-1, 0], [0, 1], [0, -1]]
+        let ROWS = grid.count
+        let COLS = grid[0].count
+        var grid = grid
+        var area = 0
+
+        func bfs(_ r: Int, _ c: Int) -> Int {
+            var queue = Deque<(Int, Int)>()
+            grid[r][c] = 0
+            queue.append((r, c))
+            var res = 1
+
+            while !queue.isEmpty {
+                let (row, col) = queue.popFirst()!
+                for dir in directions {
+                    let nr = row + dir[0]
+                    let nc = col + dir[1]
+                    if nr < 0 || nc < 0 || nr >= ROWS || nc >= COLS || grid[nr][nc] == 0 {
+                        continue
+                    }
+                    queue.append((nr, nc))
+                    grid[nr][nc] = 0
+                    res += 1
+                }
+            }
+            return res
+        }
+
+        for r in 0..<ROWS {
+            for c in 0..<COLS {
+                if grid[r][c] == 1 {
+                    area = max(area, bfs(r, c))
+                }
+            }
+        }
+
+        return area
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -476,7 +706,7 @@ class Solution:
 ```
 
 ```java
-public class DSU {
+class DSU {
     private int[] Parent, Size;
 
     public DSU(int n) {
@@ -773,6 +1003,230 @@ public class Solution {
 }
 ```
 
+```go
+type DSU struct {
+    Parent []int
+    Size   []int
+}
+
+func (dsu *DSU) find(node int) int {
+    if dsu.Parent[node] != node {
+        dsu.Parent[node] = dsu.find(dsu.Parent[node])
+    }
+    return dsu.Parent[node]
+}
+
+func (dsu *DSU) union(u, v int) bool {
+    pu := dsu.find(u)
+    pv := dsu.find(v)
+    if pu == pv {
+        return false
+    }
+    if dsu.Size[pu] >= dsu.Size[pv] {
+        dsu.Size[pu] += dsu.Size[pv]
+        dsu.Parent[pv] = pu
+    } else {
+        dsu.Size[pv] += dsu.Size[pu]
+        dsu.Parent[pu] = pv
+    }
+    return true
+}
+
+func (dsu *DSU) getSize(node int) int {
+    par := dsu.find(node)
+    return dsu.Size[par]
+}
+
+func maxAreaOfIsland(grid [][]int) int {
+    rows, cols := len(grid), len(grid[0])
+    dsu := DSU{
+        Parent: make([]int, rows*cols+1),
+        Size:   make([]int, rows*cols+1),
+    }
+
+    for i := 0; i <= rows*cols; i++ {
+        dsu.Parent[i] = i
+        dsu.Size[i] = 1
+    }
+
+    index := func(r, c int) int {
+        return r*cols + c
+    }
+
+    directions := [][]int{{1, 0}, {-1, 0}, {0, 1}, {0, -1}}
+    area := 0
+
+    for r := 0; r < rows; r++ {
+        for c := 0; c < cols; c++ {
+            if grid[r][c] == 1 {
+                for _, dir := range directions {
+                    nr, nc := r+dir[0], c+dir[1]
+                    if nr < 0 || nc < 0 || nr >= rows || 
+                       nc >= cols || grid[nr][nc] == 0 {
+                        continue
+                    }
+                    dsu.union(index(r, c), index(nr, nc))
+                }
+                area = max(area, dsu.getSize(index(r, c)))
+            }
+        }
+    }
+    return area
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class DSU(n: Int) {
+    val Parent = IntArray(n + 1) { it }
+    val Size = IntArray(n + 1) { 1 }
+
+    fun find(node: Int): Int {
+        if (Parent[node] != node) {
+            Parent[node] = find(Parent[node])
+        }
+        return Parent[node]
+    }
+
+    fun union(u: Int, v: Int): Boolean {
+        val pu = find(u)
+        val pv = find(v)
+        if (pu == pv) {
+            return false
+        }
+        if (Size[pu] >= Size[pv]) {
+            Size[pu] += Size[pv]
+            Parent[pv] = pu
+        } else {
+            Size[pv] += Size[pu]
+            Parent[pu] = pv
+        }
+        return true
+    }
+
+    fun getSize(node: Int): Int {
+        val par = find(node)
+        return Size[par]
+    }
+}
+
+class Solution {
+    fun maxAreaOfIsland(grid: Array<IntArray>): Int {
+        val rows = grid.size
+        val cols = grid[0].size
+        val dsu = DSU(rows * cols)
+
+        val index = { r: Int, c: Int -> r * cols + c }
+
+        val directions = arrayOf(
+            intArrayOf(1, 0),
+            intArrayOf(-1, 0),
+            intArrayOf(0, 1),
+            intArrayOf(0, -1)
+        )
+        var area = 0
+
+        for (r in 0 until rows) {
+            for (c in 0 until cols) {
+                if (grid[r][c] == 1) {
+                    for (dir in directions) {
+                        val nr = r + dir[0]
+                        val nc = c + dir[1]
+                        if (nr < 0 || nc < 0 || nr >= rows || 
+                            nc >= cols || grid[nr][nc] == 0) {
+                            continue
+                        }
+                        dsu.union(index(r, c), index(nr, nc))
+                    }
+                    area = maxOf(area, dsu.getSize(index(r, c)))
+                }
+            }
+        }
+        return area
+    }
+}
+```
+
+```swift
+class DSU {
+    private var parent: [Int]
+    private var size: [Int]
+
+    init(_ n: Int) {
+        parent = Array(0...n)
+        size = Array(repeating: 1, count: n + 1)
+    }
+
+    func find(_ node: Int) -> Int {
+        if parent[node] != node {
+            parent[node] = find(parent[node])
+        }
+        return parent[node]
+    }
+
+    func union(_ u: Int, _ v: Int) -> Bool {
+        let pu = find(u)
+        let pv = find(v)
+        if pu == pv {
+            return false
+        }
+        if size[pu] >= size[pv] {
+            size[pu] += size[pv]
+            parent[pv] = pu
+        } else {
+            size[pv] += size[pu]
+            parent[pu] = pv
+        }
+        return true
+    }
+
+    func getSize(_ node: Int) -> Int {
+        let par = find(node)
+        return size[par]
+    }
+}
+
+class Solution {
+    func maxAreaOfIsland(_ grid: [[Int]]) -> Int {
+        var grid = grid
+        let ROWS = grid.count
+        let COLS = grid[0].count
+        let dsu = DSU(ROWS * COLS)
+
+        func index(_ r: Int, _ c: Int) -> Int {
+            return r * COLS + c
+        }
+
+        let directions = [(1, 0), (-1, 0), (0, 1), (0, -1)]
+        var area = 0
+
+        for r in 0..<ROWS {
+            for c in 0..<COLS {
+                if grid[r][c] == 1 {
+                    for dir in directions {
+                        let nr = r + dir.0
+                        let nc = c + dir.1
+                        if nr < 0 || nc < 0 || nr >= ROWS || nc >= COLS || grid[nr][nc] == 0 {
+                            continue
+                        }
+                        dsu.union(index(r, c), index(nr, nc))
+                    }
+                    area = max(area, dsu.getSize(index(r, c)))
+                }
+            }
+        }
+
+        return area
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/max-points-on-a-line.md b/articles/max-points-on-a-line.md
new file mode 100644
index 000000000..8c87a3369
--- /dev/null
+++ b/articles/max-points-on-a-line.md
@@ -0,0 +1,384 @@
+## 1. Math
+
+::tabs-start
+
+```python
+class Solution:
+    def maxPoints(self, points: List[List[int]]) -> int:
+        n = len(points)
+        if n <= 2:
+            return n
+
+        def get_slope(p1, p2):
+            if p1[0] == p2[0]:
+                return float("inf")
+            return (p2[1] - p1[1]) / (p2[0] - p1[0])
+
+        res = 1
+        for i in range(n):
+            for j in range(i + 1, n):
+                slope = get_slope(points[i], points[j])
+                cnt = 2
+                for k in range(j + 1, n):
+                    if slope == get_slope(points[i], points[k]):
+                        cnt += 1
+                res = max(res, cnt)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int maxPoints(int[][] points) {
+        int n = points.length;
+        if (n <= 2) {
+            return n;
+        }
+
+        int res = 1;
+        for (int i = 0; i < n; i++) {
+            for (int j = i + 1; j < n; j++) {
+                double slope = getSlope(points[i], points[j]);
+                int cnt = 2;
+                for (int k = j + 1; k < n; k++) {
+                    if (slope == getSlope(points[i], points[k])) {
+                        cnt++;
+                    }
+                }
+                res = Math.max(res, cnt);
+            }
+        }
+
+        return res;
+    }
+
+    private double getSlope(int[] p1, int[] p2) {
+        if (p1[0] == p2[0]) {
+            return Double.POSITIVE_INFINITY;
+        }
+        return (double) (p2[1] - p1[1]) / (p2[0] - p1[0]);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxPoints(vector<vector<int>>& points) {
+        int n = points.size();
+        if (n <= 2) {
+            return n;
+        }
+
+        int res = 1;
+        for (int i = 0; i < n; i++) {
+            for (int j = i + 1; j < n; j++) {
+                double slope = getSlope(points[i], points[j]);
+                int cnt = 2;
+                for (int k = j + 1; k < n; k++) {
+                    if (slope == getSlope(points[i], points[k])) {
+                        cnt++;
+                    }
+                }
+                res = max(res, cnt);
+            }
+        }
+
+        return res;
+    }
+
+private:
+    double getSlope(vector<int>& p1, vector<int>& p2) {
+        if (p1[0] == p2[0]) {
+            return INFINITY;
+        }
+        return (double)(p2[1] - p1[1]) / (p2[0] - p1[0]);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} points
+     * @return {number}
+     */
+    maxPoints(points) {
+        const n = points.length;
+        if (n <= 2) {
+            return n;
+        }
+
+        let res = 1;
+        const getSlope = (p1, p2) => {
+            if (p1[0] === p2[0]) {
+                return Infinity;
+            }
+            return (p2[1] - p1[1]) / (p2[0] - p1[0]);
+        };
+
+        for (let i = 0; i < n; i++) {
+            for (let j = i + 1; j < n; j++) {
+                const slope = getSlope(points[i], points[j]);
+                let cnt = 2;
+                for (let k = j + 1; k < n; k++) {
+                    if (slope === getSlope(points[i], points[k])) {
+                        cnt++;
+                    }
+                }
+                res = Math.max(res, cnt);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 3)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 2. Math + Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def maxPoints(self, points: List[List[int]]) -> int:
+        res = 1
+        for i in range(len(points)):
+            p1 = points[i]
+            count = defaultdict(int)
+            for j in range(i + 1, len(points)):
+                p2 = points[j]
+                if p2[0] == p1[0]:
+                    slope = float("inf")
+                else:
+                    slope = (p2[1] - p1[1]) / (p2[0] - p1[0])
+                count[slope] += 1
+                res = max(res, count[slope] + 1)
+        return res
+```
+
+```java
+public class Solution {
+    public int maxPoints(int[][] points) {
+        int res = 1;
+        for (int i = 0; i < points.length; i++) {
+            Map<Double, Integer> count = new HashMap<>();
+            for (int j = i + 1; j < points.length; j++) {
+                double slope = getSlope(points[i], points[j]);
+                if (slope == -0.0) slope = 0.0;
+                
+                count.put(slope, count.getOrDefault(slope, 0) + 1);
+                res = Math.max(res, count.get(slope) + 1);
+            }
+        }
+        return res;
+    }
+
+    private double getSlope(int[] p1, int[] p2) {
+        if (p1[0] == p2[0]) {
+            return Double.POSITIVE_INFINITY;
+        }
+        return (double) (p2[1] - p1[1]) / (p2[0] - p1[0]);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxPoints(vector<vector<int>>& points) {
+        int res = 1;
+        for (int i = 0; i < points.size(); i++) {
+            vector<int>& p1 = points[i];
+            unordered_map<double, int> count;
+            for (int j = i + 1; j < points.size(); j++) {
+                vector<int>& p2 = points[j];
+                double slope = (p2[0] == p1[0]) ? INFINITY : 
+                               (double)(p2[1] - p1[1]) / (p2[0] - p1[0]);
+                count[slope]++;
+                res = max(res, count[slope] + 1);
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} points
+     * @return {number}
+     */
+    maxPoints(points) {
+        let res = 1;
+        for (let i = 0; i < points.length; i++) {
+            const p1 = points[i];
+            const count = new Map();
+            for (let j = i + 1; j < points.length; j++) {
+                const p2 = points[j];
+                const slope = (p2[0] === p1[0]) ? Infinity : 
+                              (p2[1] - p1[1]) / (p2[0] - p1[0]);
+                count.set(slope, (count.get(slope) || 0) + 1);
+                res = Math.max(res, count.get(slope) + 1);
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Math + Hash Map (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxPoints(self, points: List[List[int]]) -> int:
+        if len(points) <= 2:
+            return len(points)
+
+        def gcd(a, b):
+            return gcd(b, a % b) if b else a
+
+        res = 1
+        for i in range(len(points) - 1):
+            count = defaultdict(int)
+            for j in range(i + 1, len(points)):
+                dx = points[j][0] - points[i][0]
+                dy = points[j][1] - points[i][1]
+                g = gcd(dx, dy)
+                dx //= g
+                dy //= g
+                slope = (dx, dy)
+                count[slope] += 1
+            res = max(res, max(count.values()) + 1)
+        return res
+```
+
+```java
+public class Solution {
+    public int maxPoints(int[][] points) {
+        if (points.length <= 2) {
+            return points.length;
+        }
+
+        int res = 1;
+        for (int i = 0; i < points.length - 1; i++) {
+            Map<String, Integer> count = new HashMap<>();
+            for (int j = i + 1; j < points.length; j++) {
+                int dx = points[j][0] - points[i][0];
+                int dy = points[j][1] - points[i][1];
+                int g = gcd(dx, dy);
+                dx /= g;
+                dy /= g;
+                String slope = dx + ":" + dy;
+                count.put(slope, count.getOrDefault(slope, 0) + 1);
+            }
+            for (int val : count.values()) {
+                res = Math.max(res, val + 1);
+            }
+        }
+        return res;
+    }
+
+    private int gcd(int a, int b) {
+        return b == 0 ? a : gcd(b, a % b);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxPoints(vector<vector<int>>& points) {
+        if (points.size() <= 2) {
+            return points.size();
+        }
+
+        int res = 1;
+        for (int i = 0; i < points.size() - 1; i++) {
+            unordered_map<string, int> count;
+            for (int j = i + 1; j < points.size(); j++) {
+                int dx = points[j][0] - points[i][0];
+                int dy = points[j][1] - points[i][1];
+                int g = gcd(dx, dy);
+                dx /= g;
+                dy /= g;
+                string slope = to_string(dx) + ":" + to_string(dy);
+                count[slope]++;
+            }
+            for (const auto& [slope, freq] : count) {
+                res = max(res, freq + 1);
+            }
+        }
+        return res;
+    }
+
+private:
+    int gcd(int a, int b) {
+        return b == 0 ? a : gcd(b, a % b);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} points
+     * @return {number}
+     */
+    maxPoints(points) {
+        if (points.length <= 2) {
+            return points.length;
+        }
+
+        const gcd = (a, b) => (b === 0 ? a : gcd(b, a % b));
+
+        let res = 1;
+        for (let i = 0; i < points.length - 1; i++) {
+            const count = new Map();
+            for (let j = i + 1; j < points.length; j++) {
+                let dx = points[j][0] - points[i][0];
+                let dy = points[j][1] - points[i][1];
+                const g = gcd(dx, dy);
+                dx /= g;
+                dy /= g;
+                const slope = `${dx}:${dy}`;
+                count.set(slope, (count.get(slope) || 0) + 1);
+            }
+            for (const freq of count.values()) {
+                res = Math.max(res, freq + 1);
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 \log m)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the number of points and $m$ is the maximum value in the points.
\ No newline at end of file
diff --git a/articles/max-water-container.md b/articles/max-water-container.md
index 50aed4cdc..bb1ea6083 100644
--- a/articles/max-water-container.md
+++ b/articles/max-water-container.md
@@ -73,6 +73,57 @@ public class Solution {
 }
 ```
 
+```go
+func maxArea(heights []int) int {
+    res := 0
+    for i := 0; i < len(heights); i++ {
+        for j := i + 1; j < len(heights); j++ {
+            area := min(heights[i], heights[j]) * (j - i)
+            if area > res {
+                res = area
+            }
+        }
+    }
+    return res
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun maxArea(heights: IntArray): Int {
+        var res = 0
+        for (i in heights.indices) {
+            for (j in i + 1 until heights.size) {
+                val area = minOf(heights[i], heights[j]) * (j - i)
+                res = maxOf(res, area)
+            }
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func maxArea(_ heights: [Int]) -> Int {
+        var res = 0
+        for i in 0..<heights.count {
+            for j in (i + 1)..<heights.count {
+                res = max(res, min(heights[i], heights[j]) * (j - i))
+            }
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -192,6 +243,74 @@ public class Solution {
 }
 ```
 
+```go
+func maxArea(heights []int) int {
+    l, r := 0, len(heights) - 1
+    res := 0
+
+    for l < r {
+        area := min(heights[l], heights[r]) * (r - l)
+        if area > res {
+            res = area
+        }
+        if heights[l] <= heights[r] {
+            l++
+        } else {
+            r--
+        }
+    }
+    return res
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun maxArea(heights: IntArray): Int {
+        var l = 0
+        var r = heights.size - 1
+        var res = 0
+
+        while (l < r) {
+            val area = minOf(heights[l], heights[r]) * (r - l)
+            res = maxOf(res, area)
+            if (heights[l] <= heights[r]) {
+                l++
+            } else {
+                r--
+            }
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func maxArea(_ heights: [Int]) -> Int {
+        var l = 0, r = heights.count - 1
+        var res = 0
+
+        while l < r {
+            let area = min(heights[l], heights[r]) * (r - l)
+            res = max(res, area)
+            if heights[l] <= heights[r] {
+                l += 1
+            } else {
+                r -= 1
+            }
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/maximal-square.md b/articles/maximal-square.md
new file mode 100644
index 000000000..ab7d2fce0
--- /dev/null
+++ b/articles/maximal-square.md
@@ -0,0 +1,560 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def maximalSquare(self, matrix: List[List[str]]) -> int:
+        m, n = len(matrix), len(matrix[0])
+        res = 0
+
+        for r in range(m):
+            for c in range(n):
+                if matrix[r][c] == "0":
+                    continue
+                k = 1
+                while True:
+                    if r + k > m or c + k > n:
+                        break
+                    flag = True
+                    
+                    for i in range(r, r + k):
+                        if matrix[i][c + k - 1] == "0":
+                            flag = False
+                            break
+                    for j in range(c, c + k):
+                        if matrix[r + k - 1][j] == "0":
+                            flag = False
+                            break
+                    
+                    if not flag:
+                        break                    
+                    res = max(res, k * k)
+                    k += 1
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int maximalSquare(char[][] matrix) {
+        int m = matrix.length, n = matrix[0].length;
+        int res = 0;
+
+        for (int r = 0; r < m; r++) {
+            for (int c = 0; c < n; c++) {
+                if (matrix[r][c] == '0') {
+                    continue;
+                }
+                int k = 1;
+                while (true) {
+                    if (r + k > m || c + k > n) {
+                        break;
+                    }
+                    boolean flag = true;
+                    
+                    for (int i = r; i < r + k; i++) {
+                        if (matrix[i][c + k - 1] == '0') {
+                            flag = false;
+                            break;
+                        }
+                    }
+                    for (int j = c; j < c + k; j++) {
+                        if (matrix[r + k - 1][j] == '0') {
+                            flag = false;
+                            break;
+                        }
+                    }
+                    
+                    if (!flag) {
+                        break;
+                    }
+                    res = Math.max(res, k * k);
+                    k++;
+                }
+            }
+        }
+        
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maximalSquare(vector<vector<char>>& matrix) {
+        int m = matrix.size(), n = matrix[0].size();
+        int res = 0;
+
+        for (int r = 0; r < m; r++) {
+            for (int c = 0; c < n; c++) {
+                if (matrix[r][c] == '0') {
+                    continue;
+                }
+                int k = 1;
+                while (true) {
+                    if (r + k > m || c + k > n) {
+                        break;
+                    }
+                    bool flag = true;
+                    
+                    for (int i = r; i < r + k; i++) {
+                        if (matrix[i][c + k - 1] == '0') {
+                            flag = false;
+                            break;
+                        }
+                    }
+                    for (int j = c; j < c + k; j++) {
+                        if (matrix[r + k - 1][j] == '0') {
+                            flag = false;
+                            break;
+                        }
+                    }
+                    
+                    if (!flag) {
+                        break;
+                    }
+                    res = max(res, k * k);
+                    k++;
+                }
+            }
+        }
+        
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {character[][]} matrix
+     * @return {number}
+     */
+    maximalSquare(matrix) {
+        const m = matrix.length, n = matrix[0].length;
+        let res = 0;
+
+        for (let r = 0; r < m; r++) {
+            for (let c = 0; c < n; c++) {
+                if (matrix[r][c] === "0") {
+                    continue;
+                }
+                let k = 1;
+                while (true) {
+                    if (r + k > m || c + k > n) {
+                        break;
+                    }
+                    let flag = true;
+
+                    for (let i = r; i < r + k; i++) {
+                        if (matrix[i][c + k - 1] === "0") {
+                            flag = false;
+                            break;
+                        }
+                    }
+                    for (let j = c; j < c + k; j++) {
+                        if (matrix[r + k - 1][j] === "0") {
+                            flag = false;
+                            break;
+                        }
+                    }
+
+                    if (!flag) {
+                        break;
+                    }
+                    res = Math.max(res, k * k);
+                    k++;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O((m * n) ^ 2)$
+* Space complexity: $O(1)$
+
+> Where $m$ is the number of rows and $n$ is the number columns.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def maximalSquare(self, matrix: List[List[str]]) -> int:
+        ROWS, COLS = len(matrix), len(matrix[0])
+        cache = {}
+
+        def dfs(r, c):
+            if r >= ROWS or c >= COLS:
+                return 0
+            if (r, c) not in cache:
+                down = dfs(r + 1, c)
+                right = dfs(r, c + 1)
+                diag = dfs(r + 1, c + 1)
+                cache[(r, c)] = 0
+                if matrix[r][c] == "1":
+                    cache[(r, c)] = 1 + min(down, right, diag)
+            return cache[(r, c)]
+
+        dfs(0, 0)
+        return max(cache.values()) ** 2
+```
+
+```java
+public class Solution {
+    private int[][] dp;
+
+    public int maximalSquare(char[][] matrix) {
+        int ROWS = matrix.length, COLS = matrix[0].length;
+        dp = new int[ROWS][COLS];
+        for (int i = 0; i < ROWS; i++) {
+            for (int j = 0; j < COLS; j++) {
+                dp[i][j] = -1;
+            }
+        }
+
+        dfs(0, 0, matrix);
+        int maxSquare = 0;
+        for (int i = 0; i < ROWS; i++) {
+            for (int j = 0; j < COLS; j++) {
+                maxSquare = Math.max(maxSquare, dp[i][j]);
+            }
+        }
+        return maxSquare * maxSquare;
+    }
+
+    private int dfs(int r, int c, char[][] matrix) {
+        if (r >= matrix.length || c >= matrix[0].length) {
+            return 0;
+        }
+        if (dp[r][c] != -1) {
+            return dp[r][c];
+        }
+        int down = dfs(r + 1, c, matrix);
+        int right = dfs(r, c + 1, matrix);
+        int diag = dfs(r + 1, c + 1, matrix);
+        dp[r][c] = 0;
+        if (matrix[r][c] == '1') {
+            dp[r][c] = 1 + Math.min(down, Math.min(right, diag));
+        }
+        return dp[r][c];
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<vector<int>> dp;
+
+public:
+    int maximalSquare(vector<vector<char>>& matrix) {
+        int ROWS = matrix.size(), COLS = matrix[0].size();
+        dp = vector<vector<int>>(ROWS, vector<int>(COLS, -1));
+
+        dfs(0, 0, matrix);
+        int maxSquare = 0;
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                maxSquare = max(maxSquare, dp[r][c]);
+            }
+        }
+        return maxSquare * maxSquare;
+    }
+
+    int dfs(int r, int c, vector<vector<char>>& matrix) {
+        if (r >= matrix.size() || c >= matrix[0].size()) {
+            return 0;
+        }
+        if (dp[r][c] != -1) {
+            return dp[r][c];
+        }
+        int down = dfs(r + 1, c, matrix);
+        int right = dfs(r, c + 1, matrix);
+        int diag = dfs(r + 1, c + 1, matrix);
+        dp[r][c] = 0;
+        if (matrix[r][c] == '1') {
+            dp[r][c] = 1 + min(down, min(right, diag));
+        }
+        return dp[r][c];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {character[][]} matrix
+     * @return {number}
+     */
+    maximalSquare(matrix) {
+        const ROWS = matrix.length, COLS = matrix[0].length;
+        const dp = Array.from({ length: ROWS }, () => Array(COLS).fill(-1));
+
+        const dfs = (r, c) => {
+            if (r >= ROWS || c >= COLS) {
+                return 0;
+            }
+            if (dp[r][c] !== -1) {
+                return dp[r][c];
+            }
+            const down = dfs(r + 1, c);
+            const right = dfs(r, c + 1);
+            const diag = dfs(r + 1, c + 1);
+            dp[r][c] = 0;
+            if (matrix[r][c] === "1") {
+                dp[r][c] = 1 + Math.min(down, Math.min(right, diag));
+            }
+            return dp[r][c];
+        };
+
+        dfs(0, 0);
+        let maxSquare = 0;
+        for (let r = 0; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                maxSquare = Math.max(maxSquare, dp[r][c]);
+            }
+        }
+        return maxSquare * maxSquare;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows and $n$ is the number columns.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def maximalSquare(self, matrix: List[List[str]]) -> int:
+        m, n = len(matrix), len(matrix[0])
+        dp = [[0] * (n + 1) for _ in range(m + 1)]
+        max_square = 0
+
+        for r in range(m - 1, -1, -1):
+            for c in range(n - 1, -1, -1):
+                if matrix[r][c] == "1":
+                    dp[r][c] = 1 + min(dp[r + 1][c], dp[r][c + 1], dp[r + 1][c + 1])
+                    max_square = max(max_square, dp[r][c])
+
+        return max_square * max_square
+```
+
+```java
+public class Solution {
+    public int maximalSquare(char[][] matrix) {
+        int m = matrix.length, n = matrix[0].length;
+        int[][] dp = new int[m + 1][n + 1];
+        int maxSquare = 0;
+
+        for (int r = m - 1; r >= 0; r--) {
+            for (int c = n - 1; c >= 0; c--) {
+                if (matrix[r][c] == '1') {
+                    dp[r][c] = 1 + Math.min(dp[r + 1][c], Math.min(dp[r][c + 1], dp[r + 1][c + 1]));
+                    maxSquare = Math.max(maxSquare, dp[r][c]);
+                }
+            }
+        }
+
+        return maxSquare * maxSquare;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maximalSquare(vector<vector<char>>& matrix) {
+        int m = matrix.size(), n = matrix[0].size();
+        vector<vector<int>> dp(m + 1, vector<int>(n + 1, 0));
+        int maxSquare = 0;
+
+        for (int r = m - 1; r >= 0; r--) {
+            for (int c = n - 1; c >= 0; c--) {
+                if (matrix[r][c] == '1') {
+                    dp[r][c] = 1 + min({dp[r + 1][c], dp[r][c + 1], dp[r + 1][c + 1]});
+                    maxSquare = max(maxSquare, dp[r][c]);
+                }
+            }
+        }
+
+        return maxSquare * maxSquare;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {character[][]} matrix
+     * @return {number}
+     */
+    maximalSquare(matrix) {
+        const m = matrix.length, n = matrix[0].length;
+        const dp = Array.from({ length: m + 1 }, () => Array(n + 1).fill(0));
+        let maxSquare = 0;
+
+        for (let r = m - 1; r >= 0; r--) {
+            for (let c = n - 1; c >= 0; c--) {
+                if (matrix[r][c] === "1") {
+                    dp[r][c] = 1 + Math.min(dp[r + 1][c], dp[r][c + 1], dp[r + 1][c + 1]);
+                    maxSquare = Math.max(maxSquare, dp[r][c]);
+                }
+            }
+        }
+
+        return maxSquare * maxSquare;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows and $n$ is the number columns.
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def maximalSquare(self, matrix: List[List[str]]) -> int:
+        m, n = len(matrix), len(matrix[0])
+        dp = [0] * (n + 1)
+        max_square = 0
+
+        for r in range(m - 1, -1, -1):
+            prev = 0
+            for c in range(n - 1, -1, -1):
+                temp = dp[c]
+                if matrix[r][c] == "1":
+                    dp[c] = 1 + min(dp[c], dp[c + 1], prev)
+                    max_square = max(max_square, dp[c])
+                else:
+                    dp[c] = 0
+                prev = temp
+
+        return max_square * max_square
+```
+
+```java
+public class Solution {
+    public int maximalSquare(char[][] matrix) {
+        int m = matrix.length, n = matrix[0].length;
+        int[] dp = new int[n + 1];
+        int maxSquare = 0;
+
+        for (int r = m - 1; r >= 0; r--) {
+            int prev = 0;
+            for (int c = n - 1; c >= 0; c--) {
+                int temp = dp[c];
+                if (matrix[r][c] == '1') {
+                    dp[c] = 1 + Math.min(dp[c], Math.min(dp[c + 1], prev));
+                    maxSquare = Math.max(maxSquare, dp[c]);
+                } else {
+                    dp[c] = 0;
+                }
+                prev = temp;
+            }
+        }
+
+        return maxSquare * maxSquare;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maximalSquare(vector<vector<char>>& matrix) {
+        int m = matrix.size(), n = matrix[0].size();
+        vector<int> dp(n + 1, 0);
+        int maxSquare = 0;
+
+        for (int r = m - 1; r >= 0; r--) {
+            int prev = 0;
+            for (int c = n - 1; c >= 0; c--) {
+                int temp = dp[c];
+                if (matrix[r][c] == '1') {
+                    dp[c] = 1 + min({dp[c], dp[c + 1], prev});
+                    maxSquare = max(maxSquare, dp[c]);
+                } else {
+                    dp[c] = 0;
+                }
+                prev = temp;
+            }
+        }
+
+        return maxSquare * maxSquare;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {character[][]} matrix
+     * @return {number}
+     */
+    maximalSquare(matrix) {
+        const m = matrix.length, n = matrix[0].length;
+        const dp = new Array(n + 1).fill(0);
+        let maxSquare = 0;
+        let prev = 0;
+
+        for (let r = m - 1; r >= 0; r--) {
+            for (let c = n - 1; c >= 0; c--) {
+                const temp = dp[c];
+                if (matrix[r][c] === "1") {
+                    dp[c] = 1 + Math.min(dp[c], dp[c + 1], prev);
+                    maxSquare = Math.max(maxSquare, dp[c]);
+                } else {
+                    dp[c] = 0;
+                }
+                prev = temp;
+            }
+        }
+
+        return maxSquare * maxSquare;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(n)$
+
+> Where $m$ is the number of rows and $n$ is the number columns.
\ No newline at end of file
diff --git a/articles/maximize-score-after-n-operations.md b/articles/maximize-score-after-n-operations.md
new file mode 100644
index 000000000..bf90e9d55
--- /dev/null
+++ b/articles/maximize-score-after-n-operations.md
@@ -0,0 +1,629 @@
+## 1. Brute Force (Backtracking)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxScore(self, nums: List[int]) -> int:
+        N = len(nums)
+        visit = [False] * N
+
+        def dfs(n):
+            if n > (N // 2):
+                return 0
+
+            res = 0
+            for i in range(N):
+                if visit[i]:
+                    continue
+                visit[i] = True
+                for j in range(i + 1, N):
+                    if visit[j]:
+                        continue
+                    visit[j] = True
+                    g = gcd(nums[i], nums[j])
+                    res = max(res, n * g + dfs(n + 1))
+                    visit[j] = False
+                visit[i] = False
+
+            return res
+
+        return dfs(1)
+```
+
+```java
+public class Solution {
+    public int maxScore(int[] nums) {
+        int N = nums.length;
+        boolean[] visit = new boolean[N];
+        return dfs(nums, visit, 1, N);
+    }
+
+    private int dfs(int[] nums, boolean[] visit, int n, int N) {
+        if (n > N / 2) {
+            return 0;
+        }
+
+        int res = 0;
+        for (int i = 0; i < N; i++) {
+            if (visit[i]) continue;
+            visit[i] = true;
+            for (int j = i + 1; j < N; j++) {
+                if (visit[j]) continue;
+                visit[j] = true;
+                int g = gcd(nums[i], nums[j]);
+                res = Math.max(res, n * g + dfs(nums, visit, n + 1, N));
+                visit[j] = false;
+            }
+            visit[i] = false;
+        }
+
+        return res;
+    }
+
+    private int gcd(int a, int b) {
+        return b == 0 ? a : gcd(b, a % b);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxScore(vector<int>& nums) {
+        int N = nums.size();
+        vector<bool> visit(N, false);
+        return dfs(nums, visit, 1, N);
+    }
+
+private:
+    int dfs(vector<int>& nums, vector<bool>& visit, int n, int N) {
+        if (n > N / 2) {
+            return 0;
+        }
+
+        int res = 0;
+        for (int i = 0; i < N; i++) {
+            if (visit[i]) continue;
+            visit[i] = true;
+            for (int j = i + 1; j < N; j++) {
+                if (visit[j]) continue;
+                visit[j] = true;
+                int g = gcd(nums[i], nums[j]);
+                res = max(res, n * g + dfs(nums, visit, n + 1, N));
+                visit[j] = false;
+            }
+            visit[i] = false;
+        }
+
+        return res;
+    }
+
+    int gcd(int a, int b) {
+        return b == 0 ? a : gcd(b, a % b);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    maxScore(nums) {
+        const N = nums.length;
+        const visit = new Array(N).fill(false);
+
+        const gcd = (a, b) => {
+            return b === 0 ? a : gcd(b, a % b);
+        };
+        const dfs = (n) => {
+            if (n > N / 2) {
+                return 0;
+            }
+
+            let res = 0;
+            for (let i = 0; i < N; i++) {
+                if (visit[i]) continue;
+                visit[i] = true;
+                for (let j = i + 1; j < N; j++) {
+                    if (visit[j]) continue;
+                    visit[j] = true;
+                    let g = gcd(nums[i], nums[j]);
+                    res = Math.max(res, n * g + dfs(n + 1));
+                    visit[j] = false;
+                }
+                visit[i] = false;
+            }
+
+            return res;
+        };
+
+        return dfs(1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ n * \log m)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the size of the array $nums$ and $m$ is the maximum element in the array.
+
+---
+
+## 2. Bitmask DP (Top-Down) - I
+
+::tabs-start
+
+```python
+class Solution:
+    def maxScore(self, nums: List[int]) -> int:
+        cache = collections.defaultdict(int)
+
+        def dfs(mask, op):
+            if mask in cache:
+                return cache[mask]
+
+            for i in range(len(nums)):
+                for j in range(i + 1, len(nums)):
+                    if (1 << i) & mask or (1 << j) & mask:
+                        continue
+
+                    newMask = mask | (1 << i) | (1 << j)
+                    score = op * math.gcd(nums[i], nums[j])
+                    cache[mask] = max(
+                        cache[mask],
+                        score + dfs(newMask, op + 1)
+                    )
+
+            return cache[mask]
+
+        return dfs(0, 1)
+```
+
+```java
+public class Solution {
+    private Map<Integer, Integer> cache;
+
+    public int maxScore(int[] nums) {
+        cache = new HashMap<>();
+        return dfs(0, 1, nums);
+    }
+
+    private int dfs(int mask, int op, int[] nums) {
+        if (cache.containsKey(mask)) {
+            return cache.get(mask);
+        }
+
+        int maxScore = 0;
+        int n = nums.length;
+        for (int i = 0; i < n; i++) {
+            if ((mask & (1 << i)) != 0) continue;
+            for (int j = i + 1; j < n; j++) {
+                if ((mask & (1 << j)) != 0) continue;
+                int newMask = mask | (1 << i) | (1 << j);
+                int score = op * gcd(nums[i], nums[j]) + dfs(newMask, op + 1, nums);
+                maxScore = Math.max(maxScore, score);
+            }
+        }
+
+        cache.put(mask, maxScore);
+        return maxScore;
+    }
+
+    private int gcd(int a, int b) {
+        return b == 0 ? a : gcd(b, a % b);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxScore(vector<int>& nums) {
+        return dfs(0, 1, nums);
+    }
+
+private:
+    unordered_map<int, int> cache;
+
+    int dfs(int mask, int op, vector<int>& nums) {
+        if (cache.count(mask)) {
+            return cache[mask];
+        }
+
+        int maxScore = 0;
+        int n = nums.size();
+        for (int i = 0; i < n; i++) {
+            if ((mask & (1 << i)) != 0) continue;
+            for (int j = i + 1; j < n; j++) {
+                if ((mask & (1 << j)) != 0) continue;
+                int newMask = mask | (1 << i) | (1 << j);
+                int score = op * gcd(nums[i], nums[j]) + dfs(newMask, op + 1, nums);
+                maxScore = max(maxScore, score);
+            }
+        }
+
+        return cache[mask] = maxScore;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    maxScore(nums) {
+        const cache = new Map();
+
+        const gcd = (a, b) => (b === 0 ? a : gcd(b, a % b));
+
+        const dfs = (mask, op) => {
+            if (cache.has(mask)) {
+                return cache.get(mask);
+            }
+
+            let maxScore = 0;
+            const n = nums.length;
+            for (let i = 0; i < n; i++) {
+                if ((mask & (1 << i)) !== 0) continue;
+                for (let j = i + 1; j < n; j++) {
+                    if ((mask & (1 << j)) !== 0) continue;
+                    let newMask = mask | (1 << i) | (1 << j);
+                    let score = op * gcd(nums[i], nums[j]) + dfs(newMask, op + 1);
+                    maxScore = Math.max(maxScore, score);
+                }
+            }
+
+            cache.set(mask, maxScore);
+            return maxScore;
+        };
+
+
+        return dfs(0, 1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 * 2 ^ n * \log m)$
+* Space complexity: $O(2 ^ n)$
+
+> Where $n$ is the size of the array $nums$ and $m$ is the maximum element in the array.
+
+---
+
+## 3. Bitmask DP (Top-Down) - II
+
+::tabs-start
+
+```python
+class Solution:
+    def maxScore(self, nums: List[int]) -> int:
+        n = len(nums)
+        GCD = [[0] * n for _ in range(n)]
+        for i in range(n):
+            for j in range(i + 1, n):
+                GCD[i][j] = gcd(nums[i], nums[j])
+
+        dp = [-1] * (1 << n)
+        def dfs(mask, op):
+            if dp[mask] != -1:
+                return dp[mask]
+
+            max_score = 0
+            for i in range(n):
+                if mask & (1 << i): 
+                    continue
+                for j in range(i + 1, n):
+                    if mask & (1 << j): 
+                        continue
+                    new_mask = mask | (1 << i) | (1 << j)
+                    max_score = max(
+                        max_score,
+                        op * GCD[i][j] + dfs(new_mask, op + 1)
+                    )
+
+            dp[mask] = max_score
+            return max_score
+
+        return dfs(0, 1)
+```
+
+```java
+public class Solution {
+    private int[][] GCD;
+    private int[] dp;
+
+    public int maxScore(int[] nums) {
+        int n = nums.length;
+        GCD = new int[n][n];
+        dp = new int[1 << n];
+        Arrays.fill(dp, -1);
+
+        for (int i = 0; i < n; i++) {
+            for (int j = i + 1; j < n; j++) {
+                GCD[i][j] = gcd(nums[i], nums[j]);
+            }
+        }
+
+        return (int) dfs(0, 1, nums);
+    }
+
+    private int dfs(int mask, int op, int[] nums) {
+        if (dp[mask] != -1) return dp[mask];
+
+        int maxScore = 0;
+        for (int i = 0; i < nums.length; i++) {
+            if ((mask & (1 << i)) != 0) continue;
+            for (int j = i + 1; j < nums.length; j++) {
+                if ((mask & (1 << j)) != 0) continue;
+                int newMask = mask | (1 << i) | (1 << j);
+                maxScore = Math.max(
+                    maxScore,
+                    op * GCD[i][j] + dfs(newMask, op + 1, nums)
+                );
+            }
+        }
+        return dp[mask] = maxScore;
+    }
+
+    private int gcd(int a, int b) {
+        return b == 0 ? a : gcd(b, a % b);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxScore(vector<int>& nums) {
+        int n = nums.size();
+        GCD.assign(n, vector<int>(n, 0));
+        dp.assign(1 << n, -1);
+
+        for (int i = 0; i < n; i++) {
+            for (int j = i + 1; j < n; j++) {
+                GCD[i][j] = gcd(nums[i], nums[j]);
+            }
+        }
+
+        return dfs(0, 1, nums);
+    }
+
+private:
+    vector<vector<int>> GCD;
+    vector<int> dp;
+
+    int dfs(int mask, int op, vector<int>& nums) {
+        if (dp[mask] != -1) return dp[mask];
+
+        int maxScore = 0;
+        for (int i = 0; i < nums.size(); i++) {
+            if (mask & (1 << i)) continue;
+            for (int j = i + 1; j < nums.size(); j++) {
+                if (mask & (1 << j)) continue;
+                int newMask = mask | (1 << i) | (1 << j);
+                maxScore = max(
+                    maxScore,
+                    op * GCD[i][j] + dfs(newMask, op + 1, nums)
+                );
+            }
+        }
+        return dp[mask] = maxScore;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    maxScore(nums) {
+        const n = nums.length;
+        const GCD = Array.from({ length: n }, () => Array(n).fill(0));
+        const dp = Array(1 << n).fill(-1);
+
+        const gcd = (a, b) => (b === 0 ? a : gcd(b, a % b));
+        for (let i = 0; i < n; i++) {
+            for (let j = i + 1; j < n; j++) {
+                GCD[i][j] = gcd(nums[i], nums[j]);
+            }
+        }
+
+        const dfs = (mask, op) => {
+            if (dp[mask] !== -1) return dp[mask];
+
+            let maxScore = 0;
+            for (let i = 0; i < n; i++) {
+                if (mask & (1 << i)) continue;
+                for (let j = i + 1; j < n; j++) {
+                    if (mask & (1 << j)) continue;
+                    const newMask = mask | (1 << i) | (1 << j);
+                    maxScore = Math.max(
+                        maxScore,
+                        op * GCD[i][j] + dfs(newMask, op + 1)
+                    );
+                }
+            }
+            return dp[mask] = maxScore;
+        };
+
+        return dfs(0, 1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 * (2 ^ n + \log m))$
+* Space complexity: $O(n ^ 2 + 2 ^ n)$
+
+> Where $n$ is the size of the array $nums$ and $m$ is the maximum element in the array.
+
+---
+
+## 4. Bitmask DP (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxScore(self, nums: List[int]) -> int:
+        n = len(nums)
+        N = 1 << n
+        GCD = [[0] * n for _ in range(n)]
+        for i in range(n):
+            for j in range(i + 1, n):
+                GCD[i][j] = gcd(nums[i], nums[j])
+
+        dp = [0] * N
+        for mask in range(N - 1, -1, -1):
+            bits = bin(mask).count('1')
+            if bits % 2 == 1:
+                continue
+            op = bits // 2 + 1
+
+            for i in range(n):
+                if mask & (1 << i):
+                    continue
+                for j in range(i + 1, n):
+                    if mask & (1 << j):
+                        continue
+                    new_mask = mask | (1 << i) | (1 << j)
+                    dp[mask] = max(dp[mask], op * GCD[i][j] + dp[new_mask])
+
+        return dp[0]
+```
+
+```java
+public class Solution {
+    public int maxScore(int[] nums) {
+        int n = nums.length;
+        int N = 1 << n;
+        int[][] GCD = new int[n][n];
+
+        for (int i = 0; i < n; i++) {
+            for (int j = i + 1; j < n; j++) {
+                GCD[i][j] = gcd(nums[i], nums[j]);
+            }
+        }
+
+        int[] dp = new int[N];
+        for (int mask = N - 1; mask >= 0; mask--) {
+            int bits = Integer.bitCount(mask);
+            if (bits % 2 == 1) continue;
+            int op = bits / 2 + 1;
+
+            for (int i = 0; i < n; i++) {
+                if ((mask & (1 << i)) != 0) continue;
+                for (int j = i + 1; j < n; j++) {
+                    if ((mask & (1 << j)) != 0) continue;
+                    int newMask = mask | (1 << i) | (1 << j);
+                    dp[mask] = Math.max(dp[mask], op * GCD[i][j] + dp[newMask]);
+                }
+            }
+        }
+        return dp[0];
+    }
+
+    private int gcd(int a, int b) {
+        return b == 0 ? a : gcd(b, a % b);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxScore(vector<int>& nums) {
+        int n = nums.size();
+        int N = 1 << n;
+        vector<vector<int>> GCD(n, vector<int>(n, 0));
+
+        for (int i = 0; i < n; i++) {
+            for (int j = i + 1; j < n; j++) {
+                GCD[i][j] = __gcd(nums[i], nums[j]);
+            }
+        }
+
+        vector<int> dp(N, 0);
+        for (int mask = N - 1; mask >= 0; mask--) {
+            int bits = __builtin_popcount(mask);
+            if (bits % 2 == 1) continue;
+            int op = bits / 2 + 1;
+
+            for (int i = 0; i < n; i++) {
+                if (mask & (1 << i)) continue;
+                for (int j = i + 1; j < n; j++) {
+                    if (mask & (1 << j)) continue;
+                    int newMask = mask | (1 << i) | (1 << j);
+                    dp[mask] = max(dp[mask], op * GCD[i][j] + dp[newMask]);
+                }
+            }
+        }
+        return dp[0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    maxScore(nums) {
+        const n = nums.length;
+        const N = 1 << n;
+        const GCD = Array.from({ length: n }, () => Array(n).fill(0));
+
+        const gcd = (a, b) => (b === 0 ? a : gcd(b, a % b));
+        for (let i = 0; i < n; i++) {
+            for (let j = i + 1; j < n; j++) {
+                GCD[i][j] = gcd(nums[i], nums[j]);
+            }
+        }
+
+        const dp = Array(N).fill(0);
+        for (let mask = N - 1; mask >= 0; mask--) {
+            let bits = mask.toString(2).split("0").join("").length;
+            if (bits % 2 === 1) continue;
+            let op = bits / 2 + 1;
+
+            for (let i = 0; i < n; i++) {
+                if ((mask & (1 << i)) !== 0) continue;
+                for (let j = i + 1; j < n; j++) {
+                    if ((mask & (1 << j)) !== 0) continue;
+                    let newMask = mask | (1 << i) | (1 << j);
+                    dp[mask] = Math.max(dp[mask], op * GCD[i][j] + dp[newMask]);
+                }
+            }
+        }
+        return dp[0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 * (2 ^ n + \log m))$
+* Space complexity: $O(n ^ 2 + 2 ^ n)$
+
+> Where $n$ is the size of the array $nums$ and $m$ is the maximum element in the array.
\ No newline at end of file
diff --git a/articles/maximum-alternating-subsequence-sum.md b/articles/maximum-alternating-subsequence-sum.md
new file mode 100644
index 000000000..0f296306c
--- /dev/null
+++ b/articles/maximum-alternating-subsequence-sum.md
@@ -0,0 +1,351 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def maxAlternatingSum(self, nums: List[int]) -> int:
+        def dfs(i, even):
+            if i == len(nums):
+                return 0
+            total = nums[i] if even else -nums[i]
+            return max(total + dfs(i + 1, not even), dfs(i + 1, even))
+        
+        return dfs(0, True)
+```
+
+```java
+public class Solution {
+    public long maxAlternatingSum(int[] nums) {
+        return dfs(nums, 0, true);
+    }
+
+    private long dfs(int[] nums, int i, boolean even) {
+        if (i == nums.length) {
+            return 0;
+        }
+        long total = even ? nums[i] : -nums[i];
+        return Math.max(total + dfs(nums, i + 1, !even), dfs(nums, i + 1, even));
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long maxAlternatingSum(vector<int>& nums) {
+        return dfs(nums, 0, true);
+    }
+
+private:
+    long long dfs(vector<int>& nums, int i, bool even) {
+        if (i == nums.size()) {
+            return 0;
+        }
+        long long total = even ? nums[i] : -nums[i];
+        return max(total + dfs(nums, i + 1, !even), dfs(nums, i + 1, even));
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    maxAlternatingSum(nums) {
+        const dfs = (i, even) => {
+            if (i === nums.length) {
+                return 0;
+            }
+
+            const total = even ? nums[i] : -nums[i];
+            return Math.max(total + dfs(i + 1, !even), dfs(i + 1, even));
+        };
+
+        return dfs(0, true);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxAlternatingSum(self, nums: List[int]) -> int:
+        dp = {}
+
+        def dfs(i, even):
+            if i == len(nums):
+                return 0
+            if (i, even) in dp:
+                return dp[(i, even)]
+            
+            total = nums[i] if even else -nums[i]
+            dp[(i, even)] = max(total + dfs(i + 1, not even), dfs(i + 1, even))
+            return dp[(i, even)]
+        
+        return dfs(0, True)
+```
+
+```java
+public class Solution {
+    private long dp[][];
+
+    public long maxAlternatingSum(int[] nums) {
+        int n = nums.length;
+        dp = new long[n][2];
+        for (int i = 0; i < n; i++) {
+            dp[i][0] = -1;
+            dp[i][1] = -1;
+        }
+        return dfs(nums, 0, 1);
+    }
+
+    private long dfs(int[] nums, int i, int even) {
+        if (i == nums.length) {
+            return 0;
+        }
+        if (dp[i][even] != -1) {
+            return dp[i][even];
+        }
+
+        long total = even == 1 ? nums[i] : -nums[i];
+        dp[i][even] = Math.max(total + dfs(nums, i + 1, 1 - even), dfs(nums, i + 1, even));
+        return dp[i][even];
+    }
+}
+```
+
+```cpp
+class Solution {
+    vector<vector<long long>> dp;
+
+public:
+    long long maxAlternatingSum(vector<int>& nums) {
+        dp.assign(nums.size(), vector<long long>(2, -1));
+        return dfs(nums, 0, true);
+    }
+
+private:
+    long long dfs(vector<int>& nums, int i, bool even) {
+        if (i == nums.size()) {
+            return 0;
+        }
+        if (dp[i][even] != -1) {
+            return dp[i][even];
+        }
+        long long total = even ? nums[i] : -nums[i];
+        dp[i][even] = max(total + dfs(nums, i + 1, !even), dfs(nums, i + 1, even));
+        return dp[i][even];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    maxAlternatingSum(nums) {
+        const n = nums.length;
+        const dp = Array.from({ length: n }, () => Array(2).fill(-1));
+
+        const dfs = (i, even) => {
+            if (i === n) {
+                return 0;
+            }
+            if (dp[i][even] !== -1) {
+                return dp[i][even];
+            }
+
+            const total = even === 1 ? nums[i] : -nums[i];
+            dp[i][even] = Math.max(total + dfs(i + 1, 1 - even), dfs(i + 1, even));
+            return dp[i][even];
+        };
+
+        return dfs(0, 1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxAlternatingSum(self, nums: List[int]) -> int:
+        n = len(nums)
+        dp = [[0] * 2 for _ in range(n + 1)]  # dp[i][0] -> odd, dp[i][1] -> even
+
+        for i in range(n - 1, -1, -1):
+            dp[i][1] = max(nums[i] + dp[i + 1][0], dp[i + 1][1])  # even
+            dp[i][0] = max(-nums[i] + dp[i + 1][1], dp[i + 1][0])  # odd
+
+        return dp[0][1]
+```
+
+```java
+public class Solution {
+    public long maxAlternatingSum(int[] nums) {
+        int n = nums.length;
+        long[][] dp = new long[n + 1][2]; // dp[i][0] -> odd, dp[i][1] -> even
+
+        for (int i = n - 1; i >= 0; i--) {
+            dp[i][1] = Math.max(nums[i] + dp[i + 1][0], dp[i + 1][1]); // even
+            dp[i][0] = Math.max(-nums[i] + dp[i + 1][1], dp[i + 1][0]); // odd
+        }
+
+        return dp[0][1];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long maxAlternatingSum(vector<int>& nums) {
+        int n = nums.size();
+        vector<vector<long long>> dp(n + 1, vector<long long>(2, 0)); // dp[i][0] -> odd, dp[i][1] -> even
+
+        for (int i = n - 1; i >= 0; i--) {
+            dp[i][1] = max(nums[i] + dp[i + 1][0], dp[i + 1][1]); // even
+            dp[i][0] = max(-nums[i] + dp[i + 1][1], dp[i + 1][0]); // odd
+        }
+
+        return dp[0][1];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    maxAlternatingSum(nums) {
+        const n = nums.length;
+        const dp = Array.from({ length: n + 1 }, () => [0, 0]); // dp[i][0] -> odd, dp[i][1] -> even
+
+        for (let i = n - 1; i >= 0; i--) {
+            dp[i][1] = Math.max(nums[i] + dp[i + 1][0], dp[i + 1][1]); // even
+            dp[i][0] = Math.max(-nums[i] + dp[i + 1][1], dp[i + 1][0]); // odd
+        }
+
+        return dp[0][1]; // Result starts with even index
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxAlternatingSum(self, nums: List[int]) -> int:
+        sumEven = sumOdd = 0
+
+        for i in range(len(nums) - 1, -1, -1):
+            tmpEven = max(sumOdd + nums[i], sumEven)
+            tmpOdd = max(sumEven - nums[i], sumOdd)
+            sumEven, sumOdd = tmpEven, tmpOdd
+        
+        return sumEven
+```
+
+```java
+public class Solution {
+    public long maxAlternatingSum(int[] nums) {
+        long sumEven = 0, sumOdd = 0;
+
+        for (int i = nums.length - 1; i >= 0; i--) {
+            long tmpEven = Math.max(nums[i] + sumOdd, sumEven);
+            long tmpOdd = Math.max(-nums[i] + sumEven, sumOdd);
+            sumEven = tmpEven;
+            sumOdd = tmpOdd;
+        }
+
+        return sumEven;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long maxAlternatingSum(vector<int>& nums) {
+        long long sumEven = 0, sumOdd = 0;
+
+        for (int i = nums.size() - 1; i >= 0; i--) {
+            long long tmpEven = max(nums[i] + sumOdd, sumEven);
+            long long tmpOdd = max(-nums[i] + sumEven, sumOdd);
+            sumEven = tmpEven;
+            sumOdd = tmpOdd;
+        }
+
+        return sumEven;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    maxAlternatingSum(nums) {
+        let sumEven = 0, sumOdd = 0;
+
+        for (let i = nums.length - 1; i >= 0; i--) {
+            let tmpEven = Math.max(nums[i] + sumOdd, sumEven);
+            let tmpOdd = Math.max(-nums[i] + sumEven, sumOdd);
+            sumEven = tmpEven;
+            sumOdd = tmpOdd;
+        }
+
+        return sumEven;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/maximum-ascending-subarray-sum.md b/articles/maximum-ascending-subarray-sum.md
new file mode 100644
index 000000000..5d4e47a60
--- /dev/null
+++ b/articles/maximum-ascending-subarray-sum.md
@@ -0,0 +1,173 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def maxAscendingSum(self, nums: List[int]) -> int:
+        res = 0
+        for i in range(len(nums)):
+            curSum = nums[i]
+            for j in range(i + 1, len(nums)):
+                if nums[j] <= nums[j - 1]:
+                    break
+                curSum += nums[j]
+            res = max(res, curSum)
+        return res
+```
+
+```java
+public class Solution {
+    public int maxAscendingSum(int[] nums) {
+        int res = 0;
+        for (int i = 0; i < nums.length; i++) {
+            int curSum = nums[i];
+            for (int j = i + 1; j < nums.length; j++) {
+                if (nums[j] <= nums[j - 1]) {
+                    break;
+                }
+                curSum += nums[j];
+            }
+            res = Math.max(res, curSum);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxAscendingSum(vector<int>& nums) {
+        int res = 0;
+        for (int i = 0; i < nums.size(); i++) {
+            int curSum = nums[i];
+            for (int j = i + 1; j < nums.size(); j++) {
+                if (nums[j] <= nums[j - 1]) {
+                    break;
+                }
+                curSum += nums[j];
+            }
+            res = max(res, curSum);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    maxAscendingSum(nums) {
+        let res = 0;
+        for (let i = 0; i < nums.length; i++) {
+            let curSum = nums[i];
+            for (let j = i + 1; j < nums.length; j++) {
+                if (nums[j] <= nums[j - 1]) {
+                    break;
+                }
+                curSum += nums[j];
+            }
+            res = Math.max(res, curSum);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Iteration
+
+::tabs-start
+
+```python
+class Solution:
+    def maxAscendingSum(self, nums: List[int]) -> int:
+        res = curSum= nums[0]
+
+        for i in range(1, len(nums)):
+            if nums[i] <= nums[i - 1]:
+                curSum = 0
+
+            curSum += nums[i]
+            res = max(res, curSum)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int maxAscendingSum(int[] nums) {
+        int res = nums[0], curSum = nums[0];
+
+        for (int i = 1; i < nums.length; i++) {
+            if (nums[i] <= nums[i - 1]) {
+                curSum = 0;
+            }
+            curSum += nums[i];
+            res = Math.max(res, curSum);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxAscendingSum(vector<int>& nums) {
+        int res = nums[0], curSum = nums[0];
+
+        for (int i = 1; i < nums.size(); i++) {
+            if (nums[i] <= nums[i - 1]) {
+                curSum = 0;
+            }
+            curSum += nums[i];
+            res = max(res, curSum);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    maxAscendingSum(nums) {
+        let res = nums[0], curSum = nums[0];
+
+        for (let i = 1; i < nums.length; i++) {
+            if (nums[i] <= nums[i - 1]) {
+                curSum = 0;
+            }
+            curSum += nums[i];
+            res = Math.max(res, curSum);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/maximum-element-after-decreasing-and-rearranging.md b/articles/maximum-element-after-decreasing-and-rearranging.md
new file mode 100644
index 000000000..b7c01b0db
--- /dev/null
+++ b/articles/maximum-element-after-decreasing-and-rearranging.md
@@ -0,0 +1,158 @@
+## 1. Greedy + Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def maximumElementAfterDecrementingAndRearranging(self, arr: List[int]) -> int:
+        arr.sort()
+        prev = 0
+        for num in arr:
+            prev = min(prev + 1, num)
+        return prev
+```
+
+```java
+public class Solution {
+    public int maximumElementAfterDecrementingAndRearranging(int[] arr) {
+        Arrays.sort(arr);
+        int prev = 0;
+        for (int num : arr) {
+            prev = Math.min(prev + 1, num);
+        }
+        return prev;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maximumElementAfterDecrementingAndRearranging(vector<int>& arr) {
+        sort(arr.begin(), arr.end());
+        int prev = 0;
+        for (int num : arr) {
+            prev = min(prev + 1, num);
+        }
+        return prev;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @return {number}
+     */
+    maximumElementAfterDecrementingAndRearranging(arr) {
+        arr.sort((a, b) => a - b);
+        let prev = 0;
+        for (let num of arr) {
+            prev = Math.min(prev + 1, num);
+        }
+        return prev;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 2. Greedy
+
+::tabs-start
+
+```python
+class Solution:
+    def maximumElementAfterDecrementingAndRearranging(self, arr: List[int]) -> int:
+        n = len(arr)
+        count = [0] * (n + 1)
+
+        for num in arr:
+            count[min(num, n)] += 1
+
+        prev = 1
+        for num in range(2, n + 1):
+            prev = min(prev + count[num], num)
+
+        return prev
+```
+
+```java
+public class Solution {
+    public int maximumElementAfterDecrementingAndRearranging(int[] arr) {
+        int n = arr.length;
+        int[] count = new int[n + 1];
+
+        for (int num : arr) {
+            count[Math.min(num, n)]++;
+        }
+
+        int prev = 1;
+        for (int num = 2; num <= n; num++) {
+            prev = Math.min(prev + count[num], num);
+        }
+
+        return prev;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maximumElementAfterDecrementingAndRearranging(vector<int>& arr) {
+        int n = arr.size();
+        vector<int> count(n + 1, 0);
+
+        for (int num : arr) {
+            count[min(num, n)]++;
+        }
+
+        int prev = 1;
+        for (int num = 2; num <= n; num++) {
+            prev = min(prev + count[num], num);
+        }
+
+        return prev;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @return {number}
+     */
+    maximumElementAfterDecrementingAndRearranging(arr) {
+        let n = arr.length;
+        let count = new Array(n + 1).fill(0);
+
+        for (let num of arr) {
+            count[Math.min(num, n)]++;
+        }
+
+        let prev = 1;
+        for (let num = 2; num <= n; num++) {
+            prev = Math.min(prev + count[num], num);
+        }
+
+        return prev;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/maximum-frequency-stack.md b/articles/maximum-frequency-stack.md
new file mode 100644
index 000000000..317e2546c
--- /dev/null
+++ b/articles/maximum-frequency-stack.md
@@ -0,0 +1,525 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class FreqStack:
+
+    def __init__(self):
+        self.cnt = defaultdict(int)
+        self.stack = []
+
+    def push(self, val: int) -> None:
+        self.stack.append(val)
+        self.cnt[val] += 1
+
+    def pop(self) -> int:
+        maxCnt = max(self.cnt.values())
+        i = len(self.stack) - 1
+        while self.cnt[self.stack[i]] != maxCnt:
+            i -= 1
+        self.cnt[self.stack[i]] -= 1
+        return self.stack.pop(i)
+```
+
+```java
+public class FreqStack {
+    private Map<Integer, Integer> cnt;
+    private List<Integer> stack;
+
+    public FreqStack() {
+        cnt = new HashMap<>();
+        stack = new ArrayList<>();
+    }
+
+    public void push(int val) {
+        stack.add(val);
+        cnt.put(val, cnt.getOrDefault(val, 0) + 1);
+    }
+
+    public int pop() {
+        int maxCnt = Collections.max(cnt.values());
+        int i = stack.size() - 1;
+        while (cnt.get(stack.get(i)) != maxCnt) {
+            i--;
+        }
+        int val = stack.remove(i);
+        cnt.put(val, cnt.get(val) - 1);
+        return val;
+    }
+}
+```
+
+```cpp
+class FreqStack {
+private:
+    unordered_map<int, int> cnt;
+    vector<int> stack;
+
+public:
+    FreqStack() {}
+
+    void push(int val) {
+        stack.push_back(val);
+        cnt[val]++;
+    }
+
+    int pop() {
+        int maxCnt = 0;
+        for (auto& [_, frequency] : cnt) {
+            maxCnt = max(maxCnt, frequency);
+        }
+        int i = stack.size() - 1;
+        while (cnt[stack[i]] != maxCnt) {
+            i--;
+        }
+        int val = stack[i];
+        stack.erase(stack.begin() + i);
+        cnt[val]--;
+        return val;
+    }
+};
+```
+
+```javascript
+class FreqStack {
+    constructor() {
+        this.cnt = new Map();
+        this.stack = [];
+    }
+
+    /** 
+     * @param {number} val
+     * @return {void}
+     */
+    push(val) {
+        this.stack.push(val);
+        this.cnt.set(val, (this.cnt.get(val) || 0) + 1);
+    }
+
+    /**
+     * @return {number}
+     */
+    pop() {
+        const maxCnt = Math.max(...this.cnt.values());
+        let i = this.stack.length - 1;
+        while (this.cnt.get(this.stack[i]) !== maxCnt) {
+            i--;
+        }
+        const val = this.stack.splice(i, 1)[0];
+        this.cnt.set(val, this.cnt.get(val) - 1);
+        return val;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(1)$ time for each $push()$ function call.
+    * $O(n)$ time for each $pop()$ function call.
+* Space complexity: $O(n)$
+
+> Where $n$ is the number of elements in the stack.
+
+---
+
+## 2. Heap
+
+::tabs-start
+
+```python
+class FreqStack:
+    
+    def __init__(self):
+        self.heap = []
+        self.cnt = defaultdict(int)
+        self.index = 0
+
+    def push(self, val: int) -> None:
+        self.cnt[val] += 1
+        heapq.heappush(self.heap, (-self.cnt[val], -self.index, val))
+        self.index += 1
+
+    def pop(self) -> int:
+        _, _, val = heapq.heappop(self.heap)
+        self.cnt[val] -= 1
+        return val
+```
+
+```java
+public class FreqStack {
+    private PriorityQueue<int[]> heap;
+    private Map<Integer, Integer> cnt;
+    private int index;
+
+    public FreqStack() {
+        heap = new PriorityQueue<>((a, b) -> 
+            a[0] != b[0] ? Integer.compare(b[0], a[0]) : Integer.compare(b[1], a[1])
+        );
+        cnt = new HashMap<>();
+        index = 0;
+    }
+
+    public void push(int val) {
+        cnt.put(val, cnt.getOrDefault(val, 0) + 1);
+        heap.offer(new int[]{cnt.get(val), index++, val});
+    }
+
+    public int pop() {
+        int[] top = heap.poll();
+        int val = top[2];
+        cnt.put(val, cnt.get(val) - 1);
+        return val;
+    }
+}
+```
+
+```cpp
+class FreqStack {
+private:
+    priority_queue<vector<int>> heap; // {frequency, index, value}
+    unordered_map<int, int> cnt;
+    int index;
+
+public:
+    FreqStack() : index(0) {}
+
+    void push(int val) {
+        cnt[val]++;
+        heap.push({cnt[val], index++, val});
+    }
+
+    int pop() {
+        auto top = heap.top();
+        heap.pop();
+        int val = top[2];
+        cnt[val]--;
+        return val;
+    }
+};
+```
+
+```javascript
+class FreqStack {
+    constructor() {
+        this.heap = new MaxPriorityQueue({
+            priority: (element) => element[0] * 100000 + element[1],
+        });
+        this.cnt = new Map();
+        this.index = 0;
+    }
+
+    /** 
+     * @param {number} val
+     * @return {void}
+     */
+    push(val) {
+        this.cnt.set(val, (this.cnt.get(val) || 0) + 1);
+        this.heap.enqueue([this.cnt.get(val), this.index++, val]);
+    }
+
+    /**
+     * @return {number}
+     */
+    pop() {
+        const [, , val] = this.heap.dequeue().element;
+        this.cnt.set(val, this.cnt.get(val) - 1);
+        return val;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(\log n)$ time for each $push()$ function call.
+    * $O(\log n)$ time for each $pop()$ function call.
+* Space complexity: $O(n)$
+
+> Where $n$ is the number of elements in the stack.
+
+---
+
+## 3. Stack Of Stacks (Hash Map)
+
+::tabs-start
+
+```python
+class FreqStack:
+
+    def __init__(self):
+        self.cnt = {}
+        self.maxCnt = 0
+        self.stacks = {}
+
+    def push(self, val: int) -> None:
+        valCnt = 1 + self.cnt.get(val, 0)
+        self.cnt[val] = valCnt
+        if valCnt > self.maxCnt:
+            self.maxCnt = valCnt
+            self.stacks[valCnt] = []
+        self.stacks[valCnt].append(val)
+
+    def pop(self) -> int:
+        res = self.stacks[self.maxCnt].pop()
+        self.cnt[res] -= 1
+        if not self.stacks[self.maxCnt]:
+            self.maxCnt -= 1
+        return res
+```
+
+```java
+class FreqStack {
+    private Map<Integer, Integer> cnt;
+    private Map<Integer, Stack<Integer>> stacks;
+    private int maxCnt;
+
+    public FreqStack() {
+        cnt = new HashMap<>();
+        stacks = new HashMap<>();
+        maxCnt = 0;
+    }
+
+    public void push(int val) {
+        int valCnt = cnt.getOrDefault(val, 0) + 1;
+        cnt.put(val, valCnt);
+        if (valCnt > maxCnt) {
+            maxCnt = valCnt;
+            stacks.putIfAbsent(valCnt, new Stack<>());
+        }
+        stacks.get(valCnt).push(val);
+    }
+
+    public int pop() {
+        int res = stacks.get(maxCnt).pop();
+        cnt.put(res, cnt.get(res) - 1);
+        if (stacks.get(maxCnt).isEmpty()) {
+            maxCnt--;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class FreqStack {
+public:
+    unordered_map<int, int> cnt;
+    unordered_map<int, stack<int>> stacks;
+    int maxCnt;
+
+    FreqStack() {
+        maxCnt = 0;
+    }
+
+    void push(int val) {
+        int valCnt = ++cnt[val];
+        if (valCnt > maxCnt) {
+            maxCnt = valCnt;
+            stacks[valCnt] = stack<int>();
+        }
+        stacks[valCnt].push(val);
+    }
+
+    int pop() {
+        int res = stacks[maxCnt].top();
+        stacks[maxCnt].pop();
+        cnt[res]--;
+        if (stacks[maxCnt].empty()) {
+            maxCnt--;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class FreqStack {
+    constructor() {
+        this.cnt = new Map();
+        this.stacks = new Map();
+        this.maxCnt = 0;
+    }
+
+    /** 
+     * @param {number} val
+     * @return {void}
+     */
+    push(val) {
+        const valCnt = (this.cnt.get(val) || 0) + 1;
+        this.cnt.set(val, valCnt);
+        if (valCnt > this.maxCnt) {
+            this.maxCnt = valCnt;
+            if (!this.stacks.has(valCnt)) {
+                this.stacks.set(valCnt, []);
+            }
+        }
+        this.stacks.get(valCnt).push(val);
+    }
+
+    /**
+     * @return {number}
+     */
+    pop() {
+        const res = this.stacks.get(this.maxCnt).pop();
+        this.cnt.set(res, this.cnt.get(res) - 1);
+        if (this.stacks.get(this.maxCnt).length === 0) {
+            this.maxCnt--;
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(1)$ time for each $push()$ function call.
+    * $O(1)$ time for each $pop()$ function call.
+* Space complexity: $O(n)$
+
+> Where $n$ is the number of elements in the stack.
+
+---
+
+## 4. Stack Of Stacks (Dynamic Array)
+
+::tabs-start
+
+```python
+class FreqStack:
+
+    def __init__(self):
+        self.cnt = {}
+        self.stacks = [[]]
+
+    def push(self, val: int) -> None:
+        valCnt = 1 + self.cnt.get(val, 0)
+        self.cnt[val] = valCnt
+        if valCnt == len(self.stacks):
+            self.stacks.append([])
+        self.stacks[valCnt].append(val)
+
+    def pop(self) -> int:
+        res = self.stacks[-1].pop()
+        self.cnt[res] -= 1
+        if not self.stacks[-1]:
+            self.stacks.pop()
+        return res
+```
+
+```java
+public class FreqStack {
+    private Map<Integer, Integer> cnt;
+    private List<Stack<Integer>> stacks;
+
+    public FreqStack() {
+        cnt = new HashMap<>();
+        stacks = new ArrayList<>();
+        stacks.add(new Stack<>());
+    }
+
+    public void push(int val) {
+        int valCnt = cnt.getOrDefault(val, 0) + 1;
+        cnt.put(val, valCnt);
+        if (valCnt == stacks.size()) {
+            stacks.add(new Stack<>());
+        }
+        stacks.get(valCnt).push(val);
+    }
+
+    public int pop() {
+        Stack<Integer> topStack = stacks.get(stacks.size() - 1);
+        int res = topStack.pop();
+        cnt.put(res, cnt.get(res) - 1);
+        if (topStack.isEmpty()) {
+            stacks.remove(stacks.size() - 1);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class FreqStack {
+public:
+    unordered_map<int, int> cnt;
+    vector<stack<int>> stacks;
+
+    FreqStack() {
+        stacks.push_back(stack<int>());
+    }
+
+    void push(int val) {
+        int valCnt = ++cnt[val];
+        if (valCnt == stacks.size()) {
+            stacks.push_back(stack<int>());
+        }
+        stacks[valCnt].push(val);
+    }
+
+    int pop() {
+        stack<int>& topStack = stacks.back();
+        int res = topStack.top();
+        topStack.pop();
+        if (topStack.empty()) {
+            stacks.pop_back();
+        }
+        cnt[res]--;
+        return res;
+    }
+};
+```
+
+```javascript
+class FreqStack {
+    constructor() {
+        this.cnt = new Map();
+        this.stacks = [[]];
+    }
+
+    /** 
+     * @param {number} val
+     * @return {void}
+     */
+    push(val) {
+        const valCnt = (this.cnt.get(val) || 0) + 1;
+        this.cnt.set(val, valCnt);
+        if (valCnt === this.stacks.length) {
+            this.stacks.push([]);
+        }
+        this.stacks[valCnt].push(val);
+    }
+
+    /**
+     * @return {number}
+     */
+    pop() {
+        const topStack = this.stacks[this.stacks.length - 1];
+        const res = topStack.pop();
+        this.cnt.set(res, this.cnt.get(res) - 1);
+        if (topStack.length === 0) {
+            this.stacks.pop();
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(1)$ time for each $push()$ function call.
+    * $O(1)$ time for each $pop()$ function call.
+* Space complexity: $O(n)$
+
+> Where $n$ is the number of elements in the stack.
\ No newline at end of file
diff --git a/articles/maximum-length-of-a-concatenated-string-with-unique-characters.md b/articles/maximum-length-of-a-concatenated-string-with-unique-characters.md
new file mode 100644
index 000000000..f8cdea423
--- /dev/null
+++ b/articles/maximum-length-of-a-concatenated-string-with-unique-characters.md
@@ -0,0 +1,857 @@
+## 1. Backtracking (Hash Set)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxLength(self, arr: List[str]) -> int:
+        charSet = set()
+
+        def overlap(charSet, s):
+            prev = set()
+            for c in s:
+                if c in charSet or c in prev:
+                    return True
+                prev.add(c)
+            return False
+
+        def backtrack(i):
+            if i == len(arr):
+                return len(charSet)
+
+            res = 0
+            if not overlap(charSet, arr[i]):
+                for c in arr[i]:
+                    charSet.add(c)
+                res = backtrack(i + 1)
+                for c in arr[i]:
+                    charSet.remove(c)
+
+            return max(res, backtrack(i + 1))
+
+        return backtrack(0)
+```
+
+```java
+public class Solution {
+    public int maxLength(List<String> arr) {
+        Set<Character> charSet = new HashSet<>();
+        return backtrack(0, arr, charSet);
+    }
+
+    private boolean overlap(Set<Character> charSet, String s) {
+        Set<Character> prev = new HashSet<>();
+        for (char c : s.toCharArray()) {
+            if (charSet.contains(c) || prev.contains(c)) {
+                return true;
+            }
+            prev.add(c);
+        }
+        return false;
+    }
+
+    private int backtrack(int i, List<String> arr, Set<Character> charSet) {
+        if (i == arr.size()) {
+            return charSet.size();
+        }
+
+        int res = 0;
+        if (!overlap(charSet, arr.get(i))) {
+            for (char c : arr.get(i).toCharArray()) {
+                charSet.add(c);
+            }
+            res = backtrack(i + 1, arr, charSet);
+            for (char c : arr.get(i).toCharArray()) {
+                charSet.remove(c);
+            }
+        }
+
+        return Math.max(res, backtrack(i + 1, arr, charSet));
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxLength(vector<string>& arr) {
+        unordered_set<char> charSet;
+        return backtrack(0, arr, charSet);
+    }
+
+private:
+    bool overlap(unordered_set<char>& charSet, const string& s) {
+        unordered_set<char> prev;
+        for (char c : s) {
+            if (charSet.count(c) || prev.count(c)) {
+                return true;
+            }
+            prev.insert(c);
+        }
+        return false;
+    }
+
+    int backtrack(int i, vector<string>& arr, unordered_set<char>& charSet) {
+        if (i == arr.size()) {
+            return charSet.size();
+        }
+
+        int res = 0;
+        if (!overlap(charSet, arr[i])) {
+            for (char c : arr[i]) {
+                charSet.insert(c);
+            }
+            res = backtrack(i + 1, arr, charSet);
+            for (char c : arr[i]) {
+                charSet.erase(c);
+            }
+        }
+
+        return max(res, backtrack(i + 1, arr, charSet));
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} arr
+     * @return {number}
+     */
+    maxLength(arr) {
+        let charSet = new Set();
+
+        const overlap = (charSet, s) => {
+            let prev = new Set();
+            for (const c of s) {
+                if (charSet.has(c) || prev.has(c)) {
+                    return true;
+                }
+                prev.add(c);
+            }
+            return false;
+        };
+
+        const backtrack = (i) => {
+            if (i === arr.length) {
+                return charSet.size;
+            }
+
+            let res = 0;
+            if (!overlap(charSet, arr[i])) {
+                for (const c of arr[i]) {
+                    charSet.add(c);
+                }
+                res = backtrack(i + 1);
+                for (const c of arr[i]) {
+                    charSet.delete(c);
+                }
+            }
+
+            return Math.max(res, backtrack(i + 1));
+        };
+
+        return backtrack(0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * 2 ^ n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+> Where $n$ is the number of strings and $m$ is the maximum length of a string.
+
+---
+
+## 2. Backtracking (Boolean Array)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxLength(self, arr: List[str]) -> int:
+        charSet = [False] * 26
+
+        def getIdx(c):
+            return ord(c) - ord('a')
+
+        def overlap(charSet, s):
+            for i in range(len(s)):
+                c = getIdx(s[i])
+                if charSet[c]:
+                    for j in range(i):
+                        charSet[getIdx(s[j])] = False
+                    return True
+                charSet[c] = True
+            return False
+
+        def backtrack(i):
+            if i == len(arr):
+                return 0
+
+            res = 0
+            if not overlap(charSet, arr[i]):
+                res = len(arr[i]) + backtrack(i + 1)
+                for c in arr[i]:
+                    charSet[getIdx(c)] = False
+            return max(res, backtrack(i + 1))
+
+        return backtrack(0)
+```
+
+```java
+public class Solution {
+    public int maxLength(List<String> arr) {
+        boolean[] charSet = new boolean[26];
+        return backtrack(0, arr, charSet);
+    }
+
+    private int getIdx(char c) {
+        return c - 'a';
+    }
+
+    private boolean overlap(boolean[] charSet, String s) {
+        for (int i = 0; i < s.length(); i++) {
+            int c = getIdx(s.charAt(i));
+            if (charSet[c]) {
+                for (int j = 0; j < i; j++) {
+                    charSet[getIdx(s.charAt(j))] = false;
+                }
+                return true;
+            }
+            charSet[c] = true;
+        }
+        return false;
+    }
+
+    private int backtrack(int i, List<String> arr, boolean[] charSet) {
+        if (i == arr.size()) {
+            return 0;
+        }
+
+        int res = 0;
+        if (!overlap(charSet, arr.get(i))) {
+            res = arr.get(i).length() + backtrack(i + 1, arr, charSet);
+            for (char c : arr.get(i).toCharArray()) {
+                charSet[getIdx(c)] = false;
+            }
+        }
+        return Math.max(res, backtrack(i + 1, arr, charSet));
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxLength(vector<string>& arr) {
+        bool charSet[26] = {false};
+        return backtrack(0, arr, charSet);
+    }
+
+private:
+    int getIdx(char c) {
+        return c - 'a';
+    }
+
+    bool overlap(bool charSet[], const string& s) {
+        for (int i = 0; i < s.length(); i++) {
+            int c = getIdx(s[i]);
+            if (charSet[c]) {
+                for (int j = 0; j < i; j++) {
+                    charSet[getIdx(s[j])] = false;
+                }
+                return true;
+            }
+            charSet[c] = true;
+        }
+        return false;
+    }
+
+    int backtrack(int i, vector<string>& arr, bool charSet[]) {
+        if (i == arr.size()) {
+            return 0;
+        }
+
+        int res = 0;
+        if (!overlap(charSet, arr[i])) {
+            res = arr[i].length() + backtrack(i + 1, arr, charSet);
+            for (char c : arr[i]) {
+                charSet[getIdx(c)] = false;
+            }
+        }
+        return max(res, backtrack(i + 1, arr, charSet));
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} arr
+     * @return {number}
+     */
+    maxLength(arr) {
+        let charSet = new Array(26).fill(false);
+
+        const getIdx = (c) => c.charCodeAt(0) - 'a'.charCodeAt(0);
+
+        const overlap = (charSet, s) => {
+            for (let i = 0; i < s.length; i++) {
+                let c = getIdx(s[i]);
+                if (charSet[c]) {
+                    for (let j = 0; j < i; j++) {
+                        charSet[getIdx(s[j])] = false;
+                    }
+                    return true;
+                }
+                charSet[c] = true;
+            }
+            return false;
+        };
+
+        const backtrack = (i) => {
+            if (i === arr.length) {
+                return 0;
+            }
+
+            let res = 0;
+            if (!overlap(charSet, arr[i])) {
+                res = arr[i].length + backtrack(i + 1);
+                for (const c of arr[i]) {
+                    charSet[getIdx(c)] = false;
+                }
+            }
+            return Math.max(res, backtrack(i + 1));
+        };
+
+        return backtrack(0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * 2 ^ n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+> Where $n$ is the number of strings and $m$ is the maximum length of a string.
+
+---
+
+## 3. Recursion (Bit Mask) - I
+
+::tabs-start
+
+```python
+class Solution:
+    def maxLength(self, arr: List[str]) -> int:
+        def getIdx(c):
+            return ord(c) - ord('a')
+
+        A = []
+        for s in arr:
+            cur = 0
+            valid = True
+            for c in s:
+                if cur & (1 << getIdx(c)):
+                    valid = False
+                    break
+                cur |= (1 << getIdx(c))
+
+            if valid:
+                A.append([cur, len(s)])
+
+        def dfs(i, subSeq):
+            if i == len(A):
+                return 0
+
+            res = dfs(i + 1, subSeq)
+
+            curSeq, length = A[i][0], A[i][1]
+            if (subSeq & curSeq) == 0:
+                res = max(res, length + dfs(i + 1, subSeq | curSeq))
+            return res
+
+        return dfs(0, 0)
+```
+
+```java
+public class Solution {
+    public int maxLength(List<String> arr) {
+        List<int[]> A = new ArrayList<>();
+
+        for (String s : arr) {
+            int cur = 0;
+            boolean valid = true;
+
+            for (char c : s.toCharArray()) {
+                if ((cur & (1 << (c - 'a'))) != 0) {
+                    valid = false;
+                    break;
+                }
+                cur |= (1 << (c - 'a'));
+            }
+
+            if (valid) {
+                A.add(new int[]{cur, s.length()});
+            }
+        }
+
+        return dfs(0, 0, A);
+    }
+
+    private int dfs(int i, int subSeq, List<int[]> A) {
+        if (i == A.size()) {
+            return 0;
+        }
+
+        int res = dfs(i + 1, subSeq, A);
+
+        int curSeq = A.get(i)[0], length = A.get(i)[1];
+        if ((subSeq & curSeq) == 0) {
+            res = Math.max(res, length + dfs(i + 1, subSeq | curSeq, A));
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxLength(vector<string>& arr) {
+        vector<pair<int, int>> A;
+
+        for (const string& s : arr) {
+            int cur = 0;
+            bool valid = true;
+
+            for (char c : s) {
+                if (cur & (1 << (c - 'a'))) {
+                    valid = false;
+                    break;
+                }
+                cur |= (1 << (c - 'a'));
+            }
+
+            if (valid) {
+                A.emplace_back(cur, s.length());
+            }
+        }
+
+        return dfs(0, 0, A);
+    }
+
+private:
+    int dfs(int i, int subSeq, vector<pair<int, int>>& A) {
+        if (i == A.size()) {
+            return 0;
+        }
+
+        int res = dfs(i + 1, subSeq, A);
+
+        int curSeq = A[i].first, length = A[i].second;
+        if ((subSeq & curSeq) == 0) {
+            res = max(res, length + dfs(i + 1, subSeq | curSeq, A));
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} arr
+     * @return {number}
+     */
+    maxLength(arr) {
+        let A = [];
+
+        for (const s of arr) {
+            let cur = 0;
+            let valid = true;
+
+            for (const c of s) {
+                if (cur & (1 << (c.charCodeAt(0) - 97))) {
+                    valid = false;
+                    break;
+                }
+                cur |= (1 << (c.charCodeAt(0) - 97));
+            }
+
+            if (valid) {
+                A.push([cur, s.length]);
+            }
+        }
+
+        const dfs = (i, subSeq) => {
+            if (i === A.length) {
+                return 0;
+            }
+
+            let res = dfs(i + 1, subSeq);
+
+            let [curSeq, length] = A[i];
+            if ((subSeq & curSeq) === 0) {
+                res = Math.max(res, length + dfs(i + 1, subSeq | curSeq));
+            }
+            return res;
+        };
+
+        return dfs(0, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n + 2 ^ n)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the number of strings and $m$ is the maximum length of a string.
+
+---
+
+## 4. Recursion (Bit Mask) - II
+
+::tabs-start
+
+```python
+class Solution:
+    def maxLength(self, arr: List[str]) -> int:
+        def getIdx(c):
+            return ord(c) - ord('a')
+
+        A = []
+        for s in arr:
+            cur = 0
+            valid = True
+            for c in s:
+                if cur & (1 << getIdx(c)):
+                    valid = False
+                    break
+                cur |= (1 << getIdx(c))
+
+            if valid:
+                A.append([cur, len(s)])
+
+        def dfs(i, subSeq):
+            res = 0
+            for j in range(i, len(A)):
+                curSeq, length = A[j][0], A[j][1]
+                if (subSeq & curSeq) == 0:
+                    res = max(res, length + dfs(j + 1, subSeq | curSeq))
+            return res
+
+        return dfs(0, 0)
+```
+
+```java
+public class Solution {
+    public int maxLength(List<String> arr) {
+        List<int[]> A = new ArrayList<>();
+
+        for (String s : arr) {
+            int cur = 0;
+            boolean valid = true;
+
+            for (char c : s.toCharArray()) {
+                if ((cur & (1 << (c - 'a'))) != 0) {
+                    valid = false;
+                    break;
+                }
+                cur |= (1 << (c - 'a'));
+            }
+
+            if (valid) {
+                A.add(new int[]{cur, s.length()});
+            }
+        }
+
+        return dfs(0, 0, A);
+    }
+
+    private int dfs(int i, int subSeq, List<int[]> A) {
+        int res = 0;
+        for (int j = i; j < A.size(); j++) {
+            int curSeq = A.get(j)[0], length = A.get(j)[1];
+            if ((subSeq & curSeq) == 0) {
+                res = Math.max(res, length + dfs(j + 1, subSeq | curSeq, A));
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxLength(vector<string>& arr) {
+        vector<pair<int, int>> A;
+
+        for (const string& s : arr) {
+            int cur = 0;
+            bool valid = true;
+
+            for (char c : s) {
+                if (cur & (1 << (c - 'a'))) {
+                    valid = false;
+                    break;
+                }
+                cur |= (1 << (c - 'a'));
+            }
+
+            if (valid) {
+                A.emplace_back(cur, s.length());
+            }
+        }
+
+        return dfs(0, 0, A);
+    }
+
+private:
+    int dfs(int i, int subSeq, vector<pair<int, int>>& A) {
+        int res = 0;
+        for (int j = i; j < A.size(); j++) {
+            int curSeq = A[j].first, length = A[j].second;
+            if ((subSeq & curSeq) == 0) {
+                res = max(res, length + dfs(j + 1, subSeq | curSeq, A));
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} arr
+     * @return {number}
+     */
+    maxLength(arr) {
+        let A = [];
+
+        for (const s of arr) {
+            let cur = 0;
+            let valid = true;
+
+            for (const c of s) {
+                if (cur & (1 << (c.charCodeAt(0) - 97))) {
+                    valid = false;
+                    break;
+                }
+                cur |= (1 << (c.charCodeAt(0) - 97));
+            }
+
+            if (valid) {
+                A.push([cur, s.length]);
+            }
+        }
+
+        const dfs = (i, subSeq) => {
+            let res = 0;
+            for (let j = i; j < A.length; j++) {
+                let [curSeq, length] = A[j];
+                if ((subSeq & curSeq) === 0) {
+                    res = Math.max(res, length + dfs(j + 1, subSeq | curSeq));
+                }
+            }
+            return res;
+        };
+
+        return dfs(0, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * (m  + 2 ^ n))$
+* Space complexity: $O(n)$
+
+> Where $n$ is the number of strings and $m$ is the maximum length of a string.
+
+---
+
+## 5. Dynamic Programming
+
+::tabs-start
+
+```python
+class Solution:
+    def maxLength(self, arr: List[str]) -> int:
+        dp = {0}
+        res = 0
+
+        for s in arr:
+            cur = 0
+            valid = True
+
+            for c in s:
+                bit = 1 << (ord(c) - ord('a'))
+                if cur & bit:
+                    valid = False
+                    break
+                cur |= bit
+
+            if not valid:
+                continue
+
+            next_dp = dp.copy()
+            for seq in dp:
+                if (seq & cur) or (seq | cur) in dp:
+                    continue
+                next_dp.add(seq | cur)
+                res = max(res, bin(seq | cur).count('1'))
+            dp = next_dp
+
+        return res
+```
+
+```java
+public class Solution {
+    public int maxLength(List<String> arr) {
+        Set<Integer> dp = new HashSet<>();
+        dp.add(0);
+        int res = 0;
+
+        for (String s : arr) {
+            int cur = 0;
+            boolean valid = true;
+
+            for (char c : s.toCharArray()) {
+                int bit = 1 << (c - 'a');
+                if ((cur & bit) != 0) {
+                    valid = false;
+                    break;
+                }
+                cur |= bit;
+            }
+
+            if (!valid) {
+                continue;
+            }
+
+            Set<Integer> next_dp = new HashSet<>(dp);
+            for (int seq : dp) {
+                if ((seq & cur) != 0 || next_dp.contains(seq | cur)) {
+                    continue;
+                }
+                next_dp.add(seq | cur);
+                res = Math.max(res, Integer.bitCount(seq | cur));
+            }
+            dp = next_dp;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxLength(vector<string>& arr) {
+        unordered_set<int> dp;
+        dp.insert(0);
+        int res = 0;
+
+        for (const string& s : arr) {
+            int cur = 0;
+            bool valid = true;
+
+            for (char c : s) {
+                int bit = 1 << (c - 'a');
+                if (cur & bit) {
+                    valid = false;
+                    break;
+                }
+                cur |= bit;
+            }
+
+            if (!valid) {
+                continue;
+            }
+
+            unordered_set<int> next_dp(dp);
+            for (int seq : dp) {
+                if ((seq & cur) || next_dp.count(seq | cur)) {
+                    continue;
+                }
+                next_dp.insert(seq | cur);
+                res = max(res, __builtin_popcount(seq | cur));
+            }
+            dp = next_dp;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} arr
+     * @return {number}
+     */
+    maxLength(arr) {
+        let dp = new Set();
+        dp.add(0);
+        let res = 0;
+
+        for (const s of arr) {
+            let cur = 0;
+            let valid = true;
+
+            for (const c of s) {
+                let bit = 1 << (c.charCodeAt(0) - 97);
+                if (cur & bit) {
+                    valid = false;
+                    break;
+                }
+                cur |= bit;
+            }
+
+            if (!valid) {
+                continue;
+            }
+
+            let next_dp = new Set(dp);
+            for (let seq of dp) {
+                if ((seq & cur) || next_dp.has(seq | cur)) {
+                    continue;
+                }
+                next_dp.add(seq | cur);
+                res = Math.max(res, (seq | cur).toString(2).split('0').join('').length);
+            }
+            dp = next_dp;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * (m  + 2 ^ n))$
+* Space complexity: $O(2 ^ n)$
+
+> Where $n$ is the number of strings and $m$ is the maximum length of a string.
\ No newline at end of file
diff --git a/articles/maximum-length-of-pair-chain.md b/articles/maximum-length-of-pair-chain.md
new file mode 100644
index 000000000..2855ede51
--- /dev/null
+++ b/articles/maximum-length-of-pair-chain.md
@@ -0,0 +1,556 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def findLongestChain(self, pairs: List[List[int]]) -> int:
+        n = len(pairs)
+        pairs.sort(key=lambda x: x[1])
+
+        def dfs(i, j):
+            if i == n:
+                return 0
+
+            res = dfs(i + 1, j)
+            if j == -1 or pairs[j][1] < pairs[i][0]:
+                res = max(res, 1 + dfs(i + 1, i))
+
+            return res
+
+        return dfs(0, -1)
+```
+
+```java
+public class Solution {
+    public int findLongestChain(int[][] pairs) {
+        int n = pairs.length;
+        Arrays.sort(pairs, (a, b) -> Integer.compare(a[1], b[1]));
+        return dfs(pairs, 0, -1, n);
+    }
+
+    private int dfs(int[][] pairs, int i, int j, int n) {
+        if (i == n) {
+            return 0;
+        }
+
+        int res = dfs(pairs, i + 1, j, n);
+        if (j == -1 || pairs[j][1] < pairs[i][0]) {
+            res = Math.max(res, 1 + dfs(pairs, i + 1, i, n));
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findLongestChain(vector<vector<int>>& pairs) {
+        int n = pairs.size();
+        sort(pairs.begin(), pairs.end(), [](const auto& a, const auto& b) {
+            return a[1] < b[1];
+        });
+
+        return dfs(pairs, 0, -1, n);
+    }
+
+private:
+    int dfs(vector<vector<int>>& pairs, int i, int j, int n) {
+        if (i == n) {
+            return 0;
+        }
+
+        int res = dfs(pairs, i + 1, j, n);
+        if (j == -1 || pairs[j][1] < pairs[i][0]) {
+            res = max(res, 1 + dfs(pairs, i + 1, i, n));
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} pairs
+     * @return {number}
+     */
+    findLongestChain(pairs) {
+        pairs.sort((a, b) => a[1] - b[1]);
+        let n = pairs.length;
+
+        const dfs = (i, j) => {
+            if (i === n) {
+                return 0;
+            }
+
+            let res = dfs(i + 1, j);
+            if (j === -1 || pairs[j][1] < pairs[i][0]) {
+                res = Math.max(res, 1 + dfs(i + 1, i));
+            }
+
+            return res;
+        };
+
+        return dfs(0, -1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def findLongestChain(self, pairs: List[List[int]]) -> int:
+        n = len(pairs)
+        pairs.sort(key=lambda x: x[1])
+        dp = [[-1] * (n + 1) for _ in range(n)]
+
+        def dfs(i, j):
+            if i == n:
+                return 0
+            if dp[i][j + 1] != -1:
+                return dp[i][j + 1]
+
+            res = dfs(i + 1, j)
+            if j == -1 or pairs[j][1] < pairs[i][0]:
+                res = max(res, 1 + dfs(i + 1, i))
+            
+            dp[i][j + 1] = res
+            return res
+
+        return dfs(0, -1)
+```
+
+```java
+public class Solution {
+    private int[][] dp;
+
+    public int findLongestChain(int[][] pairs) {
+        int n = pairs.length;
+        Arrays.sort(pairs, (a, b) -> Integer.compare(a[1], b[1]));
+        dp = new int[n][n + 1];
+
+        for (int[] row : dp) {
+            Arrays.fill(row, -1);
+        }
+
+        return dfs(pairs, 0, -1, n);
+    }
+
+    private int dfs(int[][] pairs, int i, int j, int n) {
+        if (i == n) {
+            return 0;
+        }
+        if (dp[i][j + 1] != -1) {
+            return dp[i][j + 1];
+        }
+
+        int res = dfs(pairs, i + 1, j, n);
+        if (j == -1 || pairs[j][1] < pairs[i][0]) {
+            res = Math.max(res, 1 + dfs(pairs, i + 1, i, n));
+        }
+
+        dp[i][j + 1] = res;
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> dp;
+
+    int findLongestChain(vector<vector<int>>& pairs) {
+        int n = pairs.size();
+        sort(pairs.begin(), pairs.end(), [](const auto& a, const auto& b) {
+            return a[1] < b[1];
+        });
+
+        dp = vector<vector<int>>(n, vector<int>(n + 1, -1));
+        return dfs(pairs, 0, -1, n);
+    }
+
+private:
+    int dfs(vector<vector<int>>& pairs, int i, int j, int n) {
+        if (i == n) {
+            return 0;
+        }
+        if (dp[i][j + 1] != -1) {
+            return dp[i][j + 1];
+        }
+
+        int res = dfs(pairs, i + 1, j, n);
+        if (j == -1 || pairs[j][1] < pairs[i][0]) {
+            res = max(res, 1 + dfs(pairs, i + 1, i, n));
+        }
+
+        dp[i][j + 1] = res;
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} pairs
+     * @return {number}
+     */
+    findLongestChain(pairs) {
+        pairs.sort((a, b) => a[1] - b[1]);
+        let n = pairs.length;
+        let dp = Array.from({ length: n }, () => new Array(n + 1).fill(-1));
+
+        const dfs = (i, j) => {
+            if (i === n) {
+                return 0;
+            }
+            if (dp[i][j + 1] !== -1) {
+                return dp[i][j + 1];
+            }
+
+            let res = dfs(i + 1, j);
+            if (j === -1 || pairs[j][1] < pairs[i][0]) {
+                res = Math.max(res, 1 + dfs(i + 1, i));
+            }
+
+            dp[i][j + 1] = res;
+            return res;
+        };
+
+        return dfs(0, -1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def findLongestChain(self, pairs: List[List[int]]) -> int:
+        n = len(pairs)
+        pairs.sort(key=lambda x: x[1])
+        dp = [1] * n  
+
+        for i in range(n):
+            for j in range(i):
+                if pairs[j][1] < pairs[i][0]:
+                    dp[i] = max(dp[i], dp[j] + 1)
+
+        return max(dp)
+```
+
+```java
+public class Solution {
+    public int findLongestChain(int[][] pairs) {
+        int n = pairs.length;
+        Arrays.sort(pairs, (a, b) -> Integer.compare(a[1], b[1]));
+        int[] dp = new int[n];
+        Arrays.fill(dp, 1);
+
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < i; j++) {
+                if (pairs[j][1] < pairs[i][0]) {
+                    dp[i] = Math.max(dp[i], dp[j] + 1);
+                }
+            }
+        }
+
+        return Arrays.stream(dp).max().getAsInt();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findLongestChain(vector<vector<int>>& pairs) {
+        int n = pairs.size();
+        sort(pairs.begin(), pairs.end(), [](const auto& a, const auto& b) {
+            return a[1] < b[1];
+        });
+
+        vector<int> dp(n, 1);
+
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < i; j++) {
+                if (pairs[j][1] < pairs[i][0]) {
+                    dp[i] = max(dp[i], dp[j] + 1);
+                }
+            }
+        }
+
+        return *max_element(dp.begin(), dp.end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} pairs
+     * @return {number}
+     */
+    findLongestChain(pairs) {
+        let n = pairs.length;
+        pairs.sort((a, b) => a[1] - b[1]);
+        let dp = new Array(n).fill(1);
+
+        for (let i = 0; i < n; i++) {
+            for (let j = 0; j < i; j++) {
+                if (pairs[j][1] < pairs[i][0]) {
+                    dp[i] = Math.max(dp[i], dp[j] + 1);
+                }
+            }
+        }
+
+        return Math.max(...dp);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Dynamic Programming (Bianry Search)
+
+::tabs-start
+
+```python
+class Solution:
+    def findLongestChain(self, pairs: List[List[int]]) -> int:
+        pairs.sort(key=lambda x: x[0])
+        dp = []
+
+        for a, b in pairs:
+            pos = bisect_left(dp, a)
+            if pos == len(dp):
+                dp.append(b)
+            else:
+                dp[pos] = min(dp[pos], b)
+
+        return len(dp)
+```
+
+```java
+public class Solution {
+    public int findLongestChain(int[][] pairs) {
+        Arrays.sort(pairs, Comparator.comparingInt(a -> a[0]));
+        List<Integer> dp = new ArrayList<>();
+
+        for (int[] pair : pairs) {
+            int pos = binarySearch(dp, pair[0]);
+            if (pos == dp.size()) {
+                dp.add(pair[1]);
+            } else {
+                dp.set(pos, Math.min(dp.get(pos), pair[1]));
+            }
+        }
+
+        return dp.size();
+    }
+
+    private int binarySearch(List<Integer> dp, int target) {
+        int left = 0, right = dp.size() - 1;
+        while (left <= right) {
+            int mid = left + (right - left) / 2;
+            if (dp.get(mid) < target) {
+                left = mid + 1;
+            } else {
+                right = mid - 1;
+            }
+        }
+        return left;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findLongestChain(vector<vector<int>>& pairs) {
+        sort(pairs.begin(), pairs.end());
+        vector<int> dp;
+
+        for (auto& pair : pairs) {
+            auto it = lower_bound(dp.begin(), dp.end(), pair[0]);
+            if (it == dp.end()) {
+                dp.push_back(pair[1]);
+            } else {
+                *it = min(*it, pair[1]);
+            }
+        }
+
+        return dp.size();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} pairs
+     * @return {number}
+     */
+    findLongestChain(pairs) {
+        pairs.sort((a, b) => a[0] - b[0]);
+        let dp = [];
+
+        const binarySearch = (target) => {
+            let left = 0, right = dp.length - 1;
+            while (left <= right) {
+                let mid = Math.floor((left + right) / 2);
+                if (dp[mid] < target) {
+                    left = mid + 1;
+                } else {
+                    right = mid - 1;
+                }
+            }
+            return left;
+        };
+
+        for (let i = 0; i < pairs.length; i++) {
+            let pos = binarySearch(pairs[i][0]);
+            if (pos === dp.length) {
+                dp.push(pairs[i][1]);
+            } else {
+                dp[pos] = Math.min(dp[pos], pairs[i][1]);
+            }
+        }
+
+        return dp.length;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 5. Greedy
+
+::tabs-start
+
+```python
+class Solution:
+    def findLongestChain(self, pairs: List[List[int]]) -> int:
+        pairs.sort(key=lambda p: p[1])
+        length = 1
+        end = pairs[0][1]
+
+        for i in range(1, len(pairs)):
+            if end < pairs[i][0]:
+                length += 1
+                end = pairs[i][1]
+
+        return length
+```
+
+```java
+public class Solution {
+    public int findLongestChain(int[][] pairs) {
+        Arrays.sort(pairs, (a, b) -> Integer.compare(a[1], b[1]));
+        int length = 1;
+        int end = pairs[0][1];
+
+        for (int i = 1; i < pairs.length; i++) {
+            if (end < pairs[i][0]) {
+                length++;
+                end = pairs[i][1];
+            }
+        }
+
+        return length;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findLongestChain(vector<vector<int>>& pairs) {
+        sort(pairs.begin(), pairs.end(), [](const auto& a, const auto& b) {
+            return a[1] < b[1];
+        });
+
+        int length = 1, end = pairs[0][1];
+
+        for (int i = 1; i < pairs.size(); i++) {
+            if (end < pairs[i][0]) {
+                length++;
+                end = pairs[i][1];
+            }
+        }
+
+        return length;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} pairs
+     * @return {number}
+     */
+    findLongestChain(pairs) {
+        pairs.sort((a, b) => a[1] - b[1]);
+        let length = 1;
+        let end = pairs[0][1];
+
+        for (let i = 1; i < pairs.length; i++) {
+            if (end < pairs[i][0]) {
+                length++;
+                end = pairs[i][1];
+            }
+        }
+
+        return length;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n\log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
\ No newline at end of file
diff --git a/articles/maximum-nesting-depth-of-the-parentheses.md b/articles/maximum-nesting-depth-of-the-parentheses.md
new file mode 100644
index 000000000..f18d24a7f
--- /dev/null
+++ b/articles/maximum-nesting-depth-of-the-parentheses.md
@@ -0,0 +1,305 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def maxDepth(self, s: str) -> int:
+        res = 0
+
+        def dfs(i):
+            nonlocal res
+            if i == len(s):
+                return 0
+
+            cur = dfs(i + 1)
+            if s[i] == '(':
+                cur += 1
+            elif s[i] == ')':
+                cur -= 1
+            
+            res = max(res, abs(cur))
+            return cur
+
+        dfs(0)
+        return res
+```
+
+```java
+public class Solution {
+    private int res = 0;
+
+    public int maxDepth(String s) {
+        dfs(s, 0);
+        return res;
+    }
+
+    private int dfs(String s, int i) {
+        if (i == s.length()) {
+            return 0;
+        }
+
+        int cur = dfs(s, i + 1);
+        if (s.charAt(i) == '(') {
+            cur += 1;
+        } else if (s.charAt(i) == ')') {
+            cur -= 1;
+        }
+
+        res = Math.max(res, Math.abs(cur));
+        return cur;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    int res = 0;
+
+    int dfs(const string& s, int i) {
+        if (i == s.length()) {
+            return 0;
+        }
+
+        int cur = dfs(s, i + 1);
+        if (s[i] == '(') {
+            cur += 1;
+        } else if (s[i] == ')') {
+            cur -= 1;
+        }
+
+        res = max(res, abs(cur));
+        return cur;
+    }
+
+public:
+    int maxDepth(string s) {
+        dfs(s, 0);
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    maxDepth(s) {
+        let res = 0;
+
+        const dfs = (i) => {
+            if (i === s.length) {
+                return 0;
+            }
+
+            let cur = dfs(i + 1);
+            if (s[i] === '(') {
+                cur += 1;
+            } else if (s[i] === ')') {
+                cur -= 1;
+            }
+
+            res = Math.max(res, Math.abs(cur));
+            return cur;
+        };
+
+        dfs(0);
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Stack
+
+::tabs-start
+
+```python
+class Solution:
+    def maxDepth(self, s: str) -> int:
+        res, stack = 0, []
+
+        for c in s:
+            if c == "(":
+                stack.append(c)
+                res = max(res, len(stack))
+            elif c == ")":
+                stack.pop()
+
+        return res
+```
+
+```java
+public class Solution {
+    public int maxDepth(String s) {
+        int res = 0;
+        Stack<Character> stack = new Stack<>();
+
+        for (char c : s.toCharArray()) {
+            if (c == '(') {
+                stack.push(c);
+                res = Math.max(res, stack.size());
+            } else if (c == ')') {
+                stack.pop();
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxDepth(string s) {
+        int res = 0;
+        stack<char> stack;
+
+        for (char c : s) {
+            if (c == '(') {
+                stack.push(c);
+                res = max(res, (int)stack.size());
+            } else if (c == ')') {
+                stack.pop();
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    maxDepth(s) {
+        let res = 0;
+        let stack = [];
+
+        for (let c of s) {
+            if (c === '(') {
+                stack.push(c);
+                res = Math.max(res, stack.length);
+            } else if (c === ')') {
+                stack.pop();
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Iteration
+
+::tabs-start
+
+```python
+class Solution:
+    def maxDepth(self, s: str) -> int:
+        res = 0
+        cur = 0
+
+        for c in s:
+            if c == "(":
+                cur += 1
+            elif c == ")":
+                cur -= 1
+            res = max(res, cur)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int maxDepth(String s) {
+        int res = 0, cur = 0;
+
+        for (int i = 0; i < s.length(); i++) {
+            char c = s.charAt(i);
+            if (c == '(') {
+                cur++;
+            } else if (c == ')') {
+                cur--;
+            }
+            res = Math.max(res, cur);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxDepth(string s) {
+        int res = 0, cur = 0;
+
+        for (char c : s) {
+            if (c == '(') {
+                cur++;
+            } else if (c == ')') {
+                cur--;
+            }
+            res = max(res, cur);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    maxDepth(s) {
+        let res = 0, cur = 0;
+
+        for (let c of s) {
+            if (c === '(') {
+                cur++;
+            } else if (c === ')') {
+                cur--;
+            }
+            res = Math.max(res, cur);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/maximum-number-of-balloons.md b/articles/maximum-number-of-balloons.md
new file mode 100644
index 000000000..597cbf295
--- /dev/null
+++ b/articles/maximum-number-of-balloons.md
@@ -0,0 +1,185 @@
+## 1. Hash Map - I
+
+::tabs-start
+
+```python
+class Solution:
+    def maxNumberOfBalloons(self, text: str) -> int:
+        countText = Counter(text)
+        balloon = Counter("balloon")
+
+        res = len(text)
+        for c in balloon:
+            res = min(res, countText[c] // balloon[c])
+        return res
+```
+
+```java
+public class Solution {
+    public int maxNumberOfBalloons(String text) {
+        Map<Character, Integer> countText = new HashMap<>();
+        for (char c : text.toCharArray()) {
+            countText.put(c, countText.getOrDefault(c, 0) + 1);
+        }
+
+        Map<Character, Integer> balloon = new HashMap<>();
+        for (char c : "balloon".toCharArray()) {
+            balloon.put(c, balloon.getOrDefault(c, 0) + 1);
+        }
+
+        int res = text.length();
+        for (char c : balloon.keySet()) {
+            res = Math.min(res, countText.getOrDefault(c, 0) / balloon.get(c));
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxNumberOfBalloons(string text) {
+        unordered_map<char, int> countText;
+        for (char c : text) {
+            countText[c]++;
+        }
+
+        unordered_map<char, int> balloon = {{'b', 1}, {'a', 1}, 
+                                            {'l', 2}, {'o', 2}, {'n', 1}};
+
+        int res = text.length();
+        for (auto& entry : balloon) {
+            res = min(res, countText[entry.first] / entry.second);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} text
+     * @return {number}
+     */
+    maxNumberOfBalloons(text) {
+        const countText = {};
+        for (const c of text) {
+            countText[c] = (countText[c] || 0) + 1;
+        }
+
+        const balloon = { b: 1, a: 1, l: 2, o: 2, n: 1 };
+
+        let res = text.length;
+        for (const c in balloon) {
+            res = Math.min(res, Math.floor((countText[c] || 0) / balloon[c]));
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ since we have at most $26$ different characters.
+
+---
+
+## 2. Hash Map - II
+
+::tabs-start
+
+```python
+class Solution:
+    def maxNumberOfBalloons(self, text: str) -> int:
+        mp = defaultdict(int)
+        for c in text:
+            if c in "balon":
+                mp[c] += 1
+        
+        if len(mp) < 5:
+            return 0
+        
+        mp['l'] //= 2
+        mp['o'] //= 2
+        return min(mp.values())
+```
+
+```java
+public class Solution {
+    public int maxNumberOfBalloons(String text) {
+        Map<Character, Integer> mp = new HashMap<>();
+        for (char c : text.toCharArray()) {
+            if ("balon".indexOf(c) != -1) {
+                mp.put(c, mp.getOrDefault(c, 0) + 1);
+            }
+        }
+        
+        if (mp.size() < 5) {
+            return 0;
+        }
+        
+        mp.put('l', mp.get('l') / 2);
+        mp.put('o', mp.get('o') / 2);
+        return Collections.min(mp.values());
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxNumberOfBalloons(string text) {
+        unordered_map<char, int> mp;
+        for (char c : text) {
+            if (string("balon").find(c) != string::npos) {
+                mp[c]++;
+            }
+        }
+        
+        if (mp.size() < 5) {
+            return 0;
+        }
+        
+        mp['l'] /= 2;
+        mp['o'] /= 2;
+        return min({mp['b'], mp['a'], mp['l'], mp['o'], mp['n']});
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} text
+     * @return {number}
+     */
+    maxNumberOfBalloons(text) {
+        const mp = new Map();
+        for (let c of text) {
+            if ("balon".includes(c)) {
+                mp.set(c, (mp.get(c) || 0) + 1);
+            }
+        }
+        
+        if (mp.size < 5) {
+            return 0;
+        }
+        
+        mp.set('l', Math.floor(mp.get('l') / 2));
+        mp.set('o', Math.floor(mp.get('o') / 2));
+        return Math.min(...Array.from(mp.values()));
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ since $balloon$ has $5$ different characters.
\ No newline at end of file
diff --git a/articles/maximum-number-of-removable-characters.md b/articles/maximum-number-of-removable-characters.md
new file mode 100644
index 000000000..bc22c959f
--- /dev/null
+++ b/articles/maximum-number-of-removable-characters.md
@@ -0,0 +1,451 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def maximumRemovals(self, s: str, p: str, removable: List[int]) -> int:
+        n, m = len(s), len(p)
+        marked = set()
+        res = 0
+
+        for removeIdx in removable:
+            marked.add(removeIdx)
+
+            sIdx = pIdx = 0
+            while pIdx < m and sIdx < n:
+                if sIdx not in marked and s[sIdx] == p[pIdx]:
+                    pIdx += 1
+                sIdx += 1
+            if pIdx != m:
+                break
+            res += 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int maximumRemovals(String s, String p, int[] removable) {
+        int n = s.length(), m = p.length();
+        Set<Integer> marked = new HashSet<>();
+        int res = 0;
+
+        for (int removeIdx : removable) {
+            marked.add(removeIdx);
+
+            int sIdx = 0, pIdx = 0;
+            while (pIdx < m && sIdx < n) {
+                if (!marked.contains(sIdx) && s.charAt(sIdx) == p.charAt(pIdx)) {
+                    pIdx++;
+                }
+                sIdx++;
+            }
+
+            if (pIdx != m) break;
+            res++;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maximumRemovals(string s, string p, vector<int>& removable) {
+        int n = s.size(), m = p.size();
+        unordered_set<int> marked;
+        int res = 0;
+
+        for (int removeIdx : removable) {
+            marked.insert(removeIdx);
+
+            int sIdx = 0, pIdx = 0;
+            while (pIdx < m && sIdx < n) {
+                if (marked.find(sIdx) == marked.end() && s[sIdx] == p[pIdx]) {
+                    pIdx++;
+                }
+                sIdx++;
+            }
+
+            if (pIdx != m) break;
+            res++;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string} p
+     * @param {number[]} removable
+     * @return {number}
+     */
+    maximumRemovals(s, p, removable) {
+        let n = s.length, m = p.length;
+        let marked = new Set();
+        let res = 0;
+
+        for (let removeIdx of removable) {
+            marked.add(removeIdx);
+
+            let sIdx = 0, pIdx = 0;
+            while (pIdx < m && sIdx < n) {
+                if (!marked.has(sIdx) && s[sIdx] === p[pIdx]) {
+                    pIdx++;
+                }
+                sIdx++;
+            }
+
+            if (pIdx !== m) break;
+            res++;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(k * (n + m))$
+* Space complexity: $O(k)$
+
+> Where $n$ and $m$ are the lengths of the given strings $s$ and $p$ respectively. $k$ is the size of the array $removable$.
+
+---
+
+## 2. Binary Search + Hash Set
+
+::tabs-start
+
+```python
+class Solution:
+    def maximumRemovals(self, s: str, p: str, removable: List[int]) -> int:
+        def isSubseq(s, subseq, removed):
+            i1 = i2 = 0
+            while i1 < len(s) and i2 < len(subseq):
+                if i1 in removed or s[i1] != subseq[i2]:
+                    i1 += 1
+                    continue
+                i1 += 1
+                i2 += 1
+            return i2 == len(subseq)
+
+        res = 0
+        l, r = 0, len(removable) - 1
+        while l <= r:
+            m = (l + r) // 2
+            removed = set(removable[:m + 1])
+            if isSubseq(s, p, removed):
+                res = max(res, m + 1)
+                l = m + 1
+            else:
+                r = m - 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int maximumRemovals(String s, String p, int[] removable) {
+        int res = 0, l = 0, r = removable.length - 1;
+
+        while (l <= r) {
+            int m = (l + r) / 2;
+            Set<Integer> removed = new HashSet<>();
+            for (int i = 0; i <= m; i++) {
+                removed.add(removable[i]);
+            }
+
+            if (isSubseq(s, p, removed)) {
+                res = Math.max(res, m + 1);
+                l = m + 1;
+            } else {
+                r = m - 1;
+            }
+        }
+
+        return res;
+    }
+
+    private boolean isSubseq(String s, String subseq, Set<Integer> removed) {
+        int i1 = 0, i2 = 0;
+        while (i1 < s.length() && i2 < subseq.length()) {
+            if (removed.contains(i1) || s.charAt(i1) != subseq.charAt(i2)) {
+                i1++;
+                continue;
+            }
+            i1++;
+            i2++;
+        }
+        return i2 == subseq.length();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maximumRemovals(string s, string p, vector<int>& removable) {
+        int res = 0, l = 0, r = removable.size() - 1;
+
+        while (l <= r) {
+            int m = (l + r) / 2;
+            unordered_set<int> removed(removable.begin(), removable.begin() + m + 1);
+
+            if (isSubseq(s, p, removed)) {
+                res = max(res, m + 1);
+                l = m + 1;
+            } else {
+                r = m - 1;
+            }
+        }
+
+        return res;
+    }
+
+private:
+    bool isSubseq(string& s, string& subseq, unordered_set<int>& removed) {
+        int i1 = 0, i2 = 0;
+        while (i1 < s.size() && i2 < subseq.size()) {
+            if (removed.count(i1) || s[i1] != subseq[i2]) {
+                i1++;
+                continue;
+            }
+            i1++;
+            i2++;
+        }
+        return i2 == subseq.size();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string} p
+     * @param {number[]} removable
+     * @return {number}
+     */
+    maximumRemovals(s, p, removable) {
+        let res = 0, l = 0, r = removable.length - 1;
+
+        while (l <= r) {
+            let m = Math.floor((l + r) / 2);
+            let removed = new Set(removable.slice(0, m + 1));
+
+            if (this.isSubseq(s, p, removed)) {
+                res = Math.max(res, m + 1);
+                l = m + 1;
+            } else {
+                r = m - 1;
+            }
+        }
+
+        return res;
+    }
+
+    /**
+     * @param {string} s
+     * @param {string} subseq
+     * @param {Set<number>} removed
+     * @return {boolean}
+     */
+    isSubseq(s, subseq, removed) {
+        let i1 = 0, i2 = 0;
+        while (i1 < s.length && i2 < subseq.length) {
+            if (removed.has(i1) || s[i1] !== subseq[i2]) {
+                i1++;
+                continue;
+            }
+            i1++;
+            i2++;
+        }
+        return i2 === subseq.length;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O((n + m) * \log k)$
+* Space complexity: $O(k)$
+
+> Where $n$ and $m$ are the lengths of the given strings $s$ and $p$ respectively. $k$ is the size of the array $removable$.
+
+---
+
+## 3. Binary Search
+
+::tabs-start
+
+```python
+class Solution:
+    def maximumRemovals(self, s: str, p: str, removable: List[int]) -> int:
+        l, r = 0, len(removable)
+        n, m = len(s), len(p)
+
+        def isSubseq(tmpS):
+            i1 = i2 = 0
+            while i1 < n and i2 < m:
+                if tmpS[i1] == p[i2]:
+                    i2 += 1
+                i1 += 1
+            return i2 == m
+
+        while l < r:
+            mid = l + (r - l) // 2
+            tmpS = list(s)
+
+            for i in range(mid + 1):
+                tmpS[removable[i]] = '#'
+
+            if isSubseq(tmpS):
+                l = mid + 1
+            else:
+                r = mid
+
+        return l
+```
+
+```java
+public class Solution {
+    public int maximumRemovals(String s, String p, int[] removable) {
+        int l = 0, r = removable.length;
+        int n = s.length(), m = p.length();
+
+        while (l < r) {
+            int mid = l + (r - l) / 2;
+            char[] tmpS = s.toCharArray();
+
+            for (int i = 0; i <= mid; i++) {
+                tmpS[removable[i]] = '#';
+            }
+
+            if (isSubseq(tmpS, p)) {
+                l = mid + 1;
+            } else {
+                r = mid;
+            }
+        }
+
+        return l;
+    }
+
+    private boolean isSubseq(char[] s, String p) {
+        int i1 = 0, i2 = 0, n = s.length, m = p.length();
+
+        while (i1 < n && i2 < m) {
+            if (s[i1] == p.charAt(i2)) {
+                i2++;
+            }
+            i1++;
+        }
+        return i2 == m;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maximumRemovals(string s, string p, vector<int>& removable) {
+        int l = 0, r = removable.size();
+        int n = s.size(), m = p.size();
+
+        while (l < r) {
+            int mid = l + (r - l) / 2;
+            string tmpS = s;
+
+            for (int i = 0; i <= mid; i++) {
+                tmpS[removable[i]] = '#';
+            }
+
+            if (isSubseq(tmpS, p)) {
+                l = mid + 1;
+            } else {
+                r = mid;
+            }
+        }
+
+        return l;
+    }
+
+private:
+    bool isSubseq(const string& s, const string& p) {
+        int i1 = 0, i2 = 0, n = s.size(), m = p.size();
+
+        while (i1 < n && i2 < m) {
+            if (s[i1] == p[i2]) {
+                i2++;
+            }
+            i1++;
+        }
+        return i2 == m;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string} p
+     * @param {number[]} removable
+     * @return {number}
+     */
+    maximumRemovals(s, p, removable) {
+        let l = 0, r = removable.length;
+        let n = s.length, m = p.length;
+
+        const isSubseq = (tmpS) => {
+            let i1 = 0, i2 = 0;
+            while (i1 < n && i2 < m) {
+                if (tmpS[i1] === p[i2]) {
+                    i2++;
+                }
+                i1++;
+            }
+            return i2 === m;
+        };
+
+        while (l < r) {
+            let mid = Math.floor(l + (r - l) / 2);
+            let tmpS = s.split("");
+
+            for (let i = 0; i <= mid; i++) {
+                tmpS[removable[i]] = "#";
+            }
+
+            if (isSubseq(tmpS)) {
+                l = mid + 1;
+            } else {
+                r = mid;
+            }
+        }
+
+        return l;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O((n + m) * \log k)$
+* Space complexity: $O(n)$
+
+> Where $n$ and $m$ are the lengths of the given strings $s$ and $p$ respectively. $k$ is the size of the array $removable$.
\ No newline at end of file
diff --git a/articles/maximum-number-of-vowels-in-a-substring-of-given-length.md b/articles/maximum-number-of-vowels-in-a-substring-of-given-length.md
new file mode 100644
index 000000000..371aff2b3
--- /dev/null
+++ b/articles/maximum-number-of-vowels-in-a-substring-of-given-length.md
@@ -0,0 +1,385 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def maxVowels(self, s: str, k: int) -> int:
+        vowel = {'a', 'e', 'i', 'o', 'u'}
+        res = 0
+
+        for i in range(len(s) - k + 1):
+            cnt = 0
+            for j in range(i, i + k):
+                cnt += 1 if s[j] in vowel else 0
+            res = max(res, cnt)
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int maxVowels(String s, int k) {
+        Set<Character> vowels = Set.of('a', 'e', 'i', 'o', 'u');
+        int res = 0;
+
+        for (int i = 0; i <= s.length() - k; i++) {
+            int cnt = 0;
+            for (int j = i; j < i + k; j++) {
+                if (vowels.contains(s.charAt(j))) {
+                    cnt++;
+                }
+            }
+            res = Math.max(res, cnt);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxVowels(string s, int k) {
+        unordered_set<char> vowels = {'a', 'e', 'i', 'o', 'u'};
+        int res = 0;
+
+        for (int i = 0; i <= s.size() - k; i++) {
+            int cnt = 0;
+            for (int j = i; j < i + k; j++) {
+                if (vowels.count(s[j])) {
+                    cnt++;
+                }
+            }
+            res = max(res, cnt);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {number} k
+     * @return {number}
+     */
+    maxVowels(s, k) {
+        const vowels = new Set(['a', 'e', 'i', 'o', 'u']);
+        let res = 0;
+
+        for (let i = 0; i <= s.length - k; i++) {
+            let cnt = 0;
+            for (let j = i; j < i + k; j++) {
+                if (vowels.has(s[j])) {
+                    cnt++;
+                }
+            }
+            res = Math.max(res, cnt);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 2. Prefix Count
+
+::tabs-start
+
+```python
+class Solution:
+    def maxVowels(self, s: str, k: int) -> int:
+        vowel = {'a', 'e', 'i', 'o', 'u'}
+        prefix = [0] * (len(s) + 1)
+        for i in range(len(s)):
+            prefix[i + 1] = prefix[i] + (1 if s[i] in vowel else 0)
+        
+        res = 0
+        for i in range(k, len(s) + 1):
+            res = max(res, prefix[i] - prefix[i - k])
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int maxVowels(String s, int k) {
+        Set<Character> vowels = Set.of('a', 'e', 'i', 'o', 'u');
+        int[] prefix = new int[s.length() + 1];
+
+        for (int i = 0; i < s.length(); i++) {
+            prefix[i + 1] = prefix[i] + (vowels.contains(s.charAt(i)) ? 1 : 0);
+        }
+
+        int res = 0;
+        for (int i = k; i <= s.length(); i++) {
+            res = Math.max(res, prefix[i] - prefix[i - k]);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxVowels(string s, int k) {
+        unordered_set<char> vowels = {'a', 'e', 'i', 'o', 'u'};
+        vector<int> prefix(s.size() + 1, 0);
+
+        for (int i = 0; i < s.size(); i++) {
+            prefix[i + 1] = prefix[i] + (vowels.count(s[i]) ? 1 : 0);
+        }
+
+        int res = 0;
+        for (int i = k; i <= s.size(); i++) {
+            res = max(res, prefix[i] - prefix[i - k]);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {number} k
+     * @return {number}
+     */
+    maxVowels(s, k) {
+        const vowels = new Set(['a', 'e', 'i', 'o', 'u']);
+        const prefix = new Array(s.length + 1).fill(0);
+
+        for (let i = 0; i < s.length; i++) {
+            prefix[i + 1] = prefix[i] + (vowels.has(s[i]) ? 1 : 0);
+        }
+
+        let res = 0;
+        for (let i = k; i <= s.length; i++) {
+            res = Math.max(res, prefix[i] - prefix[i - k]);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Sliding Window
+
+::tabs-start
+
+```python
+class Solution:
+    def maxVowels(self, s: str, k: int) -> int:
+        vowel = {'a', 'e', 'i', 'o', 'u'}
+        
+        l = cnt = res = 0
+        for r in range(len(s)):
+            cnt += 1 if s[r] in vowel else 0
+            if r - l + 1 > k:
+                cnt -= 1 if s[l] in vowel else 0
+                l += 1
+            res = max(res, cnt)
+        return res
+```
+
+```java
+public class Solution {
+    public int maxVowels(String s, int k) {
+        Set<Character> vowels = Set.of('a', 'e', 'i', 'o', 'u');
+        
+        int l = 0, cnt = 0, res = 0;
+        for (int r = 0; r < s.length(); r++) {
+            cnt += (vowels.contains(s.charAt(r)) ? 1 : 0);
+            if (r - l + 1 > k) {
+                cnt -= (vowels.contains(s.charAt(l)) ? 1 : 0);
+                l++;
+            }
+            res = Math.max(res, cnt);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxVowels(string s, int k) {
+        unordered_set<char> vowels = {'a', 'e', 'i', 'o', 'u'};
+        
+        int l = 0, cnt = 0, res = 0;
+        for (int r = 0; r < s.length(); r++) {
+            cnt += (vowels.count(s[r]) ? 1 : 0);
+            if (r - l + 1 > k) {
+                cnt -= (vowels.count(s[l++]) ? 1 : 0);
+            }
+            res = max(res, cnt);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {number} k
+     * @return {number}
+     */
+    maxVowels(s, k) {
+        const vowels = new Set(['a', 'e', 'i', 'o', 'u']);
+        
+        let l = 0, cnt = 0, res = 0;
+        for (let r = 0; r < s.length; r++) {
+            cnt += (vowels.has(s[r]) ? 1 : 0);
+            if (r - l + 1 > k) {
+                cnt -= (vowels.has(s[l++]) ? 1 : 0);
+            }
+            res = Math.max(res, cnt);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 4. Sliding Window (Bit Mask)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxVowels(self, s: str, k: int) -> int:
+        def getId(c):
+            return ord(c) - ord('a')
+
+        mask = (1 << getId('a')) | (1 << getId('e')) | \
+               (1 << getId('i')) | (1 << getId('o')) | \
+               (1 << getId('u'))
+        
+        l = cnt = res = 0
+        for r in range(len(s)):
+            cnt += ((mask >> getId(s[r])) & 1)
+            if r - l + 1 > k:
+                cnt -= ((mask >> getId(s[l])) & 1)
+                l += 1
+            res = max(res, cnt)
+        return res
+```
+
+```java
+public class Solution {
+    public int maxVowels(String s, int k) {
+        int mask = (1 << ('a' - 'a')) | (1 << ('e' - 'a')) | 
+                   (1 << ('i' - 'a')) | (1 << ('o' - 'a')) | 
+                   (1 << ('u' - 'a'));
+
+        int l = 0, cnt = 0, res = 0;
+        for (int r = 0; r < s.length(); r++) {
+            cnt += (mask >> (s.charAt(r) - 'a')) & 1;
+            if (r - l + 1 > k) {
+                cnt -= (mask >> (s.charAt(l) - 'a')) & 1;
+                l++;
+            }
+            res = Math.max(res, cnt);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxVowels(string s, int k) {
+        int mask = (1 << ('a' - 'a')) | (1 << ('e' - 'a')) | 
+                   (1 << ('i' - 'a')) | (1 << ('o' - 'a')) | 
+                   (1 << ('u' - 'a'));
+
+        int l = 0, cnt = 0, res = 0;
+        for (int r = 0; r < s.size(); r++) {
+            cnt += (mask >> (s[r] - 'a')) & 1;
+            if (r - l + 1 > k) {
+                cnt -= (mask >> (s[l] - 'a')) & 1;
+                l++;
+            }
+            res = max(res, cnt);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {number} k
+     * @return {number}
+     */
+    maxVowels(s, k) {
+        const getId = (c) => {
+            return  c.charCodeAt(0) - 'a'.charCodeAt(0);
+        };
+        const mask = (1 << getId('a')) | (1 << getId('e')) |
+                     (1 << getId('i')) | (1 << getId('o')) |
+                     (1 << getId('u'));
+        
+        let l = 0, cnt = 0, res = 0;
+        for (let r = 0; r < s.length; r++) {
+            cnt += (mask >> getId(s.charAt(r))) & 1;
+            if (r - l + 1 > k) {
+                cnt -= (mask >> getId(s.charAt(l))) & 1;
+                l++;
+            }
+            res = Math.max(res, cnt);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/maximum-odd-binary-number.md b/articles/maximum-odd-binary-number.md
new file mode 100644
index 000000000..41846d673
--- /dev/null
+++ b/articles/maximum-odd-binary-number.md
@@ -0,0 +1,264 @@
+## 1. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def maximumOddBinaryNumber(self, s: str) -> str:
+        s = sorted(s)
+        s.reverse()
+        i = len(s) - 1
+        while i >= 0 and s[i] == "0":
+            i -= 1
+        
+        s[i], s[len(s) - 1] = s[len(s) - 1], s[i]
+        return ''.join(s)
+```
+
+```java
+public class Solution {
+    public String maximumOddBinaryNumber(String s) {
+        char[] arr = s.toCharArray();
+        Arrays.sort(arr);
+        reverse(arr);
+
+        int n = arr.length;
+        int i = n - 1;
+
+        while (i >= 0 && arr[i] == '0') {
+            i--;
+        }
+
+        char temp = arr[i];
+        arr[i] = arr[n - 1];
+        arr[n - 1] = temp;
+
+        return new String(arr);
+    }
+
+    private void reverse(char[] arr) {
+        int left = 0, right = arr.length - 1;
+        while (left < right) {
+            char temp = arr[left];
+            arr[left++] = arr[right];
+            arr[right--] = temp;
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string maximumOddBinaryNumber(string s) {
+        sort(s.begin(), s.end(), greater<char>());
+
+        int n = s.size(), i = n - 1;
+        while (i >= 0 && s[i] == '0') {
+            i--;
+        }
+        
+        swap(s[i], s[n - 1]);
+        return s;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string}
+     */
+    maximumOddBinaryNumber(s) {
+        let arr = s.split('');
+        arr.sort().reverse();
+
+        let i = arr.length - 1;
+        while (i >= 0 && arr[i] === '0') {
+            i--;
+        }
+
+        [arr[i], arr[arr.length - 1]] = [arr[arr.length - 1], arr[i]];
+        return arr.join('');
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Greedy
+
+::tabs-start
+
+```python
+class Solution:
+    def maximumOddBinaryNumber(self, s: str) -> str:
+        count = 0
+        for c in s:
+            if c == "1":
+                count += 1
+        
+        return (count - 1) * "1" + (len(s) - count) * "0" + "1"
+```
+
+```java
+public class Solution {
+    public String maximumOddBinaryNumber(String s) {
+        int count = 0;
+        for (char c : s.toCharArray()) {
+            if (c == '1') count++;
+        }
+        
+        StringBuilder result = new StringBuilder();
+        for (int i = 0; i < count - 1; i++) result.append('1');
+        for (int i = 0; i < s.length() - count; i++) result.append('0');
+        result.append('1');
+        
+        return result.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string maximumOddBinaryNumber(string s) {
+        int count = 0;
+        for (char c : s) {
+            if (c == '1') count++;
+        }
+        
+        string result((count - 1), '1');
+        result += string(s.length() - count, '0');
+        result += '1';
+        
+        return result;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string}
+     */
+    maximumOddBinaryNumber(s) {
+        let count = 0;
+        for (const c of s) {
+            if (c === '1') count++;
+        }
+        
+        return '1'.repeat(count - 1) + '0'.repeat(s.length - count) + '1';
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def maximumOddBinaryNumber(self, s: str) -> str:
+        s = [c for c in s]
+        left = 0
+
+        for i in range(len(s)):
+            if s[i] == "1":
+                s[i], s[left] = s[left], s[i]
+                left += 1
+        s[left - 1], s[len(s) - 1] = s[len(s) - 1], s[left - 1]
+        return "".join(s)
+```
+
+```java
+public class Solution {
+    public String maximumOddBinaryNumber(String s) {
+        char[] arr = s.toCharArray();
+        int left = 0;
+
+        for (int i = 0; i < arr.length; i++) {
+            if (arr[i] == '1') {
+                char temp = arr[left];
+                arr[left] = arr[i];
+                arr[i] = temp;
+                left++;
+            }
+        }
+
+        char temp = arr[left - 1];
+        arr[left - 1] = arr[arr.length - 1];
+        arr[arr.length - 1] = temp;
+
+        return new String(arr);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string maximumOddBinaryNumber(string s) {
+        vector<char> arr(s.begin(), s.end());
+        int left = 0;
+
+        for (int i = 0; i < arr.size(); i++) {
+            if (arr[i] == '1') {
+                swap(arr[left], arr[i]);
+                left++;
+            }
+        }
+        
+        swap(arr[left - 1], arr[arr.size() - 1]);
+        return string(arr.begin(), arr.end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string}
+     */
+    maximumOddBinaryNumber(s) {
+        let arr = s.split('');
+        let left = 0;
+
+        for (let i = 0; i < arr.length; i++) {
+            if (arr[i] === '1') {
+                [arr[left], arr[i]] = [arr[i], arr[left]];
+                left++;
+            }
+        }
+
+        [arr[left - 1], arr[arr.length - 1]] = [arr[arr.length - 1], arr[left - 1]];
+        return arr.join('');
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/maximum-performance-of-a-team.md b/articles/maximum-performance-of-a-team.md
new file mode 100644
index 000000000..3fc63e969
--- /dev/null
+++ b/articles/maximum-performance-of-a-team.md
@@ -0,0 +1,238 @@
+## 1. Brute Force (Recursion)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxPerformance(self, n: int, speed: List[int], efficiency: List[int], k: int) -> int:
+        MOD = 1000000007
+        res = 0
+
+        def dfs(i, k, speedSum, minEff):
+            nonlocal res
+            res = max(res, speedSum * minEff)
+            if i == n or k == 0:
+                return
+
+            dfs(i + 1, k, speedSum, minEff)
+            dfs(i + 1, k - 1, speedSum + speed[i], min(minEff, efficiency[i]))
+
+        dfs(0, k, 0, float("inf"))
+        return res % MOD
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1000000007;
+    private int[] speed, efficiency;
+    private int n;
+    private long res;
+
+    public int maxPerformance(int n, int[] speed, int[] efficiency, int k) {
+        this.n = n;
+        this.speed = speed;
+        this.efficiency = efficiency;
+        this.res = 0;
+
+        dfs(0, k, Integer.MAX_VALUE, 0);
+        return (int) (res % MOD);
+    }
+
+    private void dfs(int i, int k, int minEff, long speedSum) {
+        res = Math.max(res, speedSum * minEff);
+        if (i == n || k == 0) return;
+
+        dfs(i + 1, k, minEff, speedSum);
+        dfs(i + 1, k - 1, Math.min(minEff, efficiency[i]), speedSum + speed[i]);
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    static constexpr int MOD = 1000000007;
+    vector<int> speed, efficiency;
+    int n;
+    long long res;
+
+public:
+    int maxPerformance(int n, vector<int>& speed, vector<int>& efficiency, int k) {
+        this->n = n;
+        this->speed = speed;
+        this->efficiency = efficiency;
+        res = 0;
+
+        dfs(0, k, INT_MAX, 0);
+        return int(res % MOD);
+    }
+
+private:
+    void dfs(int i, int k, int minEff, long long speedSum) {
+        res = max(res, speedSum * minEff);
+        if (i == n || k == 0) return;
+
+        dfs(i + 1, k, minEff, speedSum);
+        dfs(i + 1, k - 1, min(minEff, efficiency[i]), speedSum + speed[i]);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[]} speed
+     * @param {number[]} efficiency
+     * @param {number} k
+     * @return {number}
+     */
+    maxPerformance(n, speed, efficiency, k) {
+        const MOD = 1000000007;
+        let res = 0;
+
+        const dfs = (i, k, minEff, speedSum) => {
+            res = Math.max(res, minEff === Infinity ? 0 : speedSum * minEff);
+            if (i === n || k === 0) return;
+
+            dfs(i + 1, k, minEff, speedSum);
+            dfs(i + 1, k - 1, Math.min(minEff, efficiency[i]), speedSum + speed[i]);
+        };
+
+        dfs(0, k, Infinity, 0);
+        return res % MOD;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Sorting + Min-Heap
+
+::tabs-start
+
+```python
+class Solution:
+    def maxPerformance(self, n: int, speed: List[int], efficiency: List[int], k: int) -> int:
+        MOD = 10**9 + 7
+        eng = sorted(zip(efficiency, speed), reverse=True)
+
+        res = speedSum = 0
+        minHeap = []
+
+        for eff, spd in eng:
+            if len(minHeap) == k:
+                speedSum -= heapq.heappop(minHeap)
+            speedSum += spd
+            heapq.heappush(minHeap, spd)
+            res = max(res, eff * speedSum)
+
+        return res % MOD
+```
+
+```java
+public class Solution {
+    public int maxPerformance(int n, int[] speed, int[] efficiency, int k) {
+        final int MOD = 1_000_000_007;
+        int[][] engineers = new int[n][2];
+
+        for (int i = 0; i < n; i++) {
+            engineers[i] = new int[]{efficiency[i], speed[i]};
+        }
+
+        Arrays.sort(engineers, (a, b) -> Integer.compare(b[0], a[0]));
+
+        PriorityQueue<Integer> minHeap = new PriorityQueue<>();
+        long speedSum = 0, res = 0;
+
+        for (int[] eng : engineers) {
+            if (minHeap.size() == k) {
+                speedSum -= minHeap.poll();
+            }
+            speedSum += eng[1];
+            minHeap.offer(eng[1]);
+            res = Math.max(res, speedSum * eng[0]);
+        }
+
+        return (int) (res % MOD);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxPerformance(int n, vector<int>& speed, vector<int>& efficiency, int k) {
+        constexpr int MOD = 1'000'000'007;
+        vector<pair<int, int>> engineers;
+
+        for (int i = 0; i < n; i++) {
+            engineers.emplace_back(efficiency[i], speed[i]);
+        }
+
+        sort(engineers.rbegin(), engineers.rend());
+
+        priority_queue<int, vector<int>, greater<int>> minHeap;
+        long long speedSum = 0, res = 0;
+
+        for (const auto& [eff, spd] : engineers) {
+            if (minHeap.size() == k) {
+                speedSum -= minHeap.top();
+                minHeap.pop();
+            }
+            speedSum += spd;
+            minHeap.push(spd);
+            res = max(res, speedSum * eff);
+        }
+
+        return res % MOD;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[]} speed
+     * @param {number[]} efficiency
+     * @param {number} k
+     * @return {number}
+     */
+    maxPerformance(n, speed, efficiency, k) {
+        const MOD = BigInt(1e9 + 7);
+        const engineers = efficiency.map((eff, i) => [eff, speed[i]]);
+        engineers.sort((a, b) => b[0] - a[0]);
+
+        const minHeap = new MinPriorityQueue();
+        let speedSum = BigInt(0), res = BigInt(0);
+
+        for (const [eff, spd] of engineers) {
+            if (minHeap.size() === k) {
+                speedSum -= BigInt(minHeap.dequeue());
+            }
+            speedSum += BigInt(spd);
+            minHeap.enqueue(spd);
+            res = res > speedSum * BigInt(eff) ? res : speedSum * BigInt(eff);
+        }
+
+        return Number(res % MOD);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * (\log n + \log k))$
+* Space complexity: $O(n + k)$
+
+> Where $n$ is the number of engineers and $k$ is the maximum number of engineers that can be selected.
\ No newline at end of file
diff --git a/articles/maximum-points-you-can-obtain-from-cards.md b/articles/maximum-points-you-can-obtain-from-cards.md
new file mode 100644
index 000000000..8d1b9294a
--- /dev/null
+++ b/articles/maximum-points-you-can-obtain-from-cards.md
@@ -0,0 +1,462 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def maxScore(self, cardPoints: List[int], k: int) -> int:
+        n = len(cardPoints)
+        res = 0
+
+        for left in range(k + 1):
+            leftSum = sum(cardPoints[:left])
+            rightSum = sum(cardPoints[n - (k - left):])
+            res = max(res, leftSum + rightSum)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int maxScore(int[] cardPoints, int k) {
+        int n = cardPoints.length;
+        int res = 0;
+
+        for (int left = 0; left <= k; left++) {
+            int leftSum = 0;
+            for (int i = 0; i < left; i++) {
+                leftSum += cardPoints[i];
+            }
+
+            int rightSum = 0;
+            for (int i = n - (k - left); i < n; i++) {
+                rightSum += cardPoints[i];
+            }
+
+            res = Math.max(res, leftSum + rightSum);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxScore(vector<int>& cardPoints, int k) {
+        int n = cardPoints.size();
+        int res = 0;
+
+        for (int left = 0; left <= k; left++) {
+            int leftSum = 0;
+            for (int i = 0; i < left; i++) {
+                leftSum += cardPoints[i];
+            }
+
+            int rightSum = 0;
+            for (int i = n - (k - left); i < n; i++) {
+                rightSum += cardPoints[i];
+            }
+
+            res = max(res, leftSum + rightSum);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} cardPoints
+     * @param {number} k
+     * @return {number}
+     */
+    maxScore(cardPoints, k) {
+        let n = cardPoints.length;
+        let res = 0;
+
+        for (let left = 0; left <= k; left++) {
+            let leftSum = 0;
+            for (let i = 0; i < left; i++) {
+                leftSum += cardPoints[i];
+            }
+
+            let rightSum = 0;
+            for (let i = n - (k - left); i < n; i++) {
+                rightSum += cardPoints[i];
+            }
+
+            res = Math.max(res, leftSum + rightSum);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(k ^ 2)$
+* Space complexity: $O(1)$ extra space.
+
+> Where $k$ is the number of cards to pick.
+
+---
+
+## 2. Prefix & Suffix Sums
+
+::tabs-start
+
+```python
+class Solution:
+    def maxScore(self, cardPoints: List[int], k: int) -> int:
+        n = len(cardPoints)
+
+        prefix = [0] * (n + 1)
+        for i in range(n):
+            prefix[i + 1] = prefix[i] + cardPoints[i]
+
+        suffix = [0] * (n + 1)
+        for i in range(n - 1, -1, -1):
+            suffix[i] = suffix[i + 1] + cardPoints[i]
+
+        res = 0
+        for left in range(k + 1):
+            right = k - left
+            res = max(res, prefix[left] + suffix[n - right])
+
+        return res
+```
+
+```java
+public class Solution {
+    public int maxScore(int[] cardPoints, int k) {
+        int n = cardPoints.length;
+
+        int[] prefix = new int[n + 1];
+        for (int i = 0; i < n; i++) {
+            prefix[i + 1] = prefix[i] + cardPoints[i];
+        }
+
+        int[] suffix = new int[n + 1];
+        for (int i = n - 1; i >= 0; i--) {
+            suffix[i] = suffix[i + 1] + cardPoints[i];
+        }
+
+        int res = 0;
+        for (int left = 0; left <= k; left++) {
+            int right = k - left;
+            res = Math.max(res, prefix[left] + suffix[n - right]);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxScore(vector<int>& cardPoints, int k) {
+        int n = cardPoints.size();
+
+        vector<int> prefix(n + 1, 0);
+        for (int i = 0; i < n; i++) {
+            prefix[i + 1] = prefix[i] + cardPoints[i];
+        }
+
+        vector<int> suffix(n + 1, 0);
+        for (int i = n - 1; i >= 0; i--) {
+            suffix[i] = suffix[i + 1] + cardPoints[i];
+        }
+
+        int res = 0;
+        for (int left = 0; left <= k; left++) {
+            int right = k - left;
+            res = max(res, prefix[left] + suffix[n - right]);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} cardPoints
+     * @param {number} k
+     * @return {number}
+     */
+    maxScore(cardPoints, k) {
+        let n = cardPoints.length;
+
+        let prefix = new Array(n + 1).fill(0);
+        for (let i = 0; i < n; i++) {
+            prefix[i + 1] = prefix[i] + cardPoints[i];
+        }
+
+        let suffix = new Array(n + 1).fill(0);
+        for (let i = n - 1; i >= 0; i--) {
+            suffix[i] = suffix[i + 1] + cardPoints[i];
+        }
+
+        let res = 0;
+        for (let left = 0; left <= k; left++) {
+            let right = k - left;
+            res = Math.max(res, prefix[left] + suffix[n - right]);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Sliding Window (Minimum Sum Window)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxScore(self, cardPoints: List[int], k: int) -> int:
+        n = len(cardPoints)
+        windowSize = n - k
+
+        if windowSize == 0:
+            return sum(cardPoints)
+
+        total = 0
+        minWindowSum = float("inf")
+        curSum = 0
+
+        for i in range(n):
+            total += cardPoints[i]
+            curSum += cardPoints[i]
+            if i >= windowSize - 1:
+                minWindowSum = min(minWindowSum, curSum)
+                curSum -= cardPoints[i - windowSize + 1]
+
+        return total - minWindowSum
+```
+
+```java
+public class Solution {
+    public int maxScore(int[] cardPoints, int k) {
+        int n = cardPoints.length;
+        int windowSize = n - k;
+
+        if (windowSize == 0) {
+            int sum = 0;
+            for (int num : cardPoints) sum += num;
+            return sum;
+        }
+
+        int total = 0;
+        int minWindowSum = Integer.MAX_VALUE;
+        int curSum = 0;
+
+        for (int i = 0; i < n; i++) {
+            total += cardPoints[i];
+            curSum += cardPoints[i];
+            if (i >= windowSize - 1) {
+                minWindowSum = Math.min(minWindowSum, curSum);
+                curSum -= cardPoints[i - windowSize + 1];
+            }
+        }
+
+        return total - minWindowSum;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxScore(vector<int>& cardPoints, int k) {
+        int n = cardPoints.size();
+        int windowSize = n - k;
+
+        if (windowSize == 0) {
+            return accumulate(cardPoints.begin(), cardPoints.end(), 0);
+        }
+
+        int total = 0;
+        int minWindowSum = INT_MAX;
+        int curSum = 0;
+
+        for (int i = 0; i < n; i++) {
+            total += cardPoints[i];
+            curSum += cardPoints[i];
+            if (i >= windowSize - 1) {
+                minWindowSum = min(minWindowSum, curSum);
+                curSum -= cardPoints[i - windowSize + 1];
+            }
+        }
+
+        return total - minWindowSum;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} cardPoints
+     * @param {number} k
+     * @return {number}
+     */
+    maxScore(cardPoints, k) {
+        let n = cardPoints.length;
+        let windowSize = n - k;
+
+        if (windowSize === 0) {
+            return cardPoints.reduce((sum, num) => sum + num, 0);
+        }
+
+        let total = 0;
+        let minWindowSum = Infinity;
+        let curSum = 0;
+
+        for (let i = 0; i < n; i++) {
+            total += cardPoints[i];
+            curSum += cardPoints[i];
+            if (i >= windowSize - 1) {
+                minWindowSum = Math.min(minWindowSum, curSum);
+                curSum -= cardPoints[i - windowSize + 1];
+            }
+        }
+
+        return total - minWindowSum;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 4. Sliding Window
+
+::tabs-start
+
+```python
+class Solution:
+    def maxScore(self, cardPoints: List[int], k: int) -> int:
+        l, r = 0, len(cardPoints) - k
+        total = sum(cardPoints[r:])
+        res = total
+
+        while r < len(cardPoints):
+            total += cardPoints[l] - cardPoints[r]
+            res = max(res, total)
+            l += 1
+            r += 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int maxScore(int[] cardPoints, int k) {
+        int l = 0, r = cardPoints.length - k;
+        int total = 0;
+
+        for (int i = r; i < cardPoints.length; i++) {
+            total += cardPoints[i];
+        }
+
+        int res = total;
+
+        while (r < cardPoints.length) {
+            total += cardPoints[l] - cardPoints[r];
+            res = Math.max(res, total);
+            l++;
+            r++;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxScore(vector<int>& cardPoints, int k) {
+        int l = 0, r = cardPoints.size() - k;
+        int total = 0;
+
+        for (int i = r; i < cardPoints.size(); i++) {
+            total += cardPoints[i];
+        }
+
+        int res = total;
+
+        while (r < cardPoints.size()) {
+            total += cardPoints[l] - cardPoints[r];
+            res = max(res, total);
+            l++;
+            r++;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} cardPoints
+     * @param {number} k
+     * @return {number}
+     */
+    maxScore(cardPoints, k) {
+        let l = 0, r = cardPoints.length - k;
+        let total = 0;
+
+        for (let i = r; i < cardPoints.length; i++) {
+            total += cardPoints[i];
+        }
+
+        let res = total;
+
+        while (r < cardPoints.length) {
+            total += cardPoints[l] - cardPoints[r];
+            res = Math.max(res, total);
+            l++;
+            r++;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(k)$
+* Space complexity: $O(1)$ extra space.
+
+> Where $k$ is the number of cards to pick.
\ No newline at end of file
diff --git a/articles/maximum-product-difference-between-two-pairs.md b/articles/maximum-product-difference-between-two-pairs.md
new file mode 100644
index 000000000..e5425c2f8
--- /dev/null
+++ b/articles/maximum-product-difference-between-two-pairs.md
@@ -0,0 +1,255 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def maxProductDifference(self, nums: List[int]) -> int:
+        n, res = len(nums), 0
+        for a in range(n):
+            for b in range(n):
+                if a == b: continue
+                for c in range(n):
+                    if a == c or b == c: continue
+                    for d in range(n):
+                        if a == d or b == d or c == d: continue
+                        res = max(res, nums[a] * nums[b] - nums[c] * nums[d])
+        return res
+```
+
+```java
+public class Solution {
+    public int maxProductDifference(int[] nums) {
+        int n = nums.length, res = 0;
+        for (int a = 0; a < n; a++) {
+            for (int b = 0; b < n; b++) {
+                if (a == b) continue;
+                for (int c = 0; c < n; c++) {
+                    if (a == c || b == c) continue;
+                    for (int d = 0; d < n; d++) {
+                        if (a == d || b == d || c == d) continue;
+                        res = Math.max(res, nums[a] * nums[b] - nums[c] * nums[d]);
+                    }
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxProductDifference(vector<int>& nums) {
+        int n = nums.size(), res = 0;
+        for (int a = 0; a < n; a++) {
+            for (int b = 0; b < n; b++) {
+                if (a == b) continue;
+                for (int c = 0; c < n; c++) {
+                    if (a == c || b == c) continue;
+                    for (int d = 0; d < n; d++) {
+                        if (a == d || b == d || c == d) continue;
+                        res = max(res, nums[a] * nums[b] - nums[c] * nums[d]);
+                    }
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    maxProductDifference(nums) {
+        const n = nums.length;
+        let res = 0;
+        for (let a = 0; a < n; a++) {
+            for (let b = 0; b < n; b++) {
+                if (a === b) continue;
+                for (let c = 0; c < n; c++) {
+                    if (a === c || b === c) continue;
+                    for (let d = 0; d < n; d++) {
+                        if (a === d || b === d || c === d) continue;
+                        res = Math.max(res, nums[a] * nums[b] - nums[c] * nums[d]);
+                    }
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 4)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def maxProductDifference(self, nums: List[int]) -> int:
+        nums.sort()
+        return nums[-1] * nums[-2] - nums[0] * nums[1]
+```
+
+```java
+public class Solution {
+    public int maxProductDifference(int[] nums) {
+        Arrays.sort(nums);
+        return nums[nums.length - 1] * nums[nums.length - 2] - nums[0] * nums[1];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxProductDifference(vector<int>& nums) {
+        sort(nums.begin(), nums.end());
+        return nums[nums.size() - 1] * nums[nums.size() - 2] - nums[0] * nums[1];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    maxProductDifference(nums) {
+        nums.sort((a, b) => a - b);
+        return nums[nums.length - 1] * nums[nums.length - 2] - nums[0] * nums[1];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 3. Two Maximums and Two Minimums
+
+::tabs-start
+
+```python
+class Solution:
+    def maxProductDifference(self, nums: List[int]) -> int:
+        max1 = max2 = 0
+        min1 = min2 = float('inf')
+
+        for num in nums:
+            if num > max1:
+                max1, max2 = num, max1
+            elif num > max2:
+                max2 = num
+            if num < min1:
+                min1, min2 = num, min1
+            elif num < min2:
+                min2 = num
+                
+        return (max1 * max2) - (min1 * min2)
+```
+
+```java
+public class Solution {
+    public int maxProductDifference(int[] nums) {
+        int max1 = 0, max2 = 0;
+        int min1 = Integer.MAX_VALUE, min2 = Integer.MAX_VALUE;
+        for (int num : nums) {
+            if (num > max1) {
+                max2 = max1;
+                max1 = num;
+            } else if (num > max2) {
+                max2 = num;
+            }
+            if (num < min1) {
+                min2 = min1;
+                min1 = num;
+            } else if (num < min2) {
+                min2 = num;
+            }
+        }
+        return (max1 * max2) - (min1 * min2);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxProductDifference(vector<int>& nums) {
+        int max1 = 0, max2 = 0;
+        int min1 = INT_MAX, min2 = INT_MAX;
+        for (int num : nums) {
+            if (num > max1) {
+                max2 = max1;
+                max1 = num;
+            } else if (num > max2) {
+                max2 = num;
+            }
+            if (num < min1) {
+                min2 = min1;
+                min1 = num;
+            } else if (num < min2) {
+                min2 = num;
+            }
+        }
+        return (max1 * max2) - (min1 * min2);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    maxProductDifference(nums) {
+        let max1 = 0, max2 = 0;
+        let min1 = Infinity, min2 = Infinity;
+        for (const num of nums) {
+            if (num > max1) {
+                max2 = max1;
+                max1 = num;
+            } else if (num > max2) {
+                max2 = num;
+            }
+            if (num < min1) {
+                min2 = min1;
+                min1 = num;
+            } else if (num < min2) {
+                min2 = num;
+            }
+        }
+        return (max1 * max2) - (min1 * min2);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/maximum-product-of-the-length-of-two-palindromic-subsequences.md b/articles/maximum-product-of-the-length-of-two-palindromic-subsequences.md
new file mode 100644
index 000000000..bd17730e3
--- /dev/null
+++ b/articles/maximum-product-of-the-length-of-two-palindromic-subsequences.md
@@ -0,0 +1,854 @@
+## 1. Recursion (Backtracking)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxProduct(self, s: str) -> int:
+        def isPal(s):
+            i, j = 0, len(s) - 1
+            while i < j:
+                if s[i] != s[j]:
+                    return False
+                i += 1
+                j -= 1
+            return True
+
+        res = 0
+        def rec(i, seq1, seq2):
+            nonlocal res
+            if i == len(s):
+                if isPal(seq1) and isPal(seq2):
+                    res = max(res, len(seq1) * len(seq2))
+                return
+            
+            rec(i + 1, seq1, seq2)
+            rec(i + 1, seq1 + s[i], seq2)
+            rec(i + 1, seq1, seq2 + s[i])
+        
+        rec(0, "", "")
+        return res
+```
+
+```java
+public class Solution {
+    private boolean isPal(String s) {
+        int i = 0, j = s.length() - 1;
+        while (i < j) {
+            if (s.charAt(i) != s.charAt(j)) return false;
+            i++;
+            j--;
+        }
+        return true;
+    }
+
+    public void rec(int i, String s, StringBuilder seq1, StringBuilder seq2, int[] res) {
+        if (i == s.length()) {
+            if (isPal(seq1.toString()) && isPal(seq2.toString())) {
+                res[0] = Math.max(res[0], seq1.length() * seq2.length());
+            }
+            return;
+        }
+
+        rec(i + 1, s, seq1, seq2, res);
+        seq1.append(s.charAt(i));
+        rec(i + 1, s, seq1, seq2, res);
+        seq1.deleteCharAt(seq1.length() - 1);
+
+        seq2.append(s.charAt(i));
+        rec(i + 1, s, seq1, seq2, res);
+        seq2.deleteCharAt(seq2.length() - 1);
+    }
+
+    public int maxProduct(String s) {
+        int[] res = new int[1];
+        rec(0, s, new StringBuilder(), new StringBuilder(), res);
+        return res[0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isPal(const string &s) {
+        int i = 0, j = s.length() - 1;
+        while (i < j) {
+            if (s[i] != s[j]) return false;
+            i++;
+            j--;
+        }
+        return true;
+    }
+
+    void rec(int i, string& s, string& seq1, string& seq2, int &res) {
+        if (i == s.length()) {
+            if (isPal(seq1) && isPal(seq2)) {
+                res = max(res, (int)seq1.length() * (int)seq2.length());
+            }
+            return;
+        }
+
+        rec(i + 1, s, seq1, seq2, res);
+        seq1.push_back(s[i]);
+        rec(i + 1, s, seq1, seq2, res);
+        seq1.pop_back();
+        seq2.push_back(s[i]);
+        rec(i + 1, s, seq1, seq2, res);
+        seq2.pop_back();
+    }
+
+    int maxProduct(string s) {
+        int res = 0;
+        string seq1 = "", seq2 = "";
+        rec(0, s, seq1, seq2, res);
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    maxProduct(s) {
+        const isPal = (str) => {
+            let i = 0, j = str.length - 1;
+            while (i < j) {
+                if (str[i] !== str[j]) return false;
+                i++;
+                j--;
+            }
+            return true;
+        };
+
+        let res = 0;
+
+        const rec = (i, seq1, seq2) => {
+            if (i === s.length) {
+                if (isPal(seq1) && isPal(seq2)) {
+                    res = Math.max(res, seq1.length * seq2.length);
+                }
+                return;
+            }
+
+            rec(i + 1, seq1, seq2);
+            rec(i + 1, seq1 + s[i], seq2);
+            rec(i + 1, seq1, seq2 + s[i]);
+        };
+
+        rec(0, "", "");
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * 3 ^ n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Bit Mask
+
+::tabs-start
+
+```python
+class Solution:
+    def maxProduct(self, s: str) -> int:
+        def isPal(s):
+            i, j = 0, len(s) - 1
+            while i < j:
+                if s[i] != s[j]:
+                    return False
+                i += 1
+                j -= 1
+            return True
+
+        N, pali = len(s), {}
+
+        for mask in range(1, 1 << N):
+            subseq = ""
+            for i in range(N):
+                if mask & (1 << i):
+                    subseq += s[i]
+                
+            if isPal(subseq):
+                pali[mask] = len(subseq)
+        
+        res = 0
+        for m1 in pali:
+            for m2 in pali:
+                if m1 & m2 == 0:
+                    res = max(res, pali[m1] * pali[m2])
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int maxProduct(String s) {
+        int N = s.length();
+        int res = 0;
+        Map<Integer, Integer> pali = new HashMap<>();
+
+        for (int mask = 1; mask < (1 << N); mask++) {
+            StringBuilder subseq = new StringBuilder();
+            for (int i = 0; i < N; i++) {
+                if ((mask & (1 << i)) != 0) {
+                    subseq.append(s.charAt(i));
+                }
+            }
+
+            if (isPal(subseq.toString())) {
+                pali.put(mask, subseq.length());
+            }
+        }
+
+        for (int m1 : pali.keySet()) {
+            for (int m2 : pali.keySet()) {
+                if ((m1 & m2) == 0) {
+                    res = Math.max(res, pali.get(m1) * pali.get(m2));
+                }
+            }
+        }
+
+        return res;
+    }
+
+    private boolean isPal(String s) {
+        int i = 0, j = s.length() - 1;
+        while (i < j) {
+            if (s.charAt(i) != s.charAt(j)) {
+                return false;
+            }
+            i++;
+            j--;
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxProduct(string s) {
+        int N = s.length();
+        int res = 0;
+        unordered_map<int, int> pali;
+
+        for (int mask = 1; mask < (1 << N); mask++) {
+            string subseq = "";
+            for (int i = 0; i < N; i++) {
+                if (mask & (1 << i)) {
+                    subseq += s[i];
+                }
+            }
+
+            if (isPal(subseq)) {
+                pali[mask] = subseq.length();
+            }
+        }
+
+        for (auto& m1 : pali) {
+            for (auto& m2 : pali) {
+                if ((m1.first & m2.first) == 0) {
+                    res = max(res, m1.second * m2.second);
+                }
+            }
+        }
+
+        return res;
+    }
+
+private:
+    bool isPal(const string& s) {
+        int i = 0, j = s.length() - 1;
+        while (i < j) {
+            if (s[i] != s[j]) {
+                return false;
+            }
+            i++;
+            j--;
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    maxProduct(s) {
+        const isPal = (str) => {
+            let i = 0, j = str.length - 1;
+            while (i < j) {
+                if (str[i] !== str[j]) return false;
+                i++;
+                j--;
+            }
+            return true;
+        };
+        
+        const N = s.length;
+        let res = 0;
+        const pali = new Map();
+
+        for (let mask = 1; mask < (1 << N); mask++) {
+            let subseq = "";
+            for (let i = 0; i < N; i++) {
+                if ((mask & (1 << i)) !== 0) {
+                    subseq += s[i];
+                }
+            }
+
+            if (isPal(subseq)) {
+                pali.set(mask, subseq.length);
+            }
+        }
+
+        for (let [m1, len1] of pali) {
+            for (let [m2, len2] of pali) {
+                if ((m1 & m2) === 0) {
+                    res = Math.max(res, len1 * len2);
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(4 ^ n)$
+* Space complexity: $O(2 ^ n)$
+
+---
+
+## 3. Bit Mask + Longest Pallindromic Subsequence
+
+::tabs-start
+
+```python
+class Solution:
+    def longestPalindromeSubseq(self, s: str) -> int:
+        n = len(s)
+        if n == 0:
+            return 0
+        
+        dp = [1] * n
+        for i in range(n - 1, -1, -1):
+            prev = 0
+            for j in range(i + 1, n):
+                tmp = dp[j]
+                if s[i] == s[j]:
+                    dp[j] = 2 + prev
+                else:
+                    dp[j] = max(dp[j - 1], dp[j])
+                prev = tmp
+        return dp[n - 1]
+    
+    def maxProduct(self, s: str) -> int:
+        n = len(s)
+        res = 0
+        
+        for i in range(1, 1 << n):
+            seq1, seq2 = [], []
+            
+            for j in range(n):
+                if (i & (1 << j)) != 0:
+                    seq1.append(s[j])
+                else:
+                    seq2.append(s[j])
+
+            if not self.isPal(seq1):
+                continue
+
+            lps = self.longestPalindromeSubseq(''.join(seq2))
+            res = max(res, len(seq1) * lps)
+        
+        return res
+    
+    def isPal(self, s: str) -> bool:
+        i, j = 0, len(s) - 1
+        while i < j:
+            if s[i] != s[j]:
+                return False
+            i += 1
+            j -= 1
+        return True
+```
+
+```java
+public class Solution {
+    public int longestPalindromeSubseq(String s) {
+        int n = s.length();
+        if (n == 0) return 0;
+        
+        int[] dp = new int[n];
+        Arrays.fill(dp, 1);
+        for (int i = n - 1; i >= 0; i--) {
+            int prev = 0;
+            for (int j = i + 1; j < n; j++) {
+                int tmp = dp[j];
+                if (s.charAt(i) == s.charAt(j)) {
+                    dp[j] = 2 + prev;
+                } else {
+                    dp[j] = Math.max(dp[j - 1], dp[j]);
+                }
+                prev = tmp;
+            }
+        }
+        return dp[n - 1];
+    }
+    
+    public int maxProduct(String s) {
+        int n = s.length();
+        int res = 0;
+        
+        for (int i = 1; i < (1 << n); i++) {
+            StringBuilder seq1 = new StringBuilder(), seq2 = new StringBuilder();
+            
+            for (int j = 0; j < n; j++) {
+                char c = s.charAt(j);
+                if ((i & (1 << j)) != 0) seq1.append(c);
+                else seq2.append(c);
+            }
+
+            if (!isPal(seq1.toString())) continue;
+            int lps = longestPalindromeSubseq(seq2.toString());
+            res = Math.max(res, seq1.length() * lps);
+        }
+        
+        return res;
+    }
+
+    private boolean isPal(String s) {
+        int i = 0, j = s.length() - 1;
+        while (i < j) {
+            if (s.charAt(i) != s.charAt(j)) {
+                return false;
+            }
+            i++;
+            j--;
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int longestPalindromeSubseq(string& s) {
+        int n = s.length();
+        if (n == 0) return 0;
+        
+        vector<int> dp(n, 1);
+        for (int i = n - 1; i >= 0; i--) {
+            int prev = 0;
+            for (int j = i + 1; j < n; j++) {
+                int tmp = dp[j];
+                if (s[i] == s[j]) {
+                    dp[j] = 2 + prev;
+                } else {
+                    dp[j] = max(dp[j - 1], dp[j]);
+                }
+                prev = tmp;
+            }
+        }
+        return dp[n - 1];
+    }
+
+    int maxProduct(string s) {
+        int n = s.length();
+        int res = 0;
+        
+        for (int i = 1; i < (1 << n); i++) {
+            string seq1 = "", seq2 = "";
+            
+            for (int j = 0; j < n; j++) {
+                if ((i & (1 << j)) != 0) seq1 += s[j];
+                else seq2 += s[j];
+            }
+
+            if (!isPal(seq1)) continue;
+
+            int lps = longestPalindromeSubseq(seq2);
+            res = max(res, int(seq1.length()) * lps);
+        }
+        
+        return res;
+    }
+
+    bool isPal(string& s) {
+        int i = 0, j = s.length() - 1;
+        while (i < j) {
+            if (s[i] != s[j]) {
+                return false;
+            }
+            i++;
+            j--;
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    longestPalindromeSubseq(s) {
+        const n = s.length;
+        if (n === 0) return 0;
+        
+        const dp = new Array(n).fill(1);
+        for (let i = n - 1; i >= 0; i--) {
+            let prev = 0;
+            for (let j = i + 1; j < n; j++) {
+                let tmp = dp[j];
+                if (s[i] === s[j]) {
+                    dp[j] = 2 + prev;
+                } else {
+                    dp[j] = Math.max(dp[j - 1], dp[j]);
+                }
+                prev = tmp;
+            }
+        }
+        return dp[n - 1];
+    }
+
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    maxProduct(s) {
+        const n = s.length;
+        let res = 0;
+        
+        for (let i = 1; i < (1 << n); i++) {
+            let seq1 = "", seq2 = "";
+            
+            for (let j = 0; j < n; j++) {
+                if ((i & (1 << j)) !== 0) seq1 += s[j];
+                else seq2 += s[j];
+            }
+
+            if (!this.isPal(seq1)) continue;
+
+            const lps = this.longestPalindromeSubseq(seq2);
+            res = Math.max(res, seq1.length * lps);
+        }
+        
+        return res;
+    }
+
+    /**
+     * @param {string} s
+     * @return {boolean}
+     */
+    isPal(s) {
+        let i = 0, j = s.length - 1;
+        while (i < j) {
+            if (s[i] !== s[j]) {
+                return false;
+            }
+            i++;
+            j--;
+        }
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 * 2 ^ n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Bit Mask + LPS (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def longestPalindromeSubseq(self, s: str, mask: int, dp: List[int]) -> int:
+        n = len(s)
+        for i in range(n - 1, -1, -1):
+            if (mask & (1 << i)) != 0:
+                continue
+
+            prev = 0
+            for j in range(i + 1, n):
+                tmp = dp[j]
+                if (mask & (1 << j)) == 0 and s[i] == s[j]:
+                    dp[j] = 2 + prev
+                else:
+                    dp[j] = max(dp[j - 1], dp[j])
+                prev = tmp
+        return dp[-1]
+
+    def maxProduct(self, s: str) -> int:
+        n = len(s)
+        res = 0
+        dp = [1] * n
+
+        for i in range(1, 1 << n):
+            m1 = self.palsize(s, i)
+            if m1 == 0:
+                continue
+
+            for j in range(n):
+                if (i & (1 << j)) == 0:
+                    dp[j] = 1
+                else:
+                    dp[j] = 0
+
+            m2 = self.longestPalindromeSubseq(s, i, dp)
+            res = max(res, m1 * m2)
+
+        return res
+
+    def palsize(self, s: str, mask: int) -> int:
+        i, j = 0, len(s) - 1
+        res = 0
+        while i <= j:
+            if (mask & (1 << i)) == 0:
+                i += 1
+            elif (mask & (1 << j)) == 0:
+                j -= 1
+            else:
+                if s[i] != s[j]:
+                    return 0
+                res += 1 if i == j else 2
+                i += 1
+                j -= 1
+        return res
+```
+
+```java
+public class Solution {
+    public int longestPalindromeSubseq(String s, int mask, int[] dp) {
+        int n = s.length();
+        for (int i = n - 1; i >= 0; i--) {
+            if ((mask & (1 << i)) != 0) continue;
+
+            int prev = 0;
+            for (int j = i + 1; j < n; j++) {
+                int tmp = dp[j];
+                if ((mask & (1 << j)) == 0 && s.charAt(i) == s.charAt(j)) {
+                    dp[j] = 2 + prev;
+                } else {
+                    dp[j] = Math.max(dp[j - 1], dp[j]);
+                }
+                prev = tmp;
+            }
+        }
+        return dp[n - 1];
+    }
+
+    public int maxProduct(String s) {
+        int n = s.length();
+        int res = 0;
+        int[] dp = new int[n];
+
+        for (int i = 1; i < (1 << n); i++) {
+            int m1 = palsize(s, i);
+            if (m1 == 0) continue;
+
+            for (int j = 0; j < n; j++) {
+                if ((i & (1 << j)) == 0) {
+                    dp[j] = 1;
+                } else {
+                    dp[j] = 0;
+                }
+            }
+            int m2 = longestPalindromeSubseq(s, i, dp);
+            res = Math.max(res, m1 * m2);
+        }
+        return res;
+    }
+
+    public int palsize(String s, int mask) {
+        int i = 0, j = s.length() - 1;
+        int res = 0;
+        while (i <= j) {
+            if ((mask & (1 << i)) == 0) i++;
+            else if ((mask & (1 << j)) == 0) j--;
+            else {
+                if (s.charAt(i) != s.charAt(j)) return 0;
+                res += (i == j) ? 1 : 2;
+                i++;
+                j--;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int longestPalindromeSubseq(string& s, int mask, vector<int>& dp) {
+        int n = s.length();
+        for (int i = n - 1; i >= 0; i--) {
+            if ((mask & (1 << i)) != 0) continue;
+
+            int prev = 0;
+            for (int j = i + 1; j < n; j++) {
+                int tmp = dp[j];
+                if ((mask & (1 << j)) == 0 && s[i] == s[j]) {
+                    dp[j] = 2 + prev;
+                } else {
+                    dp[j] = max(dp[j - 1], dp[j]);
+                }
+                prev = tmp;
+            }
+        }
+        return dp[n - 1];
+    }
+
+    int maxProduct(string s) {
+        int n = s.length();
+        int res = 0;
+        vector<int> dp(n, 1);
+
+        for (int i = 1; i < (1 << n); i++) {
+            int m1 = palsize(s, i);
+            if (m1 == 0) continue;
+
+            for (int j = 0; j < n; j++) {
+                if ((i & (1 << j)) == 0) {
+                    dp[j] = 1;
+                } else {
+                    dp[j] = 0;
+                }
+            }
+            int m2 = longestPalindromeSubseq(s, i, dp);
+            res = max(res, m1 * m2);
+        }
+
+        return res;
+    }
+
+    int palsize(string& s, int mask) {
+        int i = 0, j = s.length() - 1;
+        int res = 0;
+        while (i <= j) {
+            if ((mask & (1 << i)) == 0) i++;
+            else if ((mask & (1 << j)) == 0) j--;
+            else {
+                if (s[i] != s[j]) return 0;
+                res += (i == j) ? 1 : 2;
+                i++;
+                j--;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {number} mask
+     * @param {number[]} dp
+     * @return {number}
+     */
+    longestPalindromeSubseq(s, mask, dp) {
+        const n = s.length;
+        for (let i = n - 1; i >= 0; i--) {
+            if ((mask & (1 << i)) !== 0) continue;
+
+            let prev = 0;
+            for (let j = i + 1; j < n; j++) {
+                const tmp = dp[j];
+                if ((mask & (1 << j)) === 0 && s[i] === s[j]) {
+                    dp[j] = 2 + prev;
+                } else {
+                    dp[j] = Math.max(dp[j - 1], dp[j]);
+                }
+                prev = tmp;
+            }
+        }
+        return dp[n - 1];
+    }
+
+    /**
+     * @param {string} s
+     * @return {boolean}
+     */
+    maxProduct(s) {
+        const n = s.length;
+        let res = 0;
+        const dp = Array(n).fill(1);
+
+        for (let i = 1; i < (1 << n); i++) {
+            const m1 = this.palsize(s, i);
+            if (m1 === 0) continue;
+
+            for (let j = 0; j < n; j++) {
+                if ((i & (1 << j)) === 0) {
+                    dp[j] = 1;
+                } else {
+                    dp[j] = 0;
+                }
+            }
+            const m2 = this.longestPalindromeSubseq(s, i, dp);
+            res = Math.max(res, m1 * m2);
+        }
+        return res;
+    }
+    
+    /**
+     * @param {string} s
+     * @param {number} mask
+     * @return {number}
+     */
+    palsize(s, mask) {
+        let i = 0, j = s.length - 1;
+        let res = 0;
+        while (i <= j) {
+            if ((mask & (1 << i)) === 0) i++;
+            else if ((mask & (1 << j)) === 0) j--;
+            else {
+                if (s[i] !== s[j]) return 0;
+                res += (i === j) ? 1 : 2;
+                i++;
+                j--;
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 * 2 ^ n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/maximum-product-subarray.md b/articles/maximum-product-subarray.md
index c1e607cab..f163b341f 100644
--- a/articles/maximum-product-subarray.md
+++ b/articles/maximum-product-subarray.md
@@ -98,6 +98,64 @@ public class Solution {
 }
 ```
 
+```go
+func maxProduct(nums []int) int {
+    res := nums[0]
+    for i := 0; i < len(nums); i++ {
+        cur := nums[i]
+        res = max(res, cur)
+        for j := i + 1; j < len(nums); j++ {
+            cur *= nums[j]
+            res = max(res, cur)
+        }
+    }
+    return res
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun maxProduct(nums: IntArray): Int {
+        var res = nums[0]
+        for (i in nums.indices) {
+            var cur = nums[i]
+            res = maxOf(res, cur)
+            for (j in i + 1 until nums.size) {
+                cur *= nums[j]
+                res = maxOf(res, cur)
+            }
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func maxProduct(_ nums: [Int]) -> Int {
+        var res = nums[0]
+
+        for i in 0..<nums.count {
+            var cur = nums[i]
+            res = max(res, cur)
+            for j in (i + 1)..<nums.count {
+                cur *= nums[j]
+                res = max(res, cur)
+            }
+        }
+
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -335,6 +393,181 @@ public class Solution {
 }
 ```
 
+```go
+func maxProduct(nums []int) int {
+    res := math.MinInt32
+    for _, num := range nums {
+        res = max(res, num)
+    }
+
+    var A [][]int
+    var cur []int
+    for _, num := range nums {
+        if num == 0 {
+            if len(cur) > 0 {
+                A = append(A, cur)
+            }
+            cur = nil
+        } else {
+            cur = append(cur, num)
+        }
+    }
+    if len(cur) > 0 {
+        A = append(A, cur)
+    }
+
+    for _, sub := range A {
+        negs := 0
+        for _, i := range sub {
+            if i < 0 {
+                negs++
+            }
+        }
+        prod := 1
+        need := negs
+        if negs%2 != 0 {
+            need = negs - 1
+        }
+        negs = 0
+        j := 0
+        for i := range sub {
+            prod *= sub[i]
+            if sub[i] < 0 {
+                negs++
+                for negs > need {
+                    prod /= sub[j]
+                    if sub[j] < 0 {
+                        negs--
+                    }
+                    j++
+                }
+            }
+            if j <= i {
+                res = max(res, prod)
+            }
+        }
+    }
+    return res
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun maxProduct(nums: IntArray): Int {
+        var res = Int.MIN_VALUE
+        for (num in nums) {
+            res = maxOf(res, num)
+        }
+
+        val A = mutableListOf<MutableList<Int>>()
+        var cur = mutableListOf<Int>()
+        for (num in nums) {
+            if (num == 0) {
+                if (cur.isNotEmpty()) {
+                    A.add(cur.toMutableList())
+                }
+                cur.clear()
+            } else {
+                cur.add(num)
+            }
+        }
+        if (cur.isNotEmpty()) {
+            A.add(cur.toMutableList())
+        }
+
+        for (sub in A) {
+            var negs = 0
+            for (i in sub) {
+                if (i < 0) {
+                    negs++
+                }
+            }
+            var prod = 1
+            var need = if (negs % 2 == 0) negs else negs - 1
+            negs = 0
+            var j = 0
+            for (i in sub.indices) {
+                prod *= sub[i]
+                if (sub[i] < 0) {
+                    negs++
+                    while (negs > need) {
+                        prod /= sub[j]
+                        if (sub[j] < 0) {
+                            negs--
+                        }
+                        j++
+                    }
+                }
+                if (j <= i) {
+                    res = maxOf(res, prod)
+                }
+            }
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func maxProduct(_ nums: [Int]) -> Int {
+        var A = [[Int]]()
+        var cur = [Int]()
+        var res = Int.min
+
+        for num in nums {
+            res = max(res, num)
+            if num == 0 {
+                if !cur.isEmpty {
+                    A.append(cur)
+                }
+                cur = []
+            } else {
+                cur.append(num)
+            }
+        }
+
+        if !cur.isEmpty {
+            A.append(cur)
+        }
+
+        for sub in A {
+            let negsCount = sub.filter { $0 < 0 }.count
+            var prod = 1
+            var need = negsCount % 2 == 0 ? negsCount : negsCount - 1
+            var negs = 0
+            var j = 0
+
+            for i in 0..<sub.count {
+                prod *= sub[i]
+                if sub[i] < 0 {
+                    negs += 1
+                    while negs > need {
+                        prod /= sub[j]
+                        if sub[j] < 0 {
+                            negs -= 1
+                        }
+                        j += 1
+                    }
+                }
+                if j <= i {
+                    res = max(res, prod)
+                }
+            }
+        }
+
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -436,6 +669,68 @@ public class Solution {
 }
 ```
 
+```go
+func maxProduct(nums []int) int {
+    res := nums[0]
+    curMin, curMax := 1, 1
+    for _, num := range nums {
+        tmp := curMax * num
+        curMax = max(num*curMax, max(num*curMin, num))
+        curMin = min(tmp, min(num*curMin, num))
+        res = max(res, curMax)
+    }
+    return res
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun maxProduct(nums: IntArray): Int {
+        var res = nums[0]
+        var curMin = 1
+        var curMax = 1
+        for (num in nums) {
+            val tmp = curMax * num
+            curMax = maxOf(num * curMax, maxOf(num * curMin, num))
+            curMin = minOf(tmp, minOf(num * curMin, num))
+            res = maxOf(res, curMax)
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func maxProduct(_ nums: [Int]) -> Int {
+        var res = nums[0]
+        var curMin = 1, curMax = 1
+
+        for num in nums {
+            let tmp = curMax * num
+            curMax = max(num * curMax, num * curMin, num)
+            curMin = min(tmp, num * curMin, num)
+            res = max(res, curMax)
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -533,6 +828,75 @@ public class Solution {
 }
 ```
 
+```go
+func maxProduct(nums []int) int {
+    n := len(nums)
+    res := nums[0]
+    prefix, suffix := 0, 0
+
+    for i := 0; i < n; i++ {
+        if prefix == 0 {
+            prefix = 1
+        }
+        if suffix == 0 {
+            suffix = 1
+        }
+        
+        prefix *= nums[i]
+        suffix *= nums[n-1-i]
+        res = max(res, max(prefix, suffix))
+    }
+
+    return res
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun maxProduct(nums: IntArray): Int {
+        val n = nums.size
+        var res = nums[0]
+        var prefix = 0
+        var suffix = 0
+
+        for (i in 0 until n) {
+            if (prefix == 0) prefix = 1
+            if (suffix == 0) suffix = 1
+
+            prefix *= nums[i]
+            suffix *= nums[n - 1 - i]
+            res = maxOf(res, prefix, suffix)
+        }
+
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func maxProduct(_ nums: [Int]) -> Int {
+        let n = nums.count
+        var res = nums[0]
+        var prefix = 0, suffix = 0
+
+        for i in 0..<n {
+            prefix = nums[i] * (prefix != 0 ? prefix : 1)
+            suffix = nums[n - 1 - i] * (suffix != 0 ? suffix : 1)
+            res = max(res, max(prefix, suffix))
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/maximum-profit-in-job-scheduling.md b/articles/maximum-profit-in-job-scheduling.md
new file mode 100644
index 000000000..0c0d40541
--- /dev/null
+++ b/articles/maximum-profit-in-job-scheduling.md
@@ -0,0 +1,810 @@
+## 1. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def jobScheduling(self, startTime: List[int], endTime: List[int], profit: List[int]) -> int:
+        intervals = sorted(zip(startTime, endTime, profit))
+        cache = {}
+
+        def dfs(i):
+            if i == len(intervals):
+                return 0
+            if i in cache:
+                return cache[i]
+
+            # don't include
+            res = dfs(i + 1)
+
+            # include
+            j = i + 1
+            while j < len(intervals):
+                if intervals[i][1] <= intervals[j][0]:
+                    break
+                j += 1
+
+            cache[i] = res = max(res, intervals[i][2] + dfs(j))
+            return res
+
+        return dfs(0)
+```
+
+```java
+public class Solution {
+    private int[][] intervals;
+    private int[] cache;
+
+    public int jobScheduling(int[] startTime, int[] endTime, int[] profit) {
+        int n = startTime.length;
+        intervals = new int[n][3];
+        cache = new int[n];
+        Arrays.fill(cache, -1);
+
+        for (int i = 0; i < n; i++) {
+            intervals[i] = new int[]{startTime[i], endTime[i], profit[i]};
+        }
+        Arrays.sort(intervals, Comparator.comparingInt(a -> a[0]));
+
+        return dfs(0);
+    }
+
+    private int dfs(int i) {
+        if (i == intervals.length) {
+            return 0;
+        }
+        if (cache[i] != -1) {
+            return cache[i];
+        }
+
+        // Don't include
+        int res = dfs(i + 1);
+
+        // Include
+        int j = i + 1;
+        while (j < intervals.length && intervals[i][1] > intervals[j][0]) {
+            j++;
+        }
+
+        return cache[i] = Math.max(res, intervals[i][2] + dfs(j));
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> intervals;
+    vector<int> cache;
+
+    int jobScheduling(vector<int>& startTime, vector<int>& endTime, vector<int>& profit) {
+        int n = startTime.size();
+        intervals.resize(n, vector<int>(3));
+        cache.assign(n, -1);
+
+        for (int i = 0; i < n; i++) {
+            intervals[i] = {startTime[i], endTime[i], profit[i]};
+        }
+        sort(intervals.begin(), intervals.end());
+
+        return dfs(0);
+    }
+
+private:
+    int dfs(int i) {
+        if (i == intervals.size()) {
+            return 0;
+        }
+        if (cache[i] != -1) {
+            return cache[i];
+        }
+
+        // Don't include
+        int res = dfs(i + 1);
+
+        // Include
+        int j = i + 1;
+        while (j < intervals.size() && intervals[i][1] > intervals[j][0]) {
+            j++;
+        }
+
+        return cache[i] = max(res, intervals[i][2] + dfs(j));
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} startTime
+     * @param {number[]} endTime
+     * @param {number[]} profit
+     * @return {number}
+     */
+    jobScheduling(startTime, endTime, profit) {
+        let n = startTime.length;
+        let intervals = new Array(n).fill(null).map((_, i) => 
+            [startTime[i], endTime[i], profit[i]]
+        );
+        intervals.sort((a, b) => a[0] - b[0]);
+
+        let cache = new Array(n).fill(-1);
+
+        const dfs = (i) => {
+            if (i === n) {
+                return 0;
+            }
+            if (cache[i] !== -1) {
+                return cache[i];
+            }
+
+            // Don't include
+            let res = dfs(i + 1);
+
+            // Include
+            let j = i + 1;
+            while (j < n && intervals[i][1] > intervals[j][0]) {
+                j++;
+            }
+
+            return (cache[i] = Math.max(res, intervals[i][2] + dfs(j)));
+        };
+
+        return dfs(0);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int JobScheduling(int[] startTime, int[] endTime, int[] profit) {
+        int n = startTime.Length;
+        var intervals = new List<(int start, int end, int profit)>();
+
+        for (int i = 0; i < n; i++) {
+            intervals.Add((startTime[i], endTime[i], profit[i]));
+        }
+
+        intervals.Sort((a, b) => a.start.CompareTo(b.start));
+        Dictionary<int, int> cache = new();
+
+        int Dfs(int i) {
+            if (i == n) return 0;
+            if (cache.ContainsKey(i)) return cache[i];
+
+            // Option 1: don't include
+            int res = Dfs(i + 1);
+
+            // Option 2: include current job
+            int j = i + 1;
+            while (j < n && intervals[j].start < intervals[i].end) {
+                j++;
+            }
+
+            res = Math.Max(res, intervals[i].profit + Dfs(j));
+            cache[i] = res;
+            return res;
+        }
+
+        return Dfs(0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Dynamic Programming (Top-Down) + Binary Search
+
+::tabs-start
+
+```python
+class Solution:
+    def jobScheduling(self, startTime: List[int], endTime: List[int], profit: List[int]) -> int:
+        intervals = sorted(zip(startTime, endTime, profit))
+        cache = {}
+
+        def dfs(i):
+            if i == len(intervals):
+                return 0
+            if i in cache:
+                return cache[i]
+
+            # don't include
+            res = dfs(i + 1)
+
+            # include
+            j = bisect.bisect(intervals, (intervals[i][1], -1, -1))
+            cache[i] = res = max(res, intervals[i][2] + dfs(j))
+            return res
+
+        return dfs(0)
+```
+
+```java
+public class Solution {
+    private int[][] intervals;
+    private int[] cache;
+    
+    public int jobScheduling(int[] startTime, int[] endTime, int[] profit) {
+        int n = startTime.length;
+        intervals = new int[n][3];
+        cache = new int[n];
+        Arrays.fill(cache, -1);
+
+        for (int i = 0; i < n; i++) {
+            intervals[i] = new int[]{startTime[i], endTime[i], profit[i]};
+        }
+        Arrays.sort(intervals, Comparator.comparingInt(a -> a[0]));
+
+        return dfs(0);
+    }
+
+    private int dfs(int i) {
+        if (i == intervals.length) {
+            return 0;
+        }
+        if (cache[i] != -1) {
+            return cache[i];
+        }
+
+        int res = dfs(i + 1);
+
+        int left = i + 1, right = intervals.length, j = intervals.length;
+        while (left < right) {
+            int mid = left + (right - left) / 2;
+            if (intervals[mid][0] >= intervals[i][1]) {
+                j = mid;
+                right = mid;
+            } else {
+                left = mid + 1;
+            }
+        }
+
+        return cache[i] = Math.max(res, intervals[i][2] + dfs(j));
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> intervals;
+    vector<int> cache;
+
+    int jobScheduling(vector<int>& startTime, vector<int>& endTime, vector<int>& profit) {
+        int n = startTime.size();
+        intervals.resize(n, vector<int>(3));
+        cache.assign(n, -1);
+
+        for (int i = 0; i < n; i++) {
+            intervals[i] = {startTime[i], endTime[i], profit[i]};
+        }
+        sort(intervals.begin(), intervals.end());
+
+        return dfs(0);
+    }
+
+private:
+    int dfs(int i) {
+        if (i == intervals.size()) {
+            return 0;
+        }
+        if (cache[i] != -1) {
+            return cache[i];
+        }
+
+        int res = dfs(i + 1);
+
+        int left = i + 1, right = intervals.size(), j = intervals.size();
+        while (left < right) {
+            int mid = left + (right - left) / 2;
+            if (intervals[mid][0] >= intervals[i][1]) {
+                j = mid;
+                right = mid;
+            } else {
+                left = mid + 1;
+            }
+        }
+
+        return cache[i] = max(res, intervals[i][2] + dfs(j));
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} startTime
+     * @param {number[]} endTime
+     * @param {number[]} profit
+     * @return {number}
+     */
+    jobScheduling(startTime, endTime, profit) {
+        let n = startTime.length;
+        let intervals = new Array(n).fill(null).map((_, i) => 
+            [startTime[i], endTime[i], profit[i]]
+        );
+        intervals.sort((a, b) => a[0] - b[0]);
+
+        let cache = new Array(n).fill(-1);
+
+        const dfs = (i) => {
+            if (i === n) {
+                return 0;
+            }
+            if (cache[i] !== -1) {
+                return cache[i];
+            }
+
+            let res = dfs(i + 1);
+
+            let left = i + 1, right = n, j = n;
+            while (left < right) {
+                let mid = Math.floor((left + right) / 2);
+                if (intervals[mid][0] >= intervals[i][1]) {
+                    j = mid;
+                    right = mid;
+                } else {
+                    left = mid + 1;
+                }
+            }
+
+            return (cache[i] = Math.max(res, intervals[i][2] + dfs(j)));
+        };
+
+        return dfs(0);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    private int[][] intervals;
+    private int[] cache;
+
+    public int JobScheduling(int[] startTime, int[] endTime, int[] profit) {
+        int n = startTime.Length;
+        intervals = new int[n][];
+        cache = new int[n];
+        Array.Fill(cache, -1);
+
+        for (int i = 0; i < n; i++) {
+            intervals[i] = new int[] { startTime[i], endTime[i], profit[i] };
+        }
+
+        Array.Sort(intervals, (a, b) => a[0].CompareTo(b[0]));
+        return Dfs(0);
+    }
+
+    private int Dfs(int i) {
+        if (i == intervals.Length) return 0;
+        if (cache[i] != -1) return cache[i];
+
+        int res = Dfs(i + 1);
+
+        int left = i + 1, right = intervals.Length, j = intervals.Length;
+        while (left < right) {
+            int mid = left + (right - left) / 2;
+            if (intervals[mid][0] >= intervals[i][1]) {
+                j = mid;
+                right = mid;
+            } else {
+                left = mid + 1;
+            }
+        }
+
+        cache[i] = Math.Max(res, intervals[i][2] + Dfs(j));
+        return cache[i];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Top-Down) + Binary Search (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def jobScheduling(self, startTime: List[int], endTime: List[int], profit: List[int]) -> int:
+        n = len(startTime)
+        index = list(range(n))
+        index.sort(key=lambda i: startTime[i])
+
+        cache = [-1] * n
+
+        def dfs(i):
+            if i == n:
+                return 0
+            if cache[i] != -1:
+                return cache[i]
+
+            res = dfs(i + 1)
+
+            left, right, j = i + 1, n, n
+            while left < right:
+                mid = (left + right) // 2
+                if startTime[index[mid]] >= endTime[index[i]]:
+                    j = mid
+                    right = mid
+                else:
+                    left = mid + 1
+
+            cache[i] = res = max(res, profit[index[i]] + dfs(j))
+            return res
+
+        return dfs(0)
+```
+
+```java
+public class Solution {
+    private int[] startTime, endTime, profit, cache;
+    private Integer[] index;
+    private int n;
+
+    public int jobScheduling(int[] startTime, int[] endTime, int[] profit) {
+        this.n = startTime.length;
+        this.startTime = startTime;
+        this.endTime = endTime;
+        this.profit = profit;
+        this.index = new Integer[n];
+        this.cache = new int[n];
+        Arrays.fill(cache, -1);
+
+        for (int i = 0; i < n; i++) {
+            index[i] = i;
+        }
+        Arrays.sort(index, Comparator.comparingInt(i -> startTime[i]));
+
+        return dfs(0);
+    }
+
+    private int dfs(int i) {
+        if (i == n) {
+            return 0;
+        }
+        if (cache[i] != -1) {
+            return cache[i];
+        }
+
+        int res = dfs(i + 1);
+
+        int left = i + 1, right = n, j = n;
+        while (left < right) {
+            int mid = left + (right - left) / 2;
+            if (startTime[index[mid]] >= endTime[index[i]]) {
+                j = mid;
+                right = mid;
+            } else {
+                left = mid + 1;
+            }
+        }
+
+        return cache[i] = Math.max(res, profit[index[i]] + dfs(j));
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> startTime, endTime, profit, index, cache;
+    int n;
+
+    int jobScheduling(vector<int>& startTime, vector<int>& endTime, vector<int>& profit) {
+        this->n = startTime.size();
+        this->startTime = startTime;
+        this->endTime = endTime;
+        this->profit = profit;
+        this->index.resize(n);
+        this->cache.assign(n, -1);
+
+        for (int i = 0; i < n; i++) {
+            index[i] = i;
+        }
+        sort(index.begin(), index.end(), [&](int i, int j) {
+            return startTime[i] < startTime[j];
+        });
+
+        return dfs(0);
+    }
+
+private:
+    int dfs(int i) {
+        if (i == n) {
+            return 0;
+        }
+        if (cache[i] != -1) {
+            return cache[i];
+        }
+
+        int res = dfs(i + 1);
+
+        int left = i + 1, right = n, j = n;
+        while (left < right) {
+            int mid = left + (right - left) / 2;
+            if (startTime[index[mid]] >= endTime[index[i]]) {
+                j = mid;
+                right = mid;
+            } else {
+                left = mid + 1;
+            }
+        }
+
+        return cache[i] = max(res, profit[index[i]] + dfs(j));
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} startTime
+     * @param {number[]} endTime
+     * @param {number[]} profit
+     * @return {number}
+     */
+    jobScheduling(startTime, endTime, profit) {
+        let n = startTime.length;
+        let index = Array.from({ length: n }, (_, i) => i);
+        index.sort((a, b) => startTime[a] - startTime[b]);
+
+        let cache = new Array(n).fill(-1);
+
+        const dfs = (i) => {
+            if (i === n) {
+                return 0;
+            }
+            if (cache[i] !== -1) {
+                return cache[i];
+            }
+
+            let res = dfs(i + 1);
+
+            let left = i + 1, right = n, j = n;
+            while (left < right) {
+                let mid = Math.floor((left + right) / 2);
+                if (startTime[index[mid]] >= endTime[index[i]]) {
+                    j = mid;
+                    right = mid;
+                } else {
+                    left = mid + 1;
+                }
+            }
+
+            return (cache[i] = Math.max(res, profit[index[i]] + dfs(j)));
+        };
+
+        return dfs(0);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    private int[] startTime, endTime, profit, cache;
+    private int[] index;
+    private int n;
+
+    public int JobScheduling(int[] startTime, int[] endTime, int[] profit) {
+        this.n = startTime.Length;
+        this.startTime = startTime;
+        this.endTime = endTime;
+        this.profit = profit;
+        this.index = new int[n];
+        this.cache = new int[n];
+        Array.Fill(cache, -1);
+
+        for (int i = 0; i < n; i++) {
+            index[i] = i;
+        }
+
+        Array.Sort(index, (a, b) => startTime[a].CompareTo(startTime[b]));
+
+        return Dfs(0);
+    }
+
+    private int Dfs(int i) {
+        if (i == n) return 0;
+        if (cache[i] != -1) return cache[i];
+
+        int res = Dfs(i + 1);
+
+        int left = i + 1, right = n, j = n;
+        while (left < right) {
+            int mid = left + (right - left) / 2;
+            if (startTime[index[mid]] >= endTime[index[i]]) {
+                j = mid;
+                right = mid;
+            } else {
+                left = mid + 1;
+            }
+        }
+
+        return cache[i] = Math.Max(res, profit[index[i]] + Dfs(j));
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Dynamic Programming (Bottom-Up) + Binary Search
+
+::tabs-start
+
+```python
+class Solution:
+    def jobScheduling(self, startTime: List[int], endTime: List[int], profit: List[int]) -> int:
+        n = len(startTime)
+        index = list(range(n))
+        index.sort(key=lambda i: startTime[i])
+
+        dp = [0] * (n + 1)
+
+        for i in range(n - 1, -1, -1):
+            left, right, j = i + 1, n, n
+            while left < right:
+                mid = (left + right) // 2
+                if startTime[index[mid]] >= endTime[index[i]]:
+                    j = mid
+                    right = mid
+                else:
+                    left = mid + 1
+
+            dp[i] = max(dp[i + 1], profit[index[i]] + dp[j])
+
+        return dp[0]
+```
+
+```java
+public class Solution {
+    public int jobScheduling(int[] startTime, int[] endTime, int[] profit) {
+        int n = startTime.length;
+        Integer[] index = new Integer[n];
+        for (int i = 0; i < n; i++) index[i] = i;
+        Arrays.sort(index, Comparator.comparingInt(i -> startTime[i]));
+
+        int[] dp = new int[n + 1];
+
+        for (int i = n - 1; i >= 0; i--) {
+            int left = i + 1, right = n, j = n;
+            while (left < right) {
+                int mid = left + (right - left) / 2;
+                if (startTime[index[mid]] >= endTime[index[i]]) {
+                    j = mid;
+                    right = mid;
+                } else {
+                    left = mid + 1;
+                }
+            }
+            dp[i] = Math.max(dp[i + 1], profit[index[i]] + dp[j]);
+        }
+
+        return dp[0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int jobScheduling(vector<int>& startTime, vector<int>& endTime, vector<int>& profit) {
+        int n = startTime.size();
+        vector<int> index(n), dp(n + 1, 0);
+        for (int i = 0; i < n; i++) index[i] = i;
+        sort(index.begin(), index.end(), [&](int i, int j) {
+            return startTime[i] < startTime[j];
+        });
+
+        for (int i = n - 1; i >= 0; i--) {
+            int left = i + 1, right = n, j = n;
+            while (left < right) {
+                int mid = left + (right - left) / 2;
+                if (startTime[index[mid]] >= endTime[index[i]]) {
+                    j = mid;
+                    right = mid;
+                } else {
+                    left = mid + 1;
+                }
+            }
+            dp[i] = max(dp[i + 1], profit[index[i]] + dp[j]);
+        }
+
+        return dp[0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} startTime
+     * @param {number[]} endTime
+     * @param {number[]} profit
+     * @return {number}
+     */
+    jobScheduling(startTime, endTime, profit) {
+        let n = startTime.length;
+        let index = Array.from({ length: n }, (_, i) => i);
+        index.sort((a, b) => startTime[a] - startTime[b]);
+
+        let dp = new Array(n + 1).fill(0);
+
+        for (let i = n - 1; i >= 0; i--) {
+            let left = i + 1, right = n, j = n;
+            while (left < right) {
+                let mid = Math.floor((left + right) / 2);
+                if (startTime[index[mid]] >= endTime[index[i]]) {
+                    j = mid;
+                    right = mid;
+                } else {
+                    left = mid + 1;
+                }
+            }
+            dp[i] = Math.max(dp[i + 1], profit[index[i]] + dp[j]);
+        }
+
+        return dp[0];
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int JobScheduling(int[] startTime, int[] endTime, int[] profit) {
+        int n = startTime.Length;
+        int[] index = new int[n];
+        for (int i = 0; i < n; i++) index[i] = i;
+
+        Array.Sort(index, (a, b) => startTime[a].CompareTo(startTime[b]));
+
+        int[] dp = new int[n + 1];
+
+        for (int i = n - 1; i >= 0; i--) {
+            int left = i + 1, right = n, j = n;
+            while (left < right) {
+                int mid = left + (right - left) / 2;
+                if (startTime[index[mid]] >= endTime[index[i]]) {
+                    j = mid;
+                    right = mid;
+                } else {
+                    left = mid + 1;
+                }
+            }
+
+            dp[i] = Math.Max(dp[i + 1], profit[index[i]] + dp[j]);
+        }
+
+        return dp[0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/maximum-score-after-splitting-a-string.md b/articles/maximum-score-after-splitting-a-string.md
new file mode 100644
index 000000000..04d95fb31
--- /dev/null
+++ b/articles/maximum-score-after-splitting-a-string.md
@@ -0,0 +1,495 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def maxScore(self, s: str) -> int:
+        n, res = len(s), 0
+        for i in range(1, n):
+            left_zero = 0
+            for j in range(i):
+                if s[j] == '0':
+                    left_zero += 1
+            right_one = 0
+            for j in range(i, n):
+                if s[j] == '1':
+                    right_one += 1
+            res = max(res, left_zero + right_one)
+        return res
+```
+
+```java
+public class Solution {
+    public int maxScore(String s) {
+        int n = s.length(), res = 0;
+        for (int i = 1; i < n; i++) {
+            int leftZero = 0, rightOne = 0;
+            for (int j = 0; j < i; j++) {
+                if (s.charAt(j) == '0') {
+                    leftZero++;
+                }
+            }
+            for (int j = i; j < n; j++) {
+                if (s.charAt(j) == '1') {
+                    rightOne++;
+                }
+            }
+            res = Math.max(res, leftZero + rightOne);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxScore(string s) {
+        int n = s.size(), res = 0;
+        for (int i = 1; i < n; i++) {
+            int leftZero = 0, rightOne = 0;
+            for (int j = 0; j < i; j++) {
+                if (s[j] == '0') {
+                    leftZero++;
+                }
+            }
+            for (int j = i; j < n; j++) {
+                if (s[j] == '1') {
+                    rightOne++;
+                }
+            }
+            res = max(res, leftZero + rightOne);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    maxScore(s) {
+        const n = s.length;
+        let res = 0;
+        for (let i = 1; i < n; i++) {
+            let leftZero = 0, rightOne = 0;
+            for (let j = 0; j < i; j++) {
+                if (s[j] === '0') {
+                    leftZero++;
+                }
+            }
+            for (let j = i; j < n; j++) {
+                if (s[j] === '1') {
+                    rightOne++;
+                }
+            }
+            res = Math.max(res, leftZero + rightOne);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Prefix & Suffix Arrays
+
+::tabs-start
+
+```python
+class Solution:
+    def maxScore(self, s: str) -> int:
+        n = len(s)
+        left_zero = [0] * n
+        right_one = [0] * n
+
+        if s[0] == '0':
+            left_zero[0] = 1
+        for i in range(1, n):
+            left_zero[i] = left_zero[i - 1]
+            if s[i] == '0':
+                left_zero[i] += 1
+
+        if s[n - 1] == '1':
+            right_one[n - 1] = 1
+        for i in range(n - 2, -1, -1):
+            right_one[i] = right_one[i + 1]
+            if s[i] == '1':
+                right_one[i] += 1
+
+        res = 0
+        for i in range(1, n):
+            res = max(res, left_zero[i - 1] + right_one[i])
+        return res
+```
+
+```java
+public class Solution {
+    public int maxScore(String s) {
+        int n = s.length();
+        int[] leftZero = new int[n];
+        int[] rightOne = new int[n];
+
+        if (s.charAt(0) == '0') {
+            leftZero[0] = 1;
+        }
+        for (int i = 1; i < n; i++) {
+            leftZero[i] = leftZero[i - 1];
+            if (s.charAt(i) == '0') {
+                leftZero[i]++;
+            }
+        }
+
+        if (s.charAt(n - 1) == '1') {
+            rightOne[n - 1] = 1;
+        }
+        for (int i = n - 2; i >= 0; i--) {
+            rightOne[i] = rightOne[i + 1];
+            if (s.charAt(i) == '1') {
+                rightOne[i]++;
+            }
+        }
+
+        int res = 0;
+        for (int i = 1; i < n; i++) {
+            res = Math.max(res, leftZero[i - 1] + rightOne[i]);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxScore(string s) {
+        int n = s.size();
+        vector<int> leftZero(n, 0), rightOne(n, 0);
+
+        if (s[0] == '0') {
+            leftZero[0] = 1;
+        }
+        for (int i = 1; i < n; i++) {
+            leftZero[i] = leftZero[i - 1];
+            if (s[i] == '0') {
+                leftZero[i]++;
+            }
+        }
+
+        if (s[n - 1] == '1') {
+            rightOne[n - 1] = 1;
+        }
+        for (int i = n - 2; i >= 0; i--) {
+            rightOne[i] = rightOne[i + 1];
+            if (s[i] == '1') {
+                rightOne[i]++;
+            }
+        }
+
+        int res = 0;
+        for (int i = 1; i < n; i++) {
+            res = max(res, leftZero[i - 1] + rightOne[i]);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    maxScore(s) {
+        const n = s.length;
+        let leftZero = new Array(n).fill(0);
+        let rightOne = new Array(n).fill(0);
+
+        if (s[0] === '0') {
+            leftZero[0] = 1;
+        }
+        for (let i = 1; i < n; i++) {
+            leftZero[i] = leftZero[i - 1];
+            if (s[i] === '0') {
+                leftZero[i]++;
+            }
+        }
+
+        if (s[n - 1] === '1') {
+            rightOne[n - 1] = 1;
+        }
+        for (let i = n - 2; i >= 0; i--) {
+            rightOne[i] = rightOne[i + 1];
+            if (s[i] === '1') {
+                rightOne[i]++;
+            }
+        }
+
+        let res = 0;
+        for (let i = 1; i < n; i++) {
+            res = Math.max(res, leftZero[i - 1] + rightOne[i]);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Iteration (Two Pass)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxScore(self, s: str) -> int:
+        zero = 0
+        one = s.count('1')
+        res = 0
+
+        for i in range(len(s) - 1):
+            if s[i] == '0':
+                zero += 1
+            else:
+                one -= 1
+            res = max(res, zero + one)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int maxScore(String s) {
+        int zero = 0, one = 0, res = 0;
+
+        for (char c : s.toCharArray()) {
+            if (c == '1') {
+                one++;
+            }
+        }
+
+        for (int i = 0; i < s.length() - 1; i++) {
+            if (s.charAt(i) == '0') {
+                zero++;
+            } else {
+                one--;
+            }
+            res = Math.max(res, zero + one);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxScore(string s) {
+        int zero = 0, one = 0, res = 0;
+
+        for (char c : s) {
+            if (c == '1') {
+                one++;
+            }
+        }
+
+        for (int i = 0; i < s.size() - 1; i++) {
+            if (s[i] == '0') {
+                zero++;
+            } else {
+                one--;
+            }
+            res = max(res, zero + one);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    maxScore(s) {
+        let zero = 0, one = 0, res = 0;
+
+        for (const c of s) {
+            if (c === '1') {
+                one++;
+            }
+        }
+
+        for (let i = 0; i < s.length - 1; i++) {
+            if (s[i] === '0') {
+                zero++;
+            } else {
+                one--;
+            }
+            res = Math.max(res, zero + one);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 4. Iteration (One Pass)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxScore(self, s: str) -> int:
+        # res = Max of all (left_zeros + right_ones)
+        # res = Max of all (left_zeros + (total_ones - left_ones))
+        # res = total_ones (constant) + Max of all (left_zeros - left_ones)
+
+        zeros = 0
+        ones = 0
+
+        if s[0] == '0':
+            zeros += 1
+        else:
+            ones += 1
+
+        res = float('-inf')
+        for i in range(1, len(s)):
+            res = max(res, zeros - ones)
+            if s[i] == '0':
+                zeros += 1
+            else:
+                ones += 1
+        
+        return res + ones
+```
+
+```java
+public class Solution {
+    public int maxScore(String s) {
+        // res = Max of all (leftZeros + rightOnes)
+        // res = Max of all (leftZeros + (totalOnes - leftOnes))
+        // res = totalOnes (constant) + Max of all (leftZeros - leftOnes)
+
+        int zeros = 0, ones = 0, res = Integer.MIN_VALUE;
+
+        if (s.charAt(0) == '0') {
+            zeros++;
+        } else {
+            ones++;
+        }
+
+        for (int i = 1; i < s.length(); i++) {
+            res = Math.max(res, zeros - ones);
+            if (s.charAt(i) == '0') {
+                zeros++;
+            } else {
+                ones++;
+            }
+        }
+
+        return res + ones;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxScore(string s) {
+        // res = Max of all (leftZeros + rightOnes)
+        // res = Max of all (leftZeros + (totalOnes - leftOnes))
+        // res = totalOnes (constant) + Max of all (leftZeros - leftOnes)
+
+        int zeros = 0, ones = 0, res = INT_MIN;
+
+        if (s[0] == '0') {
+            zeros++;
+        } else {
+            ones++;
+        }
+
+        for (int i = 1; i < s.size(); i++) {
+            res = max(res, zeros - ones);
+            if (s[i] == '0') {
+                zeros++;
+            } else {
+                ones++;
+            }
+        }
+
+        return res + ones;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    maxScore(s) {
+        // res = Max of all (leftZeros + rightOnes)
+        // res = Max of all (leftZeros + (totalOnes - leftOnes))
+        // res = totalOnes (constant) + Max of all (leftZeros - leftOnes)
+
+        let zeros = 0, ones = 0, res = -Infinity;
+
+        if (s[0] === '0') {
+            zeros++;
+        } else {
+            ones++;
+        }
+
+        for (let i = 1; i < s.length; i++) {
+            res = Math.max(res, zeros - ones);
+            if (s[i] === '0') {
+                zeros++;
+            } else {
+                ones++;
+            }
+        }
+
+        return res + ones;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/maximum-score-of-a-good-subarray.md b/articles/maximum-score-of-a-good-subarray.md
new file mode 100644
index 000000000..f8b6fbdc0
--- /dev/null
+++ b/articles/maximum-score-of-a-good-subarray.md
@@ -0,0 +1,729 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def maximumScore(self, nums: List[int], k: int) -> int:
+        n, res = len(nums), 0
+
+        for i in range(k + 1):
+            minEle = nums[i]
+            for j in range(i, n):
+                minEle = min(minEle, nums[j])
+                if j >= k:
+                    res = max(res, minEle * (j - i + 1))
+
+        return res
+```
+
+```java
+public class Solution {
+    public int maximumScore(int[] nums, int k) {
+        int n = nums.length, res = 0;
+
+        for (int i = 0; i <= k; i++) {
+            int minEle = nums[i];
+            for (int j = i; j < n; j++) {
+                minEle = Math.min(minEle, nums[j]);
+                if (j >= k) {
+                    res = Math.max(res, minEle * (j - i + 1));
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maximumScore(vector<int>& nums, int k) {
+        int n = nums.size(), res = 0;
+
+        for (int i = 0; i <= k; i++) {
+            int minEle = nums[i];
+            for (int j = i; j < n; j++) {
+                minEle = min(minEle, nums[j]);
+                if (j >= k) {
+                    res = max(res, minEle * (j - i + 1));
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    maximumScore(nums, k) {
+        let n = nums.length, res = 0;
+
+        for (let i = 0; i <= k; i++) {
+            let minEle = nums[i];
+            for (let j = i; j < n; j++) {
+                minEle = Math.min(minEle, nums[j]);
+                if (j >= k) {
+                    res = Math.max(res, minEle * (j - i + 1));
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 2. Binary Search
+
+::tabs-start
+
+```python
+class Solution:
+    def maximumScore(self, nums: List[int], k: int) -> int:
+        n, res = len(nums), 0
+        arr = nums[:]
+
+        for i in range(k - 1, -1, -1):
+            arr[i] = min(arr[i], arr[i + 1])
+        for i in range(k + 1, n):
+            arr[i] = min(arr[i], arr[i - 1])
+
+        left_arr = arr[:k+1]
+        right_arr = arr[k:]
+
+        def find_right(target):
+            lo, hi = 0, len(right_arr) - 1
+            pos = 0
+            while lo <= hi:
+                mid = (lo + hi) // 2
+                if right_arr[mid] >= target:
+                    pos = mid
+                    lo = mid + 1
+                else:
+                    hi = mid - 1
+            return pos
+
+        for minVal in set(arr):
+            l = bisect_left(left_arr, minVal)
+            r = find_right(minVal)
+            res = max(res, minVal * (k - l + 1 + r))
+        return res
+```
+
+```java
+public class Solution {
+    public int maximumScore(int[] nums, int k) {
+        int n = nums.length, res = 0;
+        int[] arr = Arrays.copyOf(nums, n);
+        Set<Integer> candidates = new HashSet<>();
+        candidates.add(arr[k]);
+
+        for (int i = k - 1; i >= 0; i--) {
+            arr[i] = Math.min(arr[i], arr[i + 1]);
+            candidates.add(arr[i]);
+        }
+        for (int i = k + 1; i < n; i++) {
+            arr[i] = Math.min(arr[i], arr[i - 1]);
+            candidates.add(arr[i]);
+        }
+
+        int[] leftArr = Arrays.copyOfRange(arr, 0, k + 1);
+        int[] rightArr = Arrays.copyOfRange(arr, k, n);
+
+        for (int minVal : candidates) {
+            int l = findLeft(leftArr, minVal);
+            int r = findRight(rightArr, minVal);
+            res = Math.max(res, minVal * (k - l + 1 + r));
+        }
+        return res;
+    }
+
+    private int findLeft(int[] arr, int target) {
+        int lo = 0, hi = arr.length - 1;
+        while (lo <= hi) {
+            int mid = (lo + hi) / 2;
+            if (arr[mid] < target) {
+                lo = mid + 1;
+            } else {
+                hi = mid - 1;
+            }
+        }
+        return lo;
+    }
+
+    private int findRight(int[] arr, int target) {
+        int lo = 0, hi = arr.length - 1, pos = 0;
+        while (lo <= hi) {
+            int mid = (lo + hi) / 2;
+            if (arr[mid] >= target) {
+                pos = mid;
+                lo = mid + 1;
+            } else {
+                hi = mid - 1;
+            }
+        }
+        return pos;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maximumScore(vector<int>& nums, int k) {
+        int n = nums.size(), res = 0;
+        vector<int> arr = nums;
+
+        for (int i = k - 1; i >= 0; i--) {
+            arr[i] = min(arr[i], arr[i + 1]);
+        }
+        for (int i = k + 1; i < n; i++) {
+            arr[i] = min(arr[i], arr[i - 1]);
+        }
+
+        vector<int> leftArr(arr.begin(), arr.begin() + k + 1);
+        vector<int> rightArr(arr.begin() + k, arr.end());
+
+        set<int> candidates(arr.begin(), arr.end());
+        for (int minVal : candidates) {
+            int l = lower_bound(leftArr.begin(), leftArr.end(), minVal) - leftArr.begin();
+            int r = findRight(rightArr, minVal);
+            res = max(res, minVal * (k - l + 1 + r));
+        }
+        return res;
+    }
+
+private:
+    int findRight(vector<int>& arr, int target) {
+        int lo = 0, hi = arr.size() - 1, pos = 0;
+        while (lo <= hi) {
+            int mid = (lo + hi) / 2;
+            if (arr[mid] >= target) {
+                pos = mid;
+                lo = mid + 1;
+            } else {
+                hi = mid - 1;
+            }
+        }
+        return pos;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    maximumScore(nums, k) {
+        let n = nums.length, res = 0;
+        let arr = [...nums];
+
+        for (let i = k - 1; i >= 0; i--) {
+            arr[i] = Math.min(arr[i], arr[i + 1]);
+        }
+        for (let i = k + 1; i < n; i++) {
+            arr[i] = Math.min(arr[i], arr[i - 1]);
+        }
+
+        let leftArr = arr.slice(0, k + 1);
+        let rightArr = arr.slice(k);
+
+        const findLeft = (target) => {
+            let lo = 0, hi = leftArr.length - 1;
+            while (lo <= hi) {
+                let mid = Math.floor((lo + hi) / 2);
+                if (leftArr[mid] < target) {
+                    lo = mid + 1;
+                } else {
+                    hi = mid - 1;
+                }
+            }
+            return lo;
+        };
+
+        const findRight = (target) => {
+            let lo = 0, hi = rightArr.length - 1, pos = 0;
+            while (lo <= hi) {
+                let mid = Math.floor((lo + hi) / 2);
+                if (rightArr[mid] >= target) {
+                    pos = mid;
+                    lo = mid + 1;
+                } else {
+                    hi = mid - 1;
+                }
+            }
+            return pos;
+        };
+
+        let candidates = [...new Set(arr)];
+        for (let minVal of candidates) {
+            let l = findLeft(minVal);
+            let r = findRight(minVal);
+            res = Math.max(res, minVal * (k - l + 1 + r));
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Binary Search (Overwriting the Input)
+
+::tabs-start
+
+```python
+class Solution:
+    def maximumScore(self, nums: List[int], k: int) -> int:
+        n, res = len(nums), 0
+
+        for i in range(k - 1, -1, -1):
+            nums[i] = min(nums[i], nums[i + 1])
+        for i in range(k + 1, n):
+            nums[i] = min(nums[i], nums[i - 1])
+
+        def find_left(target):
+            lo, hi = 0, k
+            while lo <= hi:
+                mid = (lo + hi) // 2
+                if nums[mid] < target:
+                    lo = mid + 1
+                else:
+                    hi = mid - 1
+            return lo
+
+        def find_right(target):
+            lo, hi = k, n - 1
+            while lo <= hi:
+                mid = (lo + hi) // 2
+                if nums[mid] >= target:
+                    lo = mid + 1
+                else:
+                    hi = mid - 1
+            return hi
+
+        for minVal in set(nums):
+            i = find_left(minVal)
+            j = find_right(minVal)
+            res = max(res, minVal * (j - i + 1))
+        return res
+```
+
+```java
+public class Solution {
+    public int maximumScore(int[] nums, int k) {
+        int n = nums.length, res = 0;
+
+        for (int i = k - 1; i >= 0; i--) {
+            nums[i] = Math.min(nums[i], nums[i + 1]);
+        }
+        for (int i = k + 1; i < n; i++) {
+            nums[i] = Math.min(nums[i], nums[i - 1]);
+        }
+
+        Set<Integer> candidates = new TreeSet<>();
+        for (int num : nums) {
+            candidates.add(num);
+        }
+
+        for (int minVal : candidates) {
+            int i = findLeft(nums, k, minVal);
+            int j = findRight(nums, k, minVal);
+            res = Math.max(res, minVal * (j - i + 1));
+        }
+        return res;
+    }
+
+    int findLeft(int[] nums, int k, int target) {
+        int lo = 0, hi = k;
+        while (lo <= hi) {
+            int mid = (lo + hi) / 2;
+            if (nums[mid] < target) {
+                lo = mid + 1;
+            } else {
+                hi = mid - 1;
+            }
+        }
+        return lo;
+    }
+
+    int findRight(int[] nums, int k, int target) {
+        int lo = k, hi = nums.length - 1;
+        while (lo <= hi) {
+            int mid = (lo + hi) / 2;
+            if (nums[mid] >= target) {
+                lo = mid + 1;
+            } else {
+                hi = mid - 1;
+            }
+        }
+        return hi;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maximumScore(vector<int>& nums, int k) {
+        int n = nums.size(), res = 0;
+
+        for (int i = k - 1; i >= 0; i--) {
+            nums[i] = min(nums[i], nums[i + 1]);
+        }
+        for (int i = k + 1; i < n; i++) {
+            nums[i] = min(nums[i], nums[i - 1]);
+        }
+
+        auto findLeft = [&](int target) {
+            int lo = 0, hi = k;
+            while (lo <= hi) {
+                int mid = (lo + hi) / 2;
+                if (nums[mid] < target) {
+                    lo = mid + 1;
+                } else {
+                    hi = mid - 1;
+                }
+            }
+            return lo;
+        };
+
+        auto findRight = [&](int target) {
+            int lo = k, hi = n - 1;
+            while (lo <= hi) {
+                int mid = (lo + hi) / 2;
+                if (nums[mid] >= target) {
+                    lo = mid + 1;
+                } else {
+                    hi = mid - 1;
+                }
+            }
+            return hi;
+        };
+
+        set<int> candidates(nums.begin(), nums.end());
+        for (int minVal : candidates) {
+            int i = findLeft(minVal);
+            int j = findRight(minVal);
+            res = max(res, minVal * (j - i + 1));
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    maximumScore(nums, k) {
+        let n = nums.length, res = 0;
+
+        for (let i = k - 1; i >= 0; i--) {
+            nums[i] = Math.min(nums[i], nums[i + 1]);
+        }
+        for (let i = k + 1; i < n; i++) {
+            nums[i] = Math.min(nums[i], nums[i - 1]);
+        }
+
+        const findLeft = (target) => {
+            let lo = 0, hi = k;
+            while (lo <= hi) {
+                let mid = Math.floor((lo + hi) / 2);
+                if (nums[mid] < target) {
+                    lo = mid + 1;
+                } else {
+                    hi = mid - 1;
+                }
+            }
+            return lo;
+        };
+
+        const findRight = (target) => {
+            let lo = k, hi = n - 1;
+            while (lo <= hi) {
+                let mid = Math.floor((lo + hi) / 2);
+                if (nums[mid] >= target) {
+                    lo = mid + 1;
+                } else {
+                    hi = mid - 1;
+                }
+            }
+            return hi;
+        };
+
+        let candidates = new Set(nums);
+        for (let minVal of candidates) {
+            let i = findLeft(minVal);
+            let j = findRight(minVal);
+            res = Math.max(res, minVal * (j - i + 1));
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Monotonic Stack
+
+::tabs-start
+
+```python
+class Solution:
+    def maximumScore(self, nums: List[int], k: int) -> int:
+        n, res = len(nums), 0
+        stack = []
+
+        for i in range(n + 1):
+            while stack and (i == n or nums[stack[-1]] >= nums[i]):
+                mini = nums[stack.pop()]
+                j = stack[-1] if stack else -1
+                if j < k < i:
+                    res = max(res, mini * (i - j - 1))
+            stack.append(i)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int maximumScore(int[] nums, int k) {
+        int n = nums.length, res = 0;
+        Stack<Integer> stack = new Stack<>();
+
+        for (int i = 0; i <= n; i++) {
+            while (!stack.isEmpty() && (i == n || nums[stack.peek()] >= nums[i])) {
+                int mini = nums[stack.pop()];
+                int j = stack.isEmpty() ? -1 : stack.peek();
+                if (j < k && k < i) {
+                    res = Math.max(res, mini * (i - j - 1));
+                }
+            }
+            stack.push(i);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maximumScore(vector<int>& nums, int k) {
+        int n = nums.size(), res = 0;
+        stack<int> stk;
+
+        for (int i = 0; i <= n; i++) {
+            while (!stk.empty() && (i == n || nums[stk.top()] >= nums[i])) {
+                int mini = nums[stk.top()];
+                stk.pop();
+                int j = stk.empty() ? -1 : stk.top();
+                if (j < k && k < i) {
+                    res = max(res, mini * (i - j - 1));
+                }
+            }
+            stk.push(i);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    maximumScore(nums, k) {
+        let n = nums.length, res = 0;
+        let stack = [];
+
+        for (let i = 0; i <= n; i++) {
+            while (stack.length && (i === n || nums[stack[stack.length - 1]] >= nums[i])) {
+                let mini = nums[stack.pop()];
+                let j = stack.length ? stack[stack.length - 1] : -1;
+                if (j < k && k < i) {
+                    res = Math.max(res, mini * (i - j - 1));
+                }
+            }
+            stack.push(i);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 5. Greedy + Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def maximumScore(self, nums: List[int], k: int) -> int:
+        l = r = k
+        res = nums[k]
+        cur_min = nums[k]
+
+        while l > 0 or r < len(nums) - 1:
+            left = nums[l - 1] if l > 0 else 0
+            right = nums[r + 1] if r < len(nums) - 1 else 0
+
+            if left > right:
+                l -= 1
+                cur_min = min(cur_min, left)
+            else:
+                r += 1
+                cur_min = min(cur_min, right)
+
+            res = max(res, cur_min * (r - l + 1))
+
+        return res
+```
+
+```java
+public class Solution {
+    public int maximumScore(int[] nums, int k) {
+        int l = k, r = k;
+        int res = nums[k];
+        int curMin = nums[k];
+        int n = nums.length;
+
+        while (l > 0 || r < n - 1) {
+            int left = (l > 0) ? nums[l - 1] : 0;
+            int right = (r < n - 1) ? nums[r + 1] : 0;
+
+            if (left > right) {
+                l--;
+                curMin = Math.min(curMin, left);
+            } else {
+                r++;
+                curMin = Math.min(curMin, right);
+            }
+
+            res = Math.max(res, curMin * (r - l + 1));
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maximumScore(vector<int>& nums, int k) {
+        int l = k, r = k;
+        int res = nums[k];
+        int curMin = nums[k];
+        int n = nums.size();
+
+        while (l > 0 || r < n - 1) {
+            int left = (l > 0) ? nums[l - 1] : 0;
+            int right = (r < n - 1) ? nums[r + 1] : 0;
+
+            if (left > right) {
+                l--;
+                curMin = min(curMin, left);
+            } else {
+                r++;
+                curMin = min(curMin, right);
+            }
+
+            res = max(res, curMin * (r - l + 1));
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    maximumScore(nums, k) {
+        let l = k, r = k;
+        let res = nums[k];
+        let curMin = nums[k];
+        let n = nums.length;
+
+        while (l > 0 || r < n - 1) {
+            let left = (l > 0) ? nums[l - 1] : 0;
+            let right = (r < n - 1) ? nums[r + 1] : 0;
+
+            if (left > right) {
+                l--;
+                curMin = Math.min(curMin, left);
+            } else {
+                r++;
+                curMin = Math.min(curMin, right);
+            }
+
+            res = Math.max(res, curMin * (r - l + 1));
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/maximum-score-words-formed-by-letters.md b/articles/maximum-score-words-formed-by-letters.md
new file mode 100644
index 000000000..f9b510481
--- /dev/null
+++ b/articles/maximum-score-words-formed-by-letters.md
@@ -0,0 +1,676 @@
+## 1. Backtracking
+
+::tabs-start
+
+```python
+class Solution:
+    def maxScoreWords(self, words: List[str], letters: List[str], score: List[int]) -> int:
+        def can_form_word(w, letter_cnt):
+            word_cnt = Counter(w)
+            for c in word_cnt:
+                if word_cnt[c] > letter_cnt[c]:
+                    return False
+            return True
+
+        def get_score(w):
+            res = 0
+            for c in w:
+                res += score[ord(c) - ord('a')]
+            return res
+
+        letter_cnt = Counter(letters)
+
+        def backtrack(i):
+            if i == len(words):
+                return 0
+
+            res = backtrack(i + 1)  # skip
+            if can_form_word(words[i], letter_cnt):  # include (when possible)
+                for c in words[i]:
+                    letter_cnt[c] -= 1
+                res = max(res, get_score(words[i]) + backtrack(i + 1))
+                for c in words[i]:
+                    letter_cnt[c] += 1
+
+            return res
+
+        return backtrack(0)
+```
+
+```java
+public class Solution {
+    int[] letterCnt;
+    int[] score;
+
+    public int maxScoreWords(String[] words, char[] letters, int[] score) {
+        this.score = score;
+        this.letterCnt = new int[26];
+
+        for (char c : letters) {
+            letterCnt[c - 'a']++;
+        }
+
+        return backtrack(0, words);
+    }
+
+    private int canFormWord(String word) {
+        int[] wordCnt = new int[26];
+        for (char c : word.toCharArray()) {
+            wordCnt[c - 'a']++;
+            if (wordCnt[c - 'a'] > letterCnt[c - 'a']) {
+                return 0;
+            }
+        }
+        return 1;
+    }
+
+    private int getScore(String word) {
+        int res = 0;
+        for (char c : word.toCharArray()) {
+            res += score[c - 'a'];
+        }
+        return res;
+    }
+
+    private int backtrack(int i, String[] words) {
+        if (i == words.length) {
+            return 0;
+        }
+
+        int res = backtrack(i + 1, words);  // skip
+        if (canFormWord(words[i]) == 1) {  // include (when possible)
+            for (char c : words[i].toCharArray()) {
+                letterCnt[c - 'a']--;
+            }
+            res = Math.max(res, getScore(words[i]) + backtrack(i + 1, words));
+            for (char c : words[i].toCharArray()) {
+                letterCnt[c - 'a']++;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> letterCnt = vector<int>(26, 0);
+    vector<int> score;
+    vector<string> words;
+
+    int maxScoreWords(vector<string>& words, vector<char>& letters, vector<int>& score) {
+        this->words = words;
+        this->score = score;
+
+        for (char c : letters) {
+            letterCnt[c - 'a']++;
+        }
+
+        return backtrack(0);
+    }
+
+    bool canFormWord(string& word) {
+        vector<int> wordCnt(26, 0);
+        for (char c : word) {
+            wordCnt[c - 'a']++;
+            if (wordCnt[c - 'a'] > letterCnt[c - 'a']) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    int getScore(string& word) {
+        int res = 0;
+        for (char c : word) {
+            res += score[c - 'a'];
+        }
+        return res;
+    }
+
+    int backtrack(int i) {
+        if (i == words.size()) {
+            return 0;
+        }
+
+        int res = backtrack(i + 1);  // skip
+        if (canFormWord(words[i])) {  // include (when possible)
+            for (char c : words[i]) {
+                letterCnt[c - 'a']--;
+            }
+            res = max(res, getScore(words[i]) + backtrack(i + 1));
+            for (char c : words[i]) {
+                letterCnt[c - 'a']++;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @param {string[]} letters
+     * @param {number[]} score
+     * @return {number}
+     */
+    maxScoreWords(words, letters, score) {
+        const canFormWord = (w, letterCnt) => {
+            let wordCnt = new Array(26).fill(0);
+            for (let c of w) {
+                let idx = c.charCodeAt(0) - 'a'.charCodeAt(0);
+                wordCnt[idx]++;
+                if (wordCnt[idx] > letterCnt[idx]) {
+                    return false;
+                }
+            }
+            return true;
+        };
+
+        const getScore = (w) => {
+            let res = 0;
+            for (let c of w) {
+                res += score[c.charCodeAt(0) - 'a'.charCodeAt(0)];
+            }
+            return res;
+        };
+
+        let letterCnt = new Array(26).fill(0);
+        for (let c of letters) {
+            letterCnt[c.charCodeAt(0) - 'a'.charCodeAt(0)]++;
+        }
+
+        const backtrack = (i) => {
+            if (i === words.length) {
+                return 0;
+            }
+
+            let res = backtrack(i + 1); // skip
+
+            if (canFormWord(words[i], letterCnt)) { // include (when possible)
+                for (let c of words[i]) {
+                    letterCnt[c.charCodeAt(0) - 'a'.charCodeAt(0)]--;
+                }
+                res = Math.max(res, getScore(words[i]) + backtrack(i + 1));
+                for (let c of words[i]) {
+                    letterCnt[c.charCodeAt(0) - 'a'.charCodeAt(0)]++;
+                }
+            }
+
+            return res;
+        };
+
+        return backtrack(0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n * (w + m) + N)$
+* Space complexity: $O(n + w)$
+
+> Where $n$ is the number of words, $w$ is the maximum length of a word, $m$ is the size of the array $scores$, and $N$ is the size of the array $letters$.
+
+---
+
+## 2. Bactracking + Precomputation
+
+::tabs-start
+
+```python
+class Solution:
+    def maxScoreWords(self, words: List[str], letters: List[str], score: List[int]) -> int:
+        letter_cnt = [0] * 26
+        for c in letters:
+            letter_cnt[ord(c) - ord('a')] += 1
+
+        n = len(words)
+        word_scores = [0] * n
+        word_freqs = [[0] * 26 for _ in range(n)]
+
+        for i, word in enumerate(words):
+            for c in word:
+                idx = ord(c) - ord('a')
+                word_freqs[i][idx] += 1
+                word_scores[i] += score[idx]
+
+        def backtrack(i):
+            if i == n:
+                return 0
+
+            res = backtrack(i + 1)  # skip
+            can_include = all(word_freqs[i][j] <= letter_cnt[j] for j in range(26))
+
+            if can_include:  # include (when possible)
+                for j in range(26):
+                    letter_cnt[j] -= word_freqs[i][j]
+                res = max(res, word_scores[i] + backtrack(i + 1))
+                for j in range(26):
+                    letter_cnt[j] += word_freqs[i][j]
+
+            return res
+
+        return backtrack(0)
+```
+
+```java
+public class Solution {
+    private int[] letterCnt = new int[26];
+    private int[] wordScores;
+    private int[][] wordFreqs;
+    private int n;
+
+    public int maxScoreWords(String[] words, char[] letters, int[] score) {
+        Arrays.fill(letterCnt, 0);
+        for (char c : letters) {
+            letterCnt[c - 'a']++;
+        }
+
+        n = words.length;
+        wordScores = new int[n];
+        wordFreqs = new int[n][26];
+
+        for (int i = 0; i < n; i++) {
+            for (char c : words[i].toCharArray()) {
+                int idx = c - 'a';
+                wordFreqs[i][idx]++;
+                wordScores[i] += score[idx];
+            }
+        }
+
+        return backtrack(0, words);
+    }
+
+    private int backtrack(int i, String[] words) {
+        if (i == n) {
+            return 0;
+        }
+
+        int res = backtrack(i + 1, words); // skip
+        boolean canInclude = true;
+
+        for (int j = 0; j < 26; j++) {
+            if (wordFreqs[i][j] > letterCnt[j]) {
+                canInclude = false;
+                break;
+            }
+        }
+
+        if (canInclude) {  // include (when possible)
+            for (int j = 0; j < 26; j++) {
+                letterCnt[j] -= wordFreqs[i][j];
+            }
+            res = Math.max(res, wordScores[i] + backtrack(i + 1, words));
+            for (int j = 0; j < 26; j++) {
+                letterCnt[j] += wordFreqs[i][j];
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> letterCnt = vector<int>(26, 0);
+    vector<int> wordScores;
+    vector<vector<int>> wordFreqs;
+    int n;
+
+    int maxScoreWords(vector<string>& words, vector<char>& letters, vector<int>& score) {
+        fill(letterCnt.begin(), letterCnt.end(), 0);
+        for (char c : letters) {
+            letterCnt[c - 'a']++;
+        }
+
+        n = words.size();
+        wordScores = vector<int>(n, 0);
+        wordFreqs = vector<vector<int>>(n, vector<int>(26, 0));
+
+        for (int i = 0; i < n; i++) {
+            for (char c : words[i]) {
+                int idx = c - 'a';
+                wordFreqs[i][idx]++;
+                wordScores[i] += score[idx];
+            }
+        }
+
+        return backtrack(0, words);
+    }
+
+private:
+    int backtrack(int i, vector<string>& words) {
+        if (i == n) {
+            return 0;
+        }
+
+        int res = backtrack(i + 1, words); // skip
+        bool canInclude = true;
+
+        for (int j = 0; j < 26; j++) {
+            if (wordFreqs[i][j] > letterCnt[j]) {
+                canInclude = false;
+                break;
+            }
+        }
+
+        if (canInclude) {  // include (when possible)
+            for (int j = 0; j < 26; j++) {
+                letterCnt[j] -= wordFreqs[i][j];
+            }
+            res = max(res, wordScores[i] + backtrack(i + 1, words));
+            for (int j = 0; j < 26; j++) {
+                letterCnt[j] += wordFreqs[i][j];
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @param {string[]} letters
+     * @param {number[]} score
+     * @return {number}
+     */
+    maxScoreWords(words, letters, score) {
+        let letterCnt = new Array(26).fill(0);
+        for (let c of letters) {
+            letterCnt[c.charCodeAt(0) - 'a'.charCodeAt(0)]++;
+        }
+
+        let n = words.length;
+        let wordScores = new Array(n).fill(0);
+        let wordFreqs = Array.from({ length: n }, () => new Array(26).fill(0));
+
+        for (let i = 0; i < n; i++) {
+            for (let c of words[i]) {
+                let idx = c.charCodeAt(0) - 'a'.charCodeAt(0);
+                wordFreqs[i][idx]++;
+                wordScores[i] += score[idx];
+            }
+        }
+
+        const backtrack = (i) => {
+            if (i === n) {
+                return 0;
+            }
+
+            let res = backtrack(i + 1); // skip
+            let canInclude = true;
+
+            for (let j = 0; j < 26; j++) {
+                if (wordFreqs[i][j] > letterCnt[j]) {
+                    canInclude = false;
+                    break;
+                }
+            }
+
+            if (canInclude) { // include (when possible)
+                for (let j = 0; j < 26; j++) {
+                    letterCnt[j] -= wordFreqs[i][j];
+                }
+                res = Math.max(res, wordScores[i] + backtrack(i + 1));
+                for (let j = 0; j < 26; j++) {
+                    letterCnt[j] += wordFreqs[i][j];
+                }
+            }
+
+            return res;
+        };
+
+        return backtrack(0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * 2 ^ n + N)$
+* Space complexity: $O(n + w)$
+
+> Where $n$ is the number of words, $w$ is the maximum length of a word, $m$ is the size of the array $scores$, and $N$ is the size of the array $letters$.
+
+---
+
+## 3. Backtracking (Bit Mask)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxScoreWords(self, words: List[str], letters: List[str], score: List[int]) -> int:
+        letter_cnt = [0] * 26
+        for c in letters:
+            letter_cnt[ord(c) - ord('a')] += 1
+
+        n = len(words)
+        word_scores = [0] * n
+        word_freqs = [[0] * 26 for _ in range(n)]
+
+        for i, word in enumerate(words):
+            for c in word:
+                idx = ord(c) - ord('a')
+                word_freqs[i][idx] += 1
+                word_scores[i] += score[idx]
+
+        res = 0
+
+        for mask in range(1 << n):
+            cur_score = 0
+            cur_letter_cnt = letter_cnt[:]
+            valid = True
+
+            for i in range(n):
+                if mask & (1 << i):
+                    for j in range(26):
+                        if word_freqs[i][j] > cur_letter_cnt[j]:
+                            valid = False
+                            break
+                    if not valid:
+                        break
+
+                    for j in range(26):
+                        cur_letter_cnt[j] -= word_freqs[i][j]
+                    
+                    cur_score += word_scores[i]
+
+            if valid:
+                res = max(res, cur_score)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int maxScoreWords(String[] words, char[] letters, int[] score) {
+        int[] letterCnt = new int[26];
+        for (char c : letters) {
+            letterCnt[c - 'a']++;
+        }
+
+        int n = words.length;
+        int[] wordScores = new int[n];
+        int[][] wordFreqs = new int[n][26];
+
+        for (int i = 0; i < n; i++) {
+            for (char c : words[i].toCharArray()) {
+                int idx = c - 'a';
+                wordFreqs[i][idx]++;
+                wordScores[i] += score[idx];
+            }
+        }
+
+        int res = 0;
+        for (int mask = 0; mask < (1 << n); mask++) {
+            int curScore = 0;
+            int[] curLetterCnt = Arrays.copyOf(letterCnt, 26);
+            boolean valid = true;
+
+            for (int i = 0; i < n; i++) {
+                if ((mask & (1 << i)) != 0) {
+                    for (int j = 0; j < 26; j++) {
+                        if (wordFreqs[i][j] > curLetterCnt[j]) {
+                            valid = false;
+                            break;
+                        }
+                    }
+                    if (!valid) break;
+
+                    for (int j = 0; j < 26; j++) {
+                        curLetterCnt[j] -= wordFreqs[i][j];
+                    }
+
+                    curScore += wordScores[i];
+                }
+            }
+
+            if (valid) {
+                res = Math.max(res, curScore);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxScoreWords(vector<string>& words, vector<char>& letters, vector<int>& score) {
+        vector<int> letterCnt(26, 0);
+        for (char c : letters) {
+            letterCnt[c - 'a']++;
+        }
+
+        int n = words.size();
+        vector<int> wordScores(n, 0);
+        vector<vector<int>> wordFreqs(n, vector<int>(26, 0));
+
+        for (int i = 0; i < n; i++) {
+            for (char c : words[i]) {
+                int idx = c - 'a';
+                wordFreqs[i][idx]++;
+                wordScores[i] += score[idx];
+            }
+        }
+
+        int res = 0;
+        for (int mask = 0; mask < (1 << n); mask++) {
+            int curScore = 0;
+            vector<int> curLetterCnt = letterCnt;
+            bool valid = true;
+
+            for (int i = 0; i < n; i++) {
+                if (mask & (1 << i)) {
+                    for (int j = 0; j < 26; j++) {
+                        if (wordFreqs[i][j] > curLetterCnt[j]) {
+                            valid = false;
+                            break;
+                        }
+                    }
+                    if (!valid) break;
+
+                    for (int j = 0; j < 26; j++) {
+                        curLetterCnt[j] -= wordFreqs[i][j];
+                    }
+
+                    curScore += wordScores[i];
+                }
+            }
+
+            if (valid) {
+                res = max(res, curScore);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @param {string[]} letters
+     * @param {number[]} score
+     * @return {number}
+     */
+    maxScoreWords(words, letters, score) {
+        let letterCnt = new Array(26).fill(0);
+        for (let c of letters) {
+            letterCnt[c.charCodeAt(0) - 'a'.charCodeAt(0)]++;
+        }
+
+        let n = words.length;
+        let wordScores = new Array(n).fill(0);
+        let wordFreqs = Array.from({ length: n }, () => new Array(26).fill(0));
+
+        for (let i = 0; i < n; i++) {
+            for (let c of words[i]) {
+                let idx = c.charCodeAt(0) - 'a'.charCodeAt(0);
+                wordFreqs[i][idx]++;
+                wordScores[i] += score[idx];
+            }
+        }
+
+        let res = 0;
+        for (let mask = 0; mask < (1 << n); mask++) {
+            let curScore = 0;
+            let curLetterCnt = [...letterCnt];
+            let valid = true;
+
+            for (let i = 0; i < n; i++) {
+                if ((mask & (1 << i)) !== 0) {
+                    for (let j = 0; j < 26; j++) {
+                        if (wordFreqs[i][j] > curLetterCnt[j]) {
+                            valid = false;
+                            break;
+                        }
+                    }
+                    if (!valid) break;
+
+                    for (let j = 0; j < 26; j++) {
+                        curLetterCnt[j] -= wordFreqs[i][j];
+                    }
+
+                    curScore += wordScores[i];
+                }
+            }
+
+            if (valid) {
+                res = Math.max(res, curScore);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n * 2 ^ n + N)$
+* Space complexity: $O(n + w)$
+
+> Where $n$ is the number of words, $w$ is the maximum length of a word, $m$ is the size of the array $scores$, and $N$ is the size of the array $letters$.
\ No newline at end of file
diff --git a/articles/maximum-subarray-min-product.md b/articles/maximum-subarray-min-product.md
new file mode 100644
index 000000000..1ac42156b
--- /dev/null
+++ b/articles/maximum-subarray-min-product.md
@@ -0,0 +1,967 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def maxSumMinProduct(self, nums: List[int]) -> int:
+        res, MOD = 0, 1000000007
+        for i in range(len(nums)):
+            total_sum = 0
+            mini = float("inf")
+            for j in range(i, len(nums)):
+                mini = min(mini, nums[j])
+                total_sum += nums[j]
+                cur = (mini * total_sum) % MOD
+                res = max(res, cur)
+        return res
+```
+
+```java
+public class Solution {
+    public int maxSumMinProduct(int[] nums) {
+        long res = 0, MOD = 1000000007;
+        for (int i = 0; i < nums.length; i++) {
+            long totalSum = 0, mini = Long.MAX_VALUE;
+            for (int j = i; j < nums.length; j++) {
+                mini = Math.min(mini, nums[j]);
+                totalSum += nums[j];
+                long cur = (mini * totalSum) % MOD;
+                res = Math.max(res, cur);
+            }
+        }
+        return (int) res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxSumMinProduct(vector<int>& nums) {
+        long long res = 0, MOD = 1000000007;
+        for (int i = 0; i < nums.size(); i++) {
+            long long total_sum = 0, mini = INT_MAX;
+            for (int j = i; j < nums.size(); j++) {
+                mini = min(mini, (long long)nums[j]);
+                total_sum += nums[j];
+                long long cur = (mini * total_sum) % MOD;
+                res = max(res, cur);
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    maxSumMinProduct(nums) {
+        let res = 0, MOD = 1000000007;
+        for (let i = 0; i < nums.length; i++) {
+            let totalSum = 0, mini = Infinity;
+            for (let j = i; j < nums.length; j++) {
+                mini = Math.min(mini, nums[j]);
+                totalSum += nums[j];
+                let cur = (mini * totalSum) % MOD;
+                res = Math.max(res, cur);
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 2. Divide And Conquer (Brute Force)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxSumMinProduct(self, nums: List[int]) -> int:
+        MOD = 10**9 + 7
+
+        def rec(l, r):
+            if l > r:
+                return 0
+            
+            min_idx = l
+            total_sum = 0
+            for i in range(l, r + 1):
+                total_sum += nums[i]
+                if nums[i] < nums[min_idx]:
+                    min_idx = i
+            
+            cur = total_sum * nums[min_idx]
+            left = rec(l, min_idx - 1)
+            right = rec(min_idx + 1, r)
+            
+            return max(cur, left, right)
+        
+        return rec(0, len(nums) - 1) % MOD
+```
+
+```java
+public class Solution {
+    public int maxSumMinProduct(int[] nums) {
+        int MOD = 1_000_000_007;
+        return (int) (rec(nums, 0, nums.length - 1) % MOD);
+    }
+
+    private long rec(int[] nums, int l, int r) {
+        if (l > r) return 0;
+
+        int minIdx = l;
+        long totalSum = 0;
+        for (int i = l; i <= r; i++) {
+            totalSum += nums[i];
+            if (nums[i] < nums[minIdx]) {
+                minIdx = i;
+            }
+        }
+
+        long cur = totalSum * nums[minIdx];
+        long left = rec(nums, l, minIdx - 1);
+        long right = rec(nums, minIdx + 1, r);
+
+        return Math.max(cur, Math.max(left, right));
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxSumMinProduct(vector<int>& nums) {
+        const int MOD = 1e9 + 7;
+        return rec(nums, 0, nums.size() - 1) % MOD;
+    }
+
+private:
+    long long rec(vector<int>& nums, int l, int r) {
+        if (l > r) return 0;
+
+        int minIdx = l;
+        long long totalSum = 0;
+        for (int i = l; i <= r; i++) {
+            totalSum += nums[i];
+            if (nums[i] < nums[minIdx]) {
+                minIdx = i;
+            }
+        }
+
+        long long cur = totalSum * nums[minIdx];
+        long long left = rec(nums, l, minIdx - 1);
+        long long right = rec(nums, minIdx + 1, r);
+
+        return max(cur, max(left, right));
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    maxSumMinProduct(nums) {
+        const MOD = 1_000_000_007;
+
+        const rec = (l, r) => {
+            if (l > r) return 0n;
+
+            let minIdx = l;
+            let totalSum = 0n;
+            for (let i = l; i <= r; i++) {
+                totalSum += BigInt(nums[i]);
+                if (nums[i] < nums[minIdx]) {
+                    minIdx = i;
+                }
+            }
+
+            let cur = totalSum * BigInt(nums[minIdx]);
+            let left = rec(l, minIdx - 1);
+            let right = rec(minIdx + 1, r);
+            
+            if (cur < left) cur = left;
+            if (cur < right) cur = right;
+            return cur;
+        };
+
+        return Number(rec(0, nums.length - 1) % BigInt(MOD));
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 3. Divide And Conquer (Segment Tree)
+
+::tabs-start
+
+```python
+class SegmentTree:
+    def __init__(self, N, A):
+        self.n = N
+        while (self.n & (self.n - 1)) != 0:
+            self.n += 1
+        self.build(N, A)
+
+    def build(self, N, A):
+        self.tree = [(-1, float('inf'))] * (2 * self.n)
+        for i in range(N):
+            self.tree[self.n + i] = (i, A[i])
+        for i in range(self.n - 1, 0, -1):
+            self.tree[i] = min(self.tree[i << 1], self.tree[i << 1 | 1], key=lambda x: x[1])
+
+    def query(self, l, r):
+        res = (-1, float('inf'))
+        l += self.n
+        r += self.n + 1
+        while l < r:
+            if l & 1:
+                res = min(res, self.tree[l], key=lambda x: x[1])
+                l += 1
+            if r & 1:
+                r -= 1
+                res = min(res, self.tree[r], key=lambda x: x[1])
+            l >>= 1
+            r >>= 1
+        return res[0]
+
+class Solution:
+    def maxSumMinProduct(self, nums: List[int]) -> int:
+        MOD = 10**9 + 7
+        segTree = SegmentTree(len(nums), nums)
+        prefix_sum = [0] * (len(nums) + 1)
+        for i in range(0, len(nums)):
+            prefix_sum[i + 1] += prefix_sum[i] + nums[i]
+
+        def rec(l, r):
+            if l > r:
+                return 0
+            
+            min_idx = segTree.query(l, r)
+            total_sum = prefix_sum[r + 1] - prefix_sum[l]
+            cur = total_sum * nums[min_idx] 
+            left = rec(l, min_idx - 1)
+            right = rec(min_idx + 1, r)
+            
+            return max(cur, left, right)
+            
+        return rec(0, len(nums) - 1) % MOD
+```
+
+```java
+class SegmentTree {
+    private int n;
+    private long[][] tree;
+
+    public SegmentTree(int n, int[] nums) {
+        this.n = n;
+        while ((this.n & (this.n - 1)) != 0) {
+            this.n++;
+        }
+        build(n, nums);
+    }
+
+    private void build(int n, int[] nums) {
+        tree = new long[2 * this.n][2];
+        Arrays.fill(tree, new long[]{-1, Long.MAX_VALUE});
+        for (int i = 0; i < n; i++) {
+            tree[this.n + i] = new long[]{i, nums[i]};
+        }
+        for (int i = this.n - 1; i > 0; i--) {
+            tree[i] = merge(tree[i << 1], tree[i << 1 | 1]);
+        }
+    }
+
+    private long[] merge(long[] a, long[] b) {
+        return a[1] < b[1] ? a : b;
+    }
+
+    public int query(int l, int r) {
+        long[] res = new long[]{-1, Long.MAX_VALUE};
+        l += this.n;
+        r += this.n + 1;
+        while (l < r) {
+            if ((l & 1) == 1) res = merge(res, tree[l++]);
+            if ((r & 1) == 1) res = merge(res, tree[--r]);
+            l >>= 1;
+            r >>= 1;
+        }
+        return (int) res[0];
+    }
+}
+
+public class Solution {
+    public int maxSumMinProduct(int[] nums) {
+        int MOD = 1_000_000_007;
+        SegmentTree segTree = new SegmentTree(nums.length, nums);
+        long[] prefixSum = new long[nums.length + 1];
+        for (int i = 0; i < nums.length; i++) {
+            prefixSum[i + 1] = prefixSum[i] + nums[i];
+        }
+
+        return (int) (rec(0, nums.length - 1, nums, prefixSum, segTree) % MOD);
+    }
+
+    private long rec(int l, int r, int[] nums, long[] prefixSum, SegmentTree segTree) {
+        if (l > r) return 0;
+        int minIdx = segTree.query(l, r);
+        long totalSum = prefixSum[r + 1] - prefixSum[l];
+        long cur = totalSum * nums[minIdx];
+        long left = rec(l, minIdx - 1, nums, prefixSum, segTree);
+        long right = rec(minIdx + 1, r, nums, prefixSum, segTree);
+        return Math.max(cur, Math.max(left, right));
+    }
+}
+```
+
+```cpp
+class SegmentTree {
+    int n;
+    vector<pair<int, long long>> tree;
+
+public:
+    SegmentTree(int n, vector<int>& nums) : n(n) {
+        while ((this->n & (this->n - 1)) != 0) this->n++;
+        build(n, nums);
+    }
+
+    void build(int n, vector<int>& nums) {
+        tree.resize(2 * this->n, {-1, LLONG_MAX});
+        for (int i = 0; i < n; i++) {
+            tree[this->n + i] = {i, nums[i]};
+        }
+        for (int i = this->n - 1; i > 0; i--) {
+            tree[i] = min(tree[i << 1], tree[i << 1 | 1], [](auto& a, auto& b) { return a.second < b.second; });
+        }
+    }
+
+    int query(int l, int r) {
+        pair<int, long long> res = {-1, LLONG_MAX};
+        l += this->n;
+        r += this->n + 1;
+        while (l < r) {
+            if (l & 1) res = min(res, tree[l++], [](auto& a, auto& b) { return a.second < b.second; });
+            if (r & 1) res = min(res, tree[--r], [](auto& a, auto& b) { return a.second < b.second; });
+            l >>= 1;
+            r >>= 1;
+        }
+        return res.first;
+    }
+};
+
+class Solution {
+public:
+    int maxSumMinProduct(vector<int>& nums) {
+        const int MOD = 1e9 + 7;
+        SegmentTree segTree(nums.size(), nums);
+        vector<long long> prefixSum(nums.size() + 1, 0);
+        for (int i = 0; i < nums.size(); i++) {
+            prefixSum[i + 1] = prefixSum[i] + nums[i];
+        }
+
+        return rec(0, nums.size() - 1, nums, prefixSum, segTree) % MOD;
+    }
+
+private:
+    long long rec(int l, int r, vector<int>& nums, vector<long long>& prefixSum, SegmentTree& segTree) {
+        if (l > r) return 0;
+        int minIdx = segTree.query(l, r);
+        long long totalSum = prefixSum[r + 1] - prefixSum[l];
+        long long cur = totalSum * nums[minIdx];
+        long long left = rec(l, minIdx - 1, nums, prefixSum, segTree);
+        long long right = rec(minIdx + 1, r, nums, prefixSum, segTree);
+        return max(cur, max(left, right));
+    }
+};
+```
+
+```javascript
+class SegmentTree {
+    /**
+     * @constructor
+     * @param {number} n
+     * @param {number[]} nums
+     */
+    constructor(n, nums) {
+        this.n = n;
+        while ((this.n & (this.n - 1)) !== 0) {
+            this.n++;
+        }
+        this.build(n, nums);
+    }
+
+    /**
+     * @param {number} n
+     * @param {number[]} nums
+     * @return {void}
+     */
+    build(n, nums) {
+        this.tree = Array(2 * this.n).fill([BigInt(-1), BigInt(Number.MAX_SAFE_INTEGER)]);
+        for (let i = 0; i < n; i++) {
+            this.tree[this.n + i] = [BigInt(i), BigInt(nums[i])];
+        }
+        for (let i = this.n - 1; i > 0; i--) {
+            this.tree[i] = this._merge(this.tree[i << 1], this.tree[i << 1 | 1]);
+        }
+    }
+
+    /**
+     * @param {number} a
+     * @param {number} b
+     * @return {number}
+     */
+    _merge(a, b) {
+        return a[1] < b[1] ? a : b;
+    }
+
+    /**
+     * @param {number} l
+     * @param {number} r
+     * @return {number}
+     */
+    query(l, r) {
+        let res = [BigInt(-1), BigInt(Number.MAX_SAFE_INTEGER)];
+        l += this.n;
+        r += this.n + 1;
+        while (l < r) {
+            if (l & 1) res = this._merge(res, this.tree[l++]);
+            if (r & 1) res = this._merge(res, this.tree[--r]);
+            l >>= 1;
+            r >>= 1;
+        }
+        return Number(res[0]);
+    }
+}
+
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    maxSumMinProduct(nums) {
+        const MOD = BigInt(1_000_000_007);
+        const segTree = new SegmentTree(nums.length, nums);
+        const prefixSum = Array(nums.length + 1).fill(BigInt(0));
+        for (let i = 0; i < nums.length; i++) {
+            prefixSum[i + 1] = prefixSum[i] + BigInt(nums[i]);
+        }
+
+        const rec = (l, r) => {
+            if (l > r) return BigInt(0);
+            const minIdx = segTree.query(l, r);
+            const totalSum = prefixSum[r + 1] - prefixSum[l];
+            let cur = totalSum * BigInt(nums[minIdx]);
+            let left = rec(l, minIdx - 1);
+            let right = rec(minIdx + 1, r);
+            
+            if (cur < left) cur = left;
+            if (cur < right) cur = right;
+            return cur;
+        };
+
+        return Number(rec(0, nums.length - 1) % MOD);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Monotonic Stack
+
+::tabs-start
+
+```python
+class Solution:
+    def maxSumMinProduct(self, nums: List[int]) -> int:
+        n = len(nums)
+        prefix_sum = [0] * (n + 1)
+        for i in range(n):
+            prefix_sum[i + 1] = prefix_sum[i] + nums[i]
+
+        prev_min, nxt_min = [-1] * n, [n] * n
+        stack = []
+        
+        for i in range(n):
+            while stack and nums[stack[-1]] >= nums[i]:
+                stack.pop()
+            if stack:
+                prev_min[i] = stack[-1]
+            stack.append(i)
+        
+        stack.clear()
+        
+        for i in range(n - 1, -1, -1):
+            while stack and nums[stack[-1]] >= nums[i]:
+                stack.pop()
+            if stack:
+                nxt_min[i] = stack[-1]
+            stack.append(i)
+        
+        res = 0
+        
+        for i in range(n):
+            l, r = prev_min[i] + 1, nxt_min[i] - 1
+            total_sum = prefix_sum[r + 1] - prefix_sum[l]
+            res = max(res, nums[i] * total_sum)
+        
+        return res % (10 ** 9 + 7)
+```
+
+```java
+public class Solution {
+    public int maxSumMinProduct(int[] nums) {
+        int n = nums.length;
+        long[] prefixSum = new long[n + 1];
+        for (int i = 0; i < n; i++) {
+            prefixSum[i + 1] = prefixSum[i] + nums[i];
+        }
+
+        int[] prevMin = new int[n];
+        int[] nxtMin = new int[n];
+        Arrays.fill(prevMin, -1);
+        Arrays.fill(nxtMin, n);
+        
+        Stack<Integer> stack = new Stack<>();
+        for (int i = 0; i < n; i++) {
+            while (!stack.isEmpty() && nums[stack.peek()] >= nums[i]) {
+                stack.pop();
+            }
+            if (!stack.isEmpty()) {
+                prevMin[i] = stack.peek();
+            }
+            stack.push(i);
+        }
+        
+        stack.clear();
+        for (int i = n - 1; i >= 0; i--) {
+            while (!stack.isEmpty() && nums[stack.peek()] >= nums[i]) {
+                stack.pop();
+            }
+            if (!stack.isEmpty()) {
+                nxtMin[i] = stack.peek();
+            }
+            stack.push(i);
+        }
+        
+        long res = 0;
+        int MOD = 1_000_000_007;
+        for (int i = 0; i < n; i++) {
+            int l = prevMin[i] + 1, r = nxtMin[i] - 1;
+            long totalSum = prefixSum[r + 1] - prefixSum[l];
+            res = Math.max(res, nums[i] * totalSum);
+        }
+        
+        return (int)(res % MOD);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxSumMinProduct(vector<int>& nums) {
+        int n = nums.size();
+        vector<long long> prefixSum(n + 1, 0);
+        for (int i = 0; i < n; i++) {
+            prefixSum[i + 1] = prefixSum[i] + nums[i];
+        }
+
+        vector<int> prevMin(n, -1), nxtMin(n, n);
+        stack<int> stack;
+        
+        for (int i = 0; i < n; i++) {
+            while (!stack.empty() && nums[stack.top()] >= nums[i]) {
+                stack.pop();
+            }
+            if (!stack.empty()) {
+                prevMin[i] = stack.top();
+            }
+            stack.push(i);
+        }
+        
+        while (!stack.empty()) stack.pop();
+        for (int i = n - 1; i >= 0; i--) {
+            while (!stack.empty() && nums[stack.top()] >= nums[i]) {
+                stack.pop();
+            }
+            if (!stack.empty()) {
+                nxtMin[i] = stack.top();
+            }
+            stack.push(i);
+        }
+        
+        long long res = 0;
+        int MOD = 1e9 + 7;
+        for (int i = 0; i < n; i++) {
+            int l = prevMin[i] + 1, r = nxtMin[i] - 1;
+            long long totalSum = prefixSum[r + 1] - prefixSum[l];
+            res = max(res, nums[i] * totalSum);
+        }
+        
+        return res % MOD;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    maxSumMinProduct(nums) {
+        const n = nums.length;
+        const prefixSum = new Array(n + 1).fill(0);
+        for (let i = 0; i < n; i++) {
+            prefixSum[i + 1] = prefixSum[i] + nums[i];
+        }
+
+        const prevMin = new Array(n).fill(-1);
+        const nxtMin = new Array(n).fill(n);
+        const stack = [];
+        
+        for (let i = 0; i < n; i++) {
+            while (stack.length && nums[stack[stack.length - 1]] >= nums[i]) {
+                stack.pop();
+            }
+            if (stack.length) {
+                prevMin[i] = stack[stack.length - 1];
+            }
+            stack.push(i);
+        }
+        
+        stack.length = 0;
+        for (let i = n - 1; i >= 0; i--) {
+            while (stack.length && nums[stack[stack.length - 1]] >= nums[i]) {
+                stack.pop();
+            }
+            if (stack.length) {
+                nxtMin[i] = stack[stack.length - 1];
+            }
+            stack.push(i);
+        }
+        
+        let res = 0n;
+        const MOD = 10n ** 9n + 7n;
+        for (let i = 0; i < n; i++) {
+            const l = prevMin[i] + 1;
+            const r = nxtMin[i] - 1;
+            const totalSum = BigInt(prefixSum[r + 1] - prefixSum[l]);
+            const tmp = BigInt(nums[i]) * totalSum;
+            if (tmp > res) res = tmp;
+        }
+        
+        return Number(res % MOD);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 5. Monotonic Stack (Space Optimized) - I
+
+::tabs-start
+
+```python
+class Solution:
+    def maxSumMinProduct(self, nums: List[int]) -> int:
+        n = len(nums)
+        prefix = [0] * (n + 1)
+        for i in range(n):
+            prefix[i + 1] = prefix[i] + nums[i]
+
+        res = 0
+        stack = []
+
+        for i, num in enumerate(nums):
+            new_start = i
+            while stack and stack[-1][1] > num:
+                start, val = stack.pop()
+                total = prefix[i] - prefix[start]
+                res = max(res, val * total)
+                new_start = start
+            stack.append((new_start, num))
+
+        while stack:
+            start, val = stack.pop()
+            total = prefix[n] - prefix[start]
+            res = max(res, val * total)
+
+        return res % (10**9 + 7)
+```
+
+```java
+public class Solution {
+    public int maxSumMinProduct(int[] nums) {
+        int n = nums.length;
+        long[] prefix = new long[n + 1];
+        for (int i = 0; i < n; i++) {
+            prefix[i + 1] = prefix[i] + nums[i];
+        }
+
+        long res = 0;
+        Stack<int[]> stack = new Stack<>();
+        for (int i = 0; i < n; i++) {
+            int newStart = i;
+            while (!stack.isEmpty() && stack.peek()[1] > nums[i]) {
+                int[] top = stack.pop();
+                int start = top[0], val = top[1];
+                long total = prefix[i] - prefix[start];
+                res = Math.max(res, val * total);
+                newStart = start;
+            }
+            stack.push(new int[]{newStart, nums[i]});
+        }
+
+        while (!stack.isEmpty()) {
+            int[] top = stack.pop();
+            int start = top[0], val = top[1];
+            long total = prefix[n] - prefix[start];
+            res = Math.max(res, val * total);
+        }
+
+        return (int) (res % (1_000_000_007));
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxSumMinProduct(vector<int>& nums) {
+        int n = nums.size();
+        vector<long long> prefix(n + 1, 0);
+        for (int i = 0; i < n; i++) {
+            prefix[i + 1] = prefix[i] + nums[i];
+        }
+
+        long long res = 0;
+        stack<pair<int, int>> stack;
+        for (int i = 0; i < n; i++) {
+            int newStart = i;
+            while (!stack.empty() && stack.top().second > nums[i]) {
+                auto [start, val] = stack.top();
+                stack.pop();
+                long long total = prefix[i] - prefix[start];
+                res = max(res, val * total);
+                newStart = start;
+            }
+            stack.push({newStart, nums[i]});
+        }
+
+        while (!stack.empty()) {
+            auto [start, val] = stack.top();
+            stack.pop();
+            long long total = prefix[n] - prefix[start];
+            res = max(res, val * total);
+        }
+
+        return res % 1000000007;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    maxSumMinProduct(nums) {
+        const n = nums.length;
+        const prefix = new Array(n + 1).fill(0);
+        for (let i = 0; i < n; i++) {
+            prefix[i + 1] = prefix[i] + nums[i];
+        }
+
+        let res = 0n;
+        const MOD = 10n ** 9n + 7n;
+        const stack = [];
+        
+        for (let i = 0; i < n; i++) {
+            let newStart = i;
+            while (stack.length && stack[stack.length - 1][1] > nums[i]) {
+                const [start, val] = stack.pop();
+                const total = BigInt(prefix[i] - prefix[start]);
+                const tmp = BigInt(val) * total;
+                if (tmp > res) res = tmp;
+                newStart = start;
+            }
+            stack.push([newStart, nums[i]]);
+        }
+
+        while (stack.length) {
+            const [start, val] = stack.pop();
+            const total = BigInt(prefix[n] - prefix[start]);
+            const tmp = BigInt(val) * total;
+            if (tmp > res) res = tmp;
+        }
+
+        return Number(res % MOD);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 6. Monotonic Stack (Space Optimized) - II
+
+::tabs-start
+
+```python
+class Solution:
+    def maxSumMinProduct(self, nums: List[int]) -> int:
+        n = len(nums)
+        prefix_sum = [0] * (n + 1)
+        for i in range(n):
+            prefix_sum[i + 1] = prefix_sum[i] + nums[i]
+        
+        res, stack = 0, []
+        for i in range(n + 1):
+            while stack and (i == n or nums[i] < nums[stack[-1]]):
+                j = stack.pop()
+                start = 0 if not stack else stack[-1] + 1
+                res = max(res, nums[j] * (prefix_sum[i] - prefix_sum[start]))
+            stack.append(i)
+        
+        return res % (10 ** 9 + 7)
+```
+
+```java
+public class Solution {
+    public int maxSumMinProduct(int[] nums) {
+        int n = nums.length;
+        long[] prefixSum = new long[n + 1];
+        for (int i = 0; i < n; i++) {
+            prefixSum[i + 1] = prefixSum[i] + nums[i];
+        }
+        
+        long res = 0;
+        int mod = 1_000_000_007;
+        Stack<Integer> stack = new Stack<>();
+        for (int i = 0; i <= n; i++) {
+            while (!stack.isEmpty() && (i == n || nums[i] < nums[stack.peek()])) {
+                int j = stack.pop();
+                int start = stack.isEmpty() ? 0 : stack.peek() + 1;
+                res = Math.max(res, (long) nums[j] * (prefixSum[i] - prefixSum[start]));
+            }
+            stack.push(i);
+        }
+        
+        return (int) (res % mod);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxSumMinProduct(vector<int>& nums) {
+        int n = nums.size();
+        vector<long long> prefixSum(n + 1, 0);
+        for (int i = 0; i < n; i++) {
+            prefixSum[i + 1] = prefixSum[i] + nums[i];
+        }
+        
+        long long res = 0;
+        const int mod = 1e9 + 7;
+        stack<int> st;
+        for (int i = 0; i <= n; i++) {
+            while (!st.empty() && (i == n || nums[i] < nums[st.top()])) {
+                int j = st.top();
+                st.pop();
+                int start = st.empty() ? 0 : st.top() + 1;
+                res = max(res, (long long) nums[j] * (prefixSum[i] - prefixSum[start]));
+            }
+            st.push(i);
+        }
+        
+        return res % mod;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    maxSumMinProduct(nums) {
+        const n = nums.length;
+        const prefixSum = new Array(n + 1).fill(0);
+        for (let i = 0; i < n; i++) {
+            prefixSum[i + 1] = prefixSum[i] + nums[i];
+        }
+
+        let res = 0n;
+        const MOD = 10n ** 9n + 7n;
+        const stack = [];
+        for (let i = 0; i <= n; i++) {
+            while (stack.length && (i === n || nums[i] < nums[stack[stack.length - 1]])) {
+                const j = stack.pop();
+                const start = stack.length === 0 ? 0 : stack[stack.length - 1] + 1;
+                const total = BigInt(prefixSum[i] - prefixSum[start]);
+                const tmp = BigInt(nums[j]) * total;
+                if (tmp > res) res = tmp;
+            }
+            stack.push(i);
+        }
+
+        return Number(res % MOD);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/maximum-subarray.md b/articles/maximum-subarray.md
new file mode 100644
index 000000000..678ab39c8
--- /dev/null
+++ b/articles/maximum-subarray.md
@@ -0,0 +1,1250 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def maxSubArray(self, nums: List[int]) -> int:
+        n, res = len(nums), nums[0]
+        for i in range(n):
+            cur = 0
+            for j in range(i, n):
+                cur += nums[j]
+                res = max(res, cur)
+        return res
+```
+
+```java
+public class Solution {
+    public int maxSubArray(int[] nums) {
+        int n = nums.length, res = nums[0];
+        for (int i = 0; i < n; i++) {
+            int cur = 0;
+            for (int j = i; j < n; j++) {
+                cur += nums[j];
+                res = Math.max(res, cur);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxSubArray(vector<int>& nums) {
+        int n = nums.size(), res = nums[0];
+        for (int i = 0; i < n; i++) {
+            int cur = 0;
+            for (int j = i; j < n; j++) {
+                cur += nums[j];
+                res = max(res, cur);
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    maxSubArray(nums) {
+        let n = nums.length, res = nums[0];
+        for (let i = 0; i < n; i++) {
+            let cur = 0;
+            for (let j = i; j < n; j++) {
+                cur += nums[j];
+                res = Math.max(res, cur);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MaxSubArray(int[] nums) {
+        int n = nums.Length, res = nums[0];
+        for (int i = 0; i < n; i++) {
+            int cur = 0;
+            for (int j = i; j < n; j++) {
+                cur += nums[j];
+                res = Math.Max(res, cur);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```go
+func maxSubArray(nums []int) int {
+    n := len(nums)
+    res := nums[0]
+
+    for i := 0; i < n; i++ {
+        cur := 0
+        for j := i; j < n; j++ {
+            cur += nums[j]
+            if cur > res {
+                res = cur
+            }
+        }
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun maxSubArray(nums: IntArray): Int {
+        val n = nums.size
+        var res = nums[0]
+
+        for (i in 0 until n) {
+            var cur = 0
+            for (j in i until n) {
+                cur += nums[j]
+                res = maxOf(res, cur)
+            }
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func maxSubArray(_ nums: [Int]) -> Int {
+        let n = nums.count
+        var res = nums[0]
+
+        for i in 0..<n {
+            var cur = 0
+            for j in i..<n {
+                cur += nums[j]
+                res = max(res, cur)
+            }
+        }
+
+        return res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def maxSubArray(self, nums: List[int]) -> int:
+        def dfs(i, flag):
+            if i == len(nums):
+                return 0 if flag else -1e6
+            if flag:
+                return max(0, nums[i] + dfs(i + 1, True))
+            return max(dfs(i + 1, False), nums[i] + dfs(i + 1, True))
+        return dfs(0, False)
+```
+
+```java
+public class Solution {
+    public int maxSubArray(int[] nums) {
+        return dfs(nums, 0, false);
+    }
+
+    private int dfs(int[] nums, int i, boolean flag) {
+        if (i == nums.length) {
+            return flag ? 0 : (int) -1e6;
+        }
+        if (flag) {
+            return Math.max(0, nums[i] + dfs(nums, i + 1, true));
+        }
+        return Math.max(dfs(nums, i + 1, false), 
+                        nums[i] + dfs(nums, i + 1, true));
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxSubArray(vector<int>& nums) {
+        return dfs(nums, 0, false);
+    }
+
+private:
+    int dfs(vector<int>& nums, int i, bool flag) {
+        if (i == nums.size()) return flag ? 0 : -1e6;
+        if (flag) return max(0, nums[i] + dfs(nums, i + 1, true));
+        return max(dfs(nums, i + 1, false), 
+                   nums[i] + dfs(nums, i + 1, true));
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    maxSubArray(nums) {
+        const dfs = (i, flag) => {
+            if (i === nums.length) return flag ? 0 : -1e6;
+            if (flag) return Math.max(0, nums[i] + dfs(i + 1, true));
+            return Math.max(dfs(i + 1, false), 
+                            nums[i] + dfs(i + 1, true));
+        };
+        return dfs(0, false);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MaxSubArray(int[] nums) {
+        return Dfs(nums, 0, false);
+    }
+
+    private int Dfs(int[] nums, int i, bool flag) {
+        if (i == nums.Length) return flag ? 0 : (int)-1e6;
+        if (flag) return Math.Max(0, nums[i] + Dfs(nums, i + 1, true));
+        return Math.Max(Dfs(nums, i + 1, false), 
+                        nums[i] + Dfs(nums, i + 1, true));
+    }
+}
+```
+
+```go
+func maxSubArray(nums []int) int {
+    var dfs func(i int, flag bool) int
+    dfs = func(i int, flag bool) int {
+        if i == len(nums) {
+            if flag {
+                return 0
+            }
+            return -1e6 
+        }
+        if flag {
+            return max(0, nums[i] + dfs(i + 1, true))
+        }
+        return max(dfs(i + 1, false), nums[i] + dfs(i + 1, true))
+    }
+
+    return dfs(0, false)
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun maxSubArray(nums: IntArray): Int {
+        fun dfs(i: Int, flag: Boolean): Int {
+            if (i == nums.size) {
+                return if (flag) 0 else Int.MIN_VALUE
+            }
+            return if (flag) {
+                maxOf(0, nums[i] + dfs(i + 1, true))
+            } else {
+                maxOf(dfs(i + 1, false), nums[i] + dfs(i + 1, true))
+            }
+        }
+
+        return dfs(0, false)
+    }
+}
+```
+
+```swift
+class Solution {
+    func maxSubArray(_ nums: [Int]) -> Int {
+        func dfs(_ i: Int, _ flag: Bool) -> Int {
+            if i == nums.count {
+                return flag ? 0 : Int.min
+            }
+
+            if flag {
+                return max(0, nums[i] + dfs(i + 1, true))
+            }
+
+            return max(dfs(i + 1, false), nums[i] + dfs(i + 1, true))
+        }
+
+        return dfs(0, false)
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxSubArray(self, nums: List[int]) -> int:
+        memo = [[None] * 2 for _ in range(len(nums) + 1)]
+
+        def dfs(i, flag):
+            if i == len(nums):
+                return 0 if flag else -1e6
+            if memo[i][flag] is not None:
+                return memo[i][flag]
+            if flag:
+                memo[i][flag] = max(0, nums[i] + dfs(i + 1, True))
+            else:
+                memo[i][flag] = max(dfs(i + 1, False), 
+                                    nums[i] + dfs(i + 1, True))
+            return memo[i][flag]
+
+        return dfs(0, False)
+```
+
+```java
+public class Solution {
+    private int[][] memo;
+
+    public int maxSubArray(int[] nums) {
+        memo = new int[nums.length + 1][2];
+        for (int[] row : memo) Arrays.fill(row, Integer.MIN_VALUE);
+        return dfs(nums, 0, false);
+    }
+
+    private int dfs(int[] nums, int i, boolean flag) {
+        if (i == nums.length) return flag ? 0 : (int) -1e6;
+        int f = flag ? 1 : 0;
+        if (memo[i][f] != Integer.MIN_VALUE) return memo[i][f];
+        memo[i][f] = flag ? Math.max(0, nums[i] + dfs(nums, i + 1, true))
+                          : Math.max(dfs(nums, i + 1, false), 
+                                     nums[i] + dfs(nums, i + 1, true));
+        return memo[i][f];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxSubArray(vector<int>& nums) {
+        vector<vector<int>> memo(nums.size() + 1, vector<int>(2, INT_MIN));
+        return dfs(nums, 0, false, memo);
+    }
+    
+private:
+    int dfs(vector<int>& nums, int i, bool flag, vector<vector<int>>& memo) {
+        if (i == nums.size()) return flag ? 0 : -1e6;
+        int f = flag ? 1 : 0;
+        if (memo[i][f] != INT_MIN) return memo[i][f];
+        if (flag)
+            memo[i][f] = max(0, nums[i] + dfs(nums, i + 1, true, memo));
+        else
+            memo[i][f] = max(dfs(nums, i + 1, false, memo), 
+                             nums[i] + dfs(nums, i + 1, true, memo));
+        return memo[i][f];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    maxSubArray(nums) {
+        const memo = Array(nums.length + 1).fill(null).map(
+            () => [null, null]
+        );
+
+        const dfs = (i, flag) => {
+            if (i === nums.length) return flag ? 0 : -1e6;
+            if (memo[i][+flag] !== null) return memo[i][+flag];
+            memo[i][+flag] = flag ? Math.max(0, nums[i] + dfs(i + 1, true))
+                                : Math.max(dfs(i + 1, false), 
+                                           nums[i] + dfs(i + 1, true));
+            return memo[i][+flag];
+        }
+        return dfs(0, false);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    private int[,] memo;
+
+    public int MaxSubArray(int[] nums) {
+        memo = new int[nums.Length + 1, 2];
+        for (int i = 0; i <= nums.Length; i++) {
+            memo[i, 0] = memo[i, 1] = int.MinValue;
+        }
+        return Dfs(nums, 0, false);
+    }
+
+    private int Dfs(int[] nums, int i, bool flag) {
+        if (i == nums.Length) return flag ? 0 : -1000000;
+        int f = flag ? 1 : 0;
+        if (memo[i, f] != int.MinValue) return memo[i, f];
+        memo[i, f] = flag ? Math.Max(0, nums[i] + Dfs(nums, i + 1, true))
+                          : Math.Max(Dfs(nums, i + 1, false), 
+                                     nums[i] + Dfs(nums, i + 1, true));
+        return memo[i, f];
+    }
+}
+```
+
+```go
+func maxSubArray(nums []int) int {
+    memo := make([][2]*int, len(nums)+1)
+    for i := range memo {
+        memo[i] = [2]*int{nil, nil}
+    }
+
+    var dfs func(int, int) int
+    dfs = func(i, flag int) int {
+        if i == len(nums) {
+            if flag == 1 {
+                return 0
+            }
+            return -1000000
+        }
+        if memo[i][flag] != nil {
+            return *memo[i][flag]
+        }
+        if flag == 1 {
+            result := max(0, nums[i]+dfs(i+1, 1))
+            memo[i][flag] = &result
+        } else {
+            result := max(dfs(i+1, 0), nums[i]+dfs(i+1, 1))
+            memo[i][flag] = &result
+        }
+        return *memo[i][flag]
+    }
+
+    return dfs(0, 0)
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun maxSubArray(nums: IntArray): Int {
+        val memo = Array(nums.size + 1) { arrayOfNulls<Int>(2) }
+
+        fun dfs(i: Int, flag: Int): Int {
+            if (i == nums.size) {
+                return if (flag == 1) 0 else -1000000
+            }
+            if (memo[i][flag] != null) {
+                return memo[i][flag]!!
+            }
+            memo[i][flag] = if (flag == 1) {
+                maxOf(0, nums[i] + dfs(i + 1, 1))
+            } else {
+                maxOf(dfs(i + 1, 0), nums[i] + dfs(i + 1, 1))
+            }
+            return memo[i][flag]!!
+        }
+
+        return dfs(0, 0)
+    }
+}
+```
+
+```swift
+class Solution {
+    func maxSubArray(_ nums: [Int]) -> Int {
+        var memo = Array(repeating: [Int?](repeating: nil, count: 2), count: nums.count + 1)
+
+        func dfs(_ i: Int, _ flag: Bool) -> Int {
+            if i == nums.count {
+                return flag ? 0 : Int.min
+            }
+            if let value = memo[i][flag ? 1 : 0] {
+                return value
+            }
+
+            if flag {
+                memo[i][flag ? 1 : 0] = max(0, nums[i] + dfs(i + 1, true))
+            } else {
+                memo[i][flag ? 1 : 0] = max(dfs(i + 1, false), nums[i] + dfs(i + 1, true))
+            }
+
+            return memo[i][flag ? 1 : 0]!
+        }
+
+        return dfs(0, false)
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxSubArray(self, nums: List[int]) -> int:
+        n = len(nums)
+        dp = [[0] * 2 for _ in range(n)]
+        dp[n - 1][1] = dp[n - 1][0] = nums[n - 1]
+        for i in range(n - 2, -1, -1):
+            dp[i][1] = max(nums[i], nums[i] + dp[i + 1][1])
+            dp[i][0] = max(dp[i + 1][0], dp[i][1])
+        
+        return dp[0][0]
+```
+
+```java
+public class Solution {
+    public int maxSubArray(int[] nums) {
+        int n = nums.length;
+        int[][] dp = new int[n + 1][2];
+        
+        dp[n - 1][1] = dp[n - 1][0] = nums[n - 1];
+        for (int i = n - 2; i >= 0; i--) {
+            dp[i][1] = Math.max(nums[i], nums[i] + dp[i + 1][1]);
+            dp[i][0] = Math.max(dp[i + 1][0], dp[i][1]);
+        }
+        
+        return dp[0][0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxSubArray(vector<int>& nums) {
+        int n = nums.size();
+        vector<vector<int>> dp(n + 1, vector<int>(2, 0));
+        
+        dp[n - 1][1] = dp[n - 1][0] = nums[n - 1];
+        for (int i = n - 2; i >= 0; i--) {
+            dp[i][1] = max(nums[i], nums[i] + dp[i + 1][1]);
+            dp[i][0] = max(dp[i + 1][0], dp[i][1]);
+        }
+        
+        return dp[0][0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    maxSubArray(nums) {
+        const n = nums.length;
+        const dp = Array.from({ length: n + 1 }, () => Array(2).fill(0));
+        
+        dp[n - 1][1] = dp[n - 1][0] = nums[n - 1];
+        for (let i = n - 2; i >= 0; i--) {
+            dp[i][1] = Math.max(nums[i], nums[i] + dp[i + 1][1]);
+            dp[i][0] = Math.max(dp[i + 1][0], dp[i][1]);
+        }
+        
+        return dp[0][0];
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MaxSubArray(int[] nums) {
+        int n = nums.Length;
+        int[,] dp = new int[n + 1, 2];
+        
+        dp[n - 1, 1] = dp[n - 1, 0] = nums[n - 1];
+        for (int i = n - 2; i >= 0; i--) {
+            dp[i, 1] = Math.Max(nums[i], nums[i] + dp[i + 1, 1]);
+            dp[i, 0] = Math.Max(dp[i + 1, 0], dp[i, 1]);
+        }
+        
+        return dp[0, 0];
+    }
+}
+```
+
+```go
+func maxSubArray(nums []int) int {
+    n := len(nums)
+    dp := make([][]int, n)
+    for i := range dp {
+        dp[i] = make([]int, 2)
+    }
+    
+    dp[n-1][1] = nums[n-1]
+    dp[n-1][0] = nums[n-1]
+    
+    for i := n-2; i >= 0; i-- {
+        dp[i][1] = max(nums[i], nums[i] + dp[i+1][1])
+        dp[i][0] = max(dp[i+1][0], dp[i][1])
+    }
+    
+    return dp[0][0]
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun maxSubArray(nums: IntArray): Int {
+        val n = nums.size
+        val dp = Array(n) { IntArray(2) }
+        
+        dp[n-1][1] = nums[n-1]
+        dp[n-1][0] = nums[n-1]
+        
+        for (i in n-2 downTo 0) {
+            dp[i][1] = maxOf(nums[i], nums[i] + dp[i+1][1])
+            dp[i][0] = maxOf(dp[i+1][0], dp[i][1])
+        }
+        
+        return dp[0][0]
+    }
+}
+```
+
+```swift
+class Solution {
+    func maxSubArray(_ nums: [Int]) -> Int {
+        let n = nums.count
+        var dp = Array(repeating: [0, 0], count: n)
+        dp[n - 1][1] = nums[n - 1]
+        dp[n - 1][0] = nums[n - 1]
+
+        for i in (0..<n-1).reversed() {
+            dp[i][1] = max(nums[i], nums[i] + dp[i + 1][1])
+            dp[i][0] = max(dp[i + 1][0], dp[i][1])
+        }
+
+        return dp[0][0]
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 5. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxSubArray(self, nums):
+        dp = [*nums]
+        for i in range(1, len(nums)):
+            dp[i] = max(nums[i], nums[i] + dp[i - 1])
+        return max(dp)
+```
+
+```java
+public class Solution {
+    public int maxSubArray(int[] nums) {
+        int[] dp = nums.clone();
+        for (int i = 1; i < nums.length; i++) {
+            dp[i] = Math.max(nums[i], nums[i] + dp[i - 1]);
+        }
+        int maxSum = dp[0];
+        for (int sum : dp) {
+            maxSum = Math.max(maxSum, sum);
+        }
+        return maxSum;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxSubArray(vector<int>& nums) {
+        vector<int> dp(nums);
+        for (int i = 1; i < nums.size(); i++) {
+            dp[i] = max(nums[i], nums[i] + dp[i - 1]);
+        }
+        return *max_element(dp.begin(), dp.end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    maxSubArray(nums) {
+        let dp = [...nums];
+        for (let i = 1; i < nums.length; i++) {
+            dp[i] = Math.max(nums[i], nums[i] + dp[i - 1]);
+        }
+        return Math.max(...dp);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MaxSubArray(int[] nums) {
+        int[] dp = (int[])nums.Clone();
+        for (int i = 1; i < nums.Length; i++) {
+            dp[i] = Math.Max(nums[i], nums[i] + dp[i - 1]);
+        }
+        int maxSum = dp[0];
+        foreach (int sum in dp) {
+            maxSum = Math.Max(maxSum, sum);
+        }
+        return maxSum;
+    }
+}
+```
+
+```go
+func maxSubArray(nums []int) int {
+    dp := make([]int, len(nums))
+    copy(dp, nums)
+    
+    for i := 1; i < len(nums); i++ {
+        dp[i] = max(nums[i], nums[i] + dp[i-1])
+    }
+    
+    maxSum := dp[0]
+    for _, v := range dp {
+        if v > maxSum {
+            maxSum = v
+        }
+    }
+    
+    return maxSum
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun maxSubArray(nums: IntArray): Int {
+        val dp = nums.copyOf()
+        
+        for (i in 1 until nums.size) {
+            dp[i] = maxOf(nums[i], nums[i] + dp[i-1])
+        }
+        
+        return dp.maxOrNull() ?: nums[0]
+    }
+}
+```
+
+```swift
+class Solution {
+    func maxSubArray(_ nums: [Int]) -> Int {
+        var dp = nums
+
+        for i in 1..<nums.count {
+            dp[i] = max(nums[i], nums[i] + dp[i - 1])
+        }
+
+        return dp.max() ?? 0
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 6. Kadane's Algorithm
+
+::tabs-start
+
+```python
+class Solution:
+    def maxSubArray(self, nums: List[int]) -> int:
+        maxSub, curSum = nums[0], 0
+        for num in nums:
+            if curSum < 0:
+                curSum = 0
+            curSum += num
+            maxSub = max(maxSub, curSum)
+        return maxSub
+
+```
+
+```java
+public class Solution {
+    public int maxSubArray(int[] nums) {
+        int maxSub = nums[0], curSum = 0;
+        for (int num : nums) {
+            if (curSum < 0) {
+                curSum = 0;
+            }
+            curSum += num;
+            maxSub = Math.max(maxSub, curSum);
+        }
+        return maxSub;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxSubArray(vector<int>& nums) {
+        int maxSub = nums[0], curSum = 0;
+        for (int num : nums) {
+            if (curSum < 0) {
+                curSum = 0;
+            }
+            curSum += num;
+            maxSub = max(maxSub, curSum);
+        }
+        return maxSub;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    maxSubArray(nums) {
+        let maxSub = nums[0], curSum = 0;
+        for (const num of nums) {
+            if (curSum < 0) {
+                curSum = 0;
+            }
+            curSum += num;
+            maxSub = Math.max(maxSub, curSum);
+        }
+        return maxSub;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MaxSubArray(int[] nums) {
+        int maxSub = nums[0], curSum = 0;
+        foreach (int num in nums) {
+            if (curSum < 0) {
+                curSum = 0;
+            }
+            curSum += num;
+            maxSub = Math.Max(maxSub, curSum);
+        }
+        return maxSub;
+    }
+}
+```
+
+```go
+func maxSubArray(nums []int) int {
+    maxSub, curSum := nums[0], 0
+    for _, num := range nums {
+        if curSum < 0 {
+            curSum = 0
+        }
+        curSum += num
+        maxSub = max(maxSub, curSum)
+    }
+    return maxSub
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun maxSubArray(nums: IntArray): Int {
+        var maxSub = nums[0]
+        var curSum = 0
+        for (num in nums) {
+            if (curSum < 0) {
+                curSum = 0
+            }
+            curSum += num
+            maxSub = maxOf(maxSub, curSum)
+        }
+        return maxSub
+    }
+}
+```
+
+```swift
+class Solution {
+    func maxSubArray(_ nums: [Int]) -> Int {
+        var maxSub = nums[0]
+        var curSum = 0
+
+        for num in nums {
+            if curSum < 0 {
+                curSum = 0
+            }
+            curSum += num
+            maxSub = max(maxSub, curSum)
+        }
+
+        return maxSub
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 7. Divide & Conquer
+
+::tabs-start
+
+```python
+class Solution:
+    def maxSubArray(self, nums: List[int]) -> int:
+        def dfs(l, r):
+            if l > r:
+                return float("-inf")
+
+            m = (l + r) >> 1
+            leftSum = rightSum = curSum = 0
+            for i in range(m - 1, l - 1, -1):
+                curSum += nums[i]
+                leftSum = max(leftSum, curSum)
+
+            curSum = 0
+            for i in range(m + 1, r + 1):
+                curSum += nums[i]
+                rightSum = max(rightSum, curSum)
+
+            return (max(dfs(l, m - 1), 
+                        dfs(m + 1, r), 
+                        leftSum + nums[m] + rightSum))
+                        
+        return dfs(0, len(nums) - 1)
+```
+
+```java
+public class Solution {
+    public int maxSubArray(int[] nums) {
+        return dfs(nums, 0, nums.length - 1);
+    }
+    
+    private int dfs(int[] nums, int l, int r) {
+        if (l > r) {
+            return Integer.MIN_VALUE;
+        }
+        int m = (l + r) >> 1;
+        int leftSum = 0, rightSum = 0, curSum = 0;
+        for (int i = m - 1; i >= l; i--) {
+            curSum += nums[i];
+            leftSum = Math.max(leftSum, curSum);
+        }
+
+        curSum = 0;
+        for (int i = m + 1; i <= r; i++) {
+            curSum += nums[i];
+            rightSum = Math.max(rightSum, curSum);
+        }
+
+        return Math.max(dfs(nums, l, m - 1), 
+                        Math.max(dfs(nums, m + 1, r), 
+                             leftSum + nums[m] + rightSum));
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxSubArray(vector<int>& nums) {
+        return dfs(nums, 0, nums.size() - 1);
+    }
+
+private:
+    int dfs(vector<int>& nums, int l, int r) {
+        if (l > r) {
+            return INT_MIN;
+        }
+        int m = (l + r) >> 1;
+        int leftSum = 0, rightSum = 0, curSum = 0;
+        for (int i = m - 1; i >= l; --i) {
+            curSum += nums[i];
+            leftSum = max(leftSum, curSum);
+        }
+        curSum = 0;
+        for (int i = m + 1; i <= r; ++i) {
+            curSum += nums[i];
+            rightSum = max(rightSum, curSum);
+        }
+        return max(dfs(nums, l, m - 1), 
+                   max(dfs(nums, m + 1, r), 
+                       leftSum + nums[m] + rightSum));
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    maxSubArray(nums) {
+        const dfs = (l, r) => {
+            if (l > r) {
+                return -Infinity;
+            }
+            let m = (l + r) >> 1;
+            let leftSum = 0, rightSum = 0, curSum = 0;
+            for (let i = m - 1; i >= l; i--) {
+                curSum += nums[i];
+                leftSum = Math.max(leftSum, curSum);
+            }
+
+            curSum = 0;
+            for (let i = m + 1; i <= r; i++) {
+                curSum += nums[i];
+                rightSum = Math.max(rightSum, curSum);
+            }
+            return Math.max(dfs(l, m - 1), 
+                        Math.max(dfs(m + 1, r), 
+                            leftSum + nums[m] + rightSum));
+        }
+        
+        return dfs(0, nums.length - 1);
+    }
+}
+```
+
+```csharp
+public class Solution {
+     public int MaxSubArray(int[] nums) {
+        return Dfs(nums, 0, nums.Length - 1);
+    }
+    
+    private int Dfs(int[] nums, int l, int r) {
+        if (l > r) {
+            return int.MinValue;
+        }
+        int m = (l + r) >> 1;
+        int leftSum = 0, rightSum = 0, curSum = 0;
+        for (int i = m - 1; i >= l; i--) {
+            curSum += nums[i];
+            leftSum = Math.Max(leftSum, curSum);
+        }
+
+        curSum = 0;
+        for (int i = m + 1; i <= r; i++) {
+            curSum += nums[i];
+            rightSum = Math.Max(rightSum, curSum);
+        }
+
+        return Math.Max(Dfs(nums, l, m - 1), 
+                        Math.Max(Dfs(nums, m + 1, r), 
+                             leftSum + nums[m] + rightSum));
+    }
+}
+```
+
+```go
+func maxSubArray(nums []int) int {
+    var dfs func(l, r int) int
+    dfs = func(l, r int) int {
+        if l > r {
+            return math.MinInt64
+        }
+        
+        m := (l + r) >> 1
+        leftSum, rightSum, curSum := 0, 0, 0
+        
+        for i := m - 1; i >= l; i-- {
+            curSum += nums[i]
+            if curSum > leftSum {
+                leftSum = curSum
+            }
+        }
+        
+        curSum = 0
+        for i := m + 1; i <= r; i++ {
+            curSum += nums[i]
+            if curSum > rightSum {
+                rightSum = curSum
+            }
+        }
+        
+        maxLeft := dfs(l, m-1)
+        maxRight := dfs(m+1, r)
+        crossSum := leftSum + nums[m] + rightSum
+        
+        return max(max(maxLeft, maxRight), crossSum)
+    }
+    
+    return dfs(0, len(nums)-1)
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun maxSubArray(nums: IntArray): Int {
+        fun dfs(l: Int, r: Int): Int {
+            if (l > r) {
+                return Int.MIN_VALUE
+            }
+            
+            val m = (l + r) shr 1
+            var leftSum = 0
+            var rightSum = 0
+            var curSum = 0
+            
+            for (i in (m - 1) downTo l) {
+                curSum += nums[i]
+                leftSum = maxOf(leftSum, curSum)
+            }
+            
+            curSum = 0
+            for (i in (m + 1)..r) {
+                curSum += nums[i]
+                rightSum = maxOf(rightSum, curSum)
+            }
+            
+            return maxOf(
+                dfs(l, m - 1),
+                dfs(m + 1, r),
+                leftSum + nums[m] + rightSum
+            )
+        }
+        
+        return dfs(0, nums.size - 1)
+    }
+}
+```
+
+```swift
+class Solution {
+    func maxSubArray(_ nums: [Int]) -> Int {
+
+        func dfs(_ l: Int, _ r: Int) -> Int {
+            if l > r {
+                return Int.min
+            }
+
+            let m = (l + r) / 2
+            var leftSum = 0
+            var rightSum = 0
+            var curSum = 0
+
+            for i in stride(from: m - 1, through: l, by: -1) {
+                curSum += nums[i]
+                leftSum = max(leftSum, curSum)
+            }
+
+            curSum = 0
+            for i in stride(from: m + 1, to: r + 1, by: 1) {
+                curSum += nums[i]
+                rightSum = max(rightSum, curSum)
+            }
+
+            return max(dfs(l, m - 1), dfs(m + 1, r), leftSum + nums[m] + rightSum)
+        }
+
+        return dfs(0, nums.count - 1)
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(\log n)$
\ No newline at end of file
diff --git a/articles/maximum-subsequence-score.md b/articles/maximum-subsequence-score.md
new file mode 100644
index 000000000..97c461caa
--- /dev/null
+++ b/articles/maximum-subsequence-score.md
@@ -0,0 +1,412 @@
+## 1. Brute Force (Recursion)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxScore(self, nums1: List[int], nums2: List[int], k: int) -> int:
+        n = len(nums1)
+
+        def dfs(i, k, minVal, curSum):
+            if k == 0:
+                return curSum * minVal
+            if i == n or (n - i) < k:
+                return float("-inf")
+            if minVal == 0:
+                return 0
+
+            res = dfs(i + 1, k, minVal, curSum)
+            res = max(res, dfs(i + 1, k - 1, min(minVal, nums2[i]), curSum + nums1[i]))
+            return res
+
+        return dfs(0, k, float("inf"), 0)
+```
+
+```java
+public class Solution {
+    private int[] nums1, nums2;
+    private int n;
+
+    public long maxScore(int[] nums1, int[] nums2, int k) {
+        this.nums1 = nums1;
+        this.nums2 = nums2;
+        this.n = nums1.length;
+        return dfs(0, k, Integer.MAX_VALUE, 0);
+    }
+
+    private long dfs(int i, int k, int minVal, long curSum) {
+        if (k == 0) {
+            return curSum * minVal;
+        }
+        if (i == n || (n - i) < k) {
+            return Integer.MIN_VALUE;
+        }
+        if (minVal == 0) {
+            return 0;
+        }
+
+        long res = dfs(i + 1, k, minVal, curSum);
+        res = Math.max(
+                res,
+                dfs(i + 1, k - 1, Math.min(minVal, nums2[i]), curSum + nums1[i])
+            );
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<int> nums1, nums2;
+    int n;
+
+public:
+    long long maxScore(vector<int>& nums1, vector<int>& nums2, int k) {
+        this->nums1 = nums1;
+        this->nums2 = nums2;
+        this->n = nums1.size();
+        return dfs(0, k, INT_MAX, 0);
+    }
+
+private:
+    long long dfs(int i, int k, int minVal, long long curSum) {
+        if (k == 0) {
+            return curSum * minVal;
+        }
+        if (i == n || (n - i) < k) {
+            return INT_MIN;
+        }
+        if (minVal == 0) {
+            return 0;
+        }
+
+        long long res = dfs(i + 1, k, minVal, curSum);
+        res = max(res, dfs(i + 1, k - 1, min(minVal, nums2[i]), curSum + nums1[i]));
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums1
+     * @param {number[]} nums2
+     * @param {number} k
+     * @return {number}
+     */
+    maxScore(nums1, nums2, k) {
+        const n = nums1.length;
+
+        const dfs = (i, k, minVal, curSum) => {
+            if (k === 0) {
+                return curSum * minVal;
+            }
+            if (i === n || (n - i) < k) {
+                return -Infinity;
+            }
+            if (minVal === 0) {
+                return 0;
+            }
+
+            let res = dfs(i + 1, k, minVal, curSum);
+            res = Math.max(
+                    res,
+                    dfs(i + 1, k - 1, Math.min(minVal, nums2[i]), curSum + nums1[i])
+                );
+            return res;
+        };
+
+        return dfs(0, k, Infinity, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Min-Heap - I
+
+::tabs-start
+
+```python
+class Solution:
+    def maxScore(self, nums1: List[int], nums2: List[int], k: int) -> int:
+        pairs = sorted(zip(nums1, nums2), key=lambda p: p[1], reverse=True)
+
+        minHeap = []
+        n1Sum = 0
+        res = 0
+
+        for n1, n2 in pairs:
+            n1Sum += n1
+            heapq.heappush(minHeap, n1)
+
+            if len(minHeap) > k:
+                n1Sum -= heapq.heappop(minHeap)
+
+            if len(minHeap) == k:
+                res = max(res, n1Sum * n2)
+
+        return res
+```
+
+```java
+public class Solution {
+    public long maxScore(int[] nums1, int[] nums2, int k) {
+        int n = nums1.length;
+        int[][] pairs = new int[n][2];
+
+        for (int i = 0; i < n; i++) {
+            pairs[i][0] = nums1[i];
+            pairs[i][1] = nums2[i];
+        }
+
+        Arrays.sort(pairs, (a, b) -> Integer.compare(b[1], a[1]));
+
+        PriorityQueue<Integer> minHeap = new PriorityQueue<>();
+        long n1Sum = 0, res = 0;
+
+        for (int[] pair : pairs) {
+            n1Sum += pair[0];
+            minHeap.offer(pair[0]);
+
+            if (minHeap.size() > k) {
+                n1Sum -= minHeap.poll();
+            }
+
+            if (minHeap.size() == k) {
+                res = Math.max(res, n1Sum * pair[1]);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long maxScore(vector<int>& nums1, vector<int>& nums2, int k) {
+        int n = nums1.size();
+        vector<pair<int, int>> pairs(n);
+
+        for (int i = 0; i < n; i++) {
+            pairs[i] = {nums1[i], nums2[i]};
+        }
+
+        sort(pairs.begin(), pairs.end(), [](const auto& a, const auto& b) {
+            return b.second < a.second;
+        });
+
+        priority_queue<int, vector<int>, greater<int>> minHeap;
+        long long n1Sum = 0, res = 0;
+
+        for (auto& pair : pairs) {
+            n1Sum += pair.first;
+            minHeap.push(pair.first);
+
+            if (minHeap.size() > k) {
+                n1Sum -= minHeap.top();
+                minHeap.pop();
+            }
+
+            if (minHeap.size() == k) {
+                res = max(res, n1Sum * (long long)pair.second);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums1
+     * @param {number[]} nums2
+     * @param {number} k
+     * @return {number}
+     */
+    maxScore(nums1, nums2, k) {
+        let pairs = nums1.map((n1, i) => [n1, nums2[i]]);
+        pairs.sort((a, b) => b[1] - a[1]);
+
+        let minHeap = new MinPriorityQueue();
+        let n1Sum = 0, res = 0;
+
+        for (let [n1, n2] of pairs) {
+            n1Sum += n1;
+            minHeap.enqueue(n1);
+
+            if (minHeap.size() > k) {
+                n1Sum -= minHeap.dequeue();
+            }
+
+            if (minHeap.size() === k) {
+                res = Math.max(res, n1Sum * n2);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Min-Heap - II
+
+::tabs-start
+
+```python
+class Solution:
+    def maxScore(self, nums1: List[int], nums2: List[int], k: int) -> int:
+        n = len(nums1)
+        arr = [(nums2[i] << 30) | nums1[i] for i in range(n)]
+        arr.sort(reverse=True)
+
+        minHeap = []
+        n1Sum = 0
+        res = 0
+
+        for num in arr:
+            n1, n2 = num & ((1 << 30) - 1), num >> 30
+            n1Sum += n1
+            heapq.heappush(minHeap, n1)
+
+            if len(minHeap) > k:
+                n1Sum -= heapq.heappop(minHeap)
+
+            if len(minHeap) == k:
+                res = max(res, n1Sum * n2)
+
+        return res
+```
+
+```java
+public class Solution {
+    public long maxScore(int[] nums1, int[] nums2, int k) {
+        int n = nums1.length;
+        long[] arr = new long[n];
+        for (int i = 0; i < n; i++) {
+            arr[i] = ((long) nums2[i] << 30) | nums1[i];
+        }
+
+        Arrays.sort(arr);
+        PriorityQueue<Integer> minHeap = new PriorityQueue<>();
+        long n1Sum = 0, res = 0;
+
+        for (int i = n - 1; i >= 0; i--) {
+            int n1 = (int) (arr[i] & ((1L << 30) - 1));
+            int n2 = (int) (arr[i] >> 30);
+            n1Sum += n1;
+            minHeap.offer(n1);
+
+            if (minHeap.size() > k) {
+                n1Sum -= minHeap.poll();
+            }
+            if (minHeap.size() == k) {
+                res = Math.max(res, n1Sum * (long) n2);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long maxScore(vector<int>& nums1, vector<int>& nums2, int k) {
+        int n = nums1.size();
+        vector<long long> arr(n);
+        for (int i = 0; i < n; i++) {
+            arr[i] = ((long long) nums2[i] << 30) | nums1[i];
+        }
+
+        sort(arr.rbegin(), arr.rend());
+        priority_queue<int, vector<int>, greater<int>> minHeap;
+        long long n1Sum = 0, res = 0;
+
+        for (long long& num : arr) {
+            int n1 = num & ((1LL << 30) - 1);
+            int n2 = num >> 30;
+            n1Sum += n1;
+            minHeap.push(n1);
+
+            if (minHeap.size() > k) {
+                n1Sum -= minHeap.top();
+                minHeap.pop();
+            }
+            if (minHeap.size() == k) {
+                res = max(res, n1Sum * (long long)n2);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums1
+     * @param {number[]} nums2
+     * @param {number} k
+     * @return {number}
+     */
+    maxScore(nums1, nums2, k) {
+        const n = nums1.length;
+        const arr = [];
+        for (let i = 0; i < n; i++) {
+            arr.push((BigInt(nums2[i]) << BigInt(30)) | BigInt(nums1[i]));
+        }
+
+        arr.sort((a, b) => Number(b - a));
+        const minHeap = new MinPriorityQueue();
+        let n1Sum = 0n, res = 0n;
+
+        for (let num of arr) {
+            let n1 = Number(num & ((1n << 30n) - 1n));
+            let n2 = Number(num >> 30n);
+            n1Sum += BigInt(n1);
+            minHeap.enqueue(n1);
+
+            if (minHeap.size() > k) {
+                n1Sum -= BigInt(minHeap.dequeue());
+            }
+            if (minHeap.size() === k) {
+                res = BigInt(Math.max(Number(res), Number(n1Sum * BigInt(n2))));
+            }
+        }
+
+        return Number(res);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/maximum-sum-circular-subarray.md b/articles/maximum-sum-circular-subarray.md
new file mode 100644
index 000000000..d1f717448
--- /dev/null
+++ b/articles/maximum-sum-circular-subarray.md
@@ -0,0 +1,316 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def maxSubarraySumCircular(self, nums: List[int]) -> int:
+        n = len(nums)
+        res = nums[0]
+
+        for i in range(n):
+            cur_sum = 0
+            for j in range(i, i + n):
+                cur_sum += nums[j % n]
+                res = max(res, cur_sum)
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int maxSubarraySumCircular(int[] nums) {
+        int n = nums.length;
+        int res = nums[0];
+
+        for (int i = 0; i < n; i++) {
+            int curSum = 0;
+            for (int j = i; j < i + n; j++) {
+                curSum += nums[j % n];
+                res = Math.max(res, curSum);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxSubarraySumCircular(vector<int>& nums) {
+        int n = nums.size();
+        int res = nums[0];
+
+        for (int i = 0; i < n; i++) {
+            int curSum = 0;
+            for (int j = i; j < i + n; j++) {
+                curSum += nums[j % n];
+                res = max(res, curSum);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    maxSubarraySumCircular(nums) {
+        const n = nums.length;
+        let res = nums[0];
+
+        for (let i = 0; i < n; i++) {
+            let curSum = 0;
+            for (let j = i; j < i + n; j++) {
+                curSum += nums[j % n];
+                res = Math.max(res, curSum);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 2. Prefix & Suffix Sums
+
+::tabs-start
+
+```python
+class Solution:
+    def maxSubarraySumCircular(self, nums: List[int]) -> int:
+        n = len(nums)
+        right_max = [0] * n
+        right_max[-1] = nums[-1]
+        suffix_sum = nums[-1]
+        
+        for i in range(n - 2, -1, -1):
+            suffix_sum += nums[i]
+            right_max[i] = max(right_max[i + 1], suffix_sum)
+        
+        max_sum = nums[0]
+        cur_max = 0
+        prefix_sum = 0
+        
+        for i in range(n):
+            cur_max = max(cur_max, 0) + nums[i]
+            max_sum = max(max_sum, cur_max)
+            prefix_sum += nums[i]
+            if i + 1 < n:
+                max_sum = max(max_sum, prefix_sum + right_max[i + 1])
+        
+        return max_sum
+```
+
+```java
+public class Solution {
+    public int maxSubarraySumCircular(int[] nums) {
+        int n = nums.length;
+        int[] rightMax = new int[n];
+        rightMax[n - 1] = nums[n - 1];
+        int suffixSum = nums[n - 1];
+
+        for (int i = n - 2; i >= 0; i--) {
+            suffixSum += nums[i];
+            rightMax[i] = Math.max(rightMax[i + 1], suffixSum);
+        }
+
+        int maxSum = nums[0];
+        int curMax = 0;
+        int prefixSum = 0;
+
+        for (int i = 0; i < n; i++) {
+            curMax = Math.max(curMax, 0) + nums[i];
+            maxSum = Math.max(maxSum, curMax);
+            prefixSum += nums[i];
+            if (i + 1 < n) {
+                maxSum = Math.max(maxSum, prefixSum + rightMax[i + 1]);
+            }
+        }
+
+        return maxSum;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxSubarraySumCircular(vector<int>& nums) {
+        int n = nums.size();
+        vector<int> rightMax(n);
+        rightMax[n - 1] = nums[n - 1];
+        int suffixSum = nums[n - 1];
+
+        for (int i = n - 2; i >= 0; --i) {
+            suffixSum += nums[i];
+            rightMax[i] = max(rightMax[i + 1], suffixSum);
+        }
+
+        int maxSum = nums[0];
+        int curMax = 0;
+        int prefixSum = 0;
+
+        for (int i = 0; i < n; ++i) {
+            curMax = max(curMax, 0) + nums[i];
+            maxSum = max(maxSum, curMax);
+            prefixSum += nums[i];
+            if (i + 1 < n) {
+                maxSum = max(maxSum, prefixSum + rightMax[i + 1]);
+            }
+        }
+
+        return maxSum;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    maxSubarraySumCircular(nums) {
+        const n = nums.length;
+        const rightMax = new Array(n).fill(0);
+        rightMax[n - 1] = nums[n - 1];
+        let suffixSum = nums[n - 1];
+
+        for (let i = n - 2; i >= 0; i--) {
+            suffixSum += nums[i];
+            rightMax[i] = Math.max(rightMax[i + 1], suffixSum);
+        }
+
+        let maxSum = nums[0];
+        let curMax = 0;
+        let prefixSum = 0;
+
+        for (let i = 0; i < n; i++) {
+            curMax = Math.max(curMax, 0) + nums[i];
+            maxSum = Math.max(maxSum, curMax);
+            prefixSum += nums[i];
+            if (i + 1 < n) {
+                maxSum = Math.max(maxSum, prefixSum + rightMax[i + 1]);
+            }
+        }
+
+        return maxSum;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Kadane's Algorithm
+
+::tabs-start
+
+```python
+class Solution:
+    def maxSubarraySumCircular(self, nums: List[int]) -> int:
+        globMax, globMin = nums[0], nums[0]
+        curMax, curMin = 0, 0
+        total = 0
+
+        for num in nums:
+            curMax = max(curMax + num, num)
+            curMin = min(curMin + num, num)
+            total += num
+            globMax = max(globMax, curMax)
+            globMin = min(globMin, curMin)
+
+        return max(globMax, total - globMin) if globMax > 0 else globMax
+```
+
+```java
+public class Solution {
+    public int maxSubarraySumCircular(int[] nums) {
+        int globMax = nums[0], globMin = nums[0];
+        int curMax = 0, curMin = 0, total = 0;
+
+        for (int num : nums) {
+            curMax = Math.max(curMax + num, num);
+            curMin = Math.min(curMin + num, num);
+            total += num;
+            globMax = Math.max(globMax, curMax);
+            globMin = Math.min(globMin, curMin);
+        }
+
+        return globMax > 0 ? Math.max(globMax, total - globMin) : globMax;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxSubarraySumCircular(vector<int>& nums) {
+        int globMax = nums[0], globMin = nums[0];
+        int curMax = 0, curMin = 0, total = 0;
+
+        for (int& num : nums) {
+            curMax = max(curMax + num, num);
+            curMin = min(curMin + num, num);
+            total += num;
+            globMax = max(globMax, curMax);
+            globMin = min(globMin, curMin);
+        }
+
+        return globMax > 0 ? max(globMax, total - globMin) : globMax;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    maxSubarraySumCircular(nums) {
+        let globMax = nums[0], globMin = nums[0];
+        let curMax = 0, curMin = 0, total = 0;
+
+        for (const num of nums) {
+            curMax = Math.max(curMax + num, num);
+            curMin = Math.min(curMin + num, num);
+            total += num;
+            globMax = Math.max(globMax, curMax);
+            globMin = Math.min(globMin, curMin);
+        }
+
+        return globMax > 0 ? Math.max(globMax, total - globMin) : globMax;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/maximum-twin-sum-of-a-linked-list.md b/articles/maximum-twin-sum-of-a-linked-list.md
new file mode 100644
index 000000000..b896b8cae
--- /dev/null
+++ b/articles/maximum-twin-sum-of-a-linked-list.md
@@ -0,0 +1,450 @@
+## 1. Convert To Array
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def pairSum(self, head: Optional[ListNode]) -> int:
+        arr = []
+        cur = head
+        while cur:
+            arr.append(cur.val)
+            cur = cur.next
+
+        i, j = 0, len(arr) - 1
+        res = 0
+        while i < j:
+            res = max(res, arr[i] + arr[j])
+            i, j = i + 1, j - 1
+
+        return res
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public int pairSum(ListNode head) {
+        List<Integer> arr = new ArrayList<>();
+        ListNode cur = head;
+
+        while (cur != null) {
+            arr.add(cur.val);
+            cur = cur.next;
+        }
+
+        int i = 0, j = arr.size() - 1, res = 0;
+        while (i < j) {
+            res = Math.max(res, arr.get(i) + arr.get(j));
+            i++;
+            j--;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    int pairSum(ListNode* head) {
+        vector<int> arr;
+        ListNode* cur = head;
+
+        while (cur) {
+            arr.push_back(cur->val);
+            cur = cur->next;
+        }
+
+        int i = 0, j = arr.size() - 1, res = 0;
+        while (i < j) {
+            res = max(res, arr[i] + arr[j]);
+            i++;
+            j--;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @return {number}
+     */
+    pairSum(head) {
+        let arr = [];
+        let cur = head;
+
+        while (cur) {
+            arr.push(cur.val);
+            cur = cur.next;
+        }
+
+        let i = 0, j = arr.length - 1, res = 0;
+        while (i < j) {
+            res = Math.max(res, arr[i] + arr[j]);
+            i++;
+            j--;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Reverse the Second Half
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def pairSum(self, head: Optional[ListNode]) -> int:
+        slow, fast = head, head
+        while fast and fast.next:
+            slow = slow.next
+            fast = fast.next.next
+
+        prev, cur = None, slow
+        while cur:
+            nxt = cur.next
+            cur.next = prev
+            prev = cur
+            cur = nxt
+
+        res = 0
+        first, second = head, prev
+        while second:
+            res = max(res, first.val + second.val)
+            first, second = first.next, second.next
+
+        return res
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public int pairSum(ListNode head) {
+        ListNode slow = head, fast = head;
+        while (fast != null && fast.next != null) {
+            slow = slow.next;
+            fast = fast.next.next;
+        }
+
+        ListNode prev = null, cur = slow;
+        while (cur != null) {
+            ListNode nxt = cur.next;
+            cur.next = prev;
+            prev = cur;
+            cur = nxt;
+        }
+
+        int res = 0;
+        ListNode first = head, second = prev;
+        while (second != null) {
+            res = Math.max(res, first.val + second.val);
+            first = first.next;
+            second = second.next;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    int pairSum(ListNode* head) {
+        ListNode* slow = head, *fast = head;
+        while (fast && fast->next) {
+            slow = slow->next;
+            fast = fast->next->next;
+        }
+
+        ListNode* prev = nullptr, *cur = slow;
+        while (cur) {
+            ListNode* nxt = cur->next;
+            cur->next = prev;
+            prev = cur;
+            cur = nxt;
+        }
+
+        int res = 0;
+        ListNode* first = head, *second = prev;
+        while (second) {
+            res = max(res, first->val + second->val);
+            first = first->next;
+            second = second->next;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @return {number}
+     */
+    pairSum(head) {
+        let slow = head, fast = head;
+        while (fast && fast.next) {
+            slow = slow.next;
+            fast = fast.next.next;
+        }
+
+        let prev = null, cur = slow;
+        while (cur) {
+            let nxt = cur.next;
+            cur.next = prev;
+            prev = cur;
+            cur = nxt;
+        }
+
+        let res = 0, first = head, second = prev;
+        while (second) {
+            res = Math.max(res, first.val + second.val);
+            first = first.next;
+            second = second.next;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 3. Reverse the First Half
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def pairSum(self, head: Optional[ListNode]) -> int:
+        slow, fast = head, head
+        prev = None
+
+        while fast and fast.next:
+            fast = fast.next.next
+            tmp = slow.next
+            slow.next = prev
+            prev = slow
+            slow = tmp
+
+        res = 0
+        while slow:
+            res = max(res, prev.val + slow.val)
+            prev = prev.next
+            slow = slow.next
+
+        return res
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public int pairSum(ListNode head) {
+        ListNode slow = head, fast = head, prev = null;
+
+        while (fast != null && fast.next != null) {
+            fast = fast.next.next;
+            ListNode tmp = slow.next;
+            slow.next = prev;
+            prev = slow;
+            slow = tmp;
+        }
+
+        int res = 0;
+        while (slow != null) {
+            res = Math.max(res, prev.val + slow.val);
+            prev = prev.next;
+            slow = slow.next;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    int pairSum(ListNode* head) {
+        ListNode* slow = head, *fast = head, *prev = nullptr;
+
+        while (fast && fast->next) {
+            fast = fast->next->next;
+            ListNode* tmp = slow->next;
+            slow->next = prev;
+            prev = slow;
+            slow = tmp;
+        }
+
+        int res = 0;
+        while (slow) {
+            res = max(res, prev->val + slow->val);
+            prev = prev->next;
+            slow = slow->next;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @return {number}
+     */
+    pairSum(head) {
+        let slow = head, fast = head, prev = null;
+
+        while (fast && fast.next) {
+            fast = fast.next.next;
+            let tmp = slow.next;
+            slow.next = prev;
+            prev = slow;
+            slow = tmp;
+        }
+
+        let res = 0;
+        while (slow) {
+            res = Math.max(res, prev.val + slow.val);
+            prev = prev.next;
+            slow = slow.next;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/maximum-value-of-k-coins-from-piles.md b/articles/maximum-value-of-k-coins-from-piles.md
new file mode 100644
index 000000000..bf108e73c
--- /dev/null
+++ b/articles/maximum-value-of-k-coins-from-piles.md
@@ -0,0 +1,451 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def maxValueOfCoins(self, piles: List[List[int]], k: int) -> int:
+        n = len(piles)
+
+        def dfs(i, coins):
+            if i == n:
+                return 0
+
+            res = dfs(i + 1, coins)  # skip current pile
+            curPile = 0
+            for j in range(min(coins, len(piles[i]))):
+                curPile += piles[i][j]
+                res = max(res, curPile + dfs(i + 1, coins - (j + 1)))
+            return res
+
+        return dfs(0, k)
+```
+
+```java
+public class Solution {
+    public int maxValueOfCoins(List<List<Integer>> piles, int k) {
+        int n = piles.size();
+        return dfs(0, k, piles);
+    }
+
+    private int dfs(int i, int coins, List<List<Integer>> piles) {
+        if (i == piles.size()) {
+            return 0;
+        }
+
+        int res = dfs(i + 1, coins, piles);  // skip current pile
+        int curPile = 0;
+        for (int j = 0; j < Math.min(coins, piles.get(i).size()); j++) {
+            curPile += piles.get(i).get(j);
+            res = Math.max(res, curPile + dfs(i + 1, coins - (j + 1), piles));
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    int dfs(int i, int coins, const vector<vector<int>>& piles) {
+        if (i == piles.size()) {
+            return 0;
+        }
+
+        int res = dfs(i + 1, coins, piles);  // skip current pile
+        int curPile = 0;
+        for (int j = 0; j < min(coins, (int)piles[i].size()); j++) {
+            curPile += piles[i][j];
+            res = max(res, curPile + dfs(i + 1, coins - (j + 1), piles));
+        }
+        return res;
+    }
+
+public:
+    int maxValueOfCoins(vector<vector<int>>& piles, int k) {
+        int n = piles.size();
+        return dfs(0, k, piles);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} piles
+     * @param {number} k
+     * @return {number}
+     */
+    maxValueOfCoins = (piles, k) => {
+        const n = piles.length;
+
+        const dfs = (i, coins) => {
+            if (i === n) return 0;
+
+            let res = dfs(i + 1, coins); // skip current pile
+            let curPile = 0;
+            for (let j = 0; j < Math.min(coins, piles[i].length); j++) {
+                curPile += piles[i][j];
+                res = Math.max(res, curPile + dfs(i + 1, coins - (j + 1)));
+            }
+            return res;
+        };
+
+        return dfs(0, k);
+    };
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(k ^ n)$
+* Space complexity: $O(n)$ for the recursion stack.
+
+> Where $n$ is the number of piles and $k$ is the number of coins to choose.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxValueOfCoins(self, piles: List[List[int]], k: int) -> int:
+        n = len(piles)
+        dp = [[-1] * (k + 1) for _ in range(n)]
+
+        def dfs(i, coins):
+            if i == n:
+                return 0
+            if dp[i][coins] != -1:
+                return dp[i][coins]
+
+            dp[i][coins] = dfs(i + 1, coins)  # skip current pile
+            curPile = 0
+            for j in range(min(coins, len(piles[i]))):
+                curPile += piles[i][j]
+                dp[i][coins] = max(dp[i][coins], curPile + dfs(i + 1, coins - (j + 1)))
+            return dp[i][coins]
+
+        return dfs(0, k)
+```
+
+```java
+public class Solution {
+    private int[][] dp;
+
+    public int maxValueOfCoins(List<List<Integer>> piles, int k) {
+        int n = piles.size();
+        dp = new int[n][k + 1];
+        for (int[] row : dp) {
+            Arrays.fill(row, -1);
+        }
+        return dfs(0, k, piles);
+    }
+
+    private int dfs(int i, int coins, List<List<Integer>> piles) {
+        if (i == piles.size()) {
+            return 0;
+        }
+        if (dp[i][coins] != -1) {
+            return dp[i][coins];
+        }
+
+        dp[i][coins] = dfs(i + 1, coins, piles);  // skip current pile
+        int curPile = 0;
+        for (int j = 0; j < Math.min(coins, piles.get(i).size()); j++) {
+            curPile += piles.get(i).get(j);
+            dp[i][coins] = Math.max(dp[i][coins], curPile + dfs(i + 1, coins - (j + 1), piles));
+        }
+        return dp[i][coins];
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<vector<int>> dp;
+
+    int dfs(int i, int coins, const vector<vector<int>>& piles) {
+        if (i == piles.size()) {
+            return 0;
+        }
+        if (dp[i][coins] != -1) {
+            return dp[i][coins];
+        }
+
+        dp[i][coins] = dfs(i + 1, coins, piles);  // skip current pile
+        int curPile = 0;
+        for (int j = 0; j < min(coins, (int)piles[i].size()); j++) {
+            curPile += piles[i][j];
+            dp[i][coins] = max(dp[i][coins], curPile + dfs(i + 1, coins - (j + 1), piles));
+        }
+        return dp[i][coins];
+    }
+
+public:
+    int maxValueOfCoins(vector<vector<int>>& piles, int k) {
+        int n = piles.size();
+        dp = vector<vector<int>>(n, vector<int>(k + 1, -1));
+        return dfs(0, k, piles);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} piles
+     * @param {number} k
+     * @return {number}
+     */
+    maxValueOfCoins = (piles, k) => {
+        const n = piles.length;
+        const dp = Array.from({ length: n }, () => Array(k + 1).fill(-1));
+
+        const dfs = (i, coins) => {
+            if (i === n) return 0;
+            if (dp[i][coins] !== -1) return dp[i][coins];
+
+            dp[i][coins] = dfs(i + 1, coins); // skip current pile
+            let curPile = 0;
+            for (let j = 0; j < Math.min(coins, piles[i].length); j++) {
+                curPile += piles[i][j];
+                dp[i][coins] = Math.max(dp[i][coins], curPile + dfs(i + 1, coins - (j + 1)));
+            }
+            return dp[i][coins];
+        };
+
+        return dfs(0, k);
+    };
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * k)$
+* Space complexity: $O(n * k)$
+
+> Where $n$ is the number of piles, $k$ is the number of coins to choose, and $m$ is the total number of coins among all the piles.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxValueOfCoins(self, piles: List[List[int]], k: int) -> int:
+        n = len(piles)
+        dp = [[0] * (k + 1) for _ in range(n + 1)]
+        
+        for i in range(n - 1, -1, -1):
+            for coins in range(k + 1):
+                dp[i][coins] = dp[i + 1][coins]
+                
+                curPile = 0
+                for j in range(min(coins, len(piles[i]))):
+                    curPile += piles[i][j]
+                    dp[i][coins] = max(
+                        dp[i][coins],
+                        curPile + dp[i + 1][coins - (j + 1)]
+                    )
+        
+        return dp[0][k]
+```
+
+```java
+public class Solution {
+    public int maxValueOfCoins(List<List<Integer>> piles, int k) {
+        int n = piles.size();
+        int[][] dp = new int[n + 1][k + 1];
+
+        for (int i = n - 1; i >= 0; i--) {
+            for (int coins = 0; coins <= k; coins++) {
+                dp[i][coins] = dp[i + 1][coins];
+
+                int curPile = 0;
+                for (int j = 0; j < Math.min(coins, piles.get(i).size()); j++) {
+                    curPile += piles.get(i).get(j);
+                    dp[i][coins] = Math.max(
+                        dp[i][coins],
+                        curPile + dp[i + 1][coins - (j + 1)]
+                    );
+                }
+            }
+        }
+
+        return dp[0][k];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxValueOfCoins(vector<vector<int>>& piles, int k) {
+        int n = piles.size();
+        vector<vector<int>> dp(n + 1, vector<int>(k + 1, 0));
+
+        for (int i = n - 1; i >= 0; i--) {
+            for (int coins = 0; coins <= k; coins++) {
+                dp[i][coins] = dp[i + 1][coins];
+
+                int curPile = 0;
+                for (int j = 0; j < min(coins, (int)piles[i].size()); j++) {
+                    curPile += piles[i][j];
+                    dp[i][coins] = max(
+                        dp[i][coins],
+                        curPile + dp[i + 1][coins - (j + 1)]
+                    );
+                }
+            }
+        }
+
+        return dp[0][k];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} piles
+     * @param {number} k
+     * @return {number}
+     */
+    maxValueOfCoins = (piles, k) => {
+        const n = piles.length;
+        const dp = Array.from({ length: n + 1 }, () => Array(k + 1).fill(0));
+
+        for (let i = n - 1; i >= 0; i--) {
+            for (let coins = 0; coins <= k; coins++) {
+                dp[i][coins] = dp[i + 1][coins];
+
+                let curPile = 0;
+                for (let j = 0; j < Math.min(coins, piles[i].length); j++) {
+                    curPile += piles[i][j];
+                    dp[i][coins] = Math.max(
+                        dp[i][coins],
+                        curPile + dp[i + 1][coins - (j + 1)]
+                    );
+                }
+            }
+        }
+
+        return dp[0][k];
+    };
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * k)$
+* Space complexity: $O(n * k)$
+
+> Where $n$ is the number of piles, $k$ is the number of coins to choose, and $m$ is the total number of coins among all the piles.
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxValueOfCoins(self, piles: List[List[int]], k: int) -> int:
+        dp = [0] * (k + 1)
+
+        for pile in piles:
+            for coins in range(k, 0, -1):
+                curPile = 0
+                for j in range(min(coins, len(pile))):
+                    curPile += pile[j]
+                    dp[coins] = max(dp[coins], dp[coins - (j + 1)] + curPile)
+
+        return dp[k]
+```
+
+```java
+public class Solution {
+    public int maxValueOfCoins(List<List<Integer>> piles, int k) {
+        int[] dp = new int[k + 1];
+
+        for (List<Integer> pile : piles) {
+            for (int coins = k; coins >= 1; coins--) {
+                int curPile = 0;
+                for (int j = 0; j < Math.min(coins, pile.size()); j++) {
+                    curPile += pile.get(j);
+                    dp[coins] = Math.max(dp[coins], dp[coins - (j + 1)] + curPile);
+                }
+            }
+        }
+
+        return dp[k];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxValueOfCoins(vector<vector<int>>& piles, int k) {
+        vector<int> dp(k + 1, 0);
+
+        for (const auto& pile : piles) {
+            for (int coins = k; coins >= 1; coins--) {
+                int curPile = 0;
+                for (int j = 0; j < min(coins, (int)pile.size()); j++) {
+                    curPile += pile[j];
+                    dp[coins] = max(dp[coins], dp[coins - (j + 1)] + curPile);
+                }
+            }
+        }
+
+        return dp[k];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} piles
+     * @param {number} k
+     * @return {number}
+     */
+    maxValueOfCoins = (piles, k) => {
+        let dp = Array(k + 1).fill(0);
+
+        for (const pile of piles) {
+            for (let coins = k; coins >= 1; coins--) {
+                let curPile = 0;
+                for (let j = 0; j < Math.min(coins, pile.length); j++) {
+                    curPile += pile[j];
+                    dp[coins] = Math.max(dp[coins], dp[coins - (j + 1)] + curPile);
+                }
+            }
+        }
+
+        return dp[k];
+    };
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * k)$
+* Space complexity: $O(n * k)$
+
+> Where $n$ is the number of piles, $k$ is the number of coins to choose, and $m$ is the total number of coins among all the piles.
\ No newline at end of file
diff --git a/articles/maximum-width-of-binary-tree.md b/articles/maximum-width-of-binary-tree.md
new file mode 100644
index 000000000..ba741fb5d
--- /dev/null
+++ b/articles/maximum-width-of-binary-tree.md
@@ -0,0 +1,513 @@
+## 1. Breadth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def widthOfBinaryTree(self, root: Optional[TreeNode]) -> int:
+        res = 0
+        q = deque([(root, 1, 0)])  # [node, num, level]
+        prevLevel, prevNum = 0, 1
+
+        while q:
+            node, num, level = q.popleft()
+
+            if level > prevLevel:
+                prevLevel = level
+                prevNum = num
+
+            res = max(res, num - prevNum + 1)
+            if node.left:
+                q.append((node.left, 2 * num, level + 1))
+            if node.right:
+                q.append((node.right, 2 * num + 1, level + 1))
+
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public int widthOfBinaryTree(TreeNode root) {
+        if (root == null) return 0;
+
+        int res = 0;
+        Queue<Tuple> queue = new LinkedList<>();
+        queue.offer(new Tuple(root, 1, 0)); // [node, num, level]
+        int prevLevel = 0, prevNum = 1;
+
+        while (!queue.isEmpty()) {
+            Tuple current = queue.poll();
+            TreeNode node = current.node;
+            int num = current.num;
+            int level = current.level;
+
+            if (level > prevLevel) {
+                prevLevel = level;
+                prevNum = num;
+            }
+
+            res = Math.max(res, num - prevNum + 1);
+            if (node.left != null) {
+                queue.offer(new Tuple(node.left, 2 * num, level + 1));
+            }
+            if (node.right != null) {
+                queue.offer(new Tuple(node.right, 2 * num + 1, level + 1));
+            }
+        }
+
+        return res;
+    }
+
+    class Tuple {
+        TreeNode node;
+        int num, level;
+
+        Tuple(TreeNode node, int num, int level) {
+            this.node = node;
+            this.num = num;
+            this.level = level;
+        }
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int widthOfBinaryTree(TreeNode* root) {
+        if (!root) return 0;
+
+        int res = 0;
+        queue<tuple<TreeNode*, uint, int>> q; // [node, num, level]
+        q.push({root, 1, 0});
+        int prevLevel = 0, prevNum = 1;
+
+        while (!q.empty()) {
+            auto [node, num, level] = q.front();
+            q.pop();
+
+            if (level > prevLevel) {
+                prevLevel = level;
+                prevNum = num;
+            }
+
+            res = max(res, int(num - prevNum) + 1);
+            if (node->left) {
+                q.push({node->left, 2 * num, level + 1});
+            }
+            if (node->right) {
+                q.push({node->right, 2 * num + 1, level + 1});
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number}
+     */
+    widthOfBinaryTree(root) {
+        if (!root) return 0;
+
+        let res = 0n;
+        const queue = new Queue([[root, 1n, 0]]); // [node, num, level]
+        let prevLevel = 0, prevNum = 1n;
+
+        while (!queue.isEmpty()) {
+            const [node, num, level] = queue.pop();
+
+            if (level > prevLevel) {
+                prevLevel = level;
+                prevNum = num;
+            }
+
+            res = res > (num - prevNum + 1n) ? res : (num - prevNum + 1n);
+            if (node.left) {
+                queue.push([node.left, 2n * num, level + 1]);
+            }
+            if (node.right) {
+                queue.push([node.right, 2n * num + 1n, level + 1]);
+            }
+        }
+
+        return Number(res);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Breadth First Search (Optimal)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def widthOfBinaryTree(self, root: Optional[TreeNode]) -> int:
+        res = 0
+        q = deque([(root, 0)])
+
+        while q:
+            start = q[0][1]
+            for _ in range(len(q)):
+                node, num = q.popleft()
+                curNum = num - start
+                res = max(res, curNum + 1)
+                if node.left:
+                    q.append((node.left, 2 * curNum))
+                if node.right:
+                    q.append((node.right, 2 * curNum + 1))
+
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public int widthOfBinaryTree(TreeNode root) {
+        int res = 0;
+        Queue<Pair<TreeNode, Integer>> q = new LinkedList<>();
+        q.offer(new Pair<>(root, 0));
+
+        while (!q.isEmpty()) {
+            int start = q.peek().getValue();
+            for (int i = q.size(); i > 0; i--) {
+                Pair<TreeNode, Integer> pair = q.poll();
+                TreeNode node = pair.getKey();
+                int num = pair.getValue() - start;
+
+                res = Math.max(res, num + 1);
+                if (node.left != null) {
+                    q.offer(new Pair<>(node.left, 2 * num));
+                }
+                if (node.right != null) {
+                    q.offer(new Pair<>(node.right, 2 * num + 1));
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int widthOfBinaryTree(TreeNode* root) {
+        int res = 0;
+        queue<pair<TreeNode*, uint>> q;
+        q.push({root, 0});
+
+        while (!q.empty()) {
+            int start = q.front().second;
+
+            for (int i = q.size(); i > 0; --i) {
+                auto [node, num] = q.front();
+                q.pop();
+                uint curNum = num - start;
+                res = max(res, int(curNum) + 1);
+                if (node->left) {
+                    q.push({node->left, 2 * curNum});
+                }
+                if (node->right) {
+                    q.push({node->right, 2 * curNum + 1});
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number}
+     */
+    widthOfBinaryTree(root) {
+        let res = 0;
+        const q = new Queue([[root, 0]]);
+
+        while (!q.isEmpty()) {
+            const start = q.front()[1];
+
+            for (let i = q.size(); i > 0; i--) {
+                const [node, num] = q.pop();
+                const curNum = num - start;
+                res = Math.max(res, curNum + 1);
+                if (node.left) {
+                    q.push([node.left, 2 * curNum]);
+                }
+                if (node.right) {
+                    q.push([node.right, 2 * curNum + 1]);
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Depth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def widthOfBinaryTree(self, root: Optional[TreeNode]) -> int:
+        first = {}
+        res = 0
+
+        def dfs(node, level, num):
+            nonlocal res
+            if not node:
+                return
+            
+            if level not in first:
+                first[level] = num
+            
+            res = max(res, num - first[level] + 1)
+            dfs(node.left, level + 1, 2 * num)
+            dfs(node.right, level + 1, 2 * num + 1)
+
+        dfs(root, 0, 0)
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    private Map<Integer, Integer> first;
+    public int widthOfBinaryTree(TreeNode root) {
+        first = new HashMap<>();
+        int[] res = new int[1];
+        
+        dfs(root, 0, 0, res);
+        return res[0];
+    }
+
+    private void dfs(TreeNode node, int level, int num, int[] res) {
+        if (node == null) {
+            return;
+        }
+        
+        first.putIfAbsent(level, num);
+        res[0] = Math.max(res[0], num - first.get(level) + 1);
+        dfs(node.left, level + 1, 2 * num, res);
+        dfs(node.right, level + 1, 2 * num + 1, res);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+    unordered_map<int, unsigned long long> first;
+
+public:
+    int widthOfBinaryTree(TreeNode* root) {
+        unsigned long long res = 0;
+        
+        dfs(root, 0, 0, res);
+        return int(res);
+    }
+
+private:
+    void dfs(TreeNode* node, int level, unsigned long long num, unsigned long long& res) {
+        if (!node) {
+            return;
+        }
+        
+        if (!first.count(level)) {
+            first[level] = num;
+        }
+        
+        res = max(res, num - first[level] + 1);
+        dfs(node->left, level + 1, 2 * (num - first[level]), res);
+        dfs(node->right, level + 1, 2 * (num - first[level]) + 1, res);
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number}
+     */
+    widthOfBinaryTree(root) {
+        const first = new Map();
+        let res = 0;
+
+        const dfs = (node, level, curNum) => {
+            if (!node) return;
+
+            if (!first.has(level)) {
+                first.set(level, curNum);
+            }
+
+            res = Math.max(res, curNum - first.get(level) + 1);
+            dfs(node.left, level + 1, 2 * (curNum - first.get(level)));
+            dfs(node.right, level + 1, 2 * (curNum - first.get(level)) + 1);
+        };
+
+        dfs(root, 0, 0);
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/median-of-two-sorted-arrays.md b/articles/median-of-two-sorted-arrays.md
index d9f6e7d20..3ac051111 100644
--- a/articles/median-of-two-sorted-arrays.md
+++ b/articles/median-of-two-sorted-arrays.md
@@ -100,6 +100,49 @@ public class Solution {
 }
 ```
 
+```go
+func findMedianSortedArrays(nums1 []int, nums2 []int) float64 {
+    merged := append(nums1, nums2...)
+    sort.Ints(merged)
+
+    totalLen := len(merged)
+    if totalLen%2 == 0 {
+        return float64(merged[totalLen/2-1]+merged[totalLen/2]) / 2.0
+    }
+    return float64(merged[totalLen/2])
+}
+```
+
+```kotlin
+class Solution {
+    fun findMedianSortedArrays(nums1: IntArray, nums2: IntArray): Double {
+        val merged = (nums1 + nums2).sorted()
+        val totalLen = merged.size
+        return if (totalLen % 2 == 0) {
+            (merged[totalLen / 2 - 1] + merged[totalLen / 2]) / 2.0
+        } else {
+            merged[totalLen / 2].toDouble()
+        }
+    }
+}
+```
+
+```swift
+class Solution {
+    func findMedianSortedArrays(_ nums1: [Int], _ nums2: [Int]) -> Double {
+        var merged = nums1 + nums2
+        merged.sort()
+        
+        let totalLen = merged.count
+        if totalLen % 2 == 0 {
+            return (Double(merged[totalLen / 2 - 1]) + Double(merged[totalLen / 2])) / 2.0
+        } else {
+            return Double(merged[totalLen / 2])
+        }
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -290,6 +333,115 @@ public class Solution {
 }
 ```
 
+```go
+func findMedianSortedArrays(nums1 []int, nums2 []int) float64 {
+    len1, len2 := len(nums1), len(nums2)
+    i, j := 0, 0
+    median1, median2 := 0, 0
+
+    for count := 0; count < (len1+len2)/2+1; count++ {
+        median2 = median1
+        if i < len1 && j < len2 {
+            if nums1[i] > nums2[j] {
+                median1 = nums2[j]
+                j++
+            } else {
+                median1 = nums1[i]
+                i++
+            }
+        } else if i < len1 {
+            median1 = nums1[i]
+            i++
+        } else {
+            median1 = nums2[j]
+            j++
+        }
+    }
+
+    if (len1+len2)%2 == 1 {
+        return float64(median1)
+    }
+    return float64(median1+median2) / 2.0
+}
+```
+
+```kotlin
+class Solution {
+    fun findMedianSortedArrays(nums1: IntArray, nums2: IntArray): Double {
+        val len1 = nums1.size
+        val len2 = nums2.size
+        var i = 0
+        var j = 0
+        var median1 = 0
+        var median2 = 0
+
+        for (count in 0 until (len1 + len2) / 2 + 1) {
+            median2 = median1
+            when {
+                i < len1 && j < len2 -> {
+                    if (nums1[i] > nums2[j]) {
+                        median1 = nums2[j]
+                        j++
+                    } else {
+                        median1 = nums1[i]
+                        i++
+                    }
+                }
+                i < len1 -> {
+                    median1 = nums1[i]
+                    i++
+                }
+                else -> {
+                    median1 = nums2[j]
+                    j++
+                }
+            }
+        }
+
+        return if ((len1 + len2) % 2 == 1) {
+            median1.toDouble()
+        } else {
+            (median1 + median2) / 2.0
+        }
+    }
+}
+```
+
+```kotlin
+class Solution {
+    func findMedianSortedArrays(_ nums1: [Int], _ nums2: [Int]) -> Double {
+        let len1 = nums1.count, len2 = nums2.count
+        var i = 0, j = 0
+        var median1 = 0, median2 = 0
+
+        for _ in 0..<(len1 + len2) / 2 + 1 {
+            median2 = median1
+            if i < len1 && j < len2 {
+                if nums1[i] > nums2[j] {
+                    median1 = nums2[j]
+                    j += 1
+                } else {
+                    median1 = nums1[i]
+                    i += 1
+                }
+            } else if i < len1 {
+                median1 = nums1[i]
+                i += 1
+            } else {
+                median1 = nums2[j]
+                j += 1
+            }
+        }
+
+        if (len1 + len2) % 2 == 1 {
+            return Double(median1)
+        } else {
+            return (Double(median1) + Double(median2)) / 2.0
+        }
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -481,12 +633,115 @@ public class Solution {
 }
 ```
 
+```go
+func getKth(a []int, m int, b []int, n int, k int, aStart int, bStart int) int {
+    if m > n {
+        return getKth(b, n, a, m, k, bStart, aStart)
+    }
+    if m == 0 {
+        return b[bStart+k-1]
+    }
+    if k == 1 {
+        if a[aStart] < b[bStart] {
+            return a[aStart]
+        }
+        return b[bStart]
+    }
+    
+    i := min(m, k/2)
+    j := min(n, k/2)
+    
+    if a[aStart+i-1] > b[bStart+j-1] {
+        return getKth(a, m, b[bStart+j:], n-j, k-j, aStart, 0)
+    }
+    return getKth(a[aStart+i:], m-i, b, n, k-i, 0, bStart)
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+
+func findMedianSortedArrays(nums1 []int, nums2 []int) float64 {
+    left := (len(nums1) + len(nums2) + 1) / 2
+    right := (len(nums1) + len(nums2) + 2) / 2
+    return float64(getKth(nums1, len(nums1), nums2, len(nums2), left, 0, 0) +
+           getKth(nums1, len(nums1), nums2, len(nums2), right, 0, 0)) / 2.0
+}
+```
+
+```kotlin
+class Solution {
+    private fun getKth(a: IntArray, m: Int, b: IntArray, n: Int, k: Int, aStart: Int = 0, bStart: Int = 0): Int {
+        if (m > n) {
+            return getKth(b, n, a, m, k, bStart, aStart)
+        }
+        if (m == 0) {
+            return b[bStart + k - 1]
+        }
+        if (k == 1) {
+            return minOf(a[aStart], b[bStart])
+        }
+        
+        val i = minOf(m, k / 2)
+        val j = minOf(n, k / 2)
+        
+        return if (a[aStart + i - 1] > b[bStart + j - 1]) {
+            getKth(a, m, b, n - j, k - j, aStart, bStart + j)
+        } else {
+            getKth(a, m - i, b, n, k - i, aStart + i, bStart)
+        }
+    }
+    
+    fun findMedianSortedArrays(nums1: IntArray, nums2: IntArray): Double {
+        val left = (nums1.size + nums2.size + 1) / 2
+        val right = (nums1.size + nums2.size + 2) / 2
+        return (getKth(nums1, nums1.size, nums2, nums2.size, left) +
+                getKth(nums1, nums1.size, nums2, nums2.size, right)) / 2.0
+    }
+}
+```
+
+```swift
+class Solution {
+    func getKth(_ a: [Int], _ m: Int, _ b: [Int], _ n: Int, _ k: Int, _ aStart: Int = 0, _ bStart: Int = 0) -> Int {
+        if m > n {
+            return getKth(b, n, a, m, k, bStart, aStart)
+        }
+        if m == 0 {
+            return b[bStart + k - 1]
+        }
+        if k == 1 {
+            return min(a[aStart], b[bStart])
+        }
+        
+        let i = min(m, k / 2)
+        let j = min(n, k / 2)
+        
+        if a[aStart + i - 1] > b[bStart + j - 1] {
+            return getKth(a, m, b, n - j, k - j, aStart, bStart + j)
+        } else {
+            return getKth(a, m - i, b, n, k - i, aStart + i, bStart)
+        }
+    }
+    
+    func findMedianSortedArrays(_ nums1: [Int], _ nums2: [Int]) -> Double {
+        let left = (nums1.count + nums2.count + 1) / 2
+        let right = (nums1.count + nums2.count + 2) / 2
+        return (Double(getKth(nums1, nums1.count, nums2, nums2.count, left)) +
+                Double(getKth(nums1, nums1.count, nums2, nums2.count, right))) / 2.0
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(\log (m + n))$
-* Space complexity: $O(\log (m + n))$
+* Space complexity: $O(\log (m + n))$ for recursion stack.
 
 > Where $n$ is the length of $nums1$ and $m$ is the length of $nums2$.
 
@@ -694,6 +949,147 @@ public class Solution {
 }
 ```
 
+```go
+func findMedianSortedArrays(nums1 []int, nums2 []int) float64 {
+    A, B := nums1, nums2
+    total := len(A) + len(B)
+    half := (total + 1) / 2
+
+    if len(B) < len(A) {
+        A, B = B, A
+    }
+
+    l, r := 0, len(A)
+    for l <= r {
+        i := (l + r) / 2
+        j := half - i
+
+        Aleft := math.MinInt64
+        if i > 0 {
+            Aleft = A[i-1]
+        }
+        Aright := math.MaxInt64
+        if i < len(A) {
+            Aright = A[i]
+        }
+        Bleft := math.MinInt64
+        if j > 0 {
+            Bleft = B[j-1]
+        }
+        Bright := math.MaxInt64
+        if j < len(B) {
+            Bright = B[j]
+        }
+
+        if Aleft <= Bright && Bleft <= Aright {
+            if total%2 != 0 {
+                return float64(max(Aleft, Bleft))
+            }
+            return (float64(max(Aleft, Bleft)) + float64(min(Aright, Bright))) / 2.0
+        } else if Aleft > Bright {
+            r = i - 1
+        } else {
+            l = i + 1
+        }
+    }
+    return -1
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun findMedianSortedArrays(nums1: IntArray, nums2: IntArray): Double {
+        var A = nums1
+        var B = nums2
+        val total = A.size + B.size
+        val half = (total + 1) / 2
+
+        if (B.size < A.size) {
+            A = nums2
+            B = nums1
+        }
+
+        var l = 0
+        var r = A.size
+        while (l <= r) {
+            val i = (l + r) / 2
+            val j = half - i
+
+            val Aleft = if (i > 0) A[i - 1] else Int.MIN_VALUE
+            val Aright = if (i < A.size) A[i] else Int.MAX_VALUE
+            val Bleft = if (j > 0) B[j - 1] else Int.MIN_VALUE
+            val Bright = if (j < B.size) B[j] else Int.MAX_VALUE
+
+            if (Aleft <= Bright && Bleft <= Aright) {
+                return if (total % 2 != 0) {
+                    Math.max(Aleft.toDouble(), Bleft.toDouble())
+                } else {
+                    (Math.max(Aleft.toDouble(), Bleft.toDouble()) + 
+                     Math.min(Aright.toDouble(), Bright.toDouble())) / 2.0
+                }
+            } else if (Aleft > Bright) {
+                r = i - 1
+            } else {
+                l = i + 1
+            }
+        }
+        return -1.0
+    }
+}
+```
+
+```swift
+class Solution {
+    func findMedianSortedArrays(_ nums1: [Int], _ nums2: [Int]) -> Double {
+        var A = nums1, B = nums2
+        if A.count > B.count {
+            swap(&A, &B)
+        }
+
+        let total = A.count + B.count
+        let half = total / 2
+        var l = 0
+        var r = A.count
+
+        while true {
+            let i = (l + r) / 2
+            let j = half - i
+
+            let Aleft = i > 0 ? Double(A[i - 1]) : -Double.infinity
+            let Aright = i < A.count ? Double(A[i]) : Double.infinity
+            let Bleft = j > 0 ? Double(B[j - 1]) : -Double.infinity
+            let Bright = j < B.count ? Double(B[j]) : Double.infinity
+
+            if Aleft <= Bright && Bleft <= Aright {
+                if total % 2 == 1 {
+                    return min(Aright, Bright)
+                } else {
+                    return (max(Aleft, Bleft) + min(Aright, Bright)) / 2.0
+                }
+            } else if Aleft > Bright {
+                r = i - 1
+            } else {
+                l = i + 1
+            }
+        }
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/meeting-rooms-iii.md b/articles/meeting-rooms-iii.md
new file mode 100644
index 000000000..d8d33bcdb
--- /dev/null
+++ b/articles/meeting-rooms-iii.md
@@ -0,0 +1,466 @@
+## 1. Sorting + Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def mostBooked(self, n: int, meetings: List[List[int]]) -> int:
+        meetings.sort()
+        rooms = [0] * n # end time of meetings in rooms
+        meeting_count = [0] * n
+
+        for s, e in meetings:
+            min_room = 0
+            found = False
+            for i in range(n):
+                if rooms[i] <= s:
+                    found = True
+                    meeting_count[i] += 1
+                    rooms[i] = e
+                    break
+                
+                if rooms[min_room] > rooms[i]:
+                    min_room = i
+            if found:
+                continue
+            meeting_count[min_room] += 1
+            rooms[min_room] += e - s
+        
+        return meeting_count.index(max(meeting_count))
+```
+
+```java
+public class Solution {
+    public int mostBooked(int n, int[][] meetings) {
+        Arrays.sort(meetings, (a, b) -> Integer.compare(a[0], b[0]));
+        long[] rooms = new long[n]; // end times of meetings in rooms
+        int[] meetingCount = new int[n];
+
+        for (int[] meeting : meetings) {
+            int start = meeting[0], end = meeting[1];
+            int minRoom = 0;
+            boolean found = false;
+
+            for (int i = 0; i < n; i++) {
+                if (rooms[i] <= start) {
+                    meetingCount[i]++;
+                    rooms[i] = end;
+                    found = true;
+                    break;
+                }
+                if (rooms[minRoom] > rooms[i]) {
+                    minRoom = i;
+                }
+            }
+            if (found) continue;
+
+            meetingCount[minRoom]++;
+            rooms[minRoom] += end - start;
+        }
+
+        int maxIndex = 0;
+        for (int i = 1; i < n; i++) {
+            if (meetingCount[i] > meetingCount[maxIndex]) {
+                maxIndex = i;
+            }
+        }
+        return maxIndex;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int mostBooked(int n, vector<vector<int>>& meetings) {
+        sort(meetings.begin(), meetings.end());
+        vector<long> rooms(n, 0); // end times of meetings in rooms
+        vector<int> meetingCount(n, 0);
+
+        for (const auto& meeting : meetings) {
+            int start = meeting[0], end = meeting[1];
+            int minRoom = 0;
+            bool found = false;
+
+            for (int i = 0; i < n; i++) {
+                if (rooms[i] <= start) {
+                    meetingCount[i]++;
+                    rooms[i] = end;
+                    found = true;
+                    break;
+                }
+                if (rooms[minRoom] > rooms[i]) {
+                    minRoom = i;
+                }
+            }
+
+            if (found) continue;
+            meetingCount[minRoom]++;
+            rooms[minRoom] += end - start;
+        }
+
+        int maxIndex = 0;
+        for (int i = 1; i < n; i++) {
+            if (meetingCount[i] > meetingCount[maxIndex]) {
+                maxIndex = i;
+            }
+        }
+        return maxIndex;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} meetings
+     * @return {number}
+     */
+    mostBooked(n, meetings) {
+        meetings.sort((a, b) => a[0] - b[0]);
+        const rooms = new Array(n).fill(0); // end times of meetings in rooms
+        const meetingCount = new Array(n).fill(0);
+
+        for (const [start, end] of meetings) {
+            let minRoom = 0;
+            let found = false;
+
+            for (let i = 0; i < n; i++) {
+                if (rooms[i] <= start) {
+                    meetingCount[i]++;
+                    rooms[i] = end;
+                    found = true;
+                    break;
+                }
+                if (rooms[minRoom] > rooms[i]) {
+                    minRoom = i;
+                }
+            }
+
+            if (found) continue;
+            meetingCount[minRoom]++;
+            rooms[minRoom] += end - start;
+        }
+
+        return meetingCount.indexOf(Math.max(...meetingCount));
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m\log m + n * m)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the number of rooms and $m$ is the number of meetings.
+
+---
+
+## 2. Two Min-Heaps
+
+::tabs-start
+
+```python
+class Solution:
+    def mostBooked(self, n: int, meetings: List[List[int]]) -> int:
+        meetings.sort()
+        available = [i for i in range(n)]  # Min heap for available rooms
+        used = []  # Min heap for used rooms [(end_time, room_number)]
+        count = [0] * n  # Count of meetings for each room
+
+        for start, end in meetings:
+            while used and used[0][0] <= start:
+                _, room = heapq.heappop(used)
+                heapq.heappush(available, room)
+
+            if not available:
+                end_time, room = heapq.heappop(used)
+                end = end_time + (end - start)
+                heapq.heappush(available, room)
+            
+            room = heapq.heappop(available)
+            heapq.heappush(used, (end, room))
+            count[room] += 1
+
+        return count.index(max(count))
+```
+
+```java
+public class Solution {
+    public int mostBooked(int n, int[][] meetings) {
+        Arrays.sort(meetings, (a, b) -> Long.compare(a[0], b[0]));        
+        PriorityQueue<Integer> available = new PriorityQueue<>();        
+        PriorityQueue<long[]> used = new PriorityQueue<>((a, b) -> 
+            a[0] == b[0] ? Long.compare(a[1], b[1]) : Long.compare(a[0], b[0])
+        );        
+        for (int i = 0; i < n; i++) {
+            available.offer(i);
+        }        
+        int[] count = new int[n];
+
+        for (int[] meeting : meetings) {
+            long start = meeting[0];
+            long end = meeting[1];
+            while (!used.isEmpty() && used.peek()[0] <= start) {
+                int room = (int) used.poll()[1];
+                available.offer(room);
+            }
+            if (available.isEmpty()) {
+                long[] current = used.poll();
+                int room = (int) current[1];
+                end = current[0] + (end - start);
+                available.offer(room);
+            }
+
+            int room = available.poll();
+            used.offer(new long[]{end, room});
+            count[room]++;
+        }
+
+        int maxRoom = 0;
+        for (int i = 1; i < n; i++) {
+            if (count[i] > count[maxRoom]) {
+                maxRoom = i;
+            }
+        }
+        return maxRoom;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int mostBooked(int n, vector<vector<int>>& meetings) {
+        sort(meetings.begin(), meetings.end(), [](const vector<int>& a, const vector<int>& b) {
+            return (long long)a[0] < (long long)b[0];
+        });
+        priority_queue<int, vector<int>, greater<int>> available;
+        priority_queue<pair<long long, int>, vector<pair<long long, int>>, greater<pair<long long, int>>> used;
+        for (int i = 0; i < n; i++) {
+            available.push(i);
+        }
+        vector<int> count(n);
+
+        for (const auto& meeting : meetings) {
+            long long start = meeting[0];
+            long long end = meeting[1];
+            while (!used.empty() && used.top().first <= start) {
+                int room = used.top().second;
+                used.pop();
+                available.push(room);
+            }
+            if (available.empty()) {
+                auto current = used.top();
+                used.pop();
+                end = current.first + (end - start);
+                available.push(current.second);
+            }
+
+            int room = available.top();
+            available.pop();
+            used.push({end, room});
+            count[room]++;
+        }
+
+        int maxRoom = 0;
+        for (int i = 1; i < n; i++) {
+            if (count[i] > count[maxRoom]) {
+                maxRoom = i;
+            }
+        }
+        return maxRoom;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} meetings
+     * @return {number}
+     */
+    mostBooked(n, meetings) {
+        meetings.sort((a, b) => a[0] - b[0]);
+        const available = new MinPriorityQueue({ compare: (a, b) => a - b });
+        const used = new MinPriorityQueue({
+            compare: (a, b) => (a[0] === b[0] ? a[1] - b[1] : a[0] - b[0]),
+        });
+        for (let i = 0; i < n; i++) {
+            available.enqueue(i);
+        }
+        const count = new Array(n).fill(0);
+
+        for (const [start, end] of meetings) {
+            while (!used.isEmpty() && used.front()[0] <= start) {
+                const room = used.dequeue()[1];
+                available.enqueue(room);
+            }
+
+            let room;
+            let newEnd = end;
+            if (available.isEmpty()) {
+                const [endTime, usedRoom] = used.dequeue();
+                newEnd = endTime + (end - start);
+                available.enqueue(usedRoom);
+            }
+            room = available.dequeue();
+            used.enqueue([newEnd, room]);
+            count[room]++;
+        }
+
+        return count.indexOf(Math.max(...count));
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m\log m + m \log n)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the number of rooms and $m$ is the number of meetings.
+
+---
+
+## 3. One Min-Heap
+
+::tabs-start
+
+```python
+class Solution:
+    def mostBooked(self, n: int, meetings: List[List[int]]) -> int:
+        meetings.sort()
+        available = []
+        count = [0] * n
+
+        for i in range(n):
+            heapq.heappush(available, (0, i))
+
+        for start, end in meetings:
+            while available and available[0][0] < start:
+                end_time, room = heapq.heappop(available)
+                heapq.heappush(available, (start, room))
+            
+            end_time, room = heapq.heappop(available)
+            heapq.heappush(available, (end_time + (end - start), room))
+            count[room] += 1
+
+        return count.index(max(count))
+```
+
+```java
+public class Solution {
+    public int mostBooked(int n, int[][] meetings) {
+        Arrays.sort(meetings, (a, b) -> Integer.compare(a[0], b[0]));
+        PriorityQueue<long[]> available = new PriorityQueue<>((a, b) -> 
+            a[0] == b[0] ? Long.compare(a[1], b[1]) : Long.compare(a[0], b[0])
+        );
+        for (int i = 0; i < n; i++) {
+            available.offer(new long[]{0, i});
+        }
+        int[] count = new int[n];
+
+        for (int[] meeting : meetings) {
+            int start = meeting[0], end = meeting[1];
+            while (!available.isEmpty() && available.peek()[0] < start) {
+                long[] earliest = available.poll();
+                available.offer(new long[]{start, earliest[1]});
+            }
+
+            long[] room = available.poll();
+            long endTime = room[0] + (end - start);
+            available.offer(new long[]{endTime, room[1]});
+            count[(int) room[1]]++;
+        }
+
+        int maxRoom = 0;
+        for (int i = 1; i < n; i++) {
+            if (count[i] > count[maxRoom]) {
+                maxRoom = i;
+            }
+        }
+        return maxRoom;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int mostBooked(int n, vector<vector<int>>& meetings) {
+        sort(meetings.begin(), meetings.end());
+        priority_queue<pair<long long, int>, vector<pair<long long, int>>, greater<pair<long long, int>>> available;
+        for (int i = 0; i < n; i++) {
+            available.push({0, i});
+        }
+        vector<int> count(n);
+
+        for (const auto& meeting : meetings) {
+            int start = meeting[0], end = meeting[1];
+            while (!available.empty() && available.top().first < start) {
+                auto [end_time, room] = available.top();
+                available.pop();
+                available.push({start, room});
+            }
+
+            auto [end_time, room] = available.top();
+            available.pop();
+            available.push({end_time + (end - start), room});
+            count[room]++;
+        }
+
+        return max_element(count.begin(), count.end()) - count.begin();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} meetings
+     * @return {number}
+     */
+    mostBooked(n, meetings) {
+        meetings.sort((a, b) => a[0] - b[0]);
+        const available = new MinPriorityQueue({ 
+            compare: (a, b) => (a[0] === b[0] ? a[1] - b[1] : a[0] - b[0]) 
+        });
+        for (let i = 0; i < n; i++) {
+            available.enqueue([0, i]);
+        }
+        const count = new Array(n).fill(0);
+
+        for (const [start, end] of meetings) {
+            while (!available.isEmpty() && available.front()[0] < start) {
+                const [endTime, room] = available.dequeue();
+                available.enqueue([start, room]);
+            }
+
+            const [endTime, room] = available.dequeue();
+            available.enqueue([endTime + (end - start), room]);
+            count[room]++;
+        }
+
+        return count.indexOf(Math.max(...count));
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(m \log m + m \log n)$ time in average case.
+    * $O(m \log m + m * n)$ time in worst case.
+* Space complexity: $O(n)$
+
+> Where $n$ is the number of rooms and $m$ is the number of meetings.
\ No newline at end of file
diff --git a/articles/meeting-schedule-ii.md b/articles/meeting-schedule-ii.md
new file mode 100644
index 000000000..afd50a48e
--- /dev/null
+++ b/articles/meeting-schedule-ii.md
@@ -0,0 +1,1071 @@
+## 1. Min Heap
+
+::tabs-start
+
+```python
+"""
+Definition of Interval:
+class Interval(object):
+    def __init__(self, start, end):
+        self.start = start
+        self.end = end
+"""
+
+class Solution:
+    def minMeetingRooms(self, intervals: List[Interval]) -> int:
+        intervals.sort(key=lambda x: x.start)
+        min_heap = []
+
+        for interval in intervals:
+            if min_heap and min_heap[0] <= interval.start:
+                heapq.heappop(min_heap)
+            heapq.heappush(min_heap, interval.end)
+
+        return len(min_heap)
+```
+
+```java
+/**
+ * Definition of Interval:
+ * public class Interval {
+ *     public int start, end;
+ *     public Interval(int start, int end) {
+ *         this.start = start;
+ *         this.end = end;
+ *     }
+ * }
+ */
+
+public class Solution {
+    public int minMeetingRooms(List<Interval> intervals) {
+        intervals.sort((a, b) -> a.start - b.start);
+        PriorityQueue<Integer> minHeap = new PriorityQueue<>();
+        for (Interval interval : intervals) {
+            if (!minHeap.isEmpty() && minHeap.peek() <= interval.start) {
+                minHeap.poll();
+            }
+            minHeap.offer(interval.end);
+        }
+        return minHeap.size();
+    }
+}
+```
+
+```cpp
+/**
+ * Definition of Interval:
+ * class Interval {
+ * public:
+ *     int start, end;
+ *     Interval(int start, int end) {
+ *         this->start = start;
+ *         this->end = end;
+ *     }
+ * }
+ */
+
+class Solution {
+public:
+    int minMeetingRooms(vector<Interval>& intervals) {
+        sort(intervals.begin(), intervals.end(), [](auto& a, auto& b) {
+            return a.start < b.start;
+        });
+        priority_queue<int, vector<int>, greater<int>> minHeap;
+        for (const auto& interval : intervals) {
+            if (!minHeap.empty() && minHeap.top() <= interval.start) {
+                minHeap.pop();
+            }
+            minHeap.push(interval.end);
+        }
+        return minHeap.size();
+    }
+};
+```
+
+```javascript
+/**
+ * Definition of Interval:
+ * class Interval {
+ *   constructor(start, end) {
+ *     this.start = start;
+ *     this.end = end;
+ *   }
+ * }
+ */
+
+class Solution {
+    /**
+     * @param {Interval[]} intervals
+     * @returns {number}
+     */
+    minMeetingRooms(intervals) {
+        intervals.sort((a, b) => a.start - b.start);
+        const minHeap = new MinPriorityQueue();
+        for (const interval of intervals) {
+            if (!minHeap.isEmpty() && minHeap.front() <= interval.start) {
+                minHeap.pop();
+            }
+            minHeap.push(interval.end);
+        }
+        return minHeap.size();
+    }
+}
+```
+
+```csharp
+/**
+ * Definition of Interval:
+ * public class Interval {
+ *     public int start, end;
+ *     public Interval(int start, int end) {
+ *         this.start = start;
+ *         this.end = end;
+ *     }
+ * }
+ */
+
+public class Solution {
+    public int MinMeetingRooms(List<Interval> intervals) {
+        intervals.Sort((a, b) => a.start.CompareTo(b.start));
+        var minHeap = new PriorityQueue<int, int>();
+        
+        foreach (var interval in intervals) {
+            if (minHeap.Count > 0 && minHeap.Peek() <= interval.start) {
+                minHeap.Dequeue();
+            }
+            minHeap.Enqueue(interval.end, interval.end);
+        }
+        
+        return minHeap.Count;
+    }
+}
+```
+
+```go
+/**
+ * Definition of Interval:
+ * type Interval struct {
+ *    start int
+ *    end   int
+ * }
+ */
+
+func minMeetingRooms(intervals []Interval) int {
+    sort.Slice(intervals, func(i, j int) bool {
+        return intervals[i].start < intervals[j].start
+    })
+
+    pq := priorityqueue.NewWith(utils.IntComparator)
+
+    for _, interval := range intervals {
+        if pq.Size() > 0 {
+            if top, _ := pq.Peek(); top.(int) <= interval.start {
+                pq.Dequeue()
+            }
+        }
+        pq.Enqueue(interval.end)
+    }
+
+    return pq.Size()
+}
+```
+
+```kotlin
+/**
+ * Definition of Interval:
+ * class Interval(var start: Int, var end: Int) {}
+ */
+
+class Solution {
+    fun minMeetingRooms(intervals: List<Interval>): Int {
+        intervals.sortBy { it.start }
+
+        val minHeap = PriorityQueue<Int>()
+        for (interval in intervals) {
+            if (minHeap.isNotEmpty() && minHeap.peek() <= interval.start) {
+                minHeap.poll()
+            }
+            minHeap.add(interval.end)
+        }
+
+        return minHeap.size
+    }
+}
+```
+
+```swift
+/**
+ * Definition of Interval:
+ * class Interval {
+ *     var start: Int
+ *     var end: Int
+ *     init(start: Int, end: Int) {
+ *         self.start = start
+ *         self.end = end
+ *     }
+ * }
+ */
+
+class Solution {
+    func minMeetingRooms(_ intervals: [Interval]) -> Int {
+        let sortedIntervals = intervals.sorted { $0.start < $1.start }
+        var minHeap = Heap<Int>()
+        for interval in sortedIntervals {
+            if !minHeap.isEmpty, let earliest = minHeap.min!, earliest <= interval.start {
+                minHeap.removeMin()
+            }
+            minHeap.insert(interval.end)
+        }
+        return minHeap.count
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Sweep Line Algorithm
+
+::tabs-start
+
+```python
+"""
+Definition of Interval:
+class Interval(object):
+    def __init__(self, start, end):
+        self.start = start
+        self.end = end
+"""
+
+class Solution:
+    def minMeetingRooms(self, intervals: List[Interval]) -> int:
+        mp = defaultdict(int)
+        for i in intervals:
+            mp[i.start] += 1
+            mp[i.end] -= 1
+        prev = 0
+        res = 0
+        for i in sorted(mp.keys()):
+            prev += mp[i]
+            res = max(res, prev)
+        return res
+```
+
+```java
+/**
+ * Definition of Interval:
+ * public class Interval {
+ *     public int start, end;
+ *     public Interval(int start, int end) {
+ *         this.start = start;
+ *         this.end = end;
+ *     }
+ * }
+ */
+
+public class Solution {
+    public int minMeetingRooms(List<Interval> intervals) {
+        TreeMap<Integer, Integer> mp = new TreeMap<>();
+        for (Interval i : intervals) {
+            mp.put(i.start, mp.getOrDefault(i.start, 0) + 1);
+            mp.put(i.end, mp.getOrDefault(i.end, 0) - 1);
+        }
+        int prev = 0;
+        int res = 0;
+        for (int key : mp.keySet()) {
+            prev += mp.get(key);
+            res = Math.max(res, prev);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition of Interval:
+ * class Interval {
+ * public:
+ *     int start, end;
+ *     Interval(int start, int end) {
+ *         this->start = start;
+ *         this->end = end;
+ *     }
+ * }
+ */
+
+class Solution {
+public:
+    int minMeetingRooms(vector<Interval>& intervals) {
+        map<int, int> mp;
+        for (auto& i : intervals) {
+            mp[i.start]++;
+            mp[i.end]--;
+        }
+        int prev = 0, res = 0;
+        for (auto& [key, value] : mp) {
+            prev += value;
+            res = max(res, prev);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition of Interval:
+ * class Interval {
+ *   constructor(start, end) {
+ *     this.start = start;
+ *     this.end = end;
+ *   }
+ * }
+ */
+
+class Solution {
+    /**
+     * @param {Interval[]} intervals
+     * @returns {number}
+     */
+    minMeetingRooms(intervals) {
+        const mp = new Map();
+        for (const i of intervals) {
+            mp.set(i.start, (mp.get(i.start) || 0) + 1);
+            mp.set(i.end, (mp.get(i.end) || 0) - 1);
+        }
+        const sortedKeys = Array.from(mp.keys()).sort((a, b) => a - b);
+        let prev = 0, res = 0;
+        for (const key of sortedKeys) {
+            prev += mp.get(key);
+            res = Math.max(res, prev);
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition of Interval:
+ * public class Interval {
+ *     public int start, end;
+ *     public Interval(int start, int end) {
+ *         this.start = start;
+ *         this.end = end;
+ *     }
+ * }
+ */
+
+public class Solution {
+    public int MinMeetingRooms(List<Interval> intervals) {
+        var mp = new SortedDictionary<int, int>();
+        foreach (var i in intervals) {
+            if (!mp.ContainsKey(i.start)) mp[i.start] = 0;
+            if (!mp.ContainsKey(i.end)) mp[i.end] = 0;
+            mp[i.start]++;
+            mp[i.end]--;
+        }
+        int prev = 0, res = 0;
+        foreach (var kvp in mp) {
+            prev += kvp.Value;
+            res = Math.Max(res, prev);
+        }
+        return res;
+    }
+}
+```
+
+```go
+/**
+ * Definition of Interval:
+ * type Interval struct {
+ *    start int
+ *    end   int
+ * }
+ */
+
+func minMeetingRooms(intervals []Interval) int {
+    mp := make(map[int]int)
+    for _, i := range intervals {
+        mp[i.start]++
+        mp[i.end]--
+    }
+    
+    keys := make([]int, 0, len(mp))
+    for k := range mp {
+        keys = append(keys, k)
+    }
+    sort.Ints(keys)
+    
+    prev := 0
+    res := 0
+    for _, k := range keys {
+        prev += mp[k]
+        if prev > res {
+            res = prev
+        }
+    }
+    return res
+}
+```
+
+```kotlin
+/**
+ * Definition of Interval:
+ * class Interval(var start: Int, var end: Int) {}
+ */
+
+class Solution {
+    fun minMeetingRooms(intervals: List<Interval>): Int {
+        val mp = HashMap<Int, Int>()
+        for (i in intervals) {
+            mp[i.start] = mp.getOrDefault(i.start, 0) + 1
+            mp[i.end] = mp.getOrDefault(i.end, 0) - 1
+        }
+        
+        val keys = mp.keys.sorted()
+        var prev = 0
+        var res = 0
+        for (k in keys) {
+            prev += mp[k]!!
+            res = maxOf(res, prev)
+        }
+        return res
+    }
+}
+```
+
+```swift
+/**
+ * Definition of Interval:
+ * class Interval {
+ *     var start: Int
+ *     var end: Int
+ *     init(start: Int, end: Int) {
+ *         self.start = start
+ *         self.end = end
+ *     }
+ * }
+ */
+
+class Solution {
+    func minMeetingRooms(_ intervals: [Interval]) -> Int {
+        var mp = [Int: Int]()
+        for interval in intervals {
+            mp[interval.start, default: 0] += 1
+            mp[interval.end, default: 0] -= 1
+        }
+        var prev = 0
+        var res = 0
+        for key in mp.keys.sorted() {
+            prev += mp[key]!
+            res = max(res, prev)
+        }
+        return res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Two Pointers
+
+::tabs-start
+
+```python
+"""
+Definition of Interval:
+class Interval(object):
+    def __init__(self, start, end):
+        self.start = start
+        self.end = end
+"""
+
+class Solution:
+    def minMeetingRooms(self, intervals: List[Interval]) -> int:
+        start = sorted([i.start for i in intervals])
+        end = sorted([i.end for i in intervals])
+        
+        res = count = 0
+        s = e = 0
+        while s < len(intervals):
+            if start[s] < end[e]:
+                s += 1
+                count += 1
+            else:
+                e += 1
+                count -= 1
+            res = max(res, count)
+        return res
+```
+
+```java
+/**
+ * Definition of Interval:
+ * public class Interval {
+ *     public int start, end;
+ *     public Interval(int start, int end) {
+ *         this.start = start;
+ *         this.end = end;
+ *     }
+ * }
+ */
+
+public class Solution {
+    public int minMeetingRooms(List<Interval> intervals) {
+        int n = intervals.size();
+        int[] start = new int[n];
+        int[] end = new int[n];
+        
+        for (int i = 0; i < n; i++) {
+            start[i] = intervals.get(i).start;
+            end[i] = intervals.get(i).end;
+        }
+        
+        Arrays.sort(start);
+        Arrays.sort(end);
+        
+        int res = 0, count = 0, s = 0, e = 0;
+        while (s < n) {
+            if (start[s] < end[e]) {
+                s++;
+                count++;
+            } else {
+                e++;
+                count--;
+            }
+            res = Math.max(res, count);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition of Interval:
+ * class Interval {
+ * public:
+ *     int start, end;
+ *     Interval(int start, int end) {
+ *         this->start = start;
+ *         this->end = end;
+ *     }
+ * }
+ */
+
+class Solution {
+public:
+    int minMeetingRooms(vector<Interval>& intervals) {
+        vector<int> start, end;
+        
+        for (const auto& i : intervals) {
+            start.push_back(i.start);
+            end.push_back(i.end);
+        }
+        
+        sort(start.begin(), start.end());
+        sort(end.begin(), end.end());
+        
+        int res = 0, count = 0, s = 0, e = 0;
+        while (s < intervals.size()) {
+            if (start[s] < end[e]) {
+                s++;
+                count++;
+            } else {
+                e++;
+                count--;
+            }
+            res = max(res, count);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition of Interval:
+ * class Interval {
+ *   constructor(start, end) {
+ *     this.start = start;
+ *     this.end = end;
+ *   }
+ * }
+ */
+
+class Solution {
+    /**
+     * @param {Interval[]} intervals
+     * @returns {number}
+     */
+    minMeetingRooms(intervals) {
+        const start = intervals.map(i => i.start).sort((a, b) => a - b);
+        const end = intervals.map(i => i.end).sort((a, b) => a - b);
+        
+        let res = 0, count = 0, s = 0, e = 0;
+        while (s < intervals.length) {
+            if (start[s] < end[e]) {
+                s++;
+                count++;
+            } else {
+                e++;
+                count--;
+            }
+            res = Math.max(res, count);
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition of Interval:
+ * public class Interval {
+ *     public int start, end;
+ *     public Interval(int start, int end) {
+ *         this.start = start;
+ *         this.end = end;
+ *     }
+ * }
+ */
+
+public class Solution {
+    public int MinMeetingRooms(List<Interval> intervals) {
+        int n = intervals.Count;
+        int[] start = new int[n];
+        int[] end = new int[n];
+        
+        for (int i = 0; i < n; i++) {
+            start[i] = intervals[i].start;
+            end[i] = intervals[i].end;
+        }
+        
+        Array.Sort(start);
+        Array.Sort(end);
+        
+        int res = 0, count = 0, s = 0, e = 0;
+        while (s < n) {
+            if (start[s] < end[e]) {
+                s++;
+                count++;
+            } else {
+                e++;
+                count--;
+            }
+            res = Math.Max(res, count);
+        }
+        return res;
+    }
+}
+```
+
+```go
+/**
+ * Definition of Interval:
+ * type Interval struct {
+ *    start int
+ *    end   int
+ * }
+ */
+
+func minMeetingRooms(intervals []Interval) int {
+    start := make([]int, len(intervals))
+    end := make([]int, len(intervals))
+    
+    for i, interval := range intervals {
+        start[i] = interval.start
+        end[i] = interval.end
+    }
+    
+    sort.Ints(start)
+    sort.Ints(end)
+    
+    res, count := 0, 0
+    s, e := 0, 0
+    
+    for s < len(intervals) {
+        if start[s] < end[e] {
+            s++
+            count++
+        } else {
+            e++
+            count--
+        }
+        if count > res {
+            res = count
+        }
+    }
+    
+    return res
+}
+```
+
+```kotlin
+/**
+ * Definition of Interval:
+ * class Interval(var start: Int, var end: Int) {}
+ */
+
+class Solution {
+    fun minMeetingRooms(intervals: List<Interval>): Int {
+        val start = intervals.map { it.start }.sorted()
+        val end = intervals.map { it.end }.sorted()
+        
+        var res = 0
+        var count = 0
+        var s = 0
+        var e = 0
+        
+        while (s < intervals.size) {
+            if (start[s] < end[e]) {
+                s++
+                count++
+            } else {
+                e++
+                count--
+            }
+            res = maxOf(res, count)
+        }
+        
+        return res
+    }
+}
+```
+
+```swift
+/**
+ * Definition of Interval:
+ * class Interval {
+ *     var start: Int
+ *     var end: Int
+ *     init(start: Int, end: Int) {
+ *         self.start = start
+ *         self.end = end
+ *     }
+ * }
+ */
+
+class Solution {
+    func minMeetingRooms(_ intervals: [Interval]) -> Int {
+        let starts = intervals.map { $0.start }.sorted()
+        let ends = intervals.map { $0.end }.sorted()
+        
+        var res = 0, count = 0, s = 0, e = 0
+        while s < intervals.count {
+            if starts[s] < ends[e] {
+                count += 1
+                s += 1
+            } else {
+                count -= 1
+                e += 1
+            }
+            res = max(res, count)
+        }
+        return res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Greedy
+
+::tabs-start
+
+```python
+"""
+Definition of Interval:
+class Interval(object):
+    def __init__(self, start, end):
+        self.start = start
+        self.end = end
+"""
+
+class Solution:
+    def minMeetingRooms(self, intervals: List[Interval]) -> int:
+        time = []
+        for i in intervals:
+            time.append((i.start, 1))
+            time.append((i.end, -1))
+        
+        time.sort(key=lambda x: (x[0], x[1]))
+        
+        res = count = 0
+        for t in time:
+            count += t[1]
+            res = max(res, count)
+        return res
+```
+
+```java
+/**
+ * Definition of Interval:
+ * public class Interval {
+ *     public int start, end;
+ *     public Interval(int start, int end) {
+ *         this.start = start;
+ *         this.end = end;
+ *     }
+ * }
+ */
+
+public class Solution {
+    public int minMeetingRooms(List<Interval> intervals) {
+        List<int[]> time = new ArrayList<>();
+        for (Interval i : intervals) {
+            time.add(new int[] { i.start, 1 });
+            time.add(new int[] { i.end, -1 });
+        }
+        
+        time.sort((a, b) -> a[0] == b[0] ? a[1] - b[1] : a[0] - b[0]);
+        
+        int res = 0, count = 0;
+        for (int[] t : time) {
+            count += t[1];
+            res = Math.max(res, count);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition of Interval:
+ * class Interval {
+ * public:
+ *     int start, end;
+ *     Interval(int start, int end) {
+ *         this->start = start;
+ *         this->end = end;
+ *     }
+ * }
+ */
+
+class Solution {
+public:
+    int minMeetingRooms(vector<Interval>& intervals) {
+        vector<pair<int, int>> time;
+        for (const auto& i : intervals) {
+            time.push_back({i.start, 1});
+            time.push_back({i.end, -1});
+        }
+        
+        sort(time.begin(), time.end(), [](auto& a, auto& b) {
+            return a.first == b.first ? a.second < b.second : a.first < b.first;
+        });
+        
+        int res = 0, count = 0;
+        for (const auto& t : time) {
+            count += t.second;
+            res = max(res, count);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition of Interval:
+ * class Interval {
+ *   constructor(start, end) {
+ *     this.start = start;
+ *     this.end = end;
+ *   }
+ * }
+ */
+
+class Solution {
+    /**
+     * @param {Interval[]} intervals
+     * @returns {number}
+     */
+    minMeetingRooms(intervals) {
+        const time = [];
+        for (const i of intervals) {
+            time.push([i.start, 1]);
+            time.push([i.end, -1]);
+        }
+        
+        time.sort((a, b) => a[0] === b[0] ? a[1] - b[1] : a[0] - b[0]);
+        
+        let res = 0, count = 0;
+        for (const t of time) {
+            count += t[1];
+            res = Math.max(res, count);
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition of Interval:
+ * public class Interval {
+ *     public int start, end;
+ *     public Interval(int start, int end) {
+ *         this.start = start;
+ *         this.end = end;
+ *     }
+ * }
+ */
+
+public class Solution {
+    public int MinMeetingRooms(List<Interval> intervals) {
+        List<int[]> time = new List<int[]>();
+        foreach (var i in intervals) {
+            time.Add(new int[] { i.start, 1 });
+            time.Add(new int[] { i.end, -1 });
+        }
+        
+        time.Sort((a, b) => a[0] == b[0] ? 
+            a[1].CompareTo(b[1]) : a[0].CompareTo(b[0]
+        ));
+        
+        int res = 0, count = 0;
+        foreach (var t in time) {
+            count += t[1];
+            res = Math.Max(res, count);
+        }
+        return res;
+    }
+}
+```
+
+```go
+/**
+ * Definition of Interval:
+ * type Interval struct {
+ *    start int
+ *    end   int
+ * }
+ */
+
+func minMeetingRooms(intervals []Interval) int {
+	var time [][]int
+	for _, i := range intervals {
+		time = append(time, []int{i.start, 1})
+		time = append(time, []int{i.end, -1})
+	}
+
+	sort.Slice(time, func(i, j int) bool {
+		if time[i][0] == time[j][0] {
+			return time[i][1] < time[j][1]
+		}
+		return time[i][0] < time[j][0]
+	})
+
+	res, count := 0, 0
+	for _, t := range time {
+		count += t[1]
+		if count > res {
+			res = count
+		}
+	}
+	return res
+}
+```
+
+```kotlin
+/**
+ * Definition of Interval:
+ * class Interval(var start: Int, var end: Int) {}
+ */
+
+class Solution {
+    fun minMeetingRooms(intervals: Array<IntArray>): Int {
+        val time = mutableListOf<Pair<Int, Int>>()
+        
+        for (i in intervals) {
+            time.add(Pair(i.start, 1))
+            time.add(Pair(i.end, -1))
+        }
+        
+        time.sortWith(compareBy<Pair<Int, Int>> { it.first }
+            .thenBy { it.second })
+        
+        var res = 0
+        var count = 0
+        
+        for (t in time) {
+            count += t.second
+            res = maxOf(res, count)
+        }
+        
+        return res
+    }
+}
+```
+
+```swift
+/**
+ * Definition of Interval:
+ * class Interval {
+ *     var start: Int
+ *     var end: Int
+ *     init(start: Int, end: Int) {
+ *         self.start = start
+ *         self.end = end
+ *     }
+ * }
+ */
+
+class Solution {
+    func minMeetingRooms(_ intervals: [Interval]) -> Int {
+        var times = [(Int, Int)]()
+        for interval in intervals {
+            times.append((interval.start, 1))
+            times.append((interval.end, -1))
+        }
+
+        times.sort { 
+            if $0.0 != $1.0 {
+                return $0.0 < $1.0
+            } else {
+                return $0.1 < $1.1
+            }
+        }
+
+        var count = 0
+        var res = 0
+        for t in times {
+            count += t.1
+            res = max(res, count)
+        }
+
+        return res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/meeting-schedule.md b/articles/meeting-schedule.md
new file mode 100644
index 000000000..226a6a70f
--- /dev/null
+++ b/articles/meeting-schedule.md
@@ -0,0 +1,464 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+"""
+Definition of Interval:
+class Interval(object):
+    def __init__(self, start, end):
+        self.start = start
+        self.end = end
+"""
+
+class Solution:
+    def canAttendMeetings(self, intervals: List[Interval]) -> bool:
+        n = len(intervals)
+        for i in range(n):
+            A = intervals[i]
+            for j in range(i + 1, n):
+                B = intervals[j]
+                if min(A.end, B.end) > max(A.start, B.start):
+                    return False
+        return True
+```
+
+```java
+/**
+ * Definition of Interval:
+ * public class Interval {
+ *     public int start, end;
+ *     public Interval(int start, int end) {
+ *         this.start = start;
+ *         this.end = end;
+ *     }
+ * }
+ */
+
+public class Solution {
+    public boolean canAttendMeetings(List<Interval> intervals) {
+        int n = intervals.size();
+        for (int i = 0; i < n; i++) {
+            Interval A = intervals.get(i);
+            for (int j = i + 1; j < n; j++) {
+                Interval B = intervals.get(j);
+                if (Math.min(A.end, B.end) > Math.max(A.start, B.start)) {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition of Interval:
+ * class Interval {
+ * public:
+ *     int start, end;
+ *     Interval(int start, int end) {
+ *         this->start = start;
+ *         this->end = end;
+ *     }
+ * }
+ */
+
+class Solution {
+public:
+    bool canAttendMeetings(vector<Interval>& intervals) {
+        int n = intervals.size();
+        for (int i = 0; i < n; i++) {
+            Interval& A =intervals[i];
+            for (int j = i + 1; j < n; j++) {
+                Interval& B =intervals[j];
+                if (min(A.end, B.end) > max(A.start, B.start)) {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition of Interval:
+ * class Interval {
+ *   constructor(start, end) {
+ *     this.start = start;
+ *     this.end = end;
+ *   }
+ * }
+ */
+
+class Solution {
+    /**
+     * @param {Interval[]} intervals
+     * @returns {boolean}
+     */
+    canAttendMeetings(intervals) {
+        const n = intervals.length;
+        for (let i = 0; i < n; i++) {
+            const A = intervals[i];
+            for (let j = i + 1; j < n; j++) {
+                const B = intervals[j];
+                if (Math.min(A.end, B.end) > Math.max(A.start, B.start)) {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition of Interval:
+ * public class Interval {
+ *     public int start, end;
+ *     public Interval(int start, int end) {
+ *         this.start = start;
+ *         this.end = end;
+ *     }
+ * }
+ */
+
+public class Solution {
+    public bool CanAttendMeetings(List<Interval> intervals) {
+        int n = intervals.Count;
+        for (int i = 0; i < n; i++) {
+            Interval A = intervals[i];
+            for (int j = i + 1; j < n; j++) {
+                Interval B = intervals[j];
+                if (Math.Min(A.end, B.end) > Math.Max(A.start, B.start)) {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+}
+```
+
+```go
+/**
+ * Definition of Interval:
+ * type Interval struct {
+ *    start int
+ *    end   int
+ * }
+ */
+
+func canAttendMeetings(intervals []Interval) bool {
+    n := len(intervals)
+    for i := 0; i < n; i++ {
+        A := intervals[i]
+        for j := i + 1; j < n; j++ {
+            B := intervals[j]
+            if min(A.end, B.end) > max(A.start, B.start) {
+                return false
+            }
+        }
+    }
+    return true
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+/**
+ * Definition of Interval:
+ * class Interval(var start: Int, var end: Int) {}
+ */
+
+class Solution {
+    fun canAttendMeetings(intervals: List<Interval>): Boolean {
+        val n = intervals.size
+        for (i in 0 until n) {
+            val A = intervals[i]
+            for (j in i + 1 until n) {
+                val B = intervals[j]
+                if (minOf(A.end, B.end) > maxOf(A.start, B.start)) {
+                    return false
+                }
+            }
+        }
+        return true
+    }
+}
+```
+
+```swift
+/**
+ * Definition of Interval:
+ * class Interval {
+ *     var start: Int
+ *     var end: Int
+ *     init(start: Int, end: Int) {
+ *         self.start = start
+ *         self.end = end
+ *     }
+ * }
+ */
+
+class Solution {
+    func canAttendMeetings(_ intervals: [Interval]) -> Bool {
+        let n = intervals.count
+        for i in 0..<n {
+            let A = intervals[i]
+            for j in (i + 1)..<n {
+                let B = intervals[j]
+                if min(A.end, B.end) > max(A.start, B.start) {
+                    return false
+                }
+            }
+        }
+        return true
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Sorting
+
+::tabs-start
+
+```python
+"""
+Definition of Interval:
+class Interval(object):
+    def __init__(self, start, end):
+        self.start = start
+        self.end = end
+"""
+
+class Solution:
+    def canAttendMeetings(self, intervals: List[Interval]) -> bool:
+        intervals.sort(key=lambda i: i.start)
+
+        for i in range(1, len(intervals)):
+            i1 = intervals[i - 1]
+            i2 = intervals[i]
+
+            if i1.end > i2.start:
+                return False
+        return True
+```
+
+```java
+/**
+ * Definition of Interval:
+ * public class Interval {
+ *     public int start, end;
+ *     public Interval(int start, int end) {
+ *         this.start = start;
+ *         this.end = end;
+ *     }
+ * }
+ */
+
+public class Solution {
+    public boolean canAttendMeetings(List<Interval> intervals) {
+        Collections.sort(intervals, Comparator.comparingInt(i -> i.start));
+
+        for (int i = 1; i < intervals.size(); i++) {
+            Interval i1 = intervals.get(i - 1);
+            Interval i2 = intervals.get(i);
+
+            if (i1.end > i2.start) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition of Interval:
+ * class Interval {
+ * public:
+ *     int start, end;
+ *     Interval(int start, int end) {
+ *         this->start = start;
+ *         this->end = end;
+ *     }
+ * }
+ */
+
+class Solution {
+public:
+    bool canAttendMeetings(vector<Interval>& intervals) {
+        sort(intervals.begin(), intervals.end(), [](auto& x, auto& y) { 
+            return x.start < y.start; 
+        });
+        for (int i = 1; i < intervals.size(); ++i) {
+            if (intervals[i].start < intervals[i - 1].end) {
+                return false;
+            }
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition of Interval:
+ * class Interval {
+ *   constructor(start, end) {
+ *     this.start = start;
+ *     this.end = end;
+ *   }
+ * }
+ */
+
+class Solution {
+    /**
+     * @param {Interval[]} intervals
+     * @returns {boolean}
+     */
+    canAttendMeetings(intervals) {
+        intervals.sort((a, b) => a.start - b.start);
+        for (let i = 1; i < intervals.length; i++) {
+            if (intervals[i].start < intervals[i - 1].end) {
+                return false;
+            }
+        }
+        return true;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition of Interval:
+ * public class Interval {
+ *     public int start, end;
+ *     public Interval(int start, int end) {
+ *         this.start = start;
+ *         this.end = end;
+ *     }
+ * }
+ */
+
+public class Solution {
+    public bool CanAttendMeetings(List<Interval> intervals) {
+        intervals.Sort((i1, i2) => i1.start.CompareTo(i2.start));
+
+        for (int i = 1; i < intervals.Count; i++) {
+            Interval i1 = intervals[i - 1];
+            Interval i2 = intervals[i];
+
+            if (i1.end > i2.start) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+}
+```
+
+```go
+/**
+* Definition of Interval:
+* type Interval struct {
+*    start int
+*    end   int
+* }
+*/
+
+func canAttendMeetings(intervals []Interval) bool {
+    sort.Slice(intervals, func(i, j int) bool {
+        return intervals[i].start < intervals[j].start
+    })
+
+    for i := 1; i < len(intervals); i++ {
+        if intervals[i-1].end > intervals[i].start {
+            return false
+        }
+    }
+    return true
+}
+```
+
+```kotlin
+/**
+ * Definition of Interval:
+ * class Interval(var start: Int, var end: Int) {}
+ */
+
+class Solution {
+    fun canAttendMeetings(intervals: List<Interval>): Boolean {
+        intervals.sortedBy { it.start }.let {
+            for (i in 1 until it.size) {
+                if (it[i - 1].end > it[i].start) {
+                    return false
+                }
+            }
+        }
+        return true
+    }
+}
+```
+
+```swift
+/**
+ * Definition of Interval:
+ * class Interval {
+ *     var start: Int
+ *     var end: Int
+ *     init(start: Int, end: Int) {
+ *         self.start = start
+ *         self.end = end
+ *     }
+ * }
+ */
+
+class Solution {
+    func canAttendMeetings(_ intervals: [Interval]) -> Bool {
+        let sortedIntervals = intervals.sorted { $0.start < $1.start }
+        for i in 1..<sortedIntervals.count {
+            if sortedIntervals[i - 1].end > sortedIntervals[i].start {
+                return false
+            }
+        }
+        return true
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
\ No newline at end of file
diff --git a/articles/merge-in-between-linked-lists.md b/articles/merge-in-between-linked-lists.md
new file mode 100644
index 000000000..2d8a1774f
--- /dev/null
+++ b/articles/merge-in-between-linked-lists.md
@@ -0,0 +1,460 @@
+## 1. Convert To Array
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def mergeInBetween(self, list1: ListNode, a: int, b: int, list2: ListNode) -> ListNode:
+        cur = list1
+        arr = []
+        while cur:
+            arr.append(cur)
+            cur = cur.next
+        arr[a - 1].next = list2
+
+        cur = list2
+        while cur.next:
+            cur = cur.next
+        
+        cur.next = arr[b + 1]
+        return list1
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode mergeInBetween(ListNode list1, int a, int b, ListNode list2) {
+        ListNode cur = list1;
+        List<ListNode> arr = new ArrayList<>();
+        
+        while (cur != null) {
+            arr.add(cur);
+            cur = cur.next;
+        }
+        
+        arr.get(a - 1).next = list2;
+        cur = list2;
+        
+        while (cur.next != null) {
+            cur = cur.next;
+        }
+        
+        cur.next = arr.get(b + 1);
+        return list1;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* mergeInBetween(ListNode* list1, int a, int b, ListNode* list2) {
+        ListNode* cur = list1;
+        vector<ListNode*> arr;
+        
+        while (cur) {
+            arr.push_back(cur);
+            cur = cur->next;
+        }
+        
+        arr[a - 1]->next = list2;
+        cur = list2;
+        
+        while (cur->next) {
+            cur = cur->next;
+        }
+        
+        cur->next = arr[b + 1];
+        return list1;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} list1
+     * @param {number} a
+     * @param {number} b
+     * @param {ListNode} list2
+     * @return {ListNode}
+     */
+    mergeInBetween(list1, a, b, list2) {
+        let cur = list1;
+        let arr = [];
+        
+        while (cur) {
+            arr.push(cur);
+            cur = cur.next;
+        }
+        
+        arr[a - 1].next = list2;
+        cur = list2;
+        
+        while (cur.next) {
+            cur = cur.next;
+        }
+        
+        cur.next = arr[b + 1];
+        return list1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the length of the first list and $m$ is the length of the second list.
+
+---
+
+## 2. Two Pointers
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def mergeInBetween(self, list1: ListNode, a: int, b: int, list2: ListNode) -> ListNode:
+        curr = list1
+        i = 0
+        
+        while i < a - 1:
+            curr = curr.next
+            i += 1
+        head = curr
+        
+        while i <= b:
+            curr = curr.next
+            i += 1
+        
+        head.next = list2
+        
+        while list2.next:
+            list2 = list2.next
+        list2.next = curr
+        
+        return list1  
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode mergeInBetween(ListNode list1, int a, int b, ListNode list2) {
+        ListNode curr = list1;
+        int i = 0;
+        
+        while (i < a - 1) {
+            curr = curr.next;
+            i++;
+        }
+        ListNode head = curr;
+        
+        while (i <= b) {
+            curr = curr.next;
+            i++;
+        }
+        
+        head.next = list2;
+        
+        while (list2.next != null) {
+            list2 = list2.next;
+        }
+        list2.next = curr;
+        
+        return list1;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* mergeInBetween(ListNode* list1, int a, int b, ListNode* list2) {
+        ListNode* curr = list1;
+        int i = 0;
+        
+        while (i < a - 1) {
+            curr = curr->next;
+            i++;
+        }
+        ListNode* head = curr;
+        
+        while (i <= b) {
+            curr = curr->next;
+            i++;
+        }
+        head->next = list2;
+        
+        while (list2->next) {
+            list2 = list2->next;
+        }
+        list2->next = curr;
+        
+        return list1;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} list1
+     * @param {number} a
+     * @param {number} b
+     * @param {ListNode} list2
+     * @return {ListNode}
+     */
+    mergeInBetween(list1, a, b, list2) {
+        let curr = list1, i = 0;
+        
+        while (i < a - 1) {
+            curr = curr.next;
+            i++;
+        }
+        let head = curr;
+        
+        while (i <= b) {
+            curr = curr.next;
+            i++;
+        }
+        head.next = list2;
+        
+        while (list2.next) {
+            list2 = list2.next;
+        }
+        list2.next = curr;
+        
+        return list1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(1)$ extra space.
+
+> Where $n$ is the length of the first list and $m$ is the length of the second list.
+
+---
+
+## 3. Recursion
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def mergeInBetween(self, list1: ListNode, a: int, b: int, list2: ListNode) -> ListNode:
+        if a == 1 :
+            nxt = list1.next
+            list1.next = list2
+            while list2.next:
+                list2 = list2.next
+            self.mergeInBetween(nxt, 0, b - 1, list2)
+            return list1
+        
+        if b == 0:
+            list2.next = list1.next
+            return list1
+        
+        self.mergeInBetween(list1.next, a - 1, b - 1, list2)
+        return list1
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode mergeInBetween(ListNode list1, int a, int b, ListNode list2) {
+        if (a == 1) {
+            ListNode nxt = list1.next;
+            list1.next = list2;
+            
+            while (list2.next != null) {
+                list2 = list2.next;
+            }
+            mergeInBetween(nxt, 0, b - 1, list2);
+            return list1;
+        }
+        
+        if (b == 0) {
+            list2.next = list1.next;
+            return list1;
+        }
+        
+        mergeInBetween(list1.next, a - 1, b - 1, list2);
+        return list1;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* mergeInBetween(ListNode* list1, int a, int b, ListNode* list2) {
+        if (a == 1) {
+            ListNode* nxt = list1->next;
+            list1->next = list2;
+            
+            while (list2->next) {
+                list2 = list2->next;
+            }
+            mergeInBetween(nxt, 0, b - 1, list2);
+            return list1;
+        }
+        
+        if (b == 0) {
+            list2->next = list1->next;
+            return list1;
+        }
+        
+        mergeInBetween(list1->next, a - 1, b - 1, list2);
+        return list1;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} list1
+     * @param {number} a
+     * @param {number} b
+     * @param {ListNode} list2
+     * @return {ListNode}
+     */
+    mergeInBetween(list1, a, b, list2) {
+        if (a === 1) {
+            let nxt = list1.next;
+            list1.next = list2;
+            
+            while (list2.next) {
+                list2 = list2.next;
+            }
+            this.mergeInBetween(nxt, 0, b - 1, list2);
+            return list1;
+        }
+        
+        if (b === 0) {
+            list2.next = list1.next;
+            return list1;
+        }
+        
+        this.mergeInBetween(list1.next, a - 1, b - 1, list2);
+        return list1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(n)$ for recursion stack.
+
+> Where $n$ is the length of the first list and $m$ is the length of the second list.
\ No newline at end of file
diff --git a/articles/merge-intervals.md b/articles/merge-intervals.md
new file mode 100644
index 000000000..100d894b6
--- /dev/null
+++ b/articles/merge-intervals.md
@@ -0,0 +1,780 @@
+## 1. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def merge(self, intervals: List[List[int]]) -> List[List[int]]:
+        intervals.sort(key=lambda pair: pair[0])
+        output = [intervals[0]]
+
+        for start, end in intervals:
+            lastEnd = output[-1][1]
+
+            if start <= lastEnd:
+                output[-1][1] = max(lastEnd, end)
+            else:
+                output.append([start, end])
+        return output
+```
+
+```java
+public class Solution {
+    public int[][] merge(int[][] intervals) {
+        Arrays.sort(intervals, (a, b) -> Integer.compare(a[0], b[0]));
+        List<int[]> output = new ArrayList<>();
+        output.add(intervals[0]);
+
+        for (int[] interval : intervals) {
+            int start = interval[0];
+            int end = interval[1];
+            int lastEnd = output.get(output.size() - 1)[1];
+
+            if (start <= lastEnd) {
+                output.get(output.size() - 1)[1] = Math.max(lastEnd, end);
+            } else {
+                output.add(new int[]{start, end});
+            }
+        }
+        return output.toArray(new int[output.size()][]);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> merge(vector<vector<int>>& intervals) {
+        sort(intervals.begin(), intervals.end());
+        vector<vector<int>> output;
+        output.push_back(intervals[0]);
+
+        for (auto& interval : intervals) {
+            int start = interval[0];
+            int end = interval[1];
+            int lastEnd = output.back()[1];
+
+            if (start <= lastEnd) {
+                output.back()[1] = max(lastEnd, end);
+            } else {
+                output.push_back({start, end});
+            }
+        }
+        return output;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} intervals
+     * @return {number[][]}
+     */
+    merge(intervals) {
+        intervals.sort((a, b) => a[0] - b[0]);
+        const output = [];
+        output.push(intervals[0]);
+
+        for (const interval of intervals) {
+            const start = interval[0];
+            const end = interval[1];
+            const lastEnd = output[output.length - 1][1];
+
+            if (start <= lastEnd) {
+                output[output.length - 1][1] = Math.max(lastEnd, end);
+            } else {
+                output.push([start, end]);
+            }
+        }
+        return output;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[][] Merge(int[][] intervals) {
+        Array.Sort(intervals, (a, b) => a[0].CompareTo(b[0]));
+        List<int[]> output = new List<int[]>();
+        output.Add(intervals[0]);
+
+        foreach (int[] interval in intervals) {
+            int start = interval[0];
+            int end = interval[1];
+            int lastEnd = output[output.Count - 1][1];
+
+            if (start <= lastEnd) {
+                output[output.Count - 1][1] = Math.Max(lastEnd, end);
+            } else {
+                output.Add(new int[]{start, end});
+            }
+        }
+        return output.ToArray();
+    }
+}
+```
+
+```go
+func merge(intervals [][]int) [][]int {
+    sort.Slice(intervals, func(i, j int) bool {
+        return intervals[i][0] < intervals[j][0]
+    })
+    output := [][]int{intervals[0]}
+
+    for _, interval := range intervals[1:] {
+        start, end := interval[0], interval[1]
+        lastEnd := output[len(output)-1][1]
+
+        if start <= lastEnd {
+            output[len(output)-1][1] = max(lastEnd, end)
+        } else {
+            output = append(output, []int{start, end})
+        }
+    }
+    return output
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun merge(intervals: Array<IntArray>): Array<IntArray> {
+        intervals.sortBy { it[0] }
+        val output = mutableListOf(intervals[0])
+
+        for (interval in intervals.slice(1 until intervals.size)) {
+            val (start, end) = interval
+            val lastEnd = output.last()[1]
+
+            if (start <= lastEnd) {
+                output[output.size - 1][1] = maxOf(lastEnd, end)
+            } else {
+                output.add(interval)
+            }
+        }
+        return output.toTypedArray()
+    }
+}
+```
+
+```swift
+class Solution {
+    func merge(_ intervals: [[Int]]) -> [[Int]] {
+        let intervals = intervals.sorted { $0[0] < $1[0] }
+        var output: [[Int]] = [intervals[0]]
+
+        for interval in intervals {
+            let start = interval[0]
+            let end = interval[1]
+            var lastEnd = output.last![1]
+
+            if start <= lastEnd {
+                output[output.count - 1][1] = max(lastEnd, end)
+            } else {
+                output.append([start, end])
+            }
+        }
+        return output
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity:
+    * $O(1)$ or $O(n)$ space depending on the sorting algorithm.
+    * $O(n)$ for the output list.
+
+---
+
+## 2. Sweep Line Algorithm
+
+::tabs-start
+
+```python
+class Solution:
+    def merge(self, intervals: List[List[int]]) -> List[List[int]]:
+        mp = defaultdict(int)
+        for start, end in intervals:
+            mp[start] += 1
+            mp[end] -= 1
+
+        res = []
+        interval = []
+        have = 0
+        for i in sorted(mp):
+            if not interval:
+                interval.append(i)
+            have += mp[i]
+            if have == 0:
+                interval.append(i)
+                res.append(interval)
+                interval = []
+        return res
+```
+
+```java
+public class Solution {
+    public int[][] merge(int[][] intervals) {
+        TreeMap<Integer, Integer> map = new TreeMap<>();
+        
+        for (int[] interval : intervals) {
+            map.put(interval[0], map.getOrDefault(interval[0], 0) + 1);
+            map.put(interval[1], map.getOrDefault(interval[1], 0) - 1);
+        }
+        
+        List<int[]> res = new ArrayList<>();
+        int have = 0;
+        int[] interval = new int[2];
+        
+        for (int point : map.keySet()) {
+            if (have == 0) interval[0] = point;
+            have += map.get(point);
+            if (have == 0) {
+                interval[1] = point;
+                res.add(new int[] {interval[0], interval[1]});
+            }
+        }
+        
+        return res.toArray(new int[res.size()][]);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> merge(vector<vector<int>>& intervals) {
+        map<int, int> mp;
+        for (const auto& interval : intervals) {
+            mp[interval[0]]++;
+            mp[interval[1]]--;
+        }
+
+        vector<vector<int>> res;
+        vector<int> interval;
+        int have = 0;
+        for (const auto& [i, count] : mp) {
+            if (interval.empty()) {
+                interval.push_back(i);
+            }
+            have += count;
+            if (have == 0) {
+                interval.push_back(i);
+                res.push_back(interval);
+                interval.clear();
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} intervals
+     * @return {number[][]}
+     */
+    merge(intervals) {
+        const mp = new Map();
+        for (const [start, end] of intervals) {
+            mp.set(start, (mp.get(start) || 0) + 1);
+            mp.set(end, (mp.get(end) || 0) - 1);
+        }
+
+        const sortedKeys = Array.from(mp.keys()).sort((a, b) => a - b);
+        const res = [];
+        let interval = [];
+        let have = 0;
+
+        for (const i of sortedKeys) {
+            if (interval.length === 0) {
+                interval.push(i);
+            }
+            have += mp.get(i);
+            if (have === 0) {
+                interval.push(i);
+                res.push(interval);
+                interval = [];
+            }
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[][] Merge(int[][] intervals) {
+        var mp = new SortedDictionary<int, int>();
+        foreach (var point in intervals) {
+            if (!mp.ContainsKey(point[0])) mp[point[0]] = 0;
+            if (!mp.ContainsKey(point[1])) mp[point[1]] = 0;
+            mp[point[0]]++;
+            mp[point[1]]--;
+        }
+
+        var res = new List<int[]>();
+        var interval = new int[2];
+        int have = 0;
+        foreach (var kvp in mp) {
+            if (have == 0) interval[0] = kvp.Key;
+            have += kvp.Value;
+            if (have == 0) {
+                interval[1] = kvp.Key;
+                res.Add(new int[] { interval[0], interval[1] });
+            }
+        }
+        return res.ToArray();
+    }
+}
+```
+
+```go
+
+func merge(intervals [][]int) [][]int {
+    mp := make(map[int]int)
+    for _, interval := range intervals {
+        start, end := interval[0], interval[1]
+        mp[start]++
+        mp[end]--
+    }
+
+    res := [][]int{}
+    interval := []int{}
+    have := 0
+    keys := make([]int, 0, len(mp))
+    for key := range mp {
+        keys = append(keys, key)
+    }
+    sort.Ints(keys)
+
+    for _, i := range keys {
+        if len(interval) == 0 {
+            interval = append(interval, i)
+        }
+        have += mp[i]
+        if have == 0 {
+            interval = append(interval, i)
+            res = append(res, append([]int{}, interval...))
+            interval = []int{}
+        }
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun merge(intervals: Array<IntArray>): Array<IntArray> {
+        val mp = TreeMap<Int, Int>()
+        for (interval in intervals) {
+            val (start, end) = interval
+            mp[start] = mp.getOrDefault(start, 0) + 1
+            mp[end] = mp.getOrDefault(end, 0) - 1
+        }
+
+        val res = mutableListOf<IntArray>()
+        var interval = mutableListOf<Int>()
+        var have = 0
+
+        for (i in mp.keys) {
+            if (interval.isEmpty()) {
+                interval.add(i)
+            }
+            have += mp[i]!!
+            if (have == 0) {
+                interval.add(i)
+                res.add(interval.toIntArray())
+                interval = mutableListOf()
+            }
+        }
+        return res.toTypedArray()
+    }
+}
+```
+
+```swift
+class Solution {
+    func merge(_ intervals: [[Int]]) -> [[Int]] {
+        var mp = [Int: Int]()
+        
+        for interval in intervals {
+            let start = interval[0]
+            let end = interval[1]
+            mp[start, default: 0] += 1
+            mp[end, default: 0] -= 1
+        }
+
+        var res = [[Int]]()
+        var interval = [Int]()
+        var have = 0
+
+        for i in mp.keys.sorted() {
+            if interval.isEmpty {
+                interval.append(i)
+            }
+            have += mp[i, default: 0]
+            if have == 0 {
+                interval.append(i)
+                res.append(interval)
+                interval = []
+            }
+        }
+        return res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Greedy
+
+::tabs-start
+
+```python
+class Solution:
+    def merge(self, intervals: List[List[int]]) -> List[List[int]]:
+        max_val = max(interval[0] for interval in intervals)
+        
+        mp = [0] * (max_val + 1)
+        for start, end in intervals:
+            mp[start] = max(end + 1, mp[start])
+
+        res = []
+        have = -1
+        interval_start = -1
+        for i in range(len(mp)):
+            if mp[i] != 0:
+                if interval_start == -1:
+                    interval_start = i
+                have = max(mp[i] - 1, have)
+            if have == i:
+                res.append([interval_start, have])
+                have = -1
+                interval_start = -1
+
+        if interval_start != -1:
+            res.append([interval_start, have])
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[][] merge(int[][] intervals) {
+        int max = 0;
+        for (int i = 0; i < intervals.length; i++) {
+            max = Math.max(intervals[i][0], max);
+        }
+
+        int[] mp = new int[max + 1];
+        for (int i = 0; i < intervals.length; i++) {
+            int start = intervals[i][0];
+            int end = intervals[i][1];
+            mp[start] = Math.max(end + 1, mp[start]);
+        }
+
+        int r = 0;
+        int have = -1;
+        int intervalStart = -1;
+        for (int i = 0; i < mp.length; i++) {
+            if (mp[i] != 0) {
+                if (intervalStart == -1) intervalStart = i;
+                have = Math.max(mp[i] - 1, have);
+            }
+            if (have == i) {
+                intervals[r++] = new int[] { intervalStart, have };
+                have = -1;
+                intervalStart = -1;
+            }
+        }
+
+        if (intervalStart != -1) {
+            intervals[r++] = new int[] { intervalStart, have };
+        }
+        if (intervals.length == r) {
+            return intervals;
+        }
+
+        int[][] res = new int[r][];
+        for (int i = 0; i < r; i++) {
+            res[i] = intervals[i];
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> merge(vector<vector<int>>& intervals) {
+        int max_val = 0;
+        for (const auto& interval : intervals) {
+            max_val = max(interval[0], max_val);
+        }
+
+        vector<int> mp(max_val + 1, 0);
+        for (const auto& interval : intervals) {
+            int start = interval[0];
+            int end = interval[1];
+            mp[start] = max(end + 1, mp[start]);
+        }
+
+        vector<vector<int>> res;
+        int have = -1;
+        int intervalStart = -1;
+        for (int i = 0; i < mp.size(); i++) {
+            if (mp[i] != 0) {
+                if (intervalStart == -1) intervalStart = i;
+                have = max(mp[i] - 1, have);
+            }
+            if (have == i) {
+                res.push_back({intervalStart, have});
+                have = -1;
+                intervalStart = -1;
+            }
+        }
+
+        if (intervalStart != -1) {
+            res.push_back({intervalStart, have});
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} intervals
+     * @return {number[][]}
+     */
+    merge(intervals) {
+        let max = 0;
+        for (let i = 0; i < intervals.length; i++) {
+            max = Math.max(intervals[i][0], max);
+        }
+
+        let mp = new Array(max + 1).fill(0);
+        for (let i = 0; i < intervals.length; i++) {
+            let start = intervals[i][0];
+            let end = intervals[i][1];
+            mp[start] = Math.max(end + 1, mp[start]);
+        }
+
+        let res = [];
+        let have = -1;
+        let intervalStart = -1;
+        for (let i = 0; i < mp.length; i++) {
+            if (mp[i] !== 0) {
+                if (intervalStart === -1) intervalStart = i;
+                have = Math.max(mp[i] - 1, have);
+            }
+            if (have === i) {
+                res.push([intervalStart, have]);
+                have = -1;
+                intervalStart = -1;
+            }
+        }
+
+        if (intervalStart !== -1) {
+            res.push([intervalStart, have]);
+        }
+
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[][] Merge(int[][] intervals) {
+        int max = 0;
+        for (int i = 0; i < intervals.Length; i++) {
+            max = Math.Max(intervals[i][0], max);
+        }
+
+        int[] mp = new int[max + 1];
+        for (int i = 0; i < intervals.Length; i++) {
+            int start = intervals[i][0];
+            int end = intervals[i][1];
+            mp[start] = Math.Max(end + 1, mp[start]);
+        }
+
+        var res = new List<int[]>();
+        int have = -1;
+        int intervalStart = -1;
+        for (int i = 0; i < mp.Length; i++) {
+            if (mp[i] != 0) {
+                if (intervalStart == -1) intervalStart = i;
+                have = Math.Max(mp[i] - 1, have);
+            }
+            if (have == i) {
+                res.Add(new int[] { intervalStart, have });
+                have = -1;
+                intervalStart = -1;
+            }
+        }
+
+        if (intervalStart != -1) {
+            res.Add(new int[] { intervalStart, have });
+        }
+
+        return res.ToArray();
+    }
+}
+```
+
+```go
+func merge(intervals [][]int) [][]int {
+    maxVal := math.MinInt
+    for _, interval := range intervals {
+        maxVal = max(maxVal, interval[0])
+    }
+
+    mp := make([]int, maxVal+1)
+    for _, interval := range intervals {
+        start, end := interval[0], interval[1]
+        mp[start] = max(mp[start], end+1)
+    }
+
+    res := [][]int{}
+    have := -1
+    intervalStart := -1
+    for i := 0; i < len(mp); i++ {
+        if mp[i] != 0 {
+            if intervalStart == -1 {
+                intervalStart = i
+            }
+            have = max(mp[i]-1, have)
+        }
+        if have == i {
+            res = append(res, []int{intervalStart, have})
+            have = -1
+            intervalStart = -1
+        }
+    }
+
+    if intervalStart != -1 {
+        res = append(res, []int{intervalStart, have})
+    }
+
+    return res
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun merge(intervals: Array<IntArray>): Array<IntArray> {
+        var maxVal = Int.MIN_VALUE
+        for (interval in intervals) {
+            maxVal = maxOf(maxVal, interval[0])
+        }
+
+        val mp = IntArray(maxVal + 1)
+        for (interval in intervals) {
+            val (start, end) = interval
+            mp[start] = maxOf(mp[start], end + 1)
+        }
+
+        val res = mutableListOf<IntArray>()
+        var have = -1
+        var intervalStart = -1
+        for (i in mp.indices) {
+            if (mp[i] != 0) {
+                if (intervalStart == -1) {
+                    intervalStart = i
+                }
+                have = maxOf(mp[i] - 1, have)
+            }
+            if (have == i) {
+                res.add(intArrayOf(intervalStart, have))
+                have = -1
+                intervalStart = -1
+            }
+        }
+
+        if (intervalStart != -1) {
+            res.add(intArrayOf(intervalStart, have))
+        }
+
+        return res.toTypedArray()
+    }
+}
+```
+
+```swift
+class Solution {
+    func merge(_ intervals: [[Int]]) -> [[Int]] {
+        let maxVal = intervals.map { $0[0] }.max() ?? 0
+        var mp = [Int](repeating: 0, count: maxVal + 1)
+        for interval in intervals {
+            let start = interval[0]
+            let end = interval[1]
+            mp[start] = max(end + 1, mp[start])
+        }
+
+        var res = [[Int]]()
+        var have = -1
+        var intervalStart = -1
+
+        for i in 0..<mp.count {
+            if mp[i] != 0 {
+                if intervalStart == -1 {
+                    intervalStart = i
+                }
+                have = max(mp[i] - 1, have)
+            }
+            if have == i {
+                res.append([intervalStart, have])
+                have = -1
+                intervalStart = -1
+            }
+        }
+
+        if intervalStart != -1 {
+            res.append([intervalStart, have])
+        }
+
+        return res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the length of the array and $m$ is the maximum start value among all the intervals.
\ No newline at end of file
diff --git a/articles/merge-k-sorted-linked-lists.md b/articles/merge-k-sorted-linked-lists.md
index b702a5a11..6150fa6f5 100644
--- a/articles/merge-k-sorted-linked-lists.md
+++ b/articles/merge-k-sorted-linked-lists.md
@@ -168,6 +168,113 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func mergeKLists(lists []*ListNode) *ListNode {
+    nodes := make([]int, 0)
+    
+    for _, list := range lists {
+        curr := list
+        for curr != nil {
+            nodes = append(nodes, curr.Val)
+            curr = curr.Next
+        }
+    }
+    
+    sort.Ints(nodes)
+    
+    dummy := &ListNode{Val: 0}
+    curr := dummy
+    
+    for _, val := range nodes {
+        curr.Next = &ListNode{Val: val}
+        curr = curr.Next
+    }
+    
+    return dummy.Next
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var li = ListNode(5)
+ * var v = li.`val`
+ * Definition for singly-linked list.
+ * class ListNode(var `val`: Int) {
+ *     var next: ListNode? = null
+ * }
+ */
+class Solution {
+    fun mergeKLists(lists: Array<ListNode?>): ListNode? {
+        val nodes = mutableListOf<Int>()
+        
+        for (list in lists) {
+            var curr = list
+            while (curr != null) {
+                nodes.add(curr.`val`)
+                curr = curr.next
+            }
+        }
+        
+        nodes.sort()
+        
+        val dummy = ListNode(0)
+        var curr = dummy
+        
+        for (value in nodes) {
+            curr.next = ListNode(value)
+            curr = curr.next!!
+        }
+        
+        return dummy.next
+    }
+}
+```
+
+```swift
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public var val: Int
+ *     public var next: ListNode?
+ *     public init() { self.val = 0; self.next = nil; }
+ *     public init(_ val: Int) { self.val = val; self.next = nil; }
+ *     public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
+ * }
+ */
+class Solution {
+    func mergeKLists(_ lists: [ListNode?]) -> ListNode? {
+        var nodes: [Int] = []
+
+        for list in lists {
+            var lst = list
+            while lst != nil {
+                nodes.append(lst!.val)
+                lst = lst?.next
+            }
+        }
+
+        nodes.sort()
+
+        let dummy = ListNode(0)
+        var cur = dummy
+        for node in nodes {
+            cur.next = ListNode(node)
+            cur = cur.next!
+        }
+
+        return dummy.next
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -364,6 +471,123 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func mergeKLists(lists []*ListNode) *ListNode {
+    res := &ListNode{Val: 0}
+    cur := res
+    
+    for {
+        minNode := -1
+        for i := range lists {
+            if lists[i] == nil {
+                continue
+            }
+            if minNode == -1 || lists[minNode].Val > lists[i].Val {
+                minNode = i
+            }
+        }
+        
+        if minNode == -1 {
+            break
+        }
+        
+        cur.Next = lists[minNode]
+        lists[minNode] = lists[minNode].Next
+        cur = cur.Next
+    }
+    
+    return res.Next
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var li = ListNode(5)
+ * var v = li.`val`
+ * Definition for singly-linked list.
+ * class ListNode(var `val`: Int) {
+ *     var next: ListNode? = null
+ * }
+ */
+class Solution {
+    fun mergeKLists(lists: Array<ListNode?>): ListNode? {
+        val res = ListNode(0)
+        var cur = res
+        
+        while (true) {
+            var minNode = -1
+            for (i in lists.indices) {
+                if (lists[i] == null) {
+                    continue
+                }
+                if (minNode == -1 || lists[minNode]!!.`val` > lists[i]!!.`val`) {
+                    minNode = i
+                }
+            }
+            
+            if (minNode == -1) {
+                break
+            }
+            
+            cur.next = lists[minNode]
+            lists[minNode] = lists[minNode]!!.next
+            cur = cur.next!!
+        }
+        
+        return res.next
+    }
+}
+```
+
+```swift
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public var val: Int
+ *     public var next: ListNode?
+ *     public init() { self.val = 0; self.next = nil; }
+ *     public init(_ val: Int) { self.val = val; self.next = nil; }
+ *     public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
+ * }
+ */
+class Solution {
+    func mergeKLists(_ lists: [ListNode?]) -> ListNode? {
+        var lists = lists
+        let dummy = ListNode(0)
+        var cur = dummy
+
+        while true {
+            var minNodeIndex: Int? = nil
+            for i in 0..<lists.count {
+                if let node = lists[i] {
+                    if minNodeIndex == nil || node.val < lists[minNodeIndex!]?.val ?? Int.max {
+                        minNodeIndex = i
+                    }
+                }
+            }
+
+            if minNodeIndex == nil {
+                break
+            }
+            
+            cur.next = lists[minNodeIndex!]
+            lists[minNodeIndex!] = lists[minNodeIndex!]?.next
+            cur = cur.next!
+        }
+
+        return dummy.next
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -618,6 +842,157 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func mergeList(l1 *ListNode, l2 *ListNode) *ListNode {
+    dummy := &ListNode{}
+    tail := dummy
+    
+    for l1 != nil && l2 != nil {
+        if l1.Val < l2.Val {
+            tail.Next = l1
+            l1 = l1.Next
+        } else {
+            tail.Next = l2
+            l2 = l2.Next
+        }
+        tail = tail.Next
+    }
+    
+    if l1 != nil {
+        tail.Next = l1
+    }
+    if l2 != nil {
+        tail.Next = l2
+    }
+    
+    return dummy.Next
+}
+
+func mergeKLists(lists []*ListNode) *ListNode {
+    if len(lists) == 0 {
+        return nil
+    }
+    
+    for i := 1; i < len(lists); i++ {
+        lists[i] = mergeList(lists[i-1], lists[i])
+    }
+    
+    return lists[len(lists)-1]
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var li = ListNode(5)
+ * var v = li.`val`
+ * Definition for singly-linked list.
+ * class ListNode(var `val`: Int) {
+ *     var next: ListNode? = null
+ * }
+ */
+class Solution {
+    private fun mergeList(l1: ListNode?, l2: ListNode?): ListNode? {
+        val dummy = ListNode(0)
+        var tail = dummy
+        var first = l1
+        var second = l2
+        
+        while (first != null && second != null) {
+            if (first.`val` < second.`val`) {
+                tail.next = first
+                first = first.next
+            } else {
+                tail.next = second
+                second = second.next
+            }
+            tail = tail.next!!
+        }
+        
+        if (first != null) {
+            tail.next = first
+        }
+        if (second != null) {
+            tail.next = second
+        }
+        
+        return dummy.next
+    }
+    
+    fun mergeKLists(lists: Array<ListNode?>): ListNode? {
+        if (lists.isEmpty()) {
+            return null
+        }
+        
+        for (i in 1 until lists.size) {
+            lists[i] = mergeList(lists[i-1], lists[i])
+        }
+        
+        return lists.last()
+    }
+}
+```
+
+```swift
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public var val: Int
+ *     public var next: ListNode?
+ *     public init() { self.val = 0; self.next = nil; }
+ *     public init(_ val: Int) { self.val = val; self.next = nil; }
+ *     public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
+ * }
+ */
+class Solution {
+    func mergeKLists(_ lists: [ListNode?]) -> ListNode? {
+        if lists.isEmpty {
+            return nil
+        }
+
+        var lists = lists
+        for i in 1..<lists.count {
+            lists[i] = mergeList(lists[i - 1], lists[i])
+        }
+
+        return lists.last!
+    }
+
+    private func mergeList(_ l1: ListNode?, _ l2: ListNode?) -> ListNode? {
+        let dummy = ListNode(0)
+        var tail = dummy
+        var l1 = l1, l2 = l2
+
+        while l1 != nil && l2 != nil {
+            if l1!.val < l2!.val {
+                tail.next = l1
+                l1 = l1?.next
+            } else {
+                tail.next = l2
+                l2 = l2?.next
+            }
+            tail = tail.next!
+        }
+
+        if l1 != nil {
+            tail.next = l1
+        }
+        if l2 != nil {
+            tail.next = l2
+        }
+        
+        return dummy.next
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -837,6 +1212,136 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func mergeKLists(lists []*ListNode) *ListNode {
+    if len(lists) == 0 {
+        return nil
+    }
+    
+    minHeap := priorityqueue.NewWith(func(a, b interface{}) int {
+        return a.(*ListNode).Val - b.(*ListNode).Val
+    })
+    
+    for _, list := range lists {
+        if list != nil {
+            minHeap.Enqueue(list)
+        }
+    }
+    
+    res := &ListNode{Val: 0}
+    cur := res
+    
+    for !minHeap.Empty() {
+        node, _ := minHeap.Dequeue()
+        cur.Next = node.(*ListNode)
+        cur = cur.Next
+        
+        if cur.Next != nil {
+            minHeap.Enqueue(cur.Next)
+        }
+    }
+    
+    return res.Next
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var li = ListNode(5)
+ * var v = li.`val`
+ * Definition for singly-linked list.
+ * class ListNode(var `val`: Int) {
+ *     var next: ListNode? = null
+ * }
+ */
+class Solution {
+    fun mergeKLists(lists: Array<ListNode?>): ListNode? {
+        if (lists.isEmpty()) return null
+        
+        val minHeap = PriorityQueue<ListNode>(compareBy { it.`val` })
+        
+        for (list in lists) {
+            list?.let { minHeap.offer(it) }
+        }
+        
+        val res = ListNode(0)
+        var cur = res
+        
+        while (minHeap.isNotEmpty()) {
+            val node = minHeap.poll()
+            cur.next = node
+            cur = cur.next!!
+            
+            node.next?.let { minHeap.offer(it) }
+        }
+        
+        return res.next
+    }
+}
+```
+
+```swift
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public var val: Int
+ *     public var next: ListNode?
+ *     public init() { self.val = 0; self.next = nil; }
+ *     public init(_ val: Int) { self.val = val; self.next = nil; }
+ *     public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
+ * }
+ */
+struct NodeWrapper: Comparable {
+    let node: ListNode
+
+    init(_ node: ListNode) {
+        self.node = node
+    }
+
+    static func < (lhs: NodeWrapper, rhs: NodeWrapper) -> Bool {
+        return lhs.node.val < rhs.node.val
+    }
+
+    static func == (lhs: NodeWrapper, rhs: NodeWrapper) -> Bool {
+        return lhs.node.val == rhs.node.val
+    }
+}
+
+class Solution {
+    func mergeKLists(_ lists: [ListNode?]) -> ListNode? {
+        var heap = Heap<NodeWrapper>()
+
+        for list in lists {
+            if let node = list {
+                heap.insert(NodeWrapper(node))
+            }
+        }
+
+        let dummy = ListNode(0)
+        var tail = dummy
+
+        while let wrapper = heap.popMin() {
+            tail.next = wrapper.node
+            tail = tail.next!
+
+            if let next = wrapper.node.next {
+                heap.insert(NodeWrapper(next))
+            }
+        }
+
+        return dummy.next
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -870,14 +1375,17 @@ class Solution:
             return None
         if l == r:
             return lists[l]
+
         mid = l + (r - l) // 2
         left = self.divide(lists, l, mid)
         right = self.divide(lists, mid + 1, r)
+
         return self.conquer(left, right)
 
     def conquer(self, l1, l2):
         dummy = ListNode(0)
         curr = dummy
+
         while l1 and l2:
             if l1.val <= l2.val:
                 curr.next = l1
@@ -886,10 +1394,12 @@ class Solution:
                 curr.next = l2
                 l2 = l2.next
             curr = curr.next
+
         if l1:
             curr.next = l1
         else:
             curr.next = l2
+
         return dummy.next
 ```
 
@@ -920,9 +1430,11 @@ class Solution {
         if (l == r) {
             return lists[l];
         }
+
         int mid = l + (r - l) / 2; 
         ListNode left = divide(lists, l, mid);
         ListNode right = divide(lists, mid + 1, r);
+
         return conquer(left, right);
     }
 
@@ -982,15 +1494,18 @@ private:
         if (l == r) {
             return lists[l];
         }
+
         int mid = l + (r - l) / 2;
         ListNode* left = divide(lists, l, mid);
         ListNode* right = divide(lists, mid + 1, r);
+
         return conquer(left, right);
     }
 
     ListNode* conquer(ListNode* l1, ListNode* l2) {
         ListNode dummy(0);
         ListNode* curr = &dummy;
+
         while (l1 && l2) {
             if (l1->val <= l2->val) {
                 curr->next = l1;
@@ -1001,11 +1516,13 @@ private:
             }
             curr = curr->next;
         }
+
         if (l1) {
             curr->next = l1;
         } else {
             curr->next = l2;
         }
+
         return dummy.next;
     }
 };
@@ -1047,9 +1564,11 @@ class Solution {
         if (l === r) {
             return lists[l];
         }
+
         const mid = Math.floor(l + (r - l) / 2);
         const left = this.divide(lists, l, mid);
         const right = this.divide(lists, mid + 1, r);
+
         return this.conquer(left, right);
     }
 
@@ -1061,6 +1580,7 @@ class Solution {
     conquer(l1, l2) {
         const dummy = new ListNode(0);
         let curr = dummy;
+
         while (l1 && l2) {
             if (l1.val <= l2.val) {
                 curr.next = l1;
@@ -1071,6 +1591,7 @@ class Solution {
             }
             curr = curr.next;
         }
+
         curr.next = l1 ? l1 : l2;
         return dummy.next;
     }
@@ -1105,9 +1626,11 @@ public class Solution {
         if (l == r) {
             return lists[l];
         }
+
         int mid = l + (r - l) / 2;
         ListNode left = Divide(lists, l, mid);
         ListNode right = Divide(lists, mid + 1, r);
+
         return Conquer(left, right);
     }
 
@@ -1137,6 +1660,166 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func mergeKLists(lists []*ListNode) *ListNode {
+    if len(lists) == 0 {
+        return nil
+    }
+    return divide(lists, 0, len(lists)-1)
+}
+
+func divide(lists []*ListNode, left, right int) *ListNode {
+    if left > right {
+        return nil
+    }
+    if left == right {
+        return lists[left]
+    }
+
+    mid := left + (right-left)/2
+    l1 := divide(lists, left, mid)
+    l2 := divide(lists, mid+1, right)
+
+    return conquer(l1, l2)
+}
+
+func conquer(l1, l2 *ListNode) *ListNode {
+    dummy := &ListNode{}
+    curr := dummy
+
+    for l1 != nil && l2 != nil {
+        if l1.Val <= l2.Val {
+            curr.Next = l1
+            l1 = l1.Next
+        } else {
+            curr.Next = l2
+            l2 = l2.Next
+        }
+        curr = curr.Next
+    }
+
+    if l1 != nil {
+        curr.Next = l1
+    } else {
+        curr.Next = l2
+    }
+
+    return dummy.Next
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var li = ListNode(5)
+ * var v = li.`val`
+ * Definition for singly-linked list.
+ * class ListNode(var `val`: Int) {
+ *     var next: ListNode? = null
+ * }
+ */
+class Solution {
+    fun mergeKLists(lists: Array<ListNode?>): ListNode? {
+        if (lists.isEmpty()) return null
+        return divide(lists, 0, lists.size - 1)
+    }
+
+    private fun divide(lists: Array<ListNode?>, left: Int, right: Int): ListNode? {
+        if (left > right) return null
+        if (left == right) return lists[left]
+
+        val mid = left + (right - left) / 2
+        val l1 = divide(lists, left, mid)
+        val l2 = divide(lists, mid + 1, right)
+
+        return conquer(l1, l2)
+    }
+
+    private fun conquer(l1: ListNode?, l2: ListNode?): ListNode? {
+        val dummy = ListNode(0)
+        var curr = dummy
+        var list1 = l1
+        var list2 = l2
+
+        while (list1 != null && list2 != null) {
+            if (list1.`val` <= list2.`val`) {
+                curr.next = list1
+                list1 = list1.next
+            } else {
+                curr.next = list2
+                list2 = list2.next
+            }
+            curr = curr.next!!
+        }
+
+        curr.next = list1 ?: list2
+        return dummy.next
+    }
+}
+```
+
+```swift
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public var val: Int
+ *     public var next: ListNode?
+ *     public init() { self.val = 0; self.next = nil; }
+ *     public init(_ val: Int) { self.val = val; self.next = nil; }
+ *     public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
+ * }
+ */
+class Solution {
+    func mergeKLists(_ lists: [ListNode?]) -> ListNode? {
+        if lists.isEmpty {
+            return nil
+        }
+        return divide(lists, 0, lists.count - 1)
+    }
+
+    private func divide(_ lists: [ListNode?], _ l: Int, _ r: Int) -> ListNode? {
+        if l > r {
+            return nil
+        }
+        if l == r {
+            return lists[l]
+        }
+        
+        let mid = l + (r - l) / 2
+        let left = divide(lists, l, mid)
+        let right = divide(lists, mid + 1, r)
+        return conquer(left, right)
+    }
+
+    private func conquer(_ l1: ListNode?, _ l2: ListNode?) -> ListNode? {
+        let dummy = ListNode(0)
+        var curr = dummy
+        var l1 = l1, l2 = l2
+
+        while let node1 = l1, let node2 = l2 {
+            if node1.val <= node2.val {
+                curr.next = node1
+                l1 = node1.next
+            } else {
+                curr.next = node2
+                l2 = node2.next
+            }
+            curr = curr.next!
+        }
+
+        curr.next = l1 ?? l2
+        return dummy.next
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -1186,10 +1869,12 @@ class Solution:
                 tail.next = l2
                 l2 = l2.next
             tail = tail.next
+
         if l1:
             tail.next = l1
         if l2:
             tail.next = l2
+
         return dummy.next
 ```
 
@@ -1237,12 +1922,14 @@ public class Solution {
             }
             tail = tail.next;
         }
+
         if (l1 != null) {
             tail.next = l1;
         }
         if (l2 != null) {
             tail.next = l2;
         }
+
         return dummy.next;
     }
 }
@@ -1294,12 +1981,14 @@ private:
             }
             tail = tail->next;
         }
+
         if (l1) {
             tail->next = l1;
         }
         if (l2) {
             tail->next = l2;
         }
+
         return dummy.next;
     }
 };
@@ -1346,6 +2035,7 @@ class Solution {
     mergeList(l1, l2) {
         const dummy = new ListNode(0);
         let curr = dummy;
+
         while (l1 && l2) {
             if (l1.val <= l2.val) {
                 curr.next = l1;
@@ -1356,6 +2046,7 @@ class Solution {
             }
             curr = curr.next;
         }
+
         curr.next = l1 ? l1 : l2;
         return dummy.next;
     }
@@ -1407,17 +2098,178 @@ public class Solution {
             }
             tail = tail.next;
         }
+
         if (l1 != null) {
             tail.next = l1;
         }
         if (l2 != null) {
             tail.next = l2;
         }
+
         return dummy.next;
     }
 }
 ```
 
+```go
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func mergeKLists(lists []*ListNode) *ListNode {
+    if len(lists) == 0 {
+        return nil
+    }
+
+    for len(lists) > 1 {
+        var mergedLists []*ListNode
+        for i := 0; i < len(lists); i += 2 {
+            l1 := lists[i]
+            var l2 *ListNode
+            if i+1 < len(lists) {
+                l2 = lists[i+1]
+            }
+            mergedLists = append(mergedLists, mergeList(l1, l2))
+        }
+        lists = mergedLists
+    }
+    return lists[0]
+}
+
+func mergeList(l1, l2 *ListNode) *ListNode {
+    dummy := &ListNode{}
+    tail := dummy
+
+    for l1 != nil && l2 != nil {
+        if l1.Val < l2.Val {
+            tail.Next = l1
+            l1 = l1.Next
+        } else {
+            tail.Next = l2
+            l2 = l2.Next
+        }
+        tail = tail.Next
+    }
+
+    if l1 != nil {
+        tail.Next = l1
+    } else {
+        tail.Next = l2
+    }
+
+    return dummy.Next
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var li = ListNode(5)
+ * var v = li.`val`
+ * Definition for singly-linked list.
+ * class ListNode(var `val`: Int) {
+ *     var next: ListNode? = null
+ * }
+ */
+class Solution {
+    fun mergeKLists(lists: Array<ListNode?>): ListNode? {
+        if (lists.isEmpty()) return null
+
+        var currentLists = lists.toList()
+        while (currentLists.size > 1) {
+            val mergedLists = mutableListOf<ListNode?>()
+            for (i in currentLists.indices step 2) {
+                val l1 = currentLists[i]
+                val l2 = if (i + 1 < currentLists.size) currentLists[i + 1] else null
+                mergedLists.add(mergeList(l1, l2))
+            }
+            currentLists = mergedLists
+        }
+        return currentLists[0]
+    }
+
+    private fun mergeList(l1: ListNode?, l2: ListNode?): ListNode? {
+        val dummy = ListNode(0)
+        var tail = dummy
+        var list1 = l1
+        var list2 = l2
+
+        while (list1 != null && list2 != null) {
+            if (list1.`val` < list2.`val`) {
+                tail.next = list1
+                list1 = list1.next
+            } else {
+                tail.next = list2
+                list2 = list2.next
+            }
+            tail = tail.next!!
+        }
+
+        tail.next = list1 ?: list2
+        return dummy.next
+    }
+}
+```
+
+```swift
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public var val: Int
+ *     public var next: ListNode?
+ *     public init() { self.val = 0; self.next = nil; }
+ *     public init(_ val: Int) { self.val = val; self.next = nil; }
+ *     public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
+ * }
+ */
+class Solution {
+    func mergeKLists(_ lists: [ListNode?]) -> ListNode? {
+        if lists.isEmpty {
+            return nil
+        }
+        
+        var lists = lists
+        
+        while lists.count > 1 {
+            var mergedLists: [ListNode?] = []
+            
+            for i in stride(from: 0, to: lists.count, by: 2) {
+                let l1 = lists[i]
+                let l2 = i + 1 < lists.count ? lists[i + 1] : nil
+                mergedLists.append(mergeList(l1, l2))
+            }
+            
+            lists = mergedLists
+        }
+        
+        return lists[0]
+    }
+
+    private func mergeList(_ l1: ListNode?, _ l2: ListNode?) -> ListNode? {
+        let dummy = ListNode(0)
+        var tail = dummy
+        var l1 = l1, l2 = l2
+
+        while let node1 = l1, let node2 = l2 {
+            if node1.val < node2.val {
+                tail.next = node1
+                l1 = node1.next
+            } else {
+                tail.next = node2
+                l2 = node2.next
+            }
+            tail = tail.next!
+        }
+
+        tail.next = l1 ?? l2
+        return dummy.next
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/merge-sorted-array.md b/articles/merge-sorted-array.md
new file mode 100644
index 000000000..a0e701ef0
--- /dev/null
+++ b/articles/merge-sorted-array.md
@@ -0,0 +1,448 @@
+## 1. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def merge(self, nums1: List[int], m: int, nums2: List[int], n: int) -> None:
+        """
+        Do not return anything, modify nums1 in-place instead.
+        """
+        nums1[m:] = nums2[:n]
+        nums1.sort()
+```
+
+```java
+public class Solution {
+    public void merge(int[] nums1, int m, int[] nums2, int n) {
+        for (int i = 0; i < n; i++) {
+            nums1[i + m] = nums2[i];
+        }
+        Arrays.sort(nums1);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void merge(vector<int>& nums1, int m, vector<int>& nums2, int n) {
+        for (int i = 0; i < n; i++) {
+            nums1[i + m] = nums2[i];
+        }
+        sort(nums1.begin(), nums1.end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums1
+     * @param {number} m
+     * @param {number[]} nums2
+     * @param {number} n
+     * @return {void} Do not return anything, modify nums1 in-place instead.
+     */
+    merge(nums1, m, nums2, n) {
+        for (let i = 0; i < n; i++) {
+            nums1[i + m] = nums2[i];
+        }
+        nums1.sort((a, b) => a - b);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public void Merge(int[] nums1, int m, int[] nums2, int n) {
+        for (int i = 0; i < n; i++) {
+            nums1[i + m] = nums2[i];
+        }
+        Array.Sort(nums1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O((m + n) \log (m + n))$
+* Space complexity: $O(1)$ or $O(m + n)$ depending on the sorting algorithm.
+
+> Where $m$ and $n$ represent the number of elements in the arrays $nums1$ and $nums2$, respectively.
+
+---
+
+## 2. Three Pointers With Extra Space
+
+::tabs-start
+
+```python
+class Solution:
+    def merge(self, nums1: List[int], m: int, nums2: List[int], n: int) -> None:
+        """
+        Do not return anything, modify nums1 in-place instead.
+        """
+        nums1_copy = nums1[:m]
+        idx = 0
+        i = j = 0
+        while idx < m + n:
+            if j >= n or (i < m and nums1_copy[i] <= nums2[j]):
+                nums1[idx] = nums1_copy[i]
+                i += 1
+            else:
+                nums1[idx] = nums2[j]
+                j += 1
+            idx += 1
+```
+
+```java
+public class Solution {
+    public void merge(int[] nums1, int m, int[] nums2, int n) {
+        int[] nums1Copy = Arrays.copyOf(nums1, m);
+        int idx = 0, i = 0, j = 0;
+        
+        while (idx < m + n) {
+            if (j >= n || (i < m && nums1Copy[i] <= nums2[j])) {
+                nums1[idx++] = nums1Copy[i++];
+            } else {
+                nums1[idx++] = nums2[j++];
+            }
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void merge(vector<int>& nums1, int m, vector<int>& nums2, int n) {
+        vector<int> nums1Copy(nums1.begin(), nums1.begin() + m);
+        int idx = 0, i = 0, j = 0;
+        
+        while (idx < m + n) {
+            if (j >= n || (i < m && nums1Copy[i] <= nums2[j])) {
+                nums1[idx++] = nums1Copy[i++];
+            } else {
+                nums1[idx++] = nums2[j++];
+            }
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums1
+     * @param {number} m
+     * @param {number[]} nums2
+     * @param {number} n
+     * @return {void} Do not return anything, modify nums1 in-place instead.
+     */
+    merge(nums1, m, nums2, n) {
+        const nums1Copy = nums1.slice(0, m);
+        let idx = 0, i = 0, j = 0;
+
+        while (idx < m + n) {
+            if (j >= n || (i < m && nums1Copy[i] <= nums2[j])) {
+                nums1[idx++] = nums1Copy[i++];
+            } else {
+                nums1[idx++] = nums2[j++];
+            }
+        }
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public void Merge(int[] nums1, int m, int[] nums2, int n) {
+        int[] nums1Copy = new int[m];
+        Array.Copy(nums1, nums1Copy, m);
+
+        int idx = 0, i = 0, j = 0;
+
+        while (idx < m + n) {
+            if (j >= n || (i < m && nums1Copy[i] <= nums2[j])) {
+                nums1[idx++] = nums1Copy[i++];
+            } else {
+                nums1[idx++] = nums2[j++];
+            }
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m + n)$
+* Space complexity: $O(m)$
+
+> Where $m$ and $n$ represent the number of elements in the arrays $nums1$ and $nums2$, respectively.
+
+---
+
+## 3. Three Pointers Without Extra Space - I
+
+::tabs-start
+
+```python
+class Solution:
+    def merge(self, nums1: list[int], m: int, nums2: list[int], n: int) -> None:
+        """
+        Do not return anything, modify nums1 in-place instead.
+        """
+        last = m + n - 1
+
+        # Merge in reverse order
+        while m > 0 and n > 0:
+            if nums1[m - 1] > nums2[n - 1]:
+                nums1[last] = nums1[m - 1]
+                m -= 1
+            else:
+                nums1[last] = nums2[n - 1]
+                n -= 1
+            last -= 1
+
+        # Fill nums1 with leftover nums2 elements
+        while n > 0:
+            nums1[last] = nums2[n - 1]
+            n -= 1
+            last -= 1
+```
+
+```java
+public class Solution {
+    public void merge(int[] nums1, int m, int[] nums2, int n) {
+        int last = m + n - 1;
+
+        // Merge in reverse order
+        while (m > 0 && n > 0) {
+            if (nums1[m - 1] > nums2[n - 1]) {
+                nums1[last] = nums1[m - 1];
+                m--;
+            } else {
+                nums1[last] = nums2[n - 1];
+                n--;
+            }
+            last--;
+        }
+
+        // Fill nums1 with leftover nums2 elements
+        while (n > 0) {
+            nums1[last] = nums2[n - 1];
+            n--;
+            last--;
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void merge(vector<int>& nums1, int m, vector<int>& nums2, int n) {
+        int last = m + n - 1;
+
+        // Merge in reverse order
+        while (m > 0 && n > 0) {
+            if (nums1[m - 1] > nums2[n - 1]) {
+                nums1[last] = nums1[m - 1];
+                m--;
+            } else {
+                nums1[last] = nums2[n - 1];
+                n--;
+            }
+            last--;
+        }
+
+        // Fill nums1 with leftover nums2 elements
+        while (n > 0) {
+            nums1[last] = nums2[n - 1];
+            n--;
+            last--;
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums1
+     * @param {number} m
+     * @param {number[]} nums2
+     * @param {number} n
+     * @return {void} Do not return anything, modify nums1 in-place instead.
+     */
+    merge(nums1, m, nums2, n) {
+        let last = m + n - 1;
+
+        // Merge in reverse order
+        while (m > 0 && n > 0) {
+            if (nums1[m - 1] > nums2[n - 1]) {
+                nums1[last--] = nums1[m-- - 1];
+            } else {
+                nums1[last--] = nums2[n-- - 1];
+            }
+        }
+
+        // Fill nums1 with leftover nums2 elements
+        while (n > 0) {
+            nums1[last--] = nums2[n-- - 1];
+        }
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public void Merge(int[] nums1, int m, int[] nums2, int n) {
+        int last = m + n - 1;
+
+        // Merge in reverse order
+        while (m > 0 && n > 0) {
+            if (nums1[m - 1] > nums2[n - 1]) {
+                nums1[last] = nums1[m - 1];
+                m--;
+            } else {
+                nums1[last] = nums2[n - 1];
+                n--;
+            }
+            last--;
+        }
+
+        // Fill nums1 with leftover nums2 elements
+        while (n > 0) {
+            nums1[last] = nums2[n - 1];
+            n--;
+            last--;
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m + n)$
+* Space complexity: $O(1)$ extra space.
+
+> Where $m$ and $n$ represent the number of elements in the arrays $nums1$ and $nums2$, respectively.
+
+---
+
+## 4. Three Pointers Without Extra Space - II
+
+::tabs-start
+
+```python
+class Solution:
+    def merge(self, nums1: list[int], m: int, nums2: list[int], n: int) -> None:
+        """
+        Do not return anything, modify nums1 in-place instead.
+        """
+        last = m + n - 1
+        i, j = m - 1, n - 1
+
+        while j >= 0:
+            if i >= 0 and nums1[i] > nums2[j]:
+                nums1[last] = nums1[i]
+                i -= 1
+            else:
+                nums1[last] = nums2[j]
+                j -= 1
+                
+            last -= 1 
+```
+
+```java
+public class Solution {
+    public void merge(int[] nums1, int m, int[] nums2, int n) {
+        int last = m + n - 1;
+        int i = m - 1, j = n - 1;
+
+        while (j >= 0) {
+            if (i >= 0 && nums1[i] > nums2[j]) {
+                nums1[last--] = nums1[i--];
+            } else {
+                nums1[last--] = nums2[j--];
+            }
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void merge(vector<int>& nums1, int m, vector<int>& nums2, int n) {
+        int last = m + n - 1;
+        int i = m - 1, j = n - 1;
+
+        while (j >= 0) {
+            if (i >= 0 && nums1[i] > nums2[j]) {
+                nums1[last--] = nums1[i--];
+            } else {
+                nums1[last--] = nums2[j--];
+            }
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums1
+     * @param {number} m
+     * @param {number[]} nums2
+     * @param {number} n
+     * @return {void} Do not return anything, modify nums1 in-place instead.
+     */
+    merge(nums1, m, nums2, n) {
+        let last = m + n - 1;
+        let i = m - 1, j = n - 1;
+
+        while (j >= 0) {
+            if (i >= 0 && nums1[i] > nums2[j]) {
+                nums1[last--] = nums1[i--];
+            } else {
+                nums1[last--] = nums2[j--];
+            }
+        }
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public void Merge(int[] nums1, int m, int[] nums2, int n) {
+        int last = m + n - 1;
+        int i = m - 1, j = n - 1;
+
+        while (j >= 0) {
+            if (i >= 0 && nums1[i] > nums2[j]) {
+                nums1[last--] = nums1[i--];
+            } else {
+                nums1[last--] = nums2[j--];
+            }
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m + n)$
+* Space complexity: $O(1)$ extra space.
+
+> Where $m$ and $n$ represent the number of elements in the arrays $nums1$ and $nums2$, respectively.
\ No newline at end of file
diff --git a/articles/merge-strings-alternately.md b/articles/merge-strings-alternately.md
new file mode 100644
index 000000000..d61a657cd
--- /dev/null
+++ b/articles/merge-strings-alternately.md
@@ -0,0 +1,314 @@
+## 1. Two Pointers - I
+
+::tabs-start
+
+```python
+class Solution:
+    def mergeAlternately(self, word1: str, word2: str) -> str:
+        i, j = 0, 0
+        res = []
+        while i < len(word1) and j < len(word2):
+            res.append(word1[i])
+            res.append(word2[j])
+            i += 1
+            j += 1
+        res.append(word1[i:])
+        res.append(word2[j:])
+        return "".join(res)
+```
+
+```java
+public class Solution {
+    public String mergeAlternately(String word1, String word2) {
+        StringBuilder res = new StringBuilder();
+        int i = 0, j = 0;
+        while (i < word1.length() && j < word2.length()) {
+            res.append(word1.charAt(i++));
+            res.append(word2.charAt(j++));
+        }
+        res.append(word1.substring(i));
+        res.append(word2.substring(j));
+        return res.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string mergeAlternately(string word1, string word2) {
+        string res;
+        int i = 0, j = 0;
+        while (i < word1.size() && j < word2.size()) {
+            res += word1[i++];
+            res += word2[j++];
+        }
+        res += word1.substr(i);
+        res += word2.substr(j);
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} word1
+     * @param {string} word2
+     * @return {string}
+     */
+    mergeAlternately(word1, word2) {
+        let res = [];
+        let i = 0, j = 0;
+        while (i < word1.length && j < word2.length) {
+            res.push(word1[i++], word2[j++]);
+        }
+        res.push(word1.slice(i));
+        res.push(word2.slice(j));
+        return res.join("");
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public string MergeAlternately(string word1, string word2) {
+        int i = 0, j = 0;
+        StringBuilder res = new StringBuilder();
+
+        while (i < word1.Length && j < word2.Length) {
+            res.Append(word1[i]);
+            res.Append(word2[j]);
+            i++;
+            j++;
+        }
+
+        res.Append(word1.Substring(i));
+        res.Append(word2.Substring(j));
+
+        return res.ToString();
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(n + m)$ for the output string.
+
+> Where $n$ and $m$ are the lengths of the strings $word1$ and $word2$ respectively.
+
+---
+
+## 2. Two Pointers - II
+
+::tabs-start
+
+```python
+class Solution:
+    def mergeAlternately(self, word1: str, word2: str) -> str:
+        n, m = len(word1), len(word2)
+        res = []
+        i = j = 0
+        while i < n or j < m:
+            if i < n:
+                res.append(word1[i])
+            if j < m:
+                res.append(word2[j])
+            i += 1
+            j += 1
+        return "".join(res)
+```
+
+```java
+public class Solution {
+    public String mergeAlternately(String word1, String word2) {
+        int n = word1.length(), m = word2.length();
+        StringBuilder res = new StringBuilder();
+        int i = 0, j = 0;
+        while (i < n || j < m) {
+            if (i < n) res.append(word1.charAt(i++));
+            if (j < m) res.append(word2.charAt(j++));
+        }
+        return res.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string mergeAlternately(string word1, string word2) {
+        int n = word1.size(), m = word2.size();
+        string res;
+        int i = 0, j = 0;
+        while (i < n || j < m) {
+            if (i < n) res += word1[i++];
+            if (j < m) res += word2[j++];
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} word1
+     * @param {string} word2
+     * @return {string}
+     */
+    mergeAlternately(word1, word2) {
+        const n = word1.length, m = word2.length;
+        const res = [];
+        let i = 0, j = 0;
+        while (i < n || j < m) {
+            if (i < n) res.push(word1[i++]);
+            if (j < m) res.push(word2[j++]);
+        }
+        return res.join("");
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public string MergeAlternately(string word1, string word2) {
+        int n = word1.Length, m = word2.Length;
+        int i = 0, j = 0;
+        StringBuilder res = new StringBuilder();
+
+        while (i < n || j < m) {
+            if (i < n) {
+                res.Append(word1[i]);
+            }
+            if (j < m) {
+                res.Append(word2[j]);
+            }
+            i++;
+            j++;
+        }
+
+        return res.ToString();
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(n + m)$ for the output string.
+
+> Where $n$ and $m$ are the lengths of the strings $word1$ and $word2$ respectively.
+
+---
+
+## 3. One Pointer
+
+::tabs-start
+
+```python
+class Solution:
+    def mergeAlternately(self, word1: str, word2: str) -> str:
+        n, m = len(word1), len(word2)
+        res = []
+        for i in range(max(m, n)):
+            if i < n:
+                res.append(word1[i])
+            if i < m:
+                res.append(word2[i])
+        return "".join(res)
+```
+
+```java
+public class Solution {
+    public String mergeAlternately(String word1, String word2) {
+        int n = word1.length(), m = word2.length();
+        StringBuilder res = new StringBuilder();
+        for (int i = 0; i < n || i < m; i++) {
+            if (i < n) {
+                res.append(word1.charAt(i));
+            }
+            if (i < m) {
+                res.append(word2.charAt(i));
+            }
+        }
+        return res.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string mergeAlternately(string word1, string word2) {
+        int n = word1.size(), m = word2.size();
+        string res;
+        for (int i = 0; i < n || i < m; i++) {
+            if (i < n) {
+                res += word1[i];
+            }
+            if (i < m) {
+                res += word2[i];
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} word1
+     * @param {string} word2
+     * @return {string}
+     */
+    mergeAlternately(word1, word2) {
+        const n = word1.length, m = word2.length;
+        const res = [];
+        for (let i = 0; i < m || i < n; i++) {
+            if (i < n) {
+                res.push(word1.charAt(i));
+            }
+            if (i < m) {
+                res.push(word2.charAt(i));
+            }
+        }
+        return res.join("");
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public string MergeAlternately(string word1, string word2) {
+        int n = word1.Length, m = word2.Length;
+        StringBuilder res = new StringBuilder();
+
+        for (int i = 0; i < Math.Max(n, m); i++) {
+            if (i < n) {
+                res.Append(word1[i]);
+            }
+            if (i < m) {
+                res.Append(word2[i]);
+            }
+        }
+
+        return res.ToString();
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(n + m)$ for the output string.
+
+> Where $n$ and $m$ are the lengths of the strings $word1$ and $word2$ respectively.
\ No newline at end of file
diff --git a/articles/merge-triplets-to-form-target.md b/articles/merge-triplets-to-form-target.md
new file mode 100644
index 000000000..268d8ae9d
--- /dev/null
+++ b/articles/merge-triplets-to-form-target.md
@@ -0,0 +1,319 @@
+## 1. Greedy
+
+::tabs-start
+
+```python
+class Solution:
+    def mergeTriplets(self, triplets: List[List[int]], target: List[int]) -> bool:
+        good = set()
+
+        for t in triplets:
+            if t[0] > target[0] or t[1] > target[1] or t[2] > target[2]:
+                continue
+            for i, v in enumerate(t):
+                if v == target[i]:
+                    good.add(i)
+        return len(good) == 3
+```
+
+```java
+public class Solution {
+    public boolean mergeTriplets(int[][] triplets, int[] target) {
+        Set<Integer> good = new HashSet<>();
+
+        for (int[] t : triplets) {
+            if (t[0] > target[0] || t[1] > target[1] || t[2] > target[2]) {
+                continue;
+            }
+            for (int i = 0; i < t.length; i++) {
+                if (t[i] == target[i]) {
+                    good.add(i);
+                }
+            }
+        }
+        return good.size() == 3;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool mergeTriplets(vector<vector<int>>& triplets, vector<int>& target) {
+        unordered_set<int> good;
+
+        for (const auto& t : triplets) {
+            if (t[0] > target[0] || t[1] > target[1] || t[2] > target[2]) {
+                continue;
+            }
+            for (int i = 0; i < t.size(); i++) {
+                if (t[i] == target[i]) {
+                    good.insert(i);
+                }
+            }
+        }
+        return good.size() == 3;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} triplets
+     * @param {number[]} target
+     * @return {boolean}
+     */
+    mergeTriplets(triplets, target) {
+        const good = new Set();
+
+        for (const t of triplets) {
+            if (t[0] > target[0] || t[1] > target[1] || t[2] > target[2]) {
+                continue;
+            }
+            for (let i = 0; i < t.length; i++) {
+                if (t[i] === target[i]) {
+                    good.add(i);
+                }
+            }
+        }
+        return good.size === 3;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool MergeTriplets(int[][] triplets, int[] target) {
+        HashSet<int> good = new HashSet<int>();
+
+        foreach (var t in triplets) {
+            if (t[0] > target[0] || t[1] > target[1] || t[2] > target[2]) {
+                continue;
+            }
+            for (int i = 0; i < t.Length; i++) {
+                if (t[i] == target[i]) {
+                    good.Add(i);
+                }
+            }
+        }
+        return good.Count == 3;
+    }
+}
+```
+
+```go
+func mergeTriplets(triplets [][]int, target []int) bool {
+    good := make(map[int]bool)
+
+    for _, t := range triplets {
+        if t[0] > target[0] || t[1] > target[1] || t[2] > target[2] {
+            continue
+        }
+        for i, v := range t {
+            if v == target[i] {
+                good[i] = true
+            }
+        }
+    }
+    return len(good) == 3
+}
+```
+
+```kotlin
+class Solution {
+    fun mergeTriplets(triplets: Array<IntArray>, target: IntArray): Boolean {
+        val good = HashSet<Int>()
+
+        for (t in triplets) {
+            if (t[0] > target[0] || t[1] > target[1] || t[2] > target[2]) continue
+            for ((i, v) in t.withIndex()) {
+                if (v == target[i]) {
+                    good.add(i)
+                }
+            }
+        }
+        return good.size == 3
+    }
+}
+```
+
+```swift
+class Solution {
+    func mergeTriplets(_ triplets: [[Int]], _ target: [Int]) -> Bool {
+        var good = Set<Int>()
+
+        for t in triplets {
+            if t[0] > target[0] || t[1] > target[1] || t[2] > target[2] {
+                continue
+            }
+            for (i, v) in t.enumerated() {
+                if v == target[i] {
+                    good.insert(i)
+                }
+            }
+        }
+
+        return good.count == 3
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Greedy (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def mergeTriplets(self, triplets: List[List[int]], target: List[int]) -> bool:
+        x = y = z = False
+        for t in triplets:
+            x |= (t[0] == target[0] and t[1] <= target[1] and t[2] <= target[2])
+            y |= (t[0] <= target[0] and t[1] == target[1] and t[2] <= target[2])
+            z |= (t[0] <= target[0] and t[1] <= target[1] and t[2] == target[2])
+            if x and y and z:
+                return True
+        return False
+```
+
+```java
+public class Solution {
+    public boolean mergeTriplets(int[][] triplets, int[] target) {
+        boolean x = false, y = false, z = false;
+        for (int[] t : triplets) {
+            x |= (t[0] == target[0] && t[1] <= target[1] && t[2] <= target[2]);
+            y |= (t[0] <= target[0] && t[1] == target[1] && t[2] <= target[2]);
+            z |= (t[0] <= target[0] && t[1] <= target[1] && t[2] == target[2]);
+            if (x && y && z) {
+                return true;
+            }
+        }
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool mergeTriplets(vector<vector<int>>& triplets, vector<int>& target) {
+        bool x = false, y = false, z = false;
+        for (const auto& t : triplets) {
+            x |= (t[0] == target[0] && t[1] <= target[1] && t[2] <= target[2]);
+            y |= (t[0] <= target[0] && t[1] == target[1] && t[2] <= target[2]);
+            z |= (t[0] <= target[0] && t[1] <= target[1] && t[2] == target[2]);
+            if (x && y && z) return true;
+        }
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} triplets
+     * @param {number[]} target
+     * @return {boolean}
+     */
+    mergeTriplets(triplets, target) {
+        let x = false, y = false, z = false;
+        for (let t of triplets) {
+            x |= (t[0] === target[0] && t[1] <= target[1] && t[2] <= target[2]);
+            y |= (t[0] <= target[0] && t[1] === target[1] && t[2] <= target[2]);
+            z |= (t[0] <= target[0] && t[1] <= target[1] && t[2] === target[2]);
+            if (x && y && z) return true;
+        }
+        return false;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool MergeTriplets(int[][] triplets, int[] target) {
+        bool x = false, y = false, z = false;
+        foreach (var t in triplets) {
+            x |= (t[0] == target[0] && t[1] <= target[1] && t[2] <= target[2]);
+            y |= (t[0] <= target[0] && t[1] == target[1] && t[2] <= target[2]);
+            z |= (t[0] <= target[0] && t[1] <= target[1] && t[2] == target[2]);
+            if (x && y && z) return true;
+        }
+        return false;
+    }
+}
+```
+
+```go
+func mergeTriplets(triplets [][]int, target []int) bool {
+    x, y, z := false, false, false
+
+    for _, t := range triplets {
+        x = x || (t[0] == target[0] && t[1] <= target[1] && t[2] <= target[2])
+        y = y || (t[0] <= target[0] && t[1] == target[1] && t[2] <= target[2])
+        z = z || (t[0] <= target[0] && t[1] <= target[1] && t[2] == target[2])
+        
+        if x && y && z {
+            return true
+        }
+    }
+    return false
+}
+```
+
+```kotlin
+class Solution {
+    fun mergeTriplets(triplets: Array<IntArray>, target: IntArray): Boolean {
+        var x = false
+        var y = false
+        var z = false
+
+        for (t in triplets) {
+            x = x || (t[0] == target[0] && t[1] <= target[1] && t[2] <= target[2])
+            y = y || (t[0] <= target[0] && t[1] == target[1] && t[2] <= target[2])
+            z = z || (t[0] <= target[0] && t[1] <= target[1] && t[2] == target[2])
+
+            if (x && y && z) return true
+        }
+        return false
+    }
+}
+```
+
+```swift
+class Solution {
+    func mergeTriplets(_ triplets: [[Int]], _ target: [Int]) -> Bool {
+        var x = false, y = false, z = false
+
+        for t in triplets {
+            if t[0] <= target[0] && t[1] <= target[1] && t[2] <= target[2] {
+                if t[0] == target[0] { x = true }
+                if t[1] == target[1] { y = true }
+                if t[2] == target[2] { z = true }
+            }
+
+            if x && y && z {
+                return true
+            }
+        }
+
+        return false
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/merge-two-binary-trees.md b/articles/merge-two-binary-trees.md
new file mode 100644
index 000000000..0b7636434
--- /dev/null
+++ b/articles/merge-two-binary-trees.md
@@ -0,0 +1,658 @@
+## 1. Depth First Search (Creating New Tree)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def mergeTrees(self, root1: Optional[TreeNode], root2: Optional[TreeNode]) -> Optional[TreeNode]:
+        if not root1 and not root2:
+            return None
+        
+        v1 = root1.val if root1 else 0
+        v2 = root2.val if root2 else 0
+        root = TreeNode(v1 + v2)
+        
+        root.left = self.mergeTrees(root1.left if root1 else None, root2.left if root2 else None)
+        root.right = self.mergeTrees(root1.right if root1 else None, root2.right if root2 else None)
+        
+        return root
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode mergeTrees(TreeNode root1, TreeNode root2) {
+        if (root1 == null && root2 == null) {
+            return null;
+        }
+
+        int v1 = (root1 != null) ? root1.val : 0;
+        int v2 = (root2 != null) ? root2.val : 0;
+        TreeNode root = new TreeNode(v1 + v2);
+
+        root.left = mergeTrees(
+            (root1 != null) ? root1.left : null, (root2 != null) ? root2.left : null
+        );
+        root.right = mergeTrees(
+            (root1 != null) ? root1.right : null, (root2 != null) ? root2.right : null
+        );
+
+        return root;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    TreeNode* mergeTrees(TreeNode* root1, TreeNode* root2) {
+        if (!root1 && !root2) {
+            return nullptr;
+        }
+
+        int v1 = root1 ? root1->val : 0;
+        int v2 = root2 ? root2->val : 0;
+        TreeNode* root = new TreeNode(v1 + v2);
+
+        root->left = mergeTrees(root1 ? root1->left : nullptr, root2 ? root2->left : nullptr);
+        root->right = mergeTrees(root1 ? root1->right : nullptr, root2 ? root2->right : nullptr);
+
+        return root;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root1
+     * @param {TreeNode} root2
+     * @return {TreeNode}
+     */
+    mergeTrees(root1, root2) {
+        if (!root1 && !root2) {
+            return null;
+        }
+
+        const v1 = root1 ? root1.val : 0;
+        const v2 = root2 ? root2.val : 0;
+        const root = new TreeNode(v1 + v2);
+
+        root.left = this.mergeTrees(root1 ? root1.left : null, root2 ? root2.left : null);
+        root.right = this.mergeTrees(root1 ? root1.right : null, root2 ? root2.right : null);
+
+        return root;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m + n)$
+* Space complexity:
+    * $O(m + n)$ space for recursion stack.
+    * $O(m + n)$ space for the output.
+
+> Where $m$ and $n$ are the number of nodes in the given trees.
+
+---
+
+## 2. Depth First Search (In Place)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def mergeTrees(self, root1: Optional[TreeNode], root2: Optional[TreeNode]) -> Optional[TreeNode]:
+        if not root1:
+            return root2
+        if not root2:
+            return root1
+
+        root1.val += root2.val
+        root1.left = self.mergeTrees(root1.left, root2.left)
+        root1.right = self.mergeTrees(root1.right, root2.right)
+        return root1
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode mergeTrees(TreeNode root1, TreeNode root2) {
+        if (root1 == null) return root2;
+        if (root2 == null) return root1;
+
+        root1.val += root2.val;
+        root1.left = mergeTrees(root1.left, root2.left);
+        root1.right = mergeTrees(root1.right, root2.right);
+        return root1;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    TreeNode* mergeTrees(TreeNode* root1, TreeNode* root2) {
+        if (!root1) return root2;
+        if (!root2) return root1;
+
+        root1->val += root2->val;
+        root1->left = mergeTrees(root1->left, root2->left);
+        root1->right = mergeTrees(root1->right, root2->right);
+        return root1;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root1
+     * @param {TreeNode} root2
+     * @return {TreeNode}
+     */
+    mergeTrees(root1, root2) {
+        if (!root1) return root2;
+        if (!root2) return root1;
+
+        root1.val += root2.val;
+        root1.left = this.mergeTrees(root1.left, root2.left);
+        root1.right = this.mergeTrees(root1.right, root2.right);
+        return root1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(min(m, n))$
+* Space complexity: $O(min(m, n))$ for recursion stack.
+
+> Where $m$ and $n$ are the number of nodes in the given trees.
+
+---
+
+## 3. Iterative DFS (Creating New Tree)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def mergeTrees(self, root1: Optional[TreeNode], root2: Optional[TreeNode]) -> Optional[TreeNode]:
+        if not root1:
+            return root2
+        if not root2:
+            return root1
+
+        root = TreeNode(root1.val + root2.val)
+        stack = [(root1, root2, root)]
+
+        while stack:
+            node1, node2, node = stack.pop()
+            
+            if node1.left and node2.left:
+                node.left = TreeNode(node1.left.val + node2.left.val)
+                stack.append((node1.left, node2.left, node.left))
+            elif not node1.left:
+                node.left = node2.left
+            else:
+                node.left = node1.left
+
+            if node1.right and node2.right:
+                node.right = TreeNode(node1.right.val + node2.right.val)
+                stack.append((node1.right, node2.right, node.right))
+            elif not node1.right:
+                node.right = node2.right
+            else:
+                node.right = node1.right
+
+        return root
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode mergeTrees(TreeNode root1, TreeNode root2) {
+        if (root1 == null && root2 == null) return null;
+
+        int val = (root1 != null ? root1.val : 0) + (root2 != null ? root2.val : 0);
+        TreeNode root = new TreeNode(val);
+        Stack<TreeNode[]> stack = new Stack<>();
+        stack.push(new TreeNode[]{root1, root2, root});
+
+        while (!stack.isEmpty()) {
+            TreeNode[] nodes = stack.pop();
+            TreeNode node1 = nodes[0], node2 = nodes[1], node = nodes[2];
+
+            TreeNode left1 = node1 != null ? node1.left : null;
+            TreeNode left2 = node2 != null ? node2.left : null;
+            if (left1 != null || left2 != null) {
+                int leftVal = (left1 != null ? left1.val : 0) + (left2 != null ? left2.val : 0);
+                node.left = new TreeNode(leftVal);
+                stack.push(new TreeNode[]{left1, left2, node.left});
+            }
+
+            TreeNode right1 = node1 != null ? node1.right : null;
+            TreeNode right2 = node2 != null ? node2.right : null;
+            if (right1 != null || right2 != null) {
+                int rightVal = (right1 != null ? right1.val : 0) + (right2 != null ? right2.val : 0);
+                node.right = new TreeNode(rightVal);
+                stack.push(new TreeNode[]{right1, right2, node.right});
+            }
+        }
+
+        return root;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    TreeNode* mergeTrees(TreeNode* root1, TreeNode* root2) {
+        if (!root1 && !root2) return nullptr;
+
+        int val = (root1 ? root1->val : 0) + (root2 ? root2->val : 0);
+        TreeNode* root = new TreeNode(val);
+        stack<tuple<TreeNode*, TreeNode*, TreeNode*>> st;
+        st.push({root1, root2, root});
+
+        while (!st.empty()) {
+            auto [node1, node2, node] = st.top();
+            st.pop();
+
+            TreeNode* left1 = node1 ? node1->left : nullptr;
+            TreeNode* left2 = node2 ? node2->left : nullptr;
+            if (left1 || left2) {
+                int leftVal = (left1 ? left1->val : 0) + (left2 ? left2->val : 0);
+                node->left = new TreeNode(leftVal);
+                st.push({left1, left2, node->left});
+            }
+
+            TreeNode* right1 = node1 ? node1->right : nullptr;
+            TreeNode* right2 = node2 ? node2->right : nullptr;
+            if (right1 || right2) {
+                int rightVal = (right1 ? right1->val : 0) + (right2 ? right2->val : 0);
+                node->right = new TreeNode(rightVal);
+                st.push({right1, right2, node->right});
+            }
+        }
+
+        return root;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root1
+     * @param {TreeNode} root2
+     * @return {TreeNode}
+     */
+    mergeTrees(root1, root2) {
+        if (!root1 && !root2) return null;
+
+        let val = (root1 ? root1.val : 0) + (root2 ? root2.val : 0);
+        let root = new TreeNode(val);
+        let stack = [[root1, root2, root]];
+
+        while (stack.length) {
+            let [node1, node2, node] = stack.pop();
+
+            let left1 = node1 ? node1.left : null;
+            let left2 = node2 ? node2.left : null;
+            if (left1 || left2) {
+                let leftVal = (left1 ? left1.val : 0) + (left2 ? left2.val : 0);
+                node.left = new TreeNode(leftVal);
+                stack.push([left1, left2, node.left]);
+            }
+
+            let right1 = node1 ? node1.right : null;
+            let right2 = node2 ? node2.right : null;
+            if (right1 || right2) {
+                let rightVal = (right1 ? right1.val : 0) + (right2 ? right2.val : 0);
+                node.right = new TreeNode(rightVal);
+                stack.push([right1, right2, node.right]);
+            }
+        }
+
+        return root;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m + n)$
+* Space complexity:
+    * $O(m + n)$ space for the stack.
+    * $O(m + n)$ space for the output.
+
+> Where $m$ and $n$ are the number of nodes in the given trees.
+
+---
+
+## 4. Iterative DFS (In Place)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def mergeTrees(self, root1: Optional[TreeNode], root2: Optional[TreeNode]) -> Optional[TreeNode]:
+        if not root1:
+            return root2
+        if not root2:
+            return root1
+
+        stack = [(root1, root2)]
+
+        while stack:
+            node1, node2 = stack.pop()
+            if not node1 or not node2:
+                continue
+
+            node1.val += node2.val
+
+            if node1.left and node2.left:
+                stack.append((node1.left, node2.left))
+            elif not node1.left:
+                node1.left = node2.left
+
+            if node1.right and node2.right:
+                stack.append((node1.right, node2.right))
+            elif not node1.right:
+                node1.right = node2.right
+
+        return root1
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode mergeTrees(TreeNode root1, TreeNode root2) {
+        if (root1 == null) return root2;
+        if (root2 == null) return root1;
+
+        Stack<TreeNode[]> stack = new Stack<>();
+        stack.push(new TreeNode[] { root1, root2 });
+
+        while (!stack.isEmpty()) {
+            TreeNode[] nodes = stack.pop();
+            TreeNode node1 = nodes[0];
+            TreeNode node2 = nodes[1];
+
+            if (node2 == null) continue;
+
+            node1.val += node2.val;
+
+            if (node1.left == null) {
+                node1.left = node2.left;
+            } else {
+                stack.push(new TreeNode[] { node1.left, node2.left });
+            }
+
+            if (node1.right == null) {
+                node1.right = node2.right;
+            } else {
+                stack.push(new TreeNode[] { node1.right, node2.right });
+            }
+        }
+
+        return root1;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    TreeNode* mergeTrees(TreeNode* root1, TreeNode* root2) {
+        if (!root1) return root2;
+        if (!root2) return root1;
+
+        stack<pair<TreeNode*, TreeNode*>> stk;
+        stk.push({root1, root2});
+
+        while (!stk.empty()) {
+            auto [node1, node2] = stk.top();
+            stk.pop();
+
+            if (!node2) continue;
+
+            node1->val += node2->val;
+
+            if (!node1->left) {
+                node1->left = node2->left;
+            } else {
+                stk.push({node1->left, node2->left});
+            }
+
+            if (!node1->right) {
+                node1->right = node2->right;
+            } else {
+                stk.push({node1->right, node2->right});
+            }
+        }
+
+        return root1;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root1
+     * @param {TreeNode} root2
+     * @return {TreeNode}
+     */
+    mergeTrees(root1, root2) {
+        if (!root1) return root2;
+        if (!root2) return root1;
+
+        let stack = [[root1, root2]];
+
+        while (stack.length) {
+            let [node1, node2] = stack.pop();
+            if (!node1 || !node2) continue;
+
+            node1.val += node2.val;
+
+            if (node1.left && node2.left) {
+                stack.push([node1.left, node2.left]);
+            } else if (!node1.left) {
+                node1.left = node2.left;
+            }
+
+            if (node1.right && node2.right) {
+                stack.push([node1.right, node2.right]);
+            } else if (!node1.right) {
+                node1.right = node2.right;
+            }
+        }
+
+        return root1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(min(m, n))$
+* Space complexity: $O(min(m, n))$ for the stack.
+
+> Where $m$ and $n$ are the number of nodes in the given trees.
\ No newline at end of file
diff --git a/articles/merge-two-sorted-linked-lists.md b/articles/merge-two-sorted-linked-lists.md
index e25cbc918..b65407ade 100644
--- a/articles/merge-two-sorted-linked-lists.md
+++ b/articles/merge-two-sorted-linked-lists.md
@@ -153,6 +153,86 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func mergeTwoLists(list1 *ListNode, list2 *ListNode) *ListNode {
+    if list1 == nil {
+        return list2
+    }
+    if list2 == nil {
+        return list1
+    }
+    if list1.Val <= list2.Val {
+        list1.Next = mergeTwoLists(list1.Next, list2)
+        return list1
+    }
+    list2.Next = mergeTwoLists(list1, list2.Next)
+    return list2
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var li = ListNode(5)
+ * var v = li.`val`
+ * Definition for singly-linked list.
+ * class ListNode(var `val`: Int) {
+ *     var next: ListNode? = null
+ * }
+ */
+class Solution {
+    fun mergeTwoLists(list1: ListNode?, list2: ListNode?): ListNode? {
+        if (list1 == null) return list2
+        if (list2 == null) return list1
+        
+        return if (list1.`val` <= list2.`val`) {
+            list1.next = mergeTwoLists(list1.next, list2)
+            list1
+        } else {
+            list2.next = mergeTwoLists(list1, list2.next)
+            list2
+        }
+    }
+}
+```
+
+```swift
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public var val: Int
+ *     public var next: ListNode?
+ *     public init() { self.val = 0; self.next = nil; }
+ *     public init(_ val: Int) { self.val = val; self.next = nil; }
+ *     public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
+ * }
+ */
+class Solution {
+    func mergeTwoLists(_ list1: ListNode?, _ list2: ListNode?) -> ListNode? {
+        if list1 == nil {
+            return list2
+        }
+        if list2 == nil {
+            return list1
+        }
+        if list1!.val <= list2!.val {
+            list1!.next = mergeTwoLists(list1!.next, list2)
+            return list1
+        } else {
+            list2!.next = mergeTwoLists(list1, list2!.next)
+            return list2
+        }
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -355,6 +435,110 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func mergeTwoLists(list1 *ListNode, list2 *ListNode) *ListNode {
+    dummy := &ListNode{}
+    node := dummy
+
+    for list1 != nil && list2 != nil {
+        if list1.Val < list2.Val {
+            node.Next = list1
+            list1 = list1.Next
+        } else {
+            node.Next = list2
+            list2 = list2.Next
+        }
+        node = node.Next
+    }
+
+    node.Next = list1
+    if list1 == nil {
+        node.Next = list2
+    }
+
+    return dummy.Next
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var li = ListNode(5)
+ * var v = li.`val`
+ * Definition for singly-linked list.
+ * class ListNode(var `val`: Int) {
+ *     var next: ListNode? = null
+ * }
+ */
+class Solution {
+    fun mergeTwoLists(list1: ListNode?, list2: ListNode?): ListNode? {
+        val dummy = ListNode(0)
+        var node: ListNode? = dummy
+
+        var l1 = list1
+        var l2 = list2
+
+        while (l1 != null && l2 != null) {
+            if (l1.`val` < l2.`val`) {
+                node?.next = l1
+                l1 = l1.next
+            } else {
+                node?.next = l2
+                l2 = l2.next
+            }
+            node = node?.next
+        }
+
+        node?.next = l1 ?: l2
+
+        return dummy.next
+    }
+}
+```
+
+```swift
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public var val: Int
+ *     public var next: ListNode?
+ *     public init() { self.val = 0; self.next = nil; }
+ *     public init(_ val: Int) { self.val = val; self.next = nil; }
+ *     public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
+ * }
+ */
+class Solution {
+    func mergeTwoLists(_ list1: ListNode?, _ list2: ListNode?) -> ListNode? {
+        let dummy = ListNode(0)
+        var node = dummy
+        var l1 = list1
+        var l2 = list2
+
+        while l1 != nil && l2 != nil {
+            if l1!.val < l2!.val {
+                node.next = l1
+                l1 = l1?.next
+            } else {
+                node.next = l2
+                l2 = l2?.next
+            }
+            node = node.next!
+        }
+
+        node.next = l1 ?? l2
+
+        return dummy.next
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/middle-of-the-linked-list.md b/articles/middle-of-the-linked-list.md
new file mode 100644
index 000000000..935efc3d4
--- /dev/null
+++ b/articles/middle-of-the-linked-list.md
@@ -0,0 +1,339 @@
+## 1. Convert To Array
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def middleNode(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        cur = head
+        arr = []
+        while cur:
+            arr.append(cur)
+            cur = cur.next
+        return arr[len(arr) // 2]
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode middleNode(ListNode head) {
+        ArrayList<ListNode> arr = new ArrayList<>();
+        ListNode cur = head;
+        while (cur != null) {
+            arr.add(cur);
+            cur = cur.next;
+        }
+        return arr.get(arr.size() / 2);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* middleNode(ListNode* head) {
+        vector<ListNode*> arr;
+        ListNode* cur = head;
+        while (cur) {
+            arr.push_back(cur);
+            cur = cur->next;
+        }
+        return arr[arr.size() / 2];
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @return {ListNode}
+     */
+    middleNode(head) {
+        let arr = [];
+        let cur = head;
+        while (cur) {
+            arr.push(cur);
+            cur = cur.next;
+        }
+        return arr[Math.floor(arr.length / 2)];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Find Length of the List
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def middleNode(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        n, cur = 0, head
+        while cur:
+            cur = cur.next
+            n += 1
+        
+        n //= 2
+        cur = head
+        while n:
+            n -= 1
+            cur = cur.next
+        return cur
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode middleNode(ListNode head) {
+        int n = 0;
+        ListNode cur = head;
+        while (cur != null) {
+            cur = cur.next;
+            n++;
+        }
+
+        n /= 2;
+        cur = head;
+        while (n != 0) {
+            n--;
+            cur = cur.next;
+        }
+        return cur;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* middleNode(ListNode* head) {
+        int n = 0;
+        ListNode* cur = head;
+        while (cur) {
+            cur = cur->next;
+            n++;
+        }
+
+        n /= 2;
+        cur = head;
+        while (n) {
+            n--;
+            cur = cur->next;
+        }
+        return cur;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @return {ListNode}
+     */
+    middleNode(head) {
+        let n = 0;
+        let cur = head;
+        while (cur) {
+            cur = cur.next;
+            n++;
+        }
+
+        n = Math.floor(n / 2);
+        cur = head;
+        while (n) {
+            n--;
+            cur = cur.next;
+        }
+        return cur;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 3. Fast & Slow Pointers
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def middleNode(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        slow, fast = head, head
+
+        while fast and fast.next:
+            slow = slow.next
+            fast = fast.next.next
+        return slow
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode middleNode(ListNode head) {
+        ListNode slow = head, fast = head;
+
+        while (fast != null && fast.next != null) {
+            slow = slow.next;
+            fast = fast.next.next;
+        }
+        return slow;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* middleNode(ListNode* head) {
+        ListNode* slow = head;
+        ListNode* fast = head;
+
+        while (fast && fast->next) {
+            slow = slow->next;
+            fast = fast->next->next;
+        }
+        return slow;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @return {ListNode}
+     */
+    middleNode(head) {
+        let slow = head, fast = head;
+
+        while (fast && fast.next) {
+            slow = slow.next;
+            fast = fast.next.next;
+        }
+        return slow;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/min-cost-climbing-stairs.md b/articles/min-cost-climbing-stairs.md
index 6ae30128f..9433d007b 100644
--- a/articles/min-cost-climbing-stairs.md
+++ b/articles/min-cost-climbing-stairs.md
@@ -82,6 +82,57 @@ public class Solution {
 }
 ```
 
+```go
+func minCostClimbingStairs(cost []int) int {
+    var dfs func(i int) int
+    dfs = func(i int) int {
+        if i >= len(cost) {
+            return 0
+        }
+        return cost[i] + min(dfs(i+1), dfs(i+2))
+    }
+    
+    return min(dfs(0), dfs(1))
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun minCostClimbingStairs(cost: IntArray): Int {
+        fun dfs(i: Int): Int {
+            if (i >= cost.size) {
+                return 0
+            }
+            return cost[i] + minOf(dfs(i + 1), dfs(i + 2))
+        }
+        
+        return minOf(dfs(0), dfs(1))
+    }
+}
+```
+
+```swift
+class Solution {
+    func minCostClimbingStairs(_ cost: [Int]) -> Int {
+        func dfs(_ i: Int) -> Int {
+            if i >= cost.count {
+                return 0
+            }
+            return cost[i] + min(dfs(i + 1), dfs(i + 2))
+        }
+
+        return min(dfs(0), dfs(1))
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -207,6 +258,75 @@ public class Solution {
 }
 ```
 
+```go
+func minCostClimbingStairs(cost []int) int {
+    memo := make([]int, len(cost))
+    for i := 0; i < len(cost); i++ {
+        memo[i] = -1
+    }
+
+    var dfs func(i int) int
+    dfs = func(i int) int {
+        if i >= len(cost) {
+            return 0
+        }
+        if memo[i] != -1 {
+            return memo[i]
+        }
+        memo[i] = cost[i] + min(dfs(i+1), dfs(i+2))
+        return memo[i]
+    }
+    
+    return min(dfs(0), dfs(1))
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun minCostClimbingStairs(cost: IntArray): Int {
+        var memo = IntArray(cost.size){-1}
+        fun dfs(i: Int): Int {
+            if (i >= cost.size) {
+                return 0
+            }
+            if (memo[i] != -1) return memo[i]
+            memo[i] = cost[i] + minOf(dfs(i + 1), dfs(i + 2))
+            return memo[i]
+        }
+        
+        return minOf(dfs(0), dfs(1))
+    }
+}
+```
+
+```swift
+class Solution {
+    func minCostClimbingStairs(_ cost: [Int]) -> Int {
+        var memo = Array(repeating: -1, count: cost.count)
+
+        func dfs(_ i: Int) -> Int {
+            if i >= cost.count {
+                return 0
+            }
+            if memo[i] != -1 {
+                return memo[i]
+            }
+            memo[i] = cost[i] + min(dfs(i + 1), dfs(i + 2))
+            return memo[i]
+        }
+
+        return min(dfs(0), dfs(1))
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -302,6 +422,59 @@ public class Solution {
 }
 ```
 
+```go
+func minCostClimbingStairs(cost []int) int {
+    n := len(cost)
+    dp := make([]int, n+1)
+
+    for i := 2; i <= n; i++ {
+        dp[i] = min(dp[i-1] + cost[i-1],
+                    dp[i-2] + cost[i-2])
+    }
+
+    return dp[n]
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun minCostClimbingStairs(cost: IntArray): Int {
+        val n = cost.size
+        var dp = IntArray(n + 1)
+
+        for (i in 2..n) {
+            dp[i] = minOf(dp[i - 1] + cost[i - 1],
+                          dp[i - 2] + cost[i - 2])
+        }
+
+        return dp[n]
+    }
+}
+```
+
+```swift
+class Solution {
+    func minCostClimbingStairs(_ cost: [Int]) -> Int {
+        let n = cost.count
+        var dp = Array(repeating: 0, count: n + 1)
+
+        for i in 2...n {
+            dp[i] = min(dp[i - 1] + cost[i - 1], 
+                        dp[i - 2] + cost[i - 2])
+        }
+
+        return dp[n]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -373,6 +546,46 @@ public class Solution {
 }
 ```
 
+```go
+func minCostClimbingStairs(cost []int) int {
+    n := len(cost)
+    for i := n - 3; i >= 0; i-- {
+        cost[i] += min(cost[i+1], cost[i+2])
+    }
+    return min(cost[0], cost[1])
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun minCostClimbingStairs(cost: IntArray): Int {
+        val n = cost.size
+        for (i in n - 3 downTo 0) {
+            cost[i] += minOf(cost[i + 1], cost[i + 2])
+        }
+        return minOf(cost[0], cost[1])
+    }
+}
+```
+
+```swift
+class Solution {
+    func minCostClimbingStairs(_ cost: inout [Int]) -> Int {
+        for i in stride(from: cost.count - 3, through: 0, by: -1) {
+            cost[i] += min(cost[i + 1], cost[i + 2])
+        }
+        return min(cost[0], cost[1])
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/min-cost-to-connect-points.md b/articles/min-cost-to-connect-points.md
index 7db4e6bce..6688ee3a1 100644
--- a/articles/min-cost-to-connect-points.md
+++ b/articles/min-cost-to-connect-points.md
@@ -45,7 +45,7 @@ class Solution:
 ```
 
 ```java
-public class DSU {
+class DSU {
     int[] Parent, Size;
 
     public DSU(int n) {
@@ -280,6 +280,186 @@ public class Solution {
 }
 ```
 
+```go
+type DSU struct {
+	Parent []int
+	Size   []int
+}
+
+func NewDSU(n int) *DSU {
+	parent := make([]int, n)
+	size := make([]int, n)
+	for i := range parent {
+		parent[i] = i
+		size[i] = 1
+	}
+	return &DSU{Parent: parent, Size: size}
+}
+
+func (dsu *DSU) find(node int) int {
+	if dsu.Parent[node] != node {
+		dsu.Parent[node] = dsu.find(dsu.Parent[node])
+	}
+	return dsu.Parent[node]
+}
+
+func (dsu *DSU) union(u, v int) bool {
+	pu, pv := dsu.find(u), dsu.find(v)
+	if pu == pv {
+		return false
+	}
+	if dsu.Size[pu] < dsu.Size[pv] {
+		pu, pv = pv, pu
+	}
+	dsu.Size[pu] += dsu.Size[pv]
+	dsu.Parent[pv] = pu
+	return true
+}
+
+func minCostConnectPoints(points [][]int) int {
+	n := len(points)
+	dsu := NewDSU(n)
+	var edges [][]int
+	for i := 0; i < n; i++ {
+		x1, y1 := points[i][0], points[i][1]
+		for j := i + 1; j < n; j++ {
+			x2, y2 := points[j][0], points[j][1]
+			dist := int(math.Abs(float64(x1-x2)) + math.Abs(float64(y1-y2)))
+			edges = append(edges, []int{dist, i, j})
+		}
+	}
+
+	sort.Slice(edges, func(a, b int) bool {
+		return edges[a][0] < edges[b][0]
+	})
+
+	res := 0
+	for _, edge := range edges {
+		dist, u, v := edge[0], edge[1], edge[2]
+		if dsu.union(u, v) {
+			res += dist
+		}
+	}
+	return res
+}
+```
+
+```kotlin
+class DSU(n: Int) {
+    private val parent = IntArray(n) { it }
+    private val size = IntArray(n) { 1 }
+
+    fun find(node: Int): Int {
+        if (parent[node] != node) {
+            parent[node] = find(parent[node])
+        }
+        return parent[node]
+    }
+
+    fun union(u: Int, v: Int): Boolean {
+        val pu = find(u)
+        val pv = find(v)
+        if (pu == pv) return false
+        if (size[pu] < size[pv]) {
+            parent[pu] = pv
+            size[pv] += size[pu]
+        } else {
+            parent[pv] = pu
+            size[pu] += size[pv]
+        }
+        return true
+    }
+}
+
+class Solution {
+    fun minCostConnectPoints(points: Array<IntArray>): Int {
+        val n = points.size
+        val dsu = DSU(n)
+        val edges = mutableListOf<Triple<Int, Int, Int>>()
+
+        for (i in 0 until n) {
+            val (x1, y1) = points[i]
+            for (j in i + 1 until n) {
+                val (x2, y2) = points[j]
+                val dist = abs(x1 - x2) + abs(y1 - y2)
+                edges.add(Triple(dist, i, j))
+            }
+        }
+
+        edges.sortBy { it.first }
+        var res = 0
+        for ((dist, u, v) in edges) {
+            if (dsu.union(u, v)) {
+                res += dist
+            }
+        }
+        return res
+    }
+}
+```
+
+```swift
+class DSU {
+    private var parent: [Int]
+    private var size: [Int]
+
+    init(_ n: Int) {
+        parent = Array(0...n)
+        size = Array(repeating: 1, count: n + 1)
+    }
+
+    func find(_ node: Int) -> Int {
+        if parent[node] != node {
+            parent[node] = find(parent[node])
+        }
+        return parent[node]
+    }
+
+    func union(_ u: Int, _ v: Int) -> Bool {
+        let pu = find(u)
+        let pv = find(v)
+        if pu == pv {
+            return false
+        }
+        if size[pu] < size[pv] {
+            parent[pu] = pv
+            size[pv] += size[pu]
+        } else {
+            parent[pv] = pu
+            size[pu] += size[pv]
+        }
+        return true
+    }
+}
+
+class Solution {
+    func minCostConnectPoints(_ points: [[Int]]) -> Int {
+        let n = points.count
+        let dsu = DSU(n)
+        var edges = [(Int, Int, Int)]()
+
+        for i in 0..<n {
+            let x1 = points[i][0], y1 = points[i][1]
+            for j in i + 1..<n {
+                let x2 = points[j][0], y2 = points[j][1]
+                let dist = abs(x1 - x2) + abs(y1 - y2)
+                edges.append((dist, i, j))
+            }
+        }
+
+        edges.sort { $0.0 < $1.0 }
+        var res = 0
+
+        for (dist, u, v) in edges {
+            if dsu.union(u, v) {
+                res += dist
+            }
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -508,6 +688,146 @@ public class Solution {
 }
 ```
 
+```go
+func minCostConnectPoints(points [][]int) int {
+	n := len(points)
+	adj := make(map[int][][]int)
+	for i := 0; i < n; i++ {
+		x1, y1 := points[i][0], points[i][1]
+		for j := i + 1; j < n; j++ {
+			x2, y2 := points[j][0], points[j][1]
+			dist := int(math.Abs(float64(x1-x2)) + math.Abs(float64(y1-y2)))
+			adj[i] = append(adj[i], []int{dist, j})
+			adj[j] = append(adj[j], []int{dist, i})
+		}
+	}
+
+	res := 0
+	visit := make(map[int]bool)
+	pq := priorityqueue.NewWith(func(a, b interface{}) int {
+		return utils.IntComparator(a.([]int)[0], b.([]int)[0])
+	})
+	pq.Enqueue([]int{0, 0})
+
+	for len(visit) < n {
+		item, ok := pq.Dequeue()
+		if !ok {
+			continue
+		}
+		cost, point := item.([]int)[0], item.([]int)[1]
+		if visit[point] {
+			continue
+		}
+		res += cost
+		visit[point] = true
+
+		for _, edge := range adj[point] {
+			neiCost, neiPoint := edge[0], edge[1]
+			if !visit[neiPoint] {
+				pq.Enqueue([]int{neiCost, neiPoint})
+			}
+		}
+	}
+	return res
+}
+```
+
+```kotlin
+
+class Solution {
+    fun minCostConnectPoints(points: Array<IntArray>): Int {
+        val n = points.size
+        val adj = HashMap<Int, MutableList<Pair<Int, Int>>>()
+        
+        for (i in 0 until n) {
+            val (x1, y1) = points[i]
+            for (j in i + 1 until n) {
+                val (x2, y2) = points[j]
+                val dist = abs(x1 - x2) + abs(y1 - y2)
+                adj.computeIfAbsent(i) { mutableListOf() }.add(dist to j)
+                adj.computeIfAbsent(j) { mutableListOf() }.add(dist to i)
+            }
+        }
+
+        var res = 0
+        val visited = mutableSetOf<Int>()
+        val minHeap = PriorityQueue(compareBy<Pair<Int, Int>> { it.first })
+        
+        minHeap.add(0 to 0)  
+        
+        while (visited.size < n) {
+            val (cost, point) = minHeap.poll()
+            if (point in visited) continue
+            res += cost
+            visited.add(point)
+
+            for ((neiCost, nei) in adj[point] ?: emptyList()) {
+                if (nei !in visited) {
+                    minHeap.add(neiCost to nei)
+                }
+            }
+        }
+        return res
+    }
+}
+```
+
+```swift
+struct Item: Comparable {
+    let cost: Int
+    let node: Int
+
+    static func < (lhs: Item, rhs: Item) -> Bool {
+        return lhs.cost < rhs.cost
+    }
+}
+
+class Solution {
+    func minCostConnectPoints(_ points: [[Int]]) -> Int {
+        let N = points.count
+        var adj = [Int: [(Int, Int)]]()
+
+        for i in 0..<N {
+            let x1 = points[i][0], y1 = points[i][1]
+            for j in i + 1..<N {
+                let x2 = points[j][0], y2 = points[j][1]
+                let dist = abs(x1 - x2) + abs(y1 - y2)
+                adj[i, default: []].append((dist, j))
+                adj[j, default: []].append((dist, i))
+            }
+        }
+
+        var res = 0
+        var visit = Set<Int>()
+        var minHeap = Heap<Item>()
+        minHeap.insert(Item(cost: 0, node: 0))
+
+        while visit.count < N {
+            guard let item = minHeap.popMin() else { break }
+            let cost = item.cost
+            let i = item.node
+
+            if visit.contains(i) {
+                continue
+            }
+
+            res += cost
+            visit.insert(i)
+
+            if let neighbors = adj[i] {
+                for (neiCost, nei) in neighbors {
+                    if !visit.contains(nei) {
+                        minHeap.insert(Item(cost: neiCost, node: nei))
+                    }
+                }
+            }
+        }
+
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -672,6 +992,108 @@ public class Solution {
 }
 ```
 
+```go
+func minCostConnectPoints(points [][]int) int {
+	n := len(points)
+	node := 0
+	dist := make([]int, n)
+	for i := range dist {
+		dist[i] = 100000000
+	}
+	visit := make([]bool, n)
+	edges, res := 0, 0
+
+	for edges < n-1 {
+		visit[node] = true
+		nextNode := -1
+		for i := 0; i < n; i++ {
+			if visit[i] {
+				continue
+			}
+			curDist := int(math.Abs(float64(points[i][0]-points[node][0])) + 
+				math.Abs(float64(points[i][1]-points[node][1])))
+			if curDist < dist[i] {
+				dist[i] = curDist
+			}
+			if nextNode == -1 || dist[i] < dist[nextNode] {
+				nextNode = i
+			}
+		}
+		res += dist[nextNode]
+		node = nextNode
+		edges++
+	}
+	return res
+}
+```
+
+```kotlin
+class Solution {
+    fun minCostConnectPoints(points: Array<IntArray>): Int {
+        val n = points.size
+        var node = 0
+        val dist = IntArray(n) { 100000000 }
+        val visit = BooleanArray(n)
+        var edges = 0
+        var res = 0
+
+        while (edges < n - 1) {
+            visit[node] = true
+            var nextNode = -1
+            for (i in 0 until n) {
+                if (visit[i]) continue
+                val curDist = abs(points[i][0] - points[node][0]) + 
+                              abs(points[i][1] - points[node][1])
+                dist[i] = minOf(dist[i], curDist)
+                if (nextNode == -1 || dist[i] < dist[nextNode]) {
+                    nextNode = i
+                }
+            }
+            res += dist[nextNode]
+            node = nextNode
+            edges++
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func minCostConnectPoints(_ points: [[Int]]) -> Int {
+        let n = points.count
+        var node = 0
+        var dist = Array(repeating: 100000000, count: n)
+        var visit = Array(repeating: false, count: n)
+        var edges = 0
+        var res = 0
+
+        while edges < n - 1 {
+            visit[node] = true
+            var nextNode = -1
+
+            for i in 0..<n {
+                if visit[i] {
+                    continue
+                }
+                let curDist = abs(points[i][0] - points[node][0]) + 
+                              abs(points[i][1] - points[node][1])
+                dist[i] = min(dist[i], curDist)
+                if nextNode == -1 || dist[i] < dist[nextNode] {
+                    nextNode = i
+                }
+            }
+
+            res += dist[nextNode]
+            node = nextNode
+            edges += 1
+        }
+
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/minimize-deviation-in-array.md b/articles/minimize-deviation-in-array.md
new file mode 100644
index 000000000..34f231a21
--- /dev/null
+++ b/articles/minimize-deviation-in-array.md
@@ -0,0 +1,468 @@
+## 1. Sorting + Sliding Window
+
+::tabs-start
+
+```python
+class Solution:
+    def minimumDeviation(self, nums: List[int]) -> int:
+        n = len(nums)
+        arr = []
+        for i, num in enumerate(nums):
+            if num & 1:
+                arr.append((num, i))
+                arr.append((num * 2, i))
+            else:
+                while num % 2 == 0:
+                    arr.append((num, i))
+                    num //= 2
+                arr.append((num, i))
+
+        arr.sort()
+        res = float("inf")
+
+        seen = [0] * n
+        count = i = 0
+        for j in range(len(arr)):
+            seen[arr[j][1]] += 1
+            if seen[arr[j][1]] == 1:
+                count += 1
+                while count == n:
+                    res = min(res, arr[j][0] - arr[i][0])
+                    seen[arr[i][1]] -= 1
+                    if seen[arr[i][1]] == 0:
+                        count -= 1
+                    i += 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int minimumDeviation(int[] nums) {
+        int n = nums.length;
+        List<int[]> arr = new ArrayList<>();
+
+        for (int i = 0; i < n; i++) {
+            int num = nums[i];
+            if (num % 2 == 1) {
+                arr.add(new int[]{num, i});
+                arr.add(new int[]{num * 2, i});
+            } else {
+                while (num % 2 == 0) {
+                    arr.add(new int[]{num, i});
+                    num /= 2;
+                }
+                arr.add(new int[]{num, i});
+            }
+        }
+
+        arr.sort(Comparator.comparingInt(a -> a[0]));
+        int res = Integer.MAX_VALUE;
+
+        int[] seen = new int[n];
+        int count = 0, i = 0;
+        
+        for (int j = 0; j < arr.size(); j++) {
+            seen[arr.get(j)[1]]++;
+            if (seen[arr.get(j)[1]] == 1) {
+                count++;
+                while (count == n) {
+                    res = Math.min(res, arr.get(j)[0] - arr.get(i)[0]);
+                    seen[arr.get(i)[1]]--;
+                    if (seen[arr.get(i)[1]] == 0) {
+                        count--;
+                    }
+                    i++;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minimumDeviation(vector<int>& nums) {
+        int n = nums.size();
+        vector<pair<int, int>> arr;
+
+        for (int i = 0; i < n; i++) {
+            int num = nums[i];
+            if (num % 2 == 1) {
+                arr.emplace_back(num, i);
+                arr.emplace_back(num * 2, i);
+            } else {
+                while (num % 2 == 0) {
+                    arr.emplace_back(num, i);
+                    num /= 2;
+                }
+                arr.emplace_back(num, i);
+            }
+        }
+
+        sort(arr.begin(), arr.end());
+        int res = INT_MAX;
+
+        vector<int> seen(n, 0);
+        int count = 0, i = 0;
+
+        for (int j = 0; j < arr.size(); j++) {
+            seen[arr[j].second]++;
+            if (seen[arr[j].second] == 1) {
+                count++;
+                while (count == n) {
+                    res = min(res, arr[j].first - arr[i].first);
+                    seen[arr[i].second]--;
+                    if (seen[arr[i].second] == 0) {
+                        count--;
+                    }
+                    i++;
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    minimumDeviation(nums) {
+        let n = nums.length;
+        let arr = [];
+
+        for (let i = 0; i < n; i++) {
+            let num = nums[i];
+            if (num % 2 === 1) {
+                arr.push([num, i]);
+                arr.push([num * 2, i]);
+            } else {
+                while (num % 2 === 0) {
+                    arr.push([num, i]);
+                    num /= 2;
+                }
+                arr.push([num, i]);
+            }
+        }
+
+        arr.sort((a, b) => a[0] - b[0]);
+        let res = Infinity;
+
+        let seen = new Array(n).fill(0);
+        let count = 0, i = 0;
+
+        for (let j = 0; j < arr.length; j++) {
+            seen[arr[j][1]]++;
+            if (seen[arr[j][1]] === 1) {
+                count++;
+                while (count === n) {
+                    res = Math.min(res, arr[j][0] - arr[i][0]);
+                    seen[arr[i][1]]--;
+                    if (seen[arr[i][1]] === 0) {
+                        count--;
+                    }
+                    i++;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O((n \log m) * \log (n \log m))$
+* Space complexity: $O(n \log m)$
+
+> Where $n$ is the size of the array $nums$ and $m$ is the maximum element in $nums$.
+
+---
+
+## 2. Min-Heap
+
+::tabs-start
+
+```python
+class Solution:
+    def minimumDeviation(self, nums: List[int]) -> int:
+        minHeap, heapMax = [], 0
+
+        for n in nums:
+            tmp = n
+            while n % 2 == 0:
+                n //= 2
+            minHeap.append((n, max(tmp, 2 * n)))
+            heapMax = max(heapMax, n)
+
+        res = float("inf")
+        heapq.heapify(minHeap)
+
+        while len(minHeap) == len(nums):
+            n, nMax = heapq.heappop(minHeap)
+            res = min(res, heapMax - n)
+
+            if n < nMax:
+                heapq.heappush(minHeap, (n * 2, nMax))
+                heapMax = max(heapMax, n * 2)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int minimumDeviation(int[] nums) {
+        PriorityQueue<int[]> minHeap = new PriorityQueue<>((a, b) -> a[0] - b[0]);
+        int heapMax = 0;
+
+        for (int num : nums) {
+            int tmp = num;
+            while (num % 2 == 0) {
+                num /= 2;
+            }
+            minHeap.offer(new int[]{num, Math.max(tmp, 2 * num)});
+            heapMax = Math.max(heapMax, num);
+        }
+
+        int res = Integer.MAX_VALUE;
+
+        while (minHeap.size() == nums.length) {
+            int[] minElement = minHeap.poll();
+            int n = minElement[0], nMax = minElement[1];
+            res = Math.min(res, heapMax - n);
+
+            if (n < nMax) {
+                minHeap.offer(new int[]{n * 2, nMax});
+                heapMax = Math.max(heapMax, n * 2);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minimumDeviation(vector<int>& nums) {
+        priority_queue<pair<int, int>, vector<pair<int, int>>, greater<>> minHeap;
+        int heapMax = 0;
+
+        for (int num : nums) {
+            int tmp = num;
+            while (num % 2 == 0) {
+                num /= 2;
+            }
+            minHeap.push({num, max(tmp, 2 * num)});
+            heapMax = max(heapMax, num);
+        }
+
+        int res = INT_MAX;
+
+        while (minHeap.size() == nums.size()) {
+            auto [n, nMax] = minHeap.top();
+            minHeap.pop();
+            res = min(res, heapMax - n);
+
+            if (n < nMax) {
+                minHeap.push({n * 2, nMax});
+                heapMax = max(heapMax, n * 2);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    minimumDeviation(nums) {
+        const minHeap = new MinPriorityQueue(x => x[0]);
+        let heapMax = 0;
+
+        for (let num of nums) {
+            let tmp = num;
+            while (num % 2 === 0) {
+                num /= 2;
+            }
+            minHeap.enqueue([num, Math.max(tmp, num * 2)]);
+            heapMax = Math.max(heapMax, num);
+        }
+
+        let res = Infinity;
+
+        while (minHeap.size() === nums.length) {
+            let [n, nMax] = minHeap.dequeue();
+            res = Math.min(res, heapMax - n);
+
+            if (n < nMax) {
+                minHeap.enqueue([n * 2, nMax]);
+                heapMax = Math.max(heapMax, n * 2);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n *\log n * \log m)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the size of the array $nums$ and $m$ is the maximum element in $nums$.
+
+---
+
+## 3. Max-Heap
+
+::tabs-start
+
+```python
+class Solution:
+    def minimumDeviation(self, nums: List[int]) -> int:
+        maxHeap = []
+        minVal = float("inf")
+
+        for num in nums:
+            if num % 2 == 1:
+                num *= 2
+            heapq.heappush(maxHeap, -num)
+            minVal = min(minVal, num)
+
+        res = float("inf")
+
+        while maxHeap:
+            maxVal = -heapq.heappop(maxHeap)
+            res = min(res, maxVal - minVal)
+            if maxVal % 2 == 1:
+                break
+
+            nextVal = maxVal // 2
+            heapq.heappush(maxHeap, -nextVal)
+            minVal = min(minVal, nextVal)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int minimumDeviation(int[] nums) {
+        PriorityQueue<Integer> maxHeap = new PriorityQueue<>((a, b) -> b - a);
+        int minVal = Integer.MAX_VALUE;
+
+        for (int num : nums) {
+            if (num % 2 == 1) num *= 2;
+            maxHeap.offer(num);
+            minVal = Math.min(minVal, num);
+        }
+
+        int res = Integer.MAX_VALUE;
+
+        while (!maxHeap.isEmpty()) {
+            int maxVal = maxHeap.poll();
+            res = Math.min(res, maxVal - minVal);
+
+            if (maxVal % 2 == 1) break;
+
+            int nextVal = maxVal / 2;
+            maxHeap.offer(nextVal);
+            minVal = Math.min(minVal, nextVal);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minimumDeviation(vector<int>& nums) {
+        priority_queue<int> maxHeap;
+        int minVal = INT_MAX;
+
+        for (int num : nums) {
+            if (num % 2 == 1) num *= 2;
+            maxHeap.push(num);
+            minVal = min(minVal, num);
+        }
+
+        int res = INT_MAX;
+
+        while (!maxHeap.empty()) {
+            int maxVal = maxHeap.top();
+            maxHeap.pop();
+            res = min(res, maxVal - minVal);
+
+            if (maxVal % 2 == 1) break;
+
+            int nextVal = maxVal / 2;
+            maxHeap.push(nextVal);
+            minVal = min(minVal, nextVal);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    minimumDeviation(nums) {
+        const maxHeap = new MaxPriorityQueue();
+        let minVal = Infinity;
+
+        for (let num of nums) {
+            if (num % 2 === 1) num *= 2;
+            maxHeap.enqueue(num);
+            minVal = Math.min(minVal, num);
+        }
+
+        let res = Infinity;
+
+        while (!maxHeap.isEmpty()) {
+            let maxVal = maxHeap.dequeue();
+            res = Math.min(res, maxVal - minVal);
+
+            if (maxVal % 2 === 1) break;
+
+            let nextVal = maxVal / 2;
+            maxHeap.enqueue(nextVal);
+            minVal = Math.min(minVal, nextVal);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n *\log n * \log m)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the size of the array $nums$ and $m$ is the maximum element in $nums$.
\ No newline at end of file
diff --git a/articles/minimize-maximum-of-array.md b/articles/minimize-maximum-of-array.md
new file mode 100644
index 000000000..b851e40b5
--- /dev/null
+++ b/articles/minimize-maximum-of-array.md
@@ -0,0 +1,210 @@
+## 1. Binary Search
+
+::tabs-start
+
+```python
+class Solution:
+    def minimizeArrayValue(self, nums: List[int]) -> int:
+        def isValid(maxVal):
+            prefix_sum = 0
+            for i in range(len(nums)):
+                prefix_sum += nums[i]
+                if prefix_sum > maxVal * (i + 1):
+                    return False
+            return True
+
+        left, right = 0, max(nums)
+        while left < right:
+            mid = left + (right - left) // 2
+            if isValid(mid):
+                right = mid
+            else:
+                left = mid + 1
+
+        return left
+```
+
+```java
+public class Solution {
+    public int minimizeArrayValue(int[] nums) {
+        int left = 0, right = 0;
+        for (int num : nums) {
+            right = Math.max(right, num);
+        }
+
+        while (left < right) {
+            int mid = left + (right - left) / 2;
+            if (isValid(nums, mid)) {
+                right = mid;
+            } else {
+                left = mid + 1;
+            }
+        }
+
+        return left;
+    }
+
+    private boolean isValid(int[] nums, int maxVal) {
+        long prefixSum = 0;
+        for (int i = 0; i < nums.length; i++) {
+            prefixSum += nums[i];
+            if (prefixSum > (long) maxVal * (i + 1)) {
+                return false;
+            }
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minimizeArrayValue(vector<int>& nums) {
+        int left = 0, right = *max_element(nums.begin(), nums.end());
+
+        while (left < right) {
+            int mid = left + (right - left) / 2;
+            if (isValid(nums, mid)) {
+                right = mid;
+            } else {
+                left = mid + 1;
+            }
+        }
+
+        return left;
+    }
+
+private:
+    bool isValid(vector<int>& nums, int maxVal) {
+        long long prefixSum = 0;
+        for (int i = 0; i < nums.size(); i++) {
+            prefixSum += nums[i];
+            if (prefixSum > (long long)maxVal * (i + 1)) {
+                return false;
+            }
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    minimizeArrayValue(nums) {
+        const isValid = (maxVal) => {
+            let prefixSum = 0;
+            for (let i = 0; i < nums.length; i++) {
+                prefixSum += nums[i];
+                if (prefixSum > maxVal * (i + 1)) {
+                    return false;
+                }
+            }
+            return true;
+        };
+
+        let left = 0, right = Math.max(...nums);
+        while (left < right) {
+            let mid = left + Math.floor((right - left) / 2);
+            if (isValid(mid)) {
+                right = mid;
+            } else {
+                left = mid + 1;
+            }
+        }
+
+        return left;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log m)$
+* Space complexity: $O(1)$ extra space.
+
+> Where $n$ is the size of the array $nums$ and $m$ is the maximum value in the array.
+
+---
+
+## 2. Prefix Sum + Greedy
+
+::tabs-start
+
+```python
+class Solution:
+    def minimizeArrayValue(self, nums: List[int]) -> int:
+        res = total = nums[0]
+
+        for i in range(1, len(nums)):
+            total += nums[i]
+            res = max(res, math.ceil(total / (i + 1)))
+
+        return res
+```
+
+```java
+public class Solution {
+    public int minimizeArrayValue(int[] nums) {
+        int res = nums[0];
+        long total = nums[0];
+
+        for (int i = 1; i < nums.length; i++) {
+            total += nums[i];
+            res = Math.max(res, (int) Math.ceil((double) total / (i + 1)));
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minimizeArrayValue(vector<int>& nums) {
+        int res = nums[0];
+        long long total = nums[0];
+
+        for (int i = 1; i < nums.size(); i++) {
+            total += nums[i];
+            res = max(res, (int)ceil((double)total / (i + 1)));
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    minimizeArrayValue(nums) {
+        let res = nums[0];
+        let total = nums[0];
+
+        for (let i = 1; i < nums.length; i++) {
+            total += nums[i];
+            res = Math.max(res, Math.ceil(total / (i + 1)));
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/minimize-the-maximum-difference-of-pairs.md b/articles/minimize-the-maximum-difference-of-pairs.md
new file mode 100644
index 000000000..5ad0f31b1
--- /dev/null
+++ b/articles/minimize-the-maximum-difference-of-pairs.md
@@ -0,0 +1,561 @@
+## 1. Greedy + Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def minimizeMax(self, nums: List[int], p: int) -> int:
+        n = len(nums)
+        nums.sort()
+        dp = {}
+
+        def dfs(i, pairs):
+            if pairs == p:
+                return 0
+            if i >= n - 1:
+                return float('inf')
+            if (i, pairs) in dp:
+                return dp[(i, pairs)]
+
+            take = max(nums[i + 1] - nums[i], dfs(i + 2, pairs + 1))
+            skip = dfs(i + 1, pairs)
+            dp[(i, pairs)] = min(take, skip)
+            return dp[(i, pairs)]
+
+        return dfs(0, 0)
+```
+
+```java
+public class Solution {
+    private Map<String, Integer> dp;
+
+    public int minimizeMax(int[] nums, int p) {
+        Arrays.sort(nums);
+        dp = new HashMap<>();
+        return dfs(0, 0, nums, p);
+    }
+
+    private int dfs(int i, int pairs, int[] nums, int p) {
+        if (pairs == p) return 0;
+        if (i >= nums.length - 1) return Integer.MAX_VALUE;
+        
+        String key = i + "," + pairs;
+        if (dp.containsKey(key)) return dp.get(key);
+
+        int take = Math.max(nums[i + 1] - nums[i], dfs(i + 2, pairs + 1, nums, p));
+        int skip = dfs(i + 1, pairs, nums, p);
+
+        int res = Math.min(take, skip);
+        dp.put(key, res);
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+    unordered_map<long long, int> dp;
+
+public:
+    int minimizeMax(vector<int>& nums, int p) {
+        int n = nums.size();
+        sort(nums.begin(), nums.end());
+        return dfs(0, 0, nums, p);
+    }
+
+private:
+    int dfs(int i, int pairs, vector<int>& nums, int p) {
+        if (pairs == p) return 0;
+        if (i >= nums.size() - 1) return INT_MAX;
+        long long key = i;
+        key = (key << 31) | pairs;
+        if (dp.count(key)) return dp[key];
+
+        int take = max(nums[i + 1] - nums[i], dfs(i + 2, pairs + 1, nums, p));
+        int skip = dfs(i + 1, pairs, nums, p);
+
+        return dp[key] = min(take, skip);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} p
+     * @return {number}
+     */
+    minimizeMax(nums, p) {
+        nums.sort((a, b) => a - b);
+        const dp = new Map();
+
+        const dfs = (i, pairs) => {
+            if (pairs === p) return 0;
+            if (i >= nums.length - 1) return Infinity;
+
+            let key = `${i},${pairs}`;
+            if (dp.has(key)) return dp.get(key);
+
+            let take = Math.max(nums[i + 1] - nums[i], dfs(i + 2, pairs + 1));
+            let skip = dfs(i + 1, pairs);
+
+            let result = Math.min(take, skip);
+            dp.set(key, result);
+            return result;
+        };
+
+        return dfs(0, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * p)$
+* Space complexity: $O(n * p)$
+
+> Where $n$ is the size of the input array and $p$ is the number of pairs to select.
+
+---
+
+## 2. Greesy + Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def minimizeMax(self, nums: List[int], p: int) -> int:
+        n = len(nums)
+        nums.sort()
+
+        dp = [[float('inf')] * (p + 1) for _ in range(n + 1)]
+        for i in range(n + 1):
+            dp[i][0] = 0
+
+        for i in range(n - 2, -1, -1):
+            for pairs in range(1, p + 1):
+                take = float('inf')
+                if i + 1 < n:
+                    take = max(nums[i + 1] - nums[i], dp[i + 2][pairs - 1])
+                
+                skip = dp[i + 1][pairs]
+                dp[i][pairs] = min(take, skip)
+
+        return dp[0][p]
+```
+
+```java
+public class Solution {
+    public int minimizeMax(int[] nums, int p) {
+        int n = nums.length;
+        Arrays.sort(nums);
+
+        int[][] dp = new int[n + 1][p + 1];
+        for (int i = 0; i <= n; i++) {
+            Arrays.fill(dp[i], Integer.MAX_VALUE);
+            dp[i][0] = 0;
+        }
+
+        for (int i = n - 2; i >= 0; i--) {
+            for (int pairs = 1; pairs <= p; pairs++) {
+                int take = Integer.MAX_VALUE;
+                if (i + 1 < n) {
+                    take = Math.max(nums[i + 1] - nums[i], dp[i + 2][pairs - 1]);
+                }
+                int skip = dp[i + 1][pairs];
+                dp[i][pairs] = Math.min(take, skip);
+            }
+        }
+
+        return dp[0][p];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minimizeMax(vector<int>& nums, int p) {
+        int n = nums.size();
+        sort(nums.begin(), nums.end());
+
+        vector<vector<int>> dp(n + 1, vector<int>(p + 1, INT_MAX));
+        for (int i = 0; i <= n; i++) {
+            dp[i][0] = 0;
+        }
+
+        for (int i = n - 2; i >= 0; i--) {
+            for (int pairs = 1; pairs <= p; pairs++) {
+                int take = INT_MAX;
+                if (i + 1 < n) {
+                    take = max(nums[i + 1] - nums[i], dp[i + 2][pairs - 1]);
+                }
+                int skip = dp[i + 1][pairs];
+                dp[i][pairs] = min(take, skip);
+            }
+        }
+
+        return dp[0][p];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} p
+     * @return {number}
+     */
+    minimizeMax(nums, p) {
+        const n = nums.length;
+        nums.sort((a, b) => a - b);
+
+        const dp = Array.from({ length: n + 1 }, () =>
+            new Array(p + 1).fill(Infinity)
+        );
+        for (let i = 0; i <= n; i++) {
+            dp[i][0] = 0;
+        }
+
+        for (let i = n - 2; i >= 0; i--) {
+            for (let pairs = 1; pairs <= p; pairs++) {
+                let take = Infinity;
+                if (i + 1 < n) {
+                    take = Math.max(nums[i + 1] - nums[i], dp[i + 2][pairs - 1]);
+                }
+                const skip = dp[i + 1][pairs];
+                dp[i][pairs] = Math.min(take, skip);
+            }
+        }
+
+        return dp[0][p];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * p)$
+* Space complexity: $O(n * p)$
+
+> Where $n$ is the size of the input array and $p$ is the number of pairs to select.
+
+---
+
+## 3. Greesy + Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def minimizeMax(self, nums: List[int], p: int) -> int:
+        n = len(nums)
+        nums.sort()
+        
+        dp = [float('inf')] * (p + 1)
+        dp1 = [float('inf')] * (p + 1)
+        dp2 = [float('inf')] * (p + 1)
+
+        dp[0] = dp1[0] = dp2[0] = 0
+        for i in range(n - 1, -1, -1):
+            for pairs in range(1, p + 1):
+                take = float('inf')
+                if i + 1 < n:
+                    take = max(nums[i + 1] - nums[i], dp2[pairs - 1])
+                skip = dp1[pairs]
+                dp[pairs] = min(take, skip)
+            
+            dp2 = dp1[:]
+            dp1 = dp[:]
+            dp = [float('inf')] * (p + 1)
+            dp[0] = 0
+            
+        return dp1[p]
+```
+
+```java
+public class Solution {
+    public int minimizeMax(int[] nums, int p) {
+        int n = nums.length;
+        Arrays.sort(nums);
+
+        int[] dp = new int[p + 1];
+        int[] dp1 = new int[p + 1];
+        int[] dp2 = new int[p + 1];
+        Arrays.fill(dp, Integer.MAX_VALUE);
+        Arrays.fill(dp1, Integer.MAX_VALUE);
+        Arrays.fill(dp2, Integer.MAX_VALUE);
+        dp[0] = dp1[0] = dp2[0] = 0;
+
+        for (int i = n - 1; i >= 0; i--) {
+            for (int pairs = 1; pairs <= p; pairs++) {
+                int take = Integer.MAX_VALUE;
+                if (i + 1 < n) {
+                    take = Math.max(nums[i + 1] - nums[i], dp2[pairs - 1]);
+                }
+                int skip = dp1[pairs];
+                dp[pairs] = Math.min(take, skip);
+            }
+            dp2 = dp1.clone();
+            dp1 = dp.clone();
+            Arrays.fill(dp, Integer.MAX_VALUE);
+            dp[0] = 0;
+        }
+
+        return dp1[p];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minimizeMax(vector<int>& nums, int p) {
+        int n = nums.size();
+        sort(nums.begin(), nums.end());
+
+        vector<int> dp(p + 1, INT_MAX);
+        vector<int> dp1(p + 1, INT_MAX);
+        vector<int> dp2(p + 1, INT_MAX);
+
+        dp[0] = dp1[0] = dp2[0] = 0;
+
+        for (int i = n - 1; i >= 0; i--) {
+            for (int pairs = 1; pairs <= p; pairs++) {
+                int take = INT_MAX;
+                if (i + 1 < n) {
+                    take = max(nums[i + 1] - nums[i], dp2[pairs - 1]);
+                }
+                int skip = dp1[pairs];
+                dp[pairs] = min(take, skip);
+            }
+            dp2 = dp1;
+            dp1 = dp;
+            fill(dp.begin(), dp.end(), INT_MAX);
+            dp[0] = 0;
+        }
+
+        return dp1[p];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} p
+     * @return {number}
+     */
+    minimizeMax(nums, p) {
+        const n = nums.length;
+        nums.sort((a, b) => a - b);
+
+        let dp = new Array(p + 1).fill(Infinity);
+        let dp1 = new Array(p + 1).fill(Infinity);
+        let dp2 = new Array(p + 1).fill(Infinity);
+
+        dp[0] = dp1[0] = dp2[0] = 0;
+
+        for (let i = n - 1; i >= 0; i--) {
+            for (let pairs = 1; pairs <= p; pairs++) {
+                let take = Infinity;
+                if (i + 1 < n) {
+                    take = Math.max(nums[i + 1] - nums[i], dp2[pairs - 1]);
+                }
+                let skip = dp1[pairs];
+                dp[pairs] = Math.min(take, skip);
+            }
+            dp2 = dp1.slice();
+            dp1 = dp.slice();
+            dp.fill(Infinity);
+            dp[0] = 0;
+        }
+
+        return dp1[p];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * p)$
+* Space complexity: $O(p)$
+
+> Where $n$ is the size of the input array and $p$ is the number of pairs to select.
+
+---
+
+## 4. Greedy + Binary Search
+
+::tabs-start
+
+```python
+class Solution:
+    def minimizeMax(self, nums: List[int], p: int) -> int:
+        if p == 0:
+            return 0
+        
+        def isValid(threshold):
+            i, cnt = 0, 0
+            while i < len(nums) - 1:
+                if abs(nums[i] - nums[i + 1]) <= threshold:
+                    cnt += 1
+                    i += 2
+                else:
+                    i += 1
+                if cnt == p:
+                    return True
+            return False
+        
+        nums.sort()
+        l, r = 0, nums[-1] - nums[0]
+        res = nums[-1] - nums[0]
+        
+        while l <= r:
+            m = l + (r - l) // 2
+            if isValid(m):
+                res = m
+                r = m - 1
+            else:
+                l = m + 1
+                
+        return res
+```
+
+```java
+public class Solution {
+    public int minimizeMax(int[] nums, int p) {
+        if (p == 0) return 0;
+        
+        Arrays.sort(nums);
+        int left = 0, right = nums[nums.length - 1] - nums[0];
+        int result = right;
+        
+        while (left <= right) {
+            int mid = left + (right - left) / 2;
+            if (isValid(nums, mid, p)) {
+                result = mid;
+                right = mid - 1;
+            } else {
+                left = mid + 1;
+            }
+        }
+        
+        return result;
+    }
+    
+    private boolean isValid(int[] nums, int threshold, int p) {
+        int i = 0, count = 0;
+        while (i < nums.length - 1) {
+            if (Math.abs(nums[i] - nums[i + 1]) <= threshold) {
+                count++;
+                i += 2;
+            } else {
+                i++;
+            }
+            if (count == p) return true;
+        }
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minimizeMax(vector<int>& nums, int p) {
+        if (p == 0) return 0;
+        
+        sort(nums.begin(), nums.end());
+        int left = 0, right = nums.back() - nums[0];
+        int result = right;
+        
+        while (left <= right) {
+            int mid = left + (right - left) / 2;
+            if (isValid(nums, mid, p)) {
+                result = mid;
+                right = mid - 1;
+            } else {
+                left = mid + 1;
+            }
+        }
+        
+        return result;
+    }
+    
+private:
+    bool isValid(vector<int>& nums, int threshold, int p) {
+        int i = 0, count = 0;
+        while (i < nums.size() - 1) {
+            if (abs(nums[i] - nums[i + 1]) <= threshold) {
+                count++;
+                i += 2;
+            } else {
+                i++;
+            }
+            if (count == p) return true;
+        }
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} p
+     * @return {number}
+     */
+    minimizeMax(nums, p) {
+        if (p === 0) return 0;
+
+        nums.sort((a, b) => a - b);
+        let l = 0, r = nums[nums.length - 1] - nums[0], res = r;
+
+        const isValid = (threshold) => {
+            let i = 0, cnt = 0;
+            while (i < nums.length - 1) {
+                if (Math.abs(nums[i] - nums[i + 1]) <= threshold) {
+                    cnt++;
+                    i += 2;
+                } else {
+                    i++;
+                }
+                if (cnt === p) return true;
+            }
+            return false;
+        };
+
+        while (l <= r) {
+            let m = Math.floor(l + (r - l) / 2);
+            if (isValid(m)) {
+                res = m;
+                r = m - 1;
+            } else {
+                l = m + 1;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n\log n + n\log m)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+> Where $n$ is the size of the input array and $m$ is the maximum value in the array.
\ No newline at end of file
diff --git a/articles/minimum-array-end.md b/articles/minimum-array-end.md
new file mode 100644
index 000000000..2aba4edba
--- /dev/null
+++ b/articles/minimum-array-end.md
@@ -0,0 +1,320 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def minEnd(self, n: int, x: int) -> int:
+        res = x
+        for i in range(n - 1):
+            res = (res + 1) | x
+        return res
+```
+
+```java
+public class Solution {
+    public long minEnd(int n, int x) {
+        long res = x;
+        for (int i = 0; i < n - 1; i++) {
+            res = (res + 1) | x;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long minEnd(int n, int x) {
+        long long res = x;
+        for (int i = 0; i < n - 1; i++) {
+            res = (res + 1) | x;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} x
+     * @return {number}
+     */
+    minEnd(n, x) {
+        let res = BigInt(x);
+        for (let i = 0; i < n - 1; i++) {
+            res = (res + BigInt(1)) | BigInt(x);
+        }
+        return Number(res);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Binary Representation And Bit Manipulation
+
+::tabs-start
+
+```python
+class Solution:
+    def minEnd(self, n: int, x: int) -> int:
+        res = 0
+        n -= 1
+
+        x_bin = [0] * 64  # Binary representation of x
+        n_bin = [0] * 64  # Binary representation of n-1
+
+        for i in range(32):
+            x_bin[i] = (x >> i) & 1
+            n_bin[i] = (n >> i) & 1
+
+        i_x = 0
+        i_n = 0
+        while i_x < 63:
+            while i_x < 63 and x_bin[i_x] != 0:
+                i_x += 1
+            x_bin[i_x] = n_bin[i_n]
+            i_x += 1
+            i_n += 1
+
+        for i in range(64):
+            if x_bin[i] == 1:
+                res += (1 << i)
+
+        return res
+```
+
+```java
+public class Solution {
+    public long minEnd(int n, int x) {
+        long res = 0;
+        n -= 1;
+
+        int[] x_bin = new int[64]; // Binary representation of x
+        int[] n_bin = new int[64]; // Binary representation of n-1
+
+        for (int i = 0; i < 32; i++) {
+            x_bin[i] = (x >> i) & 1;
+            n_bin[i] = (n >> i) & 1;
+        }
+
+        int i_x = 0;
+        int i_n = 0;
+        while (i_x < 63) {
+            while (i_x < 63 && x_bin[i_x] != 0) {
+                i_x++;
+            }
+            x_bin[i_x] = n_bin[i_n];
+            i_x++;
+            i_n++;
+        }
+
+        for (int i = 0; i < 64; i++) {
+            if (x_bin[i] == 1) {
+                res += (1L << i);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long minEnd(int n, int x) {
+        long long res = 0;
+        n -= 1;
+
+        vector<int> x_bin(64, 0); // Binary representation of x
+        vector<int> n_bin(64, 0); // Binary representation of n-1
+
+        for (int i = 0; i < 32; i++) {
+            x_bin[i] = (x >> i) & 1;
+            n_bin[i] = (n >> i) & 1;
+        }
+
+        int i_x = 0;
+        int i_n = 0;
+        while (i_x < 63) {
+            while (i_x < 63 && x_bin[i_x] != 0) {
+                i_x++;
+            }
+            x_bin[i_x] = n_bin[i_n];
+            i_x++;
+            i_n++;
+        }
+
+        for (int i = 0; i < 64; i++) {
+            if (x_bin[i] == 1) {
+                res += (1LL << i);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} x
+     * @return {number}
+     */
+    minEnd(n, x) {
+        let res = 0n;
+        n -= 1;
+
+        const x_bin = new Array(64).fill(0); // Binary representation of x
+        const n_bin = new Array(64).fill(0); // Binary representation of n-1
+
+        for (let i = 0; i < 32; i++) {
+            x_bin[i] = (x >> i) & 1;
+            n_bin[i] = (n >> i) & 1;
+        }
+
+        let i_x = 0;
+        let i_n = 0;
+        while (i_x < 63) {
+            while (i_x < 63 && x_bin[i_x] !== 0) {
+                i_x++;
+            }
+            x_bin[i_x] = n_bin[i_n];
+            i_x++;
+            i_n++;
+        }
+
+        for (let i = 0; i < 64; i++) {
+            if (x_bin[i] === 1) {
+                res += BigInt(1) << BigInt(i);
+            }
+        }
+
+        return Number(res);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(\log n)$
+
+---
+
+## 3. Bit Manipulation
+
+::tabs-start
+
+```python
+class Solution:
+    def minEnd(self, n: int, x: int) -> int:
+        res = x
+        i_x = 1
+        i_n = 1  # for n-1
+
+        while i_n <= n - 1:
+            if i_x & x == 0:
+                if i_n & (n - 1):
+                    res = res | i_x
+                i_n = i_n << 1
+            i_x = i_x << 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public long minEnd(int n, int x) {
+        long res = x;
+        long i_x = 1;
+        long i_n = 1; // for n - 1
+
+        while (i_n <= n - 1) {
+            if ((i_x & x) == 0) {
+                if ((i_n & (n - 1)) != 0) {
+                    res = res | i_x;
+                }
+                i_n = i_n << 1;
+            }
+            i_x = i_x << 1;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long minEnd(int n, int x) {
+        long long res = x;
+        long long i_x = 1;
+        long long i_n = 1; // for n - 1
+
+        while (i_n <= n - 1) {
+            if ((i_x & x) == 0) {
+                if (i_n & (n - 1)) {
+                    res = res | i_x;
+                }
+                i_n = i_n << 1;
+            }
+            i_x = i_x << 1;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} x
+     * @return {number}
+     */
+    minEnd(n, x) {
+        let res = BigInt(x);
+        let i_x = 1n;
+        let i_n = 1n;
+        n = BigInt(n - 1);
+
+        while (i_n <= n) {
+            if ((i_x & res) === 0n) {
+                if ((i_n & n) !== 0n) {
+                    res = res | i_x;
+                }
+                i_n = i_n << 1n;
+            }
+            i_x = i_x << 1n;
+        }
+
+        return Number(res);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/minimum-changes-to-make-alternating-binary-string.md b/articles/minimum-changes-to-make-alternating-binary-string.md
new file mode 100644
index 000000000..05b5629b5
--- /dev/null
+++ b/articles/minimum-changes-to-make-alternating-binary-string.md
@@ -0,0 +1,207 @@
+## 1. Start with Zero and One 
+
+::tabs-start
+
+```python
+class Solution:
+    def minOperations(self, s: str) -> int:
+        cur = cnt1 = 0
+        for c in s:
+            if int(c) != cur:
+                cnt1 += 1
+            cur ^= 1
+        
+        cur = 1
+        cnt2 = 0
+        for c in s:
+            if int(c) != cur:
+                cnt2 += 1
+            cur ^= 1
+        
+        return min(cnt1, cnt2)
+```
+
+```java
+public class Solution {
+    public int minOperations(String s) {
+        int cur = 0, cnt1 = 0;
+        for (char c : s.toCharArray()) {
+            if (c - '0' != cur) {
+                cnt1++;
+            }
+            cur ^= 1;
+        }
+
+        cur = 1;
+        int cnt2 = 0;
+        for (char c : s.toCharArray()) {
+            if (c - '0' != cur) {
+                cnt2++;
+            }
+            cur ^= 1;
+        }
+
+        return Math.min(cnt1, cnt2);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minOperations(string s) {
+        int cur = 0, cnt1 = 0;
+        for (char c : s) {
+            if (c - '0' != cur) {
+                cnt1++;
+            }
+            cur ^= 1;
+        }
+
+        cur = 1;
+        int cnt2 = 0;
+        for (char c : s) {
+            if (c - '0' != cur) {
+                cnt2++;
+            }
+            cur ^= 1;
+        }
+
+        return min(cnt1, cnt2);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    minOperations(s) {
+        let cur = 0, cnt1 = 0;
+        for (let c of s) {
+            if (parseInt(c) !== cur) {
+                cnt1++;
+            }
+            cur ^= 1;
+        }
+
+        cur = 1;
+        let cnt2 = 0;
+        for (let c of s) {
+            if (parseInt(c) !== cur) {
+                cnt2++;
+            }
+            cur ^= 1;
+        }
+
+        return Math.min(cnt1, cnt2);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Start with Zero or One
+
+::tabs-start
+
+```python
+class Solution:
+    def minOperations(self, s: str) -> int:
+        count = 0
+
+        for i in range(len(s)):
+            if i % 2 == 0:
+                count += 1 if s[i] == '0' else 0
+            else:
+                count += 1 if s[i] == '1' else 0
+                
+        return min(count, len(s) - count)
+```
+
+```java
+public class Solution {
+    public int minOperations(String s) {
+        int count = 0;
+
+        for (int i = 0; i < s.length(); i++) {
+            if (i % 2 == 0) {
+                if (s.charAt(i) == '0') {
+                    count++;
+                }
+            } else {
+                if (s.charAt(i) == '1') {
+                    count++;
+                }
+            }
+        }
+
+        return Math.min(count, s.length() - count);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minOperations(string s) {
+        int count = 0;
+
+        for (int i = 0; i < s.size(); i++) {
+            if (i % 2 == 0) {
+                if (s[i] == '0') {
+                    count++;
+                }
+            } else {
+                if (s[i] == '1') {
+                    count++;
+                }
+            }
+        }
+
+        return min(count, (int)s.size() - count);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    minOperations(s) {
+        let count = 0;
+
+        for (let i = 0; i < s.length; i++) {
+            if (i % 2 === 0) {
+                if (s[i] === '0') {
+                    count++;
+                }
+            } else {
+                if (s[i] === '1') {
+                    count++;
+                }
+            }
+        }
+
+        return Math.min(count, s.length - count);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/minimum-cost-for-tickets.md b/articles/minimum-cost-for-tickets.md
new file mode 100644
index 000000000..1b32c8980
--- /dev/null
+++ b/articles/minimum-cost-for-tickets.md
@@ -0,0 +1,953 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def mincostTickets(self, days: List[int], costs: List[int]) -> int:
+        n = len(days)
+
+        def dfs(i):
+            if i == n:
+                return 0
+
+            res = costs[0] + dfs(i + 1)            
+            j = i
+            while j < n and days[j] < days[i] + 7:
+                j += 1
+            res = min(res, costs[1] + dfs(j))
+            
+            j = i
+            while j < n and days[j] < days[i] + 30:
+                j += 1
+            res = min(res, costs[2] + dfs(j))
+
+            return res
+        
+        return dfs(0)
+```
+
+```java
+public class Solution {
+    public int mincostTickets(int[] days, int[] costs) {
+        return dfs(0, days.length, days, costs);
+    }
+
+    private int dfs(int i, int n, int[] days, int[] costs) {
+        if (i == n) return 0;
+
+        int res = costs[0] + dfs(i + 1, n, days, costs);
+        int j = i;
+        while (j < n && days[j] < days[i] + 7) {
+            j++;
+        }
+        res = Math.min(res, costs[1] + dfs(j, n, days, costs));
+
+        j = i;
+        while (j < n && days[j] < days[i] + 30) {
+            j++;
+        }
+        res = Math.min(res, costs[2] + dfs(j, n, days, costs));
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int mincostTickets(vector<int>& days, vector<int>& costs) {
+        int n = days.size();
+
+        function<int(int)> dfs = [&](int i) -> int {
+            if (i == n) return 0;
+
+            int res = costs[0] + dfs(i + 1);
+
+            int j = i;
+            while (j < n && days[j] < days[i] + 7) {
+                j++;
+            }
+            res = min(res, costs[1] + dfs(j));
+
+            j = i;
+            while (j < n && days[j] < days[i] + 30) {
+                j++;
+            }
+            res = min(res, costs[2] + dfs(j));
+
+            return res;
+        };
+
+        return dfs(0);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} days
+     * @param {number[]} costs
+     * @return {number}
+     */
+    mincostTickets(days, costs) {
+        const n = days.length;
+
+        const dfs = (i) => {
+            if (i === n) return 0;
+
+            let res = costs[0] + dfs(i + 1);
+
+            let j = i;
+            while (j < n && days[j] < days[i] + 7) {
+                j++;
+            }
+            res = Math.min(res, costs[1] + dfs(j));
+
+            j = i;
+            while (j < n && days[j] < days[i] + 30) {
+                j++;
+            }
+            res = Math.min(res, costs[2] + dfs(j));
+
+            return res;
+        };
+
+        return dfs(0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(3 ^ n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def mincostTickets(self, days: List[int], costs: List[int]) -> int:
+        dp = {}
+
+        def dfs(i):
+            if i == len(days):
+                return 0
+            if i in dp:
+                return dp[i]
+
+            dp[i] = float("inf")
+            j = i
+            for d, c in zip([1, 7, 30], costs):
+                while j < len(days) and days[j] < days[i] + d:
+                    j += 1
+                dp[i] = min(dp[i], c + dfs(j))
+
+            return dp[i]
+
+        return dfs(0)
+```
+
+```java
+public class Solution {
+    private int[] dp;
+
+    public int mincostTickets(int[] days, int[] costs) {
+        dp = new int[days.length];
+        Arrays.fill(dp, -1);
+        return dfs(0, days, costs);
+    }
+
+    private int dfs(int i, int[] days, int[] costs) {
+        if (i == days.length) {
+            return 0;
+        }
+        if (dp[i] != -1) {
+            return dp[i];
+        }
+
+        dp[i] = Integer.MAX_VALUE;
+        int idx = 0, j = i;
+        for (int d : new int[]{1, 7, 30}) {
+            while (j < days.length && days[j] < days[i] + d) {
+                j++;
+            }
+            dp[i] = Math.min(dp[i], costs[idx] + dfs(j, days, costs));
+            idx++;
+        }
+        return dp[i];
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<int> dp;
+
+    int dfs(int i, const vector<int>& days, const vector<int>& costs) {
+        if (i == days.size()) return 0;
+        if (dp[i] != -1) return dp[i];
+
+        dp[i] = INT_MAX;
+        int idx = 0, j = i;
+        for (int d : {1, 7, 30}) {
+            while (j < days.size() && days[j] < days[i] + d) {
+                j++;
+            }
+            dp[i] = min(dp[i], costs[idx] + dfs(j, days, costs));
+            idx++;
+        }
+        return dp[i];
+    }
+
+public:
+    int mincostTickets(vector<int>& days, vector<int>& costs) {
+        dp = vector<int>(days.size(), -1);
+        return dfs(0, days, costs);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} days
+     * @param {number[]} costs
+     * @return {number}
+     */
+    mincostTickets(days, costs) {
+        const dp = new Array(days.length).fill(-1);
+
+        const dfs = (i) => {
+            if (i === days.length) return 0;
+            if (dp[i] !== -1) return dp[i];
+
+            dp[i] = Infinity;
+            let j = i;
+            [1, 7, 30].forEach((d, idx) => {
+                while (j < days.length && days[j] < days[i] + d) {
+                    j++;
+                }
+                dp[i] = Math.min(dp[i], costs[idx] + dfs(j));
+            });
+
+            return dp[i];
+        };
+
+        return dfs(0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def mincostTickets(self, days: List[int], costs: List[int]) -> int:
+        n = len(days)
+        dp = [0] * (n + 1)
+        
+        for i in range(n - 1, -1, -1):
+            dp[i] = float('inf')
+            j = i
+            for d, c in zip([1, 7, 30], costs):
+                while j < n and days[j] < days[i] + d:
+                    j += 1
+                dp[i] = min(dp[i], c + dp[j])
+        
+        return dp[0]
+```
+
+```java
+public class Solution {
+    public int mincostTickets(int[] days, int[] costs) {
+        int n = days.length;
+        int[] dp = new int[n + 1];
+        
+        for (int i = n - 1; i >= 0; i--) {
+            dp[i] = Integer.MAX_VALUE;
+            int idx = 0, j = i;
+            for (int d : new int[]{1, 7, 30}) {
+                while (j < n && days[j] < days[i] + d) {
+                    j++;
+                }
+                dp[i] = Math.min(dp[i], costs[idx] + dp[j]);
+                idx++;
+            }
+        }
+        
+        return dp[0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int mincostTickets(vector<int>& days, vector<int>& costs) {
+        int n = days.size();
+        vector<int> dp(n + 1, 0);
+
+        for (int i = n - 1; i >= 0; i--) {
+            dp[i] = INT_MAX;
+            int j = i;
+            for (int k = 0; k < 3; ++k) {
+                while (j < n && days[j] < days[i] + (k == 0 ? 1 : k == 1 ? 7 : 30)) {
+                    j++;
+                }
+                dp[i] = min(dp[i], costs[k] + dp[j]);
+            }
+        }
+
+        return dp[0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} days
+     * @param {number[]} costs
+     * @return {number}
+     */
+    mincostTickets(days, costs) {
+        const n = days.length;
+        const dp = new Array(n + 1).fill(0);
+
+        for (let i = n - 1; i >= 0; i--) {
+            dp[i] = Infinity;
+            let j = i;
+            [1, 7, 30].forEach((d, idx) => {
+                while (j < n && days[j] < days[i] + d) {
+                    j++;
+                }
+                dp[i] = Math.min(dp[i], costs[idx] + dp[j]);
+            });
+        }
+
+        return dp[0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Dynamic Programming (Bottom-Up) + Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def mincostTickets(self, days: List[int], costs: List[int]) -> int:
+        days.append(days[-1] + 30)
+        n = len(days)
+        dp = [0] * n
+        last7 = last30 = n
+
+        for i in range(n - 2, -1, -1):
+            dp[i] = dp[i + 1] + costs[0]
+
+            while last7 > i + 1 and days[last7 - 1] >= days[i] + 7:
+                last7 -= 1
+            dp[i] = min(dp[i], costs[1] + dp[last7])
+
+            while last30 > i + 1 and days[last30 - 1] >= days[i] + 30:
+                last30 -= 1
+            dp[i] = min(dp[i], costs[2] + dp[last30])
+
+        return dp[0]
+```
+
+```java
+public class Solution {
+    public int mincostTickets(int[] days, int[] costs) {
+        int n = days.length;
+        int[] dp = new int[n + 1];
+        int last7 = n, last30 = n;
+        int[] extendedDays = Arrays.copyOf(days, n + 1);
+        extendedDays[n] = days[n - 1] + 30;
+
+        for (int i = n - 1; i >= 0; i--) {
+            dp[i] = dp[i + 1] + costs[0];
+
+            while (last7 > i + 1 && extendedDays[last7 - 1] >= days[i] + 7) {
+                last7--;
+            }
+            dp[i] = Math.min(dp[i], costs[1] + dp[last7]);
+
+            while (last30 > i + 1 && extendedDays[last30 - 1] >= days[i] + 30) {
+                last30--;
+            }
+            dp[i] = Math.min(dp[i], costs[2] + dp[last30]);
+        }
+
+        return dp[0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int mincostTickets(vector<int>& days, vector<int>& costs) {
+        days.push_back(days.back() + 30);
+        int n = days.size();
+        vector<int> dp(n, 0);
+        int last7 = n, last30 = n;
+
+        for (int i = n - 2; i >= 0; --i) {
+            dp[i] = dp[i + 1] + costs[0];
+
+            while (last7 > i + 1 && days[last7 - 1] >= days[i] + 7) {
+                --last7;
+            }
+            dp[i] = min(dp[i], costs[1] + dp[last7]);
+
+            while (last30 > i + 1 && days[last30 - 1] >= days[i] + 30) {
+                --last30;
+            }
+            dp[i] = min(dp[i], costs[2] + dp[last30]);
+        }
+
+        return dp[0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} days
+     * @param {number[]} costs
+     * @return {number}
+     */
+    mincostTickets(days, costs) {
+        days.push(days[days.length - 1] + 30);
+        const n = days.length;
+        const dp = new Array(n).fill(0);
+        let last7 = n, last30 = n;
+
+        for (let i = n - 2; i >= 0; i--) {
+            dp[i] = dp[i + 1] + costs[0];
+
+            while (last7 > i + 1 && days[last7 - 1] >= days[i] + 7) {
+                last7--;
+            }
+            dp[i] = Math.min(dp[i], costs[1] + dp[last7]);
+
+            while (last30 > i + 1 && days[last30 - 1] >= days[i] + 30) {
+                last30--;
+            }
+            dp[i] = Math.min(dp[i], costs[2] + dp[last30]);
+        }
+
+        return dp[0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 5. Dynamic Programming (Space Optimized) - I
+
+::tabs-start
+
+```python
+class Solution:
+    def mincostTickets(self, days: List[int], costs: List[int]) -> int:
+        dp7, dp30 = deque(), deque()
+        dp = 0
+
+        for d in days:
+            while dp7 and dp7[0][0] + 7 <= d:
+                dp7.popleft()
+            
+            while dp30 and dp30[0][0] + 30 <= d:
+                dp30.popleft()
+            
+            dp7.append([d, dp + costs[1]])
+            dp30.append([d, dp + costs[2]])
+            dp = min(dp + costs[0], dp7[0][1], dp30[0][1])
+        
+        return dp
+```
+
+```java
+public class Solution {
+    public int mincostTickets(int[] days, int[] costs) {
+        Queue<int[]> dp7 = new LinkedList<>();
+        Queue<int[]> dp30 = new LinkedList<>();
+        int dp = 0;
+
+        for (int d : days) {
+            while (!dp7.isEmpty() && dp7.peek()[0] + 7 <= d) {
+                dp7.poll();
+            }
+
+            while (!dp30.isEmpty() && dp30.peek()[0] + 30 <= d) {
+                dp30.poll();
+            }
+
+            dp7.offer(new int[]{d, dp + costs[1]});
+            dp30.offer(new int[]{d, dp + costs[2]});
+            dp = Math.min(dp + costs[0], Math.min(dp7.peek()[1], dp30.peek()[1]));
+        }
+
+        return dp;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int mincostTickets(vector<int>& days, vector<int>& costs) {
+        queue<pair<int, int>> dp7, dp30;
+        int dp = 0;
+
+        for (int& d : days) {
+            while (!dp7.empty() && dp7.front().first + 7 <= d) {
+                dp7.pop();
+            }
+
+            while (!dp30.empty() && dp30.front().first + 30 <= d) {
+                dp30.pop();
+            }
+
+            dp7.emplace(d, dp + costs[1]);
+            dp30.emplace(d, dp + costs[2]);
+            dp = min({dp + costs[0], dp7.front().second, dp30.front().second});
+        }
+
+        return dp;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} days
+     * @param {number[]} costs
+     * @return {number}
+     */
+    mincostTickets(days, costs) {
+        const dp7 = new Queue;
+        const dp30 = new Queue;
+        let dp = 0;
+
+        for (const d of days) {
+            while (!dp7.isEmpty() && dp7.front()[0] + 7 <= d) {
+                dp7.pop();
+            }
+
+            while (!dp30.isEmpty() && dp30.front()[0] + 30 <= d) {
+                dp30.pop();
+            }
+
+            dp7.push([d, dp + costs[1]]);
+            dp30.push([d, dp + costs[2]]);
+
+            dp = Math.min(dp + costs[0], dp7.front()[1], dp30.front()[1]);
+        }
+
+        return dp;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ since we keep at most $30$ values in the queue.
+
+---
+
+## 6. Dynamic Programming (Space Optimized) - II
+
+::tabs-start
+
+```python
+class Solution:
+    def mincostTickets(self, days: List[int], costs: List[int]) -> int:
+        dp7, dp30 = deque(), deque()
+        dp = 0
+
+        last7 = last30 = 0
+        for i in range(len(days) - 1, -1, -1):
+            dp += costs[0]
+            while dp7 and dp7[-1][0] >= days[i] + 7:
+                last7 = dp7.pop()[1]
+            dp = min(dp, costs[1] + last7)
+
+            while dp30 and dp30[-1][0] >= days[i] + 30:
+                last30 = dp30.pop()[1]
+            dp = min(dp, costs[2] + last30)
+
+            dp7.appendleft([days[i], dp])
+            dp30.appendleft([days[i], dp])
+
+        return dp
+```
+
+```java
+public class Solution {
+    public int mincostTickets(int[] days, int[] costs) {
+        Deque<int[]> dp7 = new ArrayDeque<>();
+        Deque<int[]> dp30 = new ArrayDeque<>();
+        int dp = 0, last7 = 0, last30 = 0;
+
+        for (int i = days.length - 1; i >= 0; i--) {
+            dp += costs[0];
+
+            while (!dp7.isEmpty() && dp7.peekLast()[0] >= days[i] + 7) {
+                last7 = dp7.pollLast()[1];
+            }
+            dp = Math.min(dp, costs[1] + last7);
+
+            while (!dp30.isEmpty() && dp30.peekLast()[0] >= days[i] + 30) {
+                last30 = dp30.pollLast()[1];
+            }
+            dp = Math.min(dp, costs[2] + last30);
+
+            dp7.offerFirst(new int[]{days[i], dp});
+            dp30.offerFirst(new int[]{days[i], dp});
+        }
+        return dp;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int mincostTickets(vector<int>& days, vector<int>& costs) {
+        deque<pair<int, int>> dp7, dp30;
+        int dp = 0, last7 = 0, last30 = 0;
+
+        for (int i = days.size() - 1; i >= 0; --i) {
+            dp += costs[0];
+
+            while (!dp7.empty() && dp7.back().first >= days[i] + 7) {
+                last7 = dp7.back().second;
+                dp7.pop_back();
+            }
+            dp = min(dp, costs[1] + last7);
+
+            while (!dp30.empty() && dp30.back().first >= days[i] + 30) {
+                last30 = dp30.back().second;
+                dp30.pop_back();
+            }
+            dp = min(dp, costs[2] + last30);
+
+            dp7.push_front({days[i], dp});
+            dp30.push_front({days[i], dp});
+        }
+        return dp;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} days
+     * @param {number[]} costs
+     * @return {number}
+     */
+    mincostTickets(days, costs) {
+        const dp7 = new Deque();
+        const dp30 = new Deque();
+        let dp = 0, last7 = 0, last30 = 0;
+
+        for (let i = days.length - 1; i >= 0; i--) {
+            dp += costs[0];
+
+            while (!dp7.isEmpty() && dp7.back()[0] >= days[i] + 7) {
+                last7 = dp7.popBack()[1];
+            }
+            dp = Math.min(dp, costs[1] + last7);
+
+            while (!dp30.isEmpty() && dp30.back()[0] >= days[i] + 30) {
+                last30 = dp30.popBack()[1];
+            }
+            dp = Math.min(dp, costs[2] + last30);
+
+            dp7.pushFront([days[i], dp]);
+            dp30.pushFront([days[i], dp]);
+        }
+        return dp;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ since we keep at most $30$ values in the deque.
+
+---
+
+## 7. Dynamic Programming (Space Optimized) - III
+
+::tabs-start
+
+```python
+class Solution:
+    def mincostTickets(self, days: List[int], costs: List[int]) -> int:
+        dp = [0] * 366
+        i = 0
+
+        for d in range(1, 366):
+            dp[d] = dp[d - 1]
+            if i == len(days):
+                return dp[d]
+
+            if d == days[i]:
+                dp[d] += costs[0]
+                dp[d] = min(dp[d], costs[1] + dp[max(0, d - 7)])
+                dp[d] = min(dp[d], costs[2] + dp[max(0, d - 30)])
+                i += 1
+
+        return dp[365]
+```
+
+```java
+public class Solution {
+    public int mincostTickets(int[] days, int[] costs) {
+        int[] dp = new int[366];
+        int i = 0;
+
+        for (int d = 1; d < 366; d++) {
+            dp[d] = dp[d - 1];
+
+            if (i == days.length) {
+                return dp[d];
+            }
+
+            if (d == days[i]) {
+                dp[d] += costs[0];
+                dp[d] = Math.min(dp[d], costs[1] + dp[Math.max(0, d - 7)]);
+                dp[d] = Math.min(dp[d], costs[2] + dp[Math.max(0, d - 30)]);
+                i++;
+            }
+        }
+        return dp[365];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int mincostTickets(vector<int>& days, vector<int>& costs) {
+        vector<int> dp(366, 0);
+        int i = 0;
+
+        for (int d = 1; d < 366; d++) {
+            dp[d] = dp[d - 1];
+
+            if (i == days.size()) {
+                return dp[d];
+            }
+
+            if (d == days[i]) {
+                dp[d] += costs[0];
+                dp[d] = min(dp[d], costs[1] + dp[max(0, d - 7)]);
+                dp[d] = min(dp[d], costs[2] + dp[max(0, d - 30)]);
+                i++;
+            }
+        }
+        return dp[365];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} days
+     * @param {number[]} costs
+     * @return {number}
+     */
+    mincostTickets(days, costs) {
+        const dp = new Array(366).fill(0);
+        let i = 0;
+
+        for (let d = 1; d < 366; d++) {
+            dp[d] = dp[d - 1];
+
+            if (i === days.length) {
+                return dp[d];
+            }
+
+            if (d === days[i]) {
+                dp[d] += costs[0];
+                dp[d] = Math.min(dp[d], costs[1] + dp[Math.max(0, d - 7)]);
+                dp[d] = Math.min(dp[d], costs[2] + dp[Math.max(0, d - 30)]);
+                i++;
+            }
+        }
+        return dp[365];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ since the size of the $dp$ array is $366$.
+
+
+---
+
+## 8. Dynamic Programming (Space Optimized) - IV
+
+::tabs-start
+
+```python
+class Solution:
+    def mincostTickets(self, days: List[int], costs: List[int]) -> int:
+        dp = [0] * 31
+        i = 0
+
+        for d in range(1, 366):
+            if i >= len(days):
+                break
+            
+            dp[d % 31] = dp[(d - 1) % 31]
+
+            if d == days[i]:
+                dp[d % 31] += costs[0]
+                dp[d % 31] = min(dp[d % 31], costs[1] + dp[max(0, d - 7) % 31])
+                dp[d % 31] = min(dp[d % 31], costs[2] + dp[max(0, d - 30) % 31])
+                i += 1
+
+        return dp[days[-1] % 31]
+```
+
+```java
+public class Solution {
+    public int mincostTickets(int[] days, int[] costs) {
+        int[] dp = new int[31];
+        int i = 0;
+
+        for (int d = 1; d <= 365; d++) {
+            if (i >= days.length) break;
+
+            dp[d % 31] = dp[(d - 1) % 31];
+
+            if (d == days[i]) {
+                dp[d % 31] += costs[0];
+                dp[d % 31] = Math.min(dp[d % 31], costs[1] + dp[Math.max(0, d - 7) % 31]);
+                dp[d % 31] = Math.min(dp[d % 31], costs[2] + dp[Math.max(0, d - 30) % 31]);
+                i++;
+            }
+        }
+
+        return dp[days[days.length - 1] % 31];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int mincostTickets(vector<int>& days, vector<int>& costs) {
+        vector<int> dp(31, 0);
+        int i = 0;
+
+        for (int d = 1; d <= 365; d++) {
+            if (i >= days.size()) break;
+
+            dp[d % 31] = dp[(d - 1) % 31];
+
+            if (d == days[i]) {
+                dp[d % 31] += costs[0];
+                dp[d % 31] = min(dp[d % 31], costs[1] + dp[max(0, d - 7) % 31]);
+                dp[d % 31] = min(dp[d % 31], costs[2] + dp[max(0, d - 30) % 31]);
+                i++;
+            }
+        }
+
+        return dp[days.back() % 31];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} days
+     * @param {number[]} costs
+     * @return {number}
+     */
+    mincostTickets(days, costs) {
+        const dp = new Array(31).fill(0);
+        let i = 0;
+
+        for (let d = 1; d <= 365; d++) {
+            if (i >= days.length) break;
+
+            dp[d % 31] = dp[(d - 1) % 31];
+
+            if (d === days[i]) {
+                dp[d % 31] += costs[0];
+                dp[d % 31] = Math.min(dp[d % 31], costs[1] + dp[Math.max(0, d - 7) % 31]);
+                dp[d % 31] = Math.min(dp[d % 31], costs[2] + dp[Math.max(0, d - 30) % 31]);
+                i++;
+            }
+        }
+
+        return dp[days[days.length - 1] % 31];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ since the size of the $dp$ array is $31$.
\ No newline at end of file
diff --git a/articles/minimum-cost-to-cut-a-stick.md b/articles/minimum-cost-to-cut-a-stick.md
new file mode 100644
index 000000000..0ef0f2484
--- /dev/null
+++ b/articles/minimum-cost-to-cut-a-stick.md
@@ -0,0 +1,485 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def minCost(self, n: int, cuts: List[int]) -> int:
+        def dfs(l, r):
+            if r - l == 1:
+                return 0
+            res = float("inf")
+            for c in cuts:
+                if l < c < r:
+                    res = min(res, (r - l) + dfs(l, c) + dfs(c, r))
+            res = 0 if res == float("inf") else res
+            return res
+
+        return dfs(0, n)
+```
+
+```java
+public class Solution {
+    public int minCost(int n, int[] cuts) {
+        return dfs(0, n, cuts);
+    }
+
+    private int dfs(int l, int r, int[] cuts) {
+        if (r - l == 1) {
+            return 0;
+        }
+        int res = Integer.MAX_VALUE;
+        for (int c : cuts) {
+            if (l < c && c < r) {
+                res = Math.min(res, (r - l) + dfs(l, c, cuts) + dfs(c, r, cuts));
+            }
+        }
+        return res == Integer.MAX_VALUE ? 0 : res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minCost(int n, vector<int>& cuts) {
+        return dfs(0, n, cuts);
+    }
+
+private:
+    int dfs(int l, int r, vector<int>& cuts) {
+        if (r - l == 1) {
+            return 0;
+        }
+        int res = INT_MAX;
+        for (int c : cuts) {
+            if (l < c && c < r) {
+                res = min(res, (r - l) + dfs(l, c, cuts) + dfs(c, r, cuts));
+            }
+        }
+        return res == INT_MAX ? 0 : res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[]} cuts
+     * @return {number}
+     */
+    minCost(n, cuts) {
+        const dfs = (l, r) => {
+            if (r - l === 1) {
+                return 0;
+            }
+            let res = Infinity;
+            for (const c of cuts) {
+                if (l < c && c < r) {
+                    res = Math.min(res, (r - l) + dfs(l, c) + dfs(c, r));
+                }
+            }
+            return res === Infinity ? 0 : res;
+        };
+
+        return dfs(0, n);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m ^ N)$
+* Space complexity: $O(N)$ for recursion stack.
+
+> Where $m$ is the size of the $cuts$ array, $n$ is the length of the stick, and $N = min(n, m)$.
+
+---
+
+## 2. Dynamic Programming (Top-Down) - I
+
+::tabs-start
+
+```python
+class Solution:
+    def minCost(self, n: int, cuts: List[int]) -> int:
+        dp = {}
+
+        def dfs(l, r):
+            if r - l == 1:
+                return 0
+            if (l, r) in dp:
+                return dp[(l, r)]
+
+            res = float("inf")
+            for c in cuts:
+                if l < c < r:
+                    res = min(res, (r - l) + dfs(l, c) + dfs(c, r))
+            res = 0 if res == float("inf") else res
+            dp[(l, r)] = res
+            return res
+
+        return dfs(0, n)
+```
+
+```java
+public class Solution {
+    private Map<String, Integer> dp;
+
+    public int minCost(int n, int[] cuts) {
+        dp = new HashMap<>();
+        return dfs(0, n, cuts);
+    }
+
+    private int dfs(int l, int r, int[] cuts) {
+        if (r - l == 1) {
+            return 0;
+        }
+        String key = l + "," + r;
+        if (dp.containsKey(key)) {
+            return dp.get(key);
+        }
+
+        int res = Integer.MAX_VALUE;
+        for (int c : cuts) {
+            if (l < c && c < r) {
+                res = Math.min(res, (r - l) + dfs(l, c, cuts) + dfs(c, r, cuts));
+            }
+        }
+        res = res == Integer.MAX_VALUE ? 0 : res;
+        dp.put(key, res);
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minCost(int n, vector<int>& cuts) {
+        return dfs(0, n, cuts);
+    }
+
+private:
+    unordered_map<string, int> dp;
+
+    int dfs(int l, int r, vector<int>& cuts) {
+        if (r - l == 1) {
+            return 0;
+        }
+        string key = to_string(l) + "," + to_string(r);
+        if (dp.find(key) != dp.end()) {
+            return dp[key];
+        }
+
+        int res = INT_MAX;
+        for (int c : cuts) {
+            if (l < c && c < r) {
+                res = min(res, (r - l) + dfs(l, c, cuts) + dfs(c, r, cuts));
+            }
+        }
+        res = res == INT_MAX ? 0 : res;
+        dp[key] = res;
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[]} cuts
+     * @return {number}
+     */
+    minCost(n, cuts) {
+        const dp = new Map();
+
+        const dfs = (l, r) => {
+            if (r - l === 1) {
+                return 0;
+            }
+            const key = `${l},${r}`;
+            if (dp.has(key)) {
+                return dp.get(key);
+            }
+
+            let res = Infinity;
+            for (const c of cuts) {
+                if (l < c && c < r) {
+                    res = Math.min(res, (r - l) + dfs(l, c) + dfs(c, r));
+                }
+            }
+            res = res === Infinity ? 0 : res;
+            dp.set(key, res);
+            return res;
+        };
+
+        return dfs(0, n);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * N ^ 2)$
+* Space complexity: $O(N ^ 2)$ 
+
+> Where $m$ is the size of the $cuts$ array, $n$ is the length of the stick, and $N = min(n, m)$.
+
+---
+
+## 3. Dynamic Programming (Top-Down) - II
+
+::tabs-start
+
+```python
+class Solution:
+    def minCost(self, n: int, cuts: List[int]) -> int:
+        m = len(cuts)
+        cuts.sort()
+        dp = [[-1] * (m + 1) for _ in range(m + 1)]
+
+        def dfs(l, r, i, j):
+            if i > j:
+                return 0
+            if dp[i][j] != -1:
+                return dp[i][j]
+
+            res = float("inf")
+            for mid in range(i, j + 1):
+                cur = (r - l) + dfs(l, cuts[mid], i, mid - 1) + dfs(cuts[mid], r, mid + 1, j)
+                res = min(res, cur)
+
+            dp[i][j] = res
+            return res
+
+        return dfs(0, n, 0, m - 1)
+```
+
+```java
+public class Solution {
+    private int[][] dp;
+
+    public int minCost(int n, int[] cuts) {
+        int m = cuts.length;
+        Arrays.sort(cuts);
+        dp = new int[m + 1][m + 1];
+
+        for (int[] row : dp) {
+            Arrays.fill(row, -1);
+        }
+
+        return dfs(0, n, 0, m - 1, cuts);
+    }
+
+    private int dfs(int l, int r, int i, int j, int[] cuts) {
+        if (i > j) return 0;
+        if (dp[i][j] != -1) return dp[i][j];
+
+        int res = Integer.MAX_VALUE;
+        for (int mid = i; mid <= j; mid++) {
+            int cur = (r - l) + dfs(l, cuts[mid], i, mid - 1, cuts) + dfs(cuts[mid], r, mid + 1, j, cuts);
+            res = Math.min(res, cur);
+        }
+
+        dp[i][j] = res;
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<vector<int>> dp;
+
+public:
+    int minCost(int n, vector<int>& cuts) {
+        int m = cuts.size();
+        sort(cuts.begin(), cuts.end());
+        dp = vector<vector<int>>(m + 1, vector<int>(m + 1, -1));
+        return dfs(0, n, 0, m - 1, cuts);
+    }
+
+private:
+    int dfs(int l, int r, int i, int j, vector<int>& cuts) {
+        if (i > j) return 0;
+        if (dp[i][j] != -1) return dp[i][j];
+
+        int res = INT_MAX;
+        for (int mid = i; mid <= j; mid++) {
+            int cur = (r - l) + dfs(l, cuts[mid], i, mid - 1, cuts) + dfs(cuts[mid], r, mid + 1, j, cuts);
+            res = min(res, cur);
+        }
+
+        dp[i][j] = res;
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[]} cuts
+     * @return {number}
+     */
+    minCost(n, cuts) {
+        const m = cuts.length;
+        cuts.sort((a, b) => a - b);
+        const dp = Array.from({ length: m + 1 }, () => Array(m + 1).fill(-1));
+
+        const dfs = (l, r, i, j) => {
+            if (i > j) return 0;
+            if (dp[i][j] !== -1) return dp[i][j];
+
+            let res = Infinity;
+            for (let mid = i; mid <= j; mid++) {
+                const cur = (r - l) + dfs(l, cuts[mid], i, mid - 1) + dfs(cuts[mid], r, mid + 1, j);
+                res = Math.min(res, cur);
+            }
+
+            dp[i][j] = res;
+            return res;
+        };
+
+        return dfs(0, n, 0, m - 1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m\log m + m ^ 3)$
+* Space complexity: $O(m ^ 2)$
+
+> Where $m$ is the size of the $cuts$ array and $n$ is the length of the stick.
+
+---
+
+## 4. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def minCost(self, n: int, cuts: List[int]) -> int:
+        m = len(cuts)
+        cuts = [0] + sorted(cuts) + [n]
+        dp = [[0] * (m + 2) for _ in range(m + 2)]
+
+        for length in range(2, m + 2):
+            for i in range(m + 2 - length):
+                j = i + length
+                dp[i][j] = float("inf")
+                for mid in range(i + 1, j):
+                    dp[i][j] = min(
+                        dp[i][j], 
+                        cuts[j] - cuts[i] + dp[i][mid] + dp[mid][j]
+                    )
+
+        return dp[0][m + 1]
+```
+
+```java
+public class Solution {
+    public int minCost(int n, int[] cuts) {
+        int m = cuts.length;
+        int[] newCuts = new int[m + 2];
+        System.arraycopy(cuts, 0, newCuts, 1, m);
+        newCuts[0] = 0;
+        newCuts[m + 1] = n;
+        Arrays.sort(newCuts);
+
+        int[][] dp = new int[m + 2][m + 2];
+
+        for (int length = 2; length <= m + 1; length++) {
+            for (int i = 0; i + length <= m + 1; i++) {
+                int j = i + length;
+                dp[i][j] = Integer.MAX_VALUE;
+                for (int mid = i + 1; mid < j; mid++) {
+                    dp[i][j] = Math.min(dp[i][j], 
+                        newCuts[j] - newCuts[i] + dp[i][mid] + dp[mid][j]);
+                }
+            }
+        }
+
+        return dp[0][m + 1];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minCost(int n, vector<int>& cuts) {
+        int m = cuts.size();
+        cuts.push_back(0);
+        cuts.push_back(n);
+        sort(cuts.begin(), cuts.end());
+
+        vector<vector<int>> dp(m + 2, vector<int>(m + 2, 0));
+
+        for (int length = 2; length <= m + 1; length++) {
+            for (int i = 0; i + length <= m + 1; i++) {
+                int j = i + length;
+                dp[i][j] = INT_MAX;
+                for (int mid = i + 1; mid < j; mid++) {
+                    dp[i][j] = min(dp[i][j], 
+                        cuts[j] - cuts[i] + dp[i][mid] + dp[mid][j]);
+                }
+            }
+        }
+
+        return dp[0][m + 1];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[]} cuts
+     * @return {number}
+     */
+    minCost(n, cuts) {
+        const m = cuts.length;
+        cuts = [0, ...cuts.sort((a, b) => a - b), n];
+        const dp = Array.from({ length: m + 2 }, () => Array(m + 2).fill(0));
+
+        for (let length = 2; length <= m + 1; length++) {
+            for (let i = 0; i + length <= m + 1; i++) {
+                const j = i + length;
+                dp[i][j] = Infinity;
+                for (let mid = i + 1; mid < j; mid++) {
+                    dp[i][j] = Math.min(
+                        dp[i][j],
+                        cuts[j] - cuts[i] + dp[i][mid] + dp[mid][j]
+                    );
+                }
+            }
+        }
+
+        return dp[0][m + 1];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m\log m + m ^ 3)$
+* Space complexity: $O(m ^ 2)$
+
+> Where $m$ is the size of the $cuts$ array and $n$ is the length of the stick.
\ No newline at end of file
diff --git a/articles/minimum-cost-to-hire-k-workers.md b/articles/minimum-cost-to-hire-k-workers.md
new file mode 100644
index 000000000..f205b01e7
--- /dev/null
+++ b/articles/minimum-cost-to-hire-k-workers.md
@@ -0,0 +1,144 @@
+## 1. Greedy + Max-Heap
+
+::tabs-start
+
+```python
+class Solution:
+    def mincostToHireWorkers(self, quality: List[int], wage: List[int], k: int) -> float:
+        pairs = sorted([(w / q, q) for q, w in zip(quality, wage)], key=lambda p: p[0])
+
+        maxHeap = []
+        total_quality = 0
+        res = float("inf")
+
+        for rate, q in pairs:
+            heapq.heappush(maxHeap, -q)
+            total_quality += q
+
+            if len(maxHeap) > k:
+                total_quality += heapq.heappop(maxHeap)
+
+            if len(maxHeap) == k:
+                res = min(res, total_quality * rate)
+
+        return res
+```
+
+```java
+public class Solution {
+    public double mincostToHireWorkers(int[] quality, int[] wage, int k) {
+        int n = quality.length;
+        double res = Double.MAX_VALUE;
+        double totalQuality = 0;
+        
+        double[][] workers = new double[n][2];
+        for (int i = 0; i < n; i++) {
+            workers[i] = new double[]{
+                (double) wage[i] / quality[i], (double) quality[i]
+            };
+        }
+
+        Arrays.sort(workers, Comparator.comparingDouble(a -> a[0]));
+        PriorityQueue<Integer> maxHeap = new PriorityQueue<>(Collections.reverseOrder());
+
+        for (double[] worker : workers) {
+            double ratio = worker[0];
+            int q = (int) worker[1];
+
+            maxHeap.add(q);
+            totalQuality += q;
+
+            if (maxHeap.size() > k) {
+                totalQuality -= maxHeap.poll();
+            }
+
+            if (maxHeap.size() == k) {
+                res = Math.min(res, totalQuality * ratio);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    double mincostToHireWorkers(vector<int>& quality, vector<int>& wage, int k) {
+        int n = quality.size();
+        vector<pair<double, int>> workers(n);
+        for (int i = 0; i < n; i++) {
+            workers[i] = { (double)wage[i] / quality[i], quality[i] };
+        }
+
+        sort(workers.begin(), workers.end());
+        priority_queue<int> maxHeap;
+        double totalQuality = 0, res = DBL_MAX;
+
+        for (auto& worker : workers) {
+            double ratio = worker.first;
+            int q = worker.second;
+            maxHeap.push(q);
+            totalQuality += q;
+
+            if (maxHeap.size() > k) {
+                totalQuality -= maxHeap.top();
+                maxHeap.pop();
+            }
+
+            if (maxHeap.size() == k) {
+                res = min(res, totalQuality * ratio);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} quality
+     * @param {number[]} wage
+     * @param {number} k
+     * @return {number}
+     */
+    mincostToHireWorkers(quality, wage, k) {
+        const n = quality.length;
+        const workers = [];
+        for (let i = 0; i < n; i++) {
+            workers.push([wage[i] / quality[i], quality[i]]);
+        }
+
+        workers.sort((a, b) => a[0] - b[0]);
+        const maxHeap = new MaxPriorityQueue();
+        let totalQuality = 0, res = Number.MAX_VALUE;
+
+        for (let [ratio, q] of workers) {
+            maxHeap.enqueue(q);
+            totalQuality += q;
+
+            if (maxHeap.size() > k) {
+                totalQuality -= maxHeap.dequeue();
+            }
+
+            if (maxHeap.size() === k) {
+                res = Math.min(res, totalQuality * ratio);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * (\log n + \log k))$
+* Space complexity: $O(n)$
+
+> Where $n$ is the number of workers, and $k$ is the number of workers to be hired.
\ No newline at end of file
diff --git a/articles/minimum-deletions-to-make-character-frequencies-unique.md b/articles/minimum-deletions-to-make-character-frequencies-unique.md
new file mode 100644
index 000000000..60c9564fa
--- /dev/null
+++ b/articles/minimum-deletions-to-make-character-frequencies-unique.md
@@ -0,0 +1,348 @@
+## 1. Hash Set
+
+::tabs-start
+
+```python
+class Solution:
+    def minDeletions(self, s: str) -> int:
+        count = [0] * 26
+        for c in s:
+            count[ord(c) - ord('a')] += 1
+
+        used_freq = set()
+        res = 0
+        for freq in count:
+            while freq > 0 and freq in used_freq:
+                freq -= 1
+                res += 1
+            used_freq.add(freq)
+
+        return res
+```
+
+```java
+class Solution {
+    public int minDeletions(String s) {
+        int[] count = new int[26];
+        for (int i = 0; i < s.length(); i++) {
+            count[s.charAt(i) - 'a']++;
+        }
+
+        Set<Integer> usedFreq = new HashSet<>();
+        int res = 0;
+
+        for (int freq : count) {
+            while (freq > 0 && usedFreq.contains(freq)) {
+                freq--;
+                res++;
+            }
+            usedFreq.add(freq);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minDeletions(string s) {
+        vector<int> count(26, 0);
+        for (char& c : s) {
+            count[c - 'a']++;
+        }
+
+        unordered_set<int> usedFreq;
+        int res = 0;
+
+        for (int& freq : count) {
+            while (freq > 0 && usedFreq.count(freq)) {
+                freq--;
+                res++;
+            }
+            usedFreq.insert(freq);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    minDeletions(s) {
+        let count = new Array(26).fill(0);
+        for (let c of s) {
+            count[c.charCodeAt(0) - 'a'.charCodeAt(0)]++;
+        }
+
+        let usedFreq = new Set();
+        let res = 0;
+
+        for (let freq of count) {
+            while (freq > 0 && usedFreq.has(freq)) {
+                freq--;
+                res++;
+            }
+            usedFreq.add(freq);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m ^ 2)$
+* Space complexity: $O(m)$
+
+> Where $n$ is the length of the string $s$ and $m$ is the total number of unique frequncies possible.
+
+---
+
+## 2. Max-Heap
+
+::tabs-start
+
+```python
+class Solution:
+    def minDeletions(self, s: str) -> int:
+        freq = Counter(s)
+        maxHeap = [-f for f in freq.values()]
+        heapq.heapify(maxHeap)
+
+        res = 0
+        while len(maxHeap) > 1:
+            top = -heapq.heappop(maxHeap)
+            if top == -maxHeap[0]:
+                if top - 1 > 0:
+                    heapq.heappush(maxHeap, -(top - 1))
+                res += 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int minDeletions(String s) {
+        Map<Character, Integer> freq = new HashMap<>();
+        for (int i = 0; i < s.length(); i++) {
+            char c = s.charAt(i);
+            freq.put(c, freq.getOrDefault(c, 0) + 1);
+        }
+
+        PriorityQueue<Integer> maxHeap = new PriorityQueue<>((a, b) -> b - a);
+        maxHeap.addAll(freq.values());
+
+        int res = 0;
+        while (maxHeap.size() > 1) {
+            int top = maxHeap.poll();
+            if (top == maxHeap.peek()) {
+                if (top - 1 > 0) {
+                    maxHeap.add(top - 1);
+                }
+                res++;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minDeletions(string s) {
+        unordered_map<char, int> freq;
+        for (char& c : s) {
+            freq[c]++;
+        }
+
+        priority_queue<int> maxHeap;
+        for (auto& f : freq) {
+            maxHeap.push(f.second);
+        }
+
+        int res = 0;
+        while (maxHeap.size() > 1) {
+            int top = maxHeap.top();
+            maxHeap.pop();
+            if (top == maxHeap.top()) {
+                if (top - 1 > 0) {
+                    maxHeap.push(top - 1);
+                }
+                res++;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    minDeletions(s) {
+        let freq = new Map();
+        for (let c of s) {
+            freq.set(c, (freq.get(c) || 0) + 1);
+        }
+
+        const maxHeap = new MaxPriorityQueue();
+        for (let value of freq.values()) {
+            maxHeap.enqueue(value);
+        }
+
+        let res = 0;
+        while (maxHeap.size() > 1) {
+            let top = maxHeap.dequeue().element;
+            if (maxHeap.front().element === top) {
+                if (top - 1 > 0) {
+                    maxHeap.enqueue(top - 1);
+                }
+                res++;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m ^ 2 \log m)$
+* Space complexity: $O(m)$
+
+> Where $n$ is the length of the string $s$ and $m$ is the total number of unique frequncies possible.
+
+---
+
+## 3. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def minDeletions(self, s: str) -> int:
+        count = [0] * 26
+        for c in s:
+            count[ord(c) - ord('a')] += 1
+
+        count.sort(reverse=True)
+        res = 0
+        maxAllowedFreq = count[0]
+
+        for freq in count:
+            if freq > maxAllowedFreq:
+                res += freq - maxAllowedFreq
+                freq = maxAllowedFreq
+            maxAllowedFreq = max(0, freq - 1)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int minDeletions(String s) {
+        int[] count = new int[26];
+        for (int i = 0; i < s.length(); i++) {
+            count[s.charAt(i) - 'a']++;
+        }
+
+        Arrays.sort(count);
+        int res = 0;
+        int maxAllowedFreq = count[25];
+
+        for (int i = 25; i >= 0; i--) {
+            if (count[i] > maxAllowedFreq) {
+                res += count[i] - maxAllowedFreq;
+                count[i] = maxAllowedFreq;
+            }
+            maxAllowedFreq = Math.max(0, count[i] - 1);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minDeletions(string s) {
+        vector<int> count(26, 0);
+        for (char& c : s) {
+            count[c - 'a']++;
+        }
+
+        sort(count.begin(), count.end(), greater<int>());
+        int res = 0;
+        int maxAllowedFreq = count[0];
+
+        for (int& freq : count) {
+            if (freq > maxAllowedFreq) {
+                res += freq - maxAllowedFreq;
+                freq = maxAllowedFreq;
+            }
+            maxAllowedFreq = max(0, freq - 1);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    minDeletions(s) {
+        let count = new Array(26).fill(0);
+        for (let c of s) {
+            count[c.charCodeAt(0) - 'a'.charCodeAt(0)]++;
+        }
+
+        count.sort((a, b) => b - a);
+
+        let res = 0;
+        let maxAllowedFreq = count[0];
+
+        for (let i = 0; i < 26; i++) {
+            if (count[i] > maxAllowedFreq) {
+                res += count[i] - maxAllowedFreq;
+                count[i] = maxAllowedFreq;
+            }
+            maxAllowedFreq = Math.max(0, count[i] - 1);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m \log m)$
+* Space complexity: $O(m)$
+
+> Where $n$ is the length of the string $s$ and $m$ is the total number of unique frequncies possible.
\ No newline at end of file
diff --git a/articles/minimum-difference-between-highest-and-lowest-of-k-scores.md b/articles/minimum-difference-between-highest-and-lowest-of-k-scores.md
new file mode 100644
index 000000000..de7c35615
--- /dev/null
+++ b/articles/minimum-difference-between-highest-and-lowest-of-k-scores.md
@@ -0,0 +1,74 @@
+## 1. Sorting + Sliding Window
+
+::tabs-start
+
+```python
+class Solution:
+    def minimumDifference(self, nums: List[int], k: int) -> int:
+        nums.sort()
+        l, r = 0, k - 1
+        res = float("inf")
+        while r < len(nums):
+            res = min(res, nums[r] - nums[l])
+            l += 1
+            r += 1
+        return res
+```
+
+```java
+public class Solution {
+    public int minimumDifference(int[] nums, int k) {
+        Arrays.sort(nums);
+        int l = 0, r = k - 1, res = Integer.MAX_VALUE;
+        while (r < nums.length) {
+            res = Math.min(res, nums[r] - nums[l]);
+            l++;
+            r++;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minimumDifference(vector<int>& nums, int k) {
+        sort(nums.begin(), nums.end());
+        int l = 0, r = k - 1, res = INT_MAX;
+        while (r < nums.size()) {
+            res = min(res, nums[r] - nums[l]);
+            l++;
+            r++;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    minimumDifference(nums, k) {
+        nums.sort((a, b) => a - b);
+        let l = 0, r = k - 1, res = Infinity;
+        while (r < nums.length) {
+            res = Math.min(res, nums[r] - nums[l]);
+            l++;
+            r++;
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
\ No newline at end of file
diff --git a/articles/minimum-difficulty-of-a-job-schedule.md b/articles/minimum-difficulty-of-a-job-schedule.md
new file mode 100644
index 000000000..5738623eb
--- /dev/null
+++ b/articles/minimum-difficulty-of-a-job-schedule.md
@@ -0,0 +1,682 @@
+## 1. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def minDifficulty(self, jobDifficulty: List[int], d: int) -> int:
+        if len(jobDifficulty) < d:
+            return -1
+        
+        n = len(jobDifficulty)
+        dp = {}
+
+        def dfs(i, d, cur_max):
+            if i == n:
+                return 0 if d == 0 else float("inf")
+            if d == 0:
+                return float("inf")
+            if (i, d, cur_max) in dp:
+                return dp[(i, d, cur_max)]
+
+            cur_max = max(cur_max, jobDifficulty[i])
+            res = min(
+                dfs(i + 1, d, cur_max),
+                cur_max + dfs(i + 1, d - 1, -1)
+            )
+            dp[(i, d, cur_max)] = res
+            return res
+
+        return dfs(0, d, -1)
+```
+
+```java
+public class Solution {
+    private int[][][] dp;
+
+    public int minDifficulty(int[] jobDifficulty, int d) {
+        int n = jobDifficulty.length;
+        if (n < d) return -1;
+        int m = 0;
+        for (int i = 0; i < n; i++) {
+            m = Math.max(m, jobDifficulty[i]);
+        }
+
+        dp = new int[n][d + 1][m + 5];
+        for (int[][] layer : dp) {
+            for (int[] row : layer) {
+                Arrays.fill(row, -1);
+            }
+        }
+
+        return dfs(0, d, -1, jobDifficulty);
+    }
+
+    private int dfs(int i, int d, int curMax, int[] jobDifficulty) {
+        if (i == jobDifficulty.length) return d == 0 ? 0 : Integer.MAX_VALUE / 2;
+        if (d == 0) return Integer.MAX_VALUE / 2;
+        if (dp[i][d][curMax + 1] != -1) return dp[i][d][curMax + 1];
+
+        int maxSoFar = Math.max(curMax, jobDifficulty[i]);
+        int res = Math.min(
+            dfs(i + 1, d, maxSoFar, jobDifficulty),
+            maxSoFar + dfs(i + 1, d - 1, -1, jobDifficulty)
+        );
+
+        dp[i][d][curMax + 1] = res;
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+    vector<vector<vector<int>>> dp;
+
+    int dfs(int i, int d, int curMax, const vector<int>& jobDifficulty) {
+        if (i == jobDifficulty.size()) return d == 0 ? 0 : INT_MAX / 2;
+        if (d == 0) return INT_MAX / 2;
+        if (dp[i][d][curMax + 1] != -1) return dp[i][d][curMax + 1];
+
+        int maxSoFar = max(curMax, jobDifficulty[i]);
+        int res = min(
+            dfs(i + 1, d, maxSoFar, jobDifficulty),
+            maxSoFar + dfs(i + 1, d - 1, -1, jobDifficulty)
+        );
+
+        dp[i][d][curMax + 1] = res;
+        return res;
+    }
+
+public:
+    int minDifficulty(vector<int>& jobDifficulty, int d) {
+        int n = jobDifficulty.size();
+        if (n < d) return -1;
+
+        int m = *max_element(jobDifficulty.begin(), jobDifficulty.end());
+        dp = vector<vector<vector<int>>>(n, vector<vector<int>>(d + 1, vector<int>(m + 5, -1)));
+        return dfs(0, d, -1, jobDifficulty);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} jobDifficulty
+     * @param {number} d
+     * @return {number}
+     */
+    minDifficulty(jobDifficulty, d) {
+        const n = jobDifficulty.length;
+        if (n < d) return -1;
+        let m = 0;
+        for (let it of jobDifficulty) {
+            m = Math.max(m, it);
+        }
+
+        const dp = Array.from({ length: n }, () =>
+            Array.from({ length: d + 1 }, () => Array(m + 5).fill(-1))
+        );
+
+        const dfs = (i, d, curMax) => {
+            if (i === n) return d === 0 ? 0 : Infinity;
+            if (d === 0) return Infinity;
+            if (dp[i][d][curMax + 1] !== -1) return dp[i][d][curMax + 1];
+
+            const maxSoFar = Math.max(curMax, jobDifficulty[i]);
+            const res = Math.min(
+                dfs(i + 1, d, maxSoFar),
+                maxSoFar + dfs(i + 1, d - 1, -1)
+            );
+
+            dp[i][d][curMax + 1] = res;
+            return res;
+        };
+
+        return dfs(0, d, -1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * d * m)$
+* Space complexity: $O(n * d * m)$
+
+> Where $n$ is the number of jobs, $d$ is the number of days, and $m$ is the maximum difficulty value among all the job difficulties.
+
+---
+
+## 2. Dynamic Programming (Top-Down Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def minDifficulty(self, jobDifficulty: List[int], d: int) -> int:
+        if len(jobDifficulty) < d:
+            return -1
+
+        n = len(jobDifficulty)
+        dp = {}
+
+        def dfs(i, d):
+            if (i, d) in dp:
+                return dp[(i, d)]
+
+            maxi = jobDifficulty[i]
+            if d == 1:
+                idx = i
+                while i < n:
+                    maxi = max(maxi, jobDifficulty[i])
+                    i += 1
+                dp[(idx, d)] = maxi
+                return maxi
+
+            res = float("inf")
+            for j in range(i + 1, n):
+                res = min(res, maxi + dfs(j, d - 1))
+                maxi = max(maxi, jobDifficulty[j])
+            dp[(i, d)] = res
+            return res
+
+        return dfs(0, d)
+```
+
+```java
+public class Solution {
+    private int[][] dp;
+
+    public int minDifficulty(int[] jobDifficulty, int d) {
+        int n = jobDifficulty.length;
+        if (n < d) return -1;
+
+        dp = new int[n][d + 1];
+        for (int[] row : dp) Arrays.fill(row, -1);
+
+        return dfs(0, d, jobDifficulty);
+    }
+
+    private int dfs(int i, int d, int[] jobDifficulty) {
+        if (dp[i][d] != -1) return dp[i][d];
+
+        int n = jobDifficulty.length;
+        int maxi = jobDifficulty[i];
+        if (d == 1) {
+            for (int j = i; j < n; j++) {
+                maxi = Math.max(maxi, jobDifficulty[j]);
+            }
+            dp[i][d] = maxi;
+            return maxi;
+        }
+
+        int res = Integer.MAX_VALUE / 2;
+        for (int j = i + 1; j < n; j++) {
+            res = Math.min(res, maxi + dfs(j, d - 1, jobDifficulty));
+            maxi = Math.max(maxi, jobDifficulty[j]);
+        }
+        dp[i][d] = res;
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+    vector<vector<int>> dp;
+
+public:
+    int minDifficulty(vector<int>& jobDifficulty, int d) {
+        int n = jobDifficulty.size();
+        if (n < d) return -1;
+
+        dp.assign(n, vector<int>(d + 1, -1));
+        return dfs(0, d, jobDifficulty);
+    }
+
+private:
+    int dfs(int i, int d, vector<int>& jobDifficulty) {
+        if (dp[i][d] != -1) return dp[i][d];
+
+        int n = jobDifficulty.size();
+        int maxi = jobDifficulty[i];
+        if (d == 1) {
+            for (int j = i; j < n; j++) {
+                maxi = max(maxi, jobDifficulty[j]);
+            }
+            dp[i][d] = maxi;
+            return maxi;
+        }
+
+        int res = INT_MAX / 2;
+        for (int j = i + 1; j < n; j++) {
+            res = min(res, maxi + dfs(j, d - 1, jobDifficulty));
+            maxi = max(maxi, jobDifficulty[j]);
+        }
+        dp[i][d] = res;
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} jobDifficulty
+     * @param {number} d
+     * @return {number}
+     */
+    minDifficulty(jobDifficulty, d) {
+        const n = jobDifficulty.length;
+        if (n < d) return -1;
+
+        const dp = Array.from({ length: n }, () => Array(d + 1).fill(-1));
+
+        const dfs = (i, d) => {
+            if (dp[i][d] !== -1) return dp[i][d];
+
+            let maxi = jobDifficulty[i];
+            if (d === 1) {
+                for (let j = i; j < n; j++) {
+                    maxi = Math.max(maxi, jobDifficulty[j]);
+                }
+                dp[i][d] = maxi;
+                return maxi;
+            }
+
+            let res = Infinity;
+            for (let j = i + 1; j < n; j++) {
+                res = Math.min(res, maxi + dfs(j, d - 1));
+                maxi = Math.max(maxi, jobDifficulty[j]);
+            }
+            dp[i][d] = res;
+            return res;
+        };
+
+        return dfs(0, d);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 * d)$
+* Space complexity: $O(n * d)$
+
+> Where $n$ is the number of jobs and $d$ is the number of days.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def minDifficulty(self, jobDifficulty: List[int], d: int) -> int:
+        if len(jobDifficulty) < d:
+            return -1
+
+        n = len(jobDifficulty)
+        dp = [[float("inf")] * (d + 1) for _ in range(n + 1)]
+        dp[n][0] = 0
+
+        for day in range(1, d + 1):
+            for i in range(n - 1, -1, -1):
+                maxi = 0
+                for j in range(i, n - day + 1):
+                    maxi = max(maxi, jobDifficulty[j])
+                    dp[i][day] = min(dp[i][day], maxi + dp[j + 1][day - 1])
+
+        return dp[0][d]
+```
+
+```java
+public class Solution {
+    public int minDifficulty(int[] jobDifficulty, int d) {
+        int n = jobDifficulty.length;
+        if (n < d) return -1;
+
+        int[][] dp = new int[n + 1][d + 1];
+        for (int[] row : dp) Arrays.fill(row, Integer.MAX_VALUE / 2);
+        dp[n][0] = 0;
+
+        for (int day = 1; day <= d; day++) {
+            for (int i = n - 1; i >= 0; i--) {
+                int maxi = 0;
+                for (int j = i; j <= n - day; j++) {
+                    maxi = Math.max(maxi, jobDifficulty[j]);
+                    dp[i][day] = Math.min(dp[i][day], maxi + dp[j + 1][day - 1]);
+                }
+            }
+        }
+
+        return dp[0][d];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minDifficulty(vector<int>& jobDifficulty, int d) {
+        int n = jobDifficulty.size();
+        if (n < d) return -1;
+
+        vector<vector<int>> dp(n + 1, vector<int>(d + 1, INT_MAX / 2));
+        dp[n][0] = 0;
+
+        for (int day = 1; day <= d; day++) {
+            for (int i = n - 1; i >= 0; i--) {
+                int maxi = 0;
+                for (int j = i; j <= n - day; j++) {
+                    maxi = max(maxi, jobDifficulty[j]);
+                    dp[i][day] = min(dp[i][day], maxi + dp[j + 1][day - 1]);
+                }
+            }
+        }
+
+        return dp[0][d];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} jobDifficulty
+     * @param {number} d
+     * @return {number}
+     */
+    minDifficulty(jobDifficulty, d) {
+        const n = jobDifficulty.length;
+        if (n < d) return -1;
+
+        const dp = Array.from({ length: n + 1 }, () => Array(d + 1).fill(Infinity));
+        dp[n][0] = 0;
+
+        for (let day = 1; day <= d; day++) {
+            for (let i = n - 1; i >= 0; i--) {
+                let maxi = 0;
+                for (let j = i; j <= n - day; j++) {
+                    maxi = Math.max(maxi, jobDifficulty[j]);
+                    dp[i][day] = Math.min(dp[i][day], maxi + dp[j + 1][day - 1]);
+                }
+            }
+        }
+
+        return dp[0][d];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 * d)$
+* Space complexity: $O(n * d)$
+
+> Where $n$ is the number of jobs and $d$ is the number of days.
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def minDifficulty(self, jobDifficulty: List[int], d: int) -> int:
+        if len(jobDifficulty) < d:
+            return -1
+
+        n = len(jobDifficulty)
+        dp = [float("inf")] * (n + 1)
+        dp[n] = 0
+
+        for day in range(1, d + 1):
+            for i in range(n - day + 1):
+                maxi = 0
+                dp[i] = float("inf")
+                for j in range(i, n - day + 1):
+                    maxi = max(maxi, jobDifficulty[j])
+                    dp[i] = min(dp[i], maxi + dp[j + 1])
+
+        return dp[0]
+```
+
+```java
+public class Solution {
+    public int minDifficulty(int[] jobDifficulty, int d) {
+        int n = jobDifficulty.length;
+        if (n < d) return -1;
+
+        int INF = Integer.MAX_VALUE / 2;
+        int[] dp = new int[n + 1];
+        Arrays.fill(dp, INF);
+        dp[n] = 0;
+
+        for (int day = 1; day <= d; day++) {
+            for (int i = 0; i <= n - day; i++) {
+                int maxi = 0;
+                dp[i] = INF;
+                for (int j = i; j <= n - day; j++) {
+                    maxi = Math.max(maxi, jobDifficulty[j]);
+                    dp[i] = Math.min(dp[i], maxi + dp[j + 1]);
+                }
+            }
+        }
+
+        return dp[0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minDifficulty(vector<int>& jobDifficulty, int d) {
+        int n = jobDifficulty.size();
+        if (n < d) return -1;
+
+        int INF = INT_MAX / 2;
+        vector<int> dp(n + 1, INF);
+        dp[n] = 0;
+
+        for (int day = 1; day <= d; day++) {
+            for (int i = 0; i <= n - day; i++) {
+                int maxi = 0;
+                dp[i] = INF;
+                for (int j = i; j <= n - day; j++) {
+                    maxi = max(maxi, jobDifficulty[j]);
+                    dp[i] = min(dp[i], maxi + dp[j + 1]);
+                }
+            }
+        }
+
+        return dp[0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} jobDifficulty
+     * @param {number} d
+     * @return {number}
+     */
+    minDifficulty(jobDifficulty, d) {
+        const n = jobDifficulty.length;
+        if (n < d) return -1;
+
+        let dp = new Array(n + 1).fill(Infinity);
+        dp[n] = 0;
+
+        for (let day = 1; day <= d; day++) {
+            for (let i = 0; i <= n - day; i++) {
+                let maxi = 0;
+                dp[i] = Infinity;
+                for (let j = i; j <= n - day; j++) {
+                    maxi = Math.max(maxi, jobDifficulty[j]);
+                    dp[i] = Math.min(dp[i], maxi + dp[j + 1]);
+                }
+            }
+        }
+
+        return dp[0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 * d)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the number of jobs and $d$ is the number of days.
+
+---
+
+## 5. Monotonic Decreasing Stack
+
+::tabs-start
+
+```python
+class Solution:
+    def minDifficulty(self, jobDifficulty: List[int], d: int) -> int:
+        n = len(jobDifficulty)
+        if n < d:
+            return -1
+
+        dp = [float("inf")] * n
+        for day in range(1, d + 1):
+            next_dp = [float("inf")] * n
+            stack = []
+            for i in range(day - 1, n):
+                next_dp[i] = dp[i - 1] + jobDifficulty[i] if i > 0 else jobDifficulty[i]
+                while stack and jobDifficulty[stack[-1]] <= jobDifficulty[i]:
+                    j = stack.pop()
+                    next_dp[i] = min(next_dp[i], next_dp[j] - jobDifficulty[j] + jobDifficulty[i])
+                if stack:
+                    next_dp[i] = min(next_dp[i], next_dp[stack[-1]])
+                stack.append(i)
+            dp = next_dp
+
+        return dp[-1]
+```
+
+```java
+public class Solution {
+    public int minDifficulty(int[] jobDifficulty, int d) {
+        int n = jobDifficulty.length;
+        if (n < d) return -1;
+
+        int[] dp = new int[n];
+        Arrays.fill(dp, Integer.MAX_VALUE / 2);
+
+        for (int day = 1; day <= d; day++) {
+            int[] nextDp = new int[n];
+            Arrays.fill(nextDp, Integer.MAX_VALUE / 2);
+            Stack<Integer> stack = new Stack<>();
+            for (int i = day - 1; i < n; i++) {
+                nextDp[i] = (i > 0 ? dp[i - 1] : 0) + jobDifficulty[i];
+                while (!stack.isEmpty() && jobDifficulty[stack.peek()] <= jobDifficulty[i]) {
+                    int j = stack.pop();
+                    nextDp[i] = Math.min(nextDp[i], nextDp[j] - jobDifficulty[j] + jobDifficulty[i]);
+                }
+                if (!stack.isEmpty()) {
+                    nextDp[i] = Math.min(nextDp[i], nextDp[stack.peek()]);
+                }
+                stack.add(i);
+            }
+            dp = nextDp;
+        }
+
+        return dp[n - 1];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minDifficulty(vector<int>& jobDifficulty, int d) {
+        int n = jobDifficulty.size();
+        if (n < d) return -1;
+
+        vector<int> dp(n, INT_MAX / 2);
+
+        for (int day = 1; day <= d; day++) {
+            vector<int> nextDp(n, INT_MAX / 2);
+            stack<int> st;
+            for (int i = day - 1; i < n; i++) {
+                nextDp[i] = (i > 0 ? dp[i - 1] : 0) + jobDifficulty[i];
+                while (!st.empty() && jobDifficulty[st.top()] <= jobDifficulty[i]) {
+                    int j = st.top(); st.pop();
+                    nextDp[i] = min(nextDp[i], nextDp[j] - jobDifficulty[j] + jobDifficulty[i]);
+                }
+                if (!st.empty()) {
+                    nextDp[i] = min(nextDp[i], nextDp[st.top()]);
+                }
+                st.push(i);
+            }
+            dp = nextDp;
+        }
+
+        return dp[n - 1];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} jobDifficulty
+     * @param {number} d
+     * @return {number}
+     */
+    minDifficulty(jobDifficulty, d) {
+        const n = jobDifficulty.length;
+        if (n < d) return -1;
+
+        let dp = Array(n).fill(Infinity);
+
+        for (let day = 1; day <= d; day++) {
+            const nextDp = Array(n).fill(Infinity);
+            const stack = [];
+            for (let i = day - 1; i < n; i++) {
+                nextDp[i] = (i > 0 ? dp[i - 1] : 0) + jobDifficulty[i];
+                while (stack.length > 0 && jobDifficulty[stack[stack.length - 1]] <= jobDifficulty[i]) {
+                    const j = stack.pop();
+                    nextDp[i] = Math.min(nextDp[i], nextDp[j] - jobDifficulty[j] + jobDifficulty[i]);
+                }
+                if (stack.length > 0) {
+                    nextDp[i] = Math.min(nextDp[i], nextDp[stack[stack.length - 1]]);
+                }
+                stack.push(i);
+            }
+            dp = nextDp;
+        }
+
+        return dp[n - 1];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * d)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the number of jobs and $d$ is the number of days.
\ No newline at end of file
diff --git a/articles/minimum-distance-between-bst-nodes.md b/articles/minimum-distance-between-bst-nodes.md
new file mode 100644
index 000000000..d8cd6bda0
--- /dev/null
+++ b/articles/minimum-distance-between-bst-nodes.md
@@ -0,0 +1,840 @@
+## 1. Brute Force (DFS)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def minDiffInBST(self, root: Optional[TreeNode]) -> int:
+        def dfs(node):
+            if not node:
+                return float("inf")
+            res = dfs1(root, node)
+            res = min(res, dfs(node.left))
+            res = min(res, dfs(node.right))
+            return res
+        
+        def dfs1(root, node):
+            if not root:
+                return float("inf")
+                
+            res = float("inf")
+            if root != node:
+                res = abs(root.val - node.val)
+            res = min(res, dfs1(root.left, node))
+            res = min(res, dfs1(root.right, node))
+            return res
+        
+        return dfs(root)
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public int minDiffInBST(TreeNode root) {
+        return dfs(root, root);
+    }
+
+    private int dfs(TreeNode root, TreeNode node) {
+        if (node == null) {
+            return Integer.MAX_VALUE;
+        }
+        int res = dfs1(root, node);
+        res = Math.min(res, dfs(root, node.left));
+        res = Math.min(res, dfs(root, node.right));
+        return res;
+    }
+
+    private int dfs1(TreeNode root, TreeNode node) {
+        if (root == null) {
+            return Integer.MAX_VALUE;
+        }
+        int res = Integer.MAX_VALUE;
+        if (root != node) {
+            res = Math.abs(root.val - node.val);
+        }
+        res = Math.min(res, dfs1(root.left, node));
+        res = Math.min(res, dfs1(root.right, node));
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int minDiffInBST(TreeNode* root) {
+        return dfs(root, root);
+    }
+
+private:
+    int dfs(TreeNode* root, TreeNode* node) {
+        if (!node) {
+            return INT_MAX;
+        }
+        int res = dfs1(root, node);
+        res = min(res, dfs(root, node->left));
+        res = min(res, dfs(root, node->right));
+        return res;
+    }
+
+    int dfs1(TreeNode* root, TreeNode* node) {
+        if (!root) {
+            return INT_MAX;
+        }
+        int res = INT_MAX;
+        if (root != node) {
+            res = abs(root->val - node->val);
+        }
+        res = min(res, dfs1(root->left, node));
+        res = min(res, dfs1(root->right, node));
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number}
+     */
+    minDiffInBST(root) {
+        const dfs = (node) => {
+            if (!node) {
+                return Infinity;
+            }
+            let res = dfs1(root, node);
+            res = Math.min(res, dfs(node.left));
+            res = Math.min(res, dfs(node.right));
+            return res;
+        };
+
+        const dfs1 = (root, node) => {
+            if (!root) {
+                return Infinity;
+            }
+            let res = Infinity;
+            if (root !== node) {
+                res = Math.abs(root.val - node.val);
+            }
+            res = Math.min(res, dfs1(root.left, node));
+            res = Math.min(res, dfs1(root.right, node));
+            return res;
+        };
+
+        return dfs(root);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Inorder Traversal
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def minDiffInBST(self, root: Optional[TreeNode]) -> int:
+        arr = []
+
+        def dfs(node):
+            if not node:
+                return
+            dfs(node.left)
+            arr.append(node.val)
+            dfs(node.right)
+        
+        dfs(root)
+        res = arr[1] - arr[0]
+        for i in range(2, len(arr)):
+            res = min(res, arr[i] - arr[i - 1])
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public int minDiffInBST(TreeNode root) {
+        List<Integer> arr = new ArrayList<>();
+        
+        dfs(root, arr);
+        int res = arr.get(1) - arr.get(0);
+        for (int i = 2; i < arr.size(); i++) {
+            res = Math.min(res, arr.get(i) - arr.get(i - 1));
+        }
+        return res;
+    }
+    
+    private void dfs(TreeNode node, List<Integer> arr) {
+        if (node == null) {
+            return;
+        }
+        dfs(node.left, arr);
+        arr.add(node.val);
+        dfs(node.right, arr);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int minDiffInBST(TreeNode* root) {
+        vector<int> arr;
+        dfs(root, arr);
+        
+        int res = arr[1] - arr[0];
+        for (int i = 2; i < arr.size(); i++) {
+            res = min(res, arr[i] - arr[i - 1]);
+        }
+        return res;
+    }
+    
+private:
+    void dfs(TreeNode* node, vector<int>& arr) {
+        if (!node) return;
+        dfs(node->left, arr);
+        arr.push_back(node->val);
+        dfs(node->right, arr);
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number}
+     */
+    minDiffInBST(root) {
+        const arr = [];
+        
+        const dfs = (node) => {
+            if (!node) return;
+            dfs(node.left);
+            arr.push(node.val);
+            dfs(node.right);
+        };
+        
+        dfs(root);
+        let res = arr[1] - arr[0];
+        for (let i = 2; i < arr.length; i++) {
+            res = Math.min(res, arr[i] - arr[i - 1]);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Inorder Traversal (Space Optimized)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def minDiffInBST(self, root: Optional[TreeNode]) -> int:
+        prev, res = None, float("inf")
+
+        def dfs(node):
+            nonlocal prev, res
+            if not node:
+                return
+            
+            dfs(node.left)
+            if prev:
+                res = min(res, node.val - prev.val)
+            prev = node
+            dfs(node.right)
+
+        dfs(root)
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    private TreeNode prev = null;
+    private int res = Integer.MAX_VALUE;
+
+    public int minDiffInBST(TreeNode root) {
+        dfs(root);
+        return res;
+    }
+
+    private void dfs(TreeNode node) {
+        if (node == null) return;
+
+        dfs(node.left);
+        if (prev != null) {
+            res = Math.min(res, node.val - prev.val);
+        }
+        prev = node;
+        dfs(node.right);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int minDiffInBST(TreeNode* root) {
+        TreeNode* prev = nullptr;
+        int res = INT_MAX;
+
+        dfs(root, prev, res);
+        return res;
+    }
+
+private:
+    void dfs(TreeNode* node, TreeNode*& prev, int& res) {
+        if (!node) return;
+
+        dfs(node->left, prev, res);
+        if (prev) {
+            res = min(res, node->val - prev->val);
+        }
+        prev = node;
+        dfs(node->right, prev, res);
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number}
+     */
+    minDiffInBST(root) {
+        let prev = null;
+        let res = Infinity;
+
+        const dfs = (node) => {
+            if (!node) return;
+
+            dfs(node.left);
+            if (prev !== null) {
+                res = Math.min(res, node.val - prev.val);
+            }
+            prev = node;
+            dfs(node.right);
+        };
+
+        dfs(root);
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 4. Iterative DFS (Inorder Traversal)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def minDiffInBST(self, root: Optional[TreeNode]) -> int:
+        stack, prev, res = [], None, float("inf")
+        cur = root
+
+        while stack or cur:
+            while cur:
+                stack.append(cur)
+                cur = cur.left
+            
+            cur = stack.pop()
+            if prev:
+                res = min(res, cur.val - prev.val)
+            prev = cur
+            cur = cur.right
+
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public int minDiffInBST(TreeNode root) {
+        Stack<TreeNode> stack = new Stack<>();
+        TreeNode prev = null;
+        int res = Integer.MAX_VALUE;
+        TreeNode cur = root;
+
+        while (!stack.isEmpty() || cur != null) {
+            while (cur != null) {
+                stack.push(cur);
+                cur = cur.left;
+            }
+
+            cur = stack.pop();
+            if (prev != null) {
+                res = Math.min(res, cur.val - prev.val);
+            }
+            prev = cur;
+            cur = cur.right;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int minDiffInBST(TreeNode* root) {
+        stack<TreeNode*> st;
+        TreeNode* prev = nullptr;
+        TreeNode* cur = root;
+        int res = INT_MAX;
+
+        while (!st.empty() || cur) {
+            while (cur) {
+                st.push(cur);
+                cur = cur->left;
+            }
+
+            cur = st.top();
+            st.pop();
+            if (prev) {
+                res = min(res, cur->val - prev->val);
+            }
+            prev = cur;
+            cur = cur->right;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number}
+     */
+    minDiffInBST(root) {
+        let stack = [];
+        let prev = null;
+        let res = Infinity;
+        let cur = root;
+
+        while (stack.length > 0 || cur !== null) {
+            while (cur !== null) {
+                stack.push(cur);
+                cur = cur.left;
+            }
+
+            cur = stack.pop();
+            if (prev !== null) {
+                res = Math.min(res, cur.val - prev.val);
+            }
+            prev = cur;
+            cur = cur.right;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 5. Morris Traversal
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def minDiffInBST(self, root: Optional[TreeNode]) -> int:
+        prevVal = res = float("inf")
+        cur = root
+
+        while cur:
+            if not cur.left:
+                if prevVal != float("inf"):
+                    res = min(res, cur.val - prevVal)
+                prevVal = cur.val
+                cur = cur.right
+            else:
+                prev = cur.left
+                while prev.right and prev.right != cur:
+                    prev = prev.right
+
+                if not prev.right:
+                    prev.right = cur
+                    cur = cur.left
+                else:
+                    prev.right = None
+                    if prevVal != float("inf"):
+                        res = min(res, cur.val - prevVal)
+                    prevVal = cur.val
+                    cur = cur.right
+
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public int minDiffInBST(TreeNode root) {
+        int prevVal = Integer.MAX_VALUE, res = Integer.MAX_VALUE;
+        TreeNode cur = root;
+
+        while (cur != null) {
+            if (cur.left == null) {
+                if (prevVal != Integer.MAX_VALUE) {
+                    res = Math.min(res, cur.val - prevVal);
+                }
+                prevVal = cur.val;
+                cur = cur.right;
+            } else {
+                TreeNode prev = cur.left;
+                while (prev.right != null && prev.right != cur) {
+                    prev = prev.right;
+                }
+
+                if (prev.right == null) {
+                    prev.right = cur;
+                    cur = cur.left;
+                } else {
+                    prev.right = null;
+                    if (prevVal != Integer.MAX_VALUE) {
+                        res = Math.min(res, cur.val - prevVal);
+                    }
+                    prevVal = cur.val;
+                    cur = cur.right;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int minDiffInBST(TreeNode* root) {
+        int prevVal = INT_MAX, res = INT_MAX;
+        TreeNode* cur = root;
+
+        while (cur) {
+            if (!cur->left) {
+                if (prevVal != INT_MAX) {
+                    res = min(res, cur->val - prevVal);
+                }
+                prevVal = cur->val;
+                cur = cur->right;
+            } else {
+                TreeNode* prev = cur->left;
+                while (prev->right && prev->right != cur) {
+                    prev = prev->right;
+                }
+
+                if (!prev->right) {
+                    prev->right = cur;
+                    cur = cur->left;
+                } else {
+                    prev->right = nullptr;
+                    if (prevVal != INT_MAX) {
+                        res = min(res, cur->val - prevVal);
+                    }
+                    prevVal = cur->val;
+                    cur = cur->right;
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number}
+     */
+    minDiffInBST(root) {
+        let prevVal = Infinity, res = Infinity;
+        let cur = root;
+
+        while (cur !== null) {
+            if (cur.left === null) {
+                if (prevVal !== Infinity) {
+                    res = Math.min(res, cur.val - prevVal);
+                }
+                prevVal = cur.val;
+                cur = cur.right;
+            } else {
+                let prev = cur.left;
+                while (prev.right !== null && prev.right !== cur) {
+                    prev = prev.right;
+                }
+
+                if (prev.right === null) {
+                    prev.right = cur;
+                    cur = cur.left;
+                } else {
+                    prev.right = null;
+                    if (prevVal !== Infinity) {
+                        res = Math.min(res, cur.val - prevVal);
+                    }
+                    prevVal = cur.val;
+                    cur = cur.right;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/minimum-falling-path-sum-ii.md b/articles/minimum-falling-path-sum-ii.md
new file mode 100644
index 000000000..b43db319c
--- /dev/null
+++ b/articles/minimum-falling-path-sum-ii.md
@@ -0,0 +1,854 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def minFallingPathSum(self, grid: List[List[int]]) -> int:
+        N = len(grid)
+
+        def helper(r, c):
+            if r == N - 1:
+                return grid[r][c]
+            res = float("inf")
+            for next_col in range(N):
+                if c != next_col:
+                    res = min(res, grid[r][c] + helper(r + 1, next_col))
+            return res
+
+        res = float("inf")
+        for c in range(N):
+            res = min(res, helper(0, c))
+        return res
+```
+
+```java
+public class Solution {
+    private int helper(int[][] grid, int r, int c) {
+        int N = grid.length;
+        if (r == N - 1) {
+            return grid[r][c];
+        }
+        int res = Integer.MAX_VALUE;
+        for (int nextCol = 0; nextCol < N; nextCol++) {
+            if (c != nextCol) {
+                res = Math.min(res, grid[r][c] + helper(grid, r + 1, nextCol));
+            }
+        }
+        return res;
+    }
+
+    public int minFallingPathSum(int[][] grid) {
+        int N = grid.length;
+        int res = Integer.MAX_VALUE;
+        for (int c = 0; c < N; c++) {
+            res = Math.min(res, helper(grid, 0, c));
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+    int helper(vector<vector<int>>& grid, int r, int c) {
+        int N = grid.size();
+        if (r == N - 1) {
+            return grid[r][c];
+        }
+        int res = INT_MAX;
+        for (int nextCol = 0; nextCol < N; nextCol++) {
+            if (c != nextCol) {
+                res = min(res, grid[r][c] + helper(grid, r + 1, nextCol));
+            }
+        }
+        return res;
+    }
+
+public:
+    int minFallingPathSum(vector<vector<int>>& grid) {
+        int N = grid.size();
+        int res = INT_MAX;
+        for (int c = 0; c < N; c++) {
+            res = min(res, helper(grid, 0, c));
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    minFallingPathSum(grid) {
+        const N = grid.length;
+
+        const helper = (r, c) => {
+            if (r === N - 1) return grid[r][c];
+            let res = Infinity;
+            for (let nextCol = 0; nextCol < N; nextCol++) {
+                if (c !== nextCol) {
+                    res = Math.min(res, grid[r][c] + helper(r + 1, nextCol));
+                }
+            }
+            return res;
+        };
+
+        let res = Infinity;
+        for (let c = 0; c < N; c++) {
+            res = Math.min(res, helper(0, c));
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def minFallingPathSum(self, grid: List[List[int]]) -> int:
+        N = len(grid)
+        cache = {}
+
+        def helper(r, c):
+            if r == N - 1:
+                return grid[r][c]
+            if (r, c) in cache:
+                return cache[(r, c)]
+                
+            res = float("inf")
+            for next_col in range(N):
+                if c != next_col:
+                    res = min(res, grid[r][c] + helper(r + 1, next_col))
+            cache[(r, c)] = res
+            return res
+
+        res = float("inf")
+        for c in range(N):
+            res = min(res, helper(0, c))
+        return res
+```
+
+```java
+public class Solution {
+    private int[][] memo;
+
+    private int helper(int[][] grid, int r, int c) {
+        int N = grid.length;
+        if (r == N - 1) {
+            return grid[r][c];
+        }
+        if (memo[r][c] != Integer.MIN_VALUE) {
+            return memo[r][c];
+        }
+
+        int res = Integer.MAX_VALUE;
+        for (int nextCol = 0; nextCol < N; nextCol++) {
+            if (c != nextCol) {
+                res = Math.min(res, grid[r][c] + helper(grid, r + 1, nextCol));
+            }
+        }
+        memo[r][c] = res;
+        return res;
+    }
+
+    public int minFallingPathSum(int[][] grid) {
+        int N = grid.length;
+        memo = new int[N][N];
+        for (int[] row : memo) {
+            Arrays.fill(row, Integer.MIN_VALUE);
+        }
+        int res = Integer.MAX_VALUE;
+        for (int c = 0; c < N; c++) {
+            res = Math.min(res, helper(grid, 0, c));
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+    vector<vector<int>> memo;
+
+    int helper(vector<vector<int>>& grid, int r, int c) {
+        int N = grid.size();
+        if (r == N - 1) {
+            return grid[r][c];
+        }
+        if (memo[r][c] != INT_MIN) {
+            return memo[r][c];
+        }
+        int res = INT_MAX;
+        for (int nextCol = 0; nextCol < N; nextCol++) {
+            if (c != nextCol) {
+                res = min(res, grid[r][c] + helper(grid, r + 1, nextCol));
+            }
+        }
+        memo[r][c] = res;
+        return res;
+    }
+
+public:
+    int minFallingPathSum(vector<vector<int>>& grid) {
+        int N = grid.size();
+        memo.assign(N, vector<int>(N, INT_MIN));
+        int res = INT_MAX;
+        for (int c = 0; c < N; c++) {
+            res = min(res, helper(grid, 0, c));
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    minFallingPathSum(grid) {
+        const N = grid.length;
+        const memo = Array.from({ length: N }, () => Array(N).fill(-Infinity));
+
+        const helper = (r, c) => {
+            if (r === N - 1) return grid[r][c];
+            if (memo[r][c] !== -Infinity) return memo[r][c];
+            let res = Infinity;
+            for (let nextCol = 0; nextCol < N; nextCol++) {
+                if (c !== nextCol) {
+                    res = Math.min(res, grid[r][c] + helper(r + 1, nextCol));
+                }
+            }
+            memo[r][c] = res;
+            return res;
+        };
+
+        let res = Infinity;
+        for (let c = 0; c < N; c++) {
+            res = Math.min(res, helper(0, c));
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 3)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def minFallingPathSum(self, grid: List[List[int]]) -> int:
+        N = len(grid)
+        dp = [[float("inf")] * N for _ in range(N)]
+        
+        for c in range(N):
+            dp[N - 1][c] = grid[N - 1][c]
+
+        for r in range(N - 2, -1, -1):
+            for c in range(N):
+                for next_col in range(N):
+                    if c != next_col:
+                        dp[r][c] = min(dp[r][c], grid[r][c] + dp[r + 1][next_col])
+        
+        return min(dp[0])
+```
+
+```java
+public class Solution {
+    public int minFallingPathSum(int[][] grid) {
+        int N = grid.length;
+        int[][] dp = new int[N][N];
+        
+        for (int c = 0; c < N; c++) {
+            dp[N - 1][c] = grid[N - 1][c];
+        }
+        
+        for (int r = N - 2; r >= 0; r--) {
+            for (int c = 0; c < N; c++) {
+                dp[r][c] = Integer.MAX_VALUE;
+                for (int nextCol = 0; nextCol < N; nextCol++) {
+                    if (c != nextCol) {
+                        dp[r][c] = Math.min(dp[r][c], grid[r][c] + dp[r + 1][nextCol]);
+                    }
+                }
+            }
+        }
+        
+        int res = Integer.MAX_VALUE;
+        for (int c = 0; c < N; c++) {
+            res = Math.min(res, dp[0][c]);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minFallingPathSum(vector<vector<int>>& grid) {
+        int N = grid.size();
+        vector<vector<int>> dp(N, vector<int>(N, INT_MAX));
+
+        for (int c = 0; c < N; c++) {
+            dp[N - 1][c] = grid[N - 1][c];
+        }
+
+        for (int r = N - 2; r >= 0; r--) {
+            for (int c = 0; c < N; c++) {
+                dp[r][c] = INT_MAX;
+                for (int nextCol = 0; nextCol < N; nextCol++) {
+                    if (c != nextCol) {
+                        dp[r][c] = min(dp[r][c], grid[r][c] + dp[r + 1][nextCol]);
+                    }
+                }
+            }
+        }
+
+        int res = INT_MAX;
+        for (int c = 0; c < N; c++) {
+            res = min(res, dp[0][c]);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    minFallingPathSum(grid) {
+        const N = grid.length;
+        const dp = Array.from({ length: N }, () => Array(N).fill(Infinity));
+        
+        for (let c = 0; c < N; c++) {
+            dp[N - 1][c] = grid[N - 1][c];
+        }
+
+        for (let r = N - 2; r >= 0; r--) {
+            for (let c = 0; c < N; c++) {
+                for (let nextCol = 0; nextCol < N; nextCol++) {
+                    if (c !== nextCol) {
+                        dp[r][c] = Math.min(dp[r][c], grid[r][c] + dp[r + 1][nextCol]);
+                    }
+                }
+            }
+        }
+
+        return Math.min(...dp[0]);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 3)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def minFallingPathSum(self, grid: List[List[int]]) -> int:
+        N = len(grid)
+        dp = grid[0]
+
+        for r in range(1, N):
+            next_dp = [float("inf")] * N
+            for curr_c in range(N):
+                for prev_c in range(N):
+                    if prev_c != curr_c:
+                        next_dp[curr_c] = min(
+                            next_dp[curr_c],
+                            grid[r][curr_c] + dp[prev_c]
+                        )
+            dp = next_dp
+
+        return min(dp)
+```
+
+```java
+public class Solution {
+    public int minFallingPathSum(int[][] grid) {
+        int N = grid.length;
+        int[] dp = grid[0];
+
+        for (int r = 1; r < N; r++) {
+            int[] nextDp = new int[N];
+            Arrays.fill(nextDp, Integer.MAX_VALUE);
+
+            for (int currC = 0; currC < N; currC++) {
+                for (int prevC = 0; prevC < N; prevC++) {
+                    if (prevC != currC) {
+                        nextDp[currC] = Math.min(
+                            nextDp[currC],
+                            grid[r][currC] + dp[prevC]
+                        );
+                    }
+                }
+            }
+            dp = nextDp;
+        }
+
+        int res = Integer.MAX_VALUE;
+        for (int i : dp) res = Math.min(res, i);
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minFallingPathSum(vector<vector<int>>& grid) {
+        int N = grid.size();
+        vector<int> dp = grid[0];
+
+        for (int r = 1; r < N; r++) {
+            vector<int> nextDp(N, INT_MAX);
+            for (int currC = 0; currC < N; currC++) {
+                for (int prevC = 0; prevC < N; prevC++) {
+                    if (prevC != currC) {
+                        nextDp[currC] = min(
+                            nextDp[currC],
+                            grid[r][currC] + dp[prevC]
+                        );
+                    }
+                }
+            }
+            dp = nextDp;
+        }
+
+        return *min_element(dp.begin(), dp.end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    minFallingPathSum(grid) {
+        const N = grid.length;
+        let dp = grid[0];
+
+        for (let r = 1; r < N; r++) {
+            const nextDp = Array(N).fill(Infinity);
+            for (let currC = 0; currC < N; currC++) {
+                for (let prevC = 0; prevC < N; prevC++) {
+                    if (prevC !== currC) {
+                        nextDp[currC] = Math.min(
+                            nextDp[currC],
+                            grid[r][currC] + dp[prevC]
+                        );
+                    }
+                }
+            }
+            dp = nextDp;
+        }
+
+        return Math.min(...dp);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 3)$
+* Space complexity: $O(n)$
+
+---
+
+## 5. Dynamic Programming (Time Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def minFallingPathSum(self, grid: List[List[int]]) -> int:
+        def get_min_two(row):
+            two_smallest = []
+            for val, idx in row:
+                if len(two_smallest) < 2:
+                    two_smallest.append((val, idx))
+                elif two_smallest[1][0] > val:
+                    two_smallest.pop()
+                    two_smallest.append((val, idx))
+                two_smallest.sort()
+            return two_smallest
+
+        N = len(grid)
+        first_row = [(val, idx) for idx, val in enumerate(grid[0])]
+        dp = get_min_two(first_row)
+
+        for r in range(1, N):
+            next_dp = []
+            for curr_c in range(N):
+                curr_val = grid[r][curr_c]
+                min_val = float("inf")
+                for prev_val, prev_c in dp:
+                    if curr_c != prev_c:
+                        min_val = min(min_val, curr_val + prev_val)
+                next_dp.append((min_val, curr_c))
+            dp = get_min_two(next_dp)
+
+        return min(val for val, idx in dp)
+```
+
+```java
+public class Solution {
+    public List<int[]> getMinTwo(List<int[]> row) {
+        List<int[]> twoSmallest = new ArrayList<>();
+        for (int[] entry : row) {
+            if (twoSmallest.size() < 2) {
+                twoSmallest.add(entry);
+            } else if (twoSmallest.get(1)[0] > entry[0]) {
+                twoSmallest.remove(1);
+                twoSmallest.add(entry);
+            }
+            twoSmallest.sort((a, b) -> a[0] - b[0]);
+        }
+        return twoSmallest;
+    }
+
+    public int minFallingPathSum(int[][] grid) {
+        int N = grid.length;
+
+        List<int[]> firstRow = new ArrayList<>();
+        for (int i = 0; i < grid[0].length; i++) {
+            firstRow.add(new int[]{grid[0][i], i});
+        }
+
+        List<int[]> dp = getMinTwo(firstRow);
+
+        for (int r = 1; r < N; r++) {
+            List<int[]> nextDp = new ArrayList<>();
+            for (int c = 0; c < grid[0].length; c++) {
+                int currVal = grid[r][c];
+                int minVal = Integer.MAX_VALUE;
+                for (int[] prev : dp) {
+                    if (prev[1] != c) {
+                        minVal = Math.min(minVal, currVal + prev[0]);
+                    }
+                }
+                nextDp.add(new int[]{minVal, c});
+            }
+            dp = getMinTwo(nextDp);
+        }
+
+        return dp.stream().mapToInt(a -> a[0]).min().getAsInt();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minFallingPathSum(vector<vector<int>>& grid) {
+        int N = grid.size();
+
+        auto getMinTwo = [](vector<pair<int, int>>& row) {
+            vector<pair<int, int>> twoSmallest;
+            for (auto& entry : row) {
+                if (twoSmallest.size() < 2) {
+                    twoSmallest.push_back(entry);
+                } else if (twoSmallest[1].first > entry.first) {
+                    twoSmallest.pop_back();
+                    twoSmallest.push_back(entry);
+                }
+                sort(twoSmallest.begin(), twoSmallest.end());
+            }
+            return twoSmallest;
+        };
+
+        vector<pair<int, int>> firstRow;
+        for (int i = 0; i < grid[0].size(); i++) {
+            firstRow.push_back({grid[0][i], i});
+        }
+
+        vector<pair<int, int>> dp = getMinTwo(firstRow);
+
+        for (int r = 1; r < N; r++) {
+            vector<pair<int, int>> nextDp;
+            for (int c = 0; c < grid[0].size(); c++) {
+                int currVal = grid[r][c];
+                int minVal = INT_MAX;
+                for (auto& prev : dp) {
+                    if (prev.second != c) {
+                        minVal = min(minVal, currVal + prev.first);
+                    }
+                }
+                nextDp.push_back({minVal, c});
+            }
+            dp = getMinTwo(nextDp);
+        }
+
+        int result = INT_MAX;
+        for (auto& entry : dp) {
+            result = min(result, entry.first);
+        }
+        return result;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    minFallingPathSum(grid) {
+        const N = grid.length;
+
+        const getMinTwo = (row) => {
+            const twoSmallest = [];
+            for (const [val, idx] of row) {
+                if (twoSmallest.length < 2) {
+                    twoSmallest.push([val, idx]);
+                } else if (twoSmallest[1][0] > val) {
+                    twoSmallest.pop();
+                    twoSmallest.push([val, idx]);
+                }
+                twoSmallest.sort((a, b) => a[0] - b[0]);
+            }
+            return twoSmallest;
+        };
+
+        const firstRow = grid[0].map((val, idx) => [val, idx]);
+        let dp = getMinTwo(firstRow);
+
+        for (let r = 1; r < N; r++) {
+            const nextDp = [];
+            for (let c = 0; c < grid[0].length; c++) {
+                const currVal = grid[r][c];
+                let minVal = Infinity;
+                for (const [prevVal, prevC] of dp) {
+                    if (c !== prevC) {
+                        minVal = Math.min(minVal, currVal + prevVal);
+                    }
+                }
+                nextDp.push([minVal, c]);
+            }
+            dp = getMinTwo(nextDp);
+        }
+
+        return Math.min(...dp.map(([val]) => val));
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 6. Dynamic Programming (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def minFallingPathSum(self, grid: List[List[int]]) -> int:
+        n = len(grid)
+        if n == 1:
+            return grid[0][0]
+        
+        dp_idx1 = dp_idx2 = -1
+        dp_val1 = dp_val2 = 0
+
+        for i in range(n):
+            nextDp_idx1 = nextDp_idx2 = -1
+            nextDp_val1 = nextDp_val2 = float("inf")
+
+            for j in range(n):
+                cur = dp_val1 if j != dp_idx1 else dp_val2
+                cur += grid[i][j]
+
+                if nextDp_idx1 == -1 or cur < nextDp_val1:
+                    nextDp_idx2, nextDp_val2 = nextDp_idx1, nextDp_val1
+                    nextDp_idx1, nextDp_val1 = j, cur
+                elif nextDp_idx2 == -1 or cur < nextDp_val2:
+                    nextDp_idx2, nextDp_val2 = j, cur
+
+            dp_idx1, dp_idx2, dp_val1, dp_val2 = nextDp_idx1, nextDp_idx2, nextDp_val1, nextDp_val2
+
+        return dp_val1
+```
+
+```java
+public class Solution {
+    public int minFallingPathSum(int[][] grid) {
+        int n = grid.length;
+        if (n == 1) {
+            return grid[0][0];
+        }
+
+        int dpIdx1 = -1, dpIdx2 = -1;
+        int dpVal1 = 0, dpVal2 = 0;
+
+        for (int i = 0; i < n; i++) {
+            int nextDpIdx1 = -1, nextDpIdx2 = -1;
+            int nextDpVal1 = Integer.MAX_VALUE, nextDpVal2 = Integer.MAX_VALUE;
+
+            for (int j = 0; j < n; j++) {
+                int cur = (j != dpIdx1) ? dpVal1 : dpVal2;
+                cur += grid[i][j];
+
+                if (nextDpIdx1 == -1 || cur < nextDpVal1) {
+                    nextDpIdx2 = nextDpIdx1;
+                    nextDpVal2 = nextDpVal1;
+                    nextDpIdx1 = j;
+                    nextDpVal1 = cur;
+                } else if (nextDpIdx2 == -1 || cur < nextDpVal2) {
+                    nextDpIdx2 = j;
+                    nextDpVal2 = cur;
+                }
+            }
+
+            dpIdx1 = nextDpIdx1;
+            dpIdx2 = nextDpIdx2;
+            dpVal1 = nextDpVal1;
+            dpVal2 = nextDpVal2;
+        }
+
+        return dpVal1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minFallingPathSum(vector<vector<int>>& grid) {
+        int n = grid.size();
+        if (n == 1) {
+            return grid[0][0];
+        }
+
+        int dpIdx1 = -1, dpIdx2 = -1;
+        int dpVal1 = 0, dpVal2 = 0;
+
+        for (int i = 1; i < n; i++) {
+            int nextDpIdx1 = -1, nextDpIdx2 = -1;
+            int nextDpVal1 = INT_MAX, nextDpVal2 = INT_MAX;
+
+            for (int j = 0; j < n; j++) {
+                int cur = (j != dpIdx1) ? dpVal1 : dpVal2;
+                cur += grid[i][j];
+
+                if (nextDpIdx1 == -1 || cur < nextDpVal1) {
+                    nextDpIdx2 = nextDpIdx1;
+                    nextDpVal2 = nextDpVal1;
+                    nextDpIdx1 = j;
+                    nextDpVal1 = cur;
+                } else if (nextDpIdx2 == -1 || cur < nextDpVal2) {
+                    nextDpIdx2 = j;
+                    nextDpVal2 = cur;
+                }
+            }
+
+            dpIdx1 = nextDpIdx1;
+            dpIdx2 = nextDpIdx2;
+            dpVal1 = nextDpVal1;
+            dpVal2 = nextDpVal2;
+        }
+
+        return dpVal1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    minFallingPathSum(grid) {
+        const n = grid.length;
+        if (n === 1) return grid[0][0];
+
+        let dpIdx1 = -1, dpIdx2 = -1;
+        let dpVal1 = 0, dpVal2 = 0;
+
+        for (let i = 0; i < n; i++) {
+            let nextDpIdx1 = -1, nextDpIdx2 = -1;
+            let nextDpVal1 = Infinity, nextDpVal2 = Infinity;
+
+            for (let j = 0; j < n; j++) {
+                let cur = (j !== dpIdx1) ? dpVal1 : dpVal2;
+                cur += grid[i][j];
+
+                if (nextDpIdx1 === -1 || cur < nextDpVal1) {
+                    nextDpIdx2 = nextDpIdx1;
+                    nextDpVal2 = nextDpVal1;
+                    nextDpIdx1 = j;
+                    nextDpVal1 = cur;
+                } else if (nextDpIdx2 === -1 || cur < nextDpVal2) {
+                    nextDpIdx2 = j;
+                    nextDpVal2 = cur;
+                }
+            }
+
+            dpIdx1 = nextDpIdx1;
+            dpIdx2 = nextDpIdx2;
+            dpVal1 = nextDpVal1;
+            dpVal2 = nextDpVal2;
+        }
+
+        return dpVal1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/minimum-falling-path-sum.md b/articles/minimum-falling-path-sum.md
new file mode 100644
index 000000000..c12290d15
--- /dev/null
+++ b/articles/minimum-falling-path-sum.md
@@ -0,0 +1,449 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def minFallingPathSum(self, matrix: List[List[int]]) -> int:
+        N = len(matrix)
+
+        def dfs(r, c):
+            if r == N:
+                return 0
+            if c < 0 or c >= N:
+                return float("inf")
+            return matrix[r][c] + min(
+                dfs(r + 1, c - 1),
+                dfs(r + 1, c),
+                dfs(r + 1, c + 1)
+            )
+
+        res = float("inf")
+        for c in range(N):
+            res = min(res, dfs(0, c))
+        return res
+```
+
+```java
+public class Solution {
+    private int dfs(int r, int c, int[][] matrix, int N) {
+        if (r == N) return 0;
+        if (c < 0 || c >= N) return Integer.MAX_VALUE;
+        return matrix[r][c] + Math.min(
+            Math.min(dfs(r + 1, c - 1, matrix, N), dfs(r + 1, c, matrix, N)),
+            dfs(r + 1, c + 1, matrix, N)
+        );
+    }
+
+    public int minFallingPathSum(int[][] matrix) {
+        int N = matrix.length;
+        int res = Integer.MAX_VALUE;
+        for (int c = 0; c < N; c++) {
+            res = Math.min(res, dfs(0, c, matrix, N));
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    int dfs(int r, int c, vector<vector<int>>& matrix, int N) {
+        if (r == N) return 0;
+        if (c < 0 || c >= N) return INT_MAX;
+        return matrix[r][c] + min({
+            dfs(r + 1, c - 1, matrix, N),
+            dfs(r + 1, c, matrix, N),
+            dfs(r + 1, c + 1, matrix, N)
+        });
+    }
+
+public:
+    int minFallingPathSum(vector<vector<int>>& matrix) {
+        int N = matrix.size();
+        int res = INT_MAX;
+        for (int c = 0; c < N; c++) {
+            res = min(res, dfs(0, c, matrix, N));
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} matrix
+     * @return {number}
+     */
+    minFallingPathSum(matrix) {
+        const N = matrix.length;
+
+        const dfs = (r, c) => {
+            if (r === N) return 0;
+            if (c < 0 || c >= N) return Infinity;
+            return matrix[r][c] + Math.min(
+                dfs(r + 1, c - 1),
+                dfs(r + 1, c),
+                dfs(r + 1, c + 1)
+            );
+        };
+
+        let res = Infinity;
+        for (let c = 0; c < N; c++) {
+            res = Math.min(res, dfs(0, c));
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(3 ^ n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def minFallingPathSum(self, matrix: List[List[int]]) -> int:
+        N = len(matrix)
+        cache = {}
+
+        def dfs(r, c):
+            if r == N:
+                return 0
+            if c < 0 or c >= N:
+                return float("inf")
+            if (r, c) in cache:
+                return cache[(r, c)]
+            cache[(r, c)] = matrix[r][c] + min(
+                dfs(r + 1, c - 1),
+                dfs(r + 1, c),
+                dfs(r + 1, c + 1)
+            )
+            return cache[(r, c)]
+
+        res = float("inf")
+        for c in range(N):
+            res = min(res, dfs(0, c))
+        return res
+```
+
+```java
+public class Solution {
+    private int[][] cache;
+
+    private int dfs(int r, int c, int[][] matrix, int N) {
+        if (r == N) return 0;
+        if (c < 0 || c >= N) return Integer.MAX_VALUE;
+        if (cache[r][c] != Integer.MIN_VALUE) return cache[r][c];
+
+        cache[r][c] = matrix[r][c] + Math.min(
+            Math.min(dfs(r + 1, c - 1, matrix, N), dfs(r + 1, c, matrix, N)),
+            dfs(r + 1, c + 1, matrix, N)
+        );
+        return cache[r][c];
+    }
+
+    public int minFallingPathSum(int[][] matrix) {
+        int N = matrix.length;
+        cache = new int[N][N];
+        for (int[] row : cache) {
+            Arrays.fill(row, Integer.MIN_VALUE);
+        }
+
+        int res = Integer.MAX_VALUE;
+        for (int c = 0; c < N; c++) {
+            res = Math.min(res, dfs(0, c, matrix, N));
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<vector<int>> cache;
+
+    int dfs(int r, int c, vector<vector<int>>& matrix, int N) {
+        if (r == N) return 0;
+        if (c < 0 || c >= N) return INT_MAX;
+        if (cache[r][c] != INT_MIN) return cache[r][c];
+
+        cache[r][c] = matrix[r][c] + min({
+            dfs(r + 1, c - 1, matrix, N),
+            dfs(r + 1, c, matrix, N),
+            dfs(r + 1, c + 1, matrix, N)
+        });
+        return cache[r][c];
+    }
+
+public:
+    int minFallingPathSum(vector<vector<int>>& matrix) {
+        int N = matrix.size();
+        cache = vector<vector<int>>(N, vector<int>(N, INT_MIN));
+
+        int res = INT_MAX;
+        for (int c = 0; c < N; c++) {
+            res = min(res, dfs(0, c, matrix, N));
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} matrix
+     * @return {number}
+     */
+    minFallingPathSum(matrix) {
+        const N = matrix.length;
+        const cache = Array.from({ length: N }, () => Array(N).fill(null));
+
+        const dfs = (r, c) => {
+            if (r === N) return 0;
+            if (c < 0 || c >= N) return Infinity;
+            if (cache[r][c] !== null) return cache[r][c];
+
+            cache[r][c] = matrix[r][c] + Math.min(
+                dfs(r + 1, c - 1),
+                dfs(r + 1, c),
+                dfs(r + 1, c + 1)
+            );
+            return cache[r][c];
+        };
+
+        let res = Infinity;
+        for (let c = 0; c < N; c++) {
+            res = Math.min(res, dfs(0, c));
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * n)$
+* Space complexity: $O(n * n)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def minFallingPathSum(self, matrix: List[List[int]]) -> int:
+        N = len(matrix)
+        dp = matrix[0][:]
+
+        for r in range(1, N):
+            leftUp = float('inf')
+            for c in range(N):
+                midUp = dp[c]
+                rightUp = dp[c + 1] if c < N - 1 else float('inf')
+                dp[c] = matrix[r][c] + min(midUp, leftUp, rightUp)
+                leftUp = midUp
+
+        return min(dp)
+```
+
+```java
+public class Solution {
+    public int minFallingPathSum(int[][] matrix) {
+        int N = matrix.length;
+        int[] dp = new int[N];
+        for (int c = 0; c < N; c++) {
+            dp[c] = matrix[0][c];
+        }
+
+        for (int r = 1; r < N; r++) {
+            int leftUp = Integer.MAX_VALUE;
+            for (int c = 0; c < N; c++) {
+                int midUp = dp[c];
+                int rightUp = (c < N - 1) ? dp[c + 1] : Integer.MAX_VALUE;
+                dp[c] = matrix[r][c] + Math.min(midUp, Math.min(leftUp, rightUp));
+                leftUp = midUp;
+            }
+        }
+
+        int ans = Integer.MAX_VALUE;
+        for (int val : dp) {
+            ans = Math.min(ans, val);
+        }
+        return ans;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minFallingPathSum(vector<vector<int>>& matrix) {
+        int N = matrix.size();
+        vector<int> dp(N);
+        
+        for (int c = 0; c < N; c++) {
+            dp[c] = matrix[0][c];
+        }
+
+        for (int r = 1; r < N; r++) {
+            int leftUp = INT_MAX;
+            for (int c = 0; c < N; c++) {
+                int midUp = dp[c];
+                int rightUp = (c < N - 1) ? dp[c + 1] : INT_MAX;
+                dp[c] = matrix[r][c] + min(midUp, min(leftUp, rightUp));
+                leftUp = midUp;
+            }
+        }
+
+        int ans = INT_MAX;
+        for (int val : dp) {
+            ans = min(ans, val);
+        }
+        return ans;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} matrix
+     * @return {number}
+     */
+    minFallingPathSum(matrix) {
+        const N = matrix.length;
+        const dp = matrix[0].slice();
+
+        for (let r = 1; r < N; r++) {
+            let leftUp = Infinity;
+            for (let c = 0; c < N; c++) {
+                const midUp = dp[c];
+                const rightUp = (c < N - 1) ? dp[c + 1] : Infinity;
+                dp[c] = matrix[r][c] + Math.min(midUp, leftUp, rightUp);
+                leftUp = midUp;
+            }
+        }
+
+        return Math.min(...dp);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Dynamic Programming (In-Place)
+
+::tabs-start
+
+```python
+class Solution:
+    def minFallingPathSum(self, matrix: List[List[int]]) -> int:
+        N = len(matrix)
+
+        for r in range(1, N):
+            for c in range(N):
+                mid = matrix[r - 1][c]
+                left = matrix[r - 1][c - 1] if c > 0 else float("inf")
+                right = matrix[r - 1][c + 1] if c < N - 1 else float("inf")
+                matrix[r][c] = matrix[r][c] + min(mid, left, right)
+
+        return min(matrix[-1])
+```
+
+```java
+public class Solution {
+    public int minFallingPathSum(int[][] matrix) {
+        int N = matrix.length;
+
+        for (int r = 1; r < N; r++) {
+            for (int c = 0; c < N; c++) {
+                int mid = matrix[r - 1][c];
+                int left = (c > 0) ? matrix[r - 1][c - 1] : Integer.MAX_VALUE;
+                int right = (c < N - 1) ? matrix[r - 1][c + 1] : Integer.MAX_VALUE;
+                matrix[r][c] = matrix[r][c] + Math.min(mid, Math.min(left, right));
+            }
+        }
+
+        int res = Integer.MAX_VALUE;
+        for (int c = 0; c < N; c++) {
+            res = Math.min(res, matrix[N - 1][c]);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minFallingPathSum(vector<vector<int>>& matrix) {
+        int N = matrix.size();
+
+        for (int r = 1; r < N; r++) {
+            for (int c = 0; c < N; c++) {
+                int mid = matrix[r - 1][c];
+                int left = (c > 0) ? matrix[r - 1][c - 1] : INT_MAX;
+                int right = (c < N - 1) ? matrix[r - 1][c + 1] : INT_MAX;
+                matrix[r][c] = matrix[r][c] + min({mid, left, right});
+            }
+        }
+
+        return *min_element(matrix[N - 1].begin(), matrix[N - 1].end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} matrix
+     * @return {number}
+     */
+    minFallingPathSum(matrix) {
+        const N = matrix.length;
+
+        for (let r = 1; r < N; r++) {
+            for (let c = 0; c < N; c++) {
+                const mid = matrix[r - 1][c];
+                const left = c > 0 ? matrix[r - 1][c - 1] : Infinity;
+                const right = c < N - 1 ? matrix[r - 1][c + 1] : Infinity;
+                matrix[r][c] = matrix[r][c] + Math.min(mid, left, right);
+            }
+        }
+
+        return Math.min(...matrix[N - 1]);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/minimum-fuel-cost-to-report-to-the-capital.md b/articles/minimum-fuel-cost-to-report-to-the-capital.md
new file mode 100644
index 000000000..77dda576e
--- /dev/null
+++ b/articles/minimum-fuel-cost-to-report-to-the-capital.md
@@ -0,0 +1,299 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def minimumFuelCost(self, roads: list[list[int]], seats: int) -> int:
+        adj = defaultdict(list)
+        for src, dst in roads:
+            adj[src].append(dst)
+            adj[dst].append(src)
+
+        res = 0
+        def dfs(node, parent):
+            nonlocal res
+            passengers = 0
+            for child in adj[node]:
+                if child != parent:
+                    p = dfs(child, node)
+                    passengers += p
+                    res += ceil(p / seats)
+            return passengers + 1
+
+        dfs(0, -1)
+        return res
+```
+
+```java
+public class Solution {
+    private List<Integer>[] adj;
+    private long res = 0;
+
+    public long minimumFuelCost(int[][] roads, int seats) {
+        int n = roads.length + 1;
+        adj = new ArrayList[n];
+
+        for (int i = 0; i < n; i++) {
+            adj[i] = new ArrayList<>();
+        }
+
+        for (int[] road : roads) {
+            adj[road[0]].add(road[1]);
+            adj[road[1]].add(road[0]);
+        }
+
+        dfs(0, -1, seats);
+        return res;
+    }
+
+    private int dfs(int node, int parent, int seats) {
+        int passengers = 0;
+        for (int child : adj[node]) {
+            if (child != parent) {
+                int p = dfs(child, node, seats);
+                passengers += p;
+                res += Math.ceil((double) p / seats);
+            }
+        }
+        return passengers + 1;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<vector<int>> adj;
+    long long res = 0;
+
+public:
+    long long minimumFuelCost(vector<vector<int>>& roads, int seats) {
+        int n = roads.size() + 1;
+        adj.resize(n);
+
+        for (auto& road : roads) {
+            adj[road[0]].push_back(road[1]);
+            adj[road[1]].push_back(road[0]);
+        }
+
+        dfs(0, -1, seats);
+        return res;
+    }
+
+private:
+    int dfs(int node, int parent, int seats) {
+        int passengers = 0;
+        for (int child : adj[node]) {
+            if (child != parent) {
+                int p = dfs(child, node, seats);
+                passengers += p;
+                res += ceil((double) p / seats);
+            }
+        }
+        return passengers + 1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} roads
+     * @param {number} seats
+     * @return {number}
+     */
+    minimumFuelCost(roads, seats) {
+        const n = roads.length + 1;
+        const adj = Array.from({ length: n }, () => []);
+        let res = 0;
+
+        for (const [src, dst] of roads) {
+            adj[src].push(dst);
+            adj[dst].push(src);
+        }
+
+        const dfs = (node, parent) => {
+            let passengers = 0;
+            for (const child of adj[node]) {
+                if (child !== parent) {
+                    let p = dfs(child, node);
+                    passengers += p;
+                    res += Math.ceil(p / seats);
+                }
+            }
+            return passengers + 1;
+        };
+
+        dfs(0, -1);
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Topological Sort (Kahn's Algorithm)
+
+::tabs-start
+
+```python
+class Solution:
+    def minimumFuelCost(self, roads: list[list[int]], seats: int) -> int:
+        n = len(roads) + 1
+        adj = [[] for _ in range(n)]
+        indegree = [0] * n
+        passengers = [1] * n
+        res = 0
+
+        for src, dst in roads:
+            adj[src].append(dst)
+            adj[dst].append(src)
+            indegree[src] += 1
+            indegree[dst] += 1
+
+        q = deque()
+        for i in range(1, n):
+            if indegree[i] == 1:
+                q.append(i)
+
+        while q:
+            node = q.popleft()
+            res += math.ceil(passengers[node] / seats)
+            for parent in adj[node]:
+                indegree[parent] -= 1
+                if indegree[parent] == 1 and parent != 0:
+                    q.append(parent)
+                passengers[parent] += passengers[node]
+
+        return res
+```
+
+```java
+public class Solution {
+    public long minimumFuelCost(int[][] roads, int seats) {
+        int n = roads.length + 1;
+        List<Integer>[] adj = new ArrayList[n];
+        int[] indegree = new int[n];
+        int[] passengers = new int[n];
+        Arrays.fill(passengers, 1);
+        long res = 0;
+
+        for (int i = 0; i < n; i++) adj[i] = new ArrayList<>();
+
+        for (int[] road : roads) {
+            int src = road[0], dst = road[1];
+            adj[src].add(dst);
+            adj[dst].add(src);
+            indegree[src]++;
+            indegree[dst]++;
+        }
+
+        Queue<Integer> q = new LinkedList<>();
+        for (int i = 1; i < n; i++) {
+            if (indegree[i] == 1) q.offer(i);
+        }
+
+        while (!q.isEmpty()) {
+            int node = q.poll();
+            res += (int) Math.ceil((double) passengers[node] / seats);
+            for (int parent : adj[node]) {
+                if (--indegree[parent] == 1 && parent != 0) q.offer(parent);
+                passengers[parent] += passengers[node];
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long minimumFuelCost(vector<vector<int>>& roads, int seats) {
+        int n = roads.size() + 1;
+        vector<vector<int>> adj(n);
+        vector<int> indegree(n, 0), passengers(n, 1);
+        long long res = 0;
+
+        for (auto& road : roads) {
+            int src = road[0], dst = road[1];
+            adj[src].push_back(dst);
+            adj[dst].push_back(src);
+            indegree[src]++;
+            indegree[dst]++;
+        }
+
+        queue<int> q;
+        for (int i = 1; i < n; i++) {
+            if (indegree[i] == 1) q.push(i);
+        }
+
+        while (!q.empty()) {
+            int node = q.front();q.pop();
+            res += ceil((double) passengers[node] / seats);
+            for (int parent : adj[node]) {
+                if (--indegree[parent] == 1 && parent != 0) q.push(parent);
+                passengers[parent] += passengers[node];
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} roads
+     * @param {number} seats
+     * @return {number}
+     */
+    minimumFuelCost(roads, seats) {
+        const n = roads.length + 1;
+        const adj = Array.from({ length: n }, () => []);
+        const indegree = new Array(n).fill(0);
+        const passengers = new Array(n).fill(1);
+        let res = 0;
+
+        for (const [src, dst] of roads) {
+            adj[src].push(dst);
+            adj[dst].push(src);
+            indegree[src] += 1;
+            indegree[dst] += 1;
+        }
+
+        const q = new Queue();
+        for (let i = 1; i < n; i++) {
+            if (indegree[i] === 1) q.push(i);
+        }
+
+        while (!q.isEmpty()) {
+            const node = q.pop();
+            res += Math.ceil(passengers[node] / seats);
+            for (const parent of adj[node]) {
+                if (--indegree[parent] === 1 && parent !== 0) q.push(parent);
+                passengers[parent] += passengers[node];
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/minimum-height-trees.md b/articles/minimum-height-trees.md
new file mode 100644
index 000000000..19f63684e
--- /dev/null
+++ b/articles/minimum-height-trees.md
@@ -0,0 +1,847 @@
+## 1. Brute Force (DFS)
+
+::tabs-start
+
+```python
+class Solution:
+    def findMinHeightTrees(self, n: int, edges: List[List[int]]) -> List[int]:
+        adj = [[] for _ in range(n)]
+        for u, v in edges:
+            adj[u].append(v)
+            adj[v].append(u)
+        
+        def dfs(node, parent):
+            hgt = 0
+            for nei in adj[node]:
+                if nei == parent:
+                    continue
+                hgt = max(hgt, 1 + dfs(nei, node))
+            return hgt
+        
+        minHgt = n
+        res = []
+        for i in range(n):
+            curHgt = dfs(i, -1)
+            if curHgt == minHgt:
+                res.append(i)
+            elif curHgt < minHgt:
+                res = [i]
+                minHgt = curHgt
+        
+        return res
+```
+
+```java
+public class Solution {
+    private List<List<Integer>> adj;
+
+    public List<Integer> findMinHeightTrees(int n, int[][] edges) {
+        adj = new ArrayList<>();
+        for (int i = 0; i < n; i++) {
+            adj.add(new ArrayList<>());
+        }
+        for (int[] edge : edges) {
+            adj.get(edge[0]).add(edge[1]);
+            adj.get(edge[1]).add(edge[0]);
+        }
+
+        int minHgt = n;
+        List<Integer> result = new ArrayList<>();
+        for (int i = 0; i < n; i++) {
+            int curHgt = dfs(i, -1);
+            if (curHgt == minHgt) {
+                result.add(i);
+            } else if (curHgt < minHgt) {
+                result = new ArrayList<>();
+                result.add(i);
+                minHgt = curHgt;
+            }
+        }
+        return result;
+    }
+
+    private int dfs(int node, int parent) {
+        int hgt = 0;
+        for (int nei : adj.get(node)) {
+            if (nei == parent) {
+                continue;
+            }
+            hgt = Math.max(hgt, 1 + dfs(nei, node));
+        }
+        return hgt;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<vector<int>> adj;
+
+    int dfs(int node, int parent) {
+        int hgt = 0;
+        for (int nei : adj[node]) {
+            if (nei == parent)
+                continue;
+            hgt = max(hgt, 1 + dfs(nei, node));
+        }
+        return hgt;
+    }
+
+public:
+    vector<int> findMinHeightTrees(int n, vector<vector<int>>& edges) {
+        adj.resize(n);
+        for (const auto& edge : edges) {
+            adj[edge[0]].push_back(edge[1]);
+            adj[edge[1]].push_back(edge[0]);
+        }
+
+        int minHgt = n;
+        vector<int> result;
+        for (int i = 0; i < n; i++) {
+            int curHgt = dfs(i, -1);
+            if (curHgt == minHgt) {
+                result.push_back(i);
+            } else if (curHgt < minHgt) {
+                result = {i};
+                minHgt = curHgt;
+            }
+        }
+        return result;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} edges
+     * @return {number[]}
+     */
+    findMinHeightTrees(n, edges) {
+        const adj = Array.from({ length: n }, () => []);
+        for (const [u, v] of edges) {
+            adj[u].push(v);
+            adj[v].push(u);
+        }
+
+        const dfs = (node, parent) => {
+            let hgt = 0;
+            for (const nei of adj[node]) {
+                if (nei === parent) continue;
+                hgt = Math.max(hgt, 1 + dfs(nei, node));
+            }
+            return hgt;
+        };
+
+        let minHgt = n;
+        const result = [];
+        for (let i = 0; i < n; i++) {
+            const curHgt = dfs(i, -1);
+            if (curHgt === minHgt) {
+                result.push(i);
+            } else if (curHgt < minHgt) {
+                result.length = 0;
+                result.push(i);
+                minHgt = curHgt;
+            }
+        }
+        return result;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V * (V + E))$
+* Space complexity: $O(V)$
+
+> Where $V$ is the number of vertices and $E$ is the number of edges.
+
+---
+
+## 2. Dynamic Programming On Trees (Rerooting)
+
+::tabs-start
+
+```python
+class Solution:
+    def findMinHeightTrees(self, n: int, edges: List[List[int]]) -> List[int]:
+        adj = [[] for _ in range(n)]
+        for u, v in edges:
+            adj[u].append(v)
+            adj[v].append(u)
+        
+        dp = [[0] * 2 for _ in range(n)] # top two heights for each node
+
+        def dfs(node, parent):
+            for nei in adj[node]:
+                if nei == parent:
+                    continue
+                dfs(nei, node)
+                curHgt = 1 + dp[nei][0]
+                if curHgt > dp[node][0]:
+                    dp[node][1] = dp[node][0]
+                    dp[node][0] = curHgt
+                elif curHgt > dp[node][1]:
+                    dp[node][1] = curHgt
+
+        def dfs1(node, parent, topHgt):
+            if topHgt > dp[node][0]:
+                dp[node][1] = dp[node][0]
+                dp[node][0] = topHgt
+            elif topHgt > dp[node][1]:
+                dp[node][1] = topHgt
+
+            for nei in adj[node]:
+                if nei == parent:
+                    continue
+                toChild = 1 + (dp[node][1] if dp[node][0] == 1 + dp[nei][0] else dp[node][0])
+                dfs1(nei, node, toChild)
+        
+        dfs(0, -1)
+        dfs1(0, -1, 0)
+
+        minHgt, res = n, []
+        for i in range(n):
+            minHgt = min(minHgt, dp[i][0])
+        for i in range(n):
+            if minHgt == dp[i][0]:
+                res.append(i)
+        return res
+```
+
+```java
+class Solution {
+    private List<List<Integer>> adj;
+    private int[][] dp;
+
+    public List<Integer> findMinHeightTrees(int n, int[][] edges) {
+        adj = new ArrayList<>();
+        for (int i = 0; i < n; i++) {
+            adj.add(new ArrayList<>());
+        }
+        for (int[] edge : edges) {
+            adj.get(edge[0]).add(edge[1]);
+            adj.get(edge[1]).add(edge[0]);
+        }
+
+        dp = new int[n][2]; // top two heights for each node
+        dfs(0, -1);
+        dfs1(0, -1, 0);
+
+        int minHgt = n;
+        List<Integer> res = new ArrayList<>();
+        for (int i = 0; i < n; i++) {
+            minHgt = Math.min(minHgt, dp[i][0]);
+        }
+        for (int i = 0; i < n; i++) {
+            if (minHgt == dp[i][0]) {
+                res.add(i);
+            }
+        }
+        return res;
+    }
+
+    private void dfs(int node, int parent) {
+        for (int nei : adj.get(node)) {
+            if (nei == parent) continue;
+            dfs(nei, node);
+            int curHgt = 1 + dp[nei][0];
+            if (curHgt > dp[node][0]) {
+                dp[node][1] = dp[node][0];
+                dp[node][0] = curHgt;
+            } else if (curHgt > dp[node][1]) {
+                dp[node][1] = curHgt;
+            }
+        }
+    }
+
+    private void dfs1(int node, int parent, int topHgt) {
+        if (topHgt > dp[node][0]) {
+            dp[node][1] = dp[node][0];
+            dp[node][0] = topHgt;
+        } else if (topHgt > dp[node][1]) {
+            dp[node][1] = topHgt;
+        }
+
+        for (int nei : adj.get(node)) {
+            if (nei == parent) continue;
+            int toChild = 1 + ((dp[node][0] == 1 + dp[nei][0]) ? dp[node][1] : dp[node][0]);
+            dfs1(nei, node, toChild);
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<vector<int>> adj;
+    vector<vector<int>> dp;
+
+    void dfs(int node, int parent) {
+        for (int nei : adj[node]) {
+            if (nei == parent) continue;
+            dfs(nei, node);
+            int curHgt = 1 + dp[nei][0];
+            if (curHgt > dp[node][0]) {
+                dp[node][1] = dp[node][0];
+                dp[node][0] = curHgt;
+            } else if (curHgt > dp[node][1]) {
+                dp[node][1] = curHgt;
+            }
+        }
+    }
+
+    void dfs1(int node, int parent, int topHgt) {
+        if (topHgt > dp[node][0]) {
+            dp[node][1] = dp[node][0];
+            dp[node][0] = topHgt;
+        } else if (topHgt > dp[node][1]) {
+            dp[node][1] = topHgt;
+        }
+
+        for (int nei : adj[node]) {
+            if (nei == parent) continue;
+            int toChild = 1 + ((dp[node][0] == 1 + dp[nei][0]) ? dp[node][1] : dp[node][0]);
+            dfs1(nei, node, toChild);
+        }
+    }
+
+public:
+    vector<int> findMinHeightTrees(int n, vector<vector<int>>& edges) {
+        adj.resize(n);
+        dp.assign(n, vector<int>(2, 0)); // top two heights for each node
+        for (const auto& edge : edges) {
+            adj[edge[0]].push_back(edge[1]);
+            adj[edge[1]].push_back(edge[0]);
+        }
+
+        dfs(0, -1);
+        dfs1(0, -1, 0);
+
+        int minHgt = n;
+        vector<int> res;
+        for (int i = 0; i < n; i++) {
+            minHgt = min(minHgt, dp[i][0]);
+        }
+        for (int i = 0; i < n; i++) {
+            if (minHgt == dp[i][0]) {
+                res.push_back(i);
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} edges
+     * @return {number[]}
+     */
+    findMinHeightTrees(n, edges) {
+        const adj = Array.from({ length: n }, () => []);
+        for (const [u, v] of edges) {
+            adj[u].push(v);
+            adj[v].push(u);
+        }
+
+        // top two heights for each node
+        const dp = Array.from({ length: n }, () => [0, 0]);
+
+        const dfs = (node, parent) => {
+            for (const nei of adj[node]) {
+                if (nei === parent) continue;
+                dfs(nei, node);
+                const curHgt = 1 + dp[nei][0];
+                if (curHgt > dp[node][0]) {
+                    dp[node][1] = dp[node][0];
+                    dp[node][0] = curHgt;
+                } else if (curHgt > dp[node][1]) {
+                    dp[node][1] = curHgt;
+                }
+            }
+        };
+
+        const dfs1 = (node, parent, topHgt) => {
+            if (topHgt > dp[node][0]) {
+                dp[node][1] = dp[node][0];
+                dp[node][0] = topHgt;
+            } else if (topHgt > dp[node][1]) {
+                dp[node][1] = topHgt;
+            }
+
+            for (const nei of adj[node]) {
+                if (nei === parent) continue;
+                const toChild = 1 + ((dp[node][0] === 1 + dp[nei][0]) ? dp[node][1] : dp[node][0]);
+                dfs1(nei, node, toChild);
+            }
+        };
+
+        dfs(0, -1);
+        dfs1(0, -1, 0);
+
+        let minHgt = n;
+        const res = [];
+        for (let i = 0; i < n; i++) {
+            minHgt = Math.min(minHgt, dp[i][0]);
+        }
+        for (let i = 0; i < n; i++) {
+            if (minHgt === dp[i][0]) {
+                res.push(i);
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + E)$
+* Space complexity: $O(V)$
+
+> Where $V$ is the number of vertices and $E$ is the number of edges.
+
+---
+
+## 3. Find Centroids of the Tree (DFS)
+
+::tabs-start
+
+```python
+class Solution:
+    def findMinHeightTrees(self, n: int, edges: List[List[int]]) -> List[int]:
+        if n == 1:
+            return [0]
+
+        adj = [[] for _ in range(n)]
+        for u, v in edges:
+            adj[u].append(v)
+            adj[v].append(u)
+
+        def dfs(node, parent):
+            farthest_node = node
+            max_distance = 0
+            for nei in adj[node]:
+                if nei != parent:
+                    nei_node, nei_distance = dfs(nei, node)
+                    if nei_distance + 1 > max_distance:
+                        max_distance = nei_distance + 1
+                        farthest_node = nei_node
+            return farthest_node, max_distance
+
+        node_a, _ = dfs(0, -1)
+        node_b, diameter = dfs(node_a, -1)
+
+        centroids = []
+
+        def find_centroids(node, parent):
+            if node == node_b:
+                centroids.append(node)
+                return True
+            for nei in adj[node]:
+                if nei != parent:
+                    if find_centroids(nei, node):
+                        centroids.append(node)
+                        return True
+            return False
+
+        find_centroids(node_a, -1)
+        L = len(centroids)
+        if diameter % 2 == 0:
+            return [centroids[L // 2]]
+        else:
+            return [centroids[L // 2 - 1], centroids[L // 2]]
+```
+
+```java
+public class Solution {
+    private List<Integer>[] adj;
+    private List<Integer> centroids;
+    private int nodeB;
+
+    public List<Integer> findMinHeightTrees(int n, int[][] edges) {
+        if (n == 1)
+            return Collections.singletonList(0);
+
+        adj = new ArrayList[n];
+        for (int i = 0; i < n; ++i)
+            adj[i] = new ArrayList<>();
+
+        for (int[] edge : edges) {
+            adj[edge[0]].add(edge[1]);
+            adj[edge[1]].add(edge[0]);
+        }
+
+        int nodeA = dfs(0, -1)[0];
+        nodeB = dfs(nodeA, -1)[0];
+        centroids = new ArrayList<>();
+        findCentroids(nodeA, -1);
+
+        int L = centroids.size();
+        if (dfs(nodeA, -1)[1] % 2 == 0) {
+            return Collections.singletonList(centroids.get(L / 2));
+        } else {
+            return Arrays.asList(centroids.get(L / 2 - 1), centroids.get(L / 2));
+        }
+    }
+
+    private int[] dfs(int node, int parent) {
+        int farthestNode = node, maxDistance = 0;
+        for (int neighbor : adj[node]) {
+            if (neighbor != parent) {
+                int[] res = dfs(neighbor, node);
+                if (res[1] + 1 > maxDistance) {
+                    maxDistance = res[1] + 1;
+                    farthestNode = res[0];
+                }
+            }
+        }
+        return new int[] { farthestNode, maxDistance };
+    }
+
+    private boolean findCentroids(int node, int parent) {
+        if (node == nodeB) {
+            centroids.add(node);
+            return true;
+        }
+        for (int neighbor : adj[node]) {
+            if (neighbor != parent) {
+                if (findCentroids(neighbor, node)) {
+                    centroids.add(node);
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> adj;
+    vector<int> centroids;
+    int nodeB;
+
+    vector<int> findMinHeightTrees(int n, vector<vector<int>>& edges) {
+        if (n == 1)
+            return {0};
+        
+        adj.resize(n);
+        for (const auto& edge : edges) {
+            adj[edge[0]].push_back(edge[1]);
+            adj[edge[1]].push_back(edge[0]);
+        }
+
+        int nodeA = dfs(0, -1).first;
+        nodeB = dfs(nodeA, -1).first;
+        findCentroids(nodeA, -1);
+
+        int L = centroids.size();
+        if (dfs(nodeA, -1).second % 2 == 0)
+            return {centroids[L / 2]};
+        else
+            return {centroids[L / 2 - 1], centroids[L / 2]};
+    }
+
+private:
+    pair<int, int> dfs(int node, int parent) {
+        int farthestNode = node, maxDistance = 0;
+        for (int neighbor : adj[node]) {
+            if (neighbor != parent) {
+                auto res = dfs(neighbor, node);
+                if (res.second + 1 > maxDistance) {
+                    maxDistance = res.second + 1;
+                    farthestNode = res.first;
+                }
+            }
+        }
+        return {farthestNode, maxDistance};
+    }
+
+    bool findCentroids(int node, int parent) {
+        if (node == nodeB) {
+            centroids.push_back(node);
+            return true;
+        }
+        for (int neighbor : adj[node]) {
+            if (neighbor != parent) {
+                if (findCentroids(neighbor, node)) {
+                    centroids.push_back(node);
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} edges
+     * @return {number[]}
+     */
+    findMinHeightTrees(n, edges) {
+        if (n === 1) return [0];
+
+        const adj = Array.from({ length: n }, () => []);
+
+        for (const [u, v] of edges) {
+            adj[u].push(v);
+            adj[v].push(u);
+        }
+
+        const dfs = (node, parent) => {
+            let farthestNode = node;
+            let maxDistance = 0;
+
+            for (const neighbor of adj[node]) {
+                if (neighbor !== parent) {
+                    const [farthest, dist] = dfs(neighbor, node);
+                    if (dist + 1 > maxDistance) {
+                        maxDistance = dist + 1;
+                        farthestNode = farthest;
+                    }
+                }
+            }
+            return [farthestNode, maxDistance];
+        };
+
+        const findCentroids = (node, parent, centroids) => {
+            if (node === nodeB) {
+                centroids.push(node);
+                return true;
+            }
+
+            for (const neighbor of adj[node]) {
+                if (neighbor !== parent) {
+                    if (findCentroids(neighbor, node, centroids)) {
+                        centroids.push(node);
+                        return true;
+                    }
+                }
+            }
+            return false;
+        };
+
+        const [nodeA] = dfs(0, -1);
+        const [nodeB, diameter] = dfs(nodeA, -1);
+        this.nodeB = nodeB;
+
+        const centroids = [];
+        findCentroids(nodeA, -1, centroids);
+
+        const L = centroids.length;
+        return diameter % 2 === 0
+            ? [centroids[Math.floor(L / 2)]]
+            : [centroids[Math.floor(L / 2) - 1], centroids[Math.floor(L / 2)]];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + E)$
+* Space complexity: $O(V)$
+
+> Where $V$ is the number of vertices and $E$ is the number of edges.
+
+---
+
+## 4. Topological Sorting (BFS)
+
+::tabs-start
+
+```python
+class Solution:
+    def findMinHeightTrees(self, n: int, edges: List[List[int]]) -> List[int]:
+        if n == 1:
+            return [0]
+
+        adj = defaultdict(list)
+        for n1, n2 in edges:
+            adj[n1].append(n2)
+            adj[n2].append(n1)
+
+        edge_cnt = {}
+        leaves = deque()
+
+        for src, neighbors in adj.items():
+            edge_cnt[src] = len(neighbors)
+            if len(neighbors) == 1:
+                leaves.append(src)
+
+        while leaves:
+            if n <= 2:
+                return list(leaves)
+            for _ in range(len(leaves)):
+                node = leaves.popleft()
+                n -= 1
+                for nei in adj[node]:
+                    edge_cnt[nei] -= 1
+                    if edge_cnt[nei] == 1:
+                        leaves.append(nei)
+```
+
+```java
+public class Solution {
+    public List<Integer> findMinHeightTrees(int n, int[][] edges) {
+        if (n == 1) return Collections.singletonList(0);
+
+        List<Integer>[] adj = new ArrayList[n];
+        for (int i = 0; i < n; ++i)
+            adj[i] = new ArrayList<>();
+
+        for (int[] edge : edges) {
+            adj[edge[0]].add(edge[1]);
+            adj[edge[1]].add(edge[0]);
+        }
+
+        int[] edge_cnt = new int[n];
+        Queue<Integer> leaves = new LinkedList<>();
+
+        for (int i = 0; i < n; i++) {
+            edge_cnt[i] = adj[i].size();
+            if (adj[i].size() == 1)
+                leaves.offer(i);
+        }
+
+        while (!leaves.isEmpty()) {
+            if (n <= 2) return new ArrayList<>(leaves);
+            int size = leaves.size();
+            for (int i = 0; i < size; ++i) {
+                int node = leaves.poll();
+                n--;
+                for (int nei : adj[node]) {
+                    edge_cnt[nei]--;
+                    if (edge_cnt[nei] == 1)
+                        leaves.offer(nei);
+                }
+            }
+        }
+
+        return new ArrayList<>();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findMinHeightTrees(int n, vector<vector<int>>& edges) {
+        if (n == 1) return {0};
+
+        vector<vector<int>> adj(n);
+        for (auto& edge : edges) {
+            adj[edge[0]].push_back(edge[1]);
+            adj[edge[1]].push_back(edge[0]);
+        }
+
+        vector<int> edge_cnt(n);
+        queue<int> leaves;
+
+        for (int i = 0; i < n; ++i) {
+            edge_cnt[i] = adj[i].size();
+            if (adj[i].size() == 1)
+                leaves.push(i);
+        }
+
+        while (!leaves.empty()) {
+            if (n <= 2) {
+                vector<int> result;
+                while (!leaves.empty()) {
+                    result.push_back(leaves.front());
+                    leaves.pop();
+                }
+                return result;
+            }
+            int size = leaves.size();
+            for (int i = 0; i < size; ++i) {
+                int node = leaves.front();
+                leaves.pop();
+                --n;
+                for (int& nei : adj[node]) {
+                    --edge_cnt[nei];
+                    if (edge_cnt[nei] == 1)
+                        leaves.push(nei);
+                }
+            }
+        }
+
+        return {};
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} edges
+     * @return {number[]}
+     */
+    findMinHeightTrees(n, edges) {
+        if (n === 1) return [0];
+
+        const adj = Array.from({ length: n }, () => []);
+
+        for (const [n1, n2] of edges) {
+            adj[n1].push(n2);
+            adj[n2].push(n1);
+        }
+
+        const edgeCnt = Array(n).fill(0);
+        const leaves = new Queue();
+
+        for (let i = 0; i < n; i++) {
+            edgeCnt[i] = adj[i].length;
+            if (adj[i].length === 1) {
+                leaves.push(i);
+            }
+        }
+
+        while (!leaves.isEmpty()) {
+            if (n <= 2) return leaves.toArray();
+            const size = leaves.size();
+            for (let i = 0; i < size; i++) {
+                const node = leaves.pop();
+                n--;
+                for (const nei of adj[node]) {
+                    edgeCnt[nei]--;
+                    if (edgeCnt[nei] === 1) {
+                        leaves.push(nei);
+                    }
+                }
+            }
+        }
+
+        return [];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + E)$
+* Space complexity: $O(V)$
+
+> Where $V$ is the number of vertices and $E$ is the number of edges.
\ No newline at end of file
diff --git a/articles/minimum-index-of-a-valid-split.md b/articles/minimum-index-of-a-valid-split.md
new file mode 100644
index 000000000..17548cd54
--- /dev/null
+++ b/articles/minimum-index-of-a-valid-split.md
@@ -0,0 +1,385 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def minimumIndex(self, nums: List[int]) -> int:
+        n = len(nums)
+
+        for i in range(n - 1):
+            left_cnt = defaultdict(int)
+            for l in range(i + 1):
+                left_cnt[nums[l]] += 1
+
+            right_cnt = defaultdict(int)
+            for r in range(i + 1, n):
+                right_cnt[nums[r]] += 1
+
+            for num in left_cnt:
+                if left_cnt[num] > (i + 1) // 2 and right_cnt[num] > (n - i - 1) // 2:
+                    return i
+
+        return -1
+```
+
+```java
+public class Solution {
+    public int minimumIndex(List<Integer> nums) {
+        int n = nums.size();
+
+        for (int i = 0; i < n - 1; i++) {
+            Map<Integer, Integer> leftCnt = new HashMap<>();
+            for (int l = 0; l <= i; l++) {
+                int val = nums.get(l);
+                leftCnt.put(val, leftCnt.getOrDefault(val, 0) + 1);
+            }
+
+            Map<Integer, Integer> rightCnt = new HashMap<>();
+            for (int r = i + 1; r < n; r++) {
+                int val = nums.get(r);
+                rightCnt.put(val, rightCnt.getOrDefault(val, 0) + 1);
+            }
+
+            for (int num : leftCnt.keySet()) {
+                if (leftCnt.get(num) > (i + 1) / 2 && rightCnt.getOrDefault(num, 0) > (n - i - 1) / 2) {
+                    return i;
+                }
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minimumIndex(vector<int>& nums) {
+        int n = nums.size();
+
+        for (int i = 0; i < n - 1; i++) {
+            unordered_map<int, int> leftCnt, rightCnt;
+            for (int l = 0; l <= i; l++) {
+                leftCnt[nums[l]]++;
+            }
+            for (int r = i + 1; r < n; r++) {
+                rightCnt[nums[r]]++;
+            }
+
+            for (auto& [num, cnt] : leftCnt) {
+                if (cnt > (i + 1) / 2 && rightCnt[num] > (n - i - 1) / 2) {
+                    return i;
+                }
+            }
+        }
+
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    minimumIndex(nums) {
+        const n = nums.length;
+
+        for (let i = 0; i < n - 1; i++) {
+            const leftCnt = {};
+            for (let l = 0; l <= i; l++) {
+                leftCnt[nums[l]] = (leftCnt[nums[l]] || 0) + 1;
+            }
+
+            const rightCnt = {};
+            for (let r = i + 1; r < n; r++) {
+                rightCnt[nums[r]] = (rightCnt[nums[r]] || 0) + 1;
+            }
+
+            for (const num in leftCnt) {
+                if (leftCnt[num] > Math.floor((i + 1) / 2) &&
+                    (rightCnt[num] || 0) > Math.floor((n - i - 1) / 2)) {
+                    return i;
+                }
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def minimumIndex(self, nums: List[int]) -> int:
+        left = defaultdict(int)
+        right = Counter(nums)
+
+        for i in range(len(nums)):
+            left[nums[i]] += 1
+            right[nums[i]] -= 1
+
+            left_len = i + 1
+            right_len = len(nums) - i - 1
+
+            if 2 * left[nums[i]] > left_len and 2 * right[nums[i]] > right_len:
+                return i
+
+        return -1
+```
+
+```java
+public class Solution {
+    public int minimumIndex(List<Integer> nums) {
+        Map<Integer, Integer> left = new HashMap<>();
+        Map<Integer, Integer> right = new HashMap<>();
+        int n = nums.size();
+
+        for (int num : nums) {
+            right.put(num, right.getOrDefault(num, 0) + 1);
+        }
+
+        for (int i = 0; i < n; i++) {
+            int num = nums.get(i);
+            left.put(num, left.getOrDefault(num, 0) + 1);
+            right.put(num, right.get(num) - 1);
+
+            int leftLen = i + 1;
+            int rightLen = n - i - 1;
+
+            if (2 * left.get(num) > leftLen && 2 * right.get(num) > rightLen) {
+                return i;
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minimumIndex(vector<int>& nums) {
+        unordered_map<int, int> left, right;
+        int n = nums.size();
+
+        for (int num : nums) {
+            right[num]++;
+        }
+
+        for (int i = 0; i < n; i++) {
+            int num = nums[i];
+            left[num]++;
+            right[num]--;
+
+            int leftLen = i + 1;
+            int rightLen = n - i - 1;
+
+            if (2 * left[num] > leftLen && 2 * right[num] > rightLen) {
+                return i;
+            }
+        }
+
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    minimumIndex(nums) {
+        const left = {};
+        const right = {};
+        const n = nums.length;
+
+        for (const num of nums) {
+            right[num] = (right[num] || 0) + 1;
+        }
+
+        for (let i = 0; i < n; i++) {
+            const num = nums[i];
+            left[num] = (left[num] || 0) + 1;
+            right[num] -= 1;
+
+            const leftLen = i + 1;
+            const rightLen = n - i - 1;
+
+            if (2 * left[num] > leftLen && 2 * right[num] > rightLen) {
+                return i;
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Boyer-Moore Voting Algorithm
+
+::tabs-start
+
+```python
+class Solution:
+    def minimumIndex(self, nums: List[int]) -> int:
+        majority = count = 0
+        for num in nums:
+            if count == 0:
+                majority = num
+            count += (1 if majority == num else -1)
+
+        left_cnt, right_cnt = 0, nums.count(majority)
+
+        for i in range(len(nums)):
+            if nums[i] == majority:
+                left_cnt += 1
+                right_cnt -= 1
+
+            left_len = i + 1
+            right_len = len(nums) - i - 1
+
+            if 2 * left_cnt > left_len and 2 * right_cnt > right_len:
+                return i
+
+        return -1
+```
+
+```java
+public class Solution {
+    public int minimumIndex(List<Integer> nums) {
+        int majority = 0, count = 0;
+        for (int num : nums) {
+            if (count == 0) majority = num;
+            count += (majority == num) ? 1 : -1;
+        }
+
+        int leftCnt = 0, rightCnt = 0;
+        for (int num : nums) {
+            if (num == majority) rightCnt++;
+        }
+
+        int n = nums.size();
+        for (int i = 0; i < n; i++) {
+            if (nums.get(i) == majority) {
+                leftCnt++;
+                rightCnt--;
+            }
+
+            int leftLen = i + 1;
+            int rightLen = n - i - 1;
+
+            if (2 * leftCnt > leftLen && 2 * rightCnt > rightLen) {
+                return i;
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minimumIndex(vector<int>& nums) {
+        int majority = 0, count = 0;
+        for (int num : nums) {
+            if (count == 0) majority = num;
+            count += (num == majority ? 1 : -1);
+        }
+
+        int leftCnt = 0, rightCnt = count_if(nums.begin(), nums.end(),
+                                             [&](int x) { return x == majority; });
+
+        int n = nums.size();
+        for (int i = 0; i < n; i++) {
+            if (nums[i] == majority) {
+                leftCnt++;
+                rightCnt--;
+            }
+
+            int leftLen = i + 1;
+            int rightLen = n - i - 1;
+
+            if (2 * leftCnt > leftLen && 2 * rightCnt > rightLen) {
+                return i;
+            }
+        }
+
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    minimumIndex(nums) {
+        let majority = 0, count = 0;
+        for (let num of nums) {
+            if (count === 0) majority = num;
+            count += (num === majority ? 1 : -1);
+        }
+
+        let leftCnt = 0;
+        let rightCnt = nums.filter(x => x === majority).length;
+        const n = nums.length;
+
+        for (let i = 0; i < n; i++) {
+            if (nums[i] === majority) {
+                leftCnt++;
+                rightCnt--;
+            }
+
+            let leftLen = i + 1;
+            let rightLen = n - i - 1;
+
+            if (2 * leftCnt > leftLen && 2 * rightCnt > rightLen) {
+                return i;
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/minimum-interval-including-query.md b/articles/minimum-interval-including-query.md
new file mode 100644
index 000000000..3c1cf82d5
--- /dev/null
+++ b/articles/minimum-interval-including-query.md
@@ -0,0 +1,1727 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def minInterval(self, intervals: List[List[int]], queries: List[int]) -> List[int]:
+        n = len(intervals)
+        res = []
+        for q in queries:
+            cur = -1
+            for l, r in intervals:
+                if l <= q <= r:
+                    if cur == -1 or (r - l + 1) < cur:
+                        cur = r - l + 1
+            res.append(cur)
+        return res
+```
+
+```java
+public class Solution {
+    public int[] minInterval(int[][] intervals, int[] queries) {
+        int[] res = new int[queries.length];
+        int idx = 0;
+        for (int q : queries) {
+            int cur = -1;
+            for (int[] interval : intervals) {
+                int l = interval[0], r = interval[1];
+                if (l <= q && q <= r) {
+                    if (cur == -1 || (r - l + 1) < cur) {
+                        cur = r - l + 1;
+                    }
+                }
+            }
+            res[idx++] = cur;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> minInterval(vector<vector<int>>& intervals, vector<int>& queries) {
+        vector<int> res;
+        for (int q : queries) {
+            int cur = -1;
+            for (auto& interval : intervals) {
+                int l = interval[0], r = interval[1];
+                if (l <= q && q <= r) {
+                    if (cur == -1 || (r - l + 1) < cur) {
+                        cur = r - l + 1;
+                    }
+                }
+            }
+            res.push_back(cur);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} intervals
+     * @param {number[]} queries
+     * @return {number[]}
+     */
+    minInterval(intervals, queries) {
+        const res = [];
+        for (const q of queries) {
+            let cur = -1;
+            for (const [l, r] of intervals) {
+                if (l <= q && q <= r) {
+                    if (cur === -1 || (r - l + 1) < cur) {
+                        cur = r - l + 1;
+                    }
+                }
+            }
+            res.push(cur);
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[] MinInterval(int[][] intervals, int[] queries) {
+        int[] res = new int[queries.Length];
+        int idx = 0;
+        foreach (int q in queries) {
+            int cur = -1;
+            foreach (var interval in intervals) {
+                int l = interval[0], r = interval[1];
+                if (l <= q && q <= r) {
+                    if (cur == -1 || (r - l + 1) < cur) {
+                        cur = r - l + 1;
+                    }
+                }
+            }
+            res[idx++] = cur;
+        }
+        return res;
+    }
+}
+```
+
+```go
+func minInterval(intervals [][]int, queries []int) []int {
+    res := make([]int, len(queries))
+    for i, q := range queries {
+        cur := -1
+        for _, interval := range intervals {
+            l, r := interval[0], interval[1]
+            if l <= q && q <= r {
+                if cur == -1 || (r - l + 1) < cur {
+                    cur = r - l + 1
+                }
+            }
+        }
+        res[i] = cur
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun minInterval(intervals: Array<IntArray>, queries: IntArray): IntArray {
+        val res = IntArray(queries.size)
+        for ((i, q) in queries.withIndex()) {
+            var cur = -1
+            for (interval in intervals) {
+                val l = interval[0]
+                val r = interval[1]
+                if (l <= q && q <= r) {
+                    if (cur == -1 || (r - l + 1) < cur) {
+                        cur = r - l + 1
+                    }
+                }
+            }
+            res[i] = cur
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func minInterval(_ intervals: [[Int]], _ queries: [Int]) -> [Int] {
+        var res = [Int]()
+
+        for q in queries {
+            var cur = -1
+            for interval in intervals {
+                let l = interval[0]
+                let r = interval[1]
+
+                if l <= q && q <= r {
+                    if cur == -1 || (r - l + 1) < cur {
+                        cur = r - l + 1
+                    }
+                }
+            }
+            res.append(cur)
+        }
+
+        return res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(m)$ space for the output array.
+
+> Where $m$ is the length of the array $queries$ and $n$ is the length of the array $intervals$.
+
+---
+
+## 2. Sweep Line Algorithm
+
+::tabs-start
+
+```python
+class Solution:
+    def minInterval(self, intervals: List[List[int]], queries: List[int]) -> List[int]:
+        events = []
+        # Create events for intervals
+        for idx, (start, end) in enumerate(intervals):
+            events.append((start, 0, end - start + 1, idx))    
+            events.append((end, 2, end - start + 1, idx))      
+        
+        # Create events for queries
+        for i, q in enumerate(queries):
+            events.append((q, 1, i))
+        
+        # Sort by time and type (end before query)
+        events.sort(key=lambda x: (x[0], x[1]))
+        
+        # Min heap storing [size, index]
+        sizes = []  
+        ans = [-1] * len(queries)
+        inactive = [False] * len(intervals)
+        
+        for time, type, *rest in events:
+            if type == 0:  # Interval start
+                interval_size, idx = rest
+                heapq.heappush(sizes, (interval_size, idx))
+            elif type == 2: #Interval end
+                idx = rest[1]
+                inactive[idx] = True
+            else: # Query
+                query_idx = rest[0]
+                while sizes and inactive[sizes[0][1]]:
+                    heapq.heappop(sizes)
+                if sizes:
+                    ans[query_idx] = sizes[0][0]
+        
+        return ans
+```
+
+```java
+public class Solution {
+   public int[] minInterval(int[][] intervals, int[] queries) {
+       List<int[]> events = new ArrayList<>();
+       for (int i = 0; i < intervals.length; i++) {
+           events.add(new int[]{intervals[i][0], 0, intervals[i][1] - intervals[i][0] + 1, i});
+           events.add(new int[]{intervals[i][1], 2, intervals[i][1] - intervals[i][0] + 1, i}); 
+       }
+       
+       for (int i = 0; i < queries.length; i++) {
+           events.add(new int[]{queries[i], 1, i});
+       }
+       
+       // Sort by time and type (end before query)
+       events.sort((a, b) -> a[0] != b[0] ? 
+                  Integer.compare(a[0], b[0]) : 
+                  Integer.compare(a[1], b[1]));
+       
+       int[] ans = new int[queries.length];
+       Arrays.fill(ans, -1);
+       
+       // Min heap storing [size, index]
+       PriorityQueue<int[]> pq = new PriorityQueue<>((a, b) -> Integer.compare(a[0], b[0]));
+       boolean[] inactive = new boolean[intervals.length];
+       
+       for (int[] event : events) {
+           if (event[1] == 0) { // Interval start
+               pq.offer(new int[]{event[2], event[3]});
+           } 
+           else if (event[1] == 2) { // Interval end
+               inactive[event[3]] = true;
+           } 
+           else { // Query
+               while (!pq.isEmpty() && inactive[pq.peek()[1]]) {
+                   pq.poll();
+               }
+               if (!pq.isEmpty()) {
+                   ans[event[2]] = pq.peek()[0];
+               }
+           }
+       }
+       
+       return ans;
+   }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> minInterval(vector<vector<int>>& intervals, vector<int>& queries) {
+        vector<vector<int>> events;
+        // Create events for intervals
+        for (int i = 0; i < intervals.size(); i++) {
+            events.push_back({intervals[i][0], 0, intervals[i][1] - intervals[i][0] + 1, i});
+            events.push_back({intervals[i][1], 2, intervals[i][1] - intervals[i][0] + 1, i});
+        }
+        
+        // Create events for queries
+        for (int i = 0; i < queries.size(); i++) {
+            events.push_back({queries[i], 1, i});
+        }
+        
+        // Sort by time and type (end before query)
+        sort(events.begin(), events.end(), [](const vector<int>& a, const vector<int>& b) {
+            return a[0] == b[0] ? a[1] < b[1] : a[0] < b[0];
+        });
+        
+        vector<int> ans(queries.size(), -1);
+        // Min heap storing [size, index]
+        priority_queue<pair<int, int>, vector<pair<int, int>>, greater<pair<int, int>>> pq;
+        vector<bool> inactive(intervals.size(), false);
+        
+        for (const auto& event : events) {
+            if (event[1] == 0) { // Interval start
+                pq.push({event[2], event[3]});
+            } else if (event[1] == 2) { // Interval end
+                inactive[event[3]] = true;
+            } else { // Query
+                int queryIdx = event[2];
+                while (!pq.empty() && inactive[pq.top().second]) {
+                    pq.pop();
+                }
+                if (!pq.empty()) {
+                    ans[queryIdx] = pq.top().first;
+                }
+            }
+        }
+        
+        return ans;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} intervals
+     * @param {number[]} queries
+     * @return {number[]}
+     */
+    minInterval(intervals, queries) {
+        let events = [];
+        // Create events for intervals
+        for (let i = 0; i < intervals.length; i++) {
+            const [start, end] = intervals[i];
+            events.push([start, 0, end - start + 1, i]);
+            events.push([end, 2, end - start + 1, i]);
+        }
+
+        // Create events for queries
+        queries.forEach((q, i) => {
+            events.push([q, 1, i]);
+        });
+        // Sort by time and type (end before query)
+        events.sort((a, b) => a[0] - b[0] || a[1] - b[1]);
+
+        const ans = Array(queries.length).fill(-1);
+        // Min heap storing [size, index]
+        const pq = new PriorityQueue((a, b) => a[0] - b[0]);
+        const inactive = Array(intervals.length).fill(false);
+
+        for (const [time, type, ...rest] of events) {
+            if (type === 0) { // Interval start
+                pq.push([rest[0], rest[1]]);
+            } else if (type === 2) { // Interval end
+                inactive[rest[1]] = true;
+            } else { // Query
+                while (!pq.isEmpty() && inactive[pq.front()[1]]) {
+                    pq.pop();
+                }
+                if (!pq.isEmpty()) {
+                    ans[rest[0]] = pq.front()[0];
+                }
+            }
+        }
+        
+        return ans;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[] MinInterval(int[][] intervals, int[] queries) {
+        var events = new List<int[]>();
+        // Create events for intervals
+        for (int i = 0; i < intervals.Length; i++) {
+            events.Add(new int[] { intervals[i][0], 0, intervals[i][1] - intervals[i][0] + 1, i });
+            events.Add(new int[] { intervals[i][1], 2, intervals[i][1] - intervals[i][0] + 1, i });
+        }
+        
+        // Create events for queries
+        for (int i = 0; i < queries.Length; i++) {
+            events.Add(new int[] { queries[i], 1, i });
+        }
+        // Sort by time and type (end before query)
+        events.Sort((a, b) => a[0] == b[0] ? a[1].CompareTo(b[1]) : a[0].CompareTo(b[0]));
+        
+        int[] ans = new int[queries.Length];
+        Array.Fill(ans, -1);
+        // Min heap storing [size, index]
+        var pq = new PriorityQueue<(int size, int idx), int>();
+        var inactive = new bool[intervals.Length];
+        
+        foreach (var e in events) {
+            if (e[1] == 0) { // Interval start
+                pq.Enqueue((e[2], e[3]), e[2]);
+            } else if (e[1] == 2) { // Interval end
+                inactive[e[3]] = true;
+            } else {
+                int queryIdx = e[2];
+                while (pq.Count > 0 && inactive[pq.Peek().idx]) {
+                    pq.Dequeue();
+                }
+                if (pq.Count > 0) {
+                    ans[queryIdx] = pq.Peek().size;
+                }
+            }
+        }
+        
+        return ans;
+    }
+}
+```
+
+```go
+type Event struct {
+	time int
+	typ  int // 0: interval start, 1: query, 2: interval end
+	val  int // interval size or query index
+	idx  int // interval index
+}
+
+func minInterval(intervals [][]int, queries []int) []int {
+	events := []Event{}
+	
+	// Create events for intervals
+	for idx, interval := range intervals {
+		start, end := interval[0], interval[1]
+		size := end - start + 1
+		events = append(events, Event{start, 0, size, idx})
+		events = append(events, Event{end, 2, size, idx})
+	}
+	
+	// Create events for queries
+	for i, q := range queries {
+		events = append(events, Event{q, 1, i, -1})
+	}
+	
+	// Sort events by time and type
+	sort.Slice(events, func(i, j int) bool {
+		if events[i].time == events[j].time {
+			return events[i].typ < events[j].typ
+		}
+		return events[i].time < events[j].time
+	})
+
+	// Priority queue to store intervals with the smallest size on top
+	sizes := priorityqueue.NewWith(func(a, b interface{}) int {
+		return utils.IntComparator(a.([]int)[0], b.([]int)[0])
+	})
+	ans := make([]int, len(queries))
+	for i := range ans {
+		ans[i] = -1
+	}
+	inactive := make([]bool, len(intervals))
+	
+	for _, event := range events {
+		switch event.typ {
+		case 0: // Interval start
+			sizes.Enqueue([]int{event.val, event.idx})
+		case 2: // Interval end
+			inactive[event.idx] = true
+		case 1: // Query
+			queryIdx := event.val
+			for !sizes.Empty() {
+				top, _ := sizes.Peek()
+				if inactive[top.([]int)[1]] {
+					sizes.Dequeue()
+				} else {
+					break
+				}
+			}
+			if !sizes.Empty() {
+				top, _ := sizes.Peek()
+				ans[queryIdx] = top.([]int)[0]
+			}
+		}
+	}
+	return ans
+}
+```
+
+```kotlin
+data class Event(val time: Int, val type: Int, val sizeOrQueryIndex: Int, val idx: Int)
+
+class Solution {
+    fun minInterval(intervals: Array<IntArray>, queries: IntArray): IntArray {
+        val events = mutableListOf<Event>()
+        
+        // Create events for intervals
+        for ((idx, interval) in intervals.withIndex()) {
+            val (start, end) = interval
+            val size = end - start + 1
+            events.add(Event(start, 0, size, idx))
+            events.add(Event(end, 2, size, idx))
+        }
+        
+        // Create events for queries
+        for ((i, q) in queries.withIndex()) {
+            events.add(Event(q, 1, i, -1))
+        }
+        
+        // Sort events by time and type
+        events.sortWith(compareBy({ it.time }, { it.type }))
+        
+        val sizes = PriorityQueue<Pair<Int, Int>>(compareBy { it.first })
+        val ans = IntArray(queries.size) { -1 }
+        val inactive = BooleanArray(intervals.size)
+        
+        for (event in events) {
+            when (event.type) {
+                0 -> { // Interval start
+                    sizes.add(Pair(event.sizeOrQueryIndex, event.idx))
+                }
+                2 -> { // Interval end
+                    inactive[event.idx] = true
+                }
+                1 -> { // Query
+                    val queryIdx = event.sizeOrQueryIndex
+                    while (sizes.isNotEmpty() && inactive[sizes.peek().second]) {
+                        sizes.poll()
+                    }
+                    if (sizes.isNotEmpty()) {
+                        ans[queryIdx] = sizes.peek().first
+                    }
+                }
+            }
+        }
+        
+        return ans
+    }
+}
+```
+
+```swift
+struct Event {
+    let time: Int
+    let type: Int    // 0: interval start, 1: query, 2: interval end
+    let size: Int?   // interval size for start/end events
+    let idx: Int?    // index for interval (for start/end) or query index (for query)
+}
+
+struct Item: Comparable {
+    let size: Int
+    let idx: Int
+
+    static func < (lhs: Item, rhs: Item) -> Bool {
+        return lhs.size < rhs.size
+    }
+}
+
+class Solution {
+    func minInterval(_ intervals: [[Int]], _ queries: [Int]) -> [Int] {
+        var events = [Event]()
+        
+        // Create events for intervals
+        for (idx, interval) in intervals.enumerated() {
+            let start = interval[0]
+            let end = interval[1]
+            let intervalSize = end - start + 1
+            events.append(Event(time: start, type: 0, size: intervalSize, idx: idx))
+            events.append(Event(time: end, type: 2, size: intervalSize, idx: idx))
+        }
+        
+        // Create events for queries
+        for (i, q) in queries.enumerated() {
+            events.append(Event(time: q, type: 1, size: nil, idx: i))
+        }
+        
+        // Sort by time and type (end before query)
+        events.sort { (a, b) in
+            if a.time != b.time {
+                return a.time < b.time
+            }
+            return a.type < b.type
+        }
+        
+        // Min heap storing [size, index]
+        var sizes = Heap<Item>()
+        var ans = Array(repeating: -1, count: queries.count)
+        var inactive = Array(repeating: false, count: intervals.count)
+        
+        for event in events {
+            if event.type == 0 {  // Interval start
+                let intervalSize = event.size!
+                let idx = event.idx!
+                sizes.insert(Item(size: intervalSize, idx: idx))
+            } else if event.type == 2 { // Interval end
+                let idx = event.idx!
+                inactive[idx] = true
+            } else { // Query
+                let queryIdx = event.idx!
+                while !sizes.isEmpty, inactive[sizes.min!.idx] {
+                    sizes.removeMin()
+                }
+                if !sizes.isEmpty {
+                    ans[queryIdx] = sizes.min!.size
+                }
+            }
+        }
+        
+        return ans
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O((n + m) \log (n + m))$
+* Space complexity: $O(n + m)$
+
+> Where $m$ is the length of the array $queries$ and $n$ is the length of the array $intervals$.
+
+---
+
+## 3. Min Heap
+
+::tabs-start
+
+```python
+class Solution:
+    def minInterval(self, intervals: List[List[int]], queries: List[int]) -> List[int]:
+        intervals.sort()
+        minHeap = []
+        res = {}
+        i = 0
+        for q in sorted(queries):
+            while i < len(intervals) and intervals[i][0] <= q:
+                l, r = intervals[i]
+                heapq.heappush(minHeap, (r - l + 1, r))
+                i += 1
+
+            while minHeap and minHeap[0][1] < q:
+                heapq.heappop(minHeap)
+            res[q] = minHeap[0][0] if minHeap else -1
+        return [res[q] for q in queries]
+```
+
+```java
+public class Solution {
+    public int[] minInterval(int[][] intervals, int[] queries) {
+        Arrays.sort(intervals, Comparator.comparingInt(a -> a[0]));
+        PriorityQueue<int[]> minHeap = new PriorityQueue<>((a, b) -> Integer.compare(a[0], b[0]));
+        Map<Integer, Integer> res = new HashMap<>();
+        int i = 0;
+        for (int q : Arrays.stream(queries).sorted().toArray()) {
+            while (i < intervals.length && intervals[i][0] <= q) {
+                int l = intervals[i][0];
+                int r = intervals[i][1];
+                minHeap.offer(new int[]{r - l + 1, r});
+                i++;
+            }
+
+            while (!minHeap.isEmpty() && minHeap.peek()[1] < q) {
+                minHeap.poll();
+            }
+            res.put(q, minHeap.isEmpty() ? -1 : minHeap.peek()[0]);
+        }
+        int[] result = new int[queries.length];
+        for (int j = 0; j < queries.length; j++) {
+            result[j] = res.get(queries[j]);
+        }
+        return result;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> minInterval(vector<vector<int>>& intervals, vector<int>& queries) {
+        // Sort intervals based on the start value
+        sort(intervals.begin(), intervals.end(), [](auto& a, auto& b) {
+            return a[0] < b[0];
+        });
+
+        vector<int> sortedQueries = queries;
+        sort(sortedQueries.begin(), sortedQueries.end());
+        map<int, int> res;
+
+        auto cmp = [](const vector<int>& a, const vector<int>& b) {
+            return a[0] > b[0] || (a[0] == b[0] && a[1] > b[1]);
+        };
+        priority_queue<vector<int>, vector<vector<int>>, decltype(cmp)> minHeap(cmp);
+
+        int i = 0;
+        for (int q : sortedQueries) {
+            while (i < intervals.size() && intervals[i][0] <= q) {
+                int l = intervals[i][0];
+                int r = intervals[i][1];
+                minHeap.push({r - l + 1, r});
+                i++;
+            }
+
+            while (!minHeap.empty() && minHeap.top()[1] < q) {
+                minHeap.pop();
+            }
+
+            res[q] = minHeap.empty() ? -1 : minHeap.top()[0];
+        }
+
+        vector<int> result(queries.size());
+        for (int j = 0; j < queries.size(); j++) {
+            result[j] = res[queries[j]];
+        }
+        return result;
+    }
+};
+```
+
+```javascript
+/**
+ * const { MinPriorityQueue } = require('@datastructures-js/priority-queue');
+ */
+
+class Solution {
+    /**
+     * @param {number[][]} intervals
+     * @param {number[]} queries
+     * @return {number[]}
+     */
+    minInterval(intervals, queries) {
+        intervals.sort((a, b) => a[0] - b[0]);
+        const minHeap = new MinPriorityQueue(entry => entry[0]);
+        const res = {};
+        let i = 0;
+
+        const sortedQueries = [...queries].sort((a, b) => a - b);
+
+        for (const q of sortedQueries) {
+            while (i < intervals.length && intervals[i][0] <= q) {
+                const [l, r] = intervals[i];
+                minHeap.enqueue([r - l + 1, r]);
+                i += 1;
+            }
+
+            while (!minHeap.isEmpty() && minHeap.front()[1] < q) {
+                minHeap.dequeue();
+            }
+
+            res[q] = !minHeap.isEmpty() ? minHeap.front()[0] : -1;
+        }
+
+        return queries.map(q => res[q]);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[] MinInterval(int[][] intervals, int[] queries) {
+        Array.Sort(intervals, (a, b) => a[0].CompareTo(b[0]));
+
+        var minHeap = new PriorityQueue<(int Size, int End), int>();
+        var res = new Dictionary<int, int>();
+        int i = 0;
+
+        int[] sortedQueries = queries.OrderBy(q => q).ToArray();
+        foreach (int q in sortedQueries) {
+            while (i < intervals.Length && intervals[i][0] <= q) {
+                int l = intervals[i][0];
+                int r = intervals[i][1];
+                minHeap.Enqueue((r - l + 1, r), r - l + 1);
+                i++;
+            }
+
+            while (minHeap.Count > 0 && minHeap.Peek().End < q) {
+                minHeap.Dequeue();
+            }
+
+            res[q] = minHeap.Count == 0 ? -1 : minHeap.Peek().Size;
+        }
+
+        int[] result = new int[queries.Length];
+        for (int j = 0; j < queries.Length; j++) {
+            result[j] = res[queries[j]];
+        }
+
+        return result;
+    }
+}
+```
+
+```go
+func minInterval(intervals [][]int, queries []int) []int {
+    sort.Slice(intervals, func(i, j int) bool {
+        return intervals[i][0] < intervals[j][0]
+    })
+    
+    queriesWithIdx := make([][2]int, len(queries))
+    for i, q := range queries {
+        queriesWithIdx[i] = [2]int{q, i}
+    }
+    sort.Slice(queriesWithIdx, func(i, j int) bool {
+        return queriesWithIdx[i][0] < queriesWithIdx[j][0]
+    })
+    
+    comparator := func(a, b interface{}) int {
+        pair1 := a.([2]int)
+        pair2 := b.([2]int)
+        if pair1[0] != pair2[0] {
+            if pair1[0] < pair2[0] {
+                return -1
+            }
+            return 1
+        }
+        return 0
+    }
+    
+    pq := priorityqueue.NewWith(comparator)
+    res := make([]int, len(queries))
+    i := 0
+    
+    for _, qPair := range queriesWithIdx {
+        q, originalIdx := qPair[0], qPair[1]
+        
+        for i < len(intervals) && intervals[i][0] <= q {
+            size := intervals[i][1] - intervals[i][0] + 1
+            pq.Enqueue([2]int{size, intervals[i][1]})
+            i++
+        }
+        
+        for !pq.Empty() {
+            if top, _ := pq.Peek(); top.([2]int)[1] < q {
+                pq.Dequeue()
+            } else {
+                break
+            }
+        }
+        
+        if !pq.Empty() {
+            if top, _ := pq.Peek(); true {
+                res[originalIdx] = top.([2]int)[0]
+            }
+        } else {
+            res[originalIdx] = -1
+        }
+    }
+    
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun minInterval(intervals: Array<IntArray>, queries: IntArray): IntArray {
+        intervals.sortBy { it[0] }
+        
+        val queriesWithIndex = queries.withIndex()
+            .map { it.value to it.index }
+            .sortedBy { it.first }
+            
+        val minHeap = PriorityQueue<Pair<Int, Int>>(compareBy { it.first })
+        val result = IntArray(queries.size)
+        var i = 0
+        
+        for ((q, originalIdx) in queriesWithIndex) {
+            while (i < intervals.size && intervals[i][0] <= q) {
+                val size = intervals[i][1] - intervals[i][0] + 1
+                minHeap.offer(size to intervals[i][1])
+                i++
+            }
+            
+            while (minHeap.isNotEmpty() && minHeap.peek().second < q) {
+                minHeap.poll()
+            }
+            
+            result[originalIdx] = if (minHeap.isNotEmpty()) minHeap.peek().first else -1
+        }
+        
+        return result
+    }
+}
+```
+
+```swift
+struct HeapItem: Comparable {
+    let size: Int
+    let end: Int
+    static func < (lhs: HeapItem, rhs: HeapItem) -> Bool {
+        if lhs.size == rhs.size {
+            return lhs.end < rhs.end
+        }
+        return lhs.size < rhs.size
+    }
+}
+
+class Solution {
+    func minInterval(_ intervals: [[Int]], _ queries: [Int]) -> [Int] {
+        let sortedIntervals = intervals.sorted { $0[0] < $1[0] }
+        var minHeap = Heap<HeapItem>()
+        var res = [Int: Int]()
+        var i = 0
+
+        for q in queries.sorted() {
+            while i < sortedIntervals.count && sortedIntervals[i][0] <= q {
+                let l = sortedIntervals[i][0]
+                let r = sortedIntervals[i][1]
+                minHeap.insert(HeapItem(size: r - l + 1, end: r))
+                i += 1
+            }
+
+            while !minHeap.isEmpty, minHeap.min!.end < q {
+                minHeap.removeMin()
+            }
+            res[q] = minHeap.isEmpty ? -1 : minHeap.min!.size
+        }
+
+        return queries.map { res[$0] ?? -1 }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n + m \log m)$
+* Space complexity: $O(n + m)$
+
+> Where $m$ is the length of the array $queries$ and $n$ is the length of the array $intervals$.
+
+---
+
+## 4. Min Segment Tree (Lazy Propagation)
+
+::tabs-start
+
+```python
+class SegmentTree:
+    def __init__(self, N):
+        self.n = N
+        self.tree = [float('inf')] * (4 * N)
+        self.lazy = [float('inf')] * (4 * N)
+
+    def propagate(self, treeidx, lo, hi):
+        if self.lazy[treeidx] != float('inf'):
+            self.tree[treeidx] = min(self.tree[treeidx], self.lazy[treeidx])
+            if lo != hi:
+                self.lazy[2 * treeidx + 1] = min(self.lazy[2 * treeidx + 1], self.lazy[treeidx])
+                self.lazy[2 * treeidx + 2] = min(self.lazy[2 * treeidx + 2], self.lazy[treeidx])
+            self.lazy[treeidx] = float('inf')
+
+    def update(self, treeidx, lo, hi, left, right, val):
+        self.propagate(treeidx, lo, hi)
+        if lo > right or hi < left:
+            return
+        if lo >= left and hi <= right:
+            self.lazy[treeidx] = min(self.lazy[treeidx], val)
+            self.propagate(treeidx, lo, hi)
+            return
+        mid = (lo + hi) // 2
+        self.update(2 * treeidx + 1, lo, mid, left, right, val)
+        self.update(2 * treeidx + 2, mid + 1, hi, left, right, val)
+        self.tree[treeidx] = min(self.tree[2 * treeidx + 1], self.tree[2 * treeidx + 2])
+
+    def query(self, treeidx, lo, hi, idx):
+        self.propagate(treeidx, lo, hi)
+        if lo == hi:
+            return self.tree[treeidx]
+        mid = (lo + hi) // 2
+        if idx <= mid:
+            return self.query(2 * treeidx + 1, lo, mid, idx)
+        else:
+            return self.query(2 * treeidx + 2, mid + 1, hi, idx)
+
+    def update_range(self, left, right, val):
+        self.update(0, 0, self.n - 1, left, right, val)
+
+    def query_point(self, idx):
+        return self.query(0, 0, self.n - 1, idx)
+
+class Solution:
+    def minInterval(self, intervals: List[List[int]], queries: List[int]) -> List[int]:
+        points = []
+        for interval in intervals:
+            points.append(interval[0])
+            points.append(interval[1])
+        for q in queries:
+            points.append(q)
+
+        # Compress the coordinates
+        points = sorted(set(points))
+        compress = {points[i]: i for i in range(len(points))}
+
+        # Lazy Segment Tree
+        segTree = SegmentTree(len(points))
+
+        for interval in intervals:
+            start = compress[interval[0]]
+            end = compress[interval[1]]
+            length = interval[1] - interval[0] + 1
+            segTree.update_range(start, end, length)
+
+        ans = []
+        for q in queries:
+            idx = compress[q]
+            
+            # query for minSize
+            res = segTree.query_point(idx)
+            ans.append(res if res != float('inf') else -1)
+        return ans
+```
+
+```java
+class SegmentTree {
+    int n;
+    int[] tree;
+    int[] lazy;
+
+    SegmentTree(int N) {
+        this.n = N;
+        tree = new int[4 * N];
+        lazy = new int[4 * N];
+        Arrays.fill(tree, Integer.MAX_VALUE);
+        Arrays.fill(lazy, Integer.MAX_VALUE);
+    }
+
+    void propagate(int treeidx, int lo, int hi) {
+        if (lazy[treeidx] != Integer.MAX_VALUE) {
+            tree[treeidx] = Math.min(tree[treeidx], lazy[treeidx]);
+            if (lo != hi) {
+                lazy[2 * treeidx + 1] = Math.min(lazy[2 * treeidx + 1], lazy[treeidx]);
+                lazy[2 * treeidx + 2] = Math.min(lazy[2 * treeidx + 2], lazy[treeidx]);
+            }
+            lazy[treeidx] = Integer.MAX_VALUE;
+        }
+    }
+
+    void update(int treeidx, int lo, int hi, int left, int right, int val) {
+        propagate(treeidx, lo, hi);
+        if (lo > right || hi < left) return;
+        if (lo >= left && hi <= right) {
+            lazy[treeidx] = Math.min(lazy[treeidx], val);
+            propagate(treeidx, lo, hi);
+            return;
+        }
+        int mid = (lo + hi) / 2;
+        update(2 * treeidx + 1, lo, mid, left, right, val);
+        update(2 * treeidx + 2, mid + 1, hi, left, right, val);
+        tree[treeidx] = Math.min(tree[2 * treeidx + 1], tree[2 * treeidx + 2]);
+    }
+
+    int query(int treeidx, int lo, int hi, int idx) {
+        propagate(treeidx, lo, hi);
+        if (lo == hi) return tree[treeidx];
+        int mid = (lo + hi) / 2;
+        if (idx <= mid) return query(2 * treeidx + 1, lo, mid, idx);
+        else return query(2 * treeidx + 2, mid + 1, hi, idx);
+    }
+
+    void update(int left, int right, int val) {
+        update(0, 0, n - 1, left, right, val);
+    }
+
+    int query(int idx) {
+        return query(0, 0, n - 1, idx);
+    }
+}
+
+public class Solution {
+    public int[] minInterval(int[][] intervals, int[] queries) {
+        List<Integer> points = new ArrayList<>();
+        for (int[] interval : intervals) {
+            points.add(interval[0]);
+            points.add(interval[1]);
+        }
+        for (int q : queries) {
+            points.add(q);
+        }
+        points = new ArrayList<>(new HashSet<>(points));
+        Collections.sort(points);
+
+        // Compress the points to indices
+        Map<Integer, Integer> compress = new HashMap<>();
+        for (int i = 0; i < points.size(); i++) {
+            compress.put(points.get(i), i);
+        }
+
+        // Create the segment tree
+        SegmentTree segTree = new SegmentTree(points.size());
+
+        // Update the segment tree with intervals
+        for (int[] interval : intervals) {
+            int start = compress.get(interval[0]);
+            int end = compress.get(interval[1]);
+            int length = interval[1] - interval[0] + 1;
+            segTree.update(start, end, length);
+        }
+
+        // Query the segment tree for each query
+        int[] ans = new int[queries.length];
+        for (int i = 0; i < queries.length; i++) {
+            int idx = compress.get(queries[i]);
+            int res = segTree.query(idx);
+            ans[i] = (res == Integer.MAX_VALUE) ? -1 : res;
+        }
+
+        return ans;
+    }
+}
+```
+
+```cpp
+class SegmentTree {
+public:
+    int n;
+    vector<int> tree;
+    vector<int> lazy;
+
+    SegmentTree(int N) {
+        this->n = N;
+        tree.assign(4 * N, INT_MAX);
+        lazy.assign(4 * N, INT_MAX);
+    }
+
+    void propagate(int treeidx, int lo, int hi) {
+        if (lazy[treeidx] != INT_MAX) {
+            tree[treeidx] = min(tree[treeidx], lazy[treeidx]);
+            if (lo != hi) {
+                lazy[2 * treeidx + 1] = min(lazy[2 * treeidx + 1], lazy[treeidx]);
+                lazy[2 * treeidx + 2] = min(lazy[2 * treeidx + 2], lazy[treeidx]);
+            }
+            lazy[treeidx] = INT_MAX;
+        }
+    }
+
+    void update(int treeidx, int lo, int hi, int left, int right, int val) {
+        propagate(treeidx, lo, hi);
+        
+        if (lo > right || hi < left) return;
+
+        if (lo >= left && hi <= right) {
+            lazy[treeidx] = min(lazy[treeidx], val);
+            propagate(treeidx, lo, hi);
+            return;
+        }
+
+        int mid = (lo + hi) / 2;
+        update(2 * treeidx + 1, lo, mid, left, right, val);
+        update(2 * treeidx + 2, mid + 1, hi, left, right, val);
+        
+        tree[treeidx] = min(tree[2 * treeidx + 1], tree[2 * treeidx + 2]);
+    }
+
+    int query(int treeidx, int lo, int hi, int idx) {
+        propagate(treeidx, lo, hi);
+        if (lo == hi) return tree[treeidx];
+        
+        int mid = (lo + hi) / 2;
+        if (idx <= mid) return query(2 * treeidx + 1, lo, mid, idx);
+        else return query(2 * treeidx + 2, mid + 1, hi, idx);
+    }
+
+    void update(int left, int right, int val) {
+        update(0, 0, n - 1, left, right, val);
+    }
+
+    int query(int idx) {
+        return query(0, 0, n - 1, idx);
+    }
+};
+
+class Solution {
+public:
+    vector<int> minInterval(vector<vector<int>>& intervals, vector<int>& queries) {
+        vector<int> points;
+
+        for (const auto& interval : intervals) {
+            points.push_back(interval[0]);
+            points.push_back(interval[1]);
+        }
+        for (int q : queries) {
+            points.push_back(q);
+        }
+
+        sort(points.begin(), points.end());
+        points.erase(unique(points.begin(), points.end()), points.end());
+
+        // compress the coordinates
+        unordered_map<int, int> compress;
+        for (int i = 0; i < points.size(); ++i) {
+            compress[points[i]] = i;
+        }
+
+        SegmentTree segTree(points.size());
+
+        for (const auto& interval : intervals) {
+            int start = compress[interval[0]];
+            int end = compress[interval[1]];
+            int len = interval[1] - interval[0] + 1;
+            segTree.update(start, end, len);
+        }
+
+        vector<int> ans;
+        for (int q : queries) {
+            int idx = compress[q];
+            int res = segTree.query(idx);
+            ans.push_back(res == INT_MAX ? -1 : res);
+        }
+
+        return ans;
+    }
+};
+```
+
+```javascript
+class SegmentTree {
+    constructor(N) {
+        this.n = N;
+        this.tree = new Array(4 * N).fill(Infinity);
+        this.lazy = new Array(4 * N).fill(Infinity);
+    }
+
+    /**
+     * @param {number} treeidx
+     * @param {number} lo
+     * @param {number} hi
+     * @return {void}
+     */
+    propagate(treeidx, lo, hi) {
+        if (this.lazy[treeidx] !== Infinity) {
+            this.tree[treeidx] = Math.min(this.tree[treeidx], this.lazy[treeidx]);
+            if (lo !== hi) {
+                this.lazy[2 * treeidx + 1] = Math.min(this.lazy[2 * treeidx + 1], this.lazy[treeidx]);
+                this.lazy[2 * treeidx + 2] = Math.min(this.lazy[2 * treeidx + 2], this.lazy[treeidx]);
+            }
+            this.lazy[treeidx] = Infinity;
+        }
+    }
+
+    /**
+     * @param {number} treeidx
+     * @param {number} lo
+     * @param {number} hi
+     * @param {number} left
+     * @param {number} right
+     * @param {number} val
+     * @return {void}
+     */
+    update(treeidx, lo, hi, left, right, val) {
+        this.propagate(treeidx, lo, hi);
+        if (lo > right || hi < left) return;
+        if (lo >= left && hi <= right) {
+            this.lazy[treeidx] = Math.min(this.lazy[treeidx], val);
+            this.propagate(treeidx, lo, hi);
+            return;
+        }
+        const mid = Math.floor((lo + hi) / 2);
+        this.update(2 * treeidx + 1, lo, mid, left, right, val);
+        this.update(2 * treeidx + 2, mid + 1, hi, left, right, val);
+        this.tree[treeidx] = Math.min(this.tree[2 * treeidx + 1], this.tree[2 * treeidx + 2]);
+    }
+
+    /**
+     * @param {number} treeidx
+     * @param {number} lo
+     * @param {number} hi
+     * @param {number} idx
+     * @return {number}
+     */
+    query(treeidx, lo, hi, idx) {
+        this.propagate(treeidx, lo, hi);
+        if (lo === hi) return this.tree[treeidx];
+        const mid = Math.floor((lo + hi) / 2);
+        if (idx <= mid) return this.query(2 * treeidx + 1, lo, mid, idx);
+        else return this.query(2 * treeidx + 2, mid + 1, hi, idx);
+    }
+
+    /**
+     * @param {number} left
+     * @param {number} right
+     * @param {number} val
+     * @return {number}
+     */
+    updateRange(left, right, val) {
+        this.update(0, 0, this.n - 1, left, right, val);
+    }
+
+    /**
+     * @param {number} idx
+     * @return {number}
+     */
+    queryPoint(idx) {
+        return this.query(0, 0, this.n - 1, idx);
+    }
+}
+
+class Solution {
+    /**
+     * @param {number[][]} intervals
+     * @param {number[]} queries
+     * @return {number[]}
+     */
+    minInterval(intervals, queries) {
+        const points = [];
+        for (const interval of intervals) {
+            points.push(interval[0]);
+            points.push(interval[1]);
+        }
+        for (const q of queries) {
+            points.push(q);
+        }
+        const uniquePoints = [...new Set(points)].sort((a, b) => a - b);
+        const compress = new Map();
+        uniquePoints.forEach((point, idx) => {
+            compress.set(point, idx);
+        });
+        const segTree = new SegmentTree(uniquePoints.length);
+        for (const interval of intervals) {
+            const start = compress.get(interval[0]);
+            const end = compress.get(interval[1]);
+            const length = interval[1] - interval[0] + 1;
+            segTree.updateRange(start, end, length);
+        }
+        const ans = [];
+        for (const q of queries) {
+            const idx = compress.get(q);
+            const res = segTree.queryPoint(idx);
+            ans.push(res === Infinity ? -1 : res);
+        }
+        return ans;
+    }
+}
+```
+
+```csharp
+public class SegmentTree {
+    public int n;
+    public int[] tree;
+    public int[] lazy;
+
+    public SegmentTree(int N) {
+        this.n = N;
+        tree = new int[4 * N];
+        lazy = new int[4 * N];
+        Array.Fill(tree, int.MaxValue);
+        Array.Fill(lazy, int.MaxValue);
+    }
+
+    public void Propagate(int treeidx, int lo, int hi) {
+        if (lazy[treeidx] != int.MaxValue) {
+            tree[treeidx] = Math.Min(tree[treeidx], lazy[treeidx]);
+            if (lo != hi) {
+                lazy[2 * treeidx + 1] = Math.Min(lazy[2 * treeidx + 1], lazy[treeidx]);
+                lazy[2 * treeidx + 2] = Math.Min(lazy[2 * treeidx + 2], lazy[treeidx]);
+            }
+            lazy[treeidx] = int.MaxValue;
+        }
+    }
+
+    public void Update(int treeidx, int lo, int hi, int left, int right, int val) {
+        Propagate(treeidx, lo, hi);
+        if (lo > right || hi < left) return;
+        if (lo >= left && hi <= right) {
+            lazy[treeidx] = Math.Min(lazy[treeidx], val);
+            Propagate(treeidx, lo, hi);
+            return;
+        }
+        int mid = (lo + hi) / 2;
+        Update(2 * treeidx + 1, lo, mid, left, right, val);
+        Update(2 * treeidx + 2, mid + 1, hi, left, right, val);
+        tree[treeidx] = Math.Min(tree[2 * treeidx + 1], tree[2 * treeidx + 2]);
+    }
+
+    public int Query(int treeidx, int lo, int hi, int idx) {
+        Propagate(treeidx, lo, hi);
+        if (lo == hi) return tree[treeidx];
+        int mid = (lo + hi) / 2;
+        if (idx <= mid) return Query(2 * treeidx + 1, lo, mid, idx);
+        else return Query(2 * treeidx + 2, mid + 1, hi, idx);
+    }
+
+    public void Update(int left, int right, int val) {
+        Update(0, 0, n - 1, left, right, val);
+    }
+
+    public int Query(int idx) {
+        return Query(0, 0, n - 1, idx);
+    }
+}
+
+public class Solution {
+    public int[] MinInterval(int[][] intervals, int[] queries) {
+        List<int> points = new List<int>();
+        foreach (var interval in intervals) {
+            points.Add(interval[0]);
+            points.Add(interval[1]);
+        }
+        foreach (var q in queries) {
+            points.Add(q);
+        }
+        points.Sort();
+        points = new List<int>(new HashSet<int>(points));
+        Dictionary<int, int> compress = new Dictionary<int, int>();
+        for (int i = 0; i < points.Count; i++) {
+            compress[points[i]] = i;
+        }
+        SegmentTree segTree = new SegmentTree(points.Count);
+        foreach (var interval in intervals) {
+            int start = compress[interval[0]];
+            int end = compress[interval[1]];
+            int length = interval[1] - interval[0] + 1;
+            segTree.Update(start, end, length);
+        }
+        int[] ans = new int[queries.Length];
+        for (int i = 0; i < queries.Length; i++) {
+            int idx = compress[queries[i]];
+            int res = segTree.Query(idx);
+            ans[i] = (res == int.MaxValue) ? -1 : res;
+        }
+        return ans;
+    }
+}
+```
+
+```go
+type SegmentTree struct {
+    n    int
+    tree []int
+    lazy []int
+}
+
+func NewSegmentTree(n int) *SegmentTree {
+    tree := make([]int, 4*n)
+    lazy := make([]int, 4*n)
+    for i := range tree {
+        tree[i] = math.MaxInt32
+        lazy[i] = math.MaxInt32
+    }
+    return &SegmentTree{n: n, tree: tree, lazy: lazy}
+}
+
+func (st *SegmentTree) propagate(treeIdx, lo, hi int) {
+    if st.lazy[treeIdx] != math.MaxInt32 {
+        st.tree[treeIdx] = min(st.tree[treeIdx], st.lazy[treeIdx])
+        if lo != hi {
+            st.lazy[2*treeIdx+1] = min(st.lazy[2*treeIdx+1], st.lazy[treeIdx])
+            st.lazy[2*treeIdx+2] = min(st.lazy[2*treeIdx+2], st.lazy[treeIdx])
+        }
+        st.lazy[treeIdx] = math.MaxInt32
+    }
+}
+
+func (st *SegmentTree) updateRange(treeIdx, lo, hi, left, right, val int) {
+    st.propagate(treeIdx, lo, hi)
+    if lo > right || hi < left {
+        return
+    }
+    if lo >= left && hi <= right {
+        st.lazy[treeIdx] = min(st.lazy[treeIdx], val)
+        st.propagate(treeIdx, lo, hi)
+        return
+    }
+    mid := (lo + hi) / 2
+    st.updateRange(2*treeIdx+1, lo, mid, left, right, val)
+    st.updateRange(2*treeIdx+2, mid+1, hi, left, right, val)
+    st.tree[treeIdx] = min(st.tree[2*treeIdx+1], st.tree[2*treeIdx+2])
+}
+
+func (st *SegmentTree) queryPoint(treeIdx, lo, hi, idx int) int {
+    st.propagate(treeIdx, lo, hi)
+    if lo == hi {
+        return st.tree[treeIdx]
+    }
+    mid := (lo + hi) / 2
+    if idx <= mid {
+        return st.queryPoint(2*treeIdx+1, lo, mid, idx)
+    }
+    return st.queryPoint(2*treeIdx+2, mid+1, hi, idx)
+}
+
+func (st *SegmentTree) Update(left, right, val int) {
+    st.updateRange(0, 0, st.n-1, left, right, val)
+}
+
+func (st *SegmentTree) Query(idx int) int {
+    return st.queryPoint(0, 0, st.n-1, idx)
+}
+
+func minInterval(intervals [][]int, queries []int) []int {
+    points := make(map[int]bool)
+    for _, interval := range intervals {
+        points[interval[0]] = true
+        points[interval[1]] = true
+    }
+    for _, q := range queries {
+        points[q] = true
+    }
+    
+    pointsList := make([]int, 0, len(points))
+    for point := range points {
+        pointsList = append(pointsList, point)
+    }
+    sort.Ints(pointsList)
+    
+    compress := make(map[int]int)
+    for i, point := range pointsList {
+        compress[point] = i
+    }
+    
+    segTree := NewSegmentTree(len(pointsList))
+    
+    for _, interval := range intervals {
+        start := compress[interval[0]]
+        end := compress[interval[1]]
+        length := interval[1] - interval[0] + 1
+        segTree.Update(start, end, length)
+    }
+    
+    ans := make([]int, len(queries))
+    for i, q := range queries {
+        idx := compress[q]
+        res := segTree.Query(idx)
+        if res == math.MaxInt32 {
+            ans[i] = -1
+        } else {
+            ans[i] = res
+        }
+    }
+    
+    return ans
+}
+```
+
+```kotlin
+class SegmentTree(private val n: Int) {
+    private val tree = IntArray(4 * n) { Int.MAX_VALUE }
+    private val lazy = IntArray(4 * n) { Int.MAX_VALUE }
+    
+    private fun propagate(treeIdx: Int, lo: Int, hi: Int) {
+        if (lazy[treeIdx] != Int.MAX_VALUE) {
+            tree[treeIdx] = minOf(tree[treeIdx], lazy[treeIdx])
+            if (lo != hi) {
+                lazy[2 * treeIdx + 1] = minOf(lazy[2 * treeIdx + 1], lazy[treeIdx])
+                lazy[2 * treeIdx + 2] = minOf(lazy[2 * treeIdx + 2], lazy[treeIdx])
+            }
+            lazy[treeIdx] = Int.MAX_VALUE
+        }
+    }
+    
+    private fun updateRange(treeIdx: Int, lo: Int, hi: Int, left: Int, right: Int, value: Int) {
+        propagate(treeIdx, lo, hi)
+        if (lo > right || hi < left) return
+        if (lo >= left && hi <= right) {
+            lazy[treeIdx] = minOf(lazy[treeIdx], value)
+            propagate(treeIdx, lo, hi)
+            return
+        }
+        val mid = (lo + hi) / 2
+        updateRange(2 * treeIdx + 1, lo, mid, left, right, value)
+        updateRange(2 * treeIdx + 2, mid + 1, hi, left, right, value)
+        tree[treeIdx] = minOf(tree[2 * treeIdx + 1], tree[2 * treeIdx + 2])
+    }
+    
+    private fun queryPoint(treeIdx: Int, lo: Int, hi: Int, idx: Int): Int {
+        propagate(treeIdx, lo, hi)
+        if (lo == hi) return tree[treeIdx]
+        val mid = (lo + hi) / 2
+        return if (idx <= mid) {
+            queryPoint(2 * treeIdx + 1, lo, mid, idx)
+        } else {
+            queryPoint(2 * treeIdx + 2, mid + 1, hi, idx)
+        }
+    }
+    
+    fun update(left: Int, right: Int, value: Int) {
+        updateRange(0, 0, n - 1, left, right, value)
+    }
+    
+    fun query(idx: Int): Int {
+        return queryPoint(0, 0, n - 1, idx)
+    }
+}
+
+class Solution {
+    fun minInterval(intervals: Array<IntArray>, queries: IntArray): IntArray {
+        val points = mutableSetOf<Int>()
+        intervals.forEach { interval ->
+            points.add(interval[0])
+            points.add(interval[1])
+        }
+        queries.forEach { points.add(it) }
+        
+        val pointsList = points.sorted()
+        val compress = pointsList.withIndex().associate { it.value to it.index }
+        
+        val segTree = SegmentTree(pointsList.size)
+        
+        intervals.forEach { interval ->
+            val start = compress[interval[0]]!!
+            val end = compress[interval[1]]!!
+            val length = interval[1] - interval[0] + 1
+            segTree.update(start, end, length)
+        }
+        
+        return queries.map { q ->
+            val idx = compress[q]!!
+            val res = segTree.query(idx)
+            if (res == Int.MAX_VALUE) -1 else res
+        }.toIntArray()
+    }
+}
+```
+
+```swift
+class SegmentTree {
+    let n: Int
+    var tree: [Int]
+    var lazy: [Int]
+    let INF = Int.max
+
+    init(_ N: Int) {
+        self.n = N
+        self.tree = [Int](repeating: INF, count: 4 * N)
+        self.lazy = [Int](repeating: INF, count: 4 * N)
+    }
+
+    // Propagate lazy value at tree index over range [lo, hi]
+    func propagate(_ treeidx: Int, _ lo: Int, _ hi: Int) {
+        if lazy[treeidx] != INF {
+            tree[treeidx] = min(tree[treeidx], lazy[treeidx])
+            if lo != hi {
+                lazy[2 * treeidx + 1] = min(lazy[2 * treeidx + 1], lazy[treeidx])
+                lazy[2 * treeidx + 2] = min(lazy[2 * treeidx + 2], lazy[treeidx])
+            }
+            lazy[treeidx] = INF
+        }
+    }
+
+    // Update the segment tree over range [left, right] with value val
+    func update(_ treeidx: Int, _ lo: Int, _ hi: Int, _ left: Int, _ right: Int, _ val: Int) {
+        propagate(treeidx, lo, hi)
+        if lo > right || hi < left {
+            return
+        }
+        if lo >= left && hi <= right {
+            lazy[treeidx] = min(lazy[treeidx], val)
+            propagate(treeidx, lo, hi)
+            return
+        }
+        let mid = (lo + hi) / 2
+        update(2 * treeidx + 1, lo, mid, left, right, val)
+        update(2 * treeidx + 2, mid + 1, hi, left, right, val)
+        tree[treeidx] = min(tree[2 * treeidx + 1], tree[2 * treeidx + 2])
+    }
+
+    // Query the value at index idx in the original array
+    func query(_ treeidx: Int, _ lo: Int, _ hi: Int, _ idx: Int) -> Int {
+        propagate(treeidx, lo, hi)
+        if lo == hi {
+            return tree[treeidx]
+        }
+        let mid = (lo + hi) / 2
+        if idx <= mid {
+            return query(2 * treeidx + 1, lo, mid, idx)
+        } else {
+            return query(2 * treeidx + 2, mid + 1, hi, idx)
+        }
+    }
+
+    func update_range(_ left: Int, _ right: Int, _ val: Int) {
+        update(0, 0, n - 1, left, right, val)
+    }
+
+    func query_point(_ idx: Int) -> Int {
+        return query(0, 0, n - 1, idx)
+    }
+}
+
+class Solution {
+    func minInterval(_ intervals: [[Int]], _ queries: [Int]) -> [Int] {
+        var points = [Int]()
+        // Create events for intervals
+        for interval in intervals {
+            points.append(interval[0])
+            points.append(interval[1])
+        }
+        // Create events for queries
+        for q in queries {
+            points.append(q)
+        }
+        
+        // Compress the coordinates
+        let sortedPoints = Array(Set(points)).sorted()
+        var compress = [Int: Int]()
+        for (i, point) in sortedPoints.enumerated() {
+            compress[point] = i
+        }
+
+        // Lazy Segment Tree
+        let segTree = SegmentTree(sortedPoints.count)
+
+        for interval in intervals {
+            let start = compress[interval[0]]!
+            let end = compress[interval[1]]!
+            let length = interval[1] - interval[0] + 1
+            segTree.update_range(start, end, length)
+        }
+
+        var ans = [Int]()
+        for q in queries {
+            let idx = compress[q]!
+            // Query for minSize
+            let res = segTree.query_point(idx)
+            ans.append(res == segTree.INF ? -1 : res)
+        }
+        return ans
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O((n + m)\log k)$
+* Space complexity:
+    * $O(k)$ extra space.
+    * $O(m)$ space for the output array.
+
+> Where $m$ is the length of the array $queries$, $n$ is the length of the array $intervals$ and $k$ is the number of unique points.
\ No newline at end of file
diff --git a/articles/minimum-length-of-string-after-deleting-similar-ends.md b/articles/minimum-length-of-string-after-deleting-similar-ends.md
new file mode 100644
index 000000000..81155cffe
--- /dev/null
+++ b/articles/minimum-length-of-string-after-deleting-similar-ends.md
@@ -0,0 +1,86 @@
+## 1. Greedy + Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def minimumLength(self, s: str) -> int:
+        l, r = 0, len(s) - 1
+
+        while l < r and s[l] == s[r]:
+            tmp = s[l]
+            while l <= r and s[l] == tmp:
+                l += 1
+            while l <= r and s[r] == tmp:
+                r -= 1
+        return r - l + 1
+```
+
+```java
+public class Solution {
+    public int minimumLength(String s) {
+        int l = 0, r = s.length() - 1;
+
+        while (l < r && s.charAt(l) == s.charAt(r)) {
+            char tmp = s.charAt(l);
+            while (l <= r && s.charAt(l) == tmp) {
+                l++;
+            }
+            while (l <= r && s.charAt(r) == tmp) {
+                r--;
+            }
+        }
+        return r - l + 1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minimumLength(string s) {
+        int l = 0, r = s.length() - 1;
+
+        while (l < r && s[l] == s[r]) {
+            char tmp = s[l];
+            while (l <= r && s[l] == tmp) {
+                l++;
+            }
+            while (l <= r && s[r] == tmp) {
+                r--;
+            }
+        }
+        return r - l + 1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    minimumLength(s) {
+        let l = 0, r = s.length - 1;
+
+        while (l < r && s[l] === s[r]) {
+            const tmp = s[l];
+            while (l <= r && s[l] === tmp) {
+                l++;
+            }
+            while (l <= r && s[r] === tmp) {
+                r--;
+            }
+        }
+        return r - l + 1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/minimum-number-of-arrows-to-burst-balloons.md b/articles/minimum-number-of-arrows-to-burst-balloons.md
new file mode 100644
index 000000000..195e1e3e0
--- /dev/null
+++ b/articles/minimum-number-of-arrows-to-burst-balloons.md
@@ -0,0 +1,183 @@
+## 1. Greedy (Sort By Start Value)
+
+::tabs-start
+
+```python
+class Solution:
+    def findMinArrowShots(self, points: List[List[int]]) -> int:
+        points.sort()
+        res, prevEnd = len(points), points[0][1]
+
+        for i in range(1, len(points)):
+            curr = points[i]
+            if curr[0] <= prevEnd:
+                res -= 1
+                prevEnd = min(curr[1], prevEnd)
+            else:
+                prevEnd = curr[1]
+
+        return res
+```
+
+```java
+public class Solution {
+    public int findMinArrowShots(int[][] points) {
+        Arrays.sort(points, (a, b) -> Integer.compare(a[0], b[0]));
+        int res = points.length, prevEnd = points[0][1];
+
+        for (int i = 1; i < points.length; i++) {
+            int[] curr = points[i];
+            if (curr[0] <= prevEnd) {
+                res--;
+                prevEnd = Math.min(curr[1], prevEnd);
+            } else {
+                prevEnd = curr[1];
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findMinArrowShots(vector<vector<int>>& points) {
+        sort(points.begin(), points.end());
+        int res = points.size(), prevEnd = points[0][1];
+
+        for (int i = 1; i < points.size(); i++) {
+            vector<int>& curr = points[i];
+            if (curr[0] <= prevEnd) {
+                res--;
+                prevEnd = min(curr[1], prevEnd);
+            } else {
+                prevEnd = curr[1];
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} points
+     * @return {number}
+     */
+    findMinArrowShots(points) {
+        points.sort((a, b) => a[0] - b[0]);
+        let res = points.length, prevEnd = points[0][1];
+
+        for (let i = 1; i < points.length; i++) {
+            let curr = points[i];
+            if (curr[0] <= prevEnd) {
+                res--;
+                prevEnd = Math.min(curr[1], prevEnd);
+            } else {
+                prevEnd = curr[1];
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 2. Greedy (Sort By End Value)
+
+::tabs-start
+
+```python
+class Solution:
+    def findMinArrowShots(self, points: List[List[int]]) -> int:
+        points.sort(key=lambda x: x[1])
+        res, prevEnd = 1, points[0][1]
+
+        for i in range(1, len(points)):
+            if points[i][0] > prevEnd:
+                prevEnd = points[i][1]
+                res += 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int findMinArrowShots(int[][] points) {
+        Arrays.sort(points, (a, b) -> Integer.compare(a[1], b[1]));
+        int res = 1, prevEnd = points[0][1];
+
+        for (int i = 1; i < points.length; i++) {
+            if (points[i][0] > prevEnd) {
+                prevEnd = points[i][1];
+                res++;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findMinArrowShots(vector<vector<int>>& points) {
+        sort(points.begin(), points.end(), [](const auto& a, const auto& b) {
+            return a[1] < b[1];
+        });
+        int res = 1, prevEnd = points[0][1];
+
+        for (int i = 1; i < points.size(); i++) {
+            if (points[i][0] > prevEnd) {
+                prevEnd = points[i][1];
+                res++;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} points
+     * @return {number}
+     */
+    findMinArrowShots(points) {
+        points.sort((a, b) => a[1] - b[1]);
+        let res = 1, prevEnd = points[0][1];
+
+        for (let i = 1; i < points.length; i++) {
+            if (points[i][0] > prevEnd) {
+                prevEnd = points[i][1];
+                res++;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
\ No newline at end of file
diff --git a/articles/minimum-number-of-days-to-eat-n-oranges.md b/articles/minimum-number-of-days-to-eat-n-oranges.md
new file mode 100644
index 000000000..115da181e
--- /dev/null
+++ b/articles/minimum-number-of-days-to-eat-n-oranges.md
@@ -0,0 +1,354 @@
+## 1. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def minDays(self, n: int) -> int:
+        dp = {}
+
+        def dfs(n):
+            if n == 0:
+                return 0
+            if n in dp:
+                return dp[n]
+            
+            res = 1 + dfs(n - 1)
+            if n % 3 == 0:
+                res = min(res, 1 + dfs(n // 3))
+            if n % 2 == 0:
+                res = min(res, 1 + dfs(n // 2))
+
+            dp[n] = res
+            return res
+
+        return dfs(n)
+```
+
+```java
+public class Solution {
+    private Map<Integer, Integer> dp = new HashMap<>();
+
+    public int minDays(int n) {
+        return dfs(n);
+    }
+
+    private int dfs(int n) {
+        if (n == 0) return 0;
+        if (dp.containsKey(n)) return dp.get(n);
+
+        int res = 1 + dfs(n - 1);
+        if (n % 3 == 0) res = Math.min(res, 1 + dfs(n / 3));
+        if (n % 2 == 0) res = Math.min(res, 1 + dfs(n / 2));
+
+        dp.put(n, res);
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    unordered_map<int, int> dp;
+
+    int minDays(int n) {
+        return dfs(n);
+    }
+
+    int dfs(int n) {
+        if (n == 0) return 0;
+        if (dp.count(n)) return dp[n];
+
+        int res = 1 + dfs(n - 1);
+        if (n % 3 == 0) res = min(res, 1 + dfs(n / 3));
+        if (n % 2 == 0) res = min(res, 1 + dfs(n / 2));
+
+        return dp[n] = res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    minDays(n) {
+        const dp = new Map();
+
+        const dfs = (n) => {
+            if (n === 0) return 0;
+            if (dp.has(n)) return dp.get(n);
+
+            let res = 1 + dfs(n - 1);
+            if (n % 3 === 0) res = Math.min(res, 1 + dfs(n / 3));
+            if (n % 2 === 0) res = Math.min(res, 1 + dfs(n / 2));
+
+            dp.set(n, res);
+            return res;
+        };
+
+        return dfs(n);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Greedy + Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def minDays(self, n: int) -> int:
+        dp = {0: 0, 1: 1}
+
+        def dfs(n):
+            if n in dp:
+                return dp[n]
+
+            res = 1 + (n % 2) + dfs(n // 2)
+            res = min(res, 1 + (n % 3) + dfs(n // 3))
+            dp[n] = res
+            return res
+
+        return dfs(n)
+```
+
+```java
+public class Solution {
+    private Map<Integer, Integer> dp = new HashMap<>();
+
+    public int minDays(int n) {
+        dp.put(0, 0);
+        dp.put(1, 1);
+        return dfs(n);
+    }
+
+    private int dfs(int n) {
+        if (dp.containsKey(n)) return dp.get(n);
+
+        int res = 1 + (n % 2) + dfs(n / 2);
+        res = Math.min(res, 1 + (n % 3) + dfs(n / 3));
+
+        dp.put(n, res);
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    unordered_map<int, int> dp;
+
+    int minDays(int n) {
+        dp[0] = 0;
+        dp[1] = 1;
+        return dfs(n);
+    }
+
+private:
+    int dfs(int n) {
+        if (dp.count(n)) return dp[n];
+
+        int res = 1 + (n % 2) + dfs(n / 2);
+        res = min(res, 1 + (n % 3) + dfs(n / 3));
+
+        return dp[n] = res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    minDays(n) {
+        const dp = new Map();
+        dp.set(0, 0);
+        dp.set(1, 1);
+
+        const dfs = (n) => {
+            if (dp.has(n)) return dp.get(n);
+
+            let res = 1 + (n % 2) + dfs(Math.floor(n / 2));
+            res = Math.min(res, 1 + (n % 3) + dfs(Math.floor(n / 3)));
+
+            dp.set(n, res);
+            return res;
+        };
+
+        return dfs(n);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(\log n)$
+
+---
+
+## 3. Breadth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def minDays(self, n: int) -> int:
+        q = deque([n])
+        visit = set()
+        res = 0
+
+        while q:
+            res += 1
+            for _ in range(len(q)):
+                node = q.popleft()
+                nei = node - 1
+                if nei == 0:
+                    return res
+                if nei not in visit:
+                    visit.add(nei)
+                    q.append(nei)
+                for d in range(2, 4):
+                    if node % d == 0:
+                        nei = node // d
+                        if nei == 0:
+                            return res
+                        if nei not in visit:
+                            visit.add(nei)
+                            q.append(nei)
+        return res
+```
+
+```java
+public class Solution {
+    public int minDays(int n) {
+        Queue<Integer> q = new LinkedList<>();
+        Set<Integer> visit = new HashSet<>();
+        q.offer(n);
+        int res = 0;
+
+        while (!q.isEmpty()) {
+            res++;
+            for (int i = q.size(); i > 0; i--) {
+                int node = q.poll();
+                int nei = node - 1;
+                if (nei == 0) return res;
+                if (!visit.contains(nei)) {
+                    visit.add(nei);
+                    q.offer(nei);
+                }
+                for (int d = 2; d <= 3; d++) {
+                    if (node % d == 0) {
+                        nei = node / d;
+                        if (nei == 0) return res;
+                        if (!visit.contains(nei)) {
+                            visit.add(nei);
+                            q.offer(nei);
+                        }
+                    }
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minDays(int n) {
+        queue<int> q;
+        unordered_set<int> visit;
+        q.push(n);
+        int res = 0;
+
+        while (!q.empty()) {
+            res++;
+            for (int i = q.size(); i > 0; i--) {
+                int node = q.front(); q.pop();
+                int nei = node - 1;
+                if (nei == 0) return res;
+                if (visit.find(nei) == visit.end()) {
+                    visit.insert(nei);
+                    q.push(nei);
+                }
+                for (int d = 2; d <= 3; d++) {
+                    if (node % d == 0) {
+                        nei = node / d;
+                        if (nei == 0) return res;
+                        if (visit.find(nei) == visit.end()) {
+                            visit.insert(nei);
+                            q.push(nei);
+                        }
+                    }
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    minDays(n) {
+        const q = new Queue([n]);
+        const visit = new Set();
+        let res = 0;
+
+        while (!q.isEmpty()) {
+            res++;
+            for (let i = q.size(); i > 0; i--) {
+                let node = q.pop();
+                let nei = node - 1;
+                if (nei === 0) return res;
+                if (!visit.has(nei)) {
+                    visit.add(nei);
+                    q.push(nei);
+                }
+                for (let d = 2; d <= 3; d++) {
+                    if (node % d === 0) {
+                        nei = Math.floor(node / d);
+                        if (nei === 0) return res;
+                        if (!visit.has(nei)) {
+                            visit.add(nei);
+                            q.push(nei);
+                        }
+                    }
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(\log n)$
\ No newline at end of file
diff --git a/articles/minimum-number-of-flips-to-make-the-binary-string-alternating.md b/articles/minimum-number-of-flips-to-make-the-binary-string-alternating.md
new file mode 100644
index 000000000..b0afa6412
--- /dev/null
+++ b/articles/minimum-number-of-flips-to-make-the-binary-string-alternating.md
@@ -0,0 +1,701 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def minFlips(self, s: str) -> int:
+        res = n = len(s)
+        alt1, alt2 = [], []
+        for i in range(n):
+            alt1.append("0" if i % 2 == 0 else "1")
+            alt2.append("1" if i % 2 == 0 else "0")
+
+        def diff(A, B):
+            cnt = 0
+            for i in range(n):
+                cnt += 1 if (A[i] != B[i]) else 0
+            return cnt
+            
+        for i in range(n):
+            newS = s[i:] + s[:i]
+            res = min(res, min(diff(alt1, newS), diff(alt2, newS)))
+        return res
+```
+
+```java
+public class Solution {
+    public int minFlips(String s) {
+        int n = s.length(), res = n;
+        StringBuilder alt1 = new StringBuilder();
+        StringBuilder alt2 = new StringBuilder();
+
+        for (int i = 0; i < n; i++) {
+            alt1.append(i % 2 == 0 ? '0' : '1');
+            alt2.append(i % 2 == 0 ? '1' : '0');
+        }
+
+        for (int i = 0; i < n; i++) {
+            String newS = s.substring(i) + s.substring(0, i);
+            res = Math.min(res, Math.min(diff(alt1, newS), diff(alt2, newS)));
+        }
+
+        return res;
+    }
+
+    private int diff(StringBuilder a, String b) {
+        int cnt = 0;
+        for (int i = 0; i < a.length(); i++) {
+            if (a.charAt(i) != b.charAt(i)) cnt++;
+        }
+        return cnt;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minFlips(string s) {
+        int n = s.size(), res = n;
+        string alt1, alt2;
+
+        for (int i = 0; i < n; i++) {
+            alt1 += (i % 2 == 0) ? '0' : '1';
+            alt2 += (i % 2 == 0) ? '1' : '0';
+        }
+
+        for (int i = 0; i < n; i++) {
+            string newS = s.substr(i) + s.substr(0, i);
+            res = min(res, min(diff(alt1, newS), diff(alt2, newS)));
+        }
+
+        return res;
+    }
+
+private:
+    int diff(const string &a, const string &b) {
+        int cnt = 0;
+        for (int i = 0; i < a.size(); i++) {
+            if (a[i] != b[i]) cnt++;
+        }
+        return cnt;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    minFlips(s) {
+        const n = s.length;
+        let res = n;
+        let alt1 = "", alt2 = "";
+
+        for (let i = 0; i < n; i++) {
+            alt1 += i % 2 === 0 ? '0' : '1';
+            alt2 += i % 2 === 0 ? '1' : '0';
+        }
+
+        const diff = (a, b) => {
+            let cnt = 0;
+            for (let i = 0; i < a.length; i++) {
+                if (a[i] !== b[i]) cnt++;
+            }
+            return cnt;
+        };
+
+        for (let i = 0; i < n; i++) {
+            const newS = s.slice(i) + s.slice(0, i);
+            res = Math.min(res, Math.min(diff(alt1, newS), diff(alt2, newS)));
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Brute Force (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def minFlips(self, s: str) -> int:
+        n = res = len(s)
+
+        for i in range(n):
+            start_0 = 1 if s[i] != '0' else 0
+            start_1 = 1 if s[i] != '1' else 0
+            c = '0'
+            j = (i + 1) % n
+            while j != i:
+                start_1 += 1 if s[j] != c else 0
+                start_0 += 1 if s[j] == c else 0
+                c = '0' if c == '1' else '1'
+                j = (j + 1) % n
+            
+            res = min(res, min(start_1, start_0))
+        return res
+```
+
+```java
+public class Solution {
+    public int minFlips(String s) {
+        int n = s.length();
+        int res = n;
+
+        for (int i = 0; i < n; i++) {
+            int start0 = s.charAt(i) != '0' ? 1 : 0;
+            int start1 = s.charAt(i) != '1' ? 1 : 0;
+            char c = '0';
+            int j = (i + 1) % n;
+
+            while (j != i) {
+                start1 += s.charAt(j) != c ? 1 : 0;
+                start0 += s.charAt(j) == c ? 1 : 0;
+                c = c == '1' ? '0' : '1';
+                j = (j + 1) % n;
+            }
+
+            res = Math.min(res, Math.min(start1, start0));
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minFlips(string s) {
+        int n = s.size(), res = n;
+
+        for (int i = 0; i < n; i++) {
+            int start0 = (s[i] != '0') ? 1 : 0;
+            int start1 = (s[i] != '1') ? 1 : 0;
+            char c = '0';
+            int j = (i + 1) % n;
+
+            while (j != i) {
+                start1 += (s[j] != c) ? 1 : 0;
+                start0 += (s[j] == c) ? 1 : 0;
+                c = (c == '1') ? '0' : '1';
+                j = (j + 1) % n;
+            }
+
+            res = min(res, min(start1, start0));
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    minFlips(s) {
+        const n = s.length;
+        let res = n;
+
+        for (let i = 0; i < n; i++) {
+            let start0 = s[i] !== '0' ? 1 : 0;
+            let start1 = s[i] !== '1' ? 1 : 0;
+            let c = '0';
+            let j = (i + 1) % n;
+
+            while (j !== i) {
+                start1 += s[j] !== c ? 1 : 0;
+                start0 += s[j] === c ? 1 : 0;
+                c = c === '1' ? '0' : '1';
+                j = (j + 1) % n;
+            }
+
+            res = Math.min(res, Math.min(start1, start0));
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 3. Sliding Window
+
+::tabs-start
+
+```python
+class Solution:
+    def minFlips(self, s: str) -> int:
+        n = len(s)
+        s = s + s
+        alt1, alt2 = [], []
+        for i in range(len(s)):
+            alt1.append("0" if i % 2 == 0 else "1")
+            alt2.append("1" if i % 2 == 0 else "0")
+
+        res = len(s)
+        diff1, diff2 = 0, 0
+        l = 0
+
+        for r in range(len(s)):
+            if s[r] != alt1[r]:
+                diff1 += 1
+            if s[r] != alt2[r]:
+                diff2 += 1
+
+            if r - l + 1 > n:
+                if s[l] != alt1[l]:
+                    diff1 -= 1
+                if s[l] != alt2[l]:
+                    diff2 -= 1
+                l += 1
+
+            if r - l + 1 == n:
+                res = min(res, diff1, diff2)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int minFlips(String s) {
+        int n = s.length();
+        s = s + s;
+        StringBuilder alt1 = new StringBuilder();
+        StringBuilder alt2 = new StringBuilder();
+
+        for (int i = 0; i < s.length(); i++) {
+            alt1.append(i % 2 == 0 ? '0' : '1');
+            alt2.append(i % 2 == 0 ? '1' : '0');
+        }
+
+        int res = n, diff1 = 0, diff2 = 0, l = 0;
+
+        for (int r = 0; r < s.length(); r++) {
+            if (s.charAt(r) != alt1.charAt(r)) diff1++;
+            if (s.charAt(r) != alt2.charAt(r)) diff2++;
+
+            if (r - l + 1 > n) {
+                if (s.charAt(l) != alt1.charAt(l)) diff1--;
+                if (s.charAt(l) != alt2.charAt(l)) diff2--;
+                l++;
+            }
+
+            if (r - l + 1 == n) {
+                res = Math.min(res, Math.min(diff1, diff2));
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minFlips(string s) {
+        int n = s.size();
+        s += s;
+        string alt1, alt2;
+        for (int i = 0; i < s.size(); i++) {
+            alt1 += (i % 2 == 0) ? '0' : '1';
+            alt2 += (i % 2 == 0) ? '1' : '0';
+        }
+
+        int res = n, diff1 = 0, diff2 = 0, l = 0;
+
+        for (int r = 0; r < s.size(); r++) {
+            if (s[r] != alt1[r]) diff1++;
+            if (s[r] != alt2[r]) diff2++;
+
+            if (r - l + 1 > n) {
+                if (s[l] != alt1[l]) diff1--;
+                if (s[l] != alt2[l]) diff2--;
+                l++;
+            }
+
+            if (r - l + 1 == n) {
+                res = min(res, min(diff1, diff2));
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    minFlips(s) {
+        const n = s.length;
+        s = s + s;
+        let alt1 = [], alt2 = [];
+
+        for (let i = 0; i < s.length; i++) {
+            alt1.push(i % 2 === 0 ? "0" : "1");
+            alt2.push(i % 2 === 0 ? "1" : "0");
+        }
+
+        let res = n, diff1 = 0, diff2 = 0, l = 0;
+
+        for (let r = 0; r < s.length; r++) {
+            if (s[r] !== alt1[r]) diff1++;
+            if (s[r] !== alt2[r]) diff2++;
+
+            if (r - l + 1 > n) {
+                if (s[l] !== alt1[l]) diff1--;
+                if (s[l] !== alt2[l]) diff2--;
+                l++;
+            }
+
+            if (r - l + 1 === n) {
+                res = Math.min(res, diff1, diff2);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Sliding Window (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def minFlips(self, s: str) -> int:
+        res = n = len(s)
+        diff1 = diff2 = l = 0
+
+        rstart_0 = lstart_0 = '0'
+
+        for r in range(2 * n):
+            if s[r % n] != rstart_0:
+                diff1 += 1
+            if s[r % n] == rstart_0:
+                diff2 += 1
+
+            if r - l + 1 > n:
+                if s[l] != lstart_0:
+                    diff1 -= 1
+                if s[l] == lstart_0:
+                    diff2 -= 1
+                l += 1
+                lstart_0 = '1' if lstart_0 == '0' else '0'
+            
+            if r - l + 1 == n:
+                res = min(res, diff1, diff2)
+
+            rstart_0 = '1' if rstart_0 == '0' else '0'
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int minFlips(String s) {
+        int n = s.length();
+        int res = n, diff1 = 0, diff2 = 0, l = 0;
+
+        char rstart_0 = '0', lstart_0 = '0';
+
+        for (int r = 0; r < 2 * n; r++) {
+            if (s.charAt(r % n) != rstart_0) diff1++;
+            if (s.charAt(r % n) == rstart_0) diff2++;
+
+            if (r - l + 1 > n) {
+                if (s.charAt(l) != lstart_0) diff1--;
+                if (s.charAt(l) == lstart_0) diff2--;
+                l++;
+                lstart_0 = (lstart_0 == '0') ? '1' : '0';
+            }
+
+            if (r - l + 1 == n) {
+                res = Math.min(res, Math.min(diff1, diff2));
+            }
+
+            rstart_0 = (rstart_0 == '0') ? '1' : '0';
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minFlips(string s) {
+        int n = s.size();
+        int res = n, diff1 = 0, diff2 = 0, l = 0;
+
+        char rstart_0 = '0', lstart_0 = '0';
+
+        for (int r = 0; r < 2 * n; r++) {
+            if (s[r % n] != rstart_0) diff1++;
+            if (s[r % n] == rstart_0) diff2++;
+
+            if (r - l + 1 > n) {
+                if (s[l] != lstart_0) diff1--;
+                if (s[l] == lstart_0) diff2--;
+                l++;
+                lstart_0 = (lstart_0 == '0') ? '1' : '0';
+            }
+
+            if (r - l + 1 == n) {
+                res = min(res, min(diff1, diff2));
+            }
+
+            rstart_0 = (rstart_0 == '0') ? '1' : '0';
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    minFlips(s) {
+        const n = s.length;
+        let res = n, diff1 = 0, diff2 = 0, l = 0;
+
+        let rstart_0 = '0', lstart_0 = '0';
+
+        for (let r = 0; r < 2 * n; r++) {
+            if (s[r % n] !== rstart_0) diff1++;
+            if (s[r % n] === rstart_0) diff2++;
+
+            if (r - l + 1 > n) {
+                if (s[l] !== lstart_0) diff1--;
+                if (s[l] === lstart_0) diff2--;
+                l++;
+                lstart_0 = lstart_0 === '0' ? '1' : '0';
+            }
+
+            if (r - l + 1 === n) {
+                res = Math.min(res, Math.min(diff1, diff2));
+            }
+
+            rstart_0 = rstart_0 === '0' ? '1' : '0';
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 5. Dynamic Programming
+
+::tabs-start
+
+```python
+class Solution:
+    def minFlips(self, s: str) -> int:
+        start_1 = 0
+        for i in range(len(s)):
+            if i & 1:
+                start_1 += s[i] == "1"
+            else:
+                start_1 += s[i] == "0"
+
+        start_0 = len(s) - start_1
+        ans = min(start_0, start_1)
+        if len(s) % 2 == 0:
+            return ans
+
+        dp0, dp1 = start_0, start_1
+        for c in s:
+            dp0, dp1 = dp1, dp0
+            if c == "1":
+                dp0 += 1
+                dp1 -= 1
+            else:
+                dp0 -= 1
+                dp1 += 1
+            ans = min(dp0, dp1, ans)
+        return ans
+```
+
+```java
+public class Solution {
+    public int minFlips(String s) {
+        int start_1 = 0;
+        int n = s.length();
+
+        for (int i = 0; i < n; i++) {
+            if ((i & 1) == 1) {
+                start_1 += s.charAt(i) == '1' ? 1 : 0;
+            } else {
+                start_1 += s.charAt(i) == '0' ? 1 : 0;
+            }
+        }
+
+        int start_0 = n - start_1;
+        int ans = Math.min(start_0, start_1);
+        if (n % 2 == 0) {
+            return ans;
+        }
+
+        int dp0 = start_0, dp1 = start_1;
+        for (char c : s.toCharArray()) {
+            int temp = dp0;
+            dp0 = dp1;
+            dp1 = temp;
+            if (c == '1') {
+                dp0++;
+                dp1--;
+            } else {
+                dp0--;
+                dp1++;
+            }
+            ans = Math.min(ans, Math.min(dp0, dp1));
+        }
+
+        return ans;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minFlips(string s) {
+        int start_1 = 0, n = s.size();
+
+        for (int i = 0; i < n; i++) {
+            if (i & 1) {
+                start_1 += (s[i] == '1');
+            } else {
+                start_1 += (s[i] == '0');
+            }
+        }
+
+        int start_0 = n - start_1;
+        int ans = min(start_0, start_1);
+        if (n % 2 == 0) {
+            return ans;
+        }
+
+        int dp0 = start_0, dp1 = start_1;
+        for (char c : s) {
+            int temp = dp0;
+            dp0 = dp1;
+            dp1 = temp;
+            if (c == '1') {
+                dp0++;
+                dp1--;
+            } else {
+                dp0--;
+                dp1++;
+            }
+            ans = min({ans, dp0, dp1});
+        }
+
+        return ans;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    minFlips(s) {
+        let start_1 = 0;
+        const n = s.length;
+
+        for (let i = 0; i < n; i++) {
+            if (i & 1) {
+                start_1 += s[i] === '1' ? 1 : 0;
+            } else {
+                start_1 += s[i] === '0' ? 1 : 0;
+            }
+        }
+
+        let start_0 = n - start_1;
+        let ans = Math.min(start_0, start_1);
+        if (n % 2 === 0) {
+            return ans;
+        }
+
+        let dp0 = start_0, dp1 = start_1;
+        for (const c of s) {
+            [dp0, dp1] = [dp1, dp0];
+            if (c === '1') {
+                dp0++;
+                dp1--;
+            } else {
+                dp0--;
+                dp1++;
+            }
+            ans = Math.min(ans, dp0, dp1);
+        }
+
+        return ans;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/minimum-number-of-operations-to-make-array-continuous.md b/articles/minimum-number-of-operations-to-make-array-continuous.md
new file mode 100644
index 000000000..fda4f013d
--- /dev/null
+++ b/articles/minimum-number-of-operations-to-make-array-continuous.md
@@ -0,0 +1,449 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def minOperations(self, nums: List[int]) -> int:
+        N = len(nums)
+        res = float("inf")
+        nums = sorted(set(nums))
+        n = len(nums)
+
+        for i in range(n):
+            noChange = 1
+            for j in range(i + 1, n):
+                if nums[i] < nums[j] < nums[i] + N:
+                    noChange += 1
+            res = min(res, N - noChange)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int minOperations(int[] nums) {
+        int N = nums.length;
+        int res = Integer.MAX_VALUE;
+        TreeSet<Integer> set = new TreeSet<>();
+        for (int num : nums) {
+            set.add(num);
+        }
+        Integer[] sortedNums = set.toArray(new Integer[0]);
+        int n = sortedNums.length;
+
+        for (int i = 0; i < n; i++) {
+            int noChange = 1;
+            for (int j = i + 1; j < n; j++) {
+                if (sortedNums[j] < sortedNums[i] + N) {
+                    noChange++;
+                }
+            }
+            res = Math.min(res, N - noChange);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minOperations(vector<int>& nums) {
+        int N = nums.size();
+        int res = INT_MAX;
+        set<int> uniqueNums(nums.begin(), nums.end());
+        vector<int> sortedNums(uniqueNums.begin(), uniqueNums.end());
+        int n = sortedNums.size();
+
+        for (int i = 0; i < n; i++) {
+            int noChange = 1;
+            for (int j = i + 1; j < n; j++) {
+                if (sortedNums[j] < sortedNums[i] + N) {
+                    noChange++;
+                }
+            }
+            res = min(res, N - noChange);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    minOperations(nums) {
+        const N = nums.length;
+        let res = Infinity;
+        const uniqueNums = Array.from(new Set(nums)).sort((a, b) => a - b);
+        const n = uniqueNums.length;
+
+        for (let i = 0; i < n; i++) {
+            let noChange = 1;
+            for (let j = i + 1; j < n; j++) {
+                if (uniqueNums[j] < uniqueNums[i] + N) {
+                    noChange++;
+                }
+            }
+            res = Math.min(res, N - noChange);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Binary Search
+
+::tabs-start
+
+```python
+class Solution:
+    def minOperations(self, nums: List[int]) -> int:
+        N = len(nums)
+        res = float("inf")
+        nums = sorted(set(nums))
+        n = len(nums)
+
+        for i in range(n):
+            l, r = i, n
+            while l < r:
+                mid = (l + r) // 2
+                if nums[mid] < nums[i] + N:
+                    l = mid + 1
+                else:
+                    r = mid
+            noChange = l - i
+            res = min(res, N - noChange)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int minOperations(int[] nums) {
+        int N = nums.length;
+        int res = Integer.MAX_VALUE;
+        TreeSet<Integer> set = new TreeSet<>();
+        for (int num : nums) {
+            set.add(num);
+        }
+        Integer[] sortedNums = set.toArray(new Integer[0]);
+        int n = sortedNums.length;
+
+        for (int i = 0; i < n; i++) {
+            int l = i, r = n;
+            while (l < r) {
+                int mid = l + (r - l) / 2;
+                if (sortedNums[mid] < sortedNums[i] + N) {
+                    l = mid + 1;
+                } else {
+                    r = mid;
+                }
+            }
+            int noChange = l - i;
+            res = Math.min(res, N - noChange);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minOperations(vector<int>& nums) {
+        int N = nums.size();
+        int res = INT_MAX;
+        set<int> uniqueNums(nums.begin(), nums.end());
+        vector<int> sortedNums(uniqueNums.begin(), uniqueNums.end());
+        int n = sortedNums.size();
+
+        for (int i = 0; i < n; i++) {
+            int l = i, r = n;
+            while (l < r) {
+                int mid = l + (r - l) / 2;
+                if (sortedNums[mid] < sortedNums[i] + N) {
+                    l = mid + 1;
+                } else {
+                    r = mid;
+                }
+            }
+            int noChange = l - i;
+            res = min(res, N - noChange);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    minOperations(nums) {
+        const N = nums.length;
+        let res = Infinity;
+        const uniqueNums = Array.from(new Set(nums)).sort((a, b) => a - b);
+        const n = uniqueNums.length;
+
+        for (let i = 0; i < n; i++) {
+            let l = i, r = n;
+            while (l < r) {
+                const mid = Math.floor((l + r) / 2);
+                if (uniqueNums[mid] < uniqueNums[i] + N) {
+                    l = mid + 1;
+                } else {
+                    r = mid;
+                }
+            }
+            const noChange = l - i;
+            res = Math.min(res, N - noChange);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Sliding Window
+
+::tabs-start
+
+```python
+class Solution:
+    def minOperations(self, nums: List[int]) -> int:
+        length = len(nums)
+        nums = sorted(set(nums))
+        res = length
+        r = 0
+
+        for l in range(len(nums)):
+            while r < len(nums) and nums[r] < nums[l] + length:
+                r += 1
+            window = r - l
+            res = min(res, length - window)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int minOperations(int[] nums) {
+        int length = nums.length;
+        TreeSet<Integer> set = new TreeSet<>();
+        for (int num : nums) {
+            set.add(num);
+        }
+        List<Integer> sortedNums = new ArrayList<>(set);
+        int res = length, r = 0;
+
+        for (int l = 0; l < sortedNums.size(); l++) {
+            while (r < sortedNums.size() && sortedNums.get(r) < sortedNums.get(l) + length) {
+                r++;
+            }
+            int window = r - l;
+            res = Math.min(res, length - window);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minOperations(vector<int>& nums) {
+        int length = nums.size();
+        set<int> uniqueNums(nums.begin(), nums.end());
+        vector<int> sortedNums(uniqueNums.begin(), uniqueNums.end());
+        int res = length, r = 0;
+
+        for (int l = 0; l < sortedNums.size(); l++) {
+            while (r < sortedNums.size() && sortedNums[r] < sortedNums[l] + length) {
+                r++;
+            }
+            int window = r - l;
+            res = min(res, length - window);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    minOperations(nums) {
+        const length = nums.length;
+        const uniqueNums = Array.from(new Set(nums)).sort((a, b) => a - b);
+        let res = length, r = 0;
+
+        for (let l = 0; l < uniqueNums.length; l++) {
+            while (r < uniqueNums.length && uniqueNums[r] < uniqueNums[l] + length) {
+                r++;
+            }
+            const window = r - l;
+            res = Math.min(res, length - window);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Sliding Window (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def minOperations(self, nums: List[int]) -> int:
+        length = len(nums)
+        nums.sort()
+        res = length
+        n = 1
+
+        for i in range(1, length):
+            if nums[i] != nums[i - 1]:
+                nums[n] = nums[i]
+                n += 1
+        
+        l = 0
+        for r in range(n):
+            l += (nums[r] - nums[l] > length - 1)
+
+        return length - (n - l)
+```
+
+```java
+public class Solution {
+    public int minOperations(int[] nums) {
+        int length = nums.length;
+        Arrays.sort(nums);
+        int n = 1;
+
+        for (int i = 1; i < length; i++) {
+            if (nums[i] != nums[i - 1]) {
+                nums[n] = nums[i];
+                n++;
+            }
+        }
+        
+        int l = 0;
+        for (int r = 0; r < n; r++) {
+            if (nums[r] - nums[l] > length - 1) {
+                l++;
+            }
+        }
+
+        return length - (n - l);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minOperations(vector<int>& nums) {
+        int length = nums.size();
+        sort(nums.begin(), nums.end());
+        int n = 1;
+
+        for (int i = 1; i < length; i++) {
+            if (nums[i] != nums[i - 1]) {
+                nums[n] = nums[i];
+                n++;
+            }
+        }
+
+        int l = 0;
+        for (int r = 0; r < n; r++) {
+            if (nums[r] - nums[l] > length - 1) {
+                l++;
+            }
+        }
+
+        return length - (n - l);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    minOperations(nums) {
+        const length = nums.length;
+        nums.sort((a, b) => a - b);
+        let n = 1;
+
+        for (let i = 1; i < length; i++) {
+            if (nums[i] !== nums[i - 1]) {
+                nums[n] = nums[i];
+                n++;
+            }
+        }
+
+        let l = 0;
+        for (let r = 0; r < n; r++) {
+            if (nums[r] - nums[l] > length - 1) {
+                l++;
+            }
+        }
+
+        return length - (n - l);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
\ No newline at end of file
diff --git a/articles/minimum-number-of-operations-to-make-array-empty.md b/articles/minimum-number-of-operations-to-make-array-empty.md
new file mode 100644
index 000000000..fbb2aa367
--- /dev/null
+++ b/articles/minimum-number-of-operations-to-make-array-empty.md
@@ -0,0 +1,563 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def minOperations(self, nums: List[int]) -> int:
+        def dfs(cur):
+            if cur < 0:
+                return float('inf')
+            if cur == 0:
+                return 0
+            
+            ops = min(dfs(cur - 2), dfs(cur - 3))
+            return 1 + ops
+        
+        count = Counter(nums)
+        res = 0
+        for num, cnt in count.items():
+            op = dfs(cnt)
+            if op == float("inf"):
+                return -1
+            res += op
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int minOperations(int[] nums) {
+        Map<Integer, Integer> count = new HashMap<>();
+        for (int num : nums) {
+            count.put(num, count.getOrDefault(num, 0) + 1);
+        }
+
+        int res = 0;
+        for (int cnt : count.values()) {
+            int op = dfs(cnt);
+            if (op == Integer.MAX_VALUE) {
+                return -1;
+            }
+            res += op;
+        }
+
+        return res;
+    }
+
+    private int dfs(int cur) {
+        if (cur < 0) {
+            return Integer.MAX_VALUE;
+        }
+        if (cur == 0) {
+            return 0;
+        }
+
+        int ops = Math.min(dfs(cur - 2), dfs(cur - 3));
+        return ops == Integer.MAX_VALUE ? ops : 1 + ops;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minOperations(vector<int>& nums) {
+        unordered_map<int, int> count;
+        for (int num : nums) {
+            count[num]++;
+        }
+
+        int res = 0;
+        for (auto& [num, cnt] : count) {
+            int op = dfs(cnt);
+            if (op == INT_MAX) {
+                return -1;
+            }
+            res += op;
+        }
+
+        return res;
+    }
+
+private:
+    int dfs(int cur) {
+        if (cur < 0) {
+            return INT_MAX;
+        }
+        if (cur == 0) {
+            return 0;
+        }
+
+        int ops = min(dfs(cur - 2), dfs(cur - 3));
+        return ops == INT_MAX ? ops : 1 + ops;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    minOperations(nums) {
+        const dfs = (cur) => {
+            if (cur < 0) {
+                return Infinity;
+            }
+            if (cur === 0) {
+                return 0;
+            }
+
+            const ops = Math.min(dfs(cur - 2), dfs(cur - 3));
+            return isFinite(ops) ? 1 + ops : ops;
+        };
+
+        const count = new Map();
+        for (const num of nums) {
+            count.set(num, (count.get(num) || 0) + 1);
+        }
+
+        let res = 0;
+        for (const cnt of count.values()) {
+            const op = dfs(cnt);
+            if (op === Infinity) {
+                return -1;
+            }
+            res += op;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * 2 ^ m)$
+* Space complexity: $O(n + m)$
+
+> Where $n$ is the size of the array $nums$ and $m$ is the average frequency of the array elements.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def minOperations(self, nums: List[int]) -> int:
+        cache = {}
+
+        def dfs(num):
+            if num < 0:
+                return float("inf")
+            if num in [2, 3]:
+                return 1
+            if num in cache:
+                return cache[num]
+            
+            res = min(dfs(num - 2), dfs(num - 3))
+            cache[num] = res + 1
+            return cache[num]
+
+        count = Counter(nums)
+        res = 0
+        for num, cnt in count.items():
+            op = dfs(cnt)
+            if op == float("inf"):
+                return -1
+            res += op
+        
+        return res
+```
+
+```java
+public class Solution {
+    private Map<Integer, Integer> cache;
+    
+    public int minOperations(int[] nums) {
+        Map<Integer, Integer> count = new HashMap<>();
+        for (int num : nums) {
+            count.put(num, count.getOrDefault(num, 0) + 1);
+        }
+
+        cache = new HashMap<>();
+        int res = 0;
+        for (int cnt : count.values()) {
+            int op = dfs(cnt);
+            if (op == Integer.MAX_VALUE) {
+                return -1;
+            }
+            res += op;
+        }
+
+        return res;
+    }
+
+    private int dfs(int cur) {
+        if (cur < 0) {
+            return Integer.MAX_VALUE;
+        }
+        if (cur == 2 || cur == 3) {
+            return 1;
+        }
+        if (cache.containsKey(cur)) {
+            return cache.get(cur);
+        }
+
+        int res = Math.min(dfs(cur - 2), dfs(cur - 3));
+        cache.put(cur, res == Integer.MAX_VALUE ? res : res + 1);
+        return cache.get(cur);
+    }
+}
+```
+
+```cpp
+class Solution {
+    unordered_map<int, int> cache;
+public:
+    int minOperations(vector<int>& nums) {
+        unordered_map<int, int> count;
+        for (int num : nums) {
+            count[num]++;
+        }
+
+        int res = 0;
+        for (auto& [num, cnt] : count) {
+            int op = dfs(cnt);
+            if (op == INT_MAX) {
+                return -1;
+            }
+            res += op;
+        }
+
+        return res;
+    }
+
+private:
+    int dfs(int cur) {
+        if (cur < 0) {
+            return INT_MAX;
+        }
+        if (cur == 2 || cur == 3) {
+            return 1;
+        }
+        if (cache.count(cur)) {
+            return cache[cur];
+        }
+
+        int res = min(dfs(cur - 2), dfs(cur - 3));
+        cache[cur] = res == INT_MAX ? res : res + 1;
+        return cache[cur];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    minOperations(nums) {
+        const cache = new Map();
+        const dfs = (cur) => {
+            if (cur < 0) {
+                return Infinity;
+            }
+            if (cur === 2 || cur === 3) {
+                return 1;
+            }
+            if (cache.has(cur)) {
+                return cache.get(cur);
+            }
+
+            const res = Math.min(dfs(cur - 2), dfs(cur - 3));
+            cache.set(cur, isFinite(res) ? 1 + res : res);
+            return cache.get(cur);
+        };
+        
+        const count = new Map();
+        for (const num of nums) {
+            count.set(num, (count.get(num) || 0) + 1);
+        }
+
+        let res = 0;
+        for (const cnt of count.values()) {
+            const op = dfs(cnt);
+            if (!isFinite(op)) {
+                return -1;
+            }
+            res += op;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(n + m)$
+
+> Where $n$ is the size of the array $nums$ and $m$ is the average frequency of the array elements.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def minOperations(self, nums: List[int]) -> int:
+        count = Counter(nums)
+        maxf = max(count.values())
+        minOps = [0] * (maxf + 1)
+        minOps[1] = float("inf")
+
+        for i in range(2, maxf + 1):
+            minOps[i] = minOps[i - 2]
+            if i - 3 >= 0:
+                minOps[i] = min(minOps[i], minOps[i - 3])
+            if minOps[i] != float("inf"):
+                minOps[i] += 1
+
+        res = 0
+        for num, cnt in count.items():
+            op = minOps[cnt]
+            if op == float("inf"):
+                return -1
+            res += op
+
+        return res
+```
+
+```java
+public class Solution {
+    public int minOperations(int[] nums) {
+        Map<Integer, Integer> count = new HashMap<>();
+        for (int num : nums) {
+            count.put(num, count.getOrDefault(num, 0) + 1);
+        }
+
+        int maxf = count.values().stream().max(Integer::compare).orElse(0);
+        int[] minOps = new int[maxf + 1];
+        minOps[1] = Integer.MAX_VALUE;
+
+        for (int i = 2; i <= maxf; i++) {
+            minOps[i] = minOps[i - 2];
+            if (i - 3 >= 0) {
+                minOps[i] = Math.min(minOps[i], minOps[i - 3]);
+            }
+            if (minOps[i] != Integer.MAX_VALUE) {
+                minOps[i] += 1;
+            }
+        }
+
+        int res = 0;
+        for (int cnt : count.values()) {
+            int op = minOps[cnt];
+            if (op == Integer.MAX_VALUE) {
+                return -1;
+            }
+            res += op;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minOperations(vector<int>& nums) {
+        unordered_map<int, int> count;
+        for (int num : nums) {
+            count[num]++;
+        }
+
+        int maxf = 0;
+        for (auto& [num, freq] : count) {
+            maxf = max(maxf, freq);
+        }
+
+        vector<int> minOps(maxf + 1, 0);
+        minOps[1] = INT_MAX;
+
+        for (int i = 2; i <= maxf; i++) {
+            minOps[i] = minOps[i - 2];
+            if (i - 3 >= 0) {
+                minOps[i] = min(minOps[i], minOps[i - 3]);
+            }
+            if (minOps[i] != INT_MAX) {
+                minOps[i] += 1;
+            }
+        }
+
+        int res = 0;
+        for (auto& [num, cnt] : count) {
+            int op = minOps[cnt];
+            if (op == INT_MAX) {
+                return -1;
+            }
+            res += op;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    minOperations(nums) {
+        const count = new Map();
+        for (const num of nums) {
+            count.set(num, (count.get(num) || 0) + 1);
+        }
+
+        const maxf = Math.max(...count.values());
+        const minOps = Array(maxf + 1).fill(0);
+        minOps[1] = Infinity;
+
+        for (let i = 2; i <= maxf; i++) {
+            minOps[i] = minOps[i - 2];
+            if (i - 3 >= 0) {
+                minOps[i] = Math.min(minOps[i], minOps[i - 3]);
+            }
+            if (minOps[i] !== Infinity) {
+                minOps[i] += 1;
+            }
+        }
+
+        let res = 0;
+        for (const cnt of count.values()) {
+            const op = minOps[cnt];
+            if (op === Infinity) {
+                return -1;
+            }
+            res += op;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(n + m)$
+
+> Where $n$ is the size of the array $nums$ and $m$ is the average frequency of the array elements.
+
+---
+
+## 4. Greedy
+
+::tabs-start
+
+```python
+class Solution:
+    def minOperations(self, nums: List[int]) -> int:
+        count = Counter(nums)
+        res = 0
+        
+        for num, cnt in count.items():
+            if cnt == 1:
+                return -1
+            res += math.ceil(cnt / 3)
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int minOperations(int[] nums) {
+        Map<Integer, Integer> count = new HashMap<>();
+        for (int num : nums) {
+            count.put(num, count.getOrDefault(num, 0) + 1);
+        }
+
+        int res = 0;
+        for (int cnt : count.values()) {
+            if (cnt == 1) {
+                return -1;
+            }
+            res += (cnt + 2) / 3;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minOperations(vector<int>& nums) {
+        unordered_map<int, int> count;
+        for (int num : nums) {
+            count[num]++;
+        }
+
+        int res = 0;
+        for (auto& [num, cnt] : count) {
+            if (cnt == 1) {
+                return -1;
+            }
+            res += (cnt + 2) / 3;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    minOperations(nums) {
+        const count = new Map();
+        for (const num of nums) {
+            count.set(num, (count.get(num) || 0) + 1);
+        }
+
+        let res = 0;
+        for (const cnt of count.values()) {
+            if (cnt === 1) {
+                return -1;
+            }
+            res += Math.ceil(cnt / 3);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/minimum-number-of-operations-to-move-all-balls-to-each-box.md b/articles/minimum-number-of-operations-to-move-all-balls-to-each-box.md
new file mode 100644
index 000000000..c00bbfdb0
--- /dev/null
+++ b/articles/minimum-number-of-operations-to-move-all-balls-to-each-box.md
@@ -0,0 +1,325 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def minOperations(self, boxes: str) -> List[int]:
+        n = len(boxes)
+        res = [0] * n
+
+        for pos in range(n):
+            for i in range(n):
+                if boxes[i] == '1':
+                    res[pos] += abs(pos - i)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[] minOperations(String boxes) {
+        int n = boxes.length();
+        int[] res = new int[n];
+
+        for (int pos = 0; pos < n; pos++) {
+            for (int i = 0; i < n; i++) {
+                if (boxes.charAt(i) == '1') {
+                    res[pos] += Math.abs(pos - i);
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> minOperations(string boxes) {
+        int n = boxes.size();
+        vector<int> res(n, 0);
+
+        for (int pos = 0; pos < n; pos++) {
+            for (int i = 0; i < n; i++) {
+                if (boxes[i] == '1') {
+                    res[pos] += abs(pos - i);
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} boxes
+     * @return {number[]}
+     */
+    minOperations(boxes) {
+        const n = boxes.length;
+        const res = new Array(n).fill(0);
+
+        for (let pos = 0; pos < n; pos++) {
+            for (let i = 0; i < n; i++) {
+                if (boxes[i] === '1') {
+                    res[pos] += Math.abs(pos - i);
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ space for the output list.
+
+---
+
+## 2. Prefix Sum
+
+::tabs-start
+
+```python
+class Solution:
+    def minOperations(self, boxes: str) -> List[int]:
+        n = len(boxes)
+        res = [0] * n
+
+        prefix_count = [0] * (n + 1)
+        index_sum = [0] * (n + 1)
+        for i in range(n):
+            prefix_count[i + 1] = prefix_count[i] + (boxes[i] == '1')
+            index_sum[i + 1] = index_sum[i] + (i if boxes[i] == '1' else 0)
+
+        for i in range(n):
+            left = prefix_count[i]
+            left_sum = index_sum[i]
+
+            right = prefix_count[n] - prefix_count[i + 1]
+            right_sum = index_sum[n] - index_sum[i + 1]
+
+            res[i] = (i * left - left_sum) + (right_sum - i * right)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[] minOperations(String boxes) {
+        int n = boxes.length();
+        int[] res = new int[n];
+        int[] prefixCount = new int[n + 1];
+        int[] indexSum = new int[n + 1];
+
+        for (int i = 0; i < n; i++) {
+            prefixCount[i + 1] = prefixCount[i] + (boxes.charAt(i) == '1' ? 1 : 0);
+            indexSum[i + 1] = indexSum[i] + (boxes.charAt(i) == '1' ? i : 0);
+        }
+
+        for (int i = 0; i < n; i++) {
+            int left = prefixCount[i];
+            int leftSum = indexSum[i];
+
+            int right = prefixCount[n] - prefixCount[i + 1];
+            int rightSum = indexSum[n] - indexSum[i + 1];
+
+            res[i] = i * left - leftSum + (rightSum - i * right);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> minOperations(string boxes) {
+        int n = boxes.size();
+        vector<int> res(n), prefixCount(n + 1, 0), indexSum(n + 1, 0);
+
+        for (int i = 0; i < n; i++) {
+            prefixCount[i + 1] = prefixCount[i] + (boxes[i] == '1' ? 1 : 0);
+            indexSum[i + 1] = indexSum[i] + (boxes[i] == '1' ? i : 0);
+        }
+
+        for (int i = 0; i < n; i++) {
+            int left = prefixCount[i];
+            int leftSum = indexSum[i];
+            int right = prefixCount[n] - prefixCount[i + 1];
+            int rightSum = indexSum[n] - indexSum[i + 1];
+            res[i] = i * left - leftSum + (rightSum - i * right);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} boxes
+     * @return {number[]}
+     */
+    minOperations(boxes) {
+        const n = boxes.length;
+        const res = new Array(n).fill(0);
+        const prefixCount = new Array(n + 1).fill(0);
+        const indexSum = new Array(n + 1).fill(0);
+
+        for (let i = 0; i < n; i++) {
+            prefixCount[i + 1] = prefixCount[i] + (boxes[i] === '1' ? 1 : 0);
+            indexSum[i + 1] = indexSum[i] + (boxes[i] === '1' ? i : 0);
+        }
+
+        for (let i = 0; i < n; i++) {
+            const left = prefixCount[i];
+            const leftSum = indexSum[i];
+            const right = prefixCount[n] - prefixCount[i + 1];
+            const rightSum = indexSum[n] - indexSum[i + 1];
+
+            res[i] = i * left - leftSum + (rightSum - i * right);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Prefix Sum (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def minOperations(self, boxes: str) -> List[int]:
+        n = len(boxes)
+        res = [0] * n
+
+        balls = moves = 0
+        for i in range(n):
+            res[i] = balls + moves
+            moves += balls
+            balls += int(boxes[i])
+
+        balls = moves = 0
+        for i in range(n - 1, -1, -1):
+            res[i] += balls + moves
+            moves += balls
+            balls += int(boxes[i])
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[] minOperations(String boxes) {
+        int n = boxes.length();
+        int[] res = new int[n];
+
+        int balls = 0, moves = 0;
+        for (int i = 0; i < n; i++) {
+            res[i] = balls + moves;
+            moves += balls;
+            balls += boxes.charAt(i) - '0';
+        }
+
+        balls = moves = 0;
+        for (int i = n - 1; i >= 0; i--) {
+            res[i] += balls + moves;
+            moves += balls;
+            balls += boxes.charAt(i) - '0';
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> minOperations(string boxes) {
+        int n = boxes.size();
+        vector<int> res(n, 0);
+
+        int balls = 0, moves = 0;
+        for (int i = 0; i < n; i++) {
+            res[i] = balls + moves;
+            moves += balls;
+            balls += boxes[i] - '0';
+        }
+
+        balls = moves = 0;
+        for (int i = n - 1; i >= 0; i--) {
+            res[i] += balls + moves;
+            moves += balls;
+            balls += boxes[i] - '0';
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} boxes
+     * @return {number[]}
+     */
+    minOperations(boxes) {
+        const n = boxes.length;
+        const res = new Array(n).fill(0);
+
+        let balls = 0, moves = 0;
+        for (let i = 0; i < n; i++) {
+            res[i] = balls + moves;
+            moves += balls;
+            balls += Number(boxes[i]);
+        }
+
+        balls = moves = 0;
+        for (let i = n - 1; i >= 0; i--) {
+            res[i] += balls + moves;
+            moves += balls;
+            balls += Number(boxes[i]);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ space for the output list.
\ No newline at end of file
diff --git a/articles/minimum-number-of-swaps-to-make-the-string-balanced.md b/articles/minimum-number-of-swaps-to-make-the-string-balanced.md
new file mode 100644
index 000000000..8c18a3ae2
--- /dev/null
+++ b/articles/minimum-number-of-swaps-to-make-the-string-balanced.md
@@ -0,0 +1,219 @@
+## 1. Stack
+
+::tabs-start
+
+```python
+class Solution:
+    def minSwaps(self, s: str) -> int:
+        stack = []
+        for c in s:
+            if c == '[':
+                stack.append(c)
+            elif stack:
+                stack.pop()
+        return (len(stack) + 1) // 2
+```
+
+```java
+public class Solution {
+    public int minSwaps(String s) {
+        Stack<Character> stack = new Stack<>();
+        for (char c : s.toCharArray()) {
+            if (c == '[') {
+                stack.push(c);
+            } else if (!stack.isEmpty()) {
+                stack.pop();
+            }
+        }
+        return (stack.size() + 1) / 2;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minSwaps(string s) {
+        vector<char> stack;
+        for (char c : s) {
+            if (c == '[') {
+                stack.push_back(c);
+            } else if (!stack.empty()) {
+                stack.pop_back();
+            }
+        }
+        return (stack.size() + 1) / 2;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    minSwaps(s) {
+        let stack = [];
+        for (const c of s) {
+            if (c === '[') {
+                stack.push(c);
+            } else if (stack.length > 0) {
+                stack.pop();
+            }
+        }
+        return Math.floor((stack.length + 1) / 2);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Greedy - I
+
+::tabs-start
+
+```python
+class Solution:
+    def minSwaps(self, s: str) -> int:
+        close = maxClose = 0
+
+        for c in s:
+            if c == '[':
+                close -= 1
+            else:
+                close += 1
+            maxClose = max(maxClose, close)
+        
+        return (maxClose + 1) // 2
+```
+
+```java
+public class Solution {
+    public int minSwaps(String s) {
+        int close = 0, maxClose = 0;
+        for (int i = 0; i < s.length(); i++) {
+            if (s.charAt(i) == '[') close--;
+            else close++;
+            maxClose = Math.max(maxClose, close);
+        }
+        return (maxClose + 1) / 2;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minSwaps(string s) {
+        int close = 0, maxClose = 0;
+        for (auto& c : s) {
+            if (c == '[') close--;
+            else close++;
+            maxClose = max(maxClose, close);
+        }
+        return (maxClose + 1) / 2;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    minSwaps(s) {
+        let close = 0, maxClose = 0;
+        for (let i = 0; i < s.length; i++) {
+            if (s.charAt(i) == '[') close--;
+            else close++;
+            maxClose = Math.max(maxClose, close);
+        }
+        return Math.floor((maxClose + 1) / 2);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Greedy - II
+
+::tabs-start
+
+```python
+class Solution:
+    def minSwaps(self, s: str) -> int:
+        stackSize = 0
+        for c in s:
+            if c == '[':
+                stackSize += 1
+            elif stackSize > 0:
+                stackSize -= 1
+        return (stackSize + 1) // 2
+```
+
+```java
+public class Solution {
+    public int minSwaps(String s) {
+        int stackSize = 0;
+        for (int i = 0; i < s.length(); i++) {
+            if (s.charAt(i) == '[') stackSize++;
+            else if (stackSize > 0) stackSize--;
+        }
+        return (stackSize + 1) / 2;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minSwaps(string s) {
+        int stackSize = 0;
+        for (auto& c : s) {
+            if (c == '[') stackSize++;
+            else if (stackSize > 0) stackSize--;
+        }
+        return (stackSize + 1) / 2;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    minSwaps(s) {
+        let stackSize = 0;
+        for (let i = 0; i < s.length; i++) {
+            if (s.charAt(i) == '[') stackSize++;
+            else if (stackSize > 0) stackSize--;
+        }
+        return Math.floor((stackSize + 1) / 2);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/minimum-number-of-vertices-to-reach-all-nodes.md b/articles/minimum-number-of-vertices-to-reach-all-nodes.md
new file mode 100644
index 000000000..aa09f1c80
--- /dev/null
+++ b/articles/minimum-number-of-vertices-to-reach-all-nodes.md
@@ -0,0 +1,465 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def findSmallestSetOfVertices(self, n: int, edges: List[List[int]]) -> List[int]:
+        adj = [[] for _ in range(n)]
+        for u, v in edges:
+            adj[u].append(v)
+
+        res = set(range(n))
+        visited = [False] * n
+
+        def dfs(node):
+            visited[node] = True
+            for nei in adj[node]:
+                if not visited[nei]:
+                    dfs(nei)
+                res.discard(nei)
+
+        for i in range(n):
+            if not visited[i]:
+                dfs(i)
+        return list(res)
+```
+
+```java
+public class Solution {
+    public List<Integer> findSmallestSetOfVertices(int n, List<List<Integer>> edges) {
+        List<Integer>[] adj = new ArrayList[n];
+        for (int i = 0; i < n; i++) adj[i] = new ArrayList<>();
+        for (List<Integer> edge : edges) {
+            adj[edge.get(0)].add(edge.get(1));
+        }
+
+        Set<Integer> res = new HashSet<>();
+        for (int i = 0; i < n; i++) {
+            res.add(i);
+        }
+
+        boolean[] visited = new boolean[n];
+        for (int i = 0; i < n; i++) {
+            dfs(i, adj, visited, res);
+        }
+        return new ArrayList<>(res);
+    }
+
+    private void dfs(int node, List<Integer>[] adj, boolean[] visited, Set<Integer> res) {
+        visited[node] = true;
+        for (int nei : adj[node]) {
+            if (!visited[nei]) dfs(nei, adj, visited, res);
+            res.remove(nei);
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findSmallestSetOfVertices(int n, vector<vector<int>>& edges) {
+        vector<vector<int>> adj(n);
+        for (auto& edge : edges) {
+            adj[edge[0]].push_back(edge[1]);
+        }
+
+        unordered_set<int> res;
+        vector<bool> visited(n, false);
+        for (int i = 0; i < n; i++) res.insert(i);
+
+        function<void(int)> dfs = [&](int node) {
+            visited[node] = true;
+            for (int& nei : adj[node]) {
+                if (!visited[nei]) dfs(nei);
+                res.erase(nei);
+            }
+        };
+
+        for (int i = 0; i < n; i++) {
+            if (!visited[i]) dfs(i);
+        }
+        return vector<int>(res.begin(), res.end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} edges
+     * @return {number[]}
+     */
+    findSmallestSetOfVertices(n, edges) {
+        const adj = Array.from({ length: n }, () => []);
+        for (const [u, v] of edges) {
+            adj[u].push(v);
+        }
+
+        const res = new Set(Array.from({ length: n }, (_, i) => i));
+        const visited = new Array(n).fill(false);
+
+        const dfs = (node) => {
+            visited[node] = true;
+            for (const nei of adj[node]) {
+                if (!visited[nei]) dfs(nei);
+                res.delete(nei);
+            }
+        };
+
+        for (let i = 0; i < n; i++) {
+            if (!visited[i]) dfs(i);
+        }
+
+        return Array.from(res);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + E)$
+* Space complexity: $O(V + E)$
+
+> Where $V$ is the number of vertices and $E$ is the number of edges.
+
+---
+
+## 2. Iterative DFS
+
+::tabs-start
+
+```python
+class Solution:
+    def findSmallestSetOfVertices(self, n: int, edges: List[List[int]]) -> List[int]:
+        adj = [[] for _ in range(n)]
+        for u, v in edges:
+            adj[u].append(v)
+
+        res = [True] * n
+        visited = [False] * n
+        stack = []
+
+        for i in range(n):
+            if not visited[i]:
+                stack.append(i)
+                while stack:
+                    node = stack.pop()
+                    if visited[node]:
+                        continue
+                    visited[node] = True
+                    for nei in adj[node]:
+                        if not visited[nei]:
+                            stack.append(nei)
+                        res[nei] = False
+
+        return [i for i in range(n) if res[i]]
+```
+
+```java
+public class Solution {
+    public List<Integer> findSmallestSetOfVertices(int n, List<List<Integer>> edges) {
+        List<Integer>[] adj = new ArrayList[n];
+        for (int i = 0; i < n; i++) {
+            adj[i] = new ArrayList<>();
+        }
+        for (List<Integer> edge : edges) {
+            adj[edge.get(0)].add(edge.get(1));
+        }
+
+        boolean[] res = new boolean[n];
+        Arrays.fill(res, true);
+        boolean[] visited = new boolean[n];
+        Stack<Integer> stack = new Stack<>();
+
+        for (int i = 0; i < n; i++) {
+            if (!visited[i]) {
+                stack.push(i);
+                while (!stack.isEmpty()) {
+                    int node = stack.pop();
+                    if (visited[node]) continue;
+                    visited[node] = true;
+                    for (int nei : adj[node]) {
+                        if (!visited[nei]) stack.push(nei);
+                        res[nei] = false;
+                    }
+                }
+            }
+        }
+
+        List<Integer> result = new ArrayList<>();
+        for (int i = 0; i < n; i++) {
+            if (res[i]) result.add(i);
+        }
+        return result;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findSmallestSetOfVertices(int n, vector<vector<int>>& edges) {
+        vector<vector<int>> adj(n);
+        for (auto& edge : edges) {
+            adj[edge[0]].push_back(edge[1]);
+        }
+
+        vector<bool> res(n, true), visited(n, false);
+        stack<int> stack;
+
+        for (int i = 0; i < n; i++) {
+            if (!visited[i]) {
+                stack.push(i);
+                while (!stack.empty()) {
+                    int node = stack.top();
+                    stack.pop();
+                    if (visited[node]) continue;
+                    visited[node] = true;
+                    for (int nei : adj[node]) {
+                        if (!visited[nei]) stack.push(nei);
+                        res[nei] = false;
+                    }
+                }
+            }
+        }
+
+        vector<int> result;
+        for (int i = 0; i < n; i++) {
+            if (res[i]) result.push_back(i);
+        }
+        return result;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} edges
+     * @return {number[]}
+     */
+    findSmallestSetOfVertices(n, edges) {
+        const adj = Array.from({ length: n }, () => []);
+        for (const [u, v] of edges) {
+            adj[u].push(v);
+        }
+
+        const res = Array(n).fill(true);
+        const visited = Array(n).fill(false);
+        const stack = [];
+
+        for (let i = 0; i < n; i++) {
+            if (!visited[i]) {
+                stack.push(i);
+                while (stack.length) {
+                    const node = stack.pop();
+                    if (visited[node]) continue;
+                    visited[node] = true;
+                    for (const nei of adj[node]) {
+                        if (!visited[nei]) stack.push(nei);
+                        res[nei] = false;
+                    }
+                }
+            }
+        }
+
+        return res.map((val, i) => val ? i : -1).filter(i => i !== -1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + E)$
+* Space complexity: $O(V + E)$
+
+> Where $V$ is the number of vertices and $E$ is the number of edges.
+
+---
+
+## 3. Indegree Count
+
+::tabs-start
+
+```python
+class Solution:
+    def findSmallestSetOfVertices(self, n: int, edges: List[List[int]]) -> List[int]:
+        incoming = collections.defaultdict(list)
+        for src, dst in edges:
+            incoming[dst].append(src)
+
+        res = []
+        for i in range(n):
+            if not incoming[i]:
+                res.append(i)
+        return res
+```
+
+```java
+public class Solution {
+    public List<Integer> findSmallestSetOfVertices(int n, List<List<Integer>> edges) {
+        List<Integer>[] incoming = new ArrayList[n];
+        for (int i = 0; i < n; i++) {
+            incoming[i] = new ArrayList<>();
+        }
+        for (List<Integer> edge : edges) {
+            incoming[edge.get(1)].add(edge.get(0));
+        }
+
+        List<Integer> res = new ArrayList<>();
+        for (int i = 0; i < n; i++) {
+            if (incoming[i].isEmpty()) {
+                res.add(i);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findSmallestSetOfVertices(int n, vector<vector<int>>& edges) {
+        vector<vector<int>> incoming(n);
+        for (auto& edge : edges) {
+            incoming[edge[1]].push_back(edge[0]);
+        }
+
+        vector<int> res;
+        for (int i = 0; i < n; i++) {
+            if (incoming[i].empty()) {
+                res.push_back(i);
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} edges
+     * @return {number[]}
+     */
+    findSmallestSetOfVertices(n, edges) {
+        const incoming = Array.from({ length: n }, () => []);
+    
+        for (const [src, dst] of edges) {
+            incoming[dst].push(src);
+        }
+
+        const res = [];
+        for (let i = 0; i < n; i++) {
+            if (incoming[i].length === 0) {
+                res.push(i);
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + E)$
+* Space complexity: $O(V)$
+
+> Where $V$ is the number of vertices and $E$ is the number of edges.
+
+---
+
+## 4. Indegree Count
+
+::tabs-start
+
+```python
+class Solution:
+    def findSmallestSetOfVertices(self, n: int, edges: List[List[int]]) -> List[int]:
+        indegree = [False] * n
+        for src, dst in edges:
+            indegree[dst] = True
+        return [i for i in range(n) if not indegree[i]]
+```
+
+```java
+public class Solution {
+    public List<Integer> findSmallestSetOfVertices(int n, List<List<Integer>> edges) {
+        boolean[] indegree = new boolean[n];
+        for (List<Integer> edge : edges) {
+            indegree[edge.get(1)] = true;
+        }
+
+        List<Integer> res = new ArrayList<>();
+        for (int i = 0; i < n; i++) {
+            if (!indegree[i]) {
+                res.add(i);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findSmallestSetOfVertices(int n, vector<vector<int>>& edges) {
+        vector<bool> indegree(n, false);
+        for (const auto& edge : edges) {
+            indegree[edge[1]] = true;
+        }
+
+        vector<int> res;
+        for (int i = 0; i < n; i++) {
+            if (!indegree[i]) {
+                res.push_back(i);
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} edges
+     * @return {number[]}
+     */
+    findSmallestSetOfVertices(n, edges) {
+        const indegree = new Array(n).fill(false);
+        for (const [src, dst] of edges) {
+            indegree[dst] = true;
+        }
+
+        let res = [];
+        for (let i = 0; i < n; i++) {
+            if (!indegree[i]) res.push(i);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + E)$
+* Space complexity: $O(V)$
+
+> Where $V$ is the number of vertices and $E$ is the number of edges.
\ No newline at end of file
diff --git a/articles/minimum-one-bit-operations-to-make-integers-zero.md b/articles/minimum-one-bit-operations-to-make-integers-zero.md
new file mode 100644
index 000000000..7e4071ce6
--- /dev/null
+++ b/articles/minimum-one-bit-operations-to-make-integers-zero.md
@@ -0,0 +1,313 @@
+## 1. Math (Recursion)
+
+::tabs-start
+
+```python
+class Solution:
+    def minimumOneBitOperations(self, n: int) -> int:
+        if n == 0:
+            return 0
+
+        k = 1
+        while (k << 1) <= n:
+            k <<= 1
+
+        return (k << 1) - 1 - self.minimumOneBitOperations(k ^ n)
+```
+
+```java
+public class Solution {
+    public int minimumOneBitOperations(int n) {
+        if (n == 0) {
+            return 0;
+        }
+
+        int k = 1;
+        while ((k << 1) <= n) {
+            k <<= 1;
+        }
+
+        return (k << 1) - 1 - minimumOneBitOperations(k ^ n);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minimumOneBitOperations(int n) {
+        if (n == 0) {
+            return 0;
+        }
+
+        int k = 1;
+        while ((k << 1) <= n) {
+            k <<= 1;
+        }
+
+        return (k << 1) - 1 - minimumOneBitOperations(k ^ n);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    minimumOneBitOperations(n) {
+        if (n === 0) {
+            return 0;
+        }
+
+        let k = 1;
+        while ((k << 1) <= n) {
+            k <<= 1;
+        }
+
+        return (k << 1) - 1 - this.minimumOneBitOperations(k ^ n);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(\log n)$ for recursion stack.
+
+---
+
+## 2. Math (Iteration) - I
+
+::tabs-start
+
+```python
+class Solution:
+    def minimumOneBitOperations(self, n: int) -> int:
+        res = 0
+        k = 1 << 30
+        sign = 1
+
+        while n:
+            while k > n:
+                k >>= 1
+
+            res += (sign * ((k << 1) - 1))
+            sign *= -1
+            n ^= k
+
+        return res
+```
+
+```java
+public class Solution {
+    public int minimumOneBitOperations(int n) {
+        int res = 0, k = 1 << 30, sign = 1;
+
+        while (n != 0) {
+            while (k > n) {
+                k >>= 1;
+            }
+
+            res += (sign * ((k << 1) - 1));
+            sign *= -1;
+            n ^= k;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minimumOneBitOperations(int n) {
+        int res = 0, k = 1 << 30, sign = 1;
+
+        while (n != 0) {
+            while (k > n) {
+                k >>= 1;
+            }
+
+            res += sign * ((k << 1) - 1);
+            sign *= -1;
+            n ^= k;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    minimumOneBitOperations(n) {
+        let res = 0, k = 1 << 30, sign = 1;
+
+        while (n !== 0) {
+            while (k > n) {
+                k >>= 1;
+            }
+
+            res += sign * ((k << 1) - 1);
+            sign *= -1;
+            n ^= k;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Math (Iteration) - II
+
+::tabs-start
+
+```python
+class Solution:
+    def minimumOneBitOperations(self, n: int) -> int:
+        res, sign = 0, 1
+        while n:
+            res += sign * (n ^ (n - 1))
+            n &= (n - 1)
+            sign *= -1
+        return abs(res)
+```
+
+```java
+public class Solution {
+    public int minimumOneBitOperations(int n) {
+        int res = 0, sign = 1;
+        while (n != 0) {
+            res += sign * (n ^ (n - 1));
+            n &= (n - 1);
+            sign *= -1;
+        }
+        return Math.abs(res);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minimumOneBitOperations(int n) {
+        int res = 0, sign = 1;
+        while (n != 0) {
+            res += sign * (n ^ (n - 1));
+            n &= (n - 1);
+            sign *= -1;
+        }
+        return abs(res);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    minimumOneBitOperations(n) {
+        let res = 0, sign = 1;
+        while (n !== 0) {
+            res += sign * (n ^ (n - 1));
+            n &= (n - 1);
+            sign *= -1;
+        }
+        return Math.abs(res);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
+
+---
+
+## 4. Math (Grey Code)
+
+::tabs-start
+
+```python
+class Solution:
+    def minimumOneBitOperations(self, n: int) -> int:
+        res = n
+        while n:
+            n >>= 1
+            res ^= n
+        return res
+```
+
+```java
+public class Solution {
+    public int minimumOneBitOperations(int n) {
+        int res = n;
+        while (n != 0) {
+            n >>= 1;
+            res ^= n;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minimumOneBitOperations(int n) {
+        int res = n;
+        while (n != 0) {
+            n >>= 1;
+            res ^= n;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    minimumOneBitOperations(n) {
+        let res = n;
+        while (n !== 0) {
+            n >>= 1;
+            res ^= n;
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/minimum-operations-to-reduce-x-to-zero.md b/articles/minimum-operations-to-reduce-x-to-zero.md
new file mode 100644
index 000000000..e3b3ca2eb
--- /dev/null
+++ b/articles/minimum-operations-to-reduce-x-to-zero.md
@@ -0,0 +1,577 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def minOperations(self, nums: List[int], x: int) -> int:
+        n = len(nums)
+        res = n + 1
+        suffixSum = prefixSum = 0
+
+        for i in range(n - 1, -1, -1):
+            suffixSum += nums[i]
+            if suffixSum == x:
+                res = min(res, n - i)
+
+        for i in range(n):
+            prefixSum += nums[i]
+            suffixSum = 0
+            if prefixSum == x:
+                res = min(res, i + 1)
+
+            for j in range(n - 1, i, -1):
+                suffixSum += nums[j]
+                if prefixSum + suffixSum == x:
+                    res = min(res, i + 1 + n - j)
+        
+        return -1 if res == n + 1 else res
+```
+
+```java
+public class Solution {
+    public int minOperations(int[] nums, int x) {
+        int n = nums.length;
+        int res = n + 1;
+        int suffixSum = 0, prefixSum = 0;
+
+        for (int i = n - 1; i >= 0; i--) {
+            suffixSum += nums[i];
+            if (suffixSum == x) {
+                res = Math.min(res, n - i);
+            }
+        }
+
+        for (int i = 0; i < n; i++) {
+            prefixSum += nums[i];
+            suffixSum = 0;
+            if (prefixSum == x) {
+                res = Math.min(res, i + 1);
+            }
+
+            for (int j = n - 1; j > i; j--) {
+                suffixSum += nums[j];
+                if (prefixSum + suffixSum == x) {
+                    res = Math.min(res, i + 1 + n - j);
+                }
+            }
+        }
+
+        return res == n + 1 ? -1 : res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minOperations(vector<int>& nums, int x) {
+        int n = nums.size();
+        int res = n + 1, suffixSum = 0, prefixSum = 0;
+
+        for (int i = n - 1; i >= 0; i--) {
+            suffixSum += nums[i];
+            if (suffixSum == x) {
+                res = min(res, n - i);
+            }
+        }
+
+        for (int i = 0; i < n; i++) {
+            prefixSum += nums[i];
+            suffixSum = 0;
+            if (prefixSum == x) {
+                res = min(res, i + 1);
+            }
+
+            for (int j = n - 1; j > i; j--) {
+                suffixSum += nums[j];
+                if (prefixSum + suffixSum == x) {
+                    res = min(res, i + 1 + n - j);
+                }
+            }
+        }
+
+        return res == n + 1 ? -1 : res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} x
+     * @return {number}
+     */
+    minOperations(nums, x) {
+        const n = nums.length;
+        let res = n + 1, suffixSum = 0, prefixSum = 0;
+
+        for (let i = n - 1; i >= 0; i--) {
+            suffixSum += nums[i];
+            if (suffixSum === x) {
+                res = Math.min(res, n - i);
+            }
+        }
+
+        for (let i = 0; i < n; i++) {
+            prefixSum += nums[i];
+            suffixSum = 0;
+            if (prefixSum === x) {
+                res = Math.min(res, i + 1);
+            }
+
+            for (let j = n - 1; j > i; j--) {
+                suffixSum += nums[j];
+                if (prefixSum + suffixSum === x) {
+                    res = Math.min(res, i + 1 + n - j);
+                }
+            }
+        }
+
+        return res === n + 1 ? -1 : res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 2. Prefix Sum + Binary Search
+
+::tabs-start
+
+```python
+class Solution:
+    def minOperations(self, nums: List[int], x: int) -> int:
+        n = len(nums)
+        prefixSum = [0] * (n + 1)
+        for i in range(n):
+            prefixSum[i + 1] = prefixSum[i] + nums[i]
+        
+        if x > prefixSum[n]:
+            return -1
+
+        def binarySearch(target, m):
+            l, r = 1, m
+            index = n + 1
+
+            while l <= r:
+                mid = (l + r) >> 1
+                if prefixSum[mid] >= target:
+                    if prefixSum[mid] == target:
+                        index = mid
+                    r = mid - 1
+                else:
+                    l = mid + 1
+            
+            return index
+        
+        res = binarySearch(x, n)
+        suffixSum = 0
+        for i in range(n - 1, 0, -1):
+            suffixSum += nums[i]
+            if suffixSum == x:
+                res = min(res, n - i)
+                break
+            if suffixSum > x: break
+            res = min(res, binarySearch(x - suffixSum, i) + n - i)
+        
+        return -1 if res == n + 1 else res
+```
+
+```java
+public class Solution {
+    public int minOperations(int[] nums, int x) {
+        int n = nums.length;
+        int[] prefixSum = new int[n + 1];
+        for (int i = 0; i < n; i++) {
+            prefixSum[i + 1] = prefixSum[i] + nums[i];
+        }
+        
+        if (x > prefixSum[n]) {
+            return -1;
+        }
+        
+        int res = binarySearch(prefixSum, x, n);
+        int suffixSum = 0;
+        for (int i = n - 1; i > 0; i--) {
+            suffixSum += nums[i];
+            if (suffixSum == x) {
+                res = Math.min(res, n - i);
+                break;
+            }
+            if (suffixSum > x) break;
+            res = Math.min(res, binarySearch(prefixSum, x - suffixSum, i) + n - i);
+        }
+        
+        return res == n + 1 ? -1 : res;
+    }
+
+    private int binarySearch(int[] prefixSum, int target, int m) {
+        int l = 1, r = m;
+        int index = prefixSum.length;
+
+        while (l <= r) {
+            int mid = (l + r) / 2;
+            if (prefixSum[mid] >= target) {
+                if (prefixSum[mid] == target) {
+                    index = mid;
+                }
+                r = mid - 1;
+            } else {
+                l = mid + 1;
+            }
+        }
+        return index;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minOperations(vector<int>& nums, int x) {
+        int n = nums.size();
+        vector<int> prefixSum(n + 1, 0);
+        for (int i = 0; i < n; i++) {
+            prefixSum[i + 1] = prefixSum[i] + nums[i];
+        }
+
+        if (x > prefixSum[n]) {
+            return -1;
+        }
+
+        auto binarySearch = [&](int target, int m) {
+            int l = 1, r = m, index = n + 1;
+            while (l <= r) {
+                int mid = (l + r) / 2;
+                if (prefixSum[mid] >= target) {
+                    if (prefixSum[mid] == target) {
+                        index = mid;
+                    }
+                    r = mid - 1;
+                } else {
+                    l = mid + 1;
+                }
+            }
+            return index;
+        };
+
+        int res = binarySearch(x, n);
+        int suffixSum = 0;
+        for (int i = n - 1; i > 0; i--) {
+            suffixSum += nums[i];
+            if (suffixSum == x) {
+                res = min(res, n - i);
+                break;
+            }
+            if (suffixSum > x) break;
+            res = min(res, binarySearch(x - suffixSum, i) + n - i);
+        }
+
+        return res == n + 1 ? -1 : res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} x
+     * @return {number}
+     */
+    minOperations(nums, x) {
+        const n = nums.length;
+        const prefixSum = new Array(n + 1).fill(0);
+        for (let i = 0; i < n; i++) {
+            prefixSum[i + 1] = prefixSum[i] + nums[i];
+        }
+        
+        if (x > prefixSum[n]) return -1;
+
+        const binarySearch = (target, m) => {
+            let l = 1, r = m;
+            let index = n + 1;
+            while (l <= r) {
+                let mid = Math.floor((l + r) / 2);
+                if (prefixSum[mid] >= target) {
+                    if (prefixSum[mid] === target) {
+                        index = mid;
+                    }
+                    r = mid - 1;
+                } else {
+                    l = mid + 1;
+                }
+            }
+            return index;
+        };
+
+        let res = binarySearch(x, n);
+        let suffixSum = 0;
+        for (let i = n - 1; i > 0; i--) {
+            suffixSum += nums[i];
+            if (suffixSum === x) {
+                res = Math.min(res, n - i);
+                break;
+            }
+            if (suffixSum > x) break;
+            res = Math.min(res, binarySearch(x - suffixSum, i) + n - i);
+        }
+
+        return res === n + 1 ? -1 : res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Prefix Sum + Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def minOperations(self, nums: List[int], x: int) -> int:
+        total = sum(nums)
+        if total == x:
+            return len(nums)
+
+        target = total - x
+        if target < 0:
+            return -1
+        
+        res = -1
+        prefixSum = 0
+        prefixMap = {0: -1}  # prefixSum -> index
+        
+        for i, num in enumerate(nums):
+            prefixSum += num
+            if prefixSum - target in prefixMap:
+                res = max(res, i - prefixMap[prefixSum - target])
+            prefixMap[prefixSum] = i
+        
+        return len(nums) - res if res != -1 else -1
+```
+
+```java
+public class Solution {
+    public int minOperations(int[] nums, int x) {
+        int total = 0;
+        for (int num : nums) total += num;
+        if (total == x) return nums.length;
+
+        int target = total - x;
+        if (target < 0) return -1;
+        
+        Map<Integer, Integer> prefixMap = new HashMap<>();
+        prefixMap.put(0, -1);
+        int prefixSum = 0, res = -1;
+
+        for (int i = 0; i < nums.length; i++) {
+            prefixSum += nums[i];
+            if (prefixMap.containsKey(prefixSum - target)) {
+                res = Math.max(res, i - prefixMap.get(prefixSum - target));
+            }
+            prefixMap.put(prefixSum, i);
+        }
+        
+        return res == -1 ? -1 : nums.length - res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minOperations(vector<int>& nums, int x) {
+        int total = 0;
+        for (int& num : nums) total += num;
+        if (total == x) return nums.size();
+
+        int target = total - x;
+        if (target < 0) return -1;
+        
+        unordered_map<int, int> prefixMap;
+        prefixMap[0] = -1;
+        int prefixSum = 0, res = -1;
+
+        for (int i = 0; i < nums.size(); i++) {
+            prefixSum += nums[i];
+            if (prefixMap.count(prefixSum - target)) {
+                res = max(res, i - prefixMap[prefixSum - target]);
+            }
+            prefixMap[prefixSum] = i;
+        }
+
+        return res == -1 ? -1 : nums.size() - res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} x
+     * @return {number}
+     */
+    minOperations(nums, x) {
+        const total = nums.reduce((acc, num) => acc + num, 0);
+        if (total === x) return nums.length;
+
+        const target = total - x;
+        if (target < 0) return -1;
+
+        const prefixMap = new Map();
+        prefixMap.set(0, -1);
+        let prefixSum = 0, res = -1;
+
+        for (let i = 0; i < nums.length; i++) {
+            prefixSum += nums[i];
+            if (prefixMap.has(prefixSum - target)) {
+                res = Math.max(res, i - prefixMap.get(prefixSum - target));
+            }
+            prefixMap.set(prefixSum, i);
+        }
+
+        return res === -1 ? -1 : nums.length - res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Sliding Window
+
+::tabs-start
+
+```python
+class Solution:
+    def minOperations(self, nums: List[int], x: int) -> int:
+        target = sum(nums) - x
+        cur_sum = 0
+        max_window = -1
+        l = 0
+
+        for r in range(len(nums)):
+            cur_sum += nums[r]
+
+            while l <= r and cur_sum > target:
+                cur_sum -= nums[l]
+                l += 1
+
+            if cur_sum == target:
+                max_window = max(max_window, r - l + 1)
+
+        return -1 if max_window == -1 else len(nums) - max_window
+```
+
+```java
+public class Solution {
+    public int minOperations(int[] nums, int x) {
+        int target = 0;
+        for (int num : nums) target += num;
+        target -= x;
+
+        int curSum = 0, maxWindow = -1, l = 0;
+
+        for (int r = 0; r < nums.length; r++) {
+            curSum += nums[r];
+
+            while (l <= r && curSum > target) {
+                curSum -= nums[l];
+                l++;
+            }
+
+            if (curSum == target) {
+                maxWindow = Math.max(maxWindow, r - l + 1);
+            }
+        }
+
+        return maxWindow == -1 ? -1 : nums.length - maxWindow;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minOperations(vector<int>& nums, int x) {
+        int target = accumulate(nums.begin(), nums.end(), 0) - x;
+        int curSum = 0, maxWindow = -1, l = 0;
+
+        for (int r = 0; r < nums.size(); r++) {
+            curSum += nums[r];
+
+            while (l <= r && curSum > target) {
+                curSum -= nums[l];
+                l++;
+            }
+
+            if (curSum == target) {
+                maxWindow = max(maxWindow, r - l + 1);
+            }
+        }
+
+        return maxWindow == -1 ? -1 : nums.size() - maxWindow;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} x
+     * @return {number}
+     */
+    minOperations(nums, x) {
+        const target = nums.reduce((acc, num) => acc + num, 0) - x;
+        let curSum = 0, maxWindow = -1, l = 0;
+
+        for (let r = 0; r < nums.length; r++) {
+            curSum += nums[r];
+
+            while (l <= r && curSum > target) {
+                curSum -= nums[l];
+                l++;
+            }
+
+            if (curSum === target) {
+                maxWindow = Math.max(maxWindow, r - l + 1);
+            }
+        }
+
+        return maxWindow === -1 ? -1 : nums.length - maxWindow;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/minimum-path-sum.md b/articles/minimum-path-sum.md
new file mode 100644
index 000000000..37968cf67
--- /dev/null
+++ b/articles/minimum-path-sum.md
@@ -0,0 +1,395 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def minPathSum(self, grid: List[List[int]]) -> int:
+        def dfs(r, c):
+            if r == len(grid) - 1 and c == len(grid[0]) - 1:
+                return grid[r][c]
+            if r == len(grid) or c == len(grid[0]):
+                return float('inf')
+            return grid[r][c] + min(dfs(r + 1, c), dfs(r, c + 1))
+
+        return dfs(0, 0)
+```
+
+```java
+public class Solution {
+    public int minPathSum(int[][] grid) {
+        return dfs(0, 0, grid);
+    }
+
+    public int dfs(int r, int c, int[][] grid) {
+        if (r == grid.length - 1 && c == grid[0].length - 1) {
+            return grid[r][c];
+        }
+        if (r == grid.length || c == grid[0].length) {
+            return Integer.MAX_VALUE;
+        }
+        return grid[r][c] + Math.min(dfs(r + 1, c, grid), dfs(r, c + 1, grid));
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minPathSum(vector<vector<int>>& grid) {
+        return dfs(0, 0, grid);
+    }
+
+    int dfs(int r, int c, vector<vector<int>>& grid) {
+        if (r == grid.size() - 1 && c == grid[0].size() - 1) {
+            return grid[r][c];
+        }
+        if (r == grid.size() || c == grid[0].size()) {
+            return INT_MAX;
+        }
+        return grid[r][c] + min(dfs(r + 1, c, grid), dfs(r, c + 1, grid));
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    minPathSum(grid) {
+        const dfs = (r, c) => {
+            if (r === grid.length - 1 && c === grid[0].length - 1) {
+                return grid[r][c];
+            }
+            if (r === grid.length || c === grid[0].length) {
+                return Infinity;
+            }
+            return grid[r][c] + Math.min(dfs(r + 1, c), dfs(r, c + 1));
+        };
+
+        return dfs(0, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ {m + n})$
+* Space complexity: $O(m + n)$ for recursion stack.
+
+> Where $m$ is the number of rows and $n$ is the number of columns.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def minPathSum(self, grid: List[List[int]]) -> int:
+        m, n = len(grid), len(grid[0])
+        dp = [[-1] * n for _ in range(m)]
+
+        def dfs(r, c):
+            if r == m - 1 and c == n - 1:
+                return grid[r][c]
+            if r == m or c == n:
+                return float('inf')
+            if dp[r][c] != -1:
+                return dp[r][c]
+
+            dp[r][c] = grid[r][c] + min(dfs(r + 1, c), dfs(r, c + 1))
+            return dp[r][c]
+
+        return dfs(0, 0)
+```
+
+```java
+public class Solution {
+    private int[][] dp;
+
+    public int minPathSum(int[][] grid) {
+        int m = grid.length, n = grid[0].length;
+        dp = new int[m][n];
+        for (int i = 0; i < m; i++) {
+            for (int j = 0; j < n; j++) {
+                dp[i][j] = -1;
+            }
+        }
+        return dfs(0, 0, grid);
+    }
+
+    public int dfs(int r, int c, int[][] grid) {
+        if (r == grid.length - 1 && c == grid[0].length - 1) {
+            return grid[r][c];
+        }
+        if (r == grid.length || c == grid[0].length) {
+            return Integer.MAX_VALUE;
+        }
+        if (dp[r][c] != -1) {
+            return dp[r][c];
+        }
+
+        dp[r][c] = grid[r][c] + Math.min(dfs(r + 1, c, grid), dfs(r, c + 1, grid));
+        return dp[r][c];
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<vector<int>> dp;
+
+public:
+    int minPathSum(vector<vector<int>>& grid) {
+        int m = grid.size(), n = grid[0].size();
+        dp = vector<vector<int>>(m, vector<int>(n, -1));
+        return dfs(0, 0, grid);
+    }
+
+    int dfs(int r, int c, vector<vector<int>>& grid) {
+        if (r == grid.size() - 1 && c == grid[0].size() - 1) {
+            return grid[r][c];
+        }
+        if (r == grid.size() || c == grid[0].size()) {
+            return INT_MAX;
+        }
+        if (dp[r][c] != -1) {
+            return dp[r][c];
+        }
+
+        dp[r][c] = grid[r][c] + min(dfs(r + 1, c, grid), dfs(r, c + 1, grid));
+        return dp[r][c];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    minPathSum(grid) {
+        const m = grid.length, n = grid[0].length;
+        const dp = Array.from({ length: m }, () => Array(n).fill(-1));
+
+        const dfs = (r, c) => {
+            if (r === m - 1 && c === n - 1) {
+                return grid[r][c];
+            }
+            if (r === m || c === n) {
+                return Infinity;
+            }
+            if (dp[r][c] !== -1) {
+                return dp[r][c];
+            }
+
+            dp[r][c] = grid[r][c] + Math.min(dfs(r + 1, c), dfs(r, c + 1));
+            return dp[r][c];
+        };
+
+        return dfs(0, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def minPathSum(self, grid: List[List[int]]) -> int:
+        ROWS, COLS = len(grid), len(grid[0])
+        dp = [[float("inf")] * (COLS + 1) for _ in range(ROWS + 1)]
+        dp[ROWS - 1][COLS] = 0
+
+        for r in range(ROWS - 1, -1, -1):
+            for c in range(COLS - 1, -1, -1):
+                dp[r][c] = grid[r][c] + min(dp[r + 1][c], dp[r][c + 1])
+
+        return dp[0][0]
+```
+
+```java
+public class Solution {
+    public int minPathSum(int[][] grid) {
+        int ROWS = grid.length, COLS = grid[0].length;
+        int[][] dp = new int[ROWS + 1][COLS + 1];
+
+        for (int r = 0; r <= ROWS; r++) {
+            for (int c = 0; c <= COLS; c++) {
+                dp[r][c] = Integer.MAX_VALUE;
+            }
+        }
+        dp[ROWS - 1][COLS] = 0;
+
+        for (int r = ROWS - 1; r >= 0; r--) {
+            for (int c = COLS - 1; c >= 0; c--) {
+                dp[r][c] = grid[r][c] + Math.min(dp[r + 1][c], dp[r][c + 1]);
+            }
+        }
+
+        return dp[0][0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minPathSum(vector<vector<int>>& grid) {
+        int ROWS = grid.size(), COLS = grid[0].size();
+        vector<vector<int>> dp(ROWS + 1, vector<int>(COLS + 1, INT_MAX));
+        dp[ROWS - 1][COLS] = 0;
+
+        for (int r = ROWS - 1; r >= 0; r--) {
+            for (int c = COLS - 1; c >= 0; c--) {
+                dp[r][c] = grid[r][c] + min(dp[r + 1][c], dp[r][c + 1]);
+            }
+        }
+
+        return dp[0][0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    minPathSum(grid) {
+        const ROWS = grid.length, COLS = grid[0].length;
+        const dp = Array.from({ length: ROWS + 1 }, () => Array(COLS + 1).fill(Infinity));
+        dp[ROWS - 1][COLS] = 0;
+
+        for (let r = ROWS - 1; r >= 0; r--) {
+            for (let c = COLS - 1; c >= 0; c--) {
+                dp[r][c] = grid[r][c] + Math.min(dp[r + 1][c], dp[r][c + 1]);
+            }
+        }
+
+        return dp[0][0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns.
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def minPathSum(self, grid: List[List[int]]) -> int:
+        ROWS, COLS = len(grid), len(grid[0])
+        dp = [float("inf")] * (COLS + 1)
+        dp[COLS - 1] = 0
+
+        for r in range(ROWS - 1, -1, -1):
+            for c in range(COLS - 1, -1, -1):
+                dp[c] = grid[r][c] + min(dp[c], dp[c + 1])
+
+        return dp[0]
+```
+
+```java
+public class Solution {
+    public int minPathSum(int[][] grid) {
+        int ROWS = grid.length, COLS = grid[0].length;
+        int[] dp = new int[COLS + 1];
+        for (int c = 0; c <= COLS; c++) {
+            dp[c] = Integer.MAX_VALUE;
+        }
+        dp[COLS - 1] = 0;
+
+        for (int r = ROWS - 1; r >= 0; r--) {
+            for (int c = COLS - 1; c >= 0; c--) {
+                dp[c] = grid[r][c] + Math.min(dp[c], dp[c + 1]);
+            }
+        }
+
+        return dp[0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minPathSum(vector<vector<int>>& grid) {
+        int ROWS = grid.size(), COLS = grid[0].size();
+        vector<int> dp(COLS + 1, INT_MAX);
+        dp[COLS - 1] = 0;
+
+        for (int r = ROWS - 1; r >= 0; r--) {
+            for (int c = COLS - 1; c >= 0; c--) {
+                dp[c] = grid[r][c] + min(dp[c], dp[c + 1]);
+            }
+        }
+
+        return dp[0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    minPathSum(grid) {
+        const ROWS = grid.length, COLS = grid[0].length;
+        const dp = new Array(COLS + 1).fill(Infinity);
+        dp[COLS - 1] = 0;
+
+        for (let r = ROWS - 1; r >= 0; r--) {
+            for (let c = COLS - 1; c >= 0; c--) {
+                dp[c] = grid[r][c] + Math.min(dp[c], dp[c + 1]);
+            }
+        }
+
+        return dp[0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns.
\ No newline at end of file
diff --git a/articles/minimum-penalty-for-a-shop.md b/articles/minimum-penalty-for-a-shop.md
new file mode 100644
index 000000000..a3e506a88
--- /dev/null
+++ b/articles/minimum-penalty-for-a-shop.md
@@ -0,0 +1,497 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def bestClosingTime(self, customers: str) -> int:
+        n = len(customers)
+        res = n
+        minPenalty = n
+
+        for i in range(n + 1):
+            penalty = 0
+            for j in range(i):
+                if customers[j] == 'N':
+                    penalty += 1
+            for j in range(i, n):
+                if customers[j] == 'Y':
+                    penalty += 1
+                    
+            if penalty < minPenalty:
+                minPenalty = penalty
+                res = i
+
+        return res
+```
+
+```java
+public class Solution {
+    public int bestClosingTime(String customers) {
+        int n = customers.length();
+        int res = n, minPenalty = n;
+
+        for (int i = 0; i <= n; i++) {
+            int penalty = 0;
+            for (int j = 0; j < i; j++) {
+                if (customers.charAt(j) == 'N') {
+                    penalty++;
+                }
+            }
+            for (int j = i; j < n; j++) {
+                if (customers.charAt(j) == 'Y') {
+                    penalty++;
+                }
+            }
+
+            if (penalty < minPenalty) {
+                minPenalty = penalty;
+                res = i;
+            }
+        }
+        
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int bestClosingTime(string customers) {
+        int n = customers.size();
+        int res = n, minPenalty = n;
+
+        for (int i = 0; i <= n; i++) {
+            int penalty = 0;
+            for (int j = 0; j < i; j++) {
+                if (customers[j] == 'N') {
+                    penalty++;
+                }
+            }
+            for (int j = i; j < n; j++) {
+                if (customers[j] == 'Y') {
+                    penalty++;
+                }
+            }
+            
+            if (penalty < minPenalty) {
+                minPenalty = penalty;
+                res = i;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} customers
+     * @return {number}
+     */
+    bestClosingTime(customers) {
+        const n = customers.length;
+        let res = n, minPenalty = n;
+
+        for (let i = 0; i <= n; i++) {
+            let penalty = 0;
+            for (let j = 0; j < i; j++) {
+                if (customers[j] === 'N') {
+                    penalty++;
+                }
+            }
+            for (let j = i; j < n; j++) {
+                if (customers[j] === 'Y') {
+                    penalty++;
+                }
+            }
+
+            if (penalty < minPenalty) {
+                minPenalty = penalty;
+                res = i;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Prefix & Suffix
+
+::tabs-start
+
+```python
+class Solution:
+    def bestClosingTime(self, customers: str) -> int:
+        n = len(customers)
+        cnt = 0
+
+        prefixN = []
+        for c in customers:
+            prefixN.append(cnt)
+            if c == 'N':
+                cnt += 1
+        prefixN.append(cnt)
+        
+        suffixY = [0] * (n + 1)
+        for i in range(n - 1, -1, -1):
+            suffixY[i] = suffixY[i + 1]
+            if customers[i] == 'Y':
+                suffixY[i] += 1
+        
+        res = n
+        minPenalty = n
+        for i in range(n + 1):
+            penalty = prefixN[i] + suffixY[i]
+            if penalty < minPenalty:
+                minPenalty = penalty
+                res = i
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int bestClosingTime(String customers) {
+        int n = customers.length();
+        int cnt = 0;
+
+        int[] prefixN = new int[n + 1];
+        for (int i = 0; i < n; i++) {
+            prefixN[i] = cnt;
+            if (customers.charAt(i) == 'N') {
+                cnt++;
+            }
+        }
+        prefixN[n] = cnt;
+
+        int[] suffixY = new int[n + 1];
+        for (int i = n - 1; i >= 0; i--) {
+            suffixY[i] = suffixY[i + 1];
+            if (customers.charAt(i) == 'Y') {
+                suffixY[i]++;
+            }
+        }
+
+        int res = n, minPenalty = n;
+        for (int i = 0; i <= n; i++) {
+            int penalty = prefixN[i] + suffixY[i];
+            if (penalty < minPenalty) {
+                minPenalty = penalty;
+                res = i;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int bestClosingTime(string customers) {
+        int n = customers.size(), cnt = 0;
+
+        vector<int> prefixN(n + 1);
+        for (int i = 0; i < n; i++) {
+            prefixN[i] = cnt;
+            if (customers[i] == 'N') {
+                cnt++;
+            }
+        }
+        prefixN[n] = cnt;
+
+        vector<int> suffixY(n + 1, 0);
+        for (int i = n - 1; i >= 0; i--) {
+            suffixY[i] = suffixY[i + 1];
+            if (customers[i] == 'Y') {
+                suffixY[i]++;
+            }
+        }
+
+        int res = n, minPenalty = n;
+        for (int i = 0; i <= n; i++) {
+            int penalty = prefixN[i] + suffixY[i];
+            if (penalty < minPenalty) {
+                minPenalty = penalty;
+                res = i;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} customers
+     * @return {number}
+     */
+    bestClosingTime(customers) {
+        const n = customers.length;
+        let cnt = 0;
+
+        const prefixN = [];
+        for (const c of customers) {
+            prefixN.push(cnt);
+            if (c === 'N') {
+                cnt++;
+            }
+        }
+        prefixN.push(cnt);
+
+        const suffixY = new Array(n + 1).fill(0);
+        for (let i = n - 1; i >= 0; i--) {
+            suffixY[i] = suffixY[i + 1];
+            if (customers[i] === 'Y') {
+                suffixY[i]++;
+            }
+        }
+
+        let res = n, minPenalty = n;
+        for (let i = 0; i <= n; i++) {
+            const penalty = prefixN[i] + suffixY[i];
+            if (penalty < minPenalty) {
+                minPenalty = penalty;
+                res = i;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Iteration (Two Pass)
+
+::tabs-start
+
+```python
+class Solution:
+    def bestClosingTime(self, customers: str) -> int:
+        cntY = sum(c == "Y" for c in customers)
+
+        minPenalty = cntY
+        res = cntN = 0
+        for i, c in enumerate(customers):
+            if c == "Y":
+                cntY -= 1
+            else:
+                cntN += 1
+
+            penalty = cntN + cntY
+            if penalty < minPenalty:
+                res = i + 1
+                minPenalty = penalty
+
+        return res
+```
+
+```java
+public class Solution {
+    public int bestClosingTime(String customers) {
+        int cntY = 0;
+        for (char c : customers.toCharArray()) {
+            if (c == 'Y') cntY++;
+        }
+
+        int minPenalty = cntY, res = 0, cntN = 0;
+        for (int i = 0; i < customers.length(); i++) {
+            if (customers.charAt(i) == 'Y') {
+                cntY--;
+            } else {
+                cntN++;
+            }
+
+            int penalty = cntN + cntY;
+            if (penalty < minPenalty) {
+                res = i + 1;
+                minPenalty = penalty;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int bestClosingTime(string customers) {
+        int cntY = count(customers.begin(), customers.end(), 'Y');
+        
+        int minPenalty = cntY, res = 0, cntN = 0;
+        for (int i = 0; i < customers.size(); i++) {
+            if (customers[i] == 'Y') {
+                cntY--;
+            } else {
+                cntN++;
+            }
+
+            int penalty = cntN + cntY;
+            if (penalty < minPenalty) {
+                res = i + 1;
+                minPenalty = penalty;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} customers
+     * @return {number}
+     */
+    bestClosingTime(customers) {
+        let cntY = 0;
+        for (let c of customers) {
+            if (c === 'Y') cntY++;
+        }
+
+        let minPenalty = cntY, res = 0, cntN = 0;
+        for (let i = 0; i < customers.length; i++) {
+            if (customers[i] === 'Y') {
+                cntY--;
+            } else {
+                cntN++;
+            }
+
+            const penalty = cntN + cntY;
+            if (penalty < minPenalty) {
+                res = i + 1;
+                minPenalty = penalty;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 4. Iteration (One Pass)
+
+::tabs-start
+
+```python
+class Solution:
+    def bestClosingTime(self, customers: str) -> int:
+        res = minPenalty = 0
+        penalty = 0
+
+        for i, c in enumerate(customers):
+            penalty += 1 if c == 'Y' else -1
+
+            if penalty > minPenalty:
+                minPenalty = penalty
+                res = i + 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int bestClosingTime(String customers) {
+        int res = 0, minPenalty = 0, penalty = 0;
+
+        for (int i = 0; i < customers.length(); i++) {
+            penalty += customers.charAt(i) == 'Y' ? 1 : -1;
+
+            if (penalty > minPenalty) {
+                minPenalty = penalty;
+                res = i + 1;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int bestClosingTime(string customers) {
+        int res = 0, minPenalty = 0, penalty = 0;
+
+        for (int i = 0; i < customers.size(); i++) {
+            penalty += customers[i] == 'Y' ? 1 : -1;
+
+            if (penalty > minPenalty) {
+                minPenalty = penalty;
+                res = i + 1;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} customers
+     * @return {number}
+     */
+    bestClosingTime(customers) {
+        let res = 0, minPenalty = 0, penalty = 0;
+
+        for (let i = 0; i < customers.length; i++) {
+            penalty += customers[i] === 'Y' ? 1 : -1;
+
+            if (penalty > minPenalty) {
+                minPenalty = penalty;
+                res = i + 1;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/minimum-remove-to-make-valid-parentheses.md b/articles/minimum-remove-to-make-valid-parentheses.md
new file mode 100644
index 000000000..43c6d5981
--- /dev/null
+++ b/articles/minimum-remove-to-make-valid-parentheses.md
@@ -0,0 +1,646 @@
+## 1. Stack
+
+::tabs-start
+
+```python
+class Solution:
+    def minRemoveToMakeValid(self, s: str) -> str:
+        res = []
+        cnt = 0  # extra ( parentheses
+        for c in s:
+            if c == "(":
+                res.append(c)
+                cnt += 1
+            elif c == ")" and cnt > 0:
+                res.append(c)
+                cnt -= 1
+            elif c != ")":
+                res.append(c)
+
+        filtered = []
+        for c in reversed(res):
+            if c == "(" and cnt > 0:
+                cnt -= 1
+            else:
+                filtered.append(c)
+        return "".join(reversed(filtered))
+```
+
+```java
+public class Solution {
+    public String minRemoveToMakeValid(String s) {
+        StringBuilder res = new StringBuilder();
+        int cnt = 0;
+
+        for (char c : s.toCharArray()) {
+            if (c == '(') {
+                res.append(c);
+                cnt++;
+            } else if (c == ')' && cnt > 0) {
+                res.append(c);
+                cnt--;
+            } else if (c != ')') {
+                res.append(c);
+            }
+        }
+
+        StringBuilder filtered = new StringBuilder();
+        for (int i = res.length() - 1; i >= 0; i--) {
+            char c = res.charAt(i);
+            if (c == '(' && cnt > 0) {
+                cnt--;
+            } else {
+                filtered.append(c);
+            }
+        }
+        return filtered.reverse().toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string minRemoveToMakeValid(string s) {
+        string res;
+        int cnt = 0;
+
+        for (char c : s) {
+            if (c == '(') {
+                res.push_back(c);
+                cnt++;
+            } else if (c == ')' && cnt > 0) {
+                res.push_back(c);
+                cnt--;
+            } else if (c != ')') {
+                res.push_back(c);
+            }
+        }
+
+        string filtered;
+        for (int i = res.size() - 1; i >= 0; i--) {
+            char c = res[i];
+            if (c == '(' && cnt > 0) {
+                cnt--;
+            } else {
+                filtered.push_back(c);
+            }
+        }
+        reverse(filtered.begin(), filtered.end());
+        return filtered;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string}
+     */
+    minRemoveToMakeValid(s) {
+        let res = [];
+        let cnt = 0;
+
+        for (let c of s) {
+            if (c === '(') {
+                res.push(c);
+                cnt++;
+            } else if (c === ')' && cnt > 0) {
+                res.push(c);
+                cnt--;
+            } else if (c !== ')') {
+                res.push(c);
+            }
+        }
+
+        let filtered = [];
+        for (let i = res.length - 1; i >= 0; i--) {
+            let c = res[i];
+            if (c === '(' && cnt > 0) {
+                cnt--;
+            } else {
+                filtered.push(c);
+            }
+        }
+        return filtered.reverse().join('');
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public string MinRemoveToMakeValid(string s) {
+        List<char> res = new List<char>();
+        int cnt = 0;
+
+        foreach (char c in s) {
+            if (c == '(') {
+                res.Add(c);
+                cnt++;
+            } else if (c == ')' && cnt > 0) {
+                res.Add(c);
+                cnt--;
+            } else if (c != ')') {
+                res.Add(c);
+            }
+        }
+
+        List<char> filtered = new List<char>();
+        for (int i = res.Count - 1; i >= 0; i--) {
+            if (res[i] == '(' && cnt > 0) {
+                cnt--;
+            } else {
+                filtered.Add(res[i]);
+            }
+        }
+
+        filtered.Reverse();
+        return new string(filtered.ToArray());
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Without Stack
+
+::tabs-start
+
+```python
+class Solution:
+    def minRemoveToMakeValid(self, s: str) -> str:
+        arr = list(s)
+        cnt = 0  # extra ( parentheses
+        for i, c in enumerate(s):
+            if c == "(":
+                cnt += 1
+            elif c == ")" and cnt > 0:
+                cnt -= 1
+            elif c == ")":
+                arr[i] = ''
+        
+        res = []
+        for c in reversed(arr):
+            if c == '(' and cnt > 0:
+                cnt -= 1
+            else:
+                res.append(c)
+        
+        return ''.join(reversed(res))
+```
+
+```java
+public class Solution {
+    public String minRemoveToMakeValid(String s) {
+        char[] arr = s.toCharArray();
+        int cnt = 0;
+
+        for (int i = 0; i < s.length(); i++) {
+            char c = s.charAt(i);
+            if (c == '(') {
+                cnt++;
+            } else if (c == ')' && cnt > 0) {
+                cnt--;
+            } else if (c == ')') {
+                arr[i] = '\0';
+            }
+        }
+
+        StringBuilder res = new StringBuilder();
+        for (int i = arr.length - 1; i >= 0; i--) {
+            char c = arr[i];
+            if (c == '(' && cnt > 0) {
+                cnt--;
+            } else if (c != '\0') {
+                res.append(c);
+            }
+        }
+
+        return res.reverse().toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string minRemoveToMakeValid(string s) {
+        vector<char> arr(s.begin(), s.end());
+        int cnt = 0;
+
+        for (int i = 0; i < s.size(); i++) {
+            if (s[i] == '(') {
+                cnt++;
+            } else if (s[i] == ')' && cnt > 0) {
+                cnt--;
+            } else if (s[i] == ')') {
+                arr[i] = '\0';
+            }
+        }
+
+        string res;
+        for (int i = arr.size() - 1; i >= 0; i--) {
+            if (arr[i] == '(' && cnt > 0) {
+                cnt--;
+            } else if (arr[i] != '\0') {
+                res.push_back(arr[i]);
+            }
+        }
+
+        reverse(res.begin(), res.end());
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string}
+     */
+    minRemoveToMakeValid(s) {
+        let arr = [...s];
+        let cnt = 0;
+
+        for (let i = 0; i < s.length; i++) {
+            let c = s[i];
+            if (c === '(') {
+                cnt++;
+            } else if (c === ')' && cnt > 0) {
+                cnt--;
+            } else if (c === ')') {
+                arr[i] = '';
+            }
+        }
+
+        let res = [];
+        for (let i = arr.length - 1; i >= 0; i--) {
+            let c = arr[i];
+            if (c === '(' && cnt > 0) {
+                cnt--;
+            } else if (c !== '') {
+                res.push(c);
+            }
+        }
+
+        return res.reverse().join('');
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public string MinRemoveToMakeValid(string s) {
+        char[] arr = s.ToCharArray();
+        int cnt = 0;
+
+        for (int i = 0; i < s.Length; i++) {
+            if (s[i] == '(') {
+                cnt++;
+            } else if (s[i] == ')' && cnt > 0) {
+                cnt--;
+            } else if (s[i] == ')') {
+                arr[i] = '\0'; // mark invalid ')'
+            }
+        }
+
+        List<char> res = new List<char>();
+        for (int i = arr.Length - 1; i >= 0; i--) {
+            if (arr[i] == '(' && cnt > 0) {
+                cnt--;
+            } else if (arr[i] != '\0') {
+                res.Add(arr[i]);
+            }
+        }
+
+        res.Reverse();
+        return new string(res.ToArray());
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Stack (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def minRemoveToMakeValid(self, s: str) -> str:
+        s = list(s)
+        stack = []
+        for i, c in enumerate(s):
+            if c == '(':
+                stack.append(i)
+            elif c == ')':
+                if stack:
+                    stack.pop()
+                else:
+                    s[i] = ''
+        
+        while stack:
+            s[stack.pop()] = ''
+        return ''.join(s)
+```
+
+```java
+public class Solution {
+    public String minRemoveToMakeValid(String s) {
+        StringBuilder sb = new StringBuilder(s);
+        Stack<Integer> stack = new Stack<>();
+
+        for (int i = 0; i < sb.length(); i++) {
+            if (sb.charAt(i) == '(') {
+                stack.push(i);
+            } else if (sb.charAt(i) == ')') {
+                if (!stack.isEmpty()) {
+                    stack.pop();
+                } else {
+                    sb.setCharAt(i, '\0');
+                }
+            }
+        }
+
+        while (!stack.isEmpty()) {
+            sb.setCharAt(stack.pop(), '\0');
+        }
+
+        StringBuilder result = new StringBuilder();
+        for (int i = 0; i < sb.length(); i++) {
+            if (sb.charAt(i) != '\0') {
+                result.append(sb.charAt(i));
+            }
+        }
+        return result.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string minRemoveToMakeValid(string s) {
+        stack<int> stack;
+        for (int i = 0; i < s.size(); i++) {
+            if (s[i] == '(') {
+                stack.push(i);
+            } else if (s[i] == ')') {
+                if (!stack.empty()) {
+                    stack.pop();
+                } else {
+                    s[i] = '\0';
+                }
+            }
+        }
+
+        while (!stack.empty()) {
+            s[stack.top()] = '\0';
+            stack.pop();
+        }
+
+        string result;
+        for (char& c : s) {
+            if (c != '\0') {
+                result += c;
+            }
+        }
+        return result;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string}
+     */
+    minRemoveToMakeValid(s) {
+        const arr = [...s];
+        const stack = [];
+
+        for (let i = 0; i < arr.length; i++) {
+            if (arr[i] === '(') {
+                stack.push(i);
+            } else if (arr[i] === ')') {
+                if (stack.length > 0) {
+                    stack.pop();
+                } else {
+                    arr[i] = '';
+                }
+            }
+        }
+
+        while (stack.length > 0) {
+            arr[stack.pop()] = '';
+        }
+
+        return arr.join('');
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public string MinRemoveToMakeValid(string s) {
+        char[] arr = s.ToCharArray();
+        Stack<int> stack = new Stack<int>();
+
+        for (int i = 0; i < arr.Length; i++) {
+            if (arr[i] == '(') {
+                stack.Push(i);
+            } else if (arr[i] == ')') {
+                if (stack.Count > 0) {
+                    stack.Pop();
+                } else {
+                    arr[i] = '\0';
+                }
+            }
+        }
+
+        while (stack.Count > 0) {
+            arr[stack.Pop()] = '\0';
+        }
+
+        StringBuilder result = new StringBuilder();
+        foreach (char c in arr) {
+            if (c != '\0') {
+                result.Append(c);
+            }
+        }
+
+        return result.ToString();
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Without Stack (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def minRemoveToMakeValid(self, s: str) -> str:
+        openCnt = closeCnt = 0
+        for c in s:
+            closeCnt += c == ')'
+        
+        res = []
+        for c in s:
+            if c == '(':
+                if openCnt == closeCnt:
+                    continue
+                openCnt += 1
+            elif c == ')':
+                closeCnt -= 1
+                if openCnt == 0:
+                    continue
+                openCnt -= 1
+            res.append(c)
+        
+        return ''.join(res)
+```
+
+```java
+public class Solution {
+    public String minRemoveToMakeValid(String s) {
+        int openCnt = 0, closeCnt = 0;
+        for (char c : s.toCharArray()) {
+            if (c == ')') closeCnt++;
+        }
+        
+        StringBuilder res = new StringBuilder();
+        for (char c : s.toCharArray()) {
+            if (c == '(') {
+                if (openCnt == closeCnt) continue;
+                openCnt++;
+            } else if (c == ')') {
+                closeCnt--;
+                if (openCnt == 0) continue;
+                openCnt--;
+            }
+            res.append(c);
+        }
+        
+        return res.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string minRemoveToMakeValid(string s) {
+        int openCnt = 0, closeCnt = 0;
+        for (char& c : s) {
+            if (c == ')') closeCnt++;
+        }
+        
+        string res;
+        for (char& c : s) {
+            if (c == '(') {
+                if (openCnt == closeCnt) continue;
+                openCnt++;
+            } else if (c == ')') {
+                closeCnt--;
+                if (openCnt == 0) continue;
+                openCnt--;
+            }
+            res.push_back(c);
+        }
+        
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string}
+     */
+    minRemoveToMakeValid(s) {
+        let openCnt = 0, closeCnt = 0;
+        for (const c of s) {
+            if (c === ')') closeCnt++;
+        }
+        
+        let res = [];
+        for (const c of s) {
+            if (c === '(') {
+                if (openCnt === closeCnt) continue;
+                openCnt++;
+            } else if (c === ')') {
+                closeCnt--;
+                if (openCnt === 0) continue;
+                openCnt--;
+            }
+            res.push(c);
+        }
+        
+        return res.join('');
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public string MinRemoveToMakeValid(string s) {
+        int openCnt = 0, closeCnt = 0;
+        foreach (char c in s) {
+            if (c == ')') closeCnt++;
+        }
+
+        StringBuilder res = new StringBuilder();
+        foreach (char c in s) {
+            if (c == '(') {
+                if (openCnt == closeCnt) continue;
+                openCnt++;
+            } else if (c == ')') {
+                closeCnt--;
+                if (openCnt == 0) continue;
+                openCnt--;
+            }
+            res.Append(c);
+        }
+
+        return res.ToString();
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ space for the output string.
\ No newline at end of file
diff --git a/articles/minimum-score-of-a-path-between-two-cities.md b/articles/minimum-score-of-a-path-between-two-cities.md
new file mode 100644
index 000000000..820b21739
--- /dev/null
+++ b/articles/minimum-score-of-a-path-between-two-cities.md
@@ -0,0 +1,646 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def minScore(self, n: int, roads: list[list[int]]) -> int:
+        adj = defaultdict(list)
+        for src, dst, dist in roads:
+            adj[src].append((dst, dist))
+            adj[dst].append((src, dist))
+
+        res = float("inf")
+        visit = set()
+
+        def dfs(node):
+            nonlocal res
+            if node in visit:
+                return
+            visit.add(node)
+            for nei, dist in adj[node]:
+                res = min(res, dist)
+                dfs(nei)
+
+        dfs(1)
+        return res
+```
+
+```java
+public class Solution {
+    private List<int[]>[] adj;
+    private boolean[] visit;
+    private int res;
+
+    public int minScore(int n, int[][] roads) {
+        adj = new ArrayList[n + 1];
+        visit = new boolean[n + 1];
+        res = Integer.MAX_VALUE;
+
+        for (int i = 0; i <= n; i++) {
+            adj[i] = new ArrayList<>();
+        }
+
+        for (int[] road : roads) {
+            adj[road[0]].add(new int[]{road[1], road[2]});
+            adj[road[1]].add(new int[]{road[0], road[2]});
+        }
+
+        dfs(1);
+        return res;
+    }
+
+    private void dfs(int node) {
+        if (visit[node]) return;
+        visit[node] = true;
+
+        for (int[] edge : adj[node]) {
+            res = Math.min(res, edge[1]);
+            dfs(edge[0]);
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<pair<int, int>>> adj;
+    vector<bool> visit;
+    int res;
+
+    int minScore(int n, vector<vector<int>>& roads) {
+        adj.resize(n + 1);
+        visit.resize(n + 1, false);
+        res = INT_MAX;
+
+        for (auto& road : roads) {
+            adj[road[0]].push_back({road[1], road[2]});
+            adj[road[1]].push_back({road[0], road[2]});
+        }
+
+        dfs(1);
+        return res;
+    }
+
+    void dfs(int node) {
+        if (visit[node]) return;
+        visit[node] = true;
+
+        for (auto& edge : adj[node]) {
+            res = min(res, edge.second);
+            dfs(edge.first);
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} roads
+     * @return {number}
+     */
+    minScore(n, roads) {
+        const adj = Array.from({ length: n + 1 }, () => []);
+        for (const [src, dst, dist] of roads) {
+            adj[src].push([dst, dist]);
+            adj[dst].push([src, dist]);
+        }
+
+        let res = Infinity;
+        const visit = new Array(n + 1).fill(false);
+
+        const dfs = (node) => {
+            if (visit[node]) return;
+            visit[node] = true;
+
+            for (const [nei, dist] of adj[node]) {
+                res = Math.min(res, dist);
+                dfs(nei);
+            }
+        };
+
+        dfs(1);
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + E)$
+* Space complexity: $O(V + E)$
+
+> Where $V$ is the number of vertices and $E$ is the number of edges.
+
+---
+
+## 2. Breadth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def minScore(self, n: int, roads: list[list[int]]) -> int:
+        adj = [[] for _ in range(n + 1)]
+        for src, dst, dist in roads:
+            adj[src].append((dst, dist))
+            adj[dst].append((src, dist))
+
+        res = float("inf")
+        visit = [False] * (n + 1)
+        q = deque([1])
+        visit[1] = True
+
+        while q:
+            node = q.popleft()
+            for nei, dist in adj[node]:
+                res = min(res, dist)
+                if not visit[nei]:
+                    visit[nei] = True
+                    q.append(nei)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int minScore(int n, int[][] roads) {
+        List<int[]>[] adj = new ArrayList[n + 1];
+        for (int i = 0; i <= n; i++) adj[i] = new ArrayList<>();
+
+        for (int[] road : roads) {
+            adj[road[0]].add(new int[]{road[1], road[2]});
+            adj[road[1]].add(new int[]{road[0], road[2]});
+        }
+
+        int res = Integer.MAX_VALUE;
+        boolean[] visit = new boolean[n + 1];
+        Queue<Integer> q = new LinkedList<>();
+        q.offer(1);
+        visit[1] = true;
+
+        while (!q.isEmpty()) {
+            int node = q.poll();
+            for (int[] edge : adj[node]) {
+                int nei = edge[0], dist = edge[1];
+                res = Math.min(res, dist);
+                if (!visit[nei]) {
+                    visit[nei] = true;
+                    q.offer(nei);
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minScore(int n, vector<vector<int>>& roads) {
+        vector<vector<pair<int, int>>> adj(n + 1);
+        for (auto& road : roads) {
+            adj[road[0]].emplace_back(road[1], road[2]);
+            adj[road[1]].emplace_back(road[0], road[2]);
+        }
+
+        int res = INT_MAX;
+        vector<bool> visit(n + 1, false);
+        queue<int> q;
+        q.push(1);
+        visit[1] = true;
+
+        while (!q.empty()) {
+            int node = q.front();q.pop();
+            for (auto& [nei, dist] : adj[node]) {
+                res = min(res, dist);
+                if (!visit[nei]) {
+                    visit[nei] = true;
+                    q.push(nei);
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} roads
+     * @return {number}
+     */
+    minScore(n, roads) {
+        const adj = Array.from({ length: n + 1 }, () => []);
+        for (const [src, dst, dist] of roads) {
+            adj[src].push([dst, dist]);
+            adj[dst].push([src, dist]);
+        }
+
+        let res = Infinity;
+        const visit = new Array(n + 1).fill(false);
+        const q = new Queue([1]);
+        visit[1] = true;
+
+        while (!q.isEmpty()) {
+            const node = q.pop();
+            for (const [nei, dist] of adj[node]) {
+                res = Math.min(res, dist);
+                if (!visit[nei]) {
+                    visit[nei] = true;
+                    q.push(nei);
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + E)$
+* Space complexity: $O(V + E)$
+
+> Where $V$ is the number of vertices and $E$ is the number of edges.
+
+---
+
+## 3. Iterative DFS
+
+::tabs-start
+
+```python
+class Solution:
+    def minScore(self, n: int, roads: list[list[int]]) -> int:
+        adj = [[] for _ in range(n + 1)]
+        for src, dst, dist in roads:
+            adj[src].append((dst, dist))
+            adj[dst].append((src, dist))
+
+        res = float("inf")
+        visit = [False] * (n + 1)
+        stack = [1]
+        visit[1] = True
+
+        while stack:
+            node = stack.pop()
+            for nei, dist in adj[node]:
+                res = min(res, dist)
+                if not visit[nei]:
+                    visit[nei] = True
+                    stack.append(nei)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int minScore(int n, int[][] roads) {
+        List<int[]>[] adj = new ArrayList[n + 1];
+        for (int i = 0; i <= n; i++) adj[i] = new ArrayList<>();
+
+        for (int[] road : roads) {
+            adj[road[0]].add(new int[]{road[1], road[2]});
+            adj[road[1]].add(new int[]{road[0], road[2]});
+        }
+
+        int res = Integer.MAX_VALUE;
+        boolean[] visit = new boolean[n + 1];
+        Stack<Integer> stack = new Stack<>();
+        stack.push(1);
+        visit[1] = true;
+
+        while (!stack.isEmpty()) {
+            int node = stack.pop();
+            for (int[] edge : adj[node]) {
+                int nei = edge[0], dist = edge[1];
+                res = Math.min(res, dist);
+                if (!visit[nei]) {
+                    visit[nei] = true;
+                    stack.push(nei);
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minScore(int n, vector<vector<int>>& roads) {
+        vector<vector<pair<int, int>>> adj(n + 1);
+        for (auto& road : roads) {
+            adj[road[0]].emplace_back(road[1], road[2]);
+            adj[road[1]].emplace_back(road[0], road[2]);
+        }
+
+        int res = INT_MAX;
+        vector<bool> visit(n + 1, false);
+        stack<int> stk;
+        stk.push(1);
+        visit[1] = true;
+
+        while (!stk.empty()) {
+            int node = stk.top();stk.pop();
+            for (auto& [nei, dist] : adj[node]) {
+                res = min(res, dist);
+                if (!visit[nei]) {
+                    visit[nei] = true;
+                    stk.push(nei);
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} roads
+     * @return {number}
+     */
+    minScore(n, roads) {
+        const adj = Array.from({ length: n + 1 }, () => []);
+        for (const [src, dst, dist] of roads) {
+            adj[src].push([dst, dist]);
+            adj[dst].push([src, dist]);
+        }
+
+        let res = Infinity;
+        const visit = new Array(n + 1).fill(false);
+        const stack = [1];
+        visit[1] = true;
+
+        while (stack.length) {
+            const node = stack.pop();
+            for (const [nei, dist] of adj[node]) {
+                res = Math.min(res, dist);
+                if (!visit[nei]) {
+                    visit[nei] = true;
+                    stack.push(nei);
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + E)$
+* Space complexity: $O(V + E)$
+
+> Where $V$ is the number of vertices and $E$ is the number of edges.
+
+---
+
+## 4. Disjoint Set Union
+
+::tabs-start
+
+```python
+class DSU:
+    def __init__(self, n):
+        self.Parent = list(range(n + 1))
+        self.Size = [1] * (n + 1)
+
+    def find(self, node):
+        if self.Parent[node] != node:
+            self.Parent[node] = self.find(self.Parent[node])
+        return self.Parent[node]
+
+    def union(self, u, v):
+        pu, pv = self.find(u), self.find(v)
+        if pu == pv:
+            return False
+        if self.Size[pu] >= self.Size[pv]:
+            self.Size[pu] += self.Size[pv]
+            self.Parent[pv] = pu
+        else:
+            self.Size[pv] += self.Size[pu]
+            self.Parent[pu] = pv
+        return True
+
+class Solution:
+    def minScore(self, n: int, roads: list[list[int]]) -> int:
+        dsu = DSU(n)
+        for src, dst, _ in roads:
+            dsu.union(src, dst)
+
+        res = float("inf")
+        root = dsu.find(1)
+        for src, dst, dist in roads:
+            if dsu.find(src) == root:
+                res = min(res, dist)
+
+        return res
+```
+
+```java
+class DSU {
+    int[] parent, size;
+
+    public DSU(int n) {
+        parent = new int[n + 1];
+        size = new int[n + 1];
+        for (int i = 0; i <= n; i++) {
+            parent[i] = i;
+            size[i] = 1;
+        }
+    }
+
+    public int find(int node) {
+        if (parent[node] != node) {
+            parent[node] = find(parent[node]);
+        }
+        return parent[node];
+    }
+
+    public boolean union(int u, int v) {
+        int pu = find(u), pv = find(v);
+        if (pu == pv) return false;
+        if (size[pu] >= size[pv]) {
+            size[pu] += size[pv];
+            parent[pv] = pu;
+        } else {
+            size[pv] += size[pu];
+            parent[pu] = pv;
+        }
+        return true;
+    }
+}
+
+public class Solution {
+    public int minScore(int n, int[][] roads) {
+        DSU dsu = new DSU(n);
+        for (int[] road : roads) {
+            dsu.union(road[0], road[1]);
+        }
+
+        int res = Integer.MAX_VALUE;
+        int root = dsu.find(1);
+        for (int[] road : roads) {
+            if (dsu.find(road[0]) == root) {
+                res = Math.min(res, road[2]);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class DSU {
+public:
+    vector<int> parent, size;
+    
+    DSU(int n) {
+        parent.resize(n + 1);
+        size.resize(n + 1, 1);
+        for (int i = 0; i <= n; i++) {
+            parent[i] = i;
+        }
+    }
+
+    int find(int node) {
+        if (parent[node] != node) {
+            parent[node] = find(parent[node]);
+        }
+        return parent[node];
+    }
+
+    bool unionSets(int u, int v) {
+        int pu = find(u), pv = find(v);
+        if (pu == pv) return false;
+        if (size[pu] >= size[pv]) {
+            size[pu] += size[pv];
+            parent[pv] = pu;
+        } else {
+            size[pv] += size[pu];
+            parent[pu] = pv;
+        }
+        return true;
+    }
+};
+
+class Solution {
+public:
+    int minScore(int n, vector<vector<int>>& roads) {
+        DSU dsu(n);
+        for (auto& road : roads) {
+            dsu.unionSets(road[0], road[1]);
+        }
+
+        int res = INT_MAX;
+        int root = dsu.find(1);
+        for (auto& road : roads) {
+            if (dsu.find(road[0]) == root) {
+                res = min(res, road[2]);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class DSU {
+    /**
+     * @constructor
+     * @param {number} n
+     */
+    constructor(n) {
+        this.parent = Array.from({ length: n + 1 }, (_, i) => i);
+        this.size = new Array(n + 1).fill(1);
+    }
+
+    /**
+     * @param {number} node
+     * @return {number}
+     */
+    find(node) {
+        if (this.parent[node] !== node) {
+            this.parent[node] = this.find(this.parent[node]);
+        }
+        return this.parent[node];
+    }
+
+    /**
+     * @param {number} u
+     * @param {number} u=v
+     * @return {boolean}
+     */
+    union(u, v) {
+        let pu = this.find(u), pv = this.find(v);
+        if (pu === pv) return false;
+        if (this.size[pu] >= this.size[pv]) {
+            this.size[pu] += this.size[pv];
+            this.parent[pv] = pu;
+        } else {
+            this.size[pv] += this.size[pu];
+            this.parent[pu] = pv;
+        }
+        return true;
+    }
+}
+
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} roads
+     * @return {number}
+     */
+    minScore(n, roads) {
+        const dsu = new DSU(n);
+        for (const [src, dst] of roads) {
+            dsu.union(src, dst);
+        }
+
+        let res = Infinity;
+        const root = dsu.find(1);
+        for (const [src, dst, dist] of roads) {
+            if (dsu.find(src) === root) {
+                res = Math.min(res, dist);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + (E * α(V)))$
+* Space complexity: $O(V)$
+
+> Where $V$ is the number of vertices and $E$ is the number of edges in the graph. $α()$ is used for amortized complexity.
\ No newline at end of file
diff --git a/articles/minimum-size-subarray-sum.md b/articles/minimum-size-subarray-sum.md
new file mode 100644
index 000000000..683582184
--- /dev/null
+++ b/articles/minimum-size-subarray-sum.md
@@ -0,0 +1,408 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def minSubArrayLen(self, target: int, nums: List[int]) -> int:
+        n = len(nums)
+        res = float("inf")
+
+        for i in range(n):
+            curSum = 0
+            for j in range(i, n):
+                curSum += nums[j]
+                if curSum >= target:
+                    res = min(res, j - i + 1)
+                    break
+        
+        return 0 if  res == float("inf") else res
+```
+
+```java
+public class Solution {
+    public int minSubArrayLen(int target, int[] nums) {
+        int n = nums.length;
+        int res =  Integer.MAX_VALUE;
+        
+        for (int i = 0; i < n; i++) {
+            int curSum = 0, j = i;
+            while (j < n) {
+                curSum += nums[j];
+                if (curSum >= target) {
+                    res = Math.min(res, j - i + 1);
+                    break;
+                }
+                j++;
+            }
+        }
+        
+        return res == Integer.MAX_VALUE ? 0 : res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minSubArrayLen(int target, vector<int>& nums) {
+        int n = nums.size();
+        int res =  INT_MAX;
+        
+        for (int i = 0; i < n; i++) {
+            int curSum = 0, j = i;
+            while (j < n) {
+                curSum += nums[j];
+                if (curSum >= target) {
+                    res = min(res, j - i + 1);
+                    break;
+                }
+                j++;
+            }
+        }
+        
+        return res == INT_MAX ? 0 : res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} target
+     * @param {number[]} nums
+     * @return {number}
+     */
+    minSubArrayLen(target, nums) {
+        let n = nums.length;
+        let res =  Infinity;
+        
+        for (let i = 0; i < n; i++) {
+            let curSum = 0, j = i;
+            while (j < n) {
+                curSum += nums[j];
+                if (curSum >= target) {
+                    res = Math.min(res, j - i + 1);
+                    break;
+                }
+                j++;
+            }
+        }
+        
+        return res == Infinity ? 0 : res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MinSubArrayLen(int target, int[] nums) {
+        int n = nums.Length;
+        int res = int.MaxValue;
+
+        for (int i = 0; i < n; i++) {
+            int curSum = 0;
+            for (int j = i; j < n; j++) {
+                curSum += nums[j];
+                if (curSum >= target) {
+                    res = Math.Min(res, j - i + 1);
+                    break;
+                }
+            }
+        }
+
+        return res == int.MaxValue ? 0 : res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 2. Sliding Window
+
+::tabs-start
+
+```python
+class Solution:
+    def minSubArrayLen(self, target: int, nums: List[int]) -> int:
+        l, total = 0, 0
+        res = float("inf")
+
+        for r in range(len(nums)):
+            total += nums[r]
+            while total >= target:
+                res = min(r - l + 1, res)
+                total -= nums[l]
+                l += 1
+
+        return 0 if res == float("inf") else res
+```
+
+```java
+public class Solution {
+    public int minSubArrayLen(int target, int[] nums) {
+        int l = 0, total = 0;
+        int res = Integer.MAX_VALUE;
+
+        for (int r = 0; r < nums.length; r++) {
+            total += nums[r];
+            while (total >= target) {
+                res = Math.min(r - l + 1, res);
+                total -= nums[l];
+                l++;
+            }
+        }
+
+        return res == Integer.MAX_VALUE ? 0 : res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minSubArrayLen(int target, vector<int>& nums) {
+        int l = 0, total = 0, res = INT_MAX;
+
+        for (int r = 0; r < nums.size(); r++) {
+            total += nums[r];
+            while (total >= target) {
+                res = min(r - l + 1, res);
+                total -= nums[l];
+                l++;
+            }
+        }
+
+        return res == INT_MAX ? 0 : res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} target
+     * @param {number[]} nums
+     * @return {number}
+     */
+    minSubArrayLen(target, nums) {
+        let l = 0, total = 0;
+        let res = Infinity;
+
+        for (let r = 0; r < nums.length; r++) {
+            total += nums[r];
+            while (total >= target) {
+                res = Math.min(r - l + 1, res);
+                total -= nums[l];
+                l++;
+            }
+        }
+
+        return res === Infinity ? 0 : res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MinSubArrayLen(int target, int[] nums) {
+        int l = 0, total = 0;
+        int res = int.MaxValue;
+
+        for (int r = 0; r < nums.Length; r++) {
+            total += nums[r];
+
+            while (total >= target) {
+                res = Math.Min(res, r - l + 1);
+                total -= nums[l];
+                l++;
+            }
+        }
+
+        return res == int.MaxValue ? 0 : res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 3. Prefix Sum + Binary Search
+
+::tabs-start
+
+```python
+class Solution:
+    def minSubArrayLen(self, target: int, nums: List[int]) -> int:
+        n = len(nums)
+        prefixSum = [0] * (n + 1)
+        for i in range(n):
+            prefixSum[i + 1] = prefixSum[i] + nums[i]
+        
+        res = n + 1
+        for i in range(n):
+            l, r = i, n
+            while l < r:
+                mid = (l + r) // 2
+                curSum = prefixSum[mid + 1] - prefixSum[i]
+                if curSum >= target:
+                    r = mid
+                else:
+                    l = mid + 1
+            if l != n:
+                res = min(res, l - i + 1)
+
+        return res % (n + 1)
+```
+
+```java
+public class Solution {
+    public int minSubArrayLen(int target, int[] nums) {
+        int n = nums.length;
+        int[] prefixSum = new int[n + 1];
+        for (int i = 0; i < n; i++) {
+            prefixSum[i + 1] = prefixSum[i] + nums[i];
+        }
+        
+        int res = n + 1;
+        for (int i = 0; i < n; i++) {
+            int l = i, r = n;
+            while (l < r) {
+                int mid = (l + r) / 2;
+                int curSum = prefixSum[mid + 1] - prefixSum[i];
+                if (curSum >= target) {
+                    r = mid;
+                } else {
+                    l = mid + 1;
+                }
+            }
+            if (l != n) {
+                res = Math.min(res, l - i + 1);
+            }
+        }
+
+        return res % (n + 1);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minSubArrayLen(int target, vector<int>& nums) {
+        int n = nums.size();
+        vector<int> prefixSum(n + 1, 0);
+        for (int i = 0; i < n; i++) {
+            prefixSum[i + 1] = prefixSum[i] + nums[i];
+        }
+        
+        int res = n + 1;
+        for (int i = 0; i < n; i++) {
+            int l = i, r = n;
+            while (l < r) {
+                int mid = (l + r) / 2;
+                int curSum = prefixSum[mid + 1] - prefixSum[i];
+                if (curSum >= target) {
+                    r = mid;
+                } else {
+                    l = mid + 1;
+                }
+            }
+            if (l != n) {
+                res = min(res, l - i + 1);
+            }
+        }
+
+        return res % (n + 1);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} target
+     * @param {number[]} nums
+     * @return {number}
+     */
+    minSubArrayLen(target, nums) {
+        const n = nums.length;
+        const prefixSum = new Array(n + 1).fill(0);
+        for (let i = 0; i < n; i++) {
+            prefixSum[i + 1] = prefixSum[i] + nums[i];
+        }
+        
+        let res = n + 1;
+        for (let i = 0; i < n; i++) {
+            let l = i, r = n;
+            while (l < r) {
+                const mid = Math.floor((l + r) / 2);
+                const curSum = prefixSum[mid + 1] - prefixSum[i];
+                if (curSum >= target) {
+                    r = mid;
+                } else {
+                    l = mid + 1;
+                }
+            }
+            if (l !== n) {
+                res = Math.min(res, l - i + 1);
+            }
+        }
+
+        return res % (n + 1);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MinSubArrayLen(int target, int[] nums) {
+        int n = nums.Length;
+        int[] prefixSum = new int[n + 1];
+        
+        for (int i = 0; i < n; i++) {
+            prefixSum[i + 1] = prefixSum[i] + nums[i];
+        }
+
+        int res = n + 1;
+
+        for (int i = 0; i < n; i++) {
+            int l = i, r = n;
+            while (l < r) {
+                int mid = (l + r) / 2;
+                int curSum = prefixSum[mid + 1] - prefixSum[i];
+                if (curSum >= target) {
+                    r = mid;
+                } else {
+                    l = mid + 1;
+                }
+            }
+            if (l != n) {
+                res = Math.Min(res, l - i + 1);
+            }
+        }
+
+        return res % (n + 1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/minimum-stack.md b/articles/minimum-stack.md
index 7bb3e4e84..29041a02c 100644
--- a/articles/minimum-stack.md
+++ b/articles/minimum-stack.md
@@ -196,6 +196,124 @@ public class MinStack {
 }
 ```
 
+```go
+type MinStack struct {
+    stack *linkedliststack.Stack
+}
+
+func Constructor() MinStack {
+    return MinStack{stack: linkedliststack.New()}
+}
+
+func (this *MinStack) Push(val int) {
+    this.stack.Push(val)
+}
+
+func (this *MinStack) Pop() {
+    this.stack.Pop()
+}
+
+func (this *MinStack) Top() int {
+    top, _ := this.stack.Peek()
+    return top.(int)
+}
+
+func (this *MinStack) GetMin() int {
+    tmp := linkedliststack.New()
+    min := this.Top()
+
+    for !this.stack.Empty() {
+        val, _ := this.stack.Pop()
+        min = getMin(min, val.(int))
+        tmp.Push(val)
+    }
+
+    for !tmp.Empty() {
+        val, _ := tmp.Pop()
+        this.stack.Push(val)
+    }
+
+    return min
+}
+
+func getMin(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class MinStack() {
+    private val stack = ArrayDeque<Int>()
+
+    fun push(`val`: Int) {
+        stack.addLast(`val`)
+    }
+
+    fun pop() {
+        stack.removeLast()
+    }
+
+    fun top(): Int {
+        return stack.last()
+    }
+
+    fun getMin(): Int {
+        val tmp = ArrayDeque<Int>()
+        var min = stack.last()
+
+        while (stack.isNotEmpty()) {
+            min = minOf(min, stack.last())
+            tmp.addLast(stack.removeLast())
+        }
+
+        while (tmp.isNotEmpty()) {
+            stack.addLast(tmp.removeLast())
+        }
+
+        return min
+    }
+}
+```
+
+```swift
+class MinStack {
+    private var stack: [Int] = []
+
+    init() {}
+
+    func push(_ val: Int) {
+        stack.append(val)
+    }
+
+    func pop() {
+        stack.popLast()
+    }
+
+    func top() -> Int {
+        return stack.last!
+    }
+
+    func getMin() -> Int {
+        var tmp = [Int]()
+        var mini = stack.last!
+
+        while !stack.isEmpty {
+            mini = min(mini, stack.last!)
+            tmp.append(stack.removeLast())
+        }
+
+        while !tmp.isEmpty {
+            stack.append(tmp.removeLast())
+        }
+
+        return mini
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -374,6 +492,102 @@ public class MinStack {
 }
 ```
 
+```go
+type MinStack struct {
+    stack    *linkedliststack.Stack
+    minStack *linkedliststack.Stack
+}
+
+func Constructor() MinStack {
+    return MinStack{
+        stack:    linkedliststack.New(),
+        minStack: linkedliststack.New(),
+    }
+}
+
+func (this *MinStack) Push(val int) {
+    this.stack.Push(val)
+    minVal := val
+    if !this.minStack.Empty() {
+        if top, ok := this.minStack.Peek(); ok {
+            if top.(int) < val {
+                minVal = top.(int)
+            }
+        }
+    }
+    this.minStack.Push(minVal)
+}
+
+func (this *MinStack) Pop() {
+    this.stack.Pop()
+    this.minStack.Pop()
+}
+
+func (this *MinStack) Top() int {
+    top, _ := this.stack.Peek()
+    return top.(int)
+}
+
+func (this *MinStack) GetMin() int {
+    min, _ := this.minStack.Peek()
+    return min.(int)
+}
+```
+
+```kotlin
+class MinStack() {
+    private val stack = ArrayDeque<Int>()
+    private val minStack = ArrayDeque<Int>()
+
+    fun push(`val`: Int) {
+        stack.addLast(`val`)
+        val minVal = if (minStack.isNotEmpty()) minOf(`val`, minStack.last()) else `val`
+        minStack.addLast(minVal)
+    }
+
+    fun pop() {
+        stack.removeLast()
+        minStack.removeLast()
+    }
+
+    fun top(): Int {
+        return stack.last()
+    }
+
+    fun getMin(): Int {
+        return minStack.last()
+    }
+}
+```
+
+```swift
+class MinStack {
+    private var stack: [Int] = []
+    private var minStack: [Int] = []
+
+    init() {}
+
+    func push(_ val: Int) {
+        stack.append(val)
+        let minVal = min(val, minStack.last ?? val)
+        minStack.append(minVal)
+    }
+
+    func pop() {
+        stack.popLast()
+        minStack.popLast()
+    }
+
+    func top() -> Int {
+        return stack.last!
+    }
+
+    func getMin() -> Int {
+        return minStack.last!
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -393,14 +607,14 @@ class MinStack:
         self.min = float('inf')
         self.stack = []
 
-    def push(self, x: int) -> None:
+    def push(self, val: int) -> None:
         if not self.stack:
             self.stack.append(0)
-            self.min = x
+            self.min = val
         else:
-            self.stack.append(x - self.min)
-            if x < self.min:
-                self.min = x
+            self.stack.append(val - self.min)
+            if val < self.min:
+                self.min = val
 
     def pop(self) -> None:
         if not self.stack:
@@ -431,13 +645,13 @@ public class MinStack {
         stack = new Stack<>();
     }
     
-    public void push(int x) {
+    public void push(int val) {
         if (stack.isEmpty()) {
             stack.push(0L);
-            min = x;
+            min = val;
         } else {
-            stack.push(x - min);
-            if (x < min) min = x;
+            stack.push(val - min);
+            if (val < min) min = val;
         }
     }
 
@@ -471,9 +685,7 @@ private:
     std::stack<long> stack;
 
 public:
-    MinStack() {
-        
-    }
+    MinStack() {}
     
     void push(int val) {
         if (stack.empty()) {
@@ -592,6 +804,134 @@ public class MinStack {
 }
 ```
 
+```go
+type MinStack struct {
+    min   int
+    stack []int
+}
+
+func Constructor() MinStack {
+    return MinStack{
+        min:   math.MaxInt64,
+        stack: []int{},
+    }
+}
+
+func (this *MinStack) Push(val int) {
+    if len(this.stack) == 0 {
+        this.stack = append(this.stack, 0)
+        this.min = val
+    } else {
+        this.stack = append(this.stack, val - this.min)
+        if val < this.min {
+            this.min = val
+        }
+    }
+}
+
+func (this *MinStack) Pop() {
+    if len(this.stack) == 0 {
+        return
+    }
+    pop := this.stack[len(this.stack)-1]
+    this.stack = this.stack[:len(this.stack)-1]
+    if pop < 0 {
+        this.min = this.min - pop
+    }
+}
+
+func (this *MinStack) Top() int {
+    top := this.stack[len(this.stack)-1]
+    if top > 0 {
+        return top + this.min
+    }
+    return this.min
+}
+
+func (this *MinStack) GetMin() int {
+    return this.min
+}
+```
+
+```kotlin
+class MinStack() {
+    private var min: Long = Long.MAX_VALUE
+    private val stack = ArrayDeque<Long>()
+
+    fun push(`val`: Int) {
+        val valAsLong = `val`.toLong()
+        if (stack.isEmpty()) {
+            stack.addLast(0L)
+            min = valAsLong
+        } else {
+            stack.addLast(valAsLong - min)
+            if (valAsLong < min) {
+                min = valAsLong
+            }
+        }
+    }
+
+    fun pop() {
+        if (stack.isEmpty()) return
+        val pop = stack.removeLast()
+        if (pop < 0) {
+            min -= pop
+        }
+    }
+
+    fun top(): Int {
+        val top = stack.last()
+        return if (top > 0) (top + min).toInt() else min.toInt()
+    }
+
+    fun getMin(): Int {
+        return min.toInt()
+    }
+}
+```
+
+```swift
+class MinStack {
+    private var minVal: Int = Int.max
+    private var stack: [Int] = []
+
+    init() {}
+
+    func push(_ val: Int) {
+        if stack.isEmpty {
+            stack.append(0)
+            minVal = val
+        } else {
+            stack.append(val - minVal)
+            if val < minVal {
+                minVal = val
+            }
+        }
+    }
+
+    func pop() {
+        if stack.isEmpty {
+            return
+        }
+        
+        let pop = stack.removeLast()
+        
+        if pop < 0 {
+            minVal -= pop
+        }
+    }
+
+    func top() -> Int {
+        let top = stack.last!
+        return top > 0 ? top + minVal : minVal
+    }
+
+    func getMin() -> Int {
+        return minVal
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/minimum-time-to-collect-all-apples-in-a-tree.md b/articles/minimum-time-to-collect-all-apples-in-a-tree.md
new file mode 100644
index 000000000..2ea61fe99
--- /dev/null
+++ b/articles/minimum-time-to-collect-all-apples-in-a-tree.md
@@ -0,0 +1,312 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def minTime(self, n: int, edges: List[List[int]], hasApple: List[bool]) -> int:
+        adj = {i: [] for i in range(n)}
+        for par, child in edges:
+            adj[par].append(child)
+            adj[child].append(par)
+
+        def dfs(cur, par):
+            time = 0
+            for child in adj[cur]:
+                if child == par:
+                    continue
+                childTime = dfs(child, cur)
+                if childTime > 0 or hasApple[child]:
+                    time += 2 + childTime
+            return time
+
+        return dfs(0, -1)
+```
+
+```java
+public class Solution {
+    public int minTime(int n, int[][] edges, List<Boolean> hasApple) {
+        List<Integer>[] adj = new ArrayList[n];
+        for (int i = 0; i < n; i++) {
+            adj[i] = new ArrayList<>();
+        }
+        for (int[] edge : edges) {
+            adj[edge[0]].add(edge[1]);
+            adj[edge[1]].add(edge[0]);
+        }
+
+        return dfs(0, -1, adj, hasApple);
+    }
+
+    private int dfs(int cur, int parent, List<Integer>[] adj, List<Boolean> hasApple) {
+        int time = 0;
+        for (int child : adj[cur]) {
+            if (child == parent) continue;
+            int childTime = dfs(child, cur, adj, hasApple);
+            if (childTime > 0 || hasApple.get(child)) {
+                time += 2 + childTime;
+            }
+        }
+        return time;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minTime(int n, vector<vector<int>>& edges, vector<bool>& hasApple) {
+        vector<vector<int>> adj(n);
+        for (const auto& edge : edges) {
+            adj[edge[0]].push_back(edge[1]);
+            adj[edge[1]].push_back(edge[0]);
+        }
+
+        return dfs(0, -1, adj, hasApple);
+    }
+
+private:
+    int dfs(int cur, int parent, vector<vector<int>>& adj, vector<bool>& hasApple) {
+        int time = 0;
+        for (int child : adj[cur]) {
+            if (child == parent) continue;
+            int childTime = dfs(child, cur, adj, hasApple);
+            if (childTime > 0 || hasApple[child]) {
+                time += 2 + childTime;
+            }
+        }
+        return time;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} edges
+     * @param {boolean[]} hasApple
+     * @return {number}
+     */
+    minTime(n, edges, hasApple) {
+        const adj = Array.from({ length: n }, () => []);
+        for (const [parent, child] of edges) {
+            adj[parent].push(child);
+            adj[child].push(parent);
+        }
+
+        const dfs = (cur, parent) => {
+            let time = 0;
+            for (const child of adj[cur]) {
+                if (child === parent) continue;
+                const childTime = dfs(child, cur);
+                if (childTime > 0 || hasApple[child]) {
+                    time += 2 + childTime;
+                }
+            }
+            return time;
+        };
+
+        return dfs(0, -1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + E)$
+* Space complexity: $O(V + E)$
+
+> Where  $V$ is the number of vertices and $E$ is the number of edges.
+
+---
+
+## 2. Topological Sort (Kahn's Algorithm)
+
+::tabs-start
+
+```python
+class Solution:
+    def minTime(self, n: int, edges: List[List[int]], hasApple: List[bool]) -> int:
+        adj = defaultdict(list)
+        indegree = [0] * n
+        for u, v in edges:
+            adj[u].append(v)
+            adj[v].append(u)
+            indegree[u] += 1
+            indegree[v] += 1
+
+        queue = deque()
+        for i in range(1, n):
+            if indegree[i] == 1:
+                queue.append(i)
+                indegree[i] = 0
+        
+        time = [0] * n
+        while queue:
+            node = queue.popleft()
+            for nei in adj[node]:
+                if indegree[nei] <= 0:
+                    continue
+                    
+                indegree[nei] -= 1
+                if hasApple[node] or time[node] > 0:
+                    time[nei] += time[node] + 2
+                if indegree[nei] == 1 and nei != 0:
+                    queue.append(nei)
+        
+        return time[0]
+```
+
+```java
+public class Solution {
+    public int minTime(int n, int[][] edges, List<Boolean> hasApple) {
+        List<Integer>[] adj = new ArrayList[n];
+        for (int i = 0; i < n; i++) {
+            adj[i] = new ArrayList<>();
+        }
+        int[] indegree = new int[n];
+        for (int[] edge : edges) {
+            adj[edge[0]].add(edge[1]);
+            adj[edge[1]].add(edge[0]);
+            indegree[edge[0]]++;
+            indegree[edge[1]]++;
+        }
+
+        Queue<Integer> queue = new LinkedList<>();
+        for (int i = 1; i < n; i++) {
+            if (indegree[i] == 1) {
+                queue.offer(i);
+                indegree[i] = 0;
+            }
+        }
+
+        int[] time = new int[n];
+        while (!queue.isEmpty()) {
+            int node = queue.poll();
+            for (int neighbor : adj[node]) {
+                if (indegree[neighbor] <= 0) {
+                    continue;
+                }
+
+                indegree[neighbor]--;
+                if (hasApple.get(node) || time[node] > 0) {
+                    time[neighbor] += time[node] + 2;
+                }
+                if (indegree[neighbor] == 1 && neighbor != 0) {
+                    queue.offer(neighbor);
+                }
+            }
+        }
+
+        return time[0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minTime(int n, vector<vector<int>>& edges, vector<bool>& hasApple) {
+        vector<vector<int>> adj(n);
+        vector<int> indegree(n, 0);
+
+        for (const auto& edge : edges) {
+            adj[edge[0]].push_back(edge[1]);
+            adj[edge[1]].push_back(edge[0]);
+            indegree[edge[0]]++;
+            indegree[edge[1]]++;
+        }
+
+        queue<int> q;
+        for (int i = 1; i < n; ++i) {
+            if (indegree[i] == 1) {
+                q.push(i);
+                indegree[i] = 0;
+            }
+        }
+
+        vector<int> time(n, 0);
+        while (!q.empty()) {
+            int node = q.front();
+            q.pop();
+            for (int neighbor : adj[node]) {
+                if (indegree[neighbor] <= 0) {
+                    continue;
+                }
+
+                indegree[neighbor]--;
+                if (hasApple[node] || time[node] > 0) {
+                    time[neighbor] += time[node] + 2;
+                }
+                if (indegree[neighbor] == 1 && neighbor != 0) {
+                    q.push(neighbor);
+                }
+            }
+        }
+
+        return time[0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} edges
+     * @param {boolean[]} hasApple
+     * @return {number}
+     */
+    minTime(n, edges, hasApple) {
+        const adj = Array.from({ length: n }, () => []);
+        const indegree = Array(n).fill(0);
+
+        for (const [u, v] of edges) {
+            adj[u].push(v);
+            adj[v].push(u);
+            indegree[u]++;
+            indegree[v]++;
+        }
+
+        const queue = new Queue();
+        for (let i = 1; i < n; i++) {
+            if (indegree[i] === 1) {
+                queue.push(i);
+                indegree[i] = 0;
+            }
+        }
+
+        const time = Array(n).fill(0);
+        while (!queue.isEmpty()) {
+            const node = queue.pop();
+            for (const neighbor of adj[node]) {
+                if (indegree[neighbor] <= 0) {
+                    continue;
+                }
+
+                indegree[neighbor]--;
+                if (hasApple[node] || time[node] > 0) {
+                    time[neighbor] += time[node] + 2;
+                }
+                if (indegree[neighbor] === 1 && neighbor !== 0) {
+                    queue.push(neighbor);
+                }
+            }
+        }
+
+        return time[0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + E)$
+* Space complexity: $O(V + E)$
+
+> Where  $V$ is the number of vertices and $E$ is the number of edges.
\ No newline at end of file
diff --git a/articles/minimum-time-to-make-rope-colorful.md b/articles/minimum-time-to-make-rope-colorful.md
new file mode 100644
index 000000000..a9d436a9d
--- /dev/null
+++ b/articles/minimum-time-to-make-rope-colorful.md
@@ -0,0 +1,270 @@
+## 1. Two Pointers - I
+
+::tabs-start
+
+```python
+class Solution:
+    def minCost(self, colors: str, neededTime: List[int]) -> int:
+        n = len(neededTime)
+        res = i = 0
+        while i < n:
+            j = i
+            maxi = curr = 0
+            while j < n and colors[j] == colors[i]:
+                maxi = max(maxi, neededTime[j])
+                curr += neededTime[j]
+                j += 1
+            res += curr - maxi
+            i = j
+        return res
+```
+
+```java
+public class Solution {
+    public int minCost(String colors, int[] neededTime) {
+        int n = neededTime.length;
+        int res = 0, i = 0;
+        while (i < n) {
+            int j = i, maxi = 0, curr = 0;
+            while (j < n && colors.charAt(j) == colors.charAt(i)) {
+                maxi = Math.max(maxi, neededTime[j]);
+                curr += neededTime[j];
+                j++;
+            }
+            res += curr - maxi;
+            i = j;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minCost(string colors, vector<int>& neededTime) {
+        int n = neededTime.size();
+        int res = 0, i = 0;
+        while (i < n) {
+            int j = i, maxi = 0, curr = 0;
+            while (j < n && colors[j] == colors[i]) {
+                maxi = max(maxi, neededTime[j]);
+                curr += neededTime[j];
+                j++;
+            }
+            res += curr - maxi;
+            i = j;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} colors
+     * @param {number[]} neededTime
+     * @return {number}
+     */
+    minCost(colors, neededTime) {
+        const n = neededTime.length;
+        let res = 0, i = 0;
+        while (i < n) {
+            let j = i, maxi = 0, curr = 0;
+            while (j < n && colors[j] === colors[i]) {
+                maxi = Math.max(maxi, neededTime[j]);
+                curr += neededTime[j];
+                j++;
+            }
+            res += curr - maxi;
+            i = j;
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 2. Two Pointers - II
+
+::tabs-start
+
+```python
+class Solution:
+    def minCost(self, colors: str, neededTime: List[int]) -> int:
+        l, res = 0, 0
+        for r in range(1, len(colors)):
+            if colors[l] == colors[r]:
+                if neededTime[l] < neededTime[r]:
+                    res += neededTime[l]
+                    l = r
+                else:
+                    res += neededTime[r]
+            else:
+                l = r
+        return res
+```
+
+```java
+public class Solution {
+    public int minCost(String colors, int[] neededTime) {
+        int l = 0, res = 0;
+        for (int r = 1; r < colors.length(); r++) {
+            if (colors.charAt(l) == colors.charAt(r)) {
+                if (neededTime[l] < neededTime[r]) {
+                    res += neededTime[l];
+                    l = r;
+                } else {
+                    res += neededTime[r];
+                }
+            } else {
+                l = r;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minCost(string colors, vector<int>& neededTime) {
+        int l = 0, res = 0;
+        for (int r = 1; r < colors.size(); r++) {
+            if (colors[l] == colors[r]) {
+                if (neededTime[l] < neededTime[r]) {
+                    res += neededTime[l];
+                    l = r;
+                } else {
+                    res += neededTime[r];
+                }
+            } else {
+                l = r;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} colors
+     * @param {number[]} neededTime
+     * @return {number}
+     */
+    minCost(colors, neededTime) {
+        let l = 0, res = 0;
+        for (let r = 1; r < colors.length; r++) {
+            if (colors[l] === colors[r]) {
+                if (neededTime[l] < neededTime[r]) {
+                    res += neededTime[l];
+                    l = r;
+                } else {
+                    res += neededTime[r];
+                }
+            } else {
+                l = r;
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 3. Two Pointers - III
+
+::tabs-start
+
+```python
+class Solution:
+    def minCost(self, colors: str, neededTime: List[int]) -> int:
+        res = maxi = 0
+        for i in range(len(colors)):
+            if i and colors[i] != colors[i - 1]:
+                maxi = 0
+            res += min(maxi, neededTime[i])
+            maxi = max(maxi, neededTime[i])
+        return res
+```
+
+```java
+public class Solution {
+    public int minCost(String colors, int[] neededTime) {
+        int res = 0, maxi = 0;
+        for (int i = 0; i < colors.length(); i++) {
+            if (i > 0 && colors.charAt(i) != colors.charAt(i - 1)) {
+                maxi = 0;
+            }
+            res += Math.min(maxi, neededTime[i]);
+            maxi = Math.max(maxi, neededTime[i]);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minCost(string colors, vector<int>& neededTime) {
+        int res = 0, maxi = 0;
+        for (int i = 0; i < colors.size(); i++) {
+            if (i > 0 && colors[i] != colors[i - 1]) {
+                maxi = 0;
+            }
+            res += min(maxi, neededTime[i]);
+            maxi = max(maxi, neededTime[i]);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} colors
+     * @param {number[]} neededTime
+     * @return {number}
+     */
+    minCost(colors, neededTime) {
+        let res = 0, maxi = 0;
+        for (let i = 0; i < colors.length; i++) {
+            if (i > 0 && colors[i] !== colors[i - 1]) {
+                maxi = 0;
+            }
+            res += Math.min(maxi, neededTime[i]);
+            maxi = Math.max(maxi, neededTime[i]);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/minimum-window-with-characters.md b/articles/minimum-window-with-characters.md
index 9066d26c5..887cb769c 100644
--- a/articles/minimum-window-with-characters.md
+++ b/articles/minimum-window-with-characters.md
@@ -200,6 +200,127 @@ public class Solution {
 }
 ```
 
+```go
+func minWindow(s string, t string) string {
+	if t == "" {
+		return ""
+	}
+
+	countT := make(map[rune]int)
+	for _, c := range t {
+		countT[c]++
+	}
+
+	res := []int{-1, -1}
+	resLen := int(^uint(0) >> 1) 
+	for i := 0; i < len(s); i++ {
+		countS := make(map[rune]int)
+		for j := i; j < len(s); j++ {
+			countS[rune(s[j])]++
+
+			flag := true
+			for c, cnt := range countT {
+				if cnt > countS[c] {
+					flag = false
+					break
+				}
+			}
+
+			if flag && (j-i+1) < resLen {
+				resLen = j - i + 1
+				res = []int{i, j}
+			}
+		}
+	}
+
+	if res[0] == -1 {
+		return ""
+	}
+	return s[res[0]:res[1]+1]
+}
+```
+
+```kotlin
+class Solution {
+    fun minWindow(s: String, t: String): String {
+        if (t.isEmpty()) return ""
+
+        val countT = HashMap<Char, Int>()
+        for (c in t) {
+            countT[c] = countT.getOrDefault(c, 0) + 1
+        }
+
+        var res = IntArray(2) {-1}
+        var resLen = Int.MAX_VALUE
+        
+        for (i in s.indices) {
+            val countS = HashMap<Char, Int>()
+            for (j in i until s.length) {
+                countS[s[j]] = countS.getOrDefault(s[j], 0) + 1
+
+                var flag = true
+                for (c in countT.keys) {
+                    if (countT[c]!! > countS.getOrDefault(c, 0)) {
+                        flag = false
+                        break
+                    }
+                }
+
+                if (flag && (j - i + 1) < resLen) {
+                    resLen = j - i + 1
+                    res[0] = i
+                    res[1] = j
+                }
+            }
+        }
+
+        return if (res[0] == -1) "" else s.substring(res[0], res[1] + 1)
+    }
+}
+```
+
+```swift
+class Solution {
+    func minWindow(_ s: String, _ t: String) -> String {
+        if t.isEmpty {
+            return ""
+        }
+
+        var countT = [Character: Int]()
+        for c in t {
+            countT[c, default: 0] += 1
+        }
+
+        var res = [-1, -1]
+        var resLen = Int.max
+        let chars = Array(s)
+
+        for i in 0..<chars.count {
+            var countS = [Character: Int]()
+            for j in i..<chars.count {
+                countS[chars[j], default: 0] += 1
+
+                var flag = true
+                for (c, count) in countT {
+                    if count > countS[c, default: 0] {
+                        flag = false
+                        break
+                    }
+                }
+
+                if flag && (j - i + 1) < resLen {
+                    resLen = j - i + 1
+                    res = [i, j]
+                }
+            }
+        }
+
+        let (l, r) = (res[0], res[1])
+        return resLen != Int.max ? String(chars[l...r]) : ""
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -438,6 +559,144 @@ public class Solution {
 }
 ```
 
+```go
+func minWindow(s string, t string) string {
+	if t == "" {
+		return ""
+	}
+
+	countT := make(map[rune]int)
+	for _, c := range t {
+		countT[c]++
+	}
+
+	have, need := 0, len(countT)
+	res := []int{-1, -1}
+	resLen := math.MaxInt32
+	l := 0
+	window := make(map[rune]int)
+
+	for r := 0; r < len(s); r++ {
+		c := rune(s[r])
+		window[c]++
+
+		if countT[c] > 0 && window[c] == countT[c] {
+			have++
+		}
+
+		for have == need {
+			if (r - l + 1) < resLen {
+				res = []int{l, r}
+				resLen = r - l + 1
+			}
+
+			window[rune(s[l])]--
+			if countT[rune(s[l])] > 0 && window[rune(s[l])] < countT[rune(s[l])] {
+				have--
+			}
+			l++
+		}
+	}
+
+	if res[0] == -1 {
+		return ""
+	}
+	return s[res[0]:res[1]+1]
+}
+```
+
+```kotlin
+class Solution {
+    fun minWindow(s: String, t: String): String {
+        if (t.isEmpty()) return ""
+
+        val countT = HashMap<Char, Int>()
+        for (c in t) {
+            countT[c] = countT.getOrDefault(c, 0) + 1
+        }
+
+        var have = 0
+        val need = countT.size
+        val res = IntArray(2) {-1}
+        var resLen = Int.MAX_VALUE
+        var l = 0
+        val window = HashMap<Char, Int>()
+
+        for (r in s.indices) {
+            val c = s[r]
+            window[c] = window.getOrDefault(c, 0) + 1
+
+            if (countT.containsKey(c) && window[c] == countT[c]) {
+                have++
+            }
+
+            while (have == need) {
+                if ((r - l + 1) < resLen) {
+                    res[0] = l
+                    res[1] = r
+                    resLen = r - l + 1
+                }
+
+                window[s[l]] = window.getOrDefault(s[l], 0) - 1
+                if (countT.containsKey(s[l]) && (window[s[l]] ?: 0) < countT[s[l]]!!) {
+                    have--
+                }
+                l++
+            }
+        }
+
+        return if (res[0] == -1) "" else s.substring(res[0], res[1] + 1)
+    }
+}
+```
+
+```swift
+class Solution {
+    func minWindow(_ s: String, _ t: String) -> String {
+        if t.isEmpty {
+            return ""
+        }
+
+        var countT = [Character: Int]()
+        var window = [Character: Int]()
+        for c in t {
+            countT[c, default: 0] += 1
+        }
+
+        var have = 0, need = countT.count
+        var res = [-1, -1], resLen = Int.max
+        let chars = Array(s)
+        var l = 0
+
+        for r in 0..<chars.count {
+            let c = chars[r]
+            window[c, default: 0] += 1
+
+            if let count = countT[c], window[c] == count {
+                have += 1
+            }
+
+            while have == need {
+                if (r - l + 1) < resLen {
+                    res = [l, r]
+                    resLen = r - l + 1
+                }
+
+                let leftChar = chars[l]
+                window[leftChar, default: 0] -= 1
+                if let count = countT[leftChar], window[leftChar]! < count {
+                    have -= 1
+                }
+                l += 1
+            }
+        }
+
+        let (left, right) = (res[0], res[1])
+        return resLen != Int.max ? String(chars[left...right]) : ""
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/missing-number.md b/articles/missing-number.md
new file mode 100644
index 000000000..24844c099
--- /dev/null
+++ b/articles/missing-number.md
@@ -0,0 +1,500 @@
+## 1. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def missingNumber(self, nums: List[int]) -> int:
+        n = len(nums)
+        nums.sort()
+        for i in range(n):
+            if nums[i] != i:
+                return i
+        return n
+```
+
+```java
+public class Solution {
+    public int missingNumber(int[] nums) {
+        int n = nums.length;
+        Arrays.sort(nums);
+        for (int i = 0; i < n; i++) {
+            if (nums[i] != i) {
+                return i;
+            }
+        }
+        return n;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int missingNumber(vector<int>& nums) {
+        int n = nums.size();
+        sort(nums.begin(), nums.end());
+        for (int i = 0; i < n; i++) {
+            if (nums[i] != i) {
+                return i;
+            }
+        }
+        return n;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    missingNumber(nums) {
+        let n = nums.length;
+        nums.sort((a, b) => a - b);
+        for (let i = 0; i < n; i++) {
+            if (nums[i] !== i) {
+                return i;
+            }
+        }
+        return n;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MissingNumber(int[] nums) {
+        int n = nums.Length;
+        Array.Sort(nums);
+        for (int i = 0; i < n; i++) {
+            if (nums[i] != i) {
+                return i;
+            }
+        }
+        return n;
+    }
+}
+```
+
+```go
+func missingNumber(nums []int) int {
+    n := len(nums)
+    sort.Ints(nums)
+    for i := 0; i < n; i++ {
+        if nums[i] != i {
+            return i
+        }
+    }
+    return n
+}
+```
+
+```kotlin
+class Solution {
+    fun missingNumber(nums: IntArray): Int {
+        val n = nums.size
+        nums.sort()
+        for (i in 0 until n) {
+            if (nums[i] != i) {
+                return i
+            }
+        }
+        return n
+    }
+}
+```
+
+```swift
+class Solution {
+    func missingNumber(_ nums: [Int]) -> Int {
+        var nums = nums.sorted()
+        let n = nums.count
+        for i in 0..<n {
+            if nums[i] != i {
+                return i
+            }
+        }
+        return n
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 2. Hash Set
+
+::tabs-start
+
+```python
+class Solution:
+    def missingNumber(self, nums: List[int]) -> int:
+        num_set = set(nums)
+        n = len(nums)
+        for i in range(n + 1):
+            if i not in num_set:
+                return i
+```
+
+```java
+public class Solution {
+    public int missingNumber(int[] nums) {
+        Set<Integer> numSet = new HashSet<>();
+        for (int num : nums) {
+            numSet.add(num);
+        }
+        int n = nums.length;
+        for (int i = 0; i <= n; i++) {
+            if (!numSet.contains(i)) {
+                return i;
+            }
+        }
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int missingNumber(vector<int>& nums) {
+        unordered_set<int> num_set(nums.begin(), nums.end());
+        int n = nums.size();
+        for (int i = 0; i <= n; i++) {
+            if (num_set.find(i) == num_set.end()) {
+                return i;
+            }
+        }
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    missingNumber(nums) {
+        const numSet = new Set(nums);
+        const n = nums.length;
+        for (let i = 0; i <= n; i++) {
+            if (!numSet.has(i)) {
+                return i;
+            }
+        }
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MissingNumber(int[] nums) {
+        HashSet<int> numSet = new HashSet<int>(nums);
+        int n = nums.Length;
+        for (int i = 0; i <= n; i++) {
+            if (!numSet.Contains(i)) {
+                return i;
+            }
+        }
+        return -1;
+    }
+}
+```
+
+```go
+func missingNumber(nums []int) int {
+    numSet := make(map[int]struct{})
+    for _, num := range nums {
+        numSet[num] = struct{}{}
+    }
+    n := len(nums)
+    for i := 0; i <= n; i++ {
+        if _, exists := numSet[i]; !exists {
+            return i
+        }
+    }
+    return -1
+}
+```
+
+```kotlin
+class Solution {
+    fun missingNumber(nums: IntArray): Int {
+        val numSet = nums.toSet()
+        val n = nums.size
+        for (i in 0..n) {
+            if (i !in numSet) {
+                return i
+            }
+        }
+        return -1
+    }
+}
+```
+
+```swift
+class Solution {
+    func missingNumber(_ nums: [Int]) -> Int {
+        let numSet = Set(nums)
+        let n = nums.count
+        for i in 0...n {
+            if !numSet.contains(i) {
+                return i
+            }
+        }
+        return -1
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Bitwise XOR
+
+::tabs-start
+
+```python
+class Solution:
+    def missingNumber(self, nums: List[int]) -> int:
+        n = len(nums)
+        xorr = n  
+        for i in range(n):
+            xorr ^= i ^ nums[i]
+        return xorr
+```
+
+```java
+public class Solution {
+    public int missingNumber(int[] nums) {
+        int n = nums.length;
+        int xorr = n;  
+        for (int i = 0; i < n; i++) {
+            xorr ^= i ^ nums[i];
+        }
+        return xorr;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int missingNumber(vector<int>& nums) {
+        int n = nums.size();
+        int xorr = n;  
+        for (int i = 0; i < n; i++) {
+            xorr ^= i ^ nums[i];
+        }
+        return xorr;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    missingNumber(nums) {
+        let n = nums.length;
+        let xorr = n;  
+        for (let i = 0; i < n; i++) {
+            xorr ^= i ^ nums[i];
+        }
+        return xorr;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MissingNumber(int[] nums) {
+        int n = nums.Length;
+        int xorr = n;  
+        for (int i = 0; i < n; i++) {
+            xorr ^= i ^ nums[i];
+        }
+        return xorr;
+    }
+}
+```
+
+```go
+func missingNumber(nums []int) int {
+    n := len(nums)
+    xorr := n
+    for i := 0; i < n; i++ {
+        xorr ^= i ^ nums[i]
+    }
+    return xorr
+}
+```
+
+```kotlin
+class Solution {
+    fun missingNumber(nums: IntArray): Int {
+        val n = nums.size
+        var xorr = n
+        for (i in 0 until n) {
+            xorr = xorr xor i xor nums[i]
+        }
+        return xorr
+    }
+}
+```
+
+```swift
+class Solution {
+    func missingNumber(_ nums: [Int]) -> Int {
+        let n = nums.count
+        var xorr = n
+
+        for i in 0..<n {
+            xorr ^= i ^ nums[i]
+        }
+
+        return xorr
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 4. Math
+
+::tabs-start
+
+```python
+class Solution:
+    def missingNumber(self, nums: List[int]) -> int:
+        res = len(nums)
+
+        for i in range(len(nums)):
+            res += i - nums[i]
+        return res
+```
+
+```java
+public class Solution {
+    public int missingNumber(int[] nums) {
+        int res = nums.length;
+
+        for (int i = 0; i < nums.length; i++) {
+            res += i - nums[i];
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int missingNumber(vector<int>& nums) {
+        int res = nums.size();
+
+        for (int i = 0; i < nums.size(); i++) {
+            res += i - nums[i];
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    missingNumber(nums) {
+        let res = nums.length;
+
+        for (let i = 0; i < nums.length; i++) {
+            res += i - nums[i];
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MissingNumber(int[] nums) {
+        int res = nums.Length;
+
+        for (int i = 0; i < nums.Length; i++) {
+            res += i - nums[i];
+        }
+        return res;
+    }
+}
+```
+
+```go
+func missingNumber(nums []int) int {
+    res := len(nums)
+    for i := 0; i < len(nums); i++ {
+        res += i - nums[i]
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun missingNumber(nums: IntArray): Int {
+        var res = nums.size
+        for (i in nums.indices) {
+            res += i - nums[i]
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func missingNumber(_ nums: [Int]) -> Int {
+        var res = nums.count
+
+        for i in 0..<nums.count {
+            res += i - nums[i]
+        }
+
+        return res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/monotonic-array.md b/articles/monotonic-array.md
new file mode 100644
index 000000000..317997838
--- /dev/null
+++ b/articles/monotonic-array.md
@@ -0,0 +1,305 @@
+## 1. Two Pass
+
+::tabs-start
+
+```python
+class Solution:
+    def isMonotonic(self, nums: List[int]) -> bool:
+        n = len(nums)
+        increase = True
+        for i in range(1, n):
+            if nums[i] < nums[i - 1]:
+                increase = False
+                break
+        
+        if increase:
+            return True
+
+        decrease = True
+        for i in range(1, n):
+            if nums[i] > nums[i - 1]:
+                decrease = False
+                break
+        return decrease
+```
+
+```java
+public class Solution {
+    public boolean isMonotonic(int[] nums) {
+        int n = nums.length;
+        boolean increase = true;
+        for (int i = 1; i < n; i++) {
+            if (nums[i] < nums[i - 1]) {
+                increase = false;
+                break;
+            }
+        }
+        if (increase) {
+            return true;
+        }
+
+        boolean decrease = true;
+        for (int i = 1; i < n; i++) {
+            if (nums[i] > nums[i - 1]) {
+                decrease = false;
+                break;
+            }
+        }
+        return decrease;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isMonotonic(vector<int>& nums) {
+        int n = nums.size();
+        bool increase = true;
+        for (int i = 1; i < n; ++i) {
+            if (nums[i] < nums[i - 1]) {
+                increase = false;
+                break;
+            }
+        }
+        if (increase) {
+            return true;
+        }
+
+        bool decrease = true;
+        for (int i = 1; i < n; ++i) {
+            if (nums[i] > nums[i - 1]) {
+                decrease = false;
+                break;
+            }
+        }
+        return decrease;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {boolean}
+     */
+    isMonotonic(nums) {
+        const n = nums.length;
+        let increase = true;
+        for (let i = 1; i < n; i++) {
+            if (nums[i] < nums[i - 1]) {
+                increase = false;
+                break;
+            }
+        }
+        if (increase) {
+            return true;
+        }
+
+        let decrease = true;
+        for (let i = 1; i < n; i++) {
+            if (nums[i] > nums[i - 1]) {
+                decrease = false;
+                break;
+            }
+        }
+        return decrease;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. One Pass - I
+
+::tabs-start
+
+```python
+class Solution:
+    def isMonotonic(self, nums: List[int]) -> bool:
+        n = len(nums)
+        if nums[0] <= nums[-1]:
+            for i in range(1, n):
+                if nums[i] < nums[i - 1]:
+                    return False
+            return True
+        else:
+            for i in range(1, n):
+                if nums[i] > nums[i - 1]:
+                    return False
+            return True
+```
+
+```java
+public class Solution {
+    public boolean isMonotonic(int[] nums) {
+        int n = nums.length;
+        if (nums[0] <= nums[n - 1]) {
+            for (int i = 1; i < n; i++) {
+                if (nums[i] < nums[i - 1]) {
+                    return false;
+                }
+            }
+            return true;
+        } else {
+            for (int i = 1; i < n; i++) {
+                if (nums[i] > nums[i - 1]) {
+                    return false;
+                }
+            }
+            return true;
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isMonotonic(vector<int>& nums) {
+        int n = nums.size();
+        if (nums[0] <= nums[n - 1]) {
+            for (int i = 1; i < n; ++i) {
+                if (nums[i] < nums[i - 1]) {
+                    return false;
+                }
+            }
+            return true;
+        } else {
+            for (int i = 1; i < n; ++i) {
+                if (nums[i] > nums[i - 1]) {
+                    return false;
+                }
+            }
+            return true;
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {boolean}
+     */
+    isMonotonic(nums) {
+        const n = nums.length;
+        if (nums[0] <= nums[n - 1]) {
+            for (let i = 1; i < n; i++) {
+                if (nums[i] < nums[i - 1]) {
+                    return false;
+                }
+            }
+            return true;
+        } else {
+            for (let i = 1; i < n; i++) {
+                if (nums[i] > nums[i - 1]) {
+                    return false;
+                }
+            }
+            return true;
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. One Pass - II
+
+::tabs-start
+
+```python
+class Solution:
+    def isMonotonic(self, nums: List[int]) -> bool:
+        increase, decrease = True, True
+
+        for i in range(len(nums) - 1):
+            if not (nums[i] <= nums[i + 1]):
+                increase = False
+            if not (nums[i] >= nums[i + 1]):
+                decrease = False
+        return increase or decrease
+```
+
+```java
+public class Solution {
+    public boolean isMonotonic(int[] nums) {
+        boolean increase = true, decrease = true;
+
+        for (int i = 0; i < nums.length - 1; i++) {
+            if (!(nums[i] <= nums[i + 1])) {
+                increase = false;
+            }
+            if (!(nums[i] >= nums[i + 1])) {
+                decrease = false;
+            }
+        }
+        return increase || decrease;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isMonotonic(vector<int>& nums) {
+        bool increase = true, decrease = true;
+
+        for (int i = 0; i < nums.size() - 1; ++i) {
+            if (!(nums[i] <= nums[i + 1])) {
+                increase = false;
+            }
+            if (!(nums[i] >= nums[i + 1])) {
+                decrease = false;
+            }
+        }
+        return increase || decrease;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {boolean}
+     */
+    isMonotonic(nums) {
+        let increase = true, decrease = true;
+
+        for (let i = 0; i < nums.length - 1; i++) {
+            if (!(nums[i] <= nums[i + 1])) {
+                increase = false;
+            }
+            if (!(nums[i] >= nums[i + 1])) {
+                decrease = false;
+            }
+        }
+        return increase || decrease;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/move-zeroes.md b/articles/move-zeroes.md
new file mode 100644
index 000000000..46a78c170
--- /dev/null
+++ b/articles/move-zeroes.md
@@ -0,0 +1,253 @@
+## 1. Extra Space
+
+::tabs-start
+
+```python
+class Solution:
+    def moveZeroes(self, nums: List[int]) -> None:
+        """
+        Do not return anything, modify nums in-place instead.
+        """
+        tmp = []
+        for num in nums:
+            if num != 0:
+                tmp.append(num)
+        
+        for i in range(len(nums)):
+            if i < len(tmp):
+                nums[i] = tmp[i]
+            else:
+                nums[i] = 0
+```
+
+```java
+public class Solution {
+    public void moveZeroes(int[] nums) {
+        List<Integer> tmp = new ArrayList<>();
+        for (int num : nums) {
+            if (num != 0) {
+                tmp.add(num);
+            }
+        }
+
+        for (int i = 0; i < nums.length; i++) {
+            if (i < tmp.size()) {
+                nums[i] = tmp.get(i);
+            } else {
+                nums[i] = 0;
+            }
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void moveZeroes(vector<int>& nums) {
+        vector<int> tmp;
+        for (int num : nums) {
+            if (num != 0) {
+                tmp.push_back(num);
+            }
+        }
+
+        for (int i = 0; i < nums.size(); ++i) {
+            if (i < tmp.size()) {
+                nums[i] = tmp[i];
+            } else {
+                nums[i] = 0;
+            }
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {void} Do not return anything, modify nums in-place instead.
+     */
+    moveZeroes(nums) {
+        let tmp = [];
+        for (let num of nums) {
+            if (num !== 0) {
+                tmp.push(num);
+            }
+        }
+        
+        for (let i = 0; i < nums.length; i++) {
+            if (i < tmp.length) {
+                nums[i] = tmp[i];
+            } else {
+                nums[i] = 0;
+            }
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Two Pointers (Two Pass)
+::tabs-start
+
+```python
+class Solution:
+    def moveZeroes(self, nums: List[int]) -> None:
+        """
+        Do not return anything, modify nums in-place instead.
+        """
+        l = 0
+        for r in range(len(nums)):
+            if nums[r] != 0:
+                nums[l] = nums[r]
+                l += 1
+        
+        while l < len(nums):
+            nums[l] = 0
+            l += 1
+```
+
+```java
+public class Solution {
+    public void moveZeroes(int[] nums) {
+        int l = 0;
+        for (int r = 0; r < nums.length; r++) {
+            if (nums[r] != 0) {
+                nums[l++] = nums[r];
+            }
+        }
+
+        while (l < nums.length) {
+            nums[l++] = 0;
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void moveZeroes(vector<int>& nums) {
+        int l = 0;
+        for (int r = 0; r < nums.size(); r++) {
+            if (nums[r] != 0) {
+                nums[l++] = nums[r];
+            }
+        }
+
+        while (l < nums.size()) {
+            nums[l++] = 0;
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {void} Do not return anything, modify nums in-place instead.
+     */
+    moveZeroes(nums) {
+        let l = 0;
+        for (let r = 0; r < nums.length; r++) {
+            if (nums[r] != 0) {
+                nums[l++] = nums[r];
+            }
+        }
+
+        while (l < nums.length) {
+            nums[l++] = 0;
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Two Pointers (One Pass)
+
+::tabs-start
+
+```python
+class Solution:
+    def moveZeroes(self, nums: List[int]) -> None:
+        """
+        Do not return anything, modify nums in-place instead.
+        """
+        l = 0
+        for r in range(len(nums)):
+            if nums[r]:
+                nums[l], nums[r] = nums[r], nums[l]
+                l += 1
+```
+
+```java
+public class Solution {
+    public void moveZeroes(int[] nums) {
+        int l = 0;
+        for (int r = 0; r < nums.length; r++) {
+            if (nums[r] != 0) {
+                int temp = nums[l];
+                nums[l] = nums[r];
+                nums[r] = temp;
+                l++;
+            }
+        } 
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void moveZeroes(vector<int>& nums) {
+        for (int l = 0, r = 0; r < nums.size(); r++) {
+            if (nums[r]) {
+                swap(nums[l++], nums[r]);
+            }
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {void} Do not return anything, modify nums in-place instead.
+     */
+    moveZeroes(nums) {
+        for (let l = 0, r = 0; r < nums.length; r++) {
+            if (nums[r] !== 0) {
+                [nums[l], nums[r]] = [nums[r], nums[l]];
+                l++;
+            }
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/multiply-strings.md b/articles/multiply-strings.md
new file mode 100644
index 000000000..eb53364f1
--- /dev/null
+++ b/articles/multiply-strings.md
@@ -0,0 +1,774 @@
+## 1. Multiplication & Addition
+
+::tabs-start
+
+```python
+class Solution:
+    def multiply(self, num1: str, num2: str) -> str:
+        if num1 == "0" or num2 == "0":
+            return "0"
+        
+        if len(num1) < len(num2):
+            return self.multiply(num2, num1)
+        
+        res, zero = "", 0
+        for i in range(len(num2) - 1, -1, -1):
+            cur = self.mul(num1, num2[i], zero)
+            res = self.add(res, cur)
+            zero += 1
+        
+        return res
+    
+    def mul(self, s: str, d: str, zero: int) -> str:
+        i, carry = len(s) - 1, 0
+        d = int(d)
+        cur = []
+
+        while i >= 0 or carry:
+            n = int(s[i]) if i >= 0 else 0
+            prod = n * d + carry
+            cur.append(str(prod % 10))
+            carry = prod // 10
+            i -= 1
+        
+        return ''.join(cur[::-1]) + '0' * zero
+
+    def add(self, num1: str, num2: str) -> str:
+        i, j, carry = len(num1) - 1, len(num2) - 1, 0
+        res = []
+
+        while i >= 0 or j >= 0 or carry:
+            n1 = int(num1[i]) if i >= 0 else 0
+            n2 = int(num2[j]) if j >= 0 else 0
+            total = n1 + n2 + carry
+            res.append(str(total % 10))
+            carry = total // 10
+            i -= 1
+            j -= 1
+        
+        return ''.join(res[::-1])
+```
+
+```java
+public class Solution {
+    public String multiply(String num1, String num2) {
+        if (num1.equals("0") || num2.equals("0")) return "0";
+
+        if (num1.length() < num2.length()) {
+            return multiply(num2, num1);
+        }
+        
+        String res = "";
+        int zero = 0;
+        for (int i = num2.length() - 1; i >= 0; i--) {
+            String cur = mul(num1, num2.charAt(i), zero);
+            res = add(res, cur);
+            zero++;
+        }
+        
+        return res;
+    }
+    
+    private String mul(String s, char d, int zero) {
+        int i = s.length() - 1, carry = 0;
+        int digit = d - '0';
+        StringBuilder cur = new StringBuilder();
+
+        while (i >= 0 || carry > 0) {
+            int n = (i >= 0) ? s.charAt(i) - '0' : 0;
+            int prod = n * digit + carry;
+            cur.append(prod % 10);
+            carry = prod / 10;
+            i--;
+        }
+        
+        return cur.reverse().toString() + "0".repeat(zero);
+    }
+
+    private String add(String num1, String num2) {
+        int i = num1.length() - 1, j = num2.length() - 1, carry = 0;
+        StringBuilder res = new StringBuilder();
+
+        while (i >= 0 || j >= 0 || carry > 0) {
+            int n1 = (i >= 0) ? num1.charAt(i) - '0' : 0;
+            int n2 = (j >= 0) ? num2.charAt(j) - '0' : 0;
+            int total = n1 + n2 + carry;
+            res.append(total % 10);
+            carry = total / 10;
+            i--;
+            j--;
+        }
+        
+        return res.reverse().toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string multiply(string num1, string num2) {
+        if (num1 == "0" || num2 == "0") return "0";
+        
+        if (num1.size() < num2.size()) {
+            return multiply(num2, num1);
+        }
+        
+        string res = "";
+        int zero = 0;
+        for (int i = num2.size() - 1; i >= 0; --i) {
+            string cur = mul(num1, num2[i], zero);
+            res = add(res, cur);
+            zero++;
+        }
+        
+        return res;
+    }
+    
+    string mul(string s, char d, int zero) {
+        int i = s.size() - 1, carry = 0;
+        int digit = d - '0';
+        string cur;
+
+        while (i >= 0 || carry) {
+            int n = (i >= 0) ? s[i] - '0' : 0;
+            int prod = n * digit + carry;
+            cur.push_back((prod % 10) + '0');
+            carry = prod / 10;
+            i--;
+        }
+        
+        reverse(cur.begin(), cur.end());
+        return cur + string(zero, '0');
+    }
+
+    string add(string num1, string num2) {
+        int i = num1.size() - 1, j = num2.size() - 1, carry = 0;
+        string res;
+
+        while (i >= 0 || j >= 0 || carry) {
+            int n1 = (i >= 0) ? num1[i] - '0' : 0;
+            int n2 = (j >= 0) ? num2[j] - '0' : 0;
+            int total = n1 + n2 + carry;
+            res.push_back((total % 10) + '0');
+            carry = total / 10;
+            i--;
+            j--;
+        }
+        
+        reverse(res.begin(), res.end());
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} num1
+     * @param {string} num2
+     * @return {string}
+     */
+    multiply(num1, num2) {
+        if (num1 === "0" || num2 === "0") return "0";
+
+        if (num1.length < num2.length) {
+            return this.multiply(num2, num1);
+        }
+        
+        let res = "";
+        let zero = 0;
+        for (let i = num2.length - 1; i >= 0; i--) {
+            const cur = this.mul(num1, num2[i], zero);
+            res = this.add(res, cur);
+            zero++;
+        }
+        
+        return res;
+    }
+    
+    /**
+     * @param {string} s
+     * @param {Character} d
+     * @param {number} zero
+     * @return {string}
+     */
+    mul(s, d, zero) {
+        let i = s.length - 1;
+        let carry = 0;
+        const digit = Number(d);
+        let cur = "";
+
+        while (i >= 0 || carry) {
+            const n = i >= 0 ? Number(s[i]) : 0;
+            const prod = n * digit + carry;
+            cur = (prod % 10) + cur;
+            carry = Math.floor(prod / 10);
+            i--;
+        }
+        
+        return cur + "0".repeat(zero);
+    }
+
+    /**
+     * @param {string} num1
+     * @param {string} num2
+     * @return {string}
+     */
+    add(num1, num2) {
+        let i = num1.length - 1, j = num2.length - 1, carry = 0;
+        let res = "";
+
+        while (i >= 0 || j >= 0 || carry) {
+            const n1 = i >= 0 ? Number(num1[i]) : 0;
+            const n2 = j >= 0 ? Number(num2[j]) : 0;
+            const total = n1 + n2 + carry;
+            res = (total % 10) + res;
+            carry = Math.floor(total / 10);
+            i--;
+            j--;
+        }
+        
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public string Multiply(string num1, string num2) {
+        if (num1 == "0" || num2 == "0") return "0";
+
+        if (num1.Length < num2.Length) {
+            return Multiply(num2, num1);
+        }
+        
+        string res = "";
+        int zero = 0;
+        for (int i = num2.Length - 1; i >= 0; i--) {
+            string cur = Mul(num1, num2[i], zero);
+            res = Add(res, cur);
+            zero++;
+        }
+        
+        return res;
+    }
+    
+    private string Mul(string s, char d, int zero) {
+        int i = s.Length - 1, carry = 0;
+        int digit = d - '0';
+        var cur = new List<char>();
+
+        while (i >= 0 || carry > 0) {
+            int n = (i >= 0) ? s[i] - '0' : 0;
+            int prod = n * digit + carry;
+            cur.Add((char)('0' + (prod % 10)));
+            carry = prod / 10;
+            i--;
+        }
+        
+        cur.Reverse();
+        return new string(cur.ToArray()) + new string('0', zero);
+    }
+
+    private string Add(string num1, string num2) {
+        int i = num1.Length - 1, j = num2.Length - 1, carry = 0;
+        var res = new List<char>();
+
+        while (i >= 0 || j >= 0 || carry > 0) {
+            int n1 = (i >= 0) ? num1[i] - '0' : 0;
+            int n2 = (j >= 0) ? num2[j] - '0' : 0;
+            int total = n1 + n2 + carry;
+            res.Add((char)('0' + (total % 10)));
+            carry = total / 10;
+            i--;
+            j--;
+        }
+        
+        res.Reverse();
+        return new string(res.ToArray());
+    }
+}
+```
+
+```go
+func multiply(num1 string, num2 string) string {
+    if num1 == "0" || num2 == "0" {
+        return "0"
+    }
+    
+    if len(num1) < len(num2) {
+        return multiply(num2, num1)
+    }
+    
+    res, zero := "", 0
+    for i := len(num2) - 1; i >= 0; i-- {
+        cur := mul(num1, num2[i], zero)
+        res = add(res, cur)
+        zero++
+    }
+    
+    return res
+}
+
+func mul(s string, d byte, zero int) string {
+    i, carry := len(s)-1, 0
+    d = d - '0'
+    cur := make([]byte, 0)
+    
+    for i >= 0 || carry > 0 {
+        var n int
+        if i >= 0 {
+            n = int(s[i] - '0')
+        }
+        prod := n*int(d) + carry
+        cur = append(cur, byte(prod%10+'0'))
+        carry = prod / 10
+        i--
+    }
+    
+    for i := 0; i < len(cur)/2; i++ {
+        cur[i], cur[len(cur)-1-i] = cur[len(cur)-1-i], cur[i]
+    }
+    
+    result := string(cur)
+    for i := 0; i < zero; i++ {
+        result += "0"
+    }
+    return result
+}
+
+func add(num1 string, num2 string) string {
+    i, j, carry := len(num1)-1, len(num2)-1, 0
+    res := make([]byte, 0)
+    
+    for i >= 0 || j >= 0 || carry > 0 {
+        var n1, n2 int
+        if i >= 0 {
+            n1 = int(num1[i] - '0')
+        }
+        if j >= 0 {
+            n2 = int(num2[j] - '0')
+        }
+        total := n1 + n2 + carry
+        res = append(res, byte(total%10+'0'))
+        carry = total / 10
+        i--
+        j--
+    }
+    
+    for i := 0; i < len(res)/2; i++ {
+        res[i], res[len(res)-1-i] = res[len(res)-1-i], res[i]
+    }
+    
+    return string(res)
+}
+```
+
+```kotlin
+class Solution {
+    fun multiply(num1: String, num2: String): String {
+        if (num1 == "0" || num2 == "0") {
+            return "0"
+        }
+        
+        if (num1.length < num2.length) {
+            return multiply(num2, num1)
+        }
+        
+        var res = ""
+        var zero = 0
+        for (i in num2.length - 1 downTo 0) {
+            val cur = mul(num1, num2[i], zero)
+            res = add(res, cur)
+            zero++
+        }
+        
+        return res
+    }
+    
+    private fun mul(s: String, d: Char, zero: Int): String {
+        var i = s.length - 1
+        var carry = 0
+        val dInt = d - '0'
+        val cur = mutableListOf<Char>()
+        
+        while (i >= 0 || carry > 0) {
+            val n = if (i >= 0) s[i] - '0' else 0
+            val prod = n * dInt + carry
+            cur.add((prod % 10 + '0'.code).toChar())
+            carry = prod / 10
+            i--
+        }
+        
+        return cur.reversed().joinToString("") + "0".repeat(zero)
+    }
+    
+    private fun add(num1: String, num2: String): String {
+        var i = num1.length - 1
+        var j = num2.length - 1
+        var carry = 0
+        val res = mutableListOf<Char>()
+        
+        while (i >= 0 || j >= 0 || carry > 0) {
+            val n1 = if (i >= 0) num1[i] - '0' else 0
+            val n2 = if (j >= 0) num2[j] - '0' else 0
+            val total = n1 + n2 + carry
+            res.add((total % 10 + '0'.code).toChar())
+            carry = total / 10
+            i--
+            j--
+        }
+        
+        return res.reversed().joinToString("")
+    }
+}
+```
+
+```swift
+class Solution {
+    func multiply(_ num1: String, _ num2: String) -> String {
+        if num1 == "0" || num2 == "0" {
+            return "0"
+        }
+        if num1.count < num2.count {
+            return multiply(num2, num1)
+        }
+
+        var res = ""
+        var zero = 0
+        let num2Arr = Array(num2)
+
+        for i in stride(from: num2Arr.count - 1, through: 0, by: -1) {
+            let cur = mul(num1, num2Arr[i], zero)
+            res = add(res, cur)
+            zero += 1
+        }
+
+        return res
+    }
+
+    func mul(_ s: String, _ d: Character, _ zero: Int) -> String {
+        var i = s.count - 1
+        var carry = 0
+        let dInt = Int(String(d))!
+        let sArr = Array(s)
+        var cur = [String]()
+
+        while i >= 0 || carry > 0 {
+            let n = i >= 0 ? Int(String(sArr[i]))! : 0
+            let prod = n * dInt + carry
+            cur.append(String(prod % 10))
+            carry = prod / 10
+            i -= 1
+        }
+
+        let prodStr = cur.reversed().joined()
+        let zeros = String(repeating: "0", count: zero)
+        return prodStr + zeros
+    }
+
+    func add(_ num1: String, _ num2: String) -> String {
+        let s1 = Array(num1)
+        let s2 = Array(num2)
+        var i = s1.count - 1
+        var j = s2.count - 1
+        var carry = 0
+        var res = [String]()
+
+        while i >= 0 || j >= 0 || carry > 0 {
+            let n1 = i >= 0 ? Int(String(s1[i]))! : 0
+            let n2 = j >= 0 ? Int(String(s2[j]))! : 0
+            let total = n1 + n2 + carry
+            res.append(String(total % 10))
+            carry = total / 10
+            i -= 1
+            j -= 1
+        }
+
+        return res.reversed().joined()
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(min(m, n) * (m + n))$
+* Space complexity: $O(m + n)$
+
+> Where $m$ is the length of the string $num1$ and $n$ is the length of the string $num2$.
+
+---
+
+## 2. Multiplication
+
+::tabs-start
+
+```python
+class Solution:
+    def multiply(self, num1: str, num2: str) -> str:
+        if "0" in [num1, num2]:
+            return "0"
+
+        res = [0] * (len(num1) + len(num2))
+        num1, num2 = num1[::-1], num2[::-1]
+        for i1 in range(len(num1)):
+            for i2 in range(len(num2)):
+                digit = int(num1[i1]) * int(num2[i2])
+                res[i1 + i2] += digit
+                res[i1 + i2 + 1] += res[i1 + i2] // 10
+                res[i1 + i2] = res[i1 + i2] % 10
+
+        res, beg = res[::-1], 0
+        while beg < len(res) and res[beg] == 0:
+            beg += 1
+        res = map(str, res[beg:])
+        return "".join(res)
+```
+
+```java
+public class Solution {
+    public String multiply(String num1, String num2) {
+        if (num1.equals("0") || num2.equals("0")) {
+            return "0";
+        }
+
+        int[] res = new int[num1.length() + num2.length()];
+        num1 = new StringBuilder(num1).reverse().toString();
+        num2 = new StringBuilder(num2).reverse().toString();
+        for (int i1 = 0; i1 < num1.length(); i1++) {
+            for (int i2 = 0; i2 < num2.length(); i2++) {
+                int digit = (num1.charAt(i1) - '0') * (num2.charAt(i2) - '0');
+                res[i1 + i2] += digit;
+                res[i1 + i2 + 1] += res[i1 + i2] / 10;
+                res[i1 + i2] %= 10;
+            }
+        }
+
+        StringBuilder result = new StringBuilder();
+        int i = res.length - 1;
+        while (i >= 0 && res[i] == 0) {
+            i--;
+        }
+        while (i >= 0) {
+            result.append(res[i--]);
+        }
+        return result.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string multiply(string num1, string num2) {
+        if (num1 == "0" || num2 == "0") {
+            return "0";
+        }
+
+        vector<int> res(num1.length() + num2.length(), 0);
+        reverse(num1.begin(), num1.end());
+        reverse(num2.begin(), num2.end());
+        for (int i1 = 0; i1 < num1.length(); i1++) {
+            for (int i2 = 0; i2 < num2.length(); i2++) {
+                int digit = (num1[i1] - '0') * (num2[i2] - '0');
+                res[i1 + i2] += digit;
+                res[i1 + i2 + 1] += res[i1 + i2] / 10;
+                res[i1 + i2] %= 10;
+            }
+        }
+
+        stringstream result;
+        int i = res.size() - 1;
+        while (i >= 0 && res[i] == 0) {
+            i--;
+        }
+        while (i >= 0) {
+            result << res[i--];
+        }
+        return result.str();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} num1
+     * @param {string} num2
+     * @return {string}
+     */
+    multiply(num1, num2) {
+        if (num1 === '0' || num2 === '0') {
+            return '0';
+        }
+
+        const res = new Array(num1.length + num2.length).fill(0);
+        num1 = num1.split('').reverse().join('');
+        num2 = num2.split('').reverse().join('');
+        for (let i1 = 0; i1 < num1.length; i1++) {
+            for (let i2 = 0; i2 < num2.length; i2++) {
+                const digit = parseInt(num1[i1]) * parseInt(num2[i2]);
+                res[i1 + i2] += digit;
+                res[i1 + i2 + 1] += Math.floor(res[i1 + i2] / 10);
+                res[i1 + i2] %= 10;
+            }
+        }
+
+        let result = '';
+        let i = res.length - 1;
+        while (i >= 0 && res[i] === 0) {
+            i--;
+        }
+        while (i >= 0) {
+            result += res[i--];
+        }
+        return result;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public string Multiply(string num1, string num2) {
+        if (new string[] { num1, num2 }.Contains("0")) {
+            return "0";
+        }
+
+        int[] res = new int[num1.Length + num2.Length];
+        num1 = new string(num1.Reverse().ToArray());
+        num2 = new string(num2.Reverse().ToArray());
+        for (int i1 = 0; i1 < num1.Length; i1++) {
+            for (int i2 = 0; i2 < num2.Length; i2++) {
+                int digit = (num1[i1] - '0') * (num2[i2] - '0');
+                res[i1 + i2] += digit;
+                res[i1 + i2 + 1] += res[i1 + i2] / 10;
+                res[i1 + i2] %= 10;
+            }
+        }
+
+        Array.Reverse(res);
+        int beg = 0;
+        while (beg < res.Length && res[beg] == 0) {
+            beg++;
+        }
+
+        string[] result = res.Skip(beg).Select(x => x.ToString()).ToArray();
+        return string.Join("", result);
+    }
+}
+```
+
+```go
+func multiply(num1 string, num2 string) string {
+    if num1 == "0" || num2 == "0" {
+        return "0"
+    }
+    
+    res := make([]int, len(num1)+len(num2))
+    for i1 := len(num1) - 1; i1 >= 0; i1-- {
+        for i2 := len(num2) - 1; i2 >= 0; i2-- {
+            pos := len(num1) - 1 - i1 + len(num2) - 1 - i2
+            digit := int(num1[i1]-'0') * int(num2[i2]-'0')
+            
+            res[pos] += digit
+            res[pos+1] += res[pos] / 10
+            res[pos] = res[pos] % 10
+        }
+    }
+    
+    var result strings.Builder
+    start := len(res) - 1
+    for start >= 0 && res[start] == 0 {
+        start--
+    }
+    if start < 0 {
+        return "0"
+    }
+    
+    for i := start; i >= 0; i-- {
+        result.WriteString(strconv.Itoa(res[i]))
+    }
+    
+    return result.String()
+}
+```
+
+```kotlin
+class Solution {
+    fun multiply(num1: String, num2: String): String {
+        if ("0" in listOf(num1, num2)) {
+            return "0"
+        }
+        
+        val res = IntArray(num1.length + num2.length)
+        for (i1 in num1.indices.reversed()) {
+            for (i2 in num2.indices.reversed()) {
+                val pos = (num1.length - 1 - i1) + (num2.length - 1 - i2)
+                val digit = (num1[i1] - '0') * (num2[i2] - '0')
+                
+                res[pos] += digit
+                res[pos + 1] += res[pos] / 10
+                res[pos] = res[pos] % 10
+            }
+        }
+        
+        var start = res.size - 1
+        while (start >= 0 && res[start] == 0) {
+            start--
+        }
+        
+        if (start < 0) {
+            return "0"
+        }
+        
+        return buildString {
+            for (i in start downTo 0) {
+                append(res[i])
+            }
+        }
+    }
+}
+```
+
+```swift
+class Solution {
+    func multiply(_ num1: String, _ num2: String) -> String {
+        if num1 == "0" || num2 == "0" {
+            return "0"
+        }
+
+        let n1 = Array(num1.reversed()).map { Int(String($0))! }
+        let n2 = Array(num2.reversed()).map { Int(String($0))! }
+        var res = [Int](repeating: 0, count: num1.count + num2.count)
+
+        for i1 in 0..<n1.count {
+            for i2 in 0..<n2.count {
+                let digit = n1[i1] * n2[i2]
+                res[i1 + i2] += digit
+                res[i1 + i2 + 1] += res[i1 + i2] / 10
+                res[i1 + i2] %= 10
+            }
+        }
+
+        res.reverse()
+        var beg = 0
+        while beg < res.count && res[beg] == 0 {
+            beg += 1
+        }
+
+        return res[beg...].map { String($0) }.joined()
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(m + n)$
+
+> Where $m$ is the length of the string $num1$ and $n$ is the length of the string $num2$.
\ No newline at end of file
diff --git a/articles/my-calendar-i.md b/articles/my-calendar-i.md
new file mode 100644
index 000000000..f926c9e13
--- /dev/null
+++ b/articles/my-calendar-i.md
@@ -0,0 +1,405 @@
+## 1. Iteration
+
+::tabs-start
+
+```python
+class MyCalendar:
+
+    def __init__(self):
+        self.events = []
+
+    def book(self, startTime: int, endTime: int) -> bool:
+        for start, end in self.events:
+            if startTime < end and start < endTime:
+                return False
+        
+        self.events.append((startTime, endTime))
+        return True
+```
+
+```java
+public class MyCalendar {
+    private List<int[]> events;
+
+    public MyCalendar() {
+        events = new ArrayList<>();
+    }
+
+    public boolean book(int startTime, int endTime) {
+        for (int[] event : events) {
+            if (startTime < event[1] && event[0] < endTime) {
+                return false;
+            }
+        }
+        events.add(new int[]{startTime, endTime});
+        return true;
+    }
+}
+```
+
+```cpp
+class MyCalendar {
+private:
+    vector<pair<int, int>> events;
+
+public:
+    MyCalendar() {}
+
+    bool book(int startTime, int endTime) {
+        for (const auto& event : events) {
+            if (startTime < event.second && event.first < endTime) {
+                return false;
+            }
+        }
+        events.push_back({startTime, endTime});
+        return true;
+    }
+};
+```
+
+```javascript
+class MyCalendar {
+    constructor() {
+        this.events = [];
+    }
+
+    /** 
+     * @param {number} startTime 
+     * @param {number} endTime
+     * @return {boolean}
+     */
+    book(startTime, endTime) {
+        for (const [start, end] of this.events) {
+            if (startTime < end && start < endTime) {
+                return false;
+            }
+        }
+        this.events.push([startTime, endTime]);
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$ for each $book()$ function call.
+* Space complexity: $O(n)$
+
+---
+
+## 2. Binary Search Tree
+
+::tabs-start
+
+```python
+class TreeNode:
+    def __init__(self, start: int, end: int):
+        self.start = start
+        self.end = end
+        self.left = None
+        self.right = None
+
+class MyCalendar:
+
+    def __init__(self):
+        self.root = None
+
+    def _insert(self, node: TreeNode, start: int, end: int) -> bool:
+        if end <= node.start:
+            if not node.left:
+                node.left = TreeNode(start, end)
+                return True
+            return self._insert(node.left, start, end)
+        elif start >= node.end:
+            if not node.right:
+                node.right = TreeNode(start, end)
+                return True
+            return self._insert(node.right, start, end)
+        else:
+            return False
+
+    def book(self, startTime: int, endTime: int) -> bool:
+        if not self.root:
+            self.root = TreeNode(startTime, endTime)
+            return True
+        return self._insert(self.root, startTime, endTime)
+```
+
+```java
+class TreeNode {
+    int start, end;
+    TreeNode left, right;
+
+    TreeNode(int start, int end) {
+        this.start = start;
+        this.end = end;
+        this.left = null;
+        this.right = null;
+    }
+}
+
+public class MyCalendar {
+    private TreeNode root;
+
+    public MyCalendar() {
+        root = null;
+    }
+
+    private boolean insert(TreeNode node, int start, int end) {
+        if (end <= node.start) {
+            if (node.left == null) {
+                node.left = new TreeNode(start, end);
+                return true;
+            }
+            return insert(node.left, start, end);
+        } else if (start >= node.end) {
+            if (node.right == null) {
+                node.right = new TreeNode(start, end);
+                return true;
+            }
+            return insert(node.right, start, end);
+        }
+        return false;
+    }
+
+    public boolean book(int startTime, int endTime) {
+        if (root == null) {
+            root = new TreeNode(startTime, endTime);
+            return true;
+        }
+        return insert(root, startTime, endTime);
+    }
+}
+```
+
+```cpp
+class MyCalendar {
+private:
+    struct TreeNode {
+        int start, end;
+        TreeNode *left, *right;
+
+        TreeNode(int start, int end) : start(start), end(end), left(nullptr), right(nullptr) {}
+    };
+    TreeNode *root;
+
+    bool insert(TreeNode *node, int start, int end) {
+        if (end <= node->start) {
+            if (!node->left) {
+                node->left = new TreeNode(start, end);
+                return true;
+            }
+            return insert(node->left, start, end);
+        } else if (start >= node->end) {
+            if (!node->right) {
+                node->right = new TreeNode(start, end);
+                return true;
+            }
+            return insert(node->right, start, end);
+        }
+        return false;
+    }
+
+public:
+    MyCalendar() : root(nullptr) {}
+
+    bool book(int startTime, int endTime) {
+        if (!root) {
+            root = new TreeNode(startTime, endTime);
+            return true;
+        }
+        return insert(root, startTime, endTime);
+    }
+};
+```
+
+```javascript
+class TreeNode {
+    /** 
+     * @constructor
+     * @param {number} start 
+     * @param {number} end
+     */
+    constructor(start, end) {
+        this.start = start;
+        this.end = end;
+        this.left = null;
+        this.right = null;
+    }
+}
+
+class MyCalendar {
+    constructor() {
+        this.root = null;
+    }
+
+    /** 
+     * @param {TreeNode} node 
+     * @param {number} start
+     * @param {number} end
+     * @return {boolean}
+     */
+    insert(node, start, end) {
+        if (end <= node.start) {
+            if (!node.left) {
+                node.left = new TreeNode(start, end);
+                return true;
+            }
+            return this.insert(node.left, start, end);
+        } else if (start >= node.end) {
+            if (!node.right) {
+                node.right = new TreeNode(start, end);
+                return true;
+            }
+            return this.insert(node.right, start, end);
+        }
+        return false;
+    }
+
+    /** 
+     * @param {number} startTime 
+     * @param {number} endTime
+     * @return {boolean}
+     */
+    book(startTime, endTIme) {
+        if (!this.root) {
+            this.root = new TreeNode(startTime, endTime);
+            return true;
+        }
+        return this.insert(this.root, startTime, endTime);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$ in average case, $O(n)$ in worst case for each $book()$ function call.
+* Space complexity: $O(n)$
+
+---
+
+## 3. Binary Search + Ordered Set
+
+::tabs-start
+
+```python
+class MyCalendar:
+
+    def __init__(self):
+        self.events = SortedList()
+
+    def book(self, startTime: int, endTime: int) -> bool:
+        idx = self.events.bisect_left((startTime, endTime))
+        if idx > 0 and self.events[idx - 1][1] > startTime:
+            return False
+        if idx < len(self.events) and self.events[idx][0] < endTime:
+            return False
+        self.events.add((startTime, endTime))
+        return True
+```
+
+```java
+public class MyCalendar {
+    private TreeSet<int[]> events;
+
+    public MyCalendar() {
+        events = new TreeSet<>((a, b) -> a[0] - b[0]);
+    }
+
+    public boolean book(int startTime, int endTime) {
+        int[] event = new int[]{startTime, endTime};
+        int[] prev = events.floor(event);
+        int[] next = events.ceiling(event);
+
+        if ((prev != null && prev[1] > startTime) || (next != null && next[0] < endTime)) {
+            return false;
+        }
+        events.add(event);
+        return true;
+    }
+}
+```
+
+```cpp
+class MyCalendar {
+private:
+    set<pair<int, int>> events;
+    
+public:
+    MyCalendar() {}
+    
+    bool book(int startTime, int endTime) {
+        if (startTime >= endTime) {
+            return false;
+        }
+        
+        auto next = events.lower_bound({startTime, startTime});
+        if (next != events.end() && next->first < endTime) {
+            return false;
+        }
+        if (next != events.begin()) {
+            auto prev = std::prev(next);
+            if (prev->second > startTime) {
+                return false;
+            }
+        }
+        
+        events.insert({startTime, endTime});
+        return true;
+    }
+};
+```
+
+```javascript
+class MyCalendar {
+    constructor() {
+        this.events = [];
+    }
+
+    /** 
+     * @param {number} startTime 
+     * @param {number} endTime
+     * @return {boolean}
+     */
+    book(startTime, endTIme) {
+        if (startTime >= endTime) {
+            return false;
+        }
+
+        const binarySearch = (target) => {
+            let left = 0, right = this.events.length;
+            
+            while (left < right) {
+                let mid = Math.floor((left + right) / 2);
+                if (this.events[mid][0] < target) {
+                    left = mid + 1;
+                } else {
+                    right = mid;
+                }
+            }
+            return left;
+        };
+
+        const idx = binarySearch(startTime);
+        if (idx > 0 && this.events[idx - 1][1] > startTime) {
+            return false;
+        }
+        if (idx < this.events.length && this.events[idx][0] < endTime) {
+            return false;
+        }
+        this.events.splice(idx, 0, [startTime, endTime]);
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$ for each $book()$ function call.
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/n-queens-ii.md b/articles/n-queens-ii.md
new file mode 100644
index 000000000..16a94bd75
--- /dev/null
+++ b/articles/n-queens-ii.md
@@ -0,0 +1,834 @@
+## 1. Backtracking
+
+::tabs-start
+
+```python
+class Solution:
+    def totalNQueens(self, n: int) -> int:
+        res = 0
+        board = [["."] * n for i in range(n)]
+
+        def backtrack(r):
+            nonlocal res
+            if r == n:
+                res += 1
+                return
+            for c in range(n):
+                if self.isSafe(r, c, board):
+                    board[r][c] = "Q"
+                    backtrack(r + 1)
+                    board[r][c] = "."
+
+        backtrack(0)
+        return res
+    
+    def isSafe(self, r: int, c: int, board):
+        row = r - 1
+        while row >= 0:
+            if board[row][c] == "Q":
+                return False
+            row -= 1
+            
+        row, col = r - 1, c - 1
+        while row >= 0 and col >= 0:
+            if board[row][col] == "Q":
+                return False
+            row -= 1
+            col -= 1
+
+        row, col = r - 1, c + 1
+        while row >= 0 and col < len(board):
+            if board[row][col] == "Q":
+                return False
+            row -= 1
+            col += 1
+        return True
+```
+
+```java
+public class Solution {
+    private int res;
+
+    public int totalNQueens(int n) {
+        res = 0;
+        char[][] board = new char[n][n];
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < n; j++) {
+                board[i][j] = '.';
+            }
+        }
+        backtrack(0, board);
+        return res;
+    }
+
+    private void backtrack(int r, char[][] board) {
+        if (r == board.length) {
+            res++;
+            return;
+        }
+        for (int c = 0; c < board.length; c++) {
+            if (isSafe(r, c, board)) {
+                board[r][c] = 'Q';
+                backtrack(r + 1, board);
+                board[r][c] = '.';
+            }
+        }
+    }
+
+    private boolean isSafe(int r, int c, char[][] board) {
+        for (int i = r - 1; i >= 0; i--) {
+            if (board[i][c] == 'Q') return false;
+        }
+        for (int i = r - 1, j = c - 1; i >= 0 && j >= 0; i--, j--) {
+            if (board[i][j] == 'Q') return false;
+        }
+        for (int i = r - 1, j = c + 1; i >= 0 && j < board.length; i--, j++) {
+            if (board[i][j] == 'Q') return false;
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int totalNQueens(int n) {
+        int res = 0;
+        vector<string> board(n, string(n, '.'));
+        backtrack(0, board, res);
+        return res;
+    }
+
+    void backtrack(int r, vector<string>& board, int& res) {
+        if (r == board.size()) {
+            res++;
+            return;
+        }
+        for (int c = 0; c < board.size(); c++) {
+            if (isSafe(r, c, board)) {
+                board[r][c] = 'Q';
+                backtrack(r + 1, board, res);
+                board[r][c] = '.';
+            }
+        }
+    }
+
+    bool isSafe(int r, int c, vector<string>& board) {
+        for (int i = r - 1; i >= 0; i--) {
+            if (board[i][c] == 'Q') return false;
+        }
+        for (int i = r - 1, j = c - 1; i >= 0 && j >= 0; i--, j--) {
+            if (board[i][j] == 'Q') return false;
+        }
+        for (int i = r - 1, j = c + 1; i >= 0 && j < board.size(); i--, j++) {
+            if (board[i][j] == 'Q') return false;
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    totalNQueens(n) {
+        let res = 0;
+        let board = Array.from({length: n}, () => Array(n).fill('.'));
+        
+        const backtrack = (r) => {
+            if (r === n) {
+                res++;
+                return;
+            }
+            for (let c = 0; c < n; c++) {
+                if (this.isSafe(r, c, board)) {
+                    board[r][c] = 'Q';
+                    backtrack(r + 1);
+                    board[r][c] = '.';
+                }
+            }
+        }
+        
+        backtrack(0);
+        return res;
+    }
+
+    /**
+     * @param {number} r
+     * @param {number} c
+     * @param {string[][]} board
+     * @return {boolean}
+     */
+    isSafe(r, c, board) {
+        for (let i = r - 1; i >= 0; i--) {
+            if (board[i][c] === 'Q') return false;
+        }
+        for (let i = r - 1, j = c - 1; i >= 0 && j >= 0; i--, j--) {
+            if (board[i][j] === 'Q') return false;
+        }
+        for (let i = r - 1, j = c + 1; i >= 0 && j < board.length; i--, j++) {
+            if (board[i][j] === 'Q') return false;
+        }
+        return true;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    private int res = 0;
+
+    public int TotalNQueens(int n) {
+        res = 0;
+        char[][] board = new char[n][];
+        for (int i = 0; i < n; i++) {
+            board[i] = Enumerable.Repeat('.', n).ToArray();
+        }
+
+        Backtrack(0, board, n);
+        return res;
+    }
+
+    private void Backtrack(int r, char[][] board, int n) {
+        if (r == n) {
+            res++;
+            return;
+        }
+
+        for (int c = 0; c < n; c++) {
+            if (IsSafe(r, c, board)) {
+                board[r][c] = 'Q';
+                Backtrack(r + 1, board, n);
+                board[r][c] = '.';
+            }
+        }
+    }
+
+    private bool IsSafe(int r, int c, char[][] board) {
+        // Check column
+        for (int row = r - 1; row >= 0; row--) {
+            if (board[row][c] == 'Q') return false;
+        }
+
+        // Check top-left diagonal
+        for (int row = r - 1, col = c - 1; row >= 0 && col >= 0; row--, col--) {
+            if (board[row][col] == 'Q') return false;
+        }
+
+        // Check top-right diagonal
+        for (int row = r - 1, col = c + 1; row >= 0 && col < board.Length; row--, col++) {
+            if (board[row][col] == 'Q') return false;
+        }
+
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n!)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 2. Backtracking (Hash Set)
+
+::tabs-start
+
+```python
+class Solution:
+    def totalNQueens(self, n: int) -> int:
+        col = set()
+        posDiag = set()
+        negDiag = set()
+
+        res = 0
+        def backtrack(r):
+            nonlocal res
+            if r == n:
+                res += 1
+                return
+
+            for c in range(n):
+                if c in col or (r + c) in posDiag or (r - c) in negDiag:
+                    continue
+
+                col.add(c)
+                posDiag.add(r + c)
+                negDiag.add(r - c)
+
+                backtrack(r + 1)
+
+                col.remove(c)
+                posDiag.remove(r + c)
+                negDiag.remove(r - c)
+
+        backtrack(0)
+        return res
+```
+
+```java
+public class Solution {
+    Set<Integer> col = new HashSet<>();
+    Set<Integer> posDiag = new HashSet<>();
+    Set<Integer> negDiag = new HashSet<>();
+    int res;
+    
+    public int totalNQueens(int n) {
+        res = 0;
+        backtrack(0, n);
+        return res;
+    }
+
+    private void backtrack(int r, int n) {
+        if (r == n) {
+            res++;
+            return;
+        }
+
+        for (int c = 0; c < n; c++) {
+            if (col.contains(c) || posDiag.contains(r + c) || negDiag.contains(r - c)) {
+                continue;
+            }
+
+            col.add(c);
+            posDiag.add(r + c);
+            negDiag.add(r - c);
+
+            backtrack(r + 1, n);
+
+            col.remove(c);
+            posDiag.remove(r + c);
+            negDiag.remove(r - c);
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    unordered_set<int> col;
+    unordered_set<int> posDiag;
+    unordered_set<int> negDiag;
+
+    int totalNQueens(int n) {
+        int res = 0;
+        backtrack(0, n, res);
+        return res;
+    }
+
+private:
+    void backtrack(int r, int n, int& res) {
+        if (r == n) {
+            res++;
+            return;
+        }
+
+        for (int c = 0; c < n; c++) {
+            if (col.count(c) || posDiag.count(r + c) || negDiag.count(r - c)) {
+                continue;
+            }
+
+            col.insert(c);
+            posDiag.insert(r + c);
+            negDiag.insert(r - c);
+
+            backtrack(r + 1, n, res);
+
+            col.erase(c);
+            posDiag.erase(r + c);
+            negDiag.erase(r - c);
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    totalNQueens(n) {
+        const col = new Set();
+        const posDiag = new Set();
+        const negDiag = new Set();
+        let res = 0;
+
+        /**
+         * @param {number} r
+         * @return {void}
+         */
+        function backtrack(r) {
+            if (r === n) {
+                res++;
+                return;
+            }
+
+            for (let c = 0; c < n; c++) {
+                if (col.has(c) || posDiag.has(r + c) ||
+                    negDiag.has(r - c)) {
+                    continue;
+                }
+
+                col.add(c);
+                posDiag.add(r + c);
+                negDiag.add(r - c);
+
+                backtrack(r + 1);
+
+                col.delete(c);
+                posDiag.delete(r + c);
+                negDiag.delete(r - c);
+            }
+        }
+
+        backtrack(0);
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    private HashSet<int> col = new HashSet<int>();
+    private HashSet<int> posDiag = new HashSet<int>();  // r + c
+    private HashSet<int> negDiag = new HashSet<int>();  // r - c
+    private int res = 0;
+
+    public int TotalNQueens(int n) {
+        res = 0;
+        Backtrack(0, n);
+        return res;
+    }
+
+    private void Backtrack(int r, int n) {
+        if (r == n) {
+            res++;
+            return;
+        }
+
+        for (int c = 0; c < n; c++) {
+            if (col.Contains(c) || posDiag.Contains(r + c) || negDiag.Contains(r - c))
+                continue;
+
+            col.Add(c);
+            posDiag.Add(r + c);
+            negDiag.Add(r - c);
+
+            Backtrack(r + 1, n);
+
+            col.Remove(c);
+            posDiag.Remove(r + c);
+            negDiag.Remove(r - c);
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n!)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Backtracking (Boolean Array)
+
+::tabs-start
+
+```python
+class Solution:
+    def totalNQueens(self, n: int) -> int:
+        col = [False] * n
+        posDiag = [False] * (n * 2)
+        negDiag = [False] * (n * 2)
+        res = 0
+
+        def backtrack(r):
+            nonlocal res
+            if r == n:
+                res += 1
+                return
+            for c in range(n):
+                if col[c] or posDiag[r + c] or negDiag[r - c + n]:
+                    continue
+                col[c] = True
+                posDiag[r + c] = True
+                negDiag[r - c + n] = True
+
+                backtrack(r + 1)
+
+                col[c] = False
+                posDiag[r + c] = False
+                negDiag[r - c + n] = False
+
+        backtrack(0)
+        return res
+```
+
+```java
+public class Solution {
+    boolean[] col, posDiag, negDiag;
+    int res;
+
+    public int totalNQueens(int n) {
+        col = new boolean[n];
+        posDiag = new boolean[2 * n];
+        negDiag = new boolean[2 * n];
+        res = 0;
+        
+        backtrack(0, n);
+        return res;
+    }
+
+    private void backtrack(int r, int n) {
+        if (r == n) {
+            res++;
+            return;
+        }
+        for (int c = 0; c < n; c++) {
+            if (col[c] || posDiag[r + c] || negDiag[r - c + n]) {
+                continue;
+            }
+            col[c] = true;
+            posDiag[r + c] = true;
+            negDiag[r - c + n] = true;
+
+            backtrack(r + 1, n);
+
+            col[c] = false;
+            posDiag[r + c] = false;
+            negDiag[r - c + n] = false;
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<string> board;
+    vector<bool> col, posDiag, negDiag;
+
+    int totalNQueens(int n) {
+        col.resize(n, false);
+        posDiag.resize(2 * n, false);
+        negDiag.resize(2 * n, false);
+
+        int res = 0;
+        backtrack(0, n, res);
+        return res;
+    }
+
+    void backtrack(int r, int n, int& res) {
+        if (r == n) {
+            res++;
+            return;
+        }
+        for (int c = 0; c < n; c++) {
+            if (col[c] || posDiag[r + c] || negDiag[r - c + n]) {
+                continue;
+            }
+            col[c] = true;
+            posDiag[r + c] = true;
+            negDiag[r - c + n] = true;
+
+            backtrack(r + 1, n, res);
+
+            col[c] = false;
+            posDiag[r + c] = false;
+            negDiag[r - c + n] = false;
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    totalNQueens(n) {
+        const col = Array(n).fill(false);
+        const posDiag = Array(2 * n).fill(false);
+        const negDiag = Array(2 * n).fill(false);
+        let res = 0;
+
+        /**
+         * @param {number} r
+         * @return {void}
+         */
+        function backtrack(r) {
+            if (r === n) {
+                res++;
+                return;
+            }
+            for (let c = 0; c < n; c++) {
+                if (col[c] || posDiag[r + c] || negDiag[r - c + n]) {
+                    continue;
+                } 
+                col[c] = true;
+                posDiag[r + c] = true;
+                negDiag[r - c + n] = true;
+
+                backtrack(r + 1);
+                
+                col[c] = false;
+                posDiag[r + c] = false;
+                negDiag[r - c + n] = false;
+            }
+        }
+
+        backtrack(0);
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int TotalNQueens(int n) {
+        bool[] col = new bool[n];
+        bool[] posDiag = new bool[2 * n];
+        bool[] negDiag = new bool[2 * n];
+        int res = 0;
+
+        void Backtrack(int r) {
+            if (r == n) {
+                res++;
+                return;
+            }
+
+            for (int c = 0; c < n; c++) {
+                if (col[c] || posDiag[r + c] || negDiag[r - c + n])
+                    continue;
+
+                col[c] = true;
+                posDiag[r + c] = true;
+                negDiag[r - c + n] = true;
+
+                Backtrack(r + 1);
+
+                col[c] = false;
+                posDiag[r + c] = false;
+                negDiag[r - c + n] = false;
+            }
+        }
+
+        Backtrack(0);
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n!)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Backtracking (Bit Mask)
+
+::tabs-start
+
+```python
+class Solution:
+    def totalNQueens(self, n: int) -> int:
+        col = 0
+        posDiag = 0
+        negDiag = 0
+        res = 0
+
+        def backtrack(r):
+            nonlocal col, posDiag, negDiag, res
+            if r == n:
+                res += 1
+                return
+            for c in range(n):
+                if ((col & (1 << c)) or (posDiag & (1 << (r + c))) 
+                    or (negDiag & (1 << (r - c + n)))):
+                    continue
+                col ^= (1 << c)
+                posDiag ^= (1 << (r + c))
+                negDiag ^= (1 << (r - c + n))
+
+                backtrack(r + 1)
+
+                col ^= (1 << c)
+                posDiag ^= (1 << (r + c))
+                negDiag ^= (1 << (r - c + n))
+
+        backtrack(0)
+        return res
+```
+
+```java
+public class Solution {
+    private int col = 0, posDiag = 0, negDiag = 0, res = 0;
+
+    public int totalNQueens(int n) {
+        res = 0;
+        backtrack(0, n);
+        return res;
+    }
+
+    private void backtrack(int r, int n) {
+        if (r == n) {
+            res++;
+            return;
+        }
+        for (int c = 0; c < n; c++) {
+            if ((col & (1 << c)) > 0 || (posDiag & (1 << (r + c))) > 0 || 
+                (negDiag & (1 << (r - c + n))) > 0) {
+                continue;
+            }
+            col ^= (1 << c);
+            posDiag ^= (1 << (r + c));
+            negDiag ^= (1 << (r - c + n));
+
+            backtrack(r + 1, n);
+
+            col ^= (1 << c);
+            posDiag ^= (1 << (r + c));
+            negDiag ^= (1 << (r - c + n));
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int col = 0, posDiag = 0, negDiag = 0;
+    vector<string> board;
+
+    int totalNQueens(int n) {
+        int res = 0;
+        backtrack(0, n, res);
+        return res;
+    }
+
+    void backtrack(int r, int n, int& res) {
+        if (r == n) {
+            res++;
+            return;
+        }
+        for (int c = 0; c < n; c++) {
+            if ((col & (1 << c)) || (posDiag & (1 << (r + c))) || 
+                (negDiag & (1 << (r - c + n)))) {
+                continue;
+            }
+            col ^= (1 << c);
+            posDiag ^= (1 << (r + c));
+            negDiag ^= (1 << (r - c + n));
+
+            backtrack(r + 1, n, res);
+
+            col ^= (1 << c);
+            posDiag ^= (1 << (r + c));
+            negDiag ^= (1 << (r - c + n));
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    totalNQueens(n) {
+        let col = 0, posDiag = 0, negDiag = 0, res = 0;
+
+        /**
+         * @param {number} r
+         * @return {void}
+         */
+        function backtrack(r) {
+            if (r === n) {
+                res++;
+                return;
+            }
+            for (let c = 0; c < n; c++) {
+                if ((col & (1 << c)) > 0 || (posDiag & (1 << (r + c))) > 0 || 
+                    (negDiag & (1 << (r - c + n))) > 0) {
+                    continue;
+                }
+                col ^= (1 << c);
+                posDiag ^= (1 << (r + c));
+                negDiag ^= (1 << (r - c + n));
+
+                backtrack(r + 1);
+                
+                col ^= (1 << c);
+                posDiag ^= (1 << (r + c));
+                negDiag ^= (1 << (r - c + n));
+            }
+        }
+
+        backtrack(0);
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int TotalNQueens(int n) {
+        int col = 0;
+        int posDiag = 0;
+        int negDiag = 0;
+        int res = 0;
+
+        void Backtrack(int r) {
+            if (r == n) {
+                res++;
+                return;
+            }
+
+            for (int c = 0; c < n; c++) {
+                if (((col & (1 << c)) != 0) || 
+                    ((posDiag & (1 << (r + c))) != 0) || 
+                    ((negDiag & (1 << (r - c + n))) != 0))
+                    continue;
+
+                col ^= (1 << c);
+                posDiag ^= (1 << (r + c));
+                negDiag ^= (1 << (r - c + n));
+
+                Backtrack(r + 1);
+
+                col ^= (1 << c);
+                posDiag ^= (1 << (r + c));
+                negDiag ^= (1 << (r - c + n));
+            }
+        }
+
+        Backtrack(0);
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n!)$
+* Space complexity: $O(n)$ for recursion stack.
\ No newline at end of file
diff --git a/articles/n-queens.md b/articles/n-queens.md
index 100fb04e9..e75cd714b 100644
--- a/articles/n-queens.md
+++ b/articles/n-queens.md
@@ -4,7 +4,7 @@
 
 ```python
 class Solution:
-    def solveNQueens(self, n: int):
+    def solveNQueens(self, n: int) -> List[List[str]]:
         res = []
         board = [["."] * n for i in range(n)]
 
@@ -225,6 +225,166 @@ public class Solution {
 }
 ```
 
+```go
+func solveNQueens(n int) [][]string {
+    res := [][]string{}
+    board := make([][]string, n)
+    for i := range board {
+        board[i] = make([]string, n)
+        for j := range board[i] {
+            board[i][j] = "."
+        }
+    }
+
+    var backtrack func(r int)
+    backtrack = func(r int) {
+        if r == n {
+            copyBoard := make([]string, n)
+            for i := range board {
+                copyBoard[i] = ""
+                for j := range board[i] {
+                    copyBoard[i] += board[i][j]
+                }
+            }
+            res = append(res, copyBoard)
+            return
+        }
+        for c := 0; c < n; c++ {
+            if isSafe(r, c, board) {
+                board[r][c] = "Q"
+                backtrack(r + 1)
+                board[r][c] = "."
+            }
+        }
+    }
+
+    backtrack(0)
+    return res
+}
+
+func isSafe(r int, c int, board [][]string) bool {
+    for row := r - 1; row >= 0; row-- {
+        if board[row][c] == "Q" {
+            return false
+        }
+    }
+
+    for row, col := r-1, c-1; row >= 0 && col >= 0; row, col = row-1, col-1 {
+        if board[row][col] == "Q" {
+            return false
+        }
+    }
+
+    for row, col := r-1, c+1; row >= 0 && col < len(board); row, col = row-1, col+1 {
+        if board[row][col] == "Q" {
+            return false
+        }
+    }
+
+    return true
+}
+```
+
+```kotlin
+class Solution {
+    fun solveNQueens(n: Int): List<List<String>> {
+        val res = mutableListOf<List<String>>()
+        val board = Array(n) { CharArray(n) { '.' } }
+
+        fun isSafe(r: Int, c: Int): Boolean {
+            var row = r - 1
+            while (row >= 0) {
+                if (board[row][c] == 'Q') return false
+                row--
+            }
+            var col = c - 1
+            row = r - 1
+            while (row >= 0 && col >= 0) {
+                if (board[row][col] == 'Q') return false
+                row--
+                col--
+            }
+            col = c + 1
+            row = r - 1
+            while (row >= 0 && col < n) {
+                if (board[row][col] == 'Q') return false
+                row--
+                col++
+            }
+            return true
+        }
+
+        fun backtrack(r: Int) {
+            if (r == n) {
+                res.add(board.map { it.joinToString("") })
+                return
+            }
+            for (c in 0 until n) {
+                if (isSafe(r, c)) {
+                    board[r][c] = 'Q'
+                    backtrack(r + 1)
+                    board[r][c] = '.'
+                }
+            }
+        }
+
+        backtrack(0)
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func solveNQueens(_ n: Int) -> [[String]] {
+        var res = [[String]]()
+        var board = Array(repeating: Array(repeating: ".", count: n), count: n)
+        
+        func backtrack(_ r: Int) {
+            if r == n {
+                let copy = board.map { $0.joined() }
+                res.append(copy)
+                return
+            }
+            for c in 0..<n {
+                if isSafe(r, c, board) {
+                    board[r][c] = "Q"
+                    backtrack(r + 1)
+                    board[r][c] = "."
+                }
+            }
+        }
+        
+        backtrack(0)
+        return res
+    }
+    
+    private func isSafe(_ r: Int, _ c: Int, _ board: [[String]]) -> Bool {
+        var row = r - 1
+        while row >= 0 {
+            if board[row][c] == "Q" { return false }
+            row -= 1
+        }
+        
+        var row1 = r - 1, col1 = c - 1
+        while row1 >= 0, col1 >= 0 {
+            if board[row1][col1] == "Q" { return false }
+            row1 -= 1
+            col1 -= 1
+        }
+        
+        var row2 = r - 1, col2 = c + 1
+        while row2 >= 0, col2 < board.count {
+            if board[row2][col2] == "Q" { return false }
+            row2 -= 1
+            col2 += 1
+        }
+        
+        return true
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -468,6 +628,136 @@ public class Solution {
 }
 ```
 
+```go
+func solveNQueens(n int) [][]string {
+    col := make(map[int]bool)
+    posDiag := make(map[int]bool)
+    negDiag := make(map[int]bool)
+    var res [][]string
+    board := make([][]rune, n)
+    for i := range board {
+        board[i] = make([]rune, n)
+        for j := range board[i] {
+            board[i][j] = '.'
+        }
+    }
+
+    var backtrack func(r int)
+    backtrack = func(r int) {
+        if r == n {
+            solution := make([]string, n)
+            for i := range board {
+                solution[i] = string(board[i])
+            }
+            res = append(res, solution)
+            return
+        }
+
+        for c := 0; c < n; c++ {
+            if col[c] || posDiag[r+c] || negDiag[r-c] {
+                continue
+            }
+
+            col[c] = true
+            posDiag[r+c] = true
+            negDiag[r-c] = true
+            board[r][c] = 'Q'
+
+            backtrack(r + 1)
+
+            col[c] = false
+            posDiag[r+c] = false
+            negDiag[r-c] = false
+            board[r][c] = '.'
+        }
+    }
+
+    backtrack(0)
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun solveNQueens(n: Int): List<List<String>> {
+        val col = HashSet<Int>()
+        val posDiag = HashSet<Int>()
+        val negDiag = HashSet<Int>()
+        val res = mutableListOf<List<String>>()
+        val board = Array(n) { CharArray(n) { '.' } }
+
+        fun backtrack(r: Int) {
+            if (r == n) {
+                res.add(board.map { it.joinToString("") })
+                return
+            }
+
+            for (c in 0 until n) {
+                if (c in col || (r + c) in posDiag || (r - c) in negDiag) {
+                    continue
+                }
+
+                col.add(c)
+                posDiag.add(r + c)
+                negDiag.add(r - c)
+                board[r][c] = 'Q'
+
+                backtrack(r + 1)
+
+                col.remove(c)
+                posDiag.remove(r + c)
+                negDiag.remove(r - c)
+                board[r][c] = '.'
+            }
+        }
+
+        backtrack(0)
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func solveNQueens(_ n: Int) -> [[String]] {
+        var col = Set<Int>()
+        var posDiag = Set<Int>()
+        var negDiag = Set<Int>()
+        var res = [[String]]()
+        var board = Array(repeating: Array(repeating: ".", count: n), count: n)
+
+        func backtrack(_ r: Int) {
+            if r == n {
+                let copy = board.map { $0.joined() }
+                res.append(copy)
+                return
+            }
+
+            for c in 0..<n {
+                if col.contains(c) || posDiag.contains(r + c) || negDiag.contains(r - c) {
+                    continue
+                }
+
+                col.insert(c)
+                posDiag.insert(r + c)
+                negDiag.insert(r - c)
+                board[r][c] = "Q"
+
+                backtrack(r + 1)
+
+                col.remove(c)
+                posDiag.remove(r + c)
+                negDiag.remove(r - c)
+                board[r][c] = "."
+            }
+        }
+
+        backtrack(0)
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -483,7 +773,7 @@ public class Solution {
 
 ```python
 class Solution:
-    def solveNQueens(self, n: int):
+    def solveNQueens(self, n: int) -> List[List[str]]:
         col = [False] * n
         posDiag = [False] * (n * 2)
         negDiag = [False] * (n * 2)
@@ -638,7 +928,7 @@ class Solution {
                 negDiag[r - c + n] = true;
                 board[r][c] = 'Q';
 
-                backtrack(r + 1, n);
+                backtrack(r + 1);
                 
                 col[c] = false;
                 posDiag[r + c] = false;
@@ -701,6 +991,134 @@ public class Solution {
 }
 ```
 
+```go
+func solveNQueens(n int) [][]string {
+    col := make([]bool, n)
+    posDiag := make([]bool, 2*n)
+    negDiag := make([]bool, 2*n)
+    var res [][]string
+    board := make([][]rune, n)
+    for i := range board {
+        board[i] = make([]rune, n)
+        for j := range board[i] {
+            board[i][j] = '.'
+        }
+    }
+
+    var backtrack func(r int)
+    backtrack = func(r int) {
+        if r == n {
+            solution := make([]string, n)
+            for i := range board {
+                solution[i] = string(board[i])
+            }
+            res = append(res, solution)
+            return
+        }
+
+        for c := 0; c < n; c++ {
+            if col[c] || posDiag[r+c] || negDiag[r-c+n] {
+                continue
+            }
+
+            col[c] = true
+            posDiag[r+c] = true
+            negDiag[r-c+n] = true
+            board[r][c] = 'Q'
+
+            backtrack(r + 1)
+
+            col[c] = false
+            posDiag[r+c] = false
+            negDiag[r-c+n] = false
+            board[r][c] = '.'
+        }
+    }
+
+    backtrack(0)
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun solveNQueens(n: Int): List<List<String>> {
+        val col = BooleanArray(n)
+        val posDiag = BooleanArray(2 * n)
+        val negDiag = BooleanArray(2 * n)
+        val res = mutableListOf<List<String>>()
+        val board = Array(n) { CharArray(n) { '.' } }
+
+        fun backtrack(r: Int) {
+            if (r == n) {
+                res.add(board.map { it.joinToString("") })
+                return
+            }
+
+            for (c in 0 until n) {
+                if (col[c] || posDiag[r + c] || negDiag[r - c + n]) continue
+
+                col[c] = true
+                posDiag[r + c] = true
+                negDiag[r - c + n] = true
+                board[r][c] = 'Q'
+
+                backtrack(r + 1)
+
+                col[c] = false
+                posDiag[r + c] = false
+                negDiag[r - c + n] = false
+                board[r][c] = '.'
+            }
+        }
+
+        backtrack(0)
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func solveNQueens(_ n: Int) -> [[String]] {
+        var col = Array(repeating: false, count: n)
+        var posDiag = Array(repeating: false, count: 2 * n)
+        var negDiag = Array(repeating: false, count: 2 * n)
+        var res = [[String]]()
+        var board = Array(repeating: Array(repeating: ".", count: n), count: n)
+
+        func backtrack(_ r: Int) {
+            if r == n {
+                let copy = board.map { $0.joined() }
+                res.append(copy)
+                return
+            }
+            
+            for c in 0..<n {
+                if col[c] || posDiag[r + c] || negDiag[r - c + n] {
+                    continue
+                }
+                
+                col[c] = true
+                posDiag[r + c] = true
+                negDiag[r - c + n] = true
+                board[r][c] = "Q"
+
+                backtrack(r + 1)
+
+                col[c] = false
+                posDiag[r + c] = false
+                negDiag[r - c + n] = false
+                board[r][c] = "."
+            }
+        }
+
+        backtrack(0)
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -716,7 +1134,7 @@ public class Solution {
 
 ```python
 class Solution:
-    def solveNQueens(self, n: int):
+    def solveNQueens(self, n: int) -> List[List[str]]:
         col = 0
         posDiag = 0
         negDiag = 0
@@ -868,7 +1286,7 @@ class Solution {
                 negDiag ^= (1 << (r - c + n));
                 board[r][c] = 'Q';
 
-                backtrack(r + 1, n);
+                backtrack(r + 1);
                 
                 col ^= (1 << c);
                 posDiag ^= (1 << (r + c));
@@ -929,6 +1347,130 @@ public class Solution {
 }
 ```
 
+```go
+func solveNQueens(n int) [][]string {
+    var res [][]string
+    board := make([][]rune, n)
+    for i := range board {
+        board[i] = make([]rune, n)
+        for j := range board[i] {
+            board[i][j] = '.'
+        }
+    }
+
+    var backtrack func(r, col, posDiag, negDiag int)
+    backtrack = func(r, col, posDiag, negDiag int) {
+        if r == n {
+            solution := make([]string, n)
+            for i := range board {
+                solution[i] = string(board[i])
+            }
+            res = append(res, solution)
+            return
+        }
+
+        for c := 0; c < n; c++ {
+            if (col&(1<<c)) != 0 || (posDiag&(1<<(r+c))) != 0 || 
+               (negDiag&(1<<(r-c+n))) != 0 {
+                continue
+            }
+
+            col ^= (1 << c)
+            posDiag ^= (1 << (r + c))
+            negDiag ^= (1 << (r - c + n))
+            board[r][c] = 'Q'
+
+            backtrack(r+1, col, posDiag, negDiag)
+
+            col ^= (1 << c)
+            posDiag ^= (1 << (r + c))
+            negDiag ^= (1 << (r - c + n))
+            board[r][c] = '.'
+        }
+    }
+
+    backtrack(0, 0, 0, 0)
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun solveNQueens(n: Int): List<List<String>> {
+        val res = mutableListOf<List<String>>()
+        val board = Array(n) { CharArray(n) { '.' } }
+
+        fun backtrack(r: Int, col: Int, posDiag: Int, negDiag: Int) {
+            if (r == n) {
+                res.add(board.map { it.joinToString("") })
+                return
+            }
+
+            for (c in 0 until n) {
+                if ((col and (1 shl c)) != 0 || (posDiag and (1 shl (r + c))) != 0 || 
+                    (negDiag and (1 shl (r - c + n))) != 0) {
+                    continue
+                }
+
+                val newCol = col xor (1 shl c)
+                val newPosDiag = posDiag xor (1 shl (r + c))
+                val newNegDiag = negDiag xor (1 shl (r - c + n))
+                board[r][c] = 'Q'
+
+                backtrack(r + 1, newCol, newPosDiag, newNegDiag)
+
+                board[r][c] = '.'
+            }
+        }
+
+        backtrack(0, 0, 0, 0)
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func solveNQueens(_ n: Int) -> [[String]] {
+        var col = 0
+        var posDiag = 0
+        var negDiag = 0
+        var res = [[String]]()
+        var board = Array(repeating: Array(repeating: ".", count: n), count: n)
+
+        func backtrack(_ r: Int) {
+            if r == n {
+                let copy = board.map { $0.joined() }
+                res.append(copy)
+                return
+            }
+            
+            for c in 0..<n {
+                if ((col & (1 << c)) != 0 || (posDiag & (1 << (r + c))) != 0 ||
+                    (negDiag & (1 << (r - c + n))) != 0) {
+                    continue
+                }
+                
+                col ^= (1 << c)
+                posDiag ^= (1 << (r + c))
+                negDiag ^= (1 << (r - c + n))
+                board[r][c] = "Q"
+
+                backtrack(r + 1)
+
+                col ^= (1 << c)
+                posDiag ^= (1 << (r + c))
+                negDiag ^= (1 << (r - c + n))
+                board[r][c] = "."
+            }
+        }
+
+        backtrack(0)
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/n-th-tribonacci-number.md b/articles/n-th-tribonacci-number.md
new file mode 100644
index 000000000..56f6ce37a
--- /dev/null
+++ b/articles/n-th-tribonacci-number.md
@@ -0,0 +1,360 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def tribonacci(self, n: int) -> int:
+        if n <= 2:
+            return 1 if n != 0 else 0
+        return self.tribonacci(n - 1) + self.tribonacci(n - 2) + self.tribonacci(n - 3)
+```
+
+```java
+public class Solution {
+    public int tribonacci(int n) {
+        if (n <= 2) {
+            return n == 0 ? 0 : 1;
+        }
+        return tribonacci(n - 1) + tribonacci(n - 2) + tribonacci(n - 3);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int tribonacci(int n) {
+        if (n <= 2) {
+            return n == 0 ? 0 : 1;
+        }
+        return tribonacci(n - 1) + tribonacci(n - 2) + tribonacci(n - 3);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    tribonacci(n) {
+        if (n <= 2) {
+            return n === 0 ? 0 : 1;
+        }
+        return this.tribonacci(n - 1) + this.tribonacci(n - 2) + this.tribonacci(n - 3);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int Tribonacci(int n) {
+        if (n == 0) return 0;
+        if (n <= 2) return 1;
+        return Tribonacci(n - 1) + Tribonacci(n - 2) + Tribonacci(n - 3);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(3 ^ n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def __init__(self):
+        self.dp = {}
+
+    def tribonacci(self, n: int) -> int:
+        if n <= 2:
+            return 1 if n != 0 else 0
+        if n in self.dp:
+            return self.dp[n]
+            
+        self.dp[n] = self.tribonacci(n - 1) + self.tribonacci(n - 2) + self.tribonacci(n - 3)
+        return self.dp[n]
+```
+
+```java
+public class Solution {
+    private HashMap<Integer, Integer> dp = new HashMap<>();
+
+    public int tribonacci(int n) {
+        if (n <= 2) {
+            return n == 0 ? 0 : 1;
+        }
+        if (dp.containsKey(n)) {
+            return dp.get(n);
+        }
+
+        dp.put(n, tribonacci(n - 1) + tribonacci(n - 2) + tribonacci(n - 3));
+        return dp.get(n);
+    }
+}
+```
+
+```cpp
+class Solution {
+    unordered_map<int, int> dp;
+
+public:
+    int tribonacci(int n) {
+        if (n <= 2) {
+            return n == 0 ? 0 : 1;
+        }
+        if (dp.count(n)) return dp[n];
+        
+        dp[n] = tribonacci(n - 1) + tribonacci(n - 2) + tribonacci(n - 3);
+        return dp[n];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @constructor
+     */
+    constructor() {
+        this.dp = new Map();
+    }
+
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    tribonacci(n) {
+        if (n <= 2) {
+            return n === 0 ? 0 : 1;
+        }
+        if (this.dp.has(n)) {
+            return this.dp.get(n);
+        }
+        const result = this.tribonacci(n - 1) + this.tribonacci(n - 2) + this.tribonacci(n - 3);
+        this.dp.set(n, result);
+        return result;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    private Dictionary<int, int> dp = new Dictionary<int, int>();
+
+    public int Tribonacci(int n) {
+        if (n == 0) return 0;
+        if (n <= 2) return 1;
+        if (dp.ContainsKey(n)) return dp[n];
+
+        dp[n] = Tribonacci(n - 1) + Tribonacci(n - 2) + Tribonacci(n - 3);
+        return dp[n];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def tribonacci(self, n: int) -> int:
+        if n <= 2:
+            return 1 if n != 0 else 0
+
+        dp = [0] * (n + 1)
+        dp[1] = dp[2] = 1
+        for i in range(3, n + 1):
+            dp[i] = dp[i - 1] + dp[i - 2] + dp[i - 3]
+        return dp[n]
+```
+
+```java
+public class Solution {
+    public int tribonacci(int n) {
+        if (n <= 2) {
+            return n == 0 ? 0 : 1;
+        }
+
+        int[] dp = new int[n + 1];
+        dp[1] = dp[2] = 1;
+        for (int i = 3; i <= n; i++) {
+            dp[i] = dp[i - 1] + dp[i - 2] + dp[i - 3];
+        }
+        return dp[n];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int tribonacci(int n) {
+        if (n <= 2) {
+            return n == 0 ? 0 : 1;
+        }
+
+        vector<int> dp(n + 1, 0);
+        dp[1] = dp[2] = 1;
+        for (int i = 3; i <= n; i++) {
+            dp[i] = dp[i - 1] + dp[i - 2] + dp[i - 3];
+        }
+        return dp[n];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    tribonacci(n) {
+        if (n <= 2) {
+            return n === 0 ? 0 : 1;
+        }
+
+        const dp = new Array(n + 1).fill(0);
+        dp[1] = dp[2] = 1;
+        for (let i = 3; i <= n; i++) {
+            dp[i] = dp[i - 1] + dp[i - 2] + dp[i - 3];
+        }
+        return dp[n];
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int Tribonacci(int n) {
+        if (n == 0) return 0;
+        if (n <= 2) return 1;
+
+        int[] dp = new int[n + 1];
+        dp[0] = 0;
+        dp[1] = dp[2] = 1;
+
+        for (int i = 3; i <= n; i++) {
+            dp[i] = dp[i - 1] + dp[i - 2] + dp[i - 3];
+        }
+
+        return dp[n];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def tribonacci(self, n: int) -> int:
+        t = [0, 1, 1]
+
+        if n < 3:
+            return t[n]
+        
+        for i in range(3, n + 1):
+            t[i % 3] = sum(t)
+        return t[n % 3]
+```
+
+```java
+public class Solution {
+    public int tribonacci(int n) {
+        int t[] = {0, 1, 1};
+        if (n < 3) return t[n];
+
+        for (int i = 3; i <= n; ++i) {
+            t[i % 3] = t[0] + t[1] + t[2];
+        }
+        return t[n % 3];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int tribonacci(int n) {
+        int t[] = {0, 1, 1};
+        if (n < 3) return t[n];
+
+        for (int i = 3; i <= n; ++i) {
+            t[i % 3] = t[0] + t[1] + t[2];
+        }
+        return t[n % 3];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    tribonacci(n) {
+        const t = [0, 1, 1]
+        if (n < 3) return t[n];
+
+        for (let i = 3; i <= n; ++i) {
+            t[i % 3] = t[0] + t[1] + t[2];
+        }
+        return t[n % 3];
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int Tribonacci(int n) {
+        int[] t = {0, 1, 1};
+        if (n < 3) return t[n];
+
+        for (int i = 3; i <= n; i++) {
+            t[i % 3] = t[0] + t[1] + t[2];
+        }
+
+        return t[n % 3];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/naming-a-company.md b/articles/naming-a-company.md
new file mode 100644
index 000000000..dbd85775d
--- /dev/null
+++ b/articles/naming-a-company.md
@@ -0,0 +1,495 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def distinctNames(self, ideas: List[str]) -> int:
+        n = len(ideas)
+        res = set()
+        ideasSet = set(ideas)
+
+        for i in range(n):
+            for j in range(i + 1, n):
+                A, B = ideas[j][0] + ideas[i][1:], ideas[i][0] + ideas[j][1:]
+                if A not in ideasSet and B not in ideasSet:
+                    res.add(A + ' ' + B)
+                    res.add(B + ' ' + A)
+
+        return len(res)
+```
+
+```java
+public class Solution {
+    public long distinctNames(String[] ideas) {
+        int n = ideas.length;
+        Set<String> res = new HashSet<>();
+        Set<String> ideasSet = new HashSet<>(Arrays.asList(ideas));
+
+        for (int i = 0; i < n; i++) {
+            for (int j = i + 1; j < n; j++) {
+                String A = ideas[j].charAt(0) + ideas[i].substring(1);
+                String B = ideas[i].charAt(0) + ideas[j].substring(1);
+                
+                if (!ideasSet.contains(A) && !ideasSet.contains(B)) {
+                    res.add(A + " " + B);
+                    res.add(B + " " + A);
+                }
+            }
+        }
+
+        return res.size();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long distinctNames(vector<string>& ideas) {
+        int n = ideas.size();
+        unordered_set<string> res;
+        unordered_set<string> ideasSet(ideas.begin(), ideas.end());
+
+        for (int i = 0; i < n; i++) {
+            for (int j = i + 1; j < n; j++) {
+                string A = ideas[j][0] + ideas[i].substr(1);
+                string B = ideas[i][0] + ideas[j].substr(1);
+
+                if (!ideasSet.count(A) && !ideasSet.count(B)) {
+                    res.insert(A + " " + B);
+                    res.insert(B + " " + A);
+                }
+            }
+        }
+
+        return res.size();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} ideas
+     * @return {number}
+     */
+    distinctNames(ideas) {
+        let n = ideas.length;
+        let res = new Set();
+        let ideasSet = new Set(ideas);
+
+        for (let i = 0; i < n; i++) {
+            for (let j = i + 1; j < n; j++) {
+                let A = ideas[j][0] + ideas[i].slice(1);
+                let B = ideas[i][0] + ideas[j].slice(1);
+
+                if (!ideasSet.has(A) && !ideasSet.has(B)) {
+                    res.add(A + " " + B);
+                    res.add(B + " " + A);
+                }
+            }
+        }
+
+        return res.size;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n ^ 2)$
+* Space complexity: $O(m * n ^ 2)$
+
+> Where $n$ is the size of the array $ideas$ and $m$ is the average length of the strings.
+
+---
+
+## 2. Group By First Letter (Hash Map)
+
+::tabs-start
+
+```python
+class Solution:
+    def distinctNames(self, ideas: List[str]) -> int:
+        wordMap = collections.defaultdict(set)
+        for w in ideas:
+            wordMap[w[0]].add(w[1:])
+
+        res = 0
+        for char1 in wordMap:
+            for char2 in wordMap:
+                if char1 == char2:
+                    continue
+
+                intersect = sum(1 for w in wordMap[char1] if w in wordMap[char2])
+                distinct1 = len(wordMap[char1]) - intersect
+                distinct2 = len(wordMap[char2]) - intersect
+                res += distinct1 * distinct2
+
+        return res
+```
+
+```java
+public class Solution {
+    public long distinctNames(String[] ideas) {
+        Map<Character, Set<String>> wordMap = new HashMap<>();
+        for (String word : ideas) {
+            wordMap.computeIfAbsent(
+                word.charAt(0), k -> new HashSet<>()).add(word.substring(1)
+            );
+        }
+
+        long res = 0;
+        for (char char1 : wordMap.keySet()) {
+            for (char char2 : wordMap.keySet()) {
+                if (char1 == char2) continue;
+
+                int intersect = 0;
+                for (String w : wordMap.get(char1)) {
+                    if (wordMap.get(char2).contains(w)) {
+                        intersect++;
+                    }
+                }
+
+                int distinct1 = wordMap.get(char1).size() - intersect;
+                int distinct2 = wordMap.get(char2).size() - intersect;
+                res += distinct1 * 1L * distinct2;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long distinctNames(vector<string>& ideas) {
+        unordered_map<char, unordered_set<string>> wordMap;
+        for (const string& word : ideas) {
+            wordMap[word[0]].insert(word.substr(1));
+        }
+
+        long long res = 0;
+        for (auto& [char1, set1] : wordMap) {
+            for (auto& [char2, set2] : wordMap) {
+                if (char1 == char2) continue;
+
+                int intersect = 0;
+                for (const string& w : set1) {
+                    if (set2.count(w)) {
+                        intersect++;
+                    }
+                }
+
+                int distinct1 = set1.size() - intersect;
+                int distinct2 = set2.size() - intersect;
+                res += distinct1 * 1LL * distinct2;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} ideas
+     * @return {number}
+     */
+    distinctNames(ideas) {
+        const wordMap = new Map();
+        for (let word of ideas) {
+            let key = word[0];
+            if (!wordMap.has(key)) {
+                wordMap.set(key, new Set());
+            }
+            wordMap.get(key).add(word.slice(1));
+        }
+
+        let res = 0;
+        for (let [char1, set1] of wordMap) {
+            for (let [char2, set2] of wordMap) {
+                if (char1 === char2) continue;
+
+                let intersect = 0;
+                for (let w of set1) {
+                    if (set2.has(w)) {
+                        intersect++;
+                    }
+                }
+
+                let distinct1 = set1.size - intersect;
+                let distinct2 = set2.size - intersect;
+                res += distinct1 * distinct2;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(m * n)$
+
+> Where $n$ is the size of the array $ideas$ and $m$ is the average length of the strings.
+
+---
+
+## 3. Group By First Letter (Array)
+
+::tabs-start
+
+```python
+class Solution:
+    def distinctNames(self, ideas: List[str]) -> int:
+        suffixes = [set() for _ in range(26)]
+        for w in ideas:
+            suffixes[ord(w[0]) - ord('a')].add(w[1:])
+
+        res = 0
+        for i in range(26):
+            for j in range(i + 1, 26):
+                intersect = len(suffixes[i] & suffixes[j])
+                res += 2 * (len(suffixes[i]) - intersect) * (len(suffixes[j]) - intersect)
+
+        return res
+```
+
+```java
+public class Solution {
+    public long distinctNames(String[] ideas) {
+        Set<String>[] suffixes = new HashSet[26];
+        for (int i = 0; i < 26; i++) {
+            suffixes[i] = new HashSet<>();
+        }
+        for (String w : ideas) {
+            suffixes[w.charAt(0) - 'a'].add(w.substring(1));
+        }
+
+        long res = 0;
+        for (int i = 0; i < 26; i++) {
+            for (int j = i + 1; j < 26; j++) {
+                int intersect = 0;
+                for (String s : suffixes[i]) {
+                    if (suffixes[j].contains(s)) {
+                        intersect++;
+                    }
+                }
+                res += 2L * (suffixes[i].size() - intersect) * (suffixes[j].size() - intersect);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long distinctNames(vector<string>& ideas) {
+        unordered_set<string> suffixes[26];
+        for (const string& w : ideas) {
+            suffixes[w[0] - 'a'].insert(w.substr(1));
+        }
+
+        long long res = 0;
+        for (int i = 0; i < 26; i++) {
+            for (int j = i + 1; j < 26; j++) {
+                int intersect = 0;
+                for (const string& s : suffixes[i]) {
+                    if (suffixes[j].count(s)) {
+                        intersect++;
+                    }
+                }
+                res += 2LL * (suffixes[i].size() - intersect) * (suffixes[j].size() - intersect);
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} ideas
+     * @return {number}
+     */
+    distinctNames(ideas) {
+        const suffixes = Array.from({ length: 26 }, () => new Set());
+        for (let w of ideas) {
+            suffixes[w.charCodeAt(0) - 97].add(w.slice(1));
+        }
+
+        let res = 0;
+        for (let i = 0; i < 26; i++) {
+            for (let j = i + 1; j < 26; j++) {
+                let intersect = 0;
+                for (let s of suffixes[i]) {
+                    if (suffixes[j].has(s)) {
+                        intersect++;
+                    }
+                }
+                res += 2 * (suffixes[i].size - intersect) * (suffixes[j].size - intersect);
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(m * n)$
+
+> Where $n$ is the size of the array $ideas$ and $m$ is the average length of the strings.
+
+---
+
+## 4. Counting
+
+::tabs-start
+
+```python
+class Solution:
+    def distinctNames(self, ideas: List[str]) -> int:
+        mp = defaultdict(lambda: [False] * 26)
+        count = [[0] * 26 for _ in range(26)]
+        res = 0
+
+        for s in ideas:
+            first_char = ord(s[0]) - ord('a')
+            suffix = s[1:]
+            mp[suffix][first_char] = True
+
+        for suffix, arr in mp.items():
+            for i in range(26):
+                if arr[i]:
+                    for j in range(26):
+                        if not arr[j]:
+                            count[i][j] += 1
+                            res += count[j][i]
+
+        return 2 * res
+```
+
+```java
+public class Solution {
+    public long distinctNames(String[] ideas) {
+        Map<String, boolean[]> mp = new HashMap<>();
+        int[][] count = new int[26][26];
+        long res = 0;
+
+        for (String s : ideas) {
+            int firstChar = s.charAt(0) - 'a';
+            String suffix = s.substring(1);
+            mp.putIfAbsent(suffix, new boolean[26]);
+            mp.get(suffix)[firstChar] = true;
+        }
+
+        for (boolean[] arr : mp.values()) {
+            for (int i = 0; i < 26; i++) {
+                if (arr[i]) {
+                    for (int j = 0; j < 26; j++) {
+                        if (!arr[j]) {
+                            count[i][j]++;
+                            res += count[j][i];
+                        }
+                    }
+                }
+            }
+        }
+        return 2 * res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long distinctNames(vector<string>& ideas) {
+        unordered_map<string, array<bool, 26>> mp;
+        long long count[26][26] = {};
+        long long res = 0;
+
+        for (const string& s : ideas) {
+            int firstChar = s[0] - 'a';
+            string suffix = s.substr(1);
+            mp[suffix][firstChar] = true;
+        }
+
+        for (auto& [suffix, arr] : mp) {
+            for (int i = 0; i < 26; i++) {
+                if (arr[i]) {
+                    for (int j = 0; j < 26; j++) {
+                        if (!arr[j]) {
+                            count[i][j]++;
+                            res += count[j][i];
+                        }
+                    }
+                }
+            }
+        }
+        return 2 * res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} ideas
+     * @return {number}
+     */
+    distinctNames(ideas) {
+        const mp = new Map();
+        const count = Array.from({ length: 26 }, () => Array(26).fill(0));
+        let res = 0;
+
+        for (const s of ideas) {
+            const firstChar = s.charCodeAt(0) - 97;
+            const suffix = s.slice(1);
+            if (!mp.has(suffix)) mp.set(suffix, new Array(26).fill(false));
+            mp.get(suffix)[firstChar] = true;
+        }
+
+        for (const arr of mp.values()) {
+            for (let i = 0; i < 26; i++) {
+                if (arr[i]) {
+                    for (let j = 0; j < 26; j++) {
+                        if (!arr[j]) {
+                            count[i][j]++;
+                            res += count[j][i];
+                        }
+                    }
+                }
+            }
+        }
+        return 2 * res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(m * n)$
+
+> Where $n$ is the size of the array $ideas$ and $m$ is the average length of the strings.
\ No newline at end of file
diff --git a/articles/network-delay-time.md b/articles/network-delay-time.md
index 2ce22170e..ae9fb93fc 100644
--- a/articles/network-delay-time.md
+++ b/articles/network-delay-time.md
@@ -147,6 +147,109 @@ public class Solution {
 }
 ```
 
+```go
+func networkDelayTime(times [][]int, n int, k int) int {
+	adj := make(map[int][][]int)
+	for _, time := range times {
+		u, v, w := time[0], time[1], time[2]
+		adj[u] = append(adj[u], []int{v, w})
+	}
+
+	dist := make(map[int]int)
+	for i := 1; i <= n; i++ {
+		dist[i] = math.MaxInt32
+	}
+
+	var dfs func(int, int)
+	dfs = func(node int, time int) {
+		if time >= dist[node] {
+			return
+		}
+		dist[node] = time
+		for _, edge := range adj[node] {
+			nei, w := edge[0], edge[1]
+			dfs(nei, time+w)
+		}
+	}
+
+	dfs(k, 0)
+	res := 0
+	for _, time := range dist {
+		if time == math.MaxInt32 {
+			return -1
+		}
+		if time > res {
+			res = time
+		}
+	}
+	return res
+}
+```
+
+```kotlin
+class Solution {
+    fun networkDelayTime(times: Array<IntArray>, n: Int, k: Int): Int {
+        val adj = HashMap<Int, MutableList<Pair<Int, Int>>>()
+        for (time in times) {
+            val (u, v, w) = time
+            adj.computeIfAbsent(u) { mutableListOf() }.add(v to w)
+        }
+
+        val dist = HashMap<Int, Int>().apply {
+            for (node in 1..n) {
+                this[node] = Int.MAX_VALUE
+            }
+        }
+
+        fun dfs(node: Int, time: Int) {
+            if (time >= dist[node]!!) return
+            dist[node] = time
+            for ((nei, w) in adj[node] ?: emptyList()) {
+                dfs(nei, time + w)
+            }
+        }
+
+        dfs(k, 0)
+        val res = dist.values.maxOrNull() ?: Int.MAX_VALUE
+        return if (res == Int.MAX_VALUE) -1 else res
+    }
+}
+```
+
+```swift
+class Solution {
+    func networkDelayTime(_ times: [[Int]], _ n: Int, _ k: Int) -> Int {
+        var adj = [Int: [(Int, Int)]]()
+        for time in times {
+            let u = time[0], v = time[1], w = time[2]
+            adj[u, default: []].append((v, w))
+        }
+
+        var dist = [Int: Int]()
+        for node in 1...n {
+            dist[node] = Int.max
+        }
+
+        func dfs(_ node: Int, _ time: Int) {
+            if time >= dist[node]! {
+                return
+            }
+            
+            dist[node] = time
+            if let neighbors = adj[node] {
+                for (nei, w) in neighbors {
+                    dfs(nei, time + w)
+                }
+            }
+        }
+
+        dfs(k, 0)
+        let res = dist.values.max()!
+        return res == Int.max ? -1 : res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -299,6 +402,116 @@ public class Solution {
 }
 ```
 
+```go
+func networkDelayTime(times [][]int, n int, k int) int {
+	inf := math.MaxInt32
+	dist := make([][]int, n)
+	for i := range dist {
+		dist[i] = make([]int, n)
+		for j := range dist[i] {
+			dist[i][j] = inf
+		}
+	}
+
+	for _, time := range times {
+		u, v, w := time[0]-1, time[1]-1, time[2]
+		dist[u][v] = w
+	}
+	for i := 0; i < n; i++ {
+		dist[i][i] = 0
+	}
+
+	for mid := 0; mid < n; mid++ {
+		for i := 0; i < n; i++ {
+			for j := 0; j < n; j++ {
+				dist[i][j] = min(dist[i][j], dist[i][mid]+dist[mid][j])
+			}
+		}
+	}
+
+	res := 0
+	for i := 0; i < n; i++ {
+		if dist[k-1][i] == inf {
+			return -1
+		}
+		res = max(res, dist[k-1][i])
+	}
+	return res
+}
+
+func min(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}
+
+func max(a, b int) int {
+	if a > b {
+		return a
+	}
+	return b
+}
+```
+
+```kotlin
+class Solution {
+    fun networkDelayTime(times: Array<IntArray>, n: Int, k: Int): Int {
+        val inf = (Int.MAX_VALUE / 2).toInt()
+        val dist = Array(n) { IntArray(n) { inf } }
+
+        for (i in 0 until n) {
+            dist[i].fill(inf)
+            dist[i][i] = 0
+        }
+
+        for (time in times) {
+            val (u, v, w) = time
+            dist[u - 1][v - 1] = w
+        }
+
+        for (mid in 0 until n) {
+            for (i in 0 until n) {
+                for (j in 0 until n) {
+                    dist[i][j] = minOf(dist[i][j], dist[i][mid] + dist[mid][j])
+                }
+            }
+        }
+
+        val maxDelay = dist[k - 1].maxOrNull()
+        return if (maxDelay == inf) -1 else maxDelay!!
+    }
+}
+```
+
+```swift
+class Solution {
+    func networkDelayTime(_ times: [[Int]], _ n: Int, _ k: Int) -> Int {
+        let inf = Int.max / 2
+        var dist = Array(repeating: Array(repeating: inf, count: n), count: n)
+        
+        for time in times {
+            let u = time[0] - 1, v = time[1] - 1, w = time[2]
+            dist[u][v] = w
+        }
+        for i in 0..<n {
+            dist[i][i] = 0
+        }
+
+        for mid in 0..<n {
+            for i in 0..<n {
+                for j in 0..<n {
+                    dist[i][j] = min(dist[i][j], dist[i][mid] + dist[mid][j])
+                }
+            }
+        }
+
+        let res = dist[k - 1].max()!
+        return res >= inf ? -1 : res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -418,6 +631,84 @@ public class Solution {
 }
 ```
 
+```go
+func networkDelayTime(times [][]int, n int, k int) int {
+    dist := make([]int, n)
+    for i := range dist {
+        dist[i] = 1 << 31 - 1 
+    }
+    dist[k-1] = 0
+
+    for _ = range n - 1 {
+        for _, time := range times {
+            u, v, w := time[0]-1, time[1]-1, time[2]
+            if dist[u] + w < dist[v] {
+                dist[v] = dist[u] + w
+            }
+        }
+    }
+
+    maxDist := 0
+    for _, d := range dist {
+        if d == 1<<31-1 {
+            return -1
+        }
+        if d > maxDist {
+            maxDist = d
+        }
+    }
+
+    return maxDist
+}
+```
+
+```kotlin
+class Solution {
+    fun networkDelayTime(times: Array<IntArray>, n: Int, k: Int): Int {
+        val dist = IntArray(n) { Int.MAX_VALUE }
+        dist[k - 1] = 0
+
+        for (i in 0 until n - 1) {
+            for (time in times) {
+                val (u, v, w) = time
+                if (dist[u - 1] != Int.MAX_VALUE && dist[u - 1] + w < dist[v - 1]) {
+                    dist[v - 1] = dist[u - 1] + w
+                }
+            }
+        }
+
+        val maxDist = dist.maxOrNull()
+        return if (maxDist == Int.MAX_VALUE) -1 else maxDist!!
+    }
+}
+```
+
+```swift
+class Solution {
+    func networkDelayTime(_ times: [[Int]], _ n: Int, _ k: Int) -> Int {
+        var dist = Array(repeating: Int.max, count: n)
+        dist[k - 1] = 0
+
+        for _ in 0..<n - 1 {
+            var updated = false
+            for time in times {
+                let u = time[0] - 1, v = time[1] - 1, w = time[2]
+                if dist[u] != Int.max && dist[u] + w < dist[v] {
+                    dist[v] = dist[u] + w
+                    updated = true
+                }
+            }
+            if !updated {
+                break
+            }
+        }
+
+        let maxDist = dist.max()!
+        return maxDist == Int.max ? -1 : maxDist
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -606,6 +897,122 @@ public class Solution {
 }
 ```
 
+```go
+func networkDelayTime(times [][]int, n int, k int) int {
+	adj := make(map[int][][]int)
+	for _, edge := range times {
+		u, v, w := edge[0], edge[1], edge[2]
+		adj[u] = append(adj[u], []int{v, w})
+	}
+
+	dist := make(map[int]int)
+	for i := 1; i <= n; i++ {
+		dist[i] = math.MaxInt
+	}
+	dist[k] = 0
+
+	q := [][]int{{k, 0}}
+
+	for len(q) > 0 {
+		node, time := q[0][0], q[0][1]
+		q = q[1:]
+
+		if time > dist[node] {
+			continue
+		}
+		for _, nei := range adj[node] {
+			v, w := nei[0], nei[1]
+			if time+w < dist[v] {
+				dist[v] = time + w
+				q = append(q, []int{v, time + w})
+			}
+		}
+	}
+
+	res := -1
+	for _, d := range dist {
+		if d == math.MaxInt {
+			return -1
+		}
+		if d > res {
+			res = d
+		}
+	}
+	return res
+}
+```
+
+```kotlin
+class Solution {
+    fun networkDelayTime(times: Array<IntArray>, n: Int, k: Int): Int {
+        val adj = HashMap<Int, MutableList<IntArray>>()
+        for (i in 1..n) adj[i] = mutableListOf()
+        for (time in times) {
+            adj[time[0]]?.add(intArrayOf(time[1], time[2]))
+        }
+        val dist = HashMap<Int, Int>()
+        for (i in 1..n) dist[i] = Int.MAX_VALUE
+        dist[k] = 0
+
+        val q: Queue<IntArray> = LinkedList()
+        q.offer(intArrayOf(k, 0))
+
+        while (q.isNotEmpty()) {
+            val (node, time) = q.poll()
+            if (dist[node]!! < time) continue
+            adj[node]?.forEach { (nextNode, weight) ->
+                if (time + weight < dist[nextNode]!!) {
+                    dist[nextNode] = time + weight
+                    q.offer(intArrayOf(nextNode, time + weight))
+                }
+            }
+        }
+
+        val res = dist.values.maxOrNull() ?: Int.MAX_VALUE
+        return if (res == Int.MAX_VALUE) -1 else res
+    }
+}
+```
+
+```swift
+class Solution {
+    func networkDelayTime(_ times: [[Int]], _ n: Int, _ k: Int) -> Int {
+        var adj = [Int: [(Int, Int)]]()
+        for time in times {
+            let u = time[0], v = time[1], w = time[2]
+            adj[u, default: []].append((v, w))
+        }
+
+        var dist = [Int: Int]()
+        for node in 1...n {
+            dist[node] = Int.max
+        }
+        dist[k] = 0
+
+        var queue = Deque<(Int, Int)>()
+        queue.append((k, 0))
+
+        while !queue.isEmpty {
+            let (node, time) = queue.popFirst()!
+            if dist[node]! < time {
+                continue
+            }
+            if let neighbors = adj[node] {
+                for (nei, w) in neighbors {
+                    if time + w < dist[nei]! {
+                        dist[nei] = time + w
+                        queue.append((nei, time + w))
+                    }
+                }
+            }
+        }
+
+        let res = dist.values.max()!
+        return res == Int.max ? -1 : res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -819,6 +1226,129 @@ public class Solution {
 }
 ```
 
+```go
+type Edge struct {
+    node, weight int
+}
+
+func networkDelayTime(times [][]int, n int, k int) int {
+    edges := make(map[int][]Edge)
+    for _, time := range times {
+        u, v, w := time[0], time[1], time[2]
+        edges[u] = append(edges[u], Edge{node: v, weight: w})
+    }
+
+    pq := priorityqueue.NewWith(func(a, b interface{}) int {
+        return utils.IntComparator(a.(Edge).weight, b.(Edge).weight)
+    })
+    pq.Enqueue(Edge{node: k, weight: 0})
+
+    visited := make(map[int]bool)
+    t := 0
+
+    for !pq.Empty() {
+        item, _ := pq.Dequeue()
+        edge := item.(Edge)
+        node, time := edge.node, edge.weight
+
+        if visited[node] {
+            continue
+        }
+        visited[node] = true
+        t = time
+
+        for _, next := range edges[node] {
+            if !visited[next.node] {
+                pq.Enqueue(Edge{node: next.node, weight: time + next.weight})
+            }
+        }
+    }
+
+    if len(visited) == n {
+        return t
+    }
+    return -1
+}
+```
+
+```kotlin
+class Solution {
+    fun networkDelayTime(times: Array<IntArray>, n: Int, k: Int): Int {
+        val edges = HashMap<Int, MutableList<Pair<Int, Int>>>()
+        for ((u, v, w) in times) {
+            edges.computeIfAbsent(u) { mutableListOf() }.add(Pair(v, w))
+        }
+
+        val minHeap = PriorityQueue<Pair<Int, Int>>(compareBy { it.first })
+        minHeap.offer(Pair(0, k))
+        val visited = HashSet<Int>()
+        var t = 0
+
+        while (minHeap.isNotEmpty()) {
+            val (time, node) = minHeap.poll()
+            if (node in visited) continue
+            visited.add(node)
+            t = time
+
+            edges[node]?.forEach { (nextNode, weight) ->
+                if (nextNode !in visited) {
+                    minHeap.offer(Pair(time + weight, nextNode))
+                }
+            }
+        }
+
+        return if (visited.size == n) t else -1
+    }
+}
+```
+
+```swift
+struct Item: Comparable {
+    let weight: Int
+    let node: Int
+
+    static func < (lhs: Item, rhs: Item) -> Bool {
+        return lhs.weight < rhs.weight
+    }
+}
+
+class Solution {
+    func networkDelayTime(_ times: [[Int]], _ n: Int, _ k: Int) -> Int {
+        var edges = [Int: [(Int, Int)]]()
+        for time in times {
+            let u = time[0], v = time[1], w = time[2]
+            edges[u, default: []].append((v, w))
+        }
+
+        var minHeap = Heap<Item>()
+        minHeap.insert(Item(weight: 0, node: k))
+        var visit = Set<Int>()
+        var t = 0
+
+        while !minHeap.isEmpty {
+            let item = minHeap.removeMin()
+            let w1 = item.weight
+            let n1 = item.node
+
+            if visit.contains(n1) {
+                continue
+            }
+            visit.insert(n1)
+            t = w1
+
+            if let neighbors = edges[n1] {
+                for (n2, w2) in neighbors {
+                    if !visit.contains(n2) {
+                        minHeap.insert(Item(weight: w1 + w2, node: n2))
+                    }
+                }
+            }
+        }
+        return visit.count == n ? t : -1
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/new-21-game.md b/articles/new-21-game.md
new file mode 100644
index 000000000..e65fcd1da
--- /dev/null
+++ b/articles/new-21-game.md
@@ -0,0 +1,485 @@
+## 1. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def new21Game(self, n: int, k: int, maxPts: int) -> float:
+        cache = {}
+        
+        def dfs(score):
+            if score >= k:
+                return 1 if score <= n else 0
+            if score in cache:
+                return cache[score]
+            
+            prob = 0
+            for i in range(1, maxPts + 1):
+                prob += dfs(score + i)
+
+            cache[score] = prob / maxPts
+            return cache[score]
+        
+        return dfs(0)
+```
+
+```java
+public class Solution {
+    private double[] dp;
+
+    public double new21Game(int n, int k, int maxPts) {
+        dp = new double[k];
+        for (int i = 0; i < dp.length; i++) dp[i] = -1.0;
+        return dfs(0, n, k, maxPts);
+    }
+
+    private double dfs(int score, int n, int k, int maxPts) {
+        if (score >= k) {
+            return score <= n ? 1.0 : 0.0;
+        }
+        if (dp[score] != -1.0) {
+            return dp[score];
+        }
+
+        double prob = 0;
+        for (int i = 1; i <= maxPts; i++) {
+            prob += dfs(score + i, n, k, maxPts);
+        }
+
+        dp[score] = prob / maxPts;
+        return dp[score];
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<double> dp;
+
+public:
+    double new21Game(int n, int k, int maxPts) {
+        dp.resize(k, -1.0);
+        return dfs(0, n, k, maxPts);
+    }
+
+private:
+    double dfs(int score, int n, int k, int maxPts) {
+        if (score >= k) {
+            return score <= n ? 1.0 : 0.0;
+        }
+        if (dp[score] != -1.0) {
+            return dp[score];
+        }
+
+        double prob = 0;
+        for (int i = 1; i <= maxPts; i++) {
+            prob += dfs(score + i, n, k, maxPts);
+        }
+
+        dp[score] = prob / maxPts;
+        return dp[score];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} k
+     * @param {number} maxPts
+     * @return {number}
+     */
+    new21Game(n, k, maxPts) {
+        const dp = new Array(k).fill(-1);
+
+        const dfs = (score) => {
+            if (score >= k) {
+                return score <= n ? 1 : 0;
+            }
+            if (dp[score] !== -1) {
+                return dp[score];
+            }
+
+            let prob = 0;
+            for (let i = 1; i <= maxPts; i++) {
+                prob += dfs(score + i);
+            }
+
+            dp[score] = prob / maxPts;
+            return dp[score];
+        };
+
+        return dfs(0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(k * m)$
+* Space complexity: $O(k)$
+
+> Where $k$ is the threshold score, $m$ is the maximum points per draw and $n$ is the upper bound on score.
+
+---
+
+## 2. Dynamic Programming (Top-Down Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def new21Game(self, n: int, k: int, maxPts: int) -> float:
+        cache = {}
+        
+        def dfs(score):
+            if score == k - 1:
+                return min(n - k + 1, maxPts) / maxPts
+            if score > n:
+                return 0
+            if score >= k:
+                return 1.0
+            
+            if score in cache:
+                return cache[score]
+            
+            cache[score] = dfs(score + 1)
+            cache[score] -= (dfs(score + 1 + maxPts) - dfs(score + 1)) / maxPts
+            return cache[score]
+        
+        return dfs(0)
+```
+
+```java
+public class Solution {
+    private double[] dp;
+
+    public double new21Game(int n, int k, int maxPts) {
+        dp = new double[k + maxPts];
+        for (int i = 0; i < dp.length; i++) dp[i] = -1.0;
+        return dfs(0, n, k, maxPts);
+    }
+
+    private double dfs(int score, int n, int k, int maxPts) {
+        if (score == k - 1) {
+            return Math.min(n - k + 1, maxPts) / (double) maxPts;
+        }
+        if (score > n) {
+            return 0.0;
+        }
+        if (score >= k) {
+            return 1.0;
+        }
+        if (dp[score] != -1.0) {
+            return dp[score];
+        }
+
+        dp[score] = dfs(score + 1, n, k, maxPts);
+        dp[score] -= (dfs(score + 1 + maxPts, n, k, maxPts) - dfs(score + 1, n, k, maxPts)) / maxPts;
+        return dp[score];
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<double> dp;
+
+public:
+    double new21Game(int n, int k, int maxPts) {
+        dp.resize(k + maxPts, -1.0);
+        return dfs(0, n, k, maxPts);
+    }
+
+private:
+    double dfs(int score, int n, int k, int maxPts) {
+        if (score == k - 1) {
+            return min(n - k + 1, maxPts) / (double)maxPts;
+        }
+        if (score > n) {
+            return 0.0;
+        }
+        if (score >= k) {
+            return 1.0;
+        }
+        if (dp[score] != -1.0) {
+            return dp[score];
+        }
+
+        dp[score] = dfs(score + 1, n, k, maxPts);
+        dp[score] -= (dfs(score + 1 + maxPts, n, k, maxPts) - dfs(score + 1, n, k, maxPts)) / maxPts;
+        return dp[score];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} k
+     * @param {number} maxPts
+     * @return {number}
+     */
+    new21Game(n, k, maxPts) {
+        const dp = new Array(k + maxPts).fill(-1);
+
+        const dfs = (score) => {
+            if (score === k - 1) {
+                return Math.min(n - k + 1, maxPts) / maxPts;
+            }
+            if (score > n) {
+                return 0;
+            }
+            if (score >= k) {
+                return 1.0;
+            }
+            if (dp[score] !== -1) {
+                return dp[score];
+            }
+
+            dp[score] = dfs(score + 1);
+            dp[score] -= (dfs(score + 1 + maxPts) - dfs(score + 1)) / maxPts;
+            return dp[score];
+        };
+
+        return dfs(0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(k + m)$
+* Space complexity: $O(n)$
+
+> Where $k$ is the threshold score, $m$ is the maximum points per draw and $n$ is the upper bound on score.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def new21Game(self, n: int, k: int, maxPts: int) -> float:
+        dp = [0] * (n + 1)
+        dp[0] = 1.0
+
+        for score in range(1, n + 1):
+            for draw in range(1, maxPts + 1):
+                if score - draw >= 0 and score - draw < k:
+                    dp[score] += dp[score - draw] / maxPts
+
+        return sum(dp[k:n + 1])
+```
+
+```java
+public class Solution {
+    public double new21Game(int n, int k, int maxPts) {
+        double[] dp = new double[n + 1];
+        dp[0] = 1.0;
+
+        for (int score = 1; score <= n; score++) {
+            for (int draw = 1; draw <= maxPts; draw++) {
+                if (score - draw >= 0 && score - draw < k) {
+                    dp[score] += dp[score - draw] / maxPts;
+                }
+            }
+        }
+
+        double result = 0.0;
+        for (int i = k; i <= n; i++) {
+            result += dp[i];
+        }
+
+        return result;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    double new21Game(int n, int k, int maxPts) {
+        vector<double> dp(n + 1, 0.0);
+        dp[0] = 1.0;
+
+        for (int score = 1; score <= n; score++) {
+            for (int draw = 1; draw <= maxPts; draw++) {
+                if (score - draw >= 0 && score - draw < k) {
+                    dp[score] += dp[score - draw] / maxPts;
+                }
+            }
+        }
+
+        double result = 0.0;
+        for (int i = k; i <= n; i++) {
+            result += dp[i];
+        }
+
+        return result;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} k
+     * @param {number} maxPts
+     * @return {number}
+     */
+    new21Game(n, k, maxPts) {
+        const dp = new Array(n + 1).fill(0);
+        dp[0] = 1.0;
+
+        for (let score = 1; score <= n; score++) {
+            for (let draw = 1; draw <= maxPts; draw++) {
+                if (score - draw >= 0 && score - draw < k) {
+                    dp[score] += dp[score - draw] / maxPts;
+                }
+            }
+        }
+
+        let result = 0.0;
+        for (let i = k; i <= n; i++) {
+            result += dp[i];
+        }
+
+        return result;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n)$
+
+> Where $k$ is the threshold score, $m$ is the maximum points per draw and $n$ is the upper bound on score.
+
+---
+
+## 4. Dynamic Programming (Sliding Window)
+
+::tabs-start
+
+```python
+class Solution:
+    def new21Game(self, n: int, k: int, maxPts: int) -> float:
+        if k == 0:
+            return 1.0
+        
+        windowSum = 0
+        for i in range(k, k + maxPts):
+            windowSum += 1 if i <= n else 0
+        
+        dp = {}
+        for i in range(k - 1, -1, -1):
+            dp[i] = windowSum / maxPts
+            remove = 0
+            if i + maxPts <= n:
+                remove = dp.get(i + maxPts, 1)
+            windowSum += dp[i] - remove
+        return dp[0]
+```
+
+```java
+class Solution {
+    public double new21Game(int n, int k, int maxPts) {
+        if (k == 0) {
+            return 1.0;
+        }
+        double windowSum = 0.0;
+        for (int i = k; i < k + maxPts; i++) {
+            windowSum += (i <= n) ? 1.0 : 0.0;
+        }
+        HashMap<Integer, Double> dp = new HashMap<>();
+        for (int i = k - 1; i >= 0; i--) {
+            dp.put(i, windowSum / maxPts);
+            double remove = 0.0;
+            if (i + maxPts <= n) {
+                remove = dp.getOrDefault(i + maxPts, 1.0);
+            }
+            windowSum += dp.get(i) - remove;
+        }
+        return dp.get(0);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    double new21Game(int n, int k, int maxPts) {
+        if (k == 0) {
+            return 1.0;
+        }
+        double windowSum = 0.0;
+        for (int i = k; i < k + maxPts; i++) {
+            windowSum += (i <= n) ? 1.0 : 0.0;
+        }
+        unordered_map<int, double> dp;
+        for (int i = k - 1; i >= 0; i--) {
+            dp[i] = windowSum / maxPts;
+            double remove = 0.0;
+            if (i + maxPts <= n) {
+                remove = (dp.find(i + maxPts) != dp.end()) ? dp[i + maxPts] : 1.0;
+            }
+            windowSum += dp[i] - remove;
+        }
+        return dp[0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} k
+     * @param {number} maxPts
+     * @return {number}
+     */
+    new21Game(n, k, maxPts) {
+        if (k === 0) {
+            return 1.0;
+        }
+        let windowSum = 0.0;
+        for (let i = k; i < k + maxPts; i++) {
+            windowSum += (i <= n) ? 1.0 : 0.0;
+        }
+        let dp = {};
+        for (let i = k - 1; i >= 0; i--) {
+            dp[i] = windowSum / maxPts;
+            let remove = 0.0;
+            if (i + maxPts <= n) {
+                remove = (dp[i + maxPts] !== undefined) ? dp[i + maxPts] : 1.0;
+            }
+            windowSum += dp[i] - remove;
+        }
+        return dp[0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(k + m)$
+* Space complexity: $O(n)$
+
+> Where $k$ is the threshold score, $m$ is the maximum points per draw and $n$ is the upper bound on score.
\ No newline at end of file
diff --git a/articles/next-greater-element-i.md b/articles/next-greater-element-i.md
new file mode 100644
index 000000000..b81ca977a
--- /dev/null
+++ b/articles/next-greater-element-i.md
@@ -0,0 +1,334 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def nextGreaterElement(self, nums1: List[int], nums2: List[int]) -> List[int]:
+        n = len(nums2)
+        res = []
+        for num in nums1:
+            nextGreater = -1
+            for i in range(n - 1, -1, -1):
+                if nums2[i] > num:
+                    nextGreater = nums2[i]
+                elif nums2[i] == num:
+                    break
+            res.append(nextGreater)
+        return res
+```
+
+```java
+public class Solution {
+    public int[] nextGreaterElement(int[] nums1, int[] nums2) {
+        int n = nums2.length;
+        int[] res = new int[nums1.length];
+        for (int i = 0; i < nums1.length; i++) {
+            int nextGreater = -1;
+            for (int j = n - 1; j >= 0; j--) {
+                if (nums2[j] > nums1[i]) {
+                    nextGreater = nums2[j];
+                } else if (nums2[j] == nums1[i]) {
+                    break;
+                }
+            }
+            res[i] = nextGreater;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> nextGreaterElement(vector<int>& nums1, vector<int>& nums2) {
+        int n = nums2.size();
+        vector<int> res;
+        for (int num : nums1) {
+            int nextGreater = -1;
+            for (int i = n - 1; i >= 0; i--) {
+                if (nums2[i] > num) {
+                    nextGreater = nums2[i];
+                } else if (nums2[i] == num) {
+                    break;
+                }
+            }
+            res.push_back(nextGreater);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums1
+     * @param {number[]} nums2
+     * @return {number[]}
+     */
+    nextGreaterElement(nums1, nums2) {
+        const n = nums2.length;
+        const res = [];
+        for (const num of nums1) {
+            let nextGreater = -1;
+            for (let i = n - 1; i >= 0; i--) {
+                if (nums2[i] > num) {
+                    nextGreater = nums2[i];
+                } else if (nums2[i] === num) {
+                    break;
+                }
+            }
+            res.push(nextGreater);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(1)$
+
+> Where $m$ is the size of the array $nums1$ and $n$ is the size of the array $nums2$.
+
+---
+
+## 2. Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def nextGreaterElement(self, nums1: List[int], nums2: List[int]) -> List[int]:
+        nums1Idx = {num : i for i, num in enumerate(nums1)}
+        res = [-1] * len(nums1)
+
+        for i in range(len(nums2)):
+            if nums2[i] not in nums1Idx:
+                continue
+            for j in range(i + 1, len(nums2)):
+                if nums2[j] > nums2[i]:
+                    idx = nums1Idx[nums2[i]]
+                    res[idx] = nums2[j]
+                    break
+        return res
+```
+
+```java
+public class Solution {
+    public int[] nextGreaterElement(int[] nums1, int[] nums2) {
+        HashMap<Integer, Integer> nums1Idx = new HashMap<>();
+        for (int i = 0; i < nums1.length; i++) {
+            nums1Idx.put(nums1[i], i);
+        }
+        
+        int[] res = new int[nums1.length];
+        Arrays.fill(res, -1);
+
+        for (int i = 0; i < nums2.length; i++) {
+            if (!nums1Idx.containsKey(nums2[i])) {
+                continue;
+            }
+            for (int j = i + 1; j < nums2.length; j++) {
+                if (nums2[j] > nums2[i]) {
+                    int idx = nums1Idx.get(nums2[i]);
+                    res[idx] = nums2[j];
+                    break;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> nextGreaterElement(vector<int>& nums1, vector<int>& nums2) {
+        unordered_map<int, int> nums1Idx;
+        for (int i = 0; i < nums1.size(); i++) {
+            nums1Idx[nums1[i]] = i;
+        }
+
+        vector<int> res(nums1.size(), -1);
+
+        for (int i = 0; i < nums2.size(); i++) {
+            if (nums1Idx.find(nums2[i]) == nums1Idx.end()) {
+                continue;
+            }
+            for (int j = i + 1; j < nums2.size(); j++) {
+                if (nums2[j] > nums2[i]) {
+                    int idx = nums1Idx[nums2[i]];
+                    res[idx] = nums2[j];
+                    break;
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums1
+     * @param {number[]} nums2
+     * @return {number[]}
+     */
+    nextGreaterElement(nums1, nums2) {
+        const nums1Idx = new Map();
+        nums1.forEach((num, i) => nums1Idx.set(num, i));
+        
+        const res = new Array(nums1.length).fill(-1);
+
+        for (let i = 0; i < nums2.length; i++) {
+            if (!nums1Idx.has(nums2[i])) {
+                continue;
+            }
+            for (let j = i + 1; j < nums2.length; j++) {
+                if (nums2[j] > nums2[i]) {
+                    const idx = nums1Idx.get(nums2[i]);
+                    res[idx] = nums2[j];
+                    break;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(m)$
+
+> Where $m$ is the size of the array $nums1$ and $n$ is the size of the array $nums2$.
+
+---
+
+## 3. Stack
+
+::tabs-start
+
+```python
+class Solution:
+    def nextGreaterElement(self, nums1: List[int], nums2: List[int]) -> List[int]:
+        nums1Idx = {num : i for i, num in enumerate(nums1)}
+        res = [-1] * len(nums1)
+
+        stack = []
+        for i in range(len(nums2)):
+            cur = nums2[i]
+            while stack and cur > stack[-1]:
+                val = stack.pop()
+                idx = nums1Idx[val]
+                res[idx] = cur
+            if cur in nums1Idx:
+                stack.append(cur)
+        return res
+```
+
+```java
+public class Solution {
+    public int[] nextGreaterElement(int[] nums1, int[] nums2) {
+        HashMap<Integer, Integer> nums1Idx = new HashMap<>();
+        for (int i = 0; i < nums1.length; i++) {
+            nums1Idx.put(nums1[i], i);
+        }
+
+        int[] res = new int[nums1.length];
+        for (int i = 0; i < res.length; i++) {
+            res[i] = -1;
+        }
+
+        Stack<Integer> stack = new Stack<>();
+        for (int num : nums2) {
+            while (!stack.isEmpty() && num > stack.peek()) {
+                int val = stack.pop();
+                int idx = nums1Idx.get(val);
+                res[idx] = num;
+            }
+            if (nums1Idx.containsKey(num)) {
+                stack.push(num);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> nextGreaterElement(vector<int>& nums1, vector<int>& nums2) {
+        unordered_map<int, int> nums1Idx;
+        for (int i = 0; i < nums1.size(); i++) {
+            nums1Idx[nums1[i]] = i;
+        }
+
+        vector<int> res(nums1.size(), -1);
+        stack<int> stack;
+        
+        for (int num : nums2) {
+            while (!stack.empty() && num > stack.top()) {
+                int val = stack.top();
+                stack.pop();
+                int idx = nums1Idx[val];
+                res[idx] = num;
+            }
+            if (nums1Idx.find(num) != nums1Idx.end()) {
+                stack.push(num);
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums1
+     * @param {number[]} nums2
+     * @return {number[]}
+     */
+    nextGreaterElement(nums1, nums2) {
+        const nums1Idx = new Map();
+        nums1.forEach((num, i) => nums1Idx.set(num, i));
+        
+        const res = new Array(nums1.length).fill(-1);
+        const stack = [];
+
+        for (let num of nums2) {
+            while (stack.length && num > stack[stack.length - 1]) {
+                const val = stack.pop();
+                const idx = nums1Idx.get(val);
+                res[idx] = num;
+            }
+            if (nums1Idx.has(num)) {
+                stack.push(num);
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m + n)$
+* Space complexity: $O(m)$
+
+> Where $m$ is the size of the array $nums1$ and $n$ is the size of the array $nums2$.
\ No newline at end of file
diff --git a/articles/non-cyclical-number.md b/articles/non-cyclical-number.md
new file mode 100644
index 000000000..6b3053011
--- /dev/null
+++ b/articles/non-cyclical-number.md
@@ -0,0 +1,736 @@
+## 1. Hash Set
+
+::tabs-start
+
+```python
+class Solution:
+    def isHappy(self, n: int) -> bool:
+        visit = set()
+
+        while n not in visit:
+            visit.add(n)
+            n = self.sumOfSquares(n)
+            if n == 1:
+                return True
+        return False
+
+    def sumOfSquares(self, n: int) -> int:
+        output = 0
+
+        while n:
+            digit = n % 10
+            digit = digit ** 2
+            output += digit
+            n = n // 10
+        return output
+```
+
+```java
+public class Solution {
+    public boolean isHappy(int n) {
+        Set<Integer> visit = new HashSet<>();
+
+        while (!visit.contains(n)) {
+            visit.add(n);
+            n = sumOfSquares(n);
+            if (n == 1) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    private int sumOfSquares(int n) {
+        int output = 0;
+
+        while (n > 0) {
+            int digit = n % 10;
+            digit = digit * digit;
+            output += digit;
+            n /= 10;
+        }
+        return output;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isHappy(int n) {
+        unordered_set<int> visit;
+
+        while (visit.find(n) == visit.end()) {
+            visit.insert(n);
+            n = sumOfSquares(n);
+            if (n == 1) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+private:
+    int sumOfSquares(int n) {
+        int output = 0;
+
+        while (n > 0) {
+            int digit = n % 10;
+            digit = digit * digit;
+            output += digit;
+            n /= 10;
+        }
+        return output;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {boolean}
+     */
+    isHappy(n) {
+        const visit = new Set();
+
+        while (!visit.has(n)) {
+            visit.add(n);
+            n = this.sumOfSquares(n);
+            if (n === 1) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    sumOfSquares(n) {
+        let output = 0;
+
+        while (n > 0) {
+            let digit = n % 10;
+            digit = digit * digit;
+            output += digit;
+            n = Math.floor(n / 10);
+        }
+        return output;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool IsHappy(int n) {
+        HashSet<int> visit = new HashSet<int>();
+
+        while (!visit.Contains(n)) {
+            visit.Add(n);
+            n = SumOfSquares(n);
+            if (n == 1) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    private int SumOfSquares(int n) {
+        int output = 0;
+
+        while (n > 0) {
+            int digit = n % 10;
+            digit = digit * digit;
+            output += digit;
+            n /= 10;
+        }
+        return output;
+    }
+}
+```
+
+```go
+func isHappy(n int) bool {
+    visit := make(map[int]bool)
+
+    for !visit[n] {
+        visit[n] = true
+        n = sumOfSquares(n)
+        if n == 1 {
+            return true
+        }
+    }
+    return false
+}
+
+func sumOfSquares(n int) int {
+    output := 0
+    for n > 0 {
+        digit := n % 10
+        digit = digit * digit
+        output += digit
+        n = n / 10
+    }
+    return output
+}
+```
+
+```kotlin
+class Solution {
+    fun isHappy(n: Int): Boolean {
+        val visit = HashSet<Int>()
+
+        var num = n
+        while (num !in visit) {
+            visit.add(num)
+            num = sumOfSquares(num)
+            if (num == 1) {
+                return true
+            }
+        }
+        return false
+    }
+
+    fun sumOfSquares(n: Int): Int {
+        var output = 0
+        var num = n
+        while (num > 0) {
+            val digit = num % 10
+            output += digit * digit
+            num /= 10
+        }
+        return output
+    }
+}
+```
+
+```swift
+class Solution {
+    func isHappy(_ n: Int) -> Bool {
+        var visit = Set<Int>()
+        var num = n
+
+        while !visit.contains(num) {
+            visit.insert(num)
+            num = sumOfSquares(num)
+            if num == 1 {
+                return true
+            }
+        }
+        return false
+    }
+
+    private func sumOfSquares(_ n: Int) -> Int {
+        var num = n
+        var output = 0
+
+        while num > 0 {
+            let digit = num % 10
+            output += digit * digit
+            num /= 10
+        }
+        return output
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(\log n)$
+
+---
+
+## 2. Fast And Slow Pointers - I
+
+::tabs-start
+
+```python
+class Solution:
+    def isHappy(self, n: int) -> bool:
+        slow, fast = n, self.sumOfSquares(n)
+
+        while slow != fast:
+            fast = self.sumOfSquares(fast)
+            fast = self.sumOfSquares(fast)
+            slow = self.sumOfSquares(slow)
+        return True if fast == 1 else False
+    
+    def sumOfSquares(self, n: int) -> int:
+        output = 0
+
+        while n:
+            digit = n % 10
+            digit = digit ** 2
+            output += digit
+            n = n // 10
+        return output
+```
+
+```java
+public class Solution {
+    public boolean isHappy(int n) {
+        int slow = n, fast = sumOfSquares(n);
+
+        while (slow != fast) {
+            fast = sumOfSquares(fast);
+            fast = sumOfSquares(fast);
+            slow = sumOfSquares(slow);
+        }
+
+        return fast == 1;
+    }
+
+    private int sumOfSquares(int n) {
+        int output = 0;
+        while (n != 0) {
+            output += (n % 10) * (n % 10);
+            n /= 10;
+        }
+        return output;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isHappy(int n) {
+        int slow = n, fast = sumOfSquares(n);
+
+        while (slow != fast) {
+            fast = sumOfSquares(fast);
+            fast = sumOfSquares(fast);
+            slow = sumOfSquares(slow);
+        }
+
+        return fast == 1;
+    }
+
+private:
+    int sumOfSquares(int n) {
+        int output = 0;
+        while (n != 0) {
+            output += (n % 10) * (n % 10);
+            n /= 10;
+        }
+        return output;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {boolean}
+     */
+    isHappy(n) {
+        let slow = n;
+        let fast = this.sumOfSquares(n);
+
+        while (slow !== fast) {
+            fast = this.sumOfSquares(fast);
+            fast = this.sumOfSquares(fast);
+            slow = this.sumOfSquares(slow);
+        }
+
+        return fast === 1;
+    }
+
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    sumOfSquares(n) {
+        let output = 0;
+        while (n !== 0) {
+            output += (n % 10) ** 2;
+            n = Math.floor(n / 10);
+        }
+        return output;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool IsHappy(int n) {
+        int slow = n, fast = sumOfSquares(n);
+
+        while (slow != fast) {
+            fast = sumOfSquares(fast);
+            fast = sumOfSquares(fast);
+            slow = sumOfSquares(slow);
+        }
+
+        return fast == 1;
+    }
+
+    private int sumOfSquares(int n) {
+        int output = 0;
+        while (n != 0) {
+            output += (n % 10) * (n % 10);
+            n /= 10;
+        }
+        return output;
+    }
+}
+```
+
+```go
+func isHappy(n int) bool {
+    slow, fast := n, sumOfSquares(n)
+
+    for slow != fast {
+        fast = sumOfSquares(fast)
+        fast = sumOfSquares(fast)
+        slow = sumOfSquares(slow)
+    }
+
+    return fast == 1
+}
+
+func sumOfSquares(n int) int {
+    output := 0
+    for n > 0 {
+        digit := n % 10
+        output += digit * digit
+        n = n / 10
+    }
+    return output
+}
+```
+
+```kotlin
+class Solution {
+    fun isHappy(n: Int): Boolean {
+        var slow = n
+        var fast = sumOfSquares(n)
+
+        while (slow != fast) {
+            fast = sumOfSquares(fast)
+            fast = sumOfSquares(fast)
+            slow = sumOfSquares(slow)
+        }
+
+        return fast == 1
+    }
+
+    fun sumOfSquares(n: Int): Int {
+        var output = 0
+        var num = n
+        while (num > 0) {
+            val digit = num % 10
+            output += digit * digit
+            num /= 10
+        }
+        return output
+    }
+}
+```
+
+```swift
+class Solution {
+    func isHappy(_ n: Int) -> Bool {
+        var slow = n
+        var fast = sumOfSquares(n)
+
+        while slow != fast {
+            fast = sumOfSquares(fast)
+            fast = sumOfSquares(fast)
+            slow = sumOfSquares(slow)
+        }
+        return fast == 1
+    }
+
+    private func sumOfSquares(_ n: Int) -> Int {
+        var num = n
+        var output = 0
+
+        while num > 0 {
+            let digit = num % 10
+            output += digit * digit
+            num /= 10
+        }
+        return output
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Fast And Slow Pointers - II
+
+::tabs-start
+
+```python
+class Solution:
+    def isHappy(self, n: int) -> bool:
+        slow, fast = n, self.sumOfSquares(n)
+        power = lam = 1
+        
+        while slow != fast:
+            if power == lam:
+                slow = fast
+                power *= 2
+                lam = 0
+            fast = self.sumOfSquares(fast)
+            lam += 1
+        return True if fast == 1 else False
+    
+    def sumOfSquares(self, n: int) -> int:
+        output = 0
+
+        while n:
+            digit = n % 10
+            digit = digit ** 2
+            output += digit
+            n = n // 10
+        return output
+```
+
+```java
+public class Solution {
+    public boolean isHappy(int n) {
+        int slow = n, fast = sumOfSquares(n);
+        int power = 1, lam = 1;
+        while (slow != fast) {
+            if (power == lam) {
+                slow = fast;
+                power *= 2;
+                lam = 0;
+            }
+            lam++;
+            fast = sumOfSquares(fast);
+        }
+
+        return fast == 1;
+    }
+
+    private int sumOfSquares(int n) {
+        int output = 0;
+        while (n != 0) {
+            output += (n % 10) * (n % 10);
+            n /= 10;
+        }
+        return output;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isHappy(int n) {
+        int slow = n, fast = sumOfSquares(n);
+        int power = 1, lam = 1;
+
+        while (slow != fast) {
+            if (power == lam) {
+                slow = fast;
+                power *= 2;
+                lam = 0;
+            }
+            lam++;
+            fast = sumOfSquares(fast);
+        }
+
+        return fast == 1;
+    }
+
+private:
+    int sumOfSquares(int n) {
+        int output = 0;
+        while (n != 0) {
+            output += (n % 10) * (n % 10);
+            n /= 10;
+        }
+        return output;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {boolean}
+     */
+    isHappy(n) {
+        let slow = n;
+        let fast = this.sumOfSquares(n);
+        let power = 1, lam = 1;
+
+        while (slow !== fast) {
+            if (power === lam) {
+                slow = fast;
+                power *= 2;
+                lam = 0;
+            }
+            lam++;
+            fast = this.sumOfSquares(fast);
+        }
+
+        return fast === 1;
+    }
+
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    sumOfSquares(n) {
+        let output = 0;
+        while (n !== 0) {
+            output += (n % 10) ** 2;
+            n = Math.floor(n / 10);
+        }
+        return output;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool IsHappy(int n) {
+        int slow = n, fast = sumOfSquares(n);
+        int power = 1, lam = 1;
+
+        while (slow != fast) {
+            if (power == lam) {
+                slow = fast;
+                power *= 2;
+                lam = 0;
+            }
+            lam++;
+            fast = sumOfSquares(fast);
+        }
+
+        return fast == 1;
+    }
+
+    private int sumOfSquares(int n) {
+        int output = 0;
+        while (n != 0) {
+            output += (n % 10) * (n % 10);
+            n /= 10;
+        }
+        return output;
+    }
+}
+```
+
+```go
+func isHappy(n int) bool {
+    slow, fast := n, sumOfSquares(n)
+    power, lam := 1, 1
+
+    for slow != fast {
+        if power == lam {
+            slow = fast
+            power *= 2
+            lam = 0
+        }
+        fast = sumOfSquares(fast)
+        lam++
+    }
+
+    return fast == 1
+}
+
+func sumOfSquares(n int) int {
+    output := 0
+    for n > 0 {
+        digit := n % 10
+        output += digit * digit
+        n = n / 10
+    }
+    return output
+}
+```
+
+```kotlin
+class Solution {
+    fun isHappy(n: Int): Boolean {
+        var slow = n
+        var fast = sumOfSquares(n)
+        var power = 1
+        var lam = 1
+
+        while (slow != fast) {
+            if (power == lam) {
+                slow = fast
+                power *= 2
+                lam = 0
+            }
+            fast = sumOfSquares(fast)
+            lam++
+        }
+
+        return fast == 1
+    }
+
+    fun sumOfSquares(n: Int): Int {
+        var output = 0
+        var num = n
+        while (num > 0) {
+            val digit = num % 10
+            output += digit * digit
+            num /= 10
+        }
+        return output
+    }
+}
+```
+
+```swift
+class Solution {
+    func isHappy(_ n: Int) -> Bool {
+        var slow = n
+        var fast = sumOfSquares(n)
+        var power = 1
+        var lam = 1
+
+        while slow != fast {
+            if power == lam {
+                slow = fast
+                power *= 2
+                lam = 0
+            }
+            fast = sumOfSquares(fast)
+            lam += 1
+        }
+        return fast == 1
+    }
+
+    private func sumOfSquares(_ n: Int) -> Int {
+        var num = n
+        var output = 0
+
+        while num > 0 {
+            let digit = num % 10
+            output += digit * digit
+            num /= 10
+        }
+        return output
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/non-decreasing-array.md b/articles/non-decreasing-array.md
new file mode 100644
index 000000000..aed007f6c
--- /dev/null
+++ b/articles/non-decreasing-array.md
@@ -0,0 +1,105 @@
+## 1. Greedy
+
+::tabs-start
+
+```python
+class Solution:
+    def checkPossibility(self, nums: list[int]) -> bool:
+        changed = False
+
+        for i in range(len(nums) - 1):
+            if nums[i] <= nums[i + 1]:
+                continue
+            if changed:
+                return False
+            if i == 0 or nums[i + 1] >= nums[i - 1]:
+                nums[i] = nums[i + 1]
+            else:
+                nums[i + 1] = nums[i]
+            changed = True
+        return True
+```
+
+```java
+public class Solution {
+    public boolean checkPossibility(int[] nums) {
+        boolean changed = false;
+
+        for (int i = 0; i < nums.length - 1; i++) {
+            if (nums[i] <= nums[i + 1]) {
+                continue;
+            }
+            if (changed) {
+                return false;
+            }
+            if (i == 0 || nums[i + 1] >= nums[i - 1]) {
+                nums[i] = nums[i + 1];
+            } else {
+                nums[i + 1] = nums[i];
+            }
+            changed = true;
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool checkPossibility(vector<int>& nums) {
+        bool changed = false;
+
+        for (int i = 0; i < nums.size() - 1; i++) {
+            if (nums[i] <= nums[i + 1]) {
+                continue;
+            }
+            if (changed) {
+                return false;
+            }
+            if (i == 0 || nums[i + 1] >= nums[i - 1]) {
+                nums[i] = nums[i + 1];
+            } else {
+                nums[i + 1] = nums[i];
+            }
+            changed = true;
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {boolean}
+     */
+    checkPossibility(nums) {
+        let changed = false;
+
+        for (let i = 0; i < nums.length - 1; i++) {
+            if (nums[i] <= nums[i + 1]) {
+                continue;
+            }
+            if (changed) {
+                return false;
+            }
+            if (i === 0 || nums[i + 1] >= nums[i - 1]) {
+                nums[i] = nums[i + 1];
+            } else {
+                nums[i + 1] = nums[i];
+            }
+            changed = true;
+        }
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/non-overlapping-intervals.md b/articles/non-overlapping-intervals.md
new file mode 100644
index 000000000..60f0b89a1
--- /dev/null
+++ b/articles/non-overlapping-intervals.md
@@ -0,0 +1,1305 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def eraseOverlapIntervals(self, intervals: List[List[int]]) -> int:
+        intervals.sort()
+        
+        def dfs(i, prev):
+            if i == len(intervals):
+                return 0
+            res = dfs(i + 1, prev)
+            if prev == -1 or intervals[prev][1] <= intervals[i][0]:
+                res = max(res, 1 + dfs(i + 1, i))
+            return res
+        
+        return len(intervals) - dfs(0, -1)
+```
+
+```java
+public class Solution {
+    public int eraseOverlapIntervals(int[][] intervals) {
+        Arrays.sort(intervals, (a, b) -> Integer.compare(a[0], b[0]));
+        return intervals.length - dfs(intervals, 0, -1);
+    }
+
+    private int dfs(int[][] intervals, int i, int prev) {
+        if (i == intervals.length) return 0;
+        int res = dfs(intervals, i + 1, prev);
+        if (prev == -1 || intervals[prev][1] <= intervals[i][0]) {
+            res = Math.max(res, 1 + dfs(intervals, i + 1, i));
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int eraseOverlapIntervals(vector<vector<int>>& intervals) {
+        sort(intervals.begin(), intervals.end());
+        return intervals.size() - dfs(intervals, 0, -1);
+    }
+
+private:
+    int dfs(const vector<vector<int>>& intervals, int i, int prev) {
+        if (i == intervals.size()) return 0;
+        int res = dfs(intervals, i + 1, prev);
+        if (prev == -1 || intervals[prev][1] <= intervals[i][0]) {
+            res = max(res, 1 + dfs(intervals, i + 1, i));
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} intervals
+     * @return {number}
+     */
+    eraseOverlapIntervals(intervals) {
+        intervals.sort((a, b) => a[0] - b[0]);
+        
+        const dfs = (i, prev) => {
+            if (i === intervals.length) return 0;
+            let res = dfs(i + 1, prev);
+            if (prev === -1 || intervals[prev][1] <= intervals[i][0]) {
+                res = Math.max(res, 1 + dfs(i + 1, i));
+            }
+            return res;
+        };
+
+        return intervals.length - dfs(0, -1);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int EraseOverlapIntervals(int[][] intervals) {
+        Array.Sort(intervals, (a, b) => a[0].CompareTo(b[0]));
+        return intervals.Length - Dfs(intervals, 0, -1);
+    }
+
+    private int Dfs(int[][] intervals, int i, int prev) {
+        if (i == intervals.Length) return 0;
+        int res = Dfs(intervals, i + 1, prev);
+        if (prev == -1 || intervals[prev][1] <= intervals[i][0]) {
+            res = Math.Max(res, 1 + Dfs(intervals, i + 1, i));
+        }
+        return res;
+    }
+}
+```
+
+```go
+func eraseOverlapIntervals(intervals [][]int) int {
+    sort.Slice(intervals, func(i, j int) bool {
+        return intervals[i][0] < intervals[j][0]
+    })
+
+    var dfs func(i, prev int) int
+    dfs = func(i, prev int) int {
+        if i == len(intervals) {
+            return 0
+        }
+        res := dfs(i+1, prev)
+        if prev == -1 || intervals[prev][1] <= intervals[i][0] {
+            res = max(res, 1+dfs(i+1, i))
+        }
+        return res
+    }
+
+    return len(intervals) - dfs(0, -1)
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun eraseOverlapIntervals(intervals: Array<IntArray>): Int {
+        intervals.sortBy { it[0] }
+
+        fun dfs(i: Int, prev: Int): Int {
+            if (i == intervals.size) {
+                return 0
+            }
+            var res = dfs(i + 1, prev)
+            if (prev == -1 || intervals[prev][1] <= intervals[i][0]) {
+                res = maxOf(res, 1 + dfs(i + 1, i))
+            }
+            return res
+        }
+
+        return intervals.size - dfs(0, -1)
+    }
+}
+```
+
+```swift
+class Solution {
+    func eraseOverlapIntervals(_ intervals: [[Int]]) -> Int {
+        var intervals = intervals
+        intervals.sort { $0[0] < $1[0] }
+
+        func dfs(_ i: Int, _ prev: Int) -> Int {
+            if i == intervals.count {
+                return 0
+            }
+            var res = dfs(i + 1, prev)
+            if prev == -1 || intervals[prev][1] <= intervals[i][0] {
+                res = max(res, 1 + dfs(i + 1, i))
+            }
+            return res
+        }
+
+        return intervals.count - dfs(0, -1)
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def eraseOverlapIntervals(self, intervals: List[List[int]]) -> int:
+        intervals.sort(key = lambda x: x[1])
+        n = len(intervals)
+        memo = {}
+
+        def dfs(i):
+            if i in memo:
+                return memo[i]
+
+            res = 1
+            for j in range(i + 1, n):
+                if intervals[i][1] <= intervals[j][0]:
+                    res = max(res, 1 + dfs(j))
+            memo[i] = res
+            return res
+
+        return n - dfs(0)
+```
+
+```java
+public class Solution {
+    private int[] memo;
+
+    public int eraseOverlapIntervals(int[][] intervals) {
+        Arrays.sort(intervals, (a, b) -> Integer.compare(a[1], b[1]));
+        int n = intervals.length;
+        memo = new int[n];  
+        Arrays.fill(memo, -1);
+        
+        int maxNonOverlapping = dfs(intervals, 0);
+        return n - maxNonOverlapping;
+    }
+
+    private int dfs(int[][] intervals, int i) {
+        if (i >= intervals.length) return 0;
+        if (memo[i] != -1) return memo[i];
+
+        int res = 1;
+        for (int j = i + 1; j < intervals.length; j++) {
+            if (intervals[i][1] <= intervals[j][0]) {
+                res = Math.max(res, 1 + dfs(intervals, j));
+            }
+        }
+        memo[i] = res;
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int eraseOverlapIntervals(vector<vector<int>>& intervals) {
+        sort(intervals.begin(), intervals.end(), [](auto& a, auto& b) {
+            return a[1] < b[1];
+        });
+        int n = intervals.size();
+        vector<int> memo(n, -1);  
+
+        int maxNonOverlapping = dfs(intervals, 0, memo);
+        return n - maxNonOverlapping;
+    }
+
+private:
+    int dfs(const vector<vector<int>>& intervals, int i, vector<int>& memo) {
+        if (i >= intervals.size()) return 0;
+        if (memo[i] != -1) return memo[i];
+
+        int res = 1;
+        for (int j = i + 1; j < intervals.size(); j++) {
+            if (intervals[i][1] <= intervals[j][0]) {
+                res = max(res, 1 + dfs(intervals, j, memo));
+            }
+        }
+        memo[i] = res;
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} intervals
+     * @return {number}
+     */
+    eraseOverlapIntervals(intervals) {
+        intervals.sort((a, b) => a[1] - b[1]);
+        const n = intervals.length;
+        let memo = new Array(n).fill(-1);  
+
+        const dfs = (i) => {
+            if (i >= n) return 0;
+            if (memo[i] !== -1) return memo[i];
+
+            let res = 1;
+            for (let j = i + 1; j < n; j++) {
+                if (intervals[i][1] <= intervals[j][0]) {
+                    res = Math.max(res, 1 + dfs(j));
+                }
+            }
+            memo[i] = res;
+            return res;
+        };
+
+        const maxNonOverlapping = dfs(0);
+        return n - maxNonOverlapping;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    private int[] memo;
+
+    public int EraseOverlapIntervals(int[][] intervals) {
+        Array.Sort(intervals, (a, b) => a[1].CompareTo(b[1]));
+        int n = intervals.Length;
+        memo = new int[n];  
+        Array.Fill(memo, -1);
+
+        int maxNonOverlapping = Dfs(intervals, 0);
+        return n - maxNonOverlapping;
+    }
+
+    private int Dfs(int[][] intervals, int i) {
+        if (i >= intervals.Length) return 0;
+        if (memo[i] != -1) return memo[i];
+
+        int res = 1;
+        for (int j = i + 1; j < intervals.Length; j++) {
+            if (intervals[i][1] <= intervals[j][0]) {
+                res = Math.Max(res, 1 + Dfs(intervals, j));
+            }
+        }
+        memo[i] = res;
+        return res;
+    }
+}
+```
+
+```go
+func eraseOverlapIntervals(intervals [][]int) int {
+    sort.Slice(intervals, func(i, j int) bool {
+        return intervals[i][1] < intervals[j][1]
+    })
+    n := len(intervals)
+    memo := make([]int, n)
+
+    var dfs func(i int) int
+    dfs = func(i int) int {
+        if memo[i] != 0 {
+            return memo[i]
+        }
+
+        res := 1
+        for j := i + 1; j < n; j++ {
+            if intervals[i][1] <= intervals[j][0] {
+                res = max(res, 1+dfs(j))
+            }
+        }
+        memo[i] = res
+        return res
+    }
+
+    return n - dfs(0)
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun eraseOverlapIntervals(intervals: Array<IntArray>): Int {
+        intervals.sortBy { it[1] }
+        val n = intervals.size
+        val memo = IntArray(n)
+
+        fun dfs(i: Int): Int {
+            if (memo[i] != 0) {
+                return memo[i]
+            }
+
+            var res = 1
+            for (j in i + 1 until n) {
+                if (intervals[i][1] <= intervals[j][0]) {
+                    res = maxOf(res, 1 + dfs(j))
+                }
+            }
+            memo[i] = res
+            return res
+        }
+
+        return n - dfs(0)
+    }
+}
+```
+
+```swift
+class Solution {
+    func eraseOverlapIntervals(_ intervals: [[Int]]) -> Int {
+        var intervals = intervals
+        intervals.sort { $0[1] < $1[1] }
+        let n = intervals.count
+        var memo = [Int: Int]()
+
+        func dfs(_ i: Int) -> Int {
+            if let result = memo[i] {
+                return result
+            }
+
+            var res = 1
+            for j in i + 1..<n {
+                if intervals[i][1] <= intervals[j][0] {
+                    res = max(res, 1 + dfs(j))
+                }
+            }
+            memo[i] = res
+            return res
+        }
+
+        return n - dfs(0)
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def eraseOverlapIntervals(self, intervals: List[List[int]]) -> int:
+        intervals.sort(key=lambda x: x[1])
+        n = len(intervals)
+        dp = [0] * n  
+
+        for i in range(n):
+            dp[i] = 1 
+            for j in range(i):
+                if intervals[j][1] <= intervals[i][0]:  
+                    dp[i] = max(dp[i], 1 + dp[j])
+
+        max_non_overlapping = max(dp)  
+        return n - max_non_overlapping
+```
+
+```java
+public class Solution {
+    public int eraseOverlapIntervals(int[][] intervals) {
+        Arrays.sort(intervals, (a, b) -> Integer.compare(a[1], b[1]));
+        int n = intervals.length;
+        int[] dp = new int[n];  
+
+        for (int i = 0; i < n; i++) {
+            dp[i] = 1;  
+            for (int j = 0; j < i; j++) {
+                if (intervals[j][1] <= intervals[i][0]) {  
+                    dp[i] = Math.max(dp[i], 1 + dp[j]);
+                }
+            }
+        }
+
+        int maxNonOverlapping = Arrays.stream(dp).max().getAsInt();  
+        return n - maxNonOverlapping;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int eraseOverlapIntervals(vector<vector<int>>& intervals) {
+        sort(intervals.begin(), intervals.end(), [](auto& a, auto& b) {
+            return a[1] < b[1];
+        });
+        int n = intervals.size();
+        vector<int> dp(n, 0);  
+
+        for (int i = 0; i < n; i++) {
+            dp[i] = 1;  
+            for (int j = 0; j < i; j++) {
+                if (intervals[j][1] <= intervals[i][0]) {  
+                    dp[i] = max(dp[i], 1 + dp[j]);
+                }
+            }
+        }
+
+        int maxNonOverlapping = *max_element(dp.begin(), dp.end());  
+        return n - maxNonOverlapping;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} intervals
+     * @return {number}
+     */
+    eraseOverlapIntervals(intervals) {
+        intervals.sort((a, b) => a[1] - b[1]);
+        const n = intervals.length;
+        const dp = new Array(n).fill(0);  
+
+        for (let i = 0; i < n; i++) {
+            dp[i] = 1;  
+            for (let j = 0; j < i; j++) {
+                if (intervals[j][1] <= intervals[i][0]) {  
+                    dp[i] = Math.max(dp[i], 1 + dp[j]);
+                }
+            }
+        }
+
+        const maxNonOverlapping = Math.max(...dp);  
+        return n - maxNonOverlapping;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int EraseOverlapIntervals(int[][] intervals) {
+        Array.Sort(intervals, (a, b) => a[1].CompareTo(b[1]));
+        int n = intervals.Length;
+        int[] dp = new int[n];  
+
+        for (int i = 0; i < n; i++) {
+            dp[i] = 1;  
+            for (int j = 0; j < i; j++) {
+                if (intervals[j][1] <= intervals[i][0]) {  
+                    dp[i] = Math.Max(dp[i], 1 + dp[j]);
+                }
+            }
+        }
+
+        int maxNonOverlapping = 0;
+        foreach (var count in dp) {
+            maxNonOverlapping = Math.Max(maxNonOverlapping, count);
+        }  
+        return n - maxNonOverlapping;
+    }
+}
+```
+
+```go
+func eraseOverlapIntervals(intervals [][]int) int {
+    sort.Slice(intervals, func(i, j int) bool {
+        return intervals[i][1] < intervals[j][1]
+    })
+
+    n := len(intervals)
+    dp := make([]int, n)
+
+    for i := 0; i < n; i++ {
+        dp[i] = 1
+        for j := 0; j < i; j++ {
+            if intervals[j][1] <= intervals[i][0] {
+                dp[i] = max(dp[i], 1+dp[j])
+            }
+        }
+    }
+
+    maxNonOverlapping := dp[0]
+    for i := 1; i < n; i++ {
+        maxNonOverlapping = max(maxNonOverlapping, dp[i])
+    }
+
+    return n - maxNonOverlapping
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun eraseOverlapIntervals(intervals: Array<IntArray>): Int {
+        intervals.sortBy { it[1] }
+        val n = intervals.size
+        val dp = IntArray(n)
+
+        for (i in 0 until n) {
+            dp[i] = 1
+            for (j in 0 until i) {
+                if (intervals[j][1] <= intervals[i][0]) {
+                    dp[i] = maxOf(dp[i], 1 + dp[j])
+                }
+            }
+        }
+
+        val maxNonOverlapping = dp.maxOrNull() ?: 0
+        return n - maxNonOverlapping
+    }
+}
+```
+
+```swift
+class Solution {
+    func eraseOverlapIntervals(_ intervals: [[Int]]) -> Int {
+        var intervals = intervals
+        intervals.sort { $0[1] < $1[1] }
+        let n = intervals.count
+        var dp = [Int](repeating: 0, count: n)
+
+        for i in 0..<n {
+            dp[i] = 1
+            for j in 0..<i {
+                if intervals[j][1] <= intervals[i][0] {
+                    dp[i] = max(dp[i], 1 + dp[j])
+                }
+            }
+        }
+
+        let maxNonOverlapping = dp.max() ?? 0
+        return n - maxNonOverlapping
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Dynamic Programming (Binary Search)
+
+::tabs-start
+
+```python
+class Solution:
+    def eraseOverlapIntervals(self, intervals: List[List[int]]) -> int:
+        intervals.sort(key=lambda x: x[1])
+        n = len(intervals)
+        dp = [0] * n
+        dp[0] = 1
+
+        def bs(r, target):
+            l = 0
+            while l < r:
+                m = (l + r) >> 1
+                if intervals[m][1] <= target:
+                    l = m + 1
+                else:
+                    r = m
+            return l
+
+        for i in range(1, n):
+            idx = bs(i, intervals[i][0])
+            if idx == 0:
+                dp[i] = dp[i - 1]
+            else:
+                dp[i] = max(dp[i - 1], 1 + dp[idx - 1])
+        return n - dp[n - 1]
+```
+
+```java
+public class Solution {
+    public int eraseOverlapIntervals(int[][] intervals) {
+        Arrays.sort(intervals, (a, b) -> Integer.compare(a[1], b[1]));
+        int n = intervals.length;
+        int[] dp = new int[n];
+        dp[0] = 1;
+
+        for (int i = 1; i < n; i++) {
+            int idx = bs(i, intervals[i][0], intervals);
+            if (idx == 0) {
+                dp[i] = dp[i - 1];
+            } else {
+                dp[i] = Math.max(dp[i - 1], 1 + dp[idx - 1]);
+            }
+        }
+        return n - dp[n - 1];
+    }
+
+    private int bs(int r, int target, int[][] intervals) {
+        int l = 0;
+        while (l < r) {
+            int m = (l + r) >> 1;
+            if (intervals[m][1] <= target) {
+                l = m + 1;
+            } else {
+                r = m;
+            }
+        }
+        return l;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int eraseOverlapIntervals(vector<vector<int>>& intervals) {
+        sort(intervals.begin(), intervals.end(), [](auto& a, auto& b) {
+            return a[1] < b[1];
+        });
+        int n = intervals.size();
+        vector<int> dp(n);
+        dp[0] = 1;
+
+        for (int i = 1; i < n; i++) {
+            int idx = bs(i, intervals[i][0], intervals);
+            if (idx == 0) {
+                dp[i] = dp[i - 1];
+            } else {
+                dp[i] = max(dp[i - 1], 1 + dp[idx - 1]);
+            }
+        }
+        return n - dp[n - 1];
+    }
+
+    int bs(int r, int target, vector<vector<int>>& intervals) {
+        int l = 0;
+        while (l < r) {
+            int m = (l + r) >> 1;
+            if (intervals[m][1] <= target) {
+                l = m + 1;
+            } else {
+                r = m;
+            }
+        }
+        return l;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} intervals
+     * @return {number}
+     */
+    eraseOverlapIntervals(intervals) {
+        intervals.sort((a, b) => a[1] - b[1]);
+        const n = intervals.length;
+        const dp = new Array(n).fill(0);
+        dp[0] = 1;
+
+        const bs = (r, target) => {
+            let l = 0;
+            while (l < r) {
+                const m = (l + r) >> 1;
+                if (intervals[m][1] <= target) {
+                    l = m + 1;
+                } else {
+                    r = m;
+                }
+            }
+            return l;
+        }
+
+        for (let i = 1; i < n; i++) {
+            const idx = bs(i, intervals[i][0]);
+            if (idx === 0) {
+                dp[i] = dp[i - 1];
+            } else {
+                dp[i] = Math.max(dp[i - 1], 1 + dp[idx - 1]);
+            }
+        }
+        return n - dp[n - 1];
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int EraseOverlapIntervals(int[][] intervals) {
+        Array.Sort(intervals, (a, b) => a[1].CompareTo(b[1]));
+        int n = intervals.Length;
+        int[] dp = new int[n];
+        dp[0] = 1;
+
+        for (int i = 1; i < n; i++) {
+            int idx = Bs(i, intervals[i][0], intervals);
+            if (idx == 0) {
+                dp[i] = dp[i - 1];
+            } else {
+                dp[i] = Math.Max(dp[i - 1], 1 + dp[idx - 1]);
+            }
+        }
+        return n - dp[n - 1];
+    }
+
+    private int Bs(int r, int target, int[][] intervals) {
+        int l = 0;
+        while (l < r) {
+            int m = (l + r) >> 1;
+            if (intervals[m][1] <= target) {
+                l = m + 1;
+            } else {
+                r = m;
+            }
+        }
+        return l;
+    }
+}
+```
+
+```go
+func eraseOverlapIntervals(intervals [][]int) int {
+    sort.Slice(intervals, func(i, j int) bool {
+        return intervals[i][1] < intervals[j][1]
+    })
+    
+    n := len(intervals)
+    dp := make([]int, n)
+    dp[0] = 1
+
+    var bs func(r, target int) int
+    bs = func(r, target int) int {
+        l := 0
+        for l < r {
+            m := (l + r) >> 1
+            if intervals[m][1] <= target {
+                l = m + 1
+            } else {
+                r = m
+            }
+        }
+        return l
+    }
+
+    for i := 1; i < n; i++ {
+        idx := bs(i, intervals[i][0])
+        if idx == 0 {
+            dp[i] = dp[i-1]
+        } else {
+            dp[i] = max(dp[i-1], 1+dp[idx-1])
+        }
+    }
+
+    return n - dp[n-1]
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun eraseOverlapIntervals(intervals: Array<IntArray>): Int {
+        intervals.sortBy { it[1] }
+        val n = intervals.size
+        val dp = IntArray(n)
+        dp[0] = 1
+
+        fun bs(r: Int, target: Int): Int {
+            var l = 0
+            var r = r
+            while (l < r) {
+                val m = (l + r) / 2
+                if (intervals[m][1] <= target) {
+                    l = m + 1
+                } else {
+                    r = m
+                }
+            }
+            return l
+        }
+
+        for (i in 1 until n) {
+            val idx = bs(i, intervals[i][0])
+            dp[i] = if (idx == 0) dp[i - 1] else maxOf(dp[i - 1], 1 + dp[idx - 1])
+        }
+
+        return n - dp[n - 1]
+    }
+}
+```
+
+```swift
+class Solution {
+    func eraseOverlapIntervals(_ intervals: [[Int]]) -> Int {
+        var intervals = intervals
+        intervals.sort { $0[1] < $1[1] }
+        let n = intervals.count
+        var dp = [Int](repeating: 0, count: n)
+        dp[0] = 1
+
+        func bs(_ r: Int, _ target: Int) -> Int {
+            var l = 0
+            var r = r
+            while l < r {
+                let m = (l + r) >> 1
+                if intervals[m][1] <= target {
+                    l = m + 1
+                } else {
+                    r = m
+                }
+            }
+            return l
+        }
+
+        for i in 1..<n {
+            let idx = bs(i, intervals[i][0])
+            if idx == 0 {
+                dp[i] = dp[i - 1]
+            } else {
+                dp[i] = max(dp[i - 1], 1 + dp[idx - 1])
+            }
+        }
+        return n - dp[n - 1]
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 5. Greedy (Sort By Start)
+
+::tabs-start
+
+```python
+class Solution:
+    def eraseOverlapIntervals(self, intervals: List[List[int]]) -> int:
+        intervals.sort()
+        res = 0
+        prevEnd = intervals[0][1]
+        
+        for start, end in intervals[1:]:
+            if start >= prevEnd:
+                prevEnd = end
+            else:
+                res += 1
+                prevEnd = min(end, prevEnd)
+        return res
+```
+
+```java
+public class Solution {
+    public int eraseOverlapIntervals(int[][] intervals) {
+        Arrays.sort(intervals, (a, b) -> Integer.compare(a[0], b[0]));
+        int res = 0;
+        int prevEnd = intervals[0][1];
+        
+        for (int i = 1; i < intervals.length; i++) {
+            int start = intervals[i][0];
+            int end = intervals[i][1];
+            if (start >= prevEnd) {
+                prevEnd = end;
+            } else {
+                res++;
+                prevEnd = Math.min(end, prevEnd);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int eraseOverlapIntervals(vector<vector<int>>& intervals) {
+        sort(intervals.begin(), intervals.end());
+        int res = 0;
+        int prevEnd = intervals[0][1];
+
+        for (int i = 1; i < intervals.size(); i++) {
+            int start = intervals[i][0];
+            int end = intervals[i][1];
+            if (start >= prevEnd) {
+                prevEnd = end;
+            } else {
+                res++;
+                prevEnd = min(end, prevEnd);
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} intervals
+     * @return {number}
+     */
+    eraseOverlapIntervals(intervals) {
+        intervals.sort((a, b) => a[0] - b[0]);
+        let res = 0;
+        let prevEnd = intervals[0][1];
+
+        for (let i = 1; i < intervals.length; i++) {
+            const start = intervals[i][0];
+            const end = intervals[i][1];
+            if (start >= prevEnd) {
+                prevEnd = end;
+            } else {
+                res++;
+                prevEnd = Math.min(end, prevEnd);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int EraseOverlapIntervals(int[][] intervals) {
+        Array.Sort(intervals, (a, b) => a[0].CompareTo(b[0]));
+        int res = 0;
+        int prevEnd = intervals[0][1];
+        
+        for (int i = 1; i < intervals.Length; i++) {
+            int start = intervals[i][0];
+            int end = intervals[i][1];
+            if (start >= prevEnd) {
+                prevEnd = end;
+            } else {
+                res++;
+                prevEnd = Math.Min(end, prevEnd);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```go
+func eraseOverlapIntervals(intervals [][]int) int {
+    sort.Slice(intervals, func(i, j int) bool {
+        return intervals[i][0] < intervals[j][0]
+    })
+
+    res := 0
+    prevEnd := intervals[0][1]
+
+    for _, interval := range intervals[1:] {
+        start, end := interval[0], interval[1]
+        if start >= prevEnd {
+            prevEnd = end
+        } else {
+            res++
+            prevEnd = min(end, prevEnd)
+        }
+    }
+    return res
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun eraseOverlapIntervals(intervals: Array<IntArray>): Int {
+        intervals.sortBy { it[0] }
+
+        var res = 0
+        var prevEnd = intervals[0][1]
+
+        for (i in 1 until intervals.size) {
+            val (start, end) = intervals[i]
+            if (start >= prevEnd) {
+                prevEnd = end
+            } else {
+                res++
+                prevEnd = minOf(end, prevEnd)
+            }
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func eraseOverlapIntervals(_ intervals: [[Int]]) -> Int {
+        var intervals = intervals
+        intervals.sort { $0[0] < $1[0] }
+        
+        var res = 0
+        var prevEnd = intervals[0][1]
+        
+        for i in 1..<intervals.count {
+            let start = intervals[i][0]
+            let end = intervals[i][1]
+            if start >= prevEnd {
+                prevEnd = end
+            } else {
+                res += 1
+                prevEnd = min(end, prevEnd)
+            }
+        }
+        return res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 6. Greedy (Sort By End)
+
+::tabs-start
+
+```python
+class Solution:
+    def eraseOverlapIntervals(self, intervals: List[List[int]]) -> int:
+        intervals.sort(key = lambda pair: pair[1])
+        prevEnd = intervals[0][1]
+        res = 0
+
+        for i in range(1, len(intervals)):
+            if prevEnd > intervals[i][0]:
+                res += 1
+            else:
+                prevEnd = intervals[i][1]
+
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int eraseOverlapIntervals(int[][] intervals) {
+        Arrays.sort(intervals, (a, b) -> Integer.compare(a[1], b[1]));
+        int res = 0;
+        int prevEnd = intervals[0][1];
+        
+        for (int i = 1; i < intervals.length; i++) {
+            int start = intervals[i][0];
+            int end = intervals[i][1];
+            if (start < prevEnd) {
+                res++;
+            } else {
+                prevEnd = end;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int eraseOverlapIntervals(vector<vector<int>>& intervals) {
+        sort(intervals.begin(), intervals.end(), [](auto& a, auto& b) {
+            return a[1] < b[1];
+        });
+        int res = 0;
+        int prevEnd = intervals[0][1];
+
+        for (int i = 1; i < intervals.size(); i++) {
+            int start = intervals[i][0];
+            int end = intervals[i][1];
+            if (start < prevEnd) {
+                res++;
+            } else {
+                prevEnd = end;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} intervals
+     * @return {number}
+     */
+    eraseOverlapIntervals(intervals) {
+        intervals.sort((a, b) => a[1] - b[1]);
+        let res = 0;
+        let prevEnd = intervals[0][1];
+
+        for (let i = 1; i < intervals.length; i++) {
+            const start = intervals[i][0];
+            const end = intervals[i][1];
+            if (start < prevEnd) {
+                res++;
+            } else {
+                prevEnd = end;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int EraseOverlapIntervals(int[][] intervals) {
+        Array.Sort(intervals, (a, b) => a[1].CompareTo(b[1]));
+        int res = 0;
+        int prevEnd = intervals[0][1];
+        
+        for (int i = 1; i < intervals.Length; i++) {
+            int start = intervals[i][0];
+            int end = intervals[i][1];
+            if (start < prevEnd) {
+                res++;
+            } else {
+                prevEnd = end;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```go
+func eraseOverlapIntervals(intervals [][]int) int {
+    sort.Slice(intervals, func(i, j int) bool {
+        return intervals[i][1] < intervals[j][1]
+    })
+
+    prevEnd := intervals[0][1]
+    res := 0
+
+    for i := 1; i < len(intervals); i++ {
+        if prevEnd > intervals[i][0] {
+            res++
+        } else {
+            prevEnd = intervals[i][1]
+        }
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun eraseOverlapIntervals(intervals: Array<IntArray>): Int {
+        intervals.sortBy { it[1] }
+
+        var prevEnd = intervals[0][1]
+        var res = 0
+
+        for (i in 1 until intervals.size) {
+            if (prevEnd > intervals[i][0]) {
+                res++
+            } else {
+                prevEnd = intervals[i][1]
+            }
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func eraseOverlapIntervals(_ intervals: [[Int]]) -> Int {
+        var intervals = intervals
+        intervals.sort { $0[1] < $1[1] }
+        
+        var prevEnd = intervals[0][1]
+        var res = 0
+        
+        for i in 1..<intervals.count {
+            if prevEnd > intervals[i][0] {
+                res += 1
+            } else {
+                prevEnd = intervals[i][1]
+            }
+        }
+        
+        return res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
\ No newline at end of file
diff --git a/articles/number-of-closed-islands.md b/articles/number-of-closed-islands.md
new file mode 100644
index 000000000..d3ab68940
--- /dev/null
+++ b/articles/number-of-closed-islands.md
@@ -0,0 +1,836 @@
+## 1. Depth First Search - I
+
+::tabs-start
+
+```python
+class Solution:
+    def closedIsland(self, grid: List[List[int]]) -> int:
+        ROWS, COLS = len(grid), len(grid[0])
+        directions = [[0, 1], [0, -1], [1, 0], [-1, 0]]
+        visit = set()
+
+        def dfs(r, c):
+            if r < 0 or c < 0 or r == ROWS or c == COLS:
+                return 0  # False
+            if grid[r][c] == 1 or (r, c) in visit:
+                return 1  # True
+
+            visit.add((r, c))
+            res = True
+            for dx, dy in directions:
+                if not dfs(r + dx, c + dy):
+                    res = False
+            return res
+
+        res = 0
+        for r in range(ROWS):
+            for c in range(COLS):
+                if not grid[r][c] and (r, c) not in visit:
+                    res += dfs(r, c)
+
+        return res
+```
+
+```java
+public class Solution {
+    private int[][] directions = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+    private boolean[][] visit;
+    private int ROWS, COLS;
+    
+    public int closedIsland(int[][] grid) {
+        ROWS = grid.length;
+        COLS = grid[0].length;
+        visit = new boolean[ROWS][COLS];
+
+        int res = 0;
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (grid[r][c] == 0 && !visit[r][c]) {
+                    if (dfs(grid, r, c)) {
+                        res++;
+                    }
+                }
+            }
+        }
+        return res;
+    }
+
+    private boolean dfs(int[][] grid, int r, int c) {
+        if (r < 0 || c < 0 || r == ROWS || c == COLS) {
+            return false;
+        }
+        if (grid[r][c] == 1 || visit[r][c]) {
+            return true;
+        }
+
+        visit[r][c] = true;
+        boolean res = true;
+        for (int[] d : directions) {
+            if (!dfs(grid, r + d[0], c + d[1])) {
+                res = false;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+    int ROWS, COLS;
+    vector<vector<int>> directions;
+    vector<vector<bool>> visit;
+
+public:
+    int closedIsland(vector<vector<int>>& grid) {
+        ROWS = grid.size();
+        COLS = grid[0].size();
+        directions = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+        visit.assign(ROWS, vector<bool>(COLS, false));
+
+        int res = 0;
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (grid[r][c] == 0 && !visit[r][c]) {
+                    if (dfs(grid, r, c)) {
+                        res++;
+                    }
+                }
+            }
+        }
+        return res;
+    }
+
+private:
+    bool dfs(vector<vector<int>>& grid, int r, int c) {
+        if (r < 0 || c < 0 || r == ROWS || c == COLS) {
+            return false;
+        }
+        if (grid[r][c] == 1 || visit[r][c]) {
+            return true;
+        }
+
+        visit[r][c] = true;
+        bool res = true;
+        for (auto& d : directions) {
+            if (!dfs(grid, r + d[0], c + d[1])) {
+                res = false;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    closedIsland(grid) {
+        const ROWS = grid.length, COLS = grid[0].length;
+        const directions = [0, 1, 0, -1, 0];
+        const visit = Array.from({ length: ROWS }, () => Array(COLS).fill(false));
+
+        const dfs = (r, c) => {
+            if (r < 0 || c < 0 || r === ROWS || c === COLS) return false;
+            if (grid[r][c] === 1 || visit[r][c]) return true;
+
+            visit[r][c] = true;
+            let res = true;
+            for (let d = 0; d < 4; d++) {
+                if (!dfs(r + directions[d], c + directions[d + 1])) {
+                    res = false;
+                }
+            }
+            return res;
+        };
+
+        let res = 0;
+        for (let r = 0; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                if (grid[r][c] === 0 && !visit[r][c]) {
+                    if (dfs(r, c)) res++;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns in the given grid.
+
+---
+
+## 2. Depth First Search - II
+
+::tabs-start
+
+```python
+class Solution:
+    def closedIsland(self, grid: list[list[int]]) -> int:
+        ROWS, COLS = len(grid), len(grid[0])
+        directions = [0, 1, 0, -1, 0]
+
+        def dfs(r, c):
+            if r < 0 or c < 0 or r == ROWS or c == COLS or grid[r][c] == 1:
+                return
+            grid[r][c] = 1
+            for d in range(4):
+                dfs(r + directions[d], c + directions[d + 1])
+
+        for r in range(ROWS):
+            dfs(r, 0)
+            dfs(r, COLS - 1)
+        for c in range(COLS):
+            dfs(0, c)
+            dfs(ROWS - 1, c)
+
+        res = 0
+        for r in range(1, ROWS - 1):
+            for c in range(1, COLS - 1):
+                if grid[r][c] == 0:
+                    dfs(r, c)
+                    res += 1
+        return res
+```
+
+```java
+public class Solution {
+    private int ROWS, COLS;
+    private int[] directions = {0, 1, 0, -1, 0};
+
+    public int closedIsland(int[][] grid) {
+        ROWS = grid.length;
+        COLS = grid[0].length;
+
+        for (int r = 0; r < ROWS; r++) {
+            dfs(grid, r, 0);
+            dfs(grid, r, COLS - 1);
+        }
+        for (int c = 0; c < COLS; c++) {
+            dfs(grid, 0, c);
+            dfs(grid, ROWS - 1, c);
+        }
+
+        int res = 0;
+        for (int r = 1; r < ROWS - 1; r++) {
+            for (int c = 1; c < COLS - 1; c++) {
+                if (grid[r][c] == 0) {
+                    dfs(grid, r, c);
+                    res++;
+                }
+            }
+        }
+        return res;
+    }
+
+    private void dfs(int[][] grid, int r, int c) {
+        if (r < 0 || c < 0 || r >= ROWS || c >= COLS || grid[r][c] == 1) {
+            return;
+        }
+        grid[r][c] = 1;
+        for (int d = 0; d < 4; d++) {
+            dfs(grid, r + directions[d], c + directions[d + 1]);
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+    const int directions[5] = {0, 1, 0, -1, 0};
+    int ROWS, COLS;
+
+public:
+    int closedIsland(vector<vector<int>>& grid) {
+        ROWS = grid.size();
+        COLS = grid[0].size();
+
+        for (int r = 0; r < ROWS; r++) {
+            dfs(grid, r, 0);
+            dfs(grid, r, COLS - 1);
+        }
+        for (int c = 0; c < COLS; c++) {
+            dfs(grid, 0, c);
+            dfs(grid, ROWS - 1, c);
+        }
+
+        int res = 0;
+        for (int r = 1; r < ROWS - 1; r++) {
+            for (int c = 1; c < COLS - 1; c++) {
+                if (grid[r][c] == 0) {
+                    dfs(grid, r, c);
+                    res++;
+                }
+            }
+        }
+        return res;
+    }
+
+private:
+    void dfs(vector<vector<int>>& grid, int r, int c) {
+        if (r < 0 || c < 0 || r >= ROWS || c >= COLS || grid[r][c] == 1) {
+            return;
+        }
+        grid[r][c] = 1;
+        for (int d = 0; d < 4; d++) {
+            dfs(grid, r + directions[d], c + directions[d + 1]);
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    closedIsland(grid) {
+        const ROWS = grid.length, COLS = grid[0].length;
+        const directions = [0, 1, 0, -1, 0];
+
+        const dfs = (r, c) => {
+            if (r < 0 || c < 0 || r === ROWS || c === COLS || grid[r][c] === 1) return;
+            grid[r][c] = 1;
+            for (let d = 0; d < 4; d++) {
+                dfs(r + directions[d], c + directions[d + 1]);
+            }
+        };
+
+        for (let r = 0; r < ROWS; r++) {
+            dfs(r, 0);
+            dfs(r, COLS - 1);
+        }
+        for (let c = 0; c < COLS; c++) {
+            dfs(0, c);
+            dfs(ROWS - 1, c);
+        }
+
+        let res = 0;
+        for (let r = 1; r < ROWS - 1; r++) {
+            for (let c = 1; c < COLS - 1; c++) {
+                if (grid[r][c] === 0) {
+                    dfs(r, c);
+                    res++;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns in the given grid.
+
+---
+
+## 3. Breadth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def closedIsland(self, grid: list[list[int]]) -> int:
+        ROWS, COLS = len(grid), len(grid[0])
+        directions = [[0, 1], [0, -1], [1, 0], [-1, 0]]
+        visit = set()
+        res = 0
+
+        def bfs(r, c):
+            q = deque([(r, c)])
+            visit.add((r, c))
+            is_closed = True
+
+            while q:
+                x, y = q.popleft()
+                for dx, dy in directions:
+                    nx, ny = x + dx, y + dy
+                    if nx < 0 or ny < 0 or nx >= ROWS or ny >= COLS:
+                        is_closed = False
+                        continue
+                    if grid[nx][ny] == 1 or (nx, ny) in visit:
+                        continue
+                    visit.add((nx, ny))
+                    q.append((nx, ny))
+                    
+            return is_closed
+
+        for r in range(ROWS):
+            for c in range(COLS):
+                if grid[r][c] == 0 and (r, c) not in visit:
+                    res += bfs(r, c)
+
+        return res
+```
+
+```java
+public class Solution {
+    private int[][] directions = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+    private int ROWS, COLS;
+    private boolean[][] visit;
+
+    public int closedIsland(int[][] grid) {
+        ROWS = grid.length;
+        COLS = grid[0].length;
+        visit = new boolean[ROWS][COLS];
+        int res = 0;
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (grid[r][c] == 0 && !visit[r][c]) {
+                    if (bfs(grid, r, c)) res++;
+                }
+            }
+        }
+        return res;
+    }
+
+    private boolean bfs(int[][] grid, int r, int c) {
+        Queue<int[]> q = new LinkedList<>();
+        q.offer(new int[]{r, c});
+        visit[r][c] = true;
+        boolean isClosed = true;
+
+        while (!q.isEmpty()) {
+            int[] cell = q.poll();
+            int x = cell[0], y = cell[1];
+
+            for (int[] d : directions) {
+                int nx = x + d[0], ny = y + d[1];
+                if (nx < 0 || ny < 0 || nx >= ROWS || ny >= COLS) {
+                    isClosed = false;
+                    continue;
+                }
+                if (grid[nx][ny] == 1 || visit[nx][ny]) continue;
+                visit[nx][ny] = true;
+                q.offer(new int[]{nx, ny});
+            }
+        }
+        return isClosed;
+    }
+}
+```
+
+```cpp
+class Solution {
+    int directions[4][2] = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+    int ROWS, COLS;
+    vector<vector<bool>> visit;
+
+public:
+    int closedIsland(vector<vector<int>>& grid) {
+        ROWS = grid.size();
+        COLS = grid[0].size();
+        visit.assign(ROWS, vector<bool>(COLS, false));
+        int res = 0;
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (grid[r][c] == 0 && !visit[r][c]) {
+                    if (bfs(grid, r, c)) res++;
+                }
+            }
+        }
+        return res;
+    }
+
+private:
+    bool bfs(vector<vector<int>>& grid, int r, int c) {
+        queue<pair<int, int>> q;
+        q.push({r, c});
+        visit[r][c] = true;
+        bool isClosed = true;
+
+        while (!q.empty()) {
+            auto [x, y] = q.front();q.pop();
+            for (auto& d : directions) {
+                int nx = x + d[0], ny = y + d[1];
+                if (nx < 0 || ny < 0 || nx >= ROWS || ny >= COLS) {
+                    isClosed = false;
+                    continue;
+                }
+                if (grid[nx][ny] == 1 || visit[nx][ny]) continue;
+                visit[nx][ny] = true;
+                q.push({nx, ny});
+            }
+        }
+        return isClosed;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    closedIsland(grid) {
+        const ROWS = grid.length, COLS = grid[0].length;
+        const directions = [[0, 1], [0, -1], [1, 0], [-1, 0]];
+        const visit = Array.from({ length: ROWS }, () => Array(COLS).fill(false));
+        let res = 0;
+
+        const bfs = (r, c) => {
+            const q = new Queue([[r, c]]);
+            visit[r][c] = true;
+            let isClosed = true;
+
+            while (!q.isEmpty()) {
+                const [x, y] = q.pop();
+                for (const [dx, dy] of directions) {
+                    const nx = x + dx, ny = y + dy;
+                    if (nx < 0 || ny < 0 || nx >= ROWS || ny >= COLS) {
+                        isClosed = false;
+                        continue;
+                    }
+                    if (grid[nx][ny] === 1 || visit[nx][ny]) continue;
+                    visit[nx][ny] = true;
+                    q.push([nx, ny]);
+                }
+            }
+            return isClosed;
+        };
+
+        for (let r = 0; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                if (grid[r][c] === 0 && !visit[r][c]) {
+                    if (bfs(r, c)) res++;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns in the given grid.
+
+---
+
+## 4. Disjoint Set Union
+
+::tabs-start
+
+```python
+class DSU:
+    def __init__(self, n):
+        self.Parent = list(range(n + 1))
+        self.Size = [1] * (n + 1)
+
+    def find(self, node):
+        if self.Parent[node] != node:
+            self.Parent[node] = self.find(self.Parent[node])
+        return self.Parent[node]
+
+    def union(self, u, v):
+        pu, pv = self.find(u), self.find(v)
+        if pu == pv:
+            return False
+        if self.Size[pu] >= self.Size[pv]:
+            self.Size[pu] += self.Size[pv]
+            self.Parent[pv] = pu
+        else:
+            self.Size[pv] += self.Size[pu]
+            self.Parent[pu] = pv
+        return True
+
+class Solution:
+    def closedIsland(self, grid: List[List[int]]) -> int:
+        ROWS, COLS = len(grid), len(grid[0])
+        N = ROWS * COLS
+        def index(r, c):
+            return r * COLS + c
+        
+        dsu = DSU(N)
+        directions = [0, 1, 0, -1, 0]
+        for r in range(ROWS):
+            for c in range(COLS):
+                if grid[r][c] == 0:
+                    for d in range(4):
+                        nr, nc = r + directions[d], c + directions[d + 1]
+                        if min(nr, nc) < 0 or nr == ROWS or nc == COLS:
+                            dsu.union(N, index(r, c))
+                        elif grid[nr][nc] == 0:
+                            dsu.union(index(r, c), index(nr, nc))
+
+        res = 0
+        rootN = dsu.find(N)
+        for r in range(ROWS):
+            for c in range(COLS):
+                if grid[r][c] == 1:
+                    continue
+                node = index(r, c)
+                root = dsu.find(node)
+                if root == node and root != rootN:
+                    res += 1
+        return res
+```
+
+```java
+class DSU {
+    int[] Parent, Size;
+
+    public DSU(int n) {
+        Parent = new int[n + 1];
+        Size = new int[n + 1];
+        for (int i = 0; i <= n; i++) {
+            Parent[i] = i;
+            Size[i] = 1;
+        }
+    }
+
+    public int find(int node) {
+        if (Parent[node] != node) {
+            Parent[node] = find(Parent[node]);
+        }
+        return Parent[node];
+    }
+
+    public boolean union(int u, int v) {
+        int pu = find(u), pv = find(v);
+        if (pu == pv) return false;
+        if (Size[pu] >= Size[pv]) {
+            Size[pu] += Size[pv];
+            Parent[pv] = pu;
+        } else {
+            Size[pv] += Size[pu];
+            Parent[pu] = pv;
+        }
+        return true;
+    }
+}
+
+public class Solution {
+    public int closedIsland(int[][] grid) {
+        int ROWS = grid.length, COLS = grid[0].length;
+        int N = ROWS * COLS;
+        
+        DSU dsu = new DSU(N);
+        int[] directions = {0, 1, 0, -1, 0};
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (grid[r][c] == 0) {
+                    for (int d = 0; d < 4; d++) {
+                        int nr = r + directions[d], nc = c + directions[d + 1];
+                        if (nr < 0 || nc < 0 || nr == ROWS || nc == COLS) {
+                            dsu.union(N, r * COLS + c);
+                        } else if (grid[nr][nc] == 0) {
+                            dsu.union(r * COLS + c, nr * COLS + nc);
+                        }
+                    }
+                }
+            }
+        }
+
+        int res = 0, rootN = dsu.find(N);
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (grid[r][c] == 0) {
+                    int node = r * COLS + c;
+                    int root = dsu.find(node);
+                    if (root == node && root != rootN) {
+                        res++;
+                    }
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class DSU {
+public:
+    vector<int> Parent, Size;
+
+    DSU(int n) {
+        Parent.resize(n + 1);
+        Size.resize(n + 1, 1);
+        for (int i = 0; i <= n; i++) {
+            Parent[i] = i;
+        }
+    }
+
+    int find(int node) {
+        if (Parent[node] != node) {
+            Parent[node] = find(Parent[node]);
+        }
+        return Parent[node];
+    }
+
+    bool unionSets(int u, int v) {
+        int pu = find(u), pv = find(v);
+        if (pu == pv) return false;
+        if (Size[pu] >= Size[pv]) {
+            Size[pu] += Size[pv];
+            Parent[pv] = pu;
+        } else {
+            Size[pv] += Size[pu];
+            Parent[pu] = pv;
+        }
+        return true;
+    }
+};
+
+class Solution {
+public:
+    int closedIsland(vector<vector<int>>& grid) {
+        int ROWS = grid.size(), COLS = grid[0].size();
+        int N = ROWS * COLS;
+        
+        DSU dsu(N);
+        int directions[5] = {0, 1, 0, -1, 0};
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (grid[r][c] == 0) {
+                    for (int d = 0; d < 4; d++) {
+                        int nr = r + directions[d], nc = c + directions[d + 1];
+                        if (nr < 0 || nc < 0 || nr == ROWS || nc == COLS) {
+                            dsu.unionSets(N, r * COLS + c);
+                        } else if (grid[nr][nc] == 0) {
+                            dsu.unionSets(r * COLS + c, nr * COLS + nc);
+                        }
+                    }
+                }
+            }
+        }
+
+        int res = 0, rootN = dsu.find(N);
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (grid[r][c] == 0) {
+                    int node = r * COLS + c;
+                    int root = dsu.find(node);
+                    if (root == node && root != rootN) {
+                        res++;
+                    }
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class DSU {
+    /**
+     * @constructor
+     * @param {number} n
+     */
+    constructor(n) {
+        this.parent = Array.from({ length: n + 1 }, (_, i) => i);
+        this.size = new Array(n + 1).fill(1);
+    }
+
+    /**
+     * @param {number} node
+     * @return {number}
+     */
+    find(node) {
+        if (this.parent[node] !== node) {
+            this.parent[node] = this.find(this.parent[node]);
+        }
+        return this.parent[node];
+    }
+
+    /**
+     * @param {number} u
+     * @param {number} u=v
+     * @return {boolean}
+     */
+    union(u, v) {
+        let pu = this.find(u), pv = this.find(v);
+        if (pu === pv) return false;
+        if (this.size[pu] >= this.size[pv]) {
+            this.size[pu] += this.size[pv];
+            this.parent[pv] = pu;
+        } else {
+            this.size[pv] += this.size[pu];
+            this.parent[pu] = pv;
+        }
+        return true;
+    }
+}
+
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    closedIsland(grid) {
+        const ROWS = grid.length, COLS = grid[0].length;
+        const N = ROWS * COLS;
+        
+        const dsu = new DSU(N);
+        const directions = [0, 1, 0, -1, 0];
+
+        for (let r = 0; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                if (grid[r][c] === 0) {
+                    for (let d = 0; d < 4; d++) {
+                        let nr = r + directions[d], nc = c + directions[d + 1];
+                        if (nr < 0 || nc < 0 || nr === ROWS || nc === COLS) {
+                            dsu.union(N, r * COLS + c);
+                        } else if (grid[nr][nc] === 0) {
+                            dsu.union(r * COLS + c, nr * COLS + nc);
+                        }
+                    }
+                }
+            }
+        }
+
+        let res = 0, rootN = dsu.find(N);
+        for (let r = 0; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                if (grid[r][c] === 0) {
+                    let node = r * COLS + c;
+                    let root = dsu.find(node);
+                    if (root === node && root !== rootN) {
+                        res++;
+                    }
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns in the given grid.
\ No newline at end of file
diff --git a/articles/number-of-dice-rolls-with-target-sum.md b/articles/number-of-dice-rolls-with-target-sum.md
new file mode 100644
index 000000000..442065a4a
--- /dev/null
+++ b/articles/number-of-dice-rolls-with-target-sum.md
@@ -0,0 +1,573 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def numRollsToTarget(self, n: int, k: int, target: int) -> int:
+        MOD = 10**9 + 7
+
+        def count(n, target):
+            if n == 0:
+                return 1 if target == 0 else 0
+            if target < 0:
+                return 0
+
+            res = 0
+            for val in range(1, k + 1):
+                res = (res + count(n - 1, target - val)) % MOD
+            return res
+
+        return count(n, target)
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1_000_000_007;
+
+    public int numRollsToTarget(int n, int k, int target) {
+        return count(n, target, k);
+    }
+
+    private int count(int n, int target, int k) {
+        if (n == 0) {
+            return target == 0 ? 1 : 0;
+        }
+        if (target < 0) {
+            return 0;
+        }
+
+        int res = 0;
+        for (int val = 1; val <= k; val++) {
+            res = (res + count(n - 1, target - val, k)) % MOD;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    const int MOD = 1e9 + 7;
+
+public:
+    int numRollsToTarget(int n, int k, int target) {
+        return count(n, target, k);
+    }
+
+private:
+    int count(int n, int target, int k) {
+        if (n == 0) {
+            return target == 0 ? 1 : 0;
+        }
+        if (target < 0) {
+            return 0;
+        }
+
+        int res = 0;
+        for (int val = 1; val <= k; val++) {
+            res = (res + count(n - 1, target - val, k)) % MOD;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} k
+     * @param {number} target
+     * @return {number}
+     */
+    numRollsToTarget(n, k, target) {
+        const MOD = 1e9 + 7;
+
+        const count = (n, target) => {
+            if (n === 0) {
+                return target === 0 ? 1 : 0;
+            }
+            if (target < 0) {
+                return 0;
+            }
+
+            let res = 0;
+            for (let val = 1; val <= k; val++) {
+                res = (res + count(n - 1, target - val)) % MOD;
+            }
+            return res;
+        };
+
+        return count(n, target);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(k ^ n)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the number of dices, $k$ is the number of faces each dice have, and $t$ is the target value.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def numRollsToTarget(self, n: int, k: int, target: int) -> int:
+        MOD = 10**9 + 7
+        cache = {}
+
+        def count(n, target):
+            if n == 0:
+                return 1 if target == 0 else 0
+            if (n, target) in cache:
+                return cache[(n, target)]
+
+            res = 0
+            for val in range(1, k + 1):
+                if target - val >= 0:
+                    res = (res + count(n - 1, target - val)) % MOD
+            cache[(n, target)] = res
+            return res
+
+        return count(n, target)
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1_000_000_007;
+    private int[][] dp;
+
+    public int numRollsToTarget(int n, int k, int target) {
+        dp = new int[n + 1][target + 1];
+        for (int[] row : dp) {
+            Arrays.fill(row, -1);
+        }
+        return count(n, target, k);
+    }
+
+    private int count(int n, int target, int k) {
+        if (n == 0) {
+            return target == 0 ? 1 : 0;
+        }
+        if (target < 0) {
+            return 0;
+        }
+        if (dp[n][target] != -1) {
+            return dp[n][target];
+        }
+
+        int res = 0;
+        for (int val = 1; val <= k; val++) {
+            if (target - val >= 0) {
+                res = (res + count(n - 1, target - val, k)) % MOD;
+            }
+        }
+        dp[n][target] = res;
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    const int MOD = 1e9 + 7;
+    vector<vector<int>> dp;
+
+public:
+    int numRollsToTarget(int n, int k, int target) {
+        dp = vector<vector<int>>(n + 1, vector<int>(target + 1, -1));
+        return count(n, target, k);
+    }
+
+private:
+    int count(int n, int target, int k) {
+        if (n == 0) {
+            return target == 0 ? 1 : 0;
+        }
+        if (target < 0) {
+            return 0;
+        }
+        if (dp[n][target] != -1) {
+            return dp[n][target];
+        }
+
+        int res = 0;
+        for (int val = 1; val <= k; val++) {
+            if (target - val >= 0) {
+                res = (res + count(n - 1, target - val, k)) % MOD;
+            }
+        }
+        dp[n][target] = res;
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} k
+     * @param {number} target
+     * @return {number}
+     */
+    numRollsToTarget(n, k, target) {
+        const MOD = 1e9 + 7;
+        const dp = Array.from({ length: n + 1 }, () => Array(target + 1).fill(-1));
+
+        const count = (n, target) => {
+            if (n === 0) {
+                return target === 0 ? 1 : 0;
+            }
+            if (dp[n][target] !== -1) {
+                return dp[n][target];
+            }
+
+            let res = 0;
+            for (let val = 1; val <= k; val++) {
+                if (target - val >= 0) {
+                    res = (res + count(n - 1, target - val)) % MOD;
+                }
+            }
+            dp[n][target] = res;
+            return res;
+        };
+
+        return count(n, target);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * t * k)$
+* Space complexity: $O(n * t)$
+
+> Where $n$ is the number of dices, $k$ is the number of faces each dice have, and $t$ is the target value.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def numRollsToTarget(self, n: int, k: int, target: int) -> int:
+        MOD = 10**9 + 7
+        dp = [[0] * (target + 1) for _ in range(n + 1)]
+        dp[0][0] = 1
+
+        for i in range(1, n + 1):
+            for val in range(1, k + 1):
+                for t in range(val, target + 1):
+                    dp[i][t] = (dp[i][t] + dp[i - 1][t - val]) % MOD
+
+        return dp[n][target]
+```
+
+```java
+public class Solution {
+    public int numRollsToTarget(int n, int k, int target) {
+        int MOD = 1_000_000_007;
+        int[][] dp = new int[n + 1][target + 1];
+        dp[0][0] = 1;
+
+        for (int i = 1; i <= n; i++) {
+            for (int val = 1; val <= k; val++) {
+                for (int t = val; t <= target; t++) {
+                    dp[i][t] = (dp[i][t] + dp[i - 1][t - val]) % MOD;
+                }
+            }
+        }
+
+        return dp[n][target];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numRollsToTarget(int n, int k, int target) {
+        const int MOD = 1e9 + 7;
+        vector<vector<int>> dp(n + 1, vector<int>(target + 1, 0));
+        dp[0][0] = 1;
+
+        for (int i = 1; i <= n; i++) {
+            for (int val = 1; val <= k; val++) {
+                for (int t = val; t <= target; t++) {
+                    dp[i][t] = (dp[i][t] + dp[i - 1][t - val]) % MOD;
+                }
+            }
+        }
+
+        return dp[n][target];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} k
+     * @param {number} target
+     * @return {number}
+     */
+    numRollsToTarget(n, k, target) {
+        const MOD = 1e9 + 7;
+        const dp = Array.from({ length: n + 1 }, () => Array(target + 1).fill(0));
+        dp[0][0] = 1;
+
+        for (let i = 1; i <= n; i++) {
+            for (let val = 1; val <= k; val++) {
+                for (let t = val; t <= target; t++) {
+                    dp[i][t] = (dp[i][t] + dp[i - 1][t - val]) % MOD;
+                }
+            }
+        }
+
+        return dp[n][target];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * t * k)$
+* Space complexity: $O(n * t)$
+
+> Where $n$ is the number of dices, $k$ is the number of faces each dice have, and $t$ is the target value.
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def numRollsToTarget(self, n: int, k: int, target: int) -> int:
+        dp = [0] * (target + 1)
+        dp[0] = 1
+        MOD = 10**9 + 7
+
+        for dice in range(n):
+            next_dp = [0] * (target + 1)
+            for val in range(1, k + 1):
+                for total in range(val, target + 1):
+                    next_dp[total] = (next_dp[total] + dp[total - val]) % MOD
+            dp = next_dp
+
+        return dp[target]
+```
+
+```java
+public class Solution {
+    public int numRollsToTarget(int n, int k, int target) {
+        int[] dp = new int[target + 1];
+        dp[0] = 1;
+        int MOD = 1_000_000_007;
+
+        for (int dice = 0; dice < n; dice++) {
+            int[] nextDp = new int[target + 1];
+            for (int val = 1; val <= k; val++) {
+                for (int total = val; total <= target; total++) {
+                    nextDp[total] = (nextDp[total] + dp[total - val]) % MOD;
+                }
+            }
+            dp = nextDp;
+        }
+
+        return dp[target];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numRollsToTarget(int n, int k, int target) {
+        const int MOD = 1e9 + 7;
+        vector<int> dp(target + 1, 0);
+        dp[0] = 1;
+
+        for (int dice = 0; dice < n; dice++) {
+            vector<int> nextDp(target + 1, 0);
+            for (int val = 1; val <= k; val++) {
+                for (int total = val; total <= target; total++) {
+                    nextDp[total] = (nextDp[total] + dp[total - val]) % MOD;
+                }
+            }
+            dp = nextDp;
+        }
+
+        return dp[target];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} k
+     * @param {number} target
+     * @return {number}
+     */
+    numRollsToTarget(n, k, target) {
+        const MOD = 1e9 + 7;
+        let dp = Array(target + 1).fill(0);
+        dp[0] = 1;
+
+        for (let dice = 0; dice < n; dice++) {
+            const nextDp = Array(target + 1).fill(0);
+            for (let val = 1; val <= k; val++) {
+                for (let total = val; total <= target; total++) {
+                    nextDp[total] = (nextDp[total] + dp[total - val]) % MOD;
+                }
+            }
+            dp = nextDp;
+        }
+
+        return dp[target];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * t * k)$
+* Space complexity: $O(t)$
+
+> Where $n$ is the number of dices, $k$ is the number of faces each dice have, and $t$ is the target value.
+
+---
+
+## 5. Dynamic Programming (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def numRollsToTarget(self, n: int, k: int, target: int) -> int:
+        MOD = 10**9 + 7
+        dp = [0] * (target + 1)
+        dp[0] = 1
+
+        for dice in range(n):
+            for t in range(target, -1, -1):
+                ways = dp[t]
+                dp[t] = 0
+                if ways:
+                    for val in range(1, min(k + 1, target - t + 1)):
+                        dp[t + val] = (dp[t + val] + ways) % MOD
+
+        return dp[target]
+```
+
+```java
+public class Solution {
+    public int numRollsToTarget(int n, int k, int target) {
+        int MOD = 1_000_000_007;
+        int[] dp = new int[target + 1];
+        dp[0] = 1;
+
+        for (int dice = 0; dice < n; dice++) {
+            for (int t = target; t >= 0; t--) {
+                int ways = dp[t];
+                dp[t] = 0;
+                if (ways > 0) {
+                    for (int val = 1; val <= Math.min(k, target - t); val++) {
+                        dp[t + val] = (dp[t + val] + ways) % MOD;
+                    }
+                }
+            }
+        }
+
+        return dp[target];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numRollsToTarget(int n, int k, int target) {
+        const int MOD = 1e9 + 7;
+        vector<int> dp(target + 1, 0);
+        dp[0] = 1;
+
+        for (int dice = 0; dice < n; dice++) {
+            for (int t = target; t >= 0; t--) {
+                int ways = dp[t];
+                dp[t] = 0;
+                if (ways > 0) {
+                    for (int val = 1; val <= min(k, target - t); val++) {
+                        dp[t + val] = (dp[t + val] + ways) % MOD;
+                    }
+                }
+            }
+        }
+
+        return dp[target];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} k
+     * @param {number} target
+     * @return {number}
+     */
+    numRollsToTarget(n, k, target) {
+        const MOD = 1e9 + 7;
+        const dp = Array(target + 1).fill(0);
+        dp[0] = 1;
+
+        for (let dice = 0; dice < n; dice++) {
+            for (let t = target; t >= 0; t--) {
+                const ways = dp[t];
+                dp[t] = 0;
+                if (ways > 0) {
+                    for (let val = 1; val <= Math.min(k, target - t); val++) {
+                        dp[t + val] = (dp[t + val] + ways) % MOD;
+                    }
+                }
+            }
+        }
+
+        return dp[target];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * t * k)$
+* Space complexity: $O(t)$
+
+> Where $n$ is the number of dices, $k$ is the number of faces each dice have, and $t$ is the target value.
\ No newline at end of file
diff --git a/articles/number-of-enclaves.md b/articles/number-of-enclaves.md
new file mode 100644
index 000000000..a5da06e58
--- /dev/null
+++ b/articles/number-of-enclaves.md
@@ -0,0 +1,607 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def numEnclaves(self, grid: List[List[int]]) -> int:
+        ROWS, COLS = len(grid), len(grid[0])
+        direct = [[0, 1], [0, -1], [1, 0], [-1, 0]]
+
+        # Return num of land cells
+        def dfs(r, c):
+            if (r < 0 or c < 0 or 
+                r == ROWS or c == COLS or 
+                not grid[r][c] or (r, c) in visit):
+                return 0
+            visit.add((r, c))
+            res = 1
+            for dr, dc in direct:
+                res += dfs(r + dr, c + dc)
+            return res
+
+        visit = set()
+        land, borderLand = 0, 0
+        for r in range(ROWS):
+            for c in range(COLS):
+                land += grid[r][c]
+                if (grid[r][c] and (r, c) not in visit and 
+                    (c in [0, COLS - 1] or r in [0, ROWS - 1])):
+                    borderLand += dfs(r, c)
+
+        return land - borderLand
+```
+
+```java
+public class Solution {
+    private int ROWS, COLS;
+    private boolean[][] visit;
+    private int[][] direct = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+    
+    public int numEnclaves(int[][] grid) {
+        this.ROWS = grid.length;
+        this.COLS = grid[0].length;
+        this.visit = new boolean[ROWS][COLS];
+
+        int land = 0, borderLand = 0;
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                land += grid[r][c];
+                if (grid[r][c] == 1 && !visit[r][c] && 
+                    (r == 0 || r == ROWS - 1 || c == 0 || c == COLS - 1)) {
+                    borderLand += dfs(r, c, grid);
+                }
+            }
+        }
+        return land - borderLand;
+    }
+
+    private int dfs(int r, int c, int[][] grid) {
+        if (r < 0 || c < 0 || r == ROWS || c == COLS || 
+            grid[r][c] == 0 || visit[r][c]) {
+            return 0;
+        }
+        visit[r][c] = true;
+        int res = 1;
+        for (int[] d : direct) {
+            res += dfs(r + d[0], c + d[1], grid);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int ROWS, COLS;
+    vector<vector<bool>> visit;
+    vector<vector<int>> direct = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+
+    int numEnclaves(vector<vector<int>>& grid) {
+        this->ROWS = grid.size();
+        this->COLS = grid[0].size();
+        this->visit = vector<vector<bool>>(ROWS, vector<bool>(COLS, false));
+
+        int land = 0, borderLand = 0;
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                land += grid[r][c];
+                if (grid[r][c] == 1 && !visit[r][c] && 
+                    (r == 0 || r == ROWS - 1 || c == 0 || c == COLS - 1)) {
+                    borderLand += dfs(r, c, grid);
+                }
+            }
+        }
+        return land - borderLand;
+    }
+
+private:
+    int dfs(int r, int c, vector<vector<int>>& grid) {
+        if (r < 0 || c < 0 || r == ROWS || c == COLS || 
+            grid[r][c] == 0 || visit[r][c]) {
+            return 0;
+        }
+        visit[r][c] = true;
+        int res = 1;
+        for (auto& d : direct) {
+            res += dfs(r + d[0], c + d[1], grid);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    numEnclaves(grid) {
+        const ROWS = grid.length, COLS = grid[0].length;
+        const visit = Array.from({ length: ROWS }, () => 
+            Array(COLS).fill(false)
+        );
+        const direct = [0, 1, 0, -1, 0];
+
+        const dfs = (r, c) => {
+            if (r < 0 || c < 0 || r === ROWS || c === COLS || 
+                grid[r][c] === 0 || visit[r][c]) {
+                return 0;
+            }
+            visit[r][c] = true;
+            let res = 1;
+            for (let d = 0; d < 4; d++) {
+                res += dfs(r + direct[d], c + direct[d + 1]);
+            }
+            return res;
+        };
+
+        let land = 0, borderLand = 0;
+        for (let r = 0; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                land += grid[r][c];
+                if (grid[r][c] === 1 && !visit[r][c] &&
+                    (r === 0 || r === ROWS - 1 || c === 0 || c === COLS - 1)) {
+                    borderLand += dfs(r, c);
+                }
+            }
+        }
+        return land - borderLand;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns in the given grid.
+
+---
+
+## 2. Breadth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def numEnclaves(self, grid: list[list[int]]) -> int:
+        ROWS, COLS = len(grid), len(grid[0])
+        direct = [[0, 1], [0, -1], [1, 0], [-1, 0]]
+        visit = [[False] * COLS for _ in range(ROWS)]
+        q = deque()
+        
+        land, borderLand = 0, 0
+        for r in range(ROWS):
+            for c in range(COLS):
+                land += grid[r][c]
+                if (grid[r][c] == 1 and 
+                    (r in [0, ROWS - 1] or c in [0, COLS - 1])
+                ):
+                    q.append((r, c))
+                    visit[r][c] = True
+
+        while q:
+            r, c = q.popleft()
+            borderLand += 1
+            for dr, dc in direct:
+                nr, nc = r + dr, c + dc
+                if (0 <= nr < ROWS and 0 <= nc < COLS and 
+                    grid[nr][nc] == 1 and not visit[nr][nc]
+                ):
+                    q.append((nr, nc))
+                    visit[nr][nc] = True
+
+        return land - borderLand
+```
+
+```java
+public class Solution {
+    public int numEnclaves(int[][] grid) {
+        int ROWS = grid.length, COLS = grid[0].length;
+        int[][] direct = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+        boolean[][] visit = new boolean[ROWS][COLS];
+        Queue<int[]> q = new LinkedList<>();
+
+        int land = 0, borderLand = 0;
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                land += grid[r][c];
+                if (grid[r][c] == 1 && (r == 0 || r == ROWS - 1 || 
+                    c == 0 || c == COLS - 1)) {
+                    q.offer(new int[]{r, c});
+                    visit[r][c] = true;
+                }
+            }
+        }
+
+        while (!q.isEmpty()) {
+            int[] cell = q.poll();
+            int r = cell[0], c = cell[1];
+            borderLand++;
+
+            for (int[] d : direct) {
+                int nr = r + d[0], nc = c + d[1];
+                if (nr >= 0 && nc >= 0 && nr < ROWS && nc < COLS && 
+                    grid[nr][nc] == 1 && !visit[nr][nc]) {
+                    q.offer(new int[]{nr, nc});
+                    visit[nr][nc] = true;
+                }
+            }
+        }
+
+        return land - borderLand;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int ROWS, COLS;
+    vector<vector<bool>> visit;
+    vector<vector<int>> direct = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+
+    int numEnclaves(vector<vector<int>>& grid) {
+        this->ROWS = grid.size();
+        this->COLS = grid[0].size();
+        this->visit = vector<vector<bool>>(ROWS, vector<bool>(COLS, false));
+
+        int land = 0, borderLand = 0;
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                land += grid[r][c];
+                if (grid[r][c] == 1 && !visit[r][c] && 
+                    (r == 0 || r == ROWS - 1 || c == 0 || c == COLS - 1)) {
+                    borderLand += dfs(r, c, grid);
+                }
+            }
+        }
+        return land - borderLand;
+    }
+
+private:
+    int dfs(int r, int c, vector<vector<int>>& grid) {
+        if (r < 0 || c < 0 || r == ROWS || c == COLS || 
+            grid[r][c] == 0 || visit[r][c]) {
+            return 0;
+        }
+        visit[r][c] = true;
+        int res = 1;
+        for (auto& d : direct) {
+            res += dfs(r + d[0], c + d[1], grid);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    numEnclaves(grid) {
+        const ROWS = grid.length, COLS = grid[0].length;
+        const direct = [0, 1, 0, -1, 0];
+        const visit = Array.from({ length: ROWS }, () => 
+            Array(COLS).fill(false)
+        );
+        const q = new Queue();
+
+        let land = 0, borderLand = 0;
+        for (let r = 0; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                land += grid[r][c];
+                if (grid[r][c] === 1 && (r === 0 || r === ROWS - 1 || 
+                    c === 0 || c === COLS - 1)) {
+                    q.push([r, c]);
+                    visit[r][c] = true;
+                }
+            }
+        }
+
+        while (!q.isEmpty()) {
+            let [r, c] = q.pop();
+            borderLand++;
+            for (let d = 0; d < 4; d++) {
+                let nr = r + direct[d], nc = c + direct[d + 1];
+                if (nr >= 0 && nc >= 0 && nr < ROWS && nc < COLS && 
+                    grid[nr][nc] === 1 && !visit[nr][nc]) {
+                    q.push([nr, nc]);
+                    visit[nr][nc] = true;
+                }
+            }
+        }
+
+        return land - borderLand;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns in the given grid.
+
+---
+
+## 3. Disjoint Set Union
+
+::tabs-start
+
+```python
+class DSU:
+    def __init__(self, n):
+        self.Parent = list(range(n + 1))
+        self.Size = [1] * (n + 1)
+
+    def find(self, node):
+        if self.Parent[node] != node:
+            self.Parent[node] = self.find(self.Parent[node])
+        return self.Parent[node]
+
+    def union(self, u, v):
+        pu, pv = self.find(u), self.find(v)
+        if pu == pv:
+            return False
+        if self.Size[pu] >= self.Size[pv]:
+            self.Size[pu] += self.Size[pv]
+            self.Parent[pv] = pu
+        else:
+            self.Size[pv] += self.Size[pu]
+            self.Parent[pu] = pv
+        return True
+
+class Solution:
+    def numEnclaves(self, grid: list[list[int]]) -> int:
+        ROWS, COLS = len(grid), len(grid[0])
+        N = ROWS * COLS
+        def index(r, c):
+            return r * COLS + c
+
+        dsu = DSU(N)
+        directions = [0, 1, 0, -1, 0]
+        land = 0
+        for r in range(ROWS):
+            for c in range(COLS):
+                if grid[r][c] == 0:
+                    continue
+                land += 1
+                for d in range(4):
+                    nr, nc = r + directions[d], c + directions[d + 1]
+                    if 0 <= nr < ROWS and 0 <= nc < COLS:
+                        if grid[nr][nc] == 1:
+                            dsu.union(index(r, c), index(nr, nc))
+                    else:
+                        dsu.union(N, index(r, c))
+
+        borderLand = dsu.Size[dsu.find(N)]
+        return land - borderLand + 1
+```
+
+```java
+class DSU {
+    int[] Parent, Size;
+
+    public DSU(int n) {
+        Parent = new int[n + 1];
+        Size = new int[n + 1];
+        for (int i = 0; i <= n; i++) {
+            Parent[i] = i;
+            Size[i] = 1;
+        }
+    }
+
+    public int find(int node) {
+        if (Parent[node] != node) {
+            Parent[node] = find(Parent[node]);
+        }
+        return Parent[node];
+    }
+
+    public boolean union(int u, int v) {
+        int pu = find(u), pv = find(v);
+        if (pu == pv) return false;
+        if (Size[pu] >= Size[pv]) {
+            Size[pu] += Size[pv];
+            Parent[pv] = pu;
+        } else {
+            Size[pv] += Size[pu];
+            Parent[pu] = pv;
+        }
+        return true;
+    }
+}
+
+public class Solution {
+    public int numEnclaves(int[][] grid) {
+        int ROWS = grid.length, COLS = grid[0].length;
+        int N = ROWS * COLS;
+        DSU dsu = new DSU(N);
+        int[] directions = {0, 1, 0, -1, 0};
+        int land = 0;
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (grid[r][c] == 0) continue;
+                land++;
+                for (int d = 0; d < 4; d++) {
+                    int nr = r + directions[d], nc = c + directions[d + 1];
+                    if (nr >= 0 && nc >= 0 && nr < ROWS && nc < COLS) {
+                        if (grid[nr][nc] == 1) {
+                            dsu.union(r * COLS + c, nr * COLS + nc);
+                        }
+                    } else {
+                        dsu.union(N, r * COLS + c);
+                    }
+                }
+            }
+        }
+
+        int borderLand = dsu.Size[dsu.find(N)];
+        return land - borderLand + 1;
+    }
+}
+```
+
+```cpp
+class DSU {
+public:
+    vector<int> Parent, Size;
+
+    DSU(int n) {
+        Parent.resize(n + 1);
+        Size.resize(n + 1, 1);
+        for (int i = 0; i <= n; i++) {
+            Parent[i] = i;
+        }
+    }
+
+    int find(int node) {
+        if (Parent[node] != node) {
+            Parent[node] = find(Parent[node]);
+        }
+        return Parent[node];
+    }
+
+    bool unionSets(int u, int v) {
+        int pu = find(u), pv = find(v);
+        if (pu == pv) return false;
+        if (Size[pu] >= Size[pv]) {
+            Size[pu] += Size[pv];
+            Parent[pv] = pu;
+        } else {
+            Size[pv] += Size[pu];
+            Parent[pu] = pv;
+        }
+        return true;
+    }
+};
+
+class Solution {
+public:
+    int numEnclaves(vector<vector<int>>& grid) {
+        int ROWS = grid.size(), COLS = grid[0].size();
+        int N = ROWS * COLS;
+        DSU dsu(N);
+        vector<int> directions = {0, 1, 0, -1, 0};
+        int land = 0;
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (grid[r][c] == 0) continue;
+                land++;
+                for (int d = 0; d < 4; d++) {
+                    int nr = r + directions[d], nc = c + directions[d + 1];
+                    if (nr >= 0 && nc >= 0 && nr < ROWS && nc < COLS) {
+                        if (grid[nr][nc] == 1) {
+                            dsu.unionSets(r * COLS + c, nr * COLS + nc);
+                        }
+                    } else {
+                        dsu.unionSets(N, r * COLS + c);
+                    }
+                }
+            }
+        }
+
+        int borderLand = dsu.Size[dsu.find(N)];
+        return land - borderLand + 1;
+    }
+};
+```
+
+```javascript
+class DSU {
+    /**
+     * @constructor
+     * @param {number} n
+     */
+    constructor(n) {
+        this.parent = Array.from({ length: n + 1 }, (_, i) => i);
+        this.size = new Array(n + 1).fill(1);
+    }
+
+    /**
+     * @param {number} node
+     * @return {number}
+     */
+    find(node) {
+        if (this.parent[node] !== node) {
+            this.parent[node] = this.find(this.parent[node]);
+        }
+        return this.parent[node];
+    }
+
+    /**
+     * @param {number} u
+     * @param {number} u=v
+     * @return {boolean}
+     */
+    union(u, v) {
+        let pu = this.find(u), pv = this.find(v);
+        if (pu === pv) return false;
+        if (this.size[pu] >= this.size[pv]) {
+            this.size[pu] += this.size[pv];
+            this.parent[pv] = pu;
+        } else {
+            this.size[pv] += this.size[pu];
+            this.parent[pu] = pv;
+        }
+        return true;
+    }
+}
+
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    numEnclaves(grid) {
+        const ROWS = grid.length, COLS = grid[0].length;
+        const N = ROWS * COLS;
+        const dsu = new DSU(N);
+        const directions = [0, 1, 0, -1, 0];
+        let land = 0;
+
+        for (let r = 0; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                if (grid[r][c] === 0) continue;
+                land++;
+                for (let d = 0; d < 4; d++) {
+                    let nr = r + directions[d], nc = c + directions[d + 1];
+                    if (nr >= 0 && nc >= 0 && nr < ROWS && nc < COLS) {
+                        if (grid[nr][nc] === 1) {
+                            dsu.union(r * COLS + c, nr * COLS + nc);
+                        }
+                    } else {
+                        dsu.union(N, r * COLS + c);
+                    }
+                }
+            }
+        }
+
+        const borderLand = dsu.size[dsu.find(N)];
+        return land - borderLand + 1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns in the given grid.
\ No newline at end of file
diff --git a/articles/number-of-flowers-in-full-bloom.md b/articles/number-of-flowers-in-full-bloom.md
new file mode 100644
index 000000000..2b60ec927
--- /dev/null
+++ b/articles/number-of-flowers-in-full-bloom.md
@@ -0,0 +1,675 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def fullBloomFlowers(self, flowers: List[List[int]], people: List[int]) -> List[int]:
+        res = []
+
+        for time in people:
+            cnt = 0
+            for start, end in flowers:
+                if start <= time <= end:
+                    cnt += 1
+            res.append(cnt)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[] fullBloomFlowers(int[][] flowers, int[] people) {
+        int m = people.length;
+        int[] res = new int[m];
+
+        for (int i = 0; i < m; i++) {
+            int count = 0;
+            for (int[] flower : flowers) {
+                if (flower[0] <= people[i] && people[i] <= flower[1]) {
+                    count++;
+                }
+            }
+            res[i] = count;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> fullBloomFlowers(vector<vector<int>>& flowers, vector<int>& people) {
+        int m = people.size();
+        vector<int> res(m);
+
+        for (int i = 0; i < m; i++) {
+            int count = 0;
+            for (auto& flower : flowers) {
+                if (flower[0] <= people[i] && people[i] <= flower[1]) {
+                    count++;
+                }
+            }
+            res[i] = count;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} flowers
+     * @param {number[]} people
+     * @return {number[]}
+     */
+    fullBloomFlowers(flowers, people) {
+        let res = new Array(people.length).fill(0);
+
+        for (let i = 0; i < people.length; i++) {
+            let count = 0;
+            for (let [start, end] of flowers) {
+                if (start <= people[i] && people[i] <= end) {
+                    count++;
+                }
+            }
+            res[i] = count;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(m)$ for the output array.
+
+> Where $n$ is the size of the array $flowers$, and $m$ is the size of the array $people$.
+
+---
+
+## 2. Two Min-Heaps
+
+::tabs-start
+
+```python
+class Solution:
+    def fullBloomFlowers(self, flowers: List[List[int]], people: List[int]) -> List[int]:
+        people = sorted((p, i) for i, p in enumerate(people))
+        res = [0] * len(people)
+        count = 0
+
+        start = [f[0] for f in flowers]
+        end = [f[1] for f in flowers]
+        
+        heapq.heapify(start)
+        heapq.heapify(end)
+
+        for p, i in people:
+            while start and start[0] <= p:
+                heapq.heappop(start)
+                count += 1
+            while end and end[0] < p:
+                heapq.heappop(end)
+                count -= 1
+            res[i] = count
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[] fullBloomFlowers(int[][] flowers, int[] people) {
+        int m = people.length;
+        int[] res = new int[m];
+
+        List<int[]> sortedPeople = new ArrayList<>();
+        for (int i = 0; i < m; i++) {
+            sortedPeople.add(new int[]{people[i], i});
+        }
+        sortedPeople.sort(Comparator.comparingInt(a -> a[0]));
+
+        PriorityQueue<Integer> startHeap = new PriorityQueue<>();
+        PriorityQueue<Integer> endHeap = new PriorityQueue<>();
+        for (int[] f : flowers) {
+            startHeap.offer(f[0]);
+            endHeap.offer(f[1]);
+        }
+
+        int count = 0;
+        for (int[] person : sortedPeople) {
+            int p = person[0], index = person[1];
+
+            while (!startHeap.isEmpty() && startHeap.peek() <= p) {
+                startHeap.poll();
+                count++;
+            }
+            while (!endHeap.isEmpty() && endHeap.peek() < p) {
+                endHeap.poll();
+                count--;
+            }
+
+            res[index] = count;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> fullBloomFlowers(vector<vector<int>>& flowers, vector<int>& people) {
+        int m = people.size();
+        vector<int> res(m);
+
+        vector<pair<int, int>> sortedPeople;
+        for (int i = 0; i < m; i++) {
+            sortedPeople.push_back({people[i], i});
+        }
+        sort(sortedPeople.begin(), sortedPeople.end());
+
+        priority_queue<int, vector<int>, greater<int>> startHeap, endHeap;
+        for (const auto& f : flowers) {
+            startHeap.push(f[0]);
+            endHeap.push(f[1]);
+        }
+
+        int count = 0;
+        for (const auto& person : sortedPeople) {
+            int p = person.first, index = person.second;
+
+            while (!startHeap.empty() && startHeap.top() <= p) {
+                startHeap.pop();
+                count++;
+            }
+            while (!endHeap.empty() && endHeap.top() < p) {
+                endHeap.pop();
+                count--;
+            }
+
+            res[index] = count;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} flowers
+     * @param {number[]} people
+     * @return {number[]}
+     */
+    fullBloomFlowers(flowers, people) {
+        const m = people.length;
+        const res = new Array(m).fill(0);
+        
+        const sortedPeople = people.map((p, i) => [p, i]);
+        sortedPeople.sort((a, b) => a[0] - b[0]);
+
+        const startHeap = new MinPriorityQueue();
+        const endHeap = new MinPriorityQueue();
+        for (const [s, e] of flowers) {
+            startHeap.enqueue(s);
+            endHeap.enqueue(e);
+        }
+
+        let count = 0;
+        for (const [p, index] of sortedPeople) {
+            while (!startHeap.isEmpty() && startHeap.front() <= p) {
+                startHeap.dequeue();
+                count++;
+            }
+            while (!endHeap.isEmpty() && endHeap.front() < p) {
+                endHeap.dequeue();
+                count--;
+            }
+            res[index] = count;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m \log m + n \log n)$
+* Space complexity: $O(m + n)$
+
+> Where $n$ is the size of the array $flowers$, and $m$ is the size of the array $people$.
+
+---
+
+## 3. Min-Heap
+
+::tabs-start
+
+```python
+class Solution:
+    def fullBloomFlowers(self, flowers: List[List[int]], people: List[int]) -> List[int]:
+        people = sorted((p, i) for i, p in enumerate(people))
+        res = [0] * len(people)
+        flowers.sort()
+        end = []
+
+        j = 0
+        for p, i in people:
+            while j < len(flowers) and flowers[j][0] <= p:
+                heapq.heappush(end, flowers[j][1])
+                j += 1
+            while end and end[0] < p:
+                heapq.heappop(end)
+            res[i] = len(end)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[] fullBloomFlowers(int[][] flowers, int[] people) {
+        int m = people.length;
+        int[] res = new int[m];
+        int[][] indexedPeople = new int[m][2];
+        
+        for (int i = 0; i < m; i++) {
+            indexedPeople[i] = new int[]{people[i], i};
+        }
+        Arrays.sort(indexedPeople, Comparator.comparingInt(a -> a[0]));
+        Arrays.sort(flowers, Comparator.comparingInt(a -> a[0]));
+        
+        PriorityQueue<Integer> endHeap = new PriorityQueue<>();
+        int j = 0, n = flowers.length;
+
+        for (int[] person : indexedPeople) {
+            int p = person[0], index = person[1];
+
+            while (j < n && flowers[j][0] <= p) {
+                endHeap.offer(flowers[j][1]);
+                j++;
+            }
+            while (!endHeap.isEmpty() && endHeap.peek() < p) {
+                endHeap.poll();
+            }
+            res[index] = endHeap.size();
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> fullBloomFlowers(vector<vector<int>>& flowers, vector<int>& people) {
+        int m = people.size();
+        vector<int> res(m);
+        vector<pair<int, int>> indexedPeople;
+
+        for (int i = 0; i < m; i++) {
+            indexedPeople.emplace_back(people[i], i);
+        }
+        sort(indexedPeople.begin(), indexedPeople.end());
+        sort(flowers.begin(), flowers.end());
+        
+        priority_queue<int, vector<int>, greater<int>> endHeap;
+        int j = 0, n = flowers.size();
+
+        for (auto [p, index] : indexedPeople) {
+            while (j < n && flowers[j][0] <= p) {
+                endHeap.push(flowers[j][1]);
+                j++;
+            }
+            while (!endHeap.empty() && endHeap.top() < p) {
+                endHeap.pop();
+            }
+            res[index] = endHeap.size();
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} flowers
+     * @param {number[]} people
+     * @return {number[]}
+     */
+    fullBloomFlowers(flowers, people) {
+        const m = people.length;
+        const res = new Array(m).fill(0);
+        const indexedPeople = people.map((p, i) => [p, i]);
+
+        indexedPeople.sort((a, b) => a[0] - b[0]);
+        flowers.sort((a, b) => a[0] - b[0]);
+
+        const endHeap = new MinPriorityQueue();
+        let j = 0, n = flowers.length;
+
+        for (const [p, index] of indexedPeople) {
+            while (j < n && flowers[j][0] <= p) {
+                endHeap.enqueue(flowers[j][1]);
+                j++;
+            }
+            while (!endHeap.isEmpty() && endHeap.front() < p) {
+                endHeap.dequeue();
+            }
+            res[index] = endHeap.size();
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m \log m + n \log n)$
+* Space complexity: $O(m + n)$
+
+> Where $n$ is the size of the array $flowers$, and $m$ is the size of the array $people$.
+
+---
+
+## 4. Sorting + Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def fullBloomFlowers(self, flowers: List[List[int]], people: List[int]) -> List[int]:
+        start = sorted(f[0] for f in flowers)
+        end = sorted(f[1] for f in flowers)
+
+        res = [0] * len(people)
+        peopleIndex = sorted((p, i) for i, p in enumerate(people))
+
+        i = j = count = 0
+        for p, index in peopleIndex:
+            while i < len(start) and start[i] <= p:
+                count += 1
+                i += 1
+            while j < len(end) and end[j] < p:
+                count -= 1
+                j += 1
+            res[index] = count
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[] fullBloomFlowers(int[][] flowers, int[] people) {
+        int m = people.length;
+        int[] res = new int[m];
+        List<Integer> start = new ArrayList<>(), end = new ArrayList<>();
+        for (int[] f : flowers) {
+            start.add(f[0]);
+            end.add(f[1]);
+        }
+
+        Collections.sort(start);
+        Collections.sort(end);
+
+        int count = 0, i = 0, j = 0;
+        List<int[]> peopleIndex = new ArrayList<>();
+        for (int k = 0; k < m; k++) {
+            peopleIndex.add(new int[]{people[k], k});
+        }
+        peopleIndex.sort(Comparator.comparingInt(a -> a[0]));
+
+        for (int[] p : peopleIndex) {
+            int time = p[0], index = p[1];
+
+            while (i < start.size() && start.get(i) <= time) {
+                count++;
+                i++;
+            }
+            while (j < end.size() && end.get(j) < time) {
+                count--;
+                j++;
+            }
+            res[index] = count;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> fullBloomFlowers(vector<vector<int>>& flowers, vector<int>& people) {
+        int m = people.size();
+        vector<int> res(m), start, end;
+        for (auto& f : flowers) {
+            start.push_back(f[0]);
+            end.push_back(f[1]);
+        }
+
+        sort(start.begin(), start.end());
+        sort(end.begin(), end.end());
+
+        int count = 0, i = 0, j = 0;
+        vector<pair<int, int>> peopleIndex;
+        for (int k = 0; k < m; k++) {
+            peopleIndex.emplace_back(people[k], k);
+        }
+        sort(peopleIndex.begin(), peopleIndex.end());
+
+        for (auto& [p, index] : peopleIndex) {
+            while (i < start.size() && start[i] <= p) {
+                count++;
+                i++;
+            }
+            while (j < end.size() && end[j] < p) {
+                count--;
+                j++;
+            }
+            res[index] = count;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} flowers
+     * @param {number[]} people
+     * @return {number[]}
+     */
+    fullBloomFlowers(flowers, people) {
+        const start = [], end = [];
+        for (let f of flowers) {
+            start.push(f[0]);
+            end.push(f[1]);
+        }
+
+        start.sort((a, b) => a - b);
+        end.sort((a, b) => a - b);
+
+        let count = 0, i = 0, j = 0;
+        const peopleIndex = people.map((p, idx) => [p, idx]);
+        peopleIndex.sort((a, b) => a[0] - b[0]);
+
+        const res = new Array(people.length);
+
+        for (let [p, index] of peopleIndex) {
+            while (i < start.length && start[i] <= p) {
+                count++;
+                i++;
+            }
+            while (j < end.length && end[j] < p) {
+                count--;
+                j++;
+            }
+            res[index] = count;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m \log m + n \log n)$
+* Space complexity: $O(m + n)$
+
+> Where $n$ is the size of the array $flowers$, and $m$ is the size of the array $people$.
+
+---
+
+## 5. Line Sweep
+
+::tabs-start
+
+```python
+class Solution:
+    def fullBloomFlowers(self, flowers: List[List[int]], people: List[int]) -> List[int]:
+        events = []
+        for start, end in flowers:
+            events.append((start, 1))
+            events.append((end + 1, -1))
+
+        events.sort()
+        queries = sorted((p, i) for i, p in enumerate(people))
+        res = [0] * len(people)
+
+        count = j = 0
+        for time, index in queries:
+            while j < len(events) and events[j][0] <= time:
+                count += events[j][1]
+                j += 1
+            res[index] = count
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[] fullBloomFlowers(int[][] flowers, int[] people) {
+        List<int[]> events = new ArrayList<>();
+        for (int[] f : flowers) {
+            events.add(new int[]{f[0], 1});
+            events.add(new int[]{f[1] + 1, -1});
+        }
+
+        Collections.sort(events, (a, b) -> a[0] - b[0]);
+        int[][] queries = new int[people.length][2];
+        for (int i = 0; i < people.length; i++) {
+            queries[i] = new int[]{people[i], i};
+        }
+        Arrays.sort(queries, (a, b) -> Integer.compare(a[0], b[0]));
+
+        int[] res = new int[people.length];
+        int count = 0, j = 0;
+        for (int[] query : queries) {
+            int time = query[0], index = query[1];
+            while (j < events.size() && events.get(j)[0] <= time) {
+                count += events.get(j)[1];
+                j++;
+            }
+            res[index] = count;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> fullBloomFlowers(vector<vector<int>>& flowers, vector<int>& people) {
+        vector<pair<int, int>> events;        
+        for (auto& f : flowers) {
+            events.emplace_back(f[0], 1); 
+            events.emplace_back(f[1] + 1, -1);
+        }
+
+        sort(events.begin(), events.end());
+        vector<pair<int, int>> queries;
+        for (int i = 0; i < people.size(); i++) {
+            queries.emplace_back(people[i], i);
+        }
+
+        sort(queries.begin(), queries.end());
+        vector<int> res(people.size());
+        int count = 0, j = 0;
+
+        for (auto& [time, index] : queries) {
+            while (j < events.size() && events[j].first <= time) {
+                count += events[j++].second;
+            }
+            res[index] = count;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} flowers
+     * @param {number[]} people
+     * @return {number[]}
+     */
+    fullBloomFlowers(flowers, people) {
+        let events = [];
+        for (let [start, end] of flowers) {
+            events.push([start, 1]);
+            events.push([end + 1, -1]);
+        }
+
+        events.sort((a, b) => a[0] - b[0]);
+        let queries = people.map((p, i) => [p, i]).sort((a, b) => a[0] - b[0]);
+        let res = new Array(people.length).fill(0);
+
+        let count = 0, j = 0;
+        for (let [time, index] of queries) {
+            while (j < events.length && events[j][0] <= time) {
+                count += events[j][1];
+                j++;
+            }
+            res[index] = count;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m \log m + n \log n)$
+* Space complexity: $O(m + n)$
+
+> Where $n$ is the size of the array $flowers$, and $m$ is the size of the array $people$.
\ No newline at end of file
diff --git a/articles/number-of-good-pairs.md b/articles/number-of-good-pairs.md
new file mode 100644
index 000000000..ea3e819e8
--- /dev/null
+++ b/articles/number-of-good-pairs.md
@@ -0,0 +1,221 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def numIdenticalPairs(self, nums: List[int]) -> int:
+        res = 0
+        for i in range(len(nums)):
+            for j in range(i + 1, len(nums)):
+                if nums[i] == nums[j]:
+                    res += 1
+        return res
+```
+
+```java
+public class Solution {
+    public int numIdenticalPairs(int[] nums) {
+        int res = 0;
+        for (int i = 0; i < nums.length; i++) {
+            for (int j = i + 1; j < nums.length; j++) {
+                if (nums[i] == nums[j]) {
+                    res++;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numIdenticalPairs(vector<int>& nums) {
+        int res = 0;
+        for (int i = 0; i < nums.size(); i++) {
+            for (int j = i + 1; j < nums.size(); j++) {
+                if (nums[i] == nums[j]) {
+                    res++;
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    numIdenticalPairs(nums) {
+        let res = 0;
+        for (let i = 0; i < nums.length; i++) {
+            for (let j = i + 1; j < nums.length; j++) {
+                if (nums[i] == nums[j]) {
+                    res++;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Hash Map (Math)
+
+::tabs-start
+
+```python
+class Solution:
+    def numIdenticalPairs(self, nums: List[int]) -> int:
+        count = Counter(nums)
+        res = 0
+        for num, c in count.items():
+            res += c * (c - 1) // 2
+        return res
+```
+
+```java
+public class Solution {
+    public int numIdenticalPairs(int[] nums) {
+        Map<Integer, Integer> count = new HashMap<>();
+        int res = 0;
+        for (int num : nums) {
+            count.put(num, count.getOrDefault(num, 0) + 1);
+        }
+        for (int c : count.values()) {
+            res += c * (c - 1) / 2;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numIdenticalPairs(vector<int>& nums) {
+        unordered_map<int, int> count;
+        int res = 0;
+        for (int num : nums) {
+            count[num]++;
+        }
+        for (auto& [num, c] : count) {
+            res += c * (c - 1) / 2;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    numIdenticalPairs(nums) {
+        const count = {};
+        let res = 0;
+        for (const num of nums) {
+            count[num] = (count[num] || 0) + 1;
+        }
+        for (const c of Object.values(count)) {
+            res += c * (c - 1) / 2;
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def numIdenticalPairs(self, nums: List[int]) -> int:
+        count = defaultdict(int)
+        res = 0
+        for num in nums:
+            res += count[num]
+            count[num] += 1
+        return res
+```
+
+```java
+public class Solution {
+    public int numIdenticalPairs(int[] nums) {
+        Map<Integer, Integer> count = new HashMap<>();
+        int res = 0;
+        for (int num : nums) {
+            res += count.getOrDefault(num, 0);
+            count.put(num, count.getOrDefault(num, 0) + 1);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numIdenticalPairs(vector<int>& nums) {
+        unordered_map<int, int> count;
+        int res = 0;
+        for (int num : nums) {
+            res += count[num];
+            count[num]++;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    numIdenticalPairs(nums) {
+        const count = {};
+        let res = 0;
+        for (const num of nums) {
+            res += count[num] || 0;
+            count[num] = (count[num] || 0) + 1;
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/number-of-good-paths.md b/articles/number-of-good-paths.md
new file mode 100644
index 000000000..f0e16529f
--- /dev/null
+++ b/articles/number-of-good-paths.md
@@ -0,0 +1,861 @@
+## 1. Brute Force (DFS)
+
+::tabs-start
+
+```python
+class Solution:
+    def numberOfGoodPaths(self, vals: List[int], edges: List[List[int]]) -> int:
+        n = len(vals)
+        adj = [[] for _ in range(n)]
+        for u, v in edges:
+            adj[u].append(v)
+            adj[v].append(u)
+
+        def dfs(node, startNode, parent):
+            if vals[node] > vals[startNode]:
+                return 0
+
+            res = 0
+            if vals[node] == vals[startNode] and node >= startNode:
+                res += 1
+
+            for child in adj[node]:
+                if child == parent:
+                    continue
+                res += dfs(child, startNode, node)
+
+            return res
+
+
+        res = 0
+        for node in range(n):
+            res += dfs(node, node, -1)
+        return res
+```
+
+```java
+public class Solution {
+    public int numberOfGoodPaths(int[] vals, int[][] edges) {
+        int n = vals.length;
+        List<Integer>[] adj = new ArrayList[n];
+        for (int i = 0; i < n; i++) {
+            adj[i] = new ArrayList<>();
+        }
+        for (int[] edge : edges) {
+            adj[edge[0]].add(edge[1]);
+            adj[edge[1]].add(edge[0]);
+        }
+
+        int res = 0;
+        for (int node = 0; node < n; node++) {
+            res += dfs(node, node, -1, vals, adj);
+        }
+        return res;
+    }
+
+    private int dfs(int node, int startNode, int parent, int[] vals, List<Integer>[] adj) {
+        if (vals[node] > vals[startNode]) {
+            return 0;
+        }
+
+        int res = 0;
+        if (vals[node] == vals[startNode] && node >= startNode) {
+            res += 1;
+        }
+
+        for (int child : adj[node]) {
+            if (child == parent) {
+                continue;
+            }
+            res += dfs(child, startNode, node, vals, adj);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numberOfGoodPaths(vector<int>& vals, vector<vector<int>>& edges) {
+        int n = vals.size();
+        vector<vector<int>> adj(n);
+        for (auto& edge : edges) {
+            adj[edge[0]].push_back(edge[1]);
+            adj[edge[1]].push_back(edge[0]);
+        }
+
+        int res = 0;
+        for (int node = 0; node < n; node++) {
+            res += dfs(node, node, -1, vals, adj);
+        }
+        return res;
+    }
+
+private:
+    int dfs(int node, int startNode, int parent, vector<int>& vals, vector<vector<int>>& adj) {
+        if (vals[node] > vals[startNode]) {
+            return 0;
+        }
+
+        int res = 0;
+        if (vals[node] == vals[startNode] && node >= startNode) {
+            res += 1;
+        }
+
+        for (int child : adj[node]) {
+            if (child == parent) {
+                continue;
+            }
+            res += dfs(child, startNode, node, vals, adj);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} vals
+     * @param {number[][]} edges
+     * @return {number}
+     */
+    numberOfGoodPaths(vals, edges) {
+        const n = vals.length;
+        const adj = Array.from({ length: n }, () => []);
+
+        for (const [u, v] of edges) {
+            adj[u].push(v);
+            adj[v].push(u);
+        }
+
+        const dfs = (node, startNode, parent) => {
+            if (vals[node] > vals[startNode]) {
+                return 0;
+            }
+
+            let res = 0;
+            if (vals[node] === vals[startNode] && node >= startNode) {
+                res += 1;
+            }
+
+            for (const child of adj[node]) {
+                if (child === parent) continue;
+                res += dfs(child, startNode, node);
+            }
+            return res;
+        };
+
+        let res = 0;
+        for (let node = 0; node < n; node++) {
+            res += dfs(node, node, -1);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Brute Force (BFS)
+
+::tabs-start
+
+```python
+class Solution:
+    def numberOfGoodPaths(self, vals, edges):
+        n = len(vals)
+        adj = [[] for _ in range(n)]
+        for u, v in edges:
+            adj[u].append(v)
+            adj[v].append(u)
+
+        res = 0
+        for startNode in range(n):
+            q = deque([startNode])
+            visited = set([startNode])
+            count = 0
+
+            while q:
+                node = q.popleft()
+                if vals[node] == vals[startNode] and node >= startNode:
+                    count += 1
+
+                for child in adj[node]:
+                    if child not in visited and vals[child] <= vals[startNode]:
+                        visited.add(child)
+                        q.append(child)
+
+            res += count
+
+        return res
+```
+
+```java
+public class Solution {
+    public int numberOfGoodPaths(int[] vals, int[][] edges) {
+        int n = vals.length;
+        List<Integer>[] adj = new ArrayList[n];
+        for (int i = 0; i < n; i++) {
+            adj[i] = new ArrayList<>();
+        }
+        for (int[] edge : edges) {
+            adj[edge[0]].add(edge[1]);
+            adj[edge[1]].add(edge[0]);
+        }
+
+        int res = 0;
+        for (int startNode = 0; startNode < n; startNode++) {
+            Queue<Integer> q = new LinkedList<>();
+            Set<Integer> visited = new HashSet<>();
+            q.offer(startNode);
+            visited.add(startNode);
+            int count = 0;
+
+            while (!q.isEmpty()) {
+                int node = q.poll();
+                if (vals[node] == vals[startNode] && node >= startNode) {
+                    count++;
+                }
+
+                for (int child : adj[node]) {
+                    if (!visited.contains(child) && vals[child] <= vals[startNode]) {
+                        visited.add(child);
+                        q.offer(child);
+                    }
+                }
+            }
+
+            res += count;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numberOfGoodPaths(vector<int>& vals, vector<vector<int>>& edges) {
+        int n = vals.size();
+        vector<vector<int>> adj(n);
+        for (auto& edge : edges) {
+            adj[edge[0]].push_back(edge[1]);
+            adj[edge[1]].push_back(edge[0]);
+        }
+
+        int res = 0;
+        for (int startNode = 0; startNode < n; startNode++) {
+            queue<int> q;
+            unordered_set<int> visited;
+            q.push(startNode);
+            visited.insert(startNode);
+            int count = 0;
+
+            while (!q.empty()) {
+                int node = q.front();
+                q.pop();
+                if (vals[node] == vals[startNode] && node >= startNode) {
+                    count++;
+                }
+
+                for (int child : adj[node]) {
+                    if (visited.find(child) == visited.end() && vals[child] <= vals[startNode]) {
+                        visited.insert(child);
+                        q.push(child);
+                    }
+                }
+            }
+
+            res += count;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} vals
+     * @param {number[][]} edges
+     * @return {number}
+     */
+    numberOfGoodPaths(vals, edges) {
+        const n = vals.length;
+        const adj = Array.from({ length: n }, () => []);
+
+        for (const [u, v] of edges) {
+            adj[u].push(v);
+            adj[v].push(u);
+        }
+
+        let res = 0;
+        for (let startNode = 0; startNode < n; startNode++) {
+            const q = new Queue([startNode]);
+            const visited = new Set([startNode]);
+            let count = 0;
+
+            while (q.length) {
+                let node = q.shift();
+                if (vals[node] === vals[startNode] && node >= startNode) {
+                    count++;
+                }
+
+                for (const child of adj[node]) {
+                    if (!visited.has(child) && vals[child] <= vals[startNode]) {
+                        visited.add(child);
+                        q.push(child);
+                    }
+                }
+            }
+
+            res += count;
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Disjoint Set Union
+
+::tabs-start
+
+```python
+class DSU:
+    def __init__(self, n):
+        self.Parent = list(range(n + 1))
+        self.Size = [1] * (n + 1)
+
+    def find(self, node):
+        if self.Parent[node] != node:
+            self.Parent[node] = self.find(self.Parent[node])
+        return self.Parent[node]
+
+    def union(self, u, v):
+        pu, pv = self.find(u), self.find(v)
+        if pu == pv:
+            return False
+        if self.Size[pu] >= self.Size[pv]:
+            self.Size[pu] += self.Size[pv]
+            self.Parent[pv] = pu
+        else:
+            self.Size[pv] += self.Size[pu]
+            self.Parent[pu] = pv
+        return True
+
+class Solution:
+    def numberOfGoodPaths(self, vals: List[int], edges: List[List[int]]) -> int:
+        adj = collections.defaultdict(list)
+        for a, b in edges:
+            adj[a].append(b)
+            adj[b].append(a)
+
+        valToIndex = collections.defaultdict(list)
+        for i, val in enumerate(vals):
+            valToIndex[val].append(i)
+
+        res = 0
+        uf = DSU(len(vals))
+
+        for val in sorted(valToIndex.keys()):
+            for i in valToIndex[val]:
+                for nei in adj[i]:
+                    if vals[nei] <= vals[i]:
+                        uf.union(nei, i)
+
+            count = collections.defaultdict(int)
+            for i in valToIndex[val]:
+                count[uf.find(i)] += 1
+                res += count[uf.find(i)]
+
+        return res
+```
+
+```java
+class DSU {
+    private int[] parent, size;
+
+    public DSU(int n) {
+        parent = new int[n + 1];
+        size = new int[n + 1];
+        for (int i = 0; i <= n; i++) {
+            parent[i] = i;
+            size[i] = 1;
+        }
+    }
+
+    public int find(int node) {
+        if (parent[node] != node) {
+            parent[node] = find(parent[node]);
+        }
+        return parent[node];
+    }
+
+    public boolean union(int u, int v) {
+        int pu = find(u), pv = find(v);
+        if (pu == pv) return false;
+        if (size[pu] >= size[pv]) {
+            size[pu] += size[pv];
+            parent[pv] = pu;
+        } else {
+            size[pv] += size[pu];
+            parent[pu] = pv;
+        }
+        return true;
+    }
+}
+
+public class Solution {
+    public int numberOfGoodPaths(int[] vals, int[][] edges) {
+        int n = vals.length;
+        List<Integer>[] adj = new ArrayList[n];
+        for (int i = 0; i < n; i++) adj[i] = new ArrayList<>();
+
+        for (int[] edge : edges) {
+            adj[edge[0]].add(edge[1]);
+            adj[edge[1]].add(edge[0]);
+        }
+
+        TreeMap<Integer, List<Integer>> valToIndex = new TreeMap<>();
+        for (int i = 0; i < n; i++) {
+            valToIndex.putIfAbsent(vals[i], new ArrayList<>());
+            valToIndex.get(vals[i]).add(i);
+        }
+
+        DSU dsu = new DSU(n);
+        int res = 0;
+
+        for (int val : valToIndex.keySet()) {
+            for (int i : valToIndex.get(val)) {
+                for (int nei : adj[i]) {
+                    if (vals[nei] <= vals[i]) dsu.union(nei, i);
+                }
+            }
+
+            Map<Integer, Integer> count = new HashMap<>();
+            for (int i : valToIndex.get(val)) {
+                int root = dsu.find(i);
+                count.put(root, count.getOrDefault(root, 0) + 1);
+                res += count.get(root);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class DSU {
+public:
+    vector<int> parent, size;
+
+    DSU(int n) {
+        parent.resize(n + 1);
+        size.resize(n + 1, 1);
+        for (int i = 0; i <= n; i++) parent[i] = i;
+    }
+
+    int find(int node) {
+        if (parent[node] != node) parent[node] = find(parent[node]);
+        return parent[node];
+    }
+
+    bool unite(int u, int v) {
+        int pu = find(u), pv = find(v);
+        if (pu == pv) return false;
+        if (size[pu] >= size[pv]) {
+            size[pu] += size[pv];
+            parent[pv] = pu;
+        } else {
+            size[pv] += size[pu];
+            parent[pu] = pv;
+        }
+        return true;
+    }
+};
+
+class Solution {
+public:
+    int numberOfGoodPaths(vector<int>& vals, vector<vector<int>>& edges) {
+        int n = vals.size();
+        vector<vector<int>> adj(n);
+        for (auto& edge : edges) {
+            adj[edge[0]].push_back(edge[1]);
+            adj[edge[1]].push_back(edge[0]);
+        }
+
+        map<int, vector<int>> valToIndex;
+        for (int i = 0; i < n; i++) valToIndex[vals[i]].push_back(i);
+
+        DSU dsu(n);
+        int res = 0;
+
+        for (auto& [val, nodes] : valToIndex) {
+            for (int& i : nodes) {
+                for (int& nei : adj[i]) {
+                    if (vals[nei] <= vals[i]) dsu.unite(nei, i);
+                }
+            }
+
+            unordered_map<int, int> count;
+            for (int& i : nodes) {
+                int root = dsu.find(i);
+                count[root]++;
+                res += count[root];
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class DSU {
+    /**
+     * @constructor
+     * @param {number} n
+     */
+    constructor(n) {
+        this.parent = Array.from({ length: n + 1 }, (_, i) => i);
+        this.size = new Array(n + 1).fill(1);
+    }
+
+    /**
+     * @param {number} node
+     * @return {number}
+     */
+    find(node) {
+        if (this.parent[node] !== node) {
+            this.parent[node] = this.find(this.parent[node]);
+        }
+        return this.parent[node];
+    }
+
+    /**
+     * @param {number} u
+     * @param {number} u=v
+     * @return {boolean}
+     */
+    union(u, v) {
+        let pu = this.find(u), pv = this.find(v);
+        if (pu === pv) return false;
+        if (this.size[pu] >= this.size[pv]) {
+            this.size[pu] += this.size[pv];
+            this.parent[pv] = pu;
+        } else {
+            this.size[pv] += this.size[pu];
+            this.parent[pu] = pv;
+        }
+        return true;
+    }
+}
+
+class Solution {
+    /**
+     * @param {number[]} vals
+     * @param {number[][]} edges
+     * @return {number}
+     */
+    numberOfGoodPaths(vals, edges) {
+        const n = vals.length;
+        const adj = Array.from({ length: n }, () => []);
+
+        for (const [u, v] of edges) {
+            adj[u].push(v);
+            adj[v].push(u);
+        }
+
+        const valToIndex = new Map();
+        for (let i = 0; i < n; i++) {
+            if (!valToIndex.has(vals[i])) valToIndex.set(vals[i], []);
+            valToIndex.get(vals[i]).push(i);
+        }
+
+        const dsu = new DSU(n);
+        let res = 0;
+
+        for (const [val, nodes] of [...valToIndex.entries()].sort((a, b) => a[0] - b[0])) {
+            for (const i of nodes) {
+                for (const nei of adj[i]) {
+                    if (vals[nei] <= vals[i]) dsu.union(nei, i);
+                }
+            }
+
+            const count = new Map();
+            for (const i of nodes) {
+                const root = dsu.find(i);
+                count.set(root, (count.get(root) || 0) + 1);
+                res += count.get(root);
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Disjoint Set Union (Union By Value)
+
+::tabs-start
+
+```python
+class DSU:
+    def __init__(self, n, vals):
+        self.parent = list(range(n))
+        self.vals = vals
+        self.count = [1] * n # count of nodes with max value of the component
+
+    def find(self, node):
+        if self.parent[node] != node:
+            self.parent[node] = self.find(self.parent[node])
+        return self.parent[node]
+
+    def union(self, u, v):
+        pu, pv = self.find(u), self.find(v)
+        if pu == pv:
+            return 0
+        if self.vals[pu] < self.vals[pv]:
+            self.parent[pu] = pv
+        elif self.vals[pu] > self.vals[pv]:
+            self.parent[pv] = pu
+        else:
+            self.parent[pv] = pu
+            result = self.count[pu] * self.count[pv]
+            self.count[pu] += self.count[pv]
+            return result
+        
+        return 0
+
+
+class Solution:
+    def numberOfGoodPaths(self, vals: List[int], edges: List[List[int]]) -> int:
+        n = len(vals)
+        dsu = DSU(n, vals)
+
+        # Sort edges based on max value of the two nodes
+        edges.sort(key=lambda edge: max(vals[edge[0]], vals[edge[1]]))
+
+        res = n  # Each node alone is a good path
+        for u, v in edges:
+            res += dsu.union(u, v)
+        return res
+```
+
+```java
+class DSU {
+    private int[] parent, count, vals;
+
+    public DSU(int n, int[] vals) {
+        this.parent = new int[n];
+        this.vals = vals;
+        this.count = new int[n]; // count of nodes with max value of the component
+        Arrays.fill(count, 1);
+
+        for (int i = 0; i < n; i++) {
+            parent[i] = i;
+        }
+    }
+
+    public int find(int node) {
+        if (parent[node] != node) {
+            parent[node] = find(parent[node]);
+        }
+        return parent[node];
+    }
+
+    public int union(int u, int v) {
+        int pu = find(u), pv = find(v);
+        if (pu == pv) {
+            return 0;
+        }
+        if (vals[pu] < vals[pv]) {
+            parent[pu] = pv;
+        } else if (vals[pu] > vals[pv]) {
+            parent[pv] = pu;
+        } else {
+            parent[pv] = pu;
+            int result = count[pu] * count[pv];
+            count[pu] += count[pv];
+            return result;
+        }
+        return 0;
+    }
+}
+
+public class Solution {
+    public int numberOfGoodPaths(int[] vals, int[][] edges) {
+        int n = vals.length;
+        DSU dsu = new DSU(n, vals);
+
+        // Sort edges based on max value of the two nodes
+        Arrays.sort(edges, 
+            Comparator.comparingInt(edge -> Math.max(vals[edge[0]], vals[edge[1]]))
+        );
+
+        int res = n; // Each node alone is a good path
+        for (int[] edge : edges) {
+            res += dsu.union(edge[0], edge[1]);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class DSU {
+    vector<int> parent, count, vals;
+
+public:
+    DSU(int n, vector<int>& vals) : vals(vals), parent(n), count(n, 1) {
+        for (int i = 0; i < n; i++) parent[i] = i;
+    }
+
+    int find(int node) {
+        if (parent[node] != node) {
+            parent[node] = find(parent[node]);
+        }
+        return parent[node];
+    }
+
+    int unionNodes(int u, int v) {
+        int pu = find(u), pv = find(v);
+        if (pu == pv) {
+            return 0;
+        }
+        if (vals[pu] < vals[pv]) {
+            parent[pu] = pv;
+        } else if (vals[pu] > vals[pv]) {
+            parent[pv] = pu;
+        } else {
+            parent[pv] = pu;
+            int result = count[pu] * count[pv];
+            count[pu] += count[pv];
+            return result;
+        }
+        return 0;
+    }
+};
+
+class Solution {
+public:
+    int numberOfGoodPaths(vector<int>& vals, vector<vector<int>>& edges) {
+        int n = vals.size();
+        DSU dsu(n, vals);
+
+        // Sort edges based on max value of the two nodes
+        sort(edges.begin(), edges.end(), [&](auto& a, auto& b) {
+            return max(vals[a[0]], vals[a[1]]) < max(vals[b[0]], vals[b[1]]);
+        });
+
+        int res = n; // Each node alone is a good path
+        for (auto& edge : edges) {
+            res += dsu.unionNodes(edge[0], edge[1]);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class DSU {
+    /**
+     * @param {number} n
+     * @param {number[]} vals
+     */
+    constructor(n, vals) {
+        this.parent = Array(n).fill(0).map((_, i) => i);
+        this.vals = vals;
+        this.count = Array(n).fill(1); // count of nodes with max value of the component
+    }
+
+    /**
+     * @param {number} node
+     * @return {number}
+     */
+    find(node) {
+        if (this.parent[node] !== node) {
+            this.parent[node] = this.find(this.parent[node]);
+        }
+        return this.parent[node];
+    }
+
+    /**
+     * @param {number} u
+     * @param {number} v
+     * @return {number}
+     */
+    union(u, v) {
+        let pu = this.find(u), pv = this.find(v);
+        if (pu === pv) {
+            return 0;
+        }
+        if (this.vals[pu] < this.vals[pv]) {
+            this.parent[pu] = pv;
+        } else if (this.vals[pu] > this.vals[pv]) {
+            this.parent[pv] = pu;
+        } else {
+            this.parent[pv] = pu;
+            let result = this.count[pu] * this.count[pv];
+            this.count[pu] += this.count[pv];
+            return result;
+        }
+        return 0;
+    }
+}
+
+class Solution {
+    /**
+     * @param {number[]} vals
+     * @param {number[][]} edges
+     * @return {number}
+     */
+    numberOfGoodPaths(vals, edges) {
+        let n = vals.length;
+        let dsu = new DSU(n, vals);
+
+        // Sort edges based on max value of the two nodes
+        edges.sort((a, b) => 
+            Math.max(vals[a[0]], vals[a[1]]) - Math.max(vals[b[0]], vals[b[1]])
+        );
+
+        let res = n; // Each node alone is a good path
+        for (let [u, v] of edges) {
+            res += dsu.union(u, v);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n\log n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/number-of-laser-beams-in-a-bank.md b/articles/number-of-laser-beams-in-a-bank.md
new file mode 100644
index 000000000..598d7fbb2
--- /dev/null
+++ b/articles/number-of-laser-beams-in-a-bank.md
@@ -0,0 +1,110 @@
+## 1. Counting
+
+::tabs-start
+
+```python
+class Solution:
+    def numberOfBeams(self, bank: List[str]) -> int:
+        prev = bank[0].count("1")
+        res = 0
+
+        for i in range(1, len(bank)):
+            curr = bank[i].count("1")
+            if curr:
+                res += prev * curr
+                prev = curr
+
+        return res
+```
+
+```java
+public class Solution {
+    public int numberOfBeams(String[] bank) {
+        int prev = countOnes(bank[0]);
+        int res = 0;
+
+        for (int i = 1; i < bank.length; i++) {
+            int curr = countOnes(bank[i]);
+            if (curr > 0) {
+                res += prev * curr;
+                prev = curr;
+            }
+        }
+
+        return res;
+    }
+
+    private int countOnes(String s) {
+        int count = 0;
+        for (int i = 0; i < s.length(); i++) {
+            if (s.charAt(i) == '1') count++;
+        }
+        return count;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numberOfBeams(vector<string>& bank) {
+        int prev = countOnes(bank[0]);
+        int res = 0;
+
+        for (int i = 1; i < bank.size(); i++) {
+            int curr = countOnes(bank[i]);
+            if (curr > 0) {
+                res += prev * curr;
+                prev = curr;
+            }
+        }
+
+        return res;
+    }
+
+private:
+    int countOnes(const string& s) {
+        return count(s.begin(), s.end(), '1');
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} bank
+     * @return {number}
+     */
+    numberOfBeams(bank) {
+        const countOnes = (s) => {
+            let cnt = 0;
+            for (let c of s) {
+                if (c === '1') cnt += 1;
+            }
+            return cnt;
+        };
+
+        let prev = countOnes(bank[0]);
+        let res = 0;
+
+        for (let i = 1; i < bank.length; i++) {
+            let curr = countOnes(bank[i]);
+            if (curr > 0) {
+                res += prev * curr;
+                prev = curr;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(1)$ extra space.
+
+> Where $m$ is the number of rows and $n$ is the number of columns.
\ No newline at end of file
diff --git a/articles/number-of-longest-increasing-subsequence.md b/articles/number-of-longest-increasing-subsequence.md
new file mode 100644
index 000000000..f11ef6599
--- /dev/null
+++ b/articles/number-of-longest-increasing-subsequence.md
@@ -0,0 +1,699 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def findNumberOfLIS(self, nums: List[int]) -> int:
+        LIS = 0
+        res = 0
+
+        def dfs(i, length):
+            nonlocal LIS, res
+            if LIS < length:
+                LIS = length
+                res = 1
+            elif LIS == length:
+                res += 1
+
+            for j in range(i + 1, len(nums)):
+                if nums[j] <= nums[i]:
+                    continue
+                dfs(j, length + 1)
+        
+        for i in range(len(nums)):
+            dfs(i, 1)
+        return res
+```
+
+```java
+public class Solution {
+    private int LIS = 0;
+    private int res = 0;
+
+    public int findNumberOfLIS(int[] nums) {
+        for (int i = 0; i < nums.length; i++) {
+            dfs(nums, i, 1);
+        }
+        return res;
+    }
+
+    private void dfs(int[] nums, int i, int length) {
+        if (LIS < length) {
+            LIS = length;
+            res = 1;
+        } else if (LIS == length) {
+            res++;
+        }
+
+        for (int j = i + 1; j < nums.length; j++) {
+            if (nums[j] <= nums[i]) {
+                continue;
+            }
+            dfs(nums, j, length + 1);
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+    int LIS = 0;
+    int res = 0;
+
+    void dfs(vector<int>& nums, int i, int length) {
+        if (LIS < length) {
+            LIS = length;
+            res = 1;
+        } else if (LIS == length) {
+            res++;
+        }
+
+        for (int j = i + 1; j < nums.size(); j++) {
+            if (nums[j] <= nums[i]) {
+                continue;
+            }
+            dfs(nums, j, length + 1);
+        }
+    }
+
+public:
+    int findNumberOfLIS(vector<int>& nums) {
+        for (int i = 0; i < nums.size(); i++) {
+            dfs(nums, i, 1);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    findNumberOfLIS(nums) {
+        let LIS = 0;
+        let res = 0;
+
+        const dfs = (i, length) => {
+            if (LIS < length) {
+                LIS = length;
+                res = 1;
+            } else if (LIS === length) {
+                res++;
+            }
+
+            for (let j = i + 1; j < nums.length; j++) {
+                if (nums[j] <= nums[i]) continue;
+                dfs(j, length + 1);
+            }
+        };
+
+        for (let i = 0; i < nums.length; i++) {
+            dfs(i, 1);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def findNumberOfLIS(self, nums: List[int]) -> int:
+        dp = {}
+
+        def dfs(i):
+            if i in dp:
+                return
+
+            maxLen = maxCnt = 1
+            for j in range(i + 1, len(nums)):
+                if nums[j] > nums[i]:
+                    dfs(j)
+                    length, count = dp[j]
+                    if 1 + length > maxLen:
+                        maxLen = length + 1
+                        maxCnt = count
+                    elif 1 + length == maxLen:
+                        maxCnt += count
+            dp[i] = (maxLen, maxCnt)
+
+        lenLIS = res = 0
+        for i in range(len(nums)):
+            dfs(i)
+            maxLen, maxCnt = dp[i]
+            if maxLen > lenLIS:
+                lenLIS = maxLen
+                res = maxCnt
+            elif maxLen == lenLIS:
+                res += maxCnt
+
+        return res
+```
+
+```java
+public class Solution {
+    private int[][] dp;
+
+    public int findNumberOfLIS(int[] nums) {
+        int n = nums.length;
+        dp = new int[n][2]; // dp[i][0] = maxLen, dp[i][1] = maxCnt
+
+        for (int i = 0; i < n; i++) {
+            dp[i][0] = dp[i][1] = -1;
+        }
+
+        int lenLIS = 0, res = 0;
+        for (int i = 0; i < n; i++) {
+            dfs(nums, i);
+            int[] result = dp[i];
+            if (result[0] > lenLIS) {
+                lenLIS = result[0];
+                res = result[1];
+            } else if (result[0] == lenLIS) {
+                res += result[1];
+            }
+        }
+        return res;
+    }
+
+    private void dfs(int[] nums, int i) {
+        if (dp[i][0] != -1) return;
+
+        int maxLen = 1, maxCnt = 1;
+        for (int j = i + 1; j < nums.length; j++) {
+            if (nums[j] > nums[i]) {
+                dfs(nums, j);
+                int[] next = dp[j];
+                if (1 + next[0] > maxLen) {
+                    maxLen = 1 + next[0];
+                    maxCnt = next[1];
+                } else if (1 + next[0] == maxLen) {
+                    maxCnt += next[1];
+                }
+            }
+        }
+        
+        dp[i] = new int[]{maxLen, maxCnt};
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<vector<int>> dp;
+
+    void dfs(vector<int>& nums, int i) {
+        if (dp[i][0] != -1) return;
+
+        int maxLen = 1, maxCnt = 1;
+        for (int j = i + 1; j < nums.size(); j++) {
+            if (nums[j] > nums[i]) {
+                dfs(nums, j);
+                int length = dp[j][0];
+                int count = dp[j][1];
+                if (1 + length > maxLen) {
+                    maxLen = 1 + length;
+                    maxCnt = count;
+                } else if (1 + length == maxLen) {
+                    maxCnt += count;
+                }
+            }
+        }
+        dp[i] = {maxLen, maxCnt};
+    }
+
+public:
+    int findNumberOfLIS(vector<int>& nums) {
+        int n = nums.size();
+        dp.assign(n, vector<int>(2, -1));
+
+        int lenLIS = 0, res = 0;
+        for (int i = 0; i < n; i++) {
+            dfs(nums, i);
+            int maxLen = dp[i][0];
+            int maxCnt = dp[i][1];
+            if (maxLen > lenLIS) {
+                lenLIS = maxLen;
+                res = maxCnt;
+            } else if (maxLen == lenLIS) {
+                res += maxCnt;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    findNumberOfLIS(nums) {
+        const dp = new Map();
+
+        const dfs = (i) => {
+            if (dp.has(i)) return;
+
+            let maxLen = 1, maxCnt = 1;
+            for (let j = i + 1; j < nums.length; j++) {
+                if (nums[j] > nums[i]) {
+                    dfs(j);
+                    const [length, count] = dp.get(j);
+                    if (1 + length > maxLen) {
+                        maxLen = 1 + length;
+                        maxCnt = count;
+                    } else if (1 + length === maxLen) {
+                        maxCnt += count;
+                    }
+                }
+            }
+            dp.set(i, [maxLen, maxCnt]);
+        };
+
+        let lenLIS = 0, res = 0;
+        for (let i = 0; i < nums.length; i++) {
+            dfs(i);
+            const [maxLen, maxCnt] = dp.get(i);
+            if (maxLen > lenLIS) {
+                lenLIS = maxLen;
+                res = maxCnt;
+            } else if (maxLen === lenLIS) {
+                res += maxCnt;
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def findNumberOfLIS(self, nums: List[int]) -> int:
+        n = len(nums)
+        dp = [[0, 0] for _ in range(n)]
+        lenLIS, res = 0, 0
+
+        for i in range(n - 1, -1, -1):
+            maxLen, maxCnt = 1, 1
+            for j in range(i + 1, n):
+                if nums[j] > nums[i]:
+                    length, count = dp[j]
+                    if length + 1 > maxLen:
+                        maxLen, maxCnt = length + 1, count
+                    elif length + 1 == maxLen:
+                        maxCnt += count
+
+            if maxLen > lenLIS:
+                lenLIS, res = maxLen, maxCnt
+            elif maxLen == lenLIS:
+                res += maxCnt
+            dp[i] = [maxLen, maxCnt]
+
+        return res
+```
+
+```java
+public class Solution {
+    public int findNumberOfLIS(int[] nums) {
+        int n = nums.length;
+        int[][] dp = new int[n][2];
+        int lenLIS = 0, res = 0;
+
+        for (int i = n - 1; i >= 0; i--) {
+            int maxLen = 1, maxCnt = 1;
+            for (int j = i + 1; j < n; j++) {
+                if (nums[j] > nums[i]) {
+                    int length = dp[j][0];
+                    int count = dp[j][1];
+                    if (length + 1 > maxLen) {
+                        maxLen = length + 1;
+                        maxCnt = count;
+                    } else if (length + 1 == maxLen) {
+                        maxCnt += count;
+                    }
+                }
+            }
+
+            if (maxLen > lenLIS) {
+                lenLIS = maxLen;
+                res = maxCnt;
+            } else if (maxLen == lenLIS) {
+                res += maxCnt;
+            }
+            dp[i][0] = maxLen;
+            dp[i][1] = maxCnt;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findNumberOfLIS(vector<int>& nums) {
+        int n = nums.size();
+        vector<vector<int>> dp(n, vector<int>(2, 0));
+        int lenLIS = 0, res = 0;
+
+        for (int i = n - 1; i >= 0; i--) {
+            int maxLen = 1, maxCnt = 1;
+            for (int j = i + 1; j < n; j++) {
+                if (nums[j] > nums[i]) {
+                    int length = dp[j][0];
+                    int count = dp[j][1];
+                    if (length + 1 > maxLen) {
+                        maxLen = length + 1;
+                        maxCnt = count;
+                    } else if (length + 1 == maxLen) {
+                        maxCnt += count;
+                    }
+                }
+            }
+
+            if (maxLen > lenLIS) {
+                lenLIS = maxLen;
+                res = maxCnt;
+            } else if (maxLen == lenLIS) {
+                res += maxCnt;
+            }
+            dp[i][0] = maxLen;
+            dp[i][1] = maxCnt;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    findNumberOfLIS(nums) {
+        const n = nums.length;
+        const dp = Array.from({ length: n }, () => [0, 0]);
+        let lenLIS = 0, res = 0;
+
+        for (let i = n - 1; i >= 0; i--) {
+            let maxLen = 1, maxCnt = 1;
+            for (let j = i + 1; j < n; j++) {
+                if (nums[j] > nums[i]) {
+                    const [length, count] = dp[j];
+                    if (length + 1 > maxLen) {
+                        maxLen = length + 1;
+                        maxCnt = count;
+                    } else if (length + 1 === maxLen) {
+                        maxCnt += count;
+                    }
+                }
+            }
+
+            if (maxLen > lenLIS) {
+                lenLIS = maxLen;
+                res = maxCnt;
+            } else if (maxLen === lenLIS) {
+                res += maxCnt;
+            }
+            dp[i] = [maxLen, maxCnt];
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Dynamic Programming (Binary Search + Prefix Sum)
+
+::tabs-start
+
+```python
+class Solution:
+    def findNumberOfLIS(self, nums: List[int]) -> int:
+        n = len(nums)
+        dp = [[[0, 0], [nums[0], 1]]]
+
+        def bs1(num):
+            l, r = 0, len(dp) - 1
+            j = len(dp) - 1
+            while l <= r:
+                mid = (l + r) // 2
+                if dp[mid][-1][0] < num:
+                    l = mid + 1
+                else:
+                    j = mid
+                    r = mid - 1
+            return j
+
+        def bs2(i, num):
+            if i < 0:
+                return 1
+            l, r = 1, len(dp[i]) - 1
+            j = 0
+            while l <= r:
+                mid = (l + r) // 2
+                if dp[i][mid][0] >= num:
+                    j = mid
+                    l = mid + 1
+                else:
+                    r = mid - 1
+            return dp[i][-1][1] - dp[i][j][1]
+
+        LIS = 1
+        for i in range(1, n):
+            num = nums[i]
+            if num > dp[-1][-1][0]:
+                count = bs2(LIS - 1, num)
+                dp.append([[0, 0], [num, count]])
+                LIS += 1
+            else:
+                j = bs1(num)
+                count = bs2(j - 1, num)
+                dp[j].append([num, dp[j][-1][1] + count])
+
+        return dp[-1][-1][1]
+```
+
+```java
+public class Solution {
+    public int findNumberOfLIS(int[] nums) {
+        int n = nums.length;
+        List<List<int[]>> dp = new ArrayList<>();
+        List<int[]> first = new ArrayList<>();
+        first.add(new int[]{0, 0});
+        first.add(new int[]{nums[0], 1});
+        dp.add(first);
+
+        int LIS = 1;
+
+        for (int i = 1; i < n; i++) {
+            int num = nums[i];
+            if (num > dp.get(dp.size() - 1).get(dp.get(dp.size() - 1).size() - 1)[0]) {
+                int count = bs2(dp, LIS - 1, num);
+                List<int[]> newList = new ArrayList<>();
+                newList.add(new int[]{0, 0});
+                newList.add(new int[]{num, count});
+                dp.add(newList);
+                LIS++;
+            } else {
+                int j = bs1(dp, num);
+                int count = bs2(dp, j - 1, num);
+                List<int[]> list = dp.get(j);
+                int[] last = list.get(list.size() - 1);
+                list.add(new int[]{num, last[1] + count});
+            }
+        }
+
+        return dp.get(dp.size() - 1).get(dp.get(dp.size() - 1).size() - 1)[1];
+    }
+
+    private int bs1(List<List<int[]>> dp, int num) {
+        int l = 0, r = dp.size() - 1, j = dp.size() - 1;
+        while (l <= r) {
+            int mid = (l + r) / 2;
+            if (dp.get(mid).get(dp.get(mid).size() - 1)[0] < num) {
+                l = mid + 1;
+            } else {
+                j = mid;
+                r = mid - 1;
+            }
+        }
+        return j;
+    }
+
+    private int bs2(List<List<int[]>> dp, int i, int num) {
+        if (i < 0) return 1;
+        int l = 1, r = dp.get(i).size() - 1, j = 0;
+        while (l <= r) {
+            int mid = (l + r) / 2;
+            if (dp.get(i).get(mid)[0] >= num) {
+                j = mid;
+                l = mid + 1;
+            } else {
+                r = mid - 1;
+            }
+        }
+        return dp.get(i).get(dp.get(i).size() - 1)[1] - dp.get(i).get(j)[1];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findNumberOfLIS(vector<int>& nums) {
+        vector<vector<pair<int, int>>> dp = {{{0, 0}, {nums[0], 1}}};
+        int LIS = 1;
+
+        for (int i = 1; i < nums.size(); i++) {
+            int num = nums[i];
+            if (num > dp.back().back().first) {
+                int count = bs2(dp, LIS - 1, num);
+                dp.push_back({{0, 0}, {num, count}});
+                LIS++;
+            } else {
+                int j = bs1(dp, num);
+                int count = bs2(dp, j - 1, num);
+                dp[j].push_back({num, dp[j].back().second + count});
+            }
+        }
+
+        return dp.back().back().second;
+    }
+
+private:
+    int bs1(vector<vector<pair<int, int>>>& dp, int num) {
+        int l = 0, r = dp.size() - 1, j = dp.size() - 1;
+        while (l <= r) {
+            int mid = (l + r) / 2;
+            if (dp[mid].back().first < num) {
+                l = mid + 1;
+            } else {
+                j = mid;
+                r = mid - 1;
+            }
+        }
+        return j;
+    }
+
+    int bs2(vector<vector<pair<int, int>>>& dp, int i, int num) {
+        if (i < 0) return 1;
+        int l = 1, r = dp[i].size() - 1, j = 0;
+        while (l <= r) {
+            int mid = (l + r) / 2;
+            if (dp[i][mid].first >= num) {
+                j = mid;
+                l = mid + 1;
+            } else {
+                r = mid - 1;
+            }
+        }
+        return dp[i].back().second - dp[i][j].second;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    findNumberOfLIS(nums) {
+        const dp = [[[0, 0], [nums[0], 1]]];
+        let LIS = 1;
+
+        const bs1 = (num) => {
+            let l = 0, r = dp.length - 1, j = dp.length - 1;
+            while (l <= r) {
+                const mid = Math.floor((l + r) / 2);
+                if (dp[mid][dp[mid].length - 1][0] < num) {
+                    l = mid + 1;
+                } else {
+                    j = mid;
+                    r = mid - 1;
+                }
+            }
+            return j;
+        };
+
+        const bs2 = (i, num) => {
+            if (i < 0) return 1;
+            let l = 1, r = dp[i].length - 1, j = 0;
+            while (l <= r) {
+                const mid = Math.floor((l + r) / 2);
+                if (dp[i][mid][0] >= num) {
+                    j = mid;
+                    l = mid + 1;
+                } else {
+                    r = mid - 1;
+                }
+            }
+            return dp[i][dp[i].length - 1][1] - dp[i][j][1];
+        };
+
+        for (let i = 1; i < nums.length; i++) {
+            const num = nums[i];
+            if (num > dp[dp.length - 1][dp[dp.length - 1].length - 1][0]) {
+                const count = bs2(LIS - 1, num);
+                dp.push([[0, 0], [num, count]]);
+                LIS++;
+            } else {
+                const j = bs1(num);
+                const count = bs2(j - 1, num);
+                dp[j].push([num, dp[j][dp[j].length - 1][1] + count]);
+            }
+        }
+
+        return dp[dp.length - 1][dp[dp.length - 1].length - 1][1];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n\log n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/number-of-music-playlists.md b/articles/number-of-music-playlists.md
new file mode 100644
index 000000000..284e35bae
--- /dev/null
+++ b/articles/number-of-music-playlists.md
@@ -0,0 +1,340 @@
+## 1. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def numMusicPlaylists(self, n: int, goal: int, k: int) -> int:
+        mod = 10**9 + 7
+        dp = {}
+
+        def count(cur_goal, old_songs):
+            if cur_goal == 0 and old_songs == n:
+                return 1
+            if cur_goal == 0 or old_songs > n:
+                return 0
+            if (cur_goal, old_songs) in dp:
+                return dp[(cur_goal, old_songs)]
+
+            res = (n - old_songs) * count(cur_goal - 1, old_songs + 1)
+            if old_songs > k:
+                res += (old_songs - k) * count(cur_goal - 1, old_songs)
+            dp[(cur_goal, old_songs)] = res % mod
+            return dp[(cur_goal, old_songs)]
+
+        return count(goal, 0)
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1_000_000_007;
+    private int[][] dp;
+
+    public int numMusicPlaylists(int n, int goal, int k) {
+        dp = new int[goal + 1][n + 1];
+        for (int[] row : dp) {
+            Arrays.fill(row, -1);
+        }
+        return count(goal, 0, n, k);
+    }
+
+    private int count(int curGoal, int oldSongs, int n, int k) {
+        if (curGoal == 0 && oldSongs == n) return 1;
+        if (curGoal == 0 || oldSongs > n) return 0;
+        if (dp[curGoal][oldSongs] != -1) return dp[curGoal][oldSongs];
+
+        long res = (long) (n - oldSongs) * count(curGoal - 1, oldSongs + 1, n, k) % MOD;
+        if (oldSongs > k) {
+            res = (res + (long) (oldSongs - k) * count(curGoal - 1, oldSongs, n, k)) % MOD;
+        }
+        dp[curGoal][oldSongs] = (int) res;
+        return dp[curGoal][oldSongs];
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    static const int MOD = 1e9 + 7;
+    vector<vector<int>> dp;
+
+    int count(int curGoal, int oldSongs, int n, int k) {
+        if (curGoal == 0 && oldSongs == n) return 1;
+        if (curGoal == 0 || oldSongs > n) return 0;
+        if (dp[curGoal][oldSongs] != -1) return dp[curGoal][oldSongs];
+
+        long long res = (long long)(n - oldSongs) * count(curGoal - 1, oldSongs + 1, n, k) % MOD;
+        if (oldSongs > k) {
+            res = (res + (long long)(oldSongs - k) * count(curGoal - 1, oldSongs, n, k)) % MOD;
+        }
+        dp[curGoal][oldSongs] = res;
+        return dp[curGoal][oldSongs];
+    }
+
+public:
+    int numMusicPlaylists(int n, int goal, int k) {
+        dp.assign(goal + 1, vector<int>(n + 1, -1));
+        return count(goal, 0, n, k);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} goal
+     * @param {number} k
+     * @return {number}
+     */
+    numMusicPlaylists(n, goal, k) {
+        const MOD = 1e9 + 7;
+        const dp = Array.from({ length: goal + 1 }, () => Array(n + 1).fill(-1));
+
+        const count = (curGoal, oldSongs) => {
+            if (curGoal === 0 && oldSongs === n) return 1;
+            if (curGoal === 0 || oldSongs > n) return 0;
+            if (dp[curGoal][oldSongs] !== -1) return dp[curGoal][oldSongs];
+
+            let res = ((n - oldSongs) * count(curGoal - 1, oldSongs + 1)) % MOD;
+            if (oldSongs > k) {
+                res = (res + ((oldSongs - k) * count(curGoal - 1, oldSongs)) % MOD) % MOD;
+            }
+            dp[curGoal][oldSongs] = res;
+            return res;
+        };
+
+        return count(goal, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(g * n)$
+* Space complexity: $O(g * n)$
+
+> Where $g$ is the number of songs to listen and $n$ is the number of different songs.
+
+---
+
+## 2. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def numMusicPlaylists(self, n: int, goal: int, k: int) -> int:
+        mod = 10**9 + 7
+        dp = [[0] * (n + 1) for _ in range(goal + 1)]
+        dp[0][0] = 1
+
+        for cur_goal in range(1, goal + 1):
+            for old_songs in range(1, n + 1):
+                res = (dp[cur_goal - 1][old_songs - 1] * (n - old_songs + 1)) % mod
+                if old_songs > k:
+                    res = (res + dp[cur_goal - 1][old_songs] * (old_songs - k)) % mod
+                dp[cur_goal][old_songs] = res
+
+        return dp[goal][n]
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1_000_000_007;
+
+    public int numMusicPlaylists(int n, int goal, int k) {
+        int[][] dp = new int[goal + 1][n + 1];
+        dp[0][0] = 1;
+
+        for (int curGoal = 1; curGoal <= goal; curGoal++) {
+            for (int oldSongs = 1; oldSongs <= n; oldSongs++) {
+                int res  = (int) (((long) dp[curGoal - 1][oldSongs - 1] * (n - oldSongs + 1)) % MOD);
+                if (oldSongs > k) {
+                    res = (res + (int) (((long) dp[curGoal - 1][oldSongs] * (oldSongs - k)) % MOD)) % MOD;
+                }
+                dp[curGoal][oldSongs] = res;
+            }
+        }
+
+        return dp[goal][n];
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    static const int MOD = 1e9 + 7;
+
+public:
+    int numMusicPlaylists(int n, int goal, int k) {
+        vector<vector<int>> dp(goal + 1, vector<int>(n + 1, 0));
+        dp[0][0] = 1;
+
+        for (int curGoal = 1; curGoal <= goal; curGoal++) {
+            for (int oldSongs = 1; oldSongs <= n; oldSongs++) {
+                int res = (long long) dp[curGoal - 1][oldSongs - 1] * (n - oldSongs + 1) % MOD;
+                if (oldSongs > k) {
+                    res = (res + (long long) dp[curGoal - 1][oldSongs] * (oldSongs - k) % MOD) % MOD;
+                }
+                dp[curGoal][oldSongs] = res;
+            }
+        }
+
+        return dp[goal][n];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} goal
+     * @param {number} k
+     * @return {number}
+     */
+    numMusicPlaylists(n, goal, k) {
+        const MOD = 1e9 + 7;
+        const dp = Array.from({ length: goal + 1 }, () => Array(n + 1).fill(0));
+        dp[0][0] = 1;
+
+        for (let curGoal = 1; curGoal <= goal; curGoal++) {
+            for (let oldSongs = 1; oldSongs <= n; oldSongs++) {
+                let res = (dp[curGoal - 1][oldSongs - 1] * (n - oldSongs + 1)) % MOD;
+                if (oldSongs > k) {
+                    res = (res + dp[curGoal - 1][oldSongs] * (oldSongs - k)) % MOD;
+                }
+                dp[curGoal][oldSongs] = res;
+            }
+        }
+
+        return dp[goal][n];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(g * n)$
+* Space complexity: $O(g * n)$
+
+> Where $g$ is the number of songs to listen and $n$ is the number of different songs.
+
+---
+
+## 3. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def numMusicPlaylists(self, n: int, goal: int, k: int) -> int:
+        mod = 10**9 + 7
+        dp = [0] * (n + 1)
+
+        for cur_goal in range(1, goal + 1):
+            prev = 1 if cur_goal == 1 else 0
+            for old_songs in range(1, n + 1):
+                res = (prev * (n - old_songs + 1)) % mod
+                if old_songs > k:
+                    res = (res + dp[old_songs] * (old_songs - k)) % mod
+                prev = dp[old_songs]
+                dp[old_songs] = res
+
+        return dp[n]
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1_000_000_007;
+
+    public int numMusicPlaylists(int n, int goal, int k) {
+        int[] dp = new int[n + 1];
+
+        for (int curGoal = 1; curGoal <= goal; curGoal++) {
+            int prev = curGoal == 1 ? 1 : 0;
+            for (int oldSongs = 1; oldSongs <= n; oldSongs++) {
+                int res  = (int) (((long) prev * (n - oldSongs + 1)) % MOD);
+                if (oldSongs > k) {
+                    res = (res + (int) (((long) dp[oldSongs] * (oldSongs - k)) % MOD)) % MOD;
+                }
+                prev = dp[oldSongs];
+                dp[oldSongs] = res;
+            }
+        }
+
+        return dp[n];
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    static const int MOD = 1e9 + 7;
+
+public:
+    int numMusicPlaylists(int n, int goal, int k) {
+        vector<int> dp(n + 1);
+
+        for (int curGoal = 1; curGoal <= goal; curGoal++) {
+            int prev = curGoal == 1 ? 1: 0;
+            for (int oldSongs = 1; oldSongs <= n; oldSongs++) {
+                int res = (long long) prev * (n - oldSongs + 1) % MOD;
+                if (oldSongs > k) {
+                    res = (res + (long long) dp[oldSongs] * (oldSongs - k) % MOD) % MOD;
+                }
+                prev = dp[oldSongs];
+                dp[oldSongs] = res;
+            }
+        }
+
+        return dp[n];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} goal
+     * @param {number} k
+     * @return {number}
+     */
+    numMusicPlaylists(n, goal, k) {
+        const MOD = 1e9 + 7;
+        const dp = new Array(n + 1).fill(0);
+
+        for (let curGoal = 1; curGoal <= goal; curGoal++) {
+            let prev = curGoal === 1 ? 1 : 0;
+            for (let oldSongs = 1; oldSongs <= n; oldSongs++) {
+                let res = (prev * (n - oldSongs + 1)) % MOD;
+                if (oldSongs > k) {
+                    res = (res + dp[oldSongs] * (oldSongs - k)) % MOD;
+                }
+                prev = dp[oldSongs];
+                dp[oldSongs] = res;
+            }
+        }
+
+        return dp[n];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(g * n)$
+* Space complexity: $O(n)$
+
+> Where $g$ is the number of songs to listen and $n$ is the number of different songs.
\ No newline at end of file
diff --git a/articles/number-of-one-bits.md b/articles/number-of-one-bits.md
index 1656d9e26..4ea545b0d 100644
--- a/articles/number-of-one-bits.md
+++ b/articles/number-of-one-bits.md
@@ -73,6 +73,46 @@ public class Solution {
 }
 ```
 
+```go
+func hammingWeight(n int) int {
+	res := 0
+	for i := 0; i < 32; i++ {
+		if (1<<i)&n != 0 {
+			res++
+		}
+	}
+	return res
+}
+```
+
+```kotlin
+class Solution {
+    fun hammingWeight(n: Int): Int {
+        var res = 0
+        for (i in 0 until 32) {
+            if ((1 shl i) and n != 0) {
+                res++
+            }
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func hammingWeight(_ n: Int) -> Int {
+        var res = 0
+        for i in 0..<32 {
+            if (1 << i) & n != 0 {
+                res += 1
+            }
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -153,6 +193,49 @@ public class Solution {
 }
 ```
 
+```go
+func hammingWeight(n int) int {
+	res := 0
+	for n != 0 {
+		if n&1 != 0 {
+			res++
+		}
+		n >>= 1
+	}
+	return res
+}
+```
+
+```kotlin
+class Solution {
+    fun hammingWeight(n: Int): Int {
+        var res = 0
+        var num = n
+        while (num != 0) {
+            if ((num and 1) != 0) {
+                res++
+            }
+            num = num shr 1
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func hammingWeight(_ n: Int) -> Int {
+        var n = n
+        var res = 0
+        while n != 0 {
+            res += (n & 1) != 0 ? 1 : 0
+            n >>= 1
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -233,6 +316,45 @@ public class Solution {
 }
 ```
 
+```go
+func hammingWeight(n int) int {
+	res := 0
+	for n != 0 {
+		n &= n - 1
+        res++
+	}
+	return res
+}
+```
+
+```kotlin
+class Solution {
+    fun hammingWeight(n: Int): Int {
+        var res = 0
+        var num = n
+        while (num != 0) {
+            num = num and (num - 1)
+            res++
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func hammingWeight(_ n: Int) -> Int {
+        var n = n
+        var res = 0
+        while n != 0 {
+            n &= (n - 1)
+            res += 1
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -289,6 +411,28 @@ public class Solution {
 }
 ```
 
+```go
+func hammingWeight(n int) int {
+	return bits.OnesCount(uint(n))
+}
+```
+
+```kotlin
+class Solution {
+    fun hammingWeight(n: Int): Int {
+        return n.countOneBits()
+    }
+}
+```
+
+```swift
+class Solution {
+    func hammingWeight(_ n: Int) -> Int {
+        return n.nonzeroBitCount
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/number-of-pairs-of-interchangeable-rectangles.md b/articles/number-of-pairs-of-interchangeable-rectangles.md
new file mode 100644
index 000000000..bbb73e152
--- /dev/null
+++ b/articles/number-of-pairs-of-interchangeable-rectangles.md
@@ -0,0 +1,364 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def interchangeableRectangles(self, rectangles: List[List[int]]) -> int:
+        res = 0
+        for i in range(1, len(rectangles)):
+            for j in range(i):
+                if rectangles[i][0] / rectangles[i][1] == rectangles[j][0] / rectangles[j][1]:
+                    res += 1
+        return res
+```
+
+```java
+public class Solution {
+    public long interchangeableRectangles(int[][] rectangles) {
+        long res = 0;
+        for (int i = 1; i < rectangles.length; i++) {
+            for (int j = 0; j < i; j++) {
+                if ((double) rectangles[i][0] / rectangles[i][1] == (double) rectangles[j][0] / rectangles[j][1]) {
+                    res++;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long interchangeableRectangles(vector<vector<int>>& rectangles) {
+        long long res = 0;
+        for (int i = 1; i < rectangles.size(); i++) {
+            for (int j = 0; j < i; j++) {
+                if ((double) rectangles[i][0] / rectangles[i][1] == (double) rectangles[j][0] / rectangles[j][1]) {
+                    res++;
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} rectangles
+     * @return {number}
+     */
+    interchangeableRectangles(rectangles) {
+        let res = 0;
+        for (let i = 1; i < rectangles.length; i++) {
+            for (let j = 0; j < i; j++) {
+                if (rectangles[i][0] / rectangles[i][1] === rectangles[j][0] / rectangles[j][1]) {
+                    res++;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Hash Map (Two Pass)
+
+::tabs-start
+
+```python
+class Solution:
+    def interchangeableRectangles(self, rectangles: List[List[int]]) -> int:
+        count = {}
+        for w, h in rectangles:
+            count[w / h] = 1 + count.get(w / h, 0)
+
+        res = 0
+        for c in count.values():
+            if c > 1:
+                res += (c * (c - 1)) // 2
+        return res
+```
+
+```java
+public  class Solution {
+    public long interchangeableRectangles(int[][] rectangles) {
+        HashMap<Double, Integer> count = new HashMap<>();
+        for (int[] rect : rectangles) {
+            double ratio = (double) rect[0] / rect[1];
+            count.put(ratio, count.getOrDefault(ratio, 0) + 1);
+        }
+        
+        long res = 0;
+        for (int c : count.values()) {
+            if (c > 1) {
+                res += (c * 1L * (c - 1)) / 2;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long interchangeableRectangles(vector<vector<int>>& rectangles) {
+        unordered_map<double, int> count;
+        for (const auto& rect : rectangles) {
+            double ratio = (double) rect[0] / rect[1];
+            count[ratio]++;
+        }
+
+        long long res = 0;
+        for (const auto& [key, c] : count) {
+            if (c > 1) {
+                res += (c * 1LL * (c - 1)) / 2;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} rectangles
+     * @return {number}
+     */
+    interchangeableRectangles(rectangles) {
+        const count = new Map();
+        for (const [w, h] of rectangles) {
+            const ratio = w / h;
+            count.set(ratio, (count.get(ratio) || 0) + 1);
+        }
+
+        let res = 0;
+        for (const c of count.values()) {
+            if (c > 1) {
+                res += (c * (c - 1)) / 2;
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Hash Map (One Pass)
+
+::tabs-start
+
+```python
+class Solution:
+    def interchangeableRectangles(self, rectangles: List[List[int]]) -> int:
+        count = {}
+        res = 0
+        for w, h in rectangles:
+            res += count.get(w / h, 0)
+            count[w / h] = 1 + count.get(w / h, 0)
+        return res
+```
+
+```java
+public  class Solution {
+    public long interchangeableRectangles(int[][] rectangles) {
+        HashMap<Double, Integer> count = new HashMap<>();
+        long res = 0;
+        for (int[] rect : rectangles) {
+            double ratio = (double) rect[0] / rect[1];
+            res += count.getOrDefault(ratio, 0);
+            count.put(ratio, count.getOrDefault(ratio, 0) + 1);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long interchangeableRectangles(vector<vector<int>>& rectangles) {
+        unordered_map<double, int> count;
+        long long res = 0;
+        for (const auto& rect : rectangles) {
+            double ratio = (double) rect[0] / rect[1];
+            res += count[ratio];
+            count[ratio]++;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} rectangles
+     * @return {number}
+     */
+    interchangeableRectangles(rectangles) {
+        const count = new Map();
+        let res = 0;
+        for (const [w, h] of rectangles) {
+            const ratio = w / h;
+            res += count.get(ratio) || 0
+            count.set(ratio, (count.get(ratio) || 0) + 1);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Greatest Common Divisor
+
+::tabs-start
+
+```python
+class Solution:
+    def hash(self, a: int, b: int) -> int:
+        mask = a
+        mask |= (b << 31)
+        return mask
+    
+    def interchangeableRectangles(self, rectangles: List[List[int]]) -> int:
+        res = 0
+        count = {}
+        for rect in rectangles:
+            gcd = math.gcd(rect[0], rect[1])
+            key = self.hash(rect[0] // gcd, rect[1] // gcd)
+            res += count.get(key, 0)
+            count[key] = count.get(key, 0) + 1
+        return res
+```
+
+```java
+public class Solution {
+    public long hash(int a, int b) {
+        long mask = a;
+        mask |= ((long)b << 31);
+        return mask;
+    }
+    
+    public long interchangeableRectangles(int[][] rectangles) {
+        long res = 0;
+        Map<Long, Integer> count = new HashMap<>();
+        for (int[] rect : rectangles) {
+            int gcd = gcd(rect[0], rect[1]);
+            long key = hash(rect[0] / gcd, rect[1] / gcd);
+            res += count.getOrDefault(key, 0);
+            count.put(key, count.getOrDefault(key, 0) + 1);
+        }
+        return res;
+    }
+    
+    private int gcd(int a, int b) {
+        while (b != 0) {
+            a %= b;
+            int temp = a;
+            a = b;
+            b = temp;
+        }
+        return a;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long hash(int a, int b) {
+        long long mask = a;
+        mask |= ((long long)b << 31);
+        return mask;
+    }
+    
+    long long interchangeableRectangles(vector<vector<int>>& rectangles) {
+        long long res = 0;
+        unordered_map<long long, int> count;
+        for (const auto& rect : rectangles) {
+            int gcd = __gcd(rect[0], rect[1]);
+            long long key = hash(rect[0] / gcd, rect[1] / gcd);
+            res += count[key];
+            count[key]++;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} a
+     * @param {number} b
+     * @return {string}
+     */
+    hash(a, b) {
+        return `${a},${b}`;
+    }
+
+    /**
+     * @param {number[][]} rectangles
+     * @return {number}
+     */
+    interchangeableRectangles(rectangles) {
+        let res = 0;
+        const count = new Map();
+        
+        const gcd = (a, b) => {
+            while (b !== 0) {
+                a %= b;
+                [a, b] = [b, a]
+            }
+            return a;
+        };
+        
+        for (const rect of rectangles) {
+            const g = gcd(rect[0], rect[1]);
+            const key = this.hash(Math.floor(rect[0] / g), Math.floor(rect[1] / g));
+            res += count.get(key) || 0;
+            count.set(key, (count.get(key) || 0) + 1);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/number-of-senior-citizens.md b/articles/number-of-senior-citizens.md
new file mode 100644
index 000000000..11a6b0d29
--- /dev/null
+++ b/articles/number-of-senior-citizens.md
@@ -0,0 +1,149 @@
+## 1. String Parsing
+
+::tabs-start
+
+```python
+class Solution:
+    def countSeniors(self, details: List[str]) -> int:
+        res = 0
+        for d in details:
+            if int(d[11:13]) > 60:
+                res += 1
+        return res
+```
+
+```java
+public class Solution {
+    public int countSeniors(String[] details) {
+        int res = 0;
+        for (String d : details) {
+            if (Integer.parseInt(d.substring(11, 13)) > 60) {
+                res++;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countSeniors(vector<string>& details) {
+        int res = 0;
+        for (const string& d : details) {
+            if (stoi(d.substr(11, 2)) > 60) {
+                res++;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} details
+     * @return {number}
+     */
+    countSeniors(details) {
+        let res = 0;
+        for (let d of details) {
+            if (parseInt(d.slice(11, 13)) > 60) {
+                res++;
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Character-Based Extraction
+
+::tabs-start
+
+```python
+class Solution:
+    def countSeniors(self, details: List[str]) -> int:
+        res = 0
+        for d in details:
+            ten = ord(d[11]) - ord("0")
+            one = ord(d[12]) - ord("0")
+            age = one + 10 * ten
+            if age > 60:
+                res += 1
+        return res
+```
+
+```java
+public class Solution {
+    public int countSeniors(String[] details) {
+        int res = 0;
+        for (String d : details) {
+            int ten = d.charAt(11) - '0';
+            int one = d.charAt(12) - '0';
+            int age = one + 10 * ten;
+            if (age > 60) {
+                res++;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countSeniors(vector<string>& details) {
+        int res = 0;
+        for (const string& d : details) {
+            int ten = d[11] - '0';
+            int one = d[12] - '0';
+            int age = one + 10 * ten;
+            if (age > 60) {
+                res++;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} details
+     * @return {number}
+     */
+    countSeniors(details) {
+        let res = 0;
+        for (let d of details) {
+            let ten = d.charCodeAt(11) - 48;
+            let one = d.charCodeAt(12) - 48;
+            let age = one + 10 * ten;
+            if (age > 60) {
+                res++;
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/number-of-students-unable-to-eat-lunch.md b/articles/number-of-students-unable-to-eat-lunch.md
new file mode 100644
index 000000000..6ccf1609d
--- /dev/null
+++ b/articles/number-of-students-unable-to-eat-lunch.md
@@ -0,0 +1,348 @@
+## 1. Queue
+
+::tabs-start
+
+```python
+class Solution:
+    def countStudents(self, students: List[int], sandwiches: List[int]) -> int:
+        n = len(students)
+        q = deque(students)
+
+        res = n
+        for sandwich in sandwiches:
+            cnt = 0
+            while cnt < n and q[0] != sandwich:
+                cur = q.popleft()
+                q.append(cur)
+                cnt += 1
+
+            if q[0] == sandwich:
+                q.popleft()
+                res -= 1
+            else:
+                break
+        return res
+```
+
+```java
+public class Solution {
+    public int countStudents(int[] students, int[] sandwiches) {
+        int n = students.length;
+        Queue<Integer> q = new LinkedList<>();
+        for (int student : students) {
+            q.offer(student);
+        }
+
+        int res = n;
+        for (int sandwich : sandwiches) {
+            int cnt = 0;
+            while (cnt < n && q.peek() != sandwich) {
+                q.offer(q.poll());
+                cnt++;
+            }
+            if (q.peek() == sandwich) {
+                q.poll();
+                res--;
+            } else {
+                break;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countStudents(vector<int>& students, vector<int>& sandwiches) {
+        int n = students.size();
+        queue<int> q;
+        
+        for (int student : students) {
+            q.push(student);
+        }
+
+        int res = n;
+        for (int sandwich : sandwiches) {
+            int cnt = 0;
+            while (cnt < n && q.front() != sandwich) {
+                q.push(q.front());
+                q.pop();
+                cnt++;
+            }
+            if (q.front() == sandwich) {
+                q.pop();
+                res--;
+            } else {
+                break;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} students
+     * @param {number[]} sandwiches
+     * @return {number}
+     */
+    countStudents(students, sandwiches) {
+        let n = students.length;
+        let q = new Queue();
+        for (let student of students) {
+            q.push(student);
+        }
+
+        let res = n;
+        for (let sandwich of sandwiches) {
+            let cnt = 0;
+            while (cnt < n && q.front() !== sandwich) {
+                q.push(q.pop());
+                cnt++;
+            }
+
+            if (q.front() === sandwich) {
+                q.pop();
+                res--;
+            } else {
+                break;
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Iteration
+
+::tabs-start
+
+```python
+class Solution:
+    def countStudents(self, students: List[int], sandwiches: List[int]) -> int:
+        n = len(students)
+        idx = 0
+
+        res = n
+        for sandwich in sandwiches:
+            cnt = 0
+            while cnt < n and students[idx] != sandwich:
+                idx += 1
+                idx %= n
+                cnt += 1
+
+            if students[idx] == sandwich:
+                students[idx] = -1
+                res -= 1
+            else:
+                break
+        return res
+```
+
+```java
+public class Solution {
+    public int countStudents(int[] students, int[] sandwiches) {
+        int n = students.length;
+        int idx = 0;
+
+        int res = n;
+        for (int sandwich : sandwiches) {
+            int cnt = 0;
+            while (cnt < n && students[idx] != sandwich) {
+                idx++;
+                idx %= n;
+                cnt++;
+            }
+            if (students[idx] == sandwich) {
+                students[idx] = -1;
+                res--;
+            } else {
+                break;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countStudents(vector<int>& students, vector<int>& sandwiches) {
+        int n = students.size();
+        int idx = 0;
+
+        int res = n;
+        for (int sandwich : sandwiches) {
+            int cnt = 0;
+            while (cnt < n && students[idx] != sandwich) {
+                idx++;
+                idx %= n;
+                cnt++;
+            }
+            if (students[idx] == sandwich) {
+                students[idx] = -1;
+                res--;
+            } else {
+                break;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} students
+     * @param {number[]} sandwiches
+     * @return {number}
+     */
+    countStudents(students, sandwiches) {
+        let n = students.length;
+        let idx = 0;
+
+        let res = n;
+        for (let sandwich of sandwiches) {
+            let cnt = 0;
+            while (cnt < n && students[idx] !== sandwich) {
+                idx++;
+                idx %= n;
+                cnt++;
+            }
+
+            if (students[idx] === sandwich) {
+                students[idx] = -1;
+                res--;
+            } else {
+                break;
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Frequency Count
+
+::tabs-start
+
+```python
+class Solution:
+    def countStudents(self, students: List[int], sandwiches: List[int]) -> int:
+        res = len(students)
+        cnt = Counter(students)
+
+        for s in sandwiches:
+            if cnt[s] > 0:
+                res -= 1
+                cnt[s] -= 1
+            else:
+                break
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int countStudents(int[] students, int[] sandwiches) {
+        int n = students.length;
+        int res = n;
+        int[] cnt = new int[2];
+        for (int i = 0; i < n; i++) {
+            cnt[students[i]]++;
+        }
+
+        for (int i = 0; i < n; i++) {
+            if (cnt[sandwiches[i]] > 0) {
+                res--;
+                cnt[sandwiches[i]]--;
+            } else {
+                break;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countStudents(vector<int>& students, vector<int>& sandwiches) {
+        int res = students.size();
+        vector<int> cnt(2);
+        for (int& student : students) {
+            cnt[student]++;
+        }
+
+        for (int& s : sandwiches) {
+            if (cnt[s] > 0) {
+                cnt[s]--;
+                res--;
+            } else {
+                break;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} students
+     * @param {number[]} sandwiches
+     * @return {number}
+     */
+    countStudents(students, sandwiches) {
+        let res = students.length;
+        const cnt = new Int32Array(2);
+        for (let student of students) {
+            cnt[student]++;
+        }
+
+        for (let s of sandwiches) {
+            if (cnt[s] > 0) {
+                cnt[s]--;
+                res--;
+            } else {
+                break;
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/number-of-sub-arrays-of-size-k-and-average-greater-than-or-equal-to-threshold.md b/articles/number-of-sub-arrays-of-size-k-and-average-greater-than-or-equal-to-threshold.md
new file mode 100644
index 000000000..f99cc6f13
--- /dev/null
+++ b/articles/number-of-sub-arrays-of-size-k-and-average-greater-than-or-equal-to-threshold.md
@@ -0,0 +1,398 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def numOfSubarrays(self, arr: List[int], k: int, threshold: int) -> int:
+        res = 0
+        l = 0
+        
+        for r in range(k - 1, len(arr)):
+            sum_ = 0
+            for i in range(l, r + 1):
+                sum_ += arr[i]
+            
+            if sum_ / k >= threshold:
+                res += 1
+            l += 1
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int numOfSubarrays(int[] arr, int k, int threshold) {
+        int res = 0, l = 0;
+
+        for (int r = k - 1; r < arr.length; r++) {
+            int sum = 0;
+            for (int i = l; i <= r; i++) {
+                sum += arr[i];
+            }
+            if (sum / k >= threshold) {
+                res++;
+            }
+            l++;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numOfSubarrays(vector<int>& arr, int k, int threshold) {
+        int res = 0, l = 0;
+
+        for (int r = k - 1; r < arr.size(); r++) {
+            int sum = 0;
+            for (int i = l; i <= r; i++) {
+                sum += arr[i];
+            }
+            if (sum / k >= threshold) {
+                res++;
+            }
+            l++;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @param {number} k
+     * @param {number} threshold
+     * @return {number}
+     */
+    numOfSubarrays(arr, k, threshold) {
+        let res = 0, l = 0;
+
+        for (let r = k - 1; r < arr.length; r++) {
+            let sum = 0;
+            for (let i = l; i <= r; i++) {
+                sum += arr[i];
+            }
+            if (sum / k >= threshold) {
+                res++;
+            }
+            l++;
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * k)$
+* Space complexity: $O(1)$
+
+> Where $n$ is the size of the array $arr$ and $k$ is the size of the sub-array.
+
+---
+
+## 2. Prefix Sum
+
+::tabs-start
+
+```python
+class Solution:
+    def numOfSubarrays(self, arr: List[int], k: int, threshold: int) -> int:
+        prefix_sum = [0] * (len(arr) + 1)
+        for i in range(len(arr)):
+            prefix_sum[i + 1] += prefix_sum[i] + arr[i]
+
+        res = l = 0
+        for r in range(k - 1, len(arr)):
+            sum_ = prefix_sum[r + 1] - prefix_sum[l]
+            if sum_ / k >= threshold:
+                res += 1
+            l += 1
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int numOfSubarrays(int[] arr, int k, int threshold) {
+        int[] prefixSum = new int[arr.length + 1];
+        for (int i = 0; i < arr.length; i++) {
+            prefixSum[i + 1] += prefixSum[i] + arr[i];
+        }
+
+        int res = 0, l = 0;
+        for (int r = k - 1; r < arr.length; r++) {
+            int sum = prefixSum[r + 1] - prefixSum[l];
+            if (sum / k >= threshold) {
+                res++;
+            }
+            l++;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numOfSubarrays(vector<int>& arr, int k, int threshold) {
+        vector<int> prefixSum(arr.size() + 1);
+        for (int i = 0; i < arr.size(); i++) {
+            prefixSum[i + 1] += prefixSum[i] + arr[i];
+        }
+
+        int res = 0, l = 0;
+        for (int r = k - 1; r < arr.size(); r++) {
+            int sum = prefixSum[r + 1] - prefixSum[l];
+            if (sum / k >= threshold) {
+                res++;
+            }
+            l++;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @param {number} k
+     * @param {number} threshold
+     * @return {number}
+     */
+    numOfSubarrays(arr, k, threshold) {
+        const prefixSum = new Int32Array(arr.length + 1);
+        for (let i = 0; i < arr.length; i++) {
+            prefixSum[i + 1] += prefixSum[i] + arr[i];
+        }
+
+        let res = 0, l = 0;
+        for (let r = k - 1; r < arr.length; r++) {
+            const sum = prefixSum[r + 1] - prefixSum[l];
+            if (sum / k >= threshold) {
+                res++;
+            }
+            l++;
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the size of the array $arr$ and $k$ is the size of the sub-array.
+
+---
+
+## 3. Sliding Window - I
+
+::tabs-start
+
+```python
+class Solution:
+    def numOfSubarrays(self, arr: List[int], k: int, threshold: int) -> int:
+        res = 0
+        curSum = sum(arr[:k - 1])
+
+        for L in range(len(arr) - k + 1):
+            curSum += arr[L + k - 1]
+            if (curSum / k) >= threshold:
+                res += 1
+            curSum -= arr[L]
+        return res
+```
+
+```java
+public class Solution {
+    public int numOfSubarrays(int[] arr, int k, int threshold) {
+        int res = 0;
+        int curSum = 0;
+
+        for (int i = 0; i < k - 1; i++) {
+            curSum += arr[i];
+        }
+
+        for (int L = 0; L <= arr.length - k; L++) {
+            curSum += arr[L + k - 1];
+            if ((curSum / k) >= threshold) {
+                res++;
+            }
+            curSum -= arr[L];
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numOfSubarrays(vector<int>& arr, int k, int threshold) {
+        int res = 0, curSum = 0;
+
+        for (int i = 0; i < k - 1; i++) {
+            curSum += arr[i];
+        }
+
+        for (int L = 0; L <= arr.size() - k; L++) {
+            curSum += arr[L + k - 1];
+            if ((curSum / k) >= threshold) {
+                res++;
+            }
+            curSum -= arr[L];
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @param {number} k
+     * @param {number} threshold
+     * @return {number}
+     */
+    numOfSubarrays(arr, k, threshold) {
+        let res = 0;
+        let curSum = 0;
+
+        for (let i = 0; i < k - 1; i++) {
+            curSum += arr[i];
+        }
+
+        for (let L = 0; L <= arr.length - k; L++) {
+            curSum += arr[L + k - 1];
+            if ((curSum / k) >= threshold) {
+                res++;
+            }
+            curSum -= arr[L];
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+> Where $n$ is the size of the array $arr$ and $k$ is the size of the sub-array.
+
+---
+
+## 4. Sliding Window - II
+
+::tabs-start
+
+```python
+class Solution:
+    def numOfSubarrays(self, arr: List[int], k: int, threshold: int) -> int:
+        threshold *= k
+        res = curSum = 0
+        for R in range(len(arr)):
+            curSum += arr[R]
+            if R >= k - 1:
+                res += curSum >= threshold
+                curSum -= arr[R - k + 1]
+        return res
+```
+
+```java
+public class Solution {
+    public int numOfSubarrays(int[] arr, int k, int threshold) {
+        threshold *= k;
+        int res = 0, curSum = 0;
+
+        for (int R = 0; R < arr.length; R++) {
+            curSum += arr[R];
+            if (R >= k - 1) {
+                if (curSum >= threshold) {
+                    res++;
+                }
+                curSum -= arr[R - k + 1];
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numOfSubarrays(vector<int>& arr, int k, int threshold) {
+        threshold *= k;
+        int res = 0, curSum = 0;
+
+        for (int R = 0; R < arr.size(); R++) {
+            curSum += arr[R];
+            if (R >= k - 1) {
+                if (curSum >= threshold) {
+                    res++;
+                }
+                curSum -= arr[R - k + 1];
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @param {number} k
+     * @param {number} threshold
+     * @return {number}
+     */
+    numOfSubarrays(arr, k, threshold) {
+        threshold *= k;
+        let res = 0, curSum = 0;
+
+        for (let R = 0; R < arr.length; R++) {
+            curSum += arr[R];
+            if (R >= k - 1) {
+                if (curSum >= threshold) {
+                    res++;
+                }
+                curSum -= arr[R - k + 1];
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+> Where $n$ is the size of the array $arr$ and $k$ is the size of the sub-array.
\ No newline at end of file
diff --git a/articles/number-of-sub-arrays-with-odd-sum.md b/articles/number-of-sub-arrays-with-odd-sum.md
new file mode 100644
index 000000000..e13063014
--- /dev/null
+++ b/articles/number-of-sub-arrays-with-odd-sum.md
@@ -0,0 +1,521 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def numOfSubarrays(self, arr: List[int]) -> int:
+        n, res = len(arr), 0
+        mod = int(1e9 + 7)
+
+        for i in range(n):
+            curSum = 0
+            for j in range(i, n):
+                curSum += arr[j]
+                if curSum % 2:
+                    res = (res + 1) % mod
+
+        return res
+```
+
+```java
+public class Solution {
+    public int numOfSubarrays(int[] arr) {
+        int n = arr.length, res = 0;
+        int mod = (int)1e9 + 7;
+
+        for (int i = 0; i < n; i++) {
+            int curSum = 0;
+            for (int j = i; j < n; j++) {
+                curSum += arr[j];
+                if (curSum % 2 != 0) {
+                    res = (res + 1) % mod;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numOfSubarrays(vector<int>& arr) {
+        int n = arr.size(), res = 0;
+        int mod = 1e9 + 7;
+
+        for (int i = 0; i < n; i++) {
+            int curSum = 0;
+            for (int j = i; j < n; j++) {
+                curSum += arr[j];
+                if (curSum % 2 != 0) {
+                    res = (res + 1) % mod;
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @return {number}
+     */
+    numOfSubarrays(arr) {
+        const n = arr.length;
+        let res = 0;
+        const mod = 1e9 + 7;
+
+        for (let i = 0; i < n; i++) {
+            let curSum = 0;
+            for (let j = i; j < n; j++) {
+                curSum += arr[j];
+                if (curSum % 2 !== 0) {
+                    res = (res + 1) % mod;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def numOfSubarrays(self, arr: List[int]) -> int:
+        mod = 10**9 + 7
+        n = len(arr)
+        memo = {}
+
+        def dp(i: int, parity: int) -> int:
+            if i == n:
+                return 0
+
+            if (i, parity) in memo:
+                return memo[(i, parity)]
+
+            new_parity = (parity + arr[i]) % 2
+            res = new_parity + dp(i + 1, new_parity)
+            memo[(i, parity)] = res % mod
+            return memo[(i, parity)]
+
+        ans = 0
+        for i in range(n):
+            ans = (ans + dp(i, 0)) % mod
+
+        return ans
+```
+
+```java
+public class Solution {
+    int[][] memo;
+    int[] arr;
+    int mod = (int)1e9 + 7;
+
+    public int numOfSubarrays(int[] arr) {
+        int n = arr.length;
+        this.arr = arr;
+        memo = new int[n][2];
+        for (int i = 0; i < n; i++) {
+            memo[i][0] = -1;
+            memo[i][1] = -1;
+        }
+
+        int res = 0;
+        for (int i = 0; i < n; i++) {
+            res = (res + dp(i, 0)) % mod;
+        }
+        return res;
+    }
+
+    private int dp(int i, int parity) {
+        if (i == arr.length) return 0;
+        if (memo[i][parity] != -1) return memo[i][parity];
+
+        int newParity = (parity + arr[i]) % 2;
+        int res = newParity + dp(i + 1, newParity);
+        return memo[i][parity] = res % mod;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int mod = 1e9 + 7;
+    vector<vector<int>> memo;
+    vector<int> arr;
+
+    int numOfSubarrays(vector<int>& arr) {
+        this->arr = arr;
+        int n = arr.size();
+        memo.assign(n, vector<int>(2, -1));
+
+        int res = 0;
+        for (int i = 0; i < n; i++) {
+            res = (res + dp(i, 0)) % mod;
+        }
+        return res;
+    }
+
+    int dp(int i, int parity) {
+        if (i == arr.size()) return 0;
+        if (memo[i][parity] != -1) return memo[i][parity];
+
+        int newParity = (parity + arr[i]) % 2;
+        int res = newParity + dp(i + 1, newParity);
+        return memo[i][parity] = res % mod;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @return {number}
+     */
+    numOfSubarrays(arr) {
+        const mod = 1e9 + 7;
+        const n = arr.length;
+        const memo = Array.from({ length: n }, () => Array(2).fill(-1));
+
+        const dp = (i, parity) => {
+            if (i === n) return 0;
+            if (memo[i][parity] !== -1) return memo[i][parity];
+
+            const newParity = (parity + arr[i]) % 2;
+            const res = newParity + dp(i + 1, newParity);
+            return memo[i][parity] = res % mod;
+        };
+
+        let res = 0;
+        for (let i = 0; i < n; i++) {
+            res = (res + dp(i, 0)) % mod;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def numOfSubarrays(self, arr: List[int]) -> int:
+        n = len(arr)
+        mod = 10**9 + 7
+        dp = [[0] * 2 for _ in range(n + 1)]
+
+        for i in range(n - 1, -1, -1):
+            for parity in range(2):
+                new_parity = (parity + arr[i]) % 2
+                dp[i][parity] = (new_parity + dp[i + 1][new_parity]) % mod
+
+        res = 0
+        for i in range(n):
+            res = (res + dp[i][0]) % mod
+        return res
+```
+
+```java
+public class Solution {
+    public int numOfSubarrays(int[] arr) {
+        int n = arr.length;
+        int mod = (int)1e9 + 7;
+        int[][] dp = new int[n + 1][2];
+
+        for (int i = n - 1; i >= 0; i--) {
+            for (int parity = 0; parity <= 1; parity++) {
+                int newParity = (parity + arr[i]) % 2;
+                dp[i][parity] = (newParity + dp[i + 1][newParity]) % mod;
+            }
+        }
+
+        int res = 0;
+        for (int i = 0; i < n; i++) {
+            res = (res + dp[i][0]) % mod;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numOfSubarrays(vector<int>& arr) {
+        int n = arr.size(), mod = 1e9 + 7;
+        vector<vector<int>> dp(n + 1, vector<int>(2, 0));
+
+        for (int i = n - 1; i >= 0; i--) {
+            for (int parity = 0; parity <= 1; parity++) {
+                int newParity = (parity + arr[i]) % 2;
+                dp[i][parity] = (newParity + dp[i + 1][newParity]) % mod;
+            }
+        }
+
+        int res = 0;
+        for (int i = 0; i < n; i++) {
+            res = (res + dp[i][0]) % mod;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @return {number}
+     */
+    numOfSubarrays(arr) {
+        const n = arr.length;
+        const mod = 1e9 + 7;
+        const dp = Array.from({ length: n + 1 }, () => [0, 0]);
+
+        for (let i = n - 1; i >= 0; i--) {
+            for (let parity = 0; parity <= 1; parity++) {
+                const newParity = (parity + arr[i]) % 2;
+                dp[i][parity] = (newParity + dp[i + 1][newParity]) % mod;
+            }
+        }
+
+        let res = 0;
+        for (let i = 0; i < n; i++) {
+            res = (res + dp[i][0]) % mod;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Prefix Sum - I
+
+::tabs-start
+
+```python
+class Solution:
+    def numOfSubarrays(self, arr: List[int]) -> int:
+        cur_sum = odd_cnt = even_cnt = res = 0
+        MOD = 10**9 + 7
+
+        for n in arr:
+            cur_sum += n
+            if cur_sum % 2:
+                res = (res + 1 + even_cnt) % MOD
+                odd_cnt += 1
+            else:
+                res = (res + odd_cnt) % MOD
+                even_cnt += 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int numOfSubarrays(int[] arr) {
+        int curSum = 0, oddCnt = 0, evenCnt = 0, res = 0;
+        int MOD = (int)1e9 + 7;
+
+        for (int n : arr) {
+            curSum += n;
+            if (curSum % 2 != 0) {
+                res = (res + 1 + evenCnt) % MOD;
+                oddCnt++;
+            } else {
+                res = (res + oddCnt) % MOD;
+                evenCnt++;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numOfSubarrays(vector<int>& arr) {
+        long long curSum = 0, oddCnt = 0, evenCnt = 0, res = 0;
+        const int MOD = 1e9 + 7;
+
+        for (int n : arr) {
+            curSum += n;
+            if (curSum % 2 != 0) {
+                res = (res + 1 + evenCnt) % MOD;
+                oddCnt++;
+            } else {
+                res = (res + oddCnt) % MOD;
+                evenCnt++;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @return {number}
+     */
+    numOfSubarrays(arr) {
+        let curSum = 0, oddCnt = 0, evenCnt = 0, res = 0;
+        const MOD = 1e9 + 7;
+
+        for (let n of arr) {
+            curSum += n;
+            if (curSum % 2 !== 0) {
+                res = (res + 1 + evenCnt) % MOD;
+                oddCnt++;
+            } else {
+                res = (res + oddCnt) % MOD;
+                evenCnt++;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 5. Prefix Sum - II
+
+::tabs-start
+
+```python
+class Solution:
+    def numOfSubarrays(self, arr: List[int]) -> int:
+        count = [1, 0]
+        prefix = res = 0
+        MOD = 10**9 + 7
+
+        for num in arr:
+            prefix = (prefix + num) % 2
+            res = (res + count[1 - prefix]) % MOD
+            count[prefix] += 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int numOfSubarrays(int[] arr) {
+        int[] count = {1, 0};
+        int prefix = 0, res = 0;
+        int MOD = (int)1e9 + 7;
+
+        for (int num : arr) {
+            prefix = (prefix + num) % 2;
+            res = (res + count[1 - prefix]) % MOD;
+            count[prefix]++;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numOfSubarrays(vector<int>& arr) {
+        int count[2] = {1, 0};
+        int prefix = 0, res = 0;
+        const int MOD = 1e9 + 7;
+
+        for (int num : arr) {
+            prefix = (prefix + num) % 2;
+            res = (res + count[1 - prefix]) % MOD;
+            count[prefix]++;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @return {number}
+     */
+    numOfSubarrays(arr) {
+        const count = [1, 0];
+        let prefix = 0, res = 0;
+        const MOD = 1e9 + 7;
+
+        for (const num of arr) {
+            prefix = (prefix + num) % 2;
+            res = (res + count[1 - prefix]) % MOD;
+            count[prefix]++;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/number-of-submatrices-that-sum-to-target.md b/articles/number-of-submatrices-that-sum-to-target.md
new file mode 100644
index 000000000..0fe84feca
--- /dev/null
+++ b/articles/number-of-submatrices-that-sum-to-target.md
@@ -0,0 +1,549 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def numSubmatrixSumTarget(self, matrix: List[List[int]], target: int) -> int:
+        ROWS, COLS = len(matrix), len(matrix[0])
+        res = 0
+
+        for r1 in range(ROWS):
+            for r2 in range(r1, ROWS):
+                for c1 in range(COLS):
+                    for c2 in range(c1, COLS):
+                        subSum = 0
+                        for r in range(r1, r2 + 1):
+                            for c in range(c1, c2 + 1):
+                                subSum += matrix[r][c]
+
+                        if subSum == target:
+                            res += 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int numSubmatrixSumTarget(int[][] matrix, int target) {
+        int ROWS = matrix.length, COLS = matrix[0].length;
+        int res = 0;
+
+        for (int r1 = 0; r1 < ROWS; r1++) {
+            for (int r2 = r1; r2 < ROWS; r2++) {
+                for (int c1 = 0; c1 < COLS; c1++) {
+                    for (int c2 = c1; c2 < COLS; c2++) {
+                        int subSum = 0;
+                        for (int r = r1; r <= r2; r++) {
+                            for (int c = c1; c <= c2; c++) {
+                                subSum += matrix[r][c];
+                            }
+                        }
+                        if (subSum == target) {
+                            res++;
+                        }
+                    }
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numSubmatrixSumTarget(vector<vector<int>>& matrix, int target) {
+        int ROWS = matrix.size(), COLS = matrix[0].size();
+        int res = 0;
+
+        for (int r1 = 0; r1 < ROWS; r1++) {
+            for (int r2 = r1; r2 < ROWS; r2++) {
+                for (int c1 = 0; c1 < COLS; c1++) {
+                    for (int c2 = c1; c2 < COLS; c2++) {
+                        int subSum = 0;
+                        for (int r = r1; r <= r2; r++) {
+                            for (int c = c1; c <= c2; c++) {
+                                subSum += matrix[r][c];
+                            }
+                        }
+                        if (subSum == target) {
+                            res++;
+                        }
+                    }
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} matrix
+     * @param {number} target
+     * @return {number}
+     */
+    numSubmatrixSumTarget(matrix, target) {
+        const ROWS = matrix.length, COLS = matrix[0].length;
+        let res = 0;
+
+        for (let r1 = 0; r1 < ROWS; r1++) {
+            for (let r2 = r1; r2 < ROWS; r2++) {
+                for (let c1 = 0; c1 < COLS; c1++) {
+                    for (let c2 = c1; c2 < COLS; c2++) {
+                        let subSum = 0;
+                        for (let r = r1; r <= r2; r++) {
+                            for (let c = c1; c <= c2; c++) {
+                                subSum += matrix[r][c];
+                            }
+                        }
+                        if (subSum === target) {
+                            res++;
+                        }
+                    }
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m ^ 3 * n ^ 3)$
+* Space complexity: $O(1)$ extra space.
+
+> Where $m$ is the number of rows and $n$ is the number of columns of the given matrix.
+
+---
+
+## 2. Two Dimensional Prefix Sum
+
+::tabs-start
+
+```python
+class Solution:
+    def numSubmatrixSumTarget(self, matrix: List[List[int]], target: int) -> int:
+        ROWS, COLS = len(matrix), len(matrix[0])
+        sub_sum = [[0] * COLS for _ in range(ROWS)]
+
+        for r in range(ROWS):
+            for c in range(COLS):
+                top = sub_sum[r - 1][c] if r > 0 else 0
+                left = sub_sum[r][c - 1] if c > 0 else 0
+                top_left = sub_sum[r - 1][c - 1] if min(r, c) > 0 else 0
+                sub_sum[r][c] = matrix[r][c] + top + left - top_left
+
+        res = 0
+        for r1 in range(ROWS):
+            for r2 in range(r1, ROWS):
+                for c1 in range(COLS):
+                    for c2 in range(c1, COLS):
+                        top = sub_sum[r1 - 1][c2] if r1 > 0 else 0
+                        left = sub_sum[r2][c1 - 1] if c1 > 0 else 0
+                        top_left = sub_sum[r1 - 1][c1 - 1] if min(r1, c1) > 0 else 0
+                        cur_sum = sub_sum[r2][c2] - top - left + top_left
+                        if cur_sum == target:
+                            res += 1
+        return res
+```
+
+```java
+public class Solution {
+    public int numSubmatrixSumTarget(int[][] matrix, int target) {
+        int ROWS = matrix.length, COLS = matrix[0].length;
+        int[][] subSum = new int[ROWS][COLS];
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                int top = (r > 0) ? subSum[r - 1][c] : 0;
+                int left = (c > 0) ? subSum[r][c - 1] : 0;
+                int topLeft = (Math.min(r, c) > 0) ? subSum[r - 1][c - 1] : 0;
+                subSum[r][c] = matrix[r][c] + top + left - topLeft;
+            }
+        }
+
+        int res = 0;
+        for (int r1 = 0; r1 < ROWS; r1++) {
+            for (int r2 = r1; r2 < ROWS; r2++) {
+                for (int c1 = 0; c1 < COLS; c1++) {
+                    for (int c2 = c1; c2 < COLS; c2++) {
+                        int top = (r1 > 0) ? subSum[r1 - 1][c2] : 0;
+                        int left = (c1 > 0) ? subSum[r2][c1 - 1] : 0;
+                        int topLeft = (Math.min(r1, c1) > 0) ? subSum[r1 - 1][c1 - 1] : 0;
+                        int curSum = subSum[r2][c2] - top - left + topLeft;
+                        if (curSum == target) {
+                            res++;
+                        }
+                    }
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numSubmatrixSumTarget(vector<vector<int>>& matrix, int target) {
+        int ROWS = matrix.size(), COLS = matrix[0].size();
+        vector<vector<int>> subSum(ROWS, vector<int>(COLS, 0));
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                int top = (r > 0) ? subSum[r - 1][c] : 0;
+                int left = (c > 0) ? subSum[r][c - 1] : 0;
+                int topLeft = (min(r, c) > 0) ? subSum[r - 1][c - 1] : 0;
+                subSum[r][c] = matrix[r][c] + top + left - topLeft;
+            }
+        }
+
+        int res = 0;
+        for (int r1 = 0; r1 < ROWS; r1++) {
+            for (int r2 = r1; r2 < ROWS; r2++) {
+                for (int c1 = 0; c1 < COLS; c1++) {
+                    for (int c2 = c1; c2 < COLS; c2++) {
+                        int top = (r1 > 0) ? subSum[r1 - 1][c2] : 0;
+                        int left = (c1 > 0) ? subSum[r2][c1 - 1] : 0;
+                        int topLeft = (min(r1, c1) > 0) ? subSum[r1 - 1][c1 - 1] : 0;
+                        int curSum = subSum[r2][c2] - top - left + topLeft;
+                        if (curSum == target) {
+                            res++;
+                        }
+                    }
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} matrix
+     * @param {number} target
+     * @return {number}
+     */
+    numSubmatrixSumTarget(matrix, target) {
+        const ROWS = matrix.length, COLS = matrix[0].length;
+        const subSum = Array.from({ length: ROWS }, () => Array(COLS).fill(0));
+
+        for (let r = 0; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                let top = r > 0 ? subSum[r - 1][c] : 0;
+                let left = c > 0 ? subSum[r][c - 1] : 0;
+                let topLeft = Math.min(r, c) > 0 ? subSum[r - 1][c - 1] : 0;
+                subSum[r][c] = matrix[r][c] + top + left - topLeft;
+            }
+        }
+
+        let res = 0;
+        for (let r1 = 0; r1 < ROWS; r1++) {
+            for (let r2 = r1; r2 < ROWS; r2++) {
+                for (let c1 = 0; c1 < COLS; c1++) {
+                    for (let c2 = c1; c2 < COLS; c2++) {
+                        let top = r1 > 0 ? subSum[r1 - 1][c2] : 0;
+                        let left = c1 > 0 ? subSum[r2][c1 - 1] : 0;
+                        let topLeft = Math.min(r1, c1) > 0 ? subSum[r1 - 1][c1 - 1] : 0;
+                        let curSum = subSum[r2][c2] - top - left + topLeft;
+                        if (curSum === target) {
+                            res++;
+                        }
+                    }
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m ^ 2 * n ^ 2)$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns of the given matrix.
+
+---
+
+## 3. Horizontal 1D Prefix Sum
+
+::tabs-start
+
+```python
+class Solution:
+    def numSubmatrixSumTarget(self, matrix: List[List[int]], target: int) -> int:
+        ROWS, COLS = len(matrix), len(matrix[0])
+        sub_sum = [[0] * COLS for _ in range(ROWS)]
+
+        for r in range(ROWS):
+            for c in range(COLS):
+                top = sub_sum[r - 1][c] if r > 0 else 0
+                left = sub_sum[r][c - 1] if c > 0 else 0
+                top_left = sub_sum[r - 1][c - 1] if min(r, c) > 0 else 0
+                sub_sum[r][c] = matrix[r][c] + top + left - top_left
+
+        res = 0
+        for r1 in range(ROWS):
+            for r2 in range(r1, ROWS):
+                count = defaultdict(int)
+                count[0] = 1
+                for c in range(COLS):
+                    cur_sum = sub_sum[r2][c] - (sub_sum[r1 - 1][c] if r1 > 0 else 0)
+                    res += count[cur_sum - target]
+                    count[cur_sum] += 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int numSubmatrixSumTarget(int[][] matrix, int target) {
+        int ROWS = matrix.length, COLS = matrix[0].length;
+        int[][] subSum = new int[ROWS][COLS];
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                int top = (r > 0) ? subSum[r - 1][c] : 0;
+                int left = (c > 0) ? subSum[r][c - 1] : 0;
+                int topLeft = (Math.min(r, c) > 0) ? subSum[r - 1][c - 1] : 0;
+                subSum[r][c] = matrix[r][c] + top + left - topLeft;
+            }
+        }
+
+        int res = 0;
+        for (int r1 = 0; r1 < ROWS; r1++) {
+            for (int r2 = r1; r2 < ROWS; r2++) {
+                Map<Integer, Integer> count = new HashMap<>();
+                count.put(0, 1);
+                for (int c = 0; c < COLS; c++) {
+                    int curSum = subSum[r2][c] - (r1 > 0 ? subSum[r1 - 1][c] : 0);
+                    res += count.getOrDefault(curSum - target, 0);
+                    count.put(curSum, count.getOrDefault(curSum, 0) + 1);
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numSubmatrixSumTarget(vector<vector<int>>& matrix, int target) {
+        int ROWS = matrix.size(), COLS = matrix[0].size();
+        vector<vector<int>> subSum(ROWS, vector<int>(COLS, 0));
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                int top = (r > 0) ? subSum[r - 1][c] : 0;
+                int left = (c > 0) ? subSum[r][c - 1] : 0;
+                int topLeft = (min(r, c) > 0) ? subSum[r - 1][c - 1] : 0;
+                subSum[r][c] = matrix[r][c] + top + left - topLeft;
+            }
+        }
+
+        int res = 0;
+        for (int r1 = 0; r1 < ROWS; r1++) {
+            for (int r2 = r1; r2 < ROWS; r2++) {
+                unordered_map<int, int> count;
+                count[0] = 1;
+                for (int c = 0; c < COLS; c++) {
+                    int curSum = subSum[r2][c] - (r1 > 0 ? subSum[r1 - 1][c] : 0);
+                    res += count[curSum - target];
+                    count[curSum]++;
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} matrix
+     * @param {number} target
+     * @return {number}
+     */
+    numSubmatrixSumTarget(matrix, target) {
+        let ROWS = matrix.length, COLS = matrix[0].length;
+        let subSum = Array.from({ length: ROWS }, () => Array(COLS).fill(0));
+
+        for (let r = 0; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                let top = r > 0 ? subSum[r - 1][c] : 0;
+                let left = c > 0 ? subSum[r][c - 1] : 0;
+                let topLeft = Math.min(r, c) > 0 ? subSum[r - 1][c - 1] : 0;
+                subSum[r][c] = matrix[r][c] + top + left - topLeft;
+            }
+        }
+
+        let res = 0;
+        for (let r1 = 0; r1 < ROWS; r1++) {
+            for (let r2 = r1; r2 < ROWS; r2++) {
+                let count = new Map();
+                count.set(0, 1);
+                for (let c = 0; c < COLS; c++) {
+                    let curSum = subSum[r2][c] - (r1 > 0 ? subSum[r1 - 1][c] : 0);
+                    res += count.get(curSum - target) || 0;
+                    count.set(curSum, (count.get(curSum) || 0) + 1);
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m ^ 2 * n)$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns of the given matrix.
+
+---
+
+## 4. Vertical 1D Prefix Sum
+
+::tabs-start
+
+```python
+class Solution:
+    def numSubmatrixSumTarget(self, matrix: List[List[int]], target: int) -> int:
+        ROWS, COLS = len(matrix), len(matrix[0])
+        res = 0
+
+        for c1 in range(COLS):
+            row_prefix = [0] * ROWS
+            for c2 in range(c1, COLS):
+                for r in range(ROWS):
+                    row_prefix[r] += matrix[r][c2]
+
+                count = defaultdict(int)
+                count[0] = 1
+                cur_sum = 0
+                for r in range(ROWS):
+                    cur_sum += row_prefix[r]
+                    res += count[cur_sum - target]
+                    count[cur_sum] += 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int numSubmatrixSumTarget(int[][] matrix, int target) {
+        int ROWS = matrix.length, COLS = matrix[0].length, res = 0;
+
+        for (int c1 = 0; c1 < COLS; c1++) {
+            int[] rowPrefix = new int[ROWS];
+            for (int c2 = c1; c2 < COLS; c2++) {
+                for (int r = 0; r < ROWS; r++) {
+                    rowPrefix[r] += matrix[r][c2];
+                }
+
+                Map<Integer, Integer> count = new HashMap<>();
+                count.put(0, 1);
+                int curSum = 0;
+
+                for (int r = 0; r < ROWS; r++) {
+                    curSum += rowPrefix[r];
+                    res += count.getOrDefault(curSum - target, 0);
+                    count.put(curSum, count.getOrDefault(curSum, 0) + 1);
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numSubmatrixSumTarget(vector<vector<int>>& matrix, int target) {
+        int ROWS = matrix.size(), COLS = matrix[0].size(), res = 0;
+
+        for (int c1 = 0; c1 < COLS; c1++) {
+            vector<int> rowPrefix(ROWS, 0);
+            for (int c2 = c1; c2 < COLS; c2++) {
+                for (int r = 0; r < ROWS; r++) {
+                    rowPrefix[r] += matrix[r][c2];
+                }
+
+                unordered_map<int, int> count;
+                count[0] = 1;
+                int curSum = 0;
+                for (int r = 0; r < ROWS; r++) {
+                    curSum += rowPrefix[r];
+                    res += count[curSum - target];
+                    count[curSum]++;
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} matrix
+     * @param {number} target
+     * @return {number}
+     */
+    numSubmatrixSumTarget(matrix, target) {
+        let ROWS = matrix.length, COLS = matrix[0].length, res = 0;
+
+        for (let c1 = 0; c1 < COLS; c1++) {
+            let rowPrefix = new Array(ROWS).fill(0);
+            for (let c2 = c1; c2 < COLS; c2++) {
+                for (let r = 0; r < ROWS; r++) {
+                    rowPrefix[r] += matrix[r][c2];
+                }
+
+                let count = new Map();
+                count.set(0, 1);
+                let curSum = 0;
+
+                for (let r = 0; r < ROWS; r++) {
+                    curSum += rowPrefix[r];
+                    res += count.get(curSum - target) || 0;
+                    count.set(curSum, (count.get(curSum) || 0) + 1);
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n ^ 2)$
+* Space complexity: $O(m)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns of the given matrix.
\ No newline at end of file
diff --git a/articles/number-of-subsequences-that-satisfy-the-given-sum-condition.md b/articles/number-of-subsequences-that-satisfy-the-given-sum-condition.md
new file mode 100644
index 000000000..cc81b5ad0
--- /dev/null
+++ b/articles/number-of-subsequences-that-satisfy-the-given-sum-condition.md
@@ -0,0 +1,514 @@
+## 1. Brute Force (Recursion)
+
+::tabs-start
+
+```python
+class Solution:
+    def numSubseq(self, nums: List[int], target: int) -> int:
+        MOD = 1000000007
+
+        def dfs(maxi, mini, i):
+            if i == len(nums):
+                if mini != float("inf") and (maxi + mini) <= target:
+                    return 1
+                return 0
+
+            skip = dfs(maxi, mini, i + 1)
+            include = dfs(max(maxi, nums[i]), min(mini, nums[i]), i + 1)
+            return (skip + include) % MOD
+
+        return dfs(float("-inf"), float("inf"), 0)
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1000000007;
+
+    public int numSubseq(int[] nums, int target) {
+        return dfs(nums, Integer.MIN_VALUE, Integer.MAX_VALUE, 0, target);
+    }
+
+    private int dfs(int[] nums, int maxi, int mini, int i, int target) {
+        if (i == nums.length) {
+            if (mini != Integer.MAX_VALUE && (maxi + mini) <= target) {
+                return 1;
+            }
+            return 0;
+        }
+
+        int skip = dfs(nums, maxi, mini, i + 1, target);
+        int include = dfs(nums, Math.max(maxi, nums[i]), Math.min(mini, nums[i]), i + 1, target);
+        return (skip + include) % MOD;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    const int MOD = 1e9 + 7;
+
+    int numSubseq(vector<int>& nums, int target) {
+        return dfs(nums, INT_MIN, INT_MAX, 0, target);
+    }
+
+private:
+    int dfs(vector<int>& nums, int maxi, int mini, int i, int target) {
+        if (i == nums.size()) {
+            if (mini != INT_MAX && (maxi + mini) <= target) {
+                return 1;
+            }
+            return 0;
+        }
+
+        int skip = dfs(nums, maxi, mini, i + 1, target);
+        int include = dfs(nums, max(maxi, nums[i]), min(mini, nums[i]), i + 1, target);
+        return (skip + include) % MOD;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} target
+     * @return {number}
+     */
+    numSubseq(nums, target) {
+        const MOD = 1000000007;
+
+        const dfs = (maxi, mini, i) => {
+            if (i === nums.length) {
+                if (mini !== Infinity && (maxi + mini) <= target) {
+                    return 1;
+                }
+                return 0;
+            }
+
+            const skip = dfs(maxi, mini, i + 1);
+            const include = dfs(Math.max(maxi, nums[i]), Math.min(mini, nums[i]), i + 1);
+            return (skip + include) % MOD;
+        };
+
+        return dfs(-Infinity, Infinity, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Binary Search
+
+::tabs-start
+
+```python
+class Solution:
+    def numSubseq(self, nums: List[int], target: int) -> int:
+        nums.sort()
+        MOD = 1000000007
+        res = 0
+        
+        for i in range(len(nums)):
+            if nums[i] * 2 > target:
+                break
+            
+            l, r = i, len(nums) - 1
+            while l <= r:
+                mid = (l + r) // 2
+                if nums[i] + nums[mid] <= target:
+                    l = mid + 1
+                else:
+                    r = mid - 1
+            
+            count = pow(2, r - i, MOD)
+            res = (res + count) % MOD
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int numSubseq(int[] nums, int target) {
+        Arrays.sort(nums);
+        int MOD = 1000000007;
+        int res = 0;
+
+        for (int i = 0; i < nums.length; i++) {
+            if (nums[i] * 2 > target) break;
+
+            int l = i, r = nums.length - 1;
+            while (l <= r) {
+                int mid = l + (r - l) / 2;
+                if (nums[i] + nums[mid] <= target) {
+                    l = mid + 1;
+                } else {
+                    r = mid - 1;
+                }
+            }
+
+            long count = pow(2, r - i, MOD);
+            res = (int) ((res + count) % MOD);
+        }
+        return res;
+    }
+
+    private long pow(int base, int exp, int mod) {
+        long result = 1;
+        long b = base;
+        while (exp > 0) {
+            if ((exp & 1) == 1) result = (result * b) % mod;
+            b = (b * b) % mod;
+            exp >>= 1;
+        }
+        return result;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numSubseq(vector<int>& nums, int target) {
+        sort(nums.begin(), nums.end());
+        int MOD = 1000000007;
+        int res = 0;
+
+        for (int i = 0; i < nums.size(); i++) {
+            if (nums[i] * 2 > target) break;
+
+            int l = i, r = nums.size() - 1;
+            while (l <= r) {
+                int mid = l + (r - l) / 2;
+                if (nums[i] + nums[mid] <= target) {
+                    l = mid + 1;
+                } else {
+                    r = mid - 1;
+                }
+            }
+
+            long long count = powMod(2, r - i, MOD);
+            res = (res + count) % MOD;
+        }
+        return res;
+    }
+
+private:
+    long long powMod(int base, int exp, int mod) {
+        long long result = 1, b = base;
+        while (exp > 0) {
+            if (exp & 1) result = (result * b) % mod;
+            b = (b * b) % mod;
+            exp >>= 1;
+        }
+        return result;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} target
+     * @return {number}
+     */
+    numSubseq(nums, target) {
+        nums.sort((a, b) => a - b);
+        const MOD = BigInt(1000000007);
+        let res = 0n;
+
+        const powerMod = (base, exp, mod) => {
+            let result = 1n, b = BigInt(base);
+            while (exp > 0) {
+                if (exp & 1) result = (result * b) % mod;
+                b = (b * b) % mod;
+                exp >>= 1;
+            }
+            return result;
+        };
+
+        for (let i = 0; i < nums.length; i++) {
+            if (nums[i] * 2 > target) break;
+
+            let l = i, r = nums.length - 1;
+            while (l <= r) {
+                const mid = Math.floor((l + r) / 2);
+                if (nums[i] + nums[mid] <= target) {
+                    l = mid + 1;
+                } else {
+                    r = mid - 1;
+                }
+            }
+
+            const count = powerMod(2, r - i, MOD);
+            res = (res + count) % MOD;
+        }
+
+        return Number(res);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 3. Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def numSubseq(self, nums: List[int], target: int) -> int:
+        nums.sort()
+        res = 0
+        mod = 10**9 + 7
+        
+        r = len(nums) - 1
+        for i, left in enumerate(nums):
+            while i <= r and left + nums[r] > target:
+                r -= 1
+            if i <= r:
+                res += pow(2, r - i, mod)
+                res %= mod
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int numSubseq(int[] nums, int target) {
+        Arrays.sort(nums);
+        int res = 0, mod = 1000000007;
+        int r = nums.length - 1;
+        
+        for (int i = 0; i < nums.length; i++) {
+            while (i <= r && nums[i] + nums[r] > target) {
+                r--;
+            }
+            if (i <= r) {
+                res = (res + power(2, r - i, mod)) % mod;
+            }
+        }
+        return res;
+    }
+    
+    private int power(int base, int exp, int mod) {
+        long result = 1, b = base;
+        while (exp > 0) {
+            if ((exp & 1) == 1) result = (result * b) % mod;
+            b = (b * b) % mod;
+            exp >>= 1;
+        }
+        return (int) result;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numSubseq(vector<int>& nums, int target) {
+        sort(nums.begin(), nums.end());
+        int res = 0, mod = 1000000007;
+        int r = nums.size() - 1;
+        
+        for (int i = 0; i < nums.size(); i++) {
+            while (i <= r && nums[i] + nums[r] > target) {
+                r--;
+            }
+            if (i <= r) {
+                res = (res + power(2, r - i, mod)) % mod;
+            }
+        }
+        return res;
+    }
+    
+private:
+    long long power(int base, int exp, int mod) {
+        long long result = 1, b = base;
+        while (exp > 0) {
+            if (exp & 1) result = (result * b) % mod;
+            b = (b * b) % mod;
+            exp >>= 1;
+        }
+        return result;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} target
+     * @return {number}
+     */
+    numSubseq(nums, target) {
+        nums.sort((a, b) => a - b);
+        const mod = BigInt(1000000007);
+        let res = 0n;
+
+        const power = (base, exp, mod) => {
+            let result = 1n, b = BigInt(base);
+            while (exp > 0) {
+                if (exp & 1) result = (result * b) % mod;
+                b = (b * b) % mod;
+                exp >>= 1;
+            }
+            return result;
+        };
+
+        for (let i = 0, r = nums.length - 1; i < nums.length; i++) {
+            while (nums[i] + nums[r] > target && i <= r) {
+                r--;
+            }
+            if (i <= r) {
+                res = (res + power(2, r - i, mod)) % mod;
+            }
+        }
+
+        return Number(res);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 4. Two Pointers (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def numSubseq(self, nums: List[int], target: int) -> int:
+        nums.sort()
+        MOD = 1000000007
+        res = 0
+        l, r = 0, len(nums) - 1
+        power = [1] * len(nums)
+        
+        for i in range(1, len(nums)):
+            power[i] = (power[i - 1] * 2) % MOD
+        
+        while l <= r:
+            if nums[l] + nums[r] <= target:
+                res = (res + power[r - l]) % MOD
+                l += 1
+            else:
+                r -= 1
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int numSubseq(int[] nums, int target) {
+        Arrays.sort(nums);
+        int MOD = 1000000007;
+        int res = 0, l = 0, r = nums.length - 1;
+        int[] power = new int[nums.length];
+        power[0] = 1;
+
+        for (int i = 1; i < nums.length; i++) {
+            power[i] = (power[i - 1] * 2) % MOD;
+        }
+
+        while (l <= r) {
+            if (nums[l] + nums[r] <= target) {
+                res = (res + power[r - l]) % MOD;
+                l++;
+            } else {
+                r--;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numSubseq(vector<int>& nums, int target) {
+        sort(nums.begin(), nums.end());
+        int MOD = 1000000007;
+        int res = 0, l = 0, r = nums.size() - 1;
+        vector<int> power(nums.size(), 1);
+
+        for (int i = 1; i < nums.size(); i++) {
+            power[i] = (power[i - 1] * 2) % MOD;
+        }
+
+        while (l <= r) {
+            if (nums[l] + nums[r] <= target) {
+                res = (res + power[r - l]) % MOD;
+                l++;
+            } else {
+                r--;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} target
+     * @return {number}
+     */
+    numSubseq(nums, target) {
+        nums.sort((a, b) => a - b);
+        const MOD = 1000000007;
+        let res = 0, l = 0, r = nums.length - 1;
+        const power = Array(nums.length).fill(1);
+
+        for (let i = 1; i < nums.length; i++) {
+            power[i] = (power[i - 1] * 2) % MOD;
+        }
+
+        while (l <= r) {
+            if (nums[l] + nums[r] <= target) {
+                res = (res + power[r - l]) % MOD;
+                l++;
+            } else {
+                r--;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/number-of-ways-to-divide-a-long-corridor.md b/articles/number-of-ways-to-divide-a-long-corridor.md
new file mode 100644
index 000000000..cda191a27
--- /dev/null
+++ b/articles/number-of-ways-to-divide-a-long-corridor.md
@@ -0,0 +1,608 @@
+## 1. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def numberOfWays(self, corridor: str) -> int:
+        mod = 10**9 + 7
+        cache = [[-1] * 3 for i in range(len(corridor))]  # (i, seats) -> count
+
+        def dfs(i, seats):
+            if i == len(corridor):
+                return 1 if seats == 2 else 0
+            if cache[i][seats] != -1:
+                return cache[i][seats]
+
+            res = 0
+            if seats == 2:
+                if corridor[i] == "S":
+                    res = dfs(i + 1, 1)
+                else:
+                    res = (dfs(i + 1, 0) + dfs(i + 1, 2)) % mod
+            else:
+                if corridor[i] == "S":
+                    res = dfs(i + 1, seats + 1)
+                else:
+                    res = dfs(i + 1, seats)
+
+            cache[i][seats] = res
+            return res
+
+        return dfs(0, 0)
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1_000_000_007;
+    private int[][] dp;
+
+    public int numberOfWays(String corridor) {
+        int n = corridor.length();
+        dp = new int[n][3];
+        for (int i = 0; i < n; i++) {
+            Arrays.fill(dp[i], -1);
+        }
+        return dfs(0, 0, corridor);
+    }
+
+    private int dfs(int i, int seats, String corridor) {
+        if (i == corridor.length()) {
+            return seats == 2 ? 1 : 0;
+        }
+        if (dp[i][seats] != -1) {
+            return dp[i][seats];
+        }
+
+        int res = 0;
+        if (seats == 2) {
+            if (corridor.charAt(i) == 'S') {
+                res = dfs(i + 1, 1, corridor);
+            } else {
+                res = (dfs(i + 1, 0, corridor) + dfs(i + 1, 2, corridor)) % MOD;
+            }
+        } else {
+            if (corridor.charAt(i) == 'S') {
+                res = dfs(i + 1, seats + 1, corridor);
+            } else {
+                res = dfs(i + 1, seats, corridor);
+            }
+        }
+        
+        return dp[i][seats] = res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    static constexpr int MOD = 1'000'000'007;
+    vector<vector<int>> dp;
+
+    int numberOfWays(string corridor) {
+        int n = corridor.size();
+        dp.assign(n, vector<int>(3, -1));
+        return dfs(0, 0, corridor);
+    }
+
+    int dfs(int i, int seats, string& corridor) {
+        if (i == corridor.size()) {
+            return seats == 2 ? 1 : 0;
+        }
+        if (dp[i][seats] != -1) {
+            return dp[i][seats];
+        }
+
+        int res = 0;
+        if (seats == 2) {
+            if (corridor[i] == 'S') {
+                res = dfs(i + 1, 1, corridor);
+            } else {
+                res = (dfs(i + 1, 0, corridor) + dfs(i + 1, 2, corridor)) % MOD;
+            }
+        } else {
+            if (corridor[i] == 'S') {
+                res = dfs(i + 1, seats + 1, corridor);
+            } else {
+                res = dfs(i + 1, seats, corridor);
+            }
+        }
+
+        return dp[i][seats] = res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} corridor
+     * @return {number}
+     */
+    numberOfWays(corridor) {
+        const MOD = 1_000_000_007;
+        const n = corridor.length;
+        const dp = Array.from({ length: n }, () => Array(3).fill(-1));
+
+        const dfs = (i, seats) => {
+            if (i === n) return seats === 2 ? 1 : 0;
+            if (dp[i][seats] !== -1) return dp[i][seats];
+
+            let res = 0;
+            if (seats === 2) {
+                if (corridor[i] === 'S') {
+                    res = dfs(i + 1, 1);
+                } else {
+                    res = (dfs(i + 1, 0) + dfs(i + 1, 2)) % MOD;
+                }
+            } else {
+                if (corridor[i] === 'S') {
+                    res = dfs(i + 1, seats + 1);
+                } else {
+                    res = dfs(i + 1, seats);
+                }
+            }
+
+            return (dp[i][seats] = res);
+        };
+
+        return dfs(0, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def numberOfWays(self, corridor: str) -> int:
+        MOD = 1000000007
+        n = len(corridor)
+        dp = [[0] * 3 for _ in range(n + 1)]
+        dp[n][2] = 1  
+
+        for i in range(n - 1, -1, -1):
+            for seats in range(3):
+                if seats == 2:
+                    if corridor[i] == 'S':
+                        dp[i][seats] = dp[i + 1][1]
+                    else:
+                        dp[i][seats] = (dp[i + 1][0] + dp[i + 1][2]) % MOD
+                else:
+                    if corridor[i] == 'S':
+                        dp[i][seats] = dp[i + 1][seats + 1]
+                    else:
+                        dp[i][seats] = dp[i + 1][seats]
+
+        return dp[0][0]
+```
+
+```java
+public class Solution {
+    public int numberOfWays(String corridor) {
+        int MOD = 1000000007;
+        int n = corridor.length();
+        int[][] dp = new int[n + 1][3];
+        dp[n][2] = 1;
+
+        for (int i = n - 1; i >= 0; i--) {
+            for (int seats = 0; seats < 3; seats++) {
+                if (seats == 2) {
+                    if (corridor.charAt(i) == 'S') {
+                        dp[i][seats] = dp[i + 1][1];
+                    } else {
+                        dp[i][seats] = (dp[i + 1][0] + dp[i + 1][2]) % MOD;
+                    }
+                } else {
+                    if (corridor.charAt(i) == 'S') {
+                        dp[i][seats] = dp[i + 1][seats + 1];
+                    } else {
+                        dp[i][seats] = dp[i + 1][seats];
+                    }
+                }
+            }
+        }
+        return dp[0][0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numberOfWays(string corridor) {
+        int MOD = 1000000007;
+        int n = corridor.size();
+        vector<vector<int>> dp(n + 1, vector<int>(3, 0));
+        dp[n][2] = 1;
+
+        for (int i = n - 1; i >= 0; i--) {
+            for (int seats = 0; seats < 3; seats++) {
+                if (seats == 2) {
+                    if (corridor[i] == 'S') {
+                        dp[i][seats] = dp[i + 1][1];
+                    } else {
+                        dp[i][seats] = (dp[i + 1][0] + dp[i + 1][2]) % MOD;
+                    }
+                } else {
+                    if (corridor[i] == 'S') {
+                        dp[i][seats] = dp[i + 1][seats + 1];
+                    } else {
+                        dp[i][seats] = dp[i + 1][seats];
+                    }
+                }
+            }
+        }
+        return dp[0][0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} corridor
+     * @return {number}
+     */
+    numberOfWays(corridor) {
+        const MOD = 1000000007;
+        const n = corridor.length;
+        let dp = Array.from({ length: n + 1 }, () => Array(3).fill(0));
+        dp[n][2] = 1;
+
+        for (let i = n - 1; i >= 0; i--) {
+            for (let seats = 0; seats < 3; seats++) {
+                if (seats === 2) {
+                    if (corridor[i] === 'S') {
+                        dp[i][seats] = dp[i + 1][1];
+                    } else {
+                        dp[i][seats] = (dp[i + 1][0] + dp[i + 1][2]) % MOD;
+                    }
+                } else {
+                    if (corridor[i] === 'S') {
+                        dp[i][seats] = dp[i + 1][seats + 1];
+                    } else {
+                        dp[i][seats] = dp[i + 1][seats];
+                    }
+                }
+            }
+        }
+        return dp[0][0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def numberOfWays(self, corridor: str) -> int:
+        MOD = 1000000007
+        dp = [0, 0, 1]
+
+        for i in reversed(corridor):
+            new_dp = [0] * 3
+            for seats in range(3):
+                if seats == 2:
+                    new_dp[seats] = dp[1] if i == 'S' else (dp[0] + dp[2]) % MOD
+                else:
+                    new_dp[seats] = dp[seats + 1] if i == 'S' else dp[seats]
+            dp = new_dp
+
+        return dp[0]
+```
+
+```java
+public class Solution {
+    public int numberOfWays(String corridor) {
+        int MOD = 1000000007;
+        int[] dp = {0, 0, 1};
+
+        for (int i = corridor.length() - 1; i >= 0; i--) {
+            int[] new_dp = new int[3];
+            for (int seats = 0; seats < 3; seats++) {
+                if (seats == 2) {
+                    new_dp[seats] = corridor.charAt(i) == 'S' ? dp[1] : (dp[0] + dp[2]) % MOD;
+                } else {
+                    new_dp[seats] = corridor.charAt(i) == 'S' ? dp[seats + 1] : dp[seats];
+                }
+            }
+            dp = new_dp;
+        }
+        return dp[0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numberOfWays(string corridor) {
+        const int MOD = 1000000007;
+        vector<int> dp = {0, 0, 1};
+
+        for (int i = corridor.length() - 1; i >= 0; i--) {
+            vector<int> new_dp(3, 0);
+            for (int seats = 0; seats < 3; seats++) {
+                if (seats == 2) {
+                    new_dp[seats] = (corridor[i] == 'S') ? dp[1] : (dp[0] + dp[2]) % MOD;
+                } else {
+                    new_dp[seats] = (corridor[i] == 'S') ? dp[seats + 1] : dp[seats];
+                }
+            }
+            dp = new_dp;
+        }
+        return dp[0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} corridor
+     * @return {number}
+     */
+    numberOfWays(corridor) {
+        const MOD = 1000000007;
+        let dp = [0, 0, 1];
+
+        for (let i = corridor.length - 1; i >= 0; i--) {
+            let new_dp = [0, 0, 0];
+            for (let seats = 0; seats < 3; seats++) {
+                if (seats === 2) {
+                    new_dp[seats] = corridor[i] === 'S' ? dp[1] : (dp[0] + dp[2]) % MOD;
+                } else {
+                    new_dp[seats] = corridor[i] === 'S' ? dp[seats + 1] : dp[seats];
+                }
+            }
+            dp = new_dp;
+        }
+        return dp[0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 4. Combinatorics
+
+::tabs-start
+
+```python
+class Solution:
+    def numberOfWays(self, corridor: str) -> int:
+        mod = 10**9 + 7
+        seats = [i for i, c in enumerate(corridor) if c == "S"]
+
+        length = len(seats)
+        if length < 2 or length % 2 == 1:
+            return 0
+
+        res = 1
+        for i in range(1, length - 1, 2):
+            res = (res * (seats[i + 1] - seats[i])) % mod
+
+        return res
+```
+
+```java
+public class Solution {
+    public int numberOfWays(String corridor) {
+        int mod = 1_000_000_007;
+        List<Integer> seats = new ArrayList<>();
+
+        for (int i = 0; i < corridor.length(); i++) {
+            if (corridor.charAt(i) == 'S') {
+                seats.add(i);
+            }
+        }
+
+        int length = seats.size();
+        if (length < 2 || length % 2 == 1) {
+            return 0;
+        }
+
+        long res = 1;
+        for (int i = 1; i < length - 1; i += 2) {
+            res = (res * (seats.get(i + 1) - seats.get(i))) % mod;
+        }
+
+        return (int) res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numberOfWays(string corridor) {
+        int mod = 1'000'000'007;
+        vector<int> seats;
+        
+        for (int i = 0; i < corridor.size(); i++) {
+            if (corridor[i] == 'S') {
+                seats.push_back(i);
+            }
+        }
+
+        int length = seats.size();
+        if (length < 2 || length % 2 == 1) {
+            return 0;
+        }
+
+        long long res = 1;
+        for (int i = 1; i < length - 1; i += 2) {
+            res = (res * (seats[i + 1] - seats[i])) % mod;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} corridor
+     * @return {number}
+     */
+    numberOfWays(corridor) {
+        const mod = 1_000_000_007;
+        const seats = [];
+
+        for (let i = 0; i < corridor.length; i++) {
+            if (corridor[i] === 'S') {
+                seats.push(i);
+            }
+        }
+
+        const length = seats.length;
+        if (length < 2 || length % 2 === 1) {
+            return 0;
+        }
+
+        let res = 1;
+        for (let i = 1; i < length - 1; i += 2) {
+            res = (res * (seats[i + 1] - seats[i])) % mod;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 5. Combinatorics (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def numberOfWays(self, corridor: str) -> int:
+        mod = 1_000_000_007
+        count = 0
+        res = 1
+        prev = -1
+
+        for i, c in enumerate(corridor):
+            if c == 'S':
+                count += 1
+                if count > 2 and count % 2 == 1:
+                    res = (res * (i - prev)) % mod
+                prev = i
+
+        return res if count >= 2 and count % 2 == 0 else 0
+```
+
+```java
+public class Solution {
+    public int numberOfWays(String corridor) {
+        int mod = 1_000_000_007;
+        int count = 0, res = 1, prev = -1;
+
+        for (int i = 0; i < corridor.length(); i++) {
+            if (corridor.charAt(i) == 'S') {
+                count++;
+                if (count > 2 && count % 2 == 1) {
+                    res = (int)((res * (long)(i - prev)) % mod);
+                }
+                prev = i;
+            }
+        }
+
+        return (count >= 2 && count % 2 == 0) ? res : 0;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numberOfWays(string corridor) {
+        int mod = 1'000'000'007, count = 0, res = 1, prev = -1;
+
+        for (int i = 0; i < corridor.size(); i++) {
+            if (corridor[i] == 'S') {
+                count++;
+                if (count > 2 && count % 2 == 1) {
+                    res = (1LL * res * (i - prev)) % mod;
+                }
+                prev = i;
+            }
+        }
+
+        return (count >= 2 && count % 2 == 0) ? res : 0;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} corridor
+     * @return {number}
+     */
+    numberOfWays(corridor) {
+        const mod = 1_000_000_007;
+        let count = 0, res = 1, prev = -1;
+
+        for (let i = 0; i < corridor.length; i++) {
+            if (corridor[i] === 'S') {
+                count++;
+                if (count > 2 && count % 2 === 1) {
+                    res = (res * (i - prev)) % mod;
+                }
+                prev = i;
+            }
+        }
+
+        return count >= 2 && count % 2 === 0 ? res : 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/number-of-ways-to-form-a-target-string-given-a-dictionary.md b/articles/number-of-ways-to-form-a-target-string-given-a-dictionary.md
new file mode 100644
index 000000000..878690a7c
--- /dev/null
+++ b/articles/number-of-ways-to-form-a-target-string-given-a-dictionary.md
@@ -0,0 +1,568 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def numWays(self, words: List[str], target: str) -> int:
+        mod = 10**9 + 7
+        n, m = len(target), len(words[0])
+
+        def dfs(i, k):
+            if i == n:
+                return 1
+            if k == m:
+                return 0
+            
+            res = dfs(i, k + 1)
+            for w in words:
+                if w[k] != target[i]:
+                    continue
+                res = (res + dfs(i + 1, k + 1)) % mod
+            return res
+        
+        return dfs(0, 0)
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1_000_000_007;
+
+    public int numWays(String[] words, String target) {
+        return dfs(words, target, 0, 0);
+    }
+
+    private int dfs(String[] words, String target, int i, int k) {
+        if (i == target.length()) return 1;
+        if (k == words[0].length()) return 0;
+
+        int res = dfs(words, target, i, k + 1);
+        for (String w : words) {
+            if (w.charAt(k) != target.charAt(i)) {
+                continue;
+            }
+            res = (int) (res + 0L + dfs(words, target, i + 1, k + 1)) % MOD;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    static const int MOD = 1e9 + 7;
+
+    int dfs(vector<string>& words, string target, int i, int k) {
+        if (i == target.length()) return 1;
+        if (k == words[0].length()) return 0;
+
+        int res = dfs(words, target, i, k + 1);
+        for (string& w : words) {
+            if (w[k] != target[i]) {
+                continue;
+            }
+            res = (int) (res + 0LL + dfs(words, target, i + 1, k + 1)) % MOD;
+        }
+
+        return res;
+    }
+
+public:
+    int numWays(vector<string>& words, string target) {
+        return dfs(words, target, 0, 0);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @param {string} target
+     * @return {number}
+     */
+    numWays(words, target) {
+        const n = target.length;
+        const m = words[0].length;
+        const MOD = 1e9 + 7;
+
+        const dfs = (i, k) => {
+            if (i === n) return 1;
+            if (k === m) return 0;
+
+            let res = dfs(i, k + 1);
+            for (const w of words) {
+                if (w[k] != target[i]) {
+                    continue;
+                }
+                res = (res + dfs(i + 1, k + 1)) % MOD;
+            }
+
+            return res;
+        };
+
+        return dfs(0, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(N ^ m)$
+* Space complexity: $O(m)$
+
+> Where $N$ is the number of words, $m$ is the length of each word, and $n$ is the length of the $target$ string.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def numWays(self, words: List[str], target: str) -> int:
+        mod = 10**9 + 7
+        cnt = defaultdict(int)  # (index, char) --> count among all words
+        for w in words:
+            for i, c in enumerate(w):
+                cnt[(i, c)] += 1
+
+        dp = {}
+
+        def dfs(i, k):
+            if i == len(target):
+                return 1
+            if k == len(words[0]):
+                return 0
+            if (i, k) in dp:
+                return dp[(i, k)]
+
+            c = target[i]
+            dp[(i, k)] = dfs(i, k + 1)  # skip k position
+            dp[(i, k)] += cnt[(k, c)] * dfs(i + 1, k + 1)
+            dp[(i, k)] %= mod
+            return dp[(i, k)]
+
+        return dfs(0, 0)
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1_000_000_007;
+    private int[][] dp;
+    private int[][] cnt;
+
+    public int numWays(String[] words, String target) {
+        int n = target.length(), m = words[0].length();
+        cnt = new int[m][26];
+
+        for (String word : words) {
+            for (int i = 0; i < word.length(); i++) {
+                cnt[i][word.charAt(i) - 'a']++;
+            }
+        }
+
+        dp = new int[n + 1][m + 1];
+        for (int[] row : dp) {
+            Arrays.fill(row, -1);
+        }
+
+        return dfs(0, 0, target, n, m);
+    }
+
+    private int dfs(int i, int k, String target, int n, int m) {
+        if (i == n) return 1;
+        if (k == m) return 0;
+        if (dp[i][k] != -1) return dp[i][k];
+
+        int c = target.charAt(i) - 'a';
+        dp[i][k] = dfs(i, k + 1, target, n, m);  // Skip k position
+        dp[i][k] = (int) ((dp[i][k] + (long) cnt[k][c] * dfs(i + 1, k + 1, target, n, m)) % MOD);
+        return dp[i][k];
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    static const int MOD = 1e9 + 7;
+    vector<vector<int>> dp;
+    vector<vector<int>> cnt;
+
+public:
+    int numWays(vector<string>& words, string target) {
+        int n = target.size(), m = words[0].size();
+        cnt = vector<vector<int>>(m, vector<int>(26, 0));
+
+        for (const string& word : words) {
+            for (int i = 0; i < word.size(); i++) {
+                cnt[i][word[i] - 'a']++;
+            }
+        }
+
+        dp = vector<vector<int>>(n + 1, vector<int>(m + 1, -1));
+        return dfs(0, 0, target, n, m);
+    }
+
+private:
+    int dfs(int i, int k, const string& target, int n, int m) {
+        if (i == n) return 1;
+        if (k == m) return 0;
+        if (dp[i][k] != -1) return dp[i][k];
+
+        int c = target[i] - 'a';
+        dp[i][k] = dfs(i, k + 1, target, n, m);  // Skip k position
+        dp[i][k] = (dp[i][k] + (long long) cnt[k][c] * dfs(i + 1, k + 1, target, n, m)) % MOD;
+        return dp[i][k];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @param {string} target
+     * @return {number}
+     */
+    numWays(words, target) {
+        const MOD = 1e9 + 7;
+        const n = target.length, m = words[0].length;
+        const cnt = Array.from({ length: m }, () => Array(26).fill(0));
+
+        for (const word of words) {
+            for (let i = 0; i < word.length; i++) {
+                cnt[i][word.charCodeAt(i) - 97]++;
+            }
+        }
+
+        const dp = Array.from({ length: n + 1 }, () => Array(m + 1).fill(-1));
+
+        const dfs = (i, k) => {
+            if (i === n) return 1;
+            if (k === m) return 0;
+            if (dp[i][k] !== -1) return dp[i][k];
+
+            const c = target.charCodeAt(i) - 97;
+            dp[i][k] = dfs(i, k + 1);  // Skip k position
+            dp[i][k] = (dp[i][k] + cnt[k][c] * dfs(i + 1, k + 1)) % MOD;
+            return dp[i][k];
+        };
+
+        return dfs(0, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * (n + N))$
+* Space complexity: $O(n * m)$
+
+> Where $N$ is the number of words, $m$ is the length of each word, and $n$ is the length of the $target$ string.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def numWays(self, words: List[str], target: str) -> int:
+        MOD = 10**9 + 7
+        n, m = len(target), len(words[0])
+
+        cnt = [[0] * 26 for _ in range(m)]
+        for word in words:
+            for i, c in enumerate(word):
+                cnt[i][ord(c) - ord('a')] += 1
+
+        dp = [[0] * (m + 1) for _ in range(n + 1)]
+        dp[n][m] = 1
+
+        for i in range(n, -1, -1):
+            for k in range(m - 1, -1, -1):
+                dp[i][k] = dp[i][k + 1]
+                if i < n:
+                    c = ord(target[i]) - ord('a')
+                    dp[i][k] = (dp[i][k] + cnt[k][c] * dp[i + 1][k + 1]) % MOD
+
+        return dp[0][0]
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1_000_000_007;
+
+    public int numWays(String[] words, String target) {
+        int n = target.length(), m = words[0].length();
+
+        int[][] cnt = new int[m][26];
+        for (String word : words) {
+            for (int i = 0; i < word.length(); i++) {
+                cnt[i][word.charAt(i) - 'a']++;
+            }
+        }
+
+        int[][] dp = new int[n + 1][m + 1];
+        dp[n][m] = 1;
+
+        for (int i = n; i >= 0; i--) {
+            for (int k = m - 1; k >= 0; k--) {
+                dp[i][k] = dp[i][k + 1];
+                if (i < n) {
+                    int c = target.charAt(i) - 'a';
+                    dp[i][k] = (int) ((dp[i][k] + (long) cnt[k][c] * dp[i + 1][k + 1]) % MOD);
+                }
+            }
+        }
+
+        return dp[0][0];
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    static const int MOD = 1e9 + 7;
+
+public:
+    int numWays(vector<string>& words, string target) {
+        int n = target.size(), m = words[0].size();
+
+        vector<vector<int>> cnt(m, vector<int>(26, 0));
+        for (const string& word : words) {
+            for (int i = 0; i < word.size(); i++) {
+                cnt[i][word[i] - 'a']++;
+            }
+        }
+
+        vector<vector<int>> dp(n + 1, vector<int>(m + 1, 0));
+        dp[n][m] = 1;
+
+        for (int i = n; i >= 0; i--) {
+            for (int k = m - 1; k >= 0; k--) {
+                dp[i][k] = dp[i][k + 1];
+                if (i < n) {
+                    int c = target[i] - 'a';
+                    dp[i][k] = (dp[i][k] + (long long) cnt[k][c] * dp[i + 1][k + 1]) % MOD;
+                }
+            }
+        }
+
+        return dp[0][0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @param {string} target
+     * @return {number}
+     */
+    numWays(words, target) {
+        const MOD = 1e9 + 7;
+        const n = target.length, m = words[0].length;
+
+        const cnt = Array.from({ length: m }, () => Array(26).fill(0));
+        for (const word of words) {
+            for (let i = 0; i < word.length; i++) {
+                cnt[i][word.charCodeAt(i) - 'a'.charCodeAt(0)]++;
+            }
+        }
+
+        const dp = Array.from({ length: n + 1 }, () => Array(m + 1).fill(0));
+        dp[n][m] = 1;
+
+        for (let i = n; i >= 0; i--) {
+            for (let k = m - 1; k >= 0; k--) {
+                dp[i][k] = dp[i][k + 1];
+                if (i < n) {
+                    const c = target.charCodeAt(i) - 'a'.charCodeAt(0);
+                    dp[i][k] = (dp[i][k] + cnt[k][c] * dp[i + 1][k + 1]) % MOD;
+                }
+            }
+        }
+
+        return dp[0][0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * (n + N))$
+* Space complexity: $O(n * m)$
+
+> Where $N$ is the number of words, $m$ is the length of each word, and $n$ is the length of the $target$ string.
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def numWays(self, words: List[str], target: str) -> int:
+        MOD = 10**9 + 7
+        n, m = len(target), len(words[0])
+
+        cnt = [[0] * 26 for _ in range(m)]
+        for word in words:
+            for i, c in enumerate(word):
+                cnt[i][ord(c) - ord('a')] += 1
+
+        dp = [0] * (m + 1)
+        dp[m] = 1
+
+        for i in range(n, -1, -1):
+            nxt = 1 if i == n - 1 else 0
+            for k in range(m - 1, -1, -1):
+                cur = dp[k]
+                dp[k] = dp[k + 1]
+                if i < n:
+                    c = ord(target[i]) - ord('a')
+                    dp[k] = (dp[k] + cnt[k][c] * nxt) % MOD
+                nxt = cur
+            dp[m] = 0
+        
+        return dp[0]
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1_000_000_007;
+
+    public int numWays(String[] words, String target) {
+        int n = target.length(), m = words[0].length();
+
+        int[][] cnt = new int[m][26];
+        for (String word : words) {
+            for (int i = 0; i < word.length(); i++) {
+                cnt[i][word.charAt(i) - 'a']++;
+            }
+        }
+
+        int[] dp = new int[m + 1];
+        dp[m] = 1;
+
+        for (int i = n; i >= 0; i--) {
+            int nxt = i == n - 1 ? 1 : 0;
+            for (int k = m - 1; k >= 0; k--) {
+                int cur = dp[k];
+                dp[k] = dp[k + 1];
+                if (i < n) {
+                    int c = target.charAt(i) - 'a';
+                    dp[k] = (int) ((dp[k] + (long) cnt[k][c] * nxt) % MOD);
+                }
+                nxt = cur;
+            }
+            dp[m] = 0;
+        }
+
+        return dp[0];
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    static const int MOD = 1e9 + 7;
+
+public:
+    int numWays(vector<string>& words, string target) {
+        int n = target.size(), m = words[0].size();
+
+        vector<vector<int>> cnt(m, vector<int>(26, 0));
+        for (const string& word : words) {
+            for (int i = 0; i < word.size(); i++) {
+                cnt[i][word[i] - 'a']++;
+            }
+        }
+
+        vector<int> dp(m + 1);
+        dp[m] = 1;
+
+        for (int i = n; i >= 0; i--) {
+            int nxt = i == n - 1 ? 1 : 0;
+            for (int k = m - 1; k >= 0; k--) {
+                int cur = dp[k];
+                dp[k] = dp[k + 1];
+                if (i < n) {
+                    int c = target[i] - 'a';
+                    dp[k] = (dp[k] + (long long) cnt[k][c] * nxt) % MOD;
+                }
+                nxt = cur;
+            }
+            dp[m] = 0;
+        }
+
+        return dp[0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @param {string} target
+     * @return {number}
+     */
+    numWays(words, target) {
+        const MOD = 1e9 + 7;
+        const n = target.length, m = words[0].length;
+
+        const cnt = Array.from({ length: m }, () => Array(26).fill(0));
+        for (const word of words) {
+            for (let i = 0; i < word.length; i++) {
+                cnt[i][word.charCodeAt(i) - 'a'.charCodeAt(0)]++;
+            }
+        }
+
+        const dp = new Array(m + 1).fill(0);
+        dp[m] = 1;
+
+        for (let i = n; i >= 0; i--) {
+            let nxt = i === n - 1 ? 1 : 0;
+            for (let k = m - 1; k >= 0; k--) {
+                const cur = dp[k];
+                dp[k] = dp[k + 1];
+                if (i < n) {
+                    const c = target.charCodeAt(i) - 'a'.charCodeAt(0);
+                    dp[k] = (dp[k] + cnt[k][c] * nxt) % MOD;
+                }
+                nxt = cur;
+            }
+            dp[m] = 0;
+        }
+
+        return dp[0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * (n + N))$
+* Space complexity: $O(m)$
+
+> Where $N$ is the number of words, $m$ is the length of each word, and $n$ is the length of the $target$ string.
\ No newline at end of file
diff --git a/articles/number-of-ways-to-rearrange-sticks-with-k-sticks-visible.md b/articles/number-of-ways-to-rearrange-sticks-with-k-sticks-visible.md
new file mode 100644
index 000000000..d192c77b6
--- /dev/null
+++ b/articles/number-of-ways-to-rearrange-sticks-with-k-sticks-visible.md
@@ -0,0 +1,375 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def rearrangeSticks(self, n: int, k: int) -> int:
+        MOD = 10**9 + 7
+
+        def dfs(N, K):
+            if N == K:
+                return 1
+            if N == 0 or K == 0:
+                return 0
+            return (dfs(N - 1, K - 1) + (N - 1) * dfs(N - 1, K)) % MOD
+
+        return dfs(n, k)
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1_000_000_007;
+
+    public int rearrangeSticks(int n, int k) {
+        return dfs(n, k);
+    }
+
+    private int dfs(int N, int K) {
+        if (N == K) return 1;
+        if (N == 0 || K == 0) return 0;
+        return (int) ((dfs(N - 1, K - 1) + (long) (N - 1) * dfs(N - 1, K)) % MOD);
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    static const int MOD = 1e9 + 7;
+
+    int dfs(int N, int K) {
+        if (N == K) return 1;
+        if (N == 0 || K == 0) return 0;
+        return (dfs(N - 1, K - 1) + (long long)(N - 1) * dfs(N - 1, K) % MOD) % MOD;
+    }
+
+public:
+    int rearrangeSticks(int n, int k) {
+        return dfs(n, k);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} k
+     * @return {number}
+     */
+    rearrangeSticks(n, k) {
+        const MOD = 1e9 + 7;
+
+        const dfs = (N, K) => {
+            if (N === K) return 1;
+            if (N === 0 || K === 0) return 0;
+            return (dfs(N - 1, K - 1) + (N - 1) * dfs(N - 1, K)) % MOD;
+        };
+
+        return dfs(n, k);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def rearrangeSticks(self, n: int, k: int) -> int:
+        MOD = 10**9 + 7
+        dp = [[-1] * (k + 1) for _ in range(n + 1)]
+
+        def dfs(N, K):
+            if N == K:
+                return 1
+            if N == 0 or K == 0:
+                return 0
+            if dp[N][K] != -1:
+                return dp[N][K]
+            dp[N][K] = (dfs(N - 1, K - 1) + (N - 1) * dfs(N - 1, K)) % MOD
+            return dp[N][K]
+
+        return dfs(n, k)
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1_000_000_007;
+    private int[][] dp;
+
+    public int rearrangeSticks(int n, int k) {
+        dp = new int[n + 1][k + 1];
+        for (int[] row : dp) {
+            Arrays.fill(row, -1);
+        }
+        return dfs(n, k);
+    }
+
+    private int dfs(int N, int K) {
+        if (N == K) return 1;
+        if (N == 0 || K == 0) return 0;
+        if (dp[N][K] != -1) return dp[N][K];
+        dp[N][K] = (int) ((dfs(N - 1, K - 1) + (long) (N - 1) * dfs(N - 1, K)) % MOD);
+        return dp[N][K];
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    static const int MOD = 1e9 + 7;
+    vector<vector<int>> dp;
+
+    int dfs(int N, int K) {
+        if (N == K) return 1;
+        if (N == 0 || K == 0) return 0;
+        if (dp[N][K] != -1) return dp[N][K];
+        dp[N][K] = (dfs(N - 1, K - 1) + (long long)(N - 1) * dfs(N - 1, K) % MOD) % MOD;
+        return dp[N][K];
+    }
+
+public:
+    int rearrangeSticks(int n, int k) {
+        dp = vector<vector<int>>(n + 1, vector<int>(k + 1, -1));
+        return dfs(n, k);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} k
+     * @return {number}
+     */
+    rearrangeSticks(n, k) {
+        const MOD = 1e9 + 7;
+        const dp = Array.from({ length: n + 1 }, () => Array(k + 1).fill(-1));
+
+        const dfs = (N, K) => {
+            if (N === K) return 1;
+            if (N === 0 || K === 0) return 0;
+            if (dp[N][K] !== -1) return dp[N][K];
+            dp[N][K] = (dfs(N - 1, K - 1) + (N - 1) * dfs(N - 1, K)) % MOD;
+            return dp[N][K];
+        };
+
+        return dfs(n, k);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * k)$
+* Space complexity: $O(n * k)$
+
+> Where $n$ represents the total number of sticks, and $k$ denotes the number of sticks that must be visible from the left side.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def rearrangeSticks(self, n: int, k: int) -> int:
+        MOD = 10**9 + 7
+        dp = [[0] * (k + 1) for _ in range(n + 1)]
+        dp[1][1] = 1
+
+        for N in range(2, n + 1):
+            for K in range(1, k + 1):
+                dp[N][K] = (dp[N - 1][K - 1] + (N - 1) * dp[N - 1][K]) % MOD
+
+        return dp[n][k]
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1_000_000_007;
+
+    public int rearrangeSticks(int n, int k) {
+        int[][] dp = new int[n + 1][k + 1];
+        dp[1][1] = 1;
+
+        for (int N = 2; N <= n; N++) {
+            for (int K = 1; K <= k; K++) {
+                dp[N][K] = (int) ((dp[N - 1][K - 1] + (long) (N - 1) * dp[N - 1][K]) % MOD);
+            }
+        }
+
+        return dp[n][k];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int rearrangeSticks(int n, int k) {
+        const int MOD = 1e9 + 7;
+        vector<vector<int>> dp(n + 1, vector<int>(k + 1, 0));
+        dp[1][1] = 1;
+
+        for (int N = 2; N <= n; N++) {
+            for (int K = 1; K <= k; K++) {
+                dp[N][K] = (dp[N - 1][K - 1] + (N - 1) * 1LL * dp[N - 1][K]) % MOD;
+            }
+        }
+
+        return dp[n][k];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} k
+     * @return {number}
+     */
+    rearrangeSticks(n, k) {
+        const MOD = 1e9 + 7;
+        const dp = Array.from({ length: n + 1 }, () => Array(k + 1).fill(0));
+        dp[1][1] = 1;
+
+        for (let N = 2; N <= n; N++) {
+            for (let K = 1; K <= k; K++) {
+                dp[N][K] = (dp[N - 1][K - 1] + (N - 1) * dp[N - 1][K]) % MOD;
+            }
+        }
+
+        return dp[n][k];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * k)$
+* Space complexity: $O(n * k)$
+
+> Where $n$ represents the total number of sticks, and $k$ denotes the number of sticks that must be visible from the left side.
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def rearrangeSticks(self, n: int, k: int) -> int:
+        MOD = 10**9 + 7
+        dp = [0] * (k + 1)
+        dp[1] = 1
+
+        for N in range(2, n + 1):
+            prev = 0
+            for K in range(1, k + 1):
+                tmp = dp[K]
+                dp[K] = (prev + (N - 1) * dp[K]) % MOD
+                prev = tmp
+
+        return dp[k]
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1_000_000_007;
+
+    public int rearrangeSticks(int n, int k) {
+        int[] dp = new int[k + 1];
+        dp[1] = 1;
+
+        for (int N = 2; N <= n; N++) {
+            int prev = 0;
+            for (int K = 1; K <= k; K++) {
+                int tmp = dp[K];
+                dp[K] = (int) ((prev + (long) (N - 1) * dp[K]) % MOD);
+                prev = tmp;
+            }
+        }
+
+        return dp[k];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int rearrangeSticks(int n, int k) {
+        const int MOD = 1e9 + 7;
+        vector<int> dp(k + 1);
+        dp[1] = 1;
+
+        for (int N = 2; N <= n; N++) {
+            int prev = 0;
+            for (int K = 1; K <= k; K++) {
+                int tmp = dp[K];
+                dp[K] = (prev + (N - 1) * 1LL * dp[K]) % MOD;
+                prev = tmp;
+            }
+        }
+
+        return dp[k];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} k
+     * @return {number}
+     */
+    rearrangeSticks(n, k) {
+        const MOD = 1e9 + 7;
+        const dp = new Array(k + 1).fill(0);
+        dp[1] = 1;
+
+        for (let N = 2; N <= n; N++) {
+            let prev = 0;
+            for (let K = 1; K <= k; K++) {
+                const tmp = dp[K];
+                dp[K] = (prev + (N - 1) * dp[K]) % MOD;
+                prev = tmp;
+            }
+        }
+
+        return dp[k];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * k)$
+* Space complexity: $O(k)$
+
+> Where $n$ represents the total number of sticks, and $k$ denotes the number of sticks that must be visible from the left side.
\ No newline at end of file
diff --git a/articles/number-of-ways-to-split-array.md b/articles/number-of-ways-to-split-array.md
new file mode 100644
index 000000000..ca66c41c0
--- /dev/null
+++ b/articles/number-of-ways-to-split-array.md
@@ -0,0 +1,320 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def waysToSplitArray(self, nums: List[int]) -> int:
+        n = len(nums)
+        res = 0
+
+        for i in range(n - 1):
+            leftSum = 0
+            for j in range(i + 1):
+                leftSum += nums[j]
+
+            rightSum = 0
+            for j in range(i + 1, n):
+                rightSum += nums[j]
+
+            res += (1 if leftSum >= rightSum else 0)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int waysToSplitArray(int[] nums) {
+        int n = nums.length;
+        int res = 0;
+
+        for (int i = 0; i < n - 1; i++) {
+            long leftSum = 0;
+            for (int j = 0; j <= i; j++) {
+                leftSum += nums[j];
+            }
+
+            long rightSum = 0;
+            for (int j = i + 1; j < n; j++) {
+                rightSum += nums[j];
+            }
+
+            if (leftSum >= rightSum) {
+                res++;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int waysToSplitArray(vector<int>& nums) {
+        int n = nums.size();
+        int res = 0;
+
+        for (int i = 0; i < n - 1; i++) {
+            long long leftSum = 0;
+            for (int j = 0; j <= i; j++) {
+                leftSum += nums[j];
+            }
+
+            long long rightSum = 0;
+            for (int j = i + 1; j < n; j++) {
+                rightSum += nums[j];
+            }
+
+            if (leftSum >= rightSum) {
+                res++;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    waysToSplitArray(nums) {
+        let n = nums.length;
+        let res = 0;
+
+        for (let i = 0; i < n - 1; i++) {
+            let leftSum = 0;
+            for (let j = 0; j <= i; j++) {
+                leftSum += nums[j];
+            }
+
+            let rightSum = 0;
+            for (let j = i + 1; j < n; j++) {
+                rightSum += nums[j];
+            }
+
+            if (leftSum >= rightSum) {
+                res++;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Prefix Sum
+
+::tabs-start
+
+```python
+class Solution:
+    def waysToSplitArray(self, nums: List[int]) -> int:
+        n = len(nums)
+        prefix = [0] * (n + 1)
+
+        for i in range(n):
+            prefix[i + 1] = prefix[i] + nums[i]
+
+        res = 0
+        for i in range(1, n):
+            left = prefix[i]
+            right = prefix[n] - prefix[i]
+            if left >= right:
+                res += 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int waysToSplitArray(int[] nums) {
+        int n = nums.length;
+        long[] prefix = new long[n + 1];
+
+        for (int i = 0; i < n; i++) {
+            prefix[i + 1] = prefix[i] + nums[i];
+        }
+
+        int res = 0;
+        for (int i = 1; i < n; i++) {
+            long left = prefix[i];
+            long right = prefix[n] - prefix[i];
+            if (left >= right) {
+                res++;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int waysToSplitArray(vector<int>& nums) {
+        int n = nums.size();
+        vector<long long> prefix(n + 1, 0);
+
+        for (int i = 0; i < n; i++) {
+            prefix[i + 1] = prefix[i] + nums[i];
+        }
+
+        int res = 0;
+        for (int i = 1; i < n; i++) {
+            long long left = prefix[i];
+            long long right = prefix[n] - prefix[i];
+            if (left >= right) {
+                res++;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    waysToSplitArray(nums) {
+        const n = nums.length;
+        const prefix = Array(n + 1).fill(0);
+
+        for (let i = 0; i < n; i++) {
+            prefix[i + 1] = prefix[i] + nums[i];
+        }
+
+        let res = 0;
+        for (let i = 1; i < n; i++) {
+            const left = prefix[i];
+            const right = prefix[n] - prefix[i];
+            if (left >= right) {
+                res++;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Prefix Sum (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def waysToSplitArray(self, nums: List[int]) -> int:
+        right = sum(nums)
+        left = res = 0
+
+        for i in range(len(nums) - 1):
+            left += nums[i]
+            right -= nums[i]
+            res += 1 if left >= right else 0
+
+        return res
+```
+
+```java
+public class Solution {
+    public int waysToSplitArray(int[] nums) {
+        long right = 0, left = 0;
+        for (int num : nums) {
+            right += num;
+        }
+
+        int res = 0;
+        for (int i = 0; i < nums.length - 1; i++) {
+            left += nums[i];
+            right -= nums[i];
+            if (left >= right) {
+                res++;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int waysToSplitArray(vector<int>& nums) {
+        long long right = 0, left = 0;
+        for (int num : nums) {
+            right += num;
+        }
+
+        int res = 0;
+        for (int i = 0; i < nums.size() - 1; i++) {
+            left += nums[i];
+            right -= nums[i];
+            if (left >= right) {
+                res++;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    waysToSplitArray(nums) {
+        let right = nums.reduce((a, b) => a + b, 0);
+        let left = 0, res = 0;
+
+        for (let i = 0; i < nums.length - 1; i++) {
+            left += nums[i];
+            right -= nums[i];
+            if (left >= right) {
+                res++;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/number-of-ways-to-stay-in-the-same-place-after-some-steps.md b/articles/number-of-ways-to-stay-in-the-same-place-after-some-steps.md
new file mode 100644
index 000000000..2c9577d2a
--- /dev/null
+++ b/articles/number-of-ways-to-stay-in-the-same-place-after-some-steps.md
@@ -0,0 +1,503 @@
+## 1. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def numWays(self, steps: int, arrLen: int) -> int:
+        mod = 10**9 + 7
+        arrLen = min(arrLen, steps)
+        dp = {}
+
+        def dfs(i, steps):
+            if steps == 0:
+                return i == 0
+            if (i, steps) in dp:
+                return dp[(i, steps)]
+
+            res = dfs(i, steps - 1)
+            if i > 0:
+                res = (res + dfs(i - 1, steps - 1)) % mod
+            if i < arrLen - 1:
+                res = (res + dfs(i + 1, steps - 1)) % mod
+
+            dp[(i, steps)] = res
+            return res
+
+        return dfs(0, steps)
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1_000_000_007;
+    private int[][] dp;
+
+    public int numWays(int steps, int arrLen) {
+        int maxPos = Math.min(steps, arrLen);
+        dp = new int[maxPos + 1][steps + 1];
+        for (int i = 0; i <= maxPos; i++) {
+            for (int j = 0; j <= steps; j++) {
+                dp[i][j] = -1;
+            }
+        }
+        return dfs(0, steps, maxPos);
+    }
+
+    private int dfs(int i, int steps, int maxPos) {
+        if (steps == 0) {
+            return i == 0 ? 1 : 0;
+        }
+        if (dp[i][steps] != -1) {
+            return dp[i][steps];
+        }
+
+        int res = dfs(i, steps - 1, maxPos);
+        if (i > 0) {
+            res = (res + dfs(i - 1, steps - 1, maxPos)) % MOD;
+        }
+        if (i < maxPos - 1) {
+            res = (res + dfs(i + 1, steps - 1, maxPos)) % MOD;
+        }
+
+        dp[i][steps] = res;
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    static const int MOD = 1e9 + 7;
+    vector<vector<int>> dp;
+
+    int dfs(int i, int steps, int maxPos) {
+        if (steps == 0) {
+            return i == 0 ? 1 : 0;
+        }
+        if (dp[i][steps] != -1) {
+            return dp[i][steps];
+        }
+
+        int res = dfs(i, steps - 1, maxPos);
+        if (i > 0) {
+            res = (res + dfs(i - 1, steps - 1, maxPos)) % MOD;
+        }
+        if (i < maxPos - 1) {
+            res = (res + dfs(i + 1, steps - 1, maxPos)) % MOD;
+        }
+
+        dp[i][steps] = res;
+        return res;
+    }
+
+public:
+    int numWays(int steps, int arrLen) {
+        int maxPos = min(steps, arrLen);
+        dp.assign(maxPos + 1, vector<int>(steps + 1, -1));
+        return dfs(0, steps, maxPos);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} steps
+     * @param {number} arrLen
+     * @return {number}
+     */
+    numWays(steps, arrLen) {
+        const MOD = 1e9 + 7;
+        const maxPos = Math.min(steps, arrLen);
+        const dp = Array.from({ length: maxPos + 1 }, () => Array(steps + 1).fill(-1));
+
+        const dfs = (i, steps) => {
+            if (steps === 0) return i === 0 ? 1 : 0;
+            if (dp[i][steps] !== -1) return dp[i][steps];
+
+            let res = dfs(i, steps - 1);
+            if (i > 0) res = (res + dfs(i - 1, steps - 1)) % MOD;
+            if (i < maxPos - 1) res = (res + dfs(i + 1, steps - 1)) % MOD;
+
+            dp[i][steps] = res;
+            return res;
+        };
+
+        return dfs(0, steps);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * min(n, m))$
+* Space complexity: $O(n * min(n, m))$
+
+> Where $n$ is the number of steps and $m$ is the size of the array.
+
+---
+
+## 2. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def numWays(self, steps: int, arrLen: int) -> int:
+        mod = 10**9 + 7
+        arrLen = min(arrLen, steps)
+        dp = [[0] * (arrLen + 1) for _ in range(steps + 1)]
+        dp[0][0] = 1
+
+        for step in range(1, steps + 1):
+            for i in range(arrLen):
+                res = dp[step - 1][i]
+                if i > 0:
+                    res = (res + dp[step - 1][i - 1]) % mod
+                if i < arrLen - 1:
+                    res = (res + dp[step - 1][i + 1]) % mod
+                dp[step][i] = res
+
+        return dp[steps][0]
+```
+
+```java
+public class Solution {
+    public int numWays(int steps, int arrLen) {
+        final int MOD = 1_000_000_007;
+        arrLen = Math.min(arrLen, steps);
+        int[][] dp = new int[steps + 1][arrLen + 1];
+        dp[0][0] = 1;
+
+        for (int step = 1; step <= steps; step++) {
+            for (int i = 0; i < arrLen; i++) {
+                int res = dp[step - 1][i];
+                if (i > 0) {
+                    res = (res + dp[step - 1][i - 1]) % MOD;
+                }
+                if (i < arrLen - 1) {
+                    res = (res + dp[step - 1][i + 1]) % MOD;
+                }
+                dp[step][i] = res;
+            }
+        }
+
+        return dp[steps][0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numWays(int steps, int arrLen) {
+        const int MOD = 1e9 + 7;
+        arrLen = min(arrLen, steps);
+        vector<vector<int>> dp(steps + 1, vector<int>(arrLen + 1, 0));
+        dp[0][0] = 1;
+
+        for (int step = 1; step <= steps; step++) {
+            for (int i = 0; i < arrLen; i++) {
+                int res = dp[step - 1][i];
+                if (i > 0) {
+                    res = (res + dp[step - 1][i - 1]) % MOD;
+                }
+                if (i < arrLen - 1) {
+                    res = (res + dp[step - 1][i + 1]) % MOD;
+                }
+                dp[step][i] = res;
+            }
+        }
+
+        return dp[steps][0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} steps
+     * @param {number} arrLen
+     * @return {number}
+     */
+    numWays(steps, arrLen) {
+        const MOD = 1e9 + 7;
+        arrLen = Math.min(arrLen, steps);
+        const dp = Array.from({ length: steps + 1 }, () => Array(arrLen + 1).fill(0));
+        dp[0][0] = 1;
+
+        for (let step = 1; step <= steps; step++) {
+            for (let i = 0; i < arrLen; i++) {
+                let res = dp[step - 1][i];
+                if (i > 0) {
+                    res = (res + dp[step - 1][i - 1]) % MOD;
+                }
+                if (i < arrLen - 1) {
+                    res = (res + dp[step - 1][i + 1]) % MOD;
+                }
+                dp[step][i] = res;
+            }
+        }
+
+        return dp[steps][0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * min(n, m))$
+* Space complexity: $O(n * min(n, m))$
+
+> Where $n$ is the number of steps and $m$ is the size of the array.
+
+---
+
+## 3. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def numWays(self, steps: int, arrLen: int) -> int:
+        mod = 10**9 + 7
+        arrLen = min(steps, arrLen)
+        dp = [0] * arrLen
+        dp[0] = 1
+
+        for _ in range(steps):
+            next_dp = [0] * arrLen
+            for i in range(arrLen):
+                next_dp[i] = dp[i]
+                if i > 0:
+                    next_dp[i] = (next_dp[i] + dp[i - 1]) % mod
+                if i < arrLen - 1:
+                    next_dp[i] = (next_dp[i] + dp[i + 1]) % mod
+            dp = next_dp
+
+        return dp[0]
+```
+
+```java
+public class Solution {
+    public int numWays(int steps, int arrLen) {
+        final int MOD = 1_000_000_007;
+        arrLen = Math.min(steps, arrLen);
+        int[] dp = new int[arrLen];
+        dp[0] = 1;
+
+        for (int step = 0; step < steps; step++) {
+            int[] nextDp = new int[arrLen];
+            for (int i = 0; i < arrLen; i++) {
+                nextDp[i] = dp[i];
+                if (i > 0) {
+                    nextDp[i] = (nextDp[i] + dp[i - 1]) % MOD;
+                }
+                if (i < arrLen - 1) {
+                    nextDp[i] = (nextDp[i] + dp[i + 1]) % MOD;
+                }
+            }
+            dp = nextDp;
+        }
+
+        return dp[0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numWays(int steps, int arrLen) {
+        const int MOD = 1e9 + 7;
+        arrLen = min(steps, arrLen);
+        vector<int> dp(arrLen, 0);
+        dp[0] = 1;
+
+        for (int step = 0; step < steps; step++) {
+            vector<int> nextDp(arrLen, 0);
+            for (int i = 0; i < arrLen; i++) {
+                nextDp[i] = dp[i];
+                if (i > 0) {
+                    nextDp[i] = (nextDp[i] + dp[i - 1]) % MOD;
+                }
+                if (i < arrLen - 1) {
+                    nextDp[i] = (nextDp[i] + dp[i + 1]) % MOD;
+                }
+            }
+            dp = nextDp;
+        }
+
+        return dp[0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} steps
+     * @param {number} arrLen
+     * @return {number}
+     */
+    numWays(steps, arrLen) {
+        const MOD = 1e9 + 7;
+        arrLen = Math.min(steps, arrLen);
+        let dp = new Array(arrLen).fill(0);
+        dp[0] = 1;
+
+        for (let step = 0; step < steps; step++) {
+            const nextDp = new Array(arrLen).fill(0);
+            for (let i = 0; i < arrLen; i++) {
+                nextDp[i] = dp[i];
+                if (i > 0) {
+                    nextDp[i] = (nextDp[i] + dp[i - 1]) % MOD;
+                }
+                if (i < arrLen - 1) {
+                    nextDp[i] = (nextDp[i] + dp[i + 1]) % MOD;
+                }
+            }
+            dp = nextDp;
+        }
+
+        return dp[0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * min(n, m))$
+* Space complexity: $O(min(n, m))$
+
+> Where $n$ is the number of steps and $m$ is the size of the array.
+
+---
+
+## 4. Dynamic Programming (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def numWays(self, steps: int, arrLen: int) -> int:
+        mod = 10**9 + 7
+        arrLen = min(steps, arrLen)
+        dp = [0] * arrLen
+        dp[0] = 1
+
+        for _ in range(steps):
+            prev = 0
+            for i in range(arrLen):
+                cur = dp[i]
+                if i > 0:
+                    dp[i] = (dp[i] + prev) % mod
+                if i < arrLen - 1:
+                    dp[i] = (dp[i] + dp[i + 1]) % mod
+                prev = cur
+
+        return dp[0]
+```
+
+```java
+public class Solution {
+    public int numWays(int steps, int arrLen) {
+        final int MOD = 1_000_000_007;
+        arrLen = Math.min(steps, arrLen);
+        int[] dp = new int[arrLen];
+        dp[0] = 1;
+
+        for (int step = 0; step < steps; step++) {
+            int prev = 0;
+            for (int i = 0; i < arrLen; i++) {
+                int cur = dp[i];
+                if (i > 0) {
+                    dp[i] = (dp[i] + prev) % MOD;
+                }
+                if (i < arrLen - 1) {
+                    dp[i] = (dp[i] + dp[i + 1]) % MOD;
+                }
+                prev = cur;
+            }
+        }
+
+        return dp[0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numWays(int steps, int arrLen) {
+        const int MOD = 1e9 + 7;
+        arrLen = min(steps, arrLen);
+        vector<int> dp(arrLen, 0);
+        dp[0] = 1;
+
+        for (int step = 0; step < steps; step++) {
+            int prev = 0;
+            for (int i = 0; i < arrLen; i++) {
+                int cur = dp[i];
+                if (i > 0) {
+                    dp[i] = (dp[i] + prev) % MOD;
+                }
+                if (i < arrLen - 1) {
+                    dp[i] = (dp[i] + dp[i + 1]) % MOD;
+                }
+                prev = cur;
+            }
+        }
+
+        return dp[0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} steps
+     * @param {number} arrLen
+     * @return {number}
+     */
+    numWays(steps, arrLen) {
+        const MOD = 1e9 + 7;
+        arrLen = Math.min(steps, arrLen);
+        const dp = new Array(arrLen).fill(0);
+        dp[0] = 1;
+
+        for (let step = 0; step < steps; step++) {
+            for (let i = 0; i < arrLen; i++) {
+                const cur = dp[i];
+                if (i > 0) {
+                    dp[i] = (dp[i] + prev) % MOD;
+                }
+                if (i < arrLen - 1) {
+                    dp[i] = (dp[i] + dp[i + 1]) % MOD;
+                }
+                prev = cur;
+            }
+        }
+
+        return dp[0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * min(n, m))$
+* Space complexity: $O(min(n, m))$
+
+> Where $n$ is the number of steps and $m$ is the size of the array.
\ No newline at end of file
diff --git a/articles/number-of-zero-filled-subarrays.md b/articles/number-of-zero-filled-subarrays.md
new file mode 100644
index 000000000..266353c04
--- /dev/null
+++ b/articles/number-of-zero-filled-subarrays.md
@@ -0,0 +1,338 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def zeroFilledSubarray(self, nums: List[int]) -> int:
+        res = 0
+        for i in range(len(nums)):
+            for j in range(i, len(nums)):
+                if nums[j] != 0:
+                    break
+                res += 1
+        return res
+```
+
+```java
+public class Solution {
+    public long zeroFilledSubarray(int[] nums) {
+        long res = 0;
+        for (int i = 0; i < nums.length; i++) {
+            for (int j = i; j < nums.length; j++) {
+                if (nums[j] != 0) break;
+                res++;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long zeroFilledSubarray(vector<int>& nums) {
+        long long res = 0;
+        for (int i = 0; i < nums.size(); i++) {
+            for (int j = i; j < nums.size(); j++) {
+                if (nums[j] != 0) break;
+                res++;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    zeroFilledSubarray(nums) {
+        let res = 0;
+        for (let i = 0; i < nums.length; i++) {
+            for (let j = i; j < nums.length; j++) {
+                if (nums[j] != 0) break;
+                res++;
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Count Consecutive Zeros - I
+
+::tabs-start
+
+```python
+class Solution:
+    def zeroFilledSubarray(self, nums: List[int]) -> int:
+        res = i = 0
+        while i < len(nums):
+            count = 0
+            while i < len(nums) and nums[i] == 0:
+                count += 1
+                i += 1
+                res += count
+            i += 1
+        return res
+```
+
+```java
+public class Solution {
+    public long zeroFilledSubarray(int[] nums) {
+        long res = 0;
+        int i = 0;
+        while (i < nums.length) {
+            long count = 0;
+            while (i < nums.length && nums[i] == 0) {
+                count++;
+                i++;
+                res += count;
+            }
+            i++;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long zeroFilledSubarray(vector<int>& nums) {
+        long long res = 0;
+        int i = 0;
+        while (i < nums.size()) {
+            long long count = 0;
+            while (i < nums.size() && nums[i] == 0) {
+                count++;
+                i++;
+                res += count;
+            }
+            i++;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    zeroFilledSubarray(nums) {
+        let res = 0, i = 0;
+        while (i < nums.length) {
+            let count = 0;
+            while (i < nums.length && nums[i] === 0) {
+                count++;
+                i++;
+                res += count;
+            }
+            i++;
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Count Consecutive Zeros - II
+
+::tabs-start
+
+```python
+class Solution:
+    def zeroFilledSubarray(self, nums: List[int]) -> int:
+        res = count = 0
+
+        for num in nums:
+            if num == 0:
+                count += 1
+            else:
+                count = 0
+            res += count
+        
+        return res
+```
+
+```java
+public class Solution {
+    public long zeroFilledSubarray(int[] nums) {
+        long res = 0;
+        int count = 0;
+
+        for (int num : nums) {
+            if (num == 0) {
+                count++;
+            } else {
+                count = 0;
+            }
+            res += count;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long zeroFilledSubarray(vector<int>& nums) {
+        long long res = 0;
+        int count = 0;
+
+        for (int& num : nums) {
+            if (num == 0) {
+                count++;
+            } else {
+                count = 0;
+            }
+            res += count;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    zeroFilledSubarray(nums) {
+        let res = 0, count = 0;
+
+        for (let num of nums) {
+            if (num === 0) {
+                count++;
+            } else {
+                count = 0;
+            }
+            res += count;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 4. Count Consecutive Zeros (Math)
+
+::tabs-start
+
+```python
+class Solution:
+    def zeroFilledSubarray(self, nums: List[int]) -> int:
+        res = count = 0
+        for num in nums:
+            if num == 0:
+                count += 1
+            else:
+                res += (count * (count + 1)) // 2
+                count = 0
+        res += (count * (count + 1)) // 2
+        return res
+```
+
+```java
+public class Solution {
+    public long zeroFilledSubarray(int[] nums) {
+        long res = 0, count = 0;
+        for (int num : nums) {
+            if (num == 0) {
+                count++;
+            } else {
+                res += count * (count + 1) / 2;
+                count = 0;
+            }
+        }
+        res += count * (count + 1) / 2;
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long zeroFilledSubarray(vector<int>& nums) {
+        long long res = 0, count = 0;
+        for (int num : nums) {
+            if (num == 0) {
+                count++;
+            } else {
+                res += count * (count + 1) / 2;
+                count = 0;
+            }
+        }
+        res += count * (count + 1) / 2;
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    zeroFilledSubarray(nums) {
+        let res = 0, count = 0;
+        for (let num of nums) {
+            if (num === 0) {
+                count++;
+            } else {
+                res += (count * (count + 1)) / 2;
+                count = 0;
+            }
+        }
+        res += (count * (count + 1)) / 2;
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/ones-and-zeroes.md b/articles/ones-and-zeroes.md
new file mode 100644
index 000000000..4d3e53b4d
--- /dev/null
+++ b/articles/ones-and-zeroes.md
@@ -0,0 +1,531 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def findMaxForm(self, strs: List[str], m: int, n: int) -> int:
+        arr = [[0] * 2 for _ in range(len(strs))]
+        for i, s in enumerate(strs):
+            for c in s:
+                arr[i][ord(c) - ord('0')] += 1
+        
+        def dfs(i, m, n):
+            if i == len(strs):
+                return 0
+            
+            res = dfs(i + 1, m, n)
+            if m >= arr[i][0] and n >= arr[i][1]:
+                res = max(res, 1 + dfs(i + 1, m - arr[i][0], n - arr[i][1]))
+            return res
+        
+        return dfs(0, m, n)
+```
+
+```java
+public class Solution {
+    public int findMaxForm(String[] strs, int m, int n) {
+        int[][] arr = new int[strs.length][2];
+        for (int i = 0; i < strs.length; i++) {
+            for (char c : strs[i].toCharArray()) {
+                arr[i][c - '0']++;
+            }
+        }
+
+        return dfs(0, m, n, arr);
+    }
+
+    private int dfs(int i, int m, int n, int[][] arr) {
+        if (i == arr.length) {
+            return 0;
+        }
+
+        int res = dfs(i + 1, m, n, arr);
+        if (m >= arr[i][0] && n >= arr[i][1]) {
+            res = Math.max(res, 1 + dfs(i + 1, m - arr[i][0], n - arr[i][1], arr));
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findMaxForm(vector<string>& strs, int m, int n) {
+        vector<vector<int>> arr(strs.size(), vector<int>(2));
+        for (int i = 0; i < strs.size(); i++) {
+            for (char c : strs[i]) {
+                arr[i][c - '0']++;
+            }
+        }
+        return dfs(0, m, n, arr);
+    }
+
+private:
+    int dfs(int i, int m, int n, vector<vector<int>>& arr) {
+        if (i == arr.size()) {
+            return 0;
+        }
+
+        int res = dfs(i + 1, m, n, arr);
+        if (m >= arr[i][0] && n >= arr[i][1]) {
+            res = max(res, 1 + dfs(i + 1, m - arr[i][0], n - arr[i][1], arr));
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} strs
+     * @param {number} m
+     * @param {number} n
+     * @return {number}
+     */
+    findMaxForm(strs, m, n) {
+        const arr = Array.from({ length: strs.length }, () => [0, 0]);
+        for (let i = 0; i < strs.length; i++) {
+            for (const c of strs[i]) {
+                arr[i][c - "0"]++;
+            }
+        }
+
+        const dfs = (i, m, n) => {
+            if (i === strs.length) {
+                return 0;
+            }
+
+            let res = dfs(i + 1, m, n);
+            if (m >= arr[i][0] && n >= arr[i][1]) {
+                res = Math.max(res, 1 + dfs(i + 1, m - arr[i][0], n - arr[i][1]));
+            }
+            return res;
+        };
+
+        return dfs(0, m, n);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ N)$
+* Space complexity: $O(N)$ for recursion stack.
+
+> Where $N$ represents the number of binary strings, and $m$ and $n$ are the maximum allowable counts of zeros and ones, respectively.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def findMaxForm(self, strs: List[str], m: int, n: int) -> int:
+        arr = [[0] * 2 for _ in range(len(strs))]
+        for i, s in enumerate(strs):
+            for c in s:
+                arr[i][ord(c) - ord('0')] += 1
+
+        dp = {}
+
+        def dfs(i, m, n):
+            if i == len(strs):
+                return 0
+            if m == 0 and n == 0:
+                return 0
+            if (i, m, n) in dp:
+                return dp[(i, m, n)]
+
+            res = dfs(i + 1, m, n)
+            if m >= arr[i][0] and n >= arr[i][1]:
+                res = max(res, 1 + dfs(i + 1, m - arr[i][0], n - arr[i][1]))
+            dp[(i, m, n)] = res
+            return res
+
+        return dfs(0, m, n)
+```
+
+```java
+public class Solution {
+    private int[][][] dp;
+    private int[][] arr;
+
+    public int findMaxForm(String[] strs, int m, int n) {
+        arr = new int[strs.length][2];
+        for (int i = 0; i < strs.length; i++) {
+            for (char c : strs[i].toCharArray()) {
+                arr[i][c - '0']++;
+            }
+        }
+
+        dp = new int[strs.length][m + 1][n + 1];
+        for (int i = 0; i < strs.length; i++) {
+            for (int j = 0; j <= m; j++) {
+                for (int k = 0; k <= n; k++) {
+                    dp[i][j][k] = -1;
+                }
+            }
+        }
+
+        return dfs(0, m, n);
+    }
+
+    private int dfs(int i, int m, int n) {
+        if (i == arr.length) {
+            return 0;
+        }
+        if (m == 0 && n == 0) {
+            return 0;
+        }
+        if (dp[i][m][n] != -1) {
+            return dp[i][m][n];
+        }
+
+        int res = dfs(i + 1, m, n);
+        if (m >= arr[i][0] && n >= arr[i][1]) {
+            res = Math.max(res, 1 + dfs(i + 1, m - arr[i][0], n - arr[i][1]));
+        }
+        dp[i][m][n] = res;
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<vector<vector<int>>> dp;
+    vector<vector<int>> arr;
+
+public:
+    int findMaxForm(vector<string>& strs, int m, int n) {
+        arr = vector<vector<int>>(strs.size(), vector<int>(2));
+        for (int i = 0; i < strs.size(); i++) {
+            for (char c : strs[i]) {
+                arr[i][c - '0']++;
+            }
+        }
+
+        dp = vector<vector<vector<int>>>(strs.size(), vector<vector<int>>(m + 1, vector<int>(n + 1, -1)));
+        return dfs(0, m, n);
+    }
+
+private:
+    int dfs(int i, int m, int n) {
+        if (i == arr.size()) {
+            return 0;
+        }
+        if (m == 0 && n == 0) {
+            return 0;
+        }
+        if (dp[i][m][n] != -1) {
+            return dp[i][m][n];
+        }
+
+        int res = dfs(i + 1, m, n);
+        if (m >= arr[i][0] && n >= arr[i][1]) {
+            res = max(res, 1 + dfs(i + 1, m - arr[i][0], n - arr[i][1]));
+        }
+        dp[i][m][n] = res;
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} strs
+     * @param {number} m
+     * @param {number} n
+     * @return {number}
+     */
+    findMaxForm(strs, m, n) {
+        const arr = Array.from({ length: strs.length }, () => [0, 0]);
+        for (let i = 0; i < strs.length; i++) {
+            for (const c of strs[i]) {
+                arr[i][c - "0"]++;
+            }
+        }
+
+        const dp = Array.from({ length: strs.length }, () =>
+            Array.from({ length: m + 1 }, () => Array(n + 1).fill(-1))
+        );
+
+        const dfs = (i, m, n) => {
+            if (i === strs.length) return 0;
+            if (m === 0 && n === 0) return 0;
+            if (dp[i][m][n] !== -1) return dp[i][m][n];
+
+            let res = dfs(i + 1, m, n);
+            if (m >= arr[i][0] && n >= arr[i][1]) {
+                res = Math.max(res, 1 + dfs(i + 1, m - arr[i][0], n - arr[i][1]));
+            }
+            dp[i][m][n] = res;
+            return res;
+        };
+
+        return dfs(0, m, n);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n * N)$
+* Space complexity: $O(m * n * N)$
+
+> Where $N$ represents the number of binary strings, and $m$ and $n$ are the maximum allowable counts of zeros and ones, respectively.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def findMaxForm(self, strs: List[str], m: int, n: int) -> int:
+        arr = [[0] * 2 for _ in range(len(strs))]
+        for i, s in enumerate(strs):
+            for c in s:
+                arr[i][ord(c) - ord('0')] += 1
+
+        dp = [[[0] * (n + 1) for _ in range(m + 1)] for _ in range(len(strs) + 1)]
+
+        for i in range(1, len(strs) + 1):
+            for j in range(m + 1):
+                for k in range(n + 1):
+                    dp[i][j][k] = dp[i - 1][j][k]
+                    if j >= arr[i - 1][0] and k >= arr[i - 1][1]:
+                        dp[i][j][k] = max(dp[i][j][k], 1 + dp[i - 1][j - arr[i - 1][0]][k - arr[i - 1][1]])
+
+        return dp[len(strs)][m][n]
+```
+
+```java
+public class Solution {
+    public int findMaxForm(String[] strs, int m, int n) {
+        int[][] arr = new int[strs.length][2];
+        for (int i = 0; i < strs.length; i++) {
+            for (char c : strs[i].toCharArray()) {
+                arr[i][c - '0']++;
+            }
+        }
+
+        int[][][] dp = new int[strs.length + 1][m + 1][n + 1];
+
+        for (int i = 1; i <= strs.length; i++) {
+            for (int j = 0; j <= m; j++) {
+                for (int k = 0; k <= n; k++) {
+                    dp[i][j][k] = dp[i - 1][j][k];
+                    if (j >= arr[i - 1][0] && k >= arr[i - 1][1]) {
+                        dp[i][j][k] = Math.max(dp[i][j][k], 1 + dp[i - 1][j - arr[i - 1][0]][k - arr[i - 1][1]]);
+                    }
+                }
+            }
+        }
+
+        return dp[strs.length][m][n];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findMaxForm(vector<string>& strs, int m, int n) {
+        vector<vector<int>> arr(strs.size(), vector<int>(2));
+        for (int i = 0; i < strs.size(); i++) {
+            for (char c : strs[i]) {
+                arr[i][c - '0']++;
+            }
+        }
+
+        vector<vector<vector<int>>> dp(strs.size() + 1, vector<vector<int>>(m + 1, vector<int>(n + 1, 0)));
+
+        for (int i = 1; i <= strs.size(); i++) {
+            for (int j = 0; j <= m; j++) {
+                for (int k = 0; k <= n; k++) {
+                    dp[i][j][k] = dp[i - 1][j][k];
+                    if (j >= arr[i - 1][0] && k >= arr[i - 1][1]) {
+                        dp[i][j][k] = max(dp[i][j][k], 1 + dp[i - 1][j - arr[i - 1][0]][k - arr[i - 1][1]]);
+                    }
+                }
+            }
+        }
+
+        return dp[strs.size()][m][n];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} strs
+     * @param {number} m
+     * @param {number} n
+     * @return {number}
+     */
+    findMaxForm(strs, m, n) {
+        const arr = strs.map(s => {
+            const zeros = s.split('').filter(c => c === '0').length;
+            const ones = s.length - zeros;
+            return [zeros, ones];
+        });
+
+        const dp = Array.from({ length: strs.length + 1 }, () =>
+            Array.from({ length: m + 1 }, () => Array(n + 1).fill(0))
+        );
+
+        for (let i = 1; i <= strs.length; i++) {
+            for (let j = 0; j <= m; j++) {
+                for (let k = 0; k <= n; k++) {
+                    dp[i][j][k] = dp[i - 1][j][k];
+                    if (j >= arr[i - 1][0] && k >= arr[i - 1][1]) {
+                        dp[i][j][k] = Math.max(dp[i][j][k], 1 + dp[i - 1][j - arr[i - 1][0]][k - arr[i - 1][1]]);
+                    }
+                }
+            }
+        }
+
+        return dp[strs.length][m][n];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n * N)$
+* Space complexity: $O(m * n * N)$
+
+> Where $N$ represents the number of binary strings, and $m$ and $n$ are the maximum allowable counts of zeros and ones, respectively.
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def findMaxForm(self, strs: List[str], m: int, n: int) -> int:
+        arr = [[0, 0] for _ in range(len(strs))]
+        for i, s in enumerate(strs):
+            for c in s:
+                arr[i][ord(c) - ord('0')] += 1
+        
+        dp = [[0] * (n + 1) for _ in range(m + 1)]
+        
+        for zeros, ones in arr:
+            for j in range(m, zeros - 1, -1):
+                for k in range(n, ones - 1, -1):
+                    dp[j][k] = max(dp[j][k], 1 + dp[j - zeros][k - ones])
+        
+        return dp[m][n]
+```
+
+```java
+public class Solution {
+    public int findMaxForm(String[] strs, int m, int n) {
+        int[][] arr = new int[strs.length][2];
+        for (int i = 0; i < strs.length; i++) {
+            for (char c : strs[i].toCharArray()) {
+                arr[i][c - '0']++;
+            }
+        }
+
+        int[][] dp = new int[m + 1][n + 1];
+
+        for (int[] pair : arr) {
+            int zeros = pair[0], ones = pair[1];
+            for (int j = m; j >= zeros; j--) {
+                for (int k = n; k >= ones; k--) {
+                    dp[j][k] = Math.max(dp[j][k], 1 + dp[j - zeros][k - ones]);
+                }
+            }
+        }
+
+        return dp[m][n];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findMaxForm(vector<string>& strs, int m, int n) {
+        vector<vector<int>> arr(strs.size(), vector<int>(2));
+        for (int i = 0; i < strs.size(); i++) {
+            for (char c : strs[i]) {
+                arr[i][c - '0']++;
+            }
+        }
+
+        vector<vector<int>> dp(m + 1, vector<int>(n + 1, 0));
+
+        for (const auto& pair : arr) {
+            int zeros = pair[0], ones = pair[1];
+            for (int j = m; j >= zeros; j--) {
+                for (int k = n; k >= ones; k--) {
+                    dp[j][k] = max(dp[j][k], 1 + dp[j - zeros][k - ones]);
+                }
+            }
+        }
+
+        return dp[m][n];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} strs
+     * @param {number} m
+     * @param {number} n
+     * @return {number}
+     */
+    findMaxForm(strs, m, n) {
+        const arr = Array.from({ length: strs.length }, () => [0, 0]);
+        for (let i = 0; i < strs.length; i++) {
+            for (const c of strs[i]) {
+                arr[i][c - "0"]++;
+            }
+        }
+
+        const dp = Array.from({ length: m + 1 }, () => Array(n + 1).fill(0));
+
+        for (const [zeros, ones] of arr) {
+            for (let j = m; j >= zeros; j--) {
+                for (let k = n; k >= ones; k--) {
+                    dp[j][k] = Math.max(dp[j][k], 1 + dp[j - zeros][k - ones]);
+                }
+            }
+        }
+
+        return dp[m][n];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n * N)$
+* Space complexity: $O(m * n + N)$
+
+> Where $N$ represents the number of binary strings, and $m$ and $n$ are the maximum allowable counts of zeros and ones, respectively.
\ No newline at end of file
diff --git a/articles/online-stock-span.md b/articles/online-stock-span.md
new file mode 100644
index 000000000..9419b89b6
--- /dev/null
+++ b/articles/online-stock-span.md
@@ -0,0 +1,173 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class StockSpanner:
+
+    def __init__(self):
+        self.arr = []
+
+    def next(self, price: int) -> int:
+        self.arr.append(price)
+        i = len(self.arr) - 2
+        while i >= 0 and self.arr[i] <= price:
+            i -= 1
+        return len(self.arr) - i - 1
+```
+
+```java
+public class StockSpanner {
+    private List<Integer> arr;
+
+    public StockSpanner() {
+        arr = new ArrayList<>();
+    }
+
+    public int next(int price) {
+        arr.add(price);
+        int i = arr.size() - 2;
+        while (i >= 0 && arr.get(i) <= price) {
+            i--;
+        }
+        return arr.size() - i - 1;
+    }
+}
+```
+
+```cpp
+class StockSpanner {
+    vector<int> arr;
+
+public:
+    StockSpanner() {}
+
+    int next(int price) {
+        arr.push_back(price);
+        int i = arr.size() - 2;
+        while (i >= 0 && arr[i] <= price) {
+            i--;
+        }
+        return arr.size() - i - 1;
+    }
+};
+```
+
+```javascript
+class StockSpanner {
+    constructor() {
+        this.arr = [];
+    }
+
+    /**
+     * @param {number} price
+     * @return {number}
+     */
+    next(price) {
+        this.arr.push(price);
+        let i = this.arr.length - 2;
+        while (i >= 0 && this.arr[i] <= price) {
+            i--;
+        }
+        return this.arr.length - i - 1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the number of function calls.
+
+---
+
+## 2. Monotonic Decreasing Stack
+
+::tabs-start
+
+```python
+class StockSpanner:
+
+    def __init__(self):
+        self.stack = []  # pair: (price, span)
+
+    def next(self, price: int) -> int:
+        span = 1
+        while self.stack and self.stack[-1][0] <= price:
+            span += self.stack[-1][1]
+            self.stack.pop()
+        self.stack.append((price, span))
+        return span
+```
+
+```java
+public class StockSpanner {
+    private Stack<int[]> stack; // pair: [price, span]
+
+    public StockSpanner() {
+        stack = new Stack<>();
+    }
+
+    public int next(int price) {
+        int span = 1;
+        while (!stack.isEmpty() && stack.peek()[0] <= price) {
+            span += stack.pop()[1];
+        }
+        stack.push(new int[] {price, span});
+        return span;
+    }
+}
+```
+
+```cpp
+class StockSpanner {
+    stack<pair<int, int>> stack; // pair: (price, span)
+
+public:
+    StockSpanner() {}
+
+    int next(int price) {
+        int span = 1;
+        while (!stack.empty() && stack.top().first <= price) {
+            span += stack.top().second;
+            stack.pop();
+        }
+        stack.push({price, span});
+        return span;
+    }
+};
+```
+
+```javascript
+class StockSpanner {
+    constructor() {
+        this.stack = []; // pair: [price, span]
+    }
+
+    /**
+     * @param {number} price
+     * @return {number}
+     */
+    next(price) {
+        let span = 1;
+        while (this.stack.length && this.stack[this.stack.length - 1][0] <= price) {
+            span += this.stack.pop()[1];
+        }
+        this.stack.push([price, span]);
+        return span;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the number of function calls.
\ No newline at end of file
diff --git a/articles/open-the-lock.md b/articles/open-the-lock.md
new file mode 100644
index 000000000..910704fd6
--- /dev/null
+++ b/articles/open-the-lock.md
@@ -0,0 +1,620 @@
+## 1. Breadth First Search - I
+
+::tabs-start
+
+```python
+class Solution:
+    def openLock(self, deadends: List[str], target: str) -> int:
+        if "0000" in deadends:
+            return -1
+
+        def children(lock):
+            res = []
+            for i in range(4):
+                digit = str((int(lock[i]) + 1) % 10)
+                res.append(lock[:i] + digit + lock[i+1:])
+                digit = str((int(lock[i]) - 1 + 10) % 10)
+                res.append(lock[:i] + digit + lock[i+1:])
+            return res
+
+        q = deque([("0000", 0)])
+        visit = set(deadends)
+
+        while q:
+            lock, turns = q.popleft()
+            if lock == target:
+                return turns
+            for child in children(lock):
+                if child not in visit:
+                    visit.add(child)
+                    q.append((child, turns + 1))
+        return -1
+```
+
+```java
+public class Solution {
+    public int openLock(String[] deadends, String target) {
+        Set<String> visit = new HashSet<>(Arrays.asList(deadends));
+        if (visit.contains("0000")) return -1;
+
+        Queue<String> queue = new LinkedList<>();
+        queue.offer("0000");
+        visit.add("0000");
+
+        int turns = 0;
+        while (!queue.isEmpty()) {
+            int size = queue.size();
+            for (int i = 0; i < size; i++) {
+                String lock = queue.poll();
+                if (lock.equals(target)) return turns;
+
+                for (String next : children(lock)) {
+                    if (!visit.contains(next)) {
+                        queue.offer(next);
+                        visit.add(next);
+                    }
+                }
+            }
+            turns++;
+        }
+        return -1;
+    }
+
+    private List<String> children(String lock) {
+        List<String> res = new ArrayList<>();
+        for (int i = 0; i < 4; i++) {
+            char[] arr = lock.toCharArray();
+            arr[i] = (char) (((arr[i] - '0' + 1) % 10) + '0');
+            res.add(new String(arr));
+
+            arr = lock.toCharArray();
+            arr[i] = (char) (((arr[i] - '0' - 1 + 10) % 10) + '0');
+            res.add(new String(arr));
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int openLock(vector<string>& deadends, string target) {
+        unordered_set<string> visit(deadends.begin(), deadends.end());
+        if (visit.count("0000")) return -1;
+
+        queue<pair<string, int>> q;
+        q.push({"0000", 0});
+        visit.insert("0000");
+
+        while (!q.empty()) {
+            auto [lock, turns] = q.front();
+            q.pop();
+
+            if (lock == target) return turns;
+            for (string child : children(lock)) {
+                if (!visit.count(child)) {
+                    visit.insert(child);
+                    q.push({child, turns + 1});
+                }
+            }
+        }
+        return -1;
+    }
+
+private:
+    vector<string> children(string lock) {
+        vector<string> res;
+        for (int i = 0; i < 4; ++i) {
+            string next = lock;
+            next[i] = (next[i] - '0' + 1) % 10 + '0';
+            res.push_back(next);
+            
+            next = lock;
+            next[i] = (next[i] - '0' - 1 + 10) % 10 + '0';
+            res.push_back(next);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} deadends
+     * @param {string} target
+     * @return {number}
+     */
+    openLock(deadends, target) {
+        const visit = new Set(deadends);
+        if (visit.has("0000")) return -1;
+
+        const children = (lock) => {
+            const res = [];
+            for (let i = 0; i < 4; i++) {
+                const up = lock.slice(0, i) + ((+lock[i] + 1) % 10) + lock.slice(i + 1);
+                const down = lock.slice(0, i) + ((+lock[i] - 1 + 10) % 10) + lock.slice(i + 1);
+                res.push(up, down);
+            }
+            return res;
+        };
+
+        const queue = new Queue([["0000", 0]]);
+        visit.add("0000");
+
+        while (!queue.isEmpty()) {
+            const [lock, turns] = queue.pop();
+            if (lock === target) return turns;
+
+            for (const child of children(lock)) {
+                if (!visit.has(child)) {
+                    visit.add(child);
+                    queue.push([child, turns + 1]);
+                }
+            }
+        }
+        return -1;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int OpenLock(string[] deadends, string target) {
+        var dead = new HashSet<string>(deadends);
+        if (dead.Contains("0000")) return -1;
+
+        List<string> Children(string lockStr) {
+            var res = new List<string>();
+            for (int i = 0; i < 4; i++) {
+                int digit = lockStr[i] - '0';
+                string up = lockStr.Substring(0, i) + ((digit + 1) % 10) + lockStr.Substring(i + 1);
+                string down = lockStr.Substring(0, i) + ((digit + 9) % 10) + lockStr.Substring(i + 1);
+                res.Add(up);
+                res.Add(down);
+            }
+            return res;
+        }
+
+        var q = new Queue<(string, int)>();
+        q.Enqueue(("0000", 0));
+        var visited = new HashSet<string>(dead);
+
+        while (q.Count > 0) {
+            var (lockStr, turns) = q.Dequeue();
+            if (lockStr == target) return turns;
+            foreach (var child in Children(lockStr)) {
+                if (!visited.Contains(child)) {
+                    visited.Add(child);
+                    q.Enqueue((child, turns + 1));
+                }
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(d ^ n + m)$
+* Space complexity: $O(d ^ n)$
+
+> Where $d$ is the number of digits $(0 - 9)$, $n$ is the number of wheels $(4)$, and $m$ is the number of deadends.
+
+---
+
+## 2. Breadth First Search - II
+
+::tabs-start
+
+```python
+class Solution:
+    def openLock(self, deadends: List[str], target: str) -> int:
+        if target == "0000":
+            return 0
+
+        visit = set(deadends)
+        if "0000" in visit:
+            return -1
+        
+        q = deque(["0000"])
+        visit.add("0000")
+        steps = 0
+        
+        while q:
+            steps += 1
+            for _ in range(len(q)):
+                lock = q.popleft()
+                for i in range(4):
+                    for j in [1, -1]:
+                        digit = str((int(lock[i]) + j + 10) % 10)
+                        nextLock = lock[:i] + digit + lock[i+1:]
+                        if nextLock in visit:
+                            continue
+                        if nextLock == target:
+                            return steps
+                        q.append(nextLock)
+                        visit.add(nextLock)
+        return -1
+```
+
+```java
+public class Solution {
+    public int openLock(String[] deadends, String target) {
+        if (target.equals("0000")) return 0;
+
+        Set<String> visit = new HashSet<>(Arrays.asList(deadends));
+        if (visit.contains("0000")) return -1;
+
+        Queue<String> q = new LinkedList<>();
+        q.offer("0000");
+        visit.add("0000");
+        int steps = 0;
+
+        while (!q.isEmpty()) {
+            steps++;
+            for (int i = q.size(); i > 0; i--) {
+                String lock = q.poll();
+                for (int j = 0; j < 4; j++) {
+                    for (int move : new int[]{1, -1}) {
+                        char[] arr = lock.toCharArray();
+                        arr[j] = (char)((arr[j] - '0' + move + 10) % 10 + '0');
+                        String nextLock = new String(arr);
+                        if (visit.contains(nextLock)) continue;
+                        if (nextLock.equals(target)) return steps;
+                        q.offer(nextLock);
+                        visit.add(nextLock);
+                    }
+                }
+            }
+        }
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int openLock(vector<string>& deadends, string target) {
+        if (target == "0000") return 0;
+
+        unordered_set<string> visit(deadends.begin(), deadends.end());
+        if (visit.count("0000")) return -1;
+
+        queue<string> q;
+        q.push("0000");
+        visit.insert("0000");
+        int steps = 0;
+
+        while (!q.empty()) {
+            steps++;
+            for (int i = q.size(); i > 0; i--) {
+                string lock = q.front(); q.pop();
+                for (int j = 0; j < 4; j++) {
+                    for (int move : {1, -1}) {
+                        string nextLock = lock;
+                        nextLock[j] = (nextLock[j] - '0' + move + 10) % 10 + '0';
+                        if (visit.count(nextLock)) continue;
+                        if (nextLock == target) return steps;
+                        q.push(nextLock);
+                        visit.insert(nextLock);
+                    }
+                }
+            }
+        }
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} deadends
+     * @param {string} target
+     * @return {number}
+     */
+    openLock(deadends, target) {
+        if (target === "0000") return 0;
+
+        const visit = new Set(deadends);
+        if (visit.has("0000")) return -1;
+
+        const q = new Queue(["0000"]);
+        visit.add("0000");
+        let steps = 0;
+
+        while (!q.isEmpty()) {
+            steps++;
+            for (let i = q.size(); i > 0; i--) {
+                const lock = q.pop();
+                for (let j = 0; j < 4; j++) {
+                    for (let move of [1, -1]) {
+                        const digit = (parseInt(lock[j]) + move + 10) % 10;
+                        const nextLock = lock.slice(0, j) + digit + lock.slice(j + 1);
+                        if (visit.has(nextLock)) continue;
+                        if (nextLock === target) return steps;
+                        q.push(nextLock);
+                        visit.add(nextLock);
+                    }
+                }
+            }
+        }
+        return -1;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int OpenLock(string[] deadends, string target) {
+        if (target == "0000") return 0;
+
+        var visited = new HashSet<string>(deadends);
+        if (visited.Contains("0000")) return -1;
+
+        var q = new Queue<string>();
+        q.Enqueue("0000");
+        visited.Add("0000");
+        int steps = 0;
+
+        while (q.Count > 0) {
+            steps++;
+            int size = q.Count;
+            for (int i = 0; i < size; i++) {
+                string lockStr = q.Dequeue();
+                for (int j = 0; j < 4; j++) {
+                    foreach (int move in new int[] {1, -1}) {
+                        int digit = (lockStr[j] - '0' + move + 10) % 10;
+                        string nextLock = lockStr.Substring(0, j) + digit.ToString() + lockStr.Substring(j + 1);
+                        if (visited.Contains(nextLock)) continue;
+                        if (nextLock == target) return steps;
+                        q.Enqueue(nextLock);
+                        visited.Add(nextLock);
+                    }
+                }
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(d ^ n + m)$
+* Space complexity: $O(d ^ n)$
+
+> Where $d$ is the number of digits $(0 - 9)$, $n$ is the number of wheels $(4)$, and $m$ is the number of deadends.
+
+---
+
+## 3. Bidirectional Breadth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def openLock(self, deadends: List[str], target: str) -> int:
+        if target == "0000":
+            return 0
+
+        visit = set(deadends)
+        if "0000" in visit:
+            return -1
+        
+        begin = {"0000"}
+        end = {target}
+        steps = 0
+
+        while begin and end:
+            if len(begin) > len(end):
+                begin, end = end, begin
+            
+            steps += 1
+            temp = set()
+            for lock in begin:
+                for i in range(4):
+                    for j in [-1, 1]:
+                        digit = str((int(lock[i]) + j + 10) % 10)
+                        nextLock = lock[:i] + digit + lock[i+1:]
+                        
+                        if nextLock in end:
+                            return steps
+                        if nextLock in visit:
+                            continue
+                        visit.add(nextLock)
+                        temp.add(nextLock)
+            begin = temp
+        return -1
+```
+
+```java
+public class Solution {
+    public int openLock(String[] deadends, String target) {
+        if (target.equals("0000")) return 0;
+
+        Set<String> visit = new HashSet<>(Arrays.asList(deadends));
+        if (visit.contains("0000")) return -1;
+
+        Set<String> begin = new HashSet<>();
+        begin.add("0000");
+        Set<String> end = new HashSet<>();
+        end.add(target);
+        int steps = 0;
+
+        while (!begin.isEmpty() && !end.isEmpty()) {
+            if (begin.size() > end.size()) {
+                Set<String> temp = begin;
+                begin = end;
+                end = temp;
+            }
+
+            steps++;
+            Set<String> temp = new HashSet<>();
+            for (String lock : begin) {
+                for (int i = 0; i < 4; i++) {
+                    for (int j : new int[]{-1, 1}) {
+                        char[] chars = lock.toCharArray();
+                        chars[i] = (char) ((chars[i] - '0' + j + 10) % 10 + '0');
+                        String nextLock = new String(chars);
+
+                        if (end.contains(nextLock)) return steps;
+                        if (visit.contains(nextLock)) continue;
+
+                        visit.add(nextLock);
+                        temp.add(nextLock);
+                    }
+                }
+            }
+            begin = temp;
+        }
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int openLock(vector<string>& deadends, string target) {
+        if (target == "0000") return 0;
+        
+        unordered_set<string> visit(deadends.begin(), deadends.end());
+        if (visit.count("0000")) return -1;
+
+        unordered_set<string> begin = {"0000"}, end = {target};
+        int steps = 0;
+
+        while (!begin.empty() && !end.empty()) {
+            if (begin.size() > end.size()) swap(begin, end);
+            steps++;
+            unordered_set<string> temp;
+
+            for (const string& lock : begin) {
+                for (int i = 0; i < 4; ++i) {
+                    for (int j : {-1, 1}) {
+                        string nextLock = lock;
+                        nextLock[i] = (nextLock[i] - '0' + j + 10) % 10 + '0';
+
+                        if (end.count(nextLock)) return steps;
+                        if (visit.count(nextLock)) continue;
+
+                        visit.insert(nextLock);
+                        temp.insert(nextLock);
+                    }
+                }
+            }
+            begin = temp;
+        }
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} deadends
+     * @param {string} target
+     * @return {number}
+     */
+    openLock(deadends, target) {
+        if (target === "0000") return 0;
+
+        const visit = new Set(deadends);
+        if (visit.has("0000")) return -1;
+
+        let begin = new Set(["0000"]);
+        let end = new Set([target]);
+        let steps = 0;
+
+        while (begin.size > 0 && end.size > 0) {
+            if (begin.size > end.size) [begin, end] = [end, begin];
+
+            steps++;
+            const temp = new Set();
+
+            for (const lock of begin) {
+                for (let i = 0; i < 4; i++) {
+                    for (const j of [-1, 1]) {
+                        const digit = (parseInt(lock[i]) + j + 10) % 10;
+                        const nextLock = lock.slice(0, i) + digit + lock.slice(i + 1);
+
+                        if (end.has(nextLock)) return steps;
+                        if (visit.has(nextLock)) continue;
+
+                        visit.add(nextLock);
+                        temp.add(nextLock);
+                    }
+                }
+            }
+            begin = temp;
+        }
+        return -1;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int OpenLock(string[] deadends, string target) {
+        if (target == "0000") return 0;
+
+        var visit = new HashSet<string>(deadends);
+        if (visit.Contains("0000")) return -1;
+
+        var begin = new HashSet<string> { "0000" };
+        var end = new HashSet<string> { target };
+        int steps = 0;
+
+        while (begin.Count > 0 && end.Count > 0) {
+            if (begin.Count > end.Count) {
+                var tempSet = begin;
+                begin = end;
+                end = tempSet;
+            }
+
+            var temp = new HashSet<string>();
+            steps++;
+
+            foreach (var lockStr in begin) {
+                for (int i = 0; i < 4; i++) {
+                    foreach (int j in new int[] { -1, 1 }) {
+                        int digit = (lockStr[i] - '0' + j + 10) % 10;
+                        string nextLock = lockStr.Substring(0, i) + digit.ToString() + lockStr.Substring(i + 1);
+
+                        if (end.Contains(nextLock)) return steps;
+                        if (visit.Contains(nextLock)) continue;
+
+                        visit.Add(nextLock);
+                        temp.Add(nextLock);
+                    }
+                }
+            }
+
+            begin = temp;
+        }
+
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(d ^ n + m)$
+* Space complexity: $O(d ^ n)$
+
+> Where $d$ is the number of digits $(0 - 9)$, $n$ is the number of wheels $(4)$, and $m$ is the number of deadends.
\ No newline at end of file
diff --git a/articles/operations-on-tree.md b/articles/operations-on-tree.md
new file mode 100644
index 000000000..682f18874
--- /dev/null
+++ b/articles/operations-on-tree.md
@@ -0,0 +1,806 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+class LockingTree:
+
+    def __init__(self, parent: List[int]):
+        self.parent = parent
+        self.child = [[] for _ in range(len(parent))]
+        self.locked = [0] * len(parent)
+        for node in range(1, len(parent)):
+            self.child[parent[node]].append(node)
+
+    def lock(self, num: int, user: int) -> bool:
+        if self.locked[num]:
+            return False
+        self.locked[num] = user
+        return True
+
+    def unlock(self, num: int, user: int) -> bool:
+        if self.locked[num] != user:
+            return False
+        self.locked[num] = 0
+        return True
+
+    def upgrade(self, num: int, user: int) -> bool:
+        node = num
+        while node != -1:
+            if self.locked[node]:
+                return False
+            node = self.parent[node]
+
+        def dfs(node):
+            lockedCount = 0
+            if self.locked[node]:
+                lockedCount += 1
+                self.locked[node] = 0
+
+            for nei in self.child[node]:
+                lockedCount += dfs(nei)
+            return lockedCount
+
+        if dfs(num) > 0:
+            self.locked[num] = user
+            return True
+        return False
+```
+
+```java
+public class LockingTree {
+    private int[] parent;
+    private List<Integer>[] child;
+    private int[] locked;
+
+    public LockingTree(int[] parent) {
+        this.parent = parent;
+        int n = parent.length;
+        child = new ArrayList[n];
+        locked = new int[n];
+
+        for (int i = 0; i < n; i++) {
+            child[i] = new ArrayList<>();
+        }
+        for (int node = 1; node < n; node++) {
+            child[parent[node]].add(node);
+        }
+    }
+
+    public boolean lock(int num, int user) {
+        if (locked[num] != 0) {
+            return false;
+        }
+        locked[num] = user;
+        return true;
+    }
+
+    public boolean unlock(int num, int user) {
+        if (locked[num] != user) {
+            return false;
+        }
+        locked[num] = 0;
+        return true;
+    }
+
+    public boolean upgrade(int num, int user) {
+        int node = num;
+        while (node != -1) {
+            if (locked[node] != 0) {
+                return false;
+            }
+            node = parent[node];
+        }
+
+        int lockedCount = dfs(num);
+        if (lockedCount > 0) {
+            locked[num] = user;
+            return true;
+        }
+        return false;
+    }
+
+    private int dfs(int node) {
+        int lockedCount = 0;
+        if (locked[node] != 0) {
+            lockedCount++;
+            locked[node] = 0;
+        }
+        for (int nei : child[node]) {
+            lockedCount += dfs(nei);
+        }
+        return lockedCount;
+    }
+}
+```
+
+```cpp
+class LockingTree {
+private:
+    vector<int> parent;
+    vector<vector<int>> child;
+    vector<int> locked;
+
+public:
+    LockingTree(vector<int>& parent) : parent(parent), locked(parent.size()) {
+        int n = parent.size();
+        child.resize(n);
+        for (int node = 1; node < n; node++) {
+            child[parent[node]].push_back(node);
+        }
+    }
+
+    bool lock(int num, int user) {
+        if (locked[num]) {
+            return false;
+        }
+        locked[num] = user;
+        return true;
+    }
+
+    bool unlock(int num, int user) {
+        if (locked[num] != user) {
+            return false;
+        }
+        locked[num] = 0;
+        return true;
+    }
+
+    bool upgrade(int num, int user) {
+        int node = num;
+        while (node != -1) {
+            if (locked[node]) {
+                return false;
+            }
+            node = parent[node];
+        }
+
+        int lockedCount = dfs(num);
+        if (lockedCount > 0) {
+            locked[num] = user;
+            return true;
+        }
+        return false;
+    }
+
+private:
+    int dfs(int node) {
+        int lockedCount = 0;
+        if (locked[node]) {
+            lockedCount++;
+            locked[node] = 0;
+        }
+        for (int& nei : child[node]) {
+            lockedCount += dfs(nei);
+        }
+        return lockedCount;
+    }
+};
+```
+
+```javascript
+class LockingTree {
+    /**
+     * @constructor
+     * @param {number[]} parent
+     */
+    constructor(parent) {
+        this.parent = parent;
+        this.child = Array.from({ length: parent.length }, () => []);
+        this.locked = new Array(parent.length).fill(0);
+
+        for (let node = 1; node < parent.length; node++) {
+            this.child[parent[node]].push(node);
+        }
+    }
+
+    /** 
+     * @param {number} num 
+     * @param {number} user 
+     * @return {boolean} 
+     */
+    lock(num, user) {
+        if (this.locked[num] !== 0) {
+            return false;
+        }
+        this.locked[num] = user;
+        return true;
+    }
+
+    /** 
+     * @param {number} num
+     * @param {number} user
+     * @return {boolean}
+     */
+    unlock(num, user) {
+        if (this.locked[num] !== user) {
+            return false;
+        }
+        this.locked[num] = 0;
+        return true;
+    }
+
+    /** 
+     * @param {number} num
+     * @param {number} user 
+     * @return {boolean} 
+     */
+    upgrade(num, user) {
+        let node = num;
+        while (node !== -1) {
+            if (this.locked[node] !== 0) {
+                return false;
+            }
+            node = this.parent[node];
+        }
+
+        const dfs = (node) => {
+            let lockedCount = 0;
+            if (this.locked[node] !== 0) {
+                lockedCount++;
+                this.locked[node] = 0;
+            }
+            for (let nei of this.child[node]) {
+                lockedCount += dfs(nei);
+            }
+            return lockedCount;
+        };
+
+        if (dfs(num) > 0) {
+            this.locked[num] = user;
+            return true;
+        }
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(n)$ time for initialization.
+    * $O(1)$ time for each $lock()$ and $unlock()$ function call.
+    * $O(n)$ time for each $upgrade()$ function call.
+* Space complexity: $O(n)$
+
+---
+
+## 2. Breadth First Search
+
+::tabs-start
+
+```python
+class LockingTree:
+
+    def __init__(self, parent: List[int]):
+        self.parent = parent
+        self.child = [[] for _ in range(len(parent))]
+        self.locked = [0] * len(parent)
+        for node in range(1, len(parent)):
+            self.child[parent[node]].append(node)
+
+    def lock(self, num: int, user: int) -> bool:
+        if self.locked[num]:
+            return False
+        self.locked[num] = user
+        return True
+
+    def unlock(self, num: int, user: int) -> bool:
+        if self.locked[num] != user:
+            return False
+        self.locked[num] = 0
+        return True
+
+    def upgrade(self, num: int, user: int) -> bool:
+        node = num
+        while node != -1:
+            if self.locked[node]:
+                return False
+            node = self.parent[node]
+
+        lockedCount, q = 0, deque([num])
+        while q:
+            node = q.popleft()
+            if self.locked[node]:
+                self.locked[node] = 0
+                lockedCount += 1
+            q.extend(self.child[node])
+
+        if lockedCount:
+            self.locked[num] = user
+            return True
+        return False
+```
+
+```java
+public class LockingTree {
+    private int[] parent;
+    private List<Integer>[] child;
+    private int[] locked;
+
+    public LockingTree(int[] parent) {
+        this.parent = parent;
+        int n = parent.length;
+        child = new ArrayList[n];
+        locked = new int[n];
+
+        for (int i = 0; i < n; i++) {
+            child[i] = new ArrayList<>();
+        }
+        for (int node = 1; node < n; node++) {
+            child[parent[node]].add(node);
+        }
+    }
+
+    public boolean lock(int num, int user) {
+        if (locked[num] != 0) {
+            return false;
+        }
+        locked[num] = user;
+        return true;
+    }
+
+    public boolean unlock(int num, int user) {
+        if (locked[num] != user) {
+            return false;
+        }
+        locked[num] = 0;
+        return true;
+    }
+
+    public boolean upgrade(int num, int user) {
+        int node = num;
+        while (node != -1) {
+            if (locked[node] != 0) {
+                return false;
+            }
+            node = parent[node];
+        }
+
+        int lockedCount = 0;
+        Queue<Integer> q = new LinkedList<>();
+        q.offer(num);
+
+        while (!q.isEmpty()) {
+            node = q.poll();
+            if (locked[node] != 0) {
+                locked[node] = 0;
+                lockedCount++;
+            }
+            q.addAll(child[node]);
+        }
+
+        if (lockedCount > 0) {
+            locked[num] = user;
+            return true;
+        }
+        return false;
+    }
+}
+```
+
+```cpp
+class LockingTree {
+private:
+    vector<int> parent;
+    vector<vector<int>> child;
+    vector<int> locked;
+
+public:
+    LockingTree(vector<int>& parent) : parent(parent), locked(parent.size()) {
+        int n = parent.size();
+        child.resize(n);
+        for (int node = 1; node < n; node++) {
+            child[parent[node]].push_back(node);
+        }
+    }
+
+    bool lock(int num, int user) {
+        if (locked[num]) {
+            return false;
+        }
+        locked[num] = user;
+        return true;
+    }
+
+    bool unlock(int num, int user) {
+        if (locked[num] != user) {
+            return false;
+        }
+        locked[num] = 0;
+        return true;
+    }
+
+    bool upgrade(int num, int user) {
+        int node = num;
+        while (node != -1) {
+            if (locked[node]) {
+                return false;
+            }
+            node = parent[node];
+        }
+
+        int lockedCount = 0;
+        queue<int> q;
+        q.push(num);
+
+        while (!q.empty()) {
+            node = q.front(); q.pop();
+            if (locked[node]) {
+                locked[node] = 0;
+                lockedCount++;
+            }
+            for (int nei : child[node]) {
+                q.push(nei);
+            }
+        }
+
+        if (lockedCount > 0) {
+            locked[num] = user;
+            return true;
+        }
+        return false;
+    }
+};
+```
+
+```javascript
+class LockingTree {
+    /**
+     * @constructor
+     * @param {number[]} parent
+     */
+    constructor(parent) {
+        this.parent = parent;
+        this.child = Array.from({ length: parent.length }, () => []);
+        this.locked = new Array(parent.length).fill(0);
+
+        for (let node = 1; node < parent.length; node++) {
+            this.child[parent[node]].push(node);
+        }
+    }
+
+    /** 
+     * @param {number} num 
+     * @param {number} user 
+     * @return {boolean} 
+     */
+    lock(num, user) {
+        if (this.locked[num] !== 0) {
+            return false;
+        }
+        this.locked[num] = user;
+        return true;
+    }
+
+    /** 
+     * @param {number} num
+     * @param {number} user
+     * @return {boolean}
+     */
+    unlock(num, user) {
+        if (this.locked[num] !== user) {
+            return false;
+        }
+        this.locked[num] = 0;
+        return true;
+    }
+
+    /** 
+     * @param {number} num
+     * @param {number} user 
+     * @return {boolean} 
+     */
+    upgrade(num, user) {
+        let node = num;
+        while (node !== -1) {
+            if (this.locked[node] !== 0) {
+                return false;
+            }
+            node = this.parent[node];
+        }
+
+        let lockedCount = 0;
+        const q = new Queue([num]);
+
+        while (!q.isEmpty()) {
+            node = q.pop();
+            if (this.locked[node]) {
+                this.locked[node] = 0;
+                lockedCount++;
+            }
+            for (let nei of this.child[node]) {
+                q.push(nei);
+            }
+        }
+
+        if (lockedCount > 0) {
+            this.locked[num] = user;
+            return true;
+        }
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(n)$ time for initialization.
+    * $O(1)$ time for each $lock()$ and $unlock()$ function call.
+    * $O(n)$ time for each $upgrade()$ function call.
+* Space complexity: $O(n)$
+
+---
+
+## 3. Iterative DFS
+
+::tabs-start
+
+```python
+class LockingTree:
+
+    def __init__(self, parent: List[int]):
+        self.parent = parent
+        self.child = [[] for _ in range(len(parent))]
+        self.locked = [0] * len(parent)
+        for node in range(1, len(parent)):
+            self.child[parent[node]].append(node)
+
+    def lock(self, num: int, user: int) -> bool:
+        if self.locked[num]:
+            return False
+        self.locked[num] = user
+        return True
+
+    def unlock(self, num: int, user: int) -> bool:
+        if self.locked[num] != user:
+            return False
+        self.locked[num] = 0
+        return True
+
+    def upgrade(self, num: int, user: int) -> bool:
+        node = num
+        while node != -1:
+            if self.locked[node]:
+                return False
+            node = self.parent[node]
+
+        lockedCount, stack = 0, [num]
+        while stack:
+            node = stack.pop()
+            if self.locked[node]:
+                self.locked[node] = 0
+                lockedCount += 1
+            stack.extend(self.child[node])
+
+        if lockedCount:
+            self.locked[num] = user
+            return True
+        return False
+```
+
+```java
+public class LockingTree {
+    private int[] parent;
+    private List<Integer>[] child;
+    private int[] locked;
+
+    public LockingTree(int[] parent) {
+        this.parent = parent;
+        int n = parent.length;
+        child = new ArrayList[n];
+        locked = new int[n];
+
+        for (int i = 0; i < n; i++) {
+            child[i] = new ArrayList<>();
+        }
+        for (int node = 1; node < n; node++) {
+            child[parent[node]].add(node);
+        }
+    }
+
+    public boolean lock(int num, int user) {
+        if (locked[num] != 0) {
+            return false;
+        }
+        locked[num] = user;
+        return true;
+    }
+
+    public boolean unlock(int num, int user) {
+        if (locked[num] != user) {
+            return false;
+        }
+        locked[num] = 0;
+        return true;
+    }
+
+    public boolean upgrade(int num, int user) {
+        int node = num;
+        while (node != -1) {
+            if (locked[node] != 0) {
+                return false;
+            }
+            node = parent[node];
+        }
+
+        int lockedCount = 0;
+        Stack<Integer> stack = new Stack<>();
+        stack.push(num);
+
+        while (!stack.isEmpty()) {
+            node = stack.pop();
+            if (locked[node] != 0) {
+                locked[node] = 0;
+                lockedCount++;
+            }
+            for (int nei : child[node]) {
+                stack.push(nei);
+            }
+        }
+
+        if (lockedCount > 0) {
+            locked[num] = user;
+            return true;
+        }
+        return false;
+    }
+}
+```
+
+```cpp
+class LockingTree {
+private:
+    vector<int> parent;
+    vector<vector<int>> child;
+    vector<int> locked;
+
+public:
+    LockingTree(vector<int>& parent) : parent(parent), locked(parent.size()) {
+        int n = parent.size();
+        child.resize(n);
+        for (int node = 1; node < n; node++) {
+            child[parent[node]].push_back(node);
+        }
+    }
+
+    bool lock(int num, int user) {
+        if (locked[num]) {
+            return false;
+        }
+        locked[num] = user;
+        return true;
+    }
+
+    bool unlock(int num, int user) {
+        if (locked[num] != user) {
+            return false;
+        }
+        locked[num] = 0;
+        return true;
+    }
+
+    bool upgrade(int num, int user) {
+        int node = num;
+        while (node != -1) {
+            if (locked[node]) {
+                return false;
+            }
+            node = parent[node];
+        }
+
+        int lockedCount = 0;
+        stack<int> stk;
+        stk.push(num);
+
+        while (!stk.empty()) {
+            node = stk.top(); stk.pop();
+            if (locked[node]) {
+                locked[node] = 0;
+                lockedCount++;
+            }
+            for (int& nei : child[node]) {
+                stk.push(nei);
+            }
+        }
+
+        if (lockedCount > 0) {
+            locked[num] = user;
+            return true;
+        }
+        return false;
+    }
+};
+```
+
+```javascript
+class LockingTree {
+    /**
+     * @constructor
+     * @param {number[]} parent
+     */
+    constructor(parent) {
+        this.parent = parent;
+        this.child = Array.from({ length: parent.length }, () => []);
+        this.locked = new Array(parent.length).fill(0);
+
+        for (let node = 1; node < parent.length; node++) {
+            this.child[parent[node]].push(node);
+        }
+    }
+
+    /** 
+     * @param {number} num 
+     * @param {number} user 
+     * @return {boolean} 
+     */
+    lock(num, user) {
+        if (this.locked[num] !== 0) {
+            return false;
+        }
+        this.locked[num] = user;
+        return true;
+    }
+
+    /** 
+     * @param {number} num
+     * @param {number} user
+     * @return {boolean}
+     */
+    unlock(num, user) {
+        if (this.locked[num] !== user) {
+            return false;
+        }
+        this.locked[num] = 0;
+        return true;
+    }
+
+    /** 
+     * @param {number} num
+     * @param {number} user 
+     * @return {boolean} 
+     */
+    upgrade(num, user) {
+        let node = num;
+        while (node !== -1) {
+            if (this.locked[node] !== 0) {
+                return false;
+            }
+            node = this.parent[node];
+        }
+
+        let lockedCount = 0;
+        let stack = [num];
+
+        while (stack.length) {
+            node = stack.pop();
+            if (this.locked[node]) {
+                this.locked[node] = 0;
+                lockedCount++;
+            }
+            stack.push(...this.child[node]);
+        }
+
+        if (lockedCount > 0) {
+            this.locked[num] = user;
+            return true;
+        }
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(n)$ time for initialization.
+    * $O(1)$ time for each $lock()$ and $unlock()$ function call.
+    * $O(n)$ time for each $upgrade()$ function call.
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/optimal-partition-of-string.md b/articles/optimal-partition-of-string.md
new file mode 100644
index 000000000..c4d89ab77
--- /dev/null
+++ b/articles/optimal-partition-of-string.md
@@ -0,0 +1,250 @@
+## 1. Greedy (Hash Set)
+
+::tabs-start
+
+```python
+class Solution:
+    def partitionString(self, s: str) -> int:
+        curSet = set()
+        res = 1
+        for c in s:
+            if c in curSet:
+                res += 1
+                curSet.clear()
+            curSet.add(c)
+        return res
+```
+
+```java
+public class Solution {
+    public int partitionString(String s) {
+        Set<Character> curSet = new HashSet<>();
+        int res = 1;
+        for (char c : s.toCharArray()) {
+            if (curSet.contains(c)) {
+                res++;
+                curSet.clear();
+            }
+            curSet.add(c);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int partitionString(string s) {
+        unordered_set<char> curSet;
+        int res = 1;
+        for (char c : s) {
+            if (curSet.count(c)) {
+                res++;
+                curSet.clear();
+            }
+            curSet.insert(c);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    partitionString(s) {
+        let curSet = new Set();
+        let res = 1;
+        for (let c of s) {
+            if (curSet.has(c)) {
+                res++;
+                curSet.clear();
+            }
+            curSet.add(c);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ since we have at most $26$ different characters.
+
+---
+
+## 2. Greedy (Array)
+
+::tabs-start
+
+```python
+class Solution:
+    def partitionString(self, s: str) -> int:
+        lastIdx = [-1] * 26
+        res = 1
+        start = 0
+        for i, c in enumerate(s):
+            j = ord(c) - ord('a')
+            if lastIdx[j] >= start:
+                start = i
+                res += 1
+            lastIdx[j] = i
+        return res
+```
+
+```java
+public class Solution {
+    public int partitionString(String s) {
+        int[] lastIdx = new int[26];
+        Arrays.fill(lastIdx, -1);
+        int res = 1, start = 0;
+        for (int i = 0; i < s.length(); i++) {
+            int j = s.charAt(i) - 'a';
+            if (lastIdx[j] >= start) {
+                start = i;
+                res++;
+            }
+            lastIdx[j] = i;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int partitionString(string s) {
+        vector<int> lastIdx(26, -1);
+        int res = 1, start = 0;
+        for (int i = 0; i < s.size(); i++) {
+            int j = s[i] - 'a';
+            if (lastIdx[j] >= start) {
+                start = i;
+                res++;
+            }
+            lastIdx[j] = i;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    partitionString(s) {
+        const lastIdx = Array(26).fill(-1);
+        let res = 1, start = 0;
+        for (let i = 0; i < s.length; i++) {
+            const j = s.charCodeAt(i) - 97;
+            if (lastIdx[j] >= start) {
+                start = i;
+                res++;
+            }
+            lastIdx[j] = i;
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ since we have at most $26$ different characters.
+
+---
+
+## 3. Greedy (Bit Mask)
+
+::tabs-start
+
+```python
+class Solution:
+    def partitionString(self, s: str) -> int:
+        res = 1
+        mask = 0
+        for c in s:
+            i = ord(c) - ord('a')
+            if mask & (1 << i):
+                mask = 0
+                res += 1
+            mask |= (1 << i)
+        return res
+```
+
+```java
+public class Solution {
+    public int partitionString(String s) {
+        int res = 1, mask = 0;
+        for (char c : s.toCharArray()) {
+            int i = c - 'a';
+            if ((mask & (1 << i)) != 0) {
+                mask = 0;
+                res++;
+            }
+            mask |= (1 << i);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int partitionString(string s) {
+        int res = 1, mask = 0;
+        for (char c : s) {
+            int i = c - 'a';
+            if (mask & (1 << i)) {
+                mask = 0;
+                res++;
+            }
+            mask |= (1 << i);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    partitionString(s) {
+        let res = 1, mask = 0;
+        for (const c of s) {
+            const i = c.charCodeAt(0) - 97;
+            if (mask & (1 << i)) {
+                mask = 0;
+                res++;
+            }
+            mask |= (1 << i);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/out-of-boundary-paths.md b/articles/out-of-boundary-paths.md
new file mode 100644
index 000000000..ced7639b1
--- /dev/null
+++ b/articles/out-of-boundary-paths.md
@@ -0,0 +1,525 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def findPaths(self, m: int, n: int, maxMove: int, startRow: int, startColumn: int) -> int:
+        ROWS, COLS = m, n
+        MOD = 10**9 + 7
+
+        def dfs(r, c, moves):
+            if r < 0 or r >= ROWS or c < 0 or c >= COLS:
+                return 1
+            if moves == 0:
+                return 0
+
+            return (
+                dfs(r + 1, c, moves - 1) +
+                dfs(r - 1, c, moves - 1) +
+                dfs(r, c + 1, moves - 1) +
+                dfs(r, c - 1, moves - 1)
+            ) % MOD
+
+        return dfs(startRow, startColumn, maxMove)
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1_000_000_007;
+
+    private int dfs(int r, int c, int moves, int m, int n) {
+        if (r < 0 || r >= m || c < 0 || c >= n) return 1;
+        if (moves == 0) return 0;
+
+        return (
+            (dfs(r + 1, c, moves - 1, m, n) + dfs(r - 1, c, moves - 1, m, n)) % MOD +
+            (dfs(r, c + 1, moves - 1, m, n) + dfs(r, c - 1, moves - 1, m, n)) % MOD
+        ) % MOD;
+    }
+
+    public int findPaths(int m, int n, int maxMove, int startRow, int startColumn) {
+        return dfs(startRow, startColumn, maxMove, m, n);
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    int MOD = 1'000'000'007;
+
+    int dfs(int r, int c, int moves, int m, int n) {
+        if (r < 0 || r >= m || c < 0 || c >= n) return 1;
+        if (moves == 0) return 0;
+
+        return (
+            (dfs(r + 1, c, moves - 1, m, n) + dfs(r - 1, c, moves - 1, m, n)) % MOD +
+            (dfs(r, c + 1, moves - 1, m, n) + dfs(r, c - 1, moves - 1, m, n)) % MOD
+        ) % MOD;
+    }
+
+public:
+    int findPaths(int m, int n, int maxMove, int startRow, int startColumn) {
+        return dfs(startRow, startColumn, maxMove, m, n);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} m
+     * @param {number} n
+     * @param {number} maxMove
+     * @param {number} startRow
+     * @param {number} startColumn
+     * @return {number}
+     */
+    findPaths(m, n, maxMove, startRow, startColumn) {
+        const MOD = 1_000_000_007;
+
+        const dfs = (r, c, moves) => {
+            if (r < 0 || r >= m || c < 0 || c >= n) return 1;
+            if (moves === 0) return 0;
+
+            return (
+                (dfs(r + 1, c, moves - 1) + dfs(r - 1, c, moves - 1)) % MOD +
+                (dfs(r, c + 1, moves - 1) + dfs(r, c - 1, moves - 1)) % MOD
+            ) % MOD;
+        };
+
+        return dfs(startRow, startColumn, maxMove);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(4 ^ N)$
+* Space complexity: $O(N)$
+
+> Where $m$ is the number of rows, $n$ is the number of columns, and $N$ is the maximum number of allowed moves.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def findPaths(self, m: int, n: int, maxMove: int, startRow: int, startColumn: int) -> int:
+        ROWS, COLS = m, n
+        MOD = 10**9 + 7
+        cache = {}
+
+        def dfs(r, c, moves):
+            if r < 0 or r >= ROWS or c < 0 or c >= COLS:
+                return 1
+            if moves == 0:
+                return 0
+            if (r, c, moves) in cache:
+                return cache[(r, c, moves)]
+
+            cache[(r, c, moves)] = (
+                dfs(r + 1, c, moves - 1) +
+                dfs(r - 1, c, moves - 1) +
+                dfs(r, c + 1, moves - 1) +
+                dfs(r, c - 1, moves - 1)
+            ) % MOD
+            return cache[(r, c, moves)]
+
+        return dfs(startRow, startColumn, maxMove)
+```
+
+```java
+public class Solution {
+    private int[][][] dp;
+    private static final int MOD = 1_000_000_007;
+
+    private int dfs(int r, int c, int moves, int m, int n) {
+        if (r < 0 || r >= m || c < 0 || c >= n) return 1;
+        if (moves == 0) return 0;
+        if (dp[r][c][moves] != -1) return dp[r][c][moves];
+
+        dp[r][c][moves] = (
+            (dfs(r + 1, c, moves - 1, m, n) + dfs(r - 1, c, moves - 1, m, n)) % MOD +
+            (dfs(r, c + 1, moves - 1, m, n) + dfs(r, c - 1, moves - 1, m, n)) % MOD
+        ) % MOD;
+        return dp[r][c][moves];
+    }
+
+    public int findPaths(int m, int n, int maxMove, int startRow, int startColumn) {
+        dp = new int[m][n][maxMove + 1];
+        for (int[][] layer : dp) {
+            for (int[] row : layer) {
+                Arrays.fill(row, -1);
+            }
+        }
+        return dfs(startRow, startColumn, maxMove, m, n);
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<vector<vector<int>>> dp;
+    int MOD = 1'000'000'007;
+
+    int dfs(int r, int c, int moves, int m, int n) {
+        if (r < 0 || r >= m || c < 0 || c >= n) return 1;
+        if (moves == 0) return 0;
+        if (dp[r][c][moves] != -1) return dp[r][c][moves];
+
+        dp[r][c][moves] = (
+            (dfs(r + 1, c, moves - 1, m, n) + dfs(r - 1, c, moves - 1, m, n)) % MOD +
+            (dfs(r, c + 1, moves - 1, m, n) + dfs(r, c - 1, moves - 1, m, n)) % MOD
+        ) % MOD;
+        return dp[r][c][moves];
+    }
+
+public:
+    int findPaths(int m, int n, int maxMove, int startRow, int startColumn) {
+        dp = vector<vector<vector<int>>>(m, vector<vector<int>>(n, vector<int>(maxMove + 1, -1)));
+        return dfs(startRow, startColumn, maxMove, m, n);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} m
+     * @param {number} n
+     * @param {number} maxMove
+     * @param {number} startRow
+     * @param {number} startColumn
+     * @return {number}
+     */
+    findPaths(m, n, maxMove, startRow, startColumn) {
+        const MOD = 1_000_000_007;
+        const dp = Array.from({ length: m }, () => 
+            Array.from({ length: n }, () => Array(maxMove + 1).fill(-1))
+        );
+
+        const dfs = (r, c, moves) => {
+            if (r < 0 || r >= m || c < 0 || c >= n) return 1;
+            if (moves === 0) return 0;
+            if (dp[r][c][moves] !== -1) return dp[r][c][moves];
+
+            dp[r][c][moves] = (
+                (dfs(r + 1, c, moves - 1) + dfs(r - 1, c, moves - 1)) % MOD +
+                (dfs(r, c + 1, moves - 1) + dfs(r, c - 1, moves - 1)) % MOD
+            ) % MOD;
+            return dp[r][c][moves];
+        };
+
+        return dfs(startRow, startColumn, maxMove);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n * N)$
+* Space complexity: $O(m * n * N)$
+
+> Where $m$ is the number of rows, $n$ is the number of columns, and $N$ is the maximum number of allowed moves.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def findPaths(self, m: int, n: int, maxMove: int, startRow: int, startColumn: int) -> int:
+        MOD = 10**9 + 7
+        dp = [[[0] * (maxMove + 1) for _ in range(n)] for _ in range(m)]
+
+        for moves in range(1, maxMove + 1):
+            for r in range(m):
+                for c in range(n):
+                    dp[r][c][moves] = (
+                        (dp[r - 1][c][moves - 1] if r > 0 else 1) +
+                        (dp[r + 1][c][moves - 1] if r < m - 1 else 1) +
+                        (dp[r][c - 1][moves - 1] if c > 0 else 1) +
+                        (dp[r][c + 1][moves - 1] if c < n - 1 else 1)
+                    ) % MOD
+
+        return dp[startRow][startColumn][maxMove]
+```
+
+```java
+public class Solution {
+    public int findPaths(int m, int n, int maxMove, int startRow, int startColumn) {
+        final int MOD = 1_000_000_007;
+        int[][][] dp = new int[m][n][maxMove + 1];
+
+        for (int moves = 1; moves <= maxMove; moves++) {
+            for (int r = 0; r < m; r++) {
+                for (int c = 0; c < n; c++) {
+                    long up = (r > 0) ? dp[r - 1][c][moves - 1] : 1;
+                    long down = (r < m - 1) ? dp[r + 1][c][moves - 1] : 1;
+                    long left = (c > 0) ? dp[r][c - 1][moves - 1] : 1;
+                    long right = (c < n - 1) ? dp[r][c + 1][moves - 1] : 1;
+
+                    dp[r][c][moves] = (int) ((up + down + left + right) % MOD);
+                }
+            }
+        }
+
+        return dp[startRow][startColumn][maxMove];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findPaths(int m, int n, int maxMove, int startRow, int startColumn) {
+        const int MOD = 1'000'000'007;
+        vector<vector<vector<uint>>> dp(m, vector<vector<uint>>(n, vector<uint>(maxMove + 1, 0)));
+
+        for (int moves = 1; moves <= maxMove; moves++) {
+            for (int r = 0; r < m; r++) {
+                for (int c = 0; c < n; c++) {
+                    dp[r][c][moves] = (
+                        (r > 0 ? dp[r - 1][c][moves - 1] : 1) +
+                        (r < m - 1 ? dp[r + 1][c][moves - 1] : 1) +
+                        (c > 0 ? dp[r][c - 1][moves - 1] : 1) +
+                        (c < n - 1 ? dp[r][c + 1][moves - 1] : 1)
+                    ) % MOD;
+                }
+            }
+        }
+
+        return dp[startRow][startColumn][maxMove];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} m
+     * @param {number} n
+     * @param {number} maxMove
+     * @param {number} startRow
+     * @param {number} startColumn
+     * @return {number}
+     */
+    findPaths(m, n, maxMove, startRow, startColumn) {
+        const MOD = 1_000_000_007;
+        const dp = Array.from({ length: m }, () =>
+            Array.from({ length: n }, () => Array(maxMove + 1).fill(0))
+        );
+
+        for (let moves = 1; moves <= maxMove; moves++) {
+            for (let r = 0; r < m; r++) {
+                for (let c = 0; c < n; c++) {
+                    dp[r][c][moves] = (
+                        (r > 0 ? dp[r - 1][c][moves - 1] : 1) +
+                        (r < m - 1 ? dp[r + 1][c][moves - 1] : 1) +
+                        (c > 0 ? dp[r][c - 1][moves - 1] : 1) +
+                        (c < n - 1 ? dp[r][c + 1][moves - 1] : 1)
+                    ) % MOD;
+                }
+            }
+        }
+
+        return dp[startRow][startColumn][maxMove];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n * N)$
+* Space complexity: $O(m * n * N)$
+
+> Where $m$ is the number of rows, $n$ is the number of columns, and $N$ is the maximum number of allowed moves.
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def findPaths(self, m: int, n: int, maxMove: int, startRow: int, startColumn: int) -> int:
+        MOD = 10**9 + 7
+        dp = [[0] * n for _ in range(m)]
+
+        for moves in range(1, maxMove + 1):
+            tmp = [[0] * n for _ in range(m)]
+            for r in range(m):
+                for c in range(n):
+                    if r + 1 == m:
+                        tmp[r][c] = (tmp[r][c] + 1) % MOD
+                    else:
+                        tmp[r][c] = (tmp[r][c] + dp[r + 1][c]) % MOD
+                    if r - 1 < 0:
+                        tmp[r][c] = (tmp[r][c] + 1) % MOD
+                    else:
+                        tmp[r][c] = (tmp[r][c] + dp[r - 1][c]) % MOD
+                    if c + 1 == n:
+                        tmp[r][c] = (tmp[r][c] + 1) % MOD
+                    else:
+                        tmp[r][c] = (tmp[r][c] + dp[r][c + 1]) % MOD
+                    if c - 1 < 0:
+                        tmp[r][c] = (tmp[r][c] + 1) % MOD
+                    else:
+                        tmp[r][c] = (tmp[r][c] + dp[r][c - 1]) % MOD
+            dp = tmp
+
+        return dp[startRow][startColumn]
+```
+
+```java
+public class Solution {
+    public int findPaths(int m, int n, int maxMove, int startRow, int startColumn) {
+        final int MOD = 1_000_000_007;
+        int[][] dp = new int[m][n];
+
+        for (int moves = 1; moves <= maxMove; moves++) {
+            int[][] tmp = new int[m][n];
+            for (int r = 0; r < m; r++) {
+                for (int c = 0; c < n; c++) {
+                    if (r + 1 == m) {
+                        tmp[r][c] = (tmp[r][c] + 1) % MOD;
+                    } else {
+                        tmp[r][c] = (tmp[r][c] + dp[r + 1][c]) % MOD;
+                    }
+                    if (r - 1 < 0) {
+                        tmp[r][c] = (tmp[r][c] + 1) % MOD;
+                    } else {
+                        tmp[r][c] = (tmp[r][c] + dp[r - 1][c]) % MOD;
+                    }
+                    if (c + 1 == n) {
+                        tmp[r][c] = (tmp[r][c] + 1) % MOD;
+                    } else {
+                        tmp[r][c] = (tmp[r][c] + dp[r][c + 1]) % MOD;
+                    }
+                    if (c - 1 < 0) {
+                        tmp[r][c] = (tmp[r][c] + 1) % MOD;
+                    } else {
+                        tmp[r][c] = (tmp[r][c] + dp[r][c - 1]) % MOD;
+                    }
+                }
+            }
+            dp = tmp;
+        }
+
+        return dp[startRow][startColumn];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int findPaths(int m, int n, int maxMove, int startRow, int startColumn) {
+        const int MOD = 1'000'000'007;
+        vector<vector<int>> dp(m, vector<int>(n, 0));
+
+        for (int moves = 1; moves <= maxMove; moves++) {
+            vector<vector<int>> tmp(m, vector<int>(n, 0));
+            for (int r = 0; r < m; r++) {
+                for (int c = 0; c < n; c++) {
+                    if (r + 1 == m) {
+                        tmp[r][c] = (tmp[r][c] + 1) % MOD;
+                    } else {
+                        tmp[r][c] = (tmp[r][c] + dp[r + 1][c]) % MOD;
+                    }
+                    if (r - 1 < 0) {
+                        tmp[r][c] = (tmp[r][c] + 1) % MOD;
+                    } else {
+                        tmp[r][c] = (tmp[r][c] + dp[r - 1][c]) % MOD;
+                    }
+                    if (c + 1 == n) {
+                        tmp[r][c] = (tmp[r][c] + 1) % MOD;
+                    } else {
+                        tmp[r][c] = (tmp[r][c] + dp[r][c + 1]) % MOD;
+                    }
+                    if (c - 1 < 0) {
+                        tmp[r][c] = (tmp[r][c] + 1) % MOD;
+                    } else {
+                        tmp[r][c] = (tmp[r][c] + dp[r][c - 1]) % MOD;
+                    }
+                }
+            }
+            dp = tmp;
+        }
+
+        return dp[startRow][startColumn];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} m
+     * @param {number} n
+     * @param {number} maxMove
+     * @param {number} startRow
+     * @param {number} startColumn
+     * @return {number}
+     */
+    findPaths(m, n, maxMove, startRow, startColumn) {
+        const MOD = 1_000_000_007;
+        let dp = Array.from({ length: m }, () => Array(n).fill(0));
+
+        for (let moves = 1; moves <= maxMove; moves++) {
+            const tmp = Array.from({ length: m }, () => Array(n).fill(0));
+            for (let r = 0; r < m; r++) {
+                for (let c = 0; c < n; c++) {
+                    if (r + 1 === m) {
+                        tmp[r][c] = (tmp[r][c] + 1) % MOD;
+                    } else {
+                        tmp[r][c] = (tmp[r][c] + dp[r + 1][c]) % MOD;
+                    }
+                    if (r - 1 < 0) {
+                        tmp[r][c] = (tmp[r][c] + 1) % MOD;
+                    } else {
+                        tmp[r][c] = (tmp[r][c] + dp[r - 1][c]) % MOD;
+                    }
+                    if (c + 1 === n) {
+                        tmp[r][c] = (tmp[r][c] + 1) % MOD;
+                    } else {
+                        tmp[r][c] = (tmp[r][c] + dp[r][c + 1]) % MOD;
+                    }
+                    if (c - 1 < 0) {
+                        tmp[r][c] = (tmp[r][c] + 1) % MOD;
+                    } else {
+                        tmp[r][c] = (tmp[r][c] + dp[r][c - 1]) % MOD;
+                    }
+                }
+            }
+            dp = tmp;
+        }
+
+        return dp[startRow][startColumn];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n * N)$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows, $n$ is the number of columns, and $N$ is the maximum number of allowed moves.
\ No newline at end of file
diff --git a/articles/pacific-atlantic-water-flow.md b/articles/pacific-atlantic-water-flow.md
index 570d6eb22..1245a570d 100644
--- a/articles/pacific-atlantic-water-flow.md
+++ b/articles/pacific-atlantic-water-flow.md
@@ -1,4 +1,4 @@
-## 1. Backtracking
+## 1. Brute Force (Backtracking)
 
 ::tabs-start
 
@@ -247,6 +247,161 @@ public class Solution {
 }
 ```
 
+```go
+func pacificAtlantic(heights [][]int) [][]int {
+    rows, cols := len(heights), len(heights[0])
+    directions := [][]int{{1, 0}, {-1, 0}, {0, 1}, {0, -1}}
+    result := make([][]int, 0)
+    
+    var pacific, atlantic bool
+    
+    var dfs func(r, c int, prevVal int)
+    dfs = func(r, c int, prevVal int) {
+        if r < 0 || c < 0 {
+            pacific = true
+            return
+        }
+        if r >= rows || c >= cols {
+            atlantic = true
+            return
+        }
+        if heights[r][c] > prevVal {
+            return
+        }
+        
+        tmp := heights[r][c]
+        heights[r][c] = int(^uint(0) >> 1)
+        
+        for _, dir := range directions {
+            dfs(r + dir[0], c + dir[1], tmp)
+            if pacific && atlantic {
+                break
+            }
+        }
+        heights[r][c] = tmp
+    }
+    
+    for r := 0; r < rows; r++ {
+        for c := 0; c < cols; c++ {
+            pacific = false
+            atlantic = false
+            dfs(r, c, int(^uint(0) >> 1))
+            if pacific && atlantic {
+                result = append(result, []int{r, c})
+            }
+        }
+    }
+    
+    return result
+}
+```
+
+```kotlin
+class Solution {
+    private var pacific = false
+    private var atlantic = false
+    private val directions = arrayOf(
+        intArrayOf(1, 0),
+        intArrayOf(-1, 0),
+        intArrayOf(0, 1),
+        intArrayOf(0, -1)
+    )
+    
+    fun pacificAtlantic(heights: Array<IntArray>): List<List<Int>> {
+        val rows = heights.size
+        val cols = heights[0].size
+        val result = mutableListOf<List<Int>>()
+        
+        fun dfs(r: Int, c: Int, prevVal: Int) {
+            when {
+                r < 0 || c < 0 -> {
+                    pacific = true
+                    return
+                }
+                r >= rows || c >= cols -> {
+                    atlantic = true
+                    return
+                }
+                heights[r][c] > prevVal -> return
+            }
+            
+            val tmp = heights[r][c]
+            heights[r][c] = Int.MAX_VALUE
+            
+            for (dir in directions) {
+                dfs(r + dir[0], c + dir[1], tmp)
+                if (pacific && atlantic) break
+            }
+            heights[r][c] = tmp
+        }
+        
+        for (r in 0 until rows) {
+            for (c in 0 until cols) {
+                pacific = false
+                atlantic = false
+                dfs(r, c, Int.MAX_VALUE)
+                if (pacific && atlantic) {
+                    result.add(listOf(r, c))
+                }
+            }
+        }
+        
+        return result
+    }
+}
+```
+
+```swift
+class Solution {
+    func pacificAtlantic(_ heights: [[Int]]) -> [[Int]] {
+        var heights = heights
+        let ROWS = heights.count
+        let COLS = heights[0].count
+        let directions = [(1, 0), (-1, 0), (0, 1), (0, -1)]
+
+        var pacific = false
+        var atlantic = false
+
+        func dfs(_ r: Int, _ c: Int, _ prevVal: Int) {
+            if r < 0 || c < 0 {
+                pacific = true
+                return
+            }
+            if r >= ROWS || c >= COLS {
+                atlantic = true
+                return
+            }
+            if heights[r][c] > prevVal {
+                return
+            }
+
+            let tmp = heights[r][c]
+            heights[r][c] = Int.max
+            for dir in directions {
+                dfs(r + dir.0, c + dir.1, tmp)
+                if pacific && atlantic {
+                    break
+                }
+            }
+            heights[r][c] = tmp
+        }
+
+        var res = [[Int]]()
+        for r in 0..<ROWS {
+            for c in 0..<COLS {
+                pacific = false
+                atlantic = false
+                dfs(r, c, Int.max)
+                if pacific && atlantic {
+                    res.append([r, c])
+                }
+            }
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -478,6 +633,144 @@ public class Solution {
 }
 ```
 
+```go
+func pacificAtlantic(heights [][]int) [][]int {
+    rows, cols := len(heights), len(heights[0])
+    pac := make(map[[2]int]bool)
+    atl := make(map[[2]int]bool)
+    
+    var dfs func(r, c int, visit map[[2]int]bool, prevHeight int)
+    dfs = func(r, c int, visit map[[2]int]bool, prevHeight int) {
+        coord := [2]int{r, c}
+        if visit[coord] ||
+           r < 0 || c < 0 ||
+           r == rows || c == cols ||
+           heights[r][c] < prevHeight {
+            return
+        }
+        
+        visit[coord] = true
+        
+        dfs(r+1, c, visit, heights[r][c])
+        dfs(r-1, c, visit, heights[r][c])
+        dfs(r, c+1, visit, heights[r][c])
+        dfs(r, c-1, visit, heights[r][c])
+    }
+    
+    for c := 0; c < cols; c++ {
+        dfs(0, c, pac, heights[0][c])
+        dfs(rows-1, c, atl, heights[rows-1][c])
+    }
+    
+    for r := 0; r < rows; r++ {
+        dfs(r, 0, pac, heights[r][0])
+        dfs(r, cols-1, atl, heights[r][cols-1])
+    }
+    
+    result := make([][]int, 0)
+    for r := 0; r < rows; r++ {
+        for c := 0; c < cols; c++ {
+            coord := [2]int{r, c}
+            if pac[coord] && atl[coord] {
+                result = append(result, []int{r, c})
+            }
+        }
+    }
+    
+    return result
+}
+```
+
+```kotlin
+class Solution {
+    fun pacificAtlantic(heights: Array<IntArray>): List<List<Int>> {
+        val rows = heights.size
+        val cols = heights[0].size
+        val pac = HashSet<Pair<Int, Int>>()
+        val atl = HashSet<Pair<Int, Int>>()
+        
+        fun dfs(r: Int, c: Int, visit: HashSet<Pair<Int, Int>>, prevHeight: Int) {
+            val coord = r to c
+            if (coord in visit ||
+                r < 0 || c < 0 ||
+                r == rows || c == cols ||
+                heights[r][c] < prevHeight
+            ) {
+                return
+            }
+            
+            visit.add(coord)
+            
+            dfs(r + 1, c, visit, heights[r][c])
+            dfs(r - 1, c, visit, heights[r][c])
+            dfs(r, c + 1, visit, heights[r][c])
+            dfs(r, c - 1, visit, heights[r][c])
+        }
+        
+        for (c in 0 until cols) {
+            dfs(0, c, pac, heights[0][c])
+            dfs(rows - 1, c, atl, heights[rows - 1][c])
+        }
+        
+        for (r in 0 until rows) {
+            dfs(r, 0, pac, heights[r][0])
+            dfs(r, cols - 1, atl, heights[r][cols - 1])
+        }
+        
+        return (0 until rows).flatMap { r ->
+            (0 until cols).mapNotNull { c ->
+                if ((r to c) in pac && (r to c) in atl) {
+                    listOf(r, c)
+                } else null
+            }
+        }
+    }
+}
+```
+
+```swift
+class Solution {
+    func pacificAtlantic(_ heights: [[Int]]) -> [[Int]] {
+        let ROWS = heights.count
+        let COLS = heights[0].count
+        var pac = Set<[Int]>()
+        var atl = Set<[Int]>()
+
+        func dfs(_ r: Int, _ c: Int, _ visit: inout Set<[Int]>, _ prevHeight: Int) {
+            if (visit.contains([r, c]) || r < 0 || c < 0 || r == ROWS ||
+                c == COLS || heights[r][c] < prevHeight) {
+                return
+            }
+            visit.insert([r, c])
+            dfs(r + 1, c, &visit, heights[r][c])
+            dfs(r - 1, c, &visit, heights[r][c])
+            dfs(r, c + 1, &visit, heights[r][c])
+            dfs(r, c - 1, &visit, heights[r][c])
+        }
+
+        for c in 0..<COLS {
+            dfs(0, c, &pac, heights[0][c])
+            dfs(ROWS - 1, c, &atl, heights[ROWS - 1][c])
+        }
+
+        for r in 0..<ROWS {
+            dfs(r, 0, &pac, heights[r][0])
+            dfs(r, COLS - 1, &atl, heights[r][COLS - 1])
+        }
+
+        var res = [[Int]]()
+        for r in 0..<ROWS {
+            for c in 0..<COLS {
+                if pac.contains([r, c]) && atl.contains([r, c]) {
+                    res.append([r, c])
+                }
+            }
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -751,6 +1044,176 @@ public class Solution {
 }
 ```
 
+```go
+func pacificAtlantic(heights [][]int) [][]int {
+    rows, cols := len(heights), len(heights[0])
+    directions := [][]int{{1, 0}, {-1, 0}, {0, 1}, {0, -1}}
+    
+    pac := make([][]bool, rows)
+    atl := make([][]bool, rows)
+    for i := range pac {
+        pac[i] = make([]bool, cols)
+        atl[i] = make([]bool, cols)
+    }
+
+    bfs := func(source [][2]int, ocean [][]bool) {
+        q := list.New()
+        for _, s := range source {
+            q.PushBack(s)
+        }
+        for q.Len() > 0 {
+            element := q.Front()
+            q.Remove(element)
+            r, c := element.Value.([2]int)[0], element.Value.([2]int)[1]
+            ocean[r][c] = true
+            for _, dir := range directions {
+                nr, nc := r+dir[0], c+dir[1]
+                if nr >= 0 && nr < rows && nc >= 0 && nc < cols &&
+                    !ocean[nr][nc] && heights[nr][nc] >= heights[r][c] {
+                    q.PushBack([2]int{nr, nc})
+                }
+            }
+        }
+    }
+
+    pacific := [][2]int{}
+    atlantic := [][2]int{}
+    for c := 0; c < cols; c++ {
+        pacific = append(pacific, [2]int{0, c})
+        atlantic = append(atlantic, [2]int{rows - 1, c})
+    }
+    for r := 0; r < rows; r++ {
+        pacific = append(pacific, [2]int{r, 0})
+        atlantic = append(atlantic, [2]int{r, cols - 1})
+    }
+
+    bfs(pacific, pac)
+    bfs(atlantic, atl)
+
+    res := [][]int{}
+    for r := 0; r < rows; r++ {
+        for c := 0; c < cols; c++ {
+            if pac[r][c] && atl[r][c] {
+                res = append(res, []int{r, c})
+            }
+        }
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun pacificAtlantic(heights: Array<IntArray>): List<List<Int>> {
+        val rows = heights.size
+        val cols = heights[0].size
+        val directions = arrayOf(intArrayOf(1, 0), 
+                                 intArrayOf(-1, 0), 
+                                 intArrayOf(0, 1), 
+                                 intArrayOf(0, -1))
+        
+        val pac = Array(rows) { BooleanArray(cols) }
+        val atl = Array(rows) { BooleanArray(cols) }
+
+        fun bfs(source: List<IntArray>, ocean: Array<BooleanArray>) {
+            val q = LinkedList<IntArray>()
+            q.addAll(source)
+            while (q.isNotEmpty()) {
+                val (r, c) = q.poll()
+                ocean[r][c] = true
+                for (dir in directions) {
+                    val nr = r + dir[0]
+                    val nc = c + dir[1]
+                    if (nr in 0 until rows && nc in 0 until cols &&
+                        !ocean[nr][nc] && heights[nr][nc] >= heights[r][c]) {
+                        q.offer(intArrayOf(nr, nc))
+                    }
+                }
+            }
+        }
+
+        val pacific = mutableListOf<IntArray>()
+        val atlantic = mutableListOf<IntArray>()
+        for (c in 0 until cols) {
+            pacific.add(intArrayOf(0, c))
+            atlantic.add(intArrayOf(rows - 1, c))
+        }
+        for (r in 0 until rows) {
+            pacific.add(intArrayOf(r, 0))
+            atlantic.add(intArrayOf(r, cols - 1))
+        }
+
+        bfs(pacific, pac)
+        bfs(atlantic, atl)
+
+        val result = mutableListOf<List<Int>>()
+        for (r in 0 until rows) {
+            for (c in 0 until cols) {
+                if (pac[r][c] && atl[r][c]) {
+                    result.add(listOf(r, c))
+                }
+            }
+        }
+        return result
+    }
+}
+```
+
+```swift
+class Solution {
+    func pacificAtlantic(_ heights: [[Int]]) -> [[Int]] {
+        let ROWS = heights.count
+        let COLS = heights[0].count
+        let directions = [(1, 0), (-1, 0), (0, 1), (0, -1)]
+
+        var pac = Array(repeating: Array(repeating: false, count: COLS), count: ROWS)
+        var atl = Array(repeating: Array(repeating: false, count: COLS), count: ROWS)
+
+        func bfs(_ source: [(Int, Int)], _ ocean: inout [[Bool]]) {
+            var queue = Deque(source)
+            while !queue.isEmpty {
+                let (r, c) = queue.popFirst()!
+                ocean[r][c] = true
+                for dir in directions {
+                    let nr = r + dir.0
+                    let nc = c + dir.1
+                    if nr >= 0, nr < ROWS, nc >= 0, nc < COLS, 
+                       !ocean[nr][nc], heights[nr][nc] >= heights[r][c] {
+                        queue.append((nr, nc))
+                    }
+                }
+            }
+        }
+
+        var pacific: [(Int, Int)] = []
+        var atlantic: [(Int, Int)] = []
+
+        for c in 0..<COLS {
+            pacific.append((0, c))
+            atlantic.append((ROWS - 1, c))
+        }
+
+        for r in 0..<ROWS {
+            pacific.append((r, 0))
+            atlantic.append((r, COLS - 1))
+        }
+
+        bfs(pacific, &pac)
+        bfs(atlantic, &atl)
+
+        var res = [[Int]]()
+        for r in 0..<ROWS {
+            for c in 0..<COLS {
+                if pac[r][c] && atl[r][c] {
+                    res.append([r, c])
+                }
+            }
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/paint-house.md b/articles/paint-house.md
new file mode 100644
index 000000000..91b9896cd
--- /dev/null
+++ b/articles/paint-house.md
@@ -0,0 +1,445 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def min_cost(self, costs: List[List[int]]) -> int:
+        n = len(costs)
+
+        def dfs(i, prevColor):
+            if i == n:
+                return 0
+
+            res = float("inf")
+            for c in range(3):
+                if c == prevColor:
+                    continue
+                res = min(res, costs[i][c] + dfs(i + 1, c))
+            return res
+
+        return dfs(0, -1)
+```
+
+```java
+public class Solution {
+    private int[][] costs;
+    private int n;
+
+    public int minCost(int[][] costs) {
+        this.costs = costs;
+        this.n = costs.length;
+        return dfs(0, -1);
+    }
+
+    private int dfs(int i, int prevColor) {
+        if (i == n) {
+            return 0;
+        }
+
+        int res = Integer.MAX_VALUE;
+        for (int c = 0; c < 3; c++) {
+            if (c == prevColor) {
+                continue;
+            }
+            res = Math.min(res, costs[i][c] + dfs(i + 1, c));
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<vector<int>> costs;
+    int n;
+
+    int dfs(int i, int prevColor) {
+        if (i == n) {
+            return 0;
+        }
+
+        int res = INT_MAX;
+        for (int c = 0; c < 3; c++) {
+            if (c == prevColor) {
+                continue;
+            }
+            res = min(res, costs[i][c] + dfs(i + 1, c));
+        }
+        return res;
+    }
+
+public:
+    int minCost(vector<vector<int>>& costs) {
+        this->costs = costs;
+        this->n = costs.size();
+        return dfs(0, -1);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} costs
+     * @return {number}
+     */
+    minCost(costs) {
+        const n = costs.length;
+
+        const dfs = (i, prevColor) => {
+            if (i === n) return 0;
+
+            let res = Infinity;
+            for (let c = 0; c < 3; c++) {
+                if (c === prevColor) continue;
+                res = Math.min(res, costs[i][c] + dfs(i + 1, c));
+            }
+            return res;
+        };
+
+        return dfs(0, -1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def min_cost(self, costs: List[List[int]]) -> int:
+        n = len(costs)
+        dp = [[-1] * 4 for _ in range(n)]
+
+        def dfs(i, prevColor):
+            if i == n:
+                return 0
+            if dp[i][prevColor + 1] != -1:
+                return dp[i][prevColor + 1]
+
+            res = float("inf")
+            for c in range(3):
+                if c == prevColor:
+                    continue
+                res = min(res, costs[i][c] + dfs(i + 1, c))
+
+            dp[i][prevColor + 1] = res
+            return res
+
+        return dfs(0, -1)
+```
+
+```java
+public class Solution {
+    private int[][] dp;
+    private int[][] costs;
+
+    public int minCost(int[][] costs) {
+        int n = costs.length;
+        this.costs = costs;
+        this.dp = new int[n][4];
+
+        for (int i = 0; i < n; i++) {
+            Arrays.fill(dp[i], -1);
+        }
+
+        return dfs(0, -1);
+    }
+
+    private int dfs(int i, int prevColor) {
+        if (i == costs.length) {
+            return 0;
+        }
+        if (dp[i][prevColor + 1] != -1) {
+            return dp[i][prevColor + 1];
+        }
+
+        int res = Integer.MAX_VALUE;
+        for (int c = 0; c < 3; c++) {
+            if (c == prevColor) continue;
+            res = Math.min(res, costs[i][c] + dfs(i + 1, c));
+        }
+
+        return dp[i][prevColor + 1] = res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> dp;
+    vector<vector<int>> costs;
+
+    int minCost(vector<vector<int>>& costs) {
+        int n = costs.size();
+        this->costs = costs;
+        dp.assign(n, vector<int>(4, -1));
+        return dfs(0, -1);
+    }
+
+private:
+    int dfs(int i, int prevColor) {
+        if (i == costs.size()) {
+            return 0;
+        }
+        if (dp[i][prevColor + 1] != -1) {
+            return dp[i][prevColor + 1];
+        }
+
+        int res = INT_MAX;
+        for (int c = 0; c < 3; c++) {
+            if (c == prevColor) continue;
+            res = min(res, costs[i][c] + dfs(i + 1, c));
+        }
+
+        return dp[i][prevColor + 1] = res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} costs
+     * @return {number}
+     */
+    minCost(costs) {
+        const n = costs.length;
+        const dp = Array.from({ length: n }, () => Array(4).fill(-1));
+
+        const dfs = (i, prevColor) => {
+            if (i === n) {
+                return 0;
+            }
+            if (dp[i][prevColor + 1] !== -1) {
+                return dp[i][prevColor + 1];
+            }
+
+            let res = Infinity;
+            for (let c = 0; c < 3; c++) {
+                if (c === prevColor) continue;
+                res = Math.min(res, costs[i][c] + dfs(i + 1, c));
+            }
+
+            return (dp[i][prevColor + 1] = res);
+        };
+
+        return dfs(0, -1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def min_cost(self, costs: List[List[int]]) -> int:
+        n = len(costs)
+        if n == 0:
+            return 0
+        
+        dp = [[0] * 3 for _ in range(n)]
+        for c in range(3):
+            dp[0][c] = costs[0][c]
+
+        for i in range(1, n):
+            for c in range(3):
+                dp[i][c] = (
+                    costs[i][c] +
+                    min(dp[i - 1][(c + 1) % 3], dp[i - 1][(c + 2) % 3])
+                )
+
+        return min(dp[n - 1])
+```
+
+```java
+public class Solution {
+    public int minCost(int[][] costs) {
+        int n = costs.length;
+        if (n == 0) return 0;
+
+        int[][] dp = new int[n][3];
+        for (int c = 0; c < 3; c++) {
+            dp[0][c] = costs[0][c];
+        }
+
+        for (int i = 1; i < n; i++) {
+            for (int c = 0; c < 3; c++) {
+                dp[i][c] = costs[i][c] +
+                           Math.min(dp[i - 1][(c + 1) % 3], dp[i - 1][(c + 2) % 3]);
+            }
+        }
+
+        return Math.min(dp[n - 1][0], Math.min(dp[n - 1][1], dp[n - 1][2]));
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minCost(vector<vector<int>>& costs) {
+        int n = costs.size();
+        if (n == 0) return 0;
+
+        vector<vector<int>> dp(n, vector<int>(3, 0));
+        for (int c = 0; c < 3; c++) {
+            dp[0][c] = costs[0][c];
+        }
+
+        for (int i = 1; i < n; i++) {
+            for (int c = 0; c < 3; c++) {
+                dp[i][c] = costs[i][c] +
+                           min(dp[i - 1][(c + 1) % 3], dp[i - 1][(c + 2) % 3]);
+            }
+        }
+
+        return min({dp[n - 1][0], dp[n - 1][1], dp[n - 1][2]});
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} costs
+     * @return {number}
+     */
+    minCost(costs) {
+        let n = costs.length;
+        if (n === 0) return 0;
+
+        let dp = Array.from({ length: n }, () => Array(3).fill(0));
+        for (let c = 0; c < 3; c++) {
+            dp[0][c] = costs[0][c];
+        }
+
+        for (let i = 1; i < n; i++) {
+            for (let c = 0; c < 3; c++) {
+                dp[i][c] = costs[i][c] +
+                           Math.min(dp[i - 1][(c + 1) % 3], dp[i - 1][(c + 2) % 3]);
+            }
+        }
+
+        return Math.min(dp[n - 1][0], dp[n - 1][1], dp[n - 1][2]);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def minCost(self, costs: List[List[int]]) -> int:
+        dp = [0, 0, 0]
+
+        for i in range(len(costs)):
+            dp0 = costs[i][0] + min(dp[1], dp[2])
+            dp1 = costs[i][1] + min(dp[0], dp[2])
+            dp2 = costs[i][2] + min(dp[0], dp[1])
+            dp = [dp0, dp1, dp2]
+
+        return min(dp)
+```
+
+```java
+public class Solution {
+    public int minCost(int[][] costs) {
+        int dp0 = 0, dp1 = 0, dp2 = 0;
+
+        for (int i = 0; i < costs.length; i++) {
+            int newDp0 = costs[i][0] + Math.min(dp1, dp2);
+            int newDp1 = costs[i][1] + Math.min(dp0, dp2);
+            int newDp2 = costs[i][2] + Math.min(dp0, dp1);
+            dp0 = newDp0;
+            dp1 = newDp1;
+            dp2 = newDp2;
+        }
+
+        return Math.min(dp0, Math.min(dp1, dp2));
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minCost(vector<vector<int>>& costs) {
+        int dp0 = 0, dp1 = 0, dp2 = 0;
+
+        for (const auto& cost : costs) {
+            int newDp0 = cost[0] + min(dp1, dp2);
+            int newDp1 = cost[1] + min(dp0, dp2);
+            int newDp2 = cost[2] + min(dp0, dp1);
+            dp0 = newDp0;
+            dp1 = newDp1;
+            dp2 = newDp2;
+        }
+
+        return min({dp0, dp1, dp2});
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} costs
+     * @return {number}
+     */
+    minCost(costs) {
+        let dp = [0, 0, 0];
+
+        for (let i = 0; i < costs.length; i++) {
+            let dp0 = costs[i][0] + Math.min(dp[1], dp[2]);
+            let dp1 = costs[i][1] + Math.min(dp[0], dp[2]);
+            let dp2 = costs[i][2] + Math.min(dp[0], dp[1]);
+            dp = [dp0, dp1, dp2];
+        }
+
+        return Math.min(dp[0], dp[1], dp[2]);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/painting-the-walls.md b/articles/painting-the-walls.md
new file mode 100644
index 000000000..1942d0042
--- /dev/null
+++ b/articles/painting-the-walls.md
@@ -0,0 +1,430 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def paintWalls(self, cost: List[int], time: List[int]) -> int:
+
+        def dfs(i, remain):
+            if remain <= 0:
+                return 0
+            if i == len(cost):
+                return float("inf")
+            
+            paint = cost[i] + dfs(i + 1, remain - 1 - time[i])
+            skip = dfs(i + 1, remain)
+            return min(paint, skip)
+
+        return dfs(0, len(cost))
+```
+
+```java
+public class Solution {
+    public int paintWalls(int[] cost, int[] time) {
+        return dfs(cost, time, 0, cost.length);
+    }
+
+    private int dfs(int[] cost, int[] time, int i, int remain) {
+        if (remain <= 0) {
+            return 0;
+        }
+        if (i == cost.length) {
+            return Integer.MAX_VALUE;
+        }
+
+        int paint = dfs(cost, time, i + 1, remain - 1 - time[i]);
+        if (paint != Integer.MAX_VALUE) paint += cost[i];
+        int skip = dfs(cost, time, i + 1, remain);
+        return Math.min(paint, skip);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int paintWalls(vector<int>& cost, vector<int>& time) {
+        return dfs(cost, time, 0, cost.size());
+    }
+
+private:
+    int dfs(vector<int>& cost, vector<int>& time, int i, int remain) {
+        if (remain <= 0) {
+            return 0;
+        }
+        if (i == cost.size()) {
+            return INT_MAX;
+        }
+
+        int paint = dfs(cost, time, i + 1, remain - 1 - time[i]);
+        if (paint != INT_MAX) paint += cost[i];
+        
+        int skip = dfs(cost, time, i + 1, remain);
+        return min(paint, skip);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} cost
+     * @param {number[]} time
+     * @return {number}
+     */
+    paintWalls(cost, time) {
+        const dfs = (i, remain) => {
+            if (remain <= 0) {
+                return 0;
+            }
+            if (i === cost.length) {
+                return Infinity;
+            }
+
+            const paint = cost[i] + dfs(i + 1, remain - 1 - time[i]);
+            const skip = dfs(i + 1, remain);
+            return Math.min(paint, skip);
+        };
+
+        return dfs(0, cost.length);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def paintWalls(self, cost: List[int], time: List[int]) -> int:
+        dp = {}
+
+        def dfs(i, remain):
+            if remain <= 0:
+                return 0
+            if i == len(cost):
+                return float("inf")
+            if (i, remain) in dp:
+                return dp[(i, remain)]
+            
+            paint = cost[i] + dfs(i + 1, remain - 1 - time[i])
+            skip = dfs(i + 1, remain)
+            dp[(i, remain)] = min(paint, skip)
+            return dp[(i, remain)]
+
+        return dfs(0, len(cost))
+```
+
+```java
+public class Solution {
+    private int[][] dp;
+
+    public int paintWalls(int[] cost, int[] time) {
+        dp = new int[cost.length][cost.length + 1];
+        for (int[] row : dp) {
+            Arrays.fill(row, -1);
+        }
+        return dfs(cost, time, 0, cost.length);
+    }
+
+    private int dfs(int[] cost, int[] time, int i, int remain) {
+        if (remain <= 0) {
+            return 0;
+        }
+        if (i == cost.length) {
+            return Integer.MAX_VALUE;
+        }
+        if (dp[i][remain] != -1) {
+            return dp[i][remain];
+        }
+
+        int paint = dfs(cost, time, i + 1, remain - 1 - time[i]);
+        if (paint != Integer.MAX_VALUE) paint += cost[i];
+
+        int skip = dfs(cost, time, i + 1, remain);
+        return dp[i][remain] = Math.min(paint, skip);
+    }
+}
+```
+
+```cpp
+class Solution {
+    vector<vector<int>> dp;
+
+public:
+    int paintWalls(vector<int>& cost, vector<int>& time) {
+        dp.assign(cost.size(), vector<int>(cost.size() + 1, -1));
+        return dfs(cost, time, 0, cost.size());
+    }
+
+private:
+    int dfs(vector<int>& cost, vector<int>& time, int i, int remain) {
+        if (remain <= 0) {
+            return 0;
+        }
+        if (i == cost.size()) {
+            return INT_MAX;
+        }
+        if (dp[i][remain] != -1) {
+            return dp[i][remain];
+        }
+
+        int paint = dfs(cost, time, i + 1, remain - 1 - time[i]);
+        if (paint != INT_MAX) paint += cost[i];
+        
+        int skip = dfs(cost, time, i + 1, remain);
+        return dp[i][remain] = min(paint, skip);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} cost
+     * @param {number[]} time
+     * @return {number}
+     */
+    paintWalls(cost, time) {
+        const n = cost.length;
+        const dp = Array.from({ length: n }, () => Array(n + 1).fill(-1));
+        const dfs = (i, remain) => {
+            if (remain <= 0) {
+                return 0;
+            }
+            if (i === n) {
+                return Infinity;
+            }
+            if (dp[i][remain] !== -1) {
+                return dp[i][remain];
+            }
+
+            const paint = cost[i] + dfs(i + 1, remain - 1 - time[i]);
+            const skip = dfs(i + 1, remain);
+            return dp[i][remain] = Math.min(paint, skip);
+        };
+
+        return dfs(0, cost.length);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def paintWalls(self, cost: List[int], time: List[int]) -> int:
+        n = len(cost)
+        dp = [[0] * (n + 2) for _ in range(n + 1)]
+        for remain in range(1, n + 1):
+            dp[n][remain] = float("inf")
+
+        for i in range(n - 1, -1, -1):
+            for remain in range(1, n + 1):
+                paint = cost[i] + dp[i + 1][max(remain - 1 - time[i], 0)]
+                skip = dp[i + 1][remain]
+                dp[i][remain] = min(paint, skip)
+        
+        return dp[0][n]
+```
+
+```java
+public class Solution {
+    public int paintWalls(int[] cost, int[] time) {
+        int n = cost.length;
+        int[][] dp = new int[n + 1][n + 2];
+        for (int remain = 1; remain <= n; remain++) {
+            dp[n][remain] = Integer.MAX_VALUE;
+        }
+
+        for (int i = n - 1; i >= 0; i--) {
+            for (int remain = 1; remain <= n; remain++) {
+                int paint = dp[i + 1][Math.max(remain - 1 - time[i], 0)];
+                if (paint != Integer.MAX_VALUE) paint += cost[i];
+                
+                int skip = dp[i + 1][remain];
+                dp[i][remain] = Math.min(paint, skip);
+            }
+        }
+
+        return dp[0][n];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int paintWalls(vector<int>& cost, vector<int>& time) {
+        int n = cost.size();
+        vector<vector<int>> dp(n + 1, vector<int>(n + 2, 0));
+
+        for (int remain = 1; remain <= n; remain++) {
+            dp[n][remain] = INT_MAX;
+        }
+
+        for (int i = n - 1; i >= 0; i--) {
+            for (int remain = 1; remain <= n; remain++) {
+                int paint = dp[i + 1][max(remain - 1 - time[i], 0)];
+                if (paint !=  INT_MAX) paint += cost[i];
+                
+                int skip = dp[i + 1][remain];
+                dp[i][remain] = min(paint, skip);
+            }
+        }
+
+        return dp[0][n];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} cost
+     * @param {number[]} time
+     * @return {number}
+     */
+    paintWalls(cost, time) {
+        const n = cost.length;
+        const dp = Array.from({ length: n + 1 }, () => Array(n + 2).fill(0));
+
+        for (let remain = 1; remain <= n; remain++) {
+            dp[n][remain] = Infinity;
+        }
+
+        for (let i = n - 1; i >= 0; i--) {
+            for (let remain = 1; remain <= n; remain++) {
+                const paint = cost[i] + dp[i + 1][Math.max(remain - 1 - time[i], 0)];
+                const skip = dp[i + 1][remain];
+                dp[i][remain] = Math.min(paint, skip);
+            }
+        }
+
+        return dp[0][n];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def paintWalls(self, cost: List[int], time: List[int]) -> int:
+        n = len(cost)
+        dp = [float("inf")] * (n + 2)
+        dp[0] = 0
+
+        for i in range(n):
+            for remain in range(n, 0, -1):
+                paint = cost[i] + dp[max(remain - 1 - time[i], 0)]
+                dp[remain] = min(paint, dp[remain])
+        
+        return dp[n]
+```
+
+```java
+public class Solution {
+    public int paintWalls(int[] cost, int[] time) {
+        int n = cost.length;
+        int[] dp = new int[n + 2];
+        Arrays.fill(dp, Integer.MAX_VALUE);
+        dp[0] = 0;
+
+        for (int i = 0; i < n; i++) {
+            for (int remain = n; remain > 0; remain--) {
+                int paint = dp[Math.max(remain - 1 - time[i], 0)];
+                if (paint != Integer.MAX_VALUE) paint += cost[i];
+                dp[remain] = Math.min(paint, dp[remain]);
+            }
+        }
+
+        return dp[n];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int paintWalls(vector<int>& cost, vector<int>& time) {
+        int n = cost.size();
+        vector<int> dp(n + 2, INT_MAX);
+        dp[0] = 0;
+
+        for (int i = 0; i < n; i++) {
+            for (int remain = n; remain > 0; remain--) {
+                int paint = dp[max(remain - 1 - time[i], 0)];
+                if (paint != INT_MAX) paint += cost[i];
+                dp[remain] = min(paint, dp[remain]);
+            }
+        }
+
+        return dp[n];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} cost
+     * @param {number[]} time
+     * @return {number}
+     */
+    paintWalls(cost, time) {
+        const n = cost.length;
+        const dp = Array(n + 2).fill(Infinity);
+        dp[0] = 0;
+
+        for (let i = 0; i < n; i++) {
+            for (let remain = n; remain > 0; remain--) {
+                const paint = cost[i] + dp[Math.max(remain - 1 - time[i], 0)];
+                dp[remain] = Math.min(paint, dp[remain]);
+            }
+        }
+
+        return dp[n];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/palindrome-linked-list.md b/articles/palindrome-linked-list.md
new file mode 100644
index 000000000..f4f73b7bc
--- /dev/null
+++ b/articles/palindrome-linked-list.md
@@ -0,0 +1,600 @@
+## 1. Convert To Array
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def isPalindrome(self, head: Optional[ListNode]) -> bool:
+        arr = []
+        cur = head
+        while cur:
+            arr.append(cur.val)
+            cur = cur.next
+
+        l, r = 0, len(arr) - 1
+        while l < r:
+            if arr[l] != arr[r]:
+                return False
+            l, r = l + 1, r - 1
+
+        return True
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public boolean isPalindrome(ListNode head) {
+        List<Integer> arr = new ArrayList<>();
+        ListNode cur = head;
+        while (cur != null) {
+            arr.add(cur.val);
+            cur = cur.next;
+        }
+
+        int l = 0, r = arr.size() - 1;
+        while (l < r) {
+            if (!arr.get(l).equals(arr.get(r))) {
+                return false;
+            }
+            l++;
+            r--;
+        }
+
+        return true;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    bool isPalindrome(ListNode* head) {
+        std::vector<int> arr;
+        ListNode* cur = head;
+        while (cur) {
+            arr.push_back(cur->val);
+            cur = cur->next;
+        }
+
+        int l = 0, r = arr.size() - 1;
+        while (l < r) {
+            if (arr[l] != arr[r]) {
+                return false;
+            }
+            l++;
+            r--;
+        }
+
+        return true;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @return {boolean}
+     */
+    isPalindrome(head) {
+        const arr = [];
+        let cur = head;
+
+        while (cur) {
+            arr.push(cur.val);
+            cur = cur.next;
+        }
+
+        let l = 0, r = arr.length - 1;
+        while (l < r) {
+            if (arr[l] !== arr[r]) {
+                return false;
+            }
+            l++;
+            r--;
+        }
+
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Recursion
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def isPalindrome(self, head: Optional[ListNode]) -> bool:
+        self.cur = head
+
+        def rec(node):
+            if node is not None:
+                if not rec(node.next):
+                    return False
+                if self.cur.val != node.val:
+                    return False
+                self.cur = self.cur.next
+            return True
+
+        return rec(head)
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    private ListNode cur;
+
+    public boolean isPalindrome(ListNode head) {
+        cur = head;
+        return rec(head);
+    }
+
+    private boolean rec(ListNode node) {
+        if (node != null) {
+            if (!rec(node.next)) {
+                return false;
+            }
+            if (cur.val != node.val) {
+                return false;
+            }
+            cur = cur.next;
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+    ListNode* cur;
+
+    bool rec(ListNode* node) {
+        if (node != nullptr) {
+            if (!rec(node->next)) {
+                return false;
+            }
+            if (cur->val != node->val) {
+                return false;
+            }
+            cur = cur->next;
+        }
+        return true;
+    }
+
+public:
+    bool isPalindrome(ListNode* head) {
+        cur = head;
+        return rec(head);
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @return {boolean}
+     */
+    isPalindrome(head) {
+        let cur = head;
+
+        const rec = (node) => {
+            if (node !== null) {
+                if (!rec(node.next)) {
+                    return false;
+                }
+                if (cur.val !== node.val) {
+                    return false;
+                }
+                cur = cur.next;
+            }
+            return true;
+        };
+
+        return rec(head);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 3. Stack
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def isPalindrome(self, head: Optional[ListNode]) -> bool:
+        stack = []
+        cur = head
+        
+        while cur:
+            stack.append(cur.val)
+            cur = cur.next
+        
+        cur = head
+        while cur and cur.val == stack.pop():
+            cur = cur.next
+            
+        return not cur
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public boolean isPalindrome(ListNode head) {
+        Stack<Integer> stack = new Stack<>();
+        ListNode cur = head;
+
+        while (cur != null) {
+            stack.push(cur.val);
+            cur = cur.next;
+        }
+
+        cur = head;
+        while (cur != null && cur.val == stack.pop()) {
+            cur = cur.next;
+        }
+
+        return cur == null;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    bool isPalindrome(ListNode* head) {
+        stack<int> stack;
+        ListNode* cur = head;
+
+        while (cur != nullptr) {
+            stack.push(cur->val);
+            cur = cur->next;
+        }
+
+        cur = head;
+        while (cur != nullptr && cur->val == stack.top()) {
+            stack.pop();
+            cur = cur->next;
+        }
+
+        return cur == nullptr;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @return {boolean}
+     */
+    isPalindrome(head) {
+        const stack = [];
+        let cur = head;
+
+        while (cur) {
+            stack.push(cur.val);
+            cur = cur.next;
+        }
+
+        cur = head;
+        while (cur && cur.val === stack.pop()) {
+            cur = cur.next;
+        }
+
+        return cur === null;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Fast & Slow Pointers
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def isPalindrome(self, head: ListNode) -> bool:
+        fast = head
+        slow = head
+
+        # find middle (slow)
+        while fast and fast.next:
+            fast = fast.next.next
+            slow = slow.next
+
+        # reverse second half
+        prev = None
+        while slow:
+            tmp = slow.next
+            slow.next = prev
+            prev = slow
+            slow = tmp
+
+        # check palindrome
+        left, right = head, prev
+        while right:
+            if left.val != right.val:
+                return False
+            left = left.next
+            right = right.next
+        
+        return True
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public boolean isPalindrome(ListNode head) {
+        ListNode fast = head, slow = head;
+
+        // find middle (slow)
+        while (fast != null && fast.next != null) {
+            fast = fast.next.next;
+            slow = slow.next;
+        }
+
+        // reverse second half
+        ListNode prev = null;
+        while (slow != null) {
+            ListNode tmp = slow.next;
+            slow.next = prev;
+            prev = slow;
+            slow = tmp;
+        }
+
+        // check palindrome
+        ListNode left = head, right = prev;
+        while (right != null) {
+            if (left.val != right.val) {
+                return false;
+            }
+            left = left.next;
+            right = right.next;
+        }
+
+        return true;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    bool isPalindrome(ListNode* head) {
+        ListNode *fast = head, *slow = head;
+
+        // find middle (slow)
+        while (fast && fast->next) {
+            fast = fast->next->next;
+            slow = slow->next;
+        }
+
+        // reverse second half
+        ListNode *prev = nullptr;
+        while (slow) {
+            ListNode *tmp = slow->next;
+            slow->next = prev;
+            prev = slow;
+            slow = tmp;
+        }
+
+        // check palindrome
+        ListNode *left = head, *right = prev;
+        while (right) {
+            if (left->val != right->val) {
+                return false;
+            }
+            left = left->next;
+            right = right->next;
+        }
+
+        return true;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @return {boolean}
+     */
+    isPalindrome(head) {
+        let fast = head, slow = head;
+
+        // find middle (slow)
+        while (fast && fast.next) {
+            fast = fast.next.next;
+            slow = slow.next;
+        }
+
+        // reverse second half
+        let prev = null;
+        while (slow) {
+            let tmp = slow.next;
+            slow.next = prev;
+            prev = slow;
+            slow = tmp;
+        }
+
+        // check palindrome
+        let left = head, right = prev;
+        while (right) {
+            if (left.val !== right.val) {
+                return false;
+            }
+            left = left.next;
+            right = right.next;
+        }
+
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/palindrome-number.md b/articles/palindrome-number.md
new file mode 100644
index 000000000..77f44aad6
--- /dev/null
+++ b/articles/palindrome-number.md
@@ -0,0 +1,420 @@
+## 1. Convert to String
+
+::tabs-start
+
+```python
+class Solution:
+    def isPalindrome(self, x: int) -> bool:
+        s = str(x)
+        return s == s[::-1]
+```
+
+```java
+public class Solution {
+    public boolean isPalindrome(int x) {
+        String s = String.valueOf(x);
+        return s.equals(new StringBuilder(s).reverse().toString());
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isPalindrome(int x) {
+        string s = to_string(x);
+        string rev = s;
+        reverse(rev.begin(), rev.end());
+        return s == rev;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} x
+     * @return {boolean}
+     */
+    isPalindrome(x) {
+        const s = String(x);
+        return s === s.split('').reverse().join('');
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the number of digits in the given integer.
+
+---
+
+## 2. Convert to String (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def isPalindrome(self, x: int) -> bool:
+        s = str(x)
+        n = len(s)
+        for i in range(n // 2):
+            if s[i] != s[n - i - 1]:
+                return False
+        return True
+```
+
+```java
+public class Solution {
+    public boolean isPalindrome(int x) {
+        String s = String.valueOf(x);
+        int n = s.length();
+        for (int i = 0; i < n / 2; i++) {
+            if (s.charAt(i) != s.charAt(n - i - 1)) {
+                return false;
+            }
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isPalindrome(int x) {
+        string s = to_string(x);
+        int n = s.length();
+        for (int i = 0; i < n / 2; i++) {
+            if (s[i] != s[n - i - 1]) {
+                return false;
+            }
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} x
+     * @return {boolean}
+     */
+    isPalindrome(x) {
+        const s = String(x);
+        let n = s.length;
+        for (let i = 0; i < (n >> 1); i++) {
+            if (s.charAt(i) != s.charAt(n - i - 1)) {
+                return false;
+            }
+        }
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the number of digits in the given integer.
+
+---
+
+## 3. Reverse the Integer
+
+::tabs-start
+
+```python
+class Solution:
+    def isPalindrome(self, x: int) -> bool:
+        if x < 0:
+            return False
+
+        rev = 0
+        num = x
+        while num:
+            rev = (rev * 10) + (num % 10)
+            num //= 10
+
+        return rev == x
+```
+
+```java
+public class Solution {
+    public boolean isPalindrome(int x) {
+        if (x < 0) {
+            return false;
+        }
+
+        long rev = 0, num = x;
+        while (num != 0) {
+            rev = (rev * 10) + (num % 10);
+            num /= 10;
+        }
+
+        return rev == x;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isPalindrome(int x) {
+        if (x < 0) {
+            return false;
+        }
+
+        long long rev = 0, num = x;
+        while (num != 0) {
+            rev = (rev * 10) + (num % 10);
+            num /= 10;
+        }
+
+        return rev == x;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} x
+     * @return {boolean}
+     */
+    isPalindrome(x) {
+        if (x < 0) {
+            return false;
+        }
+
+        let rev = 0, num = x;
+        while (num !== 0) {
+            rev = (rev * 10) + (num % 10);
+            num = Math.floor(num / 10);
+        }
+
+        return rev === x;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+> Where $n$ is the number of digits in the given integer.
+
+---
+
+## 4. Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def isPalindrome(self, x: int) -> bool:
+        if x < 0:
+            return False
+
+        div = 1
+        while x >= 10 * div:
+            div *= 10
+
+        while x:
+            if x // div != x % 10:
+                return False
+            x = (x % div) // 10
+            div //= 100
+
+        return True
+```
+
+```java
+public class Solution {
+    public boolean isPalindrome(int x) {
+        if (x < 0) {
+            return false;
+        }
+
+        long div = 1;
+        while (x >= 10 * div) {
+            div *= 10;
+        }
+
+        while (x != 0) {
+            if (x / div != x % 10) {
+                return false;
+            }
+            x = (int) (x % div) / 10;
+            div /= 100;
+        }
+
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isPalindrome(int x) {
+        if (x < 0) {
+            return false;
+        }
+
+        long long div = 1;
+        while (x >= 10 * div) {
+            div *= 10;
+        }
+
+        while (x != 0) {
+            if (x / div != x % 10) {
+                return false;
+            }
+            x = (x % div) / 10;
+            div /= 100;
+        }
+
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} x
+     * @return {boolean}
+     */
+    isPalindrome(x) {
+        if (x < 0) {
+            return false;
+        }
+
+        let div = 1;
+        while (x >= 10 * div) {
+            div *= 10;
+        }
+
+        while (x !== 0) {
+            if (Math.floor(x / div) !== x % 10) {
+                return false;
+            }
+            x = Math.floor((x % div) / 10);
+            div = Math.floor(div / 100);
+        }
+
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+> Where $n$ is the number of digits in the given integer.
+
+---
+
+## 5. Reverse Half of the Number
+
+::tabs-start
+
+```python
+class Solution:
+    def isPalindrome(self, x: int) -> bool:
+        if x < 0 or (x != 0 and x % 10 == 0):
+            return False
+
+        rev = 0
+        while x > rev:
+            rev = (rev * 10) + (x % 10)
+            x //= 10
+
+        return x == rev or x == rev // 10
+```
+
+```java
+public class Solution {
+    public boolean isPalindrome(int x) {
+        if (x < 0 || (x != 0 && x % 10 == 0)) {
+            return false;
+        }
+
+        int rev = 0;
+        while (x > rev) {
+            rev = rev * 10 + x % 10;
+            x /= 10;
+        }
+
+        return x == rev || x == rev / 10;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isPalindrome(int x) {
+        if (x < 0 || (x != 0 && x % 10 == 0)) {
+            return false;
+        }
+
+        int rev = 0;
+        while (x > rev) {
+            rev = rev * 10 + x % 10;
+            x /= 10;
+        }
+
+        return x == rev || x == rev / 10;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} x
+     * @return {boolean}
+     */
+    isPalindrome(x) {
+        if (x < 0 || (x !== 0 && x % 10 === 0)) {
+            return false;
+        }
+
+        let rev = 0;
+        while (x > rev) {
+            rev = rev * 10 + (x % 10);
+            x = Math.floor(x / 10);
+        }
+
+        return x === rev || x === Math.floor(rev / 10);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+> Where $n$ is the number of digits in the given integer.
\ No newline at end of file
diff --git a/articles/palindrome-partitioning.md b/articles/palindrome-partitioning.md
index 5986d7db7..3e87916a5 100644
--- a/articles/palindrome-partitioning.md
+++ b/articles/palindrome-partitioning.md
@@ -1,4 +1,4 @@
-## 1. Backtracking (Pick / Not Pick)
+## 1. Backtracking - I
 
 ::tabs-start
 
@@ -201,16 +201,141 @@ public class Solution {
 }
 ```
 
+```go
+func partition(s string) [][]string {
+    res := [][]string{}
+    part := []string{}
+
+    var dfs func(j, i int)
+    dfs = func(j, i int) {
+        if i >= len(s) {
+            if i == j {
+                res = append(res, append([]string{}, part...))
+            }
+            return
+        }
+
+        if isPali(s, j, i) {
+            part = append(part, s[j:i+1])
+            dfs(i+1, i+1)
+            part = part[:len(part)-1]
+        }
+
+        dfs(j, i+1)
+    }
+
+    dfs(0, 0)
+    return res
+}
+
+func isPali(s string, l, r int) bool {
+    for l < r {
+        if s[l] != s[r] {
+            return false
+        }
+        l++
+        r--
+    }
+    return true
+}
+```
+
+```kotlin
+class Solution {
+    fun partition(s: String): List<List<String>> {
+        val res = mutableListOf<List<String>>()
+        val part = mutableListOf<String>()
+
+        fun dfs(j: Int, i: Int) {
+            if (i >= s.length) {
+                if (i == j) {
+                    res.add(part.toList())
+                }
+                return
+            }
+
+            if (isPali(s, j, i)) {
+                part.add(s.substring(j, i + 1))
+                dfs(i + 1, i + 1)
+                part.removeAt(part.size - 1)
+            }
+
+            dfs(j, i + 1)
+        }
+
+        dfs(0, 0)
+        return res
+    }
+
+    private fun isPali(s: String, l: Int, r: Int): Boolean {
+        var left = l
+        var right = r
+        while (left < right) {
+            if (s[left] != s[right]) {
+                return false
+            }
+            left++
+            right--
+        }
+        return true
+    }
+}
+```
+
+```swift
+class Solution {
+    func partition(_ s: String) -> [[String]] {
+        var res = [[String]]()
+        var part = [String]()
+        let sArray = Array(s)
+
+        func dfs(_ j: Int, _ i: Int) {
+            if i >= sArray.count {
+                if i == j {
+                    res.append(part)
+                }
+                return
+            }
+
+            if isPali(sArray, j, i) {
+                part.append(String(sArray[j...i]))
+                dfs(i + 1, i + 1)
+                part.removeLast()
+            }
+
+            dfs(j, i + 1)
+        }
+
+        func isPali(_ s: [Character], _ l: Int, _ r: Int) -> Bool {
+            var l = l, r = r
+            while l < r {
+                if s[l] != s[r] {
+                    return false
+                }
+                l += 1
+                r -= 1
+            }
+            return true
+        }
+
+        dfs(0, 0)
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n * 2 ^ n)$
-* Space complexity: $O(n)$
+* Space complexity:
+    * $O(n)$ extra space.
+    * $O(n * 2 ^ n)$ space for the output list.
 
 ---
 
-## 2. Backtracking
+## 2. Backtracking - II
 
 ::tabs-start
 
@@ -406,12 +531,128 @@ public class Solution {
 }
 ```
 
+```go
+func partition(s string) [][]string {
+    res := [][]string{}
+    part := []string{}
+
+    var dfs func(i int)
+    dfs = func(i int) {
+        if i >= len(s) {
+            res = append(res, append([]string{}, part...))
+            return
+        }
+        for j := i; j < len(s); j++ {
+            if isPali(s, i, j) {
+                part = append(part, s[i:j+1])
+                dfs(j + 1)
+                part = part[:len(part)-1]
+            }
+        }
+    }
+
+    dfs(0)
+    return res
+}
+
+func isPali(s string, l, r int) bool {
+    for l < r {
+        if s[l] != s[r] {
+            return false
+        }
+        l++
+        r--
+    }
+    return true
+}
+```
+
+```kotlin
+class Solution {
+    fun partition(s: String): List<List<String>> {
+        val res = mutableListOf<List<String>>()
+        val part = mutableListOf<String>()
+
+        fun dfs(i: Int) {
+            if (i >= s.length) {
+                res.add(part.toList())
+                return
+            }
+            for (j in i until s.length) {
+                if (isPali(s, i, j)) {
+                    part.add(s.substring(i, j + 1))
+                    dfs(j + 1)
+                    part.removeAt(part.size - 1)
+                }
+            }
+        }
+
+        dfs(0)
+        return res
+    }
+
+    private fun isPali(s: String, l: Int, r: Int): Boolean {
+        var left = l
+        var right = r
+        while (left < right) {
+            if (s[left] != s[right]) {
+                return false
+            }
+            left++
+            right--
+        }
+        return true
+    }
+}
+```
+
+```swift
+class Solution {
+    func partition(_ s: String) -> [[String]] {
+        var res = [[String]]()
+        var part = [String]()
+        let sArray = Array(s)
+
+        func dfs(_ i: Int) {
+            if i >= sArray.count {
+                res.append(part)
+                return
+            }
+            for j in i..<sArray.count {
+                if isPali(sArray, i, j) {
+                    part.append(String(sArray[i...j]))
+                    dfs(j + 1)
+                    part.removeLast()
+                }
+            }
+        }
+
+        func isPali(_ s: [Character], _ l: Int, _ r: Int) -> Bool {
+            var l = l, r = r
+            while l < r {
+                if s[l] != s[r] {
+                    return false
+                }
+                l += 1
+                r -= 1
+            }
+            return true
+        }
+
+        dfs(0)
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n * 2 ^ n)$
-* Space complexity: $O(n)$
+* Space complexity:
+    * $O(n)$ extra space.
+    * $O(n * 2 ^ n)$ space for the output list.
 
 ---
 
@@ -594,12 +835,124 @@ public class Solution {
 }
 ```
 
+```go
+func partition(s string) [][]string {
+    n := len(s)
+    dp := make([][]bool, n)
+    for i := range dp {
+        dp[i] = make([]bool, n)
+    }
+
+    for l := 1; l <= n; l++ {
+        for i := 0; i <= n-l; i++ {
+            dp[i][i+l-1] = (s[i] == s[i+l-1] && (i+1 > (i+l-2) || dp[i+1][i+l-2]))
+        }
+    }
+
+    res := [][]string{}
+    part := []string{}
+
+    var dfs func(i int)
+    dfs = func(i int) {
+        if i >= len(s) {
+            res = append(res, append([]string{}, part...))
+            return
+        }
+        for j := i; j < len(s); j++ {
+            if dp[i][j] {
+                part = append(part, s[i:j+1])
+                dfs(j + 1)
+                part = part[:len(part)-1]
+            }
+        }
+    }
+
+    dfs(0)
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun partition(s: String): List<List<String>> {
+        val n = s.length
+        val dp = Array(n) { BooleanArray(n) }
+
+        for (l in 1..n) {
+            for (i in 0..n - l) {
+                dp[i][i + l - 1] = s[i] == s[i + l - 1] && 
+                                   (i + 1 > (i + l - 2) || dp[i + 1][i + l - 2])
+            }
+        }
+
+        val res = mutableListOf<List<String>>()
+        val part = mutableListOf<String>()
+
+        fun dfs(i: Int) {
+            if (i >= s.length) {
+                res.add(part.toList())
+                return
+            }
+            for (j in i until s.length) {
+                if (dp[i][j]) {
+                    part.add(s.substring(i, j + 1))
+                    dfs(j + 1)
+                    part.removeAt(part.size - 1)
+                }
+            }
+        }
+
+        dfs(0)
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func partition(_ s: String) -> [[String]] {
+        let n = s.count
+        let sArray = Array(s)
+        var dp = Array(repeating: Array(repeating: false, count: n), count: n)
+        
+        for l in 1...n {
+            for i in 0...(n - l) {
+                dp[i][i + l - 1] = (sArray[i] == sArray[i + l - 1] &&
+                                    (i + 1 > (i + l - 2) || dp[i + 1][i + l - 2]))
+            }
+        }
+
+        var res = [[String]]()
+        var part = [String]()
+
+        func dfs(_ i: Int) {
+            if i >= sArray.count {
+                res.append(part)
+                return
+            }
+            for j in i..<sArray.count {
+                if dp[i][j] {
+                    part.append(String(sArray[i...j]))
+                    dfs(j + 1)
+                    part.removeLast()
+                }
+            }
+        }
+
+        dfs(0)
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n * 2 ^ n)$
-* Space complexity: $O(n ^ 2)$
+* Space complexity:
+    * $O(n ^ 2)$ extra space.
+    * $O(n * 2 ^ n)$ space for the output list.
 
 ---
 
@@ -791,9 +1144,124 @@ public class Solution {
 }
 ```
 
+```go
+func partition(s string) [][]string {
+    n := len(s)
+    dp := make([][]bool, n)
+    for i := range dp {
+        dp[i] = make([]bool, n)
+    }
+
+    for l := 1; l <= n; l++ {
+        for i := 0; i <= n-l; i++ {
+            dp[i][i+l-1] = (s[i] == s[i+l-1] && 
+                           (i+1 > (i+l-2) || dp[i+1][i+l-2]))
+        }
+    }
+
+    var dfs func(i int) [][]string
+    dfs = func(i int) [][]string {
+        if i >= n {
+            return [][]string{{}}
+        }
+
+        ret := [][]string{}
+        for j := i; j < n; j++ {
+            if dp[i][j] {
+                nxt := dfs(j + 1)
+                for _, part := range nxt {
+                    cur := append([]string{s[i : j+1]}, part...)
+                    ret = append(ret, cur)
+                }
+            }
+        }
+        return ret
+    }
+
+    return dfs(0)
+}
+```
+
+```kotlin
+class Solution {
+    fun partition(s: String): List<List<String>> {
+        val n = s.length
+        val dp = Array(n) { BooleanArray(n) }
+
+        for (l in 1..n) {
+            for (i in 0..n - l) {
+                dp[i][i + l - 1] = s[i] == s[i + l - 1] && 
+                                   (i + 1 > (i + l - 2) || dp[i + 1][i + l - 2])
+            }
+        }
+
+        fun dfs(i: Int): List<List<String>> {
+            if (i >= n) {
+                return listOf(emptyList())
+            }
+
+            val ret = mutableListOf<List<String>>()
+            for (j in i until n) {
+                if (dp[i][j]) {
+                    val nxt = dfs(j + 1)
+                    for (part in nxt) {
+                        val cur = listOf(s.substring(i, j + 1)) + part
+                        ret.add(cur)
+                    }
+                }
+            }
+            return ret
+        }
+
+        return dfs(0)
+    }
+}
+```
+
+```swift
+class Solution {
+    func partition(_ s: String) -> [[String]] {
+        let n = s.count
+        let sArray = Array(s)
+        var dp = Array(repeating: Array(repeating: false, count: n), count: n)
+
+        for l in 1...n {
+            for i in 0...(n - l) {
+                dp[i][i + l - 1] = (sArray[i] == sArray[i + l - 1] &&
+                                    (i + 1 > (i + l - 2) || dp[i + 1][i + l - 2]))
+            }
+        }
+
+        func dfs(_ i: Int) -> [[String]] {
+            if i >= n {
+                return [[]]
+            }
+
+            var ret = [[String]]()
+            for j in i..<n {
+                if dp[i][j] {
+                    let nextPartitions = dfs(j + 1)
+                    for part in nextPartitions {
+                        var cur = [String]()
+                        cur.append(String(sArray[i...j]))
+                        cur.append(contentsOf: part)
+                        ret.append(cur)
+                    }
+                }
+            }
+            return ret
+        }
+
+        return dfs(0)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n * 2 ^ n)$
-* Space complexity: $O(n ^ 2)$
\ No newline at end of file
+* Space complexity:
+    * $O(n ^ 2)$ extra space.
+    * $O(n * 2 ^ n)$ space for the output list.
\ No newline at end of file
diff --git a/articles/palindromic-substrings.md b/articles/palindromic-substrings.md
index e3beec032..cd1dfa352 100644
--- a/articles/palindromic-substrings.md
+++ b/articles/palindromic-substrings.md
@@ -107,6 +107,71 @@ public class Solution {
 }
 ```
 
+```go
+func countSubstrings(s string) int {
+    res := 0
+    for i := range s {
+        for j := i; j < len(s); j++ {
+            l, r := i, j
+            for l < r && s[l] == s[r] {
+                l++
+                r--
+            }
+            if l >= r {
+                res++
+            }
+        }
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun countSubstrings(s: String): Int {
+        var res = 0
+        for (i in s.indices) {
+            for (j in i until s.length) {
+                var l = i
+                var r = j
+                while (l < r && s[l] == s[r]) {
+                    l++
+                    r--
+                }
+                if (l >= r) {
+                    res++
+                }
+            }
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func countSubstrings(_ s: String) -> Int {
+        let chars = Array(s)
+        var res = 0
+
+        for i in 0..<chars.count {
+            for j in i..<chars.count {
+                var l = i, r = j
+                while l < r && chars[l] == chars[r] {
+                    l += 1
+                    r -= 1
+                }
+                if l >= r {
+                    res += 1
+                }
+            }
+        }
+
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -229,6 +294,71 @@ public class Solution {
 }
 ```
 
+```go
+func countSubstrings(s string) int {
+    n := len(s)
+    res := 0
+    dp := make([][]bool, n)
+    for i := range dp {
+        dp[i] = make([]bool, n)
+    }
+
+    for i := n - 1; i >= 0; i-- {
+        for j := i; j < n; j++ {
+            if s[i] == s[j] && (j-i <= 2 || dp[i+1][j-1]) {
+                dp[i][j] = true
+                res++
+            }
+        }
+    }
+
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun countSubstrings(s: String): Int {
+        val n = s.length
+        var res = 0
+        val dp = Array(n) { BooleanArray(n) }
+
+        for (i in n - 1 downTo 0) {
+            for (j in i until n) {
+                if (s[i] == s[j] && (j - i <= 2 || dp[i + 1][j - 1])) {
+                    dp[i][j] = true
+                    res++
+                }
+            }
+        }
+
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func countSubstrings(_ s: String) -> Int {
+        let n = s.count
+        var res = 0
+        var dp = Array(repeating: Array(repeating: false, count: n), count: n)
+        let chars = Array(s)
+
+        for i in stride(from: n - 1, through: 0, by: -1) {
+            for j in i..<n {
+                if chars[i] == chars[j] && (j - i <= 2 || dp[i + 1][j - 1]) {
+                    dp[i][j] = true
+                    res += 1
+                }
+            }
+        }
+
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -395,6 +525,92 @@ public class Solution {
 }
 ```
 
+```go
+func countSubstrings(s string) int {
+    res := 0
+
+    for i := 0; i < len(s); i++ {
+        // Odd-length
+        l, r := i, i
+        for l >= 0 && r < len(s) && s[l] == s[r] {
+            res++
+            l--
+            r++
+        }
+
+        // Even-length
+        l, r = i, i+1
+        for l >= 0 && r < len(s) && s[l] == s[r] {
+            res++
+            l--
+            r++
+        }
+    }
+
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun countSubstrings(s: String): Int {
+        var res = 0
+
+        for (i in s.indices) {
+            // Odd-length
+            var l = i
+            var r = i
+            while (l >= 0 && r < s.length && s[l] == s[r]) {
+                res++
+                l--
+                r++
+            }
+
+            // Even-length
+            l = i
+            r = i + 1
+            while (l >= 0 && r < s.length && s[l] == s[r]) {
+                res++
+                l--
+                r++
+            }
+        }
+
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func countSubstrings(_ s: String) -> Int {
+        let chars = Array(s)
+        var res = 0
+        
+        for i in 0..<chars.count {
+            // Odd length palindromes
+            var l = i, r = i
+            while l >= 0 && r < chars.count && chars[l] == chars[r] {
+                res += 1
+                l -= 1
+                r += 1
+            }
+
+            // Even length palindromes
+            l = i
+            r = i + 1
+            while l >= 0 && r < chars.count && chars[l] == chars[r] {
+                res += 1
+                l -= 1
+                r += 1
+            }
+        }
+        
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -536,6 +752,79 @@ public class Solution {
 }
 ```
 
+```go
+func countSubstrings(s string) int {
+    res := 0
+    for i := 0; i < len(s); i++ {
+        res += countPali(s, i, i)   
+        res += countPali(s, i, i+1) 
+    }
+    return res
+}
+
+func countPali(s string, l, r int) int {
+    res := 0
+    for l >= 0 && r < len(s) && s[l] == s[r] {
+        res++
+        l--
+        r++
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun countSubstrings(s: String): Int {
+        var res = 0
+        for (i in s.indices) {
+            res += countPali(s, i, i)   
+            res += countPali(s, i, i + 1) 
+        }
+        return res
+    }
+
+    private fun countPali(s: String, l: Int, r: Int): Int {
+        var left = l
+        var right = r
+        var res = 0
+        while (left >= 0 && right < s.length && s[left] == s[right]) {
+            res++
+            left--
+            right++
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func countSubstrings(_ s: String) -> Int {
+        var res = 0
+        let chars = Array(s)
+
+        for i in 0..<chars.count {
+            res += countPali(chars, i, i)
+            res += countPali(chars, i, i + 1)
+        }
+        return res
+    }
+
+    private func countPali(_ s: [Character], _ l: Int, _ r: Int) -> Int {
+        var res = 0
+        var left = l, right = r
+
+        while left >= 0 && right < s.count && s[left] == s[right] {
+            res += 1
+            left -= 1
+            right += 1
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -716,6 +1005,122 @@ public class Solution {
 }
 ```
 
+```go
+func countSubstrings(s string) int {
+    manacher := func(s string) []int {
+        t := "#" + joinWithSeparator(s, "#") + "#"
+        n := len(t)
+        p := make([]int, n)
+        l, r := 0, 0
+        for i := 0; i < n; i++ {
+            if i < r {
+                p[i] = min(r-i, p[l+(r-i)])
+            }
+            for i+p[i]+1 < n && i-p[i]-1 >= 0 && t[i+p[i]+1] == t[i-p[i]-1] {
+                p[i]++
+            }
+            if i+p[i] > r {
+                l, r = i-p[i], i+p[i]
+            }
+        }
+        return p
+    }
+    
+    p := manacher(s)
+    res := 0
+    for _, val := range p {
+        res += (val + 1) / 2
+    }
+    return res
+}
+
+func joinWithSeparator(s, sep string) string {
+    result := ""
+    for i := 0; i < len(s); i++ {
+        result += string(s[i]) + sep
+    }
+    return result[:len(result)-1]
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun countSubstrings(s: String): Int {
+        fun manacher(s: String): IntArray {
+            val t = "#" + s.toCharArray().joinToString("#") + "#"
+            val n = t.length
+            val p = IntArray(n)
+            var l = 0
+            var r = 0
+            for (i in 0 until n) {
+                if (i < r) {
+                    p[i] = minOf(r - i, p[l + (r - i)])
+                }
+                while (i + p[i] + 1 < n && i - p[i] - 1 >= 0 && 
+                       t[i + p[i] + 1] == t[i - p[i] - 1]) {
+                    p[i]++
+                }
+                if (i + p[i] > r) {
+                    l = i - p[i]
+                    r = i + p[i]
+                }
+            }
+            return p
+        }
+
+        val p = manacher(s)
+        var res = 0
+        for (i in p) {
+            res += (i + 1) / 2
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func countSubstrings(_ s: String) -> Int {
+        func manacher(_ s: String) -> [Int] {
+            let t = "#" + s.map { "\($0)#" }.joined()
+            let chars = Array(t)
+            let n = chars.count
+            var p = Array(repeating: 0, count: n)
+            var l = 0, r = 0
+
+            for i in 0..<n {
+                if i < r {
+                    p[i] = min(r - i, p[l + (r - i)])
+                }
+                while i + p[i] + 1 < n, i - p[i] - 1 >= 0,
+                      chars[i + p[i] + 1] == chars[i - p[i] - 1] {
+                    p[i] += 1
+                }
+                if i + p[i] > r {
+                    l = i - p[i]
+                    r = i + p[i]
+                }
+            }
+            return p
+        }
+
+        let p = manacher(s)
+        var res = 0
+        for i in p {
+            res += (i + 1) / 2
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/parallel-courses-iii.md b/articles/parallel-courses-iii.md
new file mode 100644
index 000000000..ca66a0769
--- /dev/null
+++ b/articles/parallel-courses-iii.md
@@ -0,0 +1,481 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def minimumTime(self, n: int, relations: list[list[int]], time: list[int]) -> int:
+        adj = defaultdict(list)
+        for src, dst in relations:
+            adj[src].append(dst)
+
+        max_time = {}
+
+        def dfs(src):
+            if src in max_time:
+                return max_time[src]
+            res = time[src - 1]
+            for nei in adj[src]:
+                res = max(res, time[src - 1] + dfs(nei))
+            max_time[src] = res
+            return res
+
+        for i in range(1, n + 1):
+            dfs(i)
+
+        return max(max_time.values())
+```
+
+```java
+public class Solution {
+    private Map<Integer, Integer> maxTime;
+    private List<Integer>[] adj;
+    private int[] time;
+
+    public int minimumTime(int n, int[][] relations, int[] time) {
+        this.time = time;
+        this.maxTime = new HashMap<>();
+        this.adj = new ArrayList[n + 1];
+
+        for (int i = 1; i <= n; i++) {
+            adj[i] = new ArrayList<>();
+        }
+        for (int[] relation : relations) {
+            adj[relation[0]].add(relation[1]);
+        }
+
+        for (int i = 1; i <= n; i++) {
+            dfs(i);
+        }
+
+        return Collections.max(maxTime.values());
+    }
+
+    private int dfs(int src) {
+        if (maxTime.containsKey(src)) {
+            return maxTime.get(src);
+        }
+
+        int res = time[src - 1];
+        for (int nei : adj[src]) {
+            res = Math.max(res, time[src - 1] + dfs(nei));
+        }
+        maxTime.put(src, res);
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    unordered_map<int, int> maxTime;
+    vector<vector<int>> adj;
+    vector<int> time;
+
+    int minimumTime(int n, vector<vector<int>>& relations, vector<int>& time) {
+        this->time = time;
+        adj.resize(n + 1);
+
+        for (auto& relation : relations) {
+            adj[relation[0]].push_back(relation[1]);
+        }
+
+        for (int i = 1; i <= n; i++) {
+            dfs(i);
+        }
+
+        int res = 0;
+        for (auto& [key, value] : maxTime) {
+            res = max(res, value);
+        }
+        return res;
+    }
+
+private:
+    int dfs(int src) {
+        if (maxTime.count(src)) {
+            return maxTime[src];
+        }
+
+        int res = time[src - 1];
+        for (int nei : adj[src]) {
+            res = max(res, time[src - 1] + dfs(nei));
+        }
+        maxTime[src] = res;
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} relations
+     * @param {number[]} time
+     * @return {number}
+     */
+    minimumTime(n, relations, time) {
+        let adj = Array.from({ length: n + 1 }, () => []);
+        let maxTime = new Map();
+
+        for (let [src, dst] of relations) {
+            adj[src].push(dst);
+        }
+
+        const dfs = (src) => {
+            if (maxTime.has(src)) {
+                return maxTime.get(src);
+            }
+
+            let res = time[src - 1];
+            for (let nei of adj[src]) {
+                res = Math.max(res, time[src - 1] + dfs(nei));
+            }
+            maxTime.set(src, res);
+            return res;
+        };
+
+        for (let i = 1; i <= n; i++) {
+            dfs(i);
+        }
+
+        return Math.max(...maxTime.values());
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + E)$
+* Space complexity: $O(V + E)$
+
+> Where $V$ is the number of courses and $E$ is the number of prerequisites.
+
+---
+
+## 2. Iterative DFS
+
+::tabs-start
+
+```python
+class Solution:
+    def minimumTime(self, n: int, relations: list[list[int]], time: list[int]) -> int:
+        adj = [[] for _ in range(n)]
+        for src, dst in relations:
+            adj[src - 1].append(dst - 1)
+
+        maxTime = [-1] * n
+        processed = [False] * n
+
+        for i in range(n):
+            if maxTime[i] == -1:
+                stack = [i]
+                while stack:
+                    node = stack.pop()
+                    if processed[node]:
+                        best = 0
+                        for nei in adj[node]:
+                            best = max(best, maxTime[nei])
+                        maxTime[node] = time[node] + best
+                    else:
+                        processed[node] = True
+                        stack.append(node)
+                        for nei in adj[node]:
+                            if maxTime[nei] == -1:
+                                stack.append(nei)
+        return max(maxTime)
+```
+
+```java
+public class Solution {
+    public int minimumTime(int n, int[][] relations, int[] time) {
+        List<Integer>[] adj = new ArrayList[n];
+        for (int i = 0; i < n; i++) adj[i] = new ArrayList<>();
+        for (int[] rel : relations) {
+            adj[rel[0] - 1].add(rel[1] - 1);
+        }
+
+        int[] maxTime = new int[n];
+        Arrays.fill(maxTime, -1);
+        boolean[] processed = new boolean[n];
+
+        for (int i = 0; i < n; i++) {
+            if (maxTime[i] == -1) {
+                Stack<Integer> stack = new Stack<>();
+                stack.push(i);
+                while (!stack.isEmpty()) {
+                    int node = stack.pop();
+                    if (processed[node]) {
+                        int best = 0;
+                        for (int nei : adj[node]) {
+                            best = Math.max(best, maxTime[nei]);
+                        }
+                        maxTime[node] = time[node] + best;
+                    } else {
+                        processed[node] = true;
+                        stack.push(node);
+                        for (int nei : adj[node]) {
+                            if (maxTime[nei] == -1) {
+                                stack.push(nei);
+                            }
+                        }
+                    }
+                }
+            }
+        }
+        return Arrays.stream(maxTime).max().getAsInt();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minimumTime(int n, vector<vector<int>>& relations, vector<int>& time) {
+        vector<vector<int>> adj(n);
+        for (auto& rel : relations) {
+            adj[rel[0] - 1].push_back(rel[1] - 1);
+        }
+
+        vector<int> maxTime(n, -1);
+        vector<bool> processed(n, false);
+
+        for (int i = 0; i < n; i++) {
+            if (maxTime[i] == -1) {
+                stack<int> stk;
+                stk.push(i);
+                while (!stk.empty()) {
+                    int node = stk.top(); stk.pop();
+                    if (processed[node]) {
+                        int best = 0;
+                        for (int nei : adj[node]) {
+                            best = max(best, maxTime[nei]);
+                        }
+                        maxTime[node] = time[node] + best;
+                    } else {
+                        processed[node] = true;
+                        stk.push(node);
+                        for (int nei : adj[node]) {
+                            if (maxTime[nei] == -1) {
+                                stk.push(nei);
+                            }
+                        }
+                    }
+                }
+            }
+        }
+        return *max_element(maxTime.begin(), maxTime.end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} relations
+     * @param {number[]} time
+     * @return {number}
+     */
+    minimumTime(n, relations, time) {
+        let adj = Array.from({ length: n }, () => []);
+        for (let [src, dst] of relations) {
+            adj[src - 1].push(dst - 1);
+        }
+
+        let maxTime = Array(n).fill(-1);
+        let processed = Array(n).fill(false);
+
+        for (let i = 0; i < n; i++) {
+            if (maxTime[i] === -1) {
+                let stack = [i];
+                while (stack.length > 0) {
+                    let node = stack.pop();
+                    if (processed[node]) {
+                        let best = 0;
+                        for (let nei of adj[node]) {
+                            best = Math.max(best, maxTime[nei]);
+                        }
+                        maxTime[node] = time[node] + best;
+                    } else {
+                        processed[node] = true;
+                        stack.push(node);
+                        for (let nei of adj[node]) {
+                            if (maxTime[nei] === -1) {
+                                stack.push(nei);
+                            }
+                        }
+                    }
+                }
+            }
+        }
+        return Math.max(...maxTime);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + E)$
+* Space complexity: $O(V + E)$
+
+> Where $V$ is the number of courses and $E$ is the number of prerequisites.
+
+---
+
+## 3. Topological Sort (Kahn's Algorithm)
+
+::tabs-start
+
+```python
+class Solution:
+    def minimumTime(self, n: int, relations: list[list[int]], time: list[int]) -> int:
+        adj = [[] for _ in range(n)]
+        indegree = [0] * n
+        maxTime = time[:]
+
+        for src, dst in relations:
+            adj[src - 1].append(dst - 1)
+            indegree[dst - 1] += 1
+
+        queue = deque([i for i in range(n) if indegree[i] == 0])
+        while queue:
+            node = queue.popleft()
+            for nei in adj[node]:
+                maxTime[nei] = max(maxTime[nei], maxTime[node] + time[nei])
+                indegree[nei] -= 1
+                if indegree[nei] == 0:
+                    queue.append(nei)
+
+        return max(maxTime)
+```
+
+```java
+public class Solution {
+    public int minimumTime(int n, int[][] relations, int[] time) {
+        List<List<Integer>> adj = new ArrayList<>();
+        int[] indegree = new int[n];
+        int[] maxTime = Arrays.copyOf(time, n);
+
+        for (int i = 0; i < n; i++) {
+            adj.add(new ArrayList<>());
+        }
+
+        for (int[] relation : relations) {
+            int src = relation[0] - 1, dst = relation[1] - 1;
+            adj.get(src).add(dst);
+            indegree[dst]++;
+        }
+
+        Queue<Integer> queue = new LinkedList<>();
+        for (int i = 0; i < n; i++) {
+            if (indegree[i] == 0) {
+                queue.add(i);
+            }
+        }
+
+        while (!queue.isEmpty()) {
+            int node = queue.poll();
+            for (int nei : adj.get(node)) {
+                maxTime[nei] = Math.max(maxTime[nei], maxTime[node] + time[nei]);
+                if (--indegree[nei] == 0) {
+                    queue.add(nei);
+                }
+            }
+        }
+
+        return Arrays.stream(maxTime).max().getAsInt();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minimumTime(int n, vector<vector<int>>& relations, vector<int>& time) {
+        vector<vector<int>> adj(n);
+        vector<int> indegree(n, 0);
+        vector<int> maxTime(time.begin(), time.end());
+
+        for (auto& relation : relations) {
+            int src = relation[0] - 1, dst = relation[1] - 1;
+            adj[src].push_back(dst);
+            indegree[dst]++;
+        }
+
+        queue<int> queue;
+        for (int i = 0; i < n; i++) {
+            if (indegree[i] == 0) {
+                queue.push(i);
+            }
+        }
+
+        while (!queue.empty()) {
+            int node = queue.front(); queue.pop();
+            for (int nei : adj[node]) {
+                maxTime[nei] = max(maxTime[nei], maxTime[node] + time[nei]);
+                if (--indegree[nei] == 0) {
+                    queue.push(nei);
+                }
+            }
+        }
+
+        return *max_element(maxTime.begin(), maxTime.end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} relations
+     * @param {number[]} time
+     * @return {number}
+     */
+    minimumTime(n, relations, time) {
+        let adj = Array.from({ length: n }, () => []);
+        let indegree = Array(n).fill(0);
+        let maxTime = [...time];
+
+        for (let [src, dst] of relations) {
+            adj[src - 1].push(dst - 1);
+            indegree[dst - 1]++;
+        }
+
+        let queue = new Queue();
+        for (let i = 0; i < n; i++) {
+            if (indegree[i] === 0) {
+                queue.push(i);
+            }
+        }
+
+        while (!queue.isEmpty()) {
+            let node = queue.pop();
+            for (let nei of adj[node]) {
+                maxTime[nei] = Math.max(maxTime[nei], maxTime[node] + time[nei]);
+                if (--indegree[nei] === 0) {
+                    queue.push(nei);
+                }
+            }
+        }
+
+        return Math.max(...maxTime);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + E)$
+* Space complexity: $O(V + E)$
+
+> Where $V$ is the number of courses and $E$ is the number of prerequisites.
\ No newline at end of file
diff --git a/articles/partition-array-for-maximum-sum.md b/articles/partition-array-for-maximum-sum.md
new file mode 100644
index 000000000..a2fb52393
--- /dev/null
+++ b/articles/partition-array-for-maximum-sum.md
@@ -0,0 +1,446 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def maxSumAfterPartitioning(self, arr: List[int], k: int) -> int:
+        def dfs(i):
+            if i >= len(arr):
+                return 0
+
+            cur_max = 0
+            res = 0
+            for j in range(i, min(len(arr), i + k)):
+                cur_max = max(cur_max, arr[j])
+                window_size = j - i + 1
+                res = max(res, dfs(j + 1) + cur_max * window_size)
+
+            return res
+
+        return dfs(0)
+```
+
+```java
+public class Solution {
+    public int maxSumAfterPartitioning(int[] arr, int k) {
+        return dfs(0, arr, k);
+    }
+
+    private int dfs(int i, int[] arr, int k) {
+        if (i >= arr.length) {
+            return 0;
+        }
+
+        int cur_max = 0;
+        int res = 0;
+        for (int j = i; j < Math.min(arr.length, i + k); j++) {
+            cur_max = Math.max(cur_max, arr[j]);
+            int window_size = j - i + 1;
+            res = Math.max(res, dfs(j + 1, arr, k) + cur_max * window_size);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxSumAfterPartitioning(vector<int>& arr, int k) {
+        return dfs(0, arr, k);
+    }
+
+private:
+    int dfs(int i, vector<int>& arr, int k) {
+        if (i >= arr.size()) {
+            return 0;
+        }
+
+        int cur_max = 0, res = 0;
+        for (int j = i; j < min((int)arr.size(), i + k); j++) {
+            cur_max = max(cur_max, arr[j]);
+            int window_size = j - i + 1;
+            res = max(res, dfs(j + 1, arr, k) + cur_max * window_size);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @param {number} k
+     * @return {number}
+     */
+    maxSumAfterPartitioning(arr, k) {
+        const dfs = (i) => {
+            if (i >= arr.length) {
+                return 0;
+            }
+
+            let cur_max = 0, res = 0;
+            for (let j = i; j < Math.min(arr.length, i + k); j++) {
+                cur_max = Math.max(cur_max, arr[j]);
+                let window_size = j - i + 1;
+                res = Math.max(res, dfs(j + 1) + cur_max * window_size);
+            }
+
+            return res;
+        };
+
+        return dfs(0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(k ^ n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+> Where $k$ is the maximum length of the subarray and $n$ is the size of the array $arr$.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxSumAfterPartitioning(self, arr: List[int], k: int) -> int:
+        cache = { len(arr) : 0 }
+
+        def dfs(i):
+            if i in cache:
+                return cache[i]
+
+            cur_max = 0
+            res = 0
+            for j in range(i, min(len(arr), i + k)):
+                cur_max = max(cur_max, arr[j])
+                window_size = j - i + 1
+                res = max(res, dfs(j + 1) + cur_max * window_size)
+
+            cache[i] = res
+            return res
+
+        return dfs(0)
+```
+
+```java
+public class Solution {
+    public int maxSumAfterPartitioning(int[] arr, int k) {
+        int[] cache = new int[arr.length + 1];
+        Arrays.fill(cache, -1);
+        cache[arr.length] = 0;
+        return dfs(0, arr, k, cache);
+    }
+
+    private int dfs(int i, int[] arr, int k, int[] cache) {
+        if (cache[i] != -1) {
+            return cache[i];
+        }
+
+        int cur_max = 0, res = 0;
+        for (int j = i; j < Math.min(arr.length, i + k); j++) {
+            cur_max = Math.max(cur_max, arr[j]);
+            int window_size = j - i + 1;
+            res = Math.max(res, dfs(j + 1, arr, k, cache) + cur_max * window_size);
+        }
+
+        cache[i] = res;
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxSumAfterPartitioning(vector<int>& arr, int k) {
+        vector<int> cache(arr.size() + 1, -1);
+        cache[arr.size()] = 0;
+        return dfs(0, arr, k, cache);
+    }
+
+private:
+    int dfs(int i, vector<int>& arr, int k, vector<int>& cache) {
+        if (cache[i] != -1) {
+            return cache[i];
+        }
+
+        int cur_max = 0, res = 0;
+        for (int j = i; j < min((int)arr.size(), i + k); j++) {
+            cur_max = max(cur_max, arr[j]);
+            int window_size = j - i + 1;
+            res = max(res, dfs(j + 1, arr, k, cache) + cur_max * window_size);
+        }
+
+        return cache[i] = res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @param {number} k
+     * @return {number}
+     */
+    maxSumAfterPartitioning(arr, k) {
+        const cache = new Array(arr.length + 1).fill(-1);
+        cache[arr.length] = 0;
+
+        const dfs = (i) => {
+            if (cache[i] !== -1) {
+                return cache[i];
+            }
+
+            let cur_max = 0, res = 0;
+            for (let j = i; j < Math.min(arr.length, i + k); j++) {
+                cur_max = Math.max(cur_max, arr[j]);
+                let window_size = j - i + 1;
+                res = Math.max(res, dfs(j + 1) + cur_max * window_size);
+            }
+
+            return (cache[i] = res);
+        };
+
+        return dfs(0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * k)$
+* Space complexity: $O(n)$
+
+> Where $k$ is the maximum length of the subarray and $n$ is the size of the array $arr$.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxSumAfterPartitioning(self, arr: List[int], k: int) -> int:
+        n = len(arr)
+        dp = [0] * (n + 1)
+
+        for i in range(n - 1, -1, -1):
+            cur_max = 0
+            for j in range(i, min(n, i + k)):
+                cur_max = max(cur_max, arr[j])
+                window_size = j - i + 1
+                dp[i] = max(dp[i], dp[j + 1] + cur_max * window_size)
+
+        return dp[0]
+```
+
+```java
+public class Solution {
+    public int maxSumAfterPartitioning(int[] arr, int k) {
+        int n = arr.length;
+        int[] dp = new int[n + 1];
+
+        for (int i = n - 1; i >= 0; i--) {
+            int cur_max = 0;
+            for (int j = i; j < Math.min(n, i + k); j++) {
+                cur_max = Math.max(cur_max, arr[j]);
+                int window_size = j - i + 1;
+                dp[i] = Math.max(dp[i], dp[j + 1] + cur_max * window_size);
+            }
+        }
+
+        return dp[0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxSumAfterPartitioning(vector<int>& arr, int k) {
+        int n = arr.size();
+        vector<int> dp(n + 1, 0);
+
+        for (int i = n - 1; i >= 0; i--) {
+            int cur_max = 0;
+            for (int j = i; j < min(n, i + k); j++) {
+                cur_max = max(cur_max, arr[j]);
+                int window_size = j - i + 1;
+                dp[i] = max(dp[i], dp[j + 1] + cur_max * window_size);
+            }
+        }
+
+        return dp[0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @param {number} k
+     * @return {number}
+     */
+    maxSumAfterPartitioning(arr, k) {
+        let n = arr.length;
+        let dp = new Array(n + 1).fill(0);
+
+        for (let i = n - 1; i >= 0; i--) {
+            let cur_max = 0;
+            for (let j = i; j < Math.min(n, i + k); j++) {
+                cur_max = Math.max(cur_max, arr[j]);
+                let window_size = j - i + 1;
+                dp[i] = Math.max(dp[i], dp[j + 1] + cur_max * window_size);
+            }
+        }
+
+        return dp[0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * k)$
+* Space complexity: $O(n)$
+
+> Where $k$ is the maximum length of the subarray and $n$ is the size of the array $arr$.
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxSumAfterPartitioning(self, arr: List[int], k: int) -> int:
+        dp = [0] * k
+        dp[0] = arr[0]
+
+        for i in range(1, len(arr)):
+            cur_max = 0
+            max_at_i = 0
+            for j in range(i, i - k, -1):
+                if j < 0:
+                    break
+                cur_max = max(cur_max, arr[j])
+                window_size = i - j + 1
+                cur_sum = cur_max * window_size
+                sub_sum = dp[(j - 1) % k] if j > 0 else 0
+                max_at_i = max(max_at_i, cur_sum + sub_sum)
+
+            dp[i % k] = max_at_i
+
+        return dp[(len(arr) - 1) % k]
+```
+
+```java
+public class Solution {
+    public int maxSumAfterPartitioning(int[] arr, int k) {
+        int n = arr.length;
+        int[] dp = new int[k];
+        dp[0] = arr[0];
+
+        for (int i = 1; i < n; i++) {
+            int cur_max = 0, max_at_i = 0;
+            for (int j = i; j > i - k; j--) {
+                if (j < 0) break;
+                cur_max = Math.max(cur_max, arr[j]);
+                int window_size = i - j + 1;
+                int cur_sum = cur_max * window_size;
+                int sub_sum = (j > 0) ? dp[(j - 1) % k] : 0;
+                max_at_i = Math.max(max_at_i, cur_sum + sub_sum);
+            }
+            dp[i % k] = max_at_i;
+        }
+
+        return dp[(n - 1) % k];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxSumAfterPartitioning(vector<int>& arr, int k) {
+        int n = arr.size();
+        vector<int> dp(k);
+        dp[0] = arr[0];
+
+        for (int i = 1; i < n; i++) {
+            int cur_max = 0, max_at_i = 0;
+            for (int j = i; j > i - k; j--) {
+                if (j < 0) break;
+                cur_max = max(cur_max, arr[j]);
+                int window_size = i - j + 1;
+                int cur_sum = cur_max * window_size;
+                int sub_sum = (j > 0) ? dp[(j - 1) % k] : 0;
+                max_at_i = max(max_at_i, cur_sum + sub_sum);
+            }
+            dp[i % k] = max_at_i;
+        }
+
+        return dp[(n - 1) % k];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @param {number} k
+     * @return {number}
+     */
+    maxSumAfterPartitioning(arr, k) {
+        const n = arr.length;
+        const dp = new Array(k).fill(0);
+        dp[0] = arr[0];
+
+        for (let i = 1; i < n; i++) {
+            let cur_max = 0, max_at_i = 0;
+            for (let j = i; j > i - k; j--) {
+                if (j < 0) break;
+                cur_max = Math.max(cur_max, arr[j]);
+                let window_size = i - j + 1;
+                let cur_sum = cur_max * window_size;
+                let sub_sum = (j > 0) ? dp[(j - 1) % k] : 0;
+                max_at_i = Math.max(max_at_i, cur_sum + sub_sum);
+            }
+            dp[i % k] = max_at_i;
+        }
+
+        return dp[(n - 1) % k];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * k)$
+* Space complexity: $O(k)$
+
+> Where $k$ is the maximum length of the subarray and $n$ is the size of the array $arr$.
\ No newline at end of file
diff --git a/articles/partition-equal-subset-sum.md b/articles/partition-equal-subset-sum.md
index 5e04a39c2..6d6fd0caa 100644
--- a/articles/partition-equal-subset-sum.md
+++ b/articles/partition-equal-subset-sum.md
@@ -140,6 +140,87 @@ public class Solution {
 }
 ```
 
+```go
+func canPartition(nums []int) bool {
+    sum := 0
+    for _, num := range nums {
+        sum += num
+    }
+    if sum%2 != 0 {
+        return false
+    }
+    
+    target := sum / 2
+    
+    var dfs func(int, int) bool
+    dfs = func(i int, target int) bool {
+        if target == 0 {
+            return true
+        }
+        if i >= len(nums) || target < 0 {
+            return false
+        }
+        
+        return dfs(i+1, target) || dfs(i+1, target-nums[i])
+    }
+    
+    return dfs(0, target)
+}
+```
+
+```kotlin
+class Solution {
+    fun canPartition(nums: IntArray): Boolean {
+        val sum = nums.sum()
+        if (sum % 2 != 0) {
+            return false
+        }
+        
+        val target = sum / 2
+        
+        fun dfs(i: Int, target: Int): Boolean {
+            if (target == 0) {
+                return true
+            }
+            if (i >= nums.size || target < 0) {
+                return false
+            }
+            
+            return dfs(i + 1, target) || dfs(i + 1, target - nums[i])
+        }
+        
+        return dfs(0, target)
+    }
+}
+```
+
+```swift
+class Solution {
+    func canPartition(_ nums: [Int]) -> Bool {
+        let totalSum = nums.reduce(0, +)
+        if totalSum % 2 != 0 {
+            return false
+        }
+
+        let target = totalSum / 2
+        let n = nums.count
+
+        func dfs(_ i: Int, _ target: Int) -> Bool {
+            if i >= n {
+                return target == 0
+            }
+            if target < 0 {
+                return false
+            }
+
+            return dfs(i + 1, target) || dfs(i + 1, target - nums[i])
+        }
+
+        return dfs(0, target)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -328,6 +409,111 @@ public class Solution {
 }
 ```
 
+```go
+func canPartition(nums []int) bool {
+    total := 0
+    for _, num := range nums {
+        total += num
+    }
+    if total%2 != 0 {
+        return false
+    }
+    
+    target := total / 2
+    n := len(nums)
+    memo := make([][]int, n+1)
+    for i := range memo {
+        memo[i] = make([]int, target+1)
+        for j := range memo[i] {
+            memo[i][j] = -1
+        }
+    }
+
+    var dfs func(int, int) bool
+    dfs = func(i, target int) bool {
+        if target == 0 {
+            return true
+        }
+        if i >= n || target < 0 {
+            return false
+        }
+        if memo[i][target] != -1 {
+            return memo[i][target] == 1
+        }
+        
+        found := dfs(i+1, target) || dfs(i+1, target-nums[i])
+        if found {
+            memo[i][target] = 1
+        } else {
+            memo[i][target] = 0
+        }
+        
+        return found
+    }
+
+    return dfs(0, target)
+}
+```
+
+```kotlin
+class Solution {
+    fun canPartition(nums: IntArray): Boolean {
+        val total = nums.sum()
+        if (total % 2 != 0) return false
+        
+        val target = total / 2
+        val n = nums.size
+        val memo = Array(n + 1) { IntArray(target + 1) { -1 } }
+
+        fun dfs(i: Int, target: Int): Boolean {
+            if (target == 0) return true
+            if (i >= n || target < 0) return false
+            if (memo[i][target] != -1) return memo[i][target] == 1
+            
+            val found = dfs(i + 1, target) || dfs(i + 1, target - nums[i])
+            memo[i][target] = if (found) 1 else 0
+            
+            return found
+        }
+
+        return dfs(0, target)
+    }
+}
+```
+
+```swift
+class Solution {
+    func canPartition(_ nums: [Int]) -> Bool {
+        let total = nums.reduce(0, +)
+        if total % 2 != 0 {
+            return false
+        }
+
+        let target = total / 2
+        let n = nums.count
+        var memo = Array(repeating: Array(repeating: -1, count: target + 1), count: n + 1)
+
+        func dfs(_ i: Int, _ target: Int) -> Bool {
+            if target == 0 {
+                return true
+            }
+            if i >= n || target < 0 {
+                return false
+            }
+            if memo[i][target] != -1 {
+                return memo[i][target] == 1
+            }
+
+            let result = dfs(i + 1, target) || dfs(i + 1, target - nums[i])
+            memo[i][target] = result ? 1 : 0
+            return result
+        }
+
+        return dfs(0, target)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -512,6 +698,101 @@ public class Solution {
 }
 ```
 
+```go
+func canPartition(nums []int) bool {
+    total := 0
+    for _, num := range nums {
+        total += num
+    }
+    if total%2 != 0 {
+        return false
+    }
+
+    target := total / 2
+    n := len(nums)
+    dp := make([][]bool, n+1)
+    for i := range dp {
+        dp[i] = make([]bool, target+1)
+    }
+
+    for i := 0; i <= n; i++ {
+        dp[i][0] = true
+    }
+
+    for i := 1; i <= n; i++ {
+        for j := 1; j <= target; j++ {
+            if nums[i-1] <= j {
+                dp[i][j] = dp[i-1][j] || dp[i-1][j-nums[i-1]]
+            } else {
+                dp[i][j] = dp[i-1][j]
+            }
+        }
+    }
+
+    return dp[n][target]
+}
+```
+
+```kotlin
+class Solution {
+    fun canPartition(nums: IntArray): Boolean {
+        val total = nums.sum()
+        if (total % 2 != 0) return false
+
+        val target = total / 2
+        val n = nums.size
+        val dp = Array(n + 1) { BooleanArray(target + 1) }
+
+        for (i in 0..n) {
+            dp[i][0] = true
+        }
+
+        for (i in 1..n) {
+            for (j in 1..target) {
+                dp[i][j] = if (nums[i - 1] <= j) {
+                    dp[i - 1][j] || dp[i - 1][j - nums[i - 1]]
+                } else {
+                    dp[i - 1][j]
+                }
+            }
+        }
+
+        return dp[n][target]
+    }
+}
+```
+
+```swift
+class Solution {
+    func canPartition(_ nums: [Int]) -> Bool {
+        let total = nums.reduce(0, +)
+        if total % 2 != 0 {
+            return false
+        }
+
+        let target = total / 2
+        let n = nums.count
+        var dp = Array(repeating: Array(repeating: false, count: target + 1), count: n + 1)
+
+        for i in 0...n {
+            dp[i][0] = true
+        }
+
+        for i in 1...n {
+            for j in 1...target {
+                if nums[i - 1] <= j {
+                    dp[i][j] = dp[i - 1][j] || dp[i - 1][j - nums[i - 1]]
+                } else {
+                    dp[i][j] = dp[i - 1][j]
+                }
+            }
+        }
+
+        return dp[n][target]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -695,6 +976,89 @@ public class Solution {
 }
 ```
 
+```go
+func canPartition(nums []int) bool {
+    total := 0
+    for _, num := range nums {
+        total += num
+    }
+    if total%2 != 0 {
+        return false
+    }
+
+    target := total / 2
+    dp := make([]bool, target+1)
+    nextDp := make([]bool, target+1)
+    dp[0] = true
+
+    for i := 0; i < len(nums); i++ {
+        for j := 1; j <= target; j++ {
+            if j >= nums[i] {
+                nextDp[j] = dp[j] || dp[j-nums[i]]
+            } else {
+                nextDp[j] = dp[j]
+            }
+        }
+        dp, nextDp = nextDp, dp
+    }
+
+    return dp[target]
+}
+```
+
+```kotlin
+class Solution {
+    fun canPartition(nums: IntArray): Boolean {
+        val total = nums.sum()
+        if (total % 2 != 0) return false
+
+        val target = total / 2
+        var dp = BooleanArray(target + 1)
+        var nextDp = BooleanArray(target + 1)
+        dp[0] = true
+
+        for (i in nums.indices) {
+            for (j in 1..target) {
+                nextDp[j] = if (j >= nums[i]) dp[j] || dp[j - nums[i]] else dp[j]
+            }
+            val temp = dp
+            dp = nextDp
+            nextDp = temp
+        }
+
+        return dp[target]
+    }
+}
+```
+
+```swift
+class Solution {
+    func canPartition(_ nums: [Int]) -> Bool {
+        if nums.reduce(0, +) % 2 != 0 {
+            return false
+        }
+
+        let target = nums.reduce(0, +) / 2
+        var dp = Array(repeating: false, count: target + 1)
+        var nextDp = Array(repeating: false, count: target + 1)
+
+        dp[0] = true
+        for num in nums {
+            for j in stride(from: target, through: 1, by: -1) {
+                if j >= num {
+                    nextDp[j] = dp[j] || dp[j - num]
+                } else {
+                    nextDp[j] = dp[j]
+                }
+            }
+            swap(&dp, &nextDp)
+        }
+
+        return dp[target]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -849,6 +1213,85 @@ public class Solution {
 }
 ```
 
+```go
+func canPartition(nums []int) bool {
+    total := 0
+    for _, num := range nums {
+        total += num
+    }
+    if total%2 != 0 {
+        return false
+    }
+
+    target := total / 2
+    dp := map[int]bool{0: true}
+
+    for i := len(nums) - 1; i >= 0; i-- {
+        nextDP := map[int]bool{}
+        for t := range dp {
+            if t+nums[i] == target {
+                return true
+            }
+            nextDP[t+nums[i]] = true
+            nextDP[t] = true
+        }
+        dp = nextDP
+    }
+
+    return false
+}
+```
+
+```kotlin
+class Solution {
+    fun canPartition(nums: IntArray): Boolean {
+        val total = nums.sum()
+        if (total % 2 != 0) return false
+
+        val target = total / 2
+        var dp = hashSetOf(0)
+
+        for (i in nums.size - 1 downTo 0) {
+            val nextDP = HashSet<Int>()
+            for (t in dp) {
+                if (t + nums[i] == target) return true
+                nextDP.add(t + nums[i])
+                nextDP.add(t)
+            }
+            dp = nextDP
+        }
+
+        return false
+    }
+}
+```
+
+```swift
+class Solution {
+    func canPartition(_ nums: [Int]) -> Bool {
+        if nums.reduce(0, +) % 2 != 0 {
+            return false
+        }
+
+        var dp: Set<Int> = [0]
+        let target = nums.reduce(0, +) / 2
+
+        for i in stride(from: nums.count - 1, through: 0, by: -1) {
+            var nextDP: Set<Int> = []
+            for t in dp {
+                if t + nums[i] == target {
+                    return true
+                }
+                nextDP.insert(t + nums[i])
+                nextDP.insert(t)
+            }
+            dp = nextDP
+        }
+        return false
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -999,6 +1442,73 @@ public class Solution {
 }
 ```
 
+```go
+func canPartition(nums []int) bool {
+    total := 0
+    for _, num := range nums {
+        total += num
+    }
+    if total%2 != 0 {
+        return false
+    }
+
+    target := total / 2
+    dp := make([]bool, target+1)
+    dp[0] = true
+
+    for _, num := range nums {
+        for j := target; j >= num; j-- {
+            dp[j] = dp[j] || dp[j-num]
+        }
+    }
+
+    return dp[target]
+}
+```
+
+```kotlin
+class Solution {
+    fun canPartition(nums: IntArray): Boolean {
+        val total = nums.sum()
+        if (total % 2 != 0) return false
+
+        val target = total / 2
+        val dp = BooleanArray(target + 1)
+        dp[0] = true
+
+        for (num in nums) {
+            for (j in target downTo num) {
+                dp[j] = dp[j] || dp[j - num]
+            }
+        }
+
+        return dp[target]
+    }
+}
+```
+
+```swift
+class Solution {
+    func canPartition(_ nums: [Int]) -> Bool {
+        if nums.reduce(0, +) % 2 != 0 {
+            return false
+        }
+
+        let target = nums.reduce(0, +) / 2
+        var dp = Array(repeating: false, count: target + 1)
+
+        dp[0] = true
+        for num in nums {
+            for j in stride(from: target, through: num, by: -1) {
+                dp[j] = dp[j] || dp[j - num]
+            }
+        }
+
+        return dp[target]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -1023,10 +1533,10 @@ class Solution:
 
         target = total // 2
         dp = 1 << 0
-        
+
         for num in nums:
             dp |= dp << num
-            
+
         return (dp & (1 << target)) != 0
 ```
 
diff --git a/articles/partition-labels.md b/articles/partition-labels.md
new file mode 100644
index 000000000..1e4e2b3a1
--- /dev/null
+++ b/articles/partition-labels.md
@@ -0,0 +1,204 @@
+## 1. Two Pointers (Greedy)
+
+::tabs-start
+
+```python
+class Solution:
+    def partitionLabels(self, s: str) -> List[int]:
+        lastIndex = {}
+        for i, c in enumerate(s):
+            lastIndex[c] = i
+        
+        res = []
+        size = end = 0
+        for i, c in enumerate(s):
+            size += 1
+            end = max(end, lastIndex[c])
+
+            if i == end:
+                res.append(size)
+                size = 0
+        return res
+```
+
+```java
+public class Solution {
+    public List<Integer> partitionLabels(String s) {
+        Map<Character, Integer> lastIndex = new HashMap<>();
+        for (int i = 0; i < s.length(); i++) {
+            lastIndex.put(s.charAt(i), i);
+        }
+        
+        List<Integer> res = new ArrayList<>();
+        int size = 0, end = 0;
+        for (int i = 0; i < s.length(); i++) {
+            size++;
+            end = Math.max(end, lastIndex.get(s.charAt(i)));
+
+            if (i == end) {
+                res.add(size);
+                size = 0;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> partitionLabels(string s) {
+        unordered_map<char, int> lastIndex;
+        for (int i = 0; i < s.size(); i++) {
+            lastIndex[s[i]] = i;
+        }
+
+        vector<int> res;
+        int size = 0, end = 0;
+        for (int i = 0; i < s.size(); i++) {
+            size++;
+            end = max(end, lastIndex[s[i]]);
+
+            if (i == end) {
+                res.push_back(size);
+                size = 0;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} S
+     * @return {number[]}
+     */
+    partitionLabels(S) {
+        let lastIndex = {};
+        for (let i = 0; i < S.length; i++) {
+            lastIndex[S[i]] = i;
+        }
+
+        let res = [];
+        let size = 0, end = 0;
+        for (let i = 0; i < S.length; i++) {
+            size++;
+            end = Math.max(end, lastIndex[S[i]]);
+
+            if (i === end) {
+                res.push(size);
+                size = 0;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<int> PartitionLabels(string s) {
+        Dictionary<char, int> lastIndex = new Dictionary<char, int>();
+        for (int i = 0; i < s.Length; i++) {
+            lastIndex[s[i]] = i;
+        }
+
+        List<int> res = new List<int>();
+        int size = 0, end = 0;
+        for (int i = 0; i < s.Length; i++) {
+            size++;
+            end = Math.Max(end, lastIndex[s[i]]);
+
+            if (i == end) {
+                res.Add(size);
+                size = 0;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```go
+func partitionLabels(s string) []int {
+    lastIndex := make(map[rune]int)
+    for i, c := range s {
+        lastIndex[c] = i
+    }
+
+    var res []int
+    size, end := 0, 0
+    for i, c := range s {
+        size++
+        if lastIndex[c] > end {
+            end = lastIndex[c]
+        }
+
+        if i == end {
+            res = append(res, size)
+            size = 0
+        }
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun partitionLabels(s: String): List<Int> {
+        val lastIndex = HashMap<Char, Int>()
+        s.forEachIndexed { i, c -> lastIndex[c] = i }
+
+        val res = mutableListOf<Int>()
+        var size = 0
+        var end = 0
+        for (i in s.indices) {
+            size++
+            end = maxOf(end, lastIndex[s[i]] ?: 0)
+
+            if (i == end) {
+                res.add(size)
+                size = 0
+            }
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func partitionLabels(_ s: String) -> [Int] {
+        var lastIndex = [Character: Int]()
+        for (i, c) in s.enumerated() {
+            lastIndex[c] = i
+        }
+
+        var res = [Int]()
+        var size = 0
+        var end = 0
+        for (i, c) in s.enumerated() {
+            size += 1
+            end = max(end, lastIndex[c]!)
+
+            if i == end {
+                res.append(size)
+                size = 0
+            }
+        }
+        return res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(m)$
+
+> Where $n$ is the length of the string $s$ and $m$ is the number of unique characters in the string $s$.
\ No newline at end of file
diff --git a/articles/partition-list.md b/articles/partition-list.md
new file mode 100644
index 000000000..d3e69dd52
--- /dev/null
+++ b/articles/partition-list.md
@@ -0,0 +1,324 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def partition(self, head: Optional[ListNode], x: int) -> Optional[ListNode]:
+        if not head:
+            return None
+        
+        less, greater = [], []
+        cur = head
+        while cur:
+            if cur.val < x:
+                less.append(cur.val)
+            else:
+                greater.append(cur.val)
+            cur = cur.next
+
+        cur = head
+        for val in less:
+            cur.val = val
+            cur = cur.next
+
+        for val in greater:
+            cur.val = val
+            cur = cur.next
+
+        return head
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode partition(ListNode head, int x) {
+        if (head == null) {
+            return null;
+        }
+
+        List<Integer> less = new ArrayList<>();
+        List<Integer> greater = new ArrayList<>();
+        ListNode cur = head;
+
+        while (cur != null) {
+            if (cur.val < x) {
+                less.add(cur.val);
+            } else {
+                greater.add(cur.val);
+            }
+            cur = cur.next;
+        }
+
+        cur = head;
+        for (int val : less) {
+            cur.val = val;
+            cur = cur.next;
+        }
+
+        for (int val : greater) {
+            cur.val = val;
+            cur = cur.next;
+        }
+
+        return head;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* partition(ListNode* head, int x) {
+        if (!head) return nullptr;
+        
+        vector<int> less, greater;
+        ListNode* cur = head;
+
+        while (cur) {
+            if (cur->val < x) {
+                less.push_back(cur->val);
+            } else {
+                greater.push_back(cur->val);
+            }
+            cur = cur->next;
+        }
+
+        cur = head;
+        for (int val : less) {
+            cur->val = val;
+            cur = cur->next;
+        }
+
+        for (int val : greater) {
+            cur->val = val;
+            cur = cur->next;
+        }
+
+        return head;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @param {number} x
+     * @return {ListNode}
+     */
+    partition(head, x) {
+        if (!head) return null;
+
+        let less = [], greater = [];
+        let cur = head;
+
+        while (cur) {
+            if (cur.val < x) {
+                less.push(cur.val);
+            } else {
+                greater.push(cur.val);
+            }
+            cur = cur.next;
+        }
+
+        cur = head;
+        for (let val of less) {
+            cur.val = val;
+            cur = cur.next;
+        }
+
+        for (let val of greater) {
+            cur.val = val;
+            cur = cur.next;
+        }
+
+        return head;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Two Pointers
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def partition(self, head: Optional[ListNode], x: int) -> Optional[ListNode]:
+        left, right = ListNode(), ListNode()
+        ltail, rtail = left, right
+
+        while head:
+            if head.val < x:
+                ltail.next = head
+                ltail = ltail.next
+            else:
+                rtail.next = head
+                rtail = rtail.next
+            head = head.next
+
+        ltail.next = right.next
+        rtail.next = None
+        return left.next
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode partition(ListNode head, int x) {
+        ListNode left = new ListNode(0), right = new ListNode(0);
+        ListNode ltail = left, rtail = right;
+
+        while (head != null) {
+            if (head.val < x) {
+                ltail.next = head;
+                ltail = ltail.next;
+            } else {
+                rtail.next = head;
+                rtail = rtail.next;
+            }
+            head = head.next;
+        }
+
+        ltail.next = right.next;
+        rtail.next = null;
+        return left.next;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* partition(ListNode* head, int x) {
+        ListNode leftDummy(0), rightDummy(0);
+        ListNode *ltail = &leftDummy, *rtail = &rightDummy;
+
+        while (head) {
+            if (head->val < x) {
+                ltail->next = head;
+                ltail = ltail->next;
+            } else {
+                rtail->next = head;
+                rtail = rtail->next;
+            }
+            head = head->next;
+        }
+
+        ltail->next = rightDummy.next;
+        rtail->next = nullptr;
+        return leftDummy.next;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @param {number} x
+     * @return {ListNode}
+     */
+    partition(head, x) {
+        let left = new ListNode(0), right = new ListNode(0);
+        let ltail = left, rtail = right;
+
+        while (head) {
+            if (head.val < x) {
+                ltail.next = head;
+                ltail = ltail.next;
+            } else {
+                rtail.next = head;
+                rtail = rtail.next;
+            }
+            head = head.next;
+        }
+
+        ltail.next = right.next;
+        rtail.next = null;
+        return left.next;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/partition-to-k-equal-sum-subsets.md b/articles/partition-to-k-equal-sum-subsets.md
new file mode 100644
index 000000000..d217736df
--- /dev/null
+++ b/articles/partition-to-k-equal-sum-subsets.md
@@ -0,0 +1,945 @@
+## 1. Backtracking
+
+::tabs-start
+
+```python
+class Solution:
+    def canPartitionKSubsets(self, nums: List[int], k: int) -> bool:
+        if sum(nums) % k != 0:
+            return False
+
+        nums.sort(reverse=True)
+        target = sum(nums) // k
+        used = [False] * len(nums)
+
+        def backtrack(i, k, subsetSum):
+            if k == 0:
+                return True
+            if subsetSum == target:
+                return backtrack(0, k - 1, 0)
+            for j in range(i, len(nums)):
+                if used[j] or subsetSum + nums[j] > target:
+                    continue
+                used[j] = True
+                if backtrack(j + 1, k, subsetSum + nums[j]):
+                    return True
+                used[j] = False
+            return False
+
+        return backtrack(0, k, 0)
+```
+
+```java
+public class Solution {
+    private boolean[] used;
+    private int target;
+    private int n;
+
+    public boolean canPartitionKSubsets(int[] nums, int k) {
+        int sum = 0;
+        for (int num : nums) sum += num;
+        if (sum % k != 0) return false;
+
+        this.target = sum / k;
+        this.n = nums.length;
+        Arrays.sort(nums);
+        for (int i = 0; i < n / 2; i++) {
+            int tmp = nums[i];
+            nums[i] = nums[n - i - 1];
+            nums[n - i - 1] = tmp;
+        }
+        used = new boolean[n];
+        return backtrack(nums, k, 0, 0);
+    }
+
+    private boolean backtrack(int[] nums, int k, int currentSum, int start) {
+        if (k == 0) return true;
+        if (currentSum == target) return backtrack(nums, k - 1, 0, 0);
+
+        for (int i = start; i < n; i++) {
+            if (used[i] || currentSum + nums[i] > target) continue;
+            used[i] = true;
+            if (backtrack(nums, k, currentSum + nums[i], i + 1)) return true;
+            used[i] = false;
+        }
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+    vector<bool> used;
+    int target;
+
+public:
+    bool canPartitionKSubsets(vector<int>& nums, int k) {
+        int sum = accumulate(nums.begin(), nums.end(), 0);
+        if (sum % k != 0) return false;
+
+        target = sum / k;
+        sort(nums.rbegin(), nums.rend());
+        used.assign(nums.size(), false);
+        return backtrack(nums, k, 0, 0);
+    }
+
+private:
+    bool backtrack(vector<int>& nums, int k, int currentSum, int start) {
+        if (k == 0) return true;
+        if (currentSum == target) return backtrack(nums, k - 1, 0, 0);
+
+        for (int i = start; i < nums.size(); i++) {
+            if (used[i] || currentSum + nums[i] > target) continue;
+            used[i] = true;
+            if (backtrack(nums, k, currentSum + nums[i], i + 1)) return true;
+            used[i] = false;
+        }
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {boolean}
+     */
+    canPartitionKSubsets(nums, k) {
+        const sum = nums.reduce((a, b) => a + b, 0);
+        if (sum % k !== 0) return false;
+
+        const target = sum / k;
+        nums.sort((a, b) => b - a);
+        const used = Array(nums.length).fill(false);
+
+        const backtrack = (i, k, subsetSum) => {
+            if (k === 0) return true;
+            if (subsetSum === target) return backtrack(0, k - 1, 0);
+
+            for (let j = i; j < nums.length; j++) {
+                if (used[j] || subsetSum + nums[j] > target) continue;
+                used[j] = true;
+                if (backtrack(j + 1, k, subsetSum + nums[j])) return true;
+                used[j] = false;
+            }
+            return false;
+        };
+
+        return backtrack(0, k, 0);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool CanPartitionKSubsets(int[] nums, int k) {
+        int totalSum = nums.Sum();
+        if (totalSum % k != 0) return false;
+
+        int target = totalSum / k;
+        Array.Sort(nums);
+        Array.Reverse(nums);
+
+        bool[] used = new bool[nums.Length];
+
+        bool Backtrack(int i, int kRemaining, int subsetSum) {
+            if (kRemaining == 0) return true;
+            if (subsetSum == target) return Backtrack(0, kRemaining - 1, 0);
+
+            for (int j = i; j < nums.Length; j++) {
+                if (used[j] || subsetSum + nums[j] > target) continue;
+
+                used[j] = true;
+                if (Backtrack(j + 1, kRemaining, subsetSum + nums[j])) return true;
+                used[j] = false;
+            }
+
+            return false;
+        }
+
+        return Backtrack(0, k, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(k * 2 ^ n)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the size of the array $nums$ and $k$ is the number of subsets.
+
+---
+
+## 2. Backtracking (Pruning)
+
+::tabs-start
+
+```python
+class Solution:
+    def canPartitionKSubsets(self, nums: List[int], k: int) -> bool:
+        total = sum(nums)
+        if total % k != 0:
+            return False
+
+        nums.sort(reverse=True)
+        target = total // k
+        used = [False] * len(nums)
+
+        def backtrack(i, k, subsetSum):
+            if k == 0:
+                return True
+            if subsetSum == target:
+                return backtrack(0, k - 1, 0)
+            for j in range(i, len(nums)):
+                if used[j] or subsetSum + nums[j] > target:
+                    continue
+                used[j] = True
+                if backtrack(j + 1, k, subsetSum + nums[j]):
+                    return True
+                used[j] = False
+
+                if subsetSum == 0: # Pruning
+                    return False
+
+            return False
+
+        return backtrack(0, k, 0)
+```
+
+```java
+public class Solution {
+    private boolean[] used;
+    private int target;
+    private int n;
+
+    public boolean canPartitionKSubsets(int[] nums, int k) {
+        int sum = 0;
+        for (int num : nums) sum += num;
+        if (sum % k != 0) return false;
+
+        this.target = sum / k;
+        this.n = nums.length;
+        Arrays.sort(nums);
+        for (int i = 0; i < n / 2; i++) {
+            int tmp = nums[i];
+            nums[i] = nums[n - i - 1];
+            nums[n - i - 1] = tmp;
+        }
+        used = new boolean[n];
+        return backtrack(nums, k, 0, 0);
+    }
+
+    private boolean backtrack(int[] nums, int k, int currentSum, int start) {
+        if (k == 0) return true;
+        if (currentSum == target) return backtrack(nums, k - 1, 0, 0);
+
+        for (int i = start; i < n; i++) {
+            if (used[i] || currentSum + nums[i] > target) continue;
+            used[i] = true;
+            if (backtrack(nums, k, currentSum + nums[i], i + 1)) return true;
+            used[i] = false;
+            if (currentSum == 0) {  // Pruning
+                return false;
+            }
+        }
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+    vector<bool> used;
+    int target;
+
+public:
+    bool canPartitionKSubsets(vector<int>& nums, int k) {
+        int sum = accumulate(nums.begin(), nums.end(), 0);
+        if (sum % k != 0) return false;
+
+        target = sum / k;
+        sort(nums.rbegin(), nums.rend());
+        used.assign(nums.size(), false);
+        return backtrack(nums, k, 0, 0);
+    }
+
+private:
+    bool backtrack(vector<int>& nums, int k, int currentSum, int start) {
+        if (k == 0) return true;
+        if (currentSum == target) return backtrack(nums, k - 1, 0, 0);
+
+        for (int i = start; i < nums.size(); i++) {
+            if (used[i] || currentSum + nums[i] > target) continue;
+            used[i] = true;
+            if (backtrack(nums, k, currentSum + nums[i], i + 1)) return true;
+            used[i] = false;
+            if (currentSum == 0) {  // Pruning
+                return false;
+            }
+        }
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {boolean}
+     */
+    canPartitionKSubsets(nums, k) {
+        const sum = nums.reduce((a, b) => a + b, 0);
+        if (sum % k !== 0) return false;
+
+        const target = sum / k;
+        nums.sort((a, b) => b - a);
+        const used = Array(nums.length).fill(false);
+
+        const backtrack = (i, k, subsetSum) => {
+            if (k === 0) return true;
+            if (subsetSum === target) return backtrack(0, k - 1, 0);
+
+            for (let j = i; j < nums.length; j++) {
+                if (used[j] || subsetSum + nums[j] > target) continue;
+                used[j] = true;
+                if (backtrack(j + 1, k, subsetSum + nums[j])) return true;
+                used[j] = false;
+                if (subsetSum === 0) {  // Pruning
+                    return false;
+                }
+            }
+            return false;
+        };
+
+        return backtrack(0, k, 0);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool CanPartitionKSubsets(int[] nums, int k) {
+        int total = nums.Sum();
+        if (total % k != 0) return false;
+
+        Array.Sort(nums);
+        Array.Reverse(nums);
+        int target = total / k;
+        bool[] used = new bool[nums.Length];
+
+        bool Backtrack(int i, int kRemaining, int subsetSum) {
+            if (kRemaining == 0) return true;
+            if (subsetSum == target) return Backtrack(0, kRemaining - 1, 0);
+
+            for (int j = i; j < nums.Length; j++) {
+                if (used[j] || subsetSum + nums[j] > target) continue;
+
+                used[j] = true;
+                if (Backtrack(j + 1, kRemaining, subsetSum + nums[j])) return true;
+                used[j] = false;
+
+                if (subsetSum == 0) return false; // Pruning
+            }
+
+            return false;
+        }
+
+        return Backtrack(0, k, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(k * 2 ^ n)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the size of the array $nums$ and $k$ is the number of subsets.
+
+---
+
+## 3. Backtracking (Bit Mask + Pruning)
+
+::tabs-start
+
+```python
+class Solution:
+    def canPartitionKSubsets(self, nums: List[int], k: int) -> bool:
+        total = sum(nums)
+        if total % k != 0:
+            return False
+
+        nums.sort(reverse=True)
+        target = total // k
+        n = len(nums)
+
+        def backtrack(i, k, subsetSum, mask):
+            if k == 0:
+                return True
+            if subsetSum == target:
+                return backtrack(0, k - 1, 0, mask)
+            for j in range(i, n):
+                if (mask & (1 << j)) == 0 or subsetSum + nums[j] > target:
+                    continue
+                if backtrack(j + 1, k, subsetSum + nums[j], mask ^ (1 << j)):
+                    return True
+                if subsetSum == 0:
+                    return False
+            return False
+
+        return backtrack(0, k, 0, (1 << n) - 1)
+```
+
+```java
+public class Solution {
+    private int target;
+    private int n;
+
+    public boolean canPartitionKSubsets(int[] nums, int k) {
+        int total = 0;
+        for (int num : nums) total += num;
+        if (total % k != 0) return false;
+
+        this.target = total / k;
+        this.n = nums.length;
+        Arrays.sort(nums);
+        reverse(nums);
+
+        return backtrack(nums, 0, k, 0, (1 << this.n) - 1);
+    }
+
+    private boolean backtrack(int[] nums, int i, int k, int subsetSum, int mask) {
+        if (k == 0) return true;
+        if (subsetSum == target) return backtrack(nums, 0, k - 1, 0, mask);
+        for (int j = i; j < n; j++) {
+            if ((mask & (1 << j)) == 0 || subsetSum + nums[j] > target) continue;
+            if (backtrack(nums, j + 1, k, subsetSum + nums[j], mask ^ (1 << j))) {
+                return true;
+            }
+            if (subsetSum == 0) return false;
+        }
+        return false;
+    }
+
+    private void reverse(int[] nums) {
+        int l = 0, r = n - 1;
+        while (l < r) {
+            int temp = nums[l];
+            nums[l++] = nums[r];
+            nums[r--] = temp;
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+    int target, n;
+
+public:
+    bool canPartitionKSubsets(vector<int>& nums, int k) {
+        int total = accumulate(nums.begin(), nums.end(), 0);
+        if (total % k != 0) return false;
+
+        target = total / k;
+        n = nums.size();
+        sort(nums.rbegin(), nums.rend());
+        return backtrack(nums, 0, k, 0, (1 << n) - 1);
+    }
+
+private:
+    bool backtrack(vector<int>& nums, int i, int k, int subsetSum, int mask) {
+        if (k == 0) return true;
+        if (subsetSum == target) return backtrack(nums, 0, k - 1, 0, mask);
+        for (int j = i; j < nums.size(); j++) {
+            if ((mask & (1 << j)) == 0 || subsetSum + nums[j] > target) continue;
+            if (backtrack(nums, j + 1, k, subsetSum + nums[j], mask ^ (1 << j))) {
+                return true;
+            }
+            if (subsetSum == 0) return false;
+        }
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {boolean}
+     */
+    canPartitionKSubsets(nums, k) {
+        const total = nums.reduce((a, b) => a + b, 0);
+        if (total % k !== 0) return false;
+
+        const target = total / k;
+        const n = nums.length;
+        nums.sort((a, b) => b - a);
+
+        const backtrack = (i, k, subsetSum, mask) => {
+            if (k === 0) return true;
+            if (subsetSum === target) return backtrack(0, k - 1, 0, mask);
+            for (let j = i; j < n; j++) {
+                if ((mask & (1 << j)) === 0 || subsetSum + nums[j] > target) {
+                    continue;
+                }
+                if (backtrack(j + 1, k, subsetSum + nums[j], mask ^ (1 << j))) {
+                    return true;
+                }
+                if (subsetSum === 0) return false;
+            }
+            return false;
+        };
+
+        return backtrack(0, k, 0, (1 << n) - 1);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool CanPartitionKSubsets(int[] nums, int k) {
+        int total = nums.Sum();
+        if (total % k != 0) return false;
+
+        Array.Sort(nums);
+        Array.Reverse(nums);
+        int target = total / k;
+        int n = nums.Length;
+
+        bool Backtrack(int i, int kRemaining, int subsetSum, int mask) {
+            if (kRemaining == 0) return true;
+            if (subsetSum == target) return Backtrack(0, kRemaining - 1, 0, mask);
+
+            for (int j = i; j < n; j++) {
+                if ((mask & (1 << j)) == 0 || subsetSum + nums[j] > target) continue;
+
+                if (Backtrack(j + 1, kRemaining, subsetSum + nums[j], mask ^ (1 << j)))
+                    return true;
+
+                if (subsetSum == 0) return false;
+            }
+
+            return false;
+        }
+
+        return Backtrack(0, k, 0, (1 << n) - 1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(k * 2 ^ n)$
+* Space complexity:
+    * $O(1)$ or $O(n)$ space depending on the sorting algorithm.
+    * $O(n)$ for the recursion stack.
+
+> Where $n$ is the size of the array $nums$ and $k$ is the number of subsets.
+
+---
+
+## 4. Dynamic Programming (Top-Down) + Bit Mask
+
+::tabs-start
+
+```python
+class Solution:
+    def canPartitionKSubsets(self, nums: List[int], k: int) -> bool:
+        total = sum(nums)
+        if total % k != 0:
+            return False
+
+        nums.sort(reverse=True)
+        target = total // k
+        n = len(nums)
+        dp = [None] * (1 << n)
+
+        def backtrack(i, k, subsetSum, mask):
+            if dp[mask] != None:
+                return dp[mask]
+            if k == 0:
+                dp[mask] = True
+                return True
+            if subsetSum == target:
+                dp[mask] = backtrack(0, k - 1, 0, mask)
+                return dp[mask]
+
+            for j in range(i, n):
+                if (mask & (1 << j)) == 0 or subsetSum + nums[j] > target:
+                    continue
+                if backtrack(j + 1, k, subsetSum + nums[j], mask ^ (1 << j)):
+                    dp[mask] = True
+                    return True
+                if subsetSum == 0:
+                    dp[mask] = False
+                    return dp[mask]
+            dp[mask] = False
+            return False
+
+        return backtrack(0, k, 0, (1 << n) - 1)
+```
+
+```java
+public class Solution {
+    private int target;
+    private int n;
+    private Boolean[] dp;
+
+    public boolean canPartitionKSubsets(int[] nums, int k) {
+        int total = 0;
+        for (int num : nums) total += num;
+        if (total % k != 0) return false;
+
+        this.target = total / k;
+        this.n = nums.length;
+        Arrays.sort(nums);
+        reverse(nums);
+        dp = new Boolean[1 << this.n];
+
+        return backtrack(nums, 0, k, 0, (1 << this.n) - 1);
+    }
+
+    private boolean backtrack(int[] nums, int i, int k, int subsetSum, int mask) {
+        if (dp[mask] != null) return dp[mask];
+        if (k == 0) {
+            dp[mask] = true;
+            return dp[mask];
+        }
+        if (subsetSum == target) {
+            dp[mask] = backtrack(nums, 0, k - 1, 0, mask);
+            return dp[mask];
+        }
+        for (int j = i; j < n; j++) {
+            if ((mask & (1 << j)) == 0 || subsetSum + nums[j] > target) continue;
+            if (backtrack(nums, j + 1, k, subsetSum + nums[j], mask ^ (1 << j))) {
+                dp[mask] = true;
+                return true;
+            }
+            if (subsetSum == 0) {
+                dp[mask] = false;
+                return false;
+            }
+        }
+        dp[mask] = false;
+        return false;
+    }
+
+    private void reverse(int[] nums) {
+        int l = 0, r = n - 1;
+        while (l < r) {
+            int temp = nums[l];
+            nums[l++] = nums[r];
+            nums[r--] = temp;
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+    int target, n;
+    vector<int> dp;
+
+public:
+    bool canPartitionKSubsets(vector<int>& nums, int k) {
+        int total = accumulate(nums.begin(), nums.end(), 0);
+        if (total % k != 0) return false;
+
+        target = total / k;
+        n = nums.size();
+        dp.assign(1 << n, -1);
+        sort(nums.rbegin(), nums.rend());
+        return backtrack(nums, 0, k, 0, (1 << n) - 1);
+    }
+
+private:
+    int backtrack(vector<int>& nums, int i, int k, int subsetSum, int mask) {
+        if (dp[mask] != -1) return dp[mask];
+        if (k == 0) {
+            dp[mask] = 1;
+            return 1;
+        }
+        if (subsetSum == target) {
+            dp[mask] = backtrack(nums, 0, k - 1, 0, mask);
+            return dp[mask];
+        }
+        for (int j = i; j < nums.size(); j++) {
+            if ((mask & (1 << j)) == 0 || subsetSum + nums[j] > target) continue;
+            if (backtrack(nums, j + 1, k, subsetSum + nums[j], mask ^ (1 << j))) {
+                dp[mask] = 1;
+                return 1;
+            }
+            if (subsetSum == 0) {
+                break;
+            }
+        }
+        dp[mask] = 0;
+        return 0;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {boolean}
+     */
+    canPartitionKSubsets(nums, k) {
+        const total = nums.reduce((a, b) => a + b, 0);
+        if (total % k !== 0) return false;
+
+        const target = total / k;
+        const n = nums.length;
+        const dp = new Array(1 << n);
+        nums.sort((a, b) => b - a);
+
+        const backtrack = (i, k, subsetSum, mask) => {
+            if (dp[mask] !== undefined) return dp[mask];
+            if (k === 0) {
+                dp[mask] = true;
+                return true;
+            }
+            if (subsetSum === target) {
+                dp[mask] = backtrack(0, k - 1, 0, mask);
+                return dp[mask];
+            }
+            for (let j = i; j < n; j++) {
+                if ((mask & (1 << j)) === 0 || subsetSum + nums[j] > target) {
+                    continue;
+                }
+                if (backtrack(j + 1, k, subsetSum + nums[j], mask ^ (1 << j))) {
+                    dp[mask] = true;
+                    return true;
+                }
+                if (subsetSum === 0) break;
+            }
+            dp[mask] = false;
+            return false;
+        };
+
+        return backtrack(0, k, 0, (1 << n) - 1);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool CanPartitionKSubsets(int[] nums, int k) {
+        int total = nums.Sum();
+        if (total % k != 0) return false;
+
+        Array.Sort(nums);
+        Array.Reverse(nums);
+
+        int target = total / k;
+        int n = nums.Length;
+        bool?[] dp = new bool?[1 << n];
+
+        bool Backtrack(int i, int kRemaining, int subsetSum, int mask) {
+            if (dp[mask].HasValue) return (bool)dp[mask];
+            if (kRemaining == 0) {
+                dp[mask] = true;
+                return true;
+            }
+            if (subsetSum == target) {
+                dp[mask] = Backtrack(0, kRemaining - 1, 0, mask);
+                return (bool)dp[mask];
+            }
+
+            for (int j = i; j < n; j++) {
+                if ((mask & (1 << j)) == 0 || subsetSum + nums[j] > target) continue;
+
+                if (Backtrack(j + 1, kRemaining, subsetSum + nums[j], mask ^ (1 << j))) {
+                    dp[mask] = true;
+                    return true;
+                }
+
+                if (subsetSum == 0) {
+                    dp[mask] = false;
+                    return false;
+                }
+            }
+
+            dp[mask] = false;
+            return false;
+        }
+
+        return Backtrack(0, k, 0, (1 << n) - 1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * 2 ^ n)$
+* Space complexity: $O(2 ^ n)$
+
+---
+
+## 5. Dynamic Programming (Bottom-Up) + Bit Mask
+
+::tabs-start
+
+```python
+class Solution:
+    def canPartitionKSubsets(self, nums: List[int], k: int) -> bool:
+        total = sum(nums)
+        if total % k != 0:
+            return False
+
+        target = total // k
+        n = len(nums)
+        N = 1 << n
+        dp = [0] + [-1] * (N - 1)
+
+        for mask in range(N):
+            if dp[mask] == -1:
+                continue
+            for i in range(n):
+                if (mask & (1 << i)) == 0 and dp[mask] + nums[i] <= target:
+                    dp[mask | (1 << i)] = (dp[mask] + nums[i]) % target
+
+        return dp[N - 1] == 0
+```
+
+```java
+public class Solution {
+    public boolean canPartitionKSubsets(int[] nums, int k) {
+        int total = 0;
+        for (int num : nums) total += num;
+        if (total % k != 0) return false;
+
+        int target = total / k;
+        int n = nums.length;
+        int N = 1 << n;
+        int[] dp = new int[N];
+        Arrays.fill(dp, -1);
+        dp[0] = 0;
+
+        for (int mask = 0; mask < N; mask++) {
+            if (dp[mask] == -1) continue;
+            for (int i = 0; i < n; i++) {
+                if ((mask & (1 << i)) == 0 && dp[mask] + nums[i] <= target) {
+                    dp[mask | (1 << i)] = (dp[mask] + nums[i]) % target;
+                }
+            }
+        }
+
+        return dp[N - 1] == 0;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool canPartitionKSubsets(vector<int>& nums, int k) {
+        int total = accumulate(nums.begin(), nums.end(), 0);
+        if (total % k != 0) return false;
+
+        int target = total / k;
+        int n = nums.size();
+        int N = 1 << n;
+        vector<int> dp(N, -1);
+        dp[0] = 0;
+
+        for (int mask = 0; mask < N; mask++) {
+            if (dp[mask] == -1) continue;
+            for (int i = 0; i < n; i++) {
+                if ((mask & (1 << i)) == 0 && dp[mask] + nums[i] <= target) {
+                    dp[mask | (1 << i)] = (dp[mask] + nums[i]) % target;
+                }
+            }
+        }
+
+        return dp[N - 1] == 0;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {boolean}
+     */
+    canPartitionKSubsets(nums, k) {
+        const total = nums.reduce((a, b) => a + b, 0);
+        if (total % k !== 0) return false;
+
+        const target = total / k;
+        nums.sort((a, b) => b - a);
+
+        const n = nums.length;
+        const N = 1 << n;
+        const dp = new Array(N).fill(-1);
+        dp[0] = 0;
+
+        for (let mask = 0; mask < N; mask++) {
+            if (dp[mask] === -1) continue;
+            for (let i = 0; i < n; i++) {
+                if ((mask & (1 << i)) === 0 && dp[mask] + nums[i] <= target) {
+                    dp[mask | (1 << i)] = (dp[mask] + nums[i]) % target;
+                }
+            }
+        }
+
+        return dp[N - 1] === 0;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool CanPartitionKSubsets(int[] nums, int k) {
+        int total = nums.Sum();
+        if (total % k != 0) return false;
+
+        int target = total / k;
+        int n = nums.Length;
+        int N = 1 << n;
+        int[] dp = new int[N];
+        for (int i = 1; i < N; i++) {
+            dp[i] = -1;
+        }
+
+        for (int mask = 0; mask < N; mask++) {
+            if (dp[mask] == -1) continue;
+            for (int i = 0; i < n; i++) {
+                if ((mask & (1 << i)) == 0 && dp[mask] + nums[i] <= target) {
+                    int nextMask = mask | (1 << i);
+                    dp[nextMask] = (dp[mask] + nums[i]) % target;
+                }
+            }
+        }
+
+        return dp[N - 1] == 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * 2 ^ n)$
+* Space complexity: $O(2 ^ n)$
\ No newline at end of file
diff --git a/articles/pascals-triangle-ii.md b/articles/pascals-triangle-ii.md
new file mode 100644
index 000000000..5a675a025
--- /dev/null
+++ b/articles/pascals-triangle-ii.md
@@ -0,0 +1,375 @@
+## 1. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def getRow(self, rowIndex: int) -> List[int]:
+        if rowIndex == 0:
+            return [1]
+
+        curRow = [1]
+        prevRow = self.getRow(rowIndex - 1)
+
+        for i in range(1, rowIndex):
+            curRow.append(prevRow[i - 1] + prevRow[i])
+
+        curRow.append(1)
+        return curRow
+```
+
+```java
+public class Solution {
+    public List<Integer> getRow(int rowIndex) {
+        if (rowIndex == 0) return Arrays.asList(1);
+
+        List<Integer> curRow = new ArrayList<>(Arrays.asList(1));
+        List<Integer> prevRow = getRow(rowIndex - 1);
+
+        for (int i = 1; i < rowIndex; i++) {
+            curRow.add(prevRow.get(i - 1) + prevRow.get(i));
+        }
+
+        curRow.add(1);
+        return curRow;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> getRow(int rowIndex) {
+        if (rowIndex == 0) return {1};
+
+        vector<int> curRow = {1};
+        vector<int> prevRow = getRow(rowIndex - 1);
+
+        for (int i = 1; i < rowIndex; i++) {
+            curRow.push_back(prevRow[i - 1] + prevRow[i]);
+        }
+
+        curRow.push_back(1); 
+        return curRow;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} rowIndex
+     * @return {number[]}
+     */
+    getRow(rowIndex) {
+        if (rowIndex === 0) return [1];
+
+        let curRow = [1];
+        let prevRow = this.getRow(rowIndex - 1);
+
+        for (let i = 1; i < rowIndex; i++) {
+            curRow.push(prevRow[i - 1] + prevRow[i]);
+        }
+
+        curRow.push(1);
+        return curRow;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def getRow(self, rowIndex: int) -> List[int]:
+        res = [[1] * (i + 1) for i in range(rowIndex + 1)]
+        for i in range(2, rowIndex + 1):
+            for j in range(1, i):
+                res[i][j] = res[i - 1][j - 1] + res[i - 1][j]
+        return res[rowIndex]
+```
+
+```java
+public class Solution {
+    public List<Integer> getRow(int rowIndex) {
+        List<List<Integer>> res = new ArrayList<>();
+        for (int i = 0; i <= rowIndex; i++) {
+            List<Integer> row = new ArrayList<>(Collections.nCopies(i + 1, 1));
+            for (int j = 1; j < i; j++) {
+                row.set(j, res.get(i - 1).get(j - 1) + res.get(i - 1).get(j));
+            }
+            res.add(row);
+        }
+        return res.get(rowIndex);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> getRow(int rowIndex) {
+        vector<vector<int>> res(rowIndex + 1);
+        for (int i = 0; i <= rowIndex; i++) {
+            res[i] = vector<int>(i + 1, 1);
+            for (int j = 1; j < i; j++) {
+                res[i][j] = res[i - 1][j - 1] + res[i - 1][j];
+            }
+        }
+        return res[rowIndex];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} rowIndex
+     * @return {number[]}
+     */
+    getRow(rowIndex) {
+        const res = Array.from({ length: rowIndex + 1 }, (_, i) => Array(i + 1).fill(1));
+        for (let i = 2; i <= rowIndex; i++) {
+            for (let j = 1; j < i; j++) {
+                res[i][j] = res[i - 1][j - 1] + res[i - 1][j];
+            }
+        }
+        return res[rowIndex];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 3. Dynamic Programming (Space Optimized - I)
+
+::tabs-start
+
+```python
+class Solution:
+    def getRow(self, rowIndex: int) -> List[int]:
+        res = [1]
+        for i in range(rowIndex):
+            next_row = [0] * (len(res) + 1)
+            for j in range(len(res)):
+                next_row[j] += res[j]
+                next_row[j + 1] += res[j]
+            res = next_row
+        return res
+```
+
+```java
+public class Solution {
+    public List<Integer> getRow(int rowIndex) {
+        List<Integer> res = new ArrayList<>();
+        res.add(1);
+        for (int i = 0; i < rowIndex; i++) {
+            List<Integer> nextRow = new ArrayList<>(Collections.nCopies(res.size() + 1, 0));
+            for (int j = 0; j < res.size(); j++) {
+                nextRow.set(j, nextRow.get(j) + res.get(j));
+                nextRow.set(j + 1, nextRow.get(j + 1) + res.get(j));
+            }
+            res = nextRow;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> getRow(int rowIndex) {
+        vector<int> res = {1};
+        for (int i = 0; i < rowIndex; i++) {
+            vector<int> nextRow(res.size() + 1, 0);
+            for (int j = 0; j < res.size(); j++) {
+                nextRow[j] += res[j];
+                nextRow[j + 1] += res[j];
+            }
+            res = nextRow;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} rowIndex
+     * @return {number[]}
+     */
+    getRow(rowIndex) {
+        let res = [1];
+        for (let i = 0; i < rowIndex; i++) {
+            const nextRow = Array(res.length + 1).fill(0);
+            for (let j = 0; j < res.length; j++) {
+                nextRow[j] += res[j];
+                nextRow[j + 1] += res[j];
+            }
+            res = nextRow;
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Dynamic Programming (Space Optimized - II)
+
+::tabs-start
+
+```python
+class Solution:
+    def getRow(self, rowIndex: int) -> List[int]:
+        row = [1] * (rowIndex + 1)
+        for i in range(1, rowIndex):
+            for j in range(i, 0, -1):
+                row[j] += row[j - 1]
+        return row
+```
+
+```java
+public class Solution {
+    public List<Integer> getRow(int rowIndex) {
+        List<Integer> row = new ArrayList<>(Collections.nCopies(rowIndex + 1, 1));
+        for (int i = 1; i < rowIndex; i++) {
+            for (int j = i; j > 0; j--) {
+                row.set(j, row.get(j) + row.get(j - 1));
+            }
+        }
+        return row;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> getRow(int rowIndex) {
+        vector<int> row(rowIndex + 1, 1);
+        for (int i = 1; i < rowIndex; i++) {
+            for (int j = i; j > 0; j--) {
+                row[j] += row[j - 1];
+            }
+        }
+        return row;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} rowIndex
+     * @return {number[]}
+     */
+    getRow(rowIndex) {
+        const row = Array(rowIndex + 1).fill(1);
+        for (let i = 1; i < rowIndex; i++) {
+            for (let j = i; j > 0; j--) {
+                row[j] += row[j - 1];
+            }
+        }
+        return row;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 5. Combinatorics
+
+::tabs-start
+
+```python
+class Solution:
+    def getRow(self, rowIndex: int) -> List[int]:
+        row = [1]
+        for i in range(1, rowIndex + 1):
+            row.append(row[-1] * (rowIndex - i + 1) // i)
+        return row
+```
+
+```java
+public class Solution {
+    public List<Integer> getRow(int rowIndex) {
+        List<Integer> row = new ArrayList<>();
+        row.add(1);
+        for (int i = 1; i <= rowIndex; i++) {
+            row.add((int)((long)row.get(row.size() - 1) * (rowIndex - i + 1) / i));
+        }
+        return row;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> getRow(int rowIndex) {
+        vector<int> row = {1};
+        for (int i = 1; i <= rowIndex; i++) {
+            row.push_back(int(row.back() * 1LL * (rowIndex - i + 1) / i));
+        }
+        return row;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} rowIndex
+     * @return {number[]}
+     */
+    getRow(rowIndex) {
+        const row = [1];
+        for (let i = 1; i <= rowIndex; i++) {
+            row.push(Math.floor(row[row.length - 1] * (rowIndex - i + 1) / i));
+        }
+        return row;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/pascals-triangle.md b/articles/pascals-triangle.md
new file mode 100644
index 000000000..2254d3bbf
--- /dev/null
+++ b/articles/pascals-triangle.md
@@ -0,0 +1,260 @@
+## 1. Combinatorics
+
+::tabs-start
+
+```python
+class Solution:
+    def generate(self, numRows: int) -> List[List[int]]:
+        res = []
+        for n in range(numRows):
+            row = [1]
+            val = 1
+            for k in range(1, n + 1):
+                val = val * (n - k + 1) // k
+                row.append(val)
+            res.append(row)
+        return res
+```
+
+```java
+public class Solution {
+    public List<List<Integer>> generate(int numRows) {
+        List<List<Integer>> res = new ArrayList<>();
+        for (int n = 0; n < numRows; n++) {
+            List<Integer> row = new ArrayList<>();
+            row.add(1);
+            int val = 1;
+            for (int k = 1; k <= n; k++) {
+                val = val * (n - k + 1) / k;
+                row.add(val);
+            }
+            res.add(row);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> generate(int numRows) {
+        vector<vector<int>> res;
+        for (int n = 0; n < numRows; n++) {
+            vector<int> row;
+            row.push_back(1);
+            int val = 1;
+            for (int k = 1; k <= n; k++) {
+                val = val * (n - k + 1) / k;
+                row.push_back(val);
+            }
+            res.push_back(row);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} numRows
+     * @return {number[][]}
+     */
+    generate(numRows) {
+        let res = [];
+        for (let n = 0; n < numRows; n++) {
+            let row = [1];
+            let val = 1;
+            for (let k = 1; k <= n; k++) {
+                val = (val * (n - k + 1)) / k;
+                row.push(val);
+            }
+            res.push(row);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 2. Dynamic Programming - I
+
+::tabs-start
+
+```python
+class Solution:
+    def generate(self, numRows: int) -> List[List[int]]:
+        res = [[1]]
+
+        for i in range(numRows - 1):
+            temp = [0] + res[-1] + [0]
+            row = []
+            for j in range(len(res[-1]) + 1):
+                row.append(temp[j] + temp[j + 1])
+            res.append(row)
+        return res
+```
+
+```java
+public class Solution {
+    public List<List<Integer>> generate(int numRows) {
+        List<List<Integer>> res = new ArrayList<>();
+        res.add(new ArrayList<>());
+        res.get(0).add(1);
+
+        for (int i = 1; i < numRows; i++) {
+            List<Integer> temp = new ArrayList<>(res.get(i - 1));
+            temp.add(0, 0);
+            temp.add(0);
+            List<Integer> row = new ArrayList<>();
+
+            for (int j = 0; j < res.get(i - 1).size() + 1; j++) {
+                row.add(temp.get(j) + temp.get(j + 1));
+            }
+
+            res.add(row);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> generate(int numRows) {
+        vector<vector<int>> res = {{1}};
+        
+        for (int i = 0; i < numRows - 1; i++) {
+            vector<int> temp = {0};
+            temp.insert(temp.end(), res.back().begin(), res.back().end());
+            temp.push_back(0);
+            vector<int> row;
+            for (size_t j = 0; j < res.back().size() + 1; j++) {
+                row.push_back(temp[j] + temp[j + 1]);
+            }
+            res.push_back(row);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} numRows
+     * @return {number[][]}
+     */
+    generate(numRows) {
+        let res = [[1]];
+
+        for (let i = 0; i < numRows - 1; i++) {
+            let temp = [0, ...res[res.length - 1], 0];
+            let row = [];
+            for (let j = 0; j < res[res.length - 1].length + 1; j++) {
+                row.push(temp[j] + temp[j + 1]);
+            }
+            res.push(row);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 3. Dynamic Programming - II
+
+::tabs-start
+
+```python
+class Solution:
+    def generate(self, numRows: int) -> List[List[int]]:
+        res = [[1] * (i + 1) for i in range(numRows)]
+        for i in range(2, numRows):
+            for j in range(1, i):
+                res[i][j] = res[i - 1][j - 1] + res[i - 1][j]
+        return res
+```
+
+```java
+public class Solution {
+    public List<List<Integer>> generate(int numRows) {
+        List<List<Integer>> res = new ArrayList<>();
+
+        for (int i = 0; i < numRows; i++) {
+            List<Integer> row = new ArrayList<>();
+            for (int j = 0; j <= i; j++) {
+                if (j == 0 || j == i) {
+                    row.add(1);
+                } else {
+                    row.add(res.get(i - 1).get(j - 1) + res.get(i - 1).get(j));
+                }
+            }
+            res.add(row);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> generate(int numRows) {
+        vector<vector<int>> res(numRows);
+
+        for (int i = 0; i < numRows; i++) {
+            res[i].resize(i + 1);
+            res[i][0] = res[i][i] = 1;
+            for (int j = 1; j < i; j++){
+                res[i][j] = res[i - 1][j - 1] + res[i - 1][j];
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} numRows
+     * @return {number[][]}
+     */
+    generate(numRows) {
+        let res = Array.from({ length: numRows }, (_, i) => Array(i + 1).fill(1));
+
+        for (let i = 2; i < numRows; i++) {
+            for (let j = 1; j < i; j++) {
+                res[i][j] = res[i - 1][j - 1] + res[i - 1][j];
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$ 
\ No newline at end of file
diff --git a/articles/path-crossing.md b/articles/path-crossing.md
new file mode 100644
index 000000000..dd4abbaf2
--- /dev/null
+++ b/articles/path-crossing.md
@@ -0,0 +1,242 @@
+## 1. Hash Set
+
+::tabs-start
+
+```python
+class Solution:
+    def isPathCrossing(self, path: str) -> bool:
+        dir = {
+            'N': [0, 1],
+            'S': [0, -1],
+            'E': [1, 0],
+            'W': [-1, 0]
+        }
+        
+        visit = set()
+        x, y = 0, 0
+
+        for c in path:
+            visit.add((x, y))
+            dx, dy = dir[c]
+            x, y = x + dx, y + dy
+            if (x, y) in visit:
+                return True
+
+        return False
+```
+
+```java
+public class Solution {
+    public boolean isPathCrossing(String path) {
+        Set<String> visit = new HashSet<>();
+        int x = 0, y = 0;
+        visit.add(x + "," + y);
+
+        for (char c : path.toCharArray()) {
+            if (c == 'N') y++;
+            else if (c == 'S') y--;
+            else if (c == 'E') x++;
+            else if (c == 'W') x--;
+
+            String pos = x + "," + y;
+            if (visit.contains(pos)) return true;
+            visit.add(pos);
+        }
+
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isPathCrossing(string path) {
+        unordered_set<string> visit;
+        int x = 0, y = 0;
+        visit.insert(to_string(x) + "," + to_string(y));
+        
+        for (char c : path) {
+            if (c == 'N') y++;
+            else if (c == 'S') y--;
+            else if (c == 'E') x++;
+            else if (c == 'W') x--;
+            
+            string pos = to_string(x) + "," + to_string(y);
+            if (visit.count(pos)) return true;
+            visit.insert(pos);
+        }
+        
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} path
+     * @return {boolean}
+     */
+    isPathCrossing(path) {
+        const visit = new Set();
+        let x = 0, y = 0;
+        visit.add(`${x},${y}`);
+
+        for (const c of path) {
+            if (c === 'N') y++;
+            else if (c === 'S') y--;
+            else if (c === 'E') x++;
+            else if (c === 'W') x--;
+
+            const pos = `${x},${y}`;
+            if (visit.has(pos)) return true;
+            visit.add(pos);
+        }
+
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Hash Set (Custom Hash)
+
+::tabs-start
+
+```python
+class Solution:
+    def isPathCrossing(self, path: str) -> bool:
+        visit = set()
+        x, y = 0, 0
+        visit.add(self.hash(x, y))
+
+        for c in path:
+            if c == 'N':
+                y += 1
+            elif c == 'S':
+                y -= 1
+            elif c == 'E':
+                x += 1
+            elif c == 'W':
+                x -= 1
+
+            pos = self.hash(x, y)
+            if pos in visit:
+                return True
+            visit.add(pos)
+
+        return False
+
+    def hash(self, x: int, y: int) -> int:
+        return (x << 32) + y
+```
+
+```java
+public class Solution {
+    public boolean isPathCrossing(String path) {
+        Set<Long> visit = new HashSet<>();
+        int x = 0, y = 0;
+        visit.add(hash(x, y));
+
+        for (char c : path.toCharArray()) {
+            if (c == 'N') y++;
+            else if (c == 'S') y--;
+            else if (c == 'E') x++;
+            else if (c == 'W') x--;
+
+            long pos = hash(x, y);
+            if (visit.contains(pos)) return true;
+            visit.add(pos);
+        }
+
+        return false;
+    }
+
+    private long hash(long x, long y) {
+        return (x << 32) + y; 
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isPathCrossing(string path) {
+        unordered_set<pair<int, int>, pair_hash> visit;
+        int x = 0, y = 0;
+        visit.insert({x, y});
+
+        for (char c : path) {
+            if (c == 'N') y++;
+            else if (c == 'S') y--;
+            else if (c == 'E') x++;
+            else if (c == 'W') x--;
+
+            if (visit.count({x, y})) return true;
+            visit.insert({x, y});
+        }
+
+        return false;
+    }
+
+private:
+    struct pair_hash {
+        template <class T1, class T2>
+        size_t operator()(const pair<T1, T2>& p) const {
+            return (hash<T1>()(p.first) << 32) + hash<T2>()(p.second);
+        }
+    };
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} path
+     * @return {boolean}
+     */
+    isPathCrossing(path) {
+        const visit = new Set();
+        let x = 0, y = 0;
+        visit.add(this.hash(x, y));
+
+        for (const c of path) {
+            if (c === 'N') y++;
+            else if (c === 'S') y--;
+            else if (c === 'E') x++;
+            else if (c === 'W') x--;
+
+            const pos = this.hash(x, y);
+            if (visit.has(pos)) return true;
+            visit.add(pos);
+        }
+
+        return false;
+    }
+
+    /**
+     * @param {number} x
+     * @param {number} x
+     * @return {number}
+     */
+    hash(x, y) {
+        return (x << 16) + y;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/path-sum.md b/articles/path-sum.md
new file mode 100644
index 000000000..ce01351cf
--- /dev/null
+++ b/articles/path-sum.md
@@ -0,0 +1,581 @@
+## 1. Depth First Search - I
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def hasPathSum(self, root: Optional[TreeNode], targetSum: int) -> bool:
+        def dfs(node, curSum):
+            if not node:
+                return False
+            
+            curSum += node.val
+            if not node.left and not node.right:
+                return curSum == targetSum
+            
+            return dfs(node.left, curSum) or dfs(node.right, curSum)
+        
+        return dfs(root, 0)
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public boolean hasPathSum(TreeNode root, int targetSum) {
+        return dfs(root, 0, targetSum);
+    }
+
+    private boolean dfs(TreeNode node, int curSum, int targetSum) {
+        if (node == null) return false;
+
+        curSum += node.val;
+        if (node.left == null && node.right == null) {
+            return curSum == targetSum;
+        }
+
+        return dfs(node.left, curSum, targetSum) || dfs(node.right, curSum, targetSum);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    bool hasPathSum(TreeNode* root, int targetSum) {
+        return dfs(root, 0, targetSum);
+    }
+
+private:
+    bool dfs(TreeNode* node, int curSum, int targetSum) {
+        if (node == nullptr) return false;
+
+        curSum += node->val;
+        if (node->left == nullptr && node->right == nullptr) {
+            return curSum == targetSum;
+        }
+
+        return dfs(node->left, curSum, targetSum) || dfs(node->right, curSum, targetSum);
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @param {number} targetSum
+     * @return {boolean}
+     */
+    hasPathSum(root, targetSum) {
+        const dfs = (node, curSum) => {
+            if (!node) return false;
+
+            curSum += node.val;
+            if (!node.left && !node.right) {
+                return curSum === targetSum;
+            }
+
+            return dfs(node.left, curSum) || dfs(node.right, curSum);
+        };
+
+        return dfs(root, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Depth First Search - II
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def hasPathSum(self, root: Optional[TreeNode], targetSum: int) -> bool:
+        if not root:
+            return False
+        
+        targetSum -= root.val
+        return (self.hasPathSum(root.left, targetSum) or 
+                self.hasPathSum(root.right, targetSum) or
+                (not targetSum and not root.left and not root.right))
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public boolean hasPathSum(TreeNode root, int targetSum) {
+        if (root == null) return false;
+        targetSum -= root.val;
+        return hasPathSum(root.left, targetSum) || 
+               hasPathSum(root.right, targetSum) || 
+               (targetSum == 0 && root.left == null && root.right == null);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    bool hasPathSum(TreeNode* root, int targetSum) {
+        if (!root) return false;
+        targetSum -= root->val;
+        return hasPathSum(root->left, targetSum) || 
+               hasPathSum(root->right, targetSum) ||
+               (targetSum == 0 && !root->left && !root->right);
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @param {number} targetSum
+     * @return {boolean}
+     */
+    hasPathSum(root, targetSum) {
+        if (!root) return false;
+        targetSum -= root.val;
+        return this.hasPathSum(root.left, targetSum) || 
+               this.hasPathSum(root.right, targetSum) ||
+               (targetSum === 0 && !root.left && !root.right);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 3. Iterative DFS
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def hasPathSum(self, root: Optional[TreeNode], targetSum: int) -> bool:
+        if not root:
+            return False
+
+        stack = [(root, targetSum - root.val)]
+        while stack:
+            node, curr_sum = stack.pop()
+            if not node.left and not node.right and curr_sum == 0:
+                return True
+            if node.right:
+                stack.append((node.right, curr_sum - node.right.val))
+            if node.left:
+                stack.append((node.left, curr_sum - node.left.val))
+        return False
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public boolean hasPathSum(TreeNode root, int targetSum) {
+        if (root == null) return false;
+
+        Stack<TreeNode> stack = new Stack<>();
+        Stack<Integer> sumStack = new Stack<>();
+        stack.push(root);
+        sumStack.push(targetSum - root.val);
+
+        while (!stack.isEmpty()) {
+            TreeNode node = stack.pop();
+            int currSum = sumStack.pop();
+
+            if (node.left == null && node.right == null && currSum == 0) {
+                return true;
+            }
+
+            if (node.right != null) {
+                stack.push(node.right);
+                sumStack.push(currSum - node.right.val);
+            }
+
+            if (node.left != null) {
+                stack.push(node.left);
+                sumStack.push(currSum - node.left.val);
+            }
+        }
+
+        return false;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    bool hasPathSum(TreeNode* root, int targetSum) {
+        if (!root) return false;
+
+        stack<pair<TreeNode*, int>> s;
+        s.push({root, targetSum - root->val});
+
+        while (!s.empty()) {
+            auto [node, currSum] = s.top();
+            s.pop();
+
+            if (!node->left && !node->right && currSum == 0) {
+                return true;
+            }
+
+            if (node->right) {
+                s.push({node->right, currSum - node->right->val});
+            }
+
+            if (node->left) {
+                s.push({node->left, currSum - node->left->val});
+            }
+        }
+
+        return false;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @param {number} targetSum
+     * @return {boolean}
+     */
+    hasPathSum(root, targetSum) {
+        if (!root) return false;
+
+        const stack = [[root, targetSum - root.val]];
+        while (stack.length) {
+            const [node, currSum] = stack.pop();
+
+            if (!node.left && !node.right && currSum === 0) {
+                return true;
+            }
+
+            if (node.right) {
+                stack.push([node.right, currSum - node.right.val]);
+            }
+
+            if (node.left) {
+                stack.push([node.left, currSum - node.left.val]);
+            }
+        }
+
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Breadth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def hasPathSum(self, root: Optional[TreeNode], targetSum: int) -> bool:
+        if not root:
+            return False
+
+        queue = deque([(root, targetSum - root.val)])
+        while queue:
+            node, curr_sum = queue.popleft()
+            if not node.left and not node.right and curr_sum == 0:
+                return True
+            if node.left:
+                queue.append((node.left, curr_sum - node.left.val))
+            if node.right:
+                queue.append((node.right, curr_sum - node.right.val))
+        return False
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public boolean hasPathSum(TreeNode root, int targetSum) {
+        if (root == null) return false;
+
+        Queue<TreeNode> nodeQueue = new LinkedList<>();
+        Queue<Integer> sumQueue = new LinkedList<>();
+        nodeQueue.add(root);
+        sumQueue.add(targetSum - root.val);
+
+        while (!nodeQueue.isEmpty()) {
+            TreeNode node = nodeQueue.poll();
+            int currSum = sumQueue.poll();
+
+            if (node.left == null && node.right == null && currSum == 0) {
+                return true;
+            }
+
+            if (node.left != null) {
+                nodeQueue.add(node.left);
+                sumQueue.add(currSum - node.left.val);
+            }
+
+            if (node.right != null) {
+                nodeQueue.add(node.right);
+                sumQueue.add(currSum - node.right.val);
+            }
+        }
+
+        return false;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    bool hasPathSum(TreeNode* root, int targetSum) {
+        if (!root) return false;
+
+        queue<pair<TreeNode*, int>> q;
+        q.push({root, targetSum - root->val});
+
+        while (!q.empty()) {
+            auto [node, currSum] = q.front();
+            q.pop();
+
+            if (!node->left && !node->right && currSum == 0) {
+                return true;
+            }
+
+            if (node->left) {
+                q.push({node->left, currSum - node->left->val});
+            }
+
+            if (node->right) {
+                q.push({node->right, currSum - node->right->val});
+            }
+        }
+
+        return false;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @param {number} targetSum
+     * @return {boolean}
+     */
+    hasPathSum(root, targetSum) {
+        if (!root) return false;
+
+        const queue = new Queue([[root, targetSum - root.val]]);
+        while (!queue.isEmpty()) {
+            const [node, currSum] = queue.pop();
+
+            if (!node.left && !node.right && currSum === 0) {
+                return true;
+            }
+
+            if (node.left) {
+                queue.push([node.left, currSum - node.left.val]);
+            }
+
+            if (node.right) {
+                queue.push([node.right, currSum - node.right.val]);
+            }
+        }
+
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/path-with-maximum-gold.md b/articles/path-with-maximum-gold.md
new file mode 100644
index 000000000..81c3d201d
--- /dev/null
+++ b/articles/path-with-maximum-gold.md
@@ -0,0 +1,508 @@
+## 1. Backtracking (DFS) - I
+
+::tabs-start
+
+```python
+class Solution:
+    def getMaximumGold(self, grid: list[list[int]]) -> int:
+        ROWS, COLS = len(grid), len(grid[0])
+        directions = [(1, 0), (-1, 0), (0, 1), (0, -1)]
+
+        def dfs(r, c, visit):
+            if min(r, c) < 0 or r == ROWS or c == COLS or grid[r][c] == 0 or (r, c) in visit:
+                return 0
+
+            visit.add((r, c))
+            res = grid[r][c]
+
+            for dr, dc in directions:
+                res = max(res, grid[r][c] + dfs(r + dr, c + dc, visit))
+
+            visit.remove((r, c))
+            return res
+
+        res = 0
+        for r in range(ROWS):
+            for c in range(COLS):
+                if grid[r][c] != 0:
+                    res = max(res, dfs(r, c, set()))
+        return res
+```
+
+```java
+public class Solution {
+    private int ROWS, COLS;
+    private int[][] directions = {{1, 0}, {-1, 0}, {0, 1}, {0, -1}};
+
+    public int getMaximumGold(int[][] grid) {
+        ROWS = grid.length;
+        COLS = grid[0].length;
+        int res = 0;
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (grid[r][c] != 0) {
+                    res = Math.max(res, dfs(grid, r, c, new boolean[ROWS][COLS]));
+                }
+            }
+        }
+        return res;
+    }
+
+    private int dfs(int[][] grid, int r, int c, boolean[][] visit) {
+        if (r < 0 || c < 0 || r >= ROWS || c >= COLS || 
+            grid[r][c] == 0 || visit[r][c]) {
+            return 0;
+        }
+
+        visit[r][c] = true;
+        int res = grid[r][c];
+
+        for (int[] d : directions) {
+            res = Math.max(res, grid[r][c] + dfs(grid, r + d[0], c + d[1], visit));
+        }
+
+        visit[r][c] = false;
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int ROWS, COLS;
+    vector<vector<int>> directions = {{1, 0}, {-1, 0}, {0, 1}, {0, -1}};
+
+    int getMaximumGold(vector<vector<int>>& grid) {
+        ROWS = grid.size();
+        COLS = grid[0].size();
+        int res = 0;
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (grid[r][c] != 0) {
+                    vector<vector<bool>> visit(ROWS, vector<bool>(COLS, false));
+                    res = max(res, dfs(grid, r, c, visit));
+                }
+            }
+        }
+        return res;
+    }
+
+private:
+    int dfs(vector<vector<int>>& grid, int r, int c, vector<vector<bool>>& visit) {
+        if (r < 0 || c < 0 || r >= ROWS || c >= COLS || grid[r][c] == 0 || visit[r][c]) {
+            return 0;
+        }
+
+        visit[r][c] = true;
+        int res = grid[r][c];
+
+        for (auto& d : directions) {
+            res = max(res, grid[r][c] + dfs(grid, r + d[0], c + d[1], visit));
+        }
+
+        visit[r][c] = false;
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    getMaximumGold(grid) {
+        const ROWS = grid.length, COLS = grid[0].length;
+        const directions = [[1, 0], [-1, 0], [0, 1], [0, -1]];
+
+        const dfs = (r, c, visit) => {
+            if (r < 0 || c < 0 || r >= ROWS || c >= COLS || grid[r][c] === 0 || visit[r][c]) {
+                return 0;
+            }
+
+            visit[r][c] = true;
+            let res = grid[r][c];
+
+            for (const [dr, dc] of directions) {
+                res = Math.max(res, grid[r][c] + dfs(r + dr, c + dc, visit));
+            }
+
+            visit[r][c] = false;
+            return res;
+        };
+
+        let res = 0;
+        for (let r = 0; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                if (grid[r][c] !== 0) {
+                    let visit = Array.from({ length: ROWS }, () => Array(COLS).fill(false));
+                    res = Math.max(res, dfs(r, c, visit));
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(N * 3 ^ N)$
+* Space complexity: $O(N)$
+
+> Where $N$ is the number of cells which contain gold.
+
+---
+
+## 2. Backtracking (DFS) - II
+
+::tabs-start
+
+```python
+class Solution:
+    def getMaximumGold(self, grid: list[list[int]]) -> int:
+        ROWS, COLS = len(grid), len(grid[0])
+        directions = [(1, 0), (-1, 0), (0, 1), (0, -1)]
+
+        def dfs(r, c):
+            if min(r, c) < 0 or r == ROWS or c == COLS or grid[r][c] == 0:
+                return 0
+            
+            gold = grid[r][c]
+            grid[r][c] = 0
+            res = 0
+
+            for dr, dc in directions:
+                res = max(res, dfs(r + dr, c + dc))
+
+            grid[r][c] = gold
+            return gold + res
+
+        res = 0
+        for r in range(ROWS):
+            for c in range(COLS):
+                if grid[r][c] != 0:
+                    res = max(res, dfs(r, c))
+        return res
+```
+
+```java
+public class Solution {
+    private int ROWS, COLS;
+    private int[][] directions = {{1, 0}, {-1, 0}, {0, 1}, {0, -1}};
+
+    public int getMaximumGold(int[][] grid) {
+        ROWS = grid.length;
+        COLS = grid[0].length;
+        int res = 0;
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (grid[r][c] != 0) {
+                    res = Math.max(res, dfs(grid, r, c));
+                }
+            }
+        }
+        return res;
+    }
+
+    private int dfs(int[][] grid, int r, int c) {
+        if (r < 0 || c < 0 || r >= ROWS || c >= COLS || grid[r][c] == 0) {
+            return 0;
+        }
+
+        int gold = grid[r][c];
+        grid[r][c] = 0;
+        int res = 0;
+
+        for (int[] d : directions) {
+            res = Math.max(res, dfs(grid, r + d[0], c + d[1]));
+        }
+
+        grid[r][c] = gold;
+        return gold + res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int ROWS, COLS;
+    vector<vector<int>> directions = {{1, 0}, {-1, 0}, {0, 1}, {0, -1}};
+
+    int getMaximumGold(vector<vector<int>>& grid) {
+        ROWS = grid.size();
+        COLS = grid[0].size();
+        int res = 0;
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (grid[r][c] != 0) {
+                    res = max(res, dfs(grid, r, c));
+                }
+            }
+        }
+        return res;
+    }
+
+private:
+    int dfs(vector<vector<int>>& grid, int r, int c) {
+        if (r < 0 || c < 0 || r >= ROWS || c >= COLS || grid[r][c] == 0) {
+            return 0;
+        }
+
+        int gold = grid[r][c];
+        grid[r][c] = 0;
+        int res = 0;
+
+        for (auto& d : directions) {
+            res = max(res, dfs(grid, r + d[0], c + d[1]));
+        }
+
+        grid[r][c] = gold;
+        return gold + res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    getMaximumGold(grid) {
+        const ROWS = grid.length, COLS = grid[0].length;
+        const directions = [[1, 0], [-1, 0], [0, 1], [0, -1]];
+
+        const dfs = (r, c) => {
+            if (r < 0 || c < 0 || r >= ROWS || c >= COLS || grid[r][c] === 0) {
+                return 0;
+            }
+
+            let gold = grid[r][c];
+            grid[r][c] = 0;
+            let res = 0;
+
+            for (const [dr, dc] of directions) {
+                res = Math.max(res, dfs(r + dr, c + dc));
+            }
+
+            grid[r][c] = gold;
+            return gold + res;
+        };
+
+        let res = 0;
+        for (let r = 0; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                if (grid[r][c] !== 0) {
+                    res = Math.max(res, dfs(r, c));
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(N * 3 ^ N)$
+* Space complexity: $O(N)$ for recursion stack.
+
+> Where $N$ is the number of cells which contain gold.
+
+---
+
+## 3. Backtracking (BFS)
+
+::tabs-start
+
+```python
+class Solution:
+    def getMaximumGold(self, grid: list[list[int]]) -> int:
+        ROWS, COLS = len(grid), len(grid[0])
+        directions = [1, 0, -1, 0, 1]
+        index = [[0] * COLS for _ in range(ROWS)]
+        idx = 0
+
+        for r in range(ROWS):
+            for c in range(COLS):
+                if grid[r][c] != 0:
+                    index[r][c] = idx
+                    idx += 1
+
+        res = 0
+        for r in range(ROWS):
+            for c in range(COLS):
+                if grid[r][c] > 0:
+                    q = deque([(r, c, grid[r][c], 1 << index[r][c])])
+                    while q:
+                        row, col, gold, mask = q.popleft()
+                        res = max(res, gold)
+
+                        for i in range(4):
+                            nr, nc = row + directions[i], col + directions[i + 1]
+                            if 0 <= nr < ROWS and 0 <= nc < COLS and grid[nr][nc] > 0:
+                                idx = index[nr][nc]
+                                if not (mask & (1 << idx)):
+                                    q.append((nr, nc, gold + grid[nr][nc], mask | (1 << idx)))
+
+        return res
+```
+
+```java
+public class Solution {
+    public int getMaximumGold(int[][] grid) {
+        int ROWS = grid.length, COLS = grid[0].length;
+        int[][] index = new int[ROWS][COLS];
+        int idx = 0;
+        int[] directions = {1, 0, -1, 0, 1};
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (grid[r][c] != 0) {
+                    index[r][c] = idx++;
+                }
+            }
+        }
+
+        int res = 0;
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (grid[r][c] > 0) {
+                    Queue<int[]> q = new LinkedList<>();
+                    q.offer(new int[]{r, c, grid[r][c], 1 << index[r][c]});
+
+                    while (!q.isEmpty()) {
+                        int[] cur = q.poll();
+                        int row = cur[0], col = cur[1], gold = cur[2], mask = cur[3];
+                        res = Math.max(res, gold);
+
+                        for (int i = 0; i < 4; i++) {
+                            int nr = row + directions[i], nc = col + directions[i + 1];
+                            if (nr >= 0 && nr < ROWS && nc >= 0 && nc < COLS && grid[nr][nc] > 0) {
+                                int newIdx = index[nr][nc];
+                                if ((mask & (1 << newIdx)) == 0) {
+                                    q.offer(new int[]{nr, nc, gold + grid[nr][nc], mask | (1 << newIdx)});
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int getMaximumGold(vector<vector<int>>& grid) {
+        int ROWS = grid.size(), COLS = grid[0].size();
+        vector<vector<int>> index(ROWS, vector<int>(COLS, 0));
+        int idx = 0;
+        int directions[] = {1, 0, -1, 0, 1};
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (grid[r][c] != 0) {
+                    index[r][c] = idx++;
+                }
+            }
+        }
+
+        int res = 0;
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (grid[r][c] > 0) {
+                    queue<tuple<int, int, int, int>> q;
+                    q.push({r, c, grid[r][c], 1 << index[r][c]});
+
+                    while (!q.empty()) {
+                        auto [row, col, gold, mask] = q.front();q.pop();
+                        res = max(res, gold);
+                        for (int i = 0; i < 4; i++) {
+                            int nr = row + directions[i], nc = col + directions[i + 1];
+                            if (nr >= 0 && nr < ROWS && nc >= 0 && nc < COLS && grid[nr][nc] > 0) {
+                                int newIdx = index[nr][nc];
+                                if ((mask & (1 << newIdx)) == 0) {
+                                    q.push({nr, nc, gold + grid[nr][nc], mask | (1 << newIdx)});
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    getMaximumGold(grid) {
+        const ROWS = grid.length, COLS = grid[0].length;
+        const index = Array.from({ length: ROWS }, () => Array(COLS).fill(0));
+        let idx = 0;
+        const directions = [1, 0, -1, 0, 1];
+
+        for (let r = 0; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                if (grid[r][c] !== 0) {
+                    index[r][c] = idx++;
+                }
+            }
+        }
+
+        let res = 0;
+        for (let r = 0; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                if (grid[r][c] > 0) {
+                    const q = new Queue([[r, c, grid[r][c], 1 << index[r][c]]]);
+
+                    while (!q.isEmpty()) {
+                        const [row, col, gold, mask] = q.pop();
+                        res = Math.max(res, gold);
+                        for (let i = 0; i < 4; i++) {
+                            const nr = row + directions[i], nc = col + directions[i + 1];
+                            if (nr >= 0 && nr < ROWS && nc >= 0 && nc < COLS && grid[nr][nc] > 0) {
+                                const newIdx = index[nr][nc];
+                                if (!(mask & (1 << newIdx))) {
+                                    q.push([nr, nc, gold + grid[nr][nc], mask | (1 << newIdx)]);
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(N * 3 ^ N)$
+* Space complexity: $O(N)$
+
+> Where $N$ is the number of cells which contain gold.
\ No newline at end of file
diff --git a/articles/path-with-maximum-probability.md b/articles/path-with-maximum-probability.md
new file mode 100644
index 000000000..b16d1e43b
--- /dev/null
+++ b/articles/path-with-maximum-probability.md
@@ -0,0 +1,632 @@
+## 1. Dijkstra's Algorithm - I
+
+::tabs-start
+
+```python
+class Solution:
+    def maxProbability(self, n: int, edges: List[List[int]], succProb: List[float], start_node: int, end_node: int) -> float:
+        adj = collections.defaultdict(list)
+        for i in range(len(edges)):
+            src, dst = edges[i]
+            adj[src].append((dst, succProb[i]))
+            adj[dst].append((src, succProb[i]))
+
+        pq = [(-1, start_node)]
+        visit = set()
+
+        while pq:
+            prob, cur = heapq.heappop(pq)
+            visit.add(cur)
+
+            if cur == end_node:
+                return -prob
+
+            for nei, edgeProb in adj[cur]:
+                if nei not in visit:
+                    heapq.heappush(pq, (prob * edgeProb, nei))
+
+        return 0.0
+```
+
+```java
+public class Solution {
+    public double maxProbability(int n, int[][] edges, double[] succProb, int start_node, int end_node) {
+        List<Pair>[] adj = new ArrayList[n];
+        for (int i = 0; i < n; i++) adj[i] = new ArrayList<>();
+
+        for (int i = 0; i < edges.length; i++) {
+            int src = edges[i][0], dst = edges[i][1];
+            adj[src].add(new Pair(dst, succProb[i]));
+            adj[dst].add(new Pair(src, succProb[i]));
+        }
+
+        double[] maxProb = new double[n];
+        maxProb[start_node] = 1.0;
+        PriorityQueue<Pair> pq = new PriorityQueue<>((a, b) -> Double.compare(b.prob, a.prob));
+        pq.offer(new Pair(start_node, 1.0));
+
+        while (!pq.isEmpty()) {
+            Pair top = pq.poll();
+            int node = top.node;
+            double curr_prob = top.prob;
+
+            if (node == end_node) return curr_prob;
+            if (curr_prob > maxProb[node]) continue;
+
+            for (Pair nei : adj[node]) {
+                double new_prob = curr_prob * nei.prob;
+                if (new_prob > maxProb[nei.node]) {
+                    maxProb[nei.node] = new_prob;
+                    pq.offer(new Pair(nei.node, new_prob));
+                }
+            }
+        }
+
+        return 0.0;
+    }
+
+    static class Pair {
+        int node;
+        double prob;
+
+        Pair(int node, double prob) {
+            this.node = node;
+            this.prob = prob;
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    double maxProbability(int n, vector<vector<int>>& edges, vector<double>& succProb, int start_node, int end_node) {
+        vector<vector<pair<int, double>>> adj(n);
+        for (int i = 0; i < edges.size(); i++) {
+            int src = edges[i][0], dst = edges[i][1];
+            adj[src].emplace_back(dst, succProb[i]);
+            adj[dst].emplace_back(src, succProb[i]);
+        }
+
+        vector<double> maxProb(n, 0.0);
+        maxProb[start_node] = 1.0;
+        priority_queue<pair<double, int>> pq;
+        pq.emplace(1.0, start_node);
+
+        while (!pq.empty()) {
+            auto [curr_prob, node] = pq.top(); pq.pop();
+
+            if (node == end_node) return curr_prob;
+            if (curr_prob > maxProb[node]) continue;
+
+            for (auto& [nei, edge_prob] : adj[node]) {
+                double new_prob = curr_prob * edge_prob;
+                if (new_prob > maxProb[nei]) {
+                    maxProb[nei] = new_prob;
+                    pq.emplace(new_prob, nei);
+                }
+            }
+        }
+
+        return 0.0;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} edges
+     * @param {number[]} succProb
+     * @param {number} start_node
+     * @param {number} end_node
+     * @return {number}
+     */
+    maxProbability(n, edges, succProb, start_node, end_node) {
+        let adj = new Map();
+        for (let i = 0; i < n; i++) adj.set(i, []);
+
+        for (let i = 0; i < edges.length; i++) {
+            let [src, dst] = edges[i];
+            adj.get(src).push([dst, succProb[i]]);
+            adj.get(dst).push([src, succProb[i]]);
+        }
+
+        let pq = new MaxPriorityQueue({ priority: x => x[0] });
+        pq.enqueue([1.0, start_node]);
+        let visited = new Set();
+
+        while (!pq.isEmpty()) {
+            let [prob, cur] = pq.dequeue().element;
+            visited.add(cur);
+
+            if (cur === end_node) return prob;
+
+            for (let [nei, edgeProb] of adj.get(cur)) {
+                if (!visited.has(nei)) {
+                    pq.enqueue([prob * edgeProb, nei]);
+                }
+            }
+        }
+
+        return 0.0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O((V + E) \log V)$
+* Space complexity: $O(V + E)$
+
+> Where $V$ is the number nodes and $E$ is the number of edges.
+
+---
+
+## 2. Dijkstra's Algorithm - II
+
+::tabs-start
+
+```python
+class Solution:
+    def maxProbability(self, n: int, edges: List[List[int]], succProb: List[float], start_node: int, end_node: int) -> float:
+        adj = [[] for _ in range(n)]
+        for i in range(len(edges)):
+            src, dst = edges[i]
+            adj[src].append((dst, succProb[i]))
+            adj[dst].append((src, succProb[i]))
+
+        maxProb = [0] * n
+        maxProb[start_node] = 1.0
+        pq = [(-1.0, start_node)]
+
+        while pq:
+            curr_prob, node = heapq.heappop(pq)
+            curr_prob *= -1
+
+            if node == end_node:
+                return curr_prob
+            if curr_prob > maxProb[node]:
+                continue
+
+            for nei, edge_prob in adj[node]:
+                new_prob = curr_prob * edge_prob
+                if new_prob > maxProb[nei]:  
+                    maxProb[nei] = new_prob
+                    heapq.heappush(pq, (-new_prob, nei))
+
+        return 0.0
+```
+
+```java
+public class Solution {
+    public double maxProbability(int n, int[][] edges, double[] succProb, int start_node, int end_node) {
+        List<Pair>[] adj = new ArrayList[n];
+        for (int i = 0; i < n; i++) adj[i] = new ArrayList<>();
+
+        for (int i = 0; i < edges.length; i++) {
+            int src = edges[i][0], dst = edges[i][1];
+            adj[src].add(new Pair(dst, succProb[i]));
+            adj[dst].add(new Pair(src, succProb[i]));
+        }
+
+        double[] maxProb = new double[n];
+        maxProb[start_node] = 1.0;
+        PriorityQueue<Pair> pq = new PriorityQueue<>((a, b) -> Double.compare(b.prob, a.prob));
+        pq.offer(new Pair(start_node, 1.0));
+
+        while (!pq.isEmpty()) {
+            Pair top = pq.poll();
+            int node = top.node;
+            double curr_prob = top.prob;
+
+            if (node == end_node) return curr_prob;
+            if (curr_prob > maxProb[node]) continue;
+
+            for (Pair nei : adj[node]) {
+                double new_prob = curr_prob * nei.prob;
+                if (new_prob > maxProb[nei.node]) {
+                    maxProb[nei.node] = new_prob;
+                    pq.offer(new Pair(nei.node, new_prob));
+                }
+            }
+        }
+
+        return 0.0;
+    }
+
+    static class Pair {
+        int node;
+        double prob;
+
+        Pair(int node, double prob) {
+            this.node = node;
+            this.prob = prob;
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    double maxProbability(int n, vector<vector<int>>& edges, vector<double>& succProb, int start_node, int end_node) {
+        vector<vector<pair<int, double>>> adj(n);
+        for (int i = 0; i < edges.size(); i++) {
+            int src = edges[i][0], dst = edges[i][1];
+            adj[src].emplace_back(dst, succProb[i]);
+            adj[dst].emplace_back(src, succProb[i]);
+        }
+
+        vector<double> maxProb(n, 0.0);
+        maxProb[start_node] = 1.0;
+        priority_queue<pair<double, int>> pq;
+        pq.emplace(1.0, start_node);
+
+        while (!pq.empty()) {
+            auto [curr_prob, node] = pq.top(); pq.pop();
+
+            if (node == end_node) return curr_prob;
+            if (curr_prob > maxProb[node]) continue;
+
+            for (auto& [nei, edge_prob] : adj[node]) {
+                double new_prob = curr_prob * edge_prob;
+                if (new_prob > maxProb[nei]) {
+                    maxProb[nei] = new_prob;
+                    pq.emplace(new_prob, nei);
+                }
+            }
+        }
+
+        return 0.0;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} edges
+     * @param {number[]} succProb
+     * @param {number} start_node
+     * @param {number} end_node
+     * @return {number}
+     */
+    maxProbability(n, edges, succProb, start_node, end_node) {
+        let adj = Array.from({ length: n }, () => []);
+        for (let i = 0; i < edges.length; i++) {
+            let [src, dst] = edges[i];
+            adj[src].push([dst, succProb[i]]);
+            adj[dst].push([src, succProb[i]]);
+        }
+
+        let maxProb = Array(n).fill(0);
+        maxProb[start_node] = 1.0;
+        let pq = new MaxPriorityQueue({ priority: x => x[1] });
+        pq.enqueue([start_node, 1.0]);
+
+        while (!pq.isEmpty()) {
+            let [node, curr_prob] = pq.dequeue().element;
+
+            if (node === end_node) return curr_prob;
+            if (curr_prob > maxProb[node]) continue;
+
+            for (let [nei, edge_prob] of adj[node]) {
+                let new_prob = curr_prob * edge_prob;
+                if (new_prob > maxProb[nei]) {
+                    maxProb[nei] = new_prob;
+                    pq.enqueue([nei, new_prob]);
+                }
+            }
+        }
+
+        return 0.0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O((V + E) \log V)$
+* Space complexity: $O(V + E)$
+
+> Where $V$ is the number nodes and $E$ is the number of edges.
+
+---
+
+## 3. Bellman Ford Algorithm
+
+::tabs-start
+
+```python
+class Solution:
+    def maxProbability(self, n: int, edges: List[List[int]], succProb: List[float], start_node: int, end_node: int) -> float:
+        maxProb = [0.0] * n
+        maxProb[start_node] = 1.0
+
+        for i in range(n):
+            updated = False
+            for j in range(len(edges)):
+                src, dst = edges[j]
+                if maxProb[src] * succProb[j] > maxProb[dst]:
+                    maxProb[dst] = maxProb[src] * succProb[j]
+                    updated = True
+
+                if maxProb[dst] * succProb[j] > maxProb[src]:
+                    maxProb[src] = maxProb[dst] * succProb[j]
+                    updated = True
+
+            if not updated:
+                break
+
+        return maxProb[end_node]
+```
+
+```java
+public class Solution {
+    public double maxProbability(int n, int[][] edges, double[] succProb, int start_node, int end_node) {
+        double[] maxProb = new double[n];
+        maxProb[start_node] = 1.0;
+
+        for (int i = 0; i < n; i++) {
+            boolean updated = false;
+            for (int j = 0; j < edges.length; j++) {
+                int src = edges[j][0], dst = edges[j][1];
+                
+                if (maxProb[src] * succProb[j] > maxProb[dst]) {
+                    maxProb[dst] = maxProb[src] * succProb[j];
+                    updated = true;
+                }
+                
+                if (maxProb[dst] * succProb[j] > maxProb[src]) {
+                    maxProb[src] = maxProb[dst] * succProb[j];
+                    updated = true;
+                }
+            }
+            if (!updated) break;
+        }
+
+        return maxProb[end_node];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    double maxProbability(int n, vector<vector<int>>& edges, vector<double>& succProb, int start_node, int end_node) {
+        vector<double> maxProb(n, 0.0);
+        maxProb[start_node] = 1.0;
+
+        for (int i = 0; i < n; i++) {
+            bool updated = false;
+            for (int j = 0; j < edges.size(); j++) {
+                int src = edges[j][0], dst = edges[j][1];
+
+                if (maxProb[src] * succProb[j] > maxProb[dst]) {
+                    maxProb[dst] = maxProb[src] * succProb[j];
+                    updated = true;
+                }
+
+                if (maxProb[dst] * succProb[j] > maxProb[src]) {
+                    maxProb[src] = maxProb[dst] * succProb[j];
+                    updated = true;
+                }
+            }
+            if (!updated) break;
+        }
+
+        return maxProb[end_node];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} edges
+     * @param {number[]} succProb
+     * @param {number} start_node
+     * @param {number} end_node
+     * @return {number}
+     */
+    maxProbability(n, edges, succProb, start_node, end_node) {
+        let maxProb = new Array(n).fill(0.0);
+        maxProb[start_node] = 1.0;
+
+        for (let i = 0; i < n; i++) {
+            let updated = false;
+            for (let j = 0; j < edges.length; j++) {
+                let [src, dst] = edges[j];
+
+                if (maxProb[src] * succProb[j] > maxProb[dst]) {
+                    maxProb[dst] = maxProb[src] * succProb[j];
+                    updated = true;
+                }
+
+                if (maxProb[dst] * succProb[j] > maxProb[src]) {
+                    maxProb[src] = maxProb[dst] * succProb[j];
+                    updated = true;
+                }
+            }
+            if (!updated) break;
+        }
+
+        return maxProb[end_node];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V * E)$
+* Space complexity: $O(V)$
+
+> Where $V$ is the number nodes and $E$ is the number of edges.
+
+---
+
+## 4. Shortest Path Faster Algorithm
+
+::tabs-start
+
+```python
+class Solution:
+    def maxProbability(self, n: int, edges: List[List[int]], succProb: List[float], start_node: int, end_node: int) -> float:
+        adj = [[] for _ in range(n)]
+        for i in range(len(edges)):
+            src, dst = edges[i]
+            adj[src].append((dst, succProb[i]))
+            adj[dst].append((src, succProb[i]))
+
+        maxProb = [0.0] * n
+        maxProb[start_node] = 1.0
+        q = deque([start_node])
+
+        while q:
+            node = q.popleft()
+
+            for nei, edge_prob in adj[node]:
+                new_prob = maxProb[node] * edge_prob
+                if new_prob > maxProb[nei]:  
+                    maxProb[nei] = new_prob
+                    q.append(nei)
+
+        return maxProb[end_node]
+```
+
+```java
+public class Solution {
+    public double maxProbability(int n, int[][] edges, double[] succProb, int start_node, int end_node) {
+        List<Pair>[] adj = new ArrayList[n];
+        for (int i = 0; i < n; i++) adj[i] = new ArrayList<>();
+
+        for (int i = 0; i < edges.length; i++) {
+            int src = edges[i][0], dst = edges[i][1];
+            adj[src].add(new Pair(dst, succProb[i]));
+            adj[dst].add(new Pair(src, succProb[i]));
+        }
+
+        double[] maxProb = new double[n];
+        maxProb[start_node] = 1.0;
+        Queue<Integer> q = new LinkedList<>();
+        q.offer(start_node);
+
+        while (!q.isEmpty()) {
+            int node = q.poll();
+
+            for (Pair nei : adj[node]) {
+                double newProb = maxProb[node] * nei.prob;
+                if (newProb > maxProb[nei.node]) {
+                    maxProb[nei.node] = newProb;
+                    q.offer(nei.node);
+                }
+            }
+        }
+
+        return maxProb[end_node];
+    }
+
+    static class Pair {
+        int node;
+        double prob;
+
+        Pair(int node, double prob) {
+            this.node = node;
+            this.prob = prob;
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    double maxProbability(int n, vector<vector<int>>& edges, vector<double>& succProb, int start_node, int end_node) {
+        vector<vector<pair<int, double>>> adj(n);
+
+        for (int i = 0; i < edges.size(); i++) {
+            int src = edges[i][0], dst = edges[i][1];
+            adj[src].emplace_back(dst, succProb[i]);
+            adj[dst].emplace_back(src, succProb[i]);
+        }
+
+        vector<double> maxProb(n, 0.0);
+        maxProb[start_node] = 1.0;
+        queue<int> q;
+        q.push(start_node);
+
+        while (!q.empty()) {
+            int node = q.front();
+            q.pop();
+
+            for (auto& [nei, edgeProb] : adj[node]) {
+                double newProb = maxProb[node] * edgeProb;
+                if (newProb > maxProb[nei]) {
+                    maxProb[nei] = newProb;
+                    q.push(nei);
+                }
+            }
+        }
+
+        return maxProb[end_node];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} edges
+     * @param {number[]} succProb
+     * @param {number} start_node
+     * @param {number} end_node
+     * @return {number}
+     */
+    maxProbability(n, edges, succProb, start_node, end_node) {
+        let adj = Array.from({ length: n }, () => []);
+        for (let i = 0; i < edges.length; i++) {
+            let [src, dst] = edges[i];
+            adj[src].push([dst, succProb[i]]);
+            adj[dst].push([src, succProb[i]]);
+        }
+
+        let maxProb = new Array(n).fill(0.0);
+        maxProb[start_node] = 1.0;
+        const q = new Queue([start_node]);
+
+        while (!q.isEmpty()) {
+            let node = q.pop();
+
+            for (let [nei, edgeProb] of adj[node]) {
+                let newProb = maxProb[node] * edgeProb;
+                if (newProb > maxProb[nei]) {
+                    maxProb[nei] = newProb;
+                    q.push(nei);
+                }
+            }
+        }
+
+        return maxProb[end_node];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V * E)$
+* Space complexity: $O(V + E)$
+
+> Where $V$ is the number nodes and $E$ is the number of edges.
\ No newline at end of file
diff --git a/articles/path-with-minimum-effort.md b/articles/path-with-minimum-effort.md
new file mode 100644
index 000000000..5f151c2c8
--- /dev/null
+++ b/articles/path-with-minimum-effort.md
@@ -0,0 +1,1066 @@
+## 1. Dijkstra's Algorithm
+
+::tabs-start
+
+```python
+class Solution:
+    def minimumEffortPath(self, heights: List[List[int]]) -> int:
+        ROWS, COLS = len(heights), len(heights[0])
+        minHeap = [[0, 0, 0]]  # [diff, row, col]
+        visit = set()
+        directions = [[0, 1], [0, -1], [1, 0], [-1, 0]]
+
+        while minHeap:
+            diff, r, c = heapq.heappop(minHeap)
+
+            if (r, c) in visit:
+                continue
+
+            visit.add((r, c))
+
+            if (r, c) == (ROWS - 1, COLS - 1):
+                return diff
+
+            for dr, dc in directions:
+                newR, newC = r + dr, c + dc
+                if (
+                    newR < 0 or newC < 0 or
+                    newR >= ROWS or newC >= COLS or
+                    (newR, newC) in visit
+                ):
+                    continue
+
+                newDiff = max(diff, abs(heights[r][c] - heights[newR][newC]))
+                heapq.heappush(minHeap, [newDiff, newR, newC])
+
+        return 0
+```
+
+```java
+public class Solution {
+    public int minimumEffortPath(int[][] heights) {
+        int rows = heights.length;
+        int cols = heights[0].length;
+        int[][] dist = new int[rows][cols];
+        for (int[] row : dist) {
+            Arrays.fill(row, Integer.MAX_VALUE);
+        }
+        dist[0][0] = 0;
+
+        PriorityQueue<int[]> minHeap = new PriorityQueue<>((a, b) -> a[0] - b[0]);
+        minHeap.offer(new int[]{0, 0, 0}); // {diff, row, col}
+
+        int[][] directions = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+
+        while (!minHeap.isEmpty()) {
+            int[] curr = minHeap.poll();
+            int diff = curr[0], r = curr[1], c = curr[2];
+
+            if (r == rows - 1 && c == cols - 1) return diff;
+            if (dist[r][c] < diff) continue;
+
+            for (int[] dir : directions) {
+                int newR = r + dir[0], newC = c + dir[1];
+                if (newR < 0 || newC < 0 || newR >= rows || newC >= cols) {
+                    continue;
+                }
+
+                int newDiff = Math.max(diff, Math.abs(heights[r][c] - heights[newR][newC]));
+                if (newDiff < dist[newR][newC]) {
+                    dist[newR][newC] = newDiff;
+                    minHeap.offer(new int[]{newDiff, newR, newC});
+                }
+            }
+        }
+
+        return 0;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minimumEffortPath(vector<vector<int>>& heights) {
+        int rows = heights.size(), cols = heights[0].size();
+        vector<vector<int>> dist(rows, vector<int>(cols, INT_MAX));
+        dist[0][0] = 0;
+
+        priority_queue<vector<int>, vector<vector<int>>, greater<>> minHeap;
+        minHeap.push({0, 0, 0}); // {diff, row, col}
+
+        vector<vector<int>> directions = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+
+        while (!minHeap.empty()) {
+            auto curr = minHeap.top();
+            minHeap.pop();
+            int diff = curr[0], r = curr[1], c = curr[2];
+
+            if (r == rows - 1 && c == cols - 1) return diff;
+            if (dist[r][c] < diff) continue;
+
+            for (auto& dir : directions) {
+                int newR = r + dir[0], newC = c + dir[1];
+                if (newR < 0 || newC < 0 || newR >= rows || newC >= cols) {
+                    continue;
+                }
+
+                int newDiff = max(diff, abs(heights[r][c] - heights[newR][newC]));
+                if (newDiff < dist[newR][newC]) {
+                    dist[newR][newC] = newDiff;
+                    minHeap.push({newDiff, newR, newC});
+                }
+            }
+        }
+
+        return 0;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} heights
+     * @return {number}
+     */
+    minimumEffortPath(heights) {
+        const rows = heights.length;
+        const cols = heights[0].length;
+        const dist = Array.from({ length: rows }, () => 
+            Array(cols).fill(Infinity)
+        );
+        dist[0][0] = 0;
+
+        const minHeap = new MinPriorityQueue(a => a[0]);
+        minHeap.enqueue([0, 0, 0]); // [diff, row, col]
+
+        const directions = [
+            [0, 1], [0, -1],
+            [1, 0], [-1, 0],
+        ];
+
+        while (!minHeap.isEmpty()) {
+            const [diff, r, c] = minHeap.dequeue();
+
+            if (r === rows - 1 && c === cols - 1) return diff;
+            if (dist[r][c] < diff) continue;
+
+            for (const [dr, dc] of directions) {
+                const newR = r + dr;
+                const newC = c + dc;
+                if (newR < 0 || newC < 0 || newR >= rows || newC >= cols) {
+                    continue;
+                }
+
+                const newDiff = Math.max(
+                    diff,
+                    Math.abs(heights[r][c] - heights[newR][newC])
+                );
+                if (newDiff < dist[newR][newC]) {
+                    dist[newR][newC] = newDiff;
+                    minHeap.enqueue([newDiff, newR, newC]);
+                }
+            }
+        }
+
+        return 0;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MinimumEffortPath(int[][] heights) {
+        int rows = heights.Length, cols = heights[0].Length;
+        var directions = new int[][] {
+            new int[] { 0, 1 },
+            new int[] { 0, -1 },
+            new int[] { 1, 0 },
+            new int[] { -1, 0 }
+        };
+
+        var minHeap = new PriorityQueue<(int diff, int r, int c), int>();
+        var visited = new HashSet<(int, int)>();
+        minHeap.Enqueue((0, 0, 0), 0);
+
+        while (minHeap.Count > 0) {
+            var current = minHeap.Dequeue();
+            int diff = current.diff, r = current.r, c = current.c;
+
+            if (visited.Contains((r, c))) continue;
+            visited.Add((r, c));
+
+            if (r == rows - 1 && c == cols - 1) {
+                return diff;
+            }
+
+            foreach (var dir in directions) {
+                int newR = r + dir[0];
+                int newC = c + dir[1];
+
+                if (newR < 0 || newC < 0 || newR >= rows || newC >= cols || visited.Contains((newR, newC))) {
+                    continue;
+                }
+
+                int newDiff = Math.Max(diff, Math.Abs(heights[r][c] - heights[newR][newC]));
+                minHeap.Enqueue((newDiff, newR, newC), newDiff);
+            }
+        }
+
+        return 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n * \log (m * n))$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns in the given matrix.
+
+---
+
+## 2. Binary Search + DFS
+
+::tabs-start
+
+```python
+class Solution:
+    def minimumEffortPath(self, heights: List[List[int]]) -> int:
+        ROWS, COLS = len(heights), len(heights[0])
+        directions = [[0, 1], [0, -1], [1, 0], [-1, 0]]
+        
+        def dfs(r, c, limit, visited):
+            if r == ROWS - 1 and c == COLS - 1:
+                return True
+                
+            visited.add((r, c))
+            for dr, dc in directions:
+                newR, newC = r + dr, c + dc
+                if (newR < 0 or newC < 0 or 
+                    newR >= ROWS or newC >= COLS or 
+                    (newR, newC) in visited or
+                    abs(heights[newR][newC] - heights[r][c]) > limit):
+                    continue
+                    
+                if dfs(newR, newC, limit, visited):
+                    return True
+            return False
+        
+        l, r = 0, 1000000
+        res = r
+        
+        while l <= r:
+            mid = (l + r) // 2
+            if dfs(0, 0, mid, set()):
+                res = mid
+                r = mid - 1
+            else:
+                l = mid + 1
+                
+        return res
+```
+
+```java
+public class Solution {
+    private int ROWS, COLS;
+    private int[][] heights;
+    private int[][] directions = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+    private boolean[][] visited;
+
+    public int minimumEffortPath(int[][] heights) {
+        this.heights = heights;
+        this.ROWS = heights.length;
+        this.COLS = heights[0].length;
+        this.visited = new boolean[ROWS][COLS];
+
+        int l = 0, r = 1_000_000, res = r;
+
+        while (l <= r) {
+            int mid = (l + r) / 2;
+            for (boolean[] row : visited) Arrays.fill(row, false);
+            if (dfs(0, 0, mid)) {
+                res = mid;
+                r = mid - 1;
+            } else {
+                l = mid + 1;
+            }
+        }
+
+        return res;
+    }
+
+    private boolean dfs(int r, int c, int limit) {
+        if (r == ROWS - 1 && c == COLS - 1) {
+            return true;
+        }
+
+        visited[r][c] = true;
+        for (int[] dir : directions) {
+            int newR = r + dir[0];
+            int newC = c + dir[1];
+            if (newR < 0 || newC < 0 || newR >= ROWS || newC >= COLS || visited[newR][newC]) {
+                continue;
+            }
+            if (Math.abs(heights[newR][newC] - heights[r][c]) > limit) {
+                continue;
+            }
+            if (dfs(newR, newC, limit)) {
+                return true;
+            }
+        }
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    int ROWS, COLS;
+    vector<vector<int>> heights;
+    vector<vector<bool>> visited;
+    vector<vector<int>> directions = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+
+public:
+    int minimumEffortPath(vector<vector<int>>& heights) {
+        this->heights = heights;
+        this->ROWS = heights.size();
+        this->COLS = heights[0].size();
+        this->visited = vector<vector<bool>>(ROWS, vector<bool>(COLS, false));
+
+        int l = 0, r = 1'000'000, res = r;
+        while (l <= r) {
+            int mid = (l + r) / 2;
+            for (auto& row : visited) {
+                fill(row.begin(), row.end(), false);
+            }
+            if (dfs(0, 0, mid)) {
+                res = mid;
+                r = mid - 1;
+            } else {
+                l = mid + 1;
+            }
+        }
+        return res;
+    }
+
+private:
+    bool dfs(int r, int c, int limit) {
+        if (r == ROWS - 1 && c == COLS - 1) {
+            return true;
+        }
+
+        visited[r][c] = true;
+        for (const auto& dir : directions) {
+            int newR = r + dir[0];
+            int newC = c + dir[1];
+            if (newR < 0 || newC < 0 || newR >= ROWS || newC >= COLS || visited[newR][newC]) {
+                continue;
+            }
+            if (abs(heights[newR][newC] - heights[r][c]) > limit) {
+                continue;
+            }
+            if (dfs(newR, newC, limit)) {
+                return true;
+            }
+        }
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} heights
+     * @return {number}
+     */
+    minimumEffortPath(heights) {
+        const ROWS = heights.length;
+        const COLS = heights[0].length;
+        const directions = [
+            [0, 1], [0, -1],
+            [1, 0], [-1, 0]
+        ];
+        let visited = Array.from({ length: ROWS }, () => 
+            Array(COLS).fill(false)
+        );
+
+        const dfs = (r, c, limit) => {
+            if (r === ROWS - 1 && c === COLS - 1) {
+                return true;
+            }
+
+            visited[r][c] = true;
+            for (const [dr, dc] of directions) {
+                const newR = r + dr;
+                const newC = c + dc;
+
+                if (newR < 0 || newC < 0 || 
+                    newR >= ROWS || newC >= COLS || 
+                    visited[newR][newC]) {
+                    continue;
+                }
+                if (Math.abs(heights[newR][newC] - heights[r][c]) > limit) {
+                    continue;
+                }
+                if (dfs(newR, newC, limit)) {
+                    return true;
+                }
+            }
+            return false;
+        };
+
+        let l = 0, r = 1_000_000, res = r;
+        while (l <= r) {
+            const mid = Math.floor((l + r) / 2);
+            for (const row of visited) {
+                row.fill(false);
+            }
+            if (dfs(0, 0, mid)) {
+                res = mid;
+                r = mid - 1;
+            } else {
+                l = mid + 1;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    private int[][] directions = new int[][] {
+        new int[] { 0, 1 },
+        new int[] { 0, -1 },
+        new int[] { 1, 0 },
+        new int[] { -1, 0 }
+    };
+
+    public int MinimumEffortPath(int[][] heights) {
+        int rows = heights.Length;
+        int cols = heights[0].Length;
+
+        bool Dfs(int r, int c, int limit, HashSet<(int, int)> visited) {
+            if (r == rows - 1 && c == cols - 1)
+                return true;
+
+            visited.Add((r, c));
+
+            foreach (var dir in directions) {
+                int newR = r + dir[0];
+                int newC = c + dir[1];
+
+                if (newR < 0 || newC < 0 || newR >= rows || newC >= cols ||
+                    visited.Contains((newR, newC)) ||
+                    Math.Abs(heights[newR][newC] - heights[r][c]) > limit)
+                    continue;
+
+                if (Dfs(newR, newC, limit, visited))
+                    return true;
+            }
+
+            return false;
+        }
+
+        int left = 0, right = 1000000, res = right;
+
+        while (left <= right) {
+            int mid = (left + right) / 2;
+            var visited = new HashSet<(int, int)>();
+            if (Dfs(0, 0, mid, visited)) {
+                res = mid;
+                right = mid - 1;
+            } else {
+                left = mid + 1;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n * \log (m * n))$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns in the given matrix.
+
+---
+
+## 3. Kruskal's Algorithm
+
+::tabs-start
+
+```python
+class DSU:
+    def __init__(self, n):
+        self.Parent = list(range(n + 1))
+        self.Size = [1] * (n + 1)
+
+    def find(self, node):
+        if self.Parent[node] != node:
+            self.Parent[node] = self.find(self.Parent[node])
+        return self.Parent[node]
+
+    def union(self, u, v):
+        pu = self.find(u)
+        pv = self.find(v)
+        if pu == pv:
+            return False
+        if self.Size[pu] < self.Size[pv]:
+            pu, pv = pv, pu
+        self.Size[pu] += self.Size[pv]
+        self.Parent[pv] = pu
+        return True
+
+
+class Solution:
+    def minimumEffortPath(self, heights: List[List[int]]) -> int:
+        ROWS, COLS = len(heights), len(heights[0])
+        edges = []
+        for r in range(ROWS):
+            for c in range(COLS):
+                if r + 1 < ROWS:
+                    edges.append((abs(heights[r][c] - heights[r + 1][c]), r * COLS + c, (r + 1) * COLS + c))
+                if c + 1 < COLS:
+                    edges.append((abs(heights[r][c] - heights[r][c + 1]), r * COLS + c, r * COLS + c + 1))
+
+        edges.sort()
+        dsu = DSU(ROWS * COLS)
+        for weight, u, v in edges:
+            dsu.union(u, v)
+            if dsu.find(0) == dsu.find(ROWS * COLS - 1):
+                return weight
+        return 0
+```
+
+```java
+class DSU {
+    private int[] Parent;
+    private int[] Size;
+
+    public DSU(int n) {
+        Parent = new int[n + 1];
+        Size = new int[n + 1];
+        for (int i = 0; i <= n; i++) {
+            Parent[i] = i;
+            Size[i] = 1;
+        }
+    }
+
+    public int find(int node) {
+        if (Parent[node] != node) {
+            Parent[node] = find(Parent[node]);
+        }
+        return Parent[node];
+    }
+
+    public boolean union(int u, int v) {
+        int pu = find(u);
+        int pv = find(v);
+        if (pu == pv) {
+            return false;
+        }
+        if (Size[pu] < Size[pv]) {
+            int temp = pu;
+            pu = pv;
+            pv = temp;
+        }
+        Size[pu] += Size[pv];
+        Parent[pv] = pu;
+        return true;
+    }
+}
+
+public class Solution {
+    public int minimumEffortPath(int[][] heights) {
+        int ROWS = heights.length;
+        int COLS = heights[0].length;
+        List<int[]> edges = new ArrayList<>();
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (r + 1 < ROWS) {
+                    edges.add(new int[]{Math.abs(heights[r][c] - heights[r + 1][c]), r * COLS + c, (r + 1) * COLS + c});
+                }
+                if (c + 1 < COLS) {
+                    edges.add(new int[]{Math.abs(heights[r][c] - heights[r][c + 1]), r * COLS + c, r * COLS + c + 1});
+                }
+            }
+        }
+
+        edges.sort(Comparator.comparingInt(a -> a[0]));
+        DSU dsu = new DSU(ROWS * COLS);
+        for (int[] edge : edges) {
+            int weight = edge[0], u = edge[1], v = edge[2];
+            dsu.union(u, v);
+            if (dsu.find(0) == dsu.find(ROWS * COLS - 1)) {
+                return weight;
+            }
+        }
+        return 0;
+    }
+}
+```
+
+```cpp
+class DSU {
+private:
+    vector<int> Parent, Size;
+
+public:
+    DSU(int n) {
+        Parent.resize(n + 1);
+        Size.resize(n + 1, 1);
+        for (int i = 0; i <= n; i++) {
+            Parent[i] = i;
+        }
+    }
+
+    int find(int node) {
+        if (Parent[node] != node) {
+            Parent[node] = find(Parent[node]);
+        }
+        return Parent[node];
+    }
+
+    bool unionSets(int u, int v) {
+        int pu = find(u);
+        int pv = find(v);
+        if (pu == pv) {
+            return false;
+        }
+        if (Size[pu] < Size[pv]) {
+            swap(pu, pv);
+        }
+        Size[pu] += Size[pv];
+        Parent[pv] = pu;
+        return true;
+    }
+};
+
+class Solution {
+public:
+    int minimumEffortPath(vector<vector<int>>& heights) {
+        int ROWS = heights.size();
+        int COLS = heights[0].size();
+        vector<tuple<int, int, int>> edges;
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (r + 1 < ROWS) {
+                    edges.push_back({abs(heights[r][c] - heights[r + 1][c]), r * COLS + c, (r + 1) * COLS + c});
+                }
+                if (c + 1 < COLS) {
+                    edges.push_back({abs(heights[r][c] - heights[r][c + 1]), r * COLS + c, r * COLS + c + 1});
+                }
+            }
+        }
+
+        sort(edges.begin(), edges.end());
+        DSU dsu(ROWS * COLS);
+        for (auto& edge : edges) {
+            int weight, u, v;
+            tie(weight, u, v) = edge;
+            dsu.unionSets(u, v);
+            if (dsu.find(0) == dsu.find(ROWS * COLS - 1)) {
+                return weight;
+            }
+        }
+        return 0;
+    }
+};
+```
+
+```javascript
+class DSU {
+    /**
+     * @constructor
+     * @param {number} n
+     */
+    constructor(n) {
+        this.Parent = Array.from({ length: n + 1 }, (_, i) => i);
+        this.Size = Array(n + 1).fill(1);
+    }
+
+    /**
+     * @param {number} node
+     * @return {number}
+     */
+    find(node) {
+        if (this.Parent[node] !== node) {
+            this.Parent[node] = this.find(this.Parent[node]);
+        }
+        return this.Parent[node];
+    }
+
+    /**
+     * @param {number} u
+     * @param {number} v
+     * @return {boolean}
+     */
+    union(u, v) {
+        let pu = this.find(u), pv = this.find(v);
+        if (pu === pv) return false;
+        if (this.Size[pu] < this.Size[pv]) [pu, pv] = [pv, pu];
+        this.Size[pu] += this.Size[pv];
+        this.Parent[pv] = pu;
+        return true;
+    }
+}
+
+class Solution {
+    /**
+     * @param {number[][]} heights
+     * @return {number}
+     */
+    minimumEffortPath(heights) {
+        const ROWS = heights.length;
+        const COLS = heights[0].length;
+        const edges = [];
+        for (let r = 0; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                if (r + 1 < ROWS) {
+                    edges.push([Math.abs(heights[r][c] - heights[r + 1][c]), r * COLS + c, (r + 1) * COLS + c]);
+                }
+                if (c + 1 < COLS) {
+                    edges.push([Math.abs(heights[r][c] - heights[r][c + 1]), r * COLS + c, r * COLS + c + 1]);
+                }
+            }
+        }
+
+        edges.sort((a, b) => a[0] - b[0]);
+        const dsu = new DSU(ROWS * COLS);
+        for (const [weight, u, v] of edges) {
+            dsu.union(u, v);
+            if (dsu.find(0) === dsu.find(ROWS * COLS - 1)) {
+                return weight;
+            }
+        }
+        return 0;
+    }
+}
+```
+
+```csharp
+public class DSU {
+    private int[] parent;
+    private int[] size;
+
+    public DSU(int n) {
+        parent = new int[n + 1];
+        size = new int[n + 1];
+        for (int i = 0; i <= n; i++) {
+            parent[i] = i;
+            size[i] = 1;
+        }
+    }
+
+    public int Find(int node) {
+        if (parent[node] != node) {
+            parent[node] = Find(parent[node]);
+        }
+        return parent[node];
+    }
+
+    public bool Union(int u, int v) {
+        int pu = Find(u);
+        int pv = Find(v);
+        if (pu == pv) return false;
+        if (size[pu] < size[pv]) {
+            (pu, pv) = (pv, pu);
+        }
+        size[pu] += size[pv];
+        parent[pv] = pu;
+        return true;
+    }
+}
+
+public class Solution {
+    public int MinimumEffortPath(int[][] heights) {
+        int rows = heights.Length;
+        int cols = heights[0].Length;
+        List<(int, int, int)> edges = new List<(int, int, int)>();
+
+        for (int r = 0; r < rows; r++) {
+            for (int c = 0; c < cols; c++) {
+                int id = r * cols + c;
+                if (r + 1 < rows) {
+                    int downId = (r + 1) * cols + c;
+                    int diff = Math.Abs(heights[r][c] - heights[r + 1][c]);
+                    edges.Add((diff, id, downId));
+                }
+                if (c + 1 < cols) {
+                    int rightId = r * cols + (c + 1);
+                    int diff = Math.Abs(heights[r][c] - heights[r][c + 1]);
+                    edges.Add((diff, id, rightId));
+                }
+            }
+        }
+
+        edges.Sort((a, b) => a.Item1.CompareTo(b.Item1));
+        DSU dsu = new DSU(rows * cols);
+
+        foreach (var (weight, u, v) in edges) {
+            dsu.Union(u, v);
+            if (dsu.Find(0) == dsu.Find(rows * cols - 1)) {
+                return weight;
+            }
+        }
+
+        return 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n * \log (m * n))$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns in the given matrix.
+
+---
+
+## 4. Shortest Path Faster Algorithm
+
+::tabs-start
+
+```python
+class Solution:
+    def minimumEffortPath(self, heights: List[List[int]]) -> int:
+        ROWS, COLS = len(heights), len(heights[0])
+        dist = [float('inf')] * (ROWS * COLS)
+        dist[0] = 0
+        in_queue = [False] * (ROWS * COLS)
+        
+        def index(r, c):
+            return r * COLS + c
+        
+        queue = deque([0])
+        in_queue[0] = True
+        directions = [(0, 1), (0, -1), (1, 0), (-1, 0)]
+
+        while queue:
+            u = queue.popleft()
+            in_queue[u] = False
+            r, c = divmod(u, COLS)
+
+            for dr, dc in directions:
+                newR, newC = r + dr, c + dc
+                if 0 <= newR < ROWS and 0 <= newC < COLS:
+                    v = index(newR, newC)
+                    weight = abs(heights[r][c] - heights[newR][newC])
+                    new_dist = max(dist[u], weight)
+                    if new_dist < dist[v]:
+                        dist[v] = new_dist
+                        if not in_queue[v]:
+                            queue.append(v)
+                            in_queue[v] = True
+        
+        return dist[ROWS * COLS - 1]
+```
+
+```java
+public class Solution {
+    public int minimumEffortPath(int[][] heights) {
+        int ROWS = heights.length, COLS = heights[0].length;
+        int[] dist = new int[ROWS * COLS];
+        Arrays.fill(dist, Integer.MAX_VALUE);
+        dist[0] = 0;
+
+        boolean[] inQueue = new boolean[ROWS * COLS];
+        Queue<Integer> queue = new LinkedList<>();
+        queue.offer(0);
+        inQueue[0] = true;
+
+        int[][] directions = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+
+        while (!queue.isEmpty()) {
+            int u = queue.poll();
+            inQueue[u] = false;
+
+            int r = u / COLS, c = u % COLS;
+
+            for (int[] dir : directions) {
+                int newR = r + dir[0], newC = c + dir[1];
+                if (newR >= 0 && newC >= 0 && newR < ROWS && newC < COLS) {
+                    int v = newR * COLS + newC;
+                    int weight = Math.abs(heights[r][c] - heights[newR][newC]);
+                    int newDist = Math.max(dist[u], weight);
+                    if (newDist < dist[v]) {
+                        dist[v] = newDist;
+                        if (!inQueue[v]) {
+                            queue.offer(v);
+                            inQueue[v] = true;
+                        }
+                    }
+                }
+            }
+        }
+
+        return dist[ROWS * COLS - 1];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minimumEffortPath(vector<vector<int>>& heights) {
+        int ROWS = heights.size(), COLS = heights[0].size();
+        vector<int> dist(ROWS * COLS, INT_MAX);
+        dist[0] = 0;
+
+        vector<bool> inQueue(ROWS * COLS, false);
+        queue<int> q;
+        q.push(0);
+        inQueue[0] = true;
+
+        vector<vector<int>> directions = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+
+        while (!q.empty()) {
+            int u = q.front();
+            q.pop();
+            inQueue[u] = false;
+
+            int r = u / COLS, c = u % COLS;
+
+            for (const auto& dir : directions) {
+                int newR = r + dir[0], newC = c + dir[1];
+                if (newR >= 0 && newC >= 0 && newR < ROWS && newC < COLS) {
+                    int v = newR * COLS + newC;
+                    int weight = abs(heights[r][c] - heights[newR][newC]);
+                    int newDist = max(dist[u], weight);
+                    if (newDist < dist[v]) {
+                        dist[v] = newDist;
+                        if (!inQueue[v]) {
+                            q.push(v);
+                            inQueue[v] = true;
+                        }
+                    }
+                }
+            }
+        }
+
+        return dist[ROWS * COLS - 1];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} heights
+     * @return {number}
+     */
+    minimumEffortPath(heights) {
+        const ROWS = heights.length, COLS = heights[0].length;
+        const dist = Array(ROWS * COLS).fill(Infinity);
+        dist[0] = 0;
+
+        const inQueue = Array(ROWS * COLS).fill(false);
+        const queue = new Queue();
+        queue.push(0);
+        inQueue[0] = true;
+
+        const directions = [
+            [0, 1], [0, -1],
+            [1, 0], [-1, 0]
+        ];
+
+        while (!queue.isEmpty()) {
+            const u = queue.pop();
+            inQueue[u] = false;
+
+            const r = Math.floor(u / COLS), c = u % COLS;
+            for (const [dr, dc] of directions) {
+                const newR = r + dr, newC = c + dc;
+                if (newR >= 0 && newC >= 0 && newR < ROWS && newC < COLS) {
+                    const v = newR * COLS + newC;
+                    const weight = Math.abs(heights[r][c] - heights[newR][newC]);
+                    const newDist = Math.max(dist[u], weight);
+                    if (newDist < dist[v]) {
+                        dist[v] = newDist;
+                        if (!inQueue[v]) {
+                            queue.push(v);
+                            inQueue[v] = true;
+                        }
+                    }
+                }
+            }
+        }
+
+        return dist[ROWS * COLS - 1];
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MinimumEffortPath(int[][] heights) {
+        int rows = heights.Length;
+        int cols = heights[0].Length;
+        int[] dist = Enumerable.Repeat(int.MaxValue, rows * cols).ToArray();
+        bool[] inQueue = new bool[rows * cols];
+        dist[0] = 0;
+
+        int Index(int r, int c) => r * cols + c;
+
+        Queue<int> queue = new Queue<int>();
+        queue.Enqueue(0);
+        inQueue[0] = true;
+
+        int[][] directions = new int[][] {
+            new int[] {0, 1}, new int[] {0, -1}, 
+            new int[] {1, 0}, new int[] {-1, 0}
+        };
+
+        while (queue.Count > 0) {
+            int u = queue.Dequeue();
+            inQueue[u] = false;
+            int r = u / cols, c = u % cols;
+
+            foreach (var dir in directions) {
+                int newR = r + dir[0], newC = c + dir[1];
+                if (newR >= 0 && newR < rows && newC >= 0 && newC < cols) {
+                    int v = Index(newR, newC);
+                    int weight = Math.Abs(heights[r][c] - heights[newR][newC]);
+                    int newDist = Math.Max(dist[u], weight);
+                    if (newDist < dist[v]) {
+                        dist[v] = newDist;
+                        if (!inQueue[v]) {
+                            queue.Enqueue(v);
+                            inQueue[v] = true;
+                        }
+                    }
+                }
+            }
+        }
+
+        return dist[rows * cols - 1];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(m * n)$ time in average case.
+    * $O(m ^ 2 * n ^ 2)$ time in worst case.
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns in the given matrix.
\ No newline at end of file
diff --git a/articles/perfect-squares.md b/articles/perfect-squares.md
new file mode 100644
index 000000000..eb92e5450
--- /dev/null
+++ b/articles/perfect-squares.md
@@ -0,0 +1,674 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def numSquares(self, n: int) -> int:
+        def dfs(target):
+            if target == 0:
+                return 0
+            
+            res = target
+            for i in range(1, target):
+                if i * i > target:
+                    break
+                res = min(res, 1 + dfs(target - i * i))
+            return res
+        
+        return dfs(n)
+```
+
+```java
+public class Solution {
+    public int numSquares(int n) {
+        return dfs(n);
+    }
+
+    private int dfs(int target) {
+        if (target == 0) {
+            return 0;
+        }
+        
+        int res = target;
+        for (int i = 1; i * i <= target; i++) {
+            res = Math.min(res, 1 + dfs(target - i * i));
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numSquares(int n) {
+        return dfs(n);
+    }
+
+private:
+    int dfs(int target) {
+        if (target == 0) {
+            return 0;
+        }
+        
+        int res = target;
+        for (int i = 1; i * i <= target; i++) {
+            res = min(res, 1 + dfs(target - i * i));
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    numSquares(n) {
+        const dfs = (target) => {
+            if (target === 0) return 0;
+
+            let res = target;
+            for (let i = 1; i * i <= target; i++) {
+                res = Math.min(res, 1 + dfs(target - i * i));
+            }
+            return res;
+        };
+
+        return dfs(n);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int NumSquares(int n) {
+        return Dfs(n);
+    }
+
+    private int Dfs(int target) {
+        if (target == 0) return 0;
+
+        int res = target;
+        for (int i = 1; i * i <= target; i++) {
+            res = Math.Min(res, 1 + Dfs(target - i * i));
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ {\sqrt {n}})$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def numSquares(self, n: int) -> int:
+        memo = {}
+
+        def dfs(target):
+            if target == 0:
+                return 0
+            if target in memo:
+                return memo[target]
+
+            res = target
+            for i in range(1, target + 1):
+                if i * i > target:
+                    break
+                res = min(res, 1 + dfs(target - i * i))
+
+            memo[target] = res
+            return res
+        
+        return dfs(n)
+```
+
+```java
+public class Solution {
+    Map<Integer, Integer> memo = new HashMap<>();
+
+    private int dfs(int target) {
+        if (target == 0) return 0;
+        if (memo.containsKey(target)) return memo.get(target);
+
+        int res = target;
+        for (int i = 1; i * i <= target; i++) {
+            res = Math.min(res, 1 + dfs(target - i * i));
+        }
+
+        memo.put(target, res);
+        return res;
+    }
+
+    public int numSquares(int n) {
+        return dfs(n);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    unordered_map<int, int> memo;
+
+    int dfs(int target) {
+        if (target == 0) return 0;
+        if (memo.count(target)) return memo[target];
+
+        int res = target;
+        for (int i = 1; i * i <= target; i++) {
+            res = min(res, 1 + dfs(target - i * i));
+        }
+
+        return memo[target] = res;
+    }
+
+    int numSquares(int n) {
+        return dfs(n);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    numSquares(n) {
+        const memo = new Map();
+    
+        const dfs = (target) => {
+            if (target === 0) return 0;
+            if (memo.has(target)) {
+                return memo.get(target);
+            }
+
+            let res = target;
+            for (let i = 1; i * i <= target; i++) {
+                res = Math.min(res, 1 + dfs(target - i * i));
+            }
+            memo.set(target, res);
+            return res;
+        };
+
+        return dfs(n);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    private Dictionary<int, int> memo = new Dictionary<int, int>();
+
+    public int NumSquares(int n) {
+        return Dfs(n);
+    }
+
+    private int Dfs(int target) {
+        if (target == 0) return 0;
+        if (memo.ContainsKey(target)) return memo[target];
+
+        int res = target;
+        for (int i = 1; i * i <= target; i++) {
+            res = Math.Min(res, 1 + Dfs(target - i * i));
+        }
+
+        memo[target] = res;
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * \sqrt {n})$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def numSquares(self, n: int) -> int:
+        dp = [n] * (n + 1)
+        dp[0] = 0
+        
+        for target in range(1, n + 1):
+            for s in range(1, target + 1):
+                square = s * s
+                if target - square < 0:
+                    break
+                dp[target] = min(dp[target], 1 + dp[target - square])
+        
+        return dp[n]
+```
+
+```java
+public class Solution {
+    public int numSquares(int n) {
+        int[] dp = new int[n + 1];
+        Arrays.fill(dp, n);
+        dp[0] = 0;
+
+        for (int target = 1; target <= n; target++) {
+            for (int s = 1; s * s <= target; s++) {
+                dp[target] = Math.min(dp[target], 1 + dp[target - s * s]);
+            }
+        }
+
+        return dp[n];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numSquares(int n) {
+        vector<int> dp(n + 1, n);
+        dp[0] = 0;
+
+        for (int target = 1; target <= n; target++) {
+            for (int s = 1; s * s <= target; s++) {
+                dp[target] = min(dp[target], 1 + dp[target - s * s]);
+            }
+        }
+
+        return dp[n];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    numSquares(n) {
+        const dp = Array(n + 1).fill(n);
+        dp[0] = 0;
+
+        for (let target = 1; target <= n; target++) {
+            for (let s = 1; s * s <= target; s++) {
+                dp[target] = Math.min(dp[target], 1 + dp[target - s * s]);
+            }
+        }
+
+        return dp[n];
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int NumSquares(int n) {
+        int[] dp = new int[n + 1];
+        Array.Fill(dp, n);
+        dp[0] = 0;
+
+        for (int target = 1; target <= n; target++) {
+            for (int s = 1; s * s <= target; s++) {
+                int square = s * s;
+                dp[target] = Math.Min(dp[target], 1 + dp[target - square]);
+            }
+        }
+
+        return dp[n];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * \sqrt {n})$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Breadth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def numSquares(self, n: int) -> int:
+        q = deque()
+        seen = set()
+        
+        res = 0
+        q.append(0)
+        while q:
+            res += 1
+            for _ in range(len(q)):
+                cur = q.popleft()
+                s = 1
+                while s * s + cur <= n:
+                    nxt = cur + s * s
+                    if nxt == n:
+                        return res
+                    if nxt not in seen:
+                        seen.add(nxt)
+                        q.append(nxt)
+                    s += 1
+                    
+        return res
+```
+
+```java
+public class Solution {
+    public int numSquares(int n) {
+        Queue<Integer> q = new LinkedList<>();
+        Set<Integer> seen = new HashSet<>();
+
+        int res = 0;
+        q.offer(0);
+        while (!q.isEmpty()) {
+            res++;
+            for (int i = q.size(); i > 0; i--) {
+                int cur = q.poll();
+                for (int s = 1; s * s + cur <= n; s++) {
+                    int next = cur + s * s;
+                    if (next == n) return res;
+                    if (!seen.contains(next)) {
+                        q.offer(next);
+                        seen.add(next);
+                    }
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numSquares(int n) {
+        queue<int> q;
+        unordered_set<int> seen;
+
+        int res = 0;
+        q.push(0);
+        while (!q.empty()) {
+            res++;
+            for (int i = q.size(); i > 0; i--) {
+                int cur = q.front(); q.pop();
+                for (int s = 1; s * s + cur <= n; s++) {
+                    int next = cur + s * s;
+                    if (next == n) return res;
+                    if (seen.find(next) == seen.end()) {
+                        q.push(next);
+                        seen.insert(next);
+                    }
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    numSquares(n) {
+        const q = new Queue;
+        const seen = new Set();
+
+        let res = 0;
+        q.push(0);
+        while (!q.isEmpty()) {
+            res++;
+            for (let i = q.size(); i > 0; i--) {
+                const cur = q.pop();
+                for (let s = 1; s * s + cur <= n; s++) {
+                    const next = cur + s * s;
+                    if (next === n) return res;
+                    if (!seen.has(next)) {
+                        q.push(next);
+                        seen.add(next);
+                    }
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int NumSquares(int n) {
+        Queue<int> q = new Queue<int>();
+        HashSet<int> seen = new HashSet<int>();
+        
+        int res = 0;
+        q.Enqueue(0);
+        
+        while (q.Count > 0) {
+            res++;
+            int size = q.Count;
+            for (int i = 0; i < size; i++) {
+                int cur = q.Dequeue();
+                int s = 1;
+                while (s * s + cur <= n) {
+                    int nxt = cur + s * s;
+                    if (nxt == n) {
+                        return res;
+                    }
+                    if (!seen.Contains(nxt)) {
+                        seen.Add(nxt);
+                        q.Enqueue(nxt);
+                    }
+                    s++;
+                }
+            }
+        }
+        
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * \sqrt {n})$
+* Space complexity: $O(n)$
+
+---
+
+## 5. Math
+
+::tabs-start
+
+```python
+class Solution:
+    def numSquares(self, n: int) -> int:
+        while n % 4 == 0:
+            n //= 4
+        
+        if n % 8 == 7:
+            return 4
+        
+        def isSquareNum(num):
+            s = int(math.sqrt(num))
+            return s * s == num
+        
+        if isSquareNum(n):
+            return 1
+        
+        i = 1
+        while i * i <= n:
+            if isSquareNum(n - i * i):
+                return 2
+            i += 1
+        
+        return 3
+```
+
+```java
+public class Solution {
+    public int numSquares(int n) {
+        while (n % 4 == 0) {
+            n /= 4;
+        }
+        
+        if (n % 8 == 7) {
+            return 4;
+        }
+        
+        if (isSquareNum(n)) {
+            return 1;
+        }
+        
+        for (int i = 1; i * i <= n; i++) {
+            if (isSquareNum(n - i * i)) {
+                return 2;
+            }
+        }
+        
+        return 3;
+    }
+    
+    private boolean isSquareNum(int num) {
+        int s = (int) Math.sqrt(num);
+        return s * s == num;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numSquares(int n) {
+        while (n % 4 == 0) {
+            n /= 4;
+        }
+        
+        if (n % 8 == 7) {
+            return 4;
+        }
+        
+        if (isSquareNum(n)) {
+            return 1;
+        }
+        
+        for (int i = 1; i * i <= n; i++) {
+            if (isSquareNum(n - i * i)) {
+                return 2;
+            }
+        }
+        
+        return 3;
+    }
+    
+private:
+    bool isSquareNum(int num) {
+        int s = (int) sqrt(num);
+        return s * s == num;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    numSquares(n) {
+        while (n % 4 === 0) {
+            n = Math.floor(n / 4);
+        }
+        
+        if (n % 8 === 7) {
+            return 4;
+        }
+        
+        const isSquareNum = (num) => {
+            const s = Math.floor(Math.sqrt(num));
+            return s * s === num;
+        };
+        
+        if (isSquareNum(n)) {
+            return 1;
+        }
+        
+        for (let i = 1; i * i <= n; i++) {
+            if (isSquareNum(n - i * i)) {
+                return 2;
+            }
+        }
+        
+        return 3;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int NumSquares(int n) {
+        while (n % 4 == 0) {
+            n /= 4;
+        }
+
+        if (n % 8 == 7) {
+            return 4;
+        }
+
+        bool IsSquareNum(int num) {
+            int s = (int)Math.Sqrt(num);
+            return s * s == num;
+        }
+
+        if (IsSquareNum(n)) {
+            return 1;
+        }
+
+        for (int i = 1; i * i <= n; i++) {
+            if (IsSquareNum(n - i * i)) {
+                return 2;
+            }
+        }
+
+        return 3;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\sqrt {n})$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/permutation-string.md b/articles/permutation-string.md
index 442c0cc0d..482890ee4 100644
--- a/articles/permutation-string.md
+++ b/articles/permutation-string.md
@@ -106,6 +106,68 @@ public class Solution {
 }
 ```
 
+```go
+func checkInclusion(s1 string, s2 string) bool {
+	s1Sorted := []rune(s1)
+	sort.Slice(s1Sorted, func(i, j int) bool {
+		return s1Sorted[i] < s1Sorted[j]
+	})
+	s1 = string(s1Sorted)
+
+	for i := 0; i < len(s2); i++ {
+		for j := i; j < len(s2); j++ {
+			subStr := s2[i : j+1]
+			subStrSorted := []rune(subStr)
+			sort.Slice(subStrSorted, func(a, b int) bool {
+				return subStrSorted[a] < subStrSorted[b]
+			})
+			if string(subStrSorted) == s1 {
+				return true
+			}
+		}
+	}
+	return false
+}
+```
+
+```kotlin
+class Solution {
+    fun checkInclusion(s1: String, s2: String): Boolean {
+        val sortedS1 = s1.toCharArray().apply { sort() }.concatToString()
+
+        for (i in s2.indices) {
+            for (j in i until s2.length) {
+                val subStr = s2.substring(i, j + 1)
+                val sortedSubStr = subStr.toCharArray().apply { sort() }.concatToString()
+                if (sortedSubStr == sortedS1) {
+                    return true
+                }
+            }
+        }
+        return false
+    }
+}
+```
+
+```swift
+class Solution {
+    func checkInclusion(_ s1: String, _ s2: String) -> Bool {
+        let s1Sorted = s1.sorted()
+        let chars = Array(s2)
+
+        for i in 0..<chars.count {
+            for j in i..<chars.count {
+                let subStr = String(chars[i...j]).sorted()
+                if subStr == s1Sorted {
+                    return true
+                }
+            }
+        }
+        return false
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -290,12 +352,103 @@ public class Solution {
 }
 ```
 
+```go
+func checkInclusion(s1 string, s2 string) bool {
+	count1 := make(map[rune]int)
+	for _, c := range s1 {
+		count1[c]++
+	}
+
+	need := len(count1)
+	for i := 0; i < len(s2); i++ {
+		count2 := make(map[rune]int)
+		cur := 0
+		for j := i; j < len(s2); j++ {
+			count2[rune(s2[j])]++
+			if count1[rune(s2[j])] < count2[rune(s2[j])] {
+				break
+			}
+			if count1[rune(s2[j])] == count2[rune(s2[j])] {
+				cur++
+			}
+			if cur == need {
+				return true
+			}
+		}
+	}
+	return false
+}
+```
+
+```kotlin
+class Solution {
+    fun checkInclusion(s1: String, s2: String): Boolean {
+        val count1 = HashMap<Char, Int>()
+        for (c in s1) {
+            count1[c] = 1 + count1.getOrDefault(c, 0)
+        }
+
+        val need = count1.size
+        for (i in s2.indices) {
+            val count2 = mutableMapOf<Char, Int>()
+            var cur = 0
+            for (j in i until s2.length) {
+                count2[s2[j]] = 1 + count2.getOrDefault(s2[j], 0)
+                if (count1.getOrDefault(s2[j], 0) < count2[s2[j]]!!) {
+                    break
+                }
+                if (count1.getOrDefault(s2[j], 0) == count2[s2[j]]!!) {
+                    cur++
+                }
+                if (cur == need) {
+                    return true
+                }
+            }
+        }
+        return false
+    }
+}
+```
+
+```swift
+class Solution {
+    func checkInclusion(_ s1: String, _ s2: String) -> Bool {
+        var count1 = [Character: Int]()
+        for c in s1 {
+            count1[c, default: 0] += 1
+        }
+        
+        let need = count1.count
+        let chars = Array(s2)
+
+        for i in 0..<chars.count {
+            var count2 = [Character: Int]()
+            var cur = 0
+
+            for j in i..<chars.count {
+                count2[chars[j], default: 0] += 1
+                if count1[chars[j], default: 0] < count2[chars[j], default: 0] {
+                    break
+                }
+                if count1[chars[j], default: 0] == count2[chars[j], default: 0] {
+                    cur += 1
+                }
+                if cur == need {
+                    return true
+                }
+            }
+        }
+        return false
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n * m)$
-* Space complexity: $O(1)$
+* Space complexity: $O(1)$ since we have at most $26$ different characters.
 
 > Where $n$ is the length of the string1 and $m$ is the length of string2.
 
@@ -545,6 +698,151 @@ public class Solution {
 }
 ```
 
+```go
+func checkInclusion(s1 string, s2 string) bool {
+	if len(s1) > len(s2) {
+		return false
+	}
+
+	s1Count := make([]int, 26)
+	s2Count := make([]int, 26)
+	for i := 0; i < len(s1); i++ {
+		s1Count[s1[i]-'a']++
+		s2Count[s2[i]-'a']++
+	}
+
+	matches := 0
+	for i := 0; i < 26; i++ {
+		if s1Count[i] == s2Count[i] {
+			matches++
+		}
+	}
+
+	l := 0
+	for r := len(s1); r < len(s2); r++ {
+		if matches == 26 {
+			return true
+		}
+
+		index := s2[r] - 'a'
+		s2Count[index]++
+		if s1Count[index] == s2Count[index] {
+			matches++
+		} else if s1Count[index]+1 == s2Count[index] {
+			matches--
+		}
+
+		index = s2[l] - 'a'
+		s2Count[index]--
+		if s1Count[index] == s2Count[index] {
+			matches++
+		} else if s1Count[index]-1 == s2Count[index] {
+			matches--
+		}
+		l++
+	}
+	return matches == 26
+}
+```
+
+```kotlin
+class Solution {
+    fun checkInclusion(s1: String, s2: String): Boolean {
+        if (s1.length > s2.length) return false
+
+        val s1Count = IntArray(26)
+        val s2Count = IntArray(26)
+        for (i in s1.indices) {
+            s1Count[s1[i] - 'a']++
+            s2Count[s2[i] - 'a']++
+        }
+
+        var matches = 0
+        for (i in 0 until 26) {
+            if (s1Count[i] == s2Count[i]) matches++
+        }
+
+        var l = 0
+        for (r in s1.length until s2.length) {
+            if (matches == 26) return true
+
+            val index = s2[r] - 'a'
+            s2Count[index]++
+            if (s1Count[index] == s2Count[index]) {
+                matches++
+            } else if (s1Count[index] + 1 == s2Count[index]) {
+                matches--
+            }
+
+            val leftIndex = s2[l] - 'a'
+            s2Count[leftIndex]--
+            if (s1Count[leftIndex] == s2Count[leftIndex]) {
+                matches++
+            } else if (s1Count[leftIndex] - 1 == s2Count[leftIndex]) {
+                matches--
+            }
+            l++
+        }
+        return matches == 26
+    }
+}
+```
+
+```swift
+class Solution {
+    func checkInclusion(_ s1: String, _ s2: String) -> Bool {
+        if s1.count > s2.count {
+            return false
+        }
+
+        var s1Count = [Int](repeating: 0, count: 26)
+        var s2Count = [Int](repeating: 0, count: 26)
+        let aAscii = Int(Character("a").asciiValue!)
+
+        let s1Array = Array(s1)
+        let s2Array = Array(s2)
+
+        for i in 0..<s1.count {
+            s1Count[Int(s1Array[i].asciiValue!) - aAscii] += 1
+            s2Count[Int(s2Array[i].asciiValue!) - aAscii] += 1
+        }
+
+        var matches = 0
+        for i in 0..<26 {
+            if s1Count[i] == s2Count[i] {
+                matches += 1
+            }
+        }
+
+        var l = 0
+        for r in s1.count..<s2.count {
+            if matches == 26 {
+                return true
+            }
+
+            var index = Int(s2Array[r].asciiValue!) - aAscii
+            s2Count[index] += 1
+            if s1Count[index] == s2Count[index] {
+                matches += 1
+            } else if s1Count[index] + 1 == s2Count[index] {
+                matches -= 1
+            }
+
+            index = Int(s2Array[l].asciiValue!) - aAscii
+            s2Count[index] -= 1
+            if s1Count[index] == s2Count[index] {
+                matches += 1
+            } else if s1Count[index] - 1 == s2Count[index] {
+                matches -= 1
+            }
+            l += 1
+        }
+
+        return matches == 26
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/permutations-ii.md b/articles/permutations-ii.md
new file mode 100644
index 000000000..83aefec3b
--- /dev/null
+++ b/articles/permutations-ii.md
@@ -0,0 +1,892 @@
+## 1. Backtracking (Hash Set)
+
+::tabs-start
+
+```python
+class Solution:
+    def permuteUnique(self, nums: List[int]) -> List[List[int]]:
+        res = set()
+
+        def backtrack(perm):
+            if len(perm) == len(nums):
+                res.add(tuple(perm))
+                return
+            
+            for i in range(len(nums)):
+                if nums[i] != float("-inf"):
+                    perm.append(nums[i])
+                    nums[i] = float("-inf")
+                    backtrack(perm)
+                    nums[i] = perm[-1]
+                    perm.pop()
+        
+        backtrack([])
+        return list(res)
+```
+
+```java
+public class Solution {
+    private Set<List<Integer>> res;
+
+    public List<List<Integer>> permuteUnique(int[] nums) {
+        res = new HashSet<>();
+        List<Integer> perm = new ArrayList<>();
+        backtrack(nums, perm);
+        return new ArrayList<>(res);
+    }
+
+    private void backtrack(int[] nums, List<Integer> perm) {
+        if (perm.size() == nums.length) {
+            res.add(new ArrayList<>(perm));
+            return;
+        }
+
+        for (int i = 0; i < nums.length; i++) {
+            if (nums[i] != Integer.MIN_VALUE) {
+                int temp = nums[i];
+                perm.add(nums[i]);
+                nums[i] = Integer.MIN_VALUE;
+                backtrack(nums, perm);
+                nums[i] = temp;
+                perm.remove(perm.size() - 1);
+            }
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+    set<vector<int>> res;
+public:
+    vector<vector<int>> permuteUnique(vector<int>& nums) {
+        vector<int> perm;
+        backtrack(nums, perm);
+        return vector<vector<int>>(res.begin(), res.end());
+    }
+
+private:
+    void backtrack(vector<int>& nums, vector<int>& perm) {
+        if (perm.size() == nums.size()) {
+            res.insert(perm);
+            return;
+        }
+
+        for (int i = 0; i < nums.size(); ++i) {
+            if (nums[i] != INT_MIN) {
+                int temp = nums[i];
+                perm.push_back(temp);
+                nums[i] = INT_MIN;
+                backtrack(nums, perm);
+                nums[i] = temp;
+                perm.pop_back();
+            }
+        }
+
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[][]}
+     */
+    permuteUnique(nums) {
+        const res = new Set();
+        const perm = [];
+
+        const backtrack = () => {
+            if (perm.length === nums.length) {
+                res.add(JSON.stringify(perm));
+                return;
+            }
+
+            for (let i = 0; i < nums.length; i++) {
+                if (nums[i] !== -Infinity) {
+                    let temp = nums[i];
+                    perm.push(nums[i]);
+                    nums[i] = -Infinity;
+                    backtrack();
+                    nums[i] = temp;
+                    perm.pop();
+                }
+            }
+        };
+
+        backtrack();
+        return Array.from(res).map(JSON.parse);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<List<int>> PermuteUnique(int[] nums) {
+        HashSet<string> resSet = new HashSet<string>();
+        List<List<int>> result = new List<List<int>>();
+        Backtrack(new List<int>(), nums, resSet, result);
+        return result;
+    }
+
+    private void Backtrack(List<int> perm, int[] nums, HashSet<string> resSet, List<List<int>> result) {
+        if (perm.Count == nums.Length) {
+            string key = string.Join(",", perm);
+            if (resSet.Add(key)) {
+                result.Add(new List<int>(perm));
+            }
+            return;
+        }
+
+        for (int i = 0; i < nums.Length; i++) {
+            if (nums[i] != int.MinValue) {
+                int temp = nums[i];
+                perm.Add(temp);
+                nums[i] = int.MinValue;
+                Backtrack(perm, nums, resSet, result);
+                nums[i] = temp;
+                perm.RemoveAt(perm.Count - 1);
+            }
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n! * n)$
+* Space complexity: $O(n! * n)$ for the hash set.
+
+---
+
+## 2. Backtracking (Hash Map)
+
+::tabs-start
+
+```python
+class Solution:
+    def permuteUnique(self, nums: List[int]) -> List[List[int]]:
+        res = []
+        perm = []
+        count = {n: 0 for n in nums}
+        for num in nums:
+            count[num] += 1
+
+        def dfs():
+            if len(perm) == len(nums):
+                res.append(perm.copy())
+                return
+            
+            for num in count:
+                if count[num] > 0:
+                    perm.append(num)
+                    count[num] -= 1
+                    dfs()
+                    count[num] += 1
+                    perm.pop()
+
+        dfs()
+        return res
+```
+
+```java
+public class Solution {
+    private Map<Integer, Integer> count;
+    private List<List<Integer>> res;
+    
+    public List<List<Integer>> permuteUnique(int[] nums) {
+        res = new ArrayList<>();
+        count = new HashMap<>();
+        List<Integer> perm = new ArrayList<>();
+
+        for (int num : nums) {
+            count.put(num, count.getOrDefault(num, 0) + 1);
+        }
+
+        dfs(nums, perm);
+        return res;
+    }
+
+    private void dfs(int[] nums, List<Integer> perm) {
+        if (perm.size() == nums.length) {
+            res.add(new ArrayList<>(perm));
+            return;
+        }
+
+        for (int num : count.keySet()) {
+            if (count.get(num) > 0) {
+                perm.add(num);
+                count.put(num, count.get(num) - 1);
+                dfs(nums, perm);
+                count.put(num, count.get(num) + 1);
+                perm.remove(perm.size() - 1);
+            }
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+    vector<vector<int>> res;
+    unordered_map<int, int> count;
+    
+public:
+    vector<vector<int>> permuteUnique(vector<int>& nums) {
+        for (int& num : nums) {
+            count[num]++;
+        }
+        vector<int> perm;
+        dfs(nums, perm);
+        return res;
+    }
+
+    void dfs(vector<int>& nums, vector<int>& perm) {
+        if (perm.size() == nums.size()) {
+            res.push_back(perm);
+            return;
+        }
+        for (auto& [num, cnt] : count) {
+            if (cnt > 0) {
+                perm.push_back(num);
+                cnt--;
+                dfs(nums, perm);
+                cnt++;
+                perm.pop_back();
+            }
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[][]}
+     */
+    permuteUnique(nums) {
+        const res = [];
+        const perm = [];
+        const count = {};
+
+        for (const num of nums) {
+            count[num] = (count[num] || 0) + 1;
+        }
+
+        const dfs = () => {
+            if (perm.length === nums.length) {
+                res.push([...perm]);
+                return;
+            }
+
+            for (const num in count) {
+                if (count[num] > 0) {
+                    perm.push(+num);
+                    count[num]--;
+                    dfs();
+                    count[num]++;
+                    perm.pop();
+                }
+            }
+        };
+
+        dfs();
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<List<int>> PermuteUnique(int[] nums) {
+        var res = new List<List<int>>();
+        var perm = new List<int>();
+        var count = new Dictionary<int, int>();
+
+        foreach (int num in nums) {
+            if (!count.ContainsKey(num)) {
+                count[num] = 0;
+            }
+            count[num]++;
+        }
+
+        void Dfs() {
+            if (perm.Count == nums.Length) {
+                res.Add(new List<int>(perm));
+                return;
+            }
+
+            foreach (var kvp in count) {
+                int num = kvp.Key;
+                if (count[num] > 0) {
+                    perm.Add(num);
+                    count[num]--;
+                    Dfs();
+                    count[num]++;
+                    perm.RemoveAt(perm.Count - 1);
+                }
+            }
+        }
+
+        Dfs();
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n! * n)$
+* Space complexity: $O(n! * n)$ for the output list.
+
+---
+
+## 3. Backtracking (Boolean Array)
+
+::tabs-start
+
+```python
+class Solution:
+    def permuteUnique(self, nums: List[int]) -> List[List[int]]:
+        res, n = [], len(nums)
+        visit = [False] * n
+        perm = []
+
+        def dfs():
+            if len(perm) == n:
+                res.append(perm.copy())
+                return
+            
+            for i in range(n):
+                if visit[i]:
+                    continue
+                
+                if i and nums[i] == nums[i - 1] and not visit[i - 1]:
+                    continue
+                visit[i] = True
+                perm.append(nums[i])
+                dfs()
+                visit[i] = False
+                perm.pop()
+
+        nums.sort()
+        dfs()
+        return res
+```
+
+```java
+public class Solution {
+    private boolean[] visit;
+    private List<List<Integer>> res;
+
+    public List<List<Integer>> permuteUnique(int[] nums) {
+        res = new ArrayList<>();
+        visit = new boolean[nums.length];
+        Arrays.sort(nums);
+        List<Integer> perm = new ArrayList<>();
+        dfs(nums, perm);
+        return res;
+    }
+
+    private void dfs(int[] nums, List<Integer> perm) {
+        if (perm.size() == nums.length) {
+            res.add(new ArrayList<>(perm));
+            return;
+        }
+
+        for (int i = 0; i < nums.length; i++) {
+            if (visit[i] || (i > 0 && nums[i] == nums[i - 1] && !visit[i - 1]))
+                continue;
+
+            visit[i] = true;
+            perm.add(nums[i]);
+            dfs(nums, perm);
+            visit[i] = false;
+            perm.remove(perm.size() - 1);
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+    vector<vector<int>> res;
+    vector<bool> visit;
+    
+public:
+    vector<vector<int>> permuteUnique(vector<int>& nums) {
+        visit.assign(nums.size(), false);
+        vector<int> perm;
+        sort(nums.begin(), nums.end());
+        dfs(nums, perm);
+        return res;
+    }
+
+    void dfs(vector<int>& nums, vector<int>& perm) {
+        if (perm.size() == nums.size()) {
+            res.push_back(perm);
+            return;
+        }
+        for (int i = 0; i < nums.size(); i++) {
+            if (visit[i] || (i > 0 && nums[i] == nums[i - 1] && !visit[i - 1]))
+                continue;
+                
+            visit[i] = true;
+            perm.push_back(nums[i]);
+            dfs(nums, perm);
+            visit[i] = false;
+            perm.pop_back();
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[][]}
+     */
+    permuteUnique(nums) {
+        const res = [];
+        const visit = new Array(nums.length).fill(false);
+        const perm = [];
+        nums.sort((a, b) => a - b);
+
+        const dfs = () => {
+            if (perm.length === nums.length) {
+                res.push([...perm]);
+                return;
+            }
+
+            for (let i = 0; i < nums.length; i++) {
+                if (visit[i] || (i > 0 && nums[i] === nums[i - 1] && !visit[i - 1]))
+                    continue;
+                
+                visit[i] = true;
+                perm.push(nums[i]);
+                dfs();
+                visit[i] = false;
+                perm.pop();
+            }
+        };
+
+        dfs();
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<List<int>> PermuteUnique(int[] nums) {
+        var res = new List<List<int>>();
+        var perm = new List<int>();
+        int n = nums.Length;
+        bool[] visit = new bool[n];
+        Array.Sort(nums);
+
+        void Dfs() {
+            if (perm.Count == n) {
+                res.Add(new List<int>(perm));
+                return;
+            }
+
+            for (int i = 0; i < n; i++) {
+                if (visit[i]) continue;
+                if (i > 0 && nums[i] == nums[i - 1] && !visit[i - 1]) continue;
+
+                visit[i] = true;
+                perm.Add(nums[i]);
+                Dfs();
+                perm.RemoveAt(perm.Count - 1);
+                visit[i] = false;
+            }
+        }
+
+        Dfs();
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n! * n)$
+* Space complexity: $O(n! * n)$ for the output list.
+
+---
+
+## 4. Backtracking (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def permuteUnique(self, nums: List[int]) -> List[List[int]]:
+        res = []
+
+        def dfs(i):
+            if i == len(nums):
+                res.append(nums.copy())
+                return
+            
+            for j in range(i, len(nums)):
+                if j > i and nums[i] == nums[j]:
+                    continue
+                
+                nums[i], nums[j] = nums[j], nums[i]
+                dfs(i + 1)
+            
+            for j in range(len(nums) - 1, i, -1):
+                nums[j], nums[i] = nums[i], nums[j]
+
+        nums.sort()
+        dfs(0)
+        return res
+```
+
+```java
+public class Solution {
+    private List<List<Integer>> res;
+
+    public List<List<Integer>> permuteUnique(int[] nums) {
+        res = new ArrayList<>();
+        Arrays.sort(nums);
+        dfs(0, nums);
+        return res;
+    }
+
+    private void dfs(int i, int[] nums) {
+        if (i == nums.length) {
+            List<Integer> temp = new ArrayList<>();
+            for (int num : nums) temp.add(num);
+            res.add(temp);
+            return;
+        }
+
+        for (int j = i; j < nums.length; j++) {
+            if (j > i && nums[j] == nums[i]) continue;
+            swap(nums, i, j);
+            dfs(i + 1, nums);
+        }
+
+        for (int j = nums.length - 1; j > i; j--) {
+            swap(nums, i, j);
+        }
+    }
+    
+    private void swap(int[] nums, int i, int j) {
+        int temp = nums[i];
+        nums[i] = nums[j];
+        nums[j] = temp;
+    }
+}
+```
+
+```cpp
+class Solution {
+    vector<vector<int>> res;
+    
+public:
+    vector<vector<int>> permuteUnique(vector<int>& nums) {
+        sort(nums.begin(), nums.end());
+        dfs(0, nums);
+        return res;
+    }
+
+    void dfs(int i, vector<int>& nums) {
+        if (i == nums.size()) {
+            res.push_back(nums);
+            return;
+        }
+
+        for (int j = i; j < nums.size(); ++j) {
+            if (j > i && nums[j] == nums[i]) continue;
+            swap(nums[i], nums[j]);
+            dfs(i + 1, nums);
+        }
+        
+        for (int j = nums.size() - 1; j > i; --j) {
+            swap(nums[i], nums[j]);
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[][]}
+     */
+    permuteUnique(nums) {
+        const res = [];
+        nums.sort((a, b) => a - b);
+
+        const dfs = (i) => {
+            if (i === nums.length) {
+                res.push([...nums]);
+                return;
+            }
+
+            for (let j = i; j < nums.length; j++) {
+                if (j > i && nums[j] === nums[i]) continue;
+                [nums[i], nums[j]] = [nums[j], nums[i]];
+                dfs(i + 1);
+            }
+
+            for (let j = nums.length - 1; j > i; j--) {
+                [nums[i], nums[j]] = [nums[j], nums[i]];
+            }
+        };
+
+        dfs(0);
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<List<int>> PermuteUnique(int[] nums) {
+        var res = new List<List<int>>();
+        Array.Sort(nums);
+        Dfs(0);
+        return res;
+
+        void Dfs(int i) {
+            if (i == nums.Length) {
+                res.Add(new List<int>(nums));
+                return;
+            }
+
+            for (int j = i; j < nums.Length; j++) {
+                if (j > i && nums[j] == nums[i]) continue;
+
+                Swap(i, j);
+                Dfs(i + 1);
+            }
+
+            for (int j = nums.Length - 1; j > i; j--) {
+                Swap(i, j);
+            }
+        }
+
+        void Swap(int a, int b) {
+            int temp = nums[a];
+            nums[a] = nums[b];
+            nums[b] = temp;
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n! * n)$
+* Space complexity: $O(n! * n)$ for the output list.
+
+---
+
+## 5. Iteration
+
+::tabs-start
+
+```python
+class Solution:
+    def permuteUnique(self, nums: List[int]) -> List[List[int]]:
+        n = len(nums)
+        nums.sort()
+        res = [nums.copy()]
+
+        while True:
+            i = n - 2
+            while i >= 0 and nums[i] >= nums[i + 1]:
+                i -= 1
+            
+            if i < 0:
+                break
+            
+            j = n - 1
+            while nums[j] <= nums[i]:
+                j -= 1            
+            nums[i], nums[j] = nums[j], nums[i]
+            
+            l, r = i + 1, n - 1
+            while l < r:
+                nums[l], nums[r] = nums[r], nums[l]
+                l, r = l + 1, r - 1
+            
+            res.append(nums.copy())
+        
+        return res
+```
+
+```java
+public class Solution {
+    public List<List<Integer>> permuteUnique(int[] nums) {
+        int n = nums.length;
+        Arrays.sort(nums);
+        List<List<Integer>> res = new ArrayList<>();
+        res.add(toList(nums));
+
+        while (true) {
+            int i = n - 2;
+            while (i >= 0 && nums[i] >= nums[i + 1]) i--;
+
+            if (i < 0) break;
+
+            int j = n - 1;
+            while (nums[j] <= nums[i]) j--;
+
+            swap(nums, i, j);
+            reverse(nums, i + 1, n - 1);
+            res.add(toList(nums));
+        }
+
+        return res;
+    }
+
+    private void reverse(int[] nums, int l, int r) {
+        while (l < r) {
+            swap(nums, l++, r--);
+        }
+    }
+
+    private void swap(int[] nums, int i, int j) {
+        int temp = nums[i];
+        nums[i] = nums[j];
+        nums[j] = temp;
+    }
+
+    private List<Integer> toList(int[] nums) {
+        List<Integer> list = new ArrayList<>();
+        for (int num : nums) list.add(num);
+        return list;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> permuteUnique(vector<int>& nums) {
+        int n = nums.size();
+        sort(nums.begin(), nums.end());
+        vector<vector<int>> res = {nums};
+
+        while (true) {
+            int i = n - 2;
+            while (i >= 0 && nums[i] >= nums[i + 1]) i--;
+
+            if (i < 0) break;
+
+            int j = n - 1;
+            while (nums[j] <= nums[i]) j--;
+
+            swap(nums[i], nums[j]);
+            reverse(nums.begin() + i + 1, nums.end());
+            res.push_back(nums);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[][]}
+     */
+    permuteUnique(nums) {
+        const n = nums.length;
+        nums.sort((a, b) => a - b);
+        const res = [nums.slice()];
+
+        while (true) {
+            let i = n - 2;
+            while (i >= 0 && nums[i] >= nums[i + 1]) i--;
+
+            if (i < 0) break;
+
+            let j = n - 1;
+            while (nums[j] <= nums[i]) j--;
+
+            [nums[i], nums[j]] = [nums[j], nums[i]];
+
+            let l = i + 1, r = n - 1;
+            while (l < r) {
+                [nums[l], nums[r]] = [nums[r], nums[l]];
+                l++;
+                r--;
+            }
+
+            res.push(nums.slice());
+        }
+
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<List<int>> PermuteUnique(int[] nums) {
+        int n = nums.Length;
+        Array.Sort(nums);
+        var res = new List<List<int>>();
+        res.Add(new List<int>(nums));
+
+        while (true) {
+            int i = n - 2;
+            while (i >= 0 && nums[i] >= nums[i + 1]) {
+                i--;
+            }
+
+            if (i < 0) break;
+
+            int j = n - 1;
+            while (nums[j] <= nums[i]) {
+                j--;
+            }
+
+            Swap(nums, i, j);
+
+            int left = i + 1, right = n - 1;
+            while (left < right) {
+                Swap(nums, left++, right--);
+            }
+
+            res.Add(new List<int>(nums));
+        }
+
+        return res;
+    }
+
+    private void Swap(int[] nums, int i, int j) {
+        int temp = nums[i];
+        nums[i] = nums[j];
+        nums[j] = temp;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n! * n)$
+* Space complexity: $O(n! * n)$ for the output list.
\ No newline at end of file
diff --git a/articles/permutations.md b/articles/permutations.md
index c5e6c202b..83dea1986 100644
--- a/articles/permutations.md
+++ b/articles/permutations.md
@@ -108,12 +108,73 @@ public class Solution {
 }
 ```
 
+```go
+func permute(nums []int) [][]int {
+    if len(nums) == 0 {
+        return [][]int{{}}
+    }
+    
+    perms := permute(nums[1:])
+    var res [][]int
+    for _, p := range perms {
+        for i := 0; i <= len(p); i++ {
+            pCopy := append([]int{}, p...)
+            pCopy = append(pCopy[:i], append([]int{nums[0]}, pCopy[i:]...)...)
+            res = append(res, pCopy)
+        }
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun permute(nums: IntArray): List<List<Int>> {
+        if (nums.isEmpty()) return listOf(listOf())
+        
+        val perms = permute(nums.sliceArray(1 until nums.size))
+        val res = mutableListOf<List<Int>>()
+        for (p in perms) {
+            for (i in 0..p.size) {
+                val pCopy = p.toMutableList()
+                pCopy.add(i, nums[0])
+                res.add(pCopy)
+            }
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func permute(_ nums: [Int]) -> [[Int]] {
+        if nums.isEmpty {
+            return [[]]
+        }
+
+        let perms = permute(Array(nums.dropFirst()))
+        var res = [[Int]]()
+
+        for p in perms {
+            for i in 0...p.count {
+                var pCopy = p
+                pCopy.insert(nums[0], at: i)
+                res.append(pCopy)
+            }
+        }
+
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n! * n ^ 2)$
-* Space complexity: $O(n! * n)$
+* Space complexity: $O(n! * n)$ for the output list.
 
 ---
 
@@ -223,12 +284,76 @@ public class Solution {
 }
 ```
 
+```go
+func permute(nums []int) [][]int {
+    perms := [][]int{{}}
+    
+    for _, num := range nums {
+        var newPerms [][]int
+        for _, p := range perms {
+            for i := 0; i <= len(p); i++ {
+                pCopy := append([]int{}, p...)
+                pCopy = append(pCopy[:i], append([]int{num}, pCopy[i:]...)...)
+                newPerms = append(newPerms, pCopy)
+            }
+        }
+        perms = newPerms
+    }
+    
+    return perms
+}
+```
+
+```kotlin
+class Solution {
+    fun permute(nums: IntArray): List<List<Int>> {
+        var perms = mutableListOf(listOf<Int>())
+        
+        for (num in nums) {
+            val newPerms = mutableListOf<List<Int>>()
+            for (p in perms) {
+                for (i in 0..p.size) {
+                    val pCopy = p.toMutableList()
+                    pCopy.add(i, num)
+                    newPerms.add(pCopy)
+                }
+            }
+            perms = newPerms
+        }
+        
+        return perms
+    }
+}
+```
+
+```swift
+class Solution {
+    func permute(_ nums: [Int]) -> [[Int]] {
+        var perms: [[Int]] = [[]]
+
+        for num in nums {
+            var newPerms = [[Int]]()
+            for p in perms {
+                for i in 0...p.count {
+                    var pCopy = p
+                    pCopy.insert(num, at: i)
+                    newPerms.append(pCopy)
+                }
+            }
+            perms = newPerms
+        }
+
+        return perms
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n! * n ^ 2)$
-* Space complexity: $O(n! * n)$
+* Space complexity: $O(n! * n)$ for the output list.
 
 ---
 
@@ -369,12 +494,93 @@ public class Solution {
 }
 ```
 
+```go
+func permute(nums []int) [][]int {
+    var res [][]int
+    backtrack(&res, []int{}, nums, make([]bool, len(nums)))
+    return res
+}
+
+func backtrack(res *[][]int, perm []int, nums []int, pick []bool) {
+    if len(perm) == len(nums) {
+        temp := append([]int{}, perm...)
+        *res = append(*res, temp)
+        return
+    }
+    for i := 0; i < len(nums); i++ {
+        if !pick[i] {
+            perm = append(perm, nums[i])
+            pick[i] = true
+            backtrack(res, perm, nums, pick)
+            perm = perm[:len(perm)-1]
+            pick[i] = false
+        }
+    }
+}
+```
+
+```kotlin
+class Solution {
+    private val res = mutableListOf<List<Int>>()
+    
+    fun permute(nums: IntArray): List<List<Int>> {
+        backtrack(mutableListOf(), nums, BooleanArray(nums.size))
+        return res
+    }
+    
+    private fun backtrack(perm: MutableList<Int>, nums: IntArray, pick: BooleanArray) {
+        if (perm.size == nums.size) {
+            res.add(ArrayList(perm))
+            return
+        }
+        for (i in nums.indices) {
+            if (!pick[i]) {
+                perm.add(nums[i])
+                pick[i] = true
+                backtrack(perm, nums, pick)
+                perm.removeAt(perm.size - 1)
+                pick[i] = false
+            }
+        }
+    }
+}
+```
+
+```swift
+class Solution {
+    func permute(_ nums: [Int]) -> [[Int]] {
+        var res = [[Int]]()
+        var pick = [Bool](repeating: false, count: nums.count)
+
+        func backtrack(_ perm: inout [Int]) {
+            if perm.count == nums.count {
+                res.append(perm)
+                return
+            }
+            for i in 0..<nums.count {
+                if !pick[i] {
+                    perm.append(nums[i])
+                    pick[i] = true
+                    backtrack(&perm)
+                    perm.popLast()
+                    pick[i] = false
+                }
+            }
+        }
+
+        var perm = [Int]()
+        backtrack(&perm)
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n! * n)$
-* Space complexity: $O(n)$
+* Space complexity: $O(n! * n)$ for the output list.
 
 ---
 
@@ -511,12 +717,86 @@ public class Solution {
 }
 ```
 
+```go
+func permute(nums []int) [][]int {
+    var res [][]int
+    backtrack(&res, []int{}, nums, 0)
+    return res
+}
+
+func backtrack(res *[][]int, perm []int, nums []int, mask int) {
+    if len(perm) == len(nums) {
+        temp := append([]int{}, perm...)
+        *res = append(*res, temp)
+        return
+    }
+    for i := 0; i < len(nums); i++ {
+        if mask&(1<<i) == 0 {
+            perm = append(perm, nums[i])
+            backtrack(res, perm, nums, mask|(1<<i))
+            perm = perm[:len(perm)-1]
+        }
+    }
+}
+```
+
+```kotlin
+class Solution {
+    private val res = mutableListOf<List<Int>>()
+    
+    fun permute(nums: IntArray): List<List<Int>> {
+        backtrack(mutableListOf(), nums, 0)
+        return res
+    }
+    
+    private fun backtrack(perm: MutableList<Int>, nums: IntArray, mask: Int) {
+        if (perm.size == nums.size) {
+            res.add(ArrayList(perm))
+            return
+        }
+        for (i in nums.indices) {
+            if (mask and (1 shl i) == 0) {
+                perm.add(nums[i])
+                backtrack(perm, nums, mask or (1 shl i))
+                perm.removeAt(perm.size - 1)
+            }
+        }
+    }
+}
+```
+
+```swift
+class Solution {
+    func permute(_ nums: [Int]) -> [[Int]] {
+        var res = [[Int]]()
+
+        func backtrack(_ perm: inout [Int], _ mask: Int) {
+            if perm.count == nums.count {
+                res.append(perm)
+                return
+            }
+            for i in 0..<nums.count {
+                if mask & (1 << i) == 0 {
+                    perm.append(nums[i])
+                    backtrack(&perm, mask | (1 << i))
+                    perm.popLast()
+                }
+            }
+        }
+
+        var perm = [Int]()
+        backtrack(&perm, 0)
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n! * n)$
-* Space complexity: $O(n)$
+* Space complexity: $O(n! * n)$ for the output list.
 
 ---
 
@@ -659,9 +939,83 @@ public class Solution {
 }
 ```
 
+```go
+func permute(nums []int) [][]int {
+    var res [][]int
+    backtrack(&res, nums, 0)
+    return res
+}
+
+func backtrack(res *[][]int, nums []int, idx int) {
+    if idx == len(nums) {
+        temp := append([]int{}, nums...)
+        *res = append(*res, temp)
+        return
+    }
+    for i := idx; i < len(nums); i++ {
+        nums[idx], nums[i] = nums[i], nums[idx]
+        backtrack(res, nums, idx+1)
+        nums[idx], nums[i] = nums[i], nums[idx]
+    }
+}
+```
+
+```kotlin
+class Solution {
+    private val res = mutableListOf<List<Int>>()
+    
+    fun permute(nums: IntArray): List<List<Int>> {
+        backtrack(nums, 0)
+        return res
+    }
+    
+    private fun backtrack(nums: IntArray, idx: Int) {
+        if (idx == nums.size) {
+            res.add(nums.toList())
+            return
+        }
+        for (i in idx until nums.size) {
+            nums.swap(idx, i)
+            backtrack(nums, idx + 1)
+            nums.swap(idx, i)
+        }
+    }
+    
+    private fun IntArray.swap(i: Int, j: Int) {
+        val temp = this[i]
+        this[i] = this[j]
+        this[j] = temp
+    }
+}
+```
+
+```swift
+class Solution {
+    func permute(_ nums: [Int]) -> [[Int]] {
+        var res = [[Int]]()
+        var nums = nums
+
+        func backtrack(_ idx: Int) {
+            if idx == nums.count {
+                res.append(nums)
+                return
+            }
+            for i in idx..<nums.count {
+                nums.swapAt(idx, i)
+                backtrack(idx + 1)
+                nums.swapAt(idx, i)
+            }
+        }
+
+        backtrack(0)
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n! * n)$
-* Space complexity: $O(n)$
\ No newline at end of file
+* Space complexity: $O(n! * n)$ for the output list.
\ No newline at end of file
diff --git a/articles/plus-one.md b/articles/plus-one.md
index ee211cccb..a5b43fb09 100644
--- a/articles/plus-one.md
+++ b/articles/plus-one.md
@@ -98,6 +98,56 @@ public class Solution {
 }
 ```
 
+```go
+func plusOne(digits []int) []int {
+    if len(digits) == 0 {
+        return []int{1}
+    }
+
+    if digits[len(digits)-1] < 9 {
+        digits[len(digits)-1]++
+        return digits
+    } else {
+        return append(plusOne(digits[:len(digits)-1]), 0)
+    }
+}
+```
+
+```kotlin
+class Solution {
+    fun plusOne(digits: IntArray): IntArray {
+        if (digits.isEmpty()) {
+            return intArrayOf(1)
+        }
+
+        if (digits[digits.size - 1] < 9) {
+            digits[digits.size - 1]++
+            return digits
+        } else {
+            return plusOne(digits.copyOfRange(0, digits.size - 1)) + intArrayOf(0)
+        }
+    }
+}
+```
+
+```swift
+class Solution {
+    func plusOne(_ digits: [Int]) -> [Int] {
+        if digits.isEmpty {
+            return [1]
+        }
+
+        var digits = digits
+        if digits[digits.count - 1] < 9 {
+            digits[digits.count - 1] += 1
+            return digits
+        } else {
+            return plusOne(Array(digits.dropLast())) + [0]
+        }
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -107,7 +157,7 @@ public class Solution {
 
 ---
 
-## 2. Iteration
+## 2. Iteration - I
 
 ::tabs-start
 
@@ -116,7 +166,7 @@ class Solution:
     def plusOne(self, digits: List[int]) -> List[int]:
         one = 1
         i = 0
-        digits = digits[::-1]
+        digits.reverse()
 
         while one:
             if i < len(digits):
@@ -129,7 +179,9 @@ class Solution:
                 digits.append(one)
                 one = 0
             i += 1
-        return digits[::-1]
+
+        digits.reverse()
+        return digits
 ```
 
 ```java
@@ -249,16 +301,103 @@ public class Solution {
 }
 ```
 
+```go
+func plusOne(digits []int) []int {
+    one := 1
+    i := 0
+    digits = reverse(digits)
+
+    for one != 0 {
+        if i < len(digits) {
+            if digits[i] == 9 {
+                digits[i] = 0
+            } else {
+                digits[i] += 1
+                one = 0
+            }
+        } else {
+            digits = append(digits, one)
+            one = 0
+        }
+        i++
+    }
+    return reverse(digits)
+}
+
+func reverse(digits []int) []int {
+    for i, j := 0, len(digits)-1; i < j; i, j = i+1, j-1 {
+        digits[i], digits[j] = digits[j], digits[i]
+    }
+    return digits
+}
+```
+
+```kotlin
+class Solution {
+    fun plusOne(digits: IntArray): IntArray {
+        var one = 1
+        var i = 0
+        val reversedDigits = digits.reversed().toMutableList()
+
+        while (one != 0) {
+            if (i < reversedDigits.size) {
+                if (reversedDigits[i] == 9) {
+                    reversedDigits[i] = 0
+                } else {
+                    reversedDigits[i] += 1
+                    one = 0
+                }
+            } else {
+                reversedDigits.add(one)
+                one = 0
+            }
+            i++
+        }
+
+        return reversedDigits.reversed().toIntArray()
+    }
+}
+```
+
+```swift
+class Solution {
+    func plusOne(_ digits: [Int]) -> [Int] {
+        var digits = digits
+        var one = 1
+        var i = 0
+        digits.reverse()
+
+        while one > 0 {
+            if i < digits.count {
+                if digits[i] == 9 {
+                    digits[i] = 0
+                } else {
+                    digits[i] += 1
+                    one = 0
+                }
+            } else {
+                digits.append(one)
+                one = 0
+            }
+            i += 1
+        }
+
+        digits.reverse()
+        return digits
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n)$
-* Space complexity: $O(1)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the language.
 
 ---
 
-## 3. Iteration (Optimal)
+## 3. Iteration - II
 
 ::tabs-start
 
@@ -352,9 +491,60 @@ public class Solution {
 }
 ```
 
+```go
+func plusOne(digits []int) []int {
+    n := len(digits)
+    for i := n - 1; i >= 0; i-- {
+        if digits[i] < 9 {
+            digits[i]++
+            return digits
+        }
+        digits[i] = 0
+    }
+
+    return append([]int{1}, digits...)
+}
+```
+
+```kotlin
+class Solution {
+    fun plusOne(digits: IntArray): IntArray {
+        val n = digits.size
+        for (i in n - 1 downTo 0) {
+            if (digits[i] < 9) {
+                digits[i]++
+                return digits
+            }
+            digits[i] = 0
+        }
+
+        return intArrayOf(1) + digits
+    }
+}
+```
+
+```swift
+class Solution {
+    func plusOne(_ digits: [Int]) -> [Int] {
+        var digits = digits
+        let n = digits.count
+
+        for i in stride(from: n - 1, through: 0, by: -1) {
+            if digits[i] < 9 {
+                digits[i] += 1
+                return digits
+            }
+            digits[i] = 0
+        }
+
+        return [1] + digits
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n)$
-* Space complexity: $O(1)$
\ No newline at end of file
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/populating-next-right-pointers-in-each-node.md b/articles/populating-next-right-pointers-in-each-node.md
new file mode 100644
index 000000000..1f7339287
--- /dev/null
+++ b/articles/populating-next-right-pointers-in-each-node.md
@@ -0,0 +1,700 @@
+## 1. Breadth First Search
+
+::tabs-start
+
+```python
+"""
+# Definition for a Node.
+class Node:
+    def __init__(self, val: int = 0, left: 'Node' = None, right: 'Node' = None, next: 'Node' = None):
+        self.val = val
+        self.left = left
+        self.right = right
+        self.next = next
+"""
+
+class Solution:
+    def connect(self, root: 'Optional[Node]') -> 'Optional[Node]':
+        if not root:
+            return None
+
+        q = deque([root])
+        while q:
+            levelSize = len(q)
+            while levelSize:
+                node = q.popleft()
+                if levelSize > 1:
+                    node.next = q[0]
+                if node.left:
+                    q.append(node.left)
+                if node.right:
+                    q.append(node.right)
+                levelSize -= 1
+
+        return root
+```
+
+```java
+/*
+// Definition for a Node.
+class Node {
+    public int val;
+    public Node left;
+    public Node right;
+    public Node next;
+
+    public Node() {}
+    
+    public Node(int _val) {
+        val = _val;
+    }
+
+    public Node(int _val, Node _left, Node _right, Node _next) {
+        val = _val;
+        left = _left;
+        right = _right;
+        next = _next;
+    }
+};
+*/
+
+public class Solution {
+    public Node connect(Node root) {
+        if (root == null) return null;
+
+        Queue<Node> q = new LinkedList<>();
+        q.add(root);
+
+        while (!q.isEmpty()) {
+            int levelSize = q.size();
+            while (levelSize > 0) {
+                Node node = q.poll();
+                if (levelSize > 1) {
+                    node.next = q.peek();
+                }
+                if (node.left != null) {
+                    q.add(node.left);
+                }
+                if (node.right != null) {
+                    q.add(node.right);
+                }
+                levelSize--;
+            }
+        }
+
+        return root;
+    }
+}
+```
+
+```cpp
+/*
+// Definition for a Node.
+class Node {
+public:
+    int val;
+    Node* left;
+    Node* right;
+    Node* next;
+
+    Node() : val(0), left(NULL), right(NULL), next(NULL) {}
+
+    Node(int _val) : val(_val), left(NULL), right(NULL), next(NULL) {}
+
+    Node(int _val, Node* _left, Node* _right, Node* _next)
+        : val(_val), left(_left), right(_right), next(_next) {}
+};
+*/
+
+class Solution {
+public:
+    Node* connect(Node* root) {
+        if (!root) return nullptr;
+
+        queue<Node*> q;
+        q.push(root);
+
+        while (!q.empty()) {
+            int levelSize = q.size();
+            while (levelSize > 0) {
+                Node* node = q.front();
+                q.pop();
+                if (levelSize > 1) {
+                    node->next = q.front();
+                }
+                if (node->left) {
+                    q.push(node->left);
+                }
+                if (node->right) {
+                    q.push(node->right);
+                }
+                levelSize--;
+            }
+        }
+
+        return root;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null, next = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *         this.next = next;
+ *     }
+ * }
+ */
+
+class Solution {
+    /**
+     * @param {Node} root
+     * @return {Node}
+     */
+    connect(root) {
+        if (!root) return null;
+
+        const q = new Queue();
+        q.push(root);
+
+        while (!q.isEmpty()) {
+            let levelSize = q.size();
+            while (levelSize > 0) {
+                let node = q.pop();
+                if (levelSize > 1) {
+                    node.next = q.front();
+                }
+                if (node.left) {
+                    q.push(node.left);
+                }
+                if (node.right) {
+                    q.push(node.right);
+                }
+                levelSize--;
+            }
+        }
+
+        return root;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(\log n)$
+
+---
+
+## 2. Depth First Search
+
+::tabs-start
+
+```python
+"""
+# Definition for a Node.
+class Node:
+    def __init__(self, val: int = 0, left: 'Node' = None, right: 'Node' = None, next: 'Node' = None):
+        self.val = val
+        self.left = left
+        self.right = right
+        self.next = next
+"""
+
+class Solution:
+    def connect(self, root: 'Optional[Node]') -> 'Optional[Node]':
+        mp = {}
+
+        def dfs(node, depth):
+            if not node:
+                return
+            
+            if depth not in mp:
+                mp[depth] = node
+            else:
+                mp[depth].next = node
+                mp[depth] = node
+            
+            dfs(node.left, depth + 1)
+            dfs(node.right, depth + 1)
+
+        dfs(root, 0)
+        return root
+```
+
+```java
+/*
+// Definition for a Node.
+class Node {
+    public int val;
+    public Node left;
+    public Node right;
+    public Node next;
+
+    public Node() {}
+    
+    public Node(int _val) {
+        val = _val;
+    }
+
+    public Node(int _val, Node _left, Node _right, Node _next) {
+        val = _val;
+        left = _left;
+        right = _right;
+        next = _next;
+    }
+};
+*/
+
+public class Solution {
+    public Node connect(Node root) {
+        Map<Integer, Node> mp = new HashMap<>();
+        dfs(root, 0, mp);
+        return root;
+    }
+
+    private void dfs(Node node, int depth, Map<Integer, Node> mp) {
+        if (node == null) return;
+        
+        if (!mp.containsKey(depth)) {
+            mp.put(depth, node);
+        } else {
+            mp.get(depth).next = node;
+            mp.put(depth, node);
+        }
+
+        dfs(node.left, depth + 1, mp);
+        dfs(node.right, depth + 1, mp);
+    }
+}
+```
+
+```cpp
+/*
+// Definition for a Node.
+class Node {
+public:
+    int val;
+    Node* left;
+    Node* right;
+    Node* next;
+
+    Node() : val(0), left(NULL), right(NULL), next(NULL) {}
+
+    Node(int _val) : val(_val), left(NULL), right(NULL), next(NULL) {}
+
+    Node(int _val, Node* _left, Node* _right, Node* _next)
+        : val(_val), left(_left), right(_right), next(_next) {}
+};
+*/
+
+class Solution {
+public:
+    Node* connect(Node* root) {
+        unordered_map<int, Node*> mp;
+        dfs(root, 0, mp);
+        return root;
+    }
+
+private:
+    void dfs(Node* node, int depth, unordered_map<int, Node*>& mp) {
+        if (!node) return;
+
+        if (mp.find(depth) == mp.end()) {
+            mp[depth] = node;
+        } else {
+            mp[depth]->next = node;
+            mp[depth] = node;
+        }
+
+        dfs(node->left, depth + 1, mp);
+        dfs(node->right, depth + 1, mp);
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null, next = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *         this.next = next;
+ *     }
+ * }
+ */
+
+class Solution {
+    /**
+     * @param {Node} root
+     * @return {Node}
+     */
+    connect(root) {
+        let mp = new Map();
+
+        const dfs = (node, depth) => {
+            if (!node) return;
+            
+            if (!mp.has(depth)) {
+                mp.set(depth, node);
+            } else {
+                mp.get(depth).next = node;
+                mp.set(depth, node);
+            }
+
+            dfs(node.left, depth + 1);
+            dfs(node.right, depth + 1);
+        };
+
+        dfs(root, 0);
+        return root;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(\log n)$
+
+---
+
+## 3. Depth First Search (Optimal)
+
+::tabs-start
+
+```python
+"""
+# Definition for a Node.
+class Node:
+    def __init__(self, val: int = 0, left: 'Node' = None, right: 'Node' = None, next: 'Node' = None):
+        self.val = val
+        self.left = left
+        self.right = right
+        self.next = next
+"""
+
+class Solution:
+    def connect(self, root: 'Optional[Node]') -> 'Optional[Node]':
+        if not root:
+            return root
+
+        if root.left:
+            root.left.next = root.right
+            if root.next:
+                root.right.next = root.next.left
+
+            self.connect(root.left)
+            self.connect(root.right)
+
+        return root
+```
+
+```java
+/*
+// Definition for a Node.
+class Node {
+    public int val;
+    public Node left;
+    public Node right;
+    public Node next;
+
+    public Node() {}
+    
+    public Node(int _val) {
+        val = _val;
+    }
+
+    public Node(int _val, Node _left, Node _right, Node _next) {
+        val = _val;
+        left = _left;
+        right = _right;
+        next = _next;
+    }
+};
+*/
+
+public class Solution {
+    public Node connect(Node root) {
+        if (root == null) return root;
+
+        if (root.left != null) {
+            root.left.next = root.right;
+            if (root.next != null) {
+                root.right.next = root.next.left;
+            }
+
+            connect(root.left);
+            connect(root.right);
+        }
+
+        return root;
+    }
+}
+```
+
+```cpp
+/*
+// Definition for a Node.
+class Node {
+public:
+    int val;
+    Node* left;
+    Node* right;
+    Node* next;
+
+    Node() : val(0), left(NULL), right(NULL), next(NULL) {}
+
+    Node(int _val) : val(_val), left(NULL), right(NULL), next(NULL) {}
+
+    Node(int _val, Node* _left, Node* _right, Node* _next)
+        : val(_val), left(_left), right(_right), next(_next) {}
+};
+*/
+
+class Solution {
+public:
+    Node* connect(Node* root) {
+        if (!root) return root;
+
+        if (root->left) {
+            root->left->next = root->right;
+            if (root->next) {
+                root->right->next = root->next->left;
+            }
+
+            connect(root->left);
+            connect(root->right);
+        }
+
+        return root;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null, next = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *         this.next = next;
+ *     }
+ * }
+ */
+
+class Solution {
+    /**
+     * @param {Node} root
+     * @return {Node}
+     */
+    connect(root) {
+        if (!root) return root;
+
+        if (root.left) {
+            root.left.next = root.right;
+            if (root.next) {
+                root.right.next = root.next.left;
+            }
+
+            this.connect(root.left);
+            this.connect(root.right);
+        }
+
+        return root;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(\log n)$ for the recursion stack.
+
+---
+
+## 4. Breadth First Search (Optimal)
+
+::tabs-start
+
+```python
+"""
+# Definition for a Node.
+class Node:
+    def __init__(self, val: int = 0, left: 'Node' = None, right: 'Node' = None, next: 'Node' = None):
+        self.val = val
+        self.left = left
+        self.right = right
+        self.next = next
+"""
+
+class Solution:
+    def connect(self, root: 'Optional[Node]') -> 'Optional[Node]':
+        cur, nxt = root, root.left if root else None
+
+        while cur and nxt:
+            cur.left.next = cur.right
+            if cur.next:
+                cur.right.next = cur.next.left
+
+            cur = cur.next
+            if not cur:
+                cur = nxt
+                nxt = cur.left
+
+        return root
+```
+
+```java
+/*
+// Definition for a Node.
+class Node {
+    public int val;
+    public Node left;
+    public Node right;
+    public Node next;
+
+    public Node() {}
+    
+    public Node(int _val) {
+        val = _val;
+    }
+
+    public Node(int _val, Node _left, Node _right, Node _next) {
+        val = _val;
+        left = _left;
+        right = _right;
+        next = _next;
+    }
+};
+*/
+
+public class Solution {
+    public Node connect(Node root) {
+        if (root == null) return null;
+
+        Node cur = root, nxt = root.left;
+
+        while (cur != null && nxt != null) {
+            cur.left.next = cur.right;
+            if (cur.next != null) {
+                cur.right.next = cur.next.left;
+            }
+
+            cur = cur.next;
+            if (cur == null) {
+                cur = nxt;
+                nxt = cur.left;
+            }
+        }
+
+        return root;
+    }
+}
+```
+
+```cpp
+/*
+// Definition for a Node.
+class Node {
+public:
+    int val;
+    Node* left;
+    Node* right;
+    Node* next;
+
+    Node() : val(0), left(NULL), right(NULL), next(NULL) {}
+
+    Node(int _val) : val(_val), left(NULL), right(NULL), next(NULL) {}
+
+    Node(int _val, Node* _left, Node* _right, Node* _next)
+        : val(_val), left(_left), right(_right), next(_next) {}
+};
+*/
+
+class Solution {
+public:
+    Node* connect(Node* root) {
+        if (!root) return nullptr;
+
+        Node* cur = root, *nxt = root->left;
+
+        while (cur && nxt) {
+            cur->left->next = cur->right;
+            if (cur->next) {
+                cur->right->next = cur->next->left;
+            }
+
+            cur = cur->next;
+            if (!cur) {
+                cur = nxt;
+                nxt = cur->left;
+            }
+        }
+
+        return root;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null, next = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *         this.next = next;
+ *     }
+ * }
+ */
+
+class Solution {
+    /**
+     * @param {Node} root
+     * @return {Node}
+     */
+    connect(root) {
+        if (!root) return null;
+
+        let cur = root, nxt = root.left;
+
+        while (cur && nxt) {
+            cur.left.next = cur.right;
+            if (cur.next) {
+                cur.right.next = cur.next.left;
+            }
+
+            cur = cur.next;
+            if (!cur) {
+                cur = nxt;
+                nxt = cur.left;
+            }
+        }
+
+        return root;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/pow-x-n.md b/articles/pow-x-n.md
new file mode 100644
index 000000000..50beeb0f4
--- /dev/null
+++ b/articles/pow-x-n.md
@@ -0,0 +1,576 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def myPow(self, x: float, n: int) -> float:
+        if x == 0:
+            return 0
+        if n == 0:
+            return 1
+
+        res = 1
+        for i in range(abs(n)):
+            res *= x
+        return res if n >= 0 else 1 / res
+```
+
+```java
+public class Solution {
+    public double myPow(double x, int n) {
+        if (x == 0) {
+            return 0;
+        }
+        if (n == 0) {
+            return 1;
+        }
+
+        double res = 1;
+        for (int i = 0; i < Math.abs(n); i++) {
+            res *= x;
+        }
+        return n >= 0 ? res : 1 / res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    double myPow(double x, int n) {
+        if (x == 0) {
+            return 0;
+        }
+        if (n == 0) {
+            return 1;
+        }
+
+        double res = 1;
+        for (int i = 0; i < abs(n); i++) {
+            res *= x;
+        }
+        return n >= 0 ? res : 1 / res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} x
+     * @param {number} n
+     * @return {number}
+     */
+    myPow(x, n) {
+        if (x === 0) {
+            return 0;
+        }
+        if (n === 0) {
+            return 1;
+        }
+
+        let res = 1;
+        for (let i = 0; i < Math.abs(n); i++) {
+            res *= x;
+        }
+        return n >= 0 ? res : 1 / res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public double MyPow(double x, int n) {
+        if (x == 0) {
+            return 0;
+        }
+        if (n == 0) {
+            return 1;
+        }
+
+        double res = 1;
+        for (int i = 0; i < Math.Abs(n); i++) {
+            res *= x;
+        }
+        return n >= 0 ? res : 1 / res;
+    }
+}
+```
+
+```go
+func myPow(x float64, n int) float64 {
+    if x == 0 {
+        return 0
+    }
+    if n == 0 {
+        return 1
+    }
+
+    res := 1.0
+    for i := 0; i < int(math.Abs(float64(n))); i++ {
+        res *= x
+    }
+
+    if n >= 0 {
+        return res
+    }
+    return 1 / res
+}
+```
+
+```kotlin
+class Solution {
+    fun myPow(x: Double, n: Int): Double {
+        if (x == 0.0) {
+            return 0.0
+        }
+        if (n == 0) {
+            return 1.0
+        }
+
+        var res = 1.0
+        for (i in 0 until Math.abs(n)) {
+            res *= x
+        }
+
+        return if (n >= 0) res else 1 / res
+    }
+}
+```
+
+```swift
+class Solution {
+    func myPow(_ x: Double, _ n: Int) -> Double {
+        if x == 0 {
+            return 0
+        }
+        if n == 0 {
+            return 1
+        }
+
+        var res: Double = 1
+        for _ in 0..<abs(n) {
+            res *= x
+        }
+        return n >= 0 ? res : 1 / res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Binary Exponentiation (Recursive)
+
+::tabs-start
+
+```python
+class Solution:
+    def myPow(self, x: float, n: int) -> float:
+        def helper(x, n):
+            if x == 0:
+                return 0
+            if n == 0:
+                return 1
+
+            res = helper(x * x, n // 2)
+            return x * res if n % 2 else res
+
+        res = helper(x, abs(n))
+        return res if n >= 0 else 1 / res
+```
+
+```java
+public class Solution {
+    public double myPow(double x, int n) {
+        if (x == 0) {
+            return 0;
+        }
+        if (n == 0) {
+            return 1;
+        }
+
+        double res = helper(x, Math.abs((long) n));
+        return (n >= 0) ? res : 1 / res;
+    }
+
+    private double helper(double x, long n) {
+        if (n == 0) {
+            return 1;
+        }
+        double half = helper(x, n / 2);
+        return (n % 2 == 0) ? half * half : x * half * half;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    double myPow(double x, int n) {
+        if (x == 0) {
+            return 0;
+        }
+        if (n == 0) {
+            return 1;
+        }
+
+        double res = helper(x, abs(static_cast<long>(n)));
+        return (n >= 0) ? res : 1 / res;
+    }
+
+private:
+    double helper(double x, long n) {
+        if (n == 0) {
+            return 1;
+        }
+        double half = helper(x, n / 2);
+        return (n % 2 == 0) ? half * half : x * half * half;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} x
+     * @param {number} n
+     * @return {number}
+     */
+    myPow(x, n) {
+        /**
+         * @param {number} x
+         * @param {number} n
+         * @return {number}
+         */
+        function helper(x, n) {
+            if (x === 0) {
+                return 0;
+            }
+            if (n === 0) {
+                return 1;
+            }
+
+            const res = helper(x * x, Math.floor(n / 2));
+            return n % 2 === 0 ? res : x * res;
+        }
+
+        const res = helper(x, Math.abs(n));
+        return n >= 0 ? res : 1 / res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public double MyPow(double x, int n) {
+        if (x == 0) {
+            return 0;
+        }
+        if (n == 0) {
+            return 1;
+        }
+
+        double res = Helper(x, Math.Abs((long) n));
+        return (n >= 0) ? res : 1 / res;
+    }
+
+    private double Helper(double x, long n) {
+        if (n == 0) {
+            return 1;
+        }
+        double half = Helper(x, n / 2);
+        return (n % 2 == 0) ? half * half : x * half * half;
+    }
+}
+```
+
+```go
+func myPow(x float64, n int) float64 {
+    var helper func(x float64, n int) float64
+    helper = func(x float64, n int) float64 {
+        if x == 0 {
+            return 0
+        }
+        if n == 0 {
+            return 1
+        }
+
+        res := helper(x*x, n/2)
+        if n%2 != 0 {
+            return x * res
+        }
+        return res
+    }
+
+    res := helper(x, int(math.Abs(float64(n))))
+    if n >= 0 {
+        return res
+    }
+    return 1 / res
+}
+```
+
+```kotlin
+class Solution {
+    fun myPow(x: Double, n: Int): Double {
+        fun helper(x: Double, n: Int): Double {
+            if (x == 0.0) {
+                return 0.0
+            }
+            if (n == 0) {
+                return 1.0
+            }
+
+            val res = helper(x * x, n / 2)
+            return if (n % 2 != 0) x * res else res
+        }
+
+        val res = helper(x, Math.abs(n))
+        return if (n >= 0) res else 1 / res
+    }
+}
+```
+
+```swift
+class Solution {
+    func myPow(_ x: Double, _ n: Int) -> Double {
+        func helper(_ x: Double, _ n: Int) -> Double {
+            if x == 0 {
+                return 0
+            }
+            if n == 0 {
+                return 1
+            }
+
+            let res = helper(x * x, n / 2)
+            return n % 2 == 0 ? res : x * res
+        }
+
+        let res = helper(x, abs(n))
+        return n >= 0 ? res : 1 / res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(\log n)$ for recursion stack.
+
+---
+
+## 3. Binary Exponentiation (Iterative)
+
+::tabs-start
+
+```python
+class Solution:
+    def myPow(self, x: float, n: int) -> float:
+        if x == 0:
+            return 0
+        if n == 0:
+            return 1
+        
+        res = 1
+        power = abs(n)
+        
+        while power:
+            if power & 1:
+                res *= x
+            x *= x
+            power >>= 1
+        
+        return res if n >= 0 else 1 / res
+```
+
+```java
+public class Solution {
+    public double myPow(double x, int n) {
+        if (x == 0) return 0;
+        if (n == 0) return 1;
+
+        double res = 1;
+        long power = Math.abs((long)n);
+
+        while (power > 0) {
+            if ((power & 1) == 1) {
+                res *= x;
+            }
+            x *= x;
+            power >>= 1;
+        }
+
+        return n >= 0 ? res : 1 / res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    double myPow(double x, int n) {
+        if (x == 0) return 0;
+        if (n == 0) return 1;
+
+        double res = 1;
+        long power = abs((long)n);
+
+        while (power) {
+            if (power & 1) {
+                res *= x;
+            }
+            x *= x;
+            power >>= 1;
+        }
+
+        return n >= 0 ? res : 1 / res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} x
+     * @param {number} n
+     * @return {number}
+     */
+    myPow(x, n) {
+        if (x === 0) return 0;
+        if (n === 0) return 1;
+
+        let res = 1;
+        let power = Math.abs(n);
+
+        while (power > 0) {
+            if (power & 1) {
+                res *= x;
+            }
+            x *= x;
+            power >>= 1;
+        }
+
+        return n >= 0 ? res : 1 / res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public double MyPow(double x, int n) {
+        if (x == 0) return 0;
+        if (n == 0) return 1;
+
+        double res = 1;
+        long power = Math.Abs((long)n);
+
+        while (power > 0) {
+            if ((power & 1) == 1) {
+                res *= x;
+            }
+            x *= x;
+            power >>= 1;
+        }
+
+        return n >= 0 ? res : 1 / res;
+    }
+}
+```
+
+```go
+func myPow(x float64, n int) float64 {
+    if x == 0 {
+        return 0
+    }
+    if n == 0 {
+        return 1
+    }
+
+    res := 1.0
+    power := int(math.Abs(float64(n)))
+
+    for power > 0 {
+        if power&1 != 0 {
+            res *= x
+        }
+        x *= x
+        power >>= 1
+    }
+
+    if n >= 0 {
+        return res
+    }
+    return 1 / res
+}
+```
+
+```kotlin
+class Solution {
+    fun myPow(x: Double, n: Int): Double {
+        var x = x
+        if (x == 0.0) {
+            return 0.0
+        }
+        if (n == 0) {
+            return 1.0
+        }
+
+        var res = 1.0
+        var power = Math.abs(n.toLong())
+
+        while (power > 0) {
+            if (power and 1 != 0L) {
+                res *= x
+            }
+            x *= x
+            power = power shr 1
+        }
+
+        return if (n >= 0) res else 1.0 / res
+    }
+}
+```
+
+```swift
+class Solution {
+    func myPow(_ x: Double, _ n: Int) -> Double {
+        if x == 0 {
+            return 0
+        }
+        if n == 0 {
+            return 1
+        }
+
+        var res: Double = 1
+        var base = x
+        var power = abs(n)
+
+        while power > 0 {
+            if power & 1 == 1 {
+                res *= base
+            }
+            base *= base
+            power >>= 1
+        }
+
+        return n >= 0 ? res : 1 / res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/power-of-four.md b/articles/power-of-four.md
new file mode 100644
index 000000000..dc54669cc
--- /dev/null
+++ b/articles/power-of-four.md
@@ -0,0 +1,367 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def isPowerOfFour(self, n: int) -> bool:
+        if n == 1:
+            return True
+        if n <= 0 or n % 4:
+            return False
+        return self.isPowerOfFour(n // 4)
+```
+
+```java
+public class Solution {
+    public boolean isPowerOfFour(int n) {
+        if (n == 1) {
+            return true;
+        }
+        if (n <= 0 || n % 4 != 0) {
+            return false;
+        }
+        return isPowerOfFour(n / 4);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isPowerOfFour(int n) {
+        if (n == 1) {
+            return true;
+        }
+        if (n <= 0 || n % 4 != 0) {
+            return false;
+        }
+        return isPowerOfFour(n / 4);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {boolean}
+     */
+    isPowerOfFour(n) {
+        if (n === 1) {
+            return true;
+        }
+        if (n <= 0 || n % 4 !== 0) {
+            return false;
+        }
+        return this.isPowerOfFour(Math.floor(n / 4));
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Iteration
+
+::tabs-start
+
+```python
+class Solution:
+    def isPowerOfFour(self, n: int) -> bool:
+        if n < 0:
+            return False
+
+        while n > 1:
+            if n % 4:
+                return False
+            n //= 4
+        
+        return n == 1
+```
+
+```java
+public class Solution {
+    public boolean isPowerOfFour(int n) {
+        if (n < 0) return false;
+
+        while (n > 1) {
+            if (n % 4 != 0) return false;
+            n /= 4;
+        }
+
+        return n == 1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isPowerOfFour(int n) {
+        if (n < 0) return false;
+
+        while (n > 1) {
+            if (n % 4 != 0) return false;
+            n /= 4;
+        }
+
+        return n == 1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {boolean}
+     */
+    isPowerOfFour(n) {
+        if (n < 0) return false;
+
+        while (n > 1) {
+            if (n % 4 !== 0) return false;
+            n = Math.floor(n / 4);
+        }
+
+        return n === 1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Math
+
+::tabs-start
+
+```python
+class Solution:
+    def isPowerOfFour(self, n: int) -> bool:
+        return n > 0 and log(n, 4) % 1 == 0
+```
+
+```java
+public class Solution {
+    public boolean isPowerOfFour(int n) {
+        return n > 0 && Math.log(n) / Math.log(4) % 1 == 0;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isPowerOfFour(int n) {
+        return n > 0 && fmod(log(n) / log(4), 1) == 0;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {boolean}
+     */
+    isPowerOfFour(n) {
+        return n > 0 && (Math.log(n) / Math.log(4)) % 1 === 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
+
+---
+
+## 4. Bit Manipulation
+
+::tabs-start
+
+```python
+class Solution:
+    def isPowerOfFour(self, n: int) -> bool:
+        if n < 0:
+            return False
+        
+        for i in range(0, 32, 2):
+            if n == (1 << i):
+                return True
+        
+        return False
+```
+
+```java
+public class Solution {
+    public boolean isPowerOfFour(int n) {
+        if (n < 0) return false;
+        
+        for (int i = 0; i < 32; i += 2) {
+            if (n == (1 << i)) {
+                return true;
+            }
+        }
+        
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isPowerOfFour(int n) {
+        if (n < 0) return false;
+
+        for (int i = 0; i < 32; i += 2) {
+            if (n == (1 << i)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {boolean}
+     */
+    isPowerOfFour(n) {
+        if (n < 0) return false;
+
+        for (let i = 0; i < 32; i += 2) {
+            if (n === (1 << i)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
+
+---
+
+## 5. Bit Mask - I
+
+::tabs-start
+
+```python
+class Solution:
+    def isPowerOfFour(self, n: int) -> bool:
+        return n > 0 and (n & (n - 1)) == 0 and (n & 0x55555555) == n
+```
+
+```java
+public class Solution {
+    public boolean isPowerOfFour(int n) {
+        return n > 0 && (n & (n - 1)) == 0 && (n & 0x55555555) == n;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isPowerOfFour(int n) {
+        return n > 0 && (n & (n - 1)) == 0 && (n & 0x55555555) == n;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {boolean}
+     */
+    isPowerOfFour(n) {
+        return n > 0 && (n & (n - 1)) === 0 && (n & 0x55555555) === n;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
+
+---
+
+## 6. Bit Mask - II
+
+::tabs-start
+
+```python
+class Solution:
+    def isPowerOfFour(self, n: int) -> bool:
+        return n > 0 and (n & (n - 1)) == 0 and (n % 3 == 1)
+```
+
+```java
+public class Solution {
+    public boolean isPowerOfFour(int n) {
+        return n > 0 && (n & (n - 1)) == 0 && (n % 3 == 1);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isPowerOfFour(int n) {
+        return n > 0 && (n & (n - 1)) == 0 && (n % 3 == 1);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {boolean}
+     */
+    isPowerOfFour(n) {
+        return n > 0 && (n & (n - 1)) === 0 && (n % 3 == 1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/power-of-two.md b/articles/power-of-two.md
new file mode 100644
index 000000000..5024ea27a
--- /dev/null
+++ b/articles/power-of-two.md
@@ -0,0 +1,351 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def isPowerOfTwo(self, n: int) -> bool:
+        if n <= 0:
+            return False
+        
+        x = 1
+        while x < n:
+            x *= 2
+        return x == n
+```
+
+```java
+public class Solution {
+    public boolean isPowerOfTwo(int n) {
+        if (n <= 0) return false;
+
+        long x = 1;
+        while (x < n) {
+            x *= 2;
+        }
+        return x == n;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isPowerOfTwo(int n) {
+        if (n <= 0) return false;
+
+        long long x = 1;
+        while (x < n) {
+            x *= 2;
+        }
+        return x == n;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {boolean}
+     */
+    isPowerOfTwo(n) {
+        if (n <= 0) return false;
+
+        let x = 1;
+        while (x < n) {
+            x *= 2;
+        }
+        return x === n;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def isPowerOfTwo(self, n: int) -> bool:
+        if n == 1:
+            return True
+        if n <= 0 or n % 2 == 1:
+            return False
+        return self.isPowerOfTwo(n // 2)
+```
+
+```java
+public class Solution {
+    public boolean isPowerOfTwo(int n) {
+        if (n == 1) {
+            return true;
+        }
+        if (n <= 0 || n % 2 == 1) {
+            return false;
+        }
+        return isPowerOfTwo(n / 2);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isPowerOfTwo(int n) {
+        if (n == 1) {
+            return true;
+        }
+        if (n <= 0 || n % 2 == 1) {
+            return false;
+        }
+        return isPowerOfTwo(n / 2);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {boolean}
+     */
+    isPowerOfTwo(n) {
+        if (n === 1) {
+            return true;
+        }
+        if (n <= 0 || n % 2 === 1) {
+            return false;
+        }
+        return this.isPowerOfTwo(Math.floor(n / 2));
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(\log n)$ for recursion stack.
+
+---
+
+## 3. Iteration
+
+::tabs-start
+
+```python
+class Solution:
+    def isPowerOfTwo(self, n: int) -> bool:
+        if n <= 0:
+            return False
+        
+        while n % 2 == 0:
+            n >>= 1
+        return n == 1
+```
+
+```java
+public class Solution {
+    public boolean isPowerOfTwo(int n) {
+        if (n <= 0) return false;
+
+        while (n % 2 == 0) {
+            n >>= 1;
+        }
+        return n == 1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isPowerOfTwo(int n) {
+        if (n <= 0) return false;
+
+        while (n % 2 == 0) {
+            n >>= 1;
+        }
+        return n == 1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {boolean}
+     */
+    isPowerOfTwo(n) {
+        if (n <= 0) return 0;
+
+        while (n % 2 === 0) {
+            n >>= 1;
+        }
+        return n === 1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
+
+---
+
+## 4. Bit Manipulation - I
+
+::tabs-start
+
+```python
+class Solution:
+    def isPowerOfTwo(self, n: int) -> bool:
+        return n > 0 and (n & (-n)) == n
+```
+
+```java
+public class Solution {
+    public boolean isPowerOfTwo(int n) {
+        return n > 0 && (n & (-n)) == n;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isPowerOfTwo(int n) {
+        return n > 0 && (n & (-n)) == n;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {boolean}
+     */
+    isPowerOfTwo(n) {
+        return n > 0 && (n & (-n)) === n;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
+
+---
+
+## 5. Bit Manipulation - II
+
+::tabs-start
+
+```python
+class Solution:
+    def isPowerOfTwo(self, n: int) -> bool:
+        return n > 0 and (n & (n - 1)) == 0
+```
+
+```java
+public class Solution {
+    public boolean isPowerOfTwo(int n) {
+        return n > 0 && (n & (n - 1)) == 0;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isPowerOfTwo(int n) {
+        return n > 0 && (n & (n - 1)) == 0;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {boolean}
+     */
+    isPowerOfTwo(n) {
+        return n > 0 && (n & (n - 1)) === 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
+
+---
+
+## 6. Math
+
+::tabs-start
+
+```python
+class Solution:
+    def isPowerOfTwo(self, n: int) -> bool:
+        return n > 0 and ((1 << 30) % n) == 0
+```
+
+```java
+public class Solution {
+    public boolean isPowerOfTwo(int n) {
+        return n > 0 && ((1 << 30) % n) == 0;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isPowerOfTwo(int n) {
+        return n > 0 && ((1 << 30) % n) == 0;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {boolean}
+     */
+    isPowerOfTwo(n) {
+        return n > 0 && ((1 << 30) % n) === 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/prefix-and-suffix-search.md b/articles/prefix-and-suffix-search.md
new file mode 100644
index 000000000..a2674805b
--- /dev/null
+++ b/articles/prefix-and-suffix-search.md
@@ -0,0 +1,596 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class WordFilter:
+
+    def __init__(self, words: List[str]):
+        self.words = words
+
+    def f(self, pref: str, suff: str) -> int:
+        for i in range(len(self.words) - 1, -1, -1):
+            w = self.words[i]
+            if len(w) < len(pref) or len(w) < len(suff):
+                continue
+
+            j, flag = 0, True
+            for c in pref:
+                if w[j] != c:
+                    flag = False
+                    break
+                j += 1
+            
+            if not flag:
+                continue
+
+            j = len(w) - len(suff)
+            for c in suff:
+                if w[j] != c:
+                    flag = False
+                    break
+                j += 1
+            
+            if flag:
+                return i
+        
+        return -1
+```
+
+```java
+public class WordFilter {
+    private String[] words;
+
+    public WordFilter(String[] words) {
+        this.words = words;
+    }
+
+    public int f(String pref, String suff) {
+        for (int i = words.length - 1; i >= 0; i--) {
+            String w = words[i];
+            if (w.length() < pref.length() || w.length() < suff.length()) {
+                continue;
+            }
+
+            boolean flag = true;
+            for (int j = 0; j < pref.length(); j++) {
+                if (w.charAt(j) != pref.charAt(j)) {
+                    flag = false;
+                    break;
+                }
+            }
+
+            if (!flag) {
+                continue;
+            }
+
+            int j = w.length() - suff.length();
+            for (int k = 0; k < suff.length(); k++) {
+                if (w.charAt(j + k) != suff.charAt(k)) {
+                    flag = false;
+                    break;
+                }
+            }
+
+            if (flag) {
+                return i;
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+```cpp
+class WordFilter {
+private:
+    vector<string> words;
+
+public:
+    WordFilter(vector<string>& words) {
+        this->words = words;
+    }
+
+    int f(string pref, string suff) {
+        for (int i = words.size() - 1; i >= 0; i--) {
+            const string& w = words[i];
+            if (w.size() < pref.size() || w.size() < suff.size()) {
+                continue;
+            }
+
+            bool flag = true;
+            for (int j = 0; j < pref.size(); j++) {
+                if (w[j] != pref[j]) {
+                    flag = false;
+                    break;
+                }
+            }
+
+            if (!flag) {
+                continue;
+            }
+
+            int j = w.size() - suff.size();
+            for (int k = 0; k < suff.size(); k++) {
+                if (w[j + k] != suff[k]) {
+                    flag = false;
+                    break;
+                }
+            }
+
+            if (flag) {
+                return i;
+            }
+        }
+
+        return -1;
+    }
+};
+```
+
+```javascript
+class WordFilter {
+    /**
+     * @constructor
+     * @param {string[]} words
+     */
+    constructor(words) {
+        this.words = words;
+    }
+
+    /** 
+     * @param {string} pref 
+     * @param {string} suff
+     * @return {number}
+     */
+    f(pref, suff) {
+        for (let i = this.words.length - 1; i >= 0; i--) {
+            const w = this.words[i];
+            if (w.length < pref.length || w.length < suff.length) {
+                continue;
+            }
+
+            let flag = true;
+            for (let j = 0; j < pref.length; j++) {
+                if (w[j] !== pref[j]) {
+                    flag = false;
+                    break;
+                }
+            }
+
+            if (!flag) {
+                continue;
+            }
+
+            let j = w.length - suff.length;
+            for (let k = 0; k < suff.length; k++) {
+                if (w[j + k] !== suff[k]) {
+                    flag = false;
+                    break;
+                }
+            }
+
+            if (flag) {
+                return i;
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(N * m * n)$
+* Space complexity: $O(1)$ extra space.
+
+> Where $N$ is the number $f()$ function calls, $n$ is the number of words, and $m$ is the average length of each word.
+
+---
+
+## 2. Hash Map
+
+::tabs-start
+
+```python
+class WordFilter:
+
+    def __init__(self, words: List[str]):
+        self.mp = {}
+        for i, w in enumerate(words):
+            for j in range(len(w)):
+                pref = w[:j + 1]
+                for k in range(len(w)):
+                    cur = pref + "$" + w[k:]
+                    self.mp[cur] = i
+
+    def f(self, pref: str, suff: str) -> int:
+        s = pref + "$" + suff
+        if s not in self.mp:
+            return -1
+        
+        return self.mp[s]
+```
+
+```java
+public class WordFilter {
+    private Map<String, Integer> mp;
+
+    public WordFilter(String[] words) {
+        mp = new HashMap<>();
+        for (int i = 0; i < words.length; i++) {
+            String w = words[i];
+            for (int j = 0; j < w.length(); j++) {
+                String pref = w.substring(0, j + 1);
+                for (int k = 0; k < w.length(); k++) {
+                    String cur = pref + "$" + w.substring(k);
+                    mp.put(cur, i);
+                }
+            }
+        }
+    }
+
+    public int f(String pref, String suff) {
+        String s = pref + "$" + suff;
+        return mp.getOrDefault(s, -1);
+    }
+}
+```
+
+```cpp
+class WordFilter {
+private:
+    unordered_map<string, int> mp;
+
+public:
+    WordFilter(vector<string>& words) {
+        for (int i = 0; i < words.size(); i++) {
+            string w = words[i];
+            for (int j = 0; j < w.size(); j++) {
+                string pref = w.substr(0, j + 1);
+                for (int k = 0; k < w.size(); k++) {
+                    string cur = pref + "$" + w.substr(k);
+                    mp[cur] = i;
+                }
+            }
+        }
+    }
+
+    int f(string pref, string suff) {
+        string s = pref + "$" + suff;
+        if (mp.find(s) == mp.end()) {
+            return -1;
+        }
+        return mp[s];
+    }
+};
+```
+
+```javascript
+class WordFilter {
+    /**
+     * @constructor
+     * @param {string[]} words
+     */
+    constructor(words) {
+        this.mp = new Map();
+        for (let i = 0; i < words.length; i++) {
+            const w = words[i];
+            for (let j = 0; j < w.length; j++) {
+                const pref = w.slice(0, j + 1);
+                for (let k = 0; k < w.length; k++) {
+                    const cur = pref + "$" + w.slice(k);
+                    this.mp.set(cur, i);
+                }
+            }
+        }
+    }
+
+    /** 
+     * @param {string} pref 
+     * @param {string} suff
+     * @return {number}
+     */
+    f(pref, suff) {
+        const s = pref + "$" + suff;
+        return this.mp.has(s) ? this.mp.get(s) : -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(n * m ^ 3)$ time for initialization.
+    * $O(m)$ for each $f()$ function call.
+* Space complexity: $O(n * m ^ 3)$
+
+> Where $n$ is the number of words and $m$ is the average length of each word.
+
+---
+
+## 3. Trie
+
+::tabs-start
+
+```python
+class TrieNode:
+    def __init__(self):
+        self.children = [None] * 27
+        self.index = -1
+
+class Trie:
+    def __init__(self):
+        self.root = TrieNode()
+    
+    def addWord(self, w, i):
+        cur = self.root
+        for ch in w:
+            c = ord(ch) - ord('a')
+            if not cur.children[c]:
+                cur.children[c] = TrieNode()
+            cur = cur.children[c]
+        cur.index = i
+    
+    def search(self, w):
+        cur = self.root
+        for ch in w:
+            c = ord(ch) - ord('a')
+            if not cur.children[c]:
+                return -1
+            cur = cur.children[c]
+        return cur.index
+
+class WordFilter:
+    def __init__(self, words: List[str]):
+        self.trie = Trie()
+        self.CHAR = '{'
+        for i, w in enumerate(words):
+            w_len = len(w)
+            for j in range(w_len):
+                suffix = w[j:]
+                for k in range(w_len + 1):
+                    prefix = w[:k]
+                    self.trie.addWord(suffix + self.CHAR + prefix, i)
+    
+    def f(self, pref: str, suff: str) -> int:
+        return self.trie.search(suff + self.CHAR + pref)
+```
+
+```java
+class TrieNode {
+    TrieNode[] children;
+    int index;
+
+    TrieNode() {
+        children = new TrieNode[27];
+        index = -1;
+    }
+}
+
+class Trie {
+    private TrieNode root;
+
+    Trie() {
+        root = new TrieNode();
+    }
+
+    void addWord(String word, int i) {
+        TrieNode cur = root;
+        for (char ch : word.toCharArray()) {
+            int c = ch == '{' ? 26 : ch - 'a';
+            if (cur.children[c] == null) {
+                cur.children[c] = new TrieNode();
+            }
+            cur = cur.children[c];
+        }
+        cur.index = i;
+    }
+
+    int search(String word) {
+        TrieNode cur = root;
+        for (char ch : word.toCharArray()) {
+            int c = ch == '{' ? 26 : ch - 'a';
+            if (cur.children[c] == null) {
+                return -1;
+            }
+            cur = cur.children[c];
+        }
+        return cur.index;
+    }
+}
+
+public class WordFilter {
+    private Trie trie;
+    private static final char CHAR = '{';
+
+    public WordFilter(String[] words) {
+        trie = new Trie();
+        for (int i = 0; i < words.length; i++) {
+            String word = words[i];
+            int wLen = word.length();
+            for (int j = 0; j < wLen; j++) {
+                String suffix = word.substring(j);
+                for (int k = 0; k <= wLen; k++) {
+                    String prefix = word.substring(0, k);
+                    trie.addWord(suffix + CHAR + prefix, i);
+                }
+            }
+        }
+    }
+
+    public int f(String pref, String suff) {
+        return trie.search(suff + CHAR + pref);
+    }
+}
+```
+
+```cpp
+class TrieNode {
+public:
+    TrieNode* children[27];
+    int index;
+
+    TrieNode() {
+        for (int i = 0; i < 27; i++) {
+            children[i] = nullptr;
+        }
+        index = -1;
+    }
+};
+
+class Trie {
+private:
+    TrieNode* root;
+
+public:
+    Trie() {
+        root = new TrieNode();
+    }
+
+    void addWord(const string& word, int i) {
+        TrieNode* cur = root;
+        for (char ch : word) {
+            int c = (ch == '{') ? 26 : (ch - 'a');
+            if (cur->children[c] == nullptr) {
+                cur->children[c] = new TrieNode();
+            }
+            cur = cur->children[c];
+        }
+        cur->index = i;
+    }
+
+    int search(const string& word) {
+        TrieNode* cur = root;
+        for (char ch : word) {
+            int c = (ch == '{') ? 26 : (ch - 'a');
+            if (cur->children[c] == nullptr) {
+                return -1;
+            }
+            cur = cur->children[c];
+        }
+        return cur->index;
+    }
+};
+
+class WordFilter {
+private:
+    Trie trie;
+    const char CHAR = '{';
+
+public:
+    WordFilter(vector<string>& words) {
+        for (int i = 0; i < words.size(); i++) {
+            string word = words[i];
+            int wLen = word.length();
+            for (int j = 0; j < wLen; j++) {
+                string suffix = word.substr(j);
+                for (int k = 0; k <= wLen; k++) {
+                    string prefix = word.substr(0, k);
+                    trie.addWord(suffix + CHAR + prefix, i);
+                }
+            }
+        }
+    }
+
+    int f(string pref, string suff) {
+        return trie.search(suff + CHAR + pref);
+    }
+};
+```
+
+```javascript
+class TrieNode {
+    constructor() {
+        this.children = Array(27).fill(null);
+        this.index = -1;
+    }
+}
+
+class Trie {
+    constructor() {
+        this.root = new TrieNode();
+    }
+
+    /**
+     * @param {string} word
+     * @param {number} i
+     * @return {void}
+     */
+    addWord(word, i) {
+        let cur = this.root;
+        for (const ch of word) {
+            const c = ch === '{' ? 26 : ch.charCodeAt(0) - 'a'.charCodeAt(0);
+            if (!cur.children[c]) {
+                cur.children[c] = new TrieNode();
+            }
+            cur = cur.children[c];
+        }
+        cur.index = i;
+    }
+
+    /**
+     * @param {string} word
+     * @return {number}
+     */
+    search(word) {
+        let cur = this.root;
+        for (const ch of word) {
+            const c = ch === '{' ? 26 : ch.charCodeAt(0) - 'a'.charCodeAt(0);
+            if (!cur.children[c]) {
+                return -1;
+            }
+            cur = cur.children[c];
+        }
+        return cur.index;
+    }
+}
+
+class WordFilter {
+    /**
+     * @constructor
+     * @param {string[]} words
+     */
+    constructor(words) {
+        this.trie = new Trie();
+        this.CHAR = '{';
+        for (let i = 0; i < words.length; i++) {
+            const word = words[i];
+            const wLen = word.length;
+            for (let j = 0; j < wLen; j++) {
+                const suffix = word.substring(j);
+                for (let k = 0; k <= wLen; k++) {
+                    const prefix = word.substring(0, k);
+                    this.trie.addWord(suffix + this.CHAR + prefix, i);
+                }
+            }
+        }
+    }
+
+    /** 
+     * @param {string} pref 
+     * @param {string} suff
+     * @return {number}
+     */
+    f(pref, suff) {
+        return this.trie.search(suff + this.CHAR + pref);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(n * m ^ 3)$ time for initialization.
+    * $O(m)$ for each $f()$ function call.
+* Space complexity: $O(n * m ^ 3)$
+
+> Where $n$ is the number of words and $m$ is the average length of each word.
\ No newline at end of file
diff --git a/articles/process-tasks-using-servers.md b/articles/process-tasks-using-servers.md
new file mode 100644
index 000000000..f79a9c753
--- /dev/null
+++ b/articles/process-tasks-using-servers.md
@@ -0,0 +1,501 @@
+## 1. Brute Force (Simulation)
+
+::tabs-start
+
+```python
+class Solution:
+    def assignTasks(self, servers: List[int], tasks: List[int]) -> List[int]:
+        n, m = len(servers), len(tasks)
+        available = [True] * n
+        finishTime = [0] * n
+        res = []
+        time = 0
+
+        for t in range(m):
+            time = max(time, t)
+
+            for i in range(n):
+                if finishTime[i] <= time:
+                    available[i] = True
+
+            if not any(available):
+                time = min(finishTime)
+                for i in range(n):
+                    if finishTime[i] <= time:
+                        available[i] = True
+
+            minIdx = -1
+            for i in range(n):
+                if (available[i] and
+                    (minIdx == -1 or servers[i] < servers[minIdx] or
+                    (servers[i] == servers[minIdx] and i < minIdx))
+                ):
+                    minIdx = i
+
+            res.append(minIdx)
+            available[minIdx] = False
+            finishTime[minIdx] = time + tasks[t]
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[] assignTasks(int[] servers, int[] tasks) {
+        int n = servers.length, m = tasks.length;
+        boolean[] available = new boolean[n];
+        Arrays.fill(available, true);
+        int[] finishTime = new int[n];
+        int[] res = new int[m];
+        int time = 0;
+
+        for (int t = 0; t < m; t++) {
+            time = Math.max(time, t);
+            for (int i = 0; i < n; i++) {
+                if (finishTime[i] <= time) {
+                    available[i] = true;
+                }
+            }
+
+            if (!anyAvailable(available)) {
+                time = Arrays.stream(finishTime).min().getAsInt();
+                for (int i = 0; i < n; i++) {
+                    if (finishTime[i] <= time) {
+                        available[i] = true;
+                    }
+                }
+            }
+
+            int minIdx = -1;
+            for (int i = 0; i < n; i++) {
+                if (available[i] && (minIdx == -1 || servers[i] < servers[minIdx] || 
+                    (servers[i] == servers[minIdx] && i < minIdx))) {
+                    minIdx = i;
+                }
+            }
+
+            res[t] = minIdx;
+            available[minIdx] = false;
+            finishTime[minIdx] = time + tasks[t];
+        }
+        return res;
+    }
+
+    private boolean anyAvailable(boolean[] available) {
+        for (boolean v : available) {
+            if (v) return true;
+        }
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> assignTasks(vector<int>& servers, vector<int>& tasks) {
+        int n = servers.size(), m = tasks.size();
+        vector<bool> available(n, true);
+        vector<int> finishTime(n, 0), res(m);
+        int time = 0;
+
+        for (int t = 0; t < m; t++) {
+            time = max(time, t);
+
+            for (int i = 0; i < n; i++) {
+                if (finishTime[i] <= time) {
+                    available[i] = true;
+                }
+            }
+
+            if (!any_of(available.begin(), available.end(), [](bool v) { return v; })) {
+                time = *min_element(finishTime.begin(), finishTime.end());
+                for (int i = 0; i < n; i++) {
+                    if (finishTime[i] <= time) {
+                        available[i] = true;
+                    }
+                }
+            }
+
+            int minIdx = -1;
+            for (int i = 0; i < n; i++) {
+                if (available[i] && (minIdx == -1 || servers[i] < servers[minIdx] || 
+                    (servers[i] == servers[minIdx] && i < minIdx))) {
+                    minIdx = i;
+                }
+            }
+
+            res[t] = minIdx;
+            available[minIdx] = false;
+            finishTime[minIdx] = time + tasks[t];
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} servers
+     * @param {number[]} tasks
+     * @return {number[]}
+     */
+    assignTasks(servers, tasks) {
+        const n = servers.length, m = tasks.length;
+        const available = Array(n).fill(true);
+        const finishTime = Array(n).fill(0);
+        const res = [];
+        let time = 0;
+
+        for (let t = 0; t < m; t++) {
+            time = Math.max(time, t);
+
+            for (let i = 0; i < n; i++) {
+                if (finishTime[i] <= time) {
+                    available[i] = true;
+                }
+            }
+
+            if (!available.some(v => v)) {
+                time = Math.min(...finishTime);
+                for (let i = 0; i < n; i++) {
+                    if (finishTime[i] <= time) {
+                        available[i] = true;
+                    }
+                }
+            }
+
+            let minIdx = -1;
+            for (let i = 0; i < n; i++) {
+                if (available[i] && (minIdx === -1 || servers[i] < servers[minIdx] || 
+                    (servers[i] === servers[minIdx] && i < minIdx))) {
+                    minIdx = i;
+                }
+            }
+
+            res.push(minIdx);
+            available[minIdx] = false;
+            finishTime[minIdx] = time + tasks[t];
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity:
+    * $O(n)$ extra space.
+    * $O(m)$ space for the output array.
+
+> Where $m$ is the number of tasks and $n$ is the number of servers.
+
+---
+
+## 2. Two Min-Heaps - I
+
+::tabs-start
+
+```python
+class Solution:
+    def assignTasks(self, servers: List[int], tasks: List[int]) -> List[int]:
+        res = [0] * len(tasks)
+        available = [(servers[i], i) for i in range(len(servers))]
+        heapq.heapify(available)
+        unavailable = []
+
+        t = 0
+        for i in range(len(tasks)):
+            t = max(t, i)
+
+            if not available:
+                t = unavailable[0][0]
+
+            while unavailable and t >= unavailable[0][0]:
+                timeFree, weight, index = heapq.heappop(unavailable)
+                heapq.heappush(available, (weight, index))
+
+            weight, index = heapq.heappop(available)
+            res[i] = index
+            heapq.heappush(unavailable, (t + tasks[i], weight, index))
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[] assignTasks(int[] servers, int[] tasks) {
+        int n = servers.length, m = tasks.length;
+        int[] res = new int[m];
+
+        PriorityQueue<int[]> available = new PriorityQueue<>(
+            (a, b) -> a[0] == b[0] ? Integer.compare(a[1], b[1]) : Integer.compare(a[0], b[0])
+        );
+        PriorityQueue<int[]> unavailable = new PriorityQueue<>(
+            Comparator.comparingInt(a -> a[0])
+        );
+
+        for (int i = 0; i < n; i++) {
+            available.offer(new int[]{servers[i], i});
+        }
+
+        int time = 0;
+        for (int i = 0; i < m; i++) {
+            time = Math.max(time, i);
+
+            if (available.isEmpty()) {
+                time = unavailable.peek()[0];
+            }
+
+            while (!unavailable.isEmpty() && unavailable.peek()[0] <= time) {
+                int[] server = unavailable.poll();
+                available.offer(new int[]{server[1], server[2]});
+            }
+
+            int[] bestServer = available.poll();
+            res[i] = bestServer[1];
+            unavailable.offer(new int[]{time + tasks[i], bestServer[0], bestServer[1]});
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> assignTasks(vector<int>& servers, vector<int>& tasks) {
+        int n = servers.size(), m = tasks.size();
+        vector<int> res(m);
+
+        priority_queue<pair<int, int>, vector<pair<int, int>>, greater<>> available;
+        priority_queue<vector<int>, vector<vector<int>>, greater<>> unavailable;
+
+        for (int i = 0; i < n; i++) {
+            available.emplace(servers[i], i);
+        }
+
+        int time = 0;
+        for (int i = 0; i < m; i++) {
+            time = max(time, i);
+
+            if (available.empty()) {
+                time = unavailable.top()[0];
+            }
+
+            while (!unavailable.empty() && unavailable.top()[0] <= time) {
+                auto server = unavailable.top(); unavailable.pop();
+                available.emplace(server[1], server[2]);
+            }
+
+            auto [weight, index] = available.top(); available.pop();
+            res[i] = index;
+            unavailable.push({time + tasks[i], weight, index});
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} servers
+     * @param {number[]} tasks
+     * @return {number[]}
+     */
+    assignTasks(servers, tasks) {
+        const n = servers.length;
+        const available = new PriorityQueue(
+            (a, b) => a[0] === b[0] ? a[1] - b[1] : a[0] - b[0]
+        );
+        const unavailable = new PriorityQueue((a, b) => a[0] - b[0]);
+        const res = new Array(tasks.length);
+
+        for (let i = 0; i < n; i++) {
+            available.enqueue([servers[i], i]);
+        }
+
+        let time = 0;
+        for (let i = 0; i < tasks.length; i++) {
+            time = Math.max(time, i);
+            if (available.isEmpty()) {
+                time = unavailable.front()[0];
+            }
+            while (!unavailable.isEmpty() && unavailable.front()[0] <= time) {
+                const [timeFree, weight, index] = unavailable.dequeue();
+                available.enqueue([weight, index]);
+            }
+            const [weight, index] = available.dequeue();
+            res[i] = index;
+            unavailable.enqueue([time + tasks[i], weight, index]);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O((n + m) \log n)$
+* Space complexity:
+    * $O(n)$ extra space.
+    * $O(m)$ space for the output array.
+
+> Where $m$ is the number of tasks and $n$ is the number of servers.
+
+---
+
+## 3. Two Min-Heaps - II
+
+::tabs-start
+
+```python
+class Solution:
+    def assignTasks(self, servers: List[int], tasks: List[int]) -> List[int]:
+        res = []
+        available = [[weight, i, 0] for i, weight in enumerate(servers)]
+        unavailable = []
+        heapq.heapify(available)
+
+        for i, task in enumerate(tasks):
+            while unavailable and unavailable[0][0] <= i or not available:
+                timeFree, weight, index = heapq.heappop(unavailable)
+                heapq.heappush(available, [weight, index, timeFree])
+
+            weight, index, timeFree = heapq.heappop(available)
+            res.append(index)
+            heapq.heappush(unavailable, [max(timeFree, i) + task, weight, index])
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[] assignTasks(int[] servers, int[] tasks) {
+        int m = tasks.length, n = servers.length;
+        int[] res = new int[m];
+        
+        PriorityQueue<int[]> available = new PriorityQueue<>((a, b) -> {
+            if(a[0] != b[0]) return Integer.compare(a[0], b[0]);
+            if(a[1] != b[1]) return Integer.compare(a[1], b[1]);
+            return Integer.compare(a[2], b[2]);
+        });
+        
+        PriorityQueue<int[]> unavailable = new PriorityQueue<>((a, b) -> {
+            if(a[0] != b[0]) return Integer.compare(a[0], b[0]);
+            if(a[1] != b[1]) return Integer.compare(a[1], b[1]);
+            return Integer.compare(a[2], b[2]);
+        });
+        
+        for (int i = 0; i < n; i++) {
+            available.offer(new int[]{servers[i], i, 0});
+        }
+        
+        for (int i = 0; i < m; i++) {
+            while ((!unavailable.isEmpty() && unavailable.peek()[0] <= i) ||
+                    available.isEmpty()) {
+                int[] server = unavailable.poll();
+                available.offer(new int[]{server[1], server[2], server[0]});
+            }
+            int[] server = available.poll();
+            res[i] = server[1];
+            unavailable.offer(new int[]{
+                Math.max(server[2], i) + tasks[i], server[0], server[1]}
+            );
+        }
+        
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> assignTasks(vector<int>& servers, vector<int>& tasks) {
+        int n = servers.size(), m = tasks.size();
+        vector<int> res(m);
+
+        priority_queue<array<int, 3>, vector<array<int, 3>>, greater<>> available;
+        priority_queue<array<int, 3>, vector<array<int, 3>>, greater<>> unavailable;
+
+        for (int i = 0; i < n; ++i) {
+            available.push({servers[i], i, 0});
+        }
+
+        for (int i = 0; i < m; ++i) {
+            while (!unavailable.empty() && (unavailable.top()[0] <= i ||
+                   available.empty())) {
+                auto [timeFree, weight, index] = unavailable.top();
+                unavailable.pop();
+                available.push({weight, index, timeFree});
+            }
+
+            auto [weight, index, timeFree] = available.top();
+            available.pop();
+            res[i] = index;
+            unavailable.push({max(timeFree, i) + tasks[i], weight, index});
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} servers
+     * @param {number[]} tasks
+     * @return {number[]}
+     */
+    assignTasks(servers, tasks) {
+        const res = new Array(tasks.length);
+        const available = new PriorityQueue(
+            (a, b) => a[0] === b[0] ? (a[1] === b[1] ? a[2] - b[2] : a[1] - b[1]) : a[0] - b[0]
+        );
+        const unavailable = new PriorityQueue(
+            (a, b) => a[0] === b[0] ? (a[1] === b[1] ? a[2] - b[2] : a[1] - b[1]) : a[0] - b[0]
+        );
+
+        for (let i = 0; i < servers.length; i++) {
+            available.enqueue([servers[i], i, 0]);
+        }
+
+        for (let i = 0; i < tasks.length; i++) {
+            while ((!unavailable.isEmpty() && unavailable.front()[0] <= i) ||
+                   available.isEmpty()) {
+                const [timeFree, weight, index] = unavailable.dequeue();
+                available.enqueue([weight, index, timeFree]);
+            }
+
+            const [weight, index, timeFree] = available.dequeue();
+            res[i] = index;
+            unavailable.enqueue([Math.max(timeFree, i) + tasks[i], weight, index]);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O((n + m) \log n)$
+* Space complexity:
+    * $O(n)$ extra space.
+    * $O(m)$ space for the output array.
+
+> Where $m$ is the number of tasks and $n$ is the number of servers.
\ No newline at end of file
diff --git a/articles/products-of-array-discluding-self.md b/articles/products-of-array-discluding-self.md
index c9719f7e2..1370fac97 100644
--- a/articles/products-of-array-discluding-self.md
+++ b/articles/products-of-array-discluding-self.md
@@ -104,12 +104,74 @@ public class Solution {
 }
 ```
 
+```go
+func productExceptSelf(nums []int) []int {
+    n := len(nums)
+    res := make([]int, n)
+
+    for i := 0; i < n; i++ {
+        prod := 1
+        for j := 0; j < n; j++ {
+            if i == j {
+                continue
+            }
+            prod *= nums[j]
+        }
+        res[i] = prod
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun productExceptSelf(nums: IntArray): IntArray {
+        val n = nums.size
+        val res = IntArray(n)
+
+        for (i in 0 until n) {
+            var prod = 1
+            for (j in 0 until n) {
+                if (i == j) continue
+                prod *= nums[j]
+            }
+            res[i] = prod
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func productExceptSelf(_ nums: [Int]) -> [Int] {
+        let n = nums.count
+        var res = [Int](repeating: 0, count: n)
+
+        for i in 0..<n {
+            var prod = 1
+            for j in 0..<n {
+                if i == j {
+                    continue
+                }
+                prod *= nums[j]
+            }
+            res[i] = prod
+        }
+
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n ^ 2)$
-* Space complexity: $O(1)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ space for the output array.
 
 ---
 
@@ -257,12 +319,108 @@ public class Solution {
 }
 ```
 
+```go
+func productExceptSelf(nums []int) []int {
+    prod := 1
+    zeroCount := 0
+
+    for _, num := range nums {
+        if num != 0 {
+            prod *= num
+        } else {
+            zeroCount++
+        }
+    }
+    
+    res := make([]int, len(nums))
+    if zeroCount > 1 {
+        return res
+    }
+
+    for i, num := range nums {
+        if zeroCount > 0 {
+            if num == 0 {
+                res[i] = prod
+            } else {
+                res[i] = 0
+            }
+        } else {
+            res[i] = prod / num
+        }
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun productExceptSelf(nums: IntArray): IntArray {
+        var prod = 1
+        var zeroCount = 0
+
+        for (num in nums) {
+            if (num != 0) {
+                prod *= num
+            } else {
+                zeroCount++
+            }
+        }
+        
+        val res = IntArray(nums.size)
+        if (zeroCount > 1) return res
+
+        for (i in nums.indices) {
+            res[i] = if (zeroCount > 0) {
+                if (nums[i] == 0) prod else 0
+            } else {
+                prod / nums[i]
+            }
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func productExceptSelf(_ nums: [Int]) -> [Int] {
+        var prod = 1
+        var zeroCount = 0
+
+        for num in nums {
+            if num != 0 {
+                prod *= num
+            } else {
+                zeroCount += 1
+            }
+        }
+        
+        if zeroCount > 1 {
+            return [Int](repeating: 0, count: nums.count)
+        }
+
+        var res = [Int](repeating: 0, count: nums.count)
+        for (i, num) in nums.enumerated() {
+            if zeroCount > 0 {
+                res[i] = num == 0 ? prod : 0
+            } else {
+                res[i] = prod / num
+            }
+        }
+
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n)$
-* Space complexity: $O(1)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ space for the output array.
 
 ---
 
@@ -389,6 +547,79 @@ public class Solution {
 }
 ```
 
+```go
+func productExceptSelf(nums []int) []int {
+    n := len(nums)
+    res := make([]int, n)
+    pref := make([]int, n)
+    suff := make([]int, n)
+
+    pref[0], suff[n-1] = 1, 1
+    for i := 1; i < n; i++ {
+        pref[i] = nums[i-1] * pref[i-1]
+    }
+    for i := n - 2; i >= 0; i-- {
+        suff[i] = nums[i+1] * suff[i+1]
+    }
+    for i := 0; i < n; i++ {
+        res[i] = pref[i] * suff[i]
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun productExceptSelf(nums: IntArray): IntArray {
+        val n = nums.size
+        val res = IntArray(n)
+        val pref = IntArray(n)
+        val suff = IntArray(n)
+
+        pref[0] = 1
+        suff[n - 1] = 1
+        for (i in 1 until n) {
+            pref[i] = nums[i - 1] * pref[i - 1]
+        }
+        for (i in n - 2 downTo 0) {
+            suff[i] = nums[i + 1] * suff[i + 1]
+        }
+        for (i in 0 until n) {
+            res[i] = pref[i] * suff[i]
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func productExceptSelf(_ nums: [Int]) -> [Int] {
+        let n = nums.count
+        var res = [Int](repeating: 0, count: n)
+        var pref = [Int](repeating: 0, count: n)
+        var suff = [Int](repeating: 0, count: n)
+
+        pref[0] = 1
+        suff[n - 1] = 1
+
+        for i in 1..<n {
+            pref[i] = nums[i - 1] * pref[i - 1]
+        }
+        
+        for i in stride(from: n - 2, through: 0, by: -1) {
+            suff[i] = nums[i + 1] * suff[i + 1]
+        }
+        
+        for i in 0..<n {
+            res[i] = pref[i] * suff[i]
+        }
+        
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -505,9 +736,78 @@ public class Solution {
 }
 ```
 
+```go
+func productExceptSelf(nums []int) []int {
+    res := make([]int, len(nums))
+    for i := range res {
+        res[i] = 1
+    }
+
+    prefix := 1
+    for i := 0; i < len(nums); i++ {
+        res[i] = prefix
+        prefix *= nums[i]
+    }
+
+    postfix := 1
+    for i := len(nums) - 1; i >= 0; i-- {
+        res[i] *= postfix
+        postfix *= nums[i]
+    }
+
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun productExceptSelf(nums: IntArray): IntArray {
+        val res = IntArray(nums.size) { 1 }
+
+        var prefix = 1
+        for (i in nums.indices) {
+            res[i] = prefix
+            prefix *= nums[i]
+        }
+
+        var postfix = 1
+        for (i in nums.size - 1 downTo 0) {
+            res[i] *= postfix
+            postfix *= nums[i]
+        }
+
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func productExceptSelf(_ nums: [Int]) -> [Int] {
+        var res = [Int](repeating: 1, count: nums.count)
+
+        var prefix = 1
+        for i in 0..<nums.count {
+            res[i] = prefix
+            prefix *= nums[i]
+        }
+
+        var postfix = 1
+        for i in stride(from: nums.count - 1, through: 0, by: -1) {
+            res[i] *= postfix
+            postfix *= nums[i]
+        }
+        
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n)$
-* Space complexity: $O(1)$
\ No newline at end of file
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ space for the output array.
\ No newline at end of file
diff --git a/articles/profitable-schemes.md b/articles/profitable-schemes.md
new file mode 100644
index 000000000..98986e70a
--- /dev/null
+++ b/articles/profitable-schemes.md
@@ -0,0 +1,529 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def profitableSchemes(self, n: int, minProfit: int, group: List[int], profit: List[int]) -> int:
+        mod = 10**9 + 7
+
+        def dfs(i, n, p):
+            if i == len(group):
+                return 1 if p >= minProfit else 0
+            
+            res = dfs(i + 1, n, p)
+            if n - group[i] >= 0:
+                res = (res + dfs(i + 1, n - group[i], p + profit[i])) % mod
+
+            return res
+        
+        return dfs(0, n, 0)
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1_000_000_007;
+
+    public int profitableSchemes(int n, int minProfit, int[] group, int[] profit) {
+        return dfs(0, n, 0, group, profit, minProfit);
+    }
+
+    private int dfs(int i, int n, int p, int[] group, int[] profit, int minProfit) {
+        if (i == group.length) {
+            return p >= minProfit ? 1 : 0;
+        }
+
+        int res = dfs(i + 1, n, p, group, profit, minProfit);
+        if (n - group[i] >= 0) {
+            res = (res + dfs(i + 1, n - group[i], p + profit[i], group, profit, minProfit)) % MOD;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    static const int MOD = 1e9 + 7;
+
+public:
+    int profitableSchemes(int n, int minProfit, vector<int>& group, vector<int>& profit) {
+        return dfs(0, n, 0, group, profit, minProfit);
+    }
+
+private:
+    int dfs(int i, int n, int p, const vector<int>& group, const vector<int>& profit, int minProfit) {
+        if (i == group.size()) {
+            return p >= minProfit ? 1 : 0;
+        }
+
+        int res = dfs(i + 1, n, p, group, profit, minProfit);
+        if (n - group[i] >= 0) {
+            res = (res + dfs(i + 1, n - group[i], p + profit[i], group, profit, minProfit)) % MOD;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} minProfit
+     * @param {number[]} group
+     * @param {number[]} profit
+     * @return {number}
+     */
+    profitableSchemes(n, minProfit, group, profit) {
+        const MOD = 1e9 + 7;
+
+        const dfs = (i, n, p) => {
+            if (i === group.length) {
+                return p >= minProfit ? 1 : 0;
+            }
+
+            let res = dfs(i + 1, n, p);
+            if (n - group[i] >= 0) {
+                res = (res + dfs(i + 1, n - group[i], p + profit[i])) % MOD;
+            }
+
+            return res;
+        };
+
+        return dfs(0, n, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ N)$
+* Space complexity: $O(N)$
+
+> Where $N$ is the size of the $group$ array.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def profitableSchemes(self, n: int, minProfit: int, group: List[int], profit: List[int]) -> int:
+        mod = 10**9 + 7
+        dp = {}
+
+        def dfs(i, n, p):
+            if i == len(group):
+                return 1 if p >= minProfit else 0
+            if (i, n, p) in dp:
+                return dp[(i, n, p)]
+
+            res = dfs(i + 1, n, p)
+            if n - group[i] >= 0:
+                nxtP = min(p + profit[i], minProfit)
+                res = (res + dfs(i + 1, n - group[i], nxtP)) % mod
+            
+            dp[(i, n, p)] = res
+            return res
+        
+        return dfs(0, n, 0)
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1_000_000_007;
+    private int[][][] dp;
+
+    public int profitableSchemes(int n, int minProfit, int[] group, int[] profit) {
+        dp = new int[group.length][n + 1][minProfit + 1];
+        for (int[][] layer : dp) {
+            for (int[] row : layer) {
+                Arrays.fill(row, -1);
+            }
+        }
+        return dfs(0, n, 0, group, profit, minProfit);
+    }
+
+    private int dfs(int i, int n, int p, int[] group, int[] profit, int minProfit) {
+        if (i == group.length) {
+            return p >= minProfit ? 1 : 0;
+        }
+        if (dp[i][n][p] != -1) {
+            return dp[i][n][p];
+        }
+
+        int res = dfs(i + 1, n, p, group, profit, minProfit);
+        if (n - group[i] >= 0) {
+            int nxtP = Math.min(p + profit[i], minProfit);
+            res = (res + dfs(i + 1, n - group[i], nxtP, group, profit, minProfit)) % MOD;
+        }
+
+        dp[i][n][p] = res;
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    static const int MOD = 1e9 + 7;
+    vector<vector<vector<int>>> dp;
+
+public:
+    int profitableSchemes(int n, int minProfit, vector<int>& group, vector<int>& profit) {
+        dp = vector<vector<vector<int>>>(group.size(), vector<vector<int>>(n + 1, vector<int>(minProfit + 1, -1)));
+        return dfs(0, n, 0, group, profit, minProfit);
+    }
+
+private:
+    int dfs(int i, int n, int p, vector<int>& group, vector<int>& profit, int minProfit) {
+        if (i == group.size()) {
+            return p >= minProfit ? 1 : 0;
+        }
+        if (dp[i][n][p] != -1) {
+            return dp[i][n][p];
+        }
+
+        int res = dfs(i + 1, n, p, group, profit, minProfit);
+        if (n >= group[i]) {
+            int nxtP = min(p + profit[i], minProfit);
+            res = (res + dfs(i + 1, n - group[i], nxtP, group, profit, minProfit)) % MOD;
+        }
+
+        dp[i][n][p] = res;
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} minProfit
+     * @param {number[]} group
+     * @param {number[]} profit
+     * @return {number}
+     */
+    profitableSchemes(n, minProfit, group, profit) {
+        const MOD = 1e9 + 7;
+        const dp = Array.from({ length: group.length }, () =>
+            Array.from({ length: n + 1 }, () => Array(minProfit + 1).fill(-1))
+        );
+
+        const dfs = (i, n, p) => {
+            if (i === group.length) {
+                return p >= minProfit ? 1 : 0;
+            }
+            if (dp[i][n][p] !== -1) {
+                return dp[i][n][p];
+            }
+
+            let res = dfs(i + 1, n, p);
+            if (n >= group[i]) {
+                const nxtP = Math.min(p + profit[i], minProfit);
+                res = (res + dfs(i + 1, n - group[i], nxtP)) % MOD;
+            }
+
+            dp[i][n][p] = res;
+            return res;
+        };
+
+        return dfs(0, n, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(N * m * n)$
+* Space complexity: $O(N * m * n)$
+
+> Where $N$ is the size of the $group$ array, $m$ is the given minimum profit, and $n$ is the number of group members.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def profitableSchemes(self, n: int, minProfit: int, group: List[int], profit: List[int]) -> int:
+        mod = 10**9 + 7
+        N = len(group)
+
+        dp = [[[0] * (minProfit + 1) for j in range(n + 2)] for i in range(N + 1)]
+        for j in range(n + 1):
+            dp[N][j][minProfit] = 1
+
+        for i in range(N - 1, -1, -1):
+            for j in range(n + 1):
+                for p in range(minProfit + 1):
+                    res = dp[i + 1][j][p]
+                    if j >= group[i]:
+                        nxtP = min(profit[i] + p, minProfit)
+                        res = (res + dp[i + 1][j - group[i]][nxtP]) % mod
+                    dp[i][j][p] = res 
+        
+        return dp[0][n][0]
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1_000_000_007;
+
+    public int profitableSchemes(int n, int minProfit, int[] group, int[] profit) {
+        int N = group.length;
+        int[][][] dp = new int[N + 1][n + 2][minProfit + 1];
+
+        for (int j = 0; j <= n; j++) {
+            dp[N][j][minProfit] = 1;
+        }
+
+        for (int i = N - 1; i >= 0; i--) {
+            for (int j = 0; j <= n; j++) {
+                for (int p = 0; p <= minProfit; p++) {
+                    int res = dp[i + 1][j][p];
+                    if (j >= group[i]) {
+                        int nxtP = Math.min(profit[i] + p, minProfit);
+                        res = (res + dp[i + 1][j - group[i]][nxtP]) % MOD;
+                    }
+                    dp[i][j][p] = res;
+                }
+            }
+        }
+
+        return dp[0][n][0];
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    static const int MOD = 1e9 + 7;
+
+public:
+    int profitableSchemes(int n, int minProfit, vector<int>& group, vector<int>& profit) {
+        int N = group.size();
+        vector<vector<vector<int>>> dp(N + 1, vector<vector<int>>(n + 2, vector<int>(minProfit + 1, 0)));
+
+        for (int j = 0; j <= n; j++) {
+            dp[N][j][minProfit] = 1;
+        }
+
+        for (int i = N - 1; i >= 0; i--) {
+            for (int j = 0; j <= n; j++) {
+                for (int p = 0; p <= minProfit; p++) {
+                    int res = dp[i + 1][j][p];
+                    if (j >= group[i]) {
+                        int nxtP = min(profit[i] + p, minProfit);
+                        res = (res + dp[i + 1][j - group[i]][nxtP]) % MOD;
+                    }
+                    dp[i][j][p] = res;
+                }
+            }
+        }
+
+        return dp[0][n][0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} minProfit
+     * @param {number[]} group
+     * @param {number[]} profit
+     * @return {number}
+     */
+    profitableSchemes(n, minProfit, group, profit) {
+        const MOD = 1e9 + 7;
+        const N = group.length;
+
+        const dp = Array.from({ length: N + 1 }, () =>
+            Array.from({ length: n + 2 }, () => Array(minProfit + 1).fill(0))
+        );
+
+        for (let j = 0; j <= n; j++) {
+            dp[N][j][minProfit] = 1;
+        }
+
+        for (let i = N - 1; i >= 0; i--) {
+            for (let j = 0; j <= n; j++) {
+                for (let p = 0; p <= minProfit; p++) {
+                    let res = dp[i + 1][j][p];
+                    if (j >= group[i]) {
+                        const nxtP = Math.min(profit[i] + p, minProfit);
+                        res = (res + dp[i + 1][j - group[i]][nxtP]) % MOD;
+                    }
+                    dp[i][j][p] = res;
+                }
+            }
+        }
+
+        return dp[0][n][0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(N * m * n)$
+* Space complexity: $O(N * m * n)$
+
+> Where $N$ is the size of the $group$ array, $m$ is the given minimum profit, and $n$ is the number of group members.
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def profitableSchemes(self, n: int, minProfit: int, group: List[int], profit: List[int]) -> int:
+        mod = 10**9 + 7
+        N = len(group)
+
+        dp = [[0] * (minProfit + 1) for j in range(n + 2)]
+        for j in range(n + 1):
+            dp[j][minProfit] = 1
+
+        for i in range(N - 1, -1, -1):
+            for j in range(n, -1, -1):
+                for p in range(minProfit + 1):
+                    res = dp[j][p]
+                    if j >= group[i]:
+                        nxtP = min(profit[i] + p, minProfit)
+                        res = (res + dp[j - group[i]][nxtP]) % mod
+                    dp[j][p] = res 
+        
+        return dp[n][0]
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1_000_000_007;
+
+    public int profitableSchemes(int n, int minProfit, int[] group, int[] profit) {
+        int N = group.length;
+        int[][] dp = new int[n + 2][minProfit + 1];
+
+        for (int j = 0; j <= n; j++) {
+            dp[j][minProfit] = 1;
+        }
+
+        for (int i = N - 1; i >= 0; i--) {
+            for (int j = n; j >= 0; j--) {
+                for (int p = 0; p <= minProfit; p++) {
+                    int res = dp[j][p];
+                    if (j >= group[i]) {
+                        int nxtP = Math.min(profit[i] + p, minProfit);
+                        res = (res + dp[j - group[i]][nxtP]) % MOD;
+                    }
+                    dp[j][p] = res;
+                }
+            }
+        }
+
+        return dp[n][0];
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    static const int MOD = 1e9 + 7;
+
+public:
+    int profitableSchemes(int n, int minProfit, vector<int>& group, vector<int>& profit) {
+        int N = group.size();
+        vector<vector<int>> dp(n + 2, vector<int>(minProfit + 1, 0));
+
+        for (int j = 0; j <= n; j++) {
+            dp[j][minProfit] = 1;
+        }
+
+        for (int i = N - 1; i >= 0; i--) {
+            for (int j = n; j >= 0; j--) {
+                for (int p = 0; p <= minProfit; p++) {
+                    int res = dp[j][p];
+                    if (j >= group[i]) {
+                        int nxtP = min(profit[i] + p, minProfit);
+                        res = (res + dp[j - group[i]][nxtP]) % MOD;
+                    }
+                    dp[j][p] = res;
+                }
+            }
+        }
+
+        return dp[n][0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} minProfit
+     * @param {number[]} group
+     * @param {number[]} profit
+     * @return {number}
+     */
+    profitableSchemes(n, minProfit, group, profit) {
+        const MOD = 1e9 + 7;
+        const N = group.length;
+
+        const dp = Array.from({ length: n + 2 }, () => 
+            Array(minProfit + 1).fill(0)
+        );
+
+        for (let j = 0; j <= n; j++) {
+            dp[j][minProfit] = 1;
+        }
+
+        for (let i = N - 1; i >= 0; i--) {
+            for (let j = n; j >= 0; j--) {
+                for (let p = 0; p <= minProfit; p++) {
+                    let res = dp[j][p];
+                    if (j >= group[i]) {
+                        const nxtP = Math.min(profit[i] + p, minProfit);
+                        res = (res + dp[j - group[i]][nxtP]) % MOD;
+                    }
+                    dp[j][p] = res;
+                }
+            }
+        }
+
+        return dp[n][0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(N * m * n)$
+* Space complexity: $O(m * n)$
+
+> Where $N$ is the size of the $group$ array, $m$ is the given minimum profit, and $n$ is the number of group members.
\ No newline at end of file
diff --git a/articles/pseudo-palindromic-paths-in-a-binary-tree.md b/articles/pseudo-palindromic-paths-in-a-binary-tree.md
new file mode 100644
index 000000000..96bf58f3b
--- /dev/null
+++ b/articles/pseudo-palindromic-paths-in-a-binary-tree.md
@@ -0,0 +1,806 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def pseudoPalindromicPaths(self, root: Optional[TreeNode]) -> int:
+        count = defaultdict(int)
+        odd = 0
+
+        def dfs(cur):
+            nonlocal odd
+            if not cur:
+                return 0
+
+            count[cur.val] += 1
+            odd_change = 1 if count[cur.val] % 2 == 1 else -1
+            odd += odd_change
+
+            if not cur.left and not cur.right:
+                res = 1 if odd <= 1 else 0
+            else:
+                res = dfs(cur.left) + dfs(cur.right)
+
+            odd -= odd_change
+            count[cur.val] -= 1
+            return res
+
+        return dfs(root)
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public int pseudoPalindromicPaths(TreeNode root) {
+        Map<Integer, Integer> count = new HashMap<>();
+        int[] odd = new int[1];
+
+        return dfs(root, count, odd);
+    }
+
+    private int dfs(TreeNode cur, Map<Integer, Integer> count, int[] odd) {
+        if (cur == null) return 0;
+
+        count.put(cur.val, count.getOrDefault(cur.val, 0) + 1);
+        int odd_change = (count.get(cur.val) % 2 == 1) ? 1 : -1;
+        odd[0] += odd_change;
+
+        int res;
+        if (cur.left == null && cur.right == null) {
+            res = (odd[0] <= 1) ? 1 : 0;
+        } else {
+            res = dfs(cur.left, count, odd) + dfs(cur.right, count, odd);
+        }
+
+        odd[0] -= odd_change;
+        count.put(cur.val, count.get(cur.val) - 1);
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int pseudoPalindromicPaths(TreeNode* root) {
+        unordered_map<int, int> count;
+        int odd = 0;
+        return dfs(root, count, odd);
+    }
+
+private:
+    int dfs(TreeNode* cur, unordered_map<int, int>& count, int& odd) {
+        if (!cur) return 0;
+
+        count[cur->val]++;
+        int odd_change = (count[cur->val] % 2 == 1) ? 1 : -1;
+        odd += odd_change;
+
+        int res;
+        if (!cur->left && !cur->right) {
+            res = (odd <= 1) ? 1 : 0;
+        } else {
+            res = dfs(cur->left, count, odd) + dfs(cur->right, count, odd);
+        }
+
+        odd -= odd_change;
+        count[cur->val]--;
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number}
+     */
+    pseudoPalindromicPaths(root) {
+        const count = new Map();
+        let odd = 0;
+
+        const dfs = (cur) => {
+            if (!cur) return 0;
+
+            count.set(cur.val, (count.get(cur.val) || 0) + 1);
+            let odd_change = (count.get(cur.val) % 2 === 1) ? 1 : -1;
+            odd += odd_change;
+
+            let res;
+            if (!cur.left && !cur.right) {
+                res = (odd <= 1) ? 1 : 0;
+            } else {
+                res = dfs(cur.left) + dfs(cur.right);
+            }
+
+            odd -= odd_change;
+            count.set(cur.val, count.get(cur.val) - 1);
+            return res;
+        };
+
+        return dfs(root);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(h)$ for recursion stack.
+
+> Where $n$ is the number of nodes and $h$ is the height of the given tree.
+
+---
+
+## 2. Depth First Search (Using Array)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def pseudoPalindromicPaths(self, root: Optional[TreeNode]) -> int:
+        count = [0] * 10
+        odd = 0
+
+        def dfs(cur):
+            nonlocal odd
+            if not cur:
+                return 0
+
+            count[cur.val] ^= 1
+            odd += 1 if count[cur.val] else -1
+
+            if not cur.left and not cur.right and odd <= 1:
+                res = 1
+            else:
+                res = dfs(cur.left) + dfs(cur.right)
+
+            odd -= 1 if count[cur.val] else -1
+            count[cur.val] ^= 1
+
+            return res
+
+        return dfs(root)
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public int pseudoPalindromicPaths(TreeNode root) {
+        int[] count = new int[10];
+        return dfs(root, count, 0);
+    }
+
+    private int dfs(TreeNode cur, int[] count, int odd) {
+        if (cur == null) return 0;
+
+        count[cur.val] ^= 1;
+        odd += count[cur.val] == 1 ? 1 : -1;
+
+        int res = (cur.left == null && cur.right == null && odd <= 1) ? 1 
+                  : dfs(cur.left, count, odd) + dfs(cur.right, count, odd);
+
+        odd += count[cur.val] == 1 ? 1 : -1;
+        count[cur.val] ^= 1;
+
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int pseudoPalindromicPaths(TreeNode* root) {
+        int count[10] = {};
+        return dfs(root, count, 0);
+    }
+
+private:
+    int dfs(TreeNode* cur, int count[], int odd) {
+        if (!cur) return 0;
+
+        count[cur->val] ^= 1;
+        odd += (count[cur->val] == 1) ? 1 : -1;
+
+        int res = (!cur->left && !cur->right && odd <= 1) ? 1 
+                  : dfs(cur->left, count, odd) + dfs(cur->right, count, odd);
+
+        odd += (count[cur->val] == 1) ? 1 : -1;
+        count[cur->val] ^= 1;
+
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number}
+     */
+    pseudoPalindromicPaths(root) {
+        const count = new Array(10).fill(0);
+
+        const dfs = (cur, odd) => {
+            if (!cur) return 0;
+
+            count[cur.val] ^= 1;
+            odd += count[cur.val] === 1 ? 1 : -1;
+
+            let res = (!cur.left && !cur.right && odd <= 1) 
+                    ? 1 : dfs(cur.left, odd) + dfs(cur.right, odd);
+
+            odd += count[cur.val] === 1 ? 1 : -1;
+            count[cur.val] ^= 1;
+
+            return res;
+        };
+
+        return dfs(root, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(h)$ for recursion stack.
+
+> Where $n$ is the number of nodes and $h$ is the height of the given tree.
+
+---
+
+## 3. Depth First Search (Bit Mask)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def pseudoPalindromicPaths(self, root: Optional[TreeNode]) -> int:
+        def dfs(node, path):
+            if not node:
+                return 0
+
+            path ^= 1 << node.val
+            if not node.left and not node.right:
+                return 1 if (path & (path - 1)) == 0 else 0
+
+            return dfs(node.left, path) + dfs(node.right, path)
+
+        return dfs(root, 0)
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public int pseudoPalindromicPaths(TreeNode root) {
+        return dfs(root, 0);
+    }
+
+    private int dfs(TreeNode node, int path) {
+        if (node == null) return 0;
+
+        path ^= (1 << node.val);
+        if (node.left == null && node.right == null) {
+            return (path & (path - 1)) == 0 ? 1 : 0;
+        }
+
+        return dfs(node.left, path) + dfs(node.right, path);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int pseudoPalindromicPaths(TreeNode* root) {
+        return dfs(root, 0);
+    }
+
+private:
+    int dfs(TreeNode* node, int path) {
+        if (!node) return 0;
+
+        path ^= (1 << node->val);
+        if (!node->left && !node->right) {
+            return (path & (path - 1)) == 0 ? 1 : 0;
+        }
+
+        return dfs(node->left, path) + dfs(node->right, path);
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number}
+     */
+    pseudoPalindromicPaths(root) {
+        const dfs = (node, path) => {
+            if (!node) return 0;
+
+            path ^= (1 << node.val);
+            if (!node.left && !node.right) {
+                return (path & (path - 1)) === 0 ? 1 : 0;
+            }
+
+            return dfs(node.left, path) + dfs(node.right, path);
+        };
+
+        return dfs(root, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(h)$ for recursion stack.
+
+> Where $n$ is the number of nodes and $h$ is the height of the given tree.
+
+---
+
+## 4. Breadth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def pseudoPalindromicPaths(self, root: Optional[TreeNode]) -> int:
+        res = 0
+        q = deque([(root, 0)])
+        while q:
+            node, path = q.popleft()
+            path ^= 1 << node.val
+
+            if not node.left and not node.right:
+                if path & (path - 1) == 0:
+                    res += 1
+                continue
+
+            if node.left:
+                q.append((node.left, path))
+            if node.right:
+                q.append((node.right, path))
+
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public int pseudoPalindromicPaths(TreeNode root) {
+        int count = 0;
+        Queue<Pair> q = new LinkedList<>();
+        q.offer(new Pair(root, 0));
+        while (!q.isEmpty()) {
+            Pair p = q.poll();
+            TreeNode node = p.node;
+            int path = p.path ^ (1 << node.val);
+
+            if (node.left == null && node.right == null) {
+                if ((path & (path - 1)) == 0) {
+                    count++;
+                }
+            } else {
+                if (node.left != null) q.offer(new Pair(node.left, path));
+                if (node.right != null) q.offer(new Pair(node.right, path));
+            }
+        }
+
+        return count;
+    }
+
+    private static class Pair {
+        TreeNode node;
+        int path;
+        Pair(TreeNode node, int path) {
+            this.node = node;
+            this.path = path;
+        }
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int pseudoPalindromicPaths(TreeNode* root) {
+        int res = 0;
+        queue<pair<TreeNode*, int>> q;
+        q.push({root, 0});
+        while (!q.empty()) {
+            auto [node, path] = q.front();q.pop();
+            path ^= (1 << node->val);
+
+            if (!node->left && !node->right) {
+                if ((path & (path - 1)) == 0) res++;
+                continue;
+            }
+
+            if (node->left) q.push({node->left, path});
+            if (node->right) q.push({node->right, path});
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number}
+     */
+    pseudoPalindromicPaths(root) {
+        let res = 0;
+        const q = new Queue([[root, 0]]);
+
+        while (!q.isEmpty()) {
+            const [node, path] = q.pop();
+            const newPath = path ^ (1 << node.val);
+
+            if (!node.left && !node.right) {
+                if ((newPath & (newPath - 1)) === 0) res++;
+                continue;
+            }
+
+            if (node.left) q.push([node.left, newPath]);
+            if (node.right) q.push([node.right, newPath]);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 5. Iterative DFS
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def pseudoPalindromicPaths(self, root: Optional[TreeNode]) -> int:
+        count = 0
+        stack = [(root, 0)]
+        while stack:
+            node, path = stack.pop()
+            path ^= (1 << node.val)
+
+            if not node.left and not node.right:
+                if path & (path - 1) == 0:
+                    count += 1
+            else:
+                if node.right:
+                    stack.append((node.right, path))
+                if node.left:
+                    stack.append((node.left, path))
+
+        return count
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public int pseudoPalindromicPaths(TreeNode root) {
+        int count = 0;
+        Stack<Pair> stack = new Stack<>();
+        stack.push(new Pair(root, 0));
+
+        while (!stack.isEmpty()) {
+            Pair p = stack.pop();
+            TreeNode node = p.node;
+            int path = p.path ^ (1 << node.val);
+
+            if (node.left == null && node.right == null) {
+                if ((path & (path - 1)) == 0) {
+                    count++;
+                }
+            } else {
+                if (node.right != null) stack.push(new Pair(node.right, path));
+                if (node.left != null) stack.push(new Pair(node.left, path));
+            }
+        }
+        return count;
+    }
+
+    private static class Pair {
+        TreeNode node;
+        int path;
+        Pair(TreeNode node, int path) {
+            this.node = node;
+            this.path = path;
+        }
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int pseudoPalindromicPaths(TreeNode* root) {
+        stack<pair<TreeNode*, int>> s;
+        s.push({root, 0});
+        int count = 0;
+
+        while (!s.empty()) {
+            auto [node, path] = s.top();
+            s.pop();
+            path ^= (1 << node->val);
+
+            if (!node->left && !node->right) {
+                if ((path & (path - 1)) == 0) count++;
+            } else {
+                if (node->right) s.push({node->right, path});
+                if (node->left) s.push({node->left, path});
+            }
+        }
+
+        return count;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number}
+     */
+    pseudoPalindromicPaths(root) {
+        let count = 0;
+        const stack = [[root, 0]];
+
+        while (stack.length) {
+            const [node, path] = stack.pop();
+            const newPath = path ^ (1 << node.val);
+
+            if (!node.left && !node.right) {
+                if ((newPath & (newPath - 1)) === 0) count++;
+            } else {
+                if (node.right) stack.push([node.right, newPath]);
+                if (node.left) stack.push([node.left, newPath]);
+            }
+        }
+
+        return count;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(h)$
+
+> Where $n$ is the number of nodes and $h$ is the height of the given tree.
\ No newline at end of file
diff --git a/articles/push-dominoes.md b/articles/push-dominoes.md
new file mode 100644
index 000000000..efe99877f
--- /dev/null
+++ b/articles/push-dominoes.md
@@ -0,0 +1,749 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def pushDominoes(self, dominoes: str) -> str:
+        n = len(dominoes)
+        res = list(dominoes)
+
+        for i in range(n):
+            if dominoes[i] != '.':
+                continue
+            
+            l, r = i - 1, i + 1
+            
+            while l >= 0 and dominoes[l] == '.':
+                l -= 1
+            
+            while r < n and dominoes[r] == '.':
+                r += 1
+            
+            left_force = dominoes[l] if l >= 0 else None
+            right_force = dominoes[r] if r < n else None
+
+            if left_force == 'R' and right_force == 'L':
+                if (i - l) < (r - i):
+                    res[i] = 'R'
+                elif (r - i) < (i - l):
+                    res[i] = 'L'
+            elif left_force == 'R':
+                res[i] = 'R'
+            elif right_force == 'L':
+                res[i] = 'L'
+
+        return "".join(res)
+```
+
+```java
+public class Solution {
+    public String pushDominoes(String dominoes) {
+        int n = dominoes.length();
+        char[] res = dominoes.toCharArray();
+
+        for (int i = 0; i < n; i++) {
+            if (dominoes.charAt(i) != '.') continue;
+
+            int l = i - 1, r = i + 1;
+
+            while (l >= 0 && dominoes.charAt(l) == '.') l--;
+            while (r < n && dominoes.charAt(r) == '.') r++;
+
+            char leftForce = (l >= 0) ? dominoes.charAt(l) : ' ';
+            char rightForce = (r < n) ? dominoes.charAt(r) : ' ';
+
+            if (leftForce == 'R' && rightForce == 'L') {
+                if ((i - l) < (r - i)) res[i] = 'R';
+                else if ((r - i) < (i - l)) res[i] = 'L';
+            } else if (leftForce == 'R') {
+                res[i] = 'R';
+            } else if (rightForce == 'L') {
+                res[i] = 'L';
+            }
+        }
+
+        return new String(res);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string pushDominoes(string dominoes) {
+        int n = dominoes.size();
+        vector<char> res(dominoes.begin(), dominoes.end());
+
+        for (int i = 0; i < n; i++) {
+            if (dominoes[i] != '.') continue;
+
+            int l = i - 1, r = i + 1;
+
+            while (l >= 0 && dominoes[l] == '.') l--;
+            while (r < n && dominoes[r] == '.') r++;
+
+            char leftForce = (l >= 0) ? dominoes[l] : ' ';
+            char rightForce = (r < n) ? dominoes[r] : ' ';
+
+            if (leftForce == 'R' && rightForce == 'L') {
+                if ((i - l) < (r - i)) res[i] = 'R';
+                else if ((r - i) < (i - l)) res[i] = 'L';
+            } else if (leftForce == 'R') {
+                res[i] = 'R';
+            } else if (rightForce == 'L') {
+                res[i] = 'L';
+            }
+        }
+
+        return string(res.begin(), res.end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} dominoes
+     * @return {string}
+     */
+    pushDominoes(dominoes) {
+        const n = dominoes.length;
+        const res = dominoes.split("");
+
+        for (let i = 0; i < n; i++) {
+            if (dominoes[i] !== ".") continue;
+
+            let l = i - 1, r = i + 1;
+
+            while (l >= 0 && dominoes[l] === ".") l--;
+            while (r < n && dominoes[r] === ".") r++;
+
+            const leftForce = l >= 0 ? dominoes[l] : null;
+            const rightForce = r < n ? dominoes[r] : null;
+
+            if (leftForce === "R" && rightForce === "L") {
+                if ((i - l) < (r - i)) res[i] = "R";
+                else if ((r - i) < (i - l)) res[i] = "L";
+            } else if (leftForce === "R") {
+                res[i] = "R";
+            } else if (rightForce === "L") {
+                res[i] = "L";
+            }
+        }
+
+        return res.join("");
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$ for only the output string.
+
+---
+
+## 2. Force From Left & Right
+
+::tabs-start
+
+```python
+class Solution:
+    def pushDominoes(self, dominoes: str) -> str:
+        n = len(dominoes)
+        left = [float('inf')] * n
+        right = [float('inf')] * n
+        res = list(dominoes)
+        
+        force = float('inf')
+        for i in range(n):
+            if dominoes[i] == 'R':
+                force = 0
+            elif dominoes[i] == 'L':
+                force = float('inf')
+            else:
+                force += 1
+            right[i] = force
+        
+        force = float('inf')
+        for i in range(n - 1, -1, -1):
+            if dominoes[i] == 'L':
+                force = 0
+            elif dominoes[i] == 'R':
+                force = float('inf')
+            else:
+                force += 1
+            left[i] = force
+        
+        for i in range(n):
+            if left[i] < right[i]:
+                res[i] = 'L'
+            elif right[i] < left[i]:
+                res[i] = 'R'
+        
+        return "".join(res)
+```
+
+```java
+public class Solution {
+    public String pushDominoes(String dominoes) {
+        int n = dominoes.length();
+        int[] left = new int[n];
+        int[] right = new int[n];
+        char[] res = dominoes.toCharArray();
+
+        int force = Integer.MAX_VALUE;
+        for (int i = 0; i < n; i++) {
+            if (dominoes.charAt(i) == 'R') {
+                force = 0;
+            } else if (dominoes.charAt(i) == 'L') {
+                force = Integer.MAX_VALUE;
+            } else {
+                force = force == Integer.MAX_VALUE ? Integer.MAX_VALUE : force + 1;
+            }
+            right[i] = force;
+        }
+
+        force = Integer.MAX_VALUE;
+        for (int i = n - 1; i >= 0; i--) {
+            if (dominoes.charAt(i) == 'L') {
+                force = 0;
+            } else if (dominoes.charAt(i) == 'R') {
+                force = Integer.MAX_VALUE;
+            } else {
+                force = force == Integer.MAX_VALUE ? Integer.MAX_VALUE : force + 1;
+            }
+            left[i] = force;
+        }
+
+        for (int i = 0; i < n; i++) {
+            if (left[i] < right[i]) {
+                res[i] = 'L';
+            } else if (right[i] < left[i]) {
+                res[i] = 'R';
+            }
+        }
+
+        return new String(res);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string pushDominoes(string dominoes) {
+        int n = dominoes.size();
+        vector<int> left(n, INT_MAX);
+        vector<int> right(n, INT_MAX);
+        vector<char> res(dominoes.begin(), dominoes.end());
+
+        int force = INT_MAX;
+        for (int i = 0; i < n; i++) {
+            if (dominoes[i] == 'R') {
+                force = 0;
+            } else if (dominoes[i] == 'L') {
+                force = INT_MAX;
+            } else {
+                force = (force == INT_MAX) ? INT_MAX : force + 1;
+            }
+            right[i] = force;
+        }
+
+        force = INT_MAX;
+        for (int i = n - 1; i >= 0; i--) {
+            if (dominoes[i] == 'L') {
+                force = 0;
+            } else if (dominoes[i] == 'R') {
+                force = INT_MAX;
+            } else {
+                force = (force == INT_MAX) ? INT_MAX : force + 1;
+            }
+            left[i] = force;
+        }
+
+        for (int i = 0; i < n; i++) {
+            if (left[i] < right[i]) {
+                res[i] = 'L';
+            } else if (right[i] < left[i]) {
+                res[i] = 'R';
+            }
+        }
+
+        return string(res.begin(), res.end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} dominoes
+     * @return {string}
+     */
+    pushDominoes(dominoes) {
+        const n = dominoes.length;
+        const left = new Array(n).fill(Infinity);
+        const right = new Array(n).fill(Infinity);
+        const res = dominoes.split("");
+
+        let force = Infinity;
+        for (let i = 0; i < n; i++) {
+            if (dominoes[i] === "R") {
+                force = 0;
+            } else if (dominoes[i] === "L") {
+                force = Infinity;
+            } else {
+                force = force === Infinity ? Infinity : force + 1;
+            }
+            right[i] = force;
+        }
+
+        force = Infinity;
+        for (let i = n - 1; i >= 0; i--) {
+            if (dominoes[i] === "L") {
+                force = 0;
+            } else if (dominoes[i] === "R") {
+                force = Infinity;
+            } else {
+                force = force === Infinity ? Infinity : force + 1;
+            }
+            left[i] = force;
+        }
+
+        for (let i = 0; i < n; i++) {
+            if (left[i] < right[i]) {
+                res[i] = "L";
+            } else if (right[i] < left[i]) {
+                res[i] = "R";
+            }
+        }
+
+        return res.join("");
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Simulation (Queue)
+
+::tabs-start
+
+```python
+class Solution:
+    def pushDominoes(self, dominoes: str) -> str:
+        dom = list(dominoes)
+        q = deque()
+
+        for i, d in enumerate(dom):
+            if d != ".":
+                q.append((i, d))
+
+        while q:
+            i, d = q.popleft()
+
+            if d == "L" and i > 0 and dom[i - 1] == ".":
+                q.append((i - 1, "L"))
+                dom[i - 1] = "L"
+            elif d == "R":
+                if i + 1 < len(dom) and dom[i + 1] == ".":
+                    if i + 2 < len(dom) and dom[i + 2] == "L":
+                        q.popleft()
+                    else:
+                        q.append((i + 1, "R"))
+                        dom[i + 1] = "R"
+
+        return "".join(dom)
+```
+
+```java
+public class Solution {
+    public String pushDominoes(String dominoes) {
+        char[] dom = dominoes.toCharArray();
+        Queue<int[]> q = new LinkedList<>();
+
+        for (int i = 0; i < dom.length; i++) {
+            if (dom[i] != '.') {
+                q.add(new int[] {i, dom[i]});
+            }
+        }
+
+        while (!q.isEmpty()) {
+            int[] curr = q.poll();
+            int i = curr[0];
+            char d = (char) curr[1];
+
+            if (d == 'L' && i > 0 && dom[i - 1] == '.') {
+                q.add(new int[] {i - 1, 'L'});
+                dom[i - 1] = 'L';
+            } else if (d == 'R') {
+                if (i + 1 < dom.length && dom[i + 1] == '.') {
+                    if (i + 2 < dom.length && dom[i + 2] == 'L') {
+                        q.poll();
+                    } else {
+                        q.add(new int[] {i + 1, 'R'});
+                        dom[i + 1] = 'R';
+                    }
+                }
+            }
+        }
+
+        return new String(dom);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string pushDominoes(string dominoes) {
+        vector<char> dom(dominoes.begin(), dominoes.end());
+        queue<pair<int, char>> q;
+
+        for (int i = 0; i < dom.size(); i++) {
+            if (dom[i] != '.') {
+                q.push({i, dom[i]});
+            }
+        }
+
+        while (!q.empty()) {
+            auto [i, d] = q.front();
+            q.pop();
+
+            if (d == 'L' && i > 0 && dom[i - 1] == '.') {
+                q.push({i - 1, 'L'});
+                dom[i - 1] = 'L';
+            } else if (d == 'R') {
+                if (i + 1 < dom.size() && dom[i + 1] == '.') {
+                    if (i + 2 < dom.size() && dom[i + 2] == 'L') {
+                        q.pop();
+                    } else {
+                        q.push({i + 1, 'R'});
+                        dom[i + 1] = 'R';
+                    }
+                }
+            }
+        }
+
+        return string(dom.begin(), dom.end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} dominoes
+     * @return {string}
+     */
+    pushDominoes(dominoes) {
+        const dom = dominoes.split("");
+        const q = new Queue();
+
+        for (let i = 0; i < dom.length; i++) {
+            if (dom[i] !== ".") {
+                q.push([i, dom[i]]);
+            }
+        }
+
+        while (!q.isEmpty()) {
+            const [i, d] = q.pop();
+
+            if (d === "L" && i > 0 && dom[i - 1] === ".") {
+                q.push([i - 1, "L"]);
+                dom[i - 1] = "L";
+            } else if (d === "R") {
+                if (i + 1 < dom.length && dom[i + 1] === ".") {
+                    if (i + 2 < dom.length && dom[i + 2] === "L") {
+                        q.pop();
+                    } else {
+                        q.push([i + 1, "R"]);
+                        dom[i + 1] = "R";
+                    }
+                }
+            }
+        }
+
+        return dom.join("");
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Iteration (Greedy)
+
+::tabs-start
+
+```python
+class Solution:
+    def pushDominoes(self, dominoes: str) -> str:
+        res = []
+        dots = 0
+        R = False
+
+        for d in dominoes:
+            if d == '.':
+                dots += 1
+            elif d == 'R':
+                if R:
+                    # Previous was 'R', and current is also 'R'.
+                    # Append 'R' for all the dots between them.
+                    res.append('R' * (dots + 1))
+                elif dots > 0:
+                    # Previous was not 'R'. The previous dots remain unchanged.
+                    res.append('.' * dots)
+                dots = 0
+                R = True  # Current is 'R'
+            else:
+                if R:
+                    # Append the previous 'R'.
+                    res.append('R')
+                    if dots > 0:
+                        # Half the dots are affected by the previous 'R'.
+                        res.append('R' * (dots // 2))
+
+                        # Add a '.' if there's an odd number of dots.
+                        if (dots % 2) != 0:
+                            res.append('.')
+
+                        # Append half the dots as 'L'.
+                        res.append('L' * (dots // 2))
+                    
+                    # Append the current 'L'.
+                    res.append('L')
+                    R, dots = False, 0
+                else:
+                    # There is no 'R' on the left.
+                    # Append 'L' for all the dots and the current 'L'.
+                    res.append('L' * (dots + 1))
+                    dots = 0
+            
+        if R:
+            # Trailing dots are affected by the last 'R'.
+            res.append('R' * (dots + 1))
+        else:
+            # Trailing dots remain unchanged as there is no previous 'R'.
+            res.append('.' * dots)
+            
+        return ''.join(res)
+```
+
+```java
+public class Solution {
+    public String pushDominoes(String dominoes) {
+        StringBuilder res = new StringBuilder();
+        int dots = 0;
+        boolean R = false;
+
+        for (char d : dominoes.toCharArray()) {
+            if (d == '.') {
+                dots++;
+            } else if (d == 'R') {
+                if (R) {
+                    // Previous was 'R', and current is also 'R'.
+                    // Append 'R' for all the dots between them.
+                    res.append("R".repeat(dots + 1));
+                } else if (dots > 0) {
+                    // Previous was not 'R'. The previous dots remain unchanged.
+                    res.append(".".repeat(dots));
+                }
+                dots = 0;
+                R = true; // Current is 'R'.
+            } else {
+                if (R) {
+                    // Append the previous 'R'.
+                    res.append("R");
+                    if (dots > 0) {
+                        // Half the dots are affected by the previous 'R'.
+                        res.append("R".repeat(dots / 2));
+
+                        // Add a '.' if there's an odd number of dots.
+                        if (dots % 2 != 0) {
+                            res.append(".");
+                        }
+
+                        // Append half the dots as 'L'.
+                        res.append("L".repeat(dots / 2));
+                    }
+                    // Append the current 'L'.
+                    res.append("L");
+                    R = false;
+                    dots = 0;
+                } else {
+                    // There is no 'R' on the left.
+                    // Append 'L' for all the dots and the current 'L'.
+                    res.append("L".repeat(dots + 1));
+                    dots = 0;
+                }
+            }
+        }
+
+        if (R) {
+            // Trailing dots are affected by the last 'R'.
+            res.append("R".repeat(dots + 1));
+        } else {
+            // Trailing dots remain unchanged as there is no previous 'R'.
+            res.append(".".repeat(dots));
+        }
+
+        return res.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string pushDominoes(string dominoes) {
+        string res = "";
+        int dots = 0;
+        bool R = false;
+
+        for (char d : dominoes) {
+            if (d == '.') {
+                dots++;
+            } else if (d == 'R') {
+                if (R) {
+                    // Previous was 'R', and current is also 'R'.
+                    // Append 'R' for all the dots between them.
+                    res += string(dots + 1, 'R');
+                } else if (dots > 0) {
+                    // Previous was not 'R'. The previous dots remain unchanged.
+                    res += string(dots, '.');
+                }
+                dots = 0;
+                R = true; // Current is 'R'.
+            } else {
+                if (R) {
+                    // Append the previous 'R'.
+                    res += 'R';
+                    if (dots > 0) {
+                        // Half the dots are affected by the previous 'R'.
+                        res += string(dots / 2, 'R');
+
+                        // Add a '.' if there's an odd number of dots.
+                        if (dots % 2 != 0) {
+                            res += '.';
+                        }
+
+                        // Append half the dots as 'L'.
+                        res += string(dots / 2, 'L');
+                    }
+                    // Append the current 'L'.
+                    res += 'L';
+                    R = false;
+                    dots = 0;
+                } else {
+                    // There is no 'R' on the left.
+                    // Append 'L' for all the dots and the current 'L'.
+                    res += string(dots + 1, 'L');
+                    dots = 0;
+                }
+            }
+        }
+
+        if (R) {
+            // Trailing dots are affected by the last 'R'.
+            res += string(dots + 1, 'R');
+        } else {
+            // Trailing dots remain unchanged as there is no previous 'R'.
+            res += string(dots, '.');
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} dominoes
+     * @return {string}
+     */
+    pushDominoes(dominoes) {
+        let res = [];
+        let dots = 0;
+        let R = false;
+
+        for (let d of dominoes) {
+            if (d === '.') {
+                dots++;
+            } else if (d === 'R') {
+                if (R) {
+                    // Previous was 'R', and current is also 'R'.
+                    // Append 'R' for all the dots between them.
+                    res.push('R'.repeat(dots + 1));
+                } else if (dots > 0) {
+                    // Previous was not 'R'. The previous dots remain unchanged.
+                    res.push('.'.repeat(dots));
+                }
+                dots = 0;
+                R = true; // Current is 'R'.
+            } else {
+                if (R) {
+                    // Append the previous 'R'.
+                    res.push('R');
+                    if (dots > 0) {
+                        // Half the dots are affected by the previous 'R'.
+                        res.push('R'.repeat(Math.floor(dots / 2)));
+
+                        // Add a '.' if there's an odd number of dots.
+                        if (dots % 2 !== 0) {
+                            res.push('.');
+                        }
+
+                        // Append half the dots as 'L'.
+                        res.push('L'.repeat(Math.floor(dots / 2)));
+                    }
+                    // Append the current 'L'.
+                    res.push('L');
+                    R = false;
+                    dots = 0;
+                } else {
+                    // There is no 'R' on the left.
+                    // Append 'L' for all the dots and the current 'L'.
+                    res.push('L'.repeat(dots + 1));
+                    dots = 0;
+                }
+            }
+        }
+
+        if (R) {
+            // Trailing dots are affected by the last 'R'.
+            res.push('R'.repeat(dots + 1));
+        } else {
+            // Trailing dots remain unchanged as there is no previous 'R'.
+            res.push('.'.repeat(dots));
+        }
+
+        return res.join('');
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for only the output string.
\ No newline at end of file
diff --git a/articles/put-marbles-in-bags.md b/articles/put-marbles-in-bags.md
new file mode 100644
index 000000000..a0abf8a29
--- /dev/null
+++ b/articles/put-marbles-in-bags.md
@@ -0,0 +1,501 @@
+## 1. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def putMarbles(self, weights: List[int], k: int) -> int:
+        n = len(weights)
+        cache = {}
+
+        def dfs(i, k):
+            if (i, k) in cache:
+                return cache[(i, k)]
+            if k == 0:
+                return [0, 0]
+            if i == n - 1 or n - i - 1 < k:
+                return [-float("inf"), float("inf")]
+
+            res = [0, float("inf")]  # [maxScore, minScore]
+
+            # make partition
+            cur = dfs(i + 1, k - 1)
+            res[0] = max(res[0], weights[i] + weights[i + 1] + cur[0])
+            res[1] = min(res[1], weights[i] + weights[i + 1] + cur[1])
+
+            # skip
+            cur = dfs(i + 1, k)
+            res[0] = max(res[0], cur[0])
+            res[1] = min(res[1], cur[1])
+
+            cache[(i, k)] = res
+            return res
+
+        ans = dfs(0, k - 1)
+        return ans[0] - ans[1]
+```
+
+```java
+public class Solution {
+    Map<String, long[]> cache = new HashMap<>();
+
+    public long putMarbles(int[] weights, int k) {
+        int n = weights.length;
+        long[] ans = dfs(0, k - 1, weights, n);
+        return ans[0] - ans[1];
+    }
+
+    private long[] dfs(int i, int k, int[] weights, int n) {
+        String key = i + "," + k;
+        if (cache.containsKey(key)) return cache.get(key);
+        if (k == 0) return new long[]{0L, 0L};
+        if (i == n - 1 || n - i - 1 < k) {
+            return new long[]{(long)-1e15, (long)1e15};
+        }
+
+        long[] res = new long[]{0L, (long)1e15};
+
+        long[] cur = dfs(i + 1, k - 1, weights, n);
+        res[0] = Math.max(res[0], weights[i] + weights[i + 1] + cur[0]);
+        res[1] = Math.min(res[1], weights[i] + weights[i + 1] + cur[1]);
+
+        cur = dfs(i + 1, k, weights, n);
+        res[0] = Math.max(res[0], cur[0]);
+        res[1] = Math.min(res[1], cur[1]);
+
+        cache.put(key, res);
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    unordered_map<string, pair<long long, long long>> cache;
+
+    long long putMarbles(vector<int>& weights, int k) {
+        int n = weights.size();
+        auto ans = dfs(0, k - 1, weights, n);
+        return ans.first - ans.second;
+    }
+
+    pair<long long, long long> dfs(int i, int k, vector<int>& weights, int n) {
+        string key = to_string(i) + "," + to_string(k);
+        if (cache.count(key)) return cache[key];
+        if (k == 0) return {0LL, 0LL};
+        if (i == n - 1 || n - i - 1 < k) {
+            return {-1000000000000000LL, 1000000000000000LL};
+        }
+
+        pair<long long, long long> res = {0LL, 1000000000000000LL};
+
+        auto cur = dfs(i + 1, k - 1, weights, n);
+        res.first = max(res.first, (long long)weights[i] + weights[i + 1] + cur.first);
+        res.second = min(res.second, (long long)weights[i] + weights[i + 1] + cur.second);
+
+        cur = dfs(i + 1, k, weights, n);
+        res.first = max(res.first, cur.first);
+        res.second = min(res.second, cur.second);
+
+        return cache[key] = res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} weights
+     * @param {number} k
+     * @return {number}
+     */
+    putMarbles(weights, k) {
+        const n = weights.length;
+        const cache = new Map();
+
+        const dfs = (i, k) => {
+            const key = `${i},${k}`;
+            if (cache.has(key)) return cache.get(key);
+            if (k === 0) return [0, 0];
+            if (i === n - 1 || n - i - 1 < k) return [-1e15, 1e15];
+
+            let res = [0, 1e15];
+
+            let cur = dfs(i + 1, k - 1);
+            res[0] = Math.max(res[0], weights[i] + weights[i + 1] + cur[0]);
+            res[1] = Math.min(res[1], weights[i] + weights[i + 1] + cur[1]);
+
+            cur = dfs(i + 1, k);
+            res[0] = Math.max(res[0], cur[0]);
+            res[1] = Math.min(res[1], cur[1]);
+
+            cache.set(key, res);
+            return res;
+        };
+
+        const ans = dfs(0, k - 1);
+        return ans[0] - ans[1];
+    }
+}
+```
+
+```csharp
+public class Solution {
+    Dictionary<string, long[]> cache = new Dictionary<string, long[]>();
+
+    public long PutMarbles(int[] weights, int k) {
+        int n = weights.Length;
+        long[] ans = Dfs(0, k - 1, weights, n);
+        return (int)(ans[0] - ans[1]);
+    }
+
+    private long[] Dfs(int i, int k, int[] weights, int n) {
+        string key = $"{i},{k}";
+        if (cache.ContainsKey(key)) return cache[key];
+        if (k == 0) return new long[] { 0L, 0L };
+        if (i == n - 1 || n - i - 1 < k) {
+            return new long[] { -1000000000000000L, 1000000000000000L };
+        }
+
+        long[] res = new long[] { 0L, 1000000000000000L };
+
+        long[] cur = Dfs(i + 1, k - 1, weights, n);
+        res[0] = Math.Max(res[0], weights[i] + weights[i + 1] + cur[0]);
+        res[1] = Math.Min(res[1], weights[i] + weights[i + 1] + cur[1]);
+
+        cur = Dfs(i + 1, k, weights, n);
+        res[0] = Math.Max(res[0], cur[0]);
+        res[1] = Math.Min(res[1], cur[1]);
+
+        cache[key] = res;
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * k)$
+* Space complexity: $O(n * k)$
+
+> Where $n$ is the number of marbles, and $k$ is the number of bags.
+
+---
+
+## 2. Greedy + Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def putMarbles(self, weights: List[int], k: int) -> int:
+        if k == 1:
+            return 0
+
+        splits = []
+        for i in range(len(weights) - 1):
+            splits.append(weights[i] + weights[i + 1])
+
+        splits.sort()
+        i = k - 1
+
+        max_score = sum(splits[-i:])
+        min_score = sum(splits[:i])
+        return max_score - min_score
+```
+
+```java
+public class Solution {
+    public long putMarbles(int[] weights, int k) {
+        if (k == 1) return 0L;
+
+        int n = weights.length;
+        List<Integer> splits = new ArrayList<>();
+
+        for (int i = 0; i < n - 1; i++) {
+            splits.add(weights[i] + weights[i + 1]);
+        }
+
+        Collections.sort(splits);
+        int i = k - 1;
+        long maxScore = 0, minScore = 0;
+
+        for (int j = 0; j < i; j++) minScore += splits.get(j);
+        for (int j = splits.size() - i; j < splits.size(); j++) {
+            maxScore += splits.get(j);
+        }
+
+        return maxScore - minScore;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long putMarbles(vector<int>& weights, int k) {
+        if (k == 1) return 0LL;
+
+        int n = weights.size();
+        vector<int> splits;
+
+        for (int i = 0; i < n - 1; ++i) {
+            splits.push_back(weights[i] + weights[i + 1]);
+        }
+
+        sort(splits.begin(), splits.end());
+        int i = k - 1;
+        long long minScore = 0, maxScore = 0;
+
+        for (int j = 0; j < i; ++j) minScore += splits[j];
+        for (int j = splits.size() - i; j < splits.size(); ++j) {
+            maxScore += splits[j];
+        }   
+
+        return maxScore - minScore;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} weights
+     * @param {number} k
+     * @return {number}
+     */
+    putMarbles(weights, k) {
+        if (k === 1) return 0;
+
+        const splits = [];
+        for (let i = 0; i < weights.length - 1; i++) {
+            splits.push(weights[i] + weights[i + 1]);
+        }
+
+        splits.sort((a, b) => a - b);
+        const i = k - 1;
+
+        let minScore = 0, maxScore = 0;
+        for (let j = 0; j < i; j++) minScore += splits[j];
+        for (let j = splits.length - i; j < splits.length; j++) {
+            maxScore += splits[j];
+        }
+
+        return maxScore - minScore;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public long PutMarbles(int[] weights, int k) {
+        if (k == 1) return 0L;
+
+        int n = weights.Length;
+        List<int> splits = new List<int>();
+
+        for (int i = 0; i < n - 1; i++) {
+            splits.Add(weights[i] + weights[i + 1]);
+        }
+
+        splits.Sort();
+        int iVal = k - 1;
+        long minScore = 0, maxScore = 0;
+
+        for (int j = 0; j < iVal; j++) minScore += splits[j];
+        for (int j = splits.Count - iVal; j < splits.Count; j++) {
+            maxScore += splits[j];
+        }
+
+        return maxScore - minScore;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the number of marbles, and $k$ is the number of bags.
+
+---
+
+## 3. Heap
+
+::tabs-start
+
+```python
+class Solution:
+    def putMarbles(self, weights: List[int], k: int) -> int:
+        if k == 1:
+            return 0
+
+        max_heap = []
+        min_heap = []
+
+        for i in range(len(weights) - 1):
+            split = weights[i] + weights[i + 1]
+
+            if len(max_heap) < k - 1:
+                heapq.heappush(max_heap, split)
+            else:
+                heapq.heappushpop(max_heap, split)
+
+            if len(min_heap) < k - 1:
+                heapq.heappush(min_heap, -split)
+            else:
+                heapq.heappushpop(min_heap, -split)
+
+        max_score = sum(max_heap)
+        min_score = -sum(min_heap)
+        return max_score - min_score
+```
+
+```java
+public class Solution {
+    public long putMarbles(int[] weights, int k) {
+        if (k == 1) return 0L;
+
+        PriorityQueue<Integer> maxHeap = new PriorityQueue<>();
+        PriorityQueue<Integer> minHeap = new PriorityQueue<>(Collections.reverseOrder());
+
+        for (int i = 0; i < weights.length - 1; i++) {
+            int split = weights[i] + weights[i + 1];
+
+            if (maxHeap.size() < k - 1) maxHeap.offer(split);
+            else if (split > maxHeap.peek()) {
+                maxHeap.poll();
+                maxHeap.offer(split);
+            }
+
+            if (minHeap.size() < k - 1) minHeap.offer(split);
+            else if (split < minHeap.peek()) {
+                minHeap.poll();
+                minHeap.offer(split);
+            }
+        }
+
+        long maxScore = 0, minScore = 0;
+        for (int val : maxHeap) maxScore += val;
+        for (int val : minHeap) minScore += val;
+
+        return maxScore - minScore;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long putMarbles(vector<int>& weights, int k) {
+        if (k == 1) return 0LL;
+
+        priority_queue<int, vector<int>, greater<int>> maxHeap;
+        priority_queue<int> minHeap;
+
+        for (int i = 0; i < weights.size() - 1; ++i) {
+            int split = weights[i] + weights[i + 1];
+
+            if ((int)maxHeap.size() < k - 1) maxHeap.push(split);
+            else if (split > maxHeap.top()) {
+                maxHeap.pop();
+                maxHeap.push(split);
+            }
+
+            if ((int)minHeap.size() < k - 1) minHeap.push(split);
+            else if (split < minHeap.top()) {
+                minHeap.pop();
+                minHeap.push(split);
+            }
+        }
+
+        long long maxScore = 0, minScore = 0;
+        while (!maxHeap.empty()) {
+            maxScore += maxHeap.top();
+            maxHeap.pop();
+        }
+        while (!minHeap.empty()) {
+            minScore += minHeap.top();
+            minHeap.pop();
+        }
+
+        return maxScore - minScore;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} weights
+     * @param {number} k
+     * @return {number}
+     */
+    putMarbles(weights, k) {
+        if (k === 1) return 0;
+
+        const minHeap = new MinPriorityQueue();
+        const maxHeap = new MaxPriorityQueue();
+
+        for (let i = 0; i < weights.length - 1; i++) {
+            const sum = weights[i] + weights[i + 1];
+
+            minHeap.enqueue(sum);
+            if (minHeap.size() > k - 1) minHeap.dequeue();
+
+            maxHeap.enqueue(sum);
+            if (maxHeap.size() > k - 1) maxHeap.dequeue();
+        }
+
+        let maxScore = 0, minScore = 0;
+        while (!minHeap.isEmpty()) maxScore += minHeap.dequeue();
+        while (!maxHeap.isEmpty()) minScore += maxHeap.dequeue();
+
+        return maxScore - minScore;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public long PutMarbles(int[] weights, int k) {
+        if (k == 1) return 0L;
+
+        var maxHeap = new PriorityQueue<int, int>();
+        var minHeap = new PriorityQueue<int, int>(
+            Comparer<int>.Create((a, b) => b.CompareTo(a))
+        );
+
+        for (int i = 0; i < weights.Length - 1; i++) {
+            int split = weights[i] + weights[i + 1];
+
+            maxHeap.Enqueue(split, split);
+            if (maxHeap.Count > k - 1) maxHeap.Dequeue();
+
+            minHeap.Enqueue(split, split);
+            if (minHeap.Count > k - 1) minHeap.Dequeue();
+        }
+
+        long maxScore = 0, minScore = 0;
+        while (maxHeap.Count > 0) maxScore += maxHeap.Dequeue();
+        while (minHeap.Count > 0) minScore += minHeap.Dequeue();
+
+        return maxScore - minScore;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log k)$
+* Space complexity: $O(k)$
+
+> Where $n$ is the number of marbles, and $k$ is the number of bags.
\ No newline at end of file
diff --git a/articles/queue-reconstruction-by-height.md b/articles/queue-reconstruction-by-height.md
new file mode 100644
index 000000000..72dbfcf5c
--- /dev/null
+++ b/articles/queue-reconstruction-by-height.md
@@ -0,0 +1,1185 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def reconstructQueue(self, people: List[List[int]]) -> List[List[int]]:
+        n = len(people)
+        mp = defaultdict(list)
+
+        for p in people:
+            mp[p[1]].append(p[0])
+        for key in mp:
+            mp[key].sort(reverse=True)
+
+        res = []
+        for i in range(n):
+            mini = -1
+            for k in mp:
+                if k > i:
+                    continue
+                cnt = 0
+                j = len(res) - 1
+                while j >= 0:
+                    if res[j][0] >= mp[k][-1]:
+                        cnt += 1
+                    j -= 1
+                if cnt == k and (mini == -1 or mp[k][-1] < mp[mini][-1]):
+                    mini = k
+
+            res.append([mp[mini].pop(), mini])
+            if not mp[mini]:
+                mp.pop(mini)
+        return res
+```
+
+```java
+public class Solution {
+    public int[][] reconstructQueue(int[][] people) {
+        int n = people.length;
+        Map<Integer, List<Integer>> mp = new HashMap<>();
+        
+        for (int[] p : people) {
+            mp.computeIfAbsent(p[1], k -> new ArrayList<>()).add(p[0]);
+        }        
+        for (int key : mp.keySet()) {
+            Collections.sort(mp.get(key), Collections.reverseOrder());
+        }
+        
+        List<int[]> res = new ArrayList<>();
+        for (int i = 0; i < n; i++) {
+            int mini = -1;
+            for (int k : mp.keySet()) {
+                if (k > i) continue;
+                
+                int cnt = 0;
+                for (int j = res.size() - 1; j >= 0; j--) {
+                    if (res.get(j)[0] >= mp.get(k).get(mp.get(k).size() - 1)) {
+                        cnt++;
+                    }
+                }
+                
+                if (cnt == k && (mini == -1 || mp.get(k).get(mp.get(k).size() - 1) < 
+                    mp.get(mini).get(mp.get(mini).size() - 1))) {
+                    mini = k;
+                }
+            }
+            
+            List<Integer> list = mp.get(mini);
+            res.add(new int[]{list.get(list.size() - 1), mini});
+            list.remove(list.size() - 1);
+            if (list.isEmpty()) {
+                mp.remove(mini);
+            }
+        }
+        
+        return res.toArray(new int[n][2]);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> reconstructQueue(vector<vector<int>>& people) {
+        int n = people.size();
+        unordered_map<int, vector<int>> mp;
+        
+        for (const auto& p : people) {
+            mp[p[1]].push_back(p[0]);
+        }
+        for (auto& pair : mp) {
+            sort(pair.second.rbegin(), pair.second.rend());
+        }
+        
+        vector<vector<int>> res;
+        for (int i = 0; i < n; i++) {
+            int mini = -1;
+            for (const auto& pair : mp) {
+                int k = pair.first;
+                if (k > i) continue;
+                
+                int cnt = 0;
+                for (int j = res.size() - 1; j >= 0; j--) {
+                    if (res[j][0] >= mp[k].back()) {
+                        cnt++;
+                    }
+                }
+                
+                if (cnt == k && (mini == -1 || mp[k].back() < mp[mini].back())) {
+                    mini = k;
+                }
+            }
+            
+            res.push_back({mp[mini].back(), mini});
+            mp[mini].pop_back();
+            if (mp[mini].empty()) {
+                mp.erase(mini);
+            }
+        }
+        
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} people
+     * @return {number[][]}
+     */
+    reconstructQueue(people) {
+        const n = people.length;
+        const mp = new Map();
+
+        for (const [h, k] of people) {
+            if (!mp.has(k)) mp.set(k, []);
+            mp.get(k).push(h);
+        }
+        for (const [k, heights] of mp) {
+            heights.sort((a, b) => b - a);
+        }
+
+        const res = [];
+        for (let i = 0; i < n; i++) {
+            let mini = -1;
+            for (const [k, heights] of mp) {
+                if (k > i) continue;
+
+                let cnt = 0;
+                for (let j = res.length - 1; j >= 0; j--) {
+                    if (res[j][0] >= heights[heights.length - 1]) cnt++;
+                }
+
+                if (cnt === k && (mini === -1 || heights[heights.length - 1] < mp.get(mini)[mp.get(mini).length - 1])) {
+                    mini = k;
+                }
+            }
+
+            res.push([mp.get(mini).pop(), mini]);
+            if (mp.get(mini).length === 0) {
+                mp.delete(mini);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n + n ^ 3)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Sorting by Height in Descending Order
+
+::tabs-start
+
+```python
+class Solution:
+    def reconstructQueue(self, people: List[List[int]]) -> List[List[int]]:
+        res = []
+        people.sort(key=lambda x: (-x[0], x[1]))
+        for p in people:
+            res.insert(p[1], p)
+        return res
+```
+
+```java
+public class Solution {
+    public int[][] reconstructQueue(int[][] people) {
+        Arrays.sort(people, (a, b) -> a[0] == b[0] ? a[1] - b[1] : b[0] - a[0]);
+        List<int[]> res = new ArrayList<>();
+        for (int[] person : people) {
+            res.add(person[1], person);
+        }
+        return res.toArray(new int[res.size()][]);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> reconstructQueue(vector<vector<int>>& people) {
+        sort(people.begin(), people.end(), [](auto& a, auto& b) {
+            return a[0] == b[0] ? a[1] < b[1] : a[0] > b[0];
+        });
+        
+        list<vector<int>> res;
+        for (const auto& p : people) {
+            auto it = res.begin();
+            advance(it, p[1]);
+            res.insert(it, p);
+        }
+        
+        return vector<vector<int>>(res.begin(), res.end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} people
+     * @return {number[][]}
+     */
+    reconstructQueue(people) {
+        people.sort((a, b) => (a[0] === b[0] ? a[1] - b[1] : b[0] - a[0]));
+        const res = [];
+        for (const [h, k] of people) {
+            res.splice(k, 0, [h, k]);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n\log n + n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Sorting by Height in Ascending Order
+
+::tabs-start
+
+```python
+class Solution:
+    def reconstructQueue(self, people: List[List[int]]) -> List[List[int]]:
+        n = len(people)
+        people.sort(key=lambda x: (x[0], -x[1]))
+        res = [[] for _ in range(n)]
+
+        for p in people:
+            cnt = i = 0
+            while i < n:
+                if not res[i]:
+                    if cnt == p[1]:
+                        break
+                    cnt += 1
+                i += 1
+            res[i] = p
+            
+        return res
+```
+
+```java
+public class Solution {
+    public int[][] reconstructQueue(int[][] people) {
+        int n = people.length;
+        Arrays.sort(people, (a, b) -> a[0] == b[0] ? b[1] - a[1] : a[0] - b[0]);
+        int[][] res = new int[n][2];
+        boolean[] used = new boolean[n];
+
+        for (int[] p : people) {
+            int cnt = 0, i = 0;
+            while (i < n) {
+                if (!used[i]) {
+                    if (cnt == p[1]) break;
+                    cnt++;
+                }
+                i++;
+            }
+            used[i] = true;
+            res[i] = p;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> reconstructQueue(vector<vector<int>>& people) {
+        sort(people.begin(), people.end(), [](auto& a, auto& b) {
+            return a[0] == b[0] ? a[1] > b[1] : a[0] < b[0];
+        });
+        
+        vector<vector<int>> res(people.size(), vector<int>());
+        for (const auto& p : people) {
+            int cnt = 0, i = 0;
+            while (i < people.size()) {
+                if (res[i].empty()) {
+                    if (cnt == p[1]) break;
+                    cnt++;
+                }
+                i++;
+            }
+            res[i] = p;
+        }
+        
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} people
+     * @return {number[][]}
+     */
+    reconstructQueue(people) {
+        people.sort((a, b) => a[0] === b[0] ? b[1] - a[1] : a[0] - b[0]);
+        const res = Array(people.length).fill(null);
+
+        for (const p of people) {
+            let cnt = 0, i = 0;
+
+            while (i < people.length) {
+                if (res[i] === null) {
+                    if (cnt === p[1]) break;
+                    cnt++;
+                }
+                i++;
+            }
+            res[i] = p;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n\log n + n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Binary Search + Segment Tree
+
+::tabs-start
+
+```python
+class SegmentTree:
+    def __init__(self, N):
+        self.n = N
+        while (self.n & (self.n - 1)) != 0:
+            self.n += 1
+        self.build(N)
+
+    def build(self, N):
+        self.tree = [0] * (2 * self.n)
+        for i in range(N):
+            self.tree[self.n + i] = 1
+        for i in range(self.n - 1, 0, -1):
+            self.tree[i] = self.tree[i << 1] + self.tree[i << 1 | 1]
+
+    def update(self, i, val):
+        self.tree[self.n + i] = val
+        j = (self.n + i) >> 1
+        while j >= 1:
+            self.tree[j] = self.tree[j << 1] + self.tree[j << 1 | 1]
+            j >>= 1
+
+    def query(self, l, r):
+        res = 0
+        l += self.n
+        r += self.n + 1
+        while l < r:
+            if l & 1:
+                res += self.tree[l]
+                l += 1
+            if r & 1:
+                r -= 1
+                res += self.tree[r]
+            l >>= 1
+            r >>= 1
+        return res
+
+class Solution:
+    def reconstructQueue(self, people: List[List[int]]) -> List[List[int]]:
+        n = len(people)
+        people.sort(key=lambda x: (x[0], -x[1]))
+        res = [[] for _ in range(n)]
+
+        segTree = SegmentTree(n)
+        for p in people:
+            l, r = 0, n - 1
+            idx = 0
+            while l <= r:
+                mid = (l + r) >> 1
+                cnt = segTree.query(0, mid)
+                if cnt > p[1]:
+                    idx = mid
+                    r = mid - 1
+                else:
+                    l = mid + 1
+                    
+            res[idx] = p
+            segTree.update(idx, 0)
+            
+        return res
+```
+
+```java
+class SegmentTree {
+    int n;
+    int[] tree;
+
+    SegmentTree(int N) {
+        this.n = N;
+        while (Integer.bitCount(n) != 1) {
+            n++;
+        }
+        build(N);
+    }
+
+    void build(int N) {
+        tree = new int[2 * n];
+        for (int i = 0; i < N; i++) {
+            tree[n + i] = 1;
+        }
+        for (int i = n - 1; i > 0; --i) {
+            tree[i] = tree[i << 1] + tree[i << 1 | 1];
+        }
+    }
+
+    void update(int i, int val) {
+        tree[n + i] = val;
+        for (int j = (n + i) >> 1; j >= 1; j >>= 1) {
+            tree[j] = tree[j << 1] + tree[j << 1 | 1];
+        }
+    }
+
+    int query(int l, int r) {
+        int res = 0;
+        for (l += n, r += n + 1; l < r; l >>= 1, r >>= 1) {
+            if ((l & 1) == 1) res += tree[l++];
+            if ((r & 1) == 1) res += tree[--r];
+        }
+        return res;
+    }
+}
+
+public class Solution {
+    public int[][] reconstructQueue(int[][] people) {
+        int n = people.length;
+        Arrays.sort(people, (a, b) -> a[0] == b[0] ? b[1] - a[1] : a[0] - b[0]);
+        int[][] res = new int[n][2];
+
+        SegmentTree segTree = new SegmentTree(n);
+        for (int[] p : people) {
+            int l = 0, r = n - 1, idx = 0;
+            while (l <= r) {
+                int mid = (l + r) >> 1;
+                int cnt = segTree.query(0, mid);
+                if (cnt > p[1]) {
+                    idx = mid;
+                    r = mid - 1;
+                } else {
+                    l = mid + 1;
+                }
+            }
+
+            res[idx] = p;
+            segTree.update(idx, 0);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class SegmentTree {
+public:
+    int n;
+    vector<int> tree;
+
+    SegmentTree(int N) {
+        this->n = N;
+        while (__builtin_popcount(n) != 1) {
+            n++;
+        }
+        build(N);
+    }
+
+    void build(int N) {
+        tree.resize(2 * n);
+        for (int i = 0; i < N; i++) {
+            tree[n + i] = 1;
+        }
+        for (int i = n - 1; i > 0; --i) {
+            tree[i] = tree[i << 1] + tree[i << 1 | 1];
+        }
+    }
+
+    void update(int i, int val) {
+        tree[n + i] = val;
+        for (int j = (n + i) >> 1; j >= 1; j >>= 1) {
+            tree[j] = tree[j << 1] + tree[j << 1 | 1];
+        }
+    }
+
+    int query(int l, int r) {
+        int res = 0;
+        for (l += n, r += n + 1; l < r; l >>= 1, r >>= 1) {
+            if (l & 1) res += tree[l++];
+            if (r & 1) res += tree[--r];
+        }
+        return res;
+    }
+};
+
+class Solution {
+public:
+    vector<vector<int>> reconstructQueue(vector<vector<int>>& people) {
+        int n = people.size();
+        sort(people.begin(), people.end(), [](auto& a, auto& b) {
+            return a[0] == b[0] ? a[1] > b[1] : a[0] < b[0];
+        });
+        vector<vector<int>> res(n, vector<int>());
+        
+        SegmentTree segTree(n);
+        for (const auto& p : people) {
+            int l = 0, r = n - 1, idx = 0;
+            while (l <= r) {
+                int mid = (l + r) >> 1;
+                int cnt = segTree.query(0, mid);
+                if (cnt > p[1]) {
+                    idx = mid;
+                    r = mid - 1;
+                } else {
+                    l = mid + 1;
+                }
+            }
+
+            res[idx] = p;
+            segTree.update(idx, 0);
+        }
+        
+        return res;
+    }
+};
+```
+
+```javascript
+class SegmentTree {
+    /**
+     * @constructor
+     * @param {number} N 
+     */
+    constructor(N) {
+        this.n = N;
+        while ((this.n & (this.n - 1)) !== 0) {
+            this.n++;
+        }
+        this.build(N);
+    }
+    
+    /**
+     * @param {number} N
+     * @return {void}
+     */
+    build(N) {
+        this.tree = new Int32Array(2 * this.n);
+        for (let i = 0; i < N; i++) {
+            this.tree[this.n + i] = 1;
+        }
+        for (let i = this.n - 1; i > 0; i--) {
+            this.tree[i] = this.tree[i << 1] + this.tree[i << 1 | 1];
+        }
+    }
+
+    /**
+     * @param {number} i 
+     * @param {number} val
+     * @return {void}
+     */
+    update(i, val) {
+        this.tree[this.n + i] = val;
+        for (let j = (this.n + i) >> 1; j >= 1; j >>= 1) {
+            this.tree[j] = this.tree[j << 1] + this.tree[j << 1 | 1];
+        }
+    }
+
+    /**
+     * @param {number} l
+     * @param {number} r
+     * @return {number}
+     */
+    query(l, r) {
+        let res = 0;
+        l += this.n;
+        r += this.n + 1;
+
+        while (l < r) {
+            if (l & 1) res += this.tree[l++];
+            if (r & 1) res += this.tree[--r];
+            l >>= 1;
+            r >>= 1;
+        }
+
+        return res;
+    }
+}
+
+class Solution {
+    /**
+     * @param {number[][]} people
+     * @return {number[][]}
+     */
+    reconstructQueue(people) {
+        const n = people.length;
+        people.sort((a, b) => a[0] === b[0] ? b[1] - a[1] : a[0] - b[0]);
+        const res = Array(n).fill(null);
+        
+        const segTree = new SegmentTree(n);
+        for (const p of people) {
+            let l = 0, r = n - 1, idx = 0;
+            while (l <= r) {
+                let mid = (l + r) >> 1;
+                let cnt = segTree.query(0, mid);
+                if (cnt > p[1]) {
+                    idx = mid;
+                    r = mid - 1;
+                } else {
+                    l = mid + 1;
+                }
+            }
+
+            res[idx] = p;
+            segTree.update(idx, 0);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n\log ^ 2 n)$
+* Space complexity: $O(n)$
+
+---
+
+## 5. Binary Search + Binary Indexed Tree (Fenwick Tree)
+
+::tabs-start
+
+```python
+class BIT:
+    def __init__(self, N):
+        self.n = N + 1
+        self.tree = [0] * self.n
+        for i in range(self.n - 1):
+            self.update(i, 1)
+
+    def update(self, index, val):
+        index += 1
+        while index < self.n:
+            self.tree[index] += val
+            index += index & -index
+
+    def prefix_sum(self, index):
+        total_sum = 0
+        while index > 0:
+            total_sum += self.tree[index]
+            index -= index & -index
+        return total_sum
+
+    def query(self, left, right):
+        return self.prefix_sum(right + 1) - self.prefix_sum(left)
+
+class Solution:
+    def reconstructQueue(self, people: List[List[int]]) -> List[List[int]]:
+        n = len(people)
+        people.sort(key=lambda x: (x[0], -x[1]))
+        res = [[] for _ in range(n)]
+
+        bit = BIT(n)
+        for p in people:
+            l, r = 0, n - 1
+            idx = 0
+            while l <= r:
+                mid = (l + r) >> 1
+                cnt = bit.query(0, mid)
+                if cnt > p[1]:
+                    idx = mid
+                    r = mid - 1
+                else:
+                    l = mid + 1
+                    
+            res[idx] = p
+            bit.update(idx, -1)
+            
+        return res
+```
+
+```java
+class BIT {
+    private int[] tree;
+    private int n;
+
+    public BIT(int N) {
+        this.n = N + 1;
+        this.tree = new int[n];
+        for (int i = 0; i < n - 1; i++) {
+            update(i, 1);
+        }
+    }
+
+    public void update(int index, int val) {
+        index++;
+        while (index < n) {
+            tree[index] += val;
+            index += index & -index;
+        }
+    }
+
+    public int prefixSum(int index) {
+        int totalSum = 0;
+        while (index > 0) {
+            totalSum += tree[index];
+            index -= index & -index;
+        }
+        return totalSum;
+    }
+
+    public int query(int left, int right) {
+        return prefixSum(right + 1) - prefixSum(left);
+    }
+}
+
+public class Solution {
+    public int[][] reconstructQueue(int[][] people) {
+        int n = people.length;
+        Arrays.sort(people, (a, b) -> a[0] == b[0] ? b[1] - a[1] : a[0] - b[0]);
+        int[][] res = new int[n][2];
+
+        BIT bit = new BIT(n);
+        for (int[] p : people) {
+            int l = 0, r = n - 1, idx = 0;
+            while (l <= r) {
+                int mid = (l + r) >> 1;
+                int cnt = bit.query(0, mid);
+                if (cnt > p[1]) {
+                    idx = mid;
+                    r = mid - 1;
+                } else {
+                    l = mid + 1;
+                }
+            }
+
+            res[idx] = p;
+            bit.update(idx, -1);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class BIT {
+    vector<int> tree;
+    int n;
+
+public:
+    BIT(int N) {
+        n = N + 1;
+        tree.resize(n, 0);
+        for (int i = 0; i < n - 1; i++) {
+            update(i, 1);
+        }
+    }
+
+    void update(int index, int val) {
+        index++;
+        while (index < n) {
+            tree[index] += val;
+            index += index & -index;
+        }
+    }
+
+    int prefixSum(int index) {
+        int totalSum = 0;
+        while (index > 0) {
+            totalSum += tree[index];
+            index -= index & -index;
+        }
+        return totalSum;
+    }
+
+    int query(int left, int right) {
+        return prefixSum(right + 1) - prefixSum(left);
+    }
+};
+
+class Solution {
+public:
+    vector<vector<int>> reconstructQueue(vector<vector<int>>& people) {
+        int n = people.size();
+        sort(people.begin(), people.end(), [](auto& a, auto& b) {
+            return a[0] == b[0] ? a[1] > b[1] : a[0] < b[0];
+        });
+        vector<vector<int>> res(n, vector<int>());
+        
+        BIT bit(n);
+        for (const auto& p : people) {
+            int l = 0, r = n - 1, idx = 0;
+            while (l <= r) {
+                int mid = (l + r) >> 1;
+                int cnt = bit.query(0, mid);
+                if (cnt > p[1]) {
+                    idx = mid;
+                    r = mid - 1;
+                } else {
+                    l = mid + 1;
+                }
+            }
+
+            res[idx] = p;
+            bit.update(idx, -1);
+        }
+        
+        return res;
+    }
+};
+```
+
+```javascript
+class BIT {
+    /**
+     * @constructor
+     * @param {number} N
+     */
+    constructor(N) {
+        this.n = N + 1;
+        this.tree = new Int32Array(this.n);
+        for (let i = 0; i < this.n - 1; i++) {
+            this.update(i, 1);
+        }
+    }
+
+    /** 
+     * @param {number} index 
+     * @param {number} val
+     * @return {void}
+     */
+    update(index, val) {
+        index++;
+        while (index < this.n) {
+            this.tree[index] += val;
+            index += index & -index;
+        }
+    }
+
+    /** 
+     * @param {number} index 
+     * @return {number}
+     */
+    prefixSum(index) {
+        let totalSum = 0;
+        while (index > 0) {
+            totalSum += this.tree[index];
+            index -= index & -index;
+        }
+        return totalSum;
+    }
+
+    /** 
+     * @param {number} left 
+     * @param {number} right
+     * @return {number}
+     */
+    query(left, right) {
+        return this.prefixSum(right + 1) - this.prefixSum(left);
+    }
+}
+
+class Solution {
+    /**
+     * @param {number[][]} people
+     * @return {number[][]}
+     */
+    reconstructQueue(people) {
+        const n = people.length;
+        people.sort((a, b) => a[0] === b[0] ? b[1] - a[1] : a[0] - b[0]);
+        const res = Array(n).fill(null);
+        
+        const bit = new BIT(n);
+        for (const p of people) {
+            let l = 0, r = n - 1, idx = 0;
+            while (l <= r) {
+                let mid = (l + r) >> 1;
+                let cnt = bit.query(0, mid);
+                if (cnt > p[1]) {
+                    idx = mid;
+                    r = mid - 1;
+                } else {
+                    l = mid + 1;
+                }
+            }
+
+            res[idx] = p;
+            bit.update(idx, -1);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n\log ^ 2 n)$
+* Space complexity: $O(n)$
+
+---
+
+## 6. Binary Indexed Tree (Fenwick Tree)
+
+::tabs-start
+
+```python
+class BIT:
+    def __init__(self, N):
+        self.n = N + 1
+        self.tree = [0] * self.n
+        for i in range(self.n - 1):
+            self.update(i, 1)
+
+    def update(self, index, val):
+        index += 1
+        while index < self.n:
+            self.tree[index] += val
+            index += index & -index
+
+    def getIdx(self, cnt, MSB):
+        idx = 0
+        while MSB:
+            nxtIdx = idx + MSB
+            if nxtIdx < self.n and cnt >= self.tree[nxtIdx]:
+                idx = nxtIdx
+                cnt -= self.tree[nxtIdx]
+            MSB >>= 1
+        return idx
+
+class Solution:
+    def reconstructQueue(self, people: List[List[int]]) -> List[List[int]]:
+        n = len(people)
+        people.sort(key=lambda x: (x[0], -x[1]))
+        res = [[] for _ in range(n)]
+
+        bit = BIT(n)
+        MSB = 1 << int(math.log(n, 2))
+        for p in people:
+            idx = bit.getIdx(p[1], MSB)
+            res[idx] = p
+            bit.update(idx, -1)
+            
+        return res
+```
+
+```java
+class BIT {
+    private int[] tree;
+    private int n;
+
+    public BIT(int N) {
+        this.n = N + 1;
+        this.tree = new int[n];
+        for (int i = 0; i < n - 1; i++) {
+            update(i, 1);
+        }
+    }
+
+    public void update(int index, int val) {
+        index++;
+        while (index < n) {
+            tree[index] += val;
+            index += index & -index;
+        }
+    }
+
+    public int getIdx(int cnt, int MSB) {
+        int idx = 0;
+        while (MSB != 0) {
+            int nxtIdx = idx + MSB;
+            if (nxtIdx < n && cnt >= tree[nxtIdx]) {
+                idx = nxtIdx;
+                cnt -= tree[nxtIdx];
+            }
+            MSB >>= 1;
+        }
+        return idx;
+    }
+}
+
+public class Solution {
+    public int[][] reconstructQueue(int[][] people) {
+        int n = people.length;
+        Arrays.sort(people, (a, b) -> a[0] == b[0] ? b[1] - a[1] : a[0] - b[0]);
+        int[][] res = new int[n][2];
+
+        BIT bit = new BIT(n);
+        int MSB = 1 << (31 - Integer.numberOfLeadingZeros(n));
+        for (int[] p : people) {
+            int idx = bit.getIdx(p[1], MSB);
+            res[idx] = p;
+            bit.update(idx, -1);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class BIT {
+    vector<int> tree;
+    int n;
+
+public:
+    BIT(int N) {
+        n = N + 1;
+        tree.resize(n, 0);
+        for (int i = 0; i < n - 1; i++) {
+            update(i, 1);
+        }
+    }
+
+    void update(int index, int val) {
+        index++;
+        while (index < n) {
+            tree[index] += val;
+            index += index & -index;
+        }
+    }
+
+    int getIdx(int cnt, int MSB) {
+        int idx = 0;
+        while (MSB != 0) {
+            int nxtIdx = idx + MSB;
+            if (nxtIdx < n && cnt >= tree[nxtIdx]) {
+                idx = nxtIdx;
+                cnt -= tree[nxtIdx];
+            }
+            MSB >>= 1;
+        }
+        return idx;
+    }
+};
+
+class Solution {
+public:
+    vector<vector<int>> reconstructQueue(vector<vector<int>>& people) {
+        int n = people.size();
+        sort(people.begin(), people.end(), [](auto& a, auto& b) {
+            return a[0] == b[0] ? a[1] > b[1] : a[0] < b[0];
+        });
+        vector<vector<int>> res(n, vector<int>());
+        
+        BIT bit(n);
+        int MSB = 1 << (31 - __builtin_clz(n));
+        for (const auto& p : people) {
+            int idx = bit.getIdx(p[1], MSB);
+            res[idx] = p;
+            bit.update(idx, -1);
+        }
+        
+        return res;
+    }
+};
+```
+
+```javascript
+class BIT {
+    /**
+     * @constructor
+     * @param {number} N
+     */
+    constructor(N) {
+        this.n = N + 1;
+        this.tree = new Int32Array(this.n);
+        for (let i = 0; i < this.n - 1; i++) {
+            this.update(i, 1);
+        }
+    }
+
+    /** 
+     * @param {number} index 
+     * @param {number} val
+     * @return {void}
+     */
+    update(index, val) {
+        index++;
+        while (index < this.n) {
+            this.tree[index] += val;
+            index += index & -index;
+        }
+    }
+
+    /** 
+     * @param {number} cnt 
+     * @param {number} MSB
+     * @return {number}
+     */
+    getIdx(cnt, MSB) {
+        let idx = 0;
+        while (MSB != 0) {
+            let nxtIdx = idx + MSB;
+            if (nxtIdx < this.n && cnt >= this.tree[nxtIdx]) {
+                idx = nxtIdx;
+                cnt -= this.tree[nxtIdx];
+            }
+            MSB >>= 1;
+        }
+        return idx;
+    }
+}
+
+class Solution {
+    /**
+     * @param {number[][]} people
+     * @return {number[][]}
+     */
+    reconstructQueue(people) {
+        const n = people.length;
+        people.sort((a, b) => a[0] === b[0] ? b[1] - a[1] : a[0] - b[0]);
+        const res = Array(n).fill(null);
+        
+        const bit = new BIT(n);
+        const MSB = 1 << Math.floor(Math.log2(n));
+        for (const p of people) {
+            let idx = bit.getIdx(p[1], MSB);
+            res[idx] = p;
+            bit.update(idx, -1);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n\log n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/range-sum-of-bst.md b/articles/range-sum-of-bst.md
new file mode 100644
index 000000000..cd0873dec
--- /dev/null
+++ b/articles/range-sum-of-bst.md
@@ -0,0 +1,408 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def rangeSumBST(self, root: Optional[TreeNode], low: int, high: int) -> int:
+        if not root:
+            return 0
+        
+        res = root.val if low <= root.val <= high else 0
+        res += self.rangeSumBST(root.left, low, high)
+        res += self.rangeSumBST(root.right, low, high)
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public int rangeSumBST(TreeNode root, int low, int high) {
+        if (root == null) return 0;
+
+        int res = (low <= root.val && root.val <= high) ? root.val : 0;
+        res += rangeSumBST(root.left, low, high);
+        res += rangeSumBST(root.right, low, high);
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int rangeSumBST(TreeNode* root, int low, int high) {
+        if (!root) return 0;
+
+        int res = (low <= root->val && root->val <= high) ? root->val : 0;
+        res += rangeSumBST(root->left, low, high);
+        res += rangeSumBST(root->right, low, high);
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @param {number} low
+     * @param {number} high
+     * @return {number}
+     */
+    rangeSumBST(root, low, high) {
+        if (!root) return 0;
+
+        let res = (low <= root.val && root.val <= high) ? root.val : 0;
+        res += this.rangeSumBST(root.left, low, high);
+        res += this.rangeSumBST(root.right, low, high);
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Depth First Search (Optimal)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def rangeSumBST(self, root: Optional[TreeNode], low: int, high: int) -> int:
+        if not root:
+            return 0
+
+        if root.val > high:
+            return self.rangeSumBST(root.left, low, high)
+        if root.val < low:
+            return self.rangeSumBST(root.right, low, high)
+
+        return (
+            root.val +
+            self.rangeSumBST(root.left, low, high) +
+            self.rangeSumBST(root.right, low, high)
+        )
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public int rangeSumBST(TreeNode root, int low, int high) {
+        if (root == null) return 0;
+
+        if (root.val > high) {
+            return rangeSumBST(root.left, low, high);
+        }
+        if (root.val < low) {
+            return rangeSumBST(root.right, low, high);
+        }
+
+        return root.val + rangeSumBST(root.left, low, high) + 
+                          rangeSumBST(root.right, low, high);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int rangeSumBST(TreeNode* root, int low, int high) {
+        if (!root) return 0;
+
+        if (root->val > high) {
+            return rangeSumBST(root->left, low, high);
+        }
+        if (root->val < low) {
+            return rangeSumBST(root->right, low, high);
+        }
+
+        return root->val + rangeSumBST(root->left, low, high) + 
+                           rangeSumBST(root->right, low, high);
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @param {number} low
+     * @param {number} high
+     * @return {number}
+     */
+    rangeSumBST(root, low, high) {
+        if (!root) return 0;
+
+        if (root.val > high) {
+            return rangeSumBST(root.left, low, high);
+        }
+        if (root.val < low) {
+            return rangeSumBST(root.right, low, high);
+        }
+
+        return root.val + this.rangeSumBST(root.left, low, high) + 
+                          this.rangeSumBST(root.right, low, high);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 3. Iterative DFS
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def rangeSumBST(self, root: Optional[TreeNode], low: int, high: int) -> int:
+        stack = [root]
+        res = 0
+
+        while stack:
+            node = stack.pop()
+            if not node:
+                continue
+
+            if low <= node.val <= high:
+                res += node.val
+            if node.val > low:
+                stack.append(node.left)
+            if node.val < high:
+                stack.append(node.right)
+
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public int rangeSumBST(TreeNode root, int low, int high) {
+        int res = 0;
+        Stack<TreeNode> stack = new Stack<>();
+        stack.push(root);
+
+        while (!stack.isEmpty()) {
+            TreeNode node = stack.pop();
+            if (node == null) continue;
+
+            if (low <= node.val && node.val <= high) {
+                res += node.val;
+            }
+            if (node.val > low) {
+                stack.push(node.left);
+            }
+            if (node.val < high) {
+                stack.push(node.right);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int rangeSumBST(TreeNode* root, int low, int high) {
+        int res = 0;
+        stack<TreeNode*> stack;
+        stack.push(root);
+
+        while (!stack.empty()) {
+            TreeNode* node = stack.top();
+            stack.pop();
+            if (!node) continue;
+
+            if (low <= node->val && node->val <= high) {
+                res += node->val;
+            }
+            if (node->val > low) {
+                stack.push(node->left);
+            }
+            if (node->val < high) {
+                stack.push(node->right);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @param {number} low
+     * @param {number} high
+     * @return {number}
+     */
+    rangeSumBST(root, low, high) {
+        let res = 0;
+        let stack = [root];
+
+        while (stack.length > 0) {
+            let node = stack.pop();
+            if (!node) continue;
+
+            if (low <= node.val && node.val <= high) {
+                res += node.val;
+            }
+            if (node.val > low) {
+                stack.push(node.left);
+            }
+            if (node.val < high) {
+                stack.push(node.right);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/range-sum-query-2d-immutable.md b/articles/range-sum-query-2d-immutable.md
new file mode 100644
index 000000000..3d19e47b0
--- /dev/null
+++ b/articles/range-sum-query-2d-immutable.md
@@ -0,0 +1,369 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class NumMatrix:
+
+    def __init__(self, matrix: list[list[int]]):
+        self.matrix = matrix
+
+    def sumRegion(self, row1: int, col1: int, row2: int, col2: int) -> int:
+        res = 0
+        for r in range(row1, row2 + 1):
+            for c in range(col1, col2 + 1):
+                res += self.matrix[r][c]
+        return res
+```
+
+```java
+public class NumMatrix {
+
+    private int[][] matrix;
+
+    public NumMatrix(int[][] matrix) {
+        this.matrix = matrix;
+    }
+
+    public int sumRegion(int row1, int col1, int row2, int col2) {
+        int res = 0;
+        for (int r = row1; r <= row2; r++) {
+            for (int c = col1; c <= col2; c++) {
+                res += matrix[r][c];
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class NumMatrix {
+private:
+    vector<vector<int>> matrix;
+
+public:
+    NumMatrix(vector<vector<int>>& matrix) {
+        this->matrix = matrix;
+    }
+
+    int sumRegion(int row1, int col1, int row2, int col2) {
+        int res = 0;
+        for (int r = row1; r <= row2; r++) {
+            for (int c = col1; c <= col2; c++) {
+                res += matrix[r][c];
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class NumMatrix {
+    /**
+     * @param {number[][]} matrix
+     */
+    constructor(matrix) {
+        this.matrix = matrix;
+    }
+
+    /** 
+     * @param {number} row1 
+     * @param {number} col1 
+     * @param {number} row2 
+     * @param {number} col2
+     * @return {number}
+     */
+    sumRegion(row1, col1, row2, col2) {
+        let res = 0;
+        for (let r = row1; r <= row2; r++) {
+            for (let c = col1; c <= col2; c++) {
+                res += this.matrix[r][c];
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$ for each query.
+* Space complexity: $O(1)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns in the matrix.
+
+---
+
+## 2. One Dimensional Prefix Sum
+
+::tabs-start
+
+```python
+class NumMatrix:
+
+    def __init__(self, matrix: list[list[int]]):
+        self.prefixSum = [[0] * len(matrix[0]) for _ in range(len(matrix))]
+        
+        for row in range(len(matrix)):
+            self.prefixSum[row][0] = matrix[row][0]
+            for col in range(1, len(matrix[0])):
+                self.prefixSum[row][col] = self.prefixSum[row][col - 1] + matrix[row][col]
+
+    def sumRegion(self, row1: int, col1: int, row2: int, col2: int) -> int:
+        res = 0
+        for row in range(row1, row2 + 1):
+            if col1 > 0:
+                res += self.prefixSum[row][col2] - self.prefixSum[row][col1 - 1]
+            else:
+                res += self.prefixSum[row][col2]
+        return res
+```
+
+```java
+public class NumMatrix {
+
+    private int[][] prefixSum;
+
+    public NumMatrix(int[][] matrix) {
+        int rows = matrix.length, cols = matrix[0].length;
+        prefixSum = new int[rows][cols];
+
+        for (int row = 0; row < rows; row++) {
+            prefixSum[row][0] = matrix[row][0];
+            for (int col = 1; col < cols; col++) {
+                prefixSum[row][col] = prefixSum[row][col - 1] + matrix[row][col];
+            }
+        }
+    }
+
+    public int sumRegion(int row1, int col1, int row2, int col2) {
+        int res = 0;
+        for (int row = row1; row <= row2; row++) {
+            if (col1 > 0) {
+                res += prefixSum[row][col2] - prefixSum[row][col1 - 1];
+            } else {
+                res += prefixSum[row][col2];
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class NumMatrix {
+private:
+    vector<vector<int>> prefixSum;
+
+public:
+    NumMatrix(vector<vector<int>>& matrix) {
+        int rows = matrix.size(), cols = matrix[0].size();
+        prefixSum = vector<vector<int>>(rows, vector<int>(cols, 0));
+
+        for (int row = 0; row < rows; row++) {
+            prefixSum[row][0] = matrix[row][0];
+            for (int col = 1; col < cols; col++) {
+                prefixSum[row][col] = prefixSum[row][col - 1] + matrix[row][col];
+            }
+        }
+    }
+
+    int sumRegion(int row1, int col1, int row2, int col2) {
+        int res = 0;
+        for (int row = row1; row <= row2; row++) {
+            if (col1 > 0) {
+                res += prefixSum[row][col2] - prefixSum[row][col1 - 1];
+            } else {
+                res += prefixSum[row][col2];
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class NumMatrix {
+    /**
+     * @param {number[][]} matrix
+     */
+    constructor(matrix) {
+        this.prefixSum = Array.from({ length: matrix.length }, () => Array(matrix[0].length).fill(0));
+
+        for (let row = 0; row < matrix.length; row++) {
+            this.prefixSum[row][0] = matrix[row][0];
+            for (let col = 1; col < matrix[0].length; col++) {
+                this.prefixSum[row][col] = this.prefixSum[row][col - 1] + matrix[row][col];
+            }
+        }
+    }
+
+    /** 
+     * @param {number} row1 
+     * @param {number} col1 
+     * @param {number} row2 
+     * @param {number} col2
+     * @return {number}
+     */
+    sumRegion(row1, col1, row2, col2) {
+        let res = 0;
+        for (let row = row1; row <= row2; row++) {
+            if (col1 > 0) {
+                res += this.prefixSum[row][col2] - this.prefixSum[row][col1 - 1];
+            } else {
+                res += this.prefixSum[row][col2];
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m)$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns in the matrix.
+
+---
+
+## 3. Two Dimensional Prefix Sum
+
+::tabs-start
+
+```python
+class NumMatrix:
+
+    def __init__(self, matrix: list[list[int]]):
+        ROWS, COLS = len(matrix), len(matrix[0])
+        self.sumMat = [[0] * (COLS + 1) for _ in range(ROWS + 1)]
+
+        for r in range(ROWS):
+            prefix = 0
+            for c in range(COLS):
+                prefix += matrix[r][c]
+                above = self.sumMat[r][c + 1]
+                self.sumMat[r + 1][c + 1] = prefix + above
+
+    def sumRegion(self, row1: int, col1: int, row2: int, col2: int) -> int:
+        row1, col1, row2, col2 = row1 + 1, col1 + 1, row2 + 1, col2 + 1
+        bottomRight = self.sumMat[row2][col2]
+        above = self.sumMat[row1 - 1][col2]
+        left = self.sumMat[row2][col1 - 1]
+        topLeft = self.sumMat[row1 - 1][col1 - 1]
+        return bottomRight - above - left + topLeft
+```
+
+```java
+public class NumMatrix {
+
+    private int[][] sumMat;
+
+    public NumMatrix(int[][] matrix) {
+        int ROWS = matrix.length, COLS = matrix[0].length;
+        sumMat = new int[ROWS + 1][COLS + 1];
+
+        for (int r = 0; r < ROWS; r++) {
+            int prefix = 0;
+            for (int c = 0; c < COLS; c++) {
+                prefix += matrix[r][c];
+                int above = sumMat[r][c + 1];
+                sumMat[r + 1][c + 1] = prefix + above;
+            }
+        }
+    }
+
+    public int sumRegion(int row1, int col1, int row2, int col2) {
+        row1++; col1++; row2++; col2++;
+        int bottomRight = sumMat[row2][col2];
+        int above = sumMat[row1 - 1][col2];
+        int left = sumMat[row2][col1 - 1];
+        int topLeft = sumMat[row1 - 1][col1 - 1];
+        return bottomRight - above - left + topLeft;
+    }
+}
+```
+
+```cpp
+class NumMatrix {
+private:
+    vector<vector<int>> sumMat;
+
+public:
+    NumMatrix(vector<vector<int>>& matrix) {
+        int ROWS = matrix.size(), COLS = matrix[0].size();
+        sumMat = vector<vector<int>>(ROWS + 1, vector<int>(COLS + 1, 0));
+
+        for (int r = 0; r < ROWS; r++) {
+            int prefix = 0;
+            for (int c = 0; c < COLS; c++) {
+                prefix += matrix[r][c];
+                int above = sumMat[r][c + 1];
+                sumMat[r + 1][c + 1] = prefix + above;
+            }
+        }
+    }
+
+    int sumRegion(int row1, int col1, int row2, int col2) {
+        row1++; col1++; row2++; col2++;
+        int bottomRight = sumMat[row2][col2];
+        int above = sumMat[row1 - 1][col2];
+        int left = sumMat[row2][col1 - 1];
+        int topLeft = sumMat[row1 - 1][col1 - 1];
+        return bottomRight - above - left + topLeft;
+    }
+};
+```
+
+```javascript
+class NumMatrix {
+    /**
+     * @param {number[][]} matrix
+     */
+    constructor(matrix) {
+        const ROWS = matrix.length, COLS = matrix[0].length;
+        this.sumMat = Array.from({ length: ROWS + 1 }, () => Array(COLS + 1).fill(0));
+
+        for (let r = 0; r < ROWS; r++) {
+            let prefix = 0;
+            for (let c = 0; c < COLS; c++) {
+                prefix += matrix[r][c];
+                const above = this.sumMat[r][c + 1];
+                this.sumMat[r + 1][c + 1] = prefix + above;
+            }
+        }
+    }
+
+    /** 
+     * @param {number} row1 
+     * @param {number} col1 
+     * @param {number} row2 
+     * @param {number} col2
+     * @return {number}
+     */
+    sumRegion(row1, col1, row2, col2) {
+        row1++; col1++; row2++; col2++;
+        const bottomRight = this.sumMat[row2][col2];
+        const above = this.sumMat[row1 - 1][col2];
+        const left = this.sumMat[row2][col1 - 1];
+        const topLeft = this.sumMat[row1 - 1][col1 - 1];
+        return bottomRight - above - left + topLeft;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$ for each query.
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns in the matrix.
\ No newline at end of file
diff --git a/articles/range-sum-query-immutable.md b/articles/range-sum-query-immutable.md
new file mode 100644
index 000000000..f53012caa
--- /dev/null
+++ b/articles/range-sum-query-immutable.md
@@ -0,0 +1,452 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class NumArray:
+    def __init__(self, nums):
+        self.nums = nums
+
+    def sumRange(self, left, right):
+        res = 0
+        for i in range(left, right + 1):
+            res += self.nums[i]
+        return res
+```
+
+```java
+public class NumArray {
+    private final int[] nums;
+
+    public NumArray(int[] nums) {
+        this.nums = nums;
+    }
+
+    public int sumRange(int left, int right) {
+        int res = 0;
+        for (int i = left; i <= right; i++) {
+            res += nums[i];
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class NumArray {
+private:
+    const vector<int>& nums;
+
+public:
+    NumArray(const vector<int>& nums) : nums(nums) {}
+
+    int sumRange(int left, int right) {
+        int res = 0;
+        for (int i = left; i <= right; i++) {
+            res += nums[i];
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class NumArray {
+    /**
+     * @param {number[]} nums
+     */
+    constructor(nums) {
+        this.nums = nums;
+    }
+
+    /** 
+     * @param {number} left 
+     * @param {number} right
+     * @return {number}
+     */
+    sumRange(left, right) {
+        let res = 0;
+        for (let i = left; i <= right; i++) {
+            res += this.nums[i];
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$ for each $sumRange()$ query.
+* Space complexity: $O(1)$ since we only make a reference to the input array.
+
+---
+
+## 2. Prefix Sum - I
+
+::tabs-start
+
+```python
+class NumArray:
+    def __init__(self, nums):
+        self.prefix = []
+        cur = 0
+        for num in nums:
+            cur += num
+            self.prefix.append(cur)
+
+    def sumRange(self, left, right):
+        rightSum = self.prefix[right]
+        leftSum = self.prefix[left - 1] if left > 0 else 0
+        return rightSum - leftSum
+```
+
+```java
+public class NumArray {
+    private int[] prefix;
+
+    public NumArray(int[] nums) {
+        prefix = new int[nums.length];
+        int cur = 0;
+        for (int i = 0; i < nums.length; i++) {
+            cur += nums[i];
+            prefix[i] = cur;
+        }
+    }
+
+    public int sumRange(int left, int right) {
+        int rightSum = prefix[right];
+        int leftSum = left > 0 ? prefix[left - 1] : 0;
+        return rightSum - leftSum;
+    }
+}
+```
+
+```cpp
+class NumArray {
+private:
+    vector<int> prefix;
+
+public:
+    NumArray(const vector<int>& nums) {
+        int cur = 0;
+        for (int num : nums) {
+            cur += num;
+            prefix.push_back(cur);
+        }
+    }
+
+    int sumRange(int left, int right) {
+        int rightSum = prefix[right];
+        int leftSum = left > 0 ? prefix[left - 1] : 0;
+        return rightSum - leftSum;
+    }
+};
+```
+
+```javascript
+class NumArray {
+    /**
+     * @param {number[]} nums
+     */
+    constructor(nums) {
+        this.prefix = [];
+        let cur = 0;
+        for (let num of nums) {
+            cur += num;
+            this.prefix.push(cur);
+        }
+    }
+
+    /** 
+     * @param {number} left 
+     * @param {number} right
+     * @return {number}
+     */
+    sumRange(left, right) {
+        const rightSum = this.prefix[right];
+        const leftSum = left > 0 ? this.prefix[left - 1] : 0;
+        return rightSum - leftSum;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$ for each $sumRange()$ query, $O(n)$ for building the prefix sum array.
+* Space complexity: $O(n)$
+
+---
+
+## 3. Prefix Sum - II
+
+::tabs-start
+
+```python
+class NumArray:
+    def __init__(self, nums):
+        self.prefix = [0] * (len(nums) + 1)
+        for i in range(len(nums)):
+            self.prefix[i + 1] = self.prefix[i] + nums[i]
+        
+
+    def sumRange(self, left, right):
+        return self.prefix[right + 1] - self.prefix[left]
+```
+
+```java
+public class NumArray {
+    private int[] prefix;
+
+    public NumArray(int[] nums) {
+        prefix = new int[nums.length + 1];
+        for (int i = 0; i < nums.length; i++) {
+            prefix[i + 1] = prefix[i] + nums[i];
+        }
+    }
+
+    public int sumRange(int left, int right) {
+        return prefix[right + 1] - prefix[left];
+    }
+}
+```
+
+```cpp
+class NumArray {
+private:
+    vector<int> prefix;
+
+public:
+    NumArray(const vector<int>& nums) {
+        prefix = vector<int>(nums.size() + 1, 0);
+        for (int i = 0; i < nums.size(); i++) {
+            prefix[i + 1] = prefix[i] + nums[i];
+        }
+    }
+
+    int sumRange(int left, int right) {
+        return prefix[right + 1] - prefix[left];
+    }
+};
+```
+
+```javascript
+class NumArray {
+    /**
+     * @param {number[]} nums
+     */
+    constructor(nums) {
+        this.prefix = new Array(nums.length + 1).fill(0);
+        for (let i = 0; i < nums.length; i++) {
+            this.prefix[i + 1] = this.prefix[i] + nums[i];
+        }
+    }
+
+    /** 
+     * @param {number} left 
+     * @param {number} right
+     * @return {number}
+     */
+    sumRange(left, right) {
+        return this.prefix[right + 1] - this.prefix[left];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$ for each $sumRange()$ query, $O(n)$ for building the prefix sum array.
+* Space complexity: $O(n)$
+
+---
+
+## 4. Segment Tree
+
+::tabs-start
+
+```python
+class SegmentTree:
+    def __init__(self, nums):
+        self.n = len(nums)
+        self.tree = [0] * (2 * self.n)
+        for i in range(self.n):
+            self.tree[self.n + i] = nums[i]
+        for i in range(self.n - 1, 0, -1):
+            self.tree[i] = self.tree[2 * i] + self.tree[2 * i + 1]
+
+    def query(self, left, right):
+        left += self.n
+        right += self.n + 1
+        res = 0
+        while left < right:
+            if left % 2 == 1:
+                res += self.tree[left]
+                left += 1
+            if right % 2 == 1:
+                right -= 1
+                res += self.tree[right]
+            left //= 2
+            right //= 2
+        return res
+
+class NumArray:
+    def __init__(self, nums):
+        self.segTree = SegmentTree(nums)
+
+    def sumRange(self, left, right):
+        return self.segTree.query(left, right)
+```
+
+```java
+class SegmentTree {
+    private int[] tree;
+    private int n;
+
+    public SegmentTree(int[] nums) {
+        n = nums.length;
+        tree = new int[2 * n];
+        for (int i = 0; i < n; i++) {
+            tree[n + i] = nums[i];
+        }
+        for (int i = n - 1; i > 0; i--) {
+            tree[i] = tree[2 * i] + tree[2 * i + 1];
+        }
+    }
+
+    public int query(int left, int right) {
+        int sum = 0;
+        left += n;
+        right += n + 1;
+        while (left < right) {
+            if (left % 2 == 1) sum += tree[left++];
+            if (right % 2 == 1) sum += tree[--right];
+            left /= 2;
+            right /= 2;
+        }
+        return sum;
+    }
+}
+
+public class NumArray {
+    private SegmentTree segTree;
+
+    public NumArray(int[] nums) {
+        segTree = new SegmentTree(nums);
+    }
+
+    public int sumRange(int left, int right) {
+        return segTree.query(left, right);
+    }
+}
+```
+
+```cpp
+class SegmentTree {
+private:
+    vector<int> tree;
+    int n;
+
+public:
+    SegmentTree(const vector<int>& nums) {
+        n = nums.size();
+        tree.resize(2 * n);
+        for (int i = 0; i < n; i++) {
+            tree[n + i] = nums[i];
+        }
+        for (int i = n - 1; i > 0; i--) {
+            tree[i] = tree[2 * i] + tree[2 * i + 1];
+        }
+    }
+
+    int query(int left, int right) {
+        int sum = 0;
+        left += n;
+        right += n + 1;
+        while (left < right) {
+            if (left % 2 == 1) sum += tree[left++];
+            if (right % 2 == 1) sum += tree[--right];
+            left /= 2;
+            right /= 2;
+        }
+        return sum;
+    }
+};
+
+class NumArray {
+private:
+    SegmentTree segTree;
+
+public:
+    NumArray(const vector<int>& nums) : segTree(nums) {}
+
+    int sumRange(int left, int right) {
+        return segTree.query(left, right);
+    }
+};
+```
+
+```javascript
+class SegmentTree {
+    /**
+     * @param {number[]} nums
+     */
+    constructor(nums) {
+        this.n = nums.length;
+        this.tree = Array(this.n * 2).fill(0);
+        for (let i = 0; i < this.n; i++) {
+            this.tree[this.n + i] = nums[i];
+        }
+        for (let i = this.n - 1; i > 0; i--) {
+            this.tree[i] = this.tree[2 * i] + this.tree[2 * i + 1];
+        }
+    }
+
+    /**
+     * @param {number} left
+     * @param {number} right
+     * @return {number}
+     */
+    query(left, right) {
+        let sum = 0;
+        left += this.n;
+        right += this.n + 1;
+        while (left < right) {
+            if (left % 2 === 1) sum += this.tree[left++];
+            if (right % 2 === 1) sum += this.tree[--right];
+            left = Math.floor(left / 2);
+            right = Math.floor(right / 2);
+        }
+        return sum;
+    }
+}
+
+class NumArray {
+    /**
+     * @param {number[]} nums
+     */
+    constructor(nums) {
+        this.segTree = new SegmentTree(nums);
+    }
+
+    /** 
+     * @param {number} left 
+     * @param {number} right
+     * @return {number}
+     */
+    sumRange(left, right) {
+        return this.segTree.query(left, right);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$ for each $sumRange()$ query, $O(n)$ for building the Segment Tree.
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/range-sum-query-mutable.md b/articles/range-sum-query-mutable.md
new file mode 100644
index 000000000..358921e03
--- /dev/null
+++ b/articles/range-sum-query-mutable.md
@@ -0,0 +1,1513 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class NumArray:
+
+    def __init__(self, nums: List[int]):
+        self.nums = nums
+
+    def update(self, index: int, val: int) -> None:
+        self.nums[index] = val
+
+    def sumRange(self, left: int, right: int) -> int:
+        res = 0
+        for i in range(left, right + 1):
+            res += self.nums[i]
+        return res
+```
+
+```java
+public class NumArray {
+    private int[] nums;
+
+    public NumArray(int[] nums) {
+        this.nums = nums;
+    }
+
+    public void update(int index, int val) {
+        nums[index] = val;
+    }
+
+    public int sumRange(int left, int right) {
+        int res = 0;
+        for (int i = left; i <= right; i++) {
+            res += nums[i];
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class NumArray {
+private:
+    vector<int> nums;
+
+public:
+    NumArray(vector<int>& nums) {
+        this->nums = nums;
+    }
+
+    void update(int index, int val) {
+        nums[index] = val;
+    }
+
+    int sumRange(int left, int right) {
+        int res = 0;
+        for (int i = left; i <= right; i++) {
+            res += nums[i];
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class NumArray {
+    /**
+     * @param {number[]} nums
+     */
+    constructor(nums) {
+        this.nums = nums;
+    }
+
+    /** 
+     * @param {number} index 
+     * @param {number} val
+     * @return {void}
+     */
+    update(index, val) {
+        this.nums[index] = val;
+    }
+
+    /** 
+     * @param {number} left 
+     * @param {number} right
+     * @return {number}
+     */
+    sumRange(left, right) {
+        let res = 0;
+        for (let i = left; i <= right; i++) {
+            res += this.nums[i];
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(n)$ for initializing the input array.
+    * $O(1)$ for each $update()$ function call.
+    * $O(n)$ for each $sumRange()$ function call.
+* Space complexity: $O(n)$
+
+---
+
+## 2. Recursive Segment Tree
+
+::tabs-start
+
+```python
+class SegmentTree:
+    def __init__(self, N, A):
+        self.n = N
+        while (self.n & (self.n - 1)) != 0:
+            self.n += 1
+        self.tree = [0] * (2 * self.n)
+        self.build(0, 0, self.n - 1, A)
+
+    def build(self, node, start, end, A):
+        if start == end:
+            if start < len(A):
+                self.tree[node] = A[start]
+        else:
+            mid = (start + end) // 2
+            left = 2 * node + 1
+            right = 2 * node + 2
+            self.build(left, start, mid, A)
+            self.build(right, mid + 1, end, A)
+            self.tree[node] = self.tree[left] + self.tree[right]
+
+    def update(self, i, val):
+        def _update(node, start, end, idx, value):
+            if start == end:
+                self.tree[node] = value
+            else:
+                mid = (start + end) // 2
+                left = 2 * node + 1
+                right = 2 * node + 2
+                if idx <= mid:
+                    _update(left, start, mid, idx, value)
+                else:
+                    _update(right, mid + 1, end, idx, value)
+                self.tree[node] = self.tree[left] + self.tree[right]
+        _update(0, 0, self.n - 1, i, val)
+
+    def query(self, l, r):
+        def _query(node, start, end, L, R):
+            if R < start or L > end:
+                return 0
+            if L <= start and end <= R:
+                return self.tree[node]
+            mid = (start + end) // 2
+            left = 2 * node + 1
+            right = 2 * node + 2
+            left_sum = _query(left, start, mid, L, R)
+            right_sum = _query(right, mid + 1, end, L, R)
+            return left_sum + right_sum
+        return _query(0, 0, self.n - 1, l, r)
+
+class NumArray:
+
+    def __init__(self, nums: List[int]):
+        self.segTree = SegmentTree(len(nums), nums)
+
+    def update(self, index: int, val: int) -> None:
+        self.segTree.update(index, val)
+
+    def sumRange(self, left: int, right: int) -> int:
+        return self.segTree.query(left, right)
+```
+
+```java
+class SegmentTree {
+    int n;
+    int[] tree;
+
+    SegmentTree(int N, int[] A) {
+        this.n = N;
+        while (Integer.bitCount(n) != 1) {
+            n++;
+        }
+        tree = new int[2 * n];
+        build(0, 0, n - 1, A);
+    }
+
+    void build(int node, int start, int end, int[] A) {
+        if (start == end) {
+            tree[node] = (start < A.length) ? A[start] : 0;
+            return;
+        }
+        int mid = start + (end - start) / 2;
+        build(node * 2 + 1, start, mid, A);
+        build(node * 2 + 2, mid + 1, end, A);
+        tree[node] = tree[node * 2 + 1] + tree[node * 2 + 2];
+    }
+
+    void update(int idx, int val) {
+        update(0, 0, n - 1, idx, val);
+    }
+
+    void update(int node, int start, int end, int idx, int val) {
+        if (start == end) {
+            tree[node] = val;
+            return;
+        }
+        int mid = start + (end - start) / 2;
+        if (idx <= mid) {
+            update(node * 2 + 1, start, mid, idx, val);
+        } else {
+            update(node * 2 + 2, mid + 1, end, idx, val);
+        }
+        tree[node] = tree[node * 2 + 1] + tree[node * 2 + 2];
+    }
+
+    int query(int l, int r) {
+        return query(0, 0, n - 1, l, r);
+    }
+
+    int query(int node, int start, int end, int l, int r) {
+        if (start > r || end < l) {
+            return 0;
+        }
+        if (start >= l && end <= r) {
+            return tree[node];
+        }
+        int mid = start + (end - start) / 2;
+        int leftSum = query(node * 2 + 1, start, mid, l, r);
+        int rightSum = query(node * 2 + 2, mid + 1, end, l, r);
+        return leftSum + rightSum;
+    }
+}
+
+public class NumArray {
+    private SegmentTree segTree;
+
+    public NumArray(int[] nums) {
+        this.segTree = new SegmentTree(nums.length, nums);
+    }
+
+    public void update(int index, int val) {
+        this.segTree.update(index, val);
+    }
+
+    public int sumRange(int left, int right) {
+        return this.segTree.query(left, right);
+    }
+}
+```
+
+```cpp
+class SegmentTree {
+public:
+    int n;
+    vector<int> tree;
+
+    SegmentTree(int N, vector<int>& A) {
+        this->n = N;
+        while (__builtin_popcount(n) != 1) {
+            n++;
+        }
+        tree.resize(2 * n);
+        build(0, 0, n - 1, A);
+    }
+
+    void build(int node, int start, int end, vector<int>& A) {
+        if (start == end) {
+            tree[node] = (start < A.size()) ? A[start] : 0;
+        } else {
+            int mid = (start + end) / 2;
+            build(2 * node + 1, start, mid, A);
+            build(2 * node + 2, mid + 1, end, A);
+            tree[node] = tree[2 * node + 1] + tree[2 * node + 2];
+        }
+    }
+
+    void update(int node, int start, int end, int idx, int val) {
+        if (start == end) {
+            tree[node] = val;
+        } else {
+            int mid = (start + end) / 2;
+            if (idx <= mid) {
+                update(2 * node + 1, start, mid, idx, val);
+            } else {
+                update(2 * node + 2, mid + 1, end, idx, val);
+            }
+            tree[node] = tree[2 * node + 1] + tree[2 * node + 2];
+        }
+    }
+
+    int query(int node, int start, int end, int l, int r) {
+        if (r < start || end < l) {
+            return 0;
+        }
+        if (l <= start && end <= r) {
+            return tree[node];
+        }
+        int mid = (start + end) / 2;
+        int leftSum = query(2 * node + 1, start, mid, l, r);
+        int rightSum = query(2 * node + 2, mid + 1, end, l, r);
+        return leftSum + rightSum;
+    }
+
+    void update(int idx, int val) {
+        update(0, 0, n - 1, idx, val);
+    }
+
+    int query(int l, int r) {
+        return query(0, 0, n - 1, l, r);
+    }
+};
+
+class NumArray {
+    SegmentTree* segTree;
+
+public:
+    NumArray(vector<int>& nums) {
+        this->segTree = new SegmentTree(nums.size(), nums);
+    }
+    
+    void update(int index, int val) {
+        this->segTree->update(index, val);
+    }
+    
+    int sumRange(int left, int right) {
+        return this->segTree->query(left, right);
+    }
+};
+```
+
+```javascript
+class SegmentTree {
+    /**
+     * @constructor
+     * @param {number} N 
+     * @param {number[]} A
+     */
+    constructor(N, A) {
+        this.n = N;
+        while ((this.n & (this.n - 1)) !== 0) {
+            this.n++;
+        }
+        this.tree = new Int32Array(2 * this.n);
+        this.build(0, 0, this.n - 1, A);
+    }
+    
+    /**
+     * @param {number} node 
+     * @param {number} start 
+     * @param {number} end 
+     * @param {number[]} A 
+     */
+    build(node, start, end, A) {
+        if (start === end) {
+            this.tree[node] = start < A.length ? A[start] : 0;
+        } else {
+            const mid = Math.floor((start + end) / 2);
+            this.build(2 * node + 1, start, mid, A);
+            this.build(2 * node + 2, mid + 1, end, A);
+            this.tree[node] = this.tree[2 * node + 1] + this.tree[2 * node + 2];
+        }
+    }
+
+    /**
+     * @param {number} node
+     * @param {number} start
+     * @param {number} end
+     * @param {number} idx
+     * @param {number} val
+     * @return {void}
+     */
+    _update(node, start, end, idx, val) {
+        if (start === end) {
+            this.tree[node] = val;
+        } else {
+            const mid = Math.floor((start + end) / 2);
+            if (idx <= mid) {
+                this._update(2 * node + 1, start, mid, idx, val);
+            } else {
+                this._update(2 * node + 2, mid + 1, end, idx, val);
+            }
+            this.tree[node] = this.tree[2 * node + 1] + this.tree[2 * node + 2];
+        }
+    }
+
+    /**
+     * @param {number} node 
+     * @param {number} start 
+     * @param {number} end 
+     * @param {number} l 
+     * @param {number} r 
+     * @return {number}
+     */
+    _query(node, start, end, l, r) {
+        if (r < start || end < l) {
+            return 0;
+        }
+        if (l <= start && end <= r) {
+            return this.tree[node];
+        }
+        const mid = Math.floor((start + end) / 2);
+        const leftSum = this._query(2 * node + 1, start, mid, l, r);
+        const rightSum = this._query(2 * node + 2, mid + 1, end, l, r);
+        return leftSum + rightSum;
+    }
+
+    /**
+     * @param {number} idx
+     * @param {number} val
+     * @return {void}
+     */
+    update(idx, val) {
+        this._update(0, 0, this.n - 1, idx, val);
+    }
+
+    /**
+     * @param {number} l 
+     * @param {number} r 
+     * @return {number}
+     */
+    query(l, r) {
+        return this._query(0, 0, this.n - 1, l, r);
+    }
+}
+
+class NumArray {
+    /**
+     * @param {number[]} nums
+     */
+    constructor(nums) {
+        this.segTree = new SegmentTree(nums.length, nums);
+    }
+
+    /** 
+     * @param {number} index 
+     * @param {number} val
+     * @return {void}
+     */
+    update(index, val) {
+        this.segTree.update(index, val);
+    }
+
+    /** 
+     * @param {number} left 
+     * @param {number} right
+     * @return {number}
+     */
+    sumRange(left, right) {
+        return this.segTree.query(left, right);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(n)$ for initializing the input array.
+    * $O(\log n)$ for each $update()$ function call.
+    * $O(\log n)$ for each $sumRange()$ function call.
+* Space complexity: $O(n)$
+
+---
+
+## 3. Iterative Segement Tree
+
+::tabs-start
+
+```python
+class SegmentTree:
+    def __init__(self, N, A):
+        self.n = N
+        while (self.n & (self.n - 1)) != 0:
+            self.n += 1
+        self.build(N, A)
+
+    def build(self, N, A):
+        self.tree = [0] * (2 * self.n)
+        for i in range(N):
+            self.tree[self.n + i] = A[i]
+        for i in range(self.n - 1, 0, -1):
+            self.tree[i] = self.tree[i << 1] + self.tree[i << 1 | 1]
+
+    def update(self, i, val):
+        self.tree[self.n + i] = val
+        j = (self.n + i) >> 1
+        while j >= 1:
+            self.tree[j] = self.tree[j << 1] + self.tree[j << 1 | 1]
+            j >>= 1
+
+    def query(self, l, r):
+        res = 0
+        l += self.n
+        r += self.n + 1
+        while l < r:
+            if l & 1:
+                res += self.tree[l]
+                l += 1
+            if r & 1:
+                r -= 1
+                res += self.tree[r]
+            l >>= 1
+            r >>= 1
+        return res
+
+class NumArray:
+
+    def __init__(self, nums: List[int]):
+        self.segTree = SegmentTree(len(nums), nums)
+
+    def update(self, index: int, val: int) -> None:
+        self.segTree.update(index, val)
+
+    def sumRange(self, left: int, right: int) -> int:
+        return self.segTree.query(left, right)
+```
+
+```java
+class SegmentTree {
+    int n;
+    int[] tree;
+
+    SegmentTree(int N, int[] A) {
+        this.n = N;
+        while (Integer.bitCount(n) != 1) {
+            n++;
+        }
+        build(N, A);
+    }
+
+    void build(int N, int[] A) {
+        tree = new int[2 * n];
+        for (int i = 0; i < N; i++) {
+            tree[n + i] = A[i];
+        }
+        for (int i = n - 1; i > 0; --i) {
+            tree[i] = tree[i << 1] + tree[i << 1 | 1];
+        }
+    }
+
+    void update(int i, int val) {
+        tree[n + i] = val;
+        for (int j = (n + i) >> 1; j >= 1; j >>= 1) {
+            tree[j] = tree[j << 1] + tree[j << 1 | 1];
+        }
+    }
+
+    int query(int l, int r) {
+        int res = 0;
+        for (l += n, r += n + 1; l < r; l >>= 1, r >>= 1) {
+            if ((l & 1) == 1) res += tree[l++];
+            if ((r & 1) == 1) res += tree[--r];
+        }
+        return res;
+    }
+}
+
+public class NumArray {
+    private int[] nums;
+    private SegmentTree segTree;
+
+    public NumArray(int[] nums) {
+        this.segTree = new SegmentTree(nums.length, nums);
+    }
+
+    public void update(int index, int val) {
+        this.segTree.update(index, val);
+    }
+
+    public int sumRange(int left, int right) {
+        return this.segTree.query(left, right);
+    }
+}
+```
+
+```cpp
+class SegmentTree {
+public:
+    int n;
+    vector<int> tree;
+
+    SegmentTree(int N, vector<int>& A) {
+        this->n = N;
+        while (__builtin_popcount(n) != 1) {
+            n++;
+        }
+        build(N, A);
+    }
+
+    void build(int N, vector<int>& A) {
+        tree.resize(2 * n);
+        for (int i = 0; i < N; i++) {
+            tree[n + i] = A[i];
+        }
+        for (int i = n - 1; i > 0; --i) {
+            tree[i] = tree[i << 1] + tree[i << 1 | 1];
+        }
+    }
+
+    void update(int i, int val) {
+        tree[n + i] = val;
+        for (int j = (n + i) >> 1; j >= 1; j >>= 1) {
+            tree[j] = tree[j << 1] + tree[j << 1 | 1];
+        }
+    }
+
+    int query(int l, int r) {
+        int res = 0;
+        for (l += n, r += n + 1; l < r; l >>= 1, r >>= 1) {
+            if (l & 1) res += tree[l++];
+            if (r & 1) res += tree[--r];
+        }
+        return res;
+    }
+};
+
+class NumArray {
+    SegmentTree* segTree;
+
+public:
+    NumArray(vector<int>& nums) {
+        this->segTree = new SegmentTree(nums.size(), nums);
+    }
+    
+    void update(int index, int val) {
+        this->segTree->update(index, val);
+    }
+    
+    int sumRange(int left, int right) {
+        return this->segTree->query(left, right);
+    }
+};
+```
+
+```javascript
+class SegmentTree {
+    /**
+     * @constructor
+     * @param {number} N 
+     * @param {number[]} A
+     */
+    constructor(N, A) {
+        this.n = N;
+        while ((this.n & (this.n - 1)) !== 0) {
+            this.n++;
+        }
+        this.build(N, A);
+    }
+    
+    /**
+     * @param {number} N 
+     * @param {number[]} A
+     * @return {void}
+     */
+    build(N, A) {
+        this.tree = new Int32Array(2 * this.n);
+        for (let i = 0; i < N; i++) {
+            this.tree[this.n + i] = A[i];
+        }
+        for (let i = this.n - 1; i > 0; i--) {
+            this.tree[i] = this.tree[i << 1] + this.tree[i << 1 | 1];
+        }
+    }
+
+    /**
+     * @param {number} i
+     * @param {number} val
+     * @return {void}
+     */
+    update(i, val) {
+        this.tree[this.n + i] = val;
+        for (let j = (this.n + i) >> 1; j >= 1; j >>= 1) {
+            this.tree[j] = this.tree[j << 1] + this.tree[j << 1 | 1];
+        }
+    }
+
+    /**
+     * @param {number} l
+     * @param {number} r
+     * @return {number}
+     */
+    query(l, r) {
+        let res = 0;
+        l += this.n;
+        r += this.n + 1;
+
+        while (l < r) {
+            if (l & 1) res += this.tree[l++];
+            if (r & 1) res += this.tree[--r];
+            l >>= 1;
+            r >>= 1;
+        }
+
+        return res;
+    }
+}
+
+class NumArray {
+    /**
+     * @param {number[]} nums
+     */
+    constructor(nums) {
+        this.segTree = new SegmentTree(nums.length, nums);
+    }
+
+    /** 
+     * @param {number} index 
+     * @param {number} val
+     * @return {void}
+     */
+    update(index, val) {
+        this.segTree.update(index, val);
+    }
+
+    /** 
+     * @param {number} left 
+     * @param {number} right
+     * @return {number}
+     */
+    sumRange(left, right) {
+        return this.segTree.query(left, right);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(n)$ for initializing the input array.
+    * $O(\log n)$ for each $update()$ function call.
+    * $O(\log n)$ for each $sumRange()$ function call.
+* Space complexity: $O(n)$
+
+---
+
+## 4. Square Root Decomposition (Update Optimized)
+
+::tabs-start
+
+```python
+class SqrtDecomposition:
+    
+    def __init__(self, nums):
+        self.A = nums[:]
+        self.n = len(nums)
+        self.block_size = int(self.n ** 0.5) + 1
+        self.blocks = [0] * self.block_size
+
+        for i in range(self.n):
+            self.blocks[i // self.block_size] += self.A[i]
+
+    def query(self, left, right):
+        total_sum = 0
+        while left <= right and left % self.block_size != 0:
+            total_sum += self.A[left]
+            left += 1
+
+        while left + self.block_size - 1 <= right:
+            total_sum += self.blocks[left // self.block_size]
+            left += self.block_size
+
+        while left <= right:
+            total_sum += self.A[left]
+            left += 1
+
+        return total_sum
+
+    def update(self, index, val):
+        block_index = index // self.block_size
+        self.blocks[block_index] += val - self.A[index]
+        self.A[index] = val
+
+class NumArray:
+
+    def __init__(self, nums: List[int]):
+        self.sq = SqrtDecomposition(nums)
+
+    def update(self, index: int, val: int) -> None:
+        self.sq.update(index, val)
+
+    def sumRange(self, left: int, right: int) -> int:
+        return self.sq.query(left, right)
+```
+
+```java
+class SqrtDecomposition {
+    private int[] nums, blocks;
+    private int blockSize, n;
+
+    public SqrtDecomposition(int[] nums) {
+        this.nums = nums.clone();
+        this.n = nums.length;
+        this.blockSize = (int) Math.sqrt(n) + 1;
+        this.blocks = new int[blockSize];
+
+        for (int i = 0; i < n; i++) {
+            blocks[i / blockSize] += nums[i];
+        }
+    }
+
+    public int query(int left, int right) {
+        int totalSum = 0;
+        while (left <= right && left % blockSize != 0) {
+            totalSum += nums[left++];
+        }
+
+        while (left + blockSize - 1 <= right) {
+            totalSum += blocks[left / blockSize];
+            left += blockSize;
+        }
+
+        while (left <= right) {
+            totalSum += nums[left++];
+        }
+
+        return totalSum;
+    }
+
+    public void update(int index, int val) {
+        int blockIndex = index / blockSize;
+        blocks[blockIndex] += val - nums[index];
+        nums[index] = val;
+    }
+}
+
+public class NumArray {
+    private SqrtDecomposition sq;
+
+    public NumArray(int[] nums) {
+        sq = new SqrtDecomposition(nums);
+    }
+
+    public void update(int index, int val) {
+        sq.update(index, val);
+    }
+
+    public int sumRange(int left, int right) {
+        return sq.query(left, right);
+    }
+}
+```
+
+```cpp
+class SqrtDecomposition {
+private:
+    vector<int> nums, blocks;
+    int blockSize, n;
+
+public:
+    SqrtDecomposition(vector<int>& nums) {
+        this->nums = nums;
+        this->n = nums.size();
+        this->blockSize = sqrt(n) + 1;
+        this->blocks.resize(blockSize, 0);
+
+        for (int i = 0; i < n; i++) {
+            blocks[i / blockSize] += nums[i];
+        }
+    }
+
+    int query(int left, int right) {
+        int totalSum = 0;
+        while (left <= right && left % blockSize != 0) {
+            totalSum += nums[left++];
+        }
+
+        while (left + blockSize - 1 <= right) {
+            totalSum += blocks[left / blockSize];
+            left += blockSize;
+        }
+
+        while (left <= right) {
+            totalSum += nums[left++];
+        }
+
+        return totalSum;
+    }
+
+    void update(int index, int val) {
+        int blockIndex = index / blockSize;
+        blocks[blockIndex] += val - nums[index];
+        nums[index] = val;
+    }
+};
+
+class NumArray {
+private:
+    SqrtDecomposition* sq;
+
+public:
+    NumArray(vector<int>& nums) {
+        sq = new SqrtDecomposition(nums);
+    }
+
+    void update(int index, int val) {
+        sq->update(index, val);
+    }
+
+    int sumRange(int left, int right) {
+        return sq->query(left, right);
+    }
+};
+```
+
+```javascript
+class SqrtDecomposition {
+    /**
+     * @param {number[]} nums
+     */
+    constructor(nums) {
+        this.nums = [...nums];
+        this.n = nums.length;
+        this.blockSize = Math.floor(Math.sqrt(this.n)) + 1;
+        this.blocks = new Array(this.blockSize).fill(0);
+
+        for (let i = 0; i < this.n; i++) {
+            this.blocks[Math.floor(i / this.blockSize)] += nums[i];
+        }
+    }
+
+    /** 
+     * @param {number} left 
+     * @param {number} right
+     * @return {number}
+     */
+    query(left, right) {
+        let totalSum = 0;
+        while (left <= right && left % this.blockSize !== 0) {
+            totalSum += this.nums[left++];
+        }
+
+        while (left + this.blockSize - 1 <= right) {
+            totalSum += this.blocks[Math.floor(left / this.blockSize)];
+            left += this.blockSize;
+        }
+
+        while (left <= right) {
+            totalSum += this.nums[left++];
+        }
+
+        return totalSum;
+    }
+
+    /** 
+     * @param {number} index 
+     * @param {number} val
+     * @return {void}
+     */
+    update(index, val) {
+        let blockIndex = Math.floor(index / this.blockSize);
+        this.blocks[blockIndex] += val - this.nums[index];
+        this.nums[index] = val;
+    }
+}
+
+class NumArray {
+    /**
+     * @param {number[]} nums
+     */
+    constructor(nums) {
+        this.sq = new SqrtDecomposition(nums);
+    }
+
+    /** 
+     * @param {number} index 
+     * @param {number} val
+     * @return {void}
+     */
+    update(index, val) {
+        this.sq.update(index, val);
+    }
+
+    /** 
+     * @param {number} left 
+     * @param {number} right
+     * @return {number}
+     */
+    sumRange(left, right) {
+        return this.sq.query(left, right);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(n)$ for initializing the input array.
+    * $O(1)$ for each $update()$ function call.
+    * $O(\sqrt {n})$ for each $sumRange()$ function call.
+* Space complexity: $O(n)$
+
+---
+
+## 5. Square Root Decomposition (Query Optimized)
+
+::tabs-start
+
+```python
+class SqrtDecomposition:
+
+    def __init__(self, nums):
+        self.A = nums[:]
+        self.prefix_sums = nums[:]
+        self.n = len(nums)
+        self.block_size = int(self.n ** 0.5) + 1
+
+        for i in range(1, self.n):
+            if i % self.block_size != 0:
+                self.prefix_sums[i] += self.prefix_sums[i - 1]
+
+    def query(self, left, right):
+        total_sum = -(self.prefix_sums[left - 1] if left % self.block_size != 0 else 0)
+
+        while left // self.block_size < right // self.block_size:
+            block_end = min(self.n - 1, (left // self.block_size) * self.block_size + self.block_size - 1)
+            total_sum += self.prefix_sums[block_end]
+            left = block_end + 1
+
+        total_sum += self.prefix_sums[right]
+        return total_sum
+
+        total_sum += self.prefix_sums[right]
+        return total_sum
+
+    def update(self, index, val):
+        diff = val - self.A[index]
+        self.A[index] = val
+
+        block_end = min(self.n - 1, (index // self.block_size) * self.block_size + self.block_size - 1)
+        for i in range(index, block_end + 1):
+            self.prefix_sums[i] += diff
+
+class NumArray:
+
+    def __init__(self, nums: List[int]):
+        self.sq = SqrtDecomposition(nums)
+
+    def update(self, index: int, val: int) -> None:
+        self.sq.update(index, val)
+
+    def sumRange(self, left: int, right: int) -> int:
+        return self.sq.query(left, right)
+```
+
+```java
+class SqrtDecomposition {
+    private int[] nums, prefixSums;
+    private int blockSize, n;
+
+    public SqrtDecomposition(int[] nums) {
+        this.nums = nums.clone();
+        this.n = nums.length;
+        this.blockSize = (int) Math.sqrt(n) + 1;
+        this.prefixSums = nums.clone();
+
+        for (int i = 1; i < n; i++) {
+            if (i % blockSize != 0) {
+                prefixSums[i] += prefixSums[i - 1];
+            }
+        }
+    }
+
+    public int query(int left, int right) {
+        int totalSum = (left % blockSize != 0) ? -prefixSums[left - 1] : 0;
+
+        while (left / blockSize < right / blockSize) {
+            int blockEnd = Math.min(n - 1, (left / blockSize) * blockSize + blockSize - 1);
+            totalSum += prefixSums[blockEnd];
+            left = blockEnd + 1;
+        }
+
+        totalSum += prefixSums[right];
+        return totalSum;
+    }
+
+    public void update(int index, int val) {
+        int diff = val - nums[index];
+        nums[index] = val;
+
+        int blockEnd = Math.min(n - 1, (index / blockSize) * blockSize + blockSize - 1);
+        for (int i = index; i <= blockEnd; i++) {
+            prefixSums[i] += diff;
+        }
+    }
+}
+
+public class NumArray {
+    private SqrtDecomposition sq;
+
+    public NumArray(int[] nums) {
+        sq = new SqrtDecomposition(nums);
+    }
+
+    public void update(int index, int val) {
+        sq.update(index, val);
+    }
+
+    public int sumRange(int left, int right) {
+        return sq.query(left, right);
+    }
+}
+```
+
+```cpp
+class SqrtDecomposition {
+private:
+    vector<int> nums, prefixSums;
+    int blockSize, n;
+
+public:
+    SqrtDecomposition(vector<int>& nums) {
+        this->nums = nums;
+        this->n = nums.size();
+        this->blockSize = sqrt(n) + 1;
+        this->prefixSums = nums;
+
+        for (int i = 1; i < n; i++) {
+            if (i % blockSize != 0) {
+                prefixSums[i] += prefixSums[i - 1];
+            }
+        }
+    }
+
+    int query(int left, int right) {
+        int totalSum = (left % blockSize != 0) ? -prefixSums[left - 1] : 0;
+
+        while (left / blockSize < right / blockSize) {
+            int blockEnd = min(n - 1, (left / blockSize) * blockSize + blockSize - 1);
+            totalSum += prefixSums[blockEnd];
+            left = blockEnd + 1;
+        }
+
+        totalSum += prefixSums[right];
+        return totalSum;
+    }
+
+    void update(int index, int val) {
+        int diff = val - nums[index];
+        nums[index] = val;
+
+        int blockEnd = min(n - 1, (index / blockSize) * blockSize + blockSize - 1);
+        for (int i = index; i <= blockEnd; i++) {
+            prefixSums[i] += diff;
+        }
+    }
+};
+
+class NumArray {
+private:
+    SqrtDecomposition* sq;
+
+public:
+    NumArray(vector<int>& nums) {
+        sq = new SqrtDecomposition(nums);
+    }
+
+    void update(int index, int val) {
+        sq->update(index, val);
+    }
+
+    int sumRange(int left, int right) {
+        return sq->query(left, right);
+    }
+};
+```
+
+```javascript
+class SqrtDecomposition {
+    /**
+     * @param {number[]} nums
+     */
+    constructor(nums) {
+        this.nums = [...nums];
+        this.n = nums.length;
+        this.blockSize = Math.floor(Math.sqrt(this.n)) + 1;
+        this.prefixSums = [...nums];
+
+        for (let i = 1; i < this.n; i++) {
+            if (i % this.blockSize !== 0) {
+                this.prefixSums[i] += this.prefixSums[i - 1];
+            }
+        }
+    }
+
+    /** 
+     * @param {number} left 
+     * @param {number} right
+     * @return {number}
+     */
+    query(left, right) {
+        let totalSum = (left % this.blockSize !== 0) ? -this.prefixSums[left - 1] : 0;
+
+        while (Math.floor(left / this.blockSize) < Math.floor(right / this.blockSize)) {
+            const blockEnd = Math.min(this.n - 1, Math.floor(left / this.blockSize) * this.blockSize + this.blockSize - 1);
+            totalSum += this.prefixSums[blockEnd];
+            left = blockEnd + 1;
+        }
+
+        totalSum += this.prefixSums[right];
+        return totalSum;
+    }
+
+    /** 
+     * @param {number} index 
+     * @param {number} val
+     * @return {void}
+     */
+    update(index, val) {
+        const diff = val - this.nums[index];
+        this.nums[index] = val;
+
+        const blockEnd = Math.min(this.n - 1, Math.floor(index / this.blockSize) * this.blockSize + this.blockSize - 1);
+        for (let i = index; i <= blockEnd; i++) {
+            this.prefixSums[i] += diff;
+        }
+    }
+}
+
+class NumArray {
+    /**
+     * @param {number[]} nums
+     */
+    constructor(nums) {
+        this.sq = new SqrtDecomposition(nums);
+    }
+
+    /** 
+     * @param {number} index 
+     * @param {number} val
+     * @return {void}
+     */
+    update(index, val) {
+        this.sq.update(index, val);
+    }
+
+    /** 
+     * @param {number} left 
+     * @param {number} right
+     * @return {number}
+     */
+    sumRange(left, right) {
+        return this.sq.query(left, right);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(n)$ for initializing the input array.
+    * $O(\sqrt {n})$ for each $update()$ function call.
+    * $O(\sqrt {n})$ for each $sumRange()$ function call.
+* Space complexity: $O(n)$
+
+---
+
+## 6. Binary Indexed Tree (Fenwick Tree)
+
+::tabs-start
+
+```python
+class BIT:
+    def __init__(self, nums):
+        self.n = len(nums) + 1
+        self.nums = [0] * self.n
+        self.tree = [0] * self.n
+        for i in range(self.n - 1):
+            self.update(i, nums[i])
+
+    def update(self, index, val):
+        index += 1
+        diff = val - self.nums[index]
+        self.nums[index] = val
+        while index < self.n:
+            self.tree[index] += diff
+            index += index & -index
+
+    def prefix_sum(self, index):
+        total_sum = 0
+        while index > 0:
+            total_sum += self.tree[index]
+            index -= index & -index
+        return total_sum
+
+    def query(self, left, right):
+        return self.prefix_sum(right + 1) - self.prefix_sum(left)
+
+
+class NumArray:
+    def __init__(self, nums: List[int]):
+        self.bit = BIT(nums)
+
+    def update(self, index: int, val: int) -> None:
+        self.bit.update(index, val)
+
+    def sumRange(self, left: int, right: int) -> int:
+        return self.bit.query(left, right)
+```
+
+```java
+class BIT {
+    private int[] nums;
+    private int[] tree;
+    private int n;
+
+    public BIT(int[] nums) {
+        this.n = nums.length + 1;
+        this.nums = new int[n];
+        this.tree = new int[n];
+        for (int i = 0; i < n - 1; i++) {
+            update(i, nums[i]);
+        }
+    }
+
+    public void update(int index, int val) {
+        index++;
+        int diff = val - nums[index];
+        nums[index] = val;
+        while (index < n) {
+            tree[index] += diff;
+            index += index & -index;
+        }
+    }
+
+    public int prefixSum(int index) {
+        int totalSum = 0;
+        while (index > 0) {
+            totalSum += tree[index];
+            index -= index & -index;
+        }
+        return totalSum;
+    }
+
+    public int query(int left, int right) {
+        return prefixSum(right + 1) - prefixSum(left);
+    }
+}
+
+public class NumArray {
+    private BIT bit;
+
+    public NumArray(int[] nums) {
+        this.bit = new BIT(nums);
+    }
+
+    public void update(int index, int val) {
+        bit.update(index, val);
+    }
+
+    public int sumRange(int left, int right) {
+        return bit.query(left, right);
+    }
+}
+```
+
+```cpp
+class BIT {
+    vector<int> nums;
+    vector<int> tree;
+    int n;
+
+public:
+    BIT(vector<int>& nums) {
+        n = nums.size() + 1;
+        this->nums.resize(n);
+        tree.resize(n, 0);
+        for (int i = 0; i < nums.size(); i++) {
+            update(i, nums[i]);
+        }
+    }
+
+    void update(int index, int val) {
+        index++;
+        int diff = val - nums[index];
+        nums[index] = val;
+        while (index < n) {
+            tree[index] += diff;
+            index += index & -index;
+        }
+    }
+
+    int prefixSum(int index) {
+        int totalSum = 0;
+        while (index > 0) {
+            totalSum += tree[index];
+            index -= index & -index;
+        }
+        return totalSum;
+    }
+
+    int query(int left, int right) {
+        return prefixSum(right + 1) - prefixSum(left);
+    }
+};
+
+class NumArray {
+    BIT bit;
+
+public:
+    NumArray(vector<int>& nums) : bit(nums) {}
+
+    void update(int index, int val) {
+        bit.update(index, val);
+    }
+
+    int sumRange(int left, int right) {
+        return bit.query(left, right);
+    }
+};
+```
+
+```javascript
+class BIT {
+    /**
+     * @constructor
+     * @param {number[]} nums
+     */
+    constructor(nums) {
+        this.n = nums.length + 1;
+        this.tree = new Int32Array(this.n);
+        this.nums = new Int32Array(this.n);
+        for (let i = 0; i < this.n - 1; i++) {
+            this.update(i, nums[i]);
+        }
+    }
+
+    /** 
+     * @param {number} index 
+     * @param {number} val
+     * @return {void}
+     */
+    update(index, val) {
+        index++;
+        const diff = val - this.nums[index];
+        this.nums[index] = val;
+        while (index < this.n) {
+            this.tree[index] += diff;
+            index += index & -index;
+        }
+    }
+
+    /** 
+     * @param {number} index 
+     * @return {number}
+     */
+    prefixSum(index) {
+        let totalSum = 0;
+        while (index > 0) {
+            totalSum += this.tree[index];
+            index -= index & -index;
+        }
+        return totalSum;
+    }
+
+    /** 
+     * @param {number} left 
+     * @param {number} right
+     * @return {number}
+     */
+    query(left, right) {
+        return this.prefixSum(right + 1) - this.prefixSum(left);
+    }
+}
+
+class NumArray {
+    /**
+     * @param {number[]} nums
+     */
+    constructor(nums) {
+        this.bit = new BIT(nums);
+    }
+
+    /** 
+     * @param {number} index 
+     * @param {number} val
+     * @return {void}
+     */
+    update(index, val) {
+        this.bit.update(index, val);
+    }
+
+    /** 
+     * @param {number} left 
+     * @param {number} right
+     * @return {number}
+     */
+    sumRange(left, right) {
+        return this.bit.query(left, right);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(n)$ for initializing the input array.
+    * $O(\log n)$ for each $update()$ function call.
+    * $O(\log n)$ for each $sumRange()$ function call.
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/rearrange-array-elements-by-sign.md b/articles/rearrange-array-elements-by-sign.md
new file mode 100644
index 000000000..a634ed75b
--- /dev/null
+++ b/articles/rearrange-array-elements-by-sign.md
@@ -0,0 +1,310 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def rearrangeArray(self, nums: List[int]) -> List[int]:
+        n = len(nums)
+        for i in range(n):
+            if ((i % 2 == 0 and nums[i] > 0) or
+                (i % 2 == 1 and nums[i] < 0)):
+                continue
+            
+            j = i + 1
+            while j < n and ((nums[j] > 0) == (nums[i] > 0)):
+                j += 1
+            
+            tmp = nums[j]
+            while j > i:
+                nums[j] = nums[j - 1]
+                j -= 1
+            nums[i] = tmp
+        return nums
+```
+
+```java
+public class Solution {
+    public int[] rearrangeArray(int[] nums) {
+        int n = nums.length;
+        for (int i = 0; i < n; i++) {
+            if ((i % 2 == 0 && nums[i] > 0) || (i % 2 == 1 && nums[i] < 0)) {
+                continue;
+            }
+            
+            int j = i + 1;
+            while (j < n && ((nums[j] > 0) == (nums[i] > 0))) {
+                j++;
+            }
+            
+            int temp = nums[j];
+            while (j > i) {
+                nums[j] = nums[j - 1];
+                j--;
+            }
+            nums[i] = temp;
+        }
+        return nums;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> rearrangeArray(vector<int>& nums) {
+        int n = nums.size();
+        for (int i = 0; i < n; i++) {
+            if ((i % 2 == 0 && nums[i] > 0) || (i % 2 == 1 && nums[i] < 0)) {
+                continue;
+            }
+            
+            int j = i + 1;
+            while (j < n && ((nums[j] > 0) == (nums[i] > 0))) {
+                j++;
+            }
+            
+            int temp = nums[j];
+            while (j > i) {
+                nums[j] = nums[j - 1];
+                j--;
+            }
+            nums[i] = temp;
+        }
+        return nums;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    rearrangeArray(nums) {
+        let n = nums.length;
+        for (let i = 0; i < n; i++) {
+            if ((i % 2 === 0 && nums[i] > 0) || (i % 2 === 1 && nums[i] < 0)) {
+                continue;
+            }
+            
+            let j = i + 1;
+            while (j < n && ((nums[j] > 0) === (nums[i] > 0))) {
+                j++;
+            }
+            
+            let temp = nums[j];
+            while (j > i) {
+                nums[j] = nums[j - 1];
+                j--;
+            }
+            nums[i] = temp;
+        }
+        return nums;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 2. Group Numbers Into Two Arrays
+
+::tabs-start
+
+```python
+class Solution:
+    def rearrangeArray(self, nums: List[int]) -> List[int]:
+        pos, neg = [], []
+        for num in nums:
+            if num > 0:
+                pos.append(num)
+            else:
+                neg.append(num)
+
+        i = 0
+        while 2 * i < len(nums):
+            nums[2 * i] = pos[i]
+            nums[2 * i + 1] = neg[i]
+            i += 1
+        return nums
+```
+
+```java
+public class Solution {
+    public int[] rearrangeArray(int[] nums) {
+        List<Integer> pos = new ArrayList<>();
+        List<Integer> neg = new ArrayList<>();
+        for (int num : nums) {
+            if (num > 0) {
+                pos.add(num);
+            } else {
+                neg.add(num);
+            }
+        }
+
+        int i = 0;
+        while (2 * i < nums.length) {
+            nums[2 * i] = pos.get(i);
+            nums[2 * i + 1] = neg.get(i);
+            i++;
+        }
+        return nums;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> rearrangeArray(vector<int>& nums) {
+        vector<int> pos, neg;
+        for (int num : nums) {
+            if (num > 0) {
+                pos.push_back(num);
+            } else {
+                neg.push_back(num);
+            }
+        }
+
+        int i = 0;
+        while (2 * i < nums.size()) {
+            nums[2 * i] = pos[i];
+            nums[2 * i + 1] = neg[i];
+            i++;
+        }
+        return nums;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    rearrangeArray(nums) {
+        const pos = [], neg = [];
+        for (const num of nums) {
+            if (num > 0) {
+                pos.push(num);
+            } else {
+                neg.push(num);
+            }
+        }
+
+        let i = 0;
+        while (2 * i < nums.length) {
+            nums[2 * i] = pos[i];
+            nums[2 * i + 1] = neg[i];
+            i++;
+        }
+        return nums;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def rearrangeArray(self, nums: List[int]) -> List[int]:
+        i, j = 0, 1
+        res = [0] * len(nums)
+        for k in range(len(nums)):
+            if nums[k] > 0:
+                res[i] = nums[k]
+                i += 2
+            else:
+                res[j] = nums[k]
+                j += 2
+        return res
+```
+
+```java
+public class Solution {
+    public int[] rearrangeArray(int[] nums) {
+        int i = 0, j = 1;
+        int[] res = new int[nums.length];
+        for (int k = 0; k < nums.length; k++) {
+            if (nums[k] > 0) {
+                res[i] = nums[k];
+                i += 2;
+            } else {
+                res[j] = nums[k];
+                j += 2;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> rearrangeArray(vector<int>& nums) {
+        int i = 0, j = 1;
+        vector<int> res(nums.size());
+        for (int k = 0; k < nums.size(); k++) {
+            if (nums[k] > 0) {
+                res[i] = nums[k];
+                i += 2;
+            } else {
+                res[j] = nums[k];
+                j += 2;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    rearrangeArray(nums) {
+        let i = 0, j = 1;
+        const res = new Array(nums.length);
+        for (let k = 0; k < nums.length; k++) {
+            if (nums[k] > 0) {
+                res[i] = nums[k];
+                i += 2;
+            } else {
+                res[j] = nums[k];
+                j += 2;
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for the output array.
\ No newline at end of file
diff --git a/articles/reconstruct-flight-path.md b/articles/reconstruct-flight-path.md
index 6143dd788..26ca58784 100644
--- a/articles/reconstruct-flight-path.md
+++ b/articles/reconstruct-flight-path.md
@@ -199,6 +199,130 @@ public class Solution {
 }
 ```
 
+```go
+func findItinerary(tickets [][]string) []string {
+    adj := make(map[string][]string)
+    for _, ticket := range tickets {
+        adj[ticket[0]] = append(adj[ticket[0]], ticket[1])
+    }
+    
+    for src := range adj {
+        sort.Strings(adj[src])
+    }
+    
+    res := []string{"JFK"}
+    
+    var dfs func(string) bool
+    dfs = func(src string) bool {
+        if len(res) == len(tickets) + 1 {
+            return true
+        }
+        
+        destinations, exists := adj[src]
+        if !exists {
+            return false
+        }
+        
+        temp := make([]string, len(destinations))
+        copy(temp, destinations)
+        
+        for i, v := range temp {
+            adj[src] = append(adj[src][:i], adj[src][i+1:]...)
+            res = append(res, v)
+            
+            if dfs(v) {
+                return true
+            }
+            
+            adj[src] = append(adj[src][:i], append([]string{v}, adj[src][i:]...)...)
+            res = res[:len(res)-1]
+        }
+        return false
+    }
+    
+    dfs("JFK")
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun findItinerary(tickets: List<List<String>>): List<String> {
+        val adj = HashMap<String, MutableList<String>>()
+        
+        tickets.sortedBy { it[1] }.forEach { (src, dst) ->
+            adj.getOrPut(src) { mutableListOf() }.add(dst)
+        }
+        
+        val res = mutableListOf("JFK")
+        
+        fun dfs(src: String): Boolean {
+            if (res.size == tickets.size + 1) {
+                return true
+            }
+            
+            val destinations = adj[src] ?: return false
+            
+            for (i in destinations.indices) {
+                val v = destinations.removeAt(i)
+                res.add(v)
+                
+                if (dfs(v)) {
+                    return true
+                }
+                
+                destinations.add(i, v)
+                res.removeAt(res.lastIndex)
+            }
+            return false
+        }
+        
+        dfs("JFK")
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func findItinerary(_ tickets: [[String]]) -> [String] {
+        var adj = [String: [String]]()
+        for ticket in tickets {
+            adj[ticket[0], default: []].append(ticket[1])
+        }
+
+        for key in adj.keys {
+            adj[key]?.sort()
+        }
+
+        var res = ["JFK"]
+
+        func dfs(_ src: String) -> Bool {
+            if res.count == tickets.count + 1 {
+                return true
+            }
+            guard let destinations = adj[src] else {
+                return false
+            }
+
+            var temp = destinations
+            for i in 0..<temp.count {
+                let v = temp[i]
+                adj[src]?.remove(at: i)
+                res.append(v)
+                if dfs(v) { return true }
+                res.removeLast()
+                adj[src]?.insert(v, at: i)
+            }
+            return false
+        }
+
+        dfs("JFK")
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -206,7 +330,7 @@ public class Solution {
 * Time complexity: $O(E * V)$
 * Space complexity: $O(E * V)$
 
-> Where $E$ is the number of tickets (edges) and $V$ is the number of airpots (vertices).
+> Where $E$ is the number of tickets (edges) and $V$ is the number of airports (vertices).
 
 ---
 
@@ -352,6 +476,96 @@ public class Solution {
 }
 ```
 
+```go
+func findItinerary(tickets [][]string) []string {
+    adj := make(map[string][]string)
+    
+    sort.Slice(tickets, func(i, j int) bool {
+        if tickets[i][0] == tickets[j][0] {
+            return tickets[i][1] > tickets[j][1]
+        }
+        return tickets[i][0] > tickets[j][0]
+    })
+    
+    for _, ticket := range tickets {
+        src, dst := ticket[0], ticket[1]
+        adj[src] = append(adj[src], dst)
+    }
+    
+    res := make([]string, 0)
+    
+    var dfs func(string)
+    dfs = func(src string) {
+        for len(adj[src]) > 0 {
+            last := len(adj[src]) - 1
+            dst := adj[src][last]
+            adj[src] = adj[src][:last]
+            dfs(dst)
+        }
+        res = append(res, src)
+    }
+    
+    dfs("JFK")
+    
+    for i := 0; i < len(res)/2; i++ {
+        res[i], res[len(res)-1-i] = res[len(res)-1-i], res[i]
+    }
+    
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun findItinerary(tickets: List<List<String>>): List<String> {
+        val adj = HashMap<String, MutableList<String>>()
+        
+        tickets.sortedWith(compareBy({ it[0] }, { it[1] }))
+            .reversed()
+            .forEach { (src, dst) ->
+                adj.getOrPut(src) { mutableListOf() }.add(dst)
+            }
+        
+        val res = mutableListOf<String>()
+        
+        fun dfs(src: String) {
+            while (adj[src]?.isNotEmpty() == true) {
+                val dst = adj[src]!!.removeAt(adj[src]!!.lastIndex)
+                dfs(dst)
+            }
+            res.add(src)
+        }
+        
+        dfs("JFK")
+        return res.reversed()
+    }
+}
+```
+
+```swift
+class Solution {
+    func findItinerary(_ tickets: [[String]]) -> [String] {
+        var adj = [String: [String]]()
+        for ticket in tickets.sorted(by: { $0[1] > $1[1] }) {
+            adj[ticket[0], default: []].append(ticket[1])
+        }
+
+        var res = [String]()
+
+        func dfs(_ src: String) {
+            while let destinations = adj[src], !destinations.isEmpty {
+                let dst = adj[src]!.removeLast()
+                dfs(dst)
+            }
+            res.append(src)
+        }
+
+        dfs("JFK")
+        return res.reversed()
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -359,7 +573,7 @@ public class Solution {
 * Time complexity: $O(E\log E)$
 * Space complexity: $O(E)$
 
-> Where $E$ is the number of tickets (edges) and $V$ is the number of airpots (vertices).
+> Where $E$ is the number of tickets (edges) and $V$ is the number of airports (vertices).
 
 ---
 
@@ -509,6 +723,90 @@ public class Solution {
 }
 ```
 
+```go
+func findItinerary(tickets [][]string) []string {
+	adj := make(map[string][]string)
+	for _, ticket := range tickets {
+		src, dst := ticket[0], ticket[1]
+		adj[src] = append(adj[src], dst)
+	}
+	for src := range adj {
+		sort.Sort(sort.Reverse(sort.StringSlice(adj[src])))
+	}
+
+	stack := []string{"JFK"}
+	var res []string
+
+	for len(stack) > 0 {
+		curr := stack[len(stack)-1]
+		if len(adj[curr]) == 0 {
+			res = append(res, stack[len(stack)-1])
+			stack = stack[:len(stack)-1]
+		} else {
+			stack = append(stack, adj[curr][len(adj[curr])-1])
+			adj[curr] = adj[curr][:len(adj[curr])-1]
+		}
+	}
+
+	for i, j := 0, len(res)-1; i < j; i, j = i+1, j-1 {
+		res[i], res[j] = res[j], res[i]
+	}
+	return res
+}
+```
+
+```kotlin
+class Solution {
+    fun findItinerary(tickets: List<List<String>>): List<String> {
+        val adj = HashMap<String, MutableList<String>>()
+        for ((src, dst) in tickets.sortedWith(
+            compareByDescending<List<String>> { it[0] }.thenByDescending { it[1] })
+        ) {
+            adj.computeIfAbsent(src) { mutableListOf() }.add(dst)
+        }
+
+        val stack = ArrayDeque<String>().apply { add("JFK") }
+        val res = mutableListOf<String>()
+
+        while (stack.isNotEmpty()) {
+            val curr = stack.last()
+            if (adj[curr].isNullOrEmpty()) {
+                res.add(stack.removeLast())
+            } else {
+                stack.add(adj[curr]!!.removeLast())
+            }
+        }
+        
+        return res.asReversed()
+    }
+}
+```
+
+```swift
+class Solution {
+    func findItinerary(_ tickets: [[String]]) -> [String] {
+        var adj = [String: [String]]()
+        for ticket in tickets.sorted(by: { $0[1] > $1[1] }) {
+            adj[ticket[0], default: []].append(ticket[1])
+        }
+
+        var stack = ["JFK"]
+        var res = [String]()
+
+        while !stack.isEmpty {
+            let curr = stack.last!
+            if adj[curr] == nil || adj[curr]!.isEmpty {
+                res.append(stack.removeLast())
+            } else {
+                stack.append(adj[curr]!.removeLast())
+            }
+        }
+
+        return res.reversed()
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -516,4 +814,4 @@ public class Solution {
 * Time complexity: $O(E\log E)$
 * Space complexity: $O(E)$
 
-> Where $E$ is the number of tickets (edges) and $V$ is the number of airpots (vertices).
\ No newline at end of file
+> Where $E$ is the number of tickets (edges) and $V$ is the number of airports (vertices).
\ No newline at end of file
diff --git a/articles/redistribute-characters-to-make-all-strings-equal.md b/articles/redistribute-characters-to-make-all-strings-equal.md
new file mode 100644
index 000000000..b825a3786
--- /dev/null
+++ b/articles/redistribute-characters-to-make-all-strings-equal.md
@@ -0,0 +1,228 @@
+## 1. Frequency Count (Hash Map)
+
+::tabs-start
+
+```python
+class Solution:
+    def makeEqual(self, words: List[str]) -> bool:
+        char_cnt = defaultdict(int)
+
+        for w in words:
+            for c in w:
+                char_cnt[c] += 1
+        
+        for c in char_cnt:
+            if char_cnt[c] % len(words):
+                return False
+        return True
+```
+
+```java
+public class Solution {
+    public boolean makeEqual(String[] words) {
+        Map<Character, Integer> charCnt = new HashMap<>();
+
+        for (String w : words) {
+            for (char c : w.toCharArray()) {
+                charCnt.put(c, charCnt.getOrDefault(c, 0) + 1);
+            }
+        }
+
+        for (int count : charCnt.values()) {
+            if (count % words.length != 0) {
+                return false;
+            }
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool makeEqual(vector<string>& words) {
+        unordered_map<char, int> charCnt;
+
+        for (const string& w : words) {
+            for (char c : w) {
+                charCnt[c]++;
+            }
+        }
+
+        for (const auto& entry : charCnt) {
+            if (entry.second % words.size() != 0) {
+                return false;
+            }
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @return {boolean}
+     */
+    makeEqual(words) {
+        const charCnt = {};
+
+        for (let w of words) {
+            for (let c of w) {
+                charCnt[c] = (charCnt[c] || 0) + 1;
+            }
+        }
+
+        for (let count of Object.values(charCnt)) {
+            if (count % words.length !== 0) {
+                return false;
+            }
+        }
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(1)$ since we have at most $26$ different characters.
+
+> Where $n$ is the number of words and $m$ is the average length of each word.
+
+---
+
+## 2. Frequency Count (Array)
+
+::tabs-start
+
+```python
+class Solution:
+    def makeEqual(self, words: List[str]) -> bool:
+        freq = [0] * 26
+        flag = 0
+        n = len(words)
+
+        for w in words:
+            for c in w:
+                i = ord(c) - ord('a')
+                if freq[i] != 0:
+                    freq[i] += 1
+                    if freq[i] % n == 0:
+                        flag += 1
+                else:
+                    freq[i] += 1
+                    if freq[i] % n != 0:
+                        flag -= 1
+                freq[i] %= n
+                
+        return flag == 0
+```
+
+```java
+public class Solution {
+    public boolean makeEqual(String[] words) {
+        int[] freq = new int[26];
+        int flag = 0;
+        int n = words.length;
+
+        for (String w : words) {
+            for (char c : w.toCharArray()) {
+                int i = c - 'a';
+                if (freq[i] != 0) {
+                    freq[i]++;
+                    if (freq[i] % n == 0) {
+                        flag++;
+                    }
+                } else {
+                    freq[i]++;
+                    if (freq[i] % n != 0) {
+                        flag--;
+                    }
+                }
+                freq[i] %= n;
+            }
+        }
+        
+        return flag == 0;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool makeEqual(vector<string>& words) {
+        vector<int> freq(26, 0);
+        int flag = 0;
+        int n = words.size();
+
+        for (const string& w : words) {
+            for (char c : w) {
+                int i = c - 'a';
+                if (freq[i] != 0) {
+                    freq[i]++;
+                    if (freq[i] % n == 0) {
+                        flag++;
+                    }
+                } else {
+                    freq[i]++;
+                    if (freq[i] % n != 0) {
+                        flag--;
+                    }
+                }
+                freq[i] %= n;
+            }
+        }
+        
+        return flag == 0;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @return {boolean}
+     */
+    makeEqual(words) {
+        const freq = Array(26).fill(0);
+        let flag = 0;
+        const n = words.length;
+
+        for (let w of words) {
+            for (let c of w) {
+                const i = c.charCodeAt(0) - 'a'.charCodeAt(0);
+                if (freq[i] !== 0) {
+                    freq[i]++;
+                    if (freq[i] % n === 0) {
+                        flag++;
+                    }
+                } else {
+                    freq[i]++;
+                    if (freq[i] % n !== 0) {
+                        flag--;
+                    }
+                }
+                freq[i] %= n;
+            }
+        }
+
+        return flag === 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(1)$ since we have at most $26$ different characters.
+
+> Where $n$ is the number of words and $m$ is the average length of each word.
\ No newline at end of file
diff --git a/articles/redundant-connection.md b/articles/redundant-connection.md
index 6da3e2fc2..154493da7 100644
--- a/articles/redundant-connection.md
+++ b/articles/redundant-connection.md
@@ -174,6 +174,118 @@ public class Solution {
 }
 ```
 
+```go
+func findRedundantConnection(edges [][]int) []int {
+    n := len(edges)
+    adj := make([][]int, n+1)
+    visit := make([]bool, n+1)
+
+    var dfs func(node, par int) bool
+    dfs = func(node, par int) bool {
+        if visit[node] {
+            return true
+        }
+        visit[node] = true
+        for _, nei := range adj[node] {
+            if nei == par {
+                continue
+            }
+            if dfs(nei, node) {
+                return true
+            }
+        }
+        return false
+    }
+
+    for _, edge := range edges {
+        u, v := edge[0], edge[1]
+        adj[u] = append(adj[u], v)
+        adj[v] = append(adj[v], u)
+        for i := 0; i <= n; i++ {
+            visit[i] = false
+        }
+        
+        if dfs(u, -1) {
+            return []int{u, v}
+        }
+    }
+    return []int{}
+}
+```
+
+```kotlin
+class Solution {
+    fun findRedundantConnection(edges: Array<IntArray>): IntArray {
+        val n = edges.size
+        val adj = Array(n + 1) { mutableListOf<Int>() }
+
+        fun dfs(node: Int, par: Int, visit: BooleanArray): Boolean {
+            if (visit[node]) {
+                return true
+            }
+            visit[node] = true
+            for (nei in adj[node]) {
+                if (nei == par) continue
+                if (dfs(nei, node, visit)) return true
+            }
+            return false
+        }
+
+        for (edge in edges) {
+            val u = edge[0]
+            val v = edge[1]
+            adj[u].add(v)
+            adj[v].add(u)
+            val visit = BooleanArray(n + 1)
+
+            if (dfs(u, -1, visit)) {
+                return intArrayOf(u, v)
+            }
+        }
+        return intArrayOf()
+    }
+}
+```
+
+```swift
+class Solution {
+    func findRedundantConnection(_ edges: [[Int]]) -> [Int] {
+        let n = edges.count
+        var adj = Array(repeating: [Int](), count: n + 1)
+
+        func dfs(_ node: Int, _ par: Int, _ visit: inout [Bool]) -> Bool {
+            if visit[node] {
+                return true
+            }
+
+            visit[node] = true
+            for nei in adj[node] {
+                if nei == par {
+                    continue
+                }
+                if dfs(nei, node, &visit) {
+                    return true
+                }
+            }
+            return false
+        }
+
+        for edge in edges {
+            let u = edge[0]
+            let v = edge[1]
+            adj[u].append(v)
+            adj[v].append(u)
+            var visit = Array(repeating: false, count: n + 1)
+
+            if dfs(u, -1, &visit) {
+                return [u, v]
+            }
+        }
+        return []
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -434,6 +546,161 @@ public class Solution {
 }
 ```
 
+```go
+func findRedundantConnection(edges [][]int) []int {
+    n := len(edges)
+    adj := make([][]int, n+1)
+    for _, edge := range edges {
+        u, v := edge[0], edge[1]
+        adj[u] = append(adj[u], v)
+        adj[v] = append(adj[v], u)
+    }
+
+    visit := make([]bool, n+1)
+    cycle := make(map[int]bool)
+    cycleStart := -1
+
+    var dfs func(node, par int) bool
+    dfs = func(node, par int) bool {
+        if visit[node] {
+            cycleStart = node
+            return true
+        }
+        
+        visit[node] = true
+        for _, nei := range adj[node] {
+            if nei == par {
+                continue
+            }
+            if dfs(nei, node) {
+                if cycleStart != -1 {
+                    cycle[node] = true
+                }
+                if node == cycleStart {
+                    cycleStart = -1
+                }
+                return true
+            }
+        }
+        return false
+    }
+
+    dfs(1, -1)
+
+    for i := len(edges) - 1; i >= 0; i-- {
+        u, v := edges[i][0], edges[i][1]
+        if cycle[u] && cycle[v] {
+            return []int{u, v}
+        }
+    }
+    return []int{}
+}
+```
+
+```kotlin
+class Solution {
+    fun findRedundantConnection(edges: Array<IntArray>): IntArray {
+        val n = edges.size
+        val adj = Array(n + 1) { mutableListOf<Int>() }
+        for ((u, v) in edges) {
+            adj[u].add(v)
+            adj[v].add(u)
+        }
+
+        val visit = BooleanArray(n + 1)
+        val cycle = HashSet<Int>()
+        var cycleStart = -1
+
+        fun dfs(node: Int, par: Int): Boolean {
+            if (visit[node]) {
+                cycleStart = node
+                return true
+            }
+            visit[node] = true
+            for (nei in adj[node]) {
+                if (nei == par) continue
+                if (dfs(nei, node)) {
+                    if (cycleStart != -1) {
+                        cycle.add(node)
+                    }
+                    if (node == cycleStart) {
+                        cycleStart = -1
+                    }
+                    return true
+                }
+            }
+            return false
+        }
+
+        dfs(1, -1)
+
+        for (i in edges.indices.reversed()) {
+            val (u, v) = edges[i]
+            if (u in cycle && v in cycle) {
+                return intArrayOf(u, v)
+            }
+        }
+        return intArrayOf()
+    }
+}
+```
+
+```swift
+class Solution {
+    func findRedundantConnection(_ edges: [[Int]]) -> [Int] {
+        let n = edges.count
+        var adj = Array(repeating: [Int](), count: n + 1)
+        
+        for edge in edges {
+            let u = edge[0]
+            let v = edge[1]
+            adj[u].append(v)
+            adj[v].append(u)
+        }
+
+        var visit = Array(repeating: false, count: n + 1)
+        var cycle = Set<Int>()
+        var cycleStart = -1
+
+        func dfs(_ node: Int, _ par: Int) -> Bool {
+            if visit[node] {
+                cycleStart = node
+                return true
+            }
+            
+            visit[node] = true
+            for nei in adj[node] {
+                if nei == par {
+                    continue
+                }
+                if dfs(nei, node) {
+                    if cycleStart != -1 {
+                        cycle.insert(node)
+                    }
+                    if node == cycleStart {
+                        cycleStart = -1
+                    }
+                    return true
+                }
+            }
+            return false
+        }
+
+        dfs(1, -1)
+
+        for edge in edges.reversed() {
+            let u = edge[0]
+            let v = edge[1]
+            if cycle.contains(u) && cycle.contains(v) {
+                return [u, v]
+            }
+        }
+
+        return []
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -445,7 +712,7 @@ public class Solution {
 
 ---
 
-## 3. Kanh's Algorithm (BFS)
+## 3. Topological Sort (Kahn's Algorithm)
 
 ::tabs-start
 
@@ -474,7 +741,7 @@ class Solution:
                 if indegree[nei] == 1:
                     q.append(nei)
 
-        for u, v in edges[::-1]:
+        for u, v in reversed(edges):
             if indegree[u] == 2 and indegree[v]:
                 return [u, v]
         return []
@@ -638,6 +905,137 @@ public class Solution {
 }
 ```
 
+```go
+func findRedundantConnection(edges [][]int) []int {
+    n := len(edges)
+    indegree := make([]int, n+1)
+    adj := make([][]int, n+1)
+    for _, edge := range edges {
+        u, v := edge[0], edge[1]
+        adj[u] = append(adj[u], v)
+        adj[v] = append(adj[v], u)
+        indegree[u]++
+        indegree[v]++
+    }
+
+    q := []int{}
+    for i := 1; i <= n; i++ {
+        if indegree[i] == 1 {
+            q = append(q, i)
+        }
+    }
+
+    for len(q) > 0 {
+        node := q[0]
+        q = q[1:]
+        indegree[node]--
+        for _, nei := range adj[node] {
+            indegree[nei]--
+            if indegree[nei] == 1 {
+                q = append(q, nei)
+            }
+        }
+    }
+
+    for i := len(edges) - 1; i >= 0; i-- {
+        u, v := edges[i][0], edges[i][1]
+        if indegree[u] == 2 && indegree[v] == 2 {
+            return []int{u, v}
+        }
+    }
+    return []int{}
+}
+```
+
+```kotlin
+class Solution {
+    fun findRedundantConnection(edges: Array<IntArray>): IntArray {
+        val n = edges.size
+        val indegree = IntArray(n + 1)
+        val adj = Array(n + 1) { mutableListOf<Int>() }
+
+        for ((u, v) in edges) {
+            adj[u].add(v)
+            adj[v].add(u)
+            indegree[u]++
+            indegree[v]++
+        }
+
+        val q: Queue<Int> = LinkedList()
+        for (i in 1..n) {
+            if (indegree[i] == 1) {
+                q.add(i)
+            }
+        }
+
+        while (q.isNotEmpty()) {
+            val node = q.poll()
+            indegree[node]--
+            for (nei in adj[node]) {
+                indegree[nei]--
+                if (indegree[nei] == 1) {
+                    q.add(nei)
+                }
+            }
+        }
+
+        for (i in edges.indices.reversed()) {
+            val (u, v) = edges[i]
+            if (indegree[u] == 2 && indegree[v] == 2) {
+                return intArrayOf(u, v)
+            }
+        }
+        return intArrayOf()
+    }
+}
+```
+
+```swift
+class Solution {
+    func findRedundantConnection(_ edges: [[Int]]) -> [Int] {
+        let n = edges.count
+        var indegree = Array(repeating: 0, count: n + 1)
+        var adj = Array(repeating: [Int](), count: n + 1)
+
+        for edge in edges {
+            let u = edge[0]
+            let v = edge[1]
+            adj[u].append(v)
+            adj[v].append(u)
+            indegree[u] += 1
+            indegree[v] += 1
+        }
+
+        var queue = Deque<Int>()
+        for i in 1...n {
+            if indegree[i] == 1 {
+                queue.append(i)
+            }
+        }
+
+        while !queue.isEmpty {
+            let node = queue.popFirst()!
+            indegree[node] -= 1
+            for nei in adj[node] {
+                indegree[nei] -= 1
+                if indegree[nei] == 1 {
+                    queue.append(nei)
+                }
+            }
+        }
+
+        for edge in edges.reversed() {
+            let u = edge[0]
+            let v = edge[1]
+            if indegree[u] == 2 && indegree[v] > 0 {
+                return [u, v]
+            }
+        }
+        return []
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -872,6 +1270,133 @@ public class Solution {
 }
 ```
 
+```go
+func findRedundantConnection(edges [][]int) []int {
+    n := len(edges)
+    par := make([]int, n+1)
+    rank := make([]int, n+1)
+    
+    for i := 0; i <= n; i++ {
+        par[i] = i
+        rank[i] = 1
+    }
+
+    var find func(int) int
+    find = func(x int) int {
+        if par[x] != x {
+            par[x] = find(par[x])
+        }
+        return par[x]
+    }
+
+    union := func(x, y int) bool {
+        rootX, rootY := find(x), find(y)
+        if rootX == rootY {
+            return false
+        }
+        if rank[rootX] > rank[rootY] {
+            par[rootY] = rootX
+            rank[rootX] += rank[rootY]
+        } else {
+            par[rootX] = rootY
+            rank[rootY] += rank[rootX]
+        }
+        return true
+    }
+
+    for _, edge := range edges {
+        if !union(edge[0], edge[1]) {
+            return edge
+        }
+    }
+    return []int{}
+}
+```
+
+```kotlin
+class Solution {
+    fun findRedundantConnection(edges: Array<IntArray>): IntArray {
+        val n = edges.size
+        val par = IntArray(n + 1) { it }
+        val rank = IntArray(n + 1) { 1 }
+
+        fun find(x: Int): Int {
+            if (par[x] != x) {
+                par[x] = find(par[x])
+            }
+            return par[x]
+        }
+
+        fun union(x: Int, y: Int): Boolean {
+            val rootX = find(x)
+            val rootY = find(y)
+            if (rootX == rootY) {
+                return false
+            }
+            if (rank[rootX] > rank[rootY]) {
+                par[rootY] = rootX
+                rank[rootX] += rank[rootY]
+            } else {
+                par[rootX] = rootY
+                rank[rootY] += rank[rootX]
+            }
+            return true
+        }
+
+        for ((u, v) in edges) {
+            if (!union(u, v)) {
+                return intArrayOf(u, v)
+            }
+        }
+        return intArrayOf()
+    }
+}
+```
+
+```swift
+class Solution {
+    func findRedundantConnection(_ edges: [[Int]]) -> [Int] {
+        var par = Array(0...edges.count)
+        var rank = Array(repeating: 1, count: edges.count + 1)
+
+        func find(_ n: Int) -> Int {
+            var p = par[n]
+            while p != par[p] {
+                par[p] = par[par[p]]
+                p = par[p]
+            }
+            return p
+        }
+
+        func union(_ n1: Int, _ n2: Int) -> Bool {
+            let p1 = find(n1)
+            let p2 = find(n2)
+
+            if p1 == p2 {
+                return false
+            }
+            if rank[p1] > rank[p2] {
+                par[p2] = p1
+                rank[p1] += rank[p2]
+            } else {
+                par[p1] = p2
+                rank[p2] += rank[p1]
+            }
+            return true
+        }
+
+        for edge in edges {
+            let n1 = edge[0]
+            let n2 = edge[1]
+            if !union(n1, n2) {
+                return [n1, n2]
+            }
+        }
+        return []
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/regular-expression-matching.md b/articles/regular-expression-matching.md
index 34eb2b86c..fd4bfda86 100644
--- a/articles/regular-expression-matching.md
+++ b/articles/regular-expression-matching.md
@@ -134,6 +134,85 @@ public class Solution {
 }
 ```
 
+```go
+func isMatch(s string, p string) bool {
+    m, n := len(s), len(p)
+
+    var dfs func(i, j int) bool
+    dfs = func(i, j int) bool {
+        if j == n {
+            return i == m
+        }
+
+        match := i < m && (s[i] == p[j] || p[j] == '.')
+        
+        if (j+1) < n && p[j+1] == '*' {
+            return dfs(i, j+2) || (match && dfs(i+1, j))
+        }
+        
+        if match {
+            return dfs(i+1, j+1)
+        }
+
+        return false
+    }
+
+    return dfs(0, 0)
+}
+```
+
+```kotlin
+class Solution {
+    fun isMatch(s: String, p: String): Boolean {
+        val m = s.length
+        val n = p.length
+
+        fun dfs(i: Int, j: Int): Boolean {
+            if (j == n) return i == m
+            
+            val match = i < m && (s[i] == p[j] || p[j] == '.')
+            
+            if ((j + 1) < n && p[j + 1] == '*') {
+                return dfs(i, j + 2) || (match && dfs(i + 1, j))
+            }
+            
+            return match && dfs(i + 1, j + 1)
+        }
+
+        return dfs(0, 0)
+    }
+}
+```
+
+```swift
+class Solution {
+    func isMatch(_ s: String, _ p: String) -> Bool {
+        let sArr = Array(s), pArr = Array(p)
+        let m = sArr.count, n = pArr.count
+
+        func dfs(_ i: Int, _ j: Int) -> Bool {
+            if j == n {
+                return i == m
+            }
+
+            let match = i < m && (sArr[i] == pArr[j] || pArr[j] == ".")
+
+            if j + 1 < n && pArr[j + 1] == "*" {
+                return dfs(i, j + 2) || (match && dfs(i + 1, j))
+            }
+
+            if match {
+                return dfs(i + 1, j + 1)
+            }
+
+            return false
+        }
+
+        return dfs(0, 0)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -303,6 +382,121 @@ public class Solution {
 }
 ```
 
+```go
+func isMatch(s string, p string) bool {
+    m, n := len(s), len(p)
+    dp := make([][]int, m+1)
+    for i := range dp {
+        dp[i] = make([]int, n+1)
+        for j := range dp[i] {
+            dp[i][j] = -1 
+        }
+    }
+
+    var dfs func(i, j int) bool
+    dfs = func(i, j int) bool {
+        if j == n {
+            return i == m
+        }
+        if dp[i][j] != -1 {
+            return dp[i][j] == 1
+        }
+
+        match := i < m && (s[i] == p[j] || p[j] == '.')
+        
+        if (j+1) < n && p[j+1] == '*' {
+            dp[i][j] = boolToInt(dfs(i, j+2) || (match && dfs(i+1, j)))
+            return dp[i][j] == 1
+        }
+        
+        if match {
+            dp[i][j] = boolToInt(dfs(i+1, j+1))
+            return dp[i][j] == 1
+        }
+        
+        dp[i][j] = 0
+        return false
+    }
+
+    return dfs(0, 0)
+}
+
+func boolToInt(b bool) int {
+    if b {
+        return 1
+    }
+    return 0
+}
+```
+
+```kotlin
+class Solution {
+    fun isMatch(s: String, p: String): Boolean {
+        val m = s.length
+        val n = p.length
+        val dp = Array(m + 1) { IntArray(n + 1) { -1 } } 
+
+        fun dfs(i: Int, j: Int): Boolean {
+            if (j == n) return i == m
+            if (dp[i][j] != -1) return dp[i][j] == 1
+
+            val match = i < m && (s[i] == p[j] || p[j] == '.')
+            
+            if ((j + 1) < n && p[j + 1] == '*') {
+                dp[i][j] = if (dfs(i, j + 2) || (match && dfs(i + 1, j))) 1 else 0
+                return dp[i][j] == 1
+            }
+            
+            if (match) {
+                dp[i][j] = if (dfs(i + 1, j + 1)) 1 else 0
+                return dp[i][j] == 1
+            }
+            
+            dp[i][j] = 0
+            return false
+        }
+
+        return dfs(0, 0)
+    }
+}
+```
+
+```swift
+class Solution {
+    func isMatch(_ s: String, _ p: String) -> Bool {
+        let sArr = Array(s), pArr = Array(p)
+        let m = sArr.count, n = pArr.count
+        var cache = [[Bool?]](repeating: [Bool?](repeating: nil, count: n + 1), count: m + 1)
+
+        func dfs(_ i: Int, _ j: Int) -> Bool {
+            if j == n {
+                return i == m
+            }
+            if let cached = cache[i][j] {
+                return cached
+            }
+
+            let match = i < m && (sArr[i] == pArr[j] || pArr[j] == ".")
+
+            if j + 1 < n && pArr[j + 1] == "*" {
+                cache[i][j] = dfs(i, j + 2) || (match && dfs(i + 1, j))
+                return cache[i][j]!
+            }
+
+            if match {
+                cache[i][j] = dfs(i + 1, j + 1)
+                return cache[i][j]!
+            }
+
+            cache[i][j] = false
+            return false
+        }
+
+        return dfs(0, 0)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -455,6 +649,85 @@ public class Solution {
 }
 ```
 
+```go
+func isMatch(s, p string) bool {
+    m, n := len(s), len(p)
+    dp := make([][]bool, m+1)
+    for i := range dp {
+        dp[i] = make([]bool, n+1)
+    }
+    dp[m][n] = true
+
+    for i := m; i >= 0; i-- {
+        for j := n - 1; j >= 0; j-- {
+            match := i < m && (s[i] == p[j] || p[j] == '.')
+            
+            if j+1 < n && p[j+1] == '*' {
+                dp[i][j] = dp[i][j+2]
+                if match {
+                    dp[i][j] = dp[i][j] || dp[i+1][j]
+                }
+            } else if match {
+                dp[i][j] = dp[i+1][j+1]
+            }
+        }
+    }
+    return dp[0][0]
+}
+```
+
+```kotlin
+class Solution {
+    fun isMatch(s: String, p: String): Boolean {
+        val m = s.length
+        val n = p.length
+        val dp = Array(m + 1) { BooleanArray(n + 1) }
+        dp[m][n] = true
+
+        for (i in m downTo 0) {
+            for (j in n - 1 downTo 0) {
+                val match = i < m && (s[i] == p[j] || p[j] == '.')
+                
+                if (j + 1 < n && p[j + 1] == '*') {
+                    dp[i][j] = dp[i][j + 2] || (match && dp[i + 1][j])
+                } else if (match) {
+                    dp[i][j] = dp[i + 1][j + 1]
+                }
+            }
+        }
+        return dp[0][0]
+    }
+}
+```
+
+```swift
+class Solution {
+    func isMatch(_ s: String, _ p: String) -> Bool {
+        let sArr = Array(s), pArr = Array(p)
+        let m = sArr.count, n = pArr.count
+        var dp = Array(repeating: Array(repeating: false, count: n + 1), count: m + 1)
+        dp[m][n] = true
+
+        for i in stride(from: m, through: 0, by: -1) {
+            for j in stride(from: n - 1, through: 0, by: -1) {
+                let match = i < m && (sArr[i] == pArr[j] || pArr[j] == ".")
+
+                if j + 1 < n && pArr[j + 1] == "*" {
+                    dp[i][j] = dp[i][j + 2]
+                    if match {
+                        dp[i][j] = dp[i][j] || dp[i + 1][j]
+                    }
+                } else if match {
+                    dp[i][j] = dp[i + 1][j + 1]
+                }
+            }
+        }
+
+        return dp[0][0]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -629,6 +902,91 @@ public class Solution {
 }
 ```
 
+```go
+func isMatch(s, p string) bool {
+    m, n := len(s), len(p)
+    dp := make([]bool, n+1)
+    dp[n] = true
+
+    for i := m; i >= 0; i-- {
+        nextDp := make([]bool, n+1)
+        nextDp[n] = i == m
+
+        for j := n - 1; j >= 0; j-- {
+            match := i < m && (s[i] == p[j] || p[j] == '.')
+            
+            if j+1 < n && p[j+1] == '*' {
+                nextDp[j] = nextDp[j+2] || (match && dp[j])
+            } else if match {
+                nextDp[j] = dp[j+1]
+            }
+        }
+        dp = nextDp
+    }
+    return dp[0]
+}
+```
+
+```kotlin
+class Solution {
+    fun isMatch(s: String, p: String): Boolean {
+        val m = s.length
+        val n = p.length
+        var dp = BooleanArray(n + 1)
+        dp[n] = true
+
+        for (i in m downTo 0) {
+            val nextDp = BooleanArray(n + 1)
+            nextDp[n] = (i == m)
+
+            for (j in n - 1 downTo 0) {
+                val match = i < m && (s[i] == p[j] || p[j] == '.')
+
+                if (j + 1 < n && p[j + 1] == '*') {
+                    nextDp[j] = nextDp[j + 2] || (match && dp[j])
+                } else if (match) {
+                    nextDp[j] = dp[j + 1]
+                }
+            }
+            dp = nextDp
+        }
+        return dp[0]
+    }
+}
+```
+
+```swift
+class Solution {
+    func isMatch(_ s: String, _ p: String) -> Bool {
+        let sArr = Array(s), pArr = Array(p)
+        var dp = Array(repeating: false, count: pArr.count + 1)
+        dp[pArr.count] = true
+        
+        for i in stride(from: sArr.count, through: 0, by: -1) {
+            var nextDp = Array(repeating: false, count: pArr.count + 1)
+            nextDp[pArr.count] = (i == sArr.count)
+
+            for j in stride(from: pArr.count - 1, through: 0, by: -1) {
+                let match = i < sArr.count && (sArr[i] == pArr[j] || pArr[j] == ".")
+
+                if j + 1 < pArr.count && pArr[j + 1] == "*" {
+                    nextDp[j] = nextDp[j + 2]
+                    if match {
+                        nextDp[j] = nextDp[j] || dp[j]
+                    }
+                } else if match {
+                    nextDp[j] = dp[j + 1]
+                }
+            }
+
+            dp = nextDp
+        }
+        
+        return dp[0]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -802,6 +1160,100 @@ public class Solution {
 }
 ```
 
+```go
+func isMatch(s, p string) bool {
+    m, n := len(s), len(p)
+    dp := make([]bool, n+1)
+    dp[n] = true
+
+    for i := m; i >= 0; i-- {
+        dp1 := dp[n]
+        dp[n] = (i == m)
+
+        for j := n - 1; j >= 0; j-- {
+            match := i < m && (s[i] == p[j] || p[j] == '.')
+            res := false
+            if j+1 < n && p[j+1] == '*' {
+                res = dp[j+2]
+                if match {
+                    res = res || dp[j]
+                }
+            } else if match {
+                res = dp1
+            }
+            dp[j], dp1 = res, dp[j]
+        }
+    }
+
+    return dp[0]
+}
+```
+
+```kotlin
+class Solution {
+    fun isMatch(s: String, p: String): Boolean {
+        val m = s.length
+        val n = p.length
+        var dp = BooleanArray(n + 1)
+        dp[n] = true
+
+        for (i in m downTo 0) {
+            var dp1 = dp[n]
+            dp[n] = (i == m)
+
+            for (j in n - 1 downTo 0) {
+                val match = i < m && (s[i] == p[j] || p[j] == '.')
+                var res = false
+                if (j + 1 < n && p[j + 1] == '*') {
+                    res = dp[j + 2]
+                    if (match) {
+                        res = res || dp[j]
+                    }
+                } else if (match) {
+                    res = dp1
+                }
+                dp1 = dp[j]
+                dp[j] = res
+            }
+        }
+        return dp[0]
+    }
+}
+```
+
+```swift
+class Solution {
+    func isMatch(_ s: String, _ p: String) -> Bool {
+        let sArr = Array(s)
+        let pArr = Array(p)
+        var dp = [Bool](repeating: false, count: pArr.count + 1)
+        dp[pArr.count] = true
+
+        for i in stride(from: sArr.count, through: 0, by: -1) {
+            var dp1 = dp[pArr.count]
+            dp[pArr.count] = (i == sArr.count)
+
+            for j in stride(from: pArr.count - 1, through: 0, by: -1) {
+                let match = i < sArr.count && (sArr[i] == pArr[j] || pArr[j] == ".")
+                var res = false
+                if j + 1 < pArr.count && pArr[j + 1] == "*" {
+                    res = dp[j + 2]
+                    if match {
+                        res = res || dp[j]
+                    }
+                } else if match {
+                    res = dp1
+                }
+                dp1 = dp[j]
+                dp[j] = res
+            }
+        }
+
+        return dp[0]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/relative-sort-array.md b/articles/relative-sort-array.md
new file mode 100644
index 000000000..8681e3fba
--- /dev/null
+++ b/articles/relative-sort-array.md
@@ -0,0 +1,551 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def relativeSortArray(self, arr1: List[int], arr2: List[int]) -> List[int]:
+        res = []
+
+        for num2 in arr2:
+            for i, num1 in enumerate(arr1):
+                if num1 == num2:
+                    res.append(num1)
+                    arr1[i] = -1
+
+        arr1.sort()
+        for i in range(len(res), len(arr1)):
+            res.append(arr1[i])
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[] relativeSortArray(int[] arr1, int[] arr2) {
+        List<Integer> res = new ArrayList<>();
+
+        for (int num2 : arr2) {
+            for (int i = 0; i < arr1.length; i++) {
+                if (arr1[i] == num2) {
+                    res.add(arr1[i]);
+                    arr1[i] = -1;
+                }
+            }
+        }
+
+        Arrays.sort(arr1);
+        for (int i = res.size(); i < arr1.length; i++) {
+            res.add(arr1[i]);
+        }
+
+        return res.stream().mapToInt(i -> i).toArray();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> relativeSortArray(vector<int>& arr1, vector<int>& arr2) {
+        vector<int> res;
+
+        for (int num2 : arr2) {
+            for (int i = 0; i < arr1.size(); i++) {
+                if (arr1[i] == num2) {
+                    res.push_back(arr1[i]);
+                    arr1[i] = -1;
+                }
+            }
+        }
+
+        sort(arr1.begin(), arr1.end());
+        for (int i = res.size(); i < arr1.size(); i++) {
+            res.push_back(arr1[i]);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr1
+     * @param {number[]} arr2
+     * @return {number[]}
+     */
+    relativeSortArray(arr1, arr2) {
+        const res = [];
+
+        for (let num2 of arr2) {
+            for (let i = 0; i < arr1.length; i++) {
+                if (arr1[i] === num2) {
+                    res.push(arr1[i]);
+                    arr1[i] = -1;
+                }
+            }
+        }
+
+        arr1.sort((a, b) => a - b);
+        for (let i = res.length; i < arr1.length; i++) {
+            res.push(arr1[i]);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n + n \log n)$
+* Space complexity:
+    * $O(1)$ or $O(n)$ depending on the sorting algorithm.
+    * $O(n)$ space for the output list.
+
+> Where $n$ is the size of the array $arr1$, and $m$ is the size of the array $arr2$.
+
+---
+
+## 2. Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def relativeSortArray(self, arr1: List[int], arr2: List[int]) -> List[int]:
+        arr2_set = set(arr2)
+        arr1_count = defaultdict(int)
+        end = []
+
+        for num in arr1:
+            if num not in arr2_set:
+                end.append(num)
+            arr1_count[num] += 1
+        end.sort()
+
+        res = []
+        for num in arr2:
+            for _ in range(arr1_count[num]):
+                res.append(num)
+        return res + end
+```
+
+```java
+public class Solution {
+    public int[] relativeSortArray(int[] arr1, int[] arr2) {
+        Set<Integer> arr2Set = new HashSet<>();
+        for (int num : arr2) arr2Set.add(num);
+
+        Map<Integer, Integer> count = new HashMap<>();
+        List<Integer> end = new ArrayList<>();
+        for (int num : arr1) {
+            if (!arr2Set.contains(num)) end.add(num);
+            count.put(num, count.getOrDefault(num, 0) + 1);
+        }
+        Collections.sort(end);
+
+        List<Integer> res = new ArrayList<>();
+        for (int num : arr2) {
+            int freq = count.get(num);
+            for (int i = 0; i < freq; i++) res.add(num);
+        }
+        res.addAll(end);
+
+        return res.stream().mapToInt(i -> i).toArray();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> relativeSortArray(vector<int>& arr1, vector<int>& arr2) {
+        unordered_set<int> arr2Set(arr2.begin(), arr2.end());
+        unordered_map<int, int> count;
+        vector<int> end;
+
+        for (int num : arr1) {
+            if (!arr2Set.count(num)) end.push_back(num);
+            count[num]++;
+        }
+
+        sort(end.begin(), end.end());
+        vector<int> res;
+
+        for (int num : arr2) {
+            for (int i = 0; i < count[num]; i++) {
+                res.push_back(num);
+            }
+        }
+
+        res.insert(res.end(), end.begin(), end.end());
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr1
+     * @param {number[]} arr2
+     * @return {number[]}
+     */
+    relativeSortArray(arr1, arr2) {
+        const arr2Set = new Set(arr2);
+        const count = {};
+        const end = [];
+
+        for (let num of arr1) {
+            if (!arr2Set.has(num)) end.push(num);
+            count[num] = (count[num] || 0) + 1;
+        }
+
+        end.sort((a, b) => a - b);
+        const res = [];
+
+        for (let num of arr2) {
+            for (let i = 0; i < count[num]; i++) {
+                res.push(num);
+            }
+        }
+
+        return res.concat(end);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m + n \log n)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the size of the array $arr1$, and $m$ is the size of the array $arr2$.
+
+---
+
+## 3. Hash Map (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def relativeSortArray(self, arr1: List[int], arr2: List[int]) -> List[int]:
+        count = {}
+        for num in arr1:
+            count[num] = count.get(num, 0) + 1
+
+        res = []
+        for num in arr2:
+            res += [num] * count.pop(num)
+
+        for num in sorted(count):
+            res += [num] * count[num]
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[] relativeSortArray(int[] arr1, int[] arr2) {
+        Map<Integer, Integer> count = new HashMap<>();
+        for (int num : arr1) {
+            count.put(num, count.getOrDefault(num, 0) + 1);
+        }
+
+        List<Integer> res = new ArrayList<>();
+        for (int num : arr2) {
+            int freq = count.remove(num);
+            for (int i = 0; i < freq; i++) {
+                res.add(num);
+            }
+        }
+
+        List<Integer> remaining = new ArrayList<>(count.keySet());
+        Collections.sort(remaining);
+        for (int num : remaining) {
+            int freq = count.get(num);
+            for (int i = 0; i < freq; i++) {
+                res.add(num);
+            }
+        }
+
+        return res.stream().mapToInt(i -> i).toArray();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> relativeSortArray(vector<int>& arr1, vector<int>& arr2) {
+        unordered_map<int, int> count;
+        for (int num : arr1) {
+            count[num]++;
+        }
+
+        vector<int> res;
+        for (int num : arr2) {
+            for (int i = 0; i < count[num]; i++) {
+                res.push_back(num);
+            }
+            count.erase(num);
+        }
+
+        vector<int> remaining;
+        for (auto& [num, freq] : count) {
+            for (int i = 0; i < freq; i++) {
+                remaining.push_back(num);
+            }
+        }
+
+        sort(remaining.begin(), remaining.end());
+        res.insert(res.end(), remaining.begin(), remaining.end());
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr1
+     * @param {number[]} arr2
+     * @return {number[]}
+     */
+    relativeSortArray(arr1, arr2) {
+        const count = {};
+        for (let num of arr1) {
+            count[num] = (count[num] || 0) + 1;
+        }
+
+        const res = [];
+        for (let num of arr2) {
+            for (let i = 0; i < count[num]; i++) {
+                res.push(num);
+            }
+            delete count[num];
+        }
+
+        const remaining = Object.keys(count).map(Number).sort((a, b) => a - b);
+        for (let num of remaining) {
+            for (let i = 0; i < count[num]; i++) {
+                res.push(num);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m + n \log n)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the size of the array $arr1$, and $m$ is the size of the array $arr2$.
+
+---
+
+## 4. Counting Sort
+
+::tabs-start
+
+```python
+class Solution:
+    def relativeSortArray(self, arr1: List[int], arr2: List[int]) -> List[int]:
+        max_val = max(arr1)
+        count = [0] * (max_val + 1)
+
+        for num in arr1:
+            count[num] += 1
+
+        res = []
+        for num in arr2:
+            res += [num] * count[num]
+            count[num] = 0
+
+        for num in range(len(count)):
+            res += [num] * count[num]
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[] relativeSortArray(int[] arr1, int[] arr2) {
+        int max = 0;
+        for (int num : arr1) max = Math.max(max, num);
+
+        int[] count = new int[max + 1];
+        for (int num : arr1) count[num]++;
+
+        List<Integer> res = new ArrayList<>();
+        for (int num : arr2) {
+            while (count[num]-- > 0) res.add(num);
+        }
+
+        for (int num = 0; num < count.length; num++) {
+            while (count[num]-- > 0) res.add(num);
+        }
+
+        return res.stream().mapToInt(i -> i).toArray();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> relativeSortArray(vector<int>& arr1, vector<int>& arr2) {
+        int max_val = *max_element(arr1.begin(), arr1.end());
+        vector<int> count(max_val + 1, 0);
+
+        for (int num : arr1) count[num]++;
+
+        vector<int> res;
+        for (int num : arr2) {
+            while (count[num]-- > 0) res.push_back(num);
+        }
+
+        for (int num = 0; num <= max_val; num++) {
+            while (count[num]-- > 0) res.push_back(num);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr1
+     * @param {number[]} arr2
+     * @return {number[]}
+     */
+    relativeSortArray(arr1, arr2) {
+        let max = Math.max(...arr1);
+        let count = new Array(max + 1).fill(0);
+
+        for (let num of arr1) count[num]++;
+
+        let res = [];
+        for (let num of arr2) {
+            while (count[num]-- > 0) res.push(num);
+        }
+
+        for (let num = 0; num < count.length; num++) {
+            while (count[num]-- > 0) res.push(num);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m + M)$
+* Space complexity:
+    * $O(M)$ extra space.
+    * $O(n)$ space for the output list.
+
+> Where $n$ is the size of the array $arr1$, $m$ is the size of the array $arr2$, and $M$ is the maximum value in the array $arr1$.
+
+---
+
+## 5. Custom Sort
+
+::tabs-start
+
+```python
+class Solution:
+    def relativeSortArray(self, arr1: List[int], arr2: List[int]) -> List[int]:
+        index = {num: i for i, num in enumerate(arr2)}
+        return sorted(arr1, key=lambda x: (index.get(x, 1000 + x)))
+```
+
+```java
+public class Solution {
+    public int[] relativeSortArray(int[] arr1, int[] arr2) {
+        Map<Integer, Integer> index = new HashMap<>();
+        for (int i = 0; i < arr2.length; i++) {
+            index.put(arr2[i], i);
+        }
+
+        Integer[] boxed = Arrays.stream(arr1).boxed().toArray(Integer[]::new);
+        Arrays.sort(boxed, (a, b) -> {
+            int ia = index.getOrDefault(a, 1000 + a);
+            int ib = index.getOrDefault(b, 1000 + b);
+            return Integer.compare(ia, ib);
+        });
+
+        return Arrays.stream(boxed).mapToInt(i -> i).toArray();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> relativeSortArray(vector<int>& arr1, vector<int>& arr2) {
+        unordered_map<int, int> index;
+        for (int i = 0; i < arr2.size(); i++) {
+            index[arr2[i]] = i;
+        }
+
+        sort(arr1.begin(), arr1.end(), [&](int a, int b) {
+            int ia = index.count(a) ? index[a] : 1000 + a;
+            int ib = index.count(b) ? index[b] : 1000 + b;
+            return ia < ib;
+        });
+
+        return arr1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr1
+     * @param {number[]} arr2
+     * @return {number[]}
+     */
+    relativeSortArray(arr1, arr2) {
+        const index = new Map();
+        arr2.forEach((num, i) => index.set(num, i));
+
+        return arr1.sort((a, b) => {
+            const ia = index.has(a) ? index.get(a) : 1000 + a;
+            const ib = index.has(b) ? index.get(b) : 1000 + b;
+            return ia - ib;
+        });
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m + n \log n)$
+* Space complexity:
+    * $O(m)$ extra space.
+    * $O(n)$ space for the output list.
+
+> Where $n$ is the size of the array $arr1$, and $m$ is the size of the array $arr2$.
\ No newline at end of file
diff --git a/articles/remove-all-adjacent-duplicates-in-string-ii.md b/articles/remove-all-adjacent-duplicates-in-string-ii.md
new file mode 100644
index 000000000..7c4ae8a82
--- /dev/null
+++ b/articles/remove-all-adjacent-duplicates-in-string-ii.md
@@ -0,0 +1,467 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def removeDuplicates(self, s: str, k: int) -> str:
+        while True:
+            flag = False
+            cur = s[0]
+            cnt = 1
+            for i in range(1, len(s)):
+                if cur != s[i]:
+                    cnt = 0
+                    cur = s[i]
+                cnt += 1
+                if cnt == k:
+                    s = s[:i - cnt + 1] + s[i + 1:]
+                    flag = True
+                    break
+
+            if not flag:
+                break
+
+        return s
+```
+
+```java
+public class Solution {
+    public String removeDuplicates(String s, int k) {
+        while (true) {
+            boolean flag = false;
+            char cur = s.charAt(0);
+            int cnt = 1;
+
+            for (int i = 1; i < s.length(); i++) {
+                if (cur != s.charAt(i)) {
+                    cnt = 0;
+                    cur = s.charAt(i);
+                }
+                cnt++;
+                if (cnt == k) {
+                    s = s.substring(0, i - cnt + 1) + s.substring(i + 1);
+                    flag = true;
+                    break;
+                }
+            }
+
+            if (!flag) {
+                break;
+            }
+        }
+
+        return s;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string removeDuplicates(string s, int k) {
+        while (true) {
+            bool flag = false;
+            char cur = s[0];
+            int cnt = 1;
+
+            for (int i = 1; i < s.size(); i++) {
+                if (cur != s[i]) {
+                    cnt = 0;
+                    cur = s[i];
+                }
+                cnt++;
+                if (cnt == k) {
+                    s = s.substr(0, i - cnt + 1) + s.substr(i + 1);
+                    flag = true;
+                    break;
+                }
+            }
+
+            if (!flag) {
+                break;
+            }
+        }
+
+        return s;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {number} k
+     * @return {string}
+     */
+    removeDuplicates(s, k) {
+        while (true) {
+            let flag = false;
+            let cur = s[0];
+            let cnt = 1;
+
+            for (let i = 1; i < s.length; i++) {
+                if (cur !== s[i]) {
+                    cnt = 0;
+                    cur = s[i];
+                }
+                cnt++;
+                if (cnt === k) {
+                    s = s.slice(0, i - cnt + 1) + s.slice(i + 1);
+                    flag = true;
+                    break;
+                }
+            }
+
+            if (!flag) {
+                break;
+            }
+        }
+
+        return s;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\frac {n ^ 2}{k})$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Stack
+
+::tabs-start
+
+```python
+class Solution:
+    def removeDuplicates(self, s: str, k: int) -> str:
+        stack = []
+        n = len(s)
+        i = 0
+        s = list(s)
+        
+        while i < n:
+            if i == 0 or s[i] != s[i - 1]:
+                stack.append(1)
+            else:
+                stack[-1] += 1
+                if stack[-1] == k:
+                    stack.pop()
+                    del s[i - k + 1:i + 1]
+                    i -= k
+                    n -= k
+            
+            i += 1
+        
+        return ''.join(s)
+```
+
+```java
+public class Solution {
+    public String removeDuplicates(String s, int k) {
+        StringBuilder sb = new StringBuilder(s);
+        Stack<Integer> stack = new Stack<>();
+        int i = 0;
+        
+        while (i < sb.length()) {
+            if (i == 0 || sb.charAt(i) != sb.charAt(i - 1)) {
+                stack.push(1);
+            } else {
+                stack.push(stack.pop() + 1);
+                if (stack.peek() == k) {
+                    stack.pop();
+                    sb.delete(i - k + 1, i + 1);
+                    i -= k;
+                }
+            }
+            i++;
+        }
+        
+        return sb.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string removeDuplicates(string s, int k) {
+        vector<int> stack;
+        int n = s.length(), i = 0;
+
+        while (i < n) {
+            if (i == 0 || s[i] != s[i - 1]) {
+                stack.push_back(1);
+            } else {
+                stack.back()++;
+                if (stack.back() == k) {
+                    stack.pop_back();
+                    s.erase(i - k + 1, k);
+                    i -= k;
+                    n -= k;
+                }
+            }
+            i++;
+        }
+
+        return s;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {number} k
+     * @return {string}
+     */
+    removeDuplicates(s, k) {
+        let stack = [];
+        let arr = s.split('');
+        let i = 0;
+
+        while (i < arr.length) {
+            if (i === 0 || arr[i] !== arr[i - 1]) {
+                stack.push(1);
+            } else {
+                stack[stack.length - 1]++;
+                if (stack[stack.length - 1] === k) {
+                    stack.pop();
+                    arr.splice(i - k + 1, k);
+                    i -= k;
+                }
+            }
+            i++;
+        }
+
+        return arr.join('');
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Stack (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def removeDuplicates(self, s: str, k: int) -> str:
+        stack = []  # [char, count]
+
+        for c in s:
+            if stack and stack[-1][0] == c:
+                stack[-1][1] += 1
+            else:
+                stack.append([c, 1])
+            if stack[-1][1] == k:
+                stack.pop()
+
+        return ''.join(char * count for char, count in stack)
+```
+
+```java
+public class Solution {
+    public String removeDuplicates(String s, int k) {
+        Stack<int[]> stack = new Stack<>(); // [char, count]
+
+        for (char c : s.toCharArray()) {
+            if (!stack.isEmpty() && stack.peek()[0] == c) {
+                stack.peek()[1]++;
+            } else {
+                stack.push(new int[] {c, 1});
+            }
+            if (stack.peek()[1] == k) {
+                stack.pop();
+            }
+        }
+
+        StringBuilder res = new StringBuilder();
+        while (!stack.isEmpty()) {
+            int[] top = stack.pop();
+            res.append(String.valueOf((char) top[0]).repeat(top[1]));
+        }
+
+        return res.reverse().toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string removeDuplicates(string s, int k) {
+        vector<pair<char, int>> stack;
+
+        for (char c : s) {
+            if (!stack.empty() && stack.back().first == c) {
+                stack.back().second++;
+            } else {
+                stack.push_back({c, 1});
+            }
+            if (stack.back().second == k) {
+                stack.pop_back();
+            }
+        }
+
+        string res;
+        for (auto& p : stack) {
+            res.append(p.second, p.first);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {number} k
+     * @return {string}
+     */
+    removeDuplicates(s, k) {
+        const stack = []; // [char, count]
+
+        for (const c of s) {
+            if (stack.length && stack[stack.length - 1][0] === c) {
+                stack[stack.length - 1][1]++;
+            } else {
+                stack.push([c, 1]);
+            }
+            if (stack[stack.length - 1][1] === k) {
+                stack.pop();
+            }
+        }
+
+        let res = "";
+        for (const [char, count] of stack) {
+            res += char.repeat(count);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def removeDuplicates(self, s: str, k: int) -> str:
+        i = 0
+        n = len(s)
+        count = [0] * n
+        s = list(s)
+        for j in range(n):
+            s[i] = s[j]
+            count[i] = 1
+            if i > 0 and s[i - 1] == s[j]:
+                count[i] += count[i - 1]
+            if count[i] == k:
+                i -= k
+            i += 1
+        return ''.join(s[:i])
+```
+
+```java
+public class Solution {
+    public String removeDuplicates(String s, int k) {
+        int i = 0, n = s.length();
+        char[] str = s.toCharArray();
+        int[] count = new int[n];
+        for (int j = 0; j < n; j++) {
+            str[i] = str[j];
+            count[i] = 1;
+            if (i > 0 && str[i - 1] == str[j]) {
+                count[i] += count[i - 1];
+            }
+            if (count[i] == k) {
+                i -= k;
+            }
+            i++;
+        }
+        return new String(str, 0, i);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string removeDuplicates(string s, int k) {
+        int i = 0, n = s.length();
+        vector<int> count(n);
+        for (int j = 0; j < n; i++, j++) {
+            s[i] = s[j];
+            count[i] = 1;
+            if (i > 0 && s[i - 1] == s[j]) {
+                count[i] += count[i - 1];
+            }
+            if (count[i] == k) i -= k;
+        }
+        return s.substr(0, i);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {number} k
+     * @return {string}
+     */
+    removeDuplicates(s, k) {
+        let i = 0;
+        const n = s.length;
+        const count = new Array(n).fill(0);
+        s = s.split('');
+        for (let j = 0; j < n; j++) {
+            s[i] = s[j];
+            count[i] = 1;
+            if (i > 0 && s[i - 1] === s[j]) {
+                count[i] += count[i - 1];
+            }
+            if (count[i] === k) {
+                i -= k;
+            }
+            i++;
+        }
+        return s.slice(0, i).join('');
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/remove-colored-pieces-if-both-neighbors-are-the-same-color.md b/articles/remove-colored-pieces-if-both-neighbors-are-the-same-color.md
new file mode 100644
index 000000000..156cbb636
--- /dev/null
+++ b/articles/remove-colored-pieces-if-both-neighbors-are-the-same-color.md
@@ -0,0 +1,322 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def winnerOfGame(self, colors: str) -> bool:
+        s = list(colors)
+
+        def removeChar(c):
+            for i in range(1, len(s) - 1):
+                if s[i] != c:
+                    continue
+
+                if s[i] == s[i + 1] == s[i - 1]:
+                    s.pop(i)
+                    return True
+            return False
+
+        while True:
+            if not removeChar('A'):
+                return False
+            if not removeChar('B'):
+                return True
+
+        return False
+```
+
+```java
+public class Solution {
+    public boolean winnerOfGame(String colors) {
+        StringBuilder s = new StringBuilder(colors);
+
+        while (true) {
+            if (!removeChar(s, 'A')) return false;
+            if (!removeChar(s, 'B')) return true;
+        }
+    }
+
+    private boolean removeChar(StringBuilder s, char c) {
+        for (int i = 1; i < s.length() - 1; i++) {
+            if (s.charAt(i) != c) continue;
+
+            if (s.charAt(i - 1) == c && s.charAt(i + 1) == c) {
+                s.deleteCharAt(i);
+                return true;
+            }
+        }
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool winnerOfGame(string colors) {
+        while (true) {
+            if (!removeChar(colors, 'A')) return false;
+            if (!removeChar(colors, 'B')) return true;
+        }
+    }
+
+private:
+    bool removeChar(string& s, char c) {
+        for (int i = 1; i < s.size() - 1; i++) {
+            if (s[i] != c) continue;
+
+            if (s[i - 1] == c && s[i + 1] == c) {
+                s.erase(i, 1);
+                return true;
+            }
+        }
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} colors
+     * @return {boolean}
+     */
+    winnerOfGame(colors) {
+        let s = colors.split("");
+
+        const removeChar = (c) => {
+            for (let i = 1; i < s.length - 1; i++) {
+                if (s[i] !== c) continue;
+
+                if (s[i - 1] === c && s[i + 1] === c) {
+                    s.splice(i, 1);
+                    return true;
+                }
+            }
+            return false;
+        };
+
+        while (true) {
+            if (!removeChar('A')) return false;
+            if (!removeChar('B')) return true;
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Greedy + Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def winnerOfGame(self, colors: str) -> bool:
+        alice = bob = l = 0
+
+        for r in range(len(colors)):
+            if colors[l] != colors[r]:
+                l = r
+
+            extra = r - l - 1
+            if extra > 0:
+                if colors[l] == 'A':
+                    alice += 1
+                else:
+                    bob += 1
+
+        return alice > bob
+```
+
+```java
+public class Solution {
+    public boolean winnerOfGame(String colors) {
+        int alice = 0, bob = 0, l = 0;
+
+        for (int r = 0; r < colors.length(); r++) {
+            if (colors.charAt(l) != colors.charAt(r)) {
+                l = r;
+            }
+
+            int extra = r - l - 1;
+            if (extra > 0) {
+                if (colors.charAt(l) == 'A') {
+                    alice++;
+                } else {
+                    bob++;
+                }
+            }
+        }
+
+        return alice > bob;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool winnerOfGame(string colors) {
+        int alice = 0, bob = 0, l = 0;
+
+        for (int r = 0; r < colors.size(); r++) {
+            if (colors[l] != colors[r]) {
+                l = r;
+            }
+
+            int extra = r - l - 1;
+            if (extra > 0) {
+                if (colors[l] == 'A') {
+                    alice++;
+                } else {
+                    bob++;
+                }
+            }
+        }
+
+        return alice > bob;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} colors
+     * @return {boolean}
+     */
+    winnerOfGame(colors) {
+        let alice = 0, bob = 0, l = 0;
+
+        for (let r = 0; r < colors.length; r++) {
+            if (colors[l] !== colors[r]) {
+                l = r;
+            }
+
+            let extra = r - l - 1;
+            if (extra > 0) {
+                if (colors[l] === 'A') {
+                    alice++;
+                } else {
+                    bob++;
+                }
+            }
+        }
+
+        return alice > bob;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 3. Greedy
+
+::tabs-start
+
+```python
+class Solution:
+    def winnerOfGame(self, colors: str) -> bool:
+        alice, bob = 0, 0
+
+        for i in range(1, len(colors) - 1):
+            if colors[i - 1] == colors[i] == colors[i + 1]:
+                if colors[i] == 'A':
+                    alice += 1
+                if colors[i] == 'B':
+                    bob += 1
+
+        return alice > bob
+```
+
+```java
+public class Solution {
+    public boolean winnerOfGame(String colors) {
+        int alice = 0, bob = 0;
+
+        for (int i = 1; i < colors.length() - 1; i++) {
+            if (colors.charAt(i - 1) == colors.charAt(i) && 
+                colors.charAt(i) == colors.charAt(i + 1)) {
+                if (colors.charAt(i) == 'A') {
+                    alice++;
+                }
+                if (colors.charAt(i) == 'B') {
+                    bob++;
+                }
+            }
+        }
+
+        return alice > bob;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool winnerOfGame(string colors) {
+        int alice = 0, bob = 0;
+
+        for (int i = 1; i < colors.size() - 1; i++) {
+            if (colors[i - 1] == colors[i] && colors[i] == colors[i + 1]) {
+                if (colors[i] == 'A') {
+                    alice++;
+                }
+                if (colors[i] == 'B') {
+                    bob++;
+                }
+            }
+        }
+
+        return alice > bob;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} colors
+     * @return {boolean}
+     */
+    winnerOfGame(colors) {
+        let alice = 0, bob = 0;
+
+        for (let i = 1; i < colors.length - 1; i++) {
+            if (colors[i - 1] === colors[i] && colors[i] === colors[i + 1]) {
+                if (colors[i] === 'A') {
+                    alice++;
+                }
+                if (colors[i] === 'B') {
+                    bob++;
+                }
+            }
+        }
+
+        return alice > bob;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/remove-covered-intervals.md b/articles/remove-covered-intervals.md
new file mode 100644
index 000000000..f71a0cfcc
--- /dev/null
+++ b/articles/remove-covered-intervals.md
@@ -0,0 +1,275 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def removeCoveredIntervals(self, intervals: List[List[int]]) -> int:
+        n = len(intervals)
+        res = n
+
+        for i in range(n):
+            for j in range(n):
+                if (i != j and intervals[j][0] <= intervals[i][0] and 
+                    intervals[j][1] >= intervals[i][1]
+                ):
+                    res -= 1
+                    break
+
+        return res
+```
+
+```java
+public class Solution {
+    public int removeCoveredIntervals(int[][] intervals) {
+        int n = intervals.length;
+        int res = n;
+
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < n; j++) {
+                if (i != j && intervals[j][0] <= intervals[i][0] && 
+                    intervals[j][1] >= intervals[i][1]) {
+                    res--;
+                    break;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int removeCoveredIntervals(vector<vector<int>>& intervals) {
+        int n = intervals.size();
+        int res = n;
+
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < n; j++) {
+                if (i != j && intervals[j][0] <= intervals[i][0] && 
+                    intervals[j][1] >= intervals[i][1]) {
+                    res--;
+                    break;
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} intervals
+     * @return {number}
+     */
+    removeCoveredIntervals(intervals) {
+        let n = intervals.length;
+        let res = n;
+
+        for (let i = 0; i < n; i++) {
+            for (let j = 0; j < n; j++) {
+                if (i !== j && intervals[j][0] <= intervals[i][0] && 
+                    intervals[j][1] >= intervals[i][1]) {
+                    res--;
+                    break;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 2. Sorting - I
+
+::tabs-start
+
+```python
+class Solution:
+    def removeCoveredIntervals(self, intervals: List[List[int]]) -> int:
+        intervals.sort(key=lambda x: (x[0], -x[1]))
+        res = 1
+        prevL, prevR = intervals[0][0], intervals[0][1]
+        for l, r in intervals:
+            if prevL <= l and prevR >= r:
+                continue
+            res += 1
+            prevL, prevR = l, r
+
+        return res
+```
+
+```java
+public class Solution {
+    public int removeCoveredIntervals(int[][] intervals) {
+        Arrays.sort(intervals, (a, b) -> 
+            a[0] == b[0] ? Integer.compare(b[1], a[1]) : Integer.compare(a[0], b[0])
+        );
+        int res = 1, prevL = intervals[0][0], prevR = intervals[0][1];
+        for (int[] interval : intervals) {
+            int l = interval[0], r = interval[1];
+            if (prevL <= l && prevR >= r) {
+                continue;
+            }
+            res++;
+            prevL = l;
+            prevR = r;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int removeCoveredIntervals(vector<vector<int>>& intervals) {
+        sort(intervals.begin(), intervals.end(), [](const auto& a, const auto& b) {
+            return a[0] == b[0] ? b[1] < a[1] : a[0] < b[0];
+        });
+
+        int res = 1, prevL = intervals[0][0], prevR = intervals[0][1];
+        for (const auto& interval : intervals) {
+            int l = interval[0], r = interval[1];
+            if (prevL <= l && prevR >= r) {
+                continue;
+            }
+            res++;
+            prevL = l;
+            prevR = r;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} intervals
+     * @return {number}
+     */
+    removeCoveredIntervals(intervals) {
+        intervals.sort((a, b) => a[0] === b[0] ? b[1] - a[1] : a[0] - b[0]);
+        let res = 1, [prevL, prevR] = intervals[0];
+        for (const [l, r] of intervals) {
+            if (prevL <= l && prevR >= r) {
+                continue;
+            }
+            res++;
+            prevL = l;
+            prevR = r;
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n\log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 3. Sorting - II
+
+::tabs-start
+
+```python
+class Solution:
+    def removeCoveredIntervals(self, intervals: List[List[int]]) -> int:
+        intervals.sort()
+        res, start, end = 1, intervals[0][0], intervals[0][1]
+
+        for l, r in intervals:
+            if start < l and end < r:
+                start = l
+                res += 1
+            end = max(end, r)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int removeCoveredIntervals(int[][] intervals) {
+        Arrays.sort(intervals, (a, b) -> a[0] - b[0]);
+        int res = 1, start = intervals[0][0], end = intervals[0][1];
+
+        for (int[] interval : intervals) {
+            int l = interval[0], r = interval[1];
+            if (start < l && end < r) {
+                start = l;
+                res++;
+            }
+            end = Math.max(end, r);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int removeCoveredIntervals(vector<vector<int>>& intervals) {
+        sort(intervals.begin(), intervals.end());
+        int res = 1, start = intervals[0][0], end = intervals[0][1];
+
+        for (const auto& interval : intervals) {
+            int l = interval[0], r = interval[1];
+            if (start < l && end < r) {
+                start = l;
+                res++;
+            }
+            end = max(end, r);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} intervals
+     * @return {number}
+     */
+    removeCoveredIntervals(intervals) {
+        intervals.sort((a, b) => a[0] - b[0]);
+        let res = 1, start = intervals[0][0], end = intervals[0][1];
+
+        for (const [l, r] of intervals) {
+            if (start < l && end < r) {
+                start = l;
+                res++;
+            }
+            end = Math.max(end, r);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
\ No newline at end of file
diff --git a/articles/remove-duplicates-from-sorted-array-ii.md b/articles/remove-duplicates-from-sorted-array-ii.md
new file mode 100644
index 000000000..8fff8a2d4
--- /dev/null
+++ b/articles/remove-duplicates-from-sorted-array-ii.md
@@ -0,0 +1,421 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def removeDuplicates(self, nums: List[int]) -> int:
+        n = len(nums)
+        if n <= 2:
+            return n
+        i = 0
+        while i < n - 1:
+            if nums[i] == nums[i + 1]:
+                j = i + 2
+                cnt = 0
+                while j < n and nums[i] == nums[j]:
+                    j += 1
+                    cnt += 1
+                for k in range(i + 2, n):
+                    if j >= n:
+                        break
+                    nums[k] = nums[j]
+                    j += 1
+                n -= cnt
+                i += 2
+            else:
+                i += 1
+        return n
+```
+
+```java
+public class Solution {
+    public int removeDuplicates(int[] nums) {
+        int n = nums.length;
+        if (n <= 2) return n;
+        int i = 0;
+        while (i < n - 1) {
+            if (nums[i] == nums[i + 1]) {
+                int j = i + 2, cnt = 0;
+                while (j < n && nums[i] == nums[j]) {
+                    j++;
+                    cnt++;
+                }
+                for (int k = i + 2; k < n; k++) {
+                    if (j >= n) break;
+                    nums[k] = nums[j++];
+                }
+                n -= cnt;
+                i += 2;
+            } else {
+                i++;
+            }
+        }
+        return n;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int removeDuplicates(vector<int>& nums) {
+        int n = nums.size();
+        if (n <= 2) return n;
+        int i = 0;
+        while (i < n - 1) {
+            if (nums[i] == nums[i + 1]) {
+                int j = i + 2, cnt = 0;
+                while (j < n && nums[i] == nums[j]) {
+                    j++;
+                    cnt++;
+                }
+                for (int k = i + 2; k < n; k++) {
+                    if (j >= n) break;
+                    nums[k] = nums[j++];
+                }
+                n -= cnt;
+                i += 2;
+            } else {
+                i++;
+            }
+        }
+        return n;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    removeDuplicates(nums) {
+        let n = nums.length;
+        if (n <= 2) return n;
+        let i = 0;
+        while (i < n - 1) {
+            if (nums[i] === nums[i + 1]) {
+                let j = i + 2, cnt = 0;
+                while (j < n && nums[i] === nums[j]) {
+                    j++;
+                    cnt++;
+                }
+                for (let k = i + 2; k < n; k++) {
+                    if (j >= n) break;
+                    nums[k] = nums[j++];
+                }
+                n -= cnt;
+                i += 2;
+            } else {
+                i++;
+            }
+        }
+        return n;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 2. Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def removeDuplicates(self, nums: List[int]) -> int:
+        n = len(nums)
+        if n <= 2:
+            return n
+        
+        count = Counter(nums)
+        i = 0
+        for num in count:
+            nums[i] = num
+            count[num] -= 1
+            i += 1
+            if count[num] >= 1:
+                nums[i] = num
+                count[num] -= 1
+                i += 1
+        return i
+```
+
+```java
+public class Solution {
+    public int removeDuplicates(int[] nums) {
+        Map<Integer, Integer> count = new HashMap<>();
+        List<Integer> arr = new ArrayList<>();
+        for (int num : nums) {
+            count.put(num, count.getOrDefault(num, 0) + 1);
+            if (count.get(num) == 1) {
+                arr.add(num);
+            }
+        }
+
+        int i = 0;
+        for (int num : arr) {
+            nums[i++] = num;
+            count.put(num, count.get(num) - 1);
+            if (count.get(num) >= 1) {
+                nums[i++] = num;
+                count.put(num, count.get(num) - 1);
+            }
+        }
+        return i;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int removeDuplicates(vector<int>& nums) {
+        unordered_map<int, int> count;
+        vector<int> arr;
+        for (int& num : nums) {
+            count[num]++;
+            if (count[num] == 1) {
+                arr.push_back(num);
+            }
+        }
+
+        int i = 0;
+        for (auto& num : arr) {
+            int& cnt = count[num];
+            nums[i++] = num;
+            cnt--;
+            if (cnt >= 1) {
+                nums[i++] = num;
+                cnt--;
+            }
+        }
+        return i;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    removeDuplicates(nums) {
+        const count = new Map();
+        for (const num of nums) {
+            count.set(num, (count.get(num) || 0) + 1);
+        }
+
+        let i = 0;
+        for (const [num, cnt] of count) {
+            nums[i++] = num;
+            count.set(num, cnt - 1);
+            if (count.get(num) >= 1) {
+                nums[i++] = num;
+                count.set(num, cnt - 1);
+            }
+        }
+        return i;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def removeDuplicates(self, nums: List[int]) -> int:
+        l, r = 0, 0
+
+        while r < len(nums):
+            count = 1
+            while r + 1 < len(nums) and nums[r] == nums[r + 1]:
+                r += 1
+                count += 1
+
+            for i in range(min(2, count)):
+                nums[l] = nums[r]
+                l += 1
+            r += 1
+        
+        return l
+```
+
+```java
+public class Solution {
+    public int removeDuplicates(int[] nums) {
+        int l = 0, r = 0;
+
+        while (r < nums.length) {
+            int count = 1;
+            while (r + 1 < nums.length && nums[r] == nums[r + 1]) {
+                r++;
+                count++;
+            }
+
+            for (int i = 0; i < Math.min(2, count); i++) {
+                nums[l] = nums[r];
+                l++;
+            }
+            r++;
+        }
+        
+        return l;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int removeDuplicates(vector<int>& nums) {
+        int l = 0, r = 0;
+
+        while (r < nums.size()) {
+            int count = 1;
+            while (r + 1 < nums.size() && nums[r] == nums[r + 1]) {
+                r++;
+                count++;
+            }
+
+            for (int i = 0; i < min(2, count); i++) {
+                nums[l] = nums[r];
+                l++;
+            }
+            r++;
+        }
+        
+        return l;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    removeDuplicates(nums) {
+        let l = 0, r = 0;
+
+        while (r < nums.length) {
+            let count = 1;
+            while (r + 1 < nums.length && nums[r] === nums[r + 1]) {
+                r++;
+                count++;
+            }
+
+            for (let i = 0; i < Math.min(2, count); i++) {
+                nums[l] = nums[r];
+                l++;
+            }
+            r++;
+        }
+        
+        return l;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 4. Two Pointers (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def removeDuplicates(self, nums: List[int]) -> int:
+        l = 0
+        for num in nums:
+            if l < 2 or num != nums[l - 2]:
+                nums[l] = num
+                l += 1
+        return l
+```
+
+```java
+public class Solution {
+    public int removeDuplicates(int[] nums) {
+        int l = 0;
+        for (int num : nums) {
+            if (l < 2 || num != nums[l - 2]) {
+                nums[l] = num;
+                l++;
+            }
+        }
+        return l;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int removeDuplicates(vector<int>& nums) {
+        int l = 0;
+        for (int num : nums) {
+            if (l < 2 || num != nums[l - 2]) {
+                nums[l] = num;
+                l++;
+            }
+        }
+        return l;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    removeDuplicates(nums) {
+        let l = 0;
+        for (let num of nums) {
+            if (l < 2 || num !== nums[l - 2]) {
+                nums[l] = num;
+                l++;
+            }
+        }
+        return l;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/remove-duplicates-from-sorted-array.md b/articles/remove-duplicates-from-sorted-array.md
new file mode 100644
index 000000000..7629a2ff3
--- /dev/null
+++ b/articles/remove-duplicates-from-sorted-array.md
@@ -0,0 +1,259 @@
+## 1. Sorted Set
+
+::tabs-start
+
+```python
+class Solution:
+    def removeDuplicates(self, nums: list[int]) -> int:
+        unique = sorted(set(nums))
+        nums[:len(unique)] = unique
+        return len(unique)
+```
+
+```java
+public class Solution {
+    public int removeDuplicates(int[] nums) {
+        TreeSet<Integer> unique = new TreeSet<>();
+        for (int num : nums) {
+            unique.add(num);
+        }
+        int i = 0;
+        for (int num : unique) {
+            nums[i++] = num;
+        }
+        return unique.size();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int removeDuplicates(vector<int>& nums) {
+        set<int> unique(nums.begin(), nums.end());
+        int i = 0;
+        for (int num : unique) {
+            nums[i++] = num;
+        }
+        return unique.size();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    removeDuplicates(nums) {
+        const unique = Array.from(new Set(nums)).sort((a, b) => a - b);
+        for (let i = 0; i < unique.length; i++) {
+            nums[i] = unique[i];
+        }
+        return unique.length;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int RemoveDuplicates(int[] nums) {
+        int[] unique = nums.Distinct().OrderBy(x => x).ToArray();
+        Array.Copy(unique, nums, unique.Length);
+        return unique.Length;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Two Pointers - I
+
+::tabs-start
+
+```python
+class Solution:
+    def removeDuplicates(self, nums: list[int]) -> int:
+        n = len(nums)
+        l = r = 0
+        while r < n:
+            nums[l] = nums[r]
+            while r < n and nums[r] == nums[l]:
+                r += 1
+            l += 1
+        return l
+```
+
+```java
+public class Solution {
+    public int removeDuplicates(int[] nums) {
+        int n = nums.length, l = 0, r = 0;
+        while (r < n) {
+            nums[l] = nums[r];
+            while (r < n && nums[r] == nums[l]) {
+                r++;
+            }
+            l++;
+        }
+        return l;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int removeDuplicates(vector<int>& nums) {
+        int n = nums.size(), l = 0, r = 0;
+        while (r < n) {
+            nums[l] = nums[r];
+            while (r < n && nums[r] == nums[l]) {
+                r++;
+            }
+            l++;
+        }
+        return l;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    removeDuplicates(nums) {
+        let n = nums.length, l = 0, r = 0;
+        while (r < n) {
+            nums[l] = nums[r];
+            while (r < n && nums[r] === nums[l]) {
+                r++;
+            }
+            l++;
+        }
+        return l;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int RemoveDuplicates(int[] nums) {
+        int n = nums.Length;
+        int l = 0, r = 0;
+
+        while (r < n) {
+            nums[l] = nums[r];
+            while (r < n && nums[r] == nums[l]) {
+                r++;
+            }
+            l++;
+        }
+
+        return l;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Two Pointers - II
+
+::tabs-start
+
+```python
+class Solution:
+    def removeDuplicates(self, nums: list[int]) -> int:
+        l = 1
+        for r in range(1, len(nums)):
+            if nums[r] != nums[r - 1]:
+                nums[l] = nums[r]
+                l += 1
+        return l
+```
+
+```java
+public class Solution {
+    public int removeDuplicates(int[] nums) {
+        int l = 1;
+        for (int r = 1; r < nums.length; r++) {
+            if (nums[r] != nums[r - 1]) {
+                nums[l++] = nums[r];
+            }
+        }
+        return l;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int removeDuplicates(vector<int>& nums) {
+        int l = 1;
+        for (int r = 1; r < nums.size(); r++) {
+            if (nums[r] != nums[r - 1]) {
+                nums[l++] = nums[r];
+            }
+        }
+        return l;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    removeDuplicates(nums) {
+        let l = 1;
+        for (let r = 1; r < nums.length; r++) {
+            if (nums[r] !== nums[r - 1]) {
+                nums[l++] = nums[r];
+            }
+        }
+        return l;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int RemoveDuplicates(int[] nums) {
+        int l = 1;
+        for (int r = 1; r < nums.Length; r++) {
+            if (nums[r] != nums[r - 1]) {
+                nums[l] = nums[r];
+                l++;
+            }
+        }
+
+        return l;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/remove-duplicates-from-sorted-list.md b/articles/remove-duplicates-from-sorted-list.md
new file mode 100644
index 000000000..9184c3e9c
--- /dev/null
+++ b/articles/remove-duplicates-from-sorted-list.md
@@ -0,0 +1,312 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def deleteDuplicates(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        if not head or not head.next:
+            return head
+        
+        head.next = self.deleteDuplicates(head.next)
+        return head if head.val != head.next.val else head.next
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode deleteDuplicates(ListNode head) {
+        if (head == null || head.next == null) return head;
+        
+        head.next = deleteDuplicates(head.next);
+        return head.val != head.next.val ? head : head.next;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* deleteDuplicates(ListNode* head) {
+        if (!head || !head->next) return head;
+        
+        head->next = deleteDuplicates(head->next);
+        return head->val != head->next->val ? head : head->next;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @return {ListNode}
+     */
+    deleteDuplicates(head) {
+        if (!head || !head.next) return head;
+
+        head.next = this.deleteDuplicates(head.next);
+        return head.val !== head.next.val ? head : head.next;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Iteration - I
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def deleteDuplicates(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        cur = head
+        while cur:
+            while cur.next and cur.next.val == cur.val:
+                cur.next = cur.next.next
+            cur = cur.next
+        return head
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode deleteDuplicates(ListNode head) {
+        ListNode cur = head;
+        while (cur != null) {
+            while (cur.next != null && cur.next.val == cur.val) {
+                cur.next = cur.next.next;
+            }
+            cur = cur.next;
+        }
+        return head;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* deleteDuplicates(ListNode* head) {
+        ListNode* cur = head;
+        while (cur) {
+            while (cur->next && cur->next->val == cur->val) {
+                cur->next = cur->next->next;
+            }
+            cur = cur->next;
+        }
+        return head;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @return {ListNode}
+     */
+    deleteDuplicates(head) {
+        let cur = head;
+        while (cur) {
+            while (cur.next && cur.next.val === cur.val) {
+                cur.next = cur.next.next;
+            }
+            cur = cur.next;
+        }
+        return head;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 3. Iteration - II
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def deleteDuplicates(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        cur = head
+        while cur and cur.next:
+            if cur.val == cur.next.val:
+                cur.next = cur.next.next
+            else:
+                cur = cur.next
+        return head
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode deleteDuplicates(ListNode head) {
+        ListNode cur = head;
+        while (cur != null && cur.next != null) {
+            if (cur.next.val == cur.val) {
+                cur.next = cur.next.next;
+            } else {
+                cur = cur.next;
+            }
+        }
+        return head;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* deleteDuplicates(ListNode* head) {
+        ListNode* cur = head;
+        while (cur && cur->next) {
+            if (cur->next->val == cur->val) {
+                cur->next = cur->next->next;
+            } else {
+                cur = cur->next;
+            }
+        }
+        return head;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @return {ListNode}
+     */
+    deleteDuplicates(head) {
+        let cur = head;
+        while (cur && cur.next) {
+            if (cur.next.val === cur.val) {
+                cur.next = cur.next.next;
+            } else {
+                cur = cur.next;
+            }
+        }
+        return head;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/remove-element.md b/articles/remove-element.md
new file mode 100644
index 000000000..14d2c78b4
--- /dev/null
+++ b/articles/remove-element.md
@@ -0,0 +1,282 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def removeElement(self, nums: list[int], val: int) -> int:
+        tmp = []
+        for num in nums:
+            if num == val:
+                continue
+            tmp.append(num)
+        for i in range(len(tmp)):
+            nums[i] = tmp[i]
+        return len(tmp)
+```
+
+```java
+public class Solution {
+    public int removeElement(int[] nums, int val) {
+        List<Integer> tmp = new ArrayList<>();
+        for (int num : nums) {
+            if (num != val) {
+                tmp.add(num);
+            }
+        }
+        for (int i = 0; i < tmp.size(); i++) {
+            nums[i] = tmp.get(i);
+        }
+        return tmp.size();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int removeElement(vector<int>& nums, int val) {
+        vector<int> tmp;
+        for (int num : nums) {
+            if (num != val) {
+                tmp.push_back(num);
+            }
+        }
+        for (int i = 0; i < tmp.size(); i++) {
+            nums[i] = tmp[i];
+        }
+        return tmp.size();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} val
+     * @return {number}
+     */
+    removeElement(nums, val) {
+        const tmp = [];
+        for (const num of nums) {
+            if (num !== val) {
+                tmp.push(num);
+            }
+        }
+        for (let i = 0; i < tmp.length; i++) {
+            nums[i] = tmp[i];
+        }
+        return tmp.length;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int RemoveElement(int[] nums, int val) {
+        List<int> tmp = new List<int>();
+        foreach (int num in nums) {
+            if (num != val) {
+                tmp.Add(num);
+            }
+        }
+
+        for (int i = 0; i < tmp.Count; i++) {
+            nums[i] = tmp[i];
+        }
+
+        return tmp.Count;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Two Pointers - I
+
+::tabs-start
+
+```python
+class Solution:
+    def removeElement(self, nums: list[int], val: int) -> int:
+        k = 0
+        for i in range(len(nums)):
+            if nums[i] != val:
+                nums[k] = nums[i]
+                k += 1
+        return k
+```
+
+```java
+public class Solution {
+    public int removeElement(int[] nums, int val) {
+        int k = 0;
+        for (int i = 0; i < nums.length; i++) {
+            if (nums[i] != val) {
+                nums[k++] = nums[i];
+            }
+        }
+        return k;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int removeElement(vector<int>& nums, int val) {
+        int k = 0;
+        for (int i = 0; i < nums.size(); i++) {
+            if (nums[i] != val) {
+                nums[k++] = nums[i];
+            }
+        }
+        return k;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} val
+     * @return {number}
+     */
+    removeElement(nums, val) {
+        let k = 0;
+        for (let i = 0; i < nums.length; i++) {
+            if (nums[i] !== val) {
+                nums[k++] = nums[i];
+            }
+        }
+        return k;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int RemoveElement(int[] nums, int val) {
+        int k = 0;
+        for (int i = 0; i < nums.Length; i++) {
+            if (nums[i] != val) {
+                nums[k++] = nums[i];
+            }
+        }
+        return k;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Two Pointers - II
+
+::tabs-start
+
+```python
+class Solution:
+    def removeElement(self, nums: list[int], val: int) -> int:
+        i = 0
+        n = len(nums)
+        while i < n:
+            if nums[i] == val:
+                n -= 1
+                nums[i] = nums[n]
+            else:
+                i += 1
+        return n
+```
+
+```java
+public class Solution {
+    public int removeElement(int[] nums, int val) {
+        int i = 0, n = nums.length;
+        while (i < n) {
+            if (nums[i] == val) {
+                nums[i] = nums[--n];
+            } else {
+                i++;
+            }
+        }
+        return n;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int removeElement(vector<int>& nums, int val) {
+        int i = 0, n = nums.size();
+        while (i < n) {
+            if (nums[i] == val) {
+                nums[i] = nums[--n];
+            } else {
+                i++;
+            }
+        }
+        return n;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} val
+     * @return {number}
+     */
+    removeElement(nums, val) {
+        let i = 0, n = nums.length;
+        while (i < n) {
+            if (nums[i] == val) {
+                nums[i] = nums[--n];
+            } else {
+                i++;
+            }
+        }
+        return n;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int RemoveElement(int[] nums, int val) {
+        int i = 0, n = nums.Length;
+        while (i < n) {
+            if (nums[i] == val) {
+                nums[i] = nums[--n];
+            } else {
+                i++;
+            }
+        }
+        return n;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/remove-k-digits.md b/articles/remove-k-digits.md
new file mode 100644
index 000000000..19ccf59dc
--- /dev/null
+++ b/articles/remove-k-digits.md
@@ -0,0 +1,344 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def removeKdigits(self, num: str, k: int) -> str:
+        num = list(num)
+        while k:
+            i = 1
+            while i < len(num) and num[i] >= num[i - 1]:
+                i += 1
+            num.pop(i - 1)
+            k -= 1
+
+        i = 0
+        while i < len(num) and num[i] == '0':
+            i += 1
+
+        num = num[i:]
+        return ''.join(num) if num else '0'
+```
+
+```java
+public class Solution {
+    public String removeKdigits(String num, int k) {
+        StringBuilder sb = new StringBuilder(num);
+        while (k > 0) {
+            int i = 1;
+            while (i < sb.length() && sb.charAt(i) >= sb.charAt(i - 1)) {
+                i++;
+            }
+            sb.deleteCharAt(i - 1);
+            k--;
+        }
+
+        int i = 0;
+        while (i < sb.length() && sb.charAt(i) == '0') {
+            i++;
+        }
+
+        sb = new StringBuilder(sb.substring(i));
+        return sb.length() == 0 ? "0" : sb.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string removeKdigits(string num, int k) {
+        while (k > 0) {
+            int i = 1;
+            while (i < num.size() && num[i] >= num[i - 1]) {
+                i++;
+            }
+            num.erase(i - 1, 1);
+            k--;
+        }
+
+        int i = 0;
+        while (i < num.size() && num[i] == '0') {
+            i++;
+        }
+
+        num = num.substr(i);
+        return num.empty() ? "0" : num;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} num
+     * @param {number} k
+     * @return {string}
+     */
+    removeKdigits(num, k) {
+        num = num.split('');
+        while (k > 0) {
+            let i = 1;
+            while (i < num.length && num[i] >= num[i - 1]) {
+                i++;
+            }
+            num.splice(i - 1, 1);
+            k--;
+        }
+
+        let i = 0;
+        while (i < num.length && num[i] === '0') {
+            i++;
+        }
+
+        num = num.slice(i);
+        return num.length === 0 ? "0" : num.join('');
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * k)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the language.
+
+---
+
+## 2. Greedy + Stack
+
+::tabs-start
+
+```python
+class Solution:
+    def removeKdigits(self, num: str, k: int) -> str:
+        stack = []
+        for c in num:
+            while k > 0 and stack and stack[-1] > c:
+                k -= 1
+                stack.pop()
+            stack.append(c)
+
+        while stack and k:
+            stack.pop()
+            k -= 1
+
+        i = 0
+        while i < len(stack) and stack[i] == '0':
+            i += 1
+
+        res = stack[i:]
+        return ''.join(res) if res else "0"
+```
+
+```java
+public class Solution {
+    public String removeKdigits(String num, int k) {
+        StringBuilder stack = new StringBuilder();
+        for (char c : num.toCharArray()) {
+            while (k > 0 && stack.length() > 0 && stack.charAt(stack.length() - 1) > c) {
+                stack.deleteCharAt(stack.length() - 1);
+                k--;
+            }
+            stack.append(c);
+        }
+
+        while (k > 0 && stack.length() > 0) {
+            stack.deleteCharAt(stack.length() - 1);
+            k--;
+        }
+
+        int i = 0;
+        while (i < stack.length() && stack.charAt(i) == '0') {
+            i++;
+        }
+
+        String res = stack.substring(i);
+        return res.isEmpty() ? "0" : res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string removeKdigits(string num, int k) {
+        string stack;
+        for (char c : num) {
+            while (k > 0 && !stack.empty() && stack.back() > c) {
+                stack.pop_back();
+                k--;
+            }
+            stack.push_back(c);
+        }
+
+        while (k > 0 && !stack.empty()) {
+            stack.pop_back();
+            k--;
+        }
+
+        int i = 0;
+        while (i < stack.size() && stack[i] == '0') {
+            i++;
+        }
+
+        string res = stack.substr(i);
+        return res.empty() ? "0" : res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} num
+     * @param {number} k
+     * @return {string}
+     */
+    removeKdigits(num, k) {
+        let stack = [];
+        for (let c of num) {
+            while (k > 0 && stack.length > 0 && stack[stack.length - 1] > c) {
+                stack.pop();
+                k--;
+            }
+            stack.push(c);
+        }
+
+        while (k > 0 && stack.length > 0) {
+            stack.pop();
+            k--;
+        }
+
+        let i = 0;
+        while (i < stack.length && stack[i] === '0') {
+            i++;
+        }
+
+        let res = stack.slice(i).join('');
+        return res === '' ? "0" : res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def removeKdigits(self, num: str, k: int) -> str:
+        l = 0
+        num = list(num)
+
+        for r in range(len(num)):
+            while l > 0 and k > 0 and num[l - 1] > num[r]:
+                l -= 1
+                k -= 1
+            num[l] = num[r]
+            l += 1
+
+        l -= k
+        i = 0
+        while i < l and num[i] == '0':
+            i += 1
+        res = ''.join(num[i:l])
+        return res if res else '0'
+```
+
+```java
+public class Solution {
+    public String removeKdigits(String num, int k) {
+        char[] numArray = num.toCharArray();
+        int l = 0;
+
+        for (int r = 0; r < numArray.length; r++) {
+            while (l > 0 && k > 0 && numArray[l - 1] > numArray[r]) {
+                l--;
+                k--;
+            }
+            numArray[l++] = numArray[r];
+        }
+
+        l -= k;
+        int i = 0;
+        while (i < l && numArray[i] == '0') {
+            i++;
+        }
+        String res = new String(numArray, i, l - i);
+        return res.isEmpty() ? "0" : res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string removeKdigits(string num, int k) {
+        int l = 0;
+        for (int r = 0; r < num.size(); r++) {
+            while (l > 0 && k > 0 && num[l - 1] > num[r]) {
+                l--;
+                k--;
+            }
+            num[l++] = num[r];
+        }
+
+        l -= k;
+        int i = 0;
+        while (i < l && num[i] == '0') {
+            i++;
+        }
+        if (i == l) return "0";
+        return num.substr(i, l - i);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} num
+     * @param {number} k
+     * @return {string}
+     */
+    removeKdigits(num, k) {
+        let numArray = num.split('');
+        let l = 0;
+
+        for (let r = 0; r < numArray.length; r++) {
+            while (l > 0 && k > 0 && numArray[l - 1] > numArray[r]) {
+                l--;
+                k--;
+            }
+            numArray[l++] = numArray[r];
+        }
+
+        l -= k;
+        let i = 0;
+        while (i < l && numArray[i] === '0') {
+            i++;
+        }
+        let res = numArray.slice(i, l).join('');
+        return res.length === 0 ? "0" : res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the language.
\ No newline at end of file
diff --git a/articles/remove-linked-list-elements.md b/articles/remove-linked-list-elements.md
new file mode 100644
index 000000000..30e4a5e94
--- /dev/null
+++ b/articles/remove-linked-list-elements.md
@@ -0,0 +1,514 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def removeElements(self, head: Optional[ListNode], val: int) -> Optional[ListNode]:
+        arr = []
+        cur = head
+
+        while cur:
+            if cur.val != val:
+                arr.append(cur.val)
+            cur = cur.next
+        
+        if not arr:
+            return None
+
+        res = ListNode(arr[0])
+        cur = res
+        for i in range(1, len(arr)):
+            node = ListNode(arr[i])
+            cur.next = node
+            cur = cur.next
+        
+        return res
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode removeElements(ListNode head, int val) {
+        List<Integer> arr = new ArrayList<>();
+        ListNode cur = head;
+
+        while (cur != null) {
+            if (cur.val != val) {
+                arr.add(cur.val);
+            }
+            cur = cur.next;
+        }
+
+        if (arr.isEmpty()) {
+            return null;
+        }
+
+        ListNode res = new ListNode(arr.get(0));
+        cur = res;
+        for (int i = 1; i < arr.size(); i++) {
+            ListNode node = new ListNode(arr.get(i));
+            cur.next = node;
+            cur = cur.next;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* removeElements(ListNode* head, int val) {
+        vector<int> arr;
+        ListNode* cur = head;
+
+        while (cur) {
+            if (cur->val != val) {
+                arr.push_back(cur->val);
+            }
+            cur = cur->next;
+        }
+
+        if (arr.empty()) {
+            return nullptr;
+        }
+
+        ListNode* res = new ListNode(arr[0]);
+        cur = res;
+        for (int i = 1; i < arr.size(); i++) {
+            ListNode* node = new ListNode(arr[i]);
+            cur->next = node;
+            cur = cur->next;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @param {number} val
+     * @return {ListNode}
+     */
+    removeElements(head, val) {
+        const arr = [];
+        let cur = head;
+
+        while (cur) {
+            if (cur.val !== val) {
+                arr.push(cur.val);
+            }
+            cur = cur.next;
+        }
+
+        if (arr.length === 0) {
+            return null;
+        }
+
+        const res = new ListNode(arr[0]);
+        cur = res;
+        for (let i = 1; i < arr.length; i++) {
+            const node = new ListNode(arr[i]);
+            cur.next = node;
+            cur = cur.next;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Recursion
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def removeElements(self, head: Optional[ListNode], val: int) -> Optional[ListNode]:
+        if not head:
+            return None
+        head.next = self.removeElements(head.next, val)
+        return head if head.val != val else head.next
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode removeElements(ListNode head, int val) {
+        if (head == null) return null;
+        head.next = removeElements(head.next, val);
+        return head.val != val ? head : head.next;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* removeElements(ListNode* head, int val) {
+        if (head == nullptr) return nullptr;
+        head->next = removeElements(head->next, val);
+        return head->val != val ? head : head->next;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @param {number} val
+     * @return {ListNode}
+     */
+    removeElements(head, val) {
+        if (head === null) return null;
+        head.next = this.removeElements(head.next, val);
+        return head.val !== val ? head : head.next;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 3. Iteration
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def removeElements(self, head: ListNode, val: int) -> ListNode:
+        dummy = ListNode(0, head)
+        prev, curr = dummy, head
+
+        while curr:
+            nxt = curr.next
+            if curr.val == val:
+                prev.next = nxt
+            else:
+                prev = curr
+            curr = nxt
+
+        return dummy.next
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode removeElements(ListNode head, int val) {
+        ListNode dummy = new ListNode(0, head);
+        ListNode prev = dummy, curr = head;
+
+        while (curr != null) {
+            ListNode nxt = curr.next;
+            if (curr.val == val) {
+                prev.next = nxt;
+            } else {
+                prev = curr;
+            }
+            curr = nxt;
+        }
+        
+        return dummy.next;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* removeElements(ListNode* head, int val) {
+        ListNode dummy(0, head);
+        ListNode *prev = &dummy, *curr = head;
+        
+        while (curr) {
+            ListNode* nxt = curr->next;
+            if (curr->val == val) {
+                prev->next = nxt;
+            } else {
+                prev = curr;
+            }
+            curr = nxt;
+        }
+        
+        return dummy.next;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @param {number} val
+     * @return {ListNode}
+     */
+    removeElements(head, val) {
+        let dummy = new ListNode(0, head);
+        let prev = dummy, curr = head;
+
+        while (curr) {
+            let nxt = curr.next;
+            if (curr.val === val) {
+                prev.next = nxt;
+            } else {
+                prev = curr;
+            }
+            curr = nxt;
+        }
+
+        return dummy.next;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 4. iteration Without Prev Pointer
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def removeElements(self, head: ListNode, val: int) -> ListNode:
+        dummy = ListNode(-1, head)
+        curr = dummy
+
+        while curr.next:
+            if curr.next.val == val:
+                curr.next = curr.next.next
+            else:
+                curr = curr.next
+
+        return dummy.next
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode removeElements(ListNode head, int val) {
+        ListNode dummy = new ListNode(-1, head);
+        ListNode curr = dummy;
+
+        while (curr.next != null) {
+            if (curr.next.val == val) {
+                curr.next = curr.next.next;
+            } else {
+                curr = curr.next;
+            }
+        }
+        
+        return dummy.next;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* removeElements(ListNode* head, int val) {
+        ListNode dummy(-1, head);
+        ListNode *curr = &dummy;
+        
+        while (curr->next) {
+            if (curr->next->val == val) {
+                curr->next = curr->next->next;
+            } else {
+                curr = curr->next;
+            }
+        }
+        
+        return dummy.next;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @param {number} val
+     * @return {ListNode}
+     */
+    removeElements(head, val) {
+        let dummy = new ListNode(-1, head);
+        let curr = dummy;
+
+        while (curr.next) {
+            if (curr.next.val === val) {
+                curr.next = curr.next.next;
+            } else {
+                curr = curr.next;
+            }
+        }
+
+        return dummy.next;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/remove-max-number-of-edges-to-keep-graph-fully-traversable.md b/articles/remove-max-number-of-edges-to-keep-graph-fully-traversable.md
new file mode 100644
index 000000000..04c3da1ac
--- /dev/null
+++ b/articles/remove-max-number-of-edges-to-keep-graph-fully-traversable.md
@@ -0,0 +1,274 @@
+## 1. Disjoint Set Union
+
+::tabs-start
+
+```python
+class DSU:
+    def __init__(self, n):
+        self.n = n
+        self.Parent = list(range(n + 1))
+        self.Size = [1] * (n + 1)
+
+    def find(self, node):
+        if self.Parent[node] != node:
+            self.Parent[node] = self.find(self.Parent[node])
+        return self.Parent[node]
+
+    def union(self, u, v):
+        pu = self.find(u)
+        pv = self.find(v)
+        if pu == pv:
+            return 0
+        if self.Size[pu] < self.Size[pv]:
+            pu, pv = pv, pu
+        self.Size[pu] += self.Size[pv]
+        self.Parent[pv] = pu
+        self.n -= 1
+        return 1
+
+    def isConnected(self):
+        return self.n == 1
+
+class Solution:
+    def maxNumEdgesToRemove(self, n: int, edges: List[List[int]]) -> int:
+        alice, bob = DSU(n), DSU(n)
+        cnt = 0
+
+        for type, src, dst in edges:
+            if type == 3:
+                cnt += (alice.union(src, dst) | bob.union(src, dst))
+
+        for type, src, dst in edges:
+            if type == 1:
+                cnt += alice.union(src, dst)
+            elif type == 2:
+                cnt += bob.union(src, dst)
+
+        if alice.isConnected() and bob.isConnected():
+            return len(edges) - cnt
+        return -1
+```
+
+```java
+class DSU {
+    private int[] parent, size;
+    private int n;
+
+    public DSU(int n) {
+        this.n = n;
+        parent = new int[n + 1];
+        size = new int[n + 1];
+        for (int i = 0; i <= n; i++) {
+            parent[i] = i;
+            size[i] = 1;
+        }
+    }
+
+    public int find(int node) {
+        if (parent[node] != node) {
+            parent[node] = find(parent[node]);
+        }
+        return parent[node];
+    }
+
+    public int union(int u, int v) {
+        int pu = find(u), pv = find(v);
+        if (pu == pv) {
+            return 0;
+        }
+        if (size[pu] < size[pv]) {
+            int temp = pu;
+            pu = pv;
+            pv = temp;
+        }
+        size[pu] += size[pv];
+        parent[pv] = pu;
+        n--;
+        return 1;
+    }
+
+    public boolean isConnected() {
+        return n == 1;
+    }
+}
+
+public class Solution {
+    public int maxNumEdgesToRemove(int n, int[][] edges) {
+        DSU alice = new DSU(n), bob = new DSU(n);
+        int cnt = 0;
+
+        for (int[] edge : edges) {
+            if (edge[0] == 3) {
+                cnt += (alice.union(edge[1], edge[2]) | bob.union(edge[1], edge[2]));
+            }
+        }
+
+        for (int[] edge : edges) {
+            if (edge[0] == 1) {
+                cnt += alice.union(edge[1], edge[2]);
+            } else if (edge[0] == 2) {
+                cnt += bob.union(edge[1], edge[2]);
+            }
+        }
+
+        if (alice.isConnected() && bob.isConnected()) {
+            return edges.length - cnt;
+        }
+        return -1;
+    }
+}
+```
+
+```cpp
+class DSU {
+private:
+    vector<int> parent, size;
+    int n;
+
+public:
+    DSU(int n) : n(n), parent(n + 1), size(n + 1, 1) {
+        for (int i = 0; i <= n; i++) {
+            parent[i] = i;
+        }
+    }
+
+    int find(int node) {
+        if (parent[node] != node) {
+            parent[node] = find(parent[node]);
+        }
+        return parent[node];
+    }
+
+    int unionSets(int u, int v) {
+        int pu = find(u), pv = find(v);
+        if (pu == pv) {
+            return 0;
+        }
+        if (size[pu] < size[pv]) {
+            swap(pu, pv);
+        }
+        size[pu] += size[pv];
+        parent[pv] = pu;
+        n--;
+        return 1;
+    }
+
+    bool isConnected() {
+        return n == 1;
+    }
+};
+
+class Solution {
+public:
+    int maxNumEdgesToRemove(int n, vector<vector<int>>& edges) {
+        DSU alice(n), bob(n);
+        int cnt = 0;
+
+        for (auto& edge : edges) {
+            if (edge[0] == 3) {
+                cnt += (alice.unionSets(edge[1], edge[2]) | bob.unionSets(edge[1], edge[2]));
+            }
+        }
+
+        for (auto& edge : edges) {
+            if (edge[0] == 1) {
+                cnt += alice.unionSets(edge[1], edge[2]);
+            } else if (edge[0] == 2) {
+                cnt += bob.unionSets(edge[1], edge[2]);
+            }
+        }
+
+        if (alice.isConnected() && bob.isConnected()) {
+            return edges.size() - cnt;
+        }
+        return -1;
+    }
+};
+```
+
+```javascript
+class DSU {
+    /**
+     * @param {number} n
+     */
+    constructor(n) {
+        this.n = n;
+        this.parent = Array(n + 1).fill(0).map((_, i) => i);
+        this.size = Array(n + 1).fill(1);
+    }
+
+    /**
+     * @param {number} node
+     * @return {number}
+     */
+    find(node) {
+        if (this.parent[node] !== node) {
+            this.parent[node] = this.find(this.parent[node]);
+        }
+        return this.parent[node];
+    }
+
+    /**
+     * @param {number} u
+     * @param {number} v
+     * @return {number}
+     */
+    union(u, v) {
+        let pu = this.find(u), pv = this.find(v);
+        if (pu === pv) {
+            return 0;
+        }
+        if (this.size[pu] < this.size[pv]) {
+            [pu, pv] = [pv, pu];
+        }
+        this.size[pu] += this.size[pv];
+        this.parent[pv] = pu;
+        this.n--;
+        return 1;
+    }
+
+    /**
+     * @return {boolean}
+     */
+    isConnected() {
+        return this.n === 1;
+    }
+}
+
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} edges
+     * @return {number}
+     */
+    maxNumEdgesToRemove(n, edges) {
+        let alice = new DSU(n), bob = new DSU(n);
+        let cnt = 0;
+
+        for (let [type, src, dst] of edges) {
+            if (type === 3) {
+                cnt += (alice.union(src, dst) | bob.union(src, dst));
+            }
+        }
+
+        for (let [type, src, dst] of edges) {
+            if (type === 1) {
+                cnt += alice.union(src, dst);
+            } else if (type === 2) {
+                cnt += bob.union(src, dst);
+            }
+        }
+
+        return alice.isConnected() && bob.isConnected() ? edges.length - cnt : -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(E * α(V))$
+* Space complexity: $O(V)$
+
+> Where $V$ is the number of verticies and $E$ is the number of edges.
\ No newline at end of file
diff --git a/articles/remove-node-from-end-of-linked-list.md b/articles/remove-node-from-end-of-linked-list.md
index e5a249ebe..ee936f416 100644
--- a/articles/remove-node-from-end-of-linked-list.md
+++ b/articles/remove-node-from-end-of-linked-list.md
@@ -159,6 +159,95 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func removeNthFromEnd(head *ListNode, n int) *ListNode {
+    nodes := []*ListNode{}
+    cur := head
+    for cur != nil {
+        nodes = append(nodes, cur)
+        cur = cur.Next
+    }
+
+    removeIndex := len(nodes) - n
+    if removeIndex == 0 {
+        return head.Next
+    }
+
+    nodes[removeIndex-1].Next = nodes[removeIndex].Next
+    return head
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var li = ListNode(5)
+ * var v = li.`val`
+ * Definition for singly-linked list.
+ * class ListNode(var `val`: Int) {
+ *     var next: ListNode? = null
+ * }
+ */
+class Solution {
+    fun removeNthFromEnd(head: ListNode?, n: Int): ListNode? {
+        val nodes = mutableListOf<ListNode?>()
+        var cur = head
+        
+        while (cur != null) {
+            nodes.add(cur)
+            cur = cur.next
+        }
+
+        val removeIndex = nodes.size - n
+        if (removeIndex == 0) {
+            return head?.next
+        }
+
+        nodes[removeIndex - 1]?.next = nodes[removeIndex]?.next
+        return head
+    }
+}
+```
+
+```swift
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public var val: Int
+ *     public var next: ListNode?
+ *     public init() { self.val = 0; self.next = nil; }
+ *     public init(_ val: Int) { self.val = val; self.next = nil; }
+ *     public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
+ * }
+ */
+class Solution {
+    func removeNthFromEnd(_ head: ListNode?, _ n: Int) -> ListNode? {
+        var nodes: [ListNode] = []
+        var cur = head
+
+        while cur != nil {
+            nodes.append(cur!)
+            cur = cur?.next
+        }
+
+        let removeIndex = nodes.count - n
+        if removeIndex == 0 {
+            return head?.next
+        }
+
+        nodes[removeIndex - 1].next = nodes[removeIndex].next
+        return head
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -362,6 +451,115 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func removeNthFromEnd(head *ListNode, n int) *ListNode {
+    N := 0
+    cur := head
+    for cur != nil {
+        N++
+        cur = cur.Next
+    }
+
+    removeIndex := N - n
+    if removeIndex == 0 {
+        return head.Next
+    }
+
+    cur = head
+    for i := 0; i < N-1; i++ {
+        if (i + 1) == removeIndex {
+            cur.Next = cur.Next.Next
+            break
+        }
+        cur = cur.Next
+    }
+    return head
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var li = ListNode(5)
+ * var v = li.`val`
+ * Definition for singly-linked list.
+ * class ListNode(var `val`: Int) {
+ *     var next: ListNode? = null
+ * }
+ */
+class Solution {
+    fun removeNthFromEnd(head: ListNode?, n: Int): ListNode? {
+        var N = 0
+        var cur = head
+
+        while (cur != null) {
+            N++
+            cur = cur.next
+        }
+
+        val removeIndex = N - n
+        if (removeIndex == 0) {
+            return head?.next
+        }
+
+        cur = head
+        for (i in 0 until N - 1) {
+            if (i + 1 == removeIndex) {
+                cur?.next = cur?.next?.next
+                break
+            }
+            cur = cur?.next
+        }
+        return head
+    }
+}
+```
+
+```swift
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public var val: Int
+ *     public var next: ListNode?
+ *     public init() { self.val = 0; self.next = nil; }
+ *     public init(_ val: Int) { self.val = val; self.next = nil; }
+ *     public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
+ * }
+ */
+class Solution {
+    func removeNthFromEnd(_ head: ListNode?, _ n: Int) -> ListNode? {
+        var N = 0
+        var cur = head
+        while cur != nil {
+            N += 1
+            cur = cur?.next
+        }
+
+        let removeIndex = N - n
+        if removeIndex == 0 {
+            return head?.next
+        }
+
+        cur = head
+        for i in 0..<(N - 1) {
+            if (i + 1) == removeIndex {
+                cur?.next = cur?.next?.next
+                break
+            }
+            cur = cur?.next
+        }
+        return head
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -536,12 +734,103 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func rec(head *ListNode, n *int) *ListNode {
+    if head == nil {
+        return nil
+    }
+
+    head.Next = rec(head.Next, n)
+    (*n)-- 
+
+    if *n == 0 {
+        return head.Next 
+    }
+    return head 
+}
+
+func removeNthFromEnd(head *ListNode, n int) *ListNode {
+    return rec(head, &n) 
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var li = ListNode(5)
+ * var v = li.`val`
+ * Definition for singly-linked list.
+ * class ListNode(var `val`: Int) {
+ *     var next: ListNode? = null
+ * }
+ */
+class Solution {
+    private fun rec(head: ListNode?, n: IntArray): ListNode? {
+        if (head == null) {
+            return null
+        }
+
+        head.next = rec(head.next, n)
+        n[0]--
+
+        return if (n[0] == 0) {
+            head.next 
+        } else {
+            head 
+        }
+    }
+
+    fun removeNthFromEnd(head: ListNode?, n: Int): ListNode? {
+        return rec(head, intArrayOf(n))
+    }
+}
+```
+
+```swift
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public var val: Int
+ *     public var next: ListNode?
+ *     public init() { self.val = 0; self.next = nil; }
+ *     public init(_ val: Int) { self.val = val; self.next = nil; }
+ *     public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
+ * }
+ */
+class Solution {
+    func rec(_ head: ListNode?, _ n: inout Int) -> ListNode? {
+        if head == nil {
+            return nil
+        }
+
+        head?.next = rec(head?.next, &n)
+        n -= 1
+        if n == 0 {
+            return head?.next
+        }
+        return head
+    }
+
+    func removeNthFromEnd(_ head: ListNode?, _ n: Int) -> ListNode? {
+        var n = n
+        return rec(head, &n)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(N)$
-* Space complexity: $O(N)$
+* Space complexity: $O(N)$ for recursion stack.
 
 ---
 
@@ -716,6 +1005,101 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func removeNthFromEnd(head *ListNode, n int) *ListNode {
+    dummy := &ListNode{Next: head}
+    left := dummy
+    right := head
+
+    for n > 0 {
+        right = right.Next
+        n--
+    }
+
+    for right != nil {
+        left = left.Next
+        right = right.Next
+    }
+
+    left.Next = left.Next.Next
+    return dummy.Next
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var li = ListNode(5)
+ * var v = li.`val`
+ * Definition for singly-linked list.
+ * class ListNode(var `val`: Int) {
+ *     var next: ListNode? = null
+ * }
+ */
+class Solution {
+    fun removeNthFromEnd(head: ListNode?, n: Int): ListNode? {
+        val dummy = ListNode(0).apply { next = head }
+        var left: ListNode? = dummy
+        var right: ListNode? = head
+
+        var count = n
+        while (count > 0) {
+            right = right?.next
+            count--
+        }
+
+        while (right != null) {
+            left = left?.next
+            right = right.next
+        }
+
+        left?.next = left?.next?.next
+        return dummy.next
+    }
+}
+```
+
+```swift
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public var val: Int
+ *     public var next: ListNode?
+ *     public init() { self.val = 0; self.next = nil; }
+ *     public init(_ val: Int) { self.val = val; self.next = nil; }
+ *     public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
+ * }
+ */
+class Solution {
+    func removeNthFromEnd(_ head: ListNode?, _ n: Int) -> ListNode? {
+        let dummy = ListNode(0, head)
+        var left: ListNode? = dummy
+        var right: ListNode? = head
+        var n = n
+
+        while n > 0 {
+            right = right?.next
+            n -= 1
+        }
+
+        while right != nil {
+            left = left?.next
+            right = right?.next
+        }
+
+        left?.next = left?.next?.next
+        return dummy.next
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/remove-nodes-from-linked-list.md b/articles/remove-nodes-from-linked-list.md
new file mode 100644
index 000000000..b629d4760
--- /dev/null
+++ b/articles/remove-nodes-from-linked-list.md
@@ -0,0 +1,574 @@
+## 1. Convert To Array
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def removeNodes(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        cur, arr = head, [ListNode(0, head)]
+        while cur:
+            arr.append(cur)
+            cur = cur.next
+        
+        rightMaxi = ListNode(0, None)
+        for i in range(len(arr) - 1, 0, -1):
+            if rightMaxi.val > arr[i].val:
+                arr[i - 1].next = rightMaxi
+            else:
+                rightMaxi = arr[i]
+        
+        return arr[0].next
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode removeNodes(ListNode head) {
+        List<ListNode> arr = new ArrayList<>();
+        arr.add(new ListNode(0, head));
+        ListNode cur = head;
+
+        while (cur != null) {
+            arr.add(cur);
+            cur = cur.next;
+        }
+
+        ListNode rightMaxi = new ListNode(0, null);
+        for (int i = arr.size() - 1; i > 0; i--) {
+            if (rightMaxi.val > arr.get(i).val) {
+                arr.get(i - 1).next = rightMaxi;
+            } else {
+                rightMaxi = arr.get(i);
+            }
+        }
+
+        return arr.get(0).next;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* removeNodes(ListNode* head) {
+        vector<ListNode*> arr;
+        arr.push_back(new ListNode(0, head));
+        ListNode* cur = head;
+
+        while (cur) {
+            arr.push_back(cur);
+            cur = cur->next;
+        }
+
+        ListNode* rightMaxi = new ListNode(0, nullptr);
+        for (int i = arr.size() - 1; i > 0; i--) {
+            if (rightMaxi->val > arr[i]->val) {
+                arr[i - 1]->next = rightMaxi;
+            } else {
+                rightMaxi = arr[i];
+            }
+        }
+
+        return arr[0]->next;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @return {ListNode}
+     */
+    removeNodes(head) {
+        let cur = head, arr = [{ val: 0, next: head }];
+        while (cur) {
+            arr.push(cur);
+            cur = cur.next;
+        }
+
+        let rightMaxi = { val: 0, next: null };
+        for (let i = arr.length - 1; i > 0; i--) {
+            if (rightMaxi.val > arr[i].val) {
+                arr[i - 1].next = rightMaxi;
+            } else {
+                rightMaxi = arr[i];
+            }
+        }
+
+        return arr[0].next;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Monotonic Decreasing Stack
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def removeNodes(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        stack = []
+        cur = head
+
+        while cur:
+            while stack and cur.val > stack[-1]:
+                stack.pop()
+            stack.append(cur.val)
+            cur = cur.next
+
+        dummy = ListNode()
+        cur = dummy
+
+        for num in stack:
+            cur.next = ListNode(num)
+            cur = cur.next
+
+        return dummy.next
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode removeNodes(ListNode head) {
+        Stack<Integer> stack = new Stack<>();
+        ListNode cur = head;
+
+        while (cur != null) {
+            while (!stack.isEmpty() && cur.val > stack.peek()) {
+                stack.pop();
+            }
+            stack.push(cur.val);
+            cur = cur.next;
+        }
+
+        ListNode dummy = new ListNode();
+        cur = dummy;
+
+        for (int num : stack) {
+            cur.next = new ListNode(num);
+            cur = cur.next;
+        }
+
+        return dummy.next;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* removeNodes(ListNode* head) {
+        vector<int> stack;
+        ListNode* cur = head;
+
+        while (cur) {
+            while (!stack.empty() && cur->val > stack.back()) {
+                stack.pop_back();
+            }
+            stack.push_back(cur->val);
+            cur = cur->next;
+        }
+
+        ListNode* dummy = new ListNode();
+        cur = dummy;
+
+        for (int num : stack) {
+            cur->next = new ListNode(num);
+            cur = cur->next;
+        }
+
+        return dummy->next;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @return {ListNode}
+     */
+    removeNodes(head) {
+        let stack = [];
+        let cur = head;
+
+        while (cur) {
+            while (stack.length && cur.val > stack[stack.length - 1]) {
+                stack.pop();
+            }
+            stack.push(cur.val);
+            cur = cur.next;
+        }
+
+        let dummy = new ListNode();
+        cur = dummy;
+
+        for (let num of stack) {
+            cur.next = new ListNode(num);
+            cur = cur.next;
+        }
+
+        return dummy.next;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Recursion
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def removeNodes(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        if not head:
+            return None
+            
+        head.next = self.removeNodes(head.next)
+        if head.next and head.val < head.next.val:
+            return head.next
+        return head
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode removeNodes(ListNode head) {
+        if (head == null) return null;
+
+        head.next = removeNodes(head.next);
+        if (head.next != null && head.val < head.next.val) {
+            return head.next;
+        }
+        return head;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* removeNodes(ListNode* head) {
+        if (!head) return nullptr;
+
+        head->next = removeNodes(head->next);
+        if (head->next && head->val < head->next->val) {
+            return head->next;
+        }
+        return head;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @return {ListNode}
+     */
+    removeNodes(head) {
+        if (!head) return null;
+
+        head.next = this.removeNodes(head.next);
+        if (head.next && head.val < head.next.val) {
+            return head.next;
+        }
+        return head;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 4. Reverse Twice
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def removeNodes(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        def reverse(head):
+            prev, cur = None, head
+            while cur:
+                tmp = cur.next
+                cur.next = prev
+                prev, cur = cur, tmp
+            return prev
+
+        head = reverse(head)
+        cur = head
+        cur_max = head.val
+
+        while cur and cur.next:
+            if cur.next.val < cur_max:
+                cur.next = cur.next.next
+            else:
+                cur_max = cur.next.val
+                cur = cur.next
+                
+        return reverse(head)
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode removeNodes(ListNode head) {
+        head = reverse(head);
+        ListNode cur = head;
+        int curMax = head.val;
+
+        while (cur != null && cur.next != null) {
+            if (cur.next.val < curMax) {
+                cur.next = cur.next.next;
+            } else {
+                curMax = cur.next.val;
+                cur = cur.next;
+            }
+        }
+        return reverse(head);
+    }
+
+    private ListNode reverse(ListNode head) {
+        ListNode prev = null, cur = head;
+        while (cur != null) {
+            ListNode tmp = cur.next;
+            cur.next = prev;
+            prev = cur;
+            cur = tmp;
+        }
+        return prev;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* reverse(ListNode* head) {
+        ListNode* prev = nullptr;
+        ListNode* cur = head;
+        while (cur) {
+            ListNode* tmp = cur->next;
+            cur->next = prev;
+            prev = cur;
+            cur = tmp;
+        }
+        return prev;
+    }
+    
+    ListNode* removeNodes(ListNode* head) {
+        head = reverse(head);
+        ListNode* cur = head;
+        int cur_max = head->val;
+
+        while (cur && cur->next) {
+            if (cur->next->val < cur_max) {
+                cur->next = cur->next->next;
+            } else {
+                cur_max = cur->next->val;
+                cur = cur->next;
+            }
+        }
+        return reverse(head);
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @return {ListNode}
+     */
+    removeNodes(head) {
+        const reverse = (head) => {
+            let prev = null, cur = head;
+            while (cur) {
+                let tmp = cur.next;
+                cur.next = prev;
+                prev = cur;
+                cur = tmp;
+            }
+            return prev;
+        };
+
+        head = reverse(head);
+        let cur = head;
+        let cur_max = head.val;
+
+        while (cur && cur.next) {
+            if (cur.next.val < cur_max) {
+                cur.next = cur.next.next;
+            } else {
+                cur_max = cur.next.val;
+                cur = cur.next;
+            }
+        }
+        return reverse(head);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/removing-stars-from-a-string.md b/articles/removing-stars-from-a-string.md
new file mode 100644
index 000000000..108454bae
--- /dev/null
+++ b/articles/removing-stars-from-a-string.md
@@ -0,0 +1,357 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def removeStars(self, s: str) -> str:
+        while True:
+            flag = False
+            for i in range(1, len(s)):
+                if s[i] == '*' and s[i - 1] != '*':
+                    s = s[:i - 1] + s[i + 1:]
+                    flag = True
+                    break
+            if not flag:
+                break
+        return s
+```
+
+```java
+public class Solution {
+    public String removeStars(String s) {
+        while (true) {
+            boolean flag = false;
+            StringBuilder sb = new StringBuilder(s);
+            for (int i = 1; i < sb.length(); i++) {
+                if (sb.charAt(i) == '*' && sb.charAt(i - 1) != '*') {
+                    sb.delete(i - 1, i + 1);
+                    flag = true;
+                    break;
+                }
+            }
+            s = sb.toString();
+            if (!flag) {
+                break;
+            }
+        }
+        return s;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string removeStars(string s) {
+        while (true) {
+            bool flag = false;
+            for (int i = 1; i < s.size(); ++i) {
+                if (s[i] == '*' && s[i - 1] != '*') {
+                    s = s.substr(0, i - 1) + s.substr(i + 1);
+                    flag = true;
+                    break;
+                }
+            }
+            if (!flag) {
+                break;
+            }
+        }
+        return s;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string}
+     */
+    removeStars(s) {
+        while (true) {
+            let flag = false;
+            for (let i = 1; i < s.length; i++) {
+                if (s[i] === '*' && s[i - 1] !== '*') {
+                    s = s.slice(0, i - 1) + s.slice(i + 1);
+                    flag = true;
+                    break;
+                }
+            }
+            if (!flag) {
+                break;
+            }
+        }
+        return s;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Brute Force (Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def removeStars(self, s: str) -> str:
+        n = len(s)
+        i = 0
+        while i < n:
+            if i and s[i] == '*' and s[i - 1] != '*':
+                s = s[:i - 1] + s[i + 1:]
+                n -= 2
+                i -= 2
+            i += 1
+        return s
+```
+
+```java
+public class Solution {
+    public String removeStars(String s) {
+        int n = s.length();
+        int i = 0;
+        while (i < n) {
+            if (i > 0 && s.charAt(i) == '*' && s.charAt(i - 1) != '*') {
+                s = s.substring(0, i - 1) + s.substring(i + 1);
+                n -= 2;
+                i -= 2;
+            }
+            i++;
+        }
+        return s;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string removeStars(string s) {
+        int n = s.length();
+        int i = 0;
+        while (i < n) {
+            if (i > 0 && s[i] == '*' && s[i - 1] != '*') {
+                s = s.substr(0, i - 1) + s.substr(i + 1);
+                n -= 2;
+                i -= 2;
+            }
+            i++;
+        }
+        return s;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string}
+     */
+    removeStars(s) {
+        let n = s.length;
+        let i = 0;
+        while (i < n) {
+            if (i > 0 && s[i] === '*' && s[i - 1] !== '*') {
+                s = s.slice(0, i - 1) + s.slice(i + 1);
+                n -= 2;
+                i -= 2;
+            }
+            i++;
+        }
+        return s;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Stack
+
+::tabs-start
+
+```python
+class Solution:
+    def removeStars(self, s: str) -> str:
+        stack = []
+        for c in s:
+            if c == "*":
+                stack and stack.pop()
+            else:
+                stack.append(c)
+        return "".join(stack)
+```
+
+```java
+public class Solution {
+    public String removeStars(String s) {
+        Stack<Character> stack = new Stack<>();
+        for (char c : s.toCharArray()) {
+            if (c == '*') {
+                if (!stack.isEmpty()) stack.pop();
+            } else {
+                stack.push(c);
+            }
+        }
+        StringBuilder res = new StringBuilder();
+        for (char c : stack) res.append(c);
+        return res.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string removeStars(string s) {
+        stack<char> stack;
+        for (char c : s) {
+            if (c == '*') {
+                if (!stack.empty()) stack.pop();
+            } else {
+                stack.push(c);
+            }
+        }
+        string res;
+        while (!stack.empty()) {
+            res += stack.top();
+            stack.pop();
+        }
+        reverse(res.begin(), res.end());
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string}
+     */
+    removeStars(s) {
+        const stack = [];
+        for (const c of s) {
+            if (c === "*") {
+                if (stack.length > 0) stack.pop();
+            } else {
+                stack.push(c);
+            }
+        }
+        return stack.join("");
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def removeStars(self, s: str) -> str:
+        l = 0
+        s = list(s)
+
+        for r in range(len(s)):
+            if s[r] == '*':
+                l -= 1
+            else:
+                s[l] = s[r]
+                l += 1
+                
+        return ''.join(s[:l])
+```
+
+```java
+public class Solution {
+    public String removeStars(String s) {
+        char[] arr = s.toCharArray();
+        int l = 0;
+
+        for (int r = 0; r < arr.length; r++) {
+            if (arr[r] == '*') {
+                l--;
+            } else {
+                arr[l] = arr[r];
+                l++;
+            }
+        }
+        return new String(arr, 0, l);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string removeStars(string s) {
+        int l = 0;
+
+        for (int r = 0; r < s.size(); r++) {
+            if (s[r] == '*') {
+                l--;
+            } else {
+                s[l] = s[r];
+                l++;
+            }
+        }
+        return s.substr(0, l);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string}
+     */
+    removeStars(s) {
+        const arr = s.split('');
+        let l = 0;
+
+        for (let r = 0; r < arr.length; r++) {
+            if (arr[r] === '*') {
+                l--;
+            } else {
+                arr[l] = arr[r];
+                l++;
+            }
+        }
+        return arr.slice(0, l).join('');
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the language.
\ No newline at end of file
diff --git a/articles/reorder-linked-list.md b/articles/reorder-linked-list.md
index 2b6491c90..75e0ef82c 100644
--- a/articles/reorder-linked-list.md
+++ b/articles/reorder-linked-list.md
@@ -189,6 +189,118 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func reorderList(head *ListNode) {
+    if head == nil {
+        return
+    }
+
+    nodes := []*ListNode{}
+    cur := head
+    for cur != nil {
+        nodes = append(nodes, cur)
+        cur = cur.Next
+    }
+
+    i, j := 0, len(nodes)-1
+    for i < j {
+        nodes[i].Next = nodes[j]
+        i++
+        if i >= j {
+            break
+        }
+        nodes[j].Next = nodes[i]
+        j--
+    }
+
+    nodes[i].Next = nil
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var li = ListNode(5)
+ * var v = li.`val`
+ * Definition for singly-linked list.
+ * class ListNode(var `val`: Int) {
+ *     var next: ListNode? = null
+ * }
+ */
+class Solution {
+    fun reorderList(head: ListNode?) {
+        if (head == null) return
+
+        val nodes = mutableListOf<ListNode>()
+        var cur: ListNode? = head
+        while (cur != null) {
+            nodes.add(cur)
+            cur = cur.next
+        }
+
+        var i = 0
+        var j = nodes.size - 1
+        while (i < j) {
+            nodes[i].next = nodes[j]
+            i++
+            if (i >= j) break
+            nodes[j].next = nodes[i]
+            j--
+        }
+
+        nodes[i].next = null
+    }
+}
+```
+
+```swift
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public var val: Int
+ *     public var next: ListNode?
+ *     public init() { self.val = 0; self.next = nil; }
+ *     public init(_ val: Int) { self.val = val; self.next = nil; }
+ *     public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
+ * }
+ */
+class Solution {
+    func reorderList(_ head: ListNode?) {
+        if head == nil {
+            return
+        }
+        
+        var nodes: [ListNode] = []
+        var cur = head
+        
+        while cur != nil {
+            nodes.append(cur!)
+            cur = cur?.next
+        }
+        
+        var i = 0, j = nodes.count - 1
+        while i < j {
+            nodes[i].next = nodes[j]
+            i += 1
+            if i >= j {
+                break
+            }
+            nodes[j].next = nodes[i]
+            j -= 1
+        }
+        
+        nodes[i].next = nil
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -215,10 +327,11 @@ class Solution:
         def rec(root: ListNode, cur: ListNode) -> ListNode:
             if not cur:
                 return root
-            root = rec(root, cur.next)
 
+            root = rec(root, cur.next)
             if not root:
                 return None
+
             tmp = None
             if root == cur or root.next == cur:
                 cur.next = None
@@ -226,8 +339,9 @@ class Solution:
                 tmp = root.next
                 root.next = cur
                 cur.next = tmp
+
             return tmp
-            
+
         head = rec(head, head.next)
 ```
 
@@ -252,10 +366,12 @@ public class Solution {
         if (cur == null) {
             return root;
         }
+
         root = rec(root, cur.next);
         if (root == null) {
             return null;
         }
+
         ListNode tmp = null;
         if (root == cur || root.next == cur) {
             cur.next = null;
@@ -264,6 +380,7 @@ public class Solution {
             root.next = cur;
             cur.next = tmp;
         }
+
         return tmp;
     }
 }
@@ -292,10 +409,12 @@ private:
         if (cur == nullptr) {
             return root;
         }
+
         root = rec(root, cur->next);
         if (root == nullptr) {
             return nullptr;
         }
+
         ListNode* tmp = nullptr;
         if (root == cur || root->next == cur) {
             cur->next = nullptr;
@@ -304,6 +423,7 @@ private:
             root->next = cur;
             cur->next = tmp;
         }
+
         return tmp;
     }
 };
@@ -338,10 +458,12 @@ class Solution {
         if (cur === null) {
             return root;
         }
+
         root = this.rec(root, cur.next);
         if (root === null) {
             return null;
         }
+
         let tmp = null;
         if (root === cur || root.next === cur) {
             cur.next = null;
@@ -350,6 +472,7 @@ class Solution {
             root.next = cur;
             cur.next = tmp;
         }
+
         return tmp;
     }
 }
@@ -377,10 +500,12 @@ public class Solution {
         if (cur == null) {
             return root;
         }
+
         root = Rec(root, cur.next);
         if (root == null) {
             return null;
         }
+
         ListNode tmp = null;
         if (root == cur || root.next == cur) {
             cur.next = null;
@@ -389,11 +514,133 @@ public class Solution {
             root.next = cur;
             cur.next = tmp;
         }
+
         return tmp;
     }
 }
 ```
 
+```go
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func reorderList(head *ListNode) {
+    if head == nil {
+        return
+    }
+
+    var rec func(root, cur *ListNode) *ListNode
+    rec = func(root, cur *ListNode) *ListNode {
+        if cur == nil {
+            return root
+        }
+
+        root = rec(root, cur.Next)
+        if root == nil {
+            return nil
+        }
+
+        var tmp *ListNode
+        if root == cur || root.Next == cur {
+            cur.Next = nil
+        } else {
+            tmp = root.Next
+            root.Next = cur
+            cur.Next = tmp
+        }
+
+        return tmp
+    }
+
+    rec(head, head.Next)
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var li = ListNode(5)
+ * var v = li.`val`
+ * Definition for singly-linked list.
+ * class ListNode(var `val`: Int) {
+ *     var next: ListNode? = null
+ * }
+ */
+class Solution {
+    fun reorderList(head: ListNode?) {
+        if (head == null) return
+
+        fun rec(root: ListNode?, cur: ListNode?): ListNode? {
+            if (cur == null) {
+                return root
+            }
+
+            var updatedRoot = rec(root, cur.next)
+            if (updatedRoot == null) {
+                return null
+            }
+
+            var tmp: ListNode? = null
+            if (updatedRoot == cur || updatedRoot?.next == cur) {
+                cur.next = null
+            } else {
+                tmp = updatedRoot.next
+                updatedRoot.next = cur
+                cur.next = tmp
+            }
+
+            return tmp
+        }
+
+        rec(head, head.next)
+    }
+}
+```
+
+```swift
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public var val: Int
+ *     public var next: ListNode?
+ *     public init() { self.val = 0; self.next = nil; }
+ *     public init(_ val: Int) { self.val = val; self.next = nil; }
+ *     public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
+ * }
+ */
+class Solution {
+    func reorderList(_ head: ListNode?) {
+        func rec(_ root: ListNode?, _ cur: ListNode?) -> ListNode? {
+            if cur == nil {
+                return root
+            }
+
+            var root = rec(root, cur?.next)
+            if root == nil {
+                return nil
+            }
+
+            var tmp: ListNode? = nil
+            if root === cur || root?.next === cur {
+                cur?.next = nil
+            } else {
+                tmp = root?.next
+                root?.next = cur
+                cur?.next = tmp
+            }
+
+            return tmp
+        }
+        
+        rec(head, head?.next)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -618,6 +865,137 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func reorderList(head *ListNode) {
+    if head == nil || head.Next == nil {
+        return
+    }
+
+    slow, fast := head, head.Next
+    for fast != nil && fast.Next != nil {
+        slow = slow.Next
+        fast = fast.Next.Next
+    }
+
+    second := slow.Next
+    slow.Next = nil
+    var prev *ListNode
+    for second != nil {
+        tmp := second.Next
+        second.Next = prev
+        prev = second
+        second = tmp
+    }
+
+    first := head
+    second = prev
+    for second != nil {
+        tmp1, tmp2 := first.Next, second.Next
+        first.Next = second
+        second.Next = tmp1
+        first, second = tmp1, tmp2
+    }
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var li = ListNode(5)
+ * var v = li.`val`
+ * Definition for singly-linked list.
+ * class ListNode(var `val`: Int) {
+ *     var next: ListNode? = null
+ * }
+ */
+class Solution {
+    fun reorderList(head: ListNode?) {
+        if (head == null || head.next == null) return
+
+        var slow: ListNode? = head
+        var fast: ListNode? = head.next
+        while (fast != null && fast.next != null) {
+            slow = slow?.next
+            fast = fast.next.next
+        }
+
+        val second = slow?.next
+        slow?.next = null
+        var prev: ListNode? = null
+        var curr = second
+        while (curr != null) {
+            val tmp = curr.next
+            curr.next = prev
+            prev = curr
+            curr = tmp
+        }
+
+        var first: ListNode? = head
+        var secondList: ListNode? = prev
+        while (first != null && secondList != null) {
+            val tmp1 = first.next
+            val tmp2 = secondList.next
+            first.next = secondList
+            secondList.next = tmp1
+            first = tmp1
+            secondList = tmp2
+        }
+    }
+}
+```
+
+```swift
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public var val: Int
+ *     public var next: ListNode?
+ *     public init() { self.val = 0; self.next = nil; }
+ *     public init(_ val: Int) { self.val = val; self.next = nil; }
+ *     public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
+ * }
+ */
+class Solution {
+    func reorderList(_ head: ListNode?) {
+        var slow = head, fast = head?.next
+        while fast != nil && fast?.next != nil {
+            slow = slow?.next
+            fast = fast?.next?.next
+        }
+
+        var second = slow?.next
+        var prev: ListNode? = nil
+        slow?.next = nil
+
+        while second != nil {
+            let tmp = second?.next
+            second?.next = prev
+            prev = second
+            second = tmp
+        }
+
+        var first = head
+        second = prev
+
+        while second != nil {
+            let tmp1 = first?.next
+            let tmp2 = second?.next
+            first?.next = second
+            second?.next = tmp1
+            first = tmp1
+            second = tmp2
+        }
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/reorder-routes-to-make-all-paths-lead-to-the-city-zero.md b/articles/reorder-routes-to-make-all-paths-lead-to-the-city-zero.md
new file mode 100644
index 000000000..ae2727f84
--- /dev/null
+++ b/articles/reorder-routes-to-make-all-paths-lead-to-the-city-zero.md
@@ -0,0 +1,385 @@
+## 1. Depth First Search - I
+
+::tabs-start
+
+```python
+class Solution:
+    def minReorder(self, n: int, connections: List[List[int]]) -> int:
+        edges = {(a, b) for a, b in connections}
+        neighbors = {city: [] for city in range(n)}
+        visit = set()
+        changes = 0
+
+        for a, b in connections:
+            neighbors[a].append(b)
+            neighbors[b].append(a)
+
+        def dfs(city):
+            nonlocal changes
+            visit.add(city)
+            for neighbor in neighbors[city]:
+                if neighbor in visit:
+                    continue
+                if (neighbor, city) not in edges:
+                    changes += 1
+                dfs(neighbor)
+
+        dfs(0)
+        return changes
+```
+
+```java
+public class Solution {
+    private Map<Integer, List<Integer>> neighbors;
+    private boolean[] visit;
+    private Set<String> edges;
+
+    public int minReorder(int n, int[][] connections) {
+        edges = new HashSet<>();
+        neighbors = new HashMap<>();
+        visit = new boolean[n];
+        int[] changes = {0};
+
+        for (int[] conn : connections) {
+            int a = conn[0], b = conn[1];
+            edges.add(a + "," + b);
+            neighbors.computeIfAbsent(a, k -> new ArrayList<>()).add(b);
+            neighbors.computeIfAbsent(b, k -> new ArrayList<>()).add(a);
+        }
+
+        dfs(0, changes);
+        return changes[0];
+    }
+
+    private void dfs(int city, int[] changes) {
+        visit[city] = true;
+        for (int neighbor : neighbors.get(city)) {
+            if (visit[neighbor]) continue;
+            if (!edges.contains(neighbor + "," + city)) {
+                changes[0]++;
+            }
+            dfs(neighbor, changes);
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minReorder(int n, vector<vector<int>>& connections) {
+        unordered_set<string> edges;
+        unordered_map<int, vector<int>> neighbors;
+        vector<bool> visit(n, false);
+        int changes = 0;
+
+        for (auto& c : connections) {
+            edges.insert(to_string(c[0]) + "," + to_string(c[1]));
+            neighbors[c[0]].push_back(c[1]);
+            neighbors[c[1]].push_back(c[0]);
+        }
+
+        function<void(int)> dfs = [&](int city) {
+            visit[city] = true;
+            for (int neighbor : neighbors[city]) {
+                if (visit[neighbor]) continue;
+                if (edges.find(to_string(neighbor) + "," + to_string(city)) == edges.end()) {
+                    changes++;
+                }
+                dfs(neighbor);
+            }
+        };
+
+        dfs(0);
+        return changes;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} connections
+     * @return {number}
+     */
+    minReorder(n, connections) {
+        const edges = new Set();
+        const neighbors = Array.from({ length: n }, () => []);
+        const visit = new Array(n).fill(false);
+        let changes = 0;
+
+        for (const [a, b] of connections) {
+            edges.add(`${a},${b}`);
+            neighbors[a].push(b);
+            neighbors[b].push(a);
+        }
+
+        const dfs = (city) => {
+            visit[city] = true;
+            for (const neighbor of neighbors[city]) {
+                if (visit[neighbor]) continue;
+                if (!edges.has(`${neighbor},${city}`)) changes++;
+                dfs(neighbor);
+            }
+        };
+
+        dfs(0);
+        return changes;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Depth First Search - II
+
+::tabs-start
+
+```python
+class Solution:
+    def minReorder(self, n: int, connections: List[List[int]]) -> int:
+        adj = [[] for _ in range(n)]
+        for u, v in connections:
+            adj[u].append(v)
+            adj[v].append(-u)
+
+        def dfs(node, parent):
+            changes = 0
+            for nei in adj[node]:
+                if abs(nei) == parent:
+                    continue
+                changes += dfs(abs(nei), node) + (nei > 0)
+            return changes
+        
+        return dfs(0, -1)
+```
+
+```java
+public class Solution {
+    public int minReorder(int n, int[][] connections) {
+        List<List<Integer>> adj = new ArrayList<>();
+        for (int i = 0; i < n; i++) adj.add(new ArrayList<>());
+
+        for (int[] conn : connections) {
+            adj.get(conn[0]).add(conn[1]);
+            adj.get(conn[1]).add(-conn[0]);
+        }
+
+        return dfs(0, -1, adj);
+    }
+
+    private int dfs(int node, int parent, List<List<Integer>> adj) {
+        int changes = 0;
+        for (int nei : adj.get(node)) {
+            if (Math.abs(nei) == parent) continue;
+            changes += dfs(Math.abs(nei), node, adj) + (nei > 0 ? 1 : 0);
+        }
+        return changes;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minReorder(int n, vector<vector<int>>& connections) {
+        vector<vector<int>> adj(n);
+        for (auto& conn : connections) {
+            int u = conn[0], v = conn[1];
+            adj[u].push_back(v);
+            adj[v].push_back(-u);
+        }
+        
+        return dfs(0, -1, adj);
+    }
+
+private:
+    int dfs(int node, int parent, vector<vector<int>>& adj) {
+        int changes = 0;
+        for (int nei : adj[node]) {
+            if (abs(nei) == parent) continue;
+            changes += dfs(abs(nei), node, adj) + (nei > 0);
+        }
+        return changes;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} connections
+     * @return {number}
+     */
+    minReorder(n, connections) {
+        const adj = Array.from({ length: n }, () => []);
+        for (const [u, v] of connections) {
+            adj[u].push(v);
+            adj[v].push(-u);
+        }
+
+        const dfs = (node, parent) => {
+            let changes = 0;
+            for (const nei of adj[node]) {
+                if (Math.abs(nei) === parent) continue;
+                changes += dfs(Math.abs(nei), node) + (nei > 0 ? 1 : 0);
+            }
+            return changes;
+        };
+
+        return dfs(0, -1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Breadth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def minReorder(self, n: int, connections: List[List[int]]) -> int:
+        adj = [[] for _ in range(n)]
+        for u, v in connections:
+            adj[u].append((v, 1))
+            adj[v].append((u, 0))
+        
+        visit = [False] * n
+        queue = deque([0])
+        visit[0] = True
+        changes = 0
+        
+        while queue:
+            node = queue.popleft()
+            for neighbor, isForward in adj[node]:
+                if not visit[neighbor]:
+                    visit[neighbor] = True
+                    changes += isForward
+                    queue.append(neighbor)
+        return changes
+```
+
+```java
+public class Solution {
+    public int minReorder(int n, int[][] connections) {
+        List<int[]>[] adj = new ArrayList[n];
+        for (int i = 0; i < n; i++) adj[i] = new ArrayList<>();
+
+        for (int[] conn : connections) {
+            adj[conn[0]].add(new int[]{conn[1], 1});
+            adj[conn[1]].add(new int[]{conn[0], 0});
+        }
+
+        boolean[] visited = new boolean[n];
+        Queue<Integer> queue = new LinkedList<>();
+        queue.add(0);
+        visited[0] = true;
+        int changes = 0;
+
+        while (!queue.isEmpty()) {
+            int node = queue.poll();
+            for (int[] edge : adj[node]) {
+                int neighbor = edge[0], isForward = edge[1];
+                if (!visited[neighbor]) {
+                    visited[neighbor] = true;
+                    changes += isForward;
+                    queue.add(neighbor);
+                }
+            }
+        }
+        return changes;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minReorder(int n, vector<vector<int>>& connections) {
+        vector<vector<pair<int, int>>> adj(n);
+        for (auto& conn : connections) {
+            adj[conn[0]].push_back({conn[1], 1});
+            adj[conn[1]].push_back({conn[0], 0});
+        }
+        
+        vector<bool> visit(n, false);
+        queue<int> q;
+        q.push(0);
+        visit[0] = true;
+        int changes = 0;
+        
+        while (!q.empty()) {
+            int node = q.front();
+            q.pop();
+            for (auto& [neighbor, isForward] : adj[node]) {
+                if (!visit[neighbor]) {
+                    visit[neighbor] = true;
+                    changes += isForward;
+                    q.push(neighbor);
+                }
+            }
+        }
+        return changes;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} connections
+     * @return {number}
+     */
+    minReorder(n, connections) {
+        const adj = Array.from({ length: n }, () => []);
+        for (const [u, v] of connections) {
+            adj[u].push([v, 1]);
+            adj[v].push([u, 0]);
+        }
+
+        const visited = Array(n).fill(false);
+        const queue = new Queue();
+        queue.push(0);
+        visited[0] = true;
+        let changes = 0;
+
+        while (!queue.isEmpty()) {
+            const node = queue.pop();
+            for (const [neighbor, isForward] of adj[node]) {
+                if (!visited[neighbor]) {
+                    visited[neighbor] = true;
+                    changes += isForward;
+                    queue.push(neighbor);
+                }
+            }
+        }
+        return changes;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/reorganize-string.md b/articles/reorganize-string.md
new file mode 100644
index 000000000..868c78dca
--- /dev/null
+++ b/articles/reorganize-string.md
@@ -0,0 +1,663 @@
+## 1. Frequency Count
+
+::tabs-start
+
+```python
+class Solution:
+    def reorganizeString(self, s: str) -> str:
+        freq = [0] * 26
+        for char in s:
+            freq[ord(char) - ord('a')] += 1
+        
+        max_freq = max(freq)
+        if max_freq > (len(s) + 1) // 2:
+            return ""
+            
+        res = []
+        while len(res) < len(s):
+            maxIdx = freq.index(max(freq))
+            char = chr(maxIdx + ord('a'))
+            res.append(char)
+            freq[maxIdx] -= 1
+            if freq[maxIdx] == 0:
+                continue
+                
+            tmp = freq[maxIdx]
+            freq[maxIdx] = float("-inf")
+            nextMaxIdx = freq.index(max(freq))
+            char = chr(nextMaxIdx + ord('a'))
+            res.append(char)
+            freq[maxIdx] = tmp
+            freq[nextMaxIdx] -= 1
+           
+        return ''.join(res)
+```
+
+```java
+public class Solution {
+    public String reorganizeString(String s) {
+        int[] freq = new int[26];
+        for (char c : s.toCharArray()) {
+            freq[c - 'a']++;
+        }
+
+        int maxFreq = Arrays.stream(freq).max().getAsInt();
+        if (maxFreq > (s.length() + 1) / 2) {
+            return "";
+        }
+
+        StringBuilder res = new StringBuilder();
+        while (res.length() < s.length()) {
+            int maxIdx = findMaxIndex(freq);
+            char maxChar = (char) (maxIdx + 'a');
+            res.append(maxChar);
+            freq[maxIdx]--;
+
+            if (freq[maxIdx] == 0) {
+                continue;
+            }
+
+            int tmp = freq[maxIdx];
+            freq[maxIdx] = Integer.MIN_VALUE;
+            int nextMaxIdx = findMaxIndex(freq);
+            char nextMaxChar = (char) (nextMaxIdx + 'a');
+            res.append(nextMaxChar);
+            freq[maxIdx] = tmp;
+            freq[nextMaxIdx]--;
+        }
+
+        return res.toString();
+    }
+
+    private int findMaxIndex(int[] freq) {
+        int maxIdx = 0;
+        for (int i = 1; i < freq.length; i++) {
+            if (freq[i] > freq[maxIdx]) {
+                maxIdx = i;
+            }
+        }
+        return maxIdx;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string reorganizeString(string s) {
+        vector<int> freq(26, 0);
+        for (char c : s) {
+            freq[c - 'a']++;
+        }
+
+        int maxFreq = *max_element(freq.begin(), freq.end());
+        if (maxFreq > (s.size() + 1) / 2) {
+            return "";
+        }
+
+        string res;
+        while (res.size() < s.size()) {
+            int maxIdx = findMaxIndex(freq);
+            char maxChar = 'a' + maxIdx;
+            res += maxChar;
+            freq[maxIdx]--;
+
+            if (freq[maxIdx] == 0) {
+                continue;
+            }
+
+            int tmp = freq[maxIdx];
+            freq[maxIdx] = INT_MIN;
+            int nextMaxIdx = findMaxIndex(freq);
+            char nextMaxChar = 'a' + nextMaxIdx;
+            res += nextMaxChar;
+            freq[maxIdx] = tmp;
+            freq[nextMaxIdx]--;
+        }
+
+        return res;
+    }
+
+private:
+    int findMaxIndex(const vector<int>& freq) {
+        int maxIdx = 0;
+        for (int i = 1; i < freq.size(); i++) {
+            if (freq[i] > freq[maxIdx]) {
+                maxIdx = i;
+            }
+        }
+        return maxIdx;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string}
+     */
+    reorganizeString(s) {
+        const freq = new Array(26).fill(0);
+        for (const char of s) {
+            freq[char.charCodeAt(0) - 'a'.charCodeAt(0)]++;
+        }
+
+        const maxFreq = Math.max(...freq);
+        if (maxFreq > Math.floor((s.length + 1) / 2)) {
+            return "";
+        }
+
+        const findMaxIndex = () => {
+            let maxIdx = 0;
+            for (let i = 1; i < freq.length; i++) {
+                if (freq[i] > freq[maxIdx]) {
+                    maxIdx = i;
+                }
+            }
+            return maxIdx;
+        };
+
+        const res = [];
+        while (res.length < s.length) {
+            const maxIdx = findMaxIndex();
+            const maxChar = String.fromCharCode(maxIdx + 'a'.charCodeAt(0));
+            res.push(maxChar);
+            freq[maxIdx]--;
+
+            if (freq[maxIdx] === 0) {
+                continue;
+            }
+
+            const tmp = freq[maxIdx];
+            freq[maxIdx] = -Infinity;
+            const nextMaxIdx = findMaxIndex();
+            const nextMaxChar = String.fromCharCode(nextMaxIdx + 'a'.charCodeAt(0));
+            res.push(nextMaxChar);
+            freq[maxIdx] = tmp;
+            freq[nextMaxIdx]--;
+        }
+
+        return res.join('');
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public string ReorganizeString(string s) {
+        int[] freq = new int[26];
+        foreach (char c in s) {
+            freq[c - 'a']++;
+        }
+
+        int maxFreq = freq.Max();
+        if (maxFreq > (s.Length + 1) / 2) {
+            return "";
+        }
+
+        List<char> res = new List<char>();
+        while (res.Count < s.Length) {
+            int maxIdx = Array.IndexOf(freq, freq.Max());
+            char ch = (char)(maxIdx + 'a');
+            res.Add(ch);
+            freq[maxIdx]--;
+
+            if (freq[maxIdx] == 0) continue;
+
+            int tmp = freq[maxIdx];
+            freq[maxIdx] = int.MinValue;
+            int nextMaxIdx = Array.IndexOf(freq, freq.Max());
+            char nextCh = (char)(nextMaxIdx + 'a');
+            res.Add(nextCh);
+            freq[maxIdx] = tmp;
+            freq[nextMaxIdx]--;
+        }
+
+        return new string(res.ToArray());
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity:
+    * $O(1)$ extra space, since we have at most $26$ different characters.
+    * $O(n)$ space for the output string.
+
+---
+
+## 2. Frequency Count (Max-Heap)
+
+::tabs-start
+
+```python
+class Solution:
+    def reorganizeString(self, s: str) -> str:
+        count = Counter(s)
+        maxHeap = [[-cnt, char] for char, cnt in count.items()]
+        heapq.heapify(maxHeap)
+        
+        prev = None
+        res = ""
+        while maxHeap or prev:
+            if prev and not maxHeap:
+                return ""
+            
+            cnt, char = heapq.heappop(maxHeap)
+            res += char
+            cnt += 1
+
+            if prev:
+                heapq.heappush(maxHeap, prev)
+                prev = None
+            
+            if cnt != 0:
+                prev = [cnt, char]
+        
+        return res
+```
+
+```java
+public class Solution {
+    public String reorganizeString(String s) {
+        int[] freq = new int[26];
+        for (char c : s.toCharArray()) {
+            freq[c - 'a']++;
+        }
+
+        PriorityQueue<int[]> maxHeap = new PriorityQueue<>((a, b) -> b[0] - a[0]);
+        for (int i = 0; i < 26; i++) {
+            if (freq[i] > 0) {
+                maxHeap.offer(new int[]{freq[i], i});
+            }
+        }
+
+        StringBuilder res = new StringBuilder();
+        int[] prev = null;
+        while (!maxHeap.isEmpty() || prev != null) {
+            if (prev != null && maxHeap.isEmpty()) {
+                return "";
+            }
+
+            int[] curr = maxHeap.poll();
+            res.append((char) (curr[1] + 'a'));
+            curr[0]--;
+
+            if (prev != null) {
+                maxHeap.offer(prev);
+                prev = null;
+            }
+
+            if (curr[0] > 0) {
+                prev = curr;
+            }
+        }
+
+        return res.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string reorganizeString(string s) {
+        vector<int> freq(26, 0);
+        for (char& c : s) {
+            freq[c - 'a']++;
+        }
+
+        priority_queue<pair<int, char>> maxHeap;
+        for (int i = 0; i < 26; i++) {
+            if (freq[i] > 0) {
+                maxHeap.push({freq[i], 'a' + i});
+            }
+        }
+
+        string res = "";
+        pair<int, char> prev = {0, ' '};
+        while (!maxHeap.empty() || prev.first > 0) {
+            if (prev.first > 0 && maxHeap.empty()) {
+                return "";
+            }
+
+            auto [count, char_] = maxHeap.top();
+            maxHeap.pop();
+            res += char_;
+            count--;
+
+            if (prev.first > 0) {
+                maxHeap.push(prev);
+            }
+
+            prev = {count, char_};
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string}
+     */
+    reorganizeString(s) {
+        const freq = new Array(26).fill(0);
+        for (const char of s) {
+            freq[char.charCodeAt(0) - 'a'.charCodeAt(0)]++;
+        }
+
+        const maxHeap = new MaxPriorityQueue({
+            priority: ([count]) => count,
+        });
+        for (let i = 0; i < 26; i++) {
+            if (freq[i] > 0) {
+                maxHeap.enqueue([freq[i], String.fromCharCode(i + 'a'.charCodeAt(0))]);
+            }
+        }
+
+        let res = '';
+        let prev = null;
+
+        while (!maxHeap.isEmpty() || prev) {
+            if (prev && maxHeap.isEmpty()) {
+                return '';
+            }
+
+            const [count, char] = maxHeap.dequeue().element;
+            res += char;
+
+            if (prev) {
+                maxHeap.enqueue(prev);
+                prev = null;
+            }
+            if (count > 1) {
+                prev = [count - 1, char];
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public string ReorganizeString(string s) {
+        Dictionary<char, int> count = new();
+        foreach (char c in s) {
+            if (!count.ContainsKey(c)) count[c] = 0;
+            count[c]++;
+        }
+
+        PriorityQueue<int[], int> maxHeap = new();
+        foreach (var kvp in count) {
+            maxHeap.Enqueue(new int[] { kvp.Value, kvp.Key }, -kvp.Value);
+        }
+
+        string res = "";
+        int[] prev = null;
+
+        while (maxHeap.Count > 0 || prev != null) {
+            if (prev != null && maxHeap.Count == 0) return "";
+
+            int[] curr = maxHeap.Dequeue();
+            res += (char)curr[1];
+            curr[0]--;
+
+            if (prev != null) {
+                maxHeap.Enqueue(prev, -prev[0]);
+                prev = null;
+            }
+
+            if (curr[0] > 0) {
+                prev = curr;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity:
+    * $O(1)$ extra space, since we have at most $26$ different characters.
+    * $O(n)$ space for the output string.
+
+---
+
+## 3. Frequency Count (Greedy)
+
+::tabs-start
+
+```python
+class Solution:
+    def reorganizeString(self, s: str) -> str:
+        freq = [0] * 26
+        for char in s:
+            freq[ord(char) - ord('a')] += 1
+
+        max_idx = freq.index(max(freq))
+        max_freq = freq[max_idx]
+        if max_freq > (len(s) + 1) // 2:
+            return ""
+        
+        res = [''] * len(s)
+        idx = 0
+        max_char = chr(max_idx + ord('a'))
+
+        while freq[max_idx] > 0:
+            res[idx] = max_char
+            idx += 2
+            freq[max_idx] -= 1
+        
+        for i in range(26):
+            while freq[i] > 0:
+                if idx >= len(s):
+                    idx = 1
+                res[idx] = chr(i + ord('a'))
+                idx += 2
+                freq[i] -= 1
+        
+        return ''.join(res)
+```
+
+```java
+public class Solution {
+    public String reorganizeString(String s) {
+        int[] freq = new int[26];
+        for (char c : s.toCharArray()) {
+            freq[c - 'a']++;
+        }
+
+        int maxIdx = 0;
+        for (int i = 1; i < 26; i++) {
+            if (freq[i] > freq[maxIdx]) {
+                maxIdx = i;
+            }
+        }
+
+        int maxFreq = freq[maxIdx];
+        if (maxFreq > (s.length() + 1) / 2) {
+            return "";
+        }
+
+        char[] res = new char[s.length()];
+        int idx = 0;
+        char maxChar = (char) (maxIdx + 'a');
+
+        while (freq[maxIdx] > 0) {
+            res[idx] = maxChar;
+            idx += 2;
+            freq[maxIdx]--;
+        }
+
+        for (int i = 0; i < 26; i++) {
+            while (freq[i] > 0) {
+                if (idx >= s.length()) {
+                    idx = 1;
+                }
+                res[idx] = (char) (i + 'a');
+                idx += 2;
+                freq[i]--;
+            }
+        }
+
+        return new String(res);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string reorganizeString(string s) {
+        vector<int> freq(26, 0);
+        for (char& c : s) {
+            freq[c - 'a']++;
+        }
+
+        int maxIdx = max_element(freq.begin(), freq.end()) - freq.begin();
+        int maxFreq = freq[maxIdx];
+        if (maxFreq > (s.size() + 1) / 2) {
+            return "";
+        }
+
+        string res(s.size(), ' ');
+        int idx = 0;
+        char maxChar = 'a' + maxIdx;
+
+        while (freq[maxIdx] > 0) {
+            res[idx] = maxChar;
+            idx += 2;
+            freq[maxIdx]--;
+        }
+
+        for (int i = 0; i < 26; i++) {
+            while (freq[i] > 0) {
+                if (idx >= s.size()) {
+                    idx = 1;
+                }
+                res[idx] = 'a' + i;
+                idx += 2;
+                freq[i]--;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string}
+     */
+    reorganizeString(s) {
+        const freq = new Array(26).fill(0);
+        for (const char of s) {
+            freq[char.charCodeAt(0) - 'a'.charCodeAt(0)]++;
+        }
+
+        let maxIdx = 0;
+        for (let i = 1; i < 26; i++) {
+            if (freq[i] > freq[maxIdx]) {
+                maxIdx = i;
+            }
+        }
+
+        const maxFreq = freq[maxIdx];
+        if (maxFreq > Math.floor((s.length + 1) / 2)) {
+            return '';
+        }
+
+        const res = new Array(s.length).fill('');
+        let idx = 0;
+        const maxChar = String.fromCharCode(maxIdx + 'a'.charCodeAt(0));
+
+        while (freq[maxIdx] > 0) {
+            res[idx] = maxChar;
+            idx += 2;
+            freq[maxIdx]--;
+        }
+
+        for (let i = 0; i < 26; i++) {
+            while (freq[i] > 0) {
+                if (idx >= s.length) {
+                    idx = 1;
+                }
+                res[idx] = String.fromCharCode(i + 'a'.charCodeAt(0));
+                idx += 2;
+                freq[i]--;
+            }
+        }
+
+        return res.join('');
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public string ReorganizeString(string s) {
+        int[] freq = new int[26];
+        foreach (char c in s) {
+            freq[c - 'a']++;
+        }
+
+        int maxIdx = 0;
+        for (int i = 1; i < 26; i++) {
+            if (freq[i] > freq[maxIdx]) {
+                maxIdx = i;
+            }
+        }
+
+        int maxFreq = freq[maxIdx];
+        if (maxFreq > (s.Length + 1) / 2) return "";
+
+        char[] res = new char[s.Length];
+        int idx = 0;
+        char maxChar = (char)(maxIdx + 'a');
+
+        while (freq[maxIdx] > 0) {
+            res[idx] = maxChar;
+            idx += 2;
+            freq[maxIdx]--;
+        }
+
+        for (int i = 0; i < 26; i++) {
+            while (freq[i] > 0) {
+                if (idx >= s.Length) idx = 1;
+                res[idx] = (char)(i + 'a');
+                idx += 2;
+                freq[i]--;
+            }
+        }
+
+        return new string(res);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity:
+    * $O(1)$ extra space, since we have at most $26$ different characters.
+    * $O(n)$ space for the output string.
\ No newline at end of file
diff --git a/articles/repeated-dna-sequences.md b/articles/repeated-dna-sequences.md
new file mode 100644
index 000000000..6976f8850
--- /dev/null
+++ b/articles/repeated-dna-sequences.md
@@ -0,0 +1,470 @@
+## 1. Hash Set
+
+::tabs-start
+
+```python
+class Solution:
+    def findRepeatedDnaSequences(self, s: str) -> List[str]:
+        seen, res = set(), set()
+
+        for l in range(len(s) - 9):
+            cur = s[l: l + 10]
+            if cur in seen:
+                res.add(cur)
+            seen.add(cur)
+        return list(res)
+```
+
+```java
+public class Solution {
+    public List<String> findRepeatedDnaSequences(String s) {
+        Set<String> seen = new HashSet<>();
+        Set<String> res = new HashSet<>();
+
+        for (int l = 0; l < s.length() - 9; l++) {
+            String cur = s.substring(l, l + 10);
+            if (seen.contains(cur)) {
+                res.add(cur);
+            }
+            seen.add(cur);
+        }
+        return new ArrayList<>(res);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<string> findRepeatedDnaSequences(string s) {
+        if (s.size() < 10) return {};
+        unordered_set<string> seen, res;
+
+        for (int l = 0; l < s.size() - 9; l++) {
+            string cur = s.substr(l, 10);
+            if (seen.count(cur)) {
+                res.insert(cur);
+            }
+            seen.insert(cur);
+        }
+        return vector<string>(res.begin(), res.end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string[]}
+     */
+    findRepeatedDnaSequences(s) {
+        const seen = new Set();
+        const res = new Set();
+
+        for (let l = 0; l < s.length - 9; l++) {
+            const cur = s.substring(l, l + 10);
+            if (seen.has(cur)) {
+                res.add(cur);
+            }
+            seen.add(cur);
+        }
+        return Array.from(res);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def findRepeatedDnaSequences(self, s: str) -> List[str]:
+        if len(s) < 10:
+            return []
+
+        mp = defaultdict(int)
+        res = []
+        for l in range(len(s) - 9):
+            cur = s[l: l + 10]
+            mp[cur] += 1
+            if mp[cur] == 2:
+                res.append(cur)
+
+        return res
+```
+
+```java
+public class Solution {
+    public List<String> findRepeatedDnaSequences(String s) {
+        if (s.length() < 10) {
+            return new ArrayList<>();
+        }
+
+        Map<String, Integer> mp = new HashMap<>();
+        List<String> res = new ArrayList<>();
+
+        for (int l = 0; l < s.length() - 9; l++) {
+            String cur = s.substring(l, l + 10);
+            mp.put(cur, mp.getOrDefault(cur, 0) + 1);
+            if (mp.get(cur) == 2) {
+                res.add(cur);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<string> findRepeatedDnaSequences(string s) {
+        if (s.size() < 10) {
+            return {};
+        }
+
+        unordered_map<string, int> mp;
+        vector<string> res;
+
+        for (int l = 0; l < s.size() - 9; l++) {
+            string cur = s.substr(l, 10);
+            mp[cur]++;
+            if (mp[cur] == 2) {
+                res.push_back(cur);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string[]}
+     */
+    findRepeatedDnaSequences(s) {
+        if (s.length < 10) {
+            return [];
+        }
+
+        const mp = new Map();
+        const res = [];
+
+        for (let l = 0; l <= s.length - 10; l++) {
+            const cur = s.substring(l, l + 10);
+            mp.set(cur, (mp.get(cur) || 0) + 1);
+            if (mp.get(cur) === 2) {
+                res.push(cur);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Rabin-Karp Algorithm (Double Hashing)
+
+::tabs-start
+
+```python
+class Solution:
+    def findRepeatedDnaSequences(self, s: str) -> List[str]:
+        n = len(s)
+        if n < 10:
+            return []
+
+        cnt = defaultdict(int)
+        res = []
+        base1, base2 = 31, 37
+        hash1 = hash2 = 0
+        power1, power2 = 1, 1
+        MOD1, MOD2 = 685683731, 768258391
+
+        for i in range(9):
+            power1 *= base1
+            power2 *= base2
+            power1 %= MOD1
+            power2 %= MOD2
+
+        for i in range(n):
+            hash1 = (hash1 * base1 + ord(s[i])) % MOD1
+            hash2 = (hash2 * base2 + ord(s[i])) % MOD2
+
+            if i >= 9:
+                key = (hash1 << 31) | hash2
+                cnt[key] += 1
+                if cnt[key] == 2:
+                    res.append(s[i - 9 : i + 1])
+
+                hash1 = (hash1 - power1 * ord(s[i - 9]) % MOD1 + MOD1) % MOD1
+                hash2 = (hash2 - power2 * ord(s[i - 9]) % MOD2 + MOD2)
+
+        return res
+```
+
+```java
+public class Solution {
+    public List<String> findRepeatedDnaSequences(String s) {
+        int n = s.length();
+        if (n < 10) return new ArrayList<>();
+
+        Map<Long, Integer> cnt = new HashMap<>();
+        List<String> res = new ArrayList<>();
+        int base1 = 31, base2 = 37;
+        long hash1 = 0, hash2 = 0, power1 = 1, power2 = 1;
+        int MOD1 = 685683731, MOD2 = 768258391;
+
+        for (int i = 0; i < 9; i++) {
+            power1 = (power1 * base1) % MOD1;
+            power2 = (power2 * base2) % MOD2;
+        }
+
+        for (int i = 0; i < n; i++) {
+            hash1 = (hash1 * base1 + s.charAt(i)) % MOD1;
+            hash2 = (hash2 * base2 + s.charAt(i)) % MOD2;
+
+            if (i >= 9) {
+                long key = (hash1 << 31) | hash2;
+                cnt.put(key, cnt.getOrDefault(key, 0) + 1);
+                if (cnt.get(key) == 2) {
+                    res.add(s.substring(i - 9, i + 1));
+                }
+
+                hash1 = (hash1 - power1 * s.charAt(i - 9) % MOD1 + MOD1) % MOD1;
+                hash2 = (hash2 - power2 * s.charAt(i - 9) % MOD2 + MOD2) % MOD2;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<string> findRepeatedDnaSequences(string s) {
+        int n = s.length();
+        if (n < 10) return {};
+
+        unordered_map<long long, int> cnt;
+        vector<string> res;
+        int base1 = 31, base2 = 37;
+        long long hash1 = 0, hash2 = 0, power1 = 1, power2 = 1;
+        int MOD1 = 685683731, MOD2 = 768258391;
+
+        for (int i = 0; i < 9; i++) {
+            power1 = (power1 * base1) % MOD1;
+            power2 = (power2 * base2) % MOD2;
+        }
+
+        for (int i = 0; i < n; i++) {
+            hash1 = (hash1 * base1 + s[i]) % MOD1;
+            hash2 = (hash2 * base2 + s[i]) % MOD2;
+
+            if (i >= 9) {
+                long long key = (hash1 << 31) | hash2;
+                cnt[key]++;
+                if (cnt[key] == 2) {
+                    res.push_back(s.substr(i - 9, 10));
+                }
+
+                hash1 = (hash1 - power1 * s[i - 9] % MOD1 + MOD1) % MOD1;
+                hash2 = (hash2 - power2 * s[i - 9] % MOD2 + MOD2) % MOD2;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string[]}
+     */
+    findRepeatedDnaSequences(s) {
+        const n = s.length;
+        if (n < 10) return [];
+
+        const cnt = new Map();
+        const res = [];
+        const base1 = 31, base2 = 37;
+        let hash1 = 0, hash2 = 0, power1 = 1, power2 = 1;
+        const MOD1 = 685683731, MOD2 = 768258391;
+
+        for (let i = 0; i < 9; i++) {
+            power1 = (power1 * base1) % MOD1;
+            power2 = (power2 * base2) % MOD2;
+        }
+
+        for (let i = 0; i < n; i++) {
+            hash1 = (hash1 * base1 + s.charCodeAt(i)) % MOD1;
+            hash2 = (hash2 * base2 + s.charCodeAt(i)) % MOD2;
+
+            if (i >= 9) {
+                const key = `${hash1},${hash2}`;
+                cnt.set(key, (cnt.get(key) || 0) + 1);
+                if (cnt.get(key) === 2) {
+                    res.push(s.substring(i - 9, i + 1));
+                }
+
+                hash1 = (hash1 - power1 * s.charCodeAt(i - 9) % MOD1 + MOD1) % MOD1;
+                hash2 = (hash2 - power2 * s.charCodeAt(i - 9) % MOD2 + MOD2) % MOD2;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Bit Mask
+
+::tabs-start
+
+```python
+class Solution:
+    def findRepeatedDnaSequences(self, s: str) -> list[str]:
+        if len(s) < 10:
+            return []
+
+        mp = {'A': 0, 'C': 1, 'G': 2, 'T': 3}
+        seen, res = set(), set()
+        mask = 0
+        for i in range(len(s)):
+            mask = ((mask << 2) | mp[s[i]]) & 0xFFFFF
+            if i >= 9:
+                if mask in seen:
+                    res.add(s[i - 9: i + 1])
+                else:
+                    seen.add(mask)
+        
+        return list(res)
+```
+
+```java
+public class Solution {
+    public List<String> findRepeatedDnaSequences(String s) {
+        if (s.length() < 10) return new ArrayList<>();
+
+        Map<Character, Integer> mp = Map.of('A', 0, 'C', 1, 'G', 2, 'T', 3);
+        Map<Integer, Integer> cnt = new HashMap<>();
+        List<String> res = new ArrayList<>();
+        int mask = 0;
+
+        for (int i = 0; i < s.length(); i++) {
+            mask = ((mask << 2) | mp.get(s.charAt(i))) & 0xFFFFF;
+            if (i >= 9) {
+                cnt.put(mask, cnt.getOrDefault(mask, 0) + 1);
+                if (cnt.get(mask) == 2) {
+                    res.add(s.substring(i - 9, i + 1));
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<string> findRepeatedDnaSequences(string s) {
+        if (s.length() < 10) return {};
+
+        unordered_map<char, int> mp = {{'A', 0}, {'C', 1}, 
+                                       {'G', 2}, {'T', 3}};
+        unordered_map<int, int> cnt;
+        vector<string> res;
+        int mask = 0;
+
+        for (int i = 0; i < s.size(); i++) {
+            mask = ((mask << 2) | mp[s[i]]) & 0xFFFFF;
+
+            if (i >= 9) {
+                cnt[mask]++;
+                if (cnt[mask] == 2) {
+                    res.push_back(s.substr(i - 9, 10));
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string[]}
+     */
+    findRepeatedDnaSequences(s) {
+        if (s.length < 10) return [];
+
+        const mp = { 'A': 0, 'C': 1, 'G': 2, 'T': 3 };
+        const cnt = new Map();
+        const res = [];
+        let mask = 0;
+
+        for (let i = 0; i < s.length; i++) {
+            mask = ((mask << 2) | mp[s[i]]) & 0xFFFFF;
+
+            if (i >= 9) {
+                cnt.set(mask, (cnt.get(mask) || 0) + 1);
+                if (cnt.get(mask) === 2) {
+                    res.push(s.substring(i - 9, i + 1));
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/replace-elements-with-greatest-element-on-right-side.md b/articles/replace-elements-with-greatest-element-on-right-side.md
new file mode 100644
index 000000000..1825436a7
--- /dev/null
+++ b/articles/replace-elements-with-greatest-element-on-right-side.md
@@ -0,0 +1,154 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def replaceElements(self, arr: List[int]) -> List[int]:
+        n = len(arr)
+        ans = [0] * n
+        for i in range(n):
+            rightMax = -1
+            for j in range(i + 1, n):
+                rightMax = max(rightMax, arr[j])
+            ans[i] = rightMax
+        return ans
+```
+
+```java
+public class Solution {
+    public int[] replaceElements(int[] arr) {
+        int n = arr.length;
+        int[] ans = new int[n];
+        for (int i = 0; i < n; i++) {
+            int rightMax = -1;
+            for (int j = i + 1; j < n; j++) {
+                rightMax = Math.max(rightMax, arr[j]);
+            }
+            ans[i] = rightMax;
+        }
+        return ans;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> replaceElements(vector<int>& arr) {
+        int n = arr.size();
+        vector<int> ans(n);
+        for (int i = 0; i < n; ++i) {
+            int rightMax = -1;
+            for (int j = i + 1; j < n; ++j) {
+                rightMax = max(rightMax, arr[j]);
+            }
+            ans[i] = rightMax;
+        }
+        return ans;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @return {number[]}
+     */
+    replaceElements(arr) {
+        let n = arr.length;
+        let ans = new Array(n);
+        for (let i = 0; i < n; i++) {
+            let rightMax = -1;
+            for (let j = i + 1; j < n; j++) {
+                rightMax = Math.max(rightMax, arr[j]);
+            }
+            ans[i] = rightMax;
+        }
+        return ans;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Suffix Max
+
+::tabs-start
+
+```python
+class Solution:
+    def replaceElements(self, arr: List[int]) -> List[int]:
+        n = len(arr)
+        ans = [0] * n
+        rightMax = -1
+        for i in range(n - 1, -1, -1):
+            ans[i] = rightMax
+            rightMax = max(arr[i], rightMax)
+        return ans 
+```
+
+```java
+public class Solution {
+    public int[] replaceElements(int[] arr) {
+        int n = arr.length;
+        int[] ans = new int[n];
+        int rightMax = -1;
+        for (int i = n - 1; i >= 0; i--) {
+            ans[i] = rightMax;
+            rightMax = Math.max(rightMax, arr[i]);
+        }
+        return ans;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> replaceElements(vector<int>& arr) {
+        int n = arr.size();
+        vector<int> ans(n);
+        int rightMax = -1;
+        for (int i = n - 1; i >= 0; --i) {
+            ans[i] = rightMax;
+            rightMax = max(rightMax, arr[i]);
+        }
+        return ans;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @return {number[]}
+     */
+    replaceElements(arr) {
+        let n = arr.length;
+        let ans = new Array(n);
+        let rightMax = -1;
+        for (let i = n - 1; i >= 0; i--) {
+            ans[i] = rightMax;
+            rightMax = Math.max(rightMax, arr[i]);
+        }
+        return ans;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/restore-ip-addresses.md b/articles/restore-ip-addresses.md
new file mode 100644
index 000000000..a0a6fd2b6
--- /dev/null
+++ b/articles/restore-ip-addresses.md
@@ -0,0 +1,278 @@
+## 1. Backtracking
+
+::tabs-start
+
+```python
+class Solution:
+    def restoreIpAddresses(self, s: str) -> List[str]:
+        res = []
+        if len(s) > 12:
+            return res
+        
+        def backtrack(i, dots, curIP):
+            if dots == 4 and i == len(s):
+                res.append(curIP[:-1])
+                return
+            if dots > 4:
+                return
+            
+            for j in range(i, min(i + 3, len(s))):
+                if i != j and s[i] == "0":
+                    continue
+                if int(s[i: j + 1]) < 256:
+                    backtrack(j + 1, dots + 1, curIP + s[i: j + 1] + ".")
+            
+        backtrack(0, 0, "")
+        return res
+```
+
+```java
+public class Solution {
+    public List<String> restoreIpAddresses(String s) {
+        List<String> res = new ArrayList<>();
+        if (s.length() > 12) return res;
+
+        backtrack(0, 0, "", s, res);
+        return res;
+    }
+
+    private void backtrack(int i, int dots, String curIP, String s, List<String> res) {
+        if (dots == 4 && i == s.length()) {
+            res.add(curIP.substring(0, curIP.length() - 1));
+            return;
+        }
+        if (dots > 4) return;
+
+        for (int j = i; j < Math.min(i + 3, s.length()); j++) {
+            if (i != j && s.charAt(i) == '0') continue;
+            if (Integer.parseInt(s.substring(i, j + 1)) < 256) {
+                backtrack(j + 1, dots + 1, curIP + s.substring(i, j + 1) + ".", s, res);
+            }
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+        vector<string> res;
+
+public:
+    vector<string> restoreIpAddresses(string s) {
+        if (s.length() > 12) return res;
+        backtrack(s, 0, 0, "");
+        return res;
+    }
+
+private:
+    void backtrack(string& s, int i, int dots, string curIP) {
+        if (dots == 4 && i == s.size()) {
+            res.push_back(curIP.substr(0, curIP.size() - 1));
+            return;
+        }
+        if (dots > 4) return;
+
+        for (int j = i; j < min(i + 3, (int)s.size()); j++) {
+            if (i != j && s[i] == '0') continue;
+            if (stoi(s.substr(i, j - i + 1)) < 256) {
+                backtrack(s, j + 1, dots + 1, curIP + s.substr(i, j - i + 1) + ".");
+            }
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string[]}
+     */
+    restoreIpAddresses(s) {
+        const res = [];
+        if (s.length > 12) return res;
+
+        const backtrack = (i, dots, curIP) => {
+            if (dots === 4 && i === s.length) {
+                res.push(curIP.slice(0, -1));
+                return;
+            }
+            if (dots > 4) return;
+
+            for (let j = i; j < Math.min(i + 3, s.length); j++) {
+                if (i !== j && s[i] === '0') continue;
+                if (parseInt(s.slice(i, j + 1)) < 256) {
+                    backtrack(j + 1, dots + 1, curIP + s.slice(i, j + 1) + '.');
+                }
+            }
+        };
+
+        backtrack(0, 0, "");
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m ^ n * n)$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is equals to $3$ as there are at most three digits in a valid segment and $n$ is equals to $4$ as there are four segments in a valid IP.
+
+---
+
+## 2. Iteration
+
+::tabs-start
+
+```python
+class Solution:
+    def restoreIpAddresses(self, s: str) -> List[str]:
+        res = []
+        if len(s) > 12:
+            return res
+        
+        def valid(num):
+            return len(num) == 1 or (int(num) < 256 and num[0] != "0")
+        
+        def add(s1, s2, s3, s4):
+            if s1 + s2 + s3 + s4 != len(s):
+                return
+            
+            num1 = s[:s1]
+            num2 = s[s1:s1+s2]
+            num3 = s[s1+s2:s1+s2+s3]
+            num4 = s[s1+s2+s3:]
+            if valid(num1) and valid(num2) and valid(num3) and valid(num4):
+                res.append(num1 + "." + num2 + "." + num3 + "." + num4)
+        
+        for seg1 in range(1, 4):
+            for seg2 in range(1, 4):
+                for seg3 in range(1, 4):
+                    for seg4 in range(1, 4):
+                        add(seg1, seg2, seg3, seg4)
+        
+        return res
+```
+
+```java
+public class Solution {
+    public List<String> restoreIpAddresses(String s) {
+        List<String> res = new ArrayList<>();
+        if (s.length() > 12) return res;
+        
+        for (int seg1 = 1; seg1 < 4; seg1++) {
+            for (int seg2 = 1; seg2 < 4; seg2++) {
+                for (int seg3 = 1; seg3 < 4; seg3++) {
+                    for (int seg4 = 1; seg4 < 4; seg4++) {
+                        if (seg1 + seg2 + seg3 + seg4 != s.length()) continue;
+                        
+                        String num1 = s.substring(0, seg1);
+                        String num2 = s.substring(seg1, seg1 + seg2);
+                        String num3 = s.substring(seg1 + seg2, seg1 + seg2 + seg3);
+                        String num4 = s.substring(seg1 + seg2 + seg3);
+
+                        if (isValid(num1) && isValid(num2) && isValid(num3) && isValid(num4)) {
+                            res.add(num1 + "." + num2 + "." + num3 + "." + num4);
+                        }
+                    }
+                }
+            }
+        }
+        return res;
+    }
+
+    private boolean isValid(String num) {
+        if (num.length() > 1 && num.charAt(0) == '0') return false;
+        int value = Integer.parseInt(num);
+        return value <= 255;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<string> restoreIpAddresses(string s) {
+        vector<string> res;
+        if (s.size() > 12) return res;
+
+        auto valid = [&](string& num) {
+            if (num.size() > 1 && num[0] == '0') return false;
+            int value = stoi(num);
+            return value <= 255;
+        };
+
+        for (int seg1 = 1; seg1 < 4; ++seg1) {
+            for (int seg2 = 1; seg2 < 4; ++seg2) {
+                for (int seg3 = 1; seg3 < 4; ++seg3) {
+                    for (int seg4 = 1; seg4 < 4; ++seg4) {
+                        if (seg1 + seg2 + seg3 + seg4 != s.size()) continue;
+                        
+                        string num1 = s.substr(0, seg1);
+                        string num2 = s.substr(seg1, seg2);
+                        string num3 = s.substr(seg1 + seg2, seg3);
+                        string num4 = s.substr(seg1 + seg2 + seg3);
+
+                        if (valid(num1) && valid(num2) && valid(num3) && valid(num4)) {
+                            res.push_back(num1 + "." + num2 + "." + num3 + "." + num4);
+                        }
+                    }
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string[]}
+     */
+    restoreIpAddresses(s) {
+        const res = [];
+        if (s.length > 12) return res;
+        
+        const isValid = (num) => {
+            if (num.length > 1 && num[0] === '0') return false;
+            const value = parseInt(num, 10);
+            return value <= 255;
+        };
+
+        for (let seg1 = 1; seg1 < 4; seg1++) {
+            for (let seg2 = 1; seg2 < 4; seg2++) {
+                for (let seg3 = 1; seg3 < 4; seg3++) {
+                    for (let seg4 = 1; seg4 < 4; seg4++) {
+                        if (seg1 + seg2 + seg3 + seg4 !== s.length) continue;
+
+                        const num1 = s.substring(0, seg1);
+                        const num2 = s.substring(seg1, seg1 + seg2);
+                        const num3 = s.substring(seg1 + seg2, seg1 + seg2 + seg3);
+                        const num4 = s.substring(seg1 + seg2 + seg3);
+
+                        if (isValid(num1) && isValid(num2) && isValid(num3) && isValid(num4)) {
+                            res.push(`${num1}.${num2}.${num3}.${num4}`);
+                        }
+                    }
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m ^ n * n)$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is equals to $3$ as there are at most three digits in a valid segment and $n$ is equals to $4$ as there are four segments in a valid IP.
\ No newline at end of file
diff --git a/articles/reveal-cards-in-increasing-order.md b/articles/reveal-cards-in-increasing-order.md
new file mode 100644
index 000000000..4759af658
--- /dev/null
+++ b/articles/reveal-cards-in-increasing-order.md
@@ -0,0 +1,406 @@
+## 1. Simulation Using Queue - I
+
+::tabs-start
+
+```python
+class Solution:
+    def deckRevealedIncreasing(self, deck: List[int]) -> List[int]:
+        deck.sort()
+        res = [0] * len(deck)
+        q = deque(range(len(deck)))
+
+        for num in deck:
+            i = q.popleft()
+            res[i] = num
+            if q:
+                q.append(q.popleft())
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[] deckRevealedIncreasing(int[] deck) {
+        Arrays.sort(deck);
+        int n = deck.length;
+        int[] res = new int[n];
+        Queue<Integer> q = new LinkedList<>();
+
+        for (int i = 0; i < n; i++) {
+            q.offer(i);
+        }
+
+        for (int num : deck) {
+            int i = q.poll();
+            res[i] = num;
+            if (!q.isEmpty()) {
+                q.offer(q.poll());
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> deckRevealedIncreasing(vector<int>& deck) {
+        sort(deck.begin(), deck.end());
+        int n = deck.size();
+        vector<int> res(n);
+        queue<int> q;
+
+        for (int i = 0; i < n; i++) {
+            q.push(i);
+        }
+
+        for (int num : deck) {
+            int i = q.front();
+            q.pop();
+            res[i] = num;
+            if (!q.empty()) {
+                q.push(q.front());
+                q.pop();
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} deck
+     * @return {number[]}
+     */
+    deckRevealedIncreasing(deck) {
+        deck.sort((a, b) => a - b);
+        let n = deck.length;
+        let res = new Array(n).fill(0);
+        const q = new Queue();
+
+        for (let i = 0; i < n; i++) {
+            q.push(i);
+        }
+
+        for (let num of deck) {
+            let i = q.pop();
+            res[i] = num;
+            if (!q.isEmpty()) {
+                q.push(q.pop());
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Simuation Using Queue - II
+
+::tabs-start
+
+```python
+class Solution:
+    def deckRevealedIncreasing(self, deck: List[int]) -> List[int]:
+        deck.sort()
+        q = deque()
+        for i in range(len(deck) - 1, -1, -1):
+            if q:
+                q.append(q.popleft())
+            q.append(deck[i])
+        return list(q)[::-1]
+```
+
+```java
+public class Solution {
+    public int[] deckRevealedIncreasing(int[] deck) {
+        Arrays.sort(deck);
+        Queue<Integer> q = new LinkedList<>();
+
+        for (int i = deck.length - 1; i >= 0; i--) {
+            if (!q.isEmpty()) {
+                q.offer(q.poll());
+            }
+            q.offer(deck[i]);
+        }
+
+        int[] res = new int[deck.length];
+        for (int i = deck.length - 1; i >= 0; i--) {
+            res[i] = q.poll();
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> deckRevealedIncreasing(vector<int>& deck) {
+        sort(deck.begin(), deck.end());
+        queue<int> q;
+
+        for (int i = deck.size() - 1; i >= 0; i--) {
+            if (!q.empty()) {
+                q.push(q.front());
+                q.pop();
+            }
+            q.push(deck[i]);
+        }
+
+        vector<int> res(deck.size());
+        for (int i = deck.size() - 1; i >= 0; i--) {
+            res[i] = q.front();
+            q.pop();
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} deck
+     * @return {number[]}
+     */
+    deckRevealedIncreasing(deck) {
+        deck.sort((a, b) => a - b);
+        const q = new Queue();
+
+        for (let i = deck.length - 1; i >= 0; i--) {
+            if (!q.isEmpty()) {
+                q.push(q.pop());
+            }
+            q.push(deck[i]);
+        }
+
+        return q.toArray().reverse();
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Simulation Using Deque
+
+::tabs-start
+
+```python
+class Solution:
+    def deckRevealedIncreasing(self, deck: List[int]) -> List[int]:
+        deck.sort()
+        dq = deque()
+        dq.append(deck.pop())
+        for i in range(len(deck) - 1, -1, -1):
+            dq.appendleft(dq.pop())
+            dq.appendleft(deck[i])
+        return list(dq)
+```
+
+```java
+public class Solution {
+    public int[] deckRevealedIncreasing(int[] deck) {
+        int n = deck.length;
+        Arrays.sort(deck);
+        Deque<Integer> dq = new LinkedList<>();
+        dq.addLast(deck[n - 1]);
+
+        for (int i = n - 2; i >= 0; i--) {
+            dq.addFirst(dq.removeLast());
+            dq.addFirst(deck[i]);
+        }
+
+        return dq.stream().mapToInt(Integer::intValue).toArray();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> deckRevealedIncreasing(vector<int>& deck) {
+        sort(deck.begin(), deck.end());
+        deque<int> dq;
+        dq.push_back(deck.back());
+
+        for (int i = deck.size() - 2; i >= 0; i--) {
+            dq.push_front(dq.back());
+            dq.pop_back();
+            dq.push_front(deck[i]);
+        }
+
+        return vector<int>(dq.begin(), dq.end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} deck
+     * @return {number[]}
+     */
+    deckRevealedIncreasing(deck) {
+        deck.sort((a, b) => a - b);
+        const dq = new Deque([deck.pop()]);
+
+        for (let i = deck.length - 1; i >= 0; i--) {
+            let val = dq.popBack();
+            dq.pushFront(val);
+            dq.pushFront(deck[i]);
+        }
+
+        let res = [];
+        while (!dq.isEmpty()) {
+            res.push(dq.popFront());
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Simulation Using Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def deckRevealedIncreasing(self, deck: List[int]) -> List[int]:
+        n = len(deck)
+        res = [0] * n
+        skip = False
+        deckIndex, i = 0, 0
+
+        deck.sort()
+
+        while deckIndex < n:
+            if res[i] == 0:
+                if not skip:
+                    res[i] = deck[deckIndex]
+                    deckIndex += 1
+                skip = not skip
+            i = (i + 1) % n
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[] deckRevealedIncreasing(int[] deck) {
+        int n = deck.length;
+        int[] res = new int[n];
+        Arrays.fill(res, 0);
+        boolean skip = false;
+        int deckIndex = 0, i = 0;
+
+        Arrays.sort(deck);
+
+        while (deckIndex < n) {
+            if (res[i] == 0) {
+                if (!skip) {
+                    res[i] = deck[deckIndex++];
+                }
+                skip = !skip;
+            }
+            i = (i + 1) % n;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> deckRevealedIncreasing(vector<int>& deck) {
+        int n = deck.size();
+        vector<int> res(n, 0);
+        bool skip = false;
+        int deckIndex = 0, i = 0;
+
+        sort(deck.begin(), deck.end());
+
+        while (deckIndex < n) {
+            if (res[i] == 0) {
+                if (!skip) {
+                    res[i] = deck[deckIndex++];
+                }
+                skip = !skip;
+            }
+            i = (i + 1) % n;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} deck
+     * @return {number[]}
+     */
+    deckRevealedIncreasing(deck) {
+        let n = deck.length;
+        let res = new Array(n).fill(0);
+        let skip = false;
+        let deckIndex = 0, i = 0;
+
+        deck.sort((a, b) => a - b);
+
+        while (deckIndex < n) {
+            if (res[i] === 0) {
+                if (!skip) {
+                    res[i] = deck[deckIndex++];
+                }
+                skip = !skip;
+            }
+            i = (i + 1) % n;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity:
+    * $O(1)$ or $O(n)$ space depending on the sorting algorithm.
+    * $O(n)$ space for the output array.
\ No newline at end of file
diff --git a/articles/reverse-a-linked-list.md b/articles/reverse-a-linked-list.md
index 97a1a6bd1..3a205a543 100644
--- a/articles/reverse-a-linked-list.md
+++ b/articles/reverse-a-linked-list.md
@@ -148,6 +148,87 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func reverseList(head *ListNode) *ListNode {
+    if head == nil {
+        return nil
+    }
+    
+    newHead := head
+    if head.Next != nil {
+        newHead = reverseList(head.Next)
+        head.Next.Next = head
+    }
+    head.Next = nil
+    
+    return newHead
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var li = ListNode(5)
+ * var v = li.`val`
+ * Definition for singly-linked list.
+ * class ListNode(var `val`: Int) {
+ *     var next: ListNode? = null
+ * }
+ */
+class Solution {
+    fun reverseList(head: ListNode?): ListNode? {
+        if (head == null) {
+            return null
+        }
+
+        var newHead = head
+        if (head.next != null) {
+            newHead = reverseList(head.next)
+            head.next?.next = head
+        }
+        head.next = null
+
+        return newHead
+    }
+}
+```
+
+```swift
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public var val: Int
+ *     public var next: ListNode?
+ *     public init() { self.val = 0; self.next = nil; }
+ *     public init(_ val: Int) { self.val = val; self.next = nil; }
+ *     public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
+ * }
+ */
+class Solution {
+    func reverseList(_ head: ListNode?) -> ListNode? {
+        if head == nil {
+            return nil
+        }
+
+        var newHead = head
+        if head?.next != nil {
+            newHead = reverseList(head?.next)
+            head?.next?.next = head
+        }
+        head?.next = nil
+
+        return newHead
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -297,6 +378,81 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func reverseList(head *ListNode) *ListNode {
+    var prev *ListNode
+    curr := head
+
+    for curr != nil {
+        temp := curr.Next
+        curr.Next = prev
+        prev = curr
+        curr = temp
+    }
+    return prev
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var li = ListNode(5)
+ * var v = li.`val`
+ * Definition for singly-linked list.
+ * class ListNode(var `val`: Int) {
+ *     var next: ListNode? = null
+ * }
+ */
+class Solution {
+    fun reverseList(head: ListNode?): ListNode? {
+        var prev: ListNode? = null
+        var curr = head
+
+        while (curr != null) {
+            val temp = curr.next
+            curr.next = prev
+            prev = curr
+            curr = temp
+        }
+        return prev
+    }
+}
+```
+
+```swift
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public var val: Int
+ *     public var next: ListNode?
+ *     public init() { self.val = 0; self.next = nil; }
+ *     public init(_ val: Int) { self.val = val; self.next = nil; }
+ *     public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
+ * }
+ */
+class Solution {
+    func reverseList(_ head: ListNode?) -> ListNode? {
+        var prev: ListNode? = nil
+        var curr = head
+
+        while curr != nil {
+            let temp = curr?.next
+            curr?.next = prev
+            prev = curr
+            curr = temp
+        }
+        return prev
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/reverse-bits.md b/articles/reverse-bits.md
index 10416b54d..84cbe88ce 100644
--- a/articles/reverse-bits.md
+++ b/articles/reverse-bits.md
@@ -122,6 +122,70 @@ public class Solution {
 }
 ```
 
+```go
+func reverseBits(n uint32) uint32 {
+	binary := ""
+	for i := 0; i < 32; i++ {
+		if n&(1<<i) != 0 {
+			binary += "1"
+		} else {
+			binary += "0"
+		}
+	}
+
+	var res uint32 = 0
+	for i, bit := range binary {
+		if bit == '1' {
+			res |= (1 << (31 - i))
+		}
+	}
+	return res
+}
+```
+
+```kotlin
+class Solution {
+    fun reverseBits(n: Int): Int {
+        var binary = ""
+        for (i in 0 until 32) {
+            binary += if ((n and (1 shl i)) != 0) "1" else "0"
+        }
+
+        var res = 0
+        for ((i, bit) in binary.reversed().withIndex()) {
+            if (bit == '1') {
+                res = res or (1 shl i)
+            }
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func reverseBits(_ n: Int) -> Int {
+        var binary = ""
+        for i in 0..<32 {
+            if (n & (1 << i)) != 0 {
+                binary += "1"
+            } else {
+                binary += "0"
+            }
+        }
+
+        var res = 0
+        for (i, bit) in binary.reversed().enumerated() {
+            if bit == "1" {
+                res |= (1 << i)
+            }
+        }
+
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -202,6 +266,44 @@ public class Solution {
 }
 ```
 
+```go
+func reverseBits(n uint32) uint32 {
+	var res uint32 = 0
+	for i := 0; i < 32; i++ {
+		bit := (n >> i) & 1
+		res |= (bit << (31 - i))
+	}
+	return res
+}
+```
+
+```kotlin
+class Solution {
+    fun reverseBits(n: Int): Int {
+        var res = 0
+        for (i in 0 until 32) {
+            val bit = (n shr i) and 1
+            res = res or (bit shl (31 - i))
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func reverseBits(_ n: Int) -> Int {
+        var res = 0
+        var num = n
+        for i in 0..<32 {
+            let bit = (num >> i) & 1
+            res |= (bit << (31 - i))
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -224,7 +326,7 @@ class Solution:
         res = ((res & 0xf0f0f0f0) >> 4) | ((res & 0x0f0f0f0f) << 4)
         res = ((res & 0xcccccccc) >> 2) | ((res & 0x33333333) << 2)
         res = ((res & 0xaaaaaaaa) >> 1) | ((res & 0x55555555) << 1)
-        return res & 0xFFFFFFFF 
+        return res & 0xFFFFFFFF
 ```
 
 ```java
@@ -288,6 +390,46 @@ public class Solution {
 }
 ```
 
+```go
+func reverseBits(n uint32) uint32 {
+	res := n
+	res = (res >> 16) | (res << 16)
+	res = ((res & 0xff00ff00) >> 8) | ((res & 0x00ff00ff) << 8)
+	res = ((res & 0xf0f0f0f0) >> 4) | ((res & 0x0f0f0f0f) << 4)
+	res = ((res & 0xcccccccc) >> 2) | ((res & 0x33333333) << 2)
+	res = ((res & 0xaaaaaaaa) >> 1) | ((res & 0x55555555) << 1)
+	return res
+}
+```
+
+```kotlin
+class Solution {
+    fun reverseBits(n: Int): Int {
+        var res = n
+        res = (res ushr 16) or (res shl 16)
+        res = ((res and 0xff00ff00.toInt()) ushr 8) or ((res and 0x00ff00ff) shl 8)
+        res = ((res and 0xf0f0f0f0.toInt()) ushr 4) or ((res and 0x0f0f0f0f) shl 4)
+        res = ((res and 0xcccccccc.toInt()) ushr 2) or ((res and 0x33333333) shl 2)
+        res = ((res and 0xaaaaaaaa.toInt()) ushr 1) or ((res and 0x55555555) shl 1)
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func reverseBits(_ n: Int) -> Int {
+        var res = n
+        res = (res >> 16) | (res << 16) & 0xFFFFFFFF
+        res = ((res & 0xff00ff00) >> 8) | ((res & 0x00ff00ff) << 8)
+        res = ((res & 0xf0f0f0f0) >> 4) | ((res & 0x0f0f0f0f) << 4)
+        res = ((res & 0xcccccccc) >> 2) | ((res & 0x33333333) << 2)
+        res = ((res & 0xaaaaaaaa) >> 1) | ((res & 0x55555555) << 1)
+        return res & 0xFFFFFFFF
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/reverse-integer.md b/articles/reverse-integer.md
new file mode 100644
index 000000000..c388a821f
--- /dev/null
+++ b/articles/reverse-integer.md
@@ -0,0 +1,565 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def reverse(self, x: int) -> int:
+        org = x
+        x = abs(x)
+        res = int(str(x)[::-1])
+        if org < 0:
+            res *= -1
+        if res < -(1 << 31) or res > (1 << 31) - 1:
+            return 0
+        return res
+```
+
+```java
+public class Solution {
+    public int reverse(int x) {
+        int org = x;
+        x = Math.abs(x);
+        long res = Long.parseLong(new StringBuilder(
+                   String.valueOf(x)).reverse().toString()
+                );
+        if (org < 0) {
+            res *= -1;
+        }
+        if (res < -(1 << 31) || res > (1 << 31) - 1) {
+            return 0;
+        }
+        return (int)res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int reverse(int x) {
+        int org = x;
+        x = abs(x);
+        string strX = to_string(x);
+        std::reverse(strX.begin(), strX.end());
+        long long res = stoll(strX); 
+        if (org < 0) {
+            res *= -1;
+        }
+        if (res < -(1LL << 31) || res > (1LL << 31) - 1) {
+            return 0;
+        }
+        return static_cast<int>(res);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} x
+     * @return {number}
+     */
+    reverse(x) {
+        const org = x;
+        x = Math.abs(x);
+        let res = parseInt(x.toString().split('').reverse().join(''));
+        if (org < 0) {
+            res *= -1;
+        }
+        if (res < -(2 ** 31) || res > (2 ** 31) - 1) {
+            return 0;
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int Reverse(int x) {
+        int org = x;
+        x = Math.Abs(x);
+        char[] arr = x.ToString().ToCharArray();
+        Array.Reverse(arr);
+        
+        long res = long.Parse(new string(arr)); 
+        if (org < 0) {
+            res *= -1; 
+        }
+        
+        if (res < int.MinValue || res > int.MaxValue) {
+            return 0; 
+        }
+        return (int)res; 
+    }
+}
+```
+
+```go
+func reverse(x int) int {
+    org := x
+    x = abs(x)
+    res := 0
+
+    for x > 0 {
+        res = res*10 + x%10
+        x /= 10
+    }
+
+    if org < 0 {
+        res = -res
+    }
+    if res < -(1 << 31) || res > (1<<31)-1 {
+        return 0
+    }
+    return res
+}
+
+func abs(x int) int {
+    if x < 0 {
+        return -x
+    }
+    return x
+}
+```
+
+```kotlin
+class Solution {
+    fun reverse(x: Int): Int {
+        val org = x
+        var num = Math.abs(x)
+        var res = 0
+
+        while (num > 0) {
+            if (res > (Int.MAX_VALUE - num % 10) / 10) {
+                return 0
+            }
+            res = res * 10 + num % 10
+            num /= 10
+        }
+
+        if (org < 0) {
+            res = -res
+        }
+        return if (res < Int.MIN_VALUE || res > Int.MAX_VALUE) 0 else res
+    }
+}
+```
+
+```swift
+class Solution {
+    func reverse(_ x: Int) -> Int {
+        let org = x
+        var x = abs(x)
+        var res = Int(String(String(x).reversed()))!
+
+        if org < 0 {
+            res *= -1
+        }
+        if res < Int32.min || res > Int32.max {
+            return 0
+        }
+
+        return res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def reverse(self, x: int) -> int:
+        def rec(n: int, rev: int) -> int:
+            if n == 0:
+                return rev
+            
+            rev = rev * 10 + n % 10
+            return rec(n // 10, rev)
+        
+        sign = -1 if x < 0 else 1
+        x = abs(x)        
+        reversed_num = rec(x, 0)
+        reversed_num *= sign        
+        if reversed_num < -(1 << 31) or reversed_num > (1 << 31) - 1:
+            return 0
+            
+        return reversed_num
+```
+
+```java
+public class Solution {
+    public int reverse(int x) {
+        long res = rec(Math.abs(x), 0) * (x < 0 ? -1 : 1);
+        if (res < Integer.MIN_VALUE || res > Integer.MAX_VALUE) {
+            return 0;
+        }
+        return (int) res;
+    }
+
+    private long rec(int n, long rev) {
+        if (n == 0) {
+            return rev;
+        }
+        rev = rev * 10 + n % 10;
+        return rec(n / 10, rev);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int reverse(int x) {
+        long res = rec(abs(x), 0) * (x < 0 ? -1 : 1);
+        if (res < INT_MIN || res > INT_MAX) {
+            return 0;
+        }
+        return (int)res;
+    }
+
+private:
+    long rec(int n, long rev) {
+        if (n == 0) {
+            return rev;
+        }
+        rev = rev * 10 + n % 10;
+        return rec(n / 10, rev);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} x
+     * @return {number}
+     */
+    reverse(x) {
+        let res = this.rec(Math.abs(x), 0) * (x < 0 ? -1 : 1);
+        if (res < -(2 ** 31) || res > (2 ** 31) - 1) {
+            return 0;
+        }
+        return res;
+    }
+
+    /**
+     * @param {number} n
+     * @param {number} rev
+     * @return {number}
+     */
+    rec(n, rev) {
+        if (n === 0) {
+            return rev;
+        }
+        rev = rev * 10 + n % 10;
+        return this.rec(Math.floor(n / 10), rev);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int Reverse(int x) {
+        long res = Rec(Math.Abs(x), 0) * (x < 0 ? -1 : 1);
+        if (res < int.MinValue || res > int.MaxValue) {
+            return 0;
+        }
+        return (int)res;
+    }
+
+    private long Rec(int n, long rev) {
+        if (n == 0) {
+            return rev;
+        }
+        rev = rev * 10 + n % 10;
+        return Rec(n / 10, rev);
+    }
+}
+```
+
+```go
+func reverse(x int) int {
+    var rec func(int, int) int
+    rec = func(n, rev int) int {
+        if n == 0 {
+            return rev
+        }
+        rev = rev*10 + n%10
+        return rec(n/10, rev)
+    }
+
+    sign := 1
+    if x < 0 {
+        sign = -1
+        x = -x
+    }
+
+    reversedNum := rec(x, 0) * sign
+    if reversedNum < -(1<<31) || reversedNum > (1<<31)-1 {
+        return 0
+    }
+    return reversedNum
+}
+```
+
+```kotlin
+class Solution {
+    fun reverse(x: Int): Int {
+        val res = rec(Math.abs(x), 0L) * if (x < 0) -1 else 1
+        return if (res < Int.MIN_VALUE || res > Int.MAX_VALUE) 0 else res.toInt()
+    }
+
+    private fun rec(n: Int, rev: Long): Long {
+        if (n == 0) return rev
+        return rec(n / 10, rev * 10 + n % 10)
+    }
+}
+```
+
+```swift
+class Solution {
+    func reverse(_ x: Int) -> Int {
+        func rec(_ n: Int, _ rev: Int) -> Int {
+            if n == 0 {
+                return rev
+            }
+            return rec(n / 10, rev * 10 + n % 10)
+        }
+
+        let sign = x < 0 ? -1 : 1
+        let reversedNum = rec(abs(x), 0) * sign
+
+        if reversedNum < Int32.min || reversedNum > Int32.max {
+            return 0
+        }
+
+        return reversedNum
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Iteration
+
+::tabs-start
+
+```python
+class Solution:
+    def reverse(self, x: int) -> int:
+        MIN = -2147483648  # -2^31,
+        MAX = 2147483647  #  2^31 - 1
+
+        res = 0
+        while x:
+            digit = int(math.fmod(x, 10))
+            x = int(x / 10)
+
+            if res > MAX // 10 or (res == MAX // 10 and digit > MAX % 10):
+                return 0
+            if res < MIN // 10 or (res == MIN // 10 and digit < MIN % 10):
+                return 0
+            res = (res * 10) + digit
+
+        return res
+```
+
+```java
+public class Solution {
+    public int reverse(int x) {
+        final int MIN = -2147483648; // -2^31
+        final int MAX = 2147483647;  // 2^31 - 1
+
+        int res = 0;
+        while (x != 0) {
+            int digit = x % 10;
+            x /= 10;
+
+            if (res > MAX / 10 || (res == MAX / 10 && digit > MAX % 10))
+                return 0;
+            if (res < MIN / 10 || (res == MIN / 10 && digit < MIN % 10))
+                return 0;
+            res = (res * 10) + digit;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int reverse(int x) {
+        const int MIN = -2147483648; // -2^31
+        const int MAX = 2147483647;  // 2^31 - 1
+
+        int res = 0;
+        while (x != 0) {
+            int digit = x % 10;
+            x /= 10;
+
+            if (res > MAX / 10 || (res == MAX / 10 && digit > MAX % 10))
+                return 0;
+            if (res < MIN / 10 || (res == MIN / 10 && digit < MIN % 10))
+                return 0;
+            res = (res * 10) + digit;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} x
+     * @return {number}
+     */
+    reverse(x) {
+        const MIN = -2147483648; // -2^31
+        const MAX = 2147483647; // 2^31 - 1
+
+        let res = 0;
+        while (x !== 0) {
+            const digit = x % 10;
+            x = Math.trunc(x / 10);
+
+            if (res > MAX / 10 || (res === MAX / 10 && digit > MAX % 10))
+                return 0;
+            if (res < MIN / 10 || (res === MIN / 10 && digit < MIN % 10))
+                return 0;
+            res = res * 10 + digit;
+        }
+
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int Reverse(int x) {
+        const int MIN = -2147483648; // -2^31
+        const int MAX = 2147483647;  // 2^31 - 1
+
+        int res = 0;
+        while (x != 0) {
+            int digit = x % 10;
+            x /= 10;
+
+            if (res > MAX / 10 || (res == MAX / 10 && digit > MAX % 10))
+                return 0;
+            if (res < MIN / 10 || (res == MIN / 10 && digit < MIN % 10))
+                return 0;
+            res = (res * 10) + digit;
+        }
+
+        return res;
+    }
+}
+```
+
+```go
+func reverse(x int) int {
+    MIN := -2147483648 // -2^31
+    MAX := 2147483647  // 2^31 - 1
+
+    res := 0
+    for x != 0 {
+        digit := int(math.Mod(float64(x), 10))
+        x = int(float64(x) / 10)
+
+        if res > MAX/10 || (res == MAX/10 && digit > MAX%10) {
+            return 0
+        }
+        if res < MIN/10 || (res == MIN/10 && digit < MIN%10) {
+            return 0
+        }
+        res = (res * 10) + digit
+    }
+
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun reverse(x: Int): Int {
+        val MIN = -2147483648 // -2^31
+        val MAX = 2147483647  // 2^31 - 1
+
+        var res = 0
+        var num = x
+        while (num != 0) {
+            val digit = (num % 10).toInt()
+            num /= 10
+
+            if (res > MAX / 10 || (res == MAX / 10 && digit > MAX % 10)) {
+                return 0
+            }
+            if (res < MIN / 10 || (res == MIN / 10 && digit < MIN % 10)) {
+                return 0
+            }
+            res = res * 10 + digit
+        }
+
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func reverse(_ x: Int) -> Int {
+        let MIN = Int32.min
+        let MAX = Int32.max
+
+        var res = 0
+        var num = x
+
+        while num != 0 {
+            let digit = num % 10
+            num /= 10
+
+            if res > MAX / 10 || (res == MAX / 10 && digit > MAX % 10) {
+                return 0
+            }
+            if res < MIN / 10 || (res == MIN / 10 && digit < MIN % 10) {
+                return 0
+            }
+            res = res * 10 + digit
+        }
+
+        return res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/reverse-linked-list-ii.md b/articles/reverse-linked-list-ii.md
new file mode 100644
index 000000000..98f00e838
--- /dev/null
+++ b/articles/reverse-linked-list-ii.md
@@ -0,0 +1,884 @@
+## 1. Recursion - I
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def reverseBetween(self, head: Optional[ListNode], left: int, right: int) -> Optional[ListNode]:
+        dummy = ListNode(0)
+        dummy.next = head
+        prev = dummy
+        for _ in range(left - 1):
+            prev = prev.next
+
+        sublist_head = prev.next
+        sublist_tail = sublist_head
+        for _ in range(right - left):
+            sublist_tail = sublist_tail.next
+
+        next_node = sublist_tail.next
+        sublist_tail.next = None
+        reversed_sublist = self.reverseList(sublist_head)
+        prev.next = reversed_sublist
+        sublist_head.next = next_node
+
+        return dummy.next
+
+    def reverseList(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        if not head:
+            return None
+
+        newHead = head
+        if head.next:
+            newHead = self.reverseList(head.next)
+            head.next.next = head
+        head.next = None
+        
+        return newHead
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode reverseBetween(ListNode head, int left, int right) {
+        ListNode dummy = new ListNode(0);
+        dummy.next = head;
+        ListNode prev = dummy;
+
+        for (int i = 0; i < left - 1; i++) {
+            prev = prev.next;
+        }
+
+        ListNode sublistHead = prev.next;
+        ListNode sublistTail = sublistHead;
+        for (int i = 0; i < right - left; i++) {
+            sublistTail = sublistTail.next;
+        }
+
+        ListNode nextNode = sublistTail.next;
+        sublistTail.next = null;
+        prev.next = reverseList(sublistHead);
+        sublistHead.next = nextNode;
+
+        return dummy.next;
+    }
+
+    private ListNode reverseList(ListNode head) {
+        if (head == null || head.next == null) {
+            return head;
+        }
+
+        ListNode newHead = reverseList(head.next);
+        head.next.next = head;
+        head.next = null;
+
+        return newHead;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* reverseBetween(ListNode* head, int left, int right) {
+        ListNode dummy(0);
+        dummy.next = head;
+        ListNode* prev = &dummy;
+
+        for (int i = 0; i < left - 1; ++i) {
+            prev = prev->next;
+        }
+
+        ListNode* sublistHead = prev->next;
+        ListNode* sublistTail = sublistHead;
+        for (int i = 0; i < right - left; ++i) {
+            sublistTail = sublistTail->next;
+        }
+
+        ListNode* nextNode = sublistTail->next;
+        sublistTail->next = nullptr;
+        prev->next = reverseList(sublistHead);
+        sublistHead->next = nextNode;
+
+        return dummy.next;
+    }
+
+private:
+    ListNode* reverseList(ListNode* head) {
+        if (!head || !head->next) {
+            return head;
+        }
+
+        ListNode* newHead = reverseList(head->next);
+        head->next->next = head;
+        head->next = nullptr;
+
+        return newHead;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @param {number} left
+     * @param {number} right
+     * @return {ListNode}
+     */
+    reverseBetween(head, left, right) {
+        const reverseList = (head) => {
+            if (!head || !head.next) {
+                return head;
+            }
+
+            const newHead = reverseList(head.next);
+            head.next.next = head;
+            head.next = null;
+
+            return newHead;
+        };
+
+        const dummy = new ListNode(0, head);
+        let prev = dummy;
+        for (let i = 0; i < left - 1; i++) {
+            prev = prev.next;
+        }
+
+        const sublistHead = prev.next;
+        let sublistTail = sublistHead;
+        for (let i = 0; i < right - left; i++) {
+            sublistTail = sublistTail.next;
+        }
+
+        const nextNode = sublistTail.next;
+        sublistTail.next = null;
+        prev.next = reverseList(sublistHead);
+        sublistHead.next = nextNode;
+
+        return dummy.next;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public int val;
+ *     public ListNode next;
+ *     public ListNode(int val=0, ListNode next=null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+public class Solution {
+    public ListNode ReverseBetween(ListNode head, int left, int right) {
+        ListNode dummy = new ListNode(0, head);
+        ListNode prev = dummy;
+
+        for (int i = 0; i < left - 1; i++) {
+            prev = prev.next;
+        }
+
+        ListNode sublistHead = prev.next;
+        ListNode sublistTail = sublistHead;
+        for (int i = 0; i < right - left; i++) {
+            sublistTail = sublistTail.next;
+        }
+
+        ListNode nextNode = sublistTail.next;
+        sublistTail.next = null;
+
+        ListNode reversedSublist = ReverseList(sublistHead);
+        prev.next = reversedSublist;
+        sublistHead.next = nextNode;
+
+        return dummy.next;
+    }
+
+    private ListNode ReverseList(ListNode head) {
+        if (head == null) return null;
+
+        ListNode newHead = head;
+        if (head.next != null) {
+            newHead = ReverseList(head.next);
+            head.next.next = head;
+        }
+        head.next = null;
+        return newHead;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Recursion - II
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def reverseBetween(self, head: Optional[ListNode], left: int, right: int) -> Optional[ListNode]:
+        def reverseList(node, n):
+            if n == 1:
+                return node, node.next
+            new_head, next_node = reverseList(node.next, n - 1)
+            node.next.next = node
+            node.next = next_node
+            return new_head, next_node
+
+        if left == 1:
+            new_head, _ = reverseList(head, right)
+            return new_head
+        
+        head.next = self.reverseBetween(head.next, left - 1, right - 1)
+        return head
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    private ListNode[] reverseList(ListNode node, int n) {
+        if (n == 1) {
+            return new ListNode[] { node, node.next };
+        }
+        ListNode[] result = reverseList(node.next, n - 1);
+        node.next.next = node;
+        node.next = result[1];
+        return new ListNode[] { result[0], node.next };
+    }
+
+    public ListNode reverseBetween(ListNode head, int left, int right) {
+        if (left == 1) {
+            return reverseList(head, right)[0];
+        }
+        head.next = reverseBetween(head.next, left - 1, right - 1);
+        return head;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+private:
+    pair<ListNode*, ListNode*> reverseList(ListNode* node, int n) {
+        if (n == 1) {
+            return {node, node->next};
+        }
+        auto result = reverseList(node->next, n - 1);
+        node->next->next = node;
+        node->next = result.second;
+        return {result.first, node->next};
+    }
+
+public:
+    ListNode* reverseBetween(ListNode* head, int left, int right) {
+        if (left == 1) {
+            return reverseList(head, right).first;
+        }
+        head->next = reverseBetween(head->next, left - 1, right - 1);
+        return head;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @param {number} left
+     * @param {number} right
+     * @return {ListNode}
+     */
+    reverseBetween(head, left, right) {
+        const reverseList = (node, n) => {
+            if (n === 1) {
+                return [node, node.next];
+            }
+            const [newHead, nextNode] = reverseList(node.next, n - 1);
+            node.next.next = node;
+            node.next = nextNode;
+            return [newHead, nextNode];
+        };
+
+        if (left === 1) {
+            return reverseList(head, right)[0];
+        }
+        head.next = this.reverseBetween(head.next, left - 1, right - 1);
+        return head;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public int val;
+ *     public ListNode next;
+ *     public ListNode(int val=0, ListNode next=null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+public class Solution {
+    private ListNode successor = null;
+
+    private ListNode ReverseList(ListNode node, int n) {
+        if (n == 1) {
+            successor = node.next;
+            return node;
+        }
+        ListNode newHead = ReverseList(node.next, n - 1);
+        node.next.next = node;
+        node.next = successor;
+        return newHead;
+    }
+
+    public ListNode ReverseBetween(ListNode head, int left, int right) {
+        if (left == 1) {
+            return ReverseList(head, right);
+        }
+        head.next = ReverseBetween(head.next, left - 1, right - 1);
+        return head;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 3. Iteration - I
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def reverseBetween(self, head: Optional[ListNode], left: int, right: int) -> Optional[ListNode]:
+        dummy = ListNode(0)
+        dummy.next = head
+        prev = dummy
+        for _ in range(left - 1):
+            prev = prev.next
+
+        sublist_head = prev.next
+        sublist_tail = sublist_head
+        for _ in range(right - left):
+            sublist_tail = sublist_tail.next
+
+        next_node = sublist_tail.next
+        sublist_tail.next = None
+        reversed_sublist = self.reverseList(sublist_head)
+        prev.next = reversed_sublist
+        sublist_head.next = next_node
+
+        return dummy.next
+
+    def reverseList(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        prev, curr = None, head
+
+        while curr:
+            temp = curr.next
+            curr.next = prev
+            prev = curr
+            curr = temp
+        return prev
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode reverseBetween(ListNode head, int left, int right) {
+        ListNode dummy = new ListNode(0);
+        dummy.next = head;
+        ListNode prev = dummy;
+
+        for (int i = 0; i < left - 1; i++) {
+            prev = prev.next;
+        }
+
+        ListNode sublistHead = prev.next;
+        ListNode sublistTail = sublistHead;
+        for (int i = 0; i < right - left; i++) {
+            sublistTail = sublistTail.next;
+        }
+
+        ListNode nextNode = sublistTail.next;
+        sublistTail.next = null;
+        prev.next = reverseList(sublistHead);
+        sublistHead.next = nextNode;
+
+        return dummy.next;
+    }
+
+    private ListNode reverseList(ListNode head) {
+        ListNode prev = null;
+        ListNode curr = head;
+
+        while (curr != null) {
+            ListNode temp = curr.next;
+            curr.next = prev;
+            prev = curr;
+            curr = temp;
+        }
+        return prev;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* reverseBetween(ListNode* head, int left, int right) {
+        ListNode dummy(0);
+        dummy.next = head;
+        ListNode* prev = &dummy;
+
+        for (int i = 0; i < left - 1; ++i) {
+            prev = prev->next;
+        }
+
+        ListNode* sublistHead = prev->next;
+        ListNode* sublistTail = sublistHead;
+        for (int i = 0; i < right - left; ++i) {
+            sublistTail = sublistTail->next;
+        }
+
+        ListNode* nextNode = sublistTail->next;
+        sublistTail->next = nullptr;
+        prev->next = reverseList(sublistHead);
+        sublistHead->next = nextNode;
+
+        return dummy.next;
+    }
+
+private:
+    ListNode* reverseList(ListNode* head) {
+        ListNode* prev = nullptr;
+        ListNode* curr = head;
+
+        while (curr) {
+            ListNode* temp = curr->next;
+            curr->next = prev;
+            prev = curr;
+            curr = temp;
+        }
+        return prev;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @param {number} left
+     * @param {number} right
+     * @return {ListNode}
+     */
+    reverseBetween(head, left, right) {
+        const reverseList = (head) => {
+            let prev = null;
+            let curr = head;
+
+            while (curr) {
+                let temp = curr.next;
+                curr.next = prev;
+                prev = curr;
+                curr = temp;
+            }
+            return prev;
+        };
+        
+        const dummy = new ListNode(0, head);
+        let prev = dummy;
+        for (let i = 0; i < left - 1; i++) {
+            prev = prev.next;
+        }
+
+        const sublistHead = prev.next;
+        let sublistTail = sublistHead;
+        for (let i = 0; i < right - left; i++) {
+            sublistTail = sublistTail.next;
+        }
+
+        const nextNode = sublistTail.next;
+        sublistTail.next = null;
+        prev.next = reverseList(sublistHead);
+        sublistHead.next = nextNode;
+
+        return dummy.next;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public int val;
+ *     public ListNode next;
+ *     public ListNode(int val=0, ListNode next=null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+public class Solution {
+    public ListNode ReverseBetween(ListNode head, int left, int right) {
+        ListNode dummy = new ListNode(0);
+        dummy.next = head;
+        ListNode prev = dummy;
+
+        for (int i = 0; i < left - 1; i++) {
+            prev = prev.next;
+        }
+
+        ListNode sublistHead = prev.next;
+        ListNode sublistTail = sublistHead;
+        for (int i = 0; i < right - left; i++) {
+            sublistTail = sublistTail.next;
+        }
+
+        ListNode nextNode = sublistTail.next;
+        sublistTail.next = null;
+
+        ListNode reversedSublist = ReverseList(sublistHead);
+        prev.next = reversedSublist;
+
+        sublistHead.next = nextNode;
+        return dummy.next;
+    }
+
+    private ListNode ReverseList(ListNode head) {
+        ListNode prev = null;
+        ListNode curr = head;
+        while (curr != null) {
+            ListNode temp = curr.next;
+            curr.next = prev;
+            prev = curr;
+            curr = temp;
+        }
+        return prev;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 4. Iteration - II
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def reverseBetween(self, head: Optional[ListNode], left: int, right: int) -> Optional[ListNode]:
+        dummy = ListNode(0, head)
+        leftPrev, cur = dummy, head
+
+        for _ in range(left - 1):
+            leftPrev, cur = cur, cur.next
+
+        prev = None
+        for _ in range(right - left + 1):
+            tmpNext = cur.next
+            cur.next = prev
+            prev, cur = cur, tmpNext
+
+        leftPrev.next.next = cur
+        leftPrev.next = prev
+
+        return dummy.next
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode reverseBetween(ListNode head, int left, int right) {
+        ListNode dummy = new ListNode(0);
+        dummy.next = head;
+        ListNode leftPrev = dummy, cur = head;
+
+        for (int i = 0; i < left - 1; i++) {
+            leftPrev = cur;
+            cur = cur.next;
+        }
+
+        ListNode prev = null;
+        for (int i = 0; i < right - left + 1; i++) {
+            ListNode tmpNext = cur.next;
+            cur.next = prev;
+            prev = cur;
+            cur = tmpNext;
+        }
+
+        leftPrev.next.next = cur;
+        leftPrev.next = prev;
+
+        return dummy.next;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* reverseBetween(ListNode* head, int left, int right) {
+        ListNode dummy(0);
+        dummy.next = head;
+        ListNode* leftPrev = &dummy;
+        ListNode* cur = head;
+
+        for (int i = 0; i < left - 1; ++i) {
+            leftPrev = cur;
+            cur = cur->next;
+        }
+
+        ListNode* prev = nullptr;
+        for (int i = 0; i < right - left + 1; ++i) {
+            ListNode* tmpNext = cur->next;
+            cur->next = prev;
+            prev = cur;
+            cur = tmpNext;
+        }
+
+        leftPrev->next->next = cur;
+        leftPrev->next = prev;
+
+        return dummy.next;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @param {number} left
+     * @param {number} right
+     * @return {ListNode}
+     */
+    reverseBetween(head, left, right) {
+        const dummy = new ListNode(0, head);
+        let leftPrev = dummy, cur = head;
+
+        for (let i = 0; i < left - 1; i++) {
+            leftPrev = cur;
+            cur = cur.next;
+        }
+
+        let prev = null;
+        for (let i = 0; i < right - left + 1; i++) {
+            const tmpNext = cur.next;
+            cur.next = prev;
+            prev = cur;
+            cur = tmpNext;
+        }
+
+        leftPrev.next.next = cur;
+        leftPrev.next = prev;
+
+        return dummy.next;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public int val;
+ *     public ListNode next;
+ *     public ListNode(int val=0, ListNode next=null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+public class Solution {
+    public ListNode ReverseBetween(ListNode head, int left, int right) {
+        ListNode dummy = new ListNode(0, head);
+        ListNode leftPrev = dummy, curr = head;
+
+        for (int i = 0; i < left - 1; i++) {
+            leftPrev = curr;
+            curr = curr.next;
+        }
+
+        ListNode prev = null;
+        for (int i = 0; i < right - left + 1; i++) {
+            ListNode tmpNext = curr.next;
+            curr.next = prev;
+            prev = curr;
+            curr = tmpNext;
+        }
+
+        leftPrev.next.next = curr;
+        leftPrev.next = prev;
+
+        return dummy.next;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/reverse-nodes-in-k-group.md b/articles/reverse-nodes-in-k-group.md
index 0fb9b9e94..f5836142d 100644
--- a/articles/reverse-nodes-in-k-group.md
+++ b/articles/reverse-nodes-in-k-group.md
@@ -179,6 +179,119 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func reverseKGroup(head *ListNode, k int) *ListNode {
+    cur := head
+    group := 0
+
+    for cur != nil && group < k {
+        cur = cur.Next
+        group++
+    }
+
+    if group == k {
+        cur = reverseKGroup(cur, k)
+        for group > 0 {
+            tmp := head.Next
+            head.Next = cur
+            cur = head
+            head = tmp
+            group--
+        }
+        head = cur
+    }
+    return head
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var li = ListNode(5)
+ * var v = li.`val`
+ * Definition for singly-linked list.
+ * class ListNode(var `val`: Int) {
+ *     var next: ListNode? = null
+ * }
+ */
+class Solution {
+    fun reverseKGroup(head: ListNode?, k: Int): ListNode? {
+        var cur = head
+        var group = 0
+
+        while (cur != null && group < k) {
+            cur = cur.next
+            group++
+        }
+
+        return if (group == k) {
+            cur = reverseKGroup(cur, k)
+            var newHead: ListNode? = null
+            var tempHead = head
+
+            while (group > 0) {
+                val tmp = tempHead!!.next
+                tempHead.next = cur
+                cur = tempHead
+                tempHead = tmp
+                group--
+            }
+            cur 
+        } else {
+            head 
+        }
+    }
+}
+```
+
+```swift
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public var val: Int
+ *     public var next: ListNode?
+ *     public init() { self.val = 0; self.next = nil; }
+ *     public init(_ val: Int) { self.val = val; self.next = nil; }
+ *     public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
+ * }
+ */
+class Solution {
+    func reverseKGroup(_ head: ListNode?, _ k: Int) -> ListNode? {
+        var cur = head
+        var group = 0
+
+        while cur != nil && group < k {
+            cur = cur!.next
+            group += 1
+        }
+
+        if group == k {
+            cur = reverseKGroup(cur, k)
+
+            var tempHead = head
+            while group > 0 {
+                let tmp = tempHead!.next
+                tempHead!.next = cur
+                cur = tempHead
+                tempHead = tmp
+                group -= 1
+            }
+
+            return cur
+        }
+
+        return head
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -437,6 +550,151 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for singly-linked list.
+ * type ListNode struct {
+ *     Val int
+ *     Next *ListNode
+ * }
+ */
+func reverseKGroup(head *ListNode, k int) *ListNode {
+    dummy := &ListNode{Next: head}
+    groupPrev := dummy
+
+    for {
+        kth := getKth(groupPrev, k)
+        if kth == nil {
+            break
+        }
+        groupNext := kth.Next
+
+        prev, curr := groupNext, groupPrev.Next
+        for curr != groupNext {
+            tmp := curr.Next
+            curr.Next = prev
+            prev = curr
+            curr = tmp
+        }
+
+        tmp := groupPrev.Next
+        groupPrev.Next = kth
+        groupPrev = tmp
+    }
+    return dummy.Next
+}
+
+func getKth(curr *ListNode, k int) *ListNode {
+    for curr != nil && k > 0 {
+        curr = curr.Next
+        k--
+    }
+    return curr
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var li = ListNode(5)
+ * var v = li.`val`
+ * Definition for singly-linked list.
+ * class ListNode(var `val`: Int) {
+ *     var next: ListNode? = null
+ * }
+ */
+class Solution {
+    fun reverseKGroup(head: ListNode?, k: Int): ListNode? {
+        val dummy = ListNode(0)
+        dummy.next = head
+        var groupPrev: ListNode? = dummy
+
+        while (true) {
+            val kth = getKth(groupPrev, k)
+            if (kth == null) {
+                break
+            }
+            val groupNext = kth.next
+
+            var prev: ListNode? = groupNext
+            var curr = groupPrev!!.next
+            while (curr != groupNext) {
+                val tmp = curr!!.next
+                curr.next = prev
+                prev = curr
+                curr = tmp
+            }
+
+            val tmp = groupPrev.next
+            groupPrev.next = kth
+            groupPrev = tmp
+        }
+        return dummy.next
+    }
+
+    private fun getKth(curr: ListNode?, k: Int): ListNode? {
+        var curr = curr
+        var k = k
+        while (curr != null && k > 0) {
+            curr = curr.next
+            k--
+        }
+        return curr
+    }
+}
+```
+
+```swift
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public var val: Int
+ *     public var next: ListNode?
+ *     public init() { self.val = 0; self.next = nil; }
+ *     public init(_ val: Int) { self.val = val; self.next = nil; }
+ *     public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
+ * }
+ */
+class Solution {
+    func reverseKGroup(_ head: ListNode?, _ k: Int) -> ListNode? {
+        let dummy = ListNode(0, head)
+        var groupPrev: ListNode? = dummy
+
+        while true {
+            guard let kth = getKth(groupPrev, k) else {
+                break
+            }
+            let groupNext = kth.next
+
+            var prev: ListNode? = kth.next
+            var curr = groupPrev?.next
+
+            while curr !== groupNext {
+                let tmp = curr?.next
+                curr?.next = prev
+                prev = curr
+                curr = tmp
+            }
+
+            let tmp = groupPrev?.next
+            groupPrev?.next = kth
+            groupPrev = tmp
+        }
+        return dummy.next
+    }
+
+    private func getKth(_ curr: ListNode?, _ k: Int) -> ListNode? {
+        var curr = curr
+        var k = k
+        while curr != nil && k > 0 {
+            curr = curr?.next
+            k -= 1
+        }
+        return curr
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/reverse-string.md b/articles/reverse-string.md
new file mode 100644
index 000000000..6c671dd5f
--- /dev/null
+++ b/articles/reverse-string.md
@@ -0,0 +1,430 @@
+## 1. Array
+
+::tabs-start
+
+```python
+class Solution:
+    def reverseString(self, s: List[str]) -> None:
+        """
+        Do not return anything, modify s in-place instead.
+        """
+        tmp = []
+        for i in range(len(s) - 1, -1, -1):
+            tmp.append(s[i])
+        for i in range(len(s)):
+            s[i] = tmp[i]
+```
+
+```java
+public class Solution {
+    public void reverseString(char[] s) {
+        char[] tmp = new char[s.length];
+        for (int i = s.length - 1, j = 0; i >= 0; i--, j++) {
+            tmp[j] = s[i];
+        }
+        for (int i = 0; i < s.length; i++) {
+            s[i] = tmp[i];
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void reverseString(vector<char>& s) {
+        vector<char> tmp;
+        for (int i = s.size() - 1; i >= 0; i--) {
+            tmp.push_back(s[i]);
+        }
+        for (int i = 0; i < s.size(); i++) {
+            s[i] = tmp[i];
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {character[]} s
+     * @return {void} Do not return anything, modify s in-place instead.
+     */
+    reverseString(s) {
+        const tmp = [];
+        for (let i = s.length - 1; i >= 0; i--) {
+            tmp.push(s[i]);
+        }
+        for (let i = 0; i < s.length; i++) {
+            s[i] = tmp[i];
+        }
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public void ReverseString(char[] s) {
+        char[] tmp = new char[s.Length];
+        int n = s.Length;
+
+        for (int i = 0; i < n; i++) {
+            tmp[i] = s[n - 1 - i];
+        }
+
+        for (int i = 0; i < n; i++) {
+            s[i] = tmp[i];
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def reverseString(self, s: List[str]) -> None:
+        """
+        Do not return anything, modify s in-place instead.
+        """
+        def reverse(l, r):
+            if l < r:
+                reverse(l + 1, r - 1)
+                s[l], s[r] = s[r], s[l]
+        
+        reverse(0, len(s) - 1)
+```
+
+```java
+public class Solution {
+    public void reverseString(char[] s) {
+        reverse(s, 0, s.length - 1);
+    }
+    
+    private void reverse(char[] s, int l, int r) {
+        if (l < r) {
+            reverse(s, l + 1, r - 1);
+            char temp = s[l];
+            s[l] = s[r];
+            s[r] = temp;
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void reverseString(vector<char>& s) {
+        reverse(s, 0, s.size() - 1);
+    }
+    
+private:
+    void reverse(vector<char>& s, int l, int r) {
+        if (l < r) {
+            reverse(s, l + 1, r - 1);
+            swap(s[l], s[r]);
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {character[]} s
+     * @return {void} Do not return anything, modify s in-place instead.
+     */
+    reverseString(s) {
+        const reverse = (l, r) => {
+            if (l < r) {
+                reverse(l + 1, r - 1);
+                [s[l], s[r]] = [s[r], s[l]];
+            }
+        };
+        reverse(0, s.length - 1);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public void ReverseString(char[] s) {
+        Reverse(s, 0, s.Length - 1);
+    }
+
+    private void Reverse(char[] s, int left, int right) {
+        if (left < right) {
+            Reverse(s, left + 1, right - 1);
+            char temp = s[left];
+            s[left] = s[right];
+            s[right] = temp;
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 3. Stack
+
+::tabs-start
+
+```python
+class Solution:
+    def reverseString(self, s: List[str]) -> None:
+        """
+        Do not return anything, modify s in-place instead.
+        """
+        stack = []
+        for c in s:
+            stack.append(c)
+        i = 0
+        while stack:
+            s[i] = stack.pop()
+            i += 1
+```
+
+```java
+public class Solution {
+    public void reverseString(char[] s) {
+        Stack<Character> stack = new Stack<>();
+        for (char c : s) {
+            stack.push(c);
+        }
+        int i = 0;
+        while (!stack.isEmpty()) {
+            s[i++] = stack.pop();
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void reverseString(vector<char>& s) {
+        stack<char> stk;
+        for (char& c : s) {
+            stk.push(c);
+        }
+        int i = 0;
+        while (!stk.empty()) {
+            s[i++] = stk.top();
+            stk.pop();
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {character[]} s
+     * @return {void} Do not return anything, modify s in-place instead.
+     */
+    reverseString(s) {
+        const stack = [];
+        for (const c of s) {
+            stack.push(c);
+        }
+        let i = 0;
+        while (stack.length) {
+            s[i++] = stack.pop();
+        }
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public void ReverseString(char[] s) {
+        Stack<char> stack = new Stack<char>();
+
+        foreach (char c in s) {
+            stack.Push(c);
+        }
+
+        for (int i = 0; i < s.Length; i++) {
+            s[i] = stack.Pop();
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Built-In Function
+
+::tabs-start
+
+```python
+class Solution:
+    def reverseString(self, s: List[str]) -> None:
+        """
+        Do not return anything, modify s in-place instead.
+        """
+        s.reverse()
+```
+
+```java
+public class Solution {
+    public void reverseString(char[] s) {
+        List<Character> list = new ArrayList<>();
+        for (char c : s) {
+            list.add(c);
+        }
+        Collections.reverse(list);
+        
+        for (int i = 0; i < s.length; i++) {
+            s[i] = list.get(i);
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void reverseString(vector<char>& s) {
+        reverse(s.begin(), s.end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {character[]} s
+     * @return {void} Do not return anything, modify s in-place instead.
+     */
+    reverseString(s) {
+        s.reverse();
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public void ReverseString(char[] s) {
+        Array.Reverse(s);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 5. Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def reverseString(self, s: List[str]) -> None:
+        """
+        Do not return anything, modify s in-place instead.
+        """
+        l, r = 0, len(s) - 1
+        while l < r:
+            s[l], s[r] = s[r], s[l]
+            l += 1
+            r -= 1
+```
+
+```java
+public class Solution {
+    public void reverseString(char[] s) {
+        int l = 0, r = s.length - 1;
+        while (l < r) {
+            char temp = s[l];
+            s[l] = s[r];
+            s[r] = temp;
+            l++;
+            r--;
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void reverseString(vector<char>& s) {
+        int l = 0, r = s.size() - 1;
+        while (l < r) {
+            swap(s[l++], s[r--]);
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {character[]} s
+     * @return {void} Do not return anything, modify s in-place instead.
+     */
+    reverseString(s) {
+        let l = 0, r = s.length - 1;
+        while (l < r) {
+            [s[l], s[r]] = [s[r], s[l]];
+            l++;
+            r--;
+        }
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public void ReverseString(char[] s) {
+        int l = 0, r = s.Length - 1;
+        while (l < r) {
+            char temp = s[l];
+            s[l] = s[r];
+            s[r] = temp;
+            l++;
+            r--;
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/reverse-words-in-a-string-iii.md b/articles/reverse-words-in-a-string-iii.md
new file mode 100644
index 000000000..b9fb3b3cb
--- /dev/null
+++ b/articles/reverse-words-in-a-string-iii.md
@@ -0,0 +1,387 @@
+## 1. Convert To String Array
+
+::tabs-start
+
+```python
+class Solution:
+    def reverseWords(self, s: str) -> str:
+        return ' '.join([w[::-1] for w in s.split(' ')])
+```
+
+```java
+public class Solution {
+    public String reverseWords(String s) {
+        String[] words = s.split(" ");
+        for (int i = 0; i < words.length; i++) {
+            words[i] = new StringBuilder(words[i]).reverse().toString();
+        }
+        return String.join(" ", words);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string reverseWords(string s) {
+        stringstream ss(s);
+        string word, res;
+        bool first = true;
+        
+        while (ss >> word) {
+            reverse(word.begin(), word.end());
+            if (first) {
+                res += word;
+                first = false;
+            } else {
+                res += " " + word;
+            }
+        }
+        
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string}
+     */
+    reverseWords(s) {
+        return s.split(' ').map(w => w.split('').reverse().join('')).join(' ');
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. String Manipulation
+
+::tabs-start
+
+```python
+class Solution:
+    def reverseWords(self, s: str) -> str:
+        tmp_str = ""
+        res = ""
+
+        for r in range(len(s) + 1):
+            if r == len(s) or s[r] == ' ':
+                res += tmp_str
+                tmp_str = ""
+                if r != len(s):
+                    res += " "
+            else:
+                tmp_str = s[r] + tmp_str
+        return res
+```
+
+```java
+public class Solution {
+    public String reverseWords(String s) {
+        String tmpStr = "";
+        StringBuilder res = new StringBuilder();
+
+        for (int r = 0; r <= s.length(); r++) {
+            if (r == s.length() || s.charAt(r) == ' ') {
+                res.append(tmpStr);
+                tmpStr = "";
+                if (r != s.length()) {
+                    res.append(" ");
+                }
+            } else {
+                tmpStr = s.charAt(r) + tmpStr;
+            }
+        }
+        return res.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string reverseWords(string s) {
+        string tmpStr = "";
+        string res = "";
+
+        for (int r = 0; r <= s.size(); r++) {
+            if (r == s.size() || s[r] == ' ') {
+                res += tmpStr;
+                tmpStr = "";
+                if (r != s.size()) {
+                    res += " ";
+                }
+            } else {
+                tmpStr = s[r] + tmpStr;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string}
+     */
+    reverseWords(s) {
+        let tmpStr = "";
+        let res = "";
+
+        for (let r = 0; r <= s.length; r++) {
+            if (r === s.length || s[r] === ' ') {
+                res += tmpStr;
+                tmpStr = "";
+                if (r !== s.length) {
+                    res += " ";
+                }
+            } else {
+                tmpStr = s[r] + tmpStr;
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Two Pointers - I
+
+::tabs-start
+
+```python
+class Solution:
+    def reverseWords(self, s: str) -> str:
+        s = list(s)
+        l = 0
+        for r in range(len(s)):
+            if s[r] == " " or r == len(s) - 1:
+                temp_l, temp_r = l, r - 1 if s[r] == " " else r
+                while temp_l < temp_r:
+                    s[temp_l], s[temp_r] = s[temp_r], s[temp_l]
+                    temp_l += 1
+                    temp_r -= 1
+                l = r + 1
+        return "".join(s)
+```
+
+```java
+public class Solution {
+    public String reverseWords(String s) {
+        char[] chars = s.toCharArray();
+        int l = 0;
+        for (int r = 0; r < chars.length; r++) {
+            if (chars[r] == ' ' || r == chars.length - 1) {
+                int tempL = l, tempR = (chars[r] == ' ') ? r - 1 : r;
+                while (tempL < tempR) {
+                    char temp = chars[tempL];
+                    chars[tempL] = chars[tempR];
+                    chars[tempR] = temp;
+                    tempL++;
+                    tempR--;
+                }
+                l = r + 1;
+            }
+        }
+        return new String(chars);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string reverseWords(string s) {
+        int l = 0;
+        for (int r = 0; r < s.size(); r++) {
+            if (r == s.size() - 1 || s[r] == ' ') {
+                int tempL = l, tempR = s[r] == ' ' ? r - 1 : r;
+                while (tempL < tempR) {
+                    swap(s[tempL], s[tempR]);
+                    tempL++;
+                    tempR--;
+                }
+                l = r + 1;
+            }
+        }
+        return s;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string}
+     */
+    reverseWords(s) {
+        let chars = s.split('');
+        let l = 0;
+        for (let r = 0; r <= chars.length; r++) {
+            if (r === chars.length || chars[r] === ' ') {
+                let tempL = l, tempR = r - 1;
+                while (tempL < tempR) {
+                    [chars[tempL], chars[tempR]] = [chars[tempR], chars[tempL]];
+                    tempL++;
+                    tempR--;
+                }
+                l = r + 1;
+            }
+        }
+        return chars.join('');
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Two Pointers - II
+
+::tabs-start
+
+```python
+class Solution:
+    def reverseWords(self, s: str) -> str:
+        def reverse(i, j):
+            while i < j:
+                s[i], s[j] = s[j], s[i]
+                i += 1
+                j -= 1
+
+        s = list(s)
+        i = 0
+        while i < len(s):
+            if s[i] != ' ':
+                j = i
+                while j < len(s) and s[j] != ' ':
+                    j += 1
+                reverse(i, j - 1)
+                i = j + 1
+        return ''.join(s) 
+```
+
+```java
+public class Solution {
+    public String reverseWords(String s) {
+        char[] arr = s.toCharArray();
+        int n = arr.length;
+
+        for (int i = 0; i < n; i++) {
+            if (arr[i] != ' ') {
+                int j = i;
+                while (j < n && arr[j] != ' ') {
+                    j++;
+                }
+                reverse(arr, i, j - 1);
+                i = j;
+            }
+        }
+        return new String(arr);
+    }
+
+    private void reverse(char[] arr, int i, int j) {
+        while (i < j) {
+            char temp = arr[i];
+            arr[i] = arr[j];
+            arr[j] = temp;
+            i++;
+            j--;
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string reverseWords(string s) {
+        int n = s.size();
+        for (int i = 0; i < n; i++) {
+            if (s[i] != ' ') {
+                int j = i;
+                while (j < n && s[j] != ' ') {
+                    j++;
+                }
+                reverse(s, i, j - 1);
+                i = j;
+            }
+        }
+        return s;
+    }
+
+private:
+    void reverse(string& s, int i, int j) {
+        while (i < j) {
+            swap(s[i], s[j]);
+            i++;
+            j--;
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string}
+     */
+    reverseWords(s) {
+        const arr = s.split('');
+        const reverse = (i, j) => {
+            while (i < j) {
+                [arr[i], arr[j]] = [arr[j], arr[i]];
+                i++;
+                j--;
+            }
+        };
+
+        for (let i = 0; i < arr.length; i++) {
+            if (arr[i] !== ' ') {
+                let j = i;
+                while (j < arr.length && arr[j] !== ' ') {
+                    j++;
+                }
+                reverse(i, j - 1);
+                i = j;
+            }
+        }
+        return arr.join('');
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/robot-bounded-in-circle.md b/articles/robot-bounded-in-circle.md
new file mode 100644
index 000000000..76ec62fc9
--- /dev/null
+++ b/articles/robot-bounded-in-circle.md
@@ -0,0 +1,107 @@
+## 1. Simulation
+
+::tabs-start
+
+```python
+class Solution:
+    def isRobotBounded(self, instructions: str) -> bool:
+        dirX, dirY = 0, 1
+        x, y = 0, 0
+
+        for d in instructions:
+            if d == "G":
+                x, y = x + dirX, y + dirY
+            elif d == "L":
+                dirX, dirY = -dirY, dirX
+            else:
+                dirX, dirY = dirY, -dirX
+
+        return (x, y) == (0, 0) or (dirX, dirY) != (0, 1)
+```
+
+```java
+public class Solution {
+    public boolean isRobotBounded(String instructions) {
+        int dirX = 0, dirY = 1;
+        int x = 0, y = 0;
+
+        for (int i = 0; i < instructions.length(); i++) {
+            char d = instructions.charAt(i);
+            if (d == 'G') {
+                x += dirX;
+                y += dirY;
+            } else if (d == 'L') {
+                int temp = dirX;
+                dirX = -dirY;
+                dirY = temp;
+            } else {
+                int temp = dirX;
+                dirX = dirY;
+                dirY = -temp;
+            }
+        }
+
+        return (x == 0 && y == 0) || (dirX != 0 || dirY != 1);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isRobotBounded(string instructions) {
+        int dirX = 0, dirY = 1;
+        int x = 0, y = 0;
+
+        for (char d : instructions) {
+            if (d == 'G') {
+                x += dirX;
+                y += dirY;
+            } else if (d == 'L') {
+                int temp = dirX;
+                dirX = -dirY;
+                dirY = temp;
+            } else {
+                int temp = dirX;
+                dirX = dirY;
+                dirY = -temp;
+            }
+        }
+
+        return (x == 0 && y == 0) || (dirX != 0 || dirY != 1);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} instructions
+     * @return {boolean}
+     */
+    isRobotBounded(instructions) {
+        let dirX = 0, dirY = 1;
+        let x = 0, y = 0;
+
+        for (const d of instructions) {
+            if (d === 'G') {
+                x += dirX;
+                y += dirY;
+            } else if (d === 'L') {
+                [dirX, dirY] = [-dirY, dirX];
+            } else {
+                [dirX, dirY] = [dirY, -dirX];
+            }
+        }
+
+        return (x === 0 && y === 0) || (dirX !== 0 || dirY !== 1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/roman-to-integer.md b/articles/roman-to-integer.md
new file mode 100644
index 000000000..b21b20e18
--- /dev/null
+++ b/articles/roman-to-integer.md
@@ -0,0 +1,95 @@
+## 1. Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def romanToInt(self, s: str) -> int:
+        roman = {
+            "I": 1, "V": 5, "X": 10,
+            "L": 50, "C": 100, "D": 500, "M": 1000
+        }
+        res = 0
+        for i in range(len(s)):
+            if i + 1 < len(s) and roman[s[i]] < roman[s[i + 1]]:
+                res -= roman[s[i]]
+            else:
+                res += roman[s[i]]
+        return res
+```
+
+```java
+public class Solution {
+    public int romanToInt(String s) {
+        Map<Character, Integer> roman = new HashMap<>();
+        roman.put('I', 1); roman.put('V', 5);
+        roman.put('X', 10); roman.put('L', 50);
+        roman.put('C', 100); roman.put('D', 500);
+        roman.put('M', 1000);
+
+        int res = 0;
+        for (int i = 0; i < s.length(); i++) {
+            if (i + 1 < s.length() && roman.get(s.charAt(i)) < roman.get(s.charAt(i + 1))) {
+                res -= roman.get(s.charAt(i));
+            } else {
+                res += roman.get(s.charAt(i));
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int romanToInt(string s) {
+        unordered_map<char, int> roman = {
+            {'I', 1}, {'V', 5}, {'X', 10},
+            {'L', 50}, {'C', 100}, {'D', 500}, {'M', 1000}
+        };
+
+        int res = 0;
+        for (int i = 0; i < s.size(); i++) {
+            if (i + 1 < s.size() && roman[s[i]] < roman[s[i + 1]]) {
+                res -= roman[s[i]];
+            } else {
+                res += roman[s[i]];
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    romanToInt(s) {
+        const roman = {
+            "I": 1, "V": 5, "X": 10,
+            "L": 50, "C": 100, "D": 500, "M": 1000
+        };
+
+        let res = 0;
+        for (let i = 0; i < s.length; i++) {
+            if (i + 1 < s.length && roman[s[i]] < roman[s[i + 1]]) {
+                res -= roman[s[i]];
+            } else {
+                res += roman[s[i]];
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ since we have $7$ characters in the hash map.
\ No newline at end of file
diff --git a/articles/rotate-array.md b/articles/rotate-array.md
new file mode 100644
index 000000000..790679e20
--- /dev/null
+++ b/articles/rotate-array.md
@@ -0,0 +1,529 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def rotate(self, nums: List[int], k: int) -> None:
+        """
+        Do not return anything, modify nums in-place instead.
+        """
+        n = len(nums)
+        k %= n
+        while k:
+            tmp = nums[n - 1]
+            for i in range(n - 1, 0, -1):
+                nums[i] = nums[i - 1]
+            nums[0] = tmp
+            k -= 1
+```
+
+```java
+public class Solution {
+    public void rotate(int[] nums, int k) {
+        int n = nums.length;
+        k %= n;
+        while (k > 0) {
+            int tmp = nums[n - 1];
+            for (int i = n - 1; i > 0; i--) {
+                nums[i] = nums[i - 1];
+            }
+            nums[0] = tmp;
+            k--;
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void rotate(vector<int>& nums, int k) {
+        int n = nums.size();
+        k %= n;
+        while (k > 0) {
+            int tmp = nums[n - 1];
+            for (int i = n - 1; i > 0; i--) {
+                nums[i] = nums[i - 1];
+            }
+            nums[0] = tmp;
+            k--;
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {void} Do not return anything, modify nums in-place instead.
+     */
+    rotate(nums, k) {
+        const n = nums.length;
+        k %= n;
+        while (k > 0) {
+            const tmp = nums[n - 1];
+            for (let i = n - 1; i > 0; i--) {
+                nums[i] = nums[i - 1];
+            }
+            nums[0] = tmp;
+            k--;
+        }
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public void Rotate(int[] nums, int k) {
+        int n = nums.Length;
+        k %= n;
+
+        while (k > 0) {
+            int tmp = nums[n - 1];
+            for (int i = n - 1; i > 0; i--) {
+                nums[i] = nums[i - 1];
+            }
+            nums[0] = tmp;
+            k--;
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * k)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 2. Extra Space
+
+::tabs-start
+
+```python
+class Solution:
+    def rotate(self, nums: List[int], k: int) -> None:
+        """
+        Do not return anything, modify nums in-place instead.
+        """
+        n = len(nums)
+        tmp = [0] * n
+        for i in range(n):
+            tmp[(i + k) % n] = nums[i]
+        
+        nums[:] = tmp
+```
+
+```java
+public class Solution {
+    public void rotate(int[] nums, int k) {
+        int n = nums.length;
+        int[] tmp = new int[n];
+        for (int i = 0; i < n; i++) {
+            tmp[(i + k) % n] = nums[i];
+        }
+        for (int i = 0; i < n; i++) {
+            nums[i] = tmp[i];
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void rotate(vector<int>& nums, int k) {
+        int n = nums.size();
+        vector<int> tmp(n);
+        for (int i = 0; i < n; i++) {
+            tmp[(i + k) % n] = nums[i];
+        }
+        for (int i = 0; i < n; i++) {
+            nums[i] = tmp[i];
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {void} Do not return anything, modify nums in-place instead.
+     */
+    rotate(nums, k) {
+        const n = nums.length;
+        const tmp = new Array(n);
+        for (let i = 0; i < n; i++) {
+            tmp[(i + k) % n] = nums[i];
+        }
+        for (let i = 0; i < n; i++) {
+            nums[i] = tmp[i];
+        }
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public void Rotate(int[] nums, int k) {
+        int n = nums.Length;
+        int[] tmp = new int[n];
+        
+        for (int i = 0; i < n; i++) {
+            tmp[(i + k) % n] = nums[i];
+        }
+
+        for (int i = 0; i < n; i++) {
+            nums[i] = tmp[i];
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ extra space.
+
+---
+
+## 3. Cyclic Traversal
+
+::tabs-start
+
+```python
+class Solution:
+    def rotate(self, nums: List[int], k: int) -> None:
+        """
+        Do not return anything, modify nums in-place instead.
+        """
+        n = len(nums)
+        k %= n
+        count = start = 0        
+
+        while count < n:
+            current = start
+            prev = nums[start]
+            while True:
+                next_idx = (current + k) % n
+                nums[next_idx], prev = prev, nums[next_idx]
+                current = next_idx
+                count += 1
+
+                if start == current:
+                    break
+            start += 1
+```
+
+```java
+public class Solution {
+    public void rotate(int[] nums, int k) {
+        int n = nums.length;
+        k %= n;
+        int count = 0;
+        
+        for (int start = 0; count < n; start++) {
+            int current = start;
+            int prev = nums[start];
+            do {
+                int nextIdx = (current + k) % n;
+                int temp = nums[nextIdx];
+                nums[nextIdx] = prev;
+                prev = temp;
+                current = nextIdx;
+                count++;
+            } while (start != current);
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void rotate(vector<int>& nums, int k) {
+        int n = nums.size();
+        k %= n;
+        int count = 0;
+        
+        for (int start = 0; count < n; start++) {
+            int current = start;
+            int prev = nums[start];
+            do {
+                int nextIdx = (current + k) % n;
+                int temp = nums[nextIdx];
+                nums[nextIdx] = prev;
+                prev = temp;
+                current = nextIdx;
+                count++;
+            } while (start != current);
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {void} Do not return anything, modify nums in-place instead.
+     */
+    rotate(nums, k) {
+        const n = nums.length;
+        k %= n;
+        let count = 0;
+        
+        for (let start = 0; count < n; start++) {
+            let current = start;
+            let prev = nums[start];
+            do {
+                const nextIdx = (current + k) % n;
+                const temp = nums[nextIdx];
+                nums[nextIdx] = prev;
+                prev = temp;
+                current = nextIdx;
+                count++;
+            } while (start !== current);
+        }
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public void Rotate(int[] nums, int k) {
+        int n = nums.Length;
+        k %= n;
+        int count = 0;
+
+        for (int start = 0; count < n; start++) {
+            int current = start;
+            int prev = nums[start];
+
+            do {
+                int nextIdx = (current + k) % n;
+                int temp = nums[nextIdx];
+                nums[nextIdx] = prev;
+                prev = temp;
+                current = nextIdx;
+                count++;
+            } while (start != current);
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 4. Using Reverse
+
+::tabs-start
+
+```python
+class Solution:
+    def rotate(self, nums: List[int], k: int) -> None:
+        """
+        Do not return anything, modify nums in-place instead.
+        """
+        n = len(nums)
+        k %= n
+
+        def reverse(l: int, r: int) -> None:
+            while l < r:
+                nums[l], nums[r] = nums[r], nums[l]
+                l, r = l + 1, r - 1
+
+        reverse(0, n - 1)
+        reverse(0, k - 1)
+        reverse(k, n - 1)
+```
+
+```java
+public class Solution {
+    public void rotate(int[] nums, int k) {
+        int n = nums.length;
+        k %= n;
+
+        reverse(nums, 0, n - 1);
+        reverse(nums, 0, k - 1);
+        reverse(nums, k, n - 1);
+    }
+
+    private void reverse(int[] nums, int l, int r) {
+        while (l < r) {
+            int temp = nums[l];
+            nums[l] = nums[r];
+            nums[r] = temp;
+            l++;
+            r--;
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void rotate(vector<int>& nums, int k) {
+        int n = nums.size();
+        k %= n;
+
+        reverse(nums, 0, n - 1);
+        reverse(nums, 0, k - 1);
+        reverse(nums, k, n - 1);
+    }
+
+private:
+    void reverse(vector<int>& nums, int l, int r) {
+        while (l < r) {
+            swap(nums[l], nums[r]);
+            l++;
+            r--;
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {void} Do not return anything, modify nums in-place instead.
+     */
+    rotate(nums, k) {
+        const n = nums.length;
+        k %= n;
+
+        const reverse = (l, r) => {
+            while (l < r) {
+                [nums[l], nums[r]] = [nums[r], nums[l]];
+                l++;
+                r--;
+            }
+        };
+
+        reverse(0, n - 1);
+        reverse(0, k - 1);
+        reverse(k, n - 1);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public void Rotate(int[] nums, int k) {
+        int n = nums.Length;
+        k %= n;
+
+        Reverse(nums, 0, n - 1);
+        Reverse(nums, 0, k - 1);
+        Reverse(nums, k, n - 1);
+    }
+
+    private void Reverse(int[] nums, int left, int right) {
+        while (left < right) {
+            int temp = nums[left];
+            nums[left] = nums[right];
+            nums[right] = temp;
+            left++;
+            right--;
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 5. One Liner
+
+::tabs-start
+
+```python
+class Solution:
+    def rotate(self, nums: List[int], k: int) -> None:
+        """
+        Do not return anything, modify nums in-place instead.
+        """
+        nums[:] = nums[-k % len(nums):] + nums[:-k % len(nums)]
+```
+
+```java
+public class Solution {
+    public void rotate(int[] nums, int k) {
+        int n = nums.length;
+        int[] rotated = Arrays.copyOfRange(nums, n - k % n, n);
+        System.arraycopy(nums, 0, nums, k % n, n - k % n);
+        System.arraycopy(rotated, 0, nums, 0, rotated.length);
+    }
+}
+```
+
+```cpp
+
+class Solution {
+public:
+    void rotate(vector<int>& nums, int k) {
+        std::rotate(nums.begin(), nums.end() - (k % nums.size()), nums.end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {void} Do not return anything, modify nums in-place instead.
+     */
+    rotate(nums, k) {
+        nums.splice(0, 0, ...nums.splice(nums.length - (k % nums.length)));
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public void Rotate(int[] nums, int k) {
+        int n = nums.Length;
+        k %= n;
+
+        int[] rotated = new int[n];
+        Array.Copy(nums, n - k, rotated, 0, k);
+        Array.Copy(nums, 0, rotated, k, n - k);
+        Array.Copy(rotated, nums, n);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the language.
\ No newline at end of file
diff --git a/articles/rotate-list.md b/articles/rotate-list.md
new file mode 100644
index 000000000..675821f82
--- /dev/null
+++ b/articles/rotate-list.md
@@ -0,0 +1,486 @@
+## 1. Convert To Array
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def rotateRight(self, head: Optional[ListNode], k: int) -> Optional[ListNode]:
+        if not head:
+            return None
+
+        arr, cur = [], head
+        while cur:
+            arr.append(cur.val)
+            cur = cur.next
+
+        n = len(arr)
+        k %= n
+        cur = head
+        for i in range(n - k, n):
+            cur.val = arr[i]
+            cur = cur.next
+
+        for i in range(n - k):
+            cur.val = arr[i]
+            cur = cur.next
+
+        return head
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode rotateRight(ListNode head, int k) {
+        if (head == null) return null;
+
+        ArrayList<Integer> arr = new ArrayList<>();
+        ListNode cur = head;
+        while (cur != null) {
+            arr.add(cur.val);
+            cur = cur.next;
+        }
+
+        int n = arr.size();
+        k %= n;
+        cur = head;
+        for (int i = n - k; i < n; i++) {
+            cur.val = arr.get(i);
+            cur = cur.next;
+        }
+        for (int i = 0; i < n - k; i++) {
+            cur.val = arr.get(i);
+            cur = cur.next;
+        }
+        return head;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* rotateRight(ListNode* head, int k) {
+        if (!head) return nullptr;
+
+        vector<int> arr;
+        ListNode* cur = head;
+        while (cur) {
+            arr.push_back(cur->val);
+            cur = cur->next;
+        }
+
+        int n = arr.size();
+        k %= n;
+        cur = head;
+        for (int i = n - k; i < n; i++) {
+            cur->val = arr[i];
+            cur = cur->next;
+        }
+        for (int i = 0; i < n - k; i++) {
+            cur->val = arr[i];
+            cur = cur->next;
+        }
+        return head;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @param {number} k
+     * @return {ListNode}
+     */
+    rotateRight(head, k) {
+        if (!head) return null;
+
+        let arr = [];
+        let cur = head;
+        while (cur) {
+            arr.push(cur.val);
+            cur = cur.next;
+        }
+
+        let n = arr.length;
+        k %= n;
+        cur = head;
+        for (let i = n - k; i < n; i++) {
+            cur.val = arr[i];
+            cur = cur.next;
+        }
+        for (let i = 0; i < n - k; i++) {
+            cur.val = arr[i];
+            cur = cur.next;
+        }
+        return head;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Iteration
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def rotateRight(self, head: ListNode, k: int) -> ListNode:
+        if not head:
+            return head
+
+        length, tail = 1, head
+        while tail.next:
+            tail = tail.next
+            length += 1
+
+        k = k % length
+        if k == 0:
+            return head
+
+        cur = head
+        for i in range(length - k - 1):
+            cur = cur.next
+        newHead = cur.next
+        cur.next = None
+        tail.next = head
+
+        return newHead
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode rotateRight(ListNode head, int k) {
+        if (head == null) {
+            return head;
+        }
+
+        int length = 1;
+        ListNode tail = head;
+        while (tail.next != null) {
+            tail = tail.next;
+            length++;
+        }
+
+        k = k % length;
+        if (k == 0) {
+            return head;
+        }
+
+        ListNode cur = head;
+        for (int i = 0; i < length - k - 1; i++) {
+            cur = cur.next;
+        }
+        ListNode newHead = cur.next;
+        cur.next = null;
+        tail.next = head;
+
+        return newHead;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* rotateRight(ListNode* head, int k) {
+        if (!head) {
+            return head;
+        }
+
+        int length = 1;
+        ListNode* tail = head;
+        while (tail->next) {
+            tail = tail->next;
+            length++;
+        }
+
+        k = k % length;
+        if (k == 0) {
+            return head;
+        }
+
+        ListNode* cur = head;
+        for (int i = 0; i < length - k - 1; i++) {
+            cur = cur->next;
+        }
+        ListNode* newHead = cur->next;
+        cur->next = nullptr;
+        tail->next = head;
+
+        return newHead;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @param {number} k
+     * @return {ListNode}
+     */
+    rotateRight(head, k) {
+        if (!head) {
+            return head;
+        }
+
+        let length = 1, tail = head;
+        while (tail.next) {
+            tail = tail.next;
+            length++;
+        }
+
+        k = k % length;
+        if (k === 0) {
+            return head;
+        }
+
+        let cur = head;
+        for (let i = 0; i < length - k - 1; i++) {
+            cur = cur.next;
+        }
+        let newHead = cur.next;
+        cur.next = null;
+        tail.next = head;
+
+        return newHead;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 3. Iteration (Using One Pointer)
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def rotateRight(self, head: ListNode, k: int) -> ListNode:
+        if not head:
+            return head
+
+        cur, n = head, 1
+        while cur.next:
+            n += 1
+            cur = cur.next
+
+        cur.next = head
+        k %= n
+        for i in range(n - k):
+            cur = cur.next
+
+        head = cur.next
+        cur.next = None
+        return head
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode rotateRight(ListNode head, int k) {
+        if (head == null) {
+            return head;
+        }
+
+        ListNode cur = head;
+        int n = 1;
+        while (cur.next != null) {
+            n++;
+            cur = cur.next;
+        }
+
+        cur.next = head;
+        k %= n;
+        for (int i = 0; i < n - k; i++) {
+            cur = cur.next;
+        }
+
+        head = cur.next;
+        cur.next = null;
+        return head;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* rotateRight(ListNode* head, int k) {
+        if (!head) {
+            return head;
+        }
+
+        ListNode* cur = head;
+        int n = 1;
+        while (cur->next) {
+            n++;
+            cur = cur->next;
+        }
+
+        cur->next = head;
+        k %= n;
+        for (int i = 0; i < n - k; i++) {
+            cur = cur->next;
+        }
+
+        head = cur->next;
+        cur->next = nullptr;
+        return head;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @param {number} k
+     * @return {ListNode}
+     */
+    rotateRight(head, k) {
+        if (!head) {
+            return head;
+        }
+
+        let cur = head, n = 1;
+        while (cur.next) {
+            n++;
+            cur = cur.next;
+        }
+
+        cur.next = head;
+        k %= n;
+        for (let i = 0; i < n - k; i++) {
+            cur = cur.next;
+        }
+
+        head = cur.next;
+        cur.next = null;
+        return head;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/rotate-matrix.md b/articles/rotate-matrix.md
new file mode 100644
index 000000000..c7ea787f1
--- /dev/null
+++ b/articles/rotate-matrix.md
@@ -0,0 +1,599 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def rotate(self, matrix: List[List[int]]) -> None:
+        n = len(matrix)
+        rotated = [[0] * n for _ in range(n)]
+        
+        for i in range(n):
+            for j in range(n):
+                rotated[j][n - 1 - i] = matrix[i][j]
+        
+        for i in range(n):
+            for j in range(n):
+                matrix[i][j] = rotated[i][j]
+```
+
+```java
+public class Solution {
+    public void rotate(int[][] matrix) {
+        int n = matrix.length;
+        int[][] rotated = new int[n][n];
+
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < n; j++) {
+                rotated[j][n - 1 - i] = matrix[i][j];
+            }
+        }
+
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < n; j++) {
+                matrix[i][j] = rotated[i][j];
+            }
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void rotate(vector<vector<int>>& matrix) {
+        int n = matrix.size();
+        vector<vector<int>> rotated(n, vector<int>(n));
+
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < n; j++) {
+                rotated[j][n - 1 - i] = matrix[i][j];
+            }
+        }
+
+        matrix = rotated;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} matrix
+     * @return {void}
+     */
+    rotate(matrix) {
+        const n = matrix.length;
+        const rotated = Array.from({ length: n }, () => 
+                        Array(n).fill(0));
+
+        for (let i = 0; i < n; i++) {
+            for (let j = 0; j < n; j++) {
+                rotated[j][n - 1 - i] = matrix[i][j];
+            }
+        }
+
+        for (let i = 0; i < n; i++) {
+            for (let j = 0; j < n; j++) {
+                matrix[i][j] = rotated[i][j];
+            }
+        }
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public void Rotate(int[][] matrix) {
+        int n = matrix.Length;
+        int[][] rotated = new int[n][]; 
+        for (int i = 0; i < n; i++) {
+            rotated[i] = new int[n]; 
+            for (int j = 0; j < n; j++) {
+                rotated[i][j] = matrix[n - 1 - j][i]; 
+            }
+        }
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < n; j++) {
+                matrix[i][j] = rotated[i][j]; 
+            }
+        }
+    }
+}
+```
+
+```go
+func rotate(matrix [][]int) {
+	n := len(matrix)
+	rotated := make([][]int, n)
+	for i := range rotated {
+		rotated[i] = make([]int, n)
+	}
+
+	for i := 0; i < n; i++ {
+		for j := 0; j < n; j++ {
+			rotated[j][n-1-i] = matrix[i][j]
+		}
+	}
+
+	for i := 0; i < n; i++ {
+		for j := 0; j < n; j++ {
+			matrix[i][j] = rotated[i][j]
+		}
+	}
+}
+```
+
+```kotlin
+class Solution {
+    fun rotate(matrix: Array<IntArray>) {
+        val n = matrix.size
+        val rotated = Array(n) { IntArray(n) }
+
+        for (i in 0 until n) {
+            for (j in 0 until n) {
+                rotated[j][n - 1 - i] = matrix[i][j]
+            }
+        }
+
+        for (i in 0 until n) {
+            for (j in 0 until n) {
+                matrix[i][j] = rotated[i][j]
+            }
+        }
+    }
+}
+```
+
+```swift
+class Solution {
+    func rotate(_ matrix: inout [[Int]]) {
+        let n = matrix.count
+        var rotated = Array(repeating: Array(repeating: 0, count: n), count: n)
+
+        for i in 0..<n {
+            for j in 0..<n {
+                rotated[j][n - 1 - i] = matrix[i][j]
+            }
+        }
+
+        for i in 0..<n {
+            for j in 0..<n {
+                matrix[i][j] = rotated[i][j]
+            }
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 2. Rotate By Four Cells
+
+::tabs-start
+
+```python
+class Solution:
+    def rotate(self, matrix: List[List[int]]) -> None:
+        l, r = 0, len(matrix) - 1
+        while l < r:
+            for i in range(r - l):
+                top, bottom = l, r
+
+                # save the topleft
+                topLeft = matrix[top][l + i]
+
+                # move bottom left into top left
+                matrix[top][l + i] = matrix[bottom - i][l]
+
+                # move bottom right into bottom left
+                matrix[bottom - i][l] = matrix[bottom][r - i]
+
+                # move top right into bottom right
+                matrix[bottom][r - i] = matrix[top + i][r]
+
+                # move top left into top right
+                matrix[top + i][r] = topLeft
+            r -= 1
+            l += 1
+```
+
+```java
+public class Solution {
+    public void rotate(int[][] matrix) {
+        int l = 0;
+        int r = matrix.length - 1;
+        
+        while ( l < r ) {
+            for(int i = 0; i < r - l; i++) {
+                int top = l;
+                int bottom = r;
+                 //save the topleft
+                int topLeft = matrix[top][l + i];
+
+                //move bottom left into top left
+                matrix[top][l + i] = matrix[bottom - i][l];
+
+                // move bottom right into bottom left
+                matrix[bottom - i][l] = matrix[bottom][r - i];
+
+                // move top right into bottom right
+                matrix[bottom][r - i] = matrix[top + i][r];
+
+                // move top left into top right
+                matrix[top + i][r] = topLeft;
+                
+            }
+            r--;
+            l++;
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void rotate(vector<vector<int>>& matrix) {
+        int l = 0;
+        int r = matrix.size() - 1;
+        
+        while ( l < r ) {
+            for(int i = 0; i < r - l; i++) {
+                int top = l;
+                int bottom = r;
+
+                //save the topleft
+                int topLeft = matrix[top][l + i];
+
+                //move bottom left into top left
+                matrix[top][l + i] = matrix[bottom - i][l];
+
+                // move bottom right into bottom left
+                matrix[bottom - i][l] = matrix[bottom][r - i];
+
+                // move top right into bottom right
+                matrix[bottom][r - i] = matrix[top + i][r];
+
+                // move top left into top right
+                matrix[top + i][r] = topLeft;
+                
+            }
+            r--;
+            l++;
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} matrix
+     * @return {void}
+     */
+    rotate(matrix) {
+        let l = 0;
+        let r = matrix.length - 1;
+
+        while (l < r) {
+            for (let i = 0; i < r - l; i++) {
+                const top = l;
+                const bottom = r;
+
+                // save the topleft
+                const topLeft = matrix[top][l + i];
+
+                // move bottom left into top left
+                matrix[top][l + i] = matrix[bottom - i][l];
+
+                // move bottom right into bottom left
+                matrix[bottom - i][l] = matrix[bottom][r - i];
+
+                // move top right into bottom right
+                matrix[bottom][r - i] = matrix[top + i][r];
+
+                // move top left into top right
+                matrix[top + i][r] = topLeft;
+            }
+            r--;
+            l++;
+        }
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public void Rotate(int[][] matrix) {
+        (int left, int right) = (0, matrix.Length -1);
+        
+        while(left < right) {
+            var limit = right - left;
+            for(var i = 0; i < limit; i++) {
+                (int top, int bottom) = (left, right);
+                
+                // save the top left position
+                var topLeft = matrix[top][left + i];
+                
+                // put the bottom left value to the top left position
+                matrix[top][left + i] = matrix[bottom - i][left];
+                
+                // put the bottom right value to the bottom left position
+                matrix[bottom - i][left] = matrix[bottom][right - i];
+                
+                // put the top right value to the bottom right position
+                matrix[bottom][right - i] = matrix[top + i][right];                 
+
+                // put the saved top left value to the top right position
+                matrix[top + i][right] = topLeft;    
+
+            }
+            left++;
+            right--;
+        }
+        
+        return;
+    }
+}
+```
+
+```go
+func rotate(matrix [][]int) {
+	l, r := 0, len(matrix)-1
+	for l < r {
+		for i := 0; i < r-l; i++ {
+			top, bottom := l, r
+
+			// save the topleft
+			topLeft := matrix[top][l+i]
+
+			// move bottom left into top left
+			matrix[top][l+i] = matrix[bottom-i][l]
+
+			// move bottom right into bottom left
+			matrix[bottom-i][l] = matrix[bottom][r-i]
+
+			// move top right into bottom right
+			matrix[bottom][r-i] = matrix[top+i][r]
+
+			// move top left into top right
+			matrix[top+i][r] = topLeft
+		}
+		r--
+		l++
+	}
+}
+```
+
+```kotlin
+class Solution {
+    fun rotate(matrix: Array<IntArray>) {
+        var l = 0
+        var r = matrix.size - 1
+        while (l < r) {
+            for (i in 0 until r - l) {
+                val top = l
+                val bottom = r
+
+                // save the topleft
+                val topLeft = matrix[top][l + i]
+
+                // move bottom left into top left
+                matrix[top][l + i] = matrix[bottom - i][l]
+
+                // move bottom right into bottom left
+                matrix[bottom - i][l] = matrix[bottom][r - i]
+
+                // move top right into bottom right
+                matrix[bottom][r - i] = matrix[top + i][r]
+
+                // move top left into top right
+                matrix[top + i][r] = topLeft
+            }
+            r--
+            l++
+        }
+    }
+}
+```
+
+```swift
+class Solution {
+    func rotate(_ matrix: inout [[Int]]) {
+        var l = 0
+        var r = matrix.count - 1
+        while l < r {
+            for i in 0..<r - l {
+                let top = l
+                let bottom = r
+
+                // save the topleft
+                let topLeft = matrix[top][l + i]
+
+                // move bottom left into top left
+                matrix[top][l + i] = matrix[bottom - i][l]
+
+                // move bottom right into bottom left
+                matrix[bottom - i][l] = matrix[bottom][r - i]
+
+                // move top right into bottom right
+                matrix[bottom][r - i] = matrix[top + i][r]
+
+                // move top left into top right
+                matrix[top + i][r] = topLeft
+            }
+            r -= 1
+            l += 1
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Reverse And Transpose
+
+::tabs-start
+
+```python
+class Solution:
+    def rotate(self, matrix: List[List[int]]) -> None:
+        # Reverse the matrix vertically
+        matrix.reverse()
+
+        # Transpose the matrix
+        for i in range(len(matrix)):
+            for j in range(i + 1, len(matrix)):
+                matrix[i][j], matrix[j][i] = matrix[j][i], matrix[i][j]
+```
+
+```java
+public class Solution {
+    public void rotate(int[][] matrix) {
+        // Reverse the matrix vertically
+        reverse(matrix);
+
+        // Transpose the matrix
+        for (int i = 0; i < matrix.length; i++) {
+            for (int j = i; j < matrix[i].length; j++) {
+                int temp = matrix[i][j];
+                matrix[i][j] = matrix[j][i];
+                matrix[j][i] = temp;
+            }
+        }
+    }
+
+    private void reverse(int[][] matrix) {
+        int n = matrix.length;
+        for (int i = 0; i < n / 2; i++) {
+            int[] temp = matrix[i];
+            matrix[i] = matrix[n - 1 - i];
+            matrix[n - 1 - i] = temp;
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void rotate(vector<vector<int>>& matrix) {
+        // Reverse the matrix vertically
+        reverse(matrix.begin(), matrix.end());
+
+        // Transpose the matrix
+        for (int i = 0; i < matrix.size(); ++i) {
+            for (int j = i + 1; j < matrix[i].size(); ++j)
+                swap(matrix[i][j], matrix[j][i]);
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} matrix
+     * @return {void}
+     */
+    rotate(matrix) {
+        // Reverse the matrix vertically
+        matrix.reverse();
+
+        // Transpose the matrix
+        for (let i = 0; i < matrix.length; i++) {
+            for (let j = i; j < matrix[i].length; j++) {
+                [matrix[i][j], matrix[j][i]] = [matrix[j][i], matrix[i][j]];
+            }
+        }
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public void Rotate(int[][] matrix) {
+        // Reverse the matrix vertically
+        Array.Reverse(matrix);
+
+        // Transpose the matrix
+        for (int i = 0; i < matrix.Length; i++) {
+            for (int j = i; j < matrix[i].Length; j++) {
+                (matrix[i][j], matrix[j][i]) = (matrix[j][i], matrix[i][j]);
+            }
+        }
+    }
+}
+```
+
+```go
+func rotate(matrix [][]int) {
+	// Reverse the matrix vertically
+	for i, j := 0, len(matrix)-1; i < j; i, j = i+1, j-1 {
+		matrix[i], matrix[j] = matrix[j], matrix[i]
+	}
+
+	// Transpose the matrix
+	for i := 0; i < len(matrix); i++ {
+		for j := i + 1; j < len(matrix); j++ {
+			matrix[i][j], matrix[j][i] = matrix[j][i], matrix[i][j]
+		}
+	}
+}
+```
+
+```kotlin
+class Solution {
+    fun rotate(matrix: Array<IntArray>) {
+        // Reverse the matrix vertically
+        matrix.reverse()
+
+        // Transpose the matrix
+        for (i in matrix.indices) {
+            for (j in i + 1 until matrix.size) {
+                val temp = matrix[i][j]
+                matrix[i][j] = matrix[j][i]
+                matrix[j][i] = temp
+            }
+        }
+    }
+}
+```
+
+```swift
+class Solution {
+    func rotate(_ matrix: inout [[Int]]) {
+        // Reverse the matrix vertically
+        matrix.reverse()
+
+        // Transpose the matrix
+        for i in 0..<matrix.count {
+            for j in i + 1..<matrix.count {
+                (matrix[i][j], matrix[j][i]) = (matrix[j][i], matrix[i][j])
+            }
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/rotting-fruit.md b/articles/rotting-fruit.md
index b03245f80..62345eea7 100644
--- a/articles/rotting-fruit.md
+++ b/articles/rotting-fruit.md
@@ -224,6 +224,164 @@ public class Solution {
 }
 ```
 
+```go
+type Pair struct {
+    row, col int
+}
+
+func orangesRotting(grid [][]int) int {
+    rows, cols := len(grid), len(grid[0])
+    queue := make([]Pair, 0)
+    fresh := 0
+    time := 0
+    
+    for r := 0; r < rows; r++ {
+        for c := 0; c < cols; c++ {
+            if grid[r][c] == 1 {
+                fresh++
+            }
+            if grid[r][c] == 2 {
+                queue = append(queue, Pair{r, c})
+            }
+        }
+    }
+    
+    directions := [][]int{{0, 1}, {0, -1}, {1, 0}, {-1, 0}}
+    
+    for fresh > 0 && len(queue) > 0 {
+        length := len(queue)
+        
+        for i := 0; i < length; i++ {
+            current := queue[0]
+            queue = queue[1:] 
+            
+            for _, dir := range directions {
+                newRow := current.row + dir[0]
+                newCol := current.col + dir[1]
+                
+                if newRow >= 0 && newRow < rows &&
+                   newCol >= 0 && newCol < cols &&
+                   grid[newRow][newCol] == 1 {
+                    grid[newRow][newCol] = 2
+                    queue = append(queue, Pair{newRow, newCol})
+                    fresh--
+                }
+            }
+        }
+        time++
+    }
+    
+    if fresh == 0 {
+        return time
+    }
+    return -1
+}
+```
+
+```kotlin
+class Solution {
+    data class Pair(val row: Int, val col: Int)
+    
+    fun orangesRotting(grid: Array<IntArray>): Int {
+        val rows = grid.size
+        val cols = grid[0].size
+        val queue = ArrayDeque<Pair>()
+        var fresh = 0
+        var time = 0
+        
+        for (r in 0 until rows) {
+            for (c in 0 until cols) {
+                if (grid[r][c] == 1) {
+                    fresh++
+                }
+                if (grid[r][c] == 2) {
+                    queue.addLast(Pair(r, c))
+                }
+            }
+        }
+        
+        val directions = arrayOf(
+            intArrayOf(0, 1),
+            intArrayOf(0, -1),
+            intArrayOf(1, 0),
+            intArrayOf(-1, 0)
+        )
+        
+        while (fresh > 0 && queue.isNotEmpty()) {
+            val length = queue.size
+            
+            repeat(length) {
+                val current = queue.removeFirst()
+                
+                for (dir in directions) {
+                    val newRow = current.row + dir[0]
+                    val newCol = current.col + dir[1]
+                    
+                    if (newRow in 0 until rows &&
+                        newCol in 0 until cols &&
+                        grid[newRow][newCol] == 1) {
+                        grid[newRow][newCol] = 2
+                        queue.addLast(Pair(newRow, newCol))
+                        fresh--
+                    }
+                }
+            }
+            time++
+        }
+        
+        return if (fresh == 0) time else -1
+    }
+}
+```
+
+```swift
+class Solution {
+    func orangesRotting(_ grid: [[Int]]) -> Int {
+        var grid = grid
+        var queue = Deque<(Int, Int)>()
+        var fresh = 0
+        var time = 0
+
+        let ROWS = grid.count
+        let COLS = grid[0].count
+
+        for r in 0..<ROWS {
+            for c in 0..<COLS {
+                if grid[r][c] == 1 {
+                    fresh += 1
+                }
+                if grid[r][c] == 2 {
+                    queue.append((r, c))
+                }
+            }
+        }
+
+        let directions = [[0, 1], [0, -1], [1, 0], [-1, 0]]
+
+        while fresh > 0 && !queue.isEmpty {
+            let length = queue.count
+            for _ in 0..<length {
+                let (r, c) = queue.popFirst()!
+
+                for dir in directions {
+                    let row = r + dir[0]
+                    let col = c + dir[1]
+
+                    if row >= 0 && row < ROWS && col >= 0 && col < COLS && grid[row][col] == 1 {
+                        grid[row][col] = 2
+                        queue.append((row, col))
+                        fresh -= 1
+                    }
+                }
+            }
+            time += 1
+        }
+
+        return fresh == 0 ? time : -1
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -485,6 +643,173 @@ public class Solution {
 }
 ```
 
+```go
+func orangesRotting(grid [][]int) int {
+    rows, cols := len(grid), len(grid[0])
+    fresh := 0
+    time := 0
+    
+    for r := 0; r < rows; r++ {
+        for c := 0; c < cols; c++ {
+            if grid[r][c] == 1 {
+                fresh++
+            }
+        }
+    }
+    
+    directions := [][]int{{0, 1}, {0, -1}, {1, 0}, {-1, 0}}
+    
+    for fresh > 0 {
+        flag := false
+        for r := 0; r < rows; r++ {
+            for c := 0; c < cols; c++ {
+                if grid[r][c] == 2 {
+                    for _, d := range directions {
+                        row, col := r+d[0], c+d[1]
+                        if row >= 0 && row < rows && 
+                           col >= 0 && col < cols && 
+                           grid[row][col] == 1 {
+                            grid[row][col] = 3
+                            fresh--
+                            flag = true
+                        }
+                    }
+                }
+            }
+        }
+        
+        if !flag {
+            return -1
+        }
+        
+        for r := 0; r < rows; r++ {
+            for c := 0; c < cols; c++ {
+                if grid[r][c] == 3 {
+                    grid[r][c] = 2
+                }
+            }
+        }
+        time++
+    }
+    
+    return time
+}
+```
+
+```kotlin
+class Solution {
+    fun orangesRotting(grid: Array<IntArray>): Int {
+        val rows = grid.size
+        val cols = grid[0].size
+        var fresh = 0
+        var time = 0
+        
+        for (r in 0 until rows) {
+            for (c in 0 until cols) {
+                if (grid[r][c] == 1) fresh++
+            }
+        }
+        
+        val directions = arrayOf(
+            intArrayOf(0, 1),
+            intArrayOf(0, -1),
+            intArrayOf(1, 0),
+            intArrayOf(-1, 0)
+        )
+        
+        while (fresh > 0) {
+            var flag = false
+            for (r in 0 until rows) {
+                for (c in 0 until cols) {
+                    if (grid[r][c] == 2) {
+                        for (d in directions) {
+                            val row = r + d[0]
+                            val col = c + d[1]
+                            if (row in 0 until rows && 
+                                col in 0 until cols && 
+                                grid[row][col] == 1) {
+                                grid[row][col] = 3
+                                fresh--
+                                flag = true
+                            }
+                        }
+                    }
+                }
+            }
+            
+            if (!flag) return -1
+            
+            for (r in 0 until rows) {
+                for (c in 0 until cols) {
+                    if (grid[r][c] == 3) grid[r][c] = 2
+                }
+            }
+            time++
+        }
+        
+        return time
+    }
+}
+```
+
+```swift
+class Solution {
+    func orangesRotting(_ grid: [[Int]]) -> Int {
+        var grid = grid
+        let ROWS = grid.count
+        let COLS = grid[0].count
+        var fresh = 0
+        var time = 0
+
+        for r in 0..<ROWS {
+            for c in 0..<COLS {
+                if grid[r][c] == 1 {
+                    fresh += 1
+                }
+            }
+        }
+
+        let directions = [[0, 1], [0, -1], [1, 0], [-1, 0]]
+
+        while fresh > 0 {
+            var flag = false
+            for r in 0..<ROWS {
+                for c in 0..<COLS {
+                    if grid[r][c] == 2 {
+                        for dir in directions {
+                            let row = r + dir[0]
+                            let col = c + dir[1]
+                            if (row >= 0 && row < ROWS && col >= 0 &&
+                                col < COLS && grid[row][col] == 1) {
+                                grid[row][col] = 3
+                                fresh -= 1
+                                flag = true
+                            }
+                        }
+                    }
+                }
+            }
+
+            if !flag {
+                return -1
+            }
+
+            for r in 0..<ROWS {
+                for c in 0..<COLS {
+                    if grid[r][c] == 3 {
+                        grid[r][c] = 2
+                    }
+                }
+            }
+
+            time += 1
+        }
+
+        return time
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/same-binary-tree.md b/articles/same-binary-tree.md
index 1414d326d..b07d14e35 100644
--- a/articles/same-binary-tree.md
+++ b/articles/same-binary-tree.md
@@ -142,6 +142,377 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func isSameTree(p *TreeNode, q *TreeNode) bool {
+    if p == nil && q == nil {
+        return true
+    }
+    if p != nil && q != nil && p.Val == q.Val {
+        return isSameTree(p.Left, q.Left) && isSameTree(p.Right, q.Right)
+    }
+    return false
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    fun isSameTree(p: TreeNode?, q: TreeNode?): Boolean {
+        if (p == null && q == null) {
+            return true
+        }
+        if (p != null && q != null && p.`val` == q.`val`) {
+            return isSameTree(p.left, q.left) && isSameTree(p.right, q.right)
+        }
+        return false
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func isSameTree(_ p: TreeNode?, _ q: TreeNode?) -> Bool {
+        if p == nil && q == nil {
+            return true
+        }
+        if let p = p, let q = q, p.val == q.val {
+            return isSameTree(p.left, q.left) && isSameTree(p.right, q.right)
+        } else {
+            return false
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$  
+  * Best Case ([balanced tree](https://www.geeksforgeeks.org/balanced-binary-tree/)): $O(log(n))$
+  * Worst Case ([degenerate tree](https://www.geeksforgeeks.org/introduction-to-degenerate-binary-tree/)): $O(n)$
+
+> Where $n$ is the number of nodes in the tree and $h$ is the height of the tree.
+
+---
+
+## 2. Iterative DFS
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+
+class Solution:
+    def isSameTree(self, p: Optional[TreeNode], q: Optional[TreeNode]) -> bool:
+        stack = [(p, q)]
+        
+        while stack:
+            node1, node2 = stack.pop()
+            
+            if not node1 and not node2:
+                continue
+            if not node1 or not node2 or node1.val != node2.val:
+                return False
+                
+            stack.append((node1.right, node2.right))
+            stack.append((node1.left, node2.left))
+        
+        return True
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+
+public class Solution {
+    public boolean isSameTree(TreeNode p, TreeNode q) {
+        Stack<TreeNode[]> stack = new Stack<>();
+        stack.push(new TreeNode[]{p, q});
+        
+        while (!stack.isEmpty()) {
+            TreeNode[] nodes = stack.pop();
+            TreeNode node1 = nodes[0], node2 = nodes[1];
+            
+            if (node1 == null && node2 == null) continue;
+            if (node1 == null || node2 == null || node1.val != node2.val) {
+                return false;
+            }
+            stack.push(new TreeNode[]{node1.right, node2.right});
+            stack.push(new TreeNode[]{node1.left, node2.left});
+        }
+        
+        return true;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+
+class Solution {
+public:
+    bool isSameTree(TreeNode* p, TreeNode* q) {
+        stack<pair<TreeNode*, TreeNode*>> stk;
+        stk.push({p, q});
+        
+        while (!stk.empty()) {
+            auto [node1, node2] = stk.top();
+            stk.pop();
+            
+            if (!node1 && !node2) continue;
+            if (!node1 || !node2 || node1->val != node2->val) return false;
+            
+            stk.push({node1->right, node2->right});
+            stk.push({node1->left, node2->left});
+        }
+        
+        return true;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+
+class Solution {
+    /**
+     * @param {TreeNode} p
+     * @param {TreeNode} q
+     * @return {boolean}
+     */
+    isSameTree(p, q) {
+        const stack = [[p, q]];
+        
+        while (stack.length) {
+            const [node1, node2] = stack.pop();
+            
+            if (!node1 && !node2) continue;
+            if (!node1 || !node2 || node1.val !== node2.val) {
+                return false;
+            }
+            stack.push([node1.right, node2.right]);
+            stack.push([node1.left, node2.left]);
+        }
+        
+        return true;
+    }
+}
+```
+
+```csharp
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+
+public class Solution {
+    public bool IsSameTree(TreeNode p, TreeNode q) {
+        var stack = new Stack<(TreeNode, TreeNode)>();
+        stack.Push((p, q));
+        
+        while (stack.Count > 0) {
+            var (node1, node2) = stack.Pop();
+            
+            if (node1 == null && node2 == null) continue;
+            if (node1 == null || node2 == null || node1.val != node2.val) {
+                return false;
+            }
+            stack.Push((node1.right, node2.right));
+            stack.Push((node1.left, node2.left));
+        }
+        
+        return true;
+    }
+}
+```
+
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func isSameTree(p *TreeNode, q *TreeNode) bool {
+    type Pair struct {
+        first, second *TreeNode
+    }
+    
+    stack := []Pair{{p, q}}
+    
+    for len(stack) > 0 {
+        lastIdx := len(stack) - 1
+        node1, node2 := stack[lastIdx].first, stack[lastIdx].second
+        stack = stack[:lastIdx]
+        
+        if node1 == nil && node2 == nil {
+            continue
+        }
+        if node1 == nil || node2 == nil || node1.Val != node2.Val {
+            return false
+        }
+        
+        stack = append(stack, Pair{node1.Right, node2.Right})
+        stack = append(stack, Pair{node1.Left, node2.Left})
+    }
+    
+    return true
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    fun isSameTree(p: TreeNode?, q: TreeNode?): Boolean {
+        val stack = ArrayDeque<Pair<TreeNode?, TreeNode?>>()
+        stack.addLast(Pair(p, q))
+        
+        while (stack.isNotEmpty()) {
+            val (node1, node2) = stack.removeLast()
+            
+            if (node1 == null && node2 == null) continue
+            if (node1 == null || node2 == null || node1.`val` != node2.`val`) {
+                return false
+            }
+            stack.addLast(Pair(node1.right, node2.right))
+            stack.addLast(Pair(node1.left, node2.left))
+        }
+        
+        return true
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func isSameTree(_ p: TreeNode?, _ q: TreeNode?) -> Bool {
+        var stack: [(TreeNode?, TreeNode?)] = [(p, q)]
+
+        while !stack.isEmpty {
+            let (node1, node2) = stack.removeLast()
+
+            if node1 == nil && node2 == nil {
+                continue
+            }
+            if node1 == nil || node2 == nil || node1!.val != node2!.val {
+                return false
+            }
+
+            stack.append((node1!.right, node2!.right))
+            stack.append((node1!.left, node2!.left))
+        }
+
+        return true
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -151,7 +522,7 @@ public class Solution {
 
 ---
 
-## 2. Breadth First Search
+## 3. Breadth First Search
 
 ::tabs-start
 
@@ -169,20 +540,21 @@ class Solution:
         q2 = deque([q])
 
         while q1 and q2:
-            nodeP = q1.popleft()
-            nodeQ = q2.popleft()
+            for _ in range(len(q1)):
+                nodeP = q1.popleft()
+                nodeQ = q2.popleft()
 
-            if nodeP is None and nodeQ is None:
-                continue
-            if nodeP is None or nodeQ is None or nodeP.val != nodeQ.val:
-                return False
+                if nodeP is None and nodeQ is None:
+                    continue
+                if nodeP is None or nodeQ is None or nodeP.val != nodeQ.val:
+                    return False
 
-            q1.append(nodeP.left)
-            q1.append(nodeP.right)
-            q2.append(nodeQ.left)
-            q2.append(nodeQ.right)
+                q1.append(nodeP.left)
+                q1.append(nodeP.right)
+                q2.append(nodeQ.left)
+                q2.append(nodeQ.right)
 
-        return True
+        return True 
 ```
 
 ```java
@@ -210,17 +582,19 @@ public class Solution {
         q2.add(q);
 
         while (!q1.isEmpty() && !q2.isEmpty()) {
-            TreeNode nodeP = q1.poll();
-            TreeNode nodeQ = q2.poll();
-
-            if (nodeP == null && nodeQ == null) continue;
-            if (nodeP == null || nodeQ == null || nodeP.val != nodeQ.val)
-                 return false;
-
-            q1.add(nodeP.left);
-            q1.add(nodeP.right);
-            q2.add(nodeQ.left);
-            q2.add(nodeQ.right);
+            for (int i = q1.size(); i > 0; i--) {
+                TreeNode nodeP = q1.poll();
+                TreeNode nodeQ = q2.poll();
+
+                if (nodeP == null && nodeQ == null) continue;
+                if (nodeP == null || nodeQ == null || nodeP.val != nodeQ.val)
+                    return false;
+
+                q1.add(nodeP.left);
+                q1.add(nodeP.right);
+                q2.add(nodeQ.left);
+                q2.add(nodeQ.right);
+            }
         }
 
         return true;
@@ -250,17 +624,19 @@ public:
         q2.push(q);
 
         while (!q1.empty() && !q2.empty()) {
-            TreeNode* nodeP = q1.front(); q1.pop();
-            TreeNode* nodeQ = q2.front(); q2.pop();
-
-            if (!nodeP && !nodeQ) continue;
-            if (!nodeP || !nodeQ || nodeP->val != nodeQ->val) 
-                return false;
-
-            q1.push(nodeP->left);
-            q1.push(nodeP->right);
-            q2.push(nodeQ->left);
-            q2.push(nodeQ->right);
+            for (int i = q1.size(); i > 0; i--) {
+                TreeNode* nodeP = q1.front(); q1.pop();
+                TreeNode* nodeQ = q2.front(); q2.pop();
+
+                if (!nodeP && !nodeQ) continue;
+                if (!nodeP || !nodeQ || nodeP->val != nodeQ->val) 
+                    return false;
+
+                q1.push(nodeP->left);
+                q1.push(nodeP->right);
+                q2.push(nodeQ->left);
+                q2.push(nodeQ->right);
+            }
         }
 
         return true;
@@ -293,17 +669,20 @@ class Solution {
         q2.push(q);
         
         while (!q1.isEmpty() && !q2.isEmpty()) {
-            let nodeP = q1.pop();
-            let nodeQ = q2.pop();
-
-            if (nodeP === null && nodeQ === null) continue;
-            if (nodeP === null || nodeQ === null || nodeP.val !== nodeQ.val) 
-                return false;
-
-            q1.push(nodeP.left);
-            q1.push(nodeP.right);
-            q2.push(nodeQ.left);
-            q2.push(nodeQ.right);
+            for (let i = q1.size(); i > 0; i--) {
+                let nodeP = q1.pop();
+                let nodeQ = q2.pop();
+
+                if (nodeP === null && nodeQ === null) continue;
+                if (nodeP === null || nodeQ === null || nodeP.val !== nodeQ.val) {
+                    return false;
+                }
+                
+                q1.push(nodeP.left);
+                q1.push(nodeP.right);
+                q2.push(nodeQ.left);
+                q2.push(nodeQ.right);
+            }
         }
 
         return true;
@@ -332,20 +711,147 @@ public class Solution {
         var q2 = new Queue<TreeNode>(new[] { q });
 
         while (q1.Count > 0 && q2.Count > 0) {
-            var nodeP = q1.Dequeue();
-            var nodeQ = q2.Dequeue();
+            for (int i = q1.Count; i > 0; i--) {
+                var nodeP = q1.Dequeue();
+                var nodeQ = q2.Dequeue();
+
+                if (nodeP == null && nodeQ == null) continue;
+                if (nodeP == null || nodeQ == null || nodeP.val != nodeQ.val) {
+                    return false;
+                }
+
+                q1.Enqueue(nodeP.left);
+                q1.Enqueue(nodeP.right);
+                q2.Enqueue(nodeQ.left);
+                q2.Enqueue(nodeQ.right);
+            }
+        }
 
-            if (nodeP == null && nodeQ == null) continue;
-            if (nodeP == null || nodeQ == null || nodeP.val != nodeQ.val)
-                 return false;
+        return true;
+    }
+}
+```
 
-            q1.Enqueue(nodeP.left);
-            q1.Enqueue(nodeP.right);
-            q2.Enqueue(nodeQ.left);
-            q2.Enqueue(nodeQ.right);
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func isSameTree(p *TreeNode, q *TreeNode) bool {
+    queue1 := []*TreeNode{p}
+    queue2 := []*TreeNode{q}
+
+    for len(queue1) > 0 && len(queue2) > 0 {
+        for i := len(queue1); i > 0; i-- {
+            nodeP := queue1[0]
+            nodeQ := queue2[0]
+            queue1 = queue1[1:]
+            queue2 = queue2[1:]
+
+            if nodeP == nil && nodeQ == nil {
+                continue
+            }
+            if nodeP == nil || nodeQ == nil || nodeP.Val != nodeQ.Val {
+                return false
+            }
+
+            queue1 = append(queue1, nodeP.Left, nodeP.Right)
+            queue2 = append(queue2, nodeQ.Left, nodeQ.Right)
         }
+    }
 
-        return true;
+    return len(queue1) == 0 && len(queue2) == 0
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    fun isSameTree(p: TreeNode?, q: TreeNode?): Boolean {
+        val q1 = ArrayDeque<TreeNode?>()
+        val q2 = ArrayDeque<TreeNode?>()
+
+        q1.add(p)
+        q2.add(q)
+
+        while (q1.isNotEmpty() && q2.isNotEmpty()) {
+            for (i in q1.size downTo 1) {
+                val nodeP = q1.removeFirst()
+                val nodeQ = q2.removeFirst()
+
+                if (nodeP == null && nodeQ == null) {
+                    continue
+                }
+                if (nodeP == null || nodeQ == null || nodeP.`val` != nodeQ.`val`) {
+                    return false
+                }
+
+                q1.add(nodeP.left)
+                q1.add(nodeP.right)
+                q2.add(nodeQ.left)
+                q2.add(nodeQ.right)
+            }
+        }
+
+        return true
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func isSameTree(_ p: TreeNode?, _ q: TreeNode?) -> Bool {
+        var q1 = Deque<TreeNode?>()
+        var q2 = Deque<TreeNode?>()
+        q1.append(p)
+        q2.append(q)
+
+        while !q1.isEmpty && !q2.isEmpty {
+            let nodeP = q1.removeFirst()
+            let nodeQ = q2.removeFirst()
+
+            if nodeP == nil && nodeQ == nil {
+                continue
+            }
+            if nodeP == nil || nodeQ == nil || nodeP!.val != nodeQ!.val {
+                return false
+            }
+
+            q1.append(nodeP!.left)
+            q1.append(nodeP!.right)
+            q2.append(nodeQ!.left)
+            q2.append(nodeQ!.right)
+        }
+
+        return true
     }
 }
 ```
diff --git a/articles/score-after-flipping-matrix.md b/articles/score-after-flipping-matrix.md
new file mode 100644
index 000000000..83c222266
--- /dev/null
+++ b/articles/score-after-flipping-matrix.md
@@ -0,0 +1,253 @@
+## 1. Greedy (Overwriting the Input)
+
+::tabs-start
+
+```python
+class Solution:
+    def matrixScore(self, grid: List[List[int]]) -> int:
+        ROWS, COLS = len(grid), len(grid[0])
+
+        for r in range(ROWS):
+            if grid[r][0] == 0:
+                for c in range(COLS):
+                    grid[r][c] ^= 1
+
+        for c in range(COLS):
+            one_cnt = sum(grid[r][c] for r in range(ROWS))
+            if one_cnt < ROWS - one_cnt:
+                for r in range(ROWS):
+                    grid[r][c] ^= 1
+
+        res = 0
+        for r in range(ROWS):
+            for c in range(COLS):
+                res += grid[r][c] << (COLS - c - 1)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int matrixScore(int[][] grid) {
+        int ROWS = grid.length, COLS = grid[0].length;
+
+        for (int r = 0; r < ROWS; r++) {
+            if (grid[r][0] == 0) {
+                for (int c = 0; c < COLS; c++) {
+                    grid[r][c] ^= 1;
+                }
+            }
+        }
+
+        for (int c = 0; c < COLS; c++) {
+            int oneCnt = 0;
+            for (int r = 0; r < ROWS; r++) {
+                oneCnt += grid[r][c];
+            }
+            if (oneCnt < ROWS - oneCnt) {
+                for (int r = 0; r < ROWS; r++) {
+                    grid[r][c] ^= 1;
+                }
+            }
+        }
+
+        int res = 0;
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                res += grid[r][c] << (COLS - c - 1);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int matrixScore(vector<vector<int>>& grid) {
+        int ROWS = grid.size(), COLS = grid[0].size();
+
+        for (int r = 0; r < ROWS; r++) {
+            if (grid[r][0] == 0) {
+                for (int c = 0; c < COLS; c++) {
+                    grid[r][c] ^= 1;
+                }
+            }
+        }
+
+        for (int c = 0; c < COLS; c++) {
+            int oneCnt = 0;
+            for (int r = 0; r < ROWS; r++) {
+                oneCnt += grid[r][c];
+            }
+            if (oneCnt < ROWS - oneCnt) {
+                for (int r = 0; r < ROWS; r++) {
+                    grid[r][c] ^= 1;
+                }
+            }
+        }
+
+        int res = 0;
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                res += grid[r][c] << (COLS - c - 1);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    matrixScore(grid) {
+        let ROWS = grid.length, COLS = grid[0].length;
+
+        for (let r = 0; r < ROWS; r++) {
+            if (grid[r][0] === 0) {
+                for (let c = 0; c < COLS; c++) {
+                    grid[r][c] ^= 1;
+                }
+            }
+        }
+
+        for (let c = 0; c < COLS; c++) {
+            let oneCnt = 0;
+            for (let r = 0; r < ROWS; r++) {
+                oneCnt += grid[r][c];
+            }
+            if (oneCnt < ROWS - oneCnt) {
+                for (let r = 0; r < ROWS; r++) {
+                    grid[r][c] ^= 1;
+                }
+            }
+        }
+
+        let res = 0;
+        for (let r = 0; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                res += grid[r][c] << (COLS - c - 1);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(1)$ extra space.
+
+> Where $m$ is the number of rows and $n$ is the number of columns.
+
+---
+
+## 2. Greedy (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def matrixScore(self, grid: List[List[int]]) -> int:
+        ROWS, COLS = len(grid), len(grid[0])
+        res = ROWS * (1 << (COLS - 1))
+
+        for c in range(1, COLS):
+            cnt = 0
+            for r in range(ROWS):
+                if grid[r][c] != grid[r][0]:
+                    cnt += 1
+
+            cnt = max(cnt, ROWS - cnt)
+            res += cnt * (1 << (COLS - c - 1))
+
+        return res
+```
+
+```java
+public class Solution {
+    public int matrixScore(int[][] grid) {
+        int ROWS = grid.length, COLS = grid[0].length;
+        int res = ROWS * (1 << (COLS - 1));
+
+        for (int c = 1; c < COLS; c++) {
+            int cnt = 0;
+            for (int r = 0; r < ROWS; r++) {
+                if (grid[r][c] != grid[r][0]) {
+                    cnt++;
+                }
+            }
+            cnt = Math.max(cnt, ROWS - cnt);
+            res += cnt * (1 << (COLS - c - 1));
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int matrixScore(vector<vector<int>>& grid) {
+        int ROWS = grid.size(), COLS = grid[0].size();
+        int res = ROWS * (1 << (COLS - 1));
+
+        for (int c = 1; c < COLS; c++) {
+            int cnt = 0;
+            for (int r = 0; r < ROWS; r++) {
+                if (grid[r][c] != grid[r][0]) {
+                    cnt++;
+                }
+            }
+            cnt = max(cnt, ROWS - cnt);
+            res += cnt * (1 << (COLS - c - 1));
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    matrixScore(grid) {
+        const ROWS = grid.length, COLS = grid[0].length;
+        let res = ROWS * (1 << (COLS - 1));
+
+        for (let c = 1; c < COLS; c++) {
+            let cnt = 0;
+            for (let r = 0; r < ROWS; r++) {
+                if (grid[r][c] !== grid[r][0]) {
+                    cnt++;
+                }
+            }
+            cnt = Math.max(cnt, ROWS - cnt);
+            res += cnt * (1 << (COLS - c - 1));
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(1)$ extra space.
+
+> Where $m$ is the number of rows and $n$ is the number of columns.
\ No newline at end of file
diff --git a/articles/score-of-a-string.md b/articles/score-of-a-string.md
new file mode 100644
index 000000000..9a5bf9bdf
--- /dev/null
+++ b/articles/score-of-a-string.md
@@ -0,0 +1,60 @@
+## 1. Iteration
+
+::tabs-start
+
+```python
+class Solution:
+    def scoreOfString(self, s: str) -> int:
+        res = 0
+        for i in range(len(s) - 1):
+            res += abs(ord(s[i]) - ord(s[i + 1]))
+        return res
+```
+
+```java
+public class Solution {
+    public int scoreOfString(String s) {
+        int res = 0;
+        for (int i = 0; i < s.length() - 1; i++) {
+            res += Math.abs(s.charAt(i) - s.charAt(i + 1));
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int scoreOfString(string s) {
+        int res = 0;
+        for (int i = 0; i < s.length() - 1; i++) {
+            res += abs(s[i] - s[i + 1]);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    scoreOfString(s) {
+        let res = 0;
+        for (let i = 0; i < s.length - 1; i++) {
+            res += Math.abs(s.charCodeAt(i) - s.charCodeAt(i + 1));
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/search-2d-matrix.md b/articles/search-2d-matrix.md
index d7c6ae888..45181e5df 100644
--- a/articles/search-2d-matrix.md
+++ b/articles/search-2d-matrix.md
@@ -78,6 +78,49 @@ public class Solution {
 }
 ```
 
+```go
+func searchMatrix(matrix [][]int, target int) bool {
+    for _, row := range matrix {
+        for _, value := range row {
+            if value == target {
+                return true
+            }
+        }
+    }
+    return false
+}
+```
+
+```kotlin
+class Solution {
+    fun searchMatrix(matrix: Array<IntArray>, target: Int): Boolean {
+        for (row in matrix) {
+            for (value in row) {
+                if (value == target) {
+                    return true
+                }
+            }
+        }
+        return false
+    }
+}
+```
+
+```swift
+class Solution {
+    func searchMatrix(_ matrix: [[Int]], _ target: Int) -> Bool {
+        for r in 0..<matrix.count {
+            for c in 0..<matrix[0].count {
+                if matrix[r][c] == target {
+                    return true
+                }
+            }
+        }
+        return false
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -195,6 +238,67 @@ public class Solution {
 }
 ```
 
+```go
+func searchMatrix(matrix [][]int, target int) bool {
+    m, n := len(matrix), len(matrix[0])
+    r, c := 0, n - 1
+
+    for r < m && c >= 0 {
+        if matrix[r][c] > target {
+            c--
+        } else if matrix[r][c] < target {
+            r++
+        } else {
+            return true
+        }
+    }
+    return false
+}
+```
+
+```kotlin
+class Solution {
+    fun searchMatrix(matrix: Array<IntArray>, target: Int): Boolean {
+        val m = matrix.size
+        val n = matrix[0].size
+        var r = 0
+        var c = n - 1
+
+        while (r < m && c >= 0) {
+            if (matrix[r][c] > target) {
+                c--
+            } else if (matrix[r][c] < target) {
+                r++
+            } else {
+                return true
+            }
+        }
+        return false
+    }
+}
+```
+
+```swift
+class Solution {
+    func searchMatrix(_ matrix: [[Int]], _ target: Int) -> Bool {
+        let m = matrix.count
+        let n = matrix[0].count
+        var r = 0, c = n - 1
+
+        while r < m && c >= 0 {
+            if matrix[r][c] > target {
+                c -= 1
+            } else if matrix[r][c] < target {
+                r += 1
+            } else {
+                return true
+            }
+        }
+        return false
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -405,11 +509,122 @@ public class Solution {
 }
 ```
 
+```go
+func searchMatrix(matrix [][]int, target int) bool {
+    rows, cols := len(matrix), len(matrix[0])
+    top, bot := 0, rows - 1
+
+    for top <= bot {
+        row := (top + bot) / 2
+        if target > matrix[row][cols-1] {
+            top = row + 1
+        } else if target < matrix[row][0] {
+            bot = row - 1
+        } else {
+            break
+        }
+    }
+
+    if !(top <= bot) {
+        return false
+    }
+    row := (top + bot) / 2
+    l, r := 0, cols - 1
+    for l <= r {
+        m := (l + r) / 2
+        if target > matrix[row][m] {
+            l = m + 1
+        } else if target < matrix[row][m] {
+            r = m - 1
+        } else {
+            return true
+        }
+    }
+    return false
+}
+```
+
+```kotlin
+class Solution {
+    fun searchMatrix(matrix: Array<IntArray>, target: Int): Boolean {
+        val rows = matrix.size
+        val cols = matrix[0].size
+        var top = 0
+        var bot = rows - 1
+
+        while (top <= bot) {
+            val row = (top + bot) / 2
+            if (target > matrix[row][cols - 1]) {
+                top = row + 1
+            } else if (target < matrix[row][0]) {
+                bot = row - 1
+            } else {
+                break
+            }
+        }
+
+        if (!(top <= bot)) return false
+        val row = (top + bot) / 2
+        var l = 0
+        var r = cols - 1
+        while (l <= r) {
+            val m = (l + r) / 2
+            if (target > matrix[row][m]) {
+                l = m + 1
+            } else if (target < matrix[row][m]) {
+                r = m - 1
+            } else {
+                return true
+            }
+        }
+        return false
+    }
+}
+```
+
+```swift
+class Solution {
+    func searchMatrix(_ matrix: [[Int]], _ target: Int) -> Bool {
+        let ROWS = matrix.count
+        let COLS = matrix[0].count
+
+        var top = 0, bot = ROWS - 1
+        while top <= bot {
+            let row = (top + bot) / 2
+            if target > matrix[row][COLS - 1] {
+                top = row + 1
+            } else if target < matrix[row][0] {
+                bot = row - 1
+            } else {
+                break
+            }
+        }
+
+        if !(top <= bot) {
+            return false
+        }
+        let row = (top + bot) / 2
+        var l = 0, r = COLS - 1
+        while l <= r {
+            let m = (l + r) / 2
+            if target > matrix[row][m] {
+                l = m + 1
+            } else if target < matrix[row][m] {
+                r = m - 1
+            } else {
+                return true
+            }
+        }
+        return false
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
-* Time complexity: $O(\log m + \log n)$
+* Time complexity: $O(\log m + \log n)$ (which reduces to $O(\log(m * n))$)
 * Space complexity: $O(1)$
 
 > Where $m$ is the number of rows and $n$ is the number of columns of matrix.
@@ -532,6 +747,76 @@ public class Solution {
 }
 ```
 
+```go
+func searchMatrix(matrix [][]int, target int) bool {
+    rows, cols := len(matrix), len(matrix[0])
+    l, r := 0, rows*cols-1
+
+    for l <= r {
+        m := l + (r-l)/2
+        row, col := m / cols, m % cols
+        if matrix[row][col] == target {
+            return true
+        } else if matrix[row][col] < target {
+            l = m + 1
+        } else {
+            r = m - 1
+        }
+    }
+    return false
+}
+```
+
+```kotlin
+class Solution {
+    fun searchMatrix(matrix: Array<IntArray>, target: Int): Boolean {
+        val rows = matrix.size
+        val cols = matrix[0].size
+        var l = 0
+        var r = rows * cols - 1
+
+        while (l <= r) {
+            val m = l + (r - l) / 2
+            val row = m / cols
+            val col = m % cols
+            if (matrix[row][col] == target) {
+                return true
+            } else if (matrix[row][col] < target) {
+                l = m + 1
+            } else {
+                r = m - 1
+            }
+        }
+        return false
+    }
+}
+```
+
+```swift
+class Solution {
+    func searchMatrix(_ matrix: [[Int]], _ target: Int) -> Bool {
+        let ROWS = matrix.count
+        let COLS = matrix[0].count
+
+        var l = 0, r = ROWS * COLS - 1
+        while l <= r {
+            let m = l + (r - l) / 2
+            let row = m / COLS
+            let col = m % COLS
+
+            if target > matrix[row][col] {
+                l = m + 1
+            } else if target < matrix[row][col] {
+                r = m - 1
+            } else {
+                return true
+            }
+        }
+        return false
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/search-for-word-ii.md b/articles/search-for-word-ii.md
index c28601fc0..519307f04 100644
--- a/articles/search-for-word-ii.md
+++ b/articles/search-for-word-ii.md
@@ -203,6 +203,132 @@ public class Solution {
 }
 ```
 
+```go
+func findWords(board [][]byte, words []string) []string {
+    var res []string
+    rows, cols := len(board), len(board[0])
+
+    var backtrack func(r, c int, i int, word string) bool
+    backtrack = func(r, c int, i int, word string) bool {
+        if i == len(word) {
+            return true
+        }
+        if r < 0 || c < 0 || r >= rows || c >= cols || board[r][c] != word[i] {
+            return false
+        }
+        board[r][c] = '*'
+        defer func() { board[r][c] = word[i] }()
+        return backtrack(r+1, c, i+1, word) ||
+            backtrack(r-1, c, i+1, word) ||
+            backtrack(r, c+1, i+1, word) ||
+            backtrack(r, c-1, i+1, word)
+    }
+
+    for _, word := range words {
+        found := false
+        for r := 0; r < rows; r++ {
+            if found {
+                break
+            }
+            for c := 0; c < cols; c++ {
+                if board[r][c] == word[0] && backtrack(r, c, 0, word) {
+                    res = append(res, word)
+                    found = true
+                    break
+                }
+            }
+        }
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun findWords(board: Array<CharArray>, words: Array<String>): List<String> {
+        val res = mutableListOf<String>()
+        val rows = board.size
+        val cols = board[0].size
+
+        fun backtrack(r: Int, c: Int, i: Int, word: String): Boolean {
+            if (i == word.length) return true
+            if (r < 0 || c < 0 || r >= rows || c >= cols || board[r][c] != word[i]) {
+                return false
+            }
+            board[r][c] = '*'
+            val ret = backtrack(r + 1, c, i + 1, word) ||
+                    backtrack(r - 1, c, i + 1, word) ||
+                    backtrack(r, c + 1, i + 1, word) ||
+                    backtrack(r, c - 1, i + 1, word)
+            board[r][c] = word[i]
+            return ret
+        }
+
+        for (word in words) {
+            var found = false
+            for (r in 0 until rows) {
+                if (found) break
+                for (c in 0 until cols) {
+                    if (board[r][c] == word[0] && backtrack(r, c, 0, word)) {
+                        res.add(word)
+                        found = true
+                        break
+                    }
+                }
+            }
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func findWords(_ board: [[Character]], _ words: [String]) -> [String] {
+        let ROWS = board.count
+        let COLS = board[0].count
+        var res: [String] = []
+        var board = board
+
+        func backtrack(_ r: Int, _ c: Int, _ i: Int, _ word: [Character]) -> Bool {
+            if i == word.count {
+                return true
+            }
+            if r < 0 || c < 0 || r >= ROWS || c >= COLS || board[r][c] != word[i] {
+                return false
+            }
+
+            board[r][c] = "*"
+            let ret = backtrack(r + 1, c, i + 1, word) ||
+                      backtrack(r - 1, c, i + 1, word) ||
+                      backtrack(r, c + 1, i + 1, word) ||
+                      backtrack(r, c - 1, i + 1, word)
+            board[r][c] = word[i]
+            return ret
+        }
+
+        for word in words {
+            var flag = false
+            let wordArray = Array(word)
+            for r in 0..<ROWS {
+                if flag { break }
+                for c in 0..<COLS {
+                    if board[r][c] != wordArray[0] {
+                        continue
+                    }
+                    if backtrack(r, c, 0, wordArray) {
+                        res.append(word)
+                        flag = true
+                        break
+                    }
+                }
+            }
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -268,7 +394,7 @@ class Solution:
 ```
 
 ```java
-public class TrieNode {
+class TrieNode {
     Map<Character, TrieNode> children;
     boolean isWord;
 
@@ -534,6 +660,198 @@ public class Solution {
 }
 ```
 
+```go
+type TrieNode struct {
+	children map[byte]*TrieNode
+	isWord   bool
+}
+
+func NewTrieNode() *TrieNode {
+	return &TrieNode{children: make(map[byte]*TrieNode)}
+}
+
+func (this *TrieNode) addWord(word string) {
+	cur := this
+	for i := 0; i < len(word); i++ {
+		c := word[i]
+		if _, found := cur.children[c]; !found {
+			cur.children[c] = NewTrieNode()
+		}
+		cur = cur.children[c]
+	}
+	cur.isWord = true
+}
+
+func findWords(board [][]byte, words []string) []string {
+    root := NewTrieNode()
+	for _, w := range words {
+		root.addWord(w)
+	}
+
+	rows, cols := len(board), len(board[0])
+	var res []string
+	visit := make(map[[2]int]bool)
+	wordSet := make(map[string]bool)
+
+	var dfs func(r, c int, node *TrieNode, word string)
+	dfs = func(r, c int, node *TrieNode, word string) {
+		if r < 0 || c < 0 || r >= rows || c >= cols || visit[[2]int{r, c}] || board[r][c] == 0 {
+			return
+		}
+
+		char := board[r][c]
+		nextNode, found := node.children[char]
+		if !found {
+			return
+		}
+
+		visit[[2]int{r, c}] = true
+		word += string(char)
+		if nextNode.isWord {
+			wordSet[word] = true
+		}
+
+		dfs(r+1, c, nextNode, word)
+		dfs(r-1, c, nextNode, word)
+		dfs(r, c+1, nextNode, word)
+		dfs(r, c-1, nextNode, word)
+
+		visit[[2]int{r, c}] = false
+	}
+
+	for r := 0; r < rows; r++ {
+		for c := 0; c < cols; c++ {
+			dfs(r, c, root, "")
+		}
+	}
+
+	for word := range wordSet {
+		res = append(res, word)
+	}
+	return res
+}
+```
+
+```kotlin
+class TrieNode {
+    val children = HashMap<Char, TrieNode>()
+    var isWord: Boolean = false
+
+    fun addWord(word: String) {
+        var cur = this
+        for (c in word) {
+            cur = cur.children.getOrPut(c) { TrieNode() }
+        }
+        cur.isWord = true
+    }
+}
+
+class Solution {
+    fun findWords(board: Array<CharArray>, words: Array<String>): List<String> {
+        val root = TrieNode()
+        for (w in words) {
+            root.addWord(w)
+        }
+
+        val rows = board.size
+        val cols = board[0].size
+        val res = HashSet<String>()
+        val visit = HashSet<Pair<Int, Int>>()
+
+        fun dfs(r: Int, c: Int, node: TrieNode, word: String) {
+            if (r < 0 || c < 0 || r >= rows || c >= cols || 
+               (r to c) in visit || board[r][c] !in node.children) {
+                return
+            }
+
+            visit.add(r to c)
+            val nextNode = node.children[board[r][c]]!!
+            val newWord = word + board[r][c]
+            if (nextNode.isWord) {
+                res.add(newWord)
+            }
+
+            dfs(r + 1, c, nextNode, newWord)
+            dfs(r - 1, c, nextNode, newWord)
+            dfs(r, c + 1, nextNode, newWord)
+            dfs(r, c - 1, nextNode, newWord)
+
+            visit.remove(r to c)
+        }
+
+        for (r in 0 until rows) {
+            for (c in 0 until cols) {
+                dfs(r, c, root, "")
+            }
+        }
+
+        return res.toList()
+    }
+}
+```
+
+```swift
+class TrieNode {
+    var children: [Character: TrieNode] = [:]
+    var isWord: Bool = false
+    
+    func addWord(_ word: String) {
+        var current = self
+        for char in word {
+            if current.children[char] == nil {
+                current.children[char] = TrieNode()
+            }
+            current = current.children[char]!
+        }
+        current.isWord = true
+    }
+}
+
+class Solution {
+    func findWords(_ board: [[Character]], _ words: [String]) -> [String] {
+        let root = TrieNode()
+        for word in words {
+            root.addWord(word)
+        }
+        
+        let ROWS = board.count
+        let COLS = board[0].count
+        var result = Set<String>()
+        var visited = Set<[Int]>()
+        
+        func dfs(_ r: Int, _ c: Int, _ node: TrieNode, _ word: String) {
+            if r < 0 || c < 0 || r >= ROWS || c >= COLS || 
+               visited.contains([r, c]) || node.children[board[r][c]] == nil {
+                return
+            }
+            
+            visited.insert([r, c])
+            let nextNode = node.children[board[r][c]]!
+            let newWord = word + String(board[r][c])
+            
+            if nextNode.isWord {
+                result.insert(newWord)
+            }
+            
+            dfs(r + 1, c, nextNode, newWord)
+            dfs(r - 1, c, nextNode, newWord)
+            dfs(r, c + 1, nextNode, newWord)
+            dfs(r, c - 1, nextNode, newWord)
+            
+            visited.remove([r, c])
+        }
+        
+        for r in 0..<ROWS {
+            for c in 0..<COLS {
+                dfs(r, c, root, "")
+            }
+        }
+        
+        return Array(result)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -615,7 +933,7 @@ class Solution:
 ```
 
 ```java
-public class TrieNode {
+class TrieNode {
     TrieNode[] children = new TrieNode[26];
     int idx = -1;
     int refs = 0;
@@ -933,6 +1251,234 @@ public class Solution {
 }
 ```
 
+```go
+type TrieNode struct {
+	children [26]*TrieNode
+	idx      int
+	refs     int
+}
+
+func NewTrieNode() *TrieNode {
+	return &TrieNode{idx: -1}
+}
+
+func (this *TrieNode) addWord(word string, i int) {
+	cur := this
+	cur.refs++
+	for _, ch := range word {
+		index := ch - 'a'
+		if cur.children[index] == nil {
+			cur.children[index] = NewTrieNode()
+		}
+		cur = cur.children[index]
+		cur.refs++
+	}
+	cur.idx = i
+}
+
+func findWords(board [][]byte, words []string) []string {
+    root := NewTrieNode()
+	for i, word := range words {
+		root.addWord(word, i)
+	}
+
+	rows, cols := len(board), len(board[0])
+	var res []string
+
+	getIndex := func(c byte) int { return int(c - 'a') }
+
+	var dfs func(r, c int, node *TrieNode)
+	dfs = func(r, c int, node *TrieNode) {
+		if r < 0 || c < 0 || r >= rows || c >= cols || 
+           board[r][c] == '*' || node.children[getIndex(board[r][c])] == nil {
+			return
+		}
+
+		tmp := board[r][c]
+		board[r][c] = '*'
+		prev := node
+		node = node.children[getIndex(tmp)]
+		if node.idx != -1 {
+			res = append(res, words[node.idx])
+			node.idx = -1
+			node.refs--
+			if node.refs == 0 {
+				prev.children[getIndex(tmp)] = nil
+				board[r][c] = tmp
+				return
+			}
+		}
+
+		dfs(r+1, c, node)
+		dfs(r-1, c, node)
+		dfs(r, c+1, node)
+		dfs(r, c-1, node)
+
+		board[r][c] = tmp
+	}
+
+	for r := 0; r < rows; r++ {
+		for c := 0; c < cols; c++ {
+			dfs(r, c, root)
+		}
+	}
+
+	return res
+}
+```
+
+```kotlin
+class TrieNode {
+    val children = Array<TrieNode?>(26) { null }
+    var idx = -1
+    var refs = 0
+
+    fun addWord(word: String, i: Int) {
+        var cur = this
+        cur.refs++
+        for (c in word) {
+            val index = c - 'a'
+            if (cur.children[index] == null) {
+                cur.children[index] = TrieNode()
+            }
+            cur = cur.children[index]!!
+            cur.refs++
+        }
+        cur.idx = i
+    }
+}
+
+class Solution {
+    fun findWords(board: Array<CharArray>, words: Array<String>): List<String> {
+        val root = TrieNode()
+        words.forEachIndexed { i, word -> root.addWord(word, i) }
+
+        val rows = board.size
+        val cols = board[0].size
+        val res = mutableListOf<String>()
+
+        fun getIndex(c: Char): Int = c - 'a'
+
+        fun dfs(r: Int, c: Int, node: TrieNode?) {
+            if (r < 0 || c < 0 || r >= rows || c >= cols || board[r][c] == '*' || 
+                node?.children?.get(getIndex(board[r][c])) == null) {
+                return
+            }
+
+            val tmp = board[r][c]
+            board[r][c] = '*'
+            val prev = node
+            val nextNode = node.children[getIndex(tmp)]
+
+            if (nextNode != null && nextNode.idx != -1) {
+                res.add(words[nextNode.idx])
+                nextNode.idx = -1
+                nextNode.refs--
+                if (nextNode.refs == 0) {
+                    prev?.children?.set(getIndex(tmp), null)
+                    board[r][c] = tmp
+                    return
+                }
+            }
+
+            dfs(r + 1, c, nextNode)
+            dfs(r - 1, c, nextNode)
+            dfs(r, c + 1, nextNode)
+            dfs(r, c - 1, nextNode)
+
+            board[r][c] = tmp
+        }
+
+        for (r in 0 until rows) {
+            for (c in 0 until cols) {
+                dfs(r, c, root)
+            }
+        }
+
+        return res
+    }
+}
+```
+
+```swift
+class TrieNode {
+    var children: [TrieNode?] = Array(repeating: nil, count: 26)
+    var idx: Int = -1
+    var refs: Int = 0
+    
+    func addWord(_ word: String, _ i: Int) {
+        var cur = self
+        cur.refs += 1
+        for c in word {
+            let index = Int(c.asciiValue! - Character("a").asciiValue!)
+            if cur.children[index] == nil {
+                cur.children[index] = TrieNode()
+            }
+            cur = cur.children[index]!
+            cur.refs += 1
+        }
+        cur.idx = i
+    }
+}
+
+class Solution {
+    func findWords(_ board: [[Character]], _ words: [String]) -> [String] {
+        let root = TrieNode()
+        for i in 0..<words.count {
+            root.addWord(words[i], i)
+        }
+        
+        let ROWS = board.count
+        let COLS = board[0].count
+        var res: [String] = []
+        var boardCopy = board
+        
+        func getIndex(_ c: Character) -> Int {
+            return Int(c.asciiValue! - Character("a").asciiValue!)
+        }
+        
+        func dfs(_ r: Int, _ c: Int, _ node: TrieNode) {
+            if r < 0 || c < 0 || r >= ROWS || c >= COLS || 
+               boardCopy[r][c] == "*" || 
+               node.children[getIndex(boardCopy[r][c])] == nil {
+                return
+            }
+            
+            let tmp = boardCopy[r][c]
+            boardCopy[r][c] = "*"
+            let prev = node
+            let nextNode = node.children[getIndex(tmp)]!
+            
+            if nextNode.idx != -1 {
+                res.append(words[nextNode.idx])
+                nextNode.idx = -1
+                nextNode.refs -= 1
+                if nextNode.refs == 0 {
+                    prev.children[getIndex(tmp)] = nil
+                    boardCopy[r][c] = tmp
+                    return
+                }
+            }
+            
+            dfs(r + 1, c, nextNode)
+            dfs(r - 1, c, nextNode)
+            dfs(r, c + 1, nextNode)
+            dfs(r, c - 1, nextNode)
+            
+            boardCopy[r][c] = tmp
+        }
+        
+        for r in 0..<ROWS {
+            for c in 0..<COLS {
+                dfs(r, c, root)
+            }
+        }
+        
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/search-for-word.md b/articles/search-for-word.md
index 08c253192..bb2895568 100644
--- a/articles/search-for-word.md
+++ b/articles/search-for-word.md
@@ -196,6 +196,116 @@ public class Solution {
 }
 ```
 
+```go
+func exist(board [][]byte, word string) bool {
+    rows, cols := len(board), len(board[0])
+    path := make(map[[2]int]bool)
+
+    var dfs func(r, c, i int) bool
+    dfs = func(r, c, i int) bool {
+        if i == len(word) {
+            return true
+        }
+        if r < 0 || c < 0 || r >= rows || c >= cols || 
+           board[r][c] != word[i] || path[[2]int{r, c}] {
+            return false
+        }
+
+        path[[2]int{r, c}] = true
+        res := dfs(r+1, c, i+1) || 
+               dfs(r-1, c, i+1) || 
+               dfs(r, c+1, i+1) || 
+               dfs(r, c-1, i+1)
+        delete(path, [2]int{r, c})
+
+        return res
+    }
+
+    for r := 0; r < rows; r++ {
+        for c := 0; c < cols; c++ {
+            if dfs(r, c, 0) {
+                return true
+            }
+        }
+    }
+    return false
+}
+```
+
+```kotlin
+class Solution {
+    fun exist(board: Array<CharArray>, word: String): Boolean {
+        val rows = board.size
+        val cols = board[0].size
+        val path = HashSet<Pair<Int, Int>>()
+
+        fun dfs(r: Int, c: Int, i: Int): Boolean {
+            if (i == word.length) return true
+            if (r < 0 || c < 0 || r >= rows || c >= cols || 
+                board[r][c] != word[i] || Pair(r, c) in path) {
+                return false
+            }
+
+            path.add(Pair(r, c))
+            val res = dfs(r + 1, c, i + 1) ||
+                      dfs(r - 1, c, i + 1) ||
+                      dfs(r, c + 1, i + 1) ||
+                      dfs(r, c - 1, i + 1)
+            path.remove(Pair(r, c))
+
+            return res
+        }
+
+        for (r in 0 until rows) {
+            for (c in 0 until cols) {
+                if (dfs(r, c, 0)) {
+                    return true
+                }
+            }
+        }
+        return false
+    }
+}
+```
+
+```swift
+class Solution {
+    func exist(_ board: [[Character]], _ word: String) -> Bool {
+        let ROWS = board.count
+        let COLS = board[0].count
+        var path = Set<[Int]>()
+        let wordArray = Array(word)
+
+        func dfs(_ r: Int, _ c: Int, _ i: Int) -> Bool {
+            if i == wordArray.count {
+                return true
+            }
+            if (r < 0 || c < 0 || r >= ROWS || c >= COLS ||
+                board[r][c] != wordArray[i] || path.contains([r, c])) {
+                return false
+            }
+
+            path.insert([r, c])
+            let res = dfs(r + 1, c, i + 1) ||
+                      dfs(r - 1, c, i + 1) ||
+                      dfs(r, c + 1, i + 1) ||
+                      dfs(r, c - 1, i + 1)
+            path.remove([r, c])
+            return res
+        }
+
+        for r in 0..<ROWS {
+            for c in 0..<COLS {
+                if dfs(r, c, 0) {
+                    return true
+                }
+            }
+        }
+        return false
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -404,6 +514,119 @@ public class Solution {
 }
 ```
 
+```go
+func exist(board [][]byte, word string) bool {
+    rows, cols := len(board), len(board[0])
+    visited := make([][]bool, rows)
+    for i := range visited {
+        visited[i] = make([]bool, cols)
+    }
+
+    var dfs func(r, c, i int) bool
+    dfs = func(r, c, i int) bool {
+        if i == len(word) {
+            return true
+        }
+        if r < 0 || c < 0 || r >= rows || c >= cols || 
+           board[r][c] != word[i] || visited[r][c] {
+            return false
+        }
+
+        visited[r][c] = true
+        res := dfs(r+1, c, i+1) || 
+               dfs(r-1, c, i+1) || 
+               dfs(r, c+1, i+1) || 
+               dfs(r, c-1, i+1)
+        visited[r][c] = false
+
+        return res
+    }
+
+    for r := 0; r < rows; r++ {
+        for c := 0; c < cols; c++ {
+            if dfs(r, c, 0) {
+                return true
+            }
+        }
+    }
+    return false
+}
+```
+
+```kotlin
+class Solution {
+    fun exist(board: Array<CharArray>, word: String): Boolean {
+        val rows = board.size
+        val cols = board[0].size
+        val visited = Array(rows) { BooleanArray(cols) }
+
+        fun dfs(r: Int, c: Int, i: Int): Boolean {
+            if (i == word.length) return true
+            if (r < 0 || c < 0 || r >= rows || c >= cols || 
+                board[r][c] != word[i] || visited[r][c]) {
+                return false
+            }
+
+            visited[r][c] = true
+            val res = dfs(r + 1, c, i + 1) || 
+                      dfs(r - 1, c, i + 1) ||
+                      dfs(r, c + 1, i + 1) || 
+                      dfs(r, c - 1, i + 1)
+            visited[r][c] = false
+
+            return res
+        }
+
+        for (r in 0 until rows) {
+            for (c in 0 until cols) {
+                if (dfs(r, c, 0)) {
+                    return true
+                }
+            }
+        }
+        return false
+    }
+}
+```
+
+```swift
+class Solution {
+    func exist(_ board: [[Character]], _ word: String) -> Bool {
+        let ROWS = board.count
+        let COLS = board[0].count
+        var visited = Array(repeating: Array(repeating: false, count: COLS), count: ROWS)
+        let wordArray = Array(word)
+
+        func dfs(_ r: Int, _ c: Int, _ i: Int) -> Bool {
+            if i == wordArray.count {
+                return true
+            }
+            if (r < 0 || c < 0 || r >= ROWS || c >= COLS ||
+                board[r][c] != wordArray[i] || visited[r][c]) {
+                return false
+            }
+
+            visited[r][c] = true
+            let res = dfs(r + 1, c, i + 1) ||
+                      dfs(r - 1, c, i + 1) ||
+                      dfs(r, c + 1, i + 1) ||
+                      dfs(r, c - 1, i + 1)
+            visited[r][c] = false
+            return res
+        }
+
+        for r in 0..<ROWS {
+            for c in 0..<COLS {
+                if dfs(r, c, 0) {
+                    return true
+                }
+            }
+        }
+        return false
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -598,6 +821,117 @@ public class Solution {
 }
 ```
 
+```go
+func exist(board [][]byte, word string) bool {
+    rows, cols := len(board), len(board[0])
+
+    var dfs func(r, c, i int) bool
+    dfs = func(r, c, i int) bool {
+        if i == len(word) {
+            return true
+        }
+        if r < 0 || c < 0 || r >= rows || c >= cols || 
+           board[r][c] != word[i] || board[r][c] == '#' {
+            return false
+        }
+
+        temp := board[r][c]
+        board[r][c] = '#'
+        res := dfs(r+1, c, i+1) || 
+               dfs(r-1, c, i+1) || 
+               dfs(r, c+1, i+1) || 
+               dfs(r, c-1, i+1)
+        board[r][c] = temp
+
+        return res
+    }
+
+    for r := 0; r < rows; r++ {
+        for c := 0; c < cols; c++ {
+            if dfs(r, c, 0) {
+                return true
+            }
+        }
+    }
+    return false
+}
+```
+
+```kotlin
+class Solution {
+    fun exist(board: Array<CharArray>, word: String): Boolean {
+        val rows = board.size
+        val cols = board[0].size
+
+        fun dfs(r: Int, c: Int, i: Int): Boolean {
+            if (i == word.length) return true
+            if (r < 0 || c < 0 || r >= rows || c >= cols || 
+                board[r][c] != word[i] || board[r][c] == '#') {
+                return false
+            }
+
+            val temp = board[r][c]
+            board[r][c] = '#'
+            val res = dfs(r + 1, c, i + 1) || 
+                      dfs(r - 1, c, i + 1) ||
+                      dfs(r, c + 1, i + 1) || 
+                      dfs(r, c - 1, i + 1)
+            board[r][c] = temp
+
+            return res
+        }
+
+        for (r in 0 until rows) {
+            for (c in 0 until cols) {
+                if (dfs(r, c, 0)) {
+                    return true
+                }
+            }
+        }
+        return false
+    }
+}
+```
+
+```swift
+class Solution {
+    func exist(_ board: [[Character]], _ word: String) -> Bool {
+        let ROWS = board.count
+        let COLS = board[0].count
+        let wordArray = Array(word)
+        var board = board
+
+        func dfs(_ r: Int, _ c: Int, _ i: Int) -> Bool {
+            if i == wordArray.count {
+                return true
+            }
+            if (r < 0 || c < 0 || r >= ROWS || c >= COLS ||
+                board[r][c] != wordArray[i] || board[r][c] == "#") {
+                return false
+            }
+
+            let temp = board[r][c]
+            board[r][c] = "#"
+            let res = dfs(r + 1, c, i + 1) ||
+                      dfs(r - 1, c, i + 1) ||
+                      dfs(r, c + 1, i + 1) ||
+                      dfs(r, c - 1, i + 1)
+            board[r][c] = temp
+            return res
+        }
+
+        for r in 0..<ROWS {
+            for c in 0..<COLS {
+                if dfs(r, c, 0) {
+                    return true
+                }
+            }
+        }
+        return false
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/search-in-a-binary-search-tree.md b/articles/search-in-a-binary-search-tree.md
new file mode 100644
index 000000000..548c56821
--- /dev/null
+++ b/articles/search-in-a-binary-search-tree.md
@@ -0,0 +1,205 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def searchBST(self, root: Optional[TreeNode], val: int) -> Optional[TreeNode]:
+        if not root or root.val == val:
+            return root
+        return self.searchBST(root.left, val) if val < root.val else self.searchBST(root.right, val)
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode searchBST(TreeNode root, int val) {
+        if (root == null || root.val == val) {
+            return root;
+        }
+        return val < root.val ? searchBST(root.left, val) : searchBST(root.right, val);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    TreeNode* searchBST(TreeNode* root, int val) {
+        if (!root || root->val == val) {
+            return root;
+        }
+        return val < root->val ? searchBST(root->left, val) : searchBST(root->right, val);
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @param {number} val
+     * @return {TreeNode}
+     */
+    searchBST(root, val) {
+        if (!root || root.val === val) {
+            return root;
+        }
+        return val < root.val ? this.searchBST(root.left, val) : this.searchBST(root.right, val);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(H)$
+* Space complexity: $O(H)$ for recursion stack.
+
+> Where $H$ is the height of the given tree.
+
+---
+
+## 2. Iteration
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def searchBST(self, root: Optional[TreeNode], val: int) -> Optional[TreeNode]:
+        while root and root.val != val:
+            root = root.left if val < root.val else root.right
+        return root
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode searchBST(TreeNode root, int val) {
+        while (root != null && root.val != val) {
+            root = val < root.val ? root.left : root.right;
+        }
+        return root;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    TreeNode* searchBST(TreeNode* root, int val) {
+        while (root && root->val != val) {
+            root = val < root->val ? root->left : root->right;
+        }
+        return root;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @param {number} val
+     * @return {TreeNode}
+     */
+    searchBST(root, val) {
+        while (root != null && root.val != val) {
+            root = val < root.val ? root.left : root.right;
+        }
+        return root;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(H)$
+* Space complexity: $O(1)$ extra space.
+
+> Where $H$ is the height of the given tree.
\ No newline at end of file
diff --git a/articles/search-in-rotated-sorted-array-ii.md b/articles/search-in-rotated-sorted-array-ii.md
new file mode 100644
index 000000000..04af02db0
--- /dev/null
+++ b/articles/search-in-rotated-sorted-array-ii.md
@@ -0,0 +1,246 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def search(self, nums: List[int], target: int) -> bool:
+        return target in nums
+```
+
+```java
+public class Solution {
+    public boolean search(int[] nums, int target) {
+        for (int num : nums) {
+            if (num == target) {
+                return true;
+            }
+        }
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool search(vector<int>& nums, int target) {
+        for (int& num : nums) {
+            if (num == target) {
+                return true;
+            }
+        }
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} target
+     * @return {boolean}
+     */
+    search(nums, target) {
+        for (let num of nums) {
+            if (num === target) {
+                return true;
+            }
+        }
+        return false;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool Search(int[] nums, int target) {
+        return nums.Contains(target);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Binary Search
+
+::tabs-start
+
+```python
+class Solution:
+    def search(self, nums: List[int], target: int) -> bool:
+        l, r = 0, len(nums) - 1
+        while l <= r:
+            m = l + (r - l) // 2
+            if nums[m] == target:
+                return True
+
+            if nums[l] < nums[m]:  # Left portion
+                if nums[l] <= target < nums[m]:
+                    r = m - 1
+                else:
+                    l = m + 1
+            elif nums[l] > nums[m]:  # Right portion
+                if nums[m] < target <= nums[r]:
+                    l = m + 1
+                else:
+                    r = m - 1
+            else:
+                l += 1
+
+        return False
+```
+
+```java
+public class Solution {
+    public boolean search(int[] nums, int target) {
+        int l = 0, r = nums.length - 1;
+
+        while (l <= r) {
+            int m = l + (r - l) / 2;
+
+            if (nums[m] == target) {
+                return true;
+            }
+
+            if (nums[l] < nums[m]) { // Left portion
+                if (nums[l] <= target && target < nums[m]) {
+                    r = m - 1;
+                } else {
+                    l = m + 1;
+                }
+            } else if (nums[l] > nums[m]) { // Right portion
+                if (nums[m] < target && target <= nums[r]) {
+                    l = m + 1;
+                } else {
+                    r = m - 1;
+                }
+            } else {
+                l++;
+            }
+        }
+
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool search(vector<int>& nums, int target) {
+        int l = 0, r = nums.size() - 1;
+
+        while (l <= r) {
+            int m = l + (r - l) / 2;
+
+            if (nums[m] == target) {
+                return true;
+            }
+
+            if (nums[l] < nums[m]) { // Left portion
+                if (nums[l] <= target && target < nums[m]) {
+                    r = m - 1;
+                } else {
+                    l = m + 1;
+                }
+            } else if (nums[l] > nums[m]) { // Right portion
+                if (nums[m] < target && target <= nums[r]) {
+                    l = m + 1;
+                } else {
+                    r = m - 1;
+                }
+            } else {
+                l++;
+            }
+        }
+
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} target
+     * @return {boolean}
+     */
+    search(nums, target) {
+        let l = 0, r = nums.length - 1;
+
+        while (l <= r) {
+            const m = Math.floor(l + (r - l) / 2);
+
+            if (nums[m] === target) {
+                return true;
+            }
+
+            if (nums[l] < nums[m]) { // Left portion
+                if (nums[l] <= target && target < nums[m]) {
+                    r = m - 1;
+                } else {
+                    l = m + 1;
+                }
+            } else if (nums[l] > nums[m]) { // Right portion
+                if (nums[m] < target && target <= nums[r]) {
+                    l = m + 1;
+                } else {
+                    r = m - 1;
+                }
+            } else {
+                l++;
+            }
+        }
+
+        return false;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool Search(int[] nums, int target) {
+        int l = 0, r = nums.Length - 1;
+        while (l <= r) {
+            int m = l + (r - l) / 2;
+            if (nums[m] == target) {
+                return true;
+            }
+
+            if (nums[l] < nums[m]) {
+                if (nums[l] <= target && target < nums[m]) {
+                    r = m - 1;
+                } else {
+                    l = m + 1;
+                }
+            } else if (nums[l] > nums[m]) {
+                if (nums[m] < target && target <= nums[r]) {
+                    l = m + 1;
+                } else {
+                    r = m - 1;
+                }
+            } else {
+                l++;
+            }
+        }
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$ in average case, $O(n)$ in worst case.
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/search-insert-position.md b/articles/search-insert-position.md
new file mode 100644
index 000000000..7e6cbd60e
--- /dev/null
+++ b/articles/search-insert-position.md
@@ -0,0 +1,483 @@
+## 1. Linear Search
+
+::tabs-start
+
+```python
+class Solution:
+    def searchInsert(self, nums: List[int], target: int) -> int:
+        for i in range(len(nums)):
+            if nums[i] >= target:
+                return i
+        return len(nums)
+```
+
+```java
+public class Solution {
+    public int searchInsert(int[] nums, int target) {
+        for (int i = 0; i < nums.length; i++) {
+            if (nums[i] >= target) {
+                return i;
+            }
+        }
+        return nums.length;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int searchInsert(vector<int>& nums, int target) {
+        for (int i = 0; i < nums.size(); i++) {
+            if (nums[i] >= target) {
+                return i;
+            }
+        }
+        return nums.size();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} target
+     * @return {number}
+     */
+    searchInsert(nums, target) {
+        for (let i = 0; i < nums.length; i++) {
+            if (nums[i] >= target) {
+                return i;
+            }
+        }
+        return nums.length;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int SearchInsert(int[] nums, int target) {
+        for (int i = 0; i < nums.Length; i++) {
+            if (nums[i] >= target) {
+                return i;
+            }
+        }
+        return nums.Length;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 2. Binary Search - I
+
+::tabs-start
+
+```python
+class Solution:
+    def searchInsert(self, nums: List[int], target: int) -> int:
+        res = len(nums)
+        l, r = 0, len(nums) - 1
+        while l <= r:
+            mid = (l + r) // 2
+            if nums[mid] == target:
+                return mid
+            if nums[mid] > target:
+                res = mid
+                r = mid - 1
+            else:
+                l = mid + 1
+        return res
+```
+
+```java
+public class Solution {
+    public int searchInsert(int[] nums, int target) {
+        int res = nums.length;
+        int l = 0, r = nums.length - 1;
+        while (l <= r) {
+            int mid = (l + r) / 2;
+            if (nums[mid] == target) {
+                return mid;
+            }
+            if (nums[mid] > target) {
+                res = mid;
+                r = mid - 1;
+            } else {
+                l = mid + 1;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int searchInsert(vector<int>& nums, int target) {
+        int res = nums.size();
+        int l = 0, r = nums.size() - 1;
+        while (l <= r) {
+            int mid = (l + r) / 2;
+            if (nums[mid] == target) {
+                return mid;
+            }
+            if (nums[mid] > target) {
+                res = mid;
+                r = mid - 1;
+            } else {
+                l = mid + 1;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} target
+     * @return {number}
+     */
+    searchInsert(nums, target) {
+        let res = nums.length;
+        let l = 0, r = nums.length - 1;
+        while (l <= r) {
+            const mid = Math.floor((l + r) / 2);
+            if (nums[mid] === target) {
+                return mid;
+            }
+            if (nums[mid] > target) {
+                res = mid;
+                r = mid - 1;
+            } else {
+                l = mid + 1;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int SearchInsert(int[] nums, int target) {
+        int res = nums.Length;
+        int l = 0, r = nums.Length - 1;
+
+        while (l <= r) {
+            int mid = (l + r) / 2;
+            if (nums[mid] == target) {
+                return mid;
+            }
+            if (nums[mid] > target) {
+                res = mid;
+                r = mid - 1;
+            } else {
+                l = mid + 1;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 3. Binary Search - II
+
+::tabs-start
+
+```python
+class Solution:
+    def searchInsert(self, nums: List[int], target: int) -> int:
+        l, r = 0, len(nums) - 1
+        while l <= r:
+            mid = (l + r) // 2
+            if nums[mid] == target:
+                return mid
+            if nums[mid] > target:
+                r = mid - 1
+            else:
+                l = mid + 1
+        return l
+```
+
+```java
+public class Solution {
+    public int searchInsert(int[] nums, int target) {
+        int l = 0, r = nums.length - 1;
+        while (l <= r) {
+            int mid = (l + r) / 2;
+            if (nums[mid] == target) {
+                return mid;
+            }
+            if (nums[mid] > target) {
+                r = mid - 1;
+            } else {
+                l = mid + 1;
+            }
+        }
+        return l;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int searchInsert(vector<int>& nums, int target) {
+        int l = 0, r = nums.size() - 1;
+        while (l <= r) {
+            int mid = (l + r) / 2;
+            if (nums[mid] == target) {
+                return mid;
+            }
+            if (nums[mid] > target) {
+                r = mid - 1;
+            } else {
+                l = mid + 1;
+            }
+        }
+        return l;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} target
+     * @return {number}
+     */
+    searchInsert(nums, target) {
+        let l = 0, r = nums.length - 1;
+        while (l <= r) {
+            const mid = Math.floor((l + r) / 2);
+            if (nums[mid] === target) {
+                return mid;
+            }
+            if (nums[mid] > target) {
+                r = mid - 1;
+            } else {
+                l = mid + 1;
+            }
+        }
+        return l;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int SearchInsert(int[] nums, int target) {
+        int l = 0, r = nums.Length - 1;
+
+        while (l <= r) {
+            int mid = (l + r) / 2;
+            if (nums[mid] == target) {
+                return mid;
+            }
+            if (nums[mid] > target) {
+                r = mid - 1;
+            } else {
+                l = mid + 1;
+            }
+        }
+
+        return l;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 4. Binary Search (Lower Bound)
+
+::tabs-start
+
+```python
+class Solution:
+    def searchInsert(self, nums: List[int], target: int) -> int:
+        l, r = 0, len(nums)
+        while l < r:
+            m = l + ((r - l) // 2)  
+            if nums[m] >= target:
+                r = m
+            elif nums[m] < target:
+                l = m + 1
+        return l
+```
+
+```java
+public class Solution {
+    public int searchInsert(int[] nums, int target) {
+        int l = 0, r = nums.length;
+        while (l < r) {
+            int m = l + (r - l) / 2;
+            if (nums[m] >= target) {
+                r = m;
+            } else {
+                l = m + 1;
+            }
+        }
+        return l;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int searchInsert(vector<int>& nums, int target) {
+        int l = 0, r = nums.size();
+        while (l < r) {
+            int m = l + (r - l) / 2;
+            if (nums[m] >= target) {
+                r = m;
+            } else {
+                l = m + 1;
+            }
+        }
+        return l;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} target
+     * @return {number}
+     */
+    searchInsert(nums, target) {
+        let l = 0, r = nums.length;
+        while (l < r) {
+            let m = l + Math.floor((r - l) / 2);
+            if (nums[m] >= target) {
+                r = m;
+            } else {
+                l = m + 1;
+            }
+        }
+        return l;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int SearchInsert(int[] nums, int target) {
+        int l = 0, r = nums.Length;
+
+        while (l < r) {
+            int m = l + (r - l) / 2;
+            if (nums[m] >= target) {
+                r = m;
+            } else {
+                l = m + 1;
+            }
+        }
+
+        return l;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
+
+---
+
+## 5. Built-In Binary Search Function
+
+::tabs-start
+
+```python
+import bisect
+class Solution:
+    def searchInsert(self, nums: List[int], target: int) -> int:
+        return bisect.bisect_left(nums, target)
+```
+
+```java
+public class Solution {
+    public int searchInsert(int[] nums, int target) {
+        int index = Arrays.binarySearch(nums, target);
+        return index >= 0 ? index : -index - 1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int searchInsert(vector<int>& nums, int target) {
+        return lower_bound(nums.begin(), nums.end(), target) - nums.begin();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} target
+     * @return {number}
+     */
+    searchInsert(nums, target) {
+        // There is no built in Binary Search function for JS.
+        let index = nums.findIndex(x => x >= target);
+        return index !== -1 ? index : nums.length
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int SearchInsert(int[] nums, int target) {
+        int idx = Array.BinarySearch(nums, target);
+        return idx >= 0 ? idx : ~idx;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/search-suggestions-system.md b/articles/search-suggestions-system.md
new file mode 100644
index 000000000..87325be56
--- /dev/null
+++ b/articles/search-suggestions-system.md
@@ -0,0 +1,589 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def suggestedProducts(self, products: List[str], searchWord: str) -> List[List[str]]:
+        res = []
+        m = len(searchWord)
+        products.sort()
+
+        for i in range(m):
+            cur = []
+            for w in products:
+                if len(w) <= i:
+                    continue
+
+                flag = True
+                for j in range(i + 1):
+                    if w[j] != searchWord[j]:
+                        flag = False
+                        break
+
+                if flag:
+                    cur.append(w)
+                    if len(cur) == 3:
+                        break
+            
+            if not cur:
+                for j in range(i, m):
+                    res.append([])
+                break
+            res.append(cur)
+
+        return res
+```
+
+```java
+public class Solution {
+    public List<List<String>> suggestedProducts(String[] products, String searchWord) {
+        List<List<String>> res = new ArrayList<>();
+        int m = searchWord.length();
+        Arrays.sort(products);
+
+        for (int i = 0; i < m; i++) {
+            List<String> cur = new ArrayList<>();
+            for (String w : products) {
+                if (w.length() <= i) continue;
+
+                boolean flag = true;
+                for (int j = 0; j <= i; j++) {
+                    if (w.charAt(j) != searchWord.charAt(j)) {
+                        flag = false;
+                        break;
+                    }
+                }
+
+                if (flag) {
+                    cur.add(w);
+                    if (cur.size() == 3) break;
+                }
+            }
+
+            if (cur.isEmpty()) {
+                while (i < m) {
+                    res.add(new ArrayList<>());
+                    i++;
+                }
+                break;
+            }
+
+            res.add(cur);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<string>> suggestedProducts(vector<string>& products, string searchWord) {
+        vector<vector<string>> res;
+        int m = searchWord.size();
+        sort(products.begin(), products.end());
+
+        for (int i = 0; i < m; i++) {
+            vector<string> cur;
+            for (const string& w : products) {
+                if (w.size() <= i) continue;
+
+                bool flag = true;
+                for (int j = 0; j <= i; j++) {
+                    if (w[j] != searchWord[j]) {
+                        flag = false;
+                        break;
+                    }
+                }
+
+                if (flag) {
+                    cur.push_back(w);
+                    if (cur.size() == 3) break;
+                }
+            }
+
+            if (cur.empty()) {
+                while (i < m) {
+                    res.push_back({});
+                    i++;
+                }
+                break;
+            }
+
+            res.push_back(cur);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} products
+     * @param {string} searchWord
+     * @return {string[][]}
+     */
+    suggestedProducts(products, searchWord) {
+        let res = [];
+        let m = searchWord.length;
+        products.sort();
+
+        for (let i = 0; i < m; i++) {
+            let cur = [];
+            for (let w of products) {
+                if (w.length <= i) continue;
+
+                let flag = true;
+                for (let j = 0; j <= i; j++) {
+                    if (w[j] !== searchWord[j]) {
+                        flag = false;
+                        break;
+                    }
+                }
+
+                if (flag) {
+                    cur.push(w);
+                    if (cur.length === 3) break;
+                }
+            }
+
+            if (cur.length === 0) {
+                while (i < m) {
+                    res.push([]);
+                    i++;
+                }
+                break;
+            }
+
+            res.push(cur);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n + m * n)$
+* Space complexity:
+    * $O(n)$ or $O(1)$ space for the sorting algorithm.
+    * $O(m * w)$ space for the output array.
+
+> Where $n$ is the total number of characters in the string array $products$, $m$ is the length of the string $searchWord$, and $w$ is the average length of each word in the given string array.
+
+---
+
+## 2. Sorting + Binary Search
+
+::tabs-start
+
+```python
+class Solution:
+    def suggestedProducts(self, products: List[str], searchWord: str) -> List[List[str]]:
+        res = []
+        m = len(searchWord)
+        products.sort()
+
+        prefix = []
+        start = 0
+
+        def binary_search(target, start):
+            l, r = start, len(products)
+            while l < r:
+                mid = l + (r - l) // 2
+                if products[mid] >= target:
+                    r = mid
+                else:
+                    l = mid + 1
+            return l
+
+        for i in range(m):
+            prefix.append(searchWord[i])
+            start = binary_search("".join(prefix), start)
+
+            cur = []
+            for j in range(start, min(start + 3, len(products))):
+                if products[j].startswith("".join(prefix)):
+                    cur.append(products[j])
+                else:
+                    break
+
+            res.append(cur)
+
+        return res
+```
+
+```java
+public class Solution {
+    public List<List<String>> suggestedProducts(String[] products, String searchWord) {
+        List<List<String>> res = new ArrayList<>();
+        int m = searchWord.length();
+        Arrays.sort(products);
+
+        StringBuilder prefix = new StringBuilder();
+        int start = 0;
+
+        for (int i = 0; i < m; i++) {
+            prefix.append(searchWord.charAt(i));
+            start = binarySearch(products, prefix.toString(), start);
+
+            List<String> cur = new ArrayList<>();
+            for (int j = start; j < Math.min(start + 3, products.length); j++) {
+                if (products[j].startsWith(prefix.toString())) {
+                    cur.add(products[j]);
+                } else {
+                    break;
+                }
+            }
+
+            res.add(cur);
+        }
+
+        return res;
+    }
+
+    private int binarySearch(String[] products, String target, int start) {
+        int l = start, r = products.length;
+        while (l < r) {
+            int mid = l + (r - l) / 2;
+            if (products[mid].compareTo(target) >= 0) {
+                r = mid;
+            } else {
+                l = mid + 1;
+            }
+        }
+        return l;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<string>> suggestedProducts(vector<string>& products, string searchWord) {
+        vector<vector<string>> res;
+        int m = searchWord.size();
+        sort(products.begin(), products.end());
+
+        string prefix = "";
+        int start = 0;
+
+        for (int i = 0; i < m; i++) {
+            prefix += searchWord[i];
+            start = binarySearch(products, prefix, start);
+
+            vector<string> cur;
+            for (int j = start; j < min(start + 3, (int)products.size()); j++) {
+                if (products[j].substr(0, prefix.size()) == prefix) {
+                    cur.push_back(products[j]);
+                } else {
+                    break;
+                }
+            }
+
+            res.push_back(cur);
+        }
+
+        return res;
+    }
+
+private:
+    int binarySearch(vector<string>& products, string target, int start) {
+        int l = start, r = products.size();
+        while (l < r) {
+            int mid = l + (r - l) / 2;
+            if (products[mid] >= target) {
+                r = mid;
+            } else {
+                l = mid + 1;
+            }
+        }
+        return l;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} products
+     * @param {string} searchWord
+     * @return {string[][]}
+     */
+    suggestedProducts(products, searchWord) {
+        let res = [];
+        let m = searchWord.length;
+        products.sort();
+
+        let prefix = [];
+        let start = 0;
+
+        for (let i = 0; i < m; i++) {
+            prefix.push(searchWord[i]);
+            start = this.binarySearch(products, prefix.join(""), start);
+
+            let cur = [];
+            for (let j = start; j < Math.min(start + 3, products.length); j++) {
+                if (products[j].startsWith(prefix.join(""))) {
+                    cur.push(products[j]);
+                } else {
+                    break;
+                }
+            }
+
+            res.push(cur);
+        }
+
+        return res;
+    }
+
+    /**
+     * @param {string[]} products
+     * @param {string} target
+     * @param {number} start
+     * @return {number}
+     */
+    binarySearch(products, target, start) {
+        let l = start, r = products.length;
+        while (l < r) {
+            let mid = Math.floor(l + (r - l) / 2);
+            if (products[mid] >= target) {
+                r = mid;
+            } else {
+                l = mid + 1;
+            }
+        }
+        return l;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n + m * w * \log N)$
+* Space complexity:
+    * $O(n)$ or $O(1)$ space for the sorting algorithm.
+    * $O(m * w)$ space for the output array.
+
+> Where $n$ is the total number of characters in the string array $products$, $N$ is the size of the array $products$, $m$ is the length of the string $searchWord$, and $w$ is the average length of each word in the given string array.
+
+---
+
+## 3. Sorting + Binary Search (Built-In Function)
+
+::tabs-start
+
+```python
+class Solution:
+    def suggestedProducts(self, products: List[str], searchWord: str) -> List[List[str]]:
+        res = []
+        m = len(searchWord)
+        products.sort()
+
+        prefix = ""
+        start = 0
+        for i in range(m):
+            prefix += searchWord[i]
+            start = bisect_left(products, prefix, start)
+            
+            cur = []
+            for j in range(start, min(start + 3, len(products))):
+                if products[j].startswith(prefix):
+                    cur.append(products[j])
+                else:
+                    break
+
+            res.append(cur)
+
+        return res
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<string>> suggestedProducts(vector<string>& products, string searchWord) {
+        vector<vector<string>> res;
+        int m = searchWord.size();
+        sort(products.begin(), products.end());
+
+        string prefix = "";
+        int start = 0;
+        for (int i = 0; i < m; i++) {
+            prefix += searchWord[i];
+            start = lower_bound(products.begin() + start, products.end(), prefix) - products.begin();
+
+            vector<string> cur;
+            for (int j = start; j < min(start + 3, (int)products.size()); j++) {
+                if (products[j].find(prefix) == 0) {
+                    cur.push_back(products[j]);
+                } else {
+                    break;
+                }
+            }
+
+            res.push_back(cur);
+        }
+
+        return res;
+    }
+};
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n + m * w * \log N)$
+* Space complexity:
+    * $O(n)$ or $O(1)$ space for the sorting algorithm.
+    * $O(m * w)$ space for the output array.
+
+> Where $n$ is the total number of characters in the string array $products$, $N$ is the size of the array $products$, $m$ is the length of the string $searchWord$, and $w$ is the average length of each word in the given string array.
+
+---
+
+## 4. Sorting + Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def suggestedProducts(self, products: List[str], searchWord: str) -> List[List[str]]:
+        res = []
+        products.sort()
+
+        l, r = 0, len(products) - 1
+        for i in range(len(searchWord)):
+            c = searchWord[i]
+
+            while l <= r and (len(products[l]) <= i or products[l][i] != c):
+                l += 1
+            while l <= r and (len(products[r]) <= i or products[r][i] != c):
+                r -= 1
+
+            res.append([])
+            remain = r - l + 1
+            for j in range(min(3, remain)):
+                res[-1].append(products[l + j])
+
+        return res
+```
+
+```java
+public class Solution {
+    public List<List<String>> suggestedProducts(String[] products, String searchWord) {
+        List<List<String>> res = new ArrayList<>();
+        Arrays.sort(products);
+
+        int l = 0, r = products.length - 1;
+        for (int i = 0; i < searchWord.length(); i++) {
+            char c = searchWord.charAt(i);
+
+            while (l <= r && (products[l].length() <= i || products[l].charAt(i) != c)) {
+                l++;
+            }
+            while (l <= r && (products[r].length() <= i || products[r].charAt(i) != c)) {
+                r--;
+            }
+
+            List<String> cur = new ArrayList<>();
+            int remain = r - l + 1;
+            for (int j = 0; j < Math.min(3, remain); j++) {
+                cur.add(products[l + j]);
+            }
+
+            res.add(cur);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<string>> suggestedProducts(vector<string>& products, string searchWord) {
+        vector<vector<string>> res;
+        sort(products.begin(), products.end());
+
+        int l = 0, r = products.size() - 1;
+        for (int i = 0; i < searchWord.size(); i++) {
+            char c = searchWord[i];
+
+            while (l <= r && (products[l].size() <= i || products[l][i] != c)) {
+                l++;
+            }
+            while (l <= r && (products[r].size() <= i || products[r][i] != c)) {
+                r--;
+            }
+
+            vector<string> cur;
+            int remain = r - l + 1;
+            for (int j = 0; j < min(3, remain); j++) {
+                cur.push_back(products[l + j]);
+            }
+
+            res.push_back(cur);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} products
+     * @param {string} searchWord
+     * @return {string[][]}
+     */
+    suggestedProducts(products, searchWord) {
+        let res = [];
+        products.sort();
+
+        let l = 0, r = products.length - 1;
+        for (let i = 0; i < searchWord.length; i++) {
+            let c = searchWord[i];
+
+            while (l <= r && (products[l].length <= i || products[l][i] !== c)) {
+                l++;
+            }
+            while (l <= r && (products[r].length <= i || products[r][i] !== c)) {
+                r--;
+            }
+
+            let cur = [];
+            let remain = r - l + 1;
+            for (let j = 0; j < Math.min(3, remain); j++) {
+                cur.push(products[l + j]);
+            }
+
+            res.push(cur);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n + m * w + N)$
+* Space complexity:
+    * $O(n)$ or $O(1)$ space for the sorting algorithm.
+    * $O(m * w)$ space for the output array.
+
+> Where $n$ is the total number of characters in the string array $products$, $N$ is the size of the array $products$, $m$ is the length of the string $searchWord$, and $w$ is the average length of each word in the given string array.
\ No newline at end of file
diff --git a/articles/seat-reservation-manager.md b/articles/seat-reservation-manager.md
new file mode 100644
index 000000000..c546e1be8
--- /dev/null
+++ b/articles/seat-reservation-manager.md
@@ -0,0 +1,407 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class SeatManager:
+
+    def __init__(self, n: int):
+        self.seats = [False] * n
+
+    def reserve(self) -> int:
+        for i in range(len(self.seats)):
+            if not self.seats[i]:
+                self.seats[i] = True
+                return i + 1
+
+    def unreserve(self, seatNumber: int) -> None:
+        self.seats[seatNumber - 1] = False
+```
+
+```java
+public class SeatManager {
+    private boolean[] seats;
+
+    public SeatManager(int n) {
+        seats = new boolean[n];
+    }
+
+    public int reserve() {
+        for (int i = 0; i < seats.length; i++) {
+            if (!seats[i]) {
+                seats[i] = true;
+                return i + 1;
+            }
+        }
+        return -1;
+    }
+
+    public void unreserve(int seatNumber) {
+        seats[seatNumber - 1] = false;
+    }
+}
+```
+
+```cpp
+class SeatManager {
+private:
+    vector<bool> seats;
+
+public:
+    SeatManager(int n) : seats(n, false) {}
+
+    int reserve() {
+        for (int i = 0; i < seats.size(); i++) {
+            if (!seats[i]) {
+                seats[i] = true;
+                return i + 1;
+            }
+        }
+        return -1;
+    }
+
+    void unreserve(int seatNumber) {
+        seats[seatNumber - 1] = false;
+    }
+};
+```
+
+```javascript
+class SeatManager {
+    /**
+     * @param {number} n
+     */
+    constructor(n) {
+        this.seats = new Array(n).fill(false);
+    }
+
+    /**
+     * @return {number}
+     */
+    reserve() {
+        for (let i = 0; i < this.seats.length; i++) {
+            if (!this.seats[i]) {
+                this.seats[i] = true;
+                return i + 1;
+            }
+        }
+    }
+
+    /**
+     * @param {number} seatNumber
+     * @return {void}
+     */
+    unreserve(seatNumber) {
+        this.seats[seatNumber - 1] = false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(n)$ time for initialization.
+    * $O(n)$ time for each $reserve()$ function call.
+    * $O(1)$ time for each $unreserve()$ function call.
+* Space complexity: $O(n)$
+
+---
+
+## 2. Min-Heap
+
+::tabs-start
+
+```python
+class SeatManager:
+    def __init__(self, n: int):
+        self.unres = list(range(1, n + 1))
+        heapq.heapify(self.unres)
+
+    def reserve(self) -> int:
+        return heapq.heappop(self.unres)
+
+    def unreserve(self, seatNumber: int) -> None:
+        heapq.heappush(self.unres, seatNumber)
+```
+
+```java
+public class SeatManager {
+    private PriorityQueue<Integer> unres;
+
+    public SeatManager(int n) {
+        unres = new PriorityQueue<>();
+        for (int i = 1; i <= n; i++) {
+            unres.offer(i);
+        }
+    }
+
+    public int reserve() {
+        return unres.poll();
+    }
+
+    public void unreserve(int seatNumber) {
+        unres.offer(seatNumber);
+    }
+}
+```
+
+```cpp
+class SeatManager {
+private:
+    priority_queue<int, vector<int>, greater<int>> unres;
+
+public:
+    SeatManager(int n) {
+        for (int i = 1; i <= n; i++) {
+            unres.push(i);
+        }
+    }
+
+    int reserve() {
+        int seat = unres.top();
+        unres.pop();
+        return seat;
+    }
+
+    void unreserve(int seatNumber) {
+        unres.push(seatNumber);
+    }
+};
+```
+
+```javascript
+class SeatManager {
+    /**
+     * @param {number} n
+     */
+    constructor(n) {
+        this.unres = new MinPriorityQueue();
+        for (let i = 1; i <= n; i++) {
+            this.unres.enqueue(i);
+        }
+    }
+
+    /**
+     * @return {number}
+     */
+    reserve() {
+        return this.unres.dequeue();
+    }
+
+    /**
+     * @param {number} seatNumber
+     * @return {void}
+     */
+    unreserve(seatNumber) {
+        this.unres.enqueue(seatNumber);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(n \log n)$ time for initialization.
+    * $O(\log n)$ time for each $reserve()$ function call.
+    * $O(\log n)$ time for each $unreserve()$ function call.
+* Space complexity: $O(n)$
+
+---
+
+## 3. Min-Heap (Optimal)
+
+::tabs-start
+
+```python
+class SeatManager:
+    def __init__(self, n: int):
+        self.minHeap = []
+        self.nextSeat = 1
+
+    def reserve(self) -> int:
+        if self.minHeap:
+            return heapq.heappop(self.minHeap)
+        
+        seat = self.nextSeat
+        self.nextSeat += 1
+        return seat
+
+    def unreserve(self, seatNumber: int) -> None:
+        heapq.heappush(self.minHeap, seatNumber)
+```
+
+```java
+public class SeatManager {
+    private PriorityQueue<Integer> minHeap;
+    private int nextSeat;
+
+    public SeatManager(int n) {
+        minHeap = new PriorityQueue<>();
+        nextSeat = 1;
+    }
+
+    public int reserve() {
+        if (!minHeap.isEmpty()) {
+            return minHeap.poll();
+        }
+        return nextSeat++;
+    }
+
+    public void unreserve(int seatNumber) {
+        minHeap.offer(seatNumber);
+    }
+}
+```
+
+```cpp
+class SeatManager {
+private:
+    priority_queue<int, vector<int>, greater<int>> minHeap;
+    int nextSeat;
+
+public:
+    SeatManager(int n) {
+        nextSeat = 1;
+    }
+
+    int reserve() {
+        if (!minHeap.empty()) {
+            int seat = minHeap.top();
+            minHeap.pop();
+            return seat;
+        }
+        return nextSeat++;
+    }
+
+    void unreserve(int seatNumber) {
+        minHeap.push(seatNumber);
+    }
+};
+```
+
+```javascript
+class SeatManager {
+    /**
+     * @param {number} n
+     */
+    constructor(n) {
+        this.minHeap = new MinPriorityQueue();
+        this.nextSeat = 1;
+    }
+
+    /**
+     * @return {number}
+     */
+    reserve() {
+        if (!this.minHeap.isEmpty()) {
+            return this.minHeap.dequeue();
+        }
+        return this.nextSeat++;
+    }
+
+    /**
+     * @param {number} seatNumber
+     * @return {void}
+     */
+    unreserve(seatNumber) {
+        this.minHeap.enqueue(seatNumber);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(1)$ time for initialization.
+    * $O(\log n)$ time for each $reserve()$ function call.
+    * $O(\log n)$ time for each $unreserve()$ function call.
+* Space complexity: $O(n)$
+
+---
+
+## 4. Ordered Set
+
+::tabs-start
+
+```python
+class SeatManager:
+    def __init__(self, n: int):
+        self.available = SortedSet()
+        self.nextSeat = 1
+
+    def reserve(self) -> int:
+        if self.available:
+            return self.available.pop(0)
+        
+        seat = self.nextSeat
+        self.nextSeat += 1
+        return seat
+
+    def unreserve(self, seatNumber: int) -> None:
+        self.available.add(seatNumber)
+```
+
+```java
+public class SeatManager {
+    private TreeSet<Integer> available;
+    private int nextSeat;
+
+    public SeatManager(int n) {
+        available = new TreeSet<>();
+        nextSeat = 1;
+    }
+
+    public int reserve() {
+        if (!available.isEmpty()) {
+            return available.pollFirst();
+        }
+        return nextSeat++;
+    }
+
+    public void unreserve(int seatNumber) {
+        available.add(seatNumber);
+    }
+}
+```
+
+```cpp
+class SeatManager {
+private:
+    set<int> available;
+    int nextSeat;
+
+public:
+    SeatManager(int n) {
+        nextSeat = 1;
+    }
+
+    int reserve() {
+        if (!available.empty()) {
+            int seat = *available.begin();
+            available.erase(available.begin());
+            return seat;
+        }
+        return nextSeat++;
+    }
+
+    void unreserve(int seatNumber) {
+        available.insert(seatNumber);
+    }
+};
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity:
+    * $O(1)$ time for initialization.
+    * $O(\log n)$ time for each $reserve()$ function call.
+    * $O(\log n)$ time for each $unreserve()$ function call.
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/sequential-digits.md b/articles/sequential-digits.md
new file mode 100644
index 000000000..b1f6bb8b8
--- /dev/null
+++ b/articles/sequential-digits.md
@@ -0,0 +1,579 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def sequentialDigits(self, low: int, high: int) -> List[int]:
+        res = []
+
+        for num in range(low, high + 1):
+            s = str(num)
+            flag = True
+            for i in range(1, len(s)):
+                if ord(s[i]) - ord(s[i - 1]) != 1:
+                    flag = False
+                    break
+            if flag:
+                res.append(num)
+
+        return res
+```
+
+```java
+public class Solution {
+    public List<Integer> sequentialDigits(int low, int high) {
+        List<Integer> res = new ArrayList<>();
+        for (int num = low; num <= high; num++) {
+            String s = String.valueOf(num);
+            boolean flag = true;
+            for (int i = 1; i < s.length(); i++) {
+                if (s.charAt(i) - s.charAt(i - 1) != 1) {
+                    flag = false;
+                    break;
+                }
+            }
+            if (flag) {
+                res.add(num);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> sequentialDigits(int low, int high) {
+        vector<int> res;
+        for (int num = low; num <= high; num++) {
+            string s = to_string(num);
+            bool flag = true;
+            for (int i = 1; i < s.size(); i++) {
+                if (s[i] - s[i - 1] != 1) {
+                    flag = false;
+                    break;
+                }
+            }
+            if (flag) {
+                res.push_back(num);
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} low
+     * @param {number} high
+     * @return {number[]}
+     */
+    sequentialDigits(low, high) {
+        const res = [];
+        for (let num = low; num <= high; num++) {
+            const s = num.toString();
+            let flag = true;
+            for (let i = 1; i < s.length; i++) {
+                if (s.charCodeAt(i) - s.charCodeAt(i - 1) !== 1) {
+                    flag = false;
+                    break;
+                }
+            }
+            if (flag) {
+                res.push(num);
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Simulation
+
+::tabs-start
+
+```python
+class Solution:
+    def sequentialDigits(self, low: int, high: int) -> List[int]:
+        res = []
+        low_digit, high_digit = len(str(low)), len(str(high))
+        
+        for digits in range(low_digit, high_digit + 1):
+            for start in range(1, 10):
+                if start + digits > 10:
+                    break
+                num = start
+                prev = start
+                for i in range(digits - 1):
+                    num = num * 10
+                    prev += 1
+                    num += prev
+                if low <= num <= high:
+                    res.append(num)
+        return res
+```
+
+```java
+public class Solution {
+    public List<Integer> sequentialDigits(int low, int high) {
+        List<Integer> res = new ArrayList<>();
+        int lowDigit = String.valueOf(low).length();
+        int highDigit = String.valueOf(high).length();
+        
+        for (int digits = lowDigit; digits <= highDigit; digits++) {
+            for (int start = 1; start < 10; start++) {
+                if (start + digits > 10) {
+                    break;
+                }
+                int num = start;
+                int prev = start;
+                for (int i = 1; i < digits; i++) {
+                    num = num * 10 + (++prev);
+                }
+                if (num >= low && num <= high) {
+                    res.add(num);
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> sequentialDigits(int low, int high) {
+        vector<int> res;
+        int lowDigit = to_string(low).length();
+        int highDigit = to_string(high).length();
+        
+        for (int digits = lowDigit; digits <= highDigit; digits++) {
+            for (int start = 1; start < 10; start++) {
+                if (start + digits > 10) {
+                    break;
+                }
+                int num = start;
+                int prev = start;
+                for (int i = 1; i < digits; i++) {
+                    num = num * 10 + (++prev);
+                }
+                if (num >= low && num <= high) {
+                    res.push_back(num);
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} low
+     * @param {number} high
+     * @return {number[]}
+     */
+    sequentialDigits(low, high) {
+        const res = [];
+        const lowDigit = low.toString().length;
+        const highDigit = high.toString().length;
+        
+        for (let digits = lowDigit; digits <= highDigit; digits++) {
+            for (let start = 1; start < 10; start++) {
+                if (start + digits > 10) {
+                    break;
+                }
+                let num = start;
+                let prev = start;
+                for (let i = 1; i < digits; i++) {
+                    num = num * 10 + (++prev);
+                }
+                if (num >= low && num <= high) {
+                    res.push(num);
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
+
+> Since, we have at most $36$ valid numbers as per the given constraints.
+
+---
+
+## 3. Breadth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def sequentialDigits(self, low: int, high: int) -> List[int]:
+        res = []
+        queue = deque(range(1, 10))
+        
+        while queue:
+            n = queue.popleft()
+            if n > high:
+                continue
+            if low <= n <= high:
+                res.append(n)
+            ones = n % 10
+            if ones < 9:
+                queue.append(n * 10 + (ones + 1))
+        
+        return res
+```
+
+```java
+public class Solution {
+    public List<Integer> sequentialDigits(int low, int high) {
+        List<Integer> res = new ArrayList<>();
+        Queue<Integer> queue = new LinkedList<>();
+        
+        for (int i = 1; i < 10; i++) {
+            queue.add(i);
+        }
+        
+        while (!queue.isEmpty()) {
+            int n = queue.poll();
+            if (n > high) {
+                continue;
+            }
+            if (n >= low && n <= high) {
+                res.add(n);
+            }
+            int ones = n % 10;
+            if (ones < 9) {
+                queue.add(n * 10 + (ones + 1));
+            }
+        }
+        
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> sequentialDigits(int low, int high) {
+        vector<int> res;
+        queue<int> queue;
+        
+        for (int i = 1; i < 10; i++) {
+            queue.push(i);
+        }
+        
+        while (!queue.empty()) {
+            int n = queue.front();
+            queue.pop();
+            
+            if (n > high) {
+                continue;
+            }
+            if (n >= low && n <= high) {
+                res.push_back(n);
+            }
+            int ones = n % 10;
+            if (ones < 9) {
+                queue.push(n * 10 + (ones + 1));
+            }
+        }
+        
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} low
+     * @param {number} high
+     * @return {number[]}
+     */
+    sequentialDigits(low, high) {
+        const res = [];
+        const queue = new Queue();
+        for (let i = 1; i < 9; i++) {
+            queue.push(i);
+        }
+        
+        while (!queue.isEmpty()) {
+            const n = queue.pop();
+            if (n > high) {
+                continue;
+            }
+            if (n >= low && n <= high) {
+                res.push(n);
+            }
+            const ones = n % 10;
+            if (ones < 9) {
+                queue.push(n * 10 + (ones + 1));
+            }
+        }
+        
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
+
+> Since, we have at most $36$ valid numbers as per the given constraints.
+
+---
+
+## 4. Depth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def sequentialDigits(self, low: int, high: int) -> List[int]:
+        res = []
+
+        def dfs(num):
+            if num > high:
+                return
+            if low <= num <= high:
+                res.append(num)
+            last_digit = num % 10
+            if last_digit < 9:
+                dfs(num * 10 + (last_digit + 1))
+
+        for i in range(1, 10):
+            dfs(i)
+
+        return sorted(res)
+```
+
+```java
+public class Solution {
+    public List<Integer> sequentialDigits(int low, int high) {
+        List<Integer> res = new ArrayList<>();
+
+        for (int i = 1; i < 10; i++) {
+            dfs(i, low, high, res);
+        }
+
+        Collections.sort(res);
+        return res;
+    }
+
+    private void dfs(int num, int low, int high, List<Integer> res) {
+        if (num > high) {
+            return;
+        }
+        if (num >= low) {
+            res.add(num);
+        }
+        int lastDigit = num % 10;
+        if (lastDigit < 9) {
+            dfs(num * 10 + (lastDigit + 1), low, high, res);
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> sequentialDigits(int low, int high) {
+        vector<int> res;
+        for (int i = 1; i < 10; i++) {
+            dfs(i, low, high, res);
+        }
+        sort(res.begin(), res.end());
+        return res;
+    }
+
+private:
+    void dfs(int num, int low, int high, vector<int>& res) {
+        if (num > high) {
+            return;
+        }
+        if (num >= low) {
+            res.push_back(num);
+        }
+        int lastDigit = num % 10;
+        if (lastDigit < 9) {
+            dfs(num * 10 + (lastDigit + 1), low, high, res);
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} low
+     * @param {number} high
+     * @return {number[]}
+     */
+    sequentialDigits(low, high) {
+        const res = [];
+
+        const dfs = (num) => {
+            if (num > high) {
+                return;
+            }
+            if (num >= low) {
+                res.push(num);
+            }
+            const lastDigit = num % 10;
+            if (lastDigit < 9) {
+                dfs(num * 10 + (lastDigit + 1));
+            }
+        };
+
+        for (let i = 1; i < 10; i++) {
+            dfs(i);
+        }
+
+        return res.sort((a, b) => a - b);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
+
+> Since, we have at most $36$ valid numbers as per the given constraints.
+
+---
+
+## 5. Sliding Window
+
+::tabs-start
+
+```python
+class Solution:
+    def sequentialDigits(self, low: int, high: int) -> List[int]:
+        nums = "123456789"
+        res = []
+        for d in range(2, 10):
+            for i in range(9 - d + 1):
+                num = int(nums[i: i + d])
+                if num > high:
+                    break
+                if low <= num <= high:
+                    res.append(num)
+        return res
+```
+
+```java
+public class Solution {
+    public List<Integer> sequentialDigits(int low, int high) {
+        String nums = "123456789";
+        List<Integer> res = new ArrayList<>();
+        
+        for (int d = 2; d <= 9; d++) {
+            for (int i = 0; i <= 9 - d; i++) {
+                int num = Integer.parseInt(nums.substring(i, i + d));
+                if (num > high) {
+                    break;
+                }
+                if (num >= low && num <= high) {
+                    res.add(num);
+                }
+            }
+        }
+        
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> sequentialDigits(int low, int high) {
+        string nums = "123456789";
+        vector<int> res;
+
+        for (int d = 2; d <= 9; d++) {
+            for (int i = 0; i <= 9 - d; i++) {
+                int num = stoi(nums.substr(i, d));
+                if (num > high) {
+                    break;
+                }
+                if (num >= low && num <= high) {
+                    res.push_back(num);
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} low
+     * @param {number} high
+     * @return {number[]}
+     */
+    sequentialDigits(low, high) {
+        const nums = "123456789";
+        const res = [];
+
+        for (let d = 2; d <= 9; d++) {
+            for (let i = 0; i <= 9 - d; i++) {
+                const num = parseInt(nums.substring(i, i + d));
+                if (num > high) {
+                    break;
+                }
+                if (num >= low && num <= high) {
+                    res.push(num);
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
+
+> Since, we have at most $36$ valid numbers as per the given constraints.
\ No newline at end of file
diff --git a/articles/serialize-and-deserialize-binary-tree.md b/articles/serialize-and-deserialize-binary-tree.md
index d937df97f..ad965e002 100644
--- a/articles/serialize-and-deserialize-binary-tree.md
+++ b/articles/serialize-and-deserialize-binary-tree.md
@@ -292,6 +292,170 @@ public class Codec {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+
+type Codec struct{}
+
+func Constructor() Codec {
+    return Codec{}
+}
+
+// Encodes a tree to a single string.
+func (this *Codec) serialize(root *TreeNode) string {
+    var res []string
+
+    var dfs func(node *TreeNode)
+    dfs = func(node *TreeNode) {
+        if node == nil {
+            res = append(res, "N")
+            return
+        }
+        res = append(res, strconv.Itoa(node.Val))
+        dfs(node.Left)
+        dfs(node.Right)
+    }
+
+    dfs(root)
+    return strings.Join(res, ",")
+}
+
+// Decodes your encoded data to tree.
+func (this *Codec) deserialize(data string) *TreeNode {
+    vals := strings.Split(data, ",")
+    i := 0
+
+    var dfs func() *TreeNode
+    dfs = func() *TreeNode {
+        if vals[i] == "N" {
+            i++
+            return nil
+        }
+        val, _ := strconv.Atoi(vals[i])
+        node := &TreeNode{Val: val}
+        i++
+        node.Left = dfs()
+        node.Right = dfs()
+        return node
+    }
+
+    return dfs()
+}
+```
+
+```kotlin
+/**
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+
+class Codec {
+
+    // Encodes a tree to a single string.
+    fun serialize(root: TreeNode?): String {
+        val res = mutableListOf<String>()
+
+        fun dfs(node: TreeNode?) {
+            if (node == null) {
+                res.add("N")
+                return
+            }
+            res.add(node.`val`.toString())
+            dfs(node.left)
+            dfs(node.right)
+        }
+
+        dfs(root)
+        return res.joinToString(",")
+    }
+
+    // Decodes your encoded data to tree.
+    fun deserialize(data: String): TreeNode? {
+        val vals = data.split(",")
+        var i = 0
+
+        fun dfs(): TreeNode? {
+            if (vals[i] == "N") {
+                i++
+                return null
+            }
+            val node = TreeNode(vals[i].toInt())
+            i++
+            node.left = dfs()
+            node.right = dfs()
+            return node
+        }
+
+        return dfs()
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init(_ val: Int) {
+ *         self.val = val
+ *         self.left = nil
+ *         self.right = nil
+ *     }
+ * }
+ */
+
+class Codec {
+
+    func serialize(_ root: TreeNode?) -> String {
+        var res = [String]()
+
+        func dfs(_ node: TreeNode?) {
+            guard let node = node else {
+                res.append("N")
+                return
+            }
+            res.append("\(node.val)")
+            dfs(node.left)
+            dfs(node.right)
+        }
+
+        dfs(root)
+        return res.joined(separator: ",")
+    }
+
+    func deserialize(_ data: String) -> TreeNode? {
+        var vals = data.split(separator: ",").map { String($0) }
+        var i = 0
+
+        func dfs() -> TreeNode? {
+            if vals[i] == "N" {
+                i += 1
+                return nil
+            }
+            let node = TreeNode(Int(vals[i])!)
+            i += 1
+            node.left = dfs()
+            node.right = dfs()
+            return node
+        }
+
+        return dfs()
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -616,6 +780,214 @@ public class Codec {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+
+type Codec struct{}
+
+func Constructor() Codec {
+    return Codec{}
+}
+
+// Encodes a tree to a single string.
+func (this *Codec) serialize(root *TreeNode) string {
+    if root == nil {
+        return "N"
+    }
+    var res []string
+    queue := []*TreeNode{root}
+
+    for len(queue) > 0 {
+        node := queue[0]
+        queue = queue[1:]
+
+        if node == nil {
+            res = append(res, "N")
+        } else {
+            res = append(res, strconv.Itoa(node.Val))
+            queue = append(queue, node.Left)
+            queue = append(queue, node.Right)
+        }
+    }
+
+    return strings.Join(res, ",")
+}
+
+// Decodes your encoded data to tree.
+func (this *Codec) deserialize(data string) *TreeNode {
+    vals := strings.Split(data, ",")
+    if vals[0] == "N" {
+        return nil
+    }
+    
+    rootVal, _ := strconv.Atoi(vals[0])
+    root := &TreeNode{Val: rootVal}
+    queue := []*TreeNode{root}
+    index := 1
+
+    for len(queue) > 0 && index < len(vals) {
+        node := queue[0]
+        queue = queue[1:]
+
+        if vals[index] != "N" {
+            leftVal, _ := strconv.Atoi(vals[index])
+            node.Left = &TreeNode{Val: leftVal}
+            queue = append(queue, node.Left)
+        }
+        index++
+
+        if index < len(vals) && vals[index] != "N" {
+            rightVal, _ := strconv.Atoi(vals[index])
+            node.Right = &TreeNode{Val: rightVal}
+            queue = append(queue, node.Right)
+        }
+        index++
+    }
+
+    return root
+}
+```
+
+```kotlin
+/**
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+
+class Codec {
+
+    // Encodes a tree to a single string.
+    fun serialize(root: TreeNode?): String {
+        if (root == null) return "N"
+        val res = mutableListOf<String>()
+        val queue: Queue<TreeNode?> = LinkedList()
+        queue.add(root)
+
+        while (queue.isNotEmpty()) {
+            val node = queue.poll()
+            if (node == null) {
+                res.add("N")
+            } else {
+                res.add(node.`val`.toString())
+                queue.add(node.left)
+                queue.add(node.right)
+            }
+        }
+
+        return res.joinToString(",")
+    }
+
+    // Decodes your encoded data to tree.
+    fun deserialize(data: String): TreeNode? {
+        val vals = data.split(",")
+        if (vals[0] == "N") return null
+
+        val root = TreeNode(vals[0].toInt())
+        val queue: Queue<TreeNode> = LinkedList()
+        queue.add(root)
+        var index = 1
+
+        while (queue.isNotEmpty() && index < vals.size) {
+            val node = queue.poll()
+
+            if (vals[index] != "N") {
+                node.left = TreeNode(vals[index].toInt())
+                queue.add(node.left!!)
+            }
+            index++
+
+            if (index < vals.size && vals[index] != "N") {
+                node.right = TreeNode(vals[index].toInt())
+                queue.add(node.right!!)
+            }
+            index++
+        }
+
+        return root
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init(_ val: Int) {
+ *         self.val = val
+ *         self.left = nil
+ *         self.right = nil
+ *     }
+ * }
+ */
+
+class Codec {
+
+    func serialize(_ root: TreeNode?) -> String {
+        guard let root = root else {
+            return "N"
+        }
+
+        var res = [String]()
+        var queue: Deque<TreeNode?> = [root]
+
+        while !queue.isEmpty {
+            let node = queue.removeFirst()
+            if let node = node {
+                res.append("\(node.val)")
+                queue.append(node.left)
+                queue.append(node.right)
+            } else {
+                res.append("N")
+            }
+        }
+
+        return res.joined(separator: ",")
+    }
+
+    func deserialize(_ data: String) -> TreeNode? {
+        let vals = data.split(separator: ",").map { String($0) }
+        guard vals[0] != "N" else {
+            return nil
+        }
+
+        let root = TreeNode(Int(vals[0])!)
+        var queue: Deque<TreeNode> = [root]
+        var index = 1
+
+        while !queue.isEmpty {
+            let node = queue.popFirst()!
+            
+            if vals[index] != "N" {
+                node.left = TreeNode(Int(vals[index])!)
+                queue.append(node.left!)
+            }
+            index += 1
+
+            if vals[index] != "N" {
+                node.right = TreeNode(Int(vals[index])!)
+                queue.append(node.right!)
+            }
+            index += 1
+        }
+
+        return root
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/set-mismatch.md b/articles/set-mismatch.md
new file mode 100644
index 000000000..f29e54444
--- /dev/null
+++ b/articles/set-mismatch.md
@@ -0,0 +1,721 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def findErrorNums(self, nums: List[int]) -> List[int]:
+        res = [0, 0]
+        n = len(nums)
+
+        for i in range(1, n + 1):
+            cnt = 0
+            for num in nums:
+                if num == i:
+                    cnt += 1
+            
+            if cnt == 0:
+                res[1] = i
+            elif cnt == 2:
+                res[0] = i
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int[] findErrorNums(int[] nums) {
+        int[] res = new int[2];
+        int n = nums.length;
+
+        for (int i = 1; i <= n; i++) {
+            int cnt = 0;
+            for (int num : nums) {
+                if (num == i) {
+                    cnt++;
+                }
+            }
+
+            if (cnt == 0) {
+                res[1] = i;
+            } else if (cnt == 2) {
+                res[0] = i;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findErrorNums(vector<int>& nums) {
+        vector<int> res(2, 0);
+        int n = nums.size();
+
+        for (int i = 1; i <= n; i++) {
+            int cnt = 0;
+            for (int num : nums) {
+                if (num == i) {
+                    cnt++;
+                }
+            }
+
+            if (cnt == 0) {
+                res[1] = i;
+            } else if (cnt == 2) {
+                res[0] = i;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    findErrorNums(nums) {
+        const res = [0, 0];
+        const n = nums.length;
+
+        for (let i = 1; i <= n; i++) {
+            let cnt = 0;
+            for (const num of nums) {
+                if (num === i) {
+                    cnt++;
+                }
+            }
+
+            if (cnt === 0) {
+                res[1] = i;
+            } else if (cnt === 2) {
+                res[0] = i;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def findErrorNums(self, nums: List[int]) -> List[int]:
+        res = [0, 1]
+        nums.sort()
+
+        for i in range(1, len(nums)):
+            if nums[i] == nums[i - 1]:
+                res[0] = nums[i]
+            elif nums[i] - nums[i - 1] == 2:
+                res[1] = nums[i] - 1
+        
+        if nums[-1] != len(nums):
+            res[1] = len(nums) 
+        return res
+```
+
+```java
+public class Solution {
+    public int[] findErrorNums(int[] nums) {
+        int[] res = {0, 1};
+        Arrays.sort(nums);
+
+        for (int i = 1; i < nums.length; i++) {
+            if (nums[i] == nums[i - 1]) {
+                res[0] = nums[i];
+            } else if (nums[i] - nums[i - 1] == 2) {
+                res[1] = nums[i] - 1;
+            }
+        }
+
+        if (nums[nums.length - 1] != nums.length) {
+            res[1] = nums.length;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findErrorNums(vector<int>& nums) {
+        vector<int> res = {0, 1};
+        sort(nums.begin(), nums.end());
+
+        for (int i = 1; i < nums.size(); i++) {
+            if (nums[i] == nums[i - 1]) {
+                res[0] = nums[i];
+            } else if (nums[i] - nums[i - 1] == 2) {
+                res[1] = nums[i] - 1;
+            }
+        }
+
+        if (nums.back() != nums.size()) {
+            res[1] = nums.size();
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    findErrorNums(nums) {
+        const res = [0, 1];
+        nums.sort((a, b) => a - b);
+
+        for (let i = 1; i < nums.length; i++) {
+            if (nums[i] === nums[i - 1]) {
+                res[0] = nums[i];
+            } else if (nums[i] - nums[i - 1] === 2) {
+                res[1] = nums[i] - 1;
+            }
+        }
+
+        if (nums[nums.length - 1] !== nums.length) {
+            res[1] = nums.length;
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 3. Frequency Count (Hash Table)
+
+::tabs-start
+
+```python
+class Solution:
+    def findErrorNums(self, nums: List[int]) -> List[int]:
+        res = [0, 0] # [duplicate, missing]
+        count = Counter(nums)
+
+        for i in range(1, len(nums) + 1):
+            if count[i] == 0:
+                res[1] = i
+            if count[i] == 2:
+                res[0] = i
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int[] findErrorNums(int[] nums) {
+        int n = nums.length;
+        int[] count = new int[n + 1];
+        int[] res = new int[2];
+
+        for (int num : nums) {
+            count[num]++;
+        }
+
+        for (int i = 1; i <= n; i++) {
+            if (count[i] == 0) {
+                res[1] = i;
+            }
+            if (count[i] == 2) {
+                res[0] = i;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findErrorNums(vector<int>& nums) {
+        int n = nums.size();
+        vector<int> count(n + 1, 0);
+        vector<int> res(2, 0);
+
+        for (int num : nums) {
+            count[num]++;
+        }
+
+        for (int i = 1; i <= n; i++) {
+            if (count[i] == 0) {
+                res[1] = i;
+            }
+            if (count[i] == 2) {
+                res[0] = i;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    findErrorNums(nums) {
+        const n = nums.length;
+        const count = Array(n + 1).fill(0);
+        const res = [0, 0];
+
+        for (const num of nums) {
+            count[num]++;
+        }
+
+        for (let i = 1; i <= n; i++) {
+            if (count[i] === 0) {
+                res[1] = i;
+            }
+            if (count[i] === 2) {
+                res[0] = i;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Negative Marking
+
+::tabs-start
+
+```python
+class Solution:
+    def findErrorNums(self, nums: List[int]) -> List[int]:
+        res = [0, 0]
+
+        for num in nums:
+            num = abs(num)
+            nums[num - 1] *= -1
+            if nums[num - 1] > 0:
+                res[0] = num
+        
+        for i, num in enumerate(nums):
+            if num > 0 and i + 1 != res[0]:
+                res[1] = i + 1
+                return res
+```
+
+```java
+public class Solution {
+    public int[] findErrorNums(int[] nums) {
+        int[] res = new int[2];
+
+        for (int num : nums) {
+            int absNum = Math.abs(num);
+            if (nums[absNum - 1] < 0) {
+                res[0] = absNum;
+            } else {
+                nums[absNum - 1] *= -1;
+            }
+        }
+
+        for (int i = 0; i < nums.length; i++) {
+            if (nums[i] > 0 && i + 1 != res[0]) {
+                res[1] = i + 1;
+                return res;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findErrorNums(vector<int>& nums) {
+        vector<int> res(2);
+
+        for (int num : nums) {
+            int absNum = abs(num);
+            if (nums[absNum - 1] < 0) {
+                res[0] = absNum;
+            } else {
+                nums[absNum - 1] *= -1;
+            }
+        }
+
+        for (int i = 0; i < nums.size(); i++) {
+            if (nums[i] > 0 && i + 1 != res[0]) {
+                res[1] = i + 1;
+                return res;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    findErrorNums(nums) {
+        const res = [0, 0];
+
+        for (let num of nums) {
+            const absNum = Math.abs(num);
+            if (nums[absNum - 1] < 0) {
+                res[0] = absNum;
+            } else {
+                nums[absNum - 1] *= -1;
+            }
+        }
+
+        for (let i = 0; i < nums.length; i++) {
+            if (nums[i] > 0 && i + 1 !== res[0]) {
+                res[1] = i + 1;
+                return res;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 5. Math
+
+::tabs-start
+
+```python
+class Solution:
+    def findErrorNums(self, nums: List[int]) -> List[int]:
+        N = len(nums)
+        x = 0 # duplicate - missing
+        y = 0 # duplicate^2 - missing^2
+
+        for i in range(1, N + 1):
+            x += nums[i - 1] - i
+            y += nums[i - 1]**2 - i**2
+        
+        missing = (y - x**2) // (2 * x)
+        duplicate = missing + x
+        return [duplicate, missing]
+```
+
+```java
+public class Solution {
+    public int[] findErrorNums(int[] nums) {
+        int N = nums.length;
+        int x = 0; // duplicate - missing
+        int y = 0; // duplicate^2 - missing^2
+
+        for (int i = 1; i <= N; i++) {
+            x += nums[i - 1] - i;
+            y += nums[i - 1] * nums[i - 1] - i * i;
+        }
+
+        int missing = (y - x * x) / (2 * x);
+        int duplicate = missing + x;
+        return new int[]{duplicate, missing};
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findErrorNums(vector<int>& nums) {
+        int N = nums.size();
+        long long x = 0; // duplicate - missing
+        long long y = 0; // duplicate^2 - missing^2
+
+        for (int i = 1; i <= N; i++) {
+            x += nums[i - 1] - i;
+            y += (long long)nums[i - 1] * nums[i - 1] - (long long)i * i;
+        }
+
+        int missing = (y - x * x) / (2 * x);
+        int duplicate = missing + x;
+        return {duplicate, missing};
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    findErrorNums(nums) {
+        const N = nums.length;
+        let x = 0; // duplicate - missing
+        let y = 0; // duplicate^2 - missing^2
+
+        for (let i = 1; i <= N; i++) {
+            x += nums[i - 1] - i;
+            y += nums[i - 1] ** 2 - i ** 2;
+        }
+
+        const missing = (y - x ** 2) / (2 * x);
+        const duplicate = missing + x;
+        return [duplicate, missing];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+
+---
+
+## 6. Bitwise XOR
+
+::tabs-start
+
+```python
+class Solution:
+    def findErrorNums(self, nums: List[int]) -> List[int]:
+        N = len(nums)
+        # a ^ a = 0
+        # xorr = (1 ^ 2 ^ ... N) ^ (nums[0] ^ nums[1] ^ ... nums[N - 1])
+        # xorr = missing ^ duplicate
+        xorr = 0 
+        for i in range(1, N + 1):
+            xorr ^= i
+            xorr ^= nums[i - 1]
+        
+        # bit that is set in only one number among (duplicate, missing),
+        # will be set in (duplicate ^ missing)
+        # take rightMost set bit for simplicity
+        rightMostBit = xorr & ~(xorr - 1)
+
+        # divide numbers (from nums, from [1, N]) into two sets w.r.t the rightMostBit
+        # xorr the numbers of these sets independently
+        x = y = 0
+        for i in range(1, N + 1):
+            if i & rightMostBit:
+                x ^= i
+            else:
+                y ^= i
+            
+            if nums[i - 1] & rightMostBit:
+                x ^= nums[i - 1]
+            else:
+                y ^= nums[i - 1]
+        
+        # identify the duplicate number from x and y
+        for num in nums:
+            if num == x:
+                return [x, y]
+        return [y, x]
+```
+
+```java
+public class Solution {
+    public int[] findErrorNums(int[] nums) {
+        int N = nums.length;
+        // a ^ a = 0
+        // xorr = (1 ^ 2 ^ ... N) ^ (nums[0] ^ nums[1] ^ ... nums[N - 1])
+        // xorr = missing ^ duplicate
+        int xorr = 0; 
+        for (int i = 1; i <= N; i++) {
+            xorr ^= i;
+            xorr ^= nums[i - 1];
+        }
+
+        // bit that is set in only one number among (duplicate, missing),
+        // will be set in (duplicate ^ missing)
+        // take rightMost set bit for simplicity
+        int rightMostBit = xorr & ~(xorr - 1);
+
+        // divide numbers (from nums, from [1, N]) into two sets w.r.t the rightMostBit
+        // xorr the numbers of these sets independently
+        int x = 0, y = 0;
+        for (int i = 1; i <= N; i++) {
+            if ((i & rightMostBit) != 0) {
+                x ^= i;
+            } else {
+                y ^= i;
+            }
+
+            if ((nums[i - 1] & rightMostBit) != 0) {
+                x ^= nums[i - 1];
+            } else {
+                y ^= nums[i - 1];
+            }
+        }
+
+        // identify the duplicate number from x and y
+        for (int num : nums) {
+            if (num == x) {
+                return new int[]{x, y};
+            }
+        }
+        return new int[]{y, x};
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> findErrorNums(vector<int>& nums) {
+        int N = nums.size();
+        // a ^ a = 0
+        // xorr = (1 ^ 2 ^ ... N) ^ (nums[0] ^ nums[1] ^ ... nums[N - 1])
+        // xorr = missing ^ duplicate
+        int xorr = 0; 
+        for (int i = 1; i <= N; i++) {
+            xorr ^= i;
+            xorr ^= nums[i - 1];
+        }
+
+        // bit that is set in only one number among (duplicate, missing),
+        // will be set in (duplicate ^ missing)
+        // take rightMost set bit for simplicity
+        int rightMostBit = xorr & ~(xorr - 1);
+
+        // divide numbers (from nums, from [1, N]) into two sets w.r.t the rightMostBit
+        // xorr the numbers of these sets independently
+        int x = 0, y = 0;
+        for (int i = 1; i <= N; i++) {
+            if (i & rightMostBit) {
+                x ^= i;
+            } else {
+                y ^= i;
+            }
+
+            if (nums[i - 1] & rightMostBit) {
+                x ^= nums[i - 1];
+            } else {
+                y ^= nums[i - 1];
+            }
+        }
+
+        // identify the duplicate number from x and y
+        for (int num : nums) {
+            if (num == x) {
+                return {x, y};
+            }
+        }
+        return {y, x};
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    findErrorNums(nums) {
+        const N = nums.length;
+        // a ^ a = 0
+        // xorr = (1 ^ 2 ^ ... N) ^ (nums[0] ^ nums[1] ^ ... nums[N - 1])
+        // xorr = missing ^ duplicate
+        let xorr = 0;
+        for (let i = 1; i <= N; i++) {
+            xorr ^= i;
+            xorr ^= nums[i - 1];
+        }
+
+        // bit that is set in only one number among (duplicate, missing),
+        // will be set in (duplicate ^ missing)
+        // take rightMost set bit for simplicity
+        const rightMostBit = xorr & ~(xorr - 1);
+
+        // divide numbers (from nums, from [1, N]) into two sets w.r.t the rightMostBit
+        // xorr the numbers of these sets independently
+        let x = 0, y = 0;
+        for (let i = 1; i <= N; i++) {
+            if (i & rightMostBit) {
+                x ^= i;
+            } else {
+                y ^= i;
+            }
+
+            if (nums[i - 1] & rightMostBit) {
+                x ^= nums[i - 1];
+            } else {
+                y ^= nums[i - 1];
+            }
+        }
+
+        // identify the duplicate number from x and y
+        for (let num of nums) {
+            if (num === x) {
+                return [x, y];
+            }
+        }
+        return [y, x];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/set-zeroes-in-matrix.md b/articles/set-zeroes-in-matrix.md
new file mode 100644
index 000000000..72cef4283
--- /dev/null
+++ b/articles/set-zeroes-in-matrix.md
@@ -0,0 +1,818 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def setZeroes(self, matrix: List[List[int]]) -> None:
+        ROWS, COLS = len(matrix), len(matrix[0])
+        mark = [[matrix[r][c] for c in range(COLS)] for r in range(ROWS)]
+
+        for r in range(ROWS):
+            for c in range(COLS):
+                if matrix[r][c] == 0:
+                    for col in range(COLS):
+                        mark[r][col] = 0
+                    for row in range(ROWS):
+                        mark[row][c] = 0
+
+        for r in range(ROWS):
+            for c in range(COLS):
+                matrix[r][c] = mark[r][c]
+```
+
+```java
+public class Solution {
+    public void setZeroes(int[][] matrix) {
+        int ROWS = matrix.length, COLS = matrix[0].length;
+        int[][] mark = new int[ROWS][COLS];
+
+        for (int r = 0; r < ROWS; r++) {
+            System.arraycopy(matrix[r], 0, mark[r], 0, COLS);
+        }
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (matrix[r][c] == 0) {
+                    for (int col = 0; col < COLS; col++) {
+                        mark[r][col] = 0;
+                    }
+                    for (int row = 0; row < ROWS; row++) {
+                        mark[row][c] = 0;
+                    }
+                }
+            }
+        }
+
+        for (int r = 0; r < ROWS; r++) {
+            System.arraycopy(mark[r], 0, matrix[r], 0, COLS);
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void setZeroes(vector<vector<int>>& matrix) {
+        int ROWS = matrix.size(), COLS = matrix[0].size();
+        vector<vector<int>> mark = matrix;
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (matrix[r][c] == 0) {
+                    for (int col = 0; col < COLS; col++) {
+                        mark[r][col] = 0;
+                    }
+                    for (int row = 0; row < ROWS; row++) {
+                        mark[row][c] = 0;
+                    }
+                }
+            }
+        }
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                matrix[r][c] = mark[r][c];
+            }
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} matrix
+     * @return {void}
+     */
+    setZeroes(matrix) {
+        const ROWS = matrix.length, COLS = matrix[0].length;
+        const mark = matrix.map(row => [...row]);
+
+        for (let r = 0; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                if (matrix[r][c] === 0) {
+                    for (let col = 0; col < COLS; col++) {
+                        mark[r][col] = 0;
+                    }
+                    for (let row = 0; row < ROWS; row++) {
+                        mark[row][c] = 0;
+                    }
+                }
+            }
+        }
+
+        for (let r = 0; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                matrix[r][c] = mark[r][c];
+            }
+        }
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public void SetZeroes(int[][] matrix) {
+        int ROWS = matrix.Length, COLS = matrix[0].Length;
+        int[][] mark = new int[ROWS][];
+        for (int r = 0; r < ROWS; r++) {
+            mark[r] = (int[]) matrix[r].Clone();
+        }
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (matrix[r][c] == 0) {
+                    for (int col = 0; col < COLS; col++) {
+                        mark[r][col] = 0;
+                    }
+                    for (int row = 0; row < ROWS; row++) {
+                        mark[row][c] = 0;
+                    }
+                }
+            }
+        }
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                matrix[r][c] = mark[r][c];
+            }
+        }
+    }
+}
+```
+
+```go
+func setZeroes(matrix [][]int) {
+    ROWS, COLS := len(matrix), len(matrix[0])
+    mark := make([][]int, ROWS)
+    for i := 0; i < ROWS; i++ {
+        mark[i] = make([]int, COLS)
+        copy(mark[i], matrix[i])
+    }
+
+    for r := 0; r < ROWS; r++ {
+        for c := 0; c < COLS; c++ {
+            if matrix[r][c] == 0 {
+                for col := 0; col < COLS; col++ {
+                    mark[r][col] = 0
+                }
+                for row := 0; row < ROWS; row++ {
+                    mark[row][c] = 0
+                }
+            }
+        }
+    }
+
+    for r := 0; r < ROWS; r++ {
+        for c := 0; c < COLS; c++ {
+            matrix[r][c] = mark[r][c]
+        }
+    }
+}
+```
+
+```kotlin
+class Solution {
+    fun setZeroes(matrix: Array<IntArray>) {
+        val ROWS = matrix.size
+        val COLS = matrix[0].size
+        val mark = Array(ROWS) { IntArray(COLS) }
+
+        for (r in 0 until ROWS) {
+            for (c in 0 until COLS) {
+                mark[r][c] = matrix[r][c]
+            }
+        }
+
+        for (r in 0 until ROWS) {
+            for (c in 0 until COLS) {
+                if (matrix[r][c] == 0) {
+                    for (col in 0 until COLS) {
+                        mark[r][col] = 0
+                    }
+                    for (row in 0 until ROWS) {
+                        mark[row][c] = 0
+                    }
+                }
+            }
+        }
+
+        for (r in 0 until ROWS) {
+            for (c in 0 until COLS) {
+                matrix[r][c] = mark[r][c]
+            }
+        }
+    }
+}
+```
+
+```swift
+class Solution {
+    func setZeroes(_ matrix: inout [[Int]]) {
+        let rows = matrix.count
+        let cols = matrix[0].count
+        var mark = matrix
+
+        for r in 0..<rows {
+            for c in 0..<cols {
+                if matrix[r][c] == 0 {
+                    for col in 0..<cols {
+                        mark[r][col] = 0
+                    }
+                    for row in 0..<rows {
+                        mark[row][c] = 0
+                    }
+                }
+            }
+        }
+
+        for r in 0..<rows {
+            for c in 0..<cols {
+                matrix[r][c] = mark[r][c]
+            }
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O((m * n) * (m + n))$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns.
+
+---
+
+## 2. Iteration
+
+::tabs-start
+
+```python
+class Solution:
+    def setZeroes(self, matrix: List[List[int]]) -> None:
+        ROWS, COLS = len(matrix), len(matrix[0])
+        rows, cols = [False] * ROWS, [False] * COLS
+
+        for r in range(ROWS):
+            for c in range(COLS):
+                if matrix[r][c] == 0:
+                    rows[r] = True
+                    cols[c] = True
+
+        for r in range(ROWS):
+            for c in range(COLS):
+                if rows[r] or cols[c]:
+                    matrix[r][c] = 0
+```
+
+```java
+public class Solution {
+    public void setZeroes(int[][] matrix) {
+        int rows = matrix.length, cols = matrix[0].length;
+        boolean[] rowZero = new boolean[rows];
+        boolean[] colZero = new boolean[cols];
+
+        for (int r = 0; r < rows; r++) {
+            for (int c = 0; c < cols; c++) {
+                if (matrix[r][c] == 0) {
+                    rowZero[r] = true;
+                    colZero[c] = true;
+                }
+            }
+        }
+
+        for (int r = 0; r < rows; r++) {
+            for (int c = 0; c < cols; c++) {
+                if (rowZero[r] || colZero[c]) {
+                    matrix[r][c] = 0;
+                }
+            }
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void setZeroes(vector<vector<int>>& matrix) {
+        int rows = matrix.size(), cols = matrix[0].size();
+        vector<bool> rowZero(rows, false);
+        vector<bool> colZero(cols, false);
+
+        for (int r = 0; r < rows; ++r) {
+            for (int c = 0; c < cols; ++c) {
+                if (matrix[r][c] == 0) {
+                    rowZero[r] = true;
+                    colZero[c] = true;
+                }
+            }
+        }
+
+        for (int r = 0; r < rows; ++r) {
+            for (int c = 0; c < cols; ++c) {
+                if (rowZero[r] || colZero[c]) {
+                    matrix[r][c] = 0;
+                }
+            }
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} matrix
+     * @return {void}
+     */
+    setZeroes(matrix) {
+        const rows = matrix.length, cols = matrix[0].length;
+        const rowZero = Array(rows).fill(false);
+        const colZero = Array(cols).fill(false);
+
+        for (let r = 0; r < rows; r++) {
+            for (let c = 0; c < cols; c++) {
+                if (matrix[r][c] === 0) {
+                    rowZero[r] = true;
+                    colZero[c] = true;
+                }
+            }
+        }
+
+        for (let r = 0; r < rows; r++) {
+            for (let c = 0; c < cols; c++) {
+                if (rowZero[r] || colZero[c]) {
+                    matrix[r][c] = 0;
+                }
+            }
+        }
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public void SetZeroes(int[][] matrix) {
+        int rows = matrix.Length, cols = matrix[0].Length;
+        bool[] rowZero = new bool[rows];
+        bool[] colZero = new bool[cols];
+
+        for (int r = 0; r < rows; r++) {
+            for (int c = 0; c < cols; c++) {
+                if (matrix[r][c] == 0) {
+                    rowZero[r] = true;
+                    colZero[c] = true;
+                }
+            }
+        }
+
+        for (int r = 0; r < rows; r++) {
+            for (int c = 0; c < cols; c++) {
+                if (rowZero[r] || colZero[c]) {
+                    matrix[r][c] = 0;
+                }
+            }
+        }
+    }
+}
+```
+
+```go
+func setZeroes(matrix [][]int) {
+    ROWS, COLS := len(matrix), len(matrix[0])
+    rows := make([]bool, ROWS)
+    cols := make([]bool, COLS)
+
+    for r := 0; r < ROWS; r++ {
+        for c := 0; c < COLS; c++ {
+            if matrix[r][c] == 0 {
+                rows[r] = true
+                cols[c] = true
+            }
+        }
+    }
+
+    for r := 0; r < ROWS; r++ {
+        for c := 0; c < COLS; c++ {
+            if rows[r] || cols[c] {
+                matrix[r][c] = 0
+            }
+        }
+    }
+}
+```
+
+```kotlin
+class Solution {
+    fun setZeroes(matrix: Array<IntArray>) {
+        val ROWS = matrix.size
+        val COLS = matrix[0].size
+        val rows = BooleanArray(ROWS)
+        val cols = BooleanArray(COLS)
+
+        for (r in 0 until ROWS) {
+            for (c in 0 until COLS) {
+                if (matrix[r][c] == 0) {
+                    rows[r] = true
+                    cols[c] = true
+                }
+            }
+        }
+
+        for (r in 0 until ROWS) {
+            for (c in 0 until COLS) {
+                if (rows[r] || cols[c]) {
+                    matrix[r][c] = 0
+                }
+            }
+        }
+    }
+}
+```
+
+```swift
+class Solution {
+    func setZeroes(_ matrix: inout [[Int]]) {
+        let rows = matrix.count
+        let cols = matrix[0].count
+        var rowFlags = Array(repeating: false, count: rows)
+        var colFlags = Array(repeating: false, count: cols)
+
+        for r in 0..<rows {
+            for c in 0..<cols {
+                if matrix[r][c] == 0 {
+                    rowFlags[r] = true
+                    colFlags[c] = true
+                }
+            }
+        }
+
+        for r in 0..<rows {
+            for c in 0..<cols {
+                if rowFlags[r] || colFlags[c] {
+                    matrix[r][c] = 0
+                }
+            }
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(m + n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns.
+
+---
+
+## 3. Iteration (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def setZeroes(self, matrix: List[List[int]]) -> None:
+        ROWS, COLS = len(matrix), len(matrix[0])
+        rowZero = False
+
+        for r in range(ROWS):
+            for c in range(COLS):
+                if matrix[r][c] == 0:
+                    matrix[0][c] = 0
+                    if r > 0:
+                        matrix[r][0] = 0
+                    else:
+                        rowZero = True
+
+        for r in range(1, ROWS):
+            for c in range(1, COLS):
+                if matrix[0][c] == 0 or matrix[r][0] == 0:
+                    matrix[r][c] = 0
+
+        if matrix[0][0] == 0:
+            for r in range(ROWS):
+                matrix[r][0] = 0
+
+        if rowZero:
+            for c in range(COLS):
+                matrix[0][c] = 0
+```
+
+```java
+public class Solution {
+    public void setZeroes(int[][] matrix) {
+        int ROWS = matrix.length, COLS = matrix[0].length;
+        boolean rowZero = false;
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (matrix[r][c] == 0) {
+                    matrix[0][c] = 0;
+                    if (r > 0) {
+                        matrix[r][0] = 0;
+                    } else {
+                        rowZero = true;
+                    }
+                }
+            }
+        }
+
+        for (int r = 1; r < ROWS; r++) {
+            for (int c = 1; c < COLS; c++) {
+                if (matrix[0][c] == 0 || matrix[r][0] == 0) {
+                    matrix[r][c] = 0;
+                }
+            }
+        }
+
+        if (matrix[0][0] == 0) {
+            for (int r = 0; r < ROWS; r++) {
+                matrix[r][0] = 0;
+            }
+        }
+
+        if (rowZero) {
+            for (int c = 0; c < COLS; c++) {
+                matrix[0][c] = 0;
+            }
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void setZeroes(vector<vector<int>>& matrix) {
+        int ROWS = matrix.size(), COLS = matrix[0].size();
+        bool rowZero = false;
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (matrix[r][c] == 0) {
+                    matrix[0][c] = 0;
+                    if (r > 0) {
+                        matrix[r][0] = 0;
+                    } else {
+                        rowZero = true;
+                    }
+                }
+            }
+        }
+
+        for (int r = 1; r < ROWS; r++) {
+            for (int c = 1; c < COLS; c++) {
+                if (matrix[0][c] == 0 || matrix[r][0] == 0) {
+                    matrix[r][c] = 0;
+                }
+            }
+        }
+
+        if (matrix[0][0] == 0) {
+            for (int r = 0; r < ROWS; r++) {
+                matrix[r][0] = 0;
+            }
+        }
+
+        if (rowZero) {
+            for (int c = 0; c < COLS; c++) {
+                matrix[0][c] = 0;
+            }
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} matrix
+     * @return {void}
+     */
+    setZeroes(matrix) {
+        const ROWS = matrix.length;
+            const COLS = matrix[0].length;
+        let rowZero = false;
+
+        for (let r = 0; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                if (matrix[r][c] == 0) {
+                    matrix[0][c] = 0;
+                    if (r > 0) {
+                        matrix[r][0] = 0;
+                    } else {
+                        rowZero = true;
+                    }
+                }
+            }
+        }
+
+        for (let r = 1; r < ROWS; r++) {
+            for (let c = 1; c < COLS; c++) {
+                if (matrix[0][c] == 0 || matrix[r][0] == 0) {
+                    matrix[r][c] = 0;
+                }
+            }
+        }
+
+        if (matrix[0][0] == 0) {
+            for (let r = 0; r < ROWS; r++) {
+                matrix[r][0] = 0;
+            }
+        }
+
+        if (rowZero) {
+            for (let c = 0; c < COLS; c++) {
+                matrix[0][c] = 0;
+            }
+        }
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public void SetZeroes(int[][] matrix) {
+        int ROWS = matrix.Length, COLS = matrix[0].Length;
+        bool rowZero = false;
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                if (matrix[r][c] == 0) {
+                    matrix[0][c] = 0;
+                    if (r > 0) {
+                        matrix[r][0] = 0;
+                    } else {
+                        rowZero = true;
+                    }
+                }
+            }
+        }
+
+        for (int r = 1; r < ROWS; r++) {
+            for (int c = 1; c < COLS; c++) {
+                if (matrix[0][c] == 0 || matrix[r][0] == 0) {
+                    matrix[r][c] = 0;
+                }
+            }
+        }
+
+        if (matrix[0][0] == 0) {
+            for (int r = 0; r < ROWS; r++) {
+                matrix[r][0] = 0;
+            }
+        }
+
+        if (rowZero) {
+            for (int c = 0; c < COLS; c++) {
+                matrix[0][c] = 0;
+            }
+        }
+    }
+}
+```
+
+```go
+func setZeroes(matrix [][]int) {
+    ROWS, COLS := len(matrix), len(matrix[0])
+    rowZero := false
+
+    for r := 0; r < ROWS; r++ {
+        for c := 0; c < COLS; c++ {
+            if matrix[r][c] == 0 {
+                matrix[0][c] = 0
+                if r > 0 {
+                    matrix[r][0] = 0
+                } else {
+                    rowZero = true
+                }
+            }
+        }
+    }
+
+    for r := 1; r < ROWS; r++ {
+        for c := 1; c < COLS; c++ {
+            if matrix[0][c] == 0 || matrix[r][0] == 0 {
+                matrix[r][c] = 0
+            }
+        }
+    }
+
+    if matrix[0][0] == 0 {
+        for r := 0; r < ROWS; r++ {
+            matrix[r][0] = 0
+        }
+    }
+
+    if rowZero {
+        for c := 0; c < COLS; c++ {
+            matrix[0][c] = 0
+        }
+    }
+}
+```
+
+```kotlin
+class Solution {
+    fun setZeroes(matrix: Array<IntArray>) {
+        val ROWS = matrix.size
+        val COLS = matrix[0].size
+        var rowZero = false
+
+        for (r in 0 until ROWS) {
+            for (c in 0 until COLS) {
+                if (matrix[r][c] == 0) {
+                    matrix[0][c] = 0
+                    if (r > 0) {
+                        matrix[r][0] = 0
+                    } else {
+                        rowZero = true
+                    }
+                }
+            }
+        }
+
+        for (r in 1 until ROWS) {
+            for (c in 1 until COLS) {
+                if (matrix[0][c] == 0 || matrix[r][0] == 0) {
+                    matrix[r][c] = 0
+                }
+            }
+        }
+
+        if (matrix[0][0] == 0) {
+            for (r in 0 until ROWS) {
+                matrix[r][0] = 0
+            }
+        }
+
+        if (rowZero) {
+            for (c in 0 until COLS) {
+                matrix[0][c] = 0
+            }
+        }
+    }
+}
+```
+
+```swift
+class Solution {
+    func setZeroes(_ matrix: inout [[Int]]) {
+        let ROWS = matrix.count
+        let COLS = matrix[0].count
+        var rowZero = false
+
+        for r in 0..<ROWS {
+            for c in 0..<COLS {
+                if matrix[r][c] == 0 {
+                    matrix[0][c] = 0
+                    if r > 0 {
+                        matrix[r][0] = 0
+                    } else {
+                        rowZero = true
+                    }
+                }
+            }
+        }
+
+        for r in 1..<ROWS {
+            for c in 1..<COLS {
+                if matrix[0][c] == 0 || matrix[r][0] == 0 {
+                    matrix[r][c] = 0
+                }
+            }
+        }
+
+        if matrix[0][0] == 0 {
+            for r in 0..<ROWS {
+                matrix[r][0] = 0
+            }
+        }
+
+        if rowZero {
+            for c in 0..<COLS {
+                matrix[0][c] = 0
+            }
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(1)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns.
\ No newline at end of file
diff --git a/articles/shift-2d-grid.md b/articles/shift-2d-grid.md
new file mode 100644
index 000000000..78f570a31
--- /dev/null
+++ b/articles/shift-2d-grid.md
@@ -0,0 +1,502 @@
+## 1. Simulation (Extra Space)
+
+::tabs-start
+
+```python
+class Solution:
+    def shiftGrid(self, grid: List[List[int]], k: int) -> List[List[int]]:
+        m, n = len(grid), len(grid[0])
+
+        while k:
+            cur = [[0] * n for _ in range(m)]
+
+            for r in range(m):
+                for c in range(n - 1):
+                    cur[r][c + 1] = grid[r][c]
+            
+            for r in range(m):
+                cur[(r + 1) % m][0] = grid[r][n - 1]
+            
+            grid = cur
+            k -= 1
+        
+        return grid
+```
+
+```java
+public class Solution {
+    public List<List<Integer>> shiftGrid(int[][] grid, int k) {
+        int m = grid.length, n = grid[0].length;
+
+        while (k > 0) {
+            int[][] cur = new int[m][n];
+
+            for (int r = 0; r < m; r++) {
+                for (int c = 0; c < n - 1; c++) {
+                    cur[r][c + 1] = grid[r][c];
+                }
+            }
+
+            for (int r = 0; r < m; r++) {
+                cur[(r + 1) % m][0] = grid[r][n - 1];
+            }
+
+            grid = cur;
+            k--;
+        }
+
+        List<List<Integer>> res = new ArrayList<>();
+        for (int r = 0; r < m; r++) {
+            List<Integer> tmp = new ArrayList<>();
+            for (int c = 0; c < n; c++) {
+                tmp.add(grid[r][c]);
+            }
+            res.add(tmp);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> shiftGrid(vector<vector<int>>& grid, int k) {
+        int m = grid.size(), n = grid[0].size();
+
+        while (k > 0) {
+            vector<vector<int>> cur(m, vector<int>(n, 0));
+
+            for (int r = 0; r < m; r++) {
+                for (int c = 0; c < n - 1; c++) {
+                    cur[r][c + 1] = grid[r][c];
+                }
+            }
+
+            for (int r = 0; r < m; r++) {
+                cur[(r + 1) % m][0] = grid[r][n - 1];
+            }
+
+            grid = cur;
+            k--;
+        }
+
+        return grid;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @param {number} k
+     * @return {number[][]}
+     */
+    shiftGrid(grid, k) {
+        const m = grid.length, n = grid[0].length;
+
+        while (k > 0) {
+            const cur = Array.from({ length: m }, () => Array(n).fill(0));
+
+            for (let r = 0; r < m; r++) {
+                for (let c = 0; c < n - 1; c++) {
+                    cur[r][c + 1] = grid[r][c];
+                }
+            }
+
+            for (let r = 0; r < m; r++) {
+                cur[(r + 1) % m][0] = grid[r][n - 1];
+            }
+
+            grid = cur;
+            k--;
+        }
+
+        return grid;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(k * m * n)$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows in the grid, $n$ is the number of columns in the grid, and $k$ is the shift count.
+
+---
+
+## 2. Simulation
+
+::tabs-start
+
+```python
+class Solution:
+    def shiftGrid(self, grid: List[List[int]], k: int) -> List[List[int]]:
+        m, n = len(grid), len(grid[0])
+
+        while k:
+            prev = grid[m - 1][n - 1]
+            for r in range(m):
+                for c in range(n):
+                    grid[r][c], prev = prev, grid[r][c]
+            k -= 1
+        
+        return grid
+```
+
+```java
+public class Solution {
+    public List<List<Integer>> shiftGrid(int[][] grid, int k) {
+        int m = grid.length, n = grid[0].length;
+
+        while (k > 0) {
+            int prev = grid[m - 1][n - 1];
+            for (int r = 0; r < m; r++) {
+                for (int c = 0; c < n; c++) {
+                    int temp = grid[r][c];
+                    grid[r][c] = prev;
+                    prev = temp;
+                }
+            }
+            k--;
+        }
+
+        List<List<Integer>> res = new ArrayList<>();
+        for (int r = 0; r < m; r++) {
+            List<Integer> tmp = new ArrayList<>();
+            for (int c = 0; c < n; c++) {
+                tmp.add(grid[r][c]);
+            }
+            res.add(tmp);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> shiftGrid(vector<vector<int>>& grid, int k) {
+        int m = grid.size(), n = grid[0].size();
+
+        while (k > 0) {
+            int prev = grid[m - 1][n - 1];
+            for (int r = 0; r < m; r++) {
+                for (int c = 0; c < n; c++) {
+                    swap(grid[r][c], prev);
+                }
+            }
+            k--;
+        }
+
+        return grid;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @param {number} k
+     * @return {number[][]}
+     */
+    shiftGrid(grid, k) {
+        const m = grid.length, n = grid[0].length;
+
+        while (k > 0) {
+            let prev = grid[m - 1][n - 1];
+            for (let r = 0; r < m; r++) {
+                for (let c = 0; c < n; c++) {
+                    [prev, grid[r][c]] = [grid[r][c], prev];
+                }
+            }
+            k--;
+        }
+
+        return grid;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(k * m * n)$
+* Space complexity: $O(m * n)$ for the output matrix.
+
+> Where $m$ is the number of rows in the grid, $n$ is the number of columns in the grid, and $k$ is the shift count.
+
+---
+
+## 3. Convert to One Dimensional Array
+
+::tabs-start
+
+```python
+class Solution:
+    def shiftGrid(self, grid: List[List[int]], k: int) -> List[List[int]]:
+        m, n = len(grid), len(grid[0])
+        N = m * n
+        k %= N
+
+        arr = [0] * N
+        for r in range(m):
+            for c in range(n):
+                arr[r * n + c] = grid[r][c]
+        
+        def reverse(l, r):
+            while l < r:
+                arr[l], arr[r] = arr[r], arr[l]
+                l += 1
+                r -= 1
+        
+        reverse(0, N - 1)
+        reverse(0, k - 1)
+        reverse(k, N - 1)
+
+        for r in range(m):
+            for c in range(n):
+                grid[r][c] = arr[r * n + c]
+        
+        return grid
+```
+
+```java
+public class Solution {
+    public List<List<Integer>> shiftGrid(int[][] grid, int k) {
+        int m = grid.length, n = grid[0].length;
+        int N = m * n;
+        k %= N;
+
+        int[] arr = new int[N];
+        for (int r = 0; r < m; r++) {
+            for (int c = 0; c < n; c++) {
+                arr[r * n + c] = grid[r][c];
+            }
+        }
+
+        reverse(arr, 0, N - 1);
+        reverse(arr, 0, k - 1);
+        reverse(arr, k, N - 1);
+
+        List<List<Integer>> res = new ArrayList<>();
+        for (int r = 0; r < m; r++) {
+            List<Integer> tmp = new ArrayList<>();
+            for (int c = 0; c < n; c++) {
+                tmp.add(arr[r * n + c]);
+            }
+            res.add(tmp);
+        }
+        return res;
+    }
+
+    private void reverse(int[] arr, int l, int r) {
+        while (l < r) {
+            int temp = arr[l];
+            arr[l] = arr[r];
+            arr[r] = temp;
+            l++;
+            r--;
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> shiftGrid(vector<vector<int>>& grid, int k) {
+        int m = grid.size(), n = grid[0].size();
+        int N = m * n;
+        k %= N;
+
+        vector<int> arr(N);
+        for (int r = 0; r < m; r++) {
+            for (int c = 0; c < n; c++) {
+                arr[r * n + c] = grid[r][c];
+            }
+        }
+
+        reverse(arr.begin(), arr.end());
+        reverse(arr.begin(), arr.begin() + k);
+        reverse(arr.begin() + k, arr.end());
+
+        for (int r = 0; r < m; r++) {
+            for (int c = 0; c < n; c++) {
+                grid[r][c] = arr[r * n + c];
+            }
+        }
+
+        return grid;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @param {number} k
+     * @return {number[][]}
+     */
+    shiftGrid(grid, k) {
+        const m = grid.length, n = grid[0].length;
+        const N = m * n;
+        k %= N;
+
+        const arr = new Array(N);
+        for (let r = 0; r < m; r++) {
+            for (let c = 0; c < n; c++) {
+                arr[r * n + c] = grid[r][c];
+            }
+        }
+
+        const reverse = (l, r) => {
+            while (l < r) {
+                [arr[l], arr[r]] = [arr[r], arr[l]];
+                l++;
+                r--;
+            }
+        };
+
+        reverse(0, N - 1);
+        reverse(0, k - 1);
+        reverse(k, N - 1);
+
+        for (let r = 0; r < m; r++) {
+            for (let c = 0; c < n; c++) {
+                grid[r][c] = arr[r * n + c];
+            }
+        }
+
+        return grid;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows in the grid and $n$ is the number of columns in the grid.
+
+---
+
+## 4. Iteration
+
+::tabs-start
+
+```python
+class Solution:
+    def shiftGrid(self, grid: List[List[int]], k: int) -> List[List[int]]:
+        M, N = len(grid), len(grid[0])
+
+        def posToVal(r, c):
+            return r * N + c
+
+        def valToPos(v):
+            return [v // N, v % N]
+
+        res = [[0] * N for _ in range(M)]
+        for r in range(M):
+            for c in range(N):
+                newVal = (posToVal(r, c) + k) % (M * N)
+                newR, newC = valToPos(newVal)
+                res[newR][newC] = grid[r][c]
+
+        return res
+```
+
+```java
+public class Solution {
+    public List<List<Integer>> shiftGrid(int[][] grid, int k) {
+        int M = grid.length, N = grid[0].length;
+        int[][] arr = new int[M][N];
+
+        for (int r = 0; r < M; r++) {
+            for (int c = 0; c < N; c++) {
+                int newVal = (r * N + c + k) % (M * N);
+                int newR = newVal / N, newC = newVal % N;
+                arr[newR][newC] = grid[r][c];
+            }
+        }
+
+        List<List<Integer>> res = new ArrayList<>();
+        for (int r = 0; r < M; r++) {
+            List<Integer> tmp = new ArrayList<>();
+            for (int c = 0; c < N; c++) {
+                tmp.add(arr[r][c]);
+            }
+            res.add(tmp);
+        }
+        return res;
+    }
+
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> shiftGrid(vector<vector<int>>& grid, int k) {
+        int M = grid.size(), N = grid[0].size();
+        vector<vector<int>> res(M, vector<int>(N));
+
+        for (int r = 0; r < M; r++) {
+            for (int c = 0; c < N; c++) {
+                int newVal = (r * N + c + k) % (M * N);
+                int newR = newVal / N, newC = newVal % N;
+                res[newR][newC] = grid[r][c];
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @param {number} k
+     * @return {number[][]}
+     */
+    shiftGrid(grid, k) {
+        const M = grid.length, N = grid[0].length;
+
+        const posToVal = (r, c) => r * N + c;
+        const valToPos = (v) => [Math.floor(v / N), v % N];
+
+        const res = Array.from({ length: M }, () => Array(N).fill(0));
+        for (let r = 0; r < M; r++) {
+            for (let c = 0; c < N; c++) {
+                const newVal = (posToVal(r, c) + k) % (M * N);
+                const [newR, newC] = valToPos(newVal);
+                res[newR][newC] = grid[r][c];
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows in the grid and $n$ is the number of columns in the grid.
\ No newline at end of file
diff --git a/articles/shifting-letters-ii.md b/articles/shifting-letters-ii.md
new file mode 100644
index 000000000..12d3e9499
--- /dev/null
+++ b/articles/shifting-letters-ii.md
@@ -0,0 +1,481 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def shiftingLetters(self, s: str, shifts: List[List[int]]) -> str:
+        s = [ord(c) - ord('a') for c in s]
+
+        for l, r, d in shifts:
+            for i in range(l, r + 1):
+                s[i] += 1 if d else -1
+                s[i] %= 26
+
+        s = [chr(ord('a') + c) for c in s]
+        return "".join(s)
+```
+
+```java
+class Solution {
+    public String shiftingLetters(String s, int[][] shifts) {
+        char[] arr = s.toCharArray();
+        int[] letters = new int[arr.length];
+
+        for (int i = 0; i < arr.length; i++) {
+            letters[i] = arr[i] - 'a';
+        }
+
+        for (int[] shift : shifts) {
+            int l = shift[0], r = shift[1], d = shift[2];
+            for (int i = l; i <= r; i++) {
+                letters[i] = (letters[i] + (d == 1 ? 1 : -1) + 26) % 26;
+            }
+        }
+
+        for (int i = 0; i < arr.length; i++) {
+            arr[i] = (char) (letters[i] + 'a');
+        }
+
+        return new String(arr);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string shiftingLetters(string s, vector<vector<int>>& shifts) {
+        vector<int> letters(s.size());
+        for (int i = 0; i < s.size(); i++) {
+            letters[i] = s[i] - 'a';
+        }
+
+        for (const auto& shift : shifts) {
+            int l = shift[0], r = shift[1], d = shift[2];
+            for (int i = l; i <= r; i++) {
+                letters[i] = (letters[i] + (d == 1 ? 1 : -1) + 26) % 26;
+            }
+        }
+
+        for (int i = 0; i < s.size(); i++) {
+            s[i] = letters[i] + 'a';
+        }
+
+        return s;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {number[][]} shifts
+     * @return {string}
+     */
+    shiftingLetters(s, shifts) {
+        let arr = Array.from(s).map(c => c.charCodeAt(0) - 97);
+
+        for (const [l, r, d] of shifts) {
+            for (let i = l; i <= r; i++) {
+                arr[i] = (arr[i] + (d === 1 ? 1 : -1) + 26) % 26;
+            }
+        }
+
+        return arr.map(c => String.fromCharCode(c + 97)).join('');
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the length of the string $s$ and $m$ is the size of the array $shifts$.
+
+---
+
+## 2. Sweep Line Algorithm
+
+::tabs-start
+
+```python
+class Solution:
+    def shiftingLetters(self, s: str, shifts: List[List[int]]) -> str:
+        prefix_diff = [0] * (len(s) + 1)
+
+        for left, right, d in shifts:
+            val = 1 if d == 1 else -1
+            prefix_diff[left] += val
+            prefix_diff[right + 1] -= val
+
+        diff = 0
+        res = [ord(c) - ord("a") for c in s]
+
+        for i in range(len(s)):
+            diff += prefix_diff[i]
+            res[i] = (diff + res[i] + 26) % 26
+
+        s = [chr(ord("a") + n) for n in res]
+        return "".join(s)
+```
+
+```java
+class Solution {
+    public String shiftingLetters(String s, int[][] shifts) {
+        int n = s.length();
+        int[] prefix_diff = new int[n + 1];
+
+        for (int[] shift : shifts) {
+            int left = shift[0], right = shift[1], d = shift[2];
+            int val = d == 1 ? 1 : -1;
+            prefix_diff[left] += val;
+            prefix_diff[right + 1] -= val;
+        }
+
+        int[] res = new int[n];
+        for (int i = 0; i < n; i++) {
+            res[i] = s.charAt(i) - 'a';
+        }
+
+        int diff = 0;
+        for (int i = 0; i < n; i++) {
+            diff += prefix_diff[i];
+            res[i] = (res[i] + diff % 26 + 26) % 26;
+        }
+
+        StringBuilder sb = new StringBuilder();
+        for (int i = 0; i < n; i++) {
+            sb.append((char) ('a' + res[i]));
+        }
+
+        return sb.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string shiftingLetters(string s, vector<vector<int>>& shifts) {
+        int n = s.size();
+        vector<int> prefix_diff(n + 1, 0);
+
+        for (auto& shift : shifts) {
+            int left = shift[0], right = shift[1], d = shift[2];
+            int val = d == 1 ? 1 : -1;
+            prefix_diff[left] += val;
+            prefix_diff[right + 1] -= val;
+        }
+
+        int diff = 0;
+        vector<int> res(n);
+        for (int i = 0; i < n; ++i) {
+            res[i] = s[i] - 'a';
+        }
+
+        for (int i = 0; i < n; ++i) {
+            diff += prefix_diff[i];
+            res[i] = (diff % 26 + res[i] + 26) % 26;
+        }
+
+        for (int i = 0; i < n; ++i) {
+            s[i] = 'a' + res[i];
+        }
+
+        return s;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {number[][]} shifts
+     * @return {string}
+     */
+    shiftingLetters(s, shifts) {
+        const n = s.length;
+        const prefix_diff = Array(n + 1).fill(0);
+
+        for (const [left, right, d] of shifts) {
+            const val = d === 1 ? 1 : -1;
+            prefix_diff[left] += val;
+            prefix_diff[right + 1] -= val;
+        }
+
+        let diff = 0;
+        const res = Array.from(s).map(c => c.charCodeAt(0) - 'a'.charCodeAt(0));
+
+        for (let i = 0; i < n; i++) {
+            diff += prefix_diff[i];
+            res[i] = (diff % 26 + res[i] + 26) % 26;
+        }
+
+        return res.map(x => String.fromCharCode('a'.charCodeAt(0) + x)).join('');
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the length of the string $s$ and $m$ is the size of the array $shifts$.
+
+---
+
+## 3. Binary Indexed Tree (Fenwick Tree)
+
+::tabs-start
+
+```python
+class BIT:
+    def __init__(self, size):
+        self.n = size + 2
+        self.tree = [0] * self.n
+
+    def update(self, index, delta):
+        index += 1
+        while index < self.n:
+            self.tree[index] += delta
+            index += index & -index
+
+    def prefix_sum(self, index):
+        index += 1
+        total = 0
+        while index > 0:
+            total += self.tree[index]
+            index -= index & -index
+        return total
+
+    def range_update(self, left, right, delta):
+        self.update(left, delta)
+        self.update(right + 1, -delta)
+
+
+class Solution:
+    def shiftingLetters(self, s: str, shifts: List[List[int]]) -> str:
+        n = len(s)
+        bit = BIT(n)
+
+        for left, right, d in shifts:
+            delta = 1 if d == 1 else -1
+            bit.range_update(left, right, delta)
+
+        res = []
+        for i in range(n):
+            shift = bit.prefix_sum(i) % 26
+            code = (ord(s[i]) - ord('a') + shift + 26) % 26
+            res.append(chr(ord('a') + code))
+
+        return ''.join(res)
+```
+
+```java
+class BIT {
+    int[] tree;
+    int n;
+
+    public BIT(int size) {
+        n = size + 2;
+        tree = new int[n];
+    }
+
+    public void update(int index, int delta) {
+        index++;
+        while (index < n) {
+            tree[index] += delta;
+            index += index & -index;
+        }
+    }
+
+    public int prefixSum(int index) {
+        index++;
+        int sum = 0;
+        while (index > 0) {
+            sum += tree[index];
+            index -= index & -index;
+        }
+        return sum;
+    }
+
+    public void rangeUpdate(int left, int right, int delta) {
+        update(left, delta);
+        update(right + 1, -delta);
+    }
+}
+
+public class Solution {
+    public String shiftingLetters(String s, int[][] shifts) {
+        int n = s.length();
+        BIT bit = new BIT(n);
+
+        for (int[] shift : shifts) {
+            int left = shift[0], right = shift[1], d = shift[2];
+            int delta = d == 1 ? 1 : -1;
+            bit.rangeUpdate(left, right, delta);
+        }
+
+        StringBuilder res = new StringBuilder();
+        for (int i = 0; i < n; i++) {
+            int shift = bit.prefixSum(i) % 26;
+            int code = (s.charAt(i) - 'a' + shift + 26) % 26;
+            res.append((char) ('a' + code));
+        }
+
+        return res.toString();
+    }
+}
+```
+
+```cpp
+class BIT {
+    vector<int> tree;
+    int n;
+public:
+    BIT(int size) {
+        n = size + 2;
+        tree.assign(n, 0);
+    }
+
+    void update(int index, int delta) {
+        index++;
+        while (index < n) {
+            tree[index] += delta;
+            index += index & -index;
+        }
+    }
+
+    int prefixSum(int index) {
+        index++;
+        int sum = 0;
+        while (index > 0) {
+            sum += tree[index];
+            index -= index & -index;
+        }
+        return sum;
+    }
+
+    void rangeUpdate(int left, int right, int delta) {
+        update(left, delta);
+        update(right + 1, -delta);
+    }
+};
+
+class Solution {
+public:
+    string shiftingLetters(string s, vector<vector<int>>& shifts) {
+        int n = s.size();
+        BIT bit(n);
+
+        for (auto& shift : shifts) {
+            int left = shift[0], right = shift[1], d = shift[2];
+            int delta = d == 1 ? 1 : -1;
+            bit.rangeUpdate(left, right, delta);
+        }
+
+        string res;
+        for (int i = 0; i < n; i++) {
+            int shift = bit.prefixSum(i) % 26;
+            int code = (s[i] - 'a' + shift + 26) % 26;
+            res += char('a' + code);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class BIT {
+    /**
+     * @constructor
+     * @param {number} size
+     */
+    constructor(size) {
+        this.n = size + 2;
+        this.tree = new Array(this.n).fill(0);
+    }
+
+    /**
+     * @param {number} index
+     * @param {number} delta
+     * @return {void}
+     */
+    update(index, delta) {
+        index++;
+        while (index < this.n) {
+            this.tree[index] += delta;
+            index += index & -index;
+        }
+    }
+
+    /**
+     * @param {number} index
+     * @return {number}
+     */
+    prefixSum(index) {
+        index++;
+        let sum = 0;
+        while (index > 0) {
+            sum += this.tree[index];
+            index -= index & -index;
+        }
+        return sum;
+    }
+
+    /**
+     * @param {number} left
+     * @param {number} right
+     * @param {number} delta
+     * @return {void}
+     */
+    rangeUpdate(left, right, delta) {
+        this.update(left, delta);
+        this.update(right + 1, -delta);
+    }
+}
+
+class Solution {
+    /**
+     * @param {string} s
+     * @param {number[][]} shifts
+     * @return {string}
+     */
+    shiftingLetters(s, shifts) {
+        const n = s.length;
+        const bit = new BIT(n);
+        for (const [left, right, d] of shifts) {
+            const delta = d === 1 ? 1 : -1;
+            bit.rangeUpdate(left, right, delta);
+        }
+
+        let res = "";
+        for (let i = 0; i < n; i++) {
+            const shift = bit.prefixSum(i) % 26;
+            const code = (s.charCodeAt(i) - 97 + shift + 26) % 26;
+            res += String.fromCharCode(97 + code);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O((m + n) * \log n)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the length of the string $s$ and $m$ is the size of the array $shifts$.
\ No newline at end of file
diff --git a/articles/shortest-bridge.md b/articles/shortest-bridge.md
new file mode 100644
index 000000000..14f78e190
--- /dev/null
+++ b/articles/shortest-bridge.md
@@ -0,0 +1,1068 @@
+## 1. Depth First Search + Breadth First Search - I
+
+::tabs-start
+
+```python
+class Solution:
+    def shortestBridge(self, grid: List[List[int]]) -> int:
+        N = len(grid)
+        direct = [[0, 1], [0, -1], [1, 0], [-1, 0]]
+
+        def invalid(r, c):
+            return r < 0 or c < 0 or r == N or c == N
+
+        visit = set()
+
+        def dfs(r, c):
+            if invalid(r, c) or not grid[r][c] or (r, c) in visit:
+                return
+            visit.add((r, c))
+            for dr, dc in direct:
+                dfs(r + dr, c + dc)
+
+        def bfs():
+            res, q = 0, deque(visit)
+            while q:
+                for _ in range(len(q)):
+                    r, c = q.popleft()
+                    for dr, dc in direct:
+                        curR, curC = r + dr, c + dc
+                        if invalid(curR, curC) or (curR, curC) in visit:
+                            continue
+                        if grid[curR][curC]:
+                            return res
+                        q.append((curR, curC))
+                        visit.add((curR, curC))
+                res += 1
+
+        for r in range(N):
+            for c in range(N):
+                if grid[r][c]:
+                    dfs(r, c)
+                    return bfs()
+```
+
+```java
+public class Solution {
+    private int N;
+    private boolean[][] visited;
+    private final int[][] direct = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+
+    public int shortestBridge(int[][] grid) {
+        N = grid.length;
+        visited = new boolean[N][N];
+
+        boolean found = false;
+        for (int r = 0; r < N; r++) {
+            if (found) break;
+            for (int c = 0; c < N; c++) {
+                if (grid[r][c] == 1) {
+                    dfs(grid, r, c);
+                    found = true;
+                    break;
+                }
+            }
+        }
+
+        return bfs(grid);
+    }
+
+    private void dfs(int[][] grid, int r, int c) {
+        if (r < 0 || c < 0 || r >= N || c >= N || grid[r][c] == 0 || visited[r][c])
+            return;
+        
+        visited[r][c] = true;
+
+        for (int[] d : direct) {
+            dfs(grid, r + d[0], c + d[1]);
+        }
+    }
+
+    private int bfs(int[][] grid) {
+        Queue<int[]> q = new LinkedList<>();
+        for (int r = 0; r < N; r++) {
+            for (int c = 0; c < N; c++) {
+                if (visited[r][c]) {
+                    q.offer(new int[]{r, c});
+                }
+            }
+        }
+
+        int res = 0;
+        while (!q.isEmpty()) {
+            for (int i = q.size(); i > 0; i--) {
+                int[] cell = q.poll();
+                int r = cell[0], c = cell[1];
+
+                for (int[] d : direct) {
+                    int curR = r + d[0], curC = c + d[1];
+
+                    if (curR < 0 || curC < 0 || curR >= N || curC >= N || visited[curR][curC])
+                        continue;
+
+                    if (grid[curR][curC] == 1) return res;
+
+                    q.offer(new int[]{curR, curC});
+                    visited[curR][curC] = true;
+                }
+            }
+            res++;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int N;
+    vector<vector<bool>> visited;
+    vector<vector<int>> direct = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+
+    int shortestBridge(vector<vector<int>>& grid) {
+        N = grid.size();
+        visited = vector<vector<bool>>(N, vector<bool>(N, false));
+
+        bool found = false;
+        for (int r = 0; r < N; r++) {
+            if (found) break;
+            for (int c = 0; c < N; c++) {
+                if (grid[r][c] == 1) {
+                    dfs(grid, r, c);
+                    found = true;
+                    break;
+                }
+            }
+        }
+
+        return bfs(grid);
+    }
+
+private:
+    void dfs(vector<vector<int>>& grid, int r, int c) {
+        if (r < 0 || c < 0 || r >= N || c >= N || grid[r][c] == 0 || visited[r][c])
+            return;
+        
+        visited[r][c] = true;
+        for (auto& d : direct) {
+            dfs(grid, r + d[0], c + d[1]);
+        }
+    }
+
+    int bfs(vector<vector<int>>& grid) {
+        queue<pair<int, int>> q;
+        for (int r = 0; r < N; r++) {
+            for (int c = 0; c < N; c++) {
+                if (visited[r][c]) {
+                    q.push({r, c});
+                }
+            }
+        }
+
+        int res = 0;
+        while (!q.empty()) {
+            for (int i = q.size(); i > 0; i--) {
+                auto [r, c] = q.front(); q.pop();
+
+                for (auto& d : direct) {
+                    int curR = r + d[0], curC = c + d[1];
+
+                    if (curR < 0 || curC < 0 || curR >= N || curC >= N || visited[curR][curC])
+                        continue;
+
+                    if (grid[curR][curC] == 1) return res;
+                    q.push({curR, curC});
+                    visited[curR][curC] = true;
+                }
+            }
+            res++;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    shortestBridge(grid) {
+        const N = grid.length;
+        const direct = [[0, 1], [0, -1], [1, 0], [-1, 0]];
+        const visited = Array.from({ length: N }, () => Array(N).fill(false));
+        const q = new Queue();
+
+        const dfs = (r, c) => {
+            if (r < 0 || c < 0 || r >= N || c >= N || grid[r][c] === 0 || visited[r][c]) 
+                return;
+            visited[r][c] = true;
+            q.push([r, c]);
+
+            for (const [dr, dc] of direct) {
+                dfs(r + dr, c + dc);
+            }
+        };
+
+        const bfs = () => {
+            let res = 0;
+            while (!q.isEmpty()) {
+                for (let i = q.size(); i > 0; i--) {
+                    const [r, c] = q.pop();
+                    for (const [dr, dc] of direct) {
+                        const curR = r + dr, curC = c + dc;
+
+                        if (curR < 0 || curC < 0 || curR >= N || curC >= N || visited[curR][curC])
+                            continue;
+                        if (grid[curR][curC] === 1) return res;
+
+                        q.push([curR, curC]);
+                        visited[curR][curC] = true;
+                    }
+                }
+                res++;
+            }
+        };
+
+        for (let r = 0; r < N; r++) {
+            for (let c = 0; c < N; c++) {
+                if (grid[r][c] === 1) {
+                    dfs(r, c);
+                    return bfs();
+                }
+            }
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 2. Depth First Search + Breadth First Search - II
+
+::tabs-start
+
+```python
+class Solution:
+    def shortestBridge(self, grid: list[list[int]]) -> int:
+        N, direct = len(grid), [(0, 1), (0, -1), (1, 0), (-1, 0)]
+
+        def dfs(r, c):
+            if 0 <= r < N and 0 <= c < N and grid[r][c] == 1:
+                grid[r][c] = 2
+                q.append((r, c))
+                for dr, dc in direct:
+                    dfs(r + dr, c + dc)
+
+        q = deque()
+        for r in range(N):
+            for c in range(N):
+                if grid[r][c]:
+                    dfs(r, c)
+                    break
+            if q: break
+
+        res = 0
+        while q:
+            for _ in range(len(q)):
+                r, c = q.popleft()
+                for dr, dc in direct:
+                    nr, nc = r + dr, c + dc
+                    if 0 <= nr < N and 0 <= nc < N:
+                        if grid[nr][nc] == 1:
+                            return res
+                        if grid[nr][nc] == 0:
+                            grid[nr][nc] = 2
+                            q.append((nr, nc))
+            res += 1
+```
+
+```java
+public class Solution {
+    private int[][] direct = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+
+    public int shortestBridge(int[][] grid) {
+        int N = grid.length;
+        Queue<int[]> q = new LinkedList<>();
+
+        boolean found = false;
+        for (int r = 0; r < N; r++) {
+            if (found) break;
+            for (int c = 0; c < N; c++) {
+                if (grid[r][c] == 1) {
+                    dfs(grid, r, c, q);
+                    found = true;
+                    break;
+                }
+            }
+        }
+
+        int res = 0;
+        while (!q.isEmpty()) {
+            for (int i = q.size(); i > 0; i--) {
+                int[] cell = q.poll();
+                int r = cell[0], c = cell[1];
+
+                for (int[] d : direct) {
+                    int nr = r + d[0], nc = c + d[1];
+
+                    if (nr < 0 || nc < 0 || nr >= N || nc >= N) continue;
+                    if (grid[nr][nc] == 1) return res;
+
+                    if (grid[nr][nc] == 0) {
+                        grid[nr][nc] = 2;
+                        q.offer(new int[]{nr, nc});
+                    }
+                }
+            }
+            res++;
+        }
+        return res;
+    }
+
+    private void dfs(int[][] grid, int r, int c, Queue<int[]> q) {
+        if (r < 0 || c < 0 || r >= grid.length || c >= grid.length || grid[r][c] != 1)
+            return;
+
+        grid[r][c] = 2;
+        q.offer(new int[]{r, c});
+        for (int[] d : direct) {
+            dfs(grid, r + d[0], c + d[1], q);
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+    vector<vector<int>> direct;
+
+public:
+    int shortestBridge(vector<vector<int>>& grid) {
+        int N = grid.size();
+        direct = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+        queue<pair<int, int>> q;
+
+        bool found = false;
+        for (int r = 0; r < N; r++) {
+            if (found) break;
+            for (int c = 0; c < N; c++) {
+                if (grid[r][c] == 1) {
+                    dfs(grid, r, c, q);
+                    found = true;
+                    break;
+                }
+            }
+        }
+
+        int res = 0;
+        while (!q.empty()) {
+            for (int i = q.size(); i > 0; i--) {
+                auto [r, c] = q.front(); q.pop();
+
+                for (auto& d : direct) {
+                    int nr = r + d[0], nc = c + d[1];
+
+                    if (nr < 0 || nc < 0 || nr >= N || nc >= N) continue;
+                    if (grid[nr][nc] == 1) return res;
+
+                    if (grid[nr][nc] == 0) {
+                        grid[nr][nc] = 2;
+                        q.push({nr, nc});
+                    }
+                }
+            }
+            res++;
+        }
+        return res;
+    }
+
+private:
+    void dfs(vector<vector<int>>& grid, int r, int c, queue<pair<int, int>>& q) {
+        if (r < 0 || c < 0 || r >= grid.size() || c >= grid.size() || grid[r][c] != 1)
+            return;
+
+        grid[r][c] = 2;
+        q.push({r, c});
+        for (auto& d : direct) {
+            dfs(grid, r + d[0], c + d[1], q);
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    shortestBridge(grid) {
+        const N = grid.length;
+        const direct = [[0, 1], [0, -1], [1, 0], [-1, 0]];
+        const q = new Queue();
+
+        const dfs = (r, c) => {
+            if (r < 0 || c < 0 || r >= N || c >= N || grid[r][c] !== 1) return;
+            grid[r][c] = 2;
+            q.push([r, c]);
+            for (const [dr, dc] of direct) {
+                dfs(r + dr, c + dc);
+            }
+        };
+
+        let found = false;
+        for (let r = 0; r < N; r++) {
+            if (found) break;
+            for (let c = 0; c < N; c++) {
+                if (grid[r][c] === 1) {
+                    dfs(r, c);
+                    found = true;
+                    break;
+                }
+            }
+        }
+
+        let res = 0;
+        while (!q.isEmpty()) {
+            for (let i = q.size(); i > 0; i--) {
+                const [r, c] = q.pop();
+                for (const [dr, dc] of direct) {
+                    let nr = r + dr, nc = c + dc;
+                    if (nr < 0 || nc < 0 || nr >= N || nc >= N) continue;
+                    if (grid[nr][nc] === 1) return res;
+                    if (grid[nr][nc] === 0) {
+                        grid[nr][nc] = 2;
+                        q.push([nr, nc]);
+                    }
+                }
+            }
+            res++;
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 3. Breadth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def shortestBridge(self, grid: list[list[int]]) -> int:
+        N, direct = len(grid), [(0, 1), (0, -1), (1, 0), (-1, 0)]
+        q2 = deque()
+
+        found = False
+        for r in range(N):
+            if found: break
+            for c in range(N):
+                if grid[r][c] == 1:
+                    q1 = deque([(r, c)])
+                    grid[r][c] = 2                    
+                    while q1:
+                        x, y = q1.popleft()
+                        q2.append((x, y))
+                        for dx, dy in direct:
+                            nx, ny = x + dx, y + dy
+                            if 0 <= nx < N and 0 <= ny < N and grid[nx][ny] == 1:
+                                grid[nx][ny] = 2
+                                q1.append((nx, ny))
+                    found = True
+                    break
+
+        res = 0
+        while q2:
+            for _ in range(len(q2)):
+                x, y = q2.popleft()
+                for dx, dy in direct:
+                    nx, ny = x + dx, y + dy
+                    if 0 <= nx < N and 0 <= ny < N:
+                        if grid[nx][ny] == 1:
+                            return res
+                        if grid[nx][ny] == 0:
+                            grid[nx][ny] = 2
+                            q2.append((nx, ny))
+            res += 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int shortestBridge(int[][] grid) {
+        int N = grid.length;
+        int[][] direct = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+        Queue<int[]> q2 = new LinkedList<>();
+
+        boolean found = false;
+        for (int r = 0; r < N; r++) {
+            if (found) break;
+            for (int c = 0; c < N; c++) {
+                if (grid[r][c] == 1) {
+                    Queue<int[]> q1 = new LinkedList<>();
+                    q1.offer(new int[]{r, c});
+                    grid[r][c] = 2;
+
+                    while (!q1.isEmpty()) {
+                        int[] cell = q1.poll();
+                        int x = cell[0], y = cell[1];
+                        q2.offer(new int[]{x, y});
+
+                        for (int[] d : direct) {
+                            int nx = x + d[0], ny = y + d[1];
+                            if (nx >= 0 && ny >= 0 && nx < N && ny < N && grid[nx][ny] == 1) {
+                                grid[nx][ny] = 2;
+                                q1.offer(new int[]{nx, ny});
+                            }
+                        }
+                    }
+                    found = true;
+                    break;
+                }
+            }
+        }
+
+        int res = 0;
+        while (!q2.isEmpty()) {
+            for (int i = q2.size(); i > 0; i--) {
+                int[] cell = q2.poll();
+                int x = cell[0], y = cell[1];
+
+                for (int[] d : direct) {
+                    int nx = x + d[0], ny = y + d[1];
+
+                    if (nx >= 0 && ny >= 0 && nx < N && ny < N) {
+                        if (grid[nx][ny] == 1) return res;
+                        if (grid[nx][ny] == 0) {
+                            grid[nx][ny] = 2;
+                            q2.offer(new int[]{nx, ny});
+                        }
+                    }
+                }
+            }
+            res++;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int shortestBridge(vector<vector<int>>& grid) {
+        int N = grid.size();
+        vector<vector<int>> direct = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+        queue<pair<int, int>> q2;
+
+        bool found = false;
+        for (int r = 0; r < N; r++) {
+            if (found) break;
+            for (int c = 0; c < N; c++) {
+                if (grid[r][c] == 1) {
+                    queue<pair<int, int>> q1;
+                    q1.push({r, c});
+                    grid[r][c] = 2;
+
+                    while (!q1.empty()) {
+                        auto [x, y] = q1.front(); q1.pop();
+                        q2.push({x, y});
+
+                        for (auto& d : direct) {
+                            int nx = x + d[0], ny = y + d[1];
+                            if (nx >= 0 && ny >= 0 && nx < N && ny < N && grid[nx][ny] == 1) {
+                                grid[nx][ny] = 2;
+                                q1.push({nx, ny});
+                            }
+                        }
+                    }
+                    found = true;
+                    break;
+                }
+            }
+        }
+
+        int res = 0;
+        while (!q2.empty()) {
+            for (int i = q2.size(); i > 0; i--) {
+                auto [x, y] = q2.front(); q2.pop();
+
+                for (auto& d : direct) {
+                    int nx = x + d[0], ny = y + d[1];
+
+                    if (nx >= 0 && ny >= 0 && nx < N && ny < N) {
+                        if (grid[nx][ny] == 1) return res;
+                        if (grid[nx][ny] == 0) {
+                            grid[nx][ny] = 2;
+                            q2.push({nx, ny});
+                        }
+                    }
+                }
+            }
+            res++;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    shortestBridge(grid) {
+        const N = grid.length;
+        const direct = [[0, 1], [0, -1], [1, 0], [-1, 0]];
+        const q2 = new Queue();
+
+        let found = false;
+        for (let r = 0; r < N; r++) {
+            if (found) break;
+            for (let c = 0; c < N; c++) {
+                if (grid[r][c] === 1) {
+                    const q1 = new Queue([[r, c]]);
+                    grid[r][c] = 2;
+
+                    while (!q1.isEmpty()) {
+                        let [x, y] = q1.pop();
+                        q2.push([x, y]);
+
+                        for (let [dx, dy] of direct) {
+                            let nx = x + dx, ny = y + dy;
+                            if (nx >= 0 && ny >= 0 && nx < N && ny < N && grid[nx][ny] === 1) {
+                                grid[nx][ny] = 2;
+                                q1.push([nx, ny]);
+                            }
+                        }
+                    }
+                    found = true;
+                    break;
+                }
+            }
+        }
+
+        let res = 0;
+        while (!q2.isEmpty()) {
+            for (let i = q2.size(); i > 0; i--) {
+                const [x, y] = q2.pop();
+
+                for (let [dx, dy] of direct) {
+                    let nx = x + dx, ny = y + dy;
+                    if (nx >= 0 && ny >= 0 && nx < N && ny < N) {
+                        if (grid[nx][ny] === 1) return res;
+                        if (grid[nx][ny] === 0) {
+                            grid[nx][ny] = 2;
+                            q2.push([nx, ny]);
+                        }
+                    }
+                }
+            }
+            res++;
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 4. Disjoint Set Union + Breadth First Search
+
+::tabs-start
+
+```python
+class DSU:
+    def __init__(self, n):
+        self.parent = list(range(n))
+        self.rank = [1] * n
+
+    def find(self, node):
+        cur = node
+        while cur != self.parent[cur]:
+            self.parent[cur] = self.parent[self.parent[cur]]
+            cur = self.parent[cur]
+        return cur
+
+    def union(self, u, v):
+        pu, pv = self.find(u), self.find(v)
+        if pu == pv:
+            return False
+        if self.rank[pv] > self.rank[pu]:
+            pu, pv = pv, pu
+        self.parent[pv] = pu
+        self.rank[pu] += self.rank[pv]
+        return True
+
+class Solution:
+    def shortestBridge(self, grid: list[list[int]]) -> int:
+        n, direct = len(grid), [(0, 1), (0, -1), (1, 0), (-1, 0)]
+        dsu = DSU(n * n + 1)
+
+        def idx(r, c):
+            return r * n + c + 1
+
+        for r in range(n):
+            for c in range(n):
+                if grid[r][c] == 1:
+                    first_island = dsu.find(idx(r, c))
+                    if c + 1 < n and grid[r][c + 1] == 1:
+                        dsu.union(idx(r, c), idx(r, c + 1))
+                    if r + 1 < n and grid[r + 1][c] == 1:
+                        dsu.union(idx(r, c), idx(r + 1, c))
+
+        q = deque()
+        for r in range(n):
+            for c in range(n):
+                if grid[r][c] == 1:
+                    if dsu.find(idx(r, c)) != first_island:
+                        continue
+                    for dx, dy in direct:
+                        nr, nc = r + dx, c + dy
+                        if 0 <= nr < n and 0 <= nc < n and grid[nr][nc] == 0:
+                            q.append((r,c))
+                            break
+
+        res = 0
+        while q:
+            for _ in range(len(q)):
+                r, c = q.popleft()
+                for dx, dy in direct:
+                    nr, nc = r + dx, c + dy
+                    if 0 <= nr < n and 0 <= nc < n:
+                        if grid[nr][nc] == 1 and dsu.union(idx(r, c), idx(nr, nc)):
+                            return res
+                        if grid[nr][nc] == 0:
+                            grid[nr][nc] = 1
+                            dsu.union(idx(r, c), idx(nr, nc))
+                            q.append((nr, nc))
+            res += 1
+```
+
+```java
+class DSU {
+    private int[] parent, rank;
+
+    public DSU(int n) {
+        parent = new int[n];
+        rank = new int[n];
+        for (int i = 0; i < n; i++) parent[i] = i;
+        Arrays.fill(rank, 1);
+    }
+
+    public int find(int node) {
+        if (parent[node] != node) {
+            parent[node] = find(parent[node]);
+        }
+        return parent[node];
+    }
+
+    public boolean union(int u, int v) {
+        int pu = find(u), pv = find(v);
+        if (pu == pv) return false;
+
+        if (rank[pv] > rank[pu]) {
+            int temp = pu;
+            pu = pv;
+            pv = temp;
+        }
+        parent[pv] = pu;
+        rank[pu] += rank[pv];
+        return true;
+    }
+}
+
+public class Solution {
+    private int n;
+    private int idx(int r, int c) {
+        return r * n + c + 1;
+    }
+
+    public int shortestBridge(int[][] grid) {
+        n = grid.length;
+        int[][] direct = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+        DSU dsu = new DSU(n * n + 1);
+        Queue<int[]> q = new LinkedList<>();
+
+
+        int firstIsland = -1;
+        for (int r = 0; r < n; r++) {
+            for (int c = 0; c < n; c++) {
+                if (grid[r][c] == 1) {
+                    firstIsland = dsu.find(idx(r, c));
+                    if (c + 1 < n && grid[r][c + 1] == 1)
+                        dsu.union(idx(r, c), idx(r, c + 1));
+                    if (r + 1 < n && grid[r + 1][c] == 1)
+                        dsu.union(idx(r, c), idx(r + 1, c));
+                }
+            }
+        }
+
+        for (int r = 0; r < n; r++) {
+            for (int c = 0; c < n; c++) {
+                if (grid[r][c] == 1 && dsu.find(idx(r, c)) == firstIsland) {
+                    for (int[] d : direct) {
+                        int nr = r + d[0], nc = c + d[1];
+                        if (nr >= 0 && nc >= 0 && nr < n && nc < n && grid[nr][nc] == 0) {
+                            q.offer(new int[]{r, c});
+                            break;
+                        }
+                    }
+                }
+            }
+        }
+
+        int res = 0;
+        while (!q.isEmpty()) {
+            for (int i = q.size(); i > 0; i--) {
+                int[] cell = q.poll();
+                int r = cell[0], c = cell[1];
+
+                for (int[] d : direct) {
+                    int nr = r + d[0], nc = c + d[1];
+                    if (nr >= 0 && nc >= 0 && nr < n && nc < n) {
+                        if (grid[nr][nc] == 1 && dsu.union(idx(r, c), idx(nr, nc))) {
+                            return res;
+                        }
+                        if (grid[nr][nc] == 0) {
+                            grid[nr][nc] = 1;
+                            dsu.union(idx(r, c), idx(nr, nc));
+                            q.offer(new int[]{nr, nc});
+                        }
+                    }
+                }
+            }
+            res++;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class DSU {
+public:
+    vector<int> parent, rank;
+
+    DSU(int n) : parent(n), rank(n, 1) {
+        for (int i = 0; i < n; i++) parent[i] = i;
+    }
+
+    int find(int node) {
+        if (parent[node] != node) 
+            parent[node] = find(parent[node]);
+        return parent[node];
+    }
+
+    bool unionSet(int u, int v) {
+        int pu = find(u), pv = find(v);
+        if (pu == pv) return false;
+        if (rank[pv] > rank[pu]) swap(pu, pv);
+        parent[pv] = pu;
+        rank[pu] += rank[pv];
+        return true;
+    }
+};
+
+class Solution {
+public:
+    int shortestBridge(vector<vector<int>>& grid) {
+        int N = grid.size();
+        vector<vector<int>> direct = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+        DSU dsu(N * N + 1);
+        queue<pair<int, int>> q;
+
+        auto idx = [&](int r, int c) {
+            return r * N + c + 1;
+        };
+
+        int firstIsland = -1;
+        for (int r = 0; r < N; r++) {
+            for (int c = 0; c < N; c++) {
+                if (grid[r][c] == 1) {
+                    firstIsland = dsu.find(idx(r, c));
+                    if (c + 1 < N && grid[r][c + 1] == 1)
+                        dsu.unionSet(idx(r, c), idx(r, c + 1));
+                    if (r + 1 < N && grid[r + 1][c] == 1)
+                        dsu.unionSet(idx(r, c), idx(r + 1, c));
+                }
+            }
+        }
+
+        for (int r = 0; r < N; r++) {
+            for (int c = 0; c < N; c++) {
+                if (grid[r][c] == 1 && dsu.find(idx(r, c)) == firstIsland) {
+                    for (auto& d : direct) {
+                        int nr = r + d[0], nc = c + d[1];
+                        if (nr >= 0 && nc >= 0 && nr < N && nc < N && grid[nr][nc] == 0) {
+                            q.push({r, c});
+                            break;
+                        }
+                    }
+                }
+            }
+        }
+
+        int res = 0;
+        while (!q.empty()) {
+            for (int i = q.size(); i > 0; i--) {
+                auto [r, c] = q.front();q.pop();
+                for (auto& d : direct) {
+                    int nr = r + d[0], nc = c + d[1];
+                    if (nr >= 0 && nc >= 0 && nr < N && nc < N) {
+                        if (grid[nr][nc] == 1 && dsu.unionSet(idx(r, c), idx(nr, nc)))
+                            return res;
+                        if (grid[nr][nc] == 0) {
+                            grid[nr][nc] = 1;
+                            dsu.unionSet(idx(r, c), idx(nr, nc));
+                            q.push({nr, nc});
+                        }
+                    }
+                }
+            }
+            res++;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class DSU {
+    /**
+     * @constructor
+     * @param {number} n
+     */
+    constructor(n) {
+        this.parent = Array.from({ length: n }, (_, i) => i);
+        this.rank = Array(n).fill(1);
+    }
+
+    /**
+     * @param {number} node
+     * @return {number}
+     */
+    find(node) {
+        if (this.parent[node] !== node) {
+            this.parent[node] = this.find(this.parent[node]);
+        }
+        return this.parent[node];
+    }
+
+    /**
+     * @param {number} u
+     * @param {number} v
+     * @return {boolean}
+     */
+    union(u, v) {
+        let pu = this.find(u),
+            pv = this.find(v);
+        if (pu === pv) return false;
+
+        if (this.rank[pv] > this.rank[pu]) [pu, pv] = [pv, pu];
+        this.parent[pv] = pu;
+        this.rank[pu] += this.rank[pv];
+        return true;
+    }
+}
+
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    shortestBridge(grid) {
+        const N = grid.length;
+        const direct = [[0, 1], [0, -1], [1, 0], [-1, 0]];
+        const dsu = new DSU(N * N + 1);
+        const q = new Queue();
+
+        const idx = (r, c) => r * N + c + 1;
+
+        let firstIsland = -1;
+        for (let r = 0; r < N; r++) {
+            for (let c = 0; c < N; c++) {
+                if (grid[r][c] === 1) {
+                    firstIsland = dsu.find(idx(r, c));
+                    if (c + 1 < N && grid[r][c + 1] === 1)
+                        dsu.union(idx(r, c), idx(r, c + 1));
+                    if (r + 1 < N && grid[r + 1][c] === 1)
+                        dsu.union(idx(r, c), idx(r + 1, c));
+                }
+            }
+        }
+
+
+        for (let r = 0; r < N; r++) {
+            for (let c = 0; c < N; c++) {
+                if (grid[r][c] === 1 && dsu.find(idx(r, c)) === firstIsland) {
+                    for (const [dx, dy] of direct) {
+                        let nr = r + dx,
+                            nc = c + dy;
+                        if (nr >= 0 && nc >= 0 && nr < N && nc < N && grid[nr][nc] === 0) {
+                            q.push([r, c]);
+                            break;
+                        }
+                    }
+                }
+            }
+        }
+
+        let res = 0;
+        while (!q.isEmpty()) {
+            for (let i = q.size(); i > 0; i--) {
+                const [r, c] = q.pop();
+                for (let [dx, dy] of direct) {
+                    let nr = r + dx,
+                        nc = c + dy;
+                    if (nr >= 0 && nc >= 0 && nr < N && nc < N) {
+                        if (grid[nr][nc] === 1 && dsu.union(idx(r, c), idx(nr, nc))) {
+                            return res;
+                        }
+                        if (grid[nr][nc] === 0) {
+                            grid[nr][nc] = 1;
+                            dsu.union(idx(r, c), idx(nr, nc));
+                            q.push([nr, nc]);
+                        }
+                    }
+                }
+            }
+            res++;
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
\ No newline at end of file
diff --git a/articles/shortest-common-supersequence.md b/articles/shortest-common-supersequence.md
new file mode 100644
index 000000000..6390ec39d
--- /dev/null
+++ b/articles/shortest-common-supersequence.md
@@ -0,0 +1,803 @@
+## 1. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def shortestCommonSupersequence(self, str1: str, str2: str) -> str:
+        cache = [[None] * (len(str2) + 1) for _ in range(len(str1) + 1)]
+        str1 = list(str1)
+        str2 = list(str2)
+
+        def dfs(i: int, j: int) -> list:
+            if cache[i][j] is not None:
+                return cache[i][j]
+            if i == len(str1):
+                cache[i][j] = str2[j:][::-1]
+                return cache[i][j]
+            if j == len(str2):
+                cache[i][j] = str1[i:][::-1]
+                return cache[i][j]
+
+            if str1[i] == str2[j]:
+                res = dfs(i + 1, j + 1) + [str1[i]]
+            else:
+                s1 = dfs(i + 1, j)
+                s2 = dfs(i, j + 1)
+                if len(s1) < len(s2):
+                    res = s1 + [str1[i]]
+                else:
+                    res = s2 + [str2[j]]
+
+            cache[i][j] = res
+            return res
+
+        return ''.join(reversed(dfs(0, 0)))
+```
+
+```java
+public class Solution {
+    private List<Character>[][] cache;
+    private int n, m;
+
+    public String shortestCommonSupersequence(String str1, String str2) {
+        n = str1.length();
+        m = str2.length();
+        cache = new ArrayList[n + 1][m + 1];
+
+        List<Character> res = dfs(0, 0, str1, str2);
+        StringBuilder sb = new StringBuilder();
+        for (int k = res.size() - 1; k >= 0; k--) sb.append(res.get(k));
+        return sb.toString();
+    }
+
+    private List<Character> dfs(int i, int j, String str1, String str2) {
+        if (cache[i][j] != null) return cache[i][j];
+        if (i == n) {
+            List<Character> res = new ArrayList<>();
+            for (int k = m - 1; k >= j; k--) {
+                res.add(str2.charAt(k));
+            }
+            cache[i][j] = res;
+            return res;
+        }
+        if (j == m) {
+            List<Character> res = new ArrayList<>();
+            for (int k = n - 1; k >= i; k--) {
+                res.add(str1.charAt(k));
+            }
+            cache[i][j] = res;
+            return res;
+        }
+
+        List<Character> res;
+        if (str1.charAt(i) == str2.charAt(j)) {
+            res = new ArrayList<>(dfs(i + 1, j + 1, str1, str2));
+            res.add(str1.charAt(i));
+        } else {
+            List<Character> s1 = dfs(i + 1, j, str1, str2);
+            List<Character> s2 = dfs(i, j + 1, str1, str2);
+
+            if (s1.size() < s2.size()) {
+                res = new ArrayList<>(s1);
+                res.add(str1.charAt(i));
+            } else {
+                res = new ArrayList<>(s2);
+                res.add(str2.charAt(j));
+            }
+        }
+
+        cache[i][j] = res;
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string shortestCommonSupersequence(const string &str1, const string &str2) {
+        n = str1.size();
+        m = str2.size();
+        cache.resize(n + 1, vector<string>(m + 1, ""));
+        cacheUsed.resize(n + 1, vector<bool>(m + 1, false));
+
+        string res = dfs(0, 0, str1, str2);
+        reverse(res.begin(), res.end());
+        return res;
+    }
+
+private:
+    int n, m;
+    vector<vector<string>> cache;
+    vector<vector<bool>> cacheUsed;
+
+    string dfs(int i, int j, const string &str1, const string &str2) {
+        if (cacheUsed[i][j]) {
+            return cache[i][j];
+        }
+        cacheUsed[i][j] = true;
+
+        if (i == n) {
+            string tail = str2.substr(j);
+            reverse(tail.begin(), tail.end());
+            cache[i][j] = tail;
+            return tail;
+        }
+        if (j == m) {
+            string tail = str1.substr(i);
+            reverse(tail.begin(), tail.end());
+            cache[i][j] = tail;
+            return tail;
+        }
+
+        if (str1[i] == str2[j]) {
+            string temp = dfs(i + 1, j + 1, str1, str2);
+            temp.push_back(str1[i]);
+            cache[i][j] = temp;
+        } else {
+            string s1 = dfs(i + 1, j, str1, str2);
+            string s2 = dfs(i, j + 1, str1, str2);
+            if (s1.size() < s2.size()) {
+                s1.push_back(str1[i]);
+                cache[i][j] = s1;
+            } else {
+                s2.push_back(str2[j]);
+                cache[i][j] = s2;
+            }
+        }
+        return cache[i][j];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} str1
+     * @param {string} str2
+     * @return {string}
+     */
+    shortestCommonSupersequence(str1, str2) {
+        const n = str1.length, m = str2.length;
+        const cache = Array.from({ length: n + 1 }, () => 
+            Array(m + 1).fill(null)
+        );
+
+        const dfs = (i, j) => {
+            if (cache[i][j] !== null) return cache[i][j];
+            if (i === n) {
+                let arr = str2.slice(j).split('');
+                arr.reverse();
+                cache[i][j] = arr;
+                return arr;
+            }
+            if (j === m) {
+                let arr = str1.slice(i).split('');
+                arr.reverse();
+                cache[i][j] = arr;
+                return arr;
+            }
+            let res;
+            if (str1[i] === str2[j]) {
+                res = [...dfs(i + 1, j + 1)];
+                res.push(str1[i]);
+            } else {
+                const s1 = dfs(i + 1, j);
+                const s2 = dfs(i, j + 1);
+                if (s1.length < s2.length) {
+                    res = [...s1];
+                    res.push(str1[i]);
+                } else {
+                    res = [...s2];
+                    res.push(str2[j]);
+                }
+            }
+            cache[i][j] = res;
+            return res;
+        };
+
+        return dfs(0, 0).reverse().join('');
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m * min(n, m))$
+* Space complexity: $O(n * m * min(n, m))$
+
+> Where $n$ and $m$ are the lengths of the strings $str1$ and $str2$ respectively.
+
+---
+
+## 2. Dynamic Programming (Top-Down) + Tracing
+
+::tabs-start
+
+```python
+class Solution:
+    def shortestCommonSupersequence(self, str1: str, str2: str) -> str:
+        n, m = len(str1), len(str2)
+        dp = [[-1] * (m + 1) for _ in range(n + 1)]
+        
+        def dfs(i, j):
+            if dp[i][j] != -1:
+                return dp[i][j]
+            if i == n:
+                dp[i][j] = m - j
+                return dp[i][j]
+            if j == m:
+                dp[i][j] = n - i
+                return dp[i][j]
+            if str1[i] == str2[j]:
+                dp[i][j] = 1 + dfs(i + 1, j + 1)
+            else:
+                dp[i][j] = 1 + min(dfs(i + 1, j), dfs(i, j + 1))
+            return dp[i][j]
+
+        dfs(0, 0)
+
+        def build_scs(i, j):
+            res = []
+            while i < n or j < m:
+                if i == n:
+                    res.extend(str2[j:])
+                    break
+                if j == m:
+                    res.extend(str1[i:])
+                    break
+                if str1[i] == str2[j]:
+                    res.append(str1[i])
+                    i += 1
+                    j += 1
+                elif dp[i + 1][j] < dp[i][j + 1]:
+                    res.append(str1[i])
+                    i += 1
+                else:
+                    res.append(str2[j])
+                    j += 1
+            return res
+
+        return ''.join(build_scs(0, 0))
+```
+
+```java
+public class Solution {
+    private int[][] dp;
+    private int n, m;
+
+    public String shortestCommonSupersequence(String str1, String str2) {
+        n = str1.length();
+        m = str2.length();
+        dp = new int[n + 1][m + 1];
+
+        for (int[] row : dp) {
+            Arrays.fill(row, -1);
+        }
+
+        dfs(0, 0, str1, str2);
+
+        return buildSCS(str1, str2);
+    }
+
+    private int dfs(int i, int j, String str1, String str2) {
+        if (dp[i][j] != -1) return dp[i][j];
+        if (i == n) return dp[i][j] = m - j;
+        if (j == m) return dp[i][j] = n - i;
+
+        if (str1.charAt(i) == str2.charAt(j)) {
+            dp[i][j] = 1 + dfs(i + 1, j + 1, str1, str2);
+        } else {
+            dp[i][j] = 1 + Math.min(dfs(i + 1, j, str1, str2), dfs(i, j + 1, str1, str2));
+        }
+        return dp[i][j];
+    }
+
+    private String buildSCS(String str1, String str2) {
+        StringBuilder res = new StringBuilder();
+        int i = 0, j = 0;
+
+        while (i < n || j < m) {
+            if (i == n) {
+                res.append(str2.substring(j));
+                break;
+            }
+            if (j == m) {
+                res.append(str1.substring(i));
+                break;
+            }
+            if (str1.charAt(i) == str2.charAt(j)) {
+                res.append(str1.charAt(i));
+                i++;
+                j++;
+            } else if (dp[i + 1][j] < dp[i][j + 1]) {
+                res.append(str1.charAt(i));
+                i++;
+            } else {
+                res.append(str2.charAt(j));
+                j++;
+            }
+        }
+
+        return res.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<vector<int>> dp;
+    int n, m;
+
+    int dfs(int i, int j, const string& str1, const string& str2) {
+        if (dp[i][j] != -1) return dp[i][j];
+        if (i == n) return dp[i][j] = m - j;
+        if (j == m) return dp[i][j] = n - i;
+
+        if (str1[i] == str2[j]) {
+            dp[i][j] = 1 + dfs(i + 1, j + 1, str1, str2);
+        } else {
+            dp[i][j] = 1 + min(dfs(i + 1, j, str1, str2), dfs(i, j + 1, str1, str2));
+        }
+        return dp[i][j];
+    }
+
+    string buildSCS(const string& str1, const string& str2) {
+        string res;
+        int i = 0, j = 0;
+
+        while (i < n || j < m) {
+            if (i == n) {
+                res += str2.substr(j);
+                break;
+            }
+            if (j == m) {
+                res += str1.substr(i);
+                break;
+            }
+            if (str1[i] == str2[j]) {
+                res += str1[i];
+                i++;
+                j++;
+            } else if (dp[i + 1][j] < dp[i][j + 1]) {
+                res += str1[i];
+                i++;
+            } else {
+                res += str2[j];
+                j++;
+            }
+        }
+
+        return res;
+    }
+
+public:
+    string shortestCommonSupersequence(string str1, string str2) {
+        n = str1.size();
+        m = str2.size();
+        dp = vector<vector<int>>(n + 1, vector<int>(m + 1, -1));
+
+        dfs(0, 0, str1, str2);
+        return buildSCS(str1, str2);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} str1
+     * @param {string} str2
+     * @return {string}
+     */
+    shortestCommonSupersequence(str1, str2) {
+        const n = str1.length, m = str2.length;
+        const dp = Array.from({ length: n + 1 }, () => 
+            Array(m + 1).fill(-1)
+        );
+
+        const dfs = (i, j) => {
+            if (dp[i][j] !== -1) return dp[i][j];
+            if (i === n) return (dp[i][j] = m - j);
+            if (j === m) return (dp[i][j] = n - i);
+
+            if (str1[i] === str2[j]) {
+                dp[i][j] = 1 + dfs(i + 1, j + 1);
+            } else {
+                dp[i][j] = 1 + Math.min(dfs(i + 1, j), dfs(i, j + 1));
+            }
+            return dp[i][j];
+        };
+
+        dfs(0, 0);
+
+        const buildSCS = () => {
+            const res = [];
+            let i = 0, j = 0;
+
+            while (i < n || j < m) {
+                if (i === n) {
+                    res.push(...str2.slice(j));
+                    break;
+                }
+                if (j === m) {
+                    res.push(...str1.slice(i));
+                    break;
+                }
+                if (str1[i] === str2[j]) {
+                    res.push(str1[i]);
+                    i++;
+                    j++;
+                } else if (dp[i + 1][j] < dp[i][j + 1]) {
+                    res.push(str1[i]);
+                    i++;
+                } else {
+                    res.push(str2[j]);
+                    j++;
+                }
+            }
+
+            return res.join('');
+        };
+
+        return buildSCS();
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n * m)$
+
+> Where $n$ and $m$ are the lengths of the strings $str1$ and $str2$ respectively.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def shortestCommonSupersequence(self, str1: str, str2: str) -> str:
+        n, m = len(str1), len(str2)
+        dp = [[""] * (m + 1) for _ in range(n + 1)]
+
+        for i in range(n + 1):
+            for j in range(m + 1):
+                if i == 0:
+                    dp[i][j] = str2[:j]
+                elif j == 0:
+                    dp[i][j] = str1[:i]
+                elif str1[i - 1] == str2[j - 1]:
+                    dp[i][j] = dp[i - 1][j - 1] + str1[i - 1]
+                else:
+                    if len(dp[i - 1][j]) < len(dp[i][j - 1]):
+                        dp[i][j] = dp[i - 1][j] + str1[i - 1]
+                    else:
+                        dp[i][j] = dp[i][j - 1] + str2[j - 1]
+
+        return dp[n][m]
+```
+
+```java
+public class Solution {
+    public String shortestCommonSupersequence(String str1, String str2) {
+        int n = str1.length(), m = str2.length();
+        String[][] dp = new String[n + 1][m + 1];
+
+        for (int i = 0; i <= n; i++) {
+            for (int j = 0; j <= m; j++) {
+                if (i == 0) {
+                    dp[i][j] = str2.substring(0, j);
+                } else if (j == 0) {
+                    dp[i][j] = str1.substring(0, i);
+                } else if (str1.charAt(i - 1) == str2.charAt(j - 1)) {
+                    dp[i][j] = dp[i - 1][j - 1] + str1.charAt(i - 1);
+                } else {
+                    dp[i][j] = dp[i - 1][j].length() < dp[i][j - 1].length() ?
+                        dp[i - 1][j] + str1.charAt(i - 1) :
+                        dp[i][j - 1] + str2.charAt(j - 1);
+                }
+            }
+        }
+
+        return dp[n][m];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string shortestCommonSupersequence(string str1, string str2) {
+        int n = str1.size(), m = str2.size();
+        vector<vector<string>> dp(n + 1, vector<string>(m + 1));
+
+        for (int i = 0; i <= n; i++) {
+            for (int j = 0; j <= m; j++) {
+                if (i == 0) {
+                    dp[i][j] = str2.substr(0, j);
+                } else if (j == 0) {
+                    dp[i][j] = str1.substr(0, i);
+                } else if (str1[i - 1] == str2[j - 1]) {
+                    dp[i][j] = dp[i - 1][j - 1] + str1[i - 1];
+                } else {
+                    dp[i][j] = dp[i - 1][j].size() < dp[i][j - 1].size() ?
+                               dp[i - 1][j] + str1[i - 1] :
+                               dp[i][j - 1] + str2[j - 1];
+                }
+            }
+        }
+
+        return dp[n][m];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} str1
+     * @param {string} str2
+     * @return {string}
+     */
+    shortestCommonSupersequence(str1, str2) {
+        const n = str1.length, m = str2.length;
+        const dp = Array.from({ length: n + 1 }, () => 
+            Array(m + 1).fill("")
+        );
+
+        for (let i = 0; i <= n; i++) {
+            for (let j = 0; j <= m; j++) {
+                if (i === 0) {
+                    dp[i][j] = str2.slice(0, j);
+                } else if (j === 0) {
+                    dp[i][j] = str1.slice(0, i);
+                } else if (str1[i - 1] === str2[j - 1]) {
+                    dp[i][j] = dp[i - 1][j - 1] + str1[i - 1];
+                } else {
+                    dp[i][j] = dp[i - 1][j].length < dp[i][j - 1].length ?
+                               dp[i - 1][j] + str1[i - 1] :
+                               dp[i][j - 1] + str2[j - 1];
+                }
+            }
+        }
+
+        return dp[n][m];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m * min(n, m))$
+* Space complexity: $O(n * m * min(n, m))$
+
+> Where $n$ and $m$ are the lengths of the strings $str1$ and $str2$ respectively.
+
+---
+
+## 4. Dynamic Programming (Bottom-Up) + Tracing
+
+::tabs-start
+
+```python
+class Solution:
+    def shortestCommonSupersequence(self, str1: str, str2: str) -> str:
+        n, m = len(str1), len(str2)
+        dp = [[0] * (m + 1) for _ in range(n + 1)]
+
+        for i in range(n + 1):
+            for j in range(m + 1):
+                if i == 0:
+                    dp[i][j] = j
+                elif j == 0:
+                    dp[i][j] = i
+                elif str1[i - 1] == str2[j - 1]:
+                    dp[i][j] = 1 + dp[i - 1][j - 1]
+                else:
+                    dp[i][j] = 1 + min(dp[i - 1][j], dp[i][j - 1])
+
+        res = []
+        i, j = n, m
+        while i > 0 and j > 0:
+            if str1[i - 1] == str2[j - 1]:
+                res.append(str1[i - 1])
+                i -= 1
+                j -= 1
+            elif dp[i - 1][j] < dp[i][j - 1]:
+                res.append(str1[i - 1])
+                i -= 1
+            else:
+                res.append(str2[j - 1])
+                j -= 1
+
+        while i > 0:
+            res.append(str1[i - 1])
+            i -= 1
+
+        while j > 0:
+            res.append(str2[j - 1])
+            j -= 1
+
+        return ''.join(reversed(res))
+```
+
+```java
+public class Solution {
+    public String shortestCommonSupersequence(String str1, String str2) {
+        int n = str1.length(), m = str2.length();
+        int[][] dp = new int[n + 1][m + 1];
+
+        for (int i = 0; i <= n; i++) {
+            for (int j = 0; j <= m; j++) {
+                if (i == 0) {
+                    dp[i][j] = j;
+                } else if (j == 0) {
+                    dp[i][j] = i;
+                } else if (str1.charAt(i - 1) == str2.charAt(j - 1)) {
+                    dp[i][j] = 1 + dp[i - 1][j - 1];
+                } else {
+                    dp[i][j] = 1 + Math.min(dp[i - 1][j], dp[i][j - 1]);
+                }
+            }
+        }
+
+        StringBuilder res = new StringBuilder();
+        int i = n, j = m;
+        while (i > 0 && j > 0) {
+            if (str1.charAt(i - 1) == str2.charAt(j - 1)) {
+                res.append(str1.charAt(i - 1));
+                i--;
+                j--;
+            } else if (dp[i - 1][j] < dp[i][j - 1]) {
+                res.append(str1.charAt(i - 1));
+                i--;
+            } else {
+                res.append(str2.charAt(j - 1));
+                j--;
+            }
+        }
+        while (i > 0) {
+            res.append(str1.charAt(i - 1));
+            i--;
+        }
+        while (j > 0) {
+            res.append(str2.charAt(j - 1));
+            j--;
+        }
+
+        return res.reverse().toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string shortestCommonSupersequence(string str1, string str2) {
+        int n = str1.size(), m = str2.size();
+        vector<vector<int>> dp(n + 1, vector<int>(m + 1, 0));
+
+        for (int i = 0; i <= n; i++) {
+            for (int j = 0; j <= m; j++) {
+                if (i == 0) {
+                    dp[i][j] = j;
+                } else if (j == 0) {
+                    dp[i][j] = i;
+                } else if (str1[i - 1] == str2[j - 1]) {
+                    dp[i][j] = 1 + dp[i - 1][j - 1];
+                } else {
+                    dp[i][j] = 1 + min(dp[i - 1][j], dp[i][j - 1]);
+                }
+            }
+        }
+
+        string res;
+        int i = n, j = m;
+        while (i > 0 && j > 0) {
+            if (str1[i - 1] == str2[j - 1]) {
+                res.push_back(str1[i - 1]);
+                i--;
+                j--;
+            } else if (dp[i - 1][j] < dp[i][j - 1]) {
+                res.push_back(str1[i - 1]);
+                i--;
+            } else {
+                res.push_back(str2[j - 1]);
+                j--;
+            }
+        }
+
+        while (i > 0) {
+            res.push_back(str1[i - 1]);
+            i--;
+        }
+
+        while (j > 0) {
+            res.push_back(str2[j - 1]);
+            j--;
+        }
+
+        reverse(res.begin(), res.end());
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} str1
+     * @param {string} str2
+     * @return {string}
+     */
+    shortestCommonSupersequence(str1, str2) {
+        const n = str1.length, m = str2.length;
+        const dp = Array.from({ length: n + 1 }, () => 
+            Array(m + 1).fill(0)
+        );
+
+        for (let i = 0; i <= n; i++) {
+            for (let j = 0; j <= m; j++) {
+                if (i === 0) {
+                    dp[i][j] = j;
+                } else if (j === 0) {
+                    dp[i][j] = i;
+                } else if (str1[i - 1] === str2[j - 1]) {
+                    dp[i][j] = 1 + dp[i - 1][j - 1];
+                } else {
+                    dp[i][j] = 1 + Math.min(dp[i - 1][j], dp[i][j - 1]);
+                }
+            }
+        }
+
+        const res = [];
+        let i = n, j = m;
+        while (i > 0 && j > 0) {
+            if (str1[i - 1] === str2[j - 1]) {
+                res.push(str1[i - 1]);
+                i--;
+                j--;
+            } else if (dp[i - 1][j] < dp[i][j - 1]) {
+                res.push(str1[i - 1]);
+                i--;
+            } else {
+                res.push(str2[j - 1]);
+                j--;
+            }
+        }
+
+        while (i > 0) {
+            res.push(str1[i - 1]);
+            i--;
+        }
+
+        while (j > 0) {
+            res.push(str2[j - 1]);
+            j--;
+        }
+
+        return res.reverse().join('');
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n * m)$
+
+> Where $n$ and $m$ are the lengths of the strings $str1$ and $str2$ respectively.
\ No newline at end of file
diff --git a/articles/shortest-path-in-binary-matrix.md b/articles/shortest-path-in-binary-matrix.md
new file mode 100644
index 000000000..c0a87d383
--- /dev/null
+++ b/articles/shortest-path-in-binary-matrix.md
@@ -0,0 +1,475 @@
+## 1. Breadth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def shortestPathBinaryMatrix(self, grid: list[list[int]]) -> int:
+        N = len(grid)
+        if grid[0][0] or grid[N - 1][N - 1]:
+            return -1
+
+        q = deque([(0, 0, 1)])  
+        visit = set((0, 0))
+        direct = [(0, 1), (1, 0), (0, -1), (-1, 0),
+                  (1, 1), (-1, -1), (1, -1), (-1, 1)]
+
+        while q:
+            r, c, length = q.popleft()
+            if r == N - 1 and c == N - 1:
+                return length
+
+            for dr, dc in direct:
+                nr, nc = r + dr, c + dc
+                if (0 <= nr < N and 0 <= nc < N and grid[nr][nc] == 0 and 
+                    (nr, nc) not in visit):
+                    q.append((nr, nc, length + 1))
+                    visit.add((nr, nc))
+
+        return -1
+```
+
+```java
+public class Solution {
+    public int shortestPathBinaryMatrix(int[][] grid) {
+        int N = grid.length;
+        if (grid[0][0] == 1 || grid[N - 1][N - 1] == 1) return -1;
+
+        int[][] directions = {{0, 1}, {1, 0}, {0, -1}, {-1, 0}, 
+                              {1, 1}, {-1, -1}, {1, -1}, {-1, 1}};
+        boolean[][] visit = new boolean[N][N];
+
+        Queue<int[]> q = new LinkedList<>();
+        q.offer(new int[]{0, 0, 1});
+        visit[0][0] = true;
+
+        while (!q.isEmpty()) {
+            int[] cell = q.poll();
+            int r = cell[0], c = cell[1], length = cell[2];
+
+            if (r == N - 1 && c == N - 1) return length;
+
+            for (int[] d : directions) {
+                int nr = r + d[0], nc = c + d[1];
+                if (nr >= 0 && nc >= 0 && nr < N && nc < N && 
+                    grid[nr][nc] == 0 && !visit[nr][nc]) {
+                    q.offer(new int[]{nr, nc, length + 1});
+                    visit[nr][nc] = true;
+                }
+            }
+        }
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int shortestPathBinaryMatrix(vector<vector<int>>& grid) {
+        int N = grid.size();
+        if (grid[0][0] == 1 || grid[N - 1][N - 1] == 1) return -1;
+
+        vector<pair<int, int>> directions = {{0, 1}, {1, 0}, {0, -1}, {-1, 0}, 
+                                             {1, 1}, {-1, -1}, {1, -1}, {-1, 1}};
+        vector<vector<bool>> visit(N, vector<bool>(N, false));
+
+        queue<tuple<int, int, int>> q;
+        q.push({0, 0, 1});
+        visit[0][0] = true;
+
+        while (!q.empty()) {
+            auto [r, c, length] = q.front();
+            q.pop();
+
+            if (r == N - 1 && c == N - 1) return length;
+
+            for (auto [dr, dc] : directions) {
+                int nr = r + dr, nc = c + dc;
+                if (nr >= 0 && nc >= 0 && nr < N && nc < N && 
+                    grid[nr][nc] == 0 && !visit[nr][nc]) {
+                    q.push({nr, nc, length + 1});
+                    visit[nr][nc] = true;
+                }
+            }
+        }
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    shortestPathBinaryMatrix(grid) {
+        const N = grid.length;
+        if (grid[0][0] === 1 || grid[N - 1][N - 1] === 1) return -1;
+
+        const directions = [
+            [0, 1], [1, 0], [0, -1], [-1, 0], 
+            [1, 1], [-1, -1], [1, -1], [-1, 1]
+        ];
+        const visit = Array.from({ length: N }, () => 
+            Array(N).fill(false)
+        );
+
+        const q = new Queue([[0, 0, 1]]);
+        visit[0][0] = true;
+
+        while (!q.isEmpty()) {
+            const [r, c, length] = q.pop();
+            if (r === N - 1 && c === N - 1) return length;
+
+            for (const [dr, dc] of directions) {
+                const nr = r + dr, nc = c + dc;
+                if (nr >= 0 && nc >= 0 && nr < N && nc < N && 
+                    grid[nr][nc] === 0 && !visit[nr][nc]) {
+                    q.push([nr, nc, length + 1]);
+                    visit[nr][nc] = true;
+                }
+            }
+        }
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 2. Breadth First Search (Overwriting the Input)
+
+::tabs-start
+
+```python
+class Solution:
+    def shortestPathBinaryMatrix(self, grid: list[list[int]]) -> int:
+        N = len(grid)
+        direct = [0, 1, 0, -1, 0, 1, 1, -1, -1, 1]
+
+        if grid[0][0] or grid[N - 1][N - 1]:
+            return -1
+        
+        q = deque([(0, 0)])
+        grid[0][0] = 1
+
+        while q:
+            r, c = q.popleft()
+            dist = grid[r][c]
+
+            if r == N - 1 and c == N - 1:
+                return dist
+
+            for d in range(9):
+                nr, nc = r + direct[d], c + direct[d + 1]
+                if 0 <= nr < N and 0 <= nc < N and grid[nr][nc] == 0:
+                    grid[nr][nc] = dist + 1
+                    q.append((nr, nc))
+
+        return -1
+```
+
+```java
+public class Solution {
+    public int shortestPathBinaryMatrix(int[][] grid) {
+        int N = grid.length;
+        int[] direct = {0, 1, 0, -1, 0, 1, 1, -1, -1, 1};
+
+        if (grid[0][0] == 1 || grid[N - 1][N - 1] == 1) 
+            return -1;
+
+        Queue<int[]> q = new LinkedList<>();
+        q.offer(new int[]{0, 0});
+        grid[0][0] = 1;
+
+        while (!q.isEmpty()) {
+            int[] cell = q.poll();
+            int r = cell[0], c = cell[1];
+            int dist = grid[r][c];
+
+            if (r == N - 1 && c == N - 1) 
+                return dist;
+
+            for (int d = 0; d < 9; d++) {
+                int nr = r + direct[d], nc = c + direct[d + 1];
+
+                if (nr >= 0 && nc >= 0 && nr < N && nc < N && grid[nr][nc] == 0) {
+                    grid[nr][nc] = dist + 1;
+                    q.offer(new int[]{nr, nc});
+                }
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int shortestPathBinaryMatrix(vector<vector<int>>& grid) {
+        int N = grid.size();
+        int direct[10] = {0, 1, 0, -1, 0, 1, 1, -1, -1, 1};
+
+        if (grid[0][0] || grid[N - 1][N - 1]) 
+            return -1;
+
+        queue<pair<int, int>> q;
+        q.push({0, 0});
+        grid[0][0] = 1;
+
+        while (!q.empty()) {
+            auto [r, c] = q.front();
+            q.pop();
+            int dist = grid[r][c];
+
+            if (r == N - 1 && c == N - 1) 
+                return dist;
+
+            for (int d = 0; d < 9; d++) {
+                int nr = r + direct[d], nc = c + direct[d + 1];
+
+                if (nr >= 0 && nc >= 0 && nr < N && nc < N && grid[nr][nc] == 0) {
+                    grid[nr][nc] = dist + 1;
+                    q.push({nr, nc});
+                }
+            }
+        }
+
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    shortestPathBinaryMatrix(grid) {
+        const N = grid.length;
+        const direct = [0, 1, 0, -1, 0, 1, 1, -1, -1, 1];
+
+        if (grid[0][0] || grid[N - 1][N - 1]) 
+            return -1;
+
+        let q = [[0, 0]];
+        grid[0][0] = 1;
+
+        while (q.length) {
+            let [r, c] = q.shift();
+            let dist = grid[r][c];
+
+            if (r === N - 1 && c === N - 1) 
+                return dist;
+
+            for (let d = 0; d < 9; d++) {
+                let nr = r + direct[d], nc = c + direct[d + 1];
+
+                if (nr >= 0 && nc >= 0 && nr < N && nc < N && grid[nr][nc] === 0) {
+                    grid[nr][nc] = dist + 1;
+                    q.push([nr, nc]);
+                }
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 3. Bidirectional Breadth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def shortestPathBinaryMatrix(self, grid: list[list[int]]) -> int:
+        N = len(grid)
+        if grid[0][0] or grid[N - 1][N - 1]:
+            return -1
+        if N == 1:
+            return 1
+
+        direct = [0, 1, 0, -1, 0, 1, 1, -1, -1, 1]
+        q1 = deque([(0, 0)])
+        q2 = deque([(N - 1, N - 1)])
+        grid[0][0] = -1
+        grid[N - 1][N - 1] = -2
+
+        res = 2
+        start, end = -1, -2
+        while q1 and q2:
+            for _ in range(len(q1)):
+                r, c = q1.popleft()
+                for d in range(9):
+                    nr, nc = r + direct[d], c + direct[d + 1]
+                    if 0 <= nr < N and 0 <= nc < N:
+                        if grid[nr][nc] == end:
+                            return res
+                        if grid[nr][nc] == 0:
+                            grid[nr][nc] = start
+                            q1.append((nr, nc))
+            
+            q1, q2 = q2, q1
+            start, end = end, start
+            res += 1
+
+        return -1
+```
+
+```java
+public class Solution {
+    public int shortestPathBinaryMatrix(int[][] grid) {
+        int N = grid.length;
+        if (grid[0][0] == 1 || grid[N - 1][N - 1] == 1) return -1;
+        if (N == 1) return 1;
+
+        int[] direct = {0, 1, 0, -1, 0, 1, 1, -1, -1, 1};
+        Queue<int[]> q1 = new LinkedList<>(), q2 = new LinkedList<>();
+        q1.offer(new int[]{0, 0});
+        q2.offer(new int[]{N - 1, N - 1});
+        grid[0][0] = -1;
+        grid[N - 1][N - 1] = -2;
+
+        int res = 2, start = -1, end = -2;
+        while (!q1.isEmpty() && !q2.isEmpty()) {
+            for (int i = q1.size(); i > 0; i--) {
+                int[] cell = q1.poll();
+                int r = cell[0], c = cell[1];
+
+                for (int d = 0; d < 9; d++) {
+                    int nr = r + direct[d], nc = c + direct[d + 1];
+                    if (nr >= 0 && nc >= 0 && nr < N && nc < N) {
+                        if (grid[nr][nc] == end) return res;
+                        if (grid[nr][nc] == 0) {
+                            grid[nr][nc] = start;
+                            q1.offer(new int[]{nr, nc});
+                        }
+                    }
+                }
+            }
+            Queue<int[]> temp = q1;
+            q1 = q2;
+            q2 = temp;
+            int tempVal = start;
+            start = end;
+            end = tempVal;
+            res++;
+        }
+
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int shortestPathBinaryMatrix(vector<vector<int>>& grid) {
+        int N = grid.size();
+        if (grid[0][0] || grid[N - 1][N - 1]) return -1;
+        if (N == 1) return 1;
+
+        int direct[10] = {0, 1, 0, -1, 0, 1, 1, -1, -1, 1};
+        queue<pair<int, int>> q1, q2;
+        q1.push({0, 0});
+        q2.push({N - 1, N - 1});
+        grid[0][0] = -1;
+        grid[N - 1][N - 1] = -2;
+
+        int res = 2, start = -1, end = -2;
+        while (!q1.empty() && !q2.empty()) {
+            for (int i = q1.size(); i > 0; i--) {
+                auto [r, c] = q1.front();
+                q1.pop();
+
+                for (int d = 0; d < 9; d++) {
+                    int nr = r + direct[d], nc = c + direct[d + 1];
+                    if (nr >= 0 && nc >= 0 && nr < N && nc < N) {
+                        if (grid[nr][nc] == end) return res;
+                        if (grid[nr][nc] == 0) {
+                            grid[nr][nc] = start;
+                            q1.push({nr, nc});
+                        }
+                    }
+                }
+            }
+            swap(q1, q2);
+            swap(start, end);
+            res++;
+        }
+
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    shortestPathBinaryMatrix(grid) {
+        const N = grid.length;
+        if (grid[0][0] || grid[N - 1][N - 1]) return -1;
+        if (N === 1) return 1;
+
+        const direct = [0, 1, 0, -1, 0, 1, 1, -1, -1, 1];
+        let q1 = new Queue([[0, 0]]);
+        let q2 = new Queue([[N - 1, N - 1]]);
+        grid[0][0] = -1;
+        grid[N - 1][N - 1] = -2;
+
+        let res = 2, start = -1, end = -2;
+        while (!q1.isEmpty() && !q2.isEmpty()) {
+            for (let i = q1.size(); i > 0; i--) {
+                const [r, c] = q1.pop();
+                for (let d = 0; d < 9; d++) {
+                    let nr = r + direct[d], nc = c + direct[d + 1];
+                    if (nr >= 0 && nc >= 0 && nr < N && nc < N) {
+                        if (grid[nr][nc] === end) return res;
+                        if (grid[nr][nc] === 0) {
+                            grid[nr][nc] = start;
+                            q1.push([nr, nc]);
+                        }
+                    }
+                }
+            }
+            [q1, q2] = [q2, q1];
+            [start, end] = [end, start];
+            res++;
+        }
+
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
\ No newline at end of file
diff --git a/articles/shortest-path-with-alternating-colors.md b/articles/shortest-path-with-alternating-colors.md
new file mode 100644
index 000000000..f5d927069
--- /dev/null
+++ b/articles/shortest-path-with-alternating-colors.md
@@ -0,0 +1,543 @@
+## 1. Breadth First Search - I
+
+::tabs-start
+
+```python
+class Solution:
+    def shortestAlternatingPaths(self, n: int, redEdges: list[list[int]], blueEdges: list[list[int]]) -> list[int]:
+        red, blue = defaultdict(list), defaultdict(list)
+        
+        for src, dst in redEdges:
+            red[src].append(dst)
+
+        for src, dst in blueEdges:
+            blue[src].append(dst)
+
+        answer = [-1 for _ in range(n)]
+        q = deque()
+        q.append((0, 0, None))  # [node, length, prev_edge_color]
+        visit = set()
+        visit.add((0, None))
+
+        while q:
+            node, length, edgeColor = q.popleft()
+            if answer[node] == -1:
+                answer[node] = length
+
+            if edgeColor != "RED":
+                for nei in red[node]:
+                    if (nei, "RED") not in visit:
+                        visit.add((nei, "RED"))
+                        q.append((nei, length + 1, "RED"))
+
+            if edgeColor != "BLUE":
+                for nei in blue[node]:
+                    if (nei, "BLUE") not in visit:
+                        visit.add((nei, "BLUE"))
+                        q.append((nei, length + 1, "BLUE"))
+
+        return answer
+```
+
+```java
+public class Solution {
+    public int[] shortestAlternatingPaths(int n, int[][] redEdges, int[][] blueEdges) {
+        List<Integer>[] red = new ArrayList[n], blue = new ArrayList[n];
+        for (int i = 0; i < n; i++) {
+            red[i] = new ArrayList<>();
+            blue[i] = new ArrayList<>();
+        }
+        for (int[] edge : redEdges) red[edge[0]].add(edge[1]);
+        for (int[] edge : blueEdges) blue[edge[0]].add(edge[1]);
+
+        int[] answer = new int[n];
+        Arrays.fill(answer, -1);
+        Queue<int[]> q = new LinkedList<>();
+        q.offer(new int[]{0, 0, -1});
+        Set<String> visit = new HashSet<>();
+        visit.add("0,-1");
+
+        while (!q.isEmpty()) {
+            int[] nodeData = q.poll();
+            int node = nodeData[0], length = nodeData[1], edgeColor = nodeData[2];
+
+            if (answer[node] == -1) answer[node] = length;
+
+            if (edgeColor != 0) {
+                for (int nei : red[node]) {
+                    if (visit.add(nei + ",0")) {
+                        q.offer(new int[]{nei, length + 1, 0});
+                    }
+                }
+            }
+            if (edgeColor != 1) {
+                for (int nei : blue[node]) {
+                    if (visit.add(nei + ",1")) {
+                        q.offer(new int[]{nei, length + 1, 1});
+                    }
+                }
+            }
+        }
+        return answer;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> shortestAlternatingPaths(int n, vector<vector<int>>& redEdges, vector<vector<int>>& blueEdges) {
+        vector<vector<int>> red(n), blue(n);
+        for (auto& edge : redEdges) red[edge[0]].push_back(edge[1]);
+        for (auto& edge : blueEdges) blue[edge[0]].push_back(edge[1]);
+
+        vector<int> answer(n, -1);
+        queue<vector<int>> q;
+        q.push({0, 0, -1});
+        unordered_set<string> visit;
+        visit.insert("0,-1");
+
+        while (!q.empty()) {
+            vector<int> nodeData = q.front();
+            q.pop();
+            int node = nodeData[0], length = nodeData[1], edgeColor = nodeData[2];
+
+            if (answer[node] == -1) answer[node] = length;
+
+            if (edgeColor != 0) {
+                for (int nei : red[node]) {
+                    string key = to_string(nei) + ",0";
+                    if (visit.insert(key).second) {
+                        q.push({nei, length + 1, 0});
+                    }
+                }
+            }
+            if (edgeColor != 1) {
+                for (int nei : blue[node]) {
+                    string key = to_string(nei) + ",1";
+                    if (visit.insert(key).second) {
+                        q.push({nei, length + 1, 1});
+                    }
+                }
+            }
+        }
+        return answer;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} redEdges
+     * @param {number[][]} blueEdges
+     * @return {number[]}
+     */
+    shortestAlternatingPaths(n, redEdges, blueEdges) {
+        const red = Array.from({ length: n }, () => []);
+        const blue = Array.from({ length: n }, () => []);
+
+        for (const [src, dst] of redEdges) red[src].push(dst);
+        for (const [src, dst] of blueEdges) blue[src].push(dst);
+
+        const answer = new Array(n).fill(-1);
+        const q = new Queue([[0, 0, null]]);
+        const visit = new Set(["0,null"]);
+
+        while (!q.isEmpty()) {
+            const [node, length, edgeColor] = q.pop();
+            if (answer[node] === -1) answer[node] = length;
+
+            if (edgeColor !== "RED") {
+                for (const nei of red[node]) {
+                    if (!visit.has(`${nei},RED`)) {
+                        visit.add(`${nei},RED`);
+                        q.push([nei, length + 1, "RED"]);
+                    }
+                }
+            }
+            if (edgeColor !== "BLUE") {
+                for (const nei of blue[node]) {
+                    if (!visit.has(`${nei},BLUE`)) {
+                        visit.add(`${nei},BLUE`);
+                        q.push([nei, length + 1, "BLUE"]);
+                    }
+                }
+            }
+        }
+        return answer;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + E)$
+* Space complexity: $O(V + E)$
+
+> Where $V$ is the number of vertices and $E$ is the number of edges.
+
+---
+
+## 2. Breadth First Search - II
+
+::tabs-start
+
+```python
+class Solution:
+    def shortestAlternatingPaths(self, n: int, redEdges: list[list[int]], blueEdges: list[list[int]]) -> list[int]:
+        def buildGraph(edges):
+            adj = [[] for _ in range(n)]
+            for u, v in edges:
+                adj[u].append(v)
+            return adj
+        
+        red, blue = buildGraph(redEdges), buildGraph(blueEdges)
+        adj = [red, blue]
+        INF = float("inf")
+        dist = [[INF] * 2 for _ in range(n)]
+        dist[0][0] = dist[0][1] = 0
+
+        q = deque([(0, 0), (0, 1)])
+        while q:
+            node, color = q.popleft()
+            for nei in adj[color][node]:
+                if dist[nei][color ^ 1] > dist[node][color] + 1:
+                    dist[nei][color ^ 1] = dist[node][color] + 1
+                    q.append((nei, color ^ 1))
+
+        answer = [0] + [-1] * (n - 1)
+        for i in range(1, n):
+            answer[i] = min(dist[i][0], dist[i][1])
+            if answer[i] == INF:
+                answer[i] = -1
+        return answer
+```
+
+```java
+public class Solution {
+    public int[] shortestAlternatingPaths(int n, int[][] redEdges, int[][] blueEdges) {
+        List<Integer>[][] adj = new ArrayList[2][n];
+        adj[0] = buildGraph(n, redEdges);
+        adj[1] = buildGraph(n, blueEdges);
+
+        int INF = Integer.MAX_VALUE;
+        int[][] dist = new int[n][2];
+
+        for (int i = 0; i < n; i++) Arrays.fill(dist[i], INF);
+        dist[0][0] = dist[0][1] = 0;
+
+        Queue<int[]> q = new LinkedList<>();
+        q.offer(new int[]{0, 0});
+        q.offer(new int[]{0, 1});
+
+        while (!q.isEmpty()) {
+            int[] cur = q.poll();
+            int node = cur[0], color = cur[1];
+
+            for (int nei : adj[color][node]) {
+                if (dist[nei][color ^ 1] > dist[node][color] + 1) {
+                    dist[nei][color ^ 1] = dist[node][color] + 1;
+                    q.offer(new int[]{nei, color ^ 1});
+                }
+            }
+        }
+
+        int[] answer = new int[n];
+        for (int i = 0; i < n; i++) {
+            answer[i] = Math.min(dist[i][0], dist[i][1]);
+            if (answer[i] == INF) answer[i] = -1;
+        }
+        return answer;
+    }
+
+    private List<Integer>[] buildGraph(int n, int[][] edges) {
+        List<Integer>[] adj = new ArrayList[n];
+        for (int i = 0; i < n; i++) {
+            adj[i] = new ArrayList<>();
+        }
+        for (int[] edge : edges) {
+            adj[edge[0]].add(edge[1]);
+        }
+        return adj;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> shortestAlternatingPaths(int n, vector<vector<int>>& redEdges, vector<vector<int>>& blueEdges) {
+        vector<vector<int>> red = buildGraph(n, redEdges);
+        vector<vector<int>> blue = buildGraph(n, blueEdges);
+        vector<vector<int>> adj[] = {red, blue};
+
+        const int INF = 1e6;
+        vector<vector<int>> dist(n, vector<int>(2, INF));
+        dist[0][0] = dist[0][1] = 0;
+
+        queue<pair<int, int>> q;
+        q.push({0, 0});
+        q.push({0, 1});
+
+        while (!q.empty()) {
+            auto [node, color] = q.front();q.pop();
+            for (int nei : adj[color][node]) {
+                if (dist[nei][color ^ 1] > dist[node][color] + 1) {
+                    dist[nei][color ^ 1] = dist[node][color] + 1;
+                    q.push({nei, color ^ 1});
+                }
+            }
+        }
+
+        vector<int> answer(n, -1);
+        for (int i = 0; i < n; i++) {
+            answer[i] = min(dist[i][0], dist[i][1]);
+            if (answer[i] == INF) answer[i] = -1;
+        }
+        return answer;
+    }
+
+private:
+    vector<vector<int>> buildGraph(int n, vector<vector<int>>& edges) {
+        vector<vector<int>> adj(n);
+        for (auto& edge : edges) {
+            adj[edge[0]].push_back(edge[1]);
+        }
+        return adj;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} redEdges
+     * @param {number[][]} blueEdges
+     * @return {number[]}
+     */
+    shortestAlternatingPaths(n, redEdges, blueEdges) {
+        const red = this.buildGraph(n, redEdges);
+        const blue = this.buildGraph(n, blueEdges);
+        const adj = [red, blue];
+        const INF = 1e6;
+        const dist = Array.from({ length: n }, () => [INF, INF]);
+        dist[0][0] = dist[0][1] = 0;
+
+        const q = new Queue([[0, 0], [0, 1]]);
+        while (!q.isEmpty()) {
+            const [node, color] = q.pop();
+            for (const nei of adj[color][node]) {
+                if (dist[nei][color ^ 1] > dist[node][color] + 1) {
+                    dist[nei][color ^ 1] = dist[node][color] + 1;
+                    q.push([nei, color ^ 1]);
+                }
+            }
+        }
+
+        return Array.from({ length: n }, (_, i) => {
+            let minDist = Math.min(dist[i][0], dist[i][1]);
+            return minDist === INF ? -1 : minDist;
+        });
+    }
+
+    /**
+     * @param {number} n
+     * @param {number[][]} edges
+     * @return {number[][]}
+     */
+    buildGraph(n, edges) {
+        const adj = Array.from({ length: n }, () => []);
+        for (const [u, v] of edges) {
+            adj[u].push(v);
+        }
+        return adj;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + E)$
+* Space complexity: $O(V + E)$
+
+> Where $V$ is the number of vertices and $E$ is the number of edges.
+
+---
+
+## 3. Depth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def shortestAlternatingPaths(self, n: int, redEdges: list[list[int]], blueEdges: list[list[int]]) -> list[int]:
+        def buildGraph(edges):
+            adj = [[] for _ in range(n)]
+            for u, v in edges:
+                adj[u].append(v)
+            return adj
+
+        red, blue = buildGraph(redEdges), buildGraph(blueEdges)
+        adj = [red, blue]
+        INF = float("inf")
+        dist = [[INF] * 2 for _ in range(n)]
+        dist[0][0] = dist[0][1] = 0
+
+        def dfs(node, color):
+            for nei in adj[color][node]:
+                if dist[nei][color ^ 1] > dist[node][color] + 1:
+                    dist[nei][color ^ 1] = dist[node][color] + 1
+                    dfs(nei, color ^ 1)
+
+        dfs(0, 0)
+        dfs(0, 1)
+
+        answer = [0] + [-1] * (n - 1)
+        for i in range(1, n):
+            answer[i] = min(dist[i][0], dist[i][1])
+            if answer[i] == INF:
+                answer[i] = -1
+
+        return answer
+```
+
+```java
+public class Solution {
+    public int[] shortestAlternatingPaths(int n, int[][] redEdges, int[][] blueEdges) {
+        List<Integer>[][] adj = new ArrayList[2][n];
+        adj[0] = buildGraph(n, redEdges);
+        adj[1] = buildGraph(n, blueEdges);
+
+        int INF = Integer.MAX_VALUE;
+        int[][] dist = new int[n][2];
+        for (int i = 0; i < n; i++) Arrays.fill(dist[i], INF);
+        dist[0][0] = dist[0][1] = 0;
+
+        dfs(0, 0, adj, dist);
+        dfs(0, 1, adj, dist);
+
+        int[] answer = new int[n];
+        for (int i = 0; i < n; i++) {
+            answer[i] = Math.min(dist[i][0], dist[i][1]);
+            if (answer[i] == INF) answer[i] = -1;
+        }
+        return answer;
+    }
+
+    private void dfs(int node, int color, List<Integer>[][] adj, int[][] dist) {
+        for (int nei : adj[color][node]) {
+            if (dist[nei][color ^ 1] > dist[node][color] + 1) {
+                dist[nei][color ^ 1] = dist[node][color] + 1;
+                dfs(nei, color ^ 1, adj, dist);
+            }
+        }
+    }
+
+    private List<Integer>[] buildGraph(int n, int[][] edges) {
+        List<Integer>[] adj = new ArrayList[n];
+        for (int i = 0; i < n; i++) {
+            adj[i] = new ArrayList<>();
+        }
+        for (int[] edge : edges) {
+            adj[edge[0]].add(edge[1]);
+        }
+        return adj;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> shortestAlternatingPaths(int n, vector<vector<int>>& redEdges, vector<vector<int>>& blueEdges) {
+        vector<vector<int>> adj[2] = {buildGraph(n, redEdges), buildGraph(n, blueEdges)};
+        
+        int INF = numeric_limits<int>::max();
+        vector<vector<int>> dist(n, vector<int>(2, INF));
+        dist[0][0] = dist[0][1] = 0;
+
+        dfs(0, 0, adj, dist);
+        dfs(0, 1, adj, dist);
+
+        vector<int> answer(n, -1);
+        for (int i = 0; i < n; i++) {
+            answer[i] = min(dist[i][0], dist[i][1]);
+            if (answer[i] == INF) answer[i] = -1;
+        }
+        return answer;
+    }
+
+private:
+    void dfs(int node, int color, vector<vector<int>> adj[], vector<vector<int>>& dist) {
+        for (int nei : adj[color][node]) {
+            if (dist[nei][color ^ 1] > dist[node][color] + 1) {
+                dist[nei][color ^ 1] = dist[node][color] + 1;
+                dfs(nei, color ^ 1, adj, dist);
+            }
+        }
+    }
+
+    vector<vector<int>> buildGraph(int n, vector<vector<int>>& edges) {
+        vector<vector<int>> adj(n);
+        for (auto& edge : edges) {
+            adj[edge[0]].push_back(edge[1]);
+        }
+        return adj;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[][]} redEdges
+     * @param {number[][]} blueEdges
+     * @return {number[]}
+     */
+    shortestAlternatingPaths(n, redEdges, blueEdges) {
+        const INF = Number.MAX_SAFE_INTEGER;
+        const adj = [Array.from({ length: n }, () => []), 
+                     Array.from({ length: n }, () => [])];
+
+        redEdges.forEach(([u, v]) => adj[0][u].push(v));
+        blueEdges.forEach(([u, v]) => adj[1][u].push(v));
+
+        const dist = Array.from({ length: n }, () => [INF, INF]);
+        dist[0][0] = dist[0][1] = 0;
+
+        const dfs = (node, color) => {
+            adj[color][node].forEach(nei => {
+                if (dist[nei][color ^ 1] > dist[node][color] + 1) {
+                    dist[nei][color ^ 1] = dist[node][color] + 1;
+                    dfs(nei, color ^ 1);
+                }
+            });
+        };
+
+        dfs(0, 0);
+        dfs(0, 1);
+
+        return dist.map(([red, blue]) => {
+            let res = Math.min(red, blue);
+            return res === INF ? -1 : res;
+        });
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + E)$
+* Space complexity: $O(V + E)$
+
+> Where $V$ is the number of vertices and $E$ is the number of edges.
\ No newline at end of file
diff --git a/articles/shuffle-the-array.md b/articles/shuffle-the-array.md
new file mode 100644
index 000000000..eded033b7
--- /dev/null
+++ b/articles/shuffle-the-array.md
@@ -0,0 +1,257 @@
+## 1. Iteration (Extra Space)
+
+::tabs-start
+
+```python
+class Solution:
+    def shuffle(self, nums: List[int], n: int) -> List[int]:
+        res = []
+        for i in range(n):
+            res.append(nums[i])
+            res.append(nums[i + n])
+        return res
+```
+
+```java
+public class Solution {
+    public int[] shuffle(int[] nums, int n) {
+        int[] res = new int[2 * n];
+        int idx = 0;
+        for (int i = 0; i < n; i++) {
+            res[idx++] = nums[i];
+            res[idx++] = nums[i + n];
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> shuffle(vector<int>& nums, int n) {
+        vector<int> res;
+        for (int i = 0; i < n; i++) {
+            res.push_back(nums[i]);
+            res.push_back(nums[i + n]);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} n
+     * @return {number[]}
+     */
+    shuffle(nums) {
+        const res = [];
+        for (let i = 0; i < n; i++) {
+            res.push(nums[i]);
+            res.push(nums[i + n]);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ extra space.
+
+---
+
+## 2. Multiplication And Modulo
+
+::tabs-start
+
+```python
+class Solution:
+    def shuffle(self, nums: List[int], n: int) -> List[int]:
+        M = max(nums) + 1
+        for i in range(2 * n):
+            if i % 2 == 0:
+                nums[i] += (nums[i // 2] % M) * M
+            else:
+                nums[i] += (nums[n + i // 2] % M) * M
+        
+        for i in range(2 * n):
+            nums[i] //= M
+
+        return nums
+```
+
+```java
+public class Solution {
+    public int[] shuffle(int[] nums, int n) {
+        int M = 1001;
+        for (int i = 0; i < 2 * n; i++) {
+            if (i % 2 == 0) {
+                nums[i] += (nums[i / 2] % M) * M;
+            } else {
+                nums[i] += (nums[n + i / 2] % M) * M;
+            }
+        }
+        for (int i = 0; i < 2 * n; i++) {
+            nums[i] /= M;
+        }
+        return nums;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> shuffle(vector<int>& nums, int n) {
+        int M = *max_element(nums.begin(), nums.end()) + 1;
+        for (int i = 0; i < 2 * n; i++) {
+            if (i % 2 == 0) {
+                nums[i] += (nums[i / 2] % M) * M;
+            } else {
+                nums[i] += (nums[n + i / 2] % M) * M;
+            }
+        }
+        for (int i = 0; i < 2 * n; i++) {
+            nums[i] /= M;
+        }
+        return nums;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} n
+     * @return {number[]}
+     */
+    shuffle(nums) {
+        const M = Math.max(...nums) + 1;
+        for (let i = 0; i < 2 * n; i++) {
+            if (i % 2 === 0) {
+                nums[i] += (nums[i >> 1] % M) * M;
+            } else {
+                nums[i] += (nums[n + (i >> 1)] % M) * M;
+            }
+        }
+        for (let i = 0; i < 2 * n; i++) {
+            nums[i] = Math.floor(nums[i] / M);
+        }
+        return nums;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 3. Bit Manipulation
+
+::tabs-start
+
+```python
+class Solution:
+    def shuffle(self, nums: List[int], n: int) -> List[int]:
+        for i in range(n):
+            nums[i] = (nums[i] << 10) | nums[i + n]  # Store x, y in nums[i]
+        
+        j = 2 * n - 1
+        for i in range(n - 1, -1, -1):
+            y = nums[i] & ((1 << 10) - 1)
+            x = nums[i] >> 10
+            nums[j] = y
+            nums[j - 1] = x
+            j -= 2
+        
+        return nums
+```
+
+```java
+public class Solution {
+    public int[] shuffle(int[] nums, int n) {
+        for (int i = 0; i < n; i++) {
+            nums[i] = (nums[i] << 10) | nums[i + n]; // Store x, y in nums[i]
+        }
+
+        int j = 2 * n - 1;
+        for (int i = n - 1; i >= 0; i--) {
+            int y = nums[i] & ((1 << 10) - 1);
+            int x = nums[i] >> 10;
+            nums[j] = y;
+            nums[j - 1] = x;
+            j -= 2;
+        }
+
+        return nums;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> shuffle(vector<int>& nums, int n) {
+        for (int i = 0; i < n; i++) {
+            nums[i] = (nums[i] << 10) | nums[i + n]; // Store x, y in nums[i]
+        }
+
+        int j = 2 * n - 1;
+        for (int i = n - 1; i >= 0; i--) {
+            int y = nums[i] & ((1 << 10) - 1);
+            int x = nums[i] >> 10;
+            nums[j] = y;
+            nums[j - 1] = x;
+            j -= 2;
+        }
+
+        return nums;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} n
+     * @return {number[]}
+     */
+    shuffle(nums) {
+        for (let i = 0; i < n; i++) {
+            nums[i] = (nums[i] << 10) | nums[i + n]; // Store x, y in nums[i]
+        }
+
+        let j = 2 * n - 1;
+        for (let i = n - 1; i >= 0; i--) {
+            let y = nums[i] & ((1 << 10) - 1);
+            let x = nums[i] >> 10;
+            nums[j] = y;
+            nums[j - 1] = x;
+            j -= 2;
+        }
+
+        return nums;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/sign-of-the-product-of-an-array.md b/articles/sign-of-the-product-of-an-array.md
new file mode 100644
index 000000000..76922c8d0
--- /dev/null
+++ b/articles/sign-of-the-product-of-an-array.md
@@ -0,0 +1,158 @@
+## 1. Count Negative Numbers
+
+::tabs-start
+
+```python
+class Solution:
+    def arraySign(self, nums: list[int]) -> int:
+        neg = 0
+        for num in nums:
+            if num == 0:
+                return 0
+            neg += (1 if num < 0 else 0)
+        return -1 if neg % 2 else 1
+```
+
+```java
+public class Solution {
+    public int arraySign(int[] nums) {
+        int neg = 0;
+        for (int num : nums) {
+            if (num == 0) {
+                return 0;
+            }
+            if (num < 0) {
+                neg++;
+            }
+        }
+        return neg % 2 == 0 ? 1 : -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int arraySign(vector<int>& nums) {
+        int neg = 0;
+        for (int num : nums) {
+            if (num == 0) {
+                return 0;
+            }
+            if (num < 0) {
+                neg++;
+            }
+        }
+        return neg % 2 == 0 ? 1 : -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    arraySign(nums) {
+        let neg = 0;
+        for (const num of nums) {
+            if (num === 0) {
+                return 0;
+            }
+            if (num < 0) {
+                neg++;
+            }
+        }
+        return neg % 2 === 0 ? 1 : -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Track the Sign of the Product
+
+::tabs-start
+
+```python
+class Solution:
+    def arraySign(self, nums: list[int]) -> int:
+        sign = 1
+        for num in nums:
+            if num == 0:
+                return 0
+            if num < 0:
+                sign *= -1
+        return sign
+```
+
+```java
+public class Solution {
+    public int arraySign(int[] nums) {
+        int sign = 1;
+        for (int num : nums) {
+            if (num == 0) {
+                return 0;
+            }
+            if (num < 0) {
+                sign *= -1;
+            }
+        }
+        return sign;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int arraySign(vector<int>& nums) {
+        int sign = 1;
+        for (int num : nums) {
+            if (num == 0) {
+                return 0;
+            }
+            if (num < 0) {
+                sign *= -1;
+            }
+        }
+        return sign;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    arraySign(nums) {
+        let sign = 1;
+        for (const num of nums) {
+            if (num === 0) {
+                return 0;
+            }
+            if (num < 0) {
+                sign *= -1;
+            }
+        }
+        return sign;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/simplify-path.md b/articles/simplify-path.md
new file mode 100644
index 000000000..ae0ecb3ee
--- /dev/null
+++ b/articles/simplify-path.md
@@ -0,0 +1,262 @@
+## 1. Stack - I
+
+::tabs-start
+
+```python
+class Solution:
+    def simplifyPath(self, path: str) -> str:
+        stack = []
+        cur = ""
+
+        for c in path + "/":
+            if c == "/":
+                if cur == "..":
+                    if stack:
+                        stack.pop()
+                elif cur != "" and cur != ".":
+                    stack.append(cur)
+                cur = ""
+            else:
+                cur += c
+
+        return "/" + "/".join(stack)
+```
+
+```java
+public class Solution {
+    public String simplifyPath(String path) {
+        Stack<String> stack = new Stack<>();
+        StringBuilder cur = new StringBuilder();
+
+        for (char c : (path + "/").toCharArray()) {
+            if (c == '/') {
+                if (cur.toString().equals("..")) {
+                    if (!stack.isEmpty()) stack.pop();
+                } else if (!cur.toString().equals("") && !cur.toString().equals(".")) {
+                    stack.push(cur.toString());
+                }
+                cur.setLength(0);
+            } else {
+                cur.append(c);
+            }
+        }
+
+        return "/" + String.join("/", stack);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string simplifyPath(string path) {
+        vector<string> stack;
+        string cur;
+
+        for (char c : path + "/") {
+            if (c == '/') {
+                if (cur == "..") {
+                    if (!stack.empty()) stack.pop_back();
+                } else if (!cur.empty() && cur != ".") {
+                    stack.push_back(cur);
+                }
+                cur.clear();
+            } else {
+                cur += c;
+            }
+        }
+
+        string result = "/";
+        for (int i = 0; i < stack.size(); ++i) {
+            if (i > 0) result += "/";
+            result += stack[i];
+        }
+
+        return result;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} path
+     * @return {string}
+     */
+    simplifyPath(path) {
+        const stack = [];
+        let cur = "";
+
+        for (const c of path + "/") {
+            if (c === "/") {
+                if (cur === "..") {
+                    if (stack.length) stack.pop();
+                } else if (cur !== "" && cur !== ".") {
+                    stack.push(cur);
+                }
+                cur = "";
+            } else {
+                cur += c;
+            }
+        }
+
+        return "/" + stack.join("/");
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public string SimplifyPath(string path) {
+        Stack<string> stack = new Stack<string>();
+        string cur = "";
+
+        foreach (char c in path + "/") {
+            if (c == '/') {
+                if (cur == "..") {
+                    if (stack.Count > 0) stack.Pop();
+                } else if (cur != "" && cur != ".") {
+                    stack.Push(cur);
+                }
+                cur = "";
+            } else {
+                cur += c;
+            }
+        }
+
+        var result = new List<string>(stack);
+        result.Reverse();
+        return "/" + string.Join("/", result);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Stack - II
+
+::tabs-start
+
+```python
+class Solution:
+    def simplifyPath(self, path: str) -> str:
+        stack = []
+        paths = path.split("/")
+
+        for cur in paths:
+            if cur == "..":
+                if stack:
+                    stack.pop()
+            elif cur != "" and cur != ".":
+                stack.append(cur)
+
+        return "/" + "/".join(stack)
+```
+
+```java
+public class Solution {
+    public String simplifyPath(String path) {
+        Stack<String> stack = new Stack<>();
+        String[] paths = path.split("/");
+
+        for (String cur : paths) {
+            if (cur.equals("..")) {
+                if (!stack.isEmpty()) stack.pop();
+            } else if (!cur.equals("") && !cur.equals(".")) {
+                stack.push(cur);
+            }
+        }
+
+        return "/" + String.join("/", stack);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string simplifyPath(string path) {
+        vector<string> stack;
+        string cur;
+        stringstream ss(path);
+        while (getline(ss, cur, '/')) {
+            if (cur.empty()) continue;
+            if (cur == "..") {
+                if (!stack.empty()) stack.pop_back();
+            } else if (!cur.empty() && cur != ".") {
+                stack.push_back(cur);
+            }
+        }
+
+        string result = "/";
+        for (int i = 0; i < stack.size(); ++i) {
+            if (i > 0) result += "/";
+            result += stack[i];
+        }
+
+        return result;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} path
+     * @return {string}
+     */
+    simplifyPath(path) {
+        const stack = [];
+        const paths = path.split("/");
+
+        for (const cur of paths) {
+            if (cur === "..") {
+                if (stack.length) {
+                    stack.pop();
+                }
+            } else if (cur !== "" && cur !== ".") {
+                stack.push(cur);
+            }
+        }
+
+        return "/" + stack.join("/");
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public string SimplifyPath(string path) {
+        Stack<string> stack = new Stack<string>();
+        string[] parts = path.Split('/');
+
+        foreach (string part in parts) {
+            if (part == "..") {
+                if (stack.Count > 0) {
+                    stack.Pop();
+                }
+            } else if (part != "" && part != ".") {
+                stack.Push(part);
+            }
+        }
+
+        var result = new List<string>(stack);
+        result.Reverse();
+        return "/" + string.Join("/", result);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/single-element-in-a-sorted-array.md b/articles/single-element-in-a-sorted-array.md
new file mode 100644
index 000000000..e2a5a8b0e
--- /dev/null
+++ b/articles/single-element-in-a-sorted-array.md
@@ -0,0 +1,438 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def singleNonDuplicate(self, nums: List[int]) -> int:
+        n = len(nums)
+        for i in range(n):
+            if ((i and nums[i] == nums[i - 1]) or
+                (i < n - 1 and nums[i] == nums[i + 1])
+            ):
+                continue
+            return nums[i]
+```
+
+```java
+public class Solution {
+    public int singleNonDuplicate(int[] nums) {
+        int n = nums.length;
+        for (int i = 0; i < n; i++) {
+            if ((i > 0 && nums[i] == nums[i - 1]) ||
+                (i < n - 1 && nums[i] == nums[i + 1])) {
+                continue;
+            }
+            return nums[i];
+        }
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int singleNonDuplicate(vector<int>& nums) {
+        int n = nums.size();
+        for (int i = 0; i < n; i++) {
+            if ((i > 0 && nums[i] == nums[i - 1]) ||
+                (i < n - 1 && nums[i] == nums[i + 1])) {
+                continue;
+            }
+            return nums[i];
+        }
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    singleNonDuplicate(nums) {
+        const n = nums.length;
+        for (let i = 0; i < n; i++) {
+            if ((i > 0 && nums[i] === nums[i - 1]) ||
+                (i < n - 1 && nums[i] === nums[i + 1])) {
+                continue;
+            }
+            return nums[i];
+        }
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Brute Force (Bitwise Xor)
+
+::tabs-start
+
+```python
+class Solution:
+    def singleNonDuplicate(self, nums: List[int]) -> int:
+        xorr = 0
+        for num in nums:
+            xorr ^= num
+        return xorr
+```
+
+```java
+public class Solution {
+    public int singleNonDuplicate(int[] nums) {
+        int xorr = 0;
+        for (int num : nums) {
+            xorr ^= num;
+        }
+        return xorr;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int singleNonDuplicate(vector<int>& nums) {
+        int xorr = 0;
+        for (int num : nums) {
+            xorr ^= num;
+        }
+        return xorr;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    singleNonDuplicate(nums) {
+        let xorr = 0;
+        for (const num of nums) {
+            xorr ^= num;
+        }
+        return xorr;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Binary Search
+
+::tabs-start
+
+```python
+class Solution:
+    def singleNonDuplicate(self, nums: List[int]) -> int:
+        l, r = 0, len(nums) - 1
+
+        while l <= r:
+            m = l + ((r - l) // 2)
+            if ((m - 1 < 0 or nums[m - 1] != nums[m]) and 
+                (m + 1 == len(nums) or nums[m] != nums[m + 1])):
+                return nums[m]
+
+            leftSize = m - 1 if nums[m - 1] == nums[m] else m
+            if leftSize % 2:
+                r = m - 1
+            else:
+                l = m + 1
+```
+
+```java
+public class Solution {
+    public int singleNonDuplicate(int[] nums) {
+        int l = 0, r = nums.length - 1;
+
+        while (l <= r) {
+            int m = l + (r - l) / 2;
+            if ((m - 1 < 0 || nums[m - 1] != nums[m]) && 
+                (m + 1 == nums.length || nums[m] != nums[m + 1])) {
+                return nums[m];
+            }
+
+            int leftSize = (m - 1 >= 0 && nums[m - 1] == nums[m]) ? m - 1 : m;
+            if (leftSize % 2 == 1) {
+                r = m - 1;
+            } else {
+                l = m + 1;
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int singleNonDuplicate(vector<int>& nums) {
+        int l = 0, r = nums.size() - 1;
+
+        while (l <= r) {
+            int m = l + (r - l) / 2;
+            if ((m - 1 < 0 || nums[m - 1] != nums[m]) && 
+                (m + 1 == nums.size() || nums[m] != nums[m + 1])) {
+                return nums[m];
+            }
+
+            int leftSize = (m - 1 >= 0 && nums[m - 1] == nums[m]) ? m - 1 : m;
+            if (leftSize % 2 == 1) {
+                r = m - 1;
+            } else {
+                l = m + 1;
+            }
+        }
+
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    singleNonDuplicate(nums) {
+        let l = 0, r = nums.length - 1;
+
+        while (l <= r) {
+            let m = l + Math.floor((r - l) / 2);
+            if ((m - 1 < 0 || nums[m - 1] !== nums[m]) && 
+                (m + 1 === nums.length || nums[m] !== nums[m + 1])) {
+                return nums[m];
+            }
+
+            let leftSize = (m - 1 >= 0 && nums[m - 1] === nums[m]) ? m - 1 : m;
+            if (leftSize % 2 === 1) {
+                r = m - 1;
+            } else {
+                l = m + 1;
+            }
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
+
+---
+
+## 4. Binary Search On Even Indexes
+
+::tabs-start
+
+```python
+class Solution:
+    def singleNonDuplicate(self, nums: List[int]) -> int:
+        l, r = 0, len(nums) - 1
+
+        while l < r:
+            m = l + (r - l) // 2
+            if m & 1:
+                m -= 1
+            if nums[m] != nums[m + 1]:
+                r = m
+            else:
+                l = m + 2
+
+        return nums[l]
+```
+
+```java
+public class Solution {
+    public int singleNonDuplicate(int[] nums) {
+        int l = 0, r = nums.length - 1;
+
+        while (l < r) {
+            int m = l + (r - l) / 2;
+            if ((m & 1) == 1) {
+                m--;
+            }
+            if (nums[m] != nums[m + 1]) {
+                r = m;
+            } else {
+                l = m + 2;
+            }
+        }
+
+        return nums[l];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int singleNonDuplicate(vector<int>& nums) {
+        int l = 0, r = nums.size() - 1;
+
+        while (l < r) {
+            int m = l + (r - l) / 2;
+            if (m & 1) {
+                m--;
+            }
+            if (nums[m] != nums[m + 1]) {
+                r = m;
+            } else {
+                l = m + 2;
+            }
+        }
+
+        return nums[l];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    singleNonDuplicate(nums) {
+        let l = 0, r = nums.length - 1;
+
+        while (l < r) {
+            let m = Math.floor(l + (r - l) / 2);
+            if (m & 1) {
+                m--;
+            }
+            if (nums[m] !== nums[m + 1]) {
+                r = m;
+            } else {
+                l = m + 2;
+            }
+        }
+
+        return nums[l];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
+
+---
+
+## 5. Binary Search + Bit Manipulation
+
+::tabs-start
+
+```python
+class Solution:
+    def singleNonDuplicate(self, nums: List[int]) -> int:
+        l, r = 0, len(nums) - 1
+
+        while l < r:
+            m = (l + r) >> 1
+            if nums[m] != nums[m ^ 1]:
+                r = m
+            else:
+                l = m + 1
+        
+        return nums[l]
+```
+
+```java
+public class Solution {
+    public int singleNonDuplicate(int[] nums) {
+        int l = 0, r = nums.length - 1;
+
+        while (l < r) {
+            int m = (l + r) >> 1;
+            if (nums[m] != nums[m ^ 1]) {
+                r = m;
+            } else {
+                l = m + 1;
+            }
+        }
+
+        return nums[l];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int singleNonDuplicate(vector<int>& nums) {
+        int l = 0, r = nums.size() - 1;
+
+        while (l < r) {
+            int m = (l + r) >> 1;
+            if (nums[m] != nums[m ^ 1]) {
+                r = m;
+            } else {
+                l = m + 1;
+            }
+        }
+
+        return nums[l];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    singleNonDuplicate(nums) {
+        let l = 0, r = nums.length - 1;
+
+        while (l < r) {
+            let m = (l + r) >> 1;
+            if (nums[m] !== nums[m ^ 1]) {
+                r = m;
+            } else {
+                l = m + 1;
+            }
+        }
+
+        return nums[l];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/single-number-iii.md b/articles/single-number-iii.md
new file mode 100644
index 000000000..5e714092d
--- /dev/null
+++ b/articles/single-number-iii.md
@@ -0,0 +1,608 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def singleNumber(self, nums: List[int]) -> List[int]:
+        n, res = len(nums), []
+
+        for i in range(n):
+            flag = True
+            for j in range(n):
+                if i != j and nums[i] == nums[j]:
+                    flag = False
+                    break
+            
+            if flag:
+                res.append(nums[i])
+                if len(res) == 2:
+                    break
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int[] singleNumber(int[] nums) {
+        int n = nums.length;
+        List<Integer> res = new ArrayList<>();
+
+        for (int i = 0; i < n; i++) {
+            boolean flag = true;
+            for (int j = 0; j < n; j++) {
+                if (i != j && nums[i] == nums[j]) {
+                    flag = false;
+                    break;
+                }
+            }
+
+            if (flag) {
+                res.add(nums[i]);
+                if (res.size() == 2) {
+                    break;
+                }
+            }
+        }
+
+        return new int[] {res.get(0), res.get(1)};
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> singleNumber(vector<int>& nums) {
+        int n = nums.size();
+        vector<int> res;
+
+        for (int i = 0; i < n; i++) {
+            bool flag = true;
+            for (int j = 0; j < n; j++) {
+                if (i != j && nums[i] == nums[j]) {
+                    flag = false;
+                    break;
+                }
+            }
+
+            if (flag) {
+                res.push_back(nums[i]);
+                if (res.size() == 2) {
+                    break;
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    singleNumber(nums) {
+        const n = nums.length;
+        const res = [];
+
+        for (let i = 0; i < n; i++) {
+            let flag = true;
+            for (let j = 0; j < n; j++) {
+                if (i !== j && nums[i] === nums[j]) {
+                    flag = false;
+                    break;
+                }
+            }
+
+            if (flag) {
+                res.push(nums[i]);
+                if (res.length === 2) {
+                    break;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 2. Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def singleNumber(self, nums: List[int]) -> List[int]:
+        count = {}
+        for num in nums:
+            count[num] = 1 + count.get(num, 0)
+        
+        return [k for k in count if count[k] == 1]
+```
+
+```java
+public class Solution {
+    public int[] singleNumber(int[] nums) {
+        Map<Integer, Integer> count = new HashMap<>();
+        for (int num : nums) {
+            count.put(num, count.getOrDefault(num, 0) + 1);
+        }
+
+        ArrayList<Integer> res = new ArrayList<>();
+        for (int key : count.keySet()) {
+            if (count.get(key) == 1) {
+                res.add(key);
+            }
+        }
+
+        return new int[] {res.get(0), res.get(1)};
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> singleNumber(vector<int>& nums) {
+        unordered_map<int, int> count;
+        for (int num : nums) {
+            count[num]++;
+        }
+
+        vector<int> res;
+        for (const auto& pair : count) {
+            if (pair.second == 1) {
+                res.push_back(pair.first);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    singleNumber(nums) {
+        const count = new Map();
+        for (const num of nums) {
+            count.set(num, (count.get(num) || 0) + 1);
+        }
+
+        const res = [];
+        for (const [key, value] of count) {
+            if (value === 1) {
+                res.push(key);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Hash Set
+
+::tabs-start
+
+```python
+class Solution:
+    def singleNumber(self, nums: List[int]) -> List[int]:
+        seen = set()
+        for num in nums:
+            if num in seen:
+                seen.remove(num)
+            else:
+                seen.add(num)
+        return list(seen)
+```
+
+```java
+public class Solution {
+    public int[] singleNumber(int[] nums) {
+        HashSet<Integer> seen = new HashSet<>();
+        for (int num : nums) {
+            if (seen.contains(num)) {
+                seen.remove(num);
+            } else {
+                seen.add(num);
+            }
+        }
+
+        int[] res = new int[2];
+        int index = 0;
+        for (int num : seen) {
+            res[index++] = num;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> singleNumber(vector<int>& nums) {
+        unordered_set<int> seen;
+        for (int& num : nums) {
+            if (seen.count(num)) {
+                seen.erase(num);
+            } else {
+                seen.insert(num);
+            }
+        }
+
+        return vector<int>(seen.begin(), seen.end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    singleNumber(nums) {
+        const seen = new Set();
+        for (const num of nums) {
+            if (seen.has(num)) {
+                seen.delete(num);
+            } else {
+                seen.add(num);
+            }
+        }
+
+        return Array.from(seen);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def singleNumber(self, nums: List[int]) -> List[int]:
+        res, n = [], len(nums)
+        nums.sort()
+
+        for i in range(n):
+            if ((i > 0 and nums[i] == nums[i - 1]) or
+                (i + 1 < n and nums[i] == nums[i + 1])):
+                continue
+            res.append(nums[i])
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int[] singleNumber(int[] nums) {
+        Arrays.sort(nums);
+        List<Integer> res = new ArrayList<>();
+        int n = nums.length;
+
+        for (int i = 0; i < n; i++) {
+            if ((i > 0 && nums[i] == nums[i - 1]) ||
+                (i + 1 < n && nums[i] == nums[i + 1])) {
+                continue;
+            }
+            res.add(nums[i]);
+        }
+
+        return res.stream().mapToInt(i -> i).toArray();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> singleNumber(vector<int>& nums) {
+        sort(nums.begin(), nums.end());
+        vector<int> res;
+        int n = nums.size();
+
+        for (int i = 0; i < n; i++) {
+            if ((i > 0 && nums[i] == nums[i - 1]) || 
+                (i + 1 < n && nums[i] == nums[i + 1])) {
+                continue;
+            }
+            res.push_back(nums[i]);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    singleNumber(nums) {
+        nums.sort((a, b) => a - b);
+        const res = [];
+        const n = nums.length;
+
+        for (let i = 0; i < n; i++) {
+            if ((i > 0 && nums[i] === nums[i - 1]) ||
+                (i + 1 < n && nums[i] === nums[i + 1])) {
+                continue;
+            }
+            res.push(nums[i]);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 5. Bitwise XOR (Least Significant Bit)
+
+::tabs-start
+
+```python
+class Solution:
+    def singleNumber(self, nums: List[int]) -> List[int]:
+        xor = 0
+        for num in nums:
+            xor ^= num
+        
+        diff_bit = 1
+        while not (xor & diff_bit):
+            diff_bit <<= 1
+        
+        a = b = 0
+        for num in nums:
+            if diff_bit & num:
+                a ^= num
+            else:
+                b ^= num
+        return [a, b]
+```
+
+```java
+public class Solution {
+    public int[] singleNumber(int[] nums) {
+        int xor = 0;
+        for (int num : nums) {
+            xor ^= num;
+        }
+
+        int diff_bit = 1;
+        while ((xor & diff_bit) == 0) {
+            diff_bit <<= 1;
+        }
+
+        int a = 0, b = 0;
+        for (int num : nums) {
+            if ((num & diff_bit) != 0) {
+                a ^= num;
+            } else {
+                b ^= num;
+            }
+        }
+        return new int[]{a, b};
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> singleNumber(vector<int>& nums) {
+        int xor_all = 0;
+        for (int& num : nums) {
+            xor_all ^= num;
+        }
+
+        int diff_bit = 1;
+        while ((xor_all & diff_bit) == 0) {
+            diff_bit <<= 1;
+        }
+
+        int a = 0, b = 0;
+        for (int& num : nums) {
+            if (num & diff_bit) {
+                a ^= num;
+            } else {
+                b ^= num;
+            }
+        }
+        return {a, b};
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    singleNumber(nums) {
+        let xor = 0;
+        for (const num of nums) {
+            xor ^= num;
+        }
+
+        let diff_bit = 1;
+        while ((xor & diff_bit) === 0) {
+            diff_bit <<= 1;
+        }
+
+        let a = 0, b = 0;
+        for (const num of nums) {
+            if (num & diff_bit) {
+                a ^= num;
+            } else {
+                b ^= num;
+            }
+        }
+        return [a, b];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 6. Bitwise XOR (Most Significant Bit)
+
+::tabs-start
+
+```python
+class Solution:
+    def singleNumber(self, nums: List[int]) -> List[int]:
+        xor = 0
+        for num in nums:
+            xor ^= num
+        
+        diff_bit = xor & (-xor)
+
+        a = b = 0
+        for num in nums:
+            if diff_bit & num:
+                a ^= num
+            else:
+                b ^= num
+        return [a, b]
+```
+
+```java
+public class Solution {
+    public int[] singleNumber(int[] nums) {
+        int xor = 0;
+        for (int num : nums) {
+            xor ^= num;
+        }
+
+        int diff_bit = xor & (-xor);
+
+        int a = 0, b = 0;
+        for (int num : nums) {
+            if ((num & diff_bit) != 0) {
+                a ^= num;
+            } else {
+                b ^= num;
+            }
+        }
+        return new int[]{a, b};
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> singleNumber(vector<int>& nums) {
+        uint xor_all = 0;
+        for (int& num : nums) {
+            xor_all ^= num;
+        }
+
+        int diff_bit = xor_all & (-xor_all);
+
+        int a = 0, b = 0;
+        for (int& num : nums) {
+            if (num & diff_bit) {
+                a ^= num;
+            } else {
+                b ^= num;
+            }
+        }
+        return {a, b};
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    singleNumber(nums) {
+        let xor = 0;
+        for (const num of nums) {
+            xor ^= num;
+        }
+
+        let diff_bit = xor & (-xor);
+
+        let a = 0, b = 0;
+        for (const num of nums) {
+            if (num & diff_bit) {
+                a ^= num;
+            } else {
+                b ^= num;
+            }
+        }
+        return [a, b];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/single-number.md b/articles/single-number.md
new file mode 100644
index 000000000..8919e9baa
--- /dev/null
+++ b/articles/single-number.md
@@ -0,0 +1,571 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def singleNumber(self, nums: List[int]) -> int:
+        for i in range(len(nums)):
+            flag = True
+            for j in range(len(nums)):
+                if i != j and nums[i] == nums[j]:
+                    flag = False
+                    break
+            if flag:
+                return nums[i]
+```
+
+```java
+public class Solution {
+    public int singleNumber(int[] nums) {
+        for (int i = 0; i < nums.length; i++) {
+            boolean flag = true;
+            for (int j = 0; j < nums.length; j++) {
+                if (i != j && nums[i] == nums[j]) {
+                    flag = false;
+                    break;
+                }
+            }
+            if (flag) {
+                return nums[i];
+            }
+        }
+        return -1; 
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int singleNumber(vector<int>& nums) {
+        for (int i = 0; i < nums.size(); i++) {
+            bool flag = true;
+            for (int j = 0; j < nums.size(); j++) {
+                if (i != j && nums[i] == nums[j]) {
+                    flag = false;
+                    break;
+                }
+            }
+            if (flag) {
+                return nums[i];
+            }
+        }
+        return -1; 
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    singleNumber(nums) {
+        for (let i = 0; i < nums.length; i++) {
+            let flag = true;
+            for (let j = 0; j < nums.length; j++) {
+                if (i !== j && nums[i] === nums[j]) {
+                    flag = false;
+                    break;
+                }
+            }
+            if (flag) {
+                return nums[i];
+            }
+        }
+        return -1;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int SingleNumber(int[] nums) {
+        for (int i = 0; i < nums.Length; i++) {
+            bool flag = true;
+            for (int j = 0; j < nums.Length; j++) {
+                if (i != j && nums[i] == nums[j]) {
+                    flag = false;
+                    break;
+                }
+            }
+            if (flag) {
+                return nums[i];
+            }
+        }
+        return -1;
+    }
+}
+```
+
+```go
+func singleNumber(nums []int) int {
+    for i := 0; i < len(nums); i++ {
+        flag := true
+        for j := 0; j < len(nums); j++ {
+            if i != j && nums[i] == nums[j] {
+                flag = false
+                break
+            }
+        }
+        if flag {
+            return nums[i]
+        }
+    }
+    return 0
+}
+```
+
+```kotlin
+class Solution {
+    fun singleNumber(nums: IntArray): Int {
+        for (i in 0..nums.size - 1) {
+            var flag = true
+            for (j in 0..nums.size - 1) {
+                if (i != j && nums[i] == nums[j]) {
+                    flag = false
+                    break
+                }
+            }
+            if (flag) return nums[i]
+        }
+        return 0
+    }
+}
+```
+
+```swift
+class Solution {
+    func singleNumber(_ nums: [Int]) -> Int {
+        for i in 0..<nums.count {
+            var flag = true
+            for j in 0..<nums.count {
+                if i != j && nums[i] == nums[j] {
+                    flag = false
+                    break
+                }
+            }
+            if flag {
+                return nums[i]
+            }
+        }
+        return -1
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Hash Set
+
+::tabs-start
+
+```python
+class Solution:
+    def singleNumber(self, nums: List[int]) -> int:
+        seen = set()
+        for num in nums:
+            if num in seen:
+                seen.remove(num)
+            else:
+                seen.add(num)
+        return list(seen)[0]
+```
+
+```java
+public class Solution {
+    public int singleNumber(int[] nums) {
+        Set<Integer> seen = new HashSet<>();
+        for (int num : nums) {
+            if (seen.contains(num)) {
+                seen.remove(num);
+            } else {
+                seen.add(num);
+            }
+        }
+        return seen.iterator().next();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int singleNumber(vector<int>& nums) {
+        unordered_set<int> seen;
+        for (int num : nums) {
+            if (seen.count(num)) {
+                seen.erase(num);
+            } else {
+                seen.insert(num);
+            }
+        }
+        return *seen.begin();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    singleNumber(nums) {
+        const seen = new Set();
+        for (const num of nums) {
+            if (seen.has(num)) {
+                seen.delete(num);
+            } else {
+                seen.add(num);
+            }
+        }
+        return Array.from(seen)[0];
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int SingleNumber(int[] nums) {
+        var seen = new HashSet<int>();
+        foreach (int num in nums) {
+            if (seen.Contains(num)) {
+                seen.Remove(num);
+            } else {
+                seen.Add(num);
+            }
+        }
+        foreach (int num in seen) {
+            return num; 
+        }
+        return -1; 
+    }
+}
+```
+
+```go
+func singleNumber(nums []int) int {
+	seen := make(map[int]bool)
+	for _, num := range nums {
+		if seen[num] {
+			delete(seen, num)
+		} else {
+			seen[num] = true
+		}
+	}
+	for num := range seen {
+		return num
+	}
+	return -1
+}
+```
+
+```kotlin
+class Solution {
+    fun singleNumber(nums: IntArray): Int {
+        val seen = HashSet<Int>()
+        for (num in nums) {
+            if (num in seen) {
+                seen.remove(num)
+            } else {
+                seen.add(num)
+            }
+        }
+        return seen.first()
+    }
+}
+```
+
+```swift
+class Solution {
+    func singleNumber(_ nums: [Int]) -> Int {
+        var seen = Set<Int>()
+
+        for num in nums {
+            if seen.contains(num) {
+                seen.remove(num)
+            } else {
+                seen.insert(num)
+            }
+        }
+
+        return seen.first!
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def singleNumber(self, nums: List[int]) -> int:
+        nums.sort()
+        i = 0
+        while i < len(nums) - 1:
+            if nums[i] == nums[i + 1]:
+                i += 2
+            else:
+                return nums[i]
+        return nums[i]
+```
+
+```java
+public class Solution {
+    public int singleNumber(int[] nums) {
+        Arrays.sort(nums);
+        int i = 0;
+        while (i < nums.length - 1) {
+            if (nums[i] == nums[i + 1]) {
+                i += 2;
+            } else {
+                return nums[i];
+            }
+        }
+        return nums[i];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int singleNumber(vector<int>& nums) {
+        sort(begin(nums), end(nums));
+        int i = 0;
+        while (i < nums.size() - 1) {
+            if (nums[i] == nums[i + 1]) {
+                i += 2;
+            } else {
+                return nums[i];
+            }
+        }
+        return nums[i];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    singleNumber(nums) {
+        nums.sort((a, b) => a - b);
+        let i = 0;
+        while (i < nums.length - 1) {
+            if (nums[i] === nums[i + 1]) {
+                i += 2;
+            } else {
+                return nums[i];
+            }
+        }
+        return nums[i];
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int SingleNumber(int[] nums) {
+        Array.Sort(nums);
+        int i = 0;
+        while (i < nums.Length - 1) {
+            if (nums[i] == nums[i + 1]) {
+                i += 2;
+            } else {
+                return nums[i];
+            }
+        }
+        return nums[i];
+    }
+}
+```
+
+```go
+func singleNumber(nums []int) int {
+	sort.Ints(nums)
+	i := 0
+	for i < len(nums)-1 {
+		if nums[i] == nums[i+1] {
+			i += 2
+		} else {
+			return nums[i]
+		}
+	}
+	return nums[i]
+}
+```
+
+```kotlin
+class Solution {
+    fun singleNumber(nums: IntArray): Int {
+        nums.sort()
+        var i = 0
+        while (i < nums.size - 1) {
+            if (nums[i] == nums[i + 1]) {
+                i += 2
+            } else {
+                return nums[i]
+            }
+        }
+        return nums[i]
+    }
+}
+```
+
+```swift
+class Solution {
+    func singleNumber(_ nums: [Int]) -> Int {
+        var nums = nums.sorted()
+        var i = 0
+
+        while i < nums.count - 1 {
+            if nums[i] == nums[i + 1] {
+                i += 2
+            } else {
+                return nums[i]
+            }
+        }
+
+        return nums[i]
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 4. Bit Manipulation
+
+::tabs-start
+
+```python
+class Solution:
+    def singleNumber(self, nums: List[int]) -> int:
+        res = 0
+        for num in nums:
+            res = num ^ res
+        return res
+```
+
+```java
+public class Solution {
+    public int singleNumber(int[] nums) {
+        int res = 0;
+        for (int num : nums) {
+            res ^= num;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int singleNumber(vector<int>& nums) {
+        int res = 0;
+        for (int num : nums) {
+            res ^= num;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    singleNumber(nums) {
+        let res = 0;
+        for (const num of nums) {
+            res ^= num;
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int SingleNumber(int[] nums) {
+        int res = 0;
+        foreach (int num in nums) {
+            res ^= num;
+        }
+        return res;
+    }
+}
+```
+
+```go
+func singleNumber(nums []int) int {
+	res := 0
+	for _, num := range nums {
+		res ^= num
+	}
+	return res
+}
+```
+
+```kotlin
+class Solution {
+    fun singleNumber(nums: IntArray): Int {
+        var res = 0
+        for (num in nums) {
+            res = res xor num
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func singleNumber(_ nums: [Int]) -> Int {
+        var res = 0
+        for num in nums {
+            res ^= num
+        }
+        return res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/single-threaded-cpu.md b/articles/single-threaded-cpu.md
new file mode 100644
index 000000000..16f487b94
--- /dev/null
+++ b/articles/single-threaded-cpu.md
@@ -0,0 +1,587 @@
+## 1. Two Min-Heaps
+
+::tabs-start
+
+```python
+class Solution:
+    def getOrder(self, tasks: List[List[int]]) -> List[int]:
+        available = []
+        pending = []
+        for i, (enqueueTime, processTime) in enumerate(tasks):
+            heapq.heappush(pending, (enqueueTime, processTime, i))
+
+        time = 0
+        res = []
+        while pending or available:
+            while pending and pending[0][0] <= time:
+                enqueueTime, processTime, i = heapq.heappop(pending)
+                heapq.heappush(available, (processTime, i))
+
+            if not available:
+                time = pending[0][0]
+                continue
+
+            processTime, i = heapq.heappop(available)
+            time += processTime
+            res.append(i)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[] getOrder(int[][] tasks) {
+        PriorityQueue<int[]> available = new PriorityQueue<>((a, b) -> 
+            a[0] == b[0] ? Integer.compare(a[1], b[1]) : Integer.compare(a[0], b[0])
+        );
+        PriorityQueue<int[]> pending = new PriorityQueue<>(Comparator.comparingInt(a -> a[0]));
+
+        int n = tasks.length;
+        for (int i = 0; i < n; i++) {
+            pending.offer(new int[]{tasks[i][0], tasks[i][1], i});
+        }
+
+        long time = 0;
+        int idx = 0;
+        int[] res = new int[n];
+        while (!pending.isEmpty() || !available.isEmpty()) {
+            while (!pending.isEmpty() && pending.peek()[0] <= time) {
+                int[] task = pending.poll();
+                available.offer(new int[]{task[1], task[2]});
+            }
+
+            if (available.isEmpty()) {
+                time = pending.peek()[0];
+                continue;
+            }
+
+            int[] task = available.poll();
+            time += task[0];
+            res[idx++] = task[1];
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> getOrder(vector<vector<int>>& tasks) {
+        priority_queue<pair<int, int>, vector<pair<int, int>>, greater<>> available;
+        priority_queue<array<int, 3>, vector<array<int, 3>>, greater<>> pending;
+
+        int n = tasks.size();
+        for (int i = 0; i < n; ++i) {
+            pending.push({tasks[i][0], tasks[i][1], i});
+        }
+
+        vector<int> res;
+        long long time = 0;
+        while (!pending.empty() || !available.empty()) {
+            while (!pending.empty() && pending.top()[0] <= time) {
+                auto [enqueueTime, processTime, index] = pending.top();
+                pending.pop();
+                available.push({processTime, index});
+            }
+
+            if (available.empty()) {
+                time = pending.top()[0];
+                continue;
+            }
+
+            auto [processTime, index] = available.top();
+            available.pop();
+            time += processTime;
+            res.push_back(index);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} tasks
+     * @return {number[]}
+     */
+    getOrder(tasks) {
+        const available = new PriorityQueue(
+            (a, b) => a[0] === b[0] ? a[1] - b[1] : a[0] - b[0]
+        );
+        const pending = new PriorityQueue(
+            (a, b) => a[0] - b[0]
+        );
+
+        tasks.forEach(([enqueueTime, processTime], i) => {
+            pending.enqueue([enqueueTime, processTime, i]);
+        });
+
+        let time = 0;
+        const res = [];
+        while (!pending.isEmpty() || !available.isEmpty()) {
+            while (!pending.isEmpty() && pending.front()[0] <= time) {
+                const [enqueueTime, processTime, i] = pending.dequeue();
+                available.enqueue([processTime, i]);
+            }
+
+            if (available.isEmpty()) {
+                time = pending.front()[0];
+                continue;
+            }
+
+            const [processTime, i] = available.dequeue();
+            time += processTime;
+            res.push(i);
+        }
+
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[] GetOrder(int[][] tasks) {
+        var available = new PriorityQueue<(int procTime, int index), (int procTime, int index)>();
+        var pending = new PriorityQueue<(int startTime, int procTime, int index), int>();
+
+        int n = tasks.Length;
+        for (int i = 0; i < n; i++) {
+            pending.Enqueue((tasks[i][0], tasks[i][1], i), tasks[i][0]);
+        }
+
+        long time = 0;
+        int[] res = new int[n];
+        int idx = 0;
+
+        while (pending.Count > 0 || available.Count > 0) {
+            while (pending.Count > 0 && pending.Peek().startTime <= time) {
+                var task = pending.Dequeue();
+                available.Enqueue((task.procTime, task.index), (task.procTime, task.index));
+            }
+
+            if (available.Count == 0) {
+                time = pending.Peek().startTime;
+                continue;
+            }
+
+            var next = available.Dequeue();
+            time += next.procTime;
+            res[idx++] = next.index;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Sorting + Min-Heap
+
+::tabs-start
+
+```python
+class Solution:
+    def getOrder(self, tasks: List[List[int]]) -> List[int]:
+        for i, t in enumerate(tasks):
+            t.append(i)
+        tasks.sort(key=lambda t: t[0])
+
+        res, minHeap = [], []
+        i, time = 0, tasks[0][0]
+
+        while minHeap or i < len(tasks):
+            while i < len(tasks) and time >= tasks[i][0]:
+                heapq.heappush(minHeap, [tasks[i][1], tasks[i][2]])
+                i += 1
+            if not minHeap:
+                time = tasks[i][0]
+            else:
+                procTime, index = heapq.heappop(minHeap)
+                time += procTime
+                res.append(index)
+        return res
+```
+
+```java
+public class Solution {
+    public int[] getOrder(int[][] tasks) {
+        int n = tasks.length;
+        for (int i = 0; i < n; i++) {
+            tasks[i] = new int[] {tasks[i][0], tasks[i][1], i};
+        }
+        Arrays.sort(tasks, Comparator.comparingInt(t -> t[0]));
+
+        int[] res = new int[n];
+        PriorityQueue<int[]> minHeap = new PriorityQueue<>((a, b) -> 
+            a[0] == b[0] ? Integer.compare(a[1], b[1]) : Integer.compare(a[0], b[0])
+        );
+
+        int i = 0, idx = 0;
+        long time = tasks[0][0];
+        while (!minHeap.isEmpty() || i < n) {
+            while (i < n && time >= tasks[i][0]) {
+                minHeap.offer(new int[]{tasks[i][1], tasks[i][2]});
+                i++;
+            }
+            if (minHeap.isEmpty()) {
+                time = tasks[i][0];
+            } else {
+                int[] task = minHeap.poll();
+                time += task[0];
+                res[idx++] = task[1];
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> getOrder(vector<vector<int>>& tasks) {
+        int n = tasks.size();
+        for (int i = 0; i < n; ++i) {
+            tasks[i].push_back(i);
+        }
+        sort(tasks.begin(), tasks.end());
+
+        vector<int> res;
+        priority_queue<array<int, 2>, vector<array<int, 2>>, greater<>> minHeap;
+
+        int i = 0;
+        long long time = tasks[0][0];
+        while (!minHeap.empty() || i < n) {
+            while (i < n && time >= tasks[i][0]) {
+                minHeap.push({tasks[i][1], tasks[i][2]});
+                i++;
+            }
+            if (minHeap.empty()) {
+                time = tasks[i][0];
+            } else {
+                auto [procTime, index] = minHeap.top();
+                minHeap.pop();
+                time += procTime;
+                res.push_back(index);
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} tasks
+     * @return {number[]}
+     */
+    getOrder(tasks) {
+        const n = tasks.length;
+        tasks = tasks.map((t, i) => [...t, i]);
+        tasks.sort((a, b) => a[0] - b[0]);
+
+        const res = [];
+        const minHeap = new PriorityQueue((a, b) => 
+            a[0] === b[0] ? a[1] - b[1] : a[0] - b[0]
+        );
+
+        let i = 0, time = tasks[0][0];
+        while (minHeap.size() || i < n) {
+            while (i < n && time >= tasks[i][0]) {
+                minHeap.enqueue([tasks[i][1], tasks[i][2]]);
+                i++;
+            }
+            if (minHeap.isEmpty()) {
+                time = tasks[i][0];
+            } else {
+                const [procTime, index] = minHeap.dequeue();
+                time += procTime;
+                res.push(index);
+            }
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[] GetOrder(int[][] tasks) {
+        int n = tasks.Length;
+        int i = 0;
+        for (; i < n; i++) {
+            tasks[i] = new int[] { tasks[i][0], tasks[i][1], i }; // {enqueueTime, processingTime, index}
+        }
+
+        Array.Sort(tasks, (a, b) => a[0].CompareTo(b[0])); // sort by enqueueTime
+
+        int[] res = new int[n];
+        var minHeap = new PriorityQueue<(int procTime, int index), (int procTime, int index)>();
+
+        int idx = 0;
+        i = 0;
+        long time = tasks[0][0];
+
+        while (minHeap.Count > 0 || i < n) {
+            while (i < n && tasks[i][0] <= time) {
+                minHeap.Enqueue((tasks[i][1], tasks[i][2]), (tasks[i][1], tasks[i][2]));
+                i++;
+            }
+
+            if (minHeap.Count == 0) {
+                time = tasks[i][0];
+            } else {
+                var task = minHeap.Dequeue();
+                time += task.procTime;
+                res[idx++] = task.index;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Sorting + Min-Heap (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def getOrder(self, tasks: List[List[int]]) -> List[int]:
+        n = len(tasks)
+        indices = list(range(n))
+        indices.sort(key=lambda i: (tasks[i][0], i))
+        
+        class Task:
+            def __init__(self, idx):
+                self.idx = idx
+                
+            def __lt__(self, other):
+                if tasks[self.idx][1] != tasks[other.idx][1]:
+                    return tasks[self.idx][1] < tasks[other.idx][1]
+                return self.idx < other.idx
+        
+        minHeap = []
+        res = []
+        time = i = 0
+        while minHeap or i < n:
+            while i < n and tasks[indices[i]][0] <= time:
+                heapq.heappush(minHeap, Task(indices[i]))
+                i += 1
+                
+            if not minHeap:
+                time = tasks[indices[i]][0]
+            else:
+                next_task = heapq.heappop(minHeap)
+                time += tasks[next_task.idx][1]
+                res.append(next_task.idx)
+                
+        return res
+```
+
+```java
+public class Solution {
+    public int[] getOrder(int[][] tasks) {
+        int n = tasks.length;
+        Integer[] indices = new Integer[n];
+        for (int i = 0; i < n; i++) {
+            indices[i] = i;
+        }
+        
+        Arrays.sort(indices, (a, b) -> 
+            tasks[a][0] != tasks[b][0] ? tasks[a][0] - tasks[b][0] : a - b
+        );
+        
+        PriorityQueue<Integer> minHeap = new PriorityQueue<>((a, b) -> 
+            tasks[a][1] != tasks[b][1] ? tasks[a][1] - tasks[b][1] : a - b
+        );
+        
+        int[] result = new int[n];
+        long time = 0;
+        int i = 0, resIndex = 0;
+        while (!minHeap.isEmpty() || i < n) {
+            while (i < n && tasks[indices[i]][0] <= time) {
+                minHeap.offer(indices[i]);
+                i++;
+            }
+            
+            if (minHeap.isEmpty()) {
+                time = tasks[indices[i]][0];
+            } else {
+                int nextIndex = minHeap.poll();
+                time += tasks[nextIndex][1];
+                result[resIndex++] = nextIndex;
+            }
+        }
+        
+        return result;
+    }
+}
+```
+
+```cpp
+// C++ Solution
+class Solution {
+public:
+    vector<int> getOrder(vector<vector<int>>& tasks) {
+        int n = tasks.size();
+        vector<int> indices(n);
+        iota(indices.begin(), indices.end(), 0);
+
+        sort(indices.begin(), indices.end(), [&](int a, int b) {
+            return tasks[a][0] < tasks[b][0] || 
+                   (tasks[a][0] == tasks[b][0] && a < b);
+        });
+        
+        auto comp = [&](int a, int b) {
+            return tasks[a][1] > tasks[b][1] || 
+                   (tasks[a][1] == tasks[b][1] && a > b);
+        };
+        priority_queue<int, vector<int>, decltype(comp)> minHeap(comp);
+        
+        vector<int> result;
+        long long time = 0;
+        int i = 0;
+        
+        while (!minHeap.empty() || i < n) {
+            while (i < n && tasks[indices[i]][0] <= time) {
+                minHeap.push(indices[i]);
+                i++;
+            }
+            
+            if (minHeap.empty()) {
+                time = tasks[indices[i]][0];
+            } else {
+                int nextIndex = minHeap.top();
+                minHeap.pop();
+                time += tasks[nextIndex][1];
+                result.push_back(nextIndex);
+            }
+        }
+        
+        return result;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} tasks
+     * @return {number[]}
+     */
+    getOrder(tasks) {
+        const n = tasks.length;
+        const indices = Array.from({ length: n }, (_, i) => i);
+        indices.sort((a, b) => {
+            if (tasks[a][0] !== tasks[b][0]) {
+                return tasks[a][0] - tasks[b][0];
+            }
+            return a - b;
+        });
+
+        const minHeap = new PriorityQueue(
+            (a, b) => {
+                if (tasks[a][1] !== tasks[b][1]) {
+                    return tasks[a][1] - tasks[b][1];
+                }
+                return a - b;
+            }
+        );
+
+        const res = [];
+        let time = 0;
+        let i = 0;
+
+        while (!minHeap.isEmpty() || i < n) {
+            while (i < n && tasks[indices[i]][0] <= time) {
+                minHeap.enqueue(indices[i]);
+                i++;
+            }
+
+            if (minHeap.size() === 0) {
+                time = tasks[indices[i]][0];
+            } else {
+                const nextIndex = minHeap.dequeue();
+                time += tasks[nextIndex][1];
+                res.push(nextIndex);
+            }
+        }
+        
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[] GetOrder(int[][] tasks) {
+        int n = tasks.Length;
+        int[] indices = new int[n];
+        int i = 0;
+        for (; i < n; i++) {
+            indices[i] = i;
+        }
+
+        Array.Sort(indices, (a, b) =>
+            tasks[a][0] != tasks[b][0] ? tasks[a][0].CompareTo(tasks[b][0]) : a.CompareTo(b)
+        );
+
+        var minHeap = new PriorityQueue<int, (int procTime, int index)>();
+
+        int[] result = new int[n];
+        long time = 0;
+        int resIndex = 0;
+        i = 0;
+
+        while (minHeap.Count > 0 || i < n) {
+            while (i < n && tasks[indices[i]][0] <= time) {
+                int idx = indices[i];
+                minHeap.Enqueue(idx, (tasks[idx][1], idx));
+                i++;
+            }
+
+            if (minHeap.Count == 0) {
+                time = tasks[indices[i]][0];
+            } else {
+                int nextIndex = minHeap.Dequeue();
+                time += tasks[nextIndex][1];
+                result[resIndex++] = nextIndex;
+            }
+        }
+
+        return result;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/sliding-window-maximum.md b/articles/sliding-window-maximum.md
index 48b622b8c..a7af08296 100644
--- a/articles/sliding-window-maximum.md
+++ b/articles/sliding-window-maximum.md
@@ -97,12 +97,68 @@ public class Solution {
 }
 ```
 
+```go
+func maxSlidingWindow(nums []int, k int) []int {
+    output := make([]int, 0, len(nums)-k+1)
+
+    for i := 0; i <= len(nums)-k; i++ {
+        maxi := nums[i]
+        for j := i; j < i+k; j++ {
+            if nums[j] > maxi {
+                maxi = nums[j]
+            }
+        }
+        output = append(output, maxi)
+    }
+
+    return output
+}
+```
+
+```kotlin
+class Solution {
+    fun maxSlidingWindow(nums: IntArray, k: Int): IntArray {
+        val output = mutableListOf<Int>()
+
+        for (i in 0..nums.size - k) {
+            var maxi = nums[i]
+            for (j in i until i + k) {
+                maxi = maxOf(maxi, nums[j])
+            }
+            output.add(maxi)
+        }
+
+        return output.toIntArray()
+    }
+}
+```
+
+```swift
+class Solution {
+    func maxSlidingWindow(_ nums: [Int], _ k: Int) -> [Int] {
+        var output = [Int]()
+
+        for i in 0...(nums.count - k) {
+            var maxi = nums[i]
+            for j in i..<(i + k) {
+                maxi = max(maxi, nums[j])
+            }
+            output.append(maxi)
+        }
+
+        return output
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n * k)$
-* Space complexity: $O(1)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n - k + 1)$ space for the output array.
 
 > Where $n$ is the length of the array and $k$ is the size of the window.
 
@@ -114,28 +170,19 @@ public class Solution {
 
 ```python
 class SegmentTree:
-    def __init__(self, N, a):
+    def __init__(self, N, A):
         self.n = N
-        self.A = a[:]
         while (self.n & (self.n - 1)) != 0:
-            self.A.append(float('-inf'))
             self.n += 1
-        self.tree = [0] * (2 * self.n)
-        self.build()
+        self.build(N, A)
 
-    def build(self):
-        for i in range(self.n):
-            self.tree[self.n + i] = self.A[i]
+    def build(self, N, A):
+        self.tree = [float('-inf')] * (2 * self.n)
+        for i in range(N):
+            self.tree[self.n + i] = A[i]
         for i in range(self.n - 1, 0, -1):
             self.tree[i] = max(self.tree[i << 1], self.tree[i << 1 | 1])
 
-    def update(self, i, val):
-        self.tree[self.n + i] = val
-        j = (self.n + i) >> 1
-        while j >= 1:
-            self.tree[j] = max(self.tree[j << 1], self.tree[j << 1 | 1])
-            j >>= 1
-
     def query(self, l, r):
         res = float('-inf')
         l += self.n
@@ -163,30 +210,22 @@ class Solution:
 ```
 
 ```java
-public class SegmentTree {
+class SegmentTree {
     int n;
-    int[] A;
     int[] tree;
-    final int NEG_INF = Integer.MIN_VALUE;
 
-    SegmentTree(int N, int[] a) {
+    SegmentTree(int N, int[] A) {
         this.n = N;
         while (Integer.bitCount(n) != 1) {
             n++;
         }
-        A = new int[n];
-        for (int i = 0; i < N; i++) {
-            A[i] = a[i];
-        }
-        for (int i = N; i < n; i++) {
-            A[i] = NEG_INF;
-        }
-        tree = new int[2 * n];
-        build();
+        build(N, A);
     }
 
-    void build() {
-        for (int i = 0; i < n; i++) {
+    void build(int N, int[] A) {
+        tree = new int[2 * n];
+        Arrays.fill(tree, Integer.MIN_VALUE);
+        for (int i = 0; i < N; i++) {
             tree[n + i] = A[i];
         }
         for (int i = n - 1; i > 0; --i) {
@@ -194,15 +233,8 @@ public class SegmentTree {
         }
     }
 
-    void update(int i, int val) {
-        tree[n + i] = val;
-        for (int j = (n + i) >> 1; j >= 1; j >>= 1) {
-            tree[j] = Math.max(tree[j << 1], tree[j << 1 | 1]);
-        }
-    }
-
     int query(int l, int r) {
-        int res = NEG_INF;
+        int res = Integer.MIN_VALUE;
         for (l += n, r += n + 1; l < r; l >>= 1, r >>= 1) {
             if ((l & 1) == 1) res = Math.max(res, tree[l++]);
             if ((r & 1) == 1) res = Math.max(res, tree[--r]);
@@ -225,26 +257,22 @@ public class Solution {
 ```
 
 ```cpp
-class Segment_tree {
+class SegmentTree {
 public:
     int n;
-    vector<int> A;
     vector<int> tree;
-    const int NEG_INF = -1e9;
 
-    Segment_tree(int N, vector<int>& a) {
+    SegmentTree(int N, vector<int>& A) {
         this->n = N;
-        this->A = a;
         while (__builtin_popcount(n) != 1) {
-            A.push_back(NEG_INF);
             n++;
         }
-        tree.resize(2 * n);
-        build();
+        build(N, A);
     }
 
-    void build() {
-        for (int i = 0; i < n; i++) {
+    void build(int N, vector<int>& A) {
+        tree.resize(2 * n, INT_MIN);
+        for (int i = 0; i < N; i++) {
             tree[n + i] = A[i];
         }
         for (int i = n - 1; i > 0; --i) {
@@ -252,15 +280,8 @@ public:
         }
     }
 
-    void update(int i, int val) {
-        tree[n + i] = val;
-        for (int j = (n + i) >> 1; j >= 1; j >>= 1) {
-            tree[j] = max(tree[j << 1], tree[j << 1 | 1]);
-        }
-    }
-
     int query(int l, int r) {
-        int res = NEG_INF;
+        int res = INT_MIN;
         for (l += n, r += n + 1; l < r; l >>= 1, r >>= 1) {
             if (l & 1) res = max(res, tree[l++]);
             if (r & 1) res = max(res, tree[--r]);
@@ -273,7 +294,7 @@ class Solution {
 public:
     vector<int> maxSlidingWindow(vector<int>& nums, int k) {
         int n = nums.size();
-        Segment_tree segTree(n, nums);
+        SegmentTree segTree(n, nums);
         vector<int> output;
         for (int i = 0; i <= n - k; i++) {
             output.push_back(segTree.query(i, i + k - 1));
@@ -288,49 +309,38 @@ class SegmentTree {
     /**
      * @constructor
      * @param {number} N 
-     * @param {number[]} a
+     * @param {number[]} A
      */
-    constructor(N, a) {
+    constructor(N, A) {
         this.n = N;
-        this.A = [...a];
-        this.NEG_INF = -Infinity;
-
         while ((this.n & (this.n - 1)) !== 0) {
-            this.A.push(this.NEG_INF);
             this.n++;
         }
-        
-        this.tree = new Array(2 * this.n).fill(0);
-        this.build();
+        this.build(N, A);
     }
 
-    build() {
-        for (let i = 0; i < this.n; i++) {
-            this.tree[this.n + i] = this.A[i];
+    /**
+     * @param {number} N 
+     * @param {number[]} A
+     * @return {void}
+     */
+    build(N, A) {
+        this.tree = new Array(2 * this.n).fill(-Infinity);
+        for (let i = 0; i < N; i++) {
+            this.tree[this.n + i] = A[i];
         }
         for (let i = this.n - 1; i > 0; i--) {
             this.tree[i] = Math.max(this.tree[i << 1], this.tree[i << 1 | 1]);
         }
     }
 
-    /**
-     * @param {number} i 
-     * @param {number} val
-     */
-    update(i, val) {
-        this.tree[this.n + i] = val;
-        for (let j = (this.n + i) >> 1; j >= 1; j >>= 1) {
-            this.tree[j] = Math.max(this.tree[j << 1], this.tree[j << 1 | 1]);
-        }
-    }
-
     /**
      * @param {number} l
      * @param {number} r
      * @return {number}
      */
     query(l, r) {
-        let res = this.NEG_INF;
+        let res = -Infinity;
         l += this.n;
         r += this.n + 1;
 
@@ -368,28 +378,20 @@ class Solution {
 ```csharp
 public class SegmentTree {
     public int n;
-    public int[] A;
     public int[] tree;
-    public const int NEG_INF = int.MinValue;
 
-    public SegmentTree(int N, int[] a) {
+    public SegmentTree(int N, int[] A) {
         this.n = N;
         while (System.Numerics.BitOperations.PopCount((uint)n) != 1) {
             n++;
         }
-        A = new int[n];
-        for (int i = 0; i < N; i++) {
-            A[i] = a[i];
-        }
-        for (int i = N; i < n; i++) {
-            A[i] = NEG_INF;
-        }
-        tree = new int[2 * n];
-        Build();
+        Build(N, A);
     }
 
-    public void Build() {
-        for (int i = 0; i < n; i++) {
+    public void Build(int N, int[] A) {
+        tree = new int[2 * n];
+        Array.Fill(tree, int.MinValue);
+        for (int i = 0; i < N; i++) {
             tree[n + i] = A[i];
         }
         for (int i = n - 1; i > 0; --i) {
@@ -397,15 +399,8 @@ public class SegmentTree {
         }
     }
 
-    public void Update(int i, int val) {
-        tree[n + i] = val;
-        for (int j = (n + i) >> 1; j >= 1; j >>= 1) {
-            tree[j] = Math.Max(tree[j << 1], tree[j << 1 | 1]);
-        }
-    }
-
     public int Query(int l, int r) {
-        int res = NEG_INF;
+        int res = int.MinValue;
         l += n;
         r += n + 1;
         while (l < r) {
@@ -431,6 +426,195 @@ public class Solution {
 }
 ```
 
+```go
+type SegmentTree struct {
+    n    int
+    tree []int
+}
+
+func NewSegmentTree(N int, A []int) *SegmentTree {
+    n := N
+    for bits.OnesCount(uint(n)) != 1 {
+        n++
+    }
+    
+    st := &SegmentTree{
+        n: n,
+    }
+    st.build(N, A)
+    return st
+}
+
+func (st *SegmentTree) build(N int, A []int) {
+    st.tree = make([]int, 2*st.n)
+    for i := range st.tree {
+        st.tree[i] = math.MinInt
+    }    
+    for i := 0; i < N; i++ {
+        st.tree[st.n+i] = A[i]
+    }
+    for i := st.n - 1; i > 0; i-- {
+        st.tree[i] = max(st.tree[i<<1], st.tree[i<<1|1])
+    }
+}
+
+func (st *SegmentTree) Query(l, r int) int {
+    res := math.MinInt
+    l += st.n
+    r += st.n + 1
+    
+    for l < r {
+        if l&1 == 1 {
+            res = max(res, st.tree[l])
+            l++
+        }
+        if r&1 == 1 {
+            r--
+            res = max(res, st.tree[r])
+        }
+        l >>= 1
+        r >>= 1
+    }
+    return res
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+
+func maxSlidingWindow(nums []int, k int) []int {
+    n := len(nums)
+    segTree := NewSegmentTree(n, nums)
+    output := make([]int, n-k+1)
+    
+    for i := 0; i <= n-k; i++ {
+        output[i] = segTree.Query(i, i+k-1)
+    }
+    
+    return output
+}
+```
+
+```kotlin
+class SegmentTree(N: Int, A: IntArray) {
+    private var n: Int = N
+    private var tree: IntArray = IntArray(0)
+    
+    init {
+        var size = N
+        while (Integer.bitCount(size) != 1) {
+            size++
+        }
+        n = size
+        build(N, A)
+    }
+    
+    private fun build(N: Int, A: IntArray) {
+        tree = IntArray(2 * n)
+        tree.fill(Int.MIN_VALUE)        
+        for (i in 0 until N) {
+            tree[n + i] = A[i]
+        }
+        for (i in n - 1 downTo 1) {
+            tree[i] = maxOf(tree[i * 2], tree[i * 2 + 1])
+        }
+    }
+    
+    fun query(l: Int, r: Int): Int {
+        var res = Int.MIN_VALUE
+        var left = l + n
+        var right = r + n + 1
+        
+        while (left < right) {
+            if (left % 2 == 1) {
+                res = maxOf(res, tree[left])
+                left++
+            }
+            if (right % 2 == 1) {
+                right--
+                res = maxOf(res, tree[right])
+            }
+            left /= 2
+            right /= 2
+        }
+        return res
+    }
+}
+
+class Solution {
+    fun maxSlidingWindow(nums: IntArray, k: Int): IntArray {
+        val n = nums.size
+        val segTree = SegmentTree(n, nums)
+        val result = IntArray(n - k + 1)
+        for (i in 0..n - k) {
+            result[i] = segTree.query(i, i + k - 1)
+        }
+        return result
+    }
+}
+```
+
+```swift
+class SegmentTree {
+    private var n: Int
+    private var tree: [Int]
+
+    init(_ N: Int, _ A: [Int]) {
+        self.n = N
+        while (self.n & (self.n - 1)) != 0 {
+            self.n += 1
+        }
+        self.tree = [Int](repeating: Int.min, count: 2 * self.n)
+        build(N, A)
+    }
+
+    private func build(_ N: Int, _ A: [Int]) {
+        for i in 0..<N {
+            tree[n + i] = A[i]
+        }
+        for i in stride(from: n - 1, through: 1, by: -1) {
+            tree[i] = max(tree[i << 1], tree[i << 1 | 1])
+        }
+    }
+
+    func query(_ l: Int, _ r: Int) -> Int {
+        var res = Int.min
+        var l = l + n
+        var r = r + n + 1
+        while l < r {
+            if l & 1 != 0 {
+                res = max(res, tree[l])
+                l += 1
+            }
+            if r & 1 != 0 {
+                r -= 1
+                res = max(res, tree[r])
+            }
+            l >>= 1
+            r >>= 1
+        }
+        return res
+    }
+}
+
+class Solution {
+    func maxSlidingWindow(_ nums: [Int], _ k: Int) -> [Int] {
+        let n = nums.count
+        let segTree = SegmentTree(n, nums)
+        var output = [Int]()
+
+        for i in 0...(n - k) {
+            output.append(segTree.query(i, i + k - 1))
+        }
+
+        return output
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -529,8 +713,9 @@ class Solution {
 ```csharp
 public class Solution {
     public int[] MaxSlidingWindow(int[] nums, int k) {
-        PriorityQueue<(int val, int idx), int> pq = new PriorityQueue<(int val, int idx), int>
-        (Comparer<int>.Create((a, b) => b.CompareTo(a)));
+        PriorityQueue<(int val, int idx), int> pq = new PriorityQueue<(int val, int idx), int>(
+            Comparer<int>.Create((a, b) => b.CompareTo(a))
+        );
         
         int[] output = new int[nums.Length - k + 1];
         int idx = 0;
@@ -551,6 +736,79 @@ public class Solution {
 }
 ```
 
+```go
+func maxSlidingWindow(nums []int, k int) []int {
+   heap := priorityqueue.NewWith(func(a, b interface{}) int {
+       return b.([2]int)[0] - a.([2]int)[0]
+   })
+   
+   output := []int{}
+   for i := 0; i < len(nums); i++ {
+       heap.Enqueue([2]int{nums[i], i})
+       if i >= k - 1 {
+           peek, _ := heap.Peek()
+           for peek.([2]int)[1] <= i - k {
+               heap.Dequeue()
+               peek, _ = heap.Peek()
+           }
+           val, _ := heap.Peek()
+           output = append(output, val.([2]int)[0])
+       }
+   }
+   return output
+}
+```
+
+```kotlin
+class Solution {
+    fun maxSlidingWindow(nums: IntArray, k: Int): IntArray {
+        val output = mutableListOf<Int>()
+        val heap = PriorityQueue<Pair<Int, Int>>(compareByDescending { it.first })
+
+        for (i in nums.indices) {
+            heap.add(Pair(nums[i], i))
+            if (i >= k - 1) {
+                while (heap.peek().second <= i - k) {
+                    heap.poll()
+                }
+                output.add(heap.peek().first)
+            }
+        }
+        return output.toIntArray()
+    }
+}
+```
+
+```swift
+class Solution {
+    func maxSlidingWindow(_ nums: [Int], _ k: Int) -> [Int] {
+        var heap = Heap<Item>()
+        var output = [Int]()
+
+        for i in 0..<nums.count {
+            heap.insert(Item(num: nums[i], index: i))
+            
+            if i >= k - 1 {
+                while heap.max!.index <= i - k {
+                    heap.removeMax()
+                }
+                output.append(heap.max!.num)
+            }
+        }
+        return output
+    }
+}
+
+struct Item: Comparable {
+    let num: Int
+    let index: Int
+
+    static func < (lhs: Item, rhs: Item) -> Bool {
+        return lhs.num < rhs.num
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -739,6 +997,116 @@ public class Solution {
 }
 ```
 
+```go
+func maxSlidingWindow(nums []int, k int) []int {
+	n := len(nums)
+	leftMax := make([]int, n)
+	rightMax := make([]int, n)
+
+	leftMax[0] = nums[0]
+	rightMax[n-1] = nums[n-1]
+
+	for i := 1; i < n; i++ {
+		if i%k == 0 {
+			leftMax[i] = nums[i]
+		} else {
+			leftMax[i] = max(leftMax[i-1], nums[i])
+		}
+	}
+
+	for i := 1; i < n; i++ {
+		if (n-1-i)%k == 0 {
+			rightMax[n-1-i] = nums[n-1-i]
+		} else {
+			rightMax[n-1-i] = max(rightMax[n-i], nums[n-1-i])
+		}
+	}
+
+	output := make([]int, n-k+1)
+
+	for i := 0; i < n-k+1; i++ {
+		output[i] = max(leftMax[i+k-1], rightMax[i])
+	}
+	return output
+}
+
+func max(a, b int) int {
+	if a > b {
+		return a
+	}
+	return b
+}
+```
+
+```kotlin
+class Solution {
+    fun maxSlidingWindow(nums: IntArray, k: Int): IntArray {
+        val n = nums.size
+        val leftMax = IntArray(n)
+        val rightMax = IntArray(n)
+        
+        leftMax[0] = nums[0]
+        rightMax[n - 1] = nums[n - 1]
+        
+        for (i in 1 until n) {
+            if (i % k == 0) {
+                leftMax[i] = nums[i]
+            } else {
+                leftMax[i] = maxOf(leftMax[i - 1], nums[i])
+            }
+            
+            if ((n - 1 - i) % k == 0) {
+                rightMax[n - 1 - i] = nums[n - 1 - i]
+            } else {
+                rightMax[n - 1 - i] = maxOf(rightMax[n - i], nums[n - 1 - i])
+            }
+        }
+        
+        val output = IntArray(n - k + 1)
+        for (i in 0..n - k) {
+            output[i] = maxOf(leftMax[i + k - 1], rightMax[i])
+        }
+        
+        return output
+    }
+}
+```
+
+```swift
+class Solution {
+    func maxSlidingWindow(_ nums: [Int], _ k: Int) -> [Int] {
+        let n = nums.count
+        var leftMax = [Int](repeating: 0, count: n)
+        var rightMax = [Int](repeating: 0, count: n)
+
+        leftMax[0] = nums[0]
+        rightMax[n - 1] = nums[n - 1]
+
+        for i in 1..<n {
+            if i % k == 0 {
+                leftMax[i] = nums[i]
+            } else {
+                leftMax[i] = max(leftMax[i - 1], nums[i])
+            }
+
+            if (n - 1 - i) % k == 0 {
+                rightMax[n - 1 - i] = nums[n - 1 - i]
+            } else {
+                rightMax[n - 1 - i] = max(rightMax[n - i], nums[n - 1 - i])
+            }
+        }
+
+        var output = [Int](repeating: 0, count: n - k + 1)
+
+        for i in 0..<(n - k + 1) {
+            output[i] = max(leftMax[i + k - 1], rightMax[i])
+        }
+
+        return output
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -901,6 +1269,92 @@ public class Solution {
 }
 ```
 
+```go
+func maxSlidingWindow(nums []int, k int) []int {
+   output := []int{}
+   q := []int{}
+   l, r := 0, 0
+   
+   for r < len(nums) {
+       for len(q) > 0 && nums[q[len(q)-1]] < nums[r] {
+           q = q[:len(q)-1]
+       }
+       q = append(q, r)
+       
+       if l > q[0] {
+           q = q[1:]
+       }
+       
+       if (r + 1) >= k {
+           output = append(output, nums[q[0]])
+           l += 1
+       }
+       r += 1
+   }
+   
+   return output
+}
+```
+
+```kotlin
+class Solution {
+    fun maxSlidingWindow(nums: IntArray, k: Int): IntArray {
+        val output = mutableListOf<Int>()
+        val q = ArrayDeque<Int>()
+        var l = 0
+        var r = 0
+        
+        while (r < nums.size) {
+            while (q.isNotEmpty() && nums[q.last()] < nums[r]) {
+                q.removeLast()
+            }
+            q.addLast(r)
+            
+            if (l > q.first()) {
+                q.removeFirst()
+            }
+            
+            if ((r + 1) >= k) {
+                output.add(nums[q.first()])
+                l += 1
+            }
+            r += 1
+        }
+        
+        return output.toIntArray()
+    }
+}
+```
+
+```swift
+class Solution {
+    func maxSlidingWindow(_ nums: [Int], _ k: Int) -> [Int] {
+        var output = [Int]()
+        var deque = [Int]() // Index
+        var l = 0, r = 0
+
+        while r < nums.count {
+            while !deque.isEmpty && nums[deque.last!] < nums[r] {
+                deque.removeLast()
+            }
+            deque.append(r)
+
+            if l > deque.first! {
+                deque.removeFirst()
+            }
+
+            if (r + 1) >= k {
+                output.append(nums[deque.first!])
+                l += 1
+            }
+            r += 1
+        }
+
+        return output
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/sliding-window-median.md b/articles/sliding-window-median.md
new file mode 100644
index 000000000..b49ca4071
--- /dev/null
+++ b/articles/sliding-window-median.md
@@ -0,0 +1,473 @@
+## 1. Brute Force (Sorting)
+
+::tabs-start
+
+```python
+class Solution:
+    def medianSlidingWindow(self, nums: List[int], k: int) -> List[float]:
+        res = []
+        for i in range(len(nums) - k + 1):
+            tmp = nums[i:i + k][:]
+            tmp.sort()
+            if k & 1:
+                res.append(tmp[k // 2])
+            else:
+                res.append((tmp[k // 2] + tmp[(k - 1) // 2]) / 2)
+        return res
+```
+
+```java
+public class Solution {
+    public double[] medianSlidingWindow(int[] nums, int k) {
+        int n = nums.length - k + 1;
+        double[] res = new double[n];
+        for (int i = 0; i < n; i++) {
+            int[] tmp = Arrays.copyOfRange(nums, i, i + k);
+            Arrays.sort(tmp);
+            if (k % 2 == 1) {
+                res[i] = tmp[k / 2];
+            } else {
+                res[i] = (tmp[k / 2] + 0L + tmp[(k - 1) / 2]) / 2.0;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<double> medianSlidingWindow(vector<int>& nums, int k) {
+        vector<double> res;
+        for (int i = 0; i <= nums.size() - k; ++i) {
+            vector<int> tmp(nums.begin() + i, nums.begin() + i + k);
+            sort(tmp.begin(), tmp.end());
+            if (k % 2 == 1) {
+                res.push_back(tmp[k / 2]);
+            } else {
+                res.push_back((tmp[k / 2] + 0LL + tmp[(k - 1) / 2]) / 2.0);
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number[]}
+     */
+    medianSlidingWindow(nums, k) {
+        const res = [];
+        for (let i = 0; i <= nums.length - k; i++) {
+            const tmp = nums.slice(i, i + k).sort((a, b) => a - b);
+            if (k % 2 === 1) {
+                res.push(tmp[Math.floor(k / 2)]);
+            } else {
+                res.push((tmp[Math.floor(k / 2)] + tmp[Math.floor((k - 1) / 2)]) / 2);
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * k\log k)$
+* Space complexity:
+    * $O(k)$ extra space.
+    * $O(n - k + 1)$ space for output array.
+
+> Where $n$ is the size of the array $nums$ and $k$ is the size of the sliding window.
+
+---
+
+## 2. Two Heaps
+
+::tabs-start
+
+```python
+class Solution:
+    def medianSlidingWindow(self, nums: List[int], k: int) -> List[float]:
+        small, large = [], []
+        d = defaultdict(int)
+
+        for i in range(k):
+            heapq.heappush(small, -nums[i])
+        for i in range(k // 2):
+            heapq.heappush(large, -heapq.heappop(small))
+
+        res = [-small[0] if k & 1 else (large[0] - small[0]) / 2]
+        for i in range(k, len(nums)):
+            d[nums[i - k]] += 1
+            balance = -1 if small and nums[i - k] <= -small[0] else 1
+
+            if small and nums[i] <= -small[0]:
+                heapq.heappush(small, -nums[i])
+                balance += 1
+            else:
+                heapq.heappush(large, nums[i])
+                balance -= 1
+
+            if balance > 0:
+                heapq.heappush(large, -heapq.heappop(small))
+            if balance < 0:
+                heapq.heappush(small, -heapq.heappop(large))
+
+            while small and d[-small[0]] > 0:
+                d[-heapq.heappop(small)] -= 1
+
+            while large and d[large[0]] > 0:
+                d[heapq.heappop(large)] -= 1
+
+            res.append(-small[0] if k & 1 else (large[0] - small[0]) / 2)
+
+        return res
+```
+
+```java
+public class Solution {
+    public double[] medianSlidingWindow(int[] nums, int k) {
+        PriorityQueue<Integer> small = new PriorityQueue<>(Collections.reverseOrder());
+        PriorityQueue<Integer> large = new PriorityQueue<>();
+        Map<Integer, Integer> d = new HashMap<>();
+
+        for (int i = 0; i < k; i++) {
+            small.add(nums[i]);
+        }
+        for (int i = 0; i < k / 2; i++) {
+            large.add(small.poll());
+        }
+
+        double[] res = new double[nums.length - k + 1];
+        res[0] = k % 2 == 1 ? small.peek() : (large.peek() + 0L + small.peek()) / 2.0;
+        for (int i = k; i < nums.length; i++) {
+            d.put(nums[i - k], d.getOrDefault(nums[i - k], 0) + 1);
+            int balance = (small.size() > 0 && nums[i - k] <= small.peek()) ? -1 : 1;
+
+            if (nums[i] <= small.peek()) {
+                small.add(nums[i]);
+                balance++;
+            } else {
+                large.add(nums[i]);
+                balance--;
+            }
+
+            if (balance > 0) {
+                large.add(small.poll());
+            }
+            if (balance < 0) {
+                small.add(large.poll());
+            }
+
+            while (!small.isEmpty() && d.getOrDefault(small.peek(), 0) > 0) {
+                d.put(small.peek(), d.get(small.peek()) - 1);
+                small.poll();
+            }
+            while (!large.isEmpty() && d.getOrDefault(large.peek(), 0) > 0) {
+                d.put(large.peek(), d.get(large.peek()) - 1);
+                large.poll();
+            }
+
+            res[i - k + 1] = k % 2 == 1 ? small.peek() : (large.peek() + 0L + small.peek()) / 2.0;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<double> medianSlidingWindow(vector<int>& nums, int k) {
+        priority_queue<int> small;
+        priority_queue<int, vector<int>, greater<int>> large;
+        unordered_map<int, int> d;
+
+        for (int i = 0; i < k; ++i) {
+            small.push(nums[i]);
+        }
+        for (int i = 0; i < k / 2; ++i) {
+            large.push(small.top());
+            small.pop();
+        }
+
+        vector<double> res;
+        res.push_back(k & 1 ? small.top() : (large.top() + 0LL + small.top()) / 2.0);
+        for (int i = k; i < nums.size(); ++i) {
+            d[nums[i - k]]++;
+            int balance = small.size() > 0 && nums[i - k] <= small.top() ? -1 : 1;
+
+            if (nums[i] <= small.top()) {
+                small.push(nums[i]);
+                balance++;
+            } else {
+                large.push(nums[i]);
+                balance--;
+            }
+
+            if (balance > 0) {
+                large.push(small.top());
+                small.pop();
+            }
+            if (balance < 0) {
+                small.push(large.top());
+                large.pop();
+            }
+
+            while (!small.empty() && d[small.top()] > 0) {
+                d[small.top()]--;
+                small.pop();
+            }
+
+            while (!large.empty() && d[large.top()] > 0) {
+                d[large.top()]--;
+                large.pop();
+            }
+
+            res.push_back(k & 1 ? small.top() : (large.top() + 0LL + small.top()) / 2.0);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number[]}
+     */
+    medianSlidingWindow(nums, k) {
+        const small = new MaxPriorityQueue({ compare: (a, b) => b - a });
+        const large = new MinPriorityQueue({ compare: (a, b) => a - b });
+        const d = new Map();
+
+        for (let i = 0; i < k; i++) {
+            small.enqueue(nums[i]);
+        }
+        for (let i = 0; i < Math.floor(k / 2); i++) {
+            large.enqueue(small.dequeue());
+        }
+
+        const res = [k % 2 === 1 ? small.front() : (large.front() + small.front()) / 2];
+        for (let i = k; i < nums.length; i++) {
+            const toRemove = nums[i - k];
+            d.set(toRemove, (d.get(toRemove) || 0) + 1);
+            let balance = small.size() > 0 && toRemove <= small.front() ? -1 : 1;
+
+            if (nums[i] <= small.front()) {
+                small.enqueue(nums[i]);
+                balance++;
+            } else {
+                large.enqueue(nums[i]);
+                balance--;
+            }
+
+            if (balance > 0) {
+                large.enqueue(small.dequeue());
+            }
+            if (balance < 0) {
+                small.enqueue(large.dequeue());
+            }
+
+            while (small.size() > 0 && d.get(small.front()) > 0) {
+                d.set(small.front(), d.get(small.front()) - 1);
+                small.dequeue();
+            }
+            while (large.size() > 0 && d.get(large.front()) > 0) {
+                d.set(large.front(), d.get(large.front()) - 1);
+                large.dequeue();
+            }
+
+            res.push(k % 2 === 1 ? small.front() : (large.front() + small.front()) / 2);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity:
+    * $O(n)$ extra space.
+    * $O(n - k + 1)$ space for output array.
+
+> Where $n$ is the size of the array $nums$ and $k$ is the size of the sliding window.
+
+---
+
+## 3. Two Multisets
+
+::tabs-start
+
+```python
+class Solution:
+    def medianSlidingWindow(self, nums: List[int], k: int) -> List[float]:
+        small, large = SortedList(), SortedList()
+        res = []
+        for i in range(len(nums)):
+            if len(small) == 0 or nums[i] <= small[-1]:
+                small.add(nums[i])
+            else:
+                large.add(nums[i])
+            if i >= k:
+                if nums[i - k] in small:
+                    small.remove(nums[i - k])
+                else:
+                    large.remove(nums[i - k])
+            if len(small) > len(large) + 1:
+                large.add(small.pop())
+            if len(large) > len(small):
+                small.add(large.pop(0))
+            if i >= k - 1:
+                res.append(small[-1] if k & 1 else (small[-1] + large[0]) / 2)
+        return res
+```
+
+```java
+public class Solution {
+    public double[] medianSlidingWindow(int[] nums, int k) {
+        TreeSet<Integer> small = new TreeSet<>((a, b) -> 
+            nums[a] != nums[b] ? Integer.compare(nums[a], nums[b]) : Integer.compare(a, b)
+        );
+        TreeSet<Integer> large = new TreeSet<>((a, b) -> 
+            nums[a] != nums[b] ? Integer.compare(nums[a], nums[b]) : Integer.compare(a, b)
+        );
+        double[] res = new double[nums.length - k + 1];
+        for (int i = 0; i < nums.length; i++) {
+            if (small.isEmpty() || nums[i] <= nums[small.last()]) small.add(i);
+            else large.add(i);
+            if (i >= k) {
+                if (small.contains(i - k)) small.remove(i - k);
+                else large.remove(i - k);
+            }
+            while (small.size() > large.size() + 1) large.add(small.pollLast());
+            while (large.size() > small.size()) small.add(large.pollFirst());
+            if (i >= k - 1) {
+                res[i - k + 1] = k % 2 == 1 ? nums[small.last()] : 
+                                 (nums[small.last()] + 0L + nums[large.first()]) / 2.0;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<double> medianSlidingWindow(vector<int>& nums, int k) {
+        multiset<int> small, large;
+        vector<double> res;
+        for (int i = 0; i < nums.size(); ++i) {
+            if (small.empty() || nums[i] <= *small.rbegin()) small.insert(nums[i]);
+            else large.insert(nums[i]);
+            if (i >= k) {
+                if (small.count(nums[i - k])) small.erase(small.find(nums[i - k]));
+                else large.erase(large.find(nums[i - k]));
+            }
+            if (small.size() > large.size() + 1) {
+                large.insert(*small.rbegin());
+                small.erase(prev(small.end()));
+            }
+            if (large.size() > small.size()) {
+                small.insert(*large.begin());
+                large.erase(large.begin());
+            }
+            if (i >= k - 1) {
+                res.push_back(
+                    k % 2 == 1 ? *small.rbegin() : 
+                                ((*small.rbegin() + 0LL + *large.begin()) / 2.0)
+                );
+            }
+        }
+        return res;
+    }
+};
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log k)$
+* Space complexity:
+    * $O(k)$ extra space.
+    * $O(n - k + 1)$ space for output array.
+
+> Where $n$ is the size of the array $nums$ and $k$ is the size of the sliding window.
+
+---
+
+## 4. Multiset
+
+::tabs-start
+
+```python
+class Solution:
+    def medianSlidingWindow(self, nums: List[int], k: int) -> List[float]:
+        window = SortedList()
+        res = []
+        for i in range(len(nums)):
+            window.add(nums[i])
+            if i >= k:
+                window.remove(nums[i - k])
+            if i >= k - 1:
+                if k % 2 == 1:
+                    res.append(float(window[k // 2]))
+                else:
+                    res.append((window[k // 2 - 1] + window[k // 2]) / 2)
+        return res
+```
+
+```cpp
+class Solution {
+public:
+    vector<double> medianSlidingWindow(vector<int>& nums, int k) {
+        multiset<int> window(nums.begin(), nums.begin() + k);
+        auto mid = next(window.begin(), k / 2);
+        vector<double> res;
+
+        for (int i = k;; i++) {
+            if (k & 1) {
+                res.push_back(*mid);
+            } else {
+                res.push_back((*mid + 0LL + *prev(mid)) / 2.0);
+            }
+
+            if (i == nums.size()) return res;
+
+            window.insert(nums[i]);
+            if (nums[i] < *mid) mid--;
+            if (nums[i - k] <= *mid) mid++;
+            window.erase(window.lower_bound(nums[i - k]));
+        }
+    }
+};
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log k)$
+* Space complexity:
+    * $O(k)$ extra space.
+    * $O(n - k + 1)$ space for output array.
+
+> Where $n$ is the size of the array $nums$ and $k$ is the size of the sliding window.
\ No newline at end of file
diff --git a/articles/smallest-string-starting-from-leaf.md b/articles/smallest-string-starting-from-leaf.md
new file mode 100644
index 000000000..d3d241adb
--- /dev/null
+++ b/articles/smallest-string-starting-from-leaf.md
@@ -0,0 +1,474 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def smallestFromLeaf(self, root: Optional[TreeNode]) -> str:
+        def dfs(root, cur):
+            if not root:
+                return
+
+            cur = chr(ord('a') + root.val) + cur
+            if root.left and root.right:
+                return min(
+                    dfs(root.left, cur),
+                    dfs(root.right, cur)
+                )
+
+            if root.right:
+                return dfs(root.right, cur)
+            if root.left:
+                return dfs(root.left, cur)
+            return cur
+
+        return dfs(root, "")
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public String smallestFromLeaf(TreeNode root) {
+        return dfs(root, "");
+    }
+
+    private String dfs(TreeNode root, String cur) {
+        if (root == null) {
+            return null;
+        }
+
+        cur = (char) ('a' + root.val) + cur;
+        if (root.left != null && root.right != null) {
+            return min(dfs(root.left, cur), dfs(root.right, cur));
+        }
+
+        if (root.right != null) {
+            return dfs(root.right, cur);
+        }
+        if (root.left != null) {
+            return dfs(root.left, cur);
+        }
+        return cur;
+    }
+
+    private String min(String a, String b) {
+        if (a == null) return b;
+        if (b == null) return a;
+        return a.compareTo(b) < 0 ? a : b;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    string smallestFromLeaf(TreeNode* root) {
+        return dfs(root, "");
+    }
+
+private:
+    string dfs(TreeNode* root, string cur) {
+        if (!root) return "";
+
+        cur = char('a' + root->val) + cur;
+        if (root->left && root->right) {
+            return min(dfs(root->left, cur), dfs(root->right, cur));
+        }
+
+        if (root->right) return dfs(root->right, cur);
+        if (root->left) return dfs(root->left, cur);
+        return cur;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {string}
+     */
+    smallestFromLeaf(root) {
+        const min = (a, b) => {
+            if (!a) return b;
+            if (!b) return a;
+            return a < b ? a : b;
+        };
+
+        const dfs = (node, cur) => {
+            if (!node) return;
+            
+            cur = String.fromCharCode(97 + node.val) + cur;
+
+            if (node.left && node.right) {
+                return min(dfs(node.left, cur), dfs(node.right, cur));
+            }
+            if (node.left) return dfs(node.left, cur);
+            if (node.right) return dfs(node.right, cur);
+            return cur;
+        };
+
+        return dfs(root, "");
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 2. Breadth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def smallestFromLeaf(self, root: Optional[TreeNode]) -> str:
+        q = deque([(root, "")])
+        res = None
+
+        while q:
+            node, cur = q.popleft()
+            cur = chr(ord('a') + node.val) + cur
+
+            if not node.left and not node.right:
+                res = min(res, cur) if res else cur
+
+            if node.left:
+                q.append((node.left, cur))
+            if node.right:
+                q.append((node.right, cur))
+
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public String smallestFromLeaf(TreeNode root) {
+        Queue<Pair<TreeNode, String>> q = new LinkedList<>();
+        q.offer(new Pair<>(root, ""));
+        String res = null;
+
+        while (!q.isEmpty()) {
+            Pair<TreeNode, String> pair = q.poll();
+            TreeNode node = pair.getKey();
+            String cur = (char) ('a' + node.val) + pair.getValue();
+
+            if (node.left == null && node.right == null) {
+                if (res == null || cur.compareTo(res) < 0) {
+                    res = cur;
+                }
+            }
+
+            if (node.left != null) q.offer(new Pair<>(node.left, cur));
+            if (node.right != null) q.offer(new Pair<>(node.right, cur));
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    string smallestFromLeaf(TreeNode* root) {
+        queue<pair<TreeNode*, string>> q;
+        q.push({root, ""});
+        string res;
+
+        while (!q.empty()) {
+            auto [node, cur] = q.front();
+            q.pop();
+            cur = char('a' + node->val) + cur;
+
+            if (!node->left && !node->right) {
+                if (res.empty() || cur < res) {
+                    res = cur;
+                }
+            }
+
+            if (node->left) q.push({node->left, cur});
+            if (node->right) q.push({node->right, cur});
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {string}
+     */
+    smallestFromLeaf(root) {
+        const q = new Queue();
+        q.push([root, ""]);
+        let res = null;
+
+        while (!q.isEmpty()) {
+            const [node, cur] = q.pop();
+            const newCur = String.fromCharCode(97 + node.val) + cur;
+
+            if (!node.left && !node.right) {
+                res = res === null || newCur < res ? newCur : res;
+            }
+
+            if (node.left) q.push([node.left, newCur]);
+            if (node.right) q.push([node.right, newCur]);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 3. Iterative DFS
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def smallestFromLeaf(self, root: Optional[TreeNode]) -> str:
+        stack = [(root, "")]
+        res = None
+
+        while stack:
+            node, cur = stack.pop()
+            cur = chr(ord('a') + node.val) + cur
+
+            if not node.left and not node.right:
+                res = min(res, cur) if res else cur
+            
+            if node.right:
+                stack.append((node.right, cur))
+            if node.left:
+                stack.append((node.left, cur))
+        
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public String smallestFromLeaf(TreeNode root) {
+        Stack<Pair<TreeNode, String>> stack = new Stack<>();
+        stack.push(new Pair<>(root, ""));
+        String res = null;
+
+        while (!stack.isEmpty()) {
+            Pair<TreeNode, String> pair = stack.pop();
+            TreeNode node = pair.getKey();
+            String cur = (char) ('a' + node.val) + pair.getValue();
+
+            if (node.left == null && node.right == null) {
+                if (res == null || cur.compareTo(res) < 0) {
+                    res = cur;
+                }
+            }
+
+            if (node.right != null) stack.push(new Pair<>(node.right, cur));
+            if (node.left != null) stack.push(new Pair<>(node.left, cur));
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    string smallestFromLeaf(TreeNode* root) {
+        stack<pair<TreeNode*, string>> stk;
+        stk.push({root, ""});
+        string res;
+
+        while (!stk.empty()) {
+            auto [node, cur] = stk.top();stk.pop();
+            cur = char('a' + node->val) + cur;
+
+            if (!node->left && !node->right) {
+                if (res.empty() || cur < res) {
+                    res = cur;
+                }
+            }
+
+            if (node->right) stk.push({node->right, cur});
+            if (node->left) stk.push({node->left, cur});
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {string}
+     */
+    smallestFromLeaf(root) {
+        const stack = [[root, ""]];
+        let res = null;
+
+        while (stack.length) {
+            const [node, cur] = stack.pop();
+            const newCur = String.fromCharCode(97 + node.val) + cur;
+
+            if (!node.left && !node.right) {
+                res = res === null || newCur < res ? newCur : res;
+            }
+
+            if (node.right) stack.push([node.right, newCur]);
+            if (node.left) stack.push([node.left, newCur]);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
\ No newline at end of file
diff --git a/articles/snakes-and-ladders.md b/articles/snakes-and-ladders.md
new file mode 100644
index 000000000..afc71ef47
--- /dev/null
+++ b/articles/snakes-and-ladders.md
@@ -0,0 +1,572 @@
+## 1. Breadth First Search - I
+
+::tabs-start
+
+```python
+class Solution:
+    def snakesAndLadders(self, board: List[List[int]]) -> int:
+        n = len(board)
+        
+        def intToPos(square):
+            r = (square - 1) // n
+            c = (square - 1) % n
+            if r % 2 == 1:
+                c = n - 1 - c
+            r = n - 1 - r
+            return r, c
+        
+        q = deque([(1, 0)])
+        visit = set()
+        
+        while q:
+            square, moves = q.popleft()
+            
+            for i in range(1, 7):
+                nextSquare = square + i
+                r, c = intToPos(nextSquare)
+                if board[r][c] != -1:
+                    nextSquare = board[r][c]
+                
+                if nextSquare == n * n:
+                    return moves + 1
+                
+                if nextSquare not in visit:
+                    visit.add(nextSquare)
+                    q.append((nextSquare, moves + 1))
+        
+        return -1
+```
+
+```java
+public class Solution {
+    public int snakesAndLadders(int[][] board) {
+        int n = board.length;
+        Queue<int[]> q = new LinkedList<>();
+        q.offer(new int[]{1, 0});
+        Set<Integer> visit = new HashSet<>();
+        
+        while (!q.isEmpty()) {
+            int[] cur = q.poll();
+            int square = cur[0], moves = cur[1];
+            
+            for (int i = 1; i <= 6; i++) {
+                int nextSquare = square + i;
+                int[] pos = intToPos(nextSquare, n);
+                int r = pos[0], c = pos[1];
+                if (board[r][c] != -1) {
+                    nextSquare = board[r][c];
+                }
+                if (nextSquare == n * n) return moves + 1;
+                if (!visit.contains(nextSquare)) {
+                    visit.add(nextSquare);
+                    q.offer(new int[]{nextSquare, moves + 1});
+                }
+            }
+        }
+        return -1;
+    }
+    
+    private int[] intToPos(int square, int n) {
+        int r = (square - 1) / n;
+        int c = (square - 1) % n;
+        if (r % 2 == 1) c = n - 1 - c;
+        r = n - 1 - r;
+        return new int[]{r, c};
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int snakesAndLadders(vector<vector<int>>& board) {
+        int n = board.size();
+        queue<pair<int, int>> q;
+        q.push({1, 0});
+        unordered_set<int> visit;
+
+        while (!q.empty()) {
+            auto [square, moves] = q.front(); q.pop();
+
+            for (int i = 1; i <= 6; i++) {
+                int nextSquare = square + i;
+                auto [r, c] = intToPos(nextSquare, n);
+                if (board[r][c] != -1) {
+                    nextSquare = board[r][c];
+                }
+                if (nextSquare == n * n) return moves + 1;
+                if (!visit.count(nextSquare)) {
+                    visit.insert(nextSquare);
+                    q.push({nextSquare, moves + 1});
+                }
+            }
+        }
+        return -1;
+    }
+    
+private:
+    pair<int, int> intToPos(int square, int n) {
+        int r = (square - 1) / n;
+        int c = (square - 1) % n;
+        if (r % 2 == 1) c = n - 1 - c;
+        r = n - 1 - r;
+        return {r, c};
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} board
+     * @return {number}
+     */
+    snakesAndLadders(board) {
+        const n = board.length;
+        const queue = new Queue([[1, 0]]);
+        const visit = new Set();
+
+        const intToPos = (square) => {
+            let r = Math.floor((square - 1) / n);
+            let c = (square - 1) % n;
+            if (r % 2 === 1) c = n - 1 - c;
+            r = n - 1 - r;
+            return [r, c];
+        };
+
+        while (!queue.isEmpty()) {
+            const [square, moves] = queue.pop();
+
+            for (let i = 1; i <= 6; i++) {
+                let nextSquare = square + i;
+                const [r, c] = intToPos(nextSquare);
+                if (board[r][c] !== -1) {
+                    nextSquare = board[r][c];
+                }
+                if (nextSquare === n * n) return moves + 1;
+                if (!visit.has(nextSquare)) {
+                    visit.add(nextSquare);
+                    queue.push([nextSquare, moves + 1]);
+                }
+            }
+        }
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 2. Breadth First Search - II
+
+::tabs-start
+
+```python
+class Solution:
+    def snakesAndLadders(self, board: List[List[int]]) -> int:
+        n = len(board)
+        
+        def intToPos(square):
+            r = (square - 1) // n
+            c = (square - 1) % n
+            if r % 2 == 1:
+                c = n - 1 - c
+            r = n - 1 - r
+            return r, c
+        
+        dist = [-1] * (n * n + 1)
+        q = deque([1])
+        dist[1] = 0
+        
+        while q:
+            square = q.popleft()
+            
+            for i in range(1, 7):
+                nextSquare = square + i
+                if nextSquare > n * n:
+                    break
+                
+                r, c = intToPos(nextSquare)
+                if board[r][c] != -1:
+                    nextSquare = board[r][c]
+                
+                if dist[nextSquare] == -1:
+                    dist[nextSquare] = dist[square] + 1
+                    if nextSquare == n * n:
+                        return dist[nextSquare]
+                    q.append(nextSquare)
+        
+        return -1
+```
+
+```java
+public class Solution {
+    public int snakesAndLadders(int[][] board) {
+        int n = board.length;
+        int[] dist = new int[n * n + 1];
+        Arrays.fill(dist, -1);
+        Queue<Integer> q = new LinkedList<>();
+        q.add(1);
+        dist[1] = 0;
+
+        while (!q.isEmpty()) {
+            int square = q.poll();
+
+            for (int i = 1; i <= 6; i++) {
+                int nextSquare = square + i;
+                if (nextSquare > n * n) {
+                    break;
+                }
+
+                int[] pos = intToPos(nextSquare, n);
+                int r = pos[0], c = pos[1];
+
+                if (board[r][c] != -1) {
+                    nextSquare = board[r][c];
+                }
+
+                if (dist[nextSquare] == -1) {
+                    dist[nextSquare] = dist[square] + 1;
+                    if (nextSquare == n * n) {
+                        return dist[nextSquare];
+                    }
+                    q.add(nextSquare);
+                }
+            }
+        }
+
+        return -1;
+    }
+
+    private int[] intToPos(int square, int n) {
+        int r = (square - 1) / n;
+        int c = (square - 1) % n;
+        if (r % 2 == 1) {
+            c = n - 1 - c;
+        }
+        r = n - 1 - r;
+        return new int[]{r, c};
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int snakesAndLadders(vector<vector<int>>& board) {
+        int n = board.size();
+        vector<int> dist(n * n + 1, -1);
+        queue<int> q;
+        q.push(1);
+        dist[1] = 0;
+
+        while (!q.empty()) {
+            int square = q.front();
+            q.pop();
+
+            for (int i = 1; i <= 6; i++) {
+                int nextSquare = square + i;
+                if (nextSquare > n * n) {
+                    break;
+                }
+
+                auto [r, c] = intToPos(nextSquare, n);
+                if (board[r][c] != -1) {
+                    nextSquare = board[r][c];
+                }
+
+                if (dist[nextSquare] == -1) {
+                    dist[nextSquare] = dist[square] + 1;
+                    if (nextSquare == n * n) {
+                        return dist[nextSquare];
+                    }
+                    q.push(nextSquare);
+                }
+            }
+        }
+
+        return -1;
+    }
+
+private:
+    pair<int, int> intToPos(int square, int n) {
+        int r = (square - 1) / n;
+        int c = (square - 1) % n;
+        if (r % 2 == 1) {
+            c = n - 1 - c;
+        }
+        r = n - 1 - r;
+        return {r, c};
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} board
+     * @return {number}
+     */
+    snakesAndLadders(board) {
+        const n = board.length;
+        const dist = new Array(n * n + 1).fill(-1);
+        const queue = new Queue([1]);
+        dist[1] = 0;
+
+        const intToPos = (square) => {
+            let r = Math.floor((square - 1) / n);
+            let c = (square - 1) % n;
+            if (r % 2 === 1) c = n - 1 - c;
+            r = n - 1 - r;
+            return [r, c];
+        };
+
+        while (!queue.isEmpty()) {
+            const square = queue.pop();
+
+            for (let i = 1; i <= 6; i++) {
+                let nextSquare = square + i;
+                if (nextSquare > n * n) break;
+
+                const [r, c] = intToPos(nextSquare, n);
+                if (board[r][c] !== -1) {
+                    nextSquare = board[r][c];
+                }
+
+                if (dist[nextSquare] === -1) {
+                    dist[nextSquare] = dist[square] + 1;
+                    if (nextSquare === n * n) {
+                        return dist[nextSquare];
+                    }
+                    queue.push(nextSquare);
+                }
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 3. Breadth First Search - III
+
+::tabs-start
+
+```python
+class Solution:
+    def snakesAndLadders(self, board: List[List[int]]) -> int:
+        n = len(board)
+        
+        def intToPos(square):
+            r = (square - 1) // n
+            c = (square - 1) % n
+            if r % 2 == 1:
+                c = n - 1 - c
+            r = n - 1 - r
+            return r, c
+        
+        q = deque([1])
+        board[n - 1][0] = 0
+        moves = 0
+        
+        while q:
+            for _ in range(len(q)):
+                square = q.popleft()
+                
+                for i in range(1, 7):
+                    nextSquare = square + i
+                    if nextSquare > n * n:
+                        break
+                    
+                    r, c = intToPos(nextSquare)
+                    if board[r][c] != -1:
+                        nextSquare = board[r][c]
+                    
+                    if board[r][c] != 0:
+                        if nextSquare == n * n:
+                            return moves + 1
+                        q.append(nextSquare)
+                        board[r][c] = 0
+            moves += 1
+        
+        return -1
+```
+
+```java
+public class Solution {
+    public int snakesAndLadders(int[][] board) {
+        int n = board.length;
+        Queue<Integer> q = new LinkedList<>();
+        q.add(1);
+        board[n - 1][0] = 0;
+        int moves = 0;
+
+        while (!q.isEmpty()) {
+            for (int it = q.size(); it > 0; it--) {
+                int square = q.poll();
+                for (int i = 1; i <= 6; i++) {
+                    int nextSquare = square + i;
+                    if (nextSquare > n * n) {
+                        break;
+                    }
+
+                    int[] pos = intToPos(nextSquare, n);
+                    int r = pos[0], c = pos[1];
+
+                    if (board[r][c] != -1) {
+                        nextSquare = board[r][c];
+                    }
+
+                    if (board[r][c] != 0) {
+                        if (nextSquare == n * n) {
+                            return moves + 1;
+                        }
+                        
+                        board[r][c] = 0;
+                        q.add(nextSquare);
+                    }
+                }
+            }
+            moves++;
+        }
+
+        return -1;
+    }
+
+    private int[] intToPos(int square, int n) {
+        int r = (square - 1) / n;
+        int c = (square - 1) % n;
+        if (r % 2 == 1) {
+            c = n - 1 - c;
+        }
+        r = n - 1 - r;
+        return new int[]{r, c};
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int snakesAndLadders(vector<vector<int>>& board) {
+        int n = board.size();
+        queue<int> q;
+        q.push(1);
+        board[n - 1][0] = 0;
+        int moves = 0;
+
+        while (!q.empty()) {
+            for (int it = q.size(); it > 0; it--) {
+                int square = q.front(); q.pop();
+                for (int i = 1; i <= 6; i++) {
+                    int nextSquare = square + i;
+                    if (nextSquare > n * n) {
+                        break;
+                    }
+
+                    auto [r, c] = intToPos(nextSquare, n);
+                    if (board[r][c] != -1) {
+                        nextSquare = board[r][c];
+                    }
+
+                    if (board[r][c] != 0) {
+                        if (nextSquare == n * n) {
+                            return moves + 1;
+                        }
+                        
+                        board[r][c] = 0;
+                        q.push(nextSquare);
+                    }
+                }
+            }
+            moves++;
+        }
+
+        return -1;
+    }
+
+private:
+    pair<int, int> intToPos(int square, int n) {
+        int r = (square - 1) / n;
+        int c = (square - 1) % n;
+        if (r % 2 == 1) {
+            c = n - 1 - c;
+        }
+        r = n - 1 - r;
+        return {r, c};
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} board
+     * @return {number}
+     */
+    snakesAndLadders(board) {
+        const n = board.length;
+        const queue = new Queue([1]);
+        board[n - 1][0] = 0;
+
+        const intToPos = (square) => {
+            let r = Math.floor((square - 1) / n);
+            let c = (square - 1) % n;
+            if (r % 2 === 1) c = n - 1 - c;
+            r = n - 1 - r;
+            return [r, c];
+        };
+
+        let moves = 0;
+        while (!queue.isEmpty()) {
+            for (let it = queue.size(); it > 0; it--) {
+                const square = queue.pop();
+                for (let i = 1; i <= 6; i++) {
+                    let nextSquare = square + i;
+                    if (nextSquare > n * n) break;
+
+                    const [r, c] = intToPos(nextSquare, n);
+                    if (board[r][c] !== -1) {
+                        nextSquare = board[r][c];
+                    }
+
+                    if (board[r][c] !== 0) {
+                        if (nextSquare === n * n) {
+                            return moves + 1;
+                        }
+                        
+                        board[r][c] = 0;
+                        queue.push(nextSquare);
+                    }
+                }
+            }
+            moves++;
+        }
+
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
\ No newline at end of file
diff --git a/articles/solving-questions-with-brainpower.md b/articles/solving-questions-with-brainpower.md
new file mode 100644
index 000000000..248ec63b3
--- /dev/null
+++ b/articles/solving-questions-with-brainpower.md
@@ -0,0 +1,233 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def mostPoints(self, questions: List[List[int]]) -> int:
+        def dfs(i):
+            if i >= len(questions):
+                return 0
+            return max(dfs(i + 1), questions[i][0] + dfs(i + 1 + questions[i][1]))
+        return dfs(0)
+```
+
+```java
+public class Solution {
+    public long mostPoints(int[][] questions) {
+        return dfs(0, questions);
+    }
+
+    private long dfs(int i, int[][] questions) {
+        if (i >= questions.length) return 0;
+        return Math.max(dfs(i + 1, questions), questions[i][0] + dfs(i + 1 + questions[i][1], questions));
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long mostPoints(vector<vector<int>>& questions) {
+        return dfs(0, questions);
+    }
+
+private:
+    long long dfs(int i, vector<vector<int>>& questions) {
+        if (i >= questions.size()) return 0;
+        return max(dfs(i + 1, questions), questions[i][0] + dfs(i + 1 + questions[i][1], questions));
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} questions
+     * @return {number}
+     */
+    mostPoints(questions) {
+        const dfs = (i) => {
+            if (i >= questions.length) return 0;
+            return Math.max(dfs(i + 1), questions[i][0] + dfs(i + 1 + questions[i][1]));
+        };
+        return dfs(0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def mostPoints(self, questions: List[List[int]]) -> int:
+        dp = {}
+        def dfs(i):
+            if i >= len(questions):
+                return 0
+            if i in dp:
+                return dp[i]
+            dp[i] = max(dfs(i + 1), questions[i][0] + dfs(i + 1 + questions[i][1]))
+            return dp[i]
+        return dfs(0)
+```
+
+```java
+public class Solution {
+    private long[] dp;
+
+    public long mostPoints(int[][] questions) {
+        dp = new long[questions.length];
+        return dfs(0, questions);
+    }
+
+    private long dfs(int i, int[][] questions) {
+        if (i >= questions.length) return 0;
+        if (dp[i] != 0) return dp[i];
+        dp[i] = Math.max(dfs(i + 1, questions), questions[i][0] + dfs(i + 1 + questions[i][1], questions));
+        return dp[i];
+    }
+}
+
+```
+
+```cpp
+class Solution {
+    vector<long long> dp;
+
+public:
+    long long mostPoints(vector<vector<int>>& questions) {
+        dp.assign(questions.size(), 0);
+        return dfs(0, questions);
+    }
+
+private:
+    long long dfs(int i, vector<vector<int>>& questions) {
+        if (i >= questions.size()) return 0;
+        if (dp[i] != 0) return dp[i];
+        dp[i] = max(dfs(i + 1, questions), questions[i][0] + dfs(i + 1 + questions[i][1], questions));
+        return dp[i];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} questions
+     * @return {number}
+     */
+    mostPoints(questions) {
+        const dp = new Array(questions.length).fill(-1);
+
+        const dfs = (i) => {
+            if (i >= questions.length) return 0;
+            if (dp[i] !== -1) return dp[i];
+            dp[i] = Math.max(dfs(i + 1), questions[i][0] + dfs(i + 1 + questions[i][1]));
+            return dp[i];
+        };
+
+        return dfs(0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def mostPoints(self, questions: List[List[int]]) -> int:
+        dp = {}
+
+        for i in range(len(questions) - 1, -1, -1):
+            dp[i] = max(
+                questions[i][0] + dp.get(i + 1 + questions[i][1], 0), 
+                dp.get(i + 1, 0)
+            )
+        return dp.get(0)
+```
+
+```java
+public class Solution {
+    public long mostPoints(int[][] questions) {
+        int n = questions.length;
+        long[] dp = new long[n + 1];
+
+        for (int i = n - 1; i >= 0; i--) {
+            dp[i] = Math.max(
+                questions[i][0] + (i + 1 + questions[i][1] < n ? dp[i + 1 + questions[i][1]] : 0), 
+                dp[i + 1]
+            );
+        }
+        return dp[0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    long long mostPoints(vector<vector<int>>& questions) {
+        int n = questions.size();
+        vector<long long> dp(n + 1, 0);
+
+        for (int i = n - 1; i >= 0; i--) {
+            dp[i] = max(
+                (long long)questions[i][0] + (i + 1 + questions[i][1] < n ? dp[i + 1 + questions[i][1]] : 0), 
+                dp[i + 1]
+            );
+        }
+        return dp[0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} questions
+     * @return {number}
+     */
+    mostPoints(questions) {
+        const n = questions.length;
+        const dp = new Array(n + 1).fill(0);
+
+        for (let i = n - 1; i >= 0; i--) {
+            dp[i] = Math.max(
+                questions[i][0] + (i + 1 + questions[i][1] < n ? dp[i + 1 + questions[i][1]] : 0), 
+                dp[i + 1]
+            );
+        }
+        return dp[0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/sort-an-array.md b/articles/sort-an-array.md
new file mode 100644
index 000000000..6b34f49d2
--- /dev/null
+++ b/articles/sort-an-array.md
@@ -0,0 +1,1372 @@
+## 1. Quick Sort
+
+::tabs-start
+
+```python
+class Solution:
+    def partition(self, nums: List[int], left: int, right: int) -> int:
+        mid = (left + right) >> 1
+        nums[mid], nums[left + 1] = nums[left + 1], nums[mid]
+
+        if nums[left] > nums[right]:
+            nums[left], nums[right] = nums[right], nums[left]
+        if nums[left + 1] > nums[right]:
+            nums[left + 1], nums[right] = nums[right], nums[left + 1]
+        if nums[left] > nums[left + 1]:
+            nums[left], nums[left + 1] = nums[left + 1], nums[left]
+
+        pivot = nums[left + 1]
+        i = left + 1
+        j = right
+
+        while True:
+            while True:
+                i += 1
+                if not nums[i] < pivot:
+                    break
+            while True:
+                j -= 1
+                if not nums[j] > pivot:
+                    break
+            if i > j:
+                break
+            nums[i], nums[j] = nums[j], nums[i]
+
+        nums[left + 1], nums[j] = nums[j], nums[left + 1]
+        return j
+
+    def quickSort(self, nums: List[int], left: int, right: int) -> None:
+        if right <= left + 1:
+            if right == left + 1 and nums[right] < nums[left]:
+                nums[left], nums[right] = nums[right], nums[left]
+            return
+
+        j = self.partition(nums, left, right)
+        self.quickSort(nums, left, j - 1)
+        self.quickSort(nums, j + 1, right)
+
+    def sortArray(self, nums: List[int]) -> List[int]:
+        self.quickSort(nums, 0, len(nums) - 1)
+        return nums
+```
+
+```java
+public class Solution {
+    private int partition(int[] nums, int left, int right) {
+        int mid = (left + right) >> 1;
+        swap(nums, mid, left + 1);
+        
+        if (nums[left] > nums[right]) 
+            swap(nums, left, right);
+        if (nums[left + 1] > nums[right]) 
+            swap(nums, left + 1, right);
+        if (nums[left] > nums[left + 1]) 
+            swap(nums, left, left + 1);
+        
+        int pivot = nums[left + 1];
+        int i = left + 1;
+        int j = right;
+        
+        while (true) {
+            while (nums[++i] < pivot);
+            while (nums[--j] > pivot);
+            if (i > j) break;
+            swap(nums, i, j);
+        }
+        
+        nums[left + 1] = nums[j];
+        nums[j] = pivot;
+        return j;
+    }
+    
+    private void swap(int[] nums, int i, int j) {
+        int temp = nums[i];
+        nums[i] = nums[j];
+        nums[j] = temp;
+    }
+    
+    private void quickSort(int[] nums, int left, int right) {
+        if (right <= left + 1) {
+            if (right == left + 1 && nums[right] < nums[left])
+                swap(nums, left, right);
+            return;
+        }
+        
+        int j = partition(nums, left, right);
+        quickSort(nums, left, j - 1);
+        quickSort(nums, j + 1, right);
+    }
+
+    public int[] sortArray(int[] nums) {
+        quickSort(nums, 0, nums.length - 1);
+        return nums;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+int partition(vector<int>& nums, int left, int right) {
+        int mid = (left + right) >> 1;
+        swap(nums[mid], nums[left + 1]);
+        
+        if (nums[left] > nums[right]) 
+            swap(nums[left], nums[right]);
+        if (nums[left + 1] > nums[right]) 
+            swap(nums[left + 1], nums[right]);
+        if (nums[left] > nums[left + 1]) 
+            swap(nums[left], nums[left + 1]);
+        
+        int pivot = nums[left + 1];
+        int i = left + 1;
+        int j = right;
+        
+        while (true) {
+            while (nums[++i] < pivot);
+            while (nums[--j] > pivot);
+            if (i > j) break;
+            swap(nums[i], nums[j]);
+        }
+        
+        nums[left + 1] = nums[j];
+        nums[j] = pivot;
+        return j;
+    }
+    
+    void quickSort(vector<int>& nums, int left, int right) {
+        if (right <= left + 1) {
+            if (right == left + 1 && nums[right] < nums[left])
+                swap(nums[left], nums[right]);
+            return;
+        }
+
+        int j = partition(nums, left, right);
+        quickSort(nums, left, j - 1);
+        quickSort(nums, j + 1, right);
+    }
+
+    vector<int> sortArray(vector<int>& nums) {
+        quickSort(nums, 0, nums.size() - 1);
+        return nums;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    sortArray(nums) {
+        function partition(left, right) {
+            const mid = (left + right) >> 1;
+            [nums[mid], nums[left + 1]] = [nums[left + 1], nums[mid]];
+            
+            if (nums[left] > nums[right])
+                [nums[left], nums[right]] = [nums[right], nums[left]];
+            if (nums[left + 1] > nums[right])
+                [nums[left + 1], nums[right]] = [nums[right], nums[left + 1]];
+            if (nums[left] > nums[left + 1])
+                [nums[left], nums[left + 1]] = [nums[left + 1], nums[left]];
+            
+            const pivot = nums[left + 1];
+            let i = left + 1;
+            let j = right;
+            
+            while (true) {
+                while (nums[++i] < pivot);
+                while (nums[--j] > pivot);
+                if (i > j) break;
+                [nums[i], nums[j]] = [nums[j], nums[i]];
+            }
+            
+            nums[left + 1] = nums[j];
+            nums[j] = pivot;
+            return j;
+        }
+        
+        function quickSort(left, right) {
+            if (right <= left + 1) {
+                if (right == left + 1 && nums[right] < nums[left])
+                    [nums[left], nums[right]] = [nums[right], nums[left]];
+                return;
+            }
+            
+            const j = partition(left, right);
+            quickSort(left, j - 1);
+            quickSort(j + 1, right);
+        }
+        
+        quickSort(0, nums.length - 1);
+        return nums;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[] SortArray(int[] nums) {
+        QuickSort(nums, 0, nums.Length - 1);
+        return nums;
+    }
+
+    private void QuickSort(int[] nums, int left, int right) {
+        if (right <= left + 1) {
+            if (right == left + 1 && nums[right] < nums[left]) {
+                Swap(nums, left, right);
+            }
+            return;
+        }
+
+        int j = Partition(nums, left, right);
+        QuickSort(nums, left, j - 1);
+        QuickSort(nums, j + 1, right);
+    }
+
+    private int Partition(int[] nums, int left, int right) {
+        int mid = (left + right) >> 1;
+        Swap(nums, mid, left + 1);
+
+        if (nums[left] > nums[right]) Swap(nums, left, right);
+        if (nums[left + 1] > nums[right]) Swap(nums, left + 1, right);
+        if (nums[left] > nums[left + 1]) Swap(nums, left, left + 1);
+
+        int pivot = nums[left + 1];
+        int i = left + 1, j = right;
+
+        while (true) {
+            while (++i <= right && nums[i] < pivot) ;
+            while (--j >= left && nums[j] > pivot) ;
+
+            if (i > j) break;
+
+            Swap(nums, i, j);
+        }
+
+        Swap(nums, left + 1, j);
+        return j;
+    }
+
+    private void Swap(int[] nums, int i, int j) {
+        int temp = nums[i];
+        nums[i] = nums[j];
+        nums[j] = temp;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$ in average case, $O(n ^ 2)$ in worst case.
+* Space complexity: $O(\log n)$ for recursive stack.
+
+---
+
+## 2. Merge Sort
+
+::tabs-start
+
+```python
+class Solution:
+    def sortArray(self, nums: List[int]) -> List[int]:
+        def merge(arr, L, M, R):
+            left, right = arr[L : M + 1], arr[M + 1 : R + 1]
+            i, j, k = L, 0, 0
+
+            while j < len(left) and k < len(right):
+                if left[j] <= right[k]:
+                    arr[i] = left[j]
+                    j += 1
+                else:
+                    arr[i] = right[k]
+                    k += 1
+                i += 1
+            while j < len(left):
+                nums[i] = left[j]
+                j += 1
+                i += 1
+            while k < len(right):
+                nums[i] = right[k]
+                k += 1
+                i += 1
+        
+        def mergeSort(arr, l, r):
+            if l == r:
+                return
+
+            m = (l + r) // 2
+            mergeSort(arr, l, m)
+            mergeSort(arr, m + 1, r)
+            merge(arr, l, m, r)
+            return
+        
+        mergeSort(nums, 0, len(nums))
+        return nums
+```
+
+```java
+public class Solution {
+    public int[] sortArray(int[] nums) {
+        mergeSort(nums, 0, nums.length - 1);
+        return nums;
+    }
+
+    private void mergeSort(int[] arr, int l, int r) {
+        if (l >= r) return;
+        int m = (l + r) / 2;
+        mergeSort(arr, l, m);
+        mergeSort(arr, m + 1, r);
+        merge(arr, l, m, r);
+    }
+
+    private void merge(int[] arr, int l, int m, int r) {
+        ArrayList<Integer> temp = new ArrayList<>();
+        int i = l;
+        int j = m + 1;
+
+        while (i <= m && j <= r) {
+            if (arr[i] <= arr[j]) {
+                temp.add(arr[i]);
+                i++;
+            } else {
+                temp.add(arr[j]);
+                j++;
+            }
+        }
+
+
+        while (i <= m) {
+            temp.add(arr[i]);
+            i++;
+        }
+
+        while (j <= r) {
+            temp.add(arr[j]);
+            j++;
+        }
+
+        for (i = l; i <= r; i++) {
+            arr[i] = temp.get(i - l);
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> sortArray(vector<int>& nums) {
+        mergeSort(nums, 0, nums.size() - 1);
+        return nums;
+    }
+
+private:
+    void mergeSort(vector<int>& arr, int l, int r) {
+        if (l >= r) return;
+        int m = (l + r) / 2;
+        mergeSort(arr, l, m);
+        mergeSort(arr, m + 1, r);
+        merge(arr, l, m, r);
+    }
+
+    void merge(vector<int>& arr, int l, int m, int r) {
+        vector<int> temp;
+        int i = l, j = m + 1;
+
+        while (i <= m && j <= r) {
+            if (arr[i] <= arr[j]) {
+                temp.push_back(arr[i++]);
+            } else {
+                temp.push_back(arr[j++]);
+            }
+        }
+
+        while (i <= m) temp.push_back(arr[i++]);
+        while (j <= r) temp.push_back(arr[j++]);
+
+        for (int i = l; i <= r; i++) {
+            arr[i] = temp[i - l];
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    sortArray(nums) {
+        this.mergeSort(nums, 0, nums.length - 1);
+        return nums;
+    }
+
+    /**
+    * @param {number[]} arr
+    * @param {number} l
+    * @param {number} r
+    * @return {void}
+    */
+    mergeSort(arr, l, r) {
+        if (l >= r) return;
+        let m = Math.floor((l + r) / 2);
+        this.mergeSort(arr, l, m);
+        this.mergeSort(arr, m + 1, r);
+        this.merge(arr, l, m, r);
+    }
+
+    /**
+    * @param {number[]} arr
+    * @param {number} l
+    * @param {number} m
+    * @param {number} r
+    * @return {void}
+    */
+    merge(arr, l, m, r) {
+        let temp = [];
+        let i = l, j = m + 1;
+
+        while (i <= m && j <= r) {
+            if (arr[i] <= arr[j]) {
+                temp.push(arr[i++]);
+            } else {
+                temp.push(arr[j++]);
+            }
+        }
+
+        while (i <= m) temp.push(arr[i++]);
+        while (j <= r) temp.push(arr[j++]);
+
+        for (let i = l; i <= r; i++) {
+            arr[i] = temp[i - l];
+        }
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[] SortArray(int[] nums) {
+        MergeSort(nums, 0, nums.Length - 1);
+        return nums;
+    }
+
+    private void MergeSort(int[] arr, int l, int r) {
+        if (l == r) return;
+
+        int m = (l + r) / 2;
+        MergeSort(arr, l, m);
+        MergeSort(arr, m + 1, r);
+        Merge(arr, l, m, r);
+    }
+
+    private void Merge(int[] arr, int L, int M, int R) {
+        int[] left = arr[L..(M + 1)];
+        int[] right = arr[(M + 1)..(R + 1)];
+
+        int i = L, j = 0, k = 0;
+
+        while (j < left.Length && k < right.Length) {
+            if (left[j] <= right[k]) {
+                arr[i++] = left[j++];
+            } else {
+                arr[i++] = right[k++];
+            }
+        }
+
+        while (j < left.Length) {
+            arr[i++] = left[j++];
+        }
+
+        while (k < right.Length) {
+            arr[i++] = right[k++];
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Heap Sort
+
+::tabs-start
+
+```python
+class Solution:
+    def sortArray(self, nums: List[int]) -> List[int]:
+        self.heapSort(nums)
+        return nums
+    
+    def heapify(self, arr, n, i):
+        l = (i << 1) + 1
+        r = (i << 1) + 2
+        largestNode = i
+        
+        if l < n and arr[l] > arr[largestNode]:
+            largestNode = l
+        
+        if r < n and arr[r] > arr[largestNode]:
+            largestNode = r
+        
+        if largestNode != i:
+            arr[i], arr[largestNode] = arr[largestNode], arr[i]
+            self.heapify(arr, n, largestNode)
+    
+    def heapSort(self, arr):
+        n = len(arr)
+        for i in range(n // 2 - 1, -1, -1):
+            self.heapify(arr, n, i)
+        
+        for i in range(n - 1, 0, -1):
+            arr[0], arr[i] = arr[i], arr[0]
+            self.heapify(arr, i, 0)
+```
+
+```java
+public class Solution {
+    public int[] sortArray(int[] nums) {
+        heapSort(nums);
+        return nums;
+    }
+    
+    private void heapify(int[] arr, int n, int i) {
+        int l = (i << 1) + 1;
+        int r = (i << 1) + 2;
+        int largestNode = i;
+        
+        if (l < n && arr[l] > arr[largestNode]) {
+            largestNode = l;
+        }
+        
+        if (r < n && arr[r] > arr[largestNode]) {
+            largestNode = r;
+        }
+        
+        if (largestNode != i) {
+            int temp = arr[i];
+            arr[i] = arr[largestNode];
+            arr[largestNode] = temp;
+            heapify(arr, n, largestNode);
+        }
+    }
+    
+    private void heapSort(int[] arr) {
+        int n = arr.length;
+        for (int i = n / 2 - 1; i >= 0; i--) {
+            heapify(arr, n, i);
+        }
+        
+        for (int i = n - 1; i > 0; i--) {
+            int temp = arr[0];
+            arr[0] = arr[i];
+            arr[i] = temp;
+            heapify(arr, i, 0);
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> sortArray(vector<int>& nums) {
+        heapSort(nums);
+        return nums;
+    }
+private:
+    void heapify(vector<int>& arr, int n, int i) {
+        int l = (i << 1) + 1;
+        int r = (i << 1) + 2;
+        int largestNode = i;
+        
+        if (l < n && arr[l] > arr[largestNode]) {
+            largestNode = l;
+        }
+        
+        if (r < n && arr[r] > arr[largestNode]) {
+            largestNode = r;
+        }
+        
+        if (largestNode != i) {
+            swap(arr[i], arr[largestNode]);
+            heapify(arr, n, largestNode);
+        }
+    }
+    
+    void heapSort(vector<int>& arr) {
+        int n = arr.size();
+        for (int i = n / 2 - 1; i >= 0; i--) {
+            heapify(arr, n, i);
+        }
+        
+        for (int i = n - 1; i > 0; i--) {
+            swap(arr[0], arr[i]);
+            heapify(arr, i, 0);
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+    * @param {number[]} nums
+    * @return {number[]}
+    */
+    sortArray(nums) {
+        this.heapSort(nums);
+        return nums;
+    }
+    
+    /**
+    * @param {number[]} arr
+    * @param {number} n
+    * @param {number} i
+    * @return {void}
+    */
+    heapify(arr, n, i) {
+        let l = (i << 1) + 1;
+        let r = (i << 1) + 2;
+        let largestNode = i;
+        
+        if (l < n && arr[l] > arr[largestNode]) {
+            largestNode = l;
+        }
+        
+        if (r < n && arr[r] > arr[largestNode]) {
+            largestNode = r;
+        }
+        
+        if (largestNode !== i) {
+            [arr[i], arr[largestNode]] = [arr[largestNode], arr[i]];
+            this.heapify(arr, n, largestNode);
+        }
+    }
+    
+    /**
+    * @param {number[]} arr
+    * @return {void}
+    */
+    heapSort(arr) {
+        let n = arr.length;
+        for (let i = Math.floor(n / 2) - 1; i >= 0; i--) {
+            this.heapify(arr, n, i);
+        }
+        
+        for (let i = n - 1; i > 0; i--) {
+            [arr[0], arr[i]] = [arr[i], arr[0]];
+            this.heapify(arr, i, 0);
+        }
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[] SortArray(int[] nums) {
+        HeapSort(nums);
+        return nums;
+    }
+
+    private void Heapify(int[] arr, int n, int i) {
+        int l = (i << 1) + 1;
+        int r = (i << 1) + 2;
+        int largestNode = i;
+
+        if (l < n && arr[l] > arr[largestNode]) {
+            largestNode = l;
+        }
+
+        if (r < n && arr[r] > arr[largestNode]) {
+            largestNode = r;
+        }
+
+        if (largestNode != i) {
+            Swap(arr, i, largestNode);
+            Heapify(arr, n, largestNode);
+        }
+    }
+
+    private void HeapSort(int[] arr) {
+        int n = arr.Length;
+
+        for (int i = n / 2 - 1; i >= 0; i--) {
+            Heapify(arr, n, i);
+        }
+
+        for (int i = n - 1; i > 0; i--) {
+            Swap(arr, 0, i);
+            Heapify(arr, i, 0);
+        }
+    }
+
+    private void Swap(int[] arr, int i, int j) {
+        int temp = arr[i];
+        arr[i] = arr[j];
+        arr[j] = temp;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(\log n)$ for recursive stack.
+
+---
+
+## 4. Counting Sort
+
+::tabs-start
+
+```python
+class Solution:
+    def sortArray(self, nums: List[int]) -> List[int]:
+        def counting_sort():
+            count = defaultdict(int)
+            minVal, maxVal = min(nums), max(nums)
+            for val in nums:
+                count[val] += 1
+
+            index = 0
+            for val in range(minVal, maxVal + 1):
+                while count[val] > 0:
+                    nums[index] = val
+                    index += 1
+                    count[val] -= 1
+
+        counting_sort()
+        return nums
+```
+
+```java
+public class Solution {
+    private void countingSort(int[] arr) {
+        HashMap<Integer,Integer> count = new HashMap<>();
+        int minVal = arr[0], maxVal = arr[0];
+        
+        for (int i = 0; i < arr.length; i++) {
+            minVal = Math.min(minVal, arr[i]);
+            maxVal = Math.max(maxVal, arr[i]);
+            count.put(arr[i], count.getOrDefault(arr[i], 0) + 1);
+        }
+        
+        int index = 0;
+        for (int val = minVal; val <= maxVal; ++val) {
+            while (count.getOrDefault(val, 0) > 0) {
+                arr[index] = val;
+                index += 1;
+                count.put(val, count.get(val) - 1);
+            }
+        }
+    }
+
+    public int[] sortArray(int[] nums) {
+        countingSort(nums);
+        return nums;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    void countingSort(vector<int> &arr) {
+        unordered_map<int, int> count;
+        int minVal = *min_element(arr.begin(), arr.end());
+        int maxVal = *max_element(arr.begin(), arr.end());
+
+        for (auto& val : arr) {
+            count[val]++;
+        }
+        
+        int index = 0;
+        for (int val = minVal; val <= maxVal; ++val) {
+            while (count[val] > 0) {
+                arr[index] = val;
+                index += 1;
+                count[val] -= 1;
+            }
+        }
+    }
+
+public:
+    vector<int> sortArray(vector<int>& nums) {
+        countingSort(nums);
+        return nums;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+    * @param {number[]} nums
+    * @return {number[]}
+    */
+    sortArray(nums) {
+        this.countingSort(nums);
+        return nums;
+    }
+    
+    /**
+    * @param {number[]} arr
+    * @return {void}
+    */
+    countingSort(arr) {
+        let count = new Map();
+        let minVal = Math.min(...nums); 
+        let maxVal = Math.max(...nums); 
+
+        nums.forEach(val => { 
+            if (!count.has(val)) {
+                count.set(val, 0);
+            }
+            count.set(val, count.get(val) + 1); 
+        });
+        
+        let index = 0;
+        for (let val = minVal; val <= maxVal; val += 1) {
+            while (count.get(val) > 0) {
+                nums[index] = val;
+                index += 1;
+                count.set(val, count.get(val) - 1);
+            }
+        }
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[] SortArray(int[] nums) {
+        CountingSort(nums);
+        return nums;
+    }
+
+    private void CountingSort(int[] nums) {
+        Dictionary<int, int> count = new Dictionary<int, int>();
+        int minVal = int.MaxValue, maxVal = int.MinValue;
+
+        foreach (int val in nums) {
+            if (!count.ContainsKey(val)) {
+                count[val] = 0;
+            }
+            count[val]++;
+            minVal = Math.Min(minVal, val);
+            maxVal = Math.Max(maxVal, val);
+        }
+
+        int index = 0;
+        for (int val = minVal; val <= maxVal; val++) {
+            if (!count.ContainsKey(val)) continue;
+            while (count[val]-- > 0) {
+                nums[index++] = val;
+            }
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + k)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the size of the array $nums$ and $k$ is the range between the minimum and maximum values in the array.
+
+---
+
+## 5. Radix Sort
+
+::tabs-start
+
+```python
+class Solution:
+    def sortArray(self, nums: List[int]) -> List[int]:
+        def countSort(arr, n, d):
+            count = [0] * 10
+            for num in arr:
+                count[(num // d) % 10] += 1
+            for i in range(1, 10):
+                count[i] += count[i - 1]
+
+            res = [0] * n
+            for i in range(n - 1, -1, -1):
+                idx = (arr[i] // d) % 10
+                res[count[idx] - 1] = arr[i]
+                count[idx] -= 1
+
+            for i in range(n):
+                arr[i] = res[i]
+
+        def radixSort(arr):
+            n = len(arr)
+            max_element = max(arr)
+            d = 1
+            while max_element // d > 0:
+                countSort(arr, n, d)
+                d *= 10
+
+        negatives = [-num for num in nums if num < 0]
+        positives = [num for num in nums if num >= 0]
+
+        if negatives:
+            radixSort(negatives)
+            negatives = [-num for num in reversed(negatives)]
+
+        if positives:
+            radixSort(positives)
+
+        return negatives + positives
+```
+
+```java
+public class Solution {
+    public int[] sortArray(int[] nums) {
+        ArrayList<Integer> negatives = new ArrayList<>();
+        ArrayList<Integer> positives = new ArrayList<>();
+
+        for (int num : nums) {
+            if (num < 0) {
+                negatives.add(-num);
+            } else {
+                positives.add(num);
+            }
+        }
+
+        if (!negatives.isEmpty()) {
+            radixSort(negatives);
+            Collections.reverse(negatives);
+            for (int i = 0; i < negatives.size(); i++) {
+                negatives.set(i, -negatives.get(i));
+            }
+        }
+
+        if (!positives.isEmpty()) {
+            radixSort(positives);
+        }
+
+        int index = 0;
+        for (int num : negatives) {
+            nums[index++] = num;
+        }
+        for (int num : positives) {
+            nums[index++] = num;
+        }
+        return nums;
+    }
+
+    private void countSort(ArrayList<Integer> arr, int n, int d) {
+        int[] count = new int[10];
+        for (int num : arr) {
+            count[(num / d) % 10]++;
+        }
+        for (int i = 1; i < 10; i++) {
+            count[i] += count[i - 1];
+        }
+
+        ArrayList<Integer> res = new ArrayList<>(Collections.nCopies(n, 0));
+        for (int i = n - 1; i >= 0; i--) {
+            int idx = (arr.get(i) / d) % 10;
+            res.set(count[idx] - 1, arr.get(i));
+            count[idx]--;
+        }
+
+        for (int i = 0; i < n; i++) {
+            arr.set(i, res.get(i));
+        }
+    }
+
+    private void radixSort(ArrayList<Integer> arr) {
+        int n = arr.size();
+        int maxElement = Collections.max(arr);
+        int d = 1;
+
+        while (maxElement / d > 0) {
+            countSort(arr, n, d);
+            d *= 10;
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> sortArray(vector<int>& nums) {
+        vector<int> negatives, positives;
+
+        for (int num : nums) {
+            if (num < 0) {
+                negatives.push_back(-num);
+            } else {
+                positives.push_back(num);
+            }
+        }
+
+        if (!negatives.empty()) {
+            radixSort(negatives);
+            reverse(negatives.begin(), negatives.end());
+            for (int& num : negatives) {
+                num = -num;
+            }
+        }
+
+        if (!positives.empty()) {
+            radixSort(positives);
+        }
+
+        int index = 0;
+        for (int& num : negatives) {
+            nums[index++] = num;
+        }
+        for (int& num : positives) {
+            nums[index++] = num;
+        }
+        return nums;
+    }
+
+private:
+    void countSort(vector<int>& arr, int n, int d) {
+        vector<int> count(10, 0);
+        for (int num : arr) {
+            count[(num / d) % 10]++;
+        }
+        for (int i = 1; i < 10; i++) {
+            count[i] += count[i - 1];
+        }
+
+        vector<int> res(n);
+        for (int i = n - 1; i >= 0; i--) {
+            int idx = (arr[i] / d) % 10;
+            res[count[idx] - 1] = arr[i];
+            count[idx]--;
+        }
+
+        for (int i = 0; i < n; i++) {
+            arr[i] = res[i];
+        }
+    }
+
+    void radixSort(vector<int>& arr) {
+        int n = arr.size();
+        int maxElement = *max_element(arr.begin(), arr.end());
+        int d = 1;
+
+        while (maxElement / d > 0) {
+            countSort(arr, n, d);
+            d *= 10;
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    sortArray(nums) {
+        const negatives = nums.filter(num => num < 0).map(num => -num);
+        const positives = nums.filter(num => num >= 0);
+
+        if (negatives.length > 0) {
+            this.radixSort(negatives);
+            negatives.reverse();
+            for (let i = 0; i < negatives.length; i++) {
+                negatives[i] = -negatives[i];
+            }
+        }
+
+        if (positives.length > 0) {
+            this.radixSort(positives);
+        }
+
+        return [...negatives, ...positives];
+    }
+
+    /**
+     * @param {number[]} arr
+     * @return {void}
+     */
+    radixSort(arr) {
+        const maxElement = Math.max(...arr);
+        let d = 1;
+
+        while (Math.floor(maxElement / d) > 0) {
+            this.countSort(arr, d);
+            d *= 10;
+        }
+    }
+
+    /**
+     * @param {number[]} arr
+     * @param {number} d
+     * @return {void}
+     */
+    countSort(arr, d) {
+        const count = Array(10).fill(0);
+        for (const num of arr) {
+            count[Math.floor(num / d) % 10]++;
+        }
+        for (let i = 1; i < 10; i++) {
+            count[i] += count[i - 1];
+        }
+
+        const res = Array(arr.length);
+        for (let i = arr.length - 1; i >= 0; i--) {
+            const idx = Math.floor(arr[i] / d) % 10;
+            res[count[idx] - 1] = arr[i];
+            count[idx]--;
+        }
+
+        for (let i = 0; i < arr.length; i++) {
+            arr[i] = res[i];
+        }
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[] SortArray(int[] nums) {
+        List<int> negatives = new List<int>();
+        List<int> positives = new List<int>();
+
+        foreach (int num in nums) {
+            if (num < 0) negatives.Add(-num);
+            else positives.Add(num);
+        }
+
+        if (negatives.Count > 0) {
+            RadixSort(negatives);
+            negatives.Reverse();
+            for (int i = 0; i < negatives.Count; i++) {
+                negatives[i] = -negatives[i];
+            }
+        }
+
+        if (positives.Count > 0) {
+            RadixSort(positives);
+        }
+
+        List<int> result = new List<int>();
+        result.AddRange(negatives);
+        result.AddRange(positives);
+
+        return result.ToArray();
+    }
+
+    private void RadixSort(List<int> arr) {
+        int n = arr.Count;
+        int maxElement = 0;
+        foreach (int num in arr) {
+            if (num > maxElement) maxElement = num;
+        }
+
+        int d = 1;
+        while (maxElement / d > 0) {
+            CountSort(arr, n, d);
+            d *= 10;
+        }
+    }
+
+    private void CountSort(List<int> arr, int n, int d) {
+        int[] count = new int[10];
+        for (int i = 0; i < n; i++) {
+            int digit = (arr[i] / d) % 10;
+            count[digit]++;
+        }
+
+        for (int i = 1; i < 10; i++) {
+            count[i] += count[i - 1];
+        }
+
+        int[] res = new int[n];
+        for (int i = n - 1; i >= 0; i--) {
+            int digit = (arr[i] / d) % 10;
+            res[--count[digit]] = arr[i];
+        }
+
+        for (int i = 0; i < n; i++) {
+            arr[i] = res[i];
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(d * n)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the size of the array $nums$ and $d$ is the number of digits in the maximum element of the array.
+
+---
+
+## 6. Shell Sort
+
+::tabs-start
+
+```python
+class Solution:
+    def sortArray(self, nums: List[int]) -> List[int]:
+        def shell_sort(nums, n):
+            gap = n // 2
+            while gap >= 1:
+                for i in range(gap, n):
+                    tmp = nums[i]
+                    j = i - gap
+                    while j >= 0 and nums[j] > tmp:
+                        nums[j + gap] = nums[j]
+                        j -= gap
+                    nums[j + gap] = tmp
+                gap //= 2
+        
+        n = len(nums)
+        if n == 1:
+            return nums
+        shell_sort(nums, n)
+        return nums
+```
+
+```java
+public class Solution {
+    private void shellSort(int[] nums, int n) {
+        int gap = n / 2;
+        while (gap >= 1) {
+            for (int i = gap; i < n; i++) {
+                int tmp = nums[i];
+                int j = i - gap;
+                while (j >= 0 && nums[j] > tmp) {
+                    nums[j + gap] = nums[j];
+                    j -= gap;
+                }
+                nums[j + gap] = tmp;
+            }
+            gap /= 2;
+        }
+    }
+
+    public int[] sortArray(int[] nums) {
+        int n = nums.length;
+        if (n == 1) return nums;
+
+        shellSort(nums, n);
+        return nums;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    void shellSort(vector<int>& nums, int n) {
+        for (int gap = n / 2; gap >= 1; gap /= 2) {
+            for (int i = gap; i < n; i++) {
+                int tmp = nums[i];
+                int j = i - gap;
+                while (j >= 0 && nums[j] > tmp) {
+                    nums[j + gap] = nums[j];
+                    j -= gap;
+                }
+                nums[j + gap] = tmp;
+            }
+        }
+    }
+
+public:
+    vector<int> sortArray(vector<int>& nums) {
+        if (nums.size() == 1) return nums;
+        shellSort(nums, nums.size());
+        return nums;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    sortArray(nums) {
+        const n = nums.length;
+        if (n === 1) return nums;
+
+        const shellSort = () => {
+            let gap = Math.floor(n / 2);
+            while (gap >= 1) {
+                for (let i = gap; i < n; i++) {
+                    let key = nums[i];
+                    let j = i - gap;
+                    while (j >= 0 && nums[j] > key) {
+                        nums[j + gap] = nums[j];
+                        j -= gap;
+                    }
+                    nums[j + gap] = key;
+                }
+                gap = Math.floor(gap / 2);
+            }
+        }
+
+        shellSort();
+        return nums;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int[] SortArray(int[] nums) {
+        int n = nums.Length;
+        if (n == 1) return nums;
+
+        ShellSort(nums, n);
+        return nums;
+    }
+
+    private void ShellSort(int[] nums, int n) {
+        int gap = n / 2;
+        while (gap >= 1) {
+            for (int i = gap; i < n; i++) {
+                int tmp = nums[i];
+                int j = i - gap;
+                while (j >= 0 && nums[j] > tmp) {
+                    nums[j + gap] = nums[j];
+                    j -= gap;
+                }
+                nums[j + gap] = tmp;
+            }
+            gap /= 2;
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$ in average case, $O(n ^ 2)$ in worst case.
+* Space complexity: $O(1)$
diff --git a/articles/sort-array-by-increasing-frequency.md b/articles/sort-array-by-increasing-frequency.md
new file mode 100644
index 000000000..04a4e1c80
--- /dev/null
+++ b/articles/sort-array-by-increasing-frequency.md
@@ -0,0 +1,79 @@
+## 1. Custom Sort
+
+::tabs-start
+
+```python
+class Solution:
+    def frequencySort(self, nums: List[int]) -> List[int]:
+        count = Counter(nums)
+        nums.sort(key=lambda n: (count[n], -n))
+        return nums
+```
+
+```java
+public class Solution {
+    public int[] frequencySort(int[] nums) {
+        Map<Integer, Integer> count = new HashMap<>();
+        for (int num : nums) {
+            count.put(num, count.getOrDefault(num, 0) + 1);
+        }
+
+        Integer[] arr = Arrays.stream(nums).boxed().toArray(Integer[]::new);
+        Arrays.sort(arr, (a, b) -> {
+            int freqA = count.get(a), freqB = count.get(b);
+            if (freqA != freqB) return Integer.compare(freqA, freqB);
+            return Integer.compare(b, a);
+        });
+
+        return Arrays.stream(arr).mapToInt(i -> i).toArray();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> frequencySort(vector<int>& nums) {
+        unordered_map<int, int> count;
+        for (int num : nums) {
+            count[num]++;
+        }
+
+        sort(nums.begin(), nums.end(), [&](int a, int b) {
+            if (count[a] != count[b]) return count[a] < count[b];
+            return a > b;
+        });
+
+        return nums;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    frequencySort(nums) {
+        const count = {};
+        for (let num of nums) {
+            count[num] = (count[num] || 0) + 1;
+        }
+
+        nums.sort((a, b) => {
+            if (count[a] !== count[b]) return count[a] - count[b];
+            return b - a;
+        });
+
+        return nums;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/sort-array-by-parity.md b/articles/sort-array-by-parity.md
new file mode 100644
index 000000000..b282d0cea
--- /dev/null
+++ b/articles/sort-array-by-parity.md
@@ -0,0 +1,325 @@
+## 1. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def sortArrayByParity(self, nums: List[int]) -> List[int]:
+        nums.sort(key = lambda x: x & 1)
+        return nums
+```
+
+```java
+public class Solution {
+    public int[] sortArrayByParity(int[] nums) {
+        Integer[] A = Arrays.stream(nums).boxed().toArray(Integer[]::new);
+        Arrays.sort(A, (a, b) -> (a & 1) - (b & 1));
+        return Arrays.stream(A).mapToInt(Integer::intValue).toArray();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> sortArrayByParity(vector<int>& nums) {
+        sort(nums.begin(), nums.end(), [&](int& a, int& b) { 
+            return (a & 1) < (b & 1); 
+        });
+        return nums;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    sortArrayByParity(nums) {
+        return nums.sort((a, b) => (a & 1) - (b & 1));
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 2. Array
+
+::tabs-start
+
+```python
+class Solution:
+    def sortArrayByParity(self, nums: List[int]) -> List[int]:
+        even, odd = [], []
+        for num in nums:
+            if num & 1:
+                odd.append(num)
+            else:
+                even.append(num)
+        
+        idx = 0
+        for e in even:
+            nums[idx] = e
+            idx += 1
+        for o in odd:
+            nums[idx] = o
+            idx += 1
+        return nums
+```
+
+```java
+public class Solution {
+    public int[] sortArrayByParity(int[] nums) {
+        List<Integer> even = new ArrayList<>();
+        List<Integer> odd = new ArrayList<>();
+        
+        for (int num : nums) {
+            if ((num & 1) == 1) {
+                odd.add(num);
+            } else {
+                even.add(num);
+            }
+        }
+        
+        int idx = 0;
+        for (int e : even) {
+            nums[idx++] = e;
+        }
+        for (int o : odd) {
+            nums[idx++] = o;
+        }
+        
+        return nums;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> sortArrayByParity(vector<int>& nums) {
+        vector<int> even, odd;
+        
+        for (int& num : nums) {
+            if (num & 1) {
+                odd.push_back(num);
+            } else {
+                even.push_back(num);
+            }
+        }
+        
+        int idx = 0;
+        for (int& e : even) {
+            nums[idx++] = e;
+        }
+        for (int& o : odd) {
+            nums[idx++] = o;
+        }
+        
+        return nums;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    sortArrayByParity(nums) {
+        const even = [];
+        const odd = [];
+        
+        for (let num of nums) {
+            if (num % 2) {
+                odd.push(num);
+            } else {
+                even.push(num);
+            }
+        }
+        
+        let idx = 0;
+        for (let e of even) {
+            nums[idx++] = e;
+        }
+        for (let o of odd) {
+            nums[idx++] = o;
+        }
+        
+        return nums;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Two Pointers - I
+
+::tabs-start
+
+```python
+class Solution:
+    def sortArrayByParity(self, nums: List[int]) -> List[int]:
+        i, j = 0, len(nums) - 1
+        while i < j:
+            if nums[i] & 1:
+                nums[i], nums[j] = nums[j], nums[i]
+                j -= 1
+            else:
+                i += 1
+        return nums
+```
+
+```java
+public class Solution {
+    public int[] sortArrayByParity(int[] nums) {
+        int i = 0, j = nums.length - 1;
+        while (i < j) {
+            if ((nums[i] & 1) == 1) {
+                int temp = nums[i];
+                nums[i] = nums[j];
+                nums[j--] = temp;
+            } else {
+                i++;
+            }
+        }
+        return nums;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> sortArrayByParity(vector<int>& nums) {
+        int i = 0, j = nums.size() - 1;
+        while (i < j) {
+            if ((nums[i] & 1) == 1) {
+                swap(nums[i], nums[j]);
+                j--;
+            } else {
+                i++;
+            }
+        }
+        return nums;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    sortArrayByParity(nums) {
+        let i = 0, j = nums.length - 1;
+        while (i < j) {
+            if ((nums[i] & 1) == 1) {
+                [nums[i], nums[j]] = [nums[j], nums[i]];
+                j--;
+            } else {
+                i++;
+            }
+        }
+        return nums;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 4. Two Pointers - II
+
+::tabs-start
+
+```python
+class Solution:
+    def sortArrayByParity(self, nums: List[int]) -> List[int]:
+        l = 0
+        for r in range(len(nums)):
+            if nums[r] % 2 == 0:
+                nums[l], nums[r] = nums[r], nums[l]
+                l += 1
+        return nums
+```
+
+```java
+public class Solution {
+    public int[] sortArrayByParity(int[] nums) {
+        for (int l = 0, r = 0; r < nums.length; r++) {
+            if (nums[r] % 2 == 0) {
+                int temp = nums[l];
+                nums[l] = nums[r];
+                nums[r] = temp;
+                l++;
+            }
+        }
+        return nums;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> sortArrayByParity(vector<int>& nums) {
+        for (int l = 0, r = 0; r < nums.size(); r++) {
+            if (nums[r] % 2 == 0) {
+                swap(nums[l], nums[r]);
+                l++;
+            }
+        }
+        return nums;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    sortArrayByParity(nums) {
+        for (let l = 0, r = 0; r < nums.length; r++) {
+            if (nums[r] % 2 == 0) {
+                [nums[l], nums[r]] = [nums[r], nums[l]];
+                l++;
+            }
+        }
+        return nums;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/sort-characters-by-frequency.md b/articles/sort-characters-by-frequency.md
new file mode 100644
index 000000000..779312faf
--- /dev/null
+++ b/articles/sort-characters-by-frequency.md
@@ -0,0 +1,340 @@
+## 1. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def frequencySort(self, s: str) -> str:
+        count = Counter(s)
+        sorted_chars = sorted(s, key=lambda x: (-count[x], x))
+        return ''.join(sorted_chars)
+```
+
+```java
+public class Solution {
+    public String frequencySort(String s) {
+        int[] count = new int[123];
+        for (char c : s.toCharArray()) {
+            count[c]++;
+        }
+
+        Character[] chars = new Character[s.length()];
+        for (int i = 0; i < s.length(); i++) {
+            chars[i] = s.charAt(i);
+        }
+
+        Arrays.sort(chars, (a, b) -> {
+            if (count[b] == count[a]) {
+                return a - b;
+            }
+            return count[b] - count[a];
+        });
+
+        StringBuilder result = new StringBuilder();
+        for (char c : chars) {
+            result.append(c);
+        }
+
+        return result.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string frequencySort(string s) {
+        vector<int> count(123);
+        for (char c : s) {
+            count[c]++;
+        }
+
+        vector<char> chars(s.begin(), s.end());
+        sort(chars.begin(), chars.end(), [&](char a, char b) {
+            if (count[b] == count[a]) {
+                return a < b;
+            }
+            return count[b] < count[a];
+        });
+
+        return string(chars.begin(), chars.end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string}
+     */
+    frequencySort(s) {
+        const count = {};
+        for (const char of s) {
+            count[char] = (count[char] || 0) + 1;
+        }
+
+        const sortedChars = [...s].sort((a, b) => {
+            if (count[b] === count[a]) {
+                return a.localeCompare(b);
+            }
+            return count[b] - count[a];
+        });
+
+        return sortedChars.join('');
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 2. Frequency Sort
+
+::tabs-start
+
+```python
+class Solution:
+    def frequencySort(self, s: str) -> str:
+        count = [0] * 123
+        for c in s:
+            count[ord(c)] += 1
+
+        freq = [(chr(i), count[i]) for i in range(123) if count[i] > 0]        
+        freq.sort(key=lambda x: (-x[1], x[0]))
+
+        return ''.join(char * freq for char, freq in freq)
+```
+
+```java
+public class Solution {
+    public String frequencySort(String s) {
+        int[] count = new int[123];
+        for (char c : s.toCharArray()) {
+            count[c]++;
+        }
+
+        List<int[]> freq = new ArrayList<>();
+        for (int i = 0; i < 123; i++) {
+            if (count[i] > 0) {
+                freq.add(new int[]{i, count[i]});
+            }
+        }
+
+        freq.sort((a, b) -> {
+            if (b[1] == a[1]) {
+                return a[0] - b[0];
+            }
+            return b[1] - a[1];
+        });
+
+        StringBuilder res = new StringBuilder();
+        for (int[] entry : freq) {
+            for (int i = 0; i < entry[1]; i++) {
+                res.append((char) entry[0]);
+            }
+        }
+
+        return res.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string frequencySort(string s) {
+        vector<int> count(123, 0);
+        for (char c : s) {
+            count[c]++;
+        }
+
+        vector<pair<char, int>> freq;
+        for (int i = 0; i < 123; i++) {
+            if (count[i] > 0) {
+                freq.emplace_back((char)i, count[i]);
+            }
+        }
+
+        sort(freq.begin(), freq.end(), [](auto& a, auto& b) {
+            if (a.second == b.second) {
+                return a.first < b.first;
+            }
+            return a.second > b.second;
+        });
+
+        string res;
+        for (const auto& entry : freq) {
+            res += string(entry.second, entry.first);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string}
+     */
+    frequencySort(s) {
+        const count = new Array(123).fill(0);
+        for (const char of s) {
+            count[char.charCodeAt(0)]++;
+        }
+
+        const freq = [];
+        for (let i = 0; i < 123; i++) {
+            if (count[i] > 0) {
+                freq.push([String.fromCharCode(i), count[i]]);
+            }
+        }
+
+        freq.sort((a, b) => {
+            if (b[1] === a[1]) {
+                return a[0].localeCompare(b[0]);
+            }
+            return b[1] - a[1];
+        });
+
+        let res = '';
+        for (const [char, freqCount] of freq) {
+            res += char.repeat(freqCount);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for the output string.
+
+---
+
+## 3. Bucket Sort
+
+::tabs-start
+
+```python
+class Solution:
+    def frequencySort(self, s: str) -> str:
+        count = Counter(s)  # char -> freq
+        buckets = defaultdict(list)  # freq -> [char]
+
+        for char, freq in count.items():
+            buckets[freq].append(char)
+
+        res = []
+        for i in range(len(s), 0, -1):
+            if i in buckets:
+                for c in buckets[i]:
+                    res.append(c * i)
+                    
+        return "".join(res)
+```
+
+```java
+public class Solution {
+    public String frequencySort(String s) {
+        Map<Character, Integer> count = new HashMap<>();
+        for (char c : s.toCharArray()) {
+            count.put(c, count.getOrDefault(c, 0) + 1);
+        }
+
+        List<List<Character>> buckets = new ArrayList<>(s.length() + 1);
+        for (int i = 0; i <= s.length(); i++) {
+            buckets.add(new ArrayList<>());
+        }
+
+        for (Map.Entry<Character, Integer> entry : count.entrySet()) {
+            buckets.get(entry.getValue()).add(entry.getKey());
+        }
+
+        StringBuilder res = new StringBuilder();
+        for (int i = s.length(); i > 0; i--) {
+            for (char c : buckets.get(i)) {
+                for (int j = 0; j < i; j++) {
+                    res.append(c);
+                }
+            }
+        }
+
+        return res.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string frequencySort(string s) {
+        unordered_map<char, int> count;
+        for (char c : s) {
+            count[c]++;
+        }
+
+        vector<vector<char>> buckets(s.size() + 1);
+        for (auto& entry : count) {
+            buckets[entry.second].push_back(entry.first);
+        }
+
+        string res;
+        for (int i = s.size(); i > 0; i--) {
+            for (char c : buckets[i]) {
+                res += string(i, c);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {string}
+     */
+    frequencySort(s) {
+        const count = {};
+        for (const char of s) {
+            count[char] = (count[char] || 0) + 1;
+        }
+
+        const buckets = Array.from({ length: s.length + 1 }, () => []);
+        for (const [char, freq] of Object.entries(count)) {
+            buckets[freq].push(char);
+        }
+
+        let res = '';
+        for (let i = s.length; i > 0; i--) {
+            for (const char of buckets[i]) {
+                res += char.repeat(i);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/sort-colors.md b/articles/sort-colors.md
new file mode 100644
index 000000000..46bc4a86a
--- /dev/null
+++ b/articles/sort-colors.md
@@ -0,0 +1,530 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def sortColors(self, nums: List[int]) -> None:
+        """
+        Do not return anything, modify nums in-place instead.
+        """
+        nums.sort()
+```
+
+```java
+public class Solution {
+    public void sortColors(int[] nums) {
+        Arrays.sort(nums);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void sortColors(vector<int>& nums) {
+        sort(nums.begin(), nums.end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {void} Do not return anything, modify nums in-place instead.
+     */
+    sortColors(nums) {
+        nums.sort((a, b) => a - b);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public void SortColors(int[] nums) {
+        Array.Sort(nums);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 2. Counting Sort
+
+::tabs-start
+
+```python
+class Solution:
+    def sortColors(self, nums: List[int]) -> None:
+        """
+        Do not return anything, modify nums in-place instead.
+        """
+        count = [0] * 3
+        for num in nums:
+            count[num] += 1
+        
+        index = 0
+        for i in range(3):
+            while count[i]:
+                count[i] -= 1
+                nums[index] = i
+                index += 1
+```
+
+```java
+public class Solution {
+    public void sortColors(int[] nums) {
+        int[] count = new int[3];
+        for (int num : nums) {
+            count[num]++;
+        }
+
+        int index = 0;
+        for (int i = 0; i < 3; i++) {
+            while (count[i]-- > 0) {
+                nums[index++] = i;
+            }
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void sortColors(vector<int>& nums) {
+        vector<int> count(3);
+        for (int& num : nums) {
+            count[num]++;
+        }
+
+        int index = 0;
+        for (int i = 0; i < 3; i++) {
+            while (count[i]-- > 0) {
+                nums[index++] = i;
+            }
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {void} Do not return anything, modify nums in-place instead.
+     */
+    sortColors(nums) {
+        const count = new Int32Array(3);
+        for (let num of nums) {
+            count[num]++;
+        }
+
+        let index = 0;
+        for (let i = 0; i < 3; i++) {
+            while (count[i]-- > 0) {
+                nums[index++] = i;
+            }
+        }
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public void SortColors(int[] nums) {
+        int[] count = new int[3];
+        foreach (int num in nums) {
+            count[num]++;
+        }
+
+        int index = 0;
+        for (int i = 0; i < 3; i++) {
+            while (count[i]-- > 0) {
+                nums[index++] = i;
+            }
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Three Pointers - I
+
+::tabs-start
+
+```python
+class Solution:
+    def sortColors(self, nums: List[int]) -> None:
+        """
+        Do not return anything, modify nums in-place instead.
+        """
+        l, r = 0, len(nums) - 1
+        i = 0
+
+        def swap(i, j):
+            temp = nums[i]
+            nums[i] = nums[j]
+            nums[j] = temp
+        
+        while i <= r:
+            if nums[i] == 0:
+                swap(l, i)
+                l += 1
+            elif nums[i] == 2:
+                swap(i, r)
+                r -= 1
+                i -= 1
+            i += 1
+```
+
+```java
+public class Solution {
+    public void sortColors(int[] nums) {
+        int i = 0, l = 0, r = nums.length - 1;
+        while (i <= r) {
+            if (nums[i] == 0) {
+                swap(nums, l, i);
+                l++;
+            } else if (nums[i] == 2) {
+                swap(nums, i, r);
+                r--;
+                i--;
+            }
+            i++;
+        }
+    }
+
+    private void swap(int[] nums, int i, int j) {
+        int temp = nums[i];
+        nums[i] = nums[j];
+        nums[j] = temp;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void sortColors(vector<int>& nums) {
+        int i = 0, l = 0, r = nums.size() - 1;
+        while (i <= r) {
+            if (nums[i] == 0) {
+                swap(nums[l], nums[i]);
+                l++;
+            } else if (nums[i] == 2) {
+                swap(nums[i], nums[r]);
+                r--;
+                i--;
+            }
+            i++;
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {void} Do not return anything, modify nums in-place instead.
+     */
+    sortColors(nums) {
+        let i = 0, l = 0, r = nums.length - 1;
+        while (i <= r) {
+            if (nums[i] == 0) {
+                [nums[l], nums[i]] = [nums[i], nums[l]];
+                l++;
+            } else if (nums[i] == 2) {
+                [nums[i], nums[r]] = [nums[r], nums[i]];
+                r--;
+                i--;
+            }
+            i++;
+        }
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public void SortColors(int[] nums) {
+        int i = 0, l = 0, r = nums.Length - 1;
+
+        while (i <= r) {
+            if (nums[i] == 0) {
+                Swap(nums, l, i);
+                l++;
+            } else if (nums[i] == 2) {
+                Swap(nums, i, r);
+                r--;
+                i--;
+            }
+            i++;
+        }
+    }
+
+    private void Swap(int[] nums, int i, int j) {
+        int temp = nums[i];
+        nums[i] = nums[j];
+        nums[j] = temp;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 4. Three Pointers - II
+
+::tabs-start
+
+```python
+class Solution:
+    def sortColors(self, nums: List[int]) -> None:
+        """
+        Do not return anything, modify nums in-place instead.
+        """
+        zero = one = two = 0
+        for i in range(len(nums)):
+            if nums[i] == 0:
+                nums[two] = 2
+                nums[one] = 1
+                nums[zero] = 0
+                two += 1
+                one += 1
+                zero += 1
+            elif nums[i] == 1:
+                nums[two] = 2
+                nums[one] = 1
+                two += 1
+                one += 1
+            else:
+                nums[two] = 2
+                two += 1
+```
+
+```java
+public class Solution {
+    public void sortColors(int[] nums) {
+        int zero = 0, one = 0, two = 0;
+        for (int i = 0; i < nums.length; i++) {
+            if (nums[i] == 0) {
+                nums[two++] = 2;
+                nums[one++] = 1;
+                nums[zero++] = 0;
+            } else if (nums[i] == 1) {
+                nums[two++] = 2;
+                nums[one++] = 1;
+            } else {
+                nums[two++] = 2;
+            }
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void sortColors(vector<int>& nums) {
+        int zero = 0, one = 0, two = 0;
+        for (int i = 0; i < nums.size(); i++) {
+            if (nums[i] == 0) {
+                nums[two++] = 2;
+                nums[one++] = 1;
+                nums[zero++] = 0;
+            } else if (nums[i] == 1) {
+                nums[two++] = 2;
+                nums[one++] = 1;
+            } else {
+                nums[two++] = 2;
+            }
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {void} Do not return anything, modify nums in-place instead.
+     */
+    sortColors(nums) {
+        let zero = 0, one = 0, two = 0;
+        for (let i = 0; i < nums.length; i++) {
+            if (nums[i] == 0) {
+                nums[two++] = 2;
+                nums[one++] = 1;
+                nums[zero++] = 0;
+            } else if (nums[i] == 1) {
+                nums[two++] = 2;
+                nums[one++] = 1;
+            } else {
+                nums[two++] = 2;
+            }
+        }
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public void SortColors(int[] nums) {
+        int zero = 0, one = 0, two = 0;
+
+        for (int i = 0; i < nums.Length; i++) {
+            if (nums[i] == 0) {
+                nums[two++] = 2;
+                nums[one++] = 1;
+                nums[zero++] = 0;
+            } else if (nums[i] == 1) {
+                nums[two++] = 2;
+                nums[one++] = 1;
+            } else {
+                nums[two++] = 2;
+            }
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 5. Three Pointers - III
+
+::tabs-start
+
+```python
+class Solution:
+    def sortColors(self, nums: List[int]) -> None:
+        """
+        Do not return anything, modify nums in-place instead.
+        """
+        zero = one = 0
+        for two in range(len(nums)):
+            tmp = nums[two]
+            nums[two] = 2
+            if tmp < 2:
+                nums[one] = 1
+                one += 1
+            if tmp < 1:
+                nums[zero] = 0
+                zero += 1
+```
+
+```java
+public class Solution {
+    public void sortColors(int[] nums) {
+        int zero = 0, one = 0;
+        for (int two = 0; two < nums.length; two++) {
+            int tmp = nums[two];
+            nums[two] = 2;
+            if (tmp < 2) {
+                nums[one++] = 1;
+            }
+            if (tmp < 1) {
+                nums[zero++] = 0;
+            }
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void sortColors(vector<int>& nums) {
+        int zero = 0, one = 0;
+        for (int two = 0; two < nums.size(); two++) {
+            int tmp = nums[two];
+            nums[two] = 2;
+            if (tmp < 2) {
+                nums[one++] = 1;
+            }
+            if (tmp < 1) {
+                nums[zero++] = 0;
+            }
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {void} Do not return anything, modify nums in-place instead.
+     */
+    sortColors(nums) {
+        let zero = 0, one = 0;
+        for (let two = 0; two < nums.length; two++) {
+            let tmp = nums[two];
+            nums[two] = 2;
+            if (tmp < 2) {
+                nums[one++] = 1;
+            }
+            if (tmp < 1) {
+                nums[zero++] = 0;
+            }
+        }
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public void SortColors(int[] nums) {
+        int zero = 0, one = 0;
+
+        for (int two = 0; two < nums.Length; two++) {
+            int tmp = nums[two];
+            nums[two] = 2;
+
+            if (tmp < 2) {
+                nums[one++] = 1;
+            }
+            if (tmp < 1) {
+                nums[zero++] = 0;
+            }
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/sort-items-by-groups-respecting-dependencies.md b/articles/sort-items-by-groups-respecting-dependencies.md
new file mode 100644
index 000000000..69ce62c62
--- /dev/null
+++ b/articles/sort-items-by-groups-respecting-dependencies.md
@@ -0,0 +1,562 @@
+## 1. Topological Sort (DFS)
+
+::tabs-start
+
+```python
+class Solution:
+    def sortItems(self, n, m, group, beforeItems):
+        for i in range(n):
+            if group[i] == -1:
+                group[i] = m
+                m += 1
+
+        item_adj = defaultdict(list)
+        group_adj = defaultdict(list)
+        for i in range(n):
+            for par in beforeItems[i]:
+                item_adj[par].append(i)
+                if group[i] != group[par]:
+                    group_adj[group[par]].append(group[i])
+
+        itm = self.topo_sort(item_adj, n)
+        if not itm: return []
+        grp = self.topo_sort(group_adj, m)
+        if not grp: return []
+
+        grouping = defaultdict(list)
+        for i in itm:
+            grouping[group[i]].append(i)
+
+        res = []
+        for g in grp:
+            res.extend(grouping[g])
+
+        return res
+
+    def topo_sort(self, adj, N):
+        visited = [0] * N
+        topo = []
+
+        def dfs(node):
+            if visited[node] == 1:
+                return True
+            if visited[node] == 2:
+                return False
+            visited[node] = 1
+            for neighbor in adj[node]:
+                if dfs(neighbor):
+                    return True
+            topo.append(node)
+            visited[node] = 2
+            return False
+
+        for i in range(N):
+            if visited[i] == 0:
+                if dfs(i):
+                    return []
+
+        return topo[::-1]
+```
+
+```java
+public class Solution {
+    public int[] sortItems(int n, int m, int[] group, List<List<Integer>> beforeItems) {
+        for (int i = 0; i < n; i++) {
+            if (group[i] == -1) {
+                group[i] = m++;
+            }
+        }
+
+        List<Integer>[] itemAdj = new ArrayList[n];
+        List<Integer>[] groupAdj = new ArrayList[m];
+        for (int i = 0; i < n; i++) {
+            itemAdj[i] = new ArrayList<>();
+        }
+        for (int i = 0; i < m; i++) {
+            groupAdj[i] = new ArrayList<>();
+        }
+
+        for (int i = 0; i < n; i++) {
+            for (int parent : beforeItems.get(i)) {
+                itemAdj[parent].add(i);
+                if (group[i] != group[parent]) {
+                    groupAdj[group[parent]].add(group[i]);
+                }
+            }
+        }
+
+        List<Integer> itm = topoSort(itemAdj, n);
+        if (itm.isEmpty()) return new int[]{};
+        List<Integer> grp = topoSort(groupAdj, m);
+        if (grp.isEmpty()) return new int[]{};
+
+        List<Integer>[] grouping = new ArrayList[m];
+        for (int i = 0; i < m; i++) {
+            grouping[i] = new ArrayList<>();
+        }
+        for (int i : itm) {
+            grouping[group[i]].add(i);
+        }
+
+        List<Integer> res = new ArrayList<>();
+        for (int g : grp) {
+            res.addAll(grouping[g]);
+        }
+
+        return res.stream().mapToInt(Integer::intValue).toArray();
+    }
+
+    private List<Integer> topoSort(List<Integer>[] adj, int N) {
+        int[] visited = new int[N];
+        List<Integer> topo = new ArrayList<>();
+
+        for (int i = 0; i < N; i++) {
+            if (visited[i] == 0) {
+                if (dfs(i, adj, visited, topo)) {
+                    return new ArrayList<>();
+                }
+            }
+        }
+
+        Collections.reverse(topo);
+        return topo;
+    }
+
+    private boolean dfs(int node, List<Integer>[] adj, int[] visited, List<Integer> topo) {
+        if (visited[node] == 1) return true;
+        if (visited[node] == 2) return false;
+        visited[node] = 1;
+        for (int neighbor : adj[node]) {
+            if (dfs(neighbor, adj, visited, topo)) {
+                return true;
+            }
+        }
+        topo.add(node);
+        visited[node] = 2;
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> sortItems(int n, int m, vector<int>& group, vector<vector<int>>& beforeItems) {
+        for (int i = 0; i < n; ++i) {
+            if (group[i] == -1) {
+                group[i] = m++;
+            }
+        }
+
+        vector<vector<int>> itemAdj(n), groupAdj(m);
+        for (int i = 0; i < n; ++i) {
+            for (int parent : beforeItems[i]) {
+                itemAdj[parent].push_back(i);
+                if (group[i] != group[parent]) {
+                    groupAdj[group[parent]].push_back(group[i]);
+                }
+            }
+        }
+
+        vector<int> itm = topoSort(itemAdj, n);
+        if (itm.empty()) return {};
+        vector<int> grp = topoSort(groupAdj, m);
+        if (grp.empty()) return {};
+
+        unordered_map<int, vector<int>> grouping;
+        for (int i : itm) {
+            grouping[group[i]].push_back(i);
+        }
+
+        vector<int> res;
+        for (int& g : grp) {
+            res.insert(res.end(), grouping[g].begin(), grouping[g].end());
+        }
+
+        return res;
+    }
+
+private:
+    vector<int> topoSort(const vector<vector<int>>& adj, int N) {
+        vector<int> visited(N, 0), topo;
+        function<bool(int)> dfs = [&](int node) {
+            if (visited[node] == 1) return true;
+            if (visited[node] == 2) return false;
+            visited[node] = 1;
+            for (int neighbor : adj[node]) {
+                if (dfs(neighbor)) return true;
+            }
+            topo.push_back(node);
+            visited[node] = 2;
+            return false;
+        };
+
+        for (int i = 0; i < N; ++i) {
+            if (visited[i] == 0 && dfs(i)) {
+                return {};
+            }
+        }
+
+        reverse(topo.begin(), topo.end());
+        return topo;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} m
+     * @param {number[]} group
+     * @param {number[][]} beforeItems
+     * @return {number[]}
+     */
+    sortItems(n, m, group, beforeItems) {
+        for (let i = 0; i < n; i++) {
+            if (group[i] === -1) {
+                group[i] = m++;
+            }
+        }
+
+        const itemAdj = Array.from({ length: n }, () => []);
+        const groupAdj = Array.from({ length: m }, () => []);
+        for (let i = 0; i < n; i++) {
+            for (const parent of beforeItems[i]) {
+                itemAdj[parent].push(i);
+                if (group[i] !== group[parent]) {
+                    groupAdj[group[parent]].push(group[i]);
+                }
+            }
+        }
+
+        const itm = this.topoSort(itemAdj, n);
+        if (!itm.length) return [];
+        const grp = this.topoSort(groupAdj, m);
+        if (!grp.length) return [];
+
+        const grouping = {};
+        for (const i of itm) {
+            if (!grouping[group[i]]) grouping[group[i]] = [];
+            grouping[group[i]].push(i);
+        }
+
+        const res = [];
+        for (const g of grp) {
+            if (grouping[g]) res.push(...grouping[g]);
+        }
+
+        return res;
+    }
+
+    /**
+     * @param {number[][]} adj
+     * @param {number} N
+     * @return {number[]}
+     */
+    topoSort(adj, N) {
+        const visited = new Array(N).fill(0);
+        const topo = [];
+
+        const dfs = (node) => {
+            if (visited[node] === 1) return true;
+            if (visited[node] === 2) return false;
+            visited[node] = 1;
+            for (const neighbor of adj[node]) {
+                if (dfs(neighbor)) return true;
+            }
+            topo.push(node);
+            visited[node] = 2;
+            return false;
+        };
+
+        for (let i = 0; i < N; i++) {
+            if (visited[i] === 0 && dfs(i)) {
+                return [];
+            }
+        }
+
+        return topo.reverse();
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + E)$
+* Space complexity: $O(V + E)$
+
+> Where $V$ is the number of items and $E$ is the total number of $beforeItems$ dependencies.
+
+---
+
+## 2. Topological Sort (Kahn's Algorithm)
+
+::tabs-start
+
+```python
+class Solution:
+    def sortItems(self, n, m, group, beforeItems):
+        for i in range(n):
+            if group[i] == -1:
+                group[i] = m
+                m += 1
+
+        item_adj = defaultdict(list)
+        group_adj = defaultdict(list)
+        item_indegree = [0] * n
+        group_indegree = [0] * m
+
+        for i in range(n):
+            for par in beforeItems[i]:
+                item_adj[par].append(i)
+                item_indegree[i] += 1
+                if group[i] != group[par]:
+                    group_adj[group[par]].append(group[i])
+                    group_indegree[group[i]] += 1
+
+        itm = self.topo_sort(item_adj, item_indegree, n)
+        if not itm: return []
+        grp = self.topo_sort(group_adj, group_indegree, m)
+        if not grp: return []
+
+        grouping = defaultdict(list)
+        for i in itm:
+            grouping[group[i]].append(i)
+
+        res = []
+        for g in grp:
+            res.extend(grouping[g])
+
+        return res
+
+    def topo_sort(self, adj, indegree, N):
+        topo = []
+        q = deque([i for i in range(N) if indegree[i] == 0])
+
+        while q:
+            node = q.popleft()
+            topo.append(node)
+            for neighbor in adj[node]:
+                indegree[neighbor] -= 1
+                if indegree[neighbor] == 0:
+                    q.append(neighbor)
+
+        return topo if len(topo) == N else []
+```
+
+```java
+public class Solution {
+    public int[] sortItems(int n, int m, int[] group, List<List<Integer>> beforeItems) {
+        for (int i = 0; i < n; i++) {
+            if (group[i] == -1) {
+                group[i] = m++;
+            }
+        }
+
+        List<List<Integer>> itemAdj = new ArrayList<>();
+        List<List<Integer>> groupAdj = new ArrayList<>();
+        for (int i = 0; i < n; i++) itemAdj.add(new ArrayList<>());
+        for (int i = 0; i < m; i++) groupAdj.add(new ArrayList<>());
+
+        int[] itemIndegree = new int[n];
+        int[] groupIndegree = new int[m];
+
+        for (int i = 0; i < n; i++) {
+            for (int par : beforeItems.get(i)) {
+                itemAdj.get(par).add(i);
+                itemIndegree[i]++;
+                if (group[i] != group[par]) {
+                    groupAdj.get(group[par]).add(group[i]);
+                    groupIndegree[group[i]]++;
+                }
+            }
+        }
+
+        List<Integer> itm = topoSort(itemAdj, itemIndegree, n);
+        if (itm.isEmpty()) return new int[0];
+        List<Integer> grp = topoSort(groupAdj, groupIndegree, m);
+        if (grp.isEmpty()) return new int[0];
+
+        Map<Integer, List<Integer>> grouping = new HashMap<>();
+        for (int i : itm) {
+            grouping.computeIfAbsent(group[i], x -> new ArrayList<>()).add(i);
+        }
+
+        List<Integer> res = new ArrayList<>();
+        for (int g : grp) {
+            res.addAll(grouping.getOrDefault(g, new ArrayList<>()));
+        }
+
+        return res.stream().mapToInt(Integer::intValue).toArray();
+    }
+
+    private List<Integer> topoSort(List<List<Integer>> adj, int[] indegree, int N) {
+        Queue<Integer> q = new LinkedList<>();
+        List<Integer> topo = new ArrayList<>();
+        for (int i = 0; i < N; i++) {
+            if (indegree[i] == 0) q.add(i);
+        }
+
+        while (!q.isEmpty()) {
+            int node = q.poll();
+            topo.add(node);
+            for (int neighbor : adj.get(node)) {
+                indegree[neighbor]--;
+                if (indegree[neighbor] == 0) q.add(neighbor);
+            }
+        }
+
+        return topo.size() == N ? topo : new ArrayList<>();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> sortItems(int n, int m, vector<int>& group, vector<vector<int>>& beforeItems) {
+        for (int i = 0; i < n; i++) {
+            if (group[i] == -1) group[i] = m++;
+        }
+
+        vector<vector<int>> itemAdj(n), groupAdj(m);
+        vector<int> itemIndegree(n, 0), groupIndegree(m, 0);
+
+        for (int i = 0; i < n; i++) {
+            for (int& par : beforeItems[i]) {
+                itemAdj[par].push_back(i);
+                itemIndegree[i]++;
+                if (group[i] != group[par]) {
+                    groupAdj[group[par]].push_back(group[i]);
+                    groupIndegree[group[i]]++;
+                }
+            }
+        }
+
+        vector<int> itm = topoSort(itemAdj, itemIndegree, n);
+        if (itm.empty()) return {};
+        vector<int> grp = topoSort(groupAdj, groupIndegree, m);
+        if (grp.empty()) return {};
+
+        unordered_map<int, vector<int>> grouping;
+        for (int& i : itm) {
+            grouping[group[i]].push_back(i);
+        }
+
+        vector<int> res;
+        for (int& g : grp) {
+            res.insert(res.end(), grouping[g].begin(), grouping[g].end());
+        }
+
+        return res;
+    }
+
+private:
+    vector<int> topoSort(vector<vector<int>>& adj, vector<int>& indegree, int N) {
+        queue<int> q;
+        vector<int> topo;
+        for (int i = 0; i < N; i++) {
+            if (indegree[i] == 0) q.push(i);
+        }
+
+        while (!q.empty()) {
+            int node = q.front(); q.pop();
+            topo.push_back(node);
+            for (int& neighbor : adj[node]) {
+                indegree[neighbor]--;
+                if (indegree[neighbor] == 0) q.push(neighbor);
+            }
+        }
+
+        return topo.size() == N ? topo : vector<int>();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} m
+     * @param {number[]} group
+     * @param {number[][]} beforeItems
+     * @return {number[]}
+     */
+    sortItems(n, m, group, beforeItems) {
+        for (let i = 0; i < n; i++) {
+            if (group[i] === -1) group[i] = m++;
+        }
+
+        const itemAdj = Array.from({ length: n }, () => []);
+        const groupAdj = Array.from({ length: m }, () => []);
+        const itemIndegree = Array(n).fill(0);
+        const groupIndegree = Array(m).fill(0);
+
+        for (let i = 0; i < n; i++) {
+            for (const par of beforeItems[i]) {
+                itemAdj[par].push(i);
+                itemIndegree[i]++;
+                if (group[i] !== group[par]) {
+                    groupAdj[group[par]].push(group[i]);
+                    groupIndegree[group[i]]++;
+                }
+            }
+        }
+
+        const itm = this.topoSort(itemAdj, itemIndegree, n);
+        if (itm.length === 0) return [];
+        const grp = this.topoSort(groupAdj, groupIndegree, m);
+        if (grp.length === 0) return [];
+
+        const grouping = new Map();
+        for (const i of itm) {
+            if (!grouping.has(group[i])) grouping.set(group[i], []);
+            grouping.get(group[i]).push(i);
+        }
+
+        const res = [];
+        for (const g of grp) {
+            if (grouping.has(g)) res.push(...grouping.get(g));
+        }
+
+        return res;
+    }
+
+    /**
+     * @param {number[][]} adj
+     * @param {number[]} indegree
+     * @param {number} N
+     * @return {number[]}
+     */
+    topoSort(adj, indegree, N) {
+        const q = new Queue();
+        const topo = [];
+        for (let i = 0; i < N; i++) {
+            if (indegree[i] === 0) q.push(i);
+        }
+
+        while (!q.isEmpty()) {
+            const node = q.pop();
+            topo.push(node);
+            for (const neighbor of adj[node]) {
+                indegree[neighbor]--;
+                if (indegree[neighbor] === 0) q.push(neighbor);
+            }
+        }
+
+        return topo.length === N ? topo : [];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(V + E)$
+* Space complexity: $O(V + E)$
+
+> Where $V$ is the number of items and $E$ is the total number of $beforeItems$ dependencies.
\ No newline at end of file
diff --git a/articles/sort-list.md b/articles/sort-list.md
new file mode 100644
index 000000000..768ec1c4c
--- /dev/null
+++ b/articles/sort-list.md
@@ -0,0 +1,730 @@
+## 1. Convert To Array
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def sortList(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        arr = []
+        cur = head
+
+        while cur:
+            arr.append(cur.val)
+            cur = cur.next
+
+        arr.sort()
+        cur = head
+        for val in arr:
+            cur.val = val
+            cur = cur.next
+
+        return head
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode sortList(ListNode head) {
+        if (head == null) return null;
+
+        List<Integer> arr = new ArrayList<>();
+        ListNode cur = head;
+
+        while (cur != null) {
+            arr.add(cur.val);
+            cur = cur.next;
+        }
+
+        Collections.sort(arr);
+        cur = head;
+        for (int val : arr) {
+            cur.val = val;
+            cur = cur.next;
+        }
+
+        return head;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* sortList(ListNode* head) {
+        if (!head) return nullptr;
+
+        vector<int> arr;
+        ListNode* cur = head;
+
+        while (cur) {
+            arr.push_back(cur->val);
+            cur = cur->next;
+        }
+
+        sort(arr.begin(), arr.end());
+        cur = head;
+        for (int val : arr) {
+            cur->val = val;
+            cur = cur->next;
+        }
+
+        return head;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @return {ListNode}
+     */
+    sortList(head) {
+        if (!head) return null;
+
+        let arr = [];
+        let cur = head;
+
+        while (cur) {
+            arr.push(cur.val);
+            cur = cur.next;
+        }
+
+        arr.sort((a, b) => a - b);
+        cur = head;
+        for (let val of arr) {
+            cur.val = val;
+            cur = cur.next;
+        }
+
+        return head;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Recursive Merge Sort
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def sortList(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        if not head or not head.next:
+            return head
+
+        left = head
+        right = self.getMid(head)
+        tmp = right.next
+        right.next = None
+        right = tmp
+
+        left = self.sortList(left)
+        right = self.sortList(right)
+        return self.merge(left, right)
+
+    def getMid(self, head):
+        slow, fast = head, head.next
+        while fast and fast.next:
+            slow = slow.next
+            fast = fast.next.next
+        return slow
+
+    def merge(self, list1, list2):
+        tail = dummy = ListNode()
+        while list1 and list2:
+            if list1.val < list2.val:
+                tail.next = list1
+                list1 = list1.next
+            else:
+                tail.next = list2
+                list2 = list2.next
+            tail = tail.next
+
+        if list1:
+            tail.next = list1
+        if list2:
+            tail.next = list2
+
+        return dummy.next
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode sortList(ListNode head) {
+        if (head == null || head.next == null) {
+            return head;
+        }
+
+        ListNode left = head;
+        ListNode right = getMid(head);
+        ListNode temp = right.next;
+        right.next = null;
+        right = temp;
+
+        left = sortList(left);
+        right = sortList(right);
+        return merge(left, right);
+    }
+
+    private ListNode getMid(ListNode head) {
+        ListNode slow = head, fast = head.next;
+        while (fast != null && fast.next != null) {
+            slow = slow.next;
+            fast = fast.next.next;
+        }
+        return slow;
+    }
+
+    private ListNode merge(ListNode list1, ListNode list2) {
+        ListNode dummy = new ListNode(0);
+        ListNode tail = dummy;
+
+        while (list1 != null && list2 != null) {
+            if (list1.val < list2.val) {
+                tail.next = list1;
+                list1 = list1.next;
+            } else {
+                tail.next = list2;
+                list2 = list2.next;
+            }
+            tail = tail.next;
+        }
+
+        if (list1 != null) {
+            tail.next = list1;
+        }
+        if (list2 != null) {
+            tail.next = list2;
+        }
+
+        return dummy.next;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* sortList(ListNode* head) {
+        if (!head || !head->next) {
+            return head;
+        }
+
+        ListNode* left = head;
+        ListNode* right = getMid(head);
+        ListNode* temp = right->next;
+        right->next = nullptr;
+        right = temp;
+
+        left = sortList(left);
+        right = sortList(right);
+        return merge(left, right);
+    }
+
+private:
+    ListNode* getMid(ListNode* head) {
+        ListNode* slow = head;
+        ListNode* fast = head->next;
+        while (fast && fast->next) {
+            slow = slow->next;
+            fast = fast->next->next;
+        }
+        return slow;
+    }
+
+    ListNode* merge(ListNode* list1, ListNode* list2) {
+        ListNode dummy(0);
+        ListNode* tail = &dummy;
+
+        while (list1 && list2) {
+            if (list1->val < list2->val) {
+                tail->next = list1;
+                list1 = list1->next;
+            } else {
+                tail->next = list2;
+                list2 = list2->next;
+            }
+            tail = tail->next;
+        }
+
+        if (list1) {
+            tail->next = list1;
+        }
+        if (list2) {
+            tail->next = list2;
+        }
+
+        return dummy.next;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @return {ListNode}
+     */
+    sortList(head) {
+        if (!head || !head.next) {
+            return head;
+        }
+
+        let left = head;
+        let right = this.getMid(head);
+        let temp = right.next;
+        right.next = null;
+        right = temp;
+
+        left = this.sortList(left);
+        right = this.sortList(right);
+        return this.merge(left, right);
+    }
+
+    /**
+     * @param {ListNode} head
+     * @return {ListNode}
+     */
+    getMid(head) {
+        let slow = head, fast = head.next;
+        while (fast && fast.next) {
+            slow = slow.next;
+            fast = fast.next.next;
+        }
+        return slow;
+    }
+
+    /**
+     * @param {ListNode} list1
+     * @param {ListNode} list2
+     * @return {ListNode}
+     */
+    merge(list1, list2) {
+        let dummy = new ListNode(0);
+        let tail = dummy;
+
+        while (list1 && list2) {
+            if (list1.val < list2.val) {
+                tail.next = list1;
+                list1 = list1.next;
+            } else {
+                tail.next = list2;
+                list2 = list2.next;
+            }
+            tail = tail.next;
+        }
+
+        if (list1) {
+            tail.next = list1;
+        }
+        if (list2) {
+            tail.next = list2;
+        }
+
+        return dummy.next;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(\log n)$ for recursion stack.
+
+---
+
+## 3. Iterative Merge Sort
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def sortList(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        if not head or not head.next:
+            return head
+        
+        length = 0
+        cur = head
+        while cur:
+            length += 1
+            cur = cur.next
+
+        dummy = ListNode(0)
+        dummy.next = head
+        step = 1
+
+        while step < length:
+            prev, curr = dummy, dummy.next
+            while curr:
+                left = curr
+                right = self.split(left, step)
+                curr = self.split(right, step)
+                merged = self.merge(left, right)
+                prev.next = merged
+                while prev.next:
+                    prev = prev.next
+            step *= 2
+
+        return dummy.next
+
+    def split(self, head, step):
+        if not head:
+            return None
+        for _ in range(step - 1):
+            if not head.next:
+                break
+            head = head.next
+        next_part = head.next
+        head.next = None
+        return next_part
+
+    def merge(self, list1, list2):
+        tail = dummy = ListNode(0)
+        while list1 and list2:
+            if list1.val < list2.val:
+                tail.next = list1
+                list1 = list1.next
+            else:
+                tail.next = list2
+                list2 = list2.next
+            tail = tail.next
+
+        tail.next = list1 or list2
+        return dummy.next
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode sortList(ListNode head) {
+        if (head == null || head.next == null) {
+            return head;
+        }
+
+        int length = 0;
+        ListNode cur = head;
+        while (cur != null) {
+            length++;
+            cur = cur.next;
+        }
+
+        ListNode dummy = new ListNode(0);
+        dummy.next = head;
+        int step = 1;
+
+        while (step < length) {
+            ListNode prev = dummy, curr = dummy.next;
+            while (curr != null) {
+                ListNode left = curr;
+                ListNode right = split(left, step);
+                curr = split(right, step);
+                ListNode merged = merge(left, right);
+                prev.next = merged;
+                while (prev.next != null) {
+                    prev = prev.next;
+                }
+            }
+            step *= 2;
+        }
+        
+        return dummy.next;
+    }
+
+    private ListNode split(ListNode head, int step) {
+        if (head == null) return null;
+        for (int i = 0; i < step - 1 && head.next != null; i++) {
+            head = head.next;
+        }
+        ListNode nextPart = head.next;
+        head.next = null;
+        return nextPart;
+    }
+
+    private ListNode merge(ListNode list1, ListNode list2) {
+        ListNode dummy = new ListNode(0);
+        ListNode tail = dummy;
+        
+        while (list1 != null && list2 != null) {
+            if (list1.val < list2.val) {
+                tail.next = list1;
+                list1 = list1.next;
+            } else {
+                tail.next = list2;
+                list2 = list2.next;
+            }
+            tail = tail.next;
+        }
+
+        tail.next = (list1 != null) ? list1 : list2;
+        return dummy.next;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+class Solution {
+public:
+    ListNode* sortList(ListNode* head) {
+        if (!head || !head->next) {
+            return head;
+        }
+
+        int length = 0;
+        ListNode* cur = head;
+        while (cur) {
+            length++;
+            cur = cur->next;
+        }
+
+        ListNode dummy(0);
+        dummy.next = head;
+        int step = 1;
+
+        while (step < length) {
+            ListNode* prev = &dummy, *curr = dummy.next;
+            while (curr) {
+                ListNode* left = curr;
+                ListNode* right = split(left, step);
+                curr = split(right, step);
+                ListNode* merged = merge(left, right);
+                prev->next = merged;
+                while (prev->next) {
+                    prev = prev->next;
+                }
+            }
+            step *= 2;
+        }
+
+        return dummy.next;
+    }
+
+private:
+    ListNode* split(ListNode* head, int step) {
+        if (!head) return nullptr;
+        for (int i = 0; i < step - 1 && head->next; i++) {
+            head = head->next;
+        }
+        ListNode* nextPart = head->next;
+        head->next = nullptr;
+        return nextPart;
+    }
+
+    ListNode* merge(ListNode* list1, ListNode* list2) {
+        ListNode dummy(0);
+        ListNode* tail = &dummy;
+
+        while (list1 && list2) {
+            if (list1->val < list2->val) {
+                tail->next = list1;
+                list1 = list1->next;
+            } else {
+                tail->next = list2;
+                list2 = list2->next;
+            }
+            tail = tail->next;
+        }
+
+        tail->next = list1 ? list1 : list2;
+        return dummy.next;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @return {ListNode}
+     */
+    sortList(head) {
+        if (!head || !head.next) {
+            return head;
+        }
+
+        let length = 0;
+        let cur = head;
+        while (cur) {
+            length++;
+            cur = cur.next;
+        }
+
+        let dummy = new ListNode(0);
+        dummy.next = head;
+        let step = 1;
+
+        while (step < length) {
+            let prev = dummy, curr = dummy.next;
+            while (curr) {
+                let left = curr;
+                let right = this.split(left, step);
+                curr = this.split(right, step);
+                let merged = this.merge(left, right);
+                prev.next = merged;
+                while (prev.next) {
+                    prev = prev.next;
+                }
+            }
+            step *= 2;
+        }
+
+        return dummy.next;
+    }
+
+    /**
+     * @param {ListNode} head
+     * @param {number} step
+     * @return {ListNode}
+     */
+    split(head, step) {
+        if (!head) return null;
+        for (let i = 0; i < step - 1 && head.next; i++) {
+            head = head.next;
+        }
+        let nextPart = head.next;
+        head.next = null;
+        return nextPart;
+    }
+
+    /**
+     * @param {ListNode} list1
+     * @param {ListNode} list2
+     * @return {ListNode}
+     */
+    merge(list1, list2) {
+        let dummy = new ListNode(0);
+        let tail = dummy;
+
+        while (list1 && list2) {
+            if (list1.val < list2.val) {
+                tail.next = list1;
+                list1 = list1.next;
+            } else {
+                tail.next = list2;
+                list2 = list2.next;
+            }
+            tail = tail.next;
+        }
+
+        tail.next = list1 || list2;
+        return dummy.next;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/sort-the-jumbled-numbers.md b/articles/sort-the-jumbled-numbers.md
new file mode 100644
index 000000000..b8c0cbf47
--- /dev/null
+++ b/articles/sort-the-jumbled-numbers.md
@@ -0,0 +1,244 @@
+## 1. Convert To Strings + Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def sortJumbled(self, mapping: List[int], nums: List[int]) -> List[int]:
+        pairs = []
+
+        for i, n in enumerate(nums):
+            n = str(n)
+            mapped_n = 0
+            for c in n:
+                mapped_n *= 10
+                mapped_n += mapping[int(c)]
+            pairs.append((mapped_n, i))
+
+        pairs.sort()
+        return [nums[p[1]] for p in pairs]
+```
+
+```java
+public class Solution {
+    public int[] sortJumbled(int[] mapping, int[] nums) {
+        int n = nums.length;
+        int[][] pairs = new int[n][2];
+
+        for (int i = 0; i < n; i++) {
+            String numStr = String.valueOf(nums[i]);
+            int mapped_n = 0;
+            for (char c : numStr.toCharArray()) {
+                mapped_n = mapped_n * 10 + mapping[c - '0'];
+            }
+            pairs[i][0] = mapped_n;
+            pairs[i][1] = i;
+        }
+
+        Arrays.sort(pairs, (a, b) -> a[0] - b[0]);
+
+        int[] res = new int[n];
+        for (int i = 0; i < n; i++) {
+            res[i] = nums[pairs[i][1]];
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> sortJumbled(vector<int>& mapping, vector<int>& nums) {
+        vector<pair<int, int>> pairs;
+
+        for (int i = 0; i < nums.size(); ++i) {
+            string numStr = to_string(nums[i]);
+            int mapped_n = 0;
+            for (char c : numStr) {
+                mapped_n = mapped_n * 10 + mapping[c - '0'];
+            }
+            pairs.push_back({mapped_n, i});
+        }
+
+        sort(pairs.begin(), pairs.end());
+
+        vector<int> res;
+        for (auto& p : pairs) {
+            res.push_back(nums[p.second]);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} mapping
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    sortJumbled(mapping, nums) {
+        let pairs = [];
+
+        for (let i = 0; i < nums.length; i++) {
+            let numStr = nums[i].toString();
+            let mapped_n = 0;
+            for (let c of numStr) {
+                mapped_n = mapped_n * 10 + mapping[parseInt(c)];
+            }
+            pairs.push([mapped_n, i]);
+        }
+
+        pairs.sort((a, b) => a[0] - b[0]);
+
+        return pairs.map(p => nums[p[1]]);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Iterate On Numbers + Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def sortJumbled(self, mapping: List[int], nums: List[int]) -> List[int]:
+        pairs = []
+
+        for i, n in enumerate(nums):
+            mapped_n = 0
+            base = 1
+
+            if n == 0:
+                mapped_n = mapping[0]
+            else:
+                while n > 0:
+                    digit = n % 10
+                    n //= 10
+                    mapped_n += base * mapping[digit]
+                    base *= 10
+
+            pairs.append((mapped_n, i))
+
+        pairs.sort()
+        return [nums[p[1]] for p in pairs]
+```
+
+```java
+public class Solution {
+    public int[] sortJumbled(int[] mapping, int[] nums) {
+        int n = nums.length;
+        int[][] pairs = new int[n][2];
+
+        for (int i = 0; i < n; i++) {
+            int mapped_n = 0, base = 1;
+            int num = nums[i];
+
+            if (num == 0) {
+                mapped_n = mapping[0];
+            } else {
+                while (num > 0) {
+                    int digit = num % 10;
+                    num /= 10;
+                    mapped_n += base * mapping[digit];
+                    base *= 10;
+                }
+            }
+
+            pairs[i][0] = mapped_n;
+            pairs[i][1] = i;
+        }
+
+        Arrays.sort(pairs, (a, b) -> Integer.compare(a[0], b[0]));
+
+        int[] res = new int[n];
+        for (int i = 0; i < n; i++) {
+            res[i] = nums[pairs[i][1]];
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> sortJumbled(vector<int>& mapping, vector<int>& nums) {
+        vector<pair<int, int>> pairs;
+
+        for (int i = 0; i < nums.size(); i++) {
+            int mapped_n = 0, base = 1;
+            int num = nums[i];
+
+            if (num == 0) {
+                mapped_n = mapping[0];
+            } else {
+                while (num > 0) {
+                    int digit = num % 10;
+                    num /= 10;
+                    mapped_n += base * mapping[digit];
+                    base *= 10;
+                }
+            }
+
+            pairs.push_back({mapped_n, i});
+        }
+
+        sort(pairs.begin(), pairs.end());
+
+        vector<int> res;
+        for (auto& p : pairs) {
+            res.push_back(nums[p.second]);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} mapping
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    sortJumbled(mapping, nums) {
+        let pairs = [];
+
+        for (let i = 0; i < nums.length; i++) {
+            let numStr = nums[i].toString();
+            let mapped_n = 0;
+            for (let c of numStr) {
+                mapped_n = mapped_n * 10 + mapping[parseInt(c)];
+            }
+            pairs.push([mapped_n, i]);
+        }
+
+        pairs.sort((a, b) => a[0] - b[0]);
+
+        return pairs.map(p => nums[p[1]]);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/sort-the-people.md b/articles/sort-the-people.md
new file mode 100644
index 000000000..c5d8ca911
--- /dev/null
+++ b/articles/sort-the-people.md
@@ -0,0 +1,256 @@
+## 1. Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def sortPeople(self, names: List[str], heights: List[int]) -> List[str]:
+        height_to_name = {}
+        for h, n in zip(heights, names):
+            height_to_name[h] = n
+
+        res = []
+        for h in reversed(sorted(heights)):
+            res.append(height_to_name[h])
+
+        return res
+```
+
+```java
+public class Solution {
+    public String[] sortPeople(String[] names, int[] heights) {
+        Map<Integer, String> map = new HashMap<>();
+        for (int i = 0; i < heights.length; i++) {
+            map.put(heights[i], names[i]);
+        }
+
+        Arrays.sort(heights);
+        String[] res = new String[heights.length];
+        for (int i = 0; i < heights.length; i++) {
+            res[i] = map.get(heights[heights.length - 1 - i]);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<string> sortPeople(vector<string>& names, vector<int>& heights) {
+        unordered_map<int, string> map;
+        for (int i = 0; i < heights.size(); i++) {
+            map[heights[i]] = names[i];
+        }
+
+        sort(heights.begin(), heights.end());
+        vector<string> res;
+        for (int i = heights.size() - 1; i >= 0; i--) {
+            res.push_back(map[heights[i]]);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} names
+     * @param {number[]} heights
+     * @return {string[]}
+     */
+    sortPeople(names, heights) {
+        const map = {};
+        for (let i = 0; i < heights.length; i++) {
+            map[heights[i]] = names[i];
+        }
+
+        heights.sort((a, b) => a - b);
+        const res = [];
+        for (let i = heights.length - 1; i >= 0; i--) {
+            res.push(map[heights[i]]);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Sorting the Pairs
+
+::tabs-start
+
+```python
+class Solution:
+    def sortPeople(self, names: List[str], heights: List[int]) -> List[str]:
+        arr = list(zip(heights, names))
+        arr.sort(reverse=True)
+        return [name for _, name in arr]
+```
+
+```java
+public class Solution {
+    public String[] sortPeople(String[] names, int[] heights) {
+        int n = names.length;
+        Pair[] arr = new Pair[n];
+
+        for (int i = 0; i < n; i++) {
+            arr[i] = new Pair(heights[i], names[i]);
+        }
+
+        Arrays.sort(arr, (a, b) -> Integer.compare(b.height, a.height));
+
+        String[] res = new String[n];
+        for (int i = 0; i < n; i++) {
+            res[i] = arr[i].name;
+        }
+
+        return res;
+    }
+
+    static class Pair {
+        int height;
+        String name;
+
+        Pair(int height, String name) {
+            this.height = height;
+            this.name = name;
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<string> sortPeople(vector<string>& names, vector<int>& heights) {
+        vector<pair<int, string>> arr;
+        for (int i = 0; i < names.size(); i++) {
+            arr.emplace_back(heights[i], names[i]);
+        }
+
+        sort(arr.begin(), arr.end(), [](auto& a, auto& b) {
+            return a.first > b.first;
+        });
+
+        vector<string> res;
+        for (auto& [_, name] : arr) {
+            res.push_back(name);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} names
+     * @param {number[]} heights
+     * @return {string[]}
+     */
+    sortPeople(names, heights) {
+        const arr = names.map((name, i) => [heights[i], name]);
+        arr.sort((a, b) => b[0] - a[0]);
+        return arr.map(pair => pair[1]);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Sorting the Indices
+
+::tabs-start
+
+```python
+class Solution:
+    def sortPeople(self, names: List[str], heights: List[int]) -> List[str]:
+        indices = list(range(len(names)))
+        indices.sort(key=lambda i: -heights[i])
+        return [names[i] for i in indices]
+```
+
+```java
+public class Solution {
+    public String[] sortPeople(String[] names, int[] heights) {
+        Integer[] indices = new Integer[names.length];
+        for (int i = 0; i < names.length; i++) {
+            indices[i] = i;
+        }
+
+        Arrays.sort(indices, (i, j) -> Integer.compare(heights[j], heights[i]));
+
+        String[] res = new String[names.length];
+        for (int i = 0; i < names.length; i++) {
+            res[i] = names[indices[i]];
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<string> sortPeople(vector<string>& names, vector<int>& heights) {
+        int n = names.size();
+        vector<int> indices(n);
+        iota(indices.begin(), indices.end(), 0);
+
+        sort(indices.begin(), indices.end(), [&](int a, int b) {
+            return heights[a] > heights[b];
+        });
+
+        vector<string> res;
+        for (int i : indices) {
+            res.push_back(names[i]);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} names
+     * @param {number[]} heights
+     * @return {string[]}
+     */
+    sortPeople(names, heights) {
+        const indices = names.map((_, i) => i);
+        indices.sort((a, b) => heights[b] - heights[a]);
+        return indices.map(i => names[i]);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/special-array-i.md b/articles/special-array-i.md
new file mode 100644
index 000000000..40ccd36c6
--- /dev/null
+++ b/articles/special-array-i.md
@@ -0,0 +1,129 @@
+## 1. Modulo Comparision
+
+::tabs-start
+
+```python
+class Solution:
+    def isArraySpecial(self, nums: List[int]) -> bool:
+        for i in range(1, len(nums)):
+            if nums[i - 1] % 2 == nums[i] % 2:
+                return False
+        return True
+```
+
+```java
+public class Solution {
+    public boolean isArraySpecial(int[] nums) {
+        for (int i = 1; i < nums.length; i++) {
+            if (nums[i - 1] % 2 == nums[i] % 2) {
+                return false;
+            }
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isArraySpecial(vector<int>& nums) {
+        for (int i = 1; i < nums.size(); i++) {
+            if (nums[i - 1] % 2 == nums[i] % 2) {
+                return false;
+            }
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {boolean}
+     */
+    isArraySpecial(nums) {
+        for (let i = 1; i < nums.length; i++) {
+            if (nums[i - 1] % 2 === nums[i] % 2) {
+                return false;
+            }
+        }
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Bitwise Comparision
+
+::tabs-start
+
+```python
+class Solution:
+    def isArraySpecial(self, nums: List[int]) -> bool:
+        for i in range(1, len(nums)):
+            if nums[i - 1] & 1 == nums[i] & 1:
+                return False
+        return True
+```
+
+```java
+public class Solution {
+    public boolean isArraySpecial(int[] nums) {
+        for (int i = 1; i < nums.length; i++) {
+            if ((nums[i - 1] & 1) == (nums[i] & 1)) {
+                return false;
+            }
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isArraySpecial(vector<int>& nums) {
+        for (int i = 1; i < nums.size(); i++) {
+            if ((nums[i - 1] & 1) == (nums[i] & 1)) {
+                return false;
+            }
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {boolean}
+     */
+    isArraySpecial(nums) {
+        for (let i = 1; i < nums.length; i++) {
+            if ((nums[i - 1] & 1) === (nums[i] & 1)) {
+                return false;
+            }
+        }
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/special-array-with-x-elements-greater-than-or-equal-x.md b/articles/special-array-with-x-elements-greater-than-or-equal-x.md
new file mode 100644
index 000000000..3ba445d99
--- /dev/null
+++ b/articles/special-array-with-x-elements-greater-than-or-equal-x.md
@@ -0,0 +1,506 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def specialArray(self, nums: List[int]) -> int:
+        for i in range(1, len(nums) + 1):
+            cnt = 0
+            for num in nums:
+                if num >= i:
+                    cnt += 1
+
+            if cnt == i:
+                return i
+
+        return -1
+```
+
+```java
+public class Solution {
+    public int specialArray(int[] nums) {
+        for (int i = 1; i <= nums.length; i++) {
+            int count = 0;
+            for (int num : nums) {
+                if (num >= i) {
+                    count++;
+                }
+            }
+            if (count == i) {
+                return i;
+            }
+        }
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int specialArray(vector<int>& nums) {
+        for (int i = 1; i <= nums.size(); i++) {
+            int count = 0;
+            for (int num : nums) {
+                if (num >= i) {
+                    count++;
+                }
+            }
+            if (count == i) {
+                return i;
+            }
+        }
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    specialArray(nums) {
+        for (let i = 1; i <= nums.length; i++) {
+            let count = 0;
+            for (let num of nums) {
+                if (num >= i) {
+                    count++;
+                }
+            }
+            if (count === i) {
+                return i;
+            }
+        }
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Binary Search
+
+::tabs-start
+
+```python
+class Solution:
+    def specialArray(self, nums: List[int]) -> int:
+        l, r = 1, len(nums)
+        while l <= r:
+            mid = (l + r) >> 1
+            cnt = sum(1 for num in nums if num >= mid)
+
+            if cnt == mid:
+                return mid
+
+            if cnt < mid:
+                r = mid - 1
+            else:
+                l = mid + 1
+
+        return -1
+```
+
+```java
+public class Solution {
+    public int specialArray(int[] nums) {
+        int l = 1, r = nums.length;
+        while (l <= r) {
+            int mid = (l + r) / 2;
+            int cnt = 0;
+            for (int num : nums) {
+                if (num >= mid) cnt++;
+            }
+
+            if (cnt == mid) return mid;
+
+            if (cnt < mid) {
+                r = mid - 1;
+            } else {
+                l = mid + 1;
+            }
+        }
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int specialArray(vector<int>& nums) {
+        int l = 1, r = nums.size();
+        while (l <= r) {
+            int mid = (l + r) / 2;
+            int cnt = 0;
+            for (int num : nums) {
+                if (num >= mid) cnt++;
+            }
+
+            if (cnt == mid) return mid;
+
+            if (cnt < mid) {
+                r = mid - 1;
+            } else {
+                l = mid + 1;
+            }
+        }
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    specialArray(nums) {
+        let l = 1, r = nums.length;
+        while (l <= r) {
+            const mid = Math.floor((l + r) / 2);
+            const cnt = nums.filter(num => num >= mid).length;
+
+            if (cnt === mid) return mid;
+
+            if (cnt < mid) {
+                r = mid - 1;
+            } else {
+                l = mid + 1;
+            }
+        }
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def specialArray(self, nums: List[int]) -> int:
+        nums.sort()
+        i = 0
+        prev = -1
+        total_right = len(nums)
+        while i < len(nums):
+            if nums[i] == total_right or (prev < total_right < nums[i]):
+                return total_right
+
+            while i + 1 < len(nums) and nums[i] == nums[i + 1]:
+                i += 1
+
+            prev = nums[i]
+            i += 1
+            total_right = len(nums) - i
+
+        return -1
+```
+
+```java
+public class Solution {
+    public int specialArray(int[] nums) {
+        Arrays.sort(nums);
+        int i = 0, prev = -1, totalRight = nums.length;
+
+        while (i < nums.length) {
+            if (nums[i] == totalRight || 
+               (prev < totalRight && totalRight < nums[i])) {
+                return totalRight;
+            }
+
+            while (i + 1 < nums.length && nums[i] == nums[i + 1]) {
+                i++;
+            }
+
+            prev = nums[i];
+            i++;
+            totalRight = nums.length - i;
+        }
+
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int specialArray(vector<int>& nums) {
+        sort(nums.begin(), nums.end());
+        int i = 0, prev = -1, totalRight = nums.size();
+
+        while (i < nums.size()) {
+            if (nums[i] == totalRight || 
+               (prev < totalRight && totalRight < nums[i])) {
+                return totalRight;
+            }
+
+            while (i + 1 < nums.size() && nums[i] == nums[i + 1]) {
+                i++;
+            }
+
+            prev = nums[i];
+            i++;
+            totalRight = nums.size() - i;
+        }
+
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    specialArray(nums) {
+        nums.sort((a, b) => a - b);
+        let i = 0, prev = -1, totalRight = nums.length;
+
+        while (i < nums.length) {
+            if (nums[i] === totalRight || 
+               (prev < totalRight && totalRight < nums[i])) {
+                return totalRight;
+            }
+
+            while (i + 1 < nums.length && nums[i] === nums[i + 1]) {
+                i++;
+            }
+
+            prev = nums[i];
+            i++;
+            totalRight = nums.length - i;
+        }
+
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 4. Sorting + Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def specialArray(self, nums: List[int]) -> int:
+        nums.sort()
+        n = len(nums)
+        i, j = 0, 1
+
+        while i < n and j <= n:
+            while i < n and j > nums[i]:
+                i += 1
+
+            if j == n - i:
+                return j
+            j += 1
+
+        return -1
+```
+
+```java
+public class Solution {
+    public int specialArray(int[] nums) {
+        Arrays.sort(nums);
+        int n = nums.length;
+        int i = 0, j = 1;
+
+        while (i < n && j <= n) {
+            while (i < n && j > nums[i]) i++;
+
+            if (j == n - i) {
+                return j;
+            }
+            j++;
+        }
+
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int specialArray(vector<int>& nums) {
+        sort(nums.begin(), nums.end());
+        int n = nums.size();
+        int i = 0, j = 1;
+
+        while (i < n && j <= n) {
+            while (i < n && j > nums[i]) i++;
+
+            if (j == n - i) {
+                return j;
+            }
+            j++;
+        }
+
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    specialArray(nums) {
+        nums.sort((a, b) => a - b);
+        const n = nums.length;
+        let i = 0, j = 1;
+
+        while (i < n && j <= n) {
+            while (i < n && j > nums[i]) i++;
+
+            if (j == n - i) {
+                return j;
+            }
+            j++;
+        }
+
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 5. Counting Sort
+
+::tabs-start
+
+```python
+class Solution:
+    def specialArray(self, nums: List[int]) -> int:
+        count = [0] * (len(nums) + 1)
+        for num in nums:
+            index = min(num, len(nums))
+            count[index] += 1
+
+        total_right = 0
+        for i in range(len(nums), -1, -1):
+            total_right += count[i]
+            if i == total_right:
+                return total_right
+        return -1
+```
+
+```java
+public class Solution {
+    public int specialArray(int[] nums) {
+        int[] count = new int[nums.length + 1];
+        for (int num : nums) {
+            int index = Math.min(num, nums.length);
+            count[index]++;
+        }
+
+        int totalRight = 0;
+        for (int i = nums.length; i >= 0; i--) {
+            totalRight += count[i];
+            if (i == totalRight) {
+                return totalRight;
+            }
+        }
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int specialArray(vector<int>& nums) {
+        vector<int> count(nums.size() + 1, 0);
+        for (int num : nums) {
+            int index = min(num, (int)nums.size());
+            count[index]++;
+        }
+
+        int totalRight = 0;
+        for (int i = nums.size(); i >= 0; --i) {
+            totalRight += count[i];
+            if (i == totalRight) {
+                return totalRight;
+            }
+        }
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    specialArray(nums) {
+        const count = new Array(nums.length + 1).fill(0);
+        for (const num of nums) {
+            const index = Math.min(num, nums.length);
+            count[index]++;
+        }
+
+        let totalRight = 0;
+        for (let i = nums.length; i >= 0; i--) {
+            totalRight += count[i];
+            if (i === totalRight) {
+                return totalRight;
+            }
+        }
+        return -1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/spiral-matrix-ii.md b/articles/spiral-matrix-ii.md
new file mode 100644
index 000000000..1df46f786
--- /dev/null
+++ b/articles/spiral-matrix-ii.md
@@ -0,0 +1,454 @@
+## 1. Iteration
+
+::tabs-start
+
+```python
+class Solution:
+    def generateMatrix(self, n: int) -> List[List[int]]:
+        mat = [[0] * n for _ in range(n)]
+        left, right = 0, n - 1
+        top, bottom = 0, n - 1
+        val = 1
+
+        while left <= right:
+            # Fill every val in top row
+            for c in range(left, right + 1):
+                mat[top][c] = val
+                val += 1
+            top += 1
+
+            # Fill every val in right col
+            for r in range(top, bottom + 1):
+                mat[r][right] = val
+                val += 1
+            right -= 1
+
+            # Fill every val in bottom row (reverse order)
+            for c in range(right, left - 1, -1):
+                mat[bottom][c] = val
+                val += 1
+            bottom -= 1
+
+            # Fill every val in the left col (reverse order)
+            for r in range(bottom, top - 1, -1):
+                mat[r][left] = val
+                val += 1
+            left += 1
+
+        return mat
+```
+
+```java
+public class Solution {
+    public int[][] generateMatrix(int n) {
+        int[][] mat = new int[n][n];
+        int left = 0, right = n - 1, top = 0, bottom = n - 1, val = 1;
+
+        while (left <= right) {
+            // Fill every val in top row
+            for (int c = left; c <= right; c++) {
+                mat[top][c] = val++;
+            }
+            top++;
+
+            // Fill every val in right col
+            for (int r = top; r <= bottom; r++) {
+                mat[r][right] = val++;
+            }
+            right--;
+
+            // Fill every val in bottom row (reverse order)
+            for (int c = right; c >= left; c--) {
+                mat[bottom][c] = val++;
+            }
+            bottom--;
+
+            // Fill every val in the left col (reverse order)
+            for (int r = bottom; r >= top; r--) {
+                mat[r][left] = val++;
+            }
+            left++;
+        }
+
+        return mat;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> generateMatrix(int n) {
+        vector<vector<int>> mat(n, vector<int>(n, 0));
+        int left = 0, right = n - 1, top = 0, bottom = n - 1, val = 1;
+
+        while (left <= right) {
+            // Fill every val in top row
+            for (int c = left; c <= right; c++) {
+                mat[top][c] = val++;
+            }
+            top++;
+
+            // Fill every val in right col
+            for (int r = top; r <= bottom; r++) {
+                mat[r][right] = val++;
+            }
+            right--;
+
+            // Fill every val in bottom row (reverse order)
+            for (int c = right; c >= left; c--) {
+                mat[bottom][c] = val++;
+            }
+            bottom--;
+
+            // Fill every val in the left col (reverse order)
+            for (int r = bottom; r >= top; r--) {
+                mat[r][left] = val++;
+            }
+            left++;
+        }
+
+        return mat;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number[][]}
+     */
+    generateMatrix(n) {
+        const mat = Array.from({ length: n }, () => Array(n).fill(0));
+        let left = 0, right = n - 1, top = 0, bottom = n - 1, val = 1;
+
+        while (left <= right) {
+            // Fill every val in top row
+            for (let c = left; c <= right; c++) {
+                mat[top][c] = val++;
+            }
+            top++;
+
+            // Fill every val in right col
+            for (let r = top; r <= bottom; r++) {
+                mat[r][right] = val++;
+            }
+            right--;
+
+            // Fill every val in bottom row (reverse order)
+            for (let c = right; c >= left; c--) {
+                mat[bottom][c] = val++;
+            }
+            bottom--;
+
+            // Fill every val in the left col (reverse order)
+            for (let r = bottom; r >= top; r--) {
+                mat[r][left] = val++;
+            }
+            left++;
+        }
+
+        return mat;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$ for the output matrix.
+
+---
+
+## 2. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def generateMatrix(self, n: int) -> List[List[int]]:
+        mat = [[0] * n for _ in range(n)]
+        
+        def fill(left, right, top, bottom, val):
+            if left > right or top > bottom:
+                return
+            
+            # Fill every val in top row
+            for c in range(left, right + 1):
+                mat[top][c] = val
+                val += 1
+            top += 1
+
+            # Fill every val in right col
+            for r in range(top, bottom + 1):
+                mat[r][right] = val
+                val += 1
+            right -= 1
+
+            # Fill every val in bottom row (reverse order)
+            for c in range(right, left - 1, -1):
+                mat[bottom][c] = val
+                val += 1
+            bottom -= 1
+
+            # Fill every val in the left col (reverse order)
+            for r in range(bottom, top - 1, -1):
+                mat[r][left] = val
+                val += 1
+            left += 1
+
+            # Recur for the inner layer
+            fill(left, right, top, bottom, val)
+
+        fill(0, n - 1, 0, n - 1, 1)
+        return mat
+```
+
+```java
+public class Solution {
+    public int[][] generateMatrix(int n) {
+        int[][] mat = new int[n][n];
+        fill(mat, 0, n - 1, 0, n - 1, 1);
+        return mat;
+    }
+    
+    private void fill(int[][] mat, int left, int right, int top, int bottom, int val) {
+        if (left > right || top > bottom) return;
+
+        // Fill every val in top row
+        for (int c = left; c <= right; c++) {
+            mat[top][c] = val++;
+        }
+        top++;
+
+        // Fill every val in right col
+        for (int r = top; r <= bottom; r++) {
+            mat[r][right] = val++;
+        }
+        right--;
+
+        // Fill every val in bottom row (reverse order)
+        for (int c = right; c >= left; c--) {
+            mat[bottom][c] = val++;
+        }
+        bottom--;
+
+        // Fill every val in the left col (reverse order)
+        for (int r = bottom; r >= top; r--) {
+            mat[r][left] = val++;
+        }
+        left++;
+
+        // Recur for the inner layer
+        fill(mat, left, right, top, bottom, val);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> generateMatrix(int n) {
+        vector<vector<int>> mat(n, vector<int>(n, 0));
+        fill(mat, 0, n - 1, 0, n - 1, 1);
+        return mat;
+    }
+    
+private:
+    void fill(vector<vector<int>> &mat, int left, int right, int top, int bottom, int val) {
+        if (left > right || top > bottom) return;
+
+        // Fill every val in top row
+        for (int c = left; c <= right; c++) {
+            mat[top][c] = val++;
+        }
+        top++;
+
+        // Fill every val in right col
+        for (int r = top; r <= bottom; r++) {
+            mat[r][right] = val++;
+        }
+        right--;
+
+        // Fill every val in bottom row (reverse order)
+        for (int c = right; c >= left; c--) {
+            mat[bottom][c] = val++;
+        }
+        bottom--;
+
+        // Fill every val in the left col (reverse order)
+        for (int r = bottom; r >= top; r--) {
+            mat[r][left] = val++;
+        }
+        left++;
+
+        // Recur for the inner layer
+        fill(mat, left, right, top, bottom, val);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number[][]}
+     */
+    generateMatrix(n) {
+        const mat = Array.from({ length: n }, () => Array(n).fill(0));
+        
+        const fill = (left, right, top, bottom, val) => {
+            if (left > right || top > bottom) return;
+
+            // Fill every val in top row
+            for (let c = left; c <= right; c++) {
+                mat[top][c] = val++;
+            }
+            top++;
+
+            // Fill every val in right col
+            for (let r = top; r <= bottom; r++) {
+                mat[r][right] = val++;
+            }
+            right--;
+
+            // Fill every val in bottom row (reverse order)
+            for (let c = right; c >= left; c--) {
+                mat[bottom][c] = val++;
+            }
+            bottom--;
+
+            // Fill every val in the left col (reverse order)
+            for (let r = bottom; r >= top; r--) {
+                mat[r][left] = val++;
+            }
+            left++;
+
+            // Recur for the inner layer
+            fill(left, right, top, bottom, val);
+        };
+
+        fill(0, n - 1, 0, n - 1, 1);
+        return mat;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity:
+    * $O(n)$ space for recursion stack.
+    * $O(n ^ 2)$ space for the output matrix.
+
+---
+
+## 3. Iteration (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def generateMatrix(self, n: int) -> List[List[int]]:
+        mat = [[0] * n for _ in range(n)]
+        r = c = 0
+        dr, dc = 0, 1
+
+        for val in range(n * n):
+            mat[r][c] = val + 1
+            if mat[(r + dr) % n][(c + dc) % n] != 0:
+                dr, dc = dc, -dr
+            r, c = r + dr, c + dc
+        
+        return mat
+```
+
+```java
+public class Solution {
+    public int[][] generateMatrix(int n) {
+        int[][] mat = new int[n][n];
+        int r = 0, c = 0, dr = 0, dc = 1;
+
+        for (int val = 0; val < n * n; val++) {
+            mat[r][c] = val + 1;
+            int nextR = (r + dr) % n, nextC = (c + dc) % n;
+            if (nextR < 0) nextR += n;
+            if (nextC < 0) nextC += n;
+            if (mat[nextR][nextC] != 0) {
+                int temp = dr;
+                dr = dc;
+                dc = -temp;
+            }
+            r += dr;
+            c += dc;
+        }
+
+        return mat;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> generateMatrix(int n) {
+        vector<vector<int>> mat(n, vector<int>(n, 0));
+        int r = 0, c = 0, dr = 0, dc = 1;
+
+        for (int val = 0; val < n * n; val++) {
+            mat[r][c] = val + 1;
+            int nextR = (r + dr) % n, nextC = (c + dc) % n;
+            if (nextR < 0) nextR += n;
+            if (nextC < 0) nextC += n;
+            if (mat[nextR][nextC] != 0) {
+                int temp = dr;
+                dr = dc;
+                dc = -temp;
+            }
+            r += dr;
+            c += dc;
+        }
+
+        return mat;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number[][]}
+     */
+    generateMatrix(n) {
+        const mat = Array.from({ length: n }, () => Array(n).fill(0));
+        let r = 0, c = 0, dr = 0, dc = 1;
+
+        for (let val = 0; val < n * n; val++) {
+            mat[r][c] = val + 1;
+            let nextR = (r + dr) % n, nextC = (c + dc) % n;
+            if (nextR < 0) nextR += n;
+            if (nextC < 0) nextC += n;
+            if (mat[nextR][nextC] !== 0) {
+                [dr, dc] = [dc, -dr];
+            }
+            r += dr;
+            c += dc;
+        }
+
+        return mat;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$ for the output matrix.
\ No newline at end of file
diff --git a/articles/spiral-matrix.md b/articles/spiral-matrix.md
new file mode 100644
index 000000000..2e82fff76
--- /dev/null
+++ b/articles/spiral-matrix.md
@@ -0,0 +1,756 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def spiralOrder(self, matrix: List[List[int]]) -> List[int]:
+        m, n = len(matrix), len(matrix[0])
+        res = []
+
+        # append all the elements in the given direction
+        def dfs(row, col, r, c, dr, dc):
+            if row == 0 or col == 0:
+                return
+            
+            for i in range(col):
+                r += dr
+                c += dc
+                res.append(matrix[r][c])
+
+            # sub-problem
+            dfs(col, row - 1, r, c, dc, -dr)
+        
+        # start by going to the right
+        dfs(m, n, 0, -1, 0, 1)
+        return res
+```
+
+```java
+public class Solution {
+    public List<Integer> spiralOrder(int[][] matrix) {
+        int m = matrix.length, n = matrix[0].length;
+        List<Integer> res = new ArrayList<>();
+
+        // append all the elements in the given direction
+        dfs(m, n, 0, -1, 0, 1, matrix, res);
+        return res;
+    }
+
+    private void dfs(int row, int col, int r, int c, 
+                     int dr, int dc, int[][] matrix, List<Integer> res) {
+        if (row == 0 || col == 0) return;
+        
+        for (int i = 0; i < col; i++) {
+            r += dr;
+            c += dc;
+            res.add(matrix[r][c]);
+        }
+
+        // sub-problem
+        dfs(col, row - 1, r, c, dc, -dr, matrix, res);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> spiralOrder(vector<vector<int>>& matrix) {
+        int m = matrix.size(), n = matrix[0].size();
+        vector<int> res;
+
+        // append all the elements in the given direction
+        dfs(m, n, 0, -1, 0, 1, matrix, res);
+        return res;
+    }
+
+    void dfs(int row, int col, int r, int c, int dr, int dc, 
+             vector<vector<int>>& matrix, vector<int>& res) {
+        if (row == 0 || col == 0) return;
+        
+        for (int i = 0; i < col; i++) {
+            r += dr;
+            c += dc;
+            res.push_back(matrix[r][c]);
+        }
+
+        // sub-problem
+        dfs(col, row - 1, r, c, dc, -dr, matrix, res);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} matrix
+     * @return {number[]}
+     */
+    spiralOrder(matrix) {
+        const m = matrix.length, n = matrix[0].length;
+        const res = [];
+
+        // append all the elements in the given direction
+        const dfs = (row, col, r, c, dr, dc) => {
+            if (row === 0 || col === 0) return;
+
+            for (let i = 0; i < col; i++) {
+                r += dr;
+                c += dc;
+                res.push(matrix[r][c]);
+            }
+
+            // sub-problem
+            dfs(col, row - 1, r, c, dc, -dr);
+        };
+
+        // start by going to the right
+        dfs(m, n, 0, -1, 0, 1);
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<int> SpiralOrder(int[][] matrix) {
+        int m = matrix.Length, n = matrix[0].Length;
+        List<int> res = new List<int>();
+
+        // append all the elements in the given direction
+        Dfs(m, n, 0, -1, 0, 1, matrix, res);
+        return res;
+    }
+
+    private void Dfs(int row, int col, int r, int c, int dr, 
+                     int dc, int[][] matrix, List<int> res) {
+        if (row == 0 || col == 0) return;
+        
+        for (int i = 0; i < col; i++) {
+            r += dr;
+            c += dc;
+            res.Add(matrix[r][c]);
+        }
+
+        // sub-problem
+        Dfs(col, row - 1, r, c, dc, -dr, matrix, res);
+    }
+}
+```
+
+```go
+func spiralOrder(matrix [][]int) []int {
+	m, n := len(matrix), len(matrix[0])
+	res := []int{}
+
+	// Helper function for DFS traversal
+	var dfs func(row, col, r, c, dr, dc int)
+	dfs = func(row, col, r, c, dr, dc int) {
+		if row == 0 || col == 0 {
+			return
+		}
+
+		for i := 0; i < col; i++ {
+			r += dr
+			c += dc
+			res = append(res, matrix[r][c])
+		}
+
+		// Recursive call with updated direction and dimensions
+		dfs(col, row-1, r, c, dc, -dr)
+	}
+
+	// Start the DFS by going to the right
+	dfs(m, n, 0, -1, 0, 1)
+	return res
+}
+```
+
+```kotlin
+class Solution {
+    fun spiralOrder(matrix: Array<IntArray>): List<Int> {
+        val m = matrix.size
+        val n = matrix[0].size
+        val res = mutableListOf<Int>()
+
+        // Helper function for DFS traversal
+        fun dfs(row: Int, col: Int, r: Int, c: Int, dr: Int, dc: Int) {
+            if (row == 0 || col == 0) return
+
+            var newRow = r
+            var newCol = c
+
+            for (i in 0 until col) {
+                newRow += dr
+                newCol += dc
+                res.add(matrix[newRow][newCol])
+            }
+
+            // Recursive call with updated direction and dimensions
+            dfs(col, row - 1, newRow, newCol, dc, -dr)
+        }
+
+        // Start the DFS by going to the right
+        dfs(m, n, 0, -1, 0, 1)
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func spiralOrder(_ matrix: [[Int]]) -> [Int] {
+        var m = matrix.count
+        var n = matrix[0].count
+        var res: [Int] = []
+
+        // append all the elements in the given direction
+        func dfs(_ row: Int, _ col: Int, _ r: inout Int, _ c: inout Int, _ dr: Int, _ dc: Int) {
+            if row == 0 || col == 0 {
+                return
+            }
+
+            for _ in 0..<col {
+                r += dr
+                c += dc
+                res.append(matrix[r][c])
+            }
+
+            // sub-problem
+            dfs(col, row - 1, &r, &c, dc, -dr)
+        }
+
+        var r = 0
+        var c = -1
+
+        // start by going to the right
+        dfs(m, n, &r, &c, 0, 1)
+        return res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity:
+    * $O(min(m, n))$ space for recursion stack.
+    * $O(m * n)$ space for the output list.
+
+> Where $m$ is the number of rows and $n$ is the number of columns.
+
+---
+
+## 2. Iteration
+
+::tabs-start
+
+```python
+class Solution:
+    def spiralOrder(self, matrix: List[List[int]]) -> List[int]:
+        res = []
+        left, right = 0, len(matrix[0])
+        top, bottom = 0, len(matrix)
+
+        while left < right and top < bottom:
+            for i in range(left, right):
+                res.append(matrix[top][i])
+            top += 1
+            for i in range(top, bottom):
+                res.append(matrix[i][right - 1])
+            right -= 1
+            if not (left < right and top < bottom):
+                break
+            for i in range(right - 1, left - 1, -1):
+                res.append(matrix[bottom - 1][i])
+            bottom -= 1
+            for i in range(bottom - 1, top - 1, -1):
+                res.append(matrix[i][left])
+            left += 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public List<Integer> spiralOrder(int[][] matrix) {
+        List<Integer> res = new ArrayList<>();
+        int left = 0, right = matrix[0].length;
+        int top = 0, bottom = matrix.length;
+
+        while (left < right && top < bottom) {
+            for (int i = left; i < right; i++) {
+                res.add(matrix[top][i]);
+            }
+            top++;
+            for (int i = top; i < bottom; i++) {
+                res.add(matrix[i][right - 1]);
+            }
+            right--;
+            if (!(left < right && top < bottom)) {
+                break;
+            }
+            for (int i = right - 1; i >= left; i--) {
+                res.add(matrix[bottom - 1][i]);
+            }
+            bottom--;
+            for (int i = bottom - 1; i >= top; i--) {
+                res.add(matrix[i][left]);
+            }
+            left++;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> spiralOrder(vector<vector<int>>& matrix) {
+        vector<int> res;
+        int left = 0, right = matrix[0].size();
+        int top = 0, bottom = matrix.size();
+
+        while (left < right && top < bottom) {
+            for (int i = left; i < right; i++) {
+                res.push_back(matrix[top][i]);
+            }
+            top++;
+            for (int i = top; i < bottom; i++) {
+                res.push_back(matrix[i][right - 1]);
+            }
+            right--;
+            if (!(left < right && top < bottom)) {
+                break;
+            }
+            for (int i = right - 1; i >= left; i--) {
+                res.push_back(matrix[bottom - 1][i]);
+            }
+            bottom--;
+            for (int i = bottom - 1; i >= top; i--) {
+                res.push_back(matrix[i][left]);
+            }
+            left++;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} matrix
+     * @return {number[]}
+     */
+    spiralOrder(matrix) {
+        const res = [];
+        let left = 0;
+            let right = matrix[0].length;
+        let top = 0;
+            let bottom = matrix.length;
+
+        while (left < right && top < bottom) {
+            for (let i = left; i < right; i++) {
+                res.push(matrix[top][i]);
+            }
+            top++;
+            for (let i = top; i < bottom; i++) {
+                res.push(matrix[i][right - 1]);
+            }
+            right--;
+            if (!(left < right && top < bottom)) {
+                break;
+            }
+            for (let i = right - 1; i >= left; i--) {
+                res.push(matrix[bottom - 1][i]);
+            }
+            bottom--;
+            for (let i = bottom - 1; i >= top; i--) {
+                res.push(matrix[i][left]);
+            }
+            left++;
+        }
+
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<int> SpiralOrder(int[][] matrix) {
+        List<int> res = new List<int>();
+        int left = 0, right = matrix[0].Length;
+        int top = 0, bottom = matrix.Length;
+
+        while (left < right && top < bottom) {
+            for (int i = left; i < right; i++) {
+                res.Add(matrix[top][i]);
+            }
+            top++;
+            for (int i = top; i < bottom; i++) {
+                res.Add(matrix[i][right - 1]);
+            }
+            right--;
+            if (!(left < right && top < bottom)) {
+                break;
+            }
+            for (int i = right - 1; i >= left; i--) {
+                res.Add(matrix[bottom - 1][i]);
+            }
+            bottom--;
+            for (int i = bottom - 1; i >= top; i--) {
+                res.Add(matrix[i][left]);
+            }
+            left++;
+        }
+
+        return res;
+    }
+}
+```
+
+```go
+func spiralOrder(matrix [][]int) []int {
+	res := []int{}
+	if len(matrix) == 0 || len(matrix[0]) == 0 {
+		return res
+	}
+
+	left, right := 0, len(matrix[0])
+	top, bottom := 0, len(matrix)
+
+	for left < right && top < bottom {
+		for i := left; i < right; i++ {
+			res = append(res, matrix[top][i])
+		}
+		top++
+
+		for i := top; i < bottom; i++ {
+			res = append(res, matrix[i][right-1])
+		}
+		right--
+
+		if !(left < right && top < bottom) {
+			break
+		}
+
+		for i := right - 1; i >= left; i-- {
+			res = append(res, matrix[bottom-1][i])
+		}
+		bottom--
+
+		for i := bottom - 1; i >= top; i-- {
+			res = append(res, matrix[i][left])
+		}
+		left++
+	}
+
+	return res
+}
+```
+
+```kotlin
+class Solution {
+    fun spiralOrder(matrix: Array<IntArray>): List<Int> {
+        val res = mutableListOf<Int>()
+        if (matrix.isEmpty() || matrix[0].isEmpty()) return res
+
+        var left = 0
+        var right = matrix[0].size
+        var top = 0
+        var bottom = matrix.size
+
+        while (left < right && top < bottom) {
+            for (i in left until right) {
+                res.add(matrix[top][i])
+            }
+            top++
+
+            for (i in top until bottom) {
+                res.add(matrix[i][right - 1])
+            }
+            right--
+
+            if (!(left < right && top < bottom)) break
+
+            for (i in right - 1 downTo left) {
+                res.add(matrix[bottom - 1][i])
+            }
+            bottom--
+
+            for (i in bottom - 1 downTo top) {
+                res.add(matrix[i][left])
+            }
+            left++
+        }
+
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func spiralOrder(_ matrix: [[Int]]) -> [Int] {
+        var res: [Int] = []
+        var left = 0, right = matrix[0].count
+        var top = 0, bottom = matrix.count
+
+        while left < right && top < bottom {
+            for i in left..<right {
+                res.append(matrix[top][i])
+            }
+            top += 1
+            for i in top..<bottom {
+                res.append(matrix[i][right - 1])
+            }
+            right -= 1
+            if !(left < right && top < bottom) {
+                break
+            }
+            for i in stride(from: right - 1, through: left, by: -1) {
+                res.append(matrix[bottom - 1][i])
+            }
+            bottom -= 1
+            for i in stride(from: bottom - 1, through: top, by: -1) {
+                res.append(matrix[i][left])
+            }
+            left += 1
+        }
+
+        return res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(m * n)$ space for the output list.
+
+> Where $m$ is the number of rows and $n$ is the number of columns.
+
+---
+
+## 3. Iteration (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def spiralOrder(self, matrix: List[List[int]]) -> List[int]:
+        res = []
+        directions = [(0, 1), (1, 0), (0, -1), (-1, 0)]
+        steps = [len(matrix[0]), len(matrix) - 1]
+
+        r, c, d = 0, -1, 0
+        while steps[d & 1]:
+            for i in range(steps[d & 1]):
+                r += directions[d][0]
+                c += directions[d][1]
+                res.append(matrix[r][c])
+            steps[d & 1] -= 1
+            d += 1
+            d %= 4
+        return res
+```
+
+```java
+public class Solution {
+    public List<Integer> spiralOrder(int[][] matrix) {
+        List<Integer> res = new ArrayList<>();
+        int[][] directions = {{0, 1}, {1, 0}, {0, -1}, {-1, 0}};
+        int[] steps = {matrix[0].length, matrix.length - 1};
+
+        int r = 0, c = -1, d = 0;
+        while (steps[d % 2] > 0) {
+            for (int i = 0; i < steps[d % 2]; i++) {
+                r += directions[d][0];
+                c += directions[d][1];
+                res.add(matrix[r][c]);
+            }
+            steps[d % 2]--;
+            d = (d + 1) % 4;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> spiralOrder(vector<vector<int>>& matrix) {
+        vector<int> res;
+        vector<pair<int, int>> directions = {{0, 1}, {1, 0}, 
+                                             {0, -1}, {-1, 0}};
+        vector<int> steps = {matrix[0].size(), matrix.size() - 1};
+
+        int r = 0, c = -1, d = 0;
+        while (steps[d % 2]) {
+            for (int i = 0; i < steps[d % 2]; i++) {
+                r += directions[d].first;
+                c += directions[d].second;
+                res.push_back(matrix[r][c]);
+            }
+            steps[d % 2]--;
+            d = (d + 1) % 4;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} matrix
+     * @return {number[]}
+     */
+    spiralOrder(matrix) {
+        const res = [];
+        const directions = [[0, 1], [1, 0], [0, -1], [-1, 0]];
+        const steps = [matrix[0].length, matrix.length - 1];
+
+        let r = 0, c = -1, d = 0;
+        while (steps[d % 2]) {
+            for (let i = 0; i < steps[d % 2]; i++) {
+                r += directions[d][0];
+                c += directions[d][1];
+                res.push(matrix[r][c]);
+            }
+            steps[d % 2]--;
+            d = (d + 1) % 4;
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<int> SpiralOrder(int[][] matrix) {
+        var res = new List<int>();
+        var directions = new (int, int)[] { (0, 1), (1, 0), 
+                                            (0, -1), (-1, 0) };
+        var steps = new int[] { matrix[0].Length, matrix.Length - 1 };
+
+        int r = 0, c = -1, d = 0;
+        while (steps[d % 2] > 0) {
+            for (int i = 0; i < steps[d % 2]; i++) {
+                r += directions[d].Item1;
+                c += directions[d].Item2;
+                res.Add(matrix[r][c]);
+            }
+            steps[d % 2]--;
+            d = (d + 1) % 4;
+        }
+        return res;
+    }
+}
+```
+
+```go
+func spiralOrder(matrix [][]int) []int {
+	res := []int{}
+	if len(matrix) == 0 || len(matrix[0]) == 0 {
+		return res
+	}
+
+	directions := [4][2]int{{0, 1}, {1, 0}, {0, -1}, {-1, 0}}
+	steps := []int{len(matrix[0]), len(matrix) - 1}
+
+	r, c, d := 0, -1, 0
+
+	for steps[d&1] > 0 {
+		for i := 0; i < steps[d&1]; i++ {
+			r += directions[d][0]
+			c += directions[d][1]
+			res = append(res, matrix[r][c])
+		}
+		steps[d&1]-- 
+		d = (d + 1) % 4 
+	}
+
+	return res
+}
+```
+
+```kotlin
+class Solution {
+    fun spiralOrder(matrix: Array<IntArray>): List<Int> {
+        val res = mutableListOf<Int>()
+        if (matrix.isEmpty() || matrix[0].isEmpty()) return res
+
+        val directions = arrayOf(
+            intArrayOf(0, 1), 
+            intArrayOf(1, 0), 
+            intArrayOf(0, -1),
+            intArrayOf(-1, 0)
+        )
+        val steps = mutableListOf(matrix[0].size, matrix.size - 1)
+
+        var r = 0
+        var c = -1
+        var d = 0
+
+        while (steps[d and 1] > 0) {
+            for (i in 0 until steps[d and 1]) {
+                r += directions[d][0]
+                c += directions[d][1]
+                res.add(matrix[r][c])
+            }
+            steps[d and 1]-- 
+            d = (d + 1) % 4 
+        }
+
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func spiralOrder(_ matrix: [[Int]]) -> [Int] {
+        var res: [Int] = []
+        let directions = [(0, 1), (1, 0), (0, -1), (-1, 0)]
+        var steps = [matrix[0].count, matrix.count - 1]
+
+        var r = 0, c = -1, d = 0
+        while steps[d & 1] > 0 {
+            for _ in 0..<steps[d & 1] {
+                r += directions[d].0
+                c += directions[d].1
+                res.append(matrix[r][c])
+            }
+            steps[d & 1] -= 1
+            d += 1
+            d %= 4
+        }
+        return res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(m * n)$ space for the output list.
+
+> Where $m$ is the number of rows and $n$ is the number of columns.
\ No newline at end of file
diff --git a/articles/split-array-largest-sum.md b/articles/split-array-largest-sum.md
new file mode 100644
index 000000000..617691f9b
--- /dev/null
+++ b/articles/split-array-largest-sum.md
@@ -0,0 +1,1088 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def splitArray(self, nums: List[int], k: int) -> int:
+        n = len(nums)
+
+        def dfs(i, m):
+            if i == n:
+                return 0 if m == 0 else float("inf")
+            if m == 0:
+                return float("inf")
+
+            res = float("inf")
+            curSum = 0
+            for j in range(i, n - m + 1):
+                curSum += nums[j]
+                res = min(res, max(curSum, dfs(j + 1, m - 1)))
+
+            return res
+
+        return dfs(0, k)
+```
+
+```java
+public class Solution {
+    public int splitArray(int[] nums, int k) {
+        int n = nums.length;
+
+        return dfs(nums, 0, k, n);
+    }
+
+    private int dfs(int[] nums, int i, int m, int n) {
+        if (i == n) {
+            return m == 0 ? 0 : Integer.MAX_VALUE;
+        }
+        if (m == 0) {
+            return Integer.MAX_VALUE;
+        }
+
+        int res = Integer.MAX_VALUE;
+        int curSum = 0;
+        for (int j = i; j <= n - m; j++) {
+            curSum += nums[j];
+            res = Math.min(res, Math.max(curSum, dfs(nums, j + 1, m - 1, n)));
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int splitArray(vector<int>& nums, int k) {
+        int n = nums.size();
+        return dfs(nums, 0, k, n);
+    }
+
+private:
+    int dfs(vector<int>& nums, int i, int m, int n) {
+        if (i == n) {
+            return m == 0 ? 0 : INT_MAX;
+        }
+        if (m == 0) {
+            return INT_MAX;
+        }
+
+        int res = INT_MAX, curSum = 0;
+        for (int j = i; j <= n - m; j++) {
+            curSum += nums[j];
+            res = min(res, max(curSum, dfs(nums, j + 1, m - 1, n)));
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    splitArray(nums, k) {
+        const n = nums.length;
+
+        const dfs = (i, m) => {
+            if (i === n) {
+                return m === 0 ? 0 : Infinity;
+            }
+            if (m === 0) {
+                return Infinity;
+            }
+
+            let res = Infinity;
+            let curSum = 0;
+            for (let j = i; j <= n - m; j++) {
+                curSum += nums[j];
+                res = Math.min(res, Math.max(curSum, dfs(j + 1, m - 1)));
+            }
+
+            return res;
+        };
+
+        return dfs(0, k);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int SplitArray(int[] nums, int k) {
+        int n = nums.Length;
+        return Dfs(nums, 0, k, n);
+    }
+
+    private int Dfs(int[] nums, int i, int m, int n) {
+        if (i == n) {
+            return m == 0 ? 0 : int.MaxValue;
+        }
+        if (m == 0) {
+            return int.MaxValue;
+        }
+
+        int res = int.MaxValue;
+        int curSum = 0;
+        for (int j = i; j <= n - m; j++) {
+            curSum += nums[j];
+            int next = Dfs(nums, j + 1, m - 1, n);
+            if (next != int.MaxValue) {
+                res = Math.Min(res, Math.Max(curSum, next));
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * 2 ^ n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def splitArray(self, nums: List[int], k: int) -> int:
+        n = len(nums)
+        dp = [[-1] * (k + 1) for _ in range(n)]
+
+        def dfs(i, m):
+            if i == n:
+                return 0 if m == 0 else float("inf")
+            if m == 0:
+                return float("inf")
+            if dp[i][m] != -1:
+                return dp[i][m]
+
+            res = float("inf")
+            curSum = 0
+            for j in range(i, n - m + 1):
+                curSum += nums[j]
+                res = min(res, max(curSum, dfs(j + 1, m - 1)))
+            
+            dp[i][m] = res
+            return res
+
+        return dfs(0, k)
+```
+
+```java
+public class Solution {
+    private int[][] dp;
+
+    public int splitArray(int[] nums, int k) {
+        int n = nums.length;
+        dp = new int[n][k + 1];
+        for (int[] it : dp) {
+            Arrays.fill(it, -1);
+        }
+        return dfs(nums, 0, k, n);
+    }
+
+    private int dfs(int[] nums, int i, int m, int n) {
+        if (i == n) {
+            return m == 0 ? 0 : Integer.MAX_VALUE;
+        }
+        if (m == 0) {
+            return Integer.MAX_VALUE;
+        }
+        if (dp[i][m] != -1) {
+            return dp[i][m];
+        }
+
+        int res = Integer.MAX_VALUE;
+        int curSum = 0;
+        for (int j = i; j <= n - m; j++) {
+            curSum += nums[j];
+            res = Math.min(res, Math.max(curSum, dfs(nums, j + 1, m - 1, n)));
+        }
+
+        return dp[i][m] = res;
+    }
+}
+```
+
+```cpp
+class Solution {
+    vector<vector<int>> dp;
+
+public:
+    int splitArray(vector<int>& nums, int k) {
+        int n = nums.size();
+        dp.assign(n, vector<int>(k + 1, -1));
+        return dfs(nums, 0, k, n);
+    }
+
+private:
+    int dfs(vector<int>& nums, int i, int m, int n) {
+        if (i == n) {
+            return m == 0 ? 0 : INT_MAX;
+        }
+        if (m == 0) {
+            return INT_MAX;
+        }
+        if (dp[i][m] != -1) {
+            return dp[i][m];
+        }
+
+        int res = INT_MAX, curSum = 0;
+        for (int j = i; j <= n - m; j++) {
+            curSum += nums[j];
+            res = min(res, max(curSum, dfs(nums, j + 1, m - 1, n)));
+        }
+
+        return dp[i][m] = res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    splitArray(nums, k) {
+        const n = nums.length;
+        const dp = Array.from({ length: n }, () => Array(k + 1).fill(-1));
+
+        const dfs = (i, m) => {
+            if (i === n) {
+                return m === 0 ? 0 : Infinity;
+            }
+            if (m === 0) {
+                return Infinity;
+            }
+            if (dp[i][m] !== -1) {
+                return dp[i][m];
+            }
+
+            let res = Infinity;
+            let curSum = 0;
+            for (let j = i; j <= n - m; j++) {
+                curSum += nums[j];
+                res = Math.min(res, Math.max(curSum, dfs(j + 1, m - 1)));
+            }
+
+            return dp[i][m] = res;
+        };
+
+        return dfs(0, k);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    private int[,] dp;
+
+    public int SplitArray(int[] nums, int k) {
+        int n = nums.Length;
+        dp = new int[n, k + 1];
+
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j <= k; j++) {
+                dp[i, j] = -1;
+            }
+        }
+
+        return Dfs(nums, 0, k, n);
+    }
+
+    private int Dfs(int[] nums, int i, int m, int n) {
+        if (i == n) {
+            return m == 0 ? 0 : int.MaxValue;
+        }
+        if (m == 0) {
+            return int.MaxValue;
+        }
+        if (dp[i, m] != -1) {
+            return dp[i, m];
+        }
+
+        int res = int.MaxValue;
+        int curSum = 0;
+        for (int j = i; j <= n - m; j++) {
+            curSum += nums[j];
+            int next = Dfs(nums, j + 1, m - 1, n);
+            if (next != int.MaxValue) {
+                res = Math.Min(res, Math.Max(curSum, next));
+            }
+        }
+
+        dp[i, m] = res;
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(k * n ^ 2)$
+* Space complexity: $O(k * n)$
+
+> Where $n$ is the size of the array $nums$ and $k$ is the number of sub-arrays to form.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def splitArray(self, nums: List[int], k: int) -> int:
+        n = len(nums)
+        dp = [[float("inf")] * (k + 1) for _ in range(n + 1)]
+        dp[n][0] = 0
+
+        for m in range(1, k + 1):
+            for i in range(n - 1, -1, -1):
+                curSum = 0
+                for j in range(i, n - m + 1):
+                    curSum += nums[j]
+                    dp[i][m] = min(dp[i][m], max(curSum, dp[j + 1][m - 1]))
+
+        return dp[0][k]
+```
+
+```java
+public class Solution {
+    public int splitArray(int[] nums, int k) {
+        int n = nums.length;
+        int[][] dp = new int[n + 1][k + 1];
+        for (int[] it : dp) {
+            Arrays.fill(it, Integer.MAX_VALUE);
+        }
+        dp[n][0] = 0;
+
+        for (int m = 1; m <= k; m++) {
+            for (int i = n - 1; i >= 0; i--) {
+                int curSum = 0;
+                for (int j = i; j < n - m + 1; j++) {
+                    curSum += nums[j];
+                    dp[i][m] = Math.min(dp[i][m], Math.max(curSum, dp[j + 1][m - 1]));
+                }
+            }
+        }
+
+        return dp[0][k];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int splitArray(vector<int>& nums, int k) {
+        int n = nums.size();
+        vector<vector<int>> dp(n + 1, vector<int>(k + 1, INT_MAX));
+        dp[n][0] = 0;
+
+        for (int m = 1; m <= k; m++) {
+            for (int i = n - 1; i >= 0; i--) {
+                int curSum = 0;
+                for (int j = i; j < n - m + 1; j++) {
+                    curSum += nums[j];
+                    dp[i][m] = min(dp[i][m], max(curSum, dp[j + 1][m - 1]));
+                }
+            }
+        }
+
+        return dp[0][k];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    splitArray(nums, k) {
+        const n = nums.length;
+        const dp = Array.from({ length: n + 1 }, () => 
+            Array(k + 1).fill(Infinity)
+        );
+        dp[n][0] = 0;
+
+        for (let m = 1; m <= k; m++) {
+            for (let i = n - 1; i >= 0; i--) {
+                let curSum = 0;
+                for (let j = i; j < n - m + 1; j++) {
+                    curSum += nums[j];
+                    dp[i][m] = Math.min(dp[i][m], Math.max(curSum, dp[j + 1][m - 1]));
+                }
+            }
+        }
+
+        return dp[0][k];
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int SplitArray(int[] nums, int k) {
+        int n = nums.Length;
+        int[,] dp = new int[n + 1, k + 1];
+
+        for (int i = 0; i <= n; i++) {
+            for (int j = 0; j <= k; j++) {
+                dp[i, j] = int.MaxValue;
+            }
+        }
+
+        dp[n, 0] = 0;
+
+        for (int m = 1; m <= k; m++) {
+            for (int i = n - 1; i >= 0; i--) {
+                int curSum = 0;
+                for (int j = i; j < n - m + 1; j++) {
+                    curSum += nums[j];
+                    if (dp[j + 1, m - 1] != int.MaxValue) {
+                        dp[i, m] = Math.Min(dp[i, m], Math.Max(curSum, dp[j + 1, m - 1]));
+                    }
+                }
+            }
+        }
+
+        return dp[0, k];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(k * n ^ 2)$
+* Space complexity: $O(k * n)$
+
+> Where $n$ is the size of the array $nums$ and $k$ is the number of sub-arrays to form.
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def splitArray(self, nums: List[int], k: int) -> int:
+        n = len(nums)
+        dp = [float("inf")] * (n + 1)
+        dp[n] = 0
+
+        for m in range(1, k + 1):
+            nextDp = [float("inf")] * (n + 1)
+            for i in range(n - 1, -1, -1):
+                curSum = 0
+                for j in range(i, n - m + 1):
+                    curSum += nums[j]
+                    nextDp[i] = min(nextDp[i], max(curSum, dp[j + 1]))
+            dp = nextDp
+
+        return dp[0]
+```
+
+```java
+public class Solution {
+    public int splitArray(int[] nums, int k) {
+        int n = nums.length;
+        int[] dp = new int[n + 1];
+        int[] nextDp = new int[n + 1];
+        Arrays.fill(dp, Integer.MAX_VALUE);
+        dp[n] = 0;
+
+        for (int m = 1; m <= k; m++) {
+            Arrays.fill(nextDp, Integer.MAX_VALUE);
+            for (int i = n - 1; i >= 0; i--) {
+                int curSum = 0;
+                for (int j = i; j < n - m + 1; j++) {
+                    curSum += nums[j];
+                    nextDp[i] = Math.min(nextDp[i], Math.max(curSum, dp[j + 1]));
+                }
+            }
+            int[] temp = dp;
+            dp = nextDp;
+            nextDp = temp;
+        }
+
+        return dp[0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int splitArray(vector<int>& nums, int k) {
+        int n = nums.size();
+        vector<int> dp(n + 1, INT_MAX), nextDp(n + 1, INT_MAX);
+        dp[n] = 0;
+
+        for (int m = 1; m <= k; m++) {
+            fill(nextDp.begin(), nextDp.end(), INT_MAX);
+            for (int i = n - 1; i >= 0; i--) {
+                int curSum = 0;
+                for (int j = i; j < n - m + 1; j++) {
+                    curSum += nums[j];
+                    nextDp[i] = min(nextDp[i], max(curSum, dp[j + 1]));
+                }
+            }
+            dp.swap(nextDp);
+        }
+
+        return dp[0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    splitArray(nums, k) {
+        const n = nums.length;
+        let dp = new Array(n + 1).fill(Infinity);
+        let nextDp = new Array(n + 1).fill(Infinity);
+        dp[n] = 0;
+
+        for (let m = 1; m <= k; m++) {
+            nextDp.fill(Infinity);
+            for (let i = n - 1; i >= 0; i--) {
+                let curSum = 0;
+                for (let j = i; j < n - m + 1; j++) {
+                    curSum += nums[j];
+                    nextDp[i] = Math.min(nextDp[i], Math.max(curSum, dp[j + 1]));
+                }
+            }
+            [dp, nextDp] = [nextDp, dp];
+        }
+
+        return dp[0];
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int SplitArray(int[] nums, int k) {
+        int n = nums.Length;
+        int[] dp = new int[n + 1];
+        int[] nextDp = new int[n + 1];
+        Array.Fill(dp, int.MaxValue);
+        dp[n] = 0;
+
+        for (int m = 1; m <= k; m++) {
+            Array.Fill(nextDp, int.MaxValue);
+            for (int i = n - 1; i >= 0; i--) {
+                int curSum = 0;
+                for (int j = i; j < n - m + 1; j++) {
+                    curSum += nums[j];
+                    if (dp[j + 1] != int.MaxValue) {
+                        nextDp[i] = Math.Min(nextDp[i], Math.Max(curSum, dp[j + 1]));
+                    }
+                }
+            }
+            var temp = dp;
+            dp = nextDp;
+            nextDp = temp;
+        }
+
+        return dp[0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(k * n ^ 2)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the size of the array $nums$ and $k$ is the number of sub-arrays to form.
+
+---
+
+## 5. Binary Search
+
+::tabs-start
+
+```python
+class Solution:
+    def splitArray(self, nums: List[int], k: int) -> int:
+        def canSplit(largest):
+            subarray = 1
+            curSum = 0
+            for num in nums:
+                curSum += num
+                if curSum > largest:
+                    subarray += 1
+                    if subarray > k:
+                        return False
+                    curSum = num
+            return True
+
+        l, r = max(nums), sum(nums)
+        res = r
+        while l <= r:
+            mid = l + (r - l) // 2
+            if canSplit(mid):
+                res = mid
+                r = mid - 1
+            else:
+                l = mid + 1
+        return res
+```
+
+```java
+public class Solution {
+    public int splitArray(int[] nums, int k) {
+        int l = 0, r = 0, res = 0;
+        for (int num : nums) {
+            l = Math.max(l, num);
+            r += num;
+        }
+        res = r;
+
+        while (l <= r) {
+            int mid = l + (r - l) / 2;
+            if (canSplit(nums, k, mid)) {
+                res = mid;
+                r = mid - 1;
+            } else {
+                l = mid + 1;
+            }
+        }
+        return res;
+    }
+
+    private boolean canSplit(int[] nums, int k, int largest) {
+        int subarray = 1, curSum = 0;
+        for (int num : nums) {
+            curSum += num;
+            if (curSum > largest) {
+                subarray++;
+                if (subarray > k) return false;
+                curSum = num;
+            }
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int splitArray(vector<int>& nums, int k) {
+        int l = *max_element(nums.begin(), nums.end());
+        int r = accumulate(nums.begin(), nums.end(), 0);
+        int res = r;
+
+        while (l <= r) {
+            int mid = l + (r - l) / 2;
+            if (canSplit(nums, k, mid)) {
+                res = mid;
+                r = mid - 1;
+            } else {
+                l = mid + 1;
+            }
+        }
+        return res;
+    }
+
+private:
+    bool canSplit(vector<int>& nums, int k, int largest) {
+        int subarray = 1, curSum = 0;
+        for (int num : nums) {
+            curSum += num;
+            if (curSum > largest) {
+                subarray++;
+                if (subarray > k) return 0;
+                curSum = num;
+            }
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    splitArray(nums, k) {
+        const canSplit = (largest) => {
+            let subarray = 1, curSum = 0;
+            for (const num of nums) {
+                curSum += num;
+                if (curSum > largest) {
+                    subarray++;
+                    if (subarray > k) return false;
+                    curSum = num;
+                }
+            }
+            return true;
+        };
+
+        let l = Math.max(...nums);
+        let r = nums.reduce((a, b) => a + b, 0);
+        let res = r;
+
+        while (l <= r) {
+            const mid = Math.floor(l + (r - l) / 2);
+            if (canSplit(mid)) {
+                res = mid;
+                r = mid - 1;
+            } else {
+                l = mid + 1;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int SplitArray(int[] nums, int k) {
+        int l = 0, r = 0, res = 0;
+        foreach (int num in nums) {
+            l = Math.Max(l, num);
+            r += num;
+        }
+        res = r;
+
+        while (l <= r) {
+            int mid = l + (r - l) / 2;
+            if (CanSplit(nums, k, mid)) {
+                res = mid;
+                r = mid - 1;
+            } else {
+                l = mid + 1;
+            }
+        }
+        return res;
+    }
+
+    private bool CanSplit(int[] nums, int k, int largest) {
+        int subarray = 1, curSum = 0;
+        foreach (int num in nums) {
+            curSum += num;
+            if (curSum > largest) {
+                subarray++;
+                if (subarray > k) return false;
+                curSum = num;
+            }
+        }
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log s)$
+* Space complexity: $O(1)$
+
+> Where $n$ is the size of the array $nums$ and $s$ is the sum of all the elements in the array.
+
+---
+
+## 6. Binary Search + Prefix Sum
+
+::tabs-start
+
+```python
+class Solution:
+    def splitArray(self, nums: List[int], k: int) -> int:
+        n = len(nums)
+        prefix = [0] * (n + 1)
+        for i in range(n):
+            prefix[i + 1] = prefix[i] + nums[i]
+
+        def canSplit(largest):
+            subarrays = 0
+            i = 0
+            while i < n:
+                l, r = i + 1, n
+                while l <= r:
+                    mid = l + (r - l) // 2
+                    if prefix[mid] - prefix[i] <= largest:
+                        l = mid + 1
+                    else:
+                        r = mid - 1
+                subarrays += 1
+                i = r
+                if subarrays > k:
+                    return False
+            return True
+
+        l, r = max(nums), sum(nums)
+        res = r
+        while l <= r:
+            mid = l + (r - l) // 2
+            if canSplit(mid):
+                res = mid
+                r = mid - 1
+            else:
+                l = mid + 1
+
+        return res
+```
+
+```java
+public class Solution {
+    private int[] prefix;
+    private int n;
+
+    public int splitArray(int[] nums, int k) {
+        n = nums.length;
+        prefix = new int[n + 1];
+        for (int i = 0; i < n; i++) {
+            prefix[i + 1] = prefix[i] + nums[i];
+        }
+
+        int l = Integer.MIN_VALUE, r = 0;
+        for (int num : nums) {
+            l = Math.max(l, num);
+            r += num;
+        }
+
+        int res = r;
+        while (l <= r) {
+            int mid = l + (r - l) / 2;
+            if (canSplit(mid, k)) {
+                res = mid;
+                r = mid - 1;
+            } else {
+                l = mid + 1;
+            }
+        }
+        return res;
+    }
+
+    private boolean canSplit(int largest, int k) {
+        int subarrays = 0, i = 0;
+        while (i < n) {
+            int l = i + 1, r = n;
+            while (l <= r) {
+                int mid = l + (r - l) / 2;
+                if (prefix[mid] - prefix[i] <= largest) {
+                    l = mid + 1;
+                } else {
+                    r = mid - 1;
+                }
+            }
+            subarrays++;
+            i = r;
+            if (subarrays > k) {
+                return false;
+            }
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<int> prefix;
+    int n;
+
+public:
+    int splitArray(vector<int>& nums, int k) {
+        n = nums.size();
+        prefix.resize(n + 1, 0);
+        for (int i = 0; i < n; ++i) {
+            prefix[i + 1] = prefix[i] + nums[i];
+        }
+
+        int l = *max_element(nums.begin(), nums.end());
+        int r = accumulate(nums.begin(), nums.end(), 0);
+        int res = r;
+
+        while (l <= r) {
+            int mid = l + (r - l) / 2;
+            if (canSplit(mid, k)) {
+                res = mid;
+                r = mid - 1;
+            } else {
+                l = mid + 1;
+            }
+        }
+
+        return res;
+    }
+
+private:
+    bool canSplit(int largest, int k) {
+        int subarrays = 0, i = 0;
+        while (i < n) {
+            int l = i + 1, r = n;
+            while (l <= r) {
+                int mid = l + (r - l) / 2;
+                if (prefix[mid] - prefix[i] <= largest) {
+                    l = mid + 1;
+                } else {
+                    r = mid - 1;
+                }
+            }
+            subarrays++;
+            i = r;
+            if (subarrays > k) {
+                return false;
+            }
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    splitArray(nums, k) {
+        const n = nums.length;
+        const prefix = new Array(n + 1).fill(0);
+        for (let i = 0; i < n; i++) {
+            prefix[i + 1] = prefix[i] + nums[i];
+        }
+
+        const canSplit = (largest) => {
+            let subarrays = 0, i = 0;
+            while (i < n) {
+                let l = i + 1, r = n;
+                while (l <= r) {
+                    const mid = Math.floor(l + (r - l) / 2);
+                    if (prefix[mid] - prefix[i] <= largest) {
+                        l = mid + 1;
+                    } else {
+                        r = mid - 1;
+                    }
+                }
+                subarrays++;
+                i = r;
+                if (subarrays > k) {
+                    return false;
+                }
+            }
+            return true;
+        };
+
+        let l = Math.max(...nums);
+        let r = nums.reduce((a, b) => a + b, 0), res = r;
+        while (l <= r) {
+            const mid = Math.floor(l + (r - l) / 2);
+            if (canSplit(mid)) {
+                res = mid;
+                r = mid - 1;
+            } else {
+                l = mid + 1;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    private int[] prefix;
+    private int n;
+
+    public int SplitArray(int[] nums, int k) {
+        n = nums.Length;
+        prefix = new int[n + 1];
+        for (int i = 0; i < n; i++) {
+            prefix[i + 1] = prefix[i] + nums[i];
+        }
+
+        int l = int.MinValue, r = 0;
+        foreach (int num in nums) {
+            l = Math.Max(l, num);
+            r += num;
+        }
+
+        int res = r;
+        while (l <= r) {
+            int mid = l + (r - l) / 2;
+            if (CanSplit(mid, k)) {
+                res = mid;
+                r = mid - 1;
+            } else {
+                l = mid + 1;
+            }
+        }
+        return res;
+    }
+
+    private bool CanSplit(int largest, int k) {
+        int subarrays = 0, i = 0;
+        while (i < n) {
+            int l = i + 1, r = n;
+            while (l <= r) {
+                int mid = l + (r - l) / 2;
+                if (prefix[mid] - prefix[i] <= largest) {
+                    l = mid + 1;
+                } else {
+                    r = mid - 1;
+                }
+            }
+            subarrays++;
+            i = r;
+            if (subarrays > k) {
+                return false;
+            }
+        }
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + (k * \log n * \log s))$
+* Space complexity: $O(n)$
+
+> Where $n$ is the size of the array $nums$, $s$ is the sum of all the elements in the array, and $k$ is the number of sub-arrays to form.
\ No newline at end of file
diff --git a/articles/split-linked-list-in-parts.md b/articles/split-linked-list-in-parts.md
new file mode 100644
index 000000000..5df42573a
--- /dev/null
+++ b/articles/split-linked-list-in-parts.md
@@ -0,0 +1,343 @@
+## 1. Convert To Array
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def splitListToParts(self, head: Optional[ListNode], k: int) -> List[Optional[ListNode]]:
+        arr, cur = [], head
+        while cur:
+            arr.append(cur)
+            cur = cur.next
+
+        N = len(arr)
+        base_len, remainder = N // k, N % k
+
+        res = [None] * k
+        start = 0
+        for i in range(k):
+            if start < N:
+                res[i] = arr[start]
+                tail = start + base_len - 1
+                if remainder:
+                    tail += 1
+                    remainder -= 1
+                arr[tail].next = None
+                start = tail + 1
+
+        return res
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode[] splitListToParts(ListNode head, int k) {
+        List<ListNode> arr = new ArrayList<>();
+        for (ListNode cur = head; cur != null; cur = cur.next) {
+            arr.add(cur);
+        }
+
+        int N = arr.size();
+        int base_len = N / k, remainder = N % k;
+
+        ListNode[] res = new ListNode[k];
+        int start = 0;
+        for (int i = 0; i < k; i++) {
+            if (start < N) {
+                res[i] = arr.get(start);
+                int tail = start + base_len - 1;
+                if (remainder > 0) {
+                    tail++;
+                    remainder--;
+                }
+                arr.get(tail).next = null;
+                start = tail + 1;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    vector<ListNode*> splitListToParts(ListNode* head, int k) {
+        vector<ListNode*> arr;
+        for (ListNode* cur = head; cur != nullptr; cur = cur->next) {
+            arr.push_back(cur);
+        }
+
+        int N = arr.size();
+        int base_len = N / k, remainder = N % k;
+
+        vector<ListNode*> res(k, nullptr);
+        int start = 0;
+        for (int i = 0; i < k; i++) {
+            if (start < N) {
+                res[i] = arr[start];
+                int tail = start + base_len - 1;
+                if (remainder > 0) {
+                    tail++;
+                    remainder--;
+                }
+                arr[tail]->next = nullptr;
+                start = tail + 1;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @param {number} k
+     * @return {ListNode[]}
+     */
+    splitListToParts(head, k) {
+        let arr = [];
+        for (let cur = head; cur !== null; cur = cur.next) {
+            arr.push(cur);
+        }
+
+        let N = arr.length;
+        let base_len = Math.floor(N / k), remainder = N % k;
+
+        let res = new Array(k).fill(null);
+        let start = 0;
+        for (let i = 0; i < k; i++) {
+            if (start < N) {
+                res[i] = arr[start];
+                let tail = start + base_len - 1;
+                if (remainder > 0) {
+                    tail++;
+                    remainder--;
+                }
+                arr[tail].next = null;
+                start = tail + 1;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Iteration
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def splitListToParts(self, head: Optional[ListNode], k: int) -> List[Optional[ListNode]]:
+        length, curr = 0, head
+        while curr:
+            curr = curr.next
+            length += 1
+
+        base_len, remainder = length // k, length % k
+        curr, res = head, []
+        
+        for i in range(k):
+            res.append(curr)
+            for j in range(base_len - 1 + (1 if remainder else 0)):
+                if not curr:
+                    break
+                curr = curr.next
+            remainder -= 1 if remainder else 0
+            if curr:
+                curr.next, curr = None, curr.next
+
+        return res
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode[] splitListToParts(ListNode head, int k) {
+        int length = 0;
+        ListNode curr = head;
+        while (curr != null) {
+            curr = curr.next;
+            length++;
+        }
+
+        int baseLen = length / k, remainder = length % k;
+        ListNode[] res = new ListNode[k];
+        curr = head;
+
+        for (int i = 0; i < k; i++) {
+            res[i] = curr;
+            for (int j = 0; j < baseLen - 1 + (remainder > 0 ? 1 : 0); j++) {
+                if (curr == null) break;
+                curr = curr.next;
+            }
+            if (curr != null) {
+                ListNode temp = curr.next;
+                curr.next = null;
+                curr = temp;
+            }
+            remainder--;
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    vector<ListNode*> splitListToParts(ListNode* head, int k) {
+        int length = 0;
+        ListNode* curr = head;
+        while (curr) {
+            curr = curr->next;
+            length++;
+        }
+
+        int baseLen = length / k, remainder = length % k;
+        vector<ListNode*> res(k, nullptr);
+        curr = head;
+
+        for (int i = 0; i < k; i++) {
+            res[i] = curr;
+            for (int j = 0; j < baseLen - 1 + (remainder > 0 ? 1 : 0); j++) {
+                if (!curr) break;
+                curr = curr->next;
+            }
+            if (curr) {
+                ListNode* temp = curr->next;
+                curr->next = nullptr;
+                curr = temp;
+            }
+            remainder--;
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @param {number} k
+     * @return {ListNode[]}
+     */
+    splitListToParts(head, k) {
+        let length = 0, curr = head;
+        while (curr) {
+            curr = curr.next;
+            length++;
+        }
+
+        let baseLen = Math.floor(length / k), remainder = length % k;
+        let res = new Array(k).fill(null);
+        curr = head;
+
+        for (let i = 0; i < k; i++) {
+            res[i] = curr;
+            for (let j = 0; j < baseLen - 1 + (remainder > 0 ? 1 : 0); j++) {
+                if (!curr) break;
+                curr = curr.next;
+            }
+            if (curr) {
+                let temp = curr.next;
+                curr.next = null;
+                curr = temp;
+            }
+            remainder--;
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n)$ space for the output array.
\ No newline at end of file
diff --git a/articles/splitting-a-string-into-descending-consecutive-values.md b/articles/splitting-a-string-into-descending-consecutive-values.md
new file mode 100644
index 000000000..b736eda11
--- /dev/null
+++ b/articles/splitting-a-string-into-descending-consecutive-values.md
@@ -0,0 +1,570 @@
+## 1. Backtracking
+
+::tabs-start
+
+```python
+class Solution:
+    def splitString(self, s: str) -> bool:
+        n = len(s)
+
+        def isValid(splits):
+            for i in range(1, len(splits)):
+                if splits[i] != splits[i - 1] - 1:
+                    return False
+            return len(splits) > 1
+
+        def dfs(i, splits):
+            if i == n:
+                return isValid(splits)
+            num = 0
+            for j in range(i, n):
+                num = num * 10 + int(s[j])
+                splits.append(num)
+                if dfs(j + 1, splits):
+                    return True
+                splits.pop()
+            return False
+
+        return dfs(0, [])
+```
+
+```java
+public class Solution {
+    public boolean splitString(String s) {
+        return dfs(s, 0, new ArrayList<>());
+    }
+
+    private boolean isValid(List<Long> splits) {
+        for (int i = 1; i < splits.size(); i++) {
+            if (splits.get(i) != splits.get(i - 1) - 1) {
+                return false;
+            }
+        }
+        return splits.size() > 1;
+    }
+
+    private boolean dfs(String s, int i, List<Long> splits) {
+        if (i == s.length()) {
+            return isValid(splits);
+        }
+        long num = 0;
+        for (int j = i; j < s.length(); j++) {
+            num = num * 10 + (s.charAt(j) - '0');
+            splits.add(num);
+            if (dfs(s, j + 1, splits)) {
+                return true;
+            }
+            splits.remove(splits.size() - 1);
+        }
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool splitString(string s) {
+        vector<long long> splits;
+        return dfs(s, 0, splits);
+    }
+
+private:
+    bool isValid(vector<long long>& splits) {
+        for (int i = 1; i < splits.size(); i++) {
+            if (splits[i] != splits[i - 1] - 1) {
+                return false;
+            }
+        }
+        return splits.size() > 1;
+    }
+
+    bool dfs(string& s, int i, vector<long long>& splits) {
+        if (i == s.size()) {
+            return isValid(splits);
+        }
+        unsigned long long num = 0;
+        for (int j = i; j < s.size(); j++) {
+            num = num * 10 + (s[j] - '0');
+            splits.push_back(num);
+            if (dfs(s, j + 1, splits)) {
+                return true;
+            }
+            splits.pop_back();
+        }
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {boolean}
+     */
+    splitString(s) {
+        const n = s.length;
+
+        const isValid = (splits) => {
+            for (let i = 1; i < splits.length; i++) {
+                if (splits[i] !== splits[i - 1] - 1) {
+                    return false;
+                }
+            }
+            return splits.length > 1;
+        };
+
+        const dfs = (i, splits) => {
+            if (i === n) {
+                return isValid(splits);
+            }
+            let num = 0;
+            for (let j = i; j < n; j++) {
+                num = num * 10 + Number(s[j]);
+                splits.push(num);
+                if (dfs(j + 1, splits)) {
+                    return true;
+                }
+                splits.pop();
+            }
+            return false;
+        };
+
+        return dfs(0, []);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Recursion - I
+
+::tabs-start
+
+```python
+class Solution:
+    def splitString(self, s: str) -> bool:
+        def dfs(index, prev):
+            if index == len(s):
+                return True
+            num = 0
+            for j in range(index, len(s)):
+                num = num * 10 + int(s[j])
+                if num + 1 == prev and dfs(j + 1, num):
+                    return True
+            return False
+
+        val = 0
+        for i in range(len(s) - 1):
+            val = val * 10 + int(s[i])
+            if dfs(i + 1, val):
+                return True
+
+        return False
+```
+
+```java
+public class Solution {
+    public boolean splitString(String s) {
+        int n = s.length();
+        long val = 0;
+        for (int i = 0; i < n - 1; i++) {
+            val = val * 10 + (s.charAt(i) - '0');
+            if (dfs(s, i + 1, val)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    private boolean dfs(String s, int index, long prev) {
+        if (index == s.length()) {
+            return true;
+        }
+        long num = 0;
+        for (int j = index; j < s.length(); j++) {
+            num = num * 10 + (s.charAt(j) - '0');
+            if (num + 1 == prev && dfs(s, j + 1, num)) {
+                return true;
+            }
+        }
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool splitString(string s) {
+        int n = s.size();
+        unsigned long long val = 0;
+        for (int i = 0; i < n - 1; i++) {
+            val = val * 10 + (s[i] - '0');
+            if (dfs(s, i + 1, val)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+private:
+    bool dfs(string& s, int index, long long prev) {
+        if (index == s.size()) {
+            return true;
+        }
+        unsigned long long num = 0;
+        for (int j = index; j < s.size(); j++) {
+            num = num * 10 + (s[j] - '0');
+            if (num + 1 == prev && dfs(s, j + 1, num)) {
+                return true;
+            }
+        }
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {boolean}
+     */
+    splitString(s) {
+        const n = s.length;
+
+        const dfs = (index, prev) => {
+            if (index === n) {
+                return true;
+            }
+            let num = 0;
+            for (let j = index; j < n; j++) {
+                num = num * 10 + Number(s[j]);
+                if (num + 1 === prev && dfs(j + 1, num)) {
+                    return true;
+                }
+            }
+            return false;
+        };
+
+        let val = 0;
+        for (let i = 0; i < n - 1; i++) {
+            val = val * 10 + Number(s[i]);
+            if (dfs(i + 1, val)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 3. Recursion - II
+
+::tabs-start
+
+```python
+class Solution:
+    def splitString(self, s: str) -> bool:
+        def dfs(index, prev):
+            if index == len(s):
+                return True
+            num = 0
+            for j in range(index, len(s)):
+                num = num * 10 + int(s[j])
+                if num + 1 == prev and dfs(j + 1, num):
+                    return True
+                if num >= prev:
+                    break
+            return False
+
+        val = 0
+        for i in range(len(s) - 1):
+            val = val * 10 + int(s[i])
+            if dfs(i + 1, val):
+                return True
+
+        return False
+```
+
+```java
+public class Solution {
+    public boolean splitString(String s) {
+        int n = s.length();
+        long val = 0;
+        for (int i = 0; i < n - 1; i++) {
+            val = val * 10 + (s.charAt(i) - '0');
+            if (dfs(s, i + 1, val)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    private boolean dfs(String s, int index, long prev) {
+        if (index == s.length()) {
+            return true;
+        }
+        long num = 0;
+        for (int j = index; j < s.length(); j++) {
+            num = num * 10 + (s.charAt(j) - '0');
+            if (num + 1 == prev && dfs(s, j + 1, num)) {
+                return true;
+            }
+            if (num >= prev) {
+                break;
+            }
+        }
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool splitString(string s) {
+        int n = s.size();
+        unsigned long long val = 0;
+        for (int i = 0; i < n - 1; i++) {
+            val = val * 10 + (s[i] - '0');
+            if (dfs(s, i + 1, val)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+private:
+    bool dfs(string& s, int index, long long prev) {
+        if (index == s.size()) {
+            return true;
+        }
+        unsigned long long num = 0;
+        for (int j = index; j < s.size(); j++) {
+            num = num * 10 + (s[j] - '0');
+            if (num + 1 == prev && dfs(s, j + 1, num)) {
+                return true;
+            }
+            if (num >= prev) {
+                break;
+            }
+        }
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {boolean}
+     */
+    splitString(s) {
+        const n = s.length;
+
+        const dfs = (index, prev) => {
+            if (index === n) {
+                return true;
+            }
+            let num = 0;
+            for (let j = index; j < n; j++) {
+                num = num * 10 + Number(s[j]);
+                if (num + 1 === prev && dfs(j + 1, num)) {
+                    return true;
+                }
+                if (num >= prev) {
+                    break;
+                }
+            }
+            return false;
+        };
+
+        let val = 0;
+        for (let i = 0; i < n - 1; i++) {
+            val = val * 10 + Number(s[i]);
+            if (dfs(i + 1, val)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 4. Stack
+
+::tabs-start
+
+```python
+class Solution:
+    def splitString(self, s: str) -> bool:
+        n = len(s)
+        stack = []
+        val = 0
+
+        for i in range(n - 1):
+            val = val * 10 + int(s[i])
+            stack.append((i + 1, val))
+
+            while stack:
+                index, prev = stack.pop()
+                num = 0
+                for j in range(index, n):
+                    num = num * 10 + int(s[j])
+                    if num + 1 == prev:
+                        if j + 1 == n:
+                            return True
+                        stack.append((j + 1, num))
+                    elif num >= prev:
+                        break
+
+        return False
+```
+
+```java
+public class Solution {
+    public boolean splitString(String s) {
+        int n = s.length();
+        Stack<long[]> stack = new Stack<>();
+        long val = 0;
+
+        for (int i = 0; i < n - 1; i++) {
+            val = val * 10 + (s.charAt(i) - '0');
+            stack.push(new long[]{i + 1, val});
+
+            while (!stack.isEmpty()) {
+                long[] top = stack.pop();
+                int index = (int) top[0];
+                long prev = top[1];
+                long num = 0;
+
+                for (int j = index; j < n; j++) {
+                    num = num * 10 + (s.charAt(j) - '0');
+                    if (num + 1 == prev) {
+                        if (j + 1 == n) {
+                            return true;
+                        }
+                        stack.push(new long[]{j + 1, num});
+                    } else if (num >= prev) {
+                        break;
+                    }
+                }
+            }
+        }
+
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool splitString(string s) {
+        int n = s.size();
+        stack<pair<int, long long>> stack;
+        unsigned long long val = 0;
+
+        for (int i = 0; i < n - 1; i++) {
+            val = val * 10 + (s[i] - '0');
+            stack.push({i + 1, val});
+
+            while (!stack.empty()) {
+                auto [index, prev] = stack.top();
+                stack.pop();
+                unsigned long long num = 0;
+
+                for (int j = index; j < n; j++) {
+                    num = num * 10 + (s[j] - '0');
+                    if (num + 1 == prev) {
+                        if (j + 1 == n) {
+                            return true;
+                        }
+                        stack.push({j + 1, num});
+                    } else if (num >= prev) {
+                        break;
+                    }
+                }
+            }
+        }
+
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {boolean}
+     */
+    splitString(s) {
+        const n = s.length;
+        let stack = [];
+        let val = 0;
+
+        for (let i = 0; i < n - 1; i++) {
+            val = val * 10 + Number(s[i]);
+            stack.push([i + 1, val]);
+
+            while (stack.length) {
+                let [index, prev] = stack.pop();
+                let num = 0;
+
+                for (let j = index; j < n; j++) {
+                    num = num * 10 + Number(s[j]);
+                    if (num + 1 === prev) {
+                        if (j + 1 === n) {
+                            return true;
+                        }
+                        stack.push([j + 1, num]);
+                    } else if (num >= prev) {
+                        break;
+                    }
+                }
+            }
+        }
+
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/sqrtx.md b/articles/sqrtx.md
new file mode 100644
index 000000000..bc2e10fa7
--- /dev/null
+++ b/articles/sqrtx.md
@@ -0,0 +1,454 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def mySqrt(self, x: int) -> int:
+        if x == 0:
+            return 0
+
+        res = 1
+        for i in range(1, x + 1):
+            if i * i > x:
+                return res
+            res = i
+
+        return res
+```
+
+```java
+public class Solution {
+    public int mySqrt(int x) {
+        if (x == 0) {
+            return 0;
+        }
+
+        int res = 1;
+        for (int i = 1; i <= x; i++) {
+            if ((long) i * i > x) {
+                return res;
+            }
+            res = i;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int mySqrt(int x) {
+        if (x == 0) {
+            return 0;
+        }
+
+        int res = 1;
+        for (int i = 1; i <= x; i++) {
+            if ((long long) i * i > x) {
+                return res;
+            }
+            res = i;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} x
+     * @return {number}
+     */
+    mySqrt(x) {
+        if (x === 0) {
+            return 0;
+        }
+
+        let res = 1;
+        for (let i = 1; i <= x; i++) {
+            if (i * i > x) {
+                return res;
+            }
+            res = i;
+        }
+
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MySqrt(int x) {
+        if (x == 0) return 0;
+
+        int res = 1;
+        for (int i = 1; i <= x; i++) {
+            if ((long)i * i > x) {
+                return res;
+            }
+            res = i;
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\sqrt {n})$
+* Space complexity: $O(1)$
+
+---
+
+## 2. In-Built Function
+
+::tabs-start
+
+```python
+class Solution:
+    def mySqrt(self, x: int) -> int:
+        return int(sqrt(x))
+```
+
+```java
+public class Solution {
+    public int mySqrt(int x) {
+        return (int) Math.sqrt(x);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int mySqrt(int x) {
+        return (int) sqrt(x);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} x
+     * @return {number}
+     */
+    mySqrt(x) {
+        return Math.floor(Math.sqrt(x));
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MySqrt(int x) {
+        return (int)Math.Sqrt(x);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Binary Search
+
+::tabs-start
+
+```python
+class Solution:
+    def mySqrt(self, x: int) -> int:
+        l, r = 0, x
+        res = 0
+
+        while l <= r:
+            m = l + (r - l) // 2
+            if m * m > x:
+                r = m - 1
+            elif m * m < x:
+                l = m + 1
+                res = m
+            else:
+                return m
+
+        return res
+```
+
+```java
+public class Solution {
+    public int mySqrt(int x) {
+        int l = 0, r = x;
+        int res = 0;
+
+        while (l <= r) {
+            int m = l + (r - l) / 2;
+            if ((long) m * m > x) {
+                r = m - 1;
+            } else if ((long) m * m < x) {
+                l = m + 1;
+                res = m;
+            } else {
+                return m;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int mySqrt(int x) {
+        int l = 0, r = x;
+        int res = 0;
+
+        while (l <= r) {
+            int m = l + (r - l) / 2;
+            if ((long long) m * m > x) {
+                r = m - 1;
+            } else if ((long long) m * m < x) {
+                l = m + 1;
+                res = m;
+            } else {
+                return m;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} x
+     * @return {number}
+     */
+    mySqrt(x) {
+        let l = 0, r = x;
+        let res = 0;
+
+        while (l <= r) {
+            const m = Math.floor(l + (r - l) / 2);
+            if (m * m > x) {
+                r = m - 1;
+            } else if (m * m < x) {
+                l = m + 1;
+                res = m;
+            } else {
+                return m;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MySqrt(int x) {
+        int l = 0, r = x;
+        int res = 0;
+
+        while (l <= r) {
+            int m = l + (r - l) / 2;
+            long sq = (long)m * m;
+
+            if (sq > x) {
+                r = m - 1;
+            } else if (sq < x) {
+                l = m + 1;
+                res = m;
+            } else {
+                return m;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
+
+---
+
+## 4. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def mySqrt(self, x: int) -> int:
+        if x < 2:
+            return x
+
+        l = self.mySqrt(x >> 2) << 1
+        r = l + 1
+        return l if r ** 2 > x else r
+```
+
+```java
+public class Solution {
+    public int mySqrt(int x) {
+        if (x < 2) {
+            return x;
+        }
+
+        int l = mySqrt(x >> 2) << 1;
+        int r = l + 1;
+        return (long) r * r > x ? l : r;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int mySqrt(int x) {
+        if (x < 2) {
+            return x;
+        }
+
+        int l = mySqrt(x >> 2) << 1;
+        int r = l + 1;
+        return (long long) r * r > x ? l : r;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} x
+     * @return {number}
+     */
+    mySqrt(x) {
+        if (x < 2) {
+            return x;
+        }
+
+        const l = this.mySqrt(x >> 2) << 1;
+        const r = l + 1;
+        return r * r > x ? l : r;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MySqrt(int x) {
+        if (x < 2) {
+            return x;
+        }
+
+        int l = MySqrt(x >> 2) << 1;
+        int r = l + 1;
+        return (long)r * r > x ? l : r;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(\log n)$ for recursion stack.
+
+---
+
+## 5. Newton's Method
+
+::tabs-start
+
+```python
+class Solution:
+    def mySqrt(self, x: int) -> int:
+        r = x
+        while r * r > x:
+            r = (r + x // r) >> 1
+        return r
+```
+
+```java
+public class Solution {
+    public int mySqrt(int x) {
+        long r = x;
+        while (r * r > x) {
+            r = (r + x / r) >> 1;
+        }
+        return (int) r;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int mySqrt(int x) {
+        long long r = x;
+        while (r * r > x) {
+            r = (r + x / r) >> 1;
+        }
+        return r;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} x
+     * @return {number}
+     */
+    mySqrt(x) {
+        let r = x;
+        while (r * r > x) {
+            r = (r + Math.floor(x / r)) >>> 1;
+        }
+        return r;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int MySqrt(int x) {
+        long r = x;
+        while (r * r > x) {
+            r = (r + x / r) >> 1;
+        }
+        return (int)r;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/squares-of-a-sorted-array.md b/articles/squares-of-a-sorted-array.md
new file mode 100644
index 000000000..c4d76f6b3
--- /dev/null
+++ b/articles/squares-of-a-sorted-array.md
@@ -0,0 +1,266 @@
+## 1. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def sortedSquares(self, nums: List[int]) -> List[int]:
+        for i in range(len(nums)):
+            nums[i] *= nums[i]
+        nums.sort()
+        return nums
+```
+
+```java
+public class Solution {
+    public int[] sortedSquares(int[] nums) {
+        for (int i = 0; i < nums.length; i++) {
+            nums[i] *= nums[i];
+        }
+        Arrays.sort(nums);
+        return nums;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> sortedSquares(vector<int>& nums) {
+        for (int i = 0; i < nums.size(); i++) {
+            nums[i] *= nums[i];
+        }
+        sort(nums.begin(), nums.end());
+        return nums;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    sortedSquares(nums) {
+        for (let i = 0; i < nums.length; i++) {
+            nums[i] *= nums[i];
+        }
+        nums.sort((a, b) => a - b);
+        return nums;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 2. Two Pointers - I
+
+::tabs-start
+
+```python
+class Solution:
+    def sortedSquares(self, nums: List[int]) -> List[int]:
+        l, r, res = 0, len(nums) - 1, []
+
+        while l <= r:
+            if (nums[l] * nums[l]) > (nums[r] * nums[r]):
+                res.append(nums[l] * nums[l])
+                l += 1
+            else:
+                res.append(nums[r] * nums[r])
+                r -= 1
+        
+        return res[::-1]
+```
+
+```java
+public class Solution {
+    public int[] sortedSquares(int[] nums) {
+        int l = 0, r = nums.length - 1;
+        ArrayList<Integer> res = new ArrayList<>();
+
+        while (l <= r) {
+            if (nums[l] * nums[l] > nums[r] * nums[r]) {
+                res.add(nums[l] * nums[l]);
+                l++;
+            } else {
+                res.add(nums[r] * nums[r]);
+                r--;
+            }
+        }
+
+        Collections.reverse(res);
+        return res.stream().mapToInt(i -> i).toArray();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> sortedSquares(vector<int>& nums) {
+        int l = 0, r = nums.size() - 1;
+        vector<int> res;
+
+        while (l <= r) {
+            if (nums[l] * nums[l] > nums[r] * nums[r]) {
+                res.push_back(nums[l] * nums[l]);
+                l++;
+            } else {
+                res.push_back(nums[r] * nums[r]);
+                r--;
+            }
+        }
+
+        reverse(res.begin(), res.end());
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    sortedSquares(nums) {
+        let l = 0, r = nums.length - 1;
+        const res = [];
+
+        while (l <= r) {
+            if (nums[l] * nums[l] > nums[r] * nums[r]) {
+                res.push(nums[l] * nums[l]);
+                l++;
+            } else {
+                res.push(nums[r] * nums[r]);
+                r--;
+            }
+        }
+
+        return res.reverse();
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for the output array.
+
+---
+
+## 3. Two Pointers - II
+
+::tabs-start
+
+```python
+class Solution:
+    def sortedSquares(self, nums: List[int]) -> List[int]:
+        n = len(nums)
+        res = [0] * n
+        l, r = 0, n - 1
+        res_index = n - 1
+
+        while l <= r:
+            if abs(nums[l]) > abs(nums[r]):
+                res[res_index] = nums[l] * nums[l]
+                l += 1
+            else:
+                res[res_index] = nums[r] * nums[r]
+                r -= 1
+            res_index -= 1
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int[] sortedSquares(int[] nums) {
+        int n = nums.length;
+        int[] res = new int[n];
+        int l = 0, r = n - 1, resIndex = n - 1;
+
+        while (l <= r) {
+            if (Math.abs(nums[l]) > Math.abs(nums[r])) {
+                res[resIndex] = nums[l] * nums[l];
+                l++;
+            } else {
+                res[resIndex] = nums[r] * nums[r];
+                r--;
+            }
+            resIndex--;
+        }
+        
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> sortedSquares(vector<int>& nums) {
+        int n = nums.size();
+        vector<int> res(n);
+        int l = 0, r = n - 1, resIndex = n - 1;
+
+        while (l <= r) {
+            if (abs(nums[l]) > abs(nums[r])) {
+                res[resIndex] = nums[l] * nums[l];
+                l++;
+            } else {
+                res[resIndex] = nums[r] * nums[r];
+                r--;
+            }
+            resIndex--;
+        }
+        
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    sortedSquares(nums) {
+        const n = nums.length;
+        const res = new Array(n);
+        let l = 0, r = n - 1, resIndex = n - 1;
+
+        while (l <= r) {
+            if (Math.abs(nums[l]) > Math.abs(nums[r])) {
+                res[resIndex] = nums[l] * nums[l];
+                l++;
+            } else {
+                res[resIndex] = nums[r] * nums[r];
+                r--;
+            }
+            resIndex--;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for the output array.
\ No newline at end of file
diff --git a/articles/stickers-to-spell-word.md b/articles/stickers-to-spell-word.md
new file mode 100644
index 000000000..2abbe91a7
--- /dev/null
+++ b/articles/stickers-to-spell-word.md
@@ -0,0 +1,580 @@
+## 1. Dynamic Programming (Top-Down) - I
+
+::tabs-start
+
+```python
+class Solution:
+    def minStickers(self, stickers: List[str], target: str) -> int:
+        stickCount = []
+        for s in stickers:
+            stickCount.append({})
+            for c in s:
+                stickCount[-1][c] = 1 + stickCount[-1].get(c, 0)
+
+        dp = {}
+
+        def dfs(t, stick):
+            if t in dp:
+                return dp[t]
+            res = 1 if stick else 0
+            remainT = ""
+            for c in t:
+                if c in stick and stick[c] > 0:
+                    stick[c] -= 1
+                else:
+                    remainT += c
+            if remainT:
+                used = float("inf")
+                for s in stickCount:
+                    if remainT[0] not in s:
+                        continue
+                    used = min(used, dfs(remainT, s.copy()))
+                dp[remainT] = used
+                res += used
+            return res
+
+        res = dfs(target, {})
+        return res if res != float("inf") else -1
+```
+
+```java
+public class Solution {
+    private List<Map<Character, Integer>> stickCount;
+    private Map<String, Integer> dp;
+    
+    public int minStickers(String[] stickers, String target) {
+        stickCount = new ArrayList<>();
+        dp = new HashMap<>();
+        
+        for (String s : stickers) {
+            Map<Character, Integer> countMap = new HashMap<>();
+            for (char c : s.toCharArray()) {
+                countMap.put(c, countMap.getOrDefault(c, 0) + 1);
+            }
+            stickCount.add(countMap);
+        }
+        
+        int res = dfs(target, new HashMap<>());
+        return res == Integer.MAX_VALUE ? -1 : res;
+    }
+    
+    private int dfs(String t, Map<Character, Integer> stick) {
+        if (t.isEmpty()) return 0;
+        if (dp.containsKey(t)) return dp.get(t);
+        
+        int res = stick.isEmpty() ? 0 : 1;
+        StringBuilder remainT = new StringBuilder();
+        
+        for (char c : t.toCharArray()) {
+            if (stick.containsKey(c) && stick.get(c) > 0) {
+                stick.put(c, stick.get(c) - 1);
+            } else {
+                remainT.append(c);
+            }
+        }
+        
+        if (remainT.length() > 0) {
+            int used = Integer.MAX_VALUE;
+            for (Map<Character, Integer> s : stickCount) {
+                if (!s.containsKey(remainT.charAt(0))) continue;
+                int curr = dfs(remainT.toString(), new HashMap<>(s));
+                if (curr != Integer.MAX_VALUE) {
+                    used = Math.min(used, curr);
+                }
+            }
+            dp.put(remainT.toString(), used);
+            if (used != Integer.MAX_VALUE && res != Integer.MAX_VALUE) {
+                res += used;
+            } else {
+                res = Integer.MAX_VALUE;
+            }
+        }
+        
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+    vector<unordered_map<char, int>> stickCount;
+    unordered_map<string, int> dp;
+    
+public:
+    int minStickers(vector<string>& stickers, string target) {
+        stickCount.clear();
+        dp.clear();
+        
+        for (const string& s : stickers) {
+            unordered_map<char, int> countMap;
+            for (char c : s) {
+                countMap[c]++;
+            }
+            stickCount.push_back(countMap);
+        }
+        
+        int res = dfs(target, unordered_map<char, int>());
+        return res == INT_MAX ? -1 : res;
+    }
+    
+private:
+    int dfs(const string& t, unordered_map<char, int> stick) {
+        if (t.empty()) return 0;
+        if (dp.count(t)) return dp[t];
+        
+        int res = stick.empty() ? 0 : 1;
+        string remainT;
+        
+        for (char c : t) {
+            if (stick.count(c) && stick[c] > 0) {
+                stick[c]--;
+            } else {
+                remainT += c;
+            }
+        }
+        
+        if (!remainT.empty()) {
+            int used = INT_MAX;
+            for (const auto& s : stickCount) {
+                if (!s.count(remainT[0])) continue;
+                int curr = dfs(remainT, unordered_map<char, int>(s));
+                if (curr != INT_MAX) {
+                    used = min(used, curr);
+                }
+            }
+            dp[remainT] = used;
+            if (used != INT_MAX && res != INT_MAX) {
+                res += used;
+            } else {
+                res = INT_MAX;
+            }
+        }
+        
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} stickers
+     * @param {string} target
+     * @return {number}
+     */
+    minStickers(stickers, target) {
+        const stickCount = [];
+        const dp = new Map();
+        
+        for (const s of stickers) {
+            const countMap = new Map();
+            for (const c of s) {
+                countMap.set(c, (countMap.get(c) || 0) + 1);
+            }
+            stickCount.push(countMap);
+        }
+
+        const dfs = (t, stick) => {
+            if (t === '') return 0;
+            if (dp.has(t)) return dp.get(t);
+            
+            let res = stick.size === 0 ? 0 : 1;
+            let remainT = '';
+            
+            for (const c of t) {
+                if (stick.has(c) && stick.get(c) > 0) {
+                    stick.set(c, stick.get(c) - 1);
+                } else {
+                    remainT += c;
+                }
+            }
+            
+            if (remainT.length > 0) {
+                let used = Infinity;
+                for (const s of stickCount) {
+                    if (!s.has(remainT[0])) continue;
+                    const newStick = new Map(s);
+                    const curr = dfs(remainT, newStick);
+                    used = Math.min(used, curr);
+                }
+                dp.set(remainT, used);
+                if (used !== Infinity && res !== Infinity) {
+                    res += used;
+                } else {
+                    res = Infinity;
+                }
+            }
+            
+            return res;
+        };
+        
+        const res = dfs(target, new Map());
+        return res === Infinity ? -1 : res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * k *2 ^ n)$
+* Space complexity: $O(m * k + 2 ^ n)$
+
+> Where $n$ is the length of the target string, $m$ is the number of stickers and $k$ is the average length of each sticker.
+
+---
+
+## 2. Dynamic Programming (Top-Down) - II
+
+::tabs-start
+
+```python
+class Solution:
+    def minStickers(self, stickers: List[str], target: str) -> int:
+        tmp = [c for c in target]
+        target = ''.join(sorted(tmp))
+        stickCount = []
+        for s in stickers:
+            stickCount.append(Counter(s))
+        
+        dp = {}
+        dp[""] = 0
+
+        def dfs(t):
+            if t in dp:
+                return dp[t]
+            
+            tarMp = Counter(t)
+            res = float("inf")
+            for s in stickCount:
+                if t[0] not in s:
+                    continue
+                remainT = []
+                for c in tarMp:
+                    if tarMp[c] > s[c]:
+                        remainT.extend([c] * (tarMp[c] - s[c]))
+                
+                remainT = ''.join(sorted(remainT))
+                res = min(res, 1 + dfs(remainT))
+            
+            dp[t] = res
+            return res
+            
+        ans = dfs(target)
+        return -1 if ans == float("inf") else ans
+```
+
+```java
+public class Solution {
+    private Map<String, Integer> dp = new HashMap<>();
+    private List<Map<Character, Integer>> stickCount = new ArrayList<>();
+
+    public int minStickers(String[] stickers, String target) {
+        dp.put("", 0);
+        for (String s : stickers) {
+            Map<Character, Integer> counter = new HashMap<>();
+            for (char c : s.toCharArray()) {
+                counter.put(c, counter.getOrDefault(c, 0) + 1);
+            }
+            stickCount.add(counter);
+        }
+        char[] targetArray = target.toCharArray();
+        Arrays.sort(targetArray);
+        target = new String(targetArray);
+
+        int ans = dfs(target);
+        return ans == Integer.MAX_VALUE ? -1 : ans;
+    }
+
+    private int dfs(String t) {
+        if (dp.containsKey(t)) {
+            return dp.get(t);
+        }
+
+        Map<Character, Integer> tarMp = new HashMap<>();
+        for (char c : t.toCharArray()) {
+            tarMp.put(c, tarMp.getOrDefault(c, 0) + 1);
+        }
+
+        int res = Integer.MAX_VALUE;
+        for (Map<Character, Integer> s : stickCount) {
+            if (!s.containsKey(t.charAt(0))) {
+                continue;
+            }
+
+            StringBuilder remainT = new StringBuilder();
+            for (Map.Entry<Character, Integer> entry : tarMp.entrySet()) {
+                char c = entry.getKey();
+                int need = entry.getValue() - s.getOrDefault(c, 0);
+                for (int i = 0; i < Math.max(0, need); i++) {
+                    remainT.append(c);
+                }
+            }
+            char[] remainArray = remainT.toString().toCharArray();
+            Arrays.sort(remainArray);
+            int cur = dfs(new String(remainArray));
+            if (cur == Integer.MAX_VALUE) cur--;
+            res = Math.min(res, 1 + cur);
+        }
+
+        dp.put(t, res);
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    unordered_map<string, int> dp;
+    vector<unordered_map<char, int>> stickCount;
+
+public:
+    int minStickers(vector<string>& stickers, string target) {
+        dp[""] = 0;
+        for (const string& s : stickers) {
+            unordered_map<char, int> counter;
+            for (char c : s) {
+                counter[c]++;
+            }
+            stickCount.push_back(counter);
+        }
+
+        sort(target.begin(), target.end());
+        int ans = dfs(target);
+        return ans == INT_MAX ? -1 : ans;
+    }
+
+    int dfs(const string& t) {
+        if (dp.find(t) != dp.end()) {
+            return dp[t];
+        }
+
+        unordered_map<char, int> tarMp;
+        for (char c : t) {
+            tarMp[c]++;
+        }
+
+        int res = INT_MAX;
+        for (auto& s : stickCount) {
+            if (s.find(t[0]) == s.end()) {
+                continue;
+            }
+
+            string remainT;
+            for (const auto& [c, count] : tarMp) {
+                int need = count - (s.count(c) ? s.at(c) : 0);
+                remainT.append(max(0, need), c);
+            }
+
+            sort(remainT.begin(), remainT.end());
+            int cur = dfs(remainT);
+            if (cur == INT_MAX) cur--;
+            res = min(res, 1 + cur);
+        }
+
+        dp[t] = res;
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} stickers
+     * @param {string} target
+     * @return {number}
+     */
+    minStickers(stickers, target) {
+        const dp = { "": 0 };
+        const stickCount = stickers.map((s) => {
+            const counter = {};
+            for (const c of s) {
+                counter[c] = (counter[c] || 0) + 1;
+            }
+            return counter;
+        });
+
+        const dfs = (t) => {
+            if (dp[t] !== undefined) return dp[t];
+
+            const tarMp = {};
+            for (const c of t) {
+                tarMp[c] = (tarMp[c] || 0) + 1;
+            }
+
+            let res = Infinity;
+            for (const s of stickCount) {
+                if (!s[t[0]]) continue;
+
+                let remainT = [];
+                for (const [c, count] of Object.entries(tarMp)) {
+                    let need = count - (s[c] || 0);
+                    while (need > 0) {
+                        remainT.push(c);
+                        need--;
+                    }
+                }
+
+                remainT = remainT.sort().join("");
+                res = Math.min(res, 1 + dfs(remainT));
+            }
+
+            dp[t] = res;
+            return res;
+        };
+
+        const ans = dfs(target.split("").sort().join(""));
+        return ans === Infinity ? -1 : ans;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * k *2 ^ n)$
+* Space complexity: $O(m * k + 2 ^ n)$
+
+> Where $n$ is the length of the target string, $m$ is the number of stickers and $k$ is the average length of each sticker.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def minStickers(self, stickers: List[str], target: str) -> int:
+        n = len(target)
+        N = 1 << n
+        dp = [-1] * N
+        dp[0] = 0
+
+        for t in range(N):
+            if dp[t] == -1:
+                continue
+            for s in stickers:
+                nextT = t
+                for c in s:
+                    for i in range(n):
+                        if target[i] == c and not ((nextT >> i) & 1):
+                            nextT |= 1 << i
+                            break
+                if dp[nextT] == -1 or dp[nextT] > dp[t] + 1:
+                    dp[nextT] = dp[t] + 1
+        return dp[N - 1]
+```
+
+```java
+public class Solution {
+    public int minStickers(String[] stickers, String target) {
+        int n = target.length();
+        int N = 1 << n;
+        int[] dp = new int[N];
+        Arrays.fill(dp, -1);
+        dp[0] = 0;
+
+        for (int t = 0; t < N; t++) {
+            if (dp[t] == -1) continue;
+            for (String s : stickers) {
+                int nextT = t;
+                for (char c : s.toCharArray()) {
+                    for (int i = 0; i < n; i++) {
+                        if (target.charAt(i) == c && ((nextT >> i) & 1) == 0) {
+                            nextT |= 1 << i;
+                            break;
+                        }
+                    }
+                }
+                if (dp[nextT] == -1 || dp[nextT] > dp[t] + 1) {
+                    dp[nextT] = dp[t] + 1;
+                }
+            }
+        }
+
+        return dp[N - 1];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minStickers(vector<string>& stickers, string target) {
+        int n = target.length();
+        int N = 1 << n;
+        vector<int> dp(N, -1);
+        dp[0] = 0;
+
+        for (int t = 0; t < N; t++) {
+            if (dp[t] == -1) continue;
+            for (string& s : stickers) {
+                int nextT = t;
+                for (char c : s) {
+                    for (int i = 0; i < n; i++) {
+                        if (target[i] == c && ((nextT >> i) & 1) == 0) {
+                            nextT |= 1 << i;
+                            break;
+                        }
+                    }
+                }
+                if (dp[nextT] == -1 || dp[nextT] > dp[t] + 1) {
+                    dp[nextT] = dp[t] + 1;
+                }
+            }
+        }
+
+        return dp[N - 1];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} stickers
+     * @param {string} target
+     * @return {number}
+     */
+    minStickers(stickers, target) {
+        const n = target.length;
+        const N = 1 << n;
+        const dp = Array(N).fill(-1);
+        dp[0] = 0;
+
+        for (let t = 0; t < N; t++) {
+            if (dp[t] === -1) continue;
+            for (let s of stickers) {
+                let nextT = t;
+                for (let c of s) {
+                    for (let i = 0; i < n; i++) {
+                        if (target[i] === c && ((nextT >> i) & 1) === 0) {
+                            nextT |= 1 << i;
+                            break;
+                        }
+                    }
+                }
+                if (dp[nextT] === -1 || dp[nextT] > dp[t] + 1) {
+                    dp[nextT] = dp[t] + 1;
+                }
+            }
+        }
+
+        return dp[N - 1];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m * k *2 ^ n)$
+* Space complexity: $O(2 ^ n)$
+
+> Where $n$ is the length of the target string, $m$ is the number of stickers and $k$ is the average length of each sticker.
\ No newline at end of file
diff --git a/articles/stone-game-ii.md b/articles/stone-game-ii.md
new file mode 100644
index 000000000..b9468738a
--- /dev/null
+++ b/articles/stone-game-ii.md
@@ -0,0 +1,540 @@
+## 1. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def stoneGameII(self, piles: List[int]) -> int:
+        dp = {}
+
+        def dfs(alice, i, M):
+            if i == len(piles):
+                return 0
+            if (alice, i, M) in dp:
+                return dp[(alice, i, M)]
+
+            res = 0 if alice else float("inf")
+            total = 0
+            for X in range(1, 2 * M + 1):
+                if i + X > len(piles):
+                    break
+                total += piles[i + X - 1]
+                if alice:
+                    res = max(res, total + dfs(not alice, i + X, max(M, X)))
+                else:
+                    res = min(res, dfs(not alice, i + X, max(M, X)))
+
+            dp[(alice, i, M)] = res
+            return res
+
+        return dfs(True, 0, 1)
+```
+
+```java
+public class Solution {
+    private int[][][] dp;
+
+    public int stoneGameII(int[] piles) {
+        int n = piles.length;
+        dp = new int[2][n][n + 1];
+        for (int[][] layer : dp) {
+            for (int[] row : layer) {
+                Arrays.fill(row, -1);
+            }
+        }
+
+        return dfs(1, 0, 1, piles);
+    }
+
+    private int dfs(int alice, int i, int M, int[] piles) {
+        if (i == piles.length) return 0;
+        if (dp[alice][i][M] != -1) return dp[alice][i][M];
+
+        int res = alice == 1 ? 0 : Integer.MAX_VALUE;
+        int total = 0;
+
+        for (int X = 1; X <= 2 * M; X++) {
+            if (i + X > piles.length) break;
+            total += piles[i + X - 1];
+            if (alice == 1) {
+                res = Math.max(res, total + dfs(0, i + X, Math.max(M, X), piles));
+            } else {
+                res = Math.min(res, dfs(1, i + X, Math.max(M, X), piles));
+            }
+        }
+
+        dp[alice][i][M] = res;
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<vector<vector<int>>> dp;
+
+public:
+    int stoneGameII(vector<int>& piles) {
+        int n = piles.size();
+        dp.resize(2, vector<vector<int>>(n, vector<int>(n + 1, -1)));
+        return dfs(1, 0, 1, piles);
+    }
+
+private:
+    int dfs(int alice, int i, int M, vector<int>& piles) {
+        if (i == piles.size()) return 0;
+        if (dp[alice][i][M] != -1) return dp[alice][i][M];
+
+        int res = alice == 1 ? 0 : INT_MAX;
+        int total = 0;
+
+        for (int X = 1; X <= 2 * M; X++) {
+            if (i + X > piles.size()) break;
+            total += piles[i + X - 1];
+            if (alice == 1) {
+                res = max(res, total + dfs(0, i + X, max(M, X), piles));
+            } else {
+                res = min(res, dfs(1, i + X, max(M, X), piles));
+            }
+        }
+
+        dp[alice][i][M] = res;
+        return dp[alice][i][M];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} piles
+     * @return {number}
+     */
+    stoneGameII(piles) {
+        const n = piles.length;
+        this.dp = Array.from({ length: 2 }, () =>
+            Array.from({ length: n }, () => Array(n + 1).fill(-1))
+        );
+
+        const dfs = (alice, i, M) => {
+            if (i === n) return 0;
+            if (this.dp[alice][i][M] !== -1) return this.dp[alice][i][M];
+
+            let res = alice === 1 ? 0 : Infinity;
+            let total = 0;
+
+            for (let X = 1; X <= 2 * M; X++) {
+                if (i + X > n) break;
+                total += piles[i + X - 1];
+                if (alice === 1) {
+                    res = Math.max(res, total + dfs(0, i + X, Math.max(M, X)));
+                } else {
+                    res = Math.min(res, dfs(1, i + X, Math.max(M, X)));
+                }
+            }
+
+            this.dp[alice][i][M] = res;
+            return res;
+        };
+
+        return dfs(1, 0, 1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 3)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 2. Dynamic Programming (Top-Down) + Suffix Sum
+
+::tabs-start
+
+```python
+class Solution:
+    def stoneGameII(self, piles: List[int]) -> int:
+        n = len(piles)
+        dp = [[None] * (n + 1) for _ in range(n)]
+        suffix_sum = [0] * n
+        suffix_sum[-1] = piles[-1]
+        for i in range(n - 2, -1, -1):
+            suffix_sum[i] = piles[i] + suffix_sum[i + 1]
+
+        def dfs(i, M):
+            if i == n:
+                return 0
+            if dp[i][M] is not None:
+                return dp[i][M]
+
+            res = 0
+            for X in range(1, 2 * M + 1):
+                if i + X > n:
+                    break
+                res = max(res, suffix_sum[i] - dfs(i + X, max(M, X)))
+            dp[i][M] = res
+            return res
+
+        return dfs(0, 1)
+```
+
+```java
+public class Solution {
+    private int[][] dp;
+    private int[] suffixSum;
+
+    public int stoneGameII(int[] piles) {
+        int n = piles.length;
+        dp = new int[n][n + 1];
+        for (int i = 0; i < n; i++) {
+            Arrays.fill(dp[i], -1);
+        }
+
+        suffixSum = new int[n];
+        suffixSum[n - 1] = piles[n - 1];
+        for (int i = n - 2; i >= 0; i--) {
+            suffixSum[i] = piles[i] + suffixSum[i + 1];
+        }
+
+        return dfs(0, 1);
+    }
+
+    private int dfs(int i, int M) {
+        if (i == suffixSum.length) return 0;
+        if (dp[i][M] != -1) return dp[i][M];
+
+        int res = 0;
+        for (int X = 1; X <= 2 * M; X++) {
+            if (i + X > suffixSum.length) break;
+            res = Math.max(res, suffixSum[i] - dfs(i + X, Math.max(M, X)));
+        }
+        
+        return dp[i][M] = res;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<vector<int>> dp;
+    vector<int> suffixSum;
+
+public:
+    int stoneGameII(vector<int>& piles) {
+        int n = piles.size();
+        dp.resize(n, vector<int>(n + 1, -1));
+        
+        suffixSum.resize(n);
+        suffixSum[n - 1] = piles[n - 1];
+        for (int i = n - 2; i >= 0; i--) {
+            suffixSum[i] = piles[i] + suffixSum[i + 1];
+        }
+
+        return dfs(0, 1, piles);
+    }
+
+private:
+    int dfs(int i, int M, vector<int>& piles) {
+        if (i == suffixSum.size()) return 0;
+        if (dp[i][M] != -1) return dp[i][M];
+
+        int res = 0;
+        for (int X = 1; X <= 2 * M; X++) {
+            if (i + X > suffixSum.size()) break;
+            res = max(res, suffixSum[i] - dfs(i + X, max(M, X), piles));
+        }
+
+        return dp[i][M] = res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} piles
+     * @return {number}
+     */
+    stoneGameII(piles) {
+        const n = piles.length;
+        const dp = Array.from({ length: n }, () => Array(n + 1).fill(-1));
+
+        const suffixSum = Array(n).fill(0);
+        suffixSum[n - 1] = piles[n - 1];
+        for (let i = n - 2; i >= 0; i--) {
+            suffixSum[i] = piles[i] + suffixSum[i + 1];
+        }
+
+        const dfs = (i, M) => {
+            if (i === n) return 0;
+            if (dp[i][M] !== -1) return dp[i][M];
+
+            let res = 0;
+            for (let X = 1; X <= 2 * M; X++) {
+                if (i + X > n) break;
+                res = Math.max(res, suffixSum[i] - dfs(i + X, Math.max(M, X)));
+            }
+
+            return dp[i][M] = res;
+        };
+
+        return dfs(0, 1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 3)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def stoneGameII(self, piles: List[int]) -> int:
+        n = len(piles)
+        dp = [[[0] * (n + 1) for _ in range(n + 1)] for _ in range(2)]
+
+        for i in range(n - 1, -1, -1):
+            for M in range(1, n + 1):
+                total = 0
+                dp[1][i][M] = 0
+                dp[0][i][M] = float("inf")
+
+                for X in range(1, 2 * M + 1):
+                    if i + X > n:
+                        break
+                    total += piles[i + X - 1]
+                    
+                    dp[1][i][M] = max(dp[1][i][M], total + dp[0][i + X][max(M, X)])
+                    dp[0][i][M] = min(dp[0][i][M], dp[1][i + X][max(M, X)])
+
+        return dp[1][0][1]
+```
+
+```java
+public class Solution {
+    public int stoneGameII(int[] piles) {
+        int n = piles.length;
+        int[][][] dp = new int[2][n + 1][n + 1];
+
+        for (int i = n - 1; i >= 0; i--) {
+            for (int M = 1; M <= n; M++) {
+                int total = 0;
+                dp[1][i][M] = 0;
+                dp[0][i][M] = Integer.MAX_VALUE;
+
+                for (int X = 1; X <= 2 * M; X++) {
+                    if (i + X > n) break;
+                    total += piles[i + X - 1];
+                    dp[1][i][M] = Math.max(dp[1][i][M], total + dp[0][i + X][Math.max(M, X)]);
+                    dp[0][i][M] = Math.min(dp[0][i][M], dp[1][i + X][Math.max(M, X)]);
+                }
+            }
+        }
+
+        return dp[1][0][1];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int stoneGameII(vector<int>& piles) {
+        int n = piles.size();
+        vector<vector<vector<int>>> dp(2, vector<vector<int>>(n + 1, vector<int>(n + 1, 0)));
+
+        for (int i = n - 1; i >= 0; i--) {
+            for (int M = 1; M <= n; M++) {
+                int total = 0;
+                dp[1][i][M] = 0;
+                dp[0][i][M] = INT_MAX;
+
+                for (int X = 1; X <= 2 * M; X++) {
+                    if (i + X > n) break;
+                    total += piles[i + X - 1];
+
+                    dp[1][i][M] = max(dp[1][i][M], total + dp[0][i + X][max(M, X)]);
+                    dp[0][i][M] = min(dp[0][i][M], dp[1][i + X][max(M, X)]);
+                }
+            }
+        }
+
+        return dp[1][0][1];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} piles
+     * @return {number}
+     */
+    stoneGameII(piles) {
+        const n = piles.length;
+        const dp = Array.from({ length: 2 }, () =>
+            Array.from({ length: n + 1 }, () => Array(n + 1).fill(0))
+        );
+
+        for (let i = n - 1; i >= 0; i--) {
+            for (let M = 1; M <= n; M++) {
+                let total = 0;
+                dp[1][i][M] = 0;
+                dp[0][i][M] = Infinity;
+
+                for (let X = 1; X <= 2 * M; X++) {
+                    if (i + X > n) break;
+                    total += piles[i + X - 1];
+
+                    dp[1][i][M] = Math.max(dp[1][i][M], total + dp[0][i + X][Math.max(M, X)]);
+                    dp[0][i][M] = Math.min(dp[0][i][M], dp[1][i + X][Math.max(M, X)]);
+                }
+            }
+        }
+
+        return dp[1][0][1];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 3)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 4. Dynamic Programming (Bottom-Up) + Suffix Sum
+
+::tabs-start
+
+```python
+class Solution:
+    def stoneGameII(self, piles: List[int]) -> int:
+        n = len(piles)
+        suffix_sum = [0] * n
+        suffix_sum[-1] = piles[-1]
+        for i in range(n - 2, -1, -1):
+            suffix_sum[i] = piles[i] + suffix_sum[i + 1]
+
+        dp = [[0] * (n + 1) for _ in range(n + 1)]
+
+        for i in range(n - 1, -1, -1):
+            for M in range(1, n + 1):
+                for X in range(1, 2 * M + 1):
+                    if i + X > n:
+                        break
+                    dp[i][M] = max(dp[i][M], suffix_sum[i] - dp[i + X][max(M, X)])
+
+        return dp[0][1]
+```
+
+```java
+public class Solution {
+    public int stoneGameII(int[] piles) {
+        int n = piles.length;
+
+        int[] suffixSum = new int[n];
+        suffixSum[n - 1] = piles[n - 1];
+        for (int i = n - 2; i >= 0; i--) {
+            suffixSum[i] = piles[i] + suffixSum[i + 1];
+        }
+
+        int[][] dp = new int[n + 1][n + 1];
+
+        for (int i = n - 1; i >= 0; i--) {
+            for (int M = 1; M <= n; M++) {
+                for (int X = 1; X <= 2 * M; X++) {
+                    if (i + X > n) break;
+                    dp[i][M] = Math.max(dp[i][M], suffixSum[i] - dp[i + X][Math.max(M, X)]);
+                }
+            }
+        }
+
+        return dp[0][1];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int stoneGameII(vector<int>& piles) {
+        int n = piles.size();
+
+        vector<int> suffixSum(n, 0);
+        suffixSum[n - 1] = piles[n - 1];
+        for (int i = n - 2; i >= 0; i--) {
+            suffixSum[i] = piles[i] + suffixSum[i + 1];
+        }
+
+        vector<vector<int>> dp(n + 1, vector<int>(n + 1, 0));
+
+        for (int i = n - 1; i >= 0; i--) {
+            for (int M = 1; M <= n; M++) {
+                for (int X = 1; X <= 2 * M; X++) {
+                    if (i + X > n) break;
+                    dp[i][M] = max(dp[i][M], suffixSum[i] - dp[i + X][max(M, X)]);
+                }
+            }
+        }
+
+        return dp[0][1];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} piles
+     * @return {number}
+     */
+    stoneGameII(piles) {
+        const n = piles.length;
+
+        const suffixSum = Array(n).fill(0);
+        suffixSum[n - 1] = piles[n - 1];
+        for (let i = n - 2; i >= 0; i--) {
+            suffixSum[i] = piles[i] + suffixSum[i + 1];
+        }
+
+        const dp = Array.from({ length: n + 1 }, () => Array(n + 1).fill(0));
+
+        for (let i = n - 1; i >= 0; i--) {
+            for (let M = 1; M <= n; M++) {
+                for (let X = 1; X <= 2 * M; X++) {
+                    if (i + X > n) break;
+                    dp[i][M] = Math.max(dp[i][M], suffixSum[i] - dp[i + X][Math.max(M, X)]);
+                }
+            }
+        }
+
+        return dp[0][1];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 3)$
+* Space complexity: $O(n ^ 2)$
\ No newline at end of file
diff --git a/articles/stone-game-iii.md b/articles/stone-game-iii.md
new file mode 100644
index 000000000..781024036
--- /dev/null
+++ b/articles/stone-game-iii.md
@@ -0,0 +1,597 @@
+## 1. Dynamic Programming (Top-Down) - I
+
+::tabs-start
+
+```python
+class Solution:
+    def stoneGameIII(self, stoneValue: List[int]) -> str:
+        n = len(stoneValue)
+        dp = [[None] * 2 for _ in range(n)]
+
+        def dfs(i, alice):
+            if i >= n:
+                return 0
+            if dp[i][alice] is not None:
+                return dp[i][alice]
+
+            res = float("-inf") if alice == 1 else float("inf")
+            score = 0
+            for j in range(i, min(i + 3, n)):
+                if alice == 1:
+                    score += stoneValue[j]
+                    res = max(res, score + dfs(j + 1, 0))
+                else:
+                    score -= stoneValue[j]
+                    res = min(res, score + dfs(j + 1, 1))
+
+            dp[i][alice] = res
+            return res
+
+        result = dfs(0, 1)
+        if result == 0:
+            return "Tie"
+        return "Alice" if result > 0 else "Bob"
+```
+
+```java
+public class Solution {
+    private Integer[][] dp;
+    private int n;
+
+    public String stoneGameIII(int[] stoneValue) {
+        n = stoneValue.length;
+        dp = new Integer[n][2];
+
+        int result = dfs(0, 1, stoneValue);
+        if (result == 0) return "Tie";
+        return result > 0 ? "Alice" : "Bob";
+    }
+
+    private int dfs(int i, int alice, int[] stoneValue) {
+        if (i >= n) return 0;
+        if (dp[i][alice] != null) return dp[i][alice];
+
+        int res = alice == 1 ? Integer.MIN_VALUE : Integer.MAX_VALUE;
+        int score = 0;
+        for (int j = i; j < Math.min(i + 3, n); j++) {
+            if (alice == 1) {
+                score += stoneValue[j];
+                res = Math.max(res, score + dfs(j + 1, 0, stoneValue));
+            } else {
+                score -= stoneValue[j];
+                res = Math.min(res, score + dfs(j + 1, 1, stoneValue));
+            }
+        }
+
+        dp[i][alice] = res;
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+    vector<vector<int>> dp;
+    int n;
+
+public:
+    string stoneGameIII(vector<int>& stoneValue) {
+        n = stoneValue.size();
+        dp.assign(n, vector<int>(2, INT_MIN));
+
+        int result = dfs(0, 1, stoneValue);
+        if (result == 0) return "Tie";
+        return result > 0 ? "Alice" : "Bob";
+    }
+
+private:
+    int dfs(int i, int alice, vector<int>& stoneValue) {
+        if (i >= n) return 0;
+        if (dp[i][alice] != INT_MIN) return dp[i][alice];
+
+        int res = alice == 1 ? INT_MIN : INT_MAX;
+        int score = 0;
+        for (int j = i; j < min(i + 3, n); j++) {
+            if (alice == 1) {
+                score += stoneValue[j];
+                res = max(res, score + dfs(j + 1, 0, stoneValue));
+            } else {
+                score -= stoneValue[j];
+                res = min(res, score + dfs(j + 1, 1, stoneValue));
+            }
+        }
+
+        dp[i][alice] = res;
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} stoneValue
+     * @return {string}
+     */
+    stoneGameIII(stoneValue) {
+        const n = stoneValue.length;
+        const dp = Array.from({ length: n }, () => [null, null]);
+
+        const dfs = (i, alice) => {
+            if (i >= n) return 0;
+            if (dp[i][alice] !== null) return dp[i][alice];
+
+            let res = alice === 1 ? -Infinity : Infinity;
+            let score = 0;
+            for (let j = i; j < Math.min(i + 3, n); j++) {
+                if (alice === 1) {
+                    score += stoneValue[j];
+                    res = Math.max(res, score + dfs(j + 1, 0));
+                } else {
+                    score -= stoneValue[j];
+                    res = Math.min(res, score + dfs(j + 1, 1));
+                }
+            }
+
+            dp[i][alice] = res;
+            return res;
+        };
+
+        const result = dfs(0, 1);
+        if (result === 0) return "Tie";
+        return result > 0 ? "Alice" : "Bob";
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public string StoneGameIII(int[] stoneValue) {
+        int n = stoneValue.Length;
+        int?[,] dp = new int?[n, 2];
+
+        int Dfs(int i, int alice) {
+            if (i >= n) return 0;
+            if (dp[i, alice].HasValue) return dp[i, alice].Value;
+
+            int res = alice == 1 ? int.MinValue : int.MaxValue;
+            int score = 0;
+
+            for (int j = i; j < Math.Min(i + 3, n); j++) {
+                if (alice == 1) {
+                    score += stoneValue[j];
+                    res = Math.Max(res, score + Dfs(j + 1, 0));
+                } else {
+                    score -= stoneValue[j];
+                    res = Math.Min(res, score + Dfs(j + 1, 1));
+                }
+            }
+
+            dp[i, alice] = res;
+            return res;
+        }
+
+        int result = Dfs(0, 1);
+        if (result == 0) return "Tie";
+        return result > 0 ? "Alice" : "Bob";
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Dynamic Programming (Top-Down) - II
+
+::tabs-start
+
+```python
+class Solution:
+    def stoneGameIII(self, stoneValue: List[int]) -> str:
+        n = len(stoneValue)
+        dp = {}
+
+        def dfs(i):
+            if i >= n:
+                return 0
+            if i in dp:
+                return dp[i]
+
+            res, total = float("-inf"), 0
+            for j in range(i, min(i + 3, n)):
+                total += stoneValue[j]
+                res = max(res, total - dfs(j + 1))
+
+            dp[i] = res
+            return res
+
+        result = dfs(0)
+        if result == 0:
+            return "Tie"
+        return "Alice" if result > 0 else "Bob"
+```
+
+```java
+public class Solution {
+    private int[] dp;
+    private int n;
+
+    public String stoneGameIII(int[] stoneValue) {
+        this.n = stoneValue.length;
+        this.dp = new int[n];
+        Arrays.fill(dp, Integer.MIN_VALUE);
+
+        int result = dfs(0, stoneValue);
+        if (result == 0) return "Tie";
+        return result > 0 ? "Alice" : "Bob";
+    }
+
+    private int dfs(int i, int[] stoneValue) {
+        if (i >= n) return 0;
+        if (dp[i] != Integer.MIN_VALUE) return dp[i];
+
+        int res = Integer.MIN_VALUE, total = 0;
+        for (int j = i; j < Math.min(i + 3, n); j++) {
+            total += stoneValue[j];
+            res = Math.max(res, total - dfs(j + 1, stoneValue));
+        }
+
+        dp[i] = res;
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string stoneGameIII(vector<int>& stoneValue) {
+        n = stoneValue.size();
+        dp.assign(n, INT_MIN);
+
+        int result = dfs(0, stoneValue);
+        if (result == 0) return "Tie";
+        return result > 0 ? "Alice" : "Bob";
+    }
+
+private:
+    vector<int> dp;
+    int n;
+
+    int dfs(int i, vector<int>& stoneValue) {
+        if (i >= n) return 0;
+        if (dp[i] != INT_MIN) return dp[i];
+
+        int res = INT_MIN, total = 0;
+        for (int j = i; j < min(i + 3, n); j++) {
+            total += stoneValue[j];
+            res = max(res, total - dfs(j + 1, stoneValue));
+        }
+
+        dp[i] = res;
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} stoneValue
+     * @return {string}
+     */
+    stoneGameIII(stoneValue) {
+        const n = stoneValue.length;
+        const dp = new Array(n);
+
+        const dfs = (i) => {
+            if (i >= n) return 0;
+            if (dp[i] !== undefined) return dp[i];
+
+            let res = -Infinity, total = 0;
+            for (let j = i; j < Math.min(i + 3, n); j++) {
+                total += stoneValue[j];
+                res = Math.max(res, total - dfs(j + 1));
+            }
+
+            dp[i] = res;
+            return res;
+        };
+
+        const result = dfs(0);
+        if (result === 0) return "Tie";
+        return result > 0 ? "Alice" : "Bob";
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public string StoneGameIII(int[] stoneValue) {
+        int n = stoneValue.Length;
+        Dictionary<int, int> dp = new Dictionary<int, int>();
+
+        int Dfs(int i) {
+            if (i >= n) return 0;
+            if (dp.ContainsKey(i)) return dp[i];
+
+            int res = int.MinValue, total = 0;
+            for (int j = i; j < Math.Min(i + 3, n); j++) {
+                total += stoneValue[j];
+                res = Math.Max(res, total - Dfs(j + 1));
+            }
+
+            dp[i] = res;
+            return res;
+        }
+
+        int result = Dfs(0);
+        if (result == 0) return "Tie";
+        return result > 0 ? "Alice" : "Bob";
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def stoneGameIII(self, stoneValue: List[int]) -> str:
+        n = len(stoneValue)
+        dp = [float("-inf")] * (n + 1)
+        dp[n] = 0
+
+        for i in range(n - 1, -1, -1):
+            total = 0
+            for j in range(i, min(i + 3, n)):
+                total += stoneValue[j]
+                dp[i] = max(dp[i], total - dp[j + 1])
+
+        result = dp[0]
+        if result == 0:
+            return "Tie"
+        return "Alice" if result > 0 else "Bob"
+```
+
+```java
+public class Solution {
+    public String stoneGameIII(int[] stoneValue) {
+        int n = stoneValue.length;
+        int[] dp = new int[n + 1];
+        Arrays.fill(dp, Integer.MIN_VALUE);
+        dp[n] = 0;
+
+        for (int i = n - 1; i >= 0; i--) {
+            int total = 0;
+            dp[i] = Integer.MIN_VALUE;
+            for (int j = i; j < Math.min(i + 3, n); j++) {
+                total += stoneValue[j];
+                dp[i] = Math.max(dp[i], total - dp[j + 1]);
+            }
+        }
+
+        int result = dp[0];
+        if (result == 0) return "Tie";
+        return result > 0 ? "Alice" : "Bob";
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string stoneGameIII(vector<int>& stoneValue) {
+        int n = stoneValue.size();
+        vector<int> dp(n + 1, INT_MIN);
+        dp[n] = 0;
+
+        for (int i = n - 1; i >= 0; i--) {
+            int total = 0;
+            dp[i] = INT_MIN;
+            for (int j = i; j < min(i + 3, n); j++) {
+                total += stoneValue[j];
+                dp[i] = max(dp[i], total - dp[j + 1]);
+            }
+        }
+
+        int result = dp[0];
+        if (result == 0) return "Tie";
+        return result > 0 ? "Alice" : "Bob";
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} stoneValue
+     * @return {string}
+     */
+    stoneGameIII(stoneValue) {
+        const n = stoneValue.length;
+        const dp = new Array(n + 1).fill(-Infinity);
+        dp[n] = 0;
+
+        for (let i = n - 1; i >= 0; i--) {
+            let total = 0;
+            dp[i] = -Infinity;
+            for (let j = i; j < Math.min(i + 3, n); j++) {
+                total += stoneValue[j];
+                dp[i] = Math.max(dp[i], total - dp[j + 1]);
+            }
+        }
+
+        const result = dp[0];
+        if (result === 0) return "Tie";
+        return result > 0 ? "Alice" : "Bob";
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public string StoneGameIII(int[] stoneValue) {
+        int n = stoneValue.Length;
+        int[] dp = new int[n + 1];
+        for (int i = 0; i <= n; i++) dp[i] = int.MinValue;
+        dp[n] = 0;
+
+        for (int i = n - 1; i >= 0; i--) {
+            int total = 0;
+            for (int j = i; j < Math.Min(i + 3, n); j++) {
+                total += stoneValue[j];
+                dp[i] = Math.Max(dp[i], total - dp[j + 1]);
+            }
+        }
+
+        int result = dp[0];
+        if (result == 0) return "Tie";
+        return result > 0 ? "Alice" : "Bob";
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def stoneGameIII(self, stoneValue: List[int]) -> str:
+        n = len(stoneValue)
+        dp = [0] * 4
+
+        for i in range(n - 1, -1, -1):
+            total = 0
+            dp[i % 4] = float("-inf")
+            for j in range(i, min(i + 3, n)):
+                total += stoneValue[j]
+                dp[i % 4] = max(dp[i % 4], total - dp[(j + 1) % 4])
+
+        if dp[0] == 0:
+            return "Tie"
+        return "Alice" if dp[0] > 0 else "Bob"
+```
+
+```java
+public class Solution {
+    public String stoneGameIII(int[] stoneValue) {
+        int n = stoneValue.length;
+        int[] dp = new int[4];
+
+        for (int i = n - 1; i >= 0; i--) {
+            int total = 0;
+            dp[i % 4] = Integer.MIN_VALUE;
+            for (int j = i; j < Math.min(i + 3, n); j++) {
+                total += stoneValue[j];
+                dp[i % 4] = Math.max(dp[i % 4], total - dp[(j + 1) % 4]);
+            }
+        }
+
+        if (dp[0] == 0) return "Tie";
+        return dp[0] > 0 ? "Alice" : "Bob";
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string stoneGameIII(vector<int>& stoneValue) {
+        int n = stoneValue.size();
+        vector<int> dp(4, 0);
+
+        for (int i = n - 1; i >= 0; --i) {
+            int total = 0;
+            dp[i % 4] = INT_MIN;
+            for (int j = i; j < min(i + 3, n); ++j) {
+                total += stoneValue[j];
+                dp[i % 4] = max(dp[i % 4], total - dp[(j + 1) % 4]);
+            }
+        }
+
+        if (dp[0] == 0) return "Tie";
+        return dp[0] > 0 ? "Alice" : "Bob";
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} stoneValue
+     * @return {string}
+     */
+    stoneGameIII(stoneValue) {
+        const n = stoneValue.length;
+        const dp = new Array(4).fill(0);
+
+        for (let i = n - 1; i >= 0; i--) {
+            let total = 0;
+            dp[i % 4] = -Infinity;
+            for (let j = i; j < Math.min(i + 3, n); j++) {
+                total += stoneValue[j];
+                dp[i % 4] = Math.max(dp[i % 4], total - dp[(j + 1) % 4]);
+            }
+        }
+
+        if (dp[0] === 0) return "Tie";
+        return dp[0] > 0 ? "Alice" : "Bob";
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public string StoneGameIII(int[] stoneValue) {
+        int n = stoneValue.Length;
+        int[] dp = new int[4];
+
+        for (int i = n - 1; i >= 0; i--) {
+            int total = 0;
+            dp[i % 4] = int.MinValue;
+
+            for (int j = i; j < Math.Min(i + 3, n); j++) {
+                total += stoneValue[j];
+                dp[i % 4] = Math.Max(dp[i % 4], total - dp[(j + 1) % 4]);
+            }
+        }
+
+        if (dp[0] == 0) return "Tie";
+        return dp[0] > 0 ? "Alice" : "Bob";
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/stone-game.md b/articles/stone-game.md
new file mode 100644
index 000000000..54e5043c1
--- /dev/null
+++ b/articles/stone-game.md
@@ -0,0 +1,525 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def stoneGame(self, piles: List[int]) -> bool:
+        def dfs(l, r):
+            if l > r:
+                return 0
+            even = (r - l) % 2 == 0
+            left = piles[l] if even else 0
+            right = piles[r] if even else 0
+            return max(dfs(l + 1, r) + left, dfs(l, r - 1) + right)
+
+        total = sum(piles)
+        alice_score = dfs(0, len(piles) - 1)
+        return alice_score > total - alice_score
+```
+
+```java
+public class Solution {
+    public boolean stoneGame(int[] piles) {
+        int total = 0;
+        for (int pile : piles) {
+            total += pile;
+        }
+
+        int aliceScore = dfs(0, piles.length - 1, piles);
+        return aliceScore > total - aliceScore;
+    }
+
+    private int dfs(int l, int r, int[] piles) {
+        if (l > r) {
+            return 0;
+        }
+        boolean even = (r - l) % 2 == 0;
+        int left = even ? piles[l] : 0;
+        int right = even ? piles[r] : 0;
+        return Math.max(dfs(l + 1, r, piles) + left, dfs(l, r - 1, piles) + right);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool stoneGame(vector<int>& piles) {
+        int total = accumulate(piles.begin(), piles.end(), 0);
+        int aliceScore = dfs(0, piles.size() - 1, piles);
+        return aliceScore > total - aliceScore;
+    }
+
+private:
+    int dfs(int l, int r, const vector<int>& piles) {
+        if (l > r) {
+            return 0;
+        }
+        bool even = (r - l) % 2 == 0;
+        int left = even ? piles[l] : 0;
+        int right = even ? piles[r] : 0;
+        return max(dfs(l + 1, r, piles) + left, dfs(l, r - 1, piles) + right);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} piles
+     * @return {boolean}
+     */
+    stoneGame(piles) {
+        const total = piles.reduce((a, b) => a + b, 0);
+
+        const dfs = (l, r) => {
+            if (l > r) {
+                return 0;
+            }
+            const even = (r - l) % 2 === 0;
+            const left = even ? piles[l] : 0;
+            const right = even ? piles[r] : 0;
+            return Math.max(dfs(l + 1, r) + left, dfs(l, r - 1) + right);
+        };
+
+        const aliceScore = dfs(0, piles.length - 1);
+        return aliceScore > total - aliceScore;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def stoneGame(self, piles: List[int]) -> bool:
+        dp = {}
+
+        def dfs(l, r):
+            if l > r:
+                return 0
+            if (l, r) in dp:
+                return dp[(l, r)]
+            even = (r - l) % 2 == 0
+            left = piles[l] if even else 0
+            right = piles[r] if even else 0
+            dp[(l, r)] = max(dfs(l + 1, r) + left, dfs(l, r - 1) + right)
+            return dp[(l, r)]
+
+        total = sum(piles)
+        alice_score = dfs(0, len(piles) - 1)
+        return alice_score > total - alice_score
+```
+
+```java
+public class Solution {
+    private int[][] dp;
+
+    public boolean stoneGame(int[] piles) {
+        int n = piles.length;
+        dp = new int[n][n];
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < n; j++) {
+                dp[i][j] = -1;
+            }
+        }
+
+        int total = 0;
+        for (int pile : piles) {
+            total += pile;
+        }
+
+        int aliceScore = dfs(0, n - 1, piles);
+        return aliceScore > total - aliceScore;
+    }
+
+    private int dfs(int l, int r, int[] piles) {
+        if (l > r) {
+            return 0;
+        }
+        if (dp[l][r] != -1) {
+            return dp[l][r];
+        }
+        boolean even = (r - l) % 2 == 0;
+        int left = even ? piles[l] : 0;
+        int right = even ? piles[r] : 0;
+        dp[l][r] = Math.max(dfs(l + 1, r, piles) + left, dfs(l, r - 1, piles) + right);
+        return dp[l][r];
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<vector<int>> dp;
+
+public:
+    bool stoneGame(vector<int>& piles) {
+        int n = piles.size();
+        dp = vector<vector<int>>(n, vector<int>(n, -1));
+        int total = accumulate(piles.begin(), piles.end(), 0);
+        int aliceScore = dfs(0, n - 1, piles);
+        return aliceScore > total - aliceScore;
+    }
+
+private:
+    int dfs(int l, int r, const vector<int>& piles) {
+        if (l > r) {
+            return 0;
+        }
+        if (dp[l][r] != -1) {
+            return dp[l][r];
+        }
+        bool even = (r - l) % 2 == 0;
+        int left = even ? piles[l] : 0;
+        int right = even ? piles[r] : 0;
+        dp[l][r] = max(dfs(l + 1, r, piles) + left, dfs(l, r - 1, piles) + right);
+        return dp[l][r];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} piles
+     * @return {boolean}
+     */
+    stoneGame(piles) {
+        const n = piles.length;
+        const dp = Array.from({ length: n }, () => Array(n).fill(-1));
+
+        const dfs = (l, r) => {
+            if (l > r) {
+                return 0;
+            }
+            if (dp[l][r] !== -1) {
+                return dp[l][r];
+            }
+            const even = (r - l) % 2 === 0;
+            const left = even ? piles[l] : 0;
+            const right = even ? piles[r] : 0;
+            dp[l][r] = Math.max(dfs(l + 1, r) + left, dfs(l, r - 1) + right);
+            return dp[l][r];
+        };
+
+        const total = piles.reduce((a, b) => a + b, 0);
+        const aliceScore = dfs(0, n - 1);
+        return aliceScore > total - aliceScore;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def stoneGame(self, piles: List[int]) -> bool:
+        n = len(piles)
+        dp = [[0] * n for _ in range(n)]
+
+        for l in range(n - 1, -1, -1):
+            for r in range(l, n):
+                even = (r - l) % 2 == 0
+                left = piles[l] if even else 0
+                right = piles[r] if even else 0
+                if l == r:
+                    dp[l][r] = left
+                else:
+                    dp[l][r] = max(dp[l + 1][r] + left, dp[l][r - 1] + right)
+
+        total = sum(piles)
+        alice_score = dp[0][n - 1]
+        return alice_score > total - alice_score
+```
+
+```java
+public class Solution {
+    public boolean stoneGame(int[] piles) {
+        int n = piles.length;
+        int[][] dp = new int[n][n];
+
+        for (int l = n - 1; l >= 0; l--) {
+            for (int r = l; r < n; r++) {
+                boolean even = (r - l) % 2 == 0;
+                int left = even ? piles[l] : 0;
+                int right = even ? piles[r] : 0;
+                if (l == r) {
+                    dp[l][r] = left;
+                } else {
+                    dp[l][r] = Math.max(dp[l + 1][r] + left, dp[l][r - 1] + right);
+                }
+            }
+        }
+
+        int total = 0;
+        for (int pile : piles) {
+            total += pile;
+        }
+
+        int aliceScore = dp[0][n - 1];
+        return aliceScore > total - aliceScore;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool stoneGame(vector<int>& piles) {
+        int n = piles.size();
+        vector<vector<int>> dp(n, vector<int>(n, 0));
+
+        for (int l = n - 1; l >= 0; l--) {
+            for (int r = l; r < n; r++) {
+                bool even = (r - l) % 2 == 0;
+                int left = even ? piles[l] : 0;
+                int right = even ? piles[r] : 0;
+                if (l == r) {
+                    dp[l][r] = left;
+                } else {
+                    dp[l][r] = max(dp[l + 1][r] + left, dp[l][r - 1] + right);
+                }
+            }
+        }
+
+        int total = accumulate(piles.begin(), piles.end(), 0);
+        int aliceScore = dp[0][n - 1];
+        return aliceScore > total - aliceScore;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} piles
+     * @return {boolean}
+     */
+    stoneGame(piles) {
+        const n = piles.length;
+        const dp = Array.from({ length: n }, () => Array(n).fill(0));
+
+        for (let l = n - 1; l >= 0; l--) {
+            for (let r = l; r < n; r++) {
+                const even = (r - l) % 2 === 0;
+                const left = even ? piles[l] : 0;
+                const right = even ? piles[r] : 0;
+                if (l === r) {
+                    dp[l][r] = left;
+                } else {
+                    dp[l][r] = Math.max(dp[l + 1][r] + left, dp[l][r - 1] + right);
+                }
+            }
+        }
+
+        const total = piles.reduce((a, b) => a + b, 0);
+        const aliceScore = dp[0][n - 1];
+        return aliceScore > total - aliceScore;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def stoneGame(self, piles: List[int]) -> bool:
+        n = len(piles)
+        dp = [0] * n
+
+        for l in reversed(range(n)):
+            for r in range(l, n):
+                even = ((r - l) % 2 == 0)
+                left = piles[l] if even else 0
+                right = piles[r] if even else 0
+
+                if l == r:
+                    dp[r] = left
+                else:
+                    dp[r] = max(dp[r] + left, dp[r - 1] + right)
+
+        total = sum(piles)
+        alice_score = dp[n - 1]
+        return alice_score > (total - alice_score)
+```
+
+```java
+public class Solution {
+    public boolean stoneGame(int[] piles) {
+        int n = piles.length;
+        int[] dp = new int[n];
+
+        for (int l = n - 1; l >= 0; l--) {
+            for (int r = l; r < n; r++) {
+                boolean even = (r - l) % 2 == 0;
+                int left = even ? piles[l] : 0;
+                int right = even ? piles[r] : 0;
+
+                if (l == r) {
+                    dp[r] = left;
+                } else {
+                    dp[r] = Math.max(dp[r] + left, dp[r - 1] + right);
+                }
+            }
+        }
+
+        int total = 0;
+        for (int pile : piles) {
+            total += pile;
+        }
+
+        int aliceScore = dp[n - 1];
+        return aliceScore > (total - aliceScore);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool stoneGame(vector<int>& piles) {
+        int n = piles.size();
+        vector<int> dp(n, 0);
+
+        for (int l = n - 1; l >= 0; l--) {
+            for (int r = l; r < n; r++) {
+                bool even = (r - l) % 2 == 0;
+                int left = even ? piles[l] : 0;
+                int right = even ? piles[r] : 0;
+
+                if (l == r) {
+                    dp[r] = left;
+                } else {
+                    dp[r] = max(dp[r] + left, dp[r - 1] + right);
+                }
+            }
+        }
+
+        int total = accumulate(piles.begin(), piles.end(), 0);
+        int aliceScore = dp[n - 1];
+        return aliceScore > (total - aliceScore);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} piles
+     * @return {boolean}
+     */
+    stoneGame(piles) {
+        const n = piles.length;
+        const dp = new Array(n).fill(0);
+
+        for (let l = n - 1; l >= 0; l--) {
+            for (let r = l; r < n; r++) {
+                const even = (r - l) % 2 === 0;
+                const left = even ? piles[l] : 0;
+                const right = even ? piles[r] : 0;
+
+                if (l === r) {
+                    dp[r] = left;
+                } else {
+                    dp[r] = Math.max(dp[r] + left, dp[r - 1] + right);
+                }
+            }
+        }
+
+        const total = piles.reduce((a, b) => a + b, 0);
+        const aliceScore = dp[n - 1];
+        return aliceScore > (total - aliceScore);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 5. Return TRUE
+
+::tabs-start
+
+```python
+class Solution:
+    def stoneGame(self, piles: List[int]) -> bool:
+        return True
+```
+
+```java
+public class Solution {
+    public boolean stoneGame(int[] piles) {
+        return true; 
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool stoneGame(vector<int>& piles) {
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} piles
+     * @return {boolean}
+     */
+    stoneGame(piles) {
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/string-compression-ii.md b/articles/string-compression-ii.md
new file mode 100644
index 000000000..d1021b9ea
--- /dev/null
+++ b/articles/string-compression-ii.md
@@ -0,0 +1,480 @@
+## 1. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def getLengthOfOptimalCompression(self, s: str, k: int) -> int:
+        cache = {}
+
+        def count(i, k, prev, prev_cnt):
+            if (i, k, prev, prev_cnt) in cache:
+                return cache[(i, k, prev, prev_cnt)]
+            if k < 0:
+                return float("inf")
+            if i == len(s):
+                return 0
+
+            if s[i] == prev:
+                incr = 1 if prev_cnt in [1, 9, 99] else 0
+                res = incr + count(i + 1, k, prev, prev_cnt + 1)
+            else:
+                res = min(
+                    count(i + 1, k - 1, prev, prev_cnt),  # delete s[i]
+                    1 + count(i + 1, k, s[i], 1)  # don't delete
+                )
+
+            cache[(i, k, prev, prev_cnt)] = res
+            return res
+
+        return count(0, k, "", 0)
+```
+
+```java
+public class Solution {
+    private final int INF = Integer.MAX_VALUE / 2;
+    private String s;
+    private int[][][][] dp;
+
+    public int getLengthOfOptimalCompression(String s, int k) {
+        this.s = s;
+        int n = s.length();
+        dp = new int[n + 1][k + 1][27][n + 1];
+        for (int[][][] arr1 : dp) {
+            for (int[][] arr2 : arr1) {
+                for (int[] arr3 : arr2) {
+                    Arrays.fill(arr3, -1);
+                }
+            }
+        }
+        return count(0, k, 26, 0);
+    }
+
+    private int count(int i, int k, int prev, int prevCnt) {
+        if (k < 0) return INF;
+        if (i == s.length()) return 0;
+        if (dp[i][k][prev][prevCnt] != -1) return dp[i][k][prev][prevCnt];
+
+        int res;
+        if (prev == (s.charAt(i) - 'a')) {
+            int incr = (prevCnt == 1 || prevCnt == 9 || prevCnt == 99) ? 1 : 0;
+            res = incr + count(i + 1, k, prev, prevCnt + 1);
+        } else {
+            res = Math.min(
+                count(i + 1, k - 1, prev, prevCnt), // delete s[i]
+                1 + count(i + 1, k, s.charAt(i) - 'a', 1) // don't delete
+            );
+        }
+
+        return dp[i][k][prev][prevCnt] = res;
+    }
+}
+```
+
+```cpp
+class Solution {
+    static const int INF = INT_MAX / 2;
+    vector<vector<vector<vector<int>>>> dp;
+
+    int count(int i, int k, int prev, int prevCnt, string& s) {
+        if (k < 0) return INF;
+        if (i == s.size()) return 0;
+        if (dp[i][k][prev][prevCnt] != -1) return dp[i][k][prev][prevCnt];
+
+        int res;
+        if (prev == s[i] - 'a') {
+            int incr = (prevCnt == 1 || prevCnt == 9 || prevCnt == 99) ? 1 : 0;
+            res = incr + count(i + 1, k, prev, prevCnt + 1, s);
+        } else {
+            res = 1 + count(i + 1, k, s[i] - 'a', 1, s); // don't delete
+            if (k > 0) {
+                res = min(res, count(i + 1, k - 1, prev, prevCnt, s)); // delete s[i]
+            }
+        }
+
+        return dp[i][k][prev][prevCnt] = res;
+    }
+
+public:
+    int getLengthOfOptimalCompression(string s, int k) {
+        int n = s.size();
+        dp = vector<vector<vector<vector<int>>>>(
+            n + 1, vector<vector<vector<int>>>(k + 1, vector<vector<int>>(27, vector<int>(101, -1)))
+        );
+        return count(0, k, 26, 0, s);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {number} k
+     * @return {number}
+     */
+    getLengthOfOptimalCompression(s, k) {
+        const INF = 1e9;
+        const n = s.length;
+        const dp = {};
+
+        const count = (i, k, prev, prevCnt) => {
+            if (k < 0) return INF;
+            if (i === n) return 0;
+            const key = `${i},${k},${prev},${prevCnt}`;
+            if (key in dp) return dp[key];
+
+            let res;
+            if (prev === s.charCodeAt(i) - 97) {
+                const incr = prevCnt === 1 || prevCnt === 9 || prevCnt === 99 ? 1 : 0;
+                res = incr + count(i + 1, k, prev, prevCnt + 1);
+            } else {
+                res = 1 + count(i + 1, k, s.charCodeAt(i) - 97, 1); // don't delete
+                if (k > 0) {
+                    res = Math.min(res, count(i + 1, k - 1, prev, prevCnt)); // delete s[i]
+                }
+            }
+
+            dp[key] = res;
+            return res;
+        };
+
+        return count(0, k, 26, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(k * n ^ 2)$
+* Space complexity: $O(k * n ^ 2)$
+
+> Where $n$ is the length of the string $s$ and $k$ is the maximum number of characters that can be deleted from the string.
+
+---
+
+## 2. Dynamic Programming (Top-Down Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def getLengthOfOptimalCompression(self, s: str, k: int) -> int:
+        n = len(s)
+        dp = {}
+
+        def dfs(i, k):
+            if n - i <= k:
+                return 0
+            if (i, k) in dp:
+                return dp[(i, k)]
+
+            res = 150
+            if k > 0:
+                res = dfs(i + 1, k - 1)
+            
+            freq = delCnt = 0
+            comp_len = 1
+            for j in range(i, n):
+                if s[i] == s[j]:
+                    if freq in [1, 9, 99]:
+                        comp_len += 1
+                    freq += 1
+                else:
+                    delCnt += 1
+                    if delCnt > k:
+                        break
+                res = min(res, comp_len + dfs(j + 1, k - delCnt))
+            dp[(i, k)] = res
+            return res
+        
+        return dfs(0, k)
+```
+
+```java
+public class Solution {
+    private int n;
+    private int[][] dp;
+
+    public int getLengthOfOptimalCompression(String s, int k) {
+        n = s.length();
+        dp = new int[n + 1][k + 1];
+        for (int[] row : dp) Arrays.fill(row, -1);
+        return dfs(0, k, s);
+    }
+
+    private int dfs(int i, int k, String s) {
+        if (n - i <= k) return 0;
+        if (dp[i][k] != -1) return dp[i][k];
+
+        int res = 150;
+        if (k > 0) res = dfs(i + 1, k - 1, s);
+
+        int freq = 0, delCnt = 0, comp_len = 1;
+        for (int j = i; j < n; j++) {
+            if (s.charAt(i) == s.charAt(j)) {
+                if (freq == 1 || freq == 9 || freq == 99) comp_len++;
+                freq++;
+            } else {
+                delCnt++;
+                if (delCnt > k) break;
+            }
+            res = Math.min(res, comp_len + dfs(j + 1, k - delCnt, s));
+        }
+        dp[i][k] = res;
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    int n;
+    vector<vector<int>> dp;
+
+    int dfs(int i, int k, const string& s) {
+        if (n - i <= k) return 0;
+        if (dp[i][k] != -1) return dp[i][k];
+
+        int res = 150;
+        if (k > 0) res = dfs(i + 1, k - 1, s);
+
+        int freq = 0, delCnt = 0, comp_len = 1;
+        for (int j = i; j < n; j++) {
+            if (s[i] == s[j]) {
+                if (freq == 1 || freq == 9 || freq == 99) comp_len++;
+                freq++;
+            } else {
+                delCnt++;
+                if (delCnt > k) break;
+            }
+            res = min(res, comp_len + dfs(j + 1, k - delCnt, s));
+        }
+        dp[i][k] = res;
+        return res;
+    }
+
+public:
+    int getLengthOfOptimalCompression(string s, int k) {
+        n = s.size();
+        dp = vector<vector<int>>(n + 1, vector<int>(k + 1, -1));
+        return dfs(0, k, s);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {number} k
+     * @return {number}
+     */
+    getLengthOfOptimalCompression(s, k) {
+        const n = s.length;
+        const dp = Array.from({ length: n + 1 }, () => Array(k + 1).fill(-1));
+
+        const dfs = (i, k) => {
+            if (n - i <= k) return 0;
+            if (dp[i][k] !== -1) return dp[i][k];
+
+            let res = 150;
+            if (k > 0) res = dfs(i + 1, k - 1);
+
+            let freq = 0, delCnt = 0, comp_len = 1;
+            for (let j = i; j < n; j++) {
+                if (s[i] === s[j]) {
+                    if (freq === 1 || freq === 9 || freq === 99) comp_len++;
+                    freq++;
+                } else {
+                    delCnt++;
+                    if (delCnt > k) break;
+                }
+                res = Math.min(res, comp_len + dfs(j + 1, k - delCnt));
+            }
+            dp[i][k] = res;
+            return res;
+        };
+
+        return dfs(0, k);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 * k)$
+* Space complexity: $O(n * k)$
+
+> Where $n$ is the length of the string $s$ and $k$ is the maximum number of characters that can be deleted from the string.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def getLengthOfOptimalCompression(self, s: str, k: int) -> int:
+        n = len(s)
+        dp = [[150] * (k + 1) for _ in range(n)]
+        dp.append([0] * (k + 1))
+
+        for i in range(n - 1, -1, -1):
+            for rem_k in range(k + 1):
+                if rem_k > 0:
+                    dp[i][rem_k] = dp[i + 1][rem_k - 1]
+
+                freq = delCnt = 0
+                comp_len = 1
+                for j in range(i, n):
+                    if s[i] == s[j]:
+                        if freq in [1, 9, 99]:
+                            comp_len += 1
+                        freq += 1
+                    else:
+                        delCnt += 1
+                        if delCnt > rem_k:
+                            break
+                    dp[i][rem_k] = min(dp[i][rem_k], comp_len + dp[j + 1][rem_k - delCnt])
+
+        return dp[0][k]
+```
+
+```java
+public class Solution {
+    public int getLengthOfOptimalCompression(String s, int k) {
+        int n = s.length();
+        int[][] dp = new int[n + 1][k + 1];
+
+        for (int i = 0; i <= n; i++) {
+            for (int j = 0; j <= k; j++) {
+                dp[i][j] = 150;
+            }
+        }
+
+        for (int remK = 0; remK <= k; remK++) {
+            dp[n][remK] = 0;
+        }
+
+        for (int i = n - 1; i >= 0; i--) {
+            for (int remK = 0; remK <= k; remK++) {
+                if (remK > 0) {
+                    dp[i][remK] = dp[i + 1][remK - 1];
+                }
+
+                int freq = 0, delCnt = 0, compLen = 1;
+                for (int j = i; j < n; j++) {
+                    if (s.charAt(i) == s.charAt(j)) {
+                        if (freq == 1 || freq == 9 || freq == 99) {
+                            compLen++;
+                        }
+                        freq++;
+                    } else {
+                        delCnt++;
+                        if (delCnt > remK) break;
+                    }
+                    dp[i][remK] = Math.min(dp[i][remK], compLen + dp[j + 1][remK - delCnt]);
+                }
+            }
+        }
+
+        return dp[0][k];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int getLengthOfOptimalCompression(string s, int k) {
+        int n = s.size();
+        vector<vector<int>> dp(n + 1, vector<int>(k + 1, 150));
+
+        for (int remK = 0; remK <= k; remK++) {
+            dp[n][remK] = 0;
+        }
+
+        for (int i = n - 1; i >= 0; i--) {
+            for (int remK = 0; remK <= k; remK++) {
+                if (remK > 0) {
+                    dp[i][remK] = dp[i + 1][remK - 1];
+                }
+
+                int freq = 0, delCnt = 0, compLen = 1;
+                for (int j = i; j < n; j++) {
+                    if (s[i] == s[j]) {
+                        if (freq == 1 || freq == 9 || freq == 99) {
+                            compLen++;
+                        }
+                        freq++;
+                    } else {
+                        delCnt++;
+                        if (delCnt > remK) break;
+                    }
+                    dp[i][remK] = min(dp[i][remK], compLen + dp[j + 1][remK - delCnt]);
+                }
+            }
+        }
+
+        return dp[0][k];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {number} k
+     * @return {number}
+     */
+    getLengthOfOptimalCompression(s, k) {
+        const n = s.length;
+        const dp = Array.from({ length: n + 1 }, () => Array(k + 1).fill(150));
+
+        for (let remK = 0; remK <= k; remK++) {
+            dp[n][remK] = 0;
+        }
+
+        for (let i = n - 1; i >= 0; i--) {
+            for (let remK = 0; remK <= k; remK++) {
+                if (remK > 0) {
+                    dp[i][remK] = dp[i + 1][remK - 1];
+                }
+
+                let freq = 0, delCnt = 0, compLen = 1;
+                for (let j = i; j < n; j++) {
+                    if (s[i] === s[j]) {
+                        if (freq === 1 || freq === 9 || freq === 99) {
+                            compLen++;
+                        }
+                        freq++;
+                    } else {
+                        delCnt++;
+                        if (delCnt > remK) break;
+                    }
+                    dp[i][remK] = Math.min(dp[i][remK], compLen + dp[j + 1][remK - delCnt]);
+                }
+            }
+        }
+
+        return dp[0][k];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 * k)$
+* Space complexity: $O(n * k)$
+
+> Where $n$ is the length of the string $s$ and $k$ is the maximum number of characters that can be deleted from the string.
\ No newline at end of file
diff --git a/articles/string-encode-and-decode.md b/articles/string-encode-and-decode.md
index 8b02832fb..ca00a45b8 100644
--- a/articles/string-encode-and-decode.md
+++ b/articles/string-encode-and-decode.md
@@ -220,12 +220,124 @@ public class Solution {
 }
 ```
 
+```go
+type Solution struct{}
+
+func (s *Solution) Encode(strs []string) string {
+	if len(strs) == 0 {
+		return ""
+	}
+	var sizes []string
+	for _, str := range strs {
+		sizes = append(sizes, strconv.Itoa(len(str)))
+	}
+	return strings.Join(sizes, ",") + "#" + strings.Join(strs, "")
+}
+
+func (s *Solution) Decode(encoded string) []string {
+	if encoded == "" {
+		return []string{}
+	}
+	parts := strings.SplitN(encoded, "#", 2)
+	sizes := strings.Split(parts[0], ",")
+	var res []string
+	i := 0
+	for _, sz := range sizes {
+		if sz == "" {
+			continue
+		}
+		length, _ := strconv.Atoi(sz)
+		res = append(res, parts[1][i:i+length])
+		i += length
+	}
+	return res
+}
+```
+
+```kotlin
+class Solution {
+    fun encode(strs: List<String>): String {
+        if (strs.isEmpty()) return ""
+        val sizes = mutableListOf<String>()
+        for (str in strs) {
+            sizes.add(str.length.toString())
+        }
+        return sizes.joinToString(",") + "#" + strs.joinToString("")
+    }
+
+    fun decode(encoded: String): List<String> {
+        if (encoded.isEmpty()) return emptyList()
+        val parts = encoded.split("#", limit = 2)
+        val sizes = parts[0].split(",")
+        val res = mutableListOf<String>()
+        var i = 0
+        for (sz in sizes) {
+            if (sz.isEmpty()) continue
+            val length = sz.toInt()
+            res.add(parts[1].substring(i, i + length))
+            i += length
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func encode(_ strs: [String]) -> String {
+        if strs.isEmpty { return "" }
+
+        var sizes: [Int] = []
+        var res = ""
+        for s in strs {
+            sizes.append(s.count)
+        }
+        for sz in sizes {
+            res += String(sz)
+            res += ","
+        }
+
+        res += "#"
+        for s in strs {
+            res += s
+        }
+        return res
+    }
+    
+    func decode(_ s: String) -> [String] {
+        if s.isEmpty { return [] }
+        let sArr = Array(s)
+        var sizes: [Int] = []
+        var res: [String] = []
+        var i = 0
+
+        while sArr[i] != "#" {
+            var cur = ""
+            while sArr[i] != "," {
+                cur.append(sArr[i])
+                i += 1
+            }
+            sizes.append(Int(cur)!)
+            i += 1
+        }
+
+        i += 1
+        for sz in sizes {
+            let substring = String(sArr[i..<i+sz])
+            res.append(substring)
+            i += sz
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
-* Time complexity: $O(m)$ for $encode()$ and $decode()$.
-* Space complexity: $O(n)$ for $encode()$ and $decode()$.
+* Time complexity: $O(m)$ for each $encode()$ and $decode()$ function calls.
+* Space complexity: $O(m + n)$ for each $encode()$ and $decode()$ function calls.
 
 > Where $m$ is the sum of lengths of all the strings and $n$ is the number of strings.
 
@@ -387,11 +499,103 @@ public class Solution {
 }
 ```
 
+```go
+type Solution struct{}
+
+func (s *Solution) Encode(strs []string) string {
+	res := ""
+	for _, str := range strs {
+		res += strconv.Itoa(len(str)) + "#" + str
+	}
+	return res
+}
+
+func (s *Solution) Decode(encoded string) []string {
+	res := []string{}
+	i := 0
+	for i < len(encoded) {
+		j := i
+		for encoded[j] != '#' {
+			j++
+		}
+		length, _ := strconv.Atoi(encoded[i:j])
+		i = j + 1
+		res = append(res, encoded[i:i+length])
+		i += length
+	}
+	return res
+}
+```
+
+```kotlin
+class Solution {
+    
+    fun encode(strs: List<String>): String {
+        val res = StringBuilder()
+        for (str in strs) {
+            res.append(str.length).append('#').append(str)
+        }
+        return res.toString()
+    }
+
+    fun decode(encoded: String): List<String> {
+        val res = mutableListOf<String>()
+        var i = 0
+        while (i < encoded.length) {
+            var j = i
+            while (encoded[j] != '#') {
+                j++
+            }
+            val length = encoded.substring(i, j).toInt()
+            i = j + 1
+            res.add(encoded.substring(i, i + length))
+            i += length
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func encode(_ strs: [String]) -> String {
+        var res = ""
+        for s in strs {
+            res += "\(s.count)#\(s)"
+        }
+        return res
+    }
+    
+    func decode(_ s: String) -> [String] {
+        var res = [String]()
+        let sArr = Array(s)
+        var i = 0
+
+        while i < sArr.count {
+            var j = i
+            while sArr[j] != "#" {
+                j += 1
+            }
+            let lengthStr = String(sArr[i..<j])
+            let length = Int(lengthStr)!
+
+            i = j + 1
+            let end = i + length
+            let substring = String(sArr[i..<end])
+            res.append(substring)
+            i = end
+        }
+
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
-* Time complexity: $O(m)$ for $encode()$ and $decode()$.
-* Space complexity: $O(1)$ for $encode()$ and $decode()$.
+* Time complexity: $O(m)$ for each $encode()$ and $decode()$ function calls.
+* Space complexity: $O(m + n)$ for each $encode()$ and $decode()$ function calls.
 
 > Where $m$ is the sum of lengths of all the strings and $n$ is the number of strings.
\ No newline at end of file
diff --git a/articles/string-matching-in-an-array.md b/articles/string-matching-in-an-array.md
new file mode 100644
index 000000000..f369be41c
--- /dev/null
+++ b/articles/string-matching-in-an-array.md
@@ -0,0 +1,1157 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def stringMatching(self, words: List[str]) -> List[str]:
+        res = []
+
+        for i in range(len(words)):
+            for j in range(len(words)):
+                if i == j:
+                    continue
+
+                if words[i] in words[j]:
+                    res.append(words[i])
+                    break
+
+        return res
+```
+
+```java
+public class Solution {
+    public List<String> stringMatching(String[] words) {
+        List<String> res = new ArrayList<>();
+
+        for (int i = 0; i < words.length; i++) {
+            for (int j = 0; j < words.length; j++) {
+                if (i == j) {
+                    continue;
+                }
+
+                if (words[j].contains(words[i])) {
+                    res.add(words[i]);
+                    break;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<string> stringMatching(vector<string>& words) {
+        vector<string> res;
+
+        for (int i = 0; i < words.size(); i++) {
+            for (int j = 0; j < words.size(); j++) {
+                if (i == j) {
+                    continue;
+                }
+
+                if (words[j].find(words[i]) != string::npos) {
+                    res.push_back(words[i]);
+                    break;
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @return {string[]}
+     */
+    stringMatching(words) {
+        let res = [];
+
+        for (let i = 0; i < words.length; i++) {
+            for (let j = 0; j < words.length; j++) {
+                if (i === j) {
+                    continue;
+                }
+
+                if (words[j].includes(words[i])) {
+                    res.push(words[i]);
+                    break;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 * m ^ 2)$
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(n * m)$ space for the output list.
+
+> Where $n$ is the number of words, and $m$ is the length of the longest word.
+
+---
+
+## 2. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def stringMatching(self, words: List[str]) -> List[str]:
+        res = []
+        words.sort(key=len)
+
+        for i in range(len(words)):
+            for j in range(i + 1, len(words)):
+                if words[i] in words[j]:
+                    res.append(words[i])
+                    break
+
+        return res
+```
+
+```java
+public class Solution {
+    public List<String> stringMatching(String[] words) {
+        List<String> res = new ArrayList<>();
+        Arrays.sort(words, Comparator.comparingInt(String::length));
+
+        for (int i = 0; i < words.length; i++) {
+            for (int j = i + 1; j < words.length; j++) {
+                if (words[j].contains(words[i])) {
+                    res.add(words[i]);
+                    break;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<string> stringMatching(vector<string>& words) {
+        vector<string> res;
+        sort(words.begin(), words.end(), [](const string& a, const string& b) {
+            return a.length() < b.length();
+        });
+
+        for (int i = 0; i < words.size(); i++) {
+            for (int j = i + 1; j < words.size(); j++) {
+                if (words[j].find(words[i]) != string::npos) {
+                    res.push_back(words[i]);
+                    break;
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @return {string[]}
+     */
+    stringMatching(words) {
+        let res = [];
+        words.sort((a, b) => a.length - b.length);
+
+        for (let i = 0; i < words.length; i++) {
+            for (let j = i + 1; j < words.length; j++) {
+                if (words[j].includes(words[i])) {
+                    res.push(words[i]);
+                    break;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 * m ^ 2)$
+* Space complexity:
+    * $O(1)$ or $O(n)$ depending on the sorting algorithm.
+    * $O(n * m)$ space for the output list.
+
+> Where $n$ is the number of words, and $m$ is the length of the longest word.
+
+---
+
+## 3. Knuth-Morris-Pratt (KMP) Algorithm
+
+::tabs-start
+
+```python
+class Solution:
+    def stringMatching(self, words: List[str]) -> List[str]:
+        def kmp(word1: str, word2: str) -> int:
+            lps = [0] * len(word2)
+            prevLPS, i = 0, 1
+
+            while i < len(word2):
+                if word2[i] == word2[prevLPS]:
+                    lps[i] = prevLPS + 1
+                    prevLPS += 1
+                    i += 1
+                elif prevLPS == 0:
+                    lps[i] = 0
+                    i += 1
+                else:
+                    prevLPS = lps[prevLPS - 1]
+
+            i = j = 0
+            while i < len(word1):
+                if word1[i] == word2[j]:
+                    i += 1
+                    j += 1
+                else:
+                    if j == 0:
+                        i += 1
+                    else:
+                        j = lps[j - 1]
+
+                if j == len(word2):
+                    return i - len(word2)
+
+            return -1
+
+        res = []
+        words.sort(key=len)
+
+        for i in range(len(words)):
+            for j in range(i + 1, len(words)):
+                if kmp(words[j], words[i]) != -1:
+                    res.append(words[i])
+                    break
+
+        return res
+```
+
+```java
+public class Solution {
+    public List<String> stringMatching(String[] words) {
+        List<String> res = new ArrayList<>();
+        Arrays.sort(words, Comparator.comparingInt(String::length));
+
+        for (int i = 0; i < words.length; i++) {
+            for (int j = i + 1; j < words.length; j++) {
+                if (kmp(words[j], words[i]) != -1) {
+                    res.add(words[i]);
+                    break;
+                }
+            }
+        }
+
+        return res;
+    }
+
+    private int kmp(String word1, String word2) {
+        int[] lps = new int[word2.length()];
+        int prevLPS = 0, i = 1;
+
+        while (i < word2.length()) {
+            if (word2.charAt(i) == word2.charAt(prevLPS)) {
+                lps[i] = prevLPS + 1;
+                prevLPS++;
+                i++;
+            } else if (prevLPS == 0) {
+                lps[i] = 0;
+                i++;
+            } else {
+                prevLPS = lps[prevLPS - 1];
+            }
+        }
+
+        i = 0;
+        int j = 0;
+        while (i < word1.length()) {
+            if (word1.charAt(i) == word2.charAt(j)) {
+                i++;
+                j++;
+            } else {
+                if (j == 0) {
+                    i++;
+                } else {
+                    j = lps[j - 1];
+                }
+            }
+
+            if (j == word2.length()) {
+                return i - word2.length();
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<string> stringMatching(vector<string>& words) {
+        vector<string> res;
+        sort(words.begin(), words.end(), [](const string& a, const string& b) {
+            return a.length() < b.length();
+        });
+
+        for (int i = 0; i < words.size(); i++) {
+            for (int j = i + 1; j < words.size(); j++) {
+                if (kmp(words[j], words[i]) != -1) {
+                    res.push_back(words[i]);
+                    break;
+                }
+            }
+        }
+
+        return res;
+    }
+
+private:
+    int kmp(const string& word1, const string& word2) {
+        vector<int> lps(word2.size(), 0);
+        int prevLPS = 0, i = 1;
+
+        while (i < word2.size()) {
+            if (word2[i] == word2[prevLPS]) {
+                lps[i++] = ++prevLPS;
+            } else if (prevLPS == 0) {
+                lps[i++] = 0;
+            } else {
+                prevLPS = lps[prevLPS - 1];
+            }
+        }
+
+        i = 0;
+        int j = 0;
+        while (i < word1.size()) {
+            if (word1[i] == word2[j]) {
+                i++;
+                j++;
+            } else {
+                if (j == 0) {
+                    i++;
+                } else {
+                    j = lps[j - 1];
+                }
+            }
+
+            if (j == word2.size()) {
+                return i - word2.size();
+            }
+        }
+
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @return {string[]}
+     */
+    stringMatching(words) {
+        const kmp = (word1, word2) => {
+            const lps = Array(word2.length).fill(0);
+            let prevLPS = 0, i = 1;
+
+            while (i < word2.length) {
+                if (word2[i] === word2[prevLPS]) {
+                    lps[i++] = ++prevLPS;
+                } else if (prevLPS === 0) {
+                    lps[i++] = 0;
+                } else {
+                    prevLPS = lps[prevLPS - 1];
+                }
+            }
+
+            i = 0;
+            let j = 0;
+            while (i < word1.length) {
+                if (word1[i] === word2[j]) {
+                    i++;
+                    j++;
+                } else {
+                    if (j === 0) {
+                        i++;
+                    } else {
+                        j = lps[j - 1];
+                    }
+                }
+
+                if (j === word2.length) {
+                    return i - word2.length;
+                }
+            }
+
+            return -1;
+        };
+
+        let res = [];
+        words.sort((a, b) => a.length - b.length);
+
+        for (let i = 0; i < words.length; i++) {
+            for (let j = i + 1; j < words.length; j++) {
+                if (kmp(words[j], words[i]) !== -1) {
+                    res.push(words[i]);
+                    break;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 * m)$
+* Space complexity:
+    * $O(m)$ extra space.
+    * $O(1)$ or $O(n)$ space depending on the sorting algorithm.
+    * $O(n * m)$ space for the output list.
+
+> Where $n$ is the number of words, and $m$ is the length of the longest word.
+
+---
+
+## 4. Rabin-Karp Algorithm (Rolling Hash)
+
+::tabs-start
+
+```python
+class Solution:
+    def stringMatching(self, words: List[str]) -> List[str]:
+        def rabinKarp(word1: str, word2: str) -> int:
+            base1, mod1 = 31, 768258391
+            base2, mod2 = 37, 685683731
+            n, m = len(word1), len(word2)
+
+            power1, power2 = 1, 1
+            for _ in range(m):
+                power1 = (power1 * base1) % mod1
+                power2 = (power2 * base2) % mod2
+
+            word1_hash1 = word1_hash2 = 0
+            word2_hash1 = word2_hash2 = 0
+
+            for i in range(m):
+                word1_hash1 = (word1_hash1 * base1 + ord(word2[i])) % mod1
+                word1_hash2 = (word1_hash2 * base2 + ord(word2[i])) % mod2
+                word2_hash1 = (word2_hash1 * base1 + ord(word1[i])) % mod1
+                word2_hash2 = (word2_hash2 * base2 + ord(word1[i])) % mod2
+
+            for i in range(n - m + 1):
+                if word2_hash1 == word1_hash1 and word2_hash2 == word1_hash2:
+                    return i
+
+                if i + m < n:
+                    word2_hash1 = (word2_hash1 * base1 - ord(word1[i]) * power1 + ord(word1[i + m])) % mod1
+                    word2_hash2 = (word2_hash2 * base2 - ord(word1[i]) * power2 + ord(word1[i + m])) % mod2
+
+                    word2_hash1 = (word2_hash1 + mod1) % mod1
+                    word2_hash2 = (word2_hash2 + mod2) % mod2
+
+            return -1
+
+        res = []
+        words.sort(key=len)
+
+        for i in range(len(words)):
+            for j in range(i + 1, len(words)):
+                if rabinKarp(words[j], words[i]) != -1:
+                    res.append(words[i])
+                    break
+
+        return res
+```
+
+```java
+public class Solution {
+    public List<String> stringMatching(String[] words) {
+        List<String> res = new ArrayList<>();
+        Arrays.sort(words, Comparator.comparingInt(String::length));
+
+        for (int i = 0; i < words.length; i++) {
+            for (int j = i + 1; j < words.length; j++) {
+                if (rabinKarp(words[j], words[i]) != -1) {
+                    res.add(words[i]);
+                    break;
+                }
+            }
+        }
+
+        return res;
+    }
+
+    private int rabinKarp(String word1, String word2) {
+        int base1 = 31, mod1 = 768258391;
+        int base2 = 37, mod2 = 685683731;
+        int n = word1.length(), m = word2.length();
+
+        long power1 = 1, power2 = 1;
+        for (int k = 0; k < m; k++) {
+            power1 = (power1 * base1) % mod1;
+            power2 = (power2 * base2) % mod2;
+        }
+
+        long word1Hash1 = 0, word1Hash2 = 0;
+        long word2Hash1 = 0, word2Hash2 = 0;
+
+        for (int i = 0; i < m; i++) {
+            word1Hash1 = (word1Hash1 * base1 + word2.charAt(i)) % mod1;
+            word1Hash2 = (word1Hash2 * base2 + word2.charAt(i)) % mod2;
+            word2Hash1 = (word2Hash1 * base1 + word1.charAt(i)) % mod1;
+            word2Hash2 = (word2Hash2 * base2 + word1.charAt(i)) % mod2;
+        }
+
+        for (int i = 0; i <= n - m; i++) {
+            if (word2Hash1 == word1Hash1 && word2Hash2 == word1Hash2) {
+                return i;
+            }
+
+            if (i + m < n) {
+                word2Hash1 = (word2Hash1 * base1 - word1.charAt(i) * power1 + word1.charAt(i + m)) % mod1;
+                word2Hash2 = (word2Hash2 * base2 - word1.charAt(i) * power2 + word1.charAt(i + m)) % mod2;
+
+                if (word2Hash1 < 0) word2Hash1 += mod1;
+                if (word2Hash2 < 0) word2Hash2 += mod2;
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<string> stringMatching(vector<string>& words) {
+        vector<string> res;
+        sort(words.begin(), words.end(), [](const string& a, const string& b) {
+            return a.length() < b.length();
+        });
+
+        for (int i = 0; i < words.size(); i++) {
+            for (int j = i + 1; j < words.size(); j++) {
+                if (rabinKarp(words[j], words[i]) != -1) {
+                    res.push_back(words[i]);
+                    break;
+                }
+            }
+        }
+
+        return res;
+    }
+
+private:
+    int rabinKarp(const string& word1, const string& word2) {
+        int base1 = 31, mod1 = 768258391;
+        int base2 = 37, mod2 = 685683731;
+        int n = word1.size(), m = word2.size();
+
+        long long power1 = 1, power2 = 1;
+        for (int i = 0; i < m; i++) {
+            power1 = (power1 * base1) % mod1;
+            power2 = (power2 * base2) % mod2;
+        }
+
+        long long word1Hash1 = 0, word1Hash2 = 0;
+        long long word2Hash1 = 0, word2Hash2 = 0;
+
+        for (int i = 0; i < m; i++) {
+            word1Hash1 = (word1Hash1 * base1 + word2[i]) % mod1;
+            word1Hash2 = (word1Hash2 * base2 + word2[i]) % mod2;
+            word2Hash1 = (word2Hash1 * base1 + word1[i]) % mod1;
+            word2Hash2 = (word2Hash2 * base2 + word1[i]) % mod2;
+        }
+
+        for (int i = 0; i <= n - m; i++) {
+            if (word2Hash1 == word1Hash1 && word2Hash2 == word1Hash2) {
+                return i;
+            }
+
+            if (i + m < n) {
+                word2Hash1 = (word2Hash1 * base1 - word1[i] * power1 + word1[i + m]) % mod1;
+                word2Hash2 = (word2Hash2 * base2 - word1[i] * power2 + word1[i + m]) % mod2;
+
+                if (word2Hash1 < 0) word2Hash1 += mod1;
+                if (word2Hash2 < 0) word2Hash2 += mod2;
+            }
+        }
+
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @return {string[]}
+     */
+    stringMatching(words) {
+        const rabinKarp = (word1, word2) => {
+            const base1 = 31, mod1 = 768258391;
+            const base2 = 37, mod2 = 685683731;
+            const n = word1.length, m = word2.length;
+
+            let power1 = 1, power2 = 1;
+            for (let k = 0; k < m; k++) {
+                power1 = (power1 * base1) % mod1;
+                power2 = (power2 * base2) % mod2;
+            }
+
+            let hash1 = 0, hash2 = 0;
+            let cur1 = 0, cur2 = 0;
+
+            for (let i = 0; i < m; i++) {
+                hash1 = (hash1 * base1 + word2.charCodeAt(i)) % mod1;
+                hash2 = (hash2 * base2 + word2.charCodeAt(i)) % mod2;
+                cur1 = (cur1 * base1 + word1.charCodeAt(i)) % mod1;
+                cur2 = (cur2 * base2 + word1.charCodeAt(i)) % mod2;
+            }
+
+            for (let i = 0; i <= n - m; i++) {
+                if (cur1 === hash1 && cur2 === hash2) {
+                    return i;
+                }
+
+                if (i + m < n) {
+                    cur1 = (cur1 * base1 - word1.charCodeAt(i) * power1 + word1.charCodeAt(i + m)) % mod1;
+                    cur2 = (cur2 * base2 - word1.charCodeAt(i) * power2 + word1.charCodeAt(i + m)) % mod2;
+
+                    cur1 = (cur1 + mod1) % mod1;
+                    cur2 = (cur2 + mod2) % mod2;
+                }
+            }
+
+            return -1;
+        };
+
+        words.sort((a, b) => a.length - b.length);
+        let res = [];
+
+        for (let i = 0; i < words.length; i++) {
+            for (let j = i + 1; j < words.length; j++) {
+                if (rabinKarp(words[j], words[i]) !== -1) {
+                    res.push(words[i]);
+                    break;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 * m)$
+* Space complexity:
+    * $O(1)$ or $O(n)$ space depending on the sorting algorithm.
+    * $O(n * m)$ space for the output list.
+
+> Where $n$ is the number of words, and $m$ is the length of the longest word.
+
+---
+
+## 5. Z-Algorithm
+
+::tabs-start
+
+```python
+class Solution:
+    def stringMatching(self, words: List[str]) -> List[str]:
+        def zAlgorithm(word1: str, word2: str) -> int:
+            s = word2 + "$" + word1
+            n = len(s)
+            z = [0] * n
+            l, r = 0, 0
+
+            for i in range(1, n):
+                if i <= r:
+                    z[i] = min(r - i + 1, z[i - l])
+                while i + z[i] < n and s[z[i]] == s[i + z[i]]:
+                    z[i] += 1
+                if i + z[i] - 1 > r:
+                    l, r = i, i + z[i] - 1
+
+            for i in range(len(word2) + 1, n):
+                if z[i] == len(word2):
+                    return i - len(word2) - 1
+
+            return -1
+
+        res = []
+        words.sort(key=len)
+
+        for i in range(len(words)):
+            for j in range(i + 1, len(words)):
+                if zAlgorithm(words[j], words[i]) != -1:
+                    res.append(words[i])
+                    break
+
+        return res
+```
+
+```java
+public class Solution {
+    public List<String> stringMatching(String[] words) {
+        List<String> res = new ArrayList<>();
+        Arrays.sort(words, Comparator.comparingInt(String::length));
+
+        for (int i = 0; i < words.length; i++) {
+            for (int j = i + 1; j < words.length; j++) {
+                if (zAlgorithm(words[j], words[i]) != -1) {
+                    res.add(words[i]);
+                    break;
+                }
+            }
+        }
+
+        return res;
+    }
+
+    private int zAlgorithm(String word1, String word2) {
+        String s = word2 + "$" + word1;
+        int n = s.length();
+        int[] z = new int[n];
+        int l = 0, r = 0;
+
+        for (int i = 1; i < n; i++) {
+            if (i <= r) {
+                z[i] = Math.min(r - i + 1, z[i - l]);
+            }
+            while (i + z[i] < n && s.charAt(z[i]) == s.charAt(i + z[i])) {
+                z[i]++;
+            }
+            if (i + z[i] - 1 > r) {
+                l = i;
+                r = i + z[i] - 1;
+            }
+        }
+
+        for (int i = word2.length() + 1; i < n; i++) {
+            if (z[i] == word2.length()) {
+                return i - word2.length() - 1;
+            }
+        }
+
+        return -1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<string> stringMatching(vector<string>& words) {
+        vector<string> res;
+        sort(words.begin(), words.end(), [](const string& a, const string& b) {
+            return a.length() < b.length();
+        });
+
+        for (int i = 0; i < words.size(); i++) {
+            for (int j = i + 1; j < words.size(); j++) {
+                if (zAlgorithm(words[j], words[i]) != -1) {
+                    res.push_back(words[i]);
+                    break;
+                }
+            }
+        }
+
+        return res;
+    }
+
+private:
+    int zAlgorithm(const string& word1, const string& word2) {
+        string s = word2 + "$" + word1;
+        int n = s.size();
+        vector<int> z(n, 0);
+        int l = 0, r = 0;
+
+        for (int i = 1; i < n; i++) {
+            if (i <= r) {
+                z[i] = min(r - i + 1, z[i - l]);
+            }
+            while (i + z[i] < n && s[z[i]] == s[i + z[i]]) {
+                z[i]++;
+            }
+            if (i + z[i] - 1 > r) {
+                l = i;
+                r = i + z[i] - 1;
+            }
+        }
+
+        for (int i = word2.size() + 1; i < n; i++) {
+            if (z[i] == word2.size()) {
+                return i - word2.size() - 1;
+            }
+        }
+
+        return -1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @return {string[]}
+     */
+    stringMatching(words) {
+        const zAlgorithm = (word1, word2) => {
+            const s = word2 + "$" + word1;
+            const n = s.length;
+            const z = Array(n).fill(0);
+            let l = 0, r = 0;
+
+            for (let i = 1; i < n; i++) {
+                if (i <= r) {
+                    z[i] = Math.min(r - i + 1, z[i - l]);
+                }
+                while (i + z[i] < n && s[z[i]] === s[i + z[i]]) {
+                    z[i]++;
+                }
+                if (i + z[i] - 1 > r) {
+                    l = i;
+                    r = i + z[i] - 1;
+                }
+            }
+
+            for (let i = word2.length + 1; i < n; i++) {
+                if (z[i] === word2.length) {
+                    return i - word2.length - 1;
+                }
+            }
+
+            return -1;
+        };
+
+        words.sort((a, b) => a.length - b.length);
+        let res = [];
+
+        for (let i = 0; i < words.length; i++) {
+            for (let j = i + 1; j < words.length; j++) {
+                if (zAlgorithm(words[j], words[i]) !== -1) {
+                    res.push(words[i]);
+                    break;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2 * m)$
+* Space complexity:
+    * $O(m)$ extra space.
+    * $O(1)$ or $O(n)$ space depending on the sorting algorithm.
+    * $O(n * m)$ space for the output list.
+
+> Where $n$ is the number of words, and $m$ is the length of the longest word.
+
+---
+
+## 6. Trie
+
+::tabs-start
+
+```python
+class TrieNode:
+    def __init__(self):
+        self.children = [None] * 26
+        self.cnt = 0
+
+class Trie:
+    def __init__(self):
+        self.root = TrieNode()
+
+    def insert_suffixes(self, word: str) -> None:
+        for i in range(len(word)):
+            node = self.root
+            for j in range(i, len(word)):
+                idx = ord(word[j]) - ord('a')
+                if not node.children[idx]:
+                    node.children[idx] = TrieNode()
+
+                node = node.children[idx]
+                node.cnt += 1
+
+    def search(self, word: str) -> bool:
+        node = self.root
+        for c in word:
+            idx = ord(c) - ord('a')
+            node = node.children[idx]
+        return node.cnt > 1
+
+class Solution:
+    def stringMatching(self, words: List[str]) -> List[str]:
+        res = []
+        trie = Trie()
+
+        for word in words:
+            trie.insert_suffixes(word)
+
+        for word in words:
+            if trie.search(word):
+                res.append(word)
+
+        return res
+```
+
+```java
+class TrieNode {
+    TrieNode[] children;
+    int cnt;
+
+    TrieNode() {
+        children = new TrieNode[26];
+        cnt = 0;
+    }
+}
+
+class Trie {
+    TrieNode root;
+
+    Trie() {
+        root = new TrieNode();
+    }
+
+    void insertSuffixes(String word) {
+        for (int i = 0; i < word.length(); i++) {
+            TrieNode node = root;
+            for (int j = i; j < word.length(); j++) {
+                int idx = word.charAt(j) - 'a';
+                if (node.children[idx] == null) {
+                    node.children[idx] = new TrieNode();
+                }
+
+                node = node.children[idx];
+                node.cnt++;
+            }
+        }
+    }
+
+    boolean search(String word) {
+        TrieNode node = root;
+        for (int i = 0; i < word.length(); i++) {
+            int idx = word.charAt(i) - 'a';
+            node = node.children[idx];
+        }
+        return node.cnt > 1;
+    }
+}
+
+class Solution {
+    public List<String> stringMatching(String[] words) {
+        List<String> res = new ArrayList<>();
+        Trie trie = new Trie();
+
+        for (String word : words) {
+            trie.insertSuffixes(word);
+        }
+
+        for (String word : words) {
+            if (trie.search(word)) {
+                res.add(word);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class TrieNode {
+public:
+    TrieNode* children[26];
+    int cnt;
+
+    TrieNode() {
+        for (int i = 0; i < 26; i++) children[i] = nullptr;
+        cnt = 0;
+    }
+};
+
+class Trie {
+public:
+    TrieNode* root;
+
+    Trie() {
+        root = new TrieNode();
+    }
+
+    void insertSuffixes(const string& word) {
+        for (int i = 0; i < word.size(); i++) {
+            TrieNode* node = root;
+            for (int j = i; j < word.size(); j++) {
+                int idx = word[j] - 'a';
+                if (!node->children[idx]) {
+                    node->children[idx] = new TrieNode();
+                }
+
+                node = node->children[idx];
+                node->cnt++;
+            }
+        }
+    }
+
+    bool search(const string& word) {
+        TrieNode* node = root;
+        for (char c : word) {
+            int idx = c - 'a';
+            node = node->children[idx];
+        }
+        return node->cnt > 1;
+    }
+};
+
+class Solution {
+public:
+    vector<string> stringMatching(vector<string>& words) {
+        vector<string> res;
+        Trie trie;
+
+        for (const string& word : words) {
+            trie.insertSuffixes(word);
+        }
+
+        for (const string& word : words) {
+            if (trie.search(word)) {
+                res.push_back(word);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class TrieNode {
+    constructor() {
+        this.children = new Array(26).fill(null);
+        this.cnt = 0;
+    }
+}
+
+class Trie {
+    constructor() {
+        this.root = new TrieNode();
+    }
+
+    /**
+     * @param {string} word
+     * @return {void}
+     */
+    insertSuffixes(word) {
+        for (let i = 0; i < word.length; i++) {
+            let node = this.root;
+            for (let j = i; j < word.length; j++) {
+                let idx = word.charCodeAt(j) - 97;
+                if (!node.children[idx]) {
+                    node.children[idx] = new TrieNode();
+                }
+
+                node = node.children[idx];
+                node.cnt++;
+            }
+        }
+    }
+
+    /**
+     * @param {string} word
+     * @return {boolean}
+     */
+    search(word) {
+        let node = this.root;
+        for (let i = 0; i < word.length; i++) {
+            let idx = word.charCodeAt(i) - 97;
+            node = node.children[idx];
+        }
+        return node.cnt > 1;
+    }
+}
+
+class Solution {
+    /**
+     * @param {string[]} words
+     * @return {string[]}
+     */
+    stringMatching(words) {
+        const res = [];
+        const trie = new Trie();
+
+        for (let word of words) {
+            trie.insertSuffixes(word);
+        }
+
+        for (let word of words) {
+            if (trie.search(word)) {
+                res.push(word);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m ^ 2)$
+* Space complexity:
+    * $O(n * m ^ 2)$ extra space.
+    * $O(n * m)$ space for the output list.
+
+> Where $n$ is the number of words, and $m$ is the length of the longest word.
\ No newline at end of file
diff --git a/articles/student-attendance-record-ii.md b/articles/student-attendance-record-ii.md
new file mode 100644
index 000000000..b941f3076
--- /dev/null
+++ b/articles/student-attendance-record-ii.md
@@ -0,0 +1,854 @@
+## 1. Dynamic Programming (Top-Down) - I
+
+::tabs-start
+
+```python
+class Solution:
+    def checkRecord(self, n: int) -> int:
+        MOD = 1000000007
+        cache = [[[-1 for _ in range(3)] for _ in range(2)] for _ in range(n + 1)]
+
+        def dfs(i, cntA, cntL):
+            if i == 0:
+                return 1
+            if cache[i][cntA][cntL] != -1:
+                return cache[i][cntA][cntL]
+
+            res = dfs(i - 1, cntA, 0) % MOD
+
+            if cntA == 0:
+                res = (res + dfs(i - 1, 1, 0)) % MOD
+
+            if cntL < 2:
+                res = (res + dfs(i - 1, cntA, cntL + 1)) % MOD
+
+            cache[i][cntA][cntL] = res
+            return res
+
+        return dfs(n, 0, 0)
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1000000007;
+    private int[][][] cache;
+
+    public int checkRecord(int n) {
+        this.cache = new int[n + 1][2][3];
+        for (int[][] matrix : cache) {
+            for (int[] row : matrix) {
+                Arrays.fill(row, -1);
+            }
+        }
+        return dfs(n, 0, 0);
+    }
+
+    private int dfs(int i, int cntA, int cntL) {
+        if (i == 0) {
+            return 1;
+        }
+        if (cache[i][cntA][cntL] != -1) {
+            return cache[i][cntA][cntL];
+        }
+
+        int res = dfs(i - 1, cntA, 0) % MOD;
+
+        if (cntA == 0) {
+            res = (res + dfs(i - 1, 1, 0)) % MOD;
+        }
+
+        if (cntL < 2) {
+            res = (res + dfs(i - 1, cntA, cntL + 1)) % MOD;
+        }
+
+        return cache[i][cntA][cntL] = res;
+    }
+}
+```
+
+```cpp
+class Solution {
+    const int MOD = 1000000007;
+    vector<vector<vector<int>>> cache;
+
+public:
+    int checkRecord(int n) {
+        cache.assign(n + 1, vector<vector<int>>(2, vector<int>(3, -1)));
+        return dfs(n, 0, 0);
+    }
+
+private:
+    int dfs(int i, int cntA, int cntL) {
+        if (i == 0) {
+            return 1;
+        }
+        if (cache[i][cntA][cntL] != -1) {
+            return cache[i][cntA][cntL];
+        }
+
+        int res = dfs(i - 1, cntA, 0) % MOD;
+
+        if (cntA == 0) {
+            res = (res + dfs(i - 1, 1, 0)) % MOD;
+        }
+
+        if (cntL < 2) {
+            res = (res + dfs(i - 1, cntA, cntL + 1)) % MOD;
+        }
+
+        return cache[i][cntA][cntL] = res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    checkRecord(n) {
+        const MOD = 1000000007;
+        let cache = Array.from({ length: n + 1 }, () =>
+            Array.from({ length: 2 }, () => new Array(3).fill(-1))
+        );
+
+        const dfs = (i, cntA, cntL) => {
+            if (i === 0) return 1;
+            if (cache[i][cntA][cntL] !== -1) return cache[i][cntA][cntL];
+
+            let res = dfs(i - 1, cntA, 0) % MOD;
+
+            if (cntA === 0) {
+                res = (res + dfs(i - 1, 1, 0)) % MOD;
+            }
+
+            if (cntL < 2) {
+                res = (res + dfs(i - 1, cntA, cntL + 1)) % MOD;
+            }
+
+            return (cache[i][cntA][cntL] = res);
+        };
+
+        return dfs(n, 0, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Dynamic Programming (Top-Down) - II
+
+::tabs-start
+
+```python
+class Solution:
+    def checkRecord(self, n: int) -> int:
+        MOD = 10**9 + 7
+        cache = {}
+
+        def count(n):
+            if n == 1:
+                # (A, L)
+                return {
+                    (0, 0): 1, (0, 1): 1, (0, 2): 0,
+                    (1, 0): 1, (1, 1): 0, (1, 2): 0
+                }
+
+            if n in cache:
+                return cache[n]
+
+            tmp = count(n - 1)
+            res = defaultdict(int)
+
+            # Choose P
+            res[(0, 0)] = ((tmp[(0, 0)] + tmp[(0, 1)]) % MOD + tmp[(0, 2)]) % MOD
+            res[(1, 0)] = ((tmp[(1, 0)] + tmp[(1, 1)]) % MOD + tmp[(1, 2)]) % MOD
+
+            # Choose L
+            res[(0, 1)] = tmp[(0, 0)]
+            res[(0, 2)] = tmp[(0, 1)]
+            res[(1, 1)] = tmp[(1, 0)]
+            res[(1, 2)] = tmp[(1, 1)]
+
+            # Choose A
+            res[(1, 0)] += ((tmp[(0, 0)] + tmp[(0, 1)]) % MOD + tmp[(0, 2)]) % MOD
+
+            cache[n] = res
+            return res
+
+        return sum(count(n).values()) % MOD
+```
+
+```java
+public class Solution {
+    private static final int MOD = 1000000007;
+    private int[][][] cache;
+    private int[][] baseCase;
+
+    public int checkRecord(int n) {
+        cache = new int[n + 1][2][3];
+        baseCase = new int[][]{{1, 1, 0}, {1, 0, 0}};
+        for (int[][] matrix : cache) {
+            for (int[] row : matrix) {
+                Arrays.fill(row, -1);
+            }
+        }
+        int[][] result = count(n);
+        int total = 0;
+        for (int[] row : result) {
+            for (int val : row) {
+                total = (total + val) % MOD;
+            }
+        }
+        return total;
+    }
+
+    private int[][] count(int n) {
+        if (n == 1) {
+            // (A, L)
+            return baseCase;
+        }
+
+        if (cache[n][0][0] != -1) {
+            return cache[n];
+        }
+
+        int[][] prev = count(n - 1);
+        int[][] res = cache[n];
+
+        // Choose P
+        res[0][0] = ((prev[0][0] + prev[0][1]) % MOD + prev[0][2]) % MOD;
+        res[1][0] = ((prev[1][0] + prev[1][1]) % MOD + prev[1][2]) % MOD;
+
+        // Choose L
+        res[0][1] = prev[0][0];
+        res[0][2] = prev[0][1];
+        res[1][1] = prev[1][0];
+        res[1][2] = prev[1][1];
+
+        // Choose A
+        res[1][0] = (res[1][0] + ((prev[0][0] + prev[0][1]) % MOD + prev[0][2]) % MOD) % MOD;
+
+        return cache[n];
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    static constexpr int MOD = 1000000007;
+    vector<vector<int>> baseCase = {{1, 1, 0}, {1, 0, 0}};
+    vector<vector<vector<int>>> cache;
+
+public:
+    int checkRecord(int n) {
+        cache.assign(n + 1, vector<vector<int>>(2, vector<int>(3, -1)));
+        const vector<vector<int>>& result = count(n);
+        int total = 0;
+        for (const auto& row : result) {
+            for (int val : row) {
+                total = (total + val) % MOD;
+            }
+        }
+        return total;
+    }
+
+private:
+    const vector<vector<int>>& count(int n) {
+        if (n == 1) {
+            return baseCase;
+        }
+
+        if (cache[n][0][0] != -1) {
+            return cache[n];
+        }
+
+        const vector<vector<int>>& prev = count(n - 1);
+        auto& res = cache[n];
+
+        // Choose P
+        res[0][0] = ((prev[0][0] + prev[0][1]) % MOD + prev[0][2]) % MOD;
+        res[1][0] = ((prev[1][0] + prev[1][1]) % MOD + prev[1][2]) % MOD;
+
+        // Choose L
+        res[0][1] = prev[0][0];
+        res[0][2] = prev[0][1];
+        res[1][1] = prev[1][0];
+        res[1][2] = prev[1][1];
+
+        // Choose A
+        res[1][0] = (res[1][0] + ((prev[0][0] + prev[0][1]) % MOD + prev[0][2]) % MOD) % MOD;
+
+        return cache[n];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    checkRecord(n) {
+        const MOD = 1000000007;
+        const baseCase = [
+            [1, 1, 0], // (A = 0, L = 0, 1, 2)
+            [1, 0, 0]  // (A = 1, L = 0, 1, 2)
+        ];
+        let cache = Array.from({ length: n + 1 }, () =>
+            Array.from({ length: 2 }, () => new Array(3).fill(-1))
+        );
+
+        const count = (n) => {
+            if (n === 1) return baseCase;
+            if (cache[n][0][0] !== -1) return cache[n];
+
+            const prev = count(n - 1);
+            const res = cache[n];
+
+            // Choose P
+            res[0][0] = ((prev[0][0] + prev[0][1]) % MOD + prev[0][2]) % MOD;
+            res[1][0] = ((prev[1][0] + prev[1][1]) % MOD + prev[1][2]) % MOD;
+
+            // Choose L
+            res[0][1] = prev[0][0];
+            res[0][2] = prev[0][1];
+            res[1][1] = prev[1][0];
+            res[1][2] = prev[1][1];
+
+            // Choose A
+            res[1][0] = (res[1][0] + ((prev[0][0] + prev[0][1]) % MOD + prev[0][2]) % MOD) % MOD;
+
+            return res;
+        };
+
+        const result = count(n);
+        let total = 0;
+        for (const row of result) {
+            for (const val of row) {
+                total = (total + val) % MOD;
+            }
+        }
+        return total;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def checkRecord(self, n: int) -> int:
+        MOD = 1000000007
+        dp = [[[0 for _ in range(3)] for _ in range(2)] for _ in range(n + 1)]
+        
+        dp[0][0][0] = 1  # Base case
+
+        for i in range(1, n + 1):
+            for cntA in range(2):
+                for cntL in range(3):
+                    # Choose P
+                    dp[i][cntA][0] = (dp[i][cntA][0] + dp[i - 1][cntA][cntL]) % MOD
+
+                    # Choose A
+                    if cntA > 0:
+                        dp[i][cntA][0] = (dp[i][cntA][0] + dp[i - 1][cntA - 1][cntL]) % MOD
+
+                    # Choose L
+                    if cntL > 0:
+                        dp[i][cntA][cntL] = (dp[i][cntA][cntL] + dp[i - 1][cntA][cntL - 1]) % MOD
+
+        return sum(dp[n][cntA][cntL] for cntA in range(2) for cntL in range(3)) % MOD
+```
+
+```java
+public class Solution {
+    public int checkRecord(int n) {
+        final int MOD = 1000000007;
+        int[][][] dp = new int[n + 1][2][3];
+
+        dp[0][0][0] = 1;
+
+        for (int i = 1; i <= n; i++) {
+            for (int cntA = 0; cntA < 2; cntA++) {
+                for (int cntL = 0; cntL < 3; cntL++) {
+                    // Choose P
+                    dp[i][cntA][0] = (dp[i][cntA][0] + dp[i - 1][cntA][cntL]) % MOD;
+
+                    // Choose A
+                    if (cntA > 0) {
+                        dp[i][cntA][0] = (dp[i][cntA][0] + dp[i - 1][cntA - 1][cntL]) % MOD;
+                    }
+
+                    // Choose L
+                    if (cntL > 0) {
+                        dp[i][cntA][cntL] = (dp[i][cntA][cntL] + dp[i - 1][cntA][cntL - 1]) % MOD;
+                    }
+                }
+            }
+        }
+
+        int result = 0;
+        for (int cntA = 0; cntA < 2; cntA++) {
+            for (int cntL = 0; cntL < 3; cntL++) {
+                result = (result + dp[n][cntA][cntL]) % MOD;
+            }
+        }
+
+        return result;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int checkRecord(int n) {
+        const int MOD = 1000000007;
+        vector<vector<vector<int>>> dp(n + 1, vector<vector<int>>(2, vector<int>(3, 0)));
+
+        dp[0][0][0] = 1;
+
+        for (int i = 1; i <= n; i++) {
+            for (int cntA = 0; cntA < 2; cntA++) {
+                for (int cntL = 0; cntL < 3; cntL++) {
+                    // Choose P
+                    dp[i][cntA][0] = (dp[i][cntA][0] + dp[i - 1][cntA][cntL]) % MOD;
+
+                    // Choose A
+                    if (cntA > 0) {
+                        dp[i][cntA][0] = (dp[i][cntA][0] + dp[i - 1][cntA - 1][cntL]) % MOD;
+                    }
+
+                    // Choose L
+                    if (cntL > 0) {
+                        dp[i][cntA][cntL] = (dp[i][cntA][cntL] + dp[i - 1][cntA][cntL - 1]) % MOD;
+                    }
+                }
+            }
+        }
+
+        int result = 0;
+        for (int cntA = 0; cntA < 2; cntA++) {
+            for (int cntL = 0; cntL < 3; cntL++) {
+                result = (result + dp[n][cntA][cntL]) % MOD;
+            }
+        }
+
+        return result;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    checkRecord(n) {
+        const MOD = 1000000007;
+        const dp = Array.from({ length: n + 1 }, () =>
+            Array.from({ length: 2 }, () => new Array(3).fill(0))
+        );
+
+        dp[0][0][0] = 1;
+
+        for (let i = 1; i <= n; i++) {
+            for (let cntA = 0; cntA < 2; cntA++) {
+                for (let cntL = 0; cntL < 3; cntL++) {
+                    // Choose P
+                    dp[i][cntA][0] = (dp[i][cntA][0] + dp[i - 1][cntA][cntL]) % MOD;
+
+                    // Choose A
+                    if (cntA > 0) {
+                        dp[i][cntA][0] = (dp[i][cntA][0] + dp[i - 1][cntA - 1][cntL]) % MOD;
+                    }
+
+                    // Choose L
+                    if (cntL > 0) {
+                        dp[i][cntA][cntL] = (dp[i][cntA][cntL] + dp[i - 1][cntA][cntL - 1]) % MOD;
+                    }
+                }
+            }
+        }
+
+        let result = 0;
+        for (let cntA = 0; cntA < 2; cntA++) {
+            for (let cntL = 0; cntL < 3; cntL++) {
+                result = (result + dp[n][cntA][cntL]) % MOD;
+            }
+        }
+
+        return result;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Dynamic Programming (Space Optimized) - I
+
+::tabs-start
+
+```python
+class Solution:
+    def checkRecord(self, n: int) -> int:
+        if n == 1:
+            return 3
+
+        MOD = 10**9 + 7
+        dp = {
+            (0, 0): 1, (0, 1): 1, (0, 2): 0,
+            (1, 0): 1, (1, 1): 0, (1, 2): 0
+        }
+
+        for i in range(n - 1):
+            ndp = defaultdict(int)
+
+            # Choose P
+            ndp[(0, 0)] = ((dp[(0, 0)] + dp[(0, 1)]) % MOD + dp[(0, 2)]) % MOD
+            ndp[(1, 0)] = ((dp[(1, 0)] + dp[(1, 1)]) % MOD + dp[(1, 2)]) % MOD
+
+            # Choose L
+            ndp[(0, 1)] = dp[(0, 0)]
+            ndp[(1, 1)] = dp[(1, 0)]
+            ndp[(0, 2)] = dp[(0, 1)]
+            ndp[(1, 2)] = dp[(1, 1)]
+
+            # Choose A
+            ndp[(1, 0)] = (ndp[(1, 0)] + (((dp[(0, 0)] + dp[(0, 1)]) % MOD + dp[(0, 2)]) % MOD)) % MOD
+
+            dp = ndp
+
+        return sum(dp.values()) % MOD
+```
+
+```java
+public class Solution {
+    public int checkRecord(int n) {
+        if (n == 1) return 3;
+
+        final int MOD = 1000000007;
+        int[][] dp = {{1, 1, 0}, {1, 0, 0}};
+
+        for (int i = 0; i < n - 1; i++) {
+            int[][] ndp = new int[2][3];
+
+            // Choose P
+            ndp[0][0] = ((dp[0][0] + dp[0][1]) % MOD + dp[0][2]) % MOD;
+            ndp[1][0] = ((dp[1][0] + dp[1][1]) % MOD + dp[1][2]) % MOD;
+
+            // Choose L
+            ndp[0][1] = dp[0][0];
+            ndp[1][1] = dp[1][0];
+            ndp[0][2] = dp[0][1];
+            ndp[1][2] = dp[1][1];
+
+            // Choose A
+            ndp[1][0] = (ndp[1][0] + ((dp[0][0] + dp[0][1]) % MOD + dp[0][2]) % MOD) % MOD;
+
+            dp = ndp;
+        }
+
+        int total = 0;
+        for (int[] row : dp) {
+            for (int val : row) {
+                total = (total + val) % MOD;
+            }
+        }
+        return total;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int checkRecord(int n) {
+        if (n == 1) return 3;
+
+        const int MOD = 1000000007;
+        vector<vector<int>> dp = {{1, 1, 0}, {1, 0, 0}};
+
+        for (int i = 0; i < n - 1; i++) {
+            vector<vector<int>> ndp(2, vector<int>(3, 0));
+
+            // Choose P
+            ndp[0][0] = ((dp[0][0] + dp[0][1]) % MOD + dp[0][2]) % MOD;
+            ndp[1][0] = ((dp[1][0] + dp[1][1]) % MOD + dp[1][2]) % MOD;
+
+            // Choose L
+            ndp[0][1] = dp[0][0];
+            ndp[1][1] = dp[1][0];
+            ndp[0][2] = dp[0][1];
+            ndp[1][2] = dp[1][1];
+
+            // Choose A
+            ndp[1][0] = (ndp[1][0] + ((dp[0][0] + dp[0][1]) % MOD + dp[0][2]) % MOD) % MOD;
+
+            swap(dp, ndp);
+        }
+
+        int total = 0;
+        for (auto& row : dp) {
+            for (int val : row) {
+                total = (total + val) % MOD;
+            }
+        }
+        return total;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    checkRecord(n) {
+        if (n === 1) return 3;
+
+        const MOD = 1000000007;
+        let dp = [[1, 1, 0], [1, 0, 0]];
+
+        for (let i = 0; i < n - 1; i++) {
+            let ndp = Array.from({ length: 2 }, () => new Array(3).fill(0));
+
+            // Choose P
+            ndp[0][0] = ((dp[0][0] + dp[0][1]) % MOD + dp[0][2]) % MOD;
+            ndp[1][0] = ((dp[1][0] + dp[1][1]) % MOD + dp[1][2]) % MOD;
+
+            // Choose L
+            ndp[0][1] = dp[0][0];
+            ndp[1][1] = dp[1][0];
+            ndp[0][2] = dp[0][1];
+            ndp[1][2] = dp[1][1];
+
+            // Choose A
+            ndp[1][0] = (ndp[1][0] + ((dp[0][0] + dp[0][1]) % MOD + dp[0][2]) % MOD) % MOD;
+
+            [dp, ndp] = [ndp, dp];
+        }
+
+        let total = 0;
+        for (let row of dp) {
+            for (let val of row) {
+                total = (total + val) % MOD;
+            }
+        }
+        return total;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 5. Dynamic Programming (Space Optimized) - II
+
+::tabs-start
+
+```python
+class Solution:
+    def checkRecord(self, n: int) -> int:
+        MOD = 1000000007
+        dp = [[0] * 3 for _ in range(2)]
+        
+        dp[0][0] = 1  # Base case
+
+        for i in range(1, n + 1):
+            next_dp = [[0] * 3 for _ in range(2)]
+
+            for cntA in range(2):
+                for cntL in range(3):
+                    # Choose P
+                    next_dp[cntA][0] = (next_dp[cntA][0] + dp[cntA][cntL]) % MOD
+
+                    # Choose A
+                    if cntA > 0:
+                        next_dp[cntA][0] = (next_dp[cntA][0] + dp[cntA - 1][cntL]) % MOD
+
+                    # Choose L
+                    if cntL > 0:
+                        next_dp[cntA][cntL] = (next_dp[cntA][cntL] + dp[cntA][cntL - 1]) % MOD
+
+            dp = next_dp
+
+        return sum(dp[cntA][cntL] for cntA in range(2) for cntL in range(3)) % MOD
+```
+
+```java
+public class Solution {
+    public int checkRecord(int n) {
+        final int MOD = 1000000007;
+        int[][] dp = new int[2][3];
+
+        dp[0][0] = 1;
+
+        for (int i = 1; i <= n; i++) {
+            int[][] nextDp = new int[2][3];
+
+            for (int cntA = 0; cntA < 2; cntA++) {
+                for (int cntL = 0; cntL < 3; cntL++) {
+                    // Choose P
+                    nextDp[cntA][0] = (nextDp[cntA][0] + dp[cntA][cntL]) % MOD;
+
+                    // Choose A
+                    if (cntA > 0) {
+                        nextDp[cntA][0] = (nextDp[cntA][0] + dp[cntA - 1][cntL]) % MOD;
+                    }
+
+                    // Choose L
+                    if (cntL > 0) {
+                        nextDp[cntA][cntL] = (nextDp[cntA][cntL] + dp[cntA][cntL - 1]) % MOD;
+                    }
+                }
+            }
+
+            dp = nextDp;
+        }
+
+        int result = 0;
+        for (int cntA = 0; cntA < 2; cntA++) {
+            for (int cntL = 0; cntL < 3; cntL++) {
+                result = (result + dp[cntA][cntL]) % MOD;
+            }
+        }
+        return result;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int checkRecord(int n) {
+        const int MOD = 1000000007;
+        vector<vector<int>> dp(2, vector<int>(3, 0));
+
+        dp[0][0] = 1;
+
+        for (int i = 1; i <= n; i++) {
+            vector<vector<int>> nextDp(2, vector<int>(3, 0));
+
+            for (int cntA = 0; cntA < 2; cntA++) {
+                for (int cntL = 0; cntL < 3; cntL++) {
+                    // Choose P
+                    nextDp[cntA][0] = (nextDp[cntA][0] + dp[cntA][cntL]) % MOD;
+
+                    // Choose A
+                    if (cntA > 0) {
+                        nextDp[cntA][0] = (nextDp[cntA][0] + dp[cntA - 1][cntL]) % MOD;
+                    }
+
+                    // Choose L
+                    if (cntL > 0) {
+                        nextDp[cntA][cntL] = (nextDp[cntA][cntL] + dp[cntA][cntL - 1]) % MOD;
+                    }
+                }
+            }
+
+            dp = nextDp;
+        }
+
+        int result = 0;
+        for (int cntA = 0; cntA < 2; cntA++) {
+            for (int cntL = 0; cntL < 3; cntL++) {
+                result = (result + dp[cntA][cntL]) % MOD;
+            }
+        }
+
+        return result;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    checkRecord(n) {
+        const MOD = 1000000007;
+        let dp = Array.from({ length: 2 }, () => new Array(3).fill(0));
+
+        dp[0][0] = 1;
+
+        for (let i = 1; i <= n; i++) {
+            let nextDp = Array.from({ length: 2 }, () => new Array(3).fill(0));
+
+            for (let cntA = 0; cntA < 2; cntA++) {
+                for (let cntL = 0; cntL < 3; cntL++) {
+                    // Choose P
+                    nextDp[cntA][0] = (nextDp[cntA][0] + dp[cntA][cntL]) % MOD;
+
+                    // Choose A
+                    if (cntA > 0) {
+                        nextDp[cntA][0] = (nextDp[cntA][0] + dp[cntA - 1][cntL]) % MOD;
+                    }
+
+                    // Choose L
+                    if (cntL > 0) {
+                        nextDp[cntA][cntL] = (nextDp[cntA][cntL] + dp[cntA][cntL - 1]) % MOD;
+                    }
+                }
+            }
+
+            dp = nextDp;
+        }
+
+        let result = 0;
+        for (let cntA = 0; cntA < 2; cntA++) {
+            for (let cntL = 0; cntL < 3; cntL++) {
+                result = (result + dp[cntA][cntL]) % MOD;
+            }
+        }
+
+        return result;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/subarray-product-less-than-k.md b/articles/subarray-product-less-than-k.md
new file mode 100644
index 000000000..dd7807c14
--- /dev/null
+++ b/articles/subarray-product-less-than-k.md
@@ -0,0 +1,313 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def numSubarrayProductLessThanK(self, nums: List[int], k: int) -> int:
+        n, res = len(nums), 0
+
+        for i in range(n):
+            curProd = 1
+            for j in range(i, n):
+                curProd *= nums[j]
+                if curProd >= k:
+                    break
+                res += 1
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int numSubarrayProductLessThanK(int[] nums, int k) {
+        int n = nums.length, res = 0;
+
+        for (int i = 0; i < n; i++) {
+            int curProd = 1;
+            for (int j = i; j < n; j++) {
+                curProd *= nums[j];
+                if (curProd >= k) break;
+                res++;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numSubarrayProductLessThanK(vector<int>& nums, int k) {
+        int n = nums.size(), res = 0;
+
+        for (int i = 0; i < n; i++) {
+            int curProd = 1;
+            for (int j = i; j < n; j++) {
+                curProd *= nums[j];
+                if (curProd >= k) break;
+                res++;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    numSubarrayProductLessThanK(nums, k) {
+        let n = nums.length, res = 0;
+
+        for (let i = 0; i < n; i++) {
+            let curProd = 1;
+            for (let j = i; j < n; j++) {
+                curProd *= nums[j];
+                if (curProd >= k) break;
+                res++;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Binary Search
+
+::tabs-start
+
+```python
+class Solution:
+    def numSubarrayProductLessThanK(self, nums: List[int], k: int) -> int:
+        if k <= 1:
+            return 0
+
+        n = len(nums)
+        res = 0
+        logs = [0] * (n + 1)
+        logK = log(k)
+        for i in range(n):
+            logs[i + 1] = logs[i] + log(nums[i])
+
+        for i in range(n):
+            l, r = i + 1, n + 1
+            while l < r:
+                mid = (l + r) >> 1
+                if logs[mid] < logs[i] + logK:
+                    l = mid + 1
+                else:
+                    r = mid
+    
+            res += l - (i + 1)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int numSubarrayProductLessThanK(int[] nums, int k) {
+        if (k <= 1) return 0;
+
+        int n = nums.length, res = 0;
+        double[] logs = new double[n + 1];
+        double logK = Math.log(k);
+
+        for (int i = 0; i < n; i++) {
+            logs[i + 1] = logs[i] + Math.log(nums[i]);
+        }
+
+        for (int i = 0; i < n; i++) {
+            int l = i + 1, r = n + 1;
+            while (l < r) {
+                int mid = (l + r) / 2;
+                if (logs[mid] < logs[i] + logK) {
+                    l = mid + 1;
+                } else {
+                    r = mid;
+                }
+            }
+            res += l - (i + 1);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numSubarrayProductLessThanK(vector<int>& nums, int k) {
+        if (k <= 1) return 0;
+
+        int n = nums.size(), res = 0;
+        vector<double> logs(n + 1, 0);
+        double logK = log(k);
+
+        for (int i = 0; i < n; i++) {
+            logs[i + 1] = logs[i] + log(nums[i]);
+        }
+
+        for (int i = 0; i < n; i++) {
+            int l = i + 1, r = n + 1;
+            while (l < r) {
+                int mid = (l + r) / 2;
+                if (logs[mid] < logs[i] + logK) {
+                    l = mid + 1;
+                } else {
+                    r = mid;
+                }
+            }
+            res += l - (i + 1);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    numSubarrayProductLessThanK(nums, k) {
+        if (k <= 1) return 0;
+
+        const n = nums.length;
+        let res = 0;
+        const logs = new Array(n + 1).fill(0);
+        const logK = Math.log(k);
+
+        for (let i = 0; i < n; i++) {
+            logs[i + 1] = logs[i] + Math.log(nums[i]);
+        }
+
+        for (let i = 0; i < n; i++) {
+            let l = i + 1, r = n + 1;
+            while (l < r) {
+                const mid = Math.floor((l + r) / 2);
+                if (logs[mid] < logs[i] + logK) {
+                    l = mid + 1;
+                } else {
+                    r = mid;
+                }
+            }
+            res += l - (i + 1);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Sliding Window
+
+::tabs-start
+
+```python
+class Solution:
+    def numSubarrayProductLessThanK(self, nums: List[int], k: int) -> int:
+        res = 0
+        l = 0
+        product = 1
+        for r in range(len(nums)):
+            product *= nums[r]
+            while l <= r and product >= k:
+                product //= nums[l]
+                l += 1
+            res += (r - l + 1)
+        return res
+```
+
+```java
+public class Solution {
+    public int numSubarrayProductLessThanK(int[] nums, int k) {
+        int res = 0, l = 0;
+        long product = 1;
+        for (int r = 0; r < nums.length; r++) {
+            product *= nums[r];
+            while (l <= r && product >= k) {
+                product /= nums[l++];
+            }
+            res += (r - l + 1);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numSubarrayProductLessThanK(vector<int>& nums, int k) {
+        int res = 0, l = 0;
+        long long product = 1;
+        for (int r = 0; r < nums.size(); r++) {
+            product *= nums[r];
+            while (l <= r && product >= k) {
+                product /= nums[l++];
+            }
+            res += (r - l + 1);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    numSubarrayProductLessThanK(nums, k) {
+        let res = 0, l = 0, product = 1;
+        for (let r = 0; r < nums.length; r++) {
+            product *= nums[r];
+            while (l <= r && product >= k) {
+                product = Math.floor(product / nums[l++]);
+            }
+            res += (r - l + 1);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/subarray-sum-equals-k.md b/articles/subarray-sum-equals-k.md
new file mode 100644
index 000000000..fa979f529
--- /dev/null
+++ b/articles/subarray-sum-equals-k.md
@@ -0,0 +1,213 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def subarraySum(self, nums: List[int], k: int) -> int:
+        res = 0
+        for i in range(len(nums)):
+            sum = 0
+            for j in range(i, len(nums)):
+                sum += nums[j]
+                if sum == k:
+                    res += 1
+        return res
+```
+
+```java
+public class Solution {
+    public int subarraySum(int[] nums, int k) {
+        int res = 0;
+        for (int i = 0; i < nums.length; i++) {
+            int sum = 0;
+            for (int j = i; j < nums.length; j++) {
+                sum += nums[j];
+                if (sum == k) res++;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int subarraySum(vector<int>& nums, int k) {
+        int res = 0;
+        for (int i = 0; i < nums.size(); i++) {
+            int sum = 0;
+            for (int j = i; j < nums.size(); j++) {
+                sum += nums[j];
+                if (sum == k) res++;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    subarraySum(nums, k) {
+        let res = 0;
+        for (let i = 0; i < nums.length; i++) {
+            let sum = 0;
+            for (let j = i; j < nums.length; j++) {
+                sum += nums[j];
+                if (sum == k) res++;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int SubarraySum(int[] nums, int k) {
+        int res = 0;
+        for (int i = 0; i < nums.Length; i++) {
+            int sum = 0;
+            for (int j = i; j < nums.Length; j++) {
+                sum += nums[j];
+                if (sum == k) {
+                    res++;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def subarraySum(self, nums: List[int], k: int) -> int:
+        res = curSum = 0
+        prefixSums = { 0 : 1 }
+
+        for num in nums:
+            curSum += num
+            diff = curSum - k
+
+            res += prefixSums.get(diff, 0)
+            prefixSums[curSum] = 1 + prefixSums.get(curSum, 0)
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int subarraySum(int[] nums, int k) {
+        int res = 0, curSum = 0;
+        Map<Integer, Integer> prefixSums = new HashMap<>();
+        prefixSums.put(0, 1);
+
+        for (int num : nums) {
+            curSum += num;
+            int diff = curSum - k;
+            res += prefixSums.getOrDefault(diff, 0);
+            prefixSums.put(curSum, prefixSums.getOrDefault(curSum, 0) + 1);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int subarraySum(vector<int>& nums, int k) {
+        int res = 0, curSum = 0;
+        unordered_map<int, int> prefixSums;
+        prefixSums[0] = 1;
+
+        for (int num : nums) {
+            curSum += num;
+            int diff = curSum - k;
+            res += prefixSums[diff];
+            prefixSums[curSum]++;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    subarraySum(nums, k) {
+        let res = 0, curSum = 0;
+        const prefixSums = new Map();
+        prefixSums.set(0, 1);
+
+        for (let num of nums) {
+            curSum += num;
+            let diff = curSum - k;
+            res += prefixSums.get(diff) || 0;
+            prefixSums.set(curSum, (prefixSums.get(curSum) || 0) + 1);
+        }
+
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int SubarraySum(int[] nums, int k) {
+        int res = 0, curSum = 0;
+        Dictionary<int, int> prefixSums = new Dictionary<int, int>();
+        prefixSums[0] = 1;
+
+        foreach (int num in nums) {
+            curSum += num;
+            int diff = curSum - k;
+
+            if (prefixSums.ContainsKey(diff)) {
+                res += prefixSums[diff];
+            }
+
+            if (!prefixSums.ContainsKey(curSum)) {
+                prefixSums[curSum] = 0;
+            }
+            prefixSums[curSum]++;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/subarray-sums-divisible-by-k.md b/articles/subarray-sums-divisible-by-k.md
new file mode 100644
index 000000000..f1faeaf61
--- /dev/null
+++ b/articles/subarray-sums-divisible-by-k.md
@@ -0,0 +1,280 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def subarraysDivByK(self, nums: List[int], k: int) -> int:
+        n, res = len(nums), 0
+
+        for i in range(n):
+            curSum = 0
+            for j in range(i, n):
+                curSum += nums[j]
+                if curSum % k == 0:
+                    res += 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int subarraysDivByK(int[] nums, int k) {
+        int n = nums.length, res = 0;
+
+        for (int i = 0; i < n; i++) {
+            int curSum = 0;
+            for (int j = i; j < n; j++) {
+                curSum += nums[j];
+                if (curSum % k == 0) {
+                    res++;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int subarraysDivByK(vector<int>& nums, int k) {
+        int n = nums.size(), res = 0;
+
+        for (int i = 0; i < n; i++) {
+            int curSum = 0;
+            for (int j = i; j < n; j++) {
+                curSum += nums[j];
+                if (curSum % k == 0) {
+                    res++;
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    subarraysDivByK(nums, k) {
+        const n = nums.length;
+        let res = 0;
+
+        for (let i = 0; i < n; i++) {
+            let curSum = 0;
+            for (let j = i; j < n; j++) {
+                curSum += nums[j];
+                if (curSum % k === 0) {
+                    res++;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Prefix Sum + Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def subarraysDivByK(self, nums: List[int], k: int) -> int:
+        prefix_sum = 0
+        res = 0
+        prefix_cnt = defaultdict(int)
+        prefix_cnt[0] = 1
+
+        for n in nums:
+            prefix_sum += n
+            remain = prefix_sum % k
+
+            res += prefix_cnt[remain]
+            prefix_cnt[remain] += 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int subarraysDivByK(int[] nums, int k) {
+        int prefixSum = 0, res = 0;
+        Map<Integer, Integer> prefixCnt = new HashMap<>();
+        prefixCnt.put(0, 1);
+
+        for (int n : nums) {
+            prefixSum += n;
+            int remain = prefixSum % k;
+            if (remain < 0) remain += k;
+
+            res += prefixCnt.getOrDefault(remain, 0);
+            prefixCnt.put(remain, prefixCnt.getOrDefault(remain, 0) + 1);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int subarraysDivByK(vector<int>& nums, int k) {
+        int prefixSum = 0, res = 0;
+        unordered_map<int, int> prefixCnt;
+        prefixCnt[0] = 1;
+
+        for (int n : nums) {
+            prefixSum += n;
+            int remain = prefixSum % k;
+            if (remain < 0) remain += k;
+
+            res += prefixCnt[remain];
+            prefixCnt[remain]++;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    subarraysDivByK(nums, k) {
+        let prefixSum = 0, res = 0;
+        const prefixCnt = new Map();
+        prefixCnt.set(0, 1);
+
+        for (let n of nums) {
+            prefixSum += n;
+            let remain = prefixSum % k;
+            if (remain < 0) remain += k;
+
+            res += prefixCnt.get(remain) || 0;
+            prefixCnt.set(remain, (prefixCnt.get(remain) || 0) + 1);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(k)$
+
+---
+
+## 3. Prefix Sum + Array
+
+::tabs-start
+
+```python
+class Solution:
+    def subarraysDivByK(self, nums: List[int], k: int) -> int:
+        count = [0] * k
+        count[0] = 1
+        prefix = res = 0
+
+        for num in nums:
+            prefix = (prefix + num + k) % k
+            res += count[prefix]
+            count[prefix] += 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int subarraysDivByK(int[] nums, int k) {
+        int[] count = new int[k];
+        count[0] = 1;
+        int prefix = 0, res = 0;
+
+        for (int num : nums) {
+            prefix = (prefix + num % k + k) % k;
+            res += count[prefix];
+            count[prefix]++;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int subarraysDivByK(vector<int>& nums, int k) {
+        vector<int> count(k, 0);
+        count[0] = 1;
+        int prefix = 0, res = 0;
+
+        for (int num : nums) {
+            prefix = (prefix + num % k + k) % k;
+            res += count[prefix];
+            count[prefix]++;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    subarraysDivByK(nums, k) {
+        const count = Array(k).fill(0);
+        count[0] = 1;
+        let prefix = 0, res = 0;
+
+        for (let num of nums) {
+            prefix = (prefix + num % k + k) % k;
+            res += count[prefix];
+            count[prefix]++;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + k)$
+* Space complexity: $O(k)$
\ No newline at end of file
diff --git a/articles/subarrays-with-k-different-integers.md b/articles/subarrays-with-k-different-integers.md
new file mode 100644
index 000000000..a2e24a470
--- /dev/null
+++ b/articles/subarrays-with-k-different-integers.md
@@ -0,0 +1,546 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def subarraysWithKDistinct(self, nums: List[int], k: int) -> int:
+        n, res = len(nums), 0
+        
+        for i in range(n):
+            seen = set()
+            for j in range(i, n):
+                seen.add(nums[j])
+                if len(seen) > k:
+                    break
+                
+                if len(seen) == k:
+                    res += 1
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int subarraysWithKDistinct(int[] nums, int k) {
+        int n = nums.length, res = 0;
+
+        for (int i = 0; i < n; i++) {
+            Set<Integer> seen = new HashSet<>();
+            for (int j = i; j < n; j++) {
+                seen.add(nums[j]);
+                if (seen.size() > k) {
+                    break;
+                }
+                if (seen.size() == k) {
+                    res++;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int subarraysWithKDistinct(vector<int>& nums, int k) {
+        int n = nums.size(), res = 0;
+
+        for (int i = 0; i < n; i++) {
+            unordered_set<int> seen;
+            for (int j = i; j < n; j++) {
+                seen.insert(nums[j]);
+                if (seen.size() > k) {
+                    break;
+                }
+                if (seen.size() == k) {
+                    res++;
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    subarraysWithKDistinct(nums, k) {
+        let n = nums.length, res = 0;
+
+        for (let i = 0; i < n; i++) {
+            let seen = new Set();
+            for (let j = i; j < n; j++) {
+                seen.add(nums[j]);
+                if (seen.size > k) {
+                    break;
+                }
+                if (seen.size === k) {
+                    res++;
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Sliding Window
+
+::tabs-start
+
+```python
+class Solution:
+    def subarraysWithKDistinct(self, nums: List[int], k: int) -> int:
+        
+        def atMostK(k):
+            count = defaultdict(int)
+            res = l = 0
+
+            for r in range(len(nums)):
+                count[nums[r]] += 1
+                if count[nums[r]] == 1:
+                    k -= 1
+                
+                while k < 0:
+                    count[nums[l]] -= 1
+                    if count[nums[l]] == 0:
+                        k += 1
+                    l += 1
+                
+                res += (r - l + 1)
+            
+            return res
+        
+        return atMostK(k) - atMostK(k - 1)
+```
+
+```java
+public class Solution {
+    public int subarraysWithKDistinct(int[] nums, int k) {
+        return atMostK(nums, k) - atMostK(nums, k - 1);
+    }
+    
+    private int atMostK(int[] nums, int k) {
+        HashMap<Integer, Integer> count = new HashMap<>();
+        int res = 0, l = 0;
+        
+        for (int r = 0; r < nums.length; r++) {
+            count.put(nums[r], count.getOrDefault(nums[r], 0) + 1);
+            if (count.get(nums[r]) == 1) {
+                k--;
+            }
+            
+            while (k < 0) {
+                count.put(nums[l], count.get(nums[l]) - 1);
+                if (count.get(nums[l]) == 0) {
+                    k++;
+                }
+                l++;
+            }
+            
+            res += (r - l + 1);
+        }
+        
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int subarraysWithKDistinct(vector<int>& nums, int k) {
+        return atMostK(nums, k) - atMostK(nums, k - 1);
+    }
+
+private:
+    int atMostK(vector<int>& nums, int k) {
+        unordered_map<int, int> count;
+        int res = 0, l = 0;
+
+        for (int r = 0; r < nums.size(); r++) {
+            count[nums[r]]++;
+            if (count[nums[r]] == 1) {
+                k--;
+            }
+
+            while (k < 0) {
+                count[nums[l]]--;
+                if (count[nums[l]] == 0) {
+                    k++;
+                }
+                l++;
+            }
+
+            res += (r - l + 1);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    subarraysWithKDistinct(nums, k) {
+        const atMostK = (k) => {
+            const count = new Map();
+            let res = 0, l = 0;
+
+            for (let r = 0; r < nums.length; r++) {
+                count.set(nums[r], (count.get(nums[r]) || 0) + 1);
+                if (count.get(nums[r]) === 1) {
+                    k--;
+                }
+
+                while (k < 0) {
+                    count.set(nums[l], count.get(nums[l]) - 1);
+                    if (count.get(nums[l]) === 0) {
+                        k++;
+                    }
+                    l++;
+                }
+
+                res += (r - l + 1);
+            }
+
+            return res;
+        };
+
+        return atMostK(k) - atMostK(k - 1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Sliding Window (One Pass) - I
+
+::tabs-start
+
+```python
+class Solution:
+    def subarraysWithKDistinct(self, nums: List[int], k: int) -> int:
+        count = defaultdict(int)
+        res = 0
+        l_far = 0
+        l_near = 0
+
+        for r in range(len(nums)):
+            count[nums[r]] += 1
+
+            while len(count) > k:
+                count[nums[l_near]] -= 1
+                if count[nums[l_near]] == 0:
+                    count.pop(nums[l_near])
+                l_near += 1
+                l_far = l_near
+
+            while count[nums[l_near]] > 1:
+                count[nums[l_near]] -= 1
+                l_near += 1
+
+            if len(count) == k:
+                res += l_near - l_far + 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int subarraysWithKDistinct(int[] nums, int k) {
+        HashMap<Integer, Integer> count = new HashMap<>();
+        int res = 0, l_far = 0, l_near = 0;
+
+        for (int r = 0; r < nums.length; r++) {
+            count.put(nums[r], count.getOrDefault(nums[r], 0) + 1);
+
+            while (count.size() > k) {
+                count.put(nums[l_near], count.get(nums[l_near]) - 1);
+                if (count.get(nums[l_near]) == 0) {
+                    count.remove(nums[l_near]);
+                }
+                l_near++;
+                l_far = l_near;
+            }
+
+            while (count.get(nums[l_near]) > 1) {
+                count.put(nums[l_near], count.get(nums[l_near]) - 1);
+                l_near++;
+            }
+
+            if (count.size() == k) {
+                res += l_near - l_far + 1;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int subarraysWithKDistinct(vector<int>& nums, int k) {
+        unordered_map<int, int> count;
+        int res = 0, l_far = 0, l_near = 0;
+
+        for (int r = 0; r < nums.size(); r++) {
+            count[nums[r]]++;
+
+            while (count.size() > k) {
+                count[nums[l_near]]--;
+                if (count[nums[l_near]] == 0) {
+                    count.erase(nums[l_near]);
+                }
+                l_near++;
+                l_far = l_near;
+            }
+
+            while (count[nums[l_near]] > 1) {
+                count[nums[l_near]]--;
+                l_near++;
+            }
+
+            if (count.size() == k) {
+                res += l_near - l_far + 1;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    subarraysWithKDistinct(nums, k) {
+        const count = new Map();
+        let res = 0, l_far = 0, l_near = 0;
+
+        for (let r = 0; r < nums.length; r++) {
+            count.set(nums[r], (count.get(nums[r]) || 0) + 1);
+
+            while (count.size > k) {
+                count.set(nums[l_near], count.get(nums[l_near]) - 1);
+                if (count.get(nums[l_near]) === 0) {
+                    count.delete(nums[l_near]);
+                }
+                l_near++;
+            }
+
+            while (count.get(nums[l_near]) > 1) {
+                count.set(nums[l_near], count.get(nums[l_near]) - 1);
+                l_near++;
+            }
+
+            if (count.size === k) {
+                res += l_near - l_far + 1;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Sliding Window (One Pass) - II
+
+::tabs-start
+
+```python
+class Solution:
+    def subarraysWithKDistinct(self, nums: List[int], k: int) -> int:
+        n = len(nums)
+        count = [0] * (n + 1)
+        res = l = cnt = 0
+
+        for r in range(n):
+            count[nums[r]] += 1
+            if count[nums[r]] == 1:
+                k -= 1
+
+            if k < 0:
+                count[nums[l]] -= 1
+                l += 1
+                k += 1
+                cnt = 0
+
+            if k == 0:
+                while count[nums[l]] > 1:
+                    count[nums[l]] -= 1
+                    l += 1
+                    cnt += 1
+
+                res += (cnt + 1)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int subarraysWithKDistinct(int[] nums, int k) {
+        int n = nums.length;
+        int[] count = new int[n + 1];
+        int res = 0, l = 0, cnt = 0;
+
+        for (int r = 0; r < n; r++) {
+            count[nums[r]]++;
+            if (count[nums[r]] == 1) {
+                k--;
+            }
+
+            if (k < 0) {
+                count[nums[l]]--;
+                l++;
+                k++;
+                cnt = 0;
+            }
+
+            if (k == 0) {
+                while (count[nums[l]] > 1) {
+                    count[nums[l]]--;
+                    l++;
+                    cnt++;
+                }
+
+                res += (cnt + 1);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int subarraysWithKDistinct(vector<int>& nums, int k) {
+        int n = nums.size();
+        vector<int> count(n + 1, 0);
+        int res = 0, l = 0, cnt = 0;
+
+        for (int r = 0; r < n; r++) {
+            count[nums[r]]++;
+            if (count[nums[r]] == 1) {
+                k--;
+            }
+
+            if (k < 0) {
+                count[nums[l]]--;
+                l++;
+                k++;
+                cnt = 0;
+            }
+
+            if (k == 0) {
+                while (count[nums[l]] > 1) {
+                    count[nums[l]]--;
+                    l++;
+                    cnt++;
+                }
+
+                res += (cnt + 1);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    subarraysWithKDistinct(nums, k) {
+        const n = nums.length;
+        const count = new Array(n + 1).fill(0);
+        let res = 0, l = 0, cnt = 0;
+
+        for (let r = 0; r < n; r++) {
+            count[nums[r]]++;
+            if (count[nums[r]] === 1) {
+                k--;
+            }
+
+            if (k < 0) {
+                count[nums[l]]--;
+                l++;
+                k++;
+                cnt = 0;
+            }
+
+            if (k === 0) {
+                while (count[nums[l]] > 1) {
+                    count[nums[l]]--;
+                    l++;
+                    cnt++;
+                }
+
+                res += (cnt + 1);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/subsets-ii.md b/articles/subsets-ii.md
index 3db9cce85..fef683226 100644
--- a/articles/subsets-ii.md
+++ b/articles/subsets-ii.md
@@ -140,6 +140,84 @@ public class Solution {
 }
 ```
 
+```go
+func subsetsWithDup(nums []int) [][]int {
+    sort.Ints(nums)
+    res := make(map[string][]int)
+
+    var backtrack func(int, []int)
+    backtrack = func(i int, subset []int) {
+        if i == len(nums) {
+            key := fmt.Sprint(subset)
+            res[key] = append([]int{}, subset...)
+            return
+        }
+
+        subset = append(subset, nums[i])
+        backtrack(i+1, subset)
+        subset = subset[:len(subset)-1]
+        backtrack(i+1, subset)
+    }
+
+    backtrack(0, []int{})
+    
+    var result [][]int
+    for _, v := range res {
+        result = append(result, v)
+    }
+    return result
+}
+```
+
+```kotlin
+class Solution {
+    fun subsetsWithDup(nums: IntArray): List<List<Int>> {
+        nums.sort()
+        val res = HashSet<List<Int>>()
+
+        fun backtrack(i: Int, subset: MutableList<Int>) {
+            if (i == nums.size) {
+                res.add(ArrayList(subset))
+                return
+            }
+
+            subset.add(nums[i])
+            backtrack(i + 1, subset)
+            subset.removeAt(subset.size - 1)
+            backtrack(i + 1, subset)
+        }
+
+        backtrack(0, mutableListOf())
+        return res.toList()
+    }
+}
+```
+
+```swift
+class Solution {
+    func subsetsWithDup(_ nums: [Int]) -> [[Int]] {
+        var res = Set<[Int]>()
+        var subset = [Int]()
+        let nums = nums.sorted()
+
+        func backtrack(_ i: Int) {
+            if i == nums.count {
+                res.insert(subset)
+                return
+            }
+
+            subset.append(nums[i])
+            backtrack(i + 1)
+            subset.removeLast()
+            backtrack(i + 1)
+        }
+
+        backtrack(0)
+        return Array(res)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -149,7 +227,7 @@ public class Solution {
 
 ---
 
-## 2. Backtracking (Pick / Not Pick)
+## 2. Backtracking - I
 
 ::tabs-start
 
@@ -294,16 +372,106 @@ public class Solution {
 }
 ```
 
+```go
+func subsetsWithDup(nums []int) [][]int {
+    var res [][]int
+    sort.Ints(nums)
+
+    var backtrack func(int, []int)
+    backtrack = func(i int, subset []int) {
+        if i == len(nums) {
+            res = append(res, append([]int{}, subset...))
+            return
+        }
+
+        subset = append(subset, nums[i])
+        backtrack(i+1, subset)
+        subset = subset[:len(subset)-1]
+
+        for i+1 < len(nums) && nums[i] == nums[i+1] {
+            i++
+        }
+
+        backtrack(i+1, subset)
+    }
+
+    backtrack(0, []int{})
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun subsetsWithDup(nums: IntArray): List<List<Int>> {
+        val res = mutableListOf<List<Int>>()
+        nums.sort()
+
+        fun backtrack(i: Int, subset: MutableList<Int>) {
+            if (i == nums.size) {
+                res.add(ArrayList(subset))
+                return
+            }
+
+            subset.add(nums[i])
+            backtrack(i + 1, subset)
+            subset.removeAt(subset.size - 1)
+
+            var j = i
+            while (j + 1 < nums.size && nums[j] == nums[j + 1]) {
+                j++
+            }
+
+            backtrack(j + 1, subset)
+        }
+
+        backtrack(0, mutableListOf())
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func subsetsWithDup(_ nums: [Int]) -> [[Int]] {
+        var res = [[Int]]()
+        var subset = [Int]()
+        let nums = nums.sorted()
+        
+        func backtrack(_ i: Int) {
+            if i == nums.count {
+                res.append(subset)
+                return
+            }
+            
+            subset.append(nums[i])
+            backtrack(i + 1)
+            subset.removeLast()
+            
+            var j = i
+            while j + 1 < nums.count && nums[j] == nums[j + 1] {
+                j += 1
+            }
+            backtrack(j + 1)
+        }
+        
+        backtrack(0)
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n * 2 ^ n)$
-* Space complexity: $O(n)$
+* Space complexity:
+    * $O(n)$ extra space.
+    * $O(2 ^ n)$ space for the output list.
 
 ---
 
-## 3. Backtracking
+## 3. Backtracking - II
 
 ::tabs-start
 
@@ -435,12 +603,89 @@ public class Solution {
 }
 ```
 
+```go
+func subsetsWithDup(nums []int) [][]int {
+    var res [][]int
+    sort.Ints(nums)
+
+    var backtrack func(int, []int)
+    backtrack = func(i int, subset []int) {
+        res = append(res, append([]int{}, subset...))
+
+        for j := i; j < len(nums); j++ {
+            if j > i && nums[j] == nums[j-1] {
+                continue
+            }
+            subset = append(subset, nums[j])
+            backtrack(j+1, subset)
+            subset = subset[:len(subset)-1]
+        }
+    }
+
+    backtrack(0, []int{})
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun subsetsWithDup(nums: IntArray): List<List<Int>> {
+        val res = mutableListOf<List<Int>>()
+        nums.sort()
+
+        fun backtrack(i: Int, subset: MutableList<Int>) {
+            res.add(ArrayList(subset))
+
+            for (j in i until nums.size) {
+                if (j > i && nums[j] == nums[j - 1]) {
+                    continue
+                }
+                subset.add(nums[j])
+                backtrack(j + 1, subset)
+                subset.removeAt(subset.size - 1)
+            }
+        }
+
+        backtrack(0, mutableListOf())
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func subsetsWithDup(_ nums: [Int]) -> [[Int]] {
+        var res = [[Int]]()
+        var subset = [Int]()
+        let nums = nums.sorted()
+        
+        func backtrack(_ i: Int) {
+            res.append(subset)
+            
+            for j in i..<nums.count {
+                if j > i && nums[j] == nums[j - 1] {
+                    continue
+                }
+                subset.append(nums[j])
+                backtrack(j + 1)
+                subset.removeLast()
+            }
+        }
+        
+        backtrack(0)
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n * 2 ^ n)$
-* Space complexity: $O(n)$
+* Space complexity:
+    * $O(n)$ extra space.
+    * $O(2 ^ n)$ space for the output list.
 
 ---
 
@@ -454,6 +699,7 @@ class Solution:
         nums.sort()
         res = [[]]
         prev_Idx = idx = 0
+
         for i in range(len(nums)):
             idx = prev_idx if i >= 1 and nums[i] == nums[i - 1] else 0
             prev_idx = len(res)
@@ -461,6 +707,7 @@ class Solution:
                 tmp = res[j].copy()
                 tmp.append(nums[i])
                 res.append(tmp)
+
         return res
 ```
 
@@ -472,6 +719,7 @@ public class Solution {
         res.add(new ArrayList<>());        
         int prevIdx = 0;
         int idx = 0;
+
         for (int i = 0; i < nums.length; i++) {
             idx = (i >= 1 && nums[i] == nums[i - 1]) ? prevIdx : 0;
             prevIdx = res.size();
@@ -481,6 +729,7 @@ public class Solution {
                 res.add(tmp);
             }
         }
+
         return res;
     }
 }
@@ -494,6 +743,7 @@ public:
         vector<vector<int>> res = {{}};
         int prevIdx = 0;
         int idx = 0;
+
         for (int i = 0; i < nums.size(); i++) {
             idx = (i >= 1 && nums[i] == nums[i - 1]) ? prevIdx : 0;
             prevIdx = res.size();
@@ -503,6 +753,7 @@ public:
                 res.push_back(tmp);
             }
         }
+
         return res;
     }
 };
@@ -519,6 +770,7 @@ class Solution {
         const res = [[]];
         let prevIdx = 0;
         let idx = 0;
+
         for (let i = 0; i < nums.length; i++) {
             idx = (i >= 1 && nums[i] === nums[i - 1]) ? prevIdx : 0;
             prevIdx = res.length;
@@ -528,6 +780,7 @@ class Solution {
                 res.push(tmp);
             }
         }
+
         return res;
     }
 }
@@ -540,6 +793,7 @@ public class Solution {
         var res = new List<List<int>> { new List<int>() };
         int prevIdx = 0;
         int idx = 0;
+
         for (int i = 0; i < nums.Length; i++) {
             idx = (i >= 1 && nums[i] == nums[i - 1]) ? prevIdx : 0;
             prevIdx = res.Count;
@@ -549,14 +803,88 @@ public class Solution {
                 res.Add(tmp);
             }
         }
+
         return res;
     }
 }
 ```
 
+```go
+func subsetsWithDup(nums []int) [][]int {
+    sort.Ints(nums)
+    res := [][]int{{}}
+    prevIdx, idx := 0, 0
+
+    for i := 0; i < len(nums); i++ {
+        if i > 0 && nums[i] == nums[i-1] {
+            idx = prevIdx
+        } else {
+            idx = 0
+        }
+        prevIdx = len(res)
+        for j := idx; j < prevIdx; j++ {
+            tmp := append([]int{}, res[j]...)
+            tmp = append(tmp, nums[i])
+            res = append(res, tmp)
+        }
+    }
+
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun subsetsWithDup(nums: IntArray): List<List<Int>> {
+        nums.sort()
+        val res = mutableListOf(listOf<Int>())
+        var prevIdx = 0
+        var idx = 0
+
+        for (i in nums.indices) {
+            idx = if (i > 0 && nums[i] == nums[i - 1]) prevIdx else 0
+            prevIdx = res.size
+            for (j in idx until prevIdx) {
+                val tmp = ArrayList(res[j])
+                tmp.add(nums[i])
+                res.add(tmp)
+            }
+        }
+
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func subsetsWithDup(_ nums: [Int]) -> [[Int]] {
+        let nums = nums.sorted()
+        var res: [[Int]] = [[]]
+        var prevIdx = 0
+        var idx = 0
+
+        for i in 0..<nums.count {
+            idx = (i >= 1 && nums[i] == nums[i - 1]) ? prevIdx : 0
+            prevIdx = res.count
+
+            for j in idx..<prevIdx {
+                var temp = res[j]
+                temp.append(nums[i])
+                res.append(temp)
+            }
+        }
+
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n * 2 ^ n)$
-* Space complexity: $O(1)$
\ No newline at end of file
+* Space complexity:
+    * $O(1)$ extra space.
+    * $O(2 ^ n)$ space for the output list.
\ No newline at end of file
diff --git a/articles/subsets.md b/articles/subsets.md
index c2e21302f..733609e9f 100644
--- a/articles/subsets.md
+++ b/articles/subsets.md
@@ -6,7 +6,6 @@
 class Solution:
     def subsets(self, nums: List[int]) -> List[List[int]]:
         res = []
-
         subset = []
 
         def dfs(i):
@@ -125,12 +124,84 @@ public class Solution {
 }
 ```
 
+```go
+func subsets(nums []int) [][]int {
+    res := [][]int{}
+    subset := []int{}
+
+    var dfs func(int)
+    dfs = func(i int) {
+        if i >= len(nums) {
+            temp := make([]int, len(subset))
+            copy(temp, subset)
+            res = append(res, temp)
+            return
+        }
+        subset = append(subset, nums[i])
+        dfs(i + 1)
+        subset = subset[:len(subset)-1]
+        dfs(i + 1)
+    }
+
+    dfs(0)
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun subsets(nums: IntArray): List<List<Int>> {
+        val res = mutableListOf<List<Int>>()
+        val subset = mutableListOf<Int>()
+
+        fun dfs(i: Int) {
+            if (i >= nums.size) {
+                res.add(subset.toList())
+                return
+            }
+            subset.add(nums[i])
+            dfs(i + 1)
+            subset.removeAt(subset.size - 1)
+            dfs(i + 1)
+        }
+
+        dfs(0)
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func subsets(_ nums: [Int]) -> [[Int]] {
+        var res = [[Int]]()
+        var subset = [Int]()
+
+        func dfs(_ i: Int) {
+            if i >= nums.count {
+                res.append(subset)
+                return
+            }
+            subset.append(nums[i])
+            dfs(i + 1)
+            subset.removeLast()
+            dfs(i + 1)
+        }
+        
+        dfs(0)
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n * 2 ^ n)$
-* Space complexity: $O(n)$
+* Space complexity:
+    * $O(n)$ extra space.
+    * $O(2 ^ n)$ for the output list.
 
 ---
 
@@ -232,12 +303,65 @@ public class Solution {
 }
 ```
 
+```go
+func subsets(nums []int) [][]int {
+    res := [][]int{{}}
+
+    for _, num := range nums {
+        n := len(res)
+        for i := 0; i < n; i++ {
+            newSubset := make([]int, len(res[i]))
+            copy(newSubset, res[i])
+            newSubset = append(newSubset, num)
+            res = append(res, newSubset)
+        }
+    }
+
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun subsets(nums: IntArray): List<List<Int>> {
+        val res = mutableListOf<List<Int>>(listOf())
+
+        for (num in nums) {
+            val n = res.size
+            for (i in 0 until n) {
+                val newSubset = res[i].toMutableList()
+                newSubset.add(num)
+                res.add(newSubset)
+            }
+        }
+
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func subsets(_ nums: [Int]) -> [[Int]] {
+        var res: [[Int]] = [[]]
+
+        for num in nums {
+            res += res.map { $0 + [num] }
+        }
+
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n * 2 ^ n)$
-* Space complexity: $O(n)$
+* Space complexity:
+    * $O(n)$ extra space.
+    * $O(2 ^ n)$ for the output list.
 
 ---
 
@@ -337,9 +461,72 @@ public class Solution {
 }
 ```
 
+```go
+func subsets(nums []int) [][]int {
+    n := len(nums)
+    res := [][]int{}
+
+    for i := 0; i < (1 << n); i++ {
+        subset := []int{}
+        for j := 0; j < n; j++ {
+            if (i & (1 << j)) != 0 {
+                subset = append(subset, nums[j])
+            }
+        }
+        res = append(res, subset)
+    }
+
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun subsets(nums: IntArray): List<List<Int>> {
+        val n = nums.size
+        val res = mutableListOf<List<Int>>()
+
+        for (i in 0 until (1 shl n)) {
+            val subset = mutableListOf<Int>()
+            for (j in 0 until n) {
+                if (i and (1 shl j) != 0) {
+                    subset.add(nums[j])
+                }
+            }
+            res.add(subset)
+        }
+
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func subsets(_ nums: [Int]) -> [[Int]] {
+        let n = nums.count
+        var res: [[Int]] = []
+
+        for i in 0..<(1 << n) {
+            var subset: [Int] = []
+            for j in 0..<n {
+                if (i & (1 << j)) != 0 {
+                    subset.append(nums[j])
+                }
+            }
+            res.append(subset)
+        }
+
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n * 2 ^ n)$
-* Space complexity: $O(n)$
\ No newline at end of file
+* Space complexity:
+    * $O(n)$ extra space.
+    * $O(2 ^ n)$ for the output list.
\ No newline at end of file
diff --git a/articles/subtree-of-a-binary-tree.md b/articles/subtree-of-a-binary-tree.md
index 953edf76b..f4e7e57f2 100644
--- a/articles/subtree-of-a-binary-tree.md
+++ b/articles/subtree-of-a-binary-tree.md
@@ -1,4 +1,4 @@
-## 1. Brute Force (DFS)
+## 1. Depth First Search (DFS)
 
 ::tabs-start
 
@@ -222,6 +222,120 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func isSubtree(root *TreeNode, subRoot *TreeNode) bool {
+    if subRoot == nil {
+        return true
+    }
+    if root == nil {
+        return false
+    }
+
+    if sameTree(root, subRoot) {
+        return true
+    }
+    return isSubtree(root.Left, subRoot) || isSubtree(root.Right, subRoot)
+}
+
+func sameTree(root *TreeNode, subRoot *TreeNode) bool {
+    if root == nil && subRoot == nil {
+        return true
+    }
+    if root != nil && subRoot != nil && root.Val == subRoot.Val {
+        return sameTree(root.Left, subRoot.Left) && sameTree(root.Right, subRoot.Right)
+    }
+    return false
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    fun isSubtree(root: TreeNode?, subRoot: TreeNode?): Boolean {
+        if (subRoot == null) {
+            return true
+        }
+        if (root == null) {
+            return false
+        }
+
+        if (sameTree(root, subRoot)) {
+            return true
+        }
+        return isSubtree(root.left, subRoot) || isSubtree(root.right, subRoot)
+    }
+
+    fun sameTree(root: TreeNode?, subRoot: TreeNode?): Boolean {
+        if (root == null && subRoot == null) {
+            return true
+        }
+        if (root != null && subRoot != null && root.`val` == subRoot.`val`) {
+            return sameTree(root.left, subRoot.left) && sameTree(root.right, subRoot.right)
+        }
+        return false
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func isSubtree(_ root: TreeNode?, _ subRoot: TreeNode?) -> Bool {
+        if subRoot == nil {
+            return true
+        }
+        if root == nil {
+            return false
+        }
+        if sameTree(root, subRoot) {
+            return true
+        }
+        return isSubtree(root?.left, subRoot) || isSubtree(root?.right, subRoot)
+    }
+
+    func sameTree(_ root: TreeNode?, _ subRoot: TreeNode?) -> Bool {
+        if root == nil && subRoot == nil {
+            return true
+        }
+        if let root = root, let subRoot = subRoot, root.val == subRoot.val {
+            return sameTree(root.left, subRoot.left) && sameTree(root.right, subRoot.right)
+        }
+        return false
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -247,11 +361,10 @@ public class Solution {
 
 class Solution: 
     def serialize(self, root: Optional[TreeNode]) -> str:
-            if root == None:
-                return "$#"
-            
-            return ("$" + str(root.val) + 
-                    self.serialize(root.left) + self.serialize(root.right))  
+        if root == None:
+            return "$#"
+
+        return ("$" + str(root.val) + self.serialize(root.left) + self.serialize(root.right))  
 
     def z_function(self, s: str) -> list:
         z = [0] * len(s)
@@ -269,10 +382,10 @@ class Solution:
         serialized_root = self.serialize(root)
         serialized_subRoot = self.serialize(subRoot)
         combined = serialized_subRoot + "|" + serialized_root
-        
+
         z_values = self.z_function(combined)
         sub_len = len(serialized_subRoot)
-        
+
         for i in range(sub_len + 1, len(combined)):
             if z_values[i] == sub_len:
                 return True
@@ -420,8 +533,7 @@ class Solution {
         if (root === null) {
             return "$#";
         }
-        return "$" + root.val + 
-                this.serialize(root.left) + this.serialize(root.right);
+        return "$" + root.val + this.serialize(root.left) + this.serialize(root.right);
     }
 
     /**
@@ -529,6 +641,182 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func serialize(root *TreeNode) string {
+    if root == nil {
+        return "$#"
+    }
+    return "$" + strconv.Itoa(root.Val) + serialize(root.Left) + serialize(root.Right)
+}
+
+func zFunction(s string) []int {
+    n := len(s)
+    z := make([]int, n)
+    l, r := 0, 0
+    
+    for i := 1; i < n; i++ {
+        if i <= r {
+            z[i] = min(r-i+1, z[i-l])
+        }
+        for i+z[i] < n && s[z[i]] == s[i+z[i]] {
+            z[i]++
+        }
+        if i+z[i]-1 > r {
+            l = i
+            r = i + z[i] - 1
+        }
+    }
+    return z
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+
+func isSubtree(root *TreeNode, subRoot *TreeNode) bool {
+    serializedRoot := serialize(root)
+    serializedSubRoot := serialize(subRoot)
+    combined := serializedSubRoot + "|" + serializedRoot
+    
+    zValues := zFunction(combined)
+    subLen := len(serializedSubRoot)
+    
+    for i := subLen + 1; i < len(combined); i++ {
+        if zValues[i] == subLen {
+            return true
+        }
+    }
+    return false
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    private fun serialize(root: TreeNode?): String {
+        return when (root) {
+            null -> "$#"
+            else -> "$${root.`val`}${serialize(root.left)}${serialize(root.right)}"
+        }
+    }
+    
+    private fun zFunction(s: String): IntArray {
+        val n = s.length
+        val z = IntArray(n)
+        var l = 0
+        var r = 0
+        
+        for (i in 1 until n) {
+            if (i <= r) {
+                z[i] = minOf(r - i + 1, z[i - l])
+            }
+            while (i + z[i] < n && s[z[i]] == s[i + z[i]]) {
+                z[i]++
+            }
+            if (i + z[i] - 1 > r) {
+                l = i
+                r = i + z[i] - 1
+            }
+        }
+        return z
+    }
+    
+    fun isSubtree(root: TreeNode?, subRoot: TreeNode?): Boolean {
+        val serializedRoot = serialize(root)
+        val serializedSubRoot = serialize(subRoot)
+        val combined = serializedSubRoot + "|" + serializedRoot
+        
+        val zValues = zFunction(combined)
+        val subLen = serializedSubRoot.length
+        
+        return (subLen + 1 until combined.length).any { i -> zValues[i] == subLen }
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func serialize(_ root: TreeNode?) -> String {
+        guard let root = root else {
+            return "$#"
+        }
+        return "$\(root.val)" + serialize(root.left) + serialize(root.right)
+    }
+
+    func zFunction(_ s: String) -> [Int] {
+        let n = s.count
+        var z = [Int](repeating: 0, count: n)
+        var l = 0, r = 0
+        let chars = Array(s)
+
+        for i in 1..<n {
+            if i <= r {
+                z[i] = min(r - i + 1, z[i - l])
+            }
+            while i + z[i] < n && chars[z[i]] == chars[i + z[i]] {
+                z[i] += 1
+            }
+            if i + z[i] - 1 > r {
+                l = i
+                r = i + z[i] - 1
+            }
+        }
+        return z
+    }
+
+    func isSubtree(_ root: TreeNode?, _ subRoot: TreeNode?) -> Bool {
+        let serializedRoot = serialize(root)
+        let serializedSubRoot = serialize(subRoot)
+        let combined = serializedSubRoot + "|" + serializedRoot
+
+        let zValues = zFunction(combined)
+        let subLen = serializedSubRoot.count
+
+        for i in (subLen + 1)..<combined.count {
+            if zValues[i] == subLen {
+                return true
+            }
+        }
+        return false
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/successful-pairs-of-spells-and-potions.md b/articles/successful-pairs-of-spells-and-potions.md
new file mode 100644
index 000000000..87faf3177
--- /dev/null
+++ b/articles/successful-pairs-of-spells-and-potions.md
@@ -0,0 +1,461 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def successfulPairs(self, spells: List[int], potions: List[int], success: int) -> List[int]:
+        res = []
+        
+        for s in spells:
+            cnt = 0
+            for p in potions:
+                if s * p >= success:
+                    cnt += 1
+            res.append(cnt)
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int[] successfulPairs(int[] spells, int[] potions, long success) {
+        int[] res = new int[spells.length];
+
+        for (int i = 0; i < spells.length; i++) {
+            int cnt = 0;
+            for (int p : potions) {
+                if ((long) spells[i] * p >= success) {
+                    cnt++;
+                }
+            }
+            res[i] = cnt;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> successfulPairs(vector<int>& spells, vector<int>& potions, long long success) {
+        vector<int> res(spells.size());
+
+        for (int i = 0; i < spells.size(); i++) {
+            int cnt = 0;
+            for (int p : potions) {
+                if ((long long) spells[i] * p >= success) {
+                    cnt++;
+                }
+            }
+            res[i] = cnt;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} spells
+     * @param {number[]} potions
+     * @param {number} success
+     * @return {number[]}
+     */
+    successfulPairs(spells, potions, success) {
+        let res = [];
+
+        for (let s of spells) {
+            let cnt = 0;
+            for (let p of potions) {
+                if (s * p >= success) {
+                    cnt++;
+                }
+            }
+            res.push(cnt);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(1)$
+
+> Where $n$ and $m$ are the sizes of the arrays $spells$ and $potions$ respectively.
+
+---
+
+## 2. Sorting + Binary Search
+
+::tabs-start
+
+```python
+class Solution:
+    def successfulPairs(self, spells: List[int], potions: List[int], success: int) -> List[int]:
+        potions.sort()
+        res = []
+        
+        for s in spells:
+            l, r = 0, len(potions) - 1
+            idx = len(potions)
+
+            while l <= r:
+                m = (l + r) // 2
+                if s * potions[m] >= success:
+                    r = m - 1
+                    idx = m
+                else:
+                    l = m + 1
+            
+            res.append(len(potions) - idx)
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int[] successfulPairs(int[] spells, int[] potions, long success) {
+        Arrays.sort(potions);
+        int[] res = new int[spells.length];
+
+        for (int i = 0; i < spells.length; i++) {
+            int l = 0, r = potions.length - 1, idx = potions.length;
+
+            while (l <= r) {
+                int m = (l + r) / 2;
+                if ((long) spells[i] * potions[m] >= success) {
+                    r = m - 1;
+                    idx = m;
+                } else {
+                    l = m + 1;
+                }
+            }
+
+            res[i] = potions.length - idx;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> successfulPairs(vector<int>& spells, vector<int>& potions, long long success) {
+        sort(potions.begin(), potions.end());
+        vector<int> res(spells.size());
+
+        for (int i = 0; i < spells.size(); i++) {
+            int l = 0, r = potions.size() - 1, idx = potions.size();
+
+            while (l <= r) {
+                int m = (l + r) / 2;
+                if ((long long) spells[i] * potions[m] >= success) {
+                    r = m - 1;
+                    idx = m;
+                } else {
+                    l = m + 1;
+                }
+            }
+
+            res[i] = potions.size() - idx;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} spells
+     * @param {number[]} potions
+     * @param {number} success
+     * @return {number[]}
+     */
+    successfulPairs(spells, potions, success) {
+        potions.sort((a, b) => a - b);
+        let res = [];
+
+        for (let s of spells) {
+            let l = 0, r = potions.length - 1, idx = potions.length;
+
+            while (l <= r) {
+                let m = Math.floor((l + r) / 2);
+                if (s * potions[m] >= success) {
+                    r = m - 1;
+                    idx = m;
+                } else {
+                    l = m + 1;
+                }
+            }
+
+            res.push(potions.length - idx);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O((m + n) * \log m)$
+* Space complexity:
+    * $O(1)$ or $O(m)$ extra space depending on the sorting algorithm.
+    * $O(n)$ space for the output array.
+
+> Where $n$ and $m$ are the sizes of the arrays $spells$ and $potions$ respectively.
+
+---
+
+## 3. Sorting + Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def successfulPairs(self, spells: List[int], potions: List[int], success: int) -> List[int]:
+        n, m = len(spells), len(potions)
+        S = spells[:]
+        count = defaultdict(int)
+        spells.sort()
+        potions.sort()
+        
+        j = m - 1
+        for i in range(n):
+            while j >= 0 and spells[i] * potions[j] >= success:
+                j -= 1
+            count[spells[i]] = m - j - 1
+        
+        res = [0] * n
+        for i in range(n):
+            res[i] = count[S[i]]
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int[] successfulPairs(int[] spells, int[] potions, long success) {
+        int n = spells.length, m = potions.length;
+        int[] S = Arrays.copyOf(spells, n);
+        Map<Integer, Integer> count = new HashMap<>();
+        Arrays.sort(spells);
+        Arrays.sort(potions);
+        
+        int j = m - 1;
+        for (int i = 0; i < n; i++) {
+            while (j >= 0 && (long) spells[i] * potions[j] >= success) {
+                j--;
+            }
+            count.put(spells[i], m - j - 1);
+        }
+        
+        int[] res = new int[n];
+        for (int i = 0; i < n; i++) {
+            res[i] = count.get(S[i]);
+        }
+        
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> successfulPairs(vector<int>& spells, vector<int>& potions, long long success) {
+        int n = spells.size(), m = potions.size();
+        vector<int> S = spells;
+        unordered_map<int, int> count;
+        sort(spells.begin(), spells.end());
+        sort(potions.begin(), potions.end());
+        
+        int j = m - 1;
+        for (int i = 0; i < n; i++) {
+            while (j >= 0 && (long long) spells[i] * potions[j] >= success) {
+                j--;
+            }
+            count[spells[i]] = m - j - 1;
+        }
+        
+        vector<int> res(n);
+        for (int i = 0; i < n; i++) {
+            res[i] = count[S[i]];
+        }
+        
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} spells
+     * @param {number[]} potions
+     * @param {number} success
+     * @return {number[]}
+     */
+    successfulPairs(spells, potions, success) {
+        const n = spells.length, m = potions.length;
+        const S = [...spells];
+        const count = new Map();
+        spells.sort((a, b) => a - b);
+        potions.sort((a, b) => a - b);
+        
+        let j = m - 1;
+        for (let i = 0; i < n; i++) {
+            while (j >= 0 && spells[i] * potions[j] >= success) {
+                j--;
+            }
+            count.set(spells[i], m - j - 1);
+        }
+        
+        return S.map(s => count.get(s));
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n + m\log m)$
+* Space complexity:
+    * $O(1)$ or $O(m + n)$ extra space depending on the sorting algorithm.
+    * $O(n)$ space for the output array.
+
+> Where $n$ and $m$ are the sizes of the arrays $spells$ and $potions$ respectively.
+
+---
+
+## 4. Sorting + Two Pointers (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def successfulPairs(self, spells: List[int], potions: List[int], success: int) -> List[int]:
+        n, m = len(spells), len(potions)
+        sIdx = list(range(n))
+        sIdx.sort(key=lambda x: spells[x])
+        potions.sort()
+
+        j = m - 1
+        res = [0] * n
+        for i in range(n):
+            while j >= 0 and spells[sIdx[i]] * potions[j] >= success:
+                j -= 1
+            res[sIdx[i]] = m - j - 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[] successfulPairs(int[] spells, int[] potions, long success) {
+        int n = spells.length, m = potions.length;
+        Integer[] sIdx = new Integer[n];
+        for (int i = 0; i < n; i++) sIdx[i] = i;
+        
+        Arrays.sort(sIdx, Comparator.comparingInt(i -> spells[i]));
+        Arrays.sort(potions);
+        
+        int j = m - 1;
+        int[] res = new int[n];
+        for (int i = 0; i < n; i++) {
+            while (j >= 0 && (long) spells[sIdx[i]] * potions[j] >= success) {
+                j--;
+            }
+            res[sIdx[i]] = m - j - 1;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> successfulPairs(vector<int>& spells, vector<int>& potions, long long success) {
+        int n = spells.size(), m = potions.size();
+        vector<int> sIdx(n);
+        for (int i = 0; i < n; i++) sIdx[i] = i;
+
+        sort(sIdx.begin(), sIdx.end(), [&](int a, int b) {
+            return spells[a] < spells[b];
+        });
+
+        sort(potions.begin(), potions.end());
+        
+        int j = m - 1;
+        vector<int> res(n);
+        for (int i = 0; i < n; i++) {
+            while (j >= 0 && (long long) spells[sIdx[i]] * potions[j] >= success) {
+                j--;
+            }
+            res[sIdx[i]] = m - j - 1;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} spells
+     * @param {number[]} potions
+     * @param {number} success
+     * @return {number[]}
+     */
+    successfulPairs(spells, potions, success) {
+        const n = spells.length, m = potions.length;
+        const sIdx = Array.from({ length: n }, (_, i) => i);
+        
+        sIdx.sort((a, b) => spells[a] - spells[b]);
+        potions.sort((a, b) => a - b);
+        
+        let j = m - 1;
+        const res = new Array(n).fill(0);
+        
+        for (let i = 0; i < n; i++) {
+            while (j >= 0 && spells[sIdx[i]] * potions[j] >= success) {
+                j--;
+            }
+            res[sIdx[i]] = m - j - 1;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n + m\log m)$
+* Space complexity:
+    * $O(1)$ or $O(m + n)$ extra space depending on the sorting algorithm.
+    * $O(n)$ space for the output array.
+
+> Where $n$ and $m$ are the sizes of the arrays $spells$ and $potions$ respectively.
\ No newline at end of file
diff --git a/articles/sum-of-absolute-differences-in-a-sorted-array.md b/articles/sum-of-absolute-differences-in-a-sorted-array.md
new file mode 100644
index 000000000..f705f47d7
--- /dev/null
+++ b/articles/sum-of-absolute-differences-in-a-sorted-array.md
@@ -0,0 +1,430 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def getSumAbsoluteDifferences(self, nums: List[int]) -> List[int]:
+        res = []
+
+        for i in nums:
+            sum = 0
+            for j in nums:
+                sum += abs(i - j)
+            res.append(sum)
+            
+        return res
+```
+
+```java
+public class Solution {
+    public int[] getSumAbsoluteDifferences(int[] nums) {
+        int n = nums.length;
+        int[] res = new int[n];
+
+        for (int i = 0; i < n; i++) {
+            int sum = 0;
+            for (int j = 0; j < n; j++) {
+                sum += Math.abs(nums[i] - nums[j]);
+            }
+            res[i] = sum;
+        }
+        
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> getSumAbsoluteDifferences(vector<int>& nums) {
+        int n = nums.size();
+        vector<int> res;
+
+        for (int i = 0; i < n; i++) {
+            int sum = 0;
+            for (int j = 0; j < n; j++) {
+                sum += abs(nums[i] - nums[j]);
+            }
+            res.push_back(sum);
+        }
+        
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    getSumAbsoluteDifferences(nums) {
+        const n = nums.length;
+        const res = [];
+
+        for (let i = 0; i < n; i++) {
+            let sum = 0;
+            for (let j = 0; j < n; j++) {
+                sum += Math.abs(nums[i] - nums[j]);
+            }
+            res.push(sum);
+        }
+        
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$ for the output array.
+
+---
+
+## 2. Prefix & Suffix Sums (Extra Space)
+
+::tabs-start
+
+```python
+class Solution:
+    def getSumAbsoluteDifferences(self, nums: List[int]) -> List[int]:
+        n = len(nums)
+        prefix_sum = [0] * n
+        suffix_sum = [0] * n
+        res = [0] * n
+        
+        prefix_sum[0] = nums[0]
+        for i in range(1, n):
+            prefix_sum[i] = prefix_sum[i - 1] + nums[i]
+        
+        suffix_sum[n - 1] = nums[n - 1]
+        for i in range(n - 2, -1, -1):
+            suffix_sum[i] = suffix_sum[i + 1] + nums[i]
+        
+        for i in range(n):
+            left_sum = (i * nums[i]) - (prefix_sum[i - 1] if i > 0 else 0)
+            right_sum = (suffix_sum[i + 1] if i < n - 1 else 0) - ((n - i - 1) * nums[i])
+            res[i] = left_sum + right_sum
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int[] getSumAbsoluteDifferences(int[] nums) {
+        int n = nums.length;
+        int[] prefixSum = new int[n];
+        int[] suffixSum = new int[n];
+        int[] res = new int[n];
+
+        prefixSum[0] = nums[0];
+        for (int i = 1; i < n; i++) {
+            prefixSum[i] = prefixSum[i - 1] + nums[i];
+        }
+
+        suffixSum[n - 1] = nums[n - 1];
+        for (int i = n - 2; i >= 0; i--) {
+            suffixSum[i] = suffixSum[i + 1] + nums[i];
+        }
+
+        for (int i = 0; i < n; i++) {
+            int leftSum = i > 0 ? (i * nums[i] - prefixSum[i - 1]) : 0;
+            int rightSum = i < n - 1 ? (suffixSum[i + 1] - (n - i - 1) * nums[i]) : 0;
+            res[i] = leftSum + rightSum;
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> getSumAbsoluteDifferences(vector<int>& nums) {
+        int n = nums.size();
+        vector<int> prefixSum(n, 0), suffixSum(n, 0), res(n, 0);
+
+        prefixSum[0] = nums[0];
+        for (int i = 1; i < n; i++) {
+            prefixSum[i] = prefixSum[i - 1] + nums[i];
+        }
+
+        suffixSum[n - 1] = nums[n - 1];
+        for (int i = n - 2; i >= 0; i--) {
+            suffixSum[i] = suffixSum[i + 1] + nums[i];
+        }
+
+        for (int i = 0; i < n; i++) {
+            int leftSum = i > 0 ? (i * nums[i] - prefixSum[i - 1]) : 0;
+            int rightSum = i < n - 1 ? (suffixSum[i + 1] - (n - i - 1) * nums[i]) : 0;
+            res[i] = leftSum + rightSum;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    getSumAbsoluteDifferences(nums) {
+        const n = nums.length;
+        const prefixSum = Array(n).fill(0);
+        const suffixSum = Array(n).fill(0);
+        const res = Array(n).fill(0);
+
+        prefixSum[0] = nums[0];
+        for (let i = 1; i < n; i++) {
+            prefixSum[i] = prefixSum[i - 1] + nums[i];
+        }
+
+        suffixSum[n - 1] = nums[n - 1];
+        for (let i = n - 2; i >= 0; i--) {
+            suffixSum[i] = suffixSum[i + 1] + nums[i];
+        }
+
+        for (let i = 0; i < n; i++) {
+            const leftSum = i > 0 ? (i * nums[i] - prefixSum[i - 1]) : 0;
+            const rightSum = i < n - 1 ? (suffixSum[i + 1] - (n - i - 1) * nums[i]) : 0;
+            res[i] = leftSum + rightSum;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Prefix & Suffix Sums
+
+::tabs-start
+
+```python
+class Solution:
+    def getSumAbsoluteDifferences(self, nums: List[int]) -> List[int]:
+        n = len(nums)
+        res = [0] * n
+        
+        res[n - 1] = nums[n - 1]
+        for i in range(n - 2, -1, -1):
+            res[i] = res[i + 1] + nums[i]
+        
+        prefix_sum = 0
+        for i in range(n):
+            left_sum = (i * nums[i]) - prefix_sum
+            right_sum = (res[i + 1] if i < n - 1 else 0) - ((n - i - 1) * nums[i])
+            res[i] = left_sum + right_sum
+            prefix_sum += nums[i]
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int[] getSumAbsoluteDifferences(int[] nums) {
+        int n = nums.length;
+        int[] res = new int[n];
+
+        res[n - 1] = nums[n - 1];
+        for (int i = n - 2; i >= 0; i--) {
+            res[i] = res[i + 1] + nums[i];
+        }
+
+        int prefixSum = 0;
+        for (int i = 0; i < n; i++) {
+            int leftSum = i * nums[i] - prefixSum;
+            int rightSum = i < n - 1 ? (res[i + 1] - (n - i - 1) * nums[i]) : 0;
+            res[i] = leftSum + rightSum;
+            prefixSum += nums[i];
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> getSumAbsoluteDifferences(vector<int>& nums) {
+        int n = nums.size();
+        vector<int> res(n, 0);
+
+        res[n - 1] = nums[n - 1];
+        for (int i = n - 2; i >= 0; i--) {
+            res[i] = res[i + 1] + nums[i];
+        }
+
+        int prefixSum = 0;
+        for (int i = 0; i < n; i++) {
+            int leftSum = i * nums[i] - prefixSum;
+            int rightSum = i < n - 1 ? (res[i + 1] - (n - i - 1) * nums[i]) : 0;
+            res[i] = leftSum + rightSum;
+            prefixSum += nums[i];
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    getSumAbsoluteDifferences(nums) {
+        const n = nums.length;
+        const res = Array(n).fill(0);
+
+        res[n - 1] = nums[n - 1];
+        for (let i = n - 2; i >= 0; i--) {
+            res[i] = res[i + 1] + nums[i];
+        }
+
+        let prefixSum = 0;
+        for (let i = 0; i < n; i++) {
+            const leftSum = i * nums[i] - prefixSum;
+            const rightSum = i < n - 1 ? (res[i + 1] - (n - i - 1) * nums[i]) : 0;
+            res[i] = leftSum + rightSum;
+            prefixSum += nums[i];
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for the output array.
+
+---
+
+## 4. Prefix & Suffix Sums (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def getSumAbsoluteDifferences(self, nums: List[int]) -> List[int]:
+        n = len(nums)
+        res = [0] * n
+        
+        total_sum = sum(nums)
+        prefix_sum = 0
+
+        for i, num in enumerate(nums):
+            total_sum -= nums[i]
+            left_sum = i * nums[i] - prefix_sum
+            right_sum = total_sum - (n - i - 1) * nums[i]
+            res[i] = left_sum + right_sum
+            prefix_sum += nums[i]
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int[] getSumAbsoluteDifferences(int[] nums) {
+        int n = nums.length;
+        int[] res = new int[n];
+        
+        int totalSum = 0, prefixSum = 0;
+        for (int num : nums) {
+            totalSum += num;
+        }
+
+        for (int i = 0; i < n; i++) {
+            totalSum -= nums[i];
+            int leftSum = i * nums[i] - prefixSum;
+            int rightSum = totalSum - (n - i - 1) * nums[i];
+            res[i] = leftSum + rightSum;
+            prefixSum += nums[i];
+        }
+        
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> getSumAbsoluteDifferences(vector<int>& nums) {
+        int n = nums.size();
+        vector<int> res(n, 0);
+        
+        int totalSum = 0, prefixSum = 0;
+        for (int& num : nums) {
+            totalSum += num;
+        }
+
+        for (int i = 0; i < n; i++) {
+            totalSum -= nums[i];
+            int leftSum = i * nums[i] - prefixSum;
+            int rightSum = totalSum - (n - i - 1) * nums[i];
+            res[i] = leftSum + rightSum;
+            prefixSum += nums[i];
+        }
+        
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number[]}
+     */
+    getSumAbsoluteDifferences(nums) {
+        const n = nums.length;
+        const res = Array(n).fill(0);
+        
+        let totalSum = nums.reduce((sum, num) => sum + num, 0);
+        let prefixSum = 0;
+
+        for (let i = 0; i < n; i++) {
+            totalSum -= nums[i];
+            const leftSum = i * nums[i] - prefixSum;
+            const rightSum = totalSum - (n - i - 1) * nums[i];
+            res[i] = leftSum + rightSum;
+            prefixSum += nums[i];
+        }
+        
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for the output array.
\ No newline at end of file
diff --git a/articles/sum-of-all-subset-xor-totals.md b/articles/sum-of-all-subset-xor-totals.md
new file mode 100644
index 000000000..b35c24e37
--- /dev/null
+++ b/articles/sum-of-all-subset-xor-totals.md
@@ -0,0 +1,414 @@
+## 1. Backtracking
+
+::tabs-start
+
+```python
+class Solution:
+    def subsetXORSum(self, nums: List[int]) -> int:
+        res = 0
+
+        def backtrack(i, subset):
+            nonlocal res
+            xorr = 0
+            for num in subset:
+                xorr ^= num
+            res += xorr
+
+            for j in range(i, len(nums)):
+                subset.append(nums[j])
+                backtrack(j + 1, subset)
+                subset.pop()
+        
+        backtrack(0, [])
+        return res
+```
+
+```java
+public class Solution {
+    int res = 0;
+
+    public int subsetXORSum(int[] nums) {
+        backtrack(0, nums, new ArrayList<>());
+        return res;
+    }
+
+    private void backtrack(int i, int[] nums, List<Integer> subset) {
+        int xorr = 0;
+        for (int num : subset) xorr ^= num;
+        res += xorr;
+
+        for (int j = i; j < nums.length; j++) {
+            subset.add(nums[j]);
+            backtrack(j + 1, nums, subset);
+            subset.remove(subset.size() - 1);
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int subsetXORSum(vector<int>& nums) {
+        int res = 0;
+        vector<int> subset;
+
+        function<void(int)> backtrack = [&](int i) {
+            int xorr = 0;
+            for (int num : subset) xorr ^= num;
+            res += xorr;
+
+            for (int j = i; j < nums.size(); ++j) {
+                subset.push_back(nums[j]);
+                backtrack(j + 1);
+                subset.pop_back();
+            }
+        };
+
+        backtrack(0);
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    subsetXORSum(nums) {
+        let res = 0;
+
+        const backtrack = (i, subset) => {
+            let xorr = 0;
+            for (let num of subset) xorr ^= num;
+            res += xorr;
+
+            for (let j = i; j < nums.length; j++) {
+                subset.push(nums[j]);
+                backtrack(j + 1, subset);
+                subset.pop();
+            }
+        };
+
+        backtrack(0, []);
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    private int res = 0;
+
+    public int SubsetXORSum(int[] nums) {
+        Backtrack(0, new List<int>(), nums);
+        return res;
+    }
+
+    private void Backtrack(int i, List<int> subset, int[] nums) {
+        int xorr = 0;
+        foreach (int num in subset) {
+            xorr ^= num;
+        }
+        res += xorr;
+
+        for (int j = i; j < nums.Length; j++) {
+            subset.Add(nums[j]);
+            Backtrack(j + 1, subset, nums);
+            subset.RemoveAt(subset.Count - 1);
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * 2 ^ n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def subsetXORSum(self, nums: List[int]) -> int:
+        def dfs(i, total):
+            if i == len(nums):
+                return total
+            return dfs(i + 1, total ^ nums[i]) + dfs(i + 1, total)
+
+        return dfs(0, 0)
+```
+
+```java
+public class Solution {
+    public int subsetXORSum(int[] nums) {
+        return dfs(nums, 0, 0);
+    }
+
+    private int dfs(int[] nums, int i, int total) {
+        if (i == nums.length) {
+            return total;
+        }
+        return dfs(nums, i + 1, total ^ nums[i]) + dfs(nums, i + 1, total);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int subsetXORSum(vector<int>& nums) {
+        return dfs(nums, 0, 0);
+    }
+
+private:
+    int dfs(vector<int>& nums, int i, int total) {
+        if (i == nums.size()) {
+            return total;
+        }
+        return dfs(nums, i + 1, total ^ nums[i]) + dfs(nums, i + 1, total);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    subsetXORSum(nums) {
+        const dfs = (i, total) => {
+            if (i === nums.length) {
+                return total;
+            }
+            return dfs(i + 1, total ^ nums[i]) + dfs(i + 1, total);
+        };
+
+        return dfs(0, 0);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int SubsetXORSum(int[] nums) {
+        return Dfs(0, 0, nums);
+    }
+
+    private int Dfs(int i, int total, int[] nums) {
+        if (i == nums.Length) {
+            return total;
+        }
+        return Dfs(i + 1, total ^ nums[i], nums) + Dfs(i + 1, total, nums);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 3. Bit Manipulation
+
+::tabs-start
+
+```python
+class Solution:
+    def subsetXORSum(self, nums: List[int]) -> int:
+        n = len(nums)
+        res = 0
+
+        for mask in range(1 << n):
+            xorr = 0
+            for i in range(n):
+                if mask & (1 << i):
+                    xorr ^= nums[i]
+            res += xorr
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int subsetXORSum(int[] nums) {
+        int n = nums.length;
+        int res = 0;
+
+        for (int mask = 0; mask < (1 << n); mask++) {
+            int xorr = 0;
+            for (int i = 0; i < n; i++) {
+                if ((mask & ( 1 << i)) != 0) {
+                    xorr ^= nums[i];
+                }
+            }
+            res += xorr;
+        }
+        
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int subsetXORSum(vector<int>& nums) {
+        int n = nums.size();
+        int res = 0;
+
+        for (int mask = 0; mask < (1 << n); mask++) {
+            int xorr = 0;
+            for (int i = 0; i < n; i++) {
+                if ((mask & ( 1 << i)) != 0) {
+                    xorr ^= nums[i];
+                }
+            }
+            res += xorr;
+        }
+        
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    subsetXORSum(nums) {
+        const n = nums.length;
+        let res = 0;
+
+        for (let mask = 0; mask < (1 << n); mask++) {
+            let xorr = 0;
+            for (let i = 0; i < n; i++) {
+                if ((mask & ( 1 << i)) !== 0) {
+                    xorr ^= nums[i];
+                }
+            }
+            res += xorr;
+        }
+        
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int SubsetXORSum(int[] nums) {
+        int n = nums.Length;
+        int res = 0;
+
+        for (int mask = 0; mask < (1 << n); mask++) {
+            int xorr = 0;
+            for (int i = 0; i < n; i++) {
+                if ((mask & (1 << i)) != 0) {
+                    xorr ^= nums[i];
+                }
+            }
+            res += xorr;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * 2 ^ n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 4. Bit Manipulation (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def subsetXORSum(self, nums: List[int]) -> int:
+        res = 0
+        for num in nums:
+            res |= num
+        return res << (len(nums) - 1)
+```
+
+```java
+public class Solution {
+    public int subsetXORSum(int[] nums) {
+        int res = 0;
+        for (int num : nums) {
+            res |= num;
+        }
+        return res << (nums.length - 1);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int subsetXORSum(vector<int>& nums) {
+        int res = 0;
+        for (int& num : nums) {
+            res |= num;
+        }
+        return res << (nums.size() - 1);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {number}
+     */
+    subsetXORSum(nums) {
+        let res = 0;
+        for (let num of nums) {
+            res |= num;
+        }
+        return res << (nums.length - 1);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int SubsetXORSum(int[] nums) {
+        int res = 0;
+        foreach (int num in nums) {
+            res |= num;
+        }
+        return res << (nums.Length - 1);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/sum-of-subarray-minimums.md b/articles/sum-of-subarray-minimums.md
new file mode 100644
index 000000000..f1103db9b
--- /dev/null
+++ b/articles/sum-of-subarray-minimums.md
@@ -0,0 +1,596 @@
+## 1. Brute FOrce
+
+::tabs-start
+
+```python
+class Solution:
+    def sumSubarrayMins(self, arr: List[int]) -> int:
+        n, res = len(arr), 0
+        MOD = 1000000007
+
+        for i in range(n):
+            minVal = arr[i]
+            for j in range(i, n):
+                minVal = min(minVal, arr[j])
+                res = (res + minVal) % MOD
+
+        return res
+```
+
+```java
+public class Solution {
+    public int sumSubarrayMins(int[] arr) {
+        int n = arr.length, res = 0;
+        int MOD = 1000000007;
+
+        for (int i = 0; i < n; i++) {
+            int minVal = arr[i];
+            for (int j = i; j < n; j++) {
+                minVal = Math.min(minVal, arr[j]);
+                res = (res + minVal) % MOD;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int sumSubarrayMins(vector<int>& arr) {
+        int n = arr.size(), res = 0;
+        const int MOD = 1000000007;
+
+        for (int i = 0; i < n; i++) {
+            int minVal = arr[i];
+            for (int j = i; j < n; j++) {
+                minVal = min(minVal, arr[j]);
+                res = (res + minVal) % MOD;
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @return {number}
+     */
+    sumSubarrayMins(arr) {
+        const n = arr.length;
+        let res = 0;
+        const MOD = 1000000007;
+
+        for (let i = 0; i < n; i++) {
+            let minVal = arr[i];
+            for (let j = i; j < n; j++) {
+                minVal = Math.min(minVal, arr[j]);
+                res = (res + minVal) % MOD;
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Monotonically Increasing Stack (Two Pass)
+
+::tabs-start
+
+```python
+class Solution:
+    def sumSubarrayMins(self, arr: List[int]) -> int:
+        MOD = 10**9 + 7
+        n = len(arr)
+        
+        # Compute previous smaller
+        prev_smaller = [-1] * n
+        stack = []
+        for i in range(n):
+            while stack and arr[stack[-1]] > arr[i]:
+                stack.pop()
+            prev_smaller[i] = stack[-1] if stack else -1
+            stack.append(i)
+        
+        # Compute next smaller
+        next_smaller = [n] * n
+        stack = []
+        for i in range(n - 1, -1, -1):
+            while stack and arr[stack[-1]] >= arr[i]:
+                stack.pop()
+            next_smaller[i] = stack[-1] if stack else n
+            stack.append(i)
+        
+        res = 0
+        for i in range(n):
+            left = i - prev_smaller[i]
+            right = next_smaller[i] - i
+            res = (res + arr[i] * left * right) % MOD
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int sumSubarrayMins(int[] arr) {
+        int MOD = 1000000007;
+        int n = arr.length;
+        
+        // Compute previous smaller
+        int[] prevSmaller = new int[n];
+        Stack<Integer> stack = new Stack<>();
+        for (int i = 0; i < n; i++) {
+            while (!stack.isEmpty() && arr[stack.peek()] > arr[i]) {
+                stack.pop();
+            }
+            prevSmaller[i] = stack.isEmpty() ? -1 : stack.peek();
+            stack.push(i);
+        }
+        
+        // Compute next smaller
+        int[] nextSmaller = new int[n];
+        stack = new Stack<>();
+        for (int i = n - 1; i >= 0; i--) {
+            while (!stack.isEmpty() && arr[stack.peek()] >= arr[i]) {
+                stack.pop();
+            }
+            nextSmaller[i] = stack.isEmpty() ? n : stack.peek();
+            stack.push(i);
+        }
+        
+        // Calculate result
+        long res = 0;
+        for (int i = 0; i < n; i++) {
+            long left = i - prevSmaller[i];
+            long right = nextSmaller[i] - i;
+            res = (res + arr[i] * left * right) % MOD;
+        }
+        
+        return (int) res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int sumSubarrayMins(vector<int>& arr) {
+        const int MOD = 1e9 + 7;
+        int n = arr.size();
+        
+        // Compute previous smaller
+        vector<int> prevSmaller(n, -1);
+        stack<int> stack;
+        for (int i = 0; i < n; i++) {
+            while (!stack.empty() && arr[stack.top()] > arr[i]) {
+                stack.pop();
+            }
+            prevSmaller[i] = stack.empty() ? -1 : stack.top();
+            stack.push(i);
+        }
+        
+        // Compute next smaller
+        vector<int> nextSmaller(n, n);
+        stack = {};
+        for (int i = n - 1; i >= 0; i--) {
+            while (!stack.empty() && arr[stack.top()] >= arr[i]) {
+                stack.pop();
+            }
+            nextSmaller[i] = stack.empty() ? n : stack.top();
+            stack.push(i);
+        }
+        
+        // Calculate result
+        long long res = 0;
+        for (int i = 0; i < n; i++) {
+            long long left = i - prevSmaller[i];
+            long long right = nextSmaller[i] - i;
+            res = (res + arr[i] * left * right) % MOD;
+        }
+        
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @return {number}
+     */
+    sumSubarrayMins(arr) {
+        const MOD = 1e9 + 7;
+        const n = arr.length;
+        
+        // Compute previous smaller
+        const prevSmaller = new Array(n).fill(-1);
+        const stack = [];
+        for (let i = 0; i < n; i++) {
+            while (stack.length > 0 && arr[stack[stack.length - 1]] > arr[i]) {
+                stack.pop();
+            }
+            prevSmaller[i] = stack.length > 0 ? stack[stack.length - 1] : -1;
+            stack.push(i);
+        }
+        
+        // Compute next smaller
+        const nextSmaller = new Array(n).fill(n);
+        stack.length = 0;
+        for (let i = n - 1; i >= 0; i--) {
+            while (stack.length > 0 && arr[stack[stack.length - 1]] >= arr[i]) {
+                stack.pop();
+            }
+            nextSmaller[i] = stack.length > 0 ? stack[stack.length - 1] : n;
+            stack.push(i);
+        }
+        
+        // Calculate result
+        let res = 0;
+        for (let i = 0; i < n; i++) {
+            const left = i - prevSmaller[i];
+            const right = nextSmaller[i] - i;
+            res = (res + arr[i] * left * right) % MOD;
+        }
+        
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Monotonically Increasing Stack (One Pass)
+
+::tabs-start
+
+```python
+class Solution:
+    def sumSubarrayMins(self, arr: List[int]) -> int:
+        MOD = 10 ** 9 + 7
+        res = 0
+        arr = [float("-inf")] + arr + [float("-inf")]
+        stack = []  # (index, num)
+
+        for i, n in enumerate(arr):
+            while stack and n < stack[-1][1]:
+                j, m = stack.pop()
+                left = j - stack[-1][0] if stack else j + 1
+                right = i - j
+                res = (res + m * left * right) % MOD
+            stack.append((i, n))
+
+        return res
+```
+
+```java
+public class Solution {
+    public int sumSubarrayMins(int[] arr) {
+        int MOD = 1000000007;
+        int res = 0;
+        int[] newArr = new int[arr.length + 2];
+        newArr[0] = Integer.MIN_VALUE;
+        newArr[newArr.length - 1] = Integer.MIN_VALUE;
+        System.arraycopy(arr, 0, newArr, 1, arr.length);
+
+        Stack<int[]> stack = new Stack<>();
+
+        for (int i = 0; i < newArr.length; i++) {
+            while (!stack.isEmpty() && newArr[i] < stack.peek()[1]) {
+                int[] top = stack.pop();
+                int j = top[0], m = top[1];
+                int left = stack.isEmpty() ? j + 1 : j - stack.peek()[0];
+                int right = i - j;
+                res = (int) ((res + (long) m * left * right) % MOD);
+            }
+            stack.push(new int[]{i, newArr[i]});
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int sumSubarrayMins(vector<int>& arr) {
+        const int MOD = 1e9 + 7;
+        int res = 0;
+        vector<int> newArr(arr.size() + 2, INT_MIN);
+        copy(arr.begin(), arr.end(), newArr.begin() + 1);
+
+        stack<pair<int, int>> stack;
+
+        for (int i = 0; i < newArr.size(); i++) {
+            while (!stack.empty() && newArr[i] < stack.top().second) {
+                auto [j, m] = stack.top();
+                stack.pop();
+                int left = stack.empty() ? j + 1 : j - stack.top().first;
+                int right = i - j;
+                res = (res + (long long) m * left * right % MOD) % MOD;
+            }
+            stack.emplace(i, newArr[i]);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @return {number}
+     */
+    sumSubarrayMins(arr) {
+        const MOD = 1e9 + 7;
+        let res = 0;
+        arr = [-Infinity, ...arr, -Infinity];
+        let stack = []; 
+
+        for (let i = 0; i < arr.length; i++) {
+            while (stack.length > 0 && arr[i] < stack[stack.length - 1][1]) {
+                let [j, m] = stack.pop();
+                let left = stack.length > 0 ? j - stack[stack.length - 1][0] : j + 1;
+                let right = i - j;
+                res = (res + m * left * right) % MOD;
+            }
+            stack.push([i, arr[i]]);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Monotonically Increasing Stack (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def sumSubarrayMins(self, arr: List[int]) -> int:
+        MOD = 10**9 + 7
+        stack = []
+        res, n = 0, len(arr)
+
+        for i in range(n + 1):
+            while stack and (i == n or arr[i] < arr[stack[-1]]):
+                j = stack.pop()
+                left = j - (stack[-1] if stack else -1)
+                right = i - j
+                res = (res + arr[j] * left * right) % MOD
+            stack.append(i)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int sumSubarrayMins(int[] arr) {
+        int MOD = 1000000007;
+        int n = arr.length;
+        Stack<Integer> stack = new Stack<>();
+        long res = 0;
+
+        for (int i = 0; i <= n; i++) {
+            while (!stack.isEmpty() && (i == n || arr[i] < arr[stack.peek()])) {
+                int j = stack.pop();
+                int left = j - (stack.isEmpty() ? -1 : stack.peek());
+                int right = i - j;
+                res = (res + (long) arr[j] * left * right) % MOD;
+            }
+            stack.push(i);
+        }
+
+        return (int) res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int sumSubarrayMins(vector<int>& arr) {
+        const int MOD = 1e9 + 7;
+        int n = arr.size();
+        stack<int> stack;
+        long long res = 0;
+
+        for (int i = 0; i <= n; i++) {
+            while (!stack.empty() && (i == n || arr[i] < arr[stack.top()])) {
+                int j = stack.top();
+                stack.pop();
+                int left = j - (stack.empty() ? -1 : stack.top());
+                int right = i - j;
+                res = (res + (long long) arr[j] * left * right) % MOD;
+            }
+            stack.push(i);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @return {number}
+     */
+    sumSubarrayMins(arr) {
+        const MOD = 1e9 + 7;
+        const n = arr.length;
+        const stack = [];
+        let res = 0;
+
+        for (let i = 0; i <= n; i++) {
+            while (stack.length > 0 && (i === n || arr[i] < arr[stack[stack.length - 1]])) {
+                const j = stack.pop();
+                const left = j - (stack.length > 0 ? stack[stack.length - 1] : -1);
+                const right = i - j;
+                res = (res + arr[j] * left * right) % MOD;
+            }
+            stack.push(i);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 5. Dynamic Programming + Stack
+
+::tabs-start
+
+```python
+class Solution:
+    def sumSubarrayMins(self, arr: List[int]) -> int:
+        MOD = 10**9 + 7
+        n = len(arr)
+        dp = [0] * n
+        stack, res = [], 0
+
+        for i in range(n):
+            while stack and arr[stack[-1]] > arr[i]:
+                stack.pop()
+            
+            j = stack[-1] if stack else -1
+            dp[i] = (dp[j] if j != -1 else 0) + arr[i] * (i - j)
+            dp[i] %= MOD
+            res = (res + dp[i]) % MOD
+            stack.append(i)
+
+        return res
+```
+
+```java
+public class Solution {
+    public int sumSubarrayMins(int[] arr) {
+        int MOD = 1000000007;
+        int n = arr.length;
+        int[] dp = new int[n];
+        Stack<Integer> stack = new Stack<>();
+        long res = 0;
+
+        for (int i = 0; i < n; i++) {
+            while (!stack.isEmpty() && arr[stack.peek()] > arr[i]) {
+                stack.pop();
+            }
+
+            int j = stack.isEmpty() ? -1 : stack.peek();
+            dp[i] = ((j != -1 ? dp[j] : 0) + arr[i] * (i - j)) % MOD;
+            res = (res + dp[i]) % MOD;
+            stack.push(i);
+        }
+
+        return (int) res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int sumSubarrayMins(vector<int>& arr) {
+        const int MOD = 1e9 + 7;
+        int n = arr.size();
+        vector<int> dp(n, 0);
+        stack<int> stack;
+        long long res = 0;
+
+        for (int i = 0; i < n; i++) {
+            while (!stack.empty() && arr[stack.top()] > arr[i]) {
+                stack.pop();
+            }
+
+            int j = stack.empty() ? -1 : stack.top();
+            dp[i] = ((j != -1 ? dp[j] : 0) + arr[i] * (i - j)) % MOD;
+            res = (res + dp[i]) % MOD;
+            stack.push(i);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} arr
+     * @return {number}
+     */
+    sumSubarrayMins(arr) {
+        const MOD = 1e9 + 7;
+        const n = arr.length;
+        const dp = new Array(n).fill(0);
+        const stack = [];
+        let res = 0;
+
+        for (let i = 0; i < n; i++) {
+            while (stack.length > 0 && arr[stack[stack.length - 1]] > arr[i]) {
+                stack.pop();
+            }
+
+            const j = stack.length > 0 ? stack[stack.length - 1] : -1;
+            dp[i] = ((j !== -1 ? dp[j] : 0) + arr[i] * (i - j)) % MOD;
+            res = (res + dp[i]) % MOD;
+            stack.push(i);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/sum-of-two-integers.md b/articles/sum-of-two-integers.md
new file mode 100644
index 000000000..6d43c0a14
--- /dev/null
+++ b/articles/sum-of-two-integers.md
@@ -0,0 +1,440 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def getSum(self, a: int, b: int) -> int:
+        return a + b
+```
+
+```java
+public class Solution {
+    public int getSum(int a, int b) {
+        return a + b; 
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int getSum(int a, int b) {
+        return a + b;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} a
+     * @param {number} b
+     * @return {number}
+     */
+    getSum(a, b) {
+        return a + b;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int GetSum(int a, int b) {
+        return a + b;
+    }
+}
+```
+
+```go
+func getSum(a int, b int) int {
+    return a + b
+}
+```
+
+```kotlin
+class Solution {
+    fun getSum(a: Int, b: Int): Int {
+        return a + b
+    }
+}
+```
+
+```swift
+class Solution {
+    func getSum(_ a: Int, _ b: Int) -> Int {
+        return a + b
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Bit Manipulation
+
+::tabs-start
+
+```python
+class Solution:
+    def getSum(self, a: int, b: int) -> int:
+        carry = 0
+        res = 0
+        mask = 0xFFFFFFFF
+
+        for i in range(32):
+            a_bit = (a >> i) & 1
+            b_bit = (b >> i) & 1
+            cur_bit = a_bit ^ b_bit ^ carry
+            carry = (a_bit + b_bit + carry) >= 2
+            if cur_bit:
+                res |= (1 << i)
+
+        if res > 0x7FFFFFFF:
+            res = ~(res ^ mask)
+            
+        return res
+```
+
+```java
+public class Solution {
+    public int getSum(int a, int b) {
+        int carry = 0, res = 0, mask = 0xFFFFFFFF;
+
+        for (int i = 0; i < 32; i++) {
+            int a_bit = (a >> i) & 1;
+            int b_bit = (b >> i) & 1;
+            int cur_bit = a_bit ^ b_bit ^ carry;
+            carry = (a_bit + b_bit + carry) >= 2 ? 1 : 0;
+            if (cur_bit != 0) {
+                res |= (1 << i);
+            }
+        }
+
+        if (res > 0x7FFFFFFF) {
+            res = ~(res ^ mask);
+        }
+        
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int getSum(int a, int b) {
+        int carry = 0, res = 0, mask = 0xFFFFFFFF;
+
+        for (int i = 0; i < 32; i++) {
+            int a_bit = (a >> i) & 1;
+            int b_bit = (b >> i) & 1;
+            int cur_bit = a_bit ^ b_bit ^ carry;
+            carry = (a_bit + b_bit + carry) >= 2 ? 1 : 0;
+            if (cur_bit) {
+                res |= (1 << i);
+            }
+        }
+
+        if (res > 0x7FFFFFFF) {
+            res = ~(res ^ mask);
+        }
+        
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} a
+     * @param {number} b
+     * @return {number}
+     */
+    getSum(a, b) {
+        let carry = 0, res = 0, mask = 0xFFFFFFFF;
+
+        for (let i = 0; i < 32; i++) {
+            let a_bit = (a >> i) & 1;
+            let b_bit = (b >> i) & 1;
+            let cur_bit = a_bit ^ b_bit ^ carry;
+            carry = (a_bit + b_bit + carry) >= 2 ? 1 : 0;
+            if (cur_bit) {
+                res |= (1 << i);
+            }
+        }
+
+        if (res > 0x7FFFFFFF) {
+            res = ~(res ^ mask);
+        }
+        
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int GetSum(int a, int b) {
+        int carry = 0, res = 0, mask = unchecked((int)0xFFFFFFFF);
+
+        for (int i = 0; i < 32; i++) {
+            int a_bit = (a >> i) & 1;
+            int b_bit = (b >> i) & 1;
+            int cur_bit = a_bit ^ b_bit ^ carry;
+            carry = (a_bit + b_bit + carry) >= 2 ? 1 : 0;
+            if (cur_bit != 0) {
+                res |= (1 << i);
+            }
+        }
+
+        if (res > Int32.MaxValue) {
+            res = ~(res ^ mask);
+        }
+        
+        return res;
+    }
+}
+```
+
+```go
+func getSum(a int, b int) int {
+    carry := 0
+    res := 0
+    mask := 0xFFFFFFFF
+
+    for i := 0; i < 32; i++ {
+        aBit := (a >> i) & 1
+        bBit := (b >> i) & 1
+        curBit := aBit ^ bBit ^ carry
+        if (aBit + bBit + carry) >= 2 {
+            carry = 1
+        } else {
+            carry = 0
+        }
+        if curBit == 1 {
+            res |= (1 << i)
+        }
+    }
+
+    if res > 0x7FFFFFFF {
+        res = ^(res ^ mask)
+    }
+
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun getSum(a: Int, b: Int): Int {
+        var carry = 0
+        var res = 0
+        val mask = 0xFFFFFFFF.toInt()
+
+        for (i in 0 until 32) {
+            val aBit = (a shr i) and 1
+            val bBit = (b shr i) and 1
+            val curBit = aBit xor bBit xor carry
+            carry = if (aBit + bBit + carry >= 2) 1 else 0
+            if (curBit == 1) {
+                res = res or (1 shl i)
+            }
+        }
+
+        if (res > 0x7FFFFFFF) {
+            res = res.inv() xor mask
+        }
+
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func getSum(_ a: Int, _ b: Int) -> Int {
+        var carry = 0
+        var res = 0
+        let mask = 0xFFFFFFFF
+
+        for i in 0..<32 {
+            let aBit = (a >> i) & 1
+            let bBit = (b >> i) & 1
+            let curBit = aBit ^ bBit ^ carry
+            carry = (aBit + bBit + carry) >= 2 ? 1 : 0
+            if curBit == 1 {
+                res |= (1 << i)
+            }
+        }
+
+        if res > 0x7FFFFFFF {
+            res = ~(res ^ mask)
+        }
+
+        return res
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Bit Manipulation (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def getSum(self, a: int, b: int) -> int:
+        mask = 0xFFFFFFFF
+        max_int = 0x7FFFFFFF
+
+        while b != 0:
+            carry = (a & b) << 1
+            a = (a ^ b) & mask
+            b = carry & mask
+
+        return a if a <= max_int else ~(a ^ mask)
+```
+
+```java
+public class Solution {
+    public int getSum(int a, int b) {
+        while (b != 0) {
+            int carry = (a & b) << 1;
+            a ^= b;
+            b = carry;
+        }
+        return a;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int getSum(int a, int b) {
+        while (b != 0) {
+            int carry = (a & b) << 1;
+            a ^= b;
+            b = carry;
+        }
+        return a;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} a
+     * @param {number} b
+     * @return {number}
+     */
+    getSum(a, b) {
+        while (b !== 0) {
+            let carry = (a & b) << 1;
+            a ^= b;
+            b = carry;
+        }
+        return a;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public int GetSum(int a, int b) {
+        while (b != 0) {
+            int carry = (a & b) << 1;
+            a ^= b;
+            b = carry;
+        }
+        return a;
+    }
+}
+```
+
+```go
+func getSum(a int, b int) int {
+    mask := 0xFFFFFFFF
+    maxInt := 0x7FFFFFFF
+
+    for b != 0 {
+        carry := (a & b) << 1
+        a = (a ^ b) & mask
+        b = carry & mask
+    }
+
+    if a <= maxInt {
+        return a
+    }
+    return ^(a ^ mask)
+}
+```
+
+```kotlin
+class Solution {
+    fun getSum(a: Int, b: Int): Int {
+        var carry = 0
+        var res = 0
+        val mask = 0xFFFFFFFF.toInt()
+
+        for (i in 0 until 32) {
+            val aBit = (a shr i) and 1
+            val bBit = (b shr i) and 1
+            val curBit = aBit xor bBit xor carry
+            carry = if (aBit + bBit + carry >= 2) 1 else 0
+            if (curBit == 1) {
+                res = res or (1 shl i)
+            }
+        }
+
+        if (res > 0x7FFFFFFF) {
+            res = res.inv() xor mask
+        }
+
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func getSum(_ a: Int, _ b: Int) -> Int {
+        let mask = 0xFFFFFFFF
+        let maxInt = 0x7FFFFFFF
+        var a = a
+        var b = b
+
+        while b != 0 {
+            let carry = (a & b) << 1
+            a = (a ^ b) & mask
+            b = carry & mask
+        }
+
+        return a <= maxInt ? a : ~(a ^ mask)
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/sum-root-to-leaf-numbers.md b/articles/sum-root-to-leaf-numbers.md
new file mode 100644
index 000000000..02bfd196e
--- /dev/null
+++ b/articles/sum-root-to-leaf-numbers.md
@@ -0,0 +1,652 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def sumNumbers(self, root: TreeNode) -> int:
+        def dfs(cur, num):
+            if not cur:
+                return 0
+
+            num = num * 10 + cur.val
+            if not cur.left and not cur.right:
+                return num
+            return dfs(cur.left, num) + dfs(cur.right, num)
+
+        return dfs(root, 0)
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public int sumNumbers(TreeNode root) {
+        return dfs(root, 0);
+    }
+
+    private int dfs(TreeNode cur, int num) {
+        if (cur == null) return 0;
+
+        num = num * 10 + cur.val;
+        if (cur.left == null && cur.right == null) return num;
+
+        return dfs(cur.left, num) + dfs(cur.right, num);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int sumNumbers(TreeNode* root) {
+        return dfs(root, 0);
+    }
+
+private:
+    int dfs(TreeNode* cur, int num) {
+        if (!cur) return 0;
+
+        num = num * 10 + cur->val;
+        if (!cur->left && !cur->right) return num;
+
+        return dfs(cur->left, num) + dfs(cur->right, num);
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number}
+     */
+    sumNumbers(root) {
+        const dfs = (cur, num) => {
+            if (!cur) return 0;
+
+            num = num * 10 + cur.val;
+            if (!cur.left && !cur.right) return num;
+
+            return dfs(cur.left, num) + dfs(cur.right, num);
+        };
+
+        return dfs(root, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(h)$ for recursion stack.
+
+> Where $n$ is the number of nodes and $h$ is the height of the given tree.
+
+---
+
+## 2. Breadth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def sumNumbers(self, root: TreeNode) -> int:
+        res = 0
+        q = deque([(root, 0)])
+        while q:
+            cur, num = q.popleft()
+            num = num * 10 + cur.val
+            if not cur.left and not cur.right:
+                res += num
+                continue
+
+            if cur.left:
+                q.append((cur.left, num))
+            if cur.right:
+                q.append((cur.right, num))
+
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public int sumNumbers(TreeNode root) {
+        int res = 0;
+        Queue<Pair<TreeNode, Integer>> q = new LinkedList<>();
+        q.offer(new Pair<>(root, 0));
+        while (!q.isEmpty()) {
+            Pair<TreeNode, Integer> p = q.poll();
+            TreeNode cur = p.getKey();
+            int num = p.getValue() * 10 + cur.val;
+            if (cur.left == null && cur.right == null) {
+                res += num;
+                continue;
+            }
+
+            if (cur.left != null) q.offer(new Pair<>(cur.left, num));
+            if (cur.right != null) q.offer(new Pair<>(cur.right, num));
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int sumNumbers(TreeNode* root) {
+        int res = 0;
+        queue<pair<TreeNode*, int>> q;
+        q.push({root, 0});
+        while (!q.empty()) {
+            auto [cur, num] = q.front();q.pop();
+            num = num * 10 + cur->val;
+            if (!cur->left && !cur->right) {
+                res += num;
+                continue;
+            }
+
+            if (cur->left) q.push({cur->left, num});
+            if (cur->right) q.push({cur->right, num});
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number}
+     */
+    sumNumbers(root) {
+        let res = 0;
+        const q = new Queue([[root, 0]]);
+        while (!q.isEmpty()) {
+            const [cur, num] = q.pop();
+            const newNum = num * 10 + cur.val;
+            if (!cur.left && !cur.right) {
+                res += newNum;
+                continue;
+            }
+
+            if (cur.left) q.push([cur.left, newNum]);
+            if (cur.right) q.push([cur.right, newNum]);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Iterative DFS
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def sumNumbers(self, root: Optional[TreeNode]) -> int:
+        res = 0
+        stack = []
+        cur, num = root, 0
+
+        while cur or stack:
+            if cur:
+                num = num * 10 + cur.val
+                if not cur.left and not cur.right:
+                    res += num
+
+                stack.append((cur.right, num))
+                cur = cur.left
+            else:
+                cur, num = stack.pop()
+
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public int sumNumbers(TreeNode root) {
+        int res = 0, num = 0;
+        Stack<Pair<TreeNode, Integer>> stack = new Stack<>();
+        TreeNode cur = root;
+
+        while (cur != null || !stack.isEmpty()) {
+            if (cur != null) {
+                num = num * 10 + cur.val;
+                if (cur.left == null && cur.right == null)
+                    res += num;
+                
+                stack.push(new Pair<>(cur.right, num));
+                cur = cur.left;
+            } else {
+                Pair<TreeNode, Integer> p = stack.pop();
+                cur = p.getKey();
+                num = p.getValue();
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int sumNumbers(TreeNode* root) {
+        int res = 0;
+        stack<pair<TreeNode*, int>> st;
+        TreeNode* cur = root;
+        int num = 0;
+
+        while (cur || !st.empty()) {
+            if (cur) {
+                num = num * 10 + cur->val;
+                if (!cur->left && !cur->right) 
+                    res += num;
+                
+                st.push({cur->right, num});
+                cur = cur->left;
+            } else {
+                cur = st.top().first;
+                num = st.top().second;
+                st.pop();
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number}
+     */
+    sumNumbers(root) {
+        let res = 0, num = 0;
+        let stack = [];
+        let cur = root;
+
+        while (cur || stack.length) {
+            if (cur) {
+                num = num * 10 + cur.val;
+                if (!cur.left && !cur.right) 
+                    res += num;
+                
+                stack.push([cur.right, num]);
+                cur = cur.left;
+            } else {
+                [cur, num] = stack.pop();
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(h)$
+
+> Where $n$ is the number of nodes and $h$ is the height of the given tree.
+
+---
+
+## 4. Morris Travrsal
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def sumNumbers(self, root: Optional[TreeNode]) -> int:
+        res = 0
+        cur = root
+        num = 0
+        power = [1] * 10
+        for i in range(1, 10):
+            power[i] *= power[i - 1] * 10
+
+        while cur:
+            if not cur.left:
+                num = num * 10 + cur.val
+                if not cur.right:
+                    res += num
+                cur = cur.right
+            else:
+                prev = cur.left
+                steps = 1
+                while prev.right and prev.right != cur:
+                    prev = prev.right
+                    steps += 1
+
+                if not prev.right:
+                    prev.right = cur
+                    num = num * 10 + cur.val
+                    cur = cur.left
+                else:
+                    prev.right = None
+                    if not prev.left:
+                        res += num
+                    num //= power[steps]
+                    cur = cur.right
+
+        return res
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public int sumNumbers(TreeNode root) {
+        int res = 0, num = 0;
+        int[] power = new int[10];
+        power[0] = 1;
+        for (int i = 1; i < 10; i++) {
+            power[i] = power[i - 1] * 10;
+        }
+
+        TreeNode cur = root;
+        while (cur != null) {
+            if (cur.left == null) {
+                num = num * 10 + cur.val;
+                if (cur.right == null) res += num;
+                cur = cur.right;
+            } else {
+                TreeNode prev = cur.left;
+                int steps = 1;
+                while (prev.right != null && prev.right != cur) {
+                    prev = prev.right;
+                    steps++;
+                }
+
+                if (prev.right == null) {
+                    prev.right = cur;
+                    num = num * 10 + cur.val;
+                    cur = cur.left;
+                } else {
+                    prev.right = null;
+                    if (prev.left == null) res += num;
+                    num /= power[steps];
+                    cur = cur.right;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int sumNumbers(TreeNode* root) {
+        int res = 0, num = 0;
+        int power[10] = {1};
+        for (int i = 1; i < 10; i++) {
+            power[i] = power[i - 1] * 10;
+        }
+
+        TreeNode* cur = root;
+        while (cur) {
+            if (!cur->left) {
+                num = num * 10 + cur->val;
+                if (!cur->right) res += num;
+                cur = cur->right;
+            } else {
+                TreeNode* prev = cur->left;
+                int steps = 1;
+                while (prev->right && prev->right != cur) {
+                    prev = prev->right;
+                    steps++;
+                }
+
+                if (!prev->right) {
+                    prev->right = cur;
+                    num = num * 10 + cur->val;
+                    cur = cur->left;
+                } else {
+                    prev->right = nullptr;
+                    if (!prev->left) res += num;
+                    num /= power[steps];
+                    cur = cur->right;
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {number}
+     */
+    sumNumbers(root) {
+        let res = 0, num = 0;
+        let power = Array(10).fill(1);
+        for (let i = 1; i < 10; i++) {
+            power[i] = power[i - 1] * 10;
+        }
+
+        let cur = root;
+        while (cur) {
+            if (!cur.left) {
+                num = num * 10 + cur.val;
+                if (!cur.right) res += num;
+                cur = cur.right;
+            } else {
+                let prev = cur.left, steps = 1;
+                while (prev.right && prev.right !== cur) {
+                    prev = prev.right;
+                    steps++;
+                }
+
+                if (!prev.right) {
+                    prev.right = cur;
+                    num = num * 10 + cur.val;
+                    cur = cur.left;
+                } else {
+                    prev.right = null;
+                    if (!prev.left) res += num;
+                    num = Math.floor(num / power[steps]);
+                    cur = cur.right;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/surrounded-regions.md b/articles/surrounded-regions.md
index 3b1783e6b..1c0c5445c 100644
--- a/articles/surrounded-regions.md
+++ b/articles/surrounded-regions.md
@@ -234,6 +234,150 @@ public class Solution {
 }
 ```
 
+```go
+func solve(board [][]byte) {
+    rows, cols := len(board), len(board[0])
+
+    var capture func(r, c int)
+    capture = func(r, c int) {
+        if r < 0 || c < 0 || r == rows || 
+           c == cols || board[r][c] != 'O' {
+            return
+        }
+        board[r][c] = 'T'
+        capture(r+1, c)
+        capture(r-1, c)
+        capture(r, c+1)
+        capture(r, c-1)
+    }
+
+    for r := 0; r < rows; r++ {
+        if board[r][0] == 'O' {
+            capture(r, 0)
+        }
+        if board[r][cols-1] == 'O' {
+            capture(r, cols-1)
+        }
+    }
+
+    for c := 0; c < cols; c++ {
+        if board[0][c] == 'O' {
+            capture(0, c)
+        }
+        if board[rows-1][c] == 'O' {
+            capture(rows-1, c)
+        }
+    }
+
+    for r := 0; r < rows; r++ {
+        for c := 0; c < cols; c++ {
+            if board[r][c] == 'O' {
+                board[r][c] = 'X'
+            } else if board[r][c] == 'T' {
+                board[r][c] = 'O'
+            }
+        }
+    }
+}
+```
+
+```kotlin
+class Solution {
+    fun solve(board: Array<CharArray>) {
+        val rows = board.size
+        val cols = board[0].size
+
+        fun capture(r: Int, c: Int) {
+            if (r < 0 || c < 0 || r == rows || 
+                c == cols || board[r][c] != 'O') {
+                return
+            }
+            board[r][c] = 'T'
+            capture(r + 1, c)
+            capture(r - 1, c)
+            capture(r, c + 1)
+            capture(r, c - 1)
+        }
+
+        for (r in 0 until rows) {
+            if (board[r][0] == 'O') {
+                capture(r, 0)
+            }
+            if (board[r][cols - 1] == 'O') {
+                capture(r, cols - 1)
+            }
+        }
+
+        for (c in 0 until cols) {
+            if (board[0][c] == 'O') {
+                capture(0, c)
+            }
+            if (board[rows - 1][c] == 'O') {
+                capture(rows - 1, c)
+            }
+        }
+
+        for (r in 0 until rows) {
+            for (c in 0 until cols) {
+                if (board[r][c] == 'O') {
+                    board[r][c] = 'X'
+                } else if (board[r][c] == 'T') {
+                    board[r][c] = 'O'
+                }
+            }
+        }
+    }
+}
+```
+
+```swift
+class Solution {
+    func solve(_ board: inout [[Character]]) {
+        let ROWS = board.count
+        let COLS = board[0].count
+
+        func capture(_ r: Int, _ c: Int) {
+            if r < 0 || c < 0 || r == ROWS || c == COLS || board[r][c] != "O" {
+                return
+            }
+            board[r][c] = "T"
+            capture(r + 1, c)
+            capture(r - 1, c)
+            capture(r, c + 1)
+            capture(r, c - 1)
+        }
+
+        for r in 0..<ROWS {
+            if board[r][0] == "O" {
+                capture(r, 0)
+            }
+            if board[r][COLS - 1] == "O" {
+                capture(r, COLS - 1)
+            }
+        }
+
+        for c in 0..<COLS {
+            if board[0][c] == "O" {
+                capture(0, c)
+            }
+            if board[ROWS - 1][c] == "O" {
+                capture(ROWS - 1, c)
+            }
+        }
+
+        for r in 0..<ROWS {
+            for c in 0..<COLS {
+                if board[r][c] == "O" {
+                    board[r][c] = "X"
+                } else if board[r][c] == "T" {
+                    board[r][c] = "O"
+                }
+            }
+        }
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -400,7 +544,7 @@ class Solution {
         let directions = [[1, 0], [-1, 0], [0, 1], [0, -1]];
         
         const capture = () => {
-            let q = [];
+            let q = new Queue();
             for (let r = 0; r < ROWS; r++) {
                 for (let c = 0; c < COLS; c++) {
                     if (r === 0 || r === ROWS - 1 || 
@@ -410,8 +554,8 @@ class Solution {
                     }
                 }
             }
-            while (q.length) {
-                let [r, c] = q.shift();
+            while (!q.isEmpty()) {
+                let [r, c] = q.pop();
                 if (board[r][c] === 'O') {
                     board[r][c] = 'T';
                     for (let [dr, dc] of directions) {
@@ -491,6 +635,150 @@ public class Solution {
 }
 ```
 
+```go
+func solve(board [][]byte) {
+    rows, cols := len(board), len(board[0])
+    directions := [][]int{{1, 0}, {-1, 0}, {0, 1}, {0, -1}}
+
+    capture := func() {
+        q := [][]int{}
+        for r := 0; r < rows; r++ {
+            for c := 0; c < cols; c++ {
+                if r == 0 || r == rows-1 || c == 0 || c == cols-1 {
+                    if board[r][c] == 'O' {
+                        q = append(q, []int{r, c})
+                    }
+                }
+            }
+        }
+        for len(q) > 0 {
+            // Dequeue
+            r, c := q[0][0], q[0][1]
+            q = q[1:]
+            if board[r][c] == 'O' {
+                board[r][c] = 'T'
+                for _, dir := range directions {
+                    nr, nc := r+dir[0], c+dir[1]
+                    if nr >= 0 && nr < rows && nc >= 0 && nc < cols {
+                        q = append(q, []int{nr, nc})
+                    }
+                }
+            }
+        }
+    }
+
+    capture()
+
+    for r := 0; r < rows; r++ {
+        for c := 0; c < cols; c++ {
+            if board[r][c] == 'O' {
+                board[r][c] = 'X'
+            } else if board[r][c] == 'T' {
+                board[r][c] = 'O'
+            }
+        }
+    }
+}
+```
+
+```kotlin
+class Solution {
+    fun solve(board: Array<CharArray>) {
+        val rows = board.size
+        val cols = board[0].size
+        val directions = arrayOf(intArrayOf(1, 0), 
+                                 intArrayOf(-1, 0), 
+                                 intArrayOf(0, 1), 
+                                 intArrayOf(0, -1))
+
+        fun capture() {
+            val q: LinkedList<IntArray> = LinkedList()
+            for (r in 0 until rows) {
+                for (c in 0 until cols) {
+                    if (r == 0 || r == rows - 1 || c == 0 || c == cols - 1) {
+                        if (board[r][c] == 'O') {
+                            q.add(intArrayOf(r, c))
+                        }
+                    }
+                }
+            }
+            while (q.isNotEmpty()) {
+                val (r, c) = q.poll()
+                if (board[r][c] == 'O') {
+                    board[r][c] = 'T'
+                    for (dir in directions) {
+                        val nr = r + dir[0]
+                        val nc = c + dir[1]
+                        if (nr in 0 until rows && nc in 0 until cols) {
+                            q.add(intArrayOf(nr, nc))
+                        }
+                    }
+                }
+            }
+        }
+
+        capture()
+
+        for (r in 0 until rows) {
+            for (c in 0 until cols) {
+                if (board[r][c] == 'O') {
+                    board[r][c] = 'X'
+                } else if (board[r][c] == 'T') {
+                    board[r][c] = 'O'
+                }
+            }
+        }
+    }
+}
+```
+
+```swift
+class Solution {
+    func solve(_ board: inout [[Character]]) {
+        let ROWS = board.count
+        let COLS = board[0].count
+        let directions = [(1, 0), (-1, 0), (0, 1), (0, -1)]
+
+        func capture() {
+            var queue = Deque<(Int, Int)>()
+            for r in 0..<ROWS {
+                for c in 0..<COLS {
+                    if (r == 0 || r == ROWS - 1 || c == 0 || c == COLS - 1) && board[r][c] == "O" {
+                        queue.append((r, c))
+                    }
+                }
+            }
+
+            while !queue.isEmpty {
+                let (r, c) = queue.popFirst()!
+                if board[r][c] == "O" {
+                    board[r][c] = "T"
+                    for dir in directions {
+                        let nr = r + dir.0
+                        let nc = c + dir.1
+                        if nr >= 0, nr < ROWS, nc >= 0, nc < COLS {
+                            queue.append((nr, nc))
+                        }
+                    }
+                }
+            }
+        }
+
+        capture()
+
+        for r in 0..<ROWS {
+            for c in 0..<COLS {
+                if board[r][c] == "O" {
+                    board[r][c] = "X"
+                } else if board[r][c] == "T" {
+                    board[r][c] = "O"
+                }
+            }
+        }
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -560,7 +848,7 @@ class Solution:
 ```
 
 ```java
-public class DSU {
+class DSU {
     int[] Parent, Size;
 
     public DSU(int n) {
@@ -866,6 +1154,228 @@ public class Solution {
 }
 ```
 
+```go
+type DSU struct {
+    Parent []int
+    Size   []int
+}
+
+func NewDSU(n int) *DSU {
+    dsu := &DSU{
+        Parent: make([]int, n+1),
+        Size:   make([]int, n+1),
+    }
+    for i := 0; i <= n; i++ {
+        dsu.Parent[i] = i
+        dsu.Size[i] = 1
+    }
+    return dsu
+}
+
+func (dsu *DSU) Find(node int) int {
+    if dsu.Parent[node] != node {
+        dsu.Parent[node] = dsu.Find(dsu.Parent[node])
+    }
+    return dsu.Parent[node]
+}
+
+func (dsu *DSU) Union(u, v int) bool {
+    pu := dsu.Find(u)
+    pv := dsu.Find(v)
+    if pu == pv {
+        return false
+    }
+    if dsu.Size[pu] >= dsu.Size[pv] {
+        dsu.Size[pu] += dsu.Size[pv]
+        dsu.Parent[pv] = pu
+    } else {
+        dsu.Size[pv] += dsu.Size[pu]
+        dsu.Parent[pu] = pv
+    }
+    return true
+}
+
+func (dsu *DSU) Connected(u, v int) bool {
+    return dsu.Find(u) == dsu.Find(v)
+}
+
+func solve(board [][]byte) {
+    rows, cols := len(board), len(board[0])
+    directions := [][]int{{1, 0}, {-1, 0}, {0, 1}, {0, -1}}
+    dsu := NewDSU(rows * cols)
+
+    for r := 0; r < rows; r++ {
+        for c := 0; c < cols; c++ {
+            if board[r][c] != 'O' {
+                continue
+            }
+            if r == 0 || c == 0 || r == rows-1 || c == cols-1 {
+                dsu.Union(rows*cols, r*cols+c)
+            } else {
+                for _, dir := range directions {
+                    nr, nc := r+dir[0], c+dir[1]
+                    if nr >= 0 && nr < rows && nc >= 0 && 
+                       nc < cols && board[nr][nc] == 'O' {
+                        dsu.Union(r*cols+c, nr*cols+nc)
+                    }
+                }
+            }
+        }
+    }
+
+    for r := 0; r < rows; r++ {
+        for c := 0; c < cols; c++ {
+            if !dsu.Connected(rows*cols, r*cols+c) {
+                board[r][c] = 'X'
+            }
+        }
+    }
+}
+```
+
+```kotlin
+class DSU(n: Int) {
+    val parent: IntArray = IntArray(n + 1) { it }
+    val size: IntArray = IntArray(n + 1) { 1 }
+
+    fun find(node: Int): Int {
+        if (parent[node] != node) {
+            parent[node] = find(parent[node])
+        }
+        return parent[node]
+    }
+
+    fun union(u: Int, v: Int): Boolean {
+        val pu = find(u)
+        val pv = find(v)
+        if (pu == pv) return false
+        if (size[pu] >= size[pv]) {
+            size[pu] += size[pv]
+            parent[pv] = pu
+        } else {
+            size[pv] += size[pu]
+            parent[pu] = pv
+        }
+        return true
+    }
+
+    fun connected(u: Int, v: Int): Boolean {
+        return find(u) == find(v)
+    }
+}
+
+class Solution {
+    fun solve(board: Array<CharArray>) {
+        val rows = board.size
+        val cols = board[0].size
+        val directions = arrayOf(intArrayOf(1, 0), 
+                                 intArrayOf(-1, 0), 
+                                 intArrayOf(0, 1), 
+                                 intArrayOf(0, -1))
+        val dsu = DSU(rows * cols)
+
+        for (r in 0 until rows) {
+            for (c in 0 until cols) {
+                if (board[r][c] != 'O') continue
+                if (r == 0 || c == 0 || r == rows - 1 || c == cols - 1) {
+                    dsu.union(rows * cols, r * cols + c)
+                } else {
+                    for (dir in directions) {
+                        val nr = r + dir[0]
+                        val nc = c + dir[1]
+                        if (nr in 0 until rows && 
+                            nc in 0 until cols && board[nr][nc] == 'O') {
+                            dsu.union(r * cols + c, nr * cols + nc)
+                        }
+                    }
+                }
+            }
+        }
+
+        for (r in 0 until rows) {
+            for (c in 0 until cols) {
+                if (!dsu.connected(rows * cols, r * cols + c)) {
+                    board[r][c] = 'X'
+                }
+            }
+        }
+    }
+}
+```
+
+```swift
+class DSU {
+    private var parent: [Int]
+    private var size: [Int]
+
+    init(_ n: Int) {
+        parent = Array(0...n)
+        size = Array(repeating: 1, count: n + 1)
+    }
+
+    func find(_ node: Int) -> Int {
+        if parent[node] != node {
+            parent[node] = find(parent[node])
+        }
+        return parent[node]
+    }
+
+    func union(_ u: Int, _ v: Int) {
+        let pu = find(u)
+        let pv = find(v)
+        if pu == pv { return }
+        if size[pu] >= size[pv] {
+            size[pu] += size[pv]
+            parent[pv] = pu
+        } else {
+            size[pv] += size[pu]
+            parent[pu] = pv
+        }
+    }
+
+    func connected(_ u: Int, _ v: Int) -> Bool {
+        return find(u) == find(v)
+    }
+}
+
+class Solution {
+    func solve(_ board: inout [[Character]]) {
+        let ROWS = board.count
+        let COLS = board[0].count
+        let directions = [(1, 0), (-1, 0), (0, 1), (0, -1)]
+        let dsu = DSU(ROWS * COLS + 1)
+        let N = ROWS * COLS
+
+        for r in 0..<ROWS {
+            for c in 0..<COLS {
+                if board[r][c] != "O" {
+                    continue
+                }
+                if r == 0 || c == 0 || r == ROWS - 1 || c == COLS - 1 {
+                    dsu.union(N, r * COLS + c)
+                } else {
+                    for dir in directions {
+                        let nr = r + dir.0
+                        let nc = c + dir.1
+                        if nr >= 0, nr < ROWS, nc >= 0, nc < COLS, board[nr][nc] == "O" {
+                            dsu.union(r * COLS + c, nr * COLS + nc)
+                        }
+                    }
+                }
+            }
+        }
+
+        for r in 0..<ROWS {
+            for c in 0..<COLS {
+                if board[r][c] == "O", !dsu.connected(N, r * COLS + c) {
+                    board[r][c] = "X"
+                }
+            }
+        }
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/swap-nodes-in-pairs.md b/articles/swap-nodes-in-pairs.md
new file mode 100644
index 000000000..89edd0eee
--- /dev/null
+++ b/articles/swap-nodes-in-pairs.md
@@ -0,0 +1,419 @@
+## 1. Convert TO Array
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def swapPairs(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        if not head:
+            return None
+        arr = []
+        cur = head
+
+        while cur:
+            arr.append(cur)
+            cur = cur.next
+
+        for i in range(0, len(arr) - 1, 2):
+            arr[i], arr[i + 1] = arr[i + 1], arr[i]
+
+        for i in range(len(arr) - 1):
+            arr[i].next = arr[i + 1]
+
+        arr[-1].next = None
+        return arr[0]
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode swapPairs(ListNode head) {
+        if (head == null) return null;
+        
+        List<ListNode> arr = new ArrayList<>();
+        ListNode cur = head;
+
+        while (cur != null) {
+            arr.add(cur);
+            cur = cur.next;
+        }
+
+        for (int i = 0; i < arr.size() - 1; i += 2) {
+            ListNode temp = arr.get(i);
+            arr.set(i, arr.get(i + 1));
+            arr.set(i + 1, temp);
+        }
+
+        for (int i = 0; i < arr.size() - 1; i++) {
+            arr.get(i).next = arr.get(i + 1);
+        }
+
+        arr.get(arr.size() - 1).next = null;
+        return arr.get(0);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* swapPairs(ListNode* head) {
+        if (!head) return nullptr;
+        
+        vector<ListNode*> arr;
+        ListNode* cur = head;
+
+        while (cur) {
+            arr.push_back(cur);
+            cur = cur->next;
+        }
+
+        for (size_t i = 0; i + 1 < arr.size(); i += 2) {
+            swap(arr[i], arr[i + 1]);
+        }
+
+        for (size_t i = 0; i + 1 < arr.size(); i++) {
+            arr[i]->next = arr[i + 1];
+        }
+
+        arr.back()->next = nullptr;
+        return arr[0];
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @return {ListNode}
+     */
+    swapPairs(head) {
+        if (!head) return null;
+
+        let arr = [];
+        let cur = head;
+
+        while (cur) {
+            arr.push(cur);
+            cur = cur.next;
+        }
+
+        for (let i = 0; i + 1 < arr.length; i += 2) {
+            [arr[i], arr[i + 1]] = [arr[i + 1], arr[i]];
+        }
+
+        for (let i = 0; i + 1 < arr.length; i++) {
+            arr[i].next = arr[i + 1];
+        }
+
+        arr[arr.length - 1].next = null;
+        return arr[0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Recursion
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def swapPairs(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        if not head or not head.next:
+            return head
+
+        cur = head
+        nxt = head.next
+        cur.next = self.swapPairs(nxt.next)
+        nxt.next = cur
+        return nxt
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode swapPairs(ListNode head) {
+        if (head == null || head.next == null) {
+            return head;
+        }
+
+        ListNode cur = head;
+        ListNode nxt = head.next;
+        cur.next = swapPairs(nxt.next);
+        nxt.next = cur;
+
+        return nxt;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* swapPairs(ListNode* head) {
+        if (!head || !head->next) {
+            return head;
+        }
+
+        ListNode* cur = head;
+        ListNode* nxt = head->next;
+        cur->next = swapPairs(nxt->next);
+        nxt->next = cur;
+
+        return nxt;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @return {ListNode}
+     */
+    swapPairs(head) {
+        if (!head || !head.next) {
+            return head;
+        }
+
+        let cur = head;
+        let nxt = head.next;
+        cur.next = this.swapPairs(nxt.next);
+        nxt.next = cur;
+
+        return nxt;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 3. Iteration
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def swapPairs(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        dummy = ListNode(0, head)
+        prev, curr = dummy, head
+
+        while curr and curr.next:
+            nxtPair = curr.next.next
+            second = curr.next
+
+            # Reverse this pair
+            second.next = curr
+            curr.next = nxtPair
+            prev.next = second
+
+            # Update pointers
+            prev = curr
+            curr = nxtPair
+
+        return dummy.next
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode swapPairs(ListNode head) {
+        ListNode dummy = new ListNode(0, head);
+        ListNode prev = dummy, curr = head;
+
+        while (curr != null && curr.next != null) {
+            ListNode nxtPair = curr.next.next;
+            ListNode second = curr.next;
+
+            // Reverse this pair
+            second.next = curr;
+            curr.next = nxtPair;
+            prev.next = second;
+
+            // Update pointers
+            prev = curr;
+            curr = nxtPair;
+        }
+
+        return dummy.next;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* swapPairs(ListNode* head) {
+        ListNode dummy(0, head);
+        ListNode* prev = &dummy, *curr = head;
+
+        while (curr && curr->next) {
+            ListNode* nxtPair = curr->next->next;
+            ListNode* second = curr->next;
+
+            // Reverse this pair
+            second->next = curr;
+            curr->next = nxtPair;
+            prev->next = second;
+
+            // Update pointers
+            prev = curr;
+            curr = nxtPair;
+        }
+
+        return dummy.next;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @return {ListNode}
+     */
+    swapPairs(head) {
+        let dummy = new ListNode(0, head);
+        let prev = dummy, curr = head;
+
+        while (curr && curr.next) {
+            let nxtPair = curr.next.next;
+            let second = curr.next;
+
+            // Reverse this pair
+            second.next = curr;
+            curr.next = nxtPair;
+            prev.next = second;
+
+            // Update pointers
+            prev = curr;
+            curr = nxtPair;
+        }
+
+        return dummy.next;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/swapping-nodes-in-a-linked-list.md b/articles/swapping-nodes-in-a-linked-list.md
new file mode 100644
index 000000000..8a0267213
--- /dev/null
+++ b/articles/swapping-nodes-in-a-linked-list.md
@@ -0,0 +1,785 @@
+## 1. Convert To Array
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def swapNodes(self, head: Optional[ListNode], k: int) -> Optional[ListNode]:
+        arr = []
+        cur = head
+        while cur:
+            arr.append(cur.val)
+            cur = cur.next
+
+        n = len(arr)
+        arr[k - 1], arr[n - k] = arr[n - k], arr[k - 1]
+        
+        cur, i = head, 0
+        while cur:
+            cur.val = arr[i]
+            cur = cur.next
+            i += 1
+
+        return head
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode swapNodes(ListNode head, int k) {
+        List<Integer> arr = new ArrayList<>();
+        ListNode cur = head;
+
+        while (cur != null) {
+            arr.add(cur.val);
+            cur = cur.next;
+        }
+
+        int n = arr.size();
+        int temp = arr.get(k - 1);
+        arr.set(k - 1, arr.get(n - k));
+        arr.set(n - k, temp);
+
+        cur = head;
+        int i = 0;
+        while (cur != null) {
+            cur.val = arr.get(i);
+            cur = cur.next;
+            i++;
+        }
+
+        return head;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* swapNodes(ListNode* head, int k) {
+        vector<int> arr;
+        ListNode* cur = head;
+
+        while (cur) {
+            arr.push_back(cur->val);
+            cur = cur->next;
+        }
+
+        int n = arr.size();
+        swap(arr[k - 1], arr[n - k]);
+
+        cur = head;
+        int i = 0;
+        while (cur) {
+            cur->val = arr[i];
+            cur = cur->next;
+            i++;
+        }
+
+        return head;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @param {number} k
+     * @return {ListNode}
+     */
+    swapNodes(head, k) {
+        let arr = [];
+        let cur = head;
+
+        while (cur) {
+            arr.push(cur.val);
+            cur = cur.next;
+        }
+
+        let n = arr.length;
+        [arr[k - 1], arr[n - k]] = [arr[n - k], arr[k - 1]];
+
+        cur = head;
+        let i = 0;
+        while (cur) {
+            cur.val = arr[i];
+            cur = cur.next;
+            i++;
+        }
+
+        return head;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Recursion
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def swapNodes(self, head: Optional[ListNode], k: int) -> Optional[ListNode]:
+        left, right, startIdx = None, None, 0
+
+        def dfs(node):
+            nonlocal left, right, startIdx
+            if not node:
+                return 0
+            
+            startIdx += 1
+            if startIdx == k:
+                left = node
+            
+            endIdx = dfs(node.next) + 1
+            if endIdx == k:
+                right = node
+            
+            return endIdx
+
+        dfs(head)
+        if left and right:
+            left.val, right.val = right.val, left.val
+
+        return head
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode swapNodes(ListNode head, int k) {
+        ListNode[] left = new ListNode[1];
+        ListNode[] right = new ListNode[1];
+        int[] startIdx = {0};
+
+        dfs(head, k, startIdx, left, right);
+        
+        if (left[0] != null && right[0] != null) {
+            int temp = left[0].val;
+            left[0].val = right[0].val;
+            right[0].val = temp;
+        }
+
+        return head;
+    }
+
+    private int dfs(ListNode node, int k, int[] startIdx, ListNode[] left, ListNode[] right) {
+        if (node == null) {
+            return 0;
+        }
+
+        startIdx[0]++;
+        if (startIdx[0] == k) {
+            left[0] = node;
+        }
+
+        int endIdx = dfs(node.next, k, startIdx, left, right) + 1;
+        if (endIdx == k) {
+            right[0] = node;
+        }
+
+        return endIdx;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* swapNodes(ListNode* head, int k) {
+        ListNode* left = nullptr;
+        ListNode* right = nullptr;
+        int startIdx = 0;
+
+        dfs(head, k, startIdx, left, right);
+
+        if (left && right) {
+            swap(left->val, right->val);
+        }
+
+        return head;
+    }
+
+private:
+    int dfs(ListNode* node, int k, int& startIdx, ListNode*& left, ListNode*& right) {
+        if (!node) {
+            return 0;
+        }
+
+        startIdx++;
+        if (startIdx == k) {
+            left = node;
+        }
+
+        int endIdx = dfs(node->next, k, startIdx, left, right) + 1;
+        if (endIdx == k) {
+            right = node;
+        }
+
+        return endIdx;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @param {number} k
+     * @return {ListNode}
+     */
+    swapNodes(head, k) {
+        let left = null, right = null, startIdx = 0;
+
+        const dfs = (node) => {
+            if (!node) return 0;
+
+            startIdx++;
+            if (startIdx === k) left = node;
+
+            let endIdx = dfs(node.next) + 1;
+            if (endIdx === k) right = node;
+
+            return endIdx;
+        };
+
+        dfs(head);
+        if (left && right) {
+            [left.val, right.val] = [right.val, left.val];
+        }
+
+        return head;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 3. Iteration (Two Pass)
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def swapNodes(self, head: Optional[ListNode], k: int) -> Optional[ListNode]:
+        n = 0
+        cur = head
+        while cur:
+            n += 1
+            cur = cur.next
+
+        left, right = None, None
+        cur = head
+        for i in range(1, n + 1):
+            if i == k:
+                left = cur
+            if i == (n - k + 1):
+                right = cur
+            cur = cur.next
+
+        left.val, right.val = right.val, left.val
+        return head
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode swapNodes(ListNode head, int k) {
+        int n = 0;
+        ListNode cur = head;
+        while (cur != null) {
+            n++;
+            cur = cur.next;
+        }
+
+        ListNode left = null, right = null;
+        cur = head;
+        for (int i = 1; i <= n; i++) {
+            if (i == k) {
+                left = cur;
+            }
+            if (i == (n - k + 1)) {
+                right = cur;
+            }
+            cur = cur.next;
+        }
+
+        int temp = left.val;
+        left.val = right.val;
+        right.val = temp;
+        
+        return head;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* swapNodes(ListNode* head, int k) {
+        int n = 0;
+        ListNode* cur = head;
+        while (cur) {
+            n++;
+            cur = cur->next;
+        }
+
+        ListNode* left = nullptr;
+        ListNode* right = nullptr;
+        cur = head;
+        for (int i = 1; i <= n; i++) {
+            if (i == k) {
+                left = cur;
+            }
+            if (i == (n - k + 1)) {
+                right = cur;
+            }
+            cur = cur->next;
+        }
+
+        swap(left->val, right->val);
+        return head;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @param {number} k
+     * @return {ListNode}
+     */
+    swapNodes(head, k) {
+        let n = 0;
+        let cur = head;
+        while (cur) {
+            n++;
+            cur = cur.next;
+        }
+
+        let left = null, right = null;
+        cur = head;
+        for (let i = 1; i <= n; i++) {
+            if (i === k) {
+                left = cur;
+            }
+            if (i === (n - k + 1)) {
+                right = cur;
+            }
+            cur = cur.next;
+        }
+
+        [left.val, right.val] = [right.val, left.val];
+        return head;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 4. Iteration (One Pass) - I
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def swapNodes(self, head: Optional[ListNode], k: int) -> Optional[ListNode]:
+        cur = head
+        for _ in range(k - 1):
+            cur = cur.next
+
+        left = cur
+        right = head
+
+        while cur.next:
+            cur = cur.next
+            right = right.next
+
+        left.val, right.val = right.val, left.val
+        return head
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode swapNodes(ListNode head, int k) {
+        ListNode cur = head;
+        for (int i = 0; i < k - 1; i++) {
+            cur = cur.next;
+        }
+
+        ListNode left = cur;
+        ListNode right = head;
+
+        while (cur.next != null) {
+            cur = cur.next;
+            right = right.next;
+        }
+
+        int temp = left.val;
+        left.val = right.val;
+        right.val = temp;
+
+        return head;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* swapNodes(ListNode* head, int k) {
+        ListNode* cur = head;
+        for (int i = 0; i < k - 1; i++) {
+            cur = cur->next;
+        }
+
+        ListNode* left = cur;
+        ListNode* right = head;
+
+        while (cur->next) {
+            cur = cur->next;
+            right = right->next;
+        }
+
+        swap(left->val, right->val);
+        return head;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @param {number} k
+     * @return {ListNode}
+     */
+    swapNodes(head, k) {
+        let cur = head;
+        for (let i = 0; i < k - 1; i++) {
+            cur = cur.next;
+        }
+
+        let left = cur;
+        let right = head;
+
+        while (cur.next) {
+            cur = cur.next;
+            right = right.next;
+        }
+
+        [left.val, right.val] = [right.val, left.val];
+        return head;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 5. Iteration (One Pass) - II
+
+::tabs-start
+
+```python
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def swapNodes(self, head: Optional[ListNode], k: int) -> Optional[ListNode]:
+        left, right = None, None
+        cur = head
+
+        while cur:
+            if right:
+                right = right.next
+            if k == 1:
+                left = cur
+                right = head
+            k -= 1
+            cur = cur.next
+
+        left.val, right.val = right.val, left.val
+        return head
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+public class Solution {
+    public ListNode swapNodes(ListNode head, int k) {
+        ListNode left = null, right = null, cur = head;
+
+        while (cur != null) {
+            if (right != null) {
+                right = right.next;
+            }
+            if (k == 1) {
+                left = cur;
+                right = head;
+            }
+            k--;
+            cur = cur.next;
+        }
+
+        int temp = left.val;
+        left.val = right.val;
+        right.val = temp;
+        
+        return head;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* swapNodes(ListNode* head, int k) {
+        ListNode* left = nullptr;
+        ListNode* right = nullptr;
+        ListNode* cur = head;
+
+        while (cur) {
+            if (right) {
+                right = right->next;
+            }
+            if (k == 1) {
+                left = cur;
+                right = head;
+            }
+            k--;
+            cur = cur->next;
+        }
+
+        swap(left->val, right->val);
+        return head;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *     constructor(val = 0, next = null) {
+ *         this.val = val;
+ *         this.next = next;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {ListNode} head
+     * @param {number} k
+     * @return {ListNode}
+     */
+    swapNodes(head, k) {
+        let left = null, right = null, cur = head;
+
+        while (cur) {
+            if (right) {
+                right = right.next;
+            }
+            if (k === 1) {
+                left = cur;
+                right = head;
+            }
+            k--;
+            cur = cur.next;
+        }
+
+        [left.val, right.val] = [right.val, left.val];
+        return head;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/swim-in-rising-water.md b/articles/swim-in-rising-water.md
index e5c507985..b87262dcb 100644
--- a/articles/swim-in-rising-water.md
+++ b/articles/swim-in-rising-water.md
@@ -156,6 +156,111 @@ public class Solution {
 }
 ```
 
+```go
+func swimInWater(grid [][]int) int {
+    n := len(grid)
+    visit := make([][]bool, n)
+    for i := range visit {
+        visit[i] = make([]bool, n)
+    }
+
+    var dfs func(r, c, t int) int
+    dfs = func(r, c, t int) int {
+        if r < 0 || c < 0 || r >= n || c >= n || visit[r][c] {
+            return 1000000
+        }
+        if r == n-1 && c == n-1 {
+            return max(t, grid[r][c])
+        }
+        visit[r][c] = true
+        t = max(t, grid[r][c])
+        
+        res := min(
+            min(dfs(r+1, c, t), dfs(r-1, c, t)),
+            min(dfs(r, c+1, t), dfs(r, c-1, t)),
+        )
+        
+        visit[r][c] = false
+        return res
+    }
+    
+    return dfs(0, 0, 0)
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun swimInWater(grid: Array<IntArray>): Int {
+        val n = grid.size
+        val visit = Array(n) { BooleanArray(n) }
+
+        fun dfs(r: Int, c: Int, t: Int): Int {
+            if (r < 0 || c < 0 || r >= n || c >= n || visit[r][c]) {
+                return 1000000
+            }
+            if (r == n - 1 && c == n - 1) return maxOf(t, grid[r][c])
+            visit[r][c] = true
+            val time = maxOf(t, grid[r][c])
+
+            val res = minOf(
+                dfs(r + 1, c, time),
+                dfs(r - 1, c, time),
+                dfs(r, c + 1, time),
+                dfs(r, c - 1, time)
+            )
+
+            visit[r][c] = false
+            return res
+        }
+
+        return dfs(0, 0, 0)
+    }
+}
+```
+
+```swift
+class Solution {
+    func swimInWater(_ grid: [[Int]]) -> Int {
+        let n = grid.count
+        var visit = Array(repeating: Array(repeating: false, count: n), count: n)
+
+        func dfs(_ node: (Int, Int), _ t: Int) -> Int {
+            let (r, c) = node
+            if r < 0 || c < 0 || r >= n || c >= n || visit[r][c] {
+                return 1000000
+            }
+            if r == n - 1 && c == n - 1 {
+                return max(t, grid[r][c])
+            }
+            visit[r][c] = true
+            let t = max(t, grid[r][c])
+            let res = min(dfs((r + 1, c), t),
+                          dfs((r - 1, c), t),
+                          dfs((r, c + 1), t),
+                          dfs((r, c - 1), t))
+            visit[r][c] = false
+            return res
+        }
+
+        return dfs((0, 0), 0)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -380,6 +485,139 @@ public class Solution {
 }
 ```
 
+```go
+func swimInWater(grid [][]int) int {
+    n := len(grid)
+    minH, maxH := grid[0][0], grid[0][0]
+    for r := 0; r < n; r++ {
+        for c := 0; c < n; c++ {
+            if grid[r][c] < minH {
+                minH = grid[r][c]
+            }
+            if grid[r][c] > maxH {
+                maxH = grid[r][c]
+            }
+        }
+    }
+
+    visit := make([][]bool, n)
+    for i := range visit {
+        visit[i] = make([]bool, n)
+    }
+
+    var dfs func(r, c, t int) bool
+    dfs = func(r, c, t int) bool {
+        if r < 0 || c < 0 || r >= n || c >= n || 
+           visit[r][c] || grid[r][c] > t {
+            return false
+        }
+        if r == n-1 && c == n-1 {
+            return true
+        }
+        visit[r][c] = true
+        found := dfs(r+1, c, t) || dfs(r-1, c, t) || 
+                 dfs(r, c+1, t) || dfs(r, c-1, t)
+        return found
+    }
+
+    for t := minH; t <= maxH; t++ {
+        if dfs(0, 0, t) {
+            return t
+        }
+        for i := range visit {
+            for j := range visit[i] {
+                visit[i][j] = false
+            }
+        }
+    }
+
+    return maxH
+}
+```
+
+```kotlin
+class Solution {
+    fun swimInWater(grid: Array<IntArray>): Int {
+        val n = grid.size
+        var minH = grid[0][0]
+        var maxH = grid[0][0]
+        for (row in grid) {
+            minH = minOf(minH, row.minOrNull() ?: minH)
+            maxH = maxOf(maxH, row.maxOrNull() ?: maxH)
+        }
+
+        val visit = Array(n) { BooleanArray(n) }
+
+        fun dfs(r: Int, c: Int, t: Int): Boolean {
+            if (r < 0 || c < 0 || r >= n || c >= n || 
+                visit[r][c] || grid[r][c] > t) {
+                return false
+            }
+            if (r == n - 1 && c == n - 1) {
+                return true
+            }
+            visit[r][c] = true
+            return dfs(r + 1, c, t) || dfs(r - 1, c, t) || 
+                   dfs(r, c + 1, t) || dfs(r, c - 1, t)
+        }
+
+        for (t in minH..maxH) {
+            if (dfs(0, 0, t)) return t
+            for (r in 0 until n) {
+                visit[r].fill(false)
+            }
+        }
+
+        return maxH
+    }
+}
+```
+
+```swift
+class Solution {
+    func swimInWater(_ grid: [[Int]]) -> Int {
+        let n = grid.count
+        var visit = Array(repeating: Array(repeating: false, count: n), count: n)
+        var minH = grid[0][0], maxH = grid[0][0]
+
+        for row in 0..<n {
+            for col in 0..<n {
+                maxH = max(maxH, grid[row][col])
+                minH = min(minH, grid[row][col])
+            }
+        }
+
+        func dfs(_ node: (Int, Int), _ t: Int) -> Bool {
+            let (r, c) = node
+            if r < 0 || c < 0 || r >= n || c >= n || visit[r][c] || grid[r][c] > t {
+                return false
+            }
+            if r == n - 1 && c == n - 1 {
+                return true
+            }
+            visit[r][c] = true
+            return dfs((r + 1, c), t) ||
+                   dfs((r - 1, c), t) ||
+                   dfs((r, c + 1), t) ||
+                   dfs((r, c - 1), t)
+        }
+
+        for t in minH...maxH {
+            if dfs((0, 0), t) {
+                return t
+            }
+            for r in 0..<n {
+                for c in 0..<n {
+                    visit[r][c] = false
+                }
+            }
+        }
+
+        return maxH
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -624,6 +862,154 @@ public class Solution {
 }
 ```
 
+```go
+func swimInWater(grid [][]int) int {
+    n := len(grid)
+    minH, maxH := grid[0][0], grid[0][0]
+    for r := 0; r < n; r++ {
+        for c := 0; c < n; c++ {
+            if grid[r][c] < minH {
+                minH = grid[r][c]
+            }
+            if grid[r][c] > maxH {
+                maxH = grid[r][c]
+            }
+        }
+    }
+
+    visit := make([][]bool, n)
+    for i := range visit {
+        visit[i] = make([]bool, n)
+    }
+
+    var dfs func(r, c, t int) bool
+    dfs = func(r, c, t int) bool {
+        if r < 0 || c < 0 || r >= n || c >= n || 
+           visit[r][c] || grid[r][c] > t {
+            return false
+        }
+        if r == n-1 && c == n-1 {
+            return true
+        }
+        visit[r][c] = true
+        found := dfs(r+1, c, t) || dfs(r-1, c, t) || 
+                 dfs(r, c+1, t) || dfs(r, c-1, t)
+        return found
+    }
+
+    l, r := minH, maxH
+    for l < r {
+        m := (l + r) / 2
+        if dfs(0, 0, m) {
+            r = m
+        } else {
+            l = m + 1
+        }
+        for i := range visit {
+            for j := range visit[i] {
+                visit[i][j] = false
+            }
+        }
+    }
+
+    return r
+}
+```
+
+```kotlin
+class Solution {
+    fun swimInWater(grid: Array<IntArray>): Int {
+        val n = grid.size
+        var minH = grid[0][0]
+        var maxH = grid[0][0]
+        for (row in grid) {
+            minH = minOf(minH, row.minOrNull() ?: minH)
+            maxH = maxOf(maxH, row.maxOrNull() ?: maxH)
+        }
+
+        val visit = Array(n) { BooleanArray(n) }
+
+        fun dfs(r: Int, c: Int, t: Int): Boolean {
+            if (r < 0 || c < 0 || r >= n || c >= n || 
+                visit[r][c] || grid[r][c] > t) {
+                return false
+            }
+            if (r == n - 1 && c == n - 1) {
+                return true
+            }
+            visit[r][c] = true
+            return dfs(r + 1, c, t) || dfs(r - 1, c, t) || 
+                   dfs(r, c + 1, t) || dfs(r, c - 1, t)
+        }
+
+        var l = minH
+        var r = maxH
+        while (l < r) {
+            val m = (l + r) / 2
+            if (dfs(0, 0, m)) {
+                r = m
+            } else {
+                l = m + 1
+            }
+            for (row in visit) {
+                row.fill(false)
+            }
+        }
+
+        return r
+    }
+}
+```
+
+```swift
+class Solution {
+    func swimInWater(_ grid: [[Int]]) -> Int {
+        let n = grid.count
+        var visit = Array(repeating: Array(repeating: false, count: n), count: n)
+        var minH = grid[0][0], maxH = grid[0][0]
+
+        for row in 0..<n {
+            for col in 0..<n {
+                maxH = max(maxH, grid[row][col])
+                minH = min(minH, grid[row][col])
+            }
+        }
+
+        func dfs(_ node: (Int, Int), _ t: Int) -> Bool {
+            let (r, c) = node
+            if r < 0 || c < 0 || r >= n || c >= n || visit[r][c] || grid[r][c] > t {
+                return false
+            }
+            if r == n - 1 && c == n - 1 {
+                return true
+            }
+            visit[r][c] = true
+            return dfs((r + 1, c), t) ||
+                   dfs((r - 1, c), t) ||
+                   dfs((r, c + 1), t) ||
+                   dfs((r, c - 1), t)
+        }
+
+        var l = minH, r = maxH
+        while l < r {
+            let m = (l + r) >> 1
+            if dfs((0, 0), m) {
+                r = m
+            } else {
+                l = m + 1
+            }
+            for row in 0..<n {
+                for col in 0..<n {
+                    visit[row][col] = false
+                }
+            }
+        }
+
+        return r
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -828,6 +1214,135 @@ public class Solution {
 }
 ```
 
+```go
+type Node struct {
+    time, r, c int
+}
+
+func swimInWater(grid [][]int) int {
+    N := len(grid)
+    directions := [][2]int{{0, 1}, {0, -1}, {1, 0}, {-1, 0}}
+
+    pq := priorityqueue.NewWith(func(a, b interface{}) int {
+        return utils.IntComparator(a.(Node).time, b.(Node).time)
+    })
+
+    pq.Enqueue(Node{grid[0][0], 0, 0})
+    visited := make(map[[2]int]bool)
+    visited[[2]int{0, 0}] = true
+
+    for !pq.Empty() {
+        item, _ := pq.Dequeue()
+        node := item.(Node)
+        t, r, c := node.time, node.r, node.c
+
+        if r == N-1 && c == N-1 {
+            return t
+        }
+
+        for _, dir := range directions {
+            neiR, neiC := r+dir[0], c+dir[1]
+            if neiR < 0 || neiC < 0 || neiR >= N || neiC >= N || 
+               visited[[2]int{neiR, neiC}] {
+                continue
+            }
+
+            visited[[2]int{neiR, neiC}] = true
+            pq.Enqueue(Node{max(t, grid[neiR][neiC]), neiR, neiC})
+        }
+    }
+
+    return -1
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun swimInWater(grid: Array<IntArray>): Int {
+        val N = grid.size
+        val directions = listOf(Pair(0, 1), Pair(0, -1), Pair(1, 0), Pair(-1, 0))
+        
+        val minHeap = PriorityQueue(compareBy<Pair<Int, Pair<Int, Int>>> { it.first })
+        minHeap.offer(Pair(grid[0][0], Pair(0, 0)))
+        
+        val visited = HashSet<Pair<Int, Int>>()
+        visited.add(Pair(0, 0))
+
+        while (minHeap.isNotEmpty()) {
+            val (t, pos) = minHeap.poll()
+            val (r, c) = pos
+
+            if (r == N - 1 && c == N - 1) return t
+
+            for ((dr, dc) in directions) {
+                val neiR = r + dr
+                val neiC = c + dc
+                if (neiR !in 0 until N || neiC !in 0 until N || Pair(neiR, neiC) in visited) {
+                    continue
+                }
+
+                visited.add(Pair(neiR, neiC))
+                minHeap.offer(Pair(maxOf(t, grid[neiR][neiC]), Pair(neiR, neiC)))
+            }
+        }
+
+        return -1
+    }
+}
+```
+
+```swift
+struct Item: Comparable {
+    let time: Int
+    let row: Int
+    let col: Int
+
+    static func < (lhs: Item, rhs: Item) -> Bool {
+        return lhs.time < rhs.time
+    }
+}
+
+class Solution {
+    func swimInWater(_ grid: [[Int]]) -> Int {
+        let N = grid.count
+        var visit = Set<[Int]>()
+        var minHeap = Heap<Item>()
+
+        let directions = [(0, 1), (0, -1), (1, 0), (-1, 0)]
+
+        minHeap.insert(Item(time: grid[0][0], row: 0, col: 0))
+        visit.insert([0, 0])
+
+        while !minHeap.isEmpty {
+            let item = minHeap.removeMin()
+            let t = item.time, r = item.row, c = item.col
+
+            if r == N - 1 && c == N - 1 {
+                return t
+            }
+
+            for (dr, dc) in directions {
+                let neiR = r + dr, neiC = c + dc
+                if neiR < 0 || neiC < 0 || neiR == N || neiC == N || visit.contains([neiR, neiC]) {
+                    continue
+                }
+                visit.insert([neiR, neiC])
+                minHeap.insert(Item(time: max(t, grid[neiR][neiC]), row: neiR, col: neiC))
+            }
+        }
+
+        return -1
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -883,7 +1398,7 @@ class Solution:
 ```
 
 ```java
-public class DSU {
+class DSU {
     private int[] Parent;
     private int[] Size;
 
@@ -1146,6 +1661,207 @@ public class Solution {
 }
 ```
 
+```go
+type DSU struct {
+    Parent, Size []int
+}
+
+func NewDSU(n int) *DSU {
+    dsu := &DSU{
+        Parent: make([]int, n+1),
+        Size:   make([]int, n+1),
+    }
+    for i := 0; i <= n; i++ {
+        dsu.Parent[i] = i
+        dsu.Size[i] = 1
+    }
+    return dsu
+}
+
+func (dsu *DSU) Find(node int) int {
+    if dsu.Parent[node] != node {
+        dsu.Parent[node] = dsu.Find(dsu.Parent[node])
+    }
+    return dsu.Parent[node]
+}
+
+func (dsu *DSU) Union(u, v int) bool {
+    pu, pv := dsu.Find(u), dsu.Find(v)
+    if pu == pv {
+        return false
+    }
+    if dsu.Size[pu] < dsu.Size[pv] {
+        pu, pv = pv, pu
+    }
+    dsu.Size[pu] += dsu.Size[pv]
+    dsu.Parent[pv] = pu
+    return true
+}
+
+func (dsu *DSU) Connected(u, v int) bool {
+    return dsu.Find(u) == dsu.Find(v)
+}
+
+func swimInWater(grid [][]int) int {
+    N := len(grid)
+    dsu := NewDSU(N * N)
+    positions := make([][3]int, 0, N*N)
+    for r := 0; r < N; r++ {
+        for c := 0; c < N; c++ {
+            positions = append(positions, [3]int{grid[r][c], r, c})
+        }
+    }
+    sort.Slice(positions, func(i, j int) bool { 
+        return positions[i][0] < positions[j][0] 
+    })
+    directions := [][2]int{{0, 1}, {1, 0}, {0, -1}, {-1, 0}}
+
+    for _, pos := range positions {
+        t, r, c := pos[0], pos[1], pos[2]
+        for _, d := range directions {
+            nr, nc := r+d[0], c+d[1]
+            if nr >= 0 && nc >= 0 && nr < N && nc < N && grid[nr][nc] <= t {
+                dsu.Union(r*N+c, nr*N+nc)
+            }
+        }
+        if dsu.Connected(0, N*N-1) {
+            return t
+        }
+    }
+    return -1
+}
+```
+
+```kotlin
+class DSU(n: Int) {
+    private val parent = IntArray(n + 1) { it }
+    private val size = IntArray(n + 1) { 1 }
+
+    fun find(node: Int): Int {
+        if (parent[node] != node) {
+            parent[node] = find(parent[node])
+        }
+        return parent[node]
+    }
+
+    fun union(u: Int, v: Int): Boolean {
+        var pu = find(u)
+        var pv = find(v)
+        if (pu == pv) return false
+        if (size[pu] < size[pv]) {
+            val temp = pu
+            pu = pv
+            pv = temp
+        }
+        size[pu] += size[pv]
+        parent[pv] = pu
+        return true
+    }
+
+    fun connected(u: Int, v: Int): Boolean {
+        return find(u) == find(v)
+    }
+}
+
+class Solution {
+    fun swimInWater(grid: Array<IntArray>): Int {
+        val N = grid.size
+        val dsu = DSU(N * N)
+        val positions = mutableListOf<Triple<Int, Int, Int>>()
+        for (r in grid.indices) {
+            for (c in grid[r].indices) {
+                positions.add(Triple(grid[r][c], r, c))
+            }
+        }
+        positions.sortBy { it.first }
+        val directions = listOf(Pair(0, 1), Pair(1, 0), Pair(0, -1), Pair(-1, 0))
+
+        for ((t, r, c) in positions) {
+            for ((dr, dc) in directions) {
+                val nr = r + dr
+                val nc = c + dc
+                if (nr in 0 until N && nc in 0 until N && grid[nr][nc] <= t) {
+                    dsu.union(r * N + c, nr * N + nc)
+                }
+            }
+            if (dsu.connected(0, N * N - 1)) {
+                return t
+            }
+        }
+        return -1
+    }
+}
+```
+
+```swift
+class DSU {
+    private var parent: [Int]
+    private var size: [Int]
+
+    init(_ n: Int) {
+        parent = Array(0...(n - 1))
+        size = Array(repeating: 1, count: n)
+    }
+
+    func find(_ node: Int) -> Int {
+        if parent[node] != node {
+            parent[node] = find(parent[node])
+        }
+        return parent[node]
+    }
+
+    func union(_ u: Int, _ v: Int) -> Bool {
+        let pu = find(u)
+        let pv = find(v)
+        if pu == pv {
+            return false
+        }
+        if size[pu] < size[pv] {
+            parent[pu] = pv
+            size[pv] += size[pu]
+        } else {
+            parent[pv] = pu
+            size[pu] += size[pv]
+        }
+        return true
+    }
+
+    func connected(_ u: Int, _ v: Int) -> Bool {
+        return find(u) == find(v)
+    }
+}
+
+class Solution {
+    func swimInWater(_ grid: [[Int]]) -> Int {
+        let N = grid.count
+        let dsu = DSU(N * N)
+        var positions = [(Int, Int, Int)]()
+        let directions = [(0, 1), (1, 0), (0, -1), (-1, 0)]
+
+        for r in 0..<N {
+            for c in 0..<N {
+                positions.append((grid[r][c], r, c))
+            }
+        }
+
+        positions.sort { $0.0 < $1.0 }
+
+        for (t, r, c) in positions {
+            for (dr, dc) in directions {
+                let nr = r + dr, nc = c + dc
+                if nr >= 0, nc >= 0, nr < N, nc < N, grid[nr][nc] <= t {
+                    dsu.union(r * N + c, nr * N + nc)
+                }
+            }
+            if dsu.connected(0, N * N - 1) {
+                return t
+            }
+        }
+        return -1
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/symmetric-tree.md b/articles/symmetric-tree.md
new file mode 100644
index 000000000..615d4dd34
--- /dev/null
+++ b/articles/symmetric-tree.md
@@ -0,0 +1,447 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def isSymmetric(self, root: Optional[TreeNode]) -> bool:
+        def dfs(left, right):
+            if not left and not right:
+                return True
+            if not left or not right:
+                return False
+            return (
+                left.val == right.val and
+                dfs(left.left, right.right) and
+                dfs(left.right, right.left)
+            )
+        return dfs(root.left, root.right)
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public boolean isSymmetric(TreeNode root) {
+        return dfs(root.left, root.right);
+    }
+
+    private boolean dfs(TreeNode left, TreeNode right) {
+        if (left == null && right == null) {
+            return true;
+        }
+        if (left == null || right == null) {
+            return false;
+        }
+        return left.val == right.val && 
+               dfs(left.left, right.right) && 
+               dfs(left.right, right.left);
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    bool isSymmetric(TreeNode* root) {
+        return dfs(root->left, root->right);
+    }
+
+private:
+    bool dfs(TreeNode* left, TreeNode* right) {
+        if (!left && !right) {
+            return true;
+        }
+        if (!left || !right) {
+            return false;
+        }
+        return (left->val == right->val) && 
+                dfs(left->left, right->right) && 
+                dfs(left->right, right->left);
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {boolean}
+     */
+    isSymmetric(root) {
+        const dfs = (left, right) => {
+            if (!left && !right) {
+                return true;
+            }
+            if (!left || !right) {
+                return false;
+            }
+            return (
+                left.val === right.val &&
+                dfs(left.left, right.right) &&
+                dfs(left.right, right.left)
+            );
+        };
+        return dfs(root.left, root.right);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Iterative DFS
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def isSymmetric(self, root: Optional[TreeNode]) -> bool:
+        if not root:
+            return True
+
+        stack = [(root.left, root.right)]
+        while stack:
+            left, right = stack.pop()
+            if not left and not right:
+                continue
+            if not left or not right or left.val != right.val:
+                return False
+            stack.append((left.left, right.right))
+            stack.append((left.right, right.left))
+        return True
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public boolean isSymmetric(TreeNode root) {
+        if (root == null) return true;
+
+        Stack<TreeNode[]> stack = new Stack<>();
+        stack.push(new TreeNode[]{root.left, root.right});
+
+        while (!stack.isEmpty()) {
+            TreeNode[] nodes = stack.pop();
+            TreeNode left = nodes[0], right = nodes[1];
+
+            if (left == null && right == null) continue;
+            if (left == null || right == null || left.val != right.val) {
+                return false;
+            }
+
+            stack.push(new TreeNode[]{left.left, right.right});
+            stack.push(new TreeNode[]{left.right, right.left});
+        }
+
+        return true;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    bool isSymmetric(TreeNode* root) {
+        if (!root) return true;
+
+        std::stack<pair<TreeNode*, TreeNode*>> stack;
+        stack.push({root->left, root->right});
+
+        while (!stack.empty()) {
+            auto [left, right] = stack.top();
+            stack.pop();
+
+            if (!left && !right) continue;
+            if (!left || !right || left->val != right->val) {
+                return false;
+            }
+            stack.push({left->left, right->right});
+            stack.push({left->right, right->left});
+        }
+
+        return true;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {boolean}
+     */
+    isSymmetric(root) {
+        if (!root) return true;
+
+        const stack = [[root.left, root.right]];
+
+        while (stack.length > 0) {
+            const [left, right] = stack.pop();
+
+            if (!left && !right) continue;
+            if (!left || !right || left.val !== right.val) {
+                return false;
+            }
+
+            stack.push([left.left, right.right]);
+            stack.push([left.right, right.left]);
+        }
+
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Breadth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def isSymmetric(self, root: Optional[TreeNode]) -> bool:
+        if not root:
+            return True
+
+        queue = deque([(root.left, root.right)])
+        while queue:
+            for _ in range(len(queue)):
+                left, right = queue.popleft()
+                if not left and not right:
+                    continue
+                if not left or not right or left.val != right.val:
+                    return False
+                queue.append((left.left, right.right))
+                queue.append((left.right, right.left))
+                
+        return True
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public boolean isSymmetric(TreeNode root) {
+        if (root == null) return true;
+
+        Queue<TreeNode[]> queue = new LinkedList<>();
+        queue.add(new TreeNode[]{root.left, root.right});
+
+        while (!queue.isEmpty()) {
+            for (int i = queue.size(); i > 0; i--) {
+                TreeNode[] nodes = queue.poll();
+                TreeNode left = nodes[0], right = nodes[1];
+
+                if (left == null && right == null) continue;
+                if (left == null || right == null || left.val != right.val) {
+                    return false;
+                }
+                queue.add(new TreeNode[]{left.left, right.right});
+                queue.add(new TreeNode[]{left.right, right.left});
+            }
+        }
+
+        return true;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    bool isSymmetric(TreeNode* root) {
+        if (!root) return true;
+
+        queue<pair<TreeNode*, TreeNode*>> queue;
+        queue.push({root->left, root->right});
+
+        while (!queue.empty()) {
+            for (int i = queue.size(); i > 0; i--) {   
+                auto [left, right] = queue.front();
+                queue.pop();
+
+                if (!left && !right) continue;
+                if (!left || !right || left->val != right->val) {
+                    return false;
+                }
+                queue.push({left->left, right->right});
+                queue.push({left->right, right->left});
+            }
+        }
+
+        return true;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @return {boolean}
+     */
+    isSymmetric(root) {
+        if (!root) return true;
+
+        const queue = new Queue([[root.left, root.right]]);
+
+        while (!queue.isEmpty()) {
+            for (let i = queue.size(); i > 0; i--) {
+                const [left, right] = queue.pop();
+
+                if (!left && !right) continue;
+                if (!left || !right || left.val !== right.val) {
+                    return false;
+                }
+                queue.push([left.left, right.right]);
+                queue.push([left.right, right.left]);
+            }
+        }
+
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/target-sum.md b/articles/target-sum.md
index 67c741932..71c10c0c2 100644
--- a/articles/target-sum.md
+++ b/articles/target-sum.md
@@ -87,6 +87,53 @@ public class Solution {
 }
 ```
 
+```go
+func findTargetSumWays(nums []int, target int) int {
+    var backtrack func(i int, total int) int
+    backtrack = func(i int, total int) int {
+        if i == len(nums) {
+            if total == target {
+                return 1
+            }
+            return 0
+        }
+        return backtrack(i+1, total+nums[i]) + backtrack(i+1, total-nums[i])
+    }
+    
+    return backtrack(0, 0)
+}
+```
+
+```kotlin
+class Solution {
+    fun findTargetSumWays(nums: IntArray, target: Int): Int {
+        fun backtrack(i: Int, total: Int): Int {
+            if (i == nums.size) {
+                return if (total == target) 1 else 0
+            }
+            return backtrack(i + 1, total + nums[i]) + 
+                   backtrack(i + 1, total - nums[i])
+        }
+        
+        return backtrack(0, 0)
+    }
+}
+```
+
+```swift
+class Solution {
+    func findTargetSumWays(_ nums: [Int], _ target: Int) -> Int {
+        func backtrack(_ i: Int, _ total: Int) -> Int {
+            if i == nums.count {
+                return total == target ? 1 : 0
+            }
+            return backtrack(i + 1, total + nums[i]) + backtrack(i + 1, total - nums[i])
+        }
+        return backtrack(0, 0)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -238,14 +285,97 @@ public class Solution {
 }
 ```
 
+```go
+func findTargetSumWays(nums []int, target int) int {
+    totalSum := 0
+    for _, num := range nums {
+        totalSum += num
+    }
+
+    dp := make([][]int, len(nums))
+    for i := range dp {
+        dp[i] = make([]int, 2*totalSum+1)
+        for j := range dp[i] {
+            dp[i][j] = math.MinInt32
+        }
+    }
+
+    var backtrack func(i, total int) int
+    backtrack = func(i, total int) int {
+        if i == len(nums) {
+            if total == target {
+                return 1
+            }
+            return 0
+        }
+
+        if dp[i][total+totalSum] != math.MinInt32 {
+            return dp[i][total+totalSum]
+        }
+
+        dp[i][total+totalSum] = (backtrack(i+1, total+nums[i]) + 
+                                 backtrack(i+1, total-nums[i]))
+        return dp[i][total+totalSum]
+    }
+
+    return backtrack(0, 0)
+}
+```
+
+```kotlin
+class Solution {
+    fun findTargetSumWays(nums: IntArray, target: Int): Int {
+        var totalSum = nums.sum()
+        var dp = Array(nums.size) { IntArray(2 * totalSum + 1) { Int.MIN_VALUE } }
+
+        fun backtrack(i: Int, total: Int): Int {
+            if (i == nums.size) {
+                return if (total == target) 1 else 0
+            }
+            if (dp[i][total + totalSum] != Int.MIN_VALUE) {
+                return dp[i][total + totalSum]
+            }
+            dp[i][total + totalSum] = backtrack(i + 1, total + nums[i]) + 
+                                      backtrack(i + 1, total - nums[i])
+            return dp[i][total + totalSum]
+        }
+        
+        return backtrack(0, 0)
+    }
+}
+```
+
+```swift
+class Solution {
+    func findTargetSumWays(_ nums: [Int], _ target: Int) -> Int {
+        let totalSum = nums.reduce(0, +)
+        var dp = Array(repeating: Array(repeating: Int.min, count: 2 * totalSum + 1), count: nums.count)
+
+        func backtrack(_ i: Int, _ total: Int) -> Int {
+            if i == nums.count {
+                return total == target ? 1 : 0
+            }
+            if dp[i][total + totalSum] != Int.min {
+                return dp[i][total + totalSum]
+            }
+            dp[i][total + totalSum] = backtrack(i + 1, total + nums[i]) + 
+                                      backtrack(i + 1, total - nums[i])
+            return dp[i][total + totalSum]
+        }
+
+        return backtrack(0, 0)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
-* Time complexity: $O(n * t)$
-* Space complexity: $O(n * t)$
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n * m)$
 
-> Where $n$ is the length of the array $nums$ and $t$ is the sum of all the elements in the array.
+> Where $n$ is the length of the array $nums$ and $m$ is the sum of all the elements in the array.
 
 ---
 
@@ -367,14 +497,74 @@ public class Solution {
 }
 ```
 
+```go
+func findTargetSumWays(nums []int, target int) int {
+    n := len(nums)
+    dp := make([]map[int]int, n+1)
+
+    for i := 0; i <= n; i++ {
+        dp[i] = make(map[int]int)
+    }
+
+    dp[0][0] = 1 
+
+    for i := 0; i < n; i++ {
+        for total, count := range dp[i] {
+            dp[i+1][total+nums[i]] += count
+            dp[i+1][total-nums[i]] += count
+        }
+    }
+
+    return dp[n][target]
+}
+```
+
+```kotlin
+class Solution {
+    fun findTargetSumWays(nums: IntArray, target: Int): Int {
+        val n = nums.size
+        val dp = Array(n + 1) { mutableMapOf<Int, Int>() }
+
+        dp[0][0] = 1 
+
+        for (i in 0 until n) {
+            for ((total, count) in dp[i]) {
+                dp[i + 1][total + nums[i]] = dp[i + 1].getOrDefault(total + nums[i], 0) + count
+                dp[i + 1][total - nums[i]] = dp[i + 1].getOrDefault(total - nums[i], 0) + count
+            }
+        }
+
+        return dp[n][target] ?: 0
+    }
+}
+```
+
+```swift
+class Solution {
+    func findTargetSumWays(_ nums: [Int], _ target: Int) -> Int {
+        let n = nums.count
+        var dp = Array(repeating: [Int: Int](), count: n + 1)
+        dp[0][0] = 1
+
+        for i in 0..<n {
+            for (total, count) in dp[i] {
+                dp[i + 1][total + nums[i], default: 0] += count
+                dp[i + 1][total - nums[i], default: 0] += count
+            }
+        }
+        return dp[n][target, default: 0]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
-* Time complexity: $O(n * t)$
-* Space complexity: $O(n * t)$
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n * m)$
 
-> Where $n$ is the length of the array $nums$ and $t$ is the sum of all the elements in the array.
+> Where $n$ is the length of the array $nums$ and $m$ is the sum of all the elements in the array.
 
 ---
 
@@ -498,11 +688,67 @@ public class Solution {
 }
 ```
 
+```go
+func findTargetSumWays(nums []int, target int) int {
+    dp := make(map[int]int)
+    dp[0] = 1 
+
+    for _, num := range nums {
+        nextDp := make(map[int]int)
+        for total, count := range dp {
+            nextDp[total+num] += count
+            nextDp[total-num] += count
+        }
+        dp = nextDp
+    }
+
+    return dp[target]
+}
+```
+
+```kotlin
+class Solution {
+    fun findTargetSumWays(nums: IntArray, target: Int): Int {
+        val dp = mutableMapOf(0 to 1) 
+
+        for (num in nums) {
+            val nextDp = mutableMapOf<Int, Int>()
+            for ((total, count) in dp) {
+                nextDp[total + num] = nextDp.getOrDefault(total + num, 0) + count
+                nextDp[total - num] = nextDp.getOrDefault(total - num, 0) + count
+            }
+            dp.clear()
+            dp.putAll(nextDp)
+        }
+
+        return dp[target] ?: 0
+    }
+}
+```
+
+```swift
+class Solution {
+    func findTargetSumWays(_ nums: [Int], _ target: Int) -> Int {
+        var dp = [0: 1]
+
+        for num in nums {
+            var nextDp = [Int: Int]()
+            for (total, count) in dp {
+                nextDp[total + num, default: 0] += count
+                nextDp[total - num, default: 0] += count
+            }
+            dp = nextDp
+        }
+        return dp[target, default: 0]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
-* Time complexity: $O(n * t)$
-* Space complexity: $O(t)$
+* Time complexity: $O(n * m)$
+* Space complexity: $O(m)$
 
-> Where $n$ is the length of the array $nums$ and $t$ is the sum of all the elements in the array.
\ No newline at end of file
+> Where $n$ is the length of the array $nums$ and $m$ is the sum of all the elements in the array.
\ No newline at end of file
diff --git a/articles/task-scheduling.md b/articles/task-scheduling.md
index f377e8d95..03e752212 100644
--- a/articles/task-scheduling.md
+++ b/articles/task-scheduling.md
@@ -236,6 +236,144 @@ public class Solution {
 }
 ```
 
+```go
+func leastInterval(tasks []byte, n int) int {
+	count := make([]int, 26)
+	for _, task := range tasks {
+		count[task-'A']++
+	}
+
+	arr := [][]int{}
+	for i := 0; i < 26; i++ {
+		if count[i] > 0 {
+			arr = append(arr, []int{count[i], i})
+		}
+	}
+
+	time := 0
+	processed := []int{}
+	for len(arr) > 0 {
+		maxi := -1
+		for i := 0; i < len(arr); i++ {
+			canProcess := true
+			for j := max(0, time-n); j < time && canProcess; j++ {
+				if processed[j] == arr[i][1] {
+					canProcess = false
+				}
+			}
+			if canProcess && (maxi == -1 || arr[maxi][0] < arr[i][0]) {
+				maxi = i
+			}
+		}
+
+		time++
+		cur := -1
+		if maxi != -1 {
+			cur = arr[maxi][1]
+			arr[maxi][0]--
+			if arr[maxi][0] == 0 {
+				arr = append(arr[:maxi], arr[maxi+1:]...)
+			}
+		}
+		processed = append(processed, cur)
+	}
+	return time
+}
+
+func max(a, b int) int {
+	if a > b {
+		return a
+	}
+	return b
+}
+```
+
+```kotlin
+class Solution {
+    fun leastInterval(tasks: CharArray, n: Int): Int {
+        val count = IntArray(26)
+        for (task in tasks) {
+            count[task - 'A']++
+        }
+
+        val arr = mutableListOf<Pair<Int, Int>>()
+        for (i in 0..25) {
+            if (count[i] > 0) {
+                arr.add(Pair(count[i], i))
+            }
+        }
+
+        var time = 0
+        val processed = mutableListOf<Int>()
+        while (arr.isNotEmpty()) {
+            var maxi = -1
+            for (i in arr.indices) {
+                val canProcess = (maxOf(0, time - n) until time).all { processed[it] != arr[i].second }
+                if (canProcess && (maxi == -1 || arr[maxi].first < arr[i].first)) {
+                    maxi = i
+                }
+            }
+
+            time++
+            var cur = -1
+            if (maxi != -1) {
+                cur = arr[maxi].second
+                arr[maxi] = Pair(arr[maxi].first - 1, arr[maxi].second)
+                if (arr[maxi].first == 0) {
+                    arr.removeAt(maxi)
+                }
+            }
+            processed.add(cur)
+        }
+        return time
+    }
+}
+```
+
+```swift
+class Solution {
+    func leastInterval(_ tasks: [Character], _ n: Int) -> Int {
+        var count = [Int](repeating: 0, count: 26)
+        for task in tasks {
+            count[Int(task.asciiValue! - Character("A").asciiValue!)] += 1
+        }
+
+        var arr = [(Int, Int)]()
+        for i in 0..<26 {
+            if count[i] > 0 {
+                arr.append((count[i], i))
+            }
+        }
+
+        var time = 0
+        var processed = [Int]()
+
+        while !arr.isEmpty {
+            var maxi = -1
+            for i in 0..<arr.count {
+                if processed[max(0, time - n)..<time].allSatisfy({ $0 != arr[i].1 }) {
+                    if maxi == -1 || arr[maxi].0 < arr[i].0 {
+                        maxi = i
+                    }
+                }
+            }
+
+            time += 1
+            var cur = -1
+            if maxi != -1 {
+                cur = arr[maxi].1
+                arr[maxi].0 -= 1
+                if arr[maxi].0 == 0 {
+                    arr.remove(at: maxi)
+                }
+            }
+            processed.append(cur)
+        }
+        return time
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -247,7 +385,7 @@ public class Solution {
 
 ---
 
-## 2. Heap
+## 2. Max-Heap
 
 ::tabs-start
 
@@ -431,12 +569,124 @@ public class Solution {
 }
 ```
 
+```go
+func leastInterval(tasks []byte, n int) int {
+    count := make(map[byte]int)
+    for _, task := range tasks {
+        count[task]++
+    }
+    
+    maxHeap := priorityqueue.NewWith(func(a, b interface{}) int {
+        return b.(int) - a.(int)
+    })
+    for _, cnt := range count {
+        maxHeap.Enqueue(cnt)
+    }
+    
+    time := 0
+    q := make([][2]int, 0)
+    
+    for maxHeap.Size() > 0 || len(q) > 0 {
+        time++
+        
+        if maxHeap.Size() == 0 {
+            time = q[0][1]
+        } else {
+            cnt, _ := maxHeap.Dequeue()
+            cnt = cnt.(int) - 1
+            if cnt.(int) > 0 {
+                q = append(q, [2]int{cnt.(int), time + n})
+            }
+        }
+        
+        if len(q) > 0 && q[0][1] == time {
+            maxHeap.Enqueue(q[0][0])
+            q = q[1:]
+        }
+    }
+    
+    return time
+}
+```
+
+```kotlin
+class Solution {
+    fun leastInterval(tasks: CharArray, n: Int): Int {
+        val count = IntArray(26)
+        for (task in tasks) {
+            count[task - 'A']++
+        }
+
+        val maxHeap = PriorityQueue<Int>(compareBy { it * -1 })
+        for (cnt in count) {
+            if (cnt > 0) {
+                maxHeap.offer(cnt)
+            }
+        }
+
+        var time = 0
+        val q = ArrayDeque<Pair<Int, Int>>()
+
+        while (maxHeap.isNotEmpty() || q.isNotEmpty()) {
+            time++
+
+            if (maxHeap.isEmpty()) {
+                time = q.first().second
+            } else {
+                val cnt = 1 + maxHeap.poll() * -1
+                if (cnt != 0) {
+                    q.addLast(Pair(cnt * -1, time + n))
+                }
+            }
+
+            if (q.isNotEmpty() && q.first().second == time) {
+                maxHeap.offer(q.removeFirst().first)
+            }
+        }
+        return time
+    }
+}
+```
+
+```swift
+class Solution {
+    func leastInterval(_ tasks: [Character], _ n: Int) -> Int {
+        var count = [Character: Int]()
+        for task in tasks {
+            count[task, default: 0] += 1
+        }
+
+        var maxHeap = Heap<Int>(Array(count.values))
+        var time = 0
+        var queue = Deque<(Int, Int)>()
+
+        while !maxHeap.isEmpty || !queue.isEmpty {
+            time += 1
+            if maxHeap.isEmpty {
+                time = queue.first!.1
+            } else {
+                let cnt = maxHeap.popMax()! - 1
+                if cnt > 0 {
+                    queue.append((cnt, time + n))
+                }
+            }
+            if let front = queue.first, front.1 == time {
+                maxHeap.insert(front.0)
+                queue.removeFirst()
+            }
+        }
+
+        return time
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(m)$
-* Space complexity: $O(m)$
+* Space complexity: $O(1)$ since we have at most $26$ different characters.
 
 > Where $m$ is the number of tasks.
 
@@ -548,12 +798,87 @@ public class Solution {
 }
 ```
 
+```go
+func leastInterval(tasks []byte, n int) int {
+    count := make([]int, 26)
+    for _, task := range tasks {
+        count[task-'A']++
+    }
+
+    sort.Ints(count)
+    maxf := count[25]
+    idle := (maxf - 1) * n
+
+    for i := 24; i >= 0; i-- {
+        idle -= min(maxf-1, count[i])
+    }
+
+    return max(0, idle) + len(tasks)
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun leastInterval(tasks: CharArray, n: Int): Int {
+        val count = IntArray(26)
+        for (task in tasks) {
+            count[task - 'A']++
+        }
+
+        count.sort()
+        val maxf = count[25]
+        var idle = (maxf - 1) * n
+
+        for (i in 24 downTo 0) {
+            idle -= min(maxf - 1, count[i])
+        }
+
+        return max(0, idle) + tasks.size
+    }
+}
+```
+
+```swift
+class Solution {
+    func leastInterval(_ tasks: [Character], _ n: Int) -> Int {
+        var count = [Int](repeating: 0, count: 26)
+        for task in tasks {
+            count[Int(task.asciiValue! - Character("A").asciiValue!)] += 1
+        }
+
+        count.sort()
+        let maxf = count[25]
+        var idle = (maxf - 1) * n
+
+        for i in stride(from: 24, through: 0, by: -1) {
+            idle -= min(maxf - 1, count[i])
+        }
+        
+        return max(0, idle) + tasks.count
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(m)$
-* Space complexity: $O(1)$
+* Space complexity: $O(1)$ since we have at most $26$ different characters.
 
 > Where $m$ is the number of tasks.
 
@@ -673,11 +998,84 @@ public class Solution {
 }
 ```
 
+```go
+func leastInterval(tasks []byte, n int) int {
+    count := make([]int, 26)
+    for _, task := range tasks {
+        count[task-'A']++
+    }
+
+    maxf := 0
+    for _, cnt := range count {
+        if cnt > maxf {
+            maxf = cnt
+        }
+    }
+
+    maxCount := 0
+    for _, cnt := range count {
+        if cnt == maxf {
+            maxCount++
+        }
+    }
+
+    time := (maxf - 1) * (n + 1) + maxCount
+    if len(tasks) > time {
+        return len(tasks)
+    }
+    return time
+}
+```
+
+```kotlin
+class Solution {
+    fun leastInterval(tasks: CharArray, n: Int): Int {
+        val count = IntArray(26)
+        for (task in tasks) {
+            count[task - 'A']++
+        }
+
+        val maxf = count.maxOrNull() ?: 0
+        var maxCount = 0
+        for (cnt in count) {
+            if (cnt == maxf) {
+                maxCount++
+            }
+        }
+
+        val time = (maxf - 1) * (n + 1) + maxCount
+        return max(tasks.size, time)
+    }
+}
+```
+
+```swift
+class Solution {
+    func leastInterval(_ tasks: [Character], _ n: Int) -> Int {
+        var count = [Int](repeating: 0, count: 26)
+        for task in tasks {
+            count[Int(task.asciiValue! - Character("A").asciiValue!)] += 1
+        }
+
+        let maxf = count.max()!
+        var maxCount = 0
+        for i in count {
+            if i == maxf {
+                maxCount += 1
+            }
+        }
+
+        let time = (maxf - 1) * (n + 1) + maxCount
+        return max(tasks.count, time)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(m)$
-* Space complexity: $O(1)$
+* Space complexity: $O(1)$ since we have at most $26$ different characters.
 
 > Where $m$ is the number of tasks.
\ No newline at end of file
diff --git a/articles/text-justification.md b/articles/text-justification.md
new file mode 100644
index 000000000..fb48dcabe
--- /dev/null
+++ b/articles/text-justification.md
@@ -0,0 +1,181 @@
+## 1. Iteration
+
+::tabs-start
+
+```python
+class Solution:
+    def fullJustify(self, words: List[str], maxWidth: int) -> List[str]:
+        res = []
+        line, length = [], 0
+        i = 0
+
+        while i < len(words):
+            if length + len(words[i]) + len(line) <= maxWidth:
+                line.append(words[i])
+                length += len(words[i])
+                i += 1
+            else:
+                # Line complete
+                extra_space = maxWidth - length
+                remainder = extra_space % max(1, (len(line) - 1))
+                space = extra_space // max(1, (len(line) - 1))
+                for j in range(max(1, len(line) - 1)):
+                    line[j] += " " * space
+                    if remainder:
+                        line[j] += " "
+                        remainder -= 1
+                res.append("".join(line))
+                line, length = [], 0
+
+        # Handling last line
+        last_line = " ".join(line)
+        trail_space = maxWidth - len(last_line)
+        res.append(last_line + " " * trail_space)
+        return res
+```
+
+```java
+public class Solution {
+    public List<String> fullJustify(String[] words, int maxWidth) {
+        List<String> res = new ArrayList<>();
+        List<String> line = new ArrayList<>();
+        int length = 0, i = 0;
+
+        while (i < words.length) {
+            // If the current word can fit in the line
+            if (length + words[i].length() + line.size() <= maxWidth) {
+                line.add(words[i]);
+                length += words[i].length();
+                i++;
+            } else {
+                // Line complete
+                int extra_space = maxWidth - length;
+                int remainder = extra_space % Math.max(1, (line.size() - 1));
+                int space = extra_space / Math.max(1, (line.size() - 1));
+
+                for (int j = 0; j < Math.max(1, line.size() - 1); j++) {
+                    line.set(j, line.get(j) + " ".repeat(space));
+                    if (remainder > 0) {
+                        line.set(j, line.get(j) + " ");
+                        remainder--;
+                    }
+                }
+
+                res.add(String.join("", line));
+                line.clear();
+                length = 0;
+            }
+        }
+
+        // Handling last line
+        String last_line = String.join(" ", line);
+        int trail_space = maxWidth - last_line.length();
+        res.add(last_line + " ".repeat(trail_space));
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<string> fullJustify(vector<string>& words, int maxWidth) {
+        vector<string> res;
+        vector<string> line;
+        int length = 0, i = 0;
+
+        while (i < words.size()) {
+            if (length + words[i].size() + line.size() <= maxWidth) {
+                line.push_back(words[i]);
+                length += words[i].size();
+                i++;
+            } else {
+                // Line complete
+                int extra_space = maxWidth - length;
+                int remainder = extra_space % max(1, (int)(line.size() - 1));
+                int space = extra_space / max(1, (int)(line.size() - 1));
+
+                for (int j = 0; j < max(1, (int)line.size() - 1); j++) {
+                    line[j] += string(space, ' ');
+                    if (remainder > 0) {
+                        line[j] += " ";
+                        remainder--;
+                    }
+                }
+
+                string justified_line = accumulate(line.begin(), line.end(), string());
+                res.push_back(justified_line);
+                line.clear();
+                length = 0;
+            }
+        }
+
+        // Handling last line
+        string last_line = accumulate(line.begin(), line.end(), string(), 
+                                      [](string a, string b) { 
+                                            return a.empty() ? b : a + " " + b;
+                                        });
+        int trail_space = maxWidth - last_line.size();
+        last_line += string(trail_space, ' ');
+        res.push_back(last_line);
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @param {number} maxWidth
+     * @return {string[]}
+     */
+    fullJustify(words, maxWidth) {
+        let res = [];
+        let line = [], length = 0, i = 0;
+
+        while (i < words.length) {
+            if (length + words[i].length + line.length <= maxWidth) {
+                line.push(words[i]);
+                length += words[i].length;
+                i++;
+            } else {
+                // Line complete
+                let extra_space = maxWidth - length;
+                let remainder = extra_space % Math.max(1, line.length - 1);
+                let space = Math.floor(extra_space / Math.max(1, line.length - 1));
+
+                for (let j = 0; j < Math.max(1, line.length - 1); j++) {
+                    line[j] += " ".repeat(space);
+                    if (remainder > 0) {
+                        line[j] += " ";
+                        remainder--;
+                    }
+                }
+
+                res.push(line.join(""));
+                line = [];
+                length = 0;
+            }
+        }
+
+        // Handling last line
+        let last_line = line.join(" ");
+        let trail_space = maxWidth - last_line.length;
+        res.push(last_line + " ".repeat(trail_space));
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n * m)$
+
+> Where $n$ is the number of words and $m$ is the average length of the words.
\ No newline at end of file
diff --git a/articles/the-number-of-beautiful-subsets.md b/articles/the-number-of-beautiful-subsets.md
new file mode 100644
index 000000000..1ed55b435
--- /dev/null
+++ b/articles/the-number-of-beautiful-subsets.md
@@ -0,0 +1,739 @@
+## 1. Backtracking
+
+::tabs-start
+
+```python
+class Solution:
+    def beautifulSubsets(self, nums: List[int], k: int) -> int:
+        def helper(i, count):
+            if i == len(nums):
+                return 1
+
+            res = helper(i + 1, count)  # Skip nums[i]
+            if not count[nums[i] + k] and not count[nums[i] - k]:
+                count[nums[i]] += 1
+                res += helper(i + 1, count)
+                count[nums[i]] -= 1
+
+            return res
+
+        return helper(0, defaultdict(int)) - 1
+```
+
+```java
+public class Solution {
+    public int beautifulSubsets(int[] nums, int k) {
+        return helper(0, new HashMap<>(), nums, k) - 1;
+    }
+
+    private int helper(int i, Map<Integer, Integer> count, int[] nums, int k) {
+        if (i == nums.length) {
+            return 1;
+        }
+
+        int res = helper(i + 1, count, nums, k); // Skip nums[i]
+
+        if (!count.containsKey(nums[i] + k) && !count.containsKey(nums[i] - k)) {
+            count.put(nums[i], count.getOrDefault(nums[i], 0) + 1);
+            res += helper(i + 1, count, nums, k);
+            count.put(nums[i], count.get(nums[i]) - 1);
+            if (count.get(nums[i]) == 0) {
+                count.remove(nums[i]);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int beautifulSubsets(vector<int>& nums, int k) {
+        unordered_map<int, int> count;
+        return helper(0, count, nums, k) - 1;
+    }
+
+private:
+    int helper(int i, unordered_map<int, int>& count, vector<int>& nums, int k) {
+        if (i == nums.size()) {
+            return 1;
+        }
+
+        int res = helper(i + 1, count, nums, k); // Skip nums[i]
+        if (!count[nums[i] + k] && !count[nums[i] - k]) {
+            count[nums[i]]++;
+            res += helper(i + 1, count, nums, k);
+            count[nums[i]]--;
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    beautifulSubsets(nums, k) {
+        const helper = (i, count) => {
+            if (i === nums.length) {
+                return 1;
+            }
+
+            let res = helper(i + 1, count); // Skip nums[i]
+
+            if (!count.has(nums[i] + k) && !count.has(nums[i] - k)) {
+                count.set(nums[i], (count.get(nums[i]) || 0) + 1);
+                res += helper(i + 1, count);
+                count.set(nums[i], count.get(nums[i]) - 1);
+                if (count.get(nums[i]) === 0) {
+                    count.delete(nums[i]);
+                }
+            }
+
+            return res;
+        };
+
+        return helper(0, new Map()) - 1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def beautifulSubsets(self, nums: List[int], k: int) -> int:
+        cnt = Counter(nums)
+        groups = []  # List of dicts
+        cache = {}
+
+        def helper(n, g):
+            if n not in g:
+                return 1
+            if n in cache:
+                return cache[n]
+            
+            skip = helper(n + k, g)
+            include = (2**g[n] - 1) * helper(n + 2 * k, g)
+            cache[n] = skip + include
+            return skip + include
+
+        visit = set()
+        for n in cnt.keys():
+            if n in visit:
+                continue
+            g = {}
+            while n - k in cnt:
+                n -= k
+            while n in cnt:
+                g[n] = cnt[n]
+                visit.add(n)
+                n += k
+            groups.append(g)
+
+        res = 1
+        for g in groups:
+            n = min(g.keys())
+            res *= helper(n, g)
+
+        return res - 1
+```
+
+```java
+public class Solution {
+    private Map<Integer, Integer> cache;
+    private Map<Integer, Integer> cnt;
+    private Set<Integer> visit;
+
+    public int beautifulSubsets(int[] nums, int k) {
+        List<Map<Integer, Integer>> groups = new ArrayList<>();
+        this.cache = new HashMap<>();
+        this.cnt = new HashMap<>();
+        this.visit = new HashSet<>();
+
+        for (int num : nums) {
+            cnt.put(num, cnt.getOrDefault(num, 0) + 1);
+        }
+
+        for (int n : cnt.keySet()) {
+            if (visit.contains(n)) {
+                continue;
+            }
+            Map<Integer, Integer> g = new HashMap<>();
+            while (cnt.containsKey(n - k)) {
+                n -= k;
+            }
+            while (cnt.containsKey(n)) {
+                g.put(n, cnt.get(n));
+                visit.add(n);
+                n += k;
+            }
+            groups.add(g);
+        }
+
+        int res = 1;
+        for (Map<Integer, Integer> g : groups) {
+            int n = Collections.min(g.keySet());
+            res *= helper(n, g, k);
+        }
+
+        return res - 1;
+    }
+
+    private int helper(int n, Map<Integer, Integer> g, int k) {
+        if (!g.containsKey(n)) {
+            return 1;
+        }
+        if (cache.containsKey(n)) {
+            return cache.get(n);
+        }
+
+        int skip = helper(n + k, g, k);
+        int include = (int) ((Math.pow(2, g.get(n)) - 1) * helper(n + 2 * k, g, k));
+        int result = skip + include;
+        cache.put(n, result);
+        return result;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int beautifulSubsets(vector<int>& nums, int k) {
+        vector<unordered_map<int, int>> groups;
+        cache.clear();
+        cnt.clear();
+        visit.clear();
+
+        for (int& num : nums) {
+            cnt[num]++;
+        }
+
+        for (auto it = cnt.begin(); it != cnt.end(); ++it) {
+            int n = it->first;
+            if (visit.count(n)) {
+                continue;
+            }
+            unordered_map<int, int> g;
+            while (cnt.count(n - k)) {
+                n -= k;
+            }
+            while (cnt.count(n)) {
+                g[n] = cnt[n];
+                visit.insert(n);
+                n += k;
+            }
+            groups.push_back(g);
+        }
+
+        int res = 1;
+        for (auto& g : groups) {
+            int n = min_element(g.begin(), g.end())->first;
+            res *= helper(n, g, k);
+        }
+        return res - 1;
+    }
+
+private:
+    unordered_map<int, int> cache;
+    unordered_map<int, int> cnt;
+    unordered_set<int> visit;
+
+    int helper(int n, unordered_map<int, int>& g, int k) {
+        if (!g.count(n)) {
+            return 1;
+        }
+        if (cache.count(n)) {
+            return cache[n];
+        }
+
+        int skip = helper(n + k, g, k);
+        int include = (pow(2, g[n]) - 1) * helper(n + 2 * k, g, k);
+        return cache[n] = skip + include;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    beautifulSubsets(nums, k) {
+        let cnt = new Map();
+        for (const num of nums) {
+            cnt.set(num, (cnt.get(num) || 0) + 1);
+        }
+
+        let groups = [];
+        let cache = new Map();
+        let visit = new Set();
+
+        for (let n of cnt.keys()) {
+            if (visit.has(n)) {
+                continue;
+            }
+            let g = new Map();
+            while (cnt.has(n - k)) {
+                n -= k;
+            }
+            while (cnt.has(n)) {
+                g.set(n, cnt.get(n));
+                visit.add(n);
+                n += k;
+            }
+            groups.push(g);
+        }
+
+        const helper = (n, g) => {
+            if (!g.has(n)) {
+                return 1;
+            }
+            if (cache.has(n)) {
+                return cache.get(n);
+            }
+
+            let skip = helper(n + k, g);
+            let include = (2 ** g.get(n) - 1) * helper(n + 2 * k, g);
+            let result = skip + include;
+            cache.set(n, result);
+            return result;
+        };
+
+        let res = 1;
+        for (const g of groups) {
+            let n = Math.min(...g.keys());
+            res *= helper(n, g);
+        }
+        return res - 1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def beautifulSubsets(self, nums: List[int], k: int) -> int:
+        cnt = Counter(nums)
+        groups = []  # List of dicts
+
+        visit = set()
+        for n in cnt.keys():
+            if n in visit:
+                continue
+            g = {}
+            while n - k in cnt:
+                n -= k
+            while n in cnt:
+                g[n] = cnt[n]
+                visit.add(n)
+                n += k
+            groups.append(g)
+
+        res = 1
+        for g in groups:
+            dp = {}
+            prev = None
+
+            for num in sorted(g):
+                count = g[num]
+                if prev is None or prev + k != num:
+                    dp[num] = (dp.get(prev, 1) * (1 + (2 ** count - 1)))
+                else:
+                    dp[num] = dp[prev] + (2 ** count - 1) * dp.get(prev - k, 1)
+                prev = num
+
+            res *= dp[prev]
+
+        return res - 1
+```
+
+```java
+class Solution {
+    public int beautifulSubsets(int[] nums, int k) {
+        Map<Integer, Integer> cnt = new HashMap<>();
+        for (int num : nums) {
+            cnt.put(num, cnt.getOrDefault(num, 0) + 1);
+        }
+
+        List<Map<Integer, Integer>> groups = new ArrayList<>();
+        Set<Integer> visit = new HashSet<>();
+
+        for (int n : cnt.keySet()) {
+            if (visit.contains(n)) {
+                continue;
+            }
+            Map<Integer, Integer> g = new HashMap<>();
+            while (cnt.containsKey(n - k)) {
+                n -= k;
+            }
+            while (cnt.containsKey(n)) {
+                g.put(n, cnt.get(n));
+                visit.add(n);
+                n += k;
+            }
+            groups.add(g);
+        }
+
+        int res = 1;
+        for (Map<Integer, Integer> g : groups) {
+            Map<Integer, Integer> dp = new HashMap<>();
+            Integer prev = null;
+
+            List<Integer> arr = new ArrayList<>(g.keySet());
+            Collections.sort(arr);
+            for (int num : arr) {
+                int count = g.get(num);
+                if (prev == null || prev + k != num) {
+                    dp.put(num, dp.getOrDefault(prev, 1) * (1 + (int) Math.pow(2, count) - 1));
+                } else {
+                    dp.put(num, dp.get(prev) + 
+                          ((int) Math.pow(2, count) - 1) * dp.getOrDefault(prev - k, 1));
+                }
+                prev = num;
+            }
+
+            res *= dp.get(prev);
+        }
+
+        return res - 1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int beautifulSubsets(vector<int>& nums, int k) {
+        unordered_map<int, int> cnt;
+        for (int num : nums) {
+            cnt[num]++;
+        }
+
+        vector<unordered_map<int, int>> groups;
+        unordered_set<int> visit;
+
+        for (auto it = cnt.begin(); it != cnt.end(); ++it) {
+            int n = it->first;
+            if (visit.count(n)) {
+                continue;
+            }
+            unordered_map<int, int> g;
+            while (cnt.count(n - k)) {
+                n -= k;
+            }
+            while (cnt.count(n)) {
+                g[n] = cnt[n];
+                visit.insert(n);
+                n += k;
+            }
+            groups.push_back(g);
+        }
+
+        int res = 1;
+        for (auto& g : groups) {
+            unordered_map<int, int> dp;
+            int prev = -1;
+
+            vector<int> keys;
+            for (auto& [num, _] : g) {
+                keys.push_back(num);
+            }
+            sort(keys.begin(), keys.end());
+
+            for (int num : keys) {
+                int count = g[num];
+                if (prev == -1 || prev + k != num) {
+                    dp[num] = dp.count(prev) ? dp[prev] * (1 + (1 << count) - 1) : 
+                                               (1 + (1 << count) - 1);
+                } else {
+                    dp[num] = dp[prev] + ((1 << count) - 1) * 
+                              (dp.count(prev - k) ? dp[prev - k] : 1);
+                }
+                prev = num;
+            }
+
+            res *= dp[prev];
+        }
+
+        return res - 1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    beautifulSubsets(nums, k) {
+        let cnt = new Map();
+        for (const num of nums) {
+            cnt.set(num, (cnt.get(num) || 0) + 1);
+        }
+
+        let groups = [];
+        let visit = new Set();
+
+        for (const n of cnt.keys()) {
+            if (visit.has(n)) {
+                continue;
+            }
+            let g = new Map();
+            let num = n;
+            while (cnt.has(num - k)) {
+                num -= k;
+            }
+            while (cnt.has(num)) {
+                g.set(num, cnt.get(num));
+                visit.add(num);
+                num += k;
+            }
+            groups.push(g);
+        }
+
+        let res = 1;
+        for (const g of groups) {
+            let dp = new Map();
+            let prev = null;
+
+            for (const num of g.keys()) {
+                let count = g.get(num);
+                if (prev === null || prev + k !== num) {
+                    dp.set(num, (dp.get(prev) || 1) * (1 + (2 ** count - 1)));
+                } else {
+                    dp.set(num, dp.get(prev) + (2 ** count - 1) * (dp.get(prev - k) || 1));
+                }
+                prev = num;
+            }
+
+            res *= dp.get(prev);
+        }
+
+        return res - 1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def beautifulSubsets(self, nums: List[int], k: int) -> int:
+        cnt = Counter(nums)
+        groups = defaultdict(dict)
+
+        # Group numbers based on their remainder with k
+        for num in nums:
+            groups[num % k][num] = cnt[num]
+
+        res = 1
+        for g in groups.values():
+            prev = 0
+            dp, ndp = 0, 1
+
+            for num in sorted(g.keys()):
+                count = g[num]
+                have = (1 << count) - 1
+                tmp = ndp
+                ndp += dp
+
+                if prev == 0 or prev + k != num:
+                    dp = have * (tmp + dp)
+                else:
+                    dp = tmp * have
+
+                prev = num
+
+            res *= (dp + ndp)
+
+        return res - 1
+```
+
+```java
+public class Solution {
+    public int beautifulSubsets(int[] nums, int k) {
+        Map<Integer, Map<Integer, Integer>> groups = new HashMap<>();
+        Map<Integer, Integer> cnt = new HashMap<>();
+        for (int num : nums) {
+            cnt.put(num, cnt.getOrDefault(num, 0) + 1);
+        }
+
+        // Group numbers based on remainder with k
+        for (int num : nums) {
+            groups.putIfAbsent(num % k, new HashMap<>());
+            groups.get(num % k).put(num, cnt.get(num));
+        }
+
+        int res = 1;
+        for (Map<Integer, Integer> g : groups.values()) {
+            int prev = 0, dp = 0, ndp = 1;
+            List<Integer> sortedKeys = new ArrayList<>(g.keySet());
+            Collections.sort(sortedKeys);
+
+            for (int num : sortedKeys) {
+                int count = g.get(num);
+                int have = (1 << count) - 1;
+                int tmp = ndp;
+                ndp += dp;
+
+                if (prev == 0 || prev + k != num) {
+                    dp = have * (tmp + dp);
+                } else {
+                    dp = tmp * have;
+                }
+
+                prev = num;
+            }
+
+            res *= (dp + ndp);
+        }
+
+        return res - 1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int beautifulSubsets(vector<int>& nums, int k) {
+        unordered_map<int, map<int, int>> groups;
+        unordered_map<int, int> cnt;
+        for (int& num : nums) {
+            cnt[num]++;
+        }
+
+        // Group numbers based on remainder with k
+        for (int num : nums) {
+            groups[num % k][num] = cnt[num];
+        }
+
+        int res = 1;
+        for (auto& [rem, g] : groups) {
+            int prev = 0, dp = 0, ndp = 1;
+
+            for (auto& [num, count] : g) {
+                int have = (1 << count) - 1;
+                int tmp = ndp;
+                ndp += dp;
+
+                if (prev == 0 || prev + k != num) {
+                    dp = have * (tmp + dp);
+                } else {
+                    dp = tmp * have;
+                }
+
+                prev = num;
+            }
+
+            res *= (dp + ndp);
+        }
+
+        return res - 1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @param {number} k
+     * @return {number}
+     */
+    beautifulSubsets(nums, k) {
+        let groups = new Map();
+        let cnt = new Map();
+        for (const num of nums) {
+            cnt.set(num, (cnt.get(num) || 0) + 1);
+        }
+
+        // Group numbers based on remainder with k
+        for (const num of nums) {
+            if (!groups.has(num % k)) {
+                groups.set(num % k, new Map());
+            }
+            groups.get(num % k).set(num, cnt.get(num));
+        }
+
+        let res = 1;
+        for (const g of groups.values()) {
+            let prev = 0, dp = 0, ndp = 1;
+            let sortedKeys = Array.from(g.keys()).sort((a, b) => a - b);
+
+            for (const num of sortedKeys) {
+                let count = g.get(num);
+                let have = (1 << count) - 1;
+                let tmp = ndp;
+                ndp += dp;
+
+                if (prev === 0 || prev + k !== num) {
+                    dp = have * (tmp + dp);
+                } else {
+                    dp = tmp * have;
+                }
+
+                prev = num;
+            }
+
+            res *= (dp + ndp);
+        }
+
+        return res - 1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/three-integer-sum.md b/articles/three-integer-sum.md
index 11a76d99b..18b4b76b7 100644
--- a/articles/three-integer-sum.md
+++ b/articles/three-integer-sum.md
@@ -105,6 +105,67 @@ public class Solution {
 }
 ```
 
+```go
+func threeSum(nums []int) [][]int {
+    res := map[[3]int]struct{}{}
+    sort.Ints(nums)
+    for i := 0; i < len(nums); i++ {
+        for j := i + 1; j < len(nums); j++ {
+            for k := j + 1; k < len(nums); k++ {
+                if nums[i]+nums[j]+nums[k] == 0 {
+                    res[[3]int{nums[i], nums[j], nums[k]}] = struct{}{}
+                }
+            }
+        }
+    }
+    var result [][]int
+    for triplet := range res {
+        result = append(result, []int{triplet[0], triplet[1], triplet[2]})
+    }
+    return result
+}
+```
+
+```kotlin
+class Solution {
+    fun threeSum(nums: IntArray): List<List<Int>> {
+        val res = HashSet<List<Int>>()
+        nums.sort()
+        for (i in nums.indices) {
+            for (j in i + 1 until nums.size) {
+                for (k in j + 1 until nums.size) {
+                    if (nums[i] + nums[j] + nums[k] == 0) {
+                        res.add(listOf(nums[i], nums[j], nums[k]))
+                    }
+                }
+            }
+        }
+        return res.map { it.toList() }
+    }
+}
+```
+
+```swift
+class Solution {
+    func threeSum(_ nums: [Int]) -> [[Int]] {
+        var res = Set<[Int]>()
+        let nums = nums.sorted()
+        
+        for i in 0..<nums.count {
+            for j in (i + 1)..<nums.count {
+                for k in (j + 1)..<nums.count {
+                    if nums[i] + nums[j] + nums[k] == 0 {
+                        let tmp = [nums[i], nums[j], nums[k]]
+                        res.insert(tmp)
+                    }
+                }
+            }
+        }
+        return Array(res)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -289,6 +350,111 @@ public class Solution {
 }
 ```
 
+```go
+func threeSum(nums []int) [][]int {
+    sort.Ints(nums)
+    count := make(map[int]int)
+    for _, num := range nums {
+        count[num]++
+    }
+
+    var res [][]int
+    for i := 0; i < len(nums); i++ {
+        count[nums[i]]--
+        if i > 0 && nums[i] == nums[i-1] {
+            continue
+        }
+
+        for j := i + 1; j < len(nums); j++ {
+            count[nums[j]]--
+            if j > i+1 && nums[j] == nums[j-1] {
+                continue
+            }
+            target := -(nums[i] + nums[j])
+            if count[target] > 0 {
+                res = append(res, []int{nums[i], nums[j], target})
+            }
+        }
+
+        for j := i + 1; j < len(nums); j++ {
+            count[nums[j]]++
+        }
+    }
+
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun threeSum(nums: IntArray): List<List<Int>> {
+        nums.sort()
+        val count = HashMap<Int, Int>()
+        for (num in nums) {
+            count[num] = count.getOrDefault(num, 0) + 1
+        }
+
+        val res = mutableListOf<List<Int>>()
+        for (i in nums.indices) {
+            count[nums[i]] = count[nums[i]]!! - 1
+            if (i > 0 && nums[i] == nums[i - 1]) continue
+
+            for (j in i + 1 until nums.size) {
+                count[nums[j]] = count[nums[j]]!! - 1
+                if (j > i + 1 && nums[j] == nums[j - 1]) continue
+
+                val target = -(nums[i] + nums[j])
+                if (count.getOrDefault(target, 0) > 0) {
+                    res.add(listOf(nums[i], nums[j], target))
+                }
+            }
+
+            for (j in i + 1 until nums.size) {
+                count[nums[j]] = count[nums[j]]!! + 1
+            }
+        }
+
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func threeSum(_ nums: [Int]) -> [[Int]] {
+        var nums = nums.sorted()
+        var count = [Int: Int]()
+        for num in nums {
+            count[num, default: 0] += 1
+        }
+
+        var res = [[Int]]()
+        for i in 0..<nums.count {
+            count[nums[i]]! -= 1
+            if i > 0 && nums[i] == nums[i - 1] {
+                continue
+            }
+            
+            for j in (i + 1)..<nums.count {
+                count[nums[j]]! -= 1
+                if j > i + 1 && nums[j] == nums[j - 1] {
+                    continue
+                }
+                let target = -(nums[i] + nums[j])
+                if let cnt = count[target], cnt > 0 {
+                    res.append([nums[i], nums[j], target])
+                }
+            }
+
+            for j in (i + 1)..<nums.count {
+                count[nums[j]]! += 1
+            }
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -466,9 +632,121 @@ public class Solution {
 }
 ```
 
+```go
+func threeSum(nums []int) [][]int {
+    res := [][]int{}
+    sort.Ints(nums)
+
+    for i := 0; i < len(nums); i++ {
+        a := nums[i]
+        if a > 0 {
+            break
+        }
+        if i > 0 && a == nums[i-1] {
+            continue
+        }
+
+        l, r := i+1, len(nums)-1
+        for l < r {
+            threeSum := a + nums[l] + nums[r]
+            if threeSum > 0 {
+                r--
+            } else if threeSum < 0 {
+                l++
+            } else {
+                res = append(res, []int{a, nums[l], nums[r]})
+                l++
+                r--
+                for l < r && nums[l] == nums[l-1] {
+                    l++
+                }
+            }
+        }
+    }
+
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun threeSum(nums: IntArray): List<List<Int>> {
+        val res = mutableListOf<List<Int>>()
+        nums.sort()
+
+        for (i in nums.indices) {
+            val a = nums[i]
+            if (a > 0) break
+            if (i > 0 && a == nums[i - 1]) continue
+
+            var l = i + 1
+            var r = nums.size - 1
+            while (l < r) {
+                val threeSum = a + nums[l] + nums[r]
+                when {
+                    threeSum > 0 -> r--
+                    threeSum < 0 -> l++
+                    else -> {
+                        res.add(listOf(a, nums[l], nums[r]))
+                        l++
+                        r--
+                        while (l < r && nums[l] == nums[l - 1]) {
+                            l++
+                        }
+                    }
+                }
+            }
+        }
+
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func threeSum(_ nums: [Int]) -> [[Int]] {
+        var res = [[Int]]()
+        var nums = nums.sorted()
+
+        for i in 0..<nums.count {
+            let a = nums[i]
+            if a > 0 {
+                break
+            }
+            if i > 0 && a == nums[i - 1] {
+                continue
+            }
+
+            var l = i + 1, r = nums.count - 1
+            while l < r {
+                let threeSum = a + nums[l] + nums[r]
+                if threeSum > 0 {
+                    r -= 1
+                } else if threeSum < 0 {
+                    l += 1
+                } else {
+                    res.append([a, nums[l], nums[r]])
+                    l += 1
+                    r -= 1
+                    while l < r && nums[l] == nums[l - 1] {
+                        l += 1
+                    }
+                }
+            }
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n ^ 2)$
-* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
\ No newline at end of file
+* Space complexity:
+    * $O(1)$ or $O(n)$ extra space depending on the sorting algorithm.
+    * $O(m)$ space for the output list.
+
+> Where $m$ is the number of triplets and $n$ is the length of the given array.
\ No newline at end of file
diff --git a/articles/time-based-key-value-store.md b/articles/time-based-key-value-store.md
index 06993720a..8fc87e0e5 100644
--- a/articles/time-based-key-value-store.md
+++ b/articles/time-based-key-value-store.md
@@ -165,6 +165,119 @@ public class TimeMap {
 }
 ```
 
+```go
+type TimeMap struct {
+   keyStore map[string]map[int][]string
+}
+
+func Constructor() TimeMap {
+   return TimeMap{
+       keyStore: make(map[string]map[int][]string),
+   }
+}
+
+func (this *TimeMap) Set(key string, value string, timestamp int) {
+   if _, exists := this.keyStore[key]; !exists {
+       this.keyStore[key] = make(map[int][]string)
+   }
+   this.keyStore[key][timestamp] = append(this.keyStore[key][timestamp], value)
+}
+
+func (this *TimeMap) Get(key string, timestamp int) string {
+   if _, exists := this.keyStore[key]; !exists {
+       return ""
+   }
+   
+   seen := 0
+   for time := range this.keyStore[key] {
+       if time <= timestamp {
+           seen = max(seen, time)
+       }
+   }
+   
+   if seen == 0 {
+       return ""
+   }
+   values := this.keyStore[key][seen]
+   return values[len(values)-1]
+}
+
+func max(a, b int) int {
+   if a > b {
+       return a
+   }
+   return b
+}
+```
+
+```kotlin
+class TimeMap() {
+    private val keyStore = HashMap<String, HashMap<Int, MutableList<String>>>()
+    
+    fun set(key: String, value: String, timestamp: Int) {
+        if (!keyStore.containsKey(key)) {
+            keyStore[key] = HashMap()
+        }
+        if (!keyStore[key]!!.containsKey(timestamp)) {
+            keyStore[key]!![timestamp] = mutableListOf()
+        }
+        keyStore[key]!![timestamp]!!.add(value)
+    }
+    
+    fun get(key: String, timestamp: Int): String {
+        if (!keyStore.containsKey(key)) {
+            return ""
+        }
+        
+        var seen = 0
+        for (time in keyStore[key]!!.keys) {
+            if (time <= timestamp) {
+                seen = maxOf(seen, time)
+            }
+        }
+        
+        if (seen == 0) {
+            return ""
+        }
+        return keyStore[key]!![seen]!!.last()
+    }
+}
+```
+
+```swift
+class TimeMap {
+    private var keyStore: [String: [Int: [String]]]
+
+    init() {
+        self.keyStore = [:]
+    }
+
+    func set(_ key: String, _ value: String, _ timestamp: Int) {
+        if keyStore[key] == nil {
+            keyStore[key] = [:]
+        }
+        if keyStore[key]![timestamp] == nil {
+            keyStore[key]![timestamp] = []
+        }
+        keyStore[key]![timestamp]!.append(value)
+    }
+
+    func get(_ key: String, _ timestamp: Int) -> String {
+        guard let timeMap = keyStore[key] else {
+            return ""
+        }
+
+        var seen = 0
+        for time in timeMap.keys {
+            if time <= timestamp {
+                seen = max(seen, time)
+            }
+        }
+        return seen == 0 ? "" : timeMap[seen]!.last!
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -327,6 +440,96 @@ public class TimeMap {
 }
 ```
 
+```go
+type TimeMap struct {
+   m map[string][]pair
+}
+
+type pair struct {
+   timestamp int
+   value string
+}
+
+func Constructor() TimeMap {
+   return TimeMap{
+       m: make(map[string][]pair),
+   }
+}
+
+func (this *TimeMap) Set(key string, value string, timestamp int)  {
+   this.m[key] = append(this.m[key], pair{timestamp, value})
+}
+
+func (this *TimeMap) Get(key string, timestamp int) string {
+   if _, exists := this.m[key]; !exists {
+       return ""
+   }
+   
+   pairs := this.m[key]
+   idx := sort.Search(len(pairs), func(i int) bool {
+       return pairs[i].timestamp > timestamp
+   })
+   
+   if idx == 0 {
+       return ""
+   }
+   return pairs[idx-1].value
+}
+```
+
+```kotlin
+class TimeMap() {
+    private val m = HashMap<String, TreeMap<Int, String>>()
+    
+    fun set(key: String, value: String, timestamp: Int) {
+        m.computeIfAbsent(key) { TreeMap() }[timestamp] = value
+    }
+    
+    fun get(key: String, timestamp: Int): String {
+        if (!m.containsKey(key)) return ""
+        return m[key]!!.floorEntry(timestamp)?.value ?: ""
+    }
+}
+```
+
+```swift
+class TimeMap {
+    private var m: [String: [(Int, String)]]
+
+    init() {
+        self.m = [:]
+    }
+
+    func set(_ key: String, _ value: String, _ timestamp: Int) {
+        if m[key] == nil {
+            m[key] = []
+        }
+        m[key]!.append((timestamp, value))
+    }
+
+    func get(_ key: String, _ timestamp: Int) -> String {
+        guard let timestamps = m[key] else {
+            return ""
+        }
+        
+        var l = 0, r = timestamps.count - 1
+        var res = ""
+
+        while l <= r {
+            let mid = (l + r) / 2
+            if timestamps[mid].0 <= timestamp {
+                res = timestamps[mid].1
+                l = mid + 1
+            } else {
+                r = mid - 1
+            }
+        }
+        
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -534,6 +737,118 @@ public class TimeMap {
 }
 ```
 
+```go
+type TimeMap struct {
+   m map[string][]pair
+}
+
+type pair struct {
+   timestamp int
+   value     string
+}
+
+func Constructor() TimeMap {
+   return TimeMap{
+       m: make(map[string][]pair),
+   }
+}
+
+func (this *TimeMap) Set(key string, value string, timestamp int) {
+   this.m[key] = append(this.m[key], pair{timestamp, value})
+}
+
+func (this *TimeMap) Get(key string, timestamp int) string {
+   if _, exists := this.m[key]; !exists {
+       return ""
+   }
+   
+   pairs := this.m[key]
+   l, r := 0, len(pairs)-1
+   
+   for l <= r {
+       mid := (l + r) / 2
+       if pairs[mid].timestamp <= timestamp {
+           if mid == len(pairs)-1 || pairs[mid+1].timestamp > timestamp {
+               return pairs[mid].value
+           }
+           l = mid + 1
+       } else {
+           r = mid - 1
+       }
+   }
+   return ""
+}
+```
+
+```kotlin
+class TimeMap() {
+    private val keyStore = HashMap<String, MutableList<Pair<String, Int>>>()
+    
+    fun set(key: String, value: String, timestamp: Int) {
+        if (!keyStore.containsKey(key)) {
+            keyStore[key] = mutableListOf()
+        }
+        keyStore[key]!!.add(Pair(value, timestamp))
+    }
+    
+    fun get(key: String, timestamp: Int): String {
+        var res = ""
+        val values = keyStore[key] ?: return res
+        var l = 0
+        var r = values.size - 1
+        
+        while (l <= r) {
+            val m = (l + r) / 2
+            if (values[m].second <= timestamp) {
+                res = values[m].first
+                l = m + 1
+            } else {
+                r = m - 1
+            }
+        }
+        return res
+    }
+}
+```
+
+```swift
+class TimeMap {
+    private var keyStore: [String: [(String, Int)]]
+
+    init() {
+        self.keyStore = [:]
+    }
+
+    func set(_ key: String, _ value: String, _ timestamp: Int) {
+        if keyStore[key] == nil {
+            keyStore[key] = []
+        }
+        keyStore[key]!.append((value, timestamp))
+    }
+
+    func get(_ key: String, _ timestamp: Int) -> String {
+        guard let values = keyStore[key] else {
+            return ""
+        }
+        
+        var res = ""
+        var l = 0, r = values.count - 1
+
+        while l <= r {
+            let m = (l + r) / 2
+            if values[m].1 <= timestamp {
+                res = values[m].0
+                l = m + 1
+            } else {
+                r = m - 1
+            }
+        }
+
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/time-needed-to-buy-tickets.md b/articles/time-needed-to-buy-tickets.md
new file mode 100644
index 000000000..b7422f54c
--- /dev/null
+++ b/articles/time-needed-to-buy-tickets.md
@@ -0,0 +1,329 @@
+## 1. Queue
+
+::tabs-start
+
+```python
+class Solution:
+    def timeRequiredToBuy(self, tickets: List[int], k: int) -> int:
+        n = len(tickets)
+        q = deque()
+
+        for i in range(n):
+            q.append(i)
+
+        time = 0
+        while q:
+            time += 1
+            cur = q.popleft()
+            tickets[cur] -= 1
+            if tickets[cur] == 0:
+                if cur == k:
+                    return time
+            else:
+                q.append(cur)
+        return time
+```
+
+```java
+public class Solution {
+    public int timeRequiredToBuy(int[] tickets, int k) {
+        int n = tickets.length;
+        Queue<Integer> queue = new LinkedList<>();
+
+        for (int i = 0; i < n; i++) {
+            queue.add(i);
+        }
+
+        int time = 0;
+        while (!queue.isEmpty()) {
+            time++;
+            int cur = queue.poll();
+            tickets[cur]--;
+            if (tickets[cur] == 0) {
+                if (cur == k) {
+                    return time;
+                }
+            } else {
+                queue.add(cur);
+            }
+        }
+        return time;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int timeRequiredToBuy(vector<int>& tickets, int k) {
+        int n = tickets.size();
+        queue<int> q;
+
+        for (int i = 0; i < n; i++) {
+            q.push(i);
+        }
+
+        int time = 0;
+        while (!q.empty()) {
+            time++;
+            int cur = q.front();
+            q.pop();
+            tickets[cur]--;
+            if (tickets[cur] == 0) {
+                if (cur == k) {
+                    return time;
+                }
+            } else {
+                q.push(cur);
+            }
+        }
+        return time;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} tickets
+     * @param {number} k
+     * @return {number}
+     */
+    timeRequiredToBuy(tickets, k) {
+        let n = tickets.length;
+        let queue = new Queue();
+
+        for (let i = 0; i < n; i++) {
+            queue.push(i);
+        }
+
+        let time = 0;
+        while (queue.size() > 0) {
+            time++;
+            let cur = queue.pop();
+            tickets[cur]--;
+            if (tickets[cur] === 0) {
+                if (cur === k) {
+                    return time;
+                }
+            } else {
+                queue.push(cur);
+            }
+        }
+        return time;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the size of the input array and $m$ is the maximum value in the input array.
+
+---
+
+## 2. Iteration
+
+::tabs-start
+
+```python
+class Solution:
+    def timeRequiredToBuy(self, tickets: List[int], k: int) -> int:
+        n = len(tickets)
+        idx = 0
+
+        time = 0
+        while True:
+            time += 1
+            tickets[idx] -= 1
+            if tickets[idx] == 0:
+                if idx == k:
+                    return time
+            idx = (idx + 1) % n
+            while tickets[idx] == 0:
+                idx = (idx + 1) % n
+        
+        return time
+```
+
+```java
+public class Solution {
+    public int timeRequiredToBuy(int[] tickets, int k) {
+        int n = tickets.length;
+        int idx = 0;
+
+        int time = 0;
+        while (true) {
+            time++;
+            tickets[idx]--;
+            if (tickets[idx] == 0) {
+                if (idx == k) {
+                    return time;
+                }
+            }
+            idx = (idx + 1) % n;
+            while (tickets[idx] == 0) {
+                idx = (idx + 1) % n;
+            }
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int timeRequiredToBuy(vector<int>& tickets, int k) {
+        int n = tickets.size();
+        int idx = 0;
+
+        int time = 0;
+        while (true) {
+            time++;
+            tickets[idx]--;
+            if (tickets[idx] == 0) {
+                if (idx == k) {
+                    return time;
+                }
+            }
+            idx = (idx + 1) % n;
+            while (tickets[idx] == 0) {
+                idx = (idx + 1) % n;
+            }
+        }
+        
+        return time;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} tickets
+     * @param {number} k
+     * @return {number}
+     */
+    timeRequiredToBuy(tickets, k) {
+        let n = tickets.length;
+        let idx = 0;
+
+        let time = 0;
+        while (true) {
+            time++;
+            tickets[idx]--;
+            if (tickets[idx] === 0) {
+                if (idx === k) {
+                    return time;
+                }
+            }
+            idx = (idx + 1) % n;
+            while (tickets[idx] === 0) {
+                idx = (idx + 1) % n;
+            }
+        }
+
+        return time;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(1)$
+
+> Where $n$ is the size of the input array and $m$ is the maximum value in the input array.
+
+---
+
+## 3. Iteration (One Pass)
+
+::tabs-start
+
+```python
+class Solution:
+    def timeRequiredToBuy(self, tickets: List[int], k: int) -> int:
+        res = 0
+
+        for i in range(len(tickets)):
+            if i <= k:
+                res += min(tickets[i], tickets[k])
+            else:
+                res += min(tickets[i], tickets[k] - 1)
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int timeRequiredToBuy(int[] tickets, int k) {
+        int res = 0;
+
+        for (int i = 0; i < tickets.length; i++) {
+            if (i <= k) {
+                res += Math.min(tickets[i], tickets[k]);
+            } else {
+                res += Math.min(tickets[i], tickets[k] - 1);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int timeRequiredToBuy(vector<int>& tickets, int k) {
+        int res = 0;
+
+        for (int i = 0; i < tickets.size(); i++) {
+            if (i <= k) {
+                res += min(tickets[i], tickets[k]);
+            } else {
+                res += min(tickets[i], tickets[k] - 1);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} tickets
+     * @param {number} k
+     * @return {number}
+     */
+    timeRequiredToBuy(tickets, k) {
+        let res = 0;
+
+        for (let i = 0; i < tickets.length; i++) {
+            if (i <= k) {
+                res += Math.min(tickets[i], tickets[k]);
+            } else {
+                res += Math.min(tickets[i], tickets[k] - 1);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/time-needed-to-inform-all-employees.md b/articles/time-needed-to-inform-all-employees.md
new file mode 100644
index 000000000..7a80a7c02
--- /dev/null
+++ b/articles/time-needed-to-inform-all-employees.md
@@ -0,0 +1,479 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def numOfMinutes(self, n: int, headID: int, manager: List[int], informTime: List[int]) -> int:
+        adj = [[] for _ in range(n)]
+        for i in range(n):
+            if i != headID:
+                adj[manager[i]].append(i)
+
+        def dfs(node):
+            res = 0
+            for child in adj[node]:
+                res = max(res, informTime[node] + dfs(child))
+            return res
+
+        return dfs(headID)
+```
+
+```java
+public class Solution {
+    public int numOfMinutes(int n, int headID, int[] manager, int[] informTime) {
+        List<Integer>[] adj = new ArrayList[n];
+        for (int i = 0; i < n; i++) {
+            adj[i] = new ArrayList<>();
+        }
+        for (int i = 0; i < n; i++) {
+            if (i != headID) {
+                adj[manager[i]].add(i);
+            }
+        }
+
+        return dfs(headID, adj, informTime);
+    }
+
+    private int dfs(int node, List<Integer>[] adj, int[] informTime) {
+        int res = 0;
+        for (int child : adj[node]) {
+            res = Math.max(res, informTime[node] + dfs(child, adj, informTime));
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numOfMinutes(int n, int headID, vector<int>& manager, vector<int>& informTime) {
+        vector<vector<int>> adj(n);
+        for (int i = 0; i < n; i++) {
+            if (i != headID) {
+                adj[manager[i]].push_back(i);
+            }
+        }
+        return dfs(headID, adj, informTime);
+    }
+
+private:
+    int dfs(int node, vector<vector<int>>& adj, vector<int>& informTime) {
+        int res = 0;
+        for (int child : adj[node]) {
+            res = max(res, informTime[node] + dfs(child, adj, informTime));
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} headID
+     * @param {number[]} manager
+     * @param {number[]} informTime
+     * @return {number}
+     */
+    numOfMinutes(n, headID, manager, informTime) {
+        const adj = Array.from({ length: n }, () => []);
+        for (let i = 0; i < n; i++) {
+            if (i !== headID) {
+                adj[manager[i]].push(i);
+            }
+        }
+
+        const dfs = (node) => {
+            let res = 0;
+            for (const child of adj[node]) {
+                res = Math.max(res, informTime[node] + dfs(child));
+            }
+            return res;
+        };
+
+        return dfs(headID);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Breadth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def numOfMinutes(self, n: int, headID: int, manager: List[int], informTime: List[int]) -> int:
+        adj = defaultdict(list)
+        for i in range(n):
+            adj[manager[i]].append(i)
+        
+        q = deque([(headID, 0)])  # (id, time)
+        res = 0
+        
+        while q:
+            node, time = q.popleft()
+            res = max(res, time)
+            for emp in adj[node]:
+                q.append((emp, time + informTime[node]))
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int numOfMinutes(int n, int headID, int[] manager, int[] informTime) {
+        Map<Integer, List<Integer>> adj = new HashMap<>();
+        for (int i = 0; i < n; i++) {
+            adj.computeIfAbsent(manager[i], k -> new ArrayList<>()).add(i);
+        }
+        
+        Queue<int[]> queue = new LinkedList<>();
+        queue.add(new int[]{headID, 0});
+        int res = 0;
+        
+        while (!queue.isEmpty()) {
+            int[] curr = queue.poll();
+            int id = curr[0], time = curr[1];
+            res = Math.max(res, time);
+            for (int emp : adj.getOrDefault(id, new ArrayList<>())) {
+                queue.add(new int[]{emp, time + informTime[id]});
+            }
+        }
+        
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numOfMinutes(int n, int headID, vector<int>& manager, vector<int>& informTime) {
+        unordered_map<int, vector<int>> adj;
+        for (int i = 0; i < n; ++i) {
+            adj[manager[i]].push_back(i);
+        }
+
+        queue<pair<int, int>> q; // {id, time}
+        q.push({headID, 0});
+        int res = 0;
+
+        while (!q.empty()) {
+            auto [id, time] = q.front();
+            q.pop();
+            res = max(res, time);
+            for (int emp : adj[id]) {
+                q.push({emp, time + informTime[id]});
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} headID
+     * @param {number[]} manager
+     * @param {number[]} informTime
+     * @return {number}
+     */
+    numOfMinutes(n, headID, manager, informTime) {
+        const adj = new Map();
+        for (let i = 0; i < n; i++) {
+            if (!adj.has(manager[i])) adj.set(manager[i], []);
+            adj.get(manager[i]).push(i);
+        }
+
+        const queue = new Queue([[headID, 0]]); // [id, time]
+        let res = 0;
+
+        while (!queue.isEmpty()) {
+            const [id, time] = queue.pop();
+            res = Math.max(res, time);
+            if (adj.has(id)) {
+                for (const emp of adj.get(id)) {
+                    queue.push([emp, time + informTime[id]]);
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Topological Sort (Kahn's Algorithm)
+
+::tabs-start
+
+```python
+class Solution:
+    def numOfMinutes(self, n: int, headID: int, manager: List[int], informTime: List[int]) -> int:
+        indegree = [0] * n
+        time = [0] * n
+
+        for i in range(n):
+            if manager[i] != -1:
+                indegree[manager[i]] += 1
+
+        queue = deque()
+        for i in range(n):
+            if indegree[i] == 0:
+                queue.append(i)
+
+        while queue:
+            node = queue.popleft()
+            time[node] += informTime[node]
+            if manager[node] != -1:
+                time[manager[node]] = max(time[manager[node]], time[node])
+                indegree[manager[node]] -= 1
+                if indegree[manager[node]] == 0:
+                    queue.append(manager[node])
+
+        return time[headID]
+```
+
+```java
+public class Solution {
+    public int numOfMinutes(int n, int headID, int[] manager, int[] informTime) {
+        int[] indegree = new int[n];
+        int[] time = new int[n];
+
+        for (int i = 0; i < n; i++) {
+            if (manager[i] != -1) {
+                indegree[manager[i]]++;
+            }
+        }
+
+        Queue<Integer> queue = new LinkedList<>();
+        for (int i = 0; i < n; i++) {
+            if (indegree[i] == 0) {
+                queue.add(i);
+            }
+        }
+
+        while (!queue.isEmpty()) {
+            int node = queue.poll();
+            time[node] += informTime[node];
+            if (manager[node] != -1) {
+                time[manager[node]] = Math.max(time[manager[node]], time[node]);
+                indegree[manager[node]]--;
+                if (indegree[manager[node]] == 0) {
+                    queue.add(manager[node]);
+                }
+            }
+        }
+
+        return time[headID];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numOfMinutes(int n, int headID, vector<int>& manager, vector<int>& informTime) {
+        vector<int> indegree(n, 0);
+        vector<int> time(n, 0);
+
+        for (int i = 0; i < n; ++i) {
+            if (manager[i] != -1) {
+                indegree[manager[i]]++;
+            }
+        }
+
+        queue<int> queue;
+        for (int i = 0; i < n; ++i) {
+            if (indegree[i] == 0) {
+                queue.push(i);
+            }
+        }
+
+        while (!queue.empty()) {
+            int node = queue.front();
+            queue.pop();
+            time[node] += informTime[node];
+            if (manager[node] != -1) {
+                time[manager[node]] = max(time[manager[node]], time[node]);
+                indegree[manager[node]]--;
+                if (indegree[manager[node]] == 0) {
+                    queue.push(manager[node]);
+                }
+            }
+        }
+
+        return time[headID];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} headID
+     * @param {number[]} manager
+     * @param {number[]} informTime
+     * @return {number}
+     */
+    numOfMinutes(n, headID, manager, informTime) {
+        const indegree = Array(n).fill(0);
+        const time = Array(n).fill(0);
+
+        for (let i = 0; i < n; i++) {
+            if (manager[i] !== -1) {
+                indegree[manager[i]]++;
+            }
+        }
+
+        const queue = new Queue();
+        for (let i = 0; i < n; i++) {
+            if (indegree[i] === 0) {
+                queue.push(i);
+            }
+        }
+
+        while (!queue.isEmpty()) {
+            const node = queue.pop();
+            time[node] += informTime[node];
+            if (manager[node] !== -1) {
+                time[manager[node]] = Math.max(time[manager[node]], time[node]);
+                indegree[manager[node]]--;
+                if (indegree[manager[node]] === 0) {
+                    queue.push(manager[node]);
+                }
+            }
+        }
+
+        return time[headID];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Depth First Search (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def numOfMinutes(self, n: int, headID: int, manager: List[int], informTime: List[int]) -> int:
+        def dfs(node):
+            if manager[node] != -1:
+                informTime[node] += dfs(manager[node])
+                manager[node] = -1
+            return informTime[node]
+        
+        res = 0
+        for node in range(n):
+            res = max(res, dfs(node))
+        return res
+```
+
+```java
+public class Solution {
+    public int numOfMinutes(int n, int headID, int[] manager, int[] informTime) {
+        int res = 0;
+        for (int node = 0; node < n; node++) {
+            res = Math.max(res, dfs(node, manager, informTime));
+        }
+        return res;
+    }
+    
+    private int dfs(int node, int[] manager, int[] informTime) {
+        if (manager[node] != -1) {
+            informTime[node] += dfs(manager[node], manager, informTime);
+            manager[node] = -1;
+        }
+        return informTime[node];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numOfMinutes(int n, int headID, vector<int>& manager, vector<int>& informTime) {
+        function<int(int)> dfs = [&](int node) {
+            if (manager[node] != -1) {
+                informTime[node] += dfs(manager[node]);
+                manager[node] = -1;
+            }
+            return informTime[node];
+        };
+        
+        int res = 0;
+        for (int node = 0; node < n; ++node) {
+            res = max(res, dfs(node));
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number} headID
+     * @param {number[]} manager
+     * @param {number[]} informTime
+     * @return {number}
+     */
+    numOfMinutes(n, headID, manager, informTime) {
+        const dfs = (node) => {
+            if (manager[node] !== -1) {
+                informTime[node] += dfs(manager[node]);
+                manager[node] = -1;
+            }
+            return informTime[node];
+        };
+
+        let res = 0;
+        for (let node = 0; node < n; node++) {
+            res = Math.max(res, dfs(node));
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
\ No newline at end of file
diff --git a/articles/top-k-elements-in-list.md b/articles/top-k-elements-in-list.md
index 95df1bc9a..7bca2df74 100644
--- a/articles/top-k-elements-in-list.md
+++ b/articles/top-k-elements-in-list.md
@@ -109,6 +109,77 @@ public class Solution {
 }
 ```
 
+```go
+func topKFrequent(nums []int, k int) []int {
+    count := make(map[int]int)
+    for _, num := range nums {
+        count[num]++
+    }
+
+    arr := make([][2]int, 0, len(count))
+    for num, cnt := range count {
+        arr = append(arr, [2]int{cnt, num})
+    }
+
+    sort.Slice(arr, func(i, j int) bool {
+        return arr[i][0] > arr[j][0]
+    })
+
+    res := make([]int, k)
+    for i := 0; i < k; i++ {
+        res[i] = arr[i][1]
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun topKFrequent(nums: IntArray, k: Int): IntArray {
+        val count = HashMap<Int, Int>()
+        for (num in nums) {
+            count[num] = count.getOrDefault(num, 0) + 1
+        }
+
+        val arr = mutableListOf<Pair<Int, Int>>()
+        for ((num, freq) in count) {
+            arr.add(Pair(freq, num))
+        }
+        arr.sortByDescending { it.first }
+
+        val res = IntArray(k)
+        for (i in 0 until k) {
+            res[i] = arr[i].second
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func topKFrequent(_ nums: [Int], _ k: Int) -> [Int] {
+        var count = [Int: Int]()
+        for num in nums {
+            count[num, default: 0] += 1
+        }
+
+        var arr = [(Int, Int)]()
+        for (num, cnt) in count {
+            arr.append((cnt, num))
+        }
+        arr.sort { $0.0 < $1.0 }
+
+        var res = [Int]()
+        while res.count < k {
+            res.append(arr.removeLast().1)
+        }
+
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -118,7 +189,7 @@ public class Solution {
 
 ---
 
-## 2. Heap
+## 2. Min-Heap
 
 ::tabs-start
 
@@ -251,6 +322,95 @@ public class Solution {
 }
 ```
 
+```go
+func topKFrequent(nums []int, k int) []int {
+    count := make(map[int]int)
+    for _, num := range nums {
+        count[num]++
+    }
+
+    heap := priorityqueue.NewWith(func(a, b interface{}) int {
+        freqA := a.([2]int)[0]
+        freqB := b.([2]int)[0]
+        return utils.IntComparator(freqA, freqB) 
+    })
+
+    for num, freq := range count {
+        heap.Enqueue([2]int{freq, num})
+        if heap.Size() > k {
+            heap.Dequeue()
+        }
+    }
+
+    res := make([]int, k)
+    for i := k - 1; i >= 0; i-- {
+        value, _ := heap.Dequeue() 
+        res[i] = value.([2]int)[1]
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun topKFrequent(nums: IntArray, k: Int): IntArray {
+        val count = HashMap<Int, Int>()
+        for (num in nums) {
+            count[num] = count.getOrDefault(num, 0) + 1
+        }
+
+        val heap = PriorityQueue<Pair<Int, Int>>(compareBy { it.first })
+        for ((num, freq) in count) {
+            heap.add(Pair(freq, num))
+            if (heap.size > k) {
+                heap.poll()
+            }
+        }
+
+        val res = IntArray(k)
+        for (i in k - 1 downTo 0) {
+            res[i] = heap.poll().second
+        }
+        return res
+    }
+}
+```
+
+```swift
+struct NumFreq: Comparable {
+    let num: Int
+    let freq: Int
+
+    static func < (lhs: NumFreq, rhs: NumFreq) -> Bool {
+        return lhs.freq < rhs.freq
+    }
+}
+
+class Solution {
+    func topKFrequent(_ nums: [Int], _ k: Int) -> [Int] {
+        var count = [Int: Int]()
+        for num in nums {
+            count[num, default: 0] += 1
+        }
+
+        var heap: Heap<NumFreq> = []        
+        for (num, freq) in count {
+            heap.insert(NumFreq(num: num, freq: freq))
+            if heap.count > k {
+                heap.removeMin()
+            }
+        }
+
+        var res = [Int]()
+        while !heap.isEmpty {
+            res.append(heap.removeMin().num)
+        }
+
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -411,9 +571,90 @@ public class Solution {
 }
 ```
 
+```go
+func topKFrequent(nums []int, k int) []int {
+    count := make(map[int]int)
+    freq := make([][]int, len(nums)+1)
+
+    for _, num := range nums {
+        count[num]++
+    }
+    for num, cnt := range count {
+        freq[cnt] = append(freq[cnt], num)
+    }
+
+    res := []int{}
+    for i := len(freq) - 1; i > 0; i-- {
+        for _, num := range freq[i] {
+            res = append(res, num)
+            if len(res) == k {
+                return res
+            }
+        }
+    }
+    return res
+}
+```
+
+```kotlin
+class Solution {
+    fun topKFrequent(nums: IntArray, k: Int): IntArray {
+        val count = HashMap<Int, Int>()
+        val freq = List(nums.size + 1) { mutableListOf<Int>() }
+
+        for (num in nums) {
+            count[num] = count.getOrDefault(num, 0) + 1
+        }
+        for ((num, cnt) in count) {
+            freq[cnt].add(num)
+        }
+
+        val res = mutableListOf<Int>()
+        for (i in freq.size - 1 downTo 1) {
+            for (num in freq[i]) {
+                res.add(num)
+                if (res.size == k) {
+                    return res.toIntArray()
+                }
+            }
+        }
+        return res.toIntArray()
+    }
+}
+```
+
+```swift
+class Solution {
+    func topKFrequent(_ nums: [Int], _ k: Int) -> [Int] {
+        var count = [Int: Int]()
+        var freq = [[Int]](repeating: [], count: nums.count + 1)
+        
+        for num in nums {
+            count[num, default: 0] += 1
+        }
+        
+        for (num, cnt) in count {
+            freq[cnt].append(num)
+        }
+        
+        var res = [Int]()
+        for i in stride(from: freq.count - 1, through: 1, by: -1) {
+            for num in freq[i] {
+                res.append(num)
+                if res.count == k {
+                    return res
+                }
+            }
+        }
+        
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
 
 * Time complexity: $O(n)$
-* Space complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/transpose-matrix.md b/articles/transpose-matrix.md
new file mode 100644
index 000000000..d92b422ab
--- /dev/null
+++ b/articles/transpose-matrix.md
@@ -0,0 +1,208 @@
+## 1. Iteration - I
+
+::tabs-start
+
+```python
+class Solution:
+    def transpose(self, matrix: List[List[int]]) -> List[List[int]]:
+        ROWS, COLS = len(matrix), len(matrix[0])
+        res = [[0] * ROWS for _ in range(COLS)]
+
+        for r in range(ROWS):
+            for c in range(COLS):
+                res[c][r] = matrix[r][c]
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[][] transpose(int[][] matrix) {
+        int ROWS = matrix.length, COLS = matrix[0].length;
+        int[][] res = new int[COLS][ROWS];
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                res[c][r] = matrix[r][c];
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> transpose(vector<vector<int>>& matrix) {
+        int ROWS = matrix.size(), COLS = matrix[0].size();
+        vector<vector<int>> res(COLS, vector<int>(ROWS));
+
+        for (int r = 0; r < ROWS; ++r) {
+            for (int c = 0; c < COLS; ++c) {
+                res[c][r] = matrix[r][c];
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} matrix
+     * @return {number[][]}
+     */
+    transpose(matrix) {
+        const ROWS = matrix.length, COLS = matrix[0].length;
+        const res = Array.from({ length: COLS }, () => Array(ROWS).fill(0));
+
+        for (let r = 0; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                res[c][r] = matrix[r][c];
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n * m)$ for the output array.
+
+> Where $n$ is the number of rows and $m$ is the number of columns in the matrix.
+
+---
+
+## 2. Iteration - II
+
+::tabs-start
+
+```python
+class Solution:
+    def transpose(self, matrix: List[List[int]]) -> List[List[int]]:
+        ROWS, COLS = len(matrix), len(matrix[0])
+
+        if ROWS == COLS:
+            for r in range(ROWS):
+                for c in range(r):
+                    matrix[r][c], matrix[c][r] = matrix[c][r], matrix[r][c]
+            
+            return matrix
+
+        res = [[0] * ROWS for _ in range(COLS)]
+
+        for r in range(ROWS):
+            for c in range(COLS):
+                res[c][r] = matrix[r][c]
+
+        return res
+```
+
+```java
+public class Solution {
+    public int[][] transpose(int[][] matrix) {
+        int ROWS = matrix.length, COLS = matrix[0].length;
+        
+        if (ROWS == COLS) {
+            for (int r = 0; r < ROWS; r++) {
+                for (int c = 0; c < r; c++) {
+                    int tmp = matrix[r][c];
+                    matrix[r][c] = matrix[c][r];
+                    matrix[c][r] = tmp;
+                }
+            }
+
+            return matrix;
+        }
+
+        int[][] res = new int[COLS][ROWS];
+
+        for (int r = 0; r < ROWS; r++) {
+            for (int c = 0; c < COLS; c++) {
+                res[c][r] = matrix[r][c];
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> transpose(vector<vector<int>>& matrix) {
+        int ROWS = matrix.size(), COLS = matrix[0].size();
+        
+        if (ROWS == COLS) {
+            for (int r = 0; r < ROWS; r++) {
+                for (int c = 0; c < r; c++) {
+                    swap(matrix[r][c], matrix[c][r]);
+                }
+            }
+            
+            return matrix;
+        }
+
+        vector<vector<int>> res(COLS, vector<int>(ROWS));
+
+        for (int r = 0; r < ROWS; ++r) {
+            for (int c = 0; c < COLS; ++c) {
+                res[c][r] = matrix[r][c];
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} matrix
+     * @return {number[][]}
+     */
+    transpose(matrix) {
+        const ROWS = matrix.length, COLS = matrix[0].length;
+
+        if (ROWS === COLS) {
+                for (let r = 0; r < ROWS; r++) {
+                    for (let c = 0; c < r; c++) {
+                        [matrix[r][c], matrix[c][r]] = [matrix[c][r], matrix[r][c]];
+                    }
+                }
+                
+                return matrix;
+            }
+
+        const res = Array.from({ length: COLS }, () => Array(ROWS).fill(0));
+
+        for (let r = 0; r < ROWS; r++) {
+            for (let c = 0; c < COLS; c++) {
+                res[c][r] = matrix[r][c];
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n * m)$
+
+> Where $n$ is the number of rows and $m$ is the number of columns in the matrix.
\ No newline at end of file
diff --git a/articles/trapping-rain-water.md b/articles/trapping-rain-water.md
index dd673b143..4e8f600b8 100644
--- a/articles/trapping-rain-water.md
+++ b/articles/trapping-rain-water.md
@@ -136,6 +136,94 @@ public class Solution {
 }
 ```
 
+```go
+func trap(height []int) int {
+    if len(height) == 0 {
+        return 0
+    }
+    n := len(height)
+    res := 0
+
+    for i := 0; i < n; i++ {
+        leftMax := height[i]
+        rightMax := height[i]
+
+        for j := 0; j < i; j++ {
+            if height[j] > leftMax {
+                leftMax = height[j]
+            }
+        }
+        for j := i + 1; j < n; j++ {
+            if height[j] > rightMax {
+                rightMax = height[j]
+            }
+        }
+
+        res += min(leftMax, rightMax) - height[i]
+    }
+    return res
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun trap(height: IntArray): Int {
+        if (height.isEmpty()) return 0
+        val n = height.size
+        var res = 0
+
+        for (i in 0 until n) {
+            var leftMax = height[i]
+            var rightMax = height[i]
+
+            for (j in 0 until i) {
+                leftMax = maxOf(leftMax, height[j])
+            }
+            for (j in i + 1 until n) {
+                rightMax = maxOf(rightMax, height[j])
+            }
+
+            res += minOf(leftMax, rightMax) - height[i]
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func trap(_ height: [Int]) -> Int {
+        if height.isEmpty {
+            return 0
+        }
+        let n = height.count
+        var res = 0
+
+        for i in 0..<n {
+            var leftMax = height[i]
+            var rightMax = height[i]
+
+            for j in 0..<i {
+                leftMax = max(leftMax, height[j])
+            }
+            for j in (i + 1)..<n {
+                rightMax = max(rightMax, height[j])
+            }
+
+            res += min(leftMax, rightMax) - height[i]
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -298,6 +386,106 @@ public class Solution {
 }
 ```
 
+```go
+func trap(height []int) int {
+    n := len(height)
+    if n == 0 {
+        return 0
+    }
+
+    leftMax := make([]int, n)
+    rightMax := make([]int, n)
+
+    leftMax[0] = height[0]
+    for i := 1; i < n; i++ {
+        leftMax[i] = max(leftMax[i-1], height[i])
+    }
+
+    rightMax[n-1] = height[n-1]
+    for i := n - 2; i >= 0; i-- {
+        rightMax[i] = max(rightMax[i+1], height[i])
+    }
+
+    res := 0
+    for i := 0; i < n; i++ {
+        res += min(leftMax[i], rightMax[i]) - height[i]
+    }
+    return res
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun trap(height: IntArray): Int {
+        val n = height.size
+        if (n == 0) return 0
+
+        val leftMax = IntArray(n)
+        val rightMax = IntArray(n)
+
+        leftMax[0] = height[0]
+        for (i in 1 until n) {
+            leftMax[i] = maxOf(leftMax[i - 1], height[i])
+        }
+
+        rightMax[n - 1] = height[n - 1]
+        for (i in n - 2 downTo 0) {
+            rightMax[i] = maxOf(rightMax[i + 1], height[i])
+        }
+
+        var res = 0
+        for (i in 0 until n) {
+            res += minOf(leftMax[i], rightMax[i]) - height[i]
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func trap(_ height: [Int]) -> Int {
+        let n = height.count
+        if n == 0 {
+            return 0
+        }
+
+        var leftMax = [Int](repeating: 0, count: n)
+        var rightMax = [Int](repeating: 0, count: n)
+
+        leftMax[0] = height[0]
+        for i in 1..<n {
+            leftMax[i] = max(leftMax[i - 1], height[i])
+        }
+
+        rightMax[n - 1] = height[n - 1]
+        for i in stride(from: n - 2, through: 0, by: -1) {
+            rightMax[i] = max(rightMax[i + 1], height[i])
+        }
+
+        var res = 0
+        for i in 0..<n {
+            res += min(leftMax[i], rightMax[i]) - height[i]
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -451,6 +639,99 @@ public class Solution {
 }
 ```
 
+```go
+func trap(height []int) int {
+    if len(height) == 0 {
+        return 0
+    }
+
+    stack := linkedliststack.New()
+    res := 0
+
+    for i := 0; i < len(height); i++ {
+        for !stack.Empty() {
+            topIndex, _ := stack.Peek() 
+            if height[i] >= height[topIndex.(int)] {
+                midIndex, _ := stack.Pop() 
+                mid := height[midIndex.(int)] 
+                if !stack.Empty() {
+                    topIndex, _ := stack.Peek() 
+                    right := height[i]
+                    left := height[topIndex.(int)]
+                    h := min(right, left) - mid
+                    w := i - topIndex.(int) - 1
+                    res += h * w
+                }
+            } else {
+                break 
+            }
+        }
+        stack.Push(i)
+    }
+    return res
+}
+
+func min(a, b int) int {
+    if a < b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun trap(height: IntArray): Int {
+        if (height.isEmpty()) return 0
+
+        val stack = ArrayDeque<Int>()
+        var res = 0
+
+        for (i in height.indices) {
+            while (stack.isNotEmpty() && height[i] >= height[stack.first()]) {
+                val mid = stack.removeFirst()
+                if (stack.isNotEmpty()) {
+                    val left = stack.first()
+                    val right = height[i]
+                    val h = minOf(right, height[left]) - height[mid]
+                    val w = i - left - 1
+                    res += h * w
+                }
+            }
+            stack.addFirst(i)
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func trap(_ height: [Int]) -> Int {
+        if height.isEmpty {
+            return 0
+        }
+        var stack = [Int]()
+        var res = 0
+
+        for i in 0..<height.count {
+            while !stack.isEmpty && height[i] >= height[stack.last!] {
+                let mid = height[stack.removeLast()]
+                if !stack.isEmpty {
+                    let right = height[i]
+                    let left = height[stack.last!]
+                    let h = min(right, left) - mid
+                    let w = i - stack.last! - 1
+                    res += h * w
+                }
+            }
+            stack.append(i)
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -596,6 +877,92 @@ public class Solution {
 }
 ```
 
+```go
+func trap(height []int) int {
+    if len(height) == 0 {
+        return 0
+    }
+
+    l, r := 0, len(height)-1
+    leftMax, rightMax := height[l], height[r]
+    res := 0
+
+    for l < r {
+        if leftMax < rightMax {
+            l++
+            leftMax = max(leftMax, height[l])
+            res += leftMax - height[l]
+        } else {
+            r--
+            rightMax = max(rightMax, height[r])
+            res += rightMax - height[r]
+        }
+    }
+    return res
+}
+
+func max(a, b int) int {
+    if a > b {
+        return a
+    }
+    return b
+}
+```
+
+```kotlin
+class Solution {
+    fun trap(height: IntArray): Int {
+        if (height.isEmpty()) return 0
+
+        var l = 0
+        var r = height.size - 1
+        var leftMax = height[l]
+        var rightMax = height[r]
+        var res = 0
+
+        while (l < r) {
+            if (leftMax < rightMax) {
+                l++
+                leftMax = maxOf(leftMax, height[l])
+                res += leftMax - height[l]
+            } else {
+                r--
+                rightMax = maxOf(rightMax, height[r])
+                res += rightMax - height[r]
+            }
+        }
+        return res
+    }
+}
+```
+
+```swift
+class Solution {
+    func trap(_ height: [Int]) -> Int {
+        if height.isEmpty {
+            return 0
+        }
+
+        var l = 0, r = height.count - 1
+        var leftMax = height[l], rightMax = height[r]
+        var res = 0
+
+        while l < r {
+            if leftMax < rightMax {
+                l += 1
+                leftMax = max(leftMax, height[l])
+                res += leftMax - height[l]
+            } else {
+                r -= 1
+                rightMax = max(rightMax, height[r])
+                res += rightMax - height[r]
+            }
+        }
+        return res
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/triangle.md b/articles/triangle.md
new file mode 100644
index 000000000..53b994a33
--- /dev/null
+++ b/articles/triangle.md
@@ -0,0 +1,535 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def minimumTotal(self, triangle: List[List[int]]) -> int:
+        def dfs(row, col):
+            if row >= len(triangle):
+                return 0
+            return triangle[row][col] + min(dfs(row + 1, col), dfs(row + 1, col + 1))
+        
+        return dfs(0, 0)
+```
+
+```java
+public class Solution {
+    public int minimumTotal(List<List<Integer>> triangle) {
+        return dfs(0, 0, triangle);
+    }
+
+    private int dfs(int row, int col, List<List<Integer>> triangle) {
+        if (row >= triangle.size()) {
+            return 0;
+        }
+        return triangle.get(row).get(col) + Math.min(dfs(row + 1, col, triangle), dfs(row + 1, col + 1, triangle));
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minimumTotal(vector<vector<int>>& triangle) {
+        return dfs(0, 0, triangle);
+    }
+
+private:
+    int dfs(int row, int col, vector<vector<int>>& triangle) {
+        if (row >= triangle.size()) {
+            return 0;
+        }
+        return triangle[row][col] + min(dfs(row + 1, col, triangle), dfs(row + 1, col + 1, triangle));
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} triangle
+     * @return {number}
+     */
+    minimumTotal(triangle) {
+        const dfs = (row, col) => {
+            if (row >= triangle.length) {
+                return 0;
+            }
+            return triangle[row][col] + Math.min(dfs(row + 1, col), dfs(row + 1, col + 1));
+        };
+        
+        return dfs(0, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def minimumTotal(self, triangle: List[List[int]]) -> int:
+        memo = [[0] * len(triangle[r]) for r in range(len(triangle))]
+        INF = float("inf")
+        for r in range(len(triangle)):
+            for c in range(len(triangle[r])):
+                memo[r][c] = INF
+
+        def dfs(row, col):
+            if row >= len(triangle):
+                return 0
+            if memo[row][col] != INF:
+                return memo[row][col]
+
+            memo[row][col] = triangle[row][col] + min(dfs(row + 1, col), dfs(row + 1, col + 1))
+            return memo[row][col]
+                
+        return dfs(0, 0)
+```
+
+```java
+public class Solution {
+    public int minimumTotal(List<List<Integer>> triangle) {
+        int[][] memo = new int[triangle.size()][];
+        int INF = Integer.MAX_VALUE;
+        for (int r = 0; r < triangle.size(); r++) {
+            memo[r] = new int[triangle.get(r).size()];
+            Arrays.fill(memo[r], INF);
+        }
+
+        return dfs(0, 0, triangle, memo);
+    }
+
+    private int dfs(int row, int col, List<List<Integer>> triangle, int[][] memo) {
+        if (row >= triangle.size()) {
+            return 0;
+        }
+        if (memo[row][col] != Integer.MAX_VALUE) {
+            return memo[row][col];
+        }
+
+        memo[row][col] = triangle.get(row).get(col) + Math.min(dfs(row + 1, col, triangle, memo), dfs(row + 1, col + 1, triangle, memo));
+        return memo[row][col];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minimumTotal(vector<vector<int>>& triangle) {
+        vector<vector<int>> memo(triangle.size(), vector<int>(0));
+        int INF = INT_MAX;
+        for (int r = 0; r < triangle.size(); ++r) {
+            memo[r].resize(triangle[r].size(), INF);
+        }
+
+        return dfs(0, 0, triangle, memo);
+    }
+
+private:
+    int dfs(int row, int col, vector<vector<int>>& triangle, vector<vector<int>>& memo) {
+        if (row >= triangle.size()) {
+            return 0;
+        }
+        if (memo[row][col] != INT_MAX) {
+            return memo[row][col];
+        }
+
+        memo[row][col] = triangle[row][col] + min(dfs(row + 1, col, triangle, memo), dfs(row + 1, col + 1, triangle, memo));
+        return memo[row][col];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} triangle
+     * @return {number}
+     */
+    minimumTotal(triangle) {
+        const memo = Array.from({ length: triangle.length }, (_, r) => Array(triangle[r].length).fill(Infinity));
+
+        const dfs = (row, col) => {
+            if (row >= triangle.length) {
+                return 0;
+            }
+            if (memo[row][col] !== Infinity) {
+                return memo[row][col];
+            }
+
+            memo[row][col] = triangle[row][col] + Math.min(dfs(row + 1, col), dfs(row + 1, col + 1));
+            return memo[row][col];
+        };
+
+        return dfs(0, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def minimumTotal(self, triangle: List[List[int]]) -> int:
+        n = len(triangle)
+        dp = [[0] * len(triangle[row]) for row in range(n)]
+        dp[-1] = triangle[-1][:]
+        
+        for row in range(n - 2, -1, -1):
+            for col in range(len(triangle[row])):
+                dp[row][col] = triangle[row][col] + min(dp[row + 1][col], dp[row + 1][col + 1])
+
+        return dp[0][0]
+```
+
+```java
+public class Solution {
+    public int minimumTotal(List<List<Integer>> triangle) {
+        int n = triangle.size();
+        int[][] dp = new int[n][n];
+        for (int col = 0; col < triangle.get(n - 1).size(); col++) {
+            dp[n - 1][col] = triangle.get(n - 1).get(col);
+        }
+
+        for (int row = n - 2; row >= 0; row--) {
+            for (int col = 0; col < triangle.get(row).size(); col++) {
+                dp[row][col] = triangle.get(row).get(col) + Math.min(dp[row + 1][col], dp[row + 1][col + 1]);
+            }
+        }
+
+        return dp[0][0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minimumTotal(vector<vector<int>>& triangle) {
+        int n = triangle.size();
+        vector<vector<int>> dp(n, vector<int>(n, 0));
+        for (int col = 0; col < triangle[n - 1].size(); ++col) {
+            dp[n - 1][col] = triangle[n - 1][col];
+        }
+
+        for (int row = n - 2; row >= 0; --row) {
+            for (int col = 0; col < triangle[row].size(); ++col) {
+                dp[row][col] = triangle[row][col] + min(dp[row + 1][col], dp[row + 1][col + 1]);
+            }
+        }
+
+        return dp[0][0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} triangle
+     * @return {number}
+     */
+    minimumTotal(triangle) {
+        const n = triangle.length;
+        const dp = Array.from({ length: n }, (_, i) => Array(triangle[i].length).fill(0));
+        for (let col = 0; col < triangle[n - 1].length; col++) {
+            dp[n - 1][col] = triangle[n - 1][col];
+        }
+
+        for (let row = n - 2; row >= 0; row--) {
+            for (let col = 0; col < triangle[row].length; col++) {
+                dp[row][col] = triangle[row][col] + Math.min(dp[row + 1][col], dp[row + 1][col + 1]);
+            }
+        }
+
+        return dp[0][0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 4. Dynamic Programming (Space Optimized) - I
+
+::tabs-start
+
+```python
+class Solution:
+    def minimumTotal(self, triangle: List[List[int]]) -> int:
+        n = len(triangle)
+        dp = triangle[0][:]
+
+        for row in range(1, n):
+            nxtDp = [0] * len(triangle[row])
+            nxtDp[0] = dp[0] + triangle[row][0]
+            for col in range(1, len(triangle[row]) - 1):
+                nxtDp[col] = triangle[row][col] + min(dp[col], dp[col - 1])
+            nxtDp[-1] = dp[-1] + triangle[row][-1]
+            dp = nxtDp
+
+        return min(dp)
+```
+
+```java
+public class Solution {
+    public int minimumTotal(List<List<Integer>> triangle) {
+        int n = triangle.size();
+        int[] dp = new int[n];
+        dp[0] = triangle.get(0).get(0);
+
+        for (int row = 1; row < n; row++) {
+            int[] nxtDp = new int[row + 1];
+            nxtDp[0] = dp[0] + triangle.get(row).get(0);
+            for (int col = 1; col < row; col++) {
+                nxtDp[col] = triangle.get(row).get(col) + Math.min(dp[col], dp[col - 1]);
+            }
+            nxtDp[row] = dp[row - 1] + triangle.get(row).get(row);
+            dp = nxtDp;
+        }
+
+        int minPath = Integer.MAX_VALUE;
+        for (int value : dp) {
+            minPath = Math.min(minPath, value);
+        }
+        return minPath;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minimumTotal(vector<vector<int>>& triangle) {
+        int n = triangle.size();
+        vector<int> dp = triangle[0];
+
+        for (int row = 1; row < n; row++) {
+            vector<int> nxtDp(row + 1, 0);
+            nxtDp[0] = dp[0] + triangle[row][0];
+            for (int col = 1; col < row; col++) {
+                nxtDp[col] = triangle[row][col] + min(dp[col], dp[col - 1]);
+            }
+            nxtDp[row] = dp[row - 1] + triangle[row][row];
+            dp = nxtDp;
+        }
+
+        return *min_element(dp.begin(), dp.end());
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} triangle
+     * @return {number}
+     */
+    minimumTotal(triangle) {
+        let n = triangle.length;
+        let dp = [...triangle[0]];
+
+        for (let row = 1; row < n; row++) {
+            let nxtDp = new Array(row + 1).fill(0);
+            nxtDp[0] = dp[0] + triangle[row][0];
+            for (let col = 1; col < row; col++) {
+                nxtDp[col] = triangle[row][col] + Math.min(dp[col], dp[col - 1]);
+            }
+            nxtDp[row] = dp[row - 1] + triangle[row][row];
+            dp = nxtDp;
+        }
+
+        return Math.min(...dp);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$ extra space.
+
+---
+
+## 5. Dynamic Programming (Space Optimized) - II
+
+::tabs-start
+
+```python
+class Solution:
+    def minimumTotal(self, triangle: List[List[int]]) -> int:
+        n = len(triangle)
+        dp = triangle[-1][:]
+
+        for row in range(n - 2, -1, -1):
+            for col in range(len(triangle[row])):
+                dp[col] = triangle[row][col] + min(dp[col], dp[col + 1])
+        
+        return dp[0]
+```
+
+```java
+public class Solution {
+    public int minimumTotal(List<List<Integer>> triangle) {
+        int n = triangle.size();
+        int[] dp = new int[n];
+        for (int i = 0; i < n; i++) {
+            dp[i] = triangle.get(n - 1).get(i);
+        }
+        
+        for (int row = n - 2; row >= 0; row--) {
+            for (int col = 0; col < triangle.get(row).size(); col++) {
+                dp[col] = triangle.get(row).get(col) + Math.min(dp[col], dp[col + 1]);
+            }
+        }
+        
+        return dp[0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minimumTotal(vector<vector<int>>& triangle) {
+        int n = triangle.size();
+        vector<int> dp(triangle.back());
+
+        for (int row = n - 2; row >= 0; --row) {
+            for (int col = 0; col < triangle[row].size(); ++col) {
+                dp[col] = triangle[row][col] + min(dp[col], dp[col + 1]);
+            }
+        }
+        
+        return dp[0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} triangle
+     * @return {number}
+     */
+    minimumTotal(triangle) {
+        const n = triangle.length;
+        const dp = [...triangle[n - 1]];
+
+        for (let row = n - 2; row >= 0; row--) {
+            for (let col = 0; col < triangle[row].length; col++) {
+                dp[col] = triangle[row][col] + Math.min(dp[col], dp[col + 1]);
+            }
+        }
+
+        return dp[0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$ extra space.
+
+---
+
+## 6. Dynamic Programming (In-Place)
+
+::tabs-start
+
+```python
+class Solution:
+    def minimumTotal(self, triangle: List[List[int]]) -> int:
+        for row in range(len(triangle) - 2, -1, -1):
+            for col in range(len(triangle[row])):
+                triangle[row][col] += min(triangle[row + 1][col], triangle[row + 1][col + 1])
+        
+        return triangle[0][0]
+```
+
+```java
+public class Solution {
+    public int minimumTotal(List<List<Integer>> triangle) {
+        for (int row = triangle.size() - 2; row >= 0; row--) {
+            for (int col = 0; col < triangle.get(row).size(); col++) {
+                triangle.get(row).set(col, triangle.get(row).get(col) + 
+                    Math.min(triangle.get(row + 1).get(col), triangle.get(row + 1).get(col + 1)));
+            }
+        }
+        return triangle.get(0).get(0);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int minimumTotal(vector<vector<int>>& triangle) {
+        for (int row = triangle.size() - 2; row >= 0; row--) {
+            for (int col = 0; col < triangle[row].size(); col++) {
+                triangle[row][col] += min(triangle[row + 1][col], triangle[row + 1][col + 1]);
+            }
+        }
+        return triangle[0][0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} triangle
+     * @return {number}
+     */
+    minimumTotal(triangle) {
+        for (let row = triangle.length - 2; row >= 0; row--) {
+            for (let col = 0; col < triangle[row].length; col++) {
+                triangle[row][col] += Math.min(triangle[row + 1][col], triangle[row + 1][col + 1]);
+            }
+        }
+        return triangle[0][0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/trim-a-binary-search-tree.md b/articles/trim-a-binary-search-tree.md
new file mode 100644
index 000000000..6a7eb3f21
--- /dev/null
+++ b/articles/trim-a-binary-search-tree.md
@@ -0,0 +1,488 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def trimBST(self, root: Optional[TreeNode], low: int, high: int) -> Optional[TreeNode]:
+        if not root:
+            return None
+
+        if root.val > high:
+            return self.trimBST(root.left, low, high)
+        if root.val < low:
+            return self.trimBST(root.right, low, high)
+
+        root.left = self.trimBST(root.left, low, high)
+        root.right = self.trimBST(root.right, low, high)
+        return root
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode trimBST(TreeNode root, int low, int high) {
+        if (root == null) {
+            return null;
+        }
+
+        if (root.val > high) {
+            return trimBST(root.left, low, high);
+        }
+        if (root.val < low) {
+            return trimBST(root.right, low, high);
+        }
+
+        root.left = trimBST(root.left, low, high);
+        root.right = trimBST(root.right, low, high);
+        return root;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    TreeNode* trimBST(TreeNode* root, int low, int high) {
+        if (!root) return nullptr;
+
+        if (root->val > high) {
+            return trimBST(root->left, low, high);
+        }
+        if (root->val < low) {
+            return trimBST(root->right, low, high);
+        }
+
+        root->left = trimBST(root->left, low, high);
+        root->right = trimBST(root->right, low, high);
+        return root;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @param {number} low
+     * @param {number} high
+     * @return {TreeNode}
+     */
+    trimBST(root, low, high) {
+        if (!root) return null;
+
+        if (root.val > high) return this.trimBST(root.left, low, high);
+        if (root.val < low) return this.trimBST(root.right, low, high);
+
+        root.left = this.trimBST(root.left, low, high);
+        root.right = this.trimBST(root.right, low, high);
+        return root;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Iterative DFS
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def trimBST(self, root, low, high):
+        while root and (root.val < low or root.val > high):
+            if root.val < low:
+                root = root.right
+            else:
+                root = root.left
+
+        stack = [root]
+        while stack:
+            node = stack.pop()
+            if not node:
+                continue
+            left_out = node.left and node.left.val < low
+            right_out = node.right and node.right.val > high
+            if left_out:
+                node.left = node.left.right
+            if right_out:
+                node.right = node.right.left
+            if left_out or right_out:
+                stack.append(node)
+            else:
+                if node.left:
+                    stack.append(node.left)
+                if node.right:
+                    stack.append(node.right)
+        return root
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode trimBST(TreeNode root, int low, int high) {
+        while (root != null && (root.val < low || root.val > high)) {
+            root = (root.val < low) ? root.right : root.left;
+        }
+
+        Stack<TreeNode> stack = new Stack<>();
+        stack.push(root);
+        
+        while (!stack.isEmpty()) {
+            TreeNode node = stack.pop();
+            if (node == null) continue;
+            
+            boolean leftOut = (node.left != null && node.left.val < low);
+            boolean rightOut = (node.right != null && node.right.val > high);
+            
+            if (leftOut) node.left = node.left.right;
+            if (rightOut) node.right = node.right.left;
+
+            if (leftOut || rightOut) {
+                stack.push(node);
+            } else {
+                if (node.left != null) stack.push(node.left);
+                if (node.right != null) stack.push(node.right);
+            }
+        }
+        
+        return root;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    TreeNode* trimBST(TreeNode* root, int low, int high) {
+        while (root && (root->val < low || root->val > high)) {
+            root = (root->val < low) ? root->right : root->left;
+        }
+
+        stack<TreeNode*> stack;
+        stack.push(root);
+
+        while (!stack.empty()) {
+            TreeNode* node = stack.top();
+            stack.pop();
+            if (!node) continue;
+
+            bool leftOut = (node->left && node->left->val < low);
+            bool rightOut = (node->right && node->right->val > high);
+
+            if (leftOut) node->left = node->left->right;
+            if (rightOut) node->right = node->right->left;
+
+            if (leftOut || rightOut) {
+                stack.push(node);
+            } else {
+                if (node->left) stack.push(node->left);
+                if (node->right) stack.push(node->right);
+            }
+        }
+
+        return root;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @param {number} low
+     * @param {number} high
+     * @return {TreeNode}
+     */
+    trimBST(root, low, high) {
+        while (root && (root.val < low || root.val > high)) {
+            root = (root.val < low) ? root.right : root.left;
+        }
+
+        const stack = [root];
+
+        while (stack.length > 0) {
+            let node = stack.pop();
+            if (!node) continue;
+
+            let leftOut = node.left && node.left.val < low;
+            let rightOut = node.right && node.right.val > high;
+
+            if (leftOut) node.left = node.left.right;
+            if (rightOut) node.right = node.right.left;
+
+            if (leftOut || rightOut) {
+                stack.push(node);
+            } else {
+                if (node.left) stack.push(node.left);
+                if (node.right) stack.push(node.right);
+            }
+        }
+
+        return root;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Iterative DFS (Optimal)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def trimBST(self, root: Optional[TreeNode], low: int, high: int) -> Optional[TreeNode]:
+        while root and (root.val < low or root.val > high):
+            root = root.right if root.val < low else root.left
+
+        tmpRoot = root
+        while root:
+            while root.left and root.left.val < low:
+                root.left = root.left.right
+            root = root.left
+
+        root = tmpRoot
+        while root:
+            while root.right and root.right.val > high:
+                root.right = root.right.left
+            root = root.right
+
+        return tmpRoot
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode trimBST(TreeNode root, int low, int high) {
+        while (root != null && (root.val < low || root.val > high)) {
+            root = (root.val < low) ? root.right : root.left;
+        }
+
+        TreeNode tmpRoot = root;
+        while (root != null) {
+            while (root.left != null && root.left.val < low) {
+                root.left = root.left.right;
+            }
+            root = root.left;
+        }
+
+        root = tmpRoot;
+        while (root != null) {
+            while (root.right != null && root.right.val > high) {
+                root.right = root.right.left;
+            }
+            root = root.right;
+        }
+
+        return tmpRoot;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    TreeNode* trimBST(TreeNode* root, int low, int high) {
+        while (root && (root->val < low || root->val > high)) {
+            root = (root->val < low) ? root->right : root->left;
+        }
+
+        TreeNode* tmpRoot = root;
+        while (root) {
+            while (root->left && root->left->val < low) {
+                root->left = root->left->right;
+            }
+            root = root->left;
+        }
+
+        root = tmpRoot;
+        while (root) {
+            while (root->right && root->right->val > high) {
+                root->right = root->right->left;
+            }
+            root = root->right;
+        }
+
+        return tmpRoot;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {TreeNode} root
+     * @param {number} low
+     * @param {number} high
+     * @return {TreeNode}
+     */
+    trimBST(root, low, high) {
+        while (root && (root.val < low || root.val > high)) {
+            root = (root.val < low) ? root.right : root.left;
+        }
+
+        let tmpRoot = root;
+        while (root) {
+            while (root.left && root.left.val < low) {
+                root.left = root.left.right;
+            }
+            root = root.left;
+        }
+
+        root = tmpRoot;
+        while (root) {
+            while (root.right && root.right.val > high) {
+                root.right = root.right.left;
+            }
+            root = root.right;
+        }
+
+        return tmpRoot;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/two-city-scheduling.md b/articles/two-city-scheduling.md
new file mode 100644
index 000000000..61f80767c
--- /dev/null
+++ b/articles/two-city-scheduling.md
@@ -0,0 +1,683 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def twoCitySchedCost(self, costs: List[List[int]]) -> int:
+        n = len(costs) // 2
+
+        def dfs(i, aCount, bCount):
+            if i == len(costs):
+                return 0
+
+            res = float("inf")
+            if aCount > 0:
+                res = costs[i][0] + dfs(i + 1, aCount - 1, bCount)
+
+            if bCount > 0:
+                res = min(res, costs[i][1] + dfs(i + 1, aCount, bCount - 1))
+            return res
+
+        return dfs(0, n, n)
+```
+
+```java
+public class Solution {
+    public int twoCitySchedCost(int[][] costs) {
+        int n = costs.length / 2;
+        return dfs(costs, 0, n, n);
+    }
+
+    private int dfs(int[][] costs, int i, int aCount, int bCount) {
+        if (i == costs.length) {
+            return 0;
+        }
+
+        int res = Integer.MAX_VALUE;
+        if (aCount > 0) {
+            res = costs[i][0] + dfs(costs, i + 1, aCount - 1, bCount);
+        }
+
+        if (bCount > 0) {
+            res = Math.min(res, costs[i][1] + dfs(costs, i + 1, aCount, bCount - 1));
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int twoCitySchedCost(vector<vector<int>>& costs) {
+        int n = costs.size() / 2;
+        return dfs(costs, 0, n, n);
+    }
+
+private:
+    int dfs(vector<vector<int>>& costs, int i, int aCount, int bCount) {
+        if (i == costs.size()) {
+            return 0;
+        }
+
+        int res = INT_MAX;
+        if (aCount > 0) {
+            res = costs[i][0] + dfs(costs, i + 1, aCount - 1, bCount);
+        }
+
+        if (bCount > 0) {
+            res = min(res, costs[i][1] + dfs(costs, i + 1, aCount, bCount - 1));
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} costs
+     * @return {number}
+     */
+    twoCitySchedCost(costs) {
+        let n = costs.length / 2;
+
+        const dfs = (i, aCount, bCount) => {
+            if (i === costs.length) {
+                return 0;
+            }
+
+            let res = Infinity;
+            if (aCount > 0) {
+                res = costs[i][0] + dfs(i + 1, aCount - 1, bCount);
+            }
+
+            if (bCount > 0) {
+                res = Math.min(res, costs[i][1] + dfs(i + 1, aCount, bCount - 1));
+            }
+
+            return res;
+        };
+
+        return dfs(0, n, n);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ N)$
+* Space complexity: $O(N)$ for recursion stack.
+
+> Where $N$ is the size of the array $costs$.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def twoCitySchedCost(self, costs: List[List[int]]) -> int:
+        n = len(costs) // 2
+        dp = [[-1] * (n + 1) for _ in range(n + 1)]
+
+        def dfs(i, aCount, bCount):
+            if i == len(costs):
+                return 0
+            if dp[aCount][bCount] != -1:
+                return dp[aCount][bCount]
+
+            res = float("inf")
+            if aCount > 0:
+                res = costs[i][0] + dfs(i + 1, aCount - 1, bCount)
+            if bCount > 0:
+                res = min(res, costs[i][1] + dfs(i + 1, aCount, bCount - 1))
+
+            dp[aCount][bCount] = res
+            return res
+
+        return dfs(0, n, n)
+```
+
+```java
+public class Solution {
+    private int[][] dp;
+
+    public int twoCitySchedCost(int[][] costs) {
+        int n = costs.length / 2;
+        dp = new int[n + 1][n + 1];
+        for (int[] row : dp) {
+            Arrays.fill(row, -1);
+        }
+        return dfs(costs, 0, n, n);
+    }
+
+    private int dfs(int[][] costs, int i, int aCount, int bCount) {
+        if (i == costs.length) {
+            return 0;
+        }
+        if (dp[aCount][bCount] != -1) {
+            return dp[aCount][bCount];
+        }
+
+        int res = Integer.MAX_VALUE;
+        if (aCount > 0) {
+            res = costs[i][0] + dfs(costs, i + 1, aCount - 1, bCount);
+        }
+        if (bCount > 0) {
+            res = Math.min(res, costs[i][1] + dfs(costs, i + 1, aCount, bCount - 1));
+        }
+
+        dp[aCount][bCount] = res;
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<vector<int>> dp;
+
+    int twoCitySchedCost(vector<vector<int>>& costs) {
+        int n = costs.size() / 2;
+        dp = vector<vector<int>>(n + 1, vector<int>(n + 1, -1));
+        return dfs(costs, 0, n, n);
+    }
+
+private:
+    int dfs(vector<vector<int>>& costs, int i, int aCount, int bCount) {
+        if (i == costs.size()) {
+            return 0;
+        }
+        if (dp[aCount][bCount] != -1) {
+            return dp[aCount][bCount];
+        }
+
+        int res = INT_MAX;
+        if (aCount > 0) {
+            res = costs[i][0] + dfs(costs, i + 1, aCount - 1, bCount);
+        }
+        if (bCount > 0) {
+            res = min(res, costs[i][1] + dfs(costs, i + 1, aCount, bCount - 1));
+        }
+
+        dp[aCount][bCount] = res;
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} costs
+     * @return {number}
+     */
+    twoCitySchedCost(costs) {
+        let n = costs.length / 2;
+        let dp = Array.from({ length: n + 1 }, () => new Array(n + 1).fill(-1));
+
+        const dfs = (i, aCount, bCount) => {
+            if (i === costs.length) {
+                return 0;
+            }
+            if (dp[aCount][bCount] !== -1) {
+                return dp[aCount][bCount];
+            }
+
+            let res = Infinity;
+            if (aCount > 0) {
+                res = costs[i][0] + dfs(i + 1, aCount - 1, bCount);
+            }
+            if (bCount > 0) {
+                res = Math.min(res, costs[i][1] + dfs(i + 1, aCount, bCount - 1));
+            }
+
+            dp[aCount][bCount] = res;
+            return res;
+        };
+
+        return dfs(0, n, n);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+> Where $n$ is the half of the size of the array $costs$.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def twoCitySchedCost(self, costs: List[List[int]]) -> int:
+        n = len(costs) // 2
+        dp = [[0] * (n + 1) for _ in range(n + 1)]
+
+        for aCount in range(n + 1):
+            for bCount in range(n + 1):
+                i = aCount + bCount
+                if i == 0:
+                    continue
+
+                dp[aCount][bCount] = float("inf")
+                if aCount > 0:
+                    dp[aCount][bCount] = min(dp[aCount][bCount], dp[aCount - 1][bCount] + costs[i - 1][0])
+                if bCount > 0:
+                    dp[aCount][bCount] = min(dp[aCount][bCount], dp[aCount][bCount - 1] + costs[i - 1][1])
+
+        return dp[n][n]
+```
+
+```java
+public class Solution {
+    public int twoCitySchedCost(int[][] costs) {
+        int n = costs.length / 2;
+        int[][] dp = new int[n + 1][n + 1];
+
+        for (int aCount = 0; aCount <= n; aCount++) {
+            for (int bCount = 0; bCount <= n; bCount++) {
+                int i = aCount + bCount;
+                if (i == 0) continue;
+
+                dp[aCount][bCount] = Integer.MAX_VALUE;
+                if (aCount > 0) {
+                    dp[aCount][bCount] = Math.min(dp[aCount][bCount], dp[aCount - 1][bCount] + costs[i - 1][0]);
+                }
+                if (bCount > 0) {
+                    dp[aCount][bCount] = Math.min(dp[aCount][bCount], dp[aCount][bCount - 1] + costs[i - 1][1]);
+                }
+            }
+        }
+
+        return dp[n][n];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int twoCitySchedCost(vector<vector<int>>& costs) {
+        int n = costs.size() / 2;
+        vector<vector<int>> dp(n + 1, vector<int>(n + 1));
+
+        for (int aCount = 0; aCount <= n; aCount++) {
+            for (int bCount = 0; bCount <= n; bCount++) {
+                int i = aCount + bCount;
+                if (i == 0) continue;
+
+                dp[aCount][bCount] = INT_MAX;
+                if (aCount > 0) {
+                    dp[aCount][bCount] = min(dp[aCount][bCount], dp[aCount - 1][bCount] + costs[i - 1][0]);
+                }
+                if (bCount > 0) {
+                    dp[aCount][bCount] = min(dp[aCount][bCount], dp[aCount][bCount - 1] + costs[i - 1][1]);
+                }
+            }
+        }
+
+        return dp[n][n];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} costs
+     * @return {number}
+     */
+    twoCitySchedCost(costs) {
+        let n = costs.length / 2;
+        let dp = Array.from({ length: n + 1 }, () => new Array(n + 1).fill(0));
+
+        for (let aCount = 0; aCount <= n; aCount++) {
+            for (let bCount = 0; bCount <= n; bCount++) {
+                let i = aCount + bCount;
+                if (i === 0) continue;
+
+                dp[aCount][bCount] = Infinity;
+                if (aCount > 0) {
+                    dp[aCount][bCount] = Math.min(dp[aCount][bCount], dp[aCount - 1][bCount] + costs[i - 1][0]);
+                }
+                if (bCount > 0) {
+                    dp[aCount][bCount] = Math.min(dp[aCount][bCount], dp[aCount][bCount - 1] + costs[i - 1][1]);
+                }
+            }
+        }
+
+        return dp[n][n];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+> Where $n$ is the half of the size of the array $costs$.
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def twoCitySchedCost(self, costs: List[List[int]]) -> int:
+        n = len(costs) // 2
+        dp = [0] * (n + 1)
+
+        for aCount in range(n + 1):
+            for bCount in range(n + 1):
+                i = aCount + bCount
+                if i == 0:
+                    continue
+
+                tmp = dp[bCount]
+                dp[bCount] = float("inf")
+                if aCount > 0:
+                    dp[bCount] = min(dp[bCount], tmp + costs[i - 1][0])
+                if bCount > 0:
+                    dp[bCount] = min(dp[bCount], dp[bCount - 1] + costs[i - 1][1])
+
+        return dp[n]
+```
+
+```java
+public class Solution {
+    public int twoCitySchedCost(int[][] costs) {
+        int n = costs.length / 2;
+        int[] dp = new int[n + 1];
+
+        for (int aCount = 0; aCount <= n; aCount++) {
+            for (int bCount = 0; bCount <= n; bCount++) {
+                int i = aCount + bCount;
+                if (i == 0) continue;
+
+                int tmp = dp[bCount];
+                dp[bCount] = Integer.MAX_VALUE;
+                if (aCount > 0) {
+                    dp[bCount] = Math.min(dp[bCount], tmp + costs[i - 1][0]);
+                }
+                if (bCount > 0) {
+                    dp[bCount] = Math.min(dp[bCount], dp[bCount - 1] + costs[i - 1][1]);
+                }
+            }
+        }
+
+        return dp[n];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int twoCitySchedCost(vector<vector<int>>& costs) {
+        int n = costs.size() / 2;
+        vector<int> dp(n + 1, 0);
+
+        for (int aCount = 0; aCount <= n; aCount++) {
+            for (int bCount = 0; bCount <= n; bCount++) {
+                int i = aCount + bCount;
+                if (i == 0) continue;
+
+                int tmp = dp[bCount];
+                dp[bCount] = INT_MAX;
+                if (aCount > 0) {
+                    dp[bCount] = min(dp[bCount], tmp + costs[i - 1][0]);
+                }
+                if (bCount > 0) {
+                    dp[bCount] = min(dp[bCount], dp[bCount - 1] + costs[i - 1][1]);
+                }
+            }
+        }
+
+        return dp[n];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} costs
+     * @return {number}
+     */
+    twoCitySchedCost(costs) {
+        let n = costs.length / 2;
+        let dp = new Array(n + 1).fill(0);
+
+        for (let aCount = 0; aCount <= n; aCount++) {
+            for (let bCount = 0; bCount <= n; bCount++) {
+                let i = aCount + bCount;
+                if (i === 0) continue;
+
+                let tmp = dp[bCount];
+                dp[bCount] = Infinity;
+                if (aCount > 0) {
+                    dp[bCount] = Math.min(dp[bCount], tmp + costs[i - 1][0]);
+                }
+                if (bCount > 0) {
+                    dp[bCount] = Math.min(dp[bCount], dp[bCount - 1] + costs[i - 1][1]);
+                }
+            }
+        }
+
+        return dp[n];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the half of the size of the array $costs$.
+
+---
+
+## 5. Greedy
+
+::tabs-start
+
+```python
+class Solution:
+    def twoCitySchedCost(self, costs: List[List[int]]) -> int:
+        diffs = []
+        for c1, c2 in costs:
+            diffs.append([c2 - c1, c1, c2])
+
+        diffs.sort()
+        res = 0
+        for i in range(len(diffs)):
+            if i < len(diffs) // 2:
+                res += diffs[i][2]
+            else:
+                res += diffs[i][1]
+
+        return res
+```
+
+```java
+public class Solution {
+    public int twoCitySchedCost(int[][] costs) {
+        List<int[]> diffs = new ArrayList<>();
+        for (int[] cost : costs) {
+            diffs.add(new int[]{cost[1] - cost[0], cost[0], cost[1]});
+        }
+
+        diffs.sort(Comparator.comparingInt(a -> a[0]));
+
+        int res = 0;
+        for (int i = 0; i < diffs.size(); i++) {
+            if (i < diffs.size() / 2) {
+                res += diffs.get(i)[2];
+            } else {
+                res += diffs.get(i)[1];
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int twoCitySchedCost(vector<vector<int>>& costs) {
+        vector<vector<int>> diffs;
+        for (auto& cost : costs) {
+            diffs.push_back({cost[1] - cost[0], cost[0], cost[1]});
+        }
+
+        sort(diffs.begin(), diffs.end());
+
+        int res = 0;
+        for (int i = 0; i < diffs.size(); i++) {
+            if (i < diffs.size() / 2) {
+                res += diffs[i][2];
+            } else {
+                res += diffs[i][1];
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} costs
+     * @return {number}
+     */
+    twoCitySchedCost(costs) {
+        let diffs = [];
+        for (let cost of costs) {
+            diffs.push([cost[1] - cost[0], cost[0], cost[1]]);
+        }
+
+        diffs.sort((a, b) => a[0] - b[0]);
+
+        let res = 0;
+        for (let i = 0; i < diffs.length; i++) {
+            if (i < diffs.length / 2) {
+                res += diffs[i][2];
+            } else {
+                res += diffs[i][1];
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 6. Greedy (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def twoCitySchedCost(self, costs: List[List[int]]) -> int:
+        costs.sort(key=lambda x: x[1] - x[0])
+        n, res = len(costs) // 2, 0
+
+        for i in range(n):
+            res += costs[i][1] + costs[i + n][0]
+        return res
+```
+
+```java
+public class Solution {
+    public int twoCitySchedCost(int[][] costs) {
+        Arrays.sort(costs, (a, b) -> Integer.compare(a[1] - a[0], b[1] - b[0]));
+        int n = costs.length / 2, res = 0;
+
+        for (int i = 0; i < n; i++) {
+            res += costs[i][1] + costs[i + n][0];
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int twoCitySchedCost(vector<vector<int>>& costs) {
+        sort(costs.begin(), costs.end(), [](const auto& a, const auto& b) {
+            return (a[1] - a[0]) < (b[1] - b[0]);
+        });
+
+        int n = costs.size() / 2, res = 0;
+        for (int i = 0; i < n; i++) {
+            res += costs[i][1] + costs[i + n][0];
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} costs
+     * @return {number}
+     */
+    twoCitySchedCost(costs) {
+        costs.sort((a, b) => (a[1] - a[0]) - (b[1] - b[0]));
+        let n = costs.length / 2, res = 0;
+
+        for (let i = 0; i < n; i++) {
+            res += costs[i][1] + costs[i + n][0];
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
\ No newline at end of file
diff --git a/articles/two-integer-sum-ii.md b/articles/two-integer-sum-ii.md
index 39a06fc55..f63e71a60 100644
--- a/articles/two-integer-sum-ii.md
+++ b/articles/two-integer-sum-ii.md
@@ -78,6 +78,49 @@ public class Solution {
 }
 ```
 
+```go
+func twoSum(numbers []int, target int) []int {
+    for i := 0; i < len(numbers); i++ {
+        for j := i + 1; j < len(numbers); j++ {
+            if numbers[i]+numbers[j] == target {
+                return []int{i + 1, j + 1}
+            }
+        }
+    }
+    return []int{}
+}
+```
+
+```kotlin
+class Solution {
+    fun twoSum(numbers: IntArray, target: Int): IntArray {
+        for (i in numbers.indices) {
+            for (j in i + 1 until numbers.size) {
+                if (numbers[i] + numbers[j] == target) {
+                    return intArrayOf(i + 1, j + 1)
+                }
+            }
+        }
+        return intArrayOf()
+    }
+}
+```
+
+```swift
+class Solution {
+    func twoSum(_ numbers: [Int], _ target: Int) -> [Int] {
+        for i in 0..<numbers.count {
+            for j in (i + 1)..<numbers.count {
+                if numbers[i] + numbers[j] == target {
+                    return [i + 1, j + 1]
+                }
+            }
+        }
+        return []
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -202,6 +245,70 @@ public class Solution {
 }
 ```
 
+```go
+func twoSum(numbers []int, target int) []int {
+    for i := 0; i < len(numbers); i++ {
+        l, r := i+1, len(numbers)-1
+        tmp := target - numbers[i]
+        for l <= r {
+            mid := l + (r-l)/2
+            if numbers[mid] == tmp {
+                return []int{i + 1, mid + 1}
+            } else if numbers[mid] < tmp {
+                l = mid + 1
+            } else {
+                r = mid - 1
+            }
+        }
+    }
+    return []int{}
+}
+```
+
+```kotlin
+class Solution {
+    fun twoSum(numbers: IntArray, target: Int): IntArray {
+        for (i in numbers.indices) {
+            var l = i + 1
+            var r = numbers.size - 1
+            val tmp = target - numbers[i]
+            while (l <= r) {
+                val mid = l + (r - l) / 2
+                when {
+                    numbers[mid] == tmp -> return intArrayOf(i + 1, mid + 1)
+                    numbers[mid] < tmp -> l = mid + 1
+                    else -> r = mid - 1
+                }
+            }
+        }
+        return intArrayOf()
+    }
+}
+```
+
+```swift
+class Solution {
+    func twoSum(_ numbers: [Int], _ target: Int) -> [Int] {
+        for i in 0..<numbers.count {
+            var l = i + 1, r = numbers.count - 1
+            let tmp = target - numbers[i]
+
+            while l <= r {
+                let mid = l + (r - l) / 2
+                if numbers[mid] == tmp {
+                    return [i + 1, mid + 1]
+                } else if numbers[mid] < tmp {
+                    l = mid + 1
+                } else {
+                    r = mid - 1
+                }
+            }
+        }
+        return []
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -297,6 +404,54 @@ public class Solution {
 }
 ```
 
+```go
+func twoSum(numbers []int, target int) []int {
+    mp := make(map[int]int)
+    for i := 0; i < len(numbers); i++ {
+        tmp := target - numbers[i]
+        if val, exists := mp[tmp]; exists {
+            return []int{val, i + 1}
+        }
+        mp[numbers[i]] = i + 1
+    }
+    return []int{}
+}
+```
+
+```kotlin
+class Solution {
+    fun twoSum(numbers: IntArray, target: Int): IntArray {
+        val mp = HashMap<Int, Int>()
+        for (i in numbers.indices) {
+            val tmp = target - numbers[i]
+            if (mp.containsKey(tmp)) {
+                return intArrayOf(mp[tmp]!!, i + 1)
+            }
+            mp[numbers[i]] = i + 1
+        }
+        return intArrayOf()
+    }
+}
+```
+
+```swift
+class Solution {
+    func twoSum(_ numbers: [Int], _ target: Int) -> [Int] {
+        var mp = [Int: Int]()
+
+        for i in 0..<numbers.count {
+            let tmp = target - numbers[i]
+            if let index = mp[tmp] {
+                return [index, i + 1]
+            }
+            mp[numbers[i]] = i + 1
+        }
+
+        return []
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -417,6 +572,64 @@ public class Solution {
 }
 ```
 
+```go
+func twoSum(numbers []int, target int) []int {
+    l, r := 0, len(numbers) - 1
+
+    for l < r {
+        curSum := numbers[l] + numbers[r]
+        if curSum > target {
+            r--
+        } else if curSum < target {
+            l++
+        } else {
+            return []int{l + 1, r + 1}
+        }
+    }
+    return []int{}
+}
+```
+
+```kotlin
+class Solution {
+    fun twoSum(numbers: IntArray, target: Int): IntArray {
+        var l = 0
+        var r = numbers.size - 1
+
+        while (l < r) {
+            val curSum = numbers[l] + numbers[r]
+            when {
+                curSum > target -> r--
+                curSum < target -> l++
+                else -> return intArrayOf(l + 1, r + 1)
+            }
+        }
+        return intArrayOf()
+    }
+}
+```
+
+```swift
+class Solution {
+    func twoSum(_ numbers: [Int], _ target: Int) -> [Int] {
+        var l = 0, r = numbers.count - 1
+
+        while l < r {
+            let curSum = numbers[l] + numbers[r]
+
+            if curSum > target {
+                r -= 1
+            } else if curSum < target {
+                l += 1
+            } else {
+                return [l + 1, r + 1]
+            }
+        }
+        return []
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/two-integer-sum.md b/articles/two-integer-sum.md
index 607956d4d..9fba0afdc 100644
--- a/articles/two-integer-sum.md
+++ b/articles/two-integer-sum.md
@@ -78,6 +78,49 @@ public class Solution {
 }
 ```
 
+```go
+func twoSum(nums []int, target int) []int {
+    for i := 0; i < len(nums); i++ {
+        for j := i + 1; j < len(nums); j++ {
+            if nums[i] + nums[j] == target {
+                return []int{i, j}
+            }
+        }
+    }
+    return []int{}
+}
+```
+
+```kotlin
+class Solution {
+    fun twoSum(nums: IntArray, target: Int): IntArray {
+        for (i in nums.indices) {
+            for (j in i + 1 until nums.size) {
+                if (nums[i] + nums[j] == target) {
+                    return intArrayOf(i, j)
+                }
+            }
+        }
+        return intArrayOf()
+    }
+}
+```
+
+```swift
+class Solution {
+    func twoSum(_ nums: [Int], _ target: Int) -> [Int] {
+        for i in 0..<nums.count {
+            for j in (i + 1)..<nums.count {
+                if nums[i] + nums[j] == target {
+                    return [i, j]
+                }
+            }
+        }
+        return []
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -229,6 +272,90 @@ public class Solution {
 }
 ```
 
+```go
+func twoSum(nums []int, target int) []int {
+    A := make([][2]int, len(nums))
+    for i, num := range nums {
+        A[i] = [2]int{num, i}
+    }
+    
+    sort.Slice(A, func(i, j int) bool {
+        return A[i][0] < A[j][0]
+    })
+    
+    i, j := 0, len(nums)-1
+    for i < j {
+        cur := A[i][0] + A[j][0]
+        if cur == target {
+            if A[i][1] < A[j][1] {
+                return []int{A[i][1], A[j][1]}
+            } else {
+                return []int{A[j][1], A[i][1]}
+            }
+        } else if cur < target {
+            i++
+        } else {
+            j--
+        }
+    }
+    return []int{}
+}
+```
+
+```kotlin
+class Solution {
+    fun twoSum(nums: IntArray, target: Int): IntArray {
+        val A = nums.mapIndexed { index, num -> num to index }.toMutableList()
+        A.sortBy { it.first }
+
+        var i = 0
+        var j = nums.size - 1
+        while (i < j) {
+            val cur = A[i].first + A[j].first
+            if (cur == target) {
+                return intArrayOf(
+                    minOf(A[i].second, A[j].second),
+                    maxOf(A[i].second, A[j].second)
+                )
+            } else if (cur < target) {
+                i++
+            } else {
+                j--
+            }
+        }
+        return intArrayOf()
+    }
+}
+```
+
+```swift
+class Solution {
+    func twoSum(_ nums: [Int], _ target: Int) -> [Int] {
+        var A = [(Int, Int)]()
+        for (i, num) in nums.enumerated() {
+            A.append((num, i))
+        }
+
+        A.sort { $0.0 < $1.0 }
+        var i = 0
+        var j = nums.count - 1
+
+        while i < j {
+            let cur = A[i].0 + A[j].0
+            if cur == target {
+                return [min(A[i].1, A[j].1), 
+                        max(A[i].1, A[j].1)]
+            } else if cur < target {
+                i += 1
+            } else {
+                j -= 1
+            }
+        }
+        return []
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -347,6 +474,65 @@ public class Solution {
 }
 ```
 
+```go
+func twoSum(nums []int, target int) []int {
+    indices := make(map[int]int)
+
+    for i, n := range nums {
+        indices[n] = i
+    }
+
+    for i, n := range nums {
+        diff := target - n
+        if j, found := indices[diff]; found && j != i {
+            return []int{i, j}
+        }
+    }
+    return []int{}
+}
+```
+
+```kotlin
+class Solution {
+    fun twoSum(nums: IntArray, target: Int): IntArray {
+        val indices = HashMap<Int, Int>()
+
+        for ((i, n) in nums.withIndex()) {
+            indices[n] = i
+        }
+
+        for ((i, n) in nums.withIndex()) {
+            val diff = target - n
+            if (indices.containsKey(diff) && indices[diff] != i) {
+                return intArrayOf(i, indices[diff]!!)
+            }
+        }
+        return intArrayOf()
+    }
+}
+```
+
+```swift
+class Solution {
+    func twoSum(_ nums: [Int], _ target: Int) -> [Int] {
+        var indices = [Int: Int]() // val -> index
+
+        for (i, n) in nums.enumerated() {
+            indices[n] = i
+        }
+
+        for (i, n) in nums.enumerated() {
+            let diff = target - n
+            if let j = indices[diff], j != i {
+                return [i, j]
+            }
+        }
+
+        return []
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -453,6 +639,56 @@ public class Solution {
 }
 ```
 
+```go
+func twoSum(nums []int, target int) []int {
+    prevMap := make(map[int]int)
+
+    for i, n := range nums {
+        diff := target - n
+        if j, found := prevMap[diff]; found {
+            return []int{j, i}
+        }
+        prevMap[n] = i
+    }
+    return []int{}
+}
+```
+
+```kotlin
+class Solution {
+    fun twoSum(nums: IntArray, target: Int): IntArray {
+        val prevMap = HashMap<Int, Int>()
+
+        for ((i, n) in nums.withIndex()) {
+            val diff = target - n
+            if (prevMap.containsKey(diff)) {
+                return intArrayOf(prevMap[diff]!!, i)
+            }
+            prevMap[n] = i
+        }
+        return intArrayOf()
+    }
+}
+```
+
+```swift
+class Solution {
+    func twoSum(_ nums: [Int], _ target: Int) -> [Int] {
+        var prevMap = [Int: Int]() // val -> index
+
+        for (i, n) in nums.enumerated() {
+            let diff = target - n
+            if let index = prevMap[diff] {
+                return [index, i]
+            }
+            prevMap[n] = i
+        }
+
+        return []
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/ugly-number.md b/articles/ugly-number.md
new file mode 100644
index 000000000..f2a68a2e5
--- /dev/null
+++ b/articles/ugly-number.md
@@ -0,0 +1,76 @@
+## 1. Math
+
+::tabs-start
+
+```python
+class Solution:
+    def isUgly(self, n: int) -> bool:
+        if n <= 0:
+            return False
+        
+        for p in [2, 3, 5]:
+            while n % p == 0:
+                n //= p
+        
+        return n == 1
+```
+
+```java
+public class Solution {
+    public boolean isUgly(int n) {
+        if (n <= 0) return false;
+
+        for (int p = 2; p <= 5 && n > 0; p++) {
+            while (n % p == 0) {
+                n /= p;
+            }
+        }
+
+        return n == 1;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isUgly(int n) {
+        if (n <= 0) return false;
+
+        for (int p = 2; p <= 5 && n > 0; p++) {
+            while (n % p == 0) {
+                n /= p;
+            }
+        }
+
+        return n == 1;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {boolean}
+     */
+    isUgly(n) {
+        if (n <= 0) return false;
+
+        for (let p of [2, 3, 5]) {
+            while (n % p == 0) {
+                n /= p;
+            }
+        }
+
+        return n === 1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/uncommon-words-from-two-sentences.md b/articles/uncommon-words-from-two-sentences.md
new file mode 100644
index 000000000..67be56a4b
--- /dev/null
+++ b/articles/uncommon-words-from-two-sentences.md
@@ -0,0 +1,183 @@
+## 1. Hash Map - I
+
+::tabs-start
+
+```python
+class Solution:
+    def uncommonFromSentences(self, s1: str, s2: str) -> List[str]:
+        count = defaultdict(int)
+        for w in s1.split(" ") + s2.split(" "):
+            count[w] += 1
+
+        res = []
+        for w, cnt in count.items():
+            if cnt == 1:
+                res.append(w)
+        return res
+```
+
+```java
+public class Solution {
+    public String[] uncommonFromSentences(String s1, String s2) {
+        String[] words = (s1 + " " + s2).split(" ");
+        Map<String, Integer> count = new HashMap<>();
+
+        for (String w : words) {
+            count.put(w, count.getOrDefault(w, 0) + 1);
+        }
+
+        List<String> res = new ArrayList<>();
+        for (Map.Entry<String, Integer> entry : count.entrySet()) {
+            if (entry.getValue() == 1) {
+                res.add(entry.getKey());
+            }
+        }
+
+        return res.toArray(new String[0]);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<string> uncommonFromSentences(string s1, string s2) {
+        unordered_map<string, int> count;
+        istringstream ss(s1 + " " + s2);
+        string w;
+        while (ss >> w) {
+            count[w]++;
+        }
+
+        vector<string> res;
+        for (auto& [word, freq] : count) {
+            if (freq == 1) {
+                res.push_back(word);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s1
+     * @param {string} s2
+     * @return {string[]}
+     */
+    uncommonFromSentences(s1, s2) {
+        const words = (s1 + " " + s2).split(" ");
+        const count = new Map();
+
+        for (const w of words) {
+            count.set(w, (count.get(w) || 0) + 1);
+        }
+
+        const res = [];
+        for (const [w, c] of count.entries()) {
+            if (c === 1) {
+                res.push(w);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(n + m)$
+
+> Where $n$ and $m$ are the lengths of the strings $s1$ and $s2$, respectively.
+
+---
+
+## 2. Hash Map - II
+
+::tabs-start
+
+```python
+class Solution:
+    def uncommonFromSentences(self, s1: str, s2: str) -> List[str]:
+        return [w for w, cnt in Counter(s1.split(" ") + s2.split(" ")).items() if cnt == 1]
+```
+
+```java
+public class Solution {
+    public String[] uncommonFromSentences(String s1, String s2) {
+        String[] words = (s1 + " " + s2).split(" ");
+        Map<String, Integer> count = new HashMap<>();
+
+        for (String w : words) {
+            count.put(w, count.getOrDefault(w, 0) + 1);
+        }
+
+        return count.entrySet()
+                    .stream()
+                    .filter(e -> e.getValue() == 1)
+                    .map(Map.Entry::getKey)
+                    .toArray(String[]::new);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<string> uncommonFromSentences(string s1, string s2) {
+        unordered_map<string, int> count;
+        istringstream ss(s1 + " " + s2);
+        string w;
+        while (ss >> w) {
+            count[w]++;
+        }
+
+        vector<string> res;
+        for (auto& [w, c] : count) {
+            if (c == 1) {
+                res.push_back(w);
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s1
+     * @param {string} s2
+     * @return {string[]}
+     */
+    uncommonFromSentences(s1, s2) {
+        const words = (s1 + " " + s2).split(" ");
+        const count = new Map();
+
+        for (const w of words) {
+            count.set(w, (count.get(w) || 0) + 1);
+        }
+
+        return [...count.entries()]
+            .filter(([_, c]) => c === 1)
+            .map(([w]) => w);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(n + m)$
+
+> Where $n$ and $m$ are the lengths of the strings $s1$ and $s2$, respectively.
\ No newline at end of file
diff --git a/articles/uncrossed-lines.md b/articles/uncrossed-lines.md
new file mode 100644
index 000000000..a08442f64
--- /dev/null
+++ b/articles/uncrossed-lines.md
@@ -0,0 +1,560 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def maxUncrossedLines(self, nums1: List[int], nums2: List[int]) -> int:
+        def dfs(i, j):
+            if i == len(nums1) or j == len(nums2):
+                return 0
+            
+            if nums1[i] == nums2[j]:
+                return 1 + dfs(i + 1, j + 1)
+            return max(dfs(i, j + 1), dfs(i + 1, j))
+        
+        return dfs(0, 0)
+```
+
+```java
+public class Solution {
+    public int maxUncrossedLines(int[] nums1, int[] nums2) {
+        int n1 = nums1.length, n2 = nums2.length;
+
+        return dfs(nums1, nums2, 0, 0);
+    }
+
+    private int dfs(int[] nums1, int[] nums2, int i, int j) {
+        if (i == nums1.length || j == nums2.length) return 0;
+
+        if (nums1[i] == nums2[j]) {
+            return 1 + dfs(nums1, nums2, i + 1, j + 1);
+        }
+        return Math.max(dfs(nums1, nums2, i, j + 1), dfs(nums1, nums2, i + 1, j));
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int dfs(vector<int>& nums1, vector<int>& nums2, int i, int j) {
+        if (i == nums1.size() || j == nums2.size()) return 0;
+        
+        if (nums1[i] == nums2[j]) {
+            return 1 + dfs(nums1, nums2, i + 1, j + 1);
+        }
+        return max(dfs(nums1, nums2, i, j + 1), dfs(nums1, nums2, i + 1, j));
+    }
+    
+    int maxUncrossedLines(vector<int>& nums1, vector<int>& nums2) {
+        return dfs(nums1, nums2, 0, 0);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums1
+     * @param {number[]} nums2
+     * @return {number}
+     */
+    maxUncrossedLines(nums1, nums2) {
+        const dfs = (i, j) => {
+            if (i === nums1.length || j === nums2.length) {
+                return 0;
+            }
+            if (nums1[i] === nums2[j]) {
+                return 1 + dfs(i + 1, j + 1);
+            }
+            return Math.max(dfs(i, j + 1), dfs(i + 1, j));
+        };
+
+        return dfs(0, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ {n + m})$
+* Space complexity: $O(n + m)$ for recursion stack.
+
+> Where $n$ and $m$ are the sizes of the arrays $nums1$ and $nums2$ respectively.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxUncrossedLines(self, nums1: List[int], nums2: List[int]) -> int:
+        dp = {}
+
+        def dfs(i, j):
+            if i == len(nums1) or j == len(nums2):
+                return 0
+
+            if (i, j) in dp:
+                return dp[(i, j)]
+
+            if nums1[i] == nums2[j]:
+                dp[(i, j)] = 1 + dfs(i + 1, j + 1)
+            else:
+                dp[(i, j)] = max(dfs(i, j + 1), dfs(i + 1, j))
+            
+            return dp[(i, j)]
+        
+        return dfs(0, 0)
+```
+
+```java
+public class Solution {
+    public int maxUncrossedLines(int[] nums1, int[] nums2) {
+        int n = nums1.length, m = nums2.length;
+        int[][] dp = new int[n][m];
+
+        for (int[] row : dp) {
+            Arrays.fill(row, -1);
+        }
+
+        return dfs(0, 0, nums1, nums2, dp);
+    }
+
+    private int dfs(int i, int j, int[] nums1, int[] nums2, int[][] dp) {
+        if (i == nums1.length || j == nums2.length) {
+            return 0;
+        }
+
+        if (dp[i][j] != -1) {
+            return dp[i][j];
+        }
+
+        if (nums1[i] == nums2[j]) {
+            dp[i][j] = 1 + dfs(i + 1, j + 1, nums1, nums2, dp);
+        } else {
+            dp[i][j] = Math.max(dfs(i, j + 1, nums1, nums2, dp), dfs(i + 1, j, nums1, nums2, dp));
+        }
+
+        return dp[i][j];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxUncrossedLines(vector<int>& nums1, vector<int>& nums2) {
+        int n = nums1.size(), m = nums2.size();
+        vector<vector<int>> dp(n, vector<int>(m, -1));
+
+        return dfs(0, 0, nums1, nums2, dp);
+    }
+
+private:
+    int dfs(int i, int j, vector<int>& nums1, vector<int>& nums2, vector<vector<int>>& dp) {
+        if (i == nums1.size() || j == nums2.size()) {
+            return 0;
+        }
+
+        if (dp[i][j] != -1) {
+            return dp[i][j];
+        }
+
+        if (nums1[i] == nums2[j]) {
+            dp[i][j] = 1 + dfs(i + 1, j + 1, nums1, nums2, dp);
+        } else {
+            dp[i][j] = max(dfs(i, j + 1, nums1, nums2, dp), dfs(i + 1, j, nums1, nums2, dp));
+        }
+
+        return dp[i][j];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums1
+     * @param {number[]} nums2
+     * @return {number}
+     */
+    maxUncrossedLines(nums1, nums2) {
+        const n = nums1.length, m = nums2.length;
+        const dp = Array.from({ length: n }, () => Array(m).fill(-1));
+
+        const dfs = (i, j) => {
+            if (i === n || j === m) {
+                return 0;
+            }
+
+            if (dp[i][j] !== -1) {
+                return dp[i][j];
+            }
+
+            if (nums1[i] === nums2[j]) {
+                dp[i][j] = 1 + dfs(i + 1, j + 1);
+            } else {
+                dp[i][j] = Math.max(dfs(i, j + 1), dfs(i + 1, j));
+            }
+
+            return dp[i][j];
+        };
+
+        return dfs(0, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n * m)$
+
+> Where $n$ and $m$ are the sizes of the arrays $nums1$ and $nums2$ respectively.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxUncrossedLines(self, nums1: List[int], nums2: List[int]) -> int:
+        n, m = len(nums1), len(nums2)
+        dp = [[0] * (m + 1) for _ in range(n + 1)]
+
+        for i in range(n):
+            for j in range(m):
+                if nums1[i] == nums2[j]:
+                    dp[i + 1][j + 1] = 1 + dp[i][j]
+                else:
+                    dp[i + 1][j + 1] = max(dp[i][j + 1], dp[i + 1][j])
+        
+        return dp[n][m]
+```
+
+```java
+public class Solution {
+    public int maxUncrossedLines(int[] nums1, int[] nums2) {
+        int n = nums1.length, m = nums2.length;
+        int[][] dp = new int[n + 1][m + 1];
+
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < m; j++) {
+                if (nums1[i] == nums2[j]) {
+                    dp[i + 1][j + 1] = 1 + dp[i][j];
+                } else {
+                    dp[i + 1][j + 1] = Math.max(dp[i][j + 1], dp[i + 1][j]);
+                }
+            }
+        }
+
+        return dp[n][m];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxUncrossedLines(vector<int>& nums1, vector<int>& nums2) {
+        int n = nums1.size(), m = nums2.size();
+        vector<vector<int>> dp(n + 1, vector<int>(m + 1, 0));
+
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < m; j++) {
+                if (nums1[i] == nums2[j]) {
+                    dp[i + 1][j + 1] = 1 + dp[i][j];
+                } else {
+                    dp[i + 1][j + 1] = max(dp[i][j + 1], dp[i + 1][j]);
+                }
+            }
+        }
+
+        return dp[n][m];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums1
+     * @param {number[]} nums2
+     * @return {number}
+     */
+    maxUncrossedLines(nums1, nums2) {
+        const n = nums1.length, m = nums2.length;
+        const dp = Array.from({ length: n + 1 }, () => Array(m + 1).fill(0));
+
+        for (let i = 0; i < n; i++) {
+            for (let j = 0; j < m; j++) {
+                if (nums1[i] === nums2[j]) {
+                    dp[i + 1][j + 1] = 1 + dp[i][j];
+                } else {
+                    dp[i + 1][j + 1] = Math.max(dp[i][j + 1], dp[i + 1][j]);
+                }
+            }
+        }
+
+        return dp[n][m];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n * m)$
+
+> Where $n$ and $m$ are the sizes of the arrays $nums1$ and $nums2$ respectively.
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxUncrossedLines(self, nums1: List[int], nums2: List[int]) -> int:
+        prev = [0] * (len(nums2) + 1)
+
+        for i in range(len(nums1)):
+            dp = [0] * (len(nums2) + 1)
+            for j in range(len(nums2)):
+                if nums1[i] == nums2[j]:
+                    dp[j + 1] = 1 + prev[j]
+                else:
+                    dp[j + 1] = max(dp[j], prev[j + 1])
+            prev = dp
+
+        return prev[len(nums2)]
+```
+
+```java
+public class Solution {
+    public int maxUncrossedLines(int[] nums1, int[] nums2) {
+        int[] prev = new int[nums2.length + 1];
+
+        for (int i = 0; i < nums1.length; i++) {
+            int[] dp = new int[nums2.length + 1];
+            for (int j = 0; j < nums2.length; j++) {
+                if (nums1[i] == nums2[j]) {
+                    dp[j + 1] = 1 + prev[j];
+                } else {
+                    dp[j + 1] = Math.max(dp[j], prev[j + 1]);
+                }
+            }
+            prev = dp;
+        }
+
+        return prev[nums2.length];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxUncrossedLines(vector<int>& nums1, vector<int>& nums2) {
+        vector<int> prev(nums2.size() + 1, 0);
+
+        for (int i = 0; i < nums1.size(); i++) {
+            vector<int> dp(nums2.size() + 1, 0);
+            for (int j = 0; j < nums2.size(); j++) {
+                if (nums1[i] == nums2[j]) {
+                    dp[j + 1] = 1 + prev[j];
+                } else {
+                    dp[j + 1] = max(dp[j], prev[j + 1]);
+                }
+            }
+            prev = dp;
+        }
+
+        return prev[nums2.size()];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums1
+     * @param {number[]} nums2
+     * @return {number}
+     */
+    maxUncrossedLines(nums1, nums2) {
+        let prev = new Array(nums2.length + 1).fill(0);
+
+        for (let i = 0; i < nums1.length; i++) {
+            const dp = new Array(nums2.length + 1).fill(0);
+            for (let j = 0; j < nums2.length; j++) {
+                if (nums1[i] === nums2[j]) {
+                    dp[j + 1] = 1 + prev[j];
+                } else {
+                    dp[j + 1] = Math.max(dp[j], prev[j + 1]);
+                }
+            }
+            prev = dp;
+        }
+
+        return prev[nums2.length];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(m)$
+
+> Where $n$ and $m$ are the sizes of the arrays $nums1$ and $nums2$ respectively.
+
+---
+
+## 5. Dynamic Programming (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def maxUncrossedLines(self, nums1: List[int], nums2: List[int]) -> int:
+        n, m = len(nums1), len(nums2)
+        if m > n:
+            n, m = m, n
+            nums1, nums2 = nums2, nums1
+
+        dp = [0] * (m + 1)
+
+        for i in range(n):
+            prev = 0
+            for j in range(m):
+                temp = dp[j + 1]
+                if nums1[i] == nums2[j]:
+                    dp[j + 1] = 1 + prev
+                else:
+                    dp[j + 1] = max(dp[j + 1], dp[j])
+                prev = temp
+
+        return dp[m]
+```
+
+```java
+public class Solution {
+    public int maxUncrossedLines(int[] nums1, int[] nums2) {
+        int n = nums1.length, m = nums2.length;
+        if (m > n) {
+            int[] tempArr = nums1;
+            nums1 = nums2;
+            nums2 = tempArr;
+            int temp = n;
+            n = m;
+            m = temp;
+        }
+
+        int[] dp = new int[m + 1];
+
+        for (int i = 0; i < n; i++) {
+            int prev = 0;
+            for (int j = 0; j < m; j++) {
+                int temp = dp[j + 1];
+                if (nums1[i] == nums2[j]) {
+                    dp[j + 1] = 1 + prev;
+                } else {
+                    dp[j + 1] = Math.max(dp[j + 1], dp[j]);
+                }
+                prev = temp;
+            }
+        }
+
+        return dp[m];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxUncrossedLines(vector<int>& nums1, vector<int>& nums2) {
+        int n = nums1.size(), m = nums2.size();
+        if (m > n) {
+            swap(nums1, nums2);
+            swap(n, m);
+        }
+
+        vector<int> dp(m + 1, 0);
+
+        for (int i = 0; i < n; i++) {
+            int prev = 0;
+            for (int j = 0; j < m; j++) {
+                int temp = dp[j + 1];
+                if (nums1[i] == nums2[j]) {
+                    dp[j + 1] = 1 + prev;
+                } else {
+                    dp[j + 1] = max(dp[j + 1], dp[j]);
+                }
+                prev = temp;
+            }
+        }
+
+        return dp[m];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums1
+     * @param {number[]} nums2
+     * @return {number}
+     */
+    maxUncrossedLines(nums1, nums2) {
+        let n = nums1.length, m = nums2.length;
+        if (m > n) {
+            [nums1, nums2] = [nums2, nums1];
+            [n, m] = [m, n];
+        }
+
+        const dp = Array(m + 1).fill(0);
+
+        for (let i = 0; i < n; i++) {
+            let prev = 0;
+            for (let j = 0; j < m; j++) {
+                const temp = dp[j + 1];
+                if (nums1[i] === nums2[j]) {
+                    dp[j + 1] = 1 + prev;
+                } else {
+                    dp[j + 1] = Math.max(dp[j + 1], dp[j]);
+                }
+                prev = temp;
+            }
+        }
+
+        return dp[m];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(min(n, m))$
+
+> Where $n$ and $m$ are the sizes of the arrays $nums1$ and $nums2$ respectively.
\ No newline at end of file
diff --git a/articles/unique-binary-search-trees-ii.md b/articles/unique-binary-search-trees-ii.md
new file mode 100644
index 000000000..3c3a4ccee
--- /dev/null
+++ b/articles/unique-binary-search-trees-ii.md
@@ -0,0 +1,670 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def generateTrees(self, n: int) -> List[Optional[TreeNode]]:
+        def generate(left, right):
+            if left > right:
+                return [None]
+
+            res = []
+            for val in range(left, right + 1):
+                for leftTree in generate(left, val - 1):
+                    for rightTree in generate(val + 1, right):
+                        root = TreeNode(val, leftTree, rightTree)
+                        res.append(root)
+            return res
+
+        return generate(1, n)
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<TreeNode> generateTrees(int n) {
+        return generate(1, n);
+    }
+
+    private List<TreeNode> generate(int left, int right) {
+        List<TreeNode> res = new ArrayList<>();
+        if (left > right) {
+            res.add(null);
+            return res;
+        }
+
+        for (int val = left; val <= right; val++) {
+            List<TreeNode> leftTrees = generate(left, val - 1);
+            List<TreeNode> rightTrees = generate(val + 1, right);
+
+            for (TreeNode leftTree : leftTrees) {
+                for (TreeNode rightTree : rightTrees) {
+                    res.add(new TreeNode(val, leftTree, rightTree));
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    vector<TreeNode*> generateTrees(int n) {
+        return generate(1, n);
+    }
+
+private:
+    vector<TreeNode*> generate(int left, int right) {
+        if (left > right) return {nullptr};
+
+        vector<TreeNode*> res;
+        for (int val = left; val <= right; val++) {
+            vector<TreeNode*> leftTrees = generate(left, val - 1);
+            vector<TreeNode*> rightTrees = generate(val + 1, right);
+
+            for (auto& leftTree : leftTrees) {
+                for (auto& rightTree : rightTrees) {
+                    res.push_back(new TreeNode(val, leftTree, rightTree));
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {number} n
+     * @return {TreeNode[]}
+     */
+    generateTrees(n) {
+        const generate = (left, right) => {
+            if (left > right) return [null];
+
+            let res = [];
+            for (let val = left; val <= right; val++) {
+                let leftTrees = generate(left, val - 1);
+                let rightTrees = generate(val + 1, right);
+
+                for (let leftTree of leftTrees) {
+                    for (let rightTree of rightTrees) {
+                        res.push(new TreeNode(val, leftTree, rightTree));
+                    }
+                }
+            }
+            return res;
+        };
+
+        return generate(1, n);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\frac {4 ^ n}{\sqrt {n}})$
+* Space complexity:
+    * $O(n)$ space for recursion stack.
+    * $O(\frac {4 ^ n}{\sqrt {n}})$ space for the output.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def generateTrees(self, n: int) -> List[Optional[TreeNode]]:
+        dp = {}
+
+        def generate(left, right):
+            if left > right:
+                return [None]
+            if (left, right) in dp:
+                return dp[(left, right)]
+
+            res = []
+            for val in range(left, right + 1):
+                for leftTree in generate(left, val - 1):
+                    for rightTree in generate(val + 1, right):
+                        root = TreeNode(val, leftTree, rightTree)
+                        res.append(root)
+
+            dp[(left, right)] = res
+            return res
+
+        return generate(1, n)
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    private List<TreeNode>[][] dp;
+
+    public List<TreeNode> generateTrees(int n) {
+        dp = new ArrayList[n + 1][n + 1];
+        return generate(1, n);
+    }
+
+    private List<TreeNode> generate(int left, int right) {
+        if (left > right) return Collections.singletonList(null);
+        if (dp[left][right] != null) return dp[left][right];
+
+        List<TreeNode> res = new ArrayList<>();
+        for (int val = left; val <= right; val++) {
+            for (TreeNode leftTree : generate(left, val - 1)) {
+                for (TreeNode rightTree : generate(val + 1, right)) {
+                    res.add(new TreeNode(val, leftTree, rightTree));
+                }
+            }
+        }
+        return dp[left][right] = res;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    vector<vector<vector<TreeNode*>>> dp;
+
+    vector<TreeNode*> generateTrees(int n) {
+        dp.resize(n + 1, vector<vector<TreeNode*>>(n + 1));
+        return generate(1, n);
+    }
+
+private:
+    vector<TreeNode*> generate(int left, int right) {
+        if (left > right) return {nullptr};
+        if (!dp[left][right].empty()) return dp[left][right];
+
+        vector<TreeNode*> res;
+        for (int val = left; val <= right; val++) {
+            for (auto& leftTree : generate(left, val - 1)) {
+                for (auto& rightTree : generate(val + 1, right)) {
+                    res.push_back(new TreeNode(val, leftTree, rightTree));
+                }
+            }
+        }
+        return dp[left][right] = res;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {number} n
+     * @return {TreeNode[]}
+     */
+    generateTrees(n) {
+        const dp = Array.from({ length: n + 1 }, () => Array(n + 1).fill(null));
+
+        const generate = (left, right) => {
+            if (left > right) return [null];
+            if (dp[left][right]) return dp[left][right];
+
+            let res = [];
+            for (let val = left; val <= right; val++) {
+                for (let leftTree of generate(left, val - 1)) {
+                    for (let rightTree of generate(val + 1, right)) {
+                        res.push(new TreeNode(val, leftTree, rightTree));
+                    }
+                }
+            }
+            return (dp[left][right] = res);
+        };
+
+        return generate(1, n);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\frac {4 ^ n}{\sqrt {n}})$
+* Space complexity:
+    * $O(n)$ space for recursion stack.
+    * $O(n ^ 2)$ extra space.
+    * $O(\frac {4 ^ n}{\sqrt {n}})$ space for the output.
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def generateTrees(self, n: int) -> List[Optional[TreeNode]]:
+        dp = [[[] for _ in range(n + 2)] for _ in range(n + 2)]
+        for i in range(1, n + 2):
+            dp[i][i - 1] = [None]
+
+        for length in range(1, n + 1):
+            for left in range(1, n - length + 2):
+                right = left + length - 1
+                dp[left][right] = []
+                for val in range(left, right + 1):
+                    for leftTree in dp[left][val - 1]:
+                        for rightTree in dp[val + 1][right]:
+                            root = TreeNode(val, leftTree, rightTree)
+                            dp[left][right].append(root)
+
+        return dp[1][n]
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<TreeNode> generateTrees(int n) {
+        List<TreeNode>[][] dp = new ArrayList[n + 2][n + 2];
+        for (int i = 1; i <= n + 1; i++) {
+            dp[i][i - 1] = new ArrayList<>();
+            dp[i][i - 1].add(null);
+        }
+
+        for (int length = 1; length <= n; length++) {
+            for (int left = 1; left + length - 1 <= n; left++) {
+                int right = left + length - 1;
+                dp[left][right] = new ArrayList<>();
+
+                for (int val = left; val <= right; val++) {
+                    for (TreeNode leftTree : dp[left][val - 1]) {
+                        for (TreeNode rightTree : dp[val + 1][right]) {
+                            dp[left][right].add(new TreeNode(val, leftTree, rightTree));
+                        }
+                    }
+                }
+            }
+        }
+        return dp[1][n];
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    vector<TreeNode*> generateTrees(int n) {
+        vector<vector<vector<TreeNode*>>> dp(n + 2, vector<vector<TreeNode*>>(n + 2));
+        for (int i = 1; i <= n + 1; i++) {
+            dp[i][i - 1].push_back(nullptr);
+        }
+
+        for (int length = 1; length <= n; length++) {
+            for (int left = 1; left + length - 1 <= n; left++) {
+                int right = left + length - 1;
+
+                for (int val = left; val <= right; val++) {
+                    for (auto& leftTree : dp[left][val - 1]) {
+                        for (auto& rightTree : dp[val + 1][right]) {
+                            dp[left][right].push_back(new TreeNode(val, leftTree, rightTree));
+                        }
+                    }
+                }
+            }
+        }
+        return dp[1][n];
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {number} n
+     * @return {TreeNode[]}
+     */
+    generateTrees(n) {
+        const dp = Array.from({ length: n + 2 }, () => Array(n + 2).fill(null));
+        for (let i = 1; i <= n + 1; i++) {
+            dp[i][i - 1] = [null];
+        }
+
+        for (let length = 1; length <= n; length++) {
+            for (let left = 1; left + length - 1 <= n; left++) {
+                let right = left + length - 1;
+                dp[left][right] = [];
+
+                for (let val = left; val <= right; val++) {
+                    for (let leftTree of dp[left][val - 1]) {
+                        for (let rightTree of dp[val + 1][right]) {
+                            dp[left][right].push(new TreeNode(val, leftTree, rightTree));
+                        }
+                    }
+                }
+            }
+        }
+        return dp[1][n];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\frac {4 ^ n}{\sqrt {n}})$
+* Space complexity:
+    * $O(n ^ 2)$ extra space.
+    * $O(\frac {4 ^ n}{\sqrt {n}})$ space for the output.
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def generateTrees(self, n: int) -> list[Optional[TreeNode]]:
+        dp = [[] for _ in range(n + 1)]
+        dp[0] = [None]
+
+        for length in range(1, n + 1):
+            dp[length] = []
+            for val in range(1, length + 1):
+                for leftTree in dp[val - 1]:
+                    for rightTree in dp[length - val]:
+                        root = TreeNode(val)
+                        root.left = leftTree
+                        root.right = self.shift(rightTree, val)
+                        dp[length].append(root)
+
+        return dp[n]
+
+    def shift(self, node: Optional[TreeNode], offset: int) -> Optional[TreeNode]:
+        if not node:
+            return None
+        root = TreeNode(node.val + offset)
+        root.left = self.shift(node.left, offset)
+        root.right = self.shift(node.right, offset)
+        return root
+```
+
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public List<TreeNode> generateTrees(int n) {
+        List<TreeNode>[] dp = new ArrayList[n + 1];
+        dp[0] = new ArrayList<>();
+        dp[0].add(null);
+
+        for (int length = 1; length <= n; length++) {
+            dp[length] = new ArrayList<>();
+            for (int val = 1; val <= length; val++) {
+                for (TreeNode leftTree : dp[val - 1]) {
+                    for (TreeNode rightTree : dp[length - val]) {
+                        TreeNode root = new TreeNode(val);
+                        root.left = leftTree;
+                        root.right = shift(rightTree, val);
+                        dp[length].add(root);
+                    }
+                }
+            }
+        }
+        return dp[n];
+    }
+
+    private TreeNode shift(TreeNode node, int offset) {
+        if (node == null) return null;
+        TreeNode root = new TreeNode(node.val + offset);
+        root.left = shift(node.left, offset);
+        root.right = shift(node.right, offset);
+        return root;
+    }
+}
+```
+
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    vector<TreeNode*> generateTrees(int n) {
+        vector<vector<TreeNode*>> dp(n + 1);
+        dp[0].push_back(nullptr);
+
+        for (int length = 1; length <= n; length++) {
+            for (int val = 1; val <= length; val++) {
+                for (auto& leftTree : dp[val - 1]) {
+                    for (auto& rightTree : dp[length - val]) {
+                        TreeNode* root = new TreeNode(val);
+                        root->left = leftTree;
+                        root->right = shift(rightTree, val);
+                        dp[length].push_back(root);
+                    }
+                }
+            }
+        }
+        return dp[n];
+    }
+
+private:
+    TreeNode* shift(TreeNode* node, int offset) {
+        if (!node) return nullptr;
+        TreeNode* root = new TreeNode(node->val + offset);
+        root->left = shift(node->left, offset);
+        root->right = shift(node->right, offset);
+        return root;
+    }
+};
+```
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     constructor(val = 0, left = null, right = null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    /**
+     * @param {number} n
+     * @return {TreeNode[]}
+     */
+    generateTrees(n) {
+        const shift = (node, offset) => {
+            if (!node) return null;
+            let root = new TreeNode(node.val + offset);
+            root.left = shift(node.left, offset);
+            root.right = shift(node.right, offset);
+            return root;
+        };
+
+        let dp = Array.from({ length: n + 1 }, () => []);
+        dp[0].push(null);
+
+        for (let length = 1; length <= n; length++) {
+            for (let val = 1; val <= length; val++) {
+                for (let leftTree of dp[val - 1]) {
+                    for (let rightTree of dp[length - val]) {
+                        let root = new TreeNode(val);
+                        root.left = leftTree;
+                        root.right = shift(rightTree, val);
+                        dp[length].push(root);
+                    }
+                }
+            }
+        }
+        return dp[n];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\frac {4 ^ n}{\sqrt {n}})$
+* Space complexity:
+    * $O(n)$ for the recursion stack.
+    * $O(n)$ extra space.
+    * $O(\frac {4 ^ n}{\sqrt {n}})$ space for the output.
\ No newline at end of file
diff --git a/articles/unique-binary-search-trees.md b/articles/unique-binary-search-trees.md
new file mode 100644
index 000000000..499868203
--- /dev/null
+++ b/articles/unique-binary-search-trees.md
@@ -0,0 +1,411 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def numTrees(self, n: int) -> int:
+        if n <= 1:
+            return 1
+
+        res = 0
+        for i in range(1, n + 1):
+            res += self.numTrees(i - 1) * self.numTrees(n - i)
+        return res
+```
+
+```java
+public class Solution {
+    public int numTrees(int n) {
+        if (n <= 1) {
+            return 1;
+        }
+
+        int res = 0;
+        for (int i = 1; i <= n; i++) {
+            res += numTrees(i - 1) * numTrees(n - i);
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numTrees(int n) {
+        if (n <= 1) {
+            return 1;
+        }
+
+        int res = 0;
+        for (int i = 1; i <= n; i++) {
+            res += numTrees(i - 1) * numTrees(n - i);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    numTrees(n) {
+        if (n <= 1) {
+            return 1;
+        }
+
+        let res = 0;
+        for (let i = 1; i <= n; i++) {
+            res += this.numTrees(i - 1) * this.numTrees(n - i);
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(3 ^ n)$
+* Space complexity: $O(n)$ for recursion stack.
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+
+    def __init__(self):
+        self.dp = {}
+
+    def numTrees(self, n: int) -> int:
+        if n <= 1:
+            return 1
+        if n in self.dp:
+            return self.dp[n]
+
+        res = 0
+        for i in range(1, n + 1):
+            res += self.numTrees(i - 1) * self.numTrees(n - i)
+
+        self.dp[n] = res
+        return res
+```
+
+```java
+public class Solution {
+    private Map<Integer, Integer> dp = new HashMap<>();
+
+    public int numTrees(int n) {
+        if (n <= 1) {
+            return 1;
+        }
+        if (dp.containsKey(n)) {
+            return dp.get(n);
+        }
+
+        int res = 0;
+        for (int i = 1; i <= n; i++) {
+            res += numTrees(i - 1) * numTrees(n - i);
+        }
+
+        dp.put(n, res);
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    unordered_map<int, int> dp;
+
+public:
+    int numTrees(int n) {
+        if (n <= 1) {
+            return 1;
+        }
+        if (dp.find(n) != dp.end()) {
+            return dp[n];
+        }
+
+        int res = 0;
+        for (int i = 1; i <= n; i++) {
+            res += numTrees(i - 1) * numTrees(n - i);
+        }
+
+        dp[n] = res;
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    constructor() {
+        this.dp = new Map();
+    }
+
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    numTrees(n) {
+        if (n <= 1) {
+            return 1;
+        }
+        if (this.dp.has(n)) {
+            return this.dp.get(n);
+        }
+
+        let res = 0;
+        for (let i = 1; i <= n; i++) {
+            res += this.numTrees(i - 1) * this.numTrees(n - i);
+        }
+
+        this.dp.set(n, res);
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def numTrees(self, n: int) -> int:
+        numTree = [1] * (n + 1)
+
+        for nodes in range(2, n + 1):
+            total = 0
+            for root in range(1, nodes + 1):
+                left = root - 1
+                right = nodes - root
+                total += numTree[left] * numTree[right]
+            numTree[nodes] = total
+
+        return numTree[n]
+```
+
+```java
+public class Solution {
+    public int numTrees(int n) {
+        int[] numTree = new int[n + 1];
+        numTree[0] = 1;
+        numTree[1] = 1;
+
+        for (int nodes = 2; nodes <= n; nodes++) {
+            int total = 0;
+            for (int root = 1; root <= nodes; root++) {
+                int left = root - 1;
+                int right = nodes - root;
+                total += numTree[left] * numTree[right];
+            }
+            numTree[nodes] = total;
+        }
+
+        return numTree[n];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numTrees(int n) {
+        vector<int> numTree(n + 1, 1);
+
+        for (int nodes = 2; nodes <= n; ++nodes) {
+            int total = 0;
+            for (int root = 1; root <= nodes; ++root) {
+                int left = root - 1;
+                int right = nodes - root;
+                total += numTree[left] * numTree[right];
+            }
+            numTree[nodes] = total;
+        }
+
+        return numTree[n];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    numTrees(n) {
+        const numTree = Array(n + 1).fill(1);
+
+        for (let nodes = 2; nodes <= n; nodes++) {
+            let total = 0;
+            for (let root = 1; root <= nodes; root++) {
+                let left = root - 1;
+                let right = nodes - root;
+                total += numTree[left] * numTree[right];
+            }
+            numTree[nodes] = total;
+        }
+
+        return numTree[n];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Catalan Numbers - I
+
+::tabs-start
+
+```python
+class Solution:
+    def numTrees(self, n: int) -> int:
+        res = 1
+        for i in range(1, n):
+            res *= (n + i + 1)
+            res //= i
+        return res // n
+```
+
+```java
+public class Solution {
+    public int numTrees(int n) {
+        long res = 1;
+        for (int i = 1; i < n; i++) {
+            res *= (n + i + 1);
+            res /= i;
+        }
+        return (int) (res / n);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numTrees(int n) {
+        long long res = 1;
+        for (int i = 1; i < n; i++) {
+            res *= (n + i + 1);
+            res /= i;
+        }
+        return res / n;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    numTrees(n) {
+        let res = 1n;
+        for (let i = 1n; i < BigInt(n); i++) {
+            res *= BigInt(n) + i + 1n;
+            res /= i;
+        }
+        return Number(res / BigInt(n));
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
+
+---
+
+## 5. Catalan Numbers - II
+
+::tabs-start
+
+```python
+class Solution:
+    def numTrees(self, n: int) -> int:
+        res = 1
+        for i in range(n):
+            res *= (4 * i + 2) / (i + 2)
+        return int(res)
+```
+
+```java
+public class Solution {
+    public int numTrees(int n) {
+        long res = 1;
+        for (int i = 0; i < n; i++) {
+            res *= (4 * i + 2) / (i + 2.0);
+        }
+        return (int) res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numTrees(int n) {
+        long long res = 1;
+        for (int i = 0; i < n; i++) {
+            res *= (4 * i + 2) / (i + 2.0);
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @return {number}
+     */
+    numTrees(n) {
+        let res = 1;
+        for (let i = 0; i < n; i++) {
+            res *= (4 * i + 2) / (i + 2);
+        }
+        return Math.floor(res);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/unique-email-addresses.md b/articles/unique-email-addresses.md
new file mode 100644
index 000000000..41aead4ae
--- /dev/null
+++ b/articles/unique-email-addresses.md
@@ -0,0 +1,197 @@
+## 1. Built-In Functions
+
+::tabs-start
+
+```python
+class Solution:
+    def numUniqueEmails(self, emails: List[str]) -> int:
+        unique = set()
+
+        for e in emails:
+            local, domain = e.split('@')
+            local = local.split("+")[0]
+            local = local.replace(".", "")
+            unique.add((local, domain))
+        return len(unique)
+```
+
+```java
+public class Solution {
+    public int numUniqueEmails(String[] emails) {
+        Set<String> unique = new HashSet<>();
+        
+        for (String e : emails) {
+            String[] parts = e.split("@");
+            String local = parts[0];
+            String domain = parts[1];
+            
+            local = local.split("\\+")[0];
+            local = local.replace(".", "");
+            unique.add(local + "@" + domain);
+        }
+        return unique.size();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numUniqueEmails(vector<string>& emails) {
+        unordered_set<string> unique;
+        
+        for (string e : emails) {
+            string local = e.substr(0, e.find('@'));
+            local = local.substr(0, local.find('+'));
+            erase(local, '.');
+            unique.insert(local + e.substr(e.find('@')));
+        }      
+        return unique.size();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} emails
+     * @return {number}
+     */
+    numUniqueEmails(emails) {
+        const unique = new Set();
+        
+        for (let e of emails) {
+            let [local, domain] = e.split('@');
+            local = local.split('+')[0];
+            local = local.replace(/\./g, '');
+            unique.add(`${local}@${domain}`);
+        }
+        return unique.size;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the number of strings in the array, and $m$ is the average length of these strings.
+
+---
+
+## 2. Iteration
+
+::tabs-start
+
+```python
+class Solution:
+    def numUniqueEmails(self, emails: List[str]) -> int:
+        unique = set()
+
+        for e in emails:
+            i, local = 0, ""
+            while e[i] not in ["@", "+"]:
+                if e[i] != ".":
+                    local += e[i]
+                i += 1
+            
+            while e[i] != "@":
+                i += 1
+            domain = e[i + 1:]
+            unique.add((local, domain))
+        return len(unique)
+```
+
+```java
+public class Solution {
+    public int numUniqueEmails(String[] emails) {
+        Set<String> unique = new HashSet<>();
+        
+        for (String e : emails) {
+            int i = 0;
+            StringBuilder local = new StringBuilder();
+            while (i < e.length() && e.charAt(i) != '@' && e.charAt(i) != '+') {
+                if (e.charAt(i) != '.') {
+                    local.append(e.charAt(i));
+                }
+                i++;
+            }
+            
+            while (i < e.length() && e.charAt(i) != '@') {
+                i++;
+            }   
+            String domain = e.substring(i + 1);
+            unique.add(local.toString() + "@" + domain);
+        }
+        return unique.size();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numUniqueEmails(vector<string>& emails) {
+        unordered_set<string> unique;
+        
+        for (string e : emails) {
+            int i = 0;
+            string local = "";
+            while (i < e.length() && e[i] != '@' && e[i] != '+') {
+                if (e[i] != '.') {
+                    local += e[i];
+                }
+                i++;
+            }
+            
+            while (i < e.length() && e[i] != '@') {
+                i++;
+            }
+            string domain = e.substr(i + 1);
+            unique.insert(local + "@" + domain);
+        }
+        return unique.size();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} emails
+     * @return {number}
+     */
+    numUniqueEmails(emails) {
+        const unique = new Set();
+        
+        for (let e of emails) {
+            let i = 0, local = "";
+            while (i < e.length && e[i] !== '@' && e[i] !== '+') {
+                if (e[i] !== '.') {
+                    local += e[i];
+                }
+                i++;
+            }
+            
+            while (i < e.length && e[i] !== '@') {
+                i++;
+            }
+            const domain = e.slice(i + 1);
+            unique.add(`${local}@${domain}`);
+        }
+        return unique.size;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(n)$
+
+> Where $n$ is the number of strings in the array, and $m$ is the average length of these strings.
\ No newline at end of file
diff --git a/articles/unique-length-3-palindromic-subsequences.md b/articles/unique-length-3-palindromic-subsequences.md
new file mode 100644
index 000000000..642af0a41
--- /dev/null
+++ b/articles/unique-length-3-palindromic-subsequences.md
@@ -0,0 +1,863 @@
+## 1. Brute Force (Recursion)
+
+::tabs-start
+
+```python
+class Solution:
+    def countPalindromicSubsequence(self, s: str) -> int:
+        res = set()
+
+        def rec(i, cur):
+            if len(cur) == 3:
+                if cur[0] == cur[2]:
+                    res.add(cur)
+                return
+            if i == len(s):
+                return
+            rec(i + 1, cur)
+            rec(i + 1, cur + s[i])
+
+        rec(0, "")
+        return len(res)
+```
+
+```java
+public class Solution {
+    public int countPalindromicSubsequence(String s) {
+        Set<String> res = new HashSet<>();
+        rec(s, 0, "", res);
+        return res.size();
+    }
+
+    private void rec(String s, int i, String cur, Set<String> res) {
+        if (cur.length() == 3) {
+            if (cur.charAt(0) == cur.charAt(2)) {
+                res.add(cur);
+            }
+            return;
+        }
+        if (i == s.length()) {
+            return;
+        }
+        rec(s, i + 1, cur, res);
+        rec(s, i + 1, cur + s.charAt(i), res);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countPalindromicSubsequence(string s) {
+        unordered_set<string> res;
+        rec(s, 0, "", res);
+        return res.size();
+    }
+
+private:
+    void rec(const string& s, int i, string cur, unordered_set<string>& res) {
+        if (cur.length() == 3) {
+            if (cur[0] == cur[2]) {
+                res.insert(cur);
+            }
+            return;
+        }
+        if (i == s.length()) {
+            return;
+        }
+        rec(s, i + 1, cur, res);
+        rec(s, i + 1, cur + s[i], res);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    countPalindromicSubsequence(s) {
+        const res = new Set();
+
+        const rec = (i, cur) => {
+            if (cur.length === 3) {
+                if (cur[0] === cur[2]) {
+                    res.add(cur);
+                }
+                return;
+            }
+            if (i === s.length) {
+                return;
+            }
+            rec(i + 1, cur);
+            rec(i + 1, cur + s[i]);
+        };
+
+        rec(0, "");
+        return res.size;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(2 ^ n)$
+* Space complexity: $O(n + m)$
+
+> Where $n$ is the length of the string $s$ and $m$ is the number of unique three length pallindromic subsequences (26 * 26 = 676).
+
+---
+
+## 2. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def countPalindromicSubsequence(self, s: str) -> int:
+        res = set()
+
+        for i in range(len(s) - 2):
+            for j in range(i + 1, len(s) - 1):
+                for k in range(j + 1, len(s)):
+                    if s[i] != s[k]:
+                        continue
+                    res.add(s[i] + s[j] + s[k])
+        return len(res)
+```
+
+```java
+public class Solution {
+    public int countPalindromicSubsequence(String s) {
+        Set<String> res = new HashSet<>();
+
+        for (int i = 0; i < s.length() - 2; i++) {
+            for (int j = i + 1; j < s.length() - 1; j++) {
+                for (int k = j + 1; k < s.length(); k++) {
+                    if (s.charAt(i) != s.charAt(k)) {
+                        continue;
+                    }
+                    res.add("" + s.charAt(i) + s.charAt(j) + s.charAt(k));
+                }
+            }
+        }
+        return res.size();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countPalindromicSubsequence(string s) {
+        unordered_set<string> res;
+
+        for (int i = 0; i < s.length() - 2; i++) {
+            for (int j = i + 1; j < s.length() - 1; j++) {
+                for (int k = j + 1; k < s.length(); k++) {
+                    if (s[i] != s[k]) {
+                        continue;
+                    }
+                    res.insert(string() + s[i] + s[j] + s[k]);
+                }
+            }
+        }
+        return res.size();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    countPalindromicSubsequence(s) {
+        const res = new Set();
+
+        for (let i = 0; i < s.length - 2; i++) {
+            for (let j = i + 1; j < s.length - 1; j++) {
+                for (let k = j + 1; k < s.length; k++) {
+                    if (s[i] !== s[k]) {
+                        continue;
+                    }
+                    res.add(s[i] + s[j] + s[k]);
+                }
+            }
+        }
+        return res.size;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 3)$
+* Space complexity: $O(m)$
+
+> Where $n$ is the length of the string $s$ and $m$ is the number of unique three length pallindromic subsequences (26 * 26 = 676).
+
+---
+
+## 3. Sequential Matching for Each Pallindrome
+
+::tabs-start
+
+```python
+class Solution:
+    def countPalindromicSubsequence(self, s: str) -> int:
+        res = 0
+        for ends in range(ord('a'), ord('z') + 1):
+            for mid in range(ord('a'), ord('z') + 1):
+                seq = chr(ends) + chr(mid) + chr(ends)
+                idx, found = 0, 0
+                for c in s:
+                    if seq[idx] == c:
+                        idx += 1
+                        if idx == 3:
+                            found = 1
+                            break
+                res += found
+        return res
+```
+
+```java
+public class Solution {
+    public int countPalindromicSubsequence(String s) {
+        int res = 0;
+        for (char ends = 'a'; ends <= 'z'; ends++) {
+            for (char mid = 'a'; mid <= 'z'; mid++) {
+                String seq = "" + ends + mid + ends;
+                int idx = 0, found = 0;
+                for (char c : s.toCharArray()) {
+                    if (seq.charAt(idx) == c) {
+                        idx++;
+                        if (idx == 3) {
+                            found = 1;
+                            break;
+                        }
+                    }
+                }
+                res += found;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countPalindromicSubsequence(string s) {
+        int res = 0;
+        for (char ends = 'a'; ends <= 'z'; ends++) {
+            for (char mid = 'a'; mid <= 'z'; mid++) {
+                string seq = string() + ends + mid + ends;
+                int idx = 0, found = 0;
+                for (char& c : s) {
+                    if (seq[idx] == c) {
+                        idx++;
+                        if (idx == 3) {
+                            found = 1;
+                            break;
+                        }
+                    }
+                }
+                res += found;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    countPalindromicSubsequence(s) {
+        let res = 0;
+        for (let ends = 'a'.charCodeAt(0); ends <= 'z'.charCodeAt(0); ends++) {
+            for (let mid = 'a'.charCodeAt(0); mid <= 'z'.charCodeAt(0); mid++) {
+                const seq = String.fromCharCode(ends) + 
+                            String.fromCharCode(mid) + 
+                            String.fromCharCode(ends);
+                let idx = 0, found = 0;
+                for (const c of s) {
+                    if (seq[idx] === c) {
+                        idx++;
+                        if (idx === 3) {
+                            found = 1;
+                            break;
+                        }
+                    }
+                }
+                res += found;
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(1)$
+
+> Where $n$ is the length of the string $s$ and $m$ is the number of unique three length pallindromic subsequences (26 * 26 = 676).
+
+---
+
+## 4. Iterate On Middle Characters
+
+::tabs-start
+
+```python
+class Solution:
+    def countPalindromicSubsequence(self, s: str) -> int:
+        res = set()
+        left = set()
+        right = collections.Counter(s)
+        
+        for i in range(len(s)):
+            right[s[i]] -= 1
+            if right[s[i]] == 0:
+                right.pop(s[i])
+            
+            for j in range(26):
+                c = chr(ord('a') + j)
+                if c in left and c in right:
+                    res.add((s[i], c))
+            left.add(s[i])
+            
+        return len(res)
+```
+
+```java
+public class Solution {
+    public int countPalindromicSubsequence(String s) {
+        Set<String> res = new HashSet<>();
+        Set<Character> left = new HashSet<>();
+        int[] right = new int[26];
+
+        for (char c : s.toCharArray()) {
+            right[c - 'a']++;
+        }
+
+        for (int i = 0; i < s.length(); i++) {
+            right[s.charAt(i) - 'a']--;
+            if (right[s.charAt(i) - 'a'] == 0) {
+                right[s.charAt(i) - 'a'] = -1;
+            }
+
+            for (int j = 0; j < 26; j++) {
+                char c = (char) (j + 'a');
+                if (left.contains(c) && right[j] > 0) {
+                    res.add("" + s.charAt(i) + c);
+                }
+            }
+            left.add(s.charAt(i));
+        }
+
+        return res.size();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countPalindromicSubsequence(string s) {
+        unordered_set<string> res;
+        unordered_set<char> left;
+        vector<int> right(26, 0);
+
+        for (char c : s) {
+            right[c - 'a']++;
+        }
+
+        for (int i = 0; i < s.length(); i++) {
+            right[s[i] - 'a']--;
+            if (right[s[i] - 'a'] == 0) {
+                right[s[i] - 'a'] = -1;
+            }
+
+            for (int j = 0; j < 26; j++) {
+                char c = 'a' + j;
+                if (left.count(c) && right[j] > 0) {
+                    res.insert(string() + s[i] + c);
+                }
+            }
+            left.insert(s[i]);
+        }
+
+        return res.size();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    countPalindromicSubsequence(s) {
+        const res = new Set();
+        const left = new Set();
+        const right = Array(26).fill(0);
+
+        for (const c of s) {
+            right[c.charCodeAt(0) - 'a'.charCodeAt(0)]++;
+        }
+
+        for (let i = 0; i < s.length; i++) {
+            right[s.charCodeAt(i) - 'a'.charCodeAt(0)]--;
+            if (right[s.charCodeAt(i) - 'a'.charCodeAt(0)] === 0) {
+                right[s.charCodeAt(i) - 'a'.charCodeAt(0)] = -1;
+            }
+
+            for (let j = 0; j < 26; j++) {
+                const c = String.fromCharCode('a'.charCodeAt(0) + j);
+                if (left.has(c) && right[j] > 0) {
+                    res.add(s[i] + c);
+                }
+            }
+            left.add(s[i]);
+        }
+
+        return res.size;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(26 * n)$
+* Space complexity: $O(m)$
+
+> Where $n$ is the length of the string $s$ and $m$ is the number of unique three length pallindromic subsequences (26 * 26 = 676).
+
+---
+
+## 5. Prefix Count
+
+::tabs-start
+
+```python
+class Solution:
+    def countPalindromicSubsequence(self, s: str) -> int:
+        n = len(s)
+        prefix = [[0] * 26 for _ in range(n + 1)]
+        firstIndex = [-1] * 26
+        lastIndex = [-1] * 26
+
+        for i in range(n):
+            j = ord(s[i]) - ord('a')
+            if firstIndex[j] == -1:
+                firstIndex[j] = i
+            lastIndex[j] = i
+            prefix[i + 1] = prefix[i][:]
+            prefix[i + 1][j] += 1
+
+        res = 0
+        for ends in range(26):
+            if firstIndex[ends] == -1 or firstIndex[ends] == lastIndex[ends]:
+                continue
+            l, r = firstIndex[ends], lastIndex[ends]
+            for mid in range(26):
+                if prefix[r][mid] - prefix[l + 1][mid] > 0:
+                    res += 1
+        return res
+```
+
+```java
+public class Solution {
+    public int countPalindromicSubsequence(String s) {
+        int n = s.length();
+        int[][] prefix = new int[n + 1][26];
+        int[] firstIndex = new int[26];
+        int[] lastIndex = new int[26];
+        Arrays.fill(firstIndex, -1);
+        Arrays.fill(lastIndex, -1);
+
+        for (int i = 0; i < n; i++) {
+            int j = s.charAt(i) - 'a';
+            if (firstIndex[j] == -1) {
+                firstIndex[j] = i;
+            }
+            lastIndex[j] = i;
+            for (int k = 0; k < 26; k++) {
+                prefix[i + 1][k] = prefix[i][k];
+            }
+            prefix[i + 1][j]++;
+        }
+
+        int res = 0;
+        for (int ends = 0; ends < 26; ends++) {
+            if (firstIndex[ends] == -1 || firstIndex[ends] == lastIndex[ends]) {
+                continue;
+            }
+            int l = firstIndex[ends], r = lastIndex[ends];
+            for (int mid = 0; mid < 26; mid++) {
+                if (prefix[r][mid] - prefix[l + 1][mid] > 0) {
+                    res++;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countPalindromicSubsequence(string s) {
+        int n = s.length();
+        vector<vector<int>> prefix(n + 1, vector<int>(26));
+        vector<int> firstIndex(26, -1);
+        vector<int> lastIndex(26, -1);
+
+        for (int i = 0; i < n; i++) {
+            int j = s[i] - 'a';
+            if (firstIndex[j] == -1) {
+                firstIndex[j] = i;
+            }
+            lastIndex[j] = i;
+            prefix[i + 1] = prefix[i];
+            prefix[i + 1][j]++;
+        }
+
+        int res = 0;
+        for (int ends = 0; ends < 26; ends++) {
+            if (firstIndex[ends] == -1 || firstIndex[ends] == lastIndex[ends]) {
+                continue;
+            }
+            int l = firstIndex[ends], r = lastIndex[ends];
+            for (int mid = 0; mid < 26; mid++) {
+                if (prefix[r][mid] - prefix[l + 1][mid] > 0) {
+                    res++;
+                }
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    countPalindromicSubsequence(s) {
+        const n = s.length;
+        const prefix = Array.from({ length: n + 1 }, () => Array(26).fill(0));
+        const firstIndex = Array(26).fill(-1);
+        const lastIndex = Array(26).fill(-1);
+
+        for (let i = 0; i < n; i++) {
+            const j = s.charCodeAt(i) - 'a'.charCodeAt(0);
+            if (firstIndex[j] === -1) {
+                firstIndex[j] = i;
+            }
+            lastIndex[j] = i;
+            for (let k = 0; k < 26; k++) {
+                prefix[i + 1][k] = prefix[i][k];
+            }
+            prefix[i + 1][j]++;
+        }
+
+        let res = 0;
+        for (let ends = 0; ends < 26; ends++) {
+            if (firstIndex[ends] === -1 || firstIndex[ends] === lastIndex[ends]) {
+                continue;
+            }
+            const l = firstIndex[ends], r = lastIndex[ends];
+            for (let mid = 0; mid < 26; mid++) {
+                if (prefix[r][mid] - prefix[l + 1][mid] > 0) {
+                    res++;
+                }
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(26 * n)$
+* Space complexity: $O(26 * n)$
+
+---
+
+## 6. First And Last Index
+
+::tabs-start
+
+```python
+class Solution:
+    def countPalindromicSubsequence(self, s: str) -> int:
+        res = 0
+
+        for i in range(26):
+            c = chr(ord('a') + i)
+            l, r = s.find(c), s.rfind(c)
+            if l == -1 or l == r:
+                continue
+            
+            mids = set()
+            for j in range(l + 1, r):
+                mids.add(s[j])
+            res += len(mids)
+        
+        return res
+```
+
+```java
+public class Solution {
+    public int countPalindromicSubsequence(String s) {
+        int res = 0;
+
+        for (char c = 'a'; c <= 'z'; c++) {
+            int l = s.indexOf(c), r = s.lastIndexOf(c);
+            if (l == -1 || l == r) continue;
+
+            Set<Character> mids = new HashSet<>();
+            for (int j = l + 1; j < r; j++) {
+                mids.add(s.charAt(j));
+            }
+            res += mids.size();
+        }
+        
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countPalindromicSubsequence(string s) {
+        int res = 0;
+
+        for (char c = 'a'; c <= 'z'; c++) {
+            int l = s.find(c), r = s.rfind(c);
+            if (l == -1 || l == r) continue;
+
+            unordered_set<char> mids;
+            for (int j = l + 1; j < r; j++) {
+                mids.insert(s[j]);
+            }
+            res += mids.size();
+        }
+        
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    countPalindromicSubsequence(s) {
+        let res = 0;
+
+        for (let i = 0; i < 26; i++) {
+            const c = String.fromCharCode('a'.charCodeAt(0) + i);
+            const l = s.indexOf(c), r = s.lastIndexOf(c);
+            if (l === -1 || l === r) continue;
+
+            const mids = new Set();
+            for (let j = l + 1; j < r; j++) {
+                mids.add(s[j]);
+            }
+            res += mids.size;
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(26 * n)$
+* Space complexity: $O(1)$ since we have at most $26$ different characters.
+
+---
+
+## 7. First And Last Index (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def countPalindromicSubsequence(self, s: str) -> int:
+        firstIndex = [-1] * 26
+        lastIndex = [-1] * 26
+
+        for i in range(len(s)):
+            j = ord(s[i]) - ord('a')
+            if firstIndex[j] == -1:
+                firstIndex[j] = i
+            lastIndex[j] = i
+
+        res = 0
+        for ends in range(26):
+            if firstIndex[ends] == -1 or firstIndex[ends] == lastIndex[ends]:
+                continue
+            l, r = firstIndex[ends], lastIndex[ends]
+            mask = 0
+            for i in range(l + 1, r):
+                c = ord(s[i]) - ord('a')
+                if mask & (1 << c):
+                    continue
+                mask |= (1 << c)
+                res += 1
+
+        return res
+```
+
+```java
+public class Solution {
+    public int countPalindromicSubsequence(String s) {
+        int[] firstIndex = new int[26];
+        int[] lastIndex = new int[26];
+        Arrays.fill(firstIndex, -1);
+        Arrays.fill(lastIndex, -1);
+
+        for (int i = 0; i < s.length(); i++) {
+            int j = s.charAt(i) - 'a';
+            if (firstIndex[j] == -1) {
+                firstIndex[j] = i;
+            }
+            lastIndex[j] = i;
+        }
+
+        int res = 0;
+        for (int ends = 0; ends < 26; ends++) {
+            if (firstIndex[ends] == -1 || firstIndex[ends] == lastIndex[ends]) {
+                continue;
+            }
+            int l = firstIndex[ends], r = lastIndex[ends];
+            int mask = 0;
+            for (int i = l + 1; i < r; i++) {
+                int c = s.charAt(i) - 'a';
+                if ((mask & (1 << c)) != 0) {
+                    continue;
+                }
+                mask |= (1 << c);
+                res++;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int countPalindromicSubsequence(string s) {
+        vector<int> firstIndex(26, -1);
+        vector<int> lastIndex(26, -1);
+
+        for (int i = 0; i < s.size(); i++) {
+            int j = s[i] - 'a';
+            if (firstIndex[j] == -1) {
+                firstIndex[j] = i;
+            }
+            lastIndex[j] = i;
+        }
+
+        int res = 0;
+        for (int ends = 0; ends < 26; ends++) {
+            if (firstIndex[ends] == -1 || firstIndex[ends] == lastIndex[ends]) {
+                continue;
+            }
+            int l = firstIndex[ends], r = lastIndex[ends];
+            int mask = 0;
+            for (int i = l + 1; i < r; i++) {
+                int c = s[i] - 'a';
+                if (mask & (1 << c)) {
+                    continue;
+                }
+                mask |= (1 << c);
+                res++;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {number}
+     */
+    countPalindromicSubsequence(s) {
+        const firstIndex = Array(26).fill(-1);
+        const lastIndex = Array(26).fill(-1);
+
+        for (let i = 0; i < s.length; i++) {
+            const j = s.charCodeAt(i) - 'a'.charCodeAt(0);
+            if (firstIndex[j] === -1) {
+                firstIndex[j] = i;
+            }
+            lastIndex[j] = i;
+        }
+
+        let res = 0;
+        for (let ends = 0; ends < 26; ends++) {
+            if (firstIndex[ends] === -1 || firstIndex[ends] === lastIndex[ends]) {
+                continue;
+            }
+            const l = firstIndex[ends], r = lastIndex[ends];
+            let mask = 0;
+            for (let i = l + 1; i < r; i++) {
+                const c = s.charCodeAt(i) - 'a'.charCodeAt(0);
+                if (mask & (1 << c)) {
+                    continue;
+                }
+                mask |= (1 << c);
+                res++;
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(26 * n)$
+* Space complexity: $O(1)$ since we have at most $26$ different characters.
\ No newline at end of file
diff --git a/articles/unique-paths-ii.md b/articles/unique-paths-ii.md
new file mode 100644
index 000000000..35178ff44
--- /dev/null
+++ b/articles/unique-paths-ii.md
@@ -0,0 +1,481 @@
+## 1. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def uniquePathsWithObstacles(self, grid: List[List[int]]) -> int:
+        M, N = len(grid), len(grid[0])
+        dp = {(M - 1, N - 1): 1}
+
+        def dfs(r, c):
+            if r == M or c == N or grid[r][c]:
+                return 0
+            if (r, c) in dp:
+                return dp[(r, c)]
+            dp[(r, c)] = dfs(r + 1, c) + dfs(r, c + 1)
+            return dp[(r, c)]
+
+        return dfs(0, 0)
+```
+
+```java
+public class Solution {
+    private int[][] dp;
+
+    public int uniquePathsWithObstacles(int[][] grid) {
+        int M = grid.length, N = grid[0].length;
+        dp = new int[M][N];
+        for (int i = 0; i < M; i++) {
+            for (int j = 0; j < N; j++) {
+                dp[i][j] = -1;
+            }
+        }
+        return dfs(0, 0, grid, M, N);
+    }
+
+    private int dfs(int r, int c, int[][] grid, int M, int N) {
+        if (r == M || c == N || grid[r][c] == 1) {
+            return 0;
+        }
+        if (r == M - 1 && c == N - 1) {
+            return 1;
+        }
+        if (dp[r][c] != -1) {
+            return dp[r][c];
+        }
+        dp[r][c] = dfs(r + 1, c, grid, M, N) + dfs(r, c + 1, grid, M, N);
+        return dp[r][c];
+    }
+}
+```
+
+```cpp
+class Solution {
+private:
+    vector<vector<int>> dp;
+
+public:
+    int uniquePathsWithObstacles(vector<vector<int>>& grid) {
+        int M = grid.size(), N = grid[0].size();
+        dp.resize(M, vector<int>(N, -1));
+        return dfs(0, 0, grid, M, N);
+    }
+
+private:
+    int dfs(int r, int c, vector<vector<int>>& grid, int M, int N) {
+        if (r == M || c == N || grid[r][c] == 1) {
+            return 0;
+        }
+        if (r == M - 1 && c == N - 1) {
+            return 1;
+        }
+        if (dp[r][c] != -1) {
+            return dp[r][c];
+        }
+        dp[r][c] = dfs(r + 1, c, grid, M, N) + dfs(r, c + 1, grid, M, N);
+        return dp[r][c];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    uniquePathsWithObstacles(grid) {
+        const M = grid.length, N = grid[0].length;
+        const dp = Array.from({ length: M }, () => Array(N).fill(-1));
+
+        const dfs = (r, c) => {
+            if (r === M || c === N || grid[r][c] === 1) {
+                return 0;
+            }
+            if (r === M - 1 && c === N - 1) {
+                return 1;
+            }
+            if (dp[r][c] !== -1) {
+                return dp[r][c];
+            }
+            dp[r][c] = dfs(r + 1, c) + dfs(r, c + 1);
+            return dp[r][c];
+        };
+
+        return dfs(0, 0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns.
+
+---
+
+## 2. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def uniquePathsWithObstacles(self, grid: List[List[int]]) -> int:
+        M, N = len(grid), len(grid[0])
+        if grid[0][0] == 1 or grid[M - 1][N - 1] == 1:
+            return 0
+        dp = [[0] * (N + 1) for _ in range(M + 1)]
+
+
+        dp[M - 1][N - 1] = 1
+
+        for r in range(M - 1, -1, -1):
+            for c in range(N - 1, -1, -1):
+                if grid[r][c] == 1:
+                    dp[r][c] = 0
+                else:
+                    dp[r][c] += dp[r + 1][c]
+                    dp[r][c] += dp[r][c + 1]
+
+        return dp[0][0]
+```
+
+```java
+public class Solution {
+    public int uniquePathsWithObstacles(int[][] grid) {
+        int M = grid.length, N = grid[0].length;
+        if (grid[0][0] == 1 || grid[M - 1][N - 1] == 1) {
+            return 0;
+        }
+
+        int[][] dp = new int[M + 1][N + 1];
+        dp[M - 1][N - 1] = 1;
+
+        for (int r = M - 1; r >= 0; r--) {
+            for (int c = N - 1; c >= 0; c--) {
+                if (grid[r][c] == 1) {
+                    dp[r][c] = 0;
+                } else {
+                    dp[r][c] += dp[r + 1][c];
+                    dp[r][c] += dp[r][c + 1];
+                }
+            }
+        }
+
+        return dp[0][0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int uniquePathsWithObstacles(vector<vector<int>>& grid) {
+        int M = grid.size(), N = grid[0].size();
+        if (grid[0][0] == 1 || grid[M - 1][N - 1] == 1) {
+            return 0;
+        }
+
+        vector<vector<uint>> dp(M + 1, vector<uint>(N + 1, 0));
+        dp[M - 1][N - 1] = 1;
+
+        for (int r = M - 1; r >= 0; r--) {
+            for (int c = N - 1; c >= 0; c--) {
+                if (grid[r][c] == 1) {
+                    dp[r][c] = 0;
+                } else {
+                    dp[r][c] += dp[r + 1][c];
+                    dp[r][c] += dp[r][c + 1];
+                }
+            }
+        }
+
+        return dp[0][0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    uniquePathsWithObstacles(grid) {
+        const M = grid.length, N = grid[0].length;
+        if (grid[0][0] === 1 || grid[M - 1][N - 1] === 1) {
+            return 0;
+        }
+
+        const dp = Array.from({ length: M + 1 }, () => Array(N + 1).fill(0));
+        dp[M - 1][N - 1] = 1;
+
+        for (let r = M - 1; r >= 0; r--) {
+            for (let c = N - 1; c >= 0; c--) {
+                if (grid[r][c] === 1) {
+                    dp[r][c] = 0;
+                } else {
+                    dp[r][c] += dp[r + 1][c];
+                    dp[r][c] += dp[r][c + 1];
+                }
+            }
+        }
+
+        return dp[0][0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(m * n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns.
+
+---
+
+## 3. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def uniquePathsWithObstacles(self, grid: List[List[int]]) -> int:
+        M, N = len(grid), len(grid[0])
+        dp = [0] * (N + 1)
+        dp[N - 1] = 1
+
+        for r in range(M - 1, -1, -1):
+            for c in range(N - 1, -1, -1):
+                if grid[r][c]:
+                    dp[c] = 0
+                else:
+                    dp[c] += dp[c + 1]
+        
+        return dp[0]
+```
+
+```java
+public class Solution {
+    public int uniquePathsWithObstacles(int[][] grid) {
+        int M = grid.length, N = grid[0].length;
+        int[] dp = new int[N + 1];
+        dp[N - 1] = 1;
+
+        for (int r = M - 1; r >= 0; r--) {
+            for (int c = N - 1; c >= 0; c--) {
+                if (grid[r][c] == 1) {
+                    dp[c] = 0;
+                } else {
+                    dp[c] += dp[c + 1];
+                }
+            }
+        }
+
+        return dp[0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int uniquePathsWithObstacles(vector<vector<int>>& grid) {
+        int M = grid.size(), N = grid[0].size();
+        vector<uint> dp(N + 1, 0);
+        dp[N - 1] = 1;
+
+        for (int r = M - 1; r >= 0; r--) {
+            for (int c = N - 1; c >= 0; c--) {
+                if (grid[r][c] == 1) {
+                    dp[c] = 0;
+                } else {
+                    dp[c] += dp[c + 1];
+                }
+            }
+        }
+
+        return dp[0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    uniquePathsWithObstacles(grid) {
+        const M = grid.length, N = grid[0].length;
+        const dp = new Array(N + 1).fill(0);
+        dp[N - 1] = 1;
+
+        for (let r = M - 1; r >= 0; r--) {
+            for (let c = N - 1; c >= 0; c--) {
+                if (grid[r][c] === 1) {
+                    dp[c] = 0;
+                } else {
+                    dp[c] += dp[c + 1];
+                }
+            }
+        }
+
+        return dp[0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(n)$
+
+> Where $m$ is the number of rows and $n$ is the number of columns.
+
+---
+
+## 4. Dynamic Programming (In-Place)
+
+::tabs-start
+
+```python
+class Solution:
+    def uniquePathsWithObstacles(self, grid: List[List[int]]) -> int:
+        M, N = len(grid), len(grid[0])
+        if grid[0][0] == 1 or grid[M - 1][N - 1] == 1:
+            return 0
+        
+        grid[M - 1][N - 1] = 1
+        
+        for r in range(M - 1, -1, -1):
+            for c in range(N - 1, -1, -1):
+                if r == M - 1 and c == N - 1:
+                    continue
+
+                if grid[r][c] == 1:
+                    grid[r][c] = 0
+                else:
+                    down = grid[r + 1][c] if r + 1 < M else 0
+                    right = grid[r][c + 1] if c + 1 < N else 0
+                    grid[r][c] = down + right
+        
+        return grid[0][0]
+```
+
+```java
+public class Solution {
+    public int uniquePathsWithObstacles(int[][] grid) {
+        int M = grid.length, N = grid[0].length;
+        if (grid[0][0] == 1 || grid[M - 1][N - 1] == 1) {
+            return 0;
+        }
+
+        grid[M - 1][N - 1] = 1;
+
+        for (int r = M - 1; r >= 0; r--) {
+            for (int c = N - 1; c >= 0; c--) {
+                if (r == M - 1 && c == N - 1) {
+                    continue;
+                }
+
+                if (grid[r][c] == 1) {
+                    grid[r][c] = 0;
+                } else {
+                    int down = (r + 1 < M) ? grid[r + 1][c] : 0;
+                    int right = (c + 1 < N) ? grid[r][c + 1] : 0;
+                    grid[r][c] = down + right;
+                }
+            }
+        }
+
+        return grid[0][0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int uniquePathsWithObstacles(vector<vector<int>>& grid) {
+        int M = grid.size(), N = grid[0].size();
+        if (grid[0][0] == 1 || grid[M - 1][N - 1] == 1) {
+            return 0;
+        }
+
+        grid[M - 1][N - 1] = 1;
+
+        for (int r = M - 1; r >= 0; r--) {
+            for (int c = N - 1; c >= 0; c--) {
+                if (r == M - 1 && c == N - 1) {
+                    continue;
+                }
+
+                if (grid[r][c] == 1) {
+                    grid[r][c] = 0;
+                } else {
+                    uint down = (r + 1 < M) ? grid[r + 1][c] : 0;
+                    uint right = (c + 1 < N) ? grid[r][c + 1] : 0;
+                    grid[r][c] = down + right;
+                }
+            }
+        }
+
+        return grid[0][0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} grid
+     * @return {number}
+     */
+    uniquePathsWithObstacles(grid) {
+        const M = grid.length, N = grid[0].length;
+        if (grid[0][0] === 1 || grid[M - 1][N - 1] === 1) {
+            return 0;
+        }
+
+        grid[M - 1][N - 1] = 1;
+
+        for (let r = M - 1; r >= 0; r--) {
+            for (let c = N - 1; c >= 0; c--) {
+                if (r === M - 1 && c === N - 1) {
+                    continue;
+                }
+
+                if (grid[r][c] === 1) {
+                    grid[r][c] = 0;
+                } else {
+                    const down = (r + 1 < M) ? grid[r + 1][c] : 0;
+                    const right = (c + 1 < N) ? grid[r][c + 1] : 0;
+                    grid[r][c] = down + right;
+                }
+            }
+        }
+
+        return grid[0][0];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m * n)$
+* Space complexity: $O(1)$ extra space.
+
+> Where $m$ is the number of rows and $n$ is the number of columns.
\ No newline at end of file
diff --git a/articles/valid-binary-search-tree.md b/articles/valid-binary-search-tree.md
index 5ee96b0f3..3b076e3c7 100644
--- a/articles/valid-binary-search-tree.md
+++ b/articles/valid-binary-search-tree.md
@@ -255,6 +255,105 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func isValidBST(root *TreeNode) bool {
+    if root == nil {
+        return true
+    }
+    return isValid(root.Left, root.Val, func(val, limit int) bool { return val < limit }) &&
+           isValid(root.Right, root.Val, func(val, limit int) bool { return val > limit }) &&
+           isValidBST(root.Left) &&
+           isValidBST(root.Right)
+}
+
+func isValid(root *TreeNode, limit int, check func(int, int) bool) bool {
+    if root == nil {
+        return true
+    }
+    if !check(root.Val, limit) {
+        return false
+    }
+    return isValid(root.Left, limit, check) && isValid(root.Right, limit, check)
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    private val leftCheck: (Int, Int) -> Boolean = { value, limit -> value < limit }
+    private val rightCheck: (Int, Int) -> Boolean = { value, limit -> value > limit }
+
+    fun isValidBST(root: TreeNode?): Boolean {
+        if (root == null) return true
+        if (!isValid(root.left, root.`val`, leftCheck) || !isValid(root.right, root.`val`, rightCheck)) {
+            return false
+        }
+        return isValidBST(root.left) && isValidBST(root.right)
+    }
+
+    private fun isValid(root: TreeNode?, limit: Int, check: (Int, Int) -> Boolean): Boolean {
+        if (root == null) return true
+        if (!check(root.`val`, limit)) return false
+        return isValid(root.left, limit, check) && isValid(root.right, limit, check)
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func isValidBST(_ root: TreeNode?) -> Bool {
+        guard let root = root else { return true }
+        if !isValid(root.left, root.val, { $0 < $1 }) || 
+           !isValid(root.right, root.val, { $0 > $1 }) {
+            return false
+        }
+
+        return isValidBST(root.left) && isValidBST(root.right)
+    }
+
+    private func isValid(_ root: TreeNode?, _ limit: Int, _ check: (Int, Int) -> Bool) -> Bool {
+        guard let root = root else { return true }
+        if !check(root.val, limit) {
+            return false
+        }
+
+        return isValid(root.left, limit, check) && isValid(root.right, limit, check)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -430,6 +529,96 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func isValidBST(root *TreeNode) bool {
+    return valid(root, math.MinInt64, math.MaxInt64)
+}
+
+func valid(node *TreeNode, left, right int64) bool {
+    if node == nil {
+        return true
+    }
+    
+    val := int64(node.Val)
+    if val <= left || val >= right {
+        return false
+    }
+    
+    return valid(node.Left, left, val) && valid(node.Right, val, right)
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    fun isValidBST(root: TreeNode?): Boolean {
+        return valid(root, Long.MIN_VALUE, Long.MAX_VALUE)
+    }
+    
+    private fun valid(node: TreeNode?, left: Long, right: Long): Boolean {
+        if (node == null) {
+            return true
+        }
+        
+        val value = node.`val`.toLong()
+        if (value <= left || value >= right) {
+            return false
+        }
+        
+        return valid(node.left, left, value) && 
+               valid(node.right, value, right)
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func isValidBST(_ root: TreeNode?) -> Bool {
+        return valid(root, Int.min, Int.max)
+    }
+
+    private func valid(_ node: TreeNode?, _ left: Int, _ right: Int) -> Bool {
+        guard let node = node else { return true }
+        if !(left < node.val && node.val < right) {
+            return false
+        }
+        return valid(node.left, left, node.val) && valid(node.right, node.val, right)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -648,6 +837,138 @@ public class Solution {
 }
 ```
 
+```go
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+type QueueItem struct {
+    node *TreeNode
+    left int64
+    right int64
+}
+
+func isValidBST(root *TreeNode) bool {
+    if root == nil {
+        return true
+    }
+    
+    queue := []QueueItem{{root, math.MinInt64, math.MaxInt64}}
+    
+    for len(queue) > 0 {
+        item := queue[0]
+        queue = queue[1:]
+        
+        val := int64(item.node.Val)
+        if val <= item.left || val >= item.right {
+            return false
+        }
+        
+        if item.node.Left != nil {
+            queue = append(queue, QueueItem{item.node.Left, item.left, val})
+        }
+        if item.node.Right != nil {
+            queue = append(queue, QueueItem{item.node.Right, val, item.right})
+        }
+    }
+    
+    return true
+}
+```
+
+```kotlin
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    private data class QueueItem(
+        val node: TreeNode,
+        val left: Long,
+        val right: Long
+    )
+    
+    fun isValidBST(root: TreeNode?): Boolean {
+        if (root == null) {
+            return true
+        }
+        
+        val queue = ArrayDeque<QueueItem>()
+        queue.addLast(QueueItem(root, Long.MIN_VALUE, Long.MAX_VALUE))
+        
+        while (queue.isNotEmpty()) {
+            val (node, left, right) = queue.removeFirst()
+            
+            val value = node.`val`.toLong()
+            if (value <= left || value >= right) {
+                return false
+            }
+            
+            node.left?.let { 
+                queue.addLast(QueueItem(it, left, value))
+            }
+            node.right?.let {
+                queue.addLast(QueueItem(it, value, right))
+            }
+        }
+        
+        return true
+    }
+}
+```
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func isValidBST(_ root: TreeNode?) -> Bool {
+        guard let root = root else { return true }
+
+        var q = Deque<(TreeNode, Int, Int)>()
+        q.append((root, Int.min, Int.max))
+
+        while !q.isEmpty {
+            let (node, left, right) = q.popFirst()!
+
+            if !(left < node.val && node.val < right) {
+                return false
+            }
+
+            if let leftNode = node.left {
+                q.append((leftNode, left, node.val))
+            }
+            if let rightNode = node.right {
+                q.append((rightNode, node.val, right))
+            }
+        }
+        return true
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/valid-palindrome-ii.md b/articles/valid-palindrome-ii.md
new file mode 100644
index 000000000..6b1fbf303
--- /dev/null
+++ b/articles/valid-palindrome-ii.md
@@ -0,0 +1,476 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def validPalindrome(self, s: str) -> bool:
+        if s == s[::-1]:
+            return True
+        
+        for i in range(len(s)):
+            newS = s[:i] + s[i + 1:]
+            if newS == newS[::-1]:
+                return True
+        
+        return False
+```
+
+```java
+public class Solution {
+    public boolean validPalindrome(String s) {
+        if (isPalindrome(s)) {
+            return true;
+        }
+
+        for (int i = 0; i < s.length(); i++) {
+            String newS = s.substring(0, i) + s.substring(i + 1);
+            if (isPalindrome(newS)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    private boolean isPalindrome(String s) {
+        int left = 0, right = s.length() - 1;
+        while (left < right) {
+            if (s.charAt(left) != s.charAt(right)) {
+                return false;
+            }
+            left++;
+            right--;
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool validPalindrome(string s) {
+        if (isPalindrome(s)) {
+            return true;
+        }
+
+        for (int i = 0; i < s.size(); i++) {
+            string newS = s.substr(0, i) + s.substr(i + 1);
+            if (isPalindrome(newS)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+private:
+    bool isPalindrome(const string& s) {
+        int left = 0, right = s.size() - 1;
+        while (left < right) {
+            if (s[left] != s[right]) {
+                return false;
+            }
+            left++;
+            right--;
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {boolean}
+     */
+    validPalindrome(s) {
+        if (this.isPalindrome(s)) {
+            return true;
+        }
+
+        for (let i = 0; i < s.length; i++) {
+            const newS = s.slice(0, i) + s.slice(i + 1);
+            if (this.isPalindrome(newS)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    /**
+     * @param {string} s
+     * @return {boolean}
+     */
+    isPalindrome(s) {
+        let left = 0, right = s.length - 1;
+        while (left < right) {
+            if (s[left] !== s[right]) {
+                return false;
+            }
+            left++;
+            right--;
+        }
+        return true;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool ValidPalindrome(string s) {
+        if (IsPalindrome(s)) return true;
+
+        for (int i = 0; i < s.Length; i++) {
+            string newS = s.Substring(0, i) + s.Substring(i + 1);
+            if (IsPalindrome(newS)) return true;
+        }
+
+        return false;
+    }
+
+    private bool IsPalindrome(string str) {
+        int left = 0, right = str.Length - 1;
+        while (left < right) {
+            if (str[left] != str[right]) return false;
+            left++;
+            right--;
+        }
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def validPalindrome(self, s: str) -> bool:
+        l, r = 0, len(s) - 1
+
+        while l < r:
+            if s[l] != s[r]:
+                skipL = s[l + 1 : r + 1]
+                skipR = s[l : r]
+                return skipL == skipL[::-1] or skipR == skipR[::-1]
+            l, r = l + 1, r - 1
+
+        return True
+```
+
+```java
+public class Solution {
+    public boolean validPalindrome(String s) {
+        int l = 0, r = s.length() - 1;
+
+        while (l < r) {
+            if (s.charAt(l) != s.charAt(r)) {
+                return isPalindrome(s.substring(0, l) + s.substring(l + 1)) || 
+                       isPalindrome(s.substring(0, r) + s.substring(r + 1));
+            }
+            l++;
+            r--;
+        }
+
+        return true;
+    }
+
+    private boolean isPalindrome(String s) {
+        int l = 0, r = s.length() - 1;
+        while (l < r) {
+            if (s.charAt(l) != s.charAt(r)) {
+                return false;
+            }
+            l++;
+            r--;
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool validPalindrome(string s) {
+        int l = 0, r = s.size() - 1;
+
+        while (l < r) {
+            if (s[l] != s[r]) {
+                return isPalindrome(s.substr(0, l) + s.substr(l + 1)) || 
+                       isPalindrome(s.substr(0, r) + s.substr(r + 1));
+            }
+            l++;
+            r--;
+        }
+
+        return true;
+    }
+
+private:
+    bool isPalindrome(string s) {
+        int l = 0, r = s.length() - 1;
+        while (l < r) {
+            if (s[l] != s[r]) {
+                return false;
+            }
+            l++;
+            r--;
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {boolean}
+     */
+    validPalindrome(s) {
+        let l = 0, r = s.length - 1;
+
+        while (l < r) {
+            if (s[l] !== s[r]) {
+                return this.isPalindrome(s.slice(0, l) + s.slice(l + 1)) || 
+                       this.isPalindrome(s.slice(0, r) + s.slice(r + 1));
+            }
+            l++;
+            r--;
+        }
+
+        return true;
+    }
+
+    /**
+     * @param {string} s
+     * @return {boolean}
+     */
+    isPalindrome(s) {
+        let left = 0, right = s.length - 1;
+        while (left < right) {
+            if (s[left] !== s[right]) {
+                return false;
+            }
+            left++;
+            right--;
+        }
+        return true;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool ValidPalindrome(string s) {
+        int l = 0, r = s.Length - 1;
+
+        while (l < r) {
+            if (s[l] != s[r]) {
+                string skipL = s.Substring(l + 1, r - l);
+                string skipR = s.Substring(l, r - l);
+                return IsPalindrome(skipL) || IsPalindrome(skipR);
+            }
+            l++;
+            r--;
+        }
+
+        return true;
+    }
+
+    private bool IsPalindrome(string str) {
+        int left = 0, right = str.Length - 1;
+        while (left < right) {
+            if (str[left] != str[right]) return false;
+            left++;
+            right--;
+        }
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Two Pointers (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def validPalindrome(self, s: str) -> bool:
+        def is_palindrome(l, r):
+            while l < r:
+                if s[l] != s[r]:
+                    return False
+                l += 1
+                r -= 1
+            return True
+
+        l, r = 0, len(s) - 1
+        while l < r:
+            if s[l] != s[r]:
+                return (is_palindrome(l + 1, r) or 
+                        is_palindrome(l, r - 1))
+            l += 1
+            r -= 1
+
+        return True
+```
+
+```java
+public class Solution {
+    public boolean validPalindrome(String s) {
+        int l = 0, r = s.length() - 1;
+
+        while (l < r) {
+            if (s.charAt(l) != s.charAt(r)) {
+                return isPalindrome(s, l + 1, r) || 
+                       isPalindrome(s, l, r - 1);
+            }
+            l++;
+            r--;
+        }
+
+        return true;
+    }
+
+    private boolean isPalindrome(String s, int l, int r) {
+        while (l < r) {
+            if (s.charAt(l) != s.charAt(r)) {
+                return false;
+            }
+            l++;
+            r--;
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool validPalindrome(string s) {
+        int l = 0, r = s.size() - 1;
+
+        while (l < r) {
+            if (s[l] != s[r]) {
+                return isPalindrome(s, l + 1, r) || 
+                       isPalindrome(s, l, r - 1);
+            }
+            l++;
+            r--;
+        }
+
+        return true;
+    }
+
+private:
+    bool isPalindrome(const string& s, int l, int r) {
+        while (l < r) {
+            if (s[l] != s[r]) {
+                return false;
+            }
+            l++;
+            r--;
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {boolean}
+     */
+    validPalindrome(s) {
+        let l = 0, r = s.length - 1;
+
+        while (l < r) {
+            if (s[l] !== s[r]) {
+                return this.isPalindrome(s, l + 1, r) || 
+                       this.isPalindrome(s, l, r - 1);
+            }
+            l++;
+            r--;
+        }
+
+        return true;
+    }
+
+    /**
+     * @param {string} s
+     * @param {number} l
+     * @param {number} r
+     * @return {boolean}
+     */
+    isPalindrome(s, l, r) {
+        while (l < r) {
+            if (s[l] !== s[r]) {
+                return false;
+            }
+            l++;
+            r--;
+        }
+        return true;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool ValidPalindrome(string s) {
+        bool IsPalindrome(int l, int r) {
+            while (l < r) {
+                if (s[l] != s[r]) return false;
+                l++;
+                r--;
+            }
+            return true;
+        }
+
+        int left = 0, right = s.Length - 1;
+        while (left < right) {
+            if (s[left] != s[right]) {
+                return IsPalindrome(left + 1, right) || IsPalindrome(left, right - 1);
+            }
+            left++;
+            right--;
+        }
+
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/valid-parenthesis-string.md b/articles/valid-parenthesis-string.md
new file mode 100644
index 000000000..c412ad605
--- /dev/null
+++ b/articles/valid-parenthesis-string.md
@@ -0,0 +1,1459 @@
+## 1. Recursion
+
+::tabs-start
+
+```python
+class Solution:
+    def checkValidString(self, s: str) -> bool:
+        
+        def dfs(i, open):
+            if open < 0:
+                return False
+            if i == len(s):
+                return open == 0
+            
+            if s[i] == '(':
+                return dfs(i + 1, open + 1)
+            elif s[i] == ')':
+                return dfs(i + 1, open - 1)
+            else:
+                return (dfs(i + 1, open) or
+                        dfs(i + 1, open + 1) or
+                        dfs(i + 1, open - 1))
+        return dfs(0, 0)
+```
+
+```java
+public class Solution {
+    public boolean checkValidString(String s) {
+        
+        return dfs(0, 0, s);
+    }
+
+    private boolean dfs(int i, int open, String s) {
+        if (open < 0) return false;
+        if (i == s.length()) return open == 0;
+
+        if (s.charAt(i) == '(') {
+            return dfs(i + 1, open + 1, s);
+        } else if (s.charAt(i) == ')') {
+            return dfs(i + 1, open - 1, s);
+        } else {
+            return dfs(i + 1, open, s) ||
+                   dfs(i + 1, open + 1, s) ||
+                   dfs(i + 1, open - 1, s);
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool checkValidString(string s) {
+        return dfs(0, 0, s);
+    }
+
+private:
+    bool dfs(int i, int open, const string& s) {
+        if (open < 0) return false;
+        if (i == s.size()) return open == 0;
+
+        if (s[i] == '(') {
+            return dfs(i + 1, open + 1, s);
+        } else if (s[i] == ')') {
+            return dfs(i + 1, open - 1, s);
+        } else {
+            return dfs(i + 1, open, s) ||
+                   dfs(i + 1, open + 1, s) ||
+                   dfs(i + 1, open - 1, s);
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {boolean}
+     */
+    checkValidString(s) {
+        function dfs(i, open) {
+            if (open < 0) return false;
+            if (i === s.length) return open === 0;
+
+            if (s[i] === '(') {
+                return dfs(i + 1, open + 1);
+            } else if (s[i] === ')') {
+                return dfs(i + 1, open - 1);
+            } else {
+                return dfs(i + 1, open) || 
+                    dfs(i + 1, open + 1) || 
+                    dfs(i + 1, open - 1);
+            }
+        }
+
+        return dfs(0, 0);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool CheckValidString(string s) {
+        return Dfs(0, 0, s);
+    }
+
+    private bool Dfs(int i, int open, string s) {
+        if (open < 0) return false;
+        if (i == s.Length) return open == 0;
+
+        if (s[i] == '(') {
+            return Dfs(i + 1, open + 1, s);
+        } else if (s[i] == ')') {
+            return Dfs(i + 1, open - 1, s);
+        } else {
+            return Dfs(i + 1, open, s) ||
+                   Dfs(i + 1, open + 1, s) ||
+                   Dfs(i + 1, open - 1, s);
+        }
+    }
+}
+```
+
+```go
+func checkValidString(s string) bool {
+    var dfs func(i, open int) bool
+    dfs = func(i, open int) bool {
+        if open < 0 {
+            return false
+        }
+        if i == len(s) {
+            return open == 0
+        }
+
+        if s[i] == '(' {
+            return dfs(i+1, open+1)
+        } else if s[i] == ')' {
+            return dfs(i+1, open-1)
+        } else {
+            return (dfs(i+1, open) || 
+                    dfs(i+1, open+1) || 
+                    dfs(i+1, open-1))
+        }
+    }
+    return dfs(0, 0)
+}
+```
+
+```kotlin
+class Solution {
+    fun checkValidString(s: String): Boolean {
+
+        fun dfs(i: Int, open: Int): Boolean {
+            if (open < 0) {
+                return false
+            }
+            if (i == s.length) {
+                return open == 0
+            }
+            
+            return when (s[i]) {
+                '(' -> dfs(i + 1, open + 1)
+                ')' -> dfs(i + 1, open - 1)
+                else -> dfs(i + 1, open) || dfs(i + 1, open + 1) || dfs(i + 1, open - 1)
+            }
+        }
+
+        return dfs(0, 0)
+    }
+}
+```
+
+```swift
+class Solution {
+    func checkValidString(_ s: String) -> Bool {
+        let chars = Array(s)
+
+        func dfs(_ i: Int, _ open: Int) -> Bool {
+            if open < 0 { return false }
+            if i == chars.count { return open == 0 }
+
+            if chars[i] == "(" {
+                return dfs(i + 1, open + 1)
+            } else if chars[i] == ")" {
+                return dfs(i + 1, open - 1)
+            } else {
+                return dfs(i + 1, open) ||
+                       dfs(i + 1, open + 1) ||
+                       dfs(i + 1, open - 1)
+            }
+        }
+
+        return dfs(0, 0)
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(3 ^ n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def checkValidString(self, s: str) -> bool:
+        n = len(s)
+        memo = [[None] * (n + 1) for _ in range(n + 1)]
+
+        def dfs(i, open):
+            if open < 0:
+                return False
+            if i == n:
+                return open == 0
+            if memo[i][open] is not None:
+                return memo[i][open]
+            
+            if s[i] == '(':
+                result = dfs(i + 1, open + 1)
+            elif s[i] == ')':
+                result = dfs(i + 1, open - 1)
+            else:
+                result = (dfs(i + 1, open) or 
+                          dfs(i + 1, open + 1) or 
+                          dfs(i + 1, open - 1))
+            
+            memo[i][open] = result
+            return result
+
+        return dfs(0, 0)
+```
+
+```java
+public class Solution {
+    public boolean checkValidString(String s) {
+        int n = s.length();
+        Boolean[][] memo = new Boolean[n + 1][n + 1];
+        return dfs(0, 0, s, memo);
+    }
+
+    private boolean dfs(int i, int open, String s, Boolean[][] memo) {
+        if (open < 0) return false;
+        if (i == s.length()) return open == 0;
+
+        if (memo[i][open] != null) return memo[i][open];
+
+        boolean result;
+        if (s.charAt(i) == '(') {
+            result = dfs(i + 1, open + 1, s, memo);
+        } else if (s.charAt(i) == ')') {
+            result = dfs(i + 1, open - 1, s, memo);
+        } else {
+            result = (dfs(i + 1, open, s, memo) || 
+                      dfs(i + 1, open + 1, s, memo) || 
+                      dfs(i + 1, open - 1, s, memo));
+        }
+        
+        memo[i][open] = result;
+        return result;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool checkValidString(string s) {
+        int n = s.size();
+        memo = vector<vector<int>>(n + 1, vector<int>(n + 1, -1));
+        return dfs(0, 0, s);
+    }
+
+private:
+    vector<vector<int>> memo;
+
+    bool dfs(int i, int open, const string& s) {
+        if (open < 0) return false;
+        if (i == s.size()) return open == 0;
+
+        if (memo[i][open] != -1) return memo[i][open] == 1;
+
+        bool result;
+        if (s[i] == '(') {
+            result = dfs(i + 1, open + 1, s);
+        } else if (s[i] == ')') {
+            result = dfs(i + 1, open - 1, s);
+        } else {
+            result = (dfs(i + 1, open, s) || 
+                      dfs(i + 1, open + 1, s) || 
+                      dfs(i + 1, open - 1, s));
+        }
+        
+        memo[i][open] = result ? 1 : 0;
+        return result;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {boolean}
+     */
+    checkValidString(s) {
+        const n = s.length;
+        const memo = Array.from({ length: n + 1 }, () => 
+                     Array(n + 1).fill(null));
+
+        function dfs(i, open) {
+            if (open < 0) return false;
+            if (i === n) return open === 0;
+
+            if (memo[i][open] !== null) return memo[i][open];
+
+            let result;
+            if (s[i] === '(') {
+                result = dfs(i + 1, open + 1);
+            } else if (s[i] === ')') {
+                result = dfs(i + 1, open - 1);
+            } else {
+                result = dfs(i + 1, open) || 
+                         dfs(i + 1, open + 1) || 
+                         dfs(i + 1, open - 1);
+            }
+            
+            memo[i][open] = result;
+            return result;
+        }
+
+        return dfs(0, 0);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool CheckValidString(string s) {
+        int n = s.Length;
+        bool?[,] memo = new bool?[n + 1, n + 1];
+        return Dfs(0, 0, s, memo);
+    }
+
+    private bool Dfs(int i, int open, string s, bool?[,] memo) {
+        if (open < 0) return false;
+        if (i == s.Length) return open == 0;
+
+        if (memo[i, open].HasValue) return memo[i, open].Value;
+
+        bool result;
+        if (s[i] == '(') {
+            result = Dfs(i + 1, open + 1, s, memo);
+        } else if (s[i] == ')') {
+            result = Dfs(i + 1, open - 1, s, memo);
+        } else {
+            result = Dfs(i + 1, open, s, memo) || 
+                     Dfs(i + 1, open + 1, s, memo) || 
+                     Dfs(i + 1, open - 1, s, memo);
+        }
+
+        memo[i, open] = result;
+        return result;
+    }
+}
+```
+
+```go
+func checkValidString(s string) bool {
+    memo := make([][]int, len(s)+1)
+    for i := range memo {
+        memo[i] = make([]int, len(s)+1)
+        for j := range memo[i] {
+            memo[i][j] = -1
+        }
+    }
+
+    var dfs func(i, open int) bool
+    dfs = func(i, open int) bool {
+        if open < 0 {
+            return false
+        }
+        if i == len(s) {
+            return open == 0
+        }
+        if memo[i][open] != -1 {
+            return memo[i][open] == 1
+        }
+
+        result := false
+        if s[i] == '(' {
+            result = dfs(i+1, open+1)
+        } else if s[i] == ')' {
+            result = dfs(i+1, open-1)
+        } else {
+            result = (dfs(i+1, open) || 
+                      dfs(i+1, open+1) || 
+                      dfs(i+1, open-1))
+        }
+
+        memo[i][open] = 1
+        if !result {
+            memo[i][open] = 0
+        }
+        return result
+    }
+    return dfs(0, 0)
+}
+```
+
+```kotlin
+class Solution {
+    fun checkValidString(s: String): Boolean {
+        val memo = Array(s.length + 1) { IntArray(s.length + 1) { -1 } }
+
+        fun dfs(i: Int, open: Int): Boolean {
+            if (open < 0) return false
+            if (i == s.length) return open == 0
+            if (memo[i][open] != -1) return memo[i][open] == 1
+
+            val result = when (s[i]) {
+                '(' -> dfs(i + 1, open + 1)
+                ')' -> dfs(i + 1, open - 1)
+                else -> (dfs(i + 1, open) || 
+                         dfs(i + 1, open + 1) || 
+                         dfs(i + 1, open - 1))
+            }
+
+            memo[i][open] = if (result) 1 else 0
+            return result
+        }
+
+        return dfs(0, 0)
+    }
+}
+```
+
+```swift
+class Solution {
+    func checkValidString(_ s: String) -> Bool {
+        let n = s.count
+        let sArr = Array(s)
+        var memo = Array(
+            repeating: Array<Bool?>(repeating: nil, count: n + 1),
+            count: n + 1
+        )
+
+        func dfs(_ i: Int, _ open: Int) -> Bool {
+            if open < 0 {
+                return false
+            }
+            if i == n {
+                return open == 0
+            }
+            if let memoized = memo[i][open] {
+                return memoized
+            }
+
+            let result: Bool
+            if sArr[i] == "(" {
+                result = dfs(i + 1, open + 1)
+            } else if sArr[i] == ")" {
+                result = dfs(i + 1, open - 1)
+            } else {
+                result = dfs(i + 1, open) ||
+                         dfs(i + 1, open + 1) ||
+                         dfs(i + 1, open - 1)
+            }
+
+            memo[i][open] = result
+            return result
+        }
+
+        return dfs(0, 0)
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 3. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def checkValidString(self, s: str) -> bool:
+        n = len(s)
+        dp = [[False] * (n + 1) for _ in range(n + 1)]
+        dp[n][0] = True
+
+        for i in range(n - 1, -1, -1):
+            for open in range(n):
+                res = False
+                if s[i] == '*':
+                    res |= dp[i + 1][open + 1]
+                    if open > 0:
+                        res |= dp[i + 1][open - 1]
+                    res |= dp[i + 1][open]
+                else:
+                    if s[i] == '(':
+                        res |= dp[i + 1][open + 1]
+                    elif open > 0:
+                        res |= dp[i + 1][open - 1]
+                dp[i][open] = res
+
+        return dp[0][0]
+```
+
+```java
+public class Solution {
+    public boolean checkValidString(String s) {
+        int n = s.length();
+        boolean[][] dp = new boolean[n + 1][n + 1];
+        dp[n][0] = true;
+
+        for (int i = n - 1; i >= 0; i--) {
+            for (int open = 0; open < n; open++) {
+                boolean res = false;
+                if (s.charAt(i) == '*') {
+                    res |= dp[i + 1][open + 1];
+                    if (open > 0) res |= dp[i + 1][open - 1];
+                    res |= dp[i + 1][open];
+                } else {
+                    if (s.charAt(i) == '(') {
+                        res |= dp[i + 1][open + 1];
+                    } else if (open > 0) {
+                        res |= dp[i + 1][open - 1];
+                    }
+                }
+                dp[i][open] = res;
+            }
+        }
+        return dp[0][0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool checkValidString(string s) {
+        int n = s.size();
+        vector<vector<bool>> dp(n + 1, vector<bool>(n + 1, false));
+        dp[n][0] = true;
+
+        for (int i = n - 1; i >= 0; --i) {
+            for (int open = 0; open < n; ++open) {
+                bool res = false;
+                if (s[i] == '*') {
+                    res |= dp[i + 1][open + 1];
+                    if (open > 0) res |= dp[i + 1][open - 1];
+                    res |= dp[i + 1][open];
+                } else {
+                    if (s[i] == '(') {
+                        res |= dp[i + 1][open + 1];
+                    } else if (open > 0) {
+                        res |= dp[i + 1][open - 1];
+                    }
+                }
+                dp[i][open] = res;
+            }
+        }
+        return dp[0][0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {boolean}
+     */
+    checkValidString(s) {
+        const n = s.length;
+        const dp = Array.from({ length: n + 1 }, () => 
+                   Array(n + 1).fill(false));
+        dp[n][0] = true;
+
+        for (let i = n - 1; i >= 0; i--) {
+            for (let open = 0; open < n; open++) {
+                let res = false;
+                if (s[i] === '*') {
+                    res ||= dp[i + 1][open + 1];
+                    if (open > 0) res ||= dp[i + 1][open - 1];
+                    res ||= dp[i + 1][open];
+                } else {
+                    if (s[i] === '(') {
+                        res ||= dp[i + 1][open + 1];
+                    } else if (open > 0) {
+                        res ||= dp[i + 1][open - 1];
+                    }
+                }
+                dp[i][open] = res;
+            }
+        }
+        return dp[0][0];
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool CheckValidString(string s) {
+        int n = s.Length;
+        bool[,] dp = new bool[n + 1, n + 1];
+        dp[n, 0] = true;
+
+        for (int i = n - 1; i >= 0; i--) {
+            for (int open = 0; open < n; open++) {
+                bool res = false;
+                if (s[i] == '*') {
+                    res |= dp[i + 1, open + 1];
+                    if (open > 0) res |= dp[i + 1, open - 1];
+                    res |= dp[i + 1, open];
+                } else {
+                    if (s[i] == '(') {
+                        res |= dp[i + 1, open + 1];
+                    } else if (open > 0) {
+                        res |= dp[i + 1, open - 1];
+                    }
+                }
+                dp[i, open] = res;
+            }
+        }
+        return dp[0, 0];
+    }
+}
+```
+
+```go
+func checkValidString(s string) bool {
+    n := len(s)
+    dp := make([][]bool, n+1)
+    for i := range dp {
+        dp[i] = make([]bool, n+1)
+    }
+    dp[n][0] = true
+
+    for i := n - 1; i >= 0; i-- {
+        for open := 0; open < n; open++ {
+            res := false
+            if s[i] == '*' {
+                res = dp[i+1][open+1]
+                if open > 0 {
+                    res = res || dp[i+1][open-1]
+                }
+                res = res || dp[i+1][open]
+            } else {
+                if s[i] == '(' {
+                    res = dp[i+1][open+1]
+                } else if open > 0 {
+                    res = dp[i+1][open-1]
+                }
+            }
+            dp[i][open] = res
+        }
+    }
+    return dp[0][0]
+}
+```
+
+```kotlin
+class Solution {
+    fun checkValidString(s: String): Boolean {
+        val n = s.length
+        val dp = Array(n + 1) { BooleanArray(n + 1) }
+        dp[n][0] = true
+
+        for (i in n - 1 downTo 0) {
+            for (open in 0 until n) {
+                var res = false
+                if (s[i] == '*') {
+                    res = dp[i + 1][open + 1]
+                    if (open > 0) {
+                        res = res || dp[i + 1][open - 1]
+                    }
+                    res = res || dp[i + 1][open]
+                } else {
+                    if (s[i] == '(') {
+                        res = dp[i + 1][open + 1]
+                    } else if (open > 0) {
+                        res = dp[i + 1][open - 1]
+                    }
+                }
+                dp[i][open] = res
+            }
+        }
+        return dp[0][0]
+    }
+}
+```
+
+```swift
+class Solution {
+    func checkValidString(_ s: String) -> Bool {
+        let n = s.count
+        var dp = Array(repeating: Array(repeating: false, count: n + 1), count: n + 1)
+        dp[n][0] = true
+
+        let chars = Array(s)
+
+        for i in stride(from: n - 1, through: 0, by: -1) {
+            for open in 0..<n {
+                var res = false
+                if chars[i] == "*" {
+                    res = res || dp[i + 1][open + 1]
+                    if open > 0 {
+                        res = res || dp[i + 1][open - 1]
+                    }
+                    res = res || dp[i + 1][open]
+                } else {
+                    if chars[i] == "(" {
+                        res = res || dp[i + 1][open + 1]
+                    } else if open > 0 {
+                        res = res || dp[i + 1][open - 1]
+                    }
+                }
+                dp[i][open] = res
+            }
+        }
+
+        return dp[0][0]
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n ^ 2)$
+
+---
+
+## 4. Dynamic Programming (Space Optimized)
+
+::tabs-start
+
+```python
+class Solution:
+    def checkValidString(self, s: str) -> bool:
+        n = len(s)
+        dp = [False] * (n + 1)
+        dp[0] = True
+
+        for i in range(n - 1, -1, -1):
+            new_dp = [False] * (n + 1)
+            for open in range(n):
+                if s[i] == '*':
+                    new_dp[open] = (dp[open + 1] or 
+                                    (open > 0 and dp[open - 1]) or 
+                                    dp[open])
+                elif s[i] == '(':
+                    new_dp[open] = dp[open + 1]
+                elif open > 0:
+                    new_dp[open] = dp[open - 1]
+            dp = new_dp
+
+        return dp[0]
+```
+
+```java
+public class Solution {
+    public boolean checkValidString(String s) {
+        int n = s.length();
+        boolean[] dp = new boolean[n + 1];
+        dp[0] = true;
+
+        for (int i = n - 1; i >= 0; i--) {
+            boolean[] newDp = new boolean[n + 1];
+            for (int open = 0; open < n; open++) {
+                if (s.charAt(i) == '*') {
+                    newDp[open] = dp[open + 1] || 
+                                  (open > 0 && dp[open - 1]) || dp[open];
+                } else if (s.charAt(i) == '(') {
+                    newDp[open] = dp[open + 1];
+                } else if (open > 0) {
+                    newDp[open] = dp[open - 1];
+                }
+            }
+            dp = newDp;
+        }
+        return dp[0];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool checkValidString(string s) {
+        int n = s.size();
+        vector<bool> dp(n + 1, false);
+        dp[0] = true;
+
+        for (int i = n - 1; i >= 0; --i) {
+            vector<bool> newDp(n + 1, false);
+            for (int open = 0; open < n; ++open) {
+                if (s[i] == '*') {
+                    newDp[open] = dp[open + 1] || 
+                                  (open > 0 && dp[open - 1]) || dp[open];
+                } else if (s[i] == '(') {
+                    newDp[open] = dp[open + 1];
+                } else if (open > 0) {
+                    newDp[open] = dp[open - 1];
+                }
+            }
+            dp = newDp;
+        }
+        return dp[0];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {boolean}
+     */
+    checkValidString(s) {
+        const n = s.length;
+        let dp = Array(n + 1).fill(false);
+        dp[0] = true;
+
+        for (let i = n - 1; i >= 0; i--) {
+            const newDp = Array(n + 1).fill(false);
+            for (let open = 0; open < n; open++) {
+                if (s[i] === '*') {
+                    newDp[open] = dp[open + 1] || 
+                                  (open > 0 && dp[open - 1]) || dp[open];
+                } else if (s[i] === '(') {
+                    newDp[open] = dp[open + 1];
+                } else if (open > 0) {
+                    newDp[open] = dp[open - 1];
+                }
+            }
+            dp = newDp;
+        }
+        return dp[0];
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool CheckValidString(string s) {
+        int n = s.Length;
+        bool[] dp = new bool[n + 1];
+        dp[0] = true;
+
+        for (int i = n - 1; i >= 0; i--) {
+            bool[] newDp = new bool[n + 1];
+            for (int open = 0; open < n; open++) {
+                if (s[i] == '*') {
+                    newDp[open] = dp[open + 1] || 
+                                  (open > 0 && dp[open - 1]) || dp[open];
+                } else if (s[i] == '(') {
+                    newDp[open] = dp[open + 1];
+                } else if (open > 0) {
+                    newDp[open] = dp[open - 1];
+                }
+            }
+            dp = newDp;
+        }
+        return dp[0];
+    }
+}
+```
+
+```go
+func checkValidString(s string) bool {
+    n := len(s)
+    dp := make([]bool, n+1)
+    dp[0] = true
+
+    for i := n - 1; i >= 0; i-- {
+        newDp := make([]bool, n+1)
+        for open := 0; open < n; open++ {
+            if s[i] == '*' {
+                newDp[open] = (dp[open+1] || 
+                               (open > 0 && dp[open-1]) || 
+                               dp[open])
+            } else if s[i] == '(' {
+                newDp[open] = dp[open+1]
+            } else if open > 0 {
+                newDp[open] = dp[open-1]
+            }
+        }
+        dp = newDp
+    }
+    return dp[0]
+}
+```
+
+```kotlin
+class Solution {
+    fun checkValidString(s: String): Boolean {
+        val n = s.length
+        var dp = BooleanArray(n + 1)
+        dp[0] = true
+
+        for (i in n - 1 downTo 0) {
+            val newDp = BooleanArray(n + 1)
+            for (open in 0 until n) {
+                newDp[open] = when (s[i]) {
+                    '*' -> (dp[open + 1] || 
+                            (open > 0 && dp[open - 1]) || 
+                            dp[open])
+                    '(' -> dp[open + 1]
+                    else -> open > 0 && dp[open - 1]
+                }
+            }
+            dp = newDp
+        }
+        return dp[0]
+    }
+}
+```
+
+```swift
+class Solution {
+    func checkValidString(_ s: String) -> Bool {
+        let n = s.count
+        var dp = Array(repeating: false, count: n + 1)
+        dp[0] = true
+
+        let chars = Array(s)
+
+        for i in stride(from: n - 1, through: 0, by: -1) {
+            var new_dp = Array(repeating: false, count: n + 1)
+            for open in 0..<n {
+                if chars[i] == "*" {
+                    new_dp[open] = dp[open + 1] || (open > 0 && dp[open - 1]) || dp[open]
+                } else if chars[i] == "(" {
+                    new_dp[open] = dp[open + 1]
+                } else if open > 0 {
+                    new_dp[open] = dp[open - 1]
+                }
+            }
+            dp = new_dp
+        }
+
+        return dp[0]
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 2)$
+* Space complexity: $O(n)$
+
+---
+
+## 5. Stack
+
+::tabs-start
+
+```python
+class Solution:
+    def checkValidString(self, s: str) -> bool:
+        left = []
+        star = []
+        for i, ch in enumerate(s):
+            if ch == '(':
+                left.append(i)
+            elif ch == '*':
+                star.append(i)
+            else:
+                if not left and not star:
+                    return False
+                if left:
+                    left.pop()
+                else:
+                    star.pop()
+        
+        while left and star:
+            if left.pop() > star.pop():
+                return False
+        return not left
+```
+
+```java
+public class Solution {
+        public boolean checkValidString(String s) {
+        Stack<Integer> left = new Stack<>();
+        Stack<Integer> star = new Stack<>();
+        for (int i = 0; i < s.length(); i++) {
+            char ch = s.charAt(i);
+            if (ch == '(') {
+                left.push(i);
+            } else if (ch == '*') {
+                star.push(i);
+            } else {
+                if (left.isEmpty() && star.isEmpty()) return false;
+                if (!left.isEmpty()) {
+                    left.pop();
+                } else{
+                    star.pop();
+                } 
+            }
+        }
+        while (!left.isEmpty() && !star.isEmpty()) {
+            if (left.pop() > star.pop()) 
+                return false;
+        }
+        return left.isEmpty();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool checkValidString(string s) {
+        stack<int> left, star;
+        for (int i = 0; i < s.size(); ++i) {
+            if (s[i] == '(') {
+                left.push(i);
+            } else if (s[i] == '*') {
+                star.push(i);
+            } else {
+                if (left.empty() && star.empty()) return false;
+                if (!left.empty()) {
+                    left.pop();
+                } else {
+                    star.pop();
+                }
+            }
+        }
+        
+        while (!left.empty() && !star.empty()) {
+            if (left.top() > star.top()) return false;
+            left.pop();
+            star.pop();
+        }
+        return left.empty();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {boolean}
+     */
+    checkValidString(s) {
+        const left = [];
+        const star = [];
+        for (let i = 0; i < s.length; i++) {
+            const ch = s[i];
+            if (ch === '(') {
+                left.push(i);
+            } else if (ch === '*') {
+                star.push(i);
+            } else {
+                if (left.length === 0 && star.length === 0) {
+                    return false;
+                }
+                if (left.length > 0) {
+                    left.pop();
+                } else {
+                    star.pop();
+                }
+            }
+        }
+        
+        while (left.length > 0 && star.length > 0) {
+            if (left.pop() > star.pop()) return false;
+        }
+        return left.length === 0;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool CheckValidString(string s) {
+        Stack<int> left = new Stack<int>();
+        Stack<int> star = new Stack<int>();
+        for (int i = 0; i < s.Length; i++) {
+            char ch = s[i];
+            if (ch == '(') {
+                left.Push(i);
+            } else if (ch == '*') {
+                star.Push(i);
+            } else {
+                if (left.Count == 0 && star.Count == 0) return false;
+                if (left.Count > 0) {
+                    left.Pop();
+                } else {
+                    star.Pop();
+                }
+            }
+        }
+        
+        while (left.Count > 0 && star.Count > 0) {
+            if (left.Pop() > star.Pop()) return false;
+        }
+        return left.Count == 0;
+    }
+}
+```
+
+```go
+func checkValidString(s string) bool {
+    var left, star []int
+    for i, ch := range s {
+        if ch == '(' {
+            left = append(left, i)
+        } else if ch == '*' {
+            star = append(star, i)
+        } else {
+            if len(left) == 0 && len(star) == 0 {
+                return false
+            }
+            if len(left) > 0 {
+                left = left[:len(left)-1]
+            } else {
+                star = star[:len(star)-1]
+            }
+        }
+    }
+
+    for len(left) > 0 && len(star) > 0 {
+        if left[len(left)-1] > star[len(star)-1] {
+            return false
+        }
+        left = left[:len(left)-1]
+        star = star[:len(star)-1]
+    }
+    return len(left) == 0
+}
+```
+
+```kotlin
+class Solution {
+    fun checkValidString(s: String): Boolean {
+        val left = ArrayDeque<Int>()
+        val star = ArrayDeque<Int>()
+
+        for ((i, ch) in s.withIndex()) {
+            when (ch) {
+                '(' -> left.addLast(i)
+                '*' -> star.addLast(i)
+                ')' -> {
+                    if (left.isEmpty() && star.isEmpty()) return false
+                    if (left.isNotEmpty()) left.removeLast()
+                    else star.removeLast()
+                }
+            }
+        }
+
+        while (left.isNotEmpty() && star.isNotEmpty()) {
+            if (left.last() > star.last()) return false
+            left.removeLast()
+            star.removeLast()
+        }
+        return left.isEmpty()
+    }
+}
+```
+
+```swift
+class Solution {
+    func checkValidString(_ s: String) -> Bool {
+        var left = [Int]()
+        var star = [Int]()
+
+        let chars = Array(s)
+
+        for (i, ch) in chars.enumerated() {
+            if ch == "(" {
+                left.append(i)
+            } else if ch == "*" {
+                star.append(i)
+            } else {
+                if left.isEmpty && star.isEmpty {
+                    return false
+                }
+                if !left.isEmpty {
+                    left.popLast()
+                } else {
+                    star.popLast()
+                }
+            }
+        }
+
+        while !left.isEmpty && !star.isEmpty {
+            if left.last! > star.last! {
+                return false
+            }
+            left.popLast()
+            star.popLast()
+        }
+
+        return left.isEmpty
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 6. Greedy
+
+::tabs-start
+
+```python
+class Solution:
+    def checkValidString(self, s: str) -> bool:
+        leftMin, leftMax = 0, 0
+
+        for c in s:
+            if c == "(":
+                leftMin, leftMax = leftMin + 1, leftMax + 1
+            elif c == ")":
+                leftMin, leftMax = leftMin - 1, leftMax - 1
+            else:
+                leftMin, leftMax = leftMin - 1, leftMax + 1
+            if leftMax < 0:
+                return False
+            if leftMin < 0:
+                leftMin = 0
+        return leftMin == 0
+```
+
+```java
+public class Solution {
+    public boolean checkValidString(String s) {
+        int leftMin = 0, leftMax = 0;
+
+        for (char c : s.toCharArray()) {
+            if (c == '(') {
+                leftMin++;
+                leftMax++;
+            } else if (c == ')') {
+                leftMin--;
+                leftMax--;
+            } else {
+                leftMin--;
+                leftMax++;
+            }
+            if (leftMax < 0) {
+                return false;
+            }
+            if (leftMin < 0) {
+                leftMin = 0;
+            }
+        }
+        return leftMin == 0;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool checkValidString(string s) {
+        int leftMin = 0, leftMax = 0;
+
+        for (char c : s) {
+            if (c == '(') {
+                leftMin++;
+                leftMax++;
+            } else if (c == ')') {
+                leftMin--;
+                leftMax--;
+            } else {
+                leftMin--;
+                leftMax++;
+            }
+            if (leftMax < 0) {
+                return false;
+            }
+            if (leftMin < 0) {
+                leftMin = 0;
+            }
+        }
+        return leftMin == 0;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @return {boolean}
+     */
+    checkValidString(s) {
+        let leftMin = 0;
+        let leftMax = 0;
+
+        for (const c of s) {
+            if (c === '(') {
+                leftMin++;
+                leftMax++;
+            } else if (c === ')') {
+                leftMin--;
+                leftMax--;
+            } else {
+                leftMin--;
+                leftMax++;
+            }
+            if (leftMax < 0) {
+                return false;
+            }
+            if (leftMin < 0) {
+                leftMin = 0;
+            }
+        }
+        return leftMin === 0;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool CheckValidString(string s) {
+        int leftMin = 0, leftMax = 0;
+
+        foreach (char c in s) {
+            if (c == '(') {
+                leftMin++;
+                leftMax++;
+            } else if (c == ')') {
+                leftMin--;
+                leftMax--;
+            } else {
+                leftMin--;
+                leftMax++;
+            }
+            if (leftMax < 0) {
+                return false;
+            }
+            if (leftMin < 0) {
+                leftMin = 0;
+            }
+        }
+        return leftMin == 0;
+    }
+}
+```
+
+```go
+func checkValidString(s string) bool {
+    leftMin, leftMax := 0, 0
+
+    for _, c := range s {
+        if c == '(' {
+            leftMin, leftMax = leftMin+1, leftMax+1
+        } else if c == ')' {
+            leftMin, leftMax = leftMin-1, leftMax-1
+        } else {
+            leftMin, leftMax = leftMin-1, leftMax+1
+        }
+        if leftMax < 0 {
+            return false
+        }
+        if leftMin < 0 {
+            leftMin = 0
+        }
+    }
+    return leftMin == 0
+}
+```
+
+```kotlin
+class Solution {
+    fun checkValidString(s: String): Boolean {
+        var leftMin = 0
+        var leftMax = 0
+
+        for (c in s) {
+            when (c) {
+                '(' -> {
+                    leftMin++
+                    leftMax++
+                }
+                ')' -> {
+                    leftMin--
+                    leftMax--
+                }
+                else -> {
+                    leftMin--
+                    leftMax++
+                }
+            }
+            if (leftMax < 0) return false
+            if (leftMin < 0) leftMin = 0
+        }
+        return leftMin == 0
+    }
+}
+```
+
+```swift
+class Solution {
+    func checkValidString(_ s: String) -> Bool {
+        var leftMin = 0
+        var leftMax = 0
+
+        for c in s {
+            if c == "(" {
+                leftMin += 1
+                leftMax += 1
+            } else if c == ")" {
+                leftMin -= 1
+                leftMax -= 1
+            } else {
+                leftMin -= 1
+                leftMax += 1
+            }
+            if leftMax < 0 {
+                return false
+            }
+            if leftMin < 0 {
+                leftMin = 0
+            }
+        }
+        return leftMin == 0
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/valid-perfect-square.md b/articles/valid-perfect-square.md
new file mode 100644
index 000000000..c5682c5d4
--- /dev/null
+++ b/articles/valid-perfect-square.md
@@ -0,0 +1,447 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def isPerfectSquare(self, num: int) -> bool:
+        for i in range(1, num + 1):
+            sq = i * i
+            if sq > num:
+                return False
+            if sq == num:
+                return True
+```
+
+```java
+public class Solution {
+    public boolean isPerfectSquare(int num) {
+        for (long i = 1; i <= num; i++) {
+            long sq = i * i;
+            if (sq > num) {
+                return false;
+            }
+            if (sq == num) {
+                return true;
+            }
+        }
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isPerfectSquare(int num) {
+        for (long long i = 1; i <= num; i++) {
+            long long sq = i * i;
+            if (sq > num) {
+                return false;
+            }
+            if (sq == num) {
+                return true;
+            }
+        }
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} num
+     * @return {boolean}
+     */
+    isPerfectSquare(num) {
+        for (let i = 1; i <= num; i++) {
+            let sq = i * i;
+            if (sq > num) {
+                return false;
+            }
+            if (sq === num) {
+                return true;
+            }
+        }
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\sqrt {n})$
+* Space complexity: $O(1)$
+
+---
+
+## 2. In-Built Function
+
+::tabs-start
+
+```python
+class Solution:
+    def isPerfectSquare(self, num: int) -> bool:
+        sqRoot = int(sqrt(num))
+        return sqRoot * sqRoot == num
+```
+
+```java
+public class Solution {
+    public boolean isPerfectSquare(int num) {
+        int sqRoot = (int) Math.sqrt(num);
+        return sqRoot * sqRoot == num;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isPerfectSquare(int num) {
+        int sqRoot = (int) sqrt(num);
+        return sqRoot * sqRoot == num;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} num
+     * @return {boolean}
+     */
+    isPerfectSquare(num) {
+        let sqRoot = Math.floor(Math.sqrt(num));
+        return sqRoot * sqRoot === num;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$
+* Space complexity: $O(1)$
+
+---
+
+## 3. Binary Search
+
+::tabs-start
+
+```python
+class Solution:
+    def isPerfectSquare(self, num: int) -> bool:
+        l, r = 1, num
+
+        while l <= r:
+            m = l + (r - l) // 2
+            sq = m * m
+            if sq > num:
+                r = m - 1
+            elif sq < num:
+                l = m + 1
+            else:
+                return True
+
+        return False
+```
+
+```java
+public class Solution {
+    public boolean isPerfectSquare(int num) {
+        long l = 1, r = num;
+
+        while (l <= r) {
+            long m = l + (r - l) / 2;
+            long sq = m * m;
+            if (sq > num) {
+                r = m - 1;
+            } else if (sq < num) {
+                l = m + 1;
+            } else {
+                return true;
+            }
+        }
+
+        return false;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isPerfectSquare(int num) {
+        long long l = 1, r = num;
+
+        while (l <= r) {
+            long long m = l + (r - l) / 2;
+            long long sq = m * m;
+            if (sq > num) {
+                r = m - 1;
+            } else if (sq < num) {
+                l = m + 1;
+            } else {
+                return true;
+            }
+        }
+
+        return false;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} num
+     * @return {boolean}
+     */
+    isPerfectSquare(num) {
+        let l = 1, r = num;
+
+        while (l <= r) {
+            let m = Math.floor(l + (r - l) / 2);
+            let sq = m * m;
+            if (sq > num) {
+                r = m - 1;
+            } else if (sq < num) {
+                l = m + 1;
+            } else {
+                return true;
+            }
+        }
+
+        return false;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
+
+---
+
+## 4. Math
+
+::tabs-start
+
+```python
+class Solution:
+    def isPerfectSquare(self, num: int) -> bool:
+        i = 1
+        while num > 0:
+            num -= i
+            i += 2
+        return num == 0
+```
+
+```java
+public class Solution {
+    public boolean isPerfectSquare(int num) {
+        int i = 1;
+        while (num > 0) {
+            num -= i;
+            i += 2;
+        }
+        return num == 0;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isPerfectSquare(int num) {
+        int i = 1;
+        while (num > 0) {
+            num -= i;
+            i += 2;
+        }
+        return num == 0;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} num
+     * @return {boolean}
+     */
+    isPerfectSquare(num) {
+        let i = 1;
+        while (num > 0) {
+            num -= i;
+            i += 2;
+        }
+        return num === 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\sqrt {n})$
+* Space complexity: $O(1)$
+
+---
+
+## 5. Newton's Method
+
+::tabs-start
+
+```python
+class Solution:
+    def isPerfectSquare(self, num: int) -> bool:
+        r = num
+        while r * r > num:
+            r = (r + (num // r)) // 2
+        return r * r == num
+```
+
+```java
+public class Solution {
+    public boolean isPerfectSquare(int num) {
+        long r = num;
+        while (r * r > num) {
+            r = (r + num / r) / 2;
+        }
+        return r * r == num;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isPerfectSquare(int num) {
+        long long r = num;
+        while (r * r > num) {
+            r = (r + num / r) / 2;
+        }
+        return r * r == num;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} num
+     * @return {boolean}
+     */
+    isPerfectSquare(num) {
+        let r = num;
+        while (r * r > num) {
+            r = Math.floor((r + Math.floor(num / r)) / 2);
+        }
+        return r * r === num;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(\log n)$
+* Space complexity: $O(1)$
+
+---
+
+## 6. Bit Manipulation
+
+::tabs-start
+
+```python
+class Solution:
+    def isPerfectSquare(self, num: int) -> bool:
+        r, mask = 0, 1 << 15
+
+        while mask > 0:
+            r |= mask
+            if r > (num // r):
+                r ^= mask
+            mask >>= 1
+        
+        return r * r == num
+```
+
+```java
+public class Solution {
+    public boolean isPerfectSquare(int num) {
+        int r = 0, mask = 1 << 15;
+
+        while (mask > 0) {
+            r |= mask;
+            if (r > (num / r)) {
+                r ^= mask;
+            }
+            mask >>= 1;
+        }
+        
+        return r * r == num;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isPerfectSquare(int num) {
+        int r = 0, mask = 1 << 15;
+
+        while (mask > 0) {
+            r |= mask;
+            if (r > (num / r)) {
+                r ^= mask;
+            }
+            mask >>= 1;
+        }
+        
+        return r * r == num;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} num
+     * @return {boolean}
+     */
+    isPerfectSquare(num) {
+        let r = 0, mask = 1 << 15;
+
+        while (mask > 0) {
+            r |= mask;
+            if (r > Math.floor(num / r)) {
+                r ^= mask;
+            }
+            mask >>= 1;
+        }
+        
+        return r * r === num;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(1)$ since we iterate at most $15$ times.
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/valid-sudoku.md b/articles/valid-sudoku.md
index 09e8c801e..74fb5deda 100644
--- a/articles/valid-sudoku.md
+++ b/articles/valid-sudoku.md
@@ -198,6 +198,131 @@ public class Solution {
 }
 ```
 
+```go
+func isValidSudoku(board [][]byte) bool {
+    for row := 0; row < 9; row++ {
+        seen := make(map[byte]bool)
+        for i := 0; i < 9; i++ {
+            if board[row][i] == '.' {
+                continue
+            }
+            if seen[board[row][i]] {
+                return false
+            }
+            seen[board[row][i]] = true
+        }
+    }
+
+    for col := 0; col < 9; col++ {
+        seen := make(map[byte]bool)
+        for i := 0; i < 9; i++ {
+            if board[i][col] == '.' {
+                continue
+            }
+            if seen[board[i][col]] {
+                return false
+            }
+            seen[board[i][col]] = true
+        }
+    }
+
+    for square := 0; square < 9; square++ {
+        seen := make(map[byte]bool)
+        for i := 0; i < 3; i++ {
+            for j := 0; j < 3; j++ {
+                row := (square / 3) * 3 + i
+                col := (square % 3) * 3 + j
+                if board[row][col] == '.' {
+                    continue
+                }
+                if seen[board[row][col]] {
+                    return false
+                }
+                seen[board[row][col]] = true
+            }
+        }
+    }
+    return true
+}
+```
+
+```kotlin
+class Solution {
+    fun isValidSudoku(board: Array<CharArray>): Boolean {
+        for (row in 0 until 9) {
+            val seen = mutableSetOf<Char>()
+            for (i in 0 until 9) {
+                if (board[row][i] == '.') continue
+                if (board[row][i] in seen) return false
+                seen.add(board[row][i])
+            }
+        }
+
+        for (col in 0 until 9) {
+            val seen = mutableSetOf<Char>()
+            for (i in 0 until 9) {
+                if (board[i][col] == '.') continue
+                if (board[i][col] in seen) return false
+                seen.add(board[i][col])
+            }
+        }
+
+        for (square in 0 until 9) {
+            val seen = mutableSetOf<Char>()
+            for (i in 0 until 3) {
+                for (j in 0 until 3) {
+                    val row = (square / 3) * 3 + i
+                    val col = (square % 3) * 3 + j
+                    if (board[row][col] == '.') continue
+                    if (board[row][col] in seen) return false
+                    seen.add(board[row][col])
+                }
+            }
+        }
+        return true
+    }
+}
+```
+
+```swift
+class Solution {
+    func isValidSudoku(_ board: [[Character]]) -> Bool {
+        for row in 0..<9 {
+            var seen = Set<Character>()
+            for i in 0..<9 {
+                if board[row][i] == "." { continue }
+                if seen.contains(board[row][i]) { return false }
+                seen.insert(board[row][i])
+            }
+        }
+
+        for col in 0..<9 {
+            var seen = Set<Character>()
+            for i in 0..<9 {
+                if board[i][col] == "." { continue }
+                if seen.contains(board[i][col]) { return false }
+                seen.insert(board[i][col])
+            }
+        }
+
+        for square in 0..<9 {
+            var seen = Set<Character>()
+            for i in 0..<3 {
+                for j in 0..<3 {
+                    let row = (square / 3) * 3 + i
+                    let col = (square % 3) * 3 + j
+                    if board[row][col] == "." { continue }
+                    if seen.contains(board[row][col]) { return false }
+                    seen.insert(board[row][col])
+                }
+            }
+        }
+        
+        return true
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -360,6 +485,100 @@ public class Solution {
 }
 ```
 
+```go
+func isValidSudoku(board [][]byte) bool {
+    rows := make([]map[byte]bool, 9)
+    cols := make([]map[byte]bool, 9)
+    squares := make([]map[byte]bool, 9)
+
+    for i := 0; i < 9; i++ {
+        rows[i] = make(map[byte]bool)
+        cols[i] = make(map[byte]bool)
+        squares[i] = make(map[byte]bool)
+    }
+
+    for r := 0; r < 9; r++ {
+        for c := 0; c < 9; c++ {
+            if board[r][c] == '.' {
+                continue
+            }
+            val := board[r][c]
+            squareIdx := (r/3)*3 + c/3
+
+            if rows[r][val] || cols[c][val] || 
+               squares[squareIdx][val] {
+                return false
+            }
+
+            rows[r][val] = true
+            cols[c][val] = true
+            squares[squareIdx][val] = true
+        }
+    }
+
+    return true
+}
+```
+
+```kotlin
+class Solution {
+    fun isValidSudoku(board: Array<CharArray>): Boolean {
+        val rows = Array(9) { HashSet<Char>() }
+        val cols = Array(9) { HashSet<Char>() }
+        val squares = Array(9) { HashSet<Char>() }
+
+        for (r in 0 until 9) {
+            for (c in 0 until 9) {
+                val value = board[r][c]
+                if (value == '.') continue
+
+                val squareIdx = (r / 3) * 3 + (c / 3)
+                if (value in rows[r] || value in cols[c] || 
+                    value in squares[squareIdx]) {
+                    return false
+                }
+
+                rows[r].add(value)
+                cols[c].add(value)
+                squares[squareIdx].add(value)
+            }
+        }
+
+        return true
+    }
+}
+```
+
+```swift
+class Solution {
+    func isValidSudoku(_ board: [[Character]]) -> Bool {
+        var cols = [Int: Set<Character>]()
+        var rows = [Int: Set<Character>]()
+        var squares = [String: Set<Character>]()
+
+        for r in 0..<9 {
+            for c in 0..<9 {
+                if board[r][c] == "." { continue }
+
+                let squareKey = "\(r / 3),\(c / 3)"
+
+                if rows[r]?.contains(board[r][c]) == true ||
+                   cols[c]?.contains(board[r][c]) == true ||
+                   squares[squareKey]?.contains(board[r][c]) == true {
+                    return false
+                }
+
+                rows[r, default: []].insert(board[r][c])
+                cols[c, default: []].insert(board[r][c])
+                squares[squareKey, default: []].insert(board[r][c])
+            }
+        }
+        
+        return true
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -513,6 +732,97 @@ public class Solution {
 }
 ```
 
+```go
+func isValidSudoku(board [][]byte) bool {
+    rows := make([]int, 9)
+    cols := make([]int, 9)
+    squares := make([]int, 9)
+
+    for r := 0; r < 9; r++ {
+        for c := 0; c < 9; c++ {
+            if board[r][c] == '.' {
+                continue
+            }
+            
+            val := board[r][c] - '1'
+            bit := 1 << val
+            squareIdx := (r/3)*3 + c/3
+
+            if rows[r]&bit != 0 || cols[c]&bit != 0 || 
+               squares[squareIdx]&bit != 0 {
+                return false
+            }
+            
+            rows[r] |= bit
+            cols[c] |= bit
+            squares[squareIdx] |= bit
+        }
+    }
+
+    return true
+}
+```
+
+```kotlin
+class Solution {
+    fun isValidSudoku(board: Array<CharArray>): Boolean {
+        val rows = IntArray(9)
+        val cols = IntArray(9)
+        val squares = IntArray(9)
+
+        for (r in 0 until 9) {
+            for (c in 0 until 9) {
+                if (board[r][c] == '.') continue
+                
+                val value = board[r][c] - '1'
+                val bit = 1 shl value
+                val squareIdx = (r / 3) * 3 + (c / 3)
+
+                if ((rows[r] and bit) != 0 || (cols[c] and bit) != 0 || 
+                    (squares[squareIdx] and bit) != 0) {
+                    return false
+                }
+
+                rows[r] = rows[r] or bit
+                cols[c] = cols[c] or bit
+                squares[squareIdx] = squares[squareIdx] or bit
+            }
+        }
+
+        return true
+    }
+}
+```
+
+```swift
+class Solution {
+    func isValidSudoku(_ board: [[Character]]) -> Bool {
+        var rows = [Int](repeating: 0, count: 9)
+        var cols = [Int](repeating: 0, count: 9)
+        var squares = [Int](repeating: 0, count: 9)
+
+        for r in 0..<9 {
+            for c in 0..<9 {
+                if board[r][c] == "." { continue }
+                
+                let val = Int(board[r][c].asciiValue! - Character("0").asciiValue!)
+                let bitmask = 1 << (val - 1)
+
+                if (rows[r] & bitmask) != 0 { return false }
+                if (cols[c] & bitmask) != 0 { return false }
+                if (squares[(r / 3) * 3 + (c / 3)] & bitmask) != 0 { return false }
+
+                rows[r] |= bitmask
+                cols[c] |= bitmask
+                squares[(r / 3) * 3 + (c / 3)] |= bitmask
+            }
+        }
+
+        return true
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/valid-tree.md b/articles/valid-tree.md
index d4c8ea3c6..7266d9836 100644
--- a/articles/valid-tree.md
+++ b/articles/valid-tree.md
@@ -203,6 +203,107 @@ public class Solution {
 }
 ```
 
+```go
+func validTree(n int, edges [][]int) bool {
+    if len(edges) > n-1 {
+		return false
+	}
+	
+	adj := make([][]int, n)
+	for _, edge := range edges {
+		u, v := edge[0], edge[1]
+		adj[u] = append(adj[u], v)
+		adj[v] = append(adj[v], u)
+	}
+
+	visit := make(map[int]bool)
+	var dfs func(node, parent int) bool
+	dfs = func(node, parent int) bool {
+		if visit[node] {
+			return false
+		}
+		visit[node] = true
+		for _, nei := range adj[node] {
+			if nei == parent {
+				continue
+			}
+			if !dfs(nei, node) {
+				return false
+			}
+		}
+		return true
+	}
+
+	return dfs(0, -1) && len(visit) == n
+}
+```
+
+```kotlin
+class Solution {
+    fun validTree(n: Int, edges: Array<IntArray>): Boolean {
+        if (edges.size > n - 1) return false
+        
+        val adj = Array(n) { mutableListOf<Int>() }
+        for ((u, v) in edges) {
+            adj[u].add(v)
+            adj[v].add(u)
+        }
+        
+        val visit = HashSet<Int>()
+        
+        fun dfs(node: Int, parent: Int): Boolean {
+            if (node in visit) return false
+            visit.add(node)
+            for (nei in adj[node]) {
+                if (nei == parent) continue
+                if (!dfs(nei, node)) return false
+            }
+            return true
+        }
+        
+        return dfs(0, -1) && visit.size == n
+    }
+}
+```
+
+```swift
+class Solution {
+    func validTree(_ n: Int, _ edges: [[Int]]) -> Bool {
+        if edges.count > (n - 1) {
+            return false
+        }
+        
+        var adj = Array(repeating: [Int](), count: n)
+        for edge in edges {
+            let u = edge[0]
+            let v = edge[1]
+            adj[u].append(v)
+            adj[v].append(u)
+        }
+        
+        var visited = Set<Int>()
+        
+        func dfs(_ node: Int, _ parent: Int) -> Bool {
+            if visited.contains(node) {
+                return false
+            }
+            visited.insert(node)
+            for nei in adj[node] {
+                if nei == parent {
+                    continue
+                }
+                if !dfs(nei, node) {
+                    return false
+                }
+            }
+            return true
+        }
+        
+        return dfs(0, -1) && visited.count == n
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -405,6 +506,114 @@ public class Solution {
 }
 ```
 
+```go
+func validTree(n int, edges [][]int) bool {
+    if len(edges) > n-1 {
+		return false
+	}
+
+	adj := make([][]int, n)
+	for _, edge := range edges {
+		u, v := edge[0], edge[1]
+		adj[u] = append(adj[u], v)
+		adj[v] = append(adj[v], u)
+	}
+
+	visit := make(map[int]bool)
+	q := [][2]int{{0, -1}} // (current node, parent node)
+	visit[0] = true
+
+	for len(q) > 0 {
+		node, parent := q[0][0], q[0][1]
+		q = q[1:]
+
+		for _, nei := range adj[node] {
+			if nei == parent {
+				continue
+			}
+			if visit[nei] {
+				return false
+			}
+			visit[nei] = true
+			q = append(q, [2]int{nei, node})
+		}
+	}
+
+	return len(visit) == n
+}
+```
+
+```kotlin
+class Solution {
+    fun validTree(n: Int, edges: Array<IntArray>): Boolean {
+        if (edges.size > n - 1) return false
+
+        val adj = Array(n) { mutableListOf<Int>() }
+        for ((u, v) in edges) {
+            adj[u].add(v)
+            adj[v].add(u)
+        }
+
+        val visit = mutableSetOf<Int>()
+        val q: Queue<Pair<Int, Int>> = LinkedList()  // Queue of (node, parent)
+        q.offer(0 to -1)
+        visit.add(0)
+
+        while (q.isNotEmpty()) {
+            val (node, parent) = q.poll()
+
+            for (nei in adj[node]) {
+                if (nei == parent) continue
+                if (nei in visit) return false
+                visit.add(nei)
+                q.offer(nei to node)
+            }
+        }
+
+        return visit.size == n
+    }
+}
+```
+
+```swift
+class Solution {
+    func validTree(_ n: Int, _ edges: [[Int]]) -> Bool {
+        if edges.count > n - 1 {
+            return false
+        }
+        
+        var adj = [[Int]](repeating: [], count: n)
+        for edge in edges {
+            let u = edge[0]
+            let v = edge[1]
+            adj[u].append(v)
+            adj[v].append(u)
+        }
+        
+        var visit = Set<Int>()
+        var q = Deque<(Int, Int)>()  // (current node, parent node)
+        q.append((0, -1))
+        visit.insert(0)
+        
+        while !q.isEmpty {
+            let (node, parent) = q.removeFirst()
+            for nei in adj[node] {
+                if nei == parent {
+                    continue
+                }
+                if visit.contains(nei) {
+                    return false
+                }
+                visit.insert(nei)
+                q.append((nei, node))
+            }
+        }
+        
+        return visit.count == n
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -461,7 +670,7 @@ class Solution:
 ```
 
 ```java
-public class DSU {
+class DSU {
     int[] Parent, Size;
     int comps;
 
@@ -700,6 +909,165 @@ public class Solution {
 }
 ```
 
+```go
+type DSU struct {
+	Parent []int
+	Size   []int
+	Comps  int
+}
+
+func NewDSU(n int) *DSU {
+	parent := make([]int, n+1)
+	size := make([]int, n+1)
+	for i := 0; i <= n; i++ {
+		parent[i] = i
+		size[i] = 1
+	}
+	return &DSU{Parent: parent, Size: size, Comps: n}
+}
+
+func (dsu *DSU) Find(node int) int {
+	if dsu.Parent[node] != node {
+		dsu.Parent[node] = dsu.Find(dsu.Parent[node])
+	}
+	return dsu.Parent[node]
+}
+
+func (dsu *DSU) Union(u, v int) bool {
+	pu, pv := dsu.Find(u), dsu.Find(v)
+	if pu == pv {
+		return false
+	}
+	dsu.Comps--
+	if dsu.Size[pu] < dsu.Size[pv] {
+		pu, pv = pv, pu
+	}
+	dsu.Size[pu] += dsu.Size[pv]
+	dsu.Parent[pv] = pu
+	return true
+}
+
+func (dsu *DSU) Components() int {
+	return dsu.Comps
+}
+
+func validTree(n int, edges [][]int) bool {
+    if len(edges) > n-1 {
+		return false
+	}
+	dsu := NewDSU(n)
+	for _, edge := range edges {
+		if !dsu.Union(edge[0], edge[1]) {
+			return false
+		}
+	}
+	return dsu.Components() == 1
+}
+```
+
+```kotlin
+class DSU(n: Int) {
+    private val parent = IntArray(n + 1) { it }
+    private val size = IntArray(n + 1) { 1 }
+    var comps = n
+        private set
+
+    fun find(node: Int): Int {
+        if (parent[node] != node) {
+            parent[node] = find(parent[node])
+        }
+        return parent[node]
+    }
+
+    fun union(u: Int, v: Int): Boolean {
+        val pu = find(u)
+        val pv = find(v)
+        if (pu == pv) return false
+
+        comps--
+        if (size[pu] < size[pv]) {
+            parent[pu] = pv
+            size[pv] += size[pu]
+        } else {
+            parent[pv] = pu
+            size[pu] += size[pv]
+        }
+        return true
+    }
+}
+
+class Solution {
+    fun validTree(n: Int, edges: Array<IntArray>): Boolean {
+        if (edges.size > n - 1) return false
+
+        val dsu = DSU(n)
+        for ((u, v) in edges) {
+            if (!dsu.union(u, v)) return false
+        }
+        return dsu.comps == 1
+    }
+}
+```
+
+```swift
+class DSU {
+    var comps: Int
+    var parent: [Int]
+    var size: [Int]
+    
+    init(_ n: Int) {
+        comps = n
+        parent = Array(0..<n)
+        size = Array(repeating: 1, count: n)
+    }
+    
+    func find(_ node: Int) -> Int {
+        if parent[node] != node {
+            parent[node] = find(parent[node])
+        }
+        return parent[node]
+    }
+    
+    func union(_ u: Int, _ v: Int) -> Bool {
+        let pu = find(u)
+        let pv = find(v)
+        if pu == pv {
+            return false
+        }
+        comps -= 1
+        if size[pu] < size[pv] {
+            parent[pu] = pv
+            size[pv] += size[pu]
+        } else {
+            parent[pv] = pu
+            size[pu] += size[pv]
+        }
+        return true
+    }
+    
+    func components() -> Int {
+        return comps
+    }
+}
+
+class Solution {
+    func validTree(_ n: Int, _ edges: [[Int]]) -> Bool {
+        if edges.count > n - 1 {
+            return false
+        }
+        
+        let dsu = DSU(n)
+        for edge in edges {
+            let u = edge[0], v = edge[1]
+            if !dsu.union(u, v) {
+                return false
+            }
+        }
+        return dsu.components() == 1
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/valid-word-abbreviation.md b/articles/valid-word-abbreviation.md
new file mode 100644
index 000000000..79c44a2e7
--- /dev/null
+++ b/articles/valid-word-abbreviation.md
@@ -0,0 +1,163 @@
+## 1. Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def validWordAbbreviation(self, word: str, abbr: str) -> bool:
+        n, m = len(word), len(abbr)
+        i = j = 0
+
+        while i < n and j < m:
+            if abbr[j] == '0':
+                return False
+
+            if word[i] == abbr[j]:
+                i, j = i + 1, j + 1
+            elif abbr[j].isalpha():
+                return False
+            else:
+                subLen = 0
+                while j < m and abbr[j].isdigit():
+                    subLen = subLen * 10 + int(abbr[j])
+                    j += 1
+                i += subLen
+
+        return i == n and j == m
+```
+
+```java
+public class Solution {
+    public boolean validWordAbbreviation(String word, String abbr) {
+        int n = word.length(), m = abbr.length();
+        int i = 0, j = 0;
+
+        while (i < n && j < m) {
+            if (abbr.charAt(j) == '0') return false;
+
+            if (Character.isLetter(abbr.charAt(j))) {
+                if (i < n && word.charAt(i) == abbr.charAt(j)) {
+                    i++;
+                    j++;
+                } else {
+                    return false;
+                }
+            } else {
+                int subLen = 0;
+                while (j < m && Character.isDigit(abbr.charAt(j))) {
+                    subLen = subLen * 10 + (abbr.charAt(j) - '0');
+                    j++;
+                }
+                i += subLen;
+            }
+        }
+
+        return i == n && j == m;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool validWordAbbreviation(string word, string abbr) {
+        int n = word.length(), m = abbr.length();
+        int i = 0, j = 0;
+
+        while (i < n && j < m) {
+            if (abbr[j] == '0') return false;
+
+            if (isalpha(abbr[j])) {
+                if (word[i] == abbr[j]) {
+                    i++; j++;
+                } else {
+                    return false;
+                }
+            } else {
+                int subLen = 0;
+                while (j < m && isdigit(abbr[j])) {
+                    subLen = subLen * 10 + (abbr[j] - '0');
+                    j++;
+                }
+                i += subLen;
+            }
+        }
+
+        return i == n && j == m;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} word
+     * @param {string} abbr
+     * @return {boolean}
+     */
+    validWordAbbreviation(word, abbr) {
+        let n = word.length, m = abbr.length;
+        let i = 0, j = 0;
+
+        while (i < n && j < m) {
+            if (abbr[j] === '0') return false;
+
+            if (isNaN(abbr[j])) {
+                if (word[i] === abbr[j]) {
+                    i++; j++;
+                } else {
+                    return false;
+                }
+            } else {
+                let subLen = 0;
+                while (j < m && !isNaN(abbr[j]) && abbr[j] !== ' ') {
+                    subLen = subLen * 10 + parseInt(abbr[j]);
+                    j++;
+                }
+                i += subLen;
+            }
+        }
+
+        return i === n && j === m;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool ValidWordAbbreviation(string word, string abbr) {
+        int n = word.Length, m = abbr.Length;
+        int i = 0, j = 0;
+
+        while (i < n && j < m) {
+            if (abbr[j] == '0') return false;
+
+            if (char.IsLetter(abbr[j])) {
+                if (i < n && word[i] == abbr[j]) {
+                    i++; j++;
+                } else {
+                    return false;
+                }
+            } else {
+                int subLen = 0;
+                while (j < m && char.IsDigit(abbr[j])) {
+                    subLen = subLen * 10 + (abbr[j] - '0');
+                    j++;
+                }
+                i += subLen;
+            }
+        }
+
+        return i == n && j == m;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(1)$
+
+> Where $n$ and $m$ are the lengths of the strings $word$ and $abbr$, respectively.
\ No newline at end of file
diff --git a/articles/validate-binary-tree-nodes.md b/articles/validate-binary-tree-nodes.md
new file mode 100644
index 000000000..fe797fbd4
--- /dev/null
+++ b/articles/validate-binary-tree-nodes.md
@@ -0,0 +1,668 @@
+## 1. Depth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def validateBinaryTreeNodes(self, n: int, leftChild: List[int], rightChild: List[int]) -> bool:
+        hasParent = set(leftChild + rightChild)
+        hasParent.discard(-1)
+        if len(hasParent) == n:
+            return False
+
+        root = -1
+        for i in range(n):
+            if i not in hasParent:
+                root = i
+                break
+
+        visit = set()
+        def dfs(i):
+            if i == -1:
+                return True
+            if i in visit:
+                return False
+            visit.add(i)
+            return dfs(leftChild[i]) and dfs(rightChild[i])
+
+        return dfs(root) and len(visit) == n
+```
+
+```java
+public class Solution {
+    private Set<Integer> visit;
+
+    public boolean validateBinaryTreeNodes(int n, int[] leftChild, int[] rightChild) {
+        Set<Integer> hasParent = new HashSet<>();
+        for (int c : leftChild) if (c != -1) hasParent.add(c);
+        for (int c : rightChild) if (c != -1) hasParent.add(c);
+        if (hasParent.size() == n) return false;
+
+        int root = -1;
+        for (int i = 0; i < n; i++) {
+            if (!hasParent.contains(i)) {
+                root = i;
+                break;
+            }
+        }
+        visit = new HashSet<>();
+        return dfs(root, leftChild, rightChild) && visit.size() == n;
+    }
+
+    private boolean dfs(int i, int[] leftChild, int[] rightChild) {
+        if (i == -1) return true;
+        if (visit.contains(i)) return false;
+        visit.add(i);
+        return dfs(leftChild[i], leftChild, rightChild) && 
+               dfs(rightChild[i], leftChild, rightChild);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    unordered_set<int> visit;
+
+    bool validateBinaryTreeNodes(int n, vector<int>& leftChild, vector<int>& rightChild) {
+        unordered_set<int> hasParent;
+        for (int c : leftChild) if (c != -1) hasParent.insert(c);
+        for (int c : rightChild) if (c != -1) hasParent.insert(c);
+        if (hasParent.size() == n) return false;
+
+        int root = -1;
+        for (int i = 0; i < n; i++) {
+            if (!hasParent.count(i)) {
+                root = i;
+                break;
+            }
+        }
+        return dfs(root, leftChild, rightChild) && visit.size() == n;
+    }
+
+private:
+    bool dfs(int i, vector<int>& leftChild, vector<int>& rightChild) {
+        if (i == -1) return true;
+        if (visit.count(i)) return false;
+        visit.insert(i);
+        return dfs(leftChild[i], leftChild, rightChild) && 
+               dfs(rightChild[i], leftChild, rightChild);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[]} leftChild
+     * @param {number[]} rightChild
+     * @return {boolean}
+     */
+    validateBinaryTreeNodes(n, leftChild, rightChild) {
+        let hasParent = new Set([...leftChild, ...rightChild].filter(c => c !== -1));
+        if (hasParent.size === n) return false;
+
+        let root = 0;
+        for (let i = 0; i < n; i++) {
+            if (!hasParent.has(i)) {
+                root = i;
+                break;
+            }
+        }
+
+        const visit = new Set();
+        const dfs = (i) => {
+            if (i === -1) return true;
+            if (visit.has(i)) return false;
+            visit.add(i);
+            return dfs(leftChild[i]) && dfs(rightChild[i]);
+        };
+
+        return dfs(root) && visit.size === n;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Breadth First Search
+
+::tabs-start
+
+```python
+class Solution:
+    def validateBinaryTreeNodes(self, n: int, leftChild: list[int], rightChild: list[int]) -> bool:
+        indegree = [0] * n
+        for i in range(n):
+            if leftChild[i] != -1:
+                indegree[leftChild[i]] += 1
+                if indegree[leftChild[i]] > 1:
+                    return False
+            if rightChild[i] != -1:
+                indegree[rightChild[i]] += 1
+                if indegree[rightChild[i]] > 1:
+                    return False
+
+        root = -1
+        for i in range(n):
+            if indegree[i] == 0:
+                if root != -1:
+                    return False
+                root = i
+
+        if root == -1:
+            return False
+
+        count = 0
+        q = deque([root])
+        while q:
+            i = q.popleft()
+            count += 1
+            if leftChild[i] != -1:
+                q.append(leftChild[i])
+            if rightChild[i] != -1:
+                q.append(rightChild[i])
+        return count == n
+```
+
+```java
+public class Solution {
+    public boolean validateBinaryTreeNodes(int n, int[] leftChild, int[] rightChild) {
+        int[] indegree = new int[n];
+        for (int i = 0; i < n; i++) {
+            if (leftChild[i] != -1) {
+                if (++indegree[leftChild[i]] > 1) return false;
+            }
+            if (rightChild[i] != -1) {
+                if (++indegree[rightChild[i]] > 1) return false;
+            }
+        }
+
+        int root = -1;
+        for (int i = 0; i < n; i++) {
+            if (indegree[i] == 0) {
+                if (root != -1) return false;
+                root = i;
+            }
+        }
+
+        if (root == -1) return false;
+
+        int count = 0;
+        Queue<Integer> q = new LinkedList<>();
+        q.offer(root);
+
+        while (!q.isEmpty()) {
+            int i = q.poll();
+            count++;
+            if (leftChild[i] != -1) q.offer(leftChild[i]);
+            if (rightChild[i] != -1) q.offer(rightChild[i]);
+        }
+        return count == n;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool validateBinaryTreeNodes(int n, vector<int>& leftChild, vector<int>& rightChild) {
+        vector<int> indegree(n, 0);
+        for (int i = 0; i < n; i++) {
+            if (leftChild[i] != -1) {
+                if (++indegree[leftChild[i]] > 1) return false;
+            }
+            if (rightChild[i] != -1) {
+                if (++indegree[rightChild[i]] > 1) return false;
+            }
+        }
+
+        int root = -1;
+        for (int i = 0; i < n; i++) {
+            if (indegree[i] == 0) {
+                if (root != -1) return false;
+                root = i;
+            }
+        }
+
+        if (root == -1) return false;
+
+        int count = 0;
+        queue<int> q;
+        q.push(root);
+
+        while (!q.empty()) {
+            int i = q.front();q.pop();
+            count++;
+            if (leftChild[i] != -1) q.push(leftChild[i]);
+            if (rightChild[i] != -1) q.push(rightChild[i]);
+        }
+        return count == n;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[]} leftChild
+     * @param {number[]} rightChild
+     * @return {boolean}
+     */
+    validateBinaryTreeNodes(n, leftChild, rightChild) {
+        let indegree = new Array(n).fill(0);
+        for (let i = 0; i < n; i++) {
+            if (leftChild[i] !== -1) {
+                if (++indegree[leftChild[i]] > 1) return false;
+            }
+            if (rightChild[i] !== -1) {
+                if (++indegree[rightChild[i]] > 1) return false;
+            }
+        }
+
+        let root = -1;
+        for (let i = 0; i < n; i++) {
+            if (indegree[i] === 0) {
+                if (root !== -1) return false;
+                root = i;
+            }
+        }
+
+        if (root === -1) return false;
+
+        let count = 0;
+        let q = new Queue([root]);
+
+        while (!q.isEmpty()) {
+            let i = q.pop();
+            count++;
+            if (leftChild[i] !== -1) q.push(leftChild[i]);
+            if (rightChild[i] !== -1) q.push(rightChild[i]);
+        }
+        return count === n;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 3. Iterative DFS
+
+::tabs-start
+
+```python
+class Solution:
+    def validateBinaryTreeNodes(self, n: int, leftChild: list[int], rightChild: list[int]) -> bool:
+        indegree = [0] * n
+        for i in range(n):
+            if leftChild[i] != -1:
+                indegree[leftChild[i]] += 1
+                if indegree[leftChild[i]] > 1:
+                    return False
+            if rightChild[i] != -1:
+                indegree[rightChild[i]] += 1
+                if indegree[rightChild[i]] > 1:
+                    return False
+
+        root = next((i for i in range(n) if indegree[i] == 0), -1)
+        if root == -1:
+            return False
+
+        count, stack = 0, [root]
+        while stack:
+            node = stack.pop()
+            count += 1
+            if leftChild[node] != -1:
+                stack.append(leftChild[node])
+            if rightChild[node] != -1:
+                stack.append(rightChild[node])
+
+        return count == n
+```
+
+```java
+public class Solution {
+    public boolean validateBinaryTreeNodes(int n, int[] leftChild, int[] rightChild) {
+        int[] indegree = new int[n];
+        for (int i = 0; i < n; i++) {
+            if (leftChild[i] != -1) {
+                if (++indegree[leftChild[i]] > 1) return false;
+            }
+            if (rightChild[i] != -1) {
+                if (++indegree[rightChild[i]] > 1) return false;
+            }
+        }
+
+        int root = -1;
+        for (int i = 0; i < n; i++) {
+            if (indegree[i] == 0) {
+                if (root != -1) return false;
+                root = i;
+            }
+        }
+
+        if (root == -1) return false;
+
+        int count = 0;
+        Stack<Integer> stack = new Stack<>();
+        stack.push(root);
+
+        while (!stack.isEmpty()) {
+            int node = stack.pop();
+            count++;
+            if (leftChild[node] != -1) stack.push(leftChild[node]);
+            if (rightChild[node] != -1) stack.push(rightChild[node]);
+        }
+        return count == n;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool validateBinaryTreeNodes(int n, vector<int>& leftChild, vector<int>& rightChild) {
+        vector<int> indegree(n, 0);
+        for (int i = 0; i < n; i++) {
+            if (leftChild[i] != -1 && ++indegree[leftChild[i]] > 1) return false;
+            if (rightChild[i] != -1 && ++indegree[rightChild[i]] > 1) return false;
+        }
+
+        int root = -1;
+        for (int i = 0; i < n; i++) {
+            if (indegree[i] == 0) {
+                if (root != -1) return false;
+                root = i;
+            }
+        }
+
+        if (root == -1) return false;
+
+        int count = 0;
+        stack<int> stk;
+        stk.push(root);
+
+        while (!stk.empty()) {
+            int node = stk.top(); stk.pop();
+            count++;
+            if (leftChild[node] != -1) stk.push(leftChild[node]);
+            if (rightChild[node] != -1) stk.push(rightChild[node]);
+        }
+        return count == n;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[]} leftChild
+     * @param {number[]} rightChild
+     * @return {boolean}
+     */
+    validateBinaryTreeNodes(n, leftChild, rightChild) {
+        let indegree = new Array(n).fill(0);
+        for (let i = 0; i < n; i++) {
+            if (leftChild[i] !== -1) {
+                if (++indegree[leftChild[i]] > 1) return false;
+            }
+            if (rightChild[i] !== -1) {
+                if (++indegree[rightChild[i]] > 1) return false;
+            }
+        }
+
+        let root = -1;
+        for (let i = 0; i < n; i++) {
+            if (indegree[i] === 0) {
+                if (root !== -1) return false;
+                root = i;
+            }
+        }
+
+        if (root === -1) return false;
+
+        let count = 0;
+        let stack = [root];
+
+        while (stack.length) {
+            let node = stack.pop();
+            count++;
+            if (leftChild[node] !== -1) stack.push(leftChild[node]);
+            if (rightChild[node] !== -1) stack.push(rightChild[node]);
+        }
+        return count === n;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 4. Disjoint Set Union
+
+::tabs-start
+
+```python
+class DSU:
+    def __init__(self, n):
+        self.Parent = list(range(n))
+        self.Components = n
+
+    def find(self, node):
+        if self.Parent[node] != node:
+            self.Parent[node] = self.find(self.Parent[node])
+        return self.Parent[node]
+
+    def union(self, parent, child):
+        parentRoot = self.find(parent)
+        childRoot = self.find(child)
+        if childRoot != child or parentRoot == childRoot:
+            return False
+
+        self.Components -= 1
+        self.Parent[childRoot] = parentRoot
+        return True
+
+class Solution:
+    def validateBinaryTreeNodes(self, n: int, leftChild: list[int], rightChild: list[int]) -> bool:
+        dsu = DSU(n)
+
+        for parent in range(n):
+            for child in (leftChild[parent], rightChild[parent]):
+                if child == -1:
+                    continue
+                if not dsu.union(parent, child):
+                    return False
+
+        return dsu.Components == 1
+```
+
+```java
+class DSU {
+    int[] Parent;
+    int Components;
+
+    public DSU(int n) {
+        Parent = new int[n];
+        for (int i = 0; i < n; i++) {
+            Parent[i] = i;
+        }
+        Components = n;
+    }
+
+    public int find(int node) {
+        if (Parent[node] != node) {
+            Parent[node] = find(Parent[node]);
+        }
+        return Parent[node];
+    }
+
+    public boolean union(int parent, int child) {
+        int parentRoot = find(parent);
+        int childRoot = find(child);
+        if (childRoot != child || parentRoot == childRoot) {
+            return false;
+        }
+
+        Components--;
+        Parent[childRoot] = parentRoot;
+        return true;
+    }
+}
+
+class Solution {
+    public boolean validateBinaryTreeNodes(int n, int[] leftChild, int[] rightChild) {
+        DSU dsu = new DSU(n);
+
+        for (int parent = 0; parent < n; parent++) {
+            for (int child : new int[]{leftChild[parent], rightChild[parent]}) {
+                if (child == -1) continue;
+                if (!dsu.union(parent, child)) return false;
+            }
+        }
+
+        return dsu.Components == 1;
+    }
+}
+```
+
+```cpp
+class DSU {
+public:
+    vector<int> Parent;
+    int Components;
+
+    DSU(int n) {
+        Parent.resize(n);
+        iota(Parent.begin(), Parent.end(), 0);
+        Components = n;
+    }
+
+    int find(int node) {
+        if (Parent[node] != node) {
+            Parent[node] = find(Parent[node]);
+        }
+        return Parent[node];
+    }
+
+    bool unionSets(int parent, int child) {
+        int parentRoot = find(parent);
+        int childRoot = find(child);
+        if (childRoot != child || parentRoot == childRoot) {
+            return false;
+        }
+
+        Components--;
+        Parent[childRoot] = parentRoot;
+        return true;
+    }
+};
+
+class Solution {
+public:
+    bool validateBinaryTreeNodes(int n, vector<int>& leftChild, vector<int>& rightChild) {
+        DSU dsu(n);
+
+        for (int parent = 0; parent < n; parent++) {
+            for (int child : {leftChild[parent], rightChild[parent]}) {
+                if (child == -1) continue;
+                if (!dsu.unionSets(parent, child)) return false;
+            }
+        }
+
+        return dsu.Components == 1;
+    }
+};
+```
+
+```javascript
+class DSU {
+    /**
+     * @constructor
+     * @param {number} n
+     */
+    constructor(n) {
+        this.Parent = Array.from({ length: n }, (_, i) => i);
+        this.Components = n;
+    }
+
+    /**
+     * @param {number} node
+     * @return {number}
+     */
+    find(node) {
+        if (this.Parent[node] !== node) {
+            this.Parent[node] = this.find(this.Parent[node]);
+        }
+        return this.Parent[node];
+    }
+
+    /**
+     * @param {number} parent
+     * @param {number} child
+     * @return {boolean}
+     */
+    union(parent, child) {
+        let parentRoot = this.find(parent);
+        let childRoot = this.find(child);
+        if (childRoot !== child || parentRoot === childRoot) {
+            return false;
+        }
+
+        this.Components--;
+        this.Parent[childRoot] = parentRoot;
+        return true;
+    }
+}
+
+class Solution {
+    /**
+     * @param {number} n
+     * @param {number[]} leftChild
+     * @param {number[]} rightChild
+     * @return {boolean}
+     */
+    validateBinaryTreeNodes(n, leftChild, rightChild) {
+        let dsu = new DSU(n);
+
+        for (let parent = 0; parent < n; parent++) {
+            for (let child of [leftChild[parent], rightChild[parent]]) {
+                if (child === -1) continue;
+                if (!dsu.union(parent, child)) return false;
+            }
+        }
+
+        return dsu.Components === 1;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
\ No newline at end of file
diff --git a/articles/validate-parentheses.md b/articles/validate-parentheses.md
index b02788724..a7e649a78 100644
--- a/articles/validate-parentheses.md
+++ b/articles/validate-parentheses.md
@@ -80,6 +80,45 @@ public class Solution {
 }
 ```
 
+```go
+func isValid(s string) bool {
+	for strings.Contains(s, "()") || strings.Contains(s, "{}") || strings.Contains(s, "[]") {
+		s = strings.ReplaceAll(s, "()", "")
+		s = strings.ReplaceAll(s, "{}", "")
+		s = strings.ReplaceAll(s, "[]", "")
+	}
+	return s == ""
+}
+```
+
+```kotlin
+class Solution {
+    fun isValid(s: String): Boolean {
+        var str = s
+        while (str.contains("()") || str.contains("{}") || str.contains("[]")) {
+            str = str.replace("()", "")
+            str = str.replace("{}", "")
+            str = str.replace("[]", "")
+        }
+        return str.isEmpty()
+    }
+}
+```
+
+```swift
+class Solution {
+    func isValid(_ s: String) -> Bool {
+        var str = s
+        while str.contains("()") || str.contains("{}") || str.contains("[]") {
+            str = str.replacingOccurrences(of: "()", with: "")
+            str = str.replacingOccurrences(of: "{}", with: "")
+            str = str.replacingOccurrences(of: "[]", with: "")
+        }
+        return str.isEmpty
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -219,6 +258,76 @@ public class Solution {
 }
 ```
 
+```go
+func isValid(s string) bool {
+    stack := linkedliststack.New()
+    closeToOpen := map[rune]rune{')': '(', ']': '[', '}': '{'}
+
+    for _, c := range s {
+        if open, exists := closeToOpen[c]; exists {
+            if !stack.Empty() {
+                top, ok := stack.Pop()
+                if ok && top.(rune) != open {
+                    return false
+                }
+            } else {
+                return false
+            }
+        } else {
+            stack.Push(c)
+        }
+    }
+
+    return stack.Empty()
+}
+```
+
+```kotlin
+class Solution {
+    fun isValid(s: String): Boolean {
+        val stack = ArrayDeque<Char>()
+        val closeToOpen = hashMapOf(')' to '(', ']' to '[', '}' to '{')
+
+        for (c in s) {
+            if (c in closeToOpen) {
+                if (stack.isNotEmpty() && stack.first() == closeToOpen[c]) {
+                    stack.removeFirst()
+                } else {
+                    return false
+                }
+            } else {
+                stack.addFirst(c)
+            }
+        }
+
+        return stack.isEmpty()
+    }
+}
+```
+
+```swift
+class Solution {
+    func isValid(_ s: String) -> Bool {
+        var stack = [Character]()
+        let closeToOpen: [Character: Character] = [")": "(", "]": "[", "}": "{"]
+
+        for c in s {
+            if let open = closeToOpen[c] {
+                if !stack.isEmpty && stack.last! == open {
+                    stack.popLast()
+                } else {
+                    return false
+                }
+            } else {
+                stack.append(c)
+            }
+        }
+        
+        return stack.isEmpty
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/validate-stack-sequences.md b/articles/validate-stack-sequences.md
new file mode 100644
index 000000000..00867b541
--- /dev/null
+++ b/articles/validate-stack-sequences.md
@@ -0,0 +1,160 @@
+## 1. Stack
+
+::tabs-start
+
+```python
+class Solution:
+    def validateStackSequences(self, pushed: List[int], popped: List[int]) -> bool:
+        i = 0
+        stack = []
+        for n in pushed:
+            stack.append(n)
+            while i < len(popped) and stack and popped[i] == stack[-1]:
+                stack.pop()
+                i += 1
+        return not stack
+```
+
+```java
+public class Solution {
+    public boolean validateStackSequences(int[] pushed, int[] popped) {
+        Stack<Integer> stack = new Stack<>();
+        int i = 0;
+        for (int n : pushed) {
+            stack.push(n);
+            while (i < popped.length && !stack.isEmpty() && popped[i] == stack.peek()) {
+                stack.pop();
+                i++;
+            }
+        }
+        return stack.isEmpty();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool validateStackSequences(vector<int>& pushed, vector<int>& popped) {
+        stack<int> stk;
+        int i = 0;
+        for (int n : pushed) {
+            stk.push(n);
+            while (i < popped.size() && !stk.empty() && popped[i] == stk.top()) {
+                stk.pop();
+                i++;
+            }
+        }
+        return stk.empty();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} pushed
+     * @param {number[]} popped
+     * @return {boolean}
+     */
+    validateStackSequences(pushed, popped) {
+        const stack = [];
+        let i = 0;
+        for (const n of pushed) {
+            stack.push(n);
+            while (i < popped.length && stack.length > 0 && popped[i] === stack[stack.length - 1]) {
+                stack.pop();
+                i++;
+            }
+        }
+        return stack.length === 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def validateStackSequences(self, pushed: List[int], popped: List[int]) -> bool:
+        l = r = 0
+        for num in pushed:
+            pushed[l] = num
+            l += 1
+            while l > 0 and pushed[l - 1] == popped[r]:
+                r += 1
+                l -= 1
+        return l == 0
+```
+
+```java
+public class Solution {
+    public boolean validateStackSequences(int[] pushed, int[] popped) {
+        int l = 0, r = 0;
+        for (int num : pushed) {
+            pushed[l++] = num;
+            while (l > 0 && pushed[l - 1] == popped[r]) {
+                r++;
+                l--;
+            }
+        }
+        return l == 0;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool validateStackSequences(vector<int>& pushed, vector<int>& popped) {
+        int l = 0, r = 0;
+        for (int& num : pushed) {
+            pushed[l++] = num;
+            while (l > 0 && pushed[l - 1] == popped[r]) {
+                r++;
+                l--;
+            }
+        }
+        return l == 0;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} pushed
+     * @param {number[]} popped
+     * @return {boolean}
+     */
+    validateStackSequences(pushed, popped) {
+        let l = 0, r = 0;
+        for (const num of pushed) {
+            pushed[l++] = num;
+            while (l > 0 && pushed[l - 1] === popped[r]) {
+                r++;
+                l--;
+            }
+        }
+        return l === 0;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$ extra space.
\ No newline at end of file
diff --git a/articles/verifying-an-alien-dictionary.md b/articles/verifying-an-alien-dictionary.md
new file mode 100644
index 000000000..86694cf0a
--- /dev/null
+++ b/articles/verifying-an-alien-dictionary.md
@@ -0,0 +1,271 @@
+## 1. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def isAlienSorted(self, words: List[str], order: str) -> bool:
+        order_index = {c: i for i, c in enumerate(order)}
+        
+        def compare(word):
+            return [order_index[c] for c in word]
+        
+        return words == sorted(words, key=compare)
+```
+
+```java
+public class Solution {
+    public boolean isAlienSorted(String[] words, String order) {
+        int[] orderIndex = new int[26];
+        for (int i = 0; i < order.length(); i++)
+            orderIndex[order.charAt(i) - 'a'] = i;
+        
+        Comparator<String> compare = (w1, w2) -> {
+            for (int i = 0; i < Math.min(w1.length(), w2.length()); i++) {
+                if (w1.charAt(i) != w2.charAt(i))
+                    return orderIndex[w1.charAt(i) - 'a'] - orderIndex[w2.charAt(i) - 'a'];
+            }
+            return w1.length() - w2.length();
+        };
+
+        String[] sortedWords = words.clone();
+        Arrays.sort(sortedWords, compare);
+        return Arrays.equals(words, sortedWords);
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isAlienSorted(vector<string>& words, string order) {
+        int orderIndex[26];
+        for (int i = 0; i < order.size(); ++i)
+            orderIndex[order[i] - 'a'] = i;
+        
+        auto compare = [&](const string &a, const string &b) {
+            for (int i = 0; i < min(a.size(), b.size()); ++i) {
+                if (a[i] != b[i])
+                    return orderIndex[a[i] - 'a'] < orderIndex[b[i] - 'a'];
+            }
+            return a.size() < b.size();
+        };
+
+        return is_sorted(words.begin(), words.end(), compare);
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @param {string} order
+     * @return {boolean}
+     */
+    isAlienSorted(words, order) {
+        let orderIndex = new Array(26).fill(0);
+        for (let i = 0; i < order.length; i++) {
+            orderIndex[order.charCodeAt(i) - 97] = i;
+        }
+
+        const compare = (w1, w2) => {
+            for (let i = 0; i < Math.min(w1.length, w2.length); i++) {
+                if (w1[i] !== w2[i]) {
+                    return orderIndex[w1.charCodeAt(i) - 97] - orderIndex[w2.charCodeAt(i) - 97];
+                }
+            }
+            return w1.length - w2.length;
+        };
+
+        let sortedWords = [...words].sort(compare);
+        return words.join() === sortedWords.join();
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool IsAlienSorted(string[] words, string order) {
+        int[] orderIndex = new int[26];
+        for (int i = 0; i < order.Length; i++) {
+            orderIndex[order[i] - 'a'] = i;
+        }
+
+        string[] sortedWords = (string[])words.Clone();
+        Array.Sort(sortedWords, (w1, w2) => {
+            for (int i = 0; i < Math.Min(w1.Length, w2.Length); i++) {
+                if (w1[i] != w2[i]) {
+                    return orderIndex[w1[i] - 'a'] - orderIndex[w2[i] - 'a'];
+                }
+            }
+            return w1.Length - w2.Length;
+        });
+
+        for (int i = 0; i < words.Length; i++) {
+            if (!words[i].Equals(sortedWords[i])) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m\log n)$
+* Space complexity: $O(n * m)$
+
+> Where $n$ is the number of words and $m$ is the average length of a word.
+
+---
+
+## 2. Comparing adjacent words
+
+::tabs-start
+
+```python
+class Solution:
+    def isAlienSorted(self, words: List[str], order: str) -> bool:
+        order_index = {c: i for i, c in enumerate(order)}
+        
+        for i in range(len(words) - 1):
+            w1, w2 = words[i], words[i + 1]
+            
+            for j in range(len(w1)):
+                if j == len(w2):
+                    return False
+                
+                if w1[j] != w2[j]:
+                    if order_index[w1[j]] > order_index[w2[j]]:
+                        return False
+                    break
+        return True
+```
+
+```java
+public class Solution {
+    public boolean isAlienSorted(String[] words, String order) {
+        int[] orderIndex = new int[26];
+        for (int i = 0; i < order.length(); i++)
+            orderIndex[order.charAt(i) - 'a'] = i;
+        
+        for (int i = 0; i < words.length - 1; i++) {
+            String w1 = words[i], w2 = words[i + 1];
+            int j = 0;
+            
+            for (; j < w1.length(); j++) {
+                if (j == w2.length()) return false;
+                if (w1.charAt(j) != w2.charAt(j)) {
+                    if (orderIndex[w1.charAt(j) - 'a'] > orderIndex[w2.charAt(j) - 'a']) {
+                        return false;
+                    }
+                    break;
+                }
+            }
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool isAlienSorted(vector<string>& words, string order) {
+        int orderIndex[26] = {0};
+        for (int i = 0; i < order.size(); ++i)
+            orderIndex[order[i] - 'a'] = i;
+        
+        for (int i = 0; i < words.size() - 1; ++i) {
+            string w1 = words[i], w2 = words[i + 1];
+            int j = 0;
+            
+            for (; j < w1.size(); ++j) {
+                if (j == w2.size()) return false;
+                if (w1[j] != w2[j]) {
+                    if (orderIndex[w1[j] - 'a'] > orderIndex[w2[j] - 'a'])
+                        return false;
+                    break;
+                }
+            }
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words
+     * @param {string} order
+     * @return {boolean}
+     */
+    isAlienSorted(words, order) {
+        let orderIndex = new Array(26).fill(0);
+        for (let i = 0; i < order.length; i++) {
+            orderIndex[order.charCodeAt(i) - 97] = i;
+        }
+        
+        for (let i = 0; i < words.length - 1; i++) {
+            let w1 = words[i], w2 = words[i + 1];
+            
+            for (let j = 0; j < w1.length; j++) {
+                if (j === w2.length) return false;
+                
+                if (w1[j] !== w2[j]) {
+                    if (orderIndex[w1.charCodeAt(j) - 97] > orderIndex[w2.charCodeAt(j) - 97])
+                        return false;
+                    break;
+                }
+            }
+        }
+        return true;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public bool IsAlienSorted(string[] words, string order) {
+        Dictionary<char, int> orderIndex = new Dictionary<char, int>();
+        for (int i = 0; i < order.Length; i++) {
+            orderIndex[order[i]] = i;
+        }
+
+        for (int i = 0; i < words.Length - 1; i++) {
+            string w1 = words[i];
+            string w2 = words[i + 1];
+
+            for (int j = 0; j < w1.Length; j++) {
+                if (j == w2.Length) {
+                    return false;
+                }
+
+                if (w1[j] != w2[j]) {
+                    if (orderIndex[w1[j]] > orderIndex[w2[j]]) {
+                        return false;
+                    }
+                    break;
+                }
+            }
+        }
+
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n * m)$
+* Space complexity: $O(1)$ since we have $26$ different characters.
+
+> Where $n$ is the number of words and $m$ is the average length of a word.
\ No newline at end of file
diff --git a/articles/widest-vertical-area-between-two-points-containing-no-points.md b/articles/widest-vertical-area-between-two-points-containing-no-points.md
new file mode 100644
index 000000000..b41a574f7
--- /dev/null
+++ b/articles/widest-vertical-area-between-two-points-containing-no-points.md
@@ -0,0 +1,212 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def maxWidthOfVerticalArea(self, points: List[List[int]]) -> int:
+        n = len(points)
+        res = 0
+
+        for i in range(1, n):
+            x1 = points[i][0]
+            for j in range(i):
+                x2 = points[j][0]
+                hasPoints = False
+                for k in range(n):
+                    if k == i or k == j:
+                        continue
+
+                    x3 = points[k][0]
+                    if x3 > min(x1, x2) and x3 < max(x1, x2):
+                        hasPoints = True
+                        break
+
+                if not hasPoints:
+                    res = max(res, abs(x1 - x2))
+
+        return res
+```
+
+```java
+public class Solution {
+    public int maxWidthOfVerticalArea(int[][] points) {
+        int n = points.length, res = 0;
+
+        for (int i = 1; i < n; i++) {
+            int x1 = points[i][0];
+            for (int j = 0; j < i; j++) {
+                int x2 = points[j][0];
+                boolean hasPoints = false;
+
+                for (int k = 0; k < n; k++) {
+                    if (k == i || k == j) continue;
+                    
+                    int x3 = points[k][0];
+                    if (x3 > Math.min(x1, x2) && x3 < Math.max(x1, x2)) {
+                        hasPoints = true;
+                        break;
+                    }
+                }
+
+                if (!hasPoints) {
+                    res = Math.max(res, Math.abs(x1 - x2));
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxWidthOfVerticalArea(vector<vector<int>>& points) {
+        int n = points.size(), res = 0;
+
+        for (int i = 1; i < n; i++) {
+            int x1 = points[i][0];
+            for (int j = 0; j < i; j++) {
+                int x2 = points[j][0];
+                bool hasPoints = false;
+
+                for (int k = 0; k < n; k++) {
+                    if (k == i || k == j) continue;
+
+                    int x3 = points[k][0];
+                    if (x3 > min(x1, x2) && x3 < max(x1, x2)) {
+                        hasPoints = true;
+                        break;
+                    }
+                }
+
+                if (!hasPoints) {
+                    res = max(res, abs(x1 - x2));
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} points
+     * @return {number}
+     */
+    maxWidthOfVerticalArea(points) {
+        let n = points.length, res = 0;
+
+        for (let i = 1; i < n; i++) {
+            let x1 = points[i][0];
+            for (let j = 0; j < i; j++) {
+                let x2 = points[j][0];
+                let hasPoints = false;
+
+                for (let k = 0; k < n; k++) {
+                    if (k === i || k === j) continue;
+
+                    let x3 = points[k][0];
+                    if (x3 > Math.min(x1, x2) && x3 < Math.max(x1, x2)) {
+                        hasPoints = true;
+                        break;
+                    }
+                }
+
+                if (!hasPoints) {
+                    res = Math.max(res, Math.abs(x1 - x2));
+                }
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n ^ 3)$
+* Space complexity: $O(1)$
+
+---
+
+## 2. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def maxWidthOfVerticalArea(self, points: List[List[int]]) -> int:
+        points.sort()
+        res = 0
+        for i in range(len(points) - 1):
+            res = max(res, points[i + 1][0] - points[i][0])
+        return res
+```
+
+```java
+public class Solution {
+    public int maxWidthOfVerticalArea(int[][] points) {
+        Arrays.sort(points, Comparator.comparingInt(a -> a[0]));
+        int res = 0;
+
+        for (int i = 0; i < points.length - 1; i++) {
+            res = Math.max(res, points[i + 1][0] - points[i][0]);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int maxWidthOfVerticalArea(vector<vector<int>>& points) {
+        sort(points.begin(), points.end(), [](const auto& a, const auto& b) {
+            return a[0] < b[0];
+        });
+
+        int res = 0;
+        for (int i = 0; i < points.size() - 1; i++) {
+            res = max(res, points[i + 1][0] - points[i][0]);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[][]} points
+     * @return {number}
+     */
+    maxWidthOfVerticalArea(points) {
+        points.sort((a, b) => a[0] - b[0]);
+        let res = 0;
+
+        for (let i = 0; i < points.length - 1; i++) {
+            res = Math.max(res, points[i + 1][0] - points[i][0]);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
\ No newline at end of file
diff --git a/articles/wiggle-sort.md b/articles/wiggle-sort.md
new file mode 100644
index 000000000..d18f99598
--- /dev/null
+++ b/articles/wiggle-sort.md
@@ -0,0 +1,293 @@
+## 1. Max-Heap
+
+::tabs-start
+
+```python
+class Solution:
+    def wiggleSort(self, nums: List[int]) -> None:
+        """
+        Do not return anything, modify nums in-place instead.
+        """
+
+        maxHeap = []
+        for num in nums:
+            heappush(maxHeap, -num)
+
+        n = len(nums)
+        for i in range(1, n, 2):
+            nums[i] = -heappop(maxHeap)
+        for i in range(0, n, 2):
+            nums[i] = -heappop(maxHeap)
+```
+
+```java
+public class Solution {
+    public void wiggleSort(int[] nums) {
+        PriorityQueue<Integer> maxHeap = new PriorityQueue<>(Collections.reverseOrder());
+        for (int num : nums) {
+            maxHeap.add(num);
+        }
+
+        for (int i = 1; i < nums.length; i += 2) {
+            nums[i] = maxHeap.poll();
+        }
+        for (int i = 0; i < nums.length; i += 2) {
+            nums[i] = maxHeap.poll();
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void wiggleSort(vector<int>& nums) {
+        priority_queue<int> maxHeap;
+        for (int& num : nums) {
+            maxHeap.push(num);
+        }
+
+        for (int i = 1; i < nums.size(); i += 2) {
+            nums[i] = maxHeap.top();
+            maxHeap.pop();
+        }
+        for (int i = 0; i < nums.size(); i += 2) {
+            nums[i] = maxHeap.top();
+            maxHeap.pop();
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {void} Do not return anything, modify nums in-place instead.
+     */
+    wiggleSort(nums) {
+        const maxHeap = new PriorityQueue((a, b) => b - a);
+        nums.forEach(num => maxHeap.enqueue(num));
+
+        for (let i = 1; i < nums.length; i += 2) {
+            nums[i] = maxHeap.dequeue();
+        }
+        for (let i = 0; i < nums.length; i += 2) {
+            nums[i] = maxHeap.dequeue();
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(n)$
+
+---
+
+## 2. Sorting
+
+::tabs-start
+
+```python
+class Solution:
+    def wiggleSort(self, nums: List[int]) -> None:
+        """
+        Do not return anything, modify nums in-place instead.
+        """
+
+        nums.sort()
+        for i in range(1, len(nums) - 1, 2):
+            nums[i], nums[i + 1] = nums[i + 1], nums[i]
+```
+
+```java
+public class Solution {
+    public void wiggleSort(int[] nums) {
+        Arrays.sort(nums);
+        for (int i = 1; i < nums.length - 1; i += 2) {
+            int temp = nums[i];
+            nums[i] = nums[i + 1];
+            nums[i + 1] = temp;
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void wiggleSort(vector<int>& nums) {
+        sort(nums.begin(), nums.end());
+        for (int i = 1; i < nums.size() - 1; i += 2) {
+            swap(nums[i], nums[i + 1]);
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {void} Do not return anything, modify nums in-place instead.
+     */
+    wiggleSort(nums) {
+        nums.sort((a, b) => a - b);
+        for (let i = 1; i < nums.length - 1; i += 2) {
+            [nums[i], nums[i + 1]] = [nums[i + 1], nums[i]];
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 3. Greedy - I
+
+::tabs-start
+
+```python
+class Solution:
+    def wiggleSort(self, nums: List[int]) -> None:
+        """
+        Do not return anything, modify nums in-place instead.
+        """
+        
+        for i in range(1, len(nums)):
+            if ((i % 2 == 1 and nums[i] < nums[i - 1]) or
+                (i % 2 == 0 and nums[i] > nums[i - 1])
+            ):
+                nums[i], nums[i - 1] = nums[i - 1], nums[i]
+```
+
+```java
+public class Solution {
+    public void wiggleSort(int[] nums) {
+        for (int i = 1; i < nums.length; i++) {
+            if ((i % 2 == 1 && nums[i] < nums[i - 1]) ||
+                (i % 2 == 0 && nums[i] > nums[i - 1])) {
+                int temp = nums[i];
+                nums[i] = nums[i - 1];
+                nums[i - 1] = temp;
+            }
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void wiggleSort(vector<int>& nums) {
+        for (int i = 1; i <nums.size(); i++) {
+            if ((i % 2 == 1 && nums[i] < nums[i - 1]) ||
+                (i % 2 == 0 && nums[i] > nums[i - 1])) {
+                swap(nums[i], nums[i - 1]);
+            }
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {void} Do not return anything, modify nums in-place instead.
+     */
+    wiggleSort(nums) {
+        for (let i = 1; i < nums.length; i++) {
+            if ((i % 2 == 1 && nums[i] < nums[i - 1]) ||
+                (i % 2 == 0 && nums[i] > nums[i - 1])) {
+                [nums[i], nums[i - 1]] = [nums[i - 1], nums[i]];
+            }
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
+
+---
+
+## 4. Greedy - II
+
+::tabs-start
+
+```python
+class Solution:
+    def wiggleSort(self, nums: List[int]) -> None:
+        """
+        Do not return anything, modify nums in-place instead.
+        """
+        
+        for i in range(1, len(nums)):
+            if (i % 2) ^ (nums[i] > nums[i - 1]):
+                nums[i], nums[i - 1] = nums[i - 1], nums[i]
+```
+
+```java
+public class Solution {
+    public void wiggleSort(int[] nums) {
+        for (int i = 1; i < nums.length; i++) {
+            if (((i % 2) ^ (nums[i] > nums[i - 1] ? 1 : 0)) != 0) {
+                int temp = nums[i];
+                nums[i] = nums[i - 1];
+                nums[i - 1] = temp;
+            }
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    void wiggleSort(vector<int>& nums) {
+        for (int i = 1; i <nums.size(); i++) {
+            if ((i % 2) ^ (nums[i] > nums[i - 1])) {
+                swap(nums[i], nums[i - 1]);
+            }
+        }
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} nums
+     * @return {void} Do not return anything, modify nums in-place instead.
+     */
+    wiggleSort(nums) {
+        for(var i = 1; i < nums.length; i++) {
+            if ((i % 2) ^ (nums[i] > nums[i - 1])) {
+                [nums[i], nums[i - 1]] = [nums[i - 1], nums[i]];
+            }
+        }
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(1)$
\ No newline at end of file
diff --git a/articles/word-break-ii.md b/articles/word-break-ii.md
new file mode 100644
index 000000000..45660e5f9
--- /dev/null
+++ b/articles/word-break-ii.md
@@ -0,0 +1,1188 @@
+## 1. Backtracking
+
+::tabs-start
+
+```python
+class Solution:
+    def wordBreak(self, s: str, wordDict: List[str]) -> List[str]:
+        wordDict = set(wordDict)
+
+        def backtrack(i):
+            if i == len(s):
+                res.append(" ".join(cur))
+                return
+
+            for j in range(i, len(s)):
+                w = s[i:j + 1]
+                if w in wordDict:
+                    cur.append(w)
+                    backtrack(j + 1)
+                    cur.pop()
+
+        cur = []
+        res = []
+        backtrack(0)
+        return res
+```
+
+```java
+public class Solution {
+    private Set<String> wordSet;
+    private List<String> res;
+
+    public List<String> wordBreak(String s, List<String> wordDict) {
+        wordSet = new HashSet<>(wordDict);
+        res = new ArrayList<>();
+        List<String> cur = new ArrayList<>();
+        backtrack(s, 0, cur);
+        return res;
+    }
+
+    private void backtrack(String s, int i, List<String> cur) {
+        if (i == s.length()) {
+            res.add(String.join(" ", cur));
+            return;
+        }
+
+        for (int j = i; j < s.length(); j++) {
+            String w = s.substring(i, j + 1);
+            if (wordSet.contains(w)) {
+                cur.add(w);
+                backtrack(s, j + 1, cur);
+                cur.remove(cur.size() - 1);
+            }
+        }
+    }
+}
+```
+
+```cpp
+class Solution {
+    unordered_set<string> wordSet;
+    vector<string> res;
+
+public:
+    vector<string> wordBreak(string s, vector<string>& wordDict) {
+        wordSet = unordered_set<string>(wordDict.begin(), wordDict.end());
+        vector<string> cur;
+        backtrack(s, 0, cur);
+        return res;
+    }
+
+private:
+    void backtrack(const string& s, int i, vector<string>& cur) {
+        if (i == s.size()) {
+            res.push_back(join(cur));
+            return;
+        }
+
+        for (int j = i; j < s.size(); ++j) {
+            string w = s.substr(i, j - i + 1);
+            if (wordSet.count(w)) {
+                cur.push_back(w);
+                backtrack(s, j + 1, cur);
+                cur.pop_back();
+            }
+        }
+    }
+
+    string join(const vector<string>& words) {
+        ostringstream oss;
+        for (int i = 0; i < words.size(); ++i) {
+            if (i > 0) oss << " ";
+            oss << words[i];
+        }
+        return oss.str();
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string[]} wordDict
+     * @return {string[]}
+     */
+    wordBreak(s, wordDict) {
+        const wordSet = new Set(wordDict);
+        const res = [];
+        const cur = [];
+
+        const backtrack = (i) => {
+            if (i === s.length) {
+                res.push(cur.join(" "));
+                return;
+            }
+
+            for (let j = i; j < s.length; j++) {
+                const w = s.substring(i, j + 1);
+                if (wordSet.has(w)) {
+                    cur.push(w);
+                    backtrack(j + 1);
+                    cur.pop();
+                }
+            }
+        };
+
+        backtrack(0);
+        return res;
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<string> WordBreak(string s, List<string> wordDict) {
+        HashSet<string> wordSet = new HashSet<string>(wordDict);
+        List<string> res = new List<string>();
+        List<string> cur = new List<string>();
+
+        void Backtrack(int i) {
+            if (i == s.Length) {
+                res.Add(string.Join(" ", cur));
+                return;
+            }
+
+            for (int j = i; j < s.Length; j++) {
+                string word = s.Substring(i, j - i + 1);
+                if (wordSet.Contains(word)) {
+                    cur.Add(word);
+                    Backtrack(j + 1);
+                    cur.RemoveAt(cur.Count - 1);
+                }
+            }
+        }
+
+        Backtrack(0);
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m + n * 2 ^ n)$
+* Space complexity: $O(m + 2 ^ n)$
+
+> Where $n$ is the length of the string $s$ and $m$ is the sum of the lengths of the strings in the $wordDict$.
+
+---
+
+## 2. Backtracking + Trie
+
+::tabs-start
+
+```python
+class TrieNode:
+    def __init__(self):
+        self.children = {}
+        self.isWord = False
+
+class Trie:
+    def __init__(self):
+        self.root = TrieNode()
+        
+    def addWord(self, word):
+        curr = self.root
+        for c in word:
+            if c not in curr.children:
+                curr.children[c] = TrieNode()
+            curr = curr.children[c]
+        curr.isWord = True
+
+class Solution:
+    def wordBreak(self, s: str, wordDict: List[str]) -> List[str]:
+        trie = Trie()
+        for word in wordDict:
+            trie.addWord(word)
+        
+        def backtrack(i, path):
+            if i == len(s):
+                res.append(" ".join(path))
+                return
+            
+            node = trie.root
+            word = []
+            for i in range(i, len(s)):
+                char = s[i]
+                if char not in node.children:
+                    break
+                
+                word.append(char)
+                node = node.children[char]
+                
+                if node.isWord:
+                    path.append("".join(word))
+                    backtrack(i + 1, path)
+                    path.pop()
+        
+        res = []
+        backtrack(0, [])
+        return res
+```
+
+```java
+class TrieNode {
+    HashMap<Character, TrieNode> children = new HashMap<>();
+    boolean isWord = false;
+}
+
+class Trie {
+    TrieNode root;
+
+    Trie() {
+        root = new TrieNode();
+    }
+
+    void addWord(String word) {
+        TrieNode curr = root;
+        for (char c : word.toCharArray()) {
+            curr.children.putIfAbsent(c, new TrieNode());
+            curr = curr.children.get(c);
+        }
+        curr.isWord = true;
+    }
+}
+
+public class Solution {
+    public List<String> wordBreak(String s, List<String> wordDict) {
+        Trie trie = new Trie();
+        for (String word : wordDict) {
+            trie.addWord(word);
+        }
+
+        List<String> res = new ArrayList<>();
+        backtrack(0, s, new ArrayList<>(), trie, res);
+        return res;
+    }
+
+    private void backtrack(int index, String s, List<String> path, Trie trie, List<String> res) {
+        if (index == s.length()) {
+            res.add(String.join(" ", path));
+            return;
+        }
+
+        TrieNode node = trie.root;
+        StringBuilder word = new StringBuilder();
+        for (int i = index; i < s.length(); i++) {
+            char c = s.charAt(i);
+            if (!node.children.containsKey(c)) {
+                break;
+            }
+
+            word.append(c);
+            node = node.children.get(c);
+
+            if (node.isWord) {
+                path.add(word.toString());
+                backtrack(i + 1, s, path, trie, res);
+                path.remove(path.size() - 1);
+            }
+        }
+    }
+}
+```
+
+```cpp
+struct TrieNode {
+    unordered_map<char, TrieNode*> children;
+    bool isWord = false;
+};
+
+class Trie {
+public:
+    TrieNode* root;
+
+    Trie() {
+        root = new TrieNode();
+    }
+
+    void addWord(const string& word) {
+        TrieNode* curr = root;
+        for (char c : word) {
+            if (!curr->children.count(c)) {
+                curr->children[c] = new TrieNode();
+            }
+            curr = curr->children[c];
+        }
+        curr->isWord = true;
+    }
+};
+
+class Solution {
+public:
+    vector<string> wordBreak(string s, vector<string>& wordDict) {
+        Trie trie;
+        for (const string& word : wordDict) {
+            trie.addWord(word);
+        }
+
+        vector<string> res;
+        vector<string> path;
+        backtrack(0, s, path, trie, res);
+        return res;
+    }
+
+private:
+    void backtrack(int index, string& s, vector<string>& path, Trie& trie, vector<string>& res) {
+        if (index == s.size()) {
+            stringstream ss;
+            for (int i = 0; i < path.size(); ++i) {
+                if (i > 0) ss << " ";
+                ss << path[i];
+            }
+            res.push_back(ss.str());
+            return;
+        }
+
+        TrieNode* node = trie.root;
+        string word;
+        for (int i = index; i < s.size(); ++i) {
+            char c = s[i];
+            if (!node->children.count(c)) break;
+
+            word.push_back(c);
+            node = node->children[c];
+
+            if (node->isWord) {
+                path.push_back(word);
+                backtrack(i + 1, s, path, trie, res);
+                path.pop_back();
+            }
+        }
+    }
+};
+```
+
+```javascript
+class TrieNode {
+    constructor() {
+        this.children = new Map();
+        this.isWord = false;
+    }
+}
+
+class Trie {
+    constructor() {
+        this.root = new TrieNode();
+    }
+
+    /**
+     * @param {string} word
+     * @return {void}
+     */
+    addWord(word) {
+        let curr = this.root;
+        for (const c of word) {
+            if (!curr.children.has(c)) {
+                curr.children.set(c, new TrieNode());
+            }
+            curr = curr.children.get(c);
+        }
+        curr.isWord = true;
+    }
+}
+
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string[]} wordDict
+     * @return {string[]}
+     */
+    wordBreak(s, wordDict) {
+        const trie = new Trie();
+        for (const word of wordDict) {
+            trie.addWord(word);
+        }
+
+        const res = [];
+        const backtrack = (index, path) => {
+            if (index === s.length) {
+                res.push(path.join(" "));
+                return;
+            }
+
+            let node = trie.root;
+            let word = "";
+            for (let i = index; i < s.length; i++) {
+                const char = s[i];
+                if (!node.children.has(char)) {
+                    break;
+                }
+
+                word += char;
+                node = node.children.get(char);
+
+                if (node.isWord) {
+                    path.push(word);
+                    backtrack(i + 1, path);
+                    path.pop();
+                }
+            }
+        };
+
+        backtrack(0, []);
+        return res;
+    }
+}
+```
+
+```csharp
+public class TrieNode {
+    public Dictionary<char, TrieNode> children = new Dictionary<char, TrieNode>();
+    public bool isWord = false;
+}
+
+public class Trie {
+    public TrieNode root = new TrieNode();
+
+    public void AddWord(string word) {
+        TrieNode curr = root;
+        foreach (char c in word) {
+            if (!curr.children.ContainsKey(c)) {
+                curr.children[c] = new TrieNode();
+            }
+            curr = curr.children[c];
+        }
+        curr.isWord = true;
+    }
+}
+
+public class Solution {
+    public List<string> WordBreak(string s, List<string> wordDict) {
+        Trie trie = new Trie();
+        foreach (string word in wordDict) {
+            trie.AddWord(word);
+        }
+
+        List<string> res = new List<string>();
+
+        void Backtrack(int index, List<string> path) {
+            if (index == s.Length) {
+                res.Add(string.Join(" ", path));
+                return;
+            }
+
+            TrieNode node = trie.root;
+            StringBuilder word = new StringBuilder();
+
+            for (int i = index; i < s.Length; i++) {
+                char c = s[i];
+                if (!node.children.ContainsKey(c)) break;
+
+                word.Append(c);
+                node = node.children[c];
+
+                if (node.isWord) {
+                    path.Add(word.ToString());
+                    Backtrack(i + 1, path);
+                    path.RemoveAt(path.Count - 1);
+                }
+            }
+        }
+
+        Backtrack(0, new List<string>());
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m + n * 2 ^ n)$
+* Space complexity: $O(m + 2 ^ n)$
+
+> Where $n$ is the length of the string $s$ and $m$ is the sum of the lengths of the strings in the $wordDict$.
+
+---
+
+## 3. Dynamic Programming (Top-Down)
+
+::tabs-start
+
+```python
+class Solution:
+    def wordBreak(self, s: str, wordDict: List[str]) -> List[str]:
+        wordDict = set(wordDict)
+        cache = {}
+
+        def backtrack(i):
+            if i == len(s):
+                return [""]
+            if i in cache:
+                return cache[i]
+
+            res = []
+            for j in range(i, len(s)):
+                w = s[i:j + 1]
+                if w not in wordDict:
+                    continue
+                strings = backtrack(j + 1)
+                for substr in strings:
+                    sentence = w
+                    if substr:
+                        sentence += " " + substr
+                    res.append(sentence)
+            cache[i] = res
+            return res
+
+        return backtrack(0)
+```
+
+```java
+public class Solution {
+    private Set<String> wordSet;
+    private Map<Integer, List<String>> cache;
+
+    public List<String> wordBreak(String s, List<String> wordDict) {
+        wordSet = new HashSet<>(wordDict);
+        cache = new HashMap<>();
+        return backtrack(s, 0);
+    }
+
+    private List<String> backtrack(String s, int i) {
+        if (i == s.length())
+            return Arrays.asList("");
+        if (cache.containsKey(i))
+            return cache.get(i);
+
+        List<String> res = new ArrayList<>();
+        for (int j = i; j < s.length(); j++) {
+            String w = s.substring(i, j + 1);
+            if (!wordSet.contains(w))
+                continue;
+            List<String> strings = backtrack(s, j + 1);
+            for (String substr : strings) {
+                String sentence = w;
+                if (!substr.isEmpty())
+                    sentence += " " + substr;
+                res.add(sentence);
+            }
+        }
+        cache.put(i, res);
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<string> wordBreak(string s, vector<string>& wordDict) {
+        wordSet = unordered_set<string>(wordDict.begin(), wordDict.end());
+        cache = unordered_map<int, vector<string>>();
+        return backtrack(s, 0);
+    }
+
+private:
+    unordered_set<string> wordSet;
+    unordered_map<int, vector<string>> cache;
+
+    vector<string> backtrack(const string& s, int i) {
+        if (i == s.size())
+            return {""};
+        if (cache.count(i))
+            return cache[i];
+
+        vector<string> res;
+        for (int j = i; j < s.size(); ++j) {
+            string w = s.substr(i, j - i + 1);
+            if (!wordSet.count(w))
+                continue;
+            vector<string> strings = backtrack(s, j + 1);
+            for (const string& substr : strings) {
+                string sentence = w;
+                if (!substr.empty())
+                    sentence += " " + substr;
+                res.push_back(sentence);
+            }
+        }
+        cache[i] = res;
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string[]} wordDict
+     * @return {string[]}
+     */
+    wordBreak(s, wordDict) {
+        const wordSet = new Set(wordDict);
+        const cache = new Map();
+
+        const backtrack = (i) => {
+            if (i === s.length) {
+                return [""];
+            }
+            if (cache.has(i)) {
+                return cache.get(i);
+            }
+
+            const res = [];
+            for (let j = i; j < s.length; j++) {
+                const w = s.substring(i, j + 1);
+                if (!wordSet.has(w)) continue;
+
+                const strings = backtrack(j + 1);
+                for (const substr of strings) {
+                    let sentence = w;
+                    if (substr) {
+                        sentence += " " + substr;
+                    }
+                    res.push(sentence);
+                }
+            }
+            cache.set(i, res);
+            return res;
+        };
+
+        return backtrack(0);
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<string> WordBreak(string s, List<string> wordDictList) {
+        HashSet<string> wordDict = new HashSet<string>(wordDictList);
+        Dictionary<int, List<string>> cache = new Dictionary<int, List<string>>();
+
+        List<string> Backtrack(int i) {
+            if (i == s.Length) return new List<string> { "" };
+            if (cache.ContainsKey(i)) return cache[i];
+
+            List<string> res = new List<string>();
+            for (int j = i; j < s.Length; j++) {
+                string w = s.Substring(i, j - i + 1);
+                if (!wordDict.Contains(w)) continue;
+
+                List<string> substrings = Backtrack(j + 1);
+                foreach (string substr in substrings) {
+                    string sentence = w;
+                    if (!string.IsNullOrEmpty(substr)) {
+                        sentence += " " + substr;
+                    }
+                    res.Add(sentence);
+                }
+            }
+
+            cache[i] = res;
+            return res;
+        }
+
+        return Backtrack(0);
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m + n * 2 ^ n)$
+* Space complexity: $O(m + n * 2 ^ n)$
+
+> Where $n$ is the length of the string $s$ and $m$ is the sum of the lengths of the strings in the $wordDict$.
+
+---
+
+## 4. Dynamic Programming (Bottom-Up)
+
+::tabs-start
+
+```python
+class Solution:
+    def wordBreak(self, s: str, wordDict: List[str]) -> List[str]:
+        wordSet = set(wordDict)
+        n = len(s)
+        dp = [[] for _ in range(n + 1)]
+        dp[0] = [""]
+
+        for i in range(1, n + 1):
+            for j in range(i):
+                if s[j:i] in wordSet:
+                    for sentence in dp[j]:
+                        dp[i].append((sentence + " " + s[j:i]).strip())
+
+        return dp[n]
+```
+
+```java
+public class Solution {
+    public List<String> wordBreak(String s, List<String> wordDict) {
+        Set<String> wordSet = new HashSet<>(wordDict);
+        int n = s.length();
+        List<String>[] dp = new ArrayList[n + 1];
+        for (int i = 0; i <= n; i++) {
+            dp[i] = new ArrayList<>();
+        }
+        dp[0].add("");
+
+        for (int i = 1; i <= n; i++) {
+            for (int j = 0; j < i; j++) {
+                if (wordSet.contains(s.substring(j, i))) {
+                    for (String sentence : dp[j]) {
+                        dp[i].add((sentence + " " + s.substring(j, i)).trim());
+                    }
+                }
+            }
+        }
+
+        return dp[n];
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<string> wordBreak(string s, vector<string>& wordDict) {
+        unordered_set<string> wordSet(wordDict.begin(), wordDict.end());
+        int n = s.size();
+        vector<vector<string>> dp(n + 1);
+        dp[0] = {""};
+        
+        for (int i = 1; i <= n; ++i) {
+            for (int j = 0; j < i; ++j) {
+                string word = s.substr(j, i - j);
+                if (wordSet.count(word)) {
+                    for (const string& sentence : dp[j]) {
+                        if (sentence.empty()) {
+                            dp[i].push_back(word);
+                        } else {
+                            dp[i].push_back(sentence + " " + word);
+                        }
+                    }
+                }
+            }
+        }
+        
+        return dp[n];
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string[]} wordDict
+     * @return {string[]}
+     */
+    wordBreak(s, wordDict) {
+        const wordSet = new Set(wordDict);
+        const n = s.length;
+        const dp = Array.from({ length: n + 1 }, () => []);
+        dp[0].push("");
+
+        for (let i = 1; i <= n; i++) {
+            for (let j = 0; j < i; j++) {
+                if (wordSet.has(s.substring(j, i))) {
+                    for (const sentence of dp[j]) {
+                        dp[i].push((sentence + " " + s.substring(j, i)).trim());
+                    }
+                }
+            }
+        }
+
+        return dp[n];
+    }
+}
+```
+
+```csharp
+public class Solution {
+    public List<string> WordBreak(string s, List<string> wordDictList) {
+        HashSet<string> wordSet = new HashSet<string>(wordDictList);
+        int n = s.Length;
+        List<string>[] dp = new List<string>[n + 1];
+        for (int i = 0; i <= n; i++) {
+            dp[i] = new List<string>();
+        }
+        dp[0].Add("");
+
+        for (int i = 1; i <= n; i++) {
+            for (int j = 0; j < i; j++) {
+                string word = s.Substring(j, i - j);
+                if (wordSet.Contains(word)) {
+                    foreach (string sentence in dp[j]) {
+                        string space = string.IsNullOrEmpty(sentence) ? "" : " ";
+                        dp[i].Add(sentence + space + word);
+                    }
+                }
+            }
+        }
+
+        return dp[n];
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m + n * 2 ^ n)$
+* Space complexity: $O(m + n * 2 ^ n)$
+
+> Where $n$ is the length of the string $s$ and $m$ is the sum of the lengths of the strings in the $wordDict$.
+
+---
+
+## 5. Dynamic Programming (Top-Down) Using Trie
+
+::tabs-start
+
+```python
+class TrieNode:
+    def __init__(self):
+        self.children = {}
+        self.isWord = False
+
+class Trie:
+    def __init__(self):
+        self.root = TrieNode()
+    
+    def addWord(self, word):
+        curr = self.root
+        for c in word:
+            if c not in curr.children:
+                curr.children[c] = TrieNode()
+            curr = curr.children[c]
+        curr.isWord = True
+
+class Solution:
+    def wordBreak(self, s: str, wordDict: List[str]) -> List[str]:
+        trie = Trie()
+        for word in wordDict:
+            trie.addWord(word)
+        
+        cache = {}
+        
+        def backtrack(index):
+            if index == len(s):
+                return [""]
+            if index in cache:
+                return cache[index]
+            
+            res = []
+            curr = trie.root
+            for i in range(index, len(s)):
+                char = s[i]
+                if char not in curr.children:
+                    break
+                curr = curr.children[char]
+                if curr.isWord:
+                    for suffix in backtrack(i + 1):
+                        if suffix:
+                            res.append(s[index:i + 1] + " " + suffix)
+                        else:
+                            res.append(s[index:i + 1])
+            
+            cache[index] = res
+            return res
+        
+        return backtrack(0)
+```
+
+```java
+class TrieNode {
+    Map<Character, TrieNode> children = new HashMap<>();
+    boolean isWord = false;
+}
+
+class Trie {
+    TrieNode root;
+
+    Trie() {
+        root = new TrieNode();
+    }
+
+    void addWord(String word) {
+        TrieNode curr = root;
+        for (char c : word.toCharArray()) {
+            curr.children.putIfAbsent(c, new TrieNode());
+            curr = curr.children.get(c);
+        }
+        curr.isWord = true;
+    }
+}
+
+public class Solution {
+    public List<String> wordBreak(String s, List<String> wordDict) {
+        Trie trie = new Trie();
+        for (String word : wordDict) {
+            trie.addWord(word);
+        }
+
+        Map<Integer, List<String>> cache = new HashMap<>();
+        return backtrack(0, s, trie, cache);
+    }
+
+    private List<String> backtrack(int index, String s, Trie trie, Map<Integer, List<String>> cache) {
+        if (index == s.length()) {
+            return Collections.singletonList("");
+        }
+
+        if (cache.containsKey(index)) {
+            return cache.get(index);
+        }
+
+        List<String> res = new ArrayList<>();
+        TrieNode curr = trie.root;
+
+        for (int i = index; i < s.length(); i++) {
+            char c = s.charAt(i);
+            if (!curr.children.containsKey(c)) {
+                break;
+            }
+            curr = curr.children.get(c);
+            if (curr.isWord) {
+                for (String suffix : backtrack(i + 1, s, trie, cache)) {
+                    if (!suffix.isEmpty()) {
+                        res.add(s.substring(index, i + 1) + " " + suffix);
+                    } else {
+                        res.add(s.substring(index, i + 1));
+                    }
+                }
+            }
+        }
+
+        cache.put(index, res);
+        return res;
+    }
+}
+```
+
+```cpp
+struct TrieNode {
+    unordered_map<char, TrieNode*> children;
+    bool isWord = false;
+};
+
+class Trie {
+public:
+    TrieNode* root;
+
+    Trie() {
+        root = new TrieNode();
+    }
+
+    void addWord(const string& word) {
+        TrieNode* curr = root;
+        for (char c : word) {
+            if (!curr->children.count(c)) {
+                curr->children[c] = new TrieNode();
+            }
+            curr = curr->children[c];
+        }
+        curr->isWord = true;
+    }
+};
+
+class Solution {
+public:
+    vector<string> wordBreak(string s, vector<string>& wordDict) {
+        Trie trie;
+        for (const string& word : wordDict) {
+            trie.addWord(word);
+        }
+
+        unordered_map<int, vector<string>> cache;
+        return backtrack(0, s, trie, cache);
+    }
+
+private:
+    vector<string> backtrack(int index, string& s, Trie& trie, unordered_map<int, vector<string>>& cache) {
+        if (index == s.size()) {
+            return {""};
+        }
+
+        if (cache.count(index)) {
+            return cache[index];
+        }
+
+        vector<string> res;
+        TrieNode* curr = trie.root;
+
+        for (int i = index; i < s.size(); ++i) {
+            char c = s[i];
+            if (!curr->children.count(c)) {
+                break;
+            }
+            curr = curr->children[c];
+            if (curr->isWord) {
+                for (const string& suffix : backtrack(i + 1, s, trie, cache)) {
+                    if (!suffix.empty()) {
+                        res.push_back(s.substr(index, i - index + 1) + " " + suffix);
+                    } else {
+                        res.push_back(s.substr(index, i - index + 1));
+                    }
+                }
+            }
+        }
+
+        return cache[index] = res;
+    }
+};
+```
+
+```javascript
+class TrieNode {
+    constructor() {
+        this.children = new Map();
+        this.isWord = false;
+    }
+}
+
+class Trie {
+    constructor() {
+        this.root = new TrieNode();
+    }
+
+    /**
+     * @param {string} word
+     * @return {void}
+     */
+    addWord(word) {
+        let curr = this.root;
+        for (const c of word) {
+            if (!curr.children.has(c)) {
+                curr.children.set(c, new TrieNode());
+            }
+            curr = curr.children.get(c);
+        }
+        curr.isWord = true;
+    }
+}
+
+class Solution {
+    /**
+     * @param {string} s
+     * @param {string[]} wordDict
+     * @return {string[]}
+     */
+    wordBreak(s, wordDict) {
+        const trie = new Trie();
+        for (const word of wordDict) {
+            trie.addWord(word);
+        }
+
+        const cache = new Map();
+
+        const backtrack = (index) => {
+            if (index === s.length) {
+                return [""];
+            }
+            if (cache.has(index)) {
+                return cache.get(index);
+            }
+
+            const res = [];
+            let curr = trie.root;
+
+            for (let i = index; i < s.length; i++) {
+                const char = s[i];
+                if (!curr.children.has(char)) {
+                    break;
+                }
+                curr = curr.children.get(char);
+                if (curr.isWord) {
+                    for (const suffix of backtrack(i + 1)) {
+                        if (suffix) {
+                            res.push(s.slice(index, i + 1) + " " + suffix);
+                        } else {
+                            res.push(s.slice(index, i + 1));
+                        }
+                    }
+                }
+            }
+
+            cache.set(index, res);
+            return res;
+        };
+
+        return backtrack(0);
+    }
+}
+```
+
+```csharp
+public class TrieNode {
+    public Dictionary<char, TrieNode> Children = new Dictionary<char, TrieNode>();
+    public bool IsWord = false;
+}
+
+public class Trie {
+    public TrieNode Root = new TrieNode();
+
+    public void AddWord(string word) {
+        TrieNode curr = Root;
+        foreach (char c in word) {
+            if (!curr.Children.ContainsKey(c)) {
+                curr.Children[c] = new TrieNode();
+            }
+            curr = curr.Children[c];
+        }
+        curr.IsWord = true;
+    }
+}
+
+public class Solution {
+    private Dictionary<int, List<string>> cache = new Dictionary<int, List<string>>();
+
+    public List<string> WordBreak(string s, List<string> wordDict) {
+        Trie trie = new Trie();
+        foreach (string word in wordDict) {
+            trie.AddWord(word);
+        }
+        return Backtrack(0, s, trie.Root, trie);
+    }
+
+    private List<string> Backtrack(int index, string s, TrieNode root, Trie trie) {
+        if (index == s.Length) return new List<string> { "" };
+        if (cache.ContainsKey(index)) return cache[index];
+
+        List<string> res = new List<string>();
+        TrieNode curr = root;
+
+        for (int i = index; i < s.Length; i++) {
+            char c = s[i];
+            if (!curr.Children.ContainsKey(c)) break;
+
+            curr = curr.Children[c];
+            if (curr.IsWord) {
+                List<string> suffixes = Backtrack(i + 1, s, root, trie);
+                foreach (string suffix in suffixes) {
+                    if (suffix == "") {
+                        res.Add(s.Substring(index, i - index + 1));
+                    } else {
+                        res.Add(s.Substring(index, i - index + 1) + " " + suffix);
+                    }
+                }
+            }
+        }
+
+        cache[index] = res;
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(m + n * 2 ^ n)$
+* Space complexity: $O(m + n * 2 ^ n)$
+
+> Where $n$ is the length of the string $s$ and $m$ is the sum of the lengths of the strings in the $wordDict$.
\ No newline at end of file
diff --git a/articles/word-break.md b/articles/word-break.md
index 86054c974..acc8366d3 100644
--- a/articles/word-break.md
+++ b/articles/word-break.md
@@ -130,6 +130,78 @@ public class Solution {
 }
 ```
 
+```go
+func wordBreak(s string, wordDict []string) bool {
+    return dfs(s, wordDict, 0)
+}
+
+func dfs(s string, wordDict []string, i int) bool {
+    if i == len(s) {
+        return true
+    }
+
+    for _, w := range wordDict {
+        if len(s[i:]) >= len(w) && s[i:i+len(w)] == w {
+            if dfs(s, wordDict, i+len(w)) {
+                return true
+            }
+        }
+    }
+
+    return false
+}
+```
+
+```kotlin
+class Solution {
+    fun wordBreak(s: String, wordDict: List<String>): Boolean {
+        return dfs(s, wordDict, 0)
+    }
+
+    private fun dfs(s: String, wordDict: List<String>, i: Int): Boolean {
+        if (i == s.length) {
+            return true
+        }
+
+        for (w in wordDict) {
+            if (s.length - i >= w.length && s.substring(i, i + w.length) == w) {
+                if (dfs(s, wordDict, i + w.length)) {
+                    return true
+                }
+            }
+        }
+
+        return false
+    }
+}
+```
+
+```swift
+class Solution {
+    func wordBreak(_ s: String, _ wordDict: [String]) -> Bool {
+        let chars = Array(s)
+
+        func dfs(_ i: Int) -> Bool {
+            if i == chars.count {
+                return true
+            }
+            
+            for w in wordDict {
+                if i + w.count <= chars.count, 
+                   String(chars[i..<i + w.count]) == w {
+                    if dfs(i + w.count) {
+                        return true
+                    }
+                }
+            }
+            return false
+        }
+
+        return dfs(0)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -266,6 +338,83 @@ public class Solution {
 }
 ```
 
+```go
+func wordBreak(s string, wordDict []string) bool {
+    wordSet := make(map[string]bool)
+    for _, w := range wordDict {
+        wordSet[w] = true
+    }
+    return dfs(s, wordSet, 0)
+}
+
+func dfs(s string, wordSet map[string]bool, i int) bool {
+    if i == len(s) {
+        return true
+    }
+
+    for j := i; j < len(s); j++ {
+        if wordSet[s[i:j+1]] {
+            if dfs(s, wordSet, j+1) {
+                return true
+            }
+        }
+    }
+
+    return false
+}
+```
+
+```kotlin
+class Solution {
+    fun wordBreak(s: String, wordDict: List<String>): Boolean {
+        val wordSet = wordDict.toHashSet()
+        return dfs(s, wordSet, 0)
+    }
+
+    private fun dfs(s: String, wordSet: HashSet<String>, i: Int): Boolean {
+        if (i == s.length) {
+            return true
+        }
+
+        for (j in i until s.length) {
+            if (wordSet.contains(s.substring(i, j + 1))) {
+                if (dfs(s, wordSet, j + 1)) {
+                    return true
+                }
+            }
+        }
+
+        return false
+    }
+}
+```
+
+```swift
+class Solution {
+    func wordBreak(_ s: String, _ wordDict: [String]) -> Bool {
+        let wordSet = Set(wordDict)
+        let chars = Array(s)
+
+        func dfs(_ i: Int) -> Bool {
+            if i == chars.count {
+                return true
+            }
+
+            for j in i..<chars.count {
+                if wordSet.contains(String(chars[i...j])) {
+                    if dfs(j + 1) {
+                        return true
+                    }
+                }
+            }
+            return false
+        }
+
+        return dfs(0)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -433,6 +582,91 @@ public class Solution {
 }
 ```
 
+```go
+func wordBreak(s string, wordDict []string) bool {
+    memo := make(map[int]bool)
+    memo[len(s)] = true
+
+    var dfs func(int) bool
+    dfs = func(i int) bool {
+        if val, found := memo[i]; found {
+            return val
+        }
+
+        for _, w := range wordDict {
+            if i+len(w) <= len(s) && s[i:i+len(w)] == w {
+                if dfs(i + len(w)) {
+                    memo[i] = true
+                    return true
+                }
+            }
+        }
+
+        memo[i] = false
+        return false
+    }
+
+    return dfs(0)
+}
+```
+
+```kotlin
+class Solution {
+    fun wordBreak(s: String, wordDict: List<String>): Boolean {
+        val memo = hashMapOf(s.length to true)
+
+        fun dfs(i: Int): Boolean {
+            memo[i]?.let { return it }
+
+            for (w in wordDict) {
+                if (i + w.length <= s.length && 
+                    s.substring(i, i + w.length) == w) {
+                    if (dfs(i + w.length)) {
+                        memo[i] = true
+                        return true
+                    }
+                }
+            }
+
+            memo[i] = false
+            return false
+        }
+
+        return dfs(0)
+    }
+}
+```
+
+```swift
+class Solution {
+    func wordBreak(_ s: String, _ wordDict: [String]) -> Bool {
+        var memo = [Int: Bool]()
+        memo[s.count] = true
+        let chars = Array(s)
+
+        func dfs(_ i: Int) -> Bool {
+            if let cached = memo[i] {
+                return cached
+            }
+
+            for w in wordDict {
+                if i + w.count <= chars.count, 
+                   String(chars[i..<i + w.count]) == w {
+                    if dfs(i + w.count) {
+                        memo[i] = true
+                        return true
+                    }
+                }
+            }
+            memo[i] = false
+            return false
+        }
+
+        return dfs(0)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -632,6 +866,109 @@ public class Solution {
 }
 ```
 
+```go
+func wordBreak(s string, wordDict []string) bool {
+    wordSet := make(map[string]bool)
+    maxLen := 0
+
+    for _, w := range wordDict {
+        wordSet[w] = true
+        if len(w) > maxLen {
+            maxLen = len(w)
+        }
+    }
+
+    memo := make(map[int]bool)
+
+    var dfs func(int) bool
+    dfs = func(i int) bool {
+        if val, found := memo[i]; found {
+            return val
+        }
+        if i == len(s) {
+            return true
+        }
+        for j := i; j < len(s) && j < i+maxLen; j++ {
+            if wordSet[s[i:j+1]] {
+                if dfs(j + 1) {
+                    memo[i] = true
+                    return true
+                }
+            }
+        }
+        memo[i] = false
+        return false
+    }
+
+    return dfs(0)
+}
+```
+
+```kotlin
+class Solution {
+    fun wordBreak(s: String, wordDict: List<String>): Boolean {
+        val wordSet = wordDict.toSet()
+        val maxLen = wordDict.maxOfOrNull { it.length } ?: 0
+        val memo = HashMap<Int, Boolean>()
+
+        fun dfs(i: Int): Boolean {
+            memo[i]?.let { return it }
+            if (i == s.length) return true
+
+            for (j in i until minOf(s.length, i + maxLen)) {
+                if (s.substring(i, j + 1) in wordSet) {
+                    if (dfs(j + 1)) {
+                        memo[i] = true
+                        return true
+                    }
+                }
+            }
+
+            memo[i] = false
+            return false
+        }
+
+        return dfs(0)
+    }
+}
+```
+
+```swift
+class Solution {
+    func wordBreak(_ s: String, _ wordDict: [String]) -> Bool {
+        let wordSet = Set(wordDict)
+        var maxLen = 0
+        for w in wordDict {
+            maxLen = max(maxLen, w.count)
+        }
+
+        var memo = [Int: Bool]()
+        let chars = Array(s)
+
+        func dfs(_ i: Int) -> Bool {
+            if let cached = memo[i] {
+                return cached
+            }
+            if i == chars.count {
+                return true
+            }
+            for j in i..<min(chars.count, i + maxLen) {
+                if wordSet.contains(String(chars[i...j])) {
+                    if dfs(j + 1) {
+                        memo[i] = true
+                        return true
+                    }
+                }
+            }
+            memo[i] = false
+            return false
+        }
+
+        return dfs(0)
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -761,6 +1098,70 @@ public class Solution {
 }
 ```
 
+```go
+func wordBreak(s string, wordDict []string) bool {
+    dp := make([]bool, len(s)+1)
+    dp[len(s)] = true
+
+    for i := len(s) - 1; i >= 0; i-- {
+        for _, w := range wordDict {
+            if i+len(w) <= len(s) && s[i:i+len(w)] == w {
+                dp[i] = dp[i+len(w)]
+            }
+            if dp[i] {
+                break
+            }
+        }
+    }
+
+    return dp[0]
+}
+```
+
+```kotlin
+class Solution {
+    fun wordBreak(s: String, wordDict: List<String>): Boolean {
+        val dp = BooleanArray(s.length + 1)
+        dp[s.length] = true
+
+        for (i in s.length - 1 downTo 0) {
+            for (w in wordDict) {
+                if (i + w.length <= s.length && 
+                    s.substring(i, i + w.length) == w) {
+                    dp[i] = dp[i + w.length]
+                }
+                if (dp[i]) break
+            }
+        }
+
+        return dp[0]
+    }
+}
+```
+
+```swift
+class Solution {
+    func wordBreak(_ s: String, _ wordDict: [String]) -> Bool {
+        var dp = Array(repeating: false, count: s.count + 1)
+        dp[s.count] = true
+        let chars = Array(s)
+
+        for i in stride(from: s.count - 1, through: 0, by: -1) {
+            for w in wordDict {
+                if i + w.count <= chars.count, String(chars[i..<i + w.count]) == w {
+                    dp[i] = dp[i + w.count]
+                }
+                if dp[i] {
+                    break
+                }
+            }
+        }
+
+        return dp[0]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -826,7 +1227,7 @@ class Solution:
 ```
 
 ```java
-public class TrieNode {
+class TrieNode {
     HashMap<Character, TrieNode> children;
     boolean isWord;
 
@@ -836,7 +1237,7 @@ public class TrieNode {
     }
 }
 
-public class Trie {
+class Trie {
     TrieNode root;
 
     public Trie() {
@@ -1114,6 +1515,193 @@ public class Solution {
 }
 ```
 
+```go
+type TrieNode struct {
+    children map[rune]*TrieNode
+    isWord   bool
+}
+
+func NewTrieNode() *TrieNode {
+    return &TrieNode{children: make(map[rune]*TrieNode)}
+}
+
+type Trie struct {
+    root *TrieNode
+}
+
+func NewTrie() *Trie {
+    return &Trie{root: NewTrieNode()}
+}
+
+func (t *Trie) Insert(word string) {
+    node := t.root
+    for _, char := range word {
+        if _, found := node.children[char]; !found {
+            node.children[char] = NewTrieNode()
+        }
+        node = node.children[char]
+    }
+    node.isWord = true
+}
+
+func (t *Trie) Search(s string, i, j int) bool {
+    node := t.root
+    for idx := i; idx <= j; idx++ {
+        char := rune(s[idx])
+        if _, found := node.children[char]; !found {
+            return false
+        }
+        node = node.children[char]
+    }
+    return node.isWord
+}
+
+func wordBreak(s string, wordDict []string) bool {
+    trie := NewTrie()
+    for _, word := range wordDict {
+        trie.Insert(word)
+    }
+
+    dp := make([]bool, len(s)+1)
+    dp[len(s)] = true
+
+    maxLength := 0
+    for _, word := range wordDict {
+        if len(word) > maxLength {
+            maxLength = len(word)
+        }
+    }
+
+    for i := len(s) - 1; i >= 0; i-- {
+        for j := i; j < len(s) && j < i+maxLength; j++ {
+            if trie.Search(s, i, j) {
+                dp[i] = dp[j+1]
+                if dp[i] {
+                    break
+                }
+            }
+        }
+    }
+
+    return dp[0]
+}
+```
+
+```kotlin
+class TrieNode {
+    val children = mutableMapOf<Char, TrieNode>()
+    var isWord = false
+}
+
+class Trie {
+    private val root = TrieNode()
+
+    fun insert(word: String) {
+        var node = root
+        for (char in word) {
+            node = node.children.computeIfAbsent(char) { TrieNode() }
+        }
+        node.isWord = true
+    }
+
+    fun search(s: String, i: Int, j: Int): Boolean {
+        var node = root
+        for (idx in i..j) {
+            val char = s[idx]
+            node = node.children[char] ?: return false
+        }
+        return node.isWord
+    }
+}
+
+class Solution {
+    fun wordBreak(s: String, wordDict: List<String>): Boolean {
+        val trie = Trie()
+        wordDict.forEach { trie.insert(it) }
+
+        val dp = BooleanArray(s.length + 1)
+        dp[s.length] = true
+
+        val maxLength = wordDict.maxOfOrNull { it.length } ?: 0
+
+        for (i in s.length - 1 downTo 0) {
+            for (j in i until minOf(s.length, i + maxLength)) {
+                if (trie.search(s, i, j)) {
+                    dp[i] = dp[j + 1]
+                    if (dp[i]) break
+                }
+            }
+        }
+
+        return dp[0]
+    }
+}
+```
+
+```swift
+class TrieNode {
+    var children = [Character: TrieNode]()
+    var isWord = false
+}
+
+class Trie {
+    private let root = TrieNode()
+
+    func insert(_ word: String) {
+        var node = root
+        for char in word {
+            if node.children[char] == nil {
+                node.children[char] = TrieNode()
+            }
+            node = node.children[char]!
+        }
+        node.isWord = true
+    }
+
+    func search(_ s: [Character], _ i: Int, _ j: Int) -> Bool {
+        var node = root
+        for idx in i...j {
+            if node.children[s[idx]] == nil {
+                return false
+            }
+            node = node.children[s[idx]]!
+        }
+        return node.isWord
+    }
+}
+
+class Solution {
+    func wordBreak(_ s: String, _ wordDict: [String]) -> Bool {
+        let trie = Trie()
+        for word in wordDict {
+            trie.insert(word)
+        }
+
+        var dp = Array(repeating: false, count: s.count + 1)
+        dp[s.count] = true
+        let chars = Array(s)
+
+        var maxLen = 0
+        for word in wordDict {
+            maxLen = max(maxLen, word.count)
+        }
+
+        for i in stride(from: s.count, through: 0, by: -1) {
+            for j in i..<min(s.count, i + maxLen) {
+                if trie.search(chars, i, j) {
+                    dp[i] = dp[j + 1]
+                    if dp[i] {
+                        break
+                    }
+                }
+            }
+        }
+
+        return dp[0]
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/word-ladder.md b/articles/word-ladder.md
index 0760887d6..ea29ccf35 100644
--- a/articles/word-ladder.md
+++ b/articles/word-ladder.md
@@ -346,6 +346,230 @@ public class Solution {
 }
 ```
 
+```go
+func ladderLength(beginWord string, endWord string, wordList []string) int {
+    if !contains(wordList, endWord) || beginWord == endWord {
+        return 0
+    }
+
+    n, m := len(wordList), len(wordList[0])
+    adj := make([][]int, n)
+    mp := make(map[string]int)
+
+    for i := 0; i < n; i++ {
+        mp[wordList[i]] = i
+    }
+
+    for i := 0; i < n; i++ {
+        for j := i + 1; j < n; j++ {
+            cnt := 0
+            for k := 0; k < m; k++ {
+                if wordList[i][k] != wordList[j][k] {
+                    cnt++
+                }
+            }
+            if cnt == 1 {
+                adj[i] = append(adj[i], j)
+                adj[j] = append(adj[j], i)
+            }
+        }
+    }
+
+    q := []int{}
+    res := 1
+    visit := make(map[int]bool)
+
+    for i := 0; i < m; i++ {
+        for c := 'a'; c <= 'z'; c++ {
+            if rune(beginWord[i]) == c {
+                continue
+            }
+            word := beginWord[:i] + string(c) + beginWord[i+1:]
+            if idx, exists := mp[word]; exists && !visit[idx] {
+                q = append(q, idx)
+                visit[idx] = true
+            }
+        }
+    }
+
+    for len(q) > 0 {
+        res++
+        size := len(q)
+        for i := 0; i < size; i++ {
+            node := q[0]
+            q = q[1:]
+            if wordList[node] == endWord {
+                return res
+            }
+            for _, nei := range adj[node] {
+                if !visit[nei] {
+                    visit[nei] = true
+                    q = append(q, nei)
+                }
+            }
+        }
+    }
+    return 0
+}
+
+func contains(wordList []string, word string) bool {
+    for _, w := range wordList {
+        if w == word {
+            return true
+        }
+    }
+    return false
+}
+```
+
+```kotlin
+class Solution {
+    fun ladderLength(beginWord: String, endWord: String, wordList: List<String>): Int {
+        if (!wordList.contains(endWord) || beginWord == endWord) {
+            return 0
+        }
+
+        val n = wordList.size
+        val m = wordList[0].length
+        val adj = Array(n) { mutableListOf<Int>() }
+        val mp = HashMap<String, Int>()
+
+        for (i in 0 until n) {
+            mp[wordList[i]] = i
+        }
+
+        for (i in 0 until n) {
+            for (j in i + 1 until n) {
+                var cnt = 0
+                for (k in 0 until m) {
+                    if (wordList[i][k] != wordList[j][k]) {
+                        cnt++
+                    }
+                }
+                if (cnt == 1) {
+                    adj[i].add(j)
+                    adj[j].add(i)
+                }
+            }
+        }
+
+        val q = ArrayDeque<Int>()
+        var res = 1
+        val visit = HashSet<Int>()
+
+        for (i in 0 until m) {
+            for (c in 'a'..'z') {
+                if (beginWord[i] == c) {
+                    continue
+                }
+                val word = beginWord.substring(0, i) + c + beginWord.substring(i + 1)
+                mp[word]?.let { idx ->
+                    if (!visit.contains(idx)) {
+                        q.add(idx)
+                        visit.add(idx)
+                    }
+                }
+            }
+        }
+
+        while (q.isNotEmpty()) {
+            res++
+            repeat(q.size) {
+                val node = q.removeFirst()
+                if (wordList[node] == endWord) {
+                    return res
+                }
+                for (nei in adj[node]) {
+                    if (!visit.contains(nei)) {
+                        visit.add(nei)
+                        q.add(nei)
+                    }
+                }
+            }
+        }
+        return 0
+    }
+}
+```
+
+```swift
+class Solution {
+    func ladderLength(_ beginWord: String, _ endWord: String, _ wordList: [String]) -> Int {
+        if !wordList.contains(endWord) || beginWord == endWord {
+            return 0
+        }
+        
+        let n = wordList.count
+        let m = wordList[0].count
+        var adj = [[Int]](repeating: [], count: n)
+        var mp = [String: Int]()
+        
+        for i in 0..<n {
+            mp[wordList[i]] = i
+        }
+        
+        let wordArrays = wordList.map { Array($0) }
+        
+        for i in 0..<n {
+            for j in (i + 1)..<n {
+                var cnt = 0
+                let arr1 = wordArrays[i]
+                let arr2 = wordArrays[j]
+                for k in 0..<m {
+                    if arr1[k] != arr2[k] {
+                        cnt += 1
+                    }
+                }
+                if cnt == 1 {
+                    adj[i].append(j)
+                    adj[j].append(i)
+                }
+            }
+        }
+        
+        var q = Deque<Int>()
+        var res = 1
+        var visit = Set<Int>()
+        let beginChars = Array(beginWord)
+        
+        for i in 0..<m {
+            for c in 97...122 {
+                let ch = Character(UnicodeScalar(c)!)
+                if ch == beginChars[i] {
+                    continue
+                }
+                let prefix = String(beginChars[0..<i])
+                let suffix = i + 1 < beginChars.count ? String(beginChars[(i + 1)...]) : ""
+                let word = prefix + String(ch) + suffix
+                if let idx = mp[word], !visit.contains(idx) {
+                    q.append(idx)
+                    visit.insert(idx)
+                }
+            }
+        }
+        
+        while !q.isEmpty {
+            res += 1
+            let levelCount = q.count
+            for _ in 0..<levelCount {
+                let node = q.removeFirst()
+                if wordList[node] == endWord {
+                    return res
+                }
+                for nei in adj[node] {
+                    if !visit.contains(nei) {
+                        visit.insert(nei)
+                        q.append(nei)
+                    }
+                }
+            }
+        }
+        
+        return 0
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -531,6 +755,139 @@ public class Solution {
 }
 ```
 
+```go
+func ladderLength(beginWord string, endWord string, wordList []string) int {
+    if !contains(wordList, endWord) || beginWord == endWord {
+        return 0
+    }
+
+    words := make(map[string]bool)
+    for _, word := range wordList {
+        words[word] = true
+    }
+
+    res := 0
+    q := []string{beginWord}
+
+    for len(q) > 0 {
+        res++
+        size := len(q)
+        for i := 0; i < size; i++ {
+            node := q[0]
+            q = q[1:]
+            
+            if node == endWord {
+                return res
+            }
+
+            for i := 0; i < len(node); i++ {
+                for c := 'a'; c <= 'z'; c++ {
+                    if rune(node[i]) == c {
+                        continue
+                    }
+                    nei := node[:i] + string(c) + node[i+1:]
+                    if words[nei] {
+                        q = append(q, nei)
+                        delete(words, nei)
+                    }
+                }
+            }
+        }
+    }
+    return 0
+}
+
+func contains(wordList []string, word string) bool {
+    for _, w := range wordList {
+        if w == word {
+            return true
+        }
+    }
+    return false
+}
+```
+
+```kotlin
+class Solution {
+    fun ladderLength(beginWord: String, endWord: String, wordList: List<String>): Int {
+        if (!wordList.contains(endWord) || beginWord == endWord) {
+            return 0
+        }
+
+        val words = wordList.toMutableSet()
+        var res = 0
+        val q = ArrayDeque<String>().apply { add(beginWord) }
+
+        while (q.isNotEmpty()) {
+            res++
+            repeat(q.size) {
+                val node = q.removeFirst()
+                
+                if (node == endWord) {
+                    return res
+                }
+
+                for (i in node.indices) {
+                    for (c in 'a'..'z') {
+                        if (node[i] == c) {
+                            continue
+                        }
+                        val nei = node.substring(0, i) + c + node.substring(i + 1)
+                        if (words.remove(nei)) {
+                            q.add(nei)
+                        }
+                    }
+                }
+            }
+        }
+        return 0
+    }
+}
+```
+
+```swift
+class Solution {
+    func ladderLength(_ beginWord: String, _ endWord: String, _ wordList: [String]) -> Int {
+        if !wordList.contains(endWord) || beginWord == endWord {
+            return 0
+        }
+
+        var words = Set(wordList)
+        var queue = Deque<String>()
+        queue.append(beginWord)
+        var res = 0
+
+        while !queue.isEmpty {
+            res += 1
+            for _ in 0..<queue.count {
+                let node = queue.popFirst()!
+                if node == endWord {
+                    return res
+                }
+                let nodeArray = Array(node)
+                for i in 0..<nodeArray.count {
+                    for c in 97...122 {
+                        let char = Character(UnicodeScalar(c)!)
+                        if char == nodeArray[i] {
+                            continue
+                        }
+                        var neiArray = nodeArray
+                        neiArray[i] = char
+                        let nei = String(neiArray)
+                        if words.contains(nei) {
+                            queue.append(nei)
+                            words.remove(nei)
+                        }
+                    }
+                }
+            }
+        }
+
+        return 0
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -772,6 +1129,161 @@ public class Solution {
 }
 ```
 
+```go
+func ladderLength(beginWord string, endWord string, wordList []string) int {
+    if !contains(wordList, endWord) {
+        return 0
+    }
+
+    nei := make(map[string][]string)
+    wordList = append(wordList, beginWord)
+
+    for _, word := range wordList {
+        for j := 0; j < len(word); j++ {
+            pattern := word[:j] + "*" + word[j+1:]
+            nei[pattern] = append(nei[pattern], word)
+        }
+    }
+
+    visit := make(map[string]bool)
+    visit[beginWord] = true
+    q := []string{beginWord}
+    res := 1
+
+    for len(q) > 0 {
+        for i := len(q); i > 0; i-- {
+            word := q[0]
+            q = q[1:]
+            
+            if word == endWord {
+                return res
+            }
+
+            for j := 0; j < len(word); j++ {
+                pattern := word[:j] + "*" + word[j+1:]
+                for _, neiWord := range nei[pattern] {
+                    if !visit[neiWord] {
+                        visit[neiWord] = true
+                        q = append(q, neiWord)
+                    }
+                }
+            }
+        }
+        res++
+    }
+    return 0
+}
+
+func contains(wordList []string, word string) bool {
+    for _, w := range wordList {
+        if w == word {
+            return true
+        }
+    }
+    return false
+}
+```
+
+```kotlin
+class Solution {
+    fun ladderLength(beginWord: String, endWord: String, wordList: List<String>): Int {
+        if (!wordList.contains(endWord)) {
+            return 0
+        }
+
+        val nei = HashMap<String, MutableList<String>>().withDefault { mutableListOf() }
+        val allWords = wordList.toMutableList().apply { add(beginWord) }
+
+        for (word in allWords) {
+            for (j in word.indices) {
+                val pattern = word.substring(0, j) + "*" + word.substring(j + 1)
+                nei[pattern] = nei.getValue(pattern).apply { add(word) }
+            }
+        }
+
+        val visit = hashSetOf(beginWord)
+        val q = ArrayDeque<String>().apply { add(beginWord) }
+        var res = 1
+
+        while (q.isNotEmpty()) {
+            repeat(q.size) {
+                val word = q.removeFirst()
+                
+                if (word == endWord) {
+                    return res
+                }
+
+                for (j in word.indices) {
+                    val pattern = word.substring(0, j) + "*" + word.substring(j + 1)
+                    for (neiWord in nei.getValue(pattern)) {
+                        if (visit.add(neiWord)) {
+                            q.add(neiWord)
+                        }
+                    }
+                }
+            }
+            res++
+        }
+        return 0
+    }
+}
+```
+
+```swift
+class Solution {
+    func ladderLength(_ beginWord: String, _ endWord: String, _ wordList: [String]) -> Int {
+        if !wordList.contains(endWord) {
+            return 0
+        }
+
+        var nei = [String: [String]]()
+        var wordList = wordList
+        wordList.append(beginWord)
+
+        for word in wordList {
+            let wordArray = Array(word)
+            for j in 0..<wordArray.count {
+                var patternArray = wordArray
+                patternArray[j] = "*"
+                let pattern = String(patternArray)
+                nei[pattern, default: []].append(word)
+            }
+        }
+
+        var visit: Set<String> = [beginWord]
+        var queue = Deque<String>()
+        queue.append(beginWord)
+        var res = 1
+
+        while !queue.isEmpty {
+            for _ in 0..<queue.count {
+                let word = queue.popFirst()!
+                if word == endWord {
+                    return res
+                }
+                let wordArray = Array(word)
+                for j in 0..<wordArray.count {
+                    var patternArray = wordArray
+                    patternArray[j] = "*"
+                    let pattern = String(patternArray)
+
+                    if let neighbors = nei[pattern] {
+                        for neiWord in neighbors {
+                            if !visit.contains(neiWord) {
+                                visit.insert(neiWord)
+                                queue.append(neiWord)
+                            }
+                        }
+                    }
+                }
+            }
+            res += 1
+        }
+        return 0
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
@@ -1023,6 +1535,184 @@ public class Solution {
 }
 ```
 
+```go
+func ladderLength(beginWord string, endWord string, wordList []string) int {
+    if len(wordList) == 0 || len(beginWord) != len(wordList[0]) {
+        return 0
+    }
+    
+    wordSet := make(map[string]bool)
+    for _, word := range wordList {
+        wordSet[word] = true
+    }
+    
+    if !wordSet[endWord] || beginWord == endWord {
+        return 0
+    }
+    
+    m := len(beginWord)
+    qb := []string{beginWord}
+    qe := []string{endWord}
+    fromBegin := map[string]int{beginWord: 1}
+    fromEnd := map[string]int{endWord: 1}
+    
+    for len(qb) > 0 && len(qe) > 0 {
+        if len(qb) > len(qe) {
+            qb, qe = qe, qb
+            fromBegin, fromEnd = fromEnd, fromBegin
+        }
+        
+        size := len(qb)
+        for i := 0; i < size; i++ {
+            word := qb[0]
+            qb = qb[1:]
+            steps := fromBegin[word]
+            
+            wordBytes := []byte(word)
+            for j := 0; j < m; j++ {
+                orig := wordBytes[j]
+                for c := byte('a'); c <= byte('z'); c++ {
+                    if c == orig {
+                        continue
+                    }
+                    wordBytes[j] = c
+                    nei := string(wordBytes)
+                    
+                    if !wordSet[nei] {
+                        continue
+                    }
+                    if val, exists := fromEnd[nei]; exists {
+                        return steps + val
+                    }
+                    if _, exists := fromBegin[nei]; !exists {
+                        fromBegin[nei] = steps + 1
+                        qb = append(qb, nei)
+                    }
+                }
+                wordBytes[j] = orig
+            }
+        }
+    }
+    return 0
+}
+```
+
+```kotlin
+class Solution {
+    fun ladderLength(beginWord: String, endWord: String, wordList: List<String>): Int {
+        if (!wordList.contains(endWord) || beginWord == endWord) {
+            return 0
+        }
+        
+        val m = wordList[0].length
+        val wordSet = wordList.toSet()
+        val qb = ArrayDeque<String>().apply { add(beginWord) }
+        val qe = ArrayDeque<String>().apply { add(endWord) }
+        val fromBegin = hashMapOf(beginWord to 1)
+        val fromEnd = hashMapOf(endWord to 1)
+        
+        while (qb.isNotEmpty() && qe.isNotEmpty()) {
+            if (qb.size > qe.size) {
+                qb.swap(qe)
+                fromBegin.swap(fromEnd)
+            }
+            
+            repeat(qb.size) {
+                val word = qb.removeFirst()
+                val steps = fromBegin[word]!!
+                
+                for (i in 0 until m) {
+                    for (c in 'a'..'z') {
+                        if (c == word[i]) continue
+                        val nei = word.substring(0, i) + c + word.substring(i + 1)
+                        
+                        if (!wordSet.contains(nei)) continue
+                        fromEnd[nei]?.let { return steps + it }
+                        if (nei !in fromBegin) {
+                            fromBegin[nei] = steps + 1
+                            qb.add(nei)
+                        }
+                    }
+                }
+            }
+        }
+        return 0
+    }
+    
+    private fun <T> ArrayDeque<T>.swap(other: ArrayDeque<T>) {
+        val temp = ArrayDeque(this)
+        this.clear()
+        this.addAll(other)
+        other.clear()
+        other.addAll(temp)
+    }
+    
+    private fun <K, V> HashMap<K, V>.swap(other: HashMap<K, V>) {
+        val temp = HashMap<K, V>()
+        temp.putAll(this)
+        this.clear()
+        this.putAll(other)
+        other.clear()
+        other.putAll(temp)
+    }
+}
+```
+
+```swift
+class Solution {
+    func ladderLength(_ beginWord: String, _ endWord: String, _ wordList: [String]) -> Int {
+        if !wordList.contains(endWord) || beginWord == endWord {
+            return 0
+        }
+
+        let m = wordList[0].count
+        var wordSet = Set(wordList)
+        var qb = Deque<String>([beginWord])
+        var qe = Deque<String>([endWord])
+        var fromBegin = [beginWord: 1]
+        var fromEnd = [endWord: 1]
+
+        while !qb.isEmpty && !qe.isEmpty {
+            if qb.count > qe.count {
+                swap(&qb, &qe)
+                swap(&fromBegin, &fromEnd)
+            }
+
+            for _ in 0..<qb.count {
+                let word = qb.popFirst()!
+                let steps = fromBegin[word]!
+
+                var wordArray = Array(word)
+                for i in 0..<m {
+                    let originalChar = wordArray[i]
+                    for c in 97...122 {
+                        let char = Character(UnicodeScalar(c)!)
+                        if char == originalChar {
+                            continue
+                        }
+                        wordArray[i] = char
+                        let nei = String(wordArray)
+
+                        if !wordSet.contains(nei) {
+                            continue
+                        }
+                        if let endSteps = fromEnd[nei] {
+                            return steps + endSteps
+                        }
+                        if fromBegin[nei] == nil {
+                            fromBegin[nei] = steps + 1
+                            qb.append(nei)
+                        }
+                    }
+                    wordArray[i] = originalChar
+                }
+            }
+        }
+        return 0
+    }
+}
+```
+
 ::tabs-end
 
 ### Time & Space Complexity
diff --git a/articles/word-pattern.md b/articles/word-pattern.md
new file mode 100644
index 000000000..c09b50aa1
--- /dev/null
+++ b/articles/word-pattern.md
@@ -0,0 +1,533 @@
+## 1. Two Hash Maps
+
+::tabs-start
+
+```python
+class Solution:
+    def wordPattern(self, pattern: str, s: str) -> bool:
+        words = s.split(" ")
+        if len(pattern) != len(words):
+            return False
+
+        charToWord = {}
+        wordToChar = {}
+
+        for c, w in zip(pattern, words):
+            if c in charToWord and charToWord[c] != w:
+                return False
+            if w in wordToChar and wordToChar[w] != c:
+                return False
+            charToWord[c] = w
+            wordToChar[w] = c
+        return True
+```
+
+```java
+public class Solution {
+    public boolean wordPattern(String pattern, String s) {
+        String[] words = s.split(" ");
+        if (pattern.length() != words.length) {
+            return false;
+        }
+
+        Map<Character, String> charToWord = new HashMap<>();
+        Map<String, Character> wordToChar = new HashMap<>();
+
+        for (int i = 0; i < pattern.length(); i++) {
+            char c = pattern.charAt(i);
+            String w = words[i];
+
+            if (charToWord.containsKey(c) && !charToWord.get(c).equals(w)) {
+                return false;
+            }
+            if (wordToChar.containsKey(w) && wordToChar.get(w) != c) {
+                return false;
+            }
+
+            charToWord.put(c, w);
+            wordToChar.put(w, c);
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool wordPattern(string pattern, string s) {
+        vector<string> words;
+        string word;
+        stringstream ss(s);
+        while (ss >> word) {
+            words.push_back(word);
+        }
+
+        if (pattern.length() != words.size()) {
+            return false;
+        }
+
+        unordered_map<char, string> charToWord;
+        unordered_map<string, char> wordToChar;
+
+        for (int i = 0; i < pattern.length(); i++) {
+            char c = pattern[i];
+            string& w = words[i];
+
+            if (charToWord.count(c) && charToWord[c] != w) {
+                return false;
+            }
+            if (wordToChar.count(w) && wordToChar[w] != c) {
+                return false;
+            }
+
+            charToWord[c] = w;
+            wordToChar[w] = c;
+        }
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} pattern
+     * @param {string} s
+     * @return {boolean}
+     */
+    wordPattern(pattern, s) {
+        const words = s.split(" ");
+        if (pattern.length !== words.length) {
+            return false;
+        }
+
+        const charToWord = new Map();
+        const wordToChar = new Map();
+
+        for (let i = 0; i < pattern.length; i++) {
+            const c = pattern[i];
+            const w = words[i];
+
+            if (charToWord.has(c) && charToWord.get(c) !== w) {
+                return false;
+            }
+            if (wordToChar.has(w) && wordToChar.get(w) !== c) {
+                return false;
+            }
+
+            charToWord.set(c, w);
+            wordToChar.set(w, c);
+        }
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(m)$
+
+> Where $n$ is the length of the string $pattern$ and $m$ is the length of the string $s$.
+
+---
+
+## 2. Two Hash Maps (Optimal)
+
+::tabs-start
+
+```python
+class Solution:
+    def wordPattern(self, pattern: str, s: str) -> bool:
+        charToWord = {}
+        wordToChar = {}
+        words = s.split()
+
+        if len(pattern) != len(words):
+            return False
+
+        for i, (c, word) in enumerate(zip(pattern, words)):
+            if charToWord.get(c, 0) != wordToChar.get(word, 0):
+                return False
+            charToWord[c] = i + 1
+            wordToChar[word] = i + 1
+
+        return True
+```
+
+```java
+public class Solution {
+    public boolean wordPattern(String pattern, String s) {
+        Map<Character, Integer> charToWord = new HashMap<>();
+        Map<String, Integer> wordToChar = new HashMap<>();
+        String[] words = s.split(" ");
+        
+        if (words.length != pattern.length()) return false;
+        
+        for (int i = 0; i < pattern.length(); i++) {
+            if (charToWord.containsKey(pattern.charAt(i)) && 
+                !words[charToWord.get(pattern.charAt(i))].equals(words[i])) {
+                return false;
+            }
+            
+            if (wordToChar.containsKey(words[i]) && 
+                pattern.charAt(wordToChar.get(words[i])) != pattern.charAt(i)) {
+                return false;
+            }
+            
+            charToWord.put(pattern.charAt(i), i);
+            wordToChar.put(words[i], i);
+        }
+        
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool wordPattern(string pattern, string s) {
+        unordered_map<char, int> charToWord;
+        unordered_map<string, int> wordToChar;
+        istringstream in(s);
+        int i = 0, n = pattern.size();
+        for (string word; in >> word; ++i) {
+            if (i == n || charToWord[pattern[i]] != wordToChar[word]) {
+                return false;
+            }
+            charToWord[pattern[i]] = wordToChar[word] = i + 1;
+        }
+        return i == n;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} pattern
+     * @param {string} s
+     * @return {boolean}
+     */
+    wordPattern(pattern, s) {
+        const charToWord = new Map();
+        const wordToChar = new Map();
+        const words = s.split(" ");
+        
+        if (pattern.length !== words.length) {
+            return false;
+        }
+        
+        for (let i = 0; i < words.length; i++) {
+            const c = pattern[i];
+            const word = words[i];
+            
+            if ((charToWord.get(c) || 0) !== (wordToChar.get(word) || 0)) {
+                return false;
+            }
+            
+            charToWord.set(c, i + 1);
+            wordToChar.set(word, i + 1);
+        }
+
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(m)$
+
+> Where $n$ is the length of the string $pattern$ and $m$ is the length of the string $s$.
+
+---
+
+## 3. Hash Set
+
+::tabs-start
+
+```python
+class Solution:
+    def wordPattern(self, pattern: str, s: str) -> bool:
+        words = s.split()
+        if len(pattern) != len(words):
+            return False
+        
+        charToWord = {}
+        store = set()
+        
+        for i, (c, w) in enumerate(zip(pattern, words)):
+            if c in charToWord:
+                if words[charToWord[c]] != w:
+                    return False
+            else:
+                if w in store:
+                    return False
+                charToWord[c] = i
+                store.add(w)
+
+        return True 
+```
+
+```java
+public class Solution {
+    public boolean wordPattern(String pattern, String s) {
+        String[] words = s.split(" ");
+        if (pattern.length() != words.length) return false;
+        
+        Map<Character, Integer> charToWord = new HashMap<>();
+        Set<String> store = new HashSet<>();
+        
+        for (int i = 0; i < pattern.length(); i++) {
+            char c = pattern.charAt(i);
+            
+            if (charToWord.containsKey(c)) {
+                if (!words[charToWord.get(c)].equals(words[i])) {
+                    return false;
+                }
+            } else {
+                if (store.contains(words[i])) {
+                    return false;
+                }
+                charToWord.put(c, i);
+                store.add(words[i]);
+            }
+        }
+        
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool wordPattern(string pattern, string s) {
+        stringstream ss(s);
+        string word;
+        vector<string> words;
+        
+        while (ss >> word) {
+            words.push_back(word);
+        }
+        
+        if (pattern.length() != words.size()) return false;
+        
+        unordered_map<char, int> charToWord;
+        set<string> store;
+        
+        for (int i = 0; i < pattern.length(); i++) {
+            char c = pattern[i];
+            
+            if (charToWord.count(c)) {
+                if (words[charToWord[c]] != words[i]) {
+                    return false;
+                }
+            } else {
+                if (store.count(words[i])) {
+                    return false;
+                }
+                charToWord[c] = i;
+                store.insert(words[i]);
+            }
+        }
+        
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} pattern
+     * @param {string} s
+     * @return {boolean}
+     */
+    wordPattern(pattern, s) {
+        const charToWord = new Map();
+        const wordToChar = new Map();
+        const words = s.split(" ");
+        
+        if (pattern.length !== words.length) {
+            return false;
+        }
+        
+        for (let i = 0; i < words.length; i++) {
+            const c = pattern[i];
+            const word = words[i];
+            
+            if ((charToWord.get(c) || 0) !== (wordToChar.get(word) || 0)) {
+                return false;
+            }
+            
+            charToWord.set(c, i + 1);
+            wordToChar.set(word, i + 1);
+        }
+
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(m)$
+
+> Where $n$ is the length of the string $pattern$ and $m$ is the length of the string $s$.
+
+---
+
+## 4. Single Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def wordPattern(self, pattern: str, s: str) -> bool:
+        words = s.split()
+        if len(pattern) != len(words):
+            return False
+        
+        charToWord = {}
+        
+        for i, (c, w) in enumerate(zip(pattern, words)):
+            if c in charToWord:
+                if words[charToWord[c]] != w:
+                    return False
+            else:
+                # iterates atmost 26 times (a - z)
+                for k in charToWord:
+                    if words[charToWord[k]] == w:
+                        return False
+                charToWord[c] = i
+
+        return True 
+```
+
+```java
+public class Solution {
+    public boolean wordPattern(String pattern, String s) {
+        String[] words = s.split(" ");
+        if (pattern.length() != words.length) {
+            return false;
+        }
+
+        Map<Character, Integer> charToWord = new HashMap<>();
+        for (int i = 0; i < pattern.length(); i++) {
+            char c = pattern.charAt(i);
+            String w = words[i];
+
+            if (charToWord.containsKey(c)) {
+                if (!words[charToWord.get(c)].equals(w)) {
+                    return false;
+                }
+            } else {
+                for (Map.Entry<Character, Integer> entry : charToWord.entrySet()) {
+                    if (words[entry.getValue()].equals(w)) {
+                        return false;
+                    }
+                }
+                charToWord.put(c, i);
+            }
+        }
+        return true;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    bool wordPattern(string pattern, string s) {
+        vector<string> words;
+        string word;
+        stringstream ss(s);
+        while (ss >> word) {
+            words.push_back(word);
+        }
+        
+        if (pattern.size() != words.size()) {
+            return false;
+        }
+
+        unordered_map<char, int> charToWord;
+        for (int i = 0; i < pattern.size(); ++i) {
+            char c = pattern[i];
+            const string& w = words[i];
+
+            if (charToWord.count(c)) {
+                if (words[charToWord[c]] != w) {
+                    return false;
+                }
+            } else {
+                for (const auto& [key, val] : charToWord) {
+                    if (words[val] == w) {
+                        return false;
+                    }
+                }
+                charToWord[c] = i;
+            }
+        }
+
+        return true;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} pattern
+     * @param {string} s
+     * @return {boolean}
+     */
+    wordPattern(pattern, s) {
+        const words = s.split(" ");
+        if (pattern.length !== words.length) {
+            return false;
+        }
+
+        const charToWord = new Map();
+        for (let i = 0; i < pattern.length; i++) {
+            const c = pattern[i];
+            const w = words[i];
+
+            if (charToWord.has(c)) {
+                if (words[charToWord.get(c)] !== w) {
+                    return false;
+                }
+            } else {
+                for (const [key, index] of charToWord.entries()) {
+                    if (words[index] === w) {
+                        return false;
+                    }
+                }
+                charToWord.set(c, i);
+            }
+        }
+        
+        return true;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n + m)$
+* Space complexity: $O(m)$
+
+> Where $n$ is the length of the string $pattern$ and $m$ is the length of the string $s$.
\ No newline at end of file
diff --git a/articles/word-subsets.md b/articles/word-subsets.md
new file mode 100644
index 000000000..d96eab686
--- /dev/null
+++ b/articles/word-subsets.md
@@ -0,0 +1,293 @@
+## 1. Brute Force
+
+::tabs-start
+
+```python
+class Solution:
+    def wordSubsets(self, words1: List[str], words2: List[str]) -> List[str]:
+        res = []
+        for w1 in words1:
+            count1 = Counter(w1)
+            is_subset = True
+
+            for w2 in words2:
+                count2 = Counter(w2)
+                for c in count2: 
+                    if count2[c] > count1[c]:
+                        is_subset = False
+                        break
+
+                if not is_subset: break
+
+            if is_subset:
+                res.append(w1)
+
+        return res
+```
+
+```java
+public class Solution {
+    public List<String> wordSubsets(String[] words1, String[] words2) {
+        List<String> res = new ArrayList<>();
+
+        for (String w1 : words1) {
+            int[] count1 = new int[26];
+            for (char c : w1.toCharArray()) count1[c - 'a']++;
+
+            boolean isSubset = true;
+            for (String w2 : words2) {
+                int[] count2 = new int[26];
+                for (char c : w2.toCharArray()) count2[c - 'a']++;
+
+                for (int i = 0; i < 26; i++) {
+                    if (count2[i] > count1[i]) {
+                        isSubset = false;
+                        break;
+                    }
+                }
+
+                if (!isSubset) break;
+            }
+
+            if (isSubset) res.add(w1);
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<string> wordSubsets(vector<string>& words1, vector<string>& words2) {
+        vector<string> res;
+
+        for (const string& w1 : words1) {
+            vector<int> count1(26, 0);
+            for (char c : w1) count1[c - 'a']++;
+
+            bool isSubset = true;
+            for (const string& w2 : words2) {
+                vector<int> count2(26, 0);
+                for (char c : w2) count2[c - 'a']++;
+
+                for (int i = 0; i < 26; i++) {
+                    if (count2[i] > count1[i]) {
+                        isSubset = false;
+                        break;
+                    }
+                }
+
+                if (!isSubset) break;
+            }
+
+            if (isSubset) res.push_back(w1);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words1
+     * @param {string[]} words2
+     * @return {string[]}
+     */
+    wordSubsets(words1, words2) {
+        const res = [];
+
+        for (const w1 of words1) {
+            const count1 = Array(26).fill(0);
+            for (const c of w1) count1[c.charCodeAt(0) - 97]++;
+
+            let isSubset = true;
+            for (const w2 of words2) {
+                const count2 = Array(26).fill(0);
+                for (const c of w2) count2[c.charCodeAt(0) - 97]++;
+
+                for (let i = 0; i < 26; i++) {
+                    if (count2[i] > count1[i]) {
+                        isSubset = false;
+                        break;
+                    }
+                }
+
+                if (!isSubset) break;
+            }
+
+            if (isSubset) res.push(w1);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(N * n + N * M * m)$
+* Space complexity:
+    * $O(1)$ extra space, since we have at most $26$ different characters.
+    * $O(N * n)$ space for the output list.
+
+> Where $N$ is the size of the array $words1$, $n$ is the length of the longest word in $words1$, $M$ is the size of the array $words2$, and $m$ is the length of the longest word in $words2$.
+
+---
+
+## 2. Greedy + Hash Map
+
+::tabs-start
+
+```python
+class Solution:
+    def wordSubsets(self, words1: List[str], words2: List[str]) -> List[str]:
+        count_2 = defaultdict(int)
+        for w in words2:
+            count_w = Counter(w)
+            for c, cnt in count_w.items():
+                count_2[c] = max(count_2[c], cnt)
+
+        res = []
+        for w in words1:
+            count_w = Counter(w)
+            flag = True
+            for c, cnt in count_2.items():
+                if count_w[c] < cnt:
+                    flag = False
+                    break
+            if flag:
+                res.append(w)
+
+        return res
+```
+
+```java
+public class Solution {
+    public List<String> wordSubsets(String[] words1, String[] words2) {
+        int[] count2 = new int[26];
+        for (String w : words2) {
+            int[] countW = new int[26];
+            for (char c : w.toCharArray()) {
+                countW[c - 'a']++;
+            }
+            for (int i = 0; i < 26; i++) {
+                count2[i] = Math.max(count2[i], countW[i]);
+            }
+        }
+
+        List<String> res = new ArrayList<>();
+        for (String w : words1) {
+            int[] countW = new int[26];
+            for (char c : w.toCharArray()) {
+                countW[c - 'a']++;
+            }
+
+            boolean flag = true;
+            for (int i = 0; i < 26; i++) {
+                if (countW[i] < count2[i]) {
+                    flag = false;
+                    break;
+                }
+            }
+
+            if (flag) {
+                res.add(w);
+            }
+        }
+
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    vector<string> wordSubsets(vector<string>& words1, vector<string>& words2) {
+        vector<int> count2(26, 0);
+        for (string& w : words2) {
+            vector<int> countW(26, 0);
+            for (char c : w) countW[c - 'a']++;
+            for (int i = 0; i < 26; ++i)
+                count2[i] = max(count2[i], countW[i]);
+        }
+
+        vector<string> res;
+        for (string& w : words1) {
+            vector<int> countW(26, 0);
+            for (char c : w) countW[c - 'a']++;
+
+            bool flag = true;
+            for (int i = 0; i < 26; ++i) {
+                if (countW[i] < count2[i]) {
+                    flag = false;
+                    break;
+                }
+            }
+
+            if (flag) res.push_back(w);
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string[]} words1
+     * @param {string[]} words2
+     * @return {string[]}
+     */
+    wordSubsets(words1, words2) {
+        const count2 = new Array(26).fill(0);
+        for (let w of words2) {
+            const countW = new Array(26).fill(0);
+            for (let c of w) {
+                countW[c.charCodeAt(0) - 97]++;
+            }
+            for (let i = 0; i < 26; i++) {
+                count2[i] = Math.max(count2[i], countW[i]);
+            }
+        }
+
+        const res = [];
+        for (let w of words1) {
+            const countW = new Array(26).fill(0);
+            for (let c of w) {
+                countW[c.charCodeAt(0) - 97]++;
+            }
+
+            let flag = true;
+            for (let i = 0; i < 26; i++) {
+                if (countW[i] < count2[i]) {
+                    flag = false;
+                    break;
+                }
+            }
+
+            if (flag) res.push(w);
+        }
+
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(N * n + M * m)$
+* Space complexity:
+    * $O(1)$ extra space, since we have at most $26$ different characters.
+    * $O(N * n)$ space for the output list.
+
+> Where $N$ is the size of the array $words1$, $n$ is the length of the longest word in $words1$, $M$ is the size of the array $words2$, and $m$ is the length of the longest word in $words2$.
\ No newline at end of file
diff --git a/articles/zigzag-conversion.md b/articles/zigzag-conversion.md
new file mode 100644
index 000000000..5df4dafff
--- /dev/null
+++ b/articles/zigzag-conversion.md
@@ -0,0 +1,226 @@
+## 1. Iteration - I
+
+::tabs-start
+
+```python
+class Solution:
+    def convert(self, s: str, numRows: int) -> str:
+        if numRows == 1:
+            return s
+
+        res = []
+        for r in range(numRows):
+            increment = 2 * (numRows - 1)
+            for i in range(r, len(s), increment):
+                res.append(s[i])
+                if r > 0 and r < numRows - 1 and i + increment - 2 * r < len(s):
+                    res.append(s[i + increment - 2 * r])
+        
+        return ''.join(res)
+```
+
+```java
+public class Solution {
+    public String convert(String s, int numRows) {
+        if (numRows == 1) {
+            return s;
+        }
+
+        StringBuilder res = new StringBuilder();
+        int len = s.length();
+
+        for (int r = 0; r < numRows; r++) {
+            int increment = 2 * (numRows - 1);
+            for (int i = r; i < len; i += increment) {
+                res.append(s.charAt(i));
+                if (r > 0 && r < numRows - 1 && i + increment - 2 * r < len) {
+                    res.append(s.charAt(i + increment - 2 * r));
+                }
+            }
+        }
+
+        return res.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string convert(string s, int numRows) {
+        if (numRows == 1) {
+            return s;
+        }
+
+        string res;
+        int len = s.size();
+
+        for (int r = 0; r < numRows; r++) {
+            int increment = 2 * (numRows - 1);
+            for (int i = r; i < len; i += increment) {
+                res += s[i];
+                if (r > 0 && r < numRows - 1 && i + increment - 2 * r < len) {
+                    res += s[i + increment - 2 * r];
+                }
+            }
+        }
+
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {number} numRows
+     * @return {string}
+     */
+    convert(s, numRows) {
+        if (numRows === 1) {
+            return s;
+        }
+
+        let res = [];
+        const len = s.length;
+
+        for (let r = 0; r < numRows; r++) {
+            const increment = 2 * (numRows - 1);
+            for (let i = r; i < len; i += increment) {
+                res.push(s[i]);
+                if (r > 0 && r < numRows - 1 && i + increment - 2 * r < len) {
+                    res.push(s[i + increment - 2 * r]);
+                }
+            }
+        }
+
+        return res.join('');
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for the ouput string.
+
+---
+
+## 2. Iteration - II
+
+::tabs-start
+
+```python
+class Solution:
+    def convert(self, s: str, numRows: int) -> str:
+        if numRows == 1 or numRows >= len(s):
+            return s
+        
+        res = [[] for _ in range(numRows)]
+        row, dir = 0, 1
+        for c in s:
+            res[row].append(c)
+            row += dir
+            if row == 0 or row == (numRows - 1):
+                dir *= -1
+        
+        return ''.join([''.join(row) for row in res])
+```
+
+```java
+public class Solution {
+    public String convert(String s, int numRows) {
+        if (numRows == 1 || numRows >= s.length()) {
+            return s;
+        }
+
+        List<Character>[] res = new ArrayList[numRows];
+        for (int i = 0; i < numRows; i++) {
+            res[i] = new ArrayList<>();
+        }
+
+        int row = 0, dir = 1;
+        for (int i = 0; i < s.length(); i++) {
+            res[row].add(s.charAt(i));
+            row += dir;
+            if (row == 0 || row == numRows - 1) {
+                dir *= -1;
+            }
+        }
+
+        StringBuilder result = new StringBuilder();
+        for (List<Character> rowList : res) {
+            for (char c : rowList) {
+                result.append(c);
+            }
+        }
+        return result.toString();
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    string convert(string s, int numRows) {
+        if (numRows == 1 || numRows >= s.size()) {
+            return s;
+        }
+
+        vector<string> res(numRows);
+        int row = 0, dir = 1;
+
+        for (char& c : s) {
+            res[row] += c;
+            row += dir;
+            if (row == 0 || row == numRows - 1) {
+                dir *= -1;
+            }
+        }
+
+        string result;
+        for (string& rowString : res) {
+            result += rowString;
+        }
+        return result;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {string} s
+     * @param {number} numRows
+     * @return {string}
+     */
+    convert(s, numRows) {
+        if (numRows === 1 || numRows >= s.length) {
+            return s;
+        }
+
+        const res = Array.from({ length: numRows }, () => []);
+        let row = 0, dir = 1;
+
+        for (const c of s) {
+            res[row].push(c);
+            row += dir;
+            if (row === 0 || row === numRows - 1) {
+                dir *= -1;
+            }
+        }
+
+        return res.map(row => row.join("")).join("");
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(n)$ for the output string.
\ No newline at end of file
diff --git a/c/1984-minimum-difference-between-highest-and-lowest-of-k-scores.c b/c/1984-minimum-difference-between-highest-and-lowest-of-k-scores.c
new file mode 100644
index 000000000..8b3cd183e
--- /dev/null
+++ b/c/1984-minimum-difference-between-highest-and-lowest-of-k-scores.c
@@ -0,0 +1,26 @@
+int cmp(const void* a, const void* b) {
+    return *(int*)a - *(int*)b;
+}
+
+int min(int a, int b){
+    if(a > b) return b;
+    return a;
+}
+
+int minimumDifference(int* nums, int numsSize, int k) {
+    if (k == 1) return 0;
+
+    qsort(nums, numsSize, sizeof(int), cmp);
+    int res = 1e5;
+    int l = 0;
+    int r = k - 1;
+
+    while (r < numsSize)
+    {
+        res = min(res, nums[r] - nums[l]);
+        l += 1;
+        r += 1;
+    }
+
+    return res;
+}
\ No newline at end of file
diff --git a/cpp/0104-maximum-depth-of-binary-tree.cpp b/cpp/0104-maximum-depth-of-binary-tree.cpp
index 75a76f696..a61f428b2 100644
--- a/cpp/0104-maximum-depth-of-binary-tree.cpp
+++ b/cpp/0104-maximum-depth-of-binary-tree.cpp
@@ -18,39 +18,90 @@
  *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
  * };
  */
+
 class Solution {
 public:
     int maxDepth(TreeNode* root) {
-        if (root == NULL) {
-            return 0;
+        // return maxDepthRecur(root);          // recursive DFS - preorder - easiest    
+        // return maxDepthStkInorder(root);     // iterative DFS - inorder 
+        return maxDepthStkPreorder(root);    // iterative DFS - preorder - easier
+        // return maxDepthQueueLevelorder(root);   // iterative BFS - levelorder - easy
+    }
+
+    int maxDepthQueueLevelorder(TreeNode* root) {
+        if (root == NULL) return 0;
+
+        queue<TreeNode*> q;
+        int ans = 0, depth = 0;
+        q.push(root);
+
+        while (!q.empty()) 
+        {            
+            int s = q.size();
+            for(int i = 0; i < s; i++) 
+            {
+                root = q.front();
+                q.pop();
+                
+                if (root->left) q.push(root->left);
+                if (root->right) q.push(root->right);
+            }
+            depth += 1;
+            ans = max(ans, depth);
+        }
+        return ans;
+    }
+
+
+    int maxDepthStkPreorder(TreeNode* root) {
+        if (root == NULL) return 0;
+
+        stack<pair<TreeNode*, int>> s;
+        int ans = 1, depth = 1;
+        s.push({root, depth});
+        while (!s.empty()) 
+        {
+            root = s.top().first;
+            depth = s.top().second;
+
+            ans = max(ans, depth);
+            s.pop();
+            if (root->left) s.push({root->left, depth + 1});
+            if (root->right) s.push({root->right, depth + 1});
+        }
+        return ans;
+    }
+
+    int maxDepthStkInorder(TreeNode* root) {
+        stack<pair<TreeNode*, int>> s;
+        int ans = 0, depth = 0;
+
+        while (root || !s.empty())
+        {
+            while (root != NULL)
+            {
+                s.push(make_pair(root, ++depth));
+                root = root->left;
+            }
+
+            root = s.top().first; 
+            ans = max(ans, depth);
+            
+            depth = s.top().second;
+            s.pop();
+            
+            root = root->right;
         }
-        return 1 + max(maxDepth(root->left), maxDepth(root->right));
+        return ans;
+    }
+
+    int maxDepthRecur(TreeNode* root) {
+        // recursive DFS
+        if (root == NULL) return 0;
+
+        // we should inc. the depth by 1 here
+        // and check for max in left and right subtrees 
+
+        return 1 + max(maxDepthRecur(root->left), maxDepthRecur(root->right));
     }
-};
-
-// class Solution {
-// public:
-//     int maxDepth(TreeNode* root) {
-//         if (root == NULL) {
-//             return 0;
-//         }
-//         queue<TreeNode*> q;
-//         q.push(root);
-//         int result = 0;
-//         while (!q.empty()) {
-//             int count = q.size();
-//             for (int i = 0; i < count; i++) {
-//                 TreeNode* node = q.front();
-//                 q.pop();
-//                 if (node->left != NULL) {
-//                     q.push(node->left);
-//                 }
-//                 if (node->right != NULL) {
-//                     q.push(node->right);
-//                 }
-//             }
-//             result++;
-//         }
-//         return result;
-//     }
-// };
+}
diff --git a/cpp/0279-perfect-squares.cpp b/cpp/0279-perfect-squares.cpp
index a76e88d91..d73953e42 100644
--- a/cpp/0279-perfect-squares.cpp
+++ b/cpp/0279-perfect-squares.cpp
@@ -23,48 +23,24 @@ using namespace std;
     Explanation: 13 = 4 + 9.
 */
 
-class Solution
-{
+class Solution {
 public:
-    int numSquares(int n)
-    {
-        // Create a vector to store all perfect squares
-        vector<int> vectorOfPerfectSquare;
-
-        // Loop through the numbers from 1 to the square root of n
-        for (int i = 1; i * i <= n; i++)
-        {
-            // If the square of i is a perfect square, push it to the vector v
-            vectorOfPerfectSquare.push_back(i * i);
-        }
-
-        // If n is equal to 1, return 1
-        if (n == 1)
-        {
-            return 1;
-        }
-
-        // Define a variable Max equal to n + 1
-        int Max = n + 1;
-        // Create a vector dp with length equal to n + 1 and fill it with Max
-        vector<int> dp(n + 1, Max);
-        // Initialize the first element of dp as 0
+    // Similar to Coin Change problem
+    int numSquares(int n) {
+        // Create the dp array to eliminate the cache
+        vector<int> dp(n + 1);
+        // Initialize the firest element of dp as 0
         dp[0] = 0;
-        // Loop through n from 1 to n
         for (int i = 1; i <= n; i++)
         {
-            // Loop through the vectorOfPerfectSquare
-            for (int j = 0; j < vectorOfPerfectSquare.size(); j++)
-            {
-                // If the value of i is greater than or equal to the current coin value
-                if (i - vectorOfPerfectSquare[j] >= 0)
-                {
-                    // Update the value of dp[i] to the minimum of dp[i] and dp[i-vectorOfPerfectSquare[j]] + 1
-                    dp[i] = min(dp[i], dp[i - vectorOfPerfectSquare[j]] + 1);
-                }
+            // Biggest is when all square is 1^2 that is when dp[i] = i
+            dp[i] = i;
+            for (int j = 1; j * j <= i; j++) {
+                // Update the value of dp[i]
+                dp[i] = min(dp[i], dp[i - j * j] + 1);
             }
         }
-        // Return the value of dp[n] if it is less than or equal to n, else return -1
-        return dp[n] > n ? -1 : dp[n];
+        // Return the value of dp[n]
+        return dp[n];
     }
-};
\ No newline at end of file
+};
diff --git a/cpp/0435-non-overlapping-intervals.cpp b/cpp/0435-non-overlapping-intervals.cpp
index 08a09eeea..ce2d229fe 100644
--- a/cpp/0435-non-overlapping-intervals.cpp
+++ b/cpp/0435-non-overlapping-intervals.cpp
@@ -11,28 +11,17 @@
 class Solution {
 public:
     int eraseOverlapIntervals(vector<vector<int>>& intervals) {
-        int n = intervals.size();
-        if (n == 1) {
-            return 0;
-        }
-        
-        sort(intervals.begin(), intervals.end(), [](const auto& a, const auto& b) {
-            return a[0] < b[0];
-        });
-        
-        int result = 0;
-        
-        int i = 0;
-        while (i < n - 1) {
-            if (intervals[i][1] > intervals[i+1][0]) {
-                if (intervals[i][1] < intervals[i+1][1]) {
-                    intervals[i+1] = intervals[i];
-                }
-                result++;
+        sort(intervals.begin(), intervals.end());
+        int prevEnd = intervals[0][1];
+        int count = 0;
+        for (int i = 1; i < intervals.size(); i++) {
+            if (prevEnd > intervals[i][0]) {
+                count++;
+                prevEnd = min(prevEnd, intervals[i][1]);
+            } else {
+                prevEnd = intervals[i][1];
             }
-            i++;
         }
-        
-        return result;
+        return count;
     }
 };
diff --git a/cpp/1249-minimum-remove-to-make-valid-parentheses.cpp b/cpp/1249-minimum-remove-to-make-valid-parentheses.cpp
new file mode 100644
index 000000000..a3bc8b0fa
--- /dev/null
+++ b/cpp/1249-minimum-remove-to-make-valid-parentheses.cpp
@@ -0,0 +1,53 @@
+/*
+* [1249] Minimum Remove to Make Valid Parentheses *
+
+Given a string s of '(' , ')' and lowercase English characters.
+
+Your task is to remove the minimum number of parentheses ( '(' or ')', in any positions ) so that the resulting parentheses string is valid and return any valid string.
+
+Formally, a parentheses string is valid if and only if:
+
+    It is the empty string, contains only lowercase characters, or
+    It can be written as AB (A concatenated with B), where A and B are valid strings, or
+    It can be written as (A), where A is a valid string.
+
+Example 1:
+
+Input: s = "lee(t(c)o)de)"
+Output: "lee(t(c)o)de"
+Explanation: "lee(t(co)de)" , "lee(t(c)ode)" would also be accepted.
+
+Time: O(n)
+Space: O(n)
+
+Runtime: 14 ms, faster than 98.14% of C++ online submissions for Minimum Remove to Make Valid Parentheses.
+Memory Usage: 14.2 MB, less than 10.57% of C++ online submissions for Minimum Remove to Make Valid Parentheses.
+*/
+
+
+
+class Solution {
+public:
+    string minRemoveToMakeValid(string s) {
+        stack<pair<char,int>> st;
+        
+        for (int i = 0; i < s.size(); i++) {
+            if (s[i] == '(') {
+                st.push(make_pair(s[i], i));
+            } else if (s[i] == ')') {
+                if (!st.empty() and st.top().first == '(') {
+                    st.pop();                
+                } else {
+                    st.push(make_pair(')', i));
+                }
+            }
+        }
+
+        while (!st.empty()) {
+            s.erase(s.begin() + st.top().second);
+            st.pop();
+        }
+
+        return s;
+    }
+};
diff --git a/cpp/1463-cherry-pickup-ii.cpp b/cpp/1463-cherry-pickup-ii.cpp
new file mode 100644
index 000000000..b7b9d5fff
--- /dev/null
+++ b/cpp/1463-cherry-pickup-ii.cpp
@@ -0,0 +1,39 @@
+#include <vector>
+#include <algorithm>
+
+using namespace std;
+
+class Solution {
+public:
+    int cherryPickup(vector<vector<int>>& grid) {
+        int rows = grid.size();
+        int cols = grid[0].size();
+
+        vector<vector<vector<int>>> dp(rows, vector<vector<int>>(cols, vector<int>(cols, 0)));
+
+        for (int i = rows - 1; i >= 0; --i) {
+            for (int j = 0; j < cols; ++j) {
+                for (int k = 0; k < cols; ++k) {
+                    int cherries = grid[i][j] + (j != k ? grid[i][k] : 0);
+                    if (i == rows - 1) {
+                        dp[i][j][k] = cherries;
+                    } else {
+                        int maxCherries = 0;
+                        for (int dj = -1; dj <= 1; ++dj) {
+                            for (int dk = -1; dk <= 1; ++dk) {
+                                int nj = j + dj;
+                                int nk = k + dk;
+                                if (nj >= 0 && nj < cols && nk >= 0 && nk < cols) {
+                                    maxCherries = max(maxCherries, dp[i + 1][nj][nk]);
+                                }
+                            }
+                        }
+                        dp[i][j][k] = cherries + maxCherries;
+                    }
+                }
+            }
+        }
+        
+        return dp[0][0][cols - 1];
+    }
+};
diff --git a/cpp/2405-optimal-partition-of-string.cpp b/cpp/2405-optimal-partition-of-string.cpp
new file mode 100644
index 000000000..4cb8b0a88
--- /dev/null
+++ b/cpp/2405-optimal-partition-of-string.cpp
@@ -0,0 +1,47 @@
+class Solution {
+public:
+    int partitionString(string s) {
+        vector<int> lastSeen(26, -1);
+        int count = 1, substringStart = 0;
+
+        for (int i = 0; i < s.length(); i++) {
+            if (lastSeen[s[i] - 'a'] >= substringStart) {
+                count++;
+                substringStart = i;
+            }
+            lastSeen[s[i] - 'a'] = i;
+        }
+
+        return count;
+    }
+};
+
+
+class Solution {
+  public:
+    int minPartitions(std::string s) {
+        // Set to keep track of characters in the current substring
+        std::unordered_set<char> currentChars;
+        // Variable to count the number of partitions
+        int partitionCount = 0;
+
+        // Iterate over each character in the string
+        for (char c : s) {
+            // If the character is already in the set, it means we've encountered a duplicate
+            if (currentChars.find(c) != currentChars.end()) {
+                // Increment the partition count and start a new substring
+                partitionCount++;
+                currentChars.clear();
+            }
+            // Add the current character to the set
+            currentChars.insert(c);
+        }
+
+        // There will be at least one partition at the end if currentChars is not empty
+        if (!currentChars.empty()) {
+            partitionCount++;
+        }
+
+        return partitionCount;
+    }
+};
diff --git a/csharp/0003-longest-substring-without-repeating-characters.cs b/csharp/0003-longest-substring-without-repeating-characters.cs
index cf6e82d7d..15f410758 100644
--- a/csharp/0003-longest-substring-without-repeating-characters.cs
+++ b/csharp/0003-longest-substring-without-repeating-characters.cs
@@ -1,14 +1,22 @@
-public class Solution {
-    public int LengthOfLongestSubstring(string s) {
+// hashset
+public class Solution
+{
+    public int LengthOfLongestSubstring(string s)
+    {
         int leftPointer = 0, rightPointer = 0, maxLength = 0;
         HashSet<int> chars = new HashSet<int>();
 
-        while (rightPointer < s.Length) {
+        while (rightPointer < s.Length)
+        {
             char currChar = s[rightPointer];
-            if (chars.Contains(currChar)) { // Move left pointer until all duplicate chars removed
+            if (chars.Contains(currChar))
+            { 
+                // Move left pointer until all duplicate chars removed
                 chars.Remove(s[leftPointer]);
                 leftPointer++;
-            } else {
+            }
+            else
+            {
                 chars.Add(currChar);
                 maxLength = Math.Max(maxLength, rightPointer - leftPointer + 1);
                 rightPointer++;
@@ -16,4 +24,38 @@ public int LengthOfLongestSubstring(string s) {
         }
         return maxLength;
     }
+}
+
+//bitmask
+public class Solution
+{
+    private Int128 ONE = 1;
+    public int LengthOfLongestSubstring(string s)
+    {
+        int Convert(char ch) => ch - ' ';
+        Int128 mask = 0;
+        int l = 0, r = 0, output = 0;
+        while (r < s.Length)
+        {
+            Int128 temp = mask ^ (ONE << Convert(s[r]));
+            if (temp < mask)
+            {
+                while (s[l] != s[r])
+                {
+                    mask ^= ONE << Convert(s[l]);
+                    l++;
+                }
+                mask ^= ONE << Convert(s[l]);
+                l++;
+            }
+            else
+            {
+                mask = temp;
+                output = Math.Max(output, r - l + 1);
+                r++;
+            }
+        }
+
+        return output;
+    }
 }
\ No newline at end of file
diff --git a/csharp/0058-length-of-last-word.cs b/csharp/0058-length-of-last-word.cs
index 2db7808e3..2b41c6661 100644
--- a/csharp/0058-length-of-last-word.cs
+++ b/csharp/0058-length-of-last-word.cs
@@ -6,3 +6,17 @@ public int LengthOfLastWord(string s) {
     }
 }
 
+public class NeetCodeSolution {
+    public int LengthOfLastWord(string s) {
+        var result = 0;
+        var i = s.Length - 1;
+        while (s[i] == ' ') --i;
+        for (; i >= 0; --i) {
+            if (s[i] == ' ') {
+                return result;
+            }
+            ++result;
+        }
+        return result;
+    }
+}
diff --git a/csharp/0069-sqrtx.cs b/csharp/0069-sqrtx.cs
new file mode 100644
index 000000000..a994a0f06
--- /dev/null
+++ b/csharp/0069-sqrtx.cs
@@ -0,0 +1,21 @@
+public class Solution 
+{
+    public int MySqrt(int x) 
+    {
+        int left = 0, right = x;
+        while (left <= right)
+        {
+            int mid = (left + right) >> 1;
+            long pow = (long)mid * mid;
+            if (pow <= x)
+            {
+                left = mid + 1;
+            }
+            else 
+            {
+                right = mid - 1;
+            }
+        }
+        return left - 1;
+    }
+}
diff --git a/csharp/0203-remove-linked-list-elements.cs b/csharp/0203-remove-linked-list-elements.cs
new file mode 100644
index 000000000..a07d5b6f1
--- /dev/null
+++ b/csharp/0203-remove-linked-list-elements.cs
@@ -0,0 +1,21 @@
+public class Solution 
+{
+    public ListNode RemoveElements(ListNode head, int val) 
+    {
+        ListNode dummy = new ListNode(0, head);
+        ListNode current = dummy;
+
+        while (current.next is not null)
+        {
+            if (current.next.val == val)
+            {
+                current.next = current.next.next;
+            }
+            else
+            {
+                current = current.next;
+            }
+        }
+        return dummy.next;
+    }
+}
\ No newline at end of file
diff --git a/csharp/0232-implement-queue-using-stacks.cs b/csharp/0232-implement-queue-using-stacks.cs
new file mode 100644
index 000000000..aba38c73a
--- /dev/null
+++ b/csharp/0232-implement-queue-using-stacks.cs
@@ -0,0 +1,47 @@
+public class MyQueue
+{
+    Stack<int> stack1;
+    Stack<int> stack2;
+
+    public MyQueue()
+    {
+        stack1 = new Stack<int>();
+        stack2 = new Stack<int>();
+    }
+
+    public void Push(int x)
+    {
+        stack1.Push(x);
+    }
+
+    public int Pop()
+    {
+        if (stack2.Count == 0)
+        {
+            while (stack1.Count > 0)
+            {
+                stack2.Push(stack1.Pop());
+            }
+        }
+
+        return stack2.Pop();
+    }
+
+    public int Peek()
+    {
+        if (stack2.Count == 0)
+        {
+            while (stack1.Count > 0)
+            {
+                stack2.Push(stack1.Pop());
+            }
+        }
+
+        return stack2.Peek();
+    }
+
+    public bool Empty()
+    {
+        return stack1.Count == 0 && stack2.Count == 0;
+    }
+}
\ No newline at end of file
diff --git a/csharp/0283-move-zeroes.cs b/csharp/0283-move-zeroes.cs
index bc970c18f..64f2b18ef 100644
--- a/csharp/0283-move-zeroes.cs
+++ b/csharp/0283-move-zeroes.cs
@@ -21,4 +21,20 @@ public void MoveZeroes(int[] nums)
             readIndex++;
         }
     }
-}
\ No newline at end of file
+}
+
+public class NeetCodeWaySolution { //NeetCodeWay
+    public void MoveZeroes(int[] nums) {
+        if (nums.Length <= 1) return;
+        int l = 0, r = 0;
+        while (r < nums.Length) {
+            if (nums[r] != 0) {
+                var t = nums[l];
+                nums[l++] = nums[r];
+                nums[r++] = t;
+            } else {
+                ++r;
+            }
+        }
+    }
+}
diff --git a/csharp/0344-reverse-string.cs b/csharp/0344-reverse-string.cs
index cd8125e1f..672ad3807 100644
--- a/csharp/0344-reverse-string.cs
+++ b/csharp/0344-reverse-string.cs
@@ -1,3 +1,20 @@
+// While Loop Solution
+class Solution
+{
+    public void ReverseString(char[] s)
+    {
+        int leftPointer = 0;
+        int rightPointer = s.Length - 1;
+        while (leftPointer < rightPointer)
+        {
+            char temp = s[leftPointer];
+            s[leftPointer++] = s[rightPointer];
+            s[rightPointer--] = temp;
+        }
+    }
+}
+
+// For Loop Solution
 public class Solution
 {
     public void ReverseString(char[] s)
diff --git a/csharp/0554-brick-wall.cs b/csharp/0554-brick-wall.cs
new file mode 100644
index 000000000..1f9e3614a
--- /dev/null
+++ b/csharp/0554-brick-wall.cs
@@ -0,0 +1,20 @@
+public class Solution {
+    public int LeastBricks(IList<IList<int>> wall) {
+        Dictionary<int, int> countGap = new Dictionary<int, int>();
+        countGap[0] = 0;
+
+        foreach (var row in wall) {
+            int total = 0;
+            for (int i = 0; i < row.Count - 1; i++) {
+                int brick = row[i];
+                total += brick;
+                if (!countGap.ContainsKey(total)) {
+                    countGap[total] = 0;
+                }
+                countGap[total]++;
+            }
+        }
+
+        return wall.Count - countGap.Values.Max();
+    }
+}
diff --git a/csharp/1343-number-of-sub-arrays-of-size-k-and-average-greater-than-or-equal-to-threshold.cs b/csharp/1343-number-of-sub-arrays-of-size-k-and-average-greater-than-or-equal-to-threshold.cs
new file mode 100644
index 000000000..91060ef8f
--- /dev/null
+++ b/csharp/1343-number-of-sub-arrays-of-size-k-and-average-greater-than-or-equal-to-threshold.cs
@@ -0,0 +1,44 @@
+/*
+
+Approach:
+1. We will initialize i, j, c, res, and sum to 0.
+2. We will calculate the sum of the first k elements and check if the average is greater than or equal to the threshold.
+3. We will increment the result if the average is greater than or equal to the threshold.
+4. We will iterate through the array and calculate the sum of the next k elements.
+5. We will check if the average is greater than or equal to the threshold and increment the result accordingly.
+6. We will return the result.
+
+Time Complexity: O(n)
+Space Complexity: O(1)
+
+*/
+public class Solution {
+    public int NumOfSubarrays(int[] arr, int k, int threshold) {
+        int i, j, c, res, sum;                          // Initialize i, j, c, res, and sum to 0.
+        i = c = sum = res = 0;                          // Initialize i, c, sum, and res to 0.
+        j = i + k - 1;                                  // Initialize j to i + k - 1.
+
+        while (c <= j) {                                // Calculate the sum of the first k elements.
+            sum = sum + arr[c];                         // Add the element at index c to the sum.
+            c++;                                        // Increment c.
+        }
+
+        res = (sum / k) >= threshold ? 1 : 0;             // Check if the average is greater than or equal to the threshold and increment the result accordingly.
+
+        while (j < arr.Length) {                       // Iterate through the array and calculate the sum of the next k elements.
+            sum = sum - arr[i++];                       // Subtract the element at index i from the sum and increment i.
+            j++;                                        // Increment j.
+            if (j < arr.Length) {                        // Check if j is less than the length of the array.
+                sum = sum + arr[j];                     // Add the element at index j to the sum.
+            }
+            else {
+                break;                                  // Break the loop if j is equal to or greater than the length of the array.
+            }
+            if ((sum / k) >= threshold) {                  // Check if the average is greater than or equal to the threshold.
+                res++;                                  // Increment the result.
+            }
+        }
+
+        return res;                                     // Return the result.
+    }
+}
diff --git a/csharp/1984-minimum-difference-between-highest-and-lowest-of-k-scores.cs b/csharp/1984-minimum-difference-between-highest-and-lowest-of-k-scores.cs
new file mode 100644
index 000000000..b7446068d
--- /dev/null
+++ b/csharp/1984-minimum-difference-between-highest-and-lowest-of-k-scores.cs
@@ -0,0 +1,13 @@
+public class Solution {
+    public int MinimumDifference(int[] nums, int k) {
+        int min = Int32.MaxValue;
+        int l = 0, r = k - 1;
+        Array.Sort(nums);
+        while (r < nums.Length) {
+            min = Math.Min(min, nums[r] - nums[l]);
+            l++;
+            r++;
+        }
+        return min;
+    }
+}
diff --git a/dart/0347-top-k-frequent-elements.dart b/dart/0347-top-k-frequent-elements.dart
index 62ccc49d9..fd3025fff 100644
--- a/dart/0347-top-k-frequent-elements.dart
+++ b/dart/0347-top-k-frequent-elements.dart
@@ -1,3 +1,31 @@
+class Solution {
+  List<int> topKFrequent(List<int> nums, int k) {
+    Map<int, int> frequencyMap = {};
+    for (int num in nums) {
+      frequencyMap[num] = (frequencyMap[num] ?? 0) + 1;
+    }
+
+    List<List<int>> frequencyList =
+        List.filled(nums.length + 1, List<int>.empty(growable: true));
+
+    frequencyMap.forEach((num, count) {
+      frequencyList[count] = [...frequencyList[count], num];
+    });
+
+    List<int> res = [];
+
+    for (var i = frequencyList.length - 1; i >= 0; i--) {
+      res.addAll(frequencyList[i]);
+
+      if (res.length == k) {
+        break;
+      }
+    }
+
+    return res;
+  }
+}
+
 class Solution {
   List<int> topKFrequent(List<int> nums, int k) {
     Map<int, int> map = {};
diff --git a/dart/0929-unique-email-addresses.dart b/dart/0929-unique-email-addresses.dart
new file mode 100644
index 000000000..82bdca704
--- /dev/null
+++ b/dart/0929-unique-email-addresses.dart
@@ -0,0 +1,20 @@
+// N is the number of emails
+// M is the maximum length of an email address
+// Time complexity: O(NM)
+// Space complexity: O(NM) 
+
+class Solution {
+  int numUniqueEmails(List<String> emails) {
+    Set<String> uniqueEmails = Set();
+    for (String email in emails) {
+      String local = email.split('@')[0];
+      String domain = email.split('@')[1];
+      local = local.replaceAll('.', '');
+      if (local.contains('+')) {
+        local = local.split('+')[0];
+      }
+      uniqueEmails.add('$local@$domain');
+    }
+    return uniqueEmails.length;
+  }
+}
diff --git a/dart/1929-concatenation-of-array.dart b/dart/1929-concatenation-of-array.dart
index dacc1a880..7faa6bfc0 100644
--- a/dart/1929-concatenation-of-array.dart
+++ b/dart/1929-concatenation-of-array.dart
@@ -1,3 +1,17 @@
+// Time Complexity: O(n)
+// Space Complexity: O(n)
+
+class Solution {
+ List<int> getConcatenation(List<int> nums) {
+  List<int> ans = List<int>.filled(2 * nums.length, 0);
+  for (int i = 0; i < nums.length; i++) {
+    ans[i] = nums[i];
+    ans[i + nums.length] = nums[i];
+  }
+  return ans;
+}
+
+  
 class Solution {
   List<int> getConcatenation(List<int> nums) {
     return nums + nums;
diff --git a/go/0034-find-first-and-last-position-of-element-in-sorted-array.go b/go/0034-find-first-and-last-position-of-element-in-sorted-array.go
new file mode 100644
index 000000000..c5277836b
--- /dev/null
+++ b/go/0034-find-first-and-last-position-of-element-in-sorted-array.go
@@ -0,0 +1,26 @@
+func searchRange(nums []int, target int) []int {
+	right := binSearch(nums, target, false)
+	left := binSearch(nums, target, true)
+	return []int{left, right}
+}
+
+func binSearch(nums []int, target int, leftBias bool) int {
+	l, r := 0, len(nums)-1
+	i := -1
+	for l <= r {
+		m := (l + r) / 2
+		if nums[m] < target {
+			l = m + 1
+		} else if nums[m] > target {
+			r = m - 1
+		} else {
+			i = m
+			if leftBias {
+				r = m - 1
+			} else {
+				l = m + 1
+			}
+		}
+	}
+	return i
+}
\ No newline at end of file
diff --git a/go/0187-repeated-dna-sequences.go b/go/0187-repeated-dna-sequences.go
new file mode 100644
index 000000000..9d48b1058
--- /dev/null
+++ b/go/0187-repeated-dna-sequences.go
@@ -0,0 +1,12 @@
+func findRepeatedDnaSequences(s string) []string {
+	seen, res := map[string]bool{}, map[string]bool{}
+
+	for l := range len(s) - 9 {
+		cur := s[l : l+10]
+		if seen[cur] {
+			res[cur] = true
+		}
+		seen[cur] = true
+	}
+	return slices.Collect(maps.Keys(res))
+}
diff --git a/go/0367-valid-perfect-square.go b/go/0367-valid-perfect-square.go
new file mode 100644
index 000000000..7acd14ee3
--- /dev/null
+++ b/go/0367-valid-perfect-square.go
@@ -0,0 +1,15 @@
+func isPerfectSquare(num int) bool {
+	l, r := 0, num
+	for l <= r {
+		m := (l + r) / 2
+		product := m * m
+		if product == num {
+			return true
+		} else if product > num {
+			r = m - 1
+		} else {
+			l = m + 1
+		}
+	}
+	return false
+}
\ No newline at end of file
diff --git a/go/0451-sort-characters-by-frequency.go b/go/0451-sort-characters-by-frequency.go
new file mode 100644
index 000000000..1c4e0ecf4
--- /dev/null
+++ b/go/0451-sort-characters-by-frequency.go
@@ -0,0 +1,29 @@
+func frequencySort(s string) string {
+    type charFreq struct {
+        c rune
+        f int
+    }
+
+    mp := map[rune]int{}
+    cs := []charFreq{}
+
+    for _, c := range s {
+        mp[c]++
+    }
+
+    for c, f := range mp {
+        cs = append(cs, charFreq{c,f})
+    }
+
+    sort.Slice(cs, func(i,j int) bool{
+        return cs[i].f > cs[j].f
+    })
+
+    ans := ""
+
+    for _, cf := range cs {
+        ans += strings.Repeat(string(cf.c), cf.f)
+    }
+
+    return ans
+}
diff --git a/go/0554-brick-wall.go b/go/0554-brick-wall.go
new file mode 100644
index 000000000..a77696410
--- /dev/null
+++ b/go/0554-brick-wall.go
@@ -0,0 +1,22 @@
+func leastBricks(wall [][]int) int {
+
+	countGap := make(map[int]int)
+	rowSum := 0
+
+	for _, row := range wall {
+		rowSum = 0
+		for _, brick := range row[0 : len(row)-1] {
+			rowSum += brick
+			countGap[rowSum]++
+		}
+	}
+
+	mostFrequentGap := 0
+	for _, gapFrequency := range countGap {
+		if gapFrequency > mostFrequentGap {
+			mostFrequentGap = gapFrequency
+		}
+	}
+
+	return len(wall) - mostFrequentGap
+}
\ No newline at end of file
diff --git a/go/0658-find-k-closest-elements.go b/go/0658-find-k-closest-elements.go
new file mode 100644
index 000000000..f14f00d1b
--- /dev/null
+++ b/go/0658-find-k-closest-elements.go
@@ -0,0 +1,13 @@
+func findClosestElements(arr []int, k int, x int) []int {
+	l, r := 0, len(arr)-k
+
+	for l < r {
+		m := (l + r) / 2
+		if x-arr[m] > arr[m+k]-x {
+			l = m + 1
+		} else {
+			r = m
+		}
+	}
+	return arr[l : l+k]
+}
diff --git a/go/0735-asteroid-collision.go b/go/0735-asteroid-collision.go
new file mode 100644
index 000000000..b5fd18c4f
--- /dev/null
+++ b/go/0735-asteroid-collision.go
@@ -0,0 +1,27 @@
+func asteroidCollision(asteroids []int) []int {
+
+	stack := []int{}
+	diff := 0
+
+	for _, asteroid := range asteroids {
+		for len(stack) > 0 && stack[len(stack)-1] > 0 && asteroid < 0 {
+			diff = stack[len(stack)-1] + asteroid
+			if diff < 0 {
+				// asteroid larger than top of stack, destroys it
+				stack = stack[0 : len(stack)-1]
+			} else if diff == 0 {
+				// asteroid and top of stack equal, both destroyed
+				stack = stack[0 : len(stack)-1]
+				asteroid = 0
+			} else {
+				// asteroid smaller than top of stack, gets destroyed
+				asteroid = 0
+			}
+		}
+		if asteroid != 0 {
+			stack = append(stack, asteroid)
+		}
+	}
+
+	return stack
+}
\ No newline at end of file
diff --git a/go/0881-boats-to-save-people.go b/go/0881-boats-to-save-people.go
new file mode 100644
index 000000000..8c070ca87
--- /dev/null
+++ b/go/0881-boats-to-save-people.go
@@ -0,0 +1,15 @@
+func numRescueBoats(people []int, limit int) int {
+	sort.Ints(people)
+
+	res := 0 // boats
+	l, r := 0, len(people)-1
+	for l <= r {
+		remain := limit - people[r]
+		r -= 1
+		res += 1
+		if l <= r && remain >= people[l] {
+			l += 1
+		}
+	}
+	return res
+}
diff --git a/go/0948-bag-of-tokens.go b/go/0948-bag-of-tokens.go
new file mode 100644
index 000000000..5b23e729d
--- /dev/null
+++ b/go/0948-bag-of-tokens.go
@@ -0,0 +1,21 @@
+func bagOfTokensScore(tokens []int, power int) int {
+	res, score := 0, 0
+	sort.Ints(tokens)
+
+	l, r := 0, len(tokens)-1
+	for l <= r {
+		if power >= tokens[l] {
+			power -= tokens[l]
+			l += 1
+			score += 1
+			res = max(res, score)
+		} else if score > 0 {
+			power += tokens[r]
+			r -= 1
+			score -= 1
+		} else {
+			break
+		}
+	}
+	return res
+}
diff --git a/go/1456-maximum-number-of-vowels-in-a-substring-of-given-length.go b/go/1456-maximum-number-of-vowels-in-a-substring-of-given-length.go
new file mode 100644
index 000000000..f2283b329
--- /dev/null
+++ b/go/1456-maximum-number-of-vowels-in-a-substring-of-given-length.go
@@ -0,0 +1,25 @@
+func maxVowels(s string, k int) int {
+	vowel := map[byte]bool{
+		'a': true,
+		'e': true,
+		'i': true,
+		'o': true,
+		'u': true,
+	}
+
+	l, cnt, res := 0, 0, 0
+	for r := range len(s) {
+		if vowel[s[r]] {
+			cnt += 1
+		}
+
+		if r-l+1 > k {
+			if vowel[s[l]] {
+				cnt -= 1
+			}
+			l += 1
+		}
+		res = max(res, cnt)
+	}
+	return res
+}
diff --git a/go/1658-minimum-operations-to-reduce-x-to-zero.go b/go/1658-minimum-operations-to-reduce-x-to-zero.go
new file mode 100644
index 000000000..f80fdc39f
--- /dev/null
+++ b/go/1658-minimum-operations-to-reduce-x-to-zero.go
@@ -0,0 +1,28 @@
+func minOperations(nums []int, x int) int {
+	sum := 0
+	for _, num := range nums {
+		sum += num
+	}
+
+	target := sum - x
+	currSum := 0
+	maxWindow := -1
+	l := 0
+	for r := range len(nums) {
+		currSum += nums[r]
+
+		for l <= r && currSum > target {
+			currSum -= nums[l]
+			l += 1
+		}
+
+		if currSum == target {
+			maxWindow = max(maxWindow, r-l+1)
+		}
+	}
+
+	if maxWindow == -1 {
+		return maxWindow
+	}
+	return len(nums) - maxWindow
+}
diff --git a/go/1898-maximum-number-of-removable-characters.go b/go/1898-maximum-number-of-removable-characters.go
new file mode 100644
index 000000000..aac684f37
--- /dev/null
+++ b/go/1898-maximum-number-of-removable-characters.go
@@ -0,0 +1,33 @@
+func maximumRemovals(s string, p string, removable []int) int {
+	l, r := 0, len(removable)-1
+	for l <= r {
+		m := (l + r) / 2
+		remove := make(map[int]bool)
+		for i := 0; i <= m; i++ {
+			remove[removable[i]] = true
+		}
+		if isSubsequence(s, p, remove) {
+			l = m + 1
+		} else {
+			r = m - 1
+		}
+	}
+	return r + 1
+}
+
+func isSubsequence(s, p string, remove map[int]bool) bool {
+	i, j := 0, 0
+	for i < len(s) && j < len(p) {
+		if remove[i] == true || s[i] != p[j] {
+			i++
+			continue
+		}
+		i++
+		j++
+	}
+	return j == len(p)
+}   
+	 
+	 
+	 
+ 
\ No newline at end of file
diff --git a/go/1963-minimum-number-of-swaps-to-make-the-string-balanced.go b/go/1963-minimum-number-of-swaps-to-make-the-string-balanced.go
new file mode 100644
index 000000000..39c8b37c2
--- /dev/null
+++ b/go/1963-minimum-number-of-swaps-to-make-the-string-balanced.go
@@ -0,0 +1,15 @@
+func minSwaps(s string) int {
+	close, maxClose := 0, 0
+	for _, c := range s {
+		if c == '[' {
+			close += -1
+		} else {
+			close += +1
+		}
+
+		if close > maxClose {
+			maxClose = close
+		}
+	}
+	return (maxClose + 1) / 2
+}
\ No newline at end of file
diff --git a/go/1968-array-with-elements-not-equal-to-average-of-neighbors.go b/go/1968-array-with-elements-not-equal-to-average-of-neighbors.go
new file mode 100644
index 000000000..019929db3
--- /dev/null
+++ b/go/1968-array-with-elements-not-equal-to-average-of-neighbors.go
@@ -0,0 +1,16 @@
+func rearrangeArray(nums []int) []int {
+	sort.Ints(nums)
+	res := []int{}
+
+	l, r := 0, len(nums)-1
+	for len(res) != len(nums) {
+		res = append(res, nums[l])
+		l += 1
+
+		if l <= r {
+			res = append(res, nums[r])
+			r -= 1
+		}
+	}
+	return res
+}
diff --git a/hints/add-two-numbers.md b/hints/add-two-numbers.md
new file mode 100644
index 000000000..2cdafc4fa
--- /dev/null
+++ b/hints/add-two-numbers.md
@@ -0,0 +1,23 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(m + n)</code> time and <code>O(1)</code> space, where <code>m</code> is the length of list <code>l1</code> and <code>n</code> is the length of list <code>l2</code>.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Try to visualize the addition of two numbers. We know that the addition of two numbers is done by starting at the one's digit. We add the numbers by going through digit by digit. We track the extra value as a <code>carry</code> because the addition of two digits can result in a number with two digits. The <code>carry</code> is then added to the next digits, and so on. How do you implement this in case of linked lists?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We track the extra value, <code>carry</code>, here as well. We iterate through the lists <code>l1</code> and <code>l2</code> until both lists reach <code>null</code>. We add the values of both nodes as well as the carry. If either of the nodes is <code>null</code>, we add <code>0</code> in its place and continue the process while tracking the carry simultaneously. Once we complete the process, if we are left with any <code>carry</code>, we add an extra node with that carry value and return the head of the result list.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/anagram-groups.md b/hints/anagram-groups.md
new file mode 100644
index 000000000..b77b383f8
--- /dev/null
+++ b/hints/anagram-groups.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(m * n)</code> time and <code>O(m)</code> space, where <code>m</code> is the number of strings and <code>n</code> is the length of the longest string.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A naive solution would be to sort each string and group them using a hash map. This would be an <code>O(m * nlogn)</code> solution. Though this solution is acceptable, can you think of a better way without sorting the strings?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    By the definition of an anagram, we only care about the frequency of each character in a string. How is this helpful in solving the problem?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can simply use an array of size <code>O(26)</code>, since the character set is <code>a</code> through <code>z</code> (<code>26</code> continuous characters), to count the frequency of each character in a string. Then, we can use this array as the key in the hash map to group the strings.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/balanced-binary-tree.md b/hints/balanced-binary-tree.md
new file mode 100644
index 000000000..51473ca01
--- /dev/null
+++ b/hints/balanced-binary-tree.md
@@ -0,0 +1,23 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the number of nodes in the tree.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would involve traversing every node and checking whether the tree rooted at each node is balanced by computing the heights of its left and right subtrees. This approach would result in an <code>O(n^2)</code> solution. Can you think of a more efficient way? Perhaps you could avoid repeatedly computing the heights for every node by determining balance and height in a single traversal.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use the Depth First Search (DFS) algorithm to compute the heights at each node. While calculating the heights of the left and right subtrees, we also check if the tree rooted at the current node is balanced. If <code>leftHeight - rightHeight > 1</code>, we update a global variable, such as <code>isBalanced = False</code>. After traversing all the nodes, the value of <code>isBalanced</code> indicates whether the entire tree is balanced or not.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/binary-search.md b/hints/binary-search.md
new file mode 100644
index 000000000..a1a01c8e2
--- /dev/null
+++ b/hints/binary-search.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(logn)</code> time and <code>O(1)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Can you find an algorithm that is useful when the array is sorted? Maybe other than linear seacrh.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    The problem name is the name of the algorithm that we can use. We need to find a target value and if it does not exist in the array return <code>-1</code>. We have <code>l</code> and <code>r</code> as the boundaries of the segment of the array in which we are searching. Try building conditions to eliminate half of the search segment at each step. Maybe sorted nature of the array can be helpful.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We compare the target value with the <code>mid</code> of the segment. For example, consider the array <code>[1, 2, 3, 4, 5]</code> and <code>target = 4</code>. The <code>mid</code> value is <code>3</code>, thus, on the next iteration we search to the right of <code>mid</code>. The remaining segment is <code>[4,5]</code>. Why?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    Because the array is sorted, all elements to the left of <code>mid</code> (including <code>3</code>) are guaranteed to be smaller than the target. Therefore, we can safely eliminate that half of the array from consideration, narrowing the search to the right half and repeat this search until we find the target.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/binary-tree-diameter.md b/hints/binary-tree-diameter.md
new file mode 100644
index 000000000..d8c6b6ec3
--- /dev/null
+++ b/hints/binary-tree-diameter.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the number of nodes in the tree.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    The diameter of a binary tree is the maximum among the sums of the left height and right height of the nodes in the tree. Why?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    Because the diameter of a binary tree is defined as the longest path between any two nodes in the tree. The path may or may not pass through the root. For any given node, the longest path that passes through it is the sum of the height of its left subtree and the height of its right subtree.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    A brute force solution would be to go through every node in the tree and compute its left height and right height, returning the maximum diameter found. This would be an <code>O(n^2)</code> solution. Can you think of a better way? Maybe we can compute the diameter as we calculate the height of the tree? Think about what information you need from each subtree during a single traversal.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We can use the Depth First Search (DFS) algorithm to calculate the height of the tree. At each node, the subtrees return their respective heights (leftHeight and rightHeight). Then we calculate the diameter at that node as <code>d = leftHeight + rightHeight</code>. We use a global variable to update the maximum diameter as needed during the traversal.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/binary-tree-from-preorder-and-inorder-traversal.md b/hints/binary-tree-from-preorder-and-inorder-traversal.md
new file mode 100644
index 000000000..d46b6141c
--- /dev/null
+++ b/hints/binary-tree-from-preorder-and-inorder-traversal.md
@@ -0,0 +1,47 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the number of nodes.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+   You can observe that the in-order traversal helps divide the array into two halves based on the root node: the left part corresponds to the left subtree, and the right part corresponds to the right subtree. Can you think of how we can get the index of the root node in the in-order array? Maybe you should look into the pre-order traversal array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    From the pre-order traversal, we know that the first node is the root node. Using this information, can you now construct the binary tree?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    After getting the root node from pre-order traversal, we then look for the index of that node in the in-order array. We can linearly search for the index but this would be an <code>O(n^2)</code> solution. Can you think of a better way? Maybe we can use a data structure to get the index of a node in <code>O(1)</code>?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We can use a hash map to get the index of any node in the in-order array in <code>O(1)</code> time. How can we implement this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 5</summary>
+    <p>
+    We use Depth First Search (DFS) to construct the tree. A global variable tracks the current index in the pre-order array. Indices <code>l</code> and <code>r</code> represent the segment in the in-order array for the current subtree. For each node in the pre-order array, we create a node, find its index in the in-order array using the hash map, and recursively build the left and right subtrees by splitting the range <code>[l, r]</code> into two parts for the left and right subtrees.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/binary-tree-maximum-path-sum.md b/hints/binary-tree-maximum-path-sum.md
new file mode 100644
index 000000000..318e1a388
--- /dev/null
+++ b/hints/binary-tree-maximum-path-sum.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the number of nodes in the given tree.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would involve checking the path sum between every pair of nodes in the tree, leading to an <code>O(n^2)</code> time complexity. Can you think of a more efficient approach? Consider what information you would need at each node to calculate the path sum if it passes through the current node.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    At a node, there are three scenarios to compute the maximum path sum that includes the current node. One includes both the left and right subtrees, with the current node as the connecting node. Another path sum includes only one of the subtrees (either left or right), but not both. Another considers the path sum extending from the current node to the parent. However, the parent’s contribution is computed during the traversal at the parent node. Can you implement this? 
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can use the Depth First Search (DFS) algorithm to traverse the tree. We maintain a global variable to track the maximum path sum. At each node, we first calculate the maximum path sum from the left and right subtrees by traversing them. After that, we compute the maximum path sum at the current node. This approach follows a post-order traversal, where we visit the subtrees before processing the current node.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We return the maximum path sum from the current node to its parent, considering only one of the subtrees (either left or right) to extend the path. While calculating the left and right subtree path sums, we also ensure that we take the maximum with <code>0</code> to avoid negative sums, indicating that we should not include the subtree path in the calculation of the maximum path at the current node.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/binary-tree-right-side-view.md b/hints/binary-tree-right-side-view.md
new file mode 100644
index 000000000..a02d2c585
--- /dev/null
+++ b/hints/binary-tree-right-side-view.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the number of nodes in the given tree.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    In the right-side view of a tree, can you identify the nodes that are visible? Maybe you could traverse the tree level by level and determine which nodes are visible from the right side.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    The nodes visible in the right-side view are the last nodes at each level of the tree. Can you think of an algorithm to identify these nodes? Maybe an algorithm that can traverse the tree level by level.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can use the Breadth First Search (BFS) algorithm to traverse the tree level by level. Once we completely visit a level, we take the last node of that level and add it to the result array. After processing all levels, we return the result.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/burst-balloons.md b/hints/burst-balloons.md
new file mode 100644
index 000000000..c553a4f8e
--- /dev/null
+++ b/hints/burst-balloons.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n ^ 3)</code> time and <code>O(n ^ 2)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Try to simulate the process recursively by passing the array to the recursive function. At each step, iterate through the array, pop an element, and recursively apply the same process to the two subarrays on both sides of the popped element, returning the maximum result from all recursive paths. This approach is exponential. Can you think of a way to optimize it? Maybe you should consider observing the subproblems instead of modifying the array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    Instead of passing the array, we can pass the range of indices <code>l</code> and <code>r</code> that need to be processed. We pad the input array with <code>1</code>s on both sides for easier computation, but <code>l</code> and <code>r</code> represent the first and last indices of the original input array. Can you think of a reverse engineering approach for popping elements?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We determine the result by considering each element as the last one to be popped in the current range. For each element, we calculate its value by multiplying it with the elements at <code>l - 1</code> and <code>r + 1</code>, then recursively solve the subproblems for the ranges <code>(l, i - 1)</code> and <code>(i + 1, r)</code>, where <code>i</code> is the current element in the given range. Can you think of a way to optimize and avoid redundant calculations?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We can use memoization to cache the results of recursive calls and avoid redundant calculations. A hash map or a <code>2D</code> array can be used to store results since the recursive function parameters <code>l</code> and <code>r</code> are within the range of the input array size.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/buy-and-sell-crypto-with-cooldown.md b/hints/buy-and-sell-crypto-with-cooldown.md
new file mode 100644
index 000000000..84988bd54
--- /dev/null
+++ b/hints/buy-and-sell-crypto-with-cooldown.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Try to think in terms of recursion and visualize it as a decision tree. Can you determine the possible decisions at each recursion step? Also, can you identify the base cases and the essential information that needs to be tracked during recursion?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    At each recursion step, we can buy only if we haven't already bought a coin, or we can sell if we own one. When buying, we subtract the coin value, and when selling, we add it. We explore all possible buying and selling options recursively, iterating through the coins from left to right using index <code>i</code>. For the cooldown condition, if we buy a coin, we increment the index <code>i</code> by two.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can use a boolean variable <code>canBuy</code> to indicate whether buying is allowed at the current recursive step. If we go out of bounds, we return <code>0</code>. This approach is exponential. Can you think of a way to optimize it?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We can use memoization to cache the results of recursive calls and avoid recalculations. A hash map or a <code>2D</code> array can be used to store these results.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/buy-and-sell-crypto.md b/hints/buy-and-sell-crypto.md
new file mode 100644
index 000000000..0597ae13a
--- /dev/null
+++ b/hints/buy-and-sell-crypto.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(1)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would be to iterate through the array with index <code>i</code>, considering it as the day to buy, and trying all possible options for selling it on the days to the right of index <code>i</code>. This would be an <code>O(n^2)</code> solution. Can you think of a better way?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    You should buy at a price and always sell at a higher price. Can you iterate through the array with index <code>i</code>, considering it as either the buying price or the selling price?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can iterate through the array with index <code>i</code>, considering it as the selling value. But what value will it be optimal to consider as buying point on the left of index <code>i</code>?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We are trying to maximize <code>profit = sell - buy</code>. If the current <code>i</code> is the sell value, we want to choose the minimum buy value to the left of <code>i</code> to maximize the profit. The result will be the maximum profit among all. However, if all profits are negative, we can return <code>0</code> since we are allowed to skip doing transaction. 
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/car-fleet.md b/hints/car-fleet.md
new file mode 100644
index 000000000..23c63e134
--- /dev/null
+++ b/hints/car-fleet.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(nlogn)</code> time and <code>O(n)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    First draw a picture of all the points which represents the positions and respective speeds of the cars. It is appropriate to represent the position and speed of each car as an array, where each cell corresponds to a car. It is also logical to sort this array based on the positions in descending order. Why?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+     Because a car can only form a fleet with another car that is ahead of it, sorting the array in descending order ensures clarity about the final speed of each car. Sorting in ascending order would create ambiguity, as the next car might form a fleet with another car while reaching the target, making it difficult to determine its final speed.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    Calculating the time for a car to reach the target is straightforward and can be done using the formula: <code>time = (target - position) / speed</code>. Now, it becomes easy to identify that two cars will form a fleet if and only if the car ahead has a time that is greater than or equal to the time of the car behind it. How can we maintain the total number of fleets happened while going through the array? Maybe a data structure is helpful.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We can use a stack to maintain the times of the fleets. As we iterate through the array (sorted in descending order of positions), we compute the time for each car to reach the target and check if it can form a fleet with the car ahead. If the current car's time is less than or equal to the top of the stack, it joins the same fleet. Otherwise, it forms a new fleet, and we push its time onto the stack. The length of the stack at the end represents the total number of fleets formed.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/cheapest-flight-path.md b/hints/cheapest-flight-path.md
new file mode 100644
index 000000000..b42275442
--- /dev/null
+++ b/hints/cheapest-flight-path.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(n + (m * k))</code> time and <code>O(n)</code> space, where <code>n</code> is the number of cities, <code>m</code> is the number of flights, and <code>k</code> is the number of stops.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Consider this as a graph problem where the cities are nodes and the flights are edges connecting two cities, with the ticket cost as the edge weight. Can you think of a shortest path algorithm to solve the problem? Perhaps a better algorithm than Dijkstra's that can intuitively handle the <code>k</code> stops condition.  
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use the Bellman-Ford algorithm. Initialize a <code>prices</code> array of size <code>n</code> with <code>Infinity</code>, setting <code>prices[source] = 0</code>. These values describe the cost to reach a city from the source city. Iterate <code>(k + 1)</code> times (stops are 0-indexed), updating the cost to each city by extending paths from cities with valid costs. We only update the cost for a city if it is less than the previous cost. How would you implement this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    At each level of iteration, we go through the given flights and use them to update the price array with the minimum costs compared to the previous level. We use a temporary prices array at each level to store the updated costs. After completing all levels, we return the result stored in <code>prices[dst]</code>. If that value is <code>Infinity</code>, we return <code>-1</code> instead.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/climbing-stairs.md b/hints/climbing-stairs.md
new file mode 100644
index 000000000..78e5ce36b
--- /dev/null
+++ b/hints/climbing-stairs.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the number of steps.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    At each step, we have two choices: climb one step or climb two steps. We can solve this by considering both options and picking the minimum using recursion. However, this results in <code>O(2^n)</code> time complexity. Can you think of a better approach? Perhaps, try to avoid the repeated work of calling recursion more than once with same parameters.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    This is a Dynamic Programming problem. We can use Memoization to avoid repeated work. Create an <code>n</code>-sized array <code>cache</code> to store the results of recursive calls. When the recursion is called with specific parameters, return the stored value if it has already been computed. How would you implement this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We start the initial recursion with <code>i = 0</code>, indicating that we are at position <code>i</code>. We first check if the current recursion with the given <code>i</code> is already cached. If it is, we immediately return the stored value. Otherwise, we perform the recursion, store the result in the cache, and then return it. Can you think of the base condition to stop the recursion?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    At each recursion, we perform two recursive calls: one for climbing one step and another for climbing two steps. The minimum return value between the two is the result for the current recursion. The base condition is to return <code>0</code> if <code>i == n</code>. This is a one-dimensional dynamic programming problem, which can be further optimized using more advanced techniques.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/clone-graph.md b/hints/clone-graph.md
new file mode 100644
index 000000000..1e332bf4a
--- /dev/null
+++ b/hints/clone-graph.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(V + E)</code> time and <code>O(E)</code> space, where <code>V</code> is the number of vertices and <code>E</code> is the number of edges in the given graph.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    We are given only the reference to the node in the graph. Cloning the entire graph means we need to clone all the nodes as well as their child nodes. We can't just clone the node and its neighbor and return the node. We also need to clone the entire graph. Can you think of a recursive way to do this, as we are cloning nodes in a nested manner? Also, can you think of a data structure that can store the nodes with their cloned references?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use the Depth First Search (DFS) algorithm. We use a hash map to map the nodes to their cloned nodes. We start from the given node. At each step of the DFS, we create a node with the current node's value. We then recursively go to the current node's neighbors and try to clone them first. After that, we add their cloned node references to the current node's neighbors list. Can you think of a base condition to stop this recursive path?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We stop this recursive path when we encounter a node that has already been cloned or visited. This DFS approach creates an exact clone of the given graph, and we return the clone of the given node.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/coin-change-ii.md b/hints/coin-change-ii.md
new file mode 100644
index 000000000..3f18a6318
--- /dev/null
+++ b/hints/coin-change-ii.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(n * a)</code> time and <code>O(n * a)</code> space, where <code>n</code> is the number of coins and <code>a</code> is the given amount.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    As we need to find the total number of combinations, think in terms of recursion and visualize it as a decision tree where multiple coin choices are available at each recursion step. Can you determine a way to allow picking the same coin multiple times? Maybe you should consider the decisions made at each recursion step.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    The given coins are unique. We recursively iterate through the coins array using index <code>i</code>, tracking the collected amount along the current path. At each step, we can either skip the current coin or pick it, ensuring the total does not exceed the target. To allow picking the same coin multiple times, we recurse with the same index but an updated amount, generating different combinations.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    If we reach the target amount, we return <code>1</code>. The recursion stops if the index goes out of bounds. We count all possible ways and return the total. This approach is exponential. Can you think of a way to optimize it? Maybe you should consider an approach to avoid redundant computations.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We can use memoization to cache the results of recursive calls and avoid redundant computations. A hash map or a <code>2D</code> array can be used to store these results.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/coin-change.md b/hints/coin-change.md
new file mode 100644
index 000000000..c8522e7cb
--- /dev/null
+++ b/hints/coin-change.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n * t)</code> time and <code>O(t)</code> space, where <code>n</code> is the number of coins and <code>t</code> is the given amount.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Think of this problem in terms of recursion and try to visualize the decision tree, as there are multiple choices at each step. We start with the given amount. At each step of recursion, we have <code>n</code> coins and branch into paths using coins that are less than or equal to the current amount. Can you express this in terms of a recurrence relation? Also, try to determine the base condition to stop the recursion.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    If the amount is <code>0</code>, we return <code>0</code> coins. The recurrence relation can be expressed as <code>min(1 + dfs(amount - coins[i]))</code>, where we return the minimum coins among all paths. This results in an <code>O(n ^ t)</code> solution, where <code>n</code> is the number of coins and <code>t</code> is the total amount. Can you think of a better approach? Perhaps consider the repeated work and find a way to avoid it.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can use memoization to avoid the repeated work of calculating the result for each recursive call. A hash map or an array of size <code>t</code> can be used to cache the computed values for a specific <code>amount</code>. At each recursion step, we iterate over every coin and extend only the valid paths. If a result has already been computed, we return it from the cache instead of recalculating it.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/combination-target-sum-ii.md b/hints/combination-target-sum-ii.md
new file mode 100644
index 000000000..ef8aabd56
--- /dev/null
+++ b/hints/combination-target-sum-ii.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n * (2^n))</code> time and <code>O(n)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute-force solution would be to create a <code>hash set</code>, which is used to detect duplicates, to get combinations without duplicates. Can you think of a better way without using a <code>hash set</code>? Maybe you should sort the input array and observe the recursive calls that are responsible for duplicate combinations.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use backtracking to generate all combinations whose sum equals the given target. When the input array contains duplicate elements, it may result in duplicate combinations. To avoid this, we can sort the array. Why does sorting help? Because as we traverse the array from left to right, we form combinations with the current element. By skipping duplicate elements, we ensure that the same combinations are not repeated for identical elements. How can you implement this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We recursively traverse the given array starting at index <code>i</code>, with a variable <code>sum</code> representing the sum of the picked elements. We explore elements from <code>i</code> to the end of the array and extend the recursive path if adding the current element results in <code>sum <= target</code>. When we processed an element, we backtrack and proceed to the next distinct element, skipping any similar elements in the middle to avoid duplicate combinations.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/combination-target-sum.md b/hints/combination-target-sum.md
new file mode 100644
index 000000000..1eca71f3f
--- /dev/null
+++ b/hints/combination-target-sum.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(2^(t/m))</code> time and <code>O(t/m)</code> space, where <code>t</code> is the given <code>target</code> and <code>m</code> is the minimum value in the given array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Can you think of this problem in terms of a decision tree, where at each step, we have <code>n</code> decisions, where <code>n</code> is the size of the array? In this decision tree, we can observe that different combinations of paths are formed. Can you think of a base condition to stop extending a path? Maybe you should consider the target value. 
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use backtracking to recursively traverse these paths and make decisions to choose an element at each step. We maintain a variable <code>sum</code>, which represents the sum of all the elements chosen in the current path. We stop this recursive path if <code>sum == target</code>, and add a copy of the chosen elements to the result. How do you implement it?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We recursively traverse the array starting from index <code>i</code>. At each step, we select an element from <code>i</code> to the end of the array. We extend the recursive path with elements where <code>sum <= target</code> after including that element. This creates multiple recursive paths, and we append the current list to the result whenever the base condition is met.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/combinations-of-a-phone-number.md b/hints/combinations-of-a-phone-number.md
new file mode 100644
index 000000000..7154a859d
--- /dev/null
+++ b/hints/combinations-of-a-phone-number.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n * (4^n))</code> time and <code>O(n)</code> space, where <code>n</code> is the length of the input string.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    We can use a hash map to pair all the digits with their corresponding letters. Think of this as a decision tree, where at each step, we have a digit, and we select one of multiple characters to proceed to the next digit in the given string <code>digits</code>. Can you think of an algorithm to generate all combinations of strings? 
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use backtracking where we select a character and process it, then backtrack to process another character. We recursively iterate on the given string with index <code>i</code>. At each step, we consider the letters from the hash map that correspond to the digit at the <code>i-th</code> index. Can you think of the base condition to stop this recursive path?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We initialize an empty string that represents the choices of the characters throughout the current recursive path. When the index <code>i</code> reaches the end of the string, we add the current string to the result list and return.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/copy-linked-list-with-random-pointer.md b/hints/copy-linked-list-with-random-pointer.md
new file mode 100644
index 000000000..73a1417ae
--- /dev/null
+++ b/hints/copy-linked-list-with-random-pointer.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the length of the given list.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    There is an extra random pointer for each node, and unlike the next pointer, which points to the next node, the random pointer can point to any random node in the list. A deep copy is meant to create completely separate nodes occupying different memory. Why can't we build a new list while iterating through the original list?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    Because, while iterating through the list, when we encounter a node and create a copy of it, we can't immediately assign the random pointer's address. This is because the random pointer might point to a node that has not yet been created. To solve this, we can first create copies of all the nodes in one iteration. However, we still can't directly assign the random pointers since we don't have the addresses of the copies of those random pointers. Can you think of a data structure to store this information? Maybe a hash data structure could help.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can use a hash data structure, such as a hash map, which takes <code>O(1)</code> time to retrieve data. This can help by mapping the original nodes to their corresponding copies. This way, we can easily retrieve the copy of any node and assign the random pointers in a subsequent pass after creating copies of all nodes in the first pass.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/count-connected-components.md b/hints/count-connected-components.md
new file mode 100644
index 000000000..4998f22ad
--- /dev/null
+++ b/hints/count-connected-components.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(V + E)</code> time and <code>O(V + E)</code> space, where <code>V</code> is the number vertices and <code>E</code> is the number of edges in the graph.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Assume there are no edges initially, so we have <code>n</code> components, as there are that many nodes given. Now, we should add the given edges between the nodes. Can you think of an algorithm to add the edges between the nodes? Also, after adding an edge, how do you determine the number of components left?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use the Union-Find (DSU) algorithm to add the given edges. For simplicity, we use Union-Find by size, where we merge the smaller component into the larger one. The Union-Find algorithm inserts the edge only between two nodes from different components. It does not add the edge if the nodes are from the same component. How do you find the number of components after adding the edges? For example, consider that nodes <code>0</code> and <code>1</code> are not connected, so there are initially two components. After adding an edge between these nodes, they become part of the same component, leaving us with one component.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We create an object of the DSU and initialize the result variable <code>res = n</code>, which indicates that there are <code>n</code> components initially. We then iterate through the given edges. For each edge, we attempt to connect the nodes using the union function of the DSU. If the union is successful, we decrement <code>res</code>; otherwise, we continue. Finally, we return <code>res</code> as the number of components.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/count-good-nodes-in-binary-tree.md b/hints/count-good-nodes-in-binary-tree.md
new file mode 100644
index 000000000..39e8783d5
--- /dev/null
+++ b/hints/count-good-nodes-in-binary-tree.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and<code>O(n)</code> space, where <code>n</code> is the number of nodes in the given tree.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would involve considering every node and checking if the path from the root to that node is valid, resulting in an <code>O(n^2)</code> time complexity. Can you think of a better approach?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use the Depth First Search (DFS) algorithm to traverse the tree. But can you think of a way to determine if the current node is a good node in a single traversal? Maybe we need to track a value while traversing the tree.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    While traversing the tree, we should track the maximum value along the current path. This allows us to determine whether the nodes we encounter are good. We can use a global variable to count the number of good nodes.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/count-number-of-islands.md b/hints/count-number-of-islands.md
new file mode 100644
index 000000000..a8cb92e6f
--- /dev/null
+++ b/hints/count-number-of-islands.md
@@ -0,0 +1,23 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(m * n)</code> time and <code>O(m * n)</code> space, where <code>m</code> is the number of rows and <code>n</code> is the number of columns in the grid.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    An island is a group of <code>1</code>'s in which every <code>1</code> is reachable from any other <code>1</code> in that group. Can you think of an algorithm that can find the number of groups by visiting a group only once? Maybe there is a recursive way of doing it.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use the Depth First Search (DFS) algorithm to traverse each group independently. We iterate through each cell of the grid. When we encounter a <code>1</code>, we perform a DFS starting at that cell and recursively visit every other <code>1</code> that is reachable. During this process, we mark the visited <code>1</code>'s as <code>0</code> to ensure we don't revisit them, as they belong to the same group. The number of groups corresponds to the number of islands.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/count-paths.md b/hints/count-paths.md
new file mode 100644
index 000000000..299793547
--- /dev/null
+++ b/hints/count-paths.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(m * n)</code> time and <code>O(m * n)</code> space, where <code>m</code> is the number of rows and <code>n</code> is the number of columns in the grid.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Try to think in terms of recursion and visualize it as a decision tree, where we have two choices at each step. Can you determine the base condition and recurrence relation?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We recursively traverse the grid using row <code>i</code> and column <code>j</code>. At each step, we explore both possibilities: moving down or moving right, ensuring we do not go out of bounds. If we reach the bottom-right cell, we return <code>1</code>.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    This approach has exponential complexity. Can you think of a way to optimize the recursion? Maybe you should consider using a dynamic programming approach.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We can use memoization to cache the results of recursive calls and avoid recalculations. A hash map or a <code>2D</code> array can be used to store these results.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/count-squares.md b/hints/count-squares.md
new file mode 100644
index 000000000..69b289bdb
--- /dev/null
+++ b/hints/count-squares.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(1)</code> time for each <code>add()</code> call, <code>O(n)</code> time for each <code>count()</code> call, and <code>O(n)</code> space, where <code>n</code> is the total number of points.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Initially, we can store the points in a global list for the <code>add()</code> call. For the <code>count()</code> call, a brute force approach would use three nested loops to check other points except for the query point, resulting in an <code>O(n^3)</code> time solution. Can you think of a better way? Maybe you should consider the observation that can be drawn from the diagonal of a square.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    In a square's diagonal, the absolute difference between the x-coordinates is equal to the absolute difference between the y-coordinates of the two endpoints, and neither difference can be zero. Using these two points, we can determine the other diagonal endpoints.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We store points in a hash map instead of a list for <code>O(1)</code> lookups, treating duplicate points as one while tracking their frequencies. For the <code>count()</code> function, we iterate through points that, along with the query point, can form a diagonal. Let the query point be <code>(qx, qy)</code> and the other point be <code>(x, y)</code>, ensuring they form a diagonal. What could be the other two points? Maybe you should consider the points forming a right-to-left diagonal, treating <code>(qx, qy)</code> as the top-right corner.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    The other two points are point1 <code>(x, qy)</code> and point2 <code>(qx, y)</code>. For counting, we simply add <code>count of point1 * count of point2</code> to the result <code>res</code>.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/count-subsequences.md b/hints/count-subsequences.md
new file mode 100644
index 000000000..53a37dcee
--- /dev/null
+++ b/hints/count-subsequences.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(m * n)</code> time and <code>O(m * n)</code> space, where <code>m</code> is the length of the string <code>s</code> and <code>n</code> is the length of the string <code>t</code>.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Try to think in terms of recursion and visualize it as a decision tree, as we need to explore all subsequences of <code>s</code>. Can you determine the possible decisions at each recursion step?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We recursively iterate through the strings using indices <code>i</code> and <code>j</code> for <code>s</code> and <code>t</code>, respectively. At each recursion step, we can either skip the current character of <code>s</code> or include it in the current path if it matches the current character of <code>t</code>. Can you determine the base conditions for this recursive function?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    If index <code>j</code> goes out of bounds, we return <code>1</code> as a valid subsequence is found. If index <code>i</code> goes out of bounds first, we return <code>0</code>. At each recursion step, we return the sum of both paths. This approach is exponential. Can you think of a way to optimize it?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We can use memoization to cache the results of recursive calls and avoid redundant computations. A hash map or a <code>2D</code> array can be used to store these results.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/counting-bits.md b/hints/counting-bits.md
new file mode 100644
index 000000000..45188a165
--- /dev/null
+++ b/hints/counting-bits.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the given integer.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A straightforward approach would be to iterate from <code>0</code> to <code>n</code> using <code>i</code>, and for each <code>i</code>, iterate through its bits to count the number of set bits. This would result in an <code>O(n \log n)</code> approach. Can you think of a better way? Maybe you should try identifying a pattern by observing the bitwise representation of consecutive numbers.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    For example, to compute set bits for <code>7</code>, add <code>1</code> to the count of set bits in <code>3</code>, which was previously computed by adding <code>1</code> to the count of set bits in <code>1</code>. Observing the pattern, for numbers less than <code>4</code>, add <code>1</code> to the count from two positions before. For numbers less than <code>8</code>, add <code>1</code> to the count from four positions before. Can you derive a dynamic programming relation from this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We find an offset for the current number based on the number before <code>offset</code> positions. The dynamic programming relation is <code>dp[i] = 1 + dp[i - offset]</code>, where <code>dp[i]</code> represents the number of set bits in <code>i</code>. The offset starts at <code>1</code> and updates when encountering a power of <code>2</code>. To simplify the power of <code>2</code> check, if <code>offset * 2</code> equals the current number, we update <code>offset</code> to the current number.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/course-schedule-ii.md b/hints/course-schedule-ii.md
new file mode 100644
index 000000000..e187980f9
--- /dev/null
+++ b/hints/course-schedule-ii.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(V + E)</code> time and <code>O(V + E)</code> space, where <code>V</code> is the number of courses (nodes) and <code>E</code> is the number of prerequisites (edges).
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Consider the problem as a graph where courses represent the nodes, and <code>prerequisite[i] = [a, b]</code> represents a directed edge from <code>a</code> to <code>b</code>. We need to determine whether the graph contains a cycle. Why? Because if there is a cycle, it is impossible to complete the courses involved in the cycle. Can you think of an algorithm to detect a cycle in a graph and also find the valid ordering if a cycle doesn't exist?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use DFS to detect a cycle in a graph. However, we also need to find the valid ordering of the courses, which can also be achieved using DFS. Alternatively, we can use the Topological Sort algorithm to find the valid ordering in this directed graph, where the graph must be acyclic to complete all the courses, and the prerequisite of a course acts as the parent node of that course. How would you implement this? 
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We compute the indegrees of all the nodes. Then, we perform a BFS starting from the nodes that have no parents (<code>indegree[node] == 0</code>). At each level, we traverse these nodes, decrement the indegree of their child nodes, and append those child nodes to the queue if their indegree becomes <code>0</code>. We only append nodes whose indegree is <code>0</code> or becomes <code>0</code> during the BFS to our result array. If the length of the result array is not equal to the number of courses, we return an empty array.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/course-schedule.md b/hints/course-schedule.md
new file mode 100644
index 000000000..1392ac134
--- /dev/null
+++ b/hints/course-schedule.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(V + E)</code> time and <code>O(V + E)</code> space, where <code>V</code> is the number of courses (nodes) and <code>E</code> is the number of prerequisites (edges).
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Consider the problem as a graph where courses represent the nodes, and <code>prerequisite[i] = [a, b]</code> represents a directed edge from <code>a</code> to <code>b</code>. We need to determine whether the graph contains a cycle. Why? Because if there is a cycle, it is impossible to complete the courses involved in the cycle. Can you think of an algorithm to detect cycle in a graph?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use the Depth First Search (DFS) algorithm to detect a cycle in a graph. We iterate over each course, run a DFS from that course, and first try to finish its prerequisite courses by recursively traversing through them. To detect a cycle, we initialize a hash set called <code>path</code>, which contains the nodes visited in the current DFS call. If we encounter a course that is already in the <code>path</code>, we can conclude that a cycle is detected. How would you implement it?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+     We run a DFS starting from each course by initializing a hash set, <code>path</code>, to track the nodes in the current DFS call. At each step of the DFS, we return <code>false</code> if the current node is already in the <code>path</code>, indicating a cycle. We recursively traverse the neighbors of the current node, and if any of the neighbor DFS calls detect a cycle, we immediately return <code>false</code>. Additionally, we clear the neighbors list of a node when no cycle is found from that node to avoid revisiting those paths again.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/daily-temperatures.md b/hints/daily-temperatures.md
new file mode 100644
index 000000000..64c1a171e
--- /dev/null
+++ b/hints/daily-temperatures.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would involve iterating through the array with index <code>i</code> and checking how far is the next greater element to the right of <code>i</code>. This would be an <code>O(n^2)</code> solution. Can you think of a better way?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    Can you consider a reverse approach? For example, in <code>[2, 1, 1, 3]</code>, the next greater element for the numbers <code>[2, 1, 1]</code> is <code>3</code>. Instead of checking for each element individually, can you think of a way where, by standing at the element <code>3</code>, you compute the result for the elements <code>[2, 1, 1]</code>?  Maybe there's a data structure that is useful here.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+   We can use a stack to maintain indices in a monotonically decreasing order, popping indices where the values are smaller than the current element. This helps us find the result by using the difference between indices while considering the values at those indices. Can you see how the stack is useful?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    In the array <code>[2, 1, 1, 3]</code>, we don't perform any pop operations while processing <code>[2, 1, 1]</code> because these elements are already in decreasing order. However, when we reach <code>3</code>, we pop elements from the stack until the top element of the stack is no longer less than the current element. For each popped element, we compute the difference between the indices and store it in the position corresponding to the popped element.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/decode-ways.md b/hints/decode-ways.md
new file mode 100644
index 000000000..56c40d46a
--- /dev/null
+++ b/hints/decode-ways.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the length of the given string.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    The characters <code>A</code> through <code>Z</code> are mapped to the numbers from <code>1</code> to <code>26</code>. A mapped number can have at most <code>2</code> digits. In the given string of digits, we can explore all possible decodings by combining one or two consecutive digits. Think of this in terms of a decision tree and explore all paths. Can you derive a recurrence relation for this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    Iterate over the string with index <code>i</code>. At each index, we have two choices: decode the current digit as a character with its mapped value, or combine the current digit with the next digit to form a two-digit value. The recurrence relation can be expressed as <code>dfs(i + 1) + dfs(i + 2)</code> where <code>dfs</code> is the recursive function. Also, consider edge cases, as not every two-digit number or a number with a leading zero is valid. How would you implement this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    A brute-force recursive solution would result in <code>O(2^n)</code> time complexity. Can you think of a better way? Perhaps you should consider the repeated work of calling the recursion multiple times with the same parameter values and find a way to avoid this. Also, can you think about the base condition of this recursive function?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    The base condition is to return <code>1</code> if <code>i</code> goes out of bounds. If the current digit is <code>'0'</code>, return <code>0</code>, as no character maps to <code>'0'</code>, making the string invalid. Use memoization to avoid repeated work by caching recursion results in an array or hash map and returning the stored value when the result is already calculated.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/depth-of-binary-tree.md b/hints/depth-of-binary-tree.md
new file mode 100644
index 000000000..51538e4c8
--- /dev/null
+++ b/hints/depth-of-binary-tree.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the number of nodes in the tree.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    From the definition of binary tree's maximum depth, Can you think of a way to achieve this recursively? Maybe you should consider the max depth of the subtrees first before computing the maxdepth at the root.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We use the Depth First Search (DFS) algorithm to find the maximum depth of a binary tree, starting from the <code>root</code>. For the subtrees rooted at the <code>left</code> and <code>right</code> children of the <code>root</code> node, we calculate their maximum depths recursively going through <code>left</code> and <code>right</code> subtrees. We return <code>1 + max(leftDepth, rightDepth)</code>. Why?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    The <code>+1</code> accounts for the current node, as it contributes to the current depth in the recursion call. We pass the maximum depth from the current node's left and right subtrees to its parent because the current maximum depth determines the longest path from the parent to a leaf node through this subtree.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/design-twitter-feed.md b/hints/design-twitter-feed.md
new file mode 100644
index 000000000..8fc7ab4f8
--- /dev/null
+++ b/hints/design-twitter-feed.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(nlogn)</code> time for each <code>getNewsFeed()</code> function call, <code>O(1)</code> time for the remaining methods, and <code>O((N * m) + (N * M) + n)</code> space, where <code>n</code> is the number of <code>followeeIds</code> associated with the <code>userId</code>, <code>m</code> is the maximum number of tweets by any user, <code>N</code> is the total number of <code>userIds</code>, and <code>M</code> is the maximum number of followees for any user.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Can you think of a data structure to store all the information, such as <code>userIds</code> and corresponding <code>followeeIds</code>, or <code>userIds</code> and their tweets? Maybe you should think of a hash data structure in terms of key-value pairs. Also, can you think of a way to determine that a tweet was posted before another tweet?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We use a hash map <code>followMap</code> to store <code>userIds</code> and their unique <code>followeeIds</code> as a <code>hash set</code>. Another hash map, <code>tweetMap</code>, stores <code>userIds</code> and their tweets as a list of <code>(count, tweetId)</code> pairs. A counter <code>count</code>, incremented with each tweet, tracks the order of tweets. The variable <code>count</code> is helpful in distinguishing the time of tweets from two users. This way of storing data makes the functions <code>follow()</code>, <code>unfollow()</code>, and <code>postTweet()</code> run in <code>O(1)</code>. Can you think of a way to implement <code>getNewsFeed()</code>? Maybe consider a brute force approach and try to optimize it.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    A naive solution would involve taking the tweets of the userId and its followeeIds into a list, sorting them in descending order based on their <code>count</code> values, and returning the top <code>10</code> tweets as the most recent ones. Can you think of a more efficient approach that avoids collecting all tweets and sorting? Perhaps consider a data structure and leverage the fact that each user's individual tweets list is already sorted.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We can use a Max-Heap to efficiently retrieve the top <code>10</code> most recent tweets. For each followee and the userId, we insert their most recent tweet from the <code>tweetMap</code> into the heap, along with the tweet's <code>count</code> and its index in the tweet list. This index is necessary because after processing a tweet, we can insert the next most recent tweet from the same user's list. By always pushing and popping tweets from the heap, we ensure that the <code>10</code> most recent tweets are retrieved without sorting all tweets.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/design-word-search-data-structure.md b/hints/design-word-search-data-structure.md
new file mode 100644
index 000000000..db99718c2
--- /dev/null
+++ b/hints/design-word-search-data-structure.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time for each function call and <code>O(t + n)</code> space, where <code>n</code> is the length of the string and <code>t</code> is the total number of nodes created in the Trie.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would be to store each added word in a list and search linearly through the list for a word every time. This would be an <code>O(m * n)</code> solution, where <code>m</code> is the size of the list and <code>n</code> is the length of the string. Can you think of a better way? Maybe there is a tree-like data structure.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use a Trie to implement adding and searching for words efficiently. Adding a word follows the standard Trie insertion process. However, when searching for a word containing <code>'.'</code>, which can match any character, we need a different approach. Instead of directly matching, we consider all possible characters at the position of <code>'.'</code> and recursively check the rest of the word for each possibility. How would you implement it?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We traverse the word with index <code>i</code>, starting at the root of the Trie. For normal characters, we search as usual. When encountering a dot (<code>'.'</code>), we try all possible characters by recursively extending the search in each direction. If any path leads to a valid word, we return <code>true</code>; otherwise, we return <code>false</code>. Although we try all paths for a dot, the time complexity is still <code>O(n)</code> because there are at most two dots (<code>'.'</code>) in the word, making the complexity <code>O((26^2) * n)</code>.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/duplicate-integer.md b/hints/duplicate-integer.md
new file mode 100644
index 000000000..7639cfb85
--- /dev/null
+++ b/hints/duplicate-integer.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would be to check every element against every other element in the array. This would be an <code>O(n^2)</code> solution. Can you think of a better way?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    Is there a way to check if an element is a duplicate without comparing it to every other element? Maybe there's a data structure that is useful here.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can use a hash data structure like a hash set or hash map to store elements we've already seen. This will allow us to check if an element is a duplicate in constant time.
+    </p>
+</details>
diff --git a/hints/eating-bananas.md b/hints/eating-bananas.md
new file mode 100644
index 000000000..41bb76a40
--- /dev/null
+++ b/hints/eating-bananas.md
@@ -0,0 +1,47 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(nlogm)</code> time and <code>O(1)</code> space, where <code>n</code> is the size of the input array, and <code>m</code> is the maximum value in the array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Given <code>h</code> is always greater than or equal to the length of piles, can you determine the upper bound for the answer? How much time does it take Koko to eat a pile with <code>x</code> bananas? 
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    It takes <code>ceil(x / k)</code> time to finish the <code>x</code> pile when Koko eats at a rate of <code>k</code> bananas per hour. Our task is to determine the minimum possible value of <code>k</code>. However, we must also ensure that at this rate, <code>k</code>, Koko can finish eating all the piles within the given <code>h</code> hours. Can you now think of the upper bound for <code>k</code>?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    The upper bound for <code>k</code> is the maximum size of all the piles. Why? Because if Koko eats the largest pile in one hour, then it is straightforward that she can eat any other pile in an hour only.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    Consider <code>m</code> to be the largest pile and <code>n</code> to be the number of piles. A brute force solution would be to linearly check all values from <code>1</code> to <code>m</code> and find the minimum possible value at which Koko can complete the task. This approach would take <code>O(n * m)</code> time. Can you think of a more efficient method? Perhaps an efficient searching algorithm could help.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 5</summary>
+    <p>
+    Rather than linearly scanning, we can use binary search. The upper bound of <code>k</code> is <code>max(piles)</code> and since we are only dealing with positive values, the lower bound is <code>1</code>. The search space of our binary search is <code>1</code> through <code>max(piles)</code>. This allows us to find the smallest possible <code>k</code> using binary search.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/edit-distance.md b/hints/edit-distance.md
new file mode 100644
index 000000000..277fa3cbe
--- /dev/null
+++ b/hints/edit-distance.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(m * n)</code> time and <code>O(m * n)</code> space, where <code>m</code> and <code>n</code> are the lengths of the strings <code>word1</code> and <code>word2</code>, respectively.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Try to think in terms of recursion and visualize it as a decision tree, as we have choices at each recursion step. Can you determine the recurrence relation and base cases?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We recursively iterate through the strings using indices <code>i</code> and <code>j</code> for <code>word1</code> and <code>word2</code>, respectively. If the characters at the current indices match, we increment both indices without counting an operation. Otherwise, we have three choices: insert the character at the current index of <code>word1</code> (increment <code>j</code>), delete the current character of <code>word1</code> (increment <code>i</code>), or replace the character at index <code>i</code> in <code>word1</code> (increment both <code>i</code> and <code>j</code>).
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    If index <code>i</code> goes out of bounds, we return the number of remaining characters in <code>word2</code> (using insert operations). If index <code>j</code> goes out of bounds, we return the number of remaining characters in <code>word1</code> (using delete operations). At each step, we return the minimum operation path. This approach is exponential. Can you think of a way to optimize it?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We can use memoization to cache the results and avoid redundant calculations. A hash map or a <code>2D</code> array can be used to store these results.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/evaluate-reverse-polish-notation.md b/hints/evaluate-reverse-polish-notation.md
new file mode 100644
index 000000000..8e63e0dfd
--- /dev/null
+++ b/hints/evaluate-reverse-polish-notation.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would involve repeatedly finding an operator <code>+ - * /</code> in the array and modifying the array by computing the result for that operator and two operands to its left. This would be an <code>O(n^2)</code> solution. Can you think of a better way? Maybe we can use a data structure to handle operations efficiently.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use a stack. We iterate through the array, and if we encounter a number, we push it onto the stack. If we encounter an operator, we pop two elements from the stack, treat them as operands, and solve the equation using the current operator. Then, we push the result back onto the stack. Why does this work?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    As the array has postfix expression, stack helps us to maintain the correct order of operations by ensuring that we always use the most recent operands (those closest to the operator) when performing the operation. After the iteration, the final result is left in the stack.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/find-duplicate-integer.md b/hints/find-duplicate-integer.md
new file mode 100644
index 000000000..e399acf89
--- /dev/null
+++ b/hints/find-duplicate-integer.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(1)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A naive approach would be to use a hash set, which takes <code>O(1)</code> time to detect duplicates. Although this solution is acceptable, it requires <code>O(n)</code> extra space. Can you think of a better solution that avoids using extra space? Consider that the elements in the given array <code>nums</code> are within the range <code>1</code> to <code>len(nums)</code>.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use the given input array itself as a hash set without creating a new one. This can be achieved by marking the positions (<code>0</code>-indexed) corresponding to the elements that have already been encountered. Can you implement this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We iterate through the array using index <code>i</code>. For each element, we use its absolute value to find the corresponding index and mark that position as negative: <code>nums[abs(nums[i]) - 1] *= -1</code>. Taking absolute value ensures we work with the original value even if it’s already negated. How can you detect duplicates?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    For example, in the array <code>[2, 1, 2, 3]</code>, where <code>2</code> is repeated, we mark the index corresponding to each element as negative. If we encounter a number whose corresponding position is already negative, it means the number is a duplicate, and we return it.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/find-median-in-a-data-stream.md b/hints/find-median-in-a-data-stream.md
new file mode 100644
index 000000000..ea07e7519
--- /dev/null
+++ b/hints/find-median-in-a-data-stream.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(logn)</code> time for <code>addNum()</code>, <code>O(1)</code> time for <code>findMedian()</code>, and <code>O(n)</code> space, where <code>n</code> is the current number of elements.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A naive solution would be to store the data stream in an array and sort it each time to find the median, resulting in <code>O(nlogn)</code> time for each <code>findMedian()</code> call. Can you think of a better way? Perhaps using a data structure that allows efficient insertion and retrieval of the median can make the solution more efficient.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    If we divide the array into two parts, we can find the median in <code>O(1)</code> if the left half can efficiently return the maximum and the right half can efficiently return the minimum. These values determine the median. However, the process changes slightly if the total number of elements is odd — in that case, the median is the element from the half with the larger size. Can you think of a data structure which is suitable to implement this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can use a Heap (Max-Heap for the left half and Min-Heap for the right half). Instead of dividing the array, we store the elements in these heaps as they arrive in the data stream. But how can you maintain equal halves of elements in these two heaps? How do you implement this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We initialize a Max-Heap and a Min-Heap. When adding an element, if the element is greater than the minimum element of the Min-Heap, we push it into the Min-Heap; otherwise, we push it into the Max-Heap. If the size difference between the two heaps becomes greater than one, we rebalance them by popping an element from the larger heap and pushing it into the smaller heap. This process ensures that the elements are evenly distributed between the two heaps, allowing us to retrieve the middle element or elements in <code>O(1)</code> time.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/find-minimum-in-rotated-sorted-array.md b/hints/find-minimum-in-rotated-sorted-array.md
new file mode 100644
index 000000000..568e4ef1f
--- /dev/null
+++ b/hints/find-minimum-in-rotated-sorted-array.md
@@ -0,0 +1,40 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(logn)</code> time and <code>O(1)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would be to do a linear search on the array to find the minimum element. This would be an <code>O(n)</code> solution. Can you think of a better way? Maybe an efficient searching algorithm is helpful.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    Given that the array is rotated after sorting, elements from the right end are moved to the left end one by one. This creates two parts of a sorted array, separated by a deflection point caused by the rotation. For example, consider the array <code>[3, 4, 1, 2]</code>. Here, the array is rotated twice, resulting in two sorted segments: <code>[3, 4]</code> and <code>[1, 2]</code>. And the minimum element will be the first element of the right segment. Can you do a binary search to find this cut?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We perform a binary search on the array with pointers <code>l</code> and <code>r</code>, which belong to two different sorted segments. For example, in <code>[3, 4, 5, 6, 1, 2, 3]</code>, <code>l = 0</code>, <code>r = 6</code>, and <code>mid = 3</code>. At least two of <code>l</code>, <code>mid</code>, and <code>r</code> will always be in the same sorted segment. Can you find conditions to eliminate one half and continue the binary search? Perhaps analyzing all possible conditions for <code>l</code>, <code>mid</code>, and <code>r</code> would help. 
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    There will be two conditions where <code>l</code> and <code>mid</code> will be in left sorted segment or <code>mid</code> and <code>r</code> will be in right sorted segement.
+    If <code>l</code> and <code>mid</code> in sorted segement, then <code>nums[l] < nums[mid]</code> and the minimum element will be in the right part. If <code>mid</code> and <code>r</code> in sorted segment, then <code>nums[m] < nums[r]</code> and the minimum element will be in the left part. After the binary search we end up finding the minimum element.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/find-target-in-rotated-sorted-array.md b/hints/find-target-in-rotated-sorted-array.md
new file mode 100644
index 000000000..7133b3821
--- /dev/null
+++ b/hints/find-target-in-rotated-sorted-array.md
@@ -0,0 +1,40 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(logn)</code> time and <code>O(1)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would be to do a linear search on the array to find the target element. This would be an <code>O(n)</code> solution. Can you think of a better way? Maybe an efficient searching algorithm is helpful.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    Given that the array is rotated after sorting, elements from the right end are moved to the left end one by one, creating two sorted segments separated by a deflection point due to the rotation. For example, consider the array <code>[3, 4, 1, 2]</code>, which is rotated twice, resulting in two sorted segments: <code>[3, 4]</code> and <code>[1, 2]</code>. In a fully sorted array, it's easy to find the target. So, if you can identify the deflection point (cut), you can perform a binary search on both segments to find the target element. Can you use binary search to find this cut?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We perform a binary search on the array with pointers <code>l</code> and <code>r</code>, which belong to two different sorted segments. For example, in <code>[3, 4, 5, 6, 1, 2, 3]</code>, <code>l = 0</code>, <code>r = 6</code>, and <code>mid = 3</code>. At least two of <code>l</code>, <code>mid</code>, and <code>r</code> will always be in the same sorted segment. Can you find conditions to eliminate one half and continue the binary search? Perhaps analyzing all possible conditions for <code>l</code>, <code>mid</code>, and <code>r</code> may help.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    There are two cases: <code>l</code> and <code>mid</code> belong to the left sorted segment, or <code>mid</code> and <code>r</code> belong to the right sorted segment.
+    If <code>l</code> and <code>mid</code> are in the same segment, <code>nums[l] < nums[mid]</code>, so the pivot index must lie in the right part. If <code>mid</code> and <code>r</code> are in the same segment, <code>nums[mid] < nums[r]</code>, so the pivot index must lie in the left part. After the binary search, we eventually find the pivot index. Once the pivot is found, it's straightforward to select the segment where the target lies and perform a binary search on that segement to find its position. If we don't find the target, we return <code>-1</code>.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/foreign-dictionary.md b/hints/foreign-dictionary.md
new file mode 100644
index 000000000..9837818a0
--- /dev/null
+++ b/hints/foreign-dictionary.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(N + V + E)</code> time and <code>O(V + E)</code> space, where <code>N</code> is the sum of the lengths of all the strings, <code>V</code> is the number of unique characters (vertices), and <code>E</code> is the number of edges.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Can you think of this as a graph problem? Characters from <code>a</code> through <code>z</code> are nodes. What could the edges represent here? How can you create edges from the given words? Perhaps you should try comparing two adjacent words.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    The relative ordering of the characters can be treated as edges. For example, consider the words ordered as <code>["ape", "apple"]</code>. <code>"ape"</code> comes before <code>"apple"</code>, which indicates that <code>'e'</code> is a predecessor of <code>'p'</code>. Therefore, there is a directed edge <code>e -> p</code>, and this dependency should be valid across all the words. In this way, we can build an adjacency list by comparing adjacent words. Can you think of an algorithm that is suitable to find a valid ordering?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can use Topological Sort to ensure every node appears after its predecessor. Using DFS, we traverse the graph built from the adjacency list. A visited map tracks nodes in the current DFS path: <code>False</code> means not in the path, and <code>True</code> means in the path. If any DFS call returns <code>True</code>, it indicates a cycle and we return immediately. How do we extract the ordering from this DFS?  
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    When we visit a node and its children and don't find a cycle, we mark the node as <code>False</code> in the map and append it to the result, treating this as a post-order traversal. If we find a cycle, we return an empty string; otherwise, we return the result list.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/gas-station.md b/hints/gas-station.md
new file mode 100644
index 000000000..52464072d
--- /dev/null
+++ b/hints/gas-station.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(1)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force approach would be to start at each gas station, simulate the process, and return the index where completing the circuit is possible. This would be an <code>O(n^2)</code> time solution. Can you think of a better way? Maybe a greedy approach works.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+   We can immediately return <code>-1</code> if <code>sum(gas) < sum(cost)</code>, as completing the circuit is impossible due to insufficient gas. Otherwise, a solution always exists because the total gas is sufficient to cover the total cost, meaning there must be a valid starting point that allows completing the circuit.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We start with a variable <code>total</code> to track the gas balance and initialize the result index to <code>0</code>. As we iterate through the array with index <code>i</code>, we accumulate the difference <code>(gas[i] - cost[i])</code>. If <code>total</code> becomes negative at any index, we reset it to <code>0</code> and update the result index to <code>(i + 1)</code>.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/generate-parentheses.md b/hints/generate-parentheses.md
new file mode 100644
index 000000000..454a10e81
--- /dev/null
+++ b/hints/generate-parentheses.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(4^n / sqrt(n))</code> time and <code>O(n)</code> space, where <code>n</code> is the number of parenthesis pairs in the string.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would be to generate all possible strings of size <code>2n</code> and add only the valid strings. This would be an <code>O(n * 2 ^ (2n))</code> solution. Can you think of a better way? Maybe you can use pruning to avoid generating invalid strings.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use backtracking with pruning. But what makes a string invalid? Can you think of a condition for this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    When the count of closing brackets exceeds the count of opening brackets, the string becomes invalid. Therefore, we can maintain two variables, <code>open</code> and <code>close</code>, to track the number of opening and closing brackets. We avoid exploring paths where <code>close > open</code>. Once the string length reaches <code>2n</code>, we add it to the result.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/hand-of-straights.md b/hints/hand-of-straights.md
new file mode 100644
index 000000000..1a35e0287
--- /dev/null
+++ b/hints/hand-of-straights.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(nlogn)</code> time and <code>O(n)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    It is observed that to form a group, the minimum value should be the starting value of the group. Additionally, the minimum value in the array serves as the starting value for one or more groups based on its frequency. Can you think of an efficient way to determine the frequencies of array elements? Maybe a specific data structure can be useful here.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use a hash map to store the elements along with their frequencies. Additionally, we sort the given array. Then, we iterate through the sorted array and try to form groups by decrementing the frequency count. If we fail to form a group at any step, we immediately return <code>false</code>. Can you think why this works?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    Sorting ensures we start with the smallest available value, while the hash map helps track element availability using frequency counts. At each step, we pick the smallest available value <code>x</code> and attempt to form a group from <code>x</code> to <code>x + groupSize - 1</code>. If all elements are present based on their frequency counts, we decrement their counts as we iterate. If we successfully form all groups, we return <code>true</code>; otherwise, we return <code>false</code>.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/house-robber-ii.md b/hints/house-robber-ii.md
new file mode 100644
index 000000000..1cc52b34d
--- /dev/null
+++ b/hints/house-robber-ii.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the number of houses.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    First, consider solving the problem to get the maximum money after robbing without the condition that 'the first and last houses are adjacent'. Can you express this using a recurrence relation? Perhaps you could draw a decision tree, as at each step, you can either rob the current house and skip the next one or skip the current house and move to the next.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    The recurrence relation can be expressed as <code>max(nums[i] + dfs(i + 2), dfs(i + 1))</code>, where <code>i</code> is the current house and <code>dfs</code> is the recursive function. The base condition for this recursion would be to return <code>0</code> when <code>i</code> goes out of bounds. This solution results in <code>O(2^n)</code> time complexity because, at each recursive step, we branch into two paths. Can you think of a way to avoid recalculating the result for the same recursive call multiple times?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can use memoization to store the result of a recursive function in a hash map or an array and immediately return this value when the function is called again with the same parameter values. How would you implement this? How would you solve the problem if the first and last houses are adjacent to each other? Perhaps you should consider skipping any one house between the two.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We can create two arrays from the given array. The first will include houses from the first house to the second-to-last house, and the second will include houses from the second house to the last house. We can run the recursive function on both arrays independently and return the maximum result between the two. Advanced techniques such as bottom-up dynamic programming can further optimize the solution.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/house-robber.md b/hints/house-robber.md
new file mode 100644
index 000000000..2a1e5d7c8
--- /dev/null
+++ b/hints/house-robber.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the number of houses.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Can you think of this problem in terms of recursion? Consider drawing a decision tree where, at each step, we can choose to rob the house or skip it. If we rob the current house, we cannot rob the next or the previous house. Can you derive a recurrence relation to solve the problem?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can recursively start from the first house and branch paths accordingly. If we rob the current house, we skip the next house; otherwise, we move to the next house. The recurrence relation can be expressed as <code>max(nums[i] + dfs(i + 2), dfs(i + 1))</code>, where <code>i</code> is the current house and <code>dfs</code> is the recursive function. Can you determine the base condition to stop the recursion?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    The base condition would be to return <code>0</code> when <code>i</code> goes out of bounds. This recursion can leads to <code>O(2^n)</code> time solution. Can you think of a better way? Maybe you should try to avoid recalculating the result for a recursive call.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We can use Memoization to avoid recalculating the result multiple times for a recursive call. By storing the result of each recursive call in a hash map or an array using <code>i</code> as the parameter, we can immediately return the stored result if the recursion is called with the same <code>i</code> value again. Further optimization can be achieved using advanced techniques like Bottom-Up dynamic programming.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/implement-prefix-tree.md b/hints/implement-prefix-tree.md
new file mode 100644
index 000000000..f2908be7f
--- /dev/null
+++ b/hints/implement-prefix-tree.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time for each function call and <code>O(t)</code> space, where <code>n</code> is the length of the given string and <code>t</code> is the total number of nodes created in the Trie.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A Trie is structured as a tree-like data structure where each node contains a hash map (or an array for fixed character sets) to store references to its child nodes, which represent characters. Each node also includes a boolean flag to indicate whether the current node marks the end of a valid word. The Trie starts with a root node that does not hold any character and serves as the entry point for all operations. The child nodes of the root and subsequent nodes represent unique characters from the words stored in the Trie, forming a hierarchical structure based on the prefixes of the words.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    To insert a word, we iterate through the characters of the word with index <code>i</code>, starting at the root of the Trie as the current node. If the current node already contains <code>word[i]</code>, we continue to the next character and move to the node that <code>word[i]</code> points to. If <code>word[i]</code> is not present, we create a new node for <code>word[i]</code> and continue the process until we reach the end of the word. We mark the boolean variable as true as it is the end of the inserted word.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    Searching for a word is similar to inserting, but instead of creating new nodes, we return <code>false</code> if we don't find a character in the path while iterating or if the end-of-word marker is not set to <code>true</code> when we reach the end of the word.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/insert-new-interval.md b/hints/insert-new-interval.md
new file mode 100644
index 000000000..a807b4c61
--- /dev/null
+++ b/hints/insert-new-interval.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(1)</code> extra space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    The given intervals are non-overlapping and sorted in ascending order based on the start value. Try to visualize them as line segments and consider how a new interval can be inserted. Maybe you should analyze different cases of inserting a new interval.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    First, we append all intervals to the output list that have an end value smaller than the start value of the new interval. Then, we encounter one of three cases: we have appended all intervals, we reach an interval whose start value is greater than the new interval’s end, or we find an overlapping interval. Can you think of a way to handle these cases efficiently?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We iterate through the remaining intervals, updating the new interval if its end value is greater than or equal to the current interval's start value. We adjust the start and end of the new interval to the minimum and maximum values, respectively. After this, any remaining intervals are appended to the output list, and we return the result.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/interleaving-string.md b/hints/interleaving-string.md
new file mode 100644
index 000000000..16a8c100a
--- /dev/null
+++ b/hints/interleaving-string.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(m * n)</code> time and <code>O(m * n)</code> space, where <code>m</code> is the length of the string <code>s1</code> and <code>n</code> is the length of the string <code>s2</code>.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    If the sum of the characters in <code>s1</code> and <code>s2</code> does not equal <code>s3</code>, we return <code>false</code>. Think in terms of recursion and visualize it as a decision tree, where we explore different combinations of portions from both strings. Can you determine the possible decisions at each recursion step?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We recursively iterate through the strings using indices <code>i</code>, <code>j</code>, and <code>k</code> for <code>s1</code>, <code>s2</code>, and <code>s3</code>, respectively. At each step, we extend the current path in two directions based on whether the <code>k</code>-th character of <code>s3</code> matches the current character of <code>s1</code> or <code>s2</code>. If any path returns <code>true</code>, we immediately return <code>true</code>. If <code>k</code> goes out of bounds, it means we have successfully formed the interleaved string, so we return <code>true</code>.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    This approach is exponential. Can you think of a way to optimize it? Since <code>k</code> depends on <code>i</code> and <code>j</code>, it can be treated as a constant, as we can derive <code>k</code> using <code>i + j</code>.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We can use memoization to cache the results of recursive calls and avoid redundant computations. Treating <code>i</code> and <code>j</code> as states, we can use a hash map or a <code>2D</code> array to store the results.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/invert-a-binary-tree.md b/hints/invert-a-binary-tree.md
new file mode 100644
index 000000000..eacb6582d
--- /dev/null
+++ b/hints/invert-a-binary-tree.md
@@ -0,0 +1,23 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the number of nodes in the tree.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    From the diagram, you can see that the left and right children of every node in the tree are swapped. Can you think of a way to achieve this recursively? Maybe an algorithm that is helpful to traverse the tree.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use the Depth First Search (DFS) algorithm. At each node, we swap its left and right children by swapping their pointers. This inverts the current node, but every node in the tree also needs to be inverted. To achieve this, we recursively visit the left and right children and perform the same operation. If the current node is <code>null</code>, we simply return.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/is-anagram.md b/hints/is-anagram.md
new file mode 100644
index 000000000..8454011d2
--- /dev/null
+++ b/hints/is-anagram.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n + m)</code> time and <code>O(1)</code> space, where <code>n</code> is the length of the string <code>s</code> and <code>m</code> is the length of the string <code>t</code>.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would be to sort the given strings and check for their equality. This would be an <code>O(nlogn + mlogm)</code> solution. Though this solution is acceptable, can you think of a better way without sorting the given strings?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    By the definition of the anagram, we can rearrange the characters. Does the order of characters matter in both the strings? Then what matters?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can just consider maintaining the frequency of each character. We can do this by having two separate hash tables for the two strings. Then, we can check whether the frequency of each character in string <code>s</code> is equal to that in string <code>t</code> and vice versa.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/is-palindrome.md b/hints/is-palindrome.md
new file mode 100644
index 000000000..697108060
--- /dev/null
+++ b/hints/is-palindrome.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(1)</code> space, where <code>n</code> is the length of the input string.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would be to create a copy of the string, reverse it, and then check for equality. This would be an <code>O(n)</code> solution with extra space. Can you think of a way to do this without <code>O(n)</code> space?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    Can you find the logic by observing the definition of pallindrome or from the brute force solution? 
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    A palindrome string is a string that is read the same from the start as well as from the end. This means the character at the start should match the character at the end at the same index. We can use the two pointer algorithm to do this efficiently.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/islands-and-treasure.md b/hints/islands-and-treasure.md
new file mode 100644
index 000000000..b7ef502de
--- /dev/null
+++ b/hints/islands-and-treasure.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(m * n)</code> time and <code>O(m * n)</code> space, where <code>m</code> is the number of rows and <code>n</code> is the number of columns in the given grid.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would be to iterate on each land cell and run a BFS from that cells to find the nearest treasure chest. This would be an <code>O((m * n)^2)</code> solution. Can you think of a better way? Sometimes it is not optimal to go from source to destination.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can see that instead of going from every cell to find the nearest treasure chest, we can do it in reverse. We can just do a BFS from all the treasure chests in grid and just explore all possible paths from those chests. Why? Because in this approach, the treasure chests self mark the cells level by level and the level number will be the distance from that cell to a treasure chest. We don't revisit a cell. This approach is called <code>Multi-Source BFS</code>. How would you implement it?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We insert all the cells <code>(row, col)</code> that represent the treasure chests into the queue. Then, we process the cells level by level, handling all the current cells in the queue at once. For each cell, we mark it as visited and store the current level value as the distance at that cell. We then try to add the neighboring cells (adjacent cells) to the queue, but only if they have not been visited and are land cells.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/jump-game-ii.md b/hints/jump-game-ii.md
new file mode 100644
index 000000000..4c7c41e30
--- /dev/null
+++ b/hints/jump-game-ii.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(1)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force approach would be to recursively explore all paths from index <code>0</code> to its reachable indices, then process those indices similarly and return the minimum steps to reach the last index. This would be an exponential approach. Can you think of a better way? Maybe a greedy approach works.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We maintain two pointers, <code>l</code> and <code>r</code>, initially set to <code>0</code>, representing the range of reachable indices. At each step, we iterate through the indices in the range <code>l</code> to <code>r</code> and determine the farthest index that can be reached from the current range.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We then update the pointers <code>l</code> and <code>r</code> to the next range, setting <code>l</code> to <code>r + 1</code> and <code>r</code> to the farthest index reachable from the current range. We continue this process until the pointers go out of bounds.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    The number of steps taken represents the minimum steps required to reach the last index, as it is guaranteed that we can reach it.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/jump-game.md b/hints/jump-game.md
new file mode 100644
index 000000000..91e7092c9
--- /dev/null
+++ b/hints/jump-game.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(1)</code> space, where <code>n</code> is the size of input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force approach would be to recursively explore all paths from index <code>0</code> to its reachable indices, then process those indices similarly, returning <code>true</code> if we reach the last index. This would be an exponential approach. Can you think of a better way? Maybe a greedy approach works.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    Instead of processing the array from index <code>0</code>, start from the last index. Let the target index be <code>goal = n - 1</code>. Iterate in reverse from index <code>n - 2</code>.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    At each iteration, we check whether the current index can reach <code>goal</code>. If it can, we update <code>goal</code> to the current index, as reaching the current index means we can also reach the <code>goal</code>.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    To determine if we can reach the last index, the <code>goal</code> should be <code>0</code> after the iteration. Otherwise, reaching the last index is not possible.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/k-closest-points-to-origin.md b/hints/k-closest-points-to-origin.md
new file mode 100644
index 000000000..277e19160
--- /dev/null
+++ b/hints/k-closest-points-to-origin.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(nlogk)</code> time and <code>O(k)</code> space, where <code>n</code> is the size of the input array, and <code>k</code> is the number of points to be returned.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A naive solution would be to sort the array in ascending order based on the distances of the points from the origin <code>(0, 0)</code> and return the first <code>k</code> points. This would take <code>O(nlogn)</code> time. Can you think of a better way? Perhaps you could use a data structure that maintains only <code>k</code> points and allows efficient insertion and removal. 
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use a Max-Heap that keeps the maximum element at its top and allows retrieval in <code>O(1)</code> time. This data structure is ideal because we need to return the <code>k</code> closest points to the origin. By maintaining only <code>k</code> points in the heap, we can efficiently remove the farthest point when the size exceeds <code>k</code>. How would you implement this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We initialize a Max-Heap that orders points based on their distances from the origin. Starting with an empty heap, we iterate through the array of points, inserting each point into the heap. If the size of the heap exceeds <code>k</code>, we remove the farthest point (the maximum element in the heap). After completing the iteration, the heap will contain the <code>k</code> closest points to the origin. Finally, we convert the heap into an array and return it. 
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/kth-largest-element-in-an-array.md b/hints/kth-largest-element-in-an-array.md
new file mode 100644
index 000000000..8d68feba3
--- /dev/null
+++ b/hints/kth-largest-element-in-an-array.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(nlogk)</code> time and <code>O(k)</code> space, where <code>n</code> is the size of the input array, and <code>k</code> represents the rank of the largest number to be returned (i.e., the <code>k-th</code> largest element).
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A naive solution would be to sort the array in descending order and return the <code>k-th</code> largest element. This would be an <code>O(nlogn)</code> solution. Can you think of a better way? Maybe you should think of a data structure which can maintain only the top <code>k</code> largest elements.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use a Min-Heap, which stores elements and keeps the smallest element at its top. When we add an element to the Min-Heap, it takes <code>O(logk)</code> time since we are storing <code>k</code> elements in it. Retrieving the top element (the smallest in the heap) takes <code>O(1)</code> time. How can this be useful for finding the <code>k-th</code> largest element?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    The <code>k-th</code> largest element is the smallest element among the top <code>k</code> largest elements. This means we only need to maintain <code>k</code> elements in our Min-Heap to efficiently determine the <code>k-th</code> largest element. Whenever the size of the Min-Heap exceeds <code>k</code>, we remove the smallest element by popping from the heap. How do you implement this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We initialize an empty Min-Heap. We iterate through the array and add elements to the heap. When the size of the heap exceeds <code>k</code>, we pop from the heap and continue. After the iteration, the top element of the heap is the <code>k-th</code> largest element. 
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/kth-largest-integer-in-a-stream.md b/hints/kth-largest-integer-in-a-stream.md
new file mode 100644
index 000000000..2d7d952e8
--- /dev/null
+++ b/hints/kth-largest-integer-in-a-stream.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(mlogk)</code> time and <code>O(k)</code> space, where <code>m</code> is the number of times <code>add()</code> is called, and <code>k</code> represents the rank of the largest number to be tracked (i.e., the <code>k-th</code> largest element).
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would involve sorting the array in every time a number is added using <code>add()</code>, and then returning the <code>k-th</code> largest element. This would take <code>O(m * nlogn)</code> time, where <code>m</code> is the number of calls to <code>add()</code> and <code>n</code> is the total number of elements added. However, do we really need to track all the elements added, given that we only need the <code>k-th</code> largest element? Maybe you should think of a data structure which can maintain only the top <code>k</code> largest elements.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use a Min-Heap, which stores elements and keeps the smallest element at its top. When we add an element to the Min-Heap, it takes <code>O(logk)</code> time since we are storing <code>k</code> elements in it. Retrieving the top element (the smallest in the heap) takes <code>O(1)</code> time. How can this be useful for finding the <code>k-th</code> largest element?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    The <code>k-th</code> largest element is the smallest element among the top <code>k</code> largest elements. This means we only need to maintain <code>k</code> elements in our Min-Heap to efficiently determine the <code>k-th</code> largest element. Whenever the size of the Min-Heap exceeds <code>k</code>, we remove the smallest element by popping from the heap. How do you implement this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We initialize a Min-Heap with the elements of the input array. When the <code>add()</code> function is called, we insert the new element into the heap. If the heap size exceeds <code>k</code>, we remove the smallest element (the root of the heap). Finally, the top element of the heap represents the <code>k-th</code> largest element and is returned.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/kth-smallest-integer-in-bst.md b/hints/kth-smallest-integer-in-bst.md
new file mode 100644
index 000000000..2af2e63de
--- /dev/null
+++ b/hints/kth-smallest-integer-in-bst.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the number of nodes in the given tree.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A naive solution would be to store the node values in an array, sort it, and then return the <code>k-th</code> value from the sorted array. This would be an <code>O(nlogn)</code> solution due to sorting. Can you think of a better way? Maybe you should try one of the traversal technique.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use the Depth First Search (DFS) algorithm to traverse the tree. Since the tree is a Binary Search Tree (BST), we can leverage its structure and perform an in-order traversal, where we first visit the left subtree, then the current node, and finally the right subtree. Why? Because we need the <code>k-th</code> smallest integer, and by visiting the left subtree first, we ensure that we encounter smaller nodes before the current node. How can you implement this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We keep a counter variable <code>cnt</code> to track the position of the current node in the ascending order of values. When <code>cnt == k</code>, we store the current node's value in a global variable and return. This allows us to identify and return the <code>k-th</code> smallest element during the in-order traversal.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/largest-rectangle-in-histogram.md b/hints/largest-rectangle-in-histogram.md
new file mode 100644
index 000000000..35976b385
--- /dev/null
+++ b/hints/largest-rectangle-in-histogram.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A rectangle has a height and a width. Can you visualize how rectangles are formed in the given input? Considering one bar at a time might help. We can try to form rectangles by going through every bar and current bar's height will be the height of the rectangle. How can you determine the width of the rectangle for the current bar being the height of the rectangle? Extending the current bar to the left and right might help determine the rectangle's width.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    For a bar with height <code>h</code>, try extending it to the left and right. We can see that we can't extend further when we encounter a bar with a smaller height than <code>h</code>. The width will be the number of bars within this extended range. A brute force solution would be to go through every bar and find the area of the rectangle it can form by extending towards the left and right. This would be an <code>O(n^2)</code> solution. Can you think of a better way? Maybe precomputing the left and right boundaries might be helpful.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">
+    <summary>Hint 3</summary>
+    <p>
+    The left and right boundaries are the positions up to which we can extend the bar at index <code>i</code>. The area of the rectangle will be <code>height[i] * (right - left + 1)</code>, which is the general formula for <code>height * width</code>. These boundaries are determined by the first smaller bars encountered to the left and right of the current bar. How can we find the left and right boundaries now? Maybe a data structure is helpful.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We can use a stack with a monotonically strictly increasing nature, but instead of storing values, we store indices in the stack and perform operations based on the values at those indices. The top of the stack will represent the smaller bar that we encounter while extending the current bar. To find the left and right boundaries, we perform this algorithm from left to right and vice versa, storing the boundaries. Then, we iterate through the array to find the area for each bar and return the maximum area we get.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/last-stone-weight.md b/hints/last-stone-weight.md
new file mode 100644
index 000000000..5404da55d
--- /dev/null
+++ b/hints/last-stone-weight.md
@@ -0,0 +1,23 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(nlogn)</code> time and <code>O(n)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A naive solution would involve simulating the process by sorting the array at each step and processing the top <code>2</code> heaviest stones, resulting in an <code>O(n * nlogn)</code> time complexity. Can you think of a better way? Consider using a data structure that efficiently supports insertion and removal of elements and maintain the sorted order. 
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use a Max-Heap, which allows us to retrieve the maximum element in <code>O(1)</code> time. We initially insert all the weights into the Max-Heap, which takes <code>O(logn)</code> time per insertion. We then simulate the process until only one or no element remains in the Max-Heap. At each step, we pop two elements from the Max-Heap which takes <code>O(logn)</code> time. If they are equal, we do not insert anything back into the heap and continue. Otherwise, we insert the difference of the two elements back into the heap.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/level-order-traversal-of-binary-tree.md b/hints/level-order-traversal-of-binary-tree.md
new file mode 100644
index 000000000..e59c454b5
--- /dev/null
+++ b/hints/level-order-traversal-of-binary-tree.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the number of nodes in the given tree.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    The level of a tree refers to the nodes that are at equal distance from the root node. Can you think of an algorithm that traverses the tree level by level, rather than going deeper into the tree?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use the Breadth First Search (BFS) algorithm to traverse the tree level by level. BFS uses a queue data structure to achieve this. At each step of BFS, we only iterate over the queue up to its size at that step. Then, we take the left and right child pointers and add them to the queue. This allows us to explore all paths simultaneously.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    The number of times we iterate the queue corresponds to the number of levels in the tree. At each step, we pop all nodes from the queue for the current level and add them collectively to the resultant array. This ensures that we capture all nodes at each level of the tree.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/linked-list-cycle-detection.md b/hints/linked-list-cycle-detection.md
new file mode 100644
index 000000000..04c8f4623
--- /dev/null
+++ b/hints/linked-list-cycle-detection.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(1)</code> space, where <code>n</code> is the length of the given list.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A naive approach would be to use a hash set, which takes <code>O(1)</code> time to detect duplicates. Although this solution is acceptable, it requires <code>O(n)</code> extra space. Can you think of a better solution that avoids using extra space? Maybe there is an efficient algorithm which uses two pointers.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use the fast and slow pointers technique, which is primarily used to detect cycles in a linked list. We iterate through the list using two pointers. The slow pointer moves one step at a time, while the fast pointer moves two steps at a time. If the list has a cycle, these two pointers will eventually meet. Why does this work?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    When there is no cycle in the list, the loop ends when the fast pointer becomes <code>null</code>. If a cycle exists, the fast pointer moves faster and continuously loops through the cycle. With each step, it reduces the gap between itself and the slow pointer by one node. For example, if the gap is <code>10</code>, the slow pointer moves by <code>1</code>, increasing the gap to <code>11</code>, while the fast pointer moves by <code>2</code>, reducing the gap to <code>9</code>. This process continues until the fast pointer catches up to the slow pointer, confirming a cycle.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/longest-common-subsequence.md b/hints/longest-common-subsequence.md
new file mode 100644
index 000000000..d25df25e5
--- /dev/null
+++ b/hints/longest-common-subsequence.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(m * n)</code> time and <code>O(m * n)</code> space, where <code>m</code> is the length of the string <code>text1</code> and <code>n</code> is the length of the string <code>text2</code>.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Try to think in terms of recursion and visualize it as a decision tree. Can you determine the possible decisions at each step? Maybe you should consider iterating through both strings recursively at the same time.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    At each recursion step, we have two choices: if the characters at the current indices of both strings match, we move both indices forward and extend the subsequence. Otherwise, we explore two paths by advancing one index at a time and recursively finding the longest subsequence. We return the maximum length between these two choices. This approach is exponential. Can you think of a way to optimize it?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We return <code>0</code> if either index goes out of bounds. To optimize, we can use memoization to cache recursive call results and avoid redundant calculations. A hash map or a <code>2D</code> array can be used to store these results.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/longest-consecutive-sequence.md b/hints/longest-consecutive-sequence.md
new file mode 100644
index 000000000..7065b8463
--- /dev/null
+++ b/hints/longest-consecutive-sequence.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would be to consider every element from the array as the start of the sequence and count the length of the sequence formed with that starting element. This would be an <code>O(n^2)</code> solution. Can you think of a better way?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    Is there any way to identify the start of a sequence? For example, in <code>[1, 2, 3, 10, 11, 12]</code>, only <code>1</code> and <code>10</code> are the beginning of a sequence. Instead of trying to form a sequence for every number, we should only consider numbers like <code>1</code> and <code>10</code>.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can consider a number <code>num</code> as the start of a sequence if and only if <code>num - 1</code> does not exist in the given array. We iterate through the array and only start building the sequence if it is the start of a sequence. This avoids repeated work. We can use a hash set for <code>O(1)</code> lookups by converting the array to a hash set.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/longest-increasing-path-in-matrix.md b/hints/longest-increasing-path-in-matrix.md
new file mode 100644
index 000000000..8008fe73f
--- /dev/null
+++ b/hints/longest-increasing-path-in-matrix.md
@@ -0,0 +1,23 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(m * n)</code> time and <code>O(m * n)</code> space, where <code>m</code> is the number of rows and <code>n</code> is the number of columns in the given matrix.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    If we move from one cell to an adjacent cell with a greater value, we won't revisit a cell, as the path is strictly increasing. A brute force approach would be to run a <code>dfs</code> from every cell and return the longest path found. This approach is exponential. Can you think of a way to optimize it to avoid redundant calculations?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use memoization to cache the results of recursive calls and avoid redundant computations. A hash map or a <code>2D</code> array can be used to store these results.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/longest-increasing-subsequence.md b/hints/longest-increasing-subsequence.md
new file mode 100644
index 000000000..36a4e3e78
--- /dev/null
+++ b/hints/longest-increasing-subsequence.md
@@ -0,0 +1,47 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(n ^ 2)</code> time and <code>O(n ^ 2)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A subsequence is formed by selecting elements while maintaining their order. Using recursion, we can generate all subsequences. The recursive function returns the length of the longest increasing subsequence up to index <code>i</code>, processing from left to right. At each step, we decide whether to include or exclude the current element.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    Since the sequence must be increasing, we represent choices by adding <code>1</code> when including an element and <code>0</code> when excluding it. In recursion, how can we ensure the current element is greater than the previous one? Perhaps additional information is needed to process it.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can store the index of the previously chosen element as <code>j</code>, making it easier to process the current element at index <code>i</code>. If and only if <code>j == -1</code> or <code>nums[i] > nums[j]</code>, we include the current element and extend the recursive path. Can you determine the recurrence relation? At most, two recursive calls are made at each recursion step.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We stop the recursion when index <code>i</code> goes out of bounds and return <code>0</code> since no more elements can be added. The initial recursion call starts with <code>j = -1</code>. At each step, we include the current element if it is greater than the previous one and continue the recursion, or we exclude it and explore the next possibility. We return the maximum value obtained from both paths.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 5</summary>
+    <p>
+    The time complexity of this approach is exponential. We can use memoization to store results of recursive calls and avoid recalculations. A hash map or a <code>2D</code> array can be used to cache these results.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/longest-palindromic-substring.md b/hints/longest-palindromic-substring.md
new file mode 100644
index 000000000..9d4dc9eb9
--- /dev/null
+++ b/hints/longest-palindromic-substring.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(n^2)</code> time and <code>O(1)</code> space, where <code>n</code> is the length of the given string.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute-force solution would be to check if every substring is a palindrome and return the maximum length among all the palindromic substring lengths. This would be an <code>O(n^3)</code> time solution. Can you think of a better way? Perhaps you should consider thinking in terms of the center of a palindrome.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    Iterate over the string with index <code>i</code> and treat the current character as the center. For this character, try to extend outward to the left and right simultaneously, but only if both characters are equal. Update the result variable accordingly. How would you implement this? Can you consider both cases: even-length and odd-length palindromes?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    Maintain two variables, <code>resLen</code> and <code>res</code>, which denote the length of the longest palindrome and the start index of that palindrome, respectively. At each index, you can create an odd-length palindrome starting at that index extending outward from both its left and right indices, i.e., <code>i - 1</code> and <code>i + 1</code>. How can you find the even-length palindrome for this index? 
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    For an even-length palindrome, consider expanding from indices <code>i</code> and <code>i + 1</code>. This two-pointer approach, extending from the center of the palindrome, will help find all palindromic substrings in the given string. Update the two result variables and return the substring starting at <code>res</code> with a length of <code>resLen</code>.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/longest-repeating-substring-with-replacement.md b/hints/longest-repeating-substring-with-replacement.md
new file mode 100644
index 000000000..808ff742f
--- /dev/null
+++ b/hints/longest-repeating-substring-with-replacement.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(m)</code> space, where <code>n</code> is the length of the given string and <code>m</code> is the number of unique characters in the string.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Which characters would you replace in a string to make all its characters unique? Can you think with respect to the frequency of the characters?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    It is always optimal to replace characters with the most frequent character in the string. Why? Because using the most frequent character minimizes the number of replacements required to make all characters in the string identical. How can you find the number of replacements now?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    The number of replacements is equal to the difference between the length of the string and the frequency of the most frequent character in the string. A brute force solution would be to consider all substrings, use a hash map for frequency counting, and return the maximum length of the substring that has at most <code>k</code> replacements. This would be an <code>O(n^2)</code> solution. Can you think of a better way?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We can use the sliding window approach. The window size will be dynamic, and we will shrink the window when the number of replacements exceeds <code>k</code>. The result will be the maximum window size observed at each iteration.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/longest-substring-without-duplicates.md b/hints/longest-substring-without-duplicates.md
new file mode 100644
index 000000000..42c7ca28a
--- /dev/null
+++ b/hints/longest-substring-without-duplicates.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(m)</code> space, where <code>n</code> is the length of the string and <code>m</code> is the number of unique characters in the string.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would be to try the substring starting at index <code>i</code> and try to find the maximum length we can form without duplicates by starting at that index. we can use a hash set to detect duplicates in <code>O(1)</code> time. Can you think of a better way?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use the sliding window algorithm. Since we only care about substrings without duplicate characters, the sliding window can help us maintain valid substring with its dynamic nature.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can iterate through the given string with index <code>r</code> as the right boundary and <code>l</code> as the left boundary of the window. We use a hash set to check if the character is present in the window or not. When we encounter a character at index <code>r</code> that is already present in the window, we shrink the window by incrementing the <code>l</code> pointer until the window no longer contains any duplicates. Also, we remove characters from the hash set that are excluded from the window as the <code>l</code> pointer moves. At each iteration, we update the result with the length of the current window, <code>r - l + 1</code>, if this length is greater than the current result.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/lowest-common-ancestor-in-binary-search-tree.md b/hints/lowest-common-ancestor-in-binary-search-tree.md
new file mode 100644
index 000000000..b7357e2b3
--- /dev/null
+++ b/hints/lowest-common-ancestor-in-binary-search-tree.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(h)</code> time and <code>O(h)</code> space, where <code>h</code> is the height of the given tree.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A Binary Search Tree (BST) is a tree in which the values of all nodes in the left subtree of a node are less than the node's value, and the values of all nodes in the right subtree are greater than the node's value. Additionally, every subtree of a BST must also satisfy this property, meaning the "less than" or "greater than" condition is valid for all nodes in the tree, not just the root. How can you use this idea to find the LCA of the given nodes in the tree?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use recursion to traverse the tree. Can you figure out the conditions we encounter when choosing a path between the left and right subtrees during traversal using the values of the two given nodes? Perhaps you can determine the LCA by traversing based on these conditions.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    If nodes <code>p</code> and <code>q</code> are in different subtrees, a split occurs, making the current node the LCA. If both are in the left or right subtree, the LCA lies in that subtree and we further choose that subtree to traverse using recursion. You should also handle other multiple scenarios to get the LCA.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    The LCA can also be one of the nodes, <code>p</code> or <code>q</code>, if the current node is equal to either of them. This is because if we encounter either <code>p</code> or <code>q</code> during the traversal, that node is the LCA.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/lru-cache.md b/hints/lru-cache.md
new file mode 100644
index 000000000..7db2c01ef
--- /dev/null
+++ b/hints/lru-cache.md
@@ -0,0 +1,47 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(1)</code> time for each <code>put()</code> and <code>get()</code> function call and an overall space of <code>O(n)</code>, where <code>n</code> is the capacity of the <code>LRU</code> cache.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Can you think of a data structure for storing data in key-value pairs? Maybe a hash-based data structure with unique keys.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use a hash map which takes <code>O(1)</code> time to get and put the values. But, how can you deal with the least recently used to be removed criteria as a key is updated by the <code>put()</code> or recently used by the <code>get()</code> functions? Can you think of a data structure to store the order of values?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    A brute-force solution would involve maintaining the order of key-value pairs in an array list, performing operations by iterating through the list to erase and insert these key-value pairs. However, this would result in an <code>O(n)</code> time complexity. Can you think of a data structure that allows removing and reinserting elements in <code>O(1)</code> time?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We can use a doubly-linked list, which allows us to remove a node from the list when we have the address of that node. Can you think of a way to store these addresses so that we can efficiently remove or update a key when needed?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 5</summary>
+    <p>
+    We can use a doubly linked list where key-value pairs are stored as nodes, with the least recently used (LRU) node at the head and the most recently used (MRU) node at the tail. Whenever a key is accessed using <code>get()</code> or <code>put()</code>, we remove the corresponding node and reinsert it at the tail. When the cache reaches its capacity, we remove the LRU node from the head of the list. Additionally, we use a hash map to store each key and the corresponding address of its node, enabling efficient operations in <code>O(1)</code> time. 
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/max-area-of-island.md b/hints/max-area-of-island.md
new file mode 100644
index 000000000..a8502e52a
--- /dev/null
+++ b/hints/max-area-of-island.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(m * n)</code> time and <code>O(m * n)</code> space, where <code>m</code> is the number of rows and <code>n</code> is the number of columns in the grid.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    An island is a group of <code>1</code>'s in which every <code>1</code> is reachable from any other <code>1</code> in that group. Can you think of an algorithm that can find the number of groups by visiting a group only once? Maybe there is a recursive way of doing it.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use the Depth First Search (DFS) algorithm to traverse each group by starting at a cell with <code>1</code> and recursively visiting all the cells that are reachable from that cell and are also <code>1</code>. Can you think about how to find the area of that island? How would you implement this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We traverse the grid, and when we encounter a <code>1</code>, we initialize a variable <code>area</code>. We then start a DFS from that cell to visit all connected <code>1</code>'s recursively, marking them as <code>0</code> to indicate they are visited. At each recursion step, we increment <code>area</code>. After completing the DFS, we update <code>maxArea</code>, which tracks the maximum area of an island in the grid, if <code>maxArea < area</code>. Finally, after traversing the grid, we return <code>maxArea</code>.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/max-water-container.md b/hints/max-water-container.md
new file mode 100644
index 000000000..02fb8859b
--- /dev/null
+++ b/hints/max-water-container.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(1)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would be to try all pairs of bars in the array, compute the water for each pair, and return the maximum water among all pairs. This would be an <code>O(n^2)</code> solution. Can you think of a better way?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    Can you think of an algorithm that runs in linear time and is commonly used in problems that deal with pairs of numbers? Find a formula to calculate the amount of water when we fix two heights.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can use the two pointer algorithm. One pointer is at the start and the other at the end. At each step, we calculate the amount of water using the formula <code>(j - i) * min(heights[i], heights[j])</code>. Then, we move the pointer that has the smaller height value. Can you think why we only move the pointer at smaller height?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    In the formula, the amount of water depends only on the minimum height. Therefore, it is appropriate to replace the smaller height value.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/maximum-product-subarray.md b/hints/maximum-product-subarray.md
new file mode 100644
index 000000000..d46997d32
--- /dev/null
+++ b/hints/maximum-product-subarray.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(1)</code> space, where  <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would be to find the product for every subarray and then return the maximum among all the products. This would be an <code>O(n ^ 2)</code> approach. Can you think of a better way? Maybe you should think of a dynamic programming approach.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    Try to identify a pattern by finding the maximum product for an array with two elements and determining what values are needed when increasing the array size to three. Perhaps you only need two values when introducing a new element.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We maintain both the minimum and maximum product values and update them when introducing a new element by considering three cases: starting a new subarray, multiplying with the previous max product, or multiplying with the previous min product. The max product is updated to the maximum of these three, while the min product is updated to the minimum. We also track a global max product for the result. This approach is known as Kadane's algorithm.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/maximum-subarray.md b/hints/maximum-subarray.md
new file mode 100644
index 000000000..f8071b628
--- /dev/null
+++ b/hints/maximum-subarray.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(1)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force approach would be to compute the sum of every subarray and return the maximum among them. This would be an <code>O(n^2)</code> approach. Can you think of a better way? Maybe you should consider a dynamic programming-based approach.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    Instead of calculating the sum for every subarray, try maintaining a running sum. Maybe you should consider whether extending the previous sum or starting fresh with the current element gives a better result. Can you think of a way to track this efficiently?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We use a variable <code>curSum</code> to track the sum of the elements. At each index, we have two choices: either add the current element to <code>curSum</code> or start a new subarray by resetting <code>curSum</code> to the current element. Maybe you should track the maximum sum at each step and update the global maximum accordingly.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    This algorithm is known as Kadane's algorithm.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/median-of-two-sorted-arrays.md b/hints/median-of-two-sorted-arrays.md
new file mode 100644
index 000000000..bfbe9c032
--- /dev/null
+++ b/hints/median-of-two-sorted-arrays.md
@@ -0,0 +1,47 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(log(min(n, m)))</code> time and <code>O(1)</code> space, where <code>n</code> is the size of <code>nums1</code> and <code>m</code> is the size of <code>nums2</code>.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would be to create a new array by merging elements from both arrays, then sorting it and returning the median. This would be an <code>O(n + m)</code> solution. Can you think of a better way? Maybe you can use the criteria of both the arrays being sorted in ascending order.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    Suppose we merged both arrays. Then, we would have <code>half = (m + n) / 2</code> elements to the left of the median. So, without merging, is there any way to use this information to find the median? You can leverage the fact that the arrays are sorted. Consider the smaller array between the two and use binary search to find the correct partition between the two arrays, which will allow you to directly find the median without fully merging the arrays. How will you implement this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We will always try to keep array <code>A</code> smaller and interchange it with array <code>B</code> if <code>len(A) > len(B)</code>. Now, we perform binary search on the number of elements we will choose from array <code>A</code>. It is straightforward that when we choose <code>x</code> elements from array <code>A</code>, we have to choose <code>half - x</code> elements from array <code>B</code>. But we should also ensure that this partition is valid. How can we do this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p> 
+    When we do a partition for both arrays, we should ensure that the maximum elements from the left partitions of both arrays are smaller than or equal to the minimum elements of the right partitions of both the arrays. This will ensure that the partition is valid, and we can then find the median. We can find the min or max of these partitions in <code>O(1)</code> as these partitions are sorted in ascending order. Why does this work?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 5</summary>
+    <p>
+    For example, consider the arrays <code>A = [1, 2, 3, 4, 5]</code> and <code>B = [1, 2, 3, 4, 5, 6, 7, 8]</code>. When we select <code>x = 2</code>, we take <code>4</code> elements from array <code>B</code>. However, this partition is not valid because value <code>4</code> from the left partition of array <code>B</code> is greater than the value <code>3</code> from the right partition of array <code>A</code>. So, we should try to take more elements from array <code>A</code> to make the partition valid. Binary search will eventually help us find a valid partition.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/meeting-schedule-ii.md b/hints/meeting-schedule-ii.md
new file mode 100644
index 000000000..1342e260f
--- /dev/null
+++ b/hints/meeting-schedule-ii.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(nlogn)</code> time and <code>O(n)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Try to visualize the meetings as line segments on a number line representing start and end times. The number of rooms required is the maximum number of overlapping meetings at any point on the number line. Can you think of a way to determine this efficiently?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We create two arrays, start and end, containing the start and end times of all meetings, respectively. After sorting both arrays, we use a two-pointer based approach. How do you implement this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We use two pointers, <code>s</code> and <code>e</code>, for the start and end arrays, respectively. We also maintain a variable <code>count</code> to track the current number of active meetings. At each iteration, we increment <code>s</code> while the start time is less than the current end time and increase <code>count</code>, as these meetings must begin before the earliest ongoing meeting ends.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    Then, we increment <code>e</code> and decrement <code>count</code> as a meeting has ended. At each step, we update the result with the maximum value of active meetings stored in <code>count</code>.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/meeting-schedule.md b/hints/meeting-schedule.md
new file mode 100644
index 000000000..0216b7b66
--- /dev/null
+++ b/hints/meeting-schedule.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(nlogn)</code> time and <code>O(n)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    If two intervals are sorted in ascending order by their start values, they overlap if the start value of the second interval is less than the end value of the first interval. And these are called overlapping intervals.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    A brute force approach would be to check every pair of intervals and return <code>false</code> if any overlap is found. This would be an <code>O(n^2)</code> solution. Can you think of a better way? Maybe you should visualize the given intervals as line segments.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We should sort the given intervals based on their start values, as this makes it easier to check for overlaps by comparing adjacent intervals. We then iterate through the intervals from left to right and return <code>false</code> if any adjacent intervals overlap.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/merge-intervals.md b/hints/merge-intervals.md
new file mode 100644
index 000000000..89af36fe5
--- /dev/null
+++ b/hints/merge-intervals.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(nlogn)</code> time and <code>O(n)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Sorting the given intervals in ascending order based on their start values is beneficial, as it helps in identifying overlapping intervals efficiently. How can you determine if two intervals overlap?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    If two intervals are sorted in ascending order by their start values, they overlap if the start value of the second interval is less than or equal to the end value of the first interval.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We iterate through the sorted intervals from left to right, starting with the first interval in the output list. From the second interval onward, we compare each interval with the last appended interval. Can you determine the possible cases for this comparison?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    The two cases are: if the current interval overlaps with the last appended interval, we update its end value to the maximum of both intervals' end values and continue. Otherwise, we append the current interval and proceed.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/merge-k-sorted-linked-lists.md b/hints/merge-k-sorted-linked-lists.md
new file mode 100644
index 000000000..aec8ab73a
--- /dev/null
+++ b/hints/merge-k-sorted-linked-lists.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(n * k)</code> time and <code>O(1)</code> space, where <code>k</code> is the total number of lists and <code>n</code> is the total number of nodes across all lists.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute-force solution would involve storing all <code>n</code> nodes in an array, sorting them, and converting the array back into a linked list, resulting in an <code>O(nlogn)</code> time complexity. Can you think of a better way? Perhaps consider leveraging the idea behind merging two sorted linked lists. 
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can merge two sorted linked lists without using any extra space. To handle <code>k</code> sorted linked lists, we can iteratively merge each linked list with a resultant merged list. How can you implement this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We iterate through the list array with index <code>i</code>, starting at <code>i = 1</code>. We merge the linked lists using <code>mergeTwoLists(lists[i], lists[i - 1])</code>, which returns the head of the merged list. This head is stored in <code>lists[i]</code>, and the process continues. Finally, the merged list is obtained at the last index, and we return its head.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/merge-triplets-to-form-target.md b/hints/merge-triplets-to-form-target.md
new file mode 100644
index 000000000..fd475aa48
--- /dev/null
+++ b/hints/merge-triplets-to-form-target.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(1)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    An important observation is that we can ignore triplets with values greater than the target triplet.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    Specifically, if a triplet <code>t</code> has any element greater than the corresponding value in <code>target</code> (i.e., <code>t[0] > target[0]</code>, <code>t[1] > target[1]</code>, or <code>t[2] > target[2]</code>), we can discard it. This is because using such a triplet in operations would exceed the target values, making it invalid.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    Now, from the remaining valid triplets, we only need to check whether the target triplet values exist. Since all values in the valid triplets are less than or equal to the corresponding values in the target triplet, finding the target triplet among them guarantees that we can achieve it.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/merge-two-sorted-linked-lists.md b/hints/merge-two-sorted-linked-lists.md
new file mode 100644
index 000000000..5fbfafd3c
--- /dev/null
+++ b/hints/merge-two-sorted-linked-lists.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n + m)</code> time and <code>O(1)</code> space, where <code>n</code> is the length of <code>list1</code> and <code>m</code> is the length of <code>list2</code>.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would involve storing the values of both linked lists in an array, sorting the array, and then converting it back into a linked list. This approach would use <code>O(n)</code> extra space and is trivial. Can you think of a better way? Perhaps the sorted nature of the lists can be leveraged.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We create a dummy node to keep track of the head of the resulting linked list while iterating through the lists. Using <code>l1</code> and <code>l2</code> as iterators for <code>list1</code> and <code>list2</code>, respectively, we traverse both lists node by node to build a final linked list that is also sorted. How do you implement this?
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    For example, consider <code>list1 = [1, 2, 3]</code> and <code>list2 = [2, 3, 4]</code>. While iterating through the lists, we move the pointers by comparing the node values from both lists. We link the next pointer of the iterator to the node with the smaller value. For instance, when <code>l1 = 1</code> and <code>l2 = 2</code>, since <code>l1 < l2</code>, we point the iterator's next pointer to <code>l1</code> and proceed.
+    </p>
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/min-cost-climbing-stairs.md b/hints/min-cost-climbing-stairs.md
new file mode 100644
index 000000000..258121826
--- /dev/null
+++ b/hints/min-cost-climbing-stairs.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the number of steps on the staircase.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Can you find the recurrence relation to solve the problem, given that at each step we have two options: going one step or two steps? Consider drawing a decision tree where we branch into two paths at each step. By exploring every path, we can get the minimum cost. However, this results in an <code>O(2^n)</code> time solution. Can you think of a better approach? Is there any repeated work in the decision tree that we can optimize?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    The recurrence relation can be expressed as <code>cost[i] + min(dfs(i + 1), dfs(i + 2))</code>, where <code>i</code> is the current position and <code>dfs</code> is the recursive function. To avoid recalculating the result of a recursive call multiple times, we can use Memoization. Initialize a <code>cache</code> array of size <code>n</code>, where <code>n</code> is the number of steps on the staircase. How would you implement this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We start the recursion from positions <code>0</code> and <code>1</code>. At each recursive step, before computing the result, we check if the result for the current position has already been calculated. If it has, we return the stored value. Otherwise, we calculate the result for the current position, store it in the cache, and then return the result. What can be the base condition for this recursion to stop?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    The base condition would be to return <code>0</code> if we are at the top of the staircase <code>i >= n</code>. This is a one-dimensional dynamic programming problem. We can further optimize the memoization solution by using advanced techniques such as Bottom-Up dynamic programming based on the recurrance relation.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/min-cost-to-connect-points.md b/hints/min-cost-to-connect-points.md
new file mode 100644
index 000000000..cc585977d
--- /dev/null
+++ b/hints/min-cost-to-connect-points.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O((n^2)logn)</code> time and <code>O(n^2)</code> space, where <code>n</code> is the number of points.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Think of this problem as a graph, where the given points represent nodes. We need to connect these nodes into a single component by creating edges. Can you think of an advanced graph algorithm that can be used to connect all points into one component?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We use Kruskal's algorithm along with Union-Find (DSU) to connect nodes into components. The final component forms the minimum spanning tree (MST), where the edges between nodes are weighted by the Manhattan distance, and the total weight of the tree is minimized. How would you implement this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We create the possible edges by iterating through every pair of points and calculating the weights as the Manhattan distance between them. Next, we sort the edges in ascending order based on their weights, as we aim to minimize the cost. Then, we traverse through these edges, connecting the nodes and adding the weight of the edge to the total cost if the edge is successfully added. The final result will be the minimum cost.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/minimum-interval-including-query.md b/hints/minimum-interval-including-query.md
new file mode 100644
index 000000000..9b56faba2
--- /dev/null
+++ b/hints/minimum-interval-including-query.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(nlogn + mlogm)</code> time and <code>O(n + m)</code> space, where <code>m</code> is the size of the array <code>queries</code> and <code>n</code> is the size of the array <code>intervals</code>.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force approach would be to iterate through each query and, for each query, check all intervals to find the result. This would be an <code>O(m * n)</code> solution. Can you think of a better way? Maybe processing the queries in sorted order could help.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We sort the intervals by start value and process the queries in ascending order. Using a pointer <code>i</code>, we add intervals to a min-heap while their start values are less than or equal to the query, storing their end values and sizes.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    The min-heap is ordered by interval size. We remove elements from the heap while the top element’s end value is less than the current query. The result for the query is the top element’s size if the heap is non-empty; otherwise, it is <code>-1</code>.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/minimum-stack.md b/hints/minimum-stack.md
new file mode 100644
index 000000000..411e300dd
--- /dev/null
+++ b/hints/minimum-stack.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(1)</code> time for each function call and <code>O(n)</code> space, where <code>n</code> is the maximum number of elements present in the stack.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would be to always check for the minimum element in the stack for the <code>getMin()</code> function call. This would be an <code>O(n)</code> appraoch. Can you think of a better way? Maybe <code>O(n)</code> extra space to store some information. 
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use a stack to maintain the elements. But how can we find the minimum element at any given time? Perhaps we should consider a prefix approach.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We use an additional stack to maintain the prefix minimum element. When popping elements from the main stack, we should also pop from this extra stack. However, when pushing onto the extra stack, we should push the minimum of the top element of the extra stack and the current element onto this extra stack.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/minimum-window-with-characters.md b/hints/minimum-window-with-characters.md
new file mode 100644
index 000000000..3df37fff9
--- /dev/null
+++ b/hints/minimum-window-with-characters.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(m)</code> space, where <code>n</code> is the length of the string <code>s</code> and <code>m</code> is the number of unique characters in <code>s</code> and <code>t</code>.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would involve checking every substring of <code>s</code> against <code>t</code> and returning the minimum length valid substring. This would be an <code>O(n^2)</code> solution. Can you think of a better way? Maybe you should think in terms of frequency of characters.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We need to find substrings in <code>s</code> that should have atleast the characters of <code>t</code>. We can use hash maps to maintain the frequencies of characters. It will be <code>O(1)</code> for lookups. Can you think of an algorithm now?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can use a dynamically sized sliding window approach on <code>s</code>. We iterate through <code>s</code> while maintaining a window. If the current window contains at least the frequency of characters from <code>t</code>, we update the result and shrink the window until it is valid. 
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We should ensure that we maintain the result substring and only update it if we find a shorter valid substring. Additionally, we need to keep track of the result substring's length so that we can return an empty string if no valid substring is found.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/missing-number.md b/hints/missing-number.md
new file mode 100644
index 000000000..2d5f6908b
--- /dev/null
+++ b/hints/missing-number.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(1)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force approach would iterate through the range of numbers from <code>0</code> to <code>n</code>, checking if each number is present in the given array. If a number is missing, it is returned. This results in an <code>O(n^2)</code> solution. Can you think of a better way? Maybe a data structure could help optimize this process.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use a hash set by inserting the given array elements into it. Then, we iterate through the range of numbers from <code>0</code> to <code>n</code> and use the hash set for <code>O(1)</code> lookups to find the missing number. Can you think of a way to further optimize this? Maybe a bitwise operator could be useful.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can use bitwise XOR. When two identical numbers are XORed, the result is <code>0</code>. Using this property, we can efficiently find the missing number.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We first compute the bitwise XOR of numbers from <code>0</code> to <code>n</code>. Then, we iterate through the array and XOR its elements as well. The missing number remains in the final XOR result since all other numbers appear twice—once in the range and once in the array—while the missing number is XORed only once.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/multiply-strings.md b/hints/multiply-strings.md
new file mode 100644
index 000000000..193cc4c27
--- /dev/null
+++ b/hints/multiply-strings.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(m*n)</code> time and <code>O(m+n)</code> space, where <code>m</code> is the length of the string <code>num1</code> and <code>n</code> is the length of the string <code>num2</code>.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Implement a helper function that takes two number strings and returns their sum. Ensure that the length of <code>num1</code> is greater than <code>num2</code>, swapping them if necessary. Can you think of a way to multiply the strings? Maybe you should first consider basic multiplication, where <code>num1</code> is multiplied by each digit of <code>num2</code>.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    When multiplying <code>num1</code> with each digit of <code>num2</code>, we iterate through <code>num2</code> in reverse order. Based on the digit's position, we pad zeros to the multiplication result accordingly—no padding for the last digit, one zero for the second last, and so on. What should be the next step after each multiplication? Maybe you should implement a helper function to handle this.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We implement a helper function that takes <code>num1</code>, a digit, and a variable <code>zeroes</code>, returning the multiplication result with <code>zeroes</code> padded at the end. A global string <code>res</code> stores the final result.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    In the main function, we iterate through <code>num2</code> in reverse order, calling the helper function to multiply <code>num1</code> with the current digit and append the appropriate number of padding zeros. We then call another helper function that takes this multiplication result and the global result string <code>res</code>, adds them, and updates <code>res</code>.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/n-queens.md b/hints/n-queens.md
new file mode 100644
index 000000000..60c5f6fef
--- /dev/null
+++ b/hints/n-queens.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n!)</code> time and <code>O(n^2)</code> space, where <code>n</code> is the size of the given square board.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A queen can move in <code>8</code> directions, and no two queens can be in the same row or column. This means we can place one queen per row or column. We iterate column-wise and try to place a queen in each column while ensuring no other queen exists in the same row, left diagonal, or left bottom diagonal. Can you think of a recursive algorithm to find all possible combinations?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use backtracking to traverse through the columns with index <code>c</code> while maintaining a board that represents the current state in the recursive path. We reach the base condition when <code>c == n</code> and we add a copy of the board to the result. How would you implement this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We initialize an empty board and recursively go through each column. For each column, we check each cell to see if we can place a queen there. We use a function to check if the cell is suitable by iterating along the left directions and verifying if the same row, left diagonal, or left bottom diagonal are free. If it is possible, we place the queen on the board, move along the recursive path, and then backtrack by removing the queen to continue to the next cell in the column.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/network-delay-time.md b/hints/network-delay-time.md
new file mode 100644
index 000000000..901cefb98
--- /dev/null
+++ b/hints/network-delay-time.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(ElogV)</code> time and <code>O(V + E)</code> space, where <code>E</code> is the number of edges and <code>V</code> is the number of vertices (nodes).
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    As we are given the source node and we need to find the minimum time to reach all nodes, this represents the shortest path from the source node to all nodes. Can you think of a standard algorithm to find the shortest path from a source to a destination? Maybe a heap-based algorithm is helpful.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use Dijkstra's algorithm to find the shortest path from a source to destination. We end up finding the shortest paths from the source to the nodes that we encounter in finding the destination. So, to find shortest path for all nodes from the source, we need to perform Dijkstra's algorithm until the heap in this algorithm becomes empty. How would you implement this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We use a Min-Heap as we need to find the minimum time. We create an adjacency list for the given times (weighted edges). We also initialize an array <code>dist[]</code> of size <code>n</code> (number of nodes) which represents the distance from the source to all nodes, initialized with infinity. We put <code>dist[source] = 0</code>. Then we continue the algorithm. After the heap becomes empty, if we don't visit any node, we return <code>-1</code>; otherwise, we return the time.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/non-cyclical-number.md b/hints/non-cyclical-number.md
new file mode 100644
index 000000000..6672425b9
--- /dev/null
+++ b/hints/non-cyclical-number.md
@@ -0,0 +1,23 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(logn)</code> time and <code>O(logn)</code> space, where <code>n</code> is the given integer.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Create a helper function that returns the sum of the squares of a number's digits. Then, simulate the given process. If we reach <code>1</code>, return <code>true</code>. However, we may get stuck in a cycle if a number is processed more than once. What data structure can be used to detect if a number has already been processed?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use a hash set to detect if a number has already been processed. At each step, we update <code>n</code> with the return value of the helper function. If the result is <code>1</code>, we return <code>true</code>. If <code>n</code> is already in the set, we return <code>false</code>. Otherwise, we add <code>n</code> to the hash set and continue.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/non-overlapping-intervals.md b/hints/non-overlapping-intervals.md
new file mode 100644
index 000000000..1e07a9c0b
--- /dev/null
+++ b/hints/non-overlapping-intervals.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(nlogn)</code> time and <code>O(n)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    If two intervals are sorted in ascending order by their start values, they overlap if the start value of the second interval is less than the end value of the first interval. And these are called overlapping intervals.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    A brute force approach would be to sort the given intervals in ascending order based on their start values and recursively explore all possibilities. This would be an exponential approach. Can you think of a better way? Maybe a greedy approach works here.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We first sort the given intervals based on their start values to efficiently check for overlaps by comparing adjacent intervals. We then iterate through the sorted intervals from left to right, keeping track of the previous interval’s end value as <code>prevEnd</code>, initially set to the end value of the first interval.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We then iterate from the second interval. If the current interval doesn't overlap, we update <code>prevEnd</code> to the current interval's end and continue. Otherwise, we set <code>prevEnd</code> to the minimum of <code>prevEnd</code> and the current interval’s end, greedily removing the interval that ends last to retain as many intervals as possible.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/number-of-one-bits.md b/hints/number-of-one-bits.md
new file mode 100644
index 000000000..788499e2b
--- /dev/null
+++ b/hints/number-of-one-bits.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(1)</code> time and <code>O(1)</code> space.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    The given integer is a <code>32</code>-bit integer. Can you think of using bitwise operators to iterate through its bits? Maybe you should consider iterating <code>32</code> times.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We iterate <code>32</code> times <code>(0 to 31)</code> using index <code>i</code>. The expression <code>(1 << i)</code> creates a bitmask with a set bit at the <code>i</code>-th position. How can you check whether the <code>i</code>-th bit is set in the given number? Maybe you should consider using the bitwise-AND <code>("&")</code>.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    Since the mask has a set bit at the <code>i</code>-th position and all <code>0</code>s elsewhere, we can perform a bitwise-AND with <code>n</code>. If <code>n</code> has a set bit at the <code>i</code>-th position, the result is positive; otherwise, it is <code>0</code>. We increment the global count if the result is positive and return it after the iteration.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/pacific-atlantic-water-flow.md b/hints/pacific-atlantic-water-flow.md
new file mode 100644
index 000000000..6ed584779
--- /dev/null
+++ b/hints/pacific-atlantic-water-flow.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(m * n)</code> time and <code>O(m * n)</code> space, where <code>m</code> is the number of rows and <code>n</code> is the number of columns in the grid.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would be to traverse each cell in the grid and run a BFS from each cell to check if it can reach both oceans. This would result in an <code>O((m * n)^2)</code> solution. Can you think of a better way? Maybe you should consider a reverse way of traversing.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use the Depth First Search (DFS) algorithm starting from the border cells of the grid. However, we reverse the condition such that the next visiting cell should have a height greater than or equal to the current cell. For the top and left borders connected to the Pacific Ocean, we use a hash set called <code>pacific</code> and run a DFS from each of these cells, visiting nodes recursively. Similarly, for the bottom and right borders connected to the Atlantic Ocean, we use a hash set called <code>atlantic</code> and run a DFS. The required coordinates are the cells that exist in both the <code>pacific</code> and <code>atlantic</code> sets. How do you implement this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We perform DFS from the border cells, using their respective hash sets. During the DFS, we recursively visit the neighbouring cells that are unvisited and have height greater than or equal to the current cell's height and add the current cell's coordinates to the corresponding hash set. Once the DFS completes, we traverse the grid and check if a cell exists in both the hash sets. If so, we add that cell to the result list.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/palindrome-partitioning.md b/hints/palindrome-partitioning.md
new file mode 100644
index 000000000..a2d81783f
--- /dev/null
+++ b/hints/palindrome-partitioning.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n * (2^n))</code> time and <code>O(n)</code> space, where <code>n</code> is the length of the input string.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    For a given string there are <code>2^n</code> possible partitions because at each index we have two decisions: we can either partition and start a new string, or continue without partitioning. Can you think of an algorithm to recursively traverse all combinations?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use backtracking to recursively traverse the string with indices <code>j</code> (start of the current substring) and <code>i</code> (current iterating index). At each step, we either skip partitioning at the current index or, if the substring from <code>j</code> to <code>i</code> is a palindrome, make a partition, update <code>j = i + 1</code>, and start a new substring. The base condition to stop the recursion is when <code>j</code> reaches the end of the string. How do you implement this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We start with <code>j = 0</code>, <code>i = 0</code> and a temporary list which stores the substrings from the partitions. Then we recursively iterate the string with the index <code>i</code>. At each step we apply the <code>2</code> decisions accordingly. At the base condition of the recursive path, we make a copy of the current partition list and add it to the result.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/palindromic-substrings.md b/hints/palindromic-substrings.md
new file mode 100644
index 000000000..5e994313c
--- /dev/null
+++ b/hints/palindromic-substrings.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(n^2)</code> time and <code>O(1)</code> space, where <code>n</code> is the length of the given string.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute-force solution would be to check if every substring is a palindrome and return the total number of palindromic substrings. This would be an <code>O(n^3)</code> time solution. Can you think of a better way? Perhaps you should consider thinking in terms of the center of a palindrome.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    Iterate over the string with index <code>i</code> and treat the current character as the center. For this character, try to extend outward to the left and right simultaneously, but only if both characters are equal. At each iteration, we increment the count of palindromes. How would you implement this? Can you consider both cases: even-length and odd-length palindromes?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    Initialize a variable <code>res</code> to track the count of palindromes. At each index, create an odd-length palindrome starting at that index extending outward from both its left and right indices, i.e., <code>i - 1</code> and <code>i + 1</code>. How can you find the even-length palindrome for this index? 
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    For an even-length palindrome, consider expanding from indices <code>i</code> and <code>i + 1</code>. This two-pointer approach, extending from the center of the palindrome, will help find all palindromic substrings in the given string and return its count.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/partition-equal-subset-sum.md b/hints/partition-equal-subset-sum.md
new file mode 100644
index 000000000..6dfc98881
--- /dev/null
+++ b/hints/partition-equal-subset-sum.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(n * t)</code> time and <code>O(n * t)</code> space, where <code>n</code> is the size of the input array and <code>t</code> is half the sum of the array elements.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    If the sum of the array elements is not even, we can immediately return <code>false</code>. Think in terms of recursion, where we try to build a subset with a sum equal to half of the total sum. If we find such a subset, the remaining elements will automatically form another subset with the same sum. The entire array can also be considered as one subset, with the other being empty. Can you visualize this as a decision tree to process the array recursively?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We recursively iterate through the array with index <code>i</code>. At each step, we decide whether to include the current element in the subset or not. Instead of forming the subset explicitly, can you think of a better approach? Maybe you only need to track the subset sum rather than generating the subset itself.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can track the subset sum using a variable <code>curSum</code>. At each step, we make two recursive calls. If adding the current element does not exceed the target, we include it. If either path leads to a solution, we immediately return <code>true</code>. Can you determine the base case for this recursion? All elements in the array are positive.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    If <code>curSum</code> equals half the sum of the array elements, we return <code>true</code>. If index <code>i</code> goes out of bounds, we return <code>false</code>. This solution is exponential, but we can use memoization to cache recursive call results and avoid redundant computations. We can use a hash map or a <code>2D</code> array with dimensions <code>n * t</code>, where <code>n</code> is the size of the input array and <code>t</code> is half the sum of the input array elements.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/partition-labels.md b/hints/partition-labels.md
new file mode 100644
index 000000000..c5e3551bb
--- /dev/null
+++ b/hints/partition-labels.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(m)</code> space, where <code>n</code> is the length of the string <code>s</code> and <code>m</code> is the number of unique characters in the string <code>s</code>.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A character has a first and last index in the given string. Can you think of a greedy approach to solve this problem? Maybe you should try iterating over one of these two indices.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We store the last index of each character in a hash map or an array. As we iterate through the string, treating each index as a potential start of a partition, we track the end of the partition using the maximum last index of the characters seen so far in the current partition. Additionally, we maintain the size of the current partition using a variable, say <code>size</code>.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We update the end of the current partition based on the maximum last index of the characters, extending the partition as needed. When the current index reaches the partition’s end, we finalize the partition, append its size to the output list, reset the size to <code>0</code>, and continue the same process for the remaining string.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/permutation-string.md b/hints/permutation-string.md
new file mode 100644
index 000000000..5abcaddf0
--- /dev/null
+++ b/hints/permutation-string.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(1)</code> space, where <code>n</code> is the maximum of the lengths of the two strings.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would be to check every substring of <code>s2</code> with <code>s1</code> by sorting <code>s1</code> as well as the substring of <code>s2</code>. This would be an <code>O(n^2)</code> solution. Can you think of a better way? Maybe we can use the freqency of the characters of both the strings as we did in checking anagrams.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We return false if the length of <code>s1</code> is greater than the length of <code>s2</code>. To count the frequency of each character in a string, we can simply use an array of size <code>O(26)</code>, since the character set consists of <code>a</code> through <code>z</code> (<code>26</code> continuous characters). Which algorithm can we use now?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We use a sliding window approach on <code>s2</code> with a fixed window size equal to the length of <code>s1</code>. To track the current window, we maintain a running frequency count of characters in <code>s2</code>. This frequency count represents the characters in the current window. At each step, if the frequency count matches that of <code>s1</code>, we return <code>true</code>.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/permutations.md b/hints/permutations.md
new file mode 100644
index 000000000..3f3d59477
--- /dev/null
+++ b/hints/permutations.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n * n!)</code> time and <code>O(n)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A permutation is the same as the array but with the numbers arranged in a different order. The given array itself is also considered a permutation. This means we should make a decision at each step to take any element from the array that has not been chosen previously. By doing this recursively, we can generate all permutations. How do you implement it?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use backtracking to explore all possible permutation paths. We initialize a temporary list to append the chosen elements and a boolean array of size <code>n</code> (the same size as the input array) to track which elements have been picked so far (<code>true</code> means the element is chosen; otherwise, <code>false</code>). At each step of recursion, we iterate through the entire array, picking elements that have not been chosen previously, and proceed further along that path. Can you think of the base condition to terminate the current recursive path?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We observe that every permutation has the same size as the input array. Therefore, we can append a copy of the list of chosen elements in the current path to the result list if the size of the list equals the size of the input array terminating the current recursive path.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/plus-one.md b/hints/plus-one.md
new file mode 100644
index 000000000..ec62b78c9
--- /dev/null
+++ b/hints/plus-one.md
@@ -0,0 +1,23 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    There are two cases when adding <code>1</code> to a number. If the rightmost digit is less than <code>9</code>, we simply increment it. Otherwise, we set it to <code>0</code> and apply the same process to the preceding digit.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We iterate through the given <code>digits</code> from right to left using index <code>i</code>. If the current digit is less than <code>9</code>, we increment it and return the array. Otherwise, we set the digit to <code>0</code> and continue. If the loop completes without returning, we insert <code>1</code> at the beginning of the array and return it.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/pow-x-n.md b/hints/pow-x-n.md
new file mode 100644
index 000000000..de42350f0
--- /dev/null
+++ b/hints/pow-x-n.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(logn)</code> time and <code>O(logn)</code> space, where <code>n</code> is the given integer.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force approach would be to iterate linearly up to <code>n</code>, multiplying by <code>x</code> each time to find <code>(x^n)</code>. If <code>n</code> is negative, return <code>(1 / (x^n))</code>; otherwise, return <code>(x^n)</code>. Can you think of a better way? Maybe a recursive approach would be more efficient.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    For example, to calculate <code>2^6</code>, instead of multiplying <code>2</code> six times, we compute <code>2^3</code> and square the result. The same logic applies recursively to find <code>2^3</code> and further break down the multiplication. What should be the base case for this recursion? Maybe you should consider the term that cannot be further broken down.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    In <code>(x^n)</code>, if <code>x</code> is <code>0</code>, we return <code>0</code>. If <code>n</code> is <code>0</code>, we return <code>1</code>, as any number raised to the power of <code>0</code> is <code>1</code>. Otherwise, we compute <code>(x^(n/2))</code> recursively and square the result. If <code>n</code> is odd, we multiply the final result by <code>x</code>. What should be the logic if <code>n</code> is negative? 
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We start the recursion with the absolute value of <code>n</code>. After computing the result as <code>res</code>, we return <code>res</code> if <code>n</code> is non-negative; otherwise, we return <code>(1 / res)</code>. 
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/products-of-array-discluding-self.md b/hints/products-of-array-discluding-self.md
new file mode 100644
index 000000000..bab9964c9
--- /dev/null
+++ b/hints/products-of-array-discluding-self.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute-force solution would be to iterate through the array with index <code>i</code> and compute the product of the array except for that index element. This would be an <code>O(n^2)</code> solution. Can you think of a better way?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    Is there a way to avoid the repeated work? Maybe we can store the results of the repeated work in an array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can use the prefix and suffix technique. First, we iterate from left to right and store the prefix products for each index in a prefix array, excluding the current index's number. Then, we iterate from right to left and store the suffix products for each index in a suffix array, also excluding the current index's number. Can you figure out the solution from here? 
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We can use the stored prefix and suffix products to compute the result array by iterating through the array and simply multiplying the prefix and suffix products at each index.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/reconstruct-flight-path.md b/hints/reconstruct-flight-path.md
new file mode 100644
index 000000000..43f336c17
--- /dev/null
+++ b/hints/reconstruct-flight-path.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(ElogE)</code> time and <code>O(E)</code> space, where <code>E</code> is the number of tickets (edges).
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Consider this problem as a graph where airports are the nodes and tickets are the edges. Since we need to utilize all the tickets exactly once, can you think of an algorithm that visits every edge exactly once? Additionally, how do you ensure the smallest lexical order is maintained?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We build an adjacency list from the given tickets, which represent directed edges. We perform a DFS to construct the result, but we first sort the neighbors' list of each node to ensure the smallest lexical order. Why? Sorting guarantees that during DFS, we visit the node with the smallest lexical order first.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    DFS would be a naive solution, as it takes <code>O(E * V)</code> time, where <code>E</code> is the number of tickets (edges) and <code>V</code> is the number of airports (nodes). In this approach, we traverse from the given source airport <code>JFK</code>, perform DFS by removing the neighbor, traversing it, and then reinserting it back. Can you think of a better way? Perhaps an advanced algorithm that incorporates DFS might be helpful?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We can use Hierholzer's algorithm, a modified DFS approach. Instead of appending the node to the result list immediately, we first visit all its neighbors. This results in a post-order traversal. After completing all the DFS calls, we reverse the path to obtain the final path, which is also called Euler's path.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/redundant-connection.md b/hints/redundant-connection.md
new file mode 100644
index 000000000..cdd3217fe
--- /dev/null
+++ b/hints/redundant-connection.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(V + E)</code> time and <code>O(V + E)</code> space, where <code>V</code> is the number vertices and <code>E</code> is the number of edges in the graph.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    There will be only one edge that creates the cycle in the given problem. Why? Because the graph is initially acyclic, and a cycle is formed only after adding one extra edge that was not present in the graph initially. Can you think of an algorithm that helps determine whether the current connecting edge forms a cycle? Perhaps a component-oriented algorithm?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use the Union-Find (DSU) algorithm to create the graph from the given edges. While connecting the edges, if we fail to connect any edge, it means this is the redundant edge, and we return it. How would you implement this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We create an instance of the DSU object and traverse through the given edges. For each edge, we attempt to connect the nodes using the union function. If the union function returns <code>false</code>, indicating that the current edge forms a cycle, we immediately return that edge.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/regular-expression-matching.md b/hints/regular-expression-matching.md
new file mode 100644
index 000000000..e17c78964
--- /dev/null
+++ b/hints/regular-expression-matching.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(m * n)</code> time and <code>O(m * n)</code> space, where <code>m</code> is the length of the string <code>s</code> and <code>n</code> is the length of the string <code>p</code>. 
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Try to think in terms of recursion and visualize it as a decision tree, where we explore different combinations to match the strings when encountering <code>*</code>. Multiple decisions are made at each step to find a valid matching path. Can you determine the possible decisions at each recursion step?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We recursively iterate through the strings using indices <code>i</code> and <code>j</code> for <code>s</code> and <code>p</code>, respectively. If the characters match or <code>p[j]</code> is <code>'.'</code>, we increment both <code>i</code> and <code>j</code> to process the remaining strings. When the next character of string <code>p</code> is <code>'*'</code>, we have two choices: skip it (treating it as zero occurrences) or match one or more characters (if <code>s[i]</code> matches <code>p[j]</code>), incrementing <code>i</code> accordingly.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    If both indices go out of bounds, we return <code>true</code>; otherwise, we return <code>false</code>. If any recursive path returns <code>true</code>, we immediately return <code>true</code>. This approach is exponential. Can you think of a way to optimize it?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We can use memoization to cache the results of recursive calls and avoid redundant calculations. A hash map or a <code>2D</code> array can be used to store these results.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/remove-node-from-end-of-linked-list.md b/hints/remove-node-from-end-of-linked-list.md
new file mode 100644
index 000000000..d73855f6f
--- /dev/null
+++ b/hints/remove-node-from-end-of-linked-list.md
@@ -0,0 +1,47 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(N)</code> time and <code>O(1)</code> space, where <code>N</code> is the length of the given list.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would involve storing the nodes of the list into an array, removing the <code>nth</code> node from the array, and then converting the array back into a linked list to return the new head. However, this requires <code>O(N)</code> extra space. Can you think of a better approach to avoid using extra space? Maybe you should first solve with a two pass approach.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use a two-pass approach by first finding the length of the list, <code>N</code>. Since removing the <code>nth</code> node from the end is equivalent to removing the <code>(N - n)th</code> node from the front, as they both mean the same. How can you remove the node in a linked list? 
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    For example, consider a three-node list <code>[1, 2, 3]</code>. If we want to remove <code>2</code>, we update the <code>next</code> pointer of <code>1</code> (initially pointing to <code>2</code>) to point to the node after <code>2</code>, which is <code>3</code>. After this operation, the list becomes <code>[1, 3]</code>, and we return the head. But, can we think of a more better approach? Maybe a greedy calculation can help.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We can solve this in one pass using a greedy approach. Move the <code>first</code> pointer <code>n</code> steps ahead. Then, start another pointer <code>second</code> at the head and iterate both pointers simultaneously until <code>first</code> reaches <code>null</code>. At this point, the <code>second</code> pointer is just before the node to be removed. We then remove the node that is next to the <code>second</code> pointer. Why does this work?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 5</summary>
+    <p>
+    This greedy approach works because the <code>second</code> pointer is <code>n</code> nodes behind the <code>first</code> pointer. When the <code>first</code> pointer reaches the end, the <code>second</code> pointer is exactly <code>n</code> nodes from the end. This positioning allows us to remove the <code>nth</code> node from the end efficiently.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/reorder-linked-list.md b/hints/reorder-linked-list.md
new file mode 100644
index 000000000..299b6c081
--- /dev/null
+++ b/hints/reorder-linked-list.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(1)</code> space, where <code>n</code> is the length of the given list.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would be to store the node values of the list in an array, reorder the values, and create a new list. Can you think of a better way? Perhaps you can try reordering the nodes directly in place, avoiding the use of extra space.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    For example, consider the list <code>[1, 2, 3, 4, 5]</code>. To reorder the list, we connect the first and last nodes, then continue with the second and second-to-last nodes, and so on. Essentially, the list is split into two halves: the first half remains as is, and the second half is reversed and merged with the first half. For instance, <code>[1, 2]</code> will merge with the reversed <code>[5, 4, 3]</code>. Can you figure out a way to implement this reordering process? Maybe dividing the list into two halves could help.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can divide the list into two halves using the fast and slow pointer approach, which helps identify the midpoint of the list. This allows us to split the list into two halves, with the heads labeled as <code>l1</code> and <code>l2</code>. Next, we reverse the second half (<code>l2</code>). After these steps, we proceed to reorder the two lists by iterating through them node by node, updating the next pointers accordingly. 
+    </p>
+</details>
diff --git a/hints/reverse-a-linked-list.md b/hints/reverse-a-linked-list.md
new file mode 100644
index 000000000..9d8db81d4
--- /dev/null
+++ b/hints/reverse-a-linked-list.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(1)</code> space, where <code>n</code> is the length of the given list.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would be to store the node values of the linked list into an array, then reverse the array, convert it back into a linked list, and return the new linked list's head. This would be an <code>O(n)</code> time solution but uses extra space. Can you think of a better way? Maybe there is an approach to reverse a linked list in place.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    As you can see, the head of the linked list becomes the tail after we reverse it. Can you think of an approach to change the references of the node pointers? Perhaps reversing a simple two-node list might help clarify the process.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    For example, consider a list <code>[2, 3]</code>, where <code>2</code> is the head of the list and <code>3</code> is the tail. When we reverse it, <code>3</code> becomes the new head, and its next pointer will point to <code>2</code>. Then, <code>2</code>'s next pointer will point to <code>null</code>. Can you figure out how to apply this approach to reverse a linked list of length <code>n</code> by iterating through it?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We can reverse the linked list in place by reversing the pointers between two nodes while keeping track of the next node's address. Before changing the next pointer of the current node, we must store the next node to ensure we don't lose the rest of the list during the reversal. This way, we can safely update the links between the previous and current nodes.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/reverse-bits.md b/hints/reverse-bits.md
new file mode 100644
index 000000000..0eb364ce9
--- /dev/null
+++ b/hints/reverse-bits.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(1)</code> time and <code>O(1)</code> space.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Given a 32-bit integer, what is the position of bit <code>i</code> after reversing the bits? Maybe you should observe the bit positions before and after reversal to find a pattern.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    After reversing the bits, the bit at position <code>i</code> moves to position <code>31 - i</code>. Can you use this observation to construct the reversed number efficiently?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We initialize <code>res</code> to <code>0</code> and iterate through the bits of the given integer <code>n</code>. We extract the bit at the <code>i</code>-th position using <code>((n >> i) & 1)</code>. If it is <code>1</code>, we set the corresponding bit in <code>res</code> at position <code>(31 - i)</code> using <code>(res |= (1 << (31 - i)))</code>.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/reverse-integer.md b/hints/reverse-integer.md
new file mode 100644
index 000000000..23b4d9c75
--- /dev/null
+++ b/hints/reverse-integer.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(1)</code> time and <code>O(1)</code> space.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A straightforward approach would be to convert the given integer to a string, reverse it, convert it back to an integer using a long type, and return 0 if the result exceeds the integer range. Can you think of a better way?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We initially declare the result <code>res</code> as an <code>int</code> with a value of <code>0</code>. We iterate through the given integer, extracting digits one by one. Before appending a digit to <code>res</code>, we consider multiple cases. Can you determine them? Maybe you should think about overflow.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    Let <code>MAX</code> be the maximum positive integer and <code>MIN</code> be the minimum negative integer. We iterate through each digit and check for overflow before updating <code>res</code>. If <code>res > MAX / 10</code> or <code>res < MIN / 10</code>, return <code>0</code>. If <code>res == MAX / 10</code> and the current digit is greater than <code>MAX % 10</code>, return <code>0</code>. If <code>res == MIN / 10</code> and the current digit is less than <code>MIN % 10</code>, return <code>0</code>. Otherwise, append the digit to <code>res</code> and continue.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/reverse-nodes-in-k-group.md b/hints/reverse-nodes-in-k-group.md
new file mode 100644
index 000000000..b686ce645
--- /dev/null
+++ b/hints/reverse-nodes-in-k-group.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(1)</code> space, where <code>n</code> is the length of the given list.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute-force solution would involve storing the linked list node values in an array, reversing the <code>k</code> groups one by one, and then converting the array back into a linked list, requiring extra space of <code>O(n)</code>. Can you think of a better way? Perhaps you could apply the idea of reversing a linked list in-place without using extra space.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can avoid extra space by reversing each group in-place while keeping track of the head of the next group. For example, consider the list <code>[1, 2, 3, 4, 5]</code> with <code>k = 2</code>. First, we reverse the group <code>[1, 2]</code> to <code>[2, 1]</code>. Then, we reverse <code>[3, 4]</code>, resulting in <code>[2, 1, 4, 3, 5]</code>. While reversing <code>[3, 4]</code>, we need to link <code>1</code> to <code>4</code> and also link <code>3</code> to <code>5</code>. How can we efficiently manage these pointers?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We create a dummy node to handle modifications to the head of the linked list, pointing its <code>next</code> pointer to the current head. We then iterate <code>k</code> nodes, storing the address of the next group's head and tracking the tail of the previous group. After reversing the current group, we reconnect it by linking the previous group's tail to the new head and the current group's tail to the next group's head. This process is repeated for all groups, and we return the new head of the linked list.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/rotate-matrix.md b/hints/rotate-matrix.md
new file mode 100644
index 000000000..3f5528d0f
--- /dev/null
+++ b/hints/rotate-matrix.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n^2)</code> time and <code>O(1)</code> space, where <code>n</code> is the length of the side of the given square matrix.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force approach would use <code>O(n^2)</code> extra space to solve the problem. Can you think of a way to avoid using extra space? Maybe you should consider observing the positions of the elements before rotating and after rotating of the matrix.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can rotate the matrix in two steps. First, we reverse the matrix vertically, meaning the first row becomes the last, the second row becomes the second last, and so on. Next, we transpose the reversed matrix, meaning rows become columns and columns become rows. How would you transpose the matrix?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    Since the given matrix is a square matrix, we only need to iterate over the upper triangular part, meaning the right upper portion of the main diagonal. In this way, we can transpose a matrix.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/rotting-fruit.md b/hints/rotting-fruit.md
new file mode 100644
index 000000000..76ce34b5b
--- /dev/null
+++ b/hints/rotting-fruit.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(m * n)</code> time and <code>O(m * n)</code> space, where <code>m</code> is the number of rows and <code>n</code> is the number of columns in the given grid.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    The DFS algorithm is not suitable for this problem because it explores nodes deeply rather than level by level. In this scenario, we need to determine which oranges rot at each second, which naturally fits a level-by-level traversal. Can you think of an algorithm designed for such a traversal?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use the Breadth First Search (BFS) algorithm. At each second, we rot the oranges that are adjacent to the rotten ones. So, we store the rotten oranges in a queue and process them in one go. The time at which a fresh orange gets rotten is the level at which it is visited. How would you implement it?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We traverse the grid and store the rotten oranges in a queue. We then run a BFS, processing the current level of rotten oranges and visiting the adjacent cells of each rotten orange. We only insert the adjacent cell into the queue if it contains a fresh orange. This process continues until the queue is empty. The level at which the BFS stops is the answer. However, we also need to check whether all oranges have rotted by traversing the grid. If any fresh orange is found, we return <code>-1</code>; otherwise, we return the level.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/same-binary-tree.md b/hints/same-binary-tree.md
new file mode 100644
index 000000000..3a79a39f2
--- /dev/null
+++ b/hints/same-binary-tree.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the number of nodes in the tree.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Can you think of an algorithm that is used to traverse the tree? Maybe in terms of recursion.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use the Depth First Search (DFS) algorithm to traverse the tree. Can you think of a way to simultaneously traverse both the trees?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We traverse both trees starting from their root nodes. At each step in the recursion, we check if the current nodes in both trees are either <code>null</code> or have the same value. If one node is <code>null</code> while the other is not, or if their values differ, we return <code>false</code>. If the values match, we recursively check their <code>left</code> and <code>right</code> subtrees. If any recursive call returns <code>false</code>, the result for the current recursive call is <code>false</code>.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/search-2d-matrix.md b/hints/search-2d-matrix.md
new file mode 100644
index 000000000..53153f798
--- /dev/null
+++ b/hints/search-2d-matrix.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(log(m * n))</code> time and <code>O(1)</code> space, where <code>m</code> is the number of rows and <code>n</code> is the number of columns in the matrix.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would be to do a linear search on the matrix. This would be an <code>O(m * n)</code> solution. Can you think of a better way? Maybe an efficient searching algorithm, as the given matrix is sorted.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use binary search, which is particularly effective when we visualize a row as a range of numbers, <code>[x, y]</code> where <code>x</code> is the first cell and <code>y</code> is the last cell of a row. Using this representation, it becomes straightforward to check if the target value falls within the range. How can you use binary search to solve the problem?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We perform a binary search on the rows to identify the row in which the target value might fall. This operation takes <code>O(logm)</code> time, where <code>m</code> is the number of rows. Now, when we find the potential row, can you find the best way to search the target in that row? The sorted nature of each row is the hint.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    Once we identify the potential row where the target might exist, we can perform a binary search on that row which acts as a one dimensional array. It takes <code>O(logn)</code> time, where <code>n</code> is the number of columns in the row.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/search-for-word-ii.md b/hints/search-for-word-ii.md
new file mode 100644
index 000000000..205964c7e
--- /dev/null
+++ b/hints/search-for-word-ii.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(m * n * 4 * (3^(t-1)) + s)</code> time and <code>O(s)</code> space, where <code>m</code> is the number of rows, <code>n</code> is the number of columns, <code>t</code> is the maximum length of any word and <code>s</code> is the sum of the lengths of all the words.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    To search for a word in the grid, we can use backtracking by starting at each cell, simultaneously iterating through the word and matching the characters with the cells, recursively visiting the neighboring cells. However, if we are given a list of words and need to search for each one, it becomes inefficient to iterate through each word and run backtracking for each. Can you think of a better way? Perhaps a data structure could help with more efficient word search and insertion.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+   We can use a Trie to efficiently search for multiple words. After inserting all words into the Trie, we traverse the grid once. For each character in the grid, we check if it exists in the current Trie node. If not, we prune the search. If we encounter an "end of word" flag in the Trie node, we know a valid word has been found. But how can we add that word to the result list? Maybe you should think about what additional information you can store in the Trie node.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    When we insert a word into the Trie, we can store the word's index. Why? Because when we want to add the word to the result list after finding a valid word, we can easily add it using the index. After adding that word, we put <code>index = -1</code> as we shouldn't add the word multiple times to the result list. How can you implement this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We insert all the words into the Trie with their indices marked. Then, we iterate through each cell in the grid. At each cell, we start at the root of the Trie and explore all possible paths. As we traverse, we match characters in the cell with those in the Trie nodes. If we encounter the end of a word, we take the index at that node and add the corresponding word to the result list. Afterward, we unmark that index and continue exploring further paths.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/search-for-word.md b/hints/search-for-word.md
new file mode 100644
index 000000000..9dcdf4102
--- /dev/null
+++ b/hints/search-for-word.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(m * (4^n))</code> time and <code>O(n)</code> space, where <code>m</code> is the number of cells in the given <code>board</code> and <code>n</code> is the size of the given <code>word</code>.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    As we can start at any cell on the board, we can explore all paths from that cell. Can you think of an algorithm to do so? Also, you should consider a way to avoid visiting a cell that has already been visited in the current path.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use a hash set to avoid revisiting a cell in the current path by inserting the <code>(row, col)</code> of the visiting cell into the hash set and exploring all paths (four directions, as we can move to four neighboring cells) from that cell. Can you think of the base condition for this recursive path? Maybe you should consider the board boundaries, and also, we can extend a path if the character at the cell matches the character in the word.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can use backtracking, starting from each cell on the board with coordinates <code>(row, col)</code> and index <code>i</code> for the given word. We return false if <code>(row, col)</code> is out of bounds or if <code>board[row][col] != word[i]</code>. When <code>i</code> reaches the end of the word, we return true, indicating a valid path. At each step, we add <code>(row, col)</code> to a hash set to avoid revisiting cells. After exploring the four possible directions, we backtrack and remove <code>(row, col)</code> from the hash set.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/serialize-and-deserialize-binary-tree.md b/hints/serialize-and-deserialize-binary-tree.md
new file mode 100644
index 000000000..a93feef8e
--- /dev/null
+++ b/hints/serialize-and-deserialize-binary-tree.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the number of nodes in the given tree.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>  
+    A straightforward way to serialize a tree is by traversing it and adding nodes to a string separated by a delimiter (example: ","), but this does not handle <code>null</code> nodes effectively. During deserialization, it becomes unclear where to stop or how to handle missing children. Can you think of a way to indicate <code>null</code> nodes explicitly?  
+    </p>  
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    Including a placeholder for <code>null</code> nodes (example: "N") during serialization ensures that the exact structure of the tree is preserved. This placeholder allows us to identify missing children and reconstruct the tree accurately during deserialization.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can use the Depth First Search (DFS) algorithm for both serialization and deserialization. During serialization, we traverse the tree and add node values to the result string separated by a delimiter, inserting <code>N</code> whenever we encounter a <code>null</code> node. During deserialization, we process the serialized string using an index <code>i</code>, create nodes for valid values, and return from the current path whenever we encounter <code>N</code>, reconstructing the tree accurately.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/set-zeroes-in-matrix.md b/hints/set-zeroes-in-matrix.md
new file mode 100644
index 000000000..663ff919e
--- /dev/null
+++ b/hints/set-zeroes-in-matrix.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(m*n)</code> time and <code>O(1)</code> space, where <code>m</code> is the number of rows and <code>n</code> is the number of columns in the given matrix.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force approach would iterate through the given matrix and update the corresponding row and column in a new matrix on the fly. This would result in an <code>O((m*n)*(m+n))</code> time and <code>O(m*n)</code> space solution. Can you think of a better way? Maybe you should consider using a single variable for a row and a single variable for a column instead of updating entire row and column.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    A better approach is to use <code>O(m+n)</code> boolean arrays. We iterate through the matrix, and when encountering a zero, we mark the respective row and column as <code>true</code>. In the second iteration, we set a cell to <code>0</code> if its corresponding row or column is marked <code>true</code>. Can you think of a way to optimize the space further?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can use the topmost row and leftmost column of the matrix as boolean arrays by marking <code>0</code> instead of <code>true</code>. However, since they overlap at one cell, we use a single variable to track the top row separately. We then iterate through the matrix and mark zeros accordingly.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    In the second iteration, we update all cells that are not part of the top row or left column accordingly. After making the necessary changes, we check the top-leftmost cell and update the corresponding column. Finally, we check the extra variable and update the top row accordingly.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/single-number.md b/hints/single-number.md
new file mode 100644
index 000000000..6aab0485f
--- /dev/null
+++ b/hints/single-number.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(1)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force approach would iterate through the array, checking each element using a nested loop. If a duplicate is found, we continue to the next element; otherwise, the current element is the required number. This results in an <code>O(n^2)</code> solution. Can you think of a better way? Maybe a data structure can help detect duplicates efficiently.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We use a hash set, iterating through the array and adding elements that are not in the set while removing those that are already present. After the iteration, the required number remains in the hash set. This results in an <code>O(n)</code> space solution. Can you further optimize it? Maybe a bitwise operator could be useful here.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    Think about the bitwise XOR <code>("^")</code>. What is the result when two identical numbers are XORed?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    When two identical numbers are XORed, they cancel out, resulting in zero. Since every number appears twice except for one, the XOR of the entire array gives the number that appears only once.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/sliding-window-maximum.md b/hints/sliding-window-maximum.md
new file mode 100644
index 000000000..3506407c3
--- /dev/null
+++ b/hints/sliding-window-maximum.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(nlogn)</code> time and <code>O(n)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would involve iterating through each window of size <code>k</code> and finding the maximum element within the window by iterating through it. This would be an <code>O(n * k)</code> solution. Can you think of a better way? Maybe think of a data structure that tells the current maximum element of the window in <code>O(1)</code> time.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    A heap is the best data structure to use when dealing with maximum or minimum values and it takes <code>O(1)</code> time to get the max or min value. Here, we use a max-heap. But what should we do if the current maximum element is no longer part of the window? Can you think of a different way of adding values to the max-heap?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We process each window by adding elements to the heap along with their indices to track whether the maximum value is still within the current window. As we move from one window to the next, an element may go out of the window but still remain in the max-heap. Is there a way to handle this situation efficiently?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We can ignore those elements that are no longer part of the current window, except when the maximum value is outside the window. In that case, we remove elements from the max-heap until the maximum value belongs to the current window. Why? Because those elements will be eventually removed when the maximum element goes out of the window. 
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/spiral-matrix.md b/hints/spiral-matrix.md
new file mode 100644
index 000000000..2b8eced0a
--- /dev/null
+++ b/hints/spiral-matrix.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(m*n)</code> time and <code>O(1)</code> extra space, where <code>m</code> is the number of rows and <code>n</code> is the number of columns in the given matrix.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Try to simulate the process as described in the problem. Think in terms of matrix layers, starting from the outermost boundaries and moving inward. Can you determine an efficient way to implement this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    Each boundary consists of four parts: the top row, right column, bottom row, and left column, which follow the spiral order and act as four pointers. For each layer, the top pointer increments by one, the right pointer decrements by one, the left pointer increments by one, and the bottom pointer decrements by one.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    At each layer, four loops traverse the matrix: one moves left to right along the top row, another moves top to bottom along the right column, the next moves right to left along the bottom row, and the last moves bottom to top along the left column. This process generates the spiral order.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/string-encode-and-decode.md b/hints/string-encode-and-decode.md
new file mode 100644
index 000000000..82bc8fbcb
--- /dev/null
+++ b/hints/string-encode-and-decode.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(m)</code> time for each <code>encode()</code> and <code>decode()</code> call and <code>O(m+n)</code> space, where <code>m</code>  is the sum of lengths of all the strings and <code>n</code> is the number of strings.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A naive solution would be to use a non-ascii character as a delimiter. Can you think of a better way?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    Try to encode and decode the strings using a smart approach based on the lengths of each string. How can you differentiate between the lengths and any numbers that might be present in the strings?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can use an encoding approach where we start with a number representing the length of the string, followed by a separator character (let's use <code>#</code> for simplicity), and then the string itself. To decode, we read the number until we reach a <code>#</code>, then use that number to read the specified number of characters as the string.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/subsets-ii.md b/hints/subsets-ii.md
new file mode 100644
index 000000000..4001ea052
--- /dev/null
+++ b/hints/subsets-ii.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(n * (2^n))</code> time and <code>O(n)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute-force solution would involve creating a hash set and inserting every subset into it. Then, converting the hash set to a list and returning it. However, this approach would require extra space of <code>O(2^n)</code>. Can you think of a better way? Maybe you should sort the input array and observe which recusive calls are resposible to make duplicate subsets.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use backtracking to generate subsets of an array. If the input contains duplicates, duplicate subsets may be created. To prevent this, we sort the array beforehand. For example, in <code>[1, 1, 2]</code>, sorting allows us to create subsets using the first <code>1</code> and skip the second <code>1</code>, ensuring unique subsets. How can you implement this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We start by sorting the input array. Then, we recursively iterate through the array from left to right, extending recursive paths by including or excluding each element. To avoid duplicate subsets, we skip an element if it is the same as the previous one. Finally, we return the generated subsets as a list.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/subsets.md b/hints/subsets.md
new file mode 100644
index 000000000..63a694ba2
--- /dev/null
+++ b/hints/subsets.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n * (2^n))</code> time and <code>O(n)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    It is straightforward that if the array is empty we return an empty array. When we have an array <code>[1]</code> which is of size <code>1</code>, we have two subsets, <code>[[], [1]]</code> as the output. Can you think why the output is so?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can see that one subset includes a number, and another does not. From this, we can conclude that we need to find the subsets that include a number and those that do not. This results in <code>2^n</code> subsets for an array of size <code>n</code> because there are many combinations for including and excluding the array of numbers. Since the elements are unique, duplicate subsets will not be formed if we ensure that we don't pick the element more than once in the current subset. Which algorithm is helpful to generate all subsets, and how would you implement it?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can use backtracking to generate all possible subsets. We iterate through the given array with an index <code>i</code> and an initially empty temporary list representing the current subset. We recursively process each index, adding the corresponding element to the current subset and continuing, which results in a subset that includes that element. Alternatively, we skip the element by not adding it to the subset and proceed to the next index, forming a subset without including that element. What can be the base condition to end this recursion?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    When the index <code>i</code> reaches the end of the array, we append a copy of the subset formed in that particular recursive path to the result list and return. All subsets of the given array are generated from these different recursive paths, which represent various combinations of "include" and "not include" steps for the elements of the array. As we are only iterating from left to right in the array, we don't pick an element more than once.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/subtree-of-a-binary-tree.md b/hints/subtree-of-a-binary-tree.md
new file mode 100644
index 000000000..79aaf1a57
--- /dev/null
+++ b/hints/subtree-of-a-binary-tree.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(m * n)</code> time and <code>O(m + n)</code> space, where <code>n</code> and <code>m</code> are the number of nodes in <code>root</code> and <code>subRoot</code>, respectively.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A subtree of a tree is a tree rooted at a specific node. We need to check whether the given <code>subRoot</code> is identical to any of the subtrees of <code>root</code>. Can you think of a recursive way to check this? Maybe you can leverage the idea of solving a problem where two trees are given, and you need to check whether they are identical in structure and values.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    When two trees are identical, it means that every node in both trees has the same value and structure. We can use the Depth First Search (DFS) algorithm to solve the problem. How do you implement this? 
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We traverse the given <code>root</code>, and at each node, we check if the subtree rooted at that node is identical to the given <code>subRoot</code>. We use a helper function, <code>sameTree(root1, root2)</code>, to determine whether the two trees passed to it are identical in both structure and values.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/sum-of-two-integers.md b/hints/sum-of-two-integers.md
new file mode 100644
index 000000000..340f197d0
--- /dev/null
+++ b/hints/sum-of-two-integers.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(1)</code> time and <code>O(1)</code> space.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force approach would use the addition operator. Can you think of a way to perform addition without using it? Maybe you should consider solving this using bit manipulation.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use the bitwise XOR operator to perform addition. If both <code>a</code> and <code>b</code> have <code>1</code> at the same bit position, the sum at that position is <code>0</code>, and a carry of <code>1</code> is generated. If the bits are different, the sum at that position is <code>1</code>. Additionally, we account for the carry from the previous step in the next iteration.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We iterate bit by bit from <code>0</code> to <code>31</code> since the given integers are 32-bit. We track the carry, initially set to <code>0</code>, and initialize the result as <code>res</code>. During iteration, the XOR of the bits at the <code>i</code>-th position of both integers and the carry determines the current bit of <code>res</code>. How can you handle negative numbers?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    To handle negative numbers, if the final result exceeds the maximum positive 32-bit integer, it means the number should be negative. We adjust it using bitwise operations: flipping the bits with <code>res ^ ((2 ^ 32) - 1)</code> and applying <code>~</code> to restore the correct two’s complement representation. This ensures the result correctly represents signed 32-bit integers.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/surrounded-regions.md b/hints/surrounded-regions.md
new file mode 100644
index 000000000..d61a1db78
--- /dev/null
+++ b/hints/surrounded-regions.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(m * n)</code> time and <code>O(m * n)</code> space, where <code>m</code> is the number of rows and <code>n</code> is the number of columns in the matrix.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    We observe that we need to capture the regions that are not connected to the <code>O</code>'s on the border of the matrix. This means there should be no path connecting the <code>O</code>'s on the border to any <code>O</code>'s in the region. Can you think of a way to check the region connected to these border <code>O</code>'s?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use the Depth First Search (<code>DFS</code>) algorithm. Instead of checking the region connected to the border <code>O</code>'s, we can reverse the approach and mark the regions that are reachable from the border <code>O</code>'s. How would you implement this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We run the DFS from every <code>'O'</code> on the border of the matrix, visiting the neighboring cells that are equal to <code>'O'</code> recursively and marking them as <code>'#'</code> to avoid revisiting. After completing all the DFS calls, we traverse the matrix again and capture the cells where <code>matrix[i][j] == 'O'</code>, and unmark the cells back to <code>'O'</code> where <code>matrix[i][j] == '#'</code>.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/swim-in-rising-water.md b/hints/swim-in-rising-water.md
new file mode 100644
index 000000000..5e098b6f0
--- /dev/null
+++ b/hints/swim-in-rising-water.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O((n^2)logn)</code> time and <code>O(n^2)</code> space, where <code>n</code> is the number of rows or columns of the square matrix.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Think of this problem as a graph where each cell represents a node. You can move from one cell to its adjacent cell if the time is greater than or equal to the adjacent cell's elevation. Note that swimming does not cost time, but you may need to wait at a cell for the time to reach the required elevation. What do you notice about the path from <code>(0, 0)</code> to <code>(n - 1, n - 1)</code>? Perhaps a greedy approach would be useful here.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can observe that the maximum elevation value along the path determines the time taken for that path. Therefore, we need to find the path where the maximum elevation is minimized. Can you think of an algorithm to find such a path from the source <code>(0, 0)</code> to the destination <code>(n - 1, n - 1)</code>? Perhaps a shortest path algorithm could be useful here.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can use Dijkstra's algorithm. We initialize a Min-heap and a matrix with infinity. We run the algorithm starting from the source <code>(0, 0)</code>, and we track the maximum elevation encountered along the paths. This maximum elevation is used as the key for comparison in Dijkstra's algorithm. If we encounter the destination <code>(n - 1, n - 1)</code>, we return the maximum elevation of the path that reached the destination.  
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/target-sum.md b/hints/target-sum.md
new file mode 100644
index 000000000..06e9e9a3e
--- /dev/null
+++ b/hints/target-sum.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(n * m)</code> time and <code>O(n * m)</code> space, where <code>n</code> is the size of the input array and <code>m</code> is the sum of all the elements in the array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Try to think in terms of recursion and visualize it as a decision tree, where we have two choices at each recursion step: assigning a positive or negative sign.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We recursively iterate through the array using index <code>i</code>, tracking the current sum along the recursive path. Each step branches into two paths, and we sum the number of ways to reach the target. If the index <code>i</code> goes out of bounds, we return <code>1</code> if the current sum equals the target; otherwise, we return <code>0</code>.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    This approach is exponential. We can use memoization to cache recursive call results and avoid redundant calculations. A hash map or a <code>2D</code> array with modifications can be used for caching. If using a <code>2D</code> array, the dimensions can be <code>(n * (2m + 1))</code>, where <code>n</code> is the array size and <code>m</code> represents the sum of the array elements.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/task-scheduling.md b/hints/task-scheduling.md
new file mode 100644
index 000000000..1b351db49
--- /dev/null
+++ b/hints/task-scheduling.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(m)</code> time and <code>O(1)</code> space, where <code>m</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    There are at most <code>26</code> different tasks, represented by <code>A</code> through <code>Z</code>. It is more efficient to count the frequency of each task and store it in a hash map or an array of size <code>26</code>. Can you think of a way to determine which task should be processed first?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We should always process the most frequent task first. After selecting the most frequent task, we must ensure that it is not processed again until after <code>n</code> seconds, due to the cooldown condition. Can you think of an efficient way to select the most frequent task and enforce the cooldown? Perhaps you could use a data structure that allows for <code>O(1)</code> time to retrieve the maximum element and another data structure to cooldown the processed tasks.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can use a Max-Heap to efficiently retrieve the most frequent task at any given instance. However, to enforce the cooldown period, we must temporarily hold off from reinserting the processed task into the heap. This is where a queue data structure comes in handy. It helps maintain the order of processed tasks. Can you implement this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We start by calculating the frequency of each task and initialize a variable <code>time</code> to track the total processing time. The task frequencies are inserted into a Max-Heap. We also use a queue to store tasks along with the time they become available after the cooldown. At each step, if the Max-Heap is empty, we update <code>time</code> to match the next available task in the queue, covering idle time. Otherwise, we process the most frequent task from the heap, decrement its frequency, and if it's still valid, add it back to the queue with its next available time. If the task at the front of the queue becomes available, we pop it and reinsert it into the heap.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/three-integer-sum.md b/hints/three-integer-sum.md
new file mode 100644
index 000000000..444e13872
--- /dev/null
+++ b/hints/three-integer-sum.md
@@ -0,0 +1,47 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n^2)</code> time and <code>O(1)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would be to check for every triplet in the array. This would be an <code>O(n^3)</code> solution. Can you think of a better way?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    Can you think of an algorithm after sorting the input array? What can we observe by rearranging the given equation in the problem?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+     We can iterate through nums with index <code>i</code> and get <code>nums[i] = -(nums[j] + nums[k])</code> after rearranging the equation, making <code>-nums[i] = nums[j] + nums[k]</code>. For each index <code>i</code>, we should efficiently  calculate the <code>j</code> and <code>k</code> pairs without duplicates. Which algorithm is suitable to find <code>j</code> and <code>k</code> pairs?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    To efficiently find the <code>j</code> and <code>k</code> pairs, we run the two pointer approach on the elements to the right of index <code>i</code> as the array is sorted. When we run two pointer algorithm, consider <code>j</code> and <code>k</code> as pointers (<code>j</code> is at left, <code>k</code> is at right) and <code>target = -nums[i]</code>, if the current sum <code>num[j] + nums[k] < target</code> then we need to increase the value of current sum by incrementing <code>j</code> pointer. Else if the current sum <code>num[j] + nums[k] > target</code> then we should decrease the value of current sum by decrementing <code>k</code> pointer. How do you deal with duplicates? 
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 5</summary>
+    <p>
+     When the current sum <code>nums[j] + nums[k] == target</code> add this pair to the result. We can move <code>j</code> or <code>k</code> pointer until <code>j < k</code> and the pairs are repeated. This ensures that no duplicate pairs are added to the result.
+    </p>
+</details>
diff --git a/hints/time-based-key-value-store.md b/hints/time-based-key-value-store.md
new file mode 100644
index 000000000..5b4e80ea6
--- /dev/null
+++ b/hints/time-based-key-value-store.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(1)</code> time for <code>set()</code>, <code>O(logn)</code> time for <code>get()</code>, and <code>O(m * n)</code> space, where <code>n</code> is the total number of values associated with a key, and <code>m</code> is the total number of keys.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Can you think of a data structure that is useful for storing key-value pairs? Perhaps a hash-based data structure where we not only store unique elements but also associate additional information with each element?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We store key-value pairs in a hash map. In this case, we store the keys as usual, but instead of a single value, we store a list of values, each paired with its corresponding timestamp. This allows us to implement the <code>set()</code> method in <code>O(1)</code>. How can you leverage this hash map to implement the <code>get()</code> method?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    A brute force solution would involve linearly going through every value associated with the key and returning the most recent value with a timestamp less than or equal to the given timestamp. This approach has a time complexity of <code>O(n)</code> for each <code>get()</code> call. Can you think of a better way? Since the timestamps in the value list are sorted in ascending order by default, maybe an efficient searching algorithm could help.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We can use binary search because the timestamps in the values list are sorted in ascending order. This makes it straightforward to find the value with the most recent timestamp that is less than or equal to the given timestamp.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/top-k-elements-in-list.md b/hints/top-k-elements-in-list.md
new file mode 100644
index 000000000..566ec05de
--- /dev/null
+++ b/hints/top-k-elements-in-list.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A naive solution would be to count the frequency of each number and then sort the array based on each element’s frequency. After that, we would select the top <code>k</code> frequent elements. This would be an <code>O(nlogn)</code> solution. Though this solution is acceptable, can you think of a better way?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    Can you think of an algorithm which involves grouping numbers based on their frequency?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    Use the bucket sort algorithm to create <code>n</code> buckets, grouping numbers based on their frequencies from <code>1</code> to <code>n</code>. Then, pick the top <code>k</code> numbers from the buckets, starting from <code>n</code> down to <code>1</code>.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/trapping-rain-water.md b/hints/trapping-rain-water.md
new file mode 100644
index 000000000..2ae54b063
--- /dev/null
+++ b/hints/trapping-rain-water.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    How can we determine the amount of water that can be trapped at a specific position in the array? Perhaps looking at the image might help clarify.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    From the image, we can see that to calculate the amount of water trapped at a position, the greater element to the left <code>l</code> and the greater element to the right <code>r</code> of the current position are crucial. The formula for the trapped water at index <code>i</code> is given by: <code>min(height[l], height[r]) - height[i]</code>.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    A brute force solution would involve iterating through the array with index <code>i</code>, finding the greater elements to the left (<code>l</code>) and right (<code>r</code>) for each index, and then calculating the trapped water for that position. The total amount of trapped water would be the sum of the water trapped at each index. Finding <code>l</code> and <code>r</code> for each index involves repeated work, resulting in an <code>O(n^2)</code> solution. Can you think of a more efficient approach? Maybe there is something that we can precompute and store in arrays.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We can store the prefix maximum in an array by iterating from left to right and the suffix maximum in another array by iterating from right to left. For example, in <code>[1, 5, 2, 3, 4]</code>, for the element <code>3</code>, the prefix maximum is <code>5</code>, and the suffix maximum is <code>4</code>. Once these arrays are built, we can iterate through the array with index <code>i</code> and calculate the total water trapped at each position using the formula: <code>min(prefix[i], suffix[i]) - height[i]</code>. 
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/two-integer-sum-ii.md b/hints/two-integer-sum-ii.md
new file mode 100644
index 000000000..a07baf4ac
--- /dev/null
+++ b/hints/two-integer-sum-ii.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(1)</code> space, where <code>n</code> is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would be to check every pair of numbers in the array. This would be an <code>O(n^2)</code> solution. Can you think of a better way?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    Can you think of an algorithm by taking the advantage of array being sorted?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+     We can use the two-pointer algorithm. If <code>nums[0] + nums[n-1] > target</code>, then we know <code>nums[n - 1]</code> can not possibly be included in any pairs. Why? Because <code>nums[n - 1]</code> is the largest element in the array. Even by adding it with <code>nums[0]</code>, which is the smallest element, we still exceed the target. You can think of the case when <code>nums[0] + nums[n - 1] < target</code>.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    We keep two pointers, one at the start and the other at the end of the array. If the sum of the numbers at the two pointers is greater than the <code>target</code>, decrement the right pointer, else increment the left pointer. Repeat this process until you find a valid pair.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/two-integer-sum.md b/hints/two-integer-sum.md
new file mode 100644
index 000000000..948aae221
--- /dev/null
+++ b/hints/two-integer-sum.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(n)</code> space, where n is the size of the input array.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would be to check every pair of numbers in the array. This would be an <code>O(n^2)</code> solution. Can you think of a better way? Maybe in terms of mathematical equation?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">
+    <summary>Hint 2</summary>
+    <p>
+    Given, We need to find indices <code>i</code> and <code>j</code> such that <code>i != j</code> and <code>nums[i] + nums[j] == target</code>. Can you rearrange the equation and try to fix any index to iterate on? 
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+     we can iterate through nums with index <code>i</code>. Let <code>difference = target - nums[i]</code> and check if <code>difference</code> exists in the hash map as we iterate through the array, else store the current element in the hashmap with its index and continue. We use a hashmap for <code>O(1)</code> lookups.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/valid-binary-search-tree.md b/hints/valid-binary-search-tree.md
new file mode 100644
index 000000000..9a691ece8
--- /dev/null
+++ b/hints/valid-binary-search-tree.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the number of nodes in the given tree.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would involve traversing the tree and, for every node, checking its entire left subtree to ensure all nodes are less than the current node, and its entire right subtree to ensure all nodes are greater. This results in an <code>O(n^2)</code> solution. Can you think of a better way? Maybe tracking values during the traversal would help.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use the Depth First Search (DFS) algorithm to traverse the tree. At each node, we need to ensure that the tree rooted at that node is a valid Binary Search Tree (BST). One way to do this is by tracking an interval that defines the lower and upper limits for the node's value in that subtree. This interval will be updated as we move down the tree, ensuring each node adheres to the BST property.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We start with the interval <code>[-infinity, infinity]</code> for the root node. As we traverse the tree, when checking the left subtree, we update the maximum value limit because all values in the left subtree must be less than the current node's value. Conversely, when checking the right subtree, we update the minimum value limit because all values in the right subtree must be greater than the current node's value.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/valid-parenthesis-string.md b/hints/valid-parenthesis-string.md
new file mode 100644
index 000000000..29baed7d5
--- /dev/null
+++ b/hints/valid-parenthesis-string.md
@@ -0,0 +1,39 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the length of the input string.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force approach would try all possibilities when encountering a <code>'*'</code> and recursively solve the problem, leading to an exponential approach. Can you think of a better way? Maybe a data structure commonly used in parenthesis problems could be useful.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can solve the problem using a stack-based approach. We maintain two stacks: one for tracking the indices of left parentheses and another for star indices. As we iterate through the string from left to right, we push indices onto their respective stacks when encountering a left parenthesis <code>'('</code> or a star <code>'*'</code>. Can you determine the logic for the right parentesis case?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+   If the left parenthesis stack is not empty, we pop from it. Otherwise, we pop from the star stack, treating the star as a left parenthesis to keep the string valid. After iterating the string, the stacks might be non-empty? Can you determine the logic for this case?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 4</summary>
+    <p>
+    Now, we try to match the remaining left parentheses with stars, ensuring the stars appear after the left parentheses in the string. We simultaneously pop from both stacks, and if the index of a left parenthesis is greater than that of a star, the string is invalid as there is no matching right parenthesis. In this case, we return <code>false</code>.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/valid-sudoku.md b/hints/valid-sudoku.md
new file mode 100644
index 000000000..51655ed8b
--- /dev/null
+++ b/hints/valid-sudoku.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(n^2)</code> time and <code>O(n^2)</code> space, where <code>n</code> is the number of rows in the square grid.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Which data structure would you prefer to use for checking duplicates?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    You can use a hash set for every row and column to check duplicates. But how can you efficiently check for the squares?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can find the index of each square by the equation <code>(row / 3) * 3 + (col / 3)</code>. Then we use hash set for <code>O(1)</code> lookups while inserting the number into its row, column and square it belongs to. We use separate hash maps for rows, columns, and squares.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/valid-tree.md b/hints/valid-tree.md
new file mode 100644
index 000000000..7e7d37358
--- /dev/null
+++ b/hints/valid-tree.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(V + E)</code> time and <code>O(V + E)</code> space, where <code>V</code> is the number vertices and <code>E</code> is the number of edges in the graph.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    According to the definition of a tree, a tree is an undirected graph with no cycles, all the nodes are connected as one component, and any two nodes have exactly one path. Can you think of a recursive algorithm to detect a cycle in the given graph and ensure it is a tree?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use the Depth First Search (DFS) algorithm to detect a cycle in the graph. Since a tree has only one component, we can start the DFS from any node, say node <code>0</code>. During the traversal, we recursively visit its neighbors (children). If we encounter any already visited node that is not the parent of the current node, we return false as it indicates a cycle. How would you implement this?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We start DFS from node <code>0</code>, assuming <code>-1</code> as its parent. We initialize a hash set <code>visit</code> to track the visited nodes in the graph. During the DFS, we first check if the current node is already in <code>visit</code>. If it is, we return false, detecting a cycle. Otherwise, we mark the node as visited and perform DFS on its neighbors, skipping the parent node to avoid revisiting it. After all DFS calls, if we have visited all nodes, we return true, as the graph is connected. Otherwise, we return false because a tree must contain all nodes.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/validate-parentheses.md b/hints/validate-parentheses.md
new file mode 100644
index 000000000..ec5216bb4
--- /dev/null
+++ b/hints/validate-parentheses.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O(n)</code> time and <code>O(n)</code> space, where <code>n</code> is the length of the given string. 
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    A brute force solution would be to continuously remove valid brackets until no more can be removed. If the remaining string is empty, return true; otherwise, return false. This would result in an <code>O(n^2)</code> solution. Can we think of a better approach? Perhaps a data structure could help.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    We can use a stack to store characters. Iterate through the string by index. For an opening bracket, push it onto the stack. If the bracket is a closing type, check for the corresponding opening bracket at the top of the stack. If we don't find the corresponding opening bracket, immediately return false. Why does this work?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    In a valid parenthesis expression, every opening bracket must have a corresponding closing bracket. The stack is used to process the valid string, and it should be empty after the entire process. This ensures that there is a valid substring between each opening and closing bracket.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/word-break.md b/hints/word-break.md
new file mode 100644
index 000000000..cb850a49c
--- /dev/null
+++ b/hints/word-break.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution as good or better than <code>O(n * m * t)</code> time and <code>O(n)</code> space, where <code>n</code> is the length of the string <code>s</code>, <code>m</code> is the number of words in <code>wordDict</code>, and <code>t</code> is the maximum length of any word in <code>wordDict</code>.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Try to think of this problem in terms of recursion, where we explore all possibilities. We iterate through the given string <code>s</code>, attempting to pick a word from <code>wordDict</code> that matches a portion of <code>s</code>, and then recursively continue processing the remaining string. Can you determine the recurrence relation and base condition?
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    The base condition is to return <code>true</code> if we reach the end of the string <code>s</code>. At each recursive call with index <code>i</code> iterating through <code>s</code>, we check all words in <code>wordDict</code> and recursively process the remaining string by incrementing <code>i</code> by the length of the matched word. If any recursive path returns <code>true</code>, we immediately return <code>true</code>. However, this solution is exponential. Can you think of an optimization? Maybe you should consider an approach that avoids repeated work.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    We can avoid recalculating results for recursive calls by using memoization. Since we iterate with index <code>i</code>, we can use a hash map or an array of the same length as <code>s</code> to cache the results of recursive calls and prevent redundant computations.
+    </p>
+</details>
\ No newline at end of file
diff --git a/hints/word-ladder.md b/hints/word-ladder.md
new file mode 100644
index 000000000..efdd32a2c
--- /dev/null
+++ b/hints/word-ladder.md
@@ -0,0 +1,31 @@
+<br>
+<details class="hint-accordion">  
+    <summary>Recommended Time & Space Complexity</summary>
+    <p>
+    You should aim for a solution with <code>O((m ^ 2) * n)</code> time and <code>O((m ^ 2) * n)</code> space, where <code>n</code> is the number of words and <code>m</code> is the length of the word. 
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 1</summary>
+    <p>
+    Consider the given problem in terms of a graph, treating strings as nodes. Think of a way to build edges where two strings have an edge if they differ by a single character. A naive approach would be to consider each pair of strings and check whether an edge can be formed. Can you think of an efficient way? For example, consider a string <code>hot</code> and think about the strings that can be formed from it by changing a single letter.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 2</summary>
+    <p>
+    To efficiently build edges, consider transforming each word into intermediate states by replacing one character with a wildcard, like <code>*</code>. For example, the word <code>hot</code> can be transformed into <code>*ot</code>, <code>h*t</code>, and <code>ho*</code>. These intermediate states act as "parents" that connect words differing by one character. For instance, <code>*ot</code> can connect to words like <code>cot</code>. For each word in the list, generate all possible patterns by replacing each character with <code>*</code> and store the word as a child of these patterns. We can run a <code>BFS</code> starting from the <code>beginWord</code>, visiting other words while avoiding revisiting by using a hash set.
+    </p>
+</details>
+
+<br>
+<details class="hint-accordion">  
+    <summary>Hint 3</summary>
+    <p>
+    When visiting a node during BFS, if the word matches the <code>endWord</code>, we immediately return <code>true</code>. Otherwise, we generate the pattern words that can be formed from the current word and attempt to visit the words connected to these pattern words. We add only unvisited words to the queue. If we exhaust all possibilities without finding the <code>endWord</code>, we return <code>false</code>.
+    </p>
+</details>
\ No newline at end of file
diff --git a/java/0068-text-justification.java b/java/0068-text-justification.java
new file mode 100644
index 000000000..4eb0811a2
--- /dev/null
+++ b/java/0068-text-justification.java
@@ -0,0 +1,43 @@
+class Solution {
+    public List<String> fullJustify(String[] words, int maxWidth) {
+        int count = 0;
+        List<String> currLine = new ArrayList<>();
+        List<String> ans = new ArrayList<>();
+        for (String w : words) {
+            if (count == 0) {
+                count += w.length();
+                currLine.add(w);
+            } else if (count + 1 + w.length() > maxWidth) {
+                ans.add(getLine(currLine, count, maxWidth));
+                currLine = new ArrayList<>(List.of(w));
+                count = w.length();
+            } else {
+                count += 1 + w.length();
+                currLine.add(w);
+            }
+        }
+        ans.add(getLastLine(currLine, maxWidth));
+        return ans;
+    }
+
+    private String getLine(List<String> words, int count, int maxWidth) {
+        if (words.size() == 0) return "";
+        if (words.size() == 1) return words.get(0) + " ".repeat(maxWidth - words.get(0).length());
+        int extraSpaces = (maxWidth - count) / (words.size() - 1);
+        int remSpaces = (maxWidth - count) % (words.size() - 1);
+        StringBuilder sb = new StringBuilder();
+        for (int i = 0; i < words.size() - 1; i++) {
+            sb.append(words.get(i)).append(" ");
+            sb.append(" ".repeat(extraSpaces));
+            if (remSpaces-- > 0)
+                sb.append(" ");
+        }
+        sb.append(words.getLast());
+        return sb.toString();
+    }
+
+    private String getLastLine(List<String> words, int maxWidth) {
+        String wordsStr = String.join(" ", words);
+        return wordsStr.toString() + " ".repeat(maxWidth - wordsStr.length());
+    }
+}
diff --git a/java/0080-remove-duplicates-from-sorted-array-ii.java b/java/0080-remove-duplicates-from-sorted-array-ii.java
index 5d3ac70c6..37953fce1 100644
--- a/java/0080-remove-duplicates-from-sorted-array-ii.java
+++ b/java/0080-remove-duplicates-from-sorted-array-ii.java
@@ -1,3 +1,50 @@
+class Solution {
+    public int removeDuplicates(int[] nums) {
+        int l = 0, r = 0, n = nums.length;
+
+        while (r < n) {
+            int count = 1;
+            while (r + 1 < n && nums[r] == nums[r + 1]) {
+                r++;
+                count++;
+            }
+
+            for (int i = 0; i < Math.min(2, count); i++) {
+                nums[l] = nums[r];
+                l++;
+            }
+            r++;
+        }
+        return l;
+    }
+}
+
+/*
+ * Time Complexity: O(n);
+ * Space Complexity: O(1);
+ */
+
+class Solution {
+    public int removeDuplicates(int[] nums) {
+        int count = 1;
+        int index1 = 0;
+        for (int i = 1; i < nums.length; i++) {
+            if (nums[i] != nums[index1]) {
+                count = 1;
+                index1++;
+                nums[index1] = nums[i];
+            } else {
+                count++;
+                if (count <= 2) {
+                    index1++;                    
+                    nums[index1] = nums[i];
+                }
+            };
+        };
+        return index1 + 1;
+    }
+}
+
 class Solution {
     public int removeDuplicates(int[] nums) {
         int k = 0;
@@ -8,4 +55,6 @@ public int removeDuplicates(int[] nums) {
         }
         return k;
     }
-}
\ No newline at end of file
+}
+
+
diff --git a/java/0280-wiggle-sort.java b/java/0280-wiggle-sort.java
new file mode 100644
index 000000000..d543e366e
--- /dev/null
+++ b/java/0280-wiggle-sort.java
@@ -0,0 +1,14 @@
+class Solution {
+    public void wiggleSort(int[] nums) {
+        for (int i = 1; i < nums.length; i++) {
+            if ((i % 2 == 0 && nums[i] > nums[i - 1]) 
+            || (i % 2 == 1 && nums[i] < nums[i - 1]))
+                swap(nums, i, i - 1);
+        }
+    }
+    private void swap(int[] nums, int i, int j) {
+        int temp = nums[i];
+        nums[i] = nums[j];
+        nums[j] = temp;
+    }
+}
diff --git a/java/0460-lfu-cache.java b/java/0460-lfu-cache.java
new file mode 100644
index 000000000..cc76af55a
--- /dev/null
+++ b/java/0460-lfu-cache.java
@@ -0,0 +1,71 @@
+class LFUCache {
+    private static class Entry {
+        int key;
+        int value;
+        int freq;
+
+        public Entry(int key, int value, int freq) {
+            this.key = key;
+            this.value = value;
+            this.freq = freq;
+        }
+    }
+
+    private final int capacity;
+    private int minFreq = 0;
+    private final Map<Integer, Entry> entries = new HashMap<>();
+    private final Map<Integer, LinkedHashSet<Entry>> freqMap = new HashMap<>();
+
+    public LFUCache(int capacity) {
+        this.capacity = capacity;
+    }
+
+    public int get(int key) {
+        Entry e = entries.get(key);
+        if (e == null) return -1;
+        updateFrequency(e);
+        return e.value;
+    }
+
+    public void put(int key, int value) {
+        if (capacity == 0) return;
+        if (entries.containsKey(key)) {
+            Entry e = entries.get(key);
+            e.value = value;
+            updateFrequency(e);
+        } else {
+            if (entries.size() == capacity) {
+                evictLeastFrequent();
+            }
+            Entry e = new Entry(key, value, 1);
+            entries.put(key, e);
+            freqMap.computeIfAbsent(1, k -> new LinkedHashSet<>()).add(e);
+            minFreq = 1; // Reset min frequency to 1 for new entry
+        }
+    }
+
+    private void updateFrequency(Entry e) {
+        int oldFreq = e.freq;
+        int newFreq = oldFreq + 1;
+
+        freqMap.get(oldFreq).remove(e);
+        if (freqMap.get(oldFreq).isEmpty()) {
+            freqMap.remove(oldFreq);
+            if (minFreq == oldFreq) minFreq++;
+        }
+
+        e.freq = newFreq;
+        freqMap.computeIfAbsent(newFreq, k -> new LinkedHashSet<>()).add(e);
+    }
+
+    private void evictLeastFrequent() {
+        LinkedHashSet<Entry> minFreqEntries = freqMap.get(minFreq);
+        Entry toRemove = minFreqEntries.iterator().next();
+        minFreqEntries.remove(toRemove);
+        if (minFreqEntries.isEmpty()) {
+            freqMap.remove(minFreq);
+        }
+
+        entries.remove(toRemove.key);
+    }
+}
diff --git a/java/0647-palindromic-substrings.java b/java/0647-palindromic-substrings.java
index e05bc1ef3..eea84eaf3 100644
--- a/java/0647-palindromic-substrings.java
+++ b/java/0647-palindromic-substrings.java
@@ -1,35 +1,26 @@
 class Solution {
-
     public int countSubstrings(String s) {
-        if (s.length() < 2) {
-            return s.length();
-        }
-        int result = 0;
+        int res = 0;
+
         for (int i = 0; i < s.length(); i++) {
-            // Odd Length
-            int left = i, right = i;
-            while (
-                left >= 0 &&
-                right < s.length() &&
-                s.charAt(left) == s.charAt(right)
-            ) {
-                result++;
-                left--;
-                right++;
-            }
-            // Even Length
-            left = i;
-            right = i + 1;
-            while (
-                left >= 0 &&
-                right < s.length() &&
-                s.charAt(left) == s.charAt(right)
-            ) {
-                result++;
-                left--;
-                right++;
-            }
+            res += countSubstrings(s, i, i);
+            res += countSubstrings(s, i, i + 1);
+        }
+
+        return res;
+    }
+
+    public int countSubstrings(String s, 
+                               int start, int end) {
+        int res = 0;
+    
+        while (start >= 0 && end < s.length() 
+               && s.charAt(start) == s.charAt(end)) {
+            ++res;
+            --start;
+            ++end;
         }
-        return result;
+
+        return res;
     }
 }
diff --git a/java/0934-shortest-bridge.java b/java/0934-shortest-bridge.java
new file mode 100644
index 000000000..193edd52a
--- /dev/null
+++ b/java/0934-shortest-bridge.java
@@ -0,0 +1,50 @@
+class Solution {
+    public int shortestBridge(int[][] grid) {
+        Queue<int[]> q = new LinkedList<>();
+        boolean[][] vis = new boolean[grid.length][grid[0].length];
+        
+        for (int i = 0; i < grid.length; i++) {
+            for (int j = 0; j < grid[0].length; j++) {
+                if (grid[i][j] == 1) {
+                    mark(grid, vis, q, i, j);
+                    i = grid.length;
+                    j = grid[0].length;
+                }
+            }
+        }
+        int count = 0;
+        int[][] dir = {{0,1}, {1,0}, {-1,0}, {0,-1}};
+        
+        while (!q.isEmpty()) {
+            int n = q.size();
+            
+            for (int k = 0; k < n; k++) {
+                int[] curr = q.poll();
+                
+                for (int j = 0; j < 4; j++) {
+                    int r = curr[0] + dir[j][0];
+                    int c = curr[1] + dir[j][1];
+
+                    if (r >= 0 && c >= 0 && r < grid.length && c < grid[0].length && !vis[r][c]) {
+                        if (grid[r][c] == 1) return count;
+                        vis[r][c] = true;
+                        q.offer(new int[]{r,c});
+                    }
+                } 
+            }
+            count++;
+        }
+        return -1;
+    }
+
+    void mark(int[][] grid, boolean[][] vis , Queue<int[]> q, int i, int j) {
+        if (i < 0 || j < 0 || i >= grid.length || j >= grid[0].length || grid[i][j] == 0 || vis[i][j]) return;
+        vis[i][j] = true;
+        q.add(new int[]{i,j});
+        mark(grid, vis, q, i + 1, j);
+        mark(grid, vis, q, i - 1, j);
+        mark(grid, vis, q, i, j + 1);
+        mark(grid, vis, q, i, j - 1);
+
+    } 
+}
diff --git a/java/1498-number-of-subsequences-that-satisfy-the-given-sum-condition.java b/java/1498-number-of-subsequences-that-satisfy-the-given-sum-condition.java
new file mode 100644
index 000000000..a0aff7933
--- /dev/null
+++ b/java/1498-number-of-subsequences-that-satisfy-the-given-sum-condition.java
@@ -0,0 +1,27 @@
+class Solution {
+    public int numSubseq(int[] nums, int target) {
+        int mod = 1000000007;
+        int n = nums.length;
+        Arrays.sort(nums);
+
+        int[] pow2 = new int[n];
+        pow2[0] = 1;
+        for (int i = 1; i < n; i++) {
+            pow2[i] = (pow2[i - 1] * 2) % mod;
+        }
+
+        int left = 0, right = n - 1;
+        int count = 0;
+
+        while (left <= right) {
+            if (nums[left] + nums[right] <= target) {
+                count = (count + pow2[right - left]) % mod;
+                left++;
+            } else {
+                right--;
+            }
+        }
+
+        return count;
+    }
+}
diff --git a/java/1968-array-with-elements-not-equal-to-average-of-neighbors.java b/java/1968-array-with-elements-not-equal-to-average-of-neighbors.java
index 954295b7e..049ea894a 100644
--- a/java/1968-array-with-elements-not-equal-to-average-of-neighbors.java
+++ b/java/1968-array-with-elements-not-equal-to-average-of-neighbors.java
@@ -1,4 +1,33 @@
 class Solution {
+  
+  // Two pass Solution
+    public int[] rearrangeArray(int[] nums) {
+       
+        Arrays.sort(nums);
+        int n = nums.length;
+        int[] result = new int[n];
+        
+        int median = 0;
+        if (n % 2 == 0) {
+            median = (nums[n / 2 - 1] + nums[n / 2]) / 2; 
+        } else {
+            median = nums[n / 2]; 
+        }
+
+        int j = 0;
+        for (int i = 0; i < n; i += 2) {
+            result[i] = nums[j++];
+        }
+
+        for (int i = 1; i < n; i += 2) {
+            result[i] = nums[j++];
+        }
+
+        return result;
+    }
+}
+
+// One Pass Solution
     public int[] rearrangeArray(int[] nums) { 
         for(int i=1; i <= nums.length-2; i++){
             if( ( ( nums[i-1] < nums[i] && nums[i] < nums[i+1] ) || ( nums[i-1] > nums[i] && nums[i] > nums[i+1] ) )){ //swap
@@ -9,4 +38,5 @@ public int[] rearrangeArray(int[] nums) {
         }
         return nums;
     }
-}
\ No newline at end of file
+}
+
diff --git a/javascript/0026-remove-duplicates-from-sorted-array.js b/javascript/0026-remove-duplicates-from-sorted-array.js
index a03be24c9..cc4ae0995 100644
--- a/javascript/0026-remove-duplicates-from-sorted-array.js
+++ b/javascript/0026-remove-duplicates-from-sorted-array.js
@@ -1,24 +1,18 @@
 /**
- * Linear 
+ * Linear
  * Time O(N) | Space O(1)
  * https://leetcode.com/problems/remove-duplicates-from-sorted-array/
  * @param {number[]} nums
  * @return {number}
  */
-var removeDuplicates = (nums) => {
-    let [left, right] = [0, 0];
+var removeDuplicates = function (nums) {
+  let swap = 1;
 
-    while (right < nums.length) {
-        const [leftVal, rightVal] = [nums[left], nums[right]];
-
-        const isEqual = (rightVal === leftVal);
-        if (!isEqual) {
-            left++;
-            nums[left] = rightVal;
-        }
-
-        right++;
+  for (let i = 1; i < nums.length; i++) {
+    if (nums[i] != nums[i - 1]) {
+      nums[swap] = nums[i];
+      swap++;
     }
-
-    return (left + 1);
+  }
+  return swap;
 };
diff --git a/javascript/0100-same-tree.js b/javascript/0100-same-tree.js
index b875bca3b..5eb4ccce6 100644
--- a/javascript/0100-same-tree.js
+++ b/javascript/0100-same-tree.js
@@ -1,29 +1,44 @@
 /**
- * https://leetcode.com/problems/same-tree/
- * TIme O(N) | Space O(H)
+ * Check if both nodes are null (end of a branch in both trees)
  * @param {TreeNode} p
  * @param {TreeNode} q
  * @return {boolean}
  */
-var isSameTree = function(p, q) {
-    const isBaseCase = !(p || q);
-    if (isBaseCase) return true;
+var isSameTree = function (p, q) {
+    // Check if both nodes are null (end of a branch in both trees)
+    const areBothNodesNull = p == null && q == null;
+    if (areBothNodesNull) return true;
 
-    const isBalanced = (p && q);
-    if (!isBalanced) return false;
+    // Check if only one node is null (mismatch in tree structure)
+    const isOnlyOneNodeNull = p == null || q == null;
+    if (isOnlyOneNodeNull) return false;
 
-    const isSame = p.val === q.val;
-    if (!isSame) return false;
+    // Check if node values are equal (mismatch in node values)
+    const doNodesHaveEqualValue = p.val == q.val;
+    if (!doNodesHaveEqualValue) return false;
 
+    // Recursively check left and right subtrees
     return dfs(p, q);
 };
 
+/**
+ * * https://leetcode.com/problems/same-tree/
+ * * Time complexity is O(N), where N is the total number of nodes in the tree.
+   * This is because in the worst-case scenario, we need to visit every node once.
+
+ * * Space complexity is O(H), where H is the height of the tree.
+   * This is because in the worst-case scenario (a skewed tree), the maximum
+   * amount of space is consumed by the recursive stack. 
+ * @param {*} p 
+ * @param {*} q 
+ * @returns 
+ */
 const dfs = (p, q) => {
     const left = isSameTree(p.left, q.left);
     const right = isSameTree(p.right, q.right);
 
     return left && right;
-}
+};
 
 /**
  * https://leetcode.com/problems/same-tree/
@@ -32,40 +47,41 @@ const dfs = (p, q) => {
  * @param {TreeNode} q
  * @return {boolean}
  */
-var isSameTree = function(p, q) {
+var isSameTree = function (p, q) {
     if (isSameNode(p, q)) return true;
 
-    return bfs([[ p, q ]]);
-}
+    return bfs([[p, q]]);
+};
 
 const bfs = (queue) => {
     while (queue.length) {
-        for (let i = (queue.length - 1); 0 <= i; i--) {
-            const [ p, q ] = queue.shift();
+        for (let i = queue.length - 1; 0 <= i; i--) {
+            const [p, q] = queue.shift();
 
             if (!isSame(p, q)) return false;
 
-            if (p.left) queue.push([ p.left, q.left ]);
-            if (p.right) queue.push([ p.right, q.right ]);
+            if (p.left) queue.push([p.left, q.left]);
+            if (p.right) queue.push([p.right, q.right]);
         }
     }
 
     return true;
-}
+};
 
 const isSameNode = (p, q) => {
     const isBaseCase = !(p || q);
     if (isBaseCase) return true;
 
-    const isBalanced = (p && q);
+    const isBalanced = p && q;
     if (!isBalanced) return false;
 
     const isSame = p.val === q.val;
     if (!isSame) return false;
 
     return true;
-}
+};
 
-const isSame = (p, q) => isSameNode(p, q)
-    && isSameNode(p.left, q.left)
-    && isSameNode(p.right, q.right);
+const isSame = (p, q) =>
+    isSameNode(p, q) &&
+    isSameNode(p.left, q.left) &&
+    isSameNode(p.right, q.right);
diff --git a/javascript/0219-contains-duplicate-ii.js b/javascript/0219-contains-duplicate-ii.js
index 633e77fa9..a72e225f8 100644
--- a/javascript/0219-contains-duplicate-ii.js
+++ b/javascript/0219-contains-duplicate-ii.js
@@ -3,26 +3,24 @@
  * @param {number} k
  * @return {boolean}
  */
-var containsNearbyDuplicate = function (nums, k) {
-    let leftPtr = 0;
-    let rightPtr = 0;
-    let windowHashMap = new Map();
-    while (rightPtr < nums.length) {
-        if (windowHashMap.has(nums[rightPtr])) {
-            return true;
+/**
+ * @param {number[]} nums
+ * @param {number} k
+ * @return {boolean}
+ */
+var containsNearbyDuplicate = function(nums, k) {
+    const window = new Set();
+    let L = 0;
+    for (let R = 0; R < nums.length; R++) {
+        if (!window.has(nums[R])) {
+            window.add(nums[R]);
         } else {
-            windowHashMap.set(nums[rightPtr], 1);
+            return true
         }
-        rightPtr++;
-        if (rightPtr - leftPtr > k) {
-            let leftPtrValue = windowHashMap.get(nums[leftPtr]);
-            leftPtrValue--;
-            if (leftPtrValue == 0) {
-                windowHashMap.delete(nums[leftPtr]);
-            } else {
-                windowHashMap.set(nums[leftPtr], leftPtrValue);
-            }
-            leftPtr++;
+
+        if (R - L + 1 > k) {
+            window.delete(nums[L])
+            L++;
         }
     }
     return false;
diff --git a/javascript/0572-subtree-of-another-tree.js b/javascript/0572-subtree-of-another-tree.js
index 286210e92..3bb99eb13 100644
--- a/javascript/0572-subtree-of-another-tree.js
+++ b/javascript/0572-subtree-of-another-tree.js
@@ -4,7 +4,7 @@
  * @param {TreeNode} subRoot
  * @return {boolean}
  */
-var isSubtree = function(root, subRoot) {
+var isSubtree = function (root, subRoot) {
     if (!root) return false
 
     if (isSame(root, subRoot)) return true
@@ -19,7 +19,7 @@ const isSame = (root, subRoot) => {
     const hasReachedEnd = !(root && subRoot)
     if (hasReachedEnd) return root === subRoot
 
-    const isMismatch = root.val !== subRoot.val
+    const isMismatch = root.val !== subRoot.val;
     if (isMismatch) return false
 
     const isLeftSame = isSame(root.left, subRoot.left)
@@ -28,10 +28,8 @@ const isSame = (root, subRoot) => {
     return isLeftSame && isRightSame
 }
 
-const hash = (val) => require('crypto')
-    .createHash('md5')
-    .update(val)
-    .digest('hex')
+const hash = (val) =>
+    require('crypto').createHash('md5').update(val).digest('hex')
 
 const merkle = (root) => {
     if (!root) return '#'
@@ -41,7 +39,7 @@ const merkle = (root) => {
     const leftMerkle = merkle(left)
     const rightMerkle = merkle(right)
 
-    const merkleVal = [ leftMerkle, val, rightMerkle ].join('')
+    const merkleVal = [leftMerkle, val, rightMerkle].join('')
     const merkleHash = hash(merkleVal)
 
     root.merkle = merkleHash
@@ -61,8 +59,8 @@ const search = (root, subRoot) => {
     return left || right
 }
 
-var isSubtree = function(root, subRoot) {
-    [ root, subRoot ].forEach(merkle)
+var isSubtree = function (root, subRoot) {
+    [root, subRoot].forEach(merkle)
 
     return search(root, subRoot)
 }
@@ -83,14 +81,58 @@ const hashify = (root, hash, postOrderKey) => {
     return hash.get(key)
 }
 
-var isSubtree = function(root, subRoot, hash = new Map (), postOrderKey = [0]) {
+var isSubtree = function (root, subRoot, hash = new Map(), postOrderKey = [0]) {
     hashify(root, hash, postOrderKey)
 
     const hashKey = [
         hashify(subRoot.left, hash, postOrderKey),
         subRoot.val,
-        hashify(subRoot.right, hash, postOrderKey)
+        hashify(subRoot.right, hash, postOrderKey),
     ].join('')
 
     return hash.has(hashKey)
-}
\ No newline at end of file
+}
+
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val, left, right) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.left = (left===undefined ? null : left)
+ *     this.right = (right===undefined ? null : right)
+ * }
+ */
+/**
+ * https://leetcode.com/problems/subtree-of-another-tree/
+ * @param {TreeNode} root
+ * @param {TreeNode} subRoot
+ * @return {boolean}
+ */
+var isSubtree = function (root, subRoot) {
+    if (!subRoot) {
+        return true
+    } else if (!root) {
+        return false
+    } else if (isSameTree(root, subRoot)) {
+        return true
+    }
+
+    const leftResult = isSubtree(root.left, subRoot)
+    const rightResult = isSubtree(root.right, subRoot)
+
+    return leftResult || rightResult
+}
+
+function isSameTree(root, subRoot) {
+    if (!root && !subRoot) {
+        return true
+    } else if (!root || !subRoot) {
+        return false
+    } else if (root.val !== subRoot.val) {
+        return false
+    }
+
+    const leftRes = isSameTree(root.left, subRoot.left)
+    const rightRes = isSameTree(root.right, subRoot.right)
+
+    return leftRes && rightRes
+}
diff --git a/javascript/0707-design-linked-list.js b/javascript/0707-design-linked-list.js
new file mode 100644
index 000000000..e6f640b97
--- /dev/null
+++ b/javascript/0707-design-linked-list.js
@@ -0,0 +1,89 @@
+class Node {
+    constructor(val) {
+        this.val = val;
+        this.prev = null;
+        this.next = null;
+    }
+}
+
+class MyLinkedList {
+    constructor() {
+        this.head = null;
+        this.tail = null;
+    }
+
+    get(index) {
+        let curr = this.head;
+        while (curr && index > 0) {
+            curr = curr.next;
+            index--;
+        }
+        return curr ? curr.val : -1;
+    }
+
+    addAtHead(val) {
+        if (this.head === null) {
+            this.head = new Node(val);
+            this.tail = this.head;
+        } else {
+            this.head.prev = new Node(val);
+            this.head.prev.next = this.head;
+            this.head = this.head.prev;
+        }
+    }
+
+    addAtTail(val) {
+        if (this.head === null) {
+            this.head = new Node(val);
+            this.tail = this.head;
+        } else {
+            this.tail.next = new Node(val);
+            this.tail.next.prev = this.tail;
+            this.tail = this.tail.next;
+        }
+    }
+
+    addAtIndex(index, val) {
+        if (index === 0) this.addAtHead(val);
+        else {
+            let curr = this.head;
+            while (curr && index > 0) {
+                curr = curr.next;
+                index--;
+            }
+            if (index === 0) {
+                if (!curr) this.addAtTail(val);
+                else {
+                    const prev = curr.prev;
+                    prev.next = new Node(val);
+                    prev.next.prev = prev;
+                    prev.next.next = curr;
+                    curr.prev = prev.next;
+                }
+            }
+        }
+    }
+
+    deleteAtIndex(index) {
+        if (!this.head) return;
+        if (index === 0) {
+            this.head = this.head.next;
+            if (this.head) this.head.prev = null;
+        } else {
+            let curr = this.head;
+            while (curr && index > 0) {
+                curr = curr.next;
+                index--;
+            }
+            if (curr && index === 0) {
+                if (!curr.next) {
+                    curr.prev.next = null;
+                    this.tail = curr.prev;
+                } else {
+                    curr.prev.next = curr.next;
+                    curr.next.prev = curr.prev;
+                }
+            }
+        }
+    }
+}
diff --git a/javascript/0909-snakes-and-ladders.js b/javascript/0909-snakes-and-ladders.js
new file mode 100644
index 000000000..b00e525cf
--- /dev/null
+++ b/javascript/0909-snakes-and-ladders.js
@@ -0,0 +1,30 @@
+/**
+ * @param {number[][]} board
+ * @return {number}
+ */
+var snakesAndLadders = function(board) {
+    let n = board.length;
+    let set = new Set();
+    let getPos = (pos) => {
+        let row = Math.floor((pos - 1) / n)
+        let col = (pos - 1) % n
+        col = row % 2 == 1 ? n - 1 - col : col;
+        row = n - 1 - row;
+        return [row, col]
+    }
+    let q = [[1, 0]]
+    while (q.length > 0){
+        [pos, moves] = q.shift();
+        for (let i = 1; i < 7; i++){
+            let newPos = i + pos;
+            let [r, c] = getPos(newPos);
+            if (board[r][c] != -1 ) newPos = board[r][c]
+            if (newPos == n * n) return moves + 1;
+            if (!set.has(newPos)) {
+                set.add(newPos)
+                q.push([newPos, moves + 1])
+            }
+        }
+    }
+    return -1   
+};
diff --git a/javascript/2348-number-of-zero-filled-subarrays.js b/javascript/2348-number-of-zero-filled-subarrays.js
index 48f56cc96..7d445f219 100644
--- a/javascript/2348-number-of-zero-filled-subarrays.js
+++ b/javascript/2348-number-of-zero-filled-subarrays.js
@@ -20,6 +20,7 @@
  * @param {number[]} nums
  * @return {number}
  */
+
 let zeroFilledSubarray = function (nums) {
     let result = 0;
     let count = 0;
@@ -31,4 +32,4 @@ let zeroFilledSubarray = function (nums) {
     }
 
     return result;
-};
+};
\ No newline at end of file
diff --git a/javascript/2621-sleep.js b/javascript/2621-sleep.js
new file mode 100644
index 000000000..3e79979bf
--- /dev/null
+++ b/javascript/2621-sleep.js
@@ -0,0 +1,12 @@
+/**
+ * @param {number} millis
+ * @return {Promise}
+ */
+async function sleep(millis) {
+    return new Promise(resolve => setTimeout(() => resolve("Completed!"), millis));
+}
+
+/** 
+ * let t = Date.now()
+ * sleep(100).then(() => console.log(Date.now() - t)) // 100
+ */
diff --git a/javascript/2623-memoize.js b/javascript/2623-memoize.js
new file mode 100644
index 000000000..9fd662e49
--- /dev/null
+++ b/javascript/2623-memoize.js
@@ -0,0 +1,24 @@
+/**
+ * @param {Function} fn
+ * @return {Function}
+ */
+function memoize(fn) {
+    let memo = {};
+    return function (...args) {
+        let argsjson = JSON.stringify(args);
+        if (memo.hasOwnProperty(argsjson))
+            return memo[argsjson];
+        return memo[argsjson] = fn(...args);
+    }
+}
+
+/** 
+ * let callCount = 0;
+ * const memoizedFn = memoize(function (a, b) {
+ *	 callCount += 1;
+ *   return a + b;
+ * })
+ * memoizedFn(2, 3) // 5
+ * memoizedFn(2, 3) // 5
+ * console.log(callCount) // 1 
+ */
diff --git a/javascript/2626-array-reduce-transformation.js b/javascript/2626-array-reduce-transformation.js
new file mode 100644
index 000000000..f695fe046
--- /dev/null
+++ b/javascript/2626-array-reduce-transformation.js
@@ -0,0 +1,12 @@
+/**
+ * @param {number[]} nums
+ * @param {Function} fn
+ * @param {number} init
+ * @return {number}
+ */
+var reduce = function (nums, fn, init) {
+    ans = init;
+    for (let n of nums)
+        ans = fn(ans, n);
+    return ans;
+};
diff --git a/javascript/2627-debounce.js b/javascript/2627-debounce.js
new file mode 100644
index 000000000..55c83420d
--- /dev/null
+++ b/javascript/2627-debounce.js
@@ -0,0 +1,19 @@
+/**
+ * @param {Function} fn
+ * @param {number} t milliseconds
+ * @return {Function}
+ */
+var debounce = function (fn, t) {
+    let timeoutHandle;
+    return function (...args) {
+        clearTimeout(timeoutHandle);
+        timeoutHandle = setTimeout(() => fn(...args), t);
+    }
+};
+
+/**
+ * const log = debounce(console.log, 100);
+ * log('Hello'); // cancelled
+ * log('Hello'); // cancelled
+ * log('Hello'); // Logged at t=100ms
+ */
diff --git a/javascript/2629-function-composition.js b/javascript/2629-function-composition.js
new file mode 100644
index 000000000..6899a5d4e
--- /dev/null
+++ b/javascript/2629-function-composition.js
@@ -0,0 +1,17 @@
+/**
+ * @param {Function[]} functions
+ * @return {Function}
+ */
+var compose = function (functions) {
+    return function (x) {
+        let ans = x;
+        for (fn of functions.reverse())
+            ans = fn(ans);
+        return ans;
+    }
+};
+
+/**
+ * const fn = compose([x => x + 1, x => 2 * x])
+ * fn(4) // 9
+ */
diff --git a/javascript/2632-curry.js b/javascript/2632-curry.js
new file mode 100644
index 000000000..ed6ee86bb
--- /dev/null
+++ b/javascript/2632-curry.js
@@ -0,0 +1,20 @@
+/**
+ * @param {Function} fn
+ * @return {Function}
+ */
+var curry = function (fn) {
+    let accum = [];
+    return function curried(...args) {
+        for (let arg of args)
+            accum.push(arg);
+        if (accum.length === fn.length)
+            return fn(...accum);
+        return curried;
+    }
+};
+
+/**
+ * function sum(a, b) { return a + b; }
+ * const csum = curry(sum);
+ * csum(1)(2) // 3
+ */
diff --git a/javascript/2634-filter-elements-from-array.js b/javascript/2634-filter-elements-from-array.js
new file mode 100644
index 000000000..57ff4277c
--- /dev/null
+++ b/javascript/2634-filter-elements-from-array.js
@@ -0,0 +1,12 @@
+/**
+ * @param {number[]} arr
+ * @param {Function} fn
+ * @return {number[]}
+ */
+var filter = function (arr, fn) {
+    ans = [];
+    for (let i = 0; i < arr.length; i++)
+        if (fn(arr[i], i))
+            ans.push(arr[i]);
+    return ans;
+};
diff --git a/javascript/2635-apply-transform-over-each-element-in-array.js b/javascript/2635-apply-transform-over-each-element-in-array.js
new file mode 100644
index 000000000..419dd3ef2
--- /dev/null
+++ b/javascript/2635-apply-transform-over-each-element-in-array.js
@@ -0,0 +1,12 @@
+/**
+ * @param {number[]} arr
+ * @param {Function} fn
+ * @return {number[]}
+ */
+const map = (arr, fn) => {
+    const result = [];
+    for (let i = 0; i < arr.length; i++) {
+        result.push(fn(arr[i], i));
+    }
+    return result;
+}
\ No newline at end of file
diff --git a/javascript/2666-allow-one-function-call.js b/javascript/2666-allow-one-function-call.js
new file mode 100644
index 000000000..34afa8fba
--- /dev/null
+++ b/javascript/2666-allow-one-function-call.js
@@ -0,0 +1,21 @@
+/**
+ * @param {Function} fn
+ * @return {Function}
+ */
+var once = function (fn) {
+    let called = false;
+    return function (...args) {
+        if (!called) {
+            called = true;
+            return fn(...args);
+        }
+    }
+};
+
+/**
+ * let fn = (a,b,c) => (a + b + c)
+ * let onceFn = once(fn)
+ *
+ * onceFn(1,2,3); // 6
+ * onceFn(2,3,6); // returns undefined without calling fn
+ */
diff --git a/javascript/2704-to-be-or-not-to-be.js b/javascript/2704-to-be-or-not-to-be.js
new file mode 100644
index 000000000..4231b276c
--- /dev/null
+++ b/javascript/2704-to-be-or-not-to-be.js
@@ -0,0 +1,21 @@
+/**
+ * Creates an expectation object for testing values.
+ * 
+ * @param {any} val - The value to be tested.
+ * @returns {Object} An object with two methods:
+ *   - toBe(expected): Returns true if val === expected, otherwise throws an error "Not Equal".
+ *   - notToBe(expected): Returns true if val !== expected, otherwise throws an error "Equal".
+ */
+const expect = (val) => {
+    const throwError = (message) => { throw new Error(message); };
+    return {
+        toBe: (expected) => val === expected || throwError("Not Equal"),
+        notToBe: (expected) => val !== expected || throwError("Equal")
+    };
+};
+
+// Example usage:
+// expect(5).toBe(5); // returns true
+// expect(5).notToBe(3); // returns true
+// expect(5).toBe(3); // throws "Not Equal"
+// expect(5).notToBe(5); // throws "Equal"
\ No newline at end of file
diff --git a/python/0005-longest-palindromic-substring.py b/python/0005-longest-palindromic-substring.py
index c5eb6e7b7..1c1508775 100644
--- a/python/0005-longest-palindromic-substring.py
+++ b/python/0005-longest-palindromic-substring.py
@@ -1,25 +1,20 @@
+
 class Solution:
     def longestPalindrome(self, s: str) -> str:
-        res = ""
-        resLen = 0
-
+        self.res = ""
+        self.lenres = 0
         for i in range(len(s)):
-            # odd length
-            l, r = i, i
-            while l >= 0 and r < len(s) and s[l] == s[r]:
-                if (r - l + 1) > resLen:
-                    res = s[l : r + 1]
-                    resLen = r - l + 1
-                l -= 1
-                r += 1
+            s1 = self.helper(s, i, i)
+            s2 = self.helper(s, i, i + 1)
+        return s2
+        
+    def helper(self, s, left, right):
+            while left >= 0 and right < len(s) and s[left] == s[right]:
+                if (right - left + 1) > self.lenres:
+                    self.res = s[left:right+1]
+                    self.lenres = right - left + 1
+                left -= 1
+                right += 1
+            return self.res
 
-            # even length
-            l, r = i, i + 1
-            while l >= 0 and r < len(s) and s[l] == s[r]:
-                if (r - l + 1) > resLen:
-                    res = s[l : r + 1]
-                    resLen = r - l + 1
-                l -= 1
-                r += 1
 
-        return res
diff --git a/python/0016-3sum-closest.py b/python/0016-3sum-closest.py
new file mode 100644
index 000000000..86c1067ce
--- /dev/null
+++ b/python/0016-3sum-closest.py
@@ -0,0 +1,26 @@
+class Solution:
+    def threeSumClosest(self, nums: List[int], target: int) -> int:
+
+        nums.sort()
+        best = float('inf')
+        
+        for i in range(len(nums) - 2):
+            
+            val = nums[i]
+            left = i + 1
+            right = len(nums) - 1
+            
+            while left < right:
+                
+                currentGap = abs(target - (val + nums[left] + nums[right]))
+                
+                if abs(best - target) > currentGap:
+                    best = val + nums[left] + nums[right]
+                if val + nums[left] + nums[right] < target:
+                    left += 1
+                elif val + nums[left] + nums[right] > target:
+                    right -= 1
+                else: #closest it can get 
+                    return target                
+                
+        return best
diff --git a/python/0020-valid-parentheses.py b/python/0020-valid-parentheses.py
index 4d0ae3424..ce3bf39cd 100644
--- a/python/0020-valid-parentheses.py
+++ b/python/0020-valid-parentheses.py
@@ -1,13 +1,13 @@
 class Solution:
     def isValid(self, s: str) -> bool:
-        Map = {")": "(", "]": "[", "}": "{"}
+        bracketMap = {")": "(", "]": "[", "}": "{"}
         stack = []
 
         for c in s:
-            if c not in Map:
+            if c not in bracketMap:
                 stack.append(c)
                 continue
-            if not stack or stack[-1] != Map[c]:
+            if not stack or stack[-1] != bracketMap[c]:
                 return False
             stack.pop()
 
diff --git a/python/0079-word-search.py b/python/0079-word-search.py
index 12991f606..a08804808 100644
--- a/python/0079-word-search.py
+++ b/python/0079-word-search.py
@@ -25,7 +25,7 @@ def dfs(r, c, i):
             return res
 
         # To prevent TLE,reverse the word if frequency of the first letter is more than the last letter's
-        count = defaultdict(int, sum(map(Counter, board), Counter()))
+        count = sum(map(Counter, board), Counter())
         if count[word[0]] > count[word[-1]]:
             word = word[::-1]
             
diff --git a/python/0081-search-in-rotated-sorted-array-ii.py b/python/0081-search-in-rotated-sorted-array-ii.py
new file mode 100644
index 000000000..88649beaa
--- /dev/null
+++ b/python/0081-search-in-rotated-sorted-array-ii.py
@@ -0,0 +1,23 @@
+class Solution:
+    def search(self, nums: List[int], target: int) -> bool:
+        left,right = 0,len(nums) - 1
+        while left <= right:
+            mid = left + (right - left) // 2
+            if nums[mid] == target:
+                return True
+
+            #Left sorted portion
+            if nums[left] < nums[mid]:
+                if nums[left] <= target < nums[mid]:
+                    right = mid - 1
+                else:
+                    left = mid + 1
+            #Right sorted portion
+            elif nums[left] > nums[mid]:
+                if nums[mid] < target <= nums[right]:
+                    left = mid + 1
+                else:
+                    right = mid - 1
+            else:
+                left += 1
+        return False 
diff --git a/python/0100-same-tree.py b/python/0100-same-tree.py
index 4d55e2588..29957cf4f 100644
--- a/python/0100-same-tree.py
+++ b/python/0100-same-tree.py
@@ -7,7 +7,7 @@
 
 
 class Solution:
-    def isSameTree(self, p: TreeNode, q: TreeNode) -> bool:
+    def isSameTree(self, p: Optional[TreeNode], q: Optional[TreeNode]) -> bool:
         if not p and not q:
             return True
         if p and q and p.val == q.val:
diff --git a/python/0112-path-sum.py b/python/0112-path-sum.py
index e1260aa30..b6d4db31c 100644
--- a/python/0112-path-sum.py
+++ b/python/0112-path-sum.py
@@ -1,7 +1,16 @@
+# Recursive Solution
 class Solution:
     def hasPathSum(self, root, sum):
         if not root:
             return False
+        sum -= root.val
+        if not root.left and not root.right:
+            return sum == 0
+        return self.hasPathSum(root.left, sum) or self.hasPathSum(root.right, sum)
+      
+# Iterative Solution
+class Solution:
+    def hasPathSum(self, root, sum):
         de = [
             (root, sum - root.val),
         ]
@@ -13,4 +22,4 @@ def hasPathSum(self, root, sum):
                 de.append((node.right, curr_sum - node.right.val))
             if node.left:
                 de.append((node.left, curr_sum - node.left.val))
-        return False
+        return False
\ No newline at end of file
diff --git a/python/0151-reverse-words-in-a-string.py b/python/0151-reverse-words-in-a-string.py
new file mode 100644
index 000000000..81f226110
--- /dev/null
+++ b/python/0151-reverse-words-in-a-string.py
@@ -0,0 +1,15 @@
+class Solution:
+    def reverseWords(self, s: str) -> str:
+        # Remove leading and trailing spaces
+        s = s.strip()
+        
+        # Split the string into words
+        words = s.split()
+        
+        # Reverse the order of words
+        words = words[::-1]
+        
+        # Join the words with a single space
+        reversed_str = ' '.join(words)
+        
+        return reversed_str
diff --git a/python/0208-implement-trie-prefix-tree.py b/python/0208-implement-trie-prefix-tree.py
index fc26daebf..4b81ae701 100644
--- a/python/0208-implement-trie-prefix-tree.py
+++ b/python/0208-implement-trie-prefix-tree.py
@@ -18,7 +18,7 @@ def insert(self, word: str) -> None:
         curr = self.root
         for c in word:
             i = ord(c) - ord("a")
-            if curr.children[i] == None:
+            if curr.children[i] is None:
                 curr.children[i] = TrieNode()
             curr = curr.children[i]
         curr.end = True
@@ -30,7 +30,7 @@ def search(self, word: str) -> bool:
         curr = self.root
         for c in word:
             i = ord(c) - ord("a")
-            if curr.children[i] == None:
+            if curr.children[i] is None:
                 return False
             curr = curr.children[i]
         return curr.end
@@ -42,7 +42,7 @@ def startsWith(self, prefix: str) -> bool:
         curr = self.root
         for c in prefix:
             i = ord(c) - ord("a")
-            if curr.children[i] == None:
+            if curr.children[i] is None:
                 return False
             curr = curr.children[i]
         return True
diff --git a/python/0215-kth-largest-element-in-an-array.py b/python/0215-kth-largest-element-in-an-array.py
index c38303db8..cbeef51cc 100644
--- a/python/0215-kth-largest-element-in-an-array.py
+++ b/python/0215-kth-largest-element-in-an-array.py
@@ -1,3 +1,16 @@
+# Solution: Sorting
+# Time Complexity:
+#   - Best Case: O(n*log(k))
+#   - Average Case: O(n*log(k))
+#   - Worst Case:O(n*log(k))
+# Extra Space Complexity: O(k)
+class Solution:
+    def findKthLargest(self, nums: List[int], k: int) -> int:
+        heapify(nums)
+        while len(nums) > k:
+            heappop(nums)
+        return nums[0]
+
 # Solution: Sorting
 # Time Complexity:
 #   - Best Case: O(n)
diff --git a/python/0225-implement-stack-using-queues.py b/python/0225-implement-stack-using-queues.py
index fac7427d7..761192340 100644
--- a/python/0225-implement-stack-using-queues.py
+++ b/python/0225-implement-stack-using-queues.py
@@ -4,18 +4,15 @@ def __init__(self):
 
     def push(self, x: int) -> None:
         self.q.append(x)
+        
+        for _ in range(len(self.q) - 1):
+            self.q.append(self.q.popleft())
 
     def pop(self) -> int:
-        for i in range(len(self.q) - 1):
-            self.push(self.q.popleft())
         return self.q.popleft()
 
     def top(self) -> int:
-        for i in range(len(self.q) - 1):
-            self.push(self.q.popleft())
-        res = self.q[0]
-        self.push(self.q.popleft())
-        return res
+        return self.q[0]
 
     def empty(self) -> bool:
         return len(self.q) == 0
diff --git a/python/0297-serialize-and-deserialize-binary-tree.py b/python/0297-serialize-and-deserialize-binary-tree.py
index 5d62ace9c..5974ab7b0 100644
--- a/python/0297-serialize-and-deserialize-binary-tree.py
+++ b/python/0297-serialize-and-deserialize-binary-tree.py
@@ -23,14 +23,12 @@ def dfs(node):
 
     def deserialize(self, data):
         vals = data.split(",")
-        self.i = 0
 
         def dfs():
-            if vals[self.i] == "N":
-                self.i += 1
+            val = vals.pop(0)
+            if val == "N":
                 return None
-            node = TreeNode(int(vals[self.i]))
-            self.i += 1
+            node = TreeNode(val=int(val))
             node.left = dfs()
             node.right = dfs()
             return node
diff --git a/python/0338-counting-bits.py b/python/0338-counting-bits.py
index 42f0a4662..ca751db47 100644
--- a/python/0338-counting-bits.py
+++ b/python/0338-counting-bits.py
@@ -8,3 +8,17 @@ def countBits(self, n: int) -> List[int]:
                 offset = i
             dp[i] = 1 + dp[i - offset]
         return dp
+
+# Another dp solution
+class Solution2:
+    def countBits(self, n: int) -> List[int]:
+        res = [0] * (n + 1)
+        for i in range(1, n + 1):
+            if i % 2 == 1:
+                res[i] = res[i - 1] + 1
+            else:
+                res[i] = res[i // 2]
+        return res
+# This solution is based on the division of odd and even numbers. 
+# I think it's easier to understand.
+# This is my full solution, covering the details: https://leetcode.com/problems/counting-bits/solutions/4411054/odd-and-even-numbers-a-easier-to-understanding-way-of-dp/
diff --git a/python/0350-intersection-of-two-arrays-ii.py b/python/0350-intersection-of-two-arrays-ii.py
new file mode 100644
index 000000000..4c9bf5001
--- /dev/null
+++ b/python/0350-intersection-of-two-arrays-ii.py
@@ -0,0 +1,17 @@
+class Solution:
+    def intersect(self, nums1: List[int], nums2: List[int]) -> List[int]:
+        counter1 = Counter(nums1)
+        counter2 = Counter(nums2)
+
+        # Using defaultdict to handle missing keys more efficiently
+        counter1 = defaultdict(int, counter1)
+        counter2 = defaultdict(int, counter2)
+
+        intersection = []
+
+        for num, freq in counter1.items():
+            min_freq = min(freq, counter2[num])
+            if min_freq > 0:
+                intersection.extend([num] * min_freq)
+
+        return intersection
diff --git a/python/0513-find-bottom-left-tree-value.py b/python/0513-find-bottom-left-tree-value.py
index ccd3ed411..f9a6f030f 100644
--- a/python/0513-find-bottom-left-tree-value.py
+++ b/python/0513-find-bottom-left-tree-value.py
@@ -4,6 +4,27 @@
 #         self.val = val
 #         self.left = left
 #         self.right = right
+# Iterative
+class Solution:
+    def findBottomLeftValue(self, root: Optional[TreeNode]) -> int:
+
+        res = []
+        q = deque()
+        q.append(root)
+        while q:
+            qlen = len(q)
+            level = []
+            for i in range(qlen):
+                node = q.popleft()
+                if node:
+                    q.append(node.left)
+                    q.append(node.right)
+                    level.append(node.val)
+            if level:
+                res.append(level)
+        return res[-1][0]
+      
+# recursive
 class Solution:
     def findBottomLeftValue(self, root: Optional[TreeNode]) -> int:
         max_height = -1
@@ -20,3 +41,4 @@ def dfs(root, depth):
         
         dfs(root, 0)
         return res
+
diff --git a/python/1074-number-of-submatrices-that-sum-to-target.py b/python/1074-number-of-submatrices-that-sum-to-target.py
new file mode 100644
index 000000000..8bfd95f42
--- /dev/null
+++ b/python/1074-number-of-submatrices-that-sum-to-target.py
@@ -0,0 +1,26 @@
+class Solution:
+    def numSubmatrixSumTarget(self, matrix: List[List[int]], target: int) -> int:
+        ROWS, COLS = len(matrix), len(matrix[0])
+        sub_sum = [[0 for i in range(COLS)] for j in range(ROWS)]
+
+        for r in range(ROWS):
+            for c in range(COLS):
+                top = sub_sum[r - 1][c] if r > 0 else 0
+                left = sub_sum[r][c - 1] if c > 0 else 0
+                top_left = sub_sum[r - 1][c - 1] if min(r, c) > 0 else 0
+                sub_sum[r][c] = matrix[r][c] + top + left - top_left
+        
+        res = 0
+        for r1 in range(ROWS):
+            for r2 in range(r1, ROWS):
+                count = defaultdict(int) # prefix_sum -> count
+                count[0] = 1
+                for c in range(COLS):
+                    cur_sum = sub_sum[r2][c] - (
+                        sub_sum[r1 - 1][c] if r1 > 0 else 0
+                    )
+                    diff = cur_sum - target
+                    res += count[diff]
+                    count[cur_sum] += 1
+
+        return res
diff --git a/python/1203-sort-items-by-groups-respecting-dependencies.py b/python/1203-sort-items-by-groups-respecting-dependencies.py
new file mode 100644
index 000000000..7da80aed8
--- /dev/null
+++ b/python/1203-sort-items-by-groups-respecting-dependencies.py
@@ -0,0 +1,63 @@
+from collections import defaultdict, deque
+from typing import List
+class Solution:
+    # This function performs topological sort on a directed graph represented by successors and predecessors_count arrays.
+    def topologicalSort(self, successors: List[List[int]], predecessors_count: List[int], num_nodes: int) -> List[int]:
+        order = []  # To store the topologically sorted nodes
+        # Initialize a deque with all nodes that have no predecessors (i.e., in-degree of 0)
+        nodes_with_no_predecessors = deque(node for node in range(num_nodes) if not predecessors_count[node])
+        
+        while nodes_with_no_predecessors:  # Process nodes while there are nodes without predecessors
+            node = nodes_with_no_predecessors.popleft()  # Get the node with no predecessors
+            order.append(node)  # Add the node to the sorted order
+            for successor in successors[node]:  # For each successor of the current node
+                predecessors_count[successor] -= 1  # Decrement the in-degree of the successor
+                if not predecessors_count[successor]:  # If the successor now has no predecessors
+                    nodes_with_no_predecessors.append(successor)  # Add it to the queue for processing
+        
+        # If the number of nodes in the order is less than the total number of nodes, a cycle was detected
+        return order if len(order) == num_nodes else []  # Return the order if all nodes were sorted, else return empty list
+
+    def sortItems(self, n: int, m: int, group: List[int], beforeItems: List[List[int]]) -> List[int]:
+        # Step 1: Assign unique group IDs to items that don't belong to any group
+        for item in range(n):
+            if group[item] == -1:  # If the item doesn't belong to any group
+                group[item] = m  # Assign a new group ID
+                m += 1  # Increment the group ID for the next item
+        
+        # Step 2: Initialize graphs for item dependencies and group dependencies
+        successors_group, successors_item = [[] for _ in range(m)], [[] for _ in range(n)]  # Graphs for group and item dependencies
+        predecessors_count_group, predecessors_count_item = [0] * m, [0] * n  # Count of incoming edges (predecessors) for each group and item
+        
+        # Step 3: Build the dependency graphs based on beforeItems
+        for item in range(n):
+            current_group = group[item]  # Get the group of the current item
+            for before in beforeItems[item]:  # Process each item that should come before the current item
+                before_group = group[before]  # Get the group of the item that should come before
+                
+                if current_group == before_group:  # If the two items belong to the same group
+                    successors_item[before].append(item)  # Add a dependency from 'before' to the current item
+                    predecessors_count_item[item] += 1  # Increment the in-degree of the current item
+                else:  # If the items belong to different groups
+                    successors_group[before_group].append(current_group)  # Add a group dependency
+                    predecessors_count_group[current_group] += 1  # Increment the in-degree of the current group
+        
+        # Step 4: Perform topological sort on both the group dependencies and item dependencies
+        groups_order = self.topologicalSort(successors_group, predecessors_count_group, m)  # Topological sort of groups
+        items_order = self.topologicalSort(successors_item, predecessors_count_item, n)  # Topological sort of items
+        
+        # Step 5: If there was a cycle detected in either group or item sorting, return an empty list
+        if not groups_order or not items_order:
+            return []  # Return an empty list if either the group or item topological sort failed
+        
+        # Step 6: Group the items based on the group IDs
+        items_grouped = [[] for _ in range(m)]  # Create an empty list for each group to store its items
+        for item in items_order:  # Process each item in topologically sorted order
+            items_grouped[group[item]].append(item)  # Add the item to the appropriate group
+        
+        # Step 7: Combine the groups in topologically sorted order
+        result = []  # The final result list to store the sorted items
+        for grp in groups_order:  # For each group in topologically sorted order
+            result.extend(items_grouped[grp])  # Add the items of the group to the result
+        
+        return result  # Return the final sorted list of items respecting both item and group dependencies
diff --git a/python/1397-find-all-good-strings.py b/python/1397-find-all-good-strings.py
new file mode 100644
index 000000000..8e628b96f
--- /dev/null
+++ b/python/1397-find-all-good-strings.py
@@ -0,0 +1,48 @@
+class Solution:
+    def findGoodStrings(self, n: int, s1: str, s2: str, evil: str) -> int:
+        a = ord('a')
+        z = ord('z')
+        
+        arr_e = list(map(ord, evil))
+        len_e = len(evil)
+        next = [0] * len_e
+
+        for i in range(1, len_e):
+            j = next[i - 1]
+            while j > 0 and evil[i] != evil[j]:
+                j = next[j - 1]
+            if evil[i] == evil[j]:
+                next[i] = j + 1
+
+        def good(s):
+            arr = list(map(ord, s))
+            len_a = len(arr)
+
+            @cache
+            def f(i, skip, reach, e):
+                if e == len_e:
+                    return 0
+                if i == len_a:
+                    return 0 if skip else 1
+
+                limit = arr[i] if reach else z
+                ans = 0
+
+                if skip:
+                    ans += f(i + 1, True, False, 0)
+
+                for c in range(a, limit + 1):
+                    ee = e
+                    while ee > 0 and arr_e[ee] != c:
+                        ee = next[ee - 1] 
+
+                    if arr_e[ee] == c:
+                        ee += 1
+
+                    ans += f(i + 1, False, reach and c == limit, ee)
+
+                return ans % int(1e9 + 7)
+
+            return f(0, True, True, 0)
+
+        return (good(s2) - good(s1) + int(evil not in s1)) % int(1e9 + 7)
diff --git a/python/1475-final-prices-with-a-special-discount-in-a-shop.py b/python/1475-final-prices-with-a-special-discount-in-a-shop.py
new file mode 100644
index 000000000..00d1f567b
--- /dev/null
+++ b/python/1475-final-prices-with-a-special-discount-in-a-shop.py
@@ -0,0 +1,19 @@
+class Solution:
+    def finalPrices(self, prices: List[int]) -> List[int]:
+        stack = []
+        res = []
+        for i in range(len(prices) - 1, -1, -1):
+            if len(stack) == 0:
+                res.append(prices[i])
+            elif len(stack) and stack[-1] <= prices[i]:
+                res.append(prices[i] - stack[-1])
+            elif len(stack) and stack[-1] > prices[i]:
+                while len(stack) and stack[-1] > prices[i]:
+                    stack.pop()
+                if len(stack) == 0:
+                    res.append(prices[i])
+                else: 
+                    res.append(prices[i] - stack[-1])
+            stack.append(prices[i])
+        res.reverse()
+        return res
diff --git a/python/1582-special-positions-in-a-binary-matrix.py b/python/1582-special-positions-in-a-binary-matrix.py
new file mode 100644
index 000000000..5e0547784
--- /dev/null
+++ b/python/1582-special-positions-in-a-binary-matrix.py
@@ -0,0 +1,18 @@
+class Solution:
+    def numSpecial(self, mat: List[List[int]]) -> int:
+        m = len(mat)
+        n = len(mat[0])
+        rowCount = [0] * m
+        colCount = [0] * n
+        res = 0
+        for r in range(m):
+            for c in range(n):
+                if mat[r][c] == 1:
+                    rowCount[r] += 1
+                    colCount[c] += 1
+        for r in range(m):
+            for c in range(n):
+                if mat[r][c] == 1 and rowCount[r] == 1 and colCount[c] == 1:
+                    res += 1
+        return res
+        
diff --git a/python/2215-find-the-difference-of-two-arrays.py b/python/2215-find-the-difference-of-two-arrays.py
index 0aea837dd..ca508425d 100644
--- a/python/2215-find-the-difference-of-two-arrays.py
+++ b/python/2215-find-the-difference-of-two-arrays.py
@@ -1,3 +1,27 @@
+# Time Complexiy: O(m + n)
+# Space Complexity: O(m + n)
+class Solution:
+    def findDifference(self, nums1: List[int], nums2: List[int]) -> List[List[int]]:
+        nums1 = set(nums1)
+        nums2 = set(nums2)
+        table = {}
+        for _, val in enumerate(nums2):
+            table[val] = 1
+
+        unik1 = []
+        unik2 = []
+        for i in nums1:
+            if i in table:
+                table[i] += 1
+            else:
+                unik1.append(i)
+        
+        for key, val in table.items():
+            if val == 1:
+                unik2.append(key)
+        return [unik1, unik2]
+
+      
 # Time Complexity: O(m + n), we check each element of nums1Set and nums2Set
 # Space Complexity: O(m + n), where m and n are length sets in worst case.
 
@@ -13,3 +37,4 @@ def findDifference(self, nums1: List[int], nums2: List[int]) -> List[List[int]]:
         lst2 = [num for num in nums2_set if num not in nums1_set]
 
         return [lst1, lst2]
+
diff --git a/python/2235-add-two-integers.py b/python/2235-add-two-integers.py
new file mode 100644
index 000000000..29d001ddb
--- /dev/null
+++ b/python/2235-add-two-integers.py
@@ -0,0 +1,3 @@
+class Solution:
+    def sum(self, num1: int, num2: int) -> int:
+        return num1 + num2
diff --git a/python/2482-difference-between-ones-and-zeros-in-row-and-column.py b/python/2482-difference-between-ones-and-zeros-in-row-and-column.py
new file mode 100644
index 000000000..c85dba8b4
--- /dev/null
+++ b/python/2482-difference-between-ones-and-zeros-in-row-and-column.py
@@ -0,0 +1,23 @@
+class Solution:
+    def onesMinusZeros(self, grid: List[List[int]]) -> List[List[int]]:
+        m , n = len(grid), len(grid[0])
+        rowCount = [[0, 0] for _ in range(m)] # (zeros, ones)
+        colCount = [[0, 0] for _ in range(n)]
+        res = []
+        for r in range(m):
+            for c in range(n):
+                if grid[r][c] == 1:
+                    rowCount[r][1] += 1
+                    colCount[c][1] += 1
+                else:
+                    rowCount[r][0] += 1
+                    colCount[c][0] += 1
+        for r in range(m):
+            row =[]
+            for c in range(n):
+                row.append(rowCount[r][1] + colCount[c][1] - 
+                            rowCount[r][0] - colCount[c][0])
+            res.append(row)
+        return res
+
+        
diff --git a/python/2554-maximum-number-of-integers-to-choose-from-a-range-i.py b/python/2554-maximum-number-of-integers-to-choose-from-a-range-i.py
new file mode 100644
index 000000000..9b36009df
--- /dev/null
+++ b/python/2554-maximum-number-of-integers-to-choose-from-a-range-i.py
@@ -0,0 +1,15 @@
+class Solution:
+    def maxCount(self, banned: List[int], n: int, maxSum: int) -> int:
+        nums = {x:1 for x in range(1, n + 1)} # hashmap for storing the required elements
+        for i in banned:
+            if nums.get(i):
+                del nums[i]
+        sum = 0
+        count = 0
+        for i in nums:
+            sum += i
+            if sum <= maxSum:
+                count += 1
+            else:
+                break
+        return count
diff --git a/ruby/0020-valid-parentheses.rb b/ruby/0020-valid-parentheses.rb
index e140c5589..fb2c83502 100644
--- a/ruby/0020-valid-parentheses.rb
+++ b/ruby/0020-valid-parentheses.rb
@@ -8,10 +8,11 @@ def is_valid(s)
   s.each_char do |char|
     if match.key?(char)
       paren << char
-    else
-      return false if paren.empty?
-      return false if match[paren.pop] != char
+      next
+    elsif paren.empty? || match[paren.pop] != char
+      return false
     end
+    paren.pop
   end
   paren.empty?
 end
diff --git a/ruby/1299-replace-elements-with-greatest-element-on-right-side.rb b/ruby/1299-replace-elements-with-greatest-element-on-right-side.rb
new file mode 100644
index 000000000..5756a5480
--- /dev/null
+++ b/ruby/1299-replace-elements-with-greatest-element-on-right-side.rb
@@ -0,0 +1,9 @@
+def replace_elements(arr)
+  right_max = -1
+  (arr.length - 1).downto(0) do |i|
+    cur_max = [right_max, arr[i]].max
+    arr[i] = right_max
+    right_max = cur_max
+  end
+  arr
+end
diff --git a/ruby/1929-concatenation-of-array.rb b/ruby/1929-concatenation-of-array.rb
index 2143f1bb6..408873a7e 100644
--- a/ruby/1929-concatenation-of-array.rb
+++ b/ruby/1929-concatenation-of-array.rb
@@ -2,4 +2,4 @@
 # @return {Integer[]}
 def get_concatenation(nums)
     nums + nums
-end
\ No newline at end of file
+end
diff --git a/rust/0021-merge-two-sorted-lists.rs b/rust/0021-merge-two-sorted-lists.rs
index bc007e53e..233ebc0dd 100644
--- a/rust/0021-merge-two-sorted-lists.rs
+++ b/rust/0021-merge-two-sorted-lists.rs
@@ -1,44 +1,46 @@
 impl Solution {
-    pub fn merge_two_lists(list1: Option<Box<ListNode>>, list2: Option<Box<ListNode>>) -> Option<Box<ListNode>> {
-        match (list1,list2) {
-            (Some(list1),None)=> Some(list1),
-            (None,Some(list2))=>Some(list2),
-            (None,None)=>None,
-            (Some(l1),Some(l2))=>{
-                if l1.val<l2.val {
-                  return Some(Box::new(ListNode{val:l1.val,next:Solution::merge_two_lists(l1.next,Some(l2))}));
-                }else {
-                  return Some(Box::new(ListNode { val: l2.val, next: Solution::merge_two_lists(Some(l1),l2.next) }))
+    pub fn merge_two_lists(
+        list1: Option<Box<ListNode>>,
+        list2: Option<Box<ListNode>>,
+    ) -> Option<Box<ListNode>> {
+        match (list1, list2) {
+            (Some(list1), None) => Some(list1),
+            (None, Some(list2)) => Some(list2),
+            (None, None) => None,
+            (Some(l1), Some(l2)) => {
+                if l1.val < l2.val {
+                    return Some(Box::new(ListNode {
+                        val: l1.val,
+                        next: Solution::merge_two_lists(l1.next, Some(l2)),
+                    }));
+                } else {
+                    return Some(Box::new(ListNode {
+                        val: l2.val,
+                        next: Solution::merge_two_lists(Some(l1), l2.next),
+                    }));
                 }
             }
         }
     }
 }
+
 //without recursion
 impl Solution {
-    pub fn merge_two_lists(mut list1: Option<Box<ListNode>>,mut list2: Option<Box<ListNode>>)->Option<Box<ListNode>>{
-        let mut ans=ListNode::new(1);
-        let mut cur=&mut ans;
-   
-   while let (Some(node1),Some(node2))=(list1.as_mut(),list2.as_mut()){
-   
-   if node1.val<node2.val{
-       cur.next=list1.take();
-       list1=cur.next.as_mut().unwrap().next.take();
-   }
-   else{
-       cur.next=list2.take();
-       list2=cur.next.as_mut().unwrap().next.take();
-   }
-   cur=cur.next.as_mut().unwrap();
-   }
-   cur.next=if list1.is_some(){
-       list1
-   }
-   else {
-       list2
-   };
-   ans.next
-}
+    pub fn merge_two_lists(
+        mut l1: Option<Box<ListNode>>,
+        mut l2: Option<Box<ListNode>>,
+    ) -> Option<Box<ListNode>> {
+        // Tail is the rightmost part of l1 that we keep swapping
+        let mut tail = &mut l1;
+        while l2.is_some() {
+            if tail.is_none() || l2.as_ref()?.val < tail.as_ref()?.val {
+                // Keep swapping the end part of l1
+                // so that the smallest nodes appear
+                // first in l1
+                std::mem::swap(tail, &mut l2);
+            }
+            tail = &mut tail.as_mut()?.next;
+        }
+        l1
+    }
 }
-
diff --git a/rust/0143-reorder-list.rs b/rust/0143-reorder-list.rs
new file mode 100644
index 000000000..49080c0b0
--- /dev/null
+++ b/rust/0143-reorder-list.rs
@@ -0,0 +1,46 @@
+impl Solution {
+    pub fn reorder_list(mut head: &mut Option<Box<ListNode>>) {
+        let mut length = 0;
+        let mut list = head.as_mut();
+        // find the total length of the list
+        // Using the slow & fast pointer is probably not possible
+        while let Some(node) = list {
+            length += 1;
+            list = node.next.as_mut();
+        }
+        // if length is less than or equal to 2 then exit the function
+        if length <= 2 {
+            return;
+        }
+        // find the middle node to split the list
+        let mut mid = head.as_mut();
+        for _ in 0..length / 2 {
+            mid = match mid {
+                None => unreachable!("Traversing half of the list. Cannot reach the end."),
+                Some(node) => node.next.as_mut(),
+            }
+        }
+        // Tail is the right half of the list.
+        // Here we use take() to break the linked list
+        // so the end of the first half now points to None
+        // and tail holds the second half of the linked list
+        let mut tail = mid.expect("Mid cannot be None.").as_mut().next.take();
+        // reverse the tail
+        let mut reversed: Option<Box<ListNode>> = None;
+        while let Some(mut node) = tail {
+            tail = node.next;
+            node.next = reversed;
+            reversed = Some(node);
+        }
+        // merge the first half(head) & the second reversed half(reversed)
+        // This solution to merge two linked lists is clever
+        // https://leetcode.com/problems/merge-two-sorted-lists/solutions/2947855/simple-and-efficient-rust-8-liner/
+        // mover is the variable that traverses and modifies "head"
+        let mut mover: &mut _ = &mut reversed;
+        while head.is_some() {
+            std::mem::swap(mover, &mut head);
+            mover = &mut mover.as_mut().unwrap().next;
+        }
+        std::mem::swap(head, &mut reversed);
+    }
+}
diff --git a/rust/0200-number-of-islands.rs b/rust/0200-number-of-islands.rs
index c92622a1f..52fb3aa2a 100644
--- a/rust/0200-number-of-islands.rs
+++ b/rust/0200-number-of-islands.rs
@@ -1,5 +1,5 @@
 impl Solution {
-    pub fn num_islands(grid: Vec<Vec<char>>) -> i32 {
+    pub fn num_islands(mut grid: Vec<Vec<char>>) -> i32 {
         fn dfs(grid: &mut Vec<Vec<char>>, x: i32, y: i32) {
             if x < 0
                 || y < 0
@@ -9,28 +9,26 @@ impl Solution {
             {
                 return;
             }
-
+    
             grid[x as usize][y as usize] = '0';
-
+    
             let directions: [(i32, i32); 4] = [(0, 1), (1, 0), (0, -1), (-1, 0)];
-
+    
             for (add_x, add_y) in directions {
                 dfs(grid, x + add_x, y + add_y);
             }
         }
-
+    
         let mut count = 0;
-        let mut new_grid = grid.clone();
-
         for x in 0..grid.len() {
             for y in 0..grid[0].len() {
-                if new_grid[x][y] == '1' {
+                if grid[x][y] == '1' {
                     count += 1;
-                    dfs(&mut new_grid, x as i32, y as i32);
+                    dfs(&mut grid, x as i32, y as i32);
                 }
             }
         }
-
+    
         count
     }
 }
diff --git a/rust/0380-insert-delete-getrandom-o1.rs b/rust/0380-insert-delete-getrandom-o1.rs
new file mode 100644
index 000000000..61913abb1
--- /dev/null
+++ b/rust/0380-insert-delete-getrandom-o1.rs
@@ -0,0 +1,40 @@
+use rand::seq::SliceRandom;
+use std::collections::HashMap;
+
+pub struct RandomizedSet {
+    mp: HashMap<i32, i32>,
+    arr: Vec<i32>,
+}
+
+impl RandomizedSet {
+    fn new() -> Self {
+        RandomizedSet {
+            mp: HashMap::new(),
+            arr: Vec::new(),
+        }
+    }
+
+    fn insert(&mut self, val: i32) -> bool {
+        let res = !self.mp.contains_key(&val);
+        if res {
+            self.mp.insert(val, self.arr.len() as i32);
+            self.arr.push(val);
+        }
+        res
+    }
+    fn remove(&mut self, val: i32) -> bool {
+        let res = self.mp.contains_key(&val);
+        if res {
+            let idx = *self.mp.get(&val).unwrap();
+            self.mp
+                .entry(*self.arr.last().unwrap())
+                .and_modify(|v| *v = idx);
+            self.arr.swap_remove(idx as usize);
+            self.mp.remove(&val);
+        }
+        res
+    }
+    fn get_random(&self) -> i32 {
+        *self.arr.choose(&mut rand::thread_rng()).unwrap()
+    }
+}
diff --git a/rust/0441-arranging-coins.rs b/rust/0441-arranging-coins.rs
new file mode 100644
index 000000000..3d92066a4
--- /dev/null
+++ b/rust/0441-arranging-coins.rs
@@ -0,0 +1,21 @@
+impl Solution {
+    pub fn arrange_coins(n: i32) -> i32 {
+        let (mut l, mut r) = (1, n);
+        let mut res = 0;
+
+        while l <= r {
+            let mid = l + (r - l) / 2;
+            let coins = (mid as i64 * (mid as i64 + 1)) / 2;
+
+            if coins > n as i64 {
+                r = mid - 1;
+            } else {
+                l = mid + 1;
+                res = mid;
+            }
+        }
+
+        res as i32
+
+    }
+}
\ No newline at end of file
diff --git a/rust/1480-running-sum-of-1d-array.rs b/rust/1480-running-sum-of-1d-array.rs
new file mode 100644
index 000000000..0b65474d3
--- /dev/null
+++ b/rust/1480-running-sum-of-1d-array.rs
@@ -0,0 +1,11 @@
+impl Solution {
+    pub fn running_sum(nums: Vec<i32>) -> Vec<i32> {
+        let mut total = 0;
+        let mut arr = Vec::new();
+        for n in nums {
+            total += n;
+            arr.push(total);
+        }
+        return arr;
+    }
+}
diff --git a/rust/2114-maximum-number-of-words-found-in-sentences.rs b/rust/2114-maximum-number-of-words-found-in-sentences.rs
new file mode 100644
index 000000000..b9d5ce8d4
--- /dev/null
+++ b/rust/2114-maximum-number-of-words-found-in-sentences.rs
@@ -0,0 +1,12 @@
+impl Solution {
+    pub fn most_words_found(sentences: Vec<String>) -> i32 {
+       let mut most = 0;
+       for sentence in sentences {
+           let size = sentence.split_whitespace().count();
+           if size > most {
+               most = size;
+           }
+       }
+       return most as i32;
+    }
+}
diff --git a/scala/0704-binary-search.scala b/scala/0704-binary-search.scala
new file mode 100644
index 000000000..ae51675d8
--- /dev/null
+++ b/scala/0704-binary-search.scala
@@ -0,0 +1,20 @@
+object Solution {
+  def search(nums: Array[Int], target: Int): Int = {
+    var left = 0
+    var right = nums.length - 1
+
+    while (left <= right) {
+      val mid = left + (right - left) / 2
+
+      if (nums(mid) == target) {
+        return mid
+      } else if (nums(mid) < target) {
+        left = mid + 1
+      } else {
+        right = mid - 1
+      }
+    }
+
+    return -1
+  }
+}
diff --git a/swift/0010-regular-expression-matching.swift b/swift/0010-regular-expression-matching.swift
new file mode 100644
index 000000000..baed11533
--- /dev/null
+++ b/swift/0010-regular-expression-matching.swift
@@ -0,0 +1,31 @@
+class Solution {
+    func isMatch(_ s: String, _ p: String) -> Bool {
+        let s = Array(s), p = Array(p)
+        var dp = [[Int]: Bool]()
+
+        func dfs(_ i: Int, _ j: Int) -> Bool {
+            if dp[[i, j]] != nil {
+                return dp[[i, j]]!
+            }
+            if i >= s.count && j >= p.count {
+                return true
+            }
+            if j >= p.count {
+                return false
+            }
+            let isMatch = i < s.count && (s[i] == p[j] || p[j] == ".")
+            if j + 1 < p.count && p[j + 1] == "*" {
+                dp[[i, j]] = dfs(i, j + 2) || (isMatch && dfs(i + 1, j))
+                return dp[[i, j]]!
+            }
+            if isMatch {
+                dp[[i, j]] = dfs(i + 1, j + 1)
+                return dp[[i, j]]!
+            }
+            dp[[i, j]] = false
+            return false
+        }
+        
+        return dfs(0, 0)
+    }
+}
\ No newline at end of file
diff --git a/swift/0073-set-matrix-zeroes.swift b/swift/0073-set-matrix-zeroes.swift
new file mode 100644
index 000000000..ec6867aca
--- /dev/null
+++ b/swift/0073-set-matrix-zeroes.swift
@@ -0,0 +1,39 @@
+class Solution {
+    func setZeroes(_ matrix: inout [[Int]]) {
+        let rows = matrix.count, cols = matrix[0].count
+        var rowZero = false
+
+        for r in 0..<rows {
+            for c in 0..<cols {
+                if matrix[r][c] == 0 {
+                    matrix[0][c] = 0
+                    if r > 0 {
+                        matrix[r][0] = 0
+                    } else {
+                        rowZero = true
+                    }
+                }
+            }
+        }
+
+        for r in 1..<rows {
+            for c in 1..<cols {
+                if matrix[0][c] == 0 || matrix[r][0] == 0 {
+                    matrix[r][c] = 0
+                }
+            }
+        }
+
+        if matrix[0][0] == 0 {
+            for r in 0..<rows {
+                matrix[r][0] = 0
+            }
+        }
+
+        if rowZero {
+            for c in 0..<cols {
+                matrix[0][c] = 0
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/swift/0143-reorder-list.swift b/swift/0143-reorder-list.swift
index f0cfe2d69..bd37c6e0b 100644
--- a/swift/0143-reorder-list.swift
+++ b/swift/0143-reorder-list.swift
@@ -1,3 +1,54 @@
+// Slow and Fast Pointer Method
+/**
+ * Question Link: https://leetcode.com/problems/reorder-list/
+ */
+
+ /**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public var val: Int
+ *     public var next: ListNode?
+ *     public init() { self.val = 0; self.next = nil; }
+ *     public init(_ val: Int) { self.val = val; self.next = nil; }
+ *     public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
+ * }
+ */
+class ReorderList {
+    func reorderList(_ head: ListNode?) {
+        var slow = head
+        var fast = head?.next
+
+        while fast != nil || fast?.next != nil {
+            slow = slow?.next
+            fast = fast?.next?.next
+        }
+
+        var second = slow?.next
+        slow?.next = nil
+        var prev: ListNode?
+
+        while second != nil {
+            var temp = second?.next
+            second?.next = prev
+            prev = second
+            second = temp
+        }
+
+        var first = head
+        second = prev
+
+        while second != nil {
+            var temp1 = first?.next
+            var temp2 = second?.next
+            first?.next = second
+            second?.next = temp1
+            first = temp1
+            second = temp2
+        }
+    }
+}
+
+// Deque 
 import DequeModule
 
 class Solution {
@@ -19,3 +70,4 @@ class Solution {
         }
     }
 }
+
diff --git a/swift/0228-summary-ranges.swift b/swift/0228-summary-ranges.swift
new file mode 100644
index 000000000..cb0736d83
--- /dev/null
+++ b/swift/0228-summary-ranges.swift
@@ -0,0 +1,27 @@
+class Solution {
+    func summaryRanges(_ nums: [Int]) -> [String] {
+        if nums.isEmpty {
+            return []
+        }
+        var l = 0
+        var res = [String]()
+        for r in 1..<nums.count {
+            if nums[r] != nums[r - 1] + 1 { 
+                if l == r - 1 {
+                    res.append("\(nums[l])")
+                } else {
+                    res.append("\(nums[l])->\(nums[r - 1])")
+                }
+                l = r
+            } 
+        }
+
+        if l == nums.count - 1 {
+            res.append("\(nums[l])")
+        } else {
+            res.append("\(nums[l])->\(nums[nums.count - 1])")
+        }
+
+        return res
+    }
+}
\ No newline at end of file
diff --git a/swift/0300-longest-increasing-subsequence.swift b/swift/0300-longest-increasing-subsequence.swift
new file mode 100644
index 000000000..ed43bb37c
--- /dev/null
+++ b/swift/0300-longest-increasing-subsequence.swift
@@ -0,0 +1,13 @@
+class Solution {
+    func lengthOfLIS(_ nums: [Int]) -> Int {
+        var dp = [Int](repeating: 1, count: nums.count)
+        for i in stride(from: nums.count - 1, to: -1, by: -1) {
+            for j in (i + 1)..<nums.count {
+                if nums[i] < nums[j] {
+                    dp[i] = max(dp[i], 1 + dp[j])
+                }
+            }
+        }
+        return dp.max() ?? -1
+    }
+}
\ No newline at end of file
diff --git a/swift/0312-burst-balloons.swift b/swift/0312-burst-balloons.swift
new file mode 100644
index 000000000..8df2fac0d
--- /dev/null
+++ b/swift/0312-burst-balloons.swift
@@ -0,0 +1,26 @@
+class Solution {
+    func maxCoins(_ nums: [Int]) -> Int {
+        var nums = [1] + nums + [1]
+        var dp = [[Int]: Int]()
+
+        func dfs(_ l: Int, _ r: Int) -> Int {
+            if l > r {
+                return 0
+            }
+            if dp[[l, r]] != nil {
+                return dp[[l, r]]!
+            }
+
+            dp[[l, r]] = 0
+            for i in l...r {
+                var coins = nums[l - 1] * nums[i] * nums[r + 1]
+                coins += dfs(l, i - 1) + dfs(i + 1, r)
+                dp[[l, r]] = max(dp[[l, r]]!, coins)
+            }
+
+            return dp[[l, r]]!
+        }
+
+        return dfs(1, nums.count - 2)
+    }
+}
\ No newline at end of file
diff --git a/swift/0329-longest-increasing-path-in-a-matrix.swift b/swift/0329-longest-increasing-path-in-a-matrix.swift
new file mode 100644
index 000000000..e01e54ea5
--- /dev/null
+++ b/swift/0329-longest-increasing-path-in-a-matrix.swift
@@ -0,0 +1,30 @@
+class Solution {
+    func longestIncreasingPath(_ matrix: [[Int]]) -> Int {
+        let rows = matrix.count, cols = matrix[0].count
+        var dp = [[Int]: Int]()
+
+        func dfs(_ r: Int, _ c: Int, _ prev: Int) -> Int {
+            if r < 0 || r == rows || c < 0 || c == cols || matrix[r][c] <= prev {
+                return 0
+            }
+            if dp[[r, c]] != nil {
+                return dp[[r, c]]!
+            }
+            var res = 1
+            res = max(res, 1 + dfs(r + 1, c, matrix[r][c]))
+            res = max(res, 1 + dfs(r - 1, c, matrix[r][c]))
+            res = max(res, 1 + dfs(r, c + 1, matrix[r][c]))
+            res = max(res, 1 + dfs(r, c - 1, matrix[r][c]))
+            dp[[r, c]] = res
+            return res
+        }
+
+        for r in 0..<rows {
+            for c in 0..<cols {
+                dfs(r, c, -1)
+            }
+        }
+
+        return dp.values.max()!
+    }
+}
\ No newline at end of file
diff --git a/swift/1493-longest-subarray-of-1s-after-deleting-one-element.swift b/swift/1493-longest-subarray-of-1s-after-deleting-one-element.swift
new file mode 100644
index 000000000..a1a712d3f
--- /dev/null
+++ b/swift/1493-longest-subarray-of-1s-after-deleting-one-element.swift
@@ -0,0 +1,22 @@
+class Solution {
+    func longestSubarray(_ nums: [Int]) -> Int {
+        var zeroCount = 0
+        var res = 0
+        var l = 0
+
+        for r in 0..<nums.count {
+            if nums[r] == 0 {
+                zeroCount += 1
+            }
+            while zeroCount > 1 {
+                if nums[l] == 0 {
+                    zeroCount -= 1
+                }
+                l += 1
+            }
+            res = max(res, r - l)
+        }
+
+        return res
+    }
+}
\ No newline at end of file
diff --git a/swift/2013-detect-squares.swift b/swift/2013-detect-squares.swift
new file mode 100644
index 000000000..09c58c0ff
--- /dev/null
+++ b/swift/2013-detect-squares.swift
@@ -0,0 +1,35 @@
+
+class DetectSquares {
+
+    var pts = [[Int]]()
+    var ptsCount = [[Int]: Int]()
+
+    init() {
+        
+    }
+    
+    func add(_ point: [Int]) {
+        ptsCount[point, default: 0] += 1
+        pts.append(point)
+    }
+    
+    func count(_ point: [Int]) -> Int {
+        var res = 0
+        var x = point[0], y = point[1]
+        for val in pts {
+            let px = val[0], py = val[1]
+            if abs(py - y) != abs(px - x) || x == px || y == py {
+                continue
+            }
+            res += ptsCount[[x, py], default: 0] * ptsCount[[px, y], default: 0]
+        }
+        return res
+    }
+}
+
+/**
+ * Your DetectSquares object will be instantiated and called as such:
+ * let obj = DetectSquares()
+ * obj.add(point)
+ * let ret_2: Int = obj.count(point)
+ */
\ No newline at end of file
diff --git a/typescript/0303-range-sum-query-immutable.ts b/typescript/0303-range-sum-query-immutable.ts
index e2d9c2efd..757a620a6 100644
--- a/typescript/0303-range-sum-query-immutable.ts
+++ b/typescript/0303-range-sum-query-immutable.ts
@@ -1,5 +1,5 @@
 class NumArray {
-
+  
     prefixSums: number[] = [];
 
     constructor(nums: number[]) {
diff --git a/typescript/0703-kth-largest-element-in-a-stream.ts b/typescript/0703-kth-largest-element-in-a-stream.ts
new file mode 100644
index 000000000..a196e11ca
--- /dev/null
+++ b/typescript/0703-kth-largest-element-in-a-stream.ts
@@ -0,0 +1,61 @@
+class KthLargest {
+    backingArray: number[];
+    size: number;
+
+    constructor(k: number, nums: number[]) {
+        this.backingArray = [];
+        this.size = k;
+        for(const num of nums) this.add(num)
+    }
+
+    add(val: number): number {
+        const newLength = this.backingArray.push(val)
+        this.shiftUp(newLength - 1);
+
+        if (newLength > this.size) this.pop();
+
+        return this.backingArray[0];
+    }
+
+    private pop() {
+        this.swap(0, this.backingArray.length - 1)
+        this.backingArray.length -= 1;
+        this.shiftDown(0)
+    }
+
+    private shiftDown(elementIndex: number) {
+        let leftChildIndex = elementIndex * 2 + 1;
+        let rightChildIndex = elementIndex * 2 + 2;
+
+        while ((leftChildIndex < this.backingArray.length && this.backingArray[leftChildIndex] < this.backingArray[elementIndex])
+        || (rightChildIndex < this.backingArray.length && this.backingArray[rightChildIndex] < this.backingArray[elementIndex])) {
+            let smallestIndex = leftChildIndex;
+            if (rightChildIndex < this.backingArray.length && this.backingArray[rightChildIndex] < this.backingArray[smallestIndex]) {
+                smallestIndex = rightChildIndex
+            }
+
+            this.swap(elementIndex, smallestIndex);
+
+            elementIndex = smallestIndex;
+            leftChildIndex = elementIndex * 2 + 1;
+            rightChildIndex = elementIndex * 2 + 2;
+        }
+    }
+
+    private shiftUp(elementIndex: number) {
+        if (elementIndex === 0) return;
+
+        let parentIndex = Math.floor((elementIndex - 1) / 2);
+        while (this.backingArray[parentIndex] > this.backingArray[elementIndex]) {
+            this.swap(elementIndex, parentIndex);
+            elementIndex = parentIndex;
+            parentIndex = Math.floor((elementIndex - 1) / 2);
+        }
+    }
+
+    private swap(indexA: number, indexB: number) {
+        const temp = this.backingArray[indexA];
+        this.backingArray[indexA] = this.backingArray[indexB];
+        this.backingArray[indexB] = temp;
+    }
+}
diff --git a/typescript/0705-design-hashset.ts b/typescript/0705-design-hashset.ts
new file mode 100644
index 000000000..b1f3816cc
--- /dev/null
+++ b/typescript/0705-design-hashset.ts
@@ -0,0 +1,65 @@
+class _ListNode { // ListNode has a confict
+    key: number;
+    next: _ListNode | undefined;
+
+    constructor(key: number) {
+        this.key = key;
+    }
+}
+
+class MyHashSet {
+    readonly ARRAY_LENGTH = Math.pow(10, 4);
+    set = new Array<_ListNode>(this.ARRAY_LENGTH);
+
+    constructor() {
+        for (let i = 0; i < this.ARRAY_LENGTH; i++)
+            this.set[i] = new _ListNode(0);
+    }
+
+    add(key: number): void {
+        let cur = this.set[key % this.set.length];
+        
+        while (cur.next) {
+            if (cur.next.key === key)
+                return;
+
+            cur = cur.next;
+        }
+
+        cur.next = new _ListNode(key);
+    }
+
+    remove(key: number): void {
+        let cur = this.set[key % this.set.length];
+        
+        while (cur.next) {
+            if (cur.next.key === key) {
+                cur.next = cur.next.next;
+                return;
+            }
+
+            cur = cur.next;
+        }
+    }
+
+    contains(key: number): boolean {
+        let cur = this.set[key % this.set.length];
+        
+        while (cur.next) {
+            if (cur.next.key === key)
+                return true;
+
+            cur = cur.next;
+        }
+
+        return false;
+    }
+}
+
+/**
+ * Your MyHashSet object will be instantiated and called as such:
+ * var obj = new MyHashSet()
+ * obj.add(key)
+ * obj.remove(key)
+ * var param_3 = obj.contains(key)
+ */
diff --git a/typescript/2469-convert-the-temperature.ts b/typescript/2469-convert-the-temperature.ts
new file mode 100644
index 000000000..59d54b405
--- /dev/null
+++ b/typescript/2469-convert-the-temperature.ts
@@ -0,0 +1,5 @@
+function convertTemperature(celsius: number): number[] {
+    const kelvin = celsius + 273.15;
+    const fahrenheit = celsius * 1.80 + 32.00;
+    return [kelvin, fahrenheit];
+};